This is manual.info, produced by makeinfo version 4.8 from manual.texi.

START-INFO-DIR-ENTRY
* mysql: (mysql).               MySQL documentation.
END-INFO-DIR-ENTRY


File: manual.info,  Node: Top,  Next: preface,  Prev: (dir),  Up: (dir)

* Menu:

* preface::                      Preface and Legal Notices
* introduction::                 General Information
* installing::                   Installing and Upgrading MySQL
* tutorial::                     Tutorial
* programs::                     MySQL Programs
* server-administration::        MySQL Server Administration
* security::                     Security
* backup-and-recovery::          Backup and Recovery
* optimization::                 Optimization
* language-structure::           Language Structure
* globalization::                Globalization
* data-types::                   Data Types
* functions::                    Functions and Operators
* sql-syntax::                   SQL Statement Syntax
* storage-engines::              Storage Engines
* ha-overview::                  High Availability and Scalability
* replication::                  Replication
* mysql-cluster::                MySQL Cluster NDB 6.1 - 7.1
* partitioning::                 Partitioning
* stored-programs-views::        Stored Programs and Views
* information-schema::           INFORMATION_SCHEMA Tables
* connectors-apis::              Connectors and APIs
* extending-mysql::              Extending MySQL
* mysql-enterprise::             MySQL Enterprise Edition
* workbench::                    MySQL Workbench
* faqs::                         MySQL 5.1 Frequently Asked Questions
* error-handling::               Errors, Error Codes, and Common Problems
* news::                         MySQL Release Notes
* restrictions::                 Restrictions and Limits
* licenses-third-party::         Licenses for Third-Party Components


File: manual.info,  Node: preface,  Next: introduction,  Prev: Top,  Up: Top

Preface and Legal Notices
*************************

This is the Reference Manual for the MySQL Database System, version
5.1, through release 5.1.73. Differences between minor versions of
MySQL 5.1 are noted in the present text with reference to release
numbers (5.1.X). For license information, see the Legal Notices. This
product may contain third-party code. For license information on
third-party code, see *Note licenses-third-party::.

This manual is not intended for use with older versions of the MySQL
software due to the many functional and other differences between MySQL
5.1 and previous versions. If you are using an earlier release of the
MySQL software, please refer to the appropriate manual. For example,
`MySQL 5.0 Reference Manual' (http://dev.mysql.com/doc/refman/5.0/en/)
covers the 5.0 series of MySQL software releases.

If you are using MySQL 5.5, please refer to the `MySQL 5.5 Reference
Manual' (http://dev.mysql.com/doc/refman/5.5/en/).

*Legal Notices*

Copyright (C) 1997, 2014, Oracle and/or its affiliates. All rights
reserved.

This software and related documentation are provided under a license
agreement containing restrictions on use and disclosure and are
protected by intellectual property laws. Except as expressly permitted
in your license agreement or allowed by law, you may not use, copy,
reproduce, translate, broadcast, modify, license, transmit, distribute,
exhibit, perform, publish, or display any part, in any form, or by any
means. Reverse engineering, disassembly, or decompilation of this
software, unless required by law for interoperability, is prohibited.

The information contained herein is subject to change without notice
and is not warranted to be error-free. If you find any errors, please
report them to us in writing.

If this software or related documentation is delivered to the U.S.
Government or anyone licensing it on behalf of the U.S. Government, the
following notice is applicable:

U.S. GOVERNMENT RIGHTS Programs, software, databases, and related
documentation and technical data delivered to U.S. Government customers
are "commercial computer software" or "commercial technical data"
pursuant to the applicable Federal Acquisition Regulation and
agency-specific supplemental regulations. As such, the use,
duplication, disclosure, modification, and adaptation shall be subject
to the restrictions and license terms set forth in the applicable
Government contract, and, to the extent applicable by the terms of the
Government contract, the additional rights set forth in FAR 52.227-19,
Commercial Computer Software License (December 2007).  Oracle USA,
Inc., 500 Oracle Parkway, Redwood City, CA 94065.

This software is developed for general use in a variety of information
management applications. It is not developed or intended for use in any
inherently dangerous applications, including applications which may
create a risk of personal injury. If you use this software in dangerous
applications, then you shall be responsible to take all appropriate
fail-safe, backup, redundancy, and other measures to ensure the safe
use of this software. Oracle Corporation and its affiliates disclaim
any liability for any damages caused by use of this software in
dangerous applications.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. MySQL is a trademark of Oracle Corporation and/or its
affiliates, and shall not be used without Oracle's express written
authorization. Other names may be trademarks of their respective owners.

This software and documentation may provide access to or information on
content, products, and services from third parties. Oracle Corporation
and its affiliates are not responsible for and expressly disclaim all
warranties of any kind with respect to third-party content, products,
and services. Oracle Corporation and its affiliates will not be
responsible for any loss, costs, or damages incurred due to your access
to or use of third-party content, products, or services.

This document in any form, software or printed matter, contains
proprietary information that is the exclusive property of Oracle.  Your
access to and use of this material is subject to the terms and
conditions of your Oracle Software License and Service Agreement, which
has been executed and with which you agree to comply. This document and
information contained herein may not be disclosed, copied, reproduced,
or distributed to anyone outside Oracle without prior written consent
of Oracle or as specifically provided below.  This document is not part
of your license agreement nor can it be incorporated into any
contractual agreement with Oracle or its subsidiaries or affiliates.

This documentation is NOT distributed under a GPL license. Use of this
documentation is subject to the following terms:

You may create a printed copy of this documentation solely for your own
personal use. Conversion to other formats is allowed as long as the
actual content is not altered or edited in any way. You shall not
publish or distribute this documentation in any form or on any media,
except if you distribute the documentation in a manner similar to how
Oracle disseminates it (that is, electronically for download on a Web
site with the software) or on a CD-ROM or similar medium, provided
however that the documentation is disseminated together with the
software on the same medium. Any other use, such as any dissemination
of printed copies or use of this documentation, in whole or in part, in
another publication, requires the prior written consent from an
authorized representative of Oracle. Oracle and/or its affiliates
reserve any and all rights to this documentation not expressly granted
above.

For more information on the terms of this license, or for details on
how the MySQL documentation is built and produced, please visit MySQL
Contact & Questions (http://dev.mysql.com/contact/).

For additional licensing information, including licenses for
third-party libraries used by MySQL products, see *Note Top::.

For help with using MySQL, please visit either the MySQL Forums
(http://forums.mysql.com) or MySQL Mailing Lists
(http://lists.mysql.com) where you can discuss your issues with other
MySQL users.

For additional documentation on MySQL products, including translations
of the documentation into other languages, and downloadable versions in
variety of formats, including HTML and PDF formats, see the MySQL
Documentation Library (http://dev.mysql.com/doc).


File: manual.info,  Node: introduction,  Next: installing,  Prev: preface,  Up: Top

1 General Information
*********************

* Menu:

* manual-info::                  About This Manual
* manual-conventions::           Typographical and Syntax Conventions
* what-is::                      Overview of the MySQL Database Management System
* mysql-nutshell::               What Is New in MySQL 5.1
* development-history::          MySQL Development History
* information-sources::          MySQL Information Sources
* bug-reports::                  How to Report Bugs or Problems
* compatibility::                MySQL Standards Compliance
* credits::                      Credits

End of Product Lifecycle

Active development for MySQL Database Server version 5.1 has ended.
Oracle offers various support offerings which may be of interest. For
details and more information, see the MySQL section of the Lifetime
Support Policy for Oracle Technology Products
(`http://www.oracle.com/us/support/lifetime-support/index.html').
Please consider upgrading to a recent version.

The MySQL(tm) software delivers a very fast, multi-threaded,
multi-user, and robust SQL (Structured Query Language) database server.
MySQL Server is intended for mission-critical, heavy-load production
systems as well as for embedding into mass-deployed software. Oracle is
a registered trademark of Oracle Corporation and/or its affiliates.
MySQL is a trademark of Oracle Corporation and/or its affiliates, and
shall not be used by Customer without Oracle's express written
authorization. Other names may be trademarks of their respective owners.

The MySQL software is Dual Licensed. Users can choose to use the MySQL
software as an Open Source product under the terms of the GNU General
Public License (`http://www.fsf.org/licenses/') or can purchase a
standard commercial license from Oracle. See
`http://www.mysql.com/company/legal/licensing/' for more information on
our licensing policies.

The following list describes some sections of particular interest in
this manual:

   * For a discussion of MySQL Database Server capabilities, see *Note
     features::.

   * For an overview of new MySQL features, see *Note mysql-nutshell::.
     For information about the changes in each version, see the Release
     Notes (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/).

   * For installation instructions, see *Note installing::.  For
     information about upgrading MySQL, see *Note upgrading::.

   * For a tutorial introduction to the MySQL Database Server, see
     *Note tutorial::.

   * For information about configuring and administering MySQL Server,
     see *Note server-administration::.

   * For information about security in MySQL, see *Note security::.

   * For information about setting up replication servers, see *Note
     replication::.

   * For information about MySQL Enterprise, the commercial MySQL
     release with advanced features and management tools, see *Note
     mysql-enterprise::.

   * For answers to a number of questions that are often asked
     concerning the MySQL Database Server and its capabilities, see
     *Note faqs::.

   * For a history of new features and bug fixes, see the Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/).

*Important*:

To report problems or bugs, please use the instructions at *Note
bug-reports::. If you find a sensitive security bug in MySQL Server,
please let us know immediately by sending an email message to
<secalert_us@oracle.com>. Exception: Support customers should report
all problems, including security bugs, to Oracle Support.


File: manual.info,  Node: manual-info,  Next: manual-conventions,  Prev: introduction,  Up: introduction

1.1 About This Manual
=====================

This is the Reference Manual for the MySQL Database System, version
5.1, through release 5.1.73.  Differences between minor versions of
MySQL 5.1 are noted in the present text with reference to release
numbers (5.1.X). For license information, see the Legal Notices. This
product may contain third-party code. For license information on
third-party code, see *Note licenses-third-party::.

This manual is not intended for use with older versions of the MySQL
software due to the many functional and other differences between MySQL
5.1 and previous versions. If you are using an earlier release of the
MySQL software, please refer to the appropriate manual. For example,
`MySQL 5.0 Reference Manual' (http://dev.mysql.com/doc/refman/5.0/en/)
covers the 5.0 series of MySQL software releases.

If you are using MySQL 5.5, please refer to the `MySQL 5.5 Reference
Manual' (http://dev.mysql.com/doc/refman/5.5/en/).

Because this manual serves as a reference, it does not provide general
instruction on SQL or relational database concepts. It also does not
teach you how to use your operating system or command-line interpreter.

The MySQL Database Software is under constant development, and the
Reference Manual is updated frequently as well. The most recent version
of the manual is available online in searchable form at
`http://dev.mysql.com/doc/'. Other formats also are available there,
including HTML, PDF, and EPUB versions.

The Reference Manual source files are written in DocBook XML format.
The HTML version and other formats are produced automatically,
primarily using the DocBook XSL stylesheets. For information about
DocBook, see `http://docbook.org/'

If you have questions about using MySQL, you can ask them using our
mailing lists or forums. See *Note mailing-lists::, and *Note forums::.
If you have suggestions concerning additions or corrections to the
manual itself, please send them to the
http://www.mysql.com/company/contact/.

This manual was originally written by David Axmark and Michael `Monty'
Widenius. It is maintained by the MySQL Documentation Team, consisting
of Paul DuBois, Edward Gilmore, Stefan Hinz, David Moss, Philip Olson,
Daniel Price, Daniel So, and Jon Stephens.


File: manual.info,  Node: manual-conventions,  Next: what-is,  Prev: manual-info,  Up: introduction

1.2 Typographical and Syntax Conventions
========================================

This manual uses certain typographical conventions:

   * `Text in this style' is used for SQL statements; database, table,
     and column names; program listings and source code; and
     environment variables. Example: `To reload the grant tables, use
     the *Note `FLUSH PRIVILEGES': flush. statement.'

   * Text in this style indicates input that you type in examples.

   * `Text in this style' indicates the names of executable programs
     and scripts, examples being *Note `mysql': mysql. (the MySQL
     command-line client program) and *Note `mysqld': mysqld. (the
     MySQL server executable).

   * TEXT IN THIS STYLE is used for variable input for which you should
     substitute a value of your own choosing.

   * _Text in this style_ is used for emphasis.

   * *Text in this style* is used in table headings and to convey
     especially strong emphasis.

   * `Text in this style' is used to indicate a program option that
     affects how the program is executed, or that supplies information
     that is needed for the program to function in a certain way.
     _Example_: `The `--host' option (short form `-h') tells the *Note
     `mysql': mysql. client program the hostname or IP address of the
     MySQL server that it should connect to'.

   * File names and directory names are written like this: `The global
     `my.cnf' file is located in the `/etc' directory.'

   * Character sequences are written like this: `To specify a wildcard,
     use the ``%'' character.'

When commands are shown that are meant to be executed from within a
particular program, the prompt shown preceding the command indicates
which command to use. For example, `shell>' indicates a command that
you execute from your login shell, `root-shell>' is similar but should
be executed as `root', and `mysql>' indicates a statement that you
execute from the *Note `mysql': mysql. client program:


     shell> type a shell command here
     root-shell> type a shell command as ROOT here
     mysql> type a mysql statement here

In some areas different systems may be distinguished from each other to
show that commands should be executed in two different environments.
For example, while working with replication the commands might be
prefixed with `master' and `slave':


     master> type a mysql command on the replication master here
     slave> type a mysql command on the replication slave here

The `shell' is your command interpreter. On Unix, this is typically a
program such as `sh', `csh', or `bash'. On Windows, the equivalent
program is `command.com' or `cmd.exe', typically run in a console
window.

When you enter a command or statement shown in an example, do not type
the prompt shown in the example.

Database, table, and column names must often be substituted into
statements. To indicate that such substitution is necessary, this
manual uses DB_NAME, TBL_NAME, and COL_NAME. For example, you might see
a statement like this:


     mysql> SELECT COL_NAME FROM DB_NAME.TBL_NAME;

This means that if you were to enter a similar statement, you would
supply your own database, table, and column names, perhaps like this:


     mysql> SELECT author_name FROM biblio_db.author_list;

SQL keywords are not case sensitive and may be written in any
lettercase. This manual uses uppercase.

In syntax descriptions, square brackets (``['' and ``]'') indicate
optional words or clauses. For example, in the following statement, `IF
EXISTS' is optional:


     DROP TABLE [IF EXISTS] TBL_NAME

When a syntax element consists of a number of alternatives, the
alternatives are separated by vertical bars (``|''). When one member
from a set of choices _may_ be chosen, the alternatives are listed
within square brackets (``['' and ``]''):


     TRIM([[BOTH | LEADING | TRAILING] [REMSTR] FROM] STR)

When one member from a set of choices _must_ be chosen, the
alternatives are listed within braces (``{'' and ``}''):


     {DESCRIBE | DESC} TBL_NAME [COL_NAME | WILD]

An ellipsis (`...') indicates the omission of a section of a statement,
typically to provide a shorter version of more complex syntax. For
example, *Note `SELECT ... INTO OUTFILE': select. is shorthand for the
form of *Note `SELECT': select. statement that has an `INTO OUTFILE'
clause following other parts of the statement.

An ellipsis can also indicate that the preceding syntax element of a
statement may be repeated. In the following example, multiple
RESET_OPTION values may be given, with each of those after the first
preceded by commas:


     RESET RESET_OPTION [,RESET_OPTION] ...

Commands for setting shell variables are shown using Bourne shell
syntax. For example, the sequence to set the `CC' environment variable
and run the `configure' command looks like this in Bourne shell syntax:


     shell> CC=gcc ./configure

If you are using `csh' or `tcsh', you must issue commands somewhat
differently:


     shell> setenv CC gcc
     shell> ./configure


File: manual.info,  Node: what-is,  Next: mysql-nutshell,  Prev: manual-conventions,  Up: introduction

1.3 Overview of the MySQL Database Management System
====================================================

* Menu:

* what-is-mysql::                What is MySQL?
* features::                     The Main Features of MySQL
* history::                      History of MySQL


File: manual.info,  Node: what-is-mysql,  Next: features,  Prev: what-is,  Up: what-is

1.3.1 What is MySQL?
--------------------

MySQL, the most popular Open Source SQL database management system, is
developed, distributed, and supported by Oracle Corporation.

The MySQL Web site (http://www.mysql.com/) provides the latest
information about MySQL software.

   * *MySQL is a database management system.*

     A database is a structured collection of data. It may be anything
     from a simple shopping list to a picture gallery or the vast
     amounts of information in a corporate network. To add, access, and
     process data stored in a computer database, you need a database
     management system such as MySQL Server.  Since computers are very
     good at handling large amounts of data, database management
     systems play a central role in computing, as standalone utilities,
     or as parts of other applications.

   * *MySQL databases are relational.*

     A relational database stores data in separate tables rather than
     putting all the data in one big storeroom. The database structures
     are organized into physical files optimized for speed. The logical
     model, with objects such as databases, tables, views, rows, and
     columns, offers a flexible programming environment. You set up
     rules governing the relationships between different data fields,
     such as one-to-one, one-to-many, unique, required or optional, and
     `pointers' between different tables. The database enforces these
     rules, so that with a well-designed database, your application
     never sees inconsistent, duplicate, orphan, out-of-date, or
     missing data.

     The SQL part of `MySQL' stands for `Structured Query Language'.
     SQL is the most common standardized language used to access
     databases.  Depending on your programming environment, you might
     enter SQL directly (for example, to generate reports), embed SQL
     statements into code written in another language, or use a
     language-specific API that hides the SQL syntax.

     SQL is defined by the ANSI/ISO SQL Standard. The SQL standard has
     been evolving since 1986 and several versions exist. In this
     manual, `SQL-92' refers to the standard released in 1992,
     `SQL:1999' refers to the standard released in 1999, and `SQL:2003'
     refers to the current version of the standard. We use the phrase
     `the SQL standard' to mean the current version of the SQL Standard
     at any time.

   * *MySQL software is Open Source.*

     Open Source means that it is possible for anyone to use and modify
     the software. Anybody can download the MySQL software from the
     Internet and use it without paying anything. If you wish, you may
     study the source code and change it to suit your needs. The MySQL
     software uses the GPL (GNU General Public License),
     `http://www.fsf.org/licenses/', to define what you may and may not
     do with the software in different situations. If you feel
     uncomfortable with the GPL or need to embed MySQL code into a
     commercial application, you can buy a commercially licensed
     version from us. See the MySQL Licensing Overview for more
     information (http://www.mysql.com/company/legal/licensing/).

   * *The MySQL Database Server is very fast, reliable, scalable, and
     easy to use.*

     If that is what you are looking for, you should give it a try.
     MySQL Server can run comfortably on a desktop or laptop, alongside
     your other applications, web servers, and so on, requiring little
     or no attention. If you dedicate an entire machine to MySQL, you
     can adjust the settings to take advantage of all the memory, CPU
     power, and I/O capacity available. MySQL can also scale up to
     clusters of machines, networked together.

     You can find a performance comparison of MySQL Server with other
     database managers on our benchmark page. See *Note
     mysql-benchmarks::.

     MySQL Server was originally developed to handle large databases
     much faster than existing solutions and has been successfully used
     in highly demanding production environments for several years.
     Although under constant development, MySQL Server today offers a
     rich and useful set of functions. Its connectivity, speed, and
     security make MySQL Server highly suited for accessing databases
     on the Internet.

   * *MySQL Server works in client/server or embedded systems.*

     The MySQL Database Software is a client/server system that
     consists of a multi-threaded SQL server that supports different
     backends, several different client programs and libraries,
     administrative tools, and a wide range of application programming
     interfaces (APIs).

     We also provide MySQL Server as an embedded multi-threaded library
     that you can link into your application to get a smaller, faster,
     easier-to-manage standalone product.

   * *A large amount of contributed MySQL software is available.*

     MySQL Server has a practical set of features developed in close
     cooperation with our users. It is very likely that your favorite
     application or language supports the MySQL Database Server.

The official way to pronounce `MySQL' is `My Ess Que Ell' (not `my
sequel'), but we do not mind if you pronounce it as `my sequel' or in
some other localized way.


File: manual.info,  Node: features,  Next: history,  Prev: what-is-mysql,  Up: what-is

1.3.2 The Main Features of MySQL
--------------------------------

This section describes some of the important characteristics of the
MySQL Database Software. See also *Note development-history::. In most
respects, the roadmap applies to all versions of MySQL. For information
about features as they are introduced into MySQL on a series-specific
basis, see the `In a Nutshell' section of the appropriate Manual:

   * MySQL 5.6: MySQL 5.6 in a Nutshell
     (http://dev.mysql.com/doc/refman/5.6/en/mysql-nutshell.html)

   * MySQL 5.5: MySQL 5.5 in a Nutshell
     (http://dev.mysql.com/doc/refman/5.5/en/mysql-nutshell.html)

   * MySQL 5.1: MySQL 5.1 in a Nutshell
     (http://dev.mysql.com/doc/refman/5.1/en/mysql-nutshell.html)

   * MySQL 5.0: MySQL 5.0 in a Nutshell
     (http://dev.mysql.com/doc/refman/5.0/en/mysql-nutshell.html)

*Internals and Portability*

   * Written in C and C++.

   * Tested with a broad range of different compilers.

   * Works on many different platforms. See
     `http://www.mysql.com/support/supportedplatforms/database.html'.

   * For portability, uses `CMake' in MySQL 5.5 and up. Previous series
     use GNU Automake, Autoconf, and Libtool.

   * Tested with Purify (a commercial memory leakage detector) as well
     as with Valgrind, a GPL tool
     (`http://developer.kde.org/~sewardj/').

   * Uses multi-layered server design with independent modules.

   * Designed to be fully multi-threaded using kernel threads, to
     easily use multiple CPUs if they are available.

   * Provides transactional and nontransactional storage engines.

   * Uses very fast B-tree disk tables (`MyISAM') with index
     compression.

   * Designed to make it relatively easy to add other storage engines.
     This is useful if you want to provide an SQL interface for an
     in-house database.

   * Uses a very fast thread-based memory allocation system.

   * Executes very fast joins using an optimized nested-loop join.

   * Implements in-memory hash tables, which are used as temporary
     tables.

   * Implements SQL functions using a highly optimized class library
     that should be as fast as possible. Usually there is no memory
     allocation at all after query initialization.

   * Provides the server as a separate program for use in a
     client/server networked environment, and as a library that can be
     embedded (linked) into standalone applications. Such applications
     can be used in isolation or in environments where no network is
     available.

*Data Types*

   * Many data types: signed/unsigned integers 1, 2, 3, 4, and 8 bytes
     long, *Note `FLOAT': floating-point-types, *Note `DOUBLE':
     floating-point-types, *Note `CHAR': char, *Note `VARCHAR': char,
     *Note `BINARY': binary-varbinary, *Note `VARBINARY':
     binary-varbinary, *Note `TEXT': blob, *Note `BLOB': blob, *Note
     `DATE': datetime, *Note `TIME': time, *Note `DATETIME': datetime,
     *Note `TIMESTAMP': datetime, *Note `YEAR': year, *Note `SET': set,
     *Note `ENUM': enum, and OpenGIS spatial types. See *Note
     data-types::.

   * Fixed-length and variable-length string types.

*Statements and Functions*

   * Full operator and function support in the *Note `SELECT': select.
     list and `WHERE' clause of queries. For example:


          mysql> SELECT CONCAT(first_name, ' ', last_name)
              -> FROM citizen
              -> WHERE income/dependents > 10000 AND age > 30;

   * Full support for SQL `GROUP BY' and `ORDER BY' clauses. Support
     for group functions (`COUNT()', `AVG()', `STD()', `SUM()', `MAX()',
     `MIN()', and `GROUP_CONCAT()').

   * Support for `LEFT OUTER JOIN' and `RIGHT OUTER JOIN' with both
     standard SQL and ODBC syntax.

   * Support for aliases on tables and columns as required by standard
     SQL.

   * Support for *Note `DELETE': delete, *Note `INSERT': insert, *Note
     `REPLACE': replace, and *Note `UPDATE': update. to return the
     number of rows that were changed (affected), or to return the
     number of rows matched instead by setting a flag when connecting
     to the server.

   * Support for MySQL-specific *Note `SHOW': show.  statements that
     retrieve information about databases, storage engines, tables, and
     indexes. MySQL 5.0 adds support for the `INFORMATION_SCHEMA'
     database, implemented according to standard SQL.

   * An *Note `EXPLAIN': explain. statement to show how the optimizer
     resolves a query.

   * Independence of function names from table or column names. For
     example, `ABS' is a valid column name. The only restriction is
     that for a function call, no spaces are permitted between the
     function name and the ``('' that follows it. See *Note
     reserved-words::.

   * You can refer to tables from different databases in the same
     statement.

*Security*

   * A privilege and password system that is very flexible and secure,
     and that enables host-based verification.

   * Password security by encryption of all password traffic when you
     connect to a server.

*Scalability and Limits*

   * Support for large databases. We use MySQL Server with databases
     that contain 50 million records. We also know of users who use
     MySQL Server with 200,000 tables and about 5,000,000,000 rows.

   * Support for up to 64 indexes per table (32 before MySQL 4.1.2).
     Each index may consist of 1 to 16 columns or parts of columns. The
     maximum index width is 767 bytes for `InnoDB' tables, or 1000 for
     `MyISAM'; before MySQL 4.1.2, the limit is 500 bytes. An index may
     use a prefix of a column for *Note `CHAR': char, *Note `VARCHAR':
     char, *Note `BLOB': blob, or *Note `TEXT': blob. column types.

*Connectivity*

   * Clients can connect to MySQL Server using several protocols:

        * Clients can connect using TCP/IP sockets on any platform.

        * On Windows systems in the NT family (NT, 2000, XP, 2003, or
          Vista), clients can connect using named pipes if the server
          is started with the `--enable-named-pipe' option.  In MySQL
          4.1 and higher, Windows servers also support shared-memory
          connections if started with the `--shared-memory' option.
          Clients can connect through shared memory by using the
          `--protocol=memory' option.

        * On Unix systems, clients can connect using Unix domain socket
          files.

   * MySQL client programs can be written in many languages. A client
     library written in C is available for clients written in C or C++,
     or for any language that provides C bindings.

   * APIs for C, C++, Eiffel, Java, Perl, PHP, Python, Ruby, and Tcl
     are available, enabling MySQL clients to be written in many
     languages. See *Note connectors-apis::.

   * The Connector/ODBC (MyODBC) interface provides MySQL support for
     client programs that use ODBC (Open Database Connectivity)
     connections. For example, you can use MS Access to connect to your
     MySQL server. Clients can be run on Windows or Unix.
     Connector/ODBC source is available. All ODBC 2.5 functions are
     supported, as are many others. See MySQL Connector/ODBC Developer
     Guide (http://dev.mysql.com/doc/connector-odbc/en/index.html).

   * The Connector/J interface provides MySQL support for Java client
     programs that use JDBC connections. Clients can be run on Windows
     or Unix. Connector/J source is available. See MySQL Connector/J
     Developer Guide
     (http://dev.mysql.com/doc/connector-j/en/index.html).

   * MySQL Connector/Net enables developers to easily create .NET
     applications that require secure, high-performance data
     connectivity with MySQL. It implements the required ADO.NET
     interfaces and integrates into ADO.NET aware tools. Developers can
     build applications using their choice of .NET languages.  MySQL
     Connector/Net is a fully managed ADO.NET driver written in 100%
     pure C#. See MySQL Connector/Net Developer Guide
     (http://dev.mysql.com/doc/connector-net/en/index.html).

*Localization*

   * The server can provide error messages to clients in many
     languages. See *Note error-message-language::.

   * Full support for several different character sets, including
     `latin1' (cp1252), `german', `big5', `ujis', and more.  For
     example, the Scandinavian characters ``aa'', ``a"'' and ``o"'' are
     permitted in table and column names. Unicode support is available
     as of MySQL 4.1.

   * All data is saved in the chosen character set.

   * Sorting and comparisons are done according to the chosen character
     set and collation (using `latin1' and Swedish collation by
     default). It is possible to change this when the MySQL server is
     started. To see an example of very advanced sorting, look at the
     Czech sorting code. MySQL Server supports many different character
     sets that can be specified at compile time and runtime.

   * As of MySQL 4.1, the server time zone can be changed dynamically,
     and individual clients can specify their own time zone. *Note
     time-zone-support::.

*Clients and Tools*

   * MySQL includes several client and utility programs. These include
     both command-line programs such as *Note `mysqldump': mysqldump.
     and *Note `mysqladmin': mysqladmin, and graphical programs such as
     *Note MySQL Workbench: workbench.

   * MySQL Server has built-in support for SQL statements to check,
     optimize, and repair tables. These statements are available from
     the command line through the *Note `mysqlcheck': mysqlcheck.
     client. MySQL also includes *Note `myisamchk': myisamchk, a very
     fast command-line utility for performing these operations on
     `MyISAM' tables. See *Note programs::.

   * MySQL programs can be invoked with the `--help' or `-?' option to
     obtain online assistance.


File: manual.info,  Node: history,  Prev: features,  Up: what-is

1.3.3 History of MySQL
----------------------

We started out with the intention of using the `mSQL' database system
to connect to our tables using our own fast low-level (ISAM) routines.
However, after some testing, we came to the conclusion that `mSQL' was
not fast enough or flexible enough for our needs. This resulted in a
new SQL interface to our database but with almost the same API
interface as `mSQL'. This API was designed to enable third-party code
that was written for use with `mSQL' to be ported easily for use with
MySQL.

MySQL is named after co-founder Monty Widenius's daughter, My.

The name of the MySQL Dolphin (our logo) is `Sakila,' which was chosen
from a huge list of names suggested by users in our `Name the Dolphin'
contest. The winning name was submitted by Ambrose Twebaze, an Open
Source software developer from Swaziland, Africa. According to Ambrose,
the feminine name Sakila has its roots in SiSwati, the local language
of Swaziland.  Sakila is also the name of a town in Arusha, Tanzania,
near Ambrose's country of origin, Uganda.


File: manual.info,  Node: mysql-nutshell,  Next: development-history,  Prev: what-is,  Up: introduction

1.4 What Is New in MySQL 5.1
============================

This section summarizes what has been added to MySQL 5.1 and what has
been deprecated for further use.

   * Added Features

   * Deprecated Features

*Added Features*

The following features have been added to MySQL 5.1:

   * Partitioning

     This capability enables distributing portions of individual tables
     across a file system, according to rules which can be set when the
     table is created. In effect, different portions of a table are
     stored as separate tables in different locations, but from the
     user point of view, the partitioned table is still a single table.
     Syntactically, this implements a number of new extensions to the
     *Note `CREATE TABLE': create-table, *Note `ALTER TABLE':
     alter-table, and `EXPLAIN ... SELECT' statements. As of MySQL
     5.1.6, queries against partitioned tables can take advantage of
     _partition pruning_. In some cases, this can result in query
     execution that is an order of magnitude faster than the same query
     against a nonpartitioned version of the same table. See *Note
     partitioning::, for further information on this functionality.
     (Author: Mikael Ronstro"m)

   * Row-based replication

     Replication capabilities in MySQL originally were based on
     propagation of SQL statements from master to slave. This is called
     _statement-based replication_. As of MySQL 5.1.5, another basis
     for replication is available.  This is called _row-based
     replication_.  Instead of sending SQL statements to the slave, the
     master writes events to its binary log that indicate how individual
     table rows are effected. As of MySQL 5.1.8, a third option is
     available: _mixed_. This will use statement-based replication by
     default, and only switch to row-based replication in particular
     cases. See *Note replication-formats::. (Authors: Lars Thalmann,
     Guilhem Bichot, Mats Kindahl)

   * Plugin API

     MySQL 5.1 adds support for a very flexible plugin API that enables
     loading and unloading of various components at runtime, without
     restarting the server. Although the work on this is not finished
     yet, _plugin full-text parsers_ are a first step in this
     direction. This permits users to implement their own input filter
     on the indexed text, enabling full-text search capability on
     arbitrary data such as PDF files or other document formats.  A
     pre-parser full-text plugin performs the actual parsing and
     extraction of the text and hands it over to the built-in MySQL
     full-text search. See *Note plugin-api::.  (Author: Sergey
     Vojtovich)

   * Event scheduler

     MySQL Events are tasks that run according to a schedule.  When you
     create an event, you are creating a named database object
     containing one or more SQL statements to be executed at one or
     more regular intervals, beginning and ending at a specific date
     and time. Conceptually, this is similar to the idea of the Unix
     `crontab' (also known as a `cron job') or the Windows Task
     Scheduler. See *Note events::. (Author: Andrey Hristov)

   * Server log tables

     Before MySQL 5.1, the server writes general query log and slow
     query log entries to log files. As of MySQL 5.1, the server's
     logging capabilities for these logs are more flexible. Log entries
     can be written to log files (as before) or to the `general_log' and
     `slow_log' tables in the `mysql' database. If logging is enabled,
     either or both destinations can be selected. The `--log-output'
     option controls the destination or destinations of log output. See
     *Note log-destinations::. (Author: Petr Chardin)

   * Upgrade program

     The *Note `mysql_upgrade': mysql-upgrade. program (available as of
     MySQL 5.1.7) checks all existing tables for incompatibilities with
     the current version of MySQL Server and repairs them if necessary.
     This program should be run for each MySQL upgrade. See *Note
     mysql-upgrade::.  (Authors: Alexey Botchkov, Mikael Widenius)

   * MySQL Cluster

     MySQL Cluster is now released as a separate product, based on
     MySQL 5.1 but with the addition of the *Note `NDBCLUSTER':
     mysql-cluster. storage engine.  Clustering support is no longer
     available in mainline MySQL 5.1 releases. MySQL Cluster releases
     are identified by a 3-part NDB version number; currently, the
     MySQL Cluster NDB 6.3, MySQL Cluster NDB 7.0, and MySQL Cluster
     NDB 7.1 release series are available for production use.

     Some of the changes in MySQL Cluster since MySQL 5.0 are listed
     here:

        * MySQL Cluster replication

          Replication between MySQL Clusters is now supported. It is
          now also possible to replicate between a MySQL Cluster and a
          noncluster database. See *Note mysql-cluster-replication::.

        * MySQL Cluster disk data storage

          Formerly, the *Note `NDBCLUSTER': mysql-cluster.  storage
          engine was strictly in-memory; now, it is possible to store
          Cluster data (but not indexes) on disk. This enables MySQL
          Cluster to scale upward with fewer hardware (RAM)
          requirements than previously. In addition, the Disk Data
          implementation includes a new `no-steal' restoration
          algorithm for fast node restarts when storing very large
          amounts of data (terabyte range). See *Note
          mysql-cluster-disk-data::, for more information.

        * Improved backups for MySQL Cluster

          A fault arising in a single data node during a Cluster backup
          no longer causes the entire backup to be aborted, as occurred
          in previous versions of MySQL Cluster.

     Many other new features and improvements have been made to the
     *Note `NDBCLUSTER': mysql-cluster. storage engine in MySQL Cluster
     NDB 7.0 and MySQL Cluster NDB 7.1; for more information about
     these, see *Note mysql-cluster-development::.

   * Backup of tablespaces

     The *Note `mysqldump': mysqldump. utility now supports an option
     for dumping tablespaces. Use `-Y' or `--all-tablespaces' to enable
     this functionality.

   * Improvements to INFORMATION_SCHEMA

     MySQL 5.1 provides much more information in its metadata database
     than was available in MySQL 5.0. New tables in the
     `INFORMATION_SCHEMA' database include *Note `FILES': files-table,
     *Note `EVENTS': events-table, *Note `PARTITIONS': partitions-table,
     *Note `PROCESSLIST': processlist-table, *Note `ENGINES':
     engines-table, and *Note `PLUGINS': plugins-table.

   * XML functions with XPath support

     `ExtractValue()' returns the content of a fragment of XML matching
     a given XPath expression. `UpdateXML()' replaces the element
     selected from a fragment of XML by an XPath expression supplied by
     the user with a second XML fragment (also user-supplied), and
     returns the modified XML.  See *Note xml-functions::. (Author:
     Alexander Barkov)

   * Load emulator

     The *Note `mysqlslap': mysqlslap. program is designed to emulate
     client load for a MySQL server and report the timing of each
     stage. It works as if multiple clients were accessing the server.
     See *Note mysqlslap::.  (Authors: Patrick Galbraith, Brian Aker)

*Deprecated Features*

The following constructs are deprecated in MySQL 5.1 and are removed as
of MySQL 5.5. Where alternatives are shown, applications should be
updated to use them.

   * The `log_bin_trust_routine_creators' system variable (use
     `log_bin_trust_function_creators').

   * The `table_type' system variable (use `storage_engine').

   * The `TYPE' table option to specify the storage engine for *Note
     `CREATE TABLE': create-table.  or *Note `ALTER TABLE':
     alter-table. (use `ENGINE').

   * The `SHOW TABLE TYPES' SQL statement (use *Note `SHOW ENGINES':
     show-engines.).

   * The *Note `SHOW INNODB STATUS': show-innodb-status. and `SHOW
     MUTEX STATUS' SQL statements (use *Note `SHOW ENGINE INNODB
     STATUS': show-engine.  *Note `SHOW ENGINE INNODB MUTEX':
     show-engine.).

   * The `SHOW PLUGIN' SQL statement (use *Note `SHOW PLUGINS':
     show-plugins.).

   * The `LOAD TABLE ... FROM MASTER' and `LOAD DATA FROM MASTER' SQL
     statements (use *Note `mysqldump': mysqldump. or *Note
     `mysqlhotcopy': mysqlhotcopy. to dump tables and *Note `mysql':
     mysql. to reload dump files).

   * The *Note `BACKUP TABLE': backup-table. and *Note `RESTORE TABLE':
     restore-table. SQL statements (use *Note `mysqldump': mysqldump. or
     *Note `mysqlhotcopy': mysqlhotcopy. to dump tables and *Note
     `mysql': mysql. to reload dump files).

   * *Note `TIMESTAMP(N)': datetime.  data type: The ability to specify
     a display width of N (use without N).

   * The `--master-XXX' server options to set replication parameters
     (use the *Note `CHANGE MASTER TO': change-master-to. statement
     instead): `--master-host', `--master-user', `--master-password',
     `--master-port', `--master-connect-retry', `--master-ssl',
     `--master-ssl-ca', `--master-ssl-capath', `--master-ssl-cert',
     `--master-ssl-cipher', `--master-ssl-key'.


File: manual.info,  Node: development-history,  Next: information-sources,  Prev: mysql-nutshell,  Up: introduction

1.5 MySQL Development History
=============================

This section describes the general MySQL development history, provides
an overview about features that have been implemented in previous
series and that are new in MySQL 5.1, the release series covered in
this manual. The maturity level this release series is general
availability. Information about maturity levels can be found in *Note
choosing-version::.

Before upgrading from one release series to the next, please see the
notes in *Note upgrading::.

The most requested features and the versions in which they were
implemented are summarized in the following table.

This table summarizes the most requested MySQL features and the
versions in which they were implemented.

Feature                MySQL Series
Unions                 4.0
Subqueries             4.1
R-trees                4.1 (for the `MyISAM' storage engine)
Stored procedures and  5.0
functions              
Views                  5.0
Cursors                5.0
XA transactions        5.0
Triggers               5.0 and 5.1
Event scheduler        5.1
Partitioning           5.1
Pluggable storage      5.1
engine API             
Plugin API             5.1
Row-based replication  5.1
Server log tables      5.1
Scalability and        5.1 (with InnoDB Plugin)
performance            
improvements           


File: manual.info,  Node: information-sources,  Next: bug-reports,  Prev: development-history,  Up: introduction

1.6 MySQL Information Sources
=============================

* Menu:

* mailing-lists::                MySQL Mailing Lists
* forums::                       MySQL Community Support at the MySQL Forums
* irc::                          MySQL Community Support on Internet Relay Chat (IRC)
* mysql-enterprise-information::  MySQL Enterprise

This section lists sources of additional information that you may find
helpful, such as the MySQL mailing lists and user forums, and Internet
Relay Chat.


File: manual.info,  Node: mailing-lists,  Next: forums,  Prev: information-sources,  Up: information-sources

1.6.1 MySQL Mailing Lists
-------------------------

* Menu:

* mailing-list-use::             Guidelines for Using the Mailing Lists

This section introduces the MySQL mailing lists and provides guidelines
as to how the lists should be used. When you subscribe to a mailing
list, you receive all postings to the list as email messages. You can
also send your own questions and answers to the list.

To subscribe to or unsubscribe from any of the mailing lists described
in this section, visit `http://lists.mysql.com/'. For most of them, you
can select the regular version of the list where you get individual
messages, or a digest version where you get one large message per day.

Please _do not_ send messages about subscribing or unsubscribing to any
of the mailing lists, because such messages are distributed
automatically to thousands of other users.

Your local site may have many subscribers to a MySQL mailing list.  If
so, the site may have a local mailing list, so that messages sent from
`lists.mysql.com' to your site are propagated to the local list. In
such cases, please contact your system administrator to be added to or
dropped from the local MySQL list.

To have traffic for a mailing list go to a separate mailbox in your
mail program, set up a filter based on the message headers.  You can
use either the `List-ID:' or `Delivered-To:' headers to identify list
messages.

The MySQL mailing lists are as follows:

   * `announce'

     The list for announcements of new versions of MySQL and related
     programs. This is a low-volume list to which all MySQL users
     should subscribe.

   * `mysql'

     The main list for general MySQL discussion. Please note that some
     topics are better discussed on the more-specialized lists. If you
     post to the wrong list, you may not get an answer.

   * `bugs'

     The list for people who want to stay informed about issues
     reported since the last release of MySQL or who want to be
     actively involved in the process of bug hunting and fixing.  See
     *Note bug-reports::.

   * `internals'

     The list for people who work on the MySQL code. This is also the
     forum for discussions on MySQL development and for posting patches.

   * `mysqldoc'

     The list for people who work on the MySQL documentation.

   * `benchmarks'

     The list for anyone interested in performance issues.  Discussions
     concentrate on database performance (not limited to MySQL), but
     also include broader categories such as performance of the kernel,
     file system, disk system, and so on.

   * `packagers'

     The list for discussions on packaging and distributing MySQL.
     This is the forum used by distribution maintainers to exchange
     ideas on packaging MySQL and on ensuring that MySQL looks and
     feels as similar as possible on all supported platforms and
     operating systems.

   * `java'

     The list for discussions about the MySQL server and Java. It is
     mostly used to discuss JDBC drivers such as MySQL Connector/J.

   * `win32'

     The list for all topics concerning the MySQL software on Microsoft
     operating systems, such as Windows 9x, Me, NT, 2000, XP, and 2003.

   * `myodbc'

     The list for all topics concerning connecting to the MySQL server
     with ODBC.

   * `gui-tools'

     The list for all topics concerning MySQL graphical user interface
     tools such as MySQL Workbench.

   * `cluster'

     The list for discussion of MySQL Cluster.

   * `dotnet'

     The list for discussion of the MySQL server and the .NET platform.
     It is mostly related to MySQL Connector/Net.

   * `plusplus'

     The list for all topics concerning programming with the C++ API
     for MySQL.

   * `perl'

     The list for all topics concerning Perl support for MySQL with
     `DBD::mysql'.

If you're unable to get an answer to your questions from a MySQL
mailing list or forum, one option is to purchase support from Oracle.
This puts you in direct contact with MySQL developers.

The following MySQL mailing lists are in languages other than English.
These lists are not operated by Oracle.

   * `<mysql-france-subscribe@yahoogroups.com>'

     A French mailing list.

   * `<list@tinc.net>'

     A Korean mailing list. To subscribe, email `subscribe mysql
     your@email.address' to this list.

   * `<mysql-de-request@lists.4t2.com>'

     A German mailing list. To subscribe, email `subscribe mysql-de
     your@email.address' to this list. You can find information about
     this mailing list at `http://www.4t2.com/mysql/'.

   * `<mysql-br-request@listas.linkway.com.br>'

     A Portuguese mailing list. To subscribe, email `subscribe mysql-br
     your@email.address' to this list.

   * `<mysql-alta@elistas.net>'

     A Spanish mailing list. To subscribe, email `subscribe mysql
     your@email.address' to this list.


File: manual.info,  Node: mailing-list-use,  Prev: mailing-lists,  Up: mailing-lists

1.6.1.1 Guidelines for Using the Mailing Lists
..............................................

Please do not post mail messages from your browser with HTML mode
turned on. Many users do not read mail with a browser.

When you answer a question sent to a mailing list, if you consider your
answer to have broad interest, you may want to post it to the list
instead of replying directly to the individual who asked. Try to make
your answer general enough that people other than the original poster
may benefit from it.  When you post to the list, please make sure that
your answer is not a duplication of a previous answer.

Try to summarize the essential part of the question in your reply. Do
not feel obliged to quote the entire original message.

When answers are sent to you individually and not to the mailing list,
it is considered good etiquette to summarize the answers and send the
summary to the mailing list so that others may have the benefit of
responses you received that helped you solve your problem.


File: manual.info,  Node: forums,  Next: irc,  Prev: mailing-lists,  Up: information-sources

1.6.2 MySQL Community Support at the MySQL Forums
-------------------------------------------------

The forums at `http://forums.mysql.com' are an important community
resource. Many forums are available, grouped into these general
categories:

   * Migration

   * MySQL Usage

   * MySQL Connectors

   * Programming Languages

   * Tools

   * 3rd-Party Applications

   * Storage Engines

   * MySQL Technology

   * SQL Standards

   * Business


File: manual.info,  Node: irc,  Next: mysql-enterprise-information,  Prev: forums,  Up: information-sources

1.6.3 MySQL Community Support on Internet Relay Chat (IRC)
----------------------------------------------------------

In addition to the various MySQL mailing lists and forums, you can find
experienced community people on Internet Relay Chat (IRC).  These are
the best networks/channels currently known to us:

*freenode* (see `http://www.freenode.net/' for servers)

   * `#mysql' is primarily for MySQL questions, but other database and
     general SQL questions are welcome.  Questions about PHP, Perl, or
     C in combination with MySQL are also common.

If you are looking for IRC client software to connect to an IRC
network, take a look at `xChat' (`http://www.xchat.org/'). X-Chat (GPL
licensed) is available for Unix as well as for Windows platforms (a free
Windows build of X-Chat is available at
`http://www.silverex.org/download/').


File: manual.info,  Node: mysql-enterprise-information,  Prev: irc,  Up: information-sources

1.6.4 MySQL Enterprise
----------------------

Oracle offers technical support in the form of MySQL Enterprise.  For
organizations that rely on the MySQL DBMS for business-critical
production applications, MySQL Enterprise is a commercial subscription
offering which includes:

   * MySQL Enterprise Server

   * MySQL Enterprise Monitor

   * Monthly Rapid Updates and Quarterly Service Packs

   * MySQL Knowledge Base

   * 24x7 Technical and Consultative Support

MySQL Enterprise is available in multiple tiers, giving you the
flexibility to choose the level of service that best matches your
needs. For more information, see MySQL Enterprise
(http://www.mysql.com/products/enterprise/).


File: manual.info,  Node: bug-reports,  Next: compatibility,  Prev: information-sources,  Up: introduction

1.7 How to Report Bugs or Problems
==================================

Before posting a bug report about a problem, please try to verify that
it is a bug and that it has not been reported already:

   * Start by searching the MySQL online manual at
     `http://dev.mysql.com/doc/'. We try to keep the manual up to date
     by updating it frequently with solutions to newly found problems.
     In addition, the release notes accompanying the manual can be
     particularly useful since it is quite possible that a newer
     version contains a solution to your problem. The release notes are
     available at the location just given for the manual.

   * If you get a parse error for an SQL statement, please check your
     syntax closely. If you cannot find something wrong with it, it is
     extremely likely that your current version of MySQL Server doesn't
     support the syntax you are using. If you are using the current
     version and the manual doesn't cover the syntax that you are
     using, MySQL Server doesn't support your statement.

     If the manual covers the syntax you are using, but you have an
     older version of MySQL Server, you should check the MySQL change
     history to see when the syntax was implemented. In this case, you
     have the option of upgrading to a newer version of MySQL Server.

   * For solutions to some common problems, see *Note problems::.

   * Search the bugs database at `http://bugs.mysql.com/' to see
     whether the bug has been reported and fixed.

   * Search the MySQL mailing list archives at
     `http://lists.mysql.com/'. See *Note mailing-lists::.

   * You can also use http://www.mysql.com/search/ to search all the
     Web pages (including the manual) that are located at the MySQL Web
     site.

If you cannot find an answer in the manual, the bugs database, or the
mailing list archives, check with your local MySQL expert. If you still
cannot find an answer to your question, please use the following
guidelines for reporting the bug.

The normal way to report bugs is to visit `http://bugs.mysql.com/',
which is the address for our bugs database. This database is public and
can be browsed and searched by anyone. If you log in to the system, you
can enter new reports.

Bugs posted in the bugs database at `http://bugs.mysql.com/' that are
corrected for a given release are noted in the release notes.

If you find a sensitive security bug in MySQL Server, please let us
know immediately by sending an email message to
<secalert_us@oracle.com>. Exception: Support customers should report
all problems, including security bugs, to Oracle Support at
`http://support.oracle.com/'.

To discuss problems with other users, you can use one of the MySQL
mailing lists. *Note mailing-lists::.

Writing a good bug report takes patience, but doing it right the first
time saves time both for us and for yourself. A good bug report,
containing a full test case for the bug, makes it very likely that we
will fix the bug in the next release. This section helps you write your
report correctly so that you do not waste your time doing things that
may not help us much or at all. Please read this section carefully and
make sure that all the information described here is included in your
report.

Preferably, you should test the problem using the latest production or
development version of MySQL Server before posting. Anyone should be
able to repeat the bug by just using `mysql test < script_file' on your
test case or by running the shell or Perl script that you include in
the bug report. Any bug that we are able to repeat has a high chance of
being fixed in the next MySQL release.

It is most helpful when a good description of the problem is included
in the bug report. That is, give a good example of everything you did
that led to the problem and describe, in exact detail, the problem
itself. The best reports are those that include a full example showing
how to reproduce the bug or problem. See *Note porting::.

Remember that it is possible for us to respond to a report containing
too much information, but not to one containing too little. People
often omit facts because they think they know the cause of a problem
and assume that some details do not matter. A good principle to follow
is that if you are in doubt about stating something, state it. It is
faster and less troublesome to write a couple more lines in your report
than to wait longer for the answer if we must ask you to provide
information that was missing from the initial report.

The most common errors made in bug reports are (a) not including the
version number of the MySQL distribution that you use, and (b) not
fully describing the platform on which the MySQL server is installed
(including the platform type and version number). These are highly
relevant pieces of information, and in 99 cases out of 100, the bug
report is useless without them. Very often we get questions like, `Why
doesn't this work for me?' Then we find that the feature requested
wasn't implemented in that MySQL version, or that a bug described in a
report has been fixed in newer MySQL versions.  Errors often are
platform-dependent. In such cases, it is next to impossible for us to
fix anything without knowing the operating system and the version
number of the platform.

If you compiled MySQL from source, remember also to provide information
about your compiler if it is related to the problem.  Often people find
bugs in compilers and think the problem is MySQL-related. Most
compilers are under development all the time and become better version
by version. To determine whether your problem depends on your compiler,
we need to know what compiler you used.  Note that every compiling
problem should be regarded as a bug and reported accordingly.

If a program produces an error message, it is very important to include
the message in your report. If we try to search for something from the
archives, it is better that the error message reported exactly matches
the one that the program produces. (Even the lettercase should be
observed.) It is best to copy and paste the entire error message into
your report. You should never try to reproduce the message from memory.

If you have a problem with Connector/ODBC (MyODBC), please try to
generate a trace file and send it with your report. See How to Report
Connector/ODBC Problems or Bugs
(http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-support-bug-report.html).

If your report includes long query output lines from test cases that
you run with the *Note `mysql': mysql. command-line tool, you can make
the output more readable by using the `--vertical' option or the `\G'
statement terminator. The *Note `EXPLAIN SELECT': explain.  example
later in this section demonstrates the use of `\G'.

Please include the following information in your report:

   * The version number of the MySQL distribution you are using (for
     example, MySQL 5.0.19). You can find out which version you are
     running by executing *Note `mysqladmin version': mysqladmin. The
     *Note `mysqladmin': mysqladmin. program can be found in the `bin'
     directory under your MySQL installation directory.

   * The manufacturer and model of the machine on which you experience
     the problem.

   * The operating system name and version. If you work with Windows,
     you can usually get the name and version number by double-clicking
     your My Computer icon and pulling down the `Help/About Windows'
     menu. For most Unix-like operating systems, you can get this
     information by executing the command `uname -a'.

   * Sometimes the amount of memory (real and virtual) is relevant.  If
     in doubt, include these values.

   * If you are using a source distribution of the MySQL software,
     include the name and version number of the compiler that you used.
     If you have a binary distribution, include the distribution name.

   * If the problem occurs during compilation, include the exact error
     messages and also a few lines of context around the offending code
     in the file where the error occurs.

   * If *Note `mysqld': mysqld. died, you should also report the
     statement that crashed *Note `mysqld': mysqld. You can usually get
     this information by running *Note `mysqld': mysqld. with query
     logging enabled, and then looking in the log after *Note `mysqld':
     mysqld. crashes. See *Note porting::.

   * If a database table is related to the problem, include the output
     from the `SHOW CREATE TABLE DB_NAME.TBL_NAME' statement in the bug
     report. This is a very easy way to get the definition of any table
     in a database. The information helps us create a situation
     matching the one that you have experienced.

   * The SQL mode in effect when the problem occurred can be
     significant, so please report the value of the `sql_mode' system
     variable. For stored procedure, stored function, and trigger
     objects, the relevant `sql_mode' value is the one in effect when
     the object was created. For a stored procedure or function, the
     *Note `SHOW CREATE PROCEDURE': show-create-procedure. or *Note
     `SHOW CREATE FUNCTION': show-create-function. statement shows the
     relevant SQL mode, or you can query `INFORMATION_SCHEMA' for the
     information:


          SELECT ROUTINE_SCHEMA, ROUTINE_NAME, SQL_MODE
          FROM INFORMATION_SCHEMA.ROUTINES;

     For triggers, you can use this statement:


          SELECT EVENT_OBJECT_SCHEMA, EVENT_OBJECT_TABLE, TRIGGER_NAME, SQL_MODE
          FROM INFORMATION_SCHEMA.TRIGGERS;

   * For performance-related bugs or problems with *Note `SELECT':
     select. statements, you should always include the output of
     `EXPLAIN SELECT ...', and at least the number of rows that the
     *Note `SELECT': select. statement produces. You should also
     include the output from `SHOW CREATE TABLE TBL_NAME' for each table
     that is involved. The more information you provide about your
     situation, the more likely it is that someone can help you.

     The following is an example of a very good bug report. The
     statements are run using the *Note `mysql': mysql.  command-line
     tool. Note the use of the `\G' statement terminator for statements
     that would otherwise provide very long output lines that are
     difficult to read.


          mysql> SHOW VARIABLES;
          mysql> SHOW COLUMNS FROM ...\G
                 <OUTPUT FROM SHOW COLUMNS>
          mysql> EXPLAIN SELECT ...\G
                 <OUTPUT FROM EXPLAIN>
          mysql> FLUSH STATUS;
          mysql> SELECT ...;
                 <A SHORT VERSION OF THE OUTPUT FROM SELECT,
                 INCLUDING THE TIME TAKEN TO RUN THE QUERY>
          mysql> SHOW STATUS;
                 <OUTPUT FROM SHOW STATUS>

   * If a bug or problem occurs while running *Note `mysqld': mysqld,
     try to provide an input script that reproduces the anomaly. This
     script should include any necessary source files. The more closely
     the script can reproduce your situation, the better. If you can
     make a reproducible test case, you should upload it to be attached
     to the bug report.

     If you cannot provide a script, you should at least include the
     output from *Note `mysqladmin variables extended-status
     processlist': mysqladmin. in your report to provide some
     information on how your system is performing.

   * If you cannot produce a test case with only a few rows, or if the
     test table is too big to be included in the bug report (more than
     10 rows), you should dump your tables using *Note `mysqldump':
     mysqldump. and create a `README' file that describes your problem.
     Create a compressed archive of your files using `tar' and `gzip' or
     `zip'. After you initiate a bug report for our bugs database at
     `http://bugs.mysql.com/', click the Files tab in the bug report
     for instructions on uploading the archive to the bugs database.

   * If you believe that the MySQL server produces a strange result
     from a statement, include not only the result, but also your
     opinion of what the result should be, and an explanation
     describing the basis for your opinion.

   * When you provide an example of the problem, it is better to use
     the table names, variable names, and so forth that exist in your
     actual situation than to come up with new names. The problem could
     be related to the name of a table or variable. These cases are
     rare, perhaps, but it is better to be safe than sorry. After all,
     it should be easier for you to provide an example that uses your
     actual situation, and it is by all means better for us. If you
     have data that you do not want to be visible to others in the bug
     report, you can upload it using the Files tab as previously
     described. If the information is really top secret and you do not
     want to show it even to us, go ahead and provide an example using
     other names, but please regard this as the last choice.

   * Include all the options given to the relevant programs, if
     possible. For example, indicate the options that you use when you
     start the *Note `mysqld': mysqld. server, as well as the options
     that you use to run any MySQL client programs. The options to
     programs such as *Note `mysqld': mysqld. and *Note `mysql': mysql,
     and to the `configure' script, are often key to resolving problems
     and are very relevant. It is never a bad idea to include them. If
     your problem involves a program written in a language such as Perl
     or PHP, please include the language processor's version number, as
     well as the version for any modules that the program uses. For
     example, if you have a Perl script that uses the `DBI' and
     `DBD::mysql' modules, include the version numbers for Perl, `DBI',
     and `DBD::mysql'.

   * If your question is related to the privilege system, please
     include the output of *Note `mysqlaccess': mysqlaccess, the output
     of *Note `mysqladmin reload': mysqladmin, and all the error
     messages you get when trying to connect. When you test your
     privileges, you should first run *Note `mysqlaccess': mysqlaccess.
     After this, execute *Note `mysqladmin reload version': mysqladmin.
     and try to connect with the program that gives you trouble.  *Note
     `mysqlaccess': mysqlaccess. can be found in the `bin' directory
     under your MySQL installation directory.

   * If you have a patch for a bug, do include it. But do not assume
     that the patch is all we need, or that we can use it, if you do
     not provide some necessary information such as test cases showing
     the bug that your patch fixes. We might find problems with your
     patch or we might not understand it at all. If so, we cannot use
     it.

     If we cannot verify the exact purpose of the patch, we will not
     use it. Test cases help us here. Show that the patch handles all
     the situations that may occur. If we find a borderline case (even
     a rare one) where the patch will not work, it may be useless.

   * Guesses about what the bug is, why it occurs, or what it depends
     on are usually wrong. Even the MySQL team cannot guess such things
     without first using a debugger to determine the real cause of a
     bug.

   * Indicate in your bug report that you have checked the reference
     manual and mail archive so that others know you have tried to
     solve the problem yourself.

   * If your data appears corrupt or you get errors when you access a
     particular table, first check your tables with *Note `CHECK
     TABLE': check-table. If that statement reports any errors:

        * The `InnoDB' crash recovery mechanism handles cleanup when
          the server is restarted after being killed, so in typical
          operation there is no need to `repair' tables. If you
          encounter an error with `InnoDB' tables, restart the server
          and see whether the problem persists, or whether the error
          affected only cached data in memory. If data is corrupted on
          disk, consider restarting with the `innodb_force_recovery'
          option enabled so that you can dump the affected tables.

        * For non-transactional tables, try to repair them with *Note
          `REPAIR TABLE': repair-table. or with *Note `myisamchk':
          myisamchk. See *Note server-administration::.

     If you are running Windows, please verify the value of
     `lower_case_table_names' using the `SHOW VARIABLES LIKE
     'lower_case_table_names'' statement. This variable affects how the
     server handles lettercase of database and table names. Its effect
     for a given value should be as described in *Note
     identifier-case-sensitivity::.

   * If you often get corrupted tables, you should try to find out when
     and why this happens. In this case, the error log in the MySQL
     data directory may contain some information about what happened.
     (This is the file with the `.err' suffix in the name.) See *Note
     error-log::. Please include any relevant information from this
     file in your bug report. Normally *Note `mysqld': mysqld. should
     _never_ crash a table if nothing killed it in the middle of an
     update. If you can find the cause of *Note `mysqld': mysqld.
     dying, it is much easier for us to provide you with a fix for the
     problem. See *Note what-is-crashing::.

   * If possible, download and install the most recent version of MySQL
     Server and check whether it solves your problem. All versions of
     the MySQL software thoroughly tested and should work without
     problems. We believe in making everything as backward-compatible
     as possible, and you should be able to switch MySQL versions
     without difficulty. See *Note which-version::.


File: manual.info,  Node: compatibility,  Next: credits,  Prev: bug-reports,  Up: introduction

1.8 MySQL Standards Compliance
==============================

* Menu:

* extensions-to-ansi::           MySQL Extensions to Standard SQL
* differences-from-ansi::        MySQL Differences from Standard SQL
* constraints::                  How MySQL Deals with Constraints

This section describes how MySQL relates to the ANSI/ISO SQL standards.
MySQL Server has many extensions to the SQL standard, and here you can
find out what they are and how to use them. You can also find
information about functionality missing from MySQL Server, and how to
work around some of the differences.

The SQL standard has been evolving since 1986 and several versions
exist. In this manual, `SQL-92' refers to the standard released in
1992, `SQL:1999' refers to the standard released in 1999, `SQL:2003'
refers to the standard released in 2003, and `SQL:2008' refers to the
most recent version of the standard, released in 2008. We use the
phrase `the SQL standard' or `standard SQL' to mean the current version
of the SQL Standard at any time.

One of our main goals with the product is to continue to work toward
compliance with the SQL standard, but without sacrificing speed or
reliability. We are not afraid to add extensions to SQL or support for
non-SQL features if this greatly increases the usability of MySQL
Server for a large segment of our user base.  The *Note `HANDLER':
handler. interface is an example of this strategy. See *Note handler::.

We continue to support transactional and nontransactional databases to
satisfy both mission-critical 24/7 usage and heavy Web or logging usage.

MySQL Server was originally designed to work with medium-sized
databases (10-100 million rows, or about 100MB per table) on small
computer systems. Today MySQL Server handles terabyte-sized databases,
but the code can also be compiled in a reduced version suitable for
hand-held and embedded devices. The compact design of the MySQL server
makes development in both directions possible without any conflicts in
the source tree.

Currently, we are not targeting real-time support, although MySQL
replication capabilities offer significant functionality.

MySQL supports ODBC levels 0 to 3.51.

MySQL supports high-availability database clustering using the *Note
`NDBCLUSTER': mysql-cluster. storage engine. See *Note mysql-cluster::.

We are implementing XML functionality beginning in MySQL 5.1, which
supports most of the W3C XPath standard. See *Note xml-functions::.

*Selecting SQL Modes*

The MySQL server can operate in different SQL modes, and can apply
these modes differently for different clients, depending on the value
of the `sql_mode' system variable. DBAs can set the global SQL mode to
match site server operating requirements, and each application can set
its session SQL mode to its own requirements.

Modes affect the SQL syntax MySQL supports and the data validation
checks it performs. This makes it easier to use MySQL in different
environments and to use MySQL together with other database servers.

For more information on setting the SQL mode, see *Note sql-mode::.

*Running MySQL in ANSI Mode*

To run MySQL Server in ANSI mode, start *Note `mysqld': mysqld.  with
the `--ansi' option. Running the server in ANSI mode is the same as
starting it with the following options:


     --transaction-isolation=SERIALIZABLE --sql-mode=ANSI

To achieve the same effect at runtime, execute these two statements:


     SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE;
     SET GLOBAL sql_mode = 'ANSI';

You can see that setting the `sql_mode' system variable to `'ANSI''
enables all SQL mode options that are relevant for ANSI mode as follows:


     mysql> SET GLOBAL sql_mode='ANSI';
     mysql> SELECT @@global.sql_mode;
             -> 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ANSI'

Running the server in ANSI mode with `--ansi' is not quite the same as
setting the SQL mode to `'ANSI'' because the `--ansi' option also sets
the transaction isolation level.

See *Note server-options::.


File: manual.info,  Node: extensions-to-ansi,  Next: differences-from-ansi,  Prev: compatibility,  Up: compatibility

1.8.1 MySQL Extensions to Standard SQL
--------------------------------------

MySQL Server supports some extensions that you probably won't find in
other SQL DBMSs. Be warned that if you use them, your code won't be
portable to other SQL servers. In some cases, you can write code that
includes MySQL extensions, but is still portable, by using comments of
the following form:


     /*! MYSQL-SPECIFIC CODE */

In this case, MySQL Server parses and executes the code within the
comment as it would any other SQL statement, but other SQL servers will
ignore the extensions. For example, MySQL Server recognizes the
`STRAIGHT_JOIN' keyword in the following statement, but other servers
will not:


     SELECT /*! STRAIGHT_JOIN */ col1 FROM table1,table2 WHERE ...

If you add a version number after the ``!'' character, the syntax within
the comment is executed only if the MySQL version is greater than or
equal to the specified version number. The `TEMPORARY' keyword in the
following comment is executed only by servers from MySQL 3.23.02 or
higher:


     CREATE /*!32302 TEMPORARY */ TABLE t (a INT);

The following descriptions list MySQL extensions, organized by category.

   * Organization of data on disk

     MySQL Server maps each database to a directory under the MySQL
     data directory, and maps tables within a database to file names in
     the database directory. This has a few implications:

        * Database and table names are case sensitive in MySQL Server
          on operating systems that have case-sensitive file names
          (such as most Unix systems). See *Note
          identifier-case-sensitivity::.

        * You can use standard system commands to back up, rename,
          move, delete, and copy tables that are managed by the
          `MyISAM' storage engine. For example, it is possible to
          rename a `MyISAM' table by renaming the `.MYD', `.MYI', and
          `.frm' files to which the table corresponds. (Nevertheless, it
          is preferable to use *Note `RENAME TABLE': rename-table. or
          `ALTER TABLE ...  RENAME' and let the server rename the
          files.)

     Prior to MySQL 5.1.6, database and table names cannot contain path
     name separator characters (``/'', ``\'').

   * General language syntax

        * By default, strings can be enclosed by either ``"'' or ``''',
          not just by ``'''. (If the `ANSI_QUOTES' SQL mode is enabled,
          strings can be enclosed only by ``''' and the server
          interprets strings enclosed by ``"'' as identifiers.)

        * ``\'' is the escape character in strings.

        * In SQL statements, you can access tables from different
          databases with the DB_NAME.TBL_NAME syntax. Some SQL servers
          provide the same functionality but call this `User space'.
          MySQL Server doesn't support tablespaces such as used in
          statements like this: `CREATE TABLE ralph.my_table ... IN
          my_tablespace'.

   * SQL statement syntax

        * The *Note `ANALYZE TABLE': analyze-table, *Note `CHECK
          TABLE': check-table, *Note `OPTIMIZE TABLE': optimize-table,
          and *Note `REPAIR TABLE': repair-table. statements.

        * The *Note `CREATE DATABASE': create-database, *Note `DROP
          DATABASE': drop-database, and *Note `ALTER DATABASE':
          alter-database.  statements. See *Note create-database::,
          *Note drop-database::, and *Note alter-database::.

        * The *Note `DO': do. statement.

        * *Note `EXPLAIN SELECT': explain. to obtain a description of
          how tables are processed by the query optimizer.

        * The *Note `FLUSH': flush. and *Note `RESET': reset.
          statements.

        * The *Note `SET': set-statement.  statement. See *Note
          set-statement::.

        * The *Note `SHOW': show. statement. See *Note show::. The
          information produced by many of the MySQL-specific *Note
          `SHOW': show. statements can be obtained in more standard
          fashion by using *Note `SELECT': select. to query
          `INFORMATION_SCHEMA'. See *Note information-schema::.

        * Use of *Note `LOAD DATA INFILE': load-data. In many cases,
          this syntax is compatible with Oracle's *Note `LOAD DATA
          INFILE': load-data. See *Note load-data::.

        * Use of *Note `RENAME TABLE': rename-table. See *Note
          rename-table::.

        * Use of *Note `REPLACE': replace. instead of *Note `DELETE':
          delete. plus *Note `INSERT': insert. See *Note replace::.

        * Use of `CHANGE COL_NAME', `DROP COL_NAME', or *Note `DROP
          INDEX': drop-index, `IGNORE' or `RENAME' in *Note `ALTER
          TABLE': alter-table.  statements. Use of multiple `ADD',
          `ALTER', `DROP', or `CHANGE' clauses in an *Note `ALTER
          TABLE': alter-table. statement.  See *Note alter-table::.

        * Use of index names, indexes on a prefix of a column, and use
          of `INDEX' or `KEY' in *Note `CREATE TABLE': create-table.
          statements. See *Note create-table::.

        * Use of `TEMPORARY' or `IF NOT EXISTS' with *Note `CREATE
          TABLE': create-table.

        * Use of `IF EXISTS' with *Note `DROP TABLE': drop-table. and
          *Note `DROP DATABASE': drop-database.

        * The capability of dropping multiple tables with a single
          *Note `DROP TABLE': drop-table. statement.

        * The `ORDER BY' and `LIMIT' clauses of the *Note `UPDATE':
          update. and *Note `DELETE': delete. statements.

        * `INSERT INTO TBL_NAME SET COL_NAME = ...' syntax.

        * The `DELAYED' clause of the *Note `INSERT': insert. and *Note
          `REPLACE': replace. statements.

        * The `LOW_PRIORITY' clause of the *Note `INSERT': insert,
          *Note `REPLACE': replace, *Note `DELETE': delete, and *Note
          `UPDATE': update. statements.

        * Use of `INTO OUTFILE' or `INTO DUMPFILE' in *Note `SELECT':
          select. statements. See *Note select::.

        * Options such as `STRAIGHT_JOIN' or `SQL_SMALL_RESULT' in
          *Note `SELECT': select. statements.

        * You don't need to name all selected columns in the `GROUP BY'
          clause. This gives better performance for some very specific,
          but quite normal queries. See *Note
          group-by-functions-and-modifiers::.

        * You can specify `ASC' and `DESC' with `GROUP BY', not just
          with `ORDER BY'.

        * The ability to set variables in a statement with the `:='
          assignment operator. See *Note user-variables::.

   * Data types

        * The *Note `MEDIUMINT': integer-types, *Note `SET': set, and
          *Note `ENUM': enum. data types, and the various *Note `BLOB':
          blob. and *Note `TEXT': blob. data types.

        * The `AUTO_INCREMENT', `BINARY', `NULL', `UNSIGNED', and
          `ZEROFILL' data type attributes.

   * Functions and operators

        * To make it easier for users who migrate from other SQL
          environments, MySQL Server supports aliases for many
          functions. For example, all string functions support both
          standard SQL syntax and ODBC syntax.

        * MySQL Server understands the `||' and `&&' operators to mean
          logical OR and AND, as in the C programming language. In
          MySQL Server, `||' and `OR' are synonyms, as are `&&' and
          `AND'.  Because of this nice syntax, MySQL Server doesn't
          support the standard SQL `||' operator for string
          concatenation; use `CONCAT()' instead. Because `CONCAT()'
          takes any number of arguments, it is easy to convert use of
          the `||' operator to MySQL Server.

        * Use of `COUNT(DISTINCT VALUE_LIST)' where VALUE_LIST has more
          than one element.

        * String comparisons are case-insensitive by default, with sort
          ordering determined by the collation of the current character
          set, which is `latin1' (cp1252 West European) by default. If
          you don't like this, you should declare your columns with the
          `BINARY' attribute or use the `BINARY' cast, which causes
          comparisons to be done using the underlying character code
          values rather than a lexical ordering.

        * The `%' operator is a synonym for `MOD()'. That is, `N % M'
          is equivalent to `MOD(N,M)'.  `%' is supported for C
          programmers and for compatibility with PostgreSQL.

        * The `=', `<>', `<=', `<', `>=', `>', `<<', `>>', `<=>', `AND',
          `OR', or `LIKE' operators may be used in expressions in the
          output column list (to the left of the `FROM') in *Note
          `SELECT': select. statements. For example:


               mysql> SELECT col1=1 AND col2=2 FROM my_table;

        * The `LAST_INSERT_ID()' function returns the most recent
          `AUTO_INCREMENT' value. See *Note information-functions::.

        * `LIKE' is permitted on numeric values.

        * The `REGEXP' and `NOT REGEXP' extended regular expression
          operators.

        * `CONCAT()' or `CHAR()' with one argument or more than two
          arguments. (In MySQL Server, these functions can take a
          variable number of arguments.)

        * The `BIT_COUNT()', `CASE', `ELT()', `FROM_DAYS()', `FORMAT()',
          `IF()', `PASSWORD()', `ENCRYPT()', `MD5()', `ENCODE()',
          `DECODE()', `PERIOD_ADD()', `PERIOD_DIFF()', `TO_DAYS()', and
          `WEEKDAY()' functions.

        * Use of `TRIM()' to trim substrings. Standard SQL supports
          removal of single characters only.

        * The `GROUP BY' functions `STD()', `BIT_OR()', `BIT_AND()',
          `BIT_XOR()', and `GROUP_CONCAT()'. See *Note
          group-by-functions-and-modifiers::.


File: manual.info,  Node: differences-from-ansi,  Next: constraints,  Prev: extensions-to-ansi,  Up: compatibility

1.8.2 MySQL Differences from Standard SQL
-----------------------------------------

* Menu:

* ansi-diff-select-into-table::  SELECT INTO TABLE
* ansi-diff-update::             UPDATE
* ansi-diff-transactions::       Transactions and Atomic Operations
* ansi-diff-foreign-keys::       Foreign Keys
* ansi-diff-comments::           '--' as the Start of a Comment

We try to make MySQL Server follow the ANSI SQL standard and the ODBC
SQL standard, but MySQL Server performs operations differently in some
cases:

   * There are several differences between the MySQL and standard SQL
     privilege systems. For example, in MySQL, privileges for a table
     are not automatically revoked when you delete a table. You must
     explicitly issue a *Note `REVOKE': revoke. statement to revoke
     privileges for a table. For more information, see *Note revoke::.

   * The `CAST()' function does not support cast to *Note `REAL':
     floating-point-types. or *Note `BIGINT': integer-types. See *Note
     cast-functions::.


File: manual.info,  Node: ansi-diff-select-into-table,  Next: ansi-diff-update,  Prev: differences-from-ansi,  Up: differences-from-ansi

1.8.2.1 SELECT INTO TABLE
.........................

MySQL Server doesn't support the `SELECT ... INTO TABLE' Sybase SQL
extension. Instead, MySQL Server supports the *Note `INSERT INTO ...
SELECT': insert-select. standard SQL syntax, which is basically the
same thing. See *Note insert-select::. For example:


     INSERT INTO tbl_temp2 (fld_id)
         SELECT tbl_temp1.fld_order_id
         FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;

Alternatively, you can use *Note `SELECT ... INTO OUTFILE':
select-into. or *Note `CREATE TABLE ... SELECT': create-table.

You can use *Note `SELECT ... INTO': select. with user-defined
variables. The same syntax can also be used inside stored routines
using cursors and local variables. See *Note select-into::.


File: manual.info,  Node: ansi-diff-update,  Next: ansi-diff-transactions,  Prev: ansi-diff-select-into-table,  Up: differences-from-ansi

1.8.2.2 UPDATE
..............

If you access a column from the table to be updated in an expression,
*Note `UPDATE': update. uses the current value of the column. The
second assignment in the following statement sets `col2' to the current
(updated) `col1' value, not the original `col1' value. The result is
that `col1' and `col2' have the same value. This behavior differs from
standard SQL.


     UPDATE t1 SET col1 = col1 + 1, col2 = col1;


File: manual.info,  Node: ansi-diff-transactions,  Next: ansi-diff-foreign-keys,  Prev: ansi-diff-update,  Up: differences-from-ansi

1.8.2.3 Transactions and Atomic Operations
..........................................

MySQL Server (version 3.23-max and all versions 4.0 and above) supports
transactions with the `InnoDB' transactional storage engine. `InnoDB'
provides _full_ ACID compliance. See *Note storage-engines::. For
information about `InnoDB' differences from standard SQL with regard to
treatment of transaction errors, see *Note innodb-error-handling::.

The other nontransactional storage engines in MySQL Server (such as
`MyISAM') follow a different paradigm for data integrity called `atomic
operations.' In transactional terms, `MyISAM' tables effectively always
operate in `autocommit = 1' mode. Atomic operations often offer
comparable integrity with higher performance.

Because MySQL Server supports both paradigms, you can decide whether
your applications are best served by the speed of atomic operations or
the use of transactional features. This choice can be made on a
per-table basis.

As noted, the tradeoff for transactional versus nontransactional
storage engines lies mostly in performance.  Transactional tables have
significantly higher memory and disk space requirements, and more CPU
overhead. On the other hand, transactional storage engines such as
`InnoDB' also offer many significant features. MySQL Server's modular
design enables the concurrent use of different storage engines to suit
different requirements and deliver optimum performance in all
situations.

But how do you use the features of MySQL Server to maintain rigorous
integrity even with the nontransactional `MyISAM' tables, and how do
these features compare with the transactional storage engines?

   * If your applications are written in a way that is dependent on
     being able to call *Note `ROLLBACK': commit.  rather than *Note
     `COMMIT': commit. in critical situations, transactions are more
     convenient.  Transactions also ensure that unfinished updates or
     corrupting activities are not committed to the database; the
     server is given the opportunity to do an automatic rollback and
     your database is saved.

     If you use nontransactional tables, you must resolve potential
     problems at the application level by including simple checks
     before updates and by running simple scripts that check the
     databases for inconsistencies and automatically repair or warn if
     such an inconsistency occurs. You can normally fix tables
     perfectly with no data integrity loss just by using the MySQL log
     or even adding one extra log.

   * More often than not, critical transactional updates can be
     rewritten to be atomic. Generally speaking, all integrity problems
     that transactions solve can be done with *Note `LOCK TABLES':
     lock-tables. or atomic updates, ensuring that there are no
     automatic aborts from the server, which is a common problem with
     transactional database systems.

   * To be safe with MySQL Server, regardless of whether you use
     transactional tables, you only need to have backups and have
     binary logging turned on. When that is true, you can recover from
     any situation that you could with any other transactional database
     system. It is always good to have backups, regardless of which
     database system you use.

The transactional paradigm has its advantages and disadvantages. Many
users and application developers depend on the ease with which they can
code around problems where an abort appears to be necessary, or is
necessary. However, even if you are new to the atomic operations
paradigm, or more familiar with transactions, do consider the speed
benefit that nontransactional tables can offer on the order of three to
five times the speed of the fastest and most optimally tuned
transactional tables.

In situations where integrity is of highest importance, MySQL Server
offers transaction-level reliability and integrity even for
nontransactional tables. If you lock tables with *Note `LOCK TABLES':
lock-tables, all updates stall until integrity checks are made. If you
obtain a `READ LOCAL' lock (as opposed to a write lock) for a table
that enables concurrent inserts at the end of the table, reads are
permitted, as are inserts by other clients. The newly inserted records
are not be seen by the client that has the read lock until it releases
the lock. With *Note `INSERT DELAYED': insert-delayed, you can write
inserts that go into a local queue until the locks are released,
without having the client wait for the insert to complete. See *Note
concurrent-inserts::, and *Note insert-delayed::.

`Atomic,' in the sense that we mean it, is nothing magical. It only
means that you can be sure that while each specific update is running,
no other user can interfere with it, and there can never be an
automatic rollback (which can happen with transactional tables if you
are not very careful). MySQL Server also guarantees that there are no
dirty reads.

Following are some techniques for working with nontransactional tables:

   * Loops that need transactions normally can be coded with the help
     of *Note `LOCK TABLES': lock-tables, and you don't need cursors to
     update records on the fly.

   * To avoid using *Note `ROLLBACK': commit, you can employ the
     following strategy:

       1. Use *Note `LOCK TABLES': lock-tables. to lock all the tables
          you want to access.

       2. Test the conditions that must be true before performing the
          update.

       3. Update if the conditions are satisfied.

       4. Use *Note `UNLOCK TABLES': lock-tables. to release your locks.

     This is usually a much faster method than using transactions with
     possible rollbacks, although not always.  The only situation this
     solution doesn't handle is when someone kills the threads in the
     middle of an update. In that case, all locks are released but some
     of the updates may not have been executed.

   * You can also use functions to update records in a single
     operation. You can get a very efficient application by using the
     following techniques:

        * Modify columns relative to their current value.

        * Update only those columns that actually have changed.

     For example, when we are updating customer information, we update
     only the customer data that has changed and test only that none of
     the changed data, or data that depends on the changed data, has
     changed compared to the original row. The test for changed data is
     done with the `WHERE' clause in the *Note `UPDATE': update.
     statement. If the record wasn't updated, we give the client a
     message: `Some of the data you have changed has been changed by
     another user.' Then we show the old row versus the new row in a
     window so that the user can decide which version of the customer
     record to use.

     This gives us something that is similar to column locking but is
     actually even better because we only update some of the columns,
     using values that are relative to their current values. This means
     that typical *Note `UPDATE': update. statements look something
     like these:


          UPDATE tablename SET pay_back=pay_back+125;

          UPDATE customer
            SET
              customer_date='current_date',
              address='new address',
              phone='new phone',
              money_owed_to_us=money_owed_to_us-125
            WHERE
              customer_id=id AND address='old address' AND phone='old phone';

     This is very efficient and works even if another client has
     changed the values in the `pay_back' or `money_owed_to_us' columns.

   * When managing unique identifiers, you can avoid statements such as
     *Note `LOCK TABLES': lock-tables. or *Note `ROLLBACK': commit.  by
     using an `AUTO_INCREMENT' column and either the `LAST_INSERT_ID()'
     SQL function or the *Note `mysql_insert_id()': mysql-insert-id. C
     API function. See *Note information-functions::, and *Note
     mysql-insert-id::.

     For situations that require row-level locking, use *Note `InnoDB':
     innodb-storage-engine. tables. Otherwise, with *Note `MyISAM':
     myisam-storage-engine. tables, you can use a flag column in the
     table and do something like the following:


          UPDATE TBL_NAME SET row_flag=1 WHERE id=ID;

     MySQL returns `1' for the number of affected rows if the row was
     found and `row_flag' wasn't `1' in the original row. You can think
     of this as though MySQL Server changed the preceding statement to:


          UPDATE TBL_NAME SET row_flag=1 WHERE id=ID AND row_flag <> 1;


File: manual.info,  Node: ansi-diff-foreign-keys,  Next: ansi-diff-comments,  Prev: ansi-diff-transactions,  Up: differences-from-ansi

1.8.2.4 Foreign Keys
....................

The `InnoDB' storage engine supports checking of foreign key
constraints, including `CASCADE', `ON DELETE', and `ON UPDATE'. See
*Note innodb-foreign-key-constraints::.

For storage engines other than `InnoDB', MySQL Server parses the
`FOREIGN KEY' syntax in *Note `CREATE TABLE': create-table. statements,
but does not use or store it. This information is also present in *Note
`mysqldump': mysqldump, and can be retrieved using Connector/ODBC. You
can see which tables have foreign key constraints by checking the *Note
`INFORMATION_SCHEMA.TABLE_CONSTRAINTS': table-constraints-table.  table
in the `INFORMATION_SCHEMA' information database. In MySQL 5.1.16 and
later, you can obtain more detailed information about foreign keys from
the *Note `INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS':
referential-constraints-table.  table.

Foreign key enforcement offers several benefits to database developers:

   * Assuming proper design of the relationships, foreign key
     constraints make it more difficult for a programmer to introduce
     an inconsistency into the database.

   * Centralized checking of constraints by the database server makes
     it unnecessary to perform these checks on the application side.
     This eliminates the possibility that different applications may
     not all check the constraints in the same way.

   * Using cascading updates and deletes can simplify the application
     code.

   * Properly designed foreign key rules aid in documenting
     relationships between tables.

Foreign keys in SQL are used to check and enforce referential
integrity, not to join tables. If you want to get results from multiple
tables from a *Note `SELECT': select.  statement, you do this by
performing a join between them:


     SELECT * FROM t1 INNER JOIN t2 ON t1.id = t2.id;

See *Note join::, and *Note example-foreign-keys::.

The `FOREIGN KEY' syntax without `ON DELETE ...' is often used by ODBC
applications to produce automatic `WHERE' clauses.

*Deviations from SQL Standards*

MySQL's implementation of foreign keys differs from the SQL standard in
the following key respects:

   * If there are several rows in the parent table that have the same
     referenced key value, *Note `InnoDB': innodb-storage-engine. acts
     in foreign key checks as if the other parent rows with the same
     key value do not exist. For example, if you have defined a
     `RESTRICT' type constraint, and there is a child row with several
     parent rows, `InnoDB' does not permit the deletion of any of those
     parent rows.

     `InnoDB' performs cascading operations through a depth-first
     algorithm, based on records in the indexes corresponding to the
     foreign key constraints.

   * A `FOREIGN KEY' constraint that references a non-`UNIQUE' key is
     not standard SQL but rather an *Note `InnoDB':
     innodb-storage-engine. extension.

   * If `ON UPDATE CASCADE' or `ON UPDATE SET NULL' recurses to update
     the _same table_ it has previously updated during the same
     cascade, it acts like `RESTRICT'. This means that you cannot use
     self-referential `ON UPDATE CASCADE' or `ON UPDATE SET NULL'
     operations. This is to prevent infinite loops resulting from
     cascaded updates. A self-referential `ON DELETE SET NULL', on the
     other hand, is possible, as is a self-referential `ON DELETE
     CASCADE'.  Cascading operations may not be nested more than 15
     levels deep.

   * In an SQL statement that inserts, deletes, or updates many rows,
     foreign key constraints (like unique constraints) are checked
     row-by-row. When performing foreign key checks, *Note `InnoDB':
     innodb-storage-engine. sets shared row-level locks on child or
     parent records that it must examine. MySQL checks foreign key
     constraints immediately; the check is not deferred to transaction
     commit. According to the SQL standard, the default behavior should
     be deferred checking. That is, constraints are only checked after
     the _entire SQL statement_ has been processed. This means that it
     is not possible to delete a row that refers to itself using a
     foreign key.

For information how *Note `InnoDB': innodb-storage-engine.  foreign
keys differ from the SQL standard, see *Note
innodb-foreign-key-constraints::.


File: manual.info,  Node: ansi-diff-comments,  Prev: ansi-diff-foreign-keys,  Up: differences-from-ansi

1.8.2.5 '-' as the Start of a Comment
.....................................

Standard SQL uses the C syntax `/* this is a comment */' for comments,
and MySQL Server supports this syntax as well. MySQL also support
extensions to this syntax that enable MySQL-specific SQL to be embedded
in the comment, as described in *Note comments::.

Standard SQL uses ``--'' as a start-comment sequence. MySQL Server uses
``#'' as the start comment character. MySQL Server 3.23.3 and up also
supports a variant of the ``--'' comment style.  That is, the ``--''
start-comment sequence must be followed by a space (or by a control
character such as a newline). The space is required to prevent problems
with automatically generated SQL queries that use constructs such as
the following, where we automatically insert the value of the payment
for `payment':


     UPDATE account SET credit=credit-payment

Consider about what happens if `payment' has a negative value such as
`-1':


     UPDATE account SET credit=credit--1

`credit--1' is a valid expression in SQL, but ``--'' is interpreted as
the start of a comment, part of the expression is discarded. The result
is a statement that has a completely different meaning than intended:


     UPDATE account SET credit=credit

The statement produces no change in value at all. This illustrates that
permitting comments to start with ``--'' can have serious consequences.

Using our implementation requires a space following the ``--'' for it
to be recognized as a start-comment sequence in MySQL Server 3.23.3 and
newer.  Therefore, `credit--1' is safe to use.

Another safe feature is that the *Note `mysql': mysql.  command-line
client ignores lines that start with ``--''.

The following information is relevant only if you are running a MySQL
version earlier than 3.23.3:

If you have an SQL script in a text file that contains ``--'' comments,
you should use the *Note `replace': replace-utility. utility as follows
to convert the comments to use ``#'' characters before executing the
script:


     shell> replace " --" " #" < text-file-with-funny-comments.sql \
              | mysql DB_NAME

That is safer than executing the script in the usual way:


     shell> mysql DB_NAME < text-file-with-funny-comments.sql

You can also edit the script file `in place' to change the ``--''
comments to ``#'' comments:


     shell> replace " --" " #" -- text-file-with-funny-comments.sql

Change them back with this command:


     shell> replace " #" " --" -- text-file-with-funny-comments.sql

See *Note replace-utility::.


File: manual.info,  Node: constraints,  Prev: differences-from-ansi,  Up: compatibility

1.8.3 How MySQL Deals with Constraints
--------------------------------------

* Menu:

* constraint-primary-key::       PRIMARY KEY and UNIQUE Index Constraints
* constraint-foreign-key::       FOREIGN KEY Constraints
* constraint-invalid-data::      Constraints on Invalid Data
* constraint-enum::              ENUM and SET Constraints

MySQL enables you to work both with transactional tables that permit
rollback and with nontransactional tables that do not.  Because of
this, constraint handling is a bit different in MySQL than in other
DBMSs. We must handle the case when you have inserted or updated a lot
of rows in a nontransactional table for which changes cannot be rolled
back when an error occurs.

The basic philosophy is that MySQL Server tries to produce an error for
anything that it can detect while parsing a statement to be executed,
and tries to recover from any errors that occur while executing the
statement. We do this in most cases, but not yet for all.

The options MySQL has when an error occurs are to stop the statement in
the middle or to recover as well as possible from the problem and
continue. By default, the server follows the latter course. This means,
for example, that the server may coerce invalid values to the closest
valid values.

Several SQL mode options are available to provide greater control over
handling of bad data values and whether to continue statement execution
or abort when errors occur. Using these options, you can configure
MySQL Server to act in a more traditional fashion that is like other
DBMSs that reject improper input. The SQL mode can be set globally at
server startup to affect all clients. Individual clients can set the
SQL mode at runtime, which enables each client to select the behavior
most appropriate for its requirements. See *Note sql-mode::.

The following sections describe how MySQL Server handles different
types of constraints.


File: manual.info,  Node: constraint-primary-key,  Next: constraint-foreign-key,  Prev: constraints,  Up: constraints

1.8.3.1 PRIMARY KEY and UNIQUE Index Constraints
................................................

Normally, errors occurs for data-change statements (such as *Note
`INSERT': insert. or *Note `UPDATE': update.) that would violate
primary-key, unique-key, or foreign-key constraints. If you are using a
transactional storage engine such as `InnoDB', MySQL automatically
rolls back the statement. If you are using a nontransactional storage
engine, MySQL stops processing the statement at the row for which the
error occurred and leaves any remaining rows unprocessed.

MySQL supports an `IGNORE' keyword for *Note `INSERT': insert, *Note
`UPDATE': update, and so forth. If you use it, MySQL ignores
primary-key or unique-key violations and continues processing with the
next row. See the section for the statement that you are using (*Note
insert::, *Note update::, and so forth).

You can get information about the number of rows actually inserted or
updated with the *Note `mysql_info()': mysql-info. C API function.  You
can also use the *Note `SHOW WARNINGS': show-warnings. statement. See
*Note mysql-info::, and *Note show-warnings::.

Currently, only `InnoDB' tables support foreign keys. See *Note
innodb-foreign-key-constraints::.


File: manual.info,  Node: constraint-foreign-key,  Next: constraint-invalid-data,  Prev: constraint-primary-key,  Up: constraints

1.8.3.2 FOREIGN KEY Constraints
...............................

Foreign keys let you cross-reference related data across tables, and
foreign key constraints
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_foreign_key_constraint)
help keep this spread-out data consistent.

MySQL supports `ON UPDATE' and `ON DELETE' foreign key references in
*Note `CREATE TABLE': create-table. and *Note `ALTER TABLE':
alter-table. statements. The available referential actions are
`RESTRICT' (the default), `CASCADE', `SET NULL', and `NO ACTION'.

`SET DEFAULT' is also supported by the MySQL Server but is currently
rejected as invalid by *Note `InnoDB': innodb-storage-engine. Since
MySQL does not support deferred constraint checking, `NO ACTION' is
treated as `RESTRICT'.  For the exact syntax supported by MySQL for
foreign keys, see *Note create-table-foreign-keys::.

`MATCH FULL', `MATCH PARTIAL', and `MATCH SIMPLE' are allowed, but
their use should be avoided, as they cause the MySQL Server to ignore
any `ON DELETE' or `ON UPDATE' clause used in the same statement.
`MATCH' options do not have any other effect in MySQL, which in effect
enforces `MATCH SIMPLE' semantics full-time.

MySQL requires that foreign key columns be indexed; if you create a
table with a foreign key constraint but no index on a given column, an
index is created.

You can obtain information about foreign keys from the *Note
`INFORMATION_SCHEMA.KEY_COLUMN_USAGE': key-column-usage-table.  table.
An example of a query against this table is shown here:


     mysql> SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, CONSTRAINT_NAME
          > FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
          > WHERE REFERENCED_TABLE_SCHEMA IS NOT NULL;
     +--------------+---------------+-------------+-----------------+
     | TABLE_SCHEMA | TABLE_NAME    | COLUMN_NAME | CONSTRAINT_NAME |
     +--------------+---------------+-------------+-----------------+
     | fk1          | myuser        | myuser_id   | f               |
     | fk1          | product_order | customer_id | f2              |
     | fk1          | product_order | product_id  | f1              |
     +--------------+---------------+-------------+-----------------+
     3 rows in set (0.01 sec)

Information about foreign keys on `InnoDB' tables can also be found in
the `INNODB_SYS_FOREIGN'
(http://dev.mysql.com/doc/refman/5.6/en/innodb-sys-foreign-table.html)
and `INNODB_SYS_FOREIGN_COLS'
(http://dev.mysql.com/doc/refman/5.6/en/innodb-sys-foreign-cols-table.html)
tables, in the `INFORMATION_SCHEMA' database.

Currently, only `InnoDB' tables support foreign keys. See *Note
innodb-foreign-key-constraints::, for information specific to foreign
key support in `InnoDB'.


File: manual.info,  Node: constraint-invalid-data,  Next: constraint-enum,  Prev: constraint-foreign-key,  Up: constraints

1.8.3.3 Constraints on Invalid Data
...................................

By default, MySQL is forgiving of invalid or improper data values and
coerces them to valid values for data entry.  However, you can enable
strict SQL mode to select more traditional treatment of bad values such
that the server rejects them and aborts the statement in which they
occur. See *Note sql-mode::.

This section describes the default (forgiving) behavior of MySQL, as
well as the strict SQL mode and how it differs.

If you are not using strict mode, then whenever you insert an
`incorrect' value into a column, such as a `NULL' into a `NOT NULL'
column or a too-large numeric value into a numeric column, MySQL sets
the column to the `best possible value' instead of producing an error:
The following rules describe in more detail how this works:

   * If you try to store an out of range value into a numeric column,
     MySQL Server instead stores zero, the smallest possible value, or
     the largest possible value, whichever is closest to the invalid
     value.

   * For strings, MySQL stores either the empty string or as much of
     the string as can be stored in the column.

   * If you try to store a string that does not start with a number
     into a numeric column, MySQL Server stores 0.

   * Invalid values for *Note `ENUM': enum. and *Note `SET': set.
     columns are handled as described in *Note constraint-enum::.

   * MySQL permits you to store certain incorrect date values into
     *Note `DATE': datetime. and *Note `DATETIME': datetime. columns
     (such as `'2000-02-31'' or `'2000-02-00''). In this case, when an
     application that has not enabled strict SQL mode, it up to the
     application to validate the dates before storing them.  If MySQL
     can store a date value and retrieve exactly the same value, MySQL
     stores it as given. If the date is totally wrong (outside the
     server's ability to store it), the special `zero' date value
     `'0000-00-00'' is stored in the column instead.

   * If you try to store `NULL' into a column that doesn't take `NULL'
     values, an error occurs for single-row *Note `INSERT': insert.
     statements. For multiple-row *Note `INSERT': insert.  statements
     or for *Note `INSERT INTO ... SELECT': insert-select. statements,
     MySQL Server stores the implicit default value for the column data
     type. In general, this is `0' for numeric types, the empty string
     (`''') for string types, and the `zero' value for date and time
     types.  Implicit default values are discussed in *Note
     data-type-defaults::.

   * If an *Note `INSERT': insert. statement specifies no value for a
     column, MySQL inserts its default value if the column definition
     includes an explicit `DEFAULT' clause. If the definition has no
     such `DEFAULT' clause, MySQL inserts the implicit default value
     for the column data type.

The reason for using the preceding rules in nonstrict mode is that we
can't check these conditions until the statement has begun executing.
We can't just roll back if we encounter a problem after updating a few
rows, because the storage engine may not support rollback. The option
of terminating the statement is not that good; in this case, the update
would be `half done,' which is probably the worst possible scenario. In
this case, it is better to `do the best you can' and then continue as
if nothing happened.

In MySQL 5.0.2 and up, you can select stricter treatment of input
values by using the `STRICT_TRANS_TABLES' or `STRICT_ALL_TABLES' SQL
modes:


     SET sql_mode = 'STRICT_TRANS_TABLES';
     SET sql_mode = 'STRICT_ALL_TABLES';

`STRICT_TRANS_TABLES' enables strict mode for transactional storage
engines, and also to some extent for nontransactional engines. It works
like this:

   * For transactional storage engines, bad data values occurring
     anywhere in a statement cause the statement to abort and roll back.

   * For nontransactional storage engines, a statement aborts if the
     error occurs in the first row to be inserted or updated. (When the
     error occurs in the first row, the statement can be aborted to
     leave the table unchanged, just as for a transactional table.)
     Errors in rows after the first do not abort the statement, because
     the table has already been changed by the first row. Instead, bad
     data values are adjusted and result in warnings rather than
     errors. In other words, with `STRICT_TRANS_TABLES', a wrong value
     causes MySQL to roll back all updates done so far, if that can be
     done without changing the table. But once the table has been
     changed, further errors result in adjustments and warnings.

For even stricter checking, enable `STRICT_ALL_TABLES'. This is the
same as `STRICT_TRANS_TABLES' except that for nontransactional storage
engines, errors abort the statement even for bad data in rows following
the first row.  This means that if an error occurs partway through a
multiple-row insert or update for a nontransactional table, a partial
update results. Earlier rows are inserted or updated, but those from
the point of the error on are not. To avoid this for nontransactional
tables, either use single-row statements or else use
`STRICT_TRANS_TABLES' if conversion warnings rather than errors are
acceptable. To avoid problems in the first place, do not use MySQL to
check column content. It is safest (and often faster) to let the
application ensure that it passes only valid values to the database.

With either of the strict mode options, you can cause errors to be
treated as warnings by using *Note `INSERT IGNORE': insert. or `UPDATE
IGNORE' rather than *Note `INSERT': insert. or *Note `UPDATE': update.
without `IGNORE'.


File: manual.info,  Node: constraint-enum,  Prev: constraint-invalid-data,  Up: constraints

1.8.3.4 ENUM and SET Constraints
................................

*Note `ENUM': enum. and *Note `SET': set. columns provide an efficient
way to define columns that can contain only a given set of values. See
*Note enum::, and *Note set::. However, before MySQL 5.0.2, *Note
`ENUM': enum. and *Note `SET': set. columns do not provide true
constraints on entry of invalid data:

   * *Note `ENUM': enum. columns always have a default value. If you
     specify no default value, then it is `NULL' for columns that can
     have `NULL', otherwise it is the first enumeration value in the
     column definition.

   * If you insert an incorrect value into an *Note `ENUM': enum.
     column or if you force a value into an *Note `ENUM': enum. column
     with `IGNORE', it is set to the reserved enumeration value of `0',
     which is displayed as an empty string in string context.

   * If you insert an incorrect value into a *Note `SET': set. column,
     the incorrect value is ignored. For example, if the column can
     contain the values `'a'', `'b'', and `'c'', an attempt to assign
     `'a,x,b,y'' results in a value of `'a,b''.

As of MySQL 5.0.2, you can configure the server to use strict SQL mode.
See *Note sql-mode::. With strict mode enabled, the definition of a
*Note `ENUM': enum. or *Note `SET': set. column does act as a
constraint on values entered into the column. An error occurs for
values that do not satisfy these conditions:

   * An *Note `ENUM': enum. value must be one of those listed in the
     column definition, or the internal numeric equivalent thereof. The
     value cannot be the error value (that is, 0 or the empty string).
     For a column defined as *Note `ENUM('a','b','c')': enum, values
     such as `''', `'d'', or `'ax'' are invalid and are rejected.

   * A *Note `SET': set. value must be the empty string or a value
     consisting only of the values listed in the column definition
     separated by commas. For a column defined as *Note
     `SET('a','b','c')': set, values such as `'d'' or `'a,b,c,d'' are
     invalid and are rejected.

Errors for invalid values can be suppressed in strict mode if you use
*Note `INSERT IGNORE': insert. or `UPDATE IGNORE'. In this case, a
warning is generated rather than an error. For *Note `ENUM': enum, the
value is inserted as the error member (`0'). For *Note `SET': set, the
value is inserted as given except that any invalid substrings are
deleted. For example, `'a,x,b,y'' results in a value of `'a,b''.


File: manual.info,  Node: credits,  Prev: compatibility,  Up: introduction

1.9 Credits
===========

* Menu:

* contributors::                 Contributors to MySQL
* documenters-translators::      Documenters and translators
* packages::                     Packages that support MySQL
* tools-used-to-create-mysql::   Tools that were used to create MySQL
* supporters::                   Supporters of MySQL

The following sections list developers, contributors, and supporters
that have helped to make MySQL what it is today.


File: manual.info,  Node: contributors,  Next: documenters-translators,  Prev: credits,  Up: credits

1.9.1 Contributors to MySQL
---------------------------

Although Oracle Corporation and/or its affiliates own all copyrights in
the `MySQL server' and the `MySQL manual', we wish to recognize those
who have made contributions of one kind or another to the `MySQL
distribution'. Contributors are listed here, in somewhat random order:

   * Gianmassimo Vigazzola <qwerg@mbox.vol.it> or <qwerg@tin.it>

     The initial port to Win32/NT.

   * Per Eric Olsson

     For constructive criticism and real testing of the dynamic record
     format.

   * Irena Pancirov <irena@mail.yacc.it>

     Win32 port with Borland compiler.  `mysqlshutdown.exe' and
     `mysqlwatch.exe'.

   * David J. Hughes

     For the effort to make a shareware SQL database. At TcX, the
     predecessor of MySQL AB, we started with `mSQL', but found that it
     couldn't satisfy our purposes so instead we wrote an SQL interface
     to our application builder Unireg. *Note `mysqladmin': mysqladmin.
     and *Note `mysql': mysql. client are programs that were largely
     influenced by their `mSQL' counterparts. We have put a lot of
     effort into making the MySQL syntax a superset of `mSQL'. Many of
     the API's ideas are borrowed from `mSQL' to make it easy to port
     free `mSQL' programs to the MySQL API.  The MySQL software doesn't
     contain any code from `mSQL'. Two files in the distribution
     (`client/insert_test.c' and `client/select_test.c') are based on
     the corresponding (noncopyrighted) files in the `mSQL'
     distribution, but are modified as examples showing the changes
     necessary to convert code from `mSQL' to MySQL Server.  (`mSQL' is
     copyrighted David J. Hughes.)

   * Patrick Lynch

     For helping us acquire http://www.mysql.com/.

   * Fred Lindberg

     For setting up qmail to handle the MySQL mailing list and for the
     incredible help we got in managing the MySQL mailing lists.

   * Igor Romanenko <igor@frog.kiev.ua>

     *Note `mysqldump': mysqldump. (previously `msqldump', but ported
     and enhanced by Monty).

   * Yuri Dario

     For keeping up and extending the MySQL OS/2 port.

   * Tim Bunce

     Author of *Note `mysqlhotcopy': mysqlhotcopy.

   * Zarko Mocnik <zarko.mocnik@dem.si>

     Sorting for Slovenian language.

   * "TAMITO" <tommy@valley.ne.jp>

     The `_MB' character set macros and the ujis and sjis character
     sets.

   * Joshua Chamas <joshua@chamas.com>

     Base for concurrent insert, extended date syntax, debugging on NT,
     and answering on the MySQL mailing list.

   * Yves Carlier <Yves.Carlier@rug.ac.be>

     *Note `mysqlaccess': mysqlaccess, a program to show the access
     rights for a user.

   * Rhys Jones <rhys@wales.com> (And GWE Technologies Limited)

     For one of the early JDBC drivers.

   * Dr Xiaokun Kelvin ZHU <X.Zhu@brad.ac.uk>

     Further development of one of the early JDBC drivers and other
     MySQL-related Java tools.

   * James Cooper <pixel@organic.com>

     For setting up a searchable mailing list archive at his site.

   * Rick Mehalick <Rick_Mehalick@i-o.com>

     For `xmysql', a graphical X client for MySQL Server.

   * Doug Sisk <sisk@wix.com>

     For providing RPM packages of MySQL for Red Hat Linux.

   * Diemand Alexander V. <axeld@vial.ethz.ch>

     For providing RPM packages of MySQL for Red Hat Linux-Alpha.

   * Antoni Pamies Olive <toni@readysoft.es>

     For providing RPM versions of a lot of MySQL clients for Intel and
     SPARC.

   * Jay Bloodworth <jay@pathways.sde.state.sc.us>

     For providing RPM versions for MySQL 3.21.

   * David Sacerdote <davids@secnet.com>

     Ideas for secure checking of DNS host names.

   * Wei-Jou Chen <jou@nematic.ieo.nctu.edu.tw>

     Some support for Chinese(BIG5) characters.

   * Wei He <hewei@mail.ied.ac.cn>

     A lot of functionality for the Chinese(GBK) character set.

   * Jan Pazdziora <adelton@fi.muni.cz>

     Czech sorting order.

   * Zeev Suraski <bourbon@netvision.net.il>

     `FROM_UNIXTIME()' time formatting, `ENCRYPT()' functions, and
     `bison' advisor. Active mailing list member.

   * Luuk de Boer <luuk@wxs.nl>

     Ported (and extended) the benchmark suite to `DBI'/`DBD'. Have
     been of great help with `crash-me' and running benchmarks. Some
     new date functions. The *Note `mysql_setpermission':
     mysql-setpermission. script.

   * Alexis Mikhailov <root@medinf.chuvashia.su>

     User-defined functions (UDFs); *Note `CREATE FUNCTION':
     create-function. and *Note `DROP FUNCTION': drop-function.

   * Andreas F. Bobak <bobak@relog.ch>

     The `AGGREGATE' extension to user-defined functions.

   * Ross Wakelin <R.Wakelin@march.co.uk>

     Help to set up InstallShield for MySQL-Win32.

   * Jethro Wright III <jetman@li.net>

     The `libmysql.dll' library.

   * James Pereria <jpereira@iafrica.com>

     Mysqlmanager, a Win32 GUI tool for administering MySQL Servers.

   * Curt Sampson <cjs@portal.ca>

     Porting of MIT-pthreads to NetBSD/Alpha and NetBSD 1.3/i386.

   * Martin Ramsch <m.ramsch@computer.org>

     Examples in the MySQL Tutorial.

   * Steve Harvey

     For making *Note `mysqlaccess': mysqlaccess. more secure.

   * Konark IA-64 Centre of Persistent Systems Private Limited

     Help with the Win64 port of the MySQL server.

   * Albert Chin-A-Young.

     Configure updates for Tru64, large file support and better TCP
     wrappers support.

   * John Birrell

     Emulation of `pthread_mutex()' for OS/2.

   * Benjamin Pflugmann

     Extended `MERGE' tables to handle `INSERTS'. Active member on the
     MySQL mailing lists.

   * Jocelyn Fournier

     Excellent spotting and reporting innumerable bugs (especially in
     the MySQL 4.1 subquery code).

   * Marc Liyanage

     Maintaining the Mac OS X packages and providing invaluable
     feedback on how to create Mac OS X packages.

   * Robert Rutherford

     Providing invaluable information and feedback about the QNX port.

   * Previous developers of NDB Cluster

     Lots of people were involved in various ways summer students,
     master thesis students, employees. In total more than 100 people
     so too many to mention here. Notable name is Ataullah Dabaghi who
     up until 1999 contributed around a third of the code base. A
     special thanks also to developers of the AXE system which provided
     much of the architectural foundations for NDB Cluster with blocks,
     signals and crash tracing functionality. Also credit should be
     given to those who believed in the ideas enough to allocate of
     their budgets for its development from 1992 to present time.

   * Google Inc.

     We wish to recognize Google Inc. for contributions to the MySQL
     distribution: Mark Callaghan's SMP Performance patches and other
     patches.

Other contributors, bugfinders, and testers: James H. Thompson,
Maurizio Menghini, Wojciech Tryc, Luca Berra, Zarko Mocnik, Wim Bonis,
Elmar Haneke, <jehamby@lightside>, <psmith@BayNetworks.com>,
<duane@connect.com.au>, Ted Deppner <ted@psyber.com>, Mike Simons,
Jaakko Hyvatti.

And lots of bug report/patches from the folks on the mailing list.

A big tribute goes to those that help us answer questions on the MySQL
mailing lists:

   * Daniel Koch <dkoch@amcity.com>

     Irix setup.

   * Luuk de Boer <luuk@wxs.nl>

     Benchmark questions.

   * Tim Sailer <tps@users.buoy.com>

     `DBD::mysql' questions.

   * Boyd Lynn Gerber <gerberb@zenez.com>

     SCO-related questions.

   * Richard Mehalick <RM186061@shellus.com>

     `xmysql'-related questions and basic installation questions.

   * Zeev Suraski <bourbon@netvision.net.il>

     Apache module configuration questions (log & auth), PHP-related
     questions, SQL syntax-related questions and other general
     questions.

   * Francesc Guasch <frankie@citel.upc.es>

     General questions.

   * Jonathan J Smith <jsmith@wtp.net>

     Questions pertaining to OS-specifics with Linux, SQL syntax, and
     other things that might need some work.

   * David Sklar <sklar@student.net>

     Using MySQL from PHP and Perl.

   * Alistair MacDonald <A.MacDonald@uel.ac.uk>

     Is flexible and can handle Linux and perhaps HP-UX.

   * John Lyon <jlyon@imag.net>

     Questions about installing MySQL on Linux systems, using either
     `.rpm' files or compiling from source.

   * Lorvid Ltd. <lorvid@WOLFENET.com>

     Simple billing/license/support/copyright issues.

   * Patrick Sherrill <patrick@coconet.com>

     ODBC and VisualC++ interface questions.

   * Randy Harmon <rjharmon@uptimecomputers.com>

     `DBD', Linux, some SQL syntax questions.


File: manual.info,  Node: documenters-translators,  Next: packages,  Prev: contributors,  Up: credits

1.9.2 Documenters and translators
---------------------------------

The following people have helped us with writing the MySQL
documentation and translating the documentation or error messages in
MySQL.

   * Paul DuBois

     Ongoing help with making this manual correct and understandable.
     That includes rewriting Monty's and David's attempts at English
     into English as other people know it.

   * Kim Aldale

     Helped to rewrite Monty's and David's early attempts at English
     into English.

   * Michael J. Miller Jr.  <mke@terrapin.turbolift.com>

     For the first MySQL manual. And a lot of spelling/language fixes
     for the FAQ (that turned into the MySQL manual a long time ago).

   * Yan Cailin

     First translator of the MySQL Reference Manual into simplified
     Chinese in early 2000 on which the Big5 and HK coded versions were
     based.

   * Jay Flaherty <fty@mediapulse.com>

     Big parts of the Perl `DBI'/`DBD' section in the manual.

   * Paul Southworth <pauls@etext.org>, Ray Loyzaga <yar@cs.su.oz.au>

     Proof-reading of the Reference Manual.

   * Therrien Gilbert <gilbert@ican.net>, Jean-Marc Pouyot
     <jmp@scalaire.fr>

     French error messages.

   * Petr Snajdr, <snajdr@pvt.net>

     Czech error messages.

   * Jaroslaw Lewandowski <jotel@itnet.com.pl>

     Polish error messages.

   * Miguel Angel Fernandez Roiz

     Spanish error messages.

   * Roy-Magne Mo <rmo@www.hivolda.no>

     Norwegian error messages and testing of MySQL 3.21.xx.

   * Timur I. Bakeyev <root@timur.tatarstan.ru>

     Russian error messages.

   * <brenno@dewinter.com> & Filippo Grassilli <phil@hyppo.com>

     Italian error messages.

   * Dirk Munzinger <dirk@trinity.saar.de>

     German error messages.

   * Billik Stefan <billik@sun.uniag.sk>

     Slovak error messages.

   * Stefan Saroiu <tzoompy@cs.washington.edu>

     Romanian error messages.

   * Peter Feher

     Hungarian error messages.

   * Roberto M. Serqueira

     Portuguese error messages.

   * Carsten H. Pedersen

     Danish error messages.

   * Arjen Lentz

     Dutch error messages, completing earlier partial translation (also
     work on consistency and spelling).


File: manual.info,  Node: packages,  Next: tools-used-to-create-mysql,  Prev: documenters-translators,  Up: credits

1.9.3 Packages that support MySQL
---------------------------------

The following is a list of creators/maintainers of some of the most
important API/packages/applications that a lot of people use with MySQL.

We cannot list every possible package here because the list would then
be way to hard to maintain. For other packages, please refer to the
software portal at `http://solutions.mysql.com/software/'.

   * Tim Bunce, Alligator Descartes

     For the `DBD' (Perl) interface.

   * Andreas Koenig <a.koenig@mind.de>

     For the Perl interface for MySQL Server.

   * Jochen Wiedmann <wiedmann@neckar-alb.de>

     For maintaining the Perl `DBD::mysql' module.

   * Eugene Chan <eugene@acenet.com.sg>

     For porting PHP for MySQL Server.

   * Georg Richter

     MySQL 4.1 testing and bug hunting. New PHP 5.0 `mysqli' extension
     (API) for use with MySQL 4.1 and up.

   * Giovanni Maruzzelli <maruzz@matrice.it>

     For porting iODBC (Unix ODBC).

   * Xavier Leroy <Xavier.Leroy@inria.fr>

     The author of LinuxThreads (used by the MySQL Server on Linux).


File: manual.info,  Node: tools-used-to-create-mysql,  Next: supporters,  Prev: packages,  Up: credits

1.9.4 Tools that were used to create MySQL
------------------------------------------

The following is a list of some of the tools we have used to create
MySQL. We use this to express our thanks to those that has created them
as without these we could not have made MySQL what it is today.

   * Free Software Foundation

     From whom we got an excellent compiler (`gcc'), an excellent
     debugger (`gdb' and the `libc' library (from which we have borrowed
     `strto.c' to get some code working in Linux).

   * Free Software Foundation & The XEmacs development team

     For a really great editor/environment.

   * Julian Seward

     Author of `valgrind', an excellent memory checker tool that has
     helped us find a lot of otherwise hard to find bugs in MySQL.

   * Dorothea Lu"tkehaus and Andreas Zeller

     For `DDD' (The Data Display Debugger) which is an excellent
     graphical front end to `gdb').


File: manual.info,  Node: supporters,  Prev: tools-used-to-create-mysql,  Up: credits

1.9.5 Supporters of MySQL
-------------------------

Although Oracle Corporation and/or its affiliates own all copyrights in
the `MySQL server' and the `MySQL manual', we wish to recognize the
following companies, which helped us finance the development of the
`MySQL server', such as by paying us for developing a new feature or
giving us hardware for development of the `MySQL server'.

   * VA Linux / Andover.net

     Funded replication.

   * NuSphere

     Editing of the MySQL manual.

   * Stork Design studio

     The MySQL Web site in use between 1998-2000.

   * Intel

     Contributed to development on Windows and Linux platforms.

   * Compaq

     Contributed to Development on Linux/Alpha.

   * SWSoft

     Development on the embedded *Note `mysqld': mysqld. version.

   * FutureQuest

     The `--skip-show-database' option.


File: manual.info,  Node: installing,  Next: tutorial,  Prev: introduction,  Up: Top

2 Installing and Upgrading MySQL
********************************

* Menu:

* general-installation-issues::  General Installation Guidance
* binary-installation::          Installing MySQL on Unix/Linux Using Generic Binaries
* windows-installation::         Installing MySQL on Microsoft Windows
* macosx-installation::          Installing MySQL on Mac OS X
* linux-installation::           Installing MySQL on Linux
* solaris-installation::         Installing MySQL on Solaris and OpenSolaris
* aix-installation::             Installing MySQL on IBM AIX
* hpux-installation::            Installing MySQL on HP-UX
* freebsd-installation::         Installing MySQL on FreeBSD
* i5os-installation::            Installing MySQL on i5/OS
* source-installation::          Installing MySQL from Source
* postinstallation::             Postinstallation Setup and Testing
* upgrading-downgrading::        Upgrading or Downgrading MySQL
* environment-variables::        Environment Variables
* perl-support::                 Perl Installation Notes

End of Product Lifecycle

Active development for MySQL Database Server version 5.1 has ended.
Oracle offers various support offerings which may be of interest. For
details and more information, see the MySQL section of the Lifetime
Support Policy for Oracle Technology Products
(`http://www.oracle.com/us/support/lifetime-support/index.html').
Please consider upgrading to a recent version.

This chapter describes how to obtain and install MySQL. A summary of
the procedure follows and later sections provide the details. If you
plan to upgrade an existing version of MySQL to a newer version rather
than install MySQL for the first time, see *Note upgrading::, for
information about upgrade procedures and about issues that you should
consider before upgrading.

If you are interested in migrating to MySQL from another database
system, you may wish to read *Note faqs-migration::, which contains
answers to some common questions concerning migration issues.

If you are migrating from MySQL Enterprise Edition to MySQL Community
Server, see *Note downgrading-from-enterprise::.

Installation of MySQL generally follows the steps outlined here:

  1. *Determine whether MySQL runs and is supported on your platform.*

     Please note that not all platforms are equally suitable for
     running MySQL, and that not all platforms on which MySQL is known
     to run are officially supported by Oracle Corporation:

  2. *Choose which distribution to install.*

     Several versions of MySQL are available, and most are available in
     several distribution formats. You can choose from pre-packaged
     distributions containing binary (precompiled) programs or source
     code. When in doubt, use a binary distribution. We also provide
     public access to our current source tree for those who want to see
     our most recent developments and help us test new code. To
     determine which version and type of distribution you should use,
     see *Note which-version::.

  3. *Download the distribution that you want to install.*

     For instructions, see *Note getting-mysql::. To verify the
     integrity of the distribution, use the instructions in *Note
     verifying-package-integrity::.

  4. *Install the distribution.*

     To install MySQL from a binary distribution, use the instructions
     in *Note binary-installation::.

     To install MySQL from a source distribution or from the current
     development source tree, use the instructions in *Note
     source-installation::.

  5. *Perform any necessary postinstallation setup.*

     After installing MySQL, see *Note postinstallation:: for
     information about making sure the MySQL server is working
     properly. Also refer to the information provided in *Note
     default-privileges::. This section describes how to secure the
     initial MySQL user accounts, _which have no passwords_ until you
     assign passwords. The section applies whether you install MySQL
     using a binary or source distribution.

  6. If you want to run the MySQL benchmark scripts, Perl support for
     MySQL must be available. See *Note perl-support::.

Instructions for installing MySQL on different platforms and
environments is available on a platform by platform basis:

   * *Unix, Linux, FreeBSD*

     For instructions on installing MySQL on most Linux and Unix
     platforms using a generic binary (for example, a `.tar.gz'
     package), see *Note binary-installation::.

     For information on building MySQL entirely from the source code
     distributions or the source code repositories, see *Note
     source-installation::

     For specific platform help on installation, configuration, and
     building from source see the corresponding platform section:

        * Linux, including notes on distribution specific methods, see
          *Note linux-installation::.

        * Solaris and OpenSolaris, including PKG and IPS formats, see
          *Note solaris-installation::.

        * IBM AIX, see *Note solaris-installation::.

        * Hewlett-Packard HP-UX, including the DEPOT package format,
          see *Note hpux-installation::.

        * FreeBSD, see *Note freebsd-installation::.

   * *Microsoft Windows*

     For instructions on installing MySQL on Microsoft Windows, using
     either a Zipped binary or an MSI package, see *Note
     windows-installation::.

     For information on using the MySQL Server Instance Config Wizard,
     see *Note mysql-config-wizard::.

     For details and instructions on building MySQL from source code
     using Microsoft Visual Studio, see *Note windows-source-build::.

   * *Mac OS X*

     For installation on Mac OS X, including using both the binary
     package and native PKG formats, see *Note macosx-installation::.

     For information on making use of the MySQL Startup Item to
     automatically start and stop MySQL, see *Note
     macosx-installation-startupitem::.

     For information on the MySQL Preference Pane, see *Note
     macosx-installation-prefpane::.

   * *IBM i5/OS*

     For instructions on installing, starting, and stopping MySQL on
     i5/OS, see *Note i5os-installation::.


File: manual.info,  Node: general-installation-issues,  Next: binary-installation,  Prev: installing,  Up: installing

2.1 General Installation Guidance
=================================

* Menu:

* supported-os::                 Operating Systems Supported by MySQL Community Server
* which-version::                Choosing Which MySQL Distribution to Install
* getting-mysql::                How to Get MySQL
* verifying-package-integrity::  Verifying Package Integrity Using MD5 Checksums or GnuPG
* installation-layouts::         Installation Layouts
* compiler-characteristics::     Compiler-Specific Build Characteristics

The immediately following sections contain the information necessary to
choose, download, and verify your distribution. The instructions in
later sections of the chapter describe how to install the distribution
that you choose. For binary distributions, see the instructions at
*Note binary-installation:: or the corresponding section for your
platform if available. To build MySQL from source, use the instructions
in *Note source-installation::.


File: manual.info,  Node: supported-os,  Next: which-version,  Prev: general-installation-issues,  Up: general-installation-issues

2.1.1 Operating Systems Supported by MySQL Community Server
-----------------------------------------------------------

MySQL is available on a number of operating systems and platforms.  For
information about those platforms that are officially supported, see
`http://www.mysql.com/support/supportedplatforms/database.html' on the
MySQL Web site.


File: manual.info,  Node: which-version,  Next: getting-mysql,  Prev: supported-os,  Up: general-installation-issues

2.1.2 Choosing Which MySQL Distribution to Install
--------------------------------------------------

* Menu:

* choosing-version::             Choosing Which Version of MySQL to Install
* choosing-distribution-format::  Choosing a Distribution Format
* many-versions::                How and When Updates Are Released

When preparing to install MySQL, you should decide which version to
use. MySQL development occurs in several release series, and you can
pick the one that best fits your needs. After deciding which version to
install, you can choose a distribution format.  Releases are available
in binary or source format.


File: manual.info,  Node: choosing-version,  Next: choosing-distribution-format,  Prev: which-version,  Up: which-version

2.1.2.1 Choosing Which Version of MySQL to Install
..................................................

The first decision to make is whether you want to use a production
(stable) release or a development release. In the MySQL development
process, multiple release series co-exist, each at a different stage of
maturity.

*Production Releases*
   * MySQL 5.6: Latest General Availability (Production) release

   * MySQL 5.5: Previous General Availability (Production) release

   * MySQL 5.1: Older General Availability (Production) release

   * MySQL 5.0: Older Production release nearing the end of the product
     lifecycle

MySQL 4.1, 4.0, and 3.23 are old releases that are no longer supported.

See http://www.mysql.com/about/legal/lifecycle/ for information about
support policies and schedules.

Normally, if you are beginning to use MySQL for the first time or
trying to port it to some system for which there is no binary
distribution, use the most recent General Availability series listed in
the preceding descriptions. All MySQL releases, even those from
development series, are checked with the MySQL benchmarks and an
extensive test suite before being issued.

If you are running an older system and want to upgrade, but do not want
to take the chance of having a nonseamless upgrade, you should upgrade
to the latest version in the same release series you are using (where
only the last part of the version number is newer than yours). We have
tried to fix only fatal bugs and make only small, relatively `safe'
changes to that version.

If you want to use new features not present in the production release
series, you can use a version from a development series.  Be aware that
development releases are not as stable as production releases.

We do not use a complete code freeze because this prevents us from
making bugfixes and other fixes that must be done. We may add small
things that should not affect anything that currently works in a
production release. Naturally, relevant bugfixes from an earlier series
propagate to later series.

If you want to use the very latest sources containing all current
patches and bugfixes, you can use one of our source code repositories
(see *Note installing-development-tree::). These are not `releases' as
such, but are available as previews of the code on which future
releases are to be based.

The naming scheme in MySQL 5.1 uses release names that consist of three
numbers and a suffix; for example, *mysql-5.1.29-rc*. The numbers
within the release name are interpreted as follows:

   * The first number (*5*) is the major version and describes the file
     format. All MySQL 5 releases have the same file format.

   * The second number (*1*) is the release level. Taken together, the
     major version and release level constitute the release series
     number.

   * The third number (*29*) is the version number within the release
     series. This is incremented for each new release. Usually you want
     the latest version for the series you have chosen.

For each minor update, the last number in the version string is
incremented. When there are major new features or minor
incompatibilities with previous versions, the second number in the
version string is incremented. When the file format changes, the first
number is increased.

Release names also include a suffix that indicates the stability level
of the release. Releases within a series progress through a set of
suffixes to indicate how the stability level improves.  The possible
suffixes are:

   * *alpha* indicates that the release is for preview purposes only.
     Known bugs should be documented in the Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/). Most alpha
     releases implement new commands and extensions. Active development
     that may involve major code changes can occur in an alpha release.
     However, we do conduct testing before issuing a release.

   * *beta* indicates that the release is appropriate for use with new
     development. Within beta releases, the features and compatibility
     should remain consistent. However, beta releases may contain
     numerous and major unaddressed bugs.

     All APIs, externally visible structures, and columns for SQL
     statements will not change during future beta, release candidate,
     or production releases.

   * *rc* indicates a Release Candidate. Release candidates are
     believed to be stable, having passed all of MySQL's internal
     testing, and with all known fatal runtime bugs fixed. However, the
     release has not been in widespread use long enough to know for
     sure that all bugs have been identified. Only minor fixes are
     added. (A release candidate is what formerly was known as a gamma
     release.)

   * If there is no suffix, it indicates that the release is a General
     Availability (GA) or Production release. GA releases are stable,
     having successfully passed through all earlier release stages and
     are believed to be reliable, free of serious bugs, and suitable
     for use in production systems.  Only critical bugfixes are applied
     to the release.

All releases of MySQL are run through our standard tests and benchmarks
to ensure that they are relatively safe to use.  Because the standard
tests are extended over time to check for all previously found bugs,
the test suite keeps getting better.

All releases have been tested at least with these tools:

   * An internal test suite

     The `mysql-test' directory contains an extensive set of test
     cases. We run these tests for every server binary. See *Note
     mysql-test-suite::, for more information about this test suite.

   * The MySQL benchmark suite

     This suite runs a range of common queries. It is also a test to
     determine whether the latest batch of optimizations actually made
     the code faster. See *Note mysql-benchmarks::.

We also perform additional integration and nonfunctional testing of the
latest MySQL version in our internal production environment.
Integration testing is done with different connectors, storage engines,
replication modes, backup, partitioning, stored programs, and so forth
in various combinations. Additional nonfunctional testing is done in
areas of performance, concurrency, stress, high volume, upgrade and
downgrade.


File: manual.info,  Node: choosing-distribution-format,  Next: many-versions,  Prev: choosing-version,  Up: which-version

2.1.2.2 Choosing a Distribution Format
......................................

After choosing which version of MySQL to install, you should decide
whether to use a binary distribution or a source distribution. In most
cases, you should probably use a binary distribution, if one exists for
your platform. Binary distributions are available in native format for
many platforms, such as RPM packages for Linux, DMG packages for Mac OS
X, and PKG packages for Solaris. Distributions are also available in
more generic formats such as Zip archives or compressed `tar' files.

Reasons to choose a binary distribution include the following:

   * Binary distributions generally are easier to install than source
     distributions.

   * To satisfy different user requirements, we provide several servers
     in binary distributions. *Note `mysqld': mysqld.  is an optimized
     server that is a smaller, faster binary.  *Note `mysqld-debug':
     mysqld. is compiled with debugging support.

     Each of these servers is compiled from the same source
     distribution, though with different configuration options.  All
     native MySQL clients can connect to servers from either MySQL
     version.

Under some circumstances, you may be better off installing MySQL from a
source distribution:

   * You want to install MySQL at some explicit location. The standard
     binary distributions are ready to run at any installation
     location, but you might require even more flexibility to place
     MySQL components where you want.

   * You want to configure *Note `mysqld': mysqld. to ensure that
     features are available that might not be included in the standard
     binary distributions. Here is a list of the most common extra
     options that you may want to use to ensure feature availability:

        * `--with-libwrap'

        * `--with-named-z-libs' (this is done for some of the binaries)

        * `--with-debug[=full]'

     For additional information, see *Note
     source-configuration-options::.

   * You want to configure *Note `mysqld': mysqld. without some
     features that are included in the standard binary distributions.
     For example, distributions normally are compiled with support for
     all character sets. If you want a smaller MySQL server, you can
     recompile it with support for only the character sets you need.

   * You want to use the latest sources from one of the Bazaar
     repositories to have access to all current bugfixes. For example,
     if you have found a bug and reported it to the MySQL development
     team, the bugfix is committed to the source repository and you can
     access it there. The bugfix does not appear in a release until a
     release actually is issued.

   * You want to read (or modify) the C and C++ code that makes up
     MySQL. For this purpose, you should get a source distribution,
     because the source code is always the ultimate manual.

   * Source distributions contain more tests and examples than binary
     distributions.


File: manual.info,  Node: many-versions,  Prev: choosing-distribution-format,  Up: which-version

2.1.2.3 How and When Updates Are Released
.........................................

MySQL is evolving quite rapidly and we want to share new developments
with other MySQL users. We try to produce a new release whenever we
have new and useful features that others also seem to have a need for.

We also try to help users who request features that are easy to
implement. We take note of what our licensed users want, and we
especially take note of what our support customers want and try to help
them in this regard.

No one is _required_ to download a new release. The Release Notes
(http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) help you determine
whether the new release has something you really want.

We use the following policy when updating MySQL:

   * Enterprise Server releases are meant to appear every 18 months,
     supplemented by quarterly service packs and monthly rapid updates.
     Community Server releases are meant to appear 2 to 3 times per
     year.

   * Releases are issued within each series. For each release, the last
     number in the version is one more than the previous release within
     the same series.

   * Binary distributions for some platforms are made by us for major
     releases. Other people may make binary distributions for other
     systems, but probably less frequently.

   * We make fixes available as soon as we have identified and
     corrected small or noncritical but annoying bugs. The fixes are
     available in source form immediately from our public Bazaar
     repositories, and are included in the next release.

   * If by any chance a security vulnerability or critical bug is found
     in a release, our policy is to fix it in a new release as soon as
     possible. (We would like other companies to do this, too!)


File: manual.info,  Node: getting-mysql,  Next: verifying-package-integrity,  Prev: which-version,  Up: general-installation-issues

2.1.3 How to Get MySQL
----------------------

Check our downloads page at `http://dev.mysql.com/downloads/' for
information about the current version of MySQL and for downloading
instructions. For a complete up-to-date list of MySQL download mirror
sites, see `http://dev.mysql.com/downloads/mirrors.html'. You can also
find information there about becoming a MySQL mirror site and how to
report a bad or out-of-date mirror.

To obtain the latest development source, see *Note
installing-development-tree::.


File: manual.info,  Node: verifying-package-integrity,  Next: installation-layouts,  Prev: getting-mysql,  Up: general-installation-issues

2.1.4 Verifying Package Integrity Using MD5 Checksums or GnuPG
--------------------------------------------------------------

* Menu:

* verifying-md5-checksum::       Verifying the MD5 Checksum
* checking-gpg-signature::       Signature Checking Using GnuPG
* checking-gpg-signature-windows::  Signature Checking Using Gpg4win for Windows
* checking-rpm-signature::       Signature Checking Using RPM

After you have downloaded the MySQL package that suits your needs and
before you attempt to install it, you should make sure that it is
intact and has not been tampered with. There are three means of
integrity checking:

   * MD5 checksums

   * Cryptographic signatures using `GnuPG', the GNU Privacy Guard

   * For RPM packages, the built-in RPM integrity verification mechanism

The following sections describe how to use these methods.

If you notice that the MD5 checksum or GPG signatures do not match,
first try to download the respective package one more time, perhaps
from another mirror site.


File: manual.info,  Node: verifying-md5-checksum,  Next: checking-gpg-signature,  Prev: verifying-package-integrity,  Up: verifying-package-integrity

2.1.4.1 Verifying the MD5 Checksum
..................................

After you have downloaded a MySQL package, you should make sure that
its MD5 checksum matches the one provided on the MySQL download pages.
Each package has an individual checksum that you can verify against the
package that you downloaded. The correct MD5 checksum is listed on the
downloads page for each MySQL product, and you will compare it against
the MD5 checksum of the file (product) that you download.

Each operating system and setup offers its own version of tools for
checking the MD5 checksum. Typically the command is named `md5sum', or
it may be named `md5', and some operating systems do not ship it at
all. On Linux, it is part of the *GNU Text Utilities* package, which is
available for a wide range of platforms. You can also download the
source code from `http://www.gnu.org/software/textutils/'. If you have
OpenSSL installed, you can use the command `openssl md5 PACKAGE_NAME'
instead. A Windows implementation of the `md5' command line utility is
available from `http://www.fourmilab.ch/md5/'.  `winMd5Sum' is a
graphical MD5 checking tool that can be obtained from
`http://www.nullriver.com/index/products/winmd5sum'.  Our Microsoft
Windows examples will assume the name `md5.exe'.

Linux and Microsoft Windows examples:


     shell> md5sum mysql-standard-5.1.73-linux-i686.tar.gz
     aaab65abbec64d5e907dcd41b8699945  mysql-standard-5.1.73-linux-i686.tar.gz


     shell> md5.exe mysql-installer-community-5.1.73.msi
     aaab65abbec64d5e907dcd41b8699945  mysql-installer-community-5.1.73.msi

You should verify that the resulting checksum (the string of
hexadecimal digits) matches the one displayed on the download page
immediately below the respective package.

*Note*:

Make sure to verify the checksum of the _archive file_ (for example,
the `.zip', `.tar.gz', or `.msi' file) and not of the files that are
contained inside of the archive. In other words, verify the file before
extracting its contents.


File: manual.info,  Node: checking-gpg-signature,  Next: checking-gpg-signature-windows,  Prev: verifying-md5-checksum,  Up: verifying-package-integrity

2.1.4.2 Signature Checking Using GnuPG
......................................

Another method of verifying the integrity and authenticity of a package
is to use cryptographic signatures. This is more reliable than using
*Note MD5 checksums: verifying-md5-checksum, but requires more work.

We sign MySQL downloadable packages with `GnuPG' (GNU Privacy Guard).
`GnuPG' is an Open Source alternative to the well-known Pretty Good
Privacy (`PGP') by Phil Zimmermann. See `http://www.gnupg.org/' for more
information about `GnuPG' and how to obtain and install it on your
system. Most Linux distributions ship with `GnuPG' installed by
default. For more information about `GnuPG', see
`http://www.openpgp.org/'.

To verify the signature for a specific package, you first need to
obtain a copy of our public GPG build key, which you can download from
`http://pgp.mit.edu/'. The key that you want to obtain is named
`mysql-build@oss.oracle.com'. Alternatively, you can cut and paste the
key directly from the following text:


     -----BEGIN PGP PUBLIC KEY BLOCK-----
     Version: GnuPG v1.4.9 (SunOS)

[encoded data, 6300 characters]
     AcOphrnJ
     =443I
     -----END PGP PUBLIC KEY BLOCK-----

To import the build key into your personal public GPG keyring, use `gpg
--import'. For example, if you have saved the key in a file named
`mysql_pubkey.asc', the import command looks like this:


     shell> gpg --import mysql_pubkey.asc
     gpg: key 5072E1F5: public key "MySQL Release Engineering
     <mysql-build@oss.oracle.com>" imported
     gpg: Total number processed: 1
     gpg:               imported: 1
     gpg: no ultimately trusted keys found

You can also download the key from the public keyserver using the
public key id, `5072E1F5':

     shell> gpg --recv-keys 5072E1F5
     gpg: requesting key 5072E1F5 from hkp server keys.gnupg.net
     gpg: key 5072E1F5: "MySQL Release Engineering <mysql-build@oss.oracle.com>"
     1 new user ID
     gpg: key 5072E1F5: "MySQL Release Engineering <mysql-build@oss.oracle.com>"
     53 new signatures
     gpg: no ultimately trusted keys found
     gpg: Total number processed: 1
     gpg:           new user IDs: 1
     gpg:         new signatures: 53

If you want to import the key into your RPM configuration to validate
RPM install packages, you should be able to import the key directly:


     shell> rpm --import mysql_pubkey.asc

If you experience problems or require RPM specific information, see
*Note checking-rpm-signature::.

After you have downloaded and imported the public build key, download
your desired MySQL package and the corresponding signature, which also
is available from the download page. The signature file has the same
name as the distribution file with an `.asc' extension, as shown by the
examples in the following table.

*MySQL Package and Signature Files for Source files*

File Type          File Name
Distribution file  `mysql-standard-5.1.73-linux-i686.tar.gz'
Signature file     `mysql-standard-5.1.73-linux-i686.tar.gz.asc'

Make sure that both files are stored in the same directory and then run
the following command to verify the signature for the distribution file:


     shell> gpg --verify PACKAGE_NAME.asc

If the downloaded package is valid, you will see a "Good signature"
similar to:


     shell> gpg --verify mysql-standard-5.1.73-linux-i686.tar.gz.asc
     gpg: Signature made Tue 01 Feb 2011 02:38:30 AM CST using DSA key ID 5072E1F5
     gpg: Good signature from "MySQL Release Engineering <mysql-build@oss.oracle.com>"

The `Good signature' message indicates that the file signature is
valid, when compared to the signature listed on our site. But you might
also see warnings, like so:


     shell> gpg --verify mysql-standard-5.1.73-linux-i686.tar.gz.asc
     gpg: Signature made Wed 23 Jan 2013 02:25:45 AM PST using DSA key ID 5072E1F5
     gpg: checking the trustdb
     gpg: no ultimately trusted keys found
     gpg: Good signature from "MySQL Release Engineering <mysql-build@oss.oracle.com>"
     gpg: WARNING: This key is not certified with a trusted signature!
     gpg:          There is no indication that the signature belongs to the owner.
     Primary key fingerprint: A4A9 4068 76FC BD3C 4567  70C8 8C71 8D3B 5072 E1F5

That is normal, as they depend on your setup and configuration.  Here
are explanations for these warnings:

   * _gpg: no ultimately trusted keys found_: This means that the
     specific key is not "ultimately trusted" by you or your web of
     trust, which is okay for the purposes of verifying file signatures.

   * _WARNING: This key is not certified with a trusted signature!
     There is no indication that the signature belongs to the owner._:
     This refers to your level of trust in your belief that you possess
     our real public key. This is a personal decision. Ideally, a MySQL
     developer would hand you the key in person, but more commonly, you
     downloaded it.  Was the download tampered with? Probably not, but
     this decision is up to you. Setting up a web of trust is one
     method for trusting them.

See the GPG documentation for more information on how to work with
public keys.


File: manual.info,  Node: checking-gpg-signature-windows,  Next: checking-rpm-signature,  Prev: checking-gpg-signature,  Up: verifying-package-integrity

2.1.4.3 Signature Checking Using Gpg4win for Windows
....................................................

The *Note checking-gpg-signature:: section describes how to verify
MySQL downloads using GPG. That guide also applies to Microsoft
Windows, but another option is to use a GUI tool like Gpg4win
(http://www.gpg4win.org/). You may use a different tool but our
examples are based on Gpg4win, and utilize its bundled `Kleopatra' GUI.

Download and install Gpg4win, and then load Kleopatra. The dialog
should look similar to:

FIGURE GOES HERE: Initial screen after loading Kleopatra

Next, add the MySQL Release Engineering certificate. Do this by
clicking `File', `Lookup Certificates on Server'. Type "Mysql Release
Engineering" into the search box and press `Search'.

FIGURE GOES HERE: Finding the MySQL Release Engineering certificate

Select the "MySQL Release Engineering" certificate. The Fingerprint and
Key-ID must be "5072E1F5", or choose `Details...' to confirm the
certificate is valid. Now, import it by clicking `Import'.  An import
dialog will be displayed, choose `Okay', and this certificate will now
be listed under the `Imported Certificates' tab.

Next, configure the trust level for our certificate. Select our
certificate, then from the main menu select `Certificates', `Change
Owner Trust...'. We suggest choosing `I believe checks are very
accurate' for our certificate, as otherwise you might not be able to
verify our signature. Select `I believe checks are very accurate' and
then press `OK'.

FIGURE GOES HERE: Changing the Trust level

Next, verify the downloaded MySQL package file. This requires files for
both the packaged file, and the signature. The signature file must have
the same name as the packaged file but with an appended `.asc'
extension, as shown by the example in the following table. The
signature is linked to on the downloads page for each MySQL product.
You must create the `.asc' file with this signature.

*MySQL Package and Signature Files for MySQL Installer for Microsoft
Windows*

File Type          File Name
Distribution file  `mysql-installer-community-5.1.73.msi'
Signature file     `mysql-installer-community-5.1.73.msi.asc'

Make sure that both files are stored in the same directory and then run
the following command to verify the signature for the distribution
file. Either drag and drop the signature (`.asc') file into Kleopatra,
or load the dialog from `File', `Decrypt/Verify Files...', and then
choose either the `.msi' or `.asc' file.

FIGURE GOES HERE: The Decrypt/Verify Files dialog

Click `Decrypt/Verify' to check the file.  The two most common results
will look like the following, and although the yellow warning looks
problematic, the following means that the file check passed with
success. You may now run this installer.

FIGURE GOES HERE: The Decrypt/Verify Results: Good

Seeing a red "The signature is bad" error means the file is invalid. Do
not execute the MSI file if you see this error.

FIGURE GOES HERE: The Decrypt/Verify Results: Bad

The *Note checking-gpg-signature:: section explains why you probably
don't see a green `Good signature' result.


File: manual.info,  Node: checking-rpm-signature,  Prev: checking-gpg-signature-windows,  Up: verifying-package-integrity

2.1.4.4 Signature Checking Using RPM
....................................

For RPM packages, there is no separate signature. RPM packages have a
built-in GPG signature and MD5 checksum. You can verify a package by
running the following command:


     shell> rpm --checksig PACKAGE_NAME.rpm

Example:


     shell> rpm --checksig MySQL-server-5.1.73-0.glibc23.i386.rpm
     MySQL-server-5.1.73-0.glibc23.i386.rpm: md5 gpg OK

*Note*:

If you are using RPM 4.1 and it complains about `(GPG) NOT OK (MISSING
KEYS: GPG#5072e1f5)', even though you have imported the MySQL public
build key into your own GPG keyring, you need to import the key into
the RPM keyring first. RPM 4.1 no longer uses your personal GPG keyring
(or GPG itself). Rather, RPM maintains a separate keyring because it is
a system-wide application and a user's GPG public keyring is a
user-specific file. To import the MySQL public key into the RPM
keyring, first obtain the key, then use `rpm --import' to import the
key. For example:


     shell> gpg --export -a 5072e1f5 > 5072e1f5.asc
     shell> rpm --import 5072e1f5.asc

Alternatively, `rpm' also supports loading the key directly from a URL,
and you can use this manual page:


     shell> rpm --import http://dev.mysql.com/doc/refman/5.1/en/checking-gpg-signature.html

If you need to obtain the MySQL public key, see *Note
checking-gpg-signature::.


File: manual.info,  Node: installation-layouts,  Next: compiler-characteristics,  Prev: verifying-package-integrity,  Up: general-installation-issues

2.1.5 Installation Layouts
--------------------------

The installation layout differs for different installation types (for
example, native packages, binary tarballs, and source tarballs), which
can lead to confusion when managing different systems or using
different installation sources. The individual layouts are given in the
corresponding installation type or platform chapter, as described
following. Note that the layout of installations from vendors other
than Oracle may differ from these layouts.

   * *Note windows-installation-layout::

   * *Note source-installation-layout::

   * *Note binary-installation-layout::

   * *Note mysql-installation-layout-linuxrpm::

   * *Note mysql-installation-layout-macosx::


File: manual.info,  Node: compiler-characteristics,  Prev: installation-layouts,  Up: general-installation-issues

2.1.6 Compiler-Specific Build Characteristics
---------------------------------------------

In some cases, the compiler used to build MySQL affects the features
available for use. The notes in this section apply for binary
distributions provided by Oracle Corporation or that you compile
yourself from source.

*`icc' (Intel C++ Compiler) Builds*

A server built with `icc' has these characteristics:

   * SSL support is not included.

   * `InnoDB Plugin' is not included.


File: manual.info,  Node: binary-installation,  Next: windows-installation,  Prev: general-installation-issues,  Up: installing

2.2 Installing MySQL on Unix/Linux Using Generic Binaries
=========================================================

Oracle provides a set of binary distributions of MySQL. These include
binary distributions in the form of compressed `tar' files (files with a
`.tar.gz' extension) for a number of platforms, as well as binaries in
platform-specific package formats for selected platforms.

This section covers the installation of MySQL from a compressed `tar'
file binary distribution. For other platform-specific package formats,
see the other platform-specific sections. For example, for Windows
distributions, see *Note windows-installation::.

To obtain MySQL, see *Note getting-mysql::.

MySQL compressed `tar' file binary distributions have names of the form
`mysql-VERSION-OS.tar.gz', where `VERSION' is a number (for example,
`5.1.73'), and OS indicates the type of operating system for which the
distribution is intended (for example, `pc-linux-i686' or `winx64').

To install MySQL from a compressed `tar' file binary distribution, your
system must have GNU `gunzip' to uncompress the distribution and a
reasonable `tar' to unpack it. If your `tar' program supports the `z'
option, it can both uncompress and unpack the file.

GNU `tar' is known to work. The standard `tar' provided with some
operating systems is not able to unpack the long file names in the
MySQL distribution. You should download and install GNU `tar', or if
available, use a preinstalled version of GNU tar. Usually this is
available as `gnutar', `gtar', or as `tar' within a GNU or Free
Software directory, such as `/usr/sfw/bin' or `/usr/local/bin'. GNU
`tar' is available from `http://www.gnu.org/software/tar/'.

*Warning*:

If you have previously installed MySQL using your operating system
native package management system, such as `yum' or `apt-get', you may
experience problems installing using a native binary. Make sure your
previous MySQL previous installation has been removed entirely (using
your package management system), and that any additional files, such as
old versions of your data files, have also been removed. You should
also check the existence of configuration files such as `/etc/my.cnf'
or the `/etc/mysql' directory have been deleted.

If you run into problems and need to file a bug report, please use the
instructions in *Note bug-reports::.

On Unix, to install a compressed `tar' file binary distribution, unpack
it at the installation location you choose (typically
`/usr/local/mysql'). This creates the directories shown in the
following table.

*MySQL Installation Layout for Generic Unix/Linux Binary Package*

Directory                        Contents of Directory
`bin'                            Client programs and the *Note `mysqld':
                                 mysqld. server
`data'                           Log files, databases
`docs'                           Manual in Info format
`man'                            Unix manual pages
`include'                        Include (header) files
`lib'                            Libraries
`scripts'                        *Note `mysql_install_db':
                                 mysql-install-db.
`share'                          Miscellaneous support files, including
                                 error messages, sample configuration
                                 files, SQL for database installation
`sql-bench'                      Benchmarks

Debug versions of the *Note `mysqld': mysqld. binary are available as
*Note `mysqld-debug': mysqld. To compile your own debug version of
MySQL from a source distribution, use the appropriate configuration
options to enable debugging support. For more information on compiling
from source, see *Note source-installation::.

To install and use a MySQL binary distribution, the basic command
sequence looks like this:


     shell> groupadd mysql
     shell> useradd -r -g mysql mysql
     shell> cd /usr/local
     shell> tar zxvf /PATH/TO/MYSQL-VERSION-OS.tar.gz
     shell> ln -s FULL-PATH-TO-MYSQL-VERSION-OS mysql
     shell> cd mysql
     shell> chown -R mysql .
     shell> chgrp -R mysql .
     shell> scripts/mysql_install_db --user=mysql
     shell> chown -R root .
     shell> chown -R mysql data
     # Next command is optional
     shell> cp support-files/my-medium.cnf /etc/my.cnf
     shell> bin/mysqld_safe --user=mysql &
     # Next command is optional
     shell> cp support-files/mysql.server /etc/init.d/mysql.server

A more detailed version of the preceding description for installing a
binary distribution follows.

*Note*:

This procedure assumes that you have `root' (administrator) access to
your system. Alternatively, you can prefix each command using the
`sudo' (Linux) or `pfexec' (OpenSolaris) command.

The procedure does not set up any passwords for MySQL accounts.  After
following the procedure, proceed to *Note default-privileges::.

*Create a mysql User and Group*

If your system does not already have a user and group for *Note
`mysqld': mysqld. to run as, you may need to create one. The following
commands add the `mysql' group and the `mysql' user. You might want to
call the user and group something else instead of `mysql'. If so,
substitute the appropriate name in the following instructions. The
syntax for `useradd' and `groupadd' may differ slightly on different
versions of Unix, or they may have different names such as `adduser'
and `addgroup'.


     shell> groupadd mysql
     shell> useradd -r -g mysql mysql

*Note*:

Because the user is required only for ownership purposes, not login
purposes, the `useradd' command uses the `-r' option to create a user
that does not have login permissions to your server host. Omit this
option to permit logins for the user (or if your `useradd' does not
support the option).

*Obtain and Unpack the Distribution*

Pick the directory under which you want to unpack the distribution and
change location into it. The example here unpacks the distribution
under `/usr/local'. The instructions, therefore, assume that you have
permission to create files and directories in `/usr/local'. If that
directory is protected, you must perform the installation as `root'.


     shell> cd /usr/local

Obtain a distribution file using the instructions in *Note
getting-mysql::. For a given release, binary distributions for all
platforms are built from the same MySQL source distribution.

Unpack the distribution, which creates the installation directory.
Then create a symbolic link to that directory.  `tar' can uncompress
and unpack the distribution if it has `z' option support:


     shell> tar zxvf /PATH/TO/MYSQL-VERSION-OS.tar.gz
     shell> ln -s FULL-PATH-TO-MYSQL-VERSION-OS mysql

The `tar' command creates a directory named `mysql-VERSION-OS'.  The
`ln' command makes a symbolic link to that directory. This enables you
to refer more easily to the installation directory as
`/usr/local/mysql'.

If your `tar' does not have `z' option support, use `gunzip' to unpack
the distribution and `tar' to unpack it. Replace the preceding `tar'
command with the following alternative command to uncompress and
extract the distribution:


     shell> gunzip < /PATH/TO/MYSQL-VERSION-OS.tar.gz | tar xvf -

*Perform Postinstallation Setup*

The remainder of the installation process involves setting up the
configuration file, creating the core databases, and starting the MySQL
server. For next steps, see *Note postinstallation::.

*Note*:

The accounts that are listed in the MySQL grant tables initially have
no passwords. After starting the server, you should set up passwords
for them using the instructions in *Note default-privileges::.


File: manual.info,  Node: windows-installation,  Next: macosx-installation,  Prev: binary-installation,  Up: installing

2.3 Installing MySQL on Microsoft Windows
=========================================

* Menu:

* windows-installation-layout::  MySQL Installation Layout on Microsoft Windows
* windows-choosing-package::     Choosing the Installation Package for Microsoft Windows
* windows-using-installer::      Installing MySQL on Microsoft Windows Using an MSI Package
* windows-notifier::             MySQL Notifier
* mysql-config-wizard::          Using the MySQL Server Instance Config Wizard
* windows-install-archive::      Installing MySQL on Microsoft Windows Using a noinstall Zip Archive
* windows-troubleshooting::      Troubleshooting a Microsoft Windows MySQL Server Installation
* windows-upgrading::            Upgrading MySQL Server on Microsoft Windows
* windows-postinstallation::     MySQL Server on Microsoft Windows Postinstallation Procedures

MySQL is available for Microsoft Windows, for both 32-bit and 64-bit
versions. For supported Windows platform information, see
`http://www.mysql.com/support/supportedplatforms/database.html'.

It is possible to run MySQL as a standard application or as a Windows
service. By using a service, you can monitor and control the operation
of the server through the standard Windows service management tools.
For more information, see *Note windows-start-service::.

Generally, you should install MySQL on Windows using an account that
has administrator rights. Otherwise, you may encounter problems with
certain operations such as editing the `PATH' environment variable or
accessing the `Service Control Manager'. Once installed, MySQL does not
need to be executed using a user with Administrator privileges.

For a list of limitations on the use of MySQL on the Windows platform,
see *Note limits-windows::.

In addition to the MySQL Server package, you may need or want
additional components to use MySQL with your application or development
environment. These include, but are not limited to:

   * To connect to the MySQL server using ODBC, you must have a
     Connector/ODBC driver. For more information, including
     installation and configuration instructions, see MySQL
     Connector/ODBC Developer Guide
     (http://dev.mysql.com/doc/connector-odbc/en/index.html).

   * To use MySQL server with .NET applications, you must have the
     Connector/Net driver. For more information, including installation
     and configuration instructions, see MySQL Connector/Net Developer
     Guide (http://dev.mysql.com/doc/connector-net/en/index.html).

MySQL distributions for Windows can be downloaded from
`http://dev.mysql.com/downloads/'. See *Note getting-mysql::.

MySQL for Windows is available in several distribution formats,
detailed below. Generally speaking, you should use a binary
distribution that includes an installer. It is simpler to use than the
others, and you need no additional tools to get MySQL up and running.
The installer for the Windows version of MySQL, combined with a GUI
Config Wizard, automatically installs MySQL, creates an option file,
starts the server, and secures the default user accounts.

   * Binary installer distribution. The installable distribution comes
     packaged as a Microsoft Windows Installer (MSI) package that you
     can install manually or automatically on your systems.  Two
     formats are available, an essentials package that contains all the
     files you need to install and configure MySQL, but no additional
     components, and a complete package that includes MySQL,
     configuration tools, benchmarks and other components. For more
     information on the specific differences, see *Note
     windows-choosing-package::

     For instructions on installing MySQL using one of the MSI
     installation packages, see *Note windows-using-installer::.

   * The standard binary distribution (packaged as a Zip file) contains
     all of the necessary files that you unpack into your chosen
     location. This package contains all of the files in the full
     Windows MSI Installer package, but does not include an
     installation program.

     For instructions on installing MySQL using the Zip file, see *Note
     windows-install-archive::.

   * The source distribution format contains all the code and support
     files for building the executables using the Visual Studio
     compiler system.

     For instructions on building MySQL from source on Windows, see
     *Note windows-source-build::.

*MySQL on Windows considerations:*

   * *Large Table Support*

     If you need tables with a size larger than 4GB, install MySQL on
     an NTFS or newer file system. Do not forget to use `MAX_ROWS' and
     `AVG_ROW_LENGTH' when you create tables. See *Note create-table::.

   * *MySQL and Virus Checking Software*

     Virus-scanning software such as Norton/Symantec Anti-Virus on
     directories containing MySQL data and temporary tables can cause
     issues, both in terms of the performance of MySQL and the
     virus-scanning software misidentifying the contents of the files
     as containing spam. This is due to the fingerprinting mechanism
     used by the virus-scanning software, and the way in which MySQL
     rapidly updates different files, which may be identified as a
     potential security risk.

     After installing MySQL Server, it is recommended that you disable
     virus scanning on the main directory (`datadir') used to store your
     MySQL table data. There is usually a system built into the
     virus-scanning software to enable specific directories to be
     ignored.

     In addition, by default, MySQL creates temporary files in the
     standard Windows temporary directory. To prevent the temporary
     files also being scanned, configure a separate temporary directory
     for MySQL temporary files and add this directory to the virus
     scanning exclusion list. To do this, add a configuration option
     for the `tmpdir' parameter to your `my.ini' configuration file.
     For more information, see *Note windows-create-option-file::.


File: manual.info,  Node: windows-installation-layout,  Next: windows-choosing-package,  Prev: windows-installation,  Up: windows-installation

2.3.1 MySQL Installation Layout on Microsoft Windows
----------------------------------------------------

For MySQL 5.1 on Windows, the default installation directory is
`C:\Program Files\MySQL\MySQL Server 5.1'. Some Windows users prefer to
install in `C:\mysql', the directory that formerly was used as the
default. However, the layout of the subdirectories remains the same.

For MySQL 5.1.23 and earlier, all of the files are located within the
parent directory, using the structure shown in the following table.

*Installation Layout for Windows Using MySQL 5.1.23 and Earlier*

Directory                        Contents of Directory
`bin'                            Client programs and the *Note `mysqld':
                                 mysqld. server
`data'                           Log files, databases
`examples'                       Example programs and scripts
`include'                        Include (header) files
`lib'                            Libraries
`scripts'                        Utility scripts
`share'                          Miscellaneous support files, including
                                 error messages, character set files,
                                 sample configuration files, SQL for
                                 database installation

For MySQL 5.1.24 and later, the default location of data directory was
changed. The remainder of the directory structure remains the same.

*Installation Layout for Microsoft Windows using MySQL 5.1.24 and later*

Directory              Contents of Directory         Notes
`bin'                  Client programs and the       
                       *Note `mysqld': mysqld.       
                       server                        
`%ALLUSERSPROFILE%\MySQL\MySQLLog files, databases          The Windows system
Server 5.1\'           (Windows XP, Windows Server   variable
                       2003)                         %ALLUSERSPROFILE%
                                                     defaults to
                                                     `C:\Documents and
                                                     Settings\All
                                                     Users\Application
                                                     Data'
`%PROGRAMDATA%\MySQL\MySQLLog files, databases (Vista,  The Windows system
Server 5.1\'           Windows 7, Windows Server     variable
                       2008, and newer)              %PROGRAMDATA%
                                                     defaults to
                                                     `C:\ProgramData'
`examples'             Example programs and scripts  
`include'              Include (header) files        
`lib'                  Libraries                     
`scripts'              Utility scripts               
`share'                Miscellaneous support files,  
                       including error messages,     
                       character set files, sample   
                       configuration files, SQL for  
                       database installation         


File: manual.info,  Node: windows-choosing-package,  Next: windows-using-installer,  Prev: windows-installation-layout,  Up: windows-installation

2.3.2 Choosing the Installation Package for Microsoft Windows
-------------------------------------------------------------

For MySQL 5.1, there are three installation package formats to choose
from when installing MySQL on Windows:

*Note*:

Using MySQL Installer is the recommended installation method for
Microsoft Windows users. The MySQL Server 5.1 release does not include
its own MySQL Installer release, but a MySQL Installer version 5.5 and
above can optionally install MySQL Server 5.1. Follow the standard
Installing MySQL on Microsoft Windows Using MySQL Installer
(http://dev.mysql.com/doc/refman/5.5/en/mysql-installer.html)
documentation but choose `Custom Install' after executing it. A MySQL
Server 5.1 option will be available, and choosing it will cause MySQL
Installer to download it for you.

*Microsoft Windows MySQL Installation package comparison*

                              Packaging                     
Feature                       Essentials     Complete       Zip
                                                            (No-install)
Installer                     Yes            Yes            No
Directory-only                                              
MySQL Server Instance Config  Yes            Yes            No
Wizard                                                      
Test Suite                    No             Yes            Yes
MySQL Server                  Yes            Yes            Yes
MySQL Client Programs         Yes            Yes            Yes
C Headers/Libraries           Yes            Yes            Yes
Embedded Server               No             Optional       Yes
Scripts and Examples          No             Optional       Yes

In the above table:

   * _Yes_ indicates that the component is installed by default.

   * _No_ indicates that the component is not installed or included.

   * _Optional_ indicates that the component is included with the
     package, but not installed unless explicitly requested using the
     Custom installation mode.

The workflow for installing using the MSI installer is shown below:

FIGURE GOES HERE: Installation Workflow for Windows Using MSI

The workflow for installing using the MSI installer is shown below:

FIGURE GOES HERE: Installation Workflow for Windows Using Zip

     *Note*:

     For the Essentials and Complete packages in the MSI installer, you
     can select individual components to be installed by using the
     Custom mode, including disable the components confiurated for
     installation by default.

     Full details on the components are suggested uses are provided
     below for reference:

   * *Windows Essentials*: This package has a file name similar to
     `mysql-essential-5.1.73-win32.msi' and is supplied as a Microsoft
     Installer (MSI) package. The package includes the minimum set of
     files needed to install MySQL on Windows, including the MySQL
     Server Instance Config Wizard. This package does not include
     optional components such as the embedded server, developer headers
     and libraries or benchmark suite.

     To install using this package, see *Note windows-using-installer::.

   * *Windows MSI Installer (Complete)*: This package has a file name
     similar to `mysql-5.1.73-win32.msi' and contains all files needed
     for a complete Windows installation, including the MySQL Server
     Instance Config Wizard. This package includes optional components
     such as the embedded server and benchmark suite.

     To install using this package, see *Note windows-using-installer::.

   * *Without installer*: This package has a file name similar to
     `mysql-noinstall-5.1.73-win32.zip' and contains all the files
     found in the Complete install package, with the exception of the
     MySQL Server Instance Config Wizard. This package does not include
     an automated installer, and must be manually installed and
     configured.

The Essentials package is recommended for most users. Both the
Essentials and Complete distributions are available as an `.msi' file
for use with the Windows Installer.  The Noinstall distribution is
packaged as a Zip archive. To use a Zip archive, you must have a tool
that can unpack `.zip' files.

When using the MSI installers you can automate the installation
process. For more information, see *Note windows-installer-msi-quiet::.
To automate the creation of a MySQL instance, see *Note
mysql-config-wizard-cmdline::.

Your choice of install package affects the installation process you
must follow. If you choose to install either an Essentials or Complete
install package, see *Note windows-using-installer::. If you choose to
install a Noinstall archive, see *Note windows-install-archive::.


File: manual.info,  Node: windows-using-installer,  Next: windows-notifier,  Prev: windows-choosing-package,  Up: windows-installation

2.3.3 Installing MySQL on Microsoft Windows Using an MSI Package
----------------------------------------------------------------

* Menu:

* windows-install-wizard::       Using the MySQL Installation Wizard for Microsoft Windows
* windows-installer-msi-quiet::  Automating MySQL Installation on Microsoft Windows Using the MSI Package
* windows-installer-uninstalling::  Removing MySQL When Installed from the MSI Package

The MSI package is designed to install and configure MySQL in such a
way that you can immediately get started using MySQL.

The MySQL Installation Wizard and MySQL Configuration Wizard are
available in the Essentials and Complete install packages. They are
recommended for most standard MySQL installations. Exceptions include
users who need to install multiple instances of MySQL on a single
server host and advanced users who want complete control of server
configuration.

   * For information on installing using the GUI MSI installer process,
     see *Note windows-install-wizard::.

   * For information on installing using the command line using the MSI
     package, see *Note windows-installer-msi-quiet::.

   * If you have previously installed MySQL using the MSI package and
     want to remove MySQL, see *Note windows-installer-uninstalling::.

The workflow sequence for using the installer is shown in the figure
below:

FIGURE GOES HERE: Installation Workflow for Windows Using MSI Installer

*Note*:

Microsoft Windows XP and later include a firewall which specifically
blocks ports. If you plan on using MySQL through a network port then
you should open and create an exception for this port before performing
the installation. To check and if necessary add an exception to the
firewall settings:

  1. First ensure that you are logged in as an Administrator or a user
     with Administrator privileges.

  2. Go to the `Control Panel', and double click the `Windows Firewall'
     icon.

  3. Choose the `Allow a program through Windows Firewall' option and
     click the `Add port' button.

  4. Enter `MySQL' into the `Name' text box and `3306' (or the port of
     your choice) into the `Port number' text box.

  5. Also ensure that the `TCP' protocol radio button is selected.

  6. If you wish, you can also limit access to the MySQL server by
     choosing the `Change scope' button.

  7. Confirm your choices by clicking the `OK' button.

Additionally, when running the MySQL Installation Wizard on Windows
Vista or newer, ensure that you are logged in as a user with
administrative rights.

*Note*:

When using Windows Vista or newer, you may want to disable User Account
Control (UAC) before performing the installation. If you do not do so,
then MySQL may be identified as a security risk, which will mean that
you need to enable MySQL. You can disable the security checking by
following these instructions:

  1. Open `Control Panel'.

  2. Under the `User Accounts and Family Safety', select `Add or remove
     user accounts.'

  3. Click the `Got to the main User Accounts page' link.

  4. Click on `Turn User Account Control on or off'. You may be
     prompted to provide permission to change this setting. Click
     `Continue'.

  5. Deselect or uncheck the check box next to `Use User Account
     Control (UAC) to help protect your computer'. Click `OK' to save
     the setting.

You will need to restart to complete the process. Click `Restart Now'
to reboot the machine and apply the changes. You can then follow the
instructions below for installing Windows.


File: manual.info,  Node: windows-install-wizard,  Next: windows-installer-msi-quiet,  Prev: windows-using-installer,  Up: windows-using-installer

2.3.3.1 Using the MySQL Installation Wizard for Microsoft Windows
.................................................................

* Menu:

* mysql-install-wizard-starting::  MySQL Installation Wizard: Downloading and Starting
* mysql-install-wizard-install-type::  MySQL Installation Wizard: Choosing an Install Type
* mysql-install-wizard-custom-install::  MySQL Installation Wizard: The Custom Install Dialog
* mysql-install-wizard-confirmation-dialog::  MySQL Installation Wizard: The Confirmation Dialog
* mysql-install-wizard-changes::  MySQL Installation Wizard: Changes Made
* mysql-install-wizard-upgrading::  MySQL Installation Wizard: Upgrading MySQL

MySQL Installation Wizard is an installer for the MySQL server that
uses the latest installer technologies for Microsoft Windows. The MySQL
Installation Wizard, in combination with the MySQL Config Wizard,
enables a user to install and configure a MySQL server that is ready
for use immediately after installation.

The MySQL Installation Wizard uses the standard Microsoft Installer
Engine (MSI) system is the standard installer for all MySQL server
distributions. See *Note mysql-install-wizard-upgrading::, for more
information on upgrading from a previous version.

If you are upgrading an installation from MySQL 5.1.31 or earlier to
MySQL 5.1.32 or later, read the notes provided in *Note
mysql-install-wizard-upgrading::.

The Microsoft Windows Installer Engine was updated with the release of
Windows XP; those using a previous version of Windows can reference
this Microsoft Knowledge Base article
(http://support.microsoft.com/default.aspx?scid=kb;EN-US;292539) for
information on upgrading to the latest version of the Windows Installer
Engine.

In addition, Microsoft has introduced the WiX (Windows Installer XML)
toolkit. This is the first highly acknowledged Open Source project from
Microsoft. We have switched to WiX because it is an Open Source project
and it enables us to handle the complete Windows installation process
in a flexible manner using scripts.

Improving the MySQL Installation Wizard depends on the support and
feedback of users like you. If you find that the MySQL Installation
Wizard is lacking some feature important to you, or if you discover a
bug, please report it in our bugs database using the instructions given
in *Note bug-reports::.


File: manual.info,  Node: mysql-install-wizard-starting,  Next: mysql-install-wizard-install-type,  Prev: windows-install-wizard,  Up: windows-install-wizard

2.3.3.2 MySQL Installation Wizard: Downloading and Starting
...........................................................

The MySQL installation packages can be downloaded from
`http://dev.mysql.com/downloads/'. If the package you download is
contained within a Zip archive, you need to extract the archive first.

The process for starting the wizard depends on the contents of the
installation package you download. If there is a `setup.exe' file
present, double-click it to start the installation process. If there is
an `.msi' file present, double-click it to start the installation
process.


File: manual.info,  Node: mysql-install-wizard-install-type,  Next: mysql-install-wizard-custom-install,  Prev: mysql-install-wizard-starting,  Up: windows-install-wizard

2.3.3.3 MySQL Installation Wizard: Choosing an Install Type
...........................................................

There are three installation types available: *Typical*, *Complete*, and
*Custom*.

The *Typical* installation type installs the MySQL server, the *Note
`mysql': mysql.  command-line client, and the command-line utilities.
The command-line clients and utilities include *Note `mysqldump':
mysqldump, *Note `myisamchk': myisamchk, and several other tools to
help you manage the MySQL server.

The *Complete* installation type installs all components included in
the installation package. The full installation package includes
components such as the embedded server library, the benchmark suite,
support scripts, and documentation.

The *Custom* installation type gives you complete control over which
packages you wish to install and the installation path that is used. See
*Note mysql-install-wizard-custom-install::, for more information on
performing a custom install.

If you choose the *Typical* or *Complete* installation types and click
the `Next' button, you advance to the confirmation screen to verify
your choices and begin the installation. If you choose the *Custom*
installation type and click the `Next' button, you advance to the
custom installation dialog, described in *Note
mysql-install-wizard-custom-install::.


File: manual.info,  Node: mysql-install-wizard-custom-install,  Next: mysql-install-wizard-confirmation-dialog,  Prev: mysql-install-wizard-install-type,  Up: windows-install-wizard

2.3.3.4 MySQL Installation Wizard: The Custom Install Dialog
............................................................

If you wish to change the installation path or the specific components
that are installed by the MySQL Installation Wizard, choose the *Custom*
installation type.

A tree view on the left side of the custom install dialog lists all
available components. Components that are not installed have a red `X'
icon; components that are installed have a gray icon. To change whether
a component is installed, click that component's icon and choose a new
option from the drop-down list that appears.

You can change the default installation path by clicking the
`Change...' button to the right of the displayed installation path.

After choosing your installation components and installation path,
click the `Next' button to advance to the confirmation dialog.


File: manual.info,  Node: mysql-install-wizard-confirmation-dialog,  Next: mysql-install-wizard-changes,  Prev: mysql-install-wizard-custom-install,  Up: windows-install-wizard

2.3.3.5 MySQL Installation Wizard: The Confirmation Dialog
..........................................................

Once you choose an installation type and optionally choose your
installation components, you advance to the confirmation dialog. Your
installation type and installation path are displayed for you to review.

To install MySQL if you are satisfied with your settings, click the
`Install' button. To change your settings, click the `Back' button.  To
exit the MySQL Installation Wizard without installing MySQL, click the
`Cancel' button.

In MySQL 5.1.47 and earlier, after installation is complete, you have
the option of registering with the MySQL web site.  Registration gives
you access to post in the MySQL forums at forums.mysql.com
(http://forums.mysql.com), along with the ability to report bugs at
bugs.mysql.com (http://bugs.mysql.com) and to subscribe to our
newsletter.

The final screen of the installer provides a summary of the
installation and gives you the option to launch the MySQL Config
Wizard, which you can use to create a configuration file, install the
MySQL service, and configure security settings.


File: manual.info,  Node: mysql-install-wizard-changes,  Next: mysql-install-wizard-upgrading,  Prev: mysql-install-wizard-confirmation-dialog,  Up: windows-install-wizard

2.3.3.6 MySQL Installation Wizard: Changes Made
...............................................

Once you click the `Install' button, the MySQL Installation Wizard
begins the installation process and makes certain changes to your
system which are described in the sections that follow.

*Changes to the Registry*

The MySQL Installation Wizard creates one Windows registry key in a
typical install situation, located in
`HKEY_LOCAL_MACHINE\SOFTWARE\MySQL AB'. For 64-bit Windows, the
registry location is `HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\MYSQL
AB'. A server version specific entry will be created for each major
version of MySQL that you install.

The MySQL Installation Wizard creates a key named after the major
version of the server that is being installed, such as `MySQL Server
5.1'. It contains two string values, `Location' and `Version'. The
`Location' string contains the path to the installation directory. In a
default installation it contains `C:\Program Files\MySQL\MySQL Server
5.1\'. The `Version' string contains the release number.  For example,
for an installation of MySQL Server 5.1.73, the key contains a value of
`5.1.73'.

These registry keys are used to help external tools identify the
installed location of the MySQL server, preventing a complete scan of
the hard-disk to determine the installation path of the MySQL server.
The registry keys are not required to run the server, and if you
install MySQL using the `noinstall' Zip archive, the registry keys are
not created.

*Changes to the Start Menu*

The MySQL Installation Wizard creates a new entry in the Windows
`Start' menu under a common MySQL menu heading named after the major
version of MySQL that you have installed. For example, if you install
MySQL 5.1, the MySQL Installation Wizard creates a `MySQL Server 5.1'
section in the `Start' menu.

The following entries are created within the new `Start' menu section:

   * `MySQL Command-Line Client': This is a shortcut to the *Note
     `mysql': mysql. command-line client and is configured to connect
     as the `root' user. The shortcut prompts for a `root' user
     password when you connect.

   * `MySQL Server Instance Config Wizard': This is a shortcut to the
     MySQL Config Wizard. Use this shortcut to configure a newly
     installed server, or to reconfigure an existing server.

   * `MySQL Documentation': This is a link to the MySQL server
     documentation that is stored locally in the MySQL server
     installation directory. This option is not available when the
     MySQL server is installed using the Essentials installation
     package.

*Changes to the File System*

The MySQL Installation Wizard by default installs the MySQL 5.1 server
to `C:\PROGRAM FILES\MySQL\MySQL Server 5.1', where PROGRAM FILES is
the default location for applications in your system, and 5.1 is the
major version of your MySQL server. This is the recommended location
for the MySQL server, replacing the former default location `C:\mysql'.

By default, all MySQL applications are stored in a common directory at
`C:\PROGRAM FILES\MySQL', where PROGRAM FILES is the default location
for applications in your Windows installation. A typical MySQL
installation on a developer machine might look like this:


     C:\Program Files\MySQL\MySQL Server 5.1
     C:\Program Files\MySQL\MySQL Workbench 5.1 OSS

This approach makes it easier to manage and maintain all MySQL
applications installed on a particular system.

In MySQL 5.1.23 and earlier, the default location for the data files
used by MySQL is located within the corresponding MySQL Server
installation directory. For MySQL 5.1.24 and later, the default
location of the data directory is the `AppData' directory configured
for the user that installed the MySQL application.


File: manual.info,  Node: mysql-install-wizard-upgrading,  Prev: mysql-install-wizard-changes,  Up: windows-install-wizard

2.3.3.7 MySQL Installation Wizard: Upgrading MySQL
..................................................

The MySQL Installation Wizard can perform server upgrades automatically
using the upgrade capabilities of MSI. That means you do not need to
remove a previous installation manually before installing a new
release. The installer automatically shuts down and removes the
previous MySQL service before installing the new version.

Automatic upgrades are available only when upgrading between
installations that have the same major and minor version numbers. For
example, you can upgrade automatically from MySQL 5.1.5 to MySQL 5.1.6,
but not from MySQL 5.0 to MySQL 5.1.

In MySQL 5.1.32 and later, the `EXE' version of the MSI installer
packages were removed. When upgrading an existing MySQL installation
from the old EXE based installer to the MSI based installer, please
keep the following notes in mind:

   * The MSI installer will not identify an existing installation that
     was installed using the old EXE installer. This means that the
     installer will not stop the existing server, or detect that the
     existing password is required before installing the new version.
     To work around this:

       1. Stop the current server manually using `net stop' or
          `mysqladmin shutdown'.

       2. Remove the existing installation manually by using the
          `Add/Remove Programs' control panel. This will keep the
          existing configuration and data files, as these are not
          removed automatically.

       3. Install the new version of MySQL using the MSI installer.
          When running the installation, skip updating the security by
          deselecting the check box on the security screen.

       4. Complete the installation, and then start the server again.
          You should be able to login with your existing user and
          password credentials.

   * You can only upgrade the version and release using the MSI
     installer. For example, you can upgrade an open source
     installation with an open source installer. You cannot upgrade an
     open source installation using the enterprise installer.

See *Note windows-upgrading::.


File: manual.info,  Node: windows-installer-msi-quiet,  Next: windows-installer-uninstalling,  Prev: windows-install-wizard,  Up: windows-using-installer

2.3.3.8 Automating MySQL Installation on Microsoft Windows Using the MSI Package
................................................................................

The Microsoft Installer (MSI) supports a both a _quiet_ and a _passive_
mode that can be used to install MySQL automatically without requiring
intervention. You can use this either in scripts to automatically
install MySQL or through a terminal connection such as Telnet where you
do not have access to the standard Windows user interface. The MSI
packages can also be used in combination with Microsoft's Group Policy
system (part of Windows Server 2003 and Windows Server 2008) to install
MySQL across multiple machines.

To install MySQL from one of the MSI packages automatically from the
command line (or within a script), you need to use the `msiexec.exe'
tool. For example, to perform a quiet installation (which shows no
dialog boxes or progress):


     shell> msiexec /i mysql-5.1.73.msi /quiet

The `/i' indicates that you want to perform an installation. The
`/quiet' option indicates that you want no interactive elements.

To provide a dialog box showing the progress during installation, and
the dialog boxes providing information on the installation and
registration of MySQL, use `/passive' mode instead of `/quiet':


     shell> msiexec /i mysql-5.1.73.msi /passive

Regardless of the mode of the installation, installing the package in
this manner performs a 'Typical' installation, and installs the default
components into the standard location.

You can also use this method to uninstall MySQL by using the
`/uninstall' or `/x' options:


     shell> msiexec /x mysql-5.1.73.msi /uninstall

To install MySQL and configure a MySQL instance from the command line,
see *Note mysql-config-wizard-cmdline::.

For information on using MSI packages to install software automatically
using Group Policy, see How to use Group Policy to remotely install
software in Windows Server 2003
(http://support.microsoft.com/kb/816102).


File: manual.info,  Node: windows-installer-uninstalling,  Prev: windows-installer-msi-quiet,  Up: windows-using-installer

2.3.3.9 Removing MySQL When Installed from the MSI Package
..........................................................

To uninstall a MySQL where you have used the MSI packages, you must use
the `Add/Remove Programs' tool within `Control Panel'. To do this:

  1. Right-click the `start' menu and choose `Control Panel'.

  2. If the Control Panel is set to category mode (you will see `Pick a
     category' at the top of the `Control Panel' window), double-click
     `Add or Remove Programs'. If the Control is set to classic mode,
     double-click the `Add or Remove Programs' icon.

  3. Find MySQL in the list of installed software. MySQL Server is
     installed against major version numbers (MySQL 5.0, MySQL 5.1,
     etc.). Select the version that you want to remove and click
     `Remove'.

  4. You will be prompted to confirm the removal. Click `Yes' to remove
     MySQL.

When MySQL is removed using this method, only the installed components
are removed. Any database information (including the tables and data),
import or export files, log files, and binary logs produced during
execution are kept in their configured location.

If you try to install MySQL again the information will be retained and
you will be prompted to enter the password configured with the original
installation.

If you want to delete MySQL completely:

   * Delete the associated data directory. On Windows XP and Windows
     Server 2003, before MySQL 5.1.24, the default data directory would
     be located within the MySQL installation directory. On MySQL
     5.1.24 and later, the default data directory is the configured
     AppData directory, which is `C:\Documents and Settings\All
     Users\Application Data\MySQL' by default.

   * On Windows 7 and Windows Server 2008, the default data directory
     location is `C:\ProgramData\Mysql'.

     *Note*:

     The `C:\ProgramData' directory is hidden by default. You must
     change your folder options to view the hidden file. Choose
     `Organize', `Folder and search options', `Show hidden folders'.


File: manual.info,  Node: windows-notifier,  Next: mysql-config-wizard,  Prev: windows-using-installer,  Up: windows-installation

2.3.4 MySQL Notifier
--------------------

* Menu:

* windows-notifier-installation::  Remote monitoring set up and installation instructions

The MySQL Notifier is a tool that enables you to monitor and adjust the
status of your local and remote MySQL Server instances through an
indicator that resides in the system tray. The MySQL Notifier also
gives quick access to several MySQL GUI tools (such as MySQL Workbench)
through its context menu.

The MySQL Notifier is installed by MySQL Installer, and (by default)
will start-up when Microsoft Windows is started.

*Note*:

To install, download and execute the MySQL Installer
(http://dev.mysql.com/downloads/installer/), be sure the MySQL Notifier
product is selected, then proceed with the installation. See the MySQL
Installer manual
(http://dev.mysql.com/doc/refman/5.5/en/mysql-installer.html) for
additional details.

For notes detailing the changes in each release of MySQL Notifier, see
the MySQL Notifier Release Notes
(http://dev.mysql.com/doc/relnotes/mysql-notifier/en/).

Visit the MySQL Notifier forum (http://forums.mysql.com/list.php?173)
for additional MySQL Notifier help and support.

Features include:

   * Start, Stop, and Restart instances of the MySQL Server.

   * Automatically detects (and adds) new MySQL Server services.  These
     are listed under `Manage Monitored Items', and may also be
     configured.

   * The Tray icon changes, depending on the status. It's green if all
     monitored MySQL Server instances are running, or red if at least
     one service is stopped. The `Update MySQL Notifier tray icon based
     on service status' option, which dictates this behavior, is
     enabled by default for each service.

   * Links to other applications like MySQL Workbench, MySQL Installer,
     and the MySQL Utilities. For example, choosing `Configure
     Instance' will load the MySQL Workbench Server Administration
     window for that particular instance.

   * If MySQL Workbench is also installed, then the `Configure
     Instance' and `SQL Editor' options are available for local (but
     not remote) MySQL instances.

   * Monitoring of both local and remote MySQL instances.

*Note*:

Remote monitoring is available since MySQL Notifier 1.1.0.

The MySQL Notifier resides in the system tray and provides visual
status information for your MySQL Server instances. A green icon is
displayed at the top left corner of the tray icon if the current MySQL
Server is running, or a red icon if the service is stopped.

The MySQL Notifier automatically adds discovered MySQL Services on the
local machine, and each service is saved and configurable. By default,
the `Automatically add new services whose name contains' option is
enabled and set to `mysql'. Related `Notifications Options' include
being notified when new services are either discovered or experience
status changes, and are also enabled by default. And uninstalling a
service will also remove the service from the MySQL Notifier.

*Note*:

The `Automatically add new services whose name contains' option default
changed from ".*mysqld.*" to "mysql" in Notifier 1.1.0.

Clicking the system tray icon will reveal several options, as seen in
the screenshots below:

The Service Instance menu is the main MySQL Notifier window, and
enables you to Stop, Start, and Restart the MySQL Server.

FIGURE GOES HERE: MySQL Notifier Service Instance menu

The `Actions' menu includes several links to external applications (if
they are installed), and a `Refresh Status' option to manually refresh
the status of all monitored services (in both local and remote
computers) and MySQL instances.

*Note*:

The main menu will not show the `Actions' menu when there are no
services being monitored by MySQL Notifier.

*Note*:

The `Refresh Status' feature is available since MySQL Notifier 1.1.0.

FIGURE GOES HERE: MySQL Notifier Actions menu

The `Actions', `Options' menu configures MySQL Notifier and includes
options to:

   * `Use colorful status icons': Enables a colorful style of icons for
     the tray of the MySQL Notifier.

   * `Run at Windows Startup': Allows the application to be loaded when
     Microsoft Windows starts.

   * `Automatically Check For Updates Every' # Weeks: Checks for a new
     version of MySQL Notifier, and runs this check every # weeks.

   * `Automatically add new services whose name contains': The text
     used to filter services and add them automatically to the
     monitored list of the local computer running MySQL Notifier, and
     on remote computers already monitoring Windows services. monitored
     services, and also filters the list of the Microsoft Windows
     services for the `Add New Service' dialog.

     Prior to version 1.1.0, this option was named "Automatically add
     new services that match this pattern."

   * `Notify me when a service is automatically added': Will display a
     balloon notification from the taskbar when a newly discovered
     service is added to the monitored services list.

   * `Notify me when a service changes status': Will display a balloon
     notification from the taskbar when a monitored service changes its
     status.

FIGURE GOES HERE: MySQL Notifier Options menu

The `Actions', `Manage Monitored Items' menu enables you to configure
the monitored services and MySQL instances. First, with the `Services'
tab open:

FIGURE GOES HERE: MySQL Notifier Manage Services menu

The `Instances' tab is similar:

FIGURE GOES HERE: MySQL Notifier Manage Instances menu

Adding a service or instance (after clicking `Add' in the `Manage
Monitored Items' window) enables you to select a running Microsoft
Windows service or instance connection, and configure MySQL Notifier to
monitor it. Add a new service or instance by clicking service name from
the list, then `OK' to accept. Multiple services and instances may be
selected.

FIGURE GOES HERE: MySQL Notifier Adding new services

And instances:

FIGURE GOES HERE: MySQL Notifier Adding new instances

*Note*:

The `Instances' tab available since MySQL Notifier 1.1.0.


File: manual.info,  Node: windows-notifier-installation,  Prev: windows-notifier,  Up: windows-notifier

2.3.4.1 Remote monitoring set up and installation instructions
..............................................................

The MySQL Notifier uses Windows Management Instrumentation (WMI) to
manage and monitor services in remote computers running Windows XP or
later. This guide explains how it works, and how to set up your system
to monitor remote MySQL instances.

*Note*:

Remote monitoring is available since MySQL Notifier 1.1.0.

In order to configure WMI, it is important to understand that the
underlying Distributed Component Object Model (DCOM) architecture is
doing the WMI work. Specifically, MySQL Notifier is using asynchronous
notification queries on remote Microsoft Windows hosts as .NET events.
These events send an asynchronous callback to the computer running the
MySQL Notifier so it knows when a service status has changed on the
remote computer. Asynchronous notifications offer the best performance
compared to semisynchronous notifications or synchronous notifications
that use timers.

Asynchronous notifications requires the remote computer to send a
callback to the client computer (thus opening a reverse connection), so
the Windows Firewall and DCOM settings must be properly configured for
the communication to function properly.

FIGURE GOES HERE: MySQL Notifier Distributed Component Object Model
(DCOM)

Most of the common errors thrown by asynchronous WMI notifications are
related to Windows Firewall blocking the communication, or to DCOM /
WMI settings not being set up properly. For a list of common errors
with solutions, see *Note windows-notifier-installation-errors::.

The following steps are required to make WMI function. These steps are
divided between two machines. A single host computer that runs MySQL
Notifier (Computer A), and multiple remote machines that are being
monitored (Computer B).

*Computer running MySQL Notifier (Computer A)*

  1. Allow for remote administration by either editing the `Group
     Policy Editor', or using `NETSH':

     Using the `Group Policy Editor':

       1. Click `Start', click `Run', type `GPEDIT.MSC', and then click
          `OK'.

       2. Under the `Local Computer Policy' heading, double-click
          `Computer Configuration'.

       3. Double-click `Administrative Templates', then `Network',
          `Network Connections', and then `Windows Firewall'.

       4. If the computer is in the domain, then double-click `Domain
          Profile'; otherwise, double-click `Standard Profile'.

       5. Click `Windows Firewall: Allow inbound remote administration
          exception'.

       6. On the Action menu either select `Edit', or double-click the
          selection from the previous step.

       7. Check the `Enabled' radio button, and then click `OK'.

     Using the `NETSH' command:

       1. Open a command prompt window with Administrative rights (you
          can right-click the Command Prompt icon and click `Run as
          Administrator').

       2. Execute the following command:


               NETSH firewall set service RemoteAdmin enable

  2. Open the DCOM port TCP 135:

       1. Open a command prompt window with Administrative rights (you
          can right-click the Command Prompt icon and click `Run as
          Administrator') .

       2. Execute the following command:


               NETSH firewall add portopening protocol=tcp port=135 name=DCOM_TCP135

  3. Add the client application which contains the sink for the
     callback (`MySqlNotifier.exe') to the Windows Firewall Exceptions
     List (use either the Windows Firewall configuration or `NETSH'):

     Using the Windows Firewall configuration:

       1. In the Control Panel, double-click `Windows Firewall'.

       2. In the Windows Firewall window's left panel, click `Allow a
          program or feature through Windows Firewall'.

       3. In the Allowed Programs window, click `Change Settings'.

       4. If `MySqlNotifier.exe' is in the Allowed programs and
          features list, make sure it is checked for the type of
          networks the computer connects to (Private, Public or both).

       5. If `MySqlNotifier.exe' is not in the list, click `Allow
          another program...'.

       6. In the `Add a Program' window, select the `MySqlNotifier.exe'
          if it exists in the Programs list, otherwise click Browse...
          and go to the directory where `MySqlNotifier.exe' was
          installed to select it, then click `Add'.

       7. Make sure `MySqlNotifier.exe' is checked for the type of
          networks the computer connects to (Private, Public or both).

     Using the `NETSH' command:

       1. Open a command prompt window with Administrative rights (you
          can right-click the Command Prompt icon and click `Run as
          Administrator').

       2. Execute the following command, where you change
          "[YOUR_INSTALL_DIRECTORY]":


               NETSH firewall add allowedprogram program=[YOUR_INSTALL_DIRECTORY]\MySqlNotifier.exe name=MySqlNotifier

  4. If Computer B is either a member of `WORKGROUP' or is in a
     different domain that is untrusted by Computer A, then the
     callback connection (Connection 2) is created as an Anonymous
     connection. To grant Anonymous connections DCOM Remote Access
     permissions:

       1. Click `Start', click `Run', type `DCOMCNFG', and then click
          `OK'.

       2. In the Component Services dialog box, expand Component
          Services, expand Computers, and then right-click `My
          Computer' and click `Properties'.

       3. In the My Computer Properties dialog box, click the `COM
          Security' tab.

       4. Under Access Permissions, click `Edit Limits'.

       5. In the Access Permission dialog box, select `ANONYMOUS LOGON
          name' in the Group or user names box. In the Allow column
          under Permissions for User, select `Remote Access', and then
          click `OK'.

*Monitored Remote Computer (Computer B)*

If the user account that is logged into the computer running the MySQL
Notifier (Computer A) is a local administrator on the remote computer
(Computer B), such that the same account is an administrator on
Computer B, you can skip to the "Allow for remote administration" step.

Setting DCOM security to allow a non-administrator user to access a
computer remotely:

  1. Grant "DCOM remote launch" and activation permissions for a user
     or group:

       1. Click `Start', click `Run', type `DCOMCNFG', and then click
          `OK'.

       2. In the Component Services dialog box, expand Component
          Services, expand Computers, and then right-click `My
          Computer' and click `Properties'.

       3. In the My Computer Properties dialog box, click the `COM
          Security' tab.

       4. Under Access Permissions, click `Edit Limits'.

       5. In the `Launch Permission' dialog box, follow these steps if
          your name or your group does not appear in the Groups or user
          names list:

            1. In the `Launch Permission' dialog box, click `Add'.

            2. In the Select Users, Computers, or Groups dialog box,
               add your name and the group in the "Enter the object
               names to select" box, and then click `OK'.

       6. In the `Launch Permission' dialog box, select your user and
          group in the Group or user names box.  In the Allow column
          under Permissions for User, select `Remote Launch', select
          `Remote Activation', and then click `OK'.

     Grant DCOM remote access permissions:

       1. Click `Start', click `Run', type `DCOMCNFG', and then click
          `OK'.

       2. In the Component Services dialog box, expand Component
          Services, expand Computers, and then right-click `My
          Computer' and click `Properties'.

       3. In the My Computer Properties dialog box, click the `COM
          Security' tab.

       4. Under Access Permissions, click `Edit Limits'.

       5. In the Access Permission dialog box, select `ANONYMOUS LOGON
          name' in the Group or user names box. In the Allow column
          under Permissions for User, select `Remote Access', and then
          click `OK'.

  2. Allowing non-administrator users access to a specific WMI
     namespace:

       1. In the Control Panel, double-click `Administrative Tools'.

       2. In the Administrative Tools window, double-click `Computer
          Management'.

       3. In the Computer Management window, expand the `Services and
          Applications' tree and double-click the `WMI Control'.

       4. Right-click the WMI Control icon and select `Properties'.

       5. In the WMI Control Properties window, click the `Security'
          tab.

       6. In the Security tab, select the namespace and click
          `Security'.

       7. Locate the appropriate account and check `Remote Enable in
          the Permissions list'.

  3. Allow for remote administration by either editing the `Group
     Policy Editor' or using `NETSH':

     Using the `Group Policy Editor':

       1. Click `Start', click `Run', type `GPEDIT.MSC', and then click
          `OK'.

       2. Under the Local Computer Policy heading, double-click
          `Computer Configuration'.

       3. Double-click `Administrative Templates', then `Network',
          `Network Connections', and then `Windows Firewall'.

       4. If the computer is in the domain, then double-click `Domain
          Profile'; otherwise, double-click `Standard Profile'.

       5. Click `Windows Firewall: Allow inbound remote administration
          exception'.

       6. On the Action menu either select `Edit', or double-click the
          selection from the previous step.

       7. Check the `Enabled' radio button, and then click `OK'.

     Using the `NETSH' command:

       1. Open a command prompt window with Administrative rights (you
          can right-click the Command Prompt icon and click Run as
          Administrator).

       2. Execute the following command:


               NETSH firewall set service RemoteAdmin enable

  4. Now, be sure the user you are logging in with uses the `Name'
     value and not the `Full Name' value:

       1. In the `Control Panel', double-click `Administrative Tools'.

       2. In the `Administrative Tools' window, double-click `Computer
          Management'.

       3. In the `Computer Management' window, expand the `System Tools
          then Local Users and Groups'.

       4. Click the `Users' node, and on the right side panel locate
          your user and make sure it uses the `Name' value to connect,
          and not the `Full Name' value.

  5. If the remote computer is running on `Windows XP Professional',
     make sure that remote logins are not being forcefully changed to
     the guest account user (also known as `ForceGuest'), which is
     enabled by default on computers that are not attached to a domain.

       1. Click Start, click Run, type `SECPOL.MSC', and then click
          `OK'.

       2. Under the `Local Policies' node, double-click `Security
          Options'.

       3. Select `Network Access: Sharing and security model for local
          accounts' and save.

*Common Errors*

   * `0x80070005'

        * DCOM Security was not configured properly (see Computer B,
          the `Setting DCOM security...' step).

        * The remote computer (Computer B) is a member of WORKGROUP or
          is in a domain that is untrusted by the client computer
          (Computer A) (see Computer A, the `Grant Anonymous
          connections DCOM Remote Access permissions' step).

   * `0x8007000E'

        * The remote computer (Computer B) is a member of WORKGROUP or
          is in a domain that is untrusted by the client computer
          (Computer A) (see Computer A, the `Grant Anonymous
          connections DCOM Remote Access permissions' step).

   * `0x80041003'

        * Access to the remote WMI namespace was not configured
          properly (see Computer B, the `Allowing non-administrator
          users access to a specific WMI namespace' step).

   * `0x800706BA'

        * The DCOM port is not open on the client computers (Computer
          A) firewall. See the `Open the DCOM port TCP 135' step for
          Computer A.

        * The remote computer (Computer B) is inaccessible because its
          network location is set to Public. Make sure you can access
          it through the Windows Explorer.


File: manual.info,  Node: mysql-config-wizard,  Next: windows-install-archive,  Prev: windows-notifier,  Up: windows-installation

2.3.5 Using the MySQL Server Instance Config Wizard
---------------------------------------------------

* Menu:

* mysql-config-wizard-starting::  Starting the MySQL Server Instance Config Wizard
* mysql-config-wizard-maintenance::  MySQL Server Instance Config Wizard: Choosing a Maintenance Option
* mysql-config-wizard-configuration-type::  MySQL Server Instance Config Wizard: Choosing a Configuration Type
* mysql-config-wizard-server-type::  MySQL Server Instance Config Wizard: The Server Type Dialog
* mysql-config-wizard-database-usage::  MySQL Server Instance Config Wizard: The Database Usage Dialog
* mysql-config-wizard-tablespace::  MySQL Server Instance Config Wizard: The InnoDB Tablespace Dialog
* mysql-config-wizard-connections::  MySQL Server Instance Config Wizard: The Concurrent Connections Dialog
* mysql-config-wizard-networking::  MySQL Server Instance Config Wizard: The Networking and Strict Mode Options Dialog
* mysql-config-wizard-character-set::  MySQL Server Instance Config Wizard: The Character Set Dialog
* mysql-config-wizard-service::  MySQL Server Instance Config Wizard: The Service Options Dialog
* mysql-config-wizard-security::  MySQL Server Instance Config Wizard: The Security Options Dialog
* mysql-config-wizard-confirmation::  MySQL Server Instance Config Wizard: The Confirmation Dialog
* mysql-config-wizard-cmdline::  MySQL Server Instance Config Wizard: Creating an Instance from the Command Line

The MySQL Server Instance Config Wizard helps automate the process of
configuring your server. It creates a custom MySQL configuration file
(`my.ini' or `my.cnf') by asking you a series of questions and then
applying your responses to a template to generate the configuration
file that is tuned to your installation.

The complete and essential MSI installation packages include the MySQL
Server Instance Config Wizard in the MySQL 5.1 server. The MySQL Server
Instance Config Wizard is only available for Windows.

The workflow sequence for using the MySQL Server Instance Config Wizard
is shown in the figure below:

FIGURE GOES HERE: MySQL Server Instance Config Wizard Workflow


File: manual.info,  Node: mysql-config-wizard-starting,  Next: mysql-config-wizard-maintenance,  Prev: mysql-config-wizard,  Up: mysql-config-wizard

2.3.5.1 Starting the MySQL Server Instance Config Wizard
........................................................

The MySQL Server Instance Config Wizard is normally started as part of
the installation process. You should only need to run the MySQL Server
Instance Config Wizard again when you need to change the configuration
parameters of your server.

If you chose not to open a port prior to installing MySQL on Windows
Vista or newer, you can choose to use the MySQL Server Instance Config
Wizard after installation. However, you must open a port in the Windows
Firewall. To do this see the instructions given in *Note
mysql-install-wizard-starting::. Rather than opening a port, you also
have the option of adding MySQL as a program that bypasses the Windows
Firewall. One or the other option is sufficient--you need not do both.
Additionally, when running the MySQL Server Config Wizard on Windows
Vista or newer, ensure that you are logged in as a user with
administrative rights.

MySQL Server Instance Config Wizard

You can launch the MySQL Config Wizard by clicking the `MySQL Server
Instance Config Wizard' entry in the `MySQL' section of the Windows
`Start' menu.

Alternatively, you can navigate to the `bin' directory of your MySQL
installation and launch the `MySQLInstanceConfig.exe' file directly.

The MySQL Server Instance Config Wizard places the `my.ini' file in the
installation directory for the MySQL server. This helps associate
configuration files with particular server instances.

To ensure that the MySQL server knows where to look for the `my.ini'
file, an argument similar to this is passed to the MySQL server as part
of the service installation:


     --defaults-file="C:\PROGRAM FILES\MYSQL\MYSQL SERVER 5.1\my.ini"

Here, C:\PROGRAM FILES\MYSQL\MYSQL SERVER 5.1 is replaced with the
installation path to the MySQL Server. The `--defaults-file' option
instructs the MySQL server to read the specified file for configuration
options when it starts.

Apart from making changes to the `my.ini' file by running the MySQL
Server Instance Config Wizard again, you can modify it by opening it
with a text editor and making any necessary changes. You can also
modify the server configuration with the
http://www.mysql.com/products/administrator/ utility. For more
information about server configuration, see *Note server-options::.

MySQL clients and utilities such as the *Note `mysql': mysql.  and
*Note `mysqldump': mysqldump. command-line clients are not able to
locate the `my.ini' file located in the server installation directory.
To configure the client and utility applications, create a new `my.ini'
file in the Windows installation directory (for example, `C:\WINDOWS').

Under Windows Server 2003, Windows Server 2000, Windows XP, and Windows
Vista, MySQL Server Instance Config Wizard will configure MySQL to work
as a Windows service. To start and stop MySQL you use the `Services'
application that is supplied as part of the Windows Administrator Tools.


File: manual.info,  Node: mysql-config-wizard-maintenance,  Next: mysql-config-wizard-configuration-type,  Prev: mysql-config-wizard-starting,  Up: mysql-config-wizard

2.3.5.2 MySQL Server Instance Config Wizard: Choosing a Maintenance Option
..........................................................................

If the MySQL Server Instance Config Wizard detects an existing
configuration file, you have the option of either reconfiguring your
existing server, or removing the server instance by deleting the
configuration file and stopping and removing the MySQL service.

To reconfigure an existing server, choose the `Re-configure Instance'
option and click the `Next' button. Any existing configuration file is
not overwritten, but renamed (within the same directory) using a
timestamp (Windows) or sequential number (Linux). To remove the
existing server instance, choose the `Remove Instance' option and click
the `Next' button.

If you choose the `Remove Instance' option, you advance to a
confirmation window. Click the `Execute' button. The MySQL Server Config
Wizard stops and removes the MySQL service, and then deletes the
configuration file. The server installation and its `data' folder are
not removed.

If you choose the `Re-configure Instance' option, you advance to the
`Configuration Type' dialog where you can choose the type of
installation that you wish to configure.


File: manual.info,  Node: mysql-config-wizard-configuration-type,  Next: mysql-config-wizard-server-type,  Prev: mysql-config-wizard-maintenance,  Up: mysql-config-wizard

2.3.5.3 MySQL Server Instance Config Wizard: Choosing a Configuration Type
..........................................................................

When you start the MySQL Server Instance Config Wizard for a new MySQL
installation, or choose the `Re-configure Instance' option for an
existing installation, you advance to the `Configuration Type' dialog.

MySQL Server Instance Config Wizard: Configuration Type

There are two configuration types available: `Detailed Configuration'
and `Standard Configuration'. The `Standard Configuration' option is
intended for new users who want to get started with MySQL quickly
without having to make many decisions about server configuration. The
`Detailed Configuration' option is intended for advanced users who want
more fine-grained control over server configuration.

If you are new to MySQL and need a server configured as a single-user
developer machine, the `Standard Configuration' should suit your needs.
Choosing the `Standard Configuration' option causes the MySQL Config
Wizard to set all configuration options automatically with the
exception of `Service Options' and `Security Options'.

The `Standard Configuration' sets options that may be incompatible with
systems where there are existing MySQL installations. If you have an
existing MySQL installation on your system in addition to the
installation you wish to configure, the `Detailed Configuration' option
is recommended.

To complete the `Standard Configuration', please refer to the sections
on `Service Options' and `Security Options' in *Note
mysql-config-wizard-service::, and *Note
mysql-config-wizard-security::, respectively.


File: manual.info,  Node: mysql-config-wizard-server-type,  Next: mysql-config-wizard-database-usage,  Prev: mysql-config-wizard-configuration-type,  Up: mysql-config-wizard

2.3.5.4 MySQL Server Instance Config Wizard: The Server Type Dialog
...................................................................

There are three different server types available to choose from.  The
server type that you choose affects the decisions that the MySQL Server
Instance Config Wizard makes with regard to memory, disk, and processor
usage.

MySQL Server Instance Config Wizard: Server Type

   * `Developer Machine': Choose this option for a typical desktop
     workstation where MySQL is intended only for personal use. It is
     assumed that many other desktop applications are running. The
     MySQL server is configured to use minimal system resources.

   * `Server Machine': Choose this option for a server machine where
     the MySQL server is running alongside other server applications
     such as FTP, email, and Web servers. The MySQL server is
     configured to use a moderate portion of the system resources.

   * `Dedicated MySQL Server Machine': Choose this option for a server
     machine that is intended to run only the MySQL server. It is
     assumed that no other applications are running. The MySQL server
     is configured to use all available system resources.

*Note*:

By selecting one of the preconfigured configurations, the values and
settings of various options in your `my.cnf' or `my.ini' will be
altered accordingly. The default values and options as described in the
reference manual may therefore be different to the options and values
that were created during the execution of the Config Wizard.


File: manual.info,  Node: mysql-config-wizard-database-usage,  Next: mysql-config-wizard-tablespace,  Prev: mysql-config-wizard-server-type,  Up: mysql-config-wizard

2.3.5.5 MySQL Server Instance Config Wizard: The Database Usage Dialog
......................................................................

The `Database Usage' dialog enables you to indicate the storage engines
that you expect to use when creating MySQL tables. The option you
choose determines whether the `InnoDB' storage engine is available and
what percentage of the server resources are available to `InnoDB'.

MySQL Server Instance Config Wizard: Usage Dialog

   * `Multifunctional Database': This option enables both the `InnoDB'
     and `MyISAM' storage engines and divides resources evenly between
     the two. This option is recommended for users who use both storage
     engines on a regular basis.

   * `Transactional Database Only': This option enables both the
     `InnoDB' and `MyISAM' storage engines, but dedicates most server
     resources to the `InnoDB' storage engine. This option is
     recommended for users who use `InnoDB' almost exclusively and make
     only minimal use of `MyISAM'.

   * `Non-Transactional Database Only': This option disables the
     `InnoDB' storage engine completely and dedicates all server
     resources to the `MyISAM' storage engine. This option is
     recommended for users who do not use `InnoDB'.

The Config Wizard uses a template to generate the server configuration
file. The `Database Usage' dialog sets one of the following option
strings:


     Multifunctional Database:        MIXED
     Transactional Database Only:     INNODB
     Non-Transactional Database Only: MYISAM

When these options are processed through the default template
(my-template.ini) the result is:


     Multifunctional Database:
     default-storage-engine=InnoDB
     _myisam_pct=50

     Transactional Database Only:
     default-storage-engine=InnoDB
     _myisam_pct=5

     Non-Transactional Database Only:
     default-storage-engine=MyISAM
     _myisam_pct=100
     skip-innodb

The `_myisam_pct' value is used to calculate the percentage of
resources dedicated to `MyISAM'. The remaining resources are allocated
to `InnoDB'.


File: manual.info,  Node: mysql-config-wizard-tablespace,  Next: mysql-config-wizard-connections,  Prev: mysql-config-wizard-database-usage,  Up: mysql-config-wizard

2.3.5.6 MySQL Server Instance Config Wizard: The InnoDB Tablespace Dialog
.........................................................................

Some users may want to locate the `InnoDB' tablespace files in a
different location than the MySQL server data directory. Placing the
tablespace files in a separate location can be desirable if your system
has a higher capacity or higher performance storage device available,
such as a RAID storage system.

MySQL Server Instance Config Wizard: InnoDB Data Tablespace

To change the default location for the `InnoDB' tablespace files,
choose a new drive from the drop-down list of drive letters and choose
a new path from the drop-down list of paths. To create a custom path,
click the `...' button.

If you are modifying the configuration of an existing server, you must
click the `Modify' button before you change the path. In this situation
you must move the existing tablespace files to the new location
manually before starting the server.


File: manual.info,  Node: mysql-config-wizard-connections,  Next: mysql-config-wizard-networking,  Prev: mysql-config-wizard-tablespace,  Up: mysql-config-wizard

2.3.5.7 MySQL Server Instance Config Wizard: The Concurrent Connections Dialog
..............................................................................

To prevent the server from running out of resources, it is important to
limit the number of concurrent connections to the MySQL server that can
be established. The `Concurrent Connections' dialog enables you to
choose the expected usage of your server, and sets the limit for
concurrent connections accordingly. It is also possible to set the
concurrent connection limit manually.

MySQL Server Instance Config Wizard: Connections

   * `Decision Support (DSS)/OLAP': Choose this option if your server
     does not require a large number of concurrent connections. The
     maximum number of connections is set at 100, with an average of 20
     concurrent connections assumed.

   * `Online Transaction Processing (OLTP)': Choose this option if your
     server requires a large number of concurrent connections. The
     maximum number of connections is set at 500.

   * `Manual Setting': Choose this option to set the maximum number of
     concurrent connections to the server manually. Choose the number
     of concurrent connections from the drop-down box provided, or
     enter the maximum number of connections into the drop-down box if
     the number you desire is not listed.


File: manual.info,  Node: mysql-config-wizard-networking,  Next: mysql-config-wizard-character-set,  Prev: mysql-config-wizard-connections,  Up: mysql-config-wizard

2.3.5.8 MySQL Server Instance Config Wizard: The Networking and Strict Mode Options Dialog
..........................................................................................

Use the `Networking Options' dialog to enable or disable TCP/IP
networking and to configure the port number that is used to connect to
the MySQL server.

MySQL Server Instance Config Wizard: Network Configuration

TCP/IP networking is enabled by default. To disable TCP/IP networking,
uncheck the box next to the `Enable TCP/IP Networking' option.

Port 3306 is used by default. To change the port used to access MySQL,
choose a new port number from the drop-down box or type a new port
number directly into the drop-down box. If the port number you choose
is in use, you are prompted to confirm your choice of port number.

Set the `Server SQL Mode' to either enable or disable strict mode.
Enabling strict mode (default) makes MySQL behave more like other
database management systems. _If you run applications that rely on
MySQL's old `forgiving' behavior, make sure to either adapt those
applications or to disable strict mode._ For more information about
strict mode, see *Note sql-mode::.


File: manual.info,  Node: mysql-config-wizard-character-set,  Next: mysql-config-wizard-service,  Prev: mysql-config-wizard-networking,  Up: mysql-config-wizard

2.3.5.9 MySQL Server Instance Config Wizard: The Character Set Dialog
.....................................................................

The MySQL server supports multiple character sets and it is possible to
set a default server character set that is applied to all tables,
columns, and databases unless overridden. Use the `Character Set'
dialog to change the default character set of the MySQL server.

MySQL Server Instance Config Wizard: Character Set

   * `Standard Character Set': Choose this option if you want to use
     `latin1' as the default server character set. `latin1' is used for
     English and many Western European languages.

   * `Best Support For Multilingualism': Choose this option if you want
     to use `utf8' as the default server character set.  This is a
     Unicode character set that can store characters from many
     different languages.

   * `Manual Selected Default Character Set / Collation': Choose this
     option if you want to pick the server's default character set
     manually. Choose the desired character set from the provided
     drop-down list.


File: manual.info,  Node: mysql-config-wizard-service,  Next: mysql-config-wizard-security,  Prev: mysql-config-wizard-character-set,  Up: mysql-config-wizard

2.3.5.10 MySQL Server Instance Config Wizard: The Service Options Dialog
........................................................................

On Windows platforms, the MySQL server can be installed as a Windows
service. When installed this way, the MySQL server can be started
automatically during system startup, and even restarted automatically
by Windows in the event of a service failure.

The MySQL Server Instance Config Wizard installs the MySQL server as a
service by default, using the service name `MySQL'. If you do not wish
to install the service, uncheck the box next to the `Install As Windows
Service' option. You can change the service name by picking a new
service name from the drop-down box provided or by entering a new
service name into the drop-down box.

*Note*:

Service names can include any legal character except forward (`/') or
backward (`\') slashes, and must be less than 256 characters long.

*Warning*:

If you are installing multiple versions of MySQL onto the same machine,
you _must_ choose a different service name for each version that you
install. If you do not choose a different service for each installed
version then the service manager information will be inconsistent and
this will cause problems when you try to uninstall a previous version.

If you have already installed multiple versions using the same service
name, you must manually edit the contents of the
`HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services' parameters
within the Windows registry to update the association of the service
name with the correct server version.

Typically, when installing multiple versions you create a service name
based on the version information. For example, you might install MySQL
5.x as `mysql5', or specific versions such as MySQL 5.1.30 as
`mysql50130'.

To install the MySQL server as a service but not have it started
automatically at startup, uncheck the box next to the `Launch the MySQL
Server Automatically' option.


File: manual.info,  Node: mysql-config-wizard-security,  Next: mysql-config-wizard-confirmation,  Prev: mysql-config-wizard-service,  Up: mysql-config-wizard

2.3.5.11 MySQL Server Instance Config Wizard: The Security Options Dialog
.........................................................................

The content of the security options portion of the MySQL Server
Instance Configuration Wizard will depend on whether this is a new
installation, or modifying an existing installation.

   * *Setting the root password for a new installation*

     _It is strongly recommended that you set a `root' password for
     your MySQL server_, and the MySQL Server Instance Config Wizard
     requires by default that you do so. If you do not wish to set a
     `root' password, uncheck the box next to the `Modify Security
     Settings' option.

     *Note*:

     If you have previously installed MySQL, but not deleted the data
     directory associated with the previous installation, you may be
     prompted to provide the current root password. The password will
     be the one configured with your old data directory. If you do not
     want to use this data, or do not know the root password, you should
     cancel the installation, delete the previous installation data,
     and then restart the installation process. For more information on
     deleting MySQL data on Microsoft Windows, see *Note
     windows-installer-uninstalling::.

     MySQL Server Instance Config Wizard: Security

   * To set the `root' password, enter the desired password into both
     the `New root password' and `Confirm' boxes.

     *Setting the root password for an existing installation*

     If you are modifying the configuration of an existing
     configuration, or you are installing an upgrade and the MySQL
     Server Instance Configuration Wizard has detected an existing
     MySQL system, then you must enter the existing password for `root'
     before changing the configuration information.

     MySQL Server Instance Config Wizard: Security (Existing
     Installation)

     If you want to change the current `root' password, enter the
     desired new password into both the `New root password' and
     `Confirm' boxes.

To permit `root' logins from across the network, check the box next to
the `Enable root access from remote machines' option. This decreases
the security of your `root' account.

To create an anonymous user account, check the box next to the `Create
An Anonymous Account' option.  Creating an anonymous account can
decrease server security and cause login and permission difficulties.
For this reason, it is not recommended.


File: manual.info,  Node: mysql-config-wizard-confirmation,  Next: mysql-config-wizard-cmdline,  Prev: mysql-config-wizard-security,  Up: mysql-config-wizard

2.3.5.12 MySQL Server Instance Config Wizard: The Confirmation Dialog
.....................................................................

The final dialog in the MySQL Server Instance Config Wizard is the
`Confirmation Dialog'. To start the configuration process, click the
`Execute' button. To return to a previous dialog, click the `Back'
button. To exit the MySQL Server Instance Config Wizard without
configuring the server, click the `Cancel' button.

MySQL Server Instance Config Wizard: Confirmation

After you click the `Execute' button, the MySQL Server Instance Config
Wizard performs a series of tasks and displays the progress onscreen as
the tasks are performed.

The MySQL Server Instance Config Wizard first determines configuration
file options based on your choices using a template prepared by MySQL
developers and engineers. This template is named `my-template.ini' and
is located in your server installation directory.

The MySQL Config Wizard then writes these options to the corresponding
configuration file.

If you chose to create a service for the MySQL server, the MySQL Server
Instance Config Wizard creates and starts the service. If you are
reconfiguring an existing service, the MySQL Server Instance Config
Wizard restarts the service to apply your configuration changes.

If you chose to set a `root' password, the MySQL Config Wizard connects
to the server, sets your new `root' password, and applies any other
security settings you may have selected.

After the MySQL Server Instance Config Wizard has completed its tasks,
it displays a summary. Click the `Finish' button to exit the MySQL
Server Config Wizard.


File: manual.info,  Node: mysql-config-wizard-cmdline,  Prev: mysql-config-wizard-confirmation,  Up: mysql-config-wizard

2.3.5.13 MySQL Server Instance Config Wizard: Creating an Instance from the Command Line
........................................................................................

In addition to using the GUI interface to the MySQL Server Instance
Config Wizard, you can also create instances automatically from the
command line.

To use the MySQL Server Instance Config Wizard on the command line, you
need to use the `MySQLInstanceConfig.exe' command that is installed
with MySQL in the `bin' directory within the installation directory.
`MySQLInstanceConfig.exe' takes a number of command-line arguments the
set the properties that would normally be selected through the GUI
interface, and then creates a new configuration file (`my.ini') by
combining these selections with a template configuration file to
produce the working configuration file.

The main command line options are provided in the table below.  Some of
the options are required, while some options are optional.

*MySQL Server Instance Config Wizard Command Line Options*

Option         Description
Required       
Parameters     
`-nPRODUCTNAME'The name of the instance when installed
`-pPATH'       Path of the base directory for
               installation. This is equivalent to the
               directory when using the `basedir'
               configuration parameter
`-vVERSION'    The version tag to use for this
               installation
Action to      
Perform        
`-i'           Install an instance
`-r'           Remove an instance
`-s'           Stop an existing instance
`-q'           Perform the operation quietly
`-lFILENAME'   Sae the installation progress in a logfile
Config File    
to Use         
`-tFILENAME'   Path to the template config file that will
               be used to generate the installed
               configuration file
`-cFILENAME'   Path to a config file to be generated

The `-t' and `-c' options work together to set the configuration
parameters for a new instance.  The `-t' option specifies the template
configuration file to use as the basic configuration, which are then
merged with the configuration parameters generated by the MySQL Server
Instance Config Wizard into the configuration file specified by the
`-c' option.

A sample template file, `my-template.ini' is provided in the toplevel
MySQL installation directory. The file contains elements are replaced
automatically by the MySQL Server Instance Config Wizard during
configuration.

If you specify a configuration file that already exists, the existing
configuration file will be saved in the file with the original, with
the date and time added. For example, the `mysql.ini' will be copied to
`mysql 2009-10-27 1646.ini.bak'.

The parameters that you can specify on the command line are listed in
the table below.

*MySQL Server Instance Config Wizard Parameters*

Parameter      Description
`ServiceName=$'Specify the name of the service to be
               created
`AddBinToPath={yesSpecifies whether to add the binary
| no}'         directory of MySQL to the standard `PATH'
               environment variable
`ServerType={DEVELOPMENTSpecify the server type. For more
| SERVER |     information, see *Note
DEDICATED}'    mysql-config-wizard-server-type::
`DatabaseType={MIXEDSpecify the default database type. For
| INNODB |     more information, see *Note
MYISAM}'       mysql-config-wizard-database-usage::
`ConnectionUsage={DSSSpecify the type of connection support,
| OLTP}'       this automates the setting for the number
               of concurrent connections (see the
               `ConnectionCount' parameter). For more
               information, see *Note
               mysql-config-wizard-connections::
`ConnectionCount=#'Specify the number of concurrent
               connections to support. For more
               information, see *Note
               mysql-config-wizard-server-type::
`SkipNetworking={yesSpecify whether network support should be
| no}'         supported. Specifying `yes' disables
               network access altogether
`Port=#'       Specify the network port number to use for
               network connections. For more information,
               see *Note mysql-config-wizard-networking::
`StrictMode={yesSpecify whether to use the `strict' SQL
| no}'         mode. For more information, see *Note
               mysql-config-wizard-networking::
`Charset=$'    Specify the default character set. For
               more information, see *Note
               mysql-config-wizard-character-set::
`RootPassword=$'Specify the root password
`RootCurrentPassword=$'Specify the current root password then
               stopping or reconfiguring an existing
               service

*Note*:

When specifying options on the command line, you can enclose the entire
command-line option and the value you are specifying using double
quotation marks. This enables you to use spaces in the options. For
example, `"-cC:\mysql.ini"'.

The following command installs a MySQL Server 5.1 instance from the
directory `C:\Program Files\MySQL\MySQL Server 5.1' using the service
name `MySQL51' and setting the root password to 1234.


     shell> MySQLInstanceConfig.exe -i -q "-lC:\mysql_install_log.txt" »
        "-nMySQL Server 5.1" "-pC:\Program Files\MySQL\MySQL Server 5.1" -v5.1.73 »
        "-tmy-template.ini" "-cC:\mytest.ini" ServerType=DEVELOPMENT DatabaseType=MIXED »
        ConnectionUsage=DSS Port=3311 ServiceName=MySQL51 RootPassword=1234

In the above example, a log file will be generated in
`mysql_install_log.txt' containing the information about the instance
creation process. The log file generated by the above example is shown
below:


     Welcome to the MySQL Server Instance Configuration Wizard 1.0.16.0
     Date: 2009-10-27 17:07:21

     Installing service ...

     Product Name:         MySQL Server 5.1
     Version:              5.1.73
     Installation Path:    C:\Program Files\MySQL\MySQL Server 5.1\

     Creating configuration file C:\mytest.ini using template my-template.ini.
     Options:
     DEVELOPMENT
     MIXED
     DSS
     STRICTMODE

     Variables:
     port: 3311
     default-character-set: latin1
     basedir: "C:/Program Files/MySQL/MySQL Server 5.1/"
     datadir: "C:/Program Files/MySQL/MySQL Server 5.1/Data/"

     Creating Windows service entry.
     Service name: "MySQL51"
     Parameters:   "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld" --defaults-file="C:\mytest.ini" MySQL51.
     Windows service MySQL51 installed.

When using the command line, the return values in the following table
indicate an error performing the specified option.

*Return Value from MySQL Server Instance Config Wizard*

Value          Description
2              Configuration template file cannot be found
3              The Windows service entry cannot be created
4              Could not connect to the Service Control Manager
5              The MySQL service cannot be started
6              The MySQL service cannot be stopped
7              The security settings cannot be applied
8              The configuration file cannot be written
9              The Windows service entry cannot be removed

You can perform an installation of MySQL automatically using the MSI
package. For more information, see *Note windows-installer-msi-quiet::.


File: manual.info,  Node: windows-install-archive,  Next: windows-troubleshooting,  Prev: mysql-config-wizard,  Up: windows-installation

2.3.6 Installing MySQL on Microsoft Windows Using a noinstall Zip Archive
-------------------------------------------------------------------------

* Menu:

* windows-extract-archive::      Extracting the Install Archive
* windows-create-option-file::   Creating an Option File
* windows-select-server::        Selecting a MySQL Server Type
* windows-server-first-start::   Starting MySQL Server on Microsoft Windows for the First Time
* windows-start-command-line::   Starting MySQL Server from the Windows Command Line
* mysql-installation-windows-path::  Customizing the PATH for MySQL Tools
* windows-start-service::        Starting MySQL Server as a Microsoft Windows Service
* windows-testing::              Testing The MySQL Server Installation on Microsoft Windows

Users who are installing from the `noinstall' package can use the
instructions in this section to manually install MySQL. The process for
installing MySQL from a Zip archive is as follows:

  1. Extract the archive to the desired install directory

  2. Create an option file

  3. Choose a MySQL server type

  4. Start the MySQL server

  5. Secure the default user accounts

This process is described in the sections that follow.


File: manual.info,  Node: windows-extract-archive,  Next: windows-create-option-file,  Prev: windows-install-archive,  Up: windows-install-archive

2.3.6.1 Extracting the Install Archive
......................................

To install MySQL manually, do the following:

  1. If you are upgrading from a previous version please refer to *Note
     windows-upgrading::, before beginning the upgrade process.

  2. Make sure that you are logged in as a user with administrator
     privileges.

  3. Choose an installation location. Traditionally, the MySQL server
     is installed in `C:\mysql'. The MySQL Installation Wizard installs
     MySQL under `C:\Program Files\MySQL'. If you do not install MySQL
     at `C:\mysql', you must specify the path to the install directory
     during startup or in an option file. See *Note
     windows-create-option-file::.

  4. Extract the install archive to the chosen installation location
     using your preferred Zip archive tool. Some tools may extract the
     archive to a folder within your chosen installation location. If
     this occurs, you can move the contents of the subfolder into the
     chosen installation location.


File: manual.info,  Node: windows-create-option-file,  Next: windows-select-server,  Prev: windows-extract-archive,  Up: windows-install-archive

2.3.6.2 Creating an Option File
...............................

If you need to specify startup options when you run the server, you can
indicate them on the command line or place them in an option file. For
options that are used every time the server starts, you may find it
most convenient to use an option file to specify your MySQL
configuration. This is particularly true under the following
circumstances:

   * The installation or data directory locations are different from
     the default locations (`C:\Program Files\MySQL\MySQL Server 5.1'
     and `C:\Program Files\MySQL\MySQL Server 5.1\data').

   * You need to tune the server settings, such as memory, cache, or
     InnoDB configuration information.

When the MySQL server starts on Windows, it looks for option files in
several locations, such as the Windows directory, `C:\', and the MySQL
installation directory (for the full list of locations, see *Note
option-files::). The Windows directory typically is named something
like `C:\WINDOWS'. You can determine its exact location from the value
of the `WINDIR' environment variable using the following command:


     C:\> echo %WINDIR%

MySQL looks for options in each location first in the `my.ini' file,
and then in the `my.cnf' file. However, to avoid confusion, it is best
if you use only one file. If your PC uses a boot loader where `C:' is
not the boot drive, your only option is to use the `my.ini' file.
Whichever option file you use, it must be a plain text file.

You can also make use of the example option files included with your
MySQL distribution; see *Note server-configuration-defaults::.

An option file can be created and modified with any text editor, such
as Notepad. For example, if MySQL is installed in `E:\mysql' and the
data directory is in `E:\mydata\data', you can create an option file
containing a `[mysqld]' section to specify values for the `basedir' and
`datadir' options:


     [mysqld]
     # set basedir to your installation path
     basedir=E:/mysql
     # set datadir to the location of your data directory
     datadir=E:/mydata/data

Note that Windows path names are specified in option files using
(forward) slashes rather than backslashes. If you do use backslashes,
double them:


     [mysqld]
     # set basedir to your installation path
     basedir=E:\\mysql
     # set datadir to the location of your data directory
     datadir=E:\\mydata\\data

The rules for use of backslash in option file values are given in *Note
option-files::.

In MySQL 5.1.23 and earlier, the MySQL installer places the data
directory directly under the directory where you install MySQL.  On
MySQL 5.1.24 and later, the data directory is located within the
`AppData' directory for the user running MySQL.

If you would like to use a data directory in a different location, you
should copy the entire contents of the `data' directory to the new
location. For example, if you want to use `E:\mydata' as the data
directory instead, you must do two things:

  1. Move the entire `data' directory and all of its contents from the
     default location (for example `C:\Program Files\MySQL\MySQL Server
     5.1\data') to `E:\mydata'.

  2. Use a `--datadir' option to specify the new data directory
     location each time you start the server.


File: manual.info,  Node: windows-select-server,  Next: windows-server-first-start,  Prev: windows-create-option-file,  Up: windows-install-archive

2.3.6.3 Selecting a MySQL Server Type
.....................................

The following table shows the available servers for Windows in MySQL
5.1.20 and earlier.

*mysqld binary types for Microsoft Windows up to MySQL 5.1.20*

Binary         Description
*Note          Optimized binary with named-pipe support
`mysqld-nt':   
mysqld.        
*Note          Optimized binary without named-pipe support
`mysqld':      
mysqld.        
*Note          Like *Note `mysqld-nt': mysqld, but compiled with full
`mysqld-debug':debugging and automatic memory allocation checking
mysqld.        

The following table shows the available servers for Windows in MySQL
5.1.21 and later.

*mysqld binary types for Microsoft Windows MySQL 5.1.21 and later*

Binary         Description
*Note          Optimized binary with named-pipe support
`mysqld':      
mysqld.        
*Note          Like *Note `mysqld': mysqld, but compiled with full
`mysqld-debug':debugging and automatic memory allocation checking
mysqld.        

All of the preceding binaries are optimized for modern Intel
processors, but should work on any Intel i386-class or higher processor.

Each of the servers in a distribution support the same set of storage
engines. The *Note `SHOW ENGINES': show-engines.  statement displays
which engines a given server supports.

All Windows MySQL 5.1 servers have support for symbolic linking of
database directories.

MySQL supports TCP/IP on all Windows platforms. MySQL servers on
Windows support named pipes as indicated in the following list.
However, the default is to use TCP/IP regardless of platform.  (Named
pipes are slower than TCP/IP in many Windows configurations.)

Use of named pipes is subject to these conditions:

   * Named pipes are enabled only if you start the server with the
     `--enable-named-pipe' option. It is necessary to use this option
     explicitly because some users have experienced problems with
     shutting down the MySQL server when named pipes were used.

   * For MySQL 5.1.20 and earlier, named-pipe connections are permitted
     only by the *Note `mysqld-nt': mysqld. and *Note `mysqld-debug':
     mysqld. servers. For MySQL 5.1.21 and later, the *Note `mysqld':
     mysqld. and *Note `mysqld-debug': mysqld. servers both contain
     support for named-pipe connections.

*Note*:

Most of the examples in this manual use *Note `mysqld': mysqld. as the
server name. If you choose to use a different server, such as *Note
`mysqld-nt': mysqld.  or *Note `mysqld-debug': mysqld, make the
appropriate substitutions in the commands that are shown in the
examples.


File: manual.info,  Node: windows-server-first-start,  Next: windows-start-command-line,  Prev: windows-select-server,  Up: windows-install-archive

2.3.6.4 Starting MySQL Server on Microsoft Windows for the First Time
.....................................................................

This section gives a general overview of starting the MySQL server. The
following sections provide more specific information for starting the
MySQL server from the command line or as a Windows service.

The information here applies primarily if you installed MySQL using the
`Noinstall' version, or if you wish to configure and test MySQL
manually rather than with the GUI tools.

The examples in these sections assume that MySQL is installed under the
default location of `C:\Program Files\MySQL\MySQL Server 5.1'. Adjust
the path names shown in the examples if you have MySQL installed in a
different location.

Clients have two options. They can use TCP/IP, or they can use a named
pipe if the server supports named-pipe connections.

MySQL for Windows also supports shared-memory connections if the server
is started with the `--shared-memory' option. Clients can connect
through shared memory by using the `--protocol=MEMORY' option.

For information about which server binary to run, see *Note
windows-select-server::.

Testing is best done from a command prompt in a console window (or `DOS
window'). In this way you can have the server display status messages
in the window where they are easy to see. If something is wrong with
your configuration, these messages make it easier for you to identify
and fix any problems.

To start the server, enter this command:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld" --console

For a server that includes `InnoDB' support, you should see the
messages similar to those following as it starts (the path names and
sizes may differ):


     InnoDB: The first specified datafile c:\ibdata\ibdata1 did not exist:
     InnoDB: a new database to be created!
     InnoDB: Setting file c:\ibdata\ibdata1 size to 209715200
     InnoDB: Database physically writes the file full: wait...
     InnoDB: Log file c:\iblogs\ib_logfile0 did not exist: new to be created
     InnoDB: Setting log file c:\iblogs\ib_logfile0 size to 31457280
     InnoDB: Log file c:\iblogs\ib_logfile1 did not exist: new to be created
     InnoDB: Setting log file c:\iblogs\ib_logfile1 size to 31457280
     InnoDB: Log file c:\iblogs\ib_logfile2 did not exist: new to be created
     InnoDB: Setting log file c:\iblogs\ib_logfile2 size to 31457280
     InnoDB: Doublewrite buffer not found: creating new
     InnoDB: Doublewrite buffer created
     InnoDB: creating foreign key constraint system tables
     InnoDB: foreign key constraint system tables created
     011024 10:58:25  InnoDB: Started

When the server finishes its startup sequence, you should see something
like this, which indicates that the server is ready to service client
connections:


     mysqld: ready for connections
     Version: '5.1.73'  socket: ''  port: 3306

The server continues to write to the console any further diagnostic
output it produces. You can open a new console window in which to run
client programs.

If you omit the `--console' option, the server writes diagnostic output
to the error log in the data directory (`C:\Program Files\MySQL\MySQL
Server 5.1\data' by default). The error log is the file with the `.err'
extension.

*Note*:

The accounts that are listed in the MySQL grant tables initially have
no passwords. After starting the server, you should set up passwords
for them using the instructions in *Note default-privileges::.


File: manual.info,  Node: windows-start-command-line,  Next: mysql-installation-windows-path,  Prev: windows-server-first-start,  Up: windows-install-archive

2.3.6.5 Starting MySQL Server from the Windows Command Line
...........................................................

The MySQL server can be started manually from the command line.  This
can be done on any version of Windows.

To start the *Note `mysqld': mysqld. server from the command line, you
should start a console window (or `DOS window') and enter this command:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld"

The path to *Note `mysqld': mysqld. may vary depending on the install
location of MySQL on your system.

You can stop the MySQL server by executing this command:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqladmin" -u root shutdown

*Note*:

If the MySQL `root' user account has a password, you need to invoke
*Note `mysqladmin': mysqladmin.  with the `-p' option and supply the
password when prompted.

This command invokes the MySQL administrative utility *Note
`mysqladmin': mysqladmin. to connect to the server and tell it to shut
down. The command connects as the MySQL `root' user, which is the
default administrative account in the MySQL grant system. Note that
users in the MySQL grant system are wholly independent from any login
users under Windows.

If *Note `mysqld': mysqld. doesn't start, check the error log to see
whether the server wrote any messages there to indicate the cause of
the problem. The error log is located in the `C:\Program
Files\MySQL\MySQL Server 5.1\data' directory. It is the file with a
suffix of `.err'. You can also try to start the server as *Note `mysqld
--console': mysqld.; in this case, you may get some useful information
on the screen that may help solve the problem.

The last option is to start *Note `mysqld': mysqld. with the
`--standalone' and `--debug' options. In this case, *Note `mysqld':
mysqld. writes a log file `C:\mysqld.trace' that should contain the
reason why *Note `mysqld': mysqld. doesn't start. See *Note
dbug-package::.

Use *Note `mysqld --verbose --help': mysqld. to display all the options
that *Note `mysqld': mysqld. supports.


File: manual.info,  Node: mysql-installation-windows-path,  Next: windows-start-service,  Prev: windows-start-command-line,  Up: windows-install-archive

2.3.6.6 Customizing the PATH for MySQL Tools
............................................

To make it easier to invoke MySQL programs, you can add the path name
of the MySQL `bin' directory to your Windows system `PATH' environment
variable:

   * On the Windows desktop, right-click the `My Computer' icon, and
     select `Properties'.

   * Next select the `Advanced' tab from the `System Properties' menu
     that appears, and click the `Environment Variables' button.

   * Under `System Variables', select `Path', and then click the `Edit'
     button. The `Edit System Variable' dialogue should appear.

   * Place your cursor at the end of the text appearing in the space
     marked `Variable Value'. (Use the `End' key to ensure that your
     cursor is positioned at the very end of the text in this space.)
     Then enter the complete path name of your MySQL `bin' directory
     (for example, `C:\Program Files\MySQL\MySQL Server 5.1\bin')

     *Note*:

     There must be a semicolon separating this path from any values
     present in this field.

     Dismiss this dialogue, and each dialogue in turn, by clicking `OK'
     until all of the dialogues that were opened have been dismissed.
     You should now be able to invoke any MySQL executable program by
     typing its name at the DOS prompt from any directory on the system,
     without having to supply the path. This includes the servers, the
     *Note `mysql': mysql. client, and all MySQL command-line utilities
     such as *Note `mysqladmin': mysqladmin.  and *Note `mysqldump':
     mysqldump.

     You should not add the MySQL `bin' directory to your Windows
     `PATH' if you are running multiple MySQL servers on the same
     machine.

*Warning*:

You must exercise great care when editing your system `PATH' by hand;
accidental deletion or modification of any portion of the existing
`PATH' value can leave you with a malfunctioning or even unusable
system.


File: manual.info,  Node: windows-start-service,  Next: windows-testing,  Prev: mysql-installation-windows-path,  Up: windows-install-archive

2.3.6.7 Starting MySQL Server as a Microsoft Windows Service
............................................................

On Windows, the recommended way to run MySQL is to install it as a
Windows service, so that MySQL starts and stops automatically when
Windows starts and stops, and can be managed using the service manager
framework. A MySQL server installed as a service can also be controlled
from the command line using `NET' commands, or with the graphical
`Services' utility. Generally, to install MySQL as a Windows service
you should be logged in using an account that has administrator rights.

The `Services' utility (the Windows `Service Control Manager') can be
found in the Windows Control Panel (under `Administrative Tools' on
Windows 2000, XP, Vista, and Server 2003). To avoid conflicts, it is
advisable to close the `Services' utility while performing server
installation or removal operations from the command line.

*Installing the service*

Before installing MySQL as a Windows service, you should first stop the
current server if it is running by using the following command:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqladmin"
               -u root shutdown

*Note*:

If the MySQL `root' user account has a password, you need to invoke
*Note `mysqladmin': mysqladmin.  with the `-p' option and supply the
password when prompted.

This command invokes the MySQL administrative utility *Note
`mysqladmin': mysqladmin. to connect to the server and tell it to shut
down. The command connects as the MySQL `root' user, which is the
default administrative account in the MySQL grant system. Note that
users in the MySQL grant system are wholly independent from any login
users under Windows.

Install the server as a service using this command:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld" --install

*Note*:

The service-installation command does not start the server.

The following additional arguments can be used when installing the
service:

   * You can specify a service name immediately following the
     `--install' option. The default service name is `MySQL'.

   * If a service name is given, it can be followed by a single option.
     By convention, this should be `--defaults-file=FILE_NAME' to
     specify the name of an option file from which the server should
     read options when it starts.

     The use of a single option other than `--defaults-file' is possible
     but discouraged.  `--defaults-file' is more flexible because it
     enables you to specify multiple startup options for the server by
     placing them in the named option file.

   * You can also specify a `--local-service' option following the
     service name. This causes the server to run using the
     `LocalService' Windows account that has limited system privileges.
     This account is available only for Windows XP or newer. If both
     `--defaults-file' and `--local-service' are given following the
     service name, they can be in any order.

For a MySQL server that is installed as a Windows service, the
following rules determine the service name and option files that the
server uses:

   * If the service-installation command specifies no service name or
     the default service name (`MySQL') following the `--install'
     option, the server uses the a service name of `MySQL' and reads
     options from the `[mysqld]' group in the standard option files.

   * If the service-installation command specifies a service name other
     than `MySQL' following the `--install' option, the server uses that
     service name. It reads options from the `[mysqld]' group and the
     group that has the same name as the service in the standard option
     files. This enables you to use the `[mysqld]' group for options
     that should be used by all MySQL services, and an option group
     with the service name for use by the server installed with that
     service name.

   * If the service-installation command specifies a `--defaults-file'
     option after the service name, the server reads options the same
     way as described in the previous item, except that it reads options
     only from the named file and ignores the standard option files.

As a more complex example, consider the following command:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld"
               --install MySQL --defaults-file=C:\my-opts.cnf

Here, the default service name (`MySQL') is given after the `--install'
option. If no `--defaults-file' option had been given, this command
would have the effect of causing the server to read the `[mysqld]'
group from the standard option files. However, because the
`--defaults-file' option is present, the server reads options from the
`[mysqld]' option group, and only from the named file.

*Note*:

On Windows, if the server is started with the `--defaults-file' and
`--install' options, `--install' must be first.  Otherwise,
`mysqld.exe' will attempt to start the MySQL server.

You can also specify options as Start parameters in the Windows
`Services' utility before you start the MySQL service.

*Starting the service*

Once a MySQL server has been installed as a service, Windows starts the
service automatically whenever Windows starts. The service also can be
started immediately from the `Services' utility, or by using a `NET
START MySQL' command. The `NET' command is not case sensitive.

When run as a service, *Note `mysqld': mysqld. has no access to a
console window, so no messages can be seen there. If *Note `mysqld':
mysqld. does not start, check the error log to see whether the server
wrote any messages there to indicate the cause of the problem. The
error log is located in the MySQL data directory (for example,
`C:\Program Files\MySQL\MySQL Server 5.1\data'). It is the file with a
suffix of `.err'.

When a MySQL server has been installed as a service, and the service is
running, Windows stops the service automatically when Windows shuts
down. The server also can be stopped manually by using the `Services'
utility, the `NET STOP MySQL' command, or the *Note `mysqladmin
shutdown': mysqladmin. command.

You also have the choice of installing the server as a manual service
if you do not wish for the service to be started automatically during
the boot process. To do this, use the `--install-manual' option rather
than the `--install' option:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld" --install-manual

*Removing the service*

To remove a server that is installed as a service, first stop it if it
is running by executing `NET STOP MySQL'.  Then use the `--remove'
option to remove it:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld" --remove

If *Note `mysqld': mysqld. is not running as a service, you can start
it from the command line. For instructions, see *Note
windows-start-command-line::.

Please see *Note windows-troubleshooting::, if you encounter
difficulties during installation.


File: manual.info,  Node: windows-testing,  Prev: windows-start-service,  Up: windows-install-archive

2.3.6.8 Testing The MySQL Server Installation on Microsoft Windows
..................................................................

You can test whether the MySQL server is working by executing any of
the following commands:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqlshow"
     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqlshow" -u root mysql
     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqladmin" version status proc
     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysql" test

*Note*:

By default, *Note `mysqlshow': mysqlshow. will try to connect using the
`ODBC' user. This user is not created by default. You should specify a
valid user, or `root' with the right password to check the operation of
the server.

If *Note `mysqld': mysqld. is slow to respond to TCP/IP connections
from client programs, there is probably a problem with your DNS. In
this case, start *Note `mysqld': mysqld.  with the `--skip-name-resolve'
option and use only `localhost' and IP addresses in the `Host' column
of the MySQL grant tables.

You can force a MySQL client to use a named-pipe connection rather than
TCP/IP by specifying the `--pipe' or `--protocol=PIPE' option, or by
specifying `.' (period) as the host name. Use the `--socket' option to
specify the name of the pipe if you do not want to use the default pipe
name.

Note that if you have set a password for the `root' account, deleted
the anonymous account, or created a new user account, then to connect
to the MySQL server you must use the appropriate `-u' and `-p' options
with the commands shown previously.  See *Note connecting::.

For more information about *Note `mysqlshow': mysqlshow, see *Note
mysqlshow::.


File: manual.info,  Node: windows-troubleshooting,  Next: windows-upgrading,  Prev: windows-install-archive,  Up: windows-installation

2.3.7 Troubleshooting a Microsoft Windows MySQL Server Installation
-------------------------------------------------------------------

When installing and running MySQL for the first time, you may encounter
certain errors that prevent the MySQL server from starting. The purpose
of this section is to help you diagnose and correct some of these
errors.

Your first resource when troubleshooting server issues is the error log
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_error_log).
The MySQL server uses the error log to record information relevant to
the error that prevents the server from starting. The error log is
located in the data directory
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_data_directory)
specified in your `my.ini' file. The default data directory location is
`C:\Program Files\MySQL\MySQL Server 5.1\data', or
`C:\ProgramData\Mysql' on Windows 7 and Windows Server 2008. The
`C:\ProgramData' directory is hidden by default. You need to change
your folder options to see the directory and contents. For more
information on the error log and understanding the content, see *Note
error-log::.

Another source of information regarding possible errors is the console
messages displayed when the MySQL service is starting. Use the `NET
START MySQL' command from the command line after installing *Note
`mysqld': mysqld. as a service to see any error messages regarding the
starting of the MySQL server as a service. See *Note
windows-start-service::.

The following examples show other common error messages you may
encounter when installing MySQL and starting the server for the first
time:

   * If the MySQL server cannot find the `mysql' privileges database or
     other critical files, you may see these messages:


          System error 1067 has occurred.
          Fatal error: Can't open privilege tables: Table 'mysql.host' doesn't exist

     These messages often occur when the MySQL base or data directories
     are installed in different locations than the default locations
     (`C:\Program Files\MySQL\MySQL Server 5.1' and `C:\Program
     Files\MySQL\MySQL Server 5.1\data', respectively).

     This situation may occur when MySQL is upgraded and installed to a
     new location, but the configuration file is not updated to reflect
     the new location. In addition, there may be old and new
     configuration files that conflict. Be sure to delete or rename any
     old configuration files when upgrading MySQL.

     If you have installed MySQL to a directory other than `C:\Program
     Files\MySQL\MySQL Server 5.1', you need to ensure that the MySQL
     server is aware of this through the use of a configuration
     (`my.ini') file. The `my.ini' file needs to be located in your
     Windows directory, typically `C:\WINDOWS'.  You can determine its
     exact location from the value of the `WINDIR' environment variable
     by issuing the following command from the command prompt:


          C:\> echo %WINDIR%

     An option file can be created and modified with any text editor,
     such as Notepad. For example, if MySQL is installed in `E:\mysql'
     and the data directory is `D:\MySQLdata', you can create the option
     file and set up a `[mysqld]' section to specify values for the
     `basedir' and `datadir' options:


          [mysqld]
          # set basedir to your installation path
          basedir=E:/mysql
          # set datadir to the location of your data directory
          datadir=D:/MySQLdata

     Note that Windows path names are specified in option files using
     (forward) slashes rather than backslashes. If you do use
     backslashes, double them:


          [mysqld]
          # set basedir to your installation path
          basedir=C:\\Program Files\\MySQL\\MySQL Server 5.1
          # set datadir to the location of your data directory
          datadir=D:\\MySQLdata

     The rules for use of backslash in option file values are given in
     *Note option-files::.

     If you change the `datadir' value in your MySQL configuration
     file, you must move the contents of the existing MySQL data
     directory before restarting the MySQL server.

     See *Note windows-create-option-file::.

   * If you reinstall or upgrade MySQL without first stopping and
     removing the existing MySQL service and install MySQL using the
     MySQL Config Wizard, you may see this error:


          Error: Cannot create Windows service for MySql. Error: 0

     This occurs when the Config Wizard tries to install the service
     and finds an existing service with the same name.

     One solution to this problem is to choose a service name other
     than `mysql' when using the configuration wizard. This enables the
     new service to be installed correctly, but leaves the outdated
     service in place. Although this is harmless, it is best to remove
     old services that are no longer in use.

     To permanently remove the old `mysql' service, execute the
     following command as a user with administrative privileges, on the
     command-line:


          C:\> sc delete mysql
          [SC] DeleteService SUCCESS

     If the `sc' utility is not available for your version of Windows,
     download the `delsrv' utility from
     `http://www.microsoft.com/windows2000/techinfo/reskit/tools/existing/delsrv-o.asp'
     and use the `delsrv mysql' syntax.


File: manual.info,  Node: windows-upgrading,  Next: windows-postinstallation,  Prev: windows-troubleshooting,  Up: windows-installation

2.3.8 Upgrading MySQL Server on Microsoft Windows
-------------------------------------------------

To upgrade MySQL on Windows, follow these steps:

  1. Review *Note upgrading::, for additional information on upgrading
     MySQL that is not specific to Windows.

  2. You should always back up your current MySQL installation before
     performing an upgrade. See *Note backup-methods::.

  3. Download the latest Windows distribution of MySQL from
     `http://dev.mysql.com/downloads/'.

  4. Before upgrading MySQL, you must stop the server. If the server is
     installed as a service, stop the service with the following
     command from the command prompt:


          C:\> NET STOP MySQL

     If you are not running the MySQL server as a service, use *Note
     `mysqladmin': mysqladmin. to stop it. For example, before
     upgrading from MySQL 5.0 to 5.1, use *Note `mysqladmin':
     mysqladmin. from MySQL 5.0 as follows:


          C:\> "C:\Program Files\MySQL\MySQL Server 5.0\bin\mysqladmin" -u root shutdown

     *Note*:

     If the MySQL `root' user account has a password, you need to
     invoke *Note `mysqladmin': mysqladmin.  with the `-p' option and
     enter the password when prompted.

  5. Before upgrading to MySQL 5.1 from a version previous to 4.1.5, or
     from a version of MySQL installed from a Zip archive to a version
     of MySQL installed with the MySQL Installation Wizard, you must
     first manually remove the previous installation and MySQL service
     (if the server is installed as a service).

     To remove the MySQL service, use the following command:


          C:\> C:\mysql\bin\mysqld --remove

     *Important*:

     If you do not remove the existing service, the MySQL Installation
     Wizard may fail to properly install the new MySQL service.

  6. When upgrading from MySQL 5.1.23 to MySQL 5.1.24, the change in
     the default location of the data directory from a directory within
     the MySQL installation to the `AppData' folder means that you must
     manually copy the data files from your old installation to the new
     location.

  7. If you are using the MySQL Installation Wizard, start the wizard
     as described in *Note windows-install-wizard::.

  8. If you are installing MySQL from a Zip archive, extract the
     archive. You may either overwrite your existing MySQL installation
     (usually located at `C:\mysql'), or install it into a different
     directory, such as `C:\mysql5'. Overwriting the existing
     installation is recommended.

  9. If you were running MySQL as a Windows service and you had to
     remove the service earlier in this procedure, reinstall the
     service. (See *Note windows-start-service::.)

 10. Restart the server. For example, use `NET START MySQL' if you run
     MySQL as a service, or invoke *Note `mysqld': mysqld. directly
     otherwise.

 11. As Administrator, run *Note `mysql_upgrade': mysql-upgrade. to
     check your tables, attempt to repair them if necessary, and update
     your grant tables if they have changed so that you can take
     advantage of any new capabilities. See *Note mysql-upgrade::.

 12. If you encounter errors, see *Note windows-troubleshooting::.


File: manual.info,  Node: windows-postinstallation,  Prev: windows-upgrading,  Up: windows-installation

2.3.9 MySQL Server on Microsoft Windows Postinstallation Procedures
-------------------------------------------------------------------

On Windows, you need not create the data directory and the grant
tables. MySQL Windows distributions include the grant tables with a set
of preinitialized accounts in the `mysql' database under the data
directory. Regarding passwords, if you installed MySQL using the
Windows Installation Wizard, you may have already assigned passwords to
the accounts. (See *Note windows-install-wizard::.) Otherwise, use the
password-assignment procedure given in *Note default-privileges::.

Before setting up passwords, you might want to try running some client
programs to make sure that you can connect to the server and that it is
operating properly. Make sure that the server is running (see *Note
windows-server-first-start::), and then issue the following commands to
verify that you can retrieve information from the server. You may need
to specify directory different from `C:\mysql\bin' on the command line.
If you used the Windows Installation Wizard, the default directory is
`C:\Program Files\MySQL\MySQL Server 5.1', and the *Note `mysql':
mysql. and *Note `mysqlshow': mysqlshow. client programs are in
`C:\Program Files\MySQL\MySQL Server 5.1\bin'. See *Note
windows-install-wizard::, for more information.

Use *Note `mysqlshow': mysqlshow. to see what databases exist:


     C:\> C:\mysql\bin\mysqlshow
     +--------------------+
     |     Databases      |
     +--------------------+
     | information_schema |
     | mysql              |
     | test               |
     +--------------------+

The list of installed databases may vary, but will always include the
minimum of `mysql' and `information_schema'. In most cases, the `test'
database will also be installed automatically.

The preceding command (and commands for other MySQL programs such as
*Note `mysql': mysql.) may not work if the correct MySQL account does
not exist. For example, the program may fail with an error, or you may
not be able to view all databases. If you installed using the MSI
packages and used the MySQL Server Instance Config Wizard, then the
`root' user will have been created automatically with the password you
supplied. In this case, you should use the `-u root' and `-p' options.
(You will also need to use the `-u root' and `-p' options if you have
already secured the initial MySQL accounts.) With `-p', you will be
prompted for the `root' password. For example:


     C:\> C:\mysql\bin\mysqlshow -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     +--------------------+
     |     Databases      |
     +--------------------+
     | information_schema |
     | mysql              |
     | test               |
     +--------------------+

If you specify a database name, *Note `mysqlshow': mysqlshow.  displays
a list of the tables within the database:


     C:\> C:\mysql\bin\mysqlshow mysql
     Database: mysql
     +---------------------------+
     |          Tables           |
     +---------------------------+
     | columns_priv              |
     | db                        |
     | event                     |
     | func                      |
     | help_category             |
     | help_keyword              |
     | help_relation             |
     | help_topic                |
     | host                      |
     | plugin                    |
     | proc                      |
     | procs_priv                |
     | servers                   |
     | tables_priv               |
     | time_zone                 |
     | time_zone_leap_second     |
     | time_zone_name            |
     | time_zone_transition      |
     | time_zone_transition_type |
     | user                      |
     +---------------------------+

Use the *Note `mysql': mysql. program to select information from a
table in the `mysql' database:


     C:\> C:\mysql\bin\mysql -e "SELECT Host,Db,User FROM mysql.db"
     +------+--------+------+
     | host | db     | user |
     +------+--------+------+
     | %    | test   |      |
     | %    | test_% |      |
     +------+--------+------+

For more information about *Note `mysqlshow': mysqlshow. and *Note
`mysql': mysql, see *Note mysqlshow::, and *Note mysql::.

If you are running a version of Windows that supports services, you can
set up the MySQL server to run automatically when Windows starts. See
*Note windows-start-service::.


File: manual.info,  Node: macosx-installation,  Next: linux-installation,  Prev: windows-installation,  Up: installing

2.4 Installing MySQL on Mac OS X
================================

* Menu:

* macosx-installation-notes::    General Notes on Installing MySQL on Mac OS X
* macosx-installation-pkg::      Installing MySQL on Mac OS X Using Native Packages
* macosx-installation-startupitem::  Installing the MySQL Startup Item
* macosx-installation-prefpane::  Installing and Using the MySQL Preference Pane
* macosx-installation-server::   Using the Bundled MySQL on Mac OS X Server

MySQL for Mac OS X is available in a number of different forms:

   * Native Package Installer format, which uses the native Mac OS X
     installer to walk you through the installation of MySQL. For more
     information, see *Note macosx-installation-pkg::.  You can use the
     package installer with Mac OS X 10.3 and later, and the package is
     available for both PowerPC and Intel architectures, and 32-bit and
     64-bit architectures. There is no Universal Binary available using
     the package installation method. The user you use to perform the
     installation must have administrator privileges.

   * Tar package format, which uses a file packaged using the Unix
     `tar' and `gzip' commands. To use this method, you will need to
     open a `Terminal' window. You do not need administrator privileges
     using this method, as you can install the MySQL server anywhere
     using this method. For more information on using this method, you
     can use the generic instructions for using a tarball, *Note
     binary-installation::.You can use the package installer with Mac
     OS X 10.3 and later, and available for both PowerPC and Intel
     architectures, and both 32-bit and 64-bit architectures. A
     Universal Binary, incorporating both Power PC and Intel
     architectures and 32-bit and 64-bit binaries is available.

     In addition to the core installation, the Package Installer also
     includes *Note macosx-installation-startupitem:: and *Note
     macosx-installation-prefpane::, both of which simplify the
     management of your installation.

   * Mac OS X server includes a version of MySQL as standard. If you
     want to use a more recent version than that supplied with the Mac
     OS X server release, you can make use of the package or tar
     formats. For more information on using the MySQL bundled with Mac
     OS X, see *Note macosx-installation-server::.

For additional information on using MySQL on Mac OS X, see *Note
macosx-installation-notes::.


File: manual.info,  Node: macosx-installation-notes,  Next: macosx-installation-pkg,  Prev: macosx-installation,  Up: macosx-installation

2.4.1 General Notes on Installing MySQL on Mac OS X
---------------------------------------------------

You should keep the following issues and notes in mind:

   * The default location for the MySQL Unix socket is different on Mac
     OS X and Mac OS X Server depending on the installation type you
     chose. The following table shows the default locations by
     installation type.

     *MySQL Unix Socket Locations on Mac OS X by Installation Type*

     Installation Type    Socket Location
     Package Installer    `/tmp/mysql.sock'
     from MySQL           
     Tarball from MySQL   `/tmp/mysql.sock'
     MySQL Bundled with   `/var/mysql/mysql.sock'
     Mac OS X Server      

     To prevent issues, you should either change the configuration of
     the socket used within your application (for example, changing
     `php.ini'), or you should configure the socket location using a
     MySQL configuration file and the `socket' option. For more
     information, see *Note server-options::.

   * You may need (or want) to create a specific `mysql' user to own
     the MySQL directory and data. On Mac OS X 10.4 and lower you can
     do this by using the `Netinfo Manager' application, located within
     the `Utilities' folder within the `Applications' folder. On Mac OS
     X 10.5 and later you can do this through the `Directory Utility'.
     From Mac OS X 10.5 and later (including Mac OS X Server 10.5) the
     `mysql' should already exist. For use in single user mode, an
     entry for `_mysql' (note the underscore prefix) should already
     exist within the system `/etc/passwd' file.

   * Due to a bug in the Mac OS X package installer, you may see this
     error message in the destination disk selection dialog:


          You cannot install this software on this disk. (null)

     If this error occurs, click the `Go Back' button once to return to
     the previous screen. Then click `Continue' to advance to the
     destination disk selection again, and you should be able to choose
     the destination disk correctly. We have reported this bug to Apple
     and it is investigating this problem.

   * If you get an `insecure startup item disabled' error when MySQL
     launches, use the following procedure. Adjust the pathnames
     appropriately for your system.

       1. Modify the `mysql.script' using this command (enter it on a
          single line):


               shell> sudo /Applications/TextEdit.app/Contents/MacOS/TextEdit
                 /usr/local/mysql/support-files/mysql.server

       2. Locate the option file that defines the `basedir' value and
          modify it to contain these lines:


               basedir=/usr/local/mysql
               datadir=/usr/local/mysql/data

          In the `/Library/StartupItems/MySQLCOM/' directory, make the
          following group ID changes from `staff' to `wheel':


               shell> sudo chgrp wheel MySQLCOM StartupParameters.plist

       3. Start the server from System Preferences or Terminal.app.

   * Because the MySQL package installer installs the MySQL contents
     into a version and platform specific directory, you can use this
     to upgrade and migrate your database between versions. You will
     need to either copy the `data' directory from the old version to
     the new version, or alternatively specify an alternative `datadir'
     value to set location of the data directory.

   * You might want to add aliases to your shell's resource file to
     make it easier to access commonly used programs such as *Note
     `mysql': mysql. and *Note `mysqladmin': mysqladmin.  from the
     command line. The syntax for `bash' is:


          alias mysql=/usr/local/mysql/bin/mysql
          alias mysqladmin=/usr/local/mysql/bin/mysqladmin

     For `tcsh', use:


          alias mysql /usr/local/mysql/bin/mysql
          alias mysqladmin /usr/local/mysql/bin/mysqladmin

     Even better, add `/usr/local/mysql/bin' to your `PATH' environment
     variable. You can do this by modifying the appropriate startup
     file for your shell.  For more information, see *Note
     invoking-programs::.

   * After you have copied over the MySQL database files from the
     previous installation and have successfully started the new
     server, you should consider removing the old installation files to
     save disk space. Additionally, you should also remove older
     versions of the Package Receipt directories located in
     `/Library/Receipts/mysql-VERSION.pkg'.


File: manual.info,  Node: macosx-installation-pkg,  Next: macosx-installation-startupitem,  Prev: macosx-installation-notes,  Up: macosx-installation

2.4.2 Installing MySQL on Mac OS X Using Native Packages
--------------------------------------------------------

You can install MySQL on Mac OS X 10.3.x (`Panther') or newer using a
Mac OS X binary package in DMG format instead of the binary tarball
distribution. Please note that older versions of Mac OS X (for example,
10.1.x or 10.2.x) are _not_ supported by this package.

The package is located inside a disk image (`.dmg') file that you first
need to mount by double-clicking its icon in the Finder. It should then
mount the image and display its contents.

*Note*:

Before proceeding with the installation, be sure to stop all running
MySQL server instances by using either the MySQL Manager Application
(on Mac OS X Server) or *Note `mysqladmin shutdown': mysqladmin. on the
command line.

When installing from the package version, you should also install the
MySQL Preference Pane, which will enable you to control the startup and
execution of your MySQL server from System Preferences. For more
information, see *Note macosx-installation-prefpane::.

When installing using the package installer, the files are installed
into a directory within `/usr/local' matching the name of the
installation version and platform. For example, the installer file
`mysql-5.1.39-osx10.5-x86_64.pkg' installs MySQL into
`/usr/local/mysql-5.1.39-osx10.5-x86_64 '. The following table shows
the layout of the installation directory.

*MySQL Installation Layout on Mac OS X*

Directory                        Contents of Directory
`bin'                            Client programs and the *Note `mysqld':
                                 mysqld. server
`data'                           Log files, databases
`docs'                           Manual in Info format
`include'                        Include (header) files
`lib'                            Libraries
`man'                            Unix manual pages
`mysql-test'                     MySQL test suite
`scripts'                        *Note `mysql_install_db':
                                 mysql-install-db.
`share'                          Miscellaneous support files, including
                                 error messages, sample configuration
                                 files, SQL for database installation
`sql-bench'                      Benchmarks
`support-files'                  Scripts and sample configuration files
`/tmp/mysql.sock'                Location of the MySQL Unix socket

During the package installer process, a symbolic link from
`/usr/local/mysql' to the version/platform specific directory created
during installation will be created automatically.

  1. Download and open the MySQL package installer, which is provided
     on a disk image (`.dmg') that includes the main MySQL installation
     package, the `MySQLStartupItem.pkg' installation package, and the
     `MySQL.prefPane'.  Double-click the disk image to open it.

  2. Double-click the MySQL installer package. It will be named
     according to the version of MySQL you have downloaded. For
     example, if you have downloaded MySQL 5.1.39, double-click
     `mysql-5.1.39-osx10.5-x86.pkg'.

  3. You will be presented with the opening installer dialog. Click
     `Continue' to begin installation.

     MySQL Package Installer: Step 1

  4. A copy of the installation instructions and other important
     information relevant to this installation are displayed. Click
     `Continue' .

  5. If you have downloaded the community version of MySQL, you will be
     shown a copy of the relevant GNU General Public License. Click
     `Continue' .

  6. Select the drive you want to use to install the MySQL Startup
     Item. The drive must have a valid, bootable, Mac OS X operating
     system installed. Click `Continue'.

     MySQL Package Installer: Step 4

  7. You will be asked to confirm the details of the installation,
     including the space required for the installation. To change the
     drive on which the startup item is installed, click either `Go
     Back' or `Change Install Location...'. To install the startup
     item, click `Install'.

  8. Once the installation has been completed successfully, you will be
     shown an `Install Succeeded' message.

For convenience, you may also want to install the startup item and
preference pane. See *Note macosx-installation-startupitem::, and *Note
macosx-installation-prefpane::.


File: manual.info,  Node: macosx-installation-startupitem,  Next: macosx-installation-prefpane,  Prev: macosx-installation-pkg,  Up: macosx-installation

2.4.3 Installing the MySQL Startup Item
---------------------------------------

The MySQL Installation Package includes a startup item that can be used
to automatically start and stop MySQL.

To install the MySQL Startup Item:

  1. Download and open the MySQL package installer, which is provided
     on a disk image (`.dmg') that includes the main MySQL installation
     package, the `MySQLStartupItem.pkg' installation package, and the
     `MySQL.prefPane'.  Double-click the disk image to open it.

  2. Double-click the `MySQLStartItem.pkg' file to start the
     installation process.

  3. You will be presented with the `Install MySQL Startup Item' dialog.

     MySQL Startup Item Installer: Step 1

     Click `Continue' to continue the installation process.

  4. A copy of the installation instructions and other important
     information relevant to this installation are displayed. Click
     `Continue' .

  5. Select the drive you want to use to install the MySQL Startup
     Item. The drive must have a valid, bootable, Mac OS X operating
     system installed. Click `Continue'.

     MySQL Startup Item Installer: Step 3

  6. You will be asked to confirm the details of the installation.  To
     change the drive on which the startup item is installed, click
     either `Go Back' or `Change Install Location...'. To install the
     startup item, click `Install'.

  7. Once the installation has been completed successfully, you will be
     shown an `Install Succeeded' message.

     MySQL Startup Item Installer: Step 5

The Startup Item for MySQL is installed into
`/Library/StartupItems/MySQLCOM'. The Startup Item installation adds a
variable `MYSQLCOM=-YES-' to the system configuration file
`/etc/hostconfig'. If you want to disable the automatic startup of
MySQL, change this variable to `MYSQLCOM=-NO-'.

After the installation, you can start and stop MySQL by running the
following commands in a terminal window. You must have administrator
privileges to perform these tasks, and you may be prompted for your
password.

If you have installed the Startup Item, use this command to start the
server:


     shell> sudo /Library/StartupItems/MySQLCOM/MySQLCOM start

If you have installed the Startup Item, use this command to stop the
server:


     shell> sudo /Library/StartupItems/MySQLCOM/MySQLCOM stop


File: manual.info,  Node: macosx-installation-prefpane,  Next: macosx-installation-server,  Prev: macosx-installation-startupitem,  Up: macosx-installation

2.4.4 Installing and Using the MySQL Preference Pane
----------------------------------------------------

The MySQL Package installer disk image also includes a custom MySQL
Preference Pane that enables you to start, stop, and control automated
startup during boot of your MySQL installation.

To install the MySQL Preference Pane:

  1. Download and open the MySQL package installer package, which is
     provided on a disk image (`.dmg') that includes the main MySQL
     installation package, the `MySQLStartupItem.pkg' installation
     package, and the `MySQL.prefPane'.  Double-click the disk image to
     open it.

  2. Double-click the `MySQL.prefPane'. The MySQL System Preferences
     will open.

  3. If this is the first time you have installed the preference pane,
     you will be asked to confirm installation and whether you want to
     install the preference pane for all users, or only the current
     user. To install the preference pane for all users you will need
     administrator privileges. If necessary, you will be prompted for
     the username and password for a user with administrator privileges.

  4. If you already have the MySQL Preference Pane installed, you will
     be asked to confirm whether you want to overwrite the existing
     MySQL Preference Pane.

*Note*:

The MySQL Preference Pane only starts and stops MySQL installation
installed from the MySQL package installation that have been installed
in the default location.

Once the MySQL Preference Pane has been installed, you can control your
MySQL server instance using the preference pane. To use the preference
pane, open the `System Preferences...' from the Apple menu. Select the
MySQL preference pane by clicking the MySQL logo within the `Other'
section of the preference panes list.

MySQL Preference Pane

The MySQL Preference Pane shows the current status of the MySQL server,
showing `stopped' (in red) if the server is not running and `running'
(in green) if the server has already been started. The preference pane
also shows the current setting for whether the MySQL server has been
set to start automatically.

   * *To start MySQL using the preference pane: *

     Click `Start MySQL Server'. You may be prompted for the username
     and password of a user with administrator privileges to start the
     MySQL server.

   * *To stop MySQL using the preference pane: *

     Click `Stop MySQL Server'. You may be prompted for the username
     and password of a user with administrator privileges to stop the
     MySQL server.

   * *To automatically start the MySQL server when the system boots:*

     Check the check box next to `Automatically Start MySQL Server on
     Startup'.

   * *To disable automatic MySQL server startup when the system boots:*

     Uncheck the check box next to `Automatically Start MySQL Server on
     Startup'.

You can close the `System Preferences...' window once you have
completed your settings.


File: manual.info,  Node: macosx-installation-server,  Prev: macosx-installation-prefpane,  Up: macosx-installation

2.4.5 Using the Bundled MySQL on Mac OS X Server
------------------------------------------------

If you are running Mac OS X Server, a version of MySQL should already
be installed. The following table shows the versions of MySQL that ship
with Mac OS X Server versions.

*MySQL Versions Preinstalled with Mac OS X Server*

Mac OS X Server        MySQL Version
Version                
10.2-10.2.2            3.23.51
10.2.3-10.2.6          3.23.53
10.3                   4.0.14
10.3.2                 4.0.16
10.4.0                 4.1.10a
10.5.0                 5.0.45
10.6.0                 5.0.82

The following table shows the installation layout of MySQL on Mac OS X
Server.

*MySQL Directory Layout for Preinstalled MySQL Installations on Mac OS X
Server*

Directory                 Contents of Directory
`/usr/bin'                Client programs
`/var/mysql'              Log files, databases
`/usr/libexec'            The *Note `mysqld': mysqld. server
`/usr/share/man'          Unix manual pages
`/usr/share/mysql/mysql-test'MySQL test suite
`/usr/share/mysql'        Miscellaneous support files, including error
                          messages, character set files, sample
                          configuration files, SQL for database
                          installation
`/var/mysql/mysql.sock'   Location of the MySQL Unix socket

*Additional Resources*

   * For more information on managing the bundled MySQL instance in Mac
     OS X Server 10.5, see Mac OS X Server: Web Technologies
     Administration For Version 10.5 Leopard
     (http://images.apple.com/server/macosx/docs/Web_Technologies_Admin_v10.5.pdf).

   * For more information on managing the bundled MySQL instance in Mac
     OS X Server 10.6, see Mac OS X Server: Web Technologies
     Administration Version 10.6 Snow Leopard
     (http://manuals.info.apple.com/en_US/WebTech_v10.6.pdf).

   * The MySQL server bundled with Mac OS X Server does not include the
     MySQL client libraries and header files required to access and use
     MySQL from a third-party driver, such as Perl DBI or PHP. For more
     information on obtaining and installing MySQL libraries, see Mac
     OS X Server version 10.5: MySQL libraries available for download
     (http://support.apple.com/kb/TA25017). Alternatively, you can
     ignore the bundled MySQL server and install MySQL from the package
     or tarball installation.


File: manual.info,  Node: linux-installation,  Next: solaris-installation,  Prev: macosx-installation,  Up: installing

2.5 Installing MySQL on Linux
=============================

* Menu:

* linux-installation-rpm::       Installing MySQL on Linux Using RPM Packages
* linux-installation-native::    Installing MySQL on Linux Using Native Package Managers

Linux supports a number of different solutions for installing MySQL.
The recommended method is to use one of the distributions from Oracle.
If you choose this method, there are several options available:

   * Installing from a generic binary package in `.tar.gz' format. See
     *Note binary-installation:: for more information.

   * Extracting and compiling MySQL from a source distribution. For
     detailed instructions, see *Note source-installation::.

   * Installing using a precompiled RPM package. For more information,
     see *Note linux-installation-rpm::.

As an alternative, you can use the native package manager within your
Linux distribution to automatically download and install MySQL for you.
Native package installations can take care of the download and
dependencies required to run MySQL, but the MySQL version will often be
some versions behind the currently available release. You will also
normally be unable to install development releases, as these are not
usually made available in the native repository. For more information
on using the native package installers, see *Note
linux-installation-native::.

*Note*:

For many Linux installations, you will want to set up MySQL to be
started automatically when your machine starts. Many of the native
package installations perform this operation for you, but for source,
binary and RPM solutions you may need to set this up separately. The
required script, *Note `mysql.server': mysql-server, can be found in
the `support-files' directory under the MySQL installation directory or
in a MySQL source tree.  You can install it as `/etc/init.d/mysql' for
automatic MySQL startup and shutdown. See *Note automatic-start::.


File: manual.info,  Node: linux-installation-rpm,  Next: linux-installation-native,  Prev: linux-installation,  Up: linux-installation

2.5.1 Installing MySQL on Linux Using RPM Packages
--------------------------------------------------

The recommended way to install MySQL on RPM-based Linux distributions
is by using the RPM packages. The RPMs that we provide to the community
should work on all versions of Linux that support RPM packages and use
`glibc' 2.3. To obtain RPM packages, see *Note getting-mysql::.

For non-RPM Linux distributions, you can install MySQL using a
`.tar.gz' package. See *Note binary-installation::.

Installations created from our Linux RPM distributions result in files
under the system directories shown in the following table.

*MySQL Installation Layout for Linux RPM Packages*

Directory                        Contents of Directory
`/usr/bin'                       Client programs and scripts
`/usr/sbin'                      The *Note `mysqld': mysqld. server
`/var/lib/mysql'                 Log files, databases
`/usr/share/info'                Manual in Info format
`/usr/share/man'                 Unix manual pages
`/usr/include/mysql'             Include (header) files
`/usr/lib/mysql'                 Libraries
`/usr/share/mysql'               Miscellaneous support files, including
                                 error messages, character set files,
                                 sample configuration files, SQL for
                                 database installation
`/usr/share/sql-bench'           Benchmarks

*Note*:

RPM distributions of MySQL are also provided by other vendors.  Be
aware that they may differ from those built by us in features,
capabilities, and conventions (including communication setup), and that
the instructions in this manual do not necessarily apply to installing
them. The vendor's instructions should be consulted instead. Because of
these differences, RPM packages built by us check whether such RPMs
built by other vendors are installed. If so, the RPM does not install
and produces a message explaining this.

Conflicts can arise when an RPM from another vendor is already
installed, such as when a vendor's convention about which files belong
with the server and which belong with the client library differ from
the breakdown used for Oracle packages. In such cases, attempts to
install an Oracle RPM with `rpm -i' may result in messages that files
in the RPM to be installed conflict with files from an installed
package (denoted `mysql-libs' in the following paragraphs).

We provide a `MySQL-shared-compat' package with each MySQL release.
This package is meant to replace `mysql-libs' and provides a
replacement-compatible client library for older MySQL series.
`MySQL-shared-compat' is set up to make `mysql-libs' obsolete, but
`rpm' explicitly refuses to replace obsoleted packages when invoked
with `-i' (unlike `-U'), which is why installation with `rpm -i'
produces a conflict.

`MySQL-shared-compat' can safely be installed alongside `mysql-libs'
because libraries are installed to different locations. Therefore, it
is possible to install shared-compat first, then manually remove
`mysql-libs' before continuing with the installation. After mysql-libs
is removed, the dynamic linker stops looking for the client library in
the location where `mysql-libs' puts it, and the library provided by
the `MySQL-shared-compat' package takes over.

Another alternative is to install packages using `yum'. In a directory
containing all RPM packages for a MySQL release, `yum install
MySQL*rpm' installs them in the correct order and removes `mysql-libs'
in one step without conflicts.

In most cases, you need to install only the `MySQL-server' and
`MySQL-client' packages to get a functional MySQL installation. The
other packages are not required for a standard installation.

RPMs for MySQL Cluster

Beginning with MySQL 5.1.24, standard MySQL server RPMs built by MySQL
no longer provide support for the *Note `NDBCLUSTER': mysql-cluster.
storage engine. MySQL Cluster users should check the MySQL Cluster
Downloads page at `http://dev.mysql.com/downloads/cluster/' for RPMs
that should work with most Linux distributions for both of these release
series.

*Important*:

When upgrading a MySQL Cluster RPM installation, you must upgrade _all_
installed RPMs, including the `Server' and `Client' RPMs.

For more information about installing MySQL Cluster from RPMs, see
*Note mysql-cluster-install-linux-rpm::.

For upgrades, if your installation was originally produced by
installing multiple RPM packages, it is best to upgrade all the
packages, not just some. For example, if you previously installed the
server and client RPMs, do not upgrade just the server RPM.

The RPM packages shown in the following list are available. The names
shown here use a suffix of `.glibc23.i386.rpm', but particular packages
can have different suffixes, described later.

   * `MySQL-server-VERSION.glibc23.i386.rpm'

     The MySQL server. You need this unless you only want to connect to
     a MySQL server running on another machine.

   * `MySQL-client-VERSION.glibc23.i386.rpm'

     The standard MySQL client programs. You probably always want to
     install this package.

   * `MySQL-devel-VERSION.glibc23.i386.rpm'

     The libraries and include files that are needed if to compile
     other MySQL clients, such as the Perl modules. Install this RPM if
     you intend to compile C API applications.

   * `MySQL-debuginfo-VERSION.glibc23.i386.rpm'

     This package contains debugging information. It is specific to Red
     Hat Enterprise Linux. `debuginfo' RPMs are never needed to use
     MySQL software; this is true both for the server and for client
     programs. However, they contain additional information that might
     be needed by a debugger to analyze a crash.

   * `MySQL-shared-VERSION.glibc23.i386.rpm'

     This package contains the shared libraries (`libmysqlclient.so*')
     that certain languages and applications need to dynamically load
     and use MySQL. It contains single-threaded and thread-safe
     libraries. Install this RPM if you intend to compile or run C API
     applications that depend on the shared client library. If you
     install this package, do not install the `MySQL-shared-compat'
     package.

   * `MySQL-shared-compat-VERSION.glibc23.i386.rpm'

     This package includes the shared libraries for older releases, up
     to the current release. It contains single-threaded and
     thread-safe libraries. Install this package instead of
     `MySQL-shared' if you have applications installed that are
     dynamically linked against older versions of MySQL but you want to
     upgrade to the current version without breaking the library
     dependencies.

   * `MySQL-shared-compat-advanced-gpl-VERSION.glibc23.i386.rpm',
     `MySQL-shared-compat-advanced-VERSION.glibc23.i386.rpm'

     These are like the `MySQL-shared-compat' package, but are for the
     `MySQL Enterprise Server - Advanced Edition' products. Install
     these packages rather than the normal `MySQL-shared-compat'
     package if you want to included shared client libraries for older
     MySQL versions.

   * `MySQL-embedded-VERSION.glibc23.i386.rpm'

     The embedded MySQL server library.

   * `MySQL-ndb-management-VERSION.glibc23.i386.rpm',
     `MySQL-ndb-storage-VERSION.glibc23.i386.rpm',
     `MySQL-ndb-tools-VERSION.glibc23.i386.rpm',
     `MySQL-ndb-extra-VERSION.glibc23.i386.rpm'

     Packages that contain additional files for MySQL Cluster
     installations.

     *Note*:

     The `MySQL-ndb-tools' RPM requires a working installation of perl.
     Prior to MySQL 5.1.18, the `DBI' and `HTML::Template' packages
     were also required. See *Note perl-support::, and *Note
     mysql-cluster-programs-ndb-size-pl::, for more information.

   * `MySQL-test-VERSION.glibc23.i386.rpm'

     This package includes the MySQL test suite.

   * `MySQL-VERSION.src.rpm'

     This contains the source code for all of the previous packages. It
     can also be used to rebuild the RPMs on other architectures (for
     example, Alpha or SPARC).

The suffix of RPM package names (following the VERSION value) has the
following syntax:


     .PLATFORM.CPU.rpm

The PLATFORM and CPU values indicate the type of system for which the
package is built.  PLATFORM indicates the platform and CPU indicates
the processor type or family.

All packages are dynamically linked against `glibc' 2.3. The PLATFORM
value indicates whether the package is platform independent or intended
for a specific platform, as shown in the following table.

*MySQL Linux Installation Packages*

PLATFORM Value     Intended Use
`glibc23'          Platform independent, should run on any Linux
                   distribution that supports `glibc' 2.3
`rhel4', `rhel5'   Red Hat Enterprise Linux 4 or 5
`sles10', `sles11' SuSE Linux Enterprise Server 10 or 11

In MySQL 5.1, only `glibc23' packages are available currently.

The CPU value indicates the processor type or family for which the
package is built.

*MySQL Installation Packages for Linux CPU Identifiers*

CPU Value          Intended Processor Type or Family
`i386', `i586',    Pentium processor or better, 32 bit
`i686'             
`x86_64'           64-bit x86 processor
`ia64'             Itanium (IA-64) processor

To see all files in an RPM package (for example, a `MySQL-server' RPM),
run a command like this:


     shell> rpm -qpl MySQL-server-VERSION.glibc23.i386.rpm

To perform a standard minimal installation, install the server and
client RPMs:


     shell> rpm -i MySQL-server-VERSION.glibc23.i386.rpm
     shell> rpm -i MySQL-client-VERSION.glibc23.i386.rpm

To install only the client programs, install just the client RPM:


     shell> rpm -i MySQL-client-VERSION.glibc23.i386.rpm

RPM provides a feature to verify the integrity and authenticity of
packages before installing them. To learn more about this feature, see
*Note verifying-package-integrity::.

The server RPM places data under the `/var/lib/mysql' directory. The
RPM also creates a login account for a user named `mysql' (if one does
not exist) to use for running the MySQL server, and creates the
appropriate entries in `/etc/init.d/' to start the server automatically
at boot time. (This means that if you have performed a previous
installation and have made changes to its startup script, you may want
to make a copy of the script so that you do not lose it when you
install a newer RPM.) See *Note automatic-start::, for more information
on how MySQL can be started automatically on system startup.

In MySQL 5.1.49 and later, during an upgrade installation using the RPM
packages, if the MySQL server is running when the upgrade occurs, the
MySQL server is stopped, the upgrade occurs, and the MySQL server is
restarted. If the MySQL server is not already running when the RPM
upgrade occurs, the MySQL server is not started at the end of the
installation.

If something goes wrong, you can find more information in the binary
installation section. See *Note binary-installation::.

*Note*:

The accounts that are listed in the MySQL grant tables initially have
no passwords. After starting the server, you should set up passwords
for them using the instructions in *Note postinstallation::.

During RPM installation, a user named `mysql' and a group named `mysql'
are created on the system.  This is done using the `useradd',
`groupadd', and `usermod' commands. Those commands require appropriate
administrative privileges, which is required for locally managed users
and groups (as listed in the `/etc/passwd' and `/etc/group' files) by
the RPM installation process being run by `root'.

If you log in as the `mysql' user, you may find that MySQL displays
`Invalid (old?) table or database name' errors that mention `.mysqlgui',
`lost+found', `.mysqlgui', `.bash_history', `.fonts.cache-1',
`.lesshst', `.mysql_history', `.profile', `.viminfo', and similar files
created by MySQL or operating system utilities. You can safely ignore
these error messages or remove the files or directories that cause them
if you do not need them.

For nonlocal user management (LDAP, NIS, and so forth), the
administrative tools may require additional authentication (such as a
password), and will fail if the installing user does not provide this
authentication. Even if they fail, the RPM installation will not abort
but succeed, and this is intentional.  If they failed, some of the
intended transfer of ownership may be missing, and it is recommended
that the system administrator then manually ensures some appropriate
user and group exists and manually transfers ownership following the
actions in the RPM spec file.


File: manual.info,  Node: linux-installation-native,  Prev: linux-installation-rpm,  Up: linux-installation

2.5.2 Installing MySQL on Linux Using Native Package Managers
-------------------------------------------------------------

Many Linux distributions include a version of the MySQL server, client
tools, and development components into the standard package management
system built into distributions such as Fedora, Debian, Ubuntu, and
Gentoo. This section provides basic instructions for installing MySQL
using these systems.

*Important*:

Native package installations can take care of the download and
dependencies required to run MySQL, but the MySQL version will often be
some way behind the currently available release. You will also normally
be unable to install development releases, as these are not usually
made available in the native repository.

Distribution specific instructions are shown below:

   * *Red Hat Linux, Fedora, CentOS*

     For Red Hat and similar distributions, the MySQL distribution is
     divided into a number of separate packages, `mysql' for the client
     tools, `mysql-server' for the server and associated tools, and
     `mysql-libs' for the libraries.  The libraries are required if you
     want to provide connectivity from different languages and
     environments such as Perl, Python and others.

     To install, use the `yum' command to specify the packages that you
     want to install. For example:


          root-shell> yum install mysql mysql-server mysql-libs mysql-server
          Loaded plugins: presto, refresh-packagekit
          Setting up Install Process
          Resolving Dependencies
          --> Running transaction check
          ---> Package mysql.x86_64 0:5.1.48-2.fc13 set to be updated
          ---> Package mysql-libs.x86_64 0:5.1.48-2.fc13 set to be updated
          ---> Package mysql-server.x86_64 0:5.1.48-2.fc13 set to be updated
          --> Processing Dependency: perl-DBD-MySQL for package: mysql-server-5.1.48-2.fc13.x86_64
          --> Running transaction check
          ---> Package perl-DBD-MySQL.x86_64 0:4.017-1.fc13 set to be updated
          --> Finished Dependency Resolution

          Dependencies Resolved

          ================================================================================
           Package               Arch          Version               Repository      Size
          ================================================================================
          Installing:
           mysql                 x86_64        5.1.48-2.fc13         updates        889 k
           mysql-libs            x86_64        5.1.48-2.fc13         updates        1.2 M
           mysql-server          x86_64        5.1.48-2.fc13         updates        8.1 M
          Installing for dependencies:
           perl-DBD-MySQL        x86_64        4.017-1.fc13          updates        136 k

          Transaction Summary
          ================================================================================
          Install       4 Package(s)
          Upgrade       0 Package(s)

          Total download size: 10 M
          Installed size: 30 M
          Is this ok [y/N]: y
          Downloading Packages:
          Setting up and reading Presto delta metadata
          Processing delta metadata
          Package(s) data still to download: 10 M
          (1/4): mysql-5.1.48-2.fc13.x86_64.rpm                    | 889 kB     00:04
          (2/4): mysql-libs-5.1.48-2.fc13.x86_64.rpm               | 1.2 MB     00:06
          (3/4): mysql-server-5.1.48-2.fc13.x86_64.rpm             | 8.1 MB     00:40
          (4/4): perl-DBD-MySQL-4.017-1.fc13.x86_64.rpm            | 136 kB     00:00
          --------------------------------------------------------------------------------
          Total                                           201 kB/s |  10 MB     00:52
          Running rpm_check_debug
          Running Transaction Test
          Transaction Test Succeeded
          Running Transaction
            Installing     : mysql-libs-5.1.48-2.fc13.x86_64                          1/4
            Installing     : mysql-5.1.48-2.fc13.x86_64                               2/4
            Installing     : perl-DBD-MySQL-4.017-1.fc13.x86_64                       3/4
            Installing     : mysql-server-5.1.48-2.fc13.x86_64                        4/4

          Installed:
            mysql.x86_64 0:5.1.48-2.fc13            mysql-libs.x86_64 0:5.1.48-2.fc13
            mysql-server.x86_64 0:5.1.48-2.fc13

          Dependency Installed:
            perl-DBD-MySQL.x86_64 0:4.017-1.fc13

          Complete!

     MySQL and the MySQL server should now be installed. A sample
     configuration file is installed into `/etc/my.cnf'. An init
     script, to start and stop the server, will have been installed into
     `/etc/init.d/mysqld'. To start the MySQL server use `service':


          root-shell> service mysqld start

     To enable the server to be started and stopped automatically
     during boot, use `chkconfig':


          root-shell> chkconfig --levels 235 mysqld on

     Which enables the MySQL server to be started (and stopped)
     automatically at the specified the run levels.

     The database tables will have been automatically created for you,
     if they do not already exist. You should, however, run *Note
     `mysql_secure_installation': mysql-secure-installation. to set the
     root passwords on your server.

   * *Debian, Ubuntu, Kubuntu*

     On Debian and related distributions, there are two packages,
     `mysql-client' and `mysql-server', for the client and server
     components respectively. You should specify an explicit version,
     for example `mysql-client-5.1', to ensure that you install the
     version of MySQL that you want.

     To download and install, including any dependencies, use the
     `apt-get' command, specifying the packages that you want to
     install.

     *Note*:

     Before installing, make sure that you update your `apt-get' index
     files to ensure you are downloading the latest available version.

     A sample installation of the MySQL packages might look like this
     (some sections trimmed for clarity):


          root-shell> apt-get install mysql-client-5.1 mysql-server-5.1
          Reading package lists... Done
          Building dependency tree
          Reading state information... Done
          The following packages were automatically installed and are no longer required:
            linux-headers-2.6.28-11 linux-headers-2.6.28-11-generic
          Use 'apt-get autoremove' to remove them.
          The following extra packages will be installed:
            bsd-mailx libdbd-mysql-perl libdbi-perl libhtml-template-perl
            libmysqlclient15off libmysqlclient16 libnet-daemon-perl libplrpc-perl mailx
            mysql-common postfix
          Suggested packages:
            dbishell libipc-sharedcache-perl tinyca procmail postfix-mysql postfix-pgsql
            postfix-ldap postfix-pcre sasl2-bin resolvconf postfix-cdb
          The following NEW packages will be installed
            bsd-mailx libdbd-mysql-perl libdbi-perl libhtml-template-perl
            libmysqlclient15off libmysqlclient16 libnet-daemon-perl libplrpc-perl mailx
            mysql-client-5.1 mysql-common mysql-server-5.1 postfix
          0 upgraded, 13 newly installed, 0 to remove and 182 not upgraded.
          Need to get 1907kB/25.3MB of archives.
          After this operation, 59.5MB of additional disk space will be used.
          Do you want to continue [Y/n]? Y
          Get: 1 http://gb.archive.ubuntu.com jaunty-updates/main mysql-common 5.1.30really5.0.75-0ubuntu10.5 [63.6kB]
          Get: 2 http://gb.archive.ubuntu.com jaunty-updates/main libmysqlclient15off 5.1.30really5.0.75-0ubuntu10.5 [1843kB]
          Fetched 1907kB in 9s (205kB/s)
          Preconfiguring packages ...
          Selecting previously deselected package mysql-common.
          (Reading database ... 121260 files and directories currently installed.)
          ...
          Processing 1 added doc-base file(s)...
          Registering documents with scrollkeeper...
          Setting up libnet-daemon-perl (0.43-1) ...
          Setting up libplrpc-perl (0.2020-1) ...
          Setting up libdbi-perl (1.607-1) ...
          Setting up libmysqlclient15off (5.1.30really5.0.75-0ubuntu10.5) ...

          Setting up libdbd-mysql-perl (4.008-1) ...
          Setting up libmysqlclient16 (5.1.31-1ubuntu2) ...

          Setting up mysql-client-5.1 (5.1.31-1ubuntu2) ...

          Setting up mysql-server-5.1 (5.1.31-1ubuntu2) ...
           * Stopping MySQL database server mysqld
             ...done.
          100825 11:46:15  InnoDB: Started; log sequence number 0 46409
          100825 11:46:15  InnoDB: Starting shutdown...
          100825 11:46:17  InnoDB: Shutdown completed; log sequence number 0 46409
          100825 11:46:17 [Warning] Forcing shutdown of 1 plugins
           * Starting MySQL database server mysqld
             ...done.
           * Checking for corrupt, not cleanly closed and upgrade needing tables.
          ...
          Processing triggers for libc6 ...
          ldconfig deferred processing now taking place

     *Note*:

     The `apt-get' command will install a number of packages, including
     the MySQL server, in order to provide the typical tools and
     application environment. This can mean that you install a large
     number of packages in addition to the main MySQL package.

     During installation, the initial database will be created, and you
     will be prompted for the MySQL root password (and confirmation). A
     configuration file will have been created in `/etc/mysql/my.cnf'.
     An init script will have been created in `/etc/init.d/mysql'.

     The server will already be started. You can manually start and
     stop the server using:


          root-shell> service mysql [start|stop]

     The service will automatically be added to the 2, 3 and 4 run
     levels, with stop scripts in the single, shutdown and restart
     levels.

   * *Gentoo Linux*

     As a source-based distribution, installing MySQL on Gentoo
     involves downloading the source, patching the Gentoo specifics,
     and then compiling the MySQL server and installing it. This
     process is handled automatically by the `emerge' command.
     Depending on the version of MySQL that you want to install, you
     may need to unmask the specific version that you want for your
     chosen platform.

     The MySQL server and client tools are provided within a single
     package, `dev-db/mysql'. You can obtain a list of the versions
     available to install by looking at the portage directory for the
     package:


          root-shell> ls /usr/portage/dev-db/mysql/mysql-5.1*
          mysql-5.1.39-r1.ebuild
          mysql-5.1.44-r1.ebuild
          mysql-5.1.44-r2.ebuild
          mysql-5.1.44-r3.ebuild
          mysql-5.1.44.ebuild
          mysql-5.1.45-r1.ebuild
          mysql-5.1.45.ebuild
          mysql-5.1.46.ebuild

     To install a specific MySQL version, you must specify the entire
     atom. For example:


          root-shell> emerge =dev-db/mysql-5.1.46

     A simpler alternative is to use the `virtual/mysql-5.1' package,
     which will install the latest version:


          root-shell> emerge =virtual/mysql-5.1

     If the package is masked (because it is not tested or certified
     for the current platform), use the `ACCEPT_KEYWORDS' environment
     variable. For example:


          root-shell> ACCEPT_KEYWORDS="~x86" emerge =virtual/mysql-5.1

     After installation, you should create a new database using *Note
     `mysql_install_db': mysql-install-db, and set the password for the
     root user on MySQL. You can use the configuration interface to set
     the password and create the initial database:


          root-shell> emerge --config =dev-db/mysql-5.1.46

     A sample configuration file will have been created for you in
     `/etc/mysql/my.cnf', and an init script will have been created in
     `/etc/init.d/mysql'.

     To enable MySQL to start automatically at the normal (default) run
     levels, you can use:


          root-shell> rc-update add mysql default


File: manual.info,  Node: solaris-installation,  Next: aix-installation,  Prev: linux-installation,  Up: installing

2.6 Installing MySQL on Solaris and OpenSolaris
===============================================

* Menu:

* solaris-installation-pkg::     Installing MySQL on Solaris Using a Solaris PKG
* solaris-installation-opensolaris::  Installing MySQL on OpenSolaris Using IPS

MySQL on Solaris and OpenSolaris is available in a number of different
formats.

   * For information on installing using the native Solaris PKG format,
     see *Note solaris-installation-pkg::.

   * On OpenSolaris, the standard package repositories include MySQL
     packages specially built for OpenSolaris that include entries for
     the Service Management Framework (SMF) to enable control of the
     installation using the SMF administration commands. For more
     information, see *Note solaris-installation-opensolaris::.

   * To use a standard `tar' binary installation, use the notes
     provided in *Note binary-installation::.  Check the notes and
     hints at the end of this section for Solaris specific notes that
     you may need before or after installation.

   * For information on installing MySQL on Solaris or OpenSolaris
     using a source distribution, first check the Solaris advice, *Note
     solaris-installation-source::. For detailed instructions on
     installing from source, see *Note source-installation::.

To obtain a binary MySQL distribution for Solaris in tarball or PKG
format, `http://dev.mysql.com/downloads/mysql/5.1.html'.

Additional notes to be aware of when installing and using MySQL on
Solaris:

   * If you want to use MySQL with the `mysql' user and group, use the
     `groupadd' and `useradd' commands:


          groupadd mysql
          useradd -g mysql mysql

   * If you install MySQL using a binary tarball distribution on
     Solaris, you may run into trouble even before you get the MySQL
     distribution unpacked, as the Solaris `tar' cannot handle long
     file names. This means that you may see errors when you try to
     unpack MySQL.

     If this occurs, you must use GNU `tar' (`gtar') to unpack the
     distribution. In Solaris 10 and OpenSolaris `gtar' is normally
     located in `/usr/sfw/bin/gtar', but may not be included in the
     default path definition.

   * When using Solaris 10 for x86_64, you should mount any file
     systems on which you intend to store `InnoDB' files with the
     `forcedirectio' option. (By default mounting is done without this
     option.) Failing to do so will cause a significant drop in
     performance when using the `InnoDB' storage engine on this
     platform.

   * If you would like MySQL to start automatically, you can copy
     `support-files/mysql.server' to `/etc/init.d' and create a
     symbolic link to it named `/etc/rc3.d/S99mysql.server'.

   * If too many processes try to connect very rapidly to *Note
     `mysqld': mysqld, you should see this error in the MySQL log:


          Error in accept: Protocol error

     You might try starting the server with the `--back_log=50' option
     as a workaround for this.

   * To configure the generation of core files on Solaris you should
     use the `coreadm' command. Because of the security implications of
     generating a core on a `setuid()' application, by default, Solaris
     does not support core files on `setuid()' programs. However, you
     can modify this behavior using `coreadm'. If you enable `setuid()'
     core files for the current user, they will be generated using the
     mode 600 and owned by the superuser.


File: manual.info,  Node: solaris-installation-pkg,  Next: solaris-installation-opensolaris,  Prev: solaris-installation,  Up: solaris-installation

2.6.1 Installing MySQL on Solaris Using a Solaris PKG
-----------------------------------------------------

You can install MySQL on Solaris and OpenSolaris using a binary package
using the native Solaris PKG format instead of the binary tarball
distribution.

To use this package, download the corresponding
`mysql-VERSION-solaris10-PLATFORM.pkg.gz' file, then uncompress it. For
example:


     shell> gunzip mysql-5.1.73-solaris10-x86_64.pkg.gz

To install a new package, use `pkgadd' and follow the onscreen prompts.
You must have root privileges to perform this operation:


     shell> pkgadd -d mysql-5.1.73-solaris10-x86_64.pkg

     The following packages are available:
       1  mysql     MySQL Community Server (GPL)
                    (i86pc) 5.1.73

     Select package(s) you wish to process (or 'all' to process
     all packages). (default: all) [?,??,q]:

The PKG installer installs all of the files and tools needed, and then
initializes your database if one does not exist. To complete the
installation, you should set the root password for MySQL as provided in
the instructions at the end of the installation.  Alternatively, you
can run the *Note `mysql_secure_installation':
mysql-secure-installation. script that comes with the installation.

By default, the PKG package installs MySQL under the root path
`/opt/mysql'. You can change only the installation root path when using
`pkgadd', which can be used to install MySQL in a different Solaris
zone. If you need to install in a specific directory, use a binary
`tar' file distribution.

The `pkg' installer copies a suitable startup script for MySQL into
`/etc/init.d/mysql'. To enable MySQL to startup and shutdown
automatically, you should create a link between this file and the init
script directories.  For example, to ensure safe startup and shutdown
of MySQL you could use the following commands to add the right links:


     shell> ln /etc/init.d/mysql /etc/rc3.d/S91mysql
     shell> ln /etc/init.d/mysql /etc/rc0.d/K02mysql

To remove MySQL, the installed package name is `mysql'. You can use
this in combination with the `pkgrm' command to remove the installation.

To upgrade when using the Solaris package file format, you must remove
the existing installation before installing the updated package.
Removal of the package does not delete the existing database
information, only the server, binaries and support files.  The typical
upgrade sequence is therefore:


     shell> mysqladmin shutdown
     shell> pkgrm mysql
     shell> pkgadd -d mysql-5.1.73-solaris10-x86_64.pkg
     shell> mysqld_safe &
     shell> mysql_upgrade

You should check the notes in *Note upgrading-downgrading:: before
performing any upgrade.


File: manual.info,  Node: solaris-installation-opensolaris,  Prev: solaris-installation-pkg,  Up: solaris-installation

2.6.2 Installing MySQL on OpenSolaris Using IPS
-----------------------------------------------

OpenSolaris includes standard packages for MySQL in the core
repository. The MySQL packages are based on a specific release of MySQL
and updated periodically. For the latest release you must use either
the native Solaris PKG, `tar', or source installations. The native
OpenSolaris packages include SMF files so that you can easily control
your MySQL installation, including automatic startup and recovery,
using the native service management tools.

To install MySQL on OpenSolaris, use the `pkg' command. You will need
to be logged in as root, or use the `pfexec' tool, as shown in the
example below:

     shell> pfexec pkg install SUNWmysql51

The package set installs three individual packages, `SUNWmysql51lib',
which contains the MySQL client libraries; `SUNWmysql51r' which contains
the root components, including SMF and configuration files; and
`SUNWmysql51u' which contains the scripts, binary tools and other
files. You can install these packages individually if you only need the
corresponding components.

The MySQL files are installed into `/usr/mysql' which symbolic links
for the sub directories (`bin', `lib', etc.) to a version specific
directory. For MySQL 5.1, the full installation is located in
`/usr/mysql/5.1'. The default data directory is `/var/mysql/5.1/data'.
The configuration file is installed in `/etc/mysql/5.1/my.cnf'. This
layout permits multiple versions of MySQL to be installed, without
overwriting the data and binaries from other versions.

Once installed, you must run *Note `mysql_install_db': mysql-install-db.
to initialize the database, and use the *Note
`mysql_secure_installation': mysql-secure-installation. to secure your
installation.

*Using SMF to manage your MySQL installation*

Once installed, you can start and stop your MySQL server using the
installed SMF configuration. The service name is `mysql', or if you
have multiple versions installed, you should use the full version name,
for example `mysql:version_51'. To start and enable MySQL to be started
at boot time:

     shell> svcadm enable mysql

To disable MySQL from starting during boot time, and shut the MySQL
server down if it is running, use:

     shell> svcadm disable mysql

To restart MySQL, for example after a configuration file changes, use
the `restart' option:

     shell> svcadm restart mysql

You can also use SMF to configure the data directory and enable full
64-bit mode. For example, to set the data directory used by MySQL:


     shell> svccfg
     svc:> select mysql:version_51
     svc:/application/database/mysql:version_51> setprop mysql/data=/data0/mysql

By default, the 32-bit binaries are used. To enable the 64-bit server
on 64-bit platforms, set the `enable_64bit' parameter. For example:

     svc:/application/database/mysql:version_51> setprop mysql/enable_64bit=1

You need to refresh the SMF after settings these options:

     shell> svcadm refresh mysql


File: manual.info,  Node: aix-installation,  Next: hpux-installation,  Prev: solaris-installation,  Up: installing

2.7 Installing MySQL on IBM AIX
===============================

* Menu:

* aix-installation-general::     General Notes on Installing MySQL on AIX

MySQL for IBM AIX is available in a number of different forms:

   * Using a binary tarball distribution provided at
     `http://dev.mysql.com/downloads/'. Please read the *Note general
     notes on AIX installation: aix-installation-general. before
     continuing. For more information on binary installations, see
     *Note binary-installation::.

   * Using a source tarball and compiling MySQL. Please read the *Note
     general notes on AIX installation: aix-installation-general.
     before continuing. You should also check the instructions on *Note
     building on AIX from source: aix-installation-source. For general
     information on building from source, see *Note
     source-installation::.


File: manual.info,  Node: aix-installation-general,  Prev: aix-installation,  Up: aix-installation

2.7.1 General Notes on Installing MySQL on AIX
----------------------------------------------

General notes on using MySQL on IBM AIX:

   * If you have problems with threads on AIX 5.3, you should upgrade
     AIX 5.3 to technology level 7 (5300-07).


File: manual.info,  Node: hpux-installation,  Next: freebsd-installation,  Prev: aix-installation,  Up: installing

2.8 Installing MySQL on HP-UX
=============================

* Menu:

* hpux-installation-general::    General Notes on Installing MySQL on HP-UX
* hpux-installation-depot::      Installing MySQL on HP-UX Using DEPOT Packages

MySQL for HP-UX is available in a number of different forms:

   * Using a DEPOT distribution provided at
     `http://dev.mysql.com/downloads/'. Please read the *Note general
     notes on HP-UX installation: hpux-installation-general. before
     continuing. For more information on DEPOT installations, see *Note
     hpux-installation-depot::.

   * Using a binary tarball distribution provided at
     `http://dev.mysql.com/downloads/'. Please read the *Note general
     notes on HP-UX installation: hpux-installation-general. before
     continuing. For more information on binary installations, see
     *Note binary-installation::.

   * Using a source tarball and compiling MySQL. Please read the *Note
     general notes on HP-UX installation: hpux-installation-general.
     before continuing. You should also check the instructions on *Note
     building on HP-UX from source: hpux-installation-source. For
     general information on building from source, see *Note
     source-installation::.


File: manual.info,  Node: hpux-installation-general,  Next: hpux-installation-depot,  Prev: hpux-installation,  Up: hpux-installation

2.8.1 General Notes on Installing MySQL on HP-UX
------------------------------------------------

Some additional notes on installing and using MySQL on HP-UX:

   * If you install MySQL using a binary tarball distribution on HP-UX,
     you may run into trouble even before you get the MySQL
     distribution unpacked, as the HP-UX `tar' cannot handle long file
     names. This means that you may see errors when you try to unpack
     MySQL.

     If this occurs, you must use GNU `tar' (`gtar') to unpack the
     distribution.

   * Because of some critical bugs in the standard HP-UX libraries, you
     should install the following patches before trying to run MySQL on
     HP-UX 11.0:


          PHKL_22840 Streams cumulative
          PHNE_22397 ARPA cumulative

     This solves the problem of getting `EWOULDBLOCK' from `recv()' and
     `EBADF' from `accept()' in threaded applications.


File: manual.info,  Node: hpux-installation-depot,  Prev: hpux-installation-general,  Up: hpux-installation

2.8.2 Installing MySQL on HP-UX Using DEPOT Packages
----------------------------------------------------

The HP-UX DEPOT format packages can be installed using the `swinstall'
command. You should install the `ncurses' and `zlib' libraries before
installing the MySQL DEPOT package. You can use the free software
`depothelper' tool to install these packages and any dependencies for
you automatically.

To install using the MySQL DEPOT packages, follow this guide:

  1. Download the MySQL DEPOT package from
     `http://dev.mysql.com/downloads/'. You must uncompress the package
     before installation:


          root-shell> gunzip mysql-5.1.48-hpux11.31-ia64-64bit.depot.gz

  2. Install the DEPOT package using `swinstall':

          root-shell> swinstall -s MYSQL-5.1.49-HPUX11.31-IA64-64BIT.DEPOT

     MySQL will be installed into a directory matching the depot
     package name, within `/usr/local'. For convenience, you may want
     to create a symbolic link to the installed directory, for example:


          root-shell> ln -s mysql-5.1.49-hpux11.31-ia64-64bit mysql

  3. Your package is now installed. You should complete the
     configuration of MySQL by creating a user and group:


          root-shell> /usr/sbin/groupadd mysql
          root-shell> /usr/sbin/useradd -g mysql -d /var/lib/mysql/ -s /bin/false mysql

  4. Create the standard database using the new user/group you have
     created, and set the permissions:


          root-shell> cd /usr/local/
          root-shell> scripts/mysql_install_db --user=mysql
          root-shell> chown -R root .
          root-shell> chown -R mysql data

  5. Finally, secure your new installation by setting the root
     passwords, and then start your MySQL server using the `mysql' user:


          root-shell> mysql_secure_installation
          root-shell> mysqld_safe --user=mysql &


File: manual.info,  Node: freebsd-installation,  Next: i5os-installation,  Prev: hpux-installation,  Up: installing

2.9 Installing MySQL on FreeBSD
===============================

This section provides information about installing MySQL on variants of
FreeBSD Unix.

You can install MySQL on FreeBSD by using the binary distribution
provided by Oracle. For more information, see *Note
binary-installation::.

The easiest (and preferred) way to install MySQL is to use the *Note
`mysql-server': mysql-server. and `mysql-client' ports available at
`http://www.freebsd.org/'. Using these ports gives you the following
benefits:

   * A working MySQL with all optimizations enabled that are known to
     work on your version of FreeBSD.

   * Automatic configuration and build.

   * Startup scripts installed in `/usr/local/etc/rc.d'.

   * The ability to use `pkg_info -L' to see which files are installed.

   * The ability to use `pkg_delete' to remove MySQL if you no longer
     want it on your machine.

The MySQL build process requires GNU make (`gmake') to work. If GNU
`make' is not available, you must install it first before compiling
MySQL.

To install using the ports system:


     # cd /usr/ports/databases/mysql51-server
     # make
     ...
     # cd /usr/ports/databases/mysql51-client
     # make
     ...

The standard port installation places the server into
`/usr/local/libexec/mysqld', with the startup script for the MySQL
server placed in `/usr/local/etc/rc.d/mysql-server'.

Some additional notes on the BSD implementation:

   * To remove MySQL after installation using the ports system:


          # cd /usr/ports/databases/mysql51-server
          # make deinstall
          ...
          # cd /usr/ports/databases/mysql51-client
          # make deinstall
          ...

   * If you get problems with the current date in MySQL, setting the
     `TZ' variable should help. See *Note environment-variables::.


File: manual.info,  Node: i5os-installation,  Next: source-installation,  Prev: freebsd-installation,  Up: installing

2.10 Installing MySQL on i5/OS
==============================

The i5/OS POWER MySQL package was created in cooperation with IBM.
MySQL works within the Portable Application Solution Environment (PASE)
on the System i series of hardware and will also provide database
services for the Zend Core for i5/OS.

MySQL for i5/OS is provided both as a `tar' file and as a save file
(`.savf') package that can be downloaded and installed directly without
any additional installation steps required. To install MySQL using the
`tar' file, see *Note binary-installation::.

MySQL is only supported on i5/OS V5R4 or later releases. The i5/OS PASE
must be installed for MySQL to operate. You must be able to login as a
user in `*SECOFR' class.

You should the installation notes and tips for i5/OS before starting
installation. See i5/OS Installation Notes.

*Before Installation:*

*Note*:

The installation package will use an existing configuration if you have
previously installed MySQL (which is identified by looking for the file
`/etc/my.cnf'). The values for the data directory (`DATADIR') and owner
of the MySQL files (`USRPRF') specified during the installation will be
ignored, and the values determined from the `/etc/my.cnf' will be used
instead.

If you want to change these parameters during a new install, you should
temporarily rename `/etc/my.cnf', install MySQL using the new
parameters you want to use, and then merge your previous `/etc/my.cnf'
configuration settings with the new `/etc/my.cnf' file that is created
during installation.

   * You must have a user profile with PASE with suitable privileges.
     The user should be within the `*SECOFR' class, such as the
     `QSECOFR' user ID. You can use the `WRKUSRPRF' command to check
     your user profile.

   * For network connections to MySQL, you must have TCP/IP enabled.
     You should also check the following:

        * Ensure that a name has defined for the system. Run the
          Configure TCP/IP (`CFGTCP') command and select option 12
          (Change TCP/IP domain information) to display this setting.
          Make sure that a value is listed in the Host name field.

        * Make sure that the system has a loopback entry which
          represents the `localhost' or `127.0.0.1'.

        * Ensure that the IP address of the IBM i machine is mapped
          correctly to the host name.

To install MySQL on i5/OS, follow these steps:

  1. On the System i machine, create a save file that will be used to
     receive the downloaded installation save file. The file should be
     located within the General Purpose Library (`QGPL'):

          CRTSAVF FILE(QGPL/MYSQLINST) TESXT('MySQL Save file')

  2. Download the MySQL installation save file in 32-bit
     (`mysql-5.1.73-i5os-power-32bit.savf') or 64-bit
     (`mysql-5.1.73-i5os-power-64bit.savf') from MySQL Downloads
     (http://dev.mysql.com/downloads/).

  3. You need to FTP the downloaded `.savf' file directly into the
     `QGPL/MYSQLINST' file on the System i server. You can do this
     through FTP using the following steps after logging in to the
     System i machine:

          ftp> bin
          ftp> cd qgpl
          ftp> put mysql-5.1.73-i5os-power.savf mysqlinst

  4. Log into the System i server using a user in the `*SECOFR' class,
     such as the `QSECOFR' user ID.

  5. You need to restore the installation library stored in the `.savf'
     save file:

          RSTLIB MYSQLINST DEV(*SAVF) SAVF(QGPL/MYSQLINST) MBROPT(*ALL) ALWOBJDIF(*ALL)

     *Note*:

     You can ignore the security changes-type message at the bottom of
     the installation panel.

  6. Once you have finished restoring the `MYSQLINST' library, check
     that all the necessary objects for installation are on the system
     by using the Display Library (`DSPLIB') command:

          DSPLIB LIB(MYSQLINST)

  7. You need to execute the installation command,
     `MYSQLINST/INSMYSQL'. You can specify three parameter settings
     during installation:

        * `DIR('/QOPENSYS/USR/LOCAL/MYSQL')' sets the installation
          location for the MySQL files. The directory will be created
          if it does not already exist.

        * `DATADIR('/QOPENSYS/USR/LOCAL/MYSQL/DATA')' sets the location
          of the directory that will be used to store the database
          files and binary logs. The default setting is
          `/QOpenSys/usr/local/mysql/data'. Note that if the installer
          detects an existing installation (due to the existence of
          `/etc/my.cnf'), then the existing setting will be used
          instead of the default.

        * `USRPRF(MYSQL)' sets the user profile that will own the files
          that are installed. The profile will be created if it does not
          already exist.

          *Note*:

          You should choose an appropriate user for using the MySQL
          server installation. The user will be used whenever you need
          to do any administration on the MySQL server.

     Once you have set the appropriate parameters, you can begin the
     installation.

     The installation copies all the necessary files into a directory
     matching the `DIR' configuration value; sets the ownership on
     those files, sets up the MySQL environment and creates the MySQL
     configuration file (in `/etc/my.cnf') completing all the steps in a
     typical binary installation process automatically. If this is a
     new installation of MySQL, or if the installer detects that this
     is a new version (because the `/etc/my.cnf' file does not exist),
     then the initial core MySQL databases will also be created during
     installation.

     Once the installation has been completed, you will get a notice
     advising you to set the password for the root user. For more
     information, *Note postinstallation::.

  8. Once the installation has completed, you can delete the
     installation file:

          DLTLIB LIB(MYSQLINST)

*Upgrading an existing MySQL instance*

You need to execute the upgrade command, `MYSQLINST/UPGMYSQL'.

*Note*:

You cannot use `MYSQLINST/UPGMYSQL' to upgrade between major versions
of MySQL (for example from 5.0 to 5.1). For information and advice on
migrating between major versions you can use the advice provided in
*Note upgrading-from-previous-series::.

You must specify 6 parameters to perform an upgrade:

   * `DIR('/QOpenSys/usr/local/')': Sets the installation location for
     the MySQL files. The directory will be created if it does not
     already exist. This is the directory that the MySQL server will be
     installed into, inside a directory with a name matching the
     version and release. For example, if installing MySQL 5.1.73 with
     the `DIR' set to `/QOpenSys/usr/local/' would result in
     `/QOpenSys/usr/local/mysql-5.1.73-i5os-power64' and a symbolic
     link to this directory will be created in
     `/QOpenSys/usr/local/mysql'.

   * `DATADIR('/QOpenSys/mysql/data')': Sets the location of the
     directory that will be upgraded.

   * `USRPRF('MYSQL')': Sets the user profile that will own the files
     that are installed. The profile will be created if it does not
     already exist; if it is created as part of the upgrade process, it
     will be disabled initially. You may wish to enable this user
     profile so that it can be used to start the MySQL server later. It
     is best practice to use the one previously created during the
     first installation.

   * `MYSQLUSR('root user')': Any user account in the current MySQL
     server with `SUPER' privileges.

   * `PASSWORD('root user password')': The password for the above
     account. This is necessary as the upgrade starts the MySQL server
     to upgrade the tables and the password is need to be able to
     shutdown the MySQL server.

   * `CURINST('path to previous install')': The full path to the
     installation that is being upgraded. For example an installation
     in `/QOpenSys/usr/local/' will be
     `/QOpenSys/usr/local/mysql-5.1.73-i5os-power64'.  Failure to
     specify this option may result in corruption of your existing data
     files.

For example:

     MYSQLINST/UPGMYSQL DIR('/QOPENSYS/USR/LOCAL/') DATADIR('/QOPENSYS/MYSQL/DATA') »
          USERPRF(MYSQL) MYSQLUSR('ROOT') PASSWORD('ROOT') CURINST('/QOPENSYS/USR/LOCAL/MYSQL-5.1.73-I5OS-POWER64')

You should receive a Program Message indicating `UPGRADE SUCCESSFUL!'
upon completion or an error message if there is a problem.You can view
the upgrade programs progression and the error in the text file
`upgrade.log' in the installation directory.

*To start MySQL*:

  1. Log into the System i server using the user profile create or
     specified during installation. By default, this is `MYSQL'.

     *Note*:

     You should start *Note `mysqld_safe': mysqld-safe. using a user
     that in the PASE environment has the id=0 (the equivalent of the
     standard Unix `root' user). If you do not use a user with this ID
     then the system will be unable to change the user when executing
     *Note `mysqld': mysqld. as set using `--user' option. If this
     happens, *Note `mysqld': mysqld. may be unable to read the files
     located within the MySQL data directory and the execution will
     fail.

  2. Enter the PASE environment using `call qp2term'.

  3. Start the MySQL server by changing to the installation directory
     and running *Note `mysqld_safe': mysqld-safe, specifying the user
     name used to install the server. The installer conveniently
     installs a symbolic link to the installation directory
     (`mysql-5.0.42-i5os-power-32bit') as `/opt/mysql/mysql':

          > cd /opt/mysql/mysql
          > bin/mysqld_safe --user=mysql &

     You should see a message similar to the following:

          Starting mysqld daemon with databases »
               from /opt/mysql/mysql-enterprise-5.0.42-i5os-power-32bit/data

If you are having problems starting MySQL server, see *Note
starting-server::.

*To stop MySQL*:

  1. Log into the System i server using the user profile create or
     specified during installation. By default, this is `MYSQL'.

  2. Enter the PASE environment using `call qp2term'.

  3. Stop the MySQL server by changing into the installation directory
     and running *Note `mysqladmin': mysqladmin, specifying the user
     name used to install the server:

          > cd /opt/mysql/mysql
          > bin/mysqladmin -u root shutdown

     If the session that you started and stopped MySQL are the same,
     you may get the log output from `mysqld':

             STOPPING server from pid file »
               /opt/mysql/mysql-enterprise-5.0.42-i5os-power-32bit/data/I5DBX.RCHLAND.IBM.COM.pid
             070718 10:34:20  mysqld ended

     If the sessions used to start and stop MySQL are different, you
     will not receive any confirmation of the shutdown.

_Note and tips_

   * A problem has been identified with the installation process on
     DBCS systems. If you are having problems install MySQL on a DBCS
     system, you need to change your job's coded character set
     identifier (`CSSID') to 37 (`EBCDIC') before executing the install
     command, `INSMYSQL'. To do this, determine your existing `CSSID'
     (using `DSPJOB' and selecting option 2), execute `CHGJOB
     CSSID(37)', run `INSMYSQL' to install MySQL and then execute
     `CHGJOB' again with your original `CSSID.'

   * If you want to use the Perl scripts that are included with MySQL,
     you need to download the iSeries Tools for Developers (5799-PTL).
     See `http://www-03.ibm.com/servers/enable/site/porting/tools/'.


File: manual.info,  Node: source-installation,  Next: postinstallation,  Prev: i5os-installation,  Up: installing

2.11 Installing MySQL from Source
=================================

* Menu:

* source-installation-layout::   MySQL Layout for Source Installation
* installing-source-distribution::  Installing MySQL Using a Standard Source Distribution
* installing-development-tree::  Installing MySQL Using a Development Source Tree
* source-configuration-options::  MySQL Source-Configuration Options
* compilation-problems::         Dealing with Problems Compiling MySQL
* compile-and-link-options::     Compiling and Linking an Optimized mysqld Server
* windows-source-build::         Installing MySQL from Source on Windows
* solaris-installation-source::  Notes on Installing MySQL on Solaris from Source
* aix-installation-source::      Notes on Installing MySQL on AIX from Source
* hpux-installation-source::     Notes on Installing MySQL on HP-UX from Source

Building MySQL from the source code enables you to customize build
parameters, compiler optimizations, and installation location. For a
list of systems on which MySQL is known to run, see
`http://www.mysql.com/support/supportedplatforms/database.html'.

Before you proceed with an installation from source, check whether we
produce a precompiled binary distribution for your platform and whether
it works for you. We put a great deal of effort into ensuring that our
binaries are built with the best possible options for optimal
performance. Instructions for installing binary distributions are
available in *Note binary-installation::.

To obtain a source distribution for MySQL, see *Note getting-mysql::.
MySQL source distributions are available as compressed `tar' files, Zip
archives, or RPM packages. Distribution files have names of the form
`mysql-VERSION.tar.gz', `mysql-VERSION.zip', or `mysql-VERSION.rpm',
where VERSION is a number like `5.1.73'.

To perform a MySQL installation using the source code:

   * To build MySQL from source on Unix-like systems, including Linux,
     commercial Unix, BSD, Mac OS X and others using a `.tar.gz' or
     RPM-based source code distribution, see *Note
     installing-source-distribution::.

   * To build MySQL from source on Windows (Windows XP or newer
     required), see *Note windows-source-build::.

   * For information on building from one of our development trees, see
     *Note installing-development-tree::.

   * For information on using the `configure' command to specify the
     source build parameters, including links to platform specific
     parameters that you might need, see *Note
     source-configuration-options::.

To install MySQL from source, your system must have the following tools:

   * GNU `gunzip' to uncompress the distribution and a reasonable `tar'
     to unpack it (if you use a `.tar.gz' distribution), or `WinZip' or
     another tool that can read `.zip' files (if you use a `.zip'
     distribution).

     GNU `tar' is known to work. The standard `tar' provided with some
     operating systems is not able to unpack the long file names in the
     MySQL distribution. You should download and install GNU `tar', or
     if available, use a preinstalled version of GNU tar. Usually this
     is available as `gnutar', `gtar', or as `tar' within a GNU or Free
     Software directory, such as `/usr/sfw/bin' or `/usr/local/bin'.
     GNU `tar' is available from `http://www.gnu.org/software/tar/'.

   * A working ANSI C++ compiler. GCC 3.4.6 or later, Sun Studio 10 or
     later, Visual Studio 2005 or later, and many current
     vendor-supplied compilers are known to work.

   * A good `make' program. Although some platforms come with their own
     `make' implementations, it is highly recommended that you use GNU
     `make' 3.75 or newer. It may already be available on your system as
     `gmake'. GNU `make' is available from
     `http://www.gnu.org/software/make/'.

   * `libtool' 1.5, available from
     `http://www.gnu.org/software/libtool/'. 1.5.24 or later is
     recommended.

If you run into problems and need to file a bug report, please use the
instructions in *Note bug-reports::.


File: manual.info,  Node: source-installation-layout,  Next: installing-source-distribution,  Prev: source-installation,  Up: source-installation

2.11.1 MySQL Layout for Source Installation
-------------------------------------------

By default, when you install MySQL after compiling it from a source
distribution, the installation step installs files under `/usr/local'.
Components are installed in the directories shown in the following
table. To configure particular installation locations, use the options
described at *Note source-configuration-options::.

*MySQL Layout for Installation from Source*

Directory                 Contents of Directory
`bin'                     Client programs and scripts
`include/mysql'           Include (header) files
`Docs'                    Manual in Info format
`man'                     Unix manual pages
`lib/mysql'               Libraries
`libexec'                 The *Note `mysqld': mysqld. server
`share/mysql'             Miscellaneous support files, including error
                          messages, sample configuration files, SQL for
                          database installation
`sql-bench'               Benchmarks
`var'                     Log files, databases

Within its installation directory, the layout of a source installation
differs from that of a binary installation in the following ways:

   * The *Note `mysqld': mysqld. server is installed in the `libexec'
     directory rather than in the `bin' directory.

   * The data directory is `var' rather than `data'.

   * *Note `mysql_install_db': mysql-install-db. is installed in the
     `bin' directory rather than in the `scripts' directory.

   * The header file and library directories are `include/mysql' and
     `lib/mysql' rather than `include' and `lib'.


File: manual.info,  Node: installing-source-distribution,  Next: installing-development-tree,  Prev: source-installation-layout,  Up: source-installation

2.11.2 Installing MySQL Using a Standard Source Distribution
------------------------------------------------------------

To install MySQL from source, first configure, build, and install from
a source package. Then follow the same postinstallation setup sequence
as for a binary installation.

If you start from a source RPM, use the following command to make a
binary RPM that you can install. If you do not have `rpmbuild', use
`rpm' instead.


     shell> rpmbuild --rebuild --clean MySQL-VERSION.src.rpm

The result is one or more binary RPM packages that you install as
indicated in *Note linux-installation-rpm::.

The sequence for installation from a compressed `tar' file source
distribution is similar to the process for installing from a generic
binary distribution that is detailed in *Note binary-installation::.
For a MySQL `.tar.gz' source distribution, the basic installation
command sequence looks like this:


     # Preconfiguration setup
     shell> groupadd mysql
     shell> useradd -g mysql mysql
     # Beginning of source-build specific instructions
     shell> tar zxvf mysql-VERSION.tar.gz
     shell> cd mysql-VERSION
     shell> ./configure --prefix=/usr/local/mysql
     shell> make
     shell> make install
     # End of source-build specific instructions
     # Postinstallation setup
     shell> cd /usr/local/mysql
     shell> chown -R mysql .
     shell> chgrp -R mysql .
     shell> bin/mysql_install_db --user=mysql
     shell> chown -R root .
     shell> chown -R mysql var
     # Next command is optional
     shell> cp support-files/my-medium.cnf /etc/my.cnf
     shell> bin/mysqld_safe --user=mysql &
     # Next command is optional
     shell> cp support-files/mysql.server /etc/init.d/mysql.server

A more detailed version of the source-build specific instructions is
shown following. Perform the following steps as the `mysql' user,
except as noted.

*Note*:

The procedure shown here does not set up any passwords for MySQL
accounts. After following the procedure, proceed to *Note
postinstallation::, for postinstallation setup and testing.

  1. Set up the `mysql' user and group that will be used to run and
     execute the MySQL server and own the database directory. For
     details, see Creating a `mysql' System User and Group, in *Note
     binary-installation::.

  2. Pick the directory under which you want to unpack the distribution
     and change location into it.

  3. Obtain a distribution file using the instructions in *Note
     getting-mysql::.

  4. Unpack the distribution into the current directory.  `tar' can
     uncompress and unpack the distribution if it has `z' option
     support:


          shell> tar zxvf /PATH/TO/MYSQL-VERSION.tar.gz

     This command creates a directory named `mysql-VERSION'.

     If your `tar' does not have `z' option support, use `gunzip' to
     unpack the distribution and `tar' to unpack it:


          shell> gunzip < /PATH/TO/MYSQL-VERSION.tar.gz | tar xvf -

  5. Change location into the top-level directory of the unpacked
     distribution:


          shell> cd mysql-VERSION

  6. Configure the source directory:


          shell> ./configure --prefix=/usr/local/mysql

     When you run `configure', you might want to specify other options.
     For example, if you need to debug *Note `mysqld': mysqld. or a
     MySQL client, run `configure' with the `--with-debug' option, and
     then recompile and link your clients with the new client library.
     See *Note porting::.

     Run `./configure --help' for a list of options. *Note
     source-configuration-options::, discusses some of the more useful
     options.

     If `configure' fails and you are going to send mail to a MySQL
     mailing list to ask for assistance, please include any lines from
     `config.log' that you think can help solve the problem. Also
     include the last couple of lines of output from `configure'. To
     file a bug report, please use the instructions in *Note
     bug-reports::.

  7. Compile the source distribution:


          shell> make

     Use `gmake' instead on systems where you are using GNU `make' and
     it has been installed as `gmake'.

     If the compile fails, see *Note compilation-problems::, for help.

  8. Install the distribution:


          shell> make install

     You might need to run this command as `root'.

The remainder of the installation process, including setting up the
configuration file, creating the core databases, and starting the MySQL
server, are identical to the remainder of the process as shown in
Generic Binary Install.

After everything has been installed, test the distribution. To start
the MySQL server, use the following command:


     shell> /usr/local/mysql/bin/mysqld_safe --user=mysql &

If you run the command as `root', you should use the `--user' option as
shown. The option value is the name of the login account that you
created in the first step to use for running the server. If you run the
*Note `mysqld_safe': mysqld-safe. command while logged in as that user,
you can omit the `--user' option.

If the command fails immediately and prints `mysqld ended', look for
information in the error log (which by default is the `HOST_NAME.err'
file in the data directory).

For more information about *Note `mysqld_safe': mysqld-safe, see *Note
mysqld-safe::.

To make it more convenient to invoke programs installed in
`/usr/local/mysql/bin', you can add that directory to your `PATH'
environment variable setting. That enables you to run a program by
typing only its name, not its entire path name. See *Note
setting-environment-variables::.

*Note*:

The accounts that are listed in the MySQL grant tables initially have
no passwords. After starting the server, you should set up passwords
for them using the instructions in *Note postinstallation::.


File: manual.info,  Node: installing-development-tree,  Next: source-configuration-options,  Prev: installing-source-distribution,  Up: source-installation

2.11.3 Installing MySQL Using a Development Source Tree
-------------------------------------------------------

This section discusses how to install MySQL from the latest development
source code. Development trees have not necessarily received the same
level of testing as standard release distributions, so this
installation method is usually required only if you need the most
recent code changes. Do not use a development tree for production
systems. If your goal is simply to get MySQL up and running on your
system, you should use a standard release distribution (either a binary
or source distribution). See *Note getting-mysql::.

To obtain the source tree, you must have Bazaar installed. The Bazaar
VCS Web site (http://bazaar-vcs.org) has instructions for downloading
and installing Bazaar on different platforms. Bazaar is supported on
any platform that supports Python, and is therefore compatible with any
Linux, Unix, Windows, or Mac OS X host.

MySQL development projects are hosted on Launchpad
(http://launchpad.net/). MySQL projects, including MySQL Server, MySQL
Workbench, and others are available from the Oracle/MySQL Engineering
(http://launchpad.net/~mysql) page. For the repositories related only to
MySQL Server, see the MySQL Server (http://launchpad.net/mysql-server)
page.

To build under Unix/Linux, you must have the following tools installed:

   * A good `make' program. Although some platforms come with their own
     `make' implementations, it is highly recommended that you use GNU
     `make' 3.75 or newer. It may already be available on your system
     as `gmake'. GNU `make' is available from
     `http://www.gnu.org/software/make/'.

   * `autoconf' 2.58 (or newer), available from
     `http://www.gnu.org/software/autoconf/'.

   * `automake' 1.8.1, available from
     `http://www.gnu.org/software/automake/'.

   * `libtool' 1.5, available from
     `http://www.gnu.org/software/libtool/'. 1.5.24 or later is
     recommended.

   * `m4', available from `http://www.gnu.org/software/m4/'.

   * `bison' 2.1 or newer, available from
     `http://www.gnu.org/software/bison/'. (Version 1 is no longer
     supported.) Use the latest version of `bison' where possible; if
     you experience problems, upgrade to a later version, rather than
     revert to an earlier one.

To build under Windows you must have Microsoft Visual C++ 2005 Express
Edition, Visual Studio .Net 2003 (7.1), or Visual Studio 2005 (8.0)
compiler system.

Once the necessary tools are installed, create a local branch of the
MySQL development tree on your machine using this procedure:

  1. To obtain a copy of the MySQL source code, you must create a new
     Bazaar branch. If you do not already have a Bazaar repository
     directory set up, you must initialize a new directory:


          shell> mkdir mysql-server
          shell> bzr init-repo --trees mysql-server

     This is a one-time operation.

  2. Assuming that you have an initialized repository directory, you
     can branch from the public MySQL server repositories to create a
     local source tree. To create a branch of a specific version:


          shell> cd mysql-server
          shell> bzr branch lp:mysql-server/5.1 mysql-5.1

     This is a one-time operation per source tree. You can branch the
     source trees for several versions of MySQL under the
     `mysql-server' directory.

  3. The initial download will take some time to complete, depending on
     the speed of your connection. Please be patient.  Once you have
     downloaded the first tree, additional trees should take
     significantly less time to download.

  4. When building from the Bazaar branch, you may want to create a
     copy of your active branch so that you can make configuration and
     other changes without affecting the original branch contents. You
     can achieve this by branching from the original branch:


          shell> bzr branch mysql-5.1 mysql-5.1-build

  5. To obtain changes made after you have set up the branch initially,
     update it using the `pull' option periodically. Use this command
     in the top-level directory of the local copy:


          shell> bzr pull

     To examine the changeset comments for the tree, use the `log'
     option to `bzr':


          shell> bzr log

     You can also browse changesets, comments, and source code online
     at the Launchpad MySQL Server (http://launchpad.net/mysql-server)
     page.

     If you see diffs (changes) or code that you have a question about,
     do not hesitate to send email to the MySQL `internals' mailing
     list. See *Note mailing-lists::. If you think you have a better
     idea on how to do something, send an email message to the list
     with a patch.

After you have the local branch, you can build MySQL server from the
source code. On Windows, the build process is different from
Unix/Linux: see *Note windows-source-build::.

On Unix/Linux, use the `autoconf' system to create the `configure'
script so that you can configure the build environment before building.
The following example shows the typical commands required to build
MySQL from a source tree.

  1. Change location to the top-level directory of the source tree;
     replace `mysql-5.1' with the appropriate directory name.


          shell> cd mysql-5.1

  2. Prepare the source tree for configuration.

     Prior to MySQL 5.1.12, you must separately configure the `InnoDB'
     storage engine. Run the following command from the main source
     directory:


          shell> (cd storage/innobase; autoreconf --force --install)

     You can omit the previous command for MySQL 5.1.12 and later, or
     if you do not require `InnoDB' support.

     Prepare the remainder of the source tree:


          shell> autoreconf --force --install

     As an alternative to the preceding `autoreconf' command, you can
     use `BUILD/autorun.sh', which acts as a shortcut for the following
     sequence of commands:


          shell> aclocal; autoheader
          shell> libtoolize --automake --force
          shell> automake --force --add-missing; autoconf

     If you get some strange errors during this stage, verify that you
     have the correct version of `libtool' installed.

  3. Configure the source tree and compile MySQL:


          shell> ./configure  # Add your favorite options here
          shell> make

     For a description of some `configure' options, see *Note
     source-configuration-options::.

     A collection of configuration scripts is located in the `BUILD/'
     subdirectory. For example, you may find it more convenient to use
     the `BUILD/compile-pentium-debug' script than the preceding set of
     shell commands. To compile on a different architecture, modify the
     script by removing flags that are Pentium-specific, or use another
     script that may be more appropriate. These scripts are provided on
     an `as-is' basis. They are not supported and their contents may
     change from release to release.

  4. When the build is done, run `make install'.  Be careful with this
     on a production machine; the installation command may overwrite
     your live release installation. If you already have MySQL
     installed and do not want to overwrite it, run `./configure' with
     values for the `--prefix', `--with-tcp-port', and
     `--with-unix-socket-path' options different from those used by
     your production server.  For additional information about
     preventing multiple servers from interfering with each other, see
     *Note multiple-servers::.

  5. Play hard with your new installation. For example, try to make new
     features crash. Start by running `make test'. See *Note
     mysql-test-suite::.

  6. If you have gotten to the `make' stage, but the distribution does
     not compile, please enter the problem into our bugs database using
     the instructions given in *Note bug-reports::. If you have
     installed the latest versions of the required tools, and they
     crash trying to process our configuration files, please report
     that also.  However, if you get a `command not found' error or a
     similar problem for required tools, do not report it. Instead,
     make sure that all the required tools are installed and that your
     `PATH' variable is set correctly so that your shell can find them.


File: manual.info,  Node: source-configuration-options,  Next: compilation-problems,  Prev: installing-development-tree,  Up: source-installation

2.11.4 MySQL Source-Configuration Options
-----------------------------------------

The `configure' script provides a great deal of control over how you
configure a MySQL source distribution.  Typically, you do this using
options on the `configure' command line. For a full list of options
supported by `configure', run this command:


     shell> ./configure --help

You can also affect `configure' using certain environment variables. See
*Note environment-variables::.

The following table shows the available `configure' options.

*MySQL Source-Configuration Option Reference (`configure')*

Formats                Description            Default        IntroducedRemoved
`--bindir=DIR'         User executables       `EPREFIX/bin'          
`--build=BUILD'        Configure for          `guessed'              
                       building on BUILD                             
`--cache-file=FILE'    Cache test results in  `disabled'             
                       FILE                                          
`-C'                   Alias for              `'                     
                       `-cache-file=config.cache'                       
`--config-cache'                                                     
`--datadir=DIR'        Read-only              `PREFIX/share'         
                       architecture-independent                       
                       data                                          
`--disable-FEATURE'    Do not include FEATURE `'                     
`--disable-community-features'Disable additional     `'             5.1.28  
                       features provided by                          
                       the community                                 
`--disable-dependency-tracking'Disable dependency     `'                     
                       tracking                                      
`--disable-grant-options'Disable GRANT options  `'                     
`--disable-largefile'  Omit support for       `'                     
                       large files                                   
`--disable-libtool-lock'Disable libtool lock   `'                     
`--disable-thread-safe-client'Compile the client     `'             5.1.7   
                       without threads                               
`--enable-FEATURE'     Enable FEATURE         `'                     
`--enable-assembler'   Use assembler          `'                     
                       versions of some                              
                       string functions if                           
                       available                                     
`--enable-debug-sync'  Compile in Debug Sync  `'             5.1.41  
                       facility                                      
`--enable-dependency-tracking'Do not reject slow     `'                     
                       dependency extractors                         
`--enable-fast-install'Optimize for fast      `yes'                  
                       installation                                  
`--enable-local-infile'Enable LOCAL for LOAD  `disabled'             
                       DATA INFILE                                   
`--enable-profiling'   Build a version with   `'             5.1.24  
                       query profiling code                          
`--enable-shared'      Build shared libraries `yes'                  
`--enable-static'      Build static libraries `yes'                  
`--enable-thread-safe-client'Compile the client     `'                     5.1.6
                       with threads                                  
`--exec-prefix=EPREFIX'Install                `'                     
                       architecture-dependent                        
                       files in EPREFIX                              
`-h'                   Display this help and  `'                     
                       exit                                          
`--help'                                                             
`--help=short'         Display options                               
                       specific to this                              
                       package                                       
`--help=recursive'     Display the short                             
                       help of all the                               
                       included packages                             
`--host=HOST'          Cross-compile to       `'                     
                       build programs to run                         
                       on HOST                                       
`--includedir=DIR'     C header files         `PREFIX/include'        
`--infodir=DIR'        Info documentation     `PREFIX/info'          
`--libdir=DIR'         Object code libraries  `EPREFIX/lib'          
`--libexecdir=DIR'     Program executables    `EPREFIX/libexec'        
`--localstatedir=DIR'  Modifiable             `PREFIX/var'           
                       single-machine data                           
`--mandir=DIR'         man documentation      `PREFIX/man'           
`-n'                   Do not create output   `'                     
                       files                                         
`--no-create'                                                        
`--oldincludedir=DIR'  C header files for     `/usr/include'         
                       non-gcc                                       
`--prefix=PREFIX'      Install                `'                     
                       architecture-independent                       
                       files in PREFIX                               
`--program-prefix=PREFIX'Prepend PREFIX to      `'                     
                       installed program                             
                       names                                         
`--program-suffix=SUFFIX'Append SUFFIX to       `'                     
                       installed program                             
                       names                                         
`--program-transform-name=PROGRAM'run sed PROGRAM on     `'                     
                       installed program                             
                       names                                         
`-q'                   Do not print           `'                     
                       `checking...' messages                        
`--quiet'                                                            
`--sbindir=DIR'        System administrative  `EPREFIX/sbin'         
                       executables                                   
`--sharedstatedir=DIR' Modifiable             `PREFIX/com'           
                       architecture-independent                       
                       data                                          
`--srcdir=DIR'         Find the sources in    `configure             
                       DIR                    directory or           
                                              ..'                    
`--sysconfdir=DIR'     Read-only              `PREFIX/etc'           
                       single-machine data                           
`--target=TARGET'      Configure for          `'                     
                       building compilers                            
                       for TARGET                                    
`-V'                   Display version        `'                     
                       information and exit                          
`--version'                                                          
`--with-PACKAGE'       Use PACKAGE            `'                     
`--with-archive-storage-engine'Enable the Archive     `no'                   5.1.9
                       Storage Engine                                
`--with-atomic-ops'    Implement atomic       `'             5.1.12  
                       operations using                              
                       pthread rwlocks or                            
                       atomic CPU                                    
                       instructions for                              
                       multi-processor                               
`--with-berkeley-db'   Use BerkeleyDB         `no'                   5.1.11
                       located in DIR                                
`--with-berkeley-db-includes'Find Berkeley DB       `'                     5.1.11
                       headers in DIR                                
`--with-berkeley-db-libs'Find Berkeley DB       `'                     5.1.11
                       libraries in DIR                              
`--with-big-tables'    Support tables with    `'                     
                       more than 4 G rows                            
                       even on 32 bit                                
                       platforms                                     
`--with-blackhole-storage-engine'Enable the Blackhole   `no'                   5.1.9
                       Storage Engine                                
`--with-charset'       Default character set  `'                     
`--with-client-ldflags'Extra linking          `'                     
                       arguments for clients                         
`--with-collation'     Default collation      `'                     
`--with-comment'       Comment about          `'                     
                       compilation                                   
                       environment                                   
`--with-csv-storage-engine'Enable the CSV         `yes'                  5.1.9
                       Storage Engine                                
`--with-darwin-mwcc'   Use Metrowerks         `'                     
                       CodeWarrior wrappers                          
                       on OS X/Darwin                                
`--with-debug'         Add debug code         `'             5.1.7   
`--with-debug=full'    Add debug code (adds                          
                       memory checker, very                          
                       slow)                                         
`--with-embedded-privilege-control'Build parts to check   `'                     
                       user's privileges                             
                       (only affects                                 
                       embedded library)                             
`--with-embedded-server'Build the embedded     `'                     
                       server                                        
`--with-error-inject'  Enable error           `'             5.1.11  
                       injection in MySQL                            
                       Server                                        
`--with-example-storage-engine'Enable the Example     `no'                   5.1.9
                       Storage Engine                                
`--with-extra-charsets'Use charsets in        `'                     
                       addition to default                           
`--with-fast-mutexes'  Compile with fast      `enabled'      5.1.5   
                       mutexes                                       
`--with-federated-storage-engine'Enable federated       `no'           5.1.3   5.1.9
                       storage engine                                
`--with-gnu-ld'        Assume the C compiler  `no'                   
                       uses GNU ld                                   
`--with-innodb'        Enable innobase        `no'           5.1.3   5.1.9
                       storage engine                                
`--with-lib-ccflags'   Extra CC options for   `'                     
                       libraries                                     
`--with-libwrap=DIR'   Compile in libwrap     `'                     
                       (tcp_wrappers) support                        
`--with-low-memory'    Try to use less        `'                     
                       memory to compile to                          
                       avoid memory                                  
                       limitations                                   
`--with-machine-type'  Set the machine type,  `'                     
                       like "powerpc"                                
`--with-max-indexes=N' Sets the maximum       `64'                   
                       number of indexes per                         
                       table                                         
`--with-mysqld-ldflags'Extra linking          `'                     
                       arguments for mysqld                          
`--with-mysqld-libs'   Extra libraries to     `'                     
                       link with for mysqld                          
`--with-mysqld-user'   What user the mysqld   `'                     
                       daemon shall be run as                        
`--with-mysqlmanager'  Build the              `Build if              
                       mysqlmanager binary    server is              
                                              built'                 
`--with-named-curses-libs'Use specified curses   `'                     
                       libraries                                     
`--with-named-thread-libs'Use specified thread   `'                     
                       libraries                                     
`--with-ndb-ccflags'   Extra CC options for   `'                     
                       ndb compile                                   
`--with-ndb-docs'      Include the NDB        `'                     
                       Cluster ndbapi and                            
                       mgmapi documentation                          
`--with-ndb-port'      Port for NDB Cluster   `'                     
                       management server                             
`--with-ndb-port-base' Port for NDB Cluster   `'                     
                       management server                             
`--with-ndb-sci=DIR'   Provide MySQL with a   `'                     
                       custom location of                            
                       sci library                                   
`--with-ndb-test'      Include the NDB        `'                     
                       Cluster ndbapi test                           
                       programs                                      
`--with-ndbcluster'    Include the NDB        `no'                   5.1.9
                       Cluster table handler                         
`--with-openssl=DIR'   Include the OpenSSL    `'                     5.1.9
                       support                                       
`--with-openssl-includes'Find OpenSSL headers   `'                     5.1.9
                       in DIR                                        
`--with-openssl-libs'  Find OpenSSL           `'                     5.1.9
                       libraries in DIR                              
`--with-other-libc=DIR'Link against libc and  `'                     
                       other standard                                
                       libraries installed in                        
                       the specified                                 
                       nonstandard location                          
`--with-pic'           Try to use only        `Use both'             
                       PIC/non-PIC objects                           
`--with-plugin-PLUGIN' Forces the named       `'             5.1.11  
                       plugin to be linked                           
                       into mysqld statically                        
`--with-plugins'       Plugins to include in  `none'         5.1.11  
                       mysqld                                        
`--with-pstack'        Use the pstack         `'                     5.1.54
                       backtrace library                             
`--with-pthread'       Force use of pthread   `'                     
                       library                                       
`--with-row-based-replication'Include row-based      `'             5.1.5   5.1.6
                       replication                                   
`--with-server-suffix' Append value to the    `'                     
                       version string                                
`--with-ssl=DIR'       Include SSL support    `'             5.1.11  
`--with-system-type'   Set the system type,   `'                     
                       like "sun-solaris10"                          
`--with-tags'          Include additional     `automatic'            
                       configurations                                
`--with-tcp-port'      Which port to use for  `3306'                 
                       MySQL services                                
`--with-unix-socket-path'Where to put the       `'                     
                       unix-domain socket                            
`--with-yassl'         Include the yaSSL      `'                     5.1.9
                       support                                       
`--with-zlib-dir=no|bundled|DIR'Provide MySQL with a   `'                     
                       custom location of                            
                       compression library                           
`--without-PACKAGE'    Do not use PACKAGE     `'                     
`--without-bench'      Skip building of the   `'                     5.1.11
                       benchmark suite                               
`--without-debug'      Build a production     `'                     5.1.6
                       version without                               
                       debugging code                                
`--without-docs'       Skip building of the   `'                     
                       documentation                                 
`--without-extra-tools'Skip building          `'                     5.1.9
                       utilities in the                              
                       tools directory                               
`--without-geometry'   Do not build           `'                     
                       geometry-related parts                        
`--without-libedit'    Use system libedit     `'                     
                       instead of bundled                            
                       copy                                          
`--without-man'        Skip building of the   `'                     
                       man pages                                     
`--without-ndb-binlog' Disable ndb binlog     `'             5.1.6   
`--without-ndb-debug'  Disable special ndb    `'                     
                       debug features                                
`--without-plugin-PLUGIN'Exclude PLUGIN         `'             5.1.11  
`--without-query-cache'Do not build query     `'                     
                       cache                                         
`--without-readline'   Use system readline    `'                     
                       instead of bundled                            
                       copy                                          
`--without-row-based-replication'Don't include          `'             5.1.7   5.1.14
                       row-based replication                         
`--without-server'     Only build the client  `'                     
`--without-uca'        Skip building of the   `'                     
                       national Unicode                              
                       collations                                    

If you are using a version of `gcc' recent enough to understand the
`-fno-exceptions' option, it is _very important_ that you use this
option.  Otherwise, you may compile a binary that crashes randomly. Also
use `-felide-constructors' and `-fno-rtti' along with
`-fno-exceptions'. When in doubt, do the following:


     CFLAGS="-O3" CXX=gcc CXXFLAGS="-O3 -felide-constructors \
            -fno-exceptions -fno-rtti" ./configure \
            --prefix=/usr/local/mysql --enable-assembler \
            --with-mysqld-ldflags=-all-static

On most systems, this gives you a fast and stable binary.

When compiling from source, you should also be aware of any platform
specific considerations that may influence and impact the build
process. Knowing and applying this information will help to ensure you
get the best performance and most stable binary for your chosen
platform. For more information, use the following sections:

   * *Note aix-installation-source::

   * *Note hpux-installation-source::

   * *Note solaris-installation-source::

Some of the `configure' options available are described here. For
options that may be of use if you have difficulties building MySQL, see
*Note compilation-problems::.

Many options configure compile-time defaults that can be overridden at
server startup. For example, the `--prefix', `--with-tcp-port', and
`with-unix-socket-path' options that configure the default installation
base directory location, TCP/IP port number, and Unix socket file can
be changed at server startup with the `--basedir', `--port', and
`--socket' options for *Note `mysqld': mysqld.

   * To compile just the MySQL client libraries and client programs and
     not the server, use the `--without-server' option:


          shell> ./configure --without-server

     If you have no C++ compiler, some client programs such as *Note
     `mysql': mysql. cannot be compiled because they require C++. In
     this case, you can remove the code in `configure' that tests for
     the C++ compiler and then run `./configure' with the
     `--without-server' option. The compile step should still try to
     build all clients, but you can ignore any warnings about files
     such as `mysql.cc'. (If `make' stops, try `make -k' to tell it to
     continue with the rest of the build even if errors occur.)

   * To build the embedded MySQL library (`libmysqld.a'), use the
     `--with-embedded-server' option.

   * To place your log files and database directories elsewhere than
     under `/usr/local/var', use a `configure' command something like
     one of these:


          shell> ./configure --prefix=/usr/local/mysql
          shell> ./configure --prefix=/usr/local \
                     --localstatedir=/usr/local/mysql/data

     The first command changes the installation prefix so that
     everything is installed under `/usr/local/mysql' rather than the
     default of `/usr/local'. The second command preserves the default
     installation prefix, but overrides the default location for
     database directories (normally `/usr/local/var') and changes it to
     `/usr/local/mysql/data'.

     You can also specify the installation directory and data directory
     locations at server startup time by using the `--basedir' and
     `--datadir' options. These can be given on the command line or in
     an MySQL option file, although it is more common to use an option
     file. See *Note option-files::.

   * The `--with-tcp-port' option specifies the port number on which
     the server listens for TCP/IP connections. The default is port
     3306. To listen on a different port, use a `configure' command
     like this:


          shell> ./configure --with-tcp-port=3307

   * On Unix, if you want the MySQL socket file location to be
     somewhere other than the default location (normally in the
     directory `/tmp' or `/var/run'), use a `configure' command like
     this:


          shell> ./configure \
                     --with-unix-socket-path=/usr/local/mysql/tmp/mysql.sock

     The socket file name must be an absolute path name. You can also
     change the location of `mysql.sock' at server startup by using a
     MySQL option file. See *Note problems-with-mysql-sock::.

   * To compile statically linked programs (for example, to make a
     binary distribution, to get better performance, or to work around
     problems with some Red Hat Linux distributions), run `configure'
     like this:


          shell> ./configure --with-client-ldflags=-all-static \
                     --with-mysqld-ldflags=-all-static

   * If you are using `gcc' and do not have `libg++' or `libstdc++'
     installed, you can tell `configure' to use `gcc' as your C++
     compiler:


          shell> CC=gcc CXX=gcc ./configure

     When you use `gcc' as your C++ compiler, it does not attempt to
     link in `libg++' or `libstdc++'. This may be a good thing to do
     even if you have those libraries installed. Some versions of them
     have caused strange problems for MySQL users in the past.

     In most cases, you can get a reasonably optimized MySQL binary by
     using the following options on the `configure' line:


          --prefix=/usr/local/mysql --enable-assembler \
          --with-mysqld-ldflags=-all-static

     The full `configure' line would, in other words, be something like
     the following for all recent `gcc' versions:


          CFLAGS="-O3 -mpentiumpro" CXX=gcc CXXFLAGS="-O3 -mpentiumpro \
          -felide-constructors -fno-exceptions -fno-rtti" ./configure \
          --prefix=/usr/local/mysql --enable-assembler \
          --with-mysqld-ldflags=-all-static

     The binaries we provide on the MySQL Web site at
     `http://dev.mysql.com/downloads/' are all compiled with full
     optimization and should work well for most users. See *Note
     binary-installation::.

   * If the build fails and produces errors about your compiler or
     linker not being able to create the shared library
     `libmysqlclient.so.N' (where N is a version number), you can work
     around this problem by giving the `--disable-shared' option to
     `configure'. In this case, `configure' does not build a shared
     `libmysqlclient.so.N' library.

   * By default, MySQL uses the `latin1' (cp1252 West European)
     character set. To change the default set, use the `--with-charset'
     option:


          shell> ./configure --with-charset=CHARSET

     CHARSET may be one of `binary', `armscii8', `ascii', `big5',
     `cp1250', `cp1251', `cp1256', `cp1257', `cp850', `cp852', `cp866',
     `cp932', `dec8', `eucjpms', `euckr', `gb2312', `gbk', `geostd8',
     `greek', `hebrew', `hp8', `keybcs2', `koi8r', `koi8u', `latin1',
     `latin2', `latin5', `latin7', `macce', `macroman', `sjis', `swe7',
     `tis620', `ucs2', `ujis', `utf8'. (Additional character sets might
     be available. Check the output from `./configure --help' for the
     current list.)

     The default collation may also be specified. MySQL uses the
     `latin1_swedish_ci' collation by default. To change this, use the
     `--with-collation' option:


          shell> ./configure --with-collation=COLLATION

     To change both the character set and the collation, use both the
     `--with-charset' and `--with-collation' options.  The collation
     must be a legal collation for the character set.  (Use the *Note
     `SHOW COLLATION': show-collation.  statement to determine which
     collations are available for each character set.)

     With the `configure' option `--with-extra-charsets=LIST', you can
     define which additional character sets should be compiled into the
     server. LIST is one of the following:

        * A list of character set names separated by spaces

        * `complex' to include all character sets that can't be
          dynamically loaded

        * `all' to include all character sets into the binaries

     Clients that want to convert characters between the server and the
     client should use the `SET NAMES' statement. See *Note
     charset-connection::.

   * To configure MySQL with debugging code, use the `--with-debug'
     option:


          shell> ./configure --with-debug

     This causes a safe memory allocator to be included that can find
     some errors and that provides output about what is happening. See
     *Note porting::.

     As of MySQL 5.1.12, using `--with-debug' to configure MySQL with
     debugging support enables you to use the
     `--debug="d,parser_debug"' option when you start the server. This
     causes the Bison parser that is used to process SQL statements to
     dump a parser trace to the server's standard error output.
     Typically, this output is written to the error log.

   * To cause the Debug Sync facility to be compiled into the server,
     use the `--enable-debug-sync' option.  This facility is used for
     testing and debugging. When compiled in, Debug Sync is disabled by
     default at runtime. To enable it, start *Note `mysqld': mysqld.
     with the `--debug-sync-timeout=N' option, where N is a timeout
     value greater than 0. (The default value is 0, which disables Debug
     Sync.) N becomes the default timeout for individual
     synchronization points.

     Debug Sync is also compiled in if you configure with the
     `--with-debug' option (which implies `--enable-debug-sync'), unless
     you also use the `--disable-debug-sync' option.

     For a description of the Debug Sync facility and how to use
     synchronization points, see MySQL Internals: Test Synchronization
     (http://dev.mysql.com/doc/internals/en/test-synchronization.html).

     The `--enable-debug-sync' and `--disable-debug-sync' options were
     added in MySQL 5.1.41.

   * If your client programs are using threads, you must compile a
     thread-safe version of the MySQL client library with the
     `--enable-thread-safe-client' configure option. This creates a
     `libmysqlclient_r' library with which you should link your
     threaded applications. See *Note c-api-threaded-clients::.

   * Some features require that the server be built with compression
     library support, such as the `COMPRESS()' and `UNCOMPRESS()'
     functions, and compression of the client/server protocol. The
     `--with-zlib-dir=no|bundled|DIR' option provides control over
     compression library support. The value `no' explicitly disables
     compression support. `bundled' causes the `zlib' library bundled
     in the MySQL sources to be used. A DIR path name specifies the
     directory in which to find the compression library sources.

   * It is possible to build MySQL with large table support using the
     `--with-big-tables' option.

     This option causes the variables that store table row counts to be
     declared as `unsigned long long' rather than `unsigned long'. This
     enables tables to hold up to approximately 1.844E+19 ((2^32)^2)
     rows rather than 2^32 (~4.295E+09) rows. Previously it was
     necessary to pass `-DBIG_TABLES' to the compiler manually in order
     to enable this feature.

   * Run `configure' with the `--disable-grant-options' option to cause
     the `--bootstrap', `--skip-grant-tables', and `--init-file'
     options for *Note `mysqld': mysqld. to be disabled. For Windows,
     the `configure.js' script recognizes the `DISABLE_GRANT_OPTIONS'
     flag, which has the same effect. The capability is available as of
     MySQL 5.1.15.

   * This option allows MySQL Community Server features to be enabled.
     Additional options may be required for individual features, such as
     `--enable-profiling' to enable statement profiling. This option
     was added in MySQL 5.1.24. It is enabled by default as of MySQL
     5.1.28; to disable it, use `--disable-community-features'.

   * When given with `--enable-community-features', the
     `--enable-profiling' option enables the statement profiling
     capability exposed by the *Note `SHOW PROFILE': show-profile. and
     *Note `SHOW PROFILES': show-profiles. statements. (See *Note
     show-profiles::.) This option was added in MySQL 5.1.24. It is
     enabled by default as of MySQL 5.1.28; to disable it, use
     `--disable-profiling'.

   * See *Note general-installation-issues::, for options that pertain
     to particular operating systems.

   * See *Note configuring-for-ssl::, for options that pertain to
     configuring MySQL to support secure (encrypted) connections.

   * Several `configure' options apply to plugin selection and building:


          --with-plugins=PLUGIN[,PLUGIN]...
          --with-plugins=GROUP
          --with-plugin-PLUGIN
          --without-plugin-PLUGIN

     PLUGIN is an individual plugin name such as `csv' or `archive'.

     As shorthand, GROUP is a configuration group name such as `none'
     (select no plugins) or `all' (select all plugins).

     You can build a plugin as static (compiled into the server) or
     dynamic (built as a dynamic library that must be installed using
     the *Note `INSTALL PLUGIN': install-plugin.  statement or the
     `--plugin-load' option before it can be used). Some plugins might
     not support static or dynamic build.

     `configure --help' shows the following information pertaining to
     plugins:

        * The plugin-related options

        * The names of all available plugins

        * For each plugin, a description of its purpose, which build
          types it supports (static or dynamic), and which plugin
          groups it is a part of.

     `--with-plugins' can take a list of one or more plugin names
     separated by commas, or a plugin group name. The named plugins are
     configured to be built as static plugins.

     `--with-plugin-PLUGIN' configures the given plugin to be built as
     a static plugin.

     `--without-plugin-PLUGIN' disables the given plugin from being
     built.

     If a plugin is named both with a `--with' and `--without' option,
     the result is undefined.

     For any plugin that is not explicitly selected or disabled, it is
     selected to be built dynamically if it supports dynamic build, and
     not built if it does not support dynamic build.  (Thus, in the
     case that no plugin options are given, all plugins that support
     dynamic build are selected to be built as dynamic plugins. Plugins
     that do not support dynamic build are not built.)


File: manual.info,  Node: compilation-problems,  Next: compile-and-link-options,  Prev: source-configuration-options,  Up: source-installation

2.11.5 Dealing with Problems Compiling MySQL
--------------------------------------------

All MySQL programs compile cleanly for us with no warnings on Solaris
or Linux using `gcc'. On other systems, warnings may occur due to
differences in system include files. For other problems, check the
following list.

The solution to many problems involves reconfiguring. If you do need to
reconfigure, take note of the following:

   * If `configure' is run after it has previously been run, it may use
     information that was gathered during its previous invocation. This
     information is stored in `config.cache'. When `configure' starts
     up, it looks for that file and reads its contents if it exists, on
     the assumption that the information is still correct. That
     assumption is invalid when you reconfigure.

   * Each time you run `configure', you must run `make' again to
     recompile. However, you may want to remove old object files from
     previous builds first because they were compiled using different
     configuration options.

To prevent old configuration information or object files from being
used, run these commands before re-running `configure':


     shell> rm config.cache
     shell> make clean

Alternatively, you can run `make distclean'.

The following list describes some of the problems that have been found
to occur most often when compiling MySQL:

   * If you get errors such as the ones shown here when compiling
     `sql_yacc.cc', you probably have run out of memory or swap space:


          Internal compiler error: program cc1plus got fatal signal 11
          Out of virtual memory
          Virtual memory exhausted

     The problem is that `gcc' requires a huge amount of memory to
     compile `sql_yacc.cc' with inline functions. Try running
     `configure' with the `--with-low-memory' option:


          shell> ./configure --with-low-memory

     This option causes `-fno-inline' to be added to the compile line
     if you are using `gcc' and `-O0' if you are using something else.
     You should try the `--with-low-memory' option even if you have so
     much memory and swap space that you think you can't possibly have
     run out. This problem has been observed to occur even on systems
     with generous hardware configurations, and the `--with-low-memory'
     option usually fixes it.

   * By default, `configure' picks `c++' as the compiler name and GNU
     `c++' links with `-lg++'. If you are using `gcc', that behavior
     can cause problems during configuration such as this:


          configure: error: installation or configuration problem:
          C++ compiler cannot create executables.

     You might also observe problems during compilation related to
     `g++', `libg++', or `libstdc++'.

     One cause of these problems is that you may not have `g++', or you
     may have `g++' but not `libg++', or `libstdc++'. Take a look at the
     `config.log' file. It should contain the exact reason why your C++
     compiler did not work. To work around these problems, you can use
     `gcc' as your C++ compiler. Try setting the environment variable
     `CXX' to `"gcc -O3"'. For example:


          shell> CXX="gcc -O3" ./configure

     This works because `gcc' compiles C++ source files as well as
     `g++' does, but does not link in `libg++' or `libstdc++' by
     default.

     Another way to fix these problems is to install `g++', `libg++',
     and `libstdc++'. However, do not use `libg++' or `libstdc++' with
     MySQL because this only increases the binary size of *Note
     `mysqld': mysqld. without providing any benefits. Some versions of
     these libraries have also caused strange problems for MySQL users
     in the past.

   * To define flags to be used by your C or C++ compilers, specify
     them using the `CFLAGS' and `CXXFLAGS' environment variables. You
     can also specify the compiler names this way using `CC' and `CXX'.
     For example:


          shell> CC=gcc
          shell> CFLAGS=-O3
          shell> CXX=gcc
          shell> CXXFLAGS=-O3
          shell> export CC CFLAGS CXX CXXFLAGS

     To see what flags you might need to specify, invoke *Note
     `mysql_config': mysql-config. with the `--cflags' option.

   * If you get errors such as those shown here when compiling *Note
     `mysqld': mysqld, `configure' did not correctly detect the type of
     the last argument to `accept()', `getsockname()', or
     `getpeername()':


          cxx: Error: mysqld.cc, line 645: In this statement, the referenced
               type of the pointer value ''length'' is ''unsigned long'',
               which is not compatible with ''int''.
          new_sock = accept(sock, (struct sockaddr *)&cAddr, &length);

     To fix this, edit the `config.h' file (which is generated by
     `configure'). Look for these lines:


          /* Define as the base type of the last arg to accept */
          #define SOCKET_SIZE_TYPE XXX

     Change `XXX' to `size_t' or `int', depending on your operating
     system.  (You must do this each time you run `configure' because
     `configure' regenerates `config.h'.)

   * If your compile fails with errors such as any of the following,
     you must upgrade your version of `make' to GNU `make':


          make: Fatal error in reader: Makefile, line 18:
          Badly formed macro assignment

     Or:


          make: file `Makefile' line 18: Must be a separator (:

     Or:


          pthread.h: No such file or directory

     Solaris and FreeBSD are known to have troublesome `make' programs.

     GNU `make' 3.75 is known to work.

   * The `sql_yacc.cc' file is generated from `sql_yacc.yy'. Normally,
     the build process does not need to create `sql_yacc.cc' because
     MySQL comes with a pregenerated copy. However, if you do need to
     re-create it, you might encounter this error:


          "sql_yacc.yy", line XXX fatal: default action causes potential...

     This is a sign that your version of `yacc' is deficient. You
     probably need to install `bison' (the GNU version of `yacc') and
     use that instead.

     Versions of `bison' older than 1.75 may report this error:


          sql_yacc.yy:#####: fatal error: maximum table size (32767) exceeded

     The maximum table size is not actually exceeded; the error is
     caused by bugs in older versions of `bison'.

   * On Debian Linux 3.0, you need to install `gawk' instead of the
     default `mawk'.

   * If you get a compilation error on Linux (for example, SuSE Linux
     8.1 or Red Hat Linux 7.3) similar to the following one, you
     probably do not have `g++' installed:


          libmysql.c:1329: warning: passing arg 5 of `gethostbyname_r' from
          incompatible pointer type
          libmysql.c:1329: too few arguments to function `gethostbyname_r'
          libmysql.c:1329: warning: assignment makes pointer from integer
          without a cast
          make[2]: *** [libmysql.lo] Error 1

     By default, the `configure' script attempts to determine the
     correct number of arguments by using `g++' (the GNU C++ compiler).
     This test yields incorrect results if `g++' is not installed.
     There are two ways to work around this problem:

        * Make sure that the GNU C++ `g++' is installed. On some Linux
          distributions, the required package is called `gpp'; on
          others, it is named `gcc-c++'.

        * Use `gcc' as your C++ compiler by setting the `CXX'
          environment variable to `gcc':


               export CXX="gcc"

     You must run `configure' again after making either of those
     changes.

For information about acquiring or updating tools, see the system
requirements in *Note source-installation::.


File: manual.info,  Node: compile-and-link-options,  Next: windows-source-build,  Prev: compilation-problems,  Up: source-installation

2.11.6 Compiling and Linking an Optimized mysqld Server
-------------------------------------------------------

Most of the following tests were performed on Linux with the MySQL
benchmarks, but they should give some indication for other operating
systems and workloads.

You obtain the fastest executables when you link with `-static'.

By using better compiler and compilation options, you can obtain a 10%
to 30% speed increase in applications. This is particularly important
if you compile the MySQL server yourself.

When we tested both the Cygnus CodeFusion and Fujitsu compilers,
neither was sufficiently bug-free to enable MySQL to be compiled with
optimizations enabled.

The standard MySQL binary distributions are compiled with support for
all character sets. When you compile MySQL yourself, include support
only for the character sets that you are going to use.  This is
controlled by the `--with-charset' option to `configure'.

Here is a list of some measurements that we have made:

   * If you link dynamically (without `-static'), the result is 13%
     slower on Linux. Note that you still can use a dynamically linked
     MySQL library for your client applications. It is the server that
     is most critical for performance.

   * For a connection from a client to a server running on the same
     host, if you connect using TCP/IP rather than a Unix socket file,
     performance is 7.5% slower. (On Unix, if you connect to the host
     name `localhost', MySQL uses a socket file by default.)

   * For TCP/IP connections from a client to a server, connecting to a
     remote server on another host is 8% to 11% slower than connecting
     to a server on the same host, even for connections faster than
     100Mb/s Ethernet.

   * When running our benchmark tests using secure connections (all
     data encrypted with internal SSL support) performance was 55%
     slower than with unencrypted connections.

   * On a Sun UltraSPARC-IIe, a server compiled with Forte 5.0 is 4%
     faster than one compiled with `gcc' 3.2.

   * On a Sun UltraSPARC-IIe, a server compiled with Forte 5.0 is 4%
     faster in 32-bit mode than in 64-bit mode.

   * Compiling on Linux-x86 using `gcc' without frame pointers
     (`-fomit-frame-pointer' or `-fomit-frame-pointer -ffixed-ebp')
     makes *Note `mysqld': mysqld. 1% to 4% faster.


File: manual.info,  Node: windows-source-build,  Next: solaris-installation-source,  Prev: compile-and-link-options,  Up: source-installation

2.11.7 Installing MySQL from Source on Windows
----------------------------------------------

These instructions describe how to build binaries from source for MySQL
5.1 on Windows. Instructions are provided for building binaries from a
standard source distribution or from the Bazaar tree that contains the
latest development source.

*Note*:

The instructions here are strictly for users who want to test MySQL on
Microsoft Windows from the latest source distribution or from the
Bazaar tree. For production use, we do not advise using a MySQL server
built by yourself from source. Normally, it is best to use precompiled
binary distributions of MySQL that are built specifically for optimal
performance on Windows by Oracle Corporation. Instructions for
installing binary distributions are available in *Note
windows-installation::.

To build MySQL on Windows from source, you must satisfy the following
system, compiler, and resource requirements:

   * Windows 2000, Windows XP, or newer version.

     Windows Vista is supported when using Visual Studio 2005 provided
     you have installed the following updates:

        * Microsoft Visual Studio 2005 Professional Edition - ENU
          Service Pack 1 (KB926601)
          (http://support.microsoft.com/?kbid=926601)

        * Security Update for Microsoft Visual Studio 2005 Professional
          Edition - ENU (KB937061)
          (http://support.microsoft.com/?kbid=937061)

        * Update for Microsoft Visual Studio 2005 Professional Edition
          - ENU (KB932232) (http://support.microsoft.com/?kbid=932232)

   * `CMake', which can be downloaded from `http://www.cmake.org'.
     After installing, modify your `PATH' environment variable to
     include the directory where `cmake' is located.

   * Microsoft Visual C++ 2005 Express Edition, Visual Studio .Net 2003
     (7.1), or Visual Studio 2005 (8.0) compiler system.

   * If you are using Visual C++ 2005 Express Edition, you must also
     install an appropriate Platform SDK. More information and links to
     downloads for various Windows platforms is available from
     `http://www.microsoft.com/downloads/details.aspx?familyid=0baf2b35-c656-4969-ace8-e4c0c0716adb'.

   * If you are compiling from a Bazaar tree or making changes to the
     parser, you need `bison' for Windows, which can be downloaded from
     `http://gnuwin32.sourceforge.net/packages/bison.htm'.  Download
     the package labeled `Complete package, excluding sources'. After
     installing the package, modify your `PATH' environment variable to
     include the directory where `bison' is located.

     *Note*:

     On Windows, the default location for `bison' is the `C:\Program
     Files\GnuWin32' directory. Some utilities, including `m4', may
     fail to find `bison' because of the space in the directory name.
     You can resolve this by installing into a directory that does not
     contain a space; for example `C:\GnuWin32'.

   * Cygwin might be necessary if you want to run the test script or
     package the compiled binaries and support files into a Zip
     archive. (Cygwin is needed only to test or package the
     distribution, not to build it.) Cygwin is available from
     `http://cygwin.com'.

   * 3GB to 5GB of disk space.

You also need a MySQL source distribution for Windows, which can be
obtained two ways:

   * Obtain a source distribution packaged by Oracle Corporation.
     These are available from `http://dev.mysql.com/downloads/'.

   * Package a source distribution yourself from the latest Bazaar
     developer source tree. For instructions on pulling the latest
     source files, see *Note installing-development-tree::.

If you find something not working as expected, or you have suggestions
about ways to improve the current build process on Windows, please send
a message to the `win32' mailing list. See *Note mailing-lists::.

*Note*:

To compile from the source code on Windows you must use the standard
source distribution (for example, `mysql-5.1.73.zip') or
`mysql-5.1.73.tar.gz'). You build from the same distribution as used to
build MySQL on Unix, Linux and other platforms. Do _not_ use the Windows
Source distributions as they do not contain the necessary configuration
script and other files.

Follow this procedure to build MySQL:

  1. If you are installing from a packaged source distribution, create
     a work directory (for example, `C:\workdir'), and unpack the source
     distribution there using `WinZip' or another Windows tool that can
     read `.zip' files.  This directory is the work directory in the
     following instructions.

     *Note*:

     Commands that are located in the `win' directory should be
     executed from the top-level source directory. Do not change
     location into the `win' directory, as the commands will not
     execute correctly.

  2. Start a command shell. If you have not configured the `PATH' and
     other environment variables for all command shells, you may be
     able to start a command shell from the `Start Menu' within the
     Windows Visual Studio menu that contains the necessary environment
     changes.

  3. Within the command shell, navigate to the work directory and run
     the following command:


          C:\workdir>win\configure.js OPTIONS

     If you have associated the `.js' file extension with an
     application such as a text editor, then you may need to use the
     following command to force `configure.js' to be executed as a
     script:


          C:\workdir>cscript win\configure.js OPTIONS

     These options are available for `configure.js':

        * `WITH_INNOBASE_STORAGE_ENGINE': Enable the *Note `InnoDB':
          innodb-storage-engine. storage engine.

        * `WITH_PARTITION_STORAGE_ENGINE': Enable user-defined
          partitioning.

        * `WITH_ARCHIVE_STORAGE_ENGINE': Enable the *Note `ARCHIVE':
          archive-storage-engine. storage engine.

        * `WITH_BLACKHOLE_STORAGE_ENGINE': Enable the *Note
          `BLACKHOLE': blackhole-storage-engine. storage engine.

        * `WITH_EXAMPLE_STORAGE_ENGINE': Enable the *Note `EXAMPLE':
          example-storage-engine. storage engine.

        * `WITH_FEDERATED_STORAGE_ENGINE': Enable the *Note
          `FEDERATED': federated-storage-engine. storage engine.

        * `WITH_NDBCLUSTER_STORAGE_ENGINE': Enable the *Note
          `NDBCLUSTER': mysql-cluster. storage engine in the MySQL
          server; cause binaries for the MySQL Cluster management and
          data node, management client, and other programs to be built.

          This option is supported only in MySQL Cluster NDB 7.0 and
          later (*Note `NDBCLUSTER': mysql-cluster. storage engine
          versions 6.4.0 and later) using the MySQL Cluster sources. It
          cannot be used to enable clustering support in other MySQL
          source trees or distributions.

        * `MYSQL_SERVER_SUFFIX=SUFFIX': Server suffix, default none.

        * `COMPILATION_COMMENT=COMMENT': Server comment, default
          "Source distribution".

        * `MYSQL_TCP_PORT=PORT': Server port, default 3306.

        * `DISABLE_GRANT_OPTIONS': Disables the `--bootstrap',
          `--skip-grant-tables', and `--init-file' options for *Note
          `mysqld': mysqld. This option is available as of MySQL 5.1.15.

     For example (type the command on one line):


          C:\workdir>win\configure.js WITH_INNOBASE_STORAGE_ENGINE
                       WITH_PARTITION_STORAGE_ENGINE MYSQL_SERVER_SUFFIX=-pro

  4. From the work directory, execute the `win\build-vs9.bat' (Windows
     Visual Studio 2008), `win\build-vs8.bat' (Windows Visual Studio
     2005), or `win\build-vs71.bat' (Windows Visual Studio 2003)
     script, depending on the version of Visual Studio you have
     installed. The script invokes `CMake', which generates the
     `mysql.sln' solution file.

     You can also use the corresponding 64-bit file (for example
     `win\build-vs8_x64.bat' or `win\build-vs9_x64.bat') to build the
     64-bit version of MySQL. However, you cannot build the 64-bit
     version with Visual Studio Express Edition. You must use Visual
     Studio 2005 (8.0) or higher.

  5. From the work directory, open the generated `mysql.sln' file with
     Visual Studio and select the proper configuration using the
     `Configuration' menu. The menu provides `Debug', `Release',
     `RelwithDebInfo', `MinRelInfo' options. Then select `Solution' >
     `Build' to build the solution.

     Remember the configuration that you use in this step. It is
     important later when you run the test script because that script
     needs to know which configuration you used.

  6. Test the server. The server built using the preceding instructions
     expects that the MySQL base directory and data directory are
     `C:\mysql' and `C:\mysql\data' by default. If you want to test
     your server using the source tree root directory and its data
     directory as the base directory and data directory, you need to
     tell the server their path names. You can either do this on the
     command line with the `--basedir' and `--datadir' options, or by
     placing appropriate options in an option file. (See *Note
     option-files::.) If you have an existing data directory elsewhere
     that you want to use, you can specify its path name instead.

     When the server is running in standalone fashion or as a service
     based on your configuration, try to connect to it from the *Note
     `mysql': mysql. interactive command-line utility.

     You can also run the standard test script, `mysql-test-run.pl'.
     This script is written in Perl, so you'll need either Cygwin or
     ActiveState Perl to run it. You may also need to install the
     modules required by the script. To run the test script, change
     location into the `mysql-test' directory under the work directory,
     set the `MTR_VS_CONFIG' environment variable to the configuration
     you selected earlier (or use the `--vs-config' option), and invoke
     `mysql-test-run.pl'. For example (using Cygwin and the `bash'
     shell):


          shell> `cd mysql-test'
          shell> `export MTR_VS_CONFIG=debug'
          shell> `./mysql-test-run.pl --force --timer'
          shell> `./mysql-test-run.pl --force --timer --ps-protocol'

When you are satisfied that the programs you have built are working
correctly, stop the server. Now you can install the distribution. One
way to do this is to use the *Note `make_win_bin_dist':
make-win-bin-dist. script in the `scripts' directory of the MySQL source
distribution (see *Note make-win-bin-dist::). This is a shell script,
so you must have Cygwin installed if you want to use it. It creates a
Zip archive of the built executables and support files that you can
unpack in the location at which you want to install MySQL.

It is also possible to install MySQL by copying directories and files
directly:

  1. Create the directories where you want to install MySQL. For
     example, to install into `C:\mysql', use these commands:


          C:\> mkdir C:\mysql
          C:\> mkdir C:\mysql\bin
          C:\> mkdir C:\mysql\data
          C:\> mkdir C:\mysql\share
          C:\> mkdir C:\mysql\scripts

     If you want to compile other clients and link them to MySQL, you
     should also create several additional directories:


          C:\> mkdir C:\mysql\include
          C:\> mkdir C:\mysql\lib
          C:\> mkdir C:\mysql\lib\debug
          C:\> mkdir C:\mysql\lib\opt

     If you want to benchmark MySQL, create this directory:


          C:\> mkdir C:\mysql\sql-bench

     Benchmarking requires Perl support for MySQL. See *Note
     perl-support::.

  2. From the work directory, copy into the `C:\mysql' directory the
     following files and directories:


          C:\> cd \workdir
          C:\workdir> mkdir C:\mysql
          C:\workdir> mkdir C:\mysql\bin
          C:\workdir> copy client\Release\*.exe C:\mysql\bin
          C:\workdir> copy sql\Release\mysqld.exe C:\mysql\bin\mysqld.exe
          C:\workdir> xcopy scripts\*.* C:\mysql\scripts /E
          C:\workdir> xcopy share\*.* C:\mysql\share /E

     If you want to compile other clients and link them to MySQL, you
     should also copy several libraries and header files:


          C:\workdir> copy lib\Release\mysqlclient.lib C:\mysql\lib\debug
          C:\workdir> copy lib\Release\libmysql.* C:\mysql\lib\debug
          C:\workdir> copy lib\Release\zlib.* C:\mysql\lib\debug
          C:\workdir> copy lib\Release\mysqlclient.lib C:\mysql\lib\opt
          C:\workdir> copy lib\Release\libmysql.* C:\mysql\lib\opt
          C:\workdir> copy lib\Release\zlib.* C:\mysql\lib\opt
          C:\workdir> copy include\*.h C:\mysql\include
          C:\workdir> copy libmysql\libmysql.def C:\mysql\include

     *Note*:

     If you have compiled a Debug solution, rather than a Release
     solution, install it by replacing `Release' with `Debug' in the
     source file names just shown.

     If you want to benchmark MySQL, you should also do this:


          C:\workdir> xcopy sql-bench\*.* C:\mysql\bench /E

After installation, set up and start the server in the same way as for
binary Windows distributions. This includes creating the system tables
by running *Note `mysql_install_db': mysql-install-db. For more
information, see *Note windows-installation::.


File: manual.info,  Node: solaris-installation-source,  Next: aix-installation-source,  Prev: windows-source-build,  Up: source-installation

2.11.8 Notes on Installing MySQL on Solaris from Source
-------------------------------------------------------

When building MySQL on Solaris you can use either the Sun Studio or GNU
cc compilers. For more information on specific notes and environments,
use the following hints.

   * When building you should ensure that your `PATH' variable includes
     the necessary tools, including `ar' for building libraries. Some
     tools are located in `/usr/ccs/bin'.

   * When running `configure', you should specify the C and C++
     compiler explicitly to ensure that the right C compiler
     combination is used:


          CC=gcc CXX=g++ ./configure

   * For detailed information on performance tuning your MySQL
     installation for Solaris, you can use the information from Krish
     Shankar
     (http://blogs.sun.com/krishs/entry/sun_studio_compiler_options_for)
     and the Sun Solaris MySQL Performance Tuning
     (http://developers.sun.com/solaris/articles/mysql_perf_tune.html)
     pages.

   * If you have an UltraSPARC system, you can get 4% better
     performance by adding `-mcpu=v8 -Wa,-xarch=v8plusa' to the `CFLAGS'
     and `CXXFLAGS' environment variables.

   * If you have Sun's Forte 5.00 (or newer) or Sun Studio compiler,
     you can run `configure' like this:


          CC=cc CFLAGS="-Xa -fast -native -xstrconst -mt" \
          CXX=CC CXXFLAGS="-noex -mt" \
          ./configure --prefix=/usr/local/mysql --enable-assembler

   * To create a 64-bit SPARC binary with Sun's Forte or Sun Studio
     compiler, use the following configuration options:


          CC=cc CFLAGS="-Xa -fast -native -xstrconst -mt -xarch=v9" \
          CXX=CC CXXFLAGS="-noex -mt -xarch=v9" ASFLAGS="-xarch=v9" \
          ./configure --prefix=/usr/local/mysql --enable-assembler

     To create a 64-bit Solaris binary using `gcc', add `-m64' to
     `CFLAGS' and `CXXFLAGS' and remove `--enable-assembler' from the
     `configure' line.

     In the MySQL benchmarks, we obtained a 4% speed increase on
     UltraSPARC when using Forte 5.0 in 32-bit mode, as compared to
     using `gcc' 3.2 with the `-mcpu' flag.

     If you create a 64-bit *Note `mysqld': mysqld. binary, it is 4%
     slower than the 32-bit binary, but can handle more threads and
     memory.

   * If you get a problem with `fdatasync' or `sched_yield', you can
     fix this by adding `LIBS=-lrt' to the `configure' line

   * Solaris does not provide static versions of all system libraries
     (`libpthreads' and `libdl'), so you cannot compile MySQL with
     `--static'. If you try to do so, you get one of the following
     errors:


          ld: fatal: library -ldl: not found
          undefined reference to `dlopen'
          cannot find -lrt

   * If you link your own MySQL client programs, you may see the
     following error at runtime:


          ld.so.1: fatal: libmysqlclient.so.#:
          open failed: No such file or directory

     To avoid this problem, use one of the following methods:

        * Use the `crle' tool to add the directory containing the
          `libmysqlclient' library file to the list of standard library
          directories. You need administrator privileges to do this.
          Make sure you update the library information, rather than
          replace it with the new path. For example, the following
          command adds the directory to the list of standard
          directories searched for libraries.


               crle -u -l /usr/local/mysql/lib

          For 64-bit libraries, add the `-64' option:


               crle -64 -u -l /usr/local/mysql/lib

        * Link clients with the `-Wl,r/full/path/to/libmysqlclient.so'
          flag rather than with `-Lpath').

        * Copy `libmysqlclient.so' to `/usr/lib'.

        * Add the path name of the directory where `libmysqlclient.so'
          is located to the `LD_RUN_PATH' environment variable before
          running your client.

   * If you have problems with `configure' trying to link with `-lz'
     when you do not have `zlib' installed, you have two options:

        * If you want to be able to use the compressed communication
          protocol, obtain and install `zlib' from `ftp.gnu.org'.

        * To build without `zlib', run `configure' with the
          `--with-named-z-libs=no' option when building MySQL.

   * If you are using `gcc' and have problems with loading user-defined
     functions (UDFs) into MySQL, try adding `-lgcc' to the link line
     for the UDF.


File: manual.info,  Node: aix-installation-source,  Next: hpux-installation-source,  Prev: solaris-installation-source,  Up: source-installation

2.11.9 Notes on Installing MySQL on AIX from Source
---------------------------------------------------

General notes on building MySQL from source on IBM AIX:

   * Automatic `xlC' detection is missing from Autoconf, so a number of
     variables need to be set before running `configure'. The following
     example uses the IBM compiler:


          export CC="xlc_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192 "
          export CXX="xlC_r -ma -O3 -qstrict -qoptimize=3 -qmaxmem=8192"
          export CFLAGS="-I /usr/local/include"
          export LDFLAGS="-L /usr/local/lib"
          export CPPFLAGS=$CFLAGS
          export CXXFLAGS=$CFLAGS

          ./configure --prefix=/usr/local \
                          --localstatedir=/var/mysql \
                          --sbindir='/usr/local/bin' \
                          --libexecdir='/usr/local/bin' \
                          --enable-thread-safe-client \
                          --enable-large-files

     The preceding options are used to compile the MySQL distribution
     that can be found at `http://www-frec.bull.com/'.

   * If you change the `-O3' to `-O2' in the preceding `configure'
     line, you must also remove the `-qstrict' option. This is a
     limitation in the IBM C compiler.

   * If you compile MySQL with `gcc', you _must_ use the
     `-fno-exceptions' flag because the exception handling in `gcc' is
     not thread-safe. There are also some known problems with IBM's
     assembler that may cause it to generate bad code when used with
     `gcc'.

   * If you have problems with signals (MySQL dies unexpectedly under
     high load), you may have found an OS bug with threads and signals.
     In this case, you can tell MySQL not to use signals by configuring
     as follows:


          CFLAGS=-DDONT_USE_THR_ALARM CXX=gcc \
          CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti \
          -DDONT_USE_THR_ALARM" \
          ./configure --prefix=/usr/local/mysql --with-debug \
              --with-low-memory

     This does not affect the performance of MySQL, but has the side
     effect that you cannot kill clients that are `sleeping' on a
     connection with *Note `mysqladmin kill': mysqladmin. or *Note
     `mysqladmin shutdown': mysqladmin. Instead, the client dies when
     it issues its next command.

   * On some versions of AIX, linking with `libbind.a' makes
     `getservbyname()' dump core. This is an AIX bug and should be
     reported to IBM.


File: manual.info,  Node: hpux-installation-source,  Prev: aix-installation-source,  Up: source-installation

2.11.10 Notes on Installing MySQL on HP-UX from Source
------------------------------------------------------

General notes on compiling MySQL on HP-UX.

   * If you are using HP-UX compiler, you can use the following command
     (which has been tested with `cc' B.11.11.04):


          CC=cc CXX=aCC CFLAGS=+DD64 CXXFLAGS=+DD64 ./configure \
              --with-extra-character-set=complex

     You can ignore any errors of the following type:


          aCC: warning 901: unknown option: `-3': use +help for online
          documentation

   * If you get the following error from `configure', verify that you
     do not have the path to the K&R compiler before the path to the
     HP-UX C and C++ compiler:


          checking for cc option to accept ANSI C... no
          configure: error: MySQL requires an ANSI C compiler (and a C++ compiler).
          Try gcc. See the Installation chapter in the Reference Manual.

   * Another reason for compile failure is that you did not define the
     `+DD64' flags as just described.


File: manual.info,  Node: postinstallation,  Next: upgrading-downgrading,  Prev: source-installation,  Up: installing

2.12 Postinstallation Setup and Testing
=======================================

* Menu:

* unix-postinstallation::        Unix Postinstallation Procedures
* default-privileges::           Securing the Initial MySQL Accounts

This section discusses post-installation items for Unix systems. If you
are using Windows, see *Note windows-postinstallation::.

After installing MySQL, there are some items that you should address.
For example:

   * You should initialize the data directory and create the MySQL
     grant tables, as describe in *Note unix-postinstallation::.

   * An important security concern is that the initial accounts in the
     grant tables have no passwords. You should assign passwords to
     prevent unauthorized access to the MySQL server. For instructions,
     see *Note default-privileges::.

   * Optionally, you can create time zone tables to enable recognition
     of named time zones. For instructions, see *Note
     mysql-tzinfo-to-sql::.

   * If you have trouble getting the server to start, see *Note
     starting-server::.

   * When you are ready to create additional user accounts, you can
     find information on the MySQL access control system and account
     management in *Note privilege-system::, and *Note
     user-account-management::.


File: manual.info,  Node: unix-postinstallation,  Next: default-privileges,  Prev: postinstallation,  Up: postinstallation

2.12.1 Unix Postinstallation Procedures
---------------------------------------

* Menu:

* mysql-install-db-problems::    Problems Running mysql_install_db
* automatic-start::              Starting and Stopping MySQL Automatically
* starting-server::              Starting and Troubleshooting the MySQL Server

After installing MySQL on Unix, you must initialize the grant tables,
start the server, and make sure that the server works satisfactorily.
You may also wish to arrange for the server to be started and stopped
automatically when your system starts and stops. You should also assign
passwords to the accounts in the grant tables.

On Unix, the grant tables are set up by the *Note `mysql_install_db':
mysql-install-db. program. For some installation methods, this program
is run for you automatically if an existing database cannot be found.

   * If you install MySQL on Linux using RPM distributions, the server
     RPM runs *Note `mysql_install_db': mysql-install-db.

   * Using the native packaging system on many platforms, including
     Debian Linux, Ubuntu Linux, Gentoo Linux and others, the *Note
     `mysql_install_db': mysql-install-db. command is run for you.

   * If you install MySQL on Mac OS X using a DMG distribution, the
     installer runs *Note `mysql_install_db': mysql-install-db.

For other platforms and installation types, including generic binary
and source installs, you will need to run *Note `mysql_install_db':
mysql-install-db. yourself.

The following procedure describes how to initialize the grant tables
(if that has not previously been done) and start the server. It also
suggests some commands that you can use to test whether the server is
accessible and working properly. For information about starting and
stopping the server automatically, see *Note automatic-start::.

After you complete the procedure and have the server running, you
should assign passwords to the accounts created by *Note
`mysql_install_db': mysql-install-db. and perhaps restrict access to
test databases. For instructions, see *Note default-privileges::.

In the examples shown here, the server runs under the user ID of the
`mysql' login account. This assumes that such an account exists. Either
create the account if it does not exist, or substitute the name of a
different existing login account that you plan to use for running the
server. For information about creating the account, see Creating a
`mysql' System User and Group, in *Note binary-installation::.

  1. Change location into the top-level directory of your MySQL
     installation, represented here by BASEDIR:


          shell> cd BASEDIR

     BASEDIR is the installation directory for your MySQL instance. It
     is likely to be something like `/usr/local/mysql' or `/usr/local'.
     The following steps assume that you have changed location to this
     directory.

     You will find several files and subdirectories in the BASEDIR
     directory. The most important for installation purposes are the
     `bin' and `scripts' subdirectories:

        * The `bin' directory contains client programs and the server.
          You should add the full path name of this directory to your
          `PATH' environment variable so that your shell finds the MySQL
          programs properly. See *Note environment-variables::.

          For some distribution types, *Note `mysqld': mysqld. is
          installed in the `libexec' directory.

        * The `scripts' directory contains the *Note
          `mysql_install_db': mysql-install-db. program used to
          initialize the `mysql' database containing the grant tables
          that store the server access permissions.

          For some distribution types, *Note `mysql_install_db':
          mysql-install-db. is installed in the `bin' directory.

  2. If necessary, ensure that the distribution contents are accessible
     to `mysql'. If you installed the distribution as `mysql', no
     further action is required. If you installed the distribution as
     `root', its contents will be owned by `root'. Change its ownership
     to `mysql' by executing the following commands as `root' in the
     installation directory. The first command changes the owner
     attribute of the files to the `mysql' user. The second changes the
     group attribute to the `mysql' group.


          shell> chown -R mysql .
          shell> chgrp -R mysql .

  3. If necessary, run the *Note `mysql_install_db': mysql-install-db.
     program to set up the initial MySQL grant tables containing the
     privileges that determine how users are permitted to connect to
     the server. You will need to do this if you used a distribution
     type for which the installation procedure does not run the program
     for you.

     Typically, *Note `mysql_install_db': mysql-install-db. needs to be
     run only the first time you install MySQL, so you can skip this
     step if you are upgrading an existing installation, However, *Note
     `mysql_install_db': mysql-install-db. does not overwrite any
     existing privilege tables, so it should be safe to run in any
     circumstances.

     The exact location of *Note `mysql_install_db': mysql-install-db.
     depends on the layout for your given installation. To initialize
     the grant tables, use one of the following commands, depending on
     whether *Note `mysql_install_db': mysql-install-db. is located in
     the `bin' or `scripts' directory:


          shell> scripts/mysql_install_db --user=mysql
          shell> bin/mysql_install_db --user=mysql

     It might be necessary to specify other options such as `--basedir'
     or `--datadir' if *Note `mysql_install_db': mysql-install-db. does
     not identify the correct locations for the installation directory
     or data directory. For example:


          shell> scripts/mysql_install_db --user=mysql \
                   --basedir=/opt/mysql/mysql \
                   --datadir=/opt/mysql/mysql/data

     The *Note `mysql_install_db': mysql-install-db. program creates the
     server's data directory with `mysql' as the owner. Under the data
     directory, it creates directories for the `mysql' database that
     holds the grant tables and the `test' database that you can use to
     test MySQL. The script also creates privilege table entries for
     `root' and anonymous-user accounts. The accounts have no passwords
     initially.  *Note default-privileges::, describes the initial
     privileges. Briefly, these privileges permit the MySQL `root' user
     to do anything, and permit anybody to create or use databases with
     a name of `test' or starting with `test_'. See *Note
     privilege-system::, for a complete listing and description of the
     grant tables.

     It is important to make sure that the database directories and
     files are owned by the `mysql' login account so that the server
     has read and write access to them when you run it later. To ensure
     this if you run *Note `mysql_install_db': mysql-install-db. as
     `root', include the `--user' option as shown. Otherwise, you
     should execute the program while logged in as `mysql', in which
     case you can omit the `--user' option from the command.

     If you do not want to have the `test' database, you can remove it
     after starting the server, using the instructions in *Note
     default-privileges::.

     If you have trouble with *Note `mysql_install_db':
     mysql-install-db.  at this point, see *Note
     mysql-install-db-problems::.

  4. Most of the MySQL installation can be owned by `root' if you like.
     The exception is that the data directory must be owned by `mysql'.
     To accomplish this, run the following commands as `root' in the
     installation directory. For some distribution types, the data
     directory might be named `var' rather than `data'; adjust the
     second command accordingly.


          shell> chown -R root .
          shell> chown -R mysql data

  5. If the plugin directory (the directory named by the `plugin_dir'
     system variable) is writable by the server, it may be possible for
     a user to write executable code to a file in the directory using
     *Note `SELECT ... INTO DUMPFILE': select-into. This can be
     prevented by making `plugin_dir' read only to the server or by
     setting `--secure-file-priv' to a directory where *Note `SELECT':
     select. writes can be made safely.

  6. If you installed MySQL using a source distribution, you may want
     to optionally copy one of the provided configuration files from
     the `support-files' directory into your `/etc' directory. There are
     different sample configuration files for different use cases,
     server types, and CPU and RAM configurations. If you want to use
     one of these standard files, you should copy it to `/etc/my.cnf',
     or `/etc/mysql/my.cnf' and edit and check the configuration before
     starting your MySQL server for the first time.

     If you do not copy one of the standard configuration files, the
     MySQL server will be started with the default settings.

     If you want MySQL to start automatically when you boot your
     machine, you can copy `support-files/mysql.server' to the location
     where your system has its startup files. More information can be
     found in the `mysql.server' script itself, and in *Note
     automatic-start::.

  7. Start the MySQL server:


          shell> bin/mysqld_safe --user=mysql &

     It is important that the MySQL server be run using an unprivileged
     (non-`root') login account. To ensure this if you run *Note
     `mysqld_safe': mysqld-safe. as `root', include the `--user' option
     as shown.  Otherwise, you should execute the program while logged
     in as `mysql', in which case you can omit the `--user' option from
     the command.

     For further instructions for running MySQL as an unprivileged
     user, see *Note changing-mysql-user::.

     If the command fails immediately and prints `mysqld ended', look
     for information in the error log (which by default is the
     `HOST_NAME.err' file in the data directory).

     If you neglected to create the grant tables by running *Note
     `mysql_install_db': mysql-install-db. before proceeding to this
     step, the following message appears in the error log file when you
     start the server:


          mysqld: Can't find file: 'host.frm'

     This error also occurs if you run *Note `mysql_install_db':
     mysql-install-db. as `root' without the `--user' option. Remove
     the `data' directory and run *Note `mysql_install_db':
     mysql-install-db. with the `--user' option as described previously.

     If you have other problems starting the server, see *Note
     starting-server::. For more information about *Note `mysqld_safe':
     mysqld-safe, see *Note mysqld-safe::.

  8. Use *Note `mysqladmin': mysqladmin. to verify that the server is
     running. The following commands provide simple tests to check
     whether the server is up and responding to connections:


          shell> bin/mysqladmin version
          shell> bin/mysqladmin variables

     The output from *Note `mysqladmin version': mysqladmin. varies
     slightly depending on your platform and version of MySQL, but
     should be similar to that shown here:


          shell> bin/mysqladmin version
          mysqladmin  Ver 14.12 Distrib 5.1.73, for pc-linux-gnu on i686
          ...

          Server version          5.1.73
          Protocol version        10
          Connection              Localhost via UNIX socket
          UNIX socket             /var/lib/mysql/mysql.sock
          Uptime:                 14 days 5 hours 5 min 21 sec

          Threads: 1  Questions: 366  Slow queries: 0
          Opens: 0  Flush tables: 1  Open tables: 19
          Queries per second avg: 0.000

     To see what else you can do with *Note `mysqladmin': mysqladmin,
     invoke it with the `--help' option.

  9. Verify that you can shut down the server:


          shell> bin/mysqladmin -u root shutdown

 10. Verify that you can start the server again. Do this by using *Note
     `mysqld_safe': mysqld-safe. or by invoking *Note `mysqld': mysqld.
     directly. For example:


          shell> bin/mysqld_safe --user=mysql &

     If *Note `mysqld_safe': mysqld-safe. fails, see *Note
     starting-server::.

 11. Run some simple tests to verify that you can retrieve information
     from the server. The output should be similar to what is shown
     here:


          shell> bin/mysqlshow
          +--------------------+
          |     Databases      |
          +--------------------+
          | information_schema |
          | mysql              |
          | test               |
          +--------------------+

          shell> bin/mysqlshow mysql
          Database: mysql
          +---------------------------+
          |          Tables           |
          +---------------------------+
          | columns_priv              |
          | db                        |
          | event                     |
          | func                      |
          | help_category             |
          | help_keyword              |
          | help_relation             |
          | help_topic                |
          | host                      |
          | plugin                    |
          | proc                      |
          | procs_priv                |
          | servers                   |
          | tables_priv               |
          | time_zone                 |
          | time_zone_leap_second     |
          | time_zone_name            |
          | time_zone_transition      |
          | time_zone_transition_type |
          | user                      |
          +---------------------------+

          shell> bin/mysql -e "SELECT Host,Db,User FROM db" mysql
          +------+--------+------+
          | host | db     | user |
          +------+--------+------+
          | %    | test   |      |
          | %    | test_% |      |
          +------+--------+------+

 12. There is a benchmark suite in the `sql-bench' directory (under the
     MySQL installation directory) that you can use to compare how MySQL
     performs on different platforms. The benchmark suite is written in
     Perl. It requires the Perl DBI module that provides a
     database-independent interface to the various databases, and some
     other additional Perl modules:


          DBI
          DBD::mysql
          Data::Dumper
          Data::ShowTable

     These modules can be obtained from CPAN (`http://www.cpan.org/').
     See also *Note perl-installation::.

     The `sql-bench/Results' directory contains the results from many
     runs against different databases and platforms. To run all tests,
     execute these commands:


          shell> cd sql-bench
          shell> perl run-all-tests

     If you do not have the `sql-bench' directory, you probably
     installed MySQL using RPM files other than the source RPM. (The
     source RPM includes the `sql-bench' benchmark directory.) In this
     case, you must first install the benchmark suite before you can
     use it. There are separate benchmark RPM files named
     `mysql-bench-VERSION.i386.rpm' that contain benchmark code and
     data.

     If you have a source distribution, there are also tests in its
     `tests' subdirectory that you can run. For example, to run
     `auto_increment.tst', execute this command from the top-level
     directory of your source distribution:


          shell> mysql -vvf test < ./tests/auto_increment.tst

     The expected result of the test can be found in the
     `./tests/auto_increment.res' file.

 13. At this point, you should have the server running. However, none
     of the initial MySQL accounts have a password, and the server
     permits permissive access to test databases. To tighten security,
     follow the instructions in *Note default-privileges::.

The MySQL 5.1 installation procedure creates time zone tables in the
`mysql' database but does not populate them. To do so, use the
instructions in *Note time-zone-support::.

To make it more convenient to invoke programs installed in the `bin'
directory under the installation directory, you can add that directory
to your `PATH' environment variable setting. That enables you to run a
program by typing only its name, not its entire path name. See *Note
setting-environment-variables::.

You can set up new accounts using the `bin/mysql_setpermission' script
if you install the `DBI' and `DBD::mysql' Perl modules. See *Note
mysql-setpermission::. For Perl module installation instructions, see
*Note perl-support::.

If you would like to use *Note `mysqlaccess': mysqlaccess. and have the
MySQL distribution in some nonstandard location, you must change the
location where *Note `mysqlaccess': mysqlaccess. expects to find the
*Note `mysql': mysql. client. Edit the `bin/mysqlaccess' script at
approximately line 18. Search for a line that looks like this:


     $MYSQL     = '/usr/local/bin/mysql';    # path to mysql executable

Change the path to reflect the location where *Note `mysql': mysql.
actually is stored on your system. If you do not do this, a `Broken
pipe' error will occur when you run *Note `mysqlaccess': mysqlaccess.


File: manual.info,  Node: mysql-install-db-problems,  Next: automatic-start,  Prev: unix-postinstallation,  Up: unix-postinstallation

2.12.1.1 Problems Running mysql_install_db
..........................................

The purpose of the *Note `mysql_install_db': mysql-install-db. program
is to generate new MySQL privilege tables. It does not overwrite
existing MySQL privilege tables, and it does not affect any other data.

If you want to re-create your privilege tables, first stop the *Note
`mysqld': mysqld. server if it is running. Then rename the `mysql'
directory under the data directory to save it, and then run *Note
`mysql_install_db': mysql-install-db. Suppose that your current
directory is the MySQL installation directory and that *Note
`mysql_install_db': mysql-install-db. is located in the `bin' directory
and the data directory is named `data'. To rename the `mysql' database
and re-run *Note `mysql_install_db': mysql-install-db, use these
commands.


     shell> mv data/mysql data/mysql.old
     shell> scripts/mysql_install_db --user=mysql

When you run *Note `mysql_install_db': mysql-install-db, you might
encounter the following problems:

   * **Note `mysql_install_db': mysql-install-db.  fails to install the
     grant tables*

     You may find that *Note `mysql_install_db': mysql-install-db. fails
     to install the grant tables and terminates after displaying the
     following messages:


          Starting mysqld daemon with databases from XXXXXX
          mysqld ended

     In this case, you should examine the error log file very
     carefully. The log should be located in the directory `XXXXXX'
     named by the error message and should indicate why *Note `mysqld':
     mysqld. did not start.  If you do not understand what happened,
     include the log when you post a bug report. See *Note
     bug-reports::.

   * *There is a *Note `mysqld': mysqld.  process running*

     This indicates that the server is running, in which case the grant
     tables have probably been created already. If so, there is no need
     to run *Note `mysql_install_db': mysql-install-db.  at all because
     it needs to be run only once (when you install MySQL the first
     time).

   * *Installing a second *Note `mysqld': mysqld. server does not work
     when one server is running*

     This can happen when you have an existing MySQL installation, but
     want to put a new installation in a different location. For
     example, you might have a production installation, but you want to
     create a second installation for testing purposes. Generally the
     problem that occurs when you try to run a second server is that it
     tries to use a network interface that is in use by the first
     server. In this case, you should see one of the following error
     messages:


          Can't start server: Bind on TCP/IP port:
          Address already in use
          Can't start server: Bind on unix socket...

     For instructions on setting up multiple servers, see *Note
     multiple-servers::.

   * *You do not have write access to the `/tmp' directory*

     If you do not have write access to create temporary files or a
     Unix socket file in the default location (the `/tmp' directory) or
     the `TMP_DIR' environment variable, if it has been set, an error
     occurs when you run *Note `mysql_install_db': mysql-install-db. or
     the *Note `mysqld': mysqld. server.

     You can specify different locations for the temporary directory
     and Unix socket file by executing these commands prior to starting
     *Note `mysql_install_db': mysql-install-db. or *Note `mysqld':
     mysqld, where SOME_TMP_DIR is the full path name to some directory
     for which you have write permission:


          shell> TMPDIR=/SOME_TMP_DIR/
          shell> MYSQL_UNIX_PORT=/SOME_TMP_DIR/mysql.sock
          shell> export TMPDIR MYSQL_UNIX_PORT

     Then you should be able to run *Note `mysql_install_db':
     mysql-install-db. and start the server with these commands:


          shell> scripts/mysql_install_db --user=mysql
          shell> bin/mysqld_safe --user=mysql &

     If *Note `mysql_install_db': mysql-install-db. is located in the
     `bin' directory, modify the first command to
     `bin/mysql_install_db'.

     See *Note problems-with-mysql-sock::, and *Note
     environment-variables::.

There are some alternatives to running the *Note `mysql_install_db':
mysql-install-db. program provided in the MySQL distribution:

   * If you want the initial privileges to be different from the
     standard defaults, you can modify *Note `mysql_install_db':
     mysql-install-db. before you run it.  However, it is preferable to
     use *Note `GRANT': grant. and *Note `REVOKE': revoke. to change the
     privileges _after_ the grant tables have been set up. In other
     words, you can run *Note `mysql_install_db': mysql-install-db, and
     then use `mysql -u root mysql' to connect to the server as the
     MySQL `root' user so that you can issue the necessary *Note
     `GRANT': grant.  and *Note `REVOKE': revoke. statements.

     If you want to install MySQL on several machines with the same
     privileges, you can put the *Note `GRANT': grant. and *Note
     `REVOKE': revoke. statements in a file and execute the file as a
     script using `mysql' after running *Note `mysql_install_db':
     mysql-install-db. For example:


          shell> scripts/mysql_install_db --user=mysql
          shell> bin/mysql -u root < your_script_file

     By doing this, you can avoid having to issue the statements
     manually on each machine.

   * It is possible to re-create the grant tables completely after they
     have previously been created. You might want to do this if you are
     just learning how to use *Note `GRANT': grant. and *Note `REVOKE':
     revoke. and have made so many modifications after running *Note
     `mysql_install_db': mysql-install-db. that you want to wipe out
     the tables and start over.

     To re-create the grant tables, remove all the `.frm', `.MYI', and
     `.MYD' files in the `mysql' database directory. Then run the *Note
     `mysql_install_db': mysql-install-db. program again.

   * You can start *Note `mysqld': mysqld. manually using the
     `--skip-grant-tables' option and add the privilege information
     yourself using *Note `mysql': mysql.:


          shell> bin/mysqld_safe --user=mysql --skip-grant-tables &
          shell> bin/mysql mysql

     From *Note `mysql': mysql, manually execute the SQL commands
     contained in *Note `mysql_install_db': mysql-install-db.  Make
     sure that you run *Note `mysqladmin flush-privileges': mysqladmin.
     or *Note `mysqladmin reload': mysqladmin. afterward to tell the
     server to reload the grant tables.

     Note that by not using *Note `mysql_install_db': mysql-install-db,
     you not only have to populate the grant tables manually, you also
     have to create them first.


File: manual.info,  Node: automatic-start,  Next: starting-server,  Prev: mysql-install-db-problems,  Up: unix-postinstallation

2.12.1.2 Starting and Stopping MySQL Automatically
..................................................

Generally, you start the *Note `mysqld': mysqld. server in one of these
ways:

   * Invoke *Note `mysqld': mysqld. directly. This works on any
     platform.

   * Invoke *Note `mysqld_safe': mysqld-safe, which tries to determine
     the proper options for *Note `mysqld': mysqld.  and then runs it
     with those options. This script is used on Unix and Unix-like
     systems. See *Note mysqld-safe::.

   * Invoke *Note `mysql.server': mysql-server. This script is used
     primarily at system startup and shutdown on systems that use
     System V-style run directories (that is, `/etc/init.d' and
     run-level specific directories), where it usually is installed
     under the name `mysql'. The *Note `mysql.server': mysql-server.
     script starts the server by invoking *Note `mysqld_safe':
     mysqld-safe. See *Note mysql-server::.

   * On Mac OS X, install a separate MySQL Startup Item package to
     enable the automatic startup of MySQL on system startup.  The
     Startup Item starts the server by invoking *Note `mysql.server':
     mysql-server. See *Note macosx-installation-startupitem::, for
     details. A MySQL Preference Pane also provides control for
     starting and stopping MySQL through the System Preferences, see
     *Note macosx-installation-prefpane::.

   * Use the Solaris/OpenSolaris service management framework (SMF)
     system to initiate and control MySQL startup. For more
     information, see *Note solaris-installation-opensolaris::.

The *Note `mysqld_safe': mysqld-safe. and *Note `mysql.server':
mysql-server. scripts, Solaris/OpenSolaris SMF, and the Mac OS X
Startup Item (or MySQL Preference Pane) can be used to start the server
manually, or automatically at system startup time. *Note
`mysql.server': mysql-server. and the Startup Item also can be used to
stop the server.

To start or stop the server manually using the *Note `mysql.server':
mysql-server. script, invoke it with `start' or `stop' arguments:


     shell> mysql.server start
     shell> mysql.server stop

Before *Note `mysql.server': mysql-server. starts the server, it
changes location to the MySQL installation directory, and then invokes
*Note `mysqld_safe': mysqld-safe. If you want the server to run as some
specific user, add an appropriate `user' option to the `[mysqld]' group
of the `/etc/my.cnf' option file, as shown later in this section. (It
is possible that you will need to edit *Note `mysql.server':
mysql-server. if you've installed a binary distribution of MySQL in a
nonstandard location. Modify it to change location into the proper
directory before it runs *Note `mysqld_safe': mysqld-safe. If you do
this, your modified version of *Note `mysql.server': mysql-server. may
be overwritten if you upgrade MySQL in the future, so you should make a
copy of your edited version that you can reinstall.)

*Note `mysql.server stop': mysql-server. stops the server by sending a
signal to it. You can also stop the server manually by executing *Note
`mysqladmin shutdown': mysqladmin.

To start and stop MySQL automatically on your server, you need to add
start and stop commands to the appropriate places in your `/etc/rc*'
files.

If you use the Linux server RPM package (`MySQL-server-VERSION.rpm'),
or a native Linux package installation, the *Note `mysql.server':
mysql-server. script may be installed in the `/etc/init.d' directory
with the name `mysql'. See *Note linux-installation-rpm::, for more
information on the Linux RPM packages.

Some vendors provide RPM packages that install a startup script under a
different name such as *Note `mysqld': mysqld.

If you install MySQL from a source distribution or using a binary
distribution format that does not install *Note `mysql.server':
mysql-server. automatically, you can install it manually. The script
can be found in the `support-files' directory under the MySQL
installation directory or in a MySQL source tree.

To install *Note `mysql.server': mysql-server. manually, copy it to the
`/etc/init.d' directory with the name *Note `mysql': mysql, and then
make it executable. Do this by changing location into the appropriate
directory where *Note `mysql.server': mysql-server. is located and
executing these commands:


     shell> cp mysql.server /etc/init.d/mysql
     shell> chmod +x /etc/init.d/mysql

*Note*:

Older Red Hat systems use the `/etc/rc.d/init.d' directory rather than
`/etc/init.d'. Adjust the preceding commands accordingly.
Alternatively, first create `/etc/init.d' as a symbolic link that
points to `/etc/rc.d/init.d':


     shell> cd /etc
     shell> ln -s rc.d/init.d .

After installing the script, the commands needed to activate it to run
at system startup depend on your operating system. On Linux, you can
use `chkconfig':


     shell> chkconfig --add mysql

On some Linux systems, the following command also seems to be necessary
to fully enable the *Note `mysql': mysql. script:


     shell> chkconfig --level 345 mysql on

On FreeBSD, startup scripts generally should go in
`/usr/local/etc/rc.d/'. The `rc(8)' manual page states that scripts in
this directory are executed only if their basename matches the `*.sh'
shell file name pattern. Any other files or directories present within
the directory are silently ignored. In other words, on FreeBSD, you
should install the `mysql.server' script as
`/usr/local/etc/rc.d/mysql.server.sh' to enable automatic startup.

As an alternative to the preceding setup, some operating systems also
use `/etc/rc.local' or `/etc/init.d/boot.local' to start additional
services on startup. To start up MySQL using this method, you could
append a command like the one following to the appropriate startup file:


     /bin/sh -c 'cd /usr/local/mysql; ./bin/mysqld_safe --user=mysql &'

For other systems, consult your operating system documentation to see
how to install startup scripts.

You can add options for *Note `mysql.server': mysql-server. in a global
`/etc/my.cnf' file. A typical `/etc/my.cnf' file might look like this:


     [mysqld]
     datadir=/usr/local/mysql/var
     socket=/var/tmp/mysql.sock
     port=3306
     user=mysql

     [mysql.server]
     basedir=/usr/local/mysql

The *Note `mysql.server': mysql-server. script supports the following
options: `basedir', `datadir', and `pid-file'. If specified, they
_must_ be placed in an option file, not on the command line. *Note
`mysql.server': mysql-server.  supports only `start' and `stop' as
command-line arguments.

The following table shows which option groups the server and each
startup script read from option files.

*MySQL Startup scripts and supported server option groups*

Script         Option Groups
*Note          `[mysqld]', `[server]', `[mysqld-MAJOR_VERSION]'
`mysqld':      
mysqld.        
*Note          `[mysqld]', `[server]', `[mysqld_safe]'
`mysqld_safe': 
mysqld-safe.   
*Note          `[mysqld]', `[mysql.server]', `[server]'
`mysql.server':
mysql-server.  

`[mysqld-MAJOR_VERSION]' means that groups with names like
`[mysqld-5.0]' and `[mysqld-5.1]' are read by servers having versions
5.0.x, 5.1.x, and so forth. This feature can be used to specify options
that can be read only by servers within a given release series.

For backward compatibility, *Note `mysql.server': mysql-server. also
reads the `[mysql_server]' group and *Note `mysqld_safe': mysqld-safe.
also reads the `[safe_mysqld]' group. However, you should update your
option files to use the `[mysql.server]' and `[mysqld_safe]' groups
instead when using MySQL 5.1.

For more information on MySQL configuration files and their structure
and contents, see *Note option-files::.


File: manual.info,  Node: starting-server,  Prev: automatic-start,  Up: unix-postinstallation

2.12.1.3 Starting and Troubleshooting the MySQL Server
......................................................

This section provides troubleshooting suggestions for problems starting
the server on Unix. If you are using Windows, see *Note
windows-troubleshooting::.

If you have problems starting the server, here are some things to try:

   * Check the error log to see why the server does not start.

   * Specify any special options needed by the storage engines you are
     using.

   * Make sure that the server knows where to find the data directory.

   * Make sure that the server can access the data directory. The
     ownership and permissions of the data directory and its contents
     must be set such that the server can read and modify them.

   * Verify that the network interfaces the server wants to use are
     available.

Some storage engines have options that control their behavior.  You can
create a `my.cnf' file and specify startup options for the engines that
you plan to use. If you are going to use storage engines that support
transactional tables (`InnoDB', *Note `NDB': mysql-cluster.), be sure
that you have them configured the way you want before starting the
server:

If you are using `InnoDB' tables, see *Note innodb-configuration::.

If you are using MySQL Cluster, see *Note mysql-cluster-configuration::.

Storage engines will use default option values if you specify none, but
it is recommended that you review the available options and specify
explicit values for those for which the defaults are not appropriate
for your installation.

When the *Note `mysqld': mysqld. server starts, it changes location to
the data directory. This is where it expects to find databases and
where it expects to write log files. The server also writes the pid
(process ID) file in the data directory.

The data directory location is hardwired in when the server is
compiled. This is where the server looks for the data directory by
default. If the data directory is located somewhere else on your
system, the server will not work properly. You can determine what the
default path settings are by invoking *Note `mysqld': mysqld. with the
`--verbose' and `--help' options.

If the default locations do not match the MySQL installation layout on
your system, you can override them by specifying options to *Note
`mysqld': mysqld. or *Note `mysqld_safe': mysqld-safe. on the command
line or in an option file.

To specify the location of the data directory explicitly, use the
`--datadir' option. However, normally you can tell *Note `mysqld':
mysqld. the location of the base directory under which MySQL is
installed and it looks for the data directory there. You can do this
with the `--basedir' option.

To check the effect of specifying path options, invoke *Note `mysqld':
mysqld. with those options followed by the `--verbose' and `--help'
options. For example, if you change location into the directory where
*Note `mysqld': mysqld. is installed and then run the following
command, it shows the effect of starting the server with a base
directory of `/usr/local':


     shell> ./mysqld --basedir=/usr/local --verbose --help

You can specify other options such as `--datadir' as well, but
`--verbose' and `--help' must be the last options.

Once you determine the path settings you want, start the server without
`--verbose' and `--help'.

If *Note `mysqld': mysqld. is currently running, you can find out what
path settings it is using by executing this command:


     shell> mysqladmin variables

Or:


     shell> mysqladmin -h HOST_NAME variables

HOST_NAME is the name of the MySQL server host.

If you get `Errcode 13' (which means `Permission denied') when starting
*Note `mysqld': mysqld, this means that the privileges of the data
directory or its contents do not permit server access. In this case,
you change the permissions for the involved files and directories so
that the server has the right to use them. You can also start the
server as `root', but this raises security issues and should be avoided.

On Unix, change location into the data directory and check the
ownership of the data directory and its contents to make sure the
server has access. For example, if the data directory is
`/usr/local/mysql/var', use this command:


     shell> ls -la /usr/local/mysql/var

If the data directory or its files or subdirectories are not owned by
the login account that you use for running the server, change their
ownership to that account. If the account is named `mysql', use these
commands:


     shell> chown -R mysql /usr/local/mysql/var
     shell> chgrp -R mysql /usr/local/mysql/var

If it possible that even with correct ownership, MySQL may fail to
start up if there is other security software running on your system
that manages application access to various parts of the file system. In
this case, you may need to reconfigure that software to enable *Note
`mysqld': mysqld. to access the directories it uses during normal
operation.

If the server fails to start up correctly, check the error log.  Log
files are located in the data directory (typically `C:\Program
Files\MySQL\MySQL Server 5.1\data' on Windows, `/usr/local/mysql/data'
for a Unix binary distribution, and `/usr/local/var' for a Unix source
distribution). Look in the data directory for files with names of the
form `HOST_NAME.err' and `HOST_NAME.log', where HOST_NAME is the name
of your server host. Then examine the last few lines of these files. On
Unix, you can use `tail' to display them:


     shell> tail HOST_NAME.err
     shell> tail HOST_NAME.log

The error log should contain information that indicates why the server
could not start.

If either of the following errors occur, it means that some other
program (perhaps another *Note `mysqld': mysqld. server) is using the
TCP/IP port or Unix socket file that *Note `mysqld': mysqld. is trying
to use:


     Can't start server: Bind on TCP/IP port: Address already in use
     Can't start server: Bind on unix socket...

Use `ps' to determine whether you have another *Note `mysqld': mysqld.
server running. If so, shut down the server before starting *Note
`mysqld': mysqld. again. (If another server is running, and you really
want to run multiple servers, you can find information about how to do
so in *Note multiple-servers::.)

If no other server is running, try to execute the command `telnet
YOUR_HOST_NAME TCP_IP_PORT_NUMBER'. (The default MySQL port number is
3306.) Then press Enter a couple of times. If you do not get an error
message like `telnet: Unable to connect to remote host: Connection
refused', some other program is using the TCP/IP port that *Note
`mysqld': mysqld. is trying to use. You will need to track down what
program this is and disable it, or else tell *Note `mysqld': mysqld. to
listen to a different port with the `--port' option. In this case, you
will also need to specify the port number for client programs when
connecting to the server using TCP/IP.

Another reason the port might be inaccessible is that you have a
firewall running that blocks connections to it. If so, modify the
firewall settings to permit access to the port.

If the server starts but you cannot connect to it, you should make sure
that you have an entry in `/etc/hosts' that looks like this:


     127.0.0.1       localhost

If you cannot get *Note `mysqld': mysqld. to start, you can try to make
a trace file to find the problem by using the `--debug' option. See
*Note dbug-package::.


File: manual.info,  Node: default-privileges,  Prev: unix-postinstallation,  Up: postinstallation

2.12.2 Securing the Initial MySQL Accounts
------------------------------------------

Part of the MySQL installation process is to set up the `mysql'
database that contains the grant tables:

   * Windows distributions contain preinitialized grant tables.

   * On Unix, the *Note `mysql_install_db': mysql-install-db. program
     populates the grant tables. Some installation methods run this
     program for you. Others require that you execute it manually.  For
     details, see *Note unix-postinstallation::.

The `mysql.user' grant table defines the initial MySQL user accounts
and their access privileges:

   * Some accounts have the user name `root'.  These are superuser
     accounts that have all privileges and can do anything. The initial
     `root' account passwords are empty, so anyone can connect to the
     MySQL server as `root' _without a password_ and be granted all
     privileges.

        * On Windows, `root' accounts are created that permit
          connections from the local host only.  Connections can be
          made by specifying the host name `localhost' or the IP address
          `127.0.0.1'. If the user selects the `Enable root access from
          remote machines' option during installation, the Windows
          installer creates another `root' account that permits
          connections from any host.

        * On Unix, each `root' account permits connections from the
          local host. Connections can be made by specifying the host
          name `localhost', the IP address `127.0.0.1', or the actual
          host name or IP address.

     An attempt to connect to the host `127.0.0.1' normally resolves to
     the `localhost' account.  However, this fails if the server is run
     with the `--skip-name-resolve' option, so the `127.0.0.1' account
     is useful in that case.

   * Some accounts are for anonymous users. These have an empty user
     name. The anonymous accounts have no password, so anyone can use
     them to connect to the MySQL server.

        * On Windows, there is one anonymous account that permits
          connections from the local host. Connections can be made by
          specifying a host name of `localhost'.  The account has no
          global privileges. (Before MySQL 5.1.16, it has all global
          privileges, just like the `root' accounts.)

        * On Unix, each anonymous account permits connections from the
          local host. Connections can be made by specifying a host name
          of `localhost' for one of the accounts, or the actual host
          name or IP address for the other.

To display which accounts exist in the `mysql.user' table and check
whether their passwords are empty, use the following statement:


     mysql> SELECT User, Host, Password FROM mysql.user;
     +------+--------------------+----------+
     | User | Host               | Password |
     +------+--------------------+----------+
     | root | localhost          |          |
     | root | myhost.example.com |          |
     | root | 127.0.0.1          |          |
     |      | localhost          |          |
     |      | myhost.example.com |          |
     +------+--------------------+----------+

This output indicates that there are several `root' and anonymous-user
accounts, none of which have passwords. The output might differ on your
system, but the presence of accounts with empty passwords means that
your MySQL installation is unprotected until you do something about it:

   * You should assign a password to each MySQL `root' account.

   * If you want to prevent clients from connecting as anonymous users
     without a password, you should either assign a password to each
     anonymous account or else remove the accounts.

In addition, the `mysql.db' table contains rows that permit all
accounts to access the `test' database and other databases with names
that start with `test_'. This is true even for accounts that otherwise
have no special privileges such as the default anonymous accounts. This
is convenient for testing but inadvisable on production servers.
Administrators who want database access restricted only to accounts
that have permissions granted explicitly for that purpose should remove
these `mysql.db' table rows.

The following instructions describe how to set up passwords for the
initial MySQL accounts, first for the `root' accounts, then for the
anonymous accounts. The instructions also cover how to remove the
anonymous accounts, should you prefer not to permit anonymous access at
all, and describe how to remove permissive access to test databases.
Replace NEWPWD in the examples with the password that you want to use.
Replace HOST_NAME with the name of the server host. You can determine
this name from the output of the preceding *Note `SELECT': select.
statement. For the output shown, HOST_NAME is `myhost.example.com'.

*Note*:

For additional information about setting passwords, see *Note
assigning-passwords::. If you forget your `root' password after setting
it, see *Note resetting-permissions::.

You might want to defer setting the passwords until later, to avoid the
need to specify them while you perform additional setup or testing.
However, be sure to set them before using your installation for
production purposes.

To set up additional accounts, see *Note adding-users::.

*Assigning root Account Passwords*

The `root' account passwords can be set several ways. The following
discussion demonstrates three methods:

   * Use the *Note `SET PASSWORD': set-password. statement

   * Use the *Note `UPDATE': update. statement

   * Use the *Note `mysqladmin': mysqladmin. command-line client program

To assign passwords using *Note `SET PASSWORD': set-password, connect
to the server as `root' and issue a *Note `SET PASSWORD': set-password.
statement for each `root' account listed in the `mysql.user' table. Be
sure to encrypt the password using the `PASSWORD()' function.

For Windows, do this:


     shell> mysql -u root
     mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('NEWPWD');
     mysql> SET PASSWORD FOR 'root'@'127.0.0.1' = PASSWORD('NEWPWD');
     mysql> SET PASSWORD FOR 'root'@'%' = PASSWORD('NEWPWD');

The last statement is unnecessary if the `mysql.user' table has no
`root' account with a host value of `%'.

For Unix, do this:


     shell> mysql -u root
     mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('NEWPWD');
     mysql> SET PASSWORD FOR 'root'@'127.0.0.1' = PASSWORD('NEWPWD');
     mysql> SET PASSWORD FOR 'root'@'HOST_NAME' = PASSWORD('NEWPWD');

You can also use a single statement that assigns a password to all
`root' accounts by using *Note `UPDATE': update. to modify the
`mysql.user' table directly. This method works on any platform:


     shell> mysql -u root
     mysql> UPDATE mysql.user SET Password = PASSWORD('NEWPWD')
         ->     WHERE User = 'root';
     mysql> FLUSH PRIVILEGES;

The *Note `FLUSH': flush. statement causes the server to reread the
grant tables. Without it, the password change remains unnoticed by the
server until you restart it.

To assign passwords to the `root' accounts using *Note `mysqladmin':
mysqladmin, execute the following commands:


     shell> mysqladmin -u root password "NEWPWD"
     shell> mysqladmin -u root -h HOST_NAME password "NEWPWD"

Those commands apply both to Windows and to Unix. The double quotation
marks around the password are not always necessary, but you should use
them if the password contains spaces or other characters that are
special to your command interpreter.

The *Note `mysqladmin': mysqladmin. method of setting the `root'
account passwords does not work for the `'root'@'127.0.0.1'' account.
Use the *Note `SET PASSWORD': set-password. method shown earlier.

After the `root' passwords have been set, you must supply the
appropriate password whenever you connect as `root' to the server. For
example, to shut down the server with *Note `mysqladmin': mysqladmin,
use this command:


     shell> mysqladmin -u root -p shutdown
     Enter password: (ENTER ROOT PASSWORD HERE)

*Assigning Anonymous Account Passwords*

The *Note `mysql': mysql. commands in the following instructions
include a `-p' option based on the assumption that you have set the
`root' account passwords using the preceding instructions and must
specify that password when connecting to the server.

To assign passwords to the anonymous accounts, connect to the server as
`root', then use either *Note `SET PASSWORD': set-password. or *Note
`UPDATE': update. Be sure to encrypt the password using the `PASSWORD()'
function.

To use *Note `SET PASSWORD': set-password. on Windows, do this:


     shell> mysql -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     mysql> SET PASSWORD FOR ''@'localhost' = PASSWORD('NEWPWD');

To use *Note `SET PASSWORD': set-password. on Unix, do this:


     shell> mysql -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     mysql> SET PASSWORD FOR ''@'localhost' = PASSWORD('NEWPWD');
     mysql> SET PASSWORD FOR ''@'HOST_NAME' = PASSWORD('NEWPWD');

To set the anonymous-user account passwords with a single *Note
`UPDATE': update. statement, do this (on any platform):


     shell> mysql -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     mysql> UPDATE mysql.user SET Password = PASSWORD('NEWPWD')
         ->     WHERE User = '';
     mysql> FLUSH PRIVILEGES;

The *Note `FLUSH': flush. statement causes the server to reread the
grant tables. Without it, the password change remains unnoticed by the
server until you restart it.

*Removing Anonymous Accounts*

If you prefer to remove any anonymous accounts rather than assigning
them passwords, do so as follows on Windows:


     shell> mysql -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     mysql> DROP USER ''@'localhost';

On Unix, remove the anonymous accounts like this:


     shell> mysql -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     mysql> DROP USER ''@'localhost';
     mysql> DROP USER ''@'HOST_NAME';

*Securing Test Databases*

By default, the `mysql.db' table contains rows that permit access by
any user to the `test' database and other databases with names that
start with `test_'. (These rows have an empty `User' column value,
which for access-checking purposes matches any user name.) This means
that such databases can be used even by accounts that otherwise possess
no privileges.  If you want to remove any-user access to test
databases, do so as follows:


     shell> mysql -u root -p
     Enter password: (ENTER ROOT PASSWORD HERE)
     mysql> DELETE FROM mysql.db WHERE Db LIKE 'test%';
     mysql> FLUSH PRIVILEGES;

The *Note `FLUSH': flush. statement causes the server to reread the
grant tables. Without it, the privilege change remains unnoticed by the
server until you restart it.

With the preceding change, only users who have global database
privileges or privileges granted explicitly for the `test' database can
use it. However, if you do not want the database to exist at all, drop
it:


     mysql> DROP DATABASE test;

*Note*:

On Windows, you can also perform the process described in this section
using the Configuration Wizard (see *Note
mysql-config-wizard-security::). On all platforms, the MySQL
distribution includes *Note `mysql_secure_installation':
mysql-secure-installation, a command-line utility that automates much
of the process of securing a MySQL installation.


File: manual.info,  Node: upgrading-downgrading,  Next: environment-variables,  Prev: postinstallation,  Up: installing

2.13 Upgrading or Downgrading MySQL
===================================

* Menu:

* upgrading::                    Upgrading MySQL
* downgrading::                  Downgrading MySQL
* checking-table-incompatibilities::  Checking Whether Tables or Indexes Must Be Rebuilt
* rebuilding-tables::            Rebuilding or Repairing Tables or Indexes
* copying-databases::            Copying MySQL Databases to Another Machine


File: manual.info,  Node: upgrading,  Next: downgrading,  Prev: upgrading-downgrading,  Up: upgrading-downgrading

2.13.1 Upgrading MySQL
----------------------

* Menu:

* upgrading-from-previous-series::  Upgrading from MySQL 5.0 to 5.1

As a general rule, to upgrade from one release series to another, go to
the next series rather than skipping a series. To upgrade from a
release series previous to MySQL 5.0, upgrade to each successive
release series in turn until you have reached MySQL 5.0, and then
proceed with the upgrade to MySQL 5.1. For example, if you currently
are running MySQL 4.1 and wish to upgrade to a newer series, upgrade to
MySQL 5.0 first before upgrading to 5.1, and so forth. For information
on upgrading to MySQL 5.0, see the `MySQL 5.0 Reference Manual'; for
earlier releases, see the `MySQL 3.23, 4.0, 4.1 Reference Manual'.

If you perform a binary (in-place) upgrade without dumping and
reloading tables, you cannot upgrade directly from MySQL 4.1 to 5.1.
This occurs due to an incompatible change in the `MyISAM' table index
format in MySQL 5.0. Upgrade from MySQL 4.1 to 5.0 and repair all
`MyISAM' tables (see *Note rebuilding-tables::). Then upgrade from
MySQL 5.0 to 5.1 and check and repair your tables.

To upgrade from MySQL 5.0 to 5.1, use the items in the following
checklist as a guide:

   * Before any upgrade, back up your databases, including the `mysql'
     database that contains the grant tables. See *Note
     backup-methods::.

   * Read _all_ the notes in *Note upgrading-from-previous-series::.
     These notes enable you to identify upgrade issues that apply to
     your current MySQL installation. Some incompatibilities discussed
     in that section require your attention _before_ upgrading. Others
     should be dealt with _after_ upgrading.

   * Read the Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) as well, which
     provide information about features that are new in MySQL 5.1 or
     differ from those found in MySQL 5.0.

   * After upgrading to a new version of MySQL, run *Note
     `mysql_upgrade': mysql-upgrade. (see *Note mysql-upgrade::). This
     program checks your tables, and attempts to repair them if
     necessary. It also updates your grant tables to make sure that
     they have the current structure so that you can take advantage of
     any new capabilities. (Some releases of MySQL introduce changes to
     the structure of the grant tables to add new privileges or
     features.)

     *Note `mysql_upgrade': mysql-upgrade. does not upgrade the contents
     of the help tables. For upgrade instructions, see *Note
     server-side-help-support::.

   * If you run MySQL Server on Windows, see *Note windows-upgrading::.

   * If you use replication, see *Note replication-upgrade::, for
     information on upgrading your replication setup.

   * If you use `InnoDB', consider setting `innodb_fast_shutdown' to 0
     before shutting down and upgrading your server. When you set
     `innodb_fast_shutdown' to 0, `InnoDB' does a slow shutdown, a full
     purge and an insert buffer merge before shutting down, which
     ensures that all data files are fully prepared in case the upgrade
     process modifies the file format.

   * If you upgrade an installation originally produced by installing
     multiple RPM packages, it is best to upgrade all the packages, not
     just some. For example, if you previously installed the server and
     client RPMs, do not upgrade just the server RPM.

   * As of MySQL 5.1.9, the `mysqld-max' server is included in binary
     distributions. There is no separate MySQL-Max distribution. As of
     MySQL 5.1.12, there is no `mysqld-max' server at all in binary
     distributions. They contain a server that includes the features
     previously included in `mysqld-max'.

   * If you have created a user-defined function (UDF) with a given
     name and upgrade MySQL to a version that implements a new built-in
     function with the same name, the UDF becomes inaccessible. To
     correct this, use *Note `DROP FUNCTION': drop-function. to drop
     the UDF, and then use *Note `CREATE FUNCTION': create-function. to
     re-create the UDF with a different nonconflicting name. The same
     is true if the new version of MySQL implements a built-in function
     with the same name as an existing stored function. See *Note
     function-resolution::, for the rules describing how the server
     interprets references to different kinds of functions.

For upgrades between versions of a MySQL release series that has
reached General Availability status, you can move the MySQL format
files and data files between different versions on systems with the
same architecture. For upgrades to a version of a MySQL release series
that is in development status, that is not necessarily true. Use of
development releases is at your own risk.

If you are cautious about using new versions, you can always rename
your old *Note `mysqld': mysqld. before installing a newer one. For
example, if you are using a version of MySQL 5.0 and want to upgrade to
5.1, rename your current server from *Note `mysqld': mysqld. to
`mysqld-5.0'. If your new *Note `mysqld': mysqld. then does something
unexpected, you can simply shut it down and restart with your old *Note
`mysqld': mysqld.

If problems occur, such as that the new *Note `mysqld': mysqld.  server
does not start or that you cannot connect without a password, verify
that you do not have an old `my.cnf' file from your previous
installation.  You can check this with the `--print-defaults' option
(for example, *Note `mysqld --print-defaults': mysqld.). If this
command displays anything other than the program name, you have an
active `my.cnf' file that affects server or client operation.

If, after an upgrade, you experience problems with compiled client
programs, such as `Commands out of sync' or unexpected core dumps, you
probably have used old header or library files when compiling your
programs. In this case, you should check the date for your `mysql.h'
file and `libmysqlclient.a' library to verify that they are from the
new MySQL distribution. If not, recompile your programs with the new
headers and libraries. Recompilation might also be necessary for
programs compiled against the shared client library if the library
major version number has changed (for example from
`libmysqlclient.so.15' to `libmysqlclient.so.16'.

If your MySQL installation contains a large amount of data that might
take a long time to convert after an in-place upgrade, you might find
it useful to create a `dummy' database instance for assessing what
conversions might be needed and the work involved to perform them. Make
a copy of your MySQL instance that contains a full copy of the `mysql'
database, plus all other databases without data. Run your upgrade
procedure on this dummy instance to see what actions might be needed so
that you can better evaluate the work involved when performing actual
data conversion on your original database instance.

It is a good idea to rebuild and reinstall the Perl `DBD::mysql' module
whenever you install a new release of MySQL. The same applies to other
MySQL interfaces as well, such as PHP `mysql' extensions and the Python
`MySQLdb' module.


File: manual.info,  Node: upgrading-from-previous-series,  Prev: upgrading,  Up: upgrading

2.13.1.1 Upgrading from MySQL 5.0 to 5.1
........................................

*After upgrading a 5.0 installation to 5.0.10 or above*, it is
_necessary_ to upgrade your grant tables. Otherwise, creating stored
procedures and functions might not work. To perform this upgrade, run
*Note `mysql_upgrade': mysql-upgrade.

*Note*:

It is good practice to back up your data before installing any new
version of software. Although MySQL works very hard to ensure a high
level of quality, you should protect your data by making a backup.

To upgrade to 5.1 from any previous version, MySQL recommends that you
dump your tables with *Note `mysqldump': mysqldump. before upgrading
and reload the dump file after upgrading. Use the `--all-databases'
option to include all databases in the dump. If your databases include
stored programs, use the `--routines' and `--events' options as well.

If you perform a binary (in-place) upgrade without dumping and
reloading tables, you cannot upgrade directly from MySQL 4.1 to 5.1.
This occurs due to an incompatible change in the `MyISAM' table index
format in MySQL 5.0. Upgrade from MySQL 4.1 to 5.0 and repair all
`MyISAM' tables (see *Note rebuilding-tables::). Then upgrade from MySQL
5.0 to 5.1 and check and repair your tables.

In general, you should do the following when upgrading from MySQL 5.0
to 5.1:

   * Read _all_ the items in these sections to see whether any of them
     might affect your applications:

        * *Note upgrading::, has general update information.

        * The items in the change lists provided later in this section
          enable you to identify upgrade issues that apply to your
          current MySQL installation. Some incompatibilities discussed
          there require your attention _before_ upgrading. Others
          should be dealt with _after_ upgrading.

        * The MySQL 5.1 Release Notes
          (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) describe
          significant new features you can use in 5.1 or that differ
          from those found in MySQL 5.0. Some of these changes may
          result in incompatibilities.

     Note particularly any changes that are marked *Known issue* or
     *Incompatible change*. These incompatibilities with earlier
     versions of MySQL may require your attention _before you upgrade_.
     Our aim is to avoid these changes, but occasionally they are
     necessary to correct problems that would be worse than an
     incompatibility between releases. If any upgrade issue applicable
     to your installation involves an incompatibility that requires
     special handling, follow the instructions given in the
     incompatibility description. Sometimes this involves dumping and
     reloading tables, or use of a statement such as *Note `CHECK
     TABLE': check-table. or *Note `REPAIR TABLE': repair-table.

     For dump and reload instructions, see *Note rebuilding-tables::.
     Any procedure that involves *Note `REPAIR TABLE': repair-table.
     with the `USE_FRM' option _must_ be done before upgrading. Use of
     this statement with a version of MySQL different from the one used
     to create the table (that is, using it after upgrading) may damage
     the table. See *Note repair-table::.

   * Before upgrading to a new version of MySQL, *Note
     checking-table-incompatibilities::, to see whether changes to
     table formats or to character sets or collations were made between
     your current version of MySQL and the version to which you are
     upgrading. If so and these changes result in an incompatibility
     between MySQL versions, you will need to upgrade the affected
     tables using the instructions in *Note rebuilding-tables::.

   * After upgrading to a new version of MySQL, run *Note
     `mysql_upgrade': mysql-upgrade. (see *Note mysql-upgrade::). This
     program checks your tables, and attempts to repair them if
     necessary. It also updates your grant tables to make sure that
     they have the current structure so that you can take advantage of
     any new capabilities. (Some releases of MySQL introduce changes to
     the structure of the grant tables to add new privileges or
     features.)

     *Note `mysql_upgrade': mysql-upgrade. does not upgrade the
     contents of the help tables. For upgrade instructions, see *Note
     server-side-help-support::.

   * If you run MySQL Server on Windows, see *Note windows-upgrading::.

   * If you use replication, see *Note replication-upgrade::, for
     information on upgrading your replication setup.

If your MySQL installation contains a large amount of data that might
take a long time to convert after an in-place upgrade, you might find
it useful to create a `dummy' database instance for assessing what
conversions might be needed and the work involved to perform them. Make
a copy of your MySQL instance that contains a full copy of the `mysql'
database, plus all other databases without data. Run your upgrade
procedure on this dummy instance to see what actions might be needed so
that you can better evaluate the work involved when performing actual
data conversion on your original database instance.

The following lists describe changes that may affect applications and
that you should watch out for when upgrading from MySQL 5.0 to 5.1.

*Configuration Changes*

   * Before MySQL 5.1.11, to build MySQL from source with SSL support
     enabled, you would invoke `configure' with either the
     `--with-openssl' or `--with-yassl' option. In MySQL 5.1.11, those
     options both have been replaced by the `--with-ssl' option. By
     default, `--with-ssl' causes the bundled yaSSL library to be used.
     To select OpenSSL instead, give the option as `--with-ssl=PATH',
     where PATH is the directory where the OpenSSL header files and
     libraries are located.

*Server Changes*

   * *Known issue*: As of MySQL 5.1.70, for new installations, the `url'
     columns in the `mysql' datatbase help tables are now created as
     type *Note `TEXT': blob. to accommodate longer URLs. For upgrades,
     *Note `mysql_upgrade': mysql-upgrade. does _not_ update the
     columns. Modify them manually using these statements:


          ALTER TABLE mysql.help_category MODIFY url TEXT NOT NULL;
          ALTER TABLE mysql.help_topic MODIFY url TEXT NOT NULL;

   * *Known issue*: *Note `mysql_upgrade': mysql-upgrade. attempts to
     upgrade tables that are incompatible with the current version of
     MySQL. (It invokes *Note `mysqlcheck': mysqlcheck. to check tables
     and, if necessary, repair them.) However this can fail for storage
     engines that do not support REPAIR TABLE, such as *Note `InnoDB':
     innodb-storage-engine, and leave tables in a nonupgradable state.

     To work around this problem, use *Note `ALTER TABLE TBL_NAME
     ENGINE=InnoDB': alter-table.  to perform a `null' alter operation
     that rebuilds the table.

   * *Known issue*: After a binary upgrade to MySQL 5.1 from a MySQL
     5.0 installation that contains *Note `ARCHIVE':
     archive-storage-engine. tables:

        * Before MySQL 5.1.42, accessing those tables will cause the
          server to crash, even if you have run *Note `mysql_upgrade':
          mysql-upgrade. or *Note `CHECK TABLE ... FOR UPGRADE':
          check-table.

        * As of MySQL 5.1.42, the server will not open 5.0 *Note
          `ARCHIVE': archive-storage-engine. tables at all.

     In either case, the solution is to use *Note `mysqldump':
     mysqldump. to dump all 5.0 *Note `ARCHIVE':
     archive-storage-engine. tables before upgrading, and reload them
     into MySQL 5.1 after upgrading.  This problem is fixed in MySQL
     5.6.4: The server can open *Note `ARCHIVE':
     archive-storage-engine. tables created in MySQL 5.0. However, it
     remains the recommended upgrade procedure to dump 5.0 *Note
     `ARCHIVE': archive-storage-engine. tables before upgrading and
     reload them after upgrading.

   * *Known issue*: The fix for Bug #23491 introduced a problem with
     *Note `SHOW CREATE VIEW': show-create-view, which is used by *Note
     `mysqldump': mysqldump. This causes an incompatibility when
     upgrading from versions affected by that bug fix (MySQL 5.0.40
     through 5.0.43, MySQL 5.1.18 through 5.1.19): If you use *Note
     `mysqldump': mysqldump.  before upgrading from an affected version
     and reload the data after upgrading to a higher version, you must
     drop and recreate your views.

   * *Known issue*: Dumps performed by using *Note `mysqldump':
     mysqldump. to generate a dump file before the upgrade and
     reloading the file after upgrading are subject to the following
     problem:

     Before MySQL 5.0.40, *Note `mysqldump': mysqldump. displays
     `SPATIAL' index definitions using prefix lengths for the indexed
     columns. These prefix lengths are accepted in MySQL 5.0, but not
     as of MySQL 5.1. If you use *Note `mysqldump': mysqldump. from
     versions of MySQL older than 5.0.40, any table containing `SPATIAL'
     indexes will cause an error when the dump file is reloaded into
     MySQL 5.1 or higher.

     For example, a table definition might look like this when dumped
     in MySQL 5.0:


          CREATE TABLE `t` (
           `g` geometry NOT NULL,
           SPATIAL KEY `g` (`g`(32))
          ) ENGINE=MyISAM DEFAULT CHARSET=latin1

     The `SPATIAL' index definition will not be accepted in MySQL 5.1.
     To work around this, edit the dump file to remove the prefix:


          CREATE TABLE `t` (
           `g` geometry NOT NULL,
           SPATIAL KEY `g` (`g`)
          ) ENGINE=MyISAM DEFAULT CHARSET=latin1

     Dump files can be large, so it may be preferable to dump table
     definitions and data separately to make it easier to edit the
     definitions:


          shell> mysqldump --no-data OTHER_ARGS > definitions.sql
          shell> mysqldump --no-create-info OTHER_ARGS > data.sql

     Then edit `definitions.sql' before reloading `definitions.sql' and
     `data.sql', in that order.

     If you upgrade to a version of MySQL 5.0 higher than 5.0.40 before
     upgrading to MySQL 5.1, this problem does not occur.

   * *Known issue*: Before MySQL 5.1.30, the *Note `CHECK TABLE ... FOR
     UPGRADE': check-table. statement did not check for incompatible
     collation changes made in MySQL 5.1.24. (This also affects *Note
     `mysqlcheck': mysqlcheck. and *Note `mysql_upgrade':
     mysql-upgrade, which cause that statement to be executed.)

     Prior to the fix made in 5.1.30, a binary upgrade (performed
     without dumping tables with *Note `mysqldump': mysqldump.  before
     the upgrade and reloading the dump file after the upgrade) would
     corrupt tables. After the fix, *Note `CHECK TABLE ... FOR
     UPGRADE': check-table. properly detects the problem and warns
     about tables that need repair.

     However, the fix is not backward compatible and can result in a
     downgrading problem under these circumstances:

       1. Perform a binary upgrade to a version of MySQL that includes
          the fix.

       2. Run *Note `CHECK TABLE ... FOR UPGRADE': check-table. (or
          *Note `mysqlcheck': mysqlcheck. or *Note `mysql_upgrade':
          mysql-upgrade.) to upgrade tables.

       3. Perform a binary downgrade to a version of MySQL that does
          not include the fix.

     The solution is to dump tables with *Note `mysqldump': mysqldump.
     before the downgrade and reload the dump file after the downgrade.
     Alternatively, drop and recreate affected indexes.

   * *Known issue*: MySQL introduces encoding for table names that have
     non-ASCII characters (see *Note identifier-mapping::). After a
     binary upgrade from MySQL 5.0 to 5.1 or higher, the server
     recognizes names that have non-ASCII characters and adds a
     `#mysql50#' prefix to them.

     As of MySQL 5.1.31, *Note `mysql_upgrade': mysql-upgrade. encodes
     these names by executing the following command:


          mysqlcheck --all-databases --check-upgrade --fix-db-names --fix-table-names

     Prior to MySQL 5.1.31, *Note `mysql_upgrade': mysql-upgrade. does
     not execute this command, so you should execute it manually if you
     have database or table names that contain nonalphanumeric
     characters.

     Prior to MySQL 5.1.23, the *Note `mysqlcheck': mysqlcheck.
     command does not perform the name encoding for views. To work
     around this problem, drop each affected view and recreate it.

     *Note `mysqlcheck': mysqlcheck. cannot fix names that contain
     literal instances of the `@' character that is used for encoding
     special characters. If you have databases or tables that contain
     this character, use *Note `mysqldump': mysqldump. to dump them
     before upgrading to MySQL 5.1, and then reload the dump file after
     upgrading.

   * *Known issue*: When upgrading from MySQL 5.0 to versions of 5.1
     prior to 5.1.23, running *Note `mysqlcheck': mysqlcheck. (or *Note
     `mysql_upgrade': mysql-upgrade, which runs *Note `mysqlcheck':
     mysqlcheck.) to upgrade tables fails for names that must be
     written as quoted identifiers. To work around this problem, rename
     each affected table to a name that does not require quoting:


          RENAME TABLE `tab``le_a` TO table_a;
          RENAME TABLE `table b` TO table_b;

     After renaming the tables, run the *Note `mysql_upgrade':
     mysql-upgrade. program. Then rename the tables back to their
     original names:


          RENAME TABLE table_a TO `tab``le_a`;
          RENAME TABLE table_b TO `table b`;

   * *Known issue*: In connection with view creation, the server created
     `arc' directories inside database directories and maintained
     useless copies of `.frm' files there. Creation and renaming
     procedures of those copies as well as creation of `arc'
     directories has been discontinued in MySQL 5.1.29.

     This change does cause a problem when downgrading to older server
     versions which manifests itself under these circumstances:

       1. Create a view `v_orig' in MySQL 5.1.29 or higher.

       2. Rename the view to `v_new' and then back to `v_orig'.

       3. Downgrade to an older 5.1.x server and run *Note
          `mysql_upgrade': mysql-upgrade.

       4. Try to rename `v_orig' to `v_new' again. This operation fails.

     As a workaround to avoid this problem, use either of these
     approaches:

        * Dump your data using *Note `mysqldump': mysqldump. before
          downgrading and reload the dump file after downgrading.

        * Instead of renaming a view after the downgrade, drop it and
          recreate it.

   * *Incompatible change*: Character set or collation changes may
     require table indexes to be rebuilt. In MySQL 5.1, these occurred
     in versions 5.1.21, 5.1.23, and 5.1.24. For details, see *Note
     checking-table-incompatibilities::.

   * *Incompatible change*: Prior to MySQL 5.1.51, if you flushed the
     logs using *Note `FLUSH LOGS': flush.  or *Note `mysqladmin
     flush-logs': mysqladmin. and *Note `mysqld': mysqld. was writing
     the error log to a file (for example, if it was started with the
     `--log-error' option), it renames the current log file with the
     suffix `-old', then created a new empty log file.  This had the
     problem that a second log-flushing operation thus caused the
     original error log file to be lost unless you saved it under a
     different name. For example, you could use the following commands
     to save the file:


          shell> mysqladmin flush-logs
          shell> mv HOST_NAME.err-old BACKUP-DIRECTORY

     To avoid the preceding file-loss problem, no renaming occurs as of
     MySQL 5.1.51; the server merely closes and reopens the log file.
     To rename the file, you can do so manually before flushing. Then
     flushing the logs reopens a new file with the original file name.
     For example, you can rename the file and create a new one using
     the following commands:


          shell> mv HOST_NAME.err HOST_NAME.err-old
          shell> mysqladmin flush-logs
          shell> mv HOST_NAME.err-old BACKUP-DIRECTORY

   * *Incompatible change*: MySQL 5.1 implements support for a plugin
     API that enables the loading and unloading of components at
     runtime, without restarting the server. *Note plugin-api::.  The
     plugin API requires the `mysql.plugin' table. After upgrading from
     an older version of MySQL, you should run the *Note
     `mysql_upgrade': mysql-upgrade. command to create this table. See
     *Note mysql-upgrade::.

     Plugins are installed in the directory named by the `plugin_dir'
     system variable.  This variable also controls the location from
     which the server loads user-defined functions (UDFs), which is a
     change from earlier versions of MySQL. That is, all UDF library
     files now must be installed in the plugin directory.  When
     upgrading from an older version of MySQL, you must migrate your
     UDF files to the plugin directory.

   * *Incompatible change*: The `table_cache' system variable has been
     renamed to `table_open_cache'. Any scripts that refer to
     `table_cache' must be updated to use the new name.

   * *Incompatible change*: In MySQL 5.1.36, options for loading
     plugins such as pluggable storage engines were changed from
     boolean to tristate format. The implementations overlap, but if
     you previously used options of the form `--PLUGIN_NAME=0' or
     `--PLUGIN_NAME=1', you should instead use `--PLUGIN_NAME=OFF' or
     `--PLUGIN_NAME=ON', respectively. For details, see *Note
     server-plugin-loading::.

   * *Incompatible change*: From MySQL 5.1.24 to 5.1.31, the *Note
     `UPDATE': update. statement was changed such that assigning `NULL'
     to a `NOT NULL' column caused an error even when strict SQL mode
     was not enabled. The original behavior before MySQL 5.1.24 was
     that such assignments caused an error only in strict SQL mode, and
     otherwise set the column to the implicit default value for the
     column data type and generated a warning. (For information about
     implicit default values, see *Note data-type-defaults::.)

     The change caused compatibility problems for applications that
     relied on the original behavior. It also caused replication
     problems between servers that had the original behavior and those
     that did not, for applications that assigned `NULL' to `NOT NULL'
     columns in *Note `UPDATE': update. statements without strict SQL
     mode enabled. The change was reverted in MySQL 5.1.32 so that
     *Note `UPDATE': update. again had the original behavior. Problems
     can still occur if you replicate between servers that have the
     modified *Note `UPDATE': update. behavior and those that do not.

   * *Incompatible change*: As of MySQL 5.1.29, the default binary
     logging mode has been changed from `MIXED' to `STATEMENT' for
     compatibility with MySQL 5.0.

   * *Incompatible change*: In MySQL 5.1.25, a change was made to the
     way that the server handles prepared statements. This affects
     prepared statements processed at the SQL level (using the *Note
     `PREPARE': prepare. statement) and those processed using the
     binary client/server protocol (using the *Note
     `mysql_stmt_prepare()': mysql-stmt-prepare. C API function).

     Previously, changes to metadata of tables or views referred to in
     a prepared statement could cause a server crash when the statement
     was next executed, or perhaps an error at execute time with a
     crash occurring later. For example, this could happen after
     dropping a table and recreating it with a different definition.

     Now metadata changes to tables or views referred to by prepared
     statements are detected and cause automatic repreparation of the
     statement when it is next executed.  Metadata changes occur for
     DDL statements such as those that create, drop, alter, rename, or
     truncate tables, or that analyze, optimize, or repair tables.
     Repreparation also occurs after referenced tables or views are
     flushed from the table definition cache, either implicitly to make
     room for new entries in the cache, or explicitly due to *Note
     `FLUSH TABLES': flush.

     Repreparation is automatic, but to the extent that it occurs,
     performance of prepared statements is diminished.

     Table content changes (for example, with *Note `INSERT': insert. or
     *Note `UPDATE': update.) do not cause repreparation, nor do *Note
     `SELECT': select.  statements.

     An incompatibility with previous versions of MySQL is that a
     prepared statement may now return a different set of columns or
     different column types from one execution to the next.  For
     example, if the prepared statement is `SELECT * FROM t1', altering
     `t1' to contain a different number of columns causes the next
     execution to return a number of columns different from the previous
     execution.

     Older versions of the client library cannot handle this change in
     behavior. For applications that use prepared statements with the
     new server, an upgrade to the new client library is strongly
     recommended.

     Along with this change to statement repreparation, the default
     value of the `table_definition_cache' system variable has been
     increased from 128 to 256. The purpose of this increase is to
     lessen the chance that prepared statements will need repreparation
     due to referred-to tables/views having been flushed from the cache
     to make room for new entries.

     A new status variable, `Com_stmt_reprepare', has been introduced
     to track the number of repreparations.

   * *Incompatible change*: The `-', `*', and `/' operators and the
     functions `POW()' and `EXP()' could misbehave when used with
     floating-point numbers. Previously they might return `+INF',
     `-INF', or `NaN' in cases of numeric overflow (including that
     caused by division by zero) or when invalid arguments were used.
     As of MySQL 5.1.24, `NULL' is returned in all such cases.

   * *Incompatible change*: As of MySQL 5.1.23, within a stored
     routine, it is no longer permissible to declare a cursor for a
     *Note `SHOW': show. or *Note `DESCRIBE': describe. statement. This
     happened to work in some instances, but is no longer supported. In
     many cases, a workaround for this change is to use the cursor with
     a *Note `SELECT': select.  query to read from an
     `INFORMATION_SCHEMA' table that produces the same information as
     the *Note `SHOW': show. statement.

   * *Incompatible change*: *Note `SHOW CREATE VIEW': show-create-view.
     displays view definitions using an `AS ALIAS_NAME' clause for each
     column. If a column is created from an expression, the default
     alias is the expression text, which can be quite long. As of MySQL
     5.1.23, aliases for column names in *Note `CREATE VIEW':
     create-view. statements are checked against the maximum column
     length of 64 characters (not the maximum alias length of 256
     characters). As a result, views created from the output of *Note
     `SHOW CREATE VIEW': show-create-view. fail if any column alias
     exceeds 64 characters. This can cause problems for replication or
     loading dump files. For additional information and workarounds, see
     *Note view-restrictions::.

   * *Incompatible change*: Several issues were identified for stored
     programs (stored procedures and functions, triggers, and events)
     and views containing non-ASCII symbols. These issues involved
     conversion errors due to incomplete character set information when
     translating these objects to and from stored format.

     To address these problems, the representation for these objects
     was changed in MySQL 5.1.21. However, the fixes affect _all_
     stored programs and views.  (For example, you will see warnings
     about `no creation context.') To avoid warnings from the server
     about the use of old definitions from any release prior to 5.1.21,
     you should dump stored programs and views with *Note `mysqldump':
     mysqldump. after upgrading to 5.1.21 or higher, and then reload
     them to recreate them with new definitions. Invoke *Note
     `mysqldump': mysqldump. with a `--default-character-set' option
     that names the non-ASCII character set that was used for the
     definitions when the objects were originally created, and the
     `--routines', `--events', and `--triggers' options to dump stored
     program definitions.

     Upgrading for triggers in particular must be handled carefully,
     for two reasons:

        * The output from *Note `mysqldump': mysqldump. does not
          contain a *Note `DROP TRIGGER': drop-trigger.  statement
          preceding each *Note `CREATE TRIGGER': create-trigger.
          statement, so reloading the dump file will fail to re-create
          the triggers unless you manually drop them after generating
          the dump file and before reloading it.

        * If you are upgrading from a very old version of MySQL 5.0
          (before 5.0.10), the trigger upgrade procedure is different
          because triggers for those versions were created using a
          different namespace (trigger names had to be unique per
          table, rather than per schema as is true now). For
          instructions on upgrading triggers from old 5.0 versions, see
          Upgrading from MySQL 4.1 to 5.0
          (http://dev.mysql.com/doc/refman/5.0/en/upgrading-from-previous-series.html).

     Assuming that you are upgrading from MySQL 5.0.10 to 5.1.20 to
     MySQL 5.1.21 or later, use the following procedure to upgrade your
     triggers:

        * Use *Note `mysqldump': mysqldump. to generate a dump file
          that contains the trigger definitions:


               mysqldump --triggers --no-create-db --no-data
                         --no-create-info --all-databases > triggers.sql

          You might need to add options to specify connection
          parameters, such as `--user' or `--password'. Also, if you
          are updating from a version of MySQL 5.1 older than 5.1.21,
          you may need to include a `--default-character-set' option
          that specifies the non-ASCII character set that was used for
          the definitions when the triggers were originally created.

          Otherwise, invoke *Note `mysqldump': mysqldump. with exactly
          the preceding options to avoid generating a dump file that
          will not have the intended effect when reloaded. For example,
          if you omit the `--no-create-db' option, your databases will
          be removed and recreated with no contents when you reload the
          dump file.

        * Drop existing triggers. To see which triggers exist, use this
          statement:


               SELECT TRIGGER_SCHEMA, EVENT_OBJECT_TABLE, TRIGGER_NAME
               FROM INFORMATION_SCHEMA.TRIGGERS;

          To generate `DROP TRIGGERS' statements for the triggers, use
          this statement:


               SELECT CONCAT('DROP TRIGGER ', TRIGGER_SCHEMA, '.', TRIGGER_NAME, ';')
               FROM INFORMATION_SCHEMA.TRIGGERS
               INTO OUTFILE '/tmp/drop_triggers.sql';

          The statement uses `INTO OUTFILE', so you must have the `FILE'
          privilege. The file will be created on the server host.  Use
          a different file name if you like. To be 100% safe, inspect
          the trigger definitions in the `drop_triggers.sql' file, and
          perhaps make a backup of the file. Then execute the statements
          in the file:


               mysql --force < /tmp/drop_triggers.sql

        * Recreate the triggers by reloading the dump file created
          earlier:


               mysql --force < triggers.sql

   * *Incompatible change*: As of MySQL 5.1.20, *Note `mysqld_safe':
     mysqld-safe. supports error logging to `syslog' on systems that
     support the `logger' command. The new `--syslog' and
     `--skip-syslog' options can be used instead of the `--log-error'
     option to control logging behavior, as described in *Note
     mysqld-safe::.

     In 5.1.21 and up, the default is `--skip-syslog', which is
     compatible with the default behavior of writing an error log file
     for releases prior to 5.1.20.

     *In 5.1.20 _only_, the following conditions apply*: 1) The default
     is to use `syslog', which is not compatible with releases prior to
     5.1.20. 2) Logging to `syslog' may fail to operate correctly in
     some cases. For these reasons, avoid using MySQL 5.1.20.

   * *Incompatible change*: As of MySQL 5.1.18, the plugin interface
     and its handling of system variables was changed. Command-line
     options such as `--skip-innodb' now cause an error if `InnoDB' is
     not built-in or plugin-loaded. You should use
     `--loose-skip-innodb' if you do not want any error even if
     `InnoDB' is not available.  The `--loose' prefix modifier should
     be used for all command-line options where you are uncertain
     whether the plugin exists and when you want the operation to
     proceed even if the option is necessarily ignored due to the
     absence of the plugin. (For a description of how `--loose' works,
     see *Note command-line-options::.)

   * *Incompatible change*: As of MySQL 5.1.15, `InnoDB' rolls back
     only the last statement on a transaction timeout. A new option,
     `--innodb_rollback_on_timeout', causes `InnoDB' to abort and roll
     back the entire transaction if a transaction timeout occurs (the
     same behavior as in MySQL 4.1).

   * *Incompatible change*: As of MySQL 5.1.15, the following
     conditions apply to enabling the `read_only' system variable:

        * If you attempt to enable `read_only' while you have any
          explicit locks (acquired with *Note `LOCK TABLES':
          lock-tables. or have a pending transaction, an error will
          occur.

        * If other clients hold explicit table locks or have pending
          transactions, the attempt to enable `read_only' blocks until
          the locks are released and the transactions end. While the
          attempt to enable `read_only' is pending, requests by other
          clients for table locks or to begin transactions also block
          until `read_only' has been set.

        * `read_only' can be enabled while you hold a global read lock
          (acquired with *Note `FLUSH TABLES WITH READ LOCK': flush.)
          because that does not involve table locks.

     Previously, the attempt to enable `read_only' would return
     immediately even if explicit locks or transactions were pending,
     so some data changes could occur for statements executing in the
     server at the same time.

   * *Incompatible change*: The number of function names affected by
     `IGNORE_SPACE' was reduced significantly in MySQL 5.1.13, from
     about 200 to about 30.  (For details about `IGNORE_SPACE', see
     *Note function-resolution::.) This change improves the consistency
     of parser operation. However, it also introduces the possibility
     of incompatibility for old SQL code that relies on the following
     conditions:

        * `IGNORE_SPACE' is disabled.

        * The presence or absence of whitespace following a function
          name is used to distinguish between a built-in function and
          stored function that have the same name (for example, `PI()'
          versus `PI ()').

     For functions that are no longer affected by `IGNORE_SPACE' as of
     MySQL 5.1.13, that strategy no longer works. Either of the
     following approaches can be used if you have code that is subject
     to the preceding incompatibility:

        * If a stored function has a name that conflicts with a
          built-in function, refer to the stored function with a schema
          name qualifier, regardless of whether whitespace is present.
          For example, write `SCHEMA_NAME.PI()' or `SCHEMA_NAME.PI ()'.

        * Alternatively, rename the stored function to use a
          nonconflicting name and change invocations of the function to
          use the new name.

   * *Incompatible change*: For `utf8' columns, the full-text parser
     incorrectly considered several nonword punctuation and whitespace
     characters as word characters, causing some searches to return
     incorrect results. The fix involves a change to the full-text
     parser in MySQL 5.1.12, so as of 5.1.12, any tables that have
     `FULLTEXT' indexes on `utf8' columns must be repaired with *Note
     `REPAIR TABLE': repair-table.:


          REPAIR TABLE TBL_NAME QUICK;

   * *Incompatible change*: Storage engines can be pluggable at
     runtime, so the distinction between disabled and invalid storage
     engines no longer applies. As of MySQL 5.1.12, this affects the
     `NO_ENGINE_SUBSTITUTION' SQL mode, as described in *Note
     sql-mode::.

   * *Incompatible change*: The structure of `FULLTEXT' indexes has been
     changed in MySQL 5.1.6. After upgrading to MySQL 5.1.6 or greater,
     any tables that have `FULLTEXT' indexes must be repaired with
     *Note `REPAIR TABLE': repair-table.:


          REPAIR TABLE TBL_NAME QUICK;

   * *Incompatible change*: In MySQL 5.1.6, when log tables were
     implemented, the default log destination for the general query and
     slow query log was `TABLE'. As of MySQL 5.1.21, this default has
     been changed to `FILE', which is compatible with MySQL 5.0, but
     incompatible with earlier releases of MySQL 5.1. If you are
     upgrading from MySQL 5.0 to 5.1.21 or higher, no logging option
     changes should be necessary. However, if you are upgrading from
     5.1.6 through 5.1.20 to 5.1.21 or higher and were using `TABLE'
     logging, use the `--log-output=TABLE' option explicitly to
     preserve your server's table-logging behavior.

   * *Incompatible change*: In very old versions of MySQL (prior to
     4.1), the *Note `TIMESTAMP': datetime. data type supported a
     display width, which was silently ignored beginning with MySQL
     4.1. This is deprecated in MySQL 5.1, and removed altogether in
     MySQL 5.5. These changes in behavior can lead to two problem
     scenarios when trying to use *Note `TIMESTAMP(N)': datetime.
     columns with a MySQL 5.5 or later server:

        * When importing a dump file (for example, one created using
          *Note `mysqldump': mysqldump.) created in a MySQL 5.0 or
          earlier server into a server from a newer release series, a
          *Note `CREATE TABLE': create-table. or *Note `ALTER TABLE':
          alter-table. statement containing *Note `TIMESTAMP(N)':
          datetime.  causes the import to fail with a syntax error.

          To fix this problem, edit the dump file in a text editor to
          replace any instances of *Note `TIMESTAMP(N)': datetime.
          with *Note `TIMESTAMP': datetime. prior to importing the
          file. Be sure to use a plain text editor for this, and not a
          word processor; otherwise, the result is almost certain to be
          unusable for importing into the MySQL server.

     You should try to handle potential issues of these types
     proactively by updating with *Note `ALTER TABLE': alter-table. any
     *Note `TIMESTAMP(N)': datetime. columns in your databases so that
     they use *Note `TIMESTAMP': datetime. instead, before performing
     any upgrades.

   * *Incompatible change*: For *Note `ENUM': enum. columns that had
     enumeration values containing commas, the commas were mapped to
     `0xff' internally. However, this rendered the commas
     indistinguishable from true `0xff' characters in the values. This
     no longer occurs. However, the fix requires that you dump and
     reload any tables that have *Note `ENUM': enum. columns containing
     true `0xff' in their values: Dump the tables using *Note
     `mysqldump': mysqldump. with the current server before upgrading
     from a version of MySQL 5.1 older than 5.1.15 to version 5.1.15 or
     newer.

   * As of MySQL 5.1.12, the `lc_time_names' system variable specifies
     the locale that controls the language used to display day and
     month names and abbreviations. This variable affects the output
     from the `DATE_FORMAT()', `DAYNAME()' and `MONTHNAME()' functions.
     See *Note locale-support::.

   * As of MySQL 5.1.9, *Note `mysqld_safe': mysqld-safe. no longer
     implicitly invokes `mysqld-max' if it exists. Instead, it invokes
     *Note `mysqld': mysqld. unless a `--mysqld' or `--mysqld-version'
     option is given to specify another server explicitly. If you
     previously relied on the implicit invocation of `mysqld-max', you
     should use an appropriate option now. As of MySQL 5.1.12, there is
     no longer any separate `mysqld-max' server, so no change should be
     necessary.

*SQL Changes*

   * *Known issue*: Prior to MySQL 5.1.17, the parser accepted invalid
     code in SQL condition handlers, leading to server crashes or
     unexpected execution behavior in stored programs. Specifically,
     the parser permitted a condition handler to refer to labels for
     blocks that enclose the handler declaration. This was incorrect
     because block label scope does not include the code for handlers
     declared within the labeled block.

     As of 5.1.17, the parser rejects this invalid construct, but if
     you perform a binary upgrade (without dumping and reloading your
     databases), existing handlers that contain the construct still are
     invalid and should be rewritten _even if they appear to function
     as you expect._

     To find affected handlers, use *Note `mysqldump': mysqldump.  to
     dump all stored procedures and functions, triggers, and events.
     Then attempt to reload them into an upgraded server.  Handlers
     that contain illegal label references will be rejected.

     For more information about condition handlers and writing them to
     avoid invalid jumps, see *Note declare-handler::.

   * *Incompatible change*: The parser accepted statements that
     contained `/* ...  */' that were not properly closed with `*/',
     such as `SELECT 1 /* + 2'. As of MySQL 5.1.23, statements that
     contain unclosed `/*'-comments now are rejected with a syntax
     error.

     This fix has the potential to cause incompatibilities.  Because of
     Bug #26302, which caused the trailing `*/' to be truncated from
     comments in views, stored routines, triggers, and events, it is
     possible that objects of those types may have been stored with
     definitions that now will be rejected as syntactically invalid.
     Such objects should be dropped and re-created so that their
     definitions do not contain truncated comments.

   * *Incompatible change*: Multiple-table *Note `DELETE': delete.
     statements containing ambiguous aliases could have unintended side
     effects such as deleting rows from the wrong table. Examples:


          DELETE FROM t1 AS a2 USING t1 AS a1 INNER JOIN t2 AS a2;
          DELETE t1 AS a2 FROM t1 AS a1 INNER JOIN t2 AS a2;

     To avoid ambiguity, declaration of aliases other than in the
     TABLE_REFERENCES part of the statement should be avoided:


          DELETE FROM t1 USING t1 AS a1 INNER JOIN t2 AS a2;
          DELETE t1 FROM t1 AS a1 INNER JOIN t2 AS a2;

     As of MySQL 5.1.23, alias declarations outside the
     TABLE_REFERENCES part of the statement are disallowed for the
     `USING' variant of multiple-table *Note `DELETE': delete. syntax.
     (In MySQL 5.5, alias declarations outside TABLE_REFERENCES are
     disallowed for all multiple-table *Note `DELETE': delete.
     statements.) Statements containing aliases that are no longer
     permitted must be rewritten.

   * *Incompatible change*: As of MySQL 5.1.8, `TYPE = ENGINE_NAME' is
     still accepted as a synonym for the `ENGINE = ENGINE_NAME' table
     option but generates a warning. You should note that this option
     is not available in MySQL 5.1.7, and *is removed altogether in
     MySQL 5.5 and produces a syntax error*.

     `TYPE' has been deprecated since MySQL 4.0.

   * *Incompatible change*: MySQL 5.1.6 introduces the `TRIGGER'
     privilege. Previously, the `SUPER' privilege was needed to create
     or drop triggers. Now those operations require the `TRIGGER'
     privilege. This is a security improvement because you no longer
     need to grant users the `SUPER' privilege to enable them to create
     triggers. However, the requirement that the account named in a
     trigger's `DEFINER' clause must have the `SUPER' privilege has
     changed to a requirement for the `TRIGGER' privilege. When
     upgrading from a previous version of MySQL 5.0 or 5.1 to MySQL
     5.1.6 or newer, be sure to update your grant tables by running
     *Note `mysql_upgrade': mysql-upgrade. This will assign the
     `TRIGGER' privilege to all accounts that had the `SUPER'
     privilege. If you fail to update the grant tables, triggers may
     fail when activated. After updating the grant tables, you can
     revoke the `SUPER' privilege from those accounts that no longer
     otherwise require it.

   * Some keywords may be reserved in MySQL 5.1 that were not reserved
     in MySQL 5.0. See *Note reserved-words::.

   * The *Note `BACKUP TABLE': backup-table, and *Note `RESTORE TABLE':
     restore-table. statements are deprecated. *Note `mysqldump':
     mysqldump. or *Note `mysqlhotcopy': mysqlhotcopy. can be used as
     alternatives.

   * The *Note `LOAD DATA FROM MASTER': load-data-from-master. and
     *Note `LOAD TABLE FROM MASTER': load-table-from-master.
     statements are deprecated. See *Note load-data-from-master::, for
     recommended alternatives.

   * The *Note `INSTALL PLUGIN': install-plugin. and *Note `UNINSTALL
     PLUGIN': uninstall-plugin. statements that are used for the plugin
     API are new. So is the `WITH PARSER' clause for `FULLTEXT' index
     creation that associates a parser plugin with a full-text index.
     *Note plugin-api::.

*C API Changes*

   * *Incompatible change*: As of MySQL 5.1.7, the *Note
     `mysql_stmt_attr_get()': mysql-stmt-attr-get. C API function
     returns a boolean rather than an unsigned int for
     `STMT_ATTR_UPDATE_MAX_LENGTH'. (Bug #16144)


File: manual.info,  Node: downgrading,  Next: checking-table-incompatibilities,  Prev: upgrading,  Up: upgrading-downgrading

2.13.2 Downgrading MySQL
------------------------

* Menu:

* downgrading-to-previous-series::  Downgrading to MySQL 5.0
* downgrading-from-enterprise::  Downgrading from MySQL Enterprise Edition to MySQL Community Server

This section describes what you should do to downgrade to an older
MySQL version in the unlikely case that the previous version worked
better than the new one.

It is always a good idea to make a backup beforehand, in case a
downgrade fails and leaves the instance in an unusable state.

To downgrade between General Availability (GA) status versions within
the same release series, typically you just install the new binaries on
top of the old ones and do not make any changes to the databases.

Downgrades between pre-GA development releases (or from a GA release to
a development release) within the same release series are not supported
and you may encounter issues.

The following items form a checklist of things you should do whenever
you perform a downgrade:

   * Read the upgrading section for the release series from which you
     are downgrading to be sure that it does not have any features you
     really need. See *Note upgrading::.

   * If there is a downgrading section for that version, you should
     read that as well.

   * To see which new features were added between the version to which
     you are downgrading and your current version, see the Release
     Notes (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/).

   * Check *Note checking-table-incompatibilities::, to see whether
     changes to table formats or to character sets or collations were
     made between your current version of MySQL and the version to
     which you are downgrading. If so and these changes result in an
     incompatibility between MySQL versions, you will need to downgrade
     the affected tables using the instructions in *Note
     rebuilding-tables::.

In most cases, you can move the MySQL format files and data files
between different GA versions on the same architecture as long as you
stay within versions for the same release series of MySQL.

If you downgrade from one release series to another, there may be
incompatibilities in table storage formats. In this case, use *Note
`mysqldump': mysqldump. to dump your tables before downgrading. After
downgrading, reload the dump file using *Note `mysql': mysql. or *Note
`mysqlimport': mysqlimport. to re-create your tables. For examples, see
*Note copying-databases::.

A typical symptom of a downward-incompatible table format change when
you downgrade is that you cannot open tables. In that case, use the
following procedure:

  1. Stop the older MySQL server that you are downgrading to.

  2. Restart the newer MySQL server you are downgrading from.

  3. Dump any tables that were inaccessible to the older server by
     using *Note `mysqldump': mysqldump. to create a dump file.

  4. Stop the newer MySQL server and restart the older one.

  5. Reload the dump file into the older server. Your tables should be
     accessible.

It might also be the case that system tables in the `mysql' database
have changed and that downgrading introduces some loss of functionality
or requires some adjustments. Here are some examples:

   * Trigger creation requires the `TRIGGER' privilege as of MySQL 5.1.
     In MySQL 5.0, there is no `TRIGGER' privilege and `SUPER' is
     required instead. If you downgrade from MySQL 5.1 to 5.0, you will
     need to give the `SUPER' privilege to those accounts that had the
     `TRIGGER' privilege in 5.1.

   * Triggers were added in MySQL 5.0, so if you downgrade from 5.0 to
     4.1, you cannot use triggers at all.

   * The `mysql.proc.comment' column definition changed between MySQL
     5.1 and 5.5. After a downgrade from 5.5 to 5.1, this table is seen
     as corrupt and in need of repair.  To workaround this problem,
     execute *Note `mysql_upgrade': mysql-upgrade. from the version of
     MySQL to which you downgraded.


File: manual.info,  Node: downgrading-to-previous-series,  Next: downgrading-from-enterprise,  Prev: downgrading,  Up: downgrading

2.13.2.1 Downgrading to MySQL 5.0
.................................

When downgrading to MySQL 5.0 from MySQL 5.1, you should keep in mind
the following issues relating to features found in MySQL 5.1, but not
in MySQL 5.0:

   * Partitioning

     MySQL 5.0 does not support user-defined partitioning. If a table
     was created as a partitioned table in 5.1 (or if an table created
     in a previous version of MySQL was altered to include partitions
     after an upgrade to 5.1), the table is accessible after downgrade
     only if you do one of the following:

        * Export the table using *Note `mysqldump': mysqldump. and then
          drop it in MySQL 5.1; import the table again following the
          downgrade to MySQL 5.0.

        * Prior to the downgrade, remove the table's partitioning using
          `ALTER TABLE TABLE_NAME REMOVE PARTITIONING'.

   * Event Scheduler

     MySQL 5.0 does not support scheduled events. If your databases
     contain scheduled event definitions, you should prevent them from
     being dumped when you use *Note `mysqldump': mysqldump. by using
     the `--skip-events' option. (See *Note mysqldump::.)

   * Stored routines

     MySQL 5.1.21 added a number of new columns to the `mysql.proc'
     table in which stored routine definitions are stored. If you are
     downgrading from MySQL 5.1.21 or later to MySQL 5.0, you cannot
     import the MySQL 5.1 routine definitions into MySQL 5.0.46 or
     earlier using the dump of `mysql.proc' created by *Note
     `mysqldump': mysqldump. (such as when using the `--all-databases'
     option).  Instead, you should run *Note `mysqldump `--routines'':
     mysqldump.  prior to performing the downgrade and run the stored
     routines DDL statements following the downgrade.

     See Bug #11986, Bug #30029, and Bug #30660, for more information.

   * Triggers

     Trigger creation requires the `TRIGGER' privilege as of MySQL 5.1.
     In MySQL 5.0, there is no `TRIGGER' privilege and `SUPER' is
     required instead. If you downgrade from MySQL 5.1 to 5.0, you will
     need to give the `SUPER' privilege to those accounts that had the
     `TRIGGER' privilege in 5.1.


File: manual.info,  Node: downgrading-from-enterprise,  Prev: downgrading-to-previous-series,  Up: downgrading

2.13.2.2 Downgrading from MySQL Enterprise Edition to MySQL Community Server
............................................................................

This section describes the steps required to downgrade from MySQL
Enterprise Edition to MySQL Community Edition. This can be done at any
time, and is required at the expiration of a MySQL Enterprise Edition
subscription if you wish to continue using MySQL Server.

When you perform such a downgrade, all commercially licensed components
of the MySQL Enterprise Edition subscription must be uninstalled. These
components and related considerations are described in the rest of this
section.

*Note*:

The issues described in this section are in addition to any that may be
encountered as a result of any upgrade or downgrade of the MySQL Server
version (such as between MySQL 5.1 and 5.0). Information about
upgrading and downgrading between MySQL release series can be found
elsewhere in this chapter; see *Note upgrading::, and *Note
downgrading::.

MySQL Enterprise Database Server

All commercial versions of MySQL Database Server must be uninstalled.

Commercially licensed extensions

All commercially licensed MySQL Enterprise Database Server extensions
must be uninstalled, including the _MySQL High Availability_ extension.
Following uninstallation of this extension, automated failover is no
longer available.

MySQL Enterprise Backup

MySQL Enterprise Backup must be uninstalled. Uninstalling this
application has the effects listed here:

   * Automated backup scripts no longer work.

   * Existing backup images taken with MySQL Enterprise Backup can no
     longer be used for recovery.

   * Third-party integration with multimedia systems such as NetBackup,
     Tivoli, and Oracle Secure Backup no longer works.

MySQL Enterprise Monitor, MySQL Query Analyzer, agents

MySQL Enterprise Monitor, MySQL Query Analyzer, and all server-side
agents must be uninstalled. Uninstalling these applications and agents
has the following effects:

   * Automated SNMP and SMTP alerts no longer work.

   * All historical MySQL, OS monitoring, query, and performance
     metrics as well as all trending data are lost.

   * All environment-specific monitoring templates, custom advisors,
     graphs and scripts are also lost.


File: manual.info,  Node: checking-table-incompatibilities,  Next: rebuilding-tables,  Prev: downgrading,  Up: upgrading-downgrading

2.13.3 Checking Whether Tables or Indexes Must Be Rebuilt
---------------------------------------------------------

A binary upgrade or downgrade is one that installs one version of MySQL
`in place' over an existing version, without dumping and reloading
tables:

  1. Stop the server for the existing version if it is running.

  2. Install a different version of MySQL. This is an upgrade if the
     new version is higher than the original version, a downgrade if
     the version is lower.

  3. Start the server for the new version.

In many cases, the tables from the previous version of MySQL can be
used without problem by the new version. However, sometimes changes
occur that require tables or table indexes to be rebuilt, as described
in this section. If you have tables that are affected by any of the
issues described here, rebuild the tables or indexes as necessary using
the instructions given in *Note rebuilding-tables::.

*Table Incompatibilities*

After a binary upgrade to MySQL 5.1 from a MySQL 5.0 installation that
contains *Note `ARCHIVE': archive-storage-engine. tables:

   * Before MySQL 5.1.42, accessing those tables will cause the server
     to crash, even if you have run *Note `mysql_upgrade':
     mysql-upgrade. or *Note `CHECK TABLE ... FOR UPGRADE': check-table.

   * As of MySQL 5.1.42, the server will not open 5.0 *Note `ARCHIVE':
     archive-storage-engine. tables at all.

In either case, the solution is to use *Note `mysqldump': mysqldump. to
dump all 5.0 *Note `ARCHIVE': archive-storage-engine. tables before
upgrading, and reload them into MySQL 5.1 after upgrading. This problem
is fixed in MySQL 5.6.4: The server can open *Note `ARCHIVE':
archive-storage-engine. tables created in MySQL 5.0.  However, it
remains the recommended upgrade procedure to dump 5.0 *Note `ARCHIVE':
archive-storage-engine. tables before upgrading and reload them after
upgrading.

*Index Incompatibilities*

If you perform a binary upgrade without dumping and reloading tables,
you cannot upgrade directly from MySQL 4.1 to 5.1 or higher. This
occurs due to an incompatible change in the `MyISAM' table index format
in MySQL 5.0. Upgrade from MySQL 4.1 to 5.0 and repair all `MyISAM'
tables. Then upgrade from MySQL 5.0 to 5.1 and check and repair your
tables.

Modifications to the handling of character sets or collations might
change the character sort order, which causes the ordering of entries
in any index that uses an affected character set or collation to be
incorrect. Such changes result in several possible problems:

   * Comparison results that differ from previous results

   * Inability to find some index values due to misordered index entries

   * Misordered `ORDER BY' results

   * Tables that *Note `CHECK TABLE': check-table. reports as being in
     need of repair

The solution to these problems is to rebuild any indexes that use an
affected character set or collation, either by dropping and re-creating
the indexes, or by dumping and reloading the entire table. In some
cases, it is possible to alter affected columns to use a different
collation. For information about rebuilding indexes, see *Note
rebuilding-tables::.

To check whether a table has indexes that must be rebuilt, consult the
following list. It indicates which versions of MySQL introduced
character set or collation changes that require indexes to be rebuilt.
Each entry indicates the version in which the change occurred and the
character sets or collations that the change affects. If the change is
associated with a particular bug report, the bug number is given.

The list applies both for binary upgrades and downgrades. For example,
Bug #27877 was fixed in MySQL 5.1.24, so it applies to upgrades from
versions older than 5.1.24 to 5.1.24 or newer, and to downgrades from
5.1.24 or newer to versions older than 5.1.24.

In many cases, you can use *Note `CHECK TABLE ... FOR UPGRADE':
check-table. to identify tables for which index rebuilding is required.
It will report this message:


     Table upgrade required.
     Please do "REPAIR TABLE `tbl_name`" or dump/reload to fix it!

In these cases, you can also use *Note `mysqlcheck --check-upgrade':
mysqlcheck. or *Note `mysql_upgrade': mysql-upgrade, which execute
*Note `CHECK TABLE': check-table. However, the use of *Note `CHECK
TABLE': check-table. applies only after upgrades, not downgrades. Also,
*Note `CHECK TABLE': check-table. is not applicable to all storage
engines. For details about which storage engines *Note `CHECK TABLE':
check-table. supports, see *Note check-table::.

These changes cause index rebuilding to be necessary:

   * MySQL 5.1.24 (Bug #27877)

     Affects indexes that use the `utf8_general_ci' or
     `ucs2_general_ci' collation for columns that contain `'ss'' LATIN
     SMALL LETTER SHARP S (German). The bug fix corrected an error in
     the original collations but introduced an incompatibility such that
     `'ss'' compares equal to characters with which it previously
     compared different.

     Affected tables can be detected by *Note `CHECK TABLE ... FOR
     UPGRADE': check-table. as of MySQL 5.1.30 (see Bug #40053).

     A workaround for this issue is implemented as of MySQL 5.1.62,
     5.5.21, and 5.6.5. The workaround involves altering affected
     columns to use the `utf8_general_mysql500_ci' and
     `ucs2_general_mysql500_ci' collations, which preserve the original
     pre-5.1.24 ordering of `utf8_general_ci' and `ucs2_general_ci'.

   * MySQL 5.0.48, 5.1.23 (Bug #27562)

     Affects indexes that use the `ascii_general_ci' collation for
     columns that contain any of these characters: `'`'' GRAVE ACCENT,
     `'['' LEFT SQUARE BRACKET, `'\'' REVERSE SOLIDUS, `']'' RIGHT
     SQUARE BRACKET, `'~'' TILDE

     Affected tables can be detected by *Note `CHECK TABLE ... FOR
     UPGRADE': check-table. as of MySQL 5.1.29 (see Bug #39585).

   * MySQL 5.0.48, 5.1.21 (Bug #29461)

     Affects indexes for columns that use any of these character sets:
     `eucjpms', `euc_kr', `gb2312', `latin7', `macce', `ujis'

     Affected tables can be detected by *Note `CHECK TABLE ... FOR
     UPGRADE': check-table. as of MySQL 5.1.29 (see Bug #39585).


File: manual.info,  Node: rebuilding-tables,  Next: copying-databases,  Prev: checking-table-incompatibilities,  Up: upgrading-downgrading

2.13.4 Rebuilding or Repairing Tables or Indexes
------------------------------------------------

This section describes how to rebuild a table. This can be necessitated
by changes to MySQL such as how data types are handled or changes to
character set handling. For example, an error in a collation might have
been corrected, necessitating a table rebuild to update the indexes for
character columns that use the collation. (For examples, see *Note
checking-table-incompatibilities::.) It might also be that a table
repair or upgrade should be done as indicated by a table check
operation such as that performed by *Note `CHECK TABLE': check-table,
*Note `mysqlcheck': mysqlcheck, or *Note `mysql_upgrade': mysql-upgrade.

Methods for rebuilding a table include dumping and reloading it, or
using *Note `ALTER TABLE': alter-table. or *Note `REPAIR TABLE':
repair-table.

*Note*:

If you are rebuilding tables because a different version of MySQL will
not handle them after a binary (in-place) upgrade or downgrade, you
must use the dump-and-reload method. Dump the tables _before_ upgrading
or downgrading using your original version of MySQL. Then reload the
tables _after_ upgrading or downgrading.

If you use the dump-and-reload method of rebuilding tables only for the
purpose of rebuilding indexes, you can perform the dump either before
or after upgrading or downgrading. Reloading still must be done
afterward.

To rebuild a table by dumping and reloading it, use *Note `mysqldump':
mysqldump. to create a dump file and *Note `mysql': mysql. to reload
the file:


     shell> mysqldump DB_NAME t1 > dump.sql
     shell> mysql DB_NAME < dump.sql

To rebuild all the tables in a single database, specify the database
name without any following table name:


     shell> mysqldump DB_NAME > dump.sql
     shell> mysql DB_NAME < dump.sql

To rebuild all tables in all databases, use the `--all-databases'
option:


     shell> mysqldump --all-databases > dump.sql
     shell> mysql < dump.sql

To rebuild a table with *Note `ALTER TABLE': alter-table, use a `null'
alteration; that is, an *Note `ALTER TABLE': alter-table. statement that
`changes' the table to use the storage engine that it already has. For
example, if `t1' is a `MyISAM' table, use this statement:


     mysql> ALTER TABLE t1 ENGINE = MyISAM;

If you are not sure which storage engine to specify in the *Note `ALTER
TABLE': alter-table. statement, use *Note `SHOW CREATE TABLE':
show-create-table. to display the table definition.

If you must rebuild a table because a table checking operation
indicates that the table is corrupt or needs an upgrade, you can use
*Note `REPAIR TABLE': repair-table. if that statement supports the
table's storage engine. For example, to repair a `MyISAM' table, use
this statement:


     mysql> REPAIR TABLE t1;

For storage engines such as `InnoDB' that *Note `REPAIR TABLE':
repair-table. does not support, use *Note `mysqldump': mysqldump. to
create a dump file and *Note `mysql': mysql. to reload the file, as
described earlier.

For specifics about which storage engines *Note `REPAIR TABLE':
repair-table. supports, see *Note repair-table::.

*Note `mysqlcheck --repair': mysqlcheck. provides command-line access
to the *Note `REPAIR TABLE': repair-table.  statement. This can be a
more convenient means of repairing tables because you can use the
`--databases' or `--all-databases' option to repair all tables in
specific databases or all databases, respectively:


     shell> mysqlcheck --repair --databases DB_NAME ...
     shell> mysqlcheck --repair --all-databases

For incompatibilities introduced in MySQL 5.1.24 by the fix for Bug
#27877 that corrected the `utf8_general_ci' and `ucs2_general_ci'
collations, a workaround is implemented as of MySQL 5.1.62, 5.5.21, and
5.6.5. Upgrade to one of those versions, then convert each affected
table using one of the following methods. In each case, the workaround
altering affected columns to use the `utf8_general_mysql500_ci' and
`ucs2_general_mysql500_ci' collations, which preserve the original
pre-5.1.24 ordering of `utf8_general_ci' and `ucs2_general_ci'.

   * To convert an affected table after a binary upgrade that leaves
     the table files in place, alter the table to use the new
     collation. Suppose that the table `t1' contains one or more
     problematic `utf8' columns. To convert the table at the table
     level, use a statement like this:


          ALTER TABLE t1
          CONVERT TO CHARACTER SET utf8 COLLATE utf8_general_mysql500_ci;

     To apply the change on a column-specific basis, use a statement
     like this (be sure to repeat the column definition as originally
     specified except for the `COLLATE' clause):


          ALTER TABLE t1
          MODIFY c1 CHAR(N) CHARACTER SET utf8 COLLATE utf8_general_mysql500_ci;

   * To upgrade the table using a dump and reload procedure, dump the
     table using *Note `mysqldump': mysqldump, modify the *Note `CREATE
     TABLE': create-table. statement in the dump file to use the new
     collation, and reload the table.

After making the appropriate changes, *Note `CHECK TABLE': check-table.
should report no error.


File: manual.info,  Node: copying-databases,  Prev: rebuilding-tables,  Up: upgrading-downgrading

2.13.5 Copying MySQL Databases to Another Machine
-------------------------------------------------

You can copy the `.frm', `.MYI', and `.MYD' files for `MyISAM' tables
between different architectures that support the same floating-point
format. (MySQL takes care of any byte-swapping issues.) See *Note
myisam-storage-engine::.

In cases where you need to transfer databases between different
architectures, you can use *Note `mysqldump': mysqldump. to create a
file containing SQL statements. You can then transfer the file to the
other machine and feed it as input to the *Note `mysql': mysql. client.

Use *Note `mysqldump --help': mysqldump. to see what options are
available.

The easiest (although not the fastest) way to move a database between
two machines is to run the following commands on the machine on which
the database is located:


     shell> mysqladmin -h 'OTHER_HOSTNAME' create DB_NAME
     shell> mysqldump DB_NAME | mysql -h 'OTHER_HOSTNAME' DB_NAME

If you want to copy a database from a remote machine over a slow
network, you can use these commands:


     shell> mysqladmin create DB_NAME
     shell> mysqldump -h 'OTHER_HOSTNAME' --compress DB_NAME | mysql DB_NAME

You can also store the dump in a file, transfer the file to the target
machine, and then load the file into the database there.  For example,
you can dump a database to a compressed file on the source machine like
this:


     shell> mysqldump --quick DB_NAME | gzip > DB_NAME.gz

Transfer the file containing the database contents to the target
machine and run these commands there:


     shell> mysqladmin create DB_NAME
     shell> gunzip < DB_NAME.gz | mysql DB_NAME

You can also use *Note `mysqldump': mysqldump. and *Note `mysqlimport':
mysqlimport. to transfer the database. For large tables, this is much
faster than simply using *Note `mysqldump': mysqldump. In the following
commands, DUMPDIR represents the full path name of the directory you
use to store the output from *Note `mysqldump': mysqldump.

First, create the directory for the output files and dump the database:


     shell> mkdir DUMPDIR
     shell> mysqldump --tab=DUMPDIR DB_NAME

Then transfer the files in the DUMPDIR directory to some corresponding
directory on the target machine and load the files into MySQL there:


     shell> mysqladmin create DB_NAME           # create database
     shell> cat DUMPDIR/*.sql | mysql DB_NAME   # create tables in database
     shell> mysqlimport DB_NAME DUMPDIR/*.txt   # load data into tables

Do not forget to copy the `mysql' database because that is where the
grant tables are stored. You might have to run commands as the MySQL
`root' user on the new machine until you have the `mysql' database in
place.

After you import the `mysql' database on the new machine, execute *Note
`mysqladmin flush-privileges': mysqladmin. so that the server reloads
the grant table information.


File: manual.info,  Node: environment-variables,  Next: perl-support,  Prev: upgrading-downgrading,  Up: installing

2.14 Environment Variables
==========================

This section lists all the environment variables that are used directly
or indirectly by MySQL. Most of these can also be found in other places
in this manual.

Note that any options on the command line take precedence over values
specified in option files and environment variables, and values in
option files take precedence over values in environment variables.

In many cases, it is preferable to use an option file instead of
environment variables to modify the behavior of MySQL. See *Note
option-files::.

To set an environment variable within `sh', `ksh', `bash', or `zsh'
shells you can use the following commands:

     shell> ENVVAR=VALUE
     shell> export ENVVAR

The `export' is required if you want other sub-commands to inherit that
value during execution. On more recent shells you can combine the
export and setting processes, like this:

     shell> export set ENVVAR=VALUE

For the `csh', or `tcsh' shells, use the `setenv' command:

     shell> setenv ENVVAR VALUE

Within the Windows Command Prompt use the *Note `set': set.  command to
specify the value of a variable:

     shell> set ENVVAR=VALUE

On Unix, Linux, Mac OS X, and Windows, the *Note `set': set.  command
without parameters will display the list of currently set variables.

*MySQL Related Environment Variables*

Variable           Description
`CXX'              The name of your C++ compiler (for running
                   `configure').
`CC'               The name of your C compiler (for running `configure').
`CFLAGS'           Flags for your C compiler (for running `configure').
`CXXFLAGS'         Flags for your C++ compiler (for running `configure').
`DBI_USER'         The default user name for Perl DBI.
`DBI_TRACE'        Trace options for Perl DBI.
`HOME'             The default path for the *Note `mysql': mysql.
                   history file is `$HOME/.mysql_history'.
`LD_RUN_PATH'      Used to specify the location of `libmysqlclient.so'.
`MYSQL_DEBUG'      Debug trace options when debugging.
`MYSQL_GROUP_SUFFIX'Option group suffix value (like specifying
                   `--defaults-group-suffix').
`MYSQL_HISTFILE'   The path to the *Note `mysql': mysql. history file.
                   If this variable is set, its value overrides the
                   default for `$HOME/.mysql_history'.
`MYSQL_HOME'       The path to the directory in which the server-specific
                   `my.cnf' file resides.
`MYSQL_HOST'       The default host name used by the *Note `mysql':
                   mysql. command-line client.
`MYSQL_PS1'        The command prompt to use in the *Note `mysql':
                   mysql. command-line client.
`MYSQL_PWD'        The default password when connecting to *Note
                   `mysqld': mysqld. Note that using this is insecure.
                   See *Note password-security-user::.
`MYSQL_TCP_PORT'   The default TCP/IP port number.
`MYSQL_UNIX_PORT'  The default Unix socket file name; used for
                   connections to `localhost'.
`PATH'             Used by the shell to find MySQL programs.
`TMPDIR'           The directory where temporary files are created.
`TZ'               This should be set to your local time zone. See *Note
                   timezone-problems::.
`UMASK'            The user-file creation mode when creating files. See
                   note following table.
`UMASK_DIR'        The user-directory creation mode when creating
                   directories. See note following table.
`USER'             The default user name on Windows and NetWare when
                   connecting to *Note `mysqld': mysqld.

For information about the *Note `mysql': mysql. history file, see *Note
mysql-logging::.

The `UMASK' and `UMASK_DIR' variables, despite their names, are used as
modes, not masks:

   * If `UMASK' is set, *Note `mysqld': mysqld.  uses `($UMASK | 0600)'
     as the mode for file creation, so that newly created files have a
     mode in the range from 0600 to 0666 (all values octal).

   * If `UMASK_DIR' is set, *Note `mysqld': mysqld. uses `($UMASK_DIR |
     0700)' as the base mode for directory creation, which then is
     AND-ed with `~(~$UMASK & 0666)', so that newly created directories
     have a mode in the range from 0700 to 0777 (all values octal). The
     AND operation may remove read and write permissions from the
     directory mode, but not execute permissions.

MySQL assumes that the value for `UMASK' or `UMASK_DIR' is in octal if
it starts with a zero.


File: manual.info,  Node: perl-support,  Prev: environment-variables,  Up: installing

2.15 Perl Installation Notes
============================

* Menu:

* perl-installation::            Installing Perl on Unix
* activestate-perl::             Installing ActiveState Perl on Windows
* perl-support-problems::        Problems Using the Perl DBI/DBD Interface

The Perl `DBI' module provides a generic interface for database access.
You can write a `DBI' script that works with many different database
engines without change. To use `DBI', you must install the `DBI'
module, as well as a DataBase Driver (DBD) module for each type of
database server you want to access. For MySQL, this driver is the
`DBD::mysql' module.

Perl, and the `DBD::MySQL' module for `DBI' must be installed if you
want to run the MySQL benchmark scripts; see *Note mysql-benchmarks::.
They are also required for the MySQL Cluster *Note `ndb_size.pl':
mysql-cluster-programs-ndb-size-pl. utility; see *Note
mysql-cluster-programs-ndb-size-pl::.

*Note*:

Perl support is not included with MySQL distributions. You can obtain
the necessary modules from `http://search.cpan.org' for Unix, or by
using the ActiveState `ppm' program on Windows. The following sections
describe how to do this.

The `DBI'/`DBD' interface requires Perl 5.6.0, and 5.6.1 or later is
preferred. DBI _does not work_ if you have an older version of Perl.
You should use `DBD::mysql' 4.009 or higher. Although earlier versions
are available, they do not support the full functionality of MySQL 5.1.


File: manual.info,  Node: perl-installation,  Next: activestate-perl,  Prev: perl-support,  Up: perl-support

2.15.1 Installing Perl on Unix
------------------------------

MySQL Perl support requires that you have installed MySQL client
programming support (libraries and header files). Most installation
methods install the necessary files. If you install MySQL from RPM
files on Linux, be sure to install the developer RPM as well. The
client programs are in the client RPM, but client programming support
is in the developer RPM.

The files you need for Perl support can be obtained from the CPAN
(Comprehensive Perl Archive Network) at `http://search.cpan.org'.

The easiest way to install Perl modules on Unix is to use the `CPAN'
module. For example:


     shell> perl -MCPAN -e shell
     cpan> install DBI
     cpan> install DBD::mysql

The `DBD::mysql' installation runs a number of tests. These tests
attempt to connect to the local MySQL server using the default user
name and password. (The default user name is your login name on Unix,
and `ODBC' on Windows. The default password is `no password.') If you
cannot connect to the server with those values (for example, if your
account has a password), the tests fail. You can use `force install
DBD::mysql' to ignore the failed tests.

`DBI' requires the `Data::Dumper' module. It may be installed; if not,
you should install it before installing `DBI'.

It is also possible to download the module distributions in the form of
compressed `tar' archives and build the modules manually. For example,
to unpack and build a DBI distribution, use a procedure such as this:

  1. Unpack the distribution into the current directory:


          shell> gunzip < DBI-VERSION.tar.gz | tar xvf -

     This command creates a directory named `DBI-VERSION'.

  2. Change location into the top-level directory of the unpacked
     distribution:


          shell> cd DBI-VERSION

  3. Build the distribution and compile everything:


          shell> perl Makefile.PL
          shell> make
          shell> make test
          shell> make install

The `make test' command is important because it verifies that the
module is working. Note that when you run that command during the
`DBD::mysql' installation to exercise the interface code, the MySQL
server must be running or the test fails.

It is a good idea to rebuild and reinstall the `DBD::mysql'
distribution whenever you install a new release of MySQL. This ensures
that the latest versions of the MySQL client libraries are installed
correctly.

If you do not have access rights to install Perl modules in the system
directory or if you want to install local Perl modules, the following
reference may be useful:
`http://learn.perl.org/faq/perlfaq8.html#How-do-I-keep-my-own-module-library-directory-'


File: manual.info,  Node: activestate-perl,  Next: perl-support-problems,  Prev: perl-installation,  Up: perl-support

2.15.2 Installing ActiveState Perl on Windows
---------------------------------------------

On Windows, you should do the following to install the MySQL `DBD'
module with ActiveState Perl:

  1. Get ActiveState Perl from
     `http://www.activestate.com/Products/ActivePerl/' and install it.

  2. Open a console window.

  3. If necessary, set the `HTTP_proxy' variable.  For example, you
     might try a setting like this:


          C:\> set HTTP_proxy=my.proxy.com:3128

  4. Start the PPM program:


          C:\> C:\perl\bin\ppm.pl

  5. If you have not previously done so, install `DBI':


          ppm> install DBI

  6. If this succeeds, run the following command:


          ppm> install DBD-mysql

This procedure should work with ActiveState Perl 5.6 or newer.

If you cannot get the procedure to work, you should install the ODBC
driver instead and connect to the MySQL server through ODBC:


     use DBI;
     $dbh= DBI->connect("DBI:ODBC:$dsn",$user,$password) ||
       die "Got error $DBI::errstr when connecting to $dsn\n";


File: manual.info,  Node: perl-support-problems,  Prev: activestate-perl,  Up: perl-support

2.15.3 Problems Using the Perl DBI/DBD Interface
------------------------------------------------

If Perl reports that it cannot find the `../mysql/mysql.so' module, the
problem is probably that Perl cannot locate the `libmysqlclient.so'
shared library. You should be able to fix this problem by one of the
following methods:

   * Copy `libmysqlclient.so' to the directory where your other shared
     libraries are located (probably `/usr/lib' or `/lib').

   * Modify the `-L' options used to compile `DBD::mysql' to reflect
     the actual location of `libmysqlclient.so'.

   * On Linux, you can add the path name of the directory where
     `libmysqlclient.so' is located to the `/etc/ld.so.conf' file.

   * Add the path name of the directory where `libmysqlclient.so' is
     located to the `LD_RUN_PATH' environment variable. Some systems
     use `LD_LIBRARY_PATH' instead.

Note that you may also need to modify the `-L' options if there are
other libraries that the linker fails to find. For example, if the
linker cannot find `libc' because it is in `/lib' and the link command
specifies `-L/usr/lib', change the `-L' option to `-L/lib' or add
`-L/lib' to the existing link command.

If you get the following errors from `DBD::mysql', you are probably
using `gcc' (or using an old binary compiled with `gcc'):


     /usr/bin/perl: can't resolve symbol '__moddi3'
     /usr/bin/perl: can't resolve symbol '__divdi3'

Add `-L/usr/lib/gcc-lib/... -lgcc' to the link command when the
`mysql.so' library gets built (check the output from `make' for
`mysql.so' when you compile the Perl client).  The `-L' option should
specify the path name of the directory where `libgcc.a' is located on
your system.

Another cause of this problem may be that Perl and MySQL are not both
compiled with `gcc'. In this case, you can solve the mismatch by
compiling both with `gcc'.

You may see the following error from `DBD::mysql' when you run the
tests:


     t/00base............install_driver(mysql) failed:
     Can't load '../blib/arch/auto/DBD/mysql/mysql.so' for module DBD::mysql:
     ../blib/arch/auto/DBD/mysql/mysql.so: undefined symbol:
     uncompress at /usr/lib/perl5/5.00503/i586-linux/DynaLoader.pm line 169.

This means that you need to include the `-lz' compression library on
the link line. That can be done by changing the following line in the
file `lib/DBD/mysql/Install.pm':


     $sysliblist .= " -lm";

Change that line to:


     $sysliblist .= " -lm -lz";

After this, you _must_ run `make realclean' and then proceed with the
installation from the beginning.


File: manual.info,  Node: tutorial,  Next: programs,  Prev: installing,  Up: Top

3 Tutorial
**********

* Menu:

* connecting-disconnecting::     Connecting to and Disconnecting from the Server
* entering-queries::             Entering Queries
* database-use::                 Creating and Using a Database
* getting-information::          Getting Information About Databases and Tables
* batch-mode::                   Using mysql in Batch Mode
* examples::                     Examples of Common Queries
* apache::                       Using MySQL with Apache

This chapter provides a tutorial introduction to MySQL by showing how
to use the *Note `mysql': mysql. client program to create and use a
simple database. *Note `mysql': mysql. (sometimes referred to as the
`terminal monitor' or just `monitor') is an interactive program that
enables you to connect to a MySQL server, run queries, and view the
results.  *Note `mysql': mysql. may also be used in batch mode: you
place your queries in a file beforehand, then tell *Note `mysql':
mysql. to execute the contents of the file. Both ways of using *Note
`mysql': mysql. are covered here.

To see a list of options provided by *Note `mysql': mysql, invoke it
with the `--help' option:


     shell> mysql --help

This chapter assumes that *Note `mysql': mysql. is installed on your
machine and that a MySQL server is available to which you can connect.
If this is not true, contact your MySQL administrator. (If _you_ are
the administrator, you need to consult the relevant portions of this
manual, such as *Note server-administration::.)

This chapter describes the entire process of setting up and using a
database. If you are interested only in accessing an existing database,
you may want to skip over the sections that describe how to create the
database and the tables it contains.

Because this chapter is tutorial in nature, many details are
necessarily omitted. Consult the relevant sections of the manual for
more information on the topics covered here.


File: manual.info,  Node: connecting-disconnecting,  Next: entering-queries,  Prev: tutorial,  Up: tutorial

3.1 Connecting to and Disconnecting from the Server
===================================================

To connect to the server, you will usually need to provide a MySQL user
name when you invoke *Note `mysql': mysql. and, most likely, a
password. If the server runs on a machine other than the one where you
log in, you will also need to specify a host name.  Contact your
administrator to find out what connection parameters you should use to
connect (that is, what host, user name, and password to use). Once you
know the proper parameters, you should be able to connect like this:


     shell> mysql -h HOST -u USER -p
     Enter password: ********

`host' and `user' represent the host name where your MySQL server is
running and the user name of your MySQL account. Substitute appropriate
values for your setup.  The `********' represents your password; enter
it when *Note `mysql': mysql. displays the `Enter password:' prompt.

If that works, you should see some introductory information followed by
a `mysql>' prompt:


     shell> mysql -h HOST -u USER -p
     Enter password: ********
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 25338 to server version: 5.1.73-standard

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql>

The `mysql>' prompt tells you that *Note `mysql': mysql. is ready for
you to enter commands.

If you are logging in on the same machine that MySQL is running on, you
can omit the host, and simply use the following:


     shell> mysql -u USER -p

If, when you attempt to log in, you get an error message such as `ERROR
2002 (HY000): Can't connect to local MySQL server through socket
'/tmp/mysql.sock' (2)', it means that the MySQL server daemon (Unix) or
service (Windows) is not running. Consult the administrator or see the
section of *Note installing:: that is appropriate to your operating
system.

For help with other problems often encountered when trying to log in,
see *Note common-errors::.

Some MySQL installations permit users to connect as the anonymous
(unnamed) user to the server running on the local host. If this is the
case on your machine, you should be able to connect to that server by
invoking *Note `mysql': mysql. without any options:


     shell> mysql

After you have connected successfully, you can disconnect any time by
typing `QUIT' (or `\q') at the `mysql>' prompt:


     mysql> QUIT
     Bye

On Unix, you can also disconnect by pressing Control+D.

Most examples in the following sections assume that you are connected
to the server. They indicate this by the `mysql>' prompt.


File: manual.info,  Node: entering-queries,  Next: database-use,  Prev: connecting-disconnecting,  Up: tutorial

3.2 Entering Queries
====================

Make sure that you are connected to the server, as discussed in the
previous section. Doing so does not in itself select any database to
work with, but that is okay. At this point, it is more important to
find out a little about how to issue queries than to jump right in
creating tables, loading data into them, and retrieving data from them.
This section describes the basic principles of entering commands, using
several queries you can try out to familiarize yourself with how *Note
`mysql': mysql.  works.

Here is a simple command that asks the server to tell you its version
number and the current date. Type it in as shown here following the
`mysql>' prompt and press Enter:


     mysql> SELECT VERSION(), CURRENT_DATE;
     +-----------------+--------------+
     | VERSION()       | CURRENT_DATE |
     +-----------------+--------------+
     | 5.1.2-alpha-log | 2005-10-11   |
     +-----------------+--------------+
     1 row in set (0.01 sec)
     mysql>

This query illustrates several things about *Note `mysql': mysql.:

   * A command normally consists of an SQL statement followed by a
     semicolon. (There are some exceptions where a semicolon may be
     omitted. `QUIT', mentioned earlier, is one of them. We'll get to
     others later.)

   * When you issue a command, *Note `mysql': mysql. sends it to the
     server for execution and displays the results, then prints another
     `mysql>' prompt to indicate that it is ready for another command.

   * *Note `mysql': mysql. displays query output in tabular form (rows
     and columns). The first row contains labels for the columns. The
     rows following are the query results. Normally, column labels are
     the names of the columns you fetch from database tables. If you're
     retrieving the value of an expression rather than a table column
     (as in the example just shown), *Note `mysql': mysql. labels the
     column using the expression itself.

   * *Note `mysql': mysql. shows how many rows were returned and how
     long the query took to execute, which gives you a rough idea of
     server performance. These values are imprecise because they
     represent wall clock time (not CPU or machine time), and because
     they are affected by factors such as server load and network
     latency. (For brevity, the `rows in set' line is sometimes not
     shown in the remaining examples in this chapter.)

Keywords may be entered in any lettercase. The following queries are
equivalent:


     mysql> SELECT VERSION(), CURRENT_DATE;
     mysql> select version(), current_date;
     mysql> SeLeCt vErSiOn(), current_DATE;

Here is another query. It demonstrates that you can use *Note `mysql':
mysql. as a simple calculator:


     mysql> SELECT SIN(PI()/4), (4+1)*5;
     +------------------+---------+
     | SIN(PI()/4)      | (4+1)*5 |
     +------------------+---------+
     | 0.70710678118655 |      25 |
     +------------------+---------+
     1 row in set (0.02 sec)

The queries shown thus far have been relatively short, single-line
statements. You can even enter multiple statements on a single line.
Just end each one with a semicolon:


     mysql> SELECT VERSION(); SELECT NOW();
     +-----------------+
     | VERSION()       |
     +-----------------+
     | 5.1.2-alpha-log |
     +-----------------+
     1 row in set (0.00 sec)

     +---------------------+
     | NOW()               |
     +---------------------+
     | 2005-10-11 15:15:00 |
     +---------------------+
     1 row in set (0.00 sec)

A command need not be given all on a single line, so lengthy commands
that require several lines are not a problem.  *Note `mysql': mysql.
determines where your statement ends by looking for the terminating
semicolon, not by looking for the end of the input line. (In other
words, *Note `mysql': mysql.  accepts free-format input: it collects
input lines but does not execute them until it sees the semicolon.)

Here is a simple multiple-line statement:


     mysql> SELECT
         -> USER()
         -> ,
         -> CURRENT_DATE;
     +---------------+--------------+
     | USER()        | CURRENT_DATE |
     +---------------+--------------+
     | jon@localhost | 2005-10-11   |
     +---------------+--------------+

In this example, notice how the prompt changes from `mysql>' to `->'
after you enter the first line of a multiple-line query. This is how
*Note `mysql': mysql. indicates that it has not yet seen a complete
statement and is waiting for the rest. The prompt is your friend,
because it provides valuable feedback. If you use that feedback, you
can always be aware of what *Note `mysql': mysql.  is waiting for.

If you decide you do not want to execute a command that you are in the
process of entering, cancel it by typing `\c':


     mysql> SELECT
         -> USER()
         -> \c
     mysql>

Here, too, notice the prompt. It switches back to `mysql>' after you
type `\c', providing feedback to indicate that *Note `mysql': mysql. is
ready for a new command.

The following table shows each of the prompts you may see and
summarizes what they mean about the state that *Note `mysql': mysql. is
in.

This table lists MySQL prompts and describes the meaning of each.

Prompt  Meaning
`mysql>'Ready for new command.
`->'    Waiting for next line of multiple-line command.
`'>'    Waiting for next line, waiting for completion of a string
        that began with a single quote (``''').
`">'    Waiting for next line, waiting for completion of a string
        that began with a double quote (``"'').
``>'    Waiting for next line, waiting for completion of an
        identifier that began with a backtick (```'').
`/*>'   Waiting for next line, waiting for completion of a
        comment that began with `/*'.

Multiple-line statements commonly occur by accident when you intend to
issue a command on a single line, but forget the terminating semicolon.
In this case, *Note `mysql': mysql.  waits for more input:


     mysql> SELECT USER()
         ->

If this happens to you (you think you've entered a statement but the
only response is a `->' prompt), most likely *Note `mysql': mysql. is
waiting for the semicolon. If you don't notice what the prompt is
telling you, you might sit there for a while before realizing what you
need to do. Enter a semicolon to complete the statement, and *Note
`mysql': mysql.  executes it:


     mysql> SELECT USER()
         -> ;
     +---------------+
     | USER()        |
     +---------------+
     | jon@localhost |
     +---------------+

The `'>' and `">' prompts occur during string collection (another way
of saying that MySQL is waiting for completion of a string). In MySQL,
you can write strings surrounded by either ``''' or ``"'' characters
(for example, `'hello'' or `"goodbye"'), and *Note `mysql': mysql. lets
you enter strings that span multiple lines. When you see a `'>' or `">'
prompt, it means that you have entered a line containing a string that
begins with a ``''' or ``"'' quote character, but have not yet entered
the matching quote that terminates the string. This often indicates
that you have inadvertently left out a quote character. For example:


     mysql> SELECT * FROM my_table WHERE name = 'Smith AND age < 30;
         '>

If you enter this *Note `SELECT': select. statement, then press `Enter'
and wait for the result, nothing happens. Instead of wondering why this
query takes so long, notice the clue provided by the `'>' prompt. It
tells you that *Note `mysql': mysql. expects to see the rest of an
unterminated string. (Do you see the error in the statement? The string
`'Smith' is missing the second single quotation mark.)

At this point, what do you do? The simplest thing is to cancel the
command. However, you cannot just type `\c' in this case, because *Note
`mysql': mysql. interprets it as part of the string that it is
collecting. Instead, enter the closing quote character (so *Note
`mysql': mysql. knows you've finished the string), then type `\c':


     mysql> SELECT * FROM my_table WHERE name = 'Smith AND age < 30;
         '> '\c
     mysql>

The prompt changes back to `mysql>', indicating that *Note `mysql':
mysql. is ready for a new command.

The ``>' prompt is similar to the `'>' and `">' prompts, but indicates
that you have begun but not completed a backtick-quoted identifier.

It is important to know what the `'>', `">', and ``>' prompts signify,
because if you mistakenly enter an unterminated string, any further
lines you type appear to be ignored by *Note `mysql': mysql.--including
a line containing `QUIT'. This can be quite confusing, especially if
you do not know that you need to supply the terminating quote before
you can cancel the current command.


File: manual.info,  Node: database-use,  Next: getting-information,  Prev: entering-queries,  Up: tutorial

3.3 Creating and Using a Database
=================================

* Menu:

* creating-database::            Creating and Selecting a Database
* creating-tables::              Creating a Table
* loading-tables::               Loading Data into a Table
* retrieving-data::              Retrieving Information from a Table

Once you know how to enter commands, you are ready to access a database.

Suppose that you have several pets in your home (your menagerie) and
you would like to keep track of various types of information about
them. You can do so by creating tables to hold your data and loading
them with the desired information. Then you can answer different sorts
of questions about your animals by retrieving data from the tables.
This section shows you how to perform the following operations:

   * Create a database

   * Create a table

   * Load data into the table

   * Retrieve data from the table in various ways

   * Use multiple tables

The menagerie database is simple (deliberately), but it is not
difficult to think of real-world situations in which a similar type of
database might be used. For example, a database like this could be used
by a farmer to keep track of livestock, or by a veterinarian to keep
track of patient records. A menagerie distribution containing some of
the queries and sample data used in the following sections can be
obtained from the MySQL Web site.  It is available in both compressed
`tar' file and Zip formats at `http://dev.mysql.com/doc/'.

Use the *Note `SHOW': show. statement to find out what databases
currently exist on the server:


     mysql> SHOW DATABASES;
     +----------+
     | Database |
     +----------+
     | mysql    |
     | test     |
     | tmp      |
     +----------+

The `mysql' database describes user access privileges. The `test'
database often is available as a workspace for users to try things out.

The list of databases displayed by the statement may be different on
your machine; *Note `SHOW DATABASES': show-databases.  does not show
databases that you have no privileges for if you do not have the *Note
`SHOW DATABASES': show-databases.  privilege. See *Note
show-databases::.

If the `test' database exists, try to access it:


     mysql> USE test
     Database changed

*Note `USE': use, like `QUIT', does not require a semicolon. (You can
terminate such statements with a semicolon if you like; it does no
harm.) The *Note `USE': use. statement is special in another way, too:
it must be given on a single line.

You can use the `test' database (if you have access to it) for the
examples that follow, but anything you create in that database can be
removed by anyone else with access to it. For this reason, you should
probably ask your MySQL administrator for permission to use a database
of your own.  Suppose that you want to call yours `menagerie'.  The
administrator needs to execute a command like this:


     mysql> GRANT ALL ON menagerie.* TO 'your_mysql_name'@'your_client_host';

where `your_mysql_name' is the MySQL user name assigned to you and
`your_client_host' is the host from which you connect to the server.


File: manual.info,  Node: creating-database,  Next: creating-tables,  Prev: database-use,  Up: database-use

3.3.1 Creating and Selecting a Database
---------------------------------------

If the administrator creates your database for you when setting up your
permissions, you can begin using it. Otherwise, you need to create it
yourself:


     mysql> CREATE DATABASE menagerie;

Under Unix, database names are case sensitive (unlike SQL keywords), so
you must always refer to your database as `menagerie', not as
`Menagerie', `MENAGERIE', or some other variant. This is also true for
table names. (Under Windows, this restriction does not apply, although
you must refer to databases and tables using the same lettercase
throughout a given query. However, for a variety of reasons, the
recommended best practice is always to use the same lettercase that was
used when the database was created.)

*Note*:

If you get an error such as `ERROR 1044 (42000): Access denied for user
'monty'@'localhost' to database 'menagerie'' when attempting to create
a database, this means that your user account does not have the
necessary privileges to do so. Discuss this with the administrator or
see *Note privilege-system::.

Creating a database does not select it for use; you must do that
explicitly. To make `menagerie' the current database, use this command:


     mysql> USE menagerie
     Database changed

Your database needs to be created only once, but you must select it for
use each time you begin a *Note `mysql': mysql.  session. You can do
this by issuing a *Note `USE': use. statement as shown in the example.
Alternatively, you can select the database on the command line when you
invoke *Note `mysql': mysql. Just specify its name after any connection
parameters that you might need to provide. For example:


     shell> mysql -h HOST -u USER -p menagerie
     Enter password: ********

*Important*:

`menagerie' in the command just shown is *not* your password. If you
want to supply your password on the command line after the `-p' option,
you must do so with no intervening space (for example, as
`-pmypassword', not as `-p mypassword'). However, putting your password
on the command line is not recommended, because doing so exposes it to
snooping by other users logged in on your machine.

*Note*:

You can see at any time which database is currently selected using
*Note `SELECT': select.  `DATABASE()'.


File: manual.info,  Node: creating-tables,  Next: loading-tables,  Prev: creating-database,  Up: database-use

3.3.2 Creating a Table
----------------------

Creating the database is the easy part, but at this point it is empty,
as *Note `SHOW TABLES': show-tables. tells you:


     mysql> SHOW TABLES;
     Empty set (0.00 sec)

The harder part is deciding what the structure of your database should
be: what tables you need and what columns should be in each of them.

You want a table that contains a record for each of your pets.  This
can be called the `pet' table, and it should contain, as a bare
minimum, each animal's name. Because the name by itself is not very
interesting, the table should contain other information. For example,
if more than one person in your family keeps pets, you might want to
list each animal's owner. You might also want to record some basic
descriptive information such as species and sex.

How about age? That might be of interest, but it is not a good thing to
store in a database. Age changes as time passes, which means you'd have
to update your records often. Instead, it is better to store a fixed
value such as date of birth. Then, whenever you need age, you can
calculate it as the difference between the current date and the birth
date. MySQL provides functions for doing date arithmetic, so this is
not difficult.  Storing birth date rather than age has other
advantages, too:

   * You can use the database for tasks such as generating reminders
     for upcoming pet birthdays. (If you think this type of query is
     somewhat silly, note that it is the same question you might ask in
     the context of a business database to identify clients to whom you
     need to send out birthday greetings in the current week or month,
     for that computer-assisted personal touch.)

   * You can calculate age in relation to dates other than the current
     date. For example, if you store death date in the database, you
     can easily calculate how old a pet was when it died.

You can probably think of other types of information that would be
useful in the `pet' table, but the ones identified so far are
sufficient: name, owner, species, sex, birth, and death.

Use a *Note `CREATE TABLE': create-table. statement to specify the
layout of your table:


     mysql> CREATE TABLE pet (name VARCHAR(20), owner VARCHAR(20),
         -> species VARCHAR(20), sex CHAR(1), birth DATE, death DATE);

*Note `VARCHAR': char. is a good choice for the `name', `owner', and
`species' columns because the column values vary in length. The lengths
in those column definitions need not all be the same, and need not be
`20'. You can normally pick any length from `1' to `65535', whatever
seems most reasonable to you.  If you make a poor choice and it turns
out later that you need a longer field, MySQL provides an *Note `ALTER
TABLE': alter-table. statement.

Several types of values can be chosen to represent sex in animal
records, such as `'m'' and `'f'', or perhaps `'male'' and `'female''.
It is simplest to use the single characters `'m'' and `'f''.

The use of the *Note `DATE': datetime. data type for the `birth' and
`death' columns is a fairly obvious choice.

Once you have created a table, *Note `SHOW TABLES': show-tables. should
produce some output:


     mysql> SHOW TABLES;
     +---------------------+
     | Tables in menagerie |
     +---------------------+
     | pet                 |
     +---------------------+

To verify that your table was created the way you expected, use a *Note
`DESCRIBE': describe. statement:


     mysql> DESCRIBE pet;
     +---------+-------------+------+-----+---------+-------+
     | Field   | Type        | Null | Key | Default | Extra |
     +---------+-------------+------+-----+---------+-------+
     | name    | varchar(20) | YES  |     | NULL    |       |
     | owner   | varchar(20) | YES  |     | NULL    |       |
     | species | varchar(20) | YES  |     | NULL    |       |
     | sex     | char(1)     | YES  |     | NULL    |       |
     | birth   | date        | YES  |     | NULL    |       |
     | death   | date        | YES  |     | NULL    |       |
     +---------+-------------+------+-----+---------+-------+

You can use *Note `DESCRIBE': describe. any time, for example, if you
forget the names of the columns in your table or what types they have.

For more information about MySQL data types, see *Note data-types::.


File: manual.info,  Node: loading-tables,  Next: retrieving-data,  Prev: creating-tables,  Up: database-use

3.3.3 Loading Data into a Table
-------------------------------

After creating your table, you need to populate it. The *Note `LOAD
DATA': load-data. and *Note `INSERT': insert. statements are useful for
this.

Suppose that your pet records can be described as shown here.  (Observe
that MySQL expects dates in `'YYYY-MM-DD'' format; this may be different
from what you are used to.)

This table illustrates the example of `pet records' mentioned in the
preceding text.

name    owner   species sex  birth          death
Fluffy  Harold  cat     f    1993-02-04     
Claws   Gwen    cat     m    1994-03-17     
Buffy   Harold  dog     f    1989-05-13     
Fang    Benny   dog     m    1990-08-27     
Bowser  Diane   dog     m    1979-08-31     1995-07-29
Chirpy  Gwen    bird    f    1998-09-11     
WhistlerGwen    bird         1997-12-09     
Slim    Benny   snake   m    1996-04-29     

Because you are beginning with an empty table, an easy way to populate
it is to create a text file containing a row for each of your animals,
then load the contents of the file into the table with a single
statement.

You could create a text file `pet.txt' containing one record per line,
with values separated by tabs, and given in the order in which the
columns were listed in the *Note `CREATE TABLE': create-table.
statement. For missing values (such as unknown sexes or death dates for
animals that are still living), you can use `NULL' values. To represent
these in your text file, use `\N' (backslash, capital-N). For example,
the record for Whistler the bird would look like this (where the
whitespace between values is a single tab character):


     Whistler        Gwen    bird    \N      1997-12-09      \N

To load the text file `pet.txt' into the `pet' table, use this
statement:


     mysql> LOAD DATA LOCAL INFILE '/path/pet.txt' INTO TABLE pet;

If you created the file on Windows with an editor that uses `\r\n' as a
line terminator, you should use this statement instead:


     mysql> LOAD DATA LOCAL INFILE '/path/pet.txt' INTO TABLE pet
         -> LINES TERMINATED BY '\r\n';

(On an Apple machine running OS X, you would likely want to use `LINES
TERMINATED BY '\r''.)

You can specify the column value separator and end of line marker
explicitly in the *Note `LOAD DATA': load-data. statement if you wish,
but the defaults are tab and linefeed. These are sufficient for the
statement to read the file `pet.txt' properly.

If the statement fails, it is likely that your MySQL installation does
not have local file capability enabled by default. See *Note
load-data-local::, for information on how to change this.

When you want to add new records one at a time, the *Note `INSERT':
insert. statement is useful. In its simplest form, you supply values
for each column, in the order in which the columns were listed in the
*Note `CREATE TABLE': create-table. statement. Suppose that Diane gets
a new hamster named `Puffball.' You could add a new record using an
*Note `INSERT': insert. statement like this:


     mysql> INSERT INTO pet
         -> VALUES ('Puffball','Diane','hamster','f','1999-03-30',NULL);

String and date values are specified as quoted strings here.  Also,
with *Note `INSERT': insert, you can insert `NULL' directly to
represent a missing value.  You do not use `\N' like you do with *Note
`LOAD DATA': load-data.

From this example, you should be able to see that there would be a lot
more typing involved to load your records initially using several *Note
`INSERT': insert. statements rather than a single *Note `LOAD DATA':
load-data.  statement.


File: manual.info,  Node: retrieving-data,  Prev: loading-tables,  Up: database-use

3.3.4 Retrieving Information from a Table
-----------------------------------------

* Menu:

* selecting-all::                Selecting All Data
* selecting-rows::               Selecting Particular Rows
* selecting-columns::            Selecting Particular Columns
* sorting-rows::                 Sorting Rows
* date-calculations::            Date Calculations
* working-with-null::            Working with NULL Values
* pattern-matching::             Pattern Matching
* counting-rows::                Counting Rows
* multiple-tables::              Using More Than one Table

The *Note `SELECT': select. statement is used to pull information from
a table. The general form of the statement is:


     SELECT WHAT_TO_SELECT
     FROM WHICH_TABLE
     WHERE CONDITIONS_TO_SATISFY;

WHAT_TO_SELECT indicates what you want to see. This can be a list of
columns, or `*' to indicate `all columns.' WHICH_TABLE indicates the
table from which you want to retrieve data. The `WHERE' clause is
optional. If it is present, CONDITIONS_TO_SATISFY specifies one or more
conditions that rows must satisfy to qualify for retrieval.


File: manual.info,  Node: selecting-all,  Next: selecting-rows,  Prev: retrieving-data,  Up: retrieving-data

3.3.4.1 Selecting All Data
..........................

The simplest form of *Note `SELECT': select.  retrieves everything from
a table:


     mysql> SELECT * FROM pet;
     +----------+--------+---------+------+------------+------------+
     | name     | owner  | species | sex  | birth      | death      |
     +----------+--------+---------+------+------------+------------+
     | Fluffy   | Harold | cat     | f    | 1993-02-04 | NULL       |
     | Claws    | Gwen   | cat     | m    | 1994-03-17 | NULL       |
     | Buffy    | Harold | dog     | f    | 1989-05-13 | NULL       |
     | Fang     | Benny  | dog     | m    | 1990-08-27 | NULL       |
     | Bowser   | Diane  | dog     | m    | 1979-08-31 | 1995-07-29 |
     | Chirpy   | Gwen   | bird    | f    | 1998-09-11 | NULL       |
     | Whistler | Gwen   | bird    | NULL | 1997-12-09 | NULL       |
     | Slim     | Benny  | snake   | m    | 1996-04-29 | NULL       |
     | Puffball | Diane  | hamster | f    | 1999-03-30 | NULL       |
     +----------+--------+---------+------+------------+------------+

This form of *Note `SELECT': select. is useful if you want to review
your entire table, for example, after you've just loaded it with your
initial data set. For example, you may happen to think that the birth
date for Bowser doesn't seem quite right. Consulting your original
pedigree papers, you find that the correct birth year should be 1989,
not 1979.

There are at least two ways to fix this:

   * Edit the file `pet.txt' to correct the error, then empty the table
     and reload it using *Note `DELETE': delete. and *Note `LOAD DATA':
     load-data.:


          mysql> DELETE FROM pet;
          mysql> LOAD DATA LOCAL INFILE 'pet.txt' INTO TABLE pet;

     However, if you do this, you must also re-enter the record for
     Puffball.

   * Fix only the erroneous record with an *Note `UPDATE': update.
     statement:


          mysql> UPDATE pet SET birth = '1989-08-31' WHERE name = 'Bowser';

     The *Note `UPDATE': update. changes only the record in question
     and does not require you to reload the table.


File: manual.info,  Node: selecting-rows,  Next: selecting-columns,  Prev: selecting-all,  Up: retrieving-data

3.3.4.2 Selecting Particular Rows
.................................

As shown in the preceding section, it is easy to retrieve an entire
table. Just omit the `WHERE' clause from the *Note `SELECT': select.
statement. But typically you don't want to see the entire table,
particularly when it becomes large. Instead, you're usually more
interested in answering a particular question, in which case you specify
some constraints on the information you want. Let's look at some
selection queries in terms of questions about your pets that they
answer.

You can select only particular rows from your table. For example, if
you want to verify the change that you made to Bowser's birth date,
select Bowser's record like this:


     mysql> SELECT * FROM pet WHERE name = 'Bowser';
     +--------+-------+---------+------+------------+------------+
     | name   | owner | species | sex  | birth      | death      |
     +--------+-------+---------+------+------------+------------+
     | Bowser | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
     +--------+-------+---------+------+------------+------------+

The output confirms that the year is correctly recorded as 1989, not
1979.

String comparisons normally are case-insensitive, so you can specify
the name as `'bowser'', `'BOWSER'', and so forth. The query result is
the same.

You can specify conditions on any column, not just `name'. For example,
if you want to know which animals were born during or after 1998, test
the `birth' column:


     mysql> SELECT * FROM pet WHERE birth >= '1998-1-1';
     +----------+-------+---------+------+------------+-------+
     | name     | owner | species | sex  | birth      | death |
     +----------+-------+---------+------+------------+-------+
     | Chirpy   | Gwen  | bird    | f    | 1998-09-11 | NULL  |
     | Puffball | Diane | hamster | f    | 1999-03-30 | NULL  |
     +----------+-------+---------+------+------------+-------+

You can combine conditions, for example, to locate female dogs:


     mysql> SELECT * FROM pet WHERE species = 'dog' AND sex = 'f';
     +-------+--------+---------+------+------------+-------+
     | name  | owner  | species | sex  | birth      | death |
     +-------+--------+---------+------+------------+-------+
     | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
     +-------+--------+---------+------+------------+-------+

The preceding query uses the `AND' logical operator. There is also an
`OR' operator:


     mysql> SELECT * FROM pet WHERE species = 'snake' OR species = 'bird';
     +----------+-------+---------+------+------------+-------+
     | name     | owner | species | sex  | birth      | death |
     +----------+-------+---------+------+------------+-------+
     | Chirpy   | Gwen  | bird    | f    | 1998-09-11 | NULL  |
     | Whistler | Gwen  | bird    | NULL | 1997-12-09 | NULL  |
     | Slim     | Benny | snake   | m    | 1996-04-29 | NULL  |
     +----------+-------+---------+------+------------+-------+

`AND' and `OR' may be intermixed, although `AND' has higher precedence
than `OR'. If you use both operators, it is a good idea to use
parentheses to indicate explicitly how conditions should be grouped:


     mysql> SELECT * FROM pet WHERE (species = 'cat' AND sex = 'm')
         -> OR (species = 'dog' AND sex = 'f');
     +-------+--------+---------+------+------------+-------+
     | name  | owner  | species | sex  | birth      | death |
     +-------+--------+---------+------+------------+-------+
     | Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
     | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
     +-------+--------+---------+------+------------+-------+


File: manual.info,  Node: selecting-columns,  Next: sorting-rows,  Prev: selecting-rows,  Up: retrieving-data

3.3.4.3 Selecting Particular Columns
....................................

If you do not want to see entire rows from your table, just name the
columns in which you are interested, separated by commas. For example,
if you want to know when your animals were born, select the `name' and
`birth' columns:


     mysql> SELECT name, birth FROM pet;
     +----------+------------+
     | name     | birth      |
     +----------+------------+
     | Fluffy   | 1993-02-04 |
     | Claws    | 1994-03-17 |
     | Buffy    | 1989-05-13 |
     | Fang     | 1990-08-27 |
     | Bowser   | 1989-08-31 |
     | Chirpy   | 1998-09-11 |
     | Whistler | 1997-12-09 |
     | Slim     | 1996-04-29 |
     | Puffball | 1999-03-30 |
     +----------+------------+

To find out who owns pets, use this query:


     mysql> SELECT owner FROM pet;
     +--------+
     | owner  |
     +--------+
     | Harold |
     | Gwen   |
     | Harold |
     | Benny  |
     | Diane  |
     | Gwen   |
     | Gwen   |
     | Benny  |
     | Diane  |
     +--------+

Notice that the query simply retrieves the `owner' column from each
record, and some of them appear more than once. To minimize the output,
retrieve each unique output record just once by adding the keyword
`DISTINCT':


     mysql> SELECT DISTINCT owner FROM pet;
     +--------+
     | owner  |
     +--------+
     | Benny  |
     | Diane  |
     | Gwen   |
     | Harold |
     +--------+

You can use a `WHERE' clause to combine row selection with column
selection. For example, to get birth dates for dogs and cats only, use
this query:


     mysql> SELECT name, species, birth FROM pet
         -> WHERE species = 'dog' OR species = 'cat';
     +--------+---------+------------+
     | name   | species | birth      |
     +--------+---------+------------+
     | Fluffy | cat     | 1993-02-04 |
     | Claws  | cat     | 1994-03-17 |
     | Buffy  | dog     | 1989-05-13 |
     | Fang   | dog     | 1990-08-27 |
     | Bowser | dog     | 1989-08-31 |
     +--------+---------+------------+


File: manual.info,  Node: sorting-rows,  Next: date-calculations,  Prev: selecting-columns,  Up: retrieving-data

3.3.4.4 Sorting Rows
....................

You may have noticed in the preceding examples that the result rows are
displayed in no particular order. It is often easier to examine query
output when the rows are sorted in some meaningful way. To sort a
result, use an `ORDER BY' clause.

Here are animal birthdays, sorted by date:


     mysql> SELECT name, birth FROM pet ORDER BY birth;
     +----------+------------+
     | name     | birth      |
     +----------+------------+
     | Buffy    | 1989-05-13 |
     | Bowser   | 1989-08-31 |
     | Fang     | 1990-08-27 |
     | Fluffy   | 1993-02-04 |
     | Claws    | 1994-03-17 |
     | Slim     | 1996-04-29 |
     | Whistler | 1997-12-09 |
     | Chirpy   | 1998-09-11 |
     | Puffball | 1999-03-30 |
     +----------+------------+

On character type columns, sorting--like all other comparison
operations--is normally performed in a case-insensitive fashion. This
means that the order is undefined for columns that are identical except
for their case. You can force a case-sensitive sort for a column by
using `BINARY' like so: `ORDER BY BINARY COL_NAME'.

The default sort order is ascending, with smallest values first. To
sort in reverse (descending) order, add the `DESC' keyword to the name
of the column you are sorting by:


     mysql> SELECT name, birth FROM pet ORDER BY birth DESC;
     +----------+------------+
     | name     | birth      |
     +----------+------------+
     | Puffball | 1999-03-30 |
     | Chirpy   | 1998-09-11 |
     | Whistler | 1997-12-09 |
     | Slim     | 1996-04-29 |
     | Claws    | 1994-03-17 |
     | Fluffy   | 1993-02-04 |
     | Fang     | 1990-08-27 |
     | Bowser   | 1989-08-31 |
     | Buffy    | 1989-05-13 |
     +----------+------------+

You can sort on multiple columns, and you can sort different columns in
different directions. For example, to sort by type of animal in
ascending order, then by birth date within animal type in descending
order (youngest animals first), use the following query:


     mysql> SELECT name, species, birth FROM pet
         -> ORDER BY species, birth DESC;
     +----------+---------+------------+
     | name     | species | birth      |
     +----------+---------+------------+
     | Chirpy   | bird    | 1998-09-11 |
     | Whistler | bird    | 1997-12-09 |
     | Claws    | cat     | 1994-03-17 |
     | Fluffy   | cat     | 1993-02-04 |
     | Fang     | dog     | 1990-08-27 |
     | Bowser   | dog     | 1989-08-31 |
     | Buffy    | dog     | 1989-05-13 |
     | Puffball | hamster | 1999-03-30 |
     | Slim     | snake   | 1996-04-29 |
     +----------+---------+------------+

The `DESC' keyword applies only to the column name immediately
preceding it (`birth'); it does not affect the `species' column sort
order.


File: manual.info,  Node: date-calculations,  Next: working-with-null,  Prev: sorting-rows,  Up: retrieving-data

3.3.4.5 Date Calculations
.........................

MySQL provides several functions that you can use to perform
calculations on dates, for example, to calculate ages or extract parts
of dates.

To determine how many years old each of your pets is, use the
`TIMESTAMPDIFF()' function. Its arguments are the unit in which you
want the result expressed, and the two date for which to take the
difference. The following query shows, for each pet, the birth date, the
current date, and the age in years. An _alias_ (`age') is used to make
the final output column label more meaningful.


     mysql> SELECT name, birth, CURDATE(),
         -> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age
         -> FROM pet;
     +----------+------------+------------+------+
     | name     | birth      | CURDATE()  | age  |
     +----------+------------+------------+------+
     | Fluffy   | 1993-02-04 | 2003-08-19 |   10 |
     | Claws    | 1994-03-17 | 2003-08-19 |    9 |
     | Buffy    | 1989-05-13 | 2003-08-19 |   14 |
     | Fang     | 1990-08-27 | 2003-08-19 |   12 |
     | Bowser   | 1989-08-31 | 2003-08-19 |   13 |
     | Chirpy   | 1998-09-11 | 2003-08-19 |    4 |
     | Whistler | 1997-12-09 | 2003-08-19 |    5 |
     | Slim     | 1996-04-29 | 2003-08-19 |    7 |
     | Puffball | 1999-03-30 | 2003-08-19 |    4 |
     +----------+------------+------------+------+

The query works, but the result could be scanned more easily if the
rows were presented in some order. This can be done by adding an `ORDER
BY name' clause to sort the output by name:


     mysql> SELECT name, birth, CURDATE(),
         -> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age
         -> FROM pet ORDER BY name;
     +----------+------------+------------+------+
     | name     | birth      | CURDATE()  | age  |
     +----------+------------+------------+------+
     | Bowser   | 1989-08-31 | 2003-08-19 |   13 |
     | Buffy    | 1989-05-13 | 2003-08-19 |   14 |
     | Chirpy   | 1998-09-11 | 2003-08-19 |    4 |
     | Claws    | 1994-03-17 | 2003-08-19 |    9 |
     | Fang     | 1990-08-27 | 2003-08-19 |   12 |
     | Fluffy   | 1993-02-04 | 2003-08-19 |   10 |
     | Puffball | 1999-03-30 | 2003-08-19 |    4 |
     | Slim     | 1996-04-29 | 2003-08-19 |    7 |
     | Whistler | 1997-12-09 | 2003-08-19 |    5 |
     +----------+------------+------------+------+

To sort the output by `age' rather than `name', just use a different
`ORDER BY' clause:


     mysql> SELECT name, birth, CURDATE(),
         -> TIMESTAMPDIFF(YEAR,birth,CURDATE()) AS age
         -> FROM pet ORDER BY age;
     +----------+------------+------------+------+
     | name     | birth      | CURDATE()  | age  |
     +----------+------------+------------+------+
     | Chirpy   | 1998-09-11 | 2003-08-19 |    4 |
     | Puffball | 1999-03-30 | 2003-08-19 |    4 |
     | Whistler | 1997-12-09 | 2003-08-19 |    5 |
     | Slim     | 1996-04-29 | 2003-08-19 |    7 |
     | Claws    | 1994-03-17 | 2003-08-19 |    9 |
     | Fluffy   | 1993-02-04 | 2003-08-19 |   10 |
     | Fang     | 1990-08-27 | 2003-08-19 |   12 |
     | Bowser   | 1989-08-31 | 2003-08-19 |   13 |
     | Buffy    | 1989-05-13 | 2003-08-19 |   14 |
     +----------+------------+------------+------+

A similar query can be used to determine age at death for animals that
have died. You determine which animals these are by checking whether
the `death' value is `NULL'. Then, for those with non-`NULL' values,
compute the difference between the `death' and `birth' values:


     mysql> SELECT name, birth, death,
         -> TIMESTAMPDIFF(YEAR,birth,death) AS age
         -> FROM pet WHERE death IS NOT NULL ORDER BY age;
     +--------+------------+------------+------+
     | name   | birth      | death      | age  |
     +--------+------------+------------+------+
     | Bowser | 1989-08-31 | 1995-07-29 |    5 |
     +--------+------------+------------+------+

The query uses `death IS NOT NULL' rather than `death <> NULL' because
`NULL' is a special value that cannot be compared using the usual
comparison operators. This is discussed later. See *Note
working-with-null::.

What if you want to know which animals have birthdays next month? For
this type of calculation, year and day are irrelevant; you simply want
to extract the month part of the `birth' column. MySQL provides several
functions for extracting parts of dates, such as `YEAR()', `MONTH()',
and `DAYOFMONTH()'.  `MONTH()' is the appropriate function here. To see
how it works, run a simple query that displays the value of both
`birth' and `MONTH(birth)':


     mysql> SELECT name, birth, MONTH(birth) FROM pet;
     +----------+------------+--------------+
     | name     | birth      | MONTH(birth) |
     +----------+------------+--------------+
     | Fluffy   | 1993-02-04 |            2 |
     | Claws    | 1994-03-17 |            3 |
     | Buffy    | 1989-05-13 |            5 |
     | Fang     | 1990-08-27 |            8 |
     | Bowser   | 1989-08-31 |            8 |
     | Chirpy   | 1998-09-11 |            9 |
     | Whistler | 1997-12-09 |           12 |
     | Slim     | 1996-04-29 |            4 |
     | Puffball | 1999-03-30 |            3 |
     +----------+------------+--------------+

Finding animals with birthdays in the upcoming month is also simple.
Suppose that the current month is April. Then the month value is `4'
and you can look for animals born in May (month `5') like this:


     mysql> SELECT name, birth FROM pet WHERE MONTH(birth) = 5;
     +-------+------------+
     | name  | birth      |
     +-------+------------+
     | Buffy | 1989-05-13 |
     +-------+------------+

There is a small complication if the current month is December. You
cannot merely add one to the month number (`12') and look for animals
born in month `13', because there is no such month.  Instead, you look
for animals born in January (month `1').

You can write the query so that it works no matter what the current
month is, so that you do not have to use the number for a particular
month.  `DATE_ADD()' enables you to add a time interval to a given
date. If you add a month to the value of `CURDATE()', then extract the
month part with `MONTH()', the result produces the month in which to
look for birthdays:


     mysql> SELECT name, birth FROM pet
         -> WHERE MONTH(birth) = MONTH(DATE_ADD(CURDATE(),INTERVAL 1 MONTH));

A different way to accomplish the same task is to add `1' to get the
next month after the current one after using the modulo function (`MOD')
to wrap the month value to `0' if it is currently `12':


     mysql> SELECT name, birth FROM pet
         -> WHERE MONTH(birth) = MOD(MONTH(CURDATE()), 12) + 1;

`MONTH()' returns a number between `1' and `12'. And
`MOD(something,12)' returns a number between `0' and `11'.  So the
addition has to be after the `MOD()', otherwise we would go from
November (`11') to January (`1').


File: manual.info,  Node: working-with-null,  Next: pattern-matching,  Prev: date-calculations,  Up: retrieving-data

3.3.4.6 Working with NULL Values
................................

The `NULL' value can be surprising until you get used to it.
Conceptually, `NULL' means `a missing unknown value' and it is treated
somewhat differently from other values.

To test for `NULL', use the `IS NULL' and `IS NOT NULL' operators, as
shown here:


     mysql> SELECT 1 IS NULL, 1 IS NOT NULL;
     +-----------+---------------+
     | 1 IS NULL | 1 IS NOT NULL |
     +-----------+---------------+
     |         0 |             1 |
     +-----------+---------------+

You cannot use arithmetic comparison operators such as `=', `<', or
`<>' to test for `NULL'. To demonstrate this for yourself, try the
following query:


     mysql> SELECT 1 = NULL, 1 <> NULL, 1 < NULL, 1 > NULL;
     +----------+-----------+----------+----------+
     | 1 = NULL | 1 <> NULL | 1 < NULL | 1 > NULL |
     +----------+-----------+----------+----------+
     |     NULL |      NULL |     NULL |     NULL |
     +----------+-----------+----------+----------+

Because the result of any arithmetic comparison with `NULL' is also
`NULL', you cannot obtain any meaningful results from such comparisons.

In MySQL, `0' or `NULL' means false and anything else means true. The
default truth value from a boolean operation is `1'.

This special treatment of `NULL' is why, in the previous section, it
was necessary to determine which animals are no longer alive using
`death IS NOT NULL' instead of `death <> NULL'.

Two `NULL' values are regarded as equal in a `GROUP BY'.

When doing an `ORDER BY', `NULL' values are presented first if you do
`ORDER BY ... ASC' and last if you do `ORDER BY ... DESC'.

A common error when working with `NULL' is to assume that it is not
possible to insert a zero or an empty string into a column defined as
`NOT NULL', but this is not the case. These are in fact values, whereas
`NULL' means `not having a value.' You can test this easily enough by
using `IS [NOT] NULL' as shown:


     mysql> SELECT 0 IS NULL, 0 IS NOT NULL, '' IS NULL, '' IS NOT NULL;
     +-----------+---------------+------------+----------------+
     | 0 IS NULL | 0 IS NOT NULL | '' IS NULL | '' IS NOT NULL |
     +-----------+---------------+------------+----------------+
     |         0 |             1 |          0 |              1 |
     +-----------+---------------+------------+----------------+

Thus it is entirely possible to insert a zero or empty string into a
`NOT NULL' column, as these are in fact `NOT NULL'. See *Note
problems-with-null::.


File: manual.info,  Node: pattern-matching,  Next: counting-rows,  Prev: working-with-null,  Up: retrieving-data

3.3.4.7 Pattern Matching
........................

MySQL provides standard SQL pattern matching as well as a form of
pattern matching based on extended regular expressions similar to those
used by Unix utilities such as `vi', `grep', and `sed'.

SQL pattern matching enables you to use ``_'' to match any single
character and ``%'' to match an arbitrary number of characters
(including zero characters). In MySQL, SQL patterns are
case-insensitive by default. Some examples are shown here. You do not
use `=' or `<>' when you use SQL patterns; use the `LIKE' or `NOT LIKE'
comparison operators instead.

To find names beginning with ``b'':


     mysql> SELECT * FROM pet WHERE name LIKE 'b%';
     +--------+--------+---------+------+------------+------------+
     | name   | owner  | species | sex  | birth      | death      |
     +--------+--------+---------+------+------------+------------+
     | Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
     | Bowser | Diane  | dog     | m    | 1989-08-31 | 1995-07-29 |
     +--------+--------+---------+------+------------+------------+

To find names ending with ``fy'':


     mysql> SELECT * FROM pet WHERE name LIKE '%fy';
     +--------+--------+---------+------+------------+-------+
     | name   | owner  | species | sex  | birth      | death |
     +--------+--------+---------+------+------------+-------+
     | Fluffy | Harold | cat     | f    | 1993-02-04 | NULL  |
     | Buffy  | Harold | dog     | f    | 1989-05-13 | NULL  |
     +--------+--------+---------+------+------------+-------+

To find names containing a ``w'':


     mysql> SELECT * FROM pet WHERE name LIKE '%w%';
     +----------+-------+---------+------+------------+------------+
     | name     | owner | species | sex  | birth      | death      |
     +----------+-------+---------+------+------------+------------+
     | Claws    | Gwen  | cat     | m    | 1994-03-17 | NULL       |
     | Bowser   | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
     | Whistler | Gwen  | bird    | NULL | 1997-12-09 | NULL       |
     +----------+-------+---------+------+------------+------------+

To find names containing exactly five characters, use five instances of
the ``_'' pattern character:


     mysql> SELECT * FROM pet WHERE name LIKE '_____';
     +-------+--------+---------+------+------------+-------+
     | name  | owner  | species | sex  | birth      | death |
     +-------+--------+---------+------+------------+-------+
     | Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
     | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
     +-------+--------+---------+------+------------+-------+

The other type of pattern matching provided by MySQL uses extended
regular expressions. When you test for a match for this type of
pattern, use the `REGEXP' and `NOT REGEXP' operators (or `RLIKE' and
`NOT RLIKE', which are synonyms).

The following list describes some characteristics of extended regular
expressions:

   * ``.'' matches any single character.

   * A character class ``[...]'' matches any character within the
     brackets. For example, ``[abc]'' matches ``a'', ``b'', or ``c''.
     To name a range of characters, use a dash.  ``[a-z]'' matches any
     letter, whereas ``[0-9]'' matches any digit.

   * ``*'' matches zero or more instances of the thing preceding it.
     For example, ``x*'' matches any number of ``x'' characters,
     ``[0-9]*'' matches any number of digits, and ``.*'' matches any
     number of anything.

   * A `REGEXP' pattern match succeeds if the pattern matches anywhere
     in the value being tested. (This differs from a `LIKE' pattern
     match, which succeeds only if the pattern matches the entire
     value.)

   * To anchor a pattern so that it must match the beginning or end of
     the value being tested, use ``^'' at the beginning or ``$'' at the
     end of the pattern.

To demonstrate how extended regular expressions work, the `LIKE'
queries shown previously are rewritten here to use `REGEXP'.

To find names beginning with ``b'', use ``^'' to match the beginning of
the name:


     mysql> SELECT * FROM pet WHERE name REGEXP '^b';
     +--------+--------+---------+------+------------+------------+
     | name   | owner  | species | sex  | birth      | death      |
     +--------+--------+---------+------+------------+------------+
     | Buffy  | Harold | dog     | f    | 1989-05-13 | NULL       |
     | Bowser | Diane  | dog     | m    | 1989-08-31 | 1995-07-29 |
     +--------+--------+---------+------+------------+------------+

If you really want to force a `REGEXP' comparison to be case sensitive,
use the `BINARY' keyword to make one of the strings a binary string.
This query matches only lowercase ``b'' at the beginning of a name:


     mysql> SELECT * FROM pet WHERE name REGEXP BINARY '^b';

To find names ending with ``fy'', use ``$'' to match the end of the
name:


     mysql> SELECT * FROM pet WHERE name REGEXP 'fy$';
     +--------+--------+---------+------+------------+-------+
     | name   | owner  | species | sex  | birth      | death |
     +--------+--------+---------+------+------------+-------+
     | Fluffy | Harold | cat     | f    | 1993-02-04 | NULL  |
     | Buffy  | Harold | dog     | f    | 1989-05-13 | NULL  |
     +--------+--------+---------+------+------------+-------+

To find names containing a ``w'', use this query:


     mysql> SELECT * FROM pet WHERE name REGEXP 'w';
     +----------+-------+---------+------+------------+------------+
     | name     | owner | species | sex  | birth      | death      |
     +----------+-------+---------+------+------------+------------+
     | Claws    | Gwen  | cat     | m    | 1994-03-17 | NULL       |
     | Bowser   | Diane | dog     | m    | 1989-08-31 | 1995-07-29 |
     | Whistler | Gwen  | bird    | NULL | 1997-12-09 | NULL       |
     +----------+-------+---------+------+------------+------------+

Because a regular expression pattern matches if it occurs anywhere in
the value, it is not necessary in the previous query to put a wildcard
on either side of the pattern to get it to match the entire value like
it would be if you used an SQL pattern.

To find names containing exactly five characters, use ``^'' and ``$''
to match the beginning and end of the name, and five instances of ``.''
in between:


     mysql> SELECT * FROM pet WHERE name REGEXP '^.....$';
     +-------+--------+---------+------+------------+-------+
     | name  | owner  | species | sex  | birth      | death |
     +-------+--------+---------+------+------------+-------+
     | Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
     | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
     +-------+--------+---------+------+------------+-------+

You could also write the previous query using the `{N}'
(`repeat-N-times') operator:


     mysql> SELECT * FROM pet WHERE name REGEXP '^.{5}$';
     +-------+--------+---------+------+------------+-------+
     | name  | owner  | species | sex  | birth      | death |
     +-------+--------+---------+------+------------+-------+
     | Claws | Gwen   | cat     | m    | 1994-03-17 | NULL  |
     | Buffy | Harold | dog     | f    | 1989-05-13 | NULL  |
     +-------+--------+---------+------+------------+-------+

*Note regexp::, provides more information about the syntax for regular
expressions.


File: manual.info,  Node: counting-rows,  Next: multiple-tables,  Prev: pattern-matching,  Up: retrieving-data

3.3.4.8 Counting Rows
.....................

Databases are often used to answer the question, `How often does a
certain type of data occur in a table?' For example, you might want to
know how many pets you have, or how many pets each owner has, or you
might want to perform various kinds of census operations on your
animals.

Counting the total number of animals you have is the same question as
`How many rows are in the `pet' table?' because there is one record per
pet. `COUNT(*)' counts the number of rows, so the query to count your
animals looks like this:


     mysql> SELECT COUNT(*) FROM pet;
     +----------+
     | COUNT(*) |
     +----------+
     |        9 |
     +----------+

Earlier, you retrieved the names of the people who owned pets.  You can
use `COUNT()' if you want to find out how many pets each owner has:


     mysql> SELECT owner, COUNT(*) FROM pet GROUP BY owner;
     +--------+----------+
     | owner  | COUNT(*) |
     +--------+----------+
     | Benny  |        2 |
     | Diane  |        2 |
     | Gwen   |        3 |
     | Harold |        2 |
     +--------+----------+

The preceding query uses `GROUP BY' to group all records for each
`owner'. The use of `COUNT()' in conjunction with `GROUP BY' is useful
for characterizing your data under various groupings. The following
examples show different ways to perform animal census operations.

Number of animals per species:


     mysql> SELECT species, COUNT(*) FROM pet GROUP BY species;
     +---------+----------+
     | species | COUNT(*) |
     +---------+----------+
     | bird    |        2 |
     | cat     |        2 |
     | dog     |        3 |
     | hamster |        1 |
     | snake   |        1 |
     +---------+----------+

Number of animals per sex:


     mysql> SELECT sex, COUNT(*) FROM pet GROUP BY sex;
     +------+----------+
     | sex  | COUNT(*) |
     +------+----------+
     | NULL |        1 |
     | f    |        4 |
     | m    |        4 |
     +------+----------+

(In this output, `NULL' indicates that the sex is unknown.)

Number of animals per combination of species and sex:


     mysql> SELECT species, sex, COUNT(*) FROM pet GROUP BY species, sex;
     +---------+------+----------+
     | species | sex  | COUNT(*) |
     +---------+------+----------+
     | bird    | NULL |        1 |
     | bird    | f    |        1 |
     | cat     | f    |        1 |
     | cat     | m    |        1 |
     | dog     | f    |        1 |
     | dog     | m    |        2 |
     | hamster | f    |        1 |
     | snake   | m    |        1 |
     +---------+------+----------+

You need not retrieve an entire table when you use `COUNT()'. For
example, the previous query, when performed just on dogs and cats, looks
like this:


     mysql> SELECT species, sex, COUNT(*) FROM pet
         -> WHERE species = 'dog' OR species = 'cat'
         -> GROUP BY species, sex;
     +---------+------+----------+
     | species | sex  | COUNT(*) |
     +---------+------+----------+
     | cat     | f    |        1 |
     | cat     | m    |        1 |
     | dog     | f    |        1 |
     | dog     | m    |        2 |
     +---------+------+----------+

Or, if you wanted the number of animals per sex only for animals whose
sex is known:


     mysql> SELECT species, sex, COUNT(*) FROM pet
         -> WHERE sex IS NOT NULL
         -> GROUP BY species, sex;
     +---------+------+----------+
     | species | sex  | COUNT(*) |
     +---------+------+----------+
     | bird    | f    |        1 |
     | cat     | f    |        1 |
     | cat     | m    |        1 |
     | dog     | f    |        1 |
     | dog     | m    |        2 |
     | hamster | f    |        1 |
     | snake   | m    |        1 |
     +---------+------+----------+

If you name columns to select in addition to the `COUNT()' value, a
`GROUP BY' clause should be present that names those same columns.
Otherwise, the following occurs:

   * If the `ONLY_FULL_GROUP_BY' SQL mode is enabled, an error occurs:


          mysql> SET sql_mode = 'ONLY_FULL_GROUP_BY';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT owner, COUNT(*) FROM pet;
          ERROR 1140 (42000): Mixing of GROUP columns (MIN(),MAX(),COUNT()...)
          with no GROUP columns is illegal if there is no GROUP BY clause

   * If `ONLY_FULL_GROUP_BY' is not enabled, the query is processed by
     treating all rows as a single group, but the value selected for
     each named column is indeterminate. The server is free to select
     the value from any row:


          mysql> SET sql_mode = '';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT owner, COUNT(*) FROM pet;
          +--------+----------+
          | owner  | COUNT(*) |
          +--------+----------+
          | Harold |        8 |
          +--------+----------+
          1 row in set (0.00 sec)

See also *Note group-by-extensions::.


File: manual.info,  Node: multiple-tables,  Prev: counting-rows,  Up: retrieving-data

3.3.4.9 Using More Than one Table
.................................

The `pet' table keeps track of which pets you have. If you want to
record other information about them, such as events in their lives like
visits to the vet or when litters are born, you need another table.
What should this table look like? It needs to contain the following
information:

   * The pet name so that you know which animal each event pertains to.

   * A date so that you know when the event occurred.

   * A field to describe the event.

   * An event type field, if you want to be able to categorize events.

Given these considerations, the *Note `CREATE TABLE': create-table.
statement for the `event' table might look like this:


     mysql> CREATE TABLE event (name VARCHAR(20), date DATE,
         -> type VARCHAR(15), remark VARCHAR(255));

As with the `pet' table, it is easiest to load the initial records by
creating a tab-delimited text file containing the following information.

This table represents `pet record' data that will appear in a tab
delimited text file, as described in the preceding text.

name        date        type        remark
Fluffy      1995-05-15  litter      4 kittens, 3 female, 1
                                    male
Buffy       1993-06-23  litter      5 puppies, 2 female, 3
                                    male
Buffy       1994-06-19  litter      3 puppies, 3 female
Chirpy      1999-03-21  vet         needed beak straightened
Slim        1997-08-03  vet         broken rib
Bowser      1991-10-12  kennel      
Fang        1991-10-12  kennel      
Fang        1998-08-28  birthday    Gave him a new chew toy
Claws       1998-03-17  birthday    Gave him a new flea
                                    collar
Whistler    1998-12-09  birthday    First birthday

Load the records like this:


     mysql> LOAD DATA LOCAL INFILE 'event.txt' INTO TABLE event;

Based on what you have learned from the queries that you have run on
the `pet' table, you should be able to perform retrievals on the
records in the `event' table; the principles are the same.  But when is
the `event' table by itself insufficient to answer questions you might
ask?

Suppose that you want to find out the ages at which each pet had its
litters. We saw earlier how to calculate ages from two dates. The
litter date of the mother is in the `event' table, but to calculate her
age on that date you need her birth date, which is stored in the `pet'
table. This means the query requires both tables:


     mysql> SELECT pet.name,
         -> (YEAR(date)-YEAR(birth)) - (RIGHT(date,5)<RIGHT(birth,5)) AS age,
         -> remark
         -> FROM pet INNER JOIN event
         ->   ON pet.name = event.name
         -> WHERE event.type = 'litter';
     +--------+------+-----------------------------+
     | name   | age  | remark                      |
     +--------+------+-----------------------------+
     | Fluffy |    2 | 4 kittens, 3 female, 1 male |
     | Buffy  |    4 | 5 puppies, 2 female, 3 male |
     | Buffy  |    5 | 3 puppies, 3 female         |
     +--------+------+-----------------------------+

There are several things to note about this query:

   * The `FROM' clause joins two tables because the query needs to pull
     information from both of them.

   * When combining (joining) information from multiple tables, you
     need to specify how records in one table can be matched to records
     in the other. This is easy because they both have a `name' column.
     The query uses an `ON' clause to match up records in the two
     tables based on the `name' values.

     The query uses an `INNER JOIN' to combine the tables. An `INNER
     JOIN' permits rows from either table to appear in the result if
     and only if both tables meet the conditions specified in the `ON'
     clause. In this example, the `ON' clause specifies that the `name'
     column in the `pet' table must match the `name' column in the
     `event' table. If a name appears in one table but not the other,
     the row will not appear in the result because the condition in the
     `ON' clause fails.

   * Because the `name' column occurs in both tables, you must be
     specific about which table you mean when referring to the column.
     This is done by prepending the table name to the column name.

You need not have two different tables to perform a join.  Sometimes it
is useful to join a table to itself, if you want to compare records in
a table to other records in that same table. For example, to find
breeding pairs among your pets, you can join the `pet' table with
itself to produce candidate pairs of males and females of like species:


     mysql> SELECT p1.name, p1.sex, p2.name, p2.sex, p1.species
         -> FROM pet AS p1 INNER JOIN pet AS p2
         ->   ON p1.species = p2.species AND p1.sex = 'f' AND p2.sex = 'm';
     +--------+------+--------+------+---------+
     | name   | sex  | name   | sex  | species |
     +--------+------+--------+------+---------+
     | Fluffy | f    | Claws  | m    | cat     |
     | Buffy  | f    | Fang   | m    | dog     |
     | Buffy  | f    | Bowser | m    | dog     |
     +--------+------+--------+------+---------+

In this query, we specify aliases for the table name to refer to the
columns and keep straight which instance of the table each column
reference is associated with.


File: manual.info,  Node: getting-information,  Next: batch-mode,  Prev: database-use,  Up: tutorial

3.4 Getting Information About Databases and Tables
==================================================

What if you forget the name of a database or table, or what the
structure of a given table is (for example, what its columns are
called)? MySQL addresses this problem through several statements that
provide information about the databases and tables it supports.

You have previously seen *Note `SHOW DATABASES': show-databases, which
lists the databases managed by the server. To find out which database
is currently selected, use the `DATABASE()' function:


     mysql> SELECT DATABASE();
     +------------+
     | DATABASE() |
     +------------+
     | menagerie  |
     +------------+

If you have not yet selected any database, the result is `NULL'.

To find out what tables the default database contains (for example,
when you are not sure about the name of a table), use this command:


     mysql> SHOW TABLES;
     +---------------------+
     | Tables_in_menagerie |
     +---------------------+
     | event               |
     | pet                 |
     +---------------------+

The name of the column in the output produced by this statement is
always `Tables_in_DB_NAME', where DB_NAME is the name of the database.
See *Note show-tables::, for more information.

If you want to find out about the structure of a table, the *Note
`DESCRIBE': describe. statement is useful; it displays information
about each of a table's columns:


     mysql> DESCRIBE pet;
     +---------+-------------+------+-----+---------+-------+
     | Field   | Type        | Null | Key | Default | Extra |
     +---------+-------------+------+-----+---------+-------+
     | name    | varchar(20) | YES  |     | NULL    |       |
     | owner   | varchar(20) | YES  |     | NULL    |       |
     | species | varchar(20) | YES  |     | NULL    |       |
     | sex     | char(1)     | YES  |     | NULL    |       |
     | birth   | date        | YES  |     | NULL    |       |
     | death   | date        | YES  |     | NULL    |       |
     +---------+-------------+------+-----+---------+-------+

`Field' indicates the column name, `Type' is the data type for the
column, `NULL' indicates whether the column can contain `NULL' values,
`Key' indicates whether the column is indexed, and `Default' specifies
the column's default value. `Extra' displays special information about
columns: If a column was created with the `AUTO_INCREMENT' option, the
value will be `auto_increment' rather than empty.

`DESC' is a short form of *Note `DESCRIBE': describe. See *Note
describe::, for more information.

You can obtain the *Note `CREATE TABLE': create-table.  statement
necessary to create an existing table using the *Note `SHOW CREATE
TABLE': show-create-table. statement. See *Note show-create-table::.

If you have indexes on a table, `SHOW INDEX FROM TBL_NAME' produces
information about them. See *Note show-index::, for more about this
statement.


File: manual.info,  Node: batch-mode,  Next: examples,  Prev: getting-information,  Up: tutorial

3.5 Using mysql in Batch Mode
=============================

In the previous sections, you used *Note `mysql': mysql.  interactively
to enter queries and view the results. You can also run *Note `mysql':
mysql. in batch mode. To do this, put the commands you want to run in a
file, then tell *Note `mysql': mysql. to read its input from the file:


     shell> mysql < BATCH-FILE

If you are running *Note `mysql': mysql. under Windows and have some
special characters in the file that cause problems, you can do this:


     C:\> mysql -e "source BATCH-FILE"

If you need to specify connection parameters on the command line, the
command might look like this:


     shell> mysql -h HOST -u USER -p < BATCH-FILE
     Enter password: ********

When you use *Note `mysql': mysql. this way, you are creating a script
file, then executing the script.

If you want the script to continue even if some of the statements in it
produce errors, you should use the `--force' command-line option.

Why use a script? Here are a few reasons:

   * If you run a query repeatedly (say, every day or every week),
     making it a script enables you to avoid retyping it each time you
     execute it.

   * You can generate new queries from existing ones that are similar
     by copying and editing script files.

   * Batch mode can also be useful while you're developing a query,
     particularly for multiple-line commands or multiple-statement
     sequences of commands. If you make a mistake, you don't have to
     retype everything. Just edit your script to correct the error,
     then tell *Note `mysql': mysql. to execute it again.

   * If you have a query that produces a lot of output, you can run the
     output through a pager rather than watching it scroll off the top
     of your screen:


          shell> mysql < BATCH-FILE | more

   * You can catch the output in a file for further processing:


          shell> mysql < BATCH-FILE > mysql.out

   * You can distribute your script to other people so that they can
     also run the commands.

   * Some situations do not allow for interactive use, for example,
     when you run a query from a `cron' job. In this case, you must use
     batch mode.

The default output format is different (more concise) when you run
*Note `mysql': mysql. in batch mode than when you use it interactively.
For example, the output of `SELECT DISTINCT species FROM pet' looks
like this when *Note `mysql': mysql. is run interactively:


     +---------+
     | species |
     +---------+
     | bird    |
     | cat     |
     | dog     |
     | hamster |
     | snake   |
     +---------+

In batch mode, the output looks like this instead:


     species
     bird
     cat
     dog
     hamster
     snake

If you want to get the interactive output format in batch mode, use
`mysql -t'. To echo to the output the commands that are executed, use
`mysql -vvv'.

You can also use scripts from the *Note `mysql': mysql. prompt by using
the `source' command or `\.' command:


     mysql> source FILENAME;
     mysql> \. FILENAME

See *Note mysql-batch-commands::, for more information.


File: manual.info,  Node: examples,  Next: apache,  Prev: batch-mode,  Up: tutorial

3.6 Examples of Common Queries
==============================

* Menu:

* example-maximum-column::       The Maximum Value for a Column
* example-maximum-row::          The Row Holding the Maximum of a Certain Column
* example-maximum-column-group::  Maximum of Column per Group
* example-maximum-column-group-row::  The Rows Holding the Group-wise Maximum of a Certain Column
* example-user-variables::       Using User-Defined Variables
* example-foreign-keys::         Using Foreign Keys
* searching-on-two-keys::        Searching on Two Keys
* calculating-days::             Calculating Visits Per Day
* example-auto-increment::       Using AUTO_INCREMENT

Here are examples of how to solve some common problems with MySQL.

Some of the examples use the table `shop' to hold the price of each
article (item number) for certain traders (dealers). Supposing that
each trader has a single fixed price per article, then (`article',
`dealer') is a primary key for the records.

Start the command-line tool *Note `mysql': mysql. and select a database:


     shell> mysql YOUR-DATABASE-NAME

(In most MySQL installations, you can use the database named `test').

You can create and populate the example table with these statements:


     CREATE TABLE shop (
         article INT(4) UNSIGNED ZEROFILL DEFAULT '0000' NOT NULL,
         dealer  CHAR(20)                 DEFAULT ''     NOT NULL,
         price   DOUBLE(16,2)             DEFAULT '0.00' NOT NULL,
         PRIMARY KEY(article, dealer));
     INSERT INTO shop VALUES
         (1,'A',3.45),(1,'B',3.99),(2,'A',10.99),(3,'B',1.45),
         (3,'C',1.69),(3,'D',1.25),(4,'D',19.95);

After issuing the statements, the table should have the following
contents:


     SELECT * FROM shop;

     +---------+--------+-------+
     | article | dealer | price |
     +---------+--------+-------+
     |    0001 | A      |  3.45 |
     |    0001 | B      |  3.99 |
     |    0002 | A      | 10.99 |
     |    0003 | B      |  1.45 |
     |    0003 | C      |  1.69 |
     |    0003 | D      |  1.25 |
     |    0004 | D      | 19.95 |
     +---------+--------+-------+


File: manual.info,  Node: example-maximum-column,  Next: example-maximum-row,  Prev: examples,  Up: examples

3.6.1 The Maximum Value for a Column
------------------------------------

`What is the highest item number?'


     SELECT MAX(article) AS article FROM shop;

     +---------+
     | article |
     +---------+
     |       4 |
     +---------+


File: manual.info,  Node: example-maximum-row,  Next: example-maximum-column-group,  Prev: example-maximum-column,  Up: examples

3.6.2 The Row Holding the Maximum of a Certain Column
-----------------------------------------------------

_Task: Find the number, dealer, and price of the most expensive
article._

This is easily done with a subquery:


     SELECT article, dealer, price
     FROM   shop
     WHERE  price=(SELECT MAX(price) FROM shop);

     +---------+--------+-------+
     | article | dealer | price |
     +---------+--------+-------+
     |    0004 | D      | 19.95 |
     +---------+--------+-------+

Other solutions are to use a `LEFT JOIN' or to sort all rows descending
by price and get only the first row using the MySQL-specific `LIMIT'
clause:


     SELECT s1.article, s1.dealer, s1.price
     FROM shop s1
     LEFT JOIN shop s2 ON s1.price < s2.price
     WHERE s2.article IS NULL;

     SELECT article, dealer, price
     FROM shop
     ORDER BY price DESC
     LIMIT 1;

*Note*:

If there were several most expensive articles, each with a price of
19.95, the `LIMIT' solution would show only one of them.


File: manual.info,  Node: example-maximum-column-group,  Next: example-maximum-column-group-row,  Prev: example-maximum-row,  Up: examples

3.6.3 Maximum of Column per Group
---------------------------------

_Task: Find the highest price per article._


     SELECT article, MAX(price) AS price
     FROM   shop
     GROUP BY article;

     +---------+-------+
     | article | price |
     +---------+-------+
     |    0001 |  3.99 |
     |    0002 | 10.99 |
     |    0003 |  1.69 |
     |    0004 | 19.95 |
     +---------+-------+


File: manual.info,  Node: example-maximum-column-group-row,  Next: example-user-variables,  Prev: example-maximum-column-group,  Up: examples

3.6.4 The Rows Holding the Group-wise Maximum of a Certain Column
-----------------------------------------------------------------

_Task: For each article, find the dealer or dealers with the most
expensive price._

This problem can be solved with a subquery like this one:


     SELECT article, dealer, price
     FROM   shop s1
     WHERE  price=(SELECT MAX(s2.price)
                   FROM shop s2
                   WHERE s1.article = s2.article);

     +---------+--------+-------+
     | article | dealer | price |
     +---------+--------+-------+
     |    0001 | B      |  3.99 |
     |    0002 | A      | 10.99 |
     |    0003 | C      |  1.69 |
     |    0004 | D      | 19.95 |
     +---------+--------+-------+

The preceding example uses a correlated subquery, which can be
inefficient (see *Note correlated-subqueries::). Other possibilities
for solving the problem are to use an uncorrelated subquery in the
`FROM' clause or a `LEFT JOIN'.

Uncorrelated subquery:


     SELECT s1.article, dealer, s1.price
     FROM shop s1
     JOIN (
       SELECT article, MAX(price) AS price
       FROM shop
       GROUP BY article) AS s2
       ON s1.article = s2.article AND s1.price = s2.price;

`LEFT JOIN':


     SELECT s1.article, s1.dealer, s1.price
     FROM shop s1
     LEFT JOIN shop s2 ON s1.article = s2.article AND s1.price < s2.price
     WHERE s2.article IS NULL;

The `LEFT JOIN' works on the basis that when `s1.price' is at its
maximum value, there is no `s2.price' with a greater value and the `s2'
rows values will be `NULL'. See *Note join::.


File: manual.info,  Node: example-user-variables,  Next: example-foreign-keys,  Prev: example-maximum-column-group-row,  Up: examples

3.6.5 Using User-Defined Variables
----------------------------------

You can employ MySQL user variables to remember results without having
to store them in temporary variables in the client. (See *Note
user-variables::.)

For example, to find the articles with the highest and lowest price you
can do this:


     mysql> SELECT @min_price:=MIN(price),@max_price:=MAX(price) FROM shop;
     mysql> SELECT * FROM shop WHERE price=@min_price OR price=@max_price;
     +---------+--------+-------+
     | article | dealer | price |
     +---------+--------+-------+
     |    0003 | D      |  1.25 |
     |    0004 | D      | 19.95 |
     +---------+--------+-------+

*Note*:

It is also possible to store the name of a database object such as a
table or a column in a user variable and then to use this variable in
an SQL statement; however, this requires the use of a prepared
statement. See *Note sql-syntax-prepared-statements::, for more
information.


File: manual.info,  Node: example-foreign-keys,  Next: searching-on-two-keys,  Prev: example-user-variables,  Up: examples

3.6.6 Using Foreign Keys
------------------------

In MySQL, `InnoDB' tables support checking of foreign key constraints.
See *Note innodb-storage-engine::, and *Note ansi-diff-foreign-keys::.

A foreign key constraint is not required merely to join two tables. For
storage engines other than `InnoDB', it is possible when defining a
column to use a `REFERENCES TBL_NAME(COL_NAME)' clause, which has no
actual effect, and _serves only as a memo or comment to you that the
column which you are currently defining is intended to refer to a
column in another table_. It is extremely important to realize when
using this syntax that:

   * MySQL does not perform any sort of `CHECK' to make sure that
     COL_NAME actually exists in TBL_NAME (or even that TBL_NAME itself
     exists).

   * MySQL does not perform any sort of action on TBL_NAME such as
     deleting rows in response to actions taken on rows in the table
     which you are defining; in other words, this syntax induces no `ON
     DELETE' or `ON UPDATE' behavior whatsoever. (Although you can
     write an `ON DELETE' or `ON UPDATE' clause as part of the
     `REFERENCES' clause, it is also ignored.)

   * This syntax creates a _column_; it does *not* create any sort of
     index or key.

You can use a column so created as a join column, as shown here:


     CREATE TABLE person (
         id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
         name CHAR(60) NOT NULL,
         PRIMARY KEY (id)
     );

     CREATE TABLE shirt (
         id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
         style ENUM('t-shirt', 'polo', 'dress') NOT NULL,
         color ENUM('red', 'blue', 'orange', 'white', 'black') NOT NULL,
         owner SMALLINT UNSIGNED NOT NULL REFERENCES person(id),
         PRIMARY KEY (id)
     );

     INSERT INTO person VALUES (NULL, 'Antonio Paz');

     SELECT @last := LAST_INSERT_ID();

     INSERT INTO shirt VALUES
     (NULL, 'polo', 'blue', @last),
     (NULL, 'dress', 'white', @last),
     (NULL, 't-shirt', 'blue', @last);

     INSERT INTO person VALUES (NULL, 'Lilliana Angelovska');

     SELECT @last := LAST_INSERT_ID();

     INSERT INTO shirt VALUES
     (NULL, 'dress', 'orange', @last),
     (NULL, 'polo', 'red', @last),
     (NULL, 'dress', 'blue', @last),
     (NULL, 't-shirt', 'white', @last);

     SELECT * FROM person;
     +----+---------------------+
     | id | name                |
     +----+---------------------+
     |  1 | Antonio Paz         |
     |  2 | Lilliana Angelovska |
     +----+---------------------+

     SELECT * FROM shirt;
     +----+---------+--------+-------+
     | id | style   | color  | owner |
     +----+---------+--------+-------+
     |  1 | polo    | blue   |     1 |
     |  2 | dress   | white  |     1 |
     |  3 | t-shirt | blue   |     1 |
     |  4 | dress   | orange |     2 |
     |  5 | polo    | red    |     2 |
     |  6 | dress   | blue   |     2 |
     |  7 | t-shirt | white  |     2 |
     +----+---------+--------+-------+

     SELECT s.* FROM person p INNER JOIN shirt s
        ON s.owner = p.id
      WHERE p.name LIKE 'Lilliana%'
        AND s.color <> 'white';

     +----+-------+--------+-------+
     | id | style | color  | owner |
     +----+-------+--------+-------+
     |  4 | dress | orange |     2 |
     |  5 | polo  | red    |     2 |
     |  6 | dress | blue   |     2 |
     +----+-------+--------+-------+

When used in this fashion, the `REFERENCES' clause is not displayed in
the output of *Note `SHOW CREATE TABLE': show-create-table. or *Note
`DESCRIBE': describe.:


     SHOW CREATE TABLE shirt\G
     *************************** 1. row ***************************
     Table: shirt
     Create Table: CREATE TABLE `shirt` (
     `id` smallint(5) unsigned NOT NULL auto_increment,
     `style` enum('t-shirt','polo','dress') NOT NULL,
     `color` enum('red','blue','orange','white','black') NOT NULL,
     `owner` smallint(5) unsigned NOT NULL,
     PRIMARY KEY  (`id`)
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1

The use of `REFERENCES' in this way as a comment or `reminder' in a
column definition works with `MyISAM' tables.


File: manual.info,  Node: searching-on-two-keys,  Next: calculating-days,  Prev: example-foreign-keys,  Up: examples

3.6.7 Searching on Two Keys
---------------------------

An `OR' using a single key is well optimized, as is the handling of
`AND'.

The one tricky case is that of searching on two different keys combined
with `OR':


     SELECT field1_index, field2_index FROM test_table
     WHERE field1_index = '1' OR  field2_index = '1'

This case is optimized. See *Note index-merge-optimization::.

You can also solve the problem efficiently by using a *Note `UNION':
union. that combines the output of two separate *Note `SELECT': select.
statements.  See *Note union::.

Each *Note `SELECT': select. searches only one key and can be optimized:


     SELECT field1_index, field2_index
         FROM test_table WHERE field1_index = '1'
     UNION
     SELECT field1_index, field2_index
         FROM test_table WHERE field2_index = '1';


File: manual.info,  Node: calculating-days,  Next: example-auto-increment,  Prev: searching-on-two-keys,  Up: examples

3.6.8 Calculating Visits Per Day
--------------------------------

The following example shows how you can use the bit group functions to
calculate the number of days per month a user has visited a Web page.


     CREATE TABLE t1 (year YEAR(4), month INT(2) UNSIGNED ZEROFILL,
                  day INT(2) UNSIGNED ZEROFILL);
     INSERT INTO t1 VALUES(2000,1,1),(2000,1,20),(2000,1,30),(2000,2,2),
                 (2000,2,23),(2000,2,23);

The example table contains year-month-day values representing visits by
users to the page. To determine how many different days in each month
these visits occur, use this query:


     SELECT year,month,BIT_COUNT(BIT_OR(1<<day)) AS days FROM t1
            GROUP BY year,month;

Which returns:


     +------+-------+------+
     | year | month | days |
     +------+-------+------+
     | 2000 |    01 |    3 |
     | 2000 |    02 |    2 |
     +------+-------+------+

The query calculates how many different days appear in the table for
each year/month combination, with automatic removal of duplicate
entries.


File: manual.info,  Node: example-auto-increment,  Prev: calculating-days,  Up: examples

3.6.9 Using AUTO_INCREMENT
--------------------------

The `AUTO_INCREMENT' attribute can be used to generate a unique
identity for new rows:


     CREATE TABLE animals (
          id MEDIUMINT NOT NULL AUTO_INCREMENT,
          name CHAR(30) NOT NULL,
          PRIMARY KEY (id)
     ) ENGINE=INNODB;

     INSERT INTO animals (name) VALUES
         ('dog'),('cat'),('penguin'),
         ('lax'),('whale'),('ostrich');

     SELECT * FROM animals;

Which returns:


     +----+---------+
     | id | name    |
     +----+---------+
     |  1 | dog     |
     |  2 | cat     |
     |  3 | penguin |
     |  4 | lax     |
     |  5 | whale   |
     |  6 | ostrich |
     +----+---------+

No value was specified for the `AUTO_INCREMENT' column, so MySQL
assigned sequence numbers automatically. You can also explicitly assign
0 to the column to generate sequence numbers. If the column is declared
`NOT NULL', it is also possible to assign `NULL' to the column to
generate sequence numbers.

You can retrieve the most recent `AUTO_INCREMENT' value with the
`LAST_INSERT_ID()' SQL function or the *Note `mysql_insert_id()':
mysql-insert-id. C API function. These functions are
connection-specific, so their return values are not affected by another
connection which is also performing inserts.

Use the smallest integer data type for the `AUTO_INCREMENT' column that
is large enough to hold the maximum sequence value you will need. When
the column reaches the upper limit of the data type, the next attempt to
generate a sequence number fails. Use the `UNSIGNED' attribute if
possible to allow a greater range. For example, if you use *Note
`TINYINT': integer-types, the maximum permissible sequence number is
127. For *Note `TINYINT UNSIGNED': integer-types, the maximum is 255.
See *Note integer-types:: for the ranges of all the integer types.

*Note*:

For a multiple-row insert, `LAST_INSERT_ID()' and *Note
`mysql_insert_id()': mysql-insert-id. actually return the
`AUTO_INCREMENT' key from the _first_ of the inserted rows. This enables
multiple-row inserts to be reproduced correctly on other servers in a
replication setup.

To start with an `AUTO_INCREMENT' value other than 1, set that value
with *Note `CREATE TABLE': create-table. or *Note `ALTER TABLE':
alter-table, like this:


     mysql> ALTER TABLE tbl AUTO_INCREMENT = 100;

*InnoDB Notes*

For `InnoDB' tables, be careful if you modify the column containing the
auto-increment value in the middle of a sequence of *Note `INSERT':
insert. statements.  For example, if you use an *Note `UPDATE': update.
statement to put a new, larger value in the auto-increment column, a
subsequent *Note `INSERT': insert. could encounter a `Duplicate entry'
error. The test whether an auto-increment value is already present
occurs if you do a *Note `DELETE': delete. followed by more *Note
`INSERT': insert. statements, or when you *Note `COMMIT': commit. the
transaction, but not after an *Note `UPDATE': update. statement.

*MyISAM Notes*

   * For `MyISAM' tables, you can specify `AUTO_INCREMENT' on a
     secondary column in a multiple-column index. In this case, the
     generated value for the `AUTO_INCREMENT' column is calculated as
     `MAX(AUTO_INCREMENT_COLUMN) + 1 WHERE prefix=GIVEN-PREFIX'.  This
     is useful when you want to put data into ordered groups.


          CREATE TABLE animals (
              grp ENUM('fish','mammal','bird') NOT NULL,
              id MEDIUMINT NOT NULL AUTO_INCREMENT,
              name CHAR(30) NOT NULL,
              PRIMARY KEY (grp,id)
          ) ENGINE=MyISAM;

          INSERT INTO animals (grp,name) VALUES
              ('mammal','dog'),('mammal','cat'),
              ('bird','penguin'),('fish','lax'),('mammal','whale'),
              ('bird','ostrich');

          SELECT * FROM animals ORDER BY grp,id;

     Which returns:


          +--------+----+---------+
          | grp    | id | name    |
          +--------+----+---------+
          | fish   |  1 | lax     |
          | mammal |  1 | dog     |
          | mammal |  2 | cat     |
          | mammal |  3 | whale   |
          | bird   |  1 | penguin |
          | bird   |  2 | ostrich |
          +--------+----+---------+

     In this case (when the `AUTO_INCREMENT' column is part of a
     multiple-column index), `AUTO_INCREMENT' values are reused if you
     delete the row with the biggest `AUTO_INCREMENT' value in any
     group. This happens even for `MyISAM' tables, for which
     `AUTO_INCREMENT' values normally are not reused.

   * If the `AUTO_INCREMENT' column is part of multiple indexes, MySQL
     generates sequence values using the index that begins with the
     `AUTO_INCREMENT' column, if there is one. For example, if the
     `animals' table contained indexes `PRIMARY KEY (grp, id)' and
     `INDEX (id)', MySQL would ignore the `PRIMARY KEY' for generating
     sequence values. As a result, the table would contain a single
     sequence, not a sequence per `grp' value.

*Further Reading*

More information about `AUTO_INCREMENT' is available here:

   * How to assign the `AUTO_INCREMENT' attribute to a column: *Note
     create-table::, and *Note alter-table::.

   * How `AUTO_INCREMENT' behaves depending on the
     `NO_AUTO_VALUE_ON_ZERO' SQL mode: *Note sql-mode::.

   * How to use the `LAST_INSERT_ID()' function to find the row that
     contains the most recent `AUTO_INCREMENT' value: *Note
     information-functions::.

   * Setting the `AUTO_INCREMENT' value to be used: *Note
     server-system-variables::.

   * `AUTO_INCREMENT' and replication: *Note
     replication-features-auto-increment::.

   * Server-system variables related to `AUTO_INCREMENT'
     (`auto_increment_increment' and `auto_increment_offset') that can
     be used for replication: *Note server-system-variables::.


File: manual.info,  Node: apache,  Prev: examples,  Up: tutorial

3.7 Using MySQL with Apache
===========================

There are programs that let you authenticate your users from a MySQL
database and also let you write your log files into a MySQL table.

You can change the Apache logging format to be easily readable by MySQL
by putting the following into the Apache configuration file:


     LogFormat \
             "\"%h\",%{%Y%m%d%H%M%S}t,%>s,\"%b\",\"%{Content-Type}o\",  \
             \"%U\",\"%{Referer}i\",\"%{User-Agent}i\""

To load a log file in that format into MySQL, you can use a statement
something like this:


     LOAD DATA INFILE '/LOCAL/ACCESS_LOG' INTO TABLE TBL_NAME
     FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"' ESCAPED BY '\\'

The named table should be created to have columns that correspond to
those that the `LogFormat' line writes to the log file.


File: manual.info,  Node: programs,  Next: server-administration,  Prev: tutorial,  Up: Top

4 MySQL Programs
****************

* Menu:

* programs-overview::            Overview of MySQL Programs
* programs-using::               Using MySQL Programs
* programs-server::              MySQL Server and Server-Startup Programs
* programs-installation::        MySQL Installation-Related Programs
* programs-client::              MySQL Client Programs
* programs-admin-utils::         MySQL Administrative and Utility Programs
* programs-development::         MySQL Program Development Utilities
* programs-miscellaneous::       Miscellaneous Programs

This chapter provides a brief overview of the MySQL command-line
programs provided by Oracle Corporation. It also discusses the general
syntax for specifying options when you run these programs.  Most
programs have options that are specific to their own operation, but the
option syntax is similar for all of them. Finally, the chapter provides
more detailed descriptions of individual programs, including which
options they recognize.


File: manual.info,  Node: programs-overview,  Next: programs-using,  Prev: programs,  Up: programs

4.1 Overview of MySQL Programs
==============================

There are many different programs in a MySQL installation. This section
provides a brief overview of them. Later sections provide a more
detailed description of each one, with the exception of MySQL Cluster
programs. Each program's description indicates its invocation syntax
and the options that it supports.  *Note mysql-cluster::, describes
programs specific to MySQL Cluster.

Most MySQL distributions include all of these programs, except for
those programs that are platform-specific. (For example, the server
startup scripts are not used on Windows.) The exception is that RPM
distributions are more specialized. There is one RPM for the server,
another for client programs, and so forth. If you appear to be missing
one or more programs, see *Note installing::, for information on types
of distributions and what they contain. It may be that you have a
distribution that does not include all programs and you need to install
an additional package.

Each MySQL program takes many different options. Most programs provide
a `--help' option that you can use to get a description of the
program's different options. For example, try *Note `mysql --help':
mysql.

You can override default option values for MySQL programs by specifying
options on the command line or in an option file. See *Note
programs-using::, for general information on invoking programs and
specifying program options.

The MySQL server, *Note `mysqld': mysqld, is the main program that does
most of the work in a MySQL installation. The server is accompanied by
several related scripts that assist you in starting and stopping the
server:

   * *Note `mysqld': mysqld.

     The SQL daemon (that is, the MySQL server). To use client
     programs, *Note `mysqld': mysqld. must be running, because clients
     gain access to databases by connecting to the server.  See *Note
     mysqld::.

   * *Note `mysqld_safe': mysqld-safe.

     A server startup script. *Note `mysqld_safe': mysqld-safe.
     attempts to start *Note `mysqld': mysqld. See *Note mysqld-safe::.

   * *Note `mysql.server': mysql-server.

     A server startup script. This script is used on systems that use
     System V-style run directories containing scripts that start
     system services for particular run levels. It invokes *Note
     `mysqld_safe': mysqld-safe. to start the MySQL server. See *Note
     mysql-server::.

   * *Note `mysqld_multi': mysqld-multi.

     A server startup script that can start or stop multiple servers
     installed on the system. See *Note mysqld-multi::. An alternative
     to *Note `mysqld_multi': mysqld-multi. is `mysqlmanager', the
     MySQL Instance Manager.  See *Note instance-manager::.

There are several programs that perform setup operations during MySQL
installation or upgrading:

   * *Note `comp_err': comp-err.

     This program is used during the MySQL build/installation process.
     It compiles error message files from the error source files. See
     *Note comp-err::.

   * `make_binary_distribution'

     This program makes a binary release of a compiled MySQL. This
     could be sent by FTP to `/pub/mysql/upload/' on `ftp.mysql.com'
     for the convenience of other MySQL users.

   * *Note `make_win_bin_dist': make-win-bin-dist.

     This program is used on Windows. It packages a MySQL distribution
     for installation after the source distribution has been built. See
     *Note make-win-bin-dist::.

   * *Note `mysql_fix_privilege_tables': mysql-fix-privilege-tables.

     This program is used after a MySQL upgrade operation. It updates
     the grant tables with any changes that have been made in newer
     versions of MySQL. See *Note mysql-fix-privilege-tables::.

     Note: As of MySQL 5.1.7, this program has been superseded by *Note
     `mysql_upgrade': mysql-upgrade. and should no longer be used.

   * *Note `mysql_install_db': mysql-install-db.

     This program creates the MySQL database and initializes the grant
     tables with default privileges. It is usually executed only once,
     when first installing MySQL on a system. See *Note
     mysql-install-db::, *Note unix-postinstallation::, and *Note
     mysql-install-db::.

   * *Note `mysql_secure_installation': mysql-secure-installation.

     This program enables you to improve the security of your MySQL
     installation. SQL. See *Note mysql-secure-installation::.

   * *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql.

     This program loads the time zone tables in the `mysql' database
     using the contents of the host system _zoneinfo_ database (the set
     of files describing time zones). SQL. See *Note
     mysql-tzinfo-to-sql::.

   * *Note `mysql_upgrade': mysql-upgrade.

     This program is used after a MySQL upgrade operation. It checks
     tables for incompatibilities and repairs them if necessary, and
     updates the grant tables with any changes that have been made in
     newer versions of MySQL. See *Note mysql-upgrade::.

MySQL client programs:

   * *Note `mysql': mysql.

     The command-line tool for interactively entering SQL statements or
     executing them from a file in batch mode. See *Note mysql::.

   * *Note `mysqladmin': mysqladmin.

     A client that performs administrative operations, such as creating
     or dropping databases, reloading the grant tables, flushing tables
     to disk, and reopening log files.  *Note `mysqladmin': mysqladmin.
     can also be used to retrieve version, process, and status
     information from the server. See *Note mysqladmin::.

   * *Note `mysqlcheck': mysqlcheck.

     A table-maintenance client that checks, repairs, analyzes, and
     optimizes tables. See *Note mysqlcheck::.

   * *Note `mysqldump': mysqldump.

     A client that dumps a MySQL database into a file as SQL, text, or
     XML. See *Note mysqldump::.

   * *Note `mysqlimport': mysqlimport.

     A client that imports text files into their respective tables
     using *Note `LOAD DATA INFILE': load-data. See *Note mysqlimport::.

   * *Note `mysqlshow': mysqlshow.

     A client that displays information about databases, tables,
     columns, and indexes. See *Note mysqlshow::.

   * *Note `mysqlslap': mysqlslap.

     A client that is designed to emulate client load for a MySQL
     server and report the timing of each stage. It works as if
     multiple clients are accessing the server. See *Note mysqlslap::.

MySQL administrative and utility programs:

   * *Note `innochecksum': innochecksum.

     An offline `InnoDB' offline file checksum utility. See *Note
     innochecksum::.

   * *Note `myisam_ftdump': myisam-ftdump.

     A utility that displays information about full-text indexes in
     `MyISAM' tables. See *Note myisam-ftdump::.

   * *Note `myisamchk': myisamchk.

     A utility to describe, check, optimize, and repair `MyISAM'
     tables. See *Note myisamchk::.

   * *Note `myisamlog': myisamlog.

     A utility that processes the contents of a `MyISAM' log file. See
     *Note myisamlog::.

   * *Note `myisampack': myisampack.

     A utility that compresses `MyISAM' tables to produce smaller
     read-only tables. See *Note myisampack::.

   * *Note `mysqlaccess': mysqlaccess.

     A script that checks the access privileges for a host name, user
     name, and database combination. See *Note mysqlaccess::.

   * *Note `mysqlbinlog': mysqlbinlog.

     A utility for reading statements from a binary log. The log of
     executed statements contained in the binary log files can be used
     to help recover from a crash. See *Note mysqlbinlog::.

   * *Note `mysqldumpslow': mysqldumpslow.

     A utility to read and summarize the contents of a slow query log.
     See *Note mysqldumpslow::.

   * *Note `mysqlhotcopy': mysqlhotcopy.

     A utility that quickly makes backups of `MyISAM' tables while the
     server is running.  See *Note mysqlhotcopy::.

   * `mysqlmanager'

     The MySQL Instance Manager, a program for monitoring and managing
     MySQL servers. See *Note instance-manager::.

     *Important*:

     MySQL Instance Manager has been deprecated and is removed in MySQL
     5.5.

   * *Note `mysql_convert_table_format': mysql-convert-table-format.

     A utility that converts tables in a database to use a given
     storage engine. See *Note mysql-convert-table-format::.

   * *Note `mysql_find_rows': mysql-find-rows.

     A utility that reads files containing SQL statements (such as
     update logs) and extracts statements that match a given regular
     expression. See *Note mysql-find-rows::.

   * *Note `mysql_fix_extensions': mysql-fix-extensions.

     A utility that converts the extensions for `MyISAM' table files to
     lowercase. This can be useful after transferring the files from a
     system with case-insensitive file names to a system with
     case-sensitive file names. See *Note mysql-fix-extensions::.

   * *Note `mysql_setpermission': mysql-setpermission.

     A utility for interactively setting permissions in the MySQL grant
     tables. See *Note mysql-setpermission::.

   * *Note `mysql_waitpid': mysql-waitpid.

     A utility that kills the process with a given process ID. See
     *Note mysql-waitpid::.

   * *Note `mysql_zap': mysql-zap.

     A utility that kills processes that match a pattern. See *Note
     mysql-zap::.

MySQL program-development utilities:

   * *Note `msql2mysql': msql2mysql.

     A shell script that converts `mSQL' programs to MySQL. It doesn't
     handle every case, but it gives a good start when converting. See
     *Note msql2mysql::.

   * *Note `mysql_config': mysql-config.

     A shell script that produces the option values needed when
     compiling MySQL programs. See *Note mysql-config::.

   * *Note `my_print_defaults': my-print-defaults.

     A utility that shows which options are present in option groups of
     option files. See *Note my-print-defaults::.

   * *Note `resolve_stack_dump': resolve-stack-dump.

     A utility program that resolves a numeric stack trace dump to
     symbols. See *Note resolve-stack-dump::.

Miscellaneous utilities:

   * *Note `perror': perror.

     A utility that displays the meaning of system or MySQL error
     codes. See *Note perror::.

   * *Note `replace': replace-utility.

     A utility program that performs string replacement in the input
     text. See *Note replace-utility::.

   * *Note `resolveip': resolveip.

     A utility program that resolves a host name to an IP address or
     vice versa. See *Note resolveip::.

Oracle Corporation also provides the *Note MySQL Workbench: workbench.
GUI tool, which is used to administer MySQL servers and databases, to
create, execute, and evaluate queries, and to migrate schemas and data
from other relational database management systems for use with MySQL.
Additional GUI tools include *Note MySQL Notifier: windows-notifier. and
MySQL for Excel
(http://dev.mysql.com/doc/mysql-for-excel/en/index.html).

MySQL client programs that communicate with the server using the MySQL
client/server library use the following environment variables.

This table describes environment variables used by MySQL client
programs that communicate with the server using the MySQL client/server
library.

Environment        Meaning
Variable           
`MYSQL_UNIX_PORT'  The default Unix socket file; used for connections to
                   `localhost'
`MYSQL_TCP_PORT'   The default port number; used for TCP/IP connections
`MYSQL_PWD'        The default password
`MYSQL_DEBUG'      Debug trace options when debugging
`TMPDIR'           The directory where temporary tables and files are
                   created

For a full list of environment variables used by MySQL programs, see
*Note environment-variables::.

Use of `MYSQL_PWD' is insecure. See *Note password-security-user::.


File: manual.info,  Node: programs-using,  Next: programs-server,  Prev: programs-overview,  Up: programs

4.2 Using MySQL Programs
========================

* Menu:

* invoking-programs::            Invoking MySQL Programs
* connecting::                   Connecting to the MySQL Server
* program-options::              Specifying Program Options
* command-line-options::         Using Options on the Command Line
* option-modifiers::             Program Option Modifiers
* option-files::                 Using Option Files
* option-file-options::          Command-Line Options that Affect Option-File Handling
* program-variables::            Using Options to Set Program Variables
* option-defaults-equals::       Option Defaults, Options Expecting Values, and the = Sign
* setting-environment-variables::  Setting Environment Variables


File: manual.info,  Node: invoking-programs,  Next: connecting,  Prev: programs-using,  Up: programs-using

4.2.1 Invoking MySQL Programs
-----------------------------

To invoke a MySQL program from the command line (that is, from your
shell or command prompt), enter the program name followed by any
options or other arguments needed to instruct the program what you want
it to do. The following commands show some sample program invocations.
``shell>'' represents the prompt for your command interpreter; it is
not part of what you type. The particular prompt you see depends on your
command interpreter. Typical prompts are `$' for `sh', `ksh', or
`bash', `%' for `csh' or `tcsh', and `C:\>' for the Windows
`command.com' or `cmd.exe' command interpreters.


     shell> mysql --user=root test
     shell> mysqladmin extended-status variables
     shell> mysqlshow --help
     shell> mysqldump -u root personnel

Arguments that begin with a single or double dash (``-'', ``--'')
specify program options.  Options typically indicate the type of
connection a program should make to the server or affect its
operational mode. Option syntax is described in *Note program-options::.

Nonoption arguments (arguments with no leading dash) provide additional
information to the program. For example, the *Note `mysql': mysql.
program interprets the first nonoption argument as a database name, so
the command `mysql --user=root test' indicates that you want to use the
`test' database.

Later sections that describe individual programs indicate which options
a program supports and describe the meaning of any additional nonoption
arguments.

Some options are common to a number of programs. The most frequently
used of these are the `--host' (or `-h'), `--user' (or `-u'), and
`--password' (or `-p') options that specify connection parameters.
They indicate the host where the MySQL server is running, and the user
name and password of your MySQL account. All MySQL client programs
understand these options; they enable you to specify which server to
connect to and the account to use on that server.  Other connection
options are `--port' (or `-P') to specify a TCP/IP port number and
`--socket' (or `-S') to specify a Unix socket file on Unix (or named
pipe name on Windows). For more information on options that specify
connection options, see *Note connecting::.

You may find it necessary to invoke MySQL programs using the path name
to the `bin' directory in which they are installed. This is likely to
be the case if you get a `program not found' error whenever you attempt
to run a MySQL program from any directory other than the `bin'
directory. To make it more convenient to use MySQL, you can add the
path name of the `bin' directory to your `PATH' environment variable
setting. That enables you to run a program by typing only its name, not
its entire path name. For example, if *Note `mysql': mysql. is
installed in `/usr/local/mysql/bin', you can run the program by
invoking it as *Note `mysql': mysql, and it is not necessary to invoke
it as `/usr/local/mysql/bin/mysql'.

Consult the documentation for your command interpreter for instructions
on setting your `PATH' variable. The syntax for setting environment
variables is interpreter-specific.  (Some information is given in *Note
setting-environment-variables::.) After modifying your `PATH' setting,
open a new console window on Windows or log in again on Unix so that
the setting goes into effect.


File: manual.info,  Node: connecting,  Next: program-options,  Prev: invoking-programs,  Up: programs-using

4.2.2 Connecting to the MySQL Server
------------------------------------

For a client program to be able to connect to the MySQL server, it must
use the proper connection parameters, such as the name of the host
where the server is running and the user name and password of your
MySQL account. Each connection parameter has a default value, but you
can override them as necessary using program options specified either
on the command line or in an option file.

The examples here use the *Note `mysql': mysql. client program, but the
principles apply to other clients such as *Note `mysqldump': mysqldump,
*Note `mysqladmin': mysqladmin, or *Note `mysqlshow': mysqlshow.

This command invokes *Note `mysql': mysql. without specifying any
connection parameters explicitly:


     shell> mysql

Because there are no parameter options, the default values apply:

   * The default host name is `localhost'. On Unix, this has a special
     meaning, as described later.

   * The default user name is `ODBC' on Windows or your Unix login name
     on Unix.

   * No password is sent if neither `-p' nor `--password' is given.

   * For *Note `mysql': mysql, the first nonoption argument is taken as
     the name of the default database. If there is no such option,
     *Note `mysql': mysql. does not select a default database.

To specify the host name and user name explicitly, as well as a
password, supply appropriate options on the command line:


     shell> mysql --host=localhost --user=myname --password=mypass mydb
     shell> mysql -h localhost -u myname -pmypass mydb

For password options, the password value is optional:

   * If you use a `-p' or `--password' option and specify the password
     value, there must be _no space_ between `-p' or `--password=' and
     the password following it.

   * If you use a `-p' or `--password' option but do not specify the
     password value, the client program prompts you to enter the
     password. The password is not displayed as you enter it. This is
     more secure than giving the password on the command line. Other
     users on your system may be able to see a password specified on
     the command line by executing a command such as `ps auxw'. See
     *Note password-security-user::.

As just mentioned, including the password value on the command line can
be a security risk. To avoid this problem, specify the `--password' or
`-p' option without any following password value:


     shell> mysql --host=localhost --user=myname --password mydb
     shell> mysql -h localhost -u myname -p mydb

When the password option has no password value, the client program
prints a prompt and waits for you to enter the password. (In these
examples, `mydb' is _not_ interpreted as a password because it is
separated from the preceding password option by a space.)

On some systems, the library routine that MySQL uses to prompt for a
password automatically limits the password to eight characters.  That
is a problem with the system library, not with MySQL.  Internally,
MySQL does not have any limit for the length of the password. To work
around the problem, change your MySQL password to a value that is eight
or fewer characters long, or put your password in an option file.

On Unix, MySQL programs treat the host name `localhost' specially, in a
way that is likely different from what you expect compared to other
network-based programs. For connections to `localhost', MySQL programs
attempt to connect to the local server by using a Unix socket file.
This occurs even if a `--port' or `-P' option is given to specify a
port number. To ensure that the client makes a TCP/IP connection to the
local server, use `--host' or `-h' to specify a host name value of
`127.0.0.1', or the IP address or name of the local server. You can
also specify the connection protocol explicitly, even for `localhost',
by using the `--protocol=TCP' option. For example:


     shell> mysql --host=127.0.0.1
     shell> mysql --protocol=TCP

The `--protocol' option enables you to establish a particular type of
connection even when the other options would normally default to some
other protocol.

On Windows, you can force a MySQL client to use a named-pipe connection
by specifying the `--pipe' or `--protocol=PIPE' option, or by
specifying `.' (period) as the host name. If named-pipe connections are
not enabled, an error occurs. Use the `--socket' option to specify the
name of the pipe if you do not want to use the default pipe name.

Connections to remote servers always use TCP/IP. This command connects
to the server running on `remote.example.com' using the default port
number (3306):


     shell> mysql --host=remote.example.com

To specify a port number explicitly, use the `--port' or `-P' option:


     shell> mysql --host=remote.example.com --port=13306

You can specify a port number for connections to a local server, too.
However, as indicated previously, connections to `localhost' on Unix
will use a socket file by default. You will need to force a TCP/IP
connection as already described or any option that specifies a port
number will be ignored.

For this command, the program uses a socket file on Unix and the
`--port' option is ignored:


     shell> mysql --port=13306 --host=localhost

To cause the port number to be used, invoke the program in either of
these ways:


     shell> mysql --port=13306 --host=127.0.0.1
     shell> mysql --port=13306 --protocol=TCP

The following list summarizes the options that can be used to control
how client programs connect to the server:

   * `--host=HOST_NAME', `-h HOST_NAME'

     The host where the server is running. The default value is
     `localhost'.

   * `--password[=PASS_VAL]', `-p[PASS_VAL]'

     The password of the MySQL account. As described earlier, the
     password value is optional, but if given, there must be _no space_
     between `-p' or `--password=' and the password following it. The
     default is to send no password.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. The server
     must be started with the `--enable-named-pipe' option to enable
     named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The port number to use for the connection, for connections made
     using TCP/IP. The default port number is 3306.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     This option explicitly specifies a protocol to use for connecting
     to the server. It is useful when the other connection parameters
     normally would cause a protocol to be used other than the one you
     want. For example, connections on Unix to `localhost' are made
     using a Unix socket file by default:


          shell> mysql --host=localhost

     To force a TCP/IP connection to be used instead, specify a
     `--protocol' option:


          shell> mysql --host=localhost --protocol=TCP

     The following table shows the permissible `--protocol' option
     values and indicates the platforms on which each value may be
     used. The values are not case sensitive.

     This table lists permissible `--protocol' option values, the
     connection protocol for each value, and the platforms on which
     each value may be used.

     `--protocol'  Connection Protocol                Permissible
     Value                                            Operating Systems
     `TCP'         TCP/IP connection to local or      All
                   remote server                      
     `SOCKET'      Unix socket file connection to     Unix only
                   local server                       
     `PIPE'        Named-pipe connection to local or  Windows only
                   remote server                      
     `MEMORY'      Shared-memory connection to local  Windows only
                   server                             

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--socket=FILE_NAME', `-S FILE_NAME'

     On Unix, the name of the Unix socket file to use, for connections
     made using a named pipe to a local server. The default Unix socket
     file name is `/tmp/mysql.sock'.

     On Windows, the name of the named pipe to use, for connections to
     a local server. The default Windows pipe name is `MySQL'. The pipe
     name is not case sensitive.

     The server must be started with the `--enable-named-pipe' option to
     enable named-pipe connections.

   * `--ssl*'

     Options that begin with `--ssl' are used for establishing a secure
     connection to the server using SSL, if the server is configured
     with SSL support. For details, see *Note ssl-options::.

   * `--user=USER_NAME', `-u USER_NAME'

     The user name of the MySQL account you want to use. The default
     user name is `ODBC' on Windows or your Unix login name on Unix.

It is possible to specify different default values to be used when you
make a connection so that you need not enter them on the command line
each time you invoke a client program. This can be done in a couple of
ways:

   * You can specify connection parameters in the `[client]' section of
     an option file. The relevant section of the file might look like
     this:


          [client]
          host=HOST_NAME
          user=USER_NAME
          password=YOUR_PASS

     *Note option-files::, discusses option files further.

   * You can specify some connection parameters using environment
     variables. The host can be specified for *Note `mysql': mysql.
     using `MYSQL_HOST'.  The MySQL user name can be specified using
     `USER' (this is for Windows and NetWare only). The password can be
     specified using `MYSQL_PWD', although this is insecure; see *Note
     password-security-user::. For a list of variables, see *Note
     environment-variables::.


File: manual.info,  Node: program-options,  Next: command-line-options,  Prev: connecting,  Up: programs-using

4.2.3 Specifying Program Options
--------------------------------

There are several ways to specify options for MySQL programs:

   * List the options on the command line following the program name.
     This is common for options that apply to a specific invocation of
     the program.

   * List the options in an option file that the program reads when it
     starts. This is common for options that you want the program to
     use each time it runs.

   * List the options in environment variables (see *Note
     setting-environment-variables::). This method is useful for
     options that you want to apply each time the program runs. In
     practice, option files are used more commonly for this purpose,
     but *Note multiple-unix-servers::, discusses one situation in
     which environment variables can be very helpful. It describes a
     handy technique that uses such variables to specify the TCP/IP
     port number and Unix socket file for the server and for client
     programs.

Options are processed in order, so if an option is specified multiple
times, the last occurrence takes precedence. The following command
causes *Note `mysql': mysql. to connect to the server running on
`localhost':


     shell> mysql -h example.com -h localhost

If conflicting or related options are given, later options take
precedence over earlier options. The following command runs *Note
`mysql': mysql. in `no column names' mode:


     shell> mysql --column-names --skip-column-names

MySQL programs determine which options are given first by examining
environment variables, then by reading option files, and then by
checking the command line. This means that environment variables have
the lowest precedence and command-line options the highest.

You can take advantage of the way that MySQL programs process options
by specifying default option values for a program in an option file.
That enables you to avoid typing them each time you run the program
while enabling you to override the defaults if necessary by using
command-line options.

An option can be specified by writing it in full or as any unambiguous
prefix. For example, the `--compress' option can be given to *Note
`mysqldump': mysqldump. as `--compr', but not as `--comp' because the
latter is ambiguous:


     shell> mysqldump --comp
     mysqldump: ambiguous option '--comp' (compatible, compress)

Be aware that the use of option prefixes can cause problems in the
event that new options are implemented for a program. A prefix that is
unambiguous now might become ambiguous in the future.


File: manual.info,  Node: command-line-options,  Next: option-modifiers,  Prev: program-options,  Up: programs-using

4.2.4 Using Options on the Command Line
---------------------------------------

Program options specified on the command line follow these rules:

   * Options are given after the command name.

   * An option argument begins with one dash or two dashes, depending
     on whether it is a short form or long form of the option name.
     Many options have both short and long forms. For example, `-?' and
     `--help' are the short and long forms of the option that instructs
     a MySQL program to display its help message.

   * Option names are case sensitive. `-v' and `-V' are both legal and
     have different meanings. (They are the corresponding short forms
     of the `--verbose' and `--version' options.)

   * Some options take a value following the option name. For example,
     `-h localhost' or `--host=localhost' indicate the MySQL server
     host to a client program. The option value tells the program the
     name of the host where the MySQL server is running.

   * For a long option that takes a value, separate the option name and
     the value by an ``='' sign.  For a short option that takes a
     value, the option value can immediately follow the option letter,
     or there can be a space between: `-hlocalhost' and `-h localhost'
     are equivalent. An exception to this rule is the option for
     specifying your MySQL password. This option can be given in long
     form as `--password=PASS_VAL' or as `--password'. In the latter
     case (with no password value given), the program prompts you for
     the password. The password option also may be given in short form
     as `-pPASS_VAL' or as `-p'. However, for the short form, if the
     password value is given, it must follow the option letter with _no
     intervening space_. The reason for this is that if a space follows
     the option letter, the program has no way to tell whether a
     following argument is supposed to be the password value or some
     other kind of argument.  Consequently, the following two commands
     have two completely different meanings:


          shell> mysql -ptest
          shell> mysql -p test

     The first command instructs *Note `mysql': mysql. to use a
     password value of `test', but specifies no default database. The
     second instructs *Note `mysql': mysql. to prompt for the password
     value and to use `test' as the default database.

   * Within option names, dash (``-'') and underscore (``_'') may be
     used interchangeably. For example, `--skip-grant-tables' and
     `--skip_grant_tables' are equivalent. (However, the leading dashes
     cannot be given as underscores.)

   * For options that take a numeric value, the value can be given with
     a suffix of `K', `M', or `G' (either uppercase or lowercase) to
     indicate a multiplier of 1024, 1024^2 or 1024^3. For example, the
     following command tells *Note `mysqladmin': mysqladmin. to ping
     the server 1024 times, sleeping 10 seconds between each ping:


          mysql> mysqladmin --count=1K --sleep=10 ping

Option values that contain spaces must be quoted when given on the
command line. For example, the `--execute' (or `-e') option can be used
with *Note `mysql': mysql. to pass SQL statements to the server. When
this option is used, *Note `mysql': mysql. executes the statements in
the option value and exits. The statements must be enclosed by quotation
marks. For example, you can use the following command to obtain a list
of user accounts:


     mysql> mysql -u root -p --execute="SELECT User, Host FROM mysql.user"
     Enter password: ******
     +------+-----------+
     | User | Host      |
     +------+-----------+
     |      | gigan     |
     | root | gigan     |
     |      | localhost |
     | jon  | localhost |
     | root | localhost |
     +------+-----------+
     shell>

Note that the long form (`--execute') is followed by an equal sign
(`=').

If you wish to use quoted values within a statement, you will either
need to escape the inner quotation marks, or use a different type of
quotation marks within the statement from those used to quote the
statement itself. The capabilities of your command processor dictate
your choices for whether you can use single or double quotation marks
and the syntax for escaping quote characters. For example, if your
command processor supports quoting with single or double quotation
marks, you can use double quotation marks around the statement, and
single quotation marks for any quoted values within the statement.

Multiple SQL statements may be passed in the option value on the
command line, separated by semicolons:


     shell> mysql -u root -p -e "SELECT VERSION();SELECT NOW()"
     Enter password: ******
     +-----------------+
     | VERSION()       |
     +-----------------+
     | 5.1.5-alpha-log |
     +-----------------+
     +---------------------+
     | NOW()               |
     +---------------------+
     | 2006-01-05 21:19:04 |
     +---------------------+

The `--execute' or `-e' option may also be used to pass commands in an
analogous fashion to the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. management client for MySQL Cluster.
See *Note mysql-cluster-install-shutdown-restart::, for an example.


File: manual.info,  Node: option-modifiers,  Next: option-files,  Prev: command-line-options,  Up: programs-using

4.2.5 Program Option Modifiers
------------------------------

Some options are `boolean' and control behavior that can be turned on
or off. For example, the *Note `mysql': mysql.  client supports a
`--column-names' option that determines whether or not to display a row
of column names at the beginning of query results. By default, this
option is enabled. However, you may want to disable it in some
instances, such as when sending the output of *Note `mysql': mysql. into
another program that expects to see only data and not an initial header
line.

To disable column names, you can specify the option using any of these
forms:


     --disable-column-names
     --skip-column-names
     --column-names=0

The `--disable' and `--skip' prefixes and the `=0' suffix all have the
same effect: They turn the option off.

The `enabled' form of the option may be specified in any of these ways:


     --column-names
     --enable-column-names
     --column-names=1

If an option is prefixed by `--loose', a program does not exit with an
error if it does not recognize the option, but instead issues only a
warning:


     shell> mysql --loose-no-such-option
     mysql: WARNING: unknown option '--loose-no-such-option'

The `--loose' prefix can be useful when you run programs from multiple
installations of MySQL on the same machine and list options in an
option file, An option that may not be recognized by all versions of a
program can be given using the `--loose' prefix (or `loose' in an
option file). Versions of the program that recognize the option process
it normally, and versions that do not recognize it issue a warning and
ignore it.

*Note `mysqld': mysqld. enables a limit to be placed on how large
client programs can set dynamic system variables. To do this, use a
`--maximum' prefix with the variable name. For example,
`--maximum-query_cache_size=4M' prevents any client from making the
query cache size larger than 4MB.


File: manual.info,  Node: option-files,  Next: option-file-options,  Prev: option-modifiers,  Up: programs-using

4.2.6 Using Option Files
------------------------

Most MySQL programs can read startup options from option files (also
sometimes called configuration files). Option files provide a
convenient way to specify commonly used options so that they need not
be entered on the command line each time you run a program. For the
MySQL server, MySQL provides a number of *Note preconfigured option
files: server-configuration-defaults.

To determine whether a program reads option files, invoke it with the
`--help' option. (For *Note `mysqld': mysqld, use `--verbose' and
`--help'.) If the program reads option files, the help message
indicates which files it looks for and which option groups it
recognizes.

*Note*:

Option files used with MySQL Cluster programs are covered in *Note
mysql-cluster-configuration::.

On Windows, MySQL programs read startup options from the following
files, in the specified order (top items are used first).

This table lists file names on Windows operating systems where MySQL
programs read startup options. The purpose of each file is described.

File Name              Purpose
``%PROGRAMDATA%'\MySQL\MySQLGlobal options
Server 5.1\my.ini',    
``%PROGRAMDATA%'\MySQL\MySQL
Server 5.1\my.cnf'     
``%WINDIR%'\my.ini',   Global options
``%WINDIR%'\my.cnf'    
`C:\my.ini',           Global options
`C:\my.cnf'            
`INSTALLDIR\my.ini',   Global options
`INSTALLDIR\my.cnf'    
`defaults-extra-file'  The file specified with
                       `--defaults-extra-file=PATH', if any

`%PROGRAMDATA%' represents the file system directory that contains
application data for all users on the host. This path defaults to
`C:\ProgramData' on Microsoft Windows Vista and greater, and
`C:\Documents and Settings\All Users\Application Data' on older
versions of Microsoft Windows.

`%WINDIR%' represents the location of your Windows directory. This is
commonly `C:\WINDOWS'. You can determine its exact location from the
value of the `WINDIR' environment variable using the following command:


     C:\> echo %WINDIR%

INSTALLDIR represents the MySQL installation directory. This is
typically `C:\PROGRAMDIR\MySQL\MySQL 5.1 Server' where PROGRAMDIR
represents the programs directory (usually `Program Files' on
English-language versions of Windows), when MySQL 5.1 has been
installed using the installation and configuration wizards. See *Note
mysql-config-wizard-starting::.

On Unix, Linux and Mac OS X, MySQL programs read startup options from
the following files, in the specified order (top items are used first).

This table lists file names on Unix, Linux and Mac OS X operating
systems where MySQL programs read startup options. The purpose of each
file is described.

File Name              Purpose
`/etc/my.cnf'          Global options
`/etc/mysql/my.cnf'    Global options (as of MySQL 5.1.15)
`SYSCONFDIR/my.cnf'    Global options
`$MYSQL_HOME/my.cnf'   Server-specific options
`defaults-extra-file'  The file specified with
                       `--defaults-extra-file=PATH', if any
`~/.my.cnf'            User-specific options

`~' represents the current user's home directory (the value of `$HOME').

SYSCONFDIR represents the directory specified with the `--sysconfdir'
option to `configure' when MySQL was built. By default, this is the
`etc' directory located under the compiled-in installation directory.
This location is used as of MySQL 5.1.10. (From 5.1.10 to 5.1.22, it
was read last, after `~/.my.cnf'.)

`MYSQL_HOME' is an environment variable containing the path to the
directory in which the server-specific `my.cnf' file resides. If
`MYSQL_HOME' is not set and you start the server using the *Note
`mysqld_safe': mysqld-safe. program, *Note `mysqld_safe': mysqld-safe.
attempts to set `MYSQL_HOME' as follows:

   * Let BASEDIR and DATADIR represent the path names of the MySQL base
     directory and data directory, respectively.

   * If there is a `my.cnf' file in DATADIR but not in BASEDIR, *Note
     `mysqld_safe': mysqld-safe. sets `MYSQL_HOME' to DATADIR.

   * Otherwise, if `MYSQL_HOME' is not set and there is no `my.cnf'
     file in DATADIR, *Note `mysqld_safe': mysqld-safe. sets
     `MYSQL_HOME' to BASEDIR.

In MySQL 5.1, use of DATADIR as the location for `my.cnf' is deprecated.

Typically, DATADIR is `/usr/local/mysql/data' for a binary installation
or `/usr/local/var' for a source installation. Note that this is the
data directory location that was specified at configuration time, not
the one specified with the `--datadir' option when *Note `mysqld':
mysqld. starts. Use of `--datadir' at runtime has no effect on where
the server looks for option files, because it looks for them before
processing any options.

MySQL looks for option files in the order just described and reads any
that exist. If an option file that you want to use does not exist,
create it with a plain text editor.

If multiple instances of a given option are found, the last instance
takes precedence. There is one exception: For *Note `mysqld': mysqld,
the _first_ instance of the `--user' option is used as a security
precaution, to prevent a user specified in an option file from being
overridden on the command line.

*Note*:

On Unix platforms, MySQL ignores configuration files that are
world-writable. This is intentional as a security measure.

Any long option that may be given on the command line when running a
MySQL program can be given in an option file as well. To get the list
of available options for a program, run it with the `--help' option.

The syntax for specifying options in an option file is similar to
command-line syntax (see *Note command-line-options::).  However, in an
option file, you omit the leading two dashes from the option name and
you specify only one option per line. For example, `--quick' and
`--host=localhost' on the command line should be specified as `quick'
and `host=localhost' on separate lines in an option file. To specify an
option of the form `--loose-OPT_NAME' in an option file, write it as
`loose-OPT_NAME'.

Empty lines in option files are ignored. Nonempty lines can take any of
the following forms:

   * `#COMMENT', `;COMMENT'

     Comment lines start with ``#'' or ``;''. A ``#'' comment can start
     in the middle of a line as well.

   * `[GROUP]'

     GROUP is the name of the program or group for which you want to
     set options. After a group line, any option-setting lines apply to
     the named group until the end of the option file or another group
     line is given. Option group names are not case sensitive.

   * `OPT_NAME'

     This is equivalent to `--OPT_NAME' on the command line.

   * `OPT_NAME=VALUE'

     This is equivalent to `--OPT_NAME=VALUE' on the command line. In
     an option file, you can have spaces around the ``='' character,
     something that is not true on the command line. You can optionally
     enclose the value within single quotation marks or double
     quotation marks, which is useful if the value contains a ``#''
     comment character.

Leading and trailing spaces are automatically deleted from option names
and values.

You can use the escape sequences ``\b'', ``\t'', ``\n'', ``\r'',
``\\'', and ``\s'' in option values to represent the backspace, tab,
newline, carriage return, backslash, and space characters. The escaping
rules in option files are:

   * If a backslash is followed by a valid escape sequence character,
     the sequence is converted to the character represented by the
     sequence. For example, ``\s'' is converted to a space.

   * If a backslash is not followed by a valid escape sequence
     character, it remains unchanged. For example, ``\S'' is retained
     as is.

The preceding rules mean that a literal backslash can be given as
``\\'', or as ``\'' if it is not followed by a valid escape sequence
character.

The rules for escape sequences in option files differ slightly from the
rules for escape sequences in string literals in SQL statements. In the
latter context, if `X' is not a valid escape sequence character, ``\X''
becomes `X' rather than ``\X''.  See *Note string-literals::.

The escaping rules for option file values are especially pertinent for
Windows path names, which use ``\'' as a path name separator. A
separator in a Windows path name must be written as ``\\'' if it is
followed by an escape sequence character. It can be written as ``\\'' or
``\'' if it is not. Alternatively, ``/'' may be used in Windows path
names and will be treated as ``\''.  Suppose that you want to specify a
base directory of `C:\Program Files\MySQL\MySQL Server 5.1' in an
option file. This can be done several ways. Some examples:


     basedir="C:\Program Files\MySQL\MySQL Server 5.1"
     basedir="C:\\Program Files\\MySQL\\MySQL Server 5.1"
     basedir="C:/Program Files/MySQL/MySQL Server 5.1"
     basedir=C:\\Program\sFiles\\MySQL\\MySQL\sServer\s5.1

If an option group name is the same as a program name, options in the
group apply specifically to that program. For example, the `[mysqld]'
and `[mysql]' groups apply to the *Note `mysqld': mysqld. server and the
*Note `mysql': mysql. client program, respectively.

The `[client]' option group is read by all client programs (but _not_ by
*Note `mysqld': mysqld.). This enables you to specify options that
apply to all clients. For example, `[client]' is the perfect group to
use to specify the password that you use to connect to the server. (But
make sure that the option file is readable and writable only by
yourself, so that other people cannot find out your password.) Be sure
not to put an option in the `[client]' group unless it is recognized by
_all_ client programs that you use. Programs that do not understand the
option quit after displaying an error message if you try to run them.

Here is a typical global option file:


     [client]
     port=3306
     socket=/tmp/mysql.sock

     [mysqld]
     port=3306
     socket=/tmp/mysql.sock
     key_buffer_size=16M
     max_allowed_packet=8M

     [mysqldump]
     quick

The preceding option file uses `VAR_NAME=VALUE' syntax for the lines
that set the `key_buffer_size' and `max_allowed_packet' variables.

Here is a typical user option file:


     [client]
     # The following password will be sent to all standard MySQL clients
     password="my_password"

     [mysql]
     no-auto-rehash
     connect_timeout=2

     [mysqlhotcopy]
     interactive-timeout

If you want to create option groups that should be read by *Note
`mysqld': mysqld. servers from a specific MySQL release series only,
you can do this by using groups with names of `[mysqld-5.0]',
`[mysqld-5.1]', and so forth. The following group indicates that the
`--new' option should be used only by MySQL servers with 5.1.x version
numbers:


     [mysqld-5.1]
     new

It is possible to use `!include' directives in option files to include
other option files and `!includedir' to search specific directories for
option files. For example, to include the `/home/mydir/myopt.cnf' file,
use the following directive:


     !include /home/mydir/myopt.cnf

To search the `/home/mydir' directory and read option files found
there, use this directive:


     !includedir /home/mydir

There is no guarantee about the order in which the option files in the
directory will be read.

*Note*:

Currently, any files to be found and included using the `!includedir'
directive on Unix operating systems _must_ have file names ending in
`.cnf'. On Windows, this directive checks for files with the `.ini' or
`.cnf' extension.

Write the contents of an included option file like any other option
file. That is, it should contain groups of options, each preceded by a
`[GROUP]' line that indicates the program to which the options apply.

While an included file is being processed, only those options in groups
that the current program is looking for are used. Other groups are
ignored. Suppose that a `my.cnf' file contains this line:


     !include /home/mydir/myopt.cnf

And suppose that `/home/mydir/myopt.cnf' looks like this:


     [mysqladmin]
     force

     [mysqld]
     key_buffer_size=16M

If `my.cnf' is processed by *Note `mysqld': mysqld, only the `[mysqld]'
group in `/home/mydir/myopt.cnf' is used. If the file is processed by
*Note `mysqladmin': mysqladmin, only the `[mysqladmin]' group is used.
If the file is processed by any other program, no options in
`/home/mydir/myopt.cnf' are used.

The `!includedir' directive is processed similarly except that all
option files in the named directory are read.


File: manual.info,  Node: option-file-options,  Next: program-variables,  Prev: option-files,  Up: programs-using

4.2.7 Command-Line Options that Affect Option-File Handling
-----------------------------------------------------------

Most MySQL programs that support option files handle the following
options. They affect option-file handling, so they must be given on the
command line and not in an option file. To work properly, each of these
options must be given before other options, with these exceptions:

   * `--print-defaults' may be used immediately after `--defaults-file'
     or `--defaults-extra-file'.

   * On Windows, if the server is started with the `--defaults-file' and
     `--install' options, `--install' must be first. See *Note
     windows-start-service::.

When specifying file names, you should avoid the use of the ``~'' shell
metacharacter because it might not be interpreted as you expect.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, the *Note `mysql':
     mysql. client normally reads the `[client]' and `[mysql]' groups.
     If the `--defaults-group-suffix=_other' option is given, *Note
     `mysql': mysql. also reads the `[client_other]' and
     `[mysql_other]' groups.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.


File: manual.info,  Node: program-variables,  Next: option-defaults-equals,  Prev: option-file-options,  Up: programs-using

4.2.8 Using Options to Set Program Variables
--------------------------------------------

Many MySQL programs have internal variables that can be set at runtime
using the *Note `SET': set-statement.  statement. See *Note
set-statement::, and *Note using-system-variables::.

Most of these program variables also can be set at server startup by
using the same syntax that applies to specifying program options. For
example, *Note `mysql': mysql. has a `max_allowed_packet' variable that
controls the maximum size of its communication buffer. To set the
`max_allowed_packet' variable for *Note `mysql': mysql. to a value of
16MB, use either of the following commands:


     shell> mysql --max_allowed_packet=16777216
     shell> mysql --max_allowed_packet=16M

The first command specifies the value in bytes. The second specifies
the value in megabytes. For variables that take a numeric value, the
value can be given with a suffix of `K', `M', or `G' (either uppercase
or lowercase) to indicate a multiplier of 1024, 1024^2 or 1024^3. (For
example, when used to set `max_allowed_packet', the suffixes indicate
units of kilobytes, megabytes, or gigabytes.)

In an option file, variable settings are given without the leading
dashes:


     [mysql]
     max_allowed_packet=16777216

Or:


     [mysql]
     max_allowed_packet=16M

If you like, underscores in a variable name can be specified as dashes.
The following option groups are equivalent. Both set the size of the
server's key buffer to 512MB:


     [mysqld]
     key_buffer_size=512M

     [mysqld]
     key-buffer-size=512M

A variable can be specified by writing it in full or as any unambiguous
prefix. For example, the `max_allowed_packet' variable can be set for
*Note `mysql': mysql. as `--max_a', but not as `--max' because the
latter is ambiguous:


     shell> mysql --max=1000000
     mysql: ambiguous option '--max=1000000' (max_allowed_packet, max_join_size)

Be aware that the use of variable prefixes can cause problems in the
event that new variables are implemented for a program. A prefix that
is unambiguous now might become ambiguous in the future.

Suffixes for specifying a value multiplier can be used when setting a
variable at server startup, but not to set the value with *Note `SET':
set-statement.  at runtime. On the other hand, with *Note `SET':
set-statement. you can assign a variable's value using an expression,
which is not true when you set a variable at server startup. For
example, the first of the following lines is legal at server startup,
but the second is not:


     shell> mysql --max_allowed_packet=16M
     shell> mysql --max_allowed_packet=16*1024*1024

Conversely, the second of the following lines is legal at runtime, but
the first is not:


     mysql> SET GLOBAL max_allowed_packet=16M;
     mysql> SET GLOBAL max_allowed_packet=16*1024*1024;

*Note*:

Before MySQL 4.0.2, the only syntax for setting program variables was
`--set-variable=OPTION=VALUE' (or `set-variable=OPTION=VALUE' in option
files). Underscores cannot be given as dashes, and the variable name
must be specified in full. This syntax still is recognized, but is
deprecated and is removed in MySQL 5.5.


File: manual.info,  Node: option-defaults-equals,  Next: setting-environment-variables,  Prev: program-variables,  Up: programs-using

4.2.9 Option Defaults, Options Expecting Values, and the = Sign
---------------------------------------------------------------

By convention, long forms of options that assign a value are written
with an equals (`=') sign, like this:


     shell> mysql --host=tonfisk --user=jon

For options that require a value (that is, not having a default value),
the equal sign is not required, and so the following is also valid:


     shell> mysql --host tonfisk --user jon

In both cases, the *Note `mysql': mysql. client attempts to connect to
a MySQL server running on the host named `tonfisk' using an account
with the user name `jon'.

Due to this behavior, problems can occasionally arise when no value is
provided for an option that expects one. Consider the following
example, where a user connects to a MySQL server running on host
`tonfisk' as user `jon':


     shell> mysql --host 85.224.35.45 --user jon
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 3
     Server version: 5.1.73 Source distribution

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql> SELECT CURRENT_USER();
     +----------------+
     | CURRENT_USER() |
     +----------------+
     | jon@%          |
     +----------------+
     1 row in set (0.00 sec)

Omitting the required value for one of these option yields an error,
such as the one shown here:


     shell> mysql --host 85.224.35.45 --user
     `mysql: option '--user' requires an argument'

In this case, *Note `mysql': mysql. was unable to find a value
following the `--user' option because nothing came after it on the
command line. However, if you omit the value for an option that is
_not_ the last option to be used, you obtain a different error that you
may not be expecting:


     shell> mysql --host --user jon
     `ERROR 2005 (HY000): Unknown MySQL server host '--user' (1)'

Because *Note `mysql': mysql. assumes that any string following
`--host' on the command line is a host name, `--host' `--user' is
interpreted as `--host=--user', and the client attempts to connect to a
MySQL server running on a host named `--user'.

Options having default values always require an equal sign when
assigning a value; failing to do so causes an error. For example, the
MySQL server `--log-error' option has the default value `HOST_NAME.err',
where HOST_NAME is the name of the host on which MySQL is running.
Assume that you are running MySQL on a computer whose host name is
`tonfisk', and consider the following invocation of *Note
`mysqld_safe': mysqld-safe.:


     shell> mysqld_safe &
     [1] 11699
     shell> 080112 12:53:40 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'.
     080112 12:53:40 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/var
     shell>

After shutting down the server, restart it as follows:


     shell> mysqld_safe --log-error &
     [1] 11699
     shell> 080112 12:53:40 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'.
     080112 12:53:40 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/var
     shell>

The result is the same, since `--log-error' is not followed by anything
else on the command line, and it supplies its own default value. (The
`&' character tells the operating system to run MySQL in the
background; it is ignored by MySQL itself.) Now suppose that you wish
to log errors to a file named `my-errors.err'. You might try starting
the server with `--log-error my-errors', but this does not have the
intended effect, as shown here:


     shell> mysqld_safe --log-error my-errors &
     [1] 31357
     shell> 080111 22:53:31 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'.
     080111 22:53:32 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/var
     080111 22:53:34 mysqld_safe mysqld from pid file /usr/local/mysql/var/tonfisk.pid ended

     [1]+  Done                    ./mysqld_safe --log-error my-errors

The server attempted to start using `/usr/local/mysql/var/tonfisk.err'
as the error log, but then shut down. Examining the last few lines of
this file shows the reason:


     shell> tail /usr/local/mysql/var/tonfisk.err
     080111 22:53:32  InnoDB: Started; log sequence number 0 46409
     `/usr/local/mysql/libexec/mysqld: Too many arguments (first extra is 'my-errors').
     Use --verbose --help to get a list of available options'
     080111 22:53:32 `[ERROR] Aborting'

     080111 22:53:32  InnoDB: Starting shutdown...
     080111 22:53:34  InnoDB: Shutdown completed; log sequence number 0 46409
     080111 22:53:34 [Note] /usr/local/mysql/libexec/mysqld: Shutdown complete

     080111 22:53:34 mysqld_safe mysqld from pid file /usr/local/mysql/var/tonfisk.pid ended

Because the `--log-error' option supplies a default value, you must use
an equal sign to assign a different value to it, as shown here:


     shell> mysqld_safe --log-error=my-errors &
     [1] 31437
     shell> 080111 22:54:15 mysqld_safe Logging to '/usr/local/mysql/var/my-errors.err'.
     080111 22:54:15 mysqld_safe Starting mysqld daemon with databases from /usr/local/mysql/var

     shell>

Now the server has been started successfully, and is logging errors to
the file `/usr/local/mysql/var/my-errors.err'.

Similar issues can arise when specifying option values in option files.
For example, consider a `my.cnf' file that contains the following:


     [mysql]

     host
     user

When the *Note `mysql': mysql. client reads this file, these entries
are parsed as `--host' `--user' or `--host=--user', with the result
shown here:


     shell> mysql
     `ERROR 2005 (HY000): Unknown MySQL server host '--user' (1)'

However, in option files, an equal sign is not assumed. Suppose the
`my.cnf' file is as shown here:


     [mysql]

     user jon

Trying to start *Note `mysql': mysql. in this case causes a different
error:


     shell> mysql
     `mysql: unknown option '--user jon''

A similar error would occur if you were to write `host tonfisk' in the
option file rather than `host=tonfisk'. Instead, you must use the equals
sign:


     [mysql]

     user=jon

Now the login attempt succeeds:


     shell> mysql
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 5
     Server version: 5.1.73 Source distribution

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql> SELECT USER();
     +---------------+
     | USER()        |
     +---------------+
     | jon@localhost |
     +---------------+
     1 row in set (0.00 sec)

This is not the same behavior as with the command line, where the equal
sign is not required:


     shell> mysql --user jon --host tonfisk
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 6
     Server version: 5.1.73 Source distribution

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql> SELECT USER();
     +---------------+
     | USER()        |
     +---------------+
     | jon@tonfisk   |
     +---------------+
     1 row in set (0.00 sec)


File: manual.info,  Node: setting-environment-variables,  Prev: option-defaults-equals,  Up: programs-using

4.2.10 Setting Environment Variables
------------------------------------

Environment variables can be set at the command prompt to affect the
current invocation of your command processor, or set permanently to
affect future invocations. To set a variable permanently, you can set
it in a startup file or by using the interface provided by your system
for this purpose. Consult the documentation for your command
interpreter for specific details.  *Note environment-variables::, lists
all environment variables that affect MySQL program operation.

To specify a value for an environment variable, use the syntax
appropriate for your command processor. For example, on Windows or
NetWare, you can set the `USER' variable to specify your MySQL account
name. To do so, use this syntax:


     SET USER=YOUR_NAME

The syntax on Unix depends on your shell. Suppose that you want to
specify the TCP/IP port number using the `MYSQL_TCP_PORT' variable.
Typical syntax (such as for `sh', `ksh', `bash', `zsh', and so on) is as
follows:


     MYSQL_TCP_PORT=3306
     export MYSQL_TCP_PORT

The first command sets the variable, and the `export' command exports
the variable to the shell environment so that its value becomes
accessible to MySQL and other processes.

For `csh' and `tcsh', use `setenv' to make the shell variable available
to the environment:


     setenv MYSQL_TCP_PORT 3306

The commands to set environment variables can be executed at your
command prompt to take effect immediately, but the settings persist
only until you log out. To have the settings take effect each time you
log in, use the interface provided by your system or place the
appropriate command or commands in a startup file that your command
interpreter reads each time it starts.

On Windows, you can set environment variables using the System Control
Panel (under Advanced).

On Unix, typical shell startup files are `.bashrc' or `.bash_profile'
for `bash', or `.tcshrc' for `tcsh'.

Suppose that your MySQL programs are installed in
`/usr/local/mysql/bin' and that you want to make it easy to invoke
these programs. To do this, set the value of the `PATH' environment
variable to include that directory. For example, if your shell is
`bash', add the following line to your `.bashrc' file:


     PATH=${PATH}:/usr/local/mysql/bin

`bash' uses different startup files for login and nonlogin shells, so
you might want to add the setting to `.bashrc' for login shells and to
`.bash_profile' for nonlogin shells to make sure that `PATH' is set
regardless.

If your shell is `tcsh', add the following line to your `.tcshrc' file:


     setenv PATH ${PATH}:/usr/local/mysql/bin

If the appropriate startup file does not exist in your home directory,
create it with a text editor.

After modifying your `PATH' setting, open a new console window on
Windows or log in again on Unix so that the setting goes into effect.


File: manual.info,  Node: programs-server,  Next: programs-installation,  Prev: programs-using,  Up: programs

4.3 MySQL Server and Server-Startup Programs
============================================

* Menu:

* mysqld::                       `mysqld' --- The MySQL Server
* mysqld-safe::                  `mysqld_safe' --- MySQL Server Startup Script
* mysql-server::                 `mysql.server' --- MySQL Server Startup Script
* mysqld-multi::                 `mysqld_multi' --- Manage Multiple MySQL Servers

This section describes *Note `mysqld': mysqld, the MySQL server, and
several programs that are used to start the server.


File: manual.info,  Node: mysqld,  Next: mysqld-safe,  Prev: programs-server,  Up: programs-server

4.3.1 `mysqld' -- The MySQL Server
----------------------------------

*Note `mysqld': mysqld, also known as MySQL Server, is the main program
that does most of the work in a MySQL installation.  MySQL Server
manages access to the MySQL data directory that contains databases and
tables. The data directory is also the default location for other
information such as log files and status files.

When MySQL server starts, it listens for network connections from
client programs and manages access to databases on behalf of those
clients.

The *Note `mysqld': mysqld. program has many options that can be
specified at startup. For a complete list of options, run this command:


     shell> mysqld --verbose --help

MySQL Server also has a set of system variables that affect its
operation as it runs. System variables can be set at server startup,
and many of them can be changed at runtime to effect dynamic server
reconfiguration. MySQL Server also has a set of status variables that
provide information about its operation.  You can monitor these status
variables to access runtime performance characteristics.

For a full description of MySQL Server command options, system
variables, and status variables, see *Note mysqld-server::. For
information about installing MySQL and setting up the initial
configuration, see *Note installing::.


File: manual.info,  Node: mysqld-safe,  Next: mysql-server,  Prev: mysqld,  Up: programs-server

4.3.2 `mysqld_safe' -- MySQL Server Startup Script
--------------------------------------------------

*Note `mysqld_safe': mysqld-safe. is the recommended way to start a
*Note `mysqld': mysqld. server on Unix and NetWare.  *Note
`mysqld_safe': mysqld-safe. adds some safety features such as
restarting the server when an error occurs and logging runtime
information to an error log file. Descriptions of error logging and
NetWare-specific behaviors are given later in this section.

*Note*:

In MySQL 5.1.20 (only), the default error logging behavior with *Note
`mysqld_safe': mysqld-safe. is to write errors to `syslog' on systems
that support the `logger' program. This differs from the default
behavior of writing an error log file for other versions.

*In 5.1.20, logging to `syslog' may fail to operate correctly in some
cases; if so, use `--skip-syslog' to use the default log file or
`--log-error=FILE_NAME' to specify a log file name explicitly.*

*Note `mysqld_safe': mysqld-safe. tries to start an executable named
*Note `mysqld': mysqld. To override the default behavior and specify
explicitly the name of the server you want to run, specify a `--mysqld'
or `--mysqld-version' option to *Note `mysqld_safe': mysqld-safe. You
can also use `--ledir' to indicate the directory where *Note
`mysqld_safe': mysqld-safe. should look for the server.

Many of the options to *Note `mysqld_safe': mysqld-safe. are the same
as the options to *Note `mysqld': mysqld. See *Note server-options::.

Options unknown to *Note `mysqld_safe': mysqld-safe. are passed to
*Note `mysqld': mysqld. if they are specified on the command line, but
ignored if they are specified in the `[mysqld_safe]' group of an option
file. See *Note option-files::.

*Note `mysqld_safe': mysqld-safe. reads all options from the
`[mysqld]', `[server]', and `[mysqld_safe]' sections in option files.
For example, if you specify a `[mysqld]' section like this, *Note
`mysqld_safe': mysqld-safe. will find and use the `--log-error' option:


     [mysqld]
     log-error=error.log

For backward compatibility, *Note `mysqld_safe': mysqld-safe. also
reads `[safe_mysqld]' sections, although it is preferable to rename
`[safe_mysqld]' sections to `[mysqld_safe]' sections.

*Note `mysqld_safe': mysqld-safe. supports the options in the following
list. It also reads option files and supports the options for
processing them described at *Note option-file-options::.

*`mysqld_safe' Options*

Format             Description                      Introduced
-autoclose         On NetWare, mysqld_safe          
                   provides a screen presence       
-basedir=path      Path to MySQL installation       
                   directory                        
-core-file-size=sizeSize of core file that mysqld    
                   should be able to create         
-datadir=path      Path to data directory           
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-help              Display help message and exit    
-ledir=path        Path to directory where server   
                   is located                       
-log-error=file_nameWrite error log to named file    
-mysqld=prog_name  Name of server program to start  
                   (in ledir directory)             
-mysqld-version=suffixSuffix for server program name   
-nice=priority     Use nice program to set server   
                   scheduling priority              
-no-defaults       Read no option files             
-open-files-limit=countNumber of files that mysqld      
                   should be able to open           
-pid-file=file_namePath name of process ID file     
-port=number       Port number on which to listen   
                   for TCP/IP connections           
-skip-kill-mysqld  Do not try to kill stray mysqld  
                   processes                        
-skip-syslog       Do not write error messages to   5.1.20
                   syslog; use error log file       
-socket=path       Socket file on which to listen   
                   for Unix socket connections      
-syslog            Write error messages to syslog   5.1.20
-syslog-tag=tag    Tag suffix for messages written  5.1.21
                   to syslog                        
-timezone=timezone Set TZ time zone environment     
                   variable to named value          
-user={user_name|user_id}Run mysqld as user having name   
                   user_name or numeric user ID     
                   user_id                          

   * `--help'

     Display a help message and exit.

   * `--autoclose'

     (NetWare only) On NetWare, *Note `mysqld_safe': mysqld-safe.
     provides a screen presence. When you unload (shut down) the *Note
     `mysqld_safe': mysqld-safe. NLM, the screen does not by default go
     away. Instead, it prompts for user input:


          *<NLM has terminated; Press any key to close the screen>*

     If you want NetWare to close the screen automatically instead, use
     the `--autoclose' option to *Note `mysqld_safe': mysqld-safe.

   * `--basedir=PATH'

     The path to the MySQL installation directory.

   * `--core-file-size=SIZE'

     The size of the core file that *Note `mysqld': mysqld.  should be
     able to create. The option value is passed to `ulimit -c'.

   * `--datadir=PATH'

     The path to the data directory.

   * `--defaults-extra-file=PATH'

     The name of an option file to be read in addition to the usual
     option files. This must be the first option on the command line if
     it is used. If the file does not exist or is otherwise
     inaccessible, the server will exit with an error.

   * `--defaults-file=FILE_NAME'

     The name of an option file to be read instead of the usual option
     files. This must be the first option on the command line if it is
     used.

   * `--ledir=PATH'

     If *Note `mysqld_safe': mysqld-safe. cannot find the server, use
     this option to indicate the path name to the directory where the
     server is located.

   * `--log-error=FILE_NAME'

     Write the error log to the given file. See *Note error-log::.

   * `--mysqld=PROG_NAME'

     The name of the server program (in the `ledir' directory) that you
     want to start.  This option is needed if you use the MySQL binary
     distribution but have the data directory outside of the binary
     distribution. If *Note `mysqld_safe': mysqld-safe.  cannot find
     the server, use the `--ledir' option to indicate the path name to
     the directory where the server is located.

   * `--mysqld-version=SUFFIX'

     This option is similar to the `--mysqld' option, but you specify
     only the suffix for the server program name. The basename is
     assumed to be *Note `mysqld': mysqld. For example, if you use
     `--mysqld-version=debug', *Note `mysqld_safe': mysqld-safe. starts
     the *Note `mysqld-debug': mysqld. program in the `ledir'
     directory. If the argument to `--mysqld-version' is empty, *Note
     `mysqld_safe': mysqld-safe. uses *Note `mysqld': mysqld. in the
     `ledir' directory.

   * `--nice=PRIORITY'

     Use the `nice' program to set the server's scheduling priority to
     the given value.

   * `--no-defaults'

     Do not read any option files. This must be the first option on the
     command line if it is used.

   * `--open-files-limit=COUNT'

     The number of files that *Note `mysqld': mysqld. should be able to
     open. The option value is passed to `ulimit -n'.

     *Note*:

     You must start *Note `mysqld_safe': mysqld-safe. as `root' for
     this to function properly.

   * `--pid-file=FILE_NAME'

     The path name of the process ID file.

   * `--port=PORT_NUM'

     The port number that the server should use when listening for
     TCP/IP connections. The port number must be 1024 or higher unless
     the server is started by the `root' system user.

   * `--skip-kill-mysqld'

     Do not try to kill stray *Note `mysqld': mysqld. processes at
     startup. This option works only on Linux.

   * `--socket=PATH'

     The Unix socket file that the server should use when listening for
     local connections.

   * `--syslog', `--skip-syslog'

     `--syslog' causes error messages to be sent to `syslog' on systems
     that support the `logger' program.  `--skip-syslog' suppresses the
     use of `syslog'; messages are written to an error log file. These
     options were added in MySQL 5.1.20.

     When `syslog' is used, the `daemon.err' syslog facility/severity is
     used for all log messages.

   * `--syslog-tag=TAG'

     For logging to `syslog', messages from *Note `mysqld_safe':
     mysqld-safe. and *Note `mysqld': mysqld.  are written with
     identifiers of `mysqld_safe' and `mysqld', respectively. To
     specify a suffix for the identifiers, use `--syslog-tag=TAG',
     which modifies the identifiers to be `mysqld_safe-TAG' and
     `mysqld-TAG'.  This option was added in MySQL 5.1.21.

   * `--timezone=TIMEZONE'

     Set the `TZ' time zone environment variable to the given option
     value. Consult your operating system documentation for legal time
     zone specification formats.

   * `--user={USER_NAME|USER_ID}'

     Run the *Note `mysqld': mysqld. server as the user having the name
     USER_NAME or the numeric user ID USER_ID.  (`User' in this context
     refers to a system login account, not a MySQL user listed in the
     grant tables.)

If you execute *Note `mysqld_safe': mysqld-safe. with the
`--defaults-file' or `--defaults-extra-file' option to name an option
file, the option must be the first one given on the command line or the
option file will not be used. For example, this command will not use
the named option file:


     mysql> mysqld_safe --port=PORT_NUM --defaults-file=FILE_NAME

Instead, use the following command:


     mysql> mysqld_safe --defaults-file=FILE_NAME --port=PORT_NUM

The *Note `mysqld_safe': mysqld-safe. script is written so that it
normally can start a server that was installed from either a source or
a binary distribution of MySQL, even though these types of
distributions typically install the server in slightly different
locations. (See *Note installation-layouts::.)  *Note `mysqld_safe':
mysqld-safe. expects one of the following conditions to be true:

   * The server and databases can be found relative to the working
     directory (the directory from which *Note `mysqld_safe':
     mysqld-safe. is invoked). For binary distributions, *Note
     `mysqld_safe': mysqld-safe. looks under its working directory for
     `bin' and `data' directories. For source distributions, it looks
     for `libexec' and `var' directories. This condition should be met
     if you execute *Note `mysqld_safe': mysqld-safe. from your MySQL
     installation directory (for example, `/usr/local/mysql' for a
     binary distribution).

   * If the server and databases cannot be found relative to the
     working directory, *Note `mysqld_safe': mysqld-safe. attempts to
     locate them by absolute path names. Typical locations are
     `/usr/local/libexec' and `/usr/local/var'. The actual locations
     are determined from the values configured into the distribution at
     the time it was built. They should be correct if MySQL is
     installed in the location specified at configuration time.

Because *Note `mysqld_safe': mysqld-safe. tries to find the server and
databases relative to its own working directory, you can install a
binary distribution of MySQL anywhere, as long as you run *Note
`mysqld_safe': mysqld-safe. from the MySQL installation directory:


     shell> cd MYSQL_INSTALLATION_DIRECTORY
     shell> bin/mysqld_safe &

If *Note `mysqld_safe': mysqld-safe. fails, even when invoked from the
MySQL installation directory, specify the `--ledir' and `--datadir'
options to indicate the directories in which the server and databases
are located on your system.

When you use *Note `mysqld_safe': mysqld-safe. to start *Note `mysqld':
mysqld, *Note `mysqld_safe': mysqld-safe.  arranges for error (and
notice) messages from itself and from *Note `mysqld': mysqld. to go to
the same destination.

As of MySQL 5.1.20, there are several *Note `mysqld_safe': mysqld-safe.
options for controlling the destination of these messages:

   * `--log-error=FILE_NAME': Write error messages to the named error
     file.

   * `--syslog': Write error messages to `syslog' on systems that
     support the `logger' program.

   * `--skip-syslog': Do not write error messages to `syslog'.
     Messages are written to the default error log file (`HOST_NAME.err'
     in the data directory), or to a named file if the `--log-error'
     option is given.

If none of these options is given, the default is `--skip-syslog'.

*Note*:

In MySQL 5.1.20 _only_, the default is `--syslog'. This differs from
logging behavior for other versions of MySQL, for which the default is
to write messages to the default error log file.

If `--log-error' and `--syslog' are both given, a warning is issued and
`--log-error' takes precedence.

When *Note `mysqld_safe': mysqld-safe. writes a message, notices go to
the logging destination (`syslog' or the error log file) and `stdout'.
Errors go to the logging destination and `stderr'.

Before MySQL 5.1.20, error logging is controlled only with the
`--log-error' option. If it is given, messages go to the named error
file. Otherwise, messages go to the default error file.

Normally, you should not edit the *Note `mysqld_safe': mysqld-safe.
script. Instead, configure *Note `mysqld_safe': mysqld-safe. by using
command-line options or options in the `[mysqld_safe]' section of a
`my.cnf' option file. In rare cases, it might be necessary to edit
*Note `mysqld_safe': mysqld-safe. to get it to start the server
properly. However, if you do this, your modified version of *Note
`mysqld_safe': mysqld-safe. might be overwritten if you upgrade MySQL
in the future, so you should make a copy of your edited version that
you can reinstall.

On NetWare, *Note `mysqld_safe': mysqld-safe. is a NetWare Loadable
Module (NLM) that is ported from the original Unix shell script.  It
starts the server as follows:

  1. Runs a number of system and option checks.

  2. Runs a check on `MyISAM' tables.

  3. Provides a screen presence for the MySQL server.

  4. Starts *Note `mysqld': mysqld, monitors it, and restarts it if it
     terminates in error.

  5. Sends error messages from *Note `mysqld': mysqld. to the
     `HOST_NAME.err' file in the data directory.

  6. Sends *Note `mysqld_safe': mysqld-safe. screen output to the
     `HOST_NAME.safe' file in the data directory.


File: manual.info,  Node: mysql-server,  Next: mysqld-multi,  Prev: mysqld-safe,  Up: programs-server

4.3.3 `mysql.server' -- MySQL Server Startup Script
---------------------------------------------------

MySQL distributions on Unix include a script named *Note
`mysql.server': mysql-server. It can be used on systems such as Linux
and Solaris that use System V-style run directories to start and stop
system services. It is also used by the Mac OS X Startup Item for MySQL.

*Note `mysql.server': mysql-server. can be found in the `support-files'
directory under your MySQL installation directory or in a MySQL source
distribution.

If you use the Linux server RPM package (`MySQL-server-VERSION.rpm'),
the *Note `mysql.server': mysql-server. script will be installed in the
`/etc/init.d' directory with the name `mysql'. You need not install it
manually.  See *Note linux-installation-rpm::, for more information on
the Linux RPM packages.

Some vendors provide RPM packages that install a startup script under a
different name such as *Note `mysqld': mysqld.

If you install MySQL from a source distribution or using a binary
distribution format that does not install *Note `mysql.server':
mysql-server. automatically, you can install it manually. Instructions
are provided in *Note automatic-start::.

*Note `mysql.server': mysql-server. reads options from the
`[mysql.server]' and `[mysqld]' sections of option files. For backward
compatibility, it also reads `[mysql_server]' sections, although you
should rename such sections to `[mysql.server]' when using MySQL 5.1.

*Note `mysql.server': mysql-server. supports the following options.

   * `--basedir=PATH'

     The path to the MySQL installation directory.

   * `--datadir=PATH'

     The path to the MySQL data directory.

   * `--pid-file=FILE_NAME'

     The path name of the file in which the server should write its
     process ID.

   * `--service-startup-timeout=SECONDS'

     How long in seconds to wait for confirmation of server startup. If
     the server does not start within this time, *Note `mysql.server':
     mysql-server. exits with an error. The default value is 900. A
     value of 0 means not to wait at all for startup. Negative values
     mean to wait forever (no timeout). This option was added in MySQL
     5.1.17. Before that, a value of 900 is always used.

   * `--use-mysqld_safe'

     Use *Note `mysqld_safe': mysqld-safe. to start the server. This is
     the default.

   * `--use-manager'

     Use Instance Manager to start the server.

   * `--user=USER_NAME'

     The login user name to use for running *Note `mysqld': mysqld.


File: manual.info,  Node: mysqld-multi,  Prev: mysql-server,  Up: programs-server

4.3.4 `mysqld_multi' -- Manage Multiple MySQL Servers
-----------------------------------------------------

*Note `mysqld_multi': mysqld-multi. is designed to manage several *Note
`mysqld': mysqld. processes that listen for connections on different
Unix socket files and TCP/IP ports. It can start or stop servers, or
report their current status. The MySQL Instance Manager is an
alternative means of managing multiple servers (see *Note
instance-manager::).

*Note `mysqld_multi': mysqld-multi. searches for groups named
`[mysqldN]' in `my.cnf' (or in the file named by the `--config-file'
option).  N can be any positive integer. This number is referred to in
the following discussion as the option group number, or GNR. Group
numbers distinguish option groups from one another and are used as
arguments to *Note `mysqld_multi': mysqld-multi. to specify which
servers you want to start, stop, or obtain a status report for.
Options listed in these groups are the same that you would use in the
`[mysqld]' group used for starting *Note `mysqld': mysqld. (See, for
example, *Note automatic-start::.) However, when using multiple
servers, it is necessary that each one use its own value for options
such as the Unix socket file and TCP/IP port number. For more
information on which options must be unique per server in a
multiple-server environment, see *Note multiple-servers::.

To invoke *Note `mysqld_multi': mysqld-multi, use the following syntax:


     shell> mysqld_multi [OPTIONS] {start|stop|report} [GNR[,GNR] ...]

`start', `stop', and `report' indicate which operation to perform.  You
can perform the designated operation for a single server or multiple
servers, depending on the GNR list that follows the option name. If
there is no list, *Note `mysqld_multi': mysqld-multi.  performs the
operation for all servers in the option file.

Each GNR value represents an option group number or range of group
numbers. The value should be the number at the end of the group name in
the option file. For example, the GNR for a group named `[mysqld17]' is
`17'. To specify a range of numbers, separate the first and last numbers
by a dash. The GNR value `10-13' represents groups `[mysqld10]' through
`[mysqld13]'. Multiple groups or group ranges can be specified on the
command line, separated by commas. There must be no whitespace
characters (spaces or tabs) in the GNR list; anything after a whitespace
character is ignored.

This command starts a single server using option group `[mysqld17]':


     shell> mysqld_multi start 17

This command stops several servers, using option groups `[mysqld8]' and
`[mysqld10]' through `[mysqld13]':


     shell> mysqld_multi stop 8,10-13

For an example of how you might set up an option file, use this command:


     shell> mysqld_multi --example

As of MySQL 5.1.18, *Note `mysqld_multi': mysqld-multi. searches for
option files as follows:

   * With `--no-defaults', no option files are read.

   * With `--defaults-file=FILE_NAME', only the named file is read.

   * Otherwise, option files in the standard list of locations are
     read, including any file named by the
     `--defaults-extra-file=FILE_NAME' option, if one is given. (If the
     option is given multiple times, the last value is used.)

Before MySQL 5.1.18, the preceding options are not recognized.  Files
in the standard locations are read, and any file named by the
`--config-file=FILE_NAME' option, if one is given. A file named by
`--config-file' is read only for `[mysqldN]' option groups, not the
`[mysqld_multi]' group.

Option files read are searched for `[mysqld_multi]' and `[mysqldN]'
option groups. The `[mysqld_multi]' group can be used for options to
*Note `mysqld_multi': mysqld-multi. itself.  `[mysqldN]' groups can be
used for options passed to specific *Note `mysqld': mysqld. instances.

As of MySQL 5.1.35, the `[mysqld]' or `[mysqld_safe]' groups can be
used for common options read by all instances of *Note `mysqld':
mysqld. or *Note `mysqld_safe': mysqld-safe. You can specify a
`--defaults-file=FILE_NAME' option to use a different configuration
file for that instance, in which case the `[mysqld]' or `[mysqld_safe]'
groups from that file will be used for that instance. Before MySQL
5.1.35, some versions of *Note `mysqld_multi': mysqld-multi. pass the
`--no-defaults' options to instances, so these techniques are
inapplicable.

*Note `mysqld_multi': mysqld-multi. supports the following options.

   * `--help'

     Display a help message and exit.

   * `--config-file=FILE_NAME'

     As of MySQL 5.1.18, this option is deprecated. If given, it is
     treated the same way as `--defaults-extra-file', described earlier.
     `--config-file' is removed in MySQL 5.5.

     Before MySQL 5.1.18, this option specifies the name of an extra
     option file. It affects where *Note `mysqld_multi': mysqld-multi.
     looks for `[mysqldN]' option groups. Without this option, all
     options are read from the usual `my.cnf' file. The option does not
     affect where *Note `mysqld_multi': mysqld-multi. reads its own
     options, which are always taken from the `[mysqld_multi]' group in
     the usual `my.cnf' file.

   * `--example'

     Display a sample option file.

   * `--log=FILE_NAME'

     Specify the name of the log file. If the file exists, log output
     is appended to it.

   * `--mysqladmin=PROG_NAME'

     The *Note `mysqladmin': mysqladmin. binary to be used to stop
     servers.

   * `--mysqld=PROG_NAME'

     The *Note `mysqld': mysqld. binary to be used. Note that you can
     specify *Note `mysqld_safe': mysqld-safe. as the value for this
     option also. If you use *Note `mysqld_safe': mysqld-safe. to start
     the server, you can include the `mysqld' or `ledir' options in the
     corresponding `[mysqldN]' option group. These options indicate the
     name of the server that *Note `mysqld_safe': mysqld-safe. should
     start and the path name of the directory where the server is
     located. (See the descriptions for these options in *Note
     mysqld-safe::.) Example:


          [mysqld38]
          mysqld = mysqld-debug
          ledir  = /opt/local/mysql/libexec

   * `--no-log'

     Print log information to `stdout' rather than to the log file. By
     default, output goes to the log file.

   * `--password=PASSWORD'

     The password of the MySQL account to use when invoking *Note
     `mysqladmin': mysqladmin. Note that the password value is not
     optional for this option, unlike for other MySQL programs.

   * `--silent'

     Silent mode; disable warnings.

   * `--tcp-ip'

     Connect to each MySQL server through the TCP/IP port instead of
     the Unix socket file. (If a socket file is missing, the server
     might still be running, but accessible only through the TCP/IP
     port.) By default, connections are made using the Unix socket
     file. This option affects `stop' and `report' operations.

   * `--user=USER_NAME'

     The user name of the MySQL account to use when invoking *Note
     `mysqladmin': mysqladmin.

   * `--verbose'

     Be more verbose.

   * `--version'

     Display version information and exit.

Some notes about *Note `mysqld_multi': mysqld-multi.:

   * *Most important*: Before using *Note `mysqld_multi': mysqld-multi.
     be sure that you understand the meanings of the options that are
     passed to the *Note `mysqld': mysqld. servers and _why_ you would
     want to have separate *Note `mysqld': mysqld. processes. Beware of
     the dangers of using multiple *Note `mysqld': mysqld. servers with
     the same data directory. Use separate data directories, unless you
     _know_ what you are doing. Starting multiple servers with the same
     data directory does _not_ give you extra performance in a threaded
     system. See *Note multiple-servers::.

   * *Important*:

     Make sure that the data directory for each server is fully
     accessible to the Unix account that the specific *Note `mysqld':
     mysqld. process is started as.  _Do not_ use the Unix ROOT account
     for this, unless you _know_ what you are doing. See *Note
     changing-mysql-user::.

   * Make sure that the MySQL account used for stopping the *Note
     `mysqld': mysqld. servers (with the *Note `mysqladmin':
     mysqladmin. program) has the same user name and password for each
     server. Also, make sure that the account has the `SHUTDOWN'
     privilege. If the servers that you want to manage have different
     user names or passwords for the administrative accounts, you might
     want to create an account on each server that has the same user
     name and password. For example, you might set up a common
     `multi_admin' account by executing the following commands for each
     server:


          shell> mysql -u root -S /tmp/mysql.sock -p
          Enter password:
          mysql> GRANT SHUTDOWN ON *.*
              -> TO 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';

     See *Note privilege-system::. You have to do this for each *Note
     `mysqld': mysqld. server. Change the connection parameters
     appropriately when connecting to each one. Note that the host name
     part of the account name must permit you to connect as
     `multi_admin' from the host where you want to run *Note
     `mysqld_multi': mysqld-multi.

   * The Unix socket file and the TCP/IP port number must be different
     for every *Note `mysqld': mysqld.  (Alternatively, if the host has
     multiple network addresses, you can use `--bind-address' to cause
     different servers to listen to different interfaces.)

   * The `--pid-file' option is very important if you are using *Note
     `mysqld_safe': mysqld-safe. to start *Note `mysqld': mysqld. (for
     example, `--mysqld=mysqld_safe') Every *Note `mysqld': mysqld.
     should have its own process ID file. The advantage of using *Note
     `mysqld_safe': mysqld-safe. instead of *Note `mysqld': mysqld. is
     that *Note `mysqld_safe': mysqld-safe. monitors its *Note
     `mysqld': mysqld. process and restarts it if the process
     terminates due to a signal sent using `kill -9' or for other
     reasons, such as a segmentation fault. Please note that the *Note
     `mysqld_safe': mysqld-safe.  script might require that you start
     it from a certain place.  This means that you might have to change
     location to a certain directory before running *Note
     `mysqld_multi': mysqld-multi. If you have problems starting,
     please see the *Note `mysqld_safe': mysqld-safe.  script. Check
     especially the lines:


          ----------------------------------------------------------------
          MY_PWD=`pwd`
          # Check if we are starting this relative (for the binary release)
          if test -d $MY_PWD/data/mysql -a \
             -f ./share/mysql/english/errmsg.sys -a \
             -x ./bin/mysqld
          ----------------------------------------------------------------

     The test performed by these lines should be successful, or you
     might encounter problems. See *Note mysqld-safe::.

   * You might want to use the `--user' option for *Note `mysqld':
     mysqld, but to do this you need to run the *Note `mysqld_multi':
     mysqld-multi. script as the Unix superuser (`root'). Having the
     option in the option file doesn't matter; you just get a warning if
     you are not the superuser and the *Note `mysqld': mysqld.
     processes are started under your own Unix account.

The following example shows how you might set up an option file for use
with *Note `mysqld_multi': mysqld-multi. The order in which the *Note
`mysqld': mysqld. programs are started or stopped depends on the order
in which they appear in the option file.  Group numbers need not form
an unbroken sequence. The first and fifth `[mysqldN]' groups were
intentionally omitted from the example to illustrate that you can have
`gaps' in the option file. This gives you more flexibility.


     # This file should probably be in your home dir (~/.my.cnf)
     # or /etc/my.cnf
     # Version 2.1 by Jani Tolonen

     [mysqld_multi]
     mysqld     = /usr/local/bin/mysqld_safe
     mysqladmin = /usr/local/bin/mysqladmin
     user       = multi_admin
     password   = multipass

     [mysqld2]
     socket     = /tmp/mysql.sock2
     port       = 3307
     pid-file   = /usr/local/mysql/var2/hostname.pid2
     datadir    = /usr/local/mysql/var2
     language   = /usr/local/share/mysql/english
     user       = john

     [mysqld3]
     socket     = /tmp/mysql.sock3
     port       = 3308
     pid-file   = /usr/local/mysql/var3/hostname.pid3
     datadir    = /usr/local/mysql/var3
     language   = /usr/local/share/mysql/swedish
     user       = monty

     [mysqld4]
     socket     = /tmp/mysql.sock4
     port       = 3309
     pid-file   = /usr/local/mysql/var4/hostname.pid4
     datadir    = /usr/local/mysql/var4
     language   = /usr/local/share/mysql/estonia
     user       = tonu

     [mysqld6]
     socket     = /tmp/mysql.sock6
     port       = 3311
     pid-file   = /usr/local/mysql/var6/hostname.pid6
     datadir    = /usr/local/mysql/var6
     language   = /usr/local/share/mysql/japanese
     user       = jani

See *Note option-files::.


File: manual.info,  Node: programs-installation,  Next: programs-client,  Prev: programs-server,  Up: programs

4.4 MySQL Installation-Related Programs
=======================================

* Menu:

* comp-err::                     `comp_err' --- Compile MySQL Error Message File
* make-win-bin-dist::            `make_win_bin_dist' --- Package MySQL Distribution as Zip Archive
* mysqlbug::                     `mysqlbug' --- Generate Bug Report
* mysql-fix-privilege-tables::   `mysql_fix_privilege_tables' --- Upgrade MySQL System Tables
* mysql-install-db::             `mysql_install_db' --- Initialize MySQL Data Directory
* mysql-secure-installation::    `mysql_secure_installation' --- Improve MySQL Installation Security
* mysql-tzinfo-to-sql::          `mysql_tzinfo_to_sql' --- Load the Time Zone Tables
* mysql-upgrade::                `mysql_upgrade' --- Check and Upgrade MySQL Tables

The programs in this section are used when installing or upgrading
MySQL.


File: manual.info,  Node: comp-err,  Next: make-win-bin-dist,  Prev: programs-installation,  Up: programs-installation

4.4.1 `comp_err' -- Compile MySQL Error Message File
----------------------------------------------------

*Note `comp_err': comp-err. creates the `errmsg.sys' file that is used
by *Note `mysqld': mysqld. to determine the error messages to display
for different error codes. *Note `comp_err': comp-err.  normally is run
automatically when MySQL is built. It compiles the `errmsg.sys' file
from the plaintext file located at `sql/share/errmsg.txt' in MySQL
source distributions.

*Note `comp_err': comp-err. also generates `mysqld_error.h',
`mysqld_ername.h', and `sql_state.h' header files.

For more information about how error messages are defined, see the
MySQL Internals Manual (http://dev.mysql.com/doc/internals/en).

Invoke *Note `comp_err': comp-err. like this:


     shell> comp_err [OPTIONS]

*Note `comp_err': comp-err. supports the following options.

   * `--help', `-?'

     Display a help message and exit.

   * `--charset=PATH', `-C PATH'

     The character set directory. The default is
     `../sql/share/charsets'.

   * `--debug=DEBUG_OPTIONS', `-# DEBUG_OPTIONS'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:O,FILE_NAME'.  The default is `d:t:O,/tmp/comp_err.trace'.

   * `--debug-info', `-T'

     Print some debugging information when the program exits.

   * `--header_file=FILE_NAME', `-H FILE_NAME'

     The name of the error header file. The default is `mysqld_error.h'.

   * `--in_file=FILE_NAME', `-F FILE_NAME'

     The name of the input file. The default is
     `../sql/share/errmsg.txt'.

   * `--name_file=FILE_NAME', `-N FILE_NAME'

     The name of the error name file. The default is `mysqld_ername.h'.

   * `--out_dir=PATH', `-D PATH'

     The name of the output base directory. The default is
     `../sql/share/'.

   * `--out_file=FILE_NAME', `-O FILE_NAME'

     The name of the output file. The default is `errmsg.sys'.

   * `--statefile=FILE_NAME', `-S FILE_NAME'

     The name for the SQLSTATE header file. The default is
     `sql_state.h'.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: make-win-bin-dist,  Next: mysqlbug,  Prev: comp-err,  Up: programs-installation

4.4.2 `make_win_bin_dist' -- Package MySQL Distribution as Zip Archive
----------------------------------------------------------------------

This script is used on Windows after building a MySQL distribution from
source to create executable programs. It packages the binaries and
support files into a Zip archive that can be unpacked at the location
where you want to install MySQL.

*Note `make_win_bin_dist': make-win-bin-dist. is a shell script, so you
must have Cygwin installed to use it.

This program's use is subject to change. Currently, you invoke it as
follows from the root directory of your source distribution:


     shell> make_win_bin_dist [OPTIONS] PACKAGE_BASENAME [COPY_DEF ...]

The PACKAGE_BASENAME argument provides the basename for the resulting
Zip archive. This name will be the name of the directory that results
from unpacking the archive.

Because you might want to include files of directories from other
builds, you can instruct this script to copy them in for you, using
COPY_DEF arguments, which have the form RELATIVE_DEST_NAME=SOURCE_NAME.

Example:


     bin/mysqld-max.exe=../my-max-build/sql/release/mysqld.exe

If you specify a directory, the entire directory will be copied.

*Note `make_win_bin_dist': make-win-bin-dist. supports the following
options.

   * `--debug'

     Pack the debug binaries and produce an error if they were not
     built.

   * `--embedded'

     Pack the embedded server and produce an error if it was not built.
     The default is to pack it if it was built.

   * `--exe-suffix=SUFFIX'

     Add a suffix to the basename of the *Note `mysql': mysql.  binary.
     For example, a suffix of `-abc' produces a binary named
     `mysqld-abc.exe'.

   * `--no-debug'

     Do not pack the debug binaries even if they were built.

   * `--no-embedded'

     Do not pack the embedded server even if it was built.

   * `--only-debug'

     Use this option when the target for this build was `Debug', and
     you just want to replace the normal binaries with debug versions
     (that is, do not use separate `debug' directories).


File: manual.info,  Node: mysqlbug,  Next: mysql-fix-privilege-tables,  Prev: make-win-bin-dist,  Up: programs-installation

4.4.3 `mysqlbug' -- Generate Bug Report
---------------------------------------

This program enables you to generate a bug report and send it to Oracle
Corporation. It is a shell script and runs on Unix.

The normal way to report bugs is to visit `http://bugs.mysql.com/',
which is the address for our bugs database. This database is public and
can be browsed and searched by anyone. If you log in to the system, you
can enter new reports. If you have no Web access, you can generate a
bug report by using the *Note `mysqlbug': mysqlbug. script.

*Note `mysqlbug': mysqlbug. helps you generate a report by determining
much of the following information automatically, but if something
important is missing, please include it with your message. *Note
`mysqlbug': mysqlbug. can be found in the `scripts' directory (source
distribution) and in the `bin' directory under your MySQL installation
directory (binary distribution).

Invoke *Note `mysqlbug': mysqlbug. without arguments:


     shell> mysqlbug

The script will place you in an editor with a copy of the report to be
sent. Edit the lines near the beginning that indicate the nature of the
problem. Then write the file to save your changes, quit the editor, and
*Note `mysqlbug': mysqlbug. will send the report by email.


File: manual.info,  Node: mysql-fix-privilege-tables,  Next: mysql-install-db,  Prev: mysqlbug,  Up: programs-installation

4.4.4 `mysql_fix_privilege_tables' -- Upgrade MySQL System Tables
-----------------------------------------------------------------

*Note*:

In MySQL 5.1.7, *Note `mysql_fix_privilege_tables':
mysql-fix-privilege-tables.  was superseded by *Note `mysql_upgrade':
mysql-upgrade, which should be used instead. See *Note mysql-upgrade::.

Some releases of MySQL introduce changes to the structure of the system
tables in the `mysql' database to add new privileges or support new
features. When you update to a new version of MySQL, update your system
tables as well to make sure that their structure is up to date.
Otherwise, there might be capabilities that you cannot take advantage
of.

*Note `mysql_fix_privilege_tables': mysql-fix-privilege-tables. is an
older script that previously was used to upgrade the system tables in
the `mysql' database after a MySQL upgrade.

Before running *Note `mysql_fix_privilege_tables':
mysql-fix-privilege-tables, make a backup of your `mysql' database.

On Unix or Unix-like systems, update the system tables by running the
*Note `mysql_fix_privilege_tables': mysql-fix-privilege-tables.  script:


     shell> mysql_fix_privilege_tables

You must run this script while the server is running. It attempts to
connect to the server running on the local host as `root'. If your
`root' account requires a password, indicate the password on the
command line like this:


     shell> mysql_fix_privilege_tables --password=ROOT_PASSWORD

The *Note `mysql_fix_privilege_tables': mysql-fix-privilege-tables.
script performs any actions necessary to convert your system tables to
the current format. You might see some `Duplicate column name' warnings
as it runs; you can ignore them.

After running the script, stop the server and restart it so that any
changes made to the system tables take effect.

On Windows systems, MySQL distributions include a
`mysql_fix_privilege_tables.sql' SQL script that you can run using the
*Note `mysql': mysql. client. For example, if your MySQL installation
is located at `C:\Program Files\MySQL\MySQL Server 5.1', the commands
look like this:


     C:\> cd "C:\Program Files\MySQL\MySQL Server 5.1"
     C:\> bin\mysql -u root -p mysql
     mysql> SOURCE share/mysql_fix_privilege_tables.sql

*Note*:

Prior to version 5.1.17, the `mysql_fix_privilege_tables.sql' script is
found in the `scripts' directory.

The *Note `mysql': mysql. command will prompt you for the `root'
password; enter it when prompted.

If your installation is located in some other directory, adjust the
path names appropriately.

As with the Unix procedure, you might see some `Duplicate column name'
warnings as *Note `mysql': mysql. processes the statements in the
`mysql_fix_privilege_tables.sql' script; you can ignore them.

After running the script, stop the server and restart it.


File: manual.info,  Node: mysql-install-db,  Next: mysql-secure-installation,  Prev: mysql-fix-privilege-tables,  Up: programs-installation

4.4.5 `mysql_install_db' -- Initialize MySQL Data Directory
-----------------------------------------------------------

*Note `mysql_install_db': mysql-install-db. initializes the MySQL data
directory and creates the system tables that it contains, if they do
not exist. *Note `mysql_install_db': mysql-install-db. is a shell
script and is available only on Unix platforms.

To invoke *Note `mysql_install_db': mysql-install-db, use the following
syntax:


     shell> mysql_install_db [OPTIONS]

Because the MySQL server, *Note `mysqld': mysqld, must access the data
directory when it runs later, you should either run *Note
`mysql_install_db': mysql-install-db. from the same system account that
will be used for running *Note `mysqld': mysqld, or run it as `root'
and specify the `--user' option to indicate the user name that *Note
`mysqld': mysqld. will run as. It might be necessary to specify other
options such as `--basedir' or `--datadir' if *Note `mysql_install_db':
mysql-install-db. does not use the correct locations for the
installation directory or data directory. For example:


     shell> bin/mysql_install_db --user=mysql \
              --basedir=/opt/mysql/mysql \
              --datadir=/opt/mysql/mysql/data

*Note `mysql_install_db': mysql-install-db. needs to invoke *Note
`mysqld': mysqld. with the `--bootstrap' and `--skip-grant-tables'
options. If MySQL was configured with the `--disable-grant-options'
option, `--bootstrap' and `--skip-grant-tables' will be disabled (see
*Note source-configuration-options::).  To handle this, set the
`MYSQLD_BOOTSTRAP' environment variable to the full path name of a
server that has all options enabled. *Note `mysql_install_db':
mysql-install-db. will use that server.

*Note*:

If you have set a custom `TMPDIR' environment variable when performing
the installation, and the specified directory is not accessible, *Note
`mysql_install_db': mysql-install-db. may fail. If so, unset `TMPDIR'
or set `TMPDIR' to point to the system temporary directory (usually
`/tmp').

*Note `mysql_install_db': mysql-install-db. supports the following
options, which can be specified on the command line or in the
`[mysql_install_db]' group of an option file.  (Options that are common
to *Note `mysqld': mysqld. can also be specified in the `[mysqld]'
group.) Other options are passed to *Note `mysqld': mysqld. For
information about option files used by MySQL programs, see *Note
option-files::.  *Note `mysql_install_db': mysql-install-db. also
supports the options for processing option files described at *Note
option-file-options::.

   * `--help'

     Display a help message and exit.

   * `--basedir=PATH'

     The path to the MySQL installation directory.

   * `--builddir=PATH'

     For use with `--srcdir' and out-of-source builds. Set this to the
     location of the directory where the built files reside.

   * `--cross-bootstrap'

     For internal use. This option is used for building system tables
     on one host intended for another.

   * `--datadir=PATH'

     The path to the MySQL data directory.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is interpreted
     relative to the current directory if given as a relative path name
     rather than a full path name.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is interpreted
     relative to the current directory if given as a relative path name
     rather than a full path name.

   * `--force'

     Cause *Note `mysql_install_db': mysql-install-db. to run even if
     DNS does not work. Grant table entries normally created using host
     names will use IP addresses instead.

   * `--ldata=PATH'

     A synonym for `--datadir'.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--rpm'

     For internal use. This option is used during the MySQL
     installation process for install operations performed using RPM
     packages.

   * `--skip-name-resolve'

     Use IP addresses rather than host names when creating grant table
     entries. This option can be useful if your DNS does not work.

   * `--srcdir=PATH'

     For internal use. This option specifies the directory under which
     *Note `mysql_install_db': mysql-install-db. looks for support
     files such as the error message file and the file for populating
     the help tables. This option was added in MySQL 5.1.14.

   * `--user=USER_NAME'

     The system (login) user name to use for running *Note `mysqld':
     mysqld. Files and directories created by *Note `mysqld': mysqld.
     will be owned by this user. You must be the system `root' user to
     use this option. By default, *Note `mysqld': mysqld. runs using
     your current login name and files and directories that it creates
     will be owned by you.

   * `--verbose'

     Verbose mode. Print more information about what the program does.

   * `--windows'

     For internal use. This option is used for creating Windows
     distributions.


File: manual.info,  Node: mysql-secure-installation,  Next: mysql-tzinfo-to-sql,  Prev: mysql-install-db,  Up: programs-installation

4.4.6 `mysql_secure_installation' -- Improve MySQL Installation Security
------------------------------------------------------------------------

This program enables you to improve the security of your MySQL
installation in the following ways:

   * You can set a password for `root' accounts.

   * You can remove `root' accounts that are accessible from outside
     the local host.

   * You can remove anonymous-user accounts.

   * You can remove the `test' database (which by default can be
     accessed by all users, even anonymous users), and privileges that
     permit anyone to access databases with names that start with
     `test_'.

*Note `mysql_secure_installation': mysql-secure-installation. helps you
implement security recommendations similar to those described at *Note
default-privileges::.

Invoke *Note `mysql_secure_installation': mysql-secure-installation.
without arguments:


     shell> mysql_secure_installation

When executed, the script prompts you to determine which actions to
perform.


File: manual.info,  Node: mysql-tzinfo-to-sql,  Next: mysql-upgrade,  Prev: mysql-secure-installation,  Up: programs-installation

4.4.7 `mysql_tzinfo_to_sql' -- Load the Time Zone Tables
--------------------------------------------------------

The *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. program loads the
time zone tables in the `mysql' database. It is used on systems that
have a _zoneinfo_ database (the set of files describing time zones).
Examples of such systems are Linux, FreeBSD, Solaris, and Mac OS X. One
likely location for these files is the `/usr/share/zoneinfo' directory
(`/usr/share/lib/zoneinfo' on Solaris). If your system does not have a
zoneinfo database, you can use the downloadable package described in
*Note time-zone-support::.

*Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. can be invoked several
ways:


     shell> mysql_tzinfo_to_sql TZ_DIR
     shell> mysql_tzinfo_to_sql TZ_FILE TZ_NAME
     shell> mysql_tzinfo_to_sql --leap TZ_FILE

For the first invocation syntax, pass the zoneinfo directory path name
to *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. and send the
output into the *Note `mysql': mysql. program. For example:


     shell> mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root mysql

*Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. reads your system's
time zone files and generates SQL statements from them.  *Note `mysql':
mysql. processes those statements to load the time zone tables.

The second syntax causes *Note `mysql_tzinfo_to_sql':
mysql-tzinfo-to-sql.  to load a single time zone file TZ_FILE that
corresponds to a time zone name TZ_NAME:


     shell> mysql_tzinfo_to_sql TZ_FILE TZ_NAME | mysql -u root mysql

If your time zone needs to account for leap seconds, invoke *Note
`mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. using the third syntax,
which initializes the leap second information.  TZ_FILE is the name of
your time zone file:


     shell> mysql_tzinfo_to_sql --leap TZ_FILE | mysql -u root mysql

After running *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql, it is
best to restart the server so that it does not continue to use any
previously cached time zone data.


File: manual.info,  Node: mysql-upgrade,  Prev: mysql-tzinfo-to-sql,  Up: programs-installation

4.4.8 `mysql_upgrade' -- Check and Upgrade MySQL Tables
-------------------------------------------------------

*Note `mysql_upgrade': mysql-upgrade. examines all tables in all
databases for incompatibilities with the current version of MySQL
Server. *Note `mysql_upgrade': mysql-upgrade. also upgrades the system
tables so that you can take advantage of new privileges or capabilities
that might have been added.

If *Note `mysql_upgrade': mysql-upgrade. finds that a table has a
possible incompatibility, it performs a table check and, if problems
are found, attempts a table repair. If the table cannot be repaired,
see *Note rebuilding-tables:: for manual table repair strategies.

You should execute *Note `mysql_upgrade': mysql-upgrade. each time you
upgrade MySQL. It supersedes the older *Note
`mysql_fix_privilege_tables': mysql-fix-privilege-tables. script, which
should no longer be used.

If you install MySQL from RPM packages on Linux, you must install the
server and client RPMs.  *Note `mysql_upgrade': mysql-upgrade. is
included in the server RPM but requires the client RPM because the
latter includes *Note `mysqlcheck': mysqlcheck. (See *Note
linux-installation-rpm::.)

*Note*:

On Windows Server 2008, Vista, and newer, you must run *Note
`mysql_upgrade': mysql-upgrade. with administrator privileges. You can
do this by running a Command Prompt as Administrator and running the
command. Failure to do so may result in the upgrade failing to execute
correctly.

*Caution*:

You should always back up your current MySQL installation _before_
performing an upgrade. See *Note backup-methods::.

Some upgrade incompatibilities may require special handling before you
upgrade your MySQL installation and run *Note `mysql_upgrade':
mysql-upgrade. See *Note upgrading::, for instructions on determining
whether any such incompatibilities apply to your installation and how
to handle them.

To use *Note `mysql_upgrade': mysql-upgrade, make sure that the server
is running. Then invoke it like this:


     shell> mysql_upgrade [OPTIONS]

After running *Note `mysql_upgrade': mysql-upgrade, stop the server and
restart it so that any changes made to the system tables take effect.

If you have multiple MySQL server instances running, invoke *Note
`mysql_upgrade': mysql-upgrade. with connection parameters appropriate
for connecting to the desired server. For example, with servers running
on the local host on parts 3306 through 3308, upgrade each of them by
connecting to the appropriate port:


     shell> mysql_upgrade --protocol=tcp -P 3306 [OTHER_OPTIONS]
     shell> mysql_upgrade --protocol=tcp -P 3307 [OTHER_OPTIONS]
     shell> mysql_upgrade --protocol=tcp -P 3308 [OTHER_OPTIONS]

For local host connections on Unix, the `--protocol=tcp' option forces
a connection using TCP/IP rather than the Unix socket file.

*Note `mysql_upgrade': mysql-upgrade. executes the following commands
to check and repair tables and to upgrade the system tables:


     mysqlcheck --no-defaults --all-databases --fix-db-names --fix-table-names
     mysqlcheck --no-defaults --check-upgrade --all-databases --auto-repair
     mysql < FIX_PRIV_TABLES

Notes about the preceding commands:

   * *Note `mysql_upgrade': mysql-upgrade. also adds `--write-binlog' or
     `--skip-write-binlog' to the *Note `mysqlcheck': mysqlcheck.
     commands, depending on whether the `--write-binlog' option was
     specified on the *Note `mysql_upgrade': mysql-upgrade.  command.

   * Because *Note `mysql_upgrade': mysql-upgrade. invokes *Note
     `mysqlcheck': mysqlcheck. with the `--all-databases' option, it
     processes all tables in all databases, which might take a long
     time to complete. Each table is locked and therefore unavailable
     to other sessions while it is being processed.  Check and repair
     operations can be time-consuming, particularly for large tables.

   * For details about what checks the `--check-upgrade' option
     entails, see the description of the `FOR UPGRADE' option of the
     *Note `CHECK TABLE': check-table. statement (see *Note
     check-table::).

   * FIX_PRIV_TABLES represents a script generated internally by *Note
     `mysql_upgrade': mysql-upgrade. that contains SQL statements to
     upgrade the tables in the `mysql' database.

   * Prior to MySQL 5.1.31, *Note `mysql_upgrade': mysql-upgrade. does
     not run the second *Note `mysqlcheck': mysqlcheck. command, which
     is necessary to re-encode database or table names that contain
     nonalphanumeric characters. (They still appear after the upgrade
     with the `#mysql50#' prefix described in *Note
     identifier-mapping::.) If you have such database or table names,
     execute the second *Note `mysqlcheck': mysqlcheck. command
     manually after executing *Note `mysql_upgrade': mysql-upgrade.

All checked and repaired tables are marked with the current MySQL
version number. This ensures that next time you run *Note
`mysql_upgrade': mysql-upgrade. with the same version of the server, it
can tell whether there is any need to check or repair the table again.

*Note `mysql_upgrade': mysql-upgrade. also saves the MySQL version
number in a file named `mysql_upgrade_info' in the data directory. This
is used to quickly check whether all tables have been checked for this
release so that table-checking can be skipped. To ignore this file and
perform the check regardless, use the `--force' option.

In MySQL 5.1.7, `mysql_upgrade ' was added as a shell script and worked
only for Unix systems. As of MySQL 5.1.10, *Note `mysql_upgrade':
mysql-upgrade. is an executable binary and is available on all systems.

*Note `mysql_upgrade': mysql-upgrade. does not upgrade the contents of
the help tables. For upgrade instructions, see *Note
server-side-help-support::.

*Note `mysql_upgrade': mysql-upgrade. supports the following options,
which can be specified on the command line or in the `[mysql_upgrade]'
and `[client]' groups of an option file.  Unrecognized options are
passed to *Note `mysqlcheck': mysqlcheck. For information about option
files, see *Note option-files::.

   * `--help'

     Display a short help message and exit.

   * `--basedir=DIR_NAME'

     The path to the MySQL installation directory. This option is
     accepted for backward compatibility but ignored.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::. This option was added in MySQL 5.1.13.

   * `--compress'

     Compress all information sent between the client and the server if
     both support compression. This option was added in MySQL 5.1.13.

   * `--datadir=DIR_NAME'

     The path to the data directory. This option is accepted for
     backward compatibility but ignored.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is
     `d:t:O,/tmp/mysql_upgrade.trace'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info', `-T'

     Print some debugging information when the program exits.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set. See *Note
     charset-configuration::.  This option was added in MySQL 5.1.13.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note
     `mysql_upgrade': mysql-upgrade. normally reads the `[client]' and
     `[mysql_upgrade]' groups. If the `--defaults-group-suffix=_other'
     option is given, *Note `mysql_upgrade': mysql-upgrade. also reads
     the `[client_other]' and `[mysql_upgrade_other]' groups.

   * `--force'

     Ignore the `mysql_upgrade_info' file and force execution even if
     *Note `mysql_upgrade': mysql-upgrade. has already been executed
     for the current version of MySQL.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Connect to the MySQL server on the given host. This option was
     added in MySQL 5.1.13.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can be
     used to prevent them from being read.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysql_upgrade': mysql-upgrade. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections. This
     option was added in MySQL 5.1.13.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections. This option was added in MySQL
     5.1.13.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::. These options were added in
     MySQL 5.1.13.

   * `--tmpdir=DIR_NAME', `-t PATH'

     The path name of the directory to use for creating temporary
     files. This option was added in MySQL 5.1.25.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.  The
     default user name is `root'.

   * `--verbose'

     Verbose mode. Print more information about what the program does.

   * `--write-binlog'

     Cause binary logging to be enabled while *Note `mysql_upgrade':
     mysql-upgrade. runs. This is the default behavior; to disable
     binary logging during the upgrade, use the inverse of this option
     (that is, start the program with `--skip-write-binlog').

     This option was introduced in MySQL 5.1.40.


File: manual.info,  Node: programs-client,  Next: programs-admin-utils,  Prev: programs-installation,  Up: programs

4.5 MySQL Client Programs
=========================

* Menu:

* mysql::                        `mysql' --- The MySQL Command-Line Tool
* mysqladmin::                   `mysqladmin' --- Client for Administering a MySQL Server
* mysqlcheck::                   `mysqlcheck' --- A Table Maintenance Program
* mysqldump::                    `mysqldump' --- A Database Backup Program
* mysqlimport::                  `mysqlimport' --- A Data Import Program
* mysqlshow::                    `mysqlshow' --- Display Database, Table, and Column Information
* mysqlslap::                    `mysqlslap' --- Load Emulation Client

This section describes client programs that connect to the MySQL server.


File: manual.info,  Node: mysql,  Next: mysqladmin,  Prev: programs-client,  Up: programs-client

4.5.1 `mysql' -- The MySQL Command-Line Tool
--------------------------------------------

* Menu:

* mysql-command-options::        mysql Options
* mysql-commands::               mysql Commands
* mysql-logging::                mysql Logging
* mysql-server-side-help::       mysql Server-Side Help
* mysql-batch-commands::         Executing SQL Statements from a Text File
* mysql-tips::                   mysql Tips

*Note `mysql': mysql. is a simple SQL shell with input line editing
capabilities. It supports interactive and noninteractive use. When used
interactively, query results are presented in an ASCII-table format.
When used noninteractively (for example, as a filter), the result is
presented in tab-separated format. The output format can be changed
using command options.

If you have problems due to insufficient memory for large result sets,
use the `--quick' option. This forces *Note `mysql': mysql. to retrieve
results from the server a row at a time rather than retrieving the
entire result set and buffering it in memory before displaying it. This
is done by returning the result set using the *Note
`mysql_use_result()': mysql-use-result. C API function in the
client/server library rather than *Note `mysql_store_result()':
mysql-store-result.

Using *Note `mysql': mysql. is very easy. Invoke it from the prompt of
your command interpreter as follows:


     shell> mysql DB_NAME

Or:


     shell> mysql --user=USER_NAME --password=YOUR_PASSWORD DB_NAME

Then type an SQL statement, end it with ``;'', `\g', or `\G' and press
Enter.

As of MySQL 5.1.10, typing `Control+C' causes *Note `mysql': mysql. to
attempt to kill the current statement. If this cannot be done, or
`Control+C' is typed again before the statement is killed, *Note
`mysql': mysql. exits. Previously, `Control+C' caused *Note `mysql':
mysql. to exit in all cases.

You can execute SQL statements in a script file (batch file) like this:


     shell> mysql DB_NAME < SCRIPT.SQL > OUTPUT.TAB

On Unix, the *Note `mysql': mysql. client logs statements executed
interactively to a history file. See *Note mysql-logging::.


File: manual.info,  Node: mysql-command-options,  Next: mysql-commands,  Prev: mysql,  Up: mysql

4.5.1.1 mysql Options
.....................

*Note `mysql': mysql. supports the following options, which can be
specified on the command line or in the `[mysql]' and `[client]' groups
of an option file. For information about option files used by MySQL
programs, see *Note option-files::.

*`mysql' Options*

Format             Description                      Introduced
-auto-rehash       Enable automatic rehashing       
-batch             Don't use history file           
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-character-sets-dir=pathDirectory where character sets   
                   are installed                    
-column-names      Write column names in results    
-column-type-info  Display result set metadata      5.1.14
-comments          Whether to retain or strip       5.1.23
                   comments in statements sent to   
                   the server                       
-compress          Compress all information sent    
                   between client and server        
-connect_timeout=valueNumber of seconds before         
                   connection timeout               
-database=dbname   The database to use              
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     
                   memory, and CPU statistics when  
                   program exits                    
-default-character-set=charset_nameSpecify default character set    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-delimiter=str     Set the statement delimiter      
-execute=statement Execute the statement and quit   
-force             Continue even if an SQL error    
                   occurs                           
-help              Display help message and exit    
-host=host_name    Connect to MySQL server on       
                   given host                       
-html              Produce HTML output              
-ignore-spaces     Ignore spaces after function     
                   names                            
-line-numbers      Write line numbers for errors    
-local-infile[={0|1}]Enable or disable for LOCAL      
                   capability for LOAD DATA INFILE  
-max_allowed_packet=valueMaximum packet length to send    
                   to or receive from server        
-max_join_size=valueThe automatic limit for rows in  
                   a join when using -safe-updates  
-named-commands    Enable named mysql commands      
-net_buffer_length=valueBuffer size for TCP/IP and       
                   socket communication             
-no-auto-rehash    Disable automatic rehashing      
-no-beep           Do not beep when errors occur    
-no-defaults       Read no option files             
-no-named-commands Disable named mysql commands     
-no-pager          Deprecated form of -skip-pager   
-no-tee            Do not copy output to a file     
-one-database      Ignore statements except those   
                   for the default database named   
                   on the command line              
-pager[=command]   Use the given command for        
                   paging query output              
-password[=password]Password to use when connecting  
                   to server                        
-pipe              On Windows, connect to server    
                   using named pipe                 
-port=port_num     TCP/IP port number to use for    
                   connection                       
-print-defaults    Print defaults                   
-prompt=format_str Set the prompt to the specified  
                   format                           
-protocol=type     Connection protocol to use       
-quick             Do not cache each query result   
-raw               Write column values without      
                   escape conversion                
-reconnect         If the connection to the server  
                   is lost, automatically try to    
                   reconnect                        
-safe-updates      Allow only UPDATE and DELETE     
                   statements that specify key      
                   values                           
-secure-auth       Do not send passwords to the     
                   server in old (pre-4.1.1) format 
-select_limit=valueThe automatic limit for SELECT   
                   statements when using            
                   -safe-updates                    
-shared-memory-base-name=nameThe name of shared memory to     
                   use for shared-memory            
                   connections                      
-show-warnings     Show warnings after each         
                   statement if there are any       
-sigint-ignore     Ignore SIGINT signals            
                   (typically the result of typing  
                   Control+C)                       
-silent            Silent mode                      
-skip-auto-rehash  Disable automatic rehashing      
-skip-column-names Do not write column names in     
                   results                          
-skip-line-numbers Skip line numbers for errors     
-skip-named-commandsDisable named mysql commands     
-skip-pager        Disable paging                   
-skip-reconnect    Disable reconnecting             
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-ssl               Enable SSL for connection        
-ssl-ca=file_name  Path of file that contains list  
                   of trusted SSL CAs               
-ssl-capath=dir_namePath of directory that contains  
                   trusted SSL CA certificates in   
                   PEM format                       
-ssl-cert=file_namePath of file that contains X509  
                   certificate in PEM format        
-ssl-cipher=cipher_listList of permitted ciphers to     
                   use for SSL encryption           
-ssl-key=file_name Path of file that contains X509  
                   key in PEM format                
-ssl-verify-server-certVerify server Common Name value  5.1.11
                   in its certificate against host  
                   name used when connecting to     
                   server                           
-table             Display output in tabular format 
-tee=file_name     Append a copy of output to       
                   named file                       
-unbuffered        Flush the buffer after each      
                   query                            
-user=user_name    MySQL user name to use when      
                   connecting to server             
-verbose           Verbose mode                     
-version           Display version information and  
                   exit                             
-vertical          Print query output rows          
                   vertically (one line per column  
                   value)                           
-wait              If the connection cannot be      
                   established, wait and retry      
                   instead of aborting              
-xml               Produce XML output               

   * `--help', `-?'

     Display a help message and exit.

   * `--auto-rehash'

     Enable automatic rehashing. This option is on by default, which
     enables database, table, and column name completion.  Use
     `--disable-auto-rehash' to disable rehashing. That causes *Note
     `mysql': mysql.  to start faster, but you must issue the `rehash'
     command or its `\#' shortcut if you want to use name completion.

     To complete a name, enter the first part and press Tab. If the
     name is unambiguous, *Note `mysql': mysql. completes it.
     Otherwise, you can press Tab again to see the possible names that
     begin with what you have typed so far. Completion does not occur
     if there is no default database.

     *Note*:

     This feature requires a MySQL client that is compiled with the
     *readline* library.  Typically, the *readline* library is not
     available on Windows.

   * `--batch', `-B'

     Print results using tab as the column separator, with each row on
     a new line. With this option, *Note `mysql': mysql. does not use
     the history file.

     Batch mode results in nontabular output format and escaping of
     special characters. Escaping may be disabled by using raw mode;
     see the description for the `--raw' option.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, use this option
     to select which interface to use for connecting to the MySQL
     server.

     This option is supported only in the version of the *Note `mysql':
     mysql. client that is supplied with MySQL Cluster, beginning with
     MySQL Cluster NDB 6.3.4. It is not available in standard MySQL 5.1
     releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--column-names'

     Write column names in results.

   * `--column-type-info', `-m'

     Display result set metadata. This option was added in MySQL
     5.1.14. (Before that, use `--debug-info'.) The `-m' short option
     was added in MySQL 5.1.21.

   * `--comments', `-c'

     Whether to preserve comments in statements sent to the server. The
     default is -skip-comments (discard comments), enable with
     -comments (preserve comments). This option was added in MySQL
     5.1.23.

   * `--compress', `-C'

     Compress all information sent between the client and the server if
     both support compression.

   * `--database=DB_NAME', `-D DB_NAME'

     The database to use. This is useful primarily in an option file.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o,/tmp/mysql.trace'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info', `-T'

     Before MySQL 5.1.14, this option prints debugging information and
     memory and CPU usage statistics when the program exits, and also
     causes display of result set metadata during execution. As of
     MySQL 5.1.14, use `--column-type-info' to display result set
     metadata.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set for the client and
     connection.

     A common issue that can occur when the operating system uses
     `utf8' or another multibyte character set is that output from the
     *Note `mysql': mysql. client is formatted incorrectly, due to the
     fact that the MySQL client uses the `latin1' character set by
     default.  You can usually fix such issues by using this option to
     force the client to use the system character set instead.

     See *Note charset-configuration::, for more information.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysql':
     mysql. normally reads the `[client]' and `[mysql]' groups. If the
     `--defaults-group-suffix=_other' option is given, *Note `mysql':
     mysql. also reads the `[client_other]' and `[mysql_other]' groups.

   * `--delimiter=STR'

     Set the statement delimiter. The default is the semicolon
     character (``;'').

   * `--disable-named-commands'

     Disable named commands. Use the `\*' form only, or use named
     commands only at the beginning of a line ending with a semicolon
     (``;'').  *Note `mysql': mysql. starts with this option _enabled_
     by default. However, even with this option, long-format commands
     still work from the first line. See *Note mysql-commands::.

   * `--execute=STATEMENT', `-e STATEMENT'

     Execute the statement and quit. The default output format is like
     that produced with `--batch'. See *Note command-line-options::,
     for some examples.  With this option, *Note `mysql': mysql. does
     not use the history file.

   * `--force', `-f'

     Continue even if an SQL error occurs.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--html', `-H'

     Produce HTML output.

   * `--ignore-spaces', `-i'

     Ignore spaces after function names. The effect of this is
     described in the discussion for the `IGNORE_SPACE' SQL mode (see
     *Note sql-mode::).

   * `--line-numbers'

     Write line numbers for errors. Disable this with
     `--skip-line-numbers'.

   * `--local-infile[={0|1}]'

     Enable or disable `LOCAL' capability for *Note `LOAD DATA INFILE':
     load-data. With no value, the option enables `LOCAL'. The option
     may be given as `--local-infile=0' or `--local-infile=1' to
     explicitly disable or enable `LOCAL'. Enabling `LOCAL' has no
     effect if the server does not also support it.

   * `--named-commands', `-G'

     Enable named *Note `mysql': mysql. commands. Long-format commands
     are permitted, not just short-format commands. For example, `quit'
     and `\q' both are recognized. Use `--skip-named-commands' to
     disable named commands. See *Note mysql-commands::.

   * `--no-auto-rehash', `-A'

     This has the same effect as `--skip-auto-rehash'.  See the
     description for `--auto-rehash'.

   * `--no-beep', `-b'

     Do not beep when errors occur.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--no-named-commands', `-g'

     Deprecated, use `--disable-named-commands' instead.
     `--no-named-commands' is removed in MySQL 5.5.

   * `--no-pager'

     Deprecated form of `--skip-pager'.  See the `--pager' option.
     `--no-pager' is removed in MySQL 5.5.

   * `--no-tee'

     Deprecated form of `--skip-tee'.  See the `--tee' option.
     `--no-tee' is removed in MySQL 5.5.

   * `--one-database', `-o'

     Ignore statements except those that occur while the default
     database is the one named on the command line. This option is
     rudimentary and should be used with care. Statement filtering is
     based only on *Note `USE': use. statements.

     Initially, *Note `mysql': mysql. executes statements in the input
     because specifying a database DB_NAME on the command line is
     equivalent to inserting *Note `USE DB_NAME': use. at the beginning
     of the input. Then, for each *Note `USE': use. statement
     encountered, *Note `mysql': mysql. accepts or rejects following
     statements depending on whether the database named is the one on
     the command line. The content of the statements is immaterial.

     Suppose that *Note `mysql': mysql. is invoked to process this set
     of statements:


          DELETE FROM db2.t2;
          USE db2;
          DROP TABLE db1.t1;
          CREATE TABLE db1.t1 (i INT);
          USE db1;
          INSERT INTO t1 (i) VALUES(1);
          CREATE TABLE db2.t1 (j INT);

     If the command line is *Note `mysql --force --one-database db1':
     mysql, *Note `mysql': mysql. handles the input as follows:

        * The *Note `DELETE': delete. statement is executed because the
          default database is `db1', even though the statement names a
          table in a different database.

        * The *Note `DROP TABLE': drop-table. and *Note `CREATE TABLE':
          create-table. statements are not executed because the default
          database is not `db1', even though the statements name a
          table in `db1'.

        * The *Note `INSERT': insert. and *Note `CREATE TABLE':
          create-table. statements are executed because the default
          database is `db1', even though the *Note `CREATE TABLE':
          create-table. statement names a table in a different database.

   * `--pager[=COMMAND]'

     Use the given command for paging query output. If the command is
     omitted, the default pager is the value of your `PAGER'
     environment variable. Valid pagers are `less', `more', `cat [>
     filename]', and so forth. This option works only on Unix and only
     in interactive mode. To disable paging, use `--skip-pager'.  *Note
     mysql-commands::, discusses output paging further.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysql': mysql. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--prompt=FORMAT_STR'

     Set the prompt to the specified format. The default is `mysql>'.
     The special sequences that the prompt can contain are described in
     *Note mysql-commands::.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--quick', `-q'

     Do not cache each query result, print each row as it is received.
     This may slow down the server if the output is suspended. With
     this option, *Note `mysql': mysql. does not use the history file.

   * `--raw', `-r'

     For tabular output, the `boxing' around columns enables one column
     value to be distinguished from another.  For nontabular output
     (such as is produced in batch mode or when the `--batch' or
     `--silent' option is given), special characters are escaped in the
     output so they can be identified easily. Newline, tab, `NUL', and
     backslash are written as `\n', `\t', `\0', and `\\'. The `--raw'
     option disables this character escaping.

     The following example demonstrates tabular versus nontabular
     output and the use of raw mode to disable escaping:


          % mysql
          mysql> SELECT CHAR(92);
          +----------+
          | CHAR(92) |
          +----------+
          | \        |
          +----------+

          % mysql -s
          mysql> SELECT CHAR(92);
          CHAR(92)
          \\

          % mysql -s -r
          mysql> SELECT CHAR(92);
          CHAR(92)
          \

   * `--reconnect'

     If the connection to the server is lost, automatically try to
     reconnect. A single reconnect attempt is made each time the
     connection is lost. To suppress reconnection behavior, use
     `--skip-reconnect'.

   * `--safe-updates', `--i-am-a-dummy', `-U'

     Permit only those *Note `UPDATE': update. and *Note `DELETE':
     delete. statements that specify which rows to modify by using key
     values. If you have set this option in an option file, you can
     override it by using `--safe-updates' on the command line. See
     *Note mysql-tips::, for more information about this option.

   * `--secure-auth'

     Do not send passwords to the server in old (pre-4.1) format.  This
     prevents connections except for servers that use the newer
     password format.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--show-warnings'

     Cause warnings to be shown after each statement if there are any.
     This option applies to interactive and batch mode.

   * `--sigint-ignore'

     Ignore `SIGINT' signals (typically the result of typing
     `Control+C').

   * `--silent', `-s'

     Silent mode. Produce less output. This option can be given
     multiple times to produce less and less output.

     This option results in nontabular output format and escaping of
     special characters. Escaping may be disabled by using raw mode;
     see the description for the `--raw' option.

   * `--skip-column-names', `-N'

     Do not write column names in results.

   * `--skip-line-numbers', `-L'

     Do not write line numbers for errors. Useful when you want to
     compare result files that include error messages.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--table', `-t'

     Display output in table format. This is the default for
     interactive use, but can be used to produce table output in batch
     mode.

   * `--tee=FILE_NAME'

     Append a copy of output to the given file. This option works only
     in interactive mode. *Note mysql-commands::, discusses tee files
     further.

   * `--unbuffered', `-n'

     Flush the buffer after each query.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose', `-v'

     Verbose mode. Produce more output about what the program does.
     This option can be given multiple times to produce more and more
     output. (For example, `-v -v -v' produces table output format even
     in batch mode.)

   * `--version', `-V'

     Display version information and exit.

   * `--vertical', `-E'

     Print query output rows vertically (one line per column value).
     Without this option, you can specify vertical output for
     individual statements by terminating them with `\G'.

   * `--wait', `-w'

     If the connection cannot be established, wait and retry instead of
     aborting.

   * `--xml', `-X'

     Produce XML output.

     *Note*:

     Prior to MySQL 5.1.12, there was no differentiation in the output
     when using this option between columns containing the `NULL' value
     and columns containing the string literal `'NULL''; both were
     represented as


          <field name="COLUMN_NAME">NULL</field>

     Beginning with MySQL 5.1.12, the output when `--xml' is used with
     *Note `mysql': mysql. matches that of *Note `mysqldump `--xml'':
     mysqldump. See *Note mysqldump:: for details.

     Beginning with MySQL 5.1.18, the XML output also uses an XML
     namespace, as shown here:


          shell> mysql --xml -uroot -e "SHOW VARIABLES LIKE 'version%'"
          <?xml version="1.0"?>

          <resultset statement="SHOW VARIABLES LIKE 'version%'" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
          <row>
          <field name="Variable_name">version</field>
          <field name="Value">5.0.40-debug</field>
          </row>

          <row>
          <field name="Variable_name">version_comment</field>
          <field name="Value">Source distribution</field>
          </row>

          <row>
          <field name="Variable_name">version_compile_machine</field>
          <field name="Value">i686</field>
          </row>

          <row>
          <field name="Variable_name">version_compile_os</field>
          <field name="Value">suse-linux-gnu</field>
          </row>
          </resultset>

     (See Bug #25946.)

You can also set the following variables by using `--VAR_NAME=VALUE'.
The `--set-variable' format is deprecated and is removed in MySQL 5.5.

   * `connect_timeout'

     The number of seconds before connection timeout. (Default value is
     `0'.)

   * `max_allowed_packet'

     The maximum size of the buffer for client/server communication.
     The default is 16MB, the maximum is 1GB.

   * `max_join_size'

     The automatic limit for rows in a join when using
     `--safe-updates'. (Default value is 1,000,000.)

   * `net_buffer_length'

     The buffer size for TCP/IP and socket communication.  (Default
     value is 16KB.)

   * `select_limit'

     The automatic limit for *Note `SELECT': select. statements when
     using `--safe-updates'. (Default value is 1,000.)


File: manual.info,  Node: mysql-commands,  Next: mysql-logging,  Prev: mysql-command-options,  Up: mysql

4.5.1.2 mysql Commands
......................

*Note `mysql': mysql. sends each SQL statement that you issue to the
server to be executed. There is also a set of commands that *Note
`mysql': mysql. itself interprets. For a list of these commands, type
`help' or `\h' at the `mysql>' prompt:


     mysql> help

     List of all MySQL commands:
     Note that all text commands must be first on line and end with ';'
     ?         (\?) Synonym for `help'.
     clear     (\c) Clear command.
     connect   (\r) Reconnect to the server. Optional arguments are db and host.
     delimiter (\d) Set statement delimiter.
     edit      (\e) Edit command with $EDITOR.
     ego       (\G) Send command to mysql server, display result vertically.
     exit      (\q) Exit mysql. Same as quit.
     go        (\g) Send command to mysql server.
     help      (\h) Display this help.
     nopager   (\n) Disable pager, print to stdout.
     notee     (\t) Don't write into outfile.
     pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
     print     (\p) Print current command.
     prompt    (\R) Change your mysql prompt.
     quit      (\q) Quit mysql.
     rehash    (\#) Rebuild completion hash.
     source    (\.) Execute an SQL script file. Takes a file name as an argument.
     status    (\s) Get status information from the server.
     system    (\!) Execute a system shell command.
     tee       (\T) Set outfile [to_outfile]. Append everything into given
                    outfile.
     use       (\u) Use another database. Takes database name as argument.
     charset   (\C) Switch to another charset. Might be needed for processing
                    binlog with multi-byte charsets.
     warnings  (\W) Show warnings after every statement.
     nowarning (\w) Don't show warnings after every statement.

     For server side help, type 'help contents'

Each command has both a long and short form. The long form is not case
sensitive; the short form is. The long form can be followed by an
optional semicolon terminator, but the short form should not.

The use of short-form commands within multi-line `/* ...  */' comments
is not supported.

   * `help [ARG]', `\h [ARG]', `\? [ARG]', `? [ARG]'

     Display a help message listing the available *Note `mysql': mysql.
     commands.

     If you provide an argument to the `help' command, *Note `mysql':
     mysql. uses it as a search string to access server-side help from
     the contents of the MySQL Reference Manual. For more information,
     see *Note mysql-server-side-help::.

   * `charset CHARSET_NAME', `\C CHARSET_NAME'

     Change the default character set and issue a `SET NAMES'
     statement. This enables the character set to remain synchronized
     on the client and server if *Note `mysql': mysql. is run with
     auto-reconnect enabled (which is not recommended), because the
     specified character set is used for reconnects. This command was
     added in MySQL 5.1.7.

   * `clear', `\c'

     Clear the current input. Use this if you change your mind about
     executing the statement that you are entering.

   * `connect [DB_NAME HOST_NAME]]', `\r [DB_NAME HOST_NAME]]'

     Reconnect to the server. The optional database name and host name
     arguments may be given to specify the default database or the host
     where the server is running. If omitted, the current values are
     used.

   * `delimiter STR', `\d STR'

     Change the string that *Note `mysql': mysql. interprets as the
     separator between SQL statements. The default is the semicolon
     character (``;'').

     The delimiter string can be specified as an unquoted or quoted
     argument on the `delimiter' command line. Quoting can be done with
     either single quote (`''), double quote (`"'), or backtick (``')
     characters. To include a quote within a quoted string, either
     quote the string with a different quote character or escape the
     quote with a backslash (``\'') character.  Backslash should be
     avoided outside of quoted strings because it is the escape
     character for MySQL. For an unquoted argument, the delimiter is
     read up to the first space or end of line. For a quoted argument,
     the delimiter is read up to the matching quote on the line.

     *Note `mysql': mysql. interprets instances of the delimiter string
     as a statement delimiter anywhere it occurs, except within quoted
     strings. Be careful about defining a delimiter that might occur
     within other words.  For example, if you define the delimiter as
     `X', you will be unable to use the word `INDEX' in statements.
     *Note `mysql': mysql. interprets this as `INDE' followed by the
     delimiter `X'.

     When the delimiter recognized by *Note `mysql': mysql. is set to
     something other than the default of ``;'', instances of that
     character are sent to the server without interpretation.  However,
     the server itself still interprets ``;'' as a statement delimiter
     and processes statements accordingly. This behavior on the server
     side comes into play for multiple-statement execution (see *Note
     c-api-multiple-queries::), and for parsing the body of stored
     procedures and functions, triggers, and events (see *Note
     stored-programs-defining::).

   * `edit', `\e'

     Edit the current input statement. *Note `mysql': mysql.  checks
     the values of the `EDITOR' and `VISUAL' environment variables to
     determine which editor to use. The default editor is `vi' if
     neither variable is set.

     The `edit' command works only in Unix.

   * `ego', `\G'

     Send the current statement to the server to be executed and
     display the result using vertical format.

   * `exit', `\q'

     Exit *Note `mysql': mysql.

   * `go', `\g'

     Send the current statement to the server to be executed.

   * `nopager', `\n'

     Disable output paging. See the description for `pager'.

     The `nopager' command works only in Unix.

   * `notee', `\t'

     Disable output copying to the tee file. See the description for
     `tee'.

   * `nowarning', `\w'

     Disable display of warnings after each statement.

   * `pager [COMMAND]', `\P [COMMAND]'

     Enable output paging. By using the `--pager' option when you invoke
     *Note `mysql': mysql, it is possible to browse or search query
     results in interactive mode with Unix programs such as `less',
     `more', or any other similar program. If you specify no value for
     the option, *Note `mysql': mysql. checks the value of the `PAGER'
     environment variable and sets the pager to that. Pager
     functionality works only in interactive mode.

     Output paging can be enabled interactively with the `pager'
     command and disabled with `nopager'. The command takes an optional
     argument; if given, the paging program is set to that. With no
     argument, the pager is set to the pager that was set on the
     command line, or `stdout' if no pager was specified.

     Output paging works only in Unix because it uses the `popen()'
     function, which does not exist on Windows. For Windows, the `tee'
     option can be used instead to save query output, although it is
     not as convenient as `pager' for browsing output in some
     situations.

   * `print', `\p'

     Print the current input statement without executing it.

   * `prompt [STR]', `\R [STR]'

     Reconfigure the *Note `mysql': mysql. prompt to the given string.
     The special character sequences that can be used in the prompt are
     described later in this section.

     If you specify the `prompt' command with no argument, *Note
     `mysql': mysql. resets the prompt to the default of `mysql>'.

   * `quit', `\q'

     Exit *Note `mysql': mysql.

   * `rehash', `\#'

     Rebuild the completion hash that enables database, table, and
     column name completion while you are entering statements. (See the
     description for the `--auto-rehash' option.)

   * `source FILE_NAME', `\.  FILE_NAME'

     Read the named file and executes the statements contained therein.
     On Windows, you can specify path name separators as `/' or `\\'.

   * `status', `\s'

     Provide status information about the connection and the server you
     are using. If you are running in `--safe-updates' mode, `status'
     also prints the values for the *Note `mysql': mysql. variables
     that affect your queries.

   * `system COMMAND', `\!  COMMAND'

     Execute the given command using your default command interpreter.

     The `system' command works only in Unix.

   * `tee [FILE_NAME]', `\T [FILE_NAME]'

     By using the `--tee' option when you invoke *Note `mysql': mysql,
     you can log statements and their output. All the data displayed on
     the screen is appended into a given file. This can be very useful
     for debugging purposes also. *Note `mysql': mysql. flushes results
     to the file after each statement, just before it prints its next
     prompt. Tee functionality works only in interactive mode.

     You can enable this feature interactively with the `tee' command.
     Without a parameter, the previous file is used. The `tee' file can
     be disabled with the `notee' command.  Executing `tee' again
     re-enables logging.

   * `use DB_NAME', `\u DB_NAME'

     Use DB_NAME as the default database.

   * `warnings', `\W'

     Enable display of warnings after each statement (if there are any).

Here are a few tips about the `pager' command:

   * You can use it to write to a file and the results go only to the
     file:


          mysql> pager cat > /tmp/log.txt

     You can also pass any options for the program that you want to use
     as your pager:


          mysql> pager less -n -i -S

   * In the preceding example, note the `-S' option. You may find it
     very useful for browsing wide query results. Sometimes a very wide
     result set is difficult to read on the screen. The `-S' option to
     `less' can make the result set much more readable because you can
     scroll it horizontally using the left-arrow and right-arrow keys.
     You can also use `-S' interactively within `less' to switch the
     horizontal-browse mode on and off. For more information, read the
     `less' manual page:


          shell> man less

   * The `-F' and `-X' options may be used with `less' to cause it to
     exit if output fits on one screen, which is convenient when no
     scrolling is necessary:


          mysql> pager less -n -i -S -F -X

   * You can specify very complex pager commands for handling query
     output:


          mysql> pager cat | tee /dr1/tmp/res.txt \
                    | tee /dr2/tmp/res2.txt | less -n -i -S

     In this example, the command would send query results to two files
     in two different directories on two different file systems mounted
     on `/dr1' and `/dr2', yet still display the results onscreen using
     `less'.

You can also combine the `tee' and `pager' functions. Have a `tee' file
enabled and `pager' set to `less', and you are able to browse the
results using the `less' program and still have everything appended
into a file the same time. The difference between the Unix `tee' used
with the `pager' command and the *Note `mysql': mysql. built-in `tee'
command is that the built-in `tee' works even if you do not have the
Unix `tee' available. The built-in `tee' also logs everything that is
printed on the screen, whereas the Unix `tee' used with `pager' does
not log quite that much.  Additionally, `tee' file logging can be turned
on and off interactively from within *Note `mysql': mysql.  This is
useful when you want to log some queries to a file, but not others.

The `prompt' command reconfigures the default `mysql>' prompt. The
string for defining the prompt can contain the following special
sequences.

This table describes `prompt' command options that are used to
configure the `mysql>' prompt.

Option      Description
`\c'        A counter that increments for each statement you issue
`\D'        The full current date
`\d'        The default database
`\h'        The server host
`\l'        The current delimiter (new in 5.1.12)
`\m'        Minutes of the current time
`\n'        A newline character
`\O'        The current month in three-letter format (Jan, Feb,
            ...)
`\o'        The current month in numeric format
`\P'        am/pm
`\p'        The current TCP/IP port or socket file
`\R'        The current time, in 24-hour military time (0-23)
`\r'        The current time, standard 12-hour time (1-12)
`\S'        Semicolon
`\s'        Seconds of the current time
`\t'        A tab character
`\U'        Your full `USER_NAME@HOST_NAME' account name
`\u'        Your user name
`\v'        The server version
`\w'        The current day of the week in three-letter format
            (Mon, Tue, ...)
`\Y'        The current year, four digits
`\y'        The current year, two digits
`\_'        A space
`\ '        A space (a space follows the backslash)
`\''        Single quote
`\"'        Double quote
`\\'        A literal ``\'' backslash character
`\X'        X, for any `X' not listed above

You can set the prompt in several ways:

   * _Use an environment variable._ You can set the `MYSQL_PS1'
     environment variable to a prompt string. For example:


          shell> export MYSQL_PS1="(\u@\h) [\d]> "

   * _Use a command-line option._ You can set the `--prompt' option on
     the command line to *Note `mysql': mysql. For example:


          shell> mysql --prompt="(\u@\h) [\d]> "
          (user@host) [database]>

   * _Use an option file._ You can set the `prompt' option in the
     `[mysql]' group of any MySQL option file, such as `/etc/my.cnf' or
     the `.my.cnf' file in your home directory.  For example:


          [mysql]
          prompt=(\\u@\\h) [\\d]>\\_

     In this example, note that the backslashes are doubled. If you set
     the prompt using the `prompt' option in an option file, it is
     advisable to double the backslashes when using the special prompt
     options. There is some overlap in the set of permissible prompt
     options and the set of special escape sequences that are
     recognized in option files. (The rules for escape sequences in
     option files are listed in *Note option-files::.) The overlap may
     cause you problems if you use single backslashes. For example,
     `\s' is interpreted as a space rather than as the current seconds
     value. The following example shows how to define a prompt within
     an option file to include the current time in `HH:MM:SS>' format:


          [mysql]
          prompt="\\r:\\m:\\s> "

   * _Set the prompt interactively._ You can change your prompt
     interactively by using the `prompt' (or `\R') command. For example:


          mysql> prompt (\u@\h) [\d]>\_
          PROMPT set to '(\u@\h) [\d]>\_'
          (USER@HOST) [DATABASE]>
          (USER@HOST) [DATABASE]> prompt
          Returning to default PROMPT of mysql>
          mysql>


File: manual.info,  Node: mysql-logging,  Next: mysql-server-side-help,  Prev: mysql-commands,  Up: mysql

4.5.1.3 mysql Logging
.....................

On Unix, the *Note `mysql': mysql. client logs statements executed
interactively to a history file. By default, this file is named
`.mysql_history' in your home directory. To specify a different file,
set the value of the `MYSQL_HISTFILE' environment variable.

*How Logging Occurs*

Statement logging occurs as follows:

   * Statements are logged only when executed interactively.
     Statements are noninteractive, for example, when read from a file
     or a pipe. It is also possible to suppress statement logging by
     using the `--batch' or `--execute' option.

   * *Note `mysql': mysql. logs each nonempty statement line
     individually.

   * If a statement spans multiple lines (not including the terminating
     delimiter), *Note `mysql': mysql.  concatenates the lines to form
     the complete statement, maps newlines to spaces, and logs the
     result, plus a delimiter.

Consequently, an input statement that spans multiple lines can be
logged twice. Consider this input:


     mysql> SELECT
         -> 'Today is'
         -> ,
         -> CONCAT()
         -> ;

In this case, *Note `mysql': mysql. logs the `SELECT', `'Today is'',
`,', `CONCAT()', and `;' lines as it reads them. It also logs the
complete statement, after mapping `SELECT\n'Today is'\n,\nCURDATE()' to
`SELECT 'Today is' , CURDATE()', plus a delimiter. Thus, these lines
appear in logged output:


     SELECT
     'Today is'
     ,
     CURDATE()
     ;
     SELECT 'Today is' , CURDATE();

*Controlling the History File*

The `.mysql_history' file should be protected with a restrictive access
mode because sensitive information might be written to it, such as the
text of SQL statements that contain passwords. See *Note
password-security-user::.

If you do not want to maintain a history file, first remove
`.mysql_history' if it exists. Then use either of the following
techniques to prevent it from being created again:

   * Set the `MYSQL_HISTFILE' environment variable to `/dev/null'. To
     cause this setting to take effect each time you log in, put it in
     one of your shell's startup files.

   * Create `.mysql_history' as a symbolic link to `/dev/null'; this
     need be done only once:


          shell> ln -s /dev/null $HOME/.mysql_history


File: manual.info,  Node: mysql-server-side-help,  Next: mysql-batch-commands,  Prev: mysql-logging,  Up: mysql

4.5.1.4 mysql Server-Side Help
..............................


     mysql> help SEARCH_STRING

If you provide an argument to the `help' command, *Note `mysql': mysql.
uses it as a search string to access server-side help from the contents
of the MySQL Reference Manual. The proper operation of this command
requires that the help tables in the `mysql' database be initialized
with help topic information (see *Note server-side-help-support::).

If there is no match for the search string, the search fails:


     mysql> help me

     Nothing found
     Please try to run 'help contents' for a list of all accessible topics

Use *Note `help contents': help. to see a list of the help categories:


     mysql> help contents
     You asked for help about help category: "Contents"
     For more information, type 'help <item>', where <item> is one of the
     following categories:
        Account Management
        Administration
        Data Definition
        Data Manipulation
        Data Types
        Functions
        Functions and Modifiers for Use with GROUP BY
        Geographic Features
        Language Structure
        Plugins
        Storage Engines
        Stored Routines
        Table Maintenance
        Transactions
        Triggers

If the search string matches multiple items, *Note `mysql': mysql.
shows a list of matching topics:


     mysql> help logs
     Many help items for your request exist.
     To make a more specific request, please type 'help <item>',
     where <item> is one of the following topics:
        SHOW
        SHOW BINARY LOGS
        SHOW ENGINE
        SHOW LOGS

Use a topic as the search string to see the help entry for that topic:


     mysql> help show binary logs
     Name: 'SHOW BINARY LOGS'
     Description:
     Syntax:
     SHOW BINARY LOGS
     SHOW MASTER LOGS

     Lists the binary log files on the server. This statement is used as
     part of the procedure described in [purge-binary-logs], that shows how
     to determine which logs can be purged.

     mysql> SHOW BINARY LOGS;
     +---------------+-----------+
     | Log_name      | File_size |
     +---------------+-----------+
     | binlog.000015 |    724935 |
     | binlog.000016 |    733481 |
     +---------------+-----------+

The search string can contain the wildcard characters ``%'' and ``_''.
These have the same meaning as for pattern-matching operations
performed with the `LIKE' operator. For example, `HELP rep%' returns a
list of topics that begin with `rep':


     mysql> HELP rep%
     Many help items for your request exist.
     To make a more specific request, please type 'help <item>',
     where <item> is one of the following
     topics:
        REPAIR TABLE
        REPEAT FUNCTION
        REPEAT LOOP
        REPLACE
        REPLACE FUNCTION


File: manual.info,  Node: mysql-batch-commands,  Next: mysql-tips,  Prev: mysql-server-side-help,  Up: mysql

4.5.1.5 Executing SQL Statements from a Text File
.................................................

The *Note `mysql': mysql. client typically is used interactively, like
this:


     shell> mysql DB_NAME

However, it is also possible to put your SQL statements in a file and
then tell *Note `mysql': mysql. to read its input from that file. To do
so, create a text file TEXT_FILE that contains the statements you wish
to execute. Then invoke *Note `mysql': mysql. as shown here:


     shell> mysql DB_NAME < TEXT_FILE

If you place a `USE DB_NAME' statement as the first statement in the
file, it is unnecessary to specify the database name on the command
line:


     shell> mysql < text_file

If you are already running *Note `mysql': mysql, you can execute an SQL
script file using the `source' command or `\.' command:


     mysql> source FILE_NAME
     mysql> \. FILE_NAME

Sometimes you may want your script to display progress information to
the user. For this you can insert statements like this:


     SELECT '<info_to_display>' AS ' ';

The statement shown outputs `<info_to_display>'.

You can also invoke *Note `mysql': mysql. with the `--verbose' option,
which causes each statement to be displayed before the result that it
produces.

As of MySQL 5.1.23, *Note `mysql': mysql. ignores Unicode byte order
mark (BOM) characters at the beginning of input files. Previously, it
read them and sent them to the server, resulting in a syntax error.
Presence of a BOM does not cause *Note `mysql': mysql. to change its
default character set. To do that, invoke *Note `mysql': mysql. with an
option such as `--default-character-set=utf8'.

For more information about batch mode, see *Note batch-mode::.


File: manual.info,  Node: mysql-tips,  Prev: mysql-batch-commands,  Up: mysql

4.5.1.6 mysql Tips
..................

* Menu:

* mysql-input-editing::          Input-Line Editing
* vertical-query-results::       Displaying Query Results Vertically
* safe-updates::                 Using the --safe-updates Option
* mysql-reconnect::              Disabling mysql Auto-Reconnect

This section describes some techniques that can help you use *Note
`mysql': mysql. more effectively.


File: manual.info,  Node: mysql-input-editing,  Next: vertical-query-results,  Prev: mysql-tips,  Up: mysql-tips

4.5.1.7 Input-Line Editing
..........................

*Note `mysql': mysql. supports input-line editing, which enables you to
modify the current input line in place or recall previous input lines.
For example, the `left-arrow' and `right-arrow' keys move horizontally
within the current input line, and the `up-arror' and `down-arrow' keys
move up and down through the set of previously entered lines.
`Backspace' deletes the character before the cursor and typing new
characters enters them at the cursor position. To enter the line, press
`Enter'.

On Windows, the editing key sequences are the same as supported for
command editing in console windows. On Unix, the key sequences depend
on the input library used to build *Note `mysql': mysql. (for example,
the `libedit' or `readline' library).

Documentation for the `libedit' and `readline' libraries is available
online. To change the set of key sequences permitted by a given input
library, define key bindings in the library startup file. This is a
file in your home directory: `.editrc' for `libedit' and `.inputrc' for
`readline'.

For example, in `libedit', `Control+W' deletes everything before the
current cursor position and `Control+U' deletes the entire line. In
`readline', `Control+W' deletes the word before the cursor and
`Control+U' deletes everything before the current cursor position. If
*Note `mysql': mysql. was built using `libedit', a user who prefers the
`readline' behavior for these two keys can put the following lines in
the `.editrc' file (creating the file if necessary):


     bind "^W" ed-delete-prev-word
     bind "^U" vi-kill-line-prev

To see the current set of key bindings, temporarily put a line that
says only `bind' at the end of `.editrc'. *Note `mysql': mysql. will
show the bindings when it starts.


File: manual.info,  Node: vertical-query-results,  Next: safe-updates,  Prev: mysql-input-editing,  Up: mysql-tips

4.5.1.8 Displaying Query Results Vertically
...........................................

Some query results are much more readable when displayed vertically,
instead of in the usual horizontal table format.  Queries can be
displayed vertically by terminating the query with \G instead of a
semicolon. For example, longer text values that include newlines often
are much easier to read with vertical output:


     mysql> SELECT * FROM mails WHERE LENGTH(txt) < 300 LIMIT 300,1\G
     *************************** 1. row ***************************
       msg_nro: 3068
          date: 2000-03-01 23:29:50
     time_zone: +0200
     mail_from: Monty
         reply: monty@no.spam.com
       mail_to: "Thimble Smith" <tim@no.spam.com>
           sbj: UTF-8
           txt: >>>>> "Thimble" == Thimble Smith writes:

     Thimble> Hi.  I think this is a good idea.  Is anyone familiar
     Thimble> with UTF-8 or Unicode? Otherwise, I'll put this on my
     Thimble> TODO list and see what happens.

     Yes, please do that.

     Regards,
     Monty
          file: inbox-jani-1
          hash: 190402944
     1 row in set (0.09 sec)


File: manual.info,  Node: safe-updates,  Next: mysql-reconnect,  Prev: vertical-query-results,  Up: mysql-tips

4.5.1.9 Using the -safe-updates Option
......................................

For beginners, a useful startup option is `--safe-updates' (or
`--i-am-a-dummy', which has the same effect). It is helpful for cases
when you might have issued a `DELETE FROM TBL_NAME' statement but
forgotten the `WHERE' clause. Normally, such a statement deletes all
rows from the table. With `--safe-updates', you can delete rows only by
specifying the key values that identify them.  This helps prevent
accidents.

When you use the `--safe-updates' option, *Note `mysql': mysql. issues
the following statement when it connects to the MySQL server:


     SET sql_safe_updates=1, sql_select_limit=1000, sql_max_join_size=1000000;

See *Note server-system-variables::.

The *Note `SET': set-statement.  statement has the following effects:

   * You are not permitted to execute an *Note `UPDATE': update. or
     *Note `DELETE': delete. statement unless you specify a key
     constraint in the `WHERE' clause or provide a `LIMIT' clause (or
     both). For example:


          UPDATE TBL_NAME SET NOT_KEY_COLUMN=VAL WHERE KEY_COLUMN=VAL;

          UPDATE TBL_NAME SET NOT_KEY_COLUMN=VAL LIMIT 1;

   * The server limits all large *Note `SELECT': select. results to
     1,000 rows unless the statement includes a `LIMIT' clause.

   * The server aborts multiple-table *Note `SELECT': select.
     statements that probably need to examine more than 1,000,000 row
     combinations.

To specify limits different from 1,000 and 1,000,000, you can override
the defaults by using the `--select_limit' and `--max_join_size'
options:


     shell> mysql --safe-updates --select_limit=500 --max_join_size=10000


File: manual.info,  Node: mysql-reconnect,  Prev: safe-updates,  Up: mysql-tips

4.5.1.10 Disabling mysql Auto-Reconnect
.......................................

If the *Note `mysql': mysql. client loses its connection to the server
while sending a statement, it immediately and automatically tries to
reconnect once to the server and send the statement again. However,
even if *Note `mysql': mysql.  succeeds in reconnecting, your first
connection has ended and all your previous session objects and settings
are lost: temporary tables, the autocommit mode, and user-defined and
session variables. Also, any current transaction rolls back.  This
behavior may be dangerous for you, as in the following example where
the server was shut down and restarted between the first and second
statements without you knowing it:


     mysql> SET @a=1;
     Query OK, 0 rows affected (0.05 sec)

     mysql> INSERT INTO t VALUES(@a);
     ERROR 2006: MySQL server has gone away
     No connection. Trying to reconnect...
     Connection id:    1
     Current database: test

     Query OK, 1 row affected (1.30 sec)

     mysql> SELECT * FROM t;
     +------+
     | a    |
     +------+
     | NULL |
     +------+
     1 row in set (0.05 sec)

The `@a' user variable has been lost with the connection, and after the
reconnection it is undefined. If it is important to have *Note `mysql':
mysql. terminate with an error if the connection has been lost, you can
start the *Note `mysql': mysql. client with the `--skip-reconnect'
option.

For more information about auto-reconnect and its effect on state
information when a reconnection occurs, see *Note auto-reconnect::.


File: manual.info,  Node: mysqladmin,  Next: mysqlcheck,  Prev: mysql,  Up: programs-client

4.5.2 `mysqladmin' -- Client for Administering a MySQL Server
-------------------------------------------------------------

*Note `mysqladmin': mysqladmin. is a client for performing
administrative operations. You can use it to check the server's
configuration and current status, to create and drop databases, and
more.

Invoke *Note `mysqladmin': mysqladmin. like this:


     shell> mysqladmin [OPTIONS] COMMAND [COMMAND-ARG] [COMMAND [COMMAND-ARG]] ...

*Note `mysqladmin': mysqladmin. supports the following commands.  Some
of the commands take an argument following the command name.

   * `create DB_NAME'

     Create a new database named DB_NAME.

   * `debug'

     Tell the server to write debug information to the error log.
     Format and content of this information is subject to change.

     Beginning with MySQL 5.1.12, this includes information about the
     Event Scheduler. See *Note events-status-info::.

   * `drop DB_NAME'

     Delete the database named DB_NAME and all its tables.

   * `extended-status'

     Display the server status variables and their values.

   * `flush-hosts'

     Flush all information in the host cache.

   * `flush-logs'

     Flush all logs.

   * `flush-privileges'

     Reload the grant tables (same as `reload').

   * `flush-status'

     Clear status variables.

   * `flush-tables'

     Flush all tables.

   * `flush-threads'

     Flush the thread cache.

   * `kill ID,ID,...'

     Kill server threads. If multiple thread ID values are given, there
     must be no spaces in the list.

   * `old-password NEW-PASSWORD'

     This is like the `password' command but stores the password using
     the old (pre-4.1) password-hashing format. (See *Note
     password-hashing::.)

   * `password NEW-PASSWORD'

     Set a new password. This changes the password to NEW-PASSWORD for
     the account that you use with *Note `mysqladmin': mysqladmin. for
     connecting to the server. Thus, the next time you invoke *Note
     `mysqladmin': mysqladmin. (or any other client program) using the
     same account, you will need to specify the new password.

     If the NEW-PASSWORD value contains spaces or other characters that
     are special to your command interpreter, you need to enclose it
     within quotation marks. On Windows, be sure to use double
     quotation marks rather than single quotation marks; single
     quotation marks are not stripped from the password, but rather are
     interpreted as part of the password. For example:


          shell> mysqladmin password "my new password"

     *Caution*:

     Do not use this command used if the server was started with the
     `--skip-grant-tables' option.  No password change will be applied.
     This is true even if you precede the `password' command with
     `flush-privileges' on the same command line to re-enable the grant
     tables because the flush operation occurs after you connect.
     However, you can use *Note `mysqladmin flush-privileges':
     mysqladmin. to re-enable the grant table and then use a separate
     *Note `mysqladmin password': mysqladmin. command to change the
     password.

   * `ping'

     Check whether the server is available. The return status from
     *Note `mysqladmin': mysqladmin. is 0 if the server is running, 1
     if it is not. This is 0 even in case of an error such as `Access
     denied', because this means that the server is running but refused
     the connection, which is different from the server not running.

   * `processlist'

     Show a list of active server threads. This is like the output of
     the *Note `SHOW PROCESSLIST': show-processlist. statement. If the
     `--verbose' option is given, the output is like that of *Note
     `SHOW FULL PROCESSLIST': show-processlist. (See *Note
     show-processlist::.)

   * `reload'

     Reload the grant tables.

   * `refresh'

     Flush all tables and close and open log files.

   * `shutdown'

     Stop the server.

   * `start-slave'

     Start replication on a slave server.

   * `status'

     Display a short server status message.

   * `stop-slave'

     Stop replication on a slave server.

   * `variables'

     Display the server system variables and their values.

   * `version'

     Display version information from the server.

All commands can be shortened to any unique prefix. For example:


     shell> mysqladmin proc stat
     +----+-------+-----------+----+---------+------+-------+------------------+
     | Id | User  | Host      | db | Command | Time | State | Info             |
     +----+-------+-----------+----+---------+------+-------+------------------+
     | 51 | monty | localhost |    | Query   | 0    |       | show processlist |
     +----+-------+-----------+----+---------+------+-------+------------------+
     Uptime: 1473624  Threads: 1  Questions: 39487
     Slow queries: 0  Opens: 541  Flush tables: 1
     Open tables: 19  Queries per second avg: 0.0268

The *Note `mysqladmin status': mysqladmin. command result displays the
following values:

   * `Uptime'

     The number of seconds the MySQL server has been running.

   * `Threads'

     The number of active threads (clients).

   * `Questions'

     The number of questions (queries) from clients since the server
     was started.

   * `Slow queries'

     The number of queries that have taken more than `long_query_time'
     seconds.  See *Note slow-query-log::.

   * `Opens'

     The number of tables the server has opened.

   * `Flush tables'

     The number of `flush-*', `refresh', and `reload' commands the
     server has executed.

   * `Open tables'

     The number of tables that currently are open.

   * `Memory in use'

     The amount of memory allocated directly by *Note `mysqld': mysqld.
     This value is displayed only when MySQL has been compiled with
     `--with-debug=full'.

   * `Maximum memory used'

     The maximum amount of memory allocated directly by *Note `mysqld':
     mysqld. This value is displayed only when MySQL has been compiled
     with `--with-debug=full'.

If you execute *Note `mysqladmin shutdown': mysqladmin. when connecting
to a local server using a Unix socket file, *Note `mysqladmin':
mysqladmin. waits until the server's process ID file has been removed,
to ensure that the server has stopped properly.

*Note `mysqladmin': mysqladmin. supports the following options, which
can be specified on the command line or in the `[mysqladmin]' and
`[client]' groups of an option file. For information about option files
used by MySQL programs, see *Note option-files::.

*`mysqladmin' Options*

Format             Description                      Introduced
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-compress          Compress all information sent    
                   between client and server        
-connect_timeout=secondsNumber of seconds before         
                   connection timeout               
-count=#           Number of iterations to make     
                   for repeated command execution   
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     5.1.14
                   memory, and CPU statistics when  
                   program exits                    
-default-character-set=charset_nameSpecify default character set    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-force             Continue even if an SQL error    
                   occurs                           
-help              Display help message and exit    
-host=host_name    Connect to MySQL server on       
                   given host                       
-no-beep           Do not beep when errors occur    5.1.17
-no-defaults       Read no option files             
-password[=password]Password to use when connecting  
                   to server                        
-pipe              On Windows, connect to server    
                   using named pipe                 
-port=port_num     TCP/IP port number to use for    
                   connection                       
-print-defaults    Print defaults                   
-protocol=type     Connection protocol to use       
-relative          Show the difference between the  
                   current and previous values      
                   when used with the -sleep option 
-shared-memory-base-name=nameThe name of shared memory to     
                   use for shared-memory            
                   connections                      
-shutdown_timeout=secondsThe maximum number of seconds    
                   to wait for server shutdown      
-silent            Silent mode                      
-sleep=delay       Execute commands repeatedly,     
                   sleeping for delay seconds in    
                   between                          
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-ssl               Enable SSL for connection        
-ssl-ca=file_name  Path of file that contains list  
                   of trusted SSL CAs               
-ssl-capath=dir_namePath of directory that contains  
                   trusted SSL CA certificates in   
                   PEM format                       
-ssl-cert=file_namePath of file that contains X509  
                   certificate in PEM format        
-ssl-cipher=cipher_listList of permitted ciphers to     
                   use for SSL encryption           
-ssl-key=file_name Path of file that contains X509  
                   key in PEM format                
-ssl-verify-server-certVerify server Common Name value  5.1.11
                   in its certificate against host  
                   name used when connecting to     
                   server                           
-user=user_name,   MySQL user name to use when      
                   connecting to server             
-verbose           Verbose mode                     
-version           Display version information and  
                   exit                             
-vertical          Print query output rows          
                   vertically (one line per column  
                   value)                           
-wait              If the connection cannot be      
                   established, wait and retry      
                   instead of aborting              

   * `--help', `-?'

     Display a help message and exit.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, use this option
     to select which interface to use for connecting to the MySQL
     server.

     This option is supported only in the version of *Note
     `mysqladmin': mysqladmin. that is supplied with MySQL Cluster,
     beginning with MySQL Cluster NDB 6.3.4. It is not available in
     standard MySQL 5.1 releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--compress', `-C'

     Compress all information sent between the client and the server if
     both support compression.

   * `--count=N', `-c N'

     The number of iterations to make for repeated command execution if
     the `--sleep' option is given.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o,/tmp/mysqladmin.trace'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.14.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set. See *Note
     charset-configuration::.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqladmin':
     mysqladmin. normally reads the `[client]' and `[mysqladmin]'
     groups. If the `--defaults-group-suffix=_other' option is given,
     *Note `mysqladmin': mysqladmin. also reads the `[client_other]' and
     `[mysqladmin_other]' groups.

   * `--force', `-f'

     Do not ask for confirmation for the `drop DB_NAME' command. With
     multiple commands, continue even if an error occurs.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--no-beep', `-b'

     Suppress the warning beep that is emitted by default for errors
     such as a failure to connect to the server. This option was added
     in MySQL 5.1.17.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqladmin': mysqladmin. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--relative', `-r'

     Show the difference between the current and previous values when
     used with the `--sleep' option. This option works only with the
     `extended-status' command.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--silent', `-s'

     Exit silently if a connection to the server cannot be established.

   * `--sleep=DELAY', `-i DELAY'

     Execute commands repeatedly, sleeping for DELAY seconds in
     between. The `--count' option determines the number of iterations.
     If `--count' is not given, *Note `mysqladmin': mysqladmin.
     executes commands indefinitely until interrupted.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.

   * `--version', `-V'

     Display version information and exit.

   * `--vertical', `-E'

     Print output vertically. This is similar to `--relative', but
     prints output vertically.

   * `--wait[=COUNT]', `-w[COUNT]'

     If the connection cannot be established, wait and retry instead of
     aborting. If a COUNT value is given, it indicates the number of
     times to retry.  The default is one time.

You can also set the following variables by using `--VAR_NAME=VALUE'
The `--set-variable' format is deprecated and is removed in MySQL 5.5.

   * `connect_timeout'

     The maximum number of seconds before connection timeout. The
     default value is 43200 (12 hours).

   * `shutdown_timeout'

     The maximum number of seconds to wait for server shutdown.  The
     default value is 3600 (1 hour).


File: manual.info,  Node: mysqlcheck,  Next: mysqldump,  Prev: mysqladmin,  Up: programs-client

4.5.3 `mysqlcheck' -- A Table Maintenance Program
-------------------------------------------------

The *Note `mysqlcheck': mysqlcheck. client performs table maintenance:
It checks, repairs, optimizes, or analyzes tables.

Each table is locked and therefore unavailable to other sessions while
it is being processed, although for check operations, the table is
locked with a `READ' lock only (see *Note lock-tables::, for more
information about `READ' and `WRITE' locks).  Table maintenance
operations can be time-consuming, particularly for large tables. If you
use the `--databases' or `--all-databases' option to process all tables
in one or more databases, an invocation of *Note `mysqlcheck':
mysqlcheck. might take a long time. (This is also true for *Note
`mysql_upgrade': mysql-upgrade. because that program invokes *Note
`mysqlcheck': mysqlcheck. to check all tables and repair them if
necessary.)

*Note `mysqlcheck': mysqlcheck. is similar in function to *Note
`myisamchk': myisamchk, but works differently. The main operational
difference is that *Note `mysqlcheck': mysqlcheck.  must be used when
the *Note `mysqld': mysqld. server is running, whereas *Note
`myisamchk': myisamchk. should be used when it is not. The benefit of
using *Note `mysqlcheck': mysqlcheck. is that you do not have to stop
the server to perform table maintenance.

*Note `mysqlcheck': mysqlcheck. uses the SQL statements *Note `CHECK
TABLE': check-table, *Note `REPAIR TABLE': repair-table, *Note `ANALYZE
TABLE': analyze-table, and *Note `OPTIMIZE TABLE': optimize-table. in a
convenient way for the user. It determines which statements to use for
the operation you want to perform, and then sends the statements to the
server to be executed. For details about which storage engines each
statement works with, see the descriptions for those statements in
*Note table-maintenance-sql::.

The `MyISAM' storage engine supports all four maintenance operations,
so *Note `mysqlcheck': mysqlcheck. can be used to perform any of them
on `MyISAM' tables.  Other storage engines do not necessarily support
all operations.  In such cases, an error message is displayed. For
example, if `test.t' is a `MEMORY' table, an attempt to check it
produces this result:


     shell> mysqlcheck test t
     test.t
     note     : The storage engine for the table doesn't support check

If *Note `mysqlcheck': mysqlcheck. is unable to repair a table, see
*Note rebuilding-tables:: for manual table repair strategies. This will
be the case, for example, for `InnoDB' tables, which can be checked with
*Note `CHECK TABLE': check-table, but not repaired with *Note `REPAIR
TABLE': repair-table.

The use of *Note `mysqlcheck': mysqlcheck. with partitioned tables is
not supported before MySQL 5.1.27.

*Caution*:

It is best to make a backup of a table before performing a table repair
operation; under some circumstances the operation might cause data
loss. Possible causes include but are not limited to file system errors.

There are three general ways to invoke *Note `mysqlcheck': mysqlcheck.:


     shell> mysqlcheck [OPTIONS] DB_NAME [TBL_NAME ...]
     shell> mysqlcheck [OPTIONS] --databases DB_NAME ...
     shell> mysqlcheck [OPTIONS] --all-databases

If you do not name any tables following DB_NAME or if you use the
`--databases' or `--all-databases' option, entire databases are checked.

*Note `mysqlcheck': mysqlcheck. has a special feature compared to other
client programs. The default behavior of checking tables (`--check')
can be changed by renaming the binary. If you want to have a tool that
repairs tables by default, you should just make a copy of *Note
`mysqlcheck': mysqlcheck. named `mysqlrepair', or make a symbolic link
to *Note `mysqlcheck': mysqlcheck. named `mysqlrepair'. If you invoke
`mysqlrepair', it repairs tables.

The names shown in the following table can be used to change *Note
`mysqlcheck': mysqlcheck. default behavior.

This table lists names that can be used to change *Note `mysqlcheck':
mysqlcheck. default behavior.

Command            Meaning
`mysqlrepair'      The default option is `--repair'
`mysqlanalyze'     The default option is `--analyze'
`mysqloptimize'    The default option is `--optimize'

*Note `mysqlcheck': mysqlcheck. supports the following options, which
can be specified on the command line or in the `[mysqlcheck]' and
`[client]' groups of an option file. For information about option files
used by MySQL programs, see *Note option-files::.

*`mysqlcheck' Options*

Format             Description                      Introduced
-all-databases     Check all tables in all          
                   databases                        
-all-in-1          Execute a single statement for   
                   each database that names all     
                   the tables from that database    
-analyze           Analyze the tables               
-auto-repair       If a checked table is            
                   corrupted, automatically fix it  
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-character-sets-dir=pathDirectory where character sets   
                   are installed                    
-check             Check the tables for errors      
-check-only-changedCheck only tables that have      
                   changed since the last check     
-check-upgrade     Invoke CHECK TABLE with the FOR  5.1.7
                   UPGRADE option                   
-compress          Compress all information sent    
                   between client and server        
-databases         Process all tables in the named  
                   databases                        
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     5.1.14
                   memory, and CPU statistics when  
                   program exits                    
-default-character-set=charset_nameSpecify default character set    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-extended          Check and repair tables          
-fast              Check only tables that have not  
                   been closed properly             
-fix-db-names      Convert database names to 5.1    5.1.7
                   format                           
-fix-table-names   Convert table names to 5.1       5.1.7
                   format                           
-force             Continue even if an SQL error    
                   occurs                           
-help              Display help message and exit    
-host=host_name    Connect to MySQL server on       
                   given host                       
-medium-check      Do a check that is faster than   
                   an -extended operation           
-no-defaults       Read no option files             
-optimize          Optimize the tables              
-password[=password]Password to use when connecting  
                   to server                        
-pipe              On Windows, connect to server    
                   using named pipe                 
-port=port_num     TCP/IP port number to use for    
                   connection                       
-print-defaults    Print defaults                   
-protocol=type     Connection protocol to use       
-quick             The fastest method of checking   
-repair            Perform a repair that can fix    
                   almost anything except unique    
                   keys that are not unique         
-shared-memory-base-name=nameThe name of shared memory to     
                   use for shared-memory            
                   connections                      
-silent            Silent mode                      
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-ssl               Enable SSL for connection        
-ssl-ca=file_name  Path of file that contains list  
                   of trusted SSL CAs               
-ssl-capath=dir_namePath of directory that contains  
                   trusted SSL CA certificates in   
                   PEM format                       
-ssl-cert=file_namePath of file that contains X509  
                   certificate in PEM format        
-ssl-cipher=cipher_listList of permitted ciphers to     
                   use for SSL encryption           
-ssl-key=file_name Path of file that contains X509  
                   key in PEM format                
-ssl-verify-server-certVerify server Common Name value  5.1.11
                   in its certificate against host  
                   name used when connecting to     
                   server                           
-tables            Overrides the -databases or -B   
                   option                           
-use-frm           For repair operations on MyISAM  
                   tables                           
-user=user_name,   MySQL user name to use when      
                   connecting to server             
-verbose           Verbose mode                     
-version           Display version information and  
                   exit                             
-write-binlog      Log ANALYZE, OPTIMIZE, REPAIR    5.1.18
                   statements to binary log.        
                   -skip-write-binlog adds          
                   NO_WRITE_TO_BINLOG to these      
                   statements.                      

   * `--help', `-?'

     Display a help message and exit.

   * `--all-databases', `-A'

     Check all tables in all databases. This is the same as using the
     `--databases' option and naming all the databases on the command
     line.

   * `--all-in-1', `-1'

     Instead of issuing a statement for each table, execute a single
     statement for each database that names all the tables from that
     database to be processed.

   * `--analyze', `-a'

     Analyze the tables.

   * `--auto-repair'

     If a checked table is corrupted, automatically fix it. Any
     necessary repairs are done after all tables have been checked.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, use this option
     to select which interface to use for connecting to the MySQL
     server.

     This option is supported only in the version of *Note
     `mysqlcheck': mysqlcheck. that is supplied with MySQL Cluster,
     beginning with MySQL Cluster NDB 6.3.4. It is not available in
     standard MySQL 5.1 releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--check', `-c'

     Check the tables for errors. This is the default operation.

   * `--check-only-changed', `-C'

     Check only tables that have changed since the last check or that
     have not been closed properly.

   * `--check-upgrade', `-g'

     Invoke *Note `CHECK TABLE': check-table. with the `FOR UPGRADE'
     option to check tables for incompatibilities with the current
     version of the server.  This option automatically enables the
     `--fix-db-names' and `--fix-table-names' options. `--check-upgrade'
     was added in MySQL 5.1.7.

   * `--compress'

     Compress all information sent between the client and the server if
     both support compression.

   * `--databases', `-B'

     Process all tables in the named databases. Normally, *Note
     `mysqlcheck': mysqlcheck. treats the first name argument on the
     command line as a database name and following names as table
     names. With this option, it treats all name arguments as database
     names.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.14.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set. See *Note
     charset-configuration::.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqlcheck':
     mysqlcheck. normally reads the `[client]' and `[mysqlcheck]'
     groups. If the `--defaults-group-suffix=_other' option is given,
     *Note `mysqlcheck': mysqlcheck. also reads the `[client_other]' and
     `[mysqlcheck_other]' groups.

   * `--extended', `-e'

     If you are using this option to check tables, it ensures that they
     are 100% consistent but takes a long time.

     If you are using this option to repair tables, it runs an extended
     repair that may not only take a long time to execute, but may
     produce a lot of garbage rows also!

   * `--fast', `-F'

     Check only tables that have not been closed properly.

   * `--fix-db-names'

     Convert database names to 5.1 format. Only database names that
     contain special characters are affected. This option was added in
     MySQL 5.1.7.

   * `--fix-table-names'

     Convert table names to 5.1 format. Only table names that contain
     special characters are affected. This option was added in MySQL
     5.1.7. As of MySQL 5.1.23, this option also applies to views.

   * `--force', `-f'

     Continue even if an SQL error occurs.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--medium-check', `-m'

     Do a check that is faster than an `--extended' operation.  This
     finds only 99.99% of all errors, which should be good enough in
     most cases.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--optimize', `-o'

     Optimize the tables.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqlcheck': mysqlcheck. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--quick', `-q'

     If you are using this option to check tables, it prevents the
     check from scanning the rows to check for incorrect links. This is
     the fastest check method.

     If you are using this option to repair tables, it tries to repair
     only the index tree. This is the fastest repair method.

   * `--repair', `-r'

     Perform a repair that can fix almost anything except unique keys
     that are not unique.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--silent', `-s'

     Silent mode. Print only error messages.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--tables'

     Override the `--databases' or `-B' option. All name arguments
     following the option are regarded as table names.

   * `--use-frm'

     For repair operations on `MyISAM' tables, get the table structure
     from the `.frm' file so that the table can be repaired even if the
     `.MYI' header is corrupted.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose', `-v'

     Verbose mode. Print information about the various stages of
     program operation.

   * `--version', `-V'

     Display version information and exit.

   * `--write-binlog'

     This option is enabled by default, so that *Note `ANALYZE TABLE':
     analyze-table, *Note `OPTIMIZE TABLE': optimize-table, and *Note
     `REPAIR TABLE': repair-table. statements generated by *Note
     `mysqlcheck': mysqlcheck. are written to the binary log. Use
     `--skip-write-binlog' to cause `NO_WRITE_TO_BINLOG' to be added to
     the statements so that they are not logged. Use the
     `--skip-write-binlog' when these statements should not be sent to
     replication slaves or run when using the binary logs for recovery
     from backup. This option was added in MySQL 5.1.18.


File: manual.info,  Node: mysqldump,  Next: mysqlimport,  Prev: mysqlcheck,  Up: programs-client

4.5.4 `mysqldump' -- A Database Backup Program
----------------------------------------------

The *Note `mysqldump': mysqldump. client is a backup program originally
written by Igor Romanenko. It can be used to dump a database or a
collection of databases for backup or transfer to another SQL server
(not necessarily a MySQL server). The dump typically contains SQL
statements to create the table, populate it, or both. However, *Note
`mysqldump': mysqldump. can also be used to generate files in CSV,
other delimited text, or XML format.

*Note `mysqldump': mysqldump. requires at least the `SELECT' privilege
for dumped tables, `SHOW VIEW' for dumped views, `TRIGGER' for dumped
triggers, and `LOCK TABLES' if the `--single-transaction' option is not
used. Certain options might require other privileges as noted in the
option descriptions.

To reload a dump file, you must have the same privileges needed to
create each of the dumped objects by issuing `CREATE' statements
manually.

*Note `mysqldump': mysqldump. output can include *Note `ALTER
DATABASE': alter-database. statements that change the database
collation. These may be used when dumping stored programs to preserve
their character encodings. To reload a dump file containing such
statements, the `ALTER' privilege for the affected database is required.

If you are performing a backup on the server and your tables all are
*Note `MyISAM': myisam-storage-engine. tables, you can also use *Note
`mysqlhotcopy': mysqlhotcopy. for this purpose.

*Syntax*

There are in general three ways to use *Note `mysqldump':
mysqldump.--in order to dump a set of one or more tables, a set of one
or more complete databases, or an entire MySQL server--as shown here:


     shell> mysqldump [OPTIONS] DB_NAME [TBL_NAME ...]
     shell> mysqldump [OPTIONS] --databases DB_NAME ...
     shell> mysqldump [OPTIONS] --all-databases

To dump entire databases, do not name any tables following DB_NAME, or
use the `--databases' or `--all-databases' option.

*Note `mysqldump': mysqldump. does not dump the `INFORMATION_SCHEMA'
database by default. As of MySQL 5.1.38, *Note `mysqldump': mysqldump.
dumps `INFORMATION_SCHEMA' if you name it explicitly on the command
line, although you must also use the `--skip-lock-tables' option.
Before 5.1.38, *Note `mysqldump': mysqldump. silently ignores
`INFORMATION_SCHEMA' even if you name it explicitly on the command line.

Before MySQL 5.1.64, *Note `mysqldump': mysqldump. does not dump the
`general_log' or `slow_query_log' tables for dumps of the `mysql'
database. As of 5.1.64, the dump includes statements to recreate those
tables so that they are not missing after reloading the dump file. Log
table contents are not dumped.

In MySQL Cluster NDB 7.1.7 and later, the `ndbinfo' information
database is ignored and not dumped by *Note `mysqldump': mysqldump.

To see a list of the options your version of *Note `mysqldump':
mysqldump. supports, execute *Note `mysqldump --help': mysqldump.

Some *Note `mysqldump': mysqldump. options are shorthand for groups of
other options:

   * Use of `--opt' is the same as specifying `--add-drop-table',
     `--add-locks', `--create-options', `--disable-keys',
     `--extended-insert', `--lock-tables', `--quick', and
     `--set-charset'. All of the options that `--opt' stands for also
     are on by default because `--opt' is on by default.

   * Use of `--compact' is the same as specifying
     `--skip-add-drop-table', `--skip-add-locks', `--skip-comments',
     `--skip-disable-keys', and `--skip-set-charset' options.

To reverse the effect of a group option, uses its `--skip-XXX' form
(`--skip-opt' or `--skip-compact').  It is also possible to select only
part of the effect of a group option by following it with options that
enable or disable specific features. Here are some examples:

   * To select the effect of `--opt' except for some features, use the
     `--skip' option for each feature. To disable extended inserts and
     memory buffering, use `--opt' `--skip-extended-insert'
     `--skip-quick'.  (Actually, `--skip-extended-insert' `--skip-quick'
     is sufficient because `--opt' is on by default.)

   * To reverse `--opt' for all features except index disabling and
     table locking, use `--skip-opt' `--disable-keys' `--lock-tables'.

When you selectively enable or disable the effect of a group option,
order is important because options are processed first to last. For
example, `--disable-keys' `--lock-tables' `--skip-opt' would not have
the intended effect; it is the same as `--skip-opt' by itself.

*Note `mysqldump': mysqldump. can retrieve and dump table contents row
by row, or it can retrieve the entire content from a table and buffer
it in memory before dumping it. Buffering in memory can be a problem if
you are dumping large tables. To dump tables row by row, use the
`--quick' option (or `--opt', which enables `--quick'). The `--opt'
option (and hence `--quick') is enabled by default, so to enable memory
buffering, use `--skip-quick'.

If you are using a recent version of *Note `mysqldump': mysqldump. to
generate a dump to be reloaded into a very old MySQL server, you should
not use the `--opt' or `--extended-insert' option. Use `--skip-opt'
instead.

*Note*:

*Note `mysqldump': mysqldump. from MySQL 5.1.21 cannot be used to
create dumps from MySQL server 5.1.20 and older. This issue is fixed in
MySQL 5.1.22. (Bug #30123)

*Note `mysqldump': mysqldump. supports the following options, which can
be specified on the command line or in the `[mysqldump]' and `[client]'
groups of an option file. For information about option files used by
MySQL programs, see *Note option-files::.

*`mysqldump' Options*

Format             Description                      Introduced
-add-drop-database Add a DROP DATABASE statement    
                   before each CREATE DATABASE      
                   statement                        
-add-drop-table    Add a DROP TABLE statement       
                   before each CREATE TABLE         
                   statement                        
-add-drop-trigger  Add a DROP TRIGGER statement     5.1.47-ndb-7.1.8
                   before each CREATE TRIGGER       
                   statement                        
-add-locks         Surround each table dump with    
                   LOCK TABLES and UNLOCK TABLES    
                   statements                       
-all-databases     Dump all tables in all databases 
-all-tablespaces   Adds to a table dump all SQL     5.1.6
                   statements needed to create any  
                   tablespaces used by an NDB       
                   Cluster table                    
-allow-keywords    Allow creation of column names   
                   that are keywords                
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-comments          Add comments to the dump file    
-compact           Produce more compact output      
-compatible=name[,name,...]Produce output that is more      
                   compatible with other database   
                   systems or with older MySQL      
                   servers                          
-complete-insert   Use complete INSERT statements   
                   that include column names        
-create-options    Include all MySQL-specific       
                   table options in CREATE TABLE    
                   statements                       
-databases         Dump several databases           
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     5.1.14
                   memory, and CPU statistics when  
                   program exits                    
-default-character-set=charset_nameSpecify default character set    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-delayed-insert    Write INSERT DELAYED statements  
                   rather than INSERT statements    
-delete-master-logsOn a master replication server,  
                   delete the binary logs after     
                   performing the dump operation    
-disable-keys      For each table, surround the     
                   INSERT statements with           
                   statements to disable and        
                   enable keys                      
-dump-date         Include dump date as "Dump       5.1.23
                   completed on" comment if         
                   -comments is given               
-events            Dump events from the dumped      5.1.8
                   databases                        
-extended-insert   Use multiple-row INSERT syntax   
                   that include several VALUES      
                   lists                            
-fields-enclosed-by=stringThis option is used with the     
                   -tab option and has the same     
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-fields-escaped-by This option is used with the     
                   -tab option and has the same     
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-fields-optionally-enclosed-by=stringThis option is used with the     
                   -tab option and has the same     
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-fields-terminated-by=stringThis option is used with the     
                   -tab option and has the same     
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-first-slave       Deprecated; use                  
                   -lock-all-tables instead         
-flush-logs        Flush the MySQL server log       
                   files before starting the dump   
-flush-privileges  Emit a FLUSH PRIVILEGES          
                   statement after dumping the      
                   mysql database                   
-help              Display help message and exit    
-hex-blob          Dump binary columns using        
                   hexadecimal notation (for        
                   example, 'abc' becomes 0x616263) 
-host              Host to connect to (IP address   
                   or hostname)                     
-ignore-table=db_name.tbl_nameDo not dump the given table      
-insert-ignore     Write INSERT IGNORE statements   
                   rather than INSERT statements    
-lines-terminated-by=stringThis option is used with the     
                   -tab option and has the same     
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-lock-all-tables   Lock all tables across all       
                   databases                        
-lock-tables       Lock all tables before dumping   
                   them                             
-log-error=file_nameAppend warnings and errors to    5.1.18
                   the named file                   
-master-data[=value]Write the binary log file name   
                   and position to the output       
-max_allowed_packet=valueMaximum packet length to send    
                   to or receive from server        
-net_buffer_length=valueBuffer size for TCP/IP and       
                   socket communication             
-no-autocommit     Enclose the INSERT statements    
                   for each dumped table within     
                   SET autocommit = 0 and COMMIT    
                   statements                       
-no-create-db      This option suppresses the       
                   CREATE DATABASE statements       
-no-create-info    Do not write CREATE TABLE        
                   statements that re-create each   
                   dumped table                     
-no-data           Do not dump table contents       
-no-defaults       Read no option files             
-no-set-names      Same as -skip-set-charset        
-no-tablespaces    Do not write any CREATE LOGFILE  5.1.14
                   GROUP or CREATE TABLESPACE       
                   statements in output             
-opt               Shorthand for -add-drop-table    
                   -add-locks -create-options       
                   -disable-keys -extended-insert   
                   -lock-tables -quick              
                   -set-charset.                    
-order-by-primary  Dump each table's rows sorted    
                   by its primary key, or by its    
                   first unique index               
-password[=password]Password to use when connecting  
                   to server                        
-pipe              On Windows, connect to server    
                   using named pipe                 
-port=port_num     TCP/IP port number to use for    
                   connection                       
-print-defaults    Print defaults                   
-protocol=type     Connection protocol to use       
-quick             Retrieve rows for a table from   
                   the server a row at a time       
-quote-names       Quote identifiers within         
                   backtick characters              
-replace           Write REPLACE statements rather  5.1.3
                   than INSERT statements           
-result-file=file  Direct output to a given file    
-routines          Dump stored routines             5.1.2
                   (procedures and functions) from  
                   the dumped databases             
-set-charset       Add SET NAMES                    
                   default_character_set to output  
-shared-memory-base-name=nameThe name of shared memory to     
                   use for shared-memory            
                   connections                      
-single-transactionThis option issues a BEGIN SQL   
                   statement before dumping data    
                   from the server                  
-skip-add-drop-tableDo not add a DROP TABLE          
                   statement before each CREATE     
                   TABLE statement                  
-skip-add-locks    Do not add locks                 
-skip-comments     Do not add comments to the dump  
                   file                             
-skip-compact      Do not produce more compact      
                   output                           
-skip-disable-keys Do not disable keys              
-skip-extended-insertTurn off extended-insert         
-skip-opt          Turn off the options set by -opt 
-skip-quick        Do not retrieve rows for a       
                   table from the server a row at   
                   a time                           
-skip-quote-names  Do not quote identifiers         
-skip-set-charset  Suppress the SET NAMES statement 
-skip-triggers     Do not dump triggers             
-skip-tz-utc       Turn off tz-utc                  5.1.2
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-ssl               Enable SSL for connection        
-ssl-ca=file_name  Path of file that contains list  
                   of trusted SSL CAs               
-ssl-capath=dir_namePath of directory that contains  
                   trusted SSL CA certificates in   
                   PEM format                       
-ssl-cert=file_namePath of file that contains X509  
                   certificate in PEM format        
-ssl-cipher=cipher_listList of permitted ciphers to     
                   use for SSL encryption           
-ssl-key=file_name Path of file that contains X509  
                   key in PEM format                
-ssl-verify-server-certVerify server Common Name value  5.1.11
                   in its certificate against host  
                   name used when connecting to     
                   server                           
-tab=path          Produce tab-separated data files 
-tables            Override the -databases or -B    
                   option                           
-triggers          Dump triggers for each dumped    
                   table                            
-tz-utc            Add SET TIME_ZONE='+00:00' to    5.1.2
                   the dump file                    
-user=user_name    MySQL user name to use when      
                   connecting to server             
-verbose           Verbose mode                     
-version           Display version information and  
                   exit                             
-where='where_condition'Dump only rows selected by the   
                   given WHERE condition            
-xml               Produce XML output               

   * `--help', `-?'

     Display a help message and exit.

   * `--add-drop-database'

     Add a *Note `DROP DATABASE': drop-database. statement before each
     *Note `CREATE DATABASE': create-database.  statement. This option
     is typically used in conjunction with the `--all-databases' or
     `--databases' option because no *Note `CREATE DATABASE':
     create-database. statements are written unless one of those
     options is specified.

   * `--add-drop-table'

     Add a *Note `DROP TABLE': drop-table. statement before each *Note
     `CREATE TABLE': create-table.  statement.

   * `--add-drop-trigger'

     Add a *Note `DROP TRIGGER': drop-trigger. statement before each
     *Note `CREATE TRIGGER': create-trigger.  statement.

     *Note*:

     This option is supported only by *Note `mysqldump': mysqldump. as
     supplied with MySQL Cluster NDB 6.3.38, MySQL Cluster NDB 7.0.19,
     MySQL Cluster NDB 7.1.8, and later MySQL Cluster releases. It is
     not available when using MySQL 5.1.

   * `--add-locks'

     Surround each table dump with *Note `LOCK TABLES': lock-tables. and
     *Note `UNLOCK TABLES': lock-tables. statements. This results in
     faster inserts when the dump file is reloaded. See *Note
     insert-speed::.

   * `--all-databases', `-A'

     Dump all tables in all databases. This is the same as using the
     `--databases' option and naming all the databases on the command
     line.

   * `--all-tablespaces', `-Y'

     Adds to a table dump all SQL statements needed to create any
     tablespaces used by an *Note `NDBCLUSTER': mysql-cluster. table.
     This information is not otherwise included in the output from
     *Note `mysqldump': mysqldump. This option is currently relevant
     only to MySQL Cluster tables.

     This option was added in MySQL 5.1.6.

   * `--allow-keywords'

     Permit creation of column names that are keywords. This works by
     prefixing each column name with the table name.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, use this option
     to select which interface to use for connecting to the MySQL
     server.

     This option is supported only in the version of *Note `mysqldump':
     mysqldump. that is supplied with MySQL Cluster, beginning with
     MySQL Cluster NDB 6.3.4. It is not available in standard MySQL 5.1
     releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--comments', `-i'

     Write additional information in the dump file such as program
     version, server version, and host. This option is enabled by
     default. To suppress this additional information, use
     `--skip-comments'.

   * `--compact'

     Produce more compact output. This option enables the
     `--skip-add-drop-table', `--skip-add-locks', `--skip-comments',
     `--skip-disable-keys', and `--skip-set-charset' options.

     *Note*:

     Prior to MySQL 5.1.21, this option did not create valid SQL if the
     database dump contained views. The recreation of views requires
     the creation and removal of temporary tables and this option
     suppressed the removal of those temporary tables. As a workaround,
     use `--compact' with the `--add-drop-table' option and then
     manually adjust the dump file.

   * `--compatible=NAME'

     Produce output that is more compatible with other database systems
     or with older MySQL servers. The value of NAME can be `ansi',
     `mysql323', `mysql40', `postgresql', `oracle', `mssql', `db2',
     `maxdb', `no_key_options', `no_table_options', or
     `no_field_options'. To use several values, separate them by
     commas. These values have the same meaning as the corresponding
     options for setting the server SQL mode. See *Note sql-mode::.

     This option does not guarantee compatibility with other servers.
     It only enables those SQL mode values that are currently available
     for making dump output more compatible.  For example,
     `--compatible=oracle' does not map data types to Oracle types or
     use Oracle comment syntax.

     _This option requires a server version of 4.1.0 or higher_. With
     older servers, it does nothing.

   * `--complete-insert', `-c'

     Use complete *Note `INSERT': insert.  statements that include
     column names.

   * `--compress', `-C'

     Compress all information sent between the client and the server if
     both support compression.

   * `--create-options'

     Include all MySQL-specific table options in the *Note `CREATE
     TABLE': create-table. statements.

   * `--databases', `-B'

     Dump several databases. Normally, *Note `mysqldump': mysqldump.
     treats the first name argument on the command line as a database
     name and following names as table names. With this option, it
     treats all name arguments as database names. *Note `CREATE
     DATABASE': create-database. and *Note `USE': use.  statements are
     included in the output before each new database.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default value is
     `d:t:o,/tmp/mysqldump.trace'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.14.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set. See *Note
     charset-configuration::.  If no character set is specified, *Note
     `mysqldump': mysqldump. uses `utf8', and earlier versions use
     `latin1'.

     Prior to MySQL 5.1.38, this option has no effect for output data
     files produced by using the `--tab' option. See the description
     for that option.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqldump':
     mysqldump. normally reads the `[client]' and `[mysqldump]' groups.
     If the `--defaults-group-suffix=_other' option is given, *Note
     `mysqldump': mysqldump. also reads the `[client_other]' and
     `[mysqldump_other]' groups.

   * `--delayed-insert'

     Write *Note `INSERT DELAYED': insert-delayed.  statements rather
     than *Note `INSERT': insert.  statements.

   * `--delete-master-logs'

     On a master replication server, delete the binary logs by sending
     a *Note `PURGE BINARY LOGS': purge-binary-logs.  statement to the
     server after performing the dump operation.  This option
     automatically enables `--master-data'.

   * `--disable-keys', `-K'

     For each table, surround the *Note `INSERT': insert. statements
     with `/*!40000 ALTER TABLE TBL_NAME DISABLE KEYS */;' and
     `/*!40000 ALTER TABLE TBL_NAME ENABLE KEYS */;' statements. This
     makes loading the dump file faster because the indexes are created
     after all rows are inserted. This option is effective only for
     nonunique indexes of `MyISAM' tables. It has no effect for other
     tables.

   * `--dump-date'

     If the `--comments' option is given, *Note `mysqldump': mysqldump.
     produces a comment at the end of the dump of the following form:


          -- Dump completed on DATE

     However, the date causes dump files taken at different times to
     appear to be different, even if the data are otherwise identical.
     `--dump-date' and `--skip-dump-date' control whether the date is
     added to the comment. The default is `--dump-date' (include the
     date in the comment).  `--skip-dump-date' suppresses date
     printing. This option was added in MySQL 5.1.23.

   * `--events', `-E'

     Include Event Scheduler events for the dumped databases in the
     output. This option was added in MySQL 5.1.8.

   * `--extended-insert', `-e'

     Use multiple-row *Note `INSERT': insert.  syntax that include
     several `VALUES' lists.  This results in a smaller dump file and
     speeds up inserts when the file is reloaded.

   * `--fields-terminated-by=...',

     `--fields-enclosed-by=...',

     `--fields-optionally-enclosed-by=...',

     `--fields-escaped-by=...'

     These options are used with the `--tab' option and have the same
     meaning as the corresponding `FIELDS' clauses for *Note `LOAD DATA
     INFILE': load-data. See *Note load-data::.

   * `--first-slave'

     Deprecated. Use `--lock-all-tables' instead.  `--first-slave' is
     removed in MySQL 5.5.

   * `--flush-logs', `-F'

     Flush the MySQL server log files before starting the dump.  This
     option requires the `RELOAD' privilege. If you use this option in
     combination with the `--all-databases' option, the logs are
     flushed _for each database dumped_. The exception is when using
     `--lock-all-tables' or `--master-data': In this case, the logs are
     flushed only once, corresponding to the moment that all tables are
     locked. If you want your dump and the log flush to happen at
     exactly the same moment, you should use `--flush-logs' together
     with either `--lock-all-tables' or `--master-data'.

   * `--flush-privileges'

     Add a *Note `FLUSH PRIVILEGES': flush. statement to the dump
     output after dumping the `mysql' database. This option should be
     used any time the dump contains the `mysql' database and any other
     database that depends on the data in the `mysql' database for
     proper restoration. This option was added in MySQL 5.1.12.

   * `--force', `-f'

     Continue even if an SQL error occurs during a table dump.

     One use for this option is to cause *Note `mysqldump': mysqldump.
     to continue executing even when it encounters a view that has
     become invalid because the definition refers to a table that has
     been dropped. Without `--force', *Note `mysqldump': mysqldump.
     exits with an error message.  With `--force', *Note `mysqldump':
     mysqldump. prints the error message, but it also writes an SQL
     comment containing the view definition to the dump output and
     continues executing.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Dump data from the MySQL server on the given host. The default
     host is `localhost'.

   * `--hex-blob'

     Dump binary columns using hexadecimal notation (for example,
     `'abc'' becomes `0x616263'). The affected data types are *Note
     `BINARY': binary-varbinary, *Note `VARBINARY': binary-varbinary,
     the *Note `BLOB': blob. types, and *Note `BIT': bit-type.

   * `--ignore-table=DB_NAME.TBL_NAME'

     Do not dump the given table, which must be specified using both
     the database and table names. To ignore multiple tables, use this
     option multiple times. This option also can be used to ignore
     views.

   * `--insert-ignore'

     Write *Note `INSERT IGNORE': insert. statements rather than *Note
     `INSERT': insert. statements.

   * `--lines-terminated-by=...'

     This option is used with the `--tab' option and has the same
     meaning as the corresponding `LINES' clause for *Note `LOAD DATA
     INFILE': load-data. See *Note load-data::.

   * `--lock-all-tables', `-x'

     Lock all tables across all databases. This is achieved by
     acquiring a global read lock for the duration of the whole dump.
     This option automatically turns off `--single-transaction' and
     `--lock-tables'.

   * `--lock-tables', `-l'

     For each dumped database, lock all tables to be dumped before
     dumping them. The tables are locked with `READ LOCAL' to permit
     concurrent inserts in the case of `MyISAM' tables. For
     transactional tables such as `InnoDB', `--single-transaction' is a
     much better option than `--lock-tables' because it does not need
     to lock the tables at all.

     Because `--lock-tables' locks tables for each database separately,
     this option does not guarantee that the tables in the dump file
     are logically consistent between databases. Tables in different
     databases may be dumped in completely different states.

   * `--log-error=FILE_NAME'

     Log warnings and errors by appending them to the named file.  The
     default is to do no logging. This option was added in MySQL 5.1.18.

   * `--master-data[=VALUE]'

     Use this option to dump a master replication server to produce a
     dump file that can be used to set up another server as a slave of
     the master. It causes the dump output to include a *Note `CHANGE
     MASTER TO': change-master-to.  statement that indicates the binary
     log coordinates (file name and position) of the dumped server.
     These are the master server coordinates from which the slave
     should start replicating after you load the dump file into the
     slave.

     If the option value is 2, the *Note `CHANGE MASTER TO':
     change-master-to. statement is written as an SQL comment, and thus
     is informative only; it has no effect when the dump file is
     reloaded. If the option value is 1, the statement is not written
     as a comment and takes effect when the dump file is reloaded. If
     no option value is specified, the default value is 1.

     This option requires the `RELOAD' privilege and the binary log
     must be enabled.

     The `--master-data' option automatically turns off
     `--lock-tables'. It also turns on `--lock-all-tables', unless
     `--single-transaction' also is specified, in which case, a global
     read lock is acquired only for a short time at the beginning of
     the dump (see the description for `--single-transaction'). In all
     cases, any action on logs happens at the exact moment of the dump.

     It is also possible to set up a slave by dumping an existing slave
     of the master. To do this, use the following procedure on the
     existing slave:

       1. Stop the slave's SQL thread and get its current status:


               mysql> STOP SLAVE SQL_THREAD;
               mysql> SHOW SLAVE STATUS;

       2. From the output of the *Note `SHOW SLAVE STATUS':
          show-slave-status. statement, the binary log coordinates of
          the master server from which the new slave should start
          replicating are the values of the `Relay_Master_Log_File' and
          `Exec_Master_Log_Pos' fields. Denote those values as
          FILE_NAME and FILE_POS.

       3. Dump the slave server:


               shell> mysqldump --master-data=2 --all-databases > dumpfile

          Using `--master-data=2' works only if binary logging has been
          enabled on the slave. Otherwise, *Note `mysqldump':
          mysqldump. fails with the error `Binlogging on server not
          active'.  In this case you must handle any locking issues in
          another manner, using one or more of `--add-locks',
          `--lock-tables', `--lock-all-tables', or
          `--single-transaction', as required by your application and
          environment.

       4. Restart the slave:


               mysql> START SLAVE;

       5. On the new slave, load the dump file:


               shell> mysql < dumpfile

       6. On the new slave, set the replication coordinates to those of
          the master server obtained earlier:


               mysql> CHANGE MASTER TO
                   -> MASTER_LOG_FILE = 'FILE_NAME', MASTER_LOG_POS = FILE_POS;

          The *Note `CHANGE MASTER TO': change-master-to.  statement
          might also need other parameters, such as `MASTER_HOST' to
          point the slave to the correct master server host. Add any
          such parameters as necessary.

   * `--no-autocommit'

     Enclose the *Note `INSERT': insert. statements for each dumped
     table within `SET autocommit = 0' and *Note `COMMIT': commit.
     statements.

   * `--no-create-db', `-n'

     This option suppresses the *Note `CREATE DATABASE':
     create-database. statements that are otherwise included in the
     output if the `--databases' or `--all-databases' option is given.

   * `--no-create-info', `-t'

     Do not write *Note `CREATE TABLE': create-table.  statements that
     re-create each dumped table.

     *Note*:

     This option does _not_ not exclude statements creating log file
     groups or tablespaces from *Note `mysqldump': mysqldump. output;
     in MySQL 5.1.14 and later, you can use the `--no-tablespaces'
     option for this purpose.

   * `--no-data', `-d'

     Do not write any table row information (that is, do not dump table
     contents). This is useful if you want to dump only the *Note
     `CREATE TABLE': create-table. statement for the table (for
     example, to create an empty copy of the table by loading the dump
     file).

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--no-set-names', `-N'

     This has the same effect as `--skip-set-charset'.

   * `--no-tablespaces', `-y'

     This option suppresses all *Note `CREATE LOGFILE GROUP':
     create-logfile-group. and *Note `CREATE TABLESPACE':
     create-tablespace. statements in the output of *Note `mysqldump':
     mysqldump.

     This option was added in MySQL 5.1.14.

   * `--opt'

     This option is shorthand. It is the same as specifying
     `--add-drop-table' `--add-locks' `--create-options'
     `--disable-keys' `--extended-insert' `--lock-tables' `--quick'
     `--set-charset'. It should give you a fast dump operation and
     produce a dump file that can be reloaded into a MySQL server
     quickly.

     _The `--opt' option is enabled by default. Use `--skip-opt' to
     disable it._ See the discussion at the beginning of this section
     for information about selectively enabling or disabling a subset
     of the options affected by `--opt'.

   * `--order-by-primary'

     Dump each table's rows sorted by its primary key, or by its first
     unique index, if such an index exists. This is useful when dumping
     a `MyISAM' table to be loaded into an `InnoDB' table, but will
     make the dump operation take considerably longer.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqldump': mysqldump. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--quick', `-q'

     This option is useful for dumping large tables. It forces *Note
     `mysqldump': mysqldump. to retrieve rows for a table from the
     server a row at a time rather than retrieving the entire row set
     and buffering it in memory before writing it out.

   * `--quote-names', `-Q'

     Quote identifiers (such as database, table, and column names)
     within ```'' characters. If the `ANSI_QUOTES' SQL mode is enabled,
     identifiers are quoted within ``"'' characters. This option is
     enabled by default. It can be disabled with `--skip-quote-names',
     but this option should be given after any option such as
     `--compatible' that may enable `--quote-names'.

   * `--replace'

     Write *Note `REPLACE': replace. statements rather than *Note
     `INSERT': insert.  statements. This option was added in MySQL
     5.1.3.

   * `--result-file=FILE_NAME', `-r FILE_NAME'

     Direct output to a given file. This option should be used on
     Windows to prevent newline ``\n'' characters from being converted
     to ``\r\n'' carriage return/newline sequences. The result file is
     created and its previous contents overwritten, even if an error
     occurs while generating the dump.

   * `--routines', `-R'

     Include stored routines (procedures and functions) for the dumped
     databases in the output. Use of this option requires the `SELECT'
     privilege for the `mysql.proc' table. The output generated by
     using `--routines' contains *Note `CREATE PROCEDURE':
     create-procedure. and *Note `CREATE FUNCTION': create-function.
     statements to re-create the routines. However, these statements do
     not include attributes such as the routine creation and
     modification timestamps. This means that when the routines are
     reloaded, they will be created with the timestamps equal to the
     reload time.

     If you require routines to be re-created with their original
     timestamp attributes, do not use `--routines'. Instead, dump and
     reload the contents of the `mysql.proc' table directly, using a
     MySQL account that has appropriate privileges for the `mysql'
     database.

     This option was added in MySQL 5.1.2. Before that, stored routines
     are not dumped. Routine `DEFINER' values are not dumped until
     MySQL 5.1.8. This means that before 5.1.8, when routines are
     reloaded, they will be created with the definer set to the
     reloading user. If you require routines to be re-created with
     their original definer, dump and load the contents of the
     `mysql.proc' table directly as described earlier.

     Prior to MySQL 5.1.62, this option had no effect when used
     together with the `--xml' option. (Bug #11760384, Bug #52792)

   * `--set-charset'

     Add `SET NAMES DEFAULT_CHARACTER_SET' to the output. This option
     is enabled by default. To suppress the `SET NAMES' statement, use
     `--skip-set-charset'.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--single-transaction'

     This option sets the transaction isolation mode to `REPEATABLE
     READ' and sends a *Note `START TRANSACTION': commit. SQL statement
     to the server before dumping data. It is useful only with
     transactional tables such as `InnoDB', because then it dumps the
     consistent state of the database at the time when *Note `START
     TRANSACTION': commit. was issued without blocking any applications.

     When using this option, you should keep in mind that only `InnoDB'
     tables are dumped in a consistent state. For example, any `MyISAM'
     or `MEMORY' tables dumped while using this option may still change
     state.

     While a `--single-transaction' dump is in process, to ensure a
     valid dump file (correct table contents and binary log
     coordinates), no other connection should use the following
     statements: *Note `ALTER TABLE': alter-table, *Note `CREATE
     TABLE': create-table, *Note `DROP TABLE': drop-table, *Note
     `RENAME TABLE': rename-table, *Note `TRUNCATE TABLE':
     truncate-table. A consistent read is not isolated from those
     statements, so use of them on a table to be dumped can cause the
     *Note `SELECT': select. that is performed by *Note `mysqldump':
     mysqldump. to retrieve the table contents to obtain incorrect
     contents or fail.

     The `--single-transaction' option and the `--lock-tables' option
     are mutually exclusive because *Note `LOCK TABLES': lock-tables.
     causes any pending transactions to be committed implicitly.

     This option is not supported for MySQL Cluster tables; the results
     cannot be guaranteed to be consistent due to the fact that the
     *Note `NDBCLUSTER': mysql-cluster.  storage engine supports only
     the `READ_COMMITTED' transaction isolation level. You should
     always use *Note `NDB': mysql-cluster. backup and restore instead.

     To dump large tables, combine the `--single-transaction' option
     with the `--quick' option.

   * `--skip-comments'

     See the description for the `--comments' option.

   * `--skip-opt'

     See the description for the `--opt' option.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--tab=PATH', `-T PATH'

     Produce tab-separated text-format data files. For each dumped
     table, *Note `mysqldump': mysqldump. creates a `TBL_NAME.sql' file
     that contains the *Note `CREATE TABLE': create-table. statement
     that creates the table, and the server writes a `TBL_NAME.txt'
     file that contains its data. The option value is the directory in
     which to write the files.

     *Note*:

     This option should be used only when *Note `mysqldump': mysqldump.
     is run on the same machine as the *Note `mysqld': mysqld. server.
     You must have the `FILE' privilege, and the server must have
     permission to write files in the directory that you specify.

     By default, the `.txt' data files are formatted using tab
     characters between column values and a newline at the end of each
     line. The format can be specified explicitly using the
     `--fields-XXX' and `--lines-terminated-by' options.

     As of MySQL 5.1.38, column values are converted to the character
     set specified by the `--default-character-set' option. Prior to
     5.1.38 or if no such option is present, values are dumped using
     the `binary' character set. In effect, there is no character set
     conversion. If a table contains columns in several character sets,
     the output data file will as well and you may not be able to
     reload the file correctly.

   * `--tables'

     Override the `--databases' or `-B' option. *Note `mysqldump':
     mysqldump.  regards all name arguments following the option as
     table names.

   * `--triggers'

     Include triggers for each dumped table in the output. This option
     is enabled by default; disable it with `--skip-triggers'.

   * `--tz-utc'

     This option enables *Note `TIMESTAMP': datetime.  columns to be
     dumped and reloaded between servers in different time zones. *Note
     `mysqldump': mysqldump. sets its connection time zone to UTC and
     adds `SET TIME_ZONE='+00:00'' to the dump file. Without this
     option, *Note `TIMESTAMP': datetime. columns are dumped and
     reloaded in the time zones local to the source and destination
     servers, which can cause the values to change if the servers are
     in different time zones.  `--tz-utc' also protects against changes
     due to daylight saving time.  `--tz-utc' is enabled by default. To
     disable it, use `--skip-tz-utc'.  This option was added in MySQL
     5.1.2.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.

   * `--version', `-V'

     Display version information and exit.

   * `--where='WHERE_CONDITION'', `-w 'WHERE_CONDITION''

     Dump only rows selected by the given `WHERE' condition. Quotes
     around the condition are mandatory if it contains spaces or other
     characters that are special to your command interpreter.

     Examples:


          --where="user='jimf'"
          -w"userid>1"
          -w"userid<1"

   * `--xml', `-X'

     Write dump output as well-formed XML.

     *`NULL', `'NULL'', and Empty Values*: For a column named
     COLUMN_NAME, the `NULL' value, an empty string, and the string
     value `'NULL'' are distinguished from one another in the output
     generated by this option as follows.

     For a column named COLUMN_NAME, the `NULL' value, an empty string,
     and the string value `'NULL'' are distinguished from one another
     in the XML output generated by the *Note `mysqldump': mysqldump.
     `--xml', `-X' option, as shown in this table.

     Value:                             XML Representation:
     `NULL' (_unknown value_)           `<field name="COLUMN_NAME"
                                        xsi:nil="true" />'
     `''' (_empty string_)              `<field
                                        name="COLUMN_NAME"></field>'
     `'NULL'' (_string value_)          `<field
                                        name="COLUMN_NAME">NULL</field>'

     Beginning with MySQL 5.1.12, the output from the *Note `mysql':
     mysql. client when run using the `--xml' option also follows the
     preceding rules. (See *Note mysql-command-options::.)

     Beginning with MySQL 5.1.18, XML output from *Note `mysqldump':
     mysqldump. includes the XML namespace, as shown here:


          shell> mysqldump --xml -u root world City
          <?xml version="1.0"?>
          <mysqldump xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
          <database name="world">
          <table_structure name="City">
          <field Field="ID" Type="int(11)" Null="NO" Key="PRI" Extra="auto_increment" />
          <field Field="Name" Type="char(35)" Null="NO" Key="" Default="" Extra="" />
          <field Field="CountryCode" Type="char(3)" Null="NO" Key="" Default="" Extra="" />
          <field Field="District" Type="char(20)" Null="NO" Key="" Default="" Extra="" />
          <field Field="Population" Type="int(11)" Null="NO" Key="" Default="0" Extra="" />
          <key Table="City" Non_unique="0" Key_name="PRIMARY" Seq_in_index="1" Column_name="ID"
          Collation="A" Cardinality="4079" Null="" Index_type="BTREE" Comment="" />
          <options Name="City" Engine="MyISAM" Version="10" Row_format="Fixed" Rows="4079"
          Avg_row_length="67" Data_length="273293" Max_data_length="18858823439613951"
          Index_length="43008" Data_free="0" Auto_increment="4080"
          Create_time="2007-03-31 01:47:01" Update_time="2007-03-31 01:47:02"
          Collation="latin1_swedish_ci" Create_options="" Comment="" />
          </table_structure>
          <table_data name="City">
          <row>
          <field name="ID">1</field>
          <field name="Name">Kabul</field>
          <field name="CountryCode">AFG</field>
          <field name="District">Kabol</field>
          <field name="Population">1780000</field>
          </row>

          ...

          <row>
          <field name="ID">4079</field>
          <field name="Name">Rafah</field>
          <field name="CountryCode">PSE</field>
          <field name="District">Rafah</field>
          <field name="Population">92020</field>
          </row>
          </table_data>
          </database>
          </mysqldump>

Prior to MySQL 5.1.62, this option prevented the `--routines' option
from working correctly--that is, no stored routines, triggers, or events
could be dumped in XML format. (Bug #11760384, Bug #52792)

You can also set the following variables by using `--VAR_NAME=VALUE'
syntax:

   * `max_allowed_packet'

     The maximum size of the buffer for client/server communication.
     The default is 24MB, the maximum is 1GB.

   * `net_buffer_length'

     The initial size of the buffer for client/server communication.
     When creating multiple-row *Note `INSERT': insert. statements (as
     with the `--extended-insert' or `--opt' option), *Note
     `mysqldump': mysqldump. creates rows up to `net_buffer_length'
     length.  If you increase this variable, you should also ensure that
     the `net_buffer_length' variable in the MySQL server is at least
     this large.

A common use of *Note `mysqldump': mysqldump. is for making a backup of
an entire database:


     shell> mysqldump DB_NAME > BACKUP-FILE.SQL

You can load the dump file back into the server like this:


     shell> mysql DB_NAME < BACKUP-FILE.SQL

Or like this:


     shell> mysql -e "source /PATH-TO-BACKUP/BACKUP-FILE.SQL" DB_NAME

*Note `mysqldump': mysqldump. is also very useful for populating
databases by copying data from one MySQL server to another:


     shell> mysqldump --opt DB_NAME | mysql --host=REMOTE_HOST -C DB_NAME

It is possible to dump several databases with one command:


     shell> mysqldump --databases DB_NAME1 [DB_NAME2 ...] > my_databases.sql

To dump all databases, use the `--all-databases' option:


     shell> mysqldump --all-databases > all_databases.sql

For `InnoDB' tables, *Note `mysqldump': mysqldump. provides a way of
making an online backup:


     shell> mysqldump --all-databases --master-data --single-transaction > all_databases.sql

This backup acquires a global read lock on all tables (using *Note
`FLUSH TABLES WITH READ LOCK': flush.) at the beginning of the dump. As
soon as this lock has been acquired, the binary log coordinates are
read and the lock is released. If long updating statements are running
when the *Note `FLUSH': flush. statement is issued, the MySQL server
may get stalled until those statements finish. After that, the dump
becomes lock free and does not disturb reads and writes on the tables.
If the update statements that the MySQL server receives are short (in
terms of execution time), the initial lock period should not be
noticeable, even with many updates.

For point-in-time recovery (also known as `roll-forward,' when you need
to restore an old backup and replay the changes that happened since
that backup), it is often useful to rotate the binary log (see *Note
binary-log::) or at least know the binary log coordinates to which the
dump corresponds:


     shell> mysqldump --all-databases --master-data=2 > all_databases.sql

Or:


     shell> mysqldump --all-databases --flush-logs --master-data=2
                   > all_databases.sql

The `--master-data' and `--single-transaction' options can be used
simultaneously, which provides a convenient way to make an online
backup suitable for use prior to point-in-time recovery if tables are
stored using the `InnoDB' storage engine.

For more information on making backups, see *Note backup-methods::, and
*Note backup-strategy-example::.

If you encounter problems backing up views, please read the section
that covers restrictions on views which describes a workaround for
backing up views when this fails due to insufficient privileges. See
*Note view-restrictions::.


File: manual.info,  Node: mysqlimport,  Next: mysqlshow,  Prev: mysqldump,  Up: programs-client

4.5.5 `mysqlimport' -- A Data Import Program
--------------------------------------------

The *Note `mysqlimport': mysqlimport. client provides a command-line
interface to the *Note `LOAD DATA INFILE': load-data. SQL statement.
Most options to *Note `mysqlimport': mysqlimport. correspond directly
to clauses of *Note `LOAD DATA INFILE': load-data. syntax. See *Note
load-data::.

Invoke *Note `mysqlimport': mysqlimport. like this:


     shell> mysqlimport [OPTIONS] DB_NAME TEXTFILE1 [TEXTFILE2 ...]

For each text file named on the command line, *Note `mysqlimport':
mysqlimport. strips any extension from the file name and uses the
result to determine the name of the table into which to import the
file's contents. For example, files named `patient.txt',
`patient.text', and `patient' all would be imported into a table named
`patient'.

*Note `mysqlimport': mysqlimport. supports the following options, which
can be specified on the command line or in the `[mysqlimport]' and
`[client]' groups of an option file. For information about option files
used by MySQL programs, see *Note option-files::.

*`mysqlimport' Options*

Format             Description                      Introduced
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-columns=column_listThis option takes a              
                   comma-separated list of column   
                   names as its value               
-compress          Compress all information sent    
                   between client and server        
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     5.1.14
                   memory, and CPU statistics when  
                   program exits                    
-default-character-set=charset_nameSpecify default character set    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-delete            Empty the table before           
                   importing the text file          
-fields-enclosed-by=stringThis option has the same         
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-fields-escaped-by This option has the same         
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-fields-optionally-enclosed-by=stringThis option has the same         
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-fields-terminated-by=string- This option has the same       
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-force             Continue even if an SQL error    
                   occurs                           
-help              Display help message and exit    
-host=host_name    Connect to MySQL server on       
                   given host                       
-ignore            See the description for the      
                   -replace option                  
-ignore-lines=#    Ignore the first N lines of the  
                   data file                        
-lines-terminated-by=stringThis option has the same         
                   meaning as the corresponding     
                   clause for LOAD DATA INFILE      
-local             Read input files locally from    
                   the client host                  
-lock-tables       Lock all tables for writing      
                   before processing any text files 
-low-priority      Use LOW_PRIORITY when loading    
                   the table.                       
-no-defaults       Read no option files             
-password[=password]Password to use when connecting  
                   to server                        
-pipe              On Windows, connect to server    
                   using named pipe                 
-port=port_num     TCP/IP port number to use for    
                   connection                       
-print-defaults    Print defaults                   
-protocol=type     Connection protocol to use       
-replace           The -replace and -ignore         
                   options control handling of      
                   input rows that duplicate        
                   existing rows on unique key      
                   values                           
-shared-memory-base-name=nameThe name of shared memory to     
                   use for shared-memory            
                   connections                      
-silent            Produce output only when errors  
                   occur                            
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-ssl               Enable SSL for connection        
-ssl-ca=file_name  Path of file that contains list  
                   of trusted SSL CAs               
-ssl-capath=dir_namePath of directory that contains  
                   trusted SSL CA certificates in   
                   PEM format                       
-ssl-cert=file_namePath of file that contains X509  
                   certificate in PEM format        
-ssl-cipher=cipher_listList of permitted ciphers to     
                   use for SSL encryption           
-ssl-key=file_name Path of file that contains X509  
                   key in PEM format                
-ssl-verify-server-certVerify server Common Name value  5.1.11
                   in its certificate against host  
                   name used when connecting to     
                   server                           
-use-threads=#     Number of threads for parallel   5.1.7
                   file-loading                     
-user=user_name,   MySQL user name to use when      
                   connecting to server             
-verbose           Verbose mode                     
-version           Display version information and  
                   exit                             

   * `--help', `-?'

     Display a help message and exit.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, this option can
     be used to select which interface is employed when connecting to
     the MySQL server.

     This option is supported only in the version of *Note
     `mysqlimport': mysqlimport. that is supplied with MySQL Cluster,
     beginning with MySQL Cluster NDB 6.3.4. It is not available in
     standard MySQL 5.1 releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--columns=COLUMN_LIST', `-c COLUMN_LIST'

     This option takes a comma-separated list of column names as its
     value. The order of the column names indicates how to match data
     file columns with table columns.

   * `--compress', `-C'

     Compress all information sent between the client and the server if
     both support compression.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.14.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set. See *Note
     charset-configuration::.

     Some options, such as `--opt', automatically enable
     `--lock-tables'. If you want to override this, use
     `--skip-lock-tables' at the end of the option list.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqlimport':
     mysqlimport. normally reads the `[client]' and `[mysqlimport]'
     groups. If the `--defaults-group-suffix=_other' option is given,
     *Note `mysqlimport': mysqlimport. also reads the `[client_other]'
     and `[mysqlimport_other]' groups.

   * `--delete', `-D'

     Empty the table before importing the text file.

   * `--fields-terminated-by=...',

     `--fields-enclosed-by=...',

     `--fields-optionally-enclosed-by=...',

     `--fields-escaped-by=...'

     These options have the same meaning as the corresponding clauses
     for *Note `LOAD DATA INFILE': load-data. See *Note load-data::.

   * `--force', `-f'

     Ignore errors. For example, if a table for a text file does not
     exist, continue processing any remaining files. Without `--force',
     *Note `mysqlimport': mysqlimport. exits if a table does not exist.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Import data to the MySQL server on the given host. The default
     host is `localhost'.

   * `--ignore', `-i'

     See the description for the `--replace' option.

   * `--ignore-lines=N'

     Ignore the first N lines of the data file.

   * `--lines-terminated-by=...'

     This option has the same meaning as the corresponding clause for
     *Note `LOAD DATA INFILE': load-data. For example, to import
     Windows files that have lines terminated with carriage
     return/linefeed pairs, use `--lines-terminated-by="\r\n"'.  (You
     might have to double the backslashes, depending on the escaping
     conventions of your command interpreter.) See *Note load-data::.

   * `--local', `-L'

     Read input files locally from the client host.

   * `--lock-tables', `-l'

     Lock _all_ tables for writing before processing any text files.
     This ensures that all tables are synchronized on the server.

   * `--low-priority'

     Use `LOW_PRIORITY' when loading the table.  This affects only
     storage engines that use only table-level locking (such as
     `MyISAM', `MEMORY', and `MERGE').

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can be
     used to prevent them from being read.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqlimport': mysqlimport. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--replace', `-r'

     The `--replace' and `--ignore' options control handling of input
     rows that duplicate existing rows on unique key values. If you
     specify `--replace', new rows replace existing rows that have the
     same unique key value.  If you specify `--ignore', input rows that
     duplicate an existing row on a unique key value are skipped. If
     you do not specify either option, an error occurs when a duplicate
     key value is found, and the rest of the text file is ignored.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--silent', `-s'

     Silent mode. Produce output only when errors occur.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--use-threads=N'

     Load files in parallel using N threads. This option was added in
     MySQL 5.1.7.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.

   * `--version', `-V'

     Display version information and exit.

Here is a sample session that demonstrates use of *Note `mysqlimport':
mysqlimport.:


     shell> mysql -e 'CREATE TABLE imptest(id INT, n VARCHAR(30))' test
     shell> ed
     a
     100     Max Sydow
     101     Count Dracula
     .
     w imptest.txt
     32
     q
     shell> od -c imptest.txt
     0000000   1   0   0  \t   M   a   x       S   y   d   o   w  \n   1   0
     0000020   1  \t   C   o   u   n   t       D   r   a   c   u   l   a  \n
     0000040
     shell> mysqlimport --local test imptest.txt
     test.imptest: Records: 2  Deleted: 0  Skipped: 0  Warnings: 0
     shell> mysql -e 'SELECT * FROM imptest' test
     +------+---------------+
     | id   | n             |
     +------+---------------+
     |  100 | Max Sydow     |
     |  101 | Count Dracula |
     +------+---------------+


File: manual.info,  Node: mysqlshow,  Next: mysqlslap,  Prev: mysqlimport,  Up: programs-client

4.5.6 `mysqlshow' -- Display Database, Table, and Column Information
--------------------------------------------------------------------

The *Note `mysqlshow': mysqlshow. client can be used to quickly see
which databases exist, their tables, or a table's columns or indexes.

*Note `mysqlshow': mysqlshow. provides a command-line interface to
several SQL *Note `SHOW': show. statements.  See *Note show::. The same
information can be obtained by using those statements directly. For
example, you can issue them from the *Note `mysql': mysql. client
program.

Invoke *Note `mysqlshow': mysqlshow. like this:


     shell> mysqlshow [OPTIONS] [DB_NAME [TBL_NAME [COL_NAME]]]

   * If no database is given, a list of database names is shown.

   * If no table is given, all matching tables in the database are
     shown.

   * If no column is given, all matching columns and column types in
     the table are shown.

The output displays only the names of those databases, tables, or
columns for which you have some privileges.

If the last argument contains shell or SQL wildcard characters (``*'',
``?'', ``%'', or ``_''), only those names that are matched by the
wildcard are shown. If a database name contains any underscores, those
should be escaped with a backslash (some Unix shells require two) to
get a list of the proper tables or columns. ``*'' and ``?'' characters
are converted into SQL ``%'' and ``_'' wildcard characters. This might
cause some confusion when you try to display the columns for a table
with a ``_'' in the name, because in this case, *Note `mysqlshow':
mysqlshow. shows you only the table names that match the pattern. This
is easily fixed by adding an extra ``%'' last on the command line as a
separate argument.

*Note `mysqlshow': mysqlshow. supports the following options, which can
be specified on the command line or in the `[mysqlshow]' and `[client]'
groups of an option file. For information about option files used by
MySQL programs, see *Note option-files::.

*`mysqlshow' Options*

Format             Description                      Introduced
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-compress          Compress all information sent    
                   between client and server        
-count             Show the number of rows per      
                   table                            
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     5.1.14
                   memory, and CPU statistics when  
                   program exits                    
-default-character-set=charset_nameSpecify default character set    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-help              Display help message and exit    
-host=host_name    Connect to MySQL server on       
                   given host                       
-keys              Show table indexes               
-no-defaults       Read no option files             
-password[=password]Password to use when connecting  
                   to server                        
-pipe              On Windows, connect to server    
                   using named pipe                 
-port=port_num     TCP/IP port number to use for    
                   connection                       
-print-defaults    Print defaults                   
-protocol=type     Connection protocol to use       
-shared-memory-base-name=nameThe name of shared memory to     
                   use for shared-memory            
                   connections                      
-show-table-type   Show a column indicating the     
                   table type                       
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-ssl               Enable SSL for connection        
-ssl-ca=file_name  Path of file that contains list  
                   of trusted SSL CAs               
-ssl-capath=dir_namePath of directory that contains  
                   trusted SSL CA certificates in   
                   PEM format                       
-ssl-cert=file_namePath of file that contains X509  
                   certificate in PEM format        
-ssl-cipher=cipher_listList of permitted ciphers to     
                   use for SSL encryption           
-ssl-key=file_name Path of file that contains X509  
                   key in PEM format                
-ssl-verify-server-certVerify server Common Name value  5.1.11
                   in its certificate against host  
                   name used when connecting to     
                   server                           
-status            Display extra information about  
                   each table                       
-user=user_name,   MySQL user name to use when      
                   connecting to server             
-verbose           Verbose mode                     
-version           Display version information and  
                   exit                             

   * `--help', `-?'

     Display a help message and exit.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, use this option
     to select which interface to use for connecting to the MySQL
     server.

     This option is supported only in the version of *Note `mysqlshow':
     mysqlshow. that is supplied with MySQL Cluster, beginning with
     MySQL Cluster NDB 6.3.4. It is not available in standard MySQL 5.1
     releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--compress', `-C'

     Compress all information sent between the client and the server if
     both support compression.

   * `--count'

     Show the number of rows per table. This can be slow for
     non-`MyISAM' tables.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.14.

   * `--default-character-set=CHARSET_NAME'

     Use CHARSET_NAME as the default character set. See *Note
     charset-configuration::.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqlshow':
     mysqlshow. normally reads the `[client]' and `[mysqlshow]' groups.
     If the `--defaults-group-suffix=_other' option is given, *Note
     `mysqlshow': mysqlshow. also reads the `[client_other]' and
     `[mysqlshow_other]' groups.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--keys', `-k'

     Show table indexes.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqlshow': mysqlshow. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

   * `--show-table-type', `-t'

     Show a column indicating the table type, as in *Note `SHOW FULL
     TABLES': show-tables. The type is `BASE TABLE' or `VIEW'.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--status', `-i'

     Display extra information about each table.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.
     This option can be used multiple times to increase the amount of
     information.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: mysqlslap,  Prev: mysqlshow,  Up: programs-client

4.5.7 `mysqlslap' -- Load Emulation Client
------------------------------------------

*Note `mysqlslap': mysqlslap. is a diagnostic program designed to
emulate client load for a MySQL server and to report the timing of each
stage. It works as if multiple clients are accessing the server. *Note
`mysqlslap': mysqlslap. is available as of MySQL 5.1.4.

Invoke *Note `mysqlslap': mysqlslap. like this:


     shell> mysqlslap [OPTIONS]

Some options such as `--create' or `--query' enable you to specify a
string containing an SQL statement or a file containing statements. If
you specify a file, by default it must contain one statement per line.
(That is, the implicit statement delimiter is the newline character.)
Use the `--delimiter' option to specify a different delimiter, which
enables you to specify statements that span multiple lines or place
multiple statements on a single line. You cannot include comments in a
file; *Note `mysqlslap': mysqlslap. does not understand them.

*Note `mysqlslap': mysqlslap. runs in three stages:

  1. Create schema, table, and optionally any stored programs or data
     to use for the test. This stage uses a single client connection.

  2. Run the load test. This stage can use many client connections.

  3. Clean up (disconnect, drop table if specified). This stage uses a
     single client connection.

Examples:

Supply your own create and query SQL statements, with 50 clients
querying and 200 selects for each (enter the command on a single line):


     mysqlslap --delimiter=";"
       --create="CREATE TABLE a (b int);INSERT INTO a VALUES (23)"
       --query="SELECT * FROM a" --concurrency=50 --iterations=200

Let *Note `mysqlslap': mysqlslap. build the query SQL statement with a
table of two *Note `INT': integer-types. columns and three *Note
`VARCHAR': char. columns. Use five clients querying 20 times each. Do
not create the table or insert the data (that is, use the previous
test's schema and data):


     mysqlslap --concurrency=5 --iterations=20
       --number-int-cols=2 --number-char-cols=3
       --auto-generate-sql

Tell the program to load the create, insert, and query SQL statements
from the specified files, where the `create.sql' file has multiple
table creation statements delimited by `';'' and multiple insert
statements delimited by `';''. The `--query' file will have multiple
queries delimited by `';''. Run all the load statements, then run all
the queries in the query file with five clients (five times each):


     mysqlslap --concurrency=5
       --iterations=5 --query=query.sql --create=create.sql
       --delimiter=";"

*Note `mysqlslap': mysqlslap. supports the following options, which can
be specified on the command line or in the `[mysqlslap]' and `[client]'
groups of an option file. For information about option files used by
MySQL programs, see *Note option-files::.

*`mysqlslap' Options*

Format             Description                      IntroducedRemoved
-auto-generate-sql Generate SQL statements                  
                   automatically when they are not          
                   supplied in files or using               
                   command options                          
-auto-generate-sql-add-autoincrementAdd AUTO_INCREMENT column to     5.1.18  
                   automatically generated tables           
-auto-generate-sql-execute-number=#Specify how many queries to      5.1.18  
                   generate automatically                   
-auto-generate-sql-guid-primaryAdd a GUID-based primary key to  5.1.18  
                   automatically generated tables           
-auto-generate-sql-load-type=typeSpecify how many queries to      5.1.16  
                   generate automatically                   
-auto-generate-sql-secondary-indexes=#Specify how many secondary       5.1.18  
                   indexes to add to automatically          
                   generated tables                         
-auto-generate-sql-unique-query-number=#How many different queries to    5.1.18  
                   generate for automatic tests.            
-auto-generate-sql-unique-write-number=#How many different queries to    5.1.18  
                   generate for                             
                   -auto-generate-sql-write-number          
-auto-generate-sql-write-number=#How many row inserts to perform  5.1.16  
                   on each thread                           
-commit=#          How many statements to execute   5.1.21  
                   before committing.                       
-compress          Compress all information sent            
                   between client and server                
-concurrency=#     Number of clients to simulate            
                   when issuing the SELECT                  
                   statement                                
-create=value      File or string containing the            
                   statement to use for creating            
                   the table                                
-create-schema=valueSchema in which to run the tests 5.1.5   
-csv=[file]        Generate output in                       
                   comma-separated values format            
-debug[=debug_options]Write a debugging log                    
-debug-check       Print debugging information      5.1.21  
                   when program exits                       
-debug-info        Print debugging information,     5.1.21  
                   memory, and CPU statistics when          
                   program exits                            
-defaults-extra-file=file_nameRead option file in addition to          
                   usual option files                       
-defaults-file=file_nameRead only named option file              
-defaults-group-suffix=strOption group suffix value                
-delimiter=str     Delimiter to use in SQL                  
                   statements                               
-detach=#          Detach (close and reopen) each   5.1.21  
                   connection after each N                  
                   statements                               
-engine=engine_nameStorage engine to use for                
                   creating the table                       
-help              Display help message and exit            
-host=host_name    Connect to MySQL server on               
                   given host                               
-iterations=#      Number of times to run the tests         
-lock-directory=pathDirectory to use for storing     5.1.5   5.1.18
                   locks                                    
-no-defaults       Read no option files                     
-no-drop           Do not drop any schema created   5.1.57  
                   during the test run                      
-number-char-cols=#Number of VARCHAR columns to             
                   use if -auto-generate-sql is             
                   specified                                
-number-int-cols=# Number of INT columns to use if          
                   -auto-generate-sql is specified          
-number-of-queries=#Limit each client to             5.1.5   
                   approximately this number of             
                   queries                                  
-only-print        Do not connect to databases.     5.1.5   
                   mysqlslap only prints what it            
                   would have done                          
-password[=password]Password to use when connecting          
                   to server                                
-pipe              On Windows, connect to server            
                   using named pipe                         
-port=port_num     TCP/IP port number to use for            
                   connection                               
-post-query=value  File or string containing the    5.1.18  
                   statement to execute after the           
                   tests have completed                     
-post-system=str   String to execute using          5.1.21  
                   system() after the tests have            
                   completed                                
-pre-query=value   File or string containing the    5.1.18  
                   statement to execute before              
                   running the tests                        
-pre-system=str    String to execute using          5.1.21  
                   system() before running the              
                   tests                                    
-preserve-schema   Preserve the schema from the     5.1.5   5.1.23
                   mysqlslap run                            
-print-defaults    Print defaults                           
-protocol=type     Connection protocol to use               
-query=value       File or string containing the            
                   SELECT statement to use for              
                   retrieving data                          
-shared-memory-base-name=nameThe name of shared memory to             
                   use for shared-memory                    
                   connections                              
-silent            Silent mode                              
-slave             Follow master locks for other    5.1.5   5.1.18
                   mysqlslap clients                        
-socket=path       For connections to localhost,            
                   the Unix socket file to use              
-ssl               Enable SSL for connection                
-ssl-ca=file_name  Path of file that contains list          
                   of trusted SSL CAs                       
-ssl-capath=dir_namePath of directory that contains          
                   trusted SSL CA certificates in           
                   PEM format                               
-ssl-cert=file_namePath of file that contains X509          
                   certificate in PEM format                
-ssl-cipher=cipher_listList of permitted ciphers to             
                   use for SSL encryption                   
-ssl-key=file_name Path of file that contains X509  5.1.11  
                   key in PEM format                        
-ssl-verify-server-certVerify server Common Name value          
                   in its certificate against host          
                   name used when connecting to             
                   server                                   
-use-threads       On Unix, the default is to use   5.1.6   5.1.18
                   fork() calls                             
-user=user_name,   MySQL user name to use when              
                   connecting to server                     
-verbose           Verbose mode                             
-version           Display version information and          
                   exit                                     

   * `--help', `-?'

     Display a help message and exit.

   * `--auto-generate-sql', `-a'

     Generate SQL statements automatically when they are not supplied
     in files or using command options.

   * `--auto-generate-sql-add-autoincrement'

     Add an `AUTO_INCREMENT' column to automatically generated tables.
     This option was added in MySQL 5.1.18.

   * `--auto-generate-sql-execute-number=N'

     Specify how many queries to generate automatically. This option
     was added in MySQL 5.1.18.

   * `--auto-generate-sql-guid-primary'

     Add a GUID-based primary key to automatically generated tables.
     This option was added in MySQL 5.1.18.

   * `--auto-generate-sql-load-type=TYPE'

     Specify the test load type. The permissible values are `read'
     (scan tables), `write' (insert into tables), `key' (read primary
     keys), `update' (update primary keys), or `mixed' (half inserts,
     half scanning selects). The default is `mixed'. This option was
     added in MySQL 5.1.16.

   * `--auto-generate-sql-secondary-indexes=N'

     Specify how many secondary indexes to add to automatically
     generated tables. By default, none are added. This option was
     added in MySQL 5.1.18.

   * `--auto-generate-sql-unique-query-number=N'

     How many different queries to generate for automatic tests.  For
     example, if you run a `key' test that performs 1000 selects, you
     can use this option with a value of 1000 to run 1000 unique
     queries, or with a value of 50 to perform 50 different selects.
     The default is 10. This option was added in MySQL 5.1.18.

   * `--auto-generate-sql-unique-write-number=N'

     How many different queries to generate for
     `--auto-generate-sql-write-number'.  The default is 10. This
     option was added in MySQL 5.1.18.

   * `--auto-generate-sql-write-number=N'

     How many row inserts to perform on each thread. The default is
     100. This option was added in MySQL 5.1.16.

   * `--commit=N'

     How many statements to execute before committing. The default is 0
     (no commits are done). This option was added in MySQL 5.1.21.

   * `--compress', `-C'

     Compress all information sent between the client and the server if
     both support compression.

   * `--concurrency=N', `-c N'

     The number of clients to simulate when issuing the *Note `SELECT':
     select. statement.

   * `--create=VALUE'

     The file or string containing the statement to use for creating
     the table.

   * `--create-schema=VALUE'

     The schema in which to run the tests. This option was added in
     MySQL 5.1.5.

     *Note*:

     If the `--auto-generate-sql' option is also given, *Note
     `mysqlslap': mysqlslap. drops the schema at the end of the test
     run. To avoid this, use the `--no-drop' option as well.

   * `--csv[=FILE_NAME]'

     Generate output in comma-separated values format. The output goes
     to the named file, or to the standard output if no file is given.
     This option was added in MySQL 5.1.5.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o,/tmp/mysqlslap.trace'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info', `-T'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.21.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqlslap':
     mysqlslap. normally reads the `[client]' and `[mysqlslap]' groups.
     If the `--defaults-group-suffix=_other' option is given, *Note
     `mysqlslap': mysqlslap. also reads the `[client_other]' and
     `[mysqlslap_other]' groups.

   * `--delimiter=STR', `-F STR'

     The delimiter to use in SQL statements supplied in files or using
     command options.

   * `--detach=N'

     Detach (close and reopen) each connection after each N statements.
     The default is 0 (connections are not detached). This option was
     added in MySQL 5.1.21.

   * `--engine=ENGINE_NAME', `-e ENGINE_NAME'

     The storage engine to use for creating tables.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--iterations=N', `-i N'

     The number of times to run the tests.

   * `--lock-directory=PATH'

     The directory to use for storing locks. This option was added in
     MySQL 5.1.5 and removed in 5.1.18.

   * `--no-drop'

     Prevent *Note `mysqlslap': mysqlslap. from dropping any schema it
     creates during the test run. This option was added in MySQL 5.1.57.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--number-char-cols=N', `-x N'

     The number of *Note `VARCHAR': char. columns to use if
     `--auto-generate-sql' is specified.

   * `--number-int-cols=N', `-y N'

     The number of *Note `INT': integer-types. columns to use if
     `--auto-generate-sql' is specified.

   * `--number-of-queries=N'

     Limit each client to approximately this many queries. Query
     counting takes into account the statement delimiter. For example,
     if you invoke *Note `mysqlslap': mysqlslap. as follows, the `;'
     delimiter is recognized so that each instance of the query string
     counts as two queries. As a result, 5 rows (not 10) are inserted.


          shell> mysqlslap --delimiter=";" --number-of-queries=10
                   --query="use test;insert into t values(null)"

     This option was added in MySQL 5.1.5.

   * `--only-print'

     Do not connect to databases. *Note `mysqlslap': mysqlslap.  only
     prints what it would have done. This option was added in MySQL
     5.1.5.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqlslap': mysqlslap. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--pipe', `-W'

     On Windows, connect to the server using a named pipe. This option
     applies only if the server supports named-pipe connections.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--post-query=VALUE'

     The file or string containing the statement to execute after the
     tests have completed. This execution is not counted for timing
     purposes. This option was added in MySQL 5.1.18.

   * `--post-system=STR'

     The string to execute using `system()' after the tests have
     completed. This execution is not counted for timing purposes. This
     option was added in MySQL 5.1.21.

   * `--pre-query=VALUE'

     The file or string containing the statement to execute before
     running the tests. This execution is not counted for timing
     purposes. This option was added in MySQL 5.1.18.

   * `--pre-system=STR'

     The string to execute using `system()' before running the tests.
     This execution is not counted for timing purposes. This option was
     added in MySQL 5.1.21.

   * `--preserve-schema'

     Preserve the schema from the *Note `mysqlslap': mysqlslap.  run.
     The `--auto-generate-sql' and `--create' options disable this
     option. This option was added in MySQL 5.1.5 and removed in MySQL
     5.1.23.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--query=VALUE', `-q VALUE'

     The file or string containing the *Note `SELECT': select.
     statement to use for retrieving data.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. This option applies only if
     the server supports shared-memory connections.

   * `--silent', `-s'

     Silent mode. No output.

   * `--slave'

     Follow master locks for other *Note `mysqlslap': mysqlslap.
     clients. Use this option if you are trying to synchronize around
     one master server with `--lock-directory' plus NFS.  This option
     was added in MySQL 5.1.5 and removed in 5.1.18.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to connect to the
     server using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--use-threads'

     On Unix, the default is to use `fork()' calls and this option
     causes `pthread' calls to be used instead. (On Windows, the
     default is to use `pthread' calls and the option has no effect.)
     This option was added in MySQL 5.1.6 and removed in 5.1.18.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.
     This option can be used multiple times to increase the amount of
     information.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: programs-admin-utils,  Next: programs-development,  Prev: programs-client,  Up: programs

4.6 MySQL Administrative and Utility Programs
=============================================

* Menu:

* innochecksum::                 `innochecksum' --- Offline InnoDB File Checksum Utility
* myisam-ftdump::                `myisam_ftdump' --- Display Full-Text Index information
* myisamchk::                    `myisamchk' --- MyISAM Table-Maintenance Utility
* myisamlog::                    `myisamlog' --- Display MyISAM Log File Contents
* myisampack::                   `myisampack' --- Generate Compressed, Read-Only MyISAM Tables
* mysqlaccess::                  `mysqlaccess' --- Client for Checking Access Privileges
* mysqlbinlog::                  `mysqlbinlog' --- Utility for Processing Binary Log Files
* mysqldumpslow::                `mysqldumpslow' --- Summarize Slow Query Log Files
* mysqlhotcopy::                 `mysqlhotcopy' --- A Database Backup Program
* instance-manager::             `mysqlmanager' --- The MySQL Instance Manager
* mysql-convert-table-format::   `mysql_convert_table_format' --- Convert Tables to Use a Given Storage Engine
* mysql-find-rows::              `mysql_find_rows' --- Extract SQL Statements from Files
* mysql-fix-extensions::         `mysql_fix_extensions' --- Normalize Table File Name Extensions
* mysql-setpermission::          `mysql_setpermission' --- Interactively Set Permissions in Grant Tables
* mysql-waitpid::                `mysql_waitpid' --- Kill Process and Wait for Its Termination
* mysql-zap::                    `mysql_zap' --- Kill Processes That Match a Pattern

This section describes administrative programs and programs that
perform miscellaneous utility operations.


File: manual.info,  Node: innochecksum,  Next: myisam-ftdump,  Prev: programs-admin-utils,  Up: programs-admin-utils

4.6.1 `innochecksum' -- Offline InnoDB File Checksum Utility
------------------------------------------------------------

*Note `innochecksum': innochecksum. prints checksums for `InnoDB'
files. This tool reads an `InnoDB' tablespace file, calculates the
checksum for each page, compares the calculated checksum to the stored
checksum, and reports mismatches, which indicate damaged pages. It was
originally developed to speed up verifying the integrity of tablespace
files after power outages but can also be used after file copies.
Because checksum mismatches will cause `InnoDB' to deliberately shut
down a running server, it can be preferable to use this tool rather
than waiting for a server in production usage to encounter the damaged
pages.

*Note `innochecksum': innochecksum. cannot be used on tablespace files
that the server already has open. For such files, you should use *Note
`CHECK TABLE': check-table. to check tables within the tablespace.

If checksum mismatches are found, you would normally restore the
tablespace from backup or start the server and attempt to use *Note
`mysqldump': mysqldump. to make a backup of the tables within the
tablespace.

Invoke *Note `innochecksum': innochecksum. like this:


     shell> innochecksum [OPTIONS] FILE_NAME

*Note `innochecksum': innochecksum. supports the following options.
For options that refer to page numbers, the numbers are zero-based.

   * `-c'

     Print a count of the number of pages in the file.

   * `-d'

     Debug mode; prints checksums for each page.

   * `-e NUM'

     End at this page number.

   * `-p NUM'

     Check only this page number.

   * `-s NUM'

     Start at this page number.

   * `-v'

     Verbose mode; print a progress indicator every five seconds.


File: manual.info,  Node: myisam-ftdump,  Next: myisamchk,  Prev: innochecksum,  Up: programs-admin-utils

4.6.2 `myisam_ftdump' -- Display Full-Text Index information
------------------------------------------------------------

*Note `myisam_ftdump': myisam-ftdump. displays information about
`FULLTEXT' indexes in `MyISAM' tables. It reads the `MyISAM' index file
directly, so it must be run on the server host where the table is
located. Before using *Note `myisam_ftdump': myisam-ftdump, be sure to
issue a `FLUSH TABLES' statement first if the server is running.

*Note `myisam_ftdump': myisam-ftdump. scans and dumps the entire index,
which is not particularly fast. On the other hand, the distribution of
words changes infrequently, so it need not be run often.

Invoke *Note `myisam_ftdump': myisam-ftdump. like this:


     shell> myisam_ftdump [OPTIONS] TBL_NAME INDEX_NUM

The TBL_NAME argument should be the name of a `MyISAM' table. You can
also specify a table by naming its index file (the file with the `.MYI'
suffix). If you do not invoke *Note `myisam_ftdump': myisam-ftdump. in
the directory where the table files are located, the table or index
file name must be preceded by the path name to the table's database
directory.  Index numbers begin with 0.

Example: Suppose that the `test' database contains a table named
`mytexttable' that has the following definition:


     CREATE TABLE mytexttable
     (
       id   INT NOT NULL,
       txt  TEXT NOT NULL,
       PRIMARY KEY (id),
       FULLTEXT (txt)
     ) ENGINE=MyISAM;

The index on `id' is index 0 and the `FULLTEXT' index on `txt' is index
1. If your working directory is the `test' database directory, invoke
*Note `myisam_ftdump': myisam-ftdump. as follows:


     shell> myisam_ftdump mytexttable 1

If the path name to the `test' database directory is
`/usr/local/mysql/data/test', you can also specify the table name
argument using that path name. This is useful if you do not invoke
*Note `myisam_ftdump': myisam-ftdump. in the database directory:


     shell> myisam_ftdump /usr/local/mysql/data/test/mytexttable 1

You can use *Note `myisam_ftdump': myisam-ftdump. to generate a list of
index entries in order of frequency of occurrence like this:


     shell> myisam_ftdump -c mytexttable 1 | sort -r

*Note `myisam_ftdump': myisam-ftdump. supports the following options:

   * `--help', `-h' `-?'

     Display a help message and exit.

   * `--count', `-c'

     Calculate per-word statistics (counts and global weights).

   * `--dump', `-d'

     Dump the index, including data offsets and word weights.

   * `--length', `-l'

     Report the length distribution.

   * `--stats', `-s'

     Report global index statistics. This is the default operation if
     no other operation is specified.

   * `--verbose', `-v'

     Verbose mode. Print more output about what the program does.


File: manual.info,  Node: myisamchk,  Next: myisamlog,  Prev: myisam-ftdump,  Up: programs-admin-utils

4.6.3 `myisamchk' -- MyISAM Table-Maintenance Utility
-----------------------------------------------------

* Menu:

* myisamchk-general-options::    myisamchk General Options
* myisamchk-check-options::      myisamchk Check Options
* myisamchk-repair-options::     myisamchk Repair Options
* myisamchk-other-options::      Other myisamchk Options
* myisamchk-table-info::         Obtaining Table Information with myisamchk
* myisamchk-memory::             myisamchk Memory Usage

The *Note `myisamchk': myisamchk. utility gets information about your
database tables or checks, repairs, or optimizes them.  *Note
`myisamchk': myisamchk. works with `MyISAM' tables (tables that have
`.MYD' and `.MYI' files for storing data and indexes).

You can also use the *Note `CHECK TABLE': check-table.  and *Note
`REPAIR TABLE': repair-table. statements to check and repair `MyISAM'
tables. See *Note check-table::, and *Note repair-table::.

The use of *Note `myisamchk': myisamchk. with partitioned tables is not
supported.

*Caution*:

It is best to make a backup of a table before performing a table repair
operation; under some circumstances the operation might cause data
loss. Possible causes include but are not limited to file system errors.

Invoke *Note `myisamchk': myisamchk. like this:


     shell> myisamchk [OPTIONS] TBL_NAME ...

The OPTIONS specify what you want *Note `myisamchk': myisamchk. to do.
They are described in the following sections. You can also get a list
of options by invoking *Note `myisamchk --help': myisamchk.

With no options, *Note `myisamchk': myisamchk. simply checks your table
as the default operation. To get more information or to tell *Note
`myisamchk': myisamchk. to take corrective action, specify options as
described in the following discussion.

TBL_NAME is the database table you want to check or repair. If you run
*Note `myisamchk': myisamchk.  somewhere other than in the database
directory, you must specify the path to the database directory, because
*Note `myisamchk': myisamchk. has no idea where the database is
located. In fact, *Note `myisamchk': myisamchk. does not actually care
whether the files you are working on are located in a database
directory. You can copy the files that correspond to a database table
into some other location and perform recovery operations on them there.

You can name several tables on the *Note `myisamchk': myisamchk.
command line if you wish. You can also specify a table by naming its
index file (the file with the `.MYI' suffix). This enables you to
specify all tables in a directory by using the pattern `*.MYI'. For
example, if you are in a database directory, you can check all the
`MyISAM' tables in that directory like this:


     shell> myisamchk *.MYI

If you are not in the database directory, you can check all the tables
there by specifying the path to the directory:


     shell> myisamchk /PATH/TO/DATABASE_DIR/*.MYI

You can even check all tables in all databases by specifying a wildcard
with the path to the MySQL data directory:


     shell> myisamchk /PATH/TO/DATADIR/*/*.MYI

The recommended way to quickly check all `MyISAM' tables is:


     shell> myisamchk --silent --fast /PATH/TO/DATADIR/*/*.MYI

If you want to check all `MyISAM' tables and repair any that are
corrupted, you can use the following command:


     shell> myisamchk --silent --force --fast --update-state \
               --key_buffer_size=64M --myisam_sort_buffer_size=64M \
               --read_buffer_size=1M --write_buffer_size=1M \
               /PATH/TO/DATADIR/*/*.MYI

This command assumes that you have more than 64MB free. For more
information about memory allocation with *Note `myisamchk': myisamchk,
see *Note myisamchk-memory::.

For additional information about using *Note `myisamchk': myisamchk, see
*Note myisam-table-maintenance::.

*Important*:

_You must ensure that no other program is using the tables while you
are running *Note `myisamchk': myisamchk._. The most effective means of
doing so is to shut down the MySQL server while running *Note
`myisamchk': myisamchk, or to lock all tables that *Note `myisamchk':
myisamchk. is being used on.

Otherwise, when you run *Note `myisamchk': myisamchk, it may display
the following error message:


     warning: clients are using or haven't closed the table properly

This means that you are trying to check a table that has been updated
by another program (such as the *Note `mysqld': mysqld. server) that
hasn't yet closed the file or that has died without closing the file
properly, which can sometimes lead to the corruption of one or more
`MyISAM' tables.

If *Note `mysqld': mysqld. is running, you must force it to flush any
table modifications that are still buffered in memory by using *Note
`FLUSH TABLES': flush. You should then ensure that no one is using the
tables while you are running *Note `myisamchk': myisamchk.

However, the easiest way to avoid this problem is to use *Note `CHECK
TABLE': check-table. instead of *Note `myisamchk': myisamchk. to check
tables. See *Note check-table::.

*Note `myisamchk': myisamchk. supports the following options, which can
be specified on the command line or in the `[myisamchk]' group of an
option file. For information about option files used by MySQL programs,
see *Note option-files::.

*`myisamchk' Options*

Format             Description                      IntroducedDeprecated
-analyze           Analyze the distribution of key          
                   values                                   
-backup            Make a backup of the .MYD file           
                   as file_name-time.BAK                    
-block-search=offsetFind the record that a block at          
                   the given offset belongs to              
-check             Check the table for errors               
-check-only-changedCheck only tables that have              
                   changed since the last check             
-correct-checksum  Correct the checksum                     
                   information for the table                
-data-file-length=lenMaximum length of the data file          
                   (when re-creating data file              
                   when it is full)                         
-debug[=debug_options]Write a debugging log                    
decode_bits=#      Decode_bits                              
-defaults-extra-file=file_nameRead option file in addition to          
                   usual option files                       
-defaults-file=file_nameRead only named option file              
-defaults-group-suffix=strOption group suffix value                
-description       Print some descriptive                   
                   information about the table              
-extend-check      Do very thorough table check or          
                   repair that tries to recover             
                   every possible row from the              
                   data file                                
-fast              Check only tables that haven't           
                   been closed properly                     
-force             Do a repair operation                    
                   automatically if myisamchk               
                   finds any errors in the table            
-force             Overwrite old temporary files.           
                   For use with the -r or -o option         
ft_max_word_len=#  Maximum word length for                  
                   FULLTEXT indexes                         
ft_min_word_len=#  Minimum word length for                  
                   FULLTEXT indexes                         
ft_stopword_file=valueUse stopwords from this file             
                   instead of built-in list                 
-HELP              Display help message and exit            
-help              Display help message and exit            
-information       Print informational statistics           
                   about the table that is checked          
key_buffer_size=#  Size of buffer used for index            
                   blocks for MyISAM tables                 
-keys-used=val     A bit-value that indicates               
                   which indexes to update                  
-max-record-length=lenSkip rows larger than the given          
                   length if myisamchk cannot               
                   allocate memory to hold them             
-medium-check      Do a check that is faster than           
                   an -extend-check operation               
myisam_block_size=#Block size to be used for                
                   MyISAM index pages                       
myisam_sort_buffer_size=#The buffer that is allocated     5.1.67  
                   when sorting the index when              
                   doing a REPAIR or when creating          
                   indexes with CREATE INDEX or             
                   ALTER TABLE                              
-no-defaults       Read no option files                     
-parallel-recover  Uses the same technique as -r            
                   and -n, but creates all the              
                   keys in parallel, using                  
                   different threads (beta)                 
-print-defaults    Print defaults                           
-quick             Achieve a faster repair by not           
                   modifying the data file.                 
read_buffer_size=# Each thread that does a                  
                   sequential scan allocates a              
                   buffer of this size for each             
                   table it scans                           
-read-only         Don't mark the table as checked          
-recover           Do a repair that can fix almost          
                   any problem except unique keys           
                   that aren't unique                       
-safe-recover      Do a repair using an old                 
                   recovery method that reads               
                   through all rows in order and            
                   updates all index trees based            
                   on the rows found                        
-set-auto-increment[=value]Force AUTO_INCREMENT numbering           
                   for new records to start at the          
                   given value                              
-set-collation=nameSpecify the collation to use             
                   for sorting table indexes                
-silent            Silent mode                              
sort_buffer_size=# The buffer that is allocated             5.1.67
                   when sorting the index when              
                   doing a REPAIR or when creating          
                   indexes with CREATE INDEX or             
                   ALTER TABLE                              
-sort-index        Sort the index tree blocks in            
                   high-low order                           
sort_key_blocks=#  sort_key_blocks                          
-sort-records=#    Sort records according to a              
                   particular index                         
-sort-recover      Force myisamchk to use sorting           
                   to resolve the keys even if the          
                   temporary files would be very            
                   large                                    
stats_method=value Specifies how MyISAM index               
                   statistics collection code               
                   should treat NULLs                       
-tmpdir=path       Path of the directory to be              
                   used for storing temporary files         
-unpack            Unpack a table that was packed           
                   with myisampack                          
-update-state      Store information in the .MYI            
                   file to indicate when the table          
                   was checked and whether the              
                   table crashed                            
-verbose           Verbose mode                             
-version           Display version information and          
                   exit                                     
write_buffer_size=#Write buffer size                        


File: manual.info,  Node: myisamchk-general-options,  Next: myisamchk-check-options,  Prev: myisamchk,  Up: myisamchk

4.6.3.1 myisamchk General Options
.................................

The options described in this section can be used for any type of table
maintenance operation performed by *Note `myisamchk': myisamchk. The
sections following this one describe options that pertain only to
specific operations, such as table checking or repairing.

   * `--help', `-?'

     Display a help message and exit. Options are grouped by type of
     operation.

   * `--HELP', `-H'

     Display a help message and exit. Options are presented in a single
     list.

   * `--debug=DEBUG_OPTIONS', `-# DEBUG_OPTIONS'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o,/tmp/myisamchk.trace'.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `myisamchk':
     myisamchk. normally reads the `[myisamchk]' group. If the
     `--defaults-group-suffix=_other' option is given, *Note
     `myisamchk': myisamchk. also reads the `[myisamchk_other]' group.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--silent', `-s'

     Silent mode. Write output only when errors occur. You can use `-s'
     twice (`-ss') to make *Note `myisamchk': myisamchk. very silent.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.
     This can be used with `-d' and `-e'. Use `-v' multiple times
     (`-vv', `-vvv') for even more output.

   * `--version', `-V'

     Display version information and exit.

   * `--wait', `-w'

     Instead of terminating with an error if the table is locked, wait
     until the table is unlocked before continuing. If you are running
     *Note `mysqld': mysqld. with external locking disabled, the table
     can be locked only by another *Note `myisamchk': myisamchk.
     command.

You can also set the following variables by using `--VAR_NAME=VALUE'
syntax:

This table lists *Note `myisamchk': myisamchk.  variables that can be
set using `--VAR_NAME=VALUE' syntax. The table also provides the
default value for each variable.

Variable                  Default Value
`decode_bits'             9
`ft_max_word_len'         version-dependent
`ft_min_word_len'         4
`ft_stopword_file'        built-in list
`key_buffer_size'         523264
`myisam_block_size'       1024
`myisam_sort_key_blocks'  16
`read_buffer_size'        262136
`sort_buffer_size'        2097144
`sort_key_blocks'         16
`stats_method'            nulls_unequal
`write_buffer_size'       262136

The possible *Note `myisamchk': myisamchk. variables and their default
values can be examined with *Note `myisamchk --help': myisamchk.:

`sort_buffer_size' is used when the keys are repaired by sorting keys,
which is the normal case when you use `--recover'. As of MySQL 5.1.67,
`myisam_sort_buffer_size' is available as an alternative name to
`sort_buffer_size'.  `myisam_sort_buffer_size' is preferable to
`sort_buffer_size' because its name corresponds to the
`myisam_sort_buffer_size' server system variable that has a similar
meaning.  `sort_buffer_size' should be considered deprecated.

`key_buffer_size' is used when you are checking the table with
`--extend-check' or when the keys are repaired by inserting keys row by
row into the table (like when doing normal inserts). Repairing through
the key buffer is used in the following cases:

   * You use `--safe-recover'.

   * The temporary files needed to sort the keys would be more than
     twice as big as when creating the key file directly.  This is
     often the case when you have large key values for *Note `CHAR':
     char, *Note `VARCHAR': char, or *Note `TEXT': blob. columns,
     because the sort operation needs to store the complete key values
     as it proceeds. If you have lots of temporary space and you can
     force *Note `myisamchk': myisamchk. to repair by sorting, you can
     use the `--sort-recover' option.

Repairing through the key buffer takes much less disk space than using
sorting, but is also much slower.

If you want a faster repair, set the `key_buffer_size' and
`myisam_sort_buffer_size' variables to about 25% of your available
memory. You can set both variables to large values, because only one of
them is used at a time.

`myisam_block_size' is the size used for index blocks.

`stats_method' influences how `NULL' values are treated for index
statistics collection when the `--analyze' option is given. It acts
like the `myisam_stats_method' system variable. For more information,
see the description of `myisam_stats_method' in *Note
server-system-variables::, and *Note myisam-index-statistics::.

`ft_min_word_len' and `ft_max_word_len' indicate the minimum and
maximum word length for `FULLTEXT' indexes.  `ft_stopword_file' names
the stopword file.  These need to be set under the following
circumstances.

If you use *Note `myisamchk': myisamchk. to perform an operation that
modifies table indexes (such as repair or analyze), the `FULLTEXT'
indexes are rebuilt using the default full-text parameter values for
minimum and maximum word length and the stopword file unless you
specify otherwise. This can result in queries failing.

The problem occurs because these parameters are known only by the
server. They are not stored in `MyISAM' index files. To avoid the
problem if you have modified the minimum or maximum word length or the
stopword file in the server, specify the same `ft_min_word_len',
`ft_max_word_len', and `ft_stopword_file' values to *Note `myisamchk':
myisamchk. that you use for *Note `mysqld': mysqld. For example, if you
have set the minimum word length to 3, you can repair a table with
*Note `myisamchk': myisamchk. like this:


     shell> myisamchk --recover --ft_min_word_len=3 TBL_NAME.MYI

To ensure that *Note `myisamchk': myisamchk. and the server use the
same values for full-text parameters, you can place each one in both
the `[mysqld]' and `[myisamchk]' sections of an option file:


     [mysqld]
     ft_min_word_len=3

     [myisamchk]
     ft_min_word_len=3

An alternative to using *Note `myisamchk': myisamchk. is to use the
*Note `REPAIR TABLE': repair-table, *Note `ANALYZE TABLE':
analyze-table, *Note `OPTIMIZE TABLE': optimize-table, or *Note `ALTER
TABLE': alter-table. These statements are performed by the server,
which knows the proper full-text parameter values to use.


File: manual.info,  Node: myisamchk-check-options,  Next: myisamchk-repair-options,  Prev: myisamchk-general-options,  Up: myisamchk

4.6.3.2 myisamchk Check Options
...............................

*Note `myisamchk': myisamchk. supports the following options for table
checking operations:

   * `--check', `-c'

     Check the table for errors. This is the default operation if you
     specify no option that selects an operation type explicitly.

   * `--check-only-changed', `-C'

     Check only tables that have changed since the last check.

   * `--extend-check', `-e'

     Check the table very thoroughly. This is quite slow if the table
     has many indexes. This option should only be used in extreme
     cases. Normally, *Note `myisamchk': myisamchk. or *Note `myisamchk
     --medium-check': myisamchk. should be able to determine whether
     there are any errors in the table.

     If you are using `--extend-check' and have plenty of memory,
     setting the `key_buffer_size' variable to a large value helps the
     repair operation run faster.

     See also the description of this option under table repair options.

     For a description of the output format, see *Note
     myisamchk-table-info::.

   * `--fast', `-F'

     Check only tables that haven't been closed properly.

   * `--force', `-f'

     Do a repair operation automatically if *Note `myisamchk':
     myisamchk. finds any errors in the table.  The repair type is the
     same as that specified with the `--recover' or `-r' option.

   * `--information', `-i'

     Print informational statistics about the table that is checked.

   * `--medium-check', `-m'

     Do a check that is faster than an `--extend-check' operation.
     This finds only 99.99% of all errors, which should be good enough
     in most cases.

   * `--read-only', `-T'

     Do not mark the table as checked. This is useful if you use *Note
     `myisamchk': myisamchk. to check a table that is in use by some
     other application that does not use locking, such as *Note
     `mysqld': mysqld. when run with external locking disabled.

   * `--update-state', `-U'

     Store information in the `.MYI' file to indicate when the table
     was checked and whether the table crashed. This should be used to
     get full benefit of the `--check-only-changed' option, but you
     shouldn't use this option if the *Note `mysqld': mysqld. server is
     using the table and you are running it with external locking
     disabled.


File: manual.info,  Node: myisamchk-repair-options,  Next: myisamchk-other-options,  Prev: myisamchk-check-options,  Up: myisamchk

4.6.3.3 myisamchk Repair Options
................................

*Note `myisamchk': myisamchk. supports the following options for table
repair operations (operations performed when an option such as
`--recover' or `--safe-recover' is given):

   * `--backup', `-B'

     Make a backup of the `.MYD' file as `FILE_NAME-TIME.BAK'

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--correct-checksum'

     Correct the checksum information for the table.

   * `--data-file-length=LEN', `-D LEN'

     The maximum length of the data file (when re-creating data file
     when it is `full').

   * `--extend-check', `-e'

     Do a repair that tries to recover every possible row from the data
     file. Normally, this also finds a lot of garbage rows. Do not use
     this option unless you are desperate.

     See also the description of this option under table checking
     options.

     For a description of the output format, see *Note
     myisamchk-table-info::.

   * `--force', `-f'

     Overwrite old intermediate files (files with names like
     `TBL_NAME.TMD') instead of aborting.

   * `--keys-used=VAL', `-k VAL'

     For *Note `myisamchk': myisamchk, the option value is a bit-value
     that indicates which indexes to update. Each binary bit of the
     option value corresponds to a table index, where the first index
     is bit 0. An option value of 0 disables updates to all indexes,
     which can be used to get faster inserts. Deactivated indexes can
     be reactivated by using *Note `myisamchk -r': myisamchk.

   * `--no-symlinks', `-l'

     Do not follow symbolic links. Normally *Note `myisamchk':
     myisamchk. repairs the table that a symlink points to. This option
     does not exist as of MySQL 4.0 because versions from 4.0 on do not
     remove symlinks during repair operations.

   * `--max-record-length=LEN'

     Skip rows larger than the given length if *Note `myisamchk':
     myisamchk. cannot allocate memory to hold them.

   * `--parallel-recover', `-p'

     Use the same technique as `-r' and `-n', but create all the keys
     in parallel, using different threads. _This is beta-quality code.
     Use at your own risk!_

   * `--quick', `-q'

     Achieve a faster repair by modifying only the index file, not the
     data file. You can specify this option twice to force *Note
     `myisamchk': myisamchk. to modify the original data file in case
     of duplicate keys.

   * `--recover', `-r'

     Do a repair that can fix almost any problem except unique keys
     that are not unique (which is an extremely unlikely error with
     `MyISAM' tables). If you want to recover a table, this is the
     option to try first. You should try `--safe-recover' only if *Note
     `myisamchk': myisamchk. reports that the table cannot be recovered
     using `--recover'. (In the unlikely case that `--recover' fails,
     the data file remains intact.)

     If you have lots of memory, you should increase the value of
     `myisam_sort_buffer_size'.

   * `--safe-recover', `-o'

     Do a repair using an old recovery method that reads through all
     rows in order and updates all index trees based on the rows found.
     This is an order of magnitude slower than `--recover', but can
     handle a couple of very unlikely cases that `--recover' cannot.
     This recovery method also uses much less disk space than
     `--recover'. Normally, you should repair first using `--recover',
     and then with `--safe-recover' only if `--recover' fails.

     If you have lots of memory, you should increase the value of
     `key_buffer_size'.

   * `--set-character-set=NAME'

     Change the character set used by the table indexes. This option
     was replaced by `--set-collation' in MySQL 5.0.3.

   * `--set-collation=NAME'

     Specify the collation to use for sorting table indexes. The
     character set name is implied by the first part of the collation
     name.

   * `--sort-recover', `-n'

     Force *Note `myisamchk': myisamchk. to use sorting to resolve the
     keys even if the temporary files would be very large.

   * `--tmpdir=PATH', `-t PATH'

     The path of the directory to be used for storing temporary files.
     If this is not set, *Note `myisamchk': myisamchk. uses the value
     of the `TMPDIR' environment variable. `--tmpdir' can be set to a
     list of directory paths that are used successively in round-robin
     fashion for creating temporary files. The separator character
     between directory names is the colon (``:'') on Unix and the
     semicolon (``;'') on Windows, NetWare, and OS/2.

   * `--unpack', `-u'

     Unpack a table that was packed with *Note `myisampack': myisampack.


File: manual.info,  Node: myisamchk-other-options,  Next: myisamchk-table-info,  Prev: myisamchk-repair-options,  Up: myisamchk

4.6.3.4 Other myisamchk Options
...............................

*Note `myisamchk': myisamchk. supports the following options for
actions other than table checks and repairs:

   * `--analyze', `-a'

     Analyze the distribution of key values. This improves join
     performance by enabling the join optimizer to better choose the
     order in which to join the tables and which indexes it should use.
     To obtain information about the key distribution, use a *Note
     `myisamchk --description --verbose TBL_NAME': myisamchk.  command
     or the `SHOW INDEX FROM TBL_NAME' statement.

   * `--block-search=OFFSET', `-b OFFSET'

     Find the record that a block at the given offset belongs to.

   * `--description', `-d'

     Print some descriptive information about the table.  Specifying
     the `--verbose' option once or twice produces additional
     information. See *Note myisamchk-table-info::.

   * `--set-auto-increment[=VALUE]', `-A[VALUE]'

     Force `AUTO_INCREMENT' numbering for new records to start at the
     given value (or higher, if there are existing records with
     `AUTO_INCREMENT' values this large). If VALUE is not specified,
     `AUTO_INCREMENT' numbers for new records begin with the largest
     value currently in the table, plus one.

   * `--sort-index', `-S'

     Sort the index tree blocks in high-low order. This optimizes seeks
     and makes table scans that use indexes faster.

   * `--sort-records=N', `-R N'

     Sort records according to a particular index. This makes your data
     much more localized and may speed up range-based *Note `SELECT':
     select. and `ORDER BY' operations that use this index. (The first
     time you use this option to sort a table, it may be very slow.)
     To determine a table's index numbers, use *Note `SHOW INDEX':
     show-index, which displays a table's indexes in the same order that
     *Note `myisamchk': myisamchk. sees them. Indexes are numbered
     beginning with 1.

     If keys are not packed (`PACK_KEYS=0'), they have the same length,
     so when *Note `myisamchk': myisamchk. sorts and moves records, it
     just overwrites record offsets in the index. If keys are packed
     (`PACK_KEYS=1'), *Note `myisamchk': myisamchk. must unpack key
     blocks first, then re-create indexes and pack the key blocks
     again. (In this case, re-creating indexes is faster than updating
     offsets for each index.)


File: manual.info,  Node: myisamchk-table-info,  Next: myisamchk-memory,  Prev: myisamchk-other-options,  Up: myisamchk

4.6.3.5 Obtaining Table Information with myisamchk
..................................................

To obtain a description of a `MyISAM' table or statistics about it, use
the commands shown here. The output from these commands is explained
later in this section.

   * *Note `myisamchk -d TBL_NAME': myisamchk.

     Runs *Note `myisamchk': myisamchk. in `describe mode' to produce a
     description of your table. If you start the MySQL server with
     external locking disabled, *Note `myisamchk': myisamchk. may
     report an error for a table that is updated while it runs.
     However, because *Note `myisamchk': myisamchk. does not change the
     table in describe mode, there is no risk of destroying data.

   * *Note `myisamchk -dv TBL_NAME': myisamchk.

     Adding `-v' runs *Note `myisamchk': myisamchk.  in verbose mode so
     that it produces more information about the table. Adding `-v' a
     second time produces even more information.

   * *Note `myisamchk -eis TBL_NAME': myisamchk.

     Shows only the most important information from a table. This
     operation is slow because it must read the entire table.

   * *Note `myisamchk -eiv TBL_NAME': myisamchk.

     This is like `-eis', but tells you what is being done.

The TBL_NAME argument can be either the name of a `MyISAM' table or the
name of its index file, as described in *Note myisamchk::.  Multiple
TBL_NAME arguments can be given.

Suppose that a table named `person' has the following structure. (The
`MAX_ROWS' table option is included so that in the example output from
*Note `myisamchk': myisamchk. shown later, some values are smaller and
fit the output format more easily.)


     CREATE TABLE person
     (
       id         INT NOT NULL AUTO_INCREMENT,
       last_name  VARCHAR(20) NOT NULL,
       first_name VARCHAR(20) NOT NULL,
       birth      DATE,
       death      DATE,
       PRIMARY KEY (id),
       INDEX (last_name, first_name),
       INDEX (birth)
     ) MAX_ROWS = 1000000;

Suppose also that the table has these data and index file sizes:


     -rw-rw----  1 mysql  mysql  9347072 Aug 19 11:47 person.MYD
     -rw-rw----  1 mysql  mysql  6066176 Aug 19 11:47 person.MYI

Example of *Note `myisamchk -dvv': myisamchk. output:


     MyISAM file:         person
     Record format:       Packed
     Character set:       latin1_swedish_ci (8)
     File-version:        1
     Creation time:       2009-08-19 16:47:41
     Recover time:        2009-08-19 16:47:56
     Status:              checked,analyzed,optimized keys
     Auto increment key:              1  Last value:                306688
     Data records:               306688  Deleted blocks:                 0
     Datafile parts:             306688  Deleted data:                   0
     Datafile pointer (bytes):        4  Keyfile pointer (bytes):        3
     Datafile length:           9347072  Keyfile length:           6066176
     Max datafile length:    4294967294  Max keyfile length:   17179868159
     Recordlength:                   54

     table description:
     Key Start Len Index   Type                 Rec/key         Root  Blocksize
     1   2     4   unique  long                       1        99328       1024
     2   6     20  multip. varchar prefix           512      3563520       1024
         27    20          varchar                  512
     3   48    3   multip. uint24 NULL           306688      6065152       1024

     Field Start Length Nullpos Nullbit Type
     1     1     1
     2     2     4                      no zeros
     3     6     21                     varchar
     4     27    21                     varchar
     5     48    3      1       1       no zeros
     6     51    3      1       2       no zeros

Explanations for the types of information *Note `myisamchk': myisamchk.
produces are given here.  `Keyfile' refers to the index file.  `Record'
and `row' are synonymous, as are `field' and `column.'

The initial part of the table description contains these values:

   * `MyISAM file'

     Name of the `MyISAM' (index) file.

   * `Record format'

     The format used to store table rows. The preceding examples use
     `Fixed length'. Other possible values are `Compressed' and
     `Packed'. (`Packed' corresponds to what `SHOW TABLE STATUS'
     reports as `Dynamic'.)

   * `Chararacter set'

     The table default character set.

   * `File-version'

     Version of `MyISAM' format. Currently always 1.

   * `Creation time'

     When the data file was created.

   * `Recover time'

     When the index/data file was last reconstructed.

   * `Status'

     Table status flags. Possible values are `crashed', `open',
     `changed', `analyzed', `optimized keys', and `sorted index pages'.

   * `Auto increment key', `Last value'

     The key number associated the table's `AUTO_INCREMENT' column, and
     the most recently generated value for this column. These fields do
     not appear if there is no such column.

   * `Data records'

     The number of rows in the table.

   * `Deleted blocks'

     How many deleted blocks still have reserved space. You can
     optimize your table to minimize this space. See *Note
     myisam-optimization::.

   * `Datafile parts'

     For dynamic-row format, this indicates how many data blocks there
     are. For an optimized table without fragmented rows, this is the
     same as `Data records'.

   * `Deleted data'

     How many bytes of unreclaimed deleted data there are. You can
     optimize your table to minimize this space. See *Note
     myisam-optimization::.

   * `Datafile pointer'

     The size of the data file pointer, in bytes. It is usually 2, 3,
     4, or 5 bytes. Most tables manage with 2 bytes, but this cannot be
     controlled from MySQL yet. For fixed tables, this is a row
     address. For dynamic tables, this is a byte address.

   * `Keyfile pointer'

     The size of the index file pointer, in bytes. It is usually 1, 2,
     or 3 bytes. Most tables manage with 2 bytes, but this is
     calculated automatically by MySQL. It is always a block address.

   * `Max datafile length'

     How long the table data file can become, in bytes.

   * `Max keyfile length'

     How long the table index file can become, in bytes.

   * `Recordlength'

     How much space each row takes, in bytes.

The `table description' part of the output includes a list of all keys
in the table. For each key, *Note `myisamchk': myisamchk. displays some
low-level information:

   * `Key'

     This key's number. This value is shown only for the first column
     of the key. If this value is missing, the line corresponds to the
     second or later column of a multiple-column key. For the table
     shown in the example, there are two `table description' lines for
     the second index. This indicates that it is a multiple-part index
     with two parts.

   * `Start'

     Where in the row this portion of the index starts.

   * `Len'

     How long this portion of the index is. For packed numbers, this
     should always be the full length of the column. For strings, it
     may be shorter than the full length of the indexed column, because
     you can index a prefix of a string column. The total length of a
     multiple-part key is the sum of the `Len' values for all key parts.

   * `Index'

     Whether a key value can exist multiple times in the index.
     Possible values are `unique' or `multip.' (multiple).

   * `Type'

     What data type this portion of the index has. This is a `MyISAM'
     data type with the possible values `packed', `stripped', or
     `empty'.

   * `Root'

     Address of the root index block.

   * `Blocksize'

     The size of each index block. By default this is 1024, but the
     value may be changed at compile time when MySQL is built from
     source.

   * `Rec/key'

     This is a statistical value used by the optimizer. It tells how
     many rows there are per value for this index. A unique index
     always has a value of 1. This may be updated after a table is
     loaded (or greatly changed) with *Note `myisamchk -a': myisamchk.
     If this is not updated at all, a default value of 30 is given.

The last part of the output provides information about each column:

   * `Field'

     The column number.

   * `Start'

     The byte position of the column within table rows.

   * `Length'

     The length of the column in bytes.

   * `Nullpos', `Nullbit'

     For columns that can be `NULL', `MyISAM' stores `NULL' values as a
     flag in a byte. Depending on how many nullable columns there are,
     there can be one or more bytes used for this purpose. The
     `Nullpos' and `Nullbit' values, if nonempty, indicate which byte
     and bit contains that flag indicating whether the column is `NULL'.

     The position and number of bytes used to store `NULL' flags is
     shown in the line for field 1. This is why there are six `Field'
     lines for the `person' table even though it has only five columns.

   * `Type'

     The data type. The value may contain any of the following
     descriptors:

        * `constant'

          All rows have the same value.

        * `no endspace'

          Do not store endspace.

        * `no endspace, not_always'

          Do not store endspace and do not do endspace compression for
          all values.

        * `no endspace, no empty'

          Do not store endspace. Do not store empty values.

        * `table-lookup'

          The column was converted to an *Note `ENUM': enum.

        * `zerofill(N)'

          The most significant N bytes in the value are always 0 and
          are not stored.

        * `no zeros'

          Do not store zeros.

        * `always zero'

          Zero values are stored using one bit.

   * `Huff tree'

     The number of the Huffman tree associated with the column.

   * `Bits'

     The number of bits used in the Huffman tree.

The `Huff tree' and `Bits' fields are displayed if the table has been
compressed with *Note `myisampack': myisampack. See *Note myisampack::,
for an example of this information.

Example of *Note `myisamchk -eiv': myisamchk. output:


     Checking MyISAM file: person
     Data records:  306688   Deleted blocks:       0
     - check file-size
     - check record delete-chain
     No recordlinks
     - check key delete-chain
     block_size 1024:
     - check index reference
     - check data record references index: 1
     Key:  1:  Keyblocks used:  98%  Packed:    0%  Max levels:  3
     - check data record references index: 2
     Key:  2:  Keyblocks used:  99%  Packed:   97%  Max levels:  3
     - check data record references index: 3
     Key:  3:  Keyblocks used:  98%  Packed:  -14%  Max levels:  3
     Total:    Keyblocks used:  98%  Packed:   89%

     - check records and index references
     *** LOTS OF ROW NUMBERS DELETED ***

     Records:            306688  M.recordlength:       25  Packed:            83%
     Recordspace used:       97% Empty space:           2% Blocks/Record:   1.00
     Record blocks:      306688  Delete blocks:         0
     Record data:       7934464  Deleted data:          0
     Lost space:         256512  Linkdata:        1156096

     User time 43.08, System time 1.68
     Maximum resident set size 0, Integral resident set size 0
     Non-physical pagefaults 0, Physical pagefaults 0, Swaps 0
     Blocks in 0 out 7, Messages in 0 out 0, Signals 0
     Voluntary context switches 0, Involuntary context switches 0
     Maximum memory usage: 1046926 bytes (1023k)

*Note `myisamchk -eiv': myisamchk. output includes the following
information:

   * `Data records'

     The number of rows in the table.

   * `Deleted blocks'

     How many deleted blocks still have reserved space. You can
     optimize your table to minimize this space. See *Note
     myisam-optimization::.

   * `Key'

     The key number.

   * `Keyblocks used'

     What percentage of the keyblocks are used. When a table has just
     been reorganized with *Note `myisamchk': myisamchk, the values are
     very high (very near theoretical maximum).

   * `Packed'

     MySQL tries to pack key values that have a common suffix.  This
     can only be used for indexes on *Note `CHAR': char. and *Note
     `VARCHAR': char. columns. For long indexed strings that have
     similar leftmost parts, this can significantly reduce the space
     used. In the preceding example, the second key is 40 bytes long
     and a 97% reduction in space is achieved.

   * `Max levels'

     How deep the B-tree for this key is. Large tables with long key
     values get high values.

   * `Records'

     How many rows are in the table.

   * `M.recordlength'

     The average row length. This is the exact row length for tables
     with fixed-length rows, because all rows have the same length.

   * `Packed'

     MySQL strips spaces from the end of strings. The `Packed' value
     indicates the percentage of savings achieved by doing this.

   * `Recordspace used'

     What percentage of the data file is used.

   * `Empty space'

     What percentage of the data file is unused.

   * `Blocks/Record'

     Average number of blocks per row (that is, how many links a
     fragmented row is composed of). This is always 1.0 for
     fixed-format tables. This value should stay as close to 1.0 as
     possible. If it gets too large, you can reorganize the table. See
     *Note myisam-optimization::.

   * `Recordblocks'

     How many blocks (links) are used. For fixed-format tables, this is
     the same as the number of rows.

   * `Deleteblocks'

     How many blocks (links) are deleted.

   * `Recorddata'

     How many bytes in the data file are used.

   * `Deleted data'

     How many bytes in the data file are deleted (unused).

   * `Lost space'

     If a row is updated to a shorter length, some space is lost.  This
     is the sum of all such losses, in bytes.

   * `Linkdata'

     When the dynamic table format is used, row fragments are linked
     with pointers (4 to 7 bytes each).  `Linkdata' is the sum of the
     amount of storage used by all such pointers.


File: manual.info,  Node: myisamchk-memory,  Prev: myisamchk-table-info,  Up: myisamchk

4.6.3.6 myisamchk Memory Usage
..............................

Memory allocation is important when you run *Note `myisamchk':
myisamchk. *Note `myisamchk': myisamchk. uses no more memory than its
memory-related variables are set to. If you are going to use *Note
`myisamchk': myisamchk. on very large tables, you should first decide
how much memory you want it to use. The default is to use only about
3MB to perform repairs. By using larger values, you can get *Note
`myisamchk': myisamchk. to operate faster. For example, if you have
more than 512MB RAM available, you could use options such as these (in
addition to any other options you might specify):


     shell> myisamchk --myisam_sort_buffer_size=256M \
                --key_buffer_size=512M \
                --read_buffer_size=64M \
                --write_buffer_size=64M ...

Using `--myisam_sort_buffer_size=16M' is probably enough for most cases.

Be aware that *Note `myisamchk': myisamchk. uses temporary files in
`TMPDIR'. If `TMPDIR' points to a memory file system, out of memory
errors can easily occur. If this happens, run *Note `myisamchk':
myisamchk. with the `--tmpdir=PATH' option to specify a directory
located on a file system that has more space.

When performing repair operations, *Note `myisamchk': myisamchk.  also
needs a lot of disk space:

   * Twice the size of the data file (the original file and a copy).
     This space is not needed if you do a repair with `--quick'; in
     this case, only the index file is re-created. _This space must be
     available on the same file system as the original data file_, as
     the copy is created in the same directory as the original.

   * Space for the new index file that replaces the old one. The old
     index file is truncated at the start of the repair operation, so
     you usually ignore this space. This space must be available on the
     same file system as the original data file.

   * When using `--recover' or `--sort-recover' (but not when using
     `--safe-recover'), you need space on disk for sorting. This space
     is allocated in the temporary directory (specified by `TMPDIR' or
     `--tmpdir=PATH').  The following formula yields the amount of
     space required:


          (LARGEST_KEY + ROW_POINTER_LENGTH) * NUMBER_OF_ROWS * 2

     You can check the length of the keys and the ROW_POINTER_LENGTH
     with *Note `myisamchk -dv TBL_NAME': myisamchk. (see *Note
     myisamchk-table-info::). The ROW_POINTER_LENGTH and NUMBER_OF_ROWS
     values are the `Datafile pointer' and `Data records' values in the
     table description. To determine the LARGEST_KEY value, check the
     `Key' lines in the table description. The `Len' column indicates
     the number of bytes for each key part. For a multiple-column
     index, the key size is the sum of the `Len' values for all key
     parts.

If you have a problem with disk space during repair, you can try
`--safe-recover' instead of `--recover'.


File: manual.info,  Node: myisamlog,  Next: myisampack,  Prev: myisamchk,  Up: programs-admin-utils

4.6.4 `myisamlog' -- Display MyISAM Log File Contents
-----------------------------------------------------

*Note `myisamlog': myisamlog. processes the contents of a `MyISAM' log
file. To create such a file, start the server with a
`--log-isam=`log_file'' option.

Invoke *Note `myisamlog': myisamlog. like this:


     shell> myisamlog [OPTIONS] [FILE_NAME [TBL_NAME] ...]

The default operation is update (`-u'). If a recovery is done (`-r'),
all writes and possibly updates and deletes are done and errors are
only counted. The default log file name is `myisam.log' if no LOG_FILE
argument is given. If tables are named on the command line, only those
tables are updated.

*Note `myisamlog': myisamlog. supports the following options:

   * `-?', `-I'

     Display a help message and exit.

   * `-c N'

     Execute only N commands.

   * `-f N'

     Specify the maximum number of open files.

   * `-i'

     Display extra information before exiting.

   * `-o OFFSET'

     Specify the starting offset.

   * `-p N'

     Remove N components from path.

   * `-r'

     Perform a recovery operation.

   * `-R RECORD_POS_FILE RECORD_POS'

     Specify record position file and record position.

   * `-u'

     Perform an update operation.

   * `-v'

     Verbose mode. Print more output about what the program does.  This
     option can be given multiple times to produce more and more output.

   * `-w WRITE_FILE'

     Specify the write file.

   * `-V'

     Display version information.


File: manual.info,  Node: myisampack,  Next: mysqlaccess,  Prev: myisamlog,  Up: programs-admin-utils

4.6.5 `myisampack' -- Generate Compressed, Read-Only MyISAM Tables
------------------------------------------------------------------

The *Note `myisampack': myisampack. utility compresses `MyISAM' tables.
*Note `myisampack': myisampack.  works by compressing each column in
the table separately.  Usually, *Note `myisampack': myisampack. packs
the data file 40% to 70%.

When the table is used later, the server reads into memory the
information needed to decompress columns. This results in much better
performance when accessing individual rows, because you only have to
uncompress exactly one row.

MySQL uses `mmap()' when possible to perform memory mapping on
compressed tables. If `mmap()' does not work, MySQL falls back to
normal read/write file operations.

Please note the following:

   * If the *Note `mysqld': mysqld. server was invoked with external
     locking disabled, it is not a good idea to invoke *Note
     `myisampack': myisampack. if the table might be updated by the
     server during the packing process. It is safest to compress tables
     with the server stopped.

   * After packing a table, it becomes read only. This is generally
     intended (such as when accessing packed tables on a CD).

   * *Note `myisampack': myisampack. does not support partitioned
     tables.

Invoke *Note `myisampack': myisampack. like this:


     shell> myisampack [OPTIONS] FILE_NAME ...

Each file name argument should be the name of an index (`.MYI') file.
If you are not in the database directory, you should specify the path
name to the file. It is permissible to omit the `.MYI' extension.

After you compress a table with *Note `myisampack': myisampack, you
should use *Note `myisamchk -rq': myisamchk. to rebuild its indexes.
*Note myisamchk::.

*Note `myisampack': myisampack. supports the following options. It also
reads option files and supports the options for processing them
described at *Note option-file-options::.

   * `--help', `-?'

     Display a help message and exit.

   * `--backup', `-b'

     Make a backup of each table's data file using the name
     `TBL_NAME.OLD'.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o'.

   * `--force', `-f'

     Produce a packed table even if it becomes larger than the original
     or if the intermediate file from an earlier invocation of *Note
     `myisampack': myisampack. exists.  (*Note `myisampack':
     myisampack. creates an intermediate file named `TBL_NAME.TMD' in
     the database directory while it compresses the table. If you kill
     *Note `myisampack': myisampack, the `.TMD' file might not be
     deleted.)  Normally, *Note `myisampack': myisampack. exits with an
     error if it finds that `TBL_NAME.TMD' exists. With `--force',
     *Note `myisampack': myisampack. packs the table anyway.

   * `--join=BIG_TBL_NAME', `-j BIG_TBL_NAME'

     Join all tables named on the command line into a single packed
     table BIG_TBL_NAME. All tables that are to be combined _must_ have
     identical structure (same column names and types, same indexes,
     and so forth).

     BIG_TBL_NAME must not exist prior to the join operation. All
     source tables named on the command line to be merged into
     BIG_TBL_NAME must exist. The source tables are read for the join
     operation but not modified. The join operation does not create a
     `.frm' file for BIG_TBL_NAME, so after the join operation
     finishes, copy the `.frm' file from one of the source tables and
     name it `BIG_TBL_NAME.frm'.

   * `--silent', `-s'

     Silent mode. Write output only when errors occur.

   * `--test', `-t'

     Do not actually pack the table, just test packing it.

   * `--tmpdir=PATH', `-T PATH'

     Use the named directory as the location where *Note `myisampack':
     myisampack. creates temporary files.

   * `--verbose', `-v'

     Verbose mode. Write information about the progress of the packing
     operation and its result.

   * `--version', `-V'

     Display version information and exit.

   * `--wait', `-w'

     Wait and retry if the table is in use. If the *Note `mysqld':
     mysqld. server was invoked with external locking disabled, it is
     not a good idea to invoke *Note `myisampack': myisampack. if the
     table might be updated by the server during the packing process.

The following sequence of commands illustrates a typical table
compression session:


     shell> ls -l station.*
     -rw-rw-r--   1 monty    my         994128 Apr 17 19:00 station.MYD
     -rw-rw-r--   1 monty    my          53248 Apr 17 19:00 station.MYI
     -rw-rw-r--   1 monty    my           5767 Apr 17 19:00 station.frm

     shell> myisamchk -dvv station

     MyISAM file:     station
     Isam-version:  2
     Creation time: 1996-03-13 10:08:58
     Recover time:  1997-02-02  3:06:43
     Data records:              1192  Deleted blocks:              0
     Datafile parts:            1192  Deleted data:                0
     Datafile pointer (bytes):     2  Keyfile pointer (bytes):     2
     Max datafile length:   54657023  Max keyfile length:   33554431
     Recordlength:               834
     Record format: Fixed length

     table description:
     Key Start Len Index   Type                 Root  Blocksize    Rec/key
     1   2     4   unique  unsigned long        1024       1024          1
     2   32    30  multip. text                10240       1024          1

     Field Start Length Type
     1     1     1
     2     2     4
     3     6     4
     4     10    1
     5     11    20
     6     31    1
     7     32    30
     8     62    35
     9     97    35
     10    132   35
     11    167   4
     12    171   16
     13    187   35
     14    222   4
     15    226   16
     16    242   20
     17    262   20
     18    282   20
     19    302   30
     20    332   4
     21    336   4
     22    340   1
     23    341   8
     24    349   8
     25    357   8
     26    365   2
     27    367   2
     28    369   4
     29    373   4
     30    377   1
     31    378   2
     32    380   8
     33    388   4
     34    392   4
     35    396   4
     36    400   4
     37    404   1
     38    405   4
     39    409   4
     40    413   4
     41    417   4
     42    421   4
     43    425   4
     44    429   20
     45    449   30
     46    479   1
     47    480   1
     48    481   79
     49    560   79
     50    639   79
     51    718   79
     52    797   8
     53    805   1
     54    806   1
     55    807   20
     56    827   4
     57    831   4

     shell> myisampack station.MYI
     Compressing station.MYI: (1192 records)
     - Calculating statistics

     normal:     20  empty-space:   16  empty-zero:     12  empty-fill:  11
     pre-space:   0  end-space:     12  table-lookups:   5  zero:         7
     Original trees:  57  After join: 17
     - Compressing file
     87.14%
     Remember to run myisamchk -rq on compressed tables

     shell> ls -l station.*
     -rw-rw-r--   1 monty    my         127874 Apr 17 19:00 station.MYD
     -rw-rw-r--   1 monty    my          55296 Apr 17 19:04 station.MYI
     -rw-rw-r--   1 monty    my           5767 Apr 17 19:00 station.frm

     shell> myisamchk -dvv station

     MyISAM file:     station
     Isam-version:  2
     Creation time: 1996-03-13 10:08:58
     Recover time:  1997-04-17 19:04:26
     Data records:               1192  Deleted blocks:              0
     Datafile parts:             1192  Deleted data:                0
     Datafile pointer (bytes):      3  Keyfile pointer (bytes):     1
     Max datafile length:    16777215  Max keyfile length:     131071
     Recordlength:                834
     Record format: Compressed

     table description:
     Key Start Len Index   Type                 Root  Blocksize    Rec/key
     1   2     4   unique  unsigned long       10240       1024          1
     2   32    30  multip. text                54272       1024          1

     Field Start Length Type                         Huff tree  Bits
     1     1     1      constant                             1     0
     2     2     4      zerofill(1)                          2     9
     3     6     4      no zeros, zerofill(1)                2     9
     4     10    1                                           3     9
     5     11    20     table-lookup                         4     0
     6     31    1                                           3     9
     7     32    30     no endspace, not_always              5     9
     8     62    35     no endspace, not_always, no empty    6     9
     9     97    35     no empty                             7     9
     10    132   35     no endspace, not_always, no empty    6     9
     11    167   4      zerofill(1)                          2     9
     12    171   16     no endspace, not_always, no empty    5     9
     13    187   35     no endspace, not_always, no empty    6     9
     14    222   4      zerofill(1)                          2     9
     15    226   16     no endspace, not_always, no empty    5     9
     16    242   20     no endspace, not_always              8     9
     17    262   20     no endspace, no empty                8     9
     18    282   20     no endspace, no empty                5     9
     19    302   30     no endspace, no empty                6     9
     20    332   4      always zero                          2     9
     21    336   4      always zero                          2     9
     22    340   1                                           3     9
     23    341   8      table-lookup                         9     0
     24    349   8      table-lookup                        10     0
     25    357   8      always zero                          2     9
     26    365   2                                           2     9
     27    367   2      no zeros, zerofill(1)                2     9
     28    369   4      no zeros, zerofill(1)                2     9
     29    373   4      table-lookup                        11     0
     30    377   1                                           3     9
     31    378   2      no zeros, zerofill(1)                2     9
     32    380   8      no zeros                             2     9
     33    388   4      always zero                          2     9
     34    392   4      table-lookup                        12     0
     35    396   4      no zeros, zerofill(1)               13     9
     36    400   4      no zeros, zerofill(1)                2     9
     37    404   1                                           2     9
     38    405   4      no zeros                             2     9
     39    409   4      always zero                          2     9
     40    413   4      no zeros                             2     9
     41    417   4      always zero                          2     9
     42    421   4      no zeros                             2     9
     43    425   4      always zero                          2     9
     44    429   20     no empty                             3     9
     45    449   30     no empty                             3     9
     46    479   1                                          14     4
     47    480   1                                          14     4
     48    481   79     no endspace, no empty               15     9
     49    560   79     no empty                             2     9
     50    639   79     no empty                             2     9
     51    718   79     no endspace                         16     9
     52    797   8      no empty                             2     9
     53    805   1                                          17     1
     54    806   1                                           3     9
     55    807   20     no empty                             3     9
     56    827   4      no zeros, zerofill(2)                2     9
     57    831   4      no zeros, zerofill(1)                2     9

*Note `myisampack': myisampack. displays the following kinds of
information:

   * `normal'

     The number of columns for which no extra packing is used.

   * `empty-space'

     The number of columns containing values that are only spaces.
     These occupy one bit.

   * `empty-zero'

     The number of columns containing values that are only binary
     zeros. These occupy one bit.

   * `empty-fill'

     The number of integer columns that do not occupy the full byte
     range of their type. These are changed to a smaller type. For
     example, a *Note `BIGINT': integer-types.  column (eight bytes)
     can be stored as a *Note `TINYINT': integer-types. column (one
     byte) if all its values are in the range from `-128' to `127'.

   * `pre-space'

     The number of decimal columns that are stored with leading spaces.
     In this case, each value contains a count for the number of
     leading spaces.

   * `end-space'

     The number of columns that have a lot of trailing spaces. In this
     case, each value contains a count for the number of trailing
     spaces.

   * `table-lookup'

     The column had only a small number of different values, which were
     converted to an *Note `ENUM': enum. before Huffman compression.

   * `zero'

     The number of columns for which all values are zero.

   * `Original trees'

     The initial number of Huffman trees.

   * `After join'

     The number of distinct Huffman trees left after joining trees to
     save some header space.

After a table has been compressed, the `Field' lines displayed by *Note
`myisamchk -dvv': myisamchk. include additional information about each
column:

   * `Type'

     The data type. The value may contain any of the following
     descriptors:

        * `constant'

          All rows have the same value.

        * `no endspace'

          Do not store endspace.

        * `no endspace, not_always'

          Do not store endspace and do not do endspace compression for
          all values.

        * `no endspace, no empty'

          Do not store endspace. Do not store empty values.

        * `table-lookup'

          The column was converted to an *Note `ENUM': enum.

        * `zerofill(N)'

          The most significant N bytes in the value are always 0 and
          are not stored.

        * `no zeros'

          Do not store zeros.

        * `always zero'

          Zero values are stored using one bit.

   * `Huff tree'

     The number of the Huffman tree associated with the column.

   * `Bits'

     The number of bits used in the Huffman tree.

After you run *Note `myisampack': myisampack, you must run *Note
`myisamchk': myisamchk. to re-create any indexes. At this time, you can
also sort the index blocks and create statistics needed for the MySQL
optimizer to work more efficiently:


     shell> myisamchk -rq --sort-index --analyze TBL_NAME.MYI

After you have installed the packed table into the MySQL database
directory, you should execute *Note `mysqladmin flush-tables':
mysqladmin. to force *Note `mysqld': mysqld. to start using the new
table.

To unpack a packed table, use the `--unpack' option to *Note
`myisamchk': myisamchk.


File: manual.info,  Node: mysqlaccess,  Next: mysqlbinlog,  Prev: myisampack,  Up: programs-admin-utils

4.6.6 `mysqlaccess' -- Client for Checking Access Privileges
------------------------------------------------------------

*Note `mysqlaccess': mysqlaccess. is a diagnostic tool that Yves
Carlier has provided for the MySQL distribution. It checks the access
privileges for a host name, user name, and database combination. Note
that *Note `mysqlaccess': mysqlaccess. checks access using only the
`user', `db', and `host' tables. It does not check table, column, or
routine privileges specified in the `tables_priv', `columns_priv', or
`procs_priv' tables.

Invoke *Note `mysqlaccess': mysqlaccess. like this:


     shell> mysqlaccess [HOST_NAME [USER_NAME [DB_NAME]]] [OPTIONS]

*Note `mysqlaccess': mysqlaccess. supports the following options.

*`mysqlaccess' Options*

Format             Description
-brief             Generate reports in single-line
                   tabular format
-commit            Copy the new access privileges
                   from the temporary tables to
                   the original grant tables
-copy              Reload the temporary grant
                   tables from original ones
-db=db_name        Specify the database name
-debug=#           Specify the debug level
-help              Display help message and exit
-host=host_name    Connect to MySQL server on
                   given host
-howto             Display some examples that show
                   how to use mysqlaccess
-old_server        Assume that the server is an
                   old MySQL server (prior to
                   MySQL 3.21)
-password[=password]Password to use when connecting
                   to server
-plan              Display suggestions and ideas
                   for future releases
-preview           Show the privilege differences
                   after making changes to the
                   temporary grant tables
-relnotes          Display release notes
-rhost=host_name   Connect to MySQL server on
                   given host
-rollback          Undo the most recent changes to
                   the temporary grant tables.
-spassword[=password]Password to use when connecting
                   to server as the superuser
-superuser=user_nameSpecify the user name for
                   connecting as the superuser
-table             Generate reports in table format
-user=user_name,   MySQL user name to use when
                   connecting to server
-version           Display version information and
                   exit

   * `--help', `-?'

     Display a help message and exit.

   * `--brief', `-b'

     Generate reports in single-line tabular format.

   * `--commit'

     Copy the new access privileges from the temporary tables to the
     original grant tables. The grant tables must be flushed for the
     new privileges to take effect. (For example, execute a *Note
     `mysqladmin reload': mysqladmin. command.)

   * `--copy'

     Reload the temporary grant tables from original ones.

   * `--db=DB_NAME', `-d DB_NAME'

     Specify the database name.

   * `--debug=N'

     Specify the debug level. N can be an integer from 0 to 3.

   * `--host=HOST_NAME', `-h HOST_NAME'

     The host name to use in the access privileges.

   * `--howto'

     Display some examples that show how to use *Note `mysqlaccess':
     mysqlaccess.

   * `--old_server'

     Assume that the server is an old MySQL server (before MySQL 3.21)
     that does not yet know how to handle full `WHERE' clauses.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you omit the
     PASSWORD value following the `--password' or `-p' option on the
     command line, *Note `mysqlaccess': mysqlaccess. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::.

   * `--plan'

     Display suggestions and ideas for future releases.

   * `--preview'

     Show the privilege differences after making changes to the
     temporary grant tables.

   * `--relnotes'

     Display the release notes.

   * `--rhost=HOST_NAME', `-H HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--rollback'

     Undo the most recent changes to the temporary grant tables.

   * `--spassword[=PASSWORD]', `-P[PASSWORD]'

     The password to use when connecting to the server as the
     superuser. If you omit the PASSWORD value following the
     `--spassword' or `-p' option on the command line, *Note
     `mysqlaccess': mysqlaccess. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::.

   * `--superuser=USER_NAME', `-U USER_NAME'

     Specify the user name for connecting as the superuser.

   * `--table', `-t'

     Generate reports in table format.

   * `--user=USER_NAME', `-u USER_NAME'

     The user name to use in the access privileges.

   * `--version', `-v'

     Display version information and exit.

If your MySQL distribution is installed in some nonstandard location,
you must change the location where *Note `mysqlaccess': mysqlaccess.
expects to find the *Note `mysql': mysql. client. Edit the
`mysqlaccess' script at approximately line 18. Search for a line that
looks like this:


     $MYSQL     = '/usr/local/bin/mysql';    # path to mysql executable

Change the path to reflect the location where *Note `mysql': mysql.
actually is stored on your system. If you do not do this, a `Broken
pipe' error will occur when you run *Note `mysqlaccess': mysqlaccess.


File: manual.info,  Node: mysqlbinlog,  Next: mysqldumpslow,  Prev: mysqlaccess,  Up: programs-admin-utils

4.6.7 `mysqlbinlog' -- Utility for Processing Binary Log Files
--------------------------------------------------------------

* Menu:

* mysqlbinlog-hexdump::          mysqlbinlog Hex Dump Format
* mysqlbinlog-row-events::       mysqlbinlog Row Event Display

The server's binary log consists of files containing `events' that
describe modifications to database contents. The server writes these
files in binary format. To display their contents in text format, use
the *Note `mysqlbinlog': mysqlbinlog. utility. You can also use *Note
`mysqlbinlog': mysqlbinlog. to display the contents of relay log files
written by a slave server in a replication setup because relay logs
have the same format as binary logs. The binary log and relay log are
discussed further in *Note binary-log::, and *Note slave-logs::.

Invoke *Note `mysqlbinlog': mysqlbinlog. like this:


     shell> mysqlbinlog [OPTIONS] LOG_FILE ...

For example, to display the contents of the binary log file named
`binlog.000003', use this command:


     shell> mysqlbinlog binlog.0000003

The output includes events contained in `binlog.000003'. For
statement-based logging, event information includes the SQL statement,
the ID of the server on which it was executed, the timestamp when the
statement was executed, how much time it took, and so forth. For
row-based logging, the event indicates a row change rather than an SQL
statement. See *Note replication-formats::, for information about
logging modes.

Events are preceded by header comments that provide additional
information. For example:


     # at 141
     #100309  9:28:36 server id 123  end_log_pos 245
       Query thread_id=3350  exec_time=11  error_code=0

In the first line, the number following `at' indicates the file offset,
or starting position, of the event in the binary log file.

The second line starts with a date and time indicating when the
statement started on the server where the event originated. For
replication, this timestamp is propagated to slave servers.  `server
id' is the `server_id' value of the server where the event originated.
`end_log_pos' indicates where the next event starts (that is, it is the
end position of the current event + 1). `thread_id' indicates which
thread executed the event.  `exec_time' is the time spent executing the
event, on a master server. On a slave, it is the difference of the end
execution time on the slave minus the beginning execution time on the
master. The difference serves as an indicator of how much replication
lags behind the master.  `error_code' indicates the result from
executing the event. Zero means that no error occurred.

*Note*:

When using event groups, the file offsets of events may be grouped
together and the comments of events may be grouped together. Do not
mistake these grouped events for blank file offsets.

The output from *Note `mysqlbinlog': mysqlbinlog. can be re-executed
(for example, by using it as input to *Note `mysql': mysql.) to redo
the statements in the log.  This is useful for recovery operations
after a server crash. For other usage examples, see the discussion
later in this section and in *Note point-in-time-recovery::.

Normally, you use *Note `mysqlbinlog': mysqlbinlog. to read binary log
files directly and apply them to the local MySQL server. It is also
possible to read binary logs from a remote server by using the
`--read-from-remote-server' option. To read remote binary logs, the
connection parameter options can be given to indicate how to connect to
the server.  These options are `--host', `--password', `--port',
`--protocol', `--socket', and `--user'; they are ignored except when
you also use the `--read-from-remote-server' option.

*Note `mysqlbinlog': mysqlbinlog. supports the following options, which
can be specified on the command line or in the `[mysqlbinlog]' and
`[client]' groups of an option file. For information about option files
used by MySQL programs, see *Note option-files::.

*`mysqlbinlog' Options*

Format             Description                      Introduced
-base64-output=valuePrint binary log entries using   5.1.5
                   base-64 encoding                 
-bind-address=ip_addressUse specified network interface  5.1.22-ndb-6.3.4
                   to connect to MySQL Server       
-character-sets-dir=pathDirectory where character sets   
                   are installed                    
-database=db_name  List entries for just this       
                   database                         
-debug[=debug_options]Write a debugging log            
-debug-check       Print debugging information      5.1.21
                   when program exits               
-debug-info        Print debugging information,     5.1.21
                   memory, and CPU statistics when  
                   program exits                    
-defaults-extra-file=file_nameRead option file in addition to  
                   usual option files               
-defaults-file=file_nameRead only named option file      
-defaults-group-suffix=strOption group suffix value        
-disable-log-bin   Disable binary logging           
-force-if-open     Read binary log files even if    5.1.15
                   open or not closed properly      
-force-read        If mysqlbinlog reads a binary    
                   log event that it does not       
                   recognize, it prints a warning   
-help              Display help message and exit    
-hexdump           Display a hex dump of the log    5.1.2
                   in comments                      
-host=host_name    Connect to MySQL server on       
                   given host                       
-local-load=path   Prepare local temporary files    
                   for LOAD DATA INFILE in the      
                   specified directory              
-no-defaults       Read no option files             
-offset=#          Skip the first N entries in the  
                   log                              
-password[=password]Password to use when connecting  
                   to server                        
-port=port_num     TCP/IP port number to use for    
                   connection                       
-position=#        Deprecated. Use -start-position  
-print-defaults    Print defaults                   
-protocol=type     Connection protocol to use       
-read-from-remote-serverRead binary log from MySQL       
                   server rather than local log     
                   file                             
-result-file=name  Direct output to named file      
-server-id=id      Extract only those events        5.1.4
                   created by the server having     
                   the given server ID              
-server-id-bits=#  Tell mysqlbinlog how to          5.1.47-ndb-7.1.6
                   interpret server IDs in binary   
                   log when log was written by a    
                   mysqld having its                
                   server-id-bits set to less than  
                   the maximum; supported only by   
                   MySQL Cluster version of         
                   mysqlbinlog                      
-set-charset=charset_nameAdd a SET NAMES charset_name     5.1.12
                   statement to the output          
-shared-memory-base-name=nameThe name of shared memory to     5.1.41
                   use for shared-memory            
                   connections                      
-short-form        Display only the statements      
                   contained in the log             
-socket=path       For connections to localhost,    
                   the Unix socket file to use      
-start-datetime=datetimeRead binary log from first       
                   event with timestamp equal to    
                   or later than datetime argument  
-start-position=#  Read binary log from first       
                   event with position equal to or  
                   greater than argument            
-stop-datetime=datetimeStop reading binary log at       
                   first event with timestamp       
                   equal to or greater than         
                   datetime argument                
-stop-position=#   Stop reading binary log at       
                   first event with position equal  
                   to or greater than argument      
-to-last-log       Do not stop at the end of        
                   requested binary log from a      
                   MySQL server, but rather         
                   continue printing to end of      
                   last binary log                  
-user=user_name,   MySQL user name to use when      
                   connecting to server             
-verbose           Reconstruct row events as SQL    5.1.28
                   statements                       
-version           Display version information and  
                   exit                             

   * `--help', `-?'

     Display a help message and exit.

   * `--base64-output[=VALUE]'

     This option determines when events should be displayed encoded as
     base-64 strings using *Note `BINLOG': binlog. statements. The
     option has these permissible values (not case sensitive):

        * `AUTO' ("automatic") or `UNSPEC' ("unspecified") displays
          *Note `BINLOG': binlog. statements automatically when
          necessary (that is, for format description events and row
          events). If no `--base64-output' option is given, the effect
          is the same as `--base64-output=AUTO'.

          *Note*:

          Automatic *Note `BINLOG': binlog.  display is the only safe
          behavior if you intend to use the output of *Note
          `mysqlbinlog': mysqlbinlog. to re-execute binary log file
          contents. The other option values are intended only for
          debugging or testing purposes because they may produce output
          that does not include all events in executable form.

        * `ALWAYS' displays *Note `BINLOG': binlog. statements whenever
          possible. If the `--base64-output' option is given without a
          value, the effect is the same as `--base64-output=ALWAYS'.

        * `NEVER' causes *Note `BINLOG': binlog. statements not to be
          displayed. *Note `mysqlbinlog': mysqlbinlog. exits with an
          error if a row event is found that must be displayed using
          *Note `BINLOG': binlog.

        * `DECODE-ROWS' specifies to *Note `mysqlbinlog': mysqlbinlog.
          that you intend for row events to be decoded and displayed as
          commented SQL statements by also specifying the `--verbose'
          option.  Like `NEVER', `DECODE-ROWS' suppresses display of
          *Note `BINLOG': binlog. statements, but unlike `NEVER', it
          does not exit with an error if a row event is found.

     The `--base64-output' option was introduced in MySQL 5.1.5, to be
     given as `--base64-output' or `--skip-base64-output' (with the
     sense of `AUTO' or `NEVER'). The option values described in the
     preceding list may be used as of MySQL 5.1.24, with the exception
     of `UNSPEC' and `DECODE-ROWS', which are available as of MySQL
     5.1.28.

     For examples that show the effect of `--base64-output' and
     `--verbose' on row event output, see *Note
     mysqlbinlog-row-events::.

   * `--bind-address=IP_ADDRESS'

     On a computer having multiple network interfaces, use this option
     to select which interface to use for connecting to the MySQL
     server.

     This option is supported only in the version of *Note
     `mysqlbinlog': mysqlbinlog. that is supplied with MySQL Cluster,
     beginning with MySQL Cluster NDB 6.3.4. It is not available in
     standard MySQL 5.1 releases.

   * `--character-sets-dir=PATH'

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--database=DB_NAME', `-d DB_NAME'

     This option causes *Note `mysqlbinlog': mysqlbinlog. to output
     entries from the binary log (local log only) that occur while
     DB_NAME is been selected as the default database by *Note `USE':
     use.

     The `--database' option for *Note `mysqlbinlog': mysqlbinlog. is
     similar to the `--binlog-do-db' option for *Note `mysqld': mysqld,
     but can be used to specify only one database. If `--database' is
     given multiple times, only the last instance is used.

     The effects of this option depend on whether the statement-based
     or row-based logging format is in use, in the same way that the
     effects of `--binlog-do-db' depend on whether statement-based or
     row-based logging is in use.

     Statement-based logging

     The `--database' option works as follows:

        * While DB_NAME is the default database, statements are output
          whether they modify tables in DB_NAME or a different database.

        * Unless DB_NAME is selected as the default database,
          statements are not output, even if they modify tables in
          DB_NAME.

        * There is an exception for *Note `CREATE DATABASE':
          create-database, *Note `ALTER DATABASE': alter-database, and
          *Note `DROP DATABASE': drop-database. The database being
          _created, altered, or dropped_ is considered to be the
          default database when determining whether to output the
          statement.

     Suppose that the binary log was created by executing these
     statements using statement-based-logging:


          INSERT INTO test.t1 (i) VALUES(100);
          INSERT INTO db2.t2 (j)  VALUES(200);
          USE test;
          INSERT INTO test.t1 (i) VALUES(101);
          INSERT INTO t1 (i)      VALUES(102);
          INSERT INTO db2.t2 (j)  VALUES(201);
          USE db2;
          INSERT INTO test.t1 (i) VALUES(103);
          INSERT INTO db2.t2 (j)  VALUES(202);
          INSERT INTO t2 (j)      VALUES(203);

     *Note `mysqlbinlog --database=test': mysqlbinlog. does not output
     the first two *Note `INSERT': insert.  statements because there is
     no default database. It outputs the three *Note `INSERT': insert.
     statements following *Note `USE test': use, but not the three
     *Note `INSERT': insert. statements following *Note `USE db2': use.

     *Note `mysqlbinlog --database=db2': mysqlbinlog. does not output
     the first two *Note `INSERT': insert.  statements because there is
     no default database. It does not output the three *Note `INSERT':
     insert.  statements following *Note `USE test': use, but does
     output the three *Note `INSERT': insert.  statements following
     *Note `USE db2': use.

     Row-based logging

     *Note `mysqlbinlog': mysqlbinlog. outputs only entries that change
     tables belonging to DB_NAME. The default database has no effect on
     this. Suppose that the binary log just described was created using
     row-based logging rather than statement-based logging. *Note
     `mysqlbinlog --database=test': mysqlbinlog. outputs only those
     entries that modify `t1' in the test database, regardless of
     whether *Note `USE': use.  was issued or what the default database
     is.

     If a server is running with `binlog_format' set to `MIXED' and you
     want it to be possible to use *Note `mysqlbinlog': mysqlbinlog.
     with the `--database' option, you must ensure that tables that are
     modified are in the database selected by *Note `USE': use. (In
     particular, no cross-database updates should be used.)

     This option did not work correctly for *Note `mysqlbinlog':
     mysqlbinlog. with row-based logging prior to MySQL 5.1.37. (Bug
     #42941)

     *Note*:

     Prior to MySQL Cluster NDB 7.0.28 and MySQL Cluster NDB 7.1.17,
     this option did not work correctly with MySQL Cluster tables
     unless, unless the binary log was generated using
     `--log-bin-use-v1-row-events=0'.  (Bug #13067813)

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is `d:t:o,/tmp/mysqlbinlog.trace'.

   * `--debug-check'

     Print some debugging information when the program exits.  This
     option was added in MySQL 5.1.21.

   * `--debug-info'

     Print debugging information and memory and CPU usage statistics
     when the program exits. This option was added in MySQL 5.1.21.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqlbinlog':
     mysqlbinlog. normally reads the `[client]' and `[mysqlbinlog]'
     groups. If the `--defaults-group-suffix=_other' option is given,
     *Note `mysqlbinlog': mysqlbinlog. also reads the `[client_other]'
     and `[mysqlbinlog_other]' groups.

   * `--disable-log-bin', `-D'

     Disable binary logging. This is useful for avoiding an endless
     loop if you use the `--to-last-log' option and are sending the
     output to the same MySQL server. This option also is useful when
     restoring after a crash to avoid duplication of the statements you
     have logged.

     This option requires that you have the `SUPER' privilege. It causes
     *Note `mysqlbinlog': mysqlbinlog. to include a `SET sql_log_bin =
     0' statement in its output to disable binary logging of the
     remaining output. The *Note `SET': set-statement.  statement is
     ineffective unless you have the `SUPER' privilege.

   * `--force-if-open', `-F'

     Read binary log files even if they are open or were not closed
     properly. This option was added in MySQL 5.1.15.

   * `--force-read', `-f'

     With this option, if *Note `mysqlbinlog': mysqlbinlog. reads a
     binary log event that it does not recognize, it prints a warning,
     ignores the event, and continues. Without this option, *Note
     `mysqlbinlog': mysqlbinlog. stops if it reads such an event.

   * `--hexdump', `-H'

     Display a hex dump of the log in comments, as described in *Note
     mysqlbinlog-hexdump::. The hex output can be helpful for
     replication debugging. This option was added in MySQL 5.1.2.

   * `--host=HOST_NAME', `-h HOST_NAME'

     Get the binary log from the MySQL server on the given host.

   * `--local-load=PATH', `-l PATH'

     Prepare local temporary files for *Note `LOAD DATA INFILE':
     load-data. in the specified directory.

     *Important*:

     These temporary files are not automatically removed by *Note
     `mysqlbinlog': mysqlbinlog. or any other MySQL program.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can be
     used to prevent them from being read.

   * `--offset=N', `-o N'

     Skip the first N entries in the log.

   * `--password[=PASSWORD]', `-p[PASSWORD]'

     The password to use when connecting to the server. If you use the
     short option form (`-p'), you _cannot_ have a space between the
     option and the password. If you omit the PASSWORD value following
     the `--password' or `-p' option on the command line, *Note
     `mysqlbinlog': mysqlbinlog. prompts for one.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use for connecting to a remote server.

   * `--position=N'

     Deprecated. Use `--start-position' instead. `--position' is
     removed in MySQL 5.5.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--protocol={TCP|SOCKET|PIPE|MEMORY}'

     The connection protocol to use for connecting to the server.  It
     is useful when the other connection parameters normally would
     cause a protocol to be used other than the one you want. For
     details on the permissible values, see *Note connecting::.

   * `--read-from-remote-server', `-R'

     Read the binary log from a MySQL server rather than reading a
     local log file. Any connection parameter options are ignored
     unless this option is given as well. These options are `--host',
     `--password', `--port', `--protocol', `--socket', and `--user'.

     This option requires that the remote server be running. It works
     only for binary log files on the remote server, not relay log
     files.

   * `--result-file=NAME', `-r NAME'

     Direct output to the given file.

   * `--server-id=ID'

     Display only those events created by the server having the given
     server ID. This option is available as of MySQL 5.1.4.

   * `--server-id-bits=N'

     Use only the first N bits of the `server_id' to identify the
     server. If the binary log was written by a *Note `mysqld': mysqld.
     with server-id-bits set to less than 32 and user data stored in
     the most significant bit, running *Note `mysqlbinlog':
     mysqlbinlog. with `--server-id-bits' set to 32 enables this data
     to be seen.

     This option was added in MySQL Cluster NDB 7.0.17 and MySQL
     Cluster NDB 7.1.6, and is supported only by the versions of *Note
     `mysqlbinlog': mysqlbinlog. supplied with these and later releases
     of MySQL Cluster.

   * `--set-charset=CHARSET_NAME'

     Add a `SET NAMES CHARSET_NAME' statement to the output to specify
     the character set to be used for processing log files. This option
     was added in MySQL 5.1.12.

   * `--shared-memory-base-name=NAME'

     On Windows, the shared-memory name to use, for connections made
     using shared memory to a local server. The default value is
     `MYSQL'. The shared-memory name is case sensitive.

     The server must be started with the `--shared-memory' option to
     enable shared-memory connections.

     This option was added in MySQL 5.1.41.

   * `--short-form', `-s'

     Display only the statements contained in the log, without any
     extra information or row-based events. This is for testing only,
     and should not be used in production systems.

   * `--socket=PATH', `-S PATH'

     For connections to `localhost', the Unix socket file to use, or,
     on Windows, the name of the named pipe to use.

   * `--start-datetime=DATETIME'

     Start reading the binary log at the first event having a timestamp
     equal to or later than the DATETIME argument. The DATETIME value
     is relative to the local time zone on the machine where you run
     *Note `mysqlbinlog': mysqlbinlog. The value should be in a format
     accepted for the *Note `DATETIME': datetime. or *Note `TIMESTAMP':
     datetime. data types. For example:


          shell> mysqlbinlog --start-datetime="2005-12-25 11:25:56" binlog.000003

     This option is useful for point-in-time recovery. See *Note
     backup-strategy-example::.

   * `--start-position=N', `-j N'

     Start reading the binary log at the first event having a position
     equal to or greater than N. This option applies to the first log
     file named on the command line.

     This option is useful for point-in-time recovery. See *Note
     backup-strategy-example::.

   * `--stop-datetime=DATETIME'

     Stop reading the binary log at the first event having a timestamp
     equal to or later than the DATETIME argument. This option is
     useful for point-in-time recovery. See the description of the
     `--start-datetime' option for information about the DATETIME value.

     This option is useful for point-in-time recovery. See *Note
     backup-strategy-example::.

   * `--stop-position=N'

     Stop reading the binary log at the first event having a position
     equal to or greater than N. This option applies to the last log
     file named on the command line.

     This option is useful for point-in-time recovery. See *Note
     backup-strategy-example::.

   * `--to-last-log', `-t'

     Do not stop at the end of the requested binary log from a MySQL
     server, but rather continue printing until the end of the last
     binary log. If you send the output to the same MySQL server, this
     may lead to an endless loop. This option requires
     `--read-from-remote-server'.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to a remote server.

   * `--verbose', `-v'

     Reconstruct row events and display them as commented SQL
     statements. If this option is given twice, the output includes
     comments to indicate column data types and some metadata. This
     option was added in MySQL 5.1.28.

     For examples that show the effect of `--base64-output' and
     `--verbose' on row event output, see *Note
     mysqlbinlog-row-events::.

   * `--version', `-V'

     Display version information and exit.

     In MySQL 5.1, the version number shown for *Note `mysqlbinlog':
     mysqlbinlog. is always 3.3.

You can also set the following variable by using `--VAR_NAME=VALUE'
syntax:

   * `open_files_limit'

     Specify the number of open file descriptors to reserve.

You can pipe the output of *Note `mysqlbinlog': mysqlbinlog. into the
*Note `mysql': mysql. client to execute the events contained in the
binary log. This technique is used to recover from a crash when you
have an old backup (see *Note point-in-time-recovery::). For example:


     shell> mysqlbinlog binlog.000001 | mysql -u root -p

Or:


     shell> mysqlbinlog binlog.[0-9]* | mysql -u root -p

You can also redirect the output of *Note `mysqlbinlog': mysqlbinlog.
to a text file instead, if you need to modify the statement log first
(for example, to remove statements that you do not want to execute for
some reason).  After editing the file, execute the statements that it
contains by using it as input to the *Note `mysql': mysql. program:


     shell> mysqlbinlog binlog.000001 > tmpfile
     shell> ... EDIT TMPFILE ...
     shell> mysql -u root -p < tmpfile

When *Note `mysqlbinlog': mysqlbinlog. is invoked with the
`--start-position' option, it displays only those events with an offset
in the binary log greater than or equal to a given position (the given
position must match the start of one event). It also has options to stop
and start when it sees an event with a given date and time. This
enables you to perform point-in-time recovery using the
`--stop-datetime' option (to be able to say, for example, `roll forward
my databases to how they were today at 10:30 a.m.').

If you have more than one binary log to execute on the MySQL server,
the safe method is to process them all using a single connection to the
server. Here is an example that demonstrates what may be _unsafe_:


     shell> mysqlbinlog binlog.000001 | mysql -u root -p # DANGER!!
     shell> mysqlbinlog binlog.000002 | mysql -u root -p # DANGER!!

Processing binary logs this way using multiple connections to the
server causes problems if the first log file contains a *Note `CREATE
TEMPORARY TABLE': create-table. statement and the second log contains a
statement that uses the temporary table. When the first *Note `mysql':
mysql. process terminates, the server drops the temporary table. When
the second *Note `mysql': mysql.  process attempts to use the table,
the server reports `unknown table.'

To avoid problems like this, use a _single_ *Note `mysql': mysql.
process to execute the contents of all binary logs that you want to
process. Here is one way to do so:


     shell> mysqlbinlog binlog.000001 binlog.000002 | mysql -u root -p

Another approach is to write all the logs to a single file and then
process the file:


     shell> mysqlbinlog binlog.000001 >  /tmp/statements.sql
     shell> mysqlbinlog binlog.000002 >> /tmp/statements.sql
     shell> mysql -u root -p -e "source /tmp/statements.sql"

*Note `mysqlbinlog': mysqlbinlog. can produce output that reproduces a
*Note `LOAD DATA INFILE': load-data. operation without the original
data file.  *Note `mysqlbinlog': mysqlbinlog. copies the data to a
temporary file and writes a *Note `LOAD DATA LOCAL INFILE': load-data.
statement that refers to the file. The default location of the
directory where these files are written is system-specific. To specify
a directory explicitly, use the `--local-load' option.

Because *Note `mysqlbinlog': mysqlbinlog. converts *Note `LOAD DATA
INFILE': load-data. statements to *Note `LOAD DATA LOCAL INFILE':
load-data. statements (that is, it adds `LOCAL'), both the client and
the server that you use to process the statements must be configured
with the `LOCAL' capability enabled. See *Note load-data-local::.

*Warning*:

The temporary files created for *Note `LOAD DATA LOCAL': load-data.
statements are _not_ automatically deleted because they are needed
until you actually execute those statements. You should delete the
temporary files yourself after you no longer need the statement log.
The files can be found in the temporary file directory and have names
like ORIGINAL_FILE_NAME-#-#.


File: manual.info,  Node: mysqlbinlog-hexdump,  Next: mysqlbinlog-row-events,  Prev: mysqlbinlog,  Up: mysqlbinlog

4.6.7.1 mysqlbinlog Hex Dump Format
...................................

The `--hexdump' option causes *Note `mysqlbinlog': mysqlbinlog. to
produce a hex dump of the binary log contents:


     shell> mysqlbinlog --hexdump master-bin.000001

The hex output consists of comment lines beginning with `#', so the
output might look like this for the preceding command:


     /*!40019 SET @@session.max_insert_delayed_threads=0*/;
     /*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
     # at 4
     #051024 17:24:13 server id 1  end_log_pos 98
     # Position  Timestamp   Type   Master ID        Size      Master Pos    Flags
     # 00000004 9d fc 5c 43   0f   01 00 00 00   5e 00 00 00   62 00 00 00   00 00
     # 00000017 04 00 35 2e 30 2e 31 35  2d 64 65 62 75 67 2d 6c |..5.0.15.debug.l|
     # 00000027 6f 67 00 00 00 00 00 00  00 00 00 00 00 00 00 00 |og..............|
     # 00000037 00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00 |................|
     # 00000047 00 00 00 00 9d fc 5c 43  13 38 0d 00 08 00 12 00 |.......C.8......|
     # 00000057 04 04 04 04 12 00 00 4b  00 04 1a                |.......K...|
     #       Start: binlog v 4, server v 5.0.15-debug-log created 051024 17:24:13
     #       at startup
     ROLLBACK;

Hex dump output currently contains the elements in the following list.
This format is subject to change. (For more information about binary
log format, see MySQL Internals: The Binary Log
(http://dev.mysql.com/doc/internals/en/binary-log.html).

   * `Position': The byte position within the log file.

   * `Timestamp': The event timestamp. In the example shown, `'9d fc 5c
     43'' is the representation of `'051024 17:24:13'' in hexadecimal.

   * `Type': The event type code. In the example shown, `'0f''
     indicates a `FORMAT_DESCRIPTION_EVENT'. The following table lists
     the possible type codes.

     This table lists event type codes found in *Note `mysqlbinlog':
     mysqlbinlog.  `--hexdump' output. The table also lists the
     corresponding name and meaning for each event code type.

     Type                               Name                    Meaning
     `00'                               `UNKNOWN_EVENT'         This event should never be present in
                                                                the log.
     `01'                               `START_EVENT_V3'        This indicates the start of a log file
                                                                written by MySQL 4 or earlier.
     `02'                               `QUERY_EVENT'           The most common type of events. These
                                                                contain statements executed on the
                                                                master.
     `03'                               `STOP_EVENT'            Indicates that master has stopped.
     `04'                               `ROTATE_EVENT'          Written when the master switches to a
                                                                new log file.
     `05'                               `INTVAR_EVENT'          Used for `AUTO_INCREMENT' values or
                                                                when the `LAST_INSERT_ID()' function is
                                                                used in the statement.
     `06'                               `LOAD_EVENT'            Used for *Note `LOAD DATA INFILE':
                                                                load-data. in MySQL 3.23.
     `07'                               `SLAVE_EVENT'           Reserved for future use.
     `08'                               `CREATE_FILE_EVENT'     Used for *Note `LOAD DATA INFILE':
                                                                load-data. statements. This indicates
                                                                the start of execution of such a
                                                                statement. A temporary file is created
                                                                on the slave. Used in MySQL 4 only.
     `09'                               `APPEND_BLOCK_EVENT'    Contains data for use in a *Note `LOAD
                                                                DATA INFILE': load-data. statement. The
                                                                data is stored in the temporary file on
                                                                the slave.
     `0a'                               `EXEC_LOAD_EVENT'       Used for *Note `LOAD DATA INFILE':
                                                                load-data. statements. The contents of
                                                                the temporary file is stored in the
                                                                table on the slave.  Used in MySQL 4
                                                                only.
     `0b'                               `DELETE_FILE_EVENT'     Rollback of a *Note `LOAD DATA INFILE':
                                                                load-data. statement. The temporary file
                                                                should be deleted on the slave.
     `0c'                               `NEW_LOAD_EVENT'        Used for *Note `LOAD DATA INFILE':
                                                                load-data. in MySQL 4 and earlier.
     `0d'                               `RAND_EVENT'            Used to send information about random
                                                                values if the `RAND()' function is used
                                                                in the statement.
     `0e'                               `USER_VAR_EVENT'        Used to replicate user variables.
     `0f'                               `FORMAT_DESCRIPTION_EVENT'This indicates the start of a log file
                                                                written by MySQL 5 or later.
     `10'                               `XID_EVENT'             Event indicating commit of an XA
                                                                transaction.
     `11'                               `BEGIN_LOAD_QUERY_EVENT'Used for *Note `LOAD DATA INFILE':
                                                                load-data. statements in MySQL 5 and
                                                                later.
     `12'                               `EXECUTE_LOAD_QUERY_EVENT'Used for *Note `LOAD DATA INFILE':
                                                                load-data. statements in MySQL 5 and
                                                                later.
     `13'                               `TABLE_MAP_EVENT'       Information about a table definition.
                                                                Used in MySQL 5.1.5 and later.
     `14'                               `PRE_GA_WRITE_ROWS_EVENT'Row data for a single table that should
                                                                be created. Used in MySQL 5.1.5 to
                                                                5.1.17.
     `15'                               `PRE_GA_UPDATE_ROWS_EVENT'Row data for a single table that needs
                                                                to be updated. Used in MySQL 5.1.5 to
                                                                5.1.17.
     `16'                               `PRE_GA_DELETE_ROWS_EVENT'Row data for a single table that should
                                                                be deleted. Used in MySQL 5.1.5 to
                                                                5.1.17.
     `17'                               `WRITE_ROWS_EVENT'      Row data for a single table that should
                                                                be created. Used in MySQL 5.1.18 and
                                                                later.
     `18'                               `UPDATE_ROWS_EVENT'     Row data for a single table that needs
                                                                to be updated. Used in MySQL 5.1.18 and
                                                                later.
     `19'                               `DELETE_ROWS_EVENT'     Row data for a single table that should
                                                                be deleted. Used in MySQL 5.1.18 and
                                                                later.
     `1a'                               `INCIDENT_EVENT'        Something out of the ordinary happened.
                                                                Added in MySQL 5.1.18.

   * `Master ID': The server ID of the master that created the event.

   * `Size': The size in bytes of the event.

   * `Master Pos': The position of the next event in the original
     master log file.

   * `Flags': 16 flags. Currently, the following flags are used. The
     others are reserved for future use.

     This table lists flag values found in *Note `mysqlbinlog':
     mysqlbinlog.  `--hexdump' output. The table also provides
     corresponding names and meanings for each flag value.

     Flag                               Name                    Meaning
     `01'                               `LOG_EVENT_BINLOG_IN_USE_F'Log file correctly closed. (Used only in
                                                                `FORMAT_DESCRIPTION_EVENT'.) If this
                                                                flag is set (if the flags are, for
                                                                example, `'01 00'') in a
                                                                `FORMAT_DESCRIPTION_EVENT', the log
                                                                file has not been properly closed. Most
                                                                probably this is because of a master
                                                                crash (for example, due to power
                                                                failure).
     `02'                                                       Reserved for future use.
     `04'                               `LOG_EVENT_THREAD_SPECIFIC_F'Set if the event is dependent on the
                                                                connection it was executed in (for
                                                                example, `'04 00''), for example, if
                                                                the event uses temporary tables.
     `08'                               `LOG_EVENT_SUPPRESS_USE_F'Set in some circumstances when the
                                                                event is not dependent on the default
                                                                database.


File: manual.info,  Node: mysqlbinlog-row-events,  Prev: mysqlbinlog-hexdump,  Up: mysqlbinlog

4.6.7.2 mysqlbinlog Row Event Display
.....................................

The following examples illustrate how *Note `mysqlbinlog': mysqlbinlog.
displays row events that specify data modifications. These correspond
to events with the `WRITE_ROWS_EVENT', `UPDATE_ROWS_EVENT', and
`DELETE_ROWS_EVENT' type codes. The `--base64-output=DECODE-ROWS' and
`--verbose' options may be used to affect row event output. These
options are available as of MySQL 5.1.28.

Suppose that the server is using row-based binary logging and that you
execute the following sequence of statements:


     CREATE TABLE t
     (
       id   INT NOT NULL,
       name VARCHAR(20) NOT NULL,
       date DATE NULL
     ) ENGINE = InnoDB;

     START TRANSACTION;
     INSERT INTO t VALUES(1, 'apple', NULL);
     UPDATE t SET name = 'pear', date = '2009-01-01' WHERE id = 1;
     DELETE FROM t WHERE id = 1;
     COMMIT;

By default, *Note `mysqlbinlog': mysqlbinlog. displays row events
encoded as base-64 strings using *Note `BINLOG': binlog. statements.
Omitting extraneous lines, the output for the row events produced by the
preceding statement sequence looks like this:


     shell> mysqlbinlog LOG_FILE
     ...
     # at 218
     #080828 15:03:08 server id 1  end_log_pos 258   Write_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAANoAAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBcBAAAAKAAAAAIBAAAQABEAAAAAAAEAA//8AQAAAAVhcHBsZQ==
     '/*!*/;
     ...
     # at 302
     #080828 15:03:08 server id 1  end_log_pos 356   Update_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAAC4BAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBgBAAAANgAAAGQBAAAQABEAAAAAAAEAA////AEAAAAFYXBwbGX4AQAAAARwZWFyIbIP
     '/*!*/;
     ...
     # at 400
     #080828 15:03:08 server id 1  end_log_pos 442   Delete_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAAJABAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBkBAAAAKgAAALoBAAAQABEAAAAAAAEAA//4AQAAAARwZWFyIbIP
     '/*!*/;

To see the row events as comments in the form of `pseudo-SQL'
statements, run *Note `mysqlbinlog': mysqlbinlog. with the `--verbose'
or `-v' option. The output will contain lines beginning with `###':


     shell> mysqlbinlog -v LOG_FILE
     ...
     # at 218
     #080828 15:03:08 server id 1  end_log_pos 258   Write_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAANoAAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBcBAAAAKAAAAAIBAAAQABEAAAAAAAEAA//8AQAAAAVhcHBsZQ==
     '/*!*/;
     ### INSERT INTO test.t
     ### SET
     ###   @1=1
     ###   @2='apple'
     ###   @3=NULL
     ...
     # at 302
     #080828 15:03:08 server id 1  end_log_pos 356   Update_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAAC4BAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBgBAAAANgAAAGQBAAAQABEAAAAAAAEAA////AEAAAAFYXBwbGX4AQAAAARwZWFyIbIP
     '/*!*/;
     ### UPDATE test.t
     ### WHERE
     ###   @1=1
     ###   @2='apple'
     ###   @3=NULL
     ### SET
     ###   @1=1
     ###   @2='pear'
     ###   @3='2009:01:01'
     ...
     # at 400
     #080828 15:03:08 server id 1  end_log_pos 442   Delete_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAAJABAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBkBAAAAKgAAALoBAAAQABEAAAAAAAEAA//4AQAAAARwZWFyIbIP
     '/*!*/;
     ### DELETE FROM test.t
     ### WHERE
     ###   @1=1
     ###   @2='pear'
     ###   @3='2009:01:01'

Specify `--verbose' or `-v' twice to also display data types and some
metadata for each column. The output will contain an additional comment
following each column change:


     shell> mysqlbinlog -vv LOG_FILE
     ...
     # at 218
     #080828 15:03:08 server id 1  end_log_pos 258   Write_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAANoAAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBcBAAAAKAAAAAIBAAAQABEAAAAAAAEAA//8AQAAAAVhcHBsZQ==
     '/*!*/;
     ### INSERT INTO test.t
     ### SET
     ###   @1=1 /* INT meta=0 nullable=0 is_null=0 */
     ###   @2='apple' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */
     ###   @3=NULL /* VARSTRING(20) meta=0 nullable=1 is_null=1 */
     ...
     # at 302
     #080828 15:03:08 server id 1  end_log_pos 356   Update_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAAC4BAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBgBAAAANgAAAGQBAAAQABEAAAAAAAEAA////AEAAAAFYXBwbGX4AQAAAARwZWFyIbIP
     '/*!*/;
     ### UPDATE test.t
     ### WHERE
     ###   @1=1 /* INT meta=0 nullable=0 is_null=0 */
     ###   @2='apple' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */
     ###   @3=NULL /* VARSTRING(20) meta=0 nullable=1 is_null=1 */
     ### SET
     ###   @1=1 /* INT meta=0 nullable=0 is_null=0 */
     ###   @2='pear' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */
     ###   @3='2009:01:01' /* DATE meta=0 nullable=1 is_null=0 */
     ...
     # at 400
     #080828 15:03:08 server id 1  end_log_pos 442   Delete_rows: table id 17 flags: STMT_END_F

     BINLOG '
     fAS3SBMBAAAALAAAAJABAAAAABEAAAAAAAAABHRlc3QAAXQAAwMPCgIUAAQ=
     fAS3SBkBAAAAKgAAALoBAAAQABEAAAAAAAEAA//4AQAAAARwZWFyIbIP
     '/*!*/;
     ### DELETE FROM test.t
     ### WHERE
     ###   @1=1 /* INT meta=0 nullable=0 is_null=0 */
     ###   @2='pear' /* VARSTRING(20) meta=20 nullable=0 is_null=0 */
     ###   @3='2009:01:01' /* DATE meta=0 nullable=1 is_null=0 */

You can tell *Note `mysqlbinlog': mysqlbinlog. to suppress the *Note
`BINLOG': binlog. statements for row events by using the
`--base64-output=DECODE-ROWS' option. This is similar to
`--base64-output=NEVER' but does not exit with an error if a row event
is found. The combination of `--base64-output=DECODE-ROWS' and
`--verbose' provides a convenient way to see row events only as SQL
statements:


     shell> mysqlbinlog -v --base64-output=DECODE-ROWS LOG_FILE
     ...
     # at 218
     #080828 15:03:08 server id 1  end_log_pos 258   Write_rows: table id 17 flags: STMT_END_F
     ### INSERT INTO test.t
     ### SET
     ###   @1=1
     ###   @2='apple'
     ###   @3=NULL
     ...
     # at 302
     #080828 15:03:08 server id 1  end_log_pos 356   Update_rows: table id 17 flags: STMT_END_F
     ### UPDATE test.t
     ### WHERE
     ###   @1=1
     ###   @2='apple'
     ###   @3=NULL
     ### SET
     ###   @1=1
     ###   @2='pear'
     ###   @3='2009:01:01'
     ...
     # at 400
     #080828 15:03:08 server id 1  end_log_pos 442   Delete_rows: table id 17 flags: STMT_END_F
     ### DELETE FROM test.t
     ### WHERE
     ###   @1=1
     ###   @2='pear'
     ###   @3='2009:01:01'

*Note*:

You should not suppress *Note `BINLOG': binlog.  statements if you
intend to re-execute *Note `mysqlbinlog': mysqlbinlog. output.

The SQL statements produced by `--verbose' for row events are much more
readable than the corresponding *Note `BINLOG': binlog. statements.
However, they do not correspond exactly to the original SQL statements
that generated the events. The following limitations apply:

   * The original column names are lost and replaced by `@N', where N
     is a column number.

   * Character set information is not available in the binary log,
     which affects string column display:

        * There is no distinction made between corresponding binary and
          nonbinary string types (*Note `BINARY': binary-varbinary. and
          *Note `CHAR': char, *Note `VARBINARY': binary-varbinary. and
          *Note `VARCHAR': char, *Note `BLOB': blob. and *Note `TEXT':
          blob.). The output uses a data type of `STRING' for
          fixed-length strings and `VARSTRING' for variable-length
          strings.

        * For multibyte character sets, the maximum number of bytes per
          character is not present in the binary log, so the length for
          string types is displayed in bytes rather than in characters.
          For example, `STRING(4)' will be used as the data type for
          values from either of these column types:


               CHAR(4) CHARACTER SET latin1
               CHAR(2) CHARACTER SET ucs2

        * Due to the storage format for events of type
          `UPDATE_ROWS_EVENT', *Note `UPDATE': update. statements are
          displayed with the `WHERE' clause preceding the `SET' clause.

Proper interpretation of row events requires the information from the
format description event at the beginning of the binary log. Because
*Note `mysqlbinlog': mysqlbinlog. does not know in advance whether the
rest of the log contains row events, by default it displays the format
description event using a *Note `BINLOG': binlog. statement in the
initial part of the output.

If the binary log is known not to contain any events requiring a *Note
`BINLOG': binlog. statement (that is, no row events), the
`--base64-output=NEVER' option can be used to prevent this header from
being written.


File: manual.info,  Node: mysqldumpslow,  Next: mysqlhotcopy,  Prev: mysqlbinlog,  Up: programs-admin-utils

4.6.8 `mysqldumpslow' -- Summarize Slow Query Log Files
-------------------------------------------------------

The MySQL slow query log contains information about queries that take a
long time to execute (see *Note slow-query-log::).  *Note
`mysqldumpslow': mysqldumpslow. parses MySQL slow query log files and
prints a summary of their contents.

Normally, *Note `mysqldumpslow': mysqldumpslow. groups queries that are
similar except for the particular values of number and string data
values. It `abstracts' these values to `N' and `'S'' when displaying
summary output. The `-a' and `-n' options can be used to modify value
abstracting behavior.

Invoke *Note `mysqldumpslow': mysqldumpslow. like this:


     shell> mysqldumpslow [OPTIONS] [LOG_FILE ...]

*Note `mysqldumpslow': mysqldumpslow. supports the following options.

*`mysqldumpslow' Options*

Format             Description
-a                 Do not abstract all numbers to
                   N and strings to S
-n num             Abstract numbers with at least
                   the specified digits
-debug             Write debugging information
-g pattern         Only consider statements that
                   match the pattern
-help              Display help message and exit
-h name            Host name of the server in the
                   log file name
-i name            Name of the server instance
-l                 Do not subtract lock time from
                   total time
-r                 Reverse the sort order
-s value           How to sort output
-t num             Display only first num queries
-verbose           Verbose mode

   * `--help'

     Display a help message and exit.

   * `-a'

     Do not abstract all numbers to `N' and strings to `'S''.

   * `--debug', `-d'

     Run in debug mode.

   * `-g PATTERN'

     Consider only queries that match the (`grep'-style) pattern.

   * `-h HOST_NAME'

     Host name of MySQL server for `*-slow.log' file name. The value can
     contain a wildcard. The default is `*' (match all).

   * `-i NAME'

     Name of server instance (if using *Note `mysql.server':
     mysql-server. startup script).

   * `-l'

     Do not subtract lock time from total time.

   * `-n N'

     Abstract numbers with at least N digits within names.

   * `-r'

     Reverse the sort order.

   * `-s SORT_TYPE'

     How to sort the output. The value of SORT_TYPE should be chosen
     from the following list:

        * `t', `at': Sort by query time or average query time

        * `l', `al': Sort by lock time or average lock time

        * `r', `ar': Sort by rows sent or average rows sent

        * `c': Sort by count

     By default, *Note `mysqldumpslow': mysqldumpslow. sorts by average
     query time (equivalent to `-s at').

   * `-t N'

     Display only the first N queries in the output.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.

Example of usage:


     shell> mysqldumpslow

     Reading mysql slow query log from /usr/local/mysql/data/mysqld51-apple-slow.log
     Count: 1  Time=4.32s (4s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
      insert into t2 select * from t1

     Count: 3  Time=2.53s (7s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
      insert into t2 select * from t1 limit N

     Count: 3  Time=2.13s (6s)  Lock=0.00s (0s)  Rows=0.0 (0), root[root]@localhost
      insert into t1 select * from t1


File: manual.info,  Node: mysqlhotcopy,  Next: instance-manager,  Prev: mysqldumpslow,  Up: programs-admin-utils

4.6.9 `mysqlhotcopy' -- A Database Backup Program
-------------------------------------------------

*Note `mysqlhotcopy': mysqlhotcopy. is a Perl script that was
originally written and contributed by Tim Bunce. It uses *Note `FLUSH
TABLES': flush, *Note `LOCK TABLES': lock-tables, and `cp' or `scp' to
make a database backup. It is a fast way to make a backup of the
database or single tables, but it can be run only on the same machine
where the database directories are located.  *Note `mysqlhotcopy':
mysqlhotcopy. works only for backing up `MyISAM' and `ARCHIVE' tables.
It runs on Unix and NetWare.

To use *Note `mysqlhotcopy': mysqlhotcopy, you must have read access to
the files for the tables that you are backing up, the `SELECT'
privilege for those tables, the `RELOAD' privilege (to be able to
execute *Note `FLUSH TABLES': flush.), and the `LOCK TABLES' privilege
(to be able to lock the tables).


     shell> mysqlhotcopy DB_NAME [/PATH/TO/NEW_DIRECTORY]


     shell> mysqlhotcopy DB_NAME_1 ... DB_NAME_N /PATH/TO/NEW_DIRECTORY

Back up tables in the given database that match a regular expression:


     shell> mysqlhotcopy DB_NAME./REGEX/

The regular expression for the table name can be negated by prefixing
it with a tilde (``~''):


     shell> mysqlhotcopy DB_NAME./~REGEX/

*Note `mysqlhotcopy': mysqlhotcopy. supports the following options,
which can be specified on the command line or in the `[mysqlhotcopy]'
and `[client]' groups of an option file. For information about option
files used by MySQL programs, see *Note option-files::.

*`mysqlhotcopy' Options*

Format             Description
-addtodest         Do not rename target directory
                   (if it exists); merely add
                   files to it
-allowold          Do not abort if a target
                   exists; rename it by adding an
                   _old suffix
-checkpoint=db_name.tbl_nameInsert checkpoint entries
-chroot=path       Base directory of the chroot
                   jail in which mysqld operates
-debug             Write a debugging log
-dryrun            Report actions without
                   performing them
-flushlog          Flush logs after all tables are
                   locked
-help              Display help message and exit
-host=host_name    Connect to MySQL server on
                   given host
-keepold           Do not delete previous
                   (renamed) target when done
-method            The method for copying files
-noindices         Do not include full index files
                   in the backup
-password[=password]Password to use when connecting
                   to server
-port=port_num     TCP/IP port number to use for
                   connection
-quiet             Be silent except for errors
-regexp            Copy all databases with names
                   that match the given regular
                   expression
-resetmaster       Reset the binary log after
                   locking all the tables
-resetslave        Reset the master.info file
                   after locking all the tables
-socket=path       For connections to localhost,
                   the Unix socket file to use
-tmpdir=path       The temporary directory
-user=user_name,   MySQL user name to use when
                   connecting to server

   * `--help', `-?'

     Display a help message and exit.

   * `--addtodest'

     Do not rename target directory (if it exists); merely add files to
     it.

   * `--allowold'

     Do not abort if a target exists; rename it by adding an `_old'
     suffix.

   * `--checkpoint=DB_NAME.TBL_NAME'

     Insert checkpoint entries into the specified database DB_NAME and
     table TBL_NAME.

   * `--chroot=PATH'

     Base directory of the `chroot' jail in which *Note `mysqld':
     mysqld. operates. The PATH value should match that of the
     `--chroot' option given to *Note `mysqld': mysqld.

   * `--debug'

     Enable debug output.

   * `--dryrun', `-n'

     Report actions without performing them.

   * `--flushlog'

     Flush logs after all tables are locked.

   * `--host=HOST_NAME', `-h HOST_NAME'

     The host name of the local host to use for making a TCP/IP
     connection to the local server. By default, the connection is made
     to `localhost' using a Unix socket file.

   * `--keepold'

     Do not delete previous (renamed) target when done.

   * `--method=COMMAND'

     The method for copying files (`cp' or `scp'). The default is `cp'.

   * `--noindices'

     Do not include full index files for *Note `MyISAM':
     myisam-storage-engine. tables in the backup.  This makes the
     backup smaller and faster. The indexes for reloaded tables can be
     reconstructed later with *Note `myisamchk -rq': myisamchk.

   * `--password=PASSWORD', `-pPASSWORD'

     The password to use when connecting to the server. The password
     value is not optional for this option, unlike for other MySQL
     programs.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--port=PORT_NUM', `-P PORT_NUM'

     The TCP/IP port number to use when connecting to the local server.

   * `--quiet', `-q'

     Be silent except for errors.

   * `--record_log_pos=DB_NAME.TBL_NAME'

     Record master and slave status in the specified database DB_NAME
     and table TBL_NAME.

   * `--regexp=EXPR'

     Copy all databases with names that match the given regular
     expression.

   * `--resetmaster'

     Reset the binary log after locking all the tables.

   * `--resetslave'

     Reset the `master.info' file after locking all the tables.

   * `--socket=PATH', `-S PATH'

     The Unix socket file to use for connections to `localhost'.

   * `--suffix=STR'

     The suffix to use for names of copied databases.

   * `--tmpdir=PATH'

     The temporary directory. The default is `/tmp'.

   * `--user=USER_NAME', `-u USER_NAME'

     The MySQL user name to use when connecting to the server.

Use `perldoc' for additional *Note `mysqlhotcopy': mysqlhotcopy.
documentation, including information about the structure of the tables
needed for the `--checkpoint' and `--record_log_pos' options:


     shell> perldoc mysqlhotcopy


File: manual.info,  Node: instance-manager,  Next: mysql-convert-table-format,  Prev: mysqlhotcopy,  Up: programs-admin-utils

4.6.10 `mysqlmanager' -- The MySQL Instance Manager
---------------------------------------------------

* Menu:

* instance-manager-command-options::  MySQL Instance Manager Command Options
* instance-manager-configuration-files::  MySQL Instance Manager Configuration Files
* instance-manager-startup-process::  Starting the MySQL Server with MySQL Instance Manager
* instance-manager-security-passwords::  Instance Manager User and Password Management
* instance-manager-security-monitoring::  MySQL Server Instance Status Monitoring
* instance-manager-security::    Connecting to MySQL Instance Manager
* instance-manager-commands::    MySQL Instance Manager Commands

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

`mysqlmanager' is the MySQL Instance Manager (IM). This program
monitors and manages MySQL Database Server instances. MySQL Instance
Manager is available for Unix-like operating systems, as well as
Windows. It runs as a daemon that listens on a TCP/IP port. On Unix, it
also listens on a Unix socket file.

MySQL Instance Manager can be used in place of the *Note `mysqld_safe':
mysqld-safe. script to start and stop one or more instances of MySQL
Server. Because Instance Manager can manage multiple server instances,
it can also be used in place of the *Note `mysqld_multi': mysqld-multi.
script. Instance Manager offers these capabilities:

   * Instance Manager can start and stop instances, and report on the
     status of instances.

   * Server instances can be treated as guarded or unguarded:

        * When Instance Manager starts, it starts each guarded
          instance. If the instance crashes, Instance Manager detects
          this and restarts it. When Instance Manager stops, it stops
          the instance.

        * A nonguarded instance is not started when Instance Manager
          starts or monitored by it. If the instance crashes after
          being started, Instance Manager does not restart it. When
          Instance Manager exits, it does not stop the instance if it
          is running.

     Instances are guarded by default. An instance can be designated as
     nonguarded by including the `nonguarded' option in the
     configuration file.

   * Instance Manager provides an interactive interface for configuring
     instances, so that the need to edit the configuration file
     manually is reduced or eliminated.

   * Instance Manager provides remote instance management. That is, it
     runs on the host where you want to control MySQL Server instances,
     but you can connect to it from a remote host to perform
     instance-management operations.

The following sections describe MySQL Instance Manager operation in
more detail.


File: manual.info,  Node: instance-manager-command-options,  Next: instance-manager-configuration-files,  Prev: instance-manager,  Up: instance-manager

4.6.10.1 MySQL Instance Manager Command Options
...............................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

The MySQL Instance Manager supports a number of command options.  For a
brief listing, invoke `mysqlmanager' with the `--help' option. Options
may be given on the command line or in the Instance Manager
configuration file. On Windows, the standard configuration file is
`my.ini' in the directory where Instance Manager is installed. On Unix,
the standard file is `/etc/my.cnf'. To specify a different
configuration file, start Instance Manager with the `--defaults-file'
option.

`mysqlmanager' supports the following options.  The options for
managing entries in the password file are described further in *Note
instance-manager-security-passwords::.

   * `--help', `-?'

     Display a help message and exit.

   * `--add-user'

     Add a new user (specified with the `--username' option) to the
     password file. This option was added in MySQL 5.1.12.

   * `--angel-pid-file=FILE_NAME'

     The file in which the angel process records its process ID when
     `mysqlmanager' runs in daemon mode (that is, when the
     `--run-as-service' option is given). The default file name is
     `mysqlmanager.angel.pid'.

     If the `--angel-pid-file' option is not given, the default angel
     PID file has the same name as the PID file except that any PID
     file extension is replaced with an extension of `.angel.pid'. (For
     example, `mysqlmanager.pid' becomes `mysqlmanager.angel.pid'.)

     This option was added in MySQL 5.1.11.

   * `--bind-address=IP'

     The IP address to bind to.

   * `--check-password-file'

     Check the validity and consistency of the password file.  This
     option was added in MySQL 5.1.12.

   * `--clean-password-file'

     Drop all users from the password file. This option was added in
     MySQL 5.1.12.

   * `--debug=DEBUG_OPTIONS', `-# DEBUG_OPTIONS'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  This option was added in MySQL 5.1.10.

   * `--default-mysqld-path=PATH'

     The path name of the MySQL Server binary. This path name is used
     for all server instance sections in the configuration file for
     which no `mysqld-path' option is present. The default value of
     this option is the compiled-in path name, which depends on how the
     MySQL distribution was configured. Example:
     `--default-mysqld-path=/usr/sbin/mysqld'

   * `--defaults-file=FILE_NAME'

     Read Instance Manager and MySQL Server settings from the given
     file. All configuration changes made by the Instance Manager will
     be written to this file. This must be the first option on the
     command line if it is used, and the file must exist.

     If this option is not given, Instance Manager uses its standard
     configuration file. On Windows, the standard file is `my.ini' in
     the directory where Instance Manager is installed. On Unix, the
     standard file is `/etc/my.cnf'.

   * `--drop-user'

     Drop a user (specified with the `--username' option) from the
     password file. This option was added in MySQL 5.1.12.

   * `--edit-user'

     Change an entry for an existing user (specified with the
     `--username' option) in the password file. This option was added
     in MySQL 5.1.12.

   * `--install'

     On Windows, install Instance Manager as a Windows service.  The
     service name is `MySQL Manager'.

   * `--list-users'

     List the users in the password file. This option was added in
     MySQL 5.1.12.

   * `--log=FILE_NAME'

     The path to the Instance Manager log file. This option has no
     effect unless the `--run-as-service' option is also given. If the
     file name specified for the option is a relative name, the log
     file is created under the directory from which Instance Manager is
     started. To ensure that the file is created in a specific
     directory, specify it as a full path name.

     If `--run-as-service' is given without `--log', the log file is
     `mysqlmanager.log' in the data directory.

     If `--run-as-service' is not given, log messages go to the
     standard output. To capture log output, you can redirect Instance
     Manager output to a file:


          mysqlmanager > im.log

   * `--monitoring-interval=SECONDS'

     The interval in seconds for monitoring server instances. The
     default value is 20 seconds. Instance Manager tries to connect to
     each monitored (guarded) instance using the nonexisting
     `MySQL_Instance_Manager' user account to check whether it is
     available/not hanging. If the result of the connection attempt
     indicates that the instance is unavailable, Instance Manager
     performs several attempts to restart the instance.

     Normally, the `MySQL_Instance_Manager' account does not exist, so
     the connection attempts by Instance Manager cause the monitored
     instance to produce messages in its general query log similar to
     the following:


          Access denied for user 'MySQL_Instance_M'@'localhost' »
              (using password: YES)

     The `nonguarded' option in the appropriate server instance section
     disables monitoring for a particular instance. If the instance
     dies after being started, Instance Manager will not restart it.
     Instance Manager tries to connect to a nonguarded instance only
     when you request the instance's status (for example, with the `SHOW
     INSTANCES' status.

     See *Note instance-manager-security-monitoring::, for more
     information.

   * `--mysqld-safe-compatible'

     Run in a *Note `mysqld_safe': mysqld-safe.-compatible manner.  For
     details, see *Note instance-manager-startup-process::. This option
     was added in MySQL 5.1.12.

   * `--password=PASSWORD', `-p PASSWORD'

     Specify the password for an entry to be added to or modified in
     the password file. Unlike the `--password'/`-P' option for most
     MySQL programs, the password value is required, not optional. See
     also *Note instance-manager-security-passwords::. This option was
     added in MySQL 5.1.12.

   * `--password-file=FILE_NAME'

     The name of the file where the Instance Manager looks for users
     and passwords. On Windows, the default is `mysqlmanager.passwd' in
     the directory where Instance Manager is installed. On Unix, the
     default file is `/etc/mysqlmanager.passwd'. See also *Note
     instance-manager-security-passwords::.

   * `--pid-file=FILE_NAME'

     The process ID file to use. On Windows, the default file is
     `mysqlmanager.pid' in the directory where Instance Manager is
     installed. On Unix, the default is `mysqlmanager.pid' in the data
     directory.

   * `--port=PORT_NUM'

     The port number to use when listening for TCP/IP connections from
     clients. The default port number (assigned by IANA) is 2273.

   * `--print-defaults'

     Print the current defaults and exit. This must be the first option
     on the command line if it is used.

   * `--print-password-line'

     Prepare an entry for the password file, print it to the standard
     output, and exit. You can redirect the output from Instance
     Manager to a file to save the entry in the file.

     Prior to MySQL 5.1.12, this option was named `--passwd'.

   * `--remove'

     On Windows, removes Instance Manager as a Windows service.  This
     assumes that Instance Manager has been run with `--install'
     previously.

   * `--run-as-service'

     On Unix, daemonize and start an angel process. The angel process
     monitors Instance Manager and restarts it if it crashes. (The
     angel process itself is simple and unlikely to crash.)

   * `--socket=PATH'

     On Unix, the socket file to use for incoming connections.  The
     default file is named `/tmp/mysqlmanager.sock'. This option has no
     meaning on Windows.

   * `--standalone'

     This option is used on Windows to run Instance Manager in
     standalone mode. You should specify it when you start Instance
     Manager from the command line.

   * `--user=USER_NAME'

     On Unix, the user name of the system account to use for starting
     and running `mysqlmanager'. This option generates a warning and
     has no effect unless you start `mysqlmanager' as `root' (so that
     it can change its effective user ID), or as the named user. It is
     recommended that you configure `mysqlmanager' to run using the
     same account used to run the *Note `mysqld': mysqld.  server.
     (`User' in this context refers to a system login account, not a
     MySQL user listed in the grant tables.)

   * `--username=USER_NAME', `-u USER_NAME'

     Specify the user name for an entry to be added to or modified in
     the password file. This option was added in MySQL 5.1.12.

   * `--version', `-V'

     Display version information and exit.

   * `--wait-timeout=N'

     The number of seconds to wait for activity on an incoming
     connection before closing it. The default is 28800 seconds (8
     hours).

     This option was added in MySQL 5.1.7. Before that, the timeout is
     30 seconds and cannot be changed.


File: manual.info,  Node: instance-manager-configuration-files,  Next: instance-manager-startup-process,  Prev: instance-manager-command-options,  Up: instance-manager

4.6.10.2 MySQL Instance Manager Configuration Files
...................................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

Instance Manager uses its standard configuration file unless it is
started with a `--defaults-file' option that specifies a different
file. On Windows, the standard file is `my.ini' in the directory where
Instance Manager is installed. On Unix, the standard file is
`/etc/my.cnf'.

Instance Manager reads options for itself from the `[manager]' section
of the configuration file, and options for server instances from
`[mysqld]' or `[mysqldN]' sections. The `[manager]' section contains any
of the options listed in *Note instance-manager-command-options::,
except for those specified as having to be given as the first option on
the command line. Here is a sample `[manager]' section:


     # MySQL Instance Manager options section
     [manager]
     default-mysqld-path = /usr/local/mysql/libexec/mysqld
     socket=/tmp/manager.sock
     pid-file=/tmp/manager.pid
     password-file = /home/cps/.mysqlmanager.passwd
     monitoring-interval = 2
     port = 1999
     bind-address = 192.168.1.5

Each `[mysqld]' or `[mysqldN]' instance section specifies options given
by Instance Manager to a server instance at startup. These are mainly
common MySQL Server options (see *Note server-options::). In addition, a
`[mysqldN]' section can contain the options in the following list,
which are specific to Instance Manager. These options are interpreted by
Instance Manager itself; it does not pass them to the server when it
attempts to start that server.

*Warning*:

The Instance Manager-specific options must not be used in a `[mysqld]'
section. If a server is started without using Instance Manager, it will
not recognize these options and will fail to start properly.

   * `mysqld-path = PATH'

     The path name of the *Note `mysqld': mysqld. server binary to use
     for the server instance.

   * `nonguarded'

     This option disables Instance Manager monitoring functionality for
     the server instance. By default, an instance is guarded: At
     Instance Manager start time, it starts the instance. It also
     monitors the instance status and attempts to restart it if it
     fails. At Instance Manager exit time, it stops the instance. None
     of these things happen for nonguarded instances.

   * `shutdown-delay = SECONDS'

     The number of seconds Instance Manager should wait for the server
     instance to shut down. The default value is 35 seconds. After the
     delay expires, Instance Manager assumes that the instance is
     hanging and attempts to terminate it.  If you use `InnoDB' with
     large tables, you should increase this value.

Here are some sample instance sections:


     [mysqld1]
     mysqld-path=/usr/local/mysql/libexec/mysqld
     socket=/tmp/mysql.sock
     port=3307
     server_id=1
     skip-stack-trace
     core-file
     log-bin
     log-error
     log=mylog
     log-slow-queries

     [mysqld2]
     nonguarded
     port=3308
     server_id=2
     mysqld-path= /home/cps/mysql/trees/mysql-5.1/sql/mysqld
     socket     = /tmp/mysql.sock5
     pid-file   = /tmp/hostname.pid5
     datadir= /home/cps/mysql_data/data_dir1
     language=/home/cps/mysql/trees/mysql-5.1/sql/share/english
     log-bin
     log=/tmp/fordel.log


File: manual.info,  Node: instance-manager-startup-process,  Next: instance-manager-security-passwords,  Prev: instance-manager-configuration-files,  Up: instance-manager

4.6.10.3 Starting the MySQL Server with MySQL Instance Manager
..............................................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

This section discusses how Instance Manager starts server instances
when it starts. However, before you start Instance Manager, you should
set up a password file for it. Otherwise, you will not be able to
connect to Instance Manager to control it after it starts. For details
about creating Instance Manager accounts, see *Note
instance-manager-security-passwords::.

On Unix, the *Note `mysqld': mysqld. MySQL database server normally is
started with the *Note `mysql.server': mysql-server.  script, which
usually resides in the `/etc/init.d/' folder. That script invokes the
*Note `mysqld_safe': mysqld-safe. script by default. However, you can
use Instance Manager instead if you modify the `/etc/my.cnf'
configuration file by adding `use-manager' to the `[mysql.server]'
section:


     [mysql.server]
     use-manager

Before MySQL 5.1.12, Instance Manager always tries to start at least
one server instance: When it starts, it reads its configuration file if
it exists to find server instance sections and prepare a list of
instances. Instance sections have names of the form `[mysqld]' or
`[mysqldN]', where N is an unsigned integer (for example, `[mysqld1]',
`[mysqld2]', and so forth).

After preparing the list of instances, Instance Manager starts the
guarded instances in the list. If there are no instances, Instance
Manager creates an instance named `mysqld' and attempts to start it
with default (compiled-in) configuration values. This means that the
Instance Manager cannot find the *Note `mysqld': mysqld. program if it
is not installed in the default location.  (*Note
installation-layouts::, describes default locations for components of
MySQL distributions.) If you have installed the MySQL server in a
nonstandard location, you should create the Instance Manager
configuration file.

The startup behavior just described is similar to that of *Note
`mysqld_safe': mysqld-safe, which always attempts to start a server.
However, it lacks the flexibility required for some operations because
it is not possible to run Instance Manager in such a way that it
refrains from starting any server instances.  For example, you cannot
invoke Instance Manager for the purpose of configuring an instance
without also starting it (a task that a MySQL installer application
might want to perform).  Consequently, MySQL 5.1.12 introduces the
following changes:

   * A new option, `--mysqld-safe-compatible', may be used to cause
     Instance Manager to run with startup behavior similar to that used
     before MySQL 5.1.12: If Instance Manager finds a `[mysqld]'
     instance section in the configuration file, it will start it. If
     Instance Manager finds no `[mysqld]' section, it creates one using
     default configuration values, writes a `[mysqld]' section to the
     configuration file if it is accessible, and starts the `mysqld'
     instance. Instance Manager also starts any other guarded instances
     listed in the configuration file.

   * Without `--mysqld-safe-compatible', Instance Manager reads its
     configuration file if it exists and starts instances for any
     guarded instance sections that it finds. If there are none, it
     starts no instances.

Instance Manager also stops all guarded server instances when it shuts
down.

The permissible options for `[mysqldN]' server instance sections are
described in *Note instance-manager-configuration-files::. In these
sections, you can use a special `mysqld-path=PATH-TO-MYSQLD-BINARY'
option that is recognized only by Instance Manager. Use this option to
let Instance Manager know where the *Note `mysqld': mysqld. binary
resides. If there are multiple instances, it may also be necessary to
set other options such as `datadir' and `port', to ensure that each
instance has a different data directory and TCP/IP port number. *Note
multiple-servers::, discusses the configuration values that must differ
for each instance when you run multiple instance on the same machine.

*Warning*:

The `[mysqld]' instance section, if it exists, must not contain any
Instance Manager-specific options.

The typical Unix startup/shutdown cycle for a MySQL server with the
MySQL Instance Manager enabled is as follows:

  1. The `/etc/init.d/mysql' script starts MySQL Instance Manager.

  2. Instance Manager starts the guarded server instances and monitors
     them.

  3. If a server instance fails, Instance Manager restarts it.

  4. If Instance Manager is shut down (for example, with the
     `/etc/init.d/mysql stop' command), it shuts down all server
     instances.


File: manual.info,  Node: instance-manager-security-passwords,  Next: instance-manager-security-monitoring,  Prev: instance-manager-startup-process,  Up: instance-manager

4.6.10.4 Instance Manager User and Password Management
......................................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

The Instance Manager stores its user information in a password file. On
Windows, the default is `mysqlmanager.passwd' in the directory where
Instance Manager is installed. On Unix, the default file is
`/etc/mysqlmanager.passwd'. To specify a different location for the
password file, use the `--password-file' option.

If the password file does not exist or contains no password entries,
you cannot connect to the Instance Manager.

*Note*:

Any Instance Manager process that is running to monitor server
instances does not notice changes to the password file. You must stop
it and restart it after making password entry changes.

Entries in the password file have the following format, where the two
fields are the account user name and encrypted password, separated by a
colon:


     petr:*35110DC9B4D8140F5DE667E28C72DD2597B5C848

Instance Manager password encryption is the same as that used by MySQL
Server. It is a one-way operation; no means are provided for decrypting
encrypted passwords.

Instance Manager accounts differ somewhat from MySQL Server accounts:

   * MySQL Server accounts are associated with a host name, user name,
     and password (see *Note user-names::).

   * Instance Manager accounts are associated with a user name and
     password only.

This means that a client can connect to Instance Manager with a given
user name from any host. To limit connections so that clients can
connect only from the local host, start Instance Manager with the
`--bind-address=127.0.0.1' option so that it listens only to the local
network interface.  Remote clients will not be able to connect. Local
clients can connect like this:


     shell> mysql -h 127.0.0.1 -P 2273

Before MySQL 5.1.12, the only option for creating password file entries
is `--passwd', which causes Instance Manager to prompt for user name and
password values and display the resulting entry. You can save the
output in the `/etc/mysqlmanager.passwd' password file to store it.
Here is an example:


     shell> mysqlmanager --passwd >> /etc/mysqlmanager.passwd
     Creating record for new user.
     Enter user name: mike
     Enter password: mikepass
     Re-type password: mikepass

At the prompts, enter the user name and password for the new Instance
Manager user. You must enter the password twice. It does not echo to
the screen, so double entry guards against entering a different
password than you intend (if the two passwords do not match, no entry
is generated).

The preceding command causes the following line to be added to
`/etc/mysqlmanager.passwd':


     mike:*BBF1F551DD9DD96A01E66EC7DDC073911BAD17BA

Use of the `--password' option fails if `mysqlmanager' is invoked
directly from an IBM 5250 terminal. To work around this, use a command
like the following from the command line to generate the password entry:


     shell> mysql -B --skip-column-name \
              -e 'SELECT CONCAT("USER_NAME",":",PASSWORD("PASS_VAL"));'

The output from the command can be used an entry in the
`/etc/mysqlmanager.passwd' file.

Beginning with MySQL 5.1.12, the `--passwd' option is renamed to
`--print-password-line' and there are several other options for
managing user accounts from the command line. For example, the
`--username' and `--password' options are available on the command line
for specifying the user name and password for an account entry. You can
use them to generate an entry with no prompting like this (type the
command on a single line):


     shell> mysqlmanager --print-password-line
              --username=mike --password=mikepass >> /etc/mysqlmanager.passwd

If you omit the `--username' or `--password' option, Instance Manager
prompts for the required value.

`--print-password-line' causes Instance Manager to send the resulting
account entry to its output, which you can append to the password file.
The following list describes other account-management options that
cause Instance Manager to operate directly on the password file.
(These options make Instance Manager scriptable for account-management
purposes.) For operations on the password file to succeed, the file
must exist and it must be accessible by Instance Manager. (The
exception is `--clean-password-file', which creates the file if it does
not exist. Alternatively, if there is no password file, manually create
it as an empty file and ensure that its ownership and access modes
permit it to be read and written by Instance Manager.) The default
password file is used unless you specify a `--password-file' option.

To ensure consistent treatment of the password file, it should be owned
by the system account that you use for running Instance Manager to
manage server instances, and you should invoke it from that account
when you use it to manage accounts in the password file.

   * Create a new user:


          mysqlmanager --add-user --username=USER_NAME [--password=PASSWORD]

     This command adds a new entry with the given user name and
     password to the password file. The `--username' (or `-u') option
     is required.  `mysqlmanager' prompts for the password if it is not
     given on the command line with the `--password' (or `-p') option.
     The command fails if the user already exists.

   * Drop an existing user:


          mysqlmanager --drop-user --username=USER_NAME

     This command removes the entry with the given user name from the
     password file. The user name is required. The command fails if the
     user does not exist.

   * Change the password for an existing user:


          mysqlmanager --edit-user --username=USER_NAME [--password=PASSWORD]

     This command changes the given user's password in the password
     file. The user name is required.  `mysqlmanager' prompts for the
     password it is not given on the command line. The command fails if
     the user does not exist.

   * List existing users:


          mysqlmanager --list-users

     This command lists the user names of the accounts in the password
     file.

   * Check the password file:


          mysqlmanager --check-password-file

     This command performs a consistency and validity check of the
     password file. The command fails if there is something wrong with
     the file.

   * Empty the password file:


          mysqlmanager --clean-password-file

     This command empties the password file, which has the effect of
     dropping all users listed in it. The option creates the password
     file if it does not exist, so it can be used to initialize a new
     password file to be used for other account-management operations.
     Take care not to use this option to reinitialize a file containing
     accounts that you do not want to drop.


File: manual.info,  Node: instance-manager-security-monitoring,  Next: instance-manager-security,  Prev: instance-manager-security-passwords,  Up: instance-manager

4.6.10.5 MySQL Server Instance Status Monitoring
................................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

To monitor the status of each guarded server instance, the MySQL
Instance Manager attempts to connect to the instance at regular
intervals using the `MySQL_Instance_Manager@localhost' user account
with a password of `check_connection'.

You are _not_ required to create this account for MySQL Server; in
fact, it is expected that it will not exist. Instance Manager can tell
that a server is operational if the server accepts the connection
attempt but refuses access for the account by returning a login error.
However, these failed connection attempts are logged by the server to
its general query log (see *Note query-log::).

Instance Manager also attempts a connection to nonguarded server
instances when you use the `SHOW INSTANCES' or `SHOW INSTANCE STATUS'
command. This is the only status monitoring done for nonguarded
instances.

Instance Manager knows if a server instance fails at startup because it
receives a status from the attempt. For an instance that starts but
later crashes, Instance Manager receives a signal because it is the
parent process of the instance.

Beginning with MySQL 5.1.12, Instance Manager tracks instance states so
that it can determine which commands are permitted for each instance.
For example, commands that modify an instance's configuration are
permitted only while the instance is offline.

Each instance is in one of the states described in the following table.
Guarded instances can be in any of the states. Nonguarded instances can
only be offline or online. Instance state information is displayed in
the `status' column of the `SHOW INSTANCES' and `SHOW INSTANCE STATUS'
commands.

This table lists MySQL server instance states and describes the meaning
of each state.

State       Meaning
`offline'   The instance has not been started and is not running.
`starting'  The instance is starting (initializing). Nonguarded
            instances cannot be in this state. A nonguarded instance
            goes directly from offline to online.
`stopping'  The instance is stopping. Nonguarded instances cannot be in
            this state.  A nonguarded instance goes directly from online
            to offline, or stays offline if startup fails.
`online'    The instance has started and is running.
`failed'    The instance was online but it crashed and is being
            restarted by Instance Manager, or else the instance failed
            to start at all and Instance Manager is again attempting to
            start it. Nonguarded instances cannot be in this state.
`crashed'   Instance Manager failed to start the instance after several
            attempts.  (Instance Manager will try again later.)
            Nonguarded instances cannot be in this state.
`abandoned' Instance Manager was not able to start the instance, has
            given up, and will make no further attempts until instructed
            otherwise. To tell Instance Manager to try again, you must
            first use `STOP INSTANCE' to put the instance in offline
            state, and then use `START INSTANCE' to start the instance.
            If it is necessary to make configuration changes for the
            instance, you must do so after putting the instance offline
            and before starting it. (Instance Manager accepts
            configuration-changing commands only for offline instances.)
            Nonguarded instances cannot be in this state.


File: manual.info,  Node: instance-manager-security,  Next: instance-manager-commands,  Prev: instance-manager-security-monitoring,  Up: instance-manager

4.6.10.6 Connecting to MySQL Instance Manager
.............................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

After you set up a password file for the MySQL Instance Manager and
Instance Manager is running, you can connect to it. The MySQL
client/server protocol is used to communicate with the Instance
Manager. For example, you can connect to it using the standard *Note
`mysql': mysql. client program:


     shell> mysql --port=2273 --host=im.example.org --user=mysql --password

Instance Manager supports the version of the MySQL client/server
protocol used by the client tools and libraries distributed with MySQL
4.1 or later, so other programs that use the MySQL C API also can
connect to it.


File: manual.info,  Node: instance-manager-commands,  Prev: instance-manager-security,  Up: instance-manager

4.6.10.7 MySQL Instance Manager Commands
........................................

*Important*:

MySQL Instance Manager has been deprecated and is removed in MySQL 5.5.

After you connect to MySQL Instance Manager, you can issue commands.
The following general principles apply to Instance Manager command
execution:

   * Commands that take an instance name fail if the name is not a
     valid instance name.

   * Commands that take an instance name (other than `CREATE INSTANCE')
     fail if the instance does not exist.

   * As of MySQL 5.1.12, commands for an instance require that the
     instance be in an appropriate state. You cannot configure or start
     an instance that is not offline. You cannot start an instance that
     is online.

   * Instance Manager maintains information about instance
     configuration in an internal (in-memory) cache. Initially, this
     information comes from the configuration file if it exists, but
     some commands change the configuration of an instance. Commands
     that modify the configuration file fail if the file does not exist
     or is not accessible to Instance Manager.

     As of MySQL 5.1.12, configuration-changing commands modify both
     the in-memory cache and the server instance section recorded in
     the configuration file to maintain consistency between them. For
     this to occur, the instance must be offline and the configuration
     file must be accessible and not malformed. If the configuration
     file cannot be updated, the command fails and the cache remains
     unchanged.

   * On Windows, the standard file is `my.ini' in the directory where
     Instance Manager is installed. On Unix, the standard configuration
     file is `/etc/my.cnf'. To specify a different configuration file,
     start Instance Manager with the `--defaults-file' option.

   * If a `[mysqld]' instance section exists in the configuration file,
     it must not contain any Instance Manager-specific options (see
     *Note instance-manager-configuration-files::).  Therefore, you
     must not add any of these options if you change the configuration
     for an instance named `mysqld'.

The following list describes the commands that Instance Manager
accepts, with examples.

   * `CREATE INSTANCE INSTANCE_NAME [OPTION_NAME[=OPTION_VALUE], ...]'

     This command configures a new instance by creating an
     `[INSTANCE_NAME]' section in the configuration file. The command
     fails if INSTANCE_NAME is not a valid instance name or the
     instance already exists.

     The created section instance is empty if no options are given.
     Otherwise, the options are added to the section.  Options should
     be given in the same format used when you write options in option
     files. (See *Note option-files:: for a description of the
     permissible syntax.) If you specify multiple options, separate
     them by commas.

     For example, to create an instance section named `[mysqld98]', you
     might write something like this were you to modify the
     configuration file directly:


          [mysqld98]
          basedir=/var/mysql98

     To achieve the same effect using `CREATE INSTANCE', issue this
     command to Instance Manager:


          mysql> CREATE INSTANCE mysqld98 basedir="/var/mysql98";
          Query OK, 0 rows affected (0,00 sec)

     `CREATE INSTANCE' creates the instance but does not start it.

     If the instance name is the (deprecated) name `mysqld', the option
     list cannot include any options that are specific to Instance
     Manager, such as `nonguarded' (see *Note
     instance-manager-configuration-files::).

     This command was added in MySQL 5.1.12.

   * `DROP INSTANCE INSTANCE_NAME'

     This command removes the configuration for INSTANCE_NAME from the
     configuration file.


          mysql> DROP INSTANCE mysqld98;
          Query OK, 0 rows affected (0,00 sec)

     The command fails if INSTANCE_NAME is not a valid instance name,
     the instance does not exist, or is not offline.

     This command was added in MySQL 5.1.12.

   * `START INSTANCE INSTANCE_NAME'

     This command attempts to start an offline instance. The command is
     asynchronous; it does not wait for the instance to start.


          mysql> START INSTANCE mysqld4;
          Query OK, 0 rows affected (0,00 sec)

   * `STOP INSTANCE INSTANCE_NAME'

     This command attempts to stop an instance. The command is
     synchronous; it waits for the instance to stop.


          mysql> STOP INSTANCE mysqld4;
          Query OK, 0 rows affected (0,00 sec)

   * `SHOW INSTANCES'

     Shows the names and status of all loaded instances.


          mysql> SHOW INSTANCES;
          +---------------+---------+
          | instance_name | status  |
          +---------------+---------+
          | mysqld3       | offline |
          | mysqld4       | online  |
          | mysqld2       | offline |
          +---------------+---------+

   * `SHOW INSTANCE STATUS INSTANCE_NAME'

     Shows status and version information for an instance.


          mysql> SHOW INSTANCE STATUS mysqld3;
          +---------------+--------+---------+
          | instance_name | status | version |
          +---------------+--------+---------+
          | mysqld3       | online | unknown |
          +---------------+--------+---------+

   * `SHOW INSTANCE OPTIONS INSTANCE_NAME'

     Shows the options used by an instance.


          mysql> SHOW INSTANCE OPTIONS mysqld3;
          +---------------+---------------------------------------------------+
          | option_name   | value                                             |
          +---------------+---------------------------------------------------+
          | instance_name | mysqld3                                           |
          | mysqld-path   | /home/cps/mysql/trees/mysql-4.1/sql/mysqld        |
          | port          | 3309                                              |
          | socket        | /tmp/mysql.sock3                                  |
          | pid-file      | hostname.pid3                                     |
          | datadir       | /home/cps/mysql_data/data_dir1/                   |
          | language      | /home/cps/mysql/trees/mysql-4.1/sql/share/english |
          +---------------+---------------------------------------------------+

   * `SHOW INSTANCE_NAME LOG FILES'

     The command lists all log files used by the instance. The result
     set contains the path to the log file and the log file size. If no
     log file path is specified in the instance section of the
     configuration file (for example, `log=/var/mysql.log'), the
     Instance Manager tries to guess its placement. If Instance Manager
     is unable to guess the log file placement you should specify the
     log file location explicitly by using a log option in the
     appropriate instance section of the configuration file.


          mysql> SHOW mysqld LOG FILES;
          +-------------+------------------------------------+----------+
          | Logfile     | Path                               | Filesize |
          +-------------+------------------------------------+----------+
          | ERROR LOG   | /home/cps/var/mysql/owlet.err      | 9186     |
          | GENERAL LOG | /home/cps/var/mysql/owlet.log      | 471503   |
          | SLOW LOG    | /home/cps/var/mysql/owlet-slow.log | 4463     |
          +-------------+------------------------------------+----------+

     `SHOW ... LOG FILES' displays information only about log files. If
     a server instance uses log tables (see *Note log-destinations::),
     no information about those tables is shown.

     Log options are described in *Note server-options::.

   * `SHOW INSTANCE_NAME LOG {ERROR | SLOW | GENERAL}
     SIZE[,OFFSET_FROM_END]'

     This command retrieves a portion of the specified log file.
     Because most users are interested in the latest log messages, the
     SIZE parameter defines the number of bytes to retrieve from the
     end of the log. To retrieve data from the middle of the log file,
     specify the optional OFFSET_FROM_END parameter. The following
     example retrieves 21 bytes of data, starting 23 bytes before the
     end of the log file and ending 2 bytes before the end:


          mysql> SHOW mysqld LOG GENERAL 21, 2;
          +---------------------+
          | Log                 |
          +---------------------+
          | using password: YES |
          +---------------------+

   * `SET INSTANCE_NAME.OPTION_NAME[=OPTION_VALUE]'

     This command edits the specified instance's configuration section
     to change or add instance options. The option is added to the
     section is it is not already present.  Otherwise, the new setting
     replaces the existing one.


          mysql> SET mysqld2.port=3322;
          Query OK, 0 rows affected (0.00 sec)

     As of MySQL 5.1.12, you can specify multiple options (separated by
     commas), and `SET' can be used only for offline instances. Each
     option must indicate the instance name:


          mysql> SET mysqld2.port=3322, mysqld3.nonguarded;
          Query OK, 0 rows affected (0.00 sec)

     Before MySQL 5.1.12, only a single option can be specified.  Also,
     changes made to the configuration file do not take effect until
     the MySQL server is restarted. In addition, these changes are not
     stored in the instance manager's local cache of instance settings
     until a `FLUSH INSTANCES' command is executed.

   * `UNSET INSTANCE_NAME.OPTION_NAME'

     This command removes an option from an instance's configuration
     section.


          mysql> UNSET mysqld2.port;
          Query OK, 0 rows affected (0.00 sec)

     As of MySQL 5.1.12, you can specify multiple options (separated by
     commas), and `UNSET' can be used only for offline instances. Each
     option must indicate the instance name:


          mysql> UNSET mysqld2.port, mysqld4.nonguarded;
          Query OK, 0 rows affected (0.00 sec)

     Before MySQL 5.1.12, only a single option can be specified.  Also,
     changes made to the configuration file do not take effect until
     the MySQL server is restarted. In addition, these changes are not
     stored in the instance manager's local cache of instance settings
     until a `FLUSH INSTANCES' command is executed.

   * `FLUSH INSTANCES'

     As of MySQL 5.1.12, `FLUSH INSTANCES' cannot be used unless all
     instances are offline. The command causes Instance Manager to
     reread the configuration file, update its in-memory configuration
     cache, and start any guarded instances.

     Before MySQL 5.1.12, this command forces Instance Manager reread
     the configuration file and to refresh internal structures. This
     command should be performed after editing the configuration file.
     The command does not restart instances.


          mysql> FLUSH INSTANCES;
          Query OK, 0 rows affected (0.04 sec)


File: manual.info,  Node: mysql-convert-table-format,  Next: mysql-find-rows,  Prev: instance-manager,  Up: programs-admin-utils

4.6.11 `mysql_convert_table_format' -- Convert Tables to Use a Given Storage Engine
-----------------------------------------------------------------------------------

*Note `mysql_convert_table_format': mysql-convert-table-format.
converts the tables in a database to use a particular storage engine
(`MyISAM' by default).  *Note `mysql_convert_table_format':
mysql-convert-table-format. is written in Perl and requires that the
`DBI' and `DBD::mysql' Perl modules be installed (see *Note
perl-support::).

Invoke *Note `mysql_convert_table_format': mysql-convert-table-format.
like this:


     shell> mysql_convert_table_format [OPTIONS]DB_NAME

The DB_NAME argument indicates the database containing the tables to be
converted.

*Note `mysql_convert_table_format': mysql-convert-table-format.
supports the options described in the following list.

   * `--help'

     Display a help message and exit.

   * `--force'

     Continue even if errors occur.

   * `--host=HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--password=PASSWORD'

     The password to use when connecting to the server. Note that the
     password value is not optional for this option, unlike for other
     MySQL programs.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--port=PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--socket=PATH'

     For connections to `localhost', the Unix socket file to use.

   * `--type=ENGINE_NAME'

     Specify the storage engine that the tables should be converted to
     use. The default is `MyISAM' if this option is not given.

   * `--user=USER_NAME'

     The MySQL user name to use when connecting to the server.

   * `--verbose'

     Verbose mode. Print more information about what the program does.

   * `--version'

     Display version information and exit.


File: manual.info,  Node: mysql-find-rows,  Next: mysql-fix-extensions,  Prev: mysql-convert-table-format,  Up: programs-admin-utils

4.6.12 `mysql_find_rows' -- Extract SQL Statements from Files
-------------------------------------------------------------

*Note `mysql_find_rows': mysql-find-rows. reads files containing SQL
statements and extracts statements that match a given regular
expression or that contain `USE DB_NAME' or *Note `SET': set-statement.
statements. The utility was written for use with update log files (as
used prior to MySQL 5.0) and as such expects statements to be
terminated with semicolon (`;') characters. It may be useful with other
files that contain SQL statements as long as statements are terminated
with semicolons.

Invoke *Note `mysql_find_rows': mysql-find-rows. like this:


     shell> mysql_find_rows [OPTIONS] [FILE_NAME ...]

Each FILE_NAME argument should be the name of file containing SQL
statements. If no file names are given, *Note `mysql_find_rows':
mysql-find-rows. reads the standard input.

Examples:


     mysql_find_rows --regexp=problem_table --rows=20 < update.log
     mysql_find_rows --regexp=problem_table  update-log.1 update-log.2

*Note `mysql_find_rows': mysql-find-rows. supports the following
options:

   * `--help', `--Information'

     Display a help message and exit.

   * `--regexp=PATTERN'

     Display queries that match the pattern.

   * `--rows=N'

     Quit after displaying N queries.

   * `--skip-use-db'

     Do not include `USE DB_NAME' statements in the output.

   * `--start_row=N'

     Start output from this row.


File: manual.info,  Node: mysql-fix-extensions,  Next: mysql-setpermission,  Prev: mysql-find-rows,  Up: programs-admin-utils

4.6.13 `mysql_fix_extensions' -- Normalize Table File Name Extensions
---------------------------------------------------------------------

*Note `mysql_fix_extensions': mysql-fix-extensions. converts the
extensions for `MyISAM' (or `ISAM') table files to their canonical
forms. It looks for files with extensions matching any lettercase
variant of `.frm', `.myd', `.myi', `.isd', and `.ism' and renames them
to have extensions of `.frm', `.MYD', `.MYI', `.ISD', and `.ISM',
respectively. This can be useful after transferring the files from a
system with case-insensitive file names (such as Windows) to a system
with case-sensitive file names.

Invoke *Note `mysql_fix_extensions': mysql-fix-extensions. like this,
where DATA_DIR is the path name to the MySQL data directory.


     shell> mysql_fix_extensions DATA_DIR


File: manual.info,  Node: mysql-setpermission,  Next: mysql-waitpid,  Prev: mysql-fix-extensions,  Up: programs-admin-utils

4.6.14 `mysql_setpermission' -- Interactively Set Permissions in Grant Tables
-----------------------------------------------------------------------------

*Note `mysql_setpermission': mysql-setpermission. is a Perl script that
was originally written and contributed by Luuk de Boer. It
interactively sets permissions in the MySQL grant tables.  *Note
`mysql_setpermission': mysql-setpermission. is written in Perl and
requires that the `DBI' and `DBD::mysql' Perl modules be installed (see
*Note perl-support::).

Invoke *Note `mysql_setpermission': mysql-setpermission. like this:


     shell> mysql_setpermission [OPTIONS]

OPTIONS should be either `--help' to display the help message, or
options that indicate how to connect to the MySQL server. The account
used when you connect determines which permissions you have when
attempting to modify existing permissions in the grant tables.

`mysql_setpermissions' also reads options from the `[client]' and
`[perl]' groups in the `.my.cnf' file in your home directory, if the
file exists.

*Note `mysql_setpermission': mysql-setpermission. supports the following
options:

   * `--help'

     Display a help message and exit.

   * `--host=HOST_NAME'

     Connect to the MySQL server on the given host.

   * `--password=PASSWORD'

     The password to use when connecting to the server. Note that the
     password value is not optional for this option, unlike for other
     MySQL programs.

     Specifying a password on the command line should be considered
     insecure. See *Note password-security-user::. You can use an
     option file to avoid giving the password on the command line.

   * `--port=PORT_NUM'

     The TCP/IP port number to use for the connection.

   * `--socket=PATH'

     For connections to `localhost', the Unix socket file to use.

   * `--user=USER_NAME'

     The MySQL user name to use when connecting to the server.


File: manual.info,  Node: mysql-waitpid,  Next: mysql-zap,  Prev: mysql-setpermission,  Up: programs-admin-utils

4.6.15 `mysql_waitpid' -- Kill Process and Wait for Its Termination
-------------------------------------------------------------------

*Note `mysql_waitpid': mysql-waitpid. signals a process to terminate
and waits for the process to exit. It uses the `kill()' system call and
Unix signals, so it runs on Unix and Unix-like systems.

Invoke *Note `mysql_waitpid': mysql-waitpid. like this:


     shell> mysql_waitpid [OPTIONS] PID WAIT_TIME

*Note `mysql_waitpid': mysql-waitpid. sends signal 0 to the process
identified by PID and waits up to WAIT_TIME seconds for the process to
terminate. PID and WAIT_TIME must be positive integers.

If process termination occurs within the wait time or the process does
not exist, *Note `mysql_waitpid': mysql-waitpid. returns 0. Otherwise,
it returns 1.

If the `kill()' system call cannot handle signal 0, `mysql_waitpid()'
uses signal 1 instead.

*Note `mysql_waitpid': mysql-waitpid. supports the following options:

   * `--help', `-?', `-I'

     Display a help message and exit.

   * `--verbose', `-v'

     Verbose mode. Display a warning if signal 0 could not be used and
     signal 1 is used instead.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: mysql-zap,  Prev: mysql-waitpid,  Up: programs-admin-utils

4.6.16 `mysql_zap' -- Kill Processes That Match a Pattern
---------------------------------------------------------

*Note `mysql_zap': mysql-zap. kills processes that match a pattern. It
uses the `ps' command and Unix signals, so it runs on Unix and
Unix-like systems.

Invoke *Note `mysql_zap': mysql-zap. like this:


     shell> mysql_zap [-SIGNAL] [-?Ift] PATTERN

A process matches if its output line from the `ps' command contains the
pattern. By default, *Note `mysql_zap': mysql-zap. asks for
confirmation for each process. Respond `y' to kill the process, or `q'
to exit *Note `mysql_zap': mysql-zap. For any other response, *Note
`mysql_zap': mysql-zap. does not attempt to kill the process.

If the `-SIGNAL' option is given, it specifies the name or number of
the signal to send to each process. Otherwise, *Note `mysql_zap':
mysql-zap.  tries first with `TERM' (signal 15) and then with *Note
`KILL': kill. (signal 9).

*Note `mysql_zap': mysql-zap. supports the following additional options:

   * `--help', `-?', `-I'

     Display a help message and exit.

   * `-f'

     Force mode. *Note `mysql_zap': mysql-zap. attempts to kill each
     process without confirmation.

   * `-t'

     Test mode. Display information about each process but do not kill
     it.


File: manual.info,  Node: programs-development,  Next: programs-miscellaneous,  Prev: programs-admin-utils,  Up: programs

4.7 MySQL Program Development Utilities
=======================================

* Menu:

* msql2mysql::                   `msql2mysql' --- Convert mSQL Programs for Use with MySQL
* mysql-config::                 `mysql_config' --- Display Options for Compiling Clients
* my-print-defaults::            `my_print_defaults' --- Display Options from Option Files
* resolve-stack-dump::           `resolve_stack_dump' --- Resolve Numeric Stack Trace Dump to Symbols

This section describes some utilities that you may find useful when
developing MySQL programs.

In shell scripts, you can use the *Note `my_print_defaults':
my-print-defaults. program to parse option files and see what options
would be used by a given program. The following example shows the
output that *Note `my_print_defaults': my-print-defaults.  might
produce when asked to show the options found in the `[client]' and
`[mysql]' groups:


     shell> my_print_defaults client mysql
     --port=3306
     --socket=/tmp/mysql.sock
     --no-auto-rehash

Note for developers: Option file handling is implemented in the C
client library simply by processing all options in the appropriate
group or groups before any command-line arguments. This works well for
programs that use the last instance of an option that is specified
multiple times. If you have a C or C++ program that handles multiply
specified options this way but that doesn't read option files, you need
add only two lines to give it that capability. Check the source code of
any of the standard MySQL clients to see how to do this.

Several other language interfaces to MySQL are based on the C client
library, and some of them provide a way to access option file contents.
These include Perl and Python. For details, see the documentation for
your preferred interface.


File: manual.info,  Node: msql2mysql,  Next: mysql-config,  Prev: programs-development,  Up: programs-development

4.7.1 `msql2mysql' -- Convert mSQL Programs for Use with MySQL
--------------------------------------------------------------

Initially, the MySQL C API was developed to be very similar to that for
the mSQL database system. Because of this, mSQL programs often can be
converted relatively easily for use with MySQL by changing the names of
the C API functions.

The *Note `msql2mysql': msql2mysql. utility performs the conversion of
mSQL C API function calls to their MySQL equivalents. *Note
`msql2mysql': msql2mysql. converts the input file in place, so make a
copy of the original before converting it. For example, use *Note
`msql2mysql': msql2mysql. like this:


     shell> cp client-prog.c client-prog.c.orig
     shell> msql2mysql client-prog.c
     client-prog.c converted

Then examine `client-prog.c' and make any post-conversion revisions
that may be necessary.

*Note `msql2mysql': msql2mysql. uses the *Note `replace':
replace-utility. utility to make the function name substitutions. See
*Note replace-utility::.


File: manual.info,  Node: mysql-config,  Next: my-print-defaults,  Prev: msql2mysql,  Up: programs-development

4.7.2 `mysql_config' -- Display Options for Compiling Clients
-------------------------------------------------------------

*Note `mysql_config': mysql-config. provides you with useful
information for compiling your MySQL client and connecting it to MySQL.
It is a shell script, so it is available only on Unix and Unix-like
systems.

*Note `mysql_config': mysql-config. supports the following options.

   * `--cflags'

     Compiler flags to find include files and critical compiler flags
     and defines used when compiling the `libmysqlclient' library. The
     options returned are tied to the specific compiler that was used
     when the library was created and might clash with the settings for
     your own compiler. Use `--include' for more portable options that
     contain only include paths.

   * `--include'

     Compiler options to find MySQL include files.

   * `--libmysqld-libs', `--embedded'

     Libraries and options required to link with the MySQL embedded
     server.

   * `--libs'

     Libraries and options required to link with the MySQL client
     library.

   * `--libs_r'

     Libraries and options required to link with the thread-safe MySQL
     client library.

   * `--plugindir'

     The default plugin directory path name, defined when configuring
     MySQL. This option was added in MySQL 5.1.24.

   * `--port'

     The default TCP/IP port number, defined when configuring MySQL.

   * `--socket'

     The default Unix socket file, defined when configuring MySQL.

   * `--version'

     Version number for the MySQL distribution.

If you invoke *Note `mysql_config': mysql-config. with no options, it
displays a list of all options that it supports, and their values:


     shell> mysql_config
     Usage: /usr/local/mysql/bin/mysql_config [options]
     Options:
       --cflags         [-I/usr/local/mysql/include/mysql -mcpu=pentiumpro]
       --include        [-I/usr/local/mysql/include/mysql]
       --libs           [-L/usr/local/mysql/lib/mysql -lmysqlclient -lz
                         -lz -lcrypt -lnsl -lm]
       --libs_r         [-L/usr/local/mysql/lib/mysql -lmysqlclient_r
                         -lz -lpthread -lcrypt -lnsl -lm -lpthread]
       --socket         [/tmp/mysql.sock]
       --port           [3306]
       --version        [5.1.69]
       --libmysqld-libs [-L/usr/local/mysql/lib/mysql -lmysqld -ldl
                         -lz -lpthread -lcrypt -lnsl -lm -lpthread -lrt]

You can use *Note `mysql_config': mysql-config. within a command line
using backticks to include the output that it produces for a particular
option. For example, to compile and link a MySQL client program, use
*Note `mysql_config': mysql-config. as follows:


     shell> gcc -c `mysql_config --cflags` progname.c
     shell> gcc -o progname progname.o `mysql_config --libs`


File: manual.info,  Node: my-print-defaults,  Next: resolve-stack-dump,  Prev: mysql-config,  Up: programs-development

4.7.3 `my_print_defaults' -- Display Options from Option Files
--------------------------------------------------------------

*Note `my_print_defaults': my-print-defaults. displays the options that
are present in option groups of option files. The output indicates what
options will be used by programs that read the specified option groups.
For example, the *Note `mysqlcheck': mysqlcheck. program reads the
`[mysqlcheck]' and `[client]' option groups. To see what options are
present in those groups in the standard option files, invoke *Note
`my_print_defaults': my-print-defaults. like this:


     shell> my_print_defaults mysqlcheck client
     --user=myusername
     --password=secret
     --host=localhost

The output consists of options, one per line, in the form that they
would be specified on the command line.

*Note `my_print_defaults': my-print-defaults. supports the following
options.

   * `--help', `-?'

     Display a help message and exit.

   * `--config-file=FILE_NAME',

     `--defaults-file=FILE_NAME', `-c FILE_NAME'

     Read only the given option file.

   * `--debug=DEBUG_OPTIONS', `-# DEBUG_OPTIONS'

     Write a debugging log. A typical DEBUG_OPTIONS string is
     `d:t:o,FILE_NAME'.  The default is
     `d:t:o,/tmp/my_print_defaults.trace'.

   * `--defaults-extra-file=FILE_NAME',

     `--extra-file=FILE_NAME', `-e FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file.

   * `--defaults-group-suffix=SUFFIX', `-g SUFFIX'

     In addition to the groups named on the command line, read groups
     that have the given suffix.

   * `--no-defaults', `-n'

     Return an empty string.

   * `--verbose', `-v'

     Verbose mode. Print more information about what the program does.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: resolve-stack-dump,  Prev: my-print-defaults,  Up: programs-development

4.7.4 `resolve_stack_dump' -- Resolve Numeric Stack Trace Dump to Symbols
-------------------------------------------------------------------------

*Note `resolve_stack_dump': resolve-stack-dump. resolves a numeric stack
dump to symbols.

Invoke *Note `resolve_stack_dump': resolve-stack-dump. like this:


     shell> resolve_stack_dump [OPTIONS] SYMBOLS_FILE [NUMERIC_DUMP_FILE]

The symbols file should include the output from the `nm --numeric-sort
mysqld' command. The numeric dump file should contain a numeric stack
track from *Note `mysqld': mysqld. If no numeric dump file is named on
the command line, the stack trace is read from the standard input.

*Note `resolve_stack_dump': resolve-stack-dump. supports the following
options.

   * `--help', `-h'

     Display a help message and exit.

   * `--numeric-dump-file=FILE_NAME', `-n FILE_NAME'

     Read the stack trace from the given file.

   * `--symbols-file=FILE_NAME', `-s FILE_NAME'

     Use the given symbols file.

   * `--version', `-V'

     Display version information and exit.

For more information, see *Note using-stack-trace::.


File: manual.info,  Node: programs-miscellaneous,  Prev: programs-development,  Up: programs

4.8 Miscellaneous Programs
==========================

* Menu:

* perror::                       `perror' --- Explain Error Codes
* replace-utility::              `replace' --- A String-Replacement Utility
* resolveip::                    `resolveip' --- Resolve Host name to IP Address or Vice Versa


File: manual.info,  Node: perror,  Next: replace-utility,  Prev: programs-miscellaneous,  Up: programs-miscellaneous

4.8.1 `perror' -- Explain Error Codes
-------------------------------------

For most system errors, MySQL displays, in addition to an internal text
message, the system error code in one of the following styles:


     message ... (errno: #)
     message ... (Errcode: #)

You can find out what the error code means by examining the
documentation for your system or by using the *Note `perror': perror.
utility.

*Note `perror': perror. prints a description for a system error code or
for a storage engine (table handler) error code.

Invoke *Note `perror': perror. like this:


     shell> perror [OPTIONS] ERRORCODE ...

Example:


     shell> perror 13 64
     OS error code  13:  Permission denied
     OS error code  64:  Machine is not on the network

To obtain the error message for a MySQL Cluster error code, invoke
*Note `perror': perror. with the `--ndb' option:


     shell> perror --ndb ERRORCODE

Note that the meaning of system error messages may be dependent on your
operating system. A given error code may mean different things on
different operating systems.

*Note `perror': perror. supports the following options.

   * `--help', `--info', `-I', `-?'

     Display a help message and exit.

   * `--ndb'

     Print the error message for a MySQL Cluster error code.

   * `--silent', `-s'

     Silent mode. Print only the error message.

   * `--verbose', `-v'

     Verbose mode. Print error code and message. This is the default
     behavior.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: replace-utility,  Next: resolveip,  Prev: perror,  Up: programs-miscellaneous

4.8.2 `replace' -- A String-Replacement Utility
-----------------------------------------------

The *Note `replace': replace-utility. utility program changes strings
in place in files or on the standard input.

Invoke *Note `replace': replace-utility. in one of the following ways:


     shell> replace FROM TO [FROM TO] ... -- FILE_NAME [FILE_NAME] ...
     shell> replace FROM TO [FROM TO] ... < FILE_NAME

FROM represents a string to look for and TO represents its replacement.
There can be one or more pairs of strings.

Use the `--' option to indicate where the string-replacement list ends
and the file names begin. In this case, any file named on the command
line is modified in place, so you may want to make a copy of the
original before converting it. REPLACE prints a message indicating
which of the input files it actually modifies.

If the `--' option is not given, *Note `replace': replace-utility.
reads the standard input and writes to the standard output.

*Note `replace': replace-utility. uses a finite state machine to match
longer strings first. It can be used to swap strings. For example, the
following command swaps `a' and `b' in the given files, `file1' and
`file2':


     shell> replace a b b a -- file1 file2 ...

The *Note `replace': replace-utility. program is used by *Note
`msql2mysql': msql2mysql. See *Note msql2mysql::.

*Note `replace': replace-utility. supports the following options.

   * `-?', `-I'

     Display a help message and exit.

   * `-#DEBUG_OPTIONS'

     Enable debugging.

   * `-s'

     Silent mode. Print less information what the program does.

   * `-v'

     Verbose mode. Print more information about what the program does.

   * `-V'

     Display version information and exit.


File: manual.info,  Node: resolveip,  Prev: replace-utility,  Up: programs-miscellaneous

4.8.3 `resolveip' -- Resolve Host name to IP Address or Vice Versa
------------------------------------------------------------------

The *Note `resolveip': resolveip. utility resolves host names to IP
addresses and vice versa.

Invoke *Note `resolveip': resolveip. like this:


     shell> resolveip [OPTIONS] {HOST_NAME|IP-ADDR} ...

*Note `resolveip': resolveip. supports the following options.

   * `--help', `--info', `-?', `-I'

     Display a help message and exit.

   * `--silent', `-s'

     Silent mode. Produce less output.

   * `--version', `-V'

     Display version information and exit.


File: manual.info,  Node: server-administration,  Next: security,  Prev: programs,  Up: Top

5 MySQL Server Administration
*****************************

* Menu:

* mysqld-server::                The MySQL Server
* server-logs::                  MySQL Server Logs
* multiple-servers::             Running Multiple MySQL Instances on One Machine

End of Product Lifecycle

Active development for MySQL Database Server version 5.1 has ended.
Oracle offers various support offerings which may be of interest. For
details and more information, see the MySQL section of the Lifetime
Support Policy for Oracle Technology Products
(`http://www.oracle.com/us/support/lifetime-support/index.html').
Please consider upgrading to a recent version.

MySQL Server (*Note `mysqld': mysqld.) is the main program that does
most of the work in a MySQL installation. This chapter provides an
overview of MySQL Server and covers general server administration:

   * Server configuration.

   * The server log files.

   * Management of multiple servers on a single machine.

For additional information on administrative topics, see also:

   * *Note security::

   * *Note backup-and-recovery::

   * *Note replication::


File: manual.info,  Node: mysqld-server,  Next: server-logs,  Prev: server-administration,  Up: server-administration

5.1 The MySQL Server
====================

* Menu:

* mysqld-option-tables::         Server Option and Variable Reference
* server-configuration-defaults::  Server Configuration Defaults
* server-options::               Server Command Options
* server-system-variables::      Server System Variables
* using-system-variables::       Using System Variables
* server-status-variables::      Server Status Variables
* sql-mode::                     Server SQL Modes
* server-plugins::               Server Plugins
* server-side-help-support::     Server-Side Help
* server-signal-response::       Server Response to Signals
* server-shutdown::              The Shutdown Process

*Note `mysqld': mysqld. is the MySQL server. The following discussion
covers these MySQL server configuration topics:

   * Startup options that the server supports. You can specify these
     options on the command line, through configuration files, or both.

   * Server system variables. These variables reflect the current state
     and values of the startup options, some of which can be modified
     while the server is running.

   * Server status variables. These variables contain counters and
     statistics about runtime operation.

   * How to set the server SQL mode. This setting modifies certain
     aspects of SQL syntax and semantics, for example for compatibility
     with code from other database systems, or to control the error
     handling for particular situations.

   * The server shutdown process. There are performance and reliability
     considerations depending on the type of table (transactional or
     nontransactional) and whether you use replication.

*Note*:

Not all storage engines are supported by all MySQL server binaries and
configurations. To find out how to determine which storage engines your
MySQL server installation supports, see *Note show-engines::.


File: manual.info,  Node: mysqld-option-tables,  Next: server-configuration-defaults,  Prev: mysqld-server,  Up: mysqld-server

5.1.1 Server Option and Variable Reference
------------------------------------------

The following table provides a list of all the command line options,
server and status variables applicable within `mysqld'.

The table lists command-line options (Cmd-line), options valid in
configuration files (Option file), server system variables (System
Var), and status variables (Status var) in one unified list, with
notification of where each option/variable is valid. If a server option
set on the command line or in an option file differs from the name of
the corresponding server system or status variable, the variable name
is noted immediately below the corresponding option. For status
variables, the scope of the variable is shown (Scope) as either global,
session, or both. Please see the corresponding sections for details on
setting and using the options and variables. Where appropriate, a
direct link to further information on the item as available.

For a version of this table that is specific to MySQL Cluster, see
*Note mysql-cluster-option-tables::.

*Option/Variable Summary*

Name           Cmd-Line    Option File System Var  Status Var  Var Scope   Dynamic
abort-slave-event-countYes         Yes                                             
Aborted_clients                                    Yes         Global      No
Aborted_connects                                    Yes         Global      No
allow-suspicious-udfsYes         Yes                                             
ansi           Yes         Yes                                             
auto_increment_increment                        Yes                     Both        Yes
auto_increment_offset                        Yes                     Both        Yes
autocommit     Yes         Yes         Yes                     Session     Yes
automatic_sp_privileges                        Yes                     Global      Yes
back_log                               Yes                     Global      No
basedir        Yes         Yes         Yes                     Global      No
big-tables     Yes         Yes                                 Session     Yes
- _Variable_:                          Yes                     Session     Yes
big_tables                                                                 
bind-address   Yes         Yes         Yes                     Global      No
Binlog_cache_disk_use                                    Yes         Global      No
binlog_cache_sizeYes         Yes         Yes                     Global      Yes
Binlog_cache_use                                    Yes         Global      No
binlog_direct_non_transactional_updatesYes         Yes         Yes                     Both        Yes
binlog-do-db   Yes         Yes                                             
binlog-format  Yes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
binlog_format                                                              
binlog-ignore-dbYes         Yes                                             
binlog-row-event-max-sizeYes         Yes                                             
bootstrap      Yes         Yes                                             
bulk_insert_buffer_sizeYes         Yes         Yes                     Both        Yes
Bytes_received                                     Yes         Both        No
Bytes_sent                                         Yes         Both        No
character_set_client                        Yes                     Both        Yes
character-set-client-handshakeYes         Yes                                             
character_set_connection                        Yes                     Both        Yes
character_set_database                        Yes                     Both        Yes
This option                                                                
is dynamic,                                                                
but only the                                                               
server should                                                              
set this                                                                   
information.                                                               
You should                                                                 
not set the                                                                
value of this                                                              
variable                                                                   
manually.                                                                  
character-set-filesystemYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
character_set_filesystem                                                            
character_set_results                        Yes                     Both        Yes
character-set-serverYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
character_set_server                                                            
character_set_system                        Yes                     Global      No
character-sets-dirYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
character_sets_dir                                                            
chroot         Yes         Yes                                             
collation_connection                        Yes                     Both        Yes
collation_database                        Yes                     Both        Yes
This option                                                                
is dynamic,                                                                
but only the                                                               
server should                                                              
set this                                                                   
information.                                                               
You should                                                                 
not set the                                                                
value of this                                                              
variable                                                                   
manually.                                                                  
collation-serverYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
collation_server                                                            
Com_admin_commands                                    Yes         Both        No
Com_alter_db                                       Yes         Both        No
Com_alter_db_upgrade                                    Yes         Both        No
Com_alter_event                                    Yes         Both        No
Com_alter_function                                    Yes         Both        No
Com_alter_procedure                                    Yes         Both        No
Com_alter_server                                    Yes         Both        No
Com_alter_table                                    Yes         Both        No
Com_alter_tablespace                                    Yes         Both        No
Com_analyze                                        Yes         Both        No
Com_assign_to_keycache                                    Yes         Both        No
Com_backup_table                                    Yes         Both        No
Com_begin                                          Yes         Both        No
Com_binlog                                         Yes         Both        No
Com_call_procedure                                    Yes         Both        No
Com_change_db                                      Yes         Both        No
Com_change_master                                    Yes         Both        No
Com_check                                          Yes         Both        No
Com_checksum                                       Yes         Both        No
Com_commit                                         Yes         Both        No
Com_create_db                                      Yes         Both        No
Com_create_event                                    Yes         Both        No
Com_create_function                                    Yes         Both        No
Com_create_index                                    Yes         Both        No
Com_create_procedure                                    Yes         Both        No
Com_create_server                                    Yes         Both        No
Com_create_table                                    Yes         Both        No
Com_create_trigger                                    Yes         Both        No
Com_create_udf                                     Yes         Both        No
Com_create_user                                    Yes         Both        No
Com_create_view                                    Yes         Both        No
Com_dealloc_sql                                    Yes         Both        No
Com_delete                                         Yes         Both        No
Com_delete_multi                                    Yes         Both        No
Com_do                                             Yes         Both        No
Com_drop_db                                        Yes         Both        No
Com_drop_event                                     Yes         Both        No
Com_drop_function                                    Yes         Both        No
Com_drop_index                                     Yes         Both        No
Com_drop_procedure                                    Yes         Both        No
Com_drop_server                                    Yes         Both        No
Com_drop_table                                     Yes         Both        No
Com_drop_trigger                                    Yes         Both        No
Com_drop_user                                      Yes         Both        No
Com_drop_view                                      Yes         Both        No
Com_empty_query                                    Yes         Both        No
Com_execute_sql                                    Yes         Both        No
Com_flush                                          Yes         Both        No
Com_grant                                          Yes         Both        No
Com_ha_close                                       Yes         Both        No
Com_ha_open                                        Yes         Both        No
Com_ha_read                                        Yes         Both        No
Com_help                                           Yes         Both        No
Com_insert                                         Yes         Both        No
Com_insert_select                                    Yes         Both        No
Com_install_plugin                                    Yes         Both        No
Com_kill                                           Yes         Both        No
Com_load                                           Yes         Both        No
Com_lock_tables                                    Yes         Both        No
Com_optimize                                       Yes         Both        No
Com_preload_keys                                    Yes         Both        No
Com_prepare_sql                                    Yes         Both        No
Com_purge                                          Yes         Both        No
Com_purge_before_date                                    Yes         Both        No
Com_release_savepoint                                    Yes         Both        No
Com_rename_table                                    Yes         Both        No
Com_rename_user                                    Yes         Both        No
Com_repair                                         Yes         Both        No
Com_replace                                        Yes         Both        No
Com_replace_select                                    Yes         Both        No
Com_reset                                          Yes         Both        No
Com_restore_table                                    Yes         Both        No
Com_revoke                                         Yes         Both        No
Com_revoke_all                                     Yes         Both        No
Com_rollback                                       Yes         Both        No
Com_rollback_to_savepoint                                    Yes         Both        No
Com_savepoint                                      Yes         Both        No
Com_select                                         Yes         Both        No
Com_set_option                                     Yes         Both        No
Com_show_authors                                    Yes         Both        No
Com_show_binlog_events                                    Yes         Both        No
Com_show_binlogs                                    Yes         Both        No
Com_show_charsets                                    Yes         Both        No
Com_show_collations                                    Yes         Both        No
Com_show_column_types                                    Yes         Both        No
Com_show_contributors                                    Yes         Both        No
Com_show_create_db                                    Yes         Both        No
Com_show_create_event                                    Yes         Both        No
Com_show_create_func                                    Yes         Both        No
Com_show_create_proc                                    Yes         Both        No
Com_show_create_table                                    Yes         Both        No
Com_show_create_trigger                                    Yes         Both        No
Com_show_databases                                    Yes         Both        No
Com_show_engine_logs                                    Yes         Both        No
Com_show_engine_mutex                                    Yes         Both        No
Com_show_engine_status                                    Yes         Both        No
Com_show_errors                                    Yes         Both        No
Com_show_events                                    Yes         Both        No
Com_show_fields                                    Yes         Both        No
Com_show_function_code                                    Yes         Both        No
Com_show_function_status                                    Yes         Both        No
Com_show_grants                                    Yes         Both        No
Com_show_keys                                      Yes         Both        No
Com_show_logs                                      Yes         Both        No
Com_show_master_status                                    Yes         Both        No
Com_show_ndb_status                                    Yes         Both        No
Com_show_new_master                                    Yes         Both        No
Com_show_open_tables                                    Yes         Both        No
Com_show_plugins                                    Yes         Both        No
Com_show_privileges                                    Yes         Both        No
Com_show_procedure_code                                    Yes         Both        No
Com_show_procedure_status                                    Yes         Both        No
Com_show_processlist                                    Yes         Both        No
Com_show_profile                                    Yes         Both        No
Com_show_profiles                                    Yes         Both        No
Com_show_slave_hosts                                    Yes         Both        No
Com_show_slave_status                                    Yes         Both        No
Com_show_status                                    Yes         Both        No
Com_show_storage_engines                                    Yes         Both        No
Com_show_table_status                                    Yes         Both        No
Com_show_tables                                    Yes         Both        No
Com_show_triggers                                    Yes         Both        No
Com_show_variables                                    Yes         Both        No
Com_show_warnings                                    Yes         Both        No
Com_slave_start                                    Yes         Both        No
Com_slave_stop                                     Yes         Both        No
Com_stmt_close                                     Yes         Both        No
Com_stmt_execute                                    Yes         Both        No
Com_stmt_fetch                                     Yes         Both        No
Com_stmt_prepare                                    Yes         Both        No
Com_stmt_reprepare                                    Yes         Both        No
Com_stmt_reset                                     Yes         Both        No
Com_stmt_send_long_data                                    Yes         Both        No
Com_truncate                                       Yes         Both        No
Com_uninstall_plugin                                    Yes         Both        No
Com_unlock_tables                                    Yes         Both        No
Com_update                                         Yes         Both        No
Com_update_multi                                    Yes         Both        No
Com_xa_commit                                      Yes         Both        No
Com_xa_end                                         Yes         Both        No
Com_xa_prepare                                     Yes         Both        No
Com_xa_recover                                     Yes         Both        No
Com_xa_rollback                                    Yes         Both        No
Com_xa_start                                       Yes         Both        No
completion_typeYes         Yes         Yes                     Both        Yes
Compression                                        Yes         Session     No
concurrent_insertYes         Yes         Yes                     Global      Yes
connect_timeoutYes         Yes         Yes                     Global      Yes
Connections                                        Yes         Global      No
console        Yes         Yes                                             
core-file      Yes         Yes                                             
Created_tmp_disk_tables                                    Yes         Both        No
Created_tmp_files                                    Yes         Global      No
Created_tmp_tables                                    Yes         Both        No
datadir        Yes         Yes         Yes                     Global      No
date_format                            Yes                     Both        No
datetime_format                        Yes                     Both        No
debug          Yes         Yes         Yes                     Both        Yes
debug_sync                             Yes                     Both        Yes
debug-sync-timeoutYes         Yes                                             
default-character-setYes         Yes                                             
default-storage-engineYes         Yes         Yes                     Both        Yes
default-table-typeYes         Yes                                             
default-time-zoneYes         Yes                                             
default_week_formatYes         Yes         Yes                     Both        Yes
defaults-extra-fileYes                                                         
defaults-file  Yes                                                         
defaults-group-suffixYes                                                         
delay-key-writeYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
delay_key_write                                                            
Delayed_errors                                     Yes         Global      No
delayed_insert_limitYes         Yes         Yes                     Global      Yes
Delayed_insert_threads                                    Yes         Global      No
delayed_insert_timeoutYes         Yes         Yes                     Global      Yes
delayed_queue_sizeYes         Yes         Yes                     Global      Yes
Delayed_writes                                     Yes         Global      No
des-key-file   Yes         Yes                                             
disconnect-slave-event-countYes         Yes                                             
div_precision_incrementYes         Yes         Yes                     Both        Yes
enable-locking Yes         Yes                                             
enable-named-pipeYes         Yes                                             
- _Variable_:                                                              
named_pipe                                                                 
enable-pstack  Yes         Yes                                             
engine-condition-pushdownYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
engine_condition_pushdown                                                            
error_count                            Yes                     Session     No
event-schedulerYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
event_scheduler                                                            
exit-info      Yes         Yes                                             
expire_logs_daysYes         Yes         Yes                     Global      Yes
external-lockingYes         Yes                                             
- _Variable_:                                                              
skip_external_locking                                                            
*Note          Yes         Yes                                             
federated:                                                                 
federated-storage-engine.                                                            
flush          Yes         Yes         Yes                     Global      Yes
Flush_commands                                     Yes         Global      No
flush_time     Yes         Yes         Yes                     Global      Yes
foreign_key_checks                        Yes                     Session     Yes
ft_boolean_syntaxYes         Yes         Yes                     Global      Yes
ft_max_word_lenYes         Yes         Yes                     Global      No
ft_min_word_lenYes         Yes         Yes                     Global      No
ft_query_expansion_limitYes         Yes         Yes                     Global      No
ft_stopword_fileYes         Yes         Yes                     Global      No
gdb            Yes         Yes                                             
general-log    Yes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
general_log                                                                
general_log_fileYes         Yes         Yes                     Global      Yes
group_concat_max_lenYes         Yes         Yes                     Both        Yes
Handler_commit                                     Yes         Both        No
Handler_delete                                     Yes         Both        No
Handler_discover                                    Yes         Both        No
Handler_prepare                                    Yes         Both        No
Handler_read_first                                    Yes         Both        No
Handler_read_key                                    Yes         Both        No
Handler_read_next                                    Yes         Both        No
Handler_read_prev                                    Yes         Both        No
Handler_read_rnd                                    Yes         Both        No
Handler_read_rnd_next                                    Yes         Both        No
Handler_rollback                                    Yes         Both        No
Handler_savepoint                                    Yes         Both        No
Handler_savepoint_rollback                                    Yes         Both        No
Handler_update                                     Yes         Both        No
Handler_write                                      Yes         Both        No
have_archive                           Yes                     Global      No
have_blackhole_engine                        Yes                     Global      No
have_community_features                        Yes                     Global      No
have_compress                          Yes                     Global      No
have_crypt                             Yes                     Global      No
have_csv                               Yes                     Global      No
have_dynamic_loading                        Yes                     Global      No
have_example_engine                        Yes                     Global      No
have_federated_engine                        Yes                     Global      No
have_geometry                          Yes                     Global      No
have_innodb                            Yes                     Global      No
have_isam                              Yes                     Global      No
have_merge_engine                        Yes                     Global      No
have_ndbcluster                        Yes                     Global      No
have_openssl                           Yes                     Global      No
have_partition_engine                        Yes                     Global      No
have_partitioning                        Yes                     Global      No
have_query_cache                        Yes                     Global      No
have_raid                              Yes                     Global      No
have_row_based_replication                        Yes                     Global      No
have_rtree_keys                        Yes                     Global      No
have_ssl                               Yes                     Global      No
have_symlink                           Yes                     Global      No
help           Yes         Yes                                             
hostname                               Yes                     Global      No
identity                               Yes                     Session     Yes
ignore-builtin-innodbYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ignore_builtin_innodb                                                            
init_connect   Yes         Yes         Yes                     Global      Yes
init-file      Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
init_file                                                                  
init-rpl-role  Yes         Yes                                             
init_slave     Yes         Yes         Yes                     Global      Yes
innodb         Yes         Yes                                             
innodb_adaptive_flushingYes         Yes         Yes                     Global      Yes
innodb_adaptive_hash_indexYes         Yes         Yes                     Global      No
innodb_additional_mem_pool_sizeYes         Yes         Yes                     Global      No
innodb_autoextend_incrementYes         Yes         Yes                     Global      Yes
innodb_autoinc_lock_modeYes         Yes         Yes                     Global      No
innodb_buffer_pool_awe_mem_mbYes         Yes         Yes                     Global      No
Innodb_buffer_pool_pages_data                                    Yes         Global      No
Innodb_buffer_pool_pages_dirty                                    Yes         Global      No
Innodb_buffer_pool_pages_flushed                                    Yes         Global      No
Innodb_buffer_pool_pages_free                                    Yes         Global      No
Innodb_buffer_pool_pages_latched                                    Yes         Global      No
Innodb_buffer_pool_pages_misc                                    Yes         Global      No
Innodb_buffer_pool_pages_total                                    Yes         Global      No
Innodb_buffer_pool_read_ahead                                    Yes         Global      No
Innodb_buffer_pool_read_ahead_evicted                                    Yes         Global      No
Innodb_buffer_pool_read_ahead_rnd                                    Yes         Global      No
Innodb_buffer_pool_read_ahead_seq                                    Yes         Global      No
Innodb_buffer_pool_read_requests                                    Yes         Global      No
Innodb_buffer_pool_reads                                    Yes         Global      No
innodb_buffer_pool_sizeYes         Yes         Yes                     Global      No
Innodb_buffer_pool_wait_free                                    Yes         Global      No
Innodb_buffer_pool_write_requests                                    Yes         Global      No
innodb_change_bufferingYes         Yes         Yes                     Global      Yes
innodb_checksumsYes         Yes         Yes                     Global      No
innodb_commit_concurrencyYes         Yes         Yes                     Global      Yes
innodb_concurrency_ticketsYes         Yes         Yes                     Global      Yes
innodb_data_file_pathYes         Yes         Yes                     Global      No
Innodb_data_fsyncs                                    Yes         Global      No
innodb_data_home_dirYes         Yes         Yes                     Global      No
Innodb_data_pending_fsyncs                                    Yes         Global      No
Innodb_data_pending_reads                                    Yes         Global      No
Innodb_data_pending_writes                                    Yes         Global      No
Innodb_data_read                                    Yes         Global      No
Innodb_data_reads                                    Yes         Global      No
Innodb_data_writes                                    Yes         Global      No
Innodb_data_written                                    Yes         Global      No
Innodb_dblwr_pages_written                                    Yes         Global      No
Innodb_dblwr_writes                                    Yes         Global      No
innodb_doublewriteYes         Yes         Yes                     Global      No
innodb_fast_shutdownYes         Yes         Yes                     Global      Yes
innodb_file_formatYes         Yes         Yes                     Global      Yes
innodb_file_format_checkYes         Yes         Yes                     Global      Yes
innodb_file_io_threadsYes         Yes         Yes                     Global      No
innodb_file_per_tableYes         Yes         Yes                     Global      No
innodb_flush_log_at_trx_commitYes         Yes         Yes                     Global      Yes
innodb_flush_methodYes         Yes         Yes                     Global      No
innodb_force_recoveryYes         Yes         Yes                     Global      No
Innodb_have_atomic_builtins                                    Yes         Global      No
innodb_io_capacityYes         Yes         Yes                     Global      No
innodb_lock_wait_timeoutYes         Yes         Yes                     Both        No
innodb_locks_unsafe_for_binlogYes         Yes         Yes                     Global      No
innodb_log_arch_dirYes         Yes         Yes                     Global      No
innodb_log_archiveYes         Yes         Yes                     Global      No
innodb_log_buffer_sizeYes         Yes         Yes                     Global      No
innodb_log_file_sizeYes         Yes         Yes                     Global      No
innodb_log_files_in_groupYes         Yes         Yes                     Global      No
innodb_log_group_home_dirYes         Yes         Yes                     Global      No
Innodb_log_waits                                    Yes         Global      No
Innodb_log_write_requests                                    Yes         Global      No
Innodb_log_writes                                    Yes         Global      No
innodb_max_dirty_pages_pctYes         Yes         Yes                     Global      Yes
innodb_max_purge_lagYes         Yes         Yes                     Global      Yes
innodb_mirrored_log_groupsYes         Yes         Yes                     Global      No
innodb_old_blocks_pctYes         Yes         Yes                     Global      Yes
innodb_old_blocks_timeYes         Yes         Yes                     Global      Yes
innodb_open_filesYes         Yes         Yes                     Global      No
Innodb_os_log_fsyncs                                    Yes         Global      No
Innodb_os_log_pending_fsyncs                                    Yes         Global      No
Innodb_os_log_pending_writes                                    Yes         Global      No
Innodb_os_log_written                                    Yes         Global      No
Innodb_page_size                                    Yes         Global      No
Innodb_pages_created                                    Yes         Global      No
Innodb_pages_read                                    Yes         Global      No
Innodb_pages_written                                    Yes         Global      No
innodb_random_read_aheadYes         Yes         Yes                     Global      Yes
innodb_read_ahead_thresholdYes         Yes         Yes                     Global      Yes
innodb_read_io_threadsYes         Yes         Yes                     Global      No
innodb_replication_delayYes         Yes         Yes                     Global      Yes
innodb_rollback_on_timeoutYes         Yes         Yes                     Global      No
Innodb_row_lock_current_waits                                    Yes         Global      No
Innodb_row_lock_time                                    Yes         Global      No
Innodb_row_lock_time_avg                                    Yes         Global      No
Innodb_row_lock_time_max                                    Yes         Global      No
Innodb_row_lock_waits                                    Yes         Global      No
Innodb_rows_deleted                                    Yes         Global      No
Innodb_rows_inserted                                    Yes         Global      No
Innodb_rows_read                                    Yes         Global      No
Innodb_rows_updated                                    Yes         Global      No
innodb_spin_wait_delayYes         Yes         Yes                     Global      Yes
innodb_stats_methodYes         Yes         Yes                     Global      Yes
innodb_stats_on_metadataYes         Yes         Yes                     Global      Yes
innodb_stats_sample_pagesYes         Yes         Yes                     Global      Yes
innodb-status-fileYes         Yes                                             
innodb_strict_modeYes         Yes         Yes                     Both        Yes
innodb_support_xaYes         Yes         Yes                     Both        Yes
innodb_sync_spin_loopsYes         Yes         Yes                     Global      Yes
innodb_table_locksYes         Yes         Yes                     Both        Yes
innodb_thread_concurrencyYes         Yes         Yes                     Global      Yes
innodb_thread_sleep_delayYes         Yes         Yes                     Global      Yes
innodb_use_legacy_cardinality_algorithmYes         Yes         Yes                     Global      Yes
innodb_use_sys_mallocYes         Yes         Yes                     Global      No
innodb_version                         Yes                     Global      No
innodb_write_io_threadsYes         Yes         Yes                     Global      No
insert_id                              Yes                     Session     Yes
install        Yes                                                         
install-manual Yes                                                         
interactive_timeoutYes         Yes         Yes                     Both        Yes
join_buffer_sizeYes         Yes         Yes                     Both        Yes
keep_files_on_createYes         Yes         Yes                     Both        Yes
Key_blocks_not_flushed                                    Yes         Global      No
Key_blocks_unused                                    Yes         Global      No
Key_blocks_used                                    Yes         Global      No
key_buffer_sizeYes         Yes         Yes                     Global      Yes
key_cache_age_thresholdYes         Yes         Yes                     Global      Yes
key_cache_block_sizeYes         Yes         Yes                     Global      Yes
key_cache_division_limitYes         Yes         Yes                     Global      Yes
Key_read_requests                                    Yes         Global      No
Key_reads                                          Yes         Global      No
Key_write_requests                                    Yes         Global      No
Key_writes                                         Yes         Global      No
language       Yes         Yes         Yes                     Global      No
large_files_support                        Yes                     Global      No
large_page_size                        Yes                     Global      No
large-pages    Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
large_pages                                                                
last_insert_id                         Yes                     Session     Yes
Last_query_cost                                    Yes         Session     No
lc_time_names                          Yes                     Both        Yes
license                                Yes                     Global      No
local_infile                           Yes                     Global      Yes
local-service  Yes                                                         
locked_in_memory                        Yes                     Global      No
log            Yes         Yes         Yes                     Global      Yes
log_bin                                Yes                     Global      No
log-bin        Yes         Yes         Yes                     Global      No
log-bin-index  Yes         Yes                                             
log-bin-trust-function-creatorsYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
log_bin_trust_function_creators                                                            
log-bin-trust-routine-creatorsYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
log_bin_trust_routine_creators                                                            
(http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#sysvar_log_bin_trust_routine_creators)                                                            
log_bin_use_v1_row_eventsYes         Yes         Yes                     Global      No
log-bin-use-v1-row-eventsYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
log_bin_use_v1_row_events                                                            
log-error      Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
log_error                                                                  
log-isam       Yes         Yes                                             
log-output     Yes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
log_output                                                                 
log-queries-not-using-indexesYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
log_queries_not_using_indexes                                                            
log-short-formatYes         Yes                                             
log-slave-updatesYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
log_slave_updates                                                            
log_slave_updatesYes         Yes         Yes                     Global      No
log-slow-admin-statementsYes         Yes                                             
log-slow-queriesYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
log_slow_queries                                                            
log-slow-slave-statementsYes         Yes                                             
log-tc         Yes         Yes                                             
log-tc-size    Yes         Yes                                             
log-warnings   Yes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
log_warnings                                                               
long_query_timeYes         Yes         Yes                     Both        Yes
low-priority-updatesYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
low_priority_updates                                                            
lower_case_file_system                        Yes                     Global      No
lower_case_table_namesYes         Yes         Yes                     Global      No
master-connect-retryYes         Yes                                             
master-host    Yes         Yes                                             
master-info-fileYes         Yes                                             
master-passwordYes         Yes                                             
master-port    Yes         Yes                                             
master-retry-countYes         Yes                                             
master-ssl     Yes         Yes                                             
master-ssl-ca  Yes         Yes                                             
master-ssl-capathYes         Yes                                             
master-ssl-certYes         Yes                                             
master-ssl-cipherYes         Yes                                             
master-ssl-key Yes         Yes                                             
master-user    Yes         Yes                                             
max_allowed_packetYes         Yes         Yes                     Global      Yes
max_binlog_cache_sizeYes         Yes         Yes                     Global      Yes
max-binlog-dump-eventsYes         Yes                                             
max_binlog_sizeYes         Yes         Yes                     Global      Yes
max_connect_errorsYes         Yes         Yes                     Global      Yes
max_connectionsYes         Yes         Yes                     Global      Yes
max_delayed_threadsYes         Yes         Yes                     Both        Yes
max_error_countYes         Yes         Yes                     Both        Yes
max_heap_table_sizeYes         Yes         Yes                     Both        Yes
max_insert_delayed_threads                        Yes                     Both        Yes
max_join_size  Yes         Yes         Yes                     Both        Yes
max_length_for_sort_dataYes         Yes         Yes                     Both        Yes
max_long_data_sizeYes         Yes         Yes                     Global      No
max_prepared_stmt_countYes         Yes         Yes                     Global      Yes
max_relay_log_sizeYes         Yes         Yes                     Global      Yes
max_seeks_for_keyYes         Yes         Yes                     Both        Yes
max_sort_lengthYes         Yes         Yes                     Both        Yes
max_sp_recursion_depthYes         Yes         Yes                     Both        Yes
Max_used_connections                                    Yes         Global      No
max_user_connectionsYes         Yes         Yes                     Both        Yes
max_write_lock_countYes         Yes         Yes                     Global      Yes
memlock        Yes         Yes         Yes                     Global      No
merge          Yes         Yes                                             
min-examined-row-limitYes         Yes         Yes                     Both        Yes
multi_range_countYes         Yes         Yes                     Both        Yes
myisam-block-sizeYes         Yes                                             
myisam_data_pointer_sizeYes         Yes         Yes                     Global      Yes
myisam_max_sort_file_sizeYes         Yes         Yes                     Global      Yes
myisam_mmap_sizeYes         Yes         Yes                     Global      No
myisam-recover Yes         Yes                                             
- _Variable_:                                                              
myisam_recover_options                                                            
myisam_recover_options                        Yes                     Global      No
myisam_repair_threadsYes         Yes         Yes                     Both        Yes
myisam_sort_buffer_sizeYes         Yes         Yes                     Both        Yes
myisam_stats_methodYes         Yes         Yes                     Both        Yes
myisam_use_mmapYes         Yes         Yes                     Global      Yes
named_pipe                             Yes                     Global      No
Ndb_api_bytes_received_count                                    Yes         Global      No
Ndb_api_bytes_received_count_session                                    Yes         Session     No
Ndb_api_bytes_received_count_slave                                    Yes         Global      No
Ndb_api_bytes_sent_count                                    Yes         Global      No
Ndb_api_bytes_sent_count_session                                    Yes         Session     No
Ndb_api_bytes_sent_count_slave                                    Yes         Global      No
Ndb_api_event_bytes_count                                    Yes         Global      No
Ndb_api_event_bytes_count_injector                                    Yes         Global      No
Ndb_api_event_data_count                                    Yes         Global      No
Ndb_api_event_data_count_injector                                    Yes         Global      No
Ndb_api_event_nondata_count                                    Yes         Global      No
Ndb_api_event_nondata_count_injector                                    Yes         Global      No
Ndb_api_pk_op_count                                    Yes         Global      No
Ndb_api_pk_op_count_session                                    Yes         Session     No
Ndb_api_pk_op_count_slave                                    Yes         Global      No
Ndb_api_pruned_scan_count                                    Yes         Global      No
Ndb_api_pruned_scan_count_session                                    Yes         Session     No
Ndb_api_pruned_scan_count_slave                                    Yes         Global      No
Ndb_api_range_scan_count                                    Yes         Global      No
Ndb_api_range_scan_count_session                                    Yes         Session     No
Ndb_api_range_scan_count_slave                                    Yes         Global      No
Ndb_api_read_row_count                                    Yes         Global      No
Ndb_api_read_row_count_session                                    Yes         Session     No
Ndb_api_read_row_count_slave                                    Yes         Global      No
Ndb_api_scan_batch_count                                    Yes         Global      No
Ndb_api_scan_batch_count_session                                    Yes         Session     No
Ndb_api_scan_batch_count_slave                                    Yes         Global      No
Ndb_api_table_scan_count                                    Yes         Global      No
Ndb_api_table_scan_count_session                                    Yes         Session     No
Ndb_api_table_scan_count_slave                                    Yes         Global      No
Ndb_api_trans_abort_count                                    Yes         Global      No
Ndb_api_trans_abort_count_session                                    Yes         Session     No
Ndb_api_trans_abort_count_slave                                    Yes         Global      No
Ndb_api_trans_close_count                                    Yes         Global      No
Ndb_api_trans_close_count_session                                    Yes         Session     No
Ndb_api_trans_close_count_slave                                    Yes         Global      No
Ndb_api_trans_commit_count                                    Yes         Global      No
Ndb_api_trans_commit_count_session                                    Yes         Session     No
Ndb_api_trans_commit_count_slave                                    Yes         Global      No
Ndb_api_trans_local_read_row_count                                    Yes         Global      No
Ndb_api_trans_local_read_row_count_session                                    Yes         Session     No
Ndb_api_trans_local_read_row_count_slave                                    Yes         Global      No
Ndb_api_trans_start_count                                    Yes         Global      No
Ndb_api_trans_start_count_session                                    Yes         Session     No
Ndb_api_trans_start_count_slave                                    Yes         Global      No
Ndb_api_uk_op_count                                    Yes         Global      No
Ndb_api_uk_op_count_session                                    Yes         Session     No
Ndb_api_uk_op_count_slave                                    Yes         Global      No
Ndb_api_wait_exec_complete_count                                    Yes         Global      No
Ndb_api_wait_exec_complete_count_session                                    Yes         Session     No
Ndb_api_wait_exec_complete_count_slave                                    Yes         Global      No
Ndb_api_wait_meta_request_count                                    Yes         Global      No
Ndb_api_wait_meta_request_count_session                                    Yes         Session     No
Ndb_api_wait_meta_request_count_slave                                    Yes         Global      No
Ndb_api_wait_nanos_count                                    Yes         Global      No
Ndb_api_wait_nanos_count_session                                    Yes         Session     No
Ndb_api_wait_nanos_count_slave                                    Yes         Global      No
Ndb_api_wait_scan_result_count                                    Yes         Global      No
Ndb_api_wait_scan_result_count_session                                    Yes         Session     No
Ndb_api_wait_scan_result_count_slave                                    Yes         Global      No
ndb_autoincrement_prefetch_szYes         Yes         Yes                     Both        Yes
ndb-batch-size Yes         Yes         Yes                     Global      No
ndb-blob-read-batch-bytesYes         Yes         Yes                     Both        Yes
ndb-blob-write-batch-bytesYes         Yes         Yes                     Both        Yes
ndb_cache_check_timeYes         Yes         Yes                     Global      Yes
ndb-cluster-connection-poolYes         Yes         Yes         Yes         Global      No
Ndb_cluster_node_id                                    Yes         Both        No
Ndb_config_from_host                                    Yes         Both        No
Ndb_config_from_port                                    Yes         Both        No
Ndb_conflict_fn_epoch                                    Yes         Global      No
Ndb_conflict_fn_epoch_trans                                    Yes         Global      No
Ndb_conflict_fn_max                                    Yes         Global      No
Ndb_conflict_fn_old                                    Yes         Global      No
Ndb_conflict_trans_conflict_commit_count                                    Yes         Global      No
Ndb_conflict_trans_detect_iter_count                                    Yes         Global      No
Ndb_conflict_trans_reject_count                                    Yes         Global      No
Ndb_conflict_trans_row_conflict_count                                    Yes         Global      No
Ndb_conflict_trans_row_reject_count                                    Yes         Global      No
ndb-connectstringYes         Yes                                             
ndb-deferred-constraintsYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
ndb_deferred_constraints                                                            
ndb_deferred_constraintsYes         Yes         Yes                     Both        Yes
ndb_distributionYes         Yes         Yes                     Global      Yes
ndb-distributionYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
ndb_distribution                                                            
ndb_eventbuffer_max_allocYes         Yes         Yes                     Global      Yes
ndb_execute_count                                    Yes         Global      No
ndb_extra_loggingYes         Yes         Yes                     Global      Yes
ndb_force_send Yes         Yes         Yes                     Both        Yes
ndb_index_stat_cache_entriesYes         Yes                                             
ndb_index_stat_enableYes         Yes                                             
ndb_index_stat_optionYes         Yes                                             
ndb_index_stat_update_freqYes         Yes                                             
ndb_join_pushdown                        Yes                     Both        Yes
ndb-log-apply-statusYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ndb_log_apply_status                                                            
ndb_log_apply_statusYes         Yes         Yes                     Global      No
ndb_log_bin    Yes                     Yes                     Both        Yes
ndb_log_binlog_indexYes                     Yes                     Global      Yes
ndb_log_empty_epochsYes         Yes         Yes                     Global      Yes
ndb-log-empty-epochsYes         Yes         Yes                     Global      Yes
ndb-log-orig   Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ndb_log_orig                                                               
ndb_log_orig   Yes         Yes         Yes                     Global      No
ndb-log-transaction-idYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ndb_log_transaction_id                                                            
ndb_log_transaction_id                        Yes                     Global      No
ndb-log-update-as-writeYes         Yes         Yes                     Global      Yes
ndb_log_updated_onlyYes         Yes         Yes                     Global      Yes
ndb-mgmd-host  Yes         Yes                                             
ndb-nodeid     Yes         Yes                     Yes         Global      No
Ndb_number_of_data_nodes                                    Yes         Global      No
ndb_optimization_delay                        Yes                     Global      Yes
ndb_optimized_node_selectionYes         Yes                                             
ndb_pruned_scan_count                                    Yes         Global      No
Ndb_pushed_queries_defined                                    Yes         Global      No
Ndb_pushed_queries_dropped                                    Yes         Global      No
Ndb_pushed_queries_executed                                    Yes         Global      No
ndb_pushed_reads                                    Yes         Global      No
ndb_report_thresh_binlog_epoch_slipYes         Yes                                             
ndb_report_thresh_binlog_mem_usageYes         Yes                                             
ndb_scan_count                                     Yes         Global      No
ndb_table_no_logging                        Yes                     Session     Yes
ndb_table_temporary                        Yes                     Session     Yes
ndb-transid-mysql-connection-mapYes                                                         
ndb_use_copying_alter_table                        Yes                     Both        No
ndb_use_exact_count                        Yes                     Both        Yes
ndb_use_transactionsYes         Yes         Yes                     Both        Yes
ndb_version                            Yes                     Global      No
ndb_version_string                        Yes                     Global      No
ndb-wait-connectedYes         Yes         Yes                     Global      No
ndb-wait-setup Yes         Yes         Yes                     Global      No
ndbcluster     Yes         Yes                                             
- _Variable_:                                                              
have_ndbcluster                                                            
ndbinfo_database                        Yes                     Global      No
ndbinfo_max_bytesYes                     Yes                     Both        Yes
ndbinfo_max_rowsYes                     Yes                     Both        Yes
ndbinfo_offline                        Yes                     Global      Yes
ndbinfo_show_hiddenYes                     Yes                     Both        Yes
ndbinfo_table_prefixYes                     Yes                     Both        Yes
ndbinfo_version                        Yes                     Global      No
net_buffer_lengthYes         Yes         Yes                     Both        Yes
net_read_timeoutYes         Yes         Yes                     Both        Yes
net_retry_countYes         Yes         Yes                     Both        Yes
net_write_timeoutYes         Yes         Yes                     Both        Yes
new            Yes         Yes         Yes                     Both        Yes
no-defaults    Yes                                                         
Not_flushed_delayed_rows                                    Yes         Global      No
old            Yes         Yes         Yes                     Global      No
old-alter-tableYes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
old_alter_table                                                            
old_passwords                          Yes                     Both        Yes
old-style-user-limitsYes         Yes                                             
one-thread     Yes         Yes                                             
Open_files                                         Yes         Global      No
open-files-limitYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
open_files_limit                                                            
Open_streams                                       Yes         Global      No
Open_table_definitions                                    Yes         Global      No
Open_tables                                        Yes         Both        No
Opened_files                                       Yes         Global      No
Opened_table_definitions                                    Yes         Both        No
Opened_tables                                      Yes         Both        No
optimizer_prune_levelYes         Yes         Yes                     Both        Yes
optimizer_search_depthYes         Yes         Yes                     Both        Yes
optimizer_switchYes         Yes         Yes                     Both        Yes
partition      Yes         Yes                                             
- _Variable_:                                                              
have_partitioning                                                            
pid-file       Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
pid_file                                                                   
plugin         Yes         Yes                                             
plugin_dir     Yes         Yes         Yes                     Global      No
plugin-load    Yes         Yes                                             
port           Yes         Yes         Yes                     Global      No
port-open-timeoutYes         Yes                                             
preload_buffer_sizeYes         Yes         Yes                     Both        Yes
prepared_stmt_count                        Yes                     Global      No
Prepared_stmt_count                                    Yes         Global      No
print-defaults Yes                                                         
profiling                              Yes                     Session     Yes
profiling_history_sizeYes         Yes         Yes                     Both        Yes
protocol_version                        Yes                     Global      No
pseudo_thread_id                        Yes                     Session     Yes
Qcache_free_blocks                                    Yes         Global      No
Qcache_free_memory                                    Yes         Global      No
Qcache_hits                                        Yes         Global      No
Qcache_inserts                                     Yes         Global      No
Qcache_lowmem_prunes                                    Yes         Global      No
Qcache_not_cached                                    Yes         Global      No
Qcache_queries_in_cache                                    Yes         Global      No
Qcache_total_blocks                                    Yes         Global      No
Queries                                            Yes         Both        No
query_alloc_block_sizeYes         Yes         Yes                     Both        Yes
query_cache_limitYes         Yes         Yes                     Global      Yes
query_cache_min_res_unitYes         Yes         Yes                     Global      Yes
query_cache_sizeYes         Yes         Yes                     Global      Yes
query_cache_typeYes         Yes         Yes                     Both        Yes
query_cache_wlock_invalidateYes         Yes         Yes                     Both        Yes
query_prealloc_sizeYes         Yes         Yes                     Both        Yes
Questions                                          Yes         Both        No
rand_seed1                             Yes                     Session     Yes
rand_seed2                             Yes                     Session     Yes
range_alloc_block_sizeYes         Yes         Yes                     Both        Yes
read_buffer_sizeYes         Yes         Yes                     Both        Yes
read_only      Yes         Yes         Yes                     Global      Yes
read_rnd_buffer_sizeYes         Yes         Yes                     Both        Yes
relay-log      Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
relay_log                                                                  
relay-log-indexYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
relay_log_index                                                            
relay_log_indexYes         Yes         Yes                     Global      No
relay-log-info-fileYes         Yes                                             
- _Variable_:                                                              
relay_log_info_file                                                            
relay_log_info_fileYes         Yes         Yes                     Global      No
relay_log_purgeYes         Yes         Yes                     Global      Yes
relay_log_space_limitYes         Yes         Yes                     Global      No
remove         Yes                                                         
replicate-do-dbYes         Yes                                             
replicate-do-tableYes         Yes                                             
replicate-ignore-dbYes         Yes                                             
replicate-ignore-tableYes         Yes                                             
replicate-rewrite-dbYes         Yes                                             
replicate-same-server-idYes         Yes                                             
replicate-wild-do-tableYes         Yes                                             
replicate-wild-ignore-tableYes         Yes                                             
report-host    Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
report_host                                                                
report-passwordYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
report_password                                                            
report-port    Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
report_port                                                                
report-user    Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
report_user                                                                
rpl_recovery_rank                        Yes                     Global      Yes
Rpl_status                                         Yes         Global      No
safe-mode      Yes         Yes                                             
safe-show-databaseYes         Yes         Yes                     Global      Yes
safe-user-createYes         Yes                                             
safemalloc-mem-limitYes         Yes                                             
secure-auth    Yes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
secure_auth                                                                
secure-file-privYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
secure_file_priv                                                            
Select_full_join                                    Yes         Both        No
Select_full_range_join                                    Yes         Both        No
Select_range                                       Yes         Both        No
Select_range_check                                    Yes         Both        No
Select_scan                                        Yes         Both        No
server-id      Yes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
server_id                                                                  
server_id_bits Yes         Yes         Yes                     Global      No
server-id-bits Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
server_id_bits                                                             
shared_memory  Yes         Yes         Yes                     Global      No
shared_memory_base_name                        Yes                     Global      No
show-slave-auth-infoYes         Yes                                             
skip-character-set-client-handshakeYes         Yes                                             
skip-concurrent-insertYes         Yes                                             
- _Variable_:                                                              
concurrent_insert                                                            
skip-event-schedulerYes         Yes                                             
skip_external_lockingYes         Yes         Yes                     Global      No
skip-grant-tablesYes         Yes                                             
skip-host-cacheYes         Yes                                             
skip-locking   Yes         Yes                                             
skip-merge     Yes         Yes                                             
skip-name-resolveYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
skip_name_resolve                                                            
skip-ndbclusterYes         Yes                                             
skip-networkingYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
skip_networking                                                            
skip-new       Yes         Yes                                             
skip-partition Yes         Yes                                             
skip-safemallocYes         Yes                                             
skip-show-databaseYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
skip_show_database                                                            
skip-slave-startYes         Yes                                             
skip-ssl       Yes         Yes                                             
skip-stack-traceYes         Yes                                             
skip-symbolic-linksYes                                                         
skip-symlink   Yes         Yes                                             
skip-thread-priorityYes         Yes                                             
slave_allow_batchingYes         Yes         Yes                     Global      Yes
slave_compressed_protocolYes         Yes         Yes                     Global      Yes
slave_exec_modeYes         Yes         Yes                     Global      Yes
Slave_heartbeat_period                                    Yes         Global      No
slave-load-tmpdirYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
slave_load_tmpdir                                                            
slave_max_allowed_packet                        Yes                     Global      Yes
slave-max-allowed-packetYes         Yes                                             
- _Variable_:                                                              
slave_max_allowed_packet                                                            
slave-net-timeoutYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
slave_net_timeout                                                            
Slave_open_temp_tables                                    Yes         Global      No
Slave_received_heartbeats                                    Yes         Global      No
Slave_retried_transactions                                    Yes         Global      No
Slave_running                                      Yes         Global      No
slave-skip-errorsYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
slave_skip_errors                                                            
slave_transaction_retriesYes         Yes         Yes                     Global      Yes
slave_type_conversionsYes         Yes         Yes                     Global      No
Slow_launch_threads                                    Yes         Both        No
slow_launch_timeYes         Yes         Yes                     Global      Yes
Slow_queries                                       Yes         Both        No
slow-query-log Yes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
slow_query_log                                                             
slow_query_log_fileYes         Yes         Yes                     Global      Yes
socket         Yes         Yes         Yes                     Global      No
sort_buffer_sizeYes         Yes         Yes                     Both        Yes
Sort_merge_passes                                    Yes         Both        No
Sort_range                                         Yes         Both        No
Sort_rows                                          Yes         Both        No
Sort_scan                                          Yes         Both        No
sporadic-binlog-dump-failYes         Yes                                             
sql_auto_is_null                        Yes                     Session     Yes
sql_big_selects                        Yes                     Session     Yes
sql_big_tables                         Yes                     Session     Yes
sql_buffer_result                        Yes                     Session     Yes
sql_log_bin                            Yes                     Session     Yes
sql_log_off                            Yes                     Session     Yes
sql_log_update                         Yes                     Session     Yes
sql_low_priority_updates                        Yes                     Both        Yes
sql_max_join_size                        Yes                     Both        Yes
sql-mode       Yes         Yes                                 Both        Yes
- _Variable_:                          Yes                     Both        Yes
sql_mode                                                                   
sql_notes                              Yes                     Session     Yes
sql_quote_show_create                        Yes                     Session     Yes
sql_safe_updates                        Yes                     Session     Yes
sql_select_limit                        Yes                     Both        Yes
sql_slave_skip_counter                        Yes                     Global      Yes
sql_warnings                           Yes                     Session     Yes
ssl            Yes         Yes                                             
Ssl_accept_renegotiates                                    Yes         Global      No
Ssl_accepts                                        Yes         Global      No
ssl-ca         Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_ca                                                                     
Ssl_callback_cache_hits                                    Yes         Global      No
ssl-capath     Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_capath                                                                 
ssl-cert       Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_cert                                                                   
ssl-cipher     Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_cipher                                                                 
Ssl_cipher                                         Yes         Both        No
Ssl_cipher_list                                    Yes         Both        No
Ssl_client_connects                                    Yes         Global      No
Ssl_connect_renegotiates                                    Yes         Global      No
Ssl_ctx_verify_depth                                    Yes         Global      No
Ssl_ctx_verify_mode                                    Yes         Global      No
Ssl_default_timeout                                    Yes         Both        No
Ssl_finished_accepts                                    Yes         Global      No
Ssl_finished_connects                                    Yes         Global      No
ssl-key        Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_key                                                                    
Ssl_session_cache_hits                                    Yes         Global      No
Ssl_session_cache_misses                                    Yes         Global      No
Ssl_session_cache_mode                                    Yes         Global      No
Ssl_session_cache_overflows                                    Yes         Global      No
Ssl_session_cache_size                                    Yes         Global      No
Ssl_session_cache_timeouts                                    Yes         Global      No
Ssl_sessions_reused                                    Yes         Both        No
Ssl_used_session_cache_entries                                    Yes         Global      No
Ssl_verify_depth                                    Yes         Both        No
Ssl_verify_mode                                    Yes         Both        No
Ssl_version                                        Yes         Both        No
standalone     Yes         Yes                                             
storage_engine                         Yes                     Both        Yes
symbolic-links Yes         Yes                                             
sync_binlog    Yes         Yes         Yes                     Global      Yes
sync_frm       Yes         Yes         Yes                     Global      Yes
sysdate-is-now Yes         Yes                                             
system_time_zone                        Yes                     Global      No
table_cache    Yes         Yes         Yes                     Global      Yes
table_definition_cache                        Yes                     Global      Yes
table_lock_wait_timeoutYes         Yes         Yes                     Global      Yes
Table_locks_immediate                                    Yes         Global      No
Table_locks_waited                                    Yes         Global      No
table_open_cache                        Yes                     Global      Yes
table_type                             Yes                     Both        Yes
tc-heuristic-recoverYes         Yes                                             
Tc_log_max_pages_used                                    Yes         Global      No
Tc_log_page_size                                    Yes         Global      No
Tc_log_page_waits                                    Yes         Global      No
temp-pool      Yes         Yes                                             
thread_cache_sizeYes         Yes         Yes                     Global      Yes
thread_concurrencyYes         Yes         Yes                     Global      No
thread_handlingYes         Yes         Yes                     Global      No
thread_stack   Yes         Yes         Yes                     Global      No
Threads_cached                                     Yes         Global      No
Threads_connected                                    Yes         Global      No
Threads_created                                    Yes         Global      No
Threads_running                                    Yes         Global      No
time_format                            Yes                     Both        No
time_zone                              Yes                     Both        Yes
timed_mutexes  Yes         Yes         Yes                     Global      Yes
timestamp                              Yes                     Session     Yes
tmp_table_size Yes         Yes         Yes                     Both        Yes
tmpdir         Yes         Yes         Yes                     Global      No
transaction_alloc_block_sizeYes         Yes         Yes                     Both        Yes
transaction_allow_batching                        Yes                     Session     Yes
transaction-isolationYes         Yes                                             
- _Variable_:                                                              
tx_isolation                                                               
transaction_prealloc_sizeYes         Yes         Yes                     Both        Yes
tx_isolation                           Yes                     Both        Yes
unique_checks                          Yes                     Session     Yes
updatable_views_with_limitYes         Yes         Yes                     Both        Yes
Uptime                                             Yes         Global      No
Uptime_since_flush_status                                    Yes         Global      No
use-symbolic-linksYes         Yes                                             
user           Yes         Yes                                             
verbose        Yes         Yes                                             
version                                Yes                     Global      No
version_comment                        Yes                     Global      No
version_compile_machine                        Yes                     Global      No
version_compile_os                        Yes                     Global      No
wait_timeout   Yes         Yes         Yes                     Both        Yes
warning_count                          Yes                     Session     No


File: manual.info,  Node: server-configuration-defaults,  Next: server-options,  Prev: mysqld-option-tables,  Up: mysqld-server

5.1.2 Server Configuration Defaults
-----------------------------------

The MySQL server has many operating parameters, which you can change at
server startup using command-line options or configuration files
(option files). It is also possible to change many parameters at
runtime. For general instructions on setting parameters at startup or
runtime, see *Note server-options::, and *Note
server-system-variables::.

MySQL provides a number of preconfigured option files that can be used
as a basis for tuning the MySQL server. Look for files named
`my-small.cnf', `my-medium.cnf', `my-large.cnf', and `my-huge.cnf',
which are sample option files for small, medium, large, and very large
systems. On Windows, the extension is `.ini' rather than `.cnf'.

*Note*:

On Windows, the `.ini' or `.cnf' option file extension might not be
displayed.

For a binary distribution, look for the sample files in or under your
installation directory. If you have a source distribution, look in the
`support-files' directory. To use a sample file as a base configuration
file, rename a copy of it and place the copy in the appropriate
location. Regarding names and appropriate location, see the general
information provided in *Note option-files::. That section also
describes option file format and syntax.


File: manual.info,  Node: server-options,  Next: server-system-variables,  Prev: server-configuration-defaults,  Up: mysqld-server

5.1.3 Server Command Options
----------------------------

When you start the *Note `mysqld': mysqld. server, you can specify
program options using any of the methods described in *Note
program-options::. The most common methods are to provide options in an
option file or on the command line. However, in most cases it is
desirable to make sure that the server uses the same options each time
it runs. The best way to ensure this is to list them in an option file.
See *Note option-files::.

*Note `mysqld': mysqld. reads options from the `[mysqld]' and `[server]'
groups. *Note `mysqld_safe': mysqld-safe. reads options from the
`[mysqld]', `[server]', `[mysqld_safe]', and `[safe_mysqld]' groups.
*Note `mysql.server': mysql-server. reads options from the `[mysqld]'
and `[mysql.server]' groups.

An embedded MySQL server usually reads options from the `[server]',
`[embedded]', and `[XXXXX_SERVER]' groups, where XXXXX is the name of
the application into which the server is embedded.

*Note `mysqld': mysqld. accepts many command options. For a brief
summary, execute *Note `mysqld --help': mysqld. To see the full list,
use *Note `mysqld --verbose --help': mysqld.

The following list shows some of the most common server options.
Additional options are described in other sections:

   * Options that affect security: See *Note security-options::.

   * SSL-related options: See *Note ssl-options::.

   * Binary log control options: See *Note binary-log::.

   * Replication-related options: See *Note replication-options::.

   * Options for loading plugins such as pluggable storage engines: See
     *Note server-plugin-loading::.

   * Options specific to particular storage engines: See *Note
     innodb-parameters::, *Note myisam-start::, and *Note
     mysql-cluster-program-options-mysqld::.

You can also set the values of server system variables by using
variable names as options, as described at the end of this section.

Some options control the size of buffers or caches. For a given buffer,
the server might need to allocate internal data structures. These
structures typically are allocated from the total memory allocated to
the buffer, and the amount of space required might be platform
dependent. This means that when you assign a value to an option that
controls a buffer size, the amount of space actually available might
differ from the value assigned. In some cases, the amount might be less
than the value assigned. It is also possible that the server will
adjust a value upward. For example, if you assign a value of 0 to an
option for which the minimal value is 1024, the server will set the
value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes
unless otherwise specified.

Some options take file name values. Unless otherwise specified, the
default file location is the data directory if the value is a relative
path name. To specify the location explicitly, use an absolute path
name. Suppose that the data directory is `/var/mysql/data'. If a
file-valued option is given as a relative path name, it will be located
under `/var/mysql/data'. If the value is an absolute path name, its
location is as given by the path name.

   * `--help', `-?'

     Options for help

     *Command-Line        `-?'            
     Format*                              
                          `--help'        

     Display a short help message and exit. Use both the `--verbose' and
     `--help' options to see the full message.

   * `--allow-suspicious-udfs'

     Options for allow-suspicious-udfs

     *Command-Line        `--allow-suspicious-udfs'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This option controls whether user-defined functions that have only
     an `xxx' symbol for the main function can be loaded. By default,
     the option is off and only UDFs that have at least one auxiliary
     symbol can be loaded; this prevents attempts at loading functions
     from shared object files other than those containing legitimate
     UDFs. See *Note udf-security::.

   * `--ansi'

     Options for ansi

     *Command-Line        `--ansi'        
     Format*                              
                          `-a'            

     Use standard (ANSI) SQL syntax instead of MySQL syntax. For more
     precise control over the server SQL mode, use the `--sql-mode'
     option instead. See *Note compatibility::, and *Note sql-mode::.

   * `--basedir=PATH', `-b PATH'

     Options for basedir

     *Command-Line        `--basedir=path'        
     Format*                              
                          `-b'            
     *System Variable     `basedir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The path to the MySQL installation directory. All paths are
     usually resolved relative to this directory.

   * `--big-tables'

     Options for big-tables

     *Command-Line        `--big-tables'        
     Format*                              
     *System Variable     `big_tables'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Enable large result sets by saving all temporary sets in files.
     This option prevents most `table full' errors, but also slows down
     queries for which in-memory tables would suffice. Since MySQL
     3.23.2, the server is able to handle large result sets
     automatically by using memory for small temporary tables and
     switching to disk tables where necessary.

   * `--bind-address=ADDR'

     Options for bind-address

     *Command-Line        `--bind-address=addr'        
     Format*                              
     *System Variable     `bind_address'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `0.0.0.0'        

     The MySQL server listens on a single network socket for TCP/IP
     connections. This socket is bound to a single address, but it is
     possible for an address to map onto multiple network interfaces.
     The default address is `0.0.0.0'.  To specify an address
     explicitly, use the `--bind-address=ADDR' option at server
     startup, where ADDR is an IPv4 address or a host name. If ADDR is
     a host name, the server resolves the name to an IPv4 address and
     binds to that address.

     The server treats different types of addresses as follows:

        * If the address is `0.0.0.0', the server accepts TCP/IP
          connections on all server host IPv4 interfaces.

        * If the address is a `regular' IPv4 address (such as
          `127.0.0.1'), the server accepts TCP/IP connections only for
          that particular IPv4 address.

     If you intend to bind the server to a specific address, be sure
     that the `mysql.user' grant table contains an account with
     administrative privileges that you can use connect to that
     address. Otherwise, you will not be able to shut down the server.
     For example, if you bind to `0.0.0.0', you can connect to the
     server using all existing accounts. But if you bind to
     `127.0.0.1', the server accepts connections only on that address.
     In this case, first make sure that the `'root'@'127.0.0.1''
     account is present in the `mysql.user' table so that you can still
     connect to the server to shut it down.

   * `--binlog-format={ROW|STATEMENT|MIXED}'

     Options for binlog-format

     *Introduced*         5.1.5           
     *Command-Line        `--binlog-format=format'        
     Format*                              
     *System Variable     `binlog_format'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (>=             
                          5.1.5,          
                          <=              
                          5.1.7)*         
     *Type*               `enumeration'        
     *Default*            `STATEMENT'        
     *Valid Values*       `ROW'           
     `STATEMENT'                          
                          *Permitted        
                          Values          
                          (>=             
                          5.1.8,          
                          <=              
                          5.1.11)*        
     *Type*               `enumeration'        
     *Default*            `STATEMENT'        
     *Valid Values*       `ROW'           
     `STATEMENT'                          
     `MIXED'                              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.12,         
                          <=              
                          5.1.28)*        
     *Type*               `enumeration'        
     *Default*            `MIXED'         
     *Valid Values*       `ROW'           
     `STATEMENT'                          
     `MIXED'                              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.29)*        
     *Type*               `enumeration'        
     *Default*            `STATEMENT'        
     *Valid Values*       `ROW'           
     `STATEMENT'                          
     `MIXED'                              

     Specify whether to use row-based, statement-based, or mixed
     replication (statement-based was the default prior to MySQL
     5.1.12; in 5.1.12, the default was changed to mixed replication;
     in 5.1.29, the default was changed back to statement-based). See
     *Note replication-formats::.  This option was added in MySQL 5.1.5.

     Under some conditions, changing this variable at runtime is not
     possible, or causes replication to fail. See *Note
     binary-log-setting::, for more information.

     *Important*:

     Setting the binary logging format without enabling binary logging
     prevents the MySQL server from starting. This is a known issue in
     MySQL 5.1 which is fixed in MySQL 5.5. (Bug #42928)

     MySQL Cluster

     The default value for this option in all MySQL Cluster NDB 6.1
     through 7.1 releases is `MIXED'. See *Note
     mysql-cluster-replication-general::, for more information.

   * `--bootstrap'

     Options for bootstrap

     *Command-Line        `--bootstrap'        
     Format*                              

     This option is used by the *Note `mysql_install_db':
     mysql-install-db.  program to create the MySQL privilege tables
     without having to start a full MySQL server.

     This option is unavailable if MySQL was configured with the
     `--disable-grant-options' option. See *Note
     source-configuration-options::.

   * `--character-sets-dir=PATH'

     Options for character-sets-dir

     *Command-Line        `--character-sets-dir=path'        
     Format*                              
     *System Variable     `character_sets_dir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The directory where character sets are installed. See *Note
     charset-configuration::.

   * `--character-set-client-handshake'

     Options for character-set-client-handshake

     *Command-Line        `--character-set-client-handshake'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Do not ignore character set information sent by the client. To
     ignore client information and use the default server character
     set, use `--skip-character-set-client-handshake'; this makes MySQL
     behave like MySQL 4.0.

   * `--character-set-filesystem=CHARSET_NAME'

     Options for character-set-filesystem

     *Introduced*         5.1.6           
     *Command-Line        `--character-set-filesystem=name'        
     Format*                              
     *System Variable     `character_set_filesystem'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `binary'        

     The file system character set. This option sets the
     `character_set_filesystem' system variable. It was added in MySQL
     5.1.6.

   * `--character-set-server=CHARSET_NAME', `-C CHARSET_NAME'

     Options for character-set-server

     *Command-Line        `--character-set-server'        
     Format*                              
     *System Variable     `character_set_server'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `latin1'        

     Use CHARSET_NAME as the default server character set. See *Note
     charset-configuration::. If you use this option to specify a
     nondefault character set, you should also use `--collation-server'
     to specify the collation.

   * `--chroot=PATH', `-r PATH'

     Options for chroot

     *Command-Line        `--chroot=dir_name'        
     Format*                              
                          `-r             
                          name'           
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     Put the *Note `mysqld': mysqld. server in a closed environment
     during startup by using the `chroot()' system call. This is a
     recommended security measure. Note that use of this option
     somewhat limits *Note `LOAD DATA INFILE': load-data. and *Note
     `SELECT ... INTO OUTFILE': select-into.

   * `--collation-server=COLLATION_NAME'

     Options for collation-server

     *Command-Line        `--collation-server'        
     Format*                              
     *System Variable     `collation_server'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `latin1_swedish_ci'        

     Use COLLATION_NAME as the default server collation. See *Note
     charset-configuration::.

   * `--console'

     Options for console

     *Command-Line        `--console'        
     Format*                              
     *Platform Specific*  Windows         

     (Windows only.) Write error log messages to `stderr' and `stdout'.
     *Note `mysqld': mysqld. does not close the console window if this
     option is used.

     If both `--log-error' and `--console' are specified, whichever
     option is given last takes precedence.

   * `--core-file'

     Options for core-file

     *Command-Line        `--core-file'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Write a core file if *Note `mysqld': mysqld. dies. The name and
     location of the core file is system dependent. On Linux, a core
     file named `core.PID' is written to the current working directory
     of the process, which for *Note `mysqld': mysqld. is the data
     directory.  PID represents the process ID of the server process.
     On Mac OS X, a core file named `core.PID' is written to the
     `/cores' directory. On Solaris, use the `coreadm' command to
     specify where to write the core file and how to name it.

     For some systems, to get a core file you must also specify the
     `--core-file-size' option to *Note `mysqld_safe': mysqld-safe. See
     *Note mysqld-safe::. On some systems, such as Solaris, you do not
     get a core file if you are also using the `--user' option. There
     might be additional restrictions or limitations. For example, it
     might be necessary to execute `ulimit -c unlimited' before
     starting the server. Consult your system documentation.

   * `--datadir=PATH', `-h PATH'

     Options for datadir

     *Command-Line        `--datadir=path'        
     Format*                              
                          `-h'            
     *System Variable     `datadir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The path to the data directory.

   * `--debug[=DEBUG_OPTIONS]', `-# [DEBUG_OPTIONS]'

     Options for debug

     *Command-Line        `--debug[=debug_options]'        
     Format*                              
     *System Variable     `debug'         
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (Unix)        `string'        
     *Default*            `d:t:i:o,/tmp/mysqld.trace'        
                          *Permitted        
                          Values*         
     *Type* (Windows)     `string'        
     *Default*            `d:t:i:O,\mysqld.trace'        

     If MySQL is configured with `--with-debug', you can use this
     option to get a trace file of what *Note `mysqld': mysqld. is
     doing. A typical DEBUG_OPTIONS string is `d:t:o,FILE_NAME'.  The
     default is `d:t:i:o,/tmp/mysqld.trace' on Unix and
     `d:t:i:O,\mysqld.trace' on Windows.

     As of MySQL 5.1.12, using `--with-debug' to configure MySQL with
     debugging support enables you to use the
     `--debug="d,parser_debug"' option when you start the server. This
     causes the Bison parser that is used to process SQL statements to
     dump a parser trace to the server's standard error output.
     Typically, this output is written to the error log.

     This option may be given multiple times. Values that begin with
     `+' or `-' are added to or subtracted from the previous value. For
     example, `--debug=T' `--debug=+P' sets the value to `P:T'.

     For more information, see *Note dbug-package::.

   * `--debug-sync-timeout[=N]'

     Options for debug-sync-timeout

     *Introduced*         5.1.41          
     *Command-Line        `--debug-sync-timeout[=#]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     Controls whether the Debug Sync facility for testing and debugging
     is enabled. Use of Debug Sync requires that MySQL be configured
     with the `--enable-debug-sync' option (see *Note
     source-configuration-options::). If Debug Sync is not compiled in,
     this option is not available. The option value is a timeout in
     seconds. The default value is 0, which disables Debug Sync. To
     enable it, specify a value greater than 0; this value also becomes
     the default timeout for individual synchronization points. If the
     option is given without a value, the timeout is set to 300 seconds.

     For a description of the Debug Sync facility and how to use
     synchronization points, see MySQL Internals: Test Synchronization
     (http://dev.mysql.com/doc/internals/en/test-synchronization.html).

     This option was added in MySQL 5.1.41.

   * `--default-character-set=CHARSET_NAME'

     Options for default-character-set

     *Deprecated*         5.0.0           
     *Command-Line        `--default-character-set=name'        
     Format*                              
                          `-C             
                          name'           
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Use CHARSET_NAME as the default character set. This option is
     deprecated in favor of `--character-set-server'. See *Note
     charset-configuration::.  `--default-character-set' is removed in
     MySQL 5.5.

   * `--default-collation=COLLATION_NAME'

     Options for default-collation

     *Deprecated*         4.1.3           
     *Command-Line        `--default-collation=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Use COLLATION_NAME as the default collation. This option is
     deprecated in favor of `--collation-server'. See *Note
     charset-configuration::.  `--default-collation' is removed in
     MySQL 5.5.

   * `--default-storage-engine=TYPE'

     Options for default-storage-engine

     *Command-Line        `--default-storage-engine=name'        
     Format*                              
     *System Variable     `storage_engine'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `MyISAM'        

     Set the default storage engine (table type) for tables. See *Note
     storage-engines::.

   * `--default-table-type=TYPE'

     Options for default-table-type

     *Deprecated*         5.0.0,          
                          by              
                          default-storage-engine        
     *Command-Line        `--default-table-type=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This option is a synonym for `--default-storage-engine'. It is
     deprecated and removed in MySQL 5.5.

   * `--default-time-zone=TIMEZONE'

     Options for default-time-zone

     *Command-Line        `--default-time-zone=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Set the default server time zone. This option sets the global
     `time_zone' system variable. If this option is not given, the
     default time zone is the same as the system time zone (given by
     the value of the `system_time_zone' system variable.

   * `--defaults-extra-file=FILE_NAME'

     Read this option file after the global option file but (on Unix)
     before the user option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-file=FILE_NAME'

     Use only the given option file. If the file does not exist or is
     otherwise inaccessible, an error occurs.  FILE_NAME is the full
     path name to the file.

   * `--defaults-group-suffix=STR'

     Read not only the usual option groups, but also groups with the
     usual names and a suffix of STR. For example, *Note `mysqld':
     mysqld. normally reads the `[mysqld]' group. If the
     `--defaults-group-suffix=_other' option is given, *Note `mysqld':
     mysqld. also reads the `[mysqld_other]' group.

   * `--delay-key-write[={OFF|ON|ALL}]'

     Options for delay-key-write

     *Command-Line        `--delay-key-write[=name]'        
     Format*                              
     *System Variable     `delay_key_write'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `ON'            
     *Valid Values*       `ON'            
     `OFF'                                
     `ALL'                                

     Specify how to use delayed key writes. Delayed key writing causes
     key buffers not to be flushed between writes for `MyISAM' tables.
     `OFF' disables delayed key writes. `ON' enables delayed key writes
     for those tables that were created with the `DELAY_KEY_WRITE'
     option.  `ALL' delays key writes for all `MyISAM' tables. See
     *Note server-parameters::, and *Note myisam-start::.

     *Note*:

     If you set this variable to `ALL', you should not use `MyISAM'
     tables from within another program (such as another MySQL server or
     *Note `myisamchk': myisamchk.) when the tables are in use.  Doing
     so leads to index corruption.

   * `--des-key-file=FILE_NAME'

     Options for des-key-file

     *Command-Line        `--des-key-file=file_name'        
     Format*                              

     Read the default DES keys from this file. These keys are used by
     the `DES_ENCRYPT()' and `DES_DECRYPT()' functions.

   * `--enable-locking'

     This option is deprecated. Use `--external-locking' instead.

   * `--enable-named-pipe'

     Options for enable-named-pipe

     *Command-Line        `--enable-named-pipe'        
     Format*                              
     *Platform Specific*  Windows         

     Enable support for named pipes. This option applies only on
     Windows. For MySQL 5.1.20 and earlier, this option is available
     only when using the *Note `mysqld-nt': mysqld. and `mysqld-debug'
     servers that support named-pipe connections. For MySQL 5.1.21 and
     later, *Note `mysqld-nt': mysqld. is not available, but support is
     included in the standard *Note `mysqld': mysqld. and *Note
     `mysqld-debug': mysqld. servers.

   * `--enable-pstack'

     Options for enable-pstack

     *Deprecated*         5.1.54          
     *Command-Line        `--enable-pstack'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This option is nonfunctional. It is deprecated as of MySQL 5.1.54
     and removed in MySQL 5.5.

   * `--engine-condition-pushdown={ON|OFF}'

     Options for engine-condition-pushdown

     *Command-Line        `--engine-condition-pushdown'        
     Format*                              
     *System Variable     `engine_condition_pushdown'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     Sets the `engine_condition_pushdown' system variable. For more
     information, see *Note condition-pushdown-optimization::.

   * `--event-scheduler[=VALUE]'

     Options for event-scheduler

     *Introduced*         5.1.6           
     *Command-Line        `--event-scheduler[=value]'        
     Format*                              
     *System Variable     `event_scheduler'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `OFF'           
     *Valid Values*       `ON'            
     `OFF'                                
     `DISABLED'                           

     Enable or disable, and start or stop, the event scheduler.  This
     option was added in MySQL 5.1.6. Note that its permitted values
     and behavior changed in MySQL 5.1.11, and again in MySQL 5.1.12.

     For detailed information, see The `--event-scheduler' Option.

   * `--exit-info[=FLAGS]', `-T [FLAGS]'

     Options for exit-info

     *Command-Line        `--exit-info[=flags]'        
     Format*                              
                          `-T             
                          [flags]'        
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     This is a bit mask of different flags that you can use for
     debugging the *Note `mysqld': mysqld. server. Do not use this
     option unless you know _exactly_ what it does!

   * `--external-locking'

     Options for external-locking

     *Command-Line        `--external-locking'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Enable external locking (system locking), which is disabled by
     default as of MySQL 4.0. Note that if you use this option on a
     system on which `lockd' does not fully work (such as Linux), it is
     easy for *Note `mysqld': mysqld. to deadlock.

     To disable external locking explicitly, use
     `--skip-external-locking'.

     External locking affects only *Note `MyISAM':
     myisam-storage-engine. table access. For more information,
     including conditions under which it can and cannot be used, see
     *Note external-locking::.

   * `--flush'

     Options for flush

     *Command-Line        `--flush'        
     Format*                              
     *System Variable     `flush'         
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Flush (synchronize) all changes to disk after each SQL statement.
     Normally, MySQL does a write of all changes to disk only after
     each SQL statement and lets the operating system handle the
     synchronizing to disk. See *Note crashing::.

   * `--gdb'

     Options for gdb

     *Command-Line        `--gdb'         
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Install an interrupt handler for `SIGINT' (needed to stop *Note
     `mysqld': mysqld. with `^C' to set breakpoints) and disable stack
     tracing and core file handling. See *Note porting::.

   * `--general-log[={0|1}]'

     Options for general-log

     *Introduced*         5.1.12          
     *Command-Line        `--general-log'        
     Format*                              
     *System Variable     `general_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Specify the initial general query log state. With no argument or
     an argument of 1, the `--general-log' option enables the log. If
     omitted or given with an argument of 0, the option disables the
     log. This option was added in MySQL 5.1.12.

   * `--init-file=FILE_NAME'

     Options for init-file

     *Command-Line        `--init-file=file_name'        
     Format*                              
     *System Variable     `init_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     Read SQL statements from this file at startup. Each statement must
     be on a single line and should not include comments.

     This option is unavailable if MySQL was configured with the
     `--disable-grant-options' option. See *Note
     source-configuration-options::.

   * `--innodb-XXX'

     Set an option for the `InnoDB' storage engine. The `InnoDB'
     options are listed in *Note innodb-parameters::.

   * `--install [SERVICE_NAME]'

     Options for install

     *Command-Line        `--install        
     Format*              [service_name]'        

     (Windows only) Install the server as a Windows service that starts
     automatically during Windows startup. The default service name is
     `MySQL' if no SERVICE_NAME value is given. For more information,
     see *Note windows-start-service::.

     *Note*:

     If the server is started with the `--defaults-file' and
     `--install' options, `--install' must be first.

   * `--install-manual [SERVICE_NAME]'

     Options for install-manual

     *Command-Line        `--install-manual        
     Format*              [service_name]'        

     (Windows only) Install the server as a Windows service that must
     be started manually. It does not start automatically during
     Windows startup. The default service name is `MySQL' if no
     SERVICE_NAME value is given. For more information, see *Note
     windows-start-service::.

     *Note*:

     If the server is started with the `--defaults-file' and
     `--install-manual' options, `--install-manual' must be first.

   * `--language=LANG_NAME, -L LANG_NAME'

     Options for language

     *Command-Line        `--language=name'        
     Format*                              
                          `-L'            
     *System Variable     `language'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           
     *Default*            `/usr/local/mysql/share/mysql/english/'        

     The language to use for error messages.  LANG_NAME can be given as
     the language name or as the full path name to the directory where
     the language files are installed. See *Note
     error-message-language::.

   * `--large-pages'

     Options for large-pages

     *Command-Line        `--large-pages'        
     Format*                              
     *System Variable     `large_pages'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Linux           
                          *Permitted        
                          Values*         
     *Type* (Linux)       `boolean'        
     *Default*            `FALSE'         

     Some hardware/operating system architectures support memory pages
     greater than the default (usually 4KB). The actual implementation
     of this support depends on the underlying hardware and operating
     system. Applications that perform a lot of memory accesses may
     obtain performance improvements by using large pages due to
     reduced Translation Lookaside Buffer (TLB) misses.

     Currently, MySQL supports only the Linux implementation of large
     page support (which is called HugeTLB in Linux). See *Note
     large-page-support::.

     `--large-pages' is disabled by default.

   * `--local-service'

     Options for local-service

     *Command-Line        `--local-service'        
     Format*                              

     (Windows only) A `--local-service' option following the service
     name causes the server to run using the `LocalService' Windows
     account that has limited system privileges. This account is
     available only for Windows XP or newer. If both `--defaults-file'
     and `--local-service' are given following the service name, they
     can be in any order. See *Note windows-start-service::.

   * `--log[=FILE_NAME]', `-l [FILE_NAME]'

     Options for log

     *Deprecated*         5.1.29,         
                          by              
                          general-log        
     *Command-Line        `--log[=file_name]'        
     Format*                              
                          `-l'            
     *System Variable     `log'           
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     This option enables logging to the general query log, which
     contains entries that record client connections and SQL statements
     received from clients. The log output destination can be selected
     with the `--log-output' option as of MySQL 5.1.6. Before 5.1.6,
     logging occurs to the general query log file. If you omit the file
     name, MySQL uses `HOST_NAME.log' as the file name. See *Note
     log-destinations::, and *Note query-log::.

     As of MySQL 5.1.29, the `--log' option is deprecated and is
     removed (along with the `log' system variable) in MySQL 5.6.
     Instead, use the `--general_log' option to enable the general
     query log and the `--general_log_file=FILE_NAME' option to set the
     general query log file name.

   * `--log-error[=FILE_NAME]'

     Options for log-error

     *Command-Line        `--log-error[=file_name]'        
     Format*                              
     *System Variable     `log_error'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     Log errors and startup messages to this file. See *Note
     error-log::. If you omit the file name, MySQL uses `HOST_NAME.err'.
     If the file name has no extension, the server adds an extension of
     `.err'.

   * `--log-isam[=FILE_NAME]'

     Options for log-isam

     *Command-Line        `--log-isam[=file_name]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     Log all `MyISAM' changes to this file (used only when debugging
     `MyISAM').

   * `--log-long-format'

     Options for log-long-format

     *Deprecated*         4.1.0           
     *Command-Line        `--log-long-format'        
     Format*                              
                          `-0'            

     Log extra information to the binary log and slow query log, if
     they have been activated. For example, the user name and timestamp
     are logged for all queries. This option is deprecated, as it now
     represents the default logging behavior.  (See the description for
     `--log-short-format'.) The `--log-queries-not-using-indexes'
     option is available for the purpose of logging queries that do not
     use indexes to the slow query log.  `--log-long-format' is removed
     in MySQL 5.5.

   * `--log-output[=VALUE,...]'

     Options for log-output

     *Introduced*         5.1.6           
     *Command-Line        `--log-output=name'        
     Format*                              
     *System Variable     `log_output'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `set'           
     *Default*            `FILE'          
     *Valid Values*       `TABLE'         
     `FILE'                               
     `NONE'                               

     This option determines the destination for general query log and
     slow query log output. The option value can be given as one or
     more of the words `TABLE', `FILE', or `NONE'. If the option is
     given without a value, the default is `FILE'. (For MySQL 5.1.6
     through 5.1.20, the default is `TABLE'.) `TABLE' select logging to
     the `general_log' and `slow_log' tables in the `mysql' database as
     a destination.  `FILE' selects logging to log files as a
     destination. `NONE' disables logging. If `NONE' is present in the
     option value, it takes precedence over any other words that are
     present.  `TABLE' and `FILE' can both be given to select to both
     log output destinations.

     This option selects log output destinations, but does not enable
     log output. To do that, use the `--general_log' and
     `--slow_query_log' options. For `FILE' logging, the
     `--general_log_file' and `-slow_query_log_file' options determine
     the log file location. (Before MySQL 5.1.29, enable the logs with
     the `--log' and `--log-slow-queries' options. The options take an
     optional file name argument to specify the log file name.) For
     more information, see *Note log-destinations::.

     The `--log-output' option was added in MySQL 5.1.6.

   * `--log-queries-not-using-indexes'

     Options for log-queries-not-using-indexes

     *Command-Line        `--log-queries-not-using-indexes'        
     Format*                              
     *System Variable     `log_queries_not_using_indexes'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     If you are using this option with the slow query log enabled,
     queries that are expected to retrieve all rows are logged. See
     *Note slow-query-log::. This option does not necessarily mean that
     no index is used. For example, a query that uses a full index scan
     uses an index but would be logged because the index would not
     limit the number of rows.

   * `--log-short-format'

     Options for log-short-format

     *Command-Line        `--log-short-format'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Log less information to the binary log and slow query log, if they
     have been activated.

   * `--log-slow-admin-statements'

     Options for log-slow-admin-statements

     *Command-Line        `--log-slow-admin-statements'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Include slow administrative statements in the statements written
     to the slow query log. Administrative statements include *Note
     `ALTER TABLE': alter-table, *Note `ANALYZE TABLE': analyze-table,
     *Note `CHECK TABLE': check-table, *Note `CREATE INDEX':
     create-index, *Note `DROP INDEX': drop-index, *Note `OPTIMIZE
     TABLE': optimize-table, and *Note `REPAIR TABLE': repair-table.

   * `--log-slow-queries[=FILE_NAME]'

     Options for log-slow-queries

     *Deprecated*         5.1.29,         
                          by              
                          slow-query-log        
     *Command-Line        `--log-slow-queries[=name]'        
     Format*                              
     *System Variable     `log_slow_queries'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     This option enables logging to the slow query log, which contains
     entries for all queries that have taken more than
     `long_query_time' seconds to execute. See the descriptions of the
     `--log-long-format' and `--log-short-format' options for details.

     The log output destination can be selected with the `--log-output'
     option as of MySQL 5.1.6. Before 5.1.6, logging occurs to the slow
     query log file. If you omit the file name, MySQL uses
     `HOST_NAME-slow.log' as the file name. See *Note
     log-destinations::, and *Note slow-query-log::.

     As of MySQL 5.1.29, the `--log-slow-queries' option is deprecated
     and is removed (along with the `log_slow_queries' system variable)
     in MySQL 5.6. Instead, use the `--slow_query_log' option to enable
     the slow query log and the `--slow_query_log_file=FILE_NAME'
     option to set the slow query log file name.

   * `--log-tc=FILE_NAME'

     Options for log-tc

     *Command-Line        `--log-tc=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `tc.log'        

     The name of the memory-mapped transaction coordinator log file
     (for XA transactions that affect multiple storage engines when the
     binary log is disabled). The default name is `tc.log'. The file is
     created under the data directory if not given as a full path name.
     Currently, this option is unused.

   * `--log-tc-size=SIZE'

     Options for log-tc-size

     *Command-Line        `--log-tc-size=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `24576'         
     *Max Value*          `18446744073709547520'        

     The size in bytes of the memory-mapped transaction coordinator
     log. The default size is 24KB.

   * `--log-warnings[=LEVEL]', `-W [LEVEL]'

     Options for log-warnings

     *Command-Line        `--log-warnings[=#]'        
     Format*                              
                          `-W             
                          [#]'            
     *System Variable     `log_warnings'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `0'             
     *Max Value*          `18446744073709547520'        

     Print out warnings such as `Aborted connection...' to the error
     log. This option is enabled (1) by default. To disable it, use
     `--log-warnings=0'. Specifying the option without a LEVEL value
     increments the current value by 1. Enabling this option by setting
     it greater than 0 is recommended, for example, if you use
     replication (you get more information about what is happening,
     such as messages about network failures and reconnections). If the
     value is greater than 1, aborted connections are written to the
     error log. See *Note communication-errors::.

     If a slave server was started with `--log-warnings' enabled, the
     slave prints messages to the error log to provide information
     about its status, such as the binary log and relay log coordinates
     where it starts its job, when it is switching to another relay
     log, when it reconnects after a disconnect, and so forth. As of
     MySQL 5.1.38, the server logs messages about statements that are
     unsafe for statement-based logging if `--log-warnings' is greater
     than 0.

   * `--low-priority-updates'

     Options for low-priority-updates

     *Command-Line        `--low-priority-updates'        
     Format*                              
     *System Variable     `low_priority_updates'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Give table-modifying operations (*Note `INSERT': insert, *Note
     `REPLACE': replace, *Note `DELETE': delete, *Note `UPDATE':
     update.) lower priority than selects. This can also be done using
     `{INSERT | REPLACE | DELETE | UPDATE} LOW_PRIORITY ...' to lower
     the priority of only one query, or by `SET LOW_PRIORITY_UPDATES=1'
     to change the priority in one thread. This affects only storage
     engines that use only table-level locking (`MyISAM', `MEMORY',
     `MERGE'). See *Note table-locking::.

   * `--min-examined-row-limit=NUMBER'

     Options for min-examined-row-limit

     *Introduced*         5.1.21          
     *Command-Line        `--min-examined-row-limit=#'        
     Format*                              
     *System Variable     `min_examined_row_limit'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     When this option is set, queries which examine fewer than NUMBER
     rows are not written to the slow query log. The default is 0.

     This option was introduced in MySQL 5.1.21.

   * `--memlock'

     Options for memlock

     *Command-Line        `--memlock'        
     Format*                              
     *System Variable     `locked_in_memory'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Lock the *Note `mysqld': mysqld. process in memory. This option
     might help if you have a problem where the operating system is
     causing *Note `mysqld': mysqld. to swap to disk.

     `--memlock' works on systems that support the `mlockall()' system
     call; this includes Solaris, most Linux distributions that use a
     2.4 or newer kernel, and perhaps other Unix systems. On Linux
     systems, you can tell whether or not `mlockall()' (and thus this
     option) is supported by checking to see whether or not it is
     defined in the system `mman.h' file, like this:


          shell> grep mlockall /usr/include/sys/mman.h

     If `mlockall()' is supported, you should see in the output of the
     previous command something like the following:


          extern int mlockall (int __flags) __THROW;

     *Important*:

     Use of this option may require you to run the server as `root',
     which, for reasons of security, is normally not a good idea. See
     *Note changing-mysql-user::.

     On Linux and perhaps other systems, you can avoid the need to run
     the server as `root' by changing the `limits.conf' file. See the
     notes regarding the memlock limit in *Note large-page-support::.

     You must not try to use this option on a system that does not
     support the `mlockall()' system call; if you do so, *Note
     `mysqld': mysqld. will very likely crash as soon as you try to
     start it.

   * `--myisam-block-size=N'

     Options for myisam-block-size

     *Command-Line        `--myisam-block-size=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1024'          
     *Min Value*          `1024'          
     *Max Value*          `16384'         

     The block size to be used for `MyISAM' index pages.

   * `--myisam-recover[=OPTION[,OPTION]...]]'

     Options for myisam-recover

     *Command-Line        `--myisam-recover[=name]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `OFF'           
     *Valid Values*       `OFF'           
     `DEFAULT'                            
     `BACKUP'                             
     `FORCE'                              
     `QUICK'                              

     Set the `MyISAM' storage engine recovery mode. The option value is
     any combination of the values of `DEFAULT', `BACKUP', `FORCE', or
     `QUICK'. If you specify multiple values, separate them by commas.
     Specifying the option with no argument is the same as specifying
     `DEFAULT', and specifying with an explicit value of `""' disables
     recovery (same as not giving the option). If recovery is enabled,
     each time *Note `mysqld': mysqld. opens a `MyISAM' table, it
     checks whether the table is marked as crashed or was not closed
     properly. (The last option works only if you are running with
     external locking disabled.) If this is the case, *Note `mysqld':
     mysqld. runs a check on the table. If the table was corrupted,
     *Note `mysqld': mysqld. attempts to repair it.

     The following options affect how the repair works.

     This table describes `--myisam-recover' options.

     Option     Description
     `DEFAULT'  Recovery without backup, forcing, or quick
                checking.
     `BACKUP'   If the data file was changed during recovery,
                save a backup of the `TBL_NAME.MYD' file as
                `TBL_NAME-DATETIME.BAK'.
     `FORCE'    Run recovery even if we would lose more than
                one row from the `.MYD' file.
     `QUICK'    Do not check the rows in the table if there
                are not any delete blocks.

     Before the server automatically repairs a table, it writes a note
     about the repair to the error log. If you want to be able to
     recover from most problems without user intervention, you should
     use the options `BACKUP,FORCE'. This forces a repair of a table
     even if some rows would be deleted, but it keeps the old data file
     as a backup so that you can later examine what happened.

     See *Note myisam-start::.

   * `--no-defaults'

     Do not read any option files. If program startup fails due to
     reading unknown options from an option file, `--no-defaults' can
     be used to prevent them from being read.

   * `--old-alter-table'

     Options for old-alter-table

     *Command-Line        `--old-alter-table'        
     Format*                              
     *System Variable     `old_alter_table'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     When this option is given, the server does not use the optimized
     method of processing an *Note `ALTER TABLE': alter-table.
     operation. It reverts to using a temporary table, copying over the
     data, and then renaming the temporary table to the original, as
     used by MySQL 5.0 and earlier. For more information on the
     operation of *Note `ALTER TABLE': alter-table, see *Note
     alter-table::.

   * `--old-style-user-limits'

     Options for old-style-user-limits

     *Command-Line        `--old-style-user-limits'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Enable old-style user limits. (Before MySQL 5.0.3, account
     resource limits were counted separately for each host from which a
     user connected rather than per account row in the `user' table.)
     See *Note user-resources::.

   * `--one-thread'

     Options for one-thread

     *Command-Line        `--one-thread'        
     Format*                              

     Only use one thread (for debugging under Linux). This option is
     available only if the server is built with debugging enabled. See
     *Note porting::.

     As of MySQL 5.1.17, this option is deprecated and is removed in
     MySQL 5.6. Use `--thread_handling=no-threads' instead.

   * `--open-files-limit=COUNT'

     Options for open-files-limit

     *Command-Line        `--open-files-limit=#'        
     Format*                              
     *System Variable     `open_files_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `platform        
                          dependent'        

     Changes the number of file descriptors available to *Note
     `mysqld': mysqld. You should try increasing the value of this
     option if *Note `mysqld': mysqld. gives you the error `Too many
     open files'.  *Note `mysqld': mysqld. uses the option value to
     reserve descriptors with `setrlimit()'. Internally, the maximum
     value for this option is the maximum unsigned integer value, but
     the actual maximum is platform dependent.  If the requested number
     of file descriptors cannot be allocated, *Note `mysqld': mysqld.
     writes a warning to the error log.

     *Note `mysqld': mysqld. may attempt to allocate more than the
     requested number of descriptors (if they are available), using the
     values of `max_connections' and `table_open_cache' to estimate
     whether more descriptors will be needed.

     On Unix, the value cannot be set less than `ulimit -n'.

   * `--partition[=VALUE]'

     Options for partition

     *Command-Line        `--partition'        
     Format*                              
     *Disabled by*        `skip-partition'        
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     Enables or disables user-defined partitioning support in the MySQL
     Server.

   * `--pid-file=PATH'

     Options for pid-file

     *Command-Line        `--pid-file=file_name'        
     Format*                              
     *System Variable     `pid_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The path name of the process ID file. The server creates the file
     in the data directory unless an absolute path name is given to
     specify a different directory. This file is used by other programs
     such as *Note `mysqld_safe': mysqld-safe. to determine the
     server's process ID.

   * `--plugin-XXX'

     Specifies an option that pertains to a server plugin. For example,
     many storage engines can be built as plugins, and for such
     engines, options for them can be specified with a `--plugin'
     prefix. Thus, the `--innodb_file_per_table' option for `InnoDB'
     can be specified as `--plugin-innodb_file_per_table'.

     For boolean options that can be enabled or disabled, the `--skip'
     prefix and other alternative formats are supported as well (see
     *Note option-modifiers::). For example,
     `--skip-plugin-innodb_file_per_table' disables
     `innodb_file_per_table'.

     The rationale for the `--plugin' prefix is that it enables plugin
     options to be specified unambiguously if there is a name conflict
     with a built-in server option. For example, were a plugin writer
     to name a plugin `sql' and implement a `mode' option, the option
     name might be `--sql-mode', which would conflict with the built-in
     option of the same name. In such cases, references to the
     conflicting name are resolved in favor of the built-in option. To
     avoid the ambiguity, users can specify the plugin option as
     `--plugin-sql-mode'. Use of the `--plugin' prefix for plugin
     options is recommended to avoid any question of ambiguity.

   * `--plugin-load=PLUGIN_LIST'

     Options for plugin-load

     *Introduced*         5.1.18          
     *Command-Line        `--plugin-load=plugin_list'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This option tells the server to load the named plugins at startup.
     The option value is a semicolon-separated list of
     `NAME=PLUGIN_LIBRARY' pairs. Each NAME is the name of the plugin,
     and PLUGIN_LIBRARY is the name of the shared library that contains
     the plugin code. Each library file must be located in the
     directory named by the `plugin_dir' system variable.  For example,
     if plugins named `myplug1' and `myplug2' have library files
     `myplug1.so' and `myplug2.so', use this option to load them at
     startup:


          shell> mysqld --plugin-load="myplug1=myplug1.so;myplug2=myplug2.so"

     Quotes are used around the argument value here because semicolon
     (`;') is interpreted as a special character by some command
     interpreters. (Unix shells treat it as a command terminator, for
     example.)

     All plugins to load must be named in the same `--plugin-load'
     option. If multiple `--plugin-load' options are given, only the
     last one is used.

     If a plugin library is named without any preceding plugin name,
     the server loads all plugins in the library.

     Each plugin is loaded for a single invocation of *Note `mysqld':
     mysqld. only. After a restart, the plugin is not loaded unless
     `--plugin-load' is used again. This is in contrast to *Note
     `INSTALL PLUGIN': install-plugin, which adds an entry to the
     `mysql.plugins' table to cause the plugin to be loaded for every
     normal server startup.

     Under normal startup, the server determines which plugins to load
     by reading the `mysql.plugins' system table. If the server is
     started with the `--skip-grant-tables' option, it does not consult
     the `mysql.plugins' table and does not load plugins listed there.
     `--plugin-load' enables plugins to be loaded even when
     `--skip-grant-tables' is given.  `--plugin-load' also enables
     plugins to be loaded at startup under configurations when plugins
     cannot be loaded at runtime.

     For additional information about plugin loading, see *Note
     server-plugin-loading::.

     This option was added in MySQL 5.1.18.

   * `--port=PORT_NUM', `-P PORT_NUM'

     Options for port

     *Command-Line        `--port=#'        
     Format*                              
                          `-P'            
     *System Variable     `port'          
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3306'          
     *Min Value*          `0'             
     *Max Value*          `65535'         

     The port number to use when listening for TCP/IP connections.  The
     port number must be 1024 or higher unless the server is started by
     the `root' system user.

   * `--port-open-timeout=NUM'

     Options for port-open-timeout

     *Introduced*         5.1.5           
     *Command-Line        `--port-open-timeout=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             

     On some systems, when the server is stopped, the TCP/IP port might
     not become available immediately. If the server is restarted
     quickly afterward, its attempt to reopen the port can fail. This
     option indicates how many seconds the server should wait for the
     TCP/IP port to become free if it cannot be opened. The default is
     not to wait. This option was added in MySQL 5.1.5.

   * `--print-defaults'

     Print the program name and all options that it gets from option
     files.

   * `--remove [SERVICE_NAME]'

     Options for remove

     *Command-Line        `--remove        
     Format*              [service_name]'        

     (Windows only) Remove a MySQL Windows service. The default service
     name is `MySQL' if no SERVICE_NAME value is given. For more
     information, see *Note windows-start-service::.

   * `--safe-mode'

     Options for safe-mode

     *Command-Line        `--safe-mode'        
     Format*                              

     Skip some optimization stages. This option is deprecated and is
     removed in MySQL 5.6.

   * `--safe-show-database'

     Options for safe-show-database

     *Deprecated*         4.0.2           
     *Command-Line        `--safe-show-database'        
     Format*                              
     *System Variable     `safe_show_database'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     This option is deprecated and does not do anything because there
     is a *Note `SHOW DATABASES': show-databases.  privilege that can
     be used to control access to database names on a per-account
     basis. See *Note privileges-provided::.  `--safe-show-database' is
     removed in MySQL 5.5.

   * `--safe-user-create'

     Options for safe-user-create

     *Command-Line        `--safe-user-create'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     If this option is enabled, a user cannot create new MySQL users by
     using the *Note `GRANT': grant.  statement unless the user has the
     `INSERT' privilege for the `mysql.user' table or any column in the
     table. If you want a user to have the ability to create new users
     that have those privileges that the user has the right to grant,
     you should grant the user the following privilege:


          GRANT INSERT(user) ON mysql.user TO 'USER_NAME'@'HOST_NAME';

     This ensures that the user cannot change any privilege columns
     directly, but has to use the *Note `GRANT': grant. statement to
     give privileges to other users.

   * `--secure-auth'

     Options for secure-auth

     *Command-Line        `--secure-auth'        
     Format*                              
     *System Variable     `secure_auth'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     This option causes the server to block connections by clients that
     attempt to use accounts that have passwords stored in the old
     (pre-4.1) format. Use it to prevent all use of passwords employing
     the old format (and hence insecure communication over the network).

     Server startup fails with an error if this option is enabled and
     the privilege tables are in pre-4.1 format. See *Note old-client::.

     The *Note `mysql': mysql. client also has a `--secure-auth'
     option, which prevents connections to a server if the server
     requires a password in old format for the client account.

   * `--secure-file-priv=PATH'

     Options for secure-file-priv

     *Introduced*         5.1.17          
     *Command-Line        `--secure-file-priv=path'        
     Format*                              
     *System Variable     `secure_file_priv'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This option limits the effect of the `LOAD_FILE()' function and the
     *Note `LOAD DATA': load-data. and *Note `SELECT ... INTO OUTFILE':
     select-into. statements to work only with files in the specified
     directory.

     This option was added in MySQL 5.1.17.

   * `--shared-memory'

     Options for shared_memory

     *Command-Line        `--shared-memory-base-name=name'        
     Format*                              
     *System Variable     `shared_memory'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Windows         

     Enable shared-memory connections by local clients. This option is
     available only on Windows.

   * `--shared-memory-base-name=NAME'

     Options for shared_memory_base_name

     *System Variable     `shared_memory_base_name'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Windows         

     The name of shared memory to use for shared-memory connections.
     This option is available only on Windows. The default name is
     `MYSQL'. The name is case sensitive.

   * `--skip-concurrent-insert'

     Turn off the ability to select and insert at the same time on
     `MyISAM' tables. (This is to be used only if you think you have
     found a bug in this feature.) See *Note concurrent-inserts::.

   * `--skip-event-scheduler'

     Options for skip-event-scheduler

     *Command-Line        `--skip-event-scheduler'        
     Format*                              
                          `--disable-event-scheduler'        

     Turns the Event Scheduler `OFF'. This is not the same as disabling
     the Event Scheduler, which requires setting
     `--event-scheduler=DISABLED'; see The `--event-scheduler' Option,
     for more information.

   * `--skip-grant-tables'

     This option causes the server to start without using the privilege
     system at all, which gives anyone with access to the server
     _unrestricted access to all databases_. You can cause a running
     server to start using the grant tables again by executing *Note
     `mysqladmin flush-privileges': mysqladmin. or *Note `mysqladmin
     reload': mysqladmin. command from a system shell, or by issuing a
     MySQL *Note `FLUSH PRIVILEGES': flush. statement after connecting
     to the server.  This option also suppresses loading of plugins
     that were installed with the *Note `INSTALL PLUGIN':
     install-plugin. statement, user-defined functions (UDFs), and,
     beginning with MySQL 5.1.17, scheduled events. To cause plugins to
     be loaded anyway, use the `--plugin-load' option.

     Note that *Note `FLUSH PRIVILEGES': flush. might be executed
     implicitly by other actions performed after startup. For example,
     *Note `mysql_upgrade': mysql-upgrade. flushes the privileges during
     the upgrade procedure.

     `--skip-grant-tables' is unavailable if MySQL was configured with
     the `--disable-grant-options' option. See *Note
     source-configuration-options::.

   * `--skip-host-cache'

     Disable use of the internal host cache for faster name-to-IP
     resolution. In this case, the server performs a DNS lookup every
     time a client connects. See *Note host-cache::.

   * `--skip-innodb'

     Disable the `InnoDB' storage engine. In this case, the server will
     not start if the default storage engine is set to *Note `InnoDB':
     innodb-storage-engine. Use `--default-storage-engine' to set the
     default to some other engine if necessary.

   * `--skip-merge'

     Disable the `MERGE' storage engine. This option was added in MySQL
     5.1.12 and removed in 5.1.14.

   * `--skip-name-resolve'

     Do not resolve host names when checking client connections.  Use
     only IP addresses. If you use this option, all `Host' column
     values in the grant tables must be IP addresses or `localhost'. See
     *Note host-cache::.

     Depending on the network configuration of your system and the
     `Host' values for your accounts, clients may need to connect using
     an explicit `--host' option, such as `--host=localhost' or
     `--host=127.0.0.1'.

   * `--skip-networking'

     Do not listen for TCP/IP connections at all. All interaction with
     *Note `mysqld': mysqld. must be made using named pipes or shared
     memory (on Windows) or Unix socket files (on Unix).  This option
     is highly recommended for systems where only local clients are
     permitted. See *Note host-cache::.

   * `--skip-partition'

     Options for skip-partition

     *Command-Line        `--skip-partition'        
     Format*                              
                          `--disable-partition'        

     Disables user-defined partitioning. Partitioned tables can be seen
     using *Note `SHOW TABLES': show-tables. or by querying the *Note
     `INFORMATION_SCHEMA.TABLES': tables-table. table, but cannot be
     created or modified, nor can data in such tables be accessed. All
     partition-specific columns in the *Note
     `INFORMATION_SCHEMA.PARTITIONS': partitions-table.  table display
     `NULL'.

     Since *Note `DROP TABLE': drop-table. removes table definition
     (`.frm') files, this statement works on partitioned tables even
     when partitioning is disabled using the option. The statement,
     however, does not remove `.par' files associated with partitioned
     tables in such cases. For this reason, you should avoid dropping
     partitioned tables with partitioning disabled, or take action to
     remove the orphaned `.par' files manually.

   * `--ssl*'

     Options that begin with `--ssl' specify whether to permit clients
     to connect using SSL and indicate where to find SSL keys and
     certificates. See *Note ssl-options::.

   * `--standalone'

     Options for standalone

     *Command-Line        `--standalone'        
     Format*                              
     *Platform Specific*  Windows         

     Available on Windows only; instructs the MySQL server not to run
     as a service.

   * `--symbolic-links', `--skip-symbolic-links'

     Options for symbolic-links

     *Command-Line        `--symbolic-links'        
     Format*                              

     Enable or disable symbolic link support. This option has different
     effects on Windows and Unix:

        * On Windows, enabling symbolic links enables you to establish
          a symbolic link to a database directory by creating a
          `DB_NAME.sym' file that contains the path to the real
          directory. See *Note windows-symbolic-links::.

        * On Unix, enabling symbolic links means that you can link a
          `MyISAM' index file or data file to another directory with
          the `INDEX DIRECTORY' or `DATA DIRECTORY' options of the
          *Note `CREATE TABLE': create-table.  statement. If you delete
          or rename the table, the files that its symbolic links point
          to also are deleted or renamed. See *Note
          symbolic-links-to-tables::.

   * `--skip-safemalloc'

     Options for skip-safemalloc

     *Command-Line        `--skip-safemalloc'        
     Format*                              

     If MySQL is configured with `--with-debug=full', all MySQL
     programs check for memory overruns during each memory allocation
     and memory freeing operation. This checking is very slow, so for
     the server you can avoid it when you do not need it by using the
     `--skip-safemalloc' option.

   * `--skip-show-database'

     Options for skip-show-database

     *Command-Line        `--skip-show-database'        
     Format*                              
     *System Variable     `skip_show_database'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     This option sets the `skip_show_database' system variable that
     controls who is permitted to use the *Note `SHOW DATABASES':
     show-databases. statement. See *Note server-system-variables::.

   * `--skip-stack-trace'

     Options for skip-stack-trace

     *Command-Line        `--skip-stack-trace'        
     Format*                              

     Do not write stack traces. This option is useful when you are
     running *Note `mysqld': mysqld. under a debugger. On some systems,
     you also must use this option to get a core file. See *Note
     porting::.

   * `--skip-thread-priority'

     Options for skip-thread-priority

     *Deprecated*         5.1.29          
     *Command-Line        `--skip-thread-priority'        
     Format*                              

     Disable using thread priorities for faster response time. This
     option is deprecated as of MySQL 5.1.29 and is removed in MySQL
     5.6.

     Prior to MySQL 5.1.29, *Note `mysqld': mysqld. makes a large
     number of invalid calls to thread scheduling routines on Linux.
     These calls do not affect performance noticeably but may be a
     source of `noise' for debugging tools.  For example, they can
     overwhelm other information of more interest in kernel logs. To
     avoid these calls, start the server with the
     `--skip-thread-priority' option.

   * `--slow-query-log[={0|1}]'

     Options for slow-query-log

     *Introduced*         5.1.12          
     *Command-Line        `--slow-query-log'from    
     Format*                      5.1.29  
     *System Variable     `slow_query_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Specify the initial slow query log state. With no argument or an
     argument of 1, the `--slow-query-log' option enables the log. If
     omitted or given with an argument of 0, the option disables the
     log. This option was added in MySQL 5.1.12.

   * `--socket=PATH'

     Options for socket

     *Command-Line        `--socket=file_name'        
     Format*                              
     *System Variable     `socket'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `/tmp/mysql.sock'        

     On Unix, this option specifies the Unix socket file to use when
     listening for local connections. The default value is
     `/tmp/mysql.sock'. If this option is given, the server creates the
     file in the data directory unless an absolute path name is given
     to specify a different directory.  On Windows, the option
     specifies the pipe name to use when listening for local
     connections that use a named pipe. The default value is `MySQL'
     (not case sensitive).

   * `--sql-mode=VALUE[,VALUE[,VALUE...]]'

     Options for sql-mode

     *Command-Line        `--sql-mode=name'        
     Format*                              
     *System Variable     `sql_mode'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `set'           
     *Default*            `'''            
     *Valid Values*       `ALLOW_INVALID_DATES'        
     `ANSI_QUOTES'                        
     `ERROR_FOR_DIVISION_BY_ZERO'                
     `HIGH_NOT_PRECEDENCE'                
     `IGNORE_SPACE'                       
     `NO_AUTO_CREATE_USER'                
     `NO_AUTO_VALUE_ON_ZERO'                
     `NO_BACKSLASH_ESCAPES'                
     `NO_DIR_IN_CREATE'                   
     `NO_ENGINE_SUBSTITUTION'                
     `NO_FIELD_OPTIONS'                   
     `NO_KEY_OPTIONS'                     
     `NO_TABLE_OPTIONS'                   
     `NO_UNSIGNED_SUBTRACTION'                
     `NO_ZERO_DATE'                       
     `NO_ZERO_IN_DATE'                    
     `ONLY_FULL_GROUP_BY'                 
     `PAD_CHAR_TO_FULL_LENGTH'                
     `PIPES_AS_CONCAT'                    
     `REAL_AS_FLOAT'                      
     `STRICT_ALL_TABLES'                  
     `STRICT_TRANS_TABLES'                

     Set the SQL mode. See *Note sql-mode::.

     *Note*:

     MySQL installation programs may configure the SQL mode during the
     installation process. If the SQL mode differs from the default or
     from what you expect, check for a setting in an option file that
     the server reads at startup.

   * `--sysdate-is-now'

     Options for sysdate-is-now

     *Introduced*         5.1.8           
     *Command-Line        `--sysdate-is-now'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     `SYSDATE()' by default returns the time at which it executes, not
     the time at which the statement in which it occurs begins
     executing. This differs from the behavior of `NOW()'.  This option
     causes `SYSDATE()' to be an alias for `NOW()'. For information
     about the implications for binary logging and replication, see the
     description for `SYSDATE()' in *Note date-and-time-functions:: and
     for `SET TIMESTAMP' in *Note server-system-variables::.

     This option was added in MySQL 5.1.8.

   * `--tc-heuristic-recover={COMMIT|ROLLBACK}'

     Options for tc-heuristic-recover

     *Command-Line        `--tc-heuristic-recover=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `COMMIT'        
     *Valid Values*       `COMMIT'        
     `ROLLBACK'                           

     The type of decision to use in the heuristic recovery process.
     Currently, this option is unused.

   * `--temp-pool'

     Options for temp-pool

     *Command-Line        `--temp-pool'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     This option causes most temporary files created by the server to
     use a small set of names, rather than a unique name for each new
     file. This works around a problem in the Linux kernel dealing with
     creating many new files with different names.  With the old
     behavior, Linux seems to `leak' memory, because it is being
     allocated to the directory entry cache rather than to the disk
     cache. As of MySQL 5.1.31, this option is ignored except on Linux.

   * `--transaction-isolation=LEVEL'

     Options for transaction-isolation

     *Command-Line        `--transaction-isolation=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `REPEATABLE-READ'        
     *Valid Values*       `READ-UNCOMMITTED'        
     `READ-COMMITTED'                     
     `REPEATABLE-READ'                    
     `SERIALIZABLE'                       

     Sets the default transaction isolation level. The `level' value
     can be `READ-UNCOMMITTED', `READ-COMMITTED', `REPEATABLE-READ', or
     `SERIALIZABLE'. See *Note set-transaction::.

     The default transaction isolation level can also be set at runtime
     using the *Note `SET TRANSACTION': set-transaction. statement or
     by setting the `tx_isolation' system variable.

   * `--tmpdir=PATH', `-t PATH'

     Options for tmpdir

     *Command-Line        `--tmpdir=path'        
     Format*                              
                          `-t'            
     *System Variable     `tmpdir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The path of the directory to use for creating temporary files.  It
     might be useful if your default `/tmp' directory resides on a
     partition that is too small to hold temporary tables. This option
     accepts several paths that are used in round-robin fashion. Paths
     should be separated by colon characters (``:'') on Unix and
     semicolon characters (``;'') on Windows, NetWare, and OS/2. If the
     MySQL server is acting as a replication slave, you should not set
     `--tmpdir' to point to a directory on a memory-based file system
     or to a directory that is cleared when the server host restarts.
     For more information about the storage location of temporary
     files, see *Note temporary-files::. A replication slave needs some
     of its temporary files to survive a machine restart so that it can
     replicate temporary tables or *Note `LOAD DATA INFILE': load-data.
     operations. If files in the temporary file directory are lost when
     the server restarts, replication fails.

   * `--user={USER_NAME|USER_ID}', `-u {USER_NAME|USER_ID}'

     Options for user

     *Command-Line        `--user=name'        
     Format*                              
                          `-u             
                          name'           
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Run the *Note `mysqld': mysqld. server as the user having the name
     USER_NAME or the numeric user ID USER_ID.  (`User' in this context
     refers to a system login account, not a MySQL user listed in the
     grant tables.)

     This option is _mandatory_ when starting *Note `mysqld': mysqld.
     as `root'. The server changes its user ID during its startup
     sequence, causing it to run as that particular user rather than as
     `root'. See *Note security-guidelines::.

     To avoid a possible security hole where a user adds a
     `--user=root' option to a `my.cnf' file (thus causing the server to
     run as `root'), *Note `mysqld': mysqld.  uses only the first
     `--user' option specified and produces a warning if there are
     multiple `--user' options. Options in `/etc/my.cnf' and
     `$MYSQL_HOME/my.cnf' are processed before command-line options, so
     it is recommended that you put a `--user' option in `/etc/my.cnf'
     and specify a value other than `root'. The option in `/etc/my.cnf'
     is found before any other `--user' options, which ensures that the
     server runs as a user other than `root', and that a warning
     results if any other `--user' option is found.

   * `--verbose', `-v'

     Use this option with the `--help' option for detailed help.

   * `--version', `-V'

     Display version information and exit.

You can assign a value to a server system variable by using an option
of the form `--VAR_NAME=VALUE'.  For example, `--key_buffer_size=32M'
sets the `key_buffer_size' variable to a value of 32MB.

Note that when you assign a value to a variable, MySQL might
automatically correct the value to stay within a given range, or adjust
the value to the closest permissible value if only certain values are
permitted.

If you want to restrict the maximum value to which a variable can be
set at runtime with *Note `SET': set-statement, you can define this by
using the `--maximum-VAR_NAME=VALUE' command-line option.

You can change the values of most system variables for a running server
with the *Note `SET': set-statement.  statement. See *Note
set-statement::.

*Note server-system-variables::, provides a full description for all
variables, and additional information for setting them at server
startup and runtime.  *Note server-parameters::, includes information on
optimizing the server by tuning system variables.


File: manual.info,  Node: server-system-variables,  Next: using-system-variables,  Prev: server-options,  Up: mysqld-server

5.1.4 Server System Variables
-----------------------------

The MySQL server maintains many system variables that indicate how it
is configured. Each system variable has a default value. System
variables can be set at server startup using options on the command
line or in an option file. Most of them can be changed dynamically
while the server is running by means of the *Note `SET': set-statement.
statement, which enables you to modify operation of the server without
having to stop and restart it. You can refer to system variable values
in expressions.

There are several ways to see the names and values of system variables:

   * To see the values that a server will use based on its compiled-in
     defaults and any option files that it reads, use this command:


          mysqld --verbose --help

   * To see the values that a server will use based on its compiled-in
     defaults, ignoring the settings in any option files, use this
     command:


          mysqld --no-defaults --verbose --help

   * To see the current values used by a running server, use the *Note
     `SHOW VARIABLES': show-variables. statement.

This section provides a description of each system variable.  Variables
with no version indicated are present in all MySQL 5.1 releases. For
historical information concerning their implementation, please see
`http://dev.mysql.com/doc/refman/5.0/en/', and
`http://dev.mysql.com/doc/refman/4.1/en/'.

The following table lists all available system variables.

*System Variable Summary*

Name           Cmd-Line    Option File System Var  Var Scope   Dynamic
auto_increment_increment                        Yes         Both        Yes
auto_increment_offset                        Yes         Both        Yes
autocommit     Yes         Yes         Yes         Session     Yes
automatic_sp_privileges                        Yes         Global      Yes
back_log                               Yes         Global      No
basedir        Yes         Yes         Yes         Global      No
big-tables     Yes         Yes                                 Yes
- _Variable_:                          Yes         Session     Yes
big_tables                                                     
bind-address   Yes         Yes         Yes         Global      No
binlog_cache_sizeYes         Yes         Yes         Global      Yes
binlog_direct_non_transactional_updatesYes         Yes         Yes         Both        Yes
binlog-format  Yes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
binlog_format                                                  
bulk_insert_buffer_sizeYes         Yes         Yes         Both        Yes
character_set_client                        Yes         Both        Yes
character_set_connection                        Yes         Both        Yes
character_set_database                        Yes         Both        Yes
This option                                                    
is dynamic,                                                    
but only the                                                   
server should                                                  
set this                                                       
information.                                                   
You should                                                     
not set the                                                    
value of this                                                  
variable                                                       
manually.                                                      
character-set-filesystemYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
character_set_filesystem                                                
character_set_results                        Yes         Both        Yes
character-set-serverYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
character_set_server                                                
character_set_system                        Yes         Global      No
character-sets-dirYes         Yes                                 No
- _Variable_:                          Yes         Global      No
character_sets_dir                                                
collation_connection                        Yes         Both        Yes
collation_database                        Yes         Both        Yes
This option                                                    
is dynamic,                                                    
but only the                                                   
server should                                                  
set this                                                       
information.                                                   
You should                                                     
not set the                                                    
value of this                                                  
variable                                                       
manually.                                                      
collation-serverYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
collation_server                                                
completion_typeYes         Yes         Yes         Both        Yes
concurrent_insertYes         Yes         Yes         Global      Yes
connect_timeoutYes         Yes         Yes         Global      Yes
datadir        Yes         Yes         Yes         Global      No
date_format                            Yes         Both        No
datetime_format                        Yes         Both        No
debug          Yes         Yes         Yes         Both        Yes
debug_sync                             Yes         Both        Yes
default-storage-engineYes         Yes         Yes         Both        Yes
default_week_formatYes         Yes         Yes         Both        Yes
delay-key-writeYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
delay_key_write                                                
delayed_insert_limitYes         Yes         Yes         Global      Yes
delayed_insert_timeoutYes         Yes         Yes         Global      Yes
delayed_queue_sizeYes         Yes         Yes         Global      Yes
div_precision_incrementYes         Yes         Yes         Both        Yes
engine-condition-pushdownYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
engine_condition_pushdown                                                
error_count                            Yes         Session     No
event-schedulerYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
event_scheduler                                                
expire_logs_daysYes         Yes         Yes         Global      Yes
flush          Yes         Yes         Yes         Global      Yes
flush_time     Yes         Yes         Yes         Global      Yes
foreign_key_checks                        Yes         Session     Yes
ft_boolean_syntaxYes         Yes         Yes         Global      Yes
ft_max_word_lenYes         Yes         Yes         Global      No
ft_min_word_lenYes         Yes         Yes         Global      No
ft_query_expansion_limitYes         Yes         Yes         Global      No
ft_stopword_fileYes         Yes         Yes         Global      No
general-log    Yes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
general_log                                                    
general_log_fileYes         Yes         Yes         Global      Yes
group_concat_max_lenYes         Yes         Yes         Both        Yes
have_archive                           Yes         Global      No
have_blackhole_engine                        Yes         Global      No
have_community_features                        Yes         Global      No
have_compress                          Yes         Global      No
have_crypt                             Yes         Global      No
have_csv                               Yes         Global      No
have_dynamic_loading                        Yes         Global      No
have_example_engine                        Yes         Global      No
have_federated_engine                        Yes         Global      No
have_geometry                          Yes         Global      No
have_innodb                            Yes         Global      No
have_isam                              Yes         Global      No
have_merge_engine                        Yes         Global      No
have_ndbcluster                        Yes         Global      No
have_openssl                           Yes         Global      No
have_partition_engine                        Yes         Global      No
have_partitioning                        Yes         Global      No
have_query_cache                        Yes         Global      No
have_raid                              Yes         Global      No
have_row_based_replication                        Yes         Global      No
have_rtree_keys                        Yes         Global      No
have_ssl                               Yes         Global      No
have_symlink                           Yes         Global      No
hostname                               Yes         Global      No
identity                               Yes         Session     Yes
ignore-builtin-innodbYes         Yes                                 No
- _Variable_:                          Yes         Global      No
ignore_builtin_innodb                                                
init_connect   Yes         Yes         Yes         Global      Yes
init-file      Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
init_file                                                      
init_slave     Yes         Yes         Yes         Global      Yes
innodb_adaptive_flushingYes         Yes         Yes         Global      Yes
innodb_adaptive_hash_indexYes         Yes         Yes         Global      No
innodb_additional_mem_pool_sizeYes         Yes         Yes         Global      No
innodb_autoextend_incrementYes         Yes         Yes         Global      Yes
innodb_autoinc_lock_modeYes         Yes         Yes         Global      No
innodb_buffer_pool_awe_mem_mbYes         Yes         Yes         Global      No
innodb_buffer_pool_sizeYes         Yes         Yes         Global      No
innodb_change_bufferingYes         Yes         Yes         Global      Yes
innodb_checksumsYes         Yes         Yes         Global      No
innodb_commit_concurrencyYes         Yes         Yes         Global      Yes
innodb_concurrency_ticketsYes         Yes         Yes         Global      Yes
innodb_data_file_pathYes         Yes         Yes         Global      No
innodb_data_home_dirYes         Yes         Yes         Global      No
innodb_doublewriteYes         Yes         Yes         Global      No
innodb_fast_shutdownYes         Yes         Yes         Global      Yes
innodb_file_formatYes         Yes         Yes         Global      Yes
innodb_file_format_checkYes         Yes         Yes         Global      Yes
innodb_file_io_threadsYes         Yes         Yes         Global      No
innodb_file_per_tableYes         Yes         Yes         Global      No
innodb_flush_log_at_trx_commitYes         Yes         Yes         Global      Yes
innodb_flush_methodYes         Yes         Yes         Global      No
innodb_force_recoveryYes         Yes         Yes         Global      No
innodb_io_capacityYes         Yes         Yes         Global      No
innodb_lock_wait_timeoutYes         Yes         Yes         Both        No
innodb_locks_unsafe_for_binlogYes         Yes         Yes         Global      No
innodb_log_arch_dirYes         Yes         Yes         Global      No
innodb_log_archiveYes         Yes         Yes         Global      No
innodb_log_buffer_sizeYes         Yes         Yes         Global      No
innodb_log_file_sizeYes         Yes         Yes         Global      No
innodb_log_files_in_groupYes         Yes         Yes         Global      No
innodb_log_group_home_dirYes         Yes         Yes         Global      No
innodb_max_dirty_pages_pctYes         Yes         Yes         Global      Yes
innodb_max_purge_lagYes         Yes         Yes         Global      Yes
innodb_mirrored_log_groupsYes         Yes         Yes         Global      No
innodb_old_blocks_pctYes         Yes         Yes         Global      Yes
innodb_old_blocks_timeYes         Yes         Yes         Global      Yes
innodb_open_filesYes         Yes         Yes         Global      No
innodb_random_read_aheadYes         Yes         Yes         Global      Yes
innodb_read_ahead_thresholdYes         Yes         Yes         Global      Yes
innodb_read_io_threadsYes         Yes         Yes         Global      No
innodb_replication_delayYes         Yes         Yes         Global      Yes
innodb_rollback_on_timeoutYes         Yes         Yes         Global      No
innodb_spin_wait_delayYes         Yes         Yes         Global      Yes
innodb_stats_methodYes         Yes         Yes         Global      Yes
innodb_stats_on_metadataYes         Yes         Yes         Global      Yes
innodb_stats_sample_pagesYes         Yes         Yes         Global      Yes
innodb_strict_modeYes         Yes         Yes         Both        Yes
innodb_support_xaYes         Yes         Yes         Both        Yes
innodb_sync_spin_loopsYes         Yes         Yes         Global      Yes
innodb_table_locksYes         Yes         Yes         Both        Yes
innodb_thread_concurrencyYes         Yes         Yes         Global      Yes
innodb_thread_sleep_delayYes         Yes         Yes         Global      Yes
innodb_use_legacy_cardinality_algorithmYes         Yes         Yes         Global      Yes
innodb_use_sys_mallocYes         Yes         Yes         Global      No
innodb_version                         Yes         Global      No
innodb_write_io_threadsYes         Yes         Yes         Global      No
insert_id                              Yes         Session     Yes
interactive_timeoutYes         Yes         Yes         Both        Yes
join_buffer_sizeYes         Yes         Yes         Both        Yes
keep_files_on_createYes         Yes         Yes         Both        Yes
key_buffer_sizeYes         Yes         Yes         Global      Yes
key_cache_age_thresholdYes         Yes         Yes         Global      Yes
key_cache_block_sizeYes         Yes         Yes         Global      Yes
key_cache_division_limitYes         Yes         Yes         Global      Yes
language       Yes         Yes         Yes         Global      No
large_files_support                        Yes         Global      No
large_page_size                        Yes         Global      No
large-pages    Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
large_pages                                                    
last_insert_id                         Yes         Session     Yes
lc_time_names                          Yes         Both        Yes
license                                Yes         Global      No
local_infile                           Yes         Global      Yes
locked_in_memory                        Yes         Global      No
log            Yes         Yes         Yes         Global      Yes
log_bin                                Yes         Global      No
log-bin        Yes         Yes         Yes         Global      No
log-bin-trust-function-creatorsYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
log_bin_trust_function_creators                                                
log-bin-trust-routine-creatorsYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
log_bin_trust_routine_creators                                                
(http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html#sysvar_log_bin_trust_routine_creators)                                                
log_bin_use_v1_row_eventsYes         Yes         Yes         Global      No
log-bin-use-v1-row-eventsYes         Yes                                 No
- _Variable_:                          Yes         Global      No
log_bin_use_v1_row_events                                                
log-error      Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
log_error                                                      
log-output     Yes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
log_output                                                     
log-queries-not-using-indexesYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
log_queries_not_using_indexes                                                
log-slave-updatesYes         Yes                                 No
- _Variable_:                          Yes         Global      No
log_slave_updates                                                
log_slave_updatesYes         Yes         Yes         Global      No
log-slow-queriesYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
log_slow_queries                                                
log-warnings   Yes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
log_warnings                                                   
long_query_timeYes         Yes         Yes         Both        Yes
low-priority-updatesYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
low_priority_updates                                                
lower_case_file_system                        Yes         Global      No
lower_case_table_namesYes         Yes         Yes         Global      No
max_allowed_packetYes         Yes         Yes         Global      Yes
max_binlog_cache_sizeYes         Yes         Yes         Global      Yes
max_binlog_sizeYes         Yes         Yes         Global      Yes
max_connect_errorsYes         Yes         Yes         Global      Yes
max_connectionsYes         Yes         Yes         Global      Yes
max_delayed_threadsYes         Yes         Yes         Both        Yes
max_error_countYes         Yes         Yes         Both        Yes
max_heap_table_sizeYes         Yes         Yes         Both        Yes
max_insert_delayed_threads                        Yes         Both        Yes
max_join_size  Yes         Yes         Yes         Both        Yes
max_length_for_sort_dataYes         Yes         Yes         Both        Yes
max_long_data_sizeYes         Yes         Yes         Global      No
max_prepared_stmt_countYes         Yes         Yes         Global      Yes
max_relay_log_sizeYes         Yes         Yes         Global      Yes
max_seeks_for_keyYes         Yes         Yes         Both        Yes
max_sort_lengthYes         Yes         Yes         Both        Yes
max_sp_recursion_depthYes         Yes         Yes         Both        Yes
max_user_connectionsYes         Yes         Yes         Both        Yes
max_write_lock_countYes         Yes         Yes         Global      Yes
memlock        Yes         Yes         Yes         Global      No
min-examined-row-limitYes         Yes         Yes         Both        Yes
multi_range_countYes         Yes         Yes         Both        Yes
myisam_data_pointer_sizeYes         Yes         Yes         Global      Yes
myisam_max_sort_file_sizeYes         Yes         Yes         Global      Yes
myisam_mmap_sizeYes         Yes         Yes         Global      No
myisam_recover_options                        Yes         Global      No
myisam_repair_threadsYes         Yes         Yes         Both        Yes
myisam_sort_buffer_sizeYes         Yes         Yes         Both        Yes
myisam_stats_methodYes         Yes         Yes         Both        Yes
myisam_use_mmapYes         Yes         Yes         Global      Yes
named_pipe                             Yes         Global      No
ndb_autoincrement_prefetch_szYes         Yes         Yes         Both        Yes
ndb-batch-size Yes         Yes         Yes         Global      No
ndb-blob-read-batch-bytesYes         Yes         Yes         Both        Yes
ndb-blob-write-batch-bytesYes         Yes         Yes         Both        Yes
ndb_cache_check_timeYes         Yes         Yes         Global      Yes
ndb-cluster-connection-poolYes         Yes         Yes         Global      No
ndb-deferred-constraintsYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
ndb_deferred_constraints                                                
ndb_deferred_constraintsYes         Yes         Yes         Both        Yes
ndb_distributionYes         Yes         Yes         Global      Yes
ndb-distributionYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
ndb_distribution                                                
ndb_eventbuffer_max_allocYes         Yes         Yes         Global      Yes
ndb_extra_loggingYes         Yes         Yes         Global      Yes
ndb_force_send Yes         Yes         Yes         Both        Yes
ndb_join_pushdown                        Yes         Both        Yes
ndb-log-apply-statusYes         Yes                                 No
- _Variable_:                          Yes         Global      No
ndb_log_apply_status                                                
ndb_log_apply_statusYes         Yes         Yes         Global      No
ndb_log_bin    Yes                     Yes         Both        Yes
ndb_log_binlog_indexYes                     Yes         Global      Yes
ndb_log_empty_epochsYes         Yes         Yes         Global      Yes
ndb-log-empty-epochsYes         Yes         Yes         Global      Yes
ndb-log-orig   Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
ndb_log_orig                                                   
ndb_log_orig   Yes         Yes         Yes         Global      No
ndb-log-transaction-idYes         Yes                                 No
- _Variable_:                          Yes         Global      No
ndb_log_transaction_id                                                
ndb_log_transaction_id                        Yes         Global      No
ndb-log-update-as-writeYes         Yes         Yes         Global      Yes
ndb_log_updated_onlyYes         Yes         Yes         Global      Yes
ndb_optimization_delay                        Yes         Global      Yes
ndb_table_no_logging                        Yes         Session     Yes
ndb_table_temporary                        Yes         Session     Yes
ndb_use_copying_alter_table                        Yes         Both        No
ndb_use_exact_count                        Yes         Both        Yes
ndb_use_transactionsYes         Yes         Yes         Both        Yes
ndb_version                            Yes         Global      No
ndb_version_string                        Yes         Global      No
ndb-wait-connectedYes         Yes         Yes         Global      No
ndb-wait-setup Yes         Yes         Yes         Global      No
ndbinfo_database                        Yes         Global      No
ndbinfo_max_bytesYes                     Yes         Both        Yes
ndbinfo_max_rowsYes                     Yes         Both        Yes
ndbinfo_offline                        Yes         Global      Yes
ndbinfo_show_hiddenYes                     Yes         Both        Yes
ndbinfo_table_prefixYes                     Yes         Both        Yes
ndbinfo_version                        Yes         Global      No
net_buffer_lengthYes         Yes         Yes         Both        Yes
net_read_timeoutYes         Yes         Yes         Both        Yes
net_retry_countYes         Yes         Yes         Both        Yes
net_write_timeoutYes         Yes         Yes         Both        Yes
new            Yes         Yes         Yes         Both        Yes
old            Yes         Yes         Yes         Global      No
old-alter-tableYes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
old_alter_table                                                
old_passwords                          Yes         Both        Yes
open-files-limitYes         Yes                                 No
- _Variable_:                          Yes         Global      No
open_files_limit                                                
optimizer_prune_levelYes         Yes         Yes         Both        Yes
optimizer_search_depthYes         Yes         Yes         Both        Yes
optimizer_switchYes         Yes         Yes         Both        Yes
pid-file       Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
pid_file                                                       
plugin_dir     Yes         Yes         Yes         Global      No
port           Yes         Yes         Yes         Global      No
preload_buffer_sizeYes         Yes         Yes         Both        Yes
prepared_stmt_count                        Yes         Global      No
profiling                              Yes         Session     Yes
profiling_history_sizeYes         Yes         Yes         Both        Yes
protocol_version                        Yes         Global      No
pseudo_thread_id                        Yes         Session     Yes
query_alloc_block_sizeYes         Yes         Yes         Both        Yes
query_cache_limitYes         Yes         Yes         Global      Yes
query_cache_min_res_unitYes         Yes         Yes         Global      Yes
query_cache_sizeYes         Yes         Yes         Global      Yes
query_cache_typeYes         Yes         Yes         Both        Yes
query_cache_wlock_invalidateYes         Yes         Yes         Both        Yes
query_prealloc_sizeYes         Yes         Yes         Both        Yes
rand_seed1                             Yes         Session     Yes
rand_seed2                             Yes         Session     Yes
range_alloc_block_sizeYes         Yes         Yes         Both        Yes
read_buffer_sizeYes         Yes         Yes         Both        Yes
read_only      Yes         Yes         Yes         Global      Yes
read_rnd_buffer_sizeYes         Yes         Yes         Both        Yes
relay-log      Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
relay_log                                                      
relay-log-indexYes         Yes                                 No
- _Variable_:                          Yes         Global      No
relay_log_index                                                
relay_log_indexYes         Yes         Yes         Global      No
relay_log_info_fileYes         Yes         Yes         Global      No
relay_log_purgeYes         Yes         Yes         Global      Yes
relay_log_space_limitYes         Yes         Yes         Global      No
report-host    Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
report_host                                                    
report-passwordYes         Yes                                 No
- _Variable_:                          Yes         Global      No
report_password                                                
report-port    Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
report_port                                                    
report-user    Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
report_user                                                    
rpl_recovery_rank                        Yes         Global      Yes
safe-show-databaseYes         Yes         Yes         Global      Yes
secure-auth    Yes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
secure_auth                                                    
secure-file-privYes         Yes                                 No
- _Variable_:                          Yes         Global      No
secure_file_priv                                                
server-id      Yes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
server_id                                                      
server_id_bits Yes         Yes         Yes         Global      No
server-id-bits Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
server_id_bits                                                 
shared_memory  Yes         Yes         Yes         Global      No
shared_memory_base_name                        Yes         Global      No
skip_external_lockingYes         Yes         Yes         Global      No
skip-name-resolveYes         Yes                                 No
- _Variable_:                          Yes         Global      No
skip_name_resolve                                                
skip-networkingYes         Yes                                 No
- _Variable_:                          Yes         Global      No
skip_networking                                                
skip-show-databaseYes         Yes                                 No
- _Variable_:                          Yes         Global      No
skip_show_database                                                
slave_allow_batchingYes         Yes         Yes         Global      Yes
slave_compressed_protocolYes         Yes         Yes         Global      Yes
slave_exec_modeYes         Yes         Yes         Global      Yes
slave-load-tmpdirYes         Yes                                 No
- _Variable_:                          Yes         Global      No
slave_load_tmpdir                                                
slave_max_allowed_packet                        Yes         Global      Yes
slave-net-timeoutYes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
slave_net_timeout                                                
slave-skip-errorsYes         Yes                                 No
- _Variable_:                          Yes         Global      No
slave_skip_errors                                                
slave_transaction_retriesYes         Yes         Yes         Global      Yes
slave_type_conversionsYes         Yes         Yes         Global      No
slow_launch_timeYes         Yes         Yes         Global      Yes
slow-query-log Yes         Yes                                 Yes
- _Variable_:                          Yes         Global      Yes
slow_query_log                                                 
slow_query_log_fileYes         Yes         Yes         Global      Yes
socket         Yes         Yes         Yes         Global      No
sort_buffer_sizeYes         Yes         Yes         Both        Yes
sql_auto_is_null                        Yes         Session     Yes
sql_big_selects                        Yes         Session     Yes
sql_big_tables                         Yes         Session     Yes
sql_buffer_result                        Yes         Session     Yes
sql_log_bin                            Yes         Session     Yes
sql_log_off                            Yes         Session     Yes
sql_log_update                         Yes         Session     Yes
sql_low_priority_updates                        Yes         Both        Yes
sql_max_join_size                        Yes         Both        Yes
sql-mode       Yes         Yes                                 Yes
- _Variable_:                          Yes         Both        Yes
sql_mode                                                       
sql_notes                              Yes         Session     Yes
sql_quote_show_create                        Yes         Session     Yes
sql_safe_updates                        Yes         Session     Yes
sql_select_limit                        Yes         Both        Yes
sql_slave_skip_counter                        Yes         Global      Yes
sql_warnings                           Yes         Session     Yes
ssl-ca         Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
ssl_ca                                                         
ssl-capath     Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
ssl_capath                                                     
ssl-cert       Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
ssl_cert                                                       
ssl-cipher     Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
ssl_cipher                                                     
ssl-key        Yes         Yes                                 No
- _Variable_:                          Yes         Global      No
ssl_key                                                        
storage_engine                         Yes         Both        Yes
sync_binlog    Yes         Yes         Yes         Global      Yes
sync_frm       Yes         Yes         Yes         Global      Yes
system_time_zone                        Yes         Global      No
table_cache    Yes         Yes         Yes         Global      Yes
table_definition_cache                        Yes         Global      Yes
table_lock_wait_timeoutYes         Yes         Yes         Global      Yes
table_open_cache                        Yes         Global      Yes
table_type                             Yes         Both        Yes
thread_cache_sizeYes         Yes         Yes         Global      Yes
thread_concurrencyYes         Yes         Yes         Global      No
thread_handlingYes         Yes         Yes         Global      No
thread_stack   Yes         Yes         Yes         Global      No
time_format                            Yes         Both        No
time_zone                              Yes         Both        Yes
timed_mutexes  Yes         Yes         Yes         Global      Yes
timestamp                              Yes         Session     Yes
tmp_table_size Yes         Yes         Yes         Both        Yes
tmpdir         Yes         Yes         Yes         Global      No
transaction_alloc_block_sizeYes         Yes         Yes         Both        Yes
transaction_allow_batching                        Yes         Session     Yes
transaction_prealloc_sizeYes         Yes         Yes         Both        Yes
tx_isolation                           Yes         Both        Yes
unique_checks                          Yes         Session     Yes
updatable_views_with_limitYes         Yes         Yes         Both        Yes
version                                Yes         Global      No
version_comment                        Yes         Global      No
version_compile_machine                        Yes         Global      No
version_compile_os                        Yes         Global      No
wait_timeout   Yes         Yes         Yes         Both        Yes
warning_count                          Yes         Session     No

For additional system variable information, see these sections:

   * *Note using-system-variables::, discusses the syntax for setting
     and displaying system variable values.

   * *Note dynamic-system-variables::, lists the variables that can be
     set at runtime.

   * Information on tuning system variables can be found in *Note
     server-parameters::.

   * *Note innodb-parameters::, lists `InnoDB' system variables.

   * *Note mysql-cluster-system-variables::, lists system variables
     which are specific to MySQL Cluster.

   * For information on server system variables specific to
     replication, see *Note replication-options::.

*Note*:

Some of the following variable descriptions refer to `enabling' or
`disabling' a variable.  These variables can be enabled with the *Note
`SET': set-statement.  statement by setting them to `ON' or `1', or
disabled by setting them to `OFF' or `0'. However, to set such a
variable on the command line or in an option file, you must set it to
`1' or `0'; setting it to `ON' or `OFF' will not work. For example, on
the command line, `--delay_key_write=1' works but
`--delay_key_write=ON' does not.

Some system variables control the size of buffers or caches. For a
given buffer, the server might need to allocate internal data
structures. These structures typically are allocated from the total
memory allocated to the buffer, and the amount of space required might
be platform dependent. This means that when you assign a value to a
system variable that controls a buffer size, the amount of space
actually available might differ from the value assigned. In some cases,
the amount might be less than the value assigned. It is also possible
that the server will adjust a value upward. For example, if you assign
a value of 0 to a variable for which the minimal value is 1024, the
server will set the value to 1024.

Values for buffer sizes, lengths, and stack sizes are given in bytes
unless otherwise specified.

Some system variables take file name values. Unless otherwise
specified, the default file location is the data directory if the value
is a relative path name. To specify the location explicitly, use an
absolute path name. Suppose that the data directory is
`/var/mysql/data'. If a file-valued variable is given as a relative
path name, it will be located under `/var/mysql/data'. If the value is
an absolute path name, its location is as given by the path name.

   * `autocommit'

     Options for autocommit

     *System Variable     `autocommit'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     The autocommit mode. If set to 1, all changes to a table take
     effect immediately. If set to 0, you must use *Note `COMMIT':
     commit. to accept a transaction or *Note `ROLLBACK': commit.  to
     cancel it. If `autocommit' is 0 and you change it to 1, MySQL
     performs an automatic *Note `COMMIT': commit. of any open
     transaction.  Another way to begin a transaction is to use a *Note
     `START TRANSACTION': commit. or *Note `BEGIN': commit.  statement.
     See *Note commit::.

     By default, client connections begin with `autocommit' set to 1.
     To cause clients to begin with a default of 0, set the server's
     `init_connect' system variable:


          SET GLOBAL init_connect='SET autocommit=0';

     The `init_connect' variable can also be set on the command line or
     in an option file. To set the variable as just shown using an
     option file, include these lines:


          [mysqld]
          init_connect='SET autocommit=0'

     The content of `init_connect' is not executed for users that have
     the `SUPER' privilege.

   * `automatic_sp_privileges'

     Options for automatic_sp_privileges

     *System Variable     `automatic_sp_privileges'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     When this variable has a value of 1 (the default), the server
     automatically grants the `EXECUTE' and `ALTER ROUTINE' privileges
     to the creator of a stored routine, if the user cannot already
     execute and alter or drop the routine. (The `ALTER ROUTINE'
     privilege is required to drop the routine.) The server also
     automatically drops those privileges from the creator when the
     routine is dropped. If `automatic_sp_privileges' is 0, the server
     does not automatically add or drop these privileges.

     The creator of a routine is the account used to execute the
     `CREATE' statement for it. This might not be the same as the
     account named as the `DEFINER' in the routine definition.

     See also *Note stored-routines-privileges::.

   * `back_log'

     Options for back_log

     *System Variable     `back_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `50'            
     *Min Value*          `1'             
     *Max Value*          `65535'         

     The number of outstanding connection requests MySQL can have.
     This comes into play when the main MySQL thread gets very many
     connection requests in a very short time. It then takes some time
     (although very little) for the main thread to check the connection
     and start a new thread. The `back_log' value indicates how many
     requests can be stacked during this short time before MySQL
     momentarily stops answering new requests. You need to increase
     this only if you expect a large number of connections in a short
     period of time.

     In other words, this value is the size of the listen queue for
     incoming TCP/IP connections. Your operating system has its own
     limit on the size of this queue. The manual page for the Unix
     `listen()' system call should have more details. Check your OS
     documentation for the maximum value for this variable. `back_log'
     cannot be set higher than your operating system limit.

   * `basedir'

     Options for basedir

     *Command-Line        `--basedir=path'        
     Format*                              
                          `-b'            
     *System Variable     `basedir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The MySQL installation base directory. This variable can be set
     with the `--basedir' option.  Relative path names for other
     variables usually are resolved relative to the base directory.

   * `big_tables'

     If set to 1, all temporary tables are stored on disk rather than
     in memory. This is a little slower, but the error `The table
     TBL_NAME is full' does not occur for *Note `SELECT': select.
     operations that require a large temporary table. The default value
     for a new connection is 0 (use in-memory temporary tables).
     Normally, you should never need to set this variable, because
     in-memory tables are automatically converted to disk-based tables
     as required.

     *Note*:

     This variable was formerly named `sql_big_tables'.

   * `bulk_insert_buffer_size'

     Options for bulk_insert_buffer_size

     *Command-Line        `--bulk_insert_buffer_size=#'        
     Format*                              
     *System Variable     `bulk_insert_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `8388608'        
     *Min Value*          `0'             
     *Max Value*          `18446744073709547520'        

     `MyISAM' uses a special tree-like cache to make bulk inserts
     faster for *Note `INSERT ... SELECT': insert-select, `INSERT ...
     VALUES (...), (...), ...', and *Note `LOAD DATA INFILE':
     load-data. when adding data to nonempty tables. This variable
     limits the size of the cache tree in bytes per thread. Setting it
     to 0 disables this optimization. The default value is 8MB.

   * `character_set_client'

     Options for character_set_client

     *System Variable     `character_set_client'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The character set for statements that arrive from the client.  The
     session value of this variable is set using the character set
     requested by the client when the client connects to the server.
     (Many clients support a `--default-character-set' option to enable
     this character set to be specified explicitly. See also *Note
     charset-connection::.) The global value of the variable is used to
     set the session value in cases when the client-requested value is
     unknown or not available, or the server is configured to ignore
     client requests:

        * The client is from a version of MySQL older than MySQL 4.1,
          and thus does not request a character set.

        * The client requests a character set not known to the server.
          For example, a Japanese-enabled client requests `sjis' when
          connecting to a server not configured with `sjis' support.

        * *Note `mysqld': mysqld. was started with the
          `--skip-character-set-client-handshake' option, which causes
          it to ignore client character set configuration. This
          reproduces MySQL 4.0 behavior and is useful should you wish
          to upgrade the server without upgrading all the clients.

     `ucs2' cannot be used as a client character set, which means that
     it also does not work for `SET NAMES' or `SET CHARACTER SET'.

   * `character_set_connection'

     Options for character_set_connection

     *System Variable     `character_set_connection'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The character set for the current connection. Used for literals
     that do not have an explicit character set specification and for
     number-to-string conversion.

   * `character_set_database'

     Options for character_set_database

     *System Variable     `character_set_database'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
     *Footnote*           This            
                          option          
                          is              
                          dynamic,        
                          but             
                          only            
                          the             
                          server          
                          should          
                          set             
                          this            
                          information.        
                          You             
                          should          
                          not             
                          set             
                          the             
                          value           
                          of              
                          this            
                          variable        
                          manually.        
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The character set used by the default database. The server sets
     this variable whenever the default database changes. If there is
     no default database, the variable has the same value as
     `character_set_server'.

   * `character_set_filesystem'

     Options for character-set-filesystem

     *Introduced*         5.1.6           
     *Command-Line        `--character-set-filesystem=name'        
     Format*                              
     *System Variable     `character_set_filesystem'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `binary'        

     The file system character set. This variable is used to interpret
     string literals that refer to file names, such as in the *Note
     `LOAD DATA INFILE': load-data. and *Note `SELECT ... INTO
     OUTFILE': select-into. statements and the `LOAD_FILE()' function.
     Such file names are converted from `character_set_client' to
     `character_set_filesystem' before the file opening attempt occurs.
     The default value is `binary', which means that no conversion
     occurs. For systems on which multibyte file names are permitted, a
     different value may be more appropriate. For example, if the
     system represents file names using UTF-8, set
     `character_set_filesystem' to `'utf8''. This variable was added in
     MySQL 5.1.6.

   * `character_set_results'

     Options for character_set_results

     *System Variable     `character_set_results'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The character set used for returning query results such as result
     sets or error messages to the client.

   * `character_set_server'

     Options for character-set-server

     *Command-Line        `--character-set-server'        
     Format*                              
     *System Variable     `character_set_server'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `latin1'        

     The server's default character set.

   * `character_set_system'

     Options for character_set_system

     *System Variable     `character_set_system'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `utf8'          

     The character set used by the server for storing identifiers.  The
     value is always `utf8'.

   * `character_sets_dir'

     Options for character-sets-dir

     *Command-Line        `--character-sets-dir=path'        
     Format*                              
     *System Variable     `character_sets_dir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The directory where character sets are installed.

   * `collation_connection'

     Options for collation_connection

     *System Variable     `collation_connection'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The collation of the connection character set.

   * `collation_database'

     Options for collation_database

     *System Variable     `collation_database'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
     *Footnote*           This            
                          option          
                          is              
                          dynamic,        
                          but             
                          only            
                          the             
                          server          
                          should          
                          set             
                          this            
                          information.        
                          You             
                          should          
                          not             
                          set             
                          the             
                          value           
                          of              
                          this            
                          variable        
                          manually.        
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The collation used by the default database. The server sets this
     variable whenever the default database changes. If there is no
     default database, the variable has the same value as
     `collation_server'.

   * `collation_server'

     Options for collation-server

     *Command-Line        `--collation-server'        
     Format*                              
     *System Variable     `collation_server'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `latin1_swedish_ci'        

     The server's default collation.

   * `completion_type'

     Options for completion_type

     *Command-Line        `--completion_type=#'        
     Format*                              
     *System Variable     `completion_type'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Valid Values*       `0'             
     `1'                                  
     `2'                                  

     The transaction completion type. This variable can take the values
     shown in the following table.

     This table describes values that may be specified for the
     `completion_type' system variable.

     Value   Description
     0       *Note `COMMIT': commit. and *Note `ROLLBACK':
             commit.  are unaffected. This is the default
             value.
     1       *Note `COMMIT': commit. and *Note `ROLLBACK':
             commit.  are equivalent to `COMMIT AND CHAIN' and
             `ROLLBACK AND CHAIN', respectively. (A new
             transaction starts immediately with the same
             isolation level as the just-terminated
             transaction.)
     2       *Note `COMMIT': commit. and *Note `ROLLBACK':
             commit.  are equivalent to `COMMIT RELEASE' and
             `ROLLBACK RELEASE', respectively.  (The server
             disconnects after terminating the transaction.)

     `completion_type' affects transactions that begin with *Note
     `START TRANSACTION': commit. or *Note `BEGIN': commit. and end
     with *Note `COMMIT': commit. or *Note `ROLLBACK': commit. It does
     not apply to implicit commits resulting from execution of the
     statements listed in *Note implicit-commit::. It also does not
     apply for *Note `XA COMMIT': xa-statements, *Note `XA ROLLBACK':
     xa-statements, or when `autocommit=1'.

   * `concurrent_insert'

     Options for concurrent_insert

     *Command-Line        `--concurrent_insert[=#]'        
     Format*                              
     *System Variable     `concurrent_insert'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     If 1 (the default), MySQL permits *Note `INSERT': insert. and
     *Note `SELECT': select. statements to run concurrently for
     `MyISAM' tables that have no free blocks in the middle of the data
     file. If you start *Note `mysqld': mysqld. with `--skip-new', this
     variable is set to 0.

     This variable can take three integer values.

     This table describes values that may be specified for the
     `concurrent_insert' system variable.

     Value   Description
     0       Disables concurrent inserts
     1       (Default) Enables concurrent insert for `MyISAM'
             tables that do not have holes
     2       Enables concurrent inserts for all `MyISAM'
             tables, even those that have holes. For a table
             with a hole, new rows are inserted at the end of
             the table if it is in use by another thread.
             Otherwise, MySQL acquires a normal write lock and
             inserts the row into the hole.

     See also *Note concurrent-inserts::.

   * `connect_timeout'

     Options for connect_timeout

     *Command-Line        `--connect_timeout=#'        
     Format*                              
     *System Variable     `connect_timeout'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.22)*        
     *Type*               `numeric'        
     *Default*            `5'             
     *Min Value*          `2'             
     *Max Value*          `31536000'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.23)*        
     *Type*               `numeric'        
     *Default*            `10'            
     *Min Value*          `2'             
     *Max Value*          `31536000'        

     The number of seconds that the *Note `mysqld': mysqld.  server
     waits for a connect packet before responding with `Bad handshake'.
     The default value is 10 seconds as of MySQL 5.1.23 and 5 seconds
     before that.

     Increasing the `connect_timeout' value might help if clients
     frequently encounter errors of the form `Lost connection to MySQL
     server at 'XXX', system error: ERRNO'.

   * `datadir'

     Options for datadir

     *Command-Line        `--datadir=path'        
     Format*                              
                          `-h'            
     *System Variable     `datadir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The MySQL data directory. This variable can be set with the
     `--datadir' option.

   * `date_format'

     This variable is unused.

   * `datetime_format'

     This variable is unused.

   * `debug'

     Options for debug

     *Command-Line        `--debug[=debug_options]'        
     Format*                              
     *System Variable     `debug'         
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (Unix)        `string'        
     *Default*            `d:t:i:o,/tmp/mysqld.trace'        
                          *Permitted        
                          Values*         
     *Type* (Windows)     `string'        
     *Default*            `d:t:i:O,\mysqld.trace'        

     This variable indicates the current debugging settings. It is
     available only for servers built with debugging support. The
     initial value comes from the value of instances of the `--debug'
     option given at server startup. The global and session values may
     be set at runtime; the `SUPER' privilege is required, even for the
     session value.

     Assigning a value that begins with `+' or `-' cause the value to
     added to or subtracted from the current value:


          mysql> SET debug = 'T';
          mysql> SELECT @@debug;
          +---------+
          | @@debug |
          +---------+
          | T       |
          +---------+

          mysql> SET debug = '+P';
          mysql> SELECT @@debug;
          +---------+
          | @@debug |
          +---------+
          | P:T     |
          +---------+

          mysql> SET debug = '-P';
          mysql> SELECT @@debug;
          +---------+
          | @@debug |
          +---------+
          | T       |
          +---------+

     This variable was added in MySQL 5.1.7.

   * `debug_sync'

     Options for debug_sync

     *Introduced*         5.1.41          
     *System Variable     `debug_sync'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This variable is the user interface to the Debug Sync facility.
     Use of Debug Sync requires that MySQL be configured with the
     `--enable-debug-sync' option (see *Note
     source-configuration-options::).  If Debug Sync is not compiled
     in, this system variable is not available.

     The global variable value is read only and indicates whether the
     facility is enabled. By default, Debug Sync is disabled and the
     value of `debug_sync' is `OFF'. If the server is started with
     `--debug-sync-timeout=N', where N is a timeout value greater than
     0, Debug Sync is enabled and the value of `debug_sync' is `ON -
     current signal' followed by the signal name. Also, N becomes the
     default timeout for individual synchronization points.

     The session value can be read by any user and will have the same
     value as the global variable. The session value can be set by
     users that have the `SUPER' privilege to control synchronization
     points.

     For a description of the Debug Sync facility and how to use
     synchronization points, see MySQL Internals: Test Synchronization
     (http://dev.mysql.com/doc/internals/en/test-synchronization.html).

     This variable was added in MySQL 5.1.41.

   * `default_week_format'

     Options for default_week_format

     *Command-Line        `--default_week_format=#'        
     Format*                              
     *System Variable     `default_week_format'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `7'             

     The default mode value to use for the `WEEK()' function. See *Note
     date-and-time-functions::.

   * `delay_key_write'

     Options for delay-key-write

     *Command-Line        `--delay-key-write[=name]'        
     Format*                              
     *System Variable     `delay_key_write'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `ON'            
     *Valid Values*       `ON'            
     `OFF'                                
     `ALL'                                

     This option applies only to `MyISAM' tables.  It can have one of
     the following values to affect handling of the `DELAY_KEY_WRITE'
     table option that can be used in *Note `CREATE TABLE':
     create-table.  statements.

     This table describes options that may be specified for the
     `delay_key_write' system variable.

     Option  Description
     `OFF'   `DELAY_KEY_WRITE' is ignored.
     `ON'    MySQL honors any `DELAY_KEY_WRITE' option
             specified in *Note `CREATE TABLE': create-table.
             statements. This is the default value.
     `ALL'   All new opened tables are treated as if they were
             created with the `DELAY_KEY_WRITE' option enabled.

     If `DELAY_KEY_WRITE' is enabled for a table, the key buffer is not
     flushed for the table on every index update, but only when the
     table is closed. This speeds up writes on keys a lot, but if you
     use this feature, you should add automatic checking of all
     `MyISAM' tables by starting the server with the `--myisam-recover'
     option (for example, `--myisam-recover=BACKUP,FORCE').  See *Note
     server-options::, and *Note myisam-start::.

     *Warning*:

     If you enable external locking with `--external-locking', there is
     no protection against index corruption for tables that use delayed
     key writes.

   * `delayed_insert_limit'

     Options for delayed_insert_limit

     *Command-Line        `--delayed_insert_limit=#'        
     Format*                              
     *System Variable     `delayed_insert_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `100'           
     *Min Value*          `1'             
     *Max Value*          `18446744073709547520'        

     After inserting `delayed_insert_limit' delayed rows, the *Note
     `INSERT DELAYED': insert-delayed.  handler thread checks whether
     there are any *Note `SELECT': select. statements pending. If so,
     it permits them to execute before continuing to insert delayed
     rows.

   * `delayed_insert_timeout'

     Options for delayed_insert_timeout

     *Command-Line        `--delayed_insert_timeout=#'        
     Format*                              
     *System Variable     `delayed_insert_timeout'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `300'           

     How many seconds an *Note `INSERT DELAYED': insert-delayed.
     handler thread should wait for *Note `INSERT': insert. statements
     before terminating.

   * `delayed_queue_size'

     Options for delayed_queue_size

     *Command-Line        `--delayed_queue_size=#'        
     Format*                              
     *System Variable     `delayed_queue_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `1000'          
     *Min Value*          `1'             
     *Max Value*          `18446744073709547520'        

     This is a per-table limit on the number of rows to queue when
     handling *Note `INSERT DELAYED': insert-delayed.  statements. If
     the queue becomes full, any client that issues an *Note `INSERT
     DELAYED': insert-delayed. statement waits until there is room in
     the queue again.

   * `div_precision_increment'

     Options for div_precision_increment

     *Command-Line        `--div_precision_increment=#'        
     Format*                              
     *System Variable     `div_precision_increment'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `4'             
     *Min Value*          `0'             
     *Max Value*          `30'            

     This variable indicates the number of digits by which to increase
     the scale of the result of division operations performed with the
     `/' operator.  The default value is 4. The minimum and maximum
     values are 0 and 30, respectively. The following example
     illustrates the effect of increasing the default value.


          mysql> SELECT 1/7;
          +--------+
          | 1/7    |
          +--------+
          | 0.1429 |
          +--------+
          mysql> SET div_precision_increment = 12;
          mysql> SELECT 1/7;
          +----------------+
          | 1/7            |
          +----------------+
          | 0.142857142857 |
          +----------------+

     For more information, see *Note dbug-package::.

   * `engine_condition_pushdown'

     Options for engine-condition-pushdown

     *Command-Line        `--engine-condition-pushdown'        
     Format*                              
     *System Variable     `engine_condition_pushdown'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     The engine condition pushdown optimization enables processing for
     certain comparisons to be `pushed down' to the storage engine
     level for more efficient execution. For more information, see
     *Note condition-pushdown-optimization::.

     Engine condition pushdown is used only by the *Note `NDBCLUSTER':
     mysql-cluster. storage engine.  Enabling this optimization on a
     MySQL Server acting as a MySQL Cluster SQL node causes `WHERE'
     conditions on unindexed columns to be evaluated on the cluster's
     data nodes and only the rows that match to be sent back to the SQL
     node that issued the query. This greatly reduces the amount of
     cluster data that must be sent over the network, increasing the
     efficiency with which results are returned.

     The `engine_condition_pushdown' variable controls whether engine
     condition pushdown is enabled. By default, this variable is `ON'
     (1). Setting it to `OFF' (0) disables pushdown.

   * `error_count'

     The number of errors that resulted from the last statement that
     generated messages. This variable is read only. See *Note
     show-errors::.

   * `event_scheduler'

     Options for event-scheduler

     *Introduced*         5.1.6           
     *Command-Line        `--event-scheduler[=value]'        
     Format*                              
     *System Variable     `event_scheduler'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `OFF'           
     *Valid Values*       `ON'            
     `OFF'                                
     `DISABLED'                           

     This variable indicates the status of the Event Scheduler; as of
     MySQL 5.1.12, possible values are `ON', `OFF', and `DISABLED', with
     the default being `OFF'. This variable and its effects on the
     Event Scheduler's operation are discussed in greater detail in the
     Overview section of the Events chapter.

     This variable was added in MySQL 5.1.6.

   * `expire_logs_days'

     Options for expire_logs_days

     *Command-Line        `--expire_logs_days=#'        
     Format*                              
     *System Variable     `expire_logs_days'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `99'            

     The number of days for automatic binary log file removal. The
     default is 0, which means `no automatic removal.' Possible
     removals happen at startup and when the binary log is flushed. Log
     flushing occurs as indicated in *Note server-logs::.

     To remove binary log files manually, use the *Note `PURGE BINARY
     LOGS': purge-binary-logs. statement.  See *Note
     purge-binary-logs::.

   * `flush'

     Options for flush

     *Command-Line        `--flush'        
     Format*                              
     *System Variable     `flush'         
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     If `ON', the server flushes (synchronizes) all changes to disk
     after each SQL statement. Normally, MySQL does a write of all
     changes to disk only after each SQL statement and lets the
     operating system handle the synchronizing to disk. See *Note
     crashing::. This variable is set to `ON' if you start *Note
     `mysqld': mysqld. with the `--flush' option.

   * `flush_time'

     Options for flush_time

     *Command-Line        `--flush_time=#'        
     Format*                              
     *System Variable     `flush_time'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             

     If this is set to a nonzero value, all tables are closed every
     `flush_time' seconds to free up resources and synchronize
     unflushed data to disk. This option is best used only on systems
     with minimal resources.

   * `foreign_key_checks'

     If set to 1 (the default), foreign key constraints for `InnoDB'
     tables are checked. If set to 0, they are ignored. Disabling
     foreign key checking can be useful for reloading `InnoDB' tables
     in an order different from that required by their parent/child
     relationships. See *Note innodb-foreign-key-constraints::.

     Setting `foreign_key_checks' to 0 also affects data definition
     statements: *Note `DROP SCHEMA': drop-database. drops a schema
     even if it contains tables that have foreign keys that are
     referred to by tables outside the schema, and *Note `DROP TABLE':
     drop-table.  drops tables that have foreign keys that are referred
     to by other tables.

     *Note*:

     Setting `foreign_key_checks' to 1 does not trigger a scan of the
     existing table data.  Therefore, rows added to the table while
     `foreign_key_checks = 0' will not be verified for consistency.

   * `ft_boolean_syntax'

     Options for ft_boolean_syntax

     *Command-Line        `--ft_boolean_syntax=name'        
     Format*                              
     *System Variable     `ft_boolean_syntax'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `+              
                          -><()~*:""&|'        

     The list of operators supported by boolean full-text searches
     performed using `IN BOOLEAN MODE'. See *Note fulltext-boolean::.

     The default variable value is `'+ -><()~*:""&|''. The rules for
     changing the value are as follows:

        * Operator function is determined by position within the string.

        * The replacement value must be 14 characters.

        * Each character must be an ASCII nonalphanumeric character.

        * Either the first or second character must be a space.

        * No duplicates are permitted except the phrase quoting
          operators in positions 11 and 12. These two characters are
          not required to be the same, but they are the only two that
          may be.

        * Positions 10, 13, and 14 (which by default are set to ``:'',
          ``&'', and ``|'') are reserved for future extensions.

   * `ft_max_word_len'

     Options for ft_max_word_len

     *Command-Line        `--ft_max_word_len=#'        
     Format*                              
     *System Variable     `ft_max_word_len'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Min Value*          `10'            

     The maximum length of the word to be included in a `FULLTEXT'
     index.

     *Note*:

     `FULLTEXT' indexes must be rebuilt after changing this variable.
     Use `REPAIR TABLE TBL_NAME QUICK'.

   * `ft_min_word_len'

     Options for ft_min_word_len

     *Command-Line        `--ft_min_word_len=#'        
     Format*                              
     *System Variable     `ft_min_word_len'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `4'             
     *Min Value*          `1'             

     The minimum length of the word to be included in a `FULLTEXT'
     index.

     *Note*:

     `FULLTEXT' indexes must be rebuilt after changing this variable.
     Use `REPAIR TABLE TBL_NAME QUICK'.

   * `ft_query_expansion_limit'

     Options for ft_query_expansion_limit

     *Command-Line        `--ft_query_expansion_limit=#'        
     Format*                              
     *System Variable     `ft_query_expansion_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `20'            
     *Min Value*          `0'             
     *Max Value*          `1000'          

     The number of top matches to use for full-text searches performed
     using `WITH QUERY EXPANSION'.

   * `ft_stopword_file'

     Options for ft_stopword_file

     *Command-Line        `--ft_stopword_file=file_name'        
     Format*                              
     *System Variable     `ft_stopword_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The file from which to read the list of stopwords for full-text
     searches. The server looks for the file in the data directory
     unless an absolute path name is given to specify a different
     directory. All the words from the file are used; comments are
     _not_ honored. By default, a built-in list of stopwords is used
     (as defined in the `storage/myisam/ft_static.c' file). Setting
     this variable to the empty string (`''') disables stopword
     filtering. See also *Note fulltext-stopwords::.

     *Note*:

     `FULLTEXT' indexes must be rebuilt after changing this variable or
     the contents of the stopword file.  Use `REPAIR TABLE TBL_NAME
     QUICK'.

   * `general_log'

     Options for general-log

     *Introduced*         5.1.12          
     *Command-Line        `--general-log'        
     Format*                              
     *System Variable     `general_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Whether the general query log is enabled. The value can be 0 (or
     `OFF') to disable the log or 1 (or `ON') to enable the log. The
     default value depends on whether the `--general_log' option is
     given (`--log' before MySQL 5.1.29).  The destination for log
     output is controlled by the `log_output' system variable; if that
     value is `NONE', no log entries are written even if the log is
     enabled. The `general_log' variable was added in MySQL 5.1.12.

   * `general_log_file'

     Options for general_log_file

     *Introduced*         5.1.12          
     *Command-Line        `--general-log-file=file_name'from    
     Format*                      5.1.29  
     *System Variable     `general_log_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `host_name.log'        

     The name of the general query log file. The default value is
     `HOST_NAME.log', but the initial value can be changed with the
     `--general_log_file' option (`--log' before MySQL 5.1.29).  This
     variable was added in MySQL 5.1.12.

   * `group_concat_max_len'

     Options for group_concat_max_len

     *Command-Line        `--group_concat_max_len=#'        
     Format*                              
     *System Variable     `group_concat_max_len'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `1024'          
     *Min Value*          `4'             
     *Max Value*          `18446744073709547520'        

     The maximum permitted result length in bytes for the
     `GROUP_CONCAT()' function. The default is 1024.

   * `have_archive'

     `YES' if *Note `mysqld': mysqld. supports `ARCHIVE' tables, `NO' if
     not. This variable was removed in MySQL 5.1.14.

   * `have_blackhole_engine'

     `YES' if *Note `mysqld': mysqld. supports `BLACKHOLE' tables, `NO'
     if not. This variable was removed in MySQL 5.1.14.

   * `have_compress'

     `YES' if the `zlib' compression library is available to the server,
     `NO' if not. If not, the `COMPRESS()' and `UNCOMPRESS()' functions
     cannot be used.

   * `have_community_features'

     `YES' if statement profiling capability is present, `NO' if not.
     If present, the `profiling' system variable controls whether this
     capability is enabled or disabled. See *Note show-profiles::.

     This variable was added in MySQL 5.1.24. It is renamed to
     `have_profiling' in MySQL 5.5.

   * `have_crypt'

     `YES' if the `crypt()' system call is available to the server, `NO'
     if not. If not, the `ENCRYPT()' function cannot be used.

   * `have_csv'

     `YES' if *Note `mysqld': mysqld. supports `CSV' tables, `NO' if
     not.

     This variable is deprecated and is removed in MySQL 5.6. Use *Note
     `SHOW ENGINES': show-engines. instead.

   * `have_dynamic_loading'

     `YES' if *Note `mysqld': mysqld. supports dynamic loading of
     plugins, `NO' if not. This variable was added in MySQL 5.1.10.

   * `have_example_engine'

     `YES' if *Note `mysqld': mysqld. supports `EXAMPLE' tables, `NO' if
     not. This variable was removed in MySQL 5.1.14.

   * `have_federated_engine'

     `YES' if *Note `mysqld': mysqld. supports `FEDERATED' tables, `NO'
     if not. This variable was removed in MySQL 5.1.14.

   * `have_geometry'

     `YES' if the server supports spatial data types, `NO' if not.

   * `have_innodb'

     `YES' if *Note `mysqld': mysqld. supports `InnoDB' tables.
     `DISABLED' if `--skip-innodb' is used.

     This variable is deprecated and is removed in MySQL 5.6. Use *Note
     `SHOW ENGINES': show-engines. instead.

   * `have_isam'

     In MySQL 5.1, this variable appears only for reasons of backward
     compatibility. It is always `NO' because `ISAM' tables are no
     longer supported. This variable was removed in MySQL 5.1.7.

   * `have_merge_engine'

     `YES' if *Note `mysqld': mysqld. supports `MERGE' tables.
     `DISABLED' if `--skip-merge' is used. This variable was removed in
     MySQL 5.1.3.

   * `have_openssl'

     `YES' if *Note `mysqld': mysqld. supports SSL connections, `NO' if
     not. As of MySQL 5.1.17, this variable is an alias for `have_ssl'.

   * `have_partitioning'

     `YES' if *Note `mysqld': mysqld. supports partitioning. Added in
     MySQL 5.1.1 as `have_partition_engine' and renamed to
     `have_partioning' in 5.1.6.

     This variable is deprecated and is removed in MySQL 5.6. Use *Note
     `SHOW PLUGINS': show-plugins. instead. For more information, see
     *Note partitioning::.

   * `have_query_cache'

     `YES' if *Note `mysqld': mysqld. supports the query cache, `NO' if
     not.

   * `have_row_based_replication'

     Options for have_row_based_replication

     *Introduced*         5.1.5           
     *Removed*            5.1.15          
     *System Variable     `have_row_based_replication'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     `YES' if the server can perform replication using row-based binary
     logging. If the value is `NO', the server can use only
     statement-based logging. See *Note replication-formats::. This
     variable was added in MySQL 5.1.5 and removed in 5.1.15.

   * `have_raid'

     In MySQL 5.1, this variable appears only for reasons of backward
     compatibility. It is always `NO' because `RAID' tables are no
     longer supported. This variable was removed in MySQL 5.1.7.

   * `have_rtree_keys'

     `YES' if `RTREE' indexes are available, `NO' if not. (These are
     used for spatial indexes in `MyISAM' tables.)

   * `have_ssl'

     `YES' if *Note `mysqld': mysqld. supports SSL connections, `NO' if
     not.  `DISABLED' indicates that the server was compiled with SSL
     support, but was not started with the appropriate `--ssl-XXX'
     options.  For more information, see *Note configuring-for-ssl::.

     This variable was added in MySQL 5.1.17. Before that, use
     `have_openssl'.

   * `have_symlink'

     `YES' if symbolic link support is enabled, `NO' if not. This is
     required on Unix for support of the `DATA DIRECTORY' and `INDEX
     DIRECTORY' table options, and on Windows for support of data
     directory symlinks. If the server is started with the
     `--skip-symbolic-links' option, the value is `DISABLED'.

   * `hostname'

     Options for hostname

     *Introduced*         5.1.17          
     *System Variable     `hostname'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The server sets this variable to the server host name at startup.
     This variable was added in MySQL 5.1.17.

   * `identity'

     This variable is a synonym for the `last_insert_id' variable. It
     exists for compatibility with other database systems. You can read
     its value with `SELECT @@identity', and set it using `SET
     identity'.

   * `init_connect'

     Options for init_connect

     *Command-Line        `--init-connect=name'        
     Format*                              
     *System Variable     `init_connect'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     A string to be executed by the server for each client that
     connects. The string consists of one or more SQL statements,
     separated by semicolon characters. For example, each client
     session begins by default with autocommit mode enabled. There is
     no global `autocommit' system variable to specify that autocommit
     should be disabled by default, but `init_connect' can be used to
     achieve the same effect:


          SET GLOBAL init_connect='SET autocommit=0';

     The `init_connect' variable can also be set on the command line or
     in an option file. To set the variable as just shown using an
     option file, include these lines:


          [mysqld]
          init_connect='SET autocommit=0'

     The content of `init_connect' is not executed for users that have
     the `SUPER' privilege. This is done so that an erroneous value for
     `init_connect' does not prevent all clients from connecting. For
     example, the value might contain a statement that has a syntax
     error, thus causing client connections to fail. Not executing
     `init_connect' for users that have the `SUPER' privilege enables
     them to open a connection and fix the `init_connect' value.

   * `init_file'

     Options for init-file

     *Command-Line        `--init-file=file_name'        
     Format*                              
     *System Variable     `init_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The name of the file specified with the `--init-file' option when
     you start the server. This should be a file containing SQL
     statements that you want the server to execute when it starts.
     Each statement must be on a single line and should not include
     comments. No statement terminator such as `;', `\g', or `\G'
     should be given at the end of each statement.

     Note that the `--init-file' option is unavailable if MySQL was
     configured with the `--disable-grant-options' option. See *Note
     source-configuration-options::.

   * `innodb_XXX'

     *Note `InnoDB': innodb-storage-engine. system variables are listed
     in *Note innodb-parameters::. These variables control many aspects
     of storage, memory use, and I/O patterns for `InnoDB' tables, and
     are especially important in MySQL 5.5 and higher, where InnoDB is
     the default storage engine
     (http://dev.mysql.com/doc/refman/5.5/en/innodb-default-se.html).

   * `insert_id'

     The value to be used by the following *Note `INSERT': insert. or
     *Note `ALTER TABLE': alter-table. statement when inserting an
     `AUTO_INCREMENT' value. This is mainly used with the binary log.

   * `interactive_timeout'

     Options for interactive_timeout

     *Command-Line        `--interactive_timeout=#'        
     Format*                              
     *System Variable     `interactive_timeout'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `28800'         
     *Min Value*          `1'             

     The number of seconds the server waits for activity on an
     interactive connection before closing it. An interactive client is
     defined as a client that uses the `CLIENT_INTERACTIVE' option to
     *Note `mysql_real_connect()': mysql-real-connect. See also
     `wait_timeout'.

   * `join_buffer_size'

     Options for join_buffer_size

     *Command-Line        `--join_buffer_size=#'        
     Format*                              
     *System Variable     `join_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type* (Other)       `numeric'        
     *Default*            `131072'        
     *Min Value*          `8200'          
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type* (Other)       `numeric'        
     *Default*            `131072'        
     *Min Value*          `8228'          
     *Max Value*          `18446744073709547520'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type* (Windows)     `numeric'        
     *Default*            `131072'        
     *Min Value*          `8200'          
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type* (Windows)     `numeric'        
     *Default*            `131072'        
     *Min Value*          `8228'          
     *Max Value*          `4294967295'        

     The minimum size of the buffer that is used for plain index scans,
     range index scans, and joins that do not use indexes and thus
     perform full table scans. Normally, the best way to get fast joins
     is to add indexes. Increase the value of `join_buffer_size' to get
     a faster full join when adding indexes is not possible. One join
     buffer is allocated for each full join between two tables. For a
     complex join between several tables for which indexes are not
     used, multiple join buffers might be necessary.

     There is no gain from setting the buffer larger than required to
     hold each matching row, and all joins allocate at least the
     minimum size, so use caution in setting this variable to a large
     value globally. It is better to keep the global setting small and
     change to a larger setting only in sessions that are doing large
     joins. Memory allocation time can cause substantial performance
     drops if the global size is larger than needed by most queries
     that use it.

     The maximum permissible setting for `join_buffer_size' is 4GB-1.
     As of MySQL 5.1.23, larger values are permitted for 64-bit
     platforms (except 64-bit Windows, for which large values are
     truncated to 4GB-1 with a warning).

     For additional information about join buffering, see *Note
     nested-loop-joins::.

   * `keep_files_on_create'

     Options for keep_files_on_create

     *Introduced*         5.1.21          
     *Command-Line        `--keep_files_on_create=#'        
     Format*                              
     *System Variable     `keep_files_on_create'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     If a `MyISAM' table is created with no `DATA DIRECTORY' option, the
     `.MYD' file is created in the database directory. By default, if
     `MyISAM' finds an existing `.MYD' file in this case, it overwrites
     it. The same applies to `.MYI' files for tables created with no
     `INDEX DIRECTORY' option. To suppress this behavior, set the
     `keep_files_on_create' variable to `ON' (1), in which case
     `MyISAM' will not overwrite existing files and returns an error
     instead. The default value is `OFF' (0).

     If a `MyISAM' table is created with a `DATA DIRECTORY' or `INDEX
     DIRECTORY' option and an existing `.MYD' or `.MYI' file is found,
     MyISAM always returns an error. It will not overwrite a file in
     the specified directory.

     This variable was added in MySQL 5.1.23.

   * `key_buffer_size'

     Options for key_buffer_size

     *Command-Line        `--key_buffer_size=#'        
     Format*                              
     *System Variable     `key_buffer_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.22)*        
     *Type*               `numeric'        
     *Default*            `8388608'        
     *Min Value*          `8'             
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.23)*        
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `8388608'        
     *Min Value*          `8'             
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.23)*        
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `8388608'        
     *Min Value*          `8'             
     *Max Value*          `OS_PER_PROCESS_LIMIT'        

     Index blocks for `MyISAM' tables are buffered and are shared by
     all threads.  `key_buffer_size' is the size of the buffer used for
     index blocks. The key buffer is also known as the key cache.

     The maximum permissible setting for `key_buffer_size' is 4GB-1 on
     32-bit platforms. As of MySQL 5.1.23, larger values are permitted
     for 64-bit platforms, except 64-bit Windows prior to MySQL 5.1.31,
     for which large values are truncated to 4GB-1 with a warning. As
     of MySQL 5.1.31, larger values are also permitted for 64-bit
     Windows. The effective maximum size might be less, depending on
     your available physical RAM and per-process RAM limits imposed by
     your operating system or hardware platform. The value of this
     variable indicates the amount of memory requested. Internally, the
     server allocates as much memory as possible up to this amount, but
     the actual allocation might be less.

     You can increase the value to get better index handling for all
     reads and multiple writes; on a system whose primary function is
     to run MySQL using the *Note `MyISAM': myisam-storage-engine.
     storage engine, 25% of the machine's total memory is an acceptable
     value for this variable. However, you should be aware that, if you
     make the value too large (for example, more than 50% of the
     machine's total memory), your system might start to page and
     become extremely slow. This is because MySQL relies on the
     operating system to perform file system caching for data reads, so
     you must leave some room for the file system cache.  You should
     also consider the memory requirements of any other storage engines
     that you may be using in addition to *Note `MyISAM':
     myisam-storage-engine.

     For even more speed when writing many rows at the same time, use
     *Note `LOCK TABLES': lock-tables. See *Note insert-speed::.

     You can check the performance of the key buffer by issuing a *Note
     `SHOW STATUS': show-status. statement and examining the
     `Key_read_requests', `Key_reads', `Key_write_requests', and
     `Key_writes' status variables.  (See *Note show::.) The
     `Key_reads/Key_read_requests' ratio should normally be less than
     0.01. The `Key_writes/Key_write_requests' ratio is usually near 1
     if you are using mostly updates and deletes, but might be much
     smaller if you tend to do updates that affect many rows at the
     same time or if you are using the `DELAY_KEY_WRITE' table option.

     The fraction of the key buffer in use can be determined using
     `key_buffer_size' in conjunction with the `Key_blocks_unused'
     status variable and the buffer block size, which is available from
     the `key_cache_block_size' system variable:


          1 - ((Key_blocks_unused * key_cache_block_size) / key_buffer_size)

     This value is an approximation because some space in the key
     buffer is allocated internally for administrative structures.
     Factors that influence the amount of overhead for these structures
     include block size and pointer size. As block size increases, the
     percentage of the key buffer lost to overhead tends to decrease.
     Larger blocks results in a smaller number of read operations
     (because more keys are obtained per read), but conversely an
     increase in reads of keys that are not examined (if not all keys
     in a block are relevant to a query).

     It is possible to create multiple `MyISAM' key caches. The size
     limit of 4GB applies to each cache individually, not as a group.
     See *Note myisam-key-cache::.

   * `key_cache_age_threshold'

     Options for key_cache_age_threshold

     *Command-Line        `--key_cache_age_threshold=#'        
     Format*                              
     *System Variable     `key_cache_age_threshold'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `300'           
     *Min Value*          `100'           
     *Max Value*          `18446744073709547520'        

     This value controls the demotion of buffers from the hot sublist
     of a key cache to the warm sublist. Lower values cause demotion to
     happen more quickly. The minimum value is 100. The default value
     is 300. See *Note myisam-key-cache::.

   * `key_cache_block_size'

     Options for key_cache_block_size

     *Command-Line        `--key_cache_block_size=#'        
     Format*                              
     *System Variable     `key_cache_block_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1024'          
     *Min Value*          `512'           
     *Max Value*          `16384'         

     The size in bytes of blocks in the key cache. The default value is
     1024. See *Note myisam-key-cache::.

   * `key_cache_division_limit'

     Options for key_cache_division_limit

     *Command-Line        `--key_cache_division_limit=#'        
     Format*                              
     *System Variable     `key_cache_division_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `100'           
     *Min Value*          `1'             
     *Max Value*          `100'           

     The division point between the hot and warm sublists of the key
     cache buffer list. The value is the percentage of the buffer list
     to use for the warm sublist. Permissible values range from 1 to
     100. The default value is 100. See *Note myisam-key-cache::.

   * `language'

     Options for language

     *Command-Line        `--language=name'        
     Format*                              
                          `-L'            
     *System Variable     `language'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           
     *Default*            `/usr/local/mysql/share/mysql/english/'        

     The directory where error messages are located. See *Note
     error-message-language::.

   * `large_files_support'

     Options for large_files_support

     *System Variable     `large_files_support'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     Whether *Note `mysqld': mysqld. was compiled with options for
     large file support.

   * `large_pages'

     Options for large-pages

     *Command-Line        `--large-pages'        
     Format*                              
     *System Variable     `large_pages'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Linux           
                          *Permitted        
                          Values*         
     *Type* (Linux)       `boolean'        
     *Default*            `FALSE'         

     Whether large page support is enabled (via the `--large-pages'
     option). See *Note large-page-support::.

   * `large_page_size'

     Options for large_page_size

     *System Variable     `large_page_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type* (Linux)       `numeric'        
     *Default*            `0'             

     If large page support is enabled, this shows the size of memory
     pages. Currently, large memory pages are supported only on Linux;
     on other platforms, the value of this variable is always 0. See
     *Note large-page-support::.

   * `last_insert_id'

     The value to be returned from `LAST_INSERT_ID()'. This is stored
     in the binary log when you use `LAST_INSERT_ID()' in a statement
     that updates a table. Setting this variable does not update the
     value returned by the *Note `mysql_insert_id()': mysql-insert-id.
     C API function.

   * `lc_time_names'

     Options for lc_time_names

     *Introduced*         5.1.12          
     *System Variable     `lc_time_names'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This variable specifies the locale that controls the language used
     to display day and month names and abbreviations. This variable
     affects the output from the `DATE_FORMAT()', `DAYNAME()' and
     `MONTHNAME()' functions. Locale names are POSIX-style values such
     as `'ja_JP'' or `'pt_BR''. The default value is `'en_US''
     regardless of your system's locale setting. For further
     information, see *Note locale-support::. This variable was added in
     MySQL 5.1.12.

   * `license'

     Options for license

     *System Variable     `license'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `GPL'           

     The type of license the server has.

   * `local_infile'

     Options for local_infile

     *System Variable     `local_infile'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     Whether `LOCAL' is supported for *Note `LOAD DATA INFILE':
     load-data. statements. If this variable is disabled, clients
     cannot use `LOCAL' in *Note `LOAD DATA': load-data. statements. See
     *Note load-data-local::.

   * `locked_in_memory'

     Options for locked_in_memory

     *System Variable     `locked_in_memory'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     Whether *Note `mysqld': mysqld. was locked in memory with
     `--memlock'.

   * `log'

     Options for log

     *Deprecated*         5.1.29,         
                          by              
                          general-log        
     *Command-Line        `--log[=file_name]'        
     Format*                              
                          `-l'            
     *System Variable     `log'           
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     Whether logging of all statements to the general query log is
     enabled. See *Note query-log::.

     This variable is deprecated as of MySQL 5.1.29 and is removed in
     MySQL 5.6. Use `general_log' instead.

   * `log_bin_trust_function_creators'

     Options for log-bin-trust-function-creators

     *Command-Line        `--log-bin-trust-function-creators'        
     Format*                              
     *System Variable     `log_bin_trust_function_creators'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This variable applies when binary logging is enabled. It controls
     whether stored function creators can be trusted not to create
     stored functions that will cause unsafe events to be written to
     the binary log. If set to 0 (the default), users are not permitted
     to create or alter stored functions unless they have the `SUPER'
     privilege in addition to the `CREATE ROUTINE' or `ALTER ROUTINE'
     privilege. A setting of 0 also enforces the restriction that a
     function must be declared with the `DETERMINISTIC' characteristic,
     or with the `READS SQL DATA' or `NO SQL' characteristic. If the
     variable is set to 1, MySQL does not enforce these restrictions on
     stored function creation. This variable also applies to trigger
     creation. See *Note stored-programs-logging::.

   * `log_error'

     Options for log-error

     *Command-Line        `--log-error[=file_name]'        
     Format*                              
     *System Variable     `log_error'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The location of the error log, or empty if the server is writing
     error message to the standard error output. See *Note error-log::.

   * `log_output'

     Options for log-output

     *Introduced*         5.1.6           
     *Command-Line        `--log-output=name'        
     Format*                              
     *System Variable     `log_output'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `set'           
     *Default*            `FILE'          
     *Valid Values*       `TABLE'         
     `FILE'                               
     `NONE'                               

     The destination for general query log and slow query log output.
     The value can be a comma-separated list of one or more of the
     words `TABLE' (log to tables), `FILE' (log to files), or `NONE'
     (do not log to tables or files). The default value is `FILE'.
     `NONE', if present, takes precedence over any other specifiers. If
     the value is `NONE' log entries are not written even if the logs
     are enabled. If the logs are not enabled, no logging occurs even
     if the value of `log_output' is not `NONE'. For more information,
     see *Note log-destinations::. This variable was added in MySQL
     5.1.6.

   * `log_queries_not_using_indexes'

     Options for log-queries-not-using-indexes

     *Command-Line        `--log-queries-not-using-indexes'        
     Format*                              
     *System Variable     `log_queries_not_using_indexes'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Whether queries that do not use indexes are logged to the slow
     query log. See *Note slow-query-log::. This variable was added in
     MySQL 5.1.11.

   * `log_slow_queries'

     Options for log-slow-queries

     *Deprecated*         5.1.29,         
                          by              
                          slow-query-log        
     *Command-Line        `--log-slow-queries[=name]'        
     Format*                              
     *System Variable     `log_slow_queries'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     Whether slow queries should be logged. `Slow' is determined by the
     value of the `long_query_time' variable. See *Note
     slow-query-log::.

     This variable is deprecated as of MySQL 5.1.29 and is removed in
     MySQL 5.6. Use `slow_query_log' instead.

   * `log_warnings'

     Options for log-warnings

     *Command-Line        `--log-warnings[=#]'        
     Format*                              
                          `-W             
                          [#]'            
     *System Variable     `log_warnings'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `0'             
     *Max Value*          `18446744073709547520'        

     Whether to produce additional warning messages to the error log.
     This variable is enabled (1) by default and can be disabled by
     setting it to 0. As of MySQL 5.1.38, the server logs messages
     about statements that are unsafe for statement-based logging if
     the value is greater than 0.  Aborted connections and
     access-denied errors for new connection attempts are logged if the
     value is greater than 1.

   * `long_query_time'

     Options for long_query_time

     *Command-Line        `--long_query_time=#'        
     Format*                              
     *System Variable     `long_query_time'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (>=             
                          5.1.21)*        
     *Type*               `numeric'        
     *Default*            `10'            
     *Min Value*          `0'             

     If a query takes longer than this many seconds, the server
     increments the `Slow_queries' status variable. If the slow query
     log is enabled, the query is logged to the slow query log file.
     This value is measured in real time, not CPU time, so a query that
     is under the threshold on a lightly loaded system might be above
     the threshold on a heavily loaded one. The default value of
     `long_query_time' is 10.  Beginning with MySQL 5.1.21, the minimum
     is 0, and the value can be specified to a resolution of
     microseconds. For logging to a file, times are written including
     the microseconds part.  For logging to tables, only integer times
     are written; the microseconds part is ignored. Prior to MySQL
     5.1.21, the minimum value is 1, and the value for this variable
     must be an integer. See *Note slow-query-log::.

   * `low_priority_updates'

     Options for low-priority-updates

     *Command-Line        `--low-priority-updates'        
     Format*                              
     *System Variable     `low_priority_updates'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     If set to `1', all *Note `INSERT': insert, *Note `UPDATE': update,
     *Note `DELETE': delete, and `LOCK TABLE WRITE' statements wait
     until there is no pending *Note `SELECT': select. or `LOCK TABLE
     READ' on the affected table. This affects only storage engines
     that use only table-level locking (such as `MyISAM', `MEMORY', and
     `MERGE'). This variable previously was named
     `sql_low_priority_updates'.

   * `lower_case_file_system'

     Options for lower_case_file_system

     *System Variable     `lower_case_file_system'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     This variable describes the case sensitivity of file names on the
     file system where the data directory is located.  `OFF' means file
     names are case sensitive, `ON' means they are not case sensitive.
     This variable is read only because it reflects a file system
     attribute and setting it would have no effect on the file system.

   * `lower_case_table_names'

     Options for lower_case_table_names

     *Command-Line        `--lower_case_table_names[=#]'        
     Format*                              
     *System Variable     `lower_case_table_names'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `2'             

     If set to 0, table names are stored as specified and comparisons
     are case sensitive. If set to 1, table names are stored in
     lowercase on disk and comparisons are not case sensitive. If set
     to 2, table names are stored as given but compared in lowercase.
     This option also applies to database names and table aliases. For
     additional information, see *Note identifier-case-sensitivity::.

     You should _not_ set this variable to 0 if you are running MySQL
     on a system that has case-insensitive file names (such as Windows
     or Mac OS X). If you set this variable to 0 on such a system and
     access `MyISAM' tablenames using different lettercases, index
     corruption may result. On Windows the default value is 1. On Mac
     OS X, the default value is 2.

     If you are using `InnoDB' tables, you should set this variable to
     1 on all platforms to force names to be converted to lowercase.
     Prior to MySQL Cluster NDB 6.3.35, MySQL Cluster NDB 7.0.15, and
     MySQL Cluster NDB 7.1.4, this is also true for tables using the
     `NDB' storage engine.

     The setting of this variable has no effect on replication
     filtering options. See *Note replication-rules::, for more
     information.

     You should not use different settings for `lower_case_table_names'
     on replication masters and slaves. In particular, you should not
     do this when the slave uses a case-sensitive file system, as this
     can cause replication to fail. For more information, see *Note
     replication-features-variables::.

   * `max_allowed_packet'

     Options for max_allowed_packet

     *Command-Line        `--max_allowed_packet=#'        
     Format*                              
     *System Variable     `max_allowed_packet'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1048576'        
     *Min Value*          `1024'          
     *Max Value*          `1073741824'        

     The maximum size of one packet or any generated/intermediate
     string.

     The packet message buffer is initialized to `net_buffer_length'
     bytes, but can grow up to `max_allowed_packet' bytes when needed.
     This value by default is small, to catch large (possibly
     incorrect) packets.

     You must increase this value if you are using large *Note `BLOB':
     blob. columns or long strings.  It should be as big as the largest
     *Note `BLOB': blob. you want to use. The protocol limit for
     `max_allowed_packet' is 1GB.  The value should be a multiple of
     1024; nonmultiples are rounded down to the nearest multiple.

     When you change the message buffer size by changing the value of
     the `max_allowed_packet' variable, you should also change the
     buffer size on the client side if your client program permits it.
     The default `max_allowed_packet' value built in to the client
     library is 1GB, but individual client programs might override
     this. For example, *Note `mysql': mysql. and *Note `mysqldump':
     mysqldump. have defaults of 16MB and 24MB, respectively. They also
     enable you to change the client-side value by setting
     `max_allowed_packet' on the command line or in an option file.

     As of MySQL 5.1.31, the session value of this variable is read
     only. Before 5.1.31, setting the session value is permitted but
     has no effect.

   * `max_connect_errors'

     Options for max_connect_errors

     *Command-Line        `--max_connect_errors=#'        
     Format*                              
     *System Variable     `max_connect_errors'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `10'            
     *Min Value*          `1'             
     *Max Value*          `18446744073709547520'        

     If more than this many successive connection requests from a host
     are interrupted without a successful connection, the server blocks
     that host from further connections. You can unblock blocked hosts
     by flushing the host cache. To do so, issue a *Note `FLUSH HOSTS':
     flush. statement or execute a *Note `mysqladmin flush-hosts':
     mysqladmin. command. If a connection is established successfully
     within fewer than `max_connect_errors' attempts after a previous
     connection was interrupted, the error count for the host is
     cleared to zero. However, once a host is blocked, flushing the
     host cache is the only way to unblock it.

   * `max_connections'

     Options for max_connections

     *Command-Line        `--max_connections=#'        
     Format*                              
     *System Variable     `max_connections'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.14)*        
     *Type*               `numeric'        
     *Default*            `100'           
                          *Permitted        
                          Values          
                          (>=             
                          5.1.15)*        
     *Type*               `numeric'        
     *Default*            `151'           
     *Min Value*          `1'             
     *Max Value*          `16384'         
                          *Permitted        
                          Values          
                          (>=             
                          5.1.17)*        
     *Type*               `numeric'        
     *Default*            `151'           
     *Min Value*          `1'             
     *Max Value*          `100000'        

     The maximum permitted number of simultaneous client connections.
     By default, this is 151, beginning with MySQL 5.1.15. (Previously,
     the default was 100.) See *Note too-many-connections::, for more
     information.

     Increasing this value increases the number of file descriptors
     that *Note `mysqld': mysqld. requires. See *Note table-cache::,
     for comments on file descriptor limits.

   * `max_delayed_threads'

     Options for max_delayed_threads

     *Command-Line        `--max_delayed_threads=#'        
     Format*                              
     *System Variable     `max_delayed_threads'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `20'            
     *Min Value*          `0'             
     *Max Value*          `16384'         

     Do not start more than this number of threads to handle *Note
     `INSERT DELAYED': insert-delayed. statements. If you try to insert
     data into a new table after all *Note `INSERT DELAYED':
     insert-delayed. threads are in use, the row is inserted as if the
     `DELAYED' attribute was not specified. If you set this to 0, MySQL
     never creates a thread to handle `DELAYED' rows; in effect, this
     disables `DELAYED' entirely.

     For the `SESSION' value of this variable, the only valid values
     are 0 or the `GLOBAL' value.

   * `max_error_count'

     Options for max_error_count

     *Command-Line        `--max_error_count=#'        
     Format*                              
     *System Variable     `max_error_count'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `64'            
     *Min Value*          `0'             
     *Max Value*          `65535'         

     The maximum number of error, warning, and note messages to be
     stored for display by the *Note `SHOW ERRORS': show-errors. and
     *Note `SHOW WARNINGS': show-warnings. statements.

   * `max_heap_table_size'

     Options for max_heap_table_size

     *Command-Line        `--max_heap_table_size=#'        
     Format*                              
     *System Variable     `max_heap_table_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `16777216'        
     *Min Value*          `16384'         
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `16777216'        
     *Min Value*          `16384'         
     *Max Value*          `1844674407370954752'        

     This variable sets the maximum size to which user-created `MEMORY'
     tables are permitted to grow. The value of the variable is used to
     calculate `MEMORY' table `MAX_ROWS' values. Setting this variable
     has no effect on any existing `MEMORY' table, unless the table is
     re-created with a statement such as *Note `CREATE TABLE':
     create-table. or altered with *Note `ALTER TABLE': alter-table. or
     *Note `TRUNCATE TABLE': truncate-table. A server restart also sets
     the maximum size of existing `MEMORY' tables to the global
     `max_heap_table_size' value.

     This variable is also used in conjunction with `tmp_table_size' to
     limit the size of internal in-memory tables. See *Note
     internal-temporary-tables::.

     `max_heap_table_size' is not replicated. See *Note
     replication-features-memory::, and *Note
     replication-features-variables::, for more information.

   * `max_insert_delayed_threads'

     Options for max_insert_delayed_threads

     *System Variable     `max_insert_delayed_threads'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     This variable is a synonym for `max_delayed_threads'.

   * `max_join_size'

     Options for max_join_size

     *Command-Line        `--max_join_size=#'        
     Format*                              
     *System Variable     `max_join_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `4294967295'        
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     Do not permit statements that probably need to examine more than
     `max_join_size' rows (for single-table statements) or row
     combinations (for multiple-table statements) or that are likely to
     do more than `max_join_size' disk seeks. By setting this value,
     you can catch statements where keys are not used properly and that
     would probably take a long time.  Set it if your users tend to
     perform joins that lack a `WHERE' clause, that take a long time, or
     that return millions of rows.

     Setting this variable to a value other than `DEFAULT' resets the
     value of `sql_big_selects' to `0'. If you set the
     `sql_big_selects' value again, the `max_join_size' variable is
     ignored.

     If a query result is in the query cache, no result size check is
     performed, because the result has previously been computed and it
     does not burden the server to send it to the client.

     This variable previously was named `sql_max_join_size'.

   * `max_length_for_sort_data'

     Options for max_length_for_sort_data

     *Command-Line        `--max_length_for_sort_data=#'        
     Format*                              
     *System Variable     `max_length_for_sort_data'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1024'          
     *Min Value*          `4'             
     *Max Value*          `8388608'        

     The cutoff on the size of index values that determines which
     `filesort' algorithm to use. See *Note order-by-optimization::.

   * `max_long_data_size'

     Options for max_long_data_size

     *Introduced*         5.1.57          
     *Deprecated*         5.1.57          
     *Command-Line        `--max_long_data_size=#'        
     Format*                              
     *System Variable     `max_long_data_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1048576'        
     *Min Value*          `1024'          
     *Max Value*          `4294967295'        

     The maximum size of parameter values that can be sent with the
     *Note `mysql_stmt_send_long_data()': mysql-stmt-send-long-data. C
     API function. If not set at server startup, the default is the
     value of the `max_allowed_packet' system variable. This variable
     is deprecated. In MySQL 5.6, it is removed and the maximum
     parameter size is controlled by `max_allowed_packet'.

   * `max_prepared_stmt_count'

     Options for max_prepared_stmt_count

     *Introduced*         5.1.10          
     *Command-Line        `--max_prepared_stmt_count=#'        
     Format*                              
     *System Variable     `max_prepared_stmt_count'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `16382'         
     *Min Value*          `0'             
     *Max Value*          `1048576'        

     This variable limits the total number of prepared statements in
     the server. (The sum of the number of prepared statements across
     all sessions.) It can be used in environments where there is the
     potential for denial-of-service attacks based on running the
     server out of memory by preparing huge numbers of statements. If
     the value is set lower than the current number of prepared
     statements, existing statements are not affected and can be used,
     but no new statements can be prepared until the current number
     drops below the limit. The default value is 16,382. The
     permissible range of values is from 0 to 1 million. Setting the
     value to 0 disables prepared statements.  This variable was added
     in MySQL 5.1.10.

   * `max_relay_log_size'

     Options for max_relay_log_size

     *Command-Line        `--max_relay_log_size=#'        
     Format*                              
     *System Variable     `max_relay_log_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `1073741824'        

     If a write by a replication slave to its relay log causes the
     current log file size to exceed the value of this variable, the
     slave rotates the relay logs (closes the current file and opens
     the next one). If `max_relay_log_size' is 0, the server uses
     `max_binlog_size' for both the binary log and the relay log. If
     `max_relay_log_size' is greater than 0, it constrains the size of
     the relay log, which enables you to have different sizes for the
     two logs. You must set `max_relay_log_size' to between 4096 bytes
     and 1GB (inclusive), or to 0. The default value is 0. See *Note
     replication-implementation-details::.

   * `max_seeks_for_key'

     Options for max_seeks_for_key

     *Command-Line        `--max_seeks_for_key=#'        
     Format*                              
     *System Variable     `max_seeks_for_key'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4294967295'        
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     Limit the assumed maximum number of seeks when looking up rows
     based on a key. The MySQL optimizer assumes that no more than this
     number of key seeks are required when searching for matching rows
     in a table by scanning an index, regardless of the actual
     cardinality of the index (see *Note show-index::). By setting this
     to a low value (say, 100), you can force MySQL to prefer indexes
     instead of table scans.

   * `max_sort_length'

     Options for max_sort_length

     *Command-Line        `--max_sort_length=#'        
     Format*                              
     *System Variable     `max_sort_length'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1024'          
     *Min Value*          `4'             
     *Max Value*          `8388608'        

     The number of bytes to use when sorting data values. Only the
     first `max_sort_length' bytes of each value are used; the rest are
     ignored.

   * `max_sp_recursion_depth'

     Options for max_sp_recursion_depth

     *Command-Line        `--max_sp_recursion_depth[=#]'        
     Format*                              
     *System Variable     `max_sp_recursion_depth'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Max Value*          `255'           

     The number of times that any given stored procedure may be called
     recursively. The default value for this option is 0, which
     completely disables recursion in stored procedures. The maximum
     value is 255.

     Stored procedure recursion increases the demand on thread stack
     space. If you increase the value of `max_sp_recursion_depth', it
     may be necessary to increase thread stack size by increasing the
     value of `thread_stack' at server startup.

   * `max_tmp_tables'

     This variable is unused.

   * `max_user_connections'

     Options for max_user_connections

     *Command-Line        `--max_user_connections=#'        
     Format*                              
     *System Variable     `max_user_connections'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     The maximum number of simultaneous connections permitted to any
     given MySQL user account. A value of 0 (the default) means `no
     limit.'

     This variable has a global value that can be set at server startup
     or runtime. It also has a read-only session value that indicates
     the effective simultaneous-connection limit that applies to the
     account associated with the current session.  The session value is
     initialized as follows:

        * If the user account has a nonzero `MAX_USER_CONNECTIONS'
          resource limit, the session `max_user_connections' value is
          set to that limit.

        * Otherwise, the session `max_user_connections' value is set to
          the global value.

     Account resource limits are specified using the *Note `GRANT':
     grant. statement. See *Note user-resources::, and *Note grant::.

   * `max_write_lock_count'

     Options for max_write_lock_count

     *Command-Line        `--max_write_lock_count=#'        
     Format*                              
     *System Variable     `max_write_lock_count'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4294967295'        
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     After this many write locks, permit some pending read lock
     requests to be processed in between.

   * `min_examined_row_limit'

     Options for min-examined-row-limit

     *Introduced*         5.1.21          
     *Command-Line        `--min-examined-row-limit=#'        
     Format*                              
     *System Variable     `min_examined_row_limit'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     Queries that examine fewer than this number of rows are not logged
     to the slow query log. This variable was added in MySQL 5.1.21.

   * `multi_range_count'

     Options for multi_range_count

     *Command-Line        `--multi_range_count=#'        
     Format*                              
     *System Variable     `multi_range_count'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `256'           
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     The maximum number of ranges to send to a table handler at once
     during range selects. The default value is 256. Sending multiple
     ranges to a handler at once can improve the performance of certain
     selects dramatically. This is especially true for the *Note
     `NDBCLUSTER': mysql-cluster. table handler, which needs to send
     the range requests to all nodes. Sending a batch of those requests
     at once reduces communication costs significantly.

     This variable is deprecated in MySQL 5.1, and is no longer
     supported in MySQL 5.5, in which arbitrarily long lists of ranges
     can be processed.

   * `myisam_data_pointer_size'

     Options for myisam_data_pointer_size

     *Command-Line        `--myisam_data_pointer_size=#'        
     Format*                              
     *System Variable     `myisam_data_pointer_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `6'             
     *Min Value*          `2'             
     *Max Value*          `7'             

     The default pointer size in bytes, to be used by *Note `CREATE
     TABLE': create-table. for `MyISAM' tables when no `MAX_ROWS'
     option is specified. This variable cannot be less than 2 or larger
     than 7. The default value is 6. See *Note full-table::.

   * `myisam_max_sort_file_size'

     Options for myisam_max_sort_file_size

     *Command-Line        `--myisam_max_sort_file_size=#'        
     Format*                              
     *System Variable     `myisam_max_sort_file_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `2147483648'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `9223372036854775807'        

     The maximum size of the temporary file that MySQL is permitted to
     use while re-creating a `MyISAM' index (during *Note `REPAIR
     TABLE': repair-table, *Note `ALTER TABLE': alter-table, or *Note
     `LOAD DATA INFILE': load-data.). If the file size would be larger
     than this value, the index is created using the key cache instead,
     which is slower. The value is given in bytes.

     The default value is 2GB. If `MyISAM' index files exceed this size
     and disk space is available, increasing the value may help
     performance. The space must be available in the file system
     containing the directory where the original index file is located.

   * `myisam_mmap_size'

     Options for myisam_mmap_size

     *Introduced*         5.1.43          
     *Command-Line        `--myisam_mmap_size=#'        
     Format*                              
     *System Variable     `myisam_mmap_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4294967295'        
     *Min Value*          `7'             
     *Max Value*          `4294967295'        

     The maximum amount of memory to use for memory mapping compressed
     *Note `MyISAM': myisam-storage-engine. files. If many compressed
     `MyISAM' tables are used, the value can be decreased to reduce the
     likelihood of memory-swapping problems. This variable was added in
     MySQL 5.1.43.

   * `myisam_recover_options'

     Options for myisam_recover_options

     *System Variable     `myisam_recover_options'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     The value of the `--myisam-recover' option. See *Note
     server-options::.

   * `myisam_repair_threads'

     Options for myisam_repair_threads

     *Command-Line        `--myisam_repair_threads=#'        
     Format*                              
     *System Variable     `myisam_repair_threads'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     If this value is greater than 1, `MyISAM' table indexes are
     created in parallel (each index in its own thread) during the
     `Repair by sorting' process. The default value is 1.

     *Note*:

     Multi-threaded repair is still _beta-quality_ code.

   * `myisam_sort_buffer_size'

     Options for myisam_sort_buffer_size

     *Command-Line        `--myisam_sort_buffer_size=#'        
     Format*                              
     *System Variable     `myisam_sort_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (Windows)     `numeric'        
     *Default*            `8388608'        
     *Min Value*          `4096'          
     *Max Value*          `4294967295'        

     The size of the buffer that is allocated when sorting `MyISAM'
     indexes during a *Note `REPAIR TABLE': repair-table. or when
     creating indexes with *Note `CREATE INDEX': create-index. or *Note
     `ALTER TABLE': alter-table.

     The maximum permissible setting for `myisam_sort_buffer_size' is
     4GB-1. As of MySQL 5.1.23, larger values are permitted for 64-bit
     platforms (except 64-bit Windows, for which large values are
     truncated to 4GB-1 with a warning).

   * `myisam_stats_method'

     Options for myisam_stats_method

     *Command-Line        `--myisam_stats_method=name'        
     Format*                              
     *System Variable     `myisam_stats_method'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `nulls_unequal'        
     *Valid Values*       `nulls_equal'        
     `nulls_unequal'                      
     `nulls_ignored'                      

     How the server treats `NULL' values when collecting statistics
     about the distribution of index values for `MyISAM' tables. This
     variable has three possible values, `nulls_equal',
     `nulls_unequal', and `nulls_ignored'. For `nulls_equal', all `NULL'
     index values are considered equal and form a single value group
     that has a size equal to the number of `NULL' values. For
     `nulls_unequal', `NULL' values are considered unequal, and each
     `NULL' forms a distinct value group of size 1. For `nulls_ignored',
     `NULL' values are ignored.

     The method that is used for generating table statistics influences
     how the optimizer chooses indexes for query execution, as
     described in *Note myisam-index-statistics::.

     Any unique prefix of a valid value may be used to set the value of
     this variable.

   * `myisam_use_mmap'

     Options for myisam_use_mmap

     *Introduced*         5.1.4           
     *Command-Line        `--myisam_use_mmap'        
     Format*                              
     *System Variable     `myisam_use_mmap'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Use memory mapping for reading and writing `MyISAM' tables. This
     variable was added in MySQL 5.1.4.

   * `named_pipe'

     Options for named_pipe

     *System Variable     `named_pipe'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Windows         
                          *Permitted        
                          Values*         
     *Type* (Windows)     `boolean'        
     *Default*            `OFF'           

     (Windows only.) Indicates whether the server supports connections
     over named pipes.

   * `net_buffer_length'

     Options for net_buffer_length

     *Command-Line        `--net_buffer_length=#'        
     Format*                              
     *System Variable     `net_buffer_length'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `16384'         
     *Min Value*          `1024'          
     *Max Value*          `1048576'        

     Each client thread is associated with a connection buffer and
     result buffer. Both begin with a size given by `net_buffer_length'
     but are dynamically enlarged up to `max_allowed_packet' bytes as
     needed. The result buffer shrinks to `net_buffer_length' after each
     SQL statement.

     This variable should not normally be changed, but if you have very
     little memory, you can set it to the expected length of statements
     sent by clients. If statements exceed this length, the connection
     buffer is automatically enlarged. The maximum value to which
     `net_buffer_length' can be set is 1MB.

     As of MySQL 5.1.31, the session value of this variable is read
     only. Before 5.1.31, setting the session value is permitted but
     has no effect.

   * `net_read_timeout'

     Options for net_read_timeout

     *Command-Line        `--net_read_timeout=#'        
     Format*                              
     *System Variable     `net_read_timeout'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `30'            
     *Min Value*          `1'             

     The number of seconds to wait for more data from a connection
     before aborting the read. Before MySQL 5.1.41, this timeout
     applies only to TCP/IP connections, not to connections made
     through Unix socket files, named pipes, or shared memory. When the
     server is reading from the client, `net_read_timeout' is the
     timeout value controlling when to abort. When the server is
     writing to the client, `net_write_timeout' is the timeout value
     controlling when to abort. See also `slave_net_timeout'.

     On Linux, the `NO_ALARM' build flag affects timeout behavior as
     indicated in the description of the `net_retry_count' system
     variable.

   * `net_retry_count'

     Options for net_retry_count

     *Command-Line        `--net_retry_count=#'        
     Format*                              
     *System Variable     `net_retry_count'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `10'            
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     If a read or write on a communication port is interrupted, retry
     this many times before giving up. This value should be set quite
     high on FreeBSD because internal interrupts are sent to all
     threads.

     On Linux, the `NO_ALARM' build flag (`-DNO_ALARM') modifies how
     the binary treats both `net_read_timeout' and `net_write_timeout'.
     With this flag enabled, neither timer cancels the current statement
     until after the failing connection has been waited on an
     additional `net_retry_count' times. This means that the effective
     timeout value becomes `(timeout setting) x (net_retry_count+1)'.

   * `net_write_timeout'

     Options for net_write_timeout

     *Command-Line        `--net_write_timeout=#'        
     Format*                              
     *System Variable     `net_write_timeout'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `60'            
     *Min Value*          `1'             

     The number of seconds to wait for a block to be written to a
     connection before aborting the write. Before MySQL 5.1.41, this
     timeout applies only to TCP/IP connections, not to connections
     made using Unix socket files, named pipes, or shared memory. See
     also `net_read_timeout'.

     On Linux, the `NO_ALARM' build flag affects timeout behavior as
     indicated in the description of the `net_retry_count' system
     variable.

   * `new'

     Options for new

     *Command-Line        `--new'         
     Format*                              
                          `-n'            
     *System Variable     `new'           
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
     *Disabled by*        `skip-new'        
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This variable was used in MySQL 4.0 to turn on some 4.1 behaviors,
     and is retained for backward compatibility. In MySQL 5.1, its
     value is always `OFF'.

   * `old'

     Options for old

     *Introduced*         5.1.18          
     *Command-Line        `--old'         
     Format*                              
     *System Variable     `old'           
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     `old' is a compatibility variable. It is disabled by default, but
     can be enabled at startup to revert the server to behaviors
     present in older versions.

     Currently, when `old' is enabled, it changes the default scope of
     index hints to that used prior to MySQL 5.1.17. That is, index
     hints with no `FOR' clause apply only to how indexes are used for
     row retrieval and not to resolution of `ORDER BY' or `GROUP BY'
     clauses. (See *Note index-hints::.) Take care about enabling this
     in a replication setup. With statement-based binary logging,
     having different modes for the master and slaves might lead to
     replication errors.

     This variable was added as `old_mode' in MySQL 5.1.17 and renamed
     to `old' in MySQL 5.1.18.

   * `old_alter_table'

     Options for old-alter-table

     *Command-Line        `--old-alter-table'        
     Format*                              
     *System Variable     `old_alter_table'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     When this variable is enabled, the server does not use the
     optimized method of processing an *Note `ALTER TABLE':
     alter-table. operation. It reverts to using a temporary table,
     copying over the data, and then renaming the temporary table to
     the original, as used by MySQL 5.0 and earlier. For more
     information on the operation of *Note `ALTER TABLE': alter-table,
     see *Note alter-table::.

   * `old_passwords'

     Options for old_passwords

     *System Variable     `old_passwords'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `0'             

     This variable controls the password hashing method used by the
     `PASSWORD()' function. It also influences password hashing
     performed by *Note `CREATE USER': create-user. and *Note `GRANT':
     grant. statements that specify a password using an `IDENTIFIED BY'
     clause.

     The value determines whether or not to use `old' native MySQL
     password hashing. A value of 0 (or `OFF') causes passwords to be
     encrypted using the format available from MySQL 4.1 on. A value of
     1 (or `ON') causes password encryption to use the older pre-4.1
     format.

     If `old_passwords=1', `PASSWORD(STR)' returns the same value as
     `OLD_PASSWORD(STR)'.  The latter function is not affected by the
     value of `old_passwords'.

     For information about hashing formats, see *Note
     password-hashing::.

   * `one_shot'

     This is not a variable, but it can be used when setting some
     variables. It is described in *Note set-statement::.

   * `open_files_limit'

     Options for open-files-limit

     *Command-Line        `--open-files-limit=#'        
     Format*                              
     *System Variable     `open_files_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `platform        
                          dependent'        

     The number of files that the operating system permits *Note
     `mysqld': mysqld. to open. This is the real value permitted by the
     system and might be different from the value you gave using the
     `--open-files-limit' option to *Note `mysqld': mysqld. or *Note
     `mysqld_safe': mysqld-safe.  The value is 0 on systems where MySQL
     cannot change the number of open files.

   * `optimizer_prune_level'

     Options for optimizer_prune_level

     *Command-Line        `--optimizer_prune_level[=#]'        
     Format*                              
     *System Variable     `optimizer_prune_level'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `1'             

     Controls the heuristics applied during query optimization to prune
     less-promising partial plans from the optimizer search space. A
     value of 0 disables heuristics so that the optimizer performs an
     exhaustive search. A value of 1 causes the optimizer to prune
     plans based on the number of rows retrieved by intermediate plans.

   * `optimizer_search_depth'

     Options for optimizer_search_depth

     *Command-Line        `--optimizer_search_depth[=#]'        
     Format*                              
     *System Variable     `optimizer_search_depth'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `62'            
     *Min Value*          `0'             
     *Max Value*          `63'            

     The maximum depth of search performed by the query optimizer.
     Values larger than the number of relations in a query result in
     better query plans, but take longer to generate an execution plan
     for a query. Values smaller than the number of relations in a
     query return an execution plan quicker, but the resulting plan may
     be far from being optimal. If set to 0, the system automatically
     picks a reasonable value. If set to 63, the optimizer switches to
     the algorithm used in MySQL 5.0.0 (and previous versions) for
     performing searches. The value of 63 is deprecated and will be
     treated as invalid in a future MySQL release.

   * `optimizer_switch'

     Options for optimizer_switch

     *Introduced*         5.1.34          
     *Command-Line        `--optimizer_switch=value'        
     Format*                              
     *System Variable     `optimizer_switch'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `set'           
     *Valid Values*       `index_merge={on|off}'        
     `index_merge_intersection={on|off}'                
     `index_merge_sort_union={on|off}'                
     `index_merge_union={on|off}'                

     The `optimizer_switch' system variable enables control over
     optimizer behaviors. The value of this variable is a set of flags,
     each of which has a value of `on' or `off' to indicate whether the
     corresponding optimizer behavior is enabled or disabled. This
     variable has global and session values and can be changed at
     runtime. The global default can be set at server startup.

     To see the current set of optimizer flags, select the variable
     value:


          mysql> SELECT @@optimizer_switch\G
          *************************** 1. row ***************************
          @@optimizer_switch: index_merge=on,index_merge_union=on,
                              index_merge_sort_union=on,index_merge_intersection=on

     For more information about the syntax of this variable and the
     optimizer behaviors that it controls, see *Note
     switchable-optimizations::.

   * `pid_file'

     Options for pid-file

     *Command-Line        `--pid-file=file_name'        
     Format*                              
     *System Variable     `pid_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The path name of the process ID (PID) file. This variable can be
     set with the `--pid-file' option.

   * `plugin_dir'

     Options for plugin_dir

     *Introduced*         5.1.2           
     *Command-Line        `--plugin_dir=path'        
     Format*                              
     *System Variable     `plugin_dir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.2)*         
     *Type* (Windows)     `directory        
                          name'           
     *Default*            `BASEDIR/lib/plugin'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.2)*         
     *Type* (Other)       `directory        
                          name'           
     *Default*            `BASEDIR/lib/mysql/plugin'        

     The path name of the plugin directory. This variable was added in
     MySQL 5.1.2.

     If the plugin directory is writable by the server, it may be
     possible for a user to write executable code to a file in the
     directory using *Note `SELECT ... INTO DUMPFILE': select. This can
     be prevented by making `plugin_dir' read only to the server or by
     setting `--secure-file-priv' to a directory where *Note `SELECT':
     select. writes can be made safely.

   * `port'

     Options for port

     *Command-Line        `--port=#'        
     Format*                              
                          `-P'            
     *System Variable     `port'          
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3306'          
     *Min Value*          `0'             
     *Max Value*          `65535'         

     The number of the port on which the server listens for TCP/IP
     connections. This variable can be set with the `--port' option.

   * `preload_buffer_size'

     Options for preload_buffer_size

     *Command-Line        `--preload_buffer_size=#'        
     Format*                              
     *System Variable     `preload_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `32768'         
     *Min Value*          `1024'          
     *Max Value*          `1073741824'        

     The size of the buffer that is allocated when preloading indexes.

   * `prepared_stmt_count'

     Options for prepared_stmt_count

     *Introduced*         5.1.10          
     *Removed*            5.1.13          
     *System Variable     `prepared_stmt_count'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     The current number of prepared statements. (The maximum number of
     statements is given by the `max_prepared_stmt_count' system
     variable.) This variable was added in MySQL 5.1.10. In MySQL
     5.1.14, it was converted to the global `Prepared_stmt_count' status
     variable.

   * `profiling'

     If set to 0 or `OFF' (the default), statement profiling is
     disabled. If set to 1 or `ON', statement profiling is enabled and
     the *Note `SHOW PROFILE': show-profile. and *Note `SHOW PROFILES':
     show-profiles. statements provide access to profiling information.
     See *Note show-profiles::. This variable was added in MySQL 5.1.24.

   * `profiling_history_size'

     The number of statements for which to maintain profiling
     information if `profiling' is enabled. The default value is 15.
     The maximum value is 100.  Setting the value to 0 effectively
     disables profiling. See *Note show-profiles::. This variable was
     added in MySQL 5.1.24.

   * `protocol_version'

     Options for protocol_version

     *System Variable     `protocol_version'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     The version of the client/server protocol used by the MySQL server.

   * `pseudo_thread_id'

     Options for pseudo_thread_id

     *System Variable     `pseudo_thread_id'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     This variable is for internal server use.

   * `query_alloc_block_size'

     Options for query_alloc_block_size

     *Command-Line        `--query_alloc_block_size=#'        
     Format*                              
     *System Variable     `query_alloc_block_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `8192'          
     *Min Value*          `1024'          
     *Max Value*          `4294967295'        
     *Block Size*         `1024'          

     The allocation size of memory blocks that are allocated for
     objects created during statement parsing and execution. If you
     have problems with memory fragmentation, it might help to increase
     this parameter.

   * `query_cache_limit'

     Options for query_cache_limit

     *Command-Line        `--query_cache_limit=#'        
     Format*                              
     *System Variable     `query_cache_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `1048576'        
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     Do not cache results that are larger than this number of bytes.
     The default value is 1MB.

   * `query_cache_min_res_unit'

     Options for query_cache_min_res_unit

     *Command-Line        `--query_cache_min_res_unit=#'        
     Format*                              
     *System Variable     `query_cache_min_res_unit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4096'          
     *Min Value*          `512'           
     *Max Value*          `4294967295'        

     The minimum size (in bytes) for blocks allocated by the query
     cache. The default value is 4096 (4KB). Tuning information for
     this variable is given in *Note query-cache-configuration::.

   * `query_cache_size'

     Options for query_cache_size

     *Command-Line        `--query_cache_size=#'        
     Format*                              
     *System Variable     `query_cache_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `18446744073709547520'        

     The amount of memory allocated for caching query results. The
     default value is 0, which disables the query cache. The
     permissible values are multiples of 1024; other values are rounded
     down to the nearest multiple. Note that `query_cache_size' bytes of
     memory are allocated even if `query_cache_type' is set to 0.  See
     *Note query-cache-configuration::, for more information.

     The query cache needs a minimum size of about 40KB to allocate its
     structures. (The exact size depends on system architecture.) If
     you set the value of `query_cache_size' too small, a warning will
     occur, as described in *Note query-cache-configuration::.

   * `query_cache_type'

     Options for query_cache_type

     *Command-Line        `--query_cache_type=#'        
     Format*                              
     *System Variable     `query_cache_type'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `1'             
     *Valid Values*       `0'             
     `1'                                  
     `2'                                  

     Set the query cache type. Setting the `GLOBAL' value sets the type
     for all clients that connect thereafter. Individual clients can
     set the `SESSION' value to affect their own use of the query
     cache. Possible values are shown in the following table.

     This table describes options that may be specified for the
     `query_cache_type' system variable.

     Option     Description
     `0' or     Do not cache results in or retrieve results
     `OFF'      from the query cache. Note that this does not
                deallocate the query cache buffer.  To do
                that, you should set `query_cache_size' to 0.
     `1' or     Cache all cacheable query results except for
     `ON'       those that begin with `SELECT SQL_NO_CACHE'.
     `2' or     Cache results only for cacheable queries that
     `DEMAND'   begin with `SELECT SQL_CACHE'.

     This variable defaults to `ON'.

     Any unique prefix of a valid value may be used to set the value of
     this variable.

   * `query_cache_wlock_invalidate'

     Options for query_cache_wlock_invalidate

     *Command-Line        `--query_cache_wlock_invalidate'        
     Format*                              
     *System Variable     `query_cache_wlock_invalidate'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Normally, when one client acquires a `WRITE' lock on a `MyISAM'
     table, other clients are not blocked from issuing statements that
     read from the table if the query results are present in the query
     cache. Setting this variable to 1 causes acquisition of a `WRITE'
     lock for a table to invalidate any queries in the query cache that
     refer to the table. This forces other clients that attempt to
     access the table to wait while the lock is in effect.

   * `query_prealloc_size'

     Options for query_prealloc_size

     *Command-Line        `--query_prealloc_size=#'        
     Format*                              
     *System Variable     `query_prealloc_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `8192'          
     *Min Value*          `8192'          
     *Max Value*          `18446744073709551615'        
     *Block Size*         `1024'          

     The size of the persistent buffer used for statement parsing and
     execution. This buffer is not freed between statements. If you are
     running complex queries, a larger `query_prealloc_size' value
     might be helpful in improving performance, because it can reduce
     the need for the server to perform memory allocation during query
     execution operations.

   * `rand_seed1'

     The `rand_seed1' and `rand_seed2' variables exist as session
     variables only, and can be set but not read. Beginning with MySQL
     5.1.18, the variables--but not their values--are shown in the
     output of *Note `SHOW VARIABLES': show-variables.

     The purpose of these variables is to support replication of the
     `RAND()' function. For statements that invoke `RAND()', the master
     passes two values to the slave, where they are used to seed the
     random number generator. The slave uses these values to set the
     session variables `rand_seed1' and `rand_seed2' so that `RAND()'
     on the slave generates the same value as on the master.

   * `rand_seed2'

     See the description for `rand_seed1'.

   * `range_alloc_block_size'

     Options for range_alloc_block_size

     *Command-Line        `--range_alloc_block_size=#'        
     Format*                              
     *System Variable     `range_alloc_block_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4096'          
     *Min Value*          `4096'          
     *Max Value*          `4294967295'        
     *Block Size*         `1024'          
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `4096'          
     *Min Value*          `4096'          
     *Max Value*          `18446744073709547520'        
     *Block Size*         `1024'          

     The size of blocks that are allocated when doing range
     optimization.

   * `read_buffer_size'

     Options for read_buffer_size

     *Command-Line        `--read_buffer_size=#'        
     Format*                              
     *System Variable     `read_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `131072'        
     *Min Value*          `8200'          
     *Max Value*          `2147479552'        

     Each thread that does a sequential scan for a `MyISAM' table
     allocates a buffer of this size (in bytes) for each table it
     scans. If you do many sequential scans, you might want to increase
     this value, which defaults to 131072. The value of this variable
     should be a multiple of 4KB. If it is set to a value that is not a
     multiple of 4KB, its value will be rounded down to the nearest
     multiple of 4KB.

     This option is also used in the following context for all search
     engines:

        * For caching the indexes in a temporary file (not a temporary
          table), when sorting rows for `ORDER BY'.

        * For bulk insert into partitions.

        * For caching results of nested queries.

     and in one other storage engine-specific way: to determine the
     memory block size for *Note `MEMORY': memory-storage-engine.
     tables.

     The maximum permissible setting for `read_buffer_size' is 2GB.

     For more information about memory use during different operations,
     see *Note memory-use::.

   * `read_only'

     Options for read_only

     *Command-Line        `--read-only'        
     Format*                              
     *System Variable     `read_only'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `false'         

     This variable is off by default. When it is enabled, the server
     permits no updates except from users that have the `SUPER'
     privilege or (on a slave server) from updates performed by slave
     threads. In replication setups, it can be useful to enable
     `read_only' on slave servers to ensure that slaves accept updates
     only from the master server and not from clients.

     `read_only' does not apply to `TEMPORARY' tables, nor does it
     prevent the server from inserting rows into the log tables (see
     *Note log-destinations::). This variable does not prevent the use
     of *Note `ANALYZE TABLE': analyze-table. or *Note `OPTIMIZE
     TABLE': optimize-table. statements because its purpose is to
     prevent changes to table structure or contents. Analysis and
     optimization do not qualify as such changes. This means, for
     example, that consistency checks on read-only slaves can be
     performed with *Note `mysqlcheck --all-databases --analyze':
     mysqlcheck.

     `read_only' exists only as a `GLOBAL' variable, so changes to its
     value require the `SUPER' privilege.  Changes to `read_only' on a
     master server are not replicated to slave servers. The value can
     be set on a slave server independent of the setting on the master.

     *Important*:

     In MySQL 5.1, enabling `read_only' prevents the use of the *Note
     `SET PASSWORD': set-password. statement by any user not having the
     `SUPER' privilege. This is not necessarily the case for all MySQL
     release series. When replicating from one MySQL release series to
     another (for example, from a MySQL 5.0 master to a MySQL 5.1 or
     later slave), you should check the documentation for the versions
     running on both master and slave to determine whether the behavior
     of `read_only' in this regard is or is not the same, and, if it is
     different, whether this has an impact on your applications.

     As of MySQL 5.1.15, the following conditions apply:

        * If you attempt to enable `read_only' while you have any
          explicit locks (acquired with *Note `LOCK TABLES':
          lock-tables.) or have a pending transaction, an error occurs.

        * If you attempt to enable `read_only' while other clients hold
          explicit table locks or have pending transactions, the
          attempt blocks until the locks are released and the
          transactions end. While the attempt to enable `read_only' is
          pending, requests by other clients for table locks or to
          begin transactions also block until `read_only' has been set.

        * `read_only' can be enabled while you hold a global read lock
          (acquired with *Note `FLUSH TABLES WITH READ LOCK': flush.)
          because that does not involve table locks.

   * `read_rnd_buffer_size'

     Options for read_rnd_buffer_size

     *Command-Line        `--read_rnd_buffer_size=#'        
     Format*                              
     *System Variable     `read_rnd_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `262144'        
     *Min Value*          `8200'          
     *Max Value*          `2147483647'        

     When reading rows from a `MyISAM' table in sorted order following
     a key-sorting operation, the rows are read through this buffer to
     avoid disk seeks. See *Note order-by-optimization::. Setting the
     variable to a large value can improve `ORDER BY' performance by a
     lot. However, this is a buffer allocated for each client, so you
     should not set the global variable to a large value. Instead,
     change the session variable only from within those clients that
     need to run large queries.

     The maximum permissible setting for `read_rnd_buffer_size' is 2GB.

     For more information about memory use during different operations,
     see *Note memory-use::.

   * `relay_log_purge'

     Options for relay_log_purge

     *Command-Line        `--relay_log_purge'        
     Format*                              
     *System Variable     `relay_log_purge'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Disables or enables automatic purging of relay log files as soon
     as they are not needed any more. The default value is 1 (`ON').

   * `relay_log_space_limit'

     Options for relay_log_space_limit

     *Command-Line        `--relay_log_space_limit=#'        
     Format*                              
     *System Variable     `relay_log_space_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     The maximum amount of space to use for all relay logs.

   * `report_host'

     Options for report-host

     *Command-Line        `--report-host=host_name'        
     Format*                              
     *System Variable     `report_host'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The value of the `--report-host' option. This variable was added
     in MySQL 5.1.24.

   * `report_password'

     Options for report-password

     *Command-Line        `--report-password=name'        
     Format*                              
     *System Variable     `report_password'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The value of the `--report-password' option. Not the same as the
     password for the MySQL replication user account. This variable was
     added in MySQL 5.1.24.

   * `report_port'

     Options for report-port

     *Command-Line        `--report-port=#'        
     Format*                              
     *System Variable     `report_port'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3306'          
     *Min Value*          `0'             
     *Max Value*          `65535'         

     The value of the `--report-port' option. This variable was added
     in MySQL 5.1.24.

   * `report_user'

     Options for report-user

     *Command-Line        `--report-user=name'        
     Format*                              
     *System Variable     `report_user'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The value of the `--report-user' option. This variable was added
     in MySQL 5.1.24.

   * `secure_auth'

     Options for secure-auth

     *Command-Line        `--secure-auth'        
     Format*                              
     *System Variable     `secure_auth'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     If this variable is enabled, the server blocks connections by
     clients that attempt to use accounts that have passwords stored in
     the old (pre-4.1) format.

     Enable this variable to prevent all use of passwords employing the
     old format (and hence insecure communication over the network).

     Server startup fails with an error if this variable is enabled and
     the privilege tables are in pre-4.1 format. See *Note old-client::.

   * `secure_file_priv'

     Options for secure-file-priv

     *Introduced*         5.1.17          
     *Command-Line        `--secure-file-priv=path'        
     Format*                              
     *System Variable     `secure_file_priv'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     By default, this variable is empty. If set to the name of a
     directory, it limits the effect of the `LOAD_FILE()' function and
     the *Note `LOAD DATA': load-data. and *Note `SELECT ... INTO
     OUTFILE': select-into. statements to work only with files in that
     directory.

     This variable was added in MySQL 5.1.17.

   * `server_id'

     Options for server-id

     *Command-Line        `--server-id=#'        
     Format*                              
     *System Variable     `server_id'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     The server ID, used in replication to give each master and slave a
     unique identity. This variable is set by the `--server-id' option.
     For each server participating in replication, you should pick a
     positive integer in the range from 1 to 2^32 - 1 to act as that
     server's ID.

   * `shared_memory'

     Options for shared_memory

     *Command-Line        `--shared-memory-base-name=name'        
     Format*                              
     *System Variable     `shared_memory'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Windows         

     (Windows only.) Whether the server permits shared-memory
     connections.

   * `shared_memory_base_name'

     Options for shared_memory_base_name

     *System Variable     `shared_memory_base_name'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Windows         

     (Windows only.) The name of shared memory to use for shared-memory
     connections. This is useful when running multiple MySQL instances
     on a single physical machine. The default name is `MYSQL'. The
     name is case sensitive.

   * `skip_external_locking'

     Options for skip_external_locking

     *Command-Line        `--skip-external-locking'        
     Format*                              
     *System Variable     `skip_external_locking'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     This is `OFF' if *Note `mysqld': mysqld.  uses external locking
     (system locking), `ON' if external locking is disabled. This
     affects only *Note `MyISAM': myisam-storage-engine. table access.

     This variable is set by the `--external-locking' or
     `--skip-external-locking' option. External locking has been
     disabled by default as of MySQL 4.0.

     External locking affects only *Note `MyISAM':
     myisam-storage-engine. table access. For more information,
     including conditions under which it can and cannot be used, see
     *Note external-locking::.

   * `skip_name_resolve'

     Options for skip-name-resolve

     *Command-Line        `--skip-name-resolve'        
     Format*                              
     *System Variable     `skip_name_resolve'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     This variable is set from the value of the `--skip-name-resolve'
     option. If it is `OFF', *Note `mysqld': mysqld.  resolves host
     names when checking client connections. If it is `ON', *Note
     `mysqld': mysqld. uses only IP numbers; in this case, all `Host'
     column values in the grant tables must be IP addresses or
     `localhost'. See *Note host-cache::.

     This variable was added in MySQL 5.1.46.

   * `skip_networking'

     Options for skip-networking

     *Command-Line        `--skip-networking'        
     Format*                              
     *System Variable     `skip_networking'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     This is `ON' if the server permits only local (non-TCP/IP)
     connections. On Unix, local connections use a Unix socket file. On
     Windows, local connections use a named pipe or shared memory. On
     NetWare, only TCP/IP connections are supported, so do not set this
     variable to `ON'. This variable can be set to `ON' with the
     `--skip-networking' option.

   * `skip_show_database'

     Options for skip-show-database

     *Command-Line        `--skip-show-database'        
     Format*                              
     *System Variable     `skip_show_database'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     This prevents people from using the *Note `SHOW DATABASES':
     show-databases. statement if they do not have the `SHOW DATABASES'
     privilege. This can improve security if you have concerns about
     users being able to see databases belonging to other users. Its
     effect depends on the `SHOW DATABASES' privilege: If the variable
     value is `ON', the *Note `SHOW DATABASES': show-databases.
     statement is permitted only to users who have the `SHOW DATABASES'
     privilege, and the statement displays all database names. If the
     value is `OFF', *Note `SHOW DATABASES': show-databases. is
     permitted to all users, but displays the names of only those
     databases for which the user has the `SHOW DATABASES' or other
     privilege. (Note that _any_ global privilege is considered a
     privilege for the database.)

   * `slow_launch_time'

     Options for slow_launch_time

     *Command-Line        `--slow_launch_time=#'        
     Format*                              
     *System Variable     `slow_launch_time'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `2'             

     If creating a thread takes longer than this many seconds, the
     server increments the `Slow_launch_threads' status variable.

   * `slow_query_log'

     Options for slow-query-log

     *Introduced*         5.1.12          
     *Command-Line        `--slow-query-log'from    
     Format*                      5.1.29  
     *System Variable     `slow_query_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Whether the slow query log is enabled. The value can be 0 (or
     `OFF') to disable the log or 1 (or `ON') to enable the log. The
     default value depends on whether the `--slow_query_log' option is
     given (`--log-slow-queries' before MySQL 5.1.29). The destination
     for log output is controlled by the `log_output' system variable;
     if that value is `NONE', no log entries are written even if the
     log is enabled. The `slow_query_log' variable was added in MySQL
     5.1.12.

     `Slow' is determined by the value of the `long_query_time'
     variable. See *Note slow-query-log::.

   * `slow_query_log_file'

     Options for slow_query_log_file

     *Introduced*         5.1.12          
     *Command-Line        `--slow-query-log-file=file_name'        
     Format*                              
     *System Variable     `slow_query_log_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `host_name-slow.log'        

     The name of the slow query log file. The default value is
     `HOST_NAME-slow.log', but the initial value can be changed with the
     `--slow_query_log_file' option (`--log-slow-queries' before MySQL
     5.1.29). This variable was added in MySQL 5.1.12.

   * `socket'

     Options for socket

     *Command-Line        `--socket=file_name'        
     Format*                              
     *System Variable     `socket'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `/tmp/mysql.sock'        

     On Unix platforms, this variable is the name of the socket file
     that is used for local client connections. The default is
     `/tmp/mysql.sock'. (For some distribution formats, the directory
     might be different, such as `/var/lib/mysql' for RPMs.)

     On Windows, this variable is the name of the named pipe that is
     used for local client connections. The default value is `MySQL'
     (not case sensitive).

   * `sort_buffer_size'

     Options for sort_buffer_size

     *Command-Line        `--sort_buffer_size=#'        
     Format*                              
     *System Variable     `sort_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type* (Other)       `numeric'        
     *Default*            `2097144'        
     *Min Value*          `32768'         
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type* (Other)       `numeric'        
     *Default*            `2097144'        
     *Min Value*          `32768'         
     *Max Value*          `18446744073709551615'        
                          *Permitted        
                          Values*         
     *Type* (Windows)     `numeric'        
     *Default*            `2097144'        
     *Min Value*          `32768'         
     *Max Value*          `4294967295'        

     Each session that needs to do a sort allocates a buffer of this
     size. `sort_buffer_size' is not specific to any storage engine and
     applies in a general manner for optimization. See *Note
     order-by-optimization::, for example.

     If you see many `Sort_merge_passes' per second in *Note `SHOW
     GLOBAL STATUS': show-status. output, you can consider increasing
     the `sort_buffer_size' value to speed up `ORDER BY' or `GROUP BY'
     operations that cannot be improved with query optimization or
     improved indexing. The entire buffer is allocated even if it is
     not all needed, so setting it larger than required globally will
     slow down most queries that sort.  It is best to increase it as a
     session setting, and only for the sessions that need a larger
     size. On Linux, there are thresholds of 256KB and 2MB where larger
     values may significantly slow down memory allocation, so you should
     consider staying below one of those values. Experiment to find the
     best value for your workload. See *Note temporary-files::.

     The maximum permissible setting for `sort_buffer_size' is 4GB-1.
     As of MySQL 5.1.23, larger values are permitted for 64-bit
     platforms (except 64-bit Windows, for which large values are
     truncated to 4GB-1 with a warning).

   * `sql_auto_is_null'

     Options for sql_auto_is_null

     *System Variable     `sql_auto_is_null'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `1'             

     If this variable is set to 1 (the default), then after a statement
     that successfully inserts an automatically generated
     `AUTO_INCREMENT' value, you can find that value by issuing a
     statement of the following form:


          SELECT * FROM TBL_NAME WHERE AUTO_COL IS NULL

     If the statement returns a row, the value returned is the same as
     if you invoked the `LAST_INSERT_ID()' function. For details,
     including the return value after a multiple-row insert, see *Note
     information-functions::. If no `AUTO_INCREMENT' value was
     successfully inserted, the *Note `SELECT': select. statement
     returns no row.

     The behavior of retrieving an `AUTO_INCREMENT' value by using an
     `IS NULL' comparison is used by some ODBC programs, such as
     Access. See Obtaining Auto-Increment Values
     (http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-usagenotes-functionality-last-insert-id.html).
     This behavior can be disabled by setting `sql_auto_is_null' to 0.

   * `sql_big_selects'

     Options for sql_big_selects

     *System Variable     `sql_big_selects'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `1'             

     If set to 0, MySQL aborts *Note `SELECT': select. statements that
     are likely to take a very long time to execute (that is,
     statements for which the optimizer estimates that the number of
     examined rows exceeds the value of `max_join_size'). This is
     useful when an inadvisable `WHERE' statement has been issued. The
     default value for a new connection is 1, which permits all *Note
     `SELECT': select.  statements.

     If you set the `max_join_size' system variable to a value other
     than `DEFAULT', `sql_big_selects' is set to 0.

   * `sql_buffer_result'

     Options for sql_buffer_result

     *System Variable     `sql_buffer_result'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `0'             

     If set to 1, `sql_buffer_result' forces results from *Note
     `SELECT': select. statements to be put into temporary tables. This
     helps MySQL free the table locks early and can be beneficial in
     cases where it takes a long time to send results to the client.
     The default value is 0.

   * `sql_log_bin'

     Options for sql_log_bin

     *System Variable     `sql_log_bin'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     If set to 0, no logging is done to the binary log for the client.
     The client must have the `SUPER' privilege to set this option. The
     default value is 1.

   * `sql_log_off'

     Options for sql_log_off

     *System Variable     `sql_log_off'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `0'             

     If set to 1, no logging is done to the general query log for this
     client. The client must have the `SUPER' privilege to set this
     option. The default value is 0.

   * `sql_log_update'

     Options for sql_log_update

     *Deprecated*         5.0.0,          
                          by              
                          sql_log_bin        
     *System Variable     `sql_log_update'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     This variable is deprecated, and is mapped to `sql_log_bin'. It is
     removed in MySQL 5.5.

   * `sql_mode'

     Options for sql-mode

     *Command-Line        `--sql-mode=name'        
     Format*                              
     *System Variable     `sql_mode'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `set'           
     *Default*            `'''            
     *Valid Values*       `ALLOW_INVALID_DATES'        
     `ANSI_QUOTES'                        
     `ERROR_FOR_DIVISION_BY_ZERO'                
     `HIGH_NOT_PRECEDENCE'                
     `IGNORE_SPACE'                       
     `NO_AUTO_CREATE_USER'                
     `NO_AUTO_VALUE_ON_ZERO'                
     `NO_BACKSLASH_ESCAPES'                
     `NO_DIR_IN_CREATE'                   
     `NO_ENGINE_SUBSTITUTION'                
     `NO_FIELD_OPTIONS'                   
     `NO_KEY_OPTIONS'                     
     `NO_TABLE_OPTIONS'                   
     `NO_UNSIGNED_SUBTRACTION'                
     `NO_ZERO_DATE'                       
     `NO_ZERO_IN_DATE'                    
     `ONLY_FULL_GROUP_BY'                 
     `PAD_CHAR_TO_FULL_LENGTH'                
     `PIPES_AS_CONCAT'                    
     `REAL_AS_FLOAT'                      
     `STRICT_ALL_TABLES'                  
     `STRICT_TRANS_TABLES'                

     The current server SQL mode, which can be set dynamically. See
     *Note sql-mode::.

     *Note*:

     MySQL installation programs may configure the SQL mode during the
     installation process. If the SQL mode differs from the default or
     from what you expect, check for a setting in an option file that
     the server reads at startup.

   * `sql_notes'

     If set to 1 (the default), warnings of `Note' level increment
     `warning_count' and the server records them. If set to 0, `Note'
     warnings do not increment `warning_count' and the server does not
     record them. *Note `mysqldump': mysqldump. includes output to set
     this variable to 0 so that reloading the dump file does not
     produce warnings for events that do not affect the integrity of
     the reload operation.

   * `sql_quote_show_create'

     If set to 1 (the default), the server quotes identifiers for *Note
     `SHOW CREATE TABLE': show-create-table. and *Note `SHOW CREATE
     DATABASE': show-create-database.  statements. If set to 0, quoting
     is disabled. This option is enabled by default so that replication
     works for identifiers that require quoting. See *Note
     show-create-table::, and *Note show-create-database::.

   * `sql_safe_updates'

     If set to 1, MySQL aborts *Note `UPDATE': update. or *Note
     `DELETE': delete. statements that do not use a key in the `WHERE'
     clause or a `LIMIT' clause. (Specifically, *Note `UPDATE': update.
     statements must have a `WHERE' clause that uses a key or a `LIMIT'
     clause, or both.  *Note `DELETE': delete. statements must have
     both.) This makes it possible to catch *Note `UPDATE': update. or
     *Note `DELETE': delete. statements where keys are not used
     properly and that would probably change or delete a large number
     of rows. The default value is 0.

   * `sql_select_limit'

     Options for sql_select_limit

     *System Variable     `sql_select_limit'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     The maximum number of rows to return from *Note `SELECT': select.
     statements. The default value for a new connection is the maximum
     number of rows that the server permits per table, which depends on
     the server configuration and may be affected if the server build
     was configured with `--with-big-tables'. Typical default values
     are (2^32)-1 or (2^64)-1. If you have changed the limit, the
     default value can be restored by assigning a value of `DEFAULT'.

     If a *Note `SELECT': select. has a `LIMIT' clause, the `LIMIT'
     takes precedence over the value of `sql_select_limit'.

   * `sql_warnings'

     This variable controls whether single-row *Note `INSERT': insert.
     statements produce an information string if warnings occur. The
     default is 0. Set the value to 1 to produce an information string.

   * `ssl_ca'

     Options for ssl-ca

     *Introduced*         5.1.11          
     *Command-Line        `--ssl-ca=file_name'        
     Format*                              
     *System Variable     `ssl_ca'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The path to a file with a list of trusted SSL CAs. This variable
     was added in MySQL 5.1.11.

   * `ssl_capath'

     Options for ssl-capath

     *Introduced*         5.1.11          
     *Command-Line        `--ssl-capath=dir_name'        
     Format*                              
     *System Variable     `ssl_capath'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The path to a directory that contains trusted SSL CA certificates
     in PEM format. This variable was added in MySQL 5.1.11.

   * `ssl_cert'

     Options for ssl-cert

     *Introduced*         5.1.11          
     *Command-Line        `--ssl-cert=file_name'        
     Format*                              
     *System Variable     `ssl_cert'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The name of the SSL certificate file to use for establishing a
     secure connection. This variable was added in MySQL 5.1.11.

   * `ssl_cipher'

     Options for ssl-cipher

     *Introduced*         5.1.11          
     *Command-Line        `--ssl-cipher=name'        
     Format*                              
     *System Variable     `ssl_cipher'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     A list of permissible ciphers to use for SSL encryption. This
     variable was added in MySQL 5.1.11.

   * `ssl_key'

     Options for ssl-key

     *Introduced*         5.1.11          
     *Command-Line        `--ssl-key=file_name'        
     Format*                              
     *System Variable     `ssl_key'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The name of the SSL key file to use for establishing a secure
     connection. This variable was added in MySQL 5.1.11.

   * `storage_engine'

     Options for storage_engine

     *System Variable     `storage_engine'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `MyISAM'        

     The default storage engine (table type). To set the storage engine
     at server startup, use the `--default-storage-engine' option. See
     *Note server-options::.

     To see which storage engines are available and enabled, use the
     *Note `SHOW ENGINES': show-engines. statement or query the
     `INFORMATION_SCHEMA' *Note `ENGINES': engines-table. table.

   * `sync_frm'

     Options for sync_frm

     *Command-Line        `--sync-frm'        
     Format*                              
     *System Variable     `sync_frm'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     If this variable is set to 1, when any nontemporary table is
     created its `.frm' file is synchronized to disk (using
     `fdatasync()'). This is slower but safer in case of a crash. The
     default is 1.

   * `system_time_zone'

     Options for system_time_zone

     *System Variable     `system_time_zone'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The server system time zone. When the server begins executing, it
     inherits a time zone setting from the machine defaults, possibly
     modified by the environment of the account used for running the
     server or the startup script. The value is used to set
     `system_time_zone'.  Typically the time zone is specified by the
     `TZ' environment variable. It also can be specified using the
     `--timezone' option of the *Note `mysqld_safe': mysqld-safe.
     script.

     The `system_time_zone' variable differs from `time_zone'.
     Although they might have the same value, the latter variable is
     used to initialize the time zone for each client that connects.
     See *Note time-zone-support::.

   * `table_cache'

     Options for table_cache

     *Deprecated*         5.1.3,          
                          by              
                          table_open_cache        
     *Removed*            5.1.3           
     *Command-Line        `--table_cache=#'        
     Format*                              
     *System Variable     `table_cache'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `64'            
     *Min Value*          `1'             
     *Max Value*          `524288'        

     This is the old name of `table_open_cache' before MySQL 5.1.3.
     From 5.1.3 on, use `table_open_cache' instead.

   * `table_definition_cache'

     Options for table_definition_cache

     *Introduced*         5.1.3           
     *System Variable     `table_definition_cache'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.24)*        
     *Type*               `numeric'        
     *Default*            `128'           
     *Min Value*          `1'             
     *Max Value*          `524288'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.25)*        
     *Type*               `numeric'        
     *Default*            `256'           
     *Min Value*          `256'           
     *Max Value*          `524288'        

     The number of table definitions (from `.frm' files) that can be
     stored in the definition cache. If you use a large number of
     tables, you can create a large table definition cache to speed up
     opening of tables. The table definition cache takes less space and
     does not use file descriptors, unlike the normal table cache. This
     variable was added in MySQL 5.1.3. The minimum and default values
     are 1 and 128 before MySQL 5.1.25. The minimum and default are
     both 256 as of MySQL 5.1.25.

   * `table_lock_wait_timeout'

     Options for table_lock_wait_timeout

     *Command-Line        `--table_lock_wait_timeout=#'        
     Format*                              
     *System Variable     `table_lock_wait_timeout'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `50'            
     *Min Value*          `1'             
     *Max Value*          `1073741824'        

     This variable is unused.

   * `table_open_cache'

     Options for table_open_cache

     *Introduced*         5.1.3           
     *System Variable     `table_open_cache'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `64'            
     *Min Value*          `1'             
     *Max Value*          `524288'        

     The number of open tables for all threads. Increasing this value
     increases the number of file descriptors that *Note `mysqld':
     mysqld. requires. You can check whether you need to increase the
     table cache by checking the `Opened_tables' status variable. See
     *Note server-status-variables::. If the value of `Opened_tables'
     is large and you do not use *Note `FLUSH TABLES': flush.  often
     (which just forces all tables to be closed and reopened), then you
     should increase the value of the `table_open_cache' variable.  For
     more information about the table cache, see *Note table-cache::.
     Before MySQL 5.1.3, this variable is called `table_cache'.

   * `table_type'

     Options for table_type

     *System Variable     `table_type'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        

     This variable is a synonym for `storage_engine'. In MySQL 5.1,
     `storage_engine' is the preferred name; `table_type' is deprecated
     and is removed in MySQL 5.5.

   * `thread_cache_size'

     Options for thread_cache_size

     *Command-Line        `--thread_cache_size=#'        
     Format*                              
     *System Variable     `thread_cache_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `16384'         

     How many threads the server should cache for reuse. When a client
     disconnects, the client's threads are put in the cache if there
     are fewer than `thread_cache_size' threads there. Requests for
     threads are satisfied by reusing threads taken from the cache if
     possible, and only when the cache is empty is a new thread
     created. This variable can be increased to improve performance if
     you have a lot of new connections.  Normally, this does not
     provide a notable performance improvement if you have a good
     thread implementation. However, if your server sees hundreds of
     connections per second you should normally set `thread_cache_size'
     high enough so that most new connections use cached threads. By
     examining the difference between the `Connections' and
     `Threads_created' status variables, you can see how efficient the
     thread cache is. For details, see *Note server-status-variables::.

   * `thread_concurrency'

     Options for thread_concurrency

     *Command-Line        `--thread_concurrency=#'        
     Format*                              
     *System Variable     `thread_concurrency'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `10'            
     *Min Value*          `1'             
     *Max Value*          `512'           

     This variable is specific to Solaris systems, for which *Note
     `mysqld': mysqld. invokes the `thr_setconcurrency()' with the
     variable value. This function enables applications to give the
     threads system a hint about the desired number of threads that
     should be run at the same time.

   * `thread_handling'

     Options for thread_handling

     *Introduced*         5.1.17          
     *Command-Line        `--thread_handling=name'        
     Format*                              
     *System Variable     `thread_handling'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `one-thread-per-connection'        
     *Valid Values*       `no-threads'        
     `one-thread-per-connection'                

     The thread-handling model used by the server for connection
     threads. The permissible values are `no-threads' (the server uses
     a single thread to handle one connection) and
     `one-thread-per-connection' (the server uses one thread to handle
     each client connection).  `no-threads' is useful for debugging
     under Linux; see *Note porting::. This variable was added in MySQL
     5.1.17

   * `thread_stack'

     Options for thread_stack

     *Command-Line        `--thread_stack=#'        
     Format*                              
     *System Variable     `thread_stack'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `196608'        
     *Min Value*          `131072'        
     *Max Value*          `4294967295'        
     *Block Size*         `1024'          

     The stack size for each thread. Many of the limits detected by the
     `crash-me' test are dependent on this value. See *Note
     mysql-benchmarks::. The default of 192KB (256KB for 64-bit
     systems) is large enough for normal operation. If the thread stack
     size is too small, it limits the complexity of the SQL statements
     that the server can handle, the recursion depth of stored
     procedures, and other memory-consuming actions.

   * `time_format'

     This variable is unused.

   * `time_zone'

     Options for time_zone

     *System Variable     `time_zone'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The current time zone. This variable is used to initialize the
     time zone for each client that connects. By default, the initial
     value of this is `'SYSTEM'' (which means, `use the value of
     `system_time_zone'').  The value can be specified explicitly at
     server startup with the `--default-time-zone' option.  See *Note
     time-zone-support::.

   * `timed_mutexes'

     Options for timed_mutexes

     *Command-Line        `--timed_mutexes'        
     Format*                              
     *System Variable     `timed_mutexes'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     This variable controls whether `InnoDB' mutexes are timed. If this
     variable is set to 0 or `OFF' (the default), mutex timing is
     disabled. If the variable is set to 1 or `ON', mutex timing is
     enabled. With timing enabled, the `os_wait_times' value in the
     output from *Note `SHOW ENGINE INNODB MUTEX': show-engine.
     indicates the amount of time (in ms) spent in operating system
     waits. Otherwise, the value is 0.

   * `timestamp'

     Options for timestamp

     *System Variable     `timestamp'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     Set the time for this client. This is used to get the original
     timestamp if you use the binary log to restore rows.
     TIMESTAMP_VALUE should be a Unix epoch timestamp (a value like
     that returned by `UNIX_TIMESTAMP()', not a value in `'YYYY-MM-DD
     hh:mm:ss'' format) or `DEFAULT'.

     Setting `timestamp' to a constant value causes it to retain that
     value until it is changed again. Setting `timestamp' to `DEFAULT'
     causes its value to be the current date and time as of the time it
     is accessed.

     `SET timestamp' affects the value returned by `NOW()' but not by
     `SYSDATE()'. This means that timestamp settings in the binary log
     have no effect on invocations of `SYSDATE()'. The server can be
     started with the `--sysdate-is-now' option to cause `SYSDATE()' to
     be an alias for `NOW()', in which case `SET timestamp' affects
     both functions.

   * `tmp_table_size'

     Options for tmp_table_size

     *Command-Line        `--tmp_table_size=#'        
     Format*                              
     *System Variable     `tmp_table_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.11)*        
     *Type*               `numeric'        
     *Default*            `33554432'        
     *Min Value*          `1024'          
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.12,         
                          <=              
                          5.1.36)*        
     *Type*               `numeric'        
     *Default*            `16777216'        
     *Min Value*          `1024'          
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.37,         
                          <=              
                          5.1.55)*        
     *Type*               `numeric'        
     *Default*            `16777216'        
     *Min Value*          `1024'          
     *Max Value*          `9223372036854775807'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.56)*        
     *Type*               `numeric'        
     *Default*            `16777216'        
     *Min Value*          `1024'          
     *Max Value*          `18446744073709551615'        

     The maximum size of internal in-memory temporary tables. (The
     actual limit is determined as the minimum of `tmp_table_size' and
     `max_heap_table_size'.) If an in-memory temporary table exceeds
     the limit, MySQL automatically converts it to an on-disk `MyISAM'
     table. Increase the value of `tmp_table_size' (and
     `max_heap_table_size' if necessary) if you do many advanced `GROUP
     BY' queries and you have lots of memory. This variable does not
     apply to user-created `MEMORY' tables.

     You can compare the number of internal on-disk temporary tables
     created to the total number of internal temporary tables created
     by comparing the values of the `Created_tmp_disk_tables' and
     `Created_tmp_tables' variables.

     See also *Note internal-temporary-tables::.

   * `tmpdir'

     Options for tmpdir

     *Command-Line        `--tmpdir=path'        
     Format*                              
                          `-t'            
     *System Variable     `tmpdir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The directory used for temporary files and temporary tables.  This
     variable can be set to a list of several paths that are used in
     round-robin fashion. Paths should be separated by colon characters
     (``:'') on Unix and semicolon characters (``;'') on Windows,
     NetWare, and OS/2.

     The multiple-directory feature can be used to spread the load
     between several physical disks. If the MySQL server is acting as a
     replication slave, you should not set `tmpdir' to point to a
     directory on a memory-based file system or to a directory that is
     cleared when the server host restarts. A replication slave needs
     some of its temporary files to survive a machine restart so that
     it can replicate temporary tables or *Note `LOAD DATA INFILE':
     load-data. operations. If files in the temporary file directory
     are lost when the server restarts, replication fails. You can set
     the slave's temporary directory using the `slave_load_tmpdir'
     variable.  In that case, the slave will not use the general
     `tmpdir' value and you can set `tmpdir' to a nonpermanent location.

   * `transaction_alloc_block_size'

     Options for transaction_alloc_block_size

     *Command-Line        `--transaction_alloc_block_size=#'        
     Format*                              
     *System Variable     `transaction_alloc_block_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `8192'          
     *Min Value*          `1024'          
     *Max Value*          `4294967295'        
     *Block Size*         `1024'          

     The amount in bytes by which to increase a per-transaction memory
     pool which needs memory. See the description of
     `transaction_prealloc_size'.

   * `transaction_prealloc_size'

     Options for transaction_prealloc_size

     *Command-Line        `--transaction_prealloc_size=#'        
     Format*                              
     *System Variable     `transaction_prealloc_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4096'          
     *Min Value*          `1024'          
     *Max Value*          `4294967295'        
     *Block Size*         `1024'          

     There is a per-transaction memory pool from which various
     transaction-related allocations take memory. The initial size of
     the pool in bytes is `transaction_prealloc_size'.  For every
     allocation that cannot be satisfied from the pool because it has
     insufficient memory available, the pool is increased by
     `transaction_alloc_block_size' bytes. When the transaction ends,
     the pool is truncated to `transaction_prealloc_size' bytes.

     By making `transaction_prealloc_size' sufficiently large to
     contain all statements within a single transaction, you can avoid
     many `malloc()' calls.

   * `tx_isolation'

     Options for tx_isolation

     *System Variable     `tx_isolation'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `REPEATABLE-READ'        
     *Valid Values*       `READ-UNCOMMITTED'        
     `READ-COMMITTED'                     
     `REPEATABLE-READ'                    
     ` SERIALIZABLE '                     

     The default transaction isolation level. Defaults to
     `REPEATABLE-READ'.

     This variable can be set directly, or indirectly using the *Note
     `SET TRANSACTION': set-transaction. statement. See *Note
     set-transaction::. If you set `tx_isolation' directly to an
     isolation level name that contains a space, the name should be
     enclosed within quotation marks, with the space replaced by a
     dash. For example:


          SET tx_isolation = 'READ-COMMITTED';

     Any unique prefix of a valid value may be used to set the value of
     this variable.

     The default transaction isolation level can also be set at startup
     using the `--transaction-isolation' server option.

   * `unique_checks'

     Options for unique_checks

     *System Variable     `unique_checks'        
     Name*                                
     *Variable Scope*     Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `1'             

     If set to 1 (the default), uniqueness checks for secondary indexes
     in `InnoDB' tables are performed. If set to 0, storage engines are
     permitted to assume that duplicate keys are not present in input
     data. If you know for certain that your data does not contain
     uniqueness violations, you can set this to 0 to speed up large
     table imports to `InnoDB'.

     Note that setting this variable to 0 does not _require_ storage
     engines to ignore duplicate keys. An engine is still permitted to
     check for them and issue duplicate-key errors if it detects them.

   * `updatable_views_with_limit'

     Options for updatable_views_with_limit

     *Command-Line        `--updatable_views_with_limit=#'        
     Format*                              
     *System Variable     `updatable_views_with_limit'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `1'             

     This variable controls whether updates to a view can be made when
     the view does not contain all columns of the primary key defined
     in the underlying table, if the update statement contains a
     `LIMIT' clause. (Such updates often are generated by GUI tools.)
     An update is an *Note `UPDATE': update. or *Note `DELETE': delete.
     statement. Primary key here means a `PRIMARY KEY', or a `UNIQUE'
     index in which no column can contain `NULL'.

     The variable can have two values:

        * `1' or `YES': Issue a warning only (not an error message).
          This is the default value.

        * `0' or `NO': Prohibit the update.

   * `version'

     The version number for the server. The value might also include a
     suffix indicating server build or configuration information.
     `-log' indicates that one or more of the general log, slow query
     log, or binary log are enabled. `-debug' indicates that the server
     was built with debugging support enabled.

   * `version_comment'

     Options for version_comment

     *System Variable     `version_comment'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The `configure' script has a `--with-comment' option that permits
     a comment to be specified when building MySQL. This variable
     contains the value of that comment.

   * `version_compile_machine'

     Options for version_compile_machine

     *System Variable     `version_compile_machine'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The type of machine or architecture on which MySQL was built.

   * `version_compile_os'

     Options for version_compile_os

     *System Variable     `version_compile_os'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The type of operating system on which MySQL was built.

   * `wait_timeout'

     Options for wait_timeout

     *Command-Line        `--wait_timeout=#'        
     Format*                              
     *System Variable     `wait_timeout'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (Other)       `numeric'        
     *Default*            `28800'         
     *Min Value*          `1'             
     *Max Value*          `31536000'        
                          *Permitted        
                          Values*         
     *Type* (Windows)     `numeric'        
     *Default*            `28800'         
     *Min Value*          `1'             
     *Max Value*          `2147483'        

     The number of seconds the server waits for activity on a
     noninteractive connection before closing it. Before MySQL 5.1.41,
     this timeout applies only to TCP/IP connections, not to
     connections made through Unix socket files, named pipes, or shared
     memory.

     On thread startup, the session `wait_timeout' value is initialized
     from the global `wait_timeout' value or from the global
     `interactive_timeout' value, depending on the type of client (as
     defined by the `CLIENT_INTERACTIVE' connect option to *Note
     `mysql_real_connect()': mysql-real-connect.). See also
     `interactive_timeout'.

   * `warning_count'

     The number of errors, warnings, and notes that resulted from the
     last statement that generated messages. This variable is read
     only. See *Note show-warnings::.


File: manual.info,  Node: using-system-variables,  Next: server-status-variables,  Prev: server-system-variables,  Up: mysqld-server

5.1.5 Using System Variables
----------------------------

* Menu:

* structured-system-variables::  Structured System Variables
* dynamic-system-variables::     Dynamic System Variables

The MySQL server maintains many system variables that indicate how it
is configured. *Note server-system-variables::, describes the meaning
of these variables. Each system variable has a default value. System
variables can be set at server startup using options on the command
line or in an option file. Most of them can be changed dynamically
while the server is running by means of the *Note `SET': set-statement.
statement, which enables you to modify operation of the server without
having to stop and restart it. You can refer to system variable values
in expressions.

The server maintains two kinds of system variables. Global variables
affect the overall operation of the server. Session variables affect
its operation for individual client connections.  A given system
variable can have both a global and a session value. Global and session
system variables are related as follows:

   * When the server starts, it initializes all global variables to
     their default values. These defaults can be changed by options
     specified on the command line or in an option file. (See *Note
     program-options::.)

   * The server also maintains a set of session variables for each
     client that connects. The client's session variables are
     initialized at connect time using the current values of the
     corresponding global variables. For example, the client's SQL mode
     is controlled by the session `sql_mode' value, which is
     initialized when the client connects to the value of the global
     `sql_mode' value.

System variable values can be set globally at server startup by using
options on the command line or in an option file. When you use a
startup option to set a variable that takes a numeric value, the value
can be given with a suffix of `K', `M', or `G' (either uppercase or
lowercase) to indicate a multiplier of 1024, 1024^2 or 1024^3; that is,
units of kilobytes, megabytes, or gigabytes, respectively. Thus, the
following command starts the server with a query cache size of 16
megabytes and a maximum packet size of one gigabyte:


     mysqld --query_cache_size=16M --max_allowed_packet=1G

Within an option file, those variables are set like this:


     [mysqld]
     query_cache_size=16M
     max_allowed_packet=1G

The lettercase of suffix letters does not matter; `16M' and `16m' are
equivalent, as are `1G' and `1g'.

If you want to restrict the maximum value to which a system variable
can be set at runtime with the *Note `SET': set-statement.  statement,
you can specify this maximum by using an option of the form
`--maximum-VAR_NAME=VALUE' at server startup. For example, to prevent
the value of `query_cache_size' from being increased to more than 32MB
at runtime, use the option `--maximum-query_cache_size=32M'.

Many system variables are dynamic and can be changed while the server
runs by using the *Note `SET': set-statement.  statement. For a list,
see *Note dynamic-system-variables::. To change a system variable with
*Note `SET': set-statement, refer to it as VAR_NAME, optionally
preceded by a modifier:

   * To indicate explicitly that a variable is a global variable,
     precede its name by `GLOBAL' or `@@global.'. The `SUPER' privilege
     is required to set global variables.

   * To indicate explicitly that a variable is a session variable,
     precede its name by `SESSION', `@@session.', or `@@'.  Setting a
     session variable requires no special privilege, but a client can
     change only its own session variables, not those of any other
     client.

   * `LOCAL' and `@@local.' are synonyms for `SESSION' and `@@session.'.

   * If no modifier is present, *Note `SET': set-statement.  changes
     the session variable.

A *Note `SET': set-statement.  statement can contain multiple variable
assignments, separated by commas. If you set several system variables,
the most recent `GLOBAL' or `SESSION' modifier in the statement is used
for following variables that have no modifier specified.

Examples:


     SET sort_buffer_size=10000;
     SET @@local.sort_buffer_size=10000;
     SET GLOBAL sort_buffer_size=1000000, SESSION sort_buffer_size=1000000;
     SET @@sort_buffer_size=1000000;
     SET @@global.sort_buffer_size=1000000, @@local.sort_buffer_size=1000000;

The `@@VAR_NAME' syntax for system variables is supported for
compatibility with some other database systems.

If you change a session system variable, the value remains in effect
until your session ends or until you change the variable to a different
value. The change is not visible to other clients.

If you change a global system variable, the value is remembered and
used for new connections until the server restarts. (To make a global
system variable setting permanent, you should set it in an option
file.) The change is visible to any client that accesses that global
variable. However, the change affects the corresponding session
variable only for clients that connect after the change. The global
variable change does not affect the session variable for any client
that is currently connected (not even that of the client that issues the
*Note `SET GLOBAL': set-statement. statement).

To prevent incorrect usage, MySQL produces an error if you use *Note
`SET GLOBAL': set-statement. with a variable that can only be used with
*Note `SET SESSION': set-statement. or if you do not specify `GLOBAL'
(or `@@global.') when setting a global variable.

To set a `SESSION' variable to the `GLOBAL' value or a `GLOBAL' value
to the compiled-in MySQL default value, use the `DEFAULT' keyword. For
example, the following two statements are identical in setting the
session value of `max_join_size' to the global value:


     SET max_join_size=DEFAULT;
     SET @@session.max_join_size=@@global.max_join_size;

Not all system variables can be set to `DEFAULT'.  In such cases, use
of `DEFAULT' results in an error.

You can refer to the values of specific global or session system
variables in expressions by using one of the `@@'-modifiers. For
example, you can retrieve values in a *Note `SELECT': select. statement
like this:


     SELECT @@global.sql_mode, @@session.sql_mode, @@sql_mode;

When you refer to a system variable in an expression as `@@VAR_NAME'
(that is, when you do not specify `@@global.' or `@@session.'), MySQL
returns the session value if it exists and the global value otherwise.
(This differs from `SET @@VAR_NAME = VALUE', which always refers to the
session value.)

*Note*:

Some variables displayed by `SHOW VARIABLES' may not be available using
`SELECT @@VAR_NAME' syntax; an `Unknown system variable' occurs. As a
workaround in such cases, you can use `SHOW VARIABLES LIKE 'VAR_NAME''.

Suffixes for specifying a value multiplier can be used when setting a
variable at server startup, but not to set the value with *Note `SET':
set-statement.  at runtime. On the other hand, with *Note `SET':
set-statement. you can assign a variable's value using an expression,
which is not true when you set a variable at server startup. For
example, the first of the following lines is legal at server startup,
but the second is not:


     shell> mysql --max_allowed_packet=16M
     shell> mysql --max_allowed_packet=16*1024*1024

Conversely, the second of the following lines is legal at runtime, but
the first is not:


     mysql> SET GLOBAL max_allowed_packet=16M;
     mysql> SET GLOBAL max_allowed_packet=16*1024*1024;

*Note*:

Some system variables can be enabled with the *Note `SET':
set-statement.  statement by setting them to `ON' or `1', or disabled
by setting them to `OFF' or `0'. However, to set such a variable on the
command line or in an option file, you must set it to `1' or `0';
setting it to `ON' or `OFF' will not work. For example, on the command
line, `--delay_key_write=1' works but `--delay_key_write=ON' does not.

To display system variable names and values, use the *Note `SHOW
VARIABLES': show-variables. statement:


     mysql> SHOW VARIABLES;
     +---------------------------------+-----------------------------------+
     | Variable_name                   | Value                             |
     +---------------------------------+-----------------------------------+
     | auto_increment_increment        | 1                                 |
     | auto_increment_offset           | 1                                 |
     | automatic_sp_privileges         | ON                                |
     | back_log                        | 50                                |
     | basedir                         | /home/mysql/                      |
     | binlog_cache_size               | 32768                             |
     | bulk_insert_buffer_size         | 8388608                           |
     | character_set_client            | latin1                            |
     | character_set_connection        | latin1                            |
     | character_set_database          | latin1                            |
     | character_set_results           | latin1                            |
     | character_set_server            | latin1                            |
     | character_set_system            | utf8                              |
     | character_sets_dir              | /home/mysql/share/mysql/charsets/ |
     | collation_connection            | latin1_swedish_ci                 |
     | collation_database              | latin1_swedish_ci                 |
     | collation_server                | latin1_swedish_ci                 |
     ...
     | innodb_additional_mem_pool_size | 1048576                           |
     | innodb_autoextend_increment     | 8                                 |
     | innodb_buffer_pool_size         | 8388608                           |
     | innodb_checksums                | ON                                |
     | innodb_commit_concurrency       | 0                                 |
     | innodb_concurrency_tickets      | 500                               |
     | innodb_data_file_path           | ibdata1:10M:autoextend            |
     | innodb_data_home_dir            |                                   |
     ...
     | version                         | 5.1.6-alpha-log                   |
     | version_comment                 | Source distribution               |
     | version_compile_machine         | i686                              |
     | version_compile_os              | suse-linux                        |
     | wait_timeout                    | 28800                             |
     +---------------------------------+-----------------------------------+

With a `LIKE' clause, the statement displays only those variables that
match the pattern. To obtain a specific variable name, use a `LIKE'
clause as shown:


     SHOW VARIABLES LIKE 'max_join_size';
     SHOW SESSION VARIABLES LIKE 'max_join_size';

To get a list of variables whose name match a pattern, use the ``%''
wildcard character in a `LIKE' clause:


     SHOW VARIABLES LIKE '%size%';
     SHOW GLOBAL VARIABLES LIKE '%size%';

Wildcard characters can be used in any position within the pattern to
be matched. Strictly speaking, because ``_'' is a wildcard that matches
any single character, you should escape it as ``\_'' to match it
literally. In practice, this is rarely necessary.

For *Note `SHOW VARIABLES': show-variables, if you specify neither
`GLOBAL' nor `SESSION', MySQL returns `SESSION' values.

The reason for requiring the `GLOBAL' keyword when setting
`GLOBAL'-only variables but not when retrieving them is to prevent
problems in the future. If we were to remove a `SESSION' variable that
has the same name as a `GLOBAL' variable, a client with the `SUPER'
privilege might accidentally change the `GLOBAL' variable rather than
just the `SESSION' variable for its own connection. If we add a
`SESSION' variable with the same name as a `GLOBAL' variable, a client
that intends to change the `GLOBAL' variable might find only its own
`SESSION' variable changed.


File: manual.info,  Node: structured-system-variables,  Next: dynamic-system-variables,  Prev: using-system-variables,  Up: using-system-variables

5.1.5.1 Structured System Variables
...................................

A structured variable differs from a regular system variable in two
respects:

   * Its value is a structure with components that specify server
     parameters considered to be closely related.

   * There might be several instances of a given type of structured
     variable. Each one has a different name and refers to a different
     resource maintained by the server.

MySQL 5.1 supports one structured variable type, which specifies
parameters governing the operation of key caches. A key cache
structured variable has these components:

   * `key_buffer_size'

   * `key_cache_block_size'

   * `key_cache_division_limit'

   * `key_cache_age_threshold'

This section describes the syntax for referring to structured
variables. Key cache variables are used for syntax examples, but
specific details about how key caches operate are found elsewhere, in
*Note myisam-key-cache::.

To refer to a component of a structured variable instance, you can use
a compound name in INSTANCE_NAME.COMPONENT_NAME format.  Examples:


     hot_cache.key_buffer_size
     hot_cache.key_cache_block_size
     cold_cache.key_cache_block_size

For each structured system variable, an instance with the name of
`default' is always predefined. If you refer to a component of a
structured variable without any instance name, the `default' instance
is used. Thus, `default.key_buffer_size' and `key_buffer_size' both
refer to the same system variable.

Structured variable instances and components follow these naming rules:

   * For a given type of structured variable, each instance must have a
     name that is unique _within_ variables of that type. However,
     instance names need not be unique _across_ structured variable
     types. For example, each structured variable has an instance named
     `default', so `default' is not unique across variable types.

   * The names of the components of each structured variable type must
     be unique across all system variable names. If this were not true
     (that is, if two different types of structured variables could
     share component member names), it would not be clear which default
     structured variable to use for references to member names that are
     not qualified by an instance name.

   * If a structured variable instance name is not legal as an unquoted
     identifier, refer to it as a quoted identifier using backticks.
     For example, `hot-cache' is not legal, but ``hot-cache`' is.

   * `global', `session', and `local' are not legal instance names. This
     avoids a conflict with notation such as `@@global.VAR_NAME' for
     referring to nonstructured system variables.

Currently, the first two rules have no possibility of being violated
because the only structured variable type is the one for key caches.
These rules will assume greater significance if some other type of
structured variable is created in the future.

With one exception, you can refer to structured variable components
using compound names in any context where simple variable names can
occur. For example, you can assign a value to a structured variable
using a command-line option:


     shell> mysqld --hot_cache.key_buffer_size=64K

In an option file, use this syntax:


     [mysqld]
     hot_cache.key_buffer_size=64K

If you start the server with this option, it creates a key cache named
`hot_cache' with a size of 64KB in addition to the default key cache
that has a default size of 8MB.

Suppose that you start the server as follows:


     shell> mysqld --key_buffer_size=256K \
              --extra_cache.key_buffer_size=128K \
              --extra_cache.key_cache_block_size=2048

In this case, the server sets the size of the default key cache to
256KB. (You could also have written `--default.key_buffer_size=256K'.)
In addition, the server creates a second key cache named `extra_cache'
that has a size of 128KB, with the size of block buffers for caching
table index blocks set to 2048 bytes.

The following example starts the server with three different key caches
having sizes in a 3:1:1 ratio:


     shell> mysqld --key_buffer_size=6M \
              --hot_cache.key_buffer_size=2M \
              --cold_cache.key_buffer_size=2M

Structured variable values may be set and retrieved at runtime as well.
For example, to set a key cache named `hot_cache' to a size of 10MB,
use either of these statements:


     mysql> SET GLOBAL hot_cache.key_buffer_size = 10*1024*1024;
     mysql> SET @@global.hot_cache.key_buffer_size = 10*1024*1024;

To retrieve the cache size, do this:


     mysql> SELECT @@global.hot_cache.key_buffer_size;

However, the following statement does not work. The variable is not
interpreted as a compound name, but as a simple string for a `LIKE'
pattern-matching operation:


     mysql> SHOW GLOBAL VARIABLES LIKE 'hot_cache.key_buffer_size';

This is the exception to being able to use structured variable names
anywhere a simple variable name may occur.


File: manual.info,  Node: dynamic-system-variables,  Prev: structured-system-variables,  Up: using-system-variables

5.1.5.2 Dynamic System Variables
................................

Many server system variables are dynamic and can be set at runtime
using *Note `SET GLOBAL': set-statement. or *Note `SET SESSION':
set-statement. You can also obtain their values using *Note `SELECT':
select. See *Note using-system-variables::.

The following table shows the full list of all dynamic system
variables. The last column indicates for each variable whether `GLOBAL'
or `SESSION' (or both) apply. The table also lists session options that
can be set with the *Note `SET': set-statement.  statement. *Note
server-system-variables::, discusses these options.

Variables that have a type of `string' take a string value. Variables
that have a type of `numeric' take a numeric value. Variables that have
a type of `boolean' can be set to 0, 1, `ON' or `OFF'. (If you set them
on the command line or in an option file, use the numeric values.)
Variables that are marked as `enumeration' normally should be set to
one of the available values for the variable, but can also be set to
the number that corresponds to the desired enumeration value. For
enumerated system variables, the first enumeration value corresponds to
0. This differs from *Note `ENUM': enum. columns, for which the first
enumeration value corresponds to 1.

*Dynamic Variable Summary*

Variable Name                 Variable Type  Variable Scope
`auto_increment_increment'    numeric        `GLOBAL' |
                                             `SESSION'
`auto_increment_offset'       numeric        `GLOBAL' |
                                             `SESSION'
`autocommit'                  boolean        `SESSION'
`automatic_sp_privileges'     boolean        `GLOBAL'
`big_tables'                  boolean        `SESSION'
`binlog_cache_size'           numeric        `GLOBAL'
`binlog_direct_non_transactional_updates'boolean        `GLOBAL' |
                                             `SESSION'
`binlog_format'               enumeration    `GLOBAL' |
                                             `SESSION'
`bulk_insert_buffer_size'     numeric        `GLOBAL' |
                                             `SESSION'
`character_set_client'        string         `GLOBAL' |
                                             `SESSION'
`character_set_connection'    string         `GLOBAL' |
                                             `SESSION'
`character_set_database'      string         `GLOBAL' |
                                             `SESSION'
`character_set_filesystem'    string         `GLOBAL' |
                                             `SESSION'
`character_set_results'       string         `GLOBAL' |
                                             `SESSION'
`character_set_server'        string         `GLOBAL' |
                                             `SESSION'
`collation_connection'        string         `GLOBAL' |
                                             `SESSION'
`collation_database'          string         `GLOBAL' |
                                             `SESSION'
`collation_server'            string         `GLOBAL' |
                                             `SESSION'
`completion_type'             numeric        `GLOBAL' |
                                             `SESSION'
`concurrent_insert'           boolean        `GLOBAL'
`connect_timeout'             numeric        `GLOBAL'
`debug'                       string         `GLOBAL' |
                                             `SESSION'
`debug_sync'                  string         `GLOBAL' |
                                             `SESSION'
`storage_engine'              enumeration    `GLOBAL' |
                                             `SESSION'
`default_week_format'         numeric        `GLOBAL' |
                                             `SESSION'
`delay_key_write'             enumeration    `GLOBAL'
`delayed_insert_limit'        numeric        `GLOBAL'
`delayed_insert_timeout'      numeric        `GLOBAL'
`delayed_queue_size'          numeric        `GLOBAL'
`div_precision_increment'     numeric        `GLOBAL' |
                                             `SESSION'
`engine_condition_pushdown'   boolean        `GLOBAL' |
                                             `SESSION'
`event_scheduler'             enumeration    `GLOBAL'
`expire_logs_days'            numeric        `GLOBAL'
`flush'                       boolean        `GLOBAL'
`flush_time'                  numeric        `GLOBAL'
`foreign_key_checks'          boolean        `SESSION'
`ft_boolean_syntax'           string         `GLOBAL'
`general_log'                 boolean        `GLOBAL'
`general_log_file'            filename       `GLOBAL'
`group_concat_max_len'        numeric        `GLOBAL' |
                                             `SESSION'
`identity'                    numeric        `SESSION'
`init_connect'                string         `GLOBAL'
`init_slave'                  string         `GLOBAL'
`innodb_adaptive_flushing'    boolean        `GLOBAL'
`innodb_autoextend_increment' numeric        `GLOBAL'
`innodb_change_buffering'     enumeration    `GLOBAL'
`innodb_commit_concurrency'   numeric        `GLOBAL'
`innodb_concurrency_tickets'  numeric        `GLOBAL'
`innodb_fast_shutdown'        numeric        `GLOBAL'
`innodb_file_format'          string         `GLOBAL'
`innodb_file_format_check'    string         `GLOBAL'
`innodb_flush_log_at_trx_commit'enumeration    `GLOBAL'
`innodb_max_dirty_pages_pct'  numeric        `GLOBAL'
`innodb_max_purge_lag'        numeric        `GLOBAL'
`innodb_old_blocks_pct'       numeric        `GLOBAL'
`innodb_old_blocks_time'      numeric        `GLOBAL'
`innodb_random_read_ahead'    boolean        `GLOBAL'
`innodb_read_ahead_threshold' numeric        `GLOBAL'
`innodb_replication_delay'    numeric        `GLOBAL'
`innodb_spin_wait_delay'      numeric        `GLOBAL'
`innodb_stats_method'         enumeration    `GLOBAL'
`innodb_stats_on_metadata'    boolean        `GLOBAL'
`innodb_stats_sample_pages'   numeric        `GLOBAL'
`innodb_strict_mode'          boolean        `GLOBAL' |
                                             `SESSION'
`innodb_support_xa'           boolean        `GLOBAL' |
                                             `SESSION'
`innodb_sync_spin_loops'      numeric        `GLOBAL'
`innodb_table_locks'          boolean        `GLOBAL' |
                                             `SESSION'
`innodb_thread_concurrency'   numeric        `GLOBAL'
`innodb_thread_sleep_delay'   numeric        `GLOBAL'
`innodb_use_legacy_cardinality_algorithm'boolean        `GLOBAL'
`insert_id'                   numeric        `SESSION'
`interactive_timeout'         numeric        `GLOBAL' |
                                             `SESSION'
`join_buffer_size'            numeric        `GLOBAL' |
                                             `SESSION'
`keep_files_on_create'        boolean        `GLOBAL' |
                                             `SESSION'
`key_buffer_size'             numeric        `GLOBAL'
`key_cache_age_threshold'     numeric        `GLOBAL'
`key_cache_block_size'        numeric        `GLOBAL'
`key_cache_division_limit'    numeric        `GLOBAL'
`last_insert_id'              numeric        `SESSION'
`lc_time_names'               string         `GLOBAL' |
                                             `SESSION'
`local_infile'                boolean        `GLOBAL'
`log'                         filename       `GLOBAL'
`log_bin_trust_function_creators'boolean        `GLOBAL'
`log_bin_trust_routine_creators'boolean        `GLOBAL'
`log_output'                  set            `GLOBAL'
`log_queries_not_using_indexes'boolean        `GLOBAL'
`log_slow_queries'            boolean        `GLOBAL'
`log_warnings'                numeric        `GLOBAL' |
                                             `SESSION'
`long_query_time'             numeric        `GLOBAL' |
                                             `SESSION'
`low_priority_updates'        boolean        `GLOBAL' |
                                             `SESSION'
`max_allowed_packet'          numeric        `GLOBAL'
`max_binlog_cache_size'       numeric        `GLOBAL'
`max_binlog_size'             numeric        `GLOBAL'
`max_connect_errors'          numeric        `GLOBAL'
`max_connections'             numeric        `GLOBAL'
`max_delayed_threads'         numeric        `GLOBAL' |
                                             `SESSION'
`max_error_count'             numeric        `GLOBAL' |
                                             `SESSION'
`max_heap_table_size'         numeric        `GLOBAL' |
                                             `SESSION'
`max_insert_delayed_threads'  numeric        `GLOBAL' |
                                             `SESSION'
`max_join_size'               numeric        `GLOBAL' |
                                             `SESSION'
`max_length_for_sort_data'    numeric        `GLOBAL' |
                                             `SESSION'
`max_prepared_stmt_count'     numeric        `GLOBAL'
`max_relay_log_size'          numeric        `GLOBAL'
`max_seeks_for_key'           numeric        `GLOBAL' |
                                             `SESSION'
`max_sort_length'             numeric        `GLOBAL' |
                                             `SESSION'
`max_sp_recursion_depth'      numeric        `GLOBAL' |
                                             `SESSION'
`max_user_connections'        numeric        `GLOBAL' |
                                             `SESSION'
`max_write_lock_count'        numeric        `GLOBAL'
`min_examined_row_limit'      numeric        `GLOBAL' |
                                             `SESSION'
`multi_range_count'           numeric        `GLOBAL' |
                                             `SESSION'
`myisam_data_pointer_size'    numeric        `GLOBAL'
`myisam_max_sort_file_size'   numeric        `GLOBAL'
`myisam_repair_threads'       numeric        `GLOBAL' |
                                             `SESSION'
`myisam_sort_buffer_size'     numeric        `GLOBAL' |
                                             `SESSION'
`myisam_stats_method'         enumeration    `GLOBAL' |
                                             `SESSION'
`myisam_use_mmap'             boolean        `GLOBAL'
`ndb_autoincrement_prefetch_sz'numeric        `GLOBAL' |
                                             `SESSION'
`ndb_blob_read_batch_bytes'   numeric        `GLOBAL' |
                                             `SESSION'
`ndb_blob_write_batch_bytes'  numeric        `GLOBAL' |
                                             `SESSION'
`ndb_cache_check_time'        numeric        `GLOBAL'
`ndb_deferred_constraints'    integer        `GLOBAL' |
                                             `SESSION'
`ndb_deferred_constraints'    integer        `GLOBAL' |
                                             `SESSION'
`ndb_distribution={KEYHASH|LINHASH}'enumeration    `GLOBAL'
`ndb_distribution'            enumeration    `GLOBAL'
`ndb_eventbuffer_max_alloc'   numeric        `GLOBAL'
`ndb_extra_logging'           numeric        `GLOBAL'
`ndb_force_send'              boolean        `GLOBAL' |
                                             `SESSION'
`ndb_join_pushdown'           boolean        `GLOBAL' |
                                             `SESSION'
`ndb_log_bin'                 boolean        `GLOBAL' |
                                             `SESSION'
`ndb_log_binlog_index'        boolean        `GLOBAL'
`ndb_log_empty_epochs'        boolean        `GLOBAL'
`ndb_log_empty_epochs'        boolean        `GLOBAL'
`ndb_log_update_as_write'     boolean        `GLOBAL'
`ndb_log_updated_only'        boolean        `GLOBAL'
`ndb_optimization_delay'      numeric        `GLOBAL'
`ndb_table_no_logging'        boolean        `SESSION'
`ndb_table_temporary'         boolean        `SESSION'
`ndb_use_exact_count'         boolean        `GLOBAL' |
                                             `SESSION'
`ndb_use_transactions'        boolean        `GLOBAL' |
                                             `SESSION'
`ndbinfo_max_bytes'           numeric        `GLOBAL' |
                                             `SESSION'
`ndbinfo_max_rows'            numeric        `GLOBAL' |
                                             `SESSION'
`ndbinfo_offline'             boolean        `GLOBAL'
`ndbinfo_show_hidden'         boolean        `GLOBAL' |
                                             `SESSION'
`ndbinfo_table_prefix'        string         `GLOBAL' |
                                             `SESSION'
`net_buffer_length'           numeric        `GLOBAL' |
                                             `SESSION'
`net_read_timeout'            numeric        `GLOBAL' |
                                             `SESSION'
`net_retry_count'             numeric        `GLOBAL' |
                                             `SESSION'
`net_write_timeout'           numeric        `GLOBAL' |
                                             `SESSION'
`new'                         boolean        `GLOBAL' |
                                             `SESSION'
`old_alter_table'             boolean        `GLOBAL' |
                                             `SESSION'
`old_passwords'               boolean        `GLOBAL' |
                                             `SESSION'
`optimizer_prune_level'       boolean        `GLOBAL' |
                                             `SESSION'
`optimizer_search_depth'      numeric        `GLOBAL' |
                                             `SESSION'
`optimizer_switch'            set            `GLOBAL' |
                                             `SESSION'
`preload_buffer_size'         numeric        `GLOBAL' |
                                             `SESSION'
`profiling'                   boolean        `SESSION'
`profiling_history_size'      numeric        `GLOBAL' |
                                             `SESSION'
`pseudo_thread_id'            numeric        `SESSION'
`query_alloc_block_size'      numeric        `GLOBAL' |
                                             `SESSION'
`query_cache_limit'           numeric        `GLOBAL'
`query_cache_min_res_unit'    numeric        `GLOBAL'
`query_cache_size'            numeric        `GLOBAL'
`query_cache_type'            enumeration    `GLOBAL' |
                                             `SESSION'
`query_cache_wlock_invalidate'boolean        `GLOBAL' |
                                             `SESSION'
`query_prealloc_size'         numeric        `GLOBAL' |
                                             `SESSION'
`rand_seed1'                  numeric        `SESSION'
`rand_seed2'                  numeric        `SESSION'
`range_alloc_block_size'      numeric        `GLOBAL' |
                                             `SESSION'
`read_buffer_size'            numeric        `GLOBAL' |
                                             `SESSION'
`read_only'                   boolean        `GLOBAL'
`read_rnd_buffer_size'        numeric        `GLOBAL' |
                                             `SESSION'
`relay_log_purge'             boolean        `GLOBAL'
`rpl_recovery_rank'           numeric        `GLOBAL'
`safe_show_database'          boolean        `GLOBAL'
`secure_auth'                 boolean        `GLOBAL'
`server_id'                   numeric        `GLOBAL'
`slave_allow_batching'        boolean        `GLOBAL'
`slave_compressed_protocol'   boolean        `GLOBAL'
`slave_exec_mode'             enumeration    `GLOBAL'
`slave_max_allowed_packet'    numeric        `GLOBAL'
`slave_net_timeout'           numeric        `GLOBAL'
`slave_transaction_retries'   numeric        `GLOBAL'
`slow_launch_time'            numeric        `GLOBAL'
`slow_query_log'              boolean        `GLOBAL'
`slow_query_log_file'         filename       `GLOBAL'
`sort_buffer_size'            numeric        `GLOBAL' |
                                             `SESSION'
`sql_auto_is_null'            boolean        `SESSION'
`sql_big_selects'             boolean        `SESSION'
`sql_big_tables'              boolean        `SESSION'
`sql_buffer_result'           boolean        `SESSION'
`sql_log_bin'                 boolean        `SESSION'
`sql_log_off'                 boolean        `SESSION'
`sql_log_update'              boolean        `SESSION'
`sql_low_priority_updates'    boolean        `GLOBAL' |
                                             `SESSION'
`sql_max_join_size'           numeric        `GLOBAL' |
                                             `SESSION'
`sql_mode'                    set            `GLOBAL' |
                                             `SESSION'
`sql_notes'                   boolean        `SESSION'
`sql_quote_show_create'       boolean        `SESSION'
`sql_safe_updates'            boolean        `SESSION'
`sql_select_limit'            numeric        `GLOBAL' |
                                             `SESSION'
`sql_slave_skip_counter'      numeric        `GLOBAL'
`sql_warnings'                boolean        `SESSION'
`storage_engine'              enumeration    `GLOBAL' |
                                             `SESSION'
`sync_binlog'                 numeric        `GLOBAL'
`sync_frm'                    boolean        `GLOBAL'
`table_cache'                 numeric        `GLOBAL'
`table_definition_cache'      numeric        `GLOBAL'
`table_lock_wait_timeout'     numeric        `GLOBAL'
`table_open_cache'            numeric        `GLOBAL'
`table_type'                  enumeration    `GLOBAL' |
                                             `SESSION'
`thread_cache_size'           numeric        `GLOBAL'
`time_zone'                   string         `GLOBAL' |
                                             `SESSION'
`timed_mutexes'               boolean        `GLOBAL'
`timestamp'                   numeric        `SESSION'
`tmp_table_size'              numeric        `GLOBAL' |
                                             `SESSION'
`transaction_alloc_block_size'numeric        `GLOBAL' |
                                             `SESSION'
`transaction_allow_batching'  boolean        `SESSION'
`transaction_prealloc_size'   numeric        `GLOBAL' |
                                             `SESSION'
`tx_isolation'                enumeration    `GLOBAL' |
                                             `SESSION'
`unique_checks'               boolean        `SESSION'
`updatable_views_with_limit'  boolean        `GLOBAL' |
                                             `SESSION'
`wait_timeout'                numeric        `GLOBAL' |
                                             `SESSION'


File: manual.info,  Node: server-status-variables,  Next: sql-mode,  Prev: using-system-variables,  Up: mysqld-server

5.1.6 Server Status Variables
-----------------------------

The server maintains many status variables that provide information
about its operation. You can view these variables and their values by
using the `SHOW [GLOBAL | SESSION] STATUS' statement (see *Note
show-status::).  The optional `GLOBAL' keyword aggregates the values
over all connections, and `SESSION' shows the values for the current
connection.


     mysql> SHOW GLOBAL STATUS;
     +-----------------------------------+------------+
     | Variable_name                     | Value      |
     +-----------------------------------+------------+
     | Aborted_clients                   | 0          |
     | Aborted_connects                  | 0          |
     | Bytes_received                    | 155372598  |
     | Bytes_sent                        | 1176560426 |
     ...
     | Connections                       | 30023      |
     | Created_tmp_disk_tables           | 0          |
     | Created_tmp_files                 | 3          |
     | Created_tmp_tables                | 2          |
     ...
     | Threads_created                   | 217        |
     | Threads_running                   | 88         |
     | Uptime                            | 1389872    |
     +-----------------------------------+------------+

Many status variables are reset to 0 by the *Note `FLUSH STATUS': flush.
statement.

The following table lists all available server status variables:

*Status Variable Summary*

Variable Name                 Variable Type  Variable Scope
`Aborted_clients'             numeric        `GLOBAL'
`Aborted_connects'            numeric        `GLOBAL'
`Binlog_cache_disk_use'       numeric        `GLOBAL'
`Binlog_cache_use'            numeric        `GLOBAL'
`Bytes_received'              numeric        `GLOBAL' |
                                             `SESSION'
`Bytes_sent'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_admin_commands'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_db'                numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_db_upgrade'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_event'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_function'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_procedure'         numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_server'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_table'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_alter_tablespace'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_analyze'                 numeric        `GLOBAL' |
                                             `SESSION'
`Com_assign_to_keycache'      numeric        `GLOBAL' |
                                             `SESSION'
`Com_backup_table'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_begin'                   numeric        `GLOBAL' |
                                             `SESSION'
`Com_binlog'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_call_procedure'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_change_db'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_change_master'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_check'                   numeric        `GLOBAL' |
                                             `SESSION'
`Com_checksum'                numeric        `GLOBAL' |
                                             `SESSION'
`Com_commit'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_db'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_event'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_function'         numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_index'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_procedure'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_server'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_table'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_trigger'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_udf'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_user'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_create_view'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_dealloc_sql'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_delete'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_delete_multi'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_do'                      numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_db'                 numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_event'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_function'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_index'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_procedure'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_server'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_table'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_trigger'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_user'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_drop_view'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_empty_query'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_execute_sql'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_flush'                   numeric        `GLOBAL' |
                                             `SESSION'
`Com_grant'                   numeric        `GLOBAL' |
                                             `SESSION'
`Com_ha_close'                numeric        `GLOBAL' |
                                             `SESSION'
`Com_ha_open'                 numeric        `GLOBAL' |
                                             `SESSION'
`Com_ha_read'                 numeric        `GLOBAL' |
                                             `SESSION'
`Com_help'                    numeric        `GLOBAL' |
                                             `SESSION'
`Com_insert'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_insert_select'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_install_plugin'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_kill'                    numeric        `GLOBAL' |
                                             `SESSION'
`Com_load'                    numeric        `GLOBAL' |
                                             `SESSION'
`Com_lock_tables'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_optimize'                numeric        `GLOBAL' |
                                             `SESSION'
`Com_preload_keys'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_prepare_sql'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_purge'                   numeric        `GLOBAL' |
                                             `SESSION'
`Com_purge_before_date'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_release_savepoint'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_rename_table'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_rename_user'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_repair'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_replace'                 numeric        `GLOBAL' |
                                             `SESSION'
`Com_replace_select'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_reset'                   numeric        `GLOBAL' |
                                             `SESSION'
`Com_restore_table'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_revoke'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_revoke_all'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_rollback'                numeric        `GLOBAL' |
                                             `SESSION'
`Com_rollback_to_savepoint'   numeric        `GLOBAL' |
                                             `SESSION'
`Com_savepoint'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_select'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_set_option'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_authors'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_binlog_events'      numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_binlogs'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_charsets'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_collations'         numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_column_types'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_contributors'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_create_db'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_create_event'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_create_func'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_create_proc'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_create_table'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_create_trigger'     numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_databases'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_engine_logs'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_engine_mutex'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_engine_status'      numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_errors'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_events'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_fields'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_function_code'      numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_function_status'    numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_grants'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_keys'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_logs'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_master_status'      numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_ndb_status'         numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_new_master'         numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_open_tables'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_plugins'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_privileges'         numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_procedure_code'     numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_procedure_status'   numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_processlist'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_profile'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_profiles'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_slave_hosts'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_slave_status'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_status'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_storage_engines'    numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_table_status'       numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_tables'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_triggers'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_variables'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_show_warnings'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_slave_start'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_slave_stop'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_close'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_execute'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_fetch'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_prepare'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_reprepare'          numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_reset'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_stmt_send_long_data'     numeric        `GLOBAL' |
                                             `SESSION'
`Com_truncate'                numeric        `GLOBAL' |
                                             `SESSION'
`Com_uninstall_plugin'        numeric        `GLOBAL' |
                                             `SESSION'
`Com_unlock_tables'           numeric        `GLOBAL' |
                                             `SESSION'
`Com_update'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_update_multi'            numeric        `GLOBAL' |
                                             `SESSION'
`Com_xa_commit'               numeric        `GLOBAL' |
                                             `SESSION'
`Com_xa_end'                  numeric        `GLOBAL' |
                                             `SESSION'
`Com_xa_prepare'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_xa_recover'              numeric        `GLOBAL' |
                                             `SESSION'
`Com_xa_rollback'             numeric        `GLOBAL' |
                                             `SESSION'
`Com_xa_start'                numeric        `GLOBAL' |
                                             `SESSION'
`Compression'                 numeric        `SESSION'
`Connections'                 numeric        `GLOBAL'
`Created_tmp_disk_tables'     numeric        `GLOBAL' |
                                             `SESSION'
`Created_tmp_files'           numeric        `GLOBAL'
`Created_tmp_tables'          numeric        `GLOBAL' |
                                             `SESSION'
`Delayed_errors'              numeric        `GLOBAL'
`Delayed_insert_threads'      numeric        `GLOBAL'
`Delayed_writes'              numeric        `GLOBAL'
`Flush_commands'              numeric        `GLOBAL'
`Handler_commit'              numeric        `GLOBAL' |
                                             `SESSION'
`Handler_delete'              numeric        `GLOBAL' |
                                             `SESSION'
`Handler_discover'            numeric        `GLOBAL' |
                                             `SESSION'
`Handler_prepare'             numeric        `GLOBAL' |
                                             `SESSION'
`Handler_read_first'          numeric        `GLOBAL' |
                                             `SESSION'
`Handler_read_key'            numeric        `GLOBAL' |
                                             `SESSION'
`Handler_read_next'           numeric        `GLOBAL' |
                                             `SESSION'
`Handler_read_prev'           numeric        `GLOBAL' |
                                             `SESSION'
`Handler_read_rnd'            numeric        `GLOBAL' |
                                             `SESSION'
`Handler_read_rnd_next'       numeric        `GLOBAL' |
                                             `SESSION'
`Handler_rollback'            numeric        `GLOBAL' |
                                             `SESSION'
`Handler_savepoint'           numeric        `GLOBAL' |
                                             `SESSION'
`Handler_savepoint_rollback'  numeric        `GLOBAL' |
                                             `SESSION'
`Handler_update'              numeric        `GLOBAL' |
                                             `SESSION'
`Handler_write'               numeric        `GLOBAL' |
                                             `SESSION'
`Innodb_buffer_pool_pages_data'numeric        `GLOBAL'
`Innodb_buffer_pool_pages_dirty'numeric        `GLOBAL'
`Innodb_buffer_pool_pages_flushed'numeric        `GLOBAL'
`Innodb_buffer_pool_pages_free'numeric        `GLOBAL'
`Innodb_buffer_pool_pages_latched'numeric        `GLOBAL'
`Innodb_buffer_pool_pages_misc'numeric        `GLOBAL'
`Innodb_buffer_pool_pages_total'numeric        `GLOBAL'
`Innodb_buffer_pool_read_ahead'numeric        `GLOBAL'
`Innodb_buffer_pool_read_ahead_evicted'numeric        `GLOBAL'
`Innodb_buffer_pool_read_ahead_rnd'numeric        `GLOBAL'
`Innodb_buffer_pool_read_ahead_seq'numeric        `GLOBAL'
`Innodb_buffer_pool_read_requests'numeric        `GLOBAL'
`Innodb_buffer_pool_reads'    numeric        `GLOBAL'
`Innodb_buffer_pool_wait_free'numeric        `GLOBAL'
`Innodb_buffer_pool_write_requests'numeric        `GLOBAL'
`Innodb_data_fsyncs'          numeric        `GLOBAL'
`Innodb_data_pending_fsyncs'  numeric        `GLOBAL'
`Innodb_data_pending_reads'   numeric        `GLOBAL'
`Innodb_data_pending_writes'  numeric        `GLOBAL'
`Innodb_data_read'            numeric        `GLOBAL'
`Innodb_data_reads'           numeric        `GLOBAL'
`Innodb_data_writes'          numeric        `GLOBAL'
`Innodb_data_written'         numeric        `GLOBAL'
`Innodb_dblwr_pages_written'  numeric        `GLOBAL'
`Innodb_dblwr_writes'         numeric        `GLOBAL'
`Innodb_have_atomic_builtins' numeric        `GLOBAL'
`Innodb_log_waits'            numeric        `GLOBAL'
`Innodb_log_write_requests'   numeric        `GLOBAL'
`Innodb_log_writes'           numeric        `GLOBAL'
`Innodb_os_log_fsyncs'        numeric        `GLOBAL'
`Innodb_os_log_pending_fsyncs'numeric        `GLOBAL'
`Innodb_os_log_pending_writes'numeric        `GLOBAL'
`Innodb_os_log_written'       numeric        `GLOBAL'
`Innodb_page_size'            numeric        `GLOBAL'
`Innodb_pages_created'        numeric        `GLOBAL'
`Innodb_pages_read'           numeric        `GLOBAL'
`Innodb_pages_written'        numeric        `GLOBAL'
`Innodb_row_lock_current_waits'numeric        `GLOBAL'
`Innodb_row_lock_time'        numeric        `GLOBAL'
`Innodb_row_lock_time_avg'    numeric        `GLOBAL'
`Innodb_row_lock_time_max'    numeric        `GLOBAL'
`Innodb_row_lock_waits'       numeric        `GLOBAL'
`Innodb_rows_deleted'         numeric        `GLOBAL'
`Innodb_rows_inserted'        numeric        `GLOBAL'
`Innodb_rows_read'            numeric        `GLOBAL'
`Innodb_rows_updated'         numeric        `GLOBAL'
`Key_blocks_not_flushed'      numeric        `GLOBAL'
`Key_blocks_unused'           numeric        `GLOBAL'
`Key_blocks_used'             numeric        `GLOBAL'
`Key_read_requests'           numeric        `GLOBAL'
`Key_reads'                   numeric        `GLOBAL'
`Key_write_requests'          numeric        `GLOBAL'
`Key_writes'                  numeric        `GLOBAL'
`Last_query_cost'             numeric        `SESSION'
`Max_used_connections'        numeric        `GLOBAL'
`Ndb_api_bytes_received_count'numeric        `GLOBAL'
`Ndb_api_bytes_received_count_session'numeric        `SESSION'
`Ndb_api_bytes_received_count_slave'numeric        `GLOBAL'
`Ndb_api_bytes_sent_count'    numeric        `GLOBAL'
`Ndb_api_bytes_sent_count_session'numeric        `SESSION'
`Ndb_api_bytes_sent_count_slave'numeric        `GLOBAL'
`Ndb_api_event_bytes_count'   numeric        `GLOBAL'
`Ndb_api_event_bytes_count_injector'numeric        `GLOBAL'
`Ndb_api_event_data_count'    numeric        `GLOBAL'
`Ndb_api_event_data_count_injector'numeric        `GLOBAL'
`Ndb_api_event_nondata_count' numeric        `GLOBAL'
`Ndb_api_event_nondata_count_injector'numeric        `GLOBAL'
`Ndb_api_pk_op_count'         numeric        `GLOBAL'
`Ndb_api_pk_op_count_session' numeric        `SESSION'
`Ndb_api_pk_op_count_slave'   numeric        `GLOBAL'
`Ndb_api_pruned_scan_count'   numeric        `GLOBAL'
`Ndb_api_pruned_scan_count_session'numeric        `SESSION'
`Ndb_api_pruned_scan_count_slave'numeric        `GLOBAL'
`Ndb_api_range_scan_count'    numeric        `GLOBAL'
`Ndb_api_range_scan_count_session'numeric        `SESSION'
`Ndb_api_range_scan_count_slave'numeric        `GLOBAL'
`Ndb_api_read_row_count'      numeric        `GLOBAL'
`Ndb_api_read_row_count_session'numeric        `SESSION'
`Ndb_api_read_row_count_slave'numeric        `GLOBAL'
`Ndb_api_scan_batch_count'    numeric        `GLOBAL'
`Ndb_api_scan_batch_count_session'numeric        `SESSION'
`Ndb_api_scan_batch_count_slave'numeric        `GLOBAL'
`Ndb_api_table_scan_count'    numeric        `GLOBAL'
`Ndb_api_table_scan_count_session'numeric        `SESSION'
`Ndb_api_table_scan_count_slave'numeric        `GLOBAL'
`Ndb_api_trans_abort_count'   numeric        `GLOBAL'
`Ndb_api_trans_abort_count_session'numeric        `SESSION'
`Ndb_api_trans_abort_count_slave'numeric        `GLOBAL'
`Ndb_api_trans_close_count'   numeric        `GLOBAL'
`Ndb_api_trans_close_count_session'numeric        `SESSION'
`Ndb_api_trans_close_count_slave'numeric        `GLOBAL'
`Ndb_api_trans_commit_count'  numeric        `GLOBAL'
`Ndb_api_trans_commit_count_session'numeric        `SESSION'
`Ndb_api_trans_commit_count_slave'numeric        `GLOBAL'
`Ndb_api_trans_local_read_row_count'numeric        `GLOBAL'
`Ndb_api_trans_local_read_row_count_session'numeric        `SESSION'
`Ndb_api_trans_local_read_row_count_slave'numeric        `GLOBAL'
`Ndb_api_trans_start_count'   numeric        `GLOBAL'
`Ndb_api_trans_start_count_session'numeric        `SESSION'
`Ndb_api_trans_start_count_slave'numeric        `GLOBAL'
`Ndb_api_uk_op_count'         numeric        `GLOBAL'
`Ndb_api_uk_op_count_session' numeric        `SESSION'
`Ndb_api_uk_op_count_slave'   numeric        `GLOBAL'
`Ndb_api_wait_exec_complete_count'numeric        `GLOBAL'
`Ndb_api_wait_exec_complete_count_session'numeric        `SESSION'
`Ndb_api_wait_exec_complete_count_slave'numeric        `GLOBAL'
`Ndb_api_wait_meta_request_count'numeric        `GLOBAL'
`Ndb_api_wait_meta_request_count_session'numeric        `SESSION'
`Ndb_api_wait_meta_request_count_slave'numeric        `GLOBAL'
`Ndb_api_wait_nanos_count'    numeric        `GLOBAL'
`Ndb_api_wait_nanos_count_session'numeric        `SESSION'
`Ndb_api_wait_nanos_count_slave'numeric        `GLOBAL'
`Ndb_api_wait_scan_result_count'numeric        `GLOBAL'
`Ndb_api_wait_scan_result_count_session'numeric        `SESSION'
`Ndb_api_wait_scan_result_count_slave'numeric        `GLOBAL'
`ndb_cluster_connection_pool' numeric        `GLOBAL'
`Ndb_cluster_node_id'         numeric        `GLOBAL' |
                                             `SESSION'
`Ndb_config_from_host'        numeric        `GLOBAL' |
                                             `SESSION'
`Ndb_config_from_port'        numeric        `GLOBAL' |
                                             `SESSION'
`Ndb_conflict_fn_epoch'       numeric        `GLOBAL'
`Ndb_conflict_fn_epoch_trans' numeric        `GLOBAL'
`Ndb_conflict_fn_max'         numeric        `GLOBAL'
`Ndb_conflict_fn_old'         numeric        `GLOBAL'
`Ndb_conflict_trans_conflict_commit_count'numeric        `GLOBAL'
`Ndb_conflict_trans_detect_iter_count'numeric        `GLOBAL'
`Ndb_conflict_trans_reject_count'numeric        `GLOBAL'
`Ndb_conflict_trans_row_conflict_count'numeric        `GLOBAL'
`Ndb_conflict_trans_row_reject_count'numeric        `GLOBAL'
`ndb_execute_count'           numeric        `GLOBAL'
`ndb-nodeid'                  numeric        `GLOBAL'
`Ndb_number_of_data_nodes'    numeric        `GLOBAL'
`ndb_pruned_scan_count'       numeric        `GLOBAL'
`Ndb_pushed_queries_defined'  numeric        `GLOBAL'
`Ndb_pushed_queries_dropped'  numeric        `GLOBAL'
`Ndb_pushed_queries_executed' numeric        `GLOBAL'
`ndb_pushed_reads'            numeric        `GLOBAL'
`ndb_scan_count'              numeric        `GLOBAL'
`Not_flushed_delayed_rows'    numeric        `GLOBAL'
`Open_files'                  numeric        `GLOBAL'
`Open_streams'                numeric        `GLOBAL'
`Open_table_definitions'      numeric        `GLOBAL'
`Open_tables'                 numeric        `GLOBAL' |
                                             `SESSION'
`Opened_files'                numeric        `GLOBAL'
`Opened_table_definitions'    numeric        `GLOBAL' |
                                             `SESSION'
`Opened_tables'               numeric        `GLOBAL' |
                                             `SESSION'
`Prepared_stmt_count'         numeric        `GLOBAL'
`Qcache_free_blocks'          numeric        `GLOBAL'
`Qcache_free_memory'          numeric        `GLOBAL'
`Qcache_hits'                 numeric        `GLOBAL'
`Qcache_inserts'              numeric        `GLOBAL'
`Qcache_lowmem_prunes'        numeric        `GLOBAL'
`Qcache_not_cached'           numeric        `GLOBAL'
`Qcache_queries_in_cache'     numeric        `GLOBAL'
`Qcache_total_blocks'         numeric        `GLOBAL'
`Queries'                     numeric        `GLOBAL' |
                                             `SESSION'
`Questions'                   numeric        `GLOBAL' |
                                             `SESSION'
`Rpl_status'                  string         `GLOBAL'
`Select_full_join'            numeric        `GLOBAL' |
                                             `SESSION'
`Select_full_range_join'      numeric        `GLOBAL' |
                                             `SESSION'
`Select_range'                numeric        `GLOBAL' |
                                             `SESSION'
`Select_range_check'          numeric        `GLOBAL' |
                                             `SESSION'
`Select_scan'                 numeric        `GLOBAL' |
                                             `SESSION'
`Slave_heartbeat_period'                     `GLOBAL'
`Slave_open_temp_tables'      numeric        `GLOBAL'
`Slave_received_heartbeats'                  `GLOBAL'
`Slave_retried_transactions'  numeric        `GLOBAL'
`Slave_running'               boolean        `GLOBAL'
`Slow_launch_threads'         numeric        `GLOBAL' |
                                             `SESSION'
`Slow_queries'                numeric        `GLOBAL' |
                                             `SESSION'
`Sort_merge_passes'           numeric        `GLOBAL' |
                                             `SESSION'
`Sort_range'                  numeric        `GLOBAL' |
                                             `SESSION'
`Sort_rows'                   numeric        `GLOBAL' |
                                             `SESSION'
`Sort_scan'                   numeric        `GLOBAL' |
                                             `SESSION'
`Ssl_accept_renegotiates'     numeric        `GLOBAL'
`Ssl_accepts'                 numeric        `GLOBAL'
`Ssl_callback_cache_hits'     numeric        `GLOBAL'
`Ssl_cipher'                  string         `GLOBAL' |
                                             `SESSION'
`Ssl_cipher_list'             string         `GLOBAL' |
                                             `SESSION'
`Ssl_client_connects'         numeric        `GLOBAL'
`Ssl_connect_renegotiates'    numeric        `GLOBAL'
`Ssl_ctx_verify_depth'        numeric        `GLOBAL'
`Ssl_ctx_verify_mode'         numeric        `GLOBAL'
`Ssl_default_timeout'         numeric        `GLOBAL' |
                                             `SESSION'
`Ssl_finished_accepts'        numeric        `GLOBAL'
`Ssl_finished_connects'       numeric        `GLOBAL'
`Ssl_session_cache_hits'      numeric        `GLOBAL'
`Ssl_session_cache_misses'    numeric        `GLOBAL'
`Ssl_session_cache_mode'      string         `GLOBAL'
`Ssl_session_cache_overflows' numeric        `GLOBAL'
`Ssl_session_cache_size'      numeric        `GLOBAL'
`Ssl_session_cache_timeouts'  numeric        `GLOBAL'
`Ssl_sessions_reused'         numeric        `GLOBAL' |
                                             `SESSION'
`Ssl_used_session_cache_entries'numeric        `GLOBAL'
`Ssl_verify_depth'            numeric        `GLOBAL' |
                                             `SESSION'
`Ssl_verify_mode'             numeric        `GLOBAL' |
                                             `SESSION'
`Ssl_version'                 string         `GLOBAL' |
                                             `SESSION'
`Table_locks_immediate'       numeric        `GLOBAL'
`Table_locks_waited'          numeric        `GLOBAL'
`Tc_log_max_pages_used'       numeric        `GLOBAL'
`Tc_log_page_size'            numeric        `GLOBAL'
`Tc_log_page_waits'           numeric        `GLOBAL'
`Threads_cached'              numeric        `GLOBAL'
`Threads_connected'           numeric        `GLOBAL'
`Threads_created'             numeric        `GLOBAL'
`Threads_running'             numeric        `GLOBAL'
`Uptime'                      numeric        `GLOBAL'
`Uptime_since_flush_status'   numeric        `GLOBAL'

The status variables have the following meanings. For meanings of
status variables specific to MySQL Cluster, see *Note
mysql-cluster-status-variables::.

   * `Aborted_clients'

     The number of connections that were aborted because the client
     died without closing the connection properly. See *Note
     communication-errors::.

   * `Aborted_connects'

     The number of failed attempts to connect to the MySQL server.  See
     *Note communication-errors::.

   * `Binlog_cache_disk_use'

     The number of transactions that used the temporary binary log
     cache but that exceeded the value of `binlog_cache_size' and used a
     temporary file to store statements from the transaction.

   * `Binlog_cache_use'

     The number of transactions that used the temporary binary log
     cache.

   * `Bytes_received'

     The number of bytes received from all clients.

   * `Bytes_sent'

     The number of bytes sent to all clients.

   * `Com_XXX'

     The `Com_XXX' statement counter variables indicate the number of
     times each XXX statement has been executed.  There is one status
     variable for each type of statement. For example, `Com_delete' and
     `Com_update' count *Note `DELETE': delete. and *Note `UPDATE':
     update. statements, respectively. `Com_delete_multi' and
     `Com_update_multi' are similar but apply to *Note `DELETE':
     delete. and *Note `UPDATE': update. statements that use
     multiple-table syntax.

     If a query result is returned from query cache, the server
     increments the `Qcache_hits' status variable, not `Com_select'. See
     *Note query-cache-status-and-maintenance::.

     All of the `Com_stmt_XXX' variables are increased even if a
     prepared statement argument is unknown or an error occurred during
     execution. In other words, their values correspond to the number
     of requests issued, not to the number of requests successfully
     completed.

     The `Com_stmt_XXX' status variables are as follows:

        * `Com_stmt_prepare'

        * `Com_stmt_execute'

        * `Com_stmt_fetch'

        * `Com_stmt_send_long_data'

        * `Com_stmt_reset'

        * `Com_stmt_close'

     Those variables stand for prepared statement commands. Their names
     refer to the `COM_XXX' command set used in the network layer. In
     other words, their values increase whenever prepared statement API
     calls such as `mysql_stmt_prepare()', `mysql_stmt_execute()', and
     so forth are executed. However, `Com_stmt_prepare',
     `Com_stmt_execute' and `Com_stmt_close' also increase for *Note
     `PREPARE': prepare, *Note `EXECUTE': execute, or *Note `DEALLOCATE
     PREPARE': deallocate-prepare, respectively. Additionally, the
     values of the older statement counter variables `Com_prepare_sql',
     `Com_execute_sql', and `Com_dealloc_sql' increase for the *Note
     `PREPARE': prepare, *Note `EXECUTE': execute, and *Note
     `DEALLOCATE PREPARE': deallocate-prepare. statements.
     `Com_stmt_fetch' stands for the total number of network
     round-trips issued when fetching from cursors.

     `Com_stmt_reprepare' indicates the number of times statements were
     automatically reprepared by the server after metadata changes to
     tables or views referred to by the statement. This variable was
     added in MySQL 5.1.25. A reprepare operation increments
     `Com_stmt_reprepare', and also `Com_stmt_prepare'.

   * `Compression'

     Whether the client connection uses compression in the
     client/server protocol. Added in MySQL 5.1.2.

   * `Connections'

     The number of connection attempts (successful or not) to the MySQL
     server.

   * `Created_tmp_disk_tables'

     The number of internal on-disk temporary tables created by the
     server while executing statements.

     If an internal temporary table is created initially as an
     in-memory table but becomes too large, MySQL automatically
     converts it to an on-disk table. The maximum size for in-memory
     temporary tables is the minimum of the `tmp_table_size' and
     `max_heap_table_size' values.  If `Created_tmp_disk_tables' is
     large, you may want to increase the `tmp_table_size' or
     `max_heap_table_size' value to lessen the likelihood that internal
     temporary tables in memory will be converted to on-disk tables.

     You can compare the number of internal on-disk temporary tables
     created to the total number of internal temporary tables created
     by comparing the values of the `Created_tmp_disk_tables' and
     `Created_tmp_tables' variables.

     See also *Note internal-temporary-tables::.

   * `Created_tmp_files'

     How many temporary files *Note `mysqld': mysqld. has created.

   * `Created_tmp_tables'

     The number of internal temporary tables created by the server
     while executing statements.

     You can compare the number of internal on-disk temporary tables
     created to the total number of internal temporary tables created
     by comparing the values of the `Created_tmp_disk_tables' and
     `Created_tmp_tables' variables.

     See also *Note internal-temporary-tables::.

     Each invocation of the *Note `SHOW STATUS': show-status. statement
     uses an internal temporary table and increments the global
     `Created_tmp_tables' value.

   * `Delayed_errors'

     The number of rows written with *Note `INSERT DELAYED':
     insert-delayed. for which some error occurred (probably `duplicate
     key').

   * `Delayed_insert_threads'

     The number of *Note `INSERT DELAYED': insert-delayed.  handler
     threads in use.

   * `Delayed_writes'

     The number of *Note `INSERT DELAYED': insert-delayed.  rows
     written.

   * `Flush_commands'

     The number of times the server flushes tables, whether because a
     user executed a *Note `FLUSH TABLES': flush. statement or due to
     internal server operation. It is also incremented by receipt of a
     `COM_REFRESH' packet. This is in contrast to `Com_flush', which
     indicates how many `FLUSH' statements have been executed, whether
     *Note `FLUSH TABLES': flush, *Note `FLUSH LOGS': flush, and so
     forth.

   * `Handler_commit'

     The number of internal *Note `COMMIT': commit.  statements.

   * `Handler_delete'

     The number of times that rows have been deleted from tables.

   * `Handler_prepare'

     A counter for the prepare phase of two-phase commit operations.

   * `Handler_read_first'

     The number of times the first entry in an index was read. If this
     value is high, it suggests that the server is doing a lot of full
     index scans; for example, `SELECT col1 FROM foo', assuming that
     `col1' is indexed.

   * `Handler_read_key'

     The number of requests to read a row based on a key. If this value
     is high, it is a good indication that your tables are properly
     indexed for your queries.

   * `Handler_read_next'

     The number of requests to read the next row in key order. This
     value is incremented if you are querying an index column with a
     range constraint or if you are doing an index scan.

   * `Handler_read_prev'

     The number of requests to read the previous row in key order.
     This read method is mainly used to optimize `ORDER BY ... DESC'.

   * `Handler_read_rnd'

     The number of requests to read a row based on a fixed position.
     This value is high if you are doing a lot of queries that require
     sorting of the result. You probably have a lot of queries that
     require MySQL to scan entire tables or you have joins that do not
     use keys properly.

   * `Handler_read_rnd_next'

     The number of requests to read the next row in the data file.
     This value is high if you are doing a lot of table scans.
     Generally this suggests that your tables are not properly indexed
     or that your queries are not written to take advantage of the
     indexes you have.

   * `Handler_rollback'

     The number of requests for a storage engine to perform a rollback
     operation.

   * `Handler_savepoint'

     The number of requests for a storage engine to place a savepoint.

   * `Handler_savepoint_rollback'

     The number of requests for a storage engine to roll back to a
     savepoint.

   * `Handler_update'

     The number of requests to update a row in a table.

   * `Handler_write'

     The number of requests to insert a row in a table.

   * `Innodb_buffer_pool_pages_data'

     The number of pages containing data (dirty or clean).

   * `Innodb_buffer_pool_pages_dirty'

     The number of pages currently dirty.

   * `Innodb_buffer_pool_pages_flushed'

     The number of buffer pool page-flush requests.

   * `Innodb_buffer_pool_pages_free'

     The number of free pages.

   * `Innodb_buffer_pool_pages_latched'

     The number of latched pages in `InnoDB' buffer pool. These are
     pages currently being read or written or that cannot be flushed or
     removed for some other reason.  Calculation of this variable is
     expensive, so as of MySQL 5.1.28, it is available only when the
     `UNIV_DEBUG' system is defined at server build time.

   * `Innodb_buffer_pool_pages_misc'

     The number of pages that are busy because they have been allocated
     for administrative overhead such as row locks or the adaptive hash
     index. This value can also be calculated as
     `Innodb_buffer_pool_pages_total' - `Innodb_buffer_pool_pages_free'
     - `Innodb_buffer_pool_pages_data'.

   * `Innodb_buffer_pool_pages_total'

     The total size of the buffer pool, in pages.

   * `Innodb_buffer_pool_read_ahead'

     (`InnoDB Plugin' only) The number of pages read into the `InnoDB'
     buffer pool by the read-ahead background thread.

     This variable was added in MySQL 5.1.41.

   * `Innodb_buffer_pool_read_ahead_evicted'

     (`InnoDB Plugin' only) The number of pages read into the `InnoDB'
     buffer pool by the read-ahead background thread that were
     subsequently evicted without having been accessed by queries.

     This variable was added in MySQL 5.1.41.

   * `Innodb_buffer_pool_read_ahead_rnd'

     The number of `random' read-aheads initiated by `InnoDB'. This
     happens when a query scans a large portion of a table but in
     random order.

     For `InnoDB Plugin', this variable was removed in MySQL 5.1.41.

   * `Innodb_buffer_pool_read_ahead_seq'

     The number of sequential read-aheads initiated by `InnoDB'. This
     happens when `InnoDB' does a sequential full table scan.

     For `InnoDB Plugin', this variable was removed in MySQL 5.1.41.

   * `Innodb_buffer_pool_read_requests'

     The number of logical read requests.

   * `Innodb_buffer_pool_reads'

     The number of logical reads that `InnoDB' could not satisfy from
     the buffer pool, and had to read directly from the disk.

   * `Innodb_buffer_pool_wait_free'

     Normally, writes to the `InnoDB' buffer pool happen in the
     background. However, if it is necessary to read or create a page
     and no clean pages are available, it is also necessary to wait for
     pages to be flushed first. This counter counts instances of these
     waits. If the buffer pool size has been set properly, this value
     should be small.

   * `Innodb_buffer_pool_write_requests'

     The number writes done to the `InnoDB' buffer pool.

   * `Innodb_data_fsyncs'

     The number of `fsync()' operations so far.

   * `Innodb_data_pending_fsyncs'

     The current number of pending `fsync()' operations.

   * `Innodb_data_pending_reads'

     The current number of pending reads.

   * `Innodb_data_pending_writes'

     The current number of pending writes.

   * `Innodb_data_read'

     The amount of data read since the server was started.

   * `Innodb_data_reads'

     The total number of data reads.

   * `Innodb_data_writes'

     The total number of data writes.

   * `Innodb_data_written'

     The amount of data written so far, in bytes.

   * `Innodb_dblwr_pages_written'

     The number of pages that have been written for doublewrite
     operations. See *Note innodb-disk-io::.

   * `Innodb_dblwr_writes'

     The number of doublewrite operations that have been performed.
     See *Note innodb-disk-io::.

   * `Innodb_have_atomic_builtins'

     (`InnoDB Plugin' only) Indicates whether the server was built with
     atomic instructions. This variable was added in MySQL 5.1.38.

   * `Innodb_log_waits'

     The number of times that the log buffer was too small and a wait
     was required for it to be flushed before continuing.

   * `Innodb_log_write_requests'

     The number of log write requests.

   * `Innodb_log_writes'

     The number of physical writes to the log file.

   * `Innodb_os_log_fsyncs'

     The number of `fsync()' writes done to the log file.

   * `Innodb_os_log_pending_fsyncs'

     The number of pending log file `fsync()' operations.

   * `Innodb_os_log_pending_writes'

     The number of pending log file writes.

   * `Innodb_os_log_written'

     The number of bytes written to the log file.

   * `Innodb_page_size'

     The compiled-in `InnoDB' page size (default 16KB). Many values are
     counted in pages; the page size enables them to be easily
     converted to bytes.

   * `Innodb_pages_created'

     The number of pages created.

   * `Innodb_pages_read'

     The number of pages read.

   * `Innodb_pages_written'

     The number of pages written.

   * `Innodb_row_lock_current_waits'

     The number of row locks currently being waited for.

   * `Innodb_row_lock_time'

     The total time spent in acquiring row locks, in milliseconds.

   * `Innodb_row_lock_time_avg'

     The average time to acquire a row lock, in milliseconds.

   * `Innodb_row_lock_time_max'

     The maximum time to acquire a row lock, in milliseconds.

   * `Innodb_row_lock_waits'

     The number of times a row lock had to be waited for.

   * `Innodb_rows_deleted'

     The number of rows deleted from `InnoDB' tables.

   * `Innodb_rows_inserted'

     The number of rows inserted into `InnoDB' tables.

   * `Innodb_rows_read'

     The number of rows read from `InnoDB' tables.

   * `Innodb_rows_updated'

     The number of rows updated in `InnoDB' tables.

   * `Key_blocks_not_flushed'

     The number of key blocks in the key cache that have changed but
     have not yet been flushed to disk.

   * `Key_blocks_unused'

     The number of unused blocks in the key cache. You can use this
     value to determine how much of the key cache is in use; see the
     discussion of `key_buffer_size' in *Note server-system-variables::.

   * `Key_blocks_used'

     The number of used blocks in the key cache. This value is a
     high-water mark that indicates the maximum number of blocks that
     have ever been in use at one time.

   * `Key_read_requests'

     The number of requests to read a key block from the cache.

   * `Key_reads'

     The number of physical reads of a key block from disk. If
     `Key_reads' is large, then your `key_buffer_size' value is
     probably too small. The cache miss rate can be calculated as
     `Key_reads'/`Key_read_requests'.

   * `Key_write_requests'

     The number of requests to write a key block to the cache.

   * `Key_writes'

     The number of physical writes of a key block to disk.

   * `Last_query_cost'

     The total cost of the last compiled query as computed by the query
     optimizer. This is useful for comparing the cost of different
     query plans for the same query. The default value of 0 means that
     no query has been compiled yet. The default value is 0.
     `Last_query_cost' has session scope.

     The `Last_query_cost' value can be computed accurately only for
     simple `flat' queries, not complex queries such as those with
     subqueries or *Note `UNION': union. For the latter, the value is
     set to 0.

   * `Max_used_connections'

     The maximum number of connections that have been in use
     simultaneously since the server started.

   * `Not_flushed_delayed_rows'

     The number of rows waiting to be written in *Note `INSERT
     DELAYED': insert-delayed. queues.

   * `Open_files'

     The number of files that are open. This count includes regular
     files opened by the server. It does not include other types of
     files such as sockets or pipes. Also, the count does not include
     files that storage engines open using their own internal functions
     rather than asking the server level to do so.

   * `Open_streams'

     The number of streams that are open (used mainly for logging).

   * `Open_table_definitions'

     The number of cached `.frm' files. This variable was added in
     MySQL 5.1.3.

   * `Open_tables'

     The number of tables that are open.

   * `Opened_files'

     The number of files that have been opened with `my_open()' (a
     `mysys' library function). Parts of the server that open files
     without using this function do not increment the count. This
     variable was added in MySQL 5.1.21.

   * `Opened_table_definitions'

     The number of `.frm' files that have been cached. This variable
     was added in MySQL 5.1.24.

   * `Opened_tables'

     The number of tables that have been opened. If `Opened_tables' is
     big, your `table_open_cache' value is probably too small.

   * `Prepared_stmt_count'

     The current number of prepared statements. (The maximum number of
     statements is given by the `max_prepared_stmt_count' system
     variable.) This variable was added in MySQL 5.1.14.

   * `Qcache_free_blocks'

     The number of free memory blocks in the query cache.

   * `Qcache_free_memory'

     The amount of free memory for the query cache.

   * `Qcache_hits'

     The number of query cache hits.

   * `Qcache_inserts'

     The number of queries added to the query cache.

   * `Qcache_lowmem_prunes'

     The number of queries that were deleted from the query cache
     because of low memory.

   * `Qcache_not_cached'

     The number of noncached queries (not cacheable, or not cached due
     to the `query_cache_type' setting).

   * `Qcache_queries_in_cache'

     The number of queries registered in the query cache.

   * `Qcache_total_blocks'

     The total number of blocks in the query cache.

   * `Queries'

     The number of statements executed by the server. This variable
     includes statements executed within stored programs, unlike the
     `Questions' variable. It does not count `COM_PING' or
     `COM_STATISTICS' commands. This variable was added in MySQL 5.1.31.

   * `Questions'

     The number of statements executed by the server. As of MySQL
     5.1.31, this includes only statements sent to the server by
     clients and no longer includes statements executed within stored
     programs, unlike the `Queries' variable. This variable does not
     count `COM_PING', `COM_STATISTICS', `COM_STMT_PREPARE',
     `COM_STMT_CLOSE', or `COM_STMT_RESET' commands.

   * `Rpl_status'

     The status of fail-safe replication (not implemented). This
     variable is unused and is removed in MySQL 5.6.

   * `Select_full_join'

     The number of joins that perform table scans because they do not
     use indexes. If this value is not 0, you should carefully check
     the indexes of your tables.

   * `Select_full_range_join'

     The number of joins that used a range search on a reference table.

   * `Select_range'

     The number of joins that used ranges on the first table. This is
     normally not a critical issue even if the value is quite large.

   * `Select_range_check'

     The number of joins without keys that check for key usage after
     each row. If this is not 0, you should carefully check the indexes
     of your tables.

   * `Select_scan'

     The number of joins that did a full scan of the first table.

   * `Slave_open_temp_tables'

     The number of temporary tables that the slave SQL thread currently
     has open. If the value is greater than zero, it is not safe to
     shut down the slave; see *Note replication-features-temptables::.

   * `Slave_retried_transactions'

     The total number of times since startup that the replication slave
     SQL thread has retried transactions.

   * `Slave_running'

     This is `ON' if this server is a replication slave that is
     connected to a replication master, and both the I/O and SQL
     threads are running; otherwise, it is `OFF'.

   * `Slow_launch_threads'

     The number of threads that have taken more than `slow_launch_time'
     seconds to create.

   * `Slow_queries'

     The number of queries that have taken more than `long_query_time'
     seconds. This counter increments regardless of whether the slow
     query log is enabled. For information about that log, see *Note
     slow-query-log::.

   * `Sort_merge_passes'

     The number of merge passes that the sort algorithm has had to do.
     If this value is large, you should consider increasing the value
     of the `sort_buffer_size' system variable.

   * `Sort_range'

     The number of sorts that were done using ranges.

   * `Sort_rows'

     The number of sorted rows.

   * `Sort_scan'

     The number of sorts that were done by scanning the table.

   * `Ssl_accept_renegotiates'

     The number of negotiates needed to establish the connection.

   * `Ssl_accepts'

     The number of accepted SSL connections.

   * `Ssl_callback_cache_hits'

     The number of callback cache hits.

   * `Ssl_cipher'

     The current SSL cipher (empty for non-SSL connections).

   * `Ssl_cipher_list'

     The list of possible SSL ciphers (empty for non-SSL connections).

   * `Ssl_client_connects'

     The number of SSL connection attempts to an SSL-enabled master.

   * `Ssl_connect_renegotiates'

     The number of negotiates needed to establish the connection to an
     SSL-enabled master.

   * `Ssl_ctx_verify_depth'

     The SSL context verification depth (how many certificates in the
     chain are tested).

   * `Ssl_ctx_verify_mode'

     The SSL context verification mode.

   * `Ssl_default_timeout'

     The default SSL timeout.

   * `Ssl_finished_accepts'

     The number of successful SSL connections to the server.

   * `Ssl_finished_connects'

     The number of successful slave connections to an SSL-enabled
     master.

   * `Ssl_session_cache_hits'

     The number of SSL session cache hits.

   * `Ssl_session_cache_misses'

     The number of SSL session cache misses.

   * `Ssl_session_cache_mode'

     The SSL session cache mode.

   * `Ssl_session_cache_overflows'

     The number of SSL session cache overflows.

   * `Ssl_session_cache_size'

     The SSL session cache size.

   * `Ssl_session_cache_timeouts'

     The number of SSL session cache timeouts.

   * `Ssl_sessions_reused'

     How many SSL connections were reused from the cache.

   * `Ssl_used_session_cache_entries'

     How many SSL session cache entries were used.

   * `Ssl_verify_depth'

     The verification depth for replication SSL connections.

   * `Ssl_verify_mode'

     The verification mode for replication SSL connections.

   * `Ssl_version'

     The SSL protocol version of the connection.

   * `Table_locks_immediate'

     The number of times that a request for a table lock could be
     granted immediately.

   * `Table_locks_waited'

     The number of times that a request for a table lock could not be
     granted immediately and a wait was needed. If this is high and you
     have performance problems, you should first optimize your queries,
     and then either split your table or tables or use replication.

   * `Tc_log_max_pages_used'

     For the memory-mapped implementation of the log that is used by
     *Note `mysqld': mysqld. when it acts as the transaction
     coordinator for recovery of internal XA transactions, this
     variable indicates the largest number of pages used for the log
     since the server started. If the product of
     `Tc_log_max_pages_used' and `Tc_log_page_size' is always
     significantly less than the log size, the size is larger than
     necessary and can be reduced. (The size is set by the
     `--log-tc-size' option.  Currently, this variable is unused: It is
     unneeded for binary log-based recovery, and the memory-mapped
     recovery log method is not used unless the number of storage
     engines capable of two-phase commit is greater than one.
     (`InnoDB' is the only applicable engine.)

   * `Tc_log_page_size'

     The page size used for the memory-mapped implementation of the XA
     recovery log. The default value is determined using
     `getpagesize()'. Currently, this variable is unused for the same
     reasons as described for `Tc_log_max_pages_used'.

   * `Tc_log_page_waits'

     For the memory-mapped implementation of the recovery log, this
     variable increments each time the server was not able to commit a
     transaction and had to wait for a free page in the log. If this
     value is large, you might want to increase the log size (with the
     `--log-tc-size' option). For binary log-based recovery, this
     variable increments each time the binary log cannot be closed
     because there are two-phase commits in progress. (The close
     operation waits until all such transactions are finished.)

   * `Threads_cached'

     The number of threads in the thread cache.

   * `Threads_connected'

     The number of currently open connections.

   * `Threads_created'

     The number of threads created to handle connections. If
     `Threads_created' is big, you may want to increase the
     `thread_cache_size' value. The cache miss rate can be calculated as
     `Threads_created'/`Connections'.

   * `Threads_running'

     The number of threads that are not sleeping.

   * `Uptime'

     The number of seconds that the server has been up.

   * `Uptime_since_flush_status'

     The number of seconds since the most recent `FLUSH STATUS'
     statement. This variable was added in 5.1.24.


File: manual.info,  Node: sql-mode,  Next: server-plugins,  Prev: server-status-variables,  Up: mysqld-server

5.1.7 Server SQL Modes
----------------------

The MySQL server can operate in different SQL modes, and can apply
these modes differently for different clients, depending on the value
of the `sql_mode' system variable. DBAs can set the global SQL mode to
match site server operating requirements, and each application can set
its session SQL mode to its own requirements.

Modes affect the SQL syntax MySQL supports and the data validation
checks it performs. This makes it easier to use MySQL in different
environments and to use MySQL together with other database servers.

   * *Note sql-mode-setting::

   * *Note sql-mode-important::

   * *Note sql-mode-full::

   * *Note sql-mode-strict::

   * *Note sql-mode-combo::

When working with `InnoDB' tables using the InnoDB Plugin, consider
also the `innodb_strict_mode' system variable. It enables additional
error checks for `InnoDB' tables.

*Setting the SQL Mode*

The default SQL mode is empty (no modes set).

To set the SQL mode at server startup, use the `--sql-mode="MODES"'
option on the command line, or `sql-mode="MODES"' in an option file
such as `my.cnf' (Unix operating systems) or `my.ini' (Windows).  MODES
is a list of different modes separated by commas. To clear the SQL mode
explicitly, set it to an empty string using `--sql-mode=""' on the
command line, or `sql-mode=""' in an option file.

*Note*:

MySQL installation programs may configure the SQL mode during the
installation process. If the SQL mode differs from the default or from
what you expect, check for a setting in an option file that the server
reads at startup.

To change the SQL mode at runtime, set the global or session `sql_mode'
system variable using a *Note `SET': set-statement.  statement:


     SET GLOBAL sql_mode = 'MODES';
     SET SESSION sql_mode = 'MODES';

Setting the `GLOBAL' variable requires the `SUPER' privilege and
affects the operation of all clients that connect from that time on.
Setting the `SESSION' variable affects only the current client. Each
client can change its session `sql_mode' value at any time.

To determine the current global or session `sql_mode' value, use the
following statements:


     SELECT @@GLOBAL.sql_mode;
     SELECT @@SESSION.sql_mode;

*Important*:

SQL mode and user-defined partitioning

Changing the server SQL mode after creating and inserting data into
partitioned tables can cause major changes in the behavior of such
tables, and could lead to loss or corruption of data. It is strongly
recommended that you never change the SQL mode once you have created
tables employing user-defined partitioning.

When replicating partitioned tables, differing SQL modes on master and
slave can also lead to problems. For best results, you should always
use the same server SQL mode on the master and on the slave.

See *Note partitioning-limitations::, for more information.

*The Most Important SQL Modes*

The most important `sql_mode' values are probably these:

   * `ANSI'

     This mode changes syntax and behavior to conform more closely to
     standard SQL. It is one of the special combination modes listed at
     the end of this section.

   * `STRICT_TRANS_TABLES'

     If a value could not be inserted as given into a transactional
     table, abort the statement. For a nontransactional table, abort
     the statement if the value occurs in a single-row statement or the
     first row of a multiple-row statement. More details are given
     later in this section.

   * `TRADITIONAL'

     Make MySQL behave like a `traditional' SQL database system. A
     simple description of this mode is `give an error instead of a
     warning' when inserting an incorrect value into a column. It is
     one of the special combination modes listed at the end of this
     section.

     *Note*:

     The *Note `INSERT': insert. or *Note `UPDATE': update. aborts as
     soon as the error is noticed. This may not be what you want if you
     are using a nontransactional storage engine, because data changes
     made prior to the error may not be rolled back, resulting in a
     `partially done' update.

When this manual refers to `strict mode,' it means a mode with either
or both `STRICT_TRANS_TABLES' or `STRICT_ALL_TABLES' enabled.

*Full List of SQL Modes*

The following list describes all supported SQL modes:

   * `ALLOW_INVALID_DATES'

     Do not perform full checking of dates. Check only that the month
     is in the range from 1 to 12 and the day is in the range from 1 to
     31. This is very convenient for Web applications where you obtain
     year, month, and day in three different fields and you want to
     store exactly what the user inserted (without date validation).
     This mode applies to *Note `DATE': datetime. and *Note `DATETIME':
     datetime. columns. It does not apply *Note `TIMESTAMP': datetime.
     columns, which always require a valid date.

     The server requires that month and day values be legal, and not
     merely in the range 1 to 12 and 1 to 31, respectively.  With
     strict mode disabled, invalid dates such as `'2004-04-31'' are
     converted to `'0000-00-00'' and a warning is generated.  With
     strict mode enabled, invalid dates generate an error. To permit
     such dates, enable `ALLOW_INVALID_DATES'.

   * `ANSI_QUOTES'

     Treat ``"'' as an identifier quote character (like the ```'' quote
     character) and not as a string quote character. You can still use
     ```'' to quote identifiers with this mode enabled. With
     `ANSI_QUOTES' enabled, you cannot use double quotation marks to
     quote literal strings, because it is interpreted as an identifier.

   * `ERROR_FOR_DIVISION_BY_ZERO'

     The `ERROR_FOR_DIVISION_BY_ZERO' mode affects handling of division
     by zero, which includes `MOD(N,0)'.  For data-change operations
     (*Note `INSERT': insert, *Note `UPDATE': update.), its effect also
     depends on whether strict SQL mode is enabled.

        * If this mode is not enabled, division by zero inserts `NULL'
          and produces no warning.

        * If this mode is enabled, division by zero inserts `NULL' and
          produces a warning.

        * If this mode and strict mode are enabled, division by zero
          produces an error, unless `IGNORE' is given as well. For
          `INSERT IGNORE' and `UPDATE IGNORE', division by zero inserts
          `NULL' and produces a warning.

     For *Note `SELECT': select, division by zero returns `NULL'.
     Enabling `ERROR_FOR_DIVISION_BY_ZERO' causes a warning to be
     produced as well, regardless of whether strict mode is enabled.

   * `HIGH_NOT_PRECEDENCE'

     The precedence of the `NOT' operator is such that expressions such
     as `NOT a BETWEEN b AND c' are parsed as `NOT (a BETWEEN b AND
     c)'. In some older versions of MySQL, the expression was parsed as
     `(NOT a) BETWEEN b AND c'. The old higher-precedence behavior can
     be obtained by enabling the `HIGH_NOT_PRECEDENCE' SQL mode.


          mysql> SET sql_mode = '';
          mysql> SELECT NOT 1 BETWEEN -5 AND 5;
                  -> 0
          mysql> SET sql_mode = 'HIGH_NOT_PRECEDENCE';
          mysql> SELECT NOT 1 BETWEEN -5 AND 5;
                  -> 1

   * `IGNORE_SPACE'

     Permit spaces between a function name and the ``('' character.
     This causes built-in function names to be treated as reserved
     words. As a result, identifiers that are the same as function
     names must be quoted as described in *Note identifiers::. For
     example, because there is a `COUNT()' function, the use of `count'
     as a table name in the following statement causes an error:


          mysql> CREATE TABLE count (i INT);
          ERROR 1064 (42000): You have an error in your SQL syntax

     The table name should be quoted:


          mysql> CREATE TABLE `count` (i INT);
          Query OK, 0 rows affected (0.00 sec)

     The `IGNORE_SPACE' SQL mode applies to built-in functions, not to
     user-defined functions or stored functions. It is always
     permissible to have spaces after a UDF or stored function name,
     regardless of whether `IGNORE_SPACE' is enabled.

     For further discussion of `IGNORE_SPACE', see *Note
     function-resolution::.

   * `NO_AUTO_CREATE_USER'

     Prevent the *Note `GRANT': grant. statement from automatically
     creating new users if it would otherwise do so, unless a nonempty
     password also is specified.

   * `NO_AUTO_VALUE_ON_ZERO'

     `NO_AUTO_VALUE_ON_ZERO' affects handling of `AUTO_INCREMENT'
     columns.  Normally, you generate the next sequence number for the
     column by inserting either `NULL' or `0' into it.
     `NO_AUTO_VALUE_ON_ZERO' suppresses this behavior for `0' so that
     only `NULL' generates the next sequence number.

     This mode can be useful if `0' has been stored in a table's
     `AUTO_INCREMENT' column.  (Storing `0' is not a recommended
     practice, by the way.) For example, if you dump the table with
     *Note `mysqldump': mysqldump. and then reload it, MySQL normally
     generates new sequence numbers when it encounters the `0' values,
     resulting in a table with contents different from the one that was
     dumped. Enabling `NO_AUTO_VALUE_ON_ZERO' before reloading the dump
     file solves this problem.  *Note `mysqldump': mysqldump. now
     automatically includes in its output a statement that enables
     `NO_AUTO_VALUE_ON_ZERO', to avoid this problem.

   * `NO_BACKSLASH_ESCAPES'

     Disable the use of the backslash character (``\'') as an escape
     character within strings. With this mode enabled, backslash
     becomes an ordinary character like any other.

   * `NO_DIR_IN_CREATE'

     When creating a table, ignore all `INDEX DIRECTORY' and `DATA
     DIRECTORY' directives. This option is useful on slave replication
     servers.

   * `NO_ENGINE_SUBSTITUTION'

     Control automatic substitution of the default storage engine when
     a statement such as *Note `CREATE TABLE': create-table. or *Note
     `ALTER TABLE': alter-table.  specifies a storage engine that is
     disabled or not compiled in.

     Up through MySQL 5.1.11, with `NO_ENGINE_SUBSTITUTION' disabled,
     the default engine is used and a warning occurs if the desired
     engine is known but disabled or not compiled in.  If the desired
     engine is invalid (not a known engine name), an error occurs and
     the table is not created or altered.

     With `NO_ENGINE_SUBSTITUTION' enabled, an error occurs and the
     table is not created or altered if the desired engine is
     unavailable for any reason (whether disabled or invalid).

     As of MySQL 5.1.12, storage engines can be pluggable at runtime,
     so the distinction between disabled and invalid no longer applies.
     All unavailable engines are treated the same way:

     With `NO_ENGINE_SUBSTITUTION' disabled, for *Note `CREATE TABLE':
     create-table. the default engine is used and a warning occurs if
     the desired engine is unavailable. For *Note `ALTER TABLE':
     alter-table, a warning occurs and the table is not altered.

     With `NO_ENGINE_SUBSTITUTION' enabled, an error occurs and the
     table is not created or altered if the desired engine is
     unavailable.

   * `NO_FIELD_OPTIONS'

     Do not print MySQL-specific column options in the output of *Note
     `SHOW CREATE TABLE': show-create-table. This mode is used by *Note
     `mysqldump': mysqldump. in portability mode.

   * `NO_KEY_OPTIONS'

     Do not print MySQL-specific index options in the output of *Note
     `SHOW CREATE TABLE': show-create-table. This mode is used by *Note
     `mysqldump': mysqldump. in portability mode.

   * `NO_TABLE_OPTIONS'

     Do not print MySQL-specific table options (such as `ENGINE') in
     the output of *Note `SHOW CREATE TABLE': show-create-table. This
     mode is used by *Note `mysqldump': mysqldump. in portability mode.

   * `NO_UNSIGNED_SUBTRACTION'

     By default, subtraction between integer operands produces an
     `UNSIGNED' result if any operand is`UNSIGNED'. When
     `NO_UNSIGNED_SUBTRACTION' is enabled, the subtraction result is
     signed, _even if any operand is unsigned_. For example, compare the
     type of column `c2' in table `t1' with that of column `c2' in
     table `t2':


          mysql> SET sql_mode='';
          mysql> CREATE TABLE test (c1 BIGINT UNSIGNED NOT NULL);
          mysql> CREATE TABLE t1 SELECT c1 - 1 AS c2 FROM test;
          mysql> DESCRIBE t1;
          +-------+---------------------+------+-----+---------+-------+
          | Field | Type                | Null | Key | Default | Extra |
          +-------+---------------------+------+-----+---------+-------+
          | c2    | bigint(21) unsigned |      |     | 0       |       |
          +-------+---------------------+------+-----+---------+-------+

          mysql> SET sql_mode='NO_UNSIGNED_SUBTRACTION';
          mysql> CREATE TABLE t2 SELECT c1 - 1 AS c2 FROM test;
          mysql> DESCRIBE t2;
          +-------+------------+------+-----+---------+-------+
          | Field | Type       | Null | Key | Default | Extra |
          +-------+------------+------+-----+---------+-------+
          | c2    | bigint(21) |      |     | 0       |       |
          +-------+------------+------+-----+---------+-------+

     Note that this means that `BIGINT UNSIGNED' is not 100% usable in
     all contexts. See *Note cast-functions::.


          mysql> SET sql_mode = '';
          mysql> SELECT CAST(0 AS UNSIGNED) - 1;
          +-------------------------+
          | CAST(0 AS UNSIGNED) - 1 |
          +-------------------------+
          |    18446744073709551615 |
          +-------------------------+

          mysql> SET sql_mode = 'NO_UNSIGNED_SUBTRACTION';
          mysql> SELECT CAST(0 AS UNSIGNED) - 1;
          +-------------------------+
          | CAST(0 AS UNSIGNED) - 1 |
          +-------------------------+
          |                      -1 |
          +-------------------------+

   * `NO_ZERO_DATE'

     The `NO_ZERO_DATE' mode affects whether the server permits
     `'0000-00-00'' as a valid date. Its effect also depends on whether
     strict SQL mode is enabled.

        * If this mode is not enabled, `'0000-00-00'' is permitted and
          inserts produce no warning.

        * If this mode is enabled, `'0000-00-00'' is permitted and
          inserts produce a warning.

        * If this mode and strict mode are enabled, `'0000-00-00'' is
          not permitted and inserts produce an error, unless `IGNORE'
          is given as well. For `INSERT IGNORE' and `UPDATE IGNORE',
          `'0000-00-00'' is permitted and inserts produce a warning.

   * `NO_ZERO_IN_DATE'

     The `NO_ZERO_IN_DATE' mode affects whether the server permits
     dates in which the year part is nonzero but the month or day part
     is 0. (This mode affects dates such as `'2010-00-01'' or
     `'2010-01-00'', but not `'0000-00-00''. To control whether the
     server permits `'0000-00-00'', use the `NO_ZERO_DATE' mode.) The
     effect of `NO_ZERO_IN_DATE' also depends on whether strict SQL
     mode is enabled.

        * If this mode is not enabled, dates with zero parts are
          permitted and inserts produce no warning.

        * If this mode is enabled, dates with zero parts are inserted
          as `'0000-00-00'' and produce a warning.

        * If this mode and strict mode are enabled, dates with zero
          parts are not permitted and inserts produce an error, unless
          `IGNORE' is given as well. For `INSERT IGNORE' and `UPDATE
          IGNORE', dates with zero parts are inserted as `'0000-00-00''
          and produce a warning.

   * `ONLY_FULL_GROUP_BY'

     Do not permit queries for which the select list or (as of MySQL
     5.1.10) `HAVING' condition refer to nonaggregated columns that are
     not named in the `GROUP BY' clause.

     The following queries are invalid with `ONLY_FULL_GROUP_BY'
     enabled.  The first is invalid because the nonaggregated `address'
     column in the select list is not named in the `GROUP BY' clause,
     and the second because `max_age' in the `HAVING' clause is not
     named in the `GROUP BY' clause:


          mysql> SELECT name, address, MAX(age) FROM t GROUP BY name;
          ERROR 1055 (42000): 't.address' isn't in GROUP BY


          mysql> SELECT name, MAX(age) AS max_age FROM t GROUP BY name
              -> HAVING max_age < 30;
          Empty set (0.00 sec)
          ERROR 1463 (42000): Non-grouping field 'max_age' is used in HAVING clause

     In the second example, the query could be rewritten to use `HAVING
     MAX(age)' instead, so that the reference is to a column named in
     an aggregate function.  (`max_age' fails because it _is_ an
     aggregate function.)

     If a query has aggregate functions and no `GROUP BY' clause, it
     cannot have nonaggregated columns in the select list or `ORDER BY'
     list with `ONLY_FULL_GROUP_BY' enabled:


          mysql> SELECT name, MAX(age) FROM t;
          ERROR 1140 (42000): Mixing of GROUP columns (MIN(),MAX(),COUNT(),...)
          with no GROUP columns is illegal if there is no GROUP BY clause

     For additional discussion, see *Note group-by-extensions::.

   * `PAD_CHAR_TO_FULL_LENGTH'

     By default, trailing spaces are trimmed from *Note `CHAR': char.
     column values on retrieval. If `PAD_CHAR_TO_FULL_LENGTH' is
     enabled, trimming does not occur and retrieved *Note `CHAR': char.
     values are padded to their full length. This mode does not apply to
     *Note `VARCHAR': char. columns, for which trailing spaces are
     retained on retrieval. This mode was added in MySQL 5.1.20.


          mysql> CREATE TABLE t1 (c1 CHAR(10));
          Query OK, 0 rows affected (0.37 sec)

          mysql> INSERT INTO t1 (c1) VALUES('xy');
          Query OK, 1 row affected (0.01 sec)

          mysql> SET sql_mode = '';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT c1, CHAR_LENGTH(c1) FROM t1;
          +------+-----------------+
          | c1   | CHAR_LENGTH(c1) |
          +------+-----------------+
          | xy   |               2 |
          +------+-----------------+
          1 row in set (0.00 sec)

          mysql> SET sql_mode = 'PAD_CHAR_TO_FULL_LENGTH';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT c1, CHAR_LENGTH(c1) FROM t1;
          +------------+-----------------+
          | c1         | CHAR_LENGTH(c1) |
          +------------+-----------------+
          | xy         |              10 |
          +------------+-----------------+
          1 row in set (0.00 sec)

   * `PIPES_AS_CONCAT'

     Treat `||' as a string concatenation operator (same as `CONCAT()')
     rather than as a synonym for `OR'.

   * `REAL_AS_FLOAT'

     Treat *Note `REAL': floating-point-types. as a synonym for *Note
     `FLOAT': floating-point-types. By default, MySQL treats *Note
     `REAL': floating-point-types. as a synonym for *Note `DOUBLE':
     floating-point-types.

   * `STRICT_ALL_TABLES'

     Enable strict mode for all storage engines. Invalid data values
     are rejected. Additional details follow.

   * `STRICT_TRANS_TABLES'

     Enable strict mode for transactional storage engines, and when
     possible for nontransactional storage engines. Additional details
     follow.

*Strict SQL Mode*

Strict mode controls how MySQL handles invalid or missing values in
data-change statements such as *Note `INSERT': insert. or *Note
`UPDATE': update. A value can be invalid for several reasons. For
example, it might have the wrong data type for the column, or it might
be out of range. A value is missing when a new row to be inserted does
not contain a value for a non-`NULL' column that has no explicit
`DEFAULT' clause in its definition. (For a `NULL' column, `NULL' is
inserted if the value is missing.)

If strict mode is not in effect, MySQL inserts adjusted values for
invalid or missing values and produces warnings (see *Note
show-warnings::). In strict mode, you can produce this behavior by using
*Note `INSERT IGNORE': insert. or *Note `UPDATE IGNORE': update.

For statements such as *Note `SELECT': select. that do not change data,
invalid values generate a warning in strict mode, not an error.

Strict mode does not affect whether foreign key constraints are
checked. `foreign_key_checks' can be used for that. (See *Note
server-system-variables::.)

Strict SQL mode is in effect if either `STRICT_ALL_TABLES' or
`STRICT_TRANS_TABLES' is enabled, although the effects of these modes
differ somewhat:

   * For transactional tables, an error occurs for invalid or missing
     values in a data-change statement when either `STRICT_ALL_TABLES'
     or `STRICT_TRANS_TABLES' is enabled. The statement is aborted and
     rolled back.

   * For nontransactional tables, the behavior is the same for either
     mode if the bad value occurs in the first row to be inserted or
     updated: The statement is aborted and the table remains unchanged.
     If the statement inserts or modifies multiple rows and the bad
     value occurs in the second or later row, the result depends on
     which strict mode is enabled:

        * For `STRICT_ALL_TABLES', MySQL returns an error and ignores
          the rest of the rows.  However, because the earlier rows have
          been inserted or updated, the result is a partial update. To
          avoid this, use single-row statements, which can be aborted
          without changing the table.

        * For `STRICT_TRANS_TABLES', MySQL converts an invalid value to
          the closest valid value for the column and inserts the
          adjusted value. If a value is missing, MySQL inserts the
          implicit default value for the column data type. In either
          case, MySQL generates a warning rather than an error and
          continues processing the statement. Implicit defaults are
          described in *Note data-type-defaults::.

Strict mode also affects handling of division by zero, zero dates, and
zeros in dates, in conjunction with the `ERROR_FOR_DIVISION_BY_ZERO',
`NO_ZERO_DATE', and `NO_ZERO_IN_DATE' modes. For details, see the
descriptions of those modes.

*Combination SQL Modes*

The following special modes are provided as shorthand for combinations
of mode values from the preceding list.

   * `ANSI'

     Equivalent to `REAL_AS_FLOAT', `PIPES_AS_CONCAT', `ANSI_QUOTES',
     `IGNORE_SPACE'.

     As of MySQL 5.1.18, `ANSI' mode also causes the server to return
     an error for queries where a set function S with an outer reference
     `S(OUTER_REF)' cannot be aggregated in the outer query against
     which the outer reference has been resolved. This is such a query:


          SELECT * FROM t1 WHERE t1.a IN (SELECT MAX(t1.b) FROM t2 WHERE ...);

     Here, `MAX(t1.b)' cannot aggregated in the outer query because it
     appears in the `WHERE' clause of that query. Standard SQL requires
     an error in this situation. If `ANSI' mode is not enabled, the
     server treats `S(OUTER_REF)' in such queries the same way that it
     would interpret `S(CONST)', as was always done prior to 5.1.18.

     See *Note compatibility::.

   * `DB2'

     Equivalent to `PIPES_AS_CONCAT', `ANSI_QUOTES', `IGNORE_SPACE',
     `NO_KEY_OPTIONS', `NO_TABLE_OPTIONS', `NO_FIELD_OPTIONS'.

   * `MAXDB'

     Equivalent to `PIPES_AS_CONCAT', `ANSI_QUOTES', `IGNORE_SPACE',
     `NO_KEY_OPTIONS', `NO_TABLE_OPTIONS', `NO_FIELD_OPTIONS',
     `NO_AUTO_CREATE_USER'.

   * `MSSQL'

     Equivalent to `PIPES_AS_CONCAT', `ANSI_QUOTES', `IGNORE_SPACE',
     `NO_KEY_OPTIONS', `NO_TABLE_OPTIONS', `NO_FIELD_OPTIONS'.

   * `MYSQL323'

     Equivalent to `NO_FIELD_OPTIONS', `HIGH_NOT_PRECEDENCE'.

   * `MYSQL40'

     Equivalent to `NO_FIELD_OPTIONS', `HIGH_NOT_PRECEDENCE'.

   * `ORACLE'

     Equivalent to `PIPES_AS_CONCAT', `ANSI_QUOTES', `IGNORE_SPACE',
     `NO_KEY_OPTIONS', `NO_TABLE_OPTIONS', `NO_FIELD_OPTIONS',
     `NO_AUTO_CREATE_USER'.

   * `POSTGRESQL'

     Equivalent to `PIPES_AS_CONCAT', `ANSI_QUOTES', `IGNORE_SPACE',
     `NO_KEY_OPTIONS', `NO_TABLE_OPTIONS', `NO_FIELD_OPTIONS'.

   * `TRADITIONAL'

     Equivalent to `STRICT_TRANS_TABLES', `STRICT_ALL_TABLES',
     `NO_ZERO_IN_DATE', `NO_ZERO_DATE', `ERROR_FOR_DIVISION_BY_ZERO',
     `NO_AUTO_CREATE_USER'.


File: manual.info,  Node: server-plugins,  Next: server-side-help-support,  Prev: sql-mode,  Up: mysqld-server

5.1.8 Server Plugins
--------------------

* Menu:

* server-plugin-loading::        Installing and Uninstalling Plugins
* obtaining-plugin-information::  Obtaining Server Plugin Information

MySQL 5.1 and up supports a plugin API that enables creation of server
components. Plugins can be loaded at server startup, or loaded and
unloaded at runtime without restarting the server. The components
supported by this interface include, but are not limited to, storage
engines, full-text parser plugins, partitioning support, and server
extensions.


File: manual.info,  Node: server-plugin-loading,  Next: obtaining-plugin-information,  Prev: server-plugins,  Up: server-plugins

5.1.8.1 Installing and Uninstalling Plugins
...........................................

Server plugins must be loaded in to the server before they can be used.
MySQL enables you to load a plugin at server startup or at runtime. It
is also possible to control the activation of loaded plugins at
startup, and to unload them at runtime.

   * Installing plugins

   * Controlling plugin activation

   * Uninstalling plugins

*Installing Plugins*

Server plugins must be known to the server before they can be used. A
plugin can be made known several ways, as described here. In the
following descriptions, PLUGIN_NAME stands for a plugin name such as
`innodb' or `csv'.

*Built-in plugins:*

A plugin that is built in to the server is known by the server
automatically. Normally, the server enables the plugin at startup,
although this can be changed with the `--PLUGIN_NAME' option.

*Plugins registered in the `mysql.plugin' table:*

The `mysql.plugin' table serves as a registry of plugins. The server
normally enables each plugin listed in the table at startup, although
whether a given plugin is enabled can be changed with the
`--PLUGIN_NAME' option. If the server is started with the
`--skip-grant-tables' option, it does not consult this table and does
not load the plugins listed there.

*Plugins named with the `--plugin-load' option:*

A plugin that is located in a plugin library file can be loaded at
server startup with the `--plugin-load' option. Normally, the server
enables the plugin at startup, although this can be changed with the
`--PLUGIN_NAME' option.

The option value is a semicolon-separated list of `NAME=PLUGIN_LIBRARY'
pairs. Each NAME is the name of the plugin, and PLUGIN_LIBRARY is the
name of the shared library that contains the plugin code. If a plugin
library is named without any preceding plugin name, the server loads
all plugins in the library. Each library file must be located in the
directory named by the `plugin_dir' system variable.

This option does not register any plugin in the `mysql.plugin' table.
For subsequent restarts, the server loads the plugin again only if
`--plugin-load' is given again.  That is, this option effects a
one-time installation that persists only for one server invocation.

`--plugin-load' enables plugins to be loaded even when
`--skip-grant-tables' is given (which causes the server to ignore the
`mysql.plugin' table).  `--plugin-load' also enables plugins to be
loaded at startup under configurations when plugins cannot be loaded at
runtime.

*Plugins installed with the *Note `INSTALL PLUGIN': install-plugin.
statement:*

A plugin that is located in a plugin library file can be loaded at
runtime with the `INSTALL PLUGIN' statement. The statement also
registers the plugin in the `mysql.plugin' table to cause the server to
load it on subsequent restarts. For this reason, `INSTALL PLUGIN'
requires the `INSERT' privilege for the `mysql.plugin' table.

If a plugin is named both using a `--plugin-load' option and in the
`mysql.plugin' table, the server starts but writes these messages to
the error log:


     100310 19:15:44 [ERROR] Function 'PLUGIN_NAME' already exists
     100310 19:15:44 [Warning] Couldn't load plugin named 'PLUGIN_NAME'
     with soname 'PLUGIN_OBJECT_FILE'.

Example: The `--plugin-load' option installs a plugin at server
startup. To install a plugin named `myplugin' in a plugin library file
named `somepluglib.so', use these lines in a `my.cnf' file:


     [mysqld]
     plugin-load=myplugin=somepluglib.so

In this case, the plugin is not registered in `mysql.plugin'.
Restarting the server without the `--plugin-load' option causes the
plugin not to be loaded at startup.

Alternatively, the *Note `INSTALL PLUGIN': install-plugin.  statement
causes the server to load the plugin code from the library file at
runtime:


     mysql> INSTALL PLUGIN myplugin SONAME 'somepluglib.so';

*Note `INSTALL PLUGIN': install-plugin. also causes `permanent' plugin
registration: The server lists the plugin in the `mysql.plugin' table to
ensure that it is loaded on subsequent server restarts.

Many plugins can be loaded either at server startup or at runtime.
However, if a plugin is designed such that it must be loaded and
initialized during server startup, use `--plugin-load' rather than
*Note `INSTALL PLUGIN': install-plugin.

While a plugin is loaded, information about it is available at runtime
from several sources, such as the *Note `INFORMATION_SCHEMA.PLUGINS':
plugins-table. table and the *Note `SHOW PLUGINS': show-plugins.
statement.  For more information, see *Note
obtaining-plugin-information::.

*Controlling Plugin Activation*

If the server knows about a plugin when it starts (for example, because
the plugin is named using a `--plugin-load' option or registered in the
`mysql.plugin' table), the server loads and enables the plugin by
default. It is possible to control activation for such a plugin using a
`--PLUGIN_NAME[=VALUE]' startup option named after the plugin. In the
following descriptions, PLUGIN_NAME stands for a plugin name such as
`innodb' or `csv'. As with other options, dashes and underscores are
interchangeable in option names. For example, `--my_plugin=ON' and
`--my-plugin=ON' are equivalent.

As of MySQL 5.1.36, these options control plugin loading:

   * `--PLUGIN_NAME=OFF'

     Tells the server to disable the plugin.

   * `--PLUGIN_NAME[=ON]'

     Tells the server to enable the plugin. (Specifying the option as
     `--PLUGIN_NAME' without a value has the same effect.) If the
     plugin fails to initialize, the server runs with the plugin
     disabled.

   * `--PLUGIN_NAME=FORCE'

     Tells the server to enable the plugin, but if plugin
     initialization fails, the server does not start. In other words,
     this option forces the server to run with the plugin enabled or
     not at all.

The values `OFF', `ON', and `FORCE' are not case sensitive.

Suppose that `CSV', `BLACKHOLE', and `ARCHIVE' are built-in pluggable
storage engines and that you want the server to load them at startup,
subject to these conditions: The server is permitted to run if `CSV'
initialization fails, but must require that `BLACKHOLE' initialization
succeeds, and `ARCHIVE' should be disabled. To accomplish that, use
these lines in an option file:


     [mysqld]
     csv=ON
     blackhole=FORCE
     archive=OFF

The `--enable-PLUGIN_NAME' option format is supported as a synonym for
`--PLUGIN_NAME=ON'.  The `--disable-PLUGIN_NAME' and
`--skip-PLUGIN_NAME' option formats are supported as synonyms for
`--PLUGIN_NAME=OFF'.

Before MySQL 5.1.36, plugin options are boolean options (see *Note
option-modifiers::). That is, any of these options enable the plugin:


     --PLUGIN_NAME
     --PLUGIN_NAME=1
     --enable-PLUGIN_NAME

And these options disable the plugin:


     --PLUGIN_NAME=0
     --disable-PLUGIN_NAME
     --skip-PLUGIN_NAME

If you upgrade to MySQL 5.1.36 or later from an older version and
previously used options of the form `--PLUGIN_NAME=0' or
`--PLUGIN_NAME=1', the equivalent options are now `--PLUGIN_NAME=OFF'
and `--PLUGIN_NAME=ON', respectively. You also have the choice of
requiring plugins to start successfully by using `--PLUGIN_NAME=FORCE'.

If a plugin is disabled, either explicitly with `OFF' or implicitly
because it was enabled with `ON' but failed to initialize, aspects of
server operation that require the plugin will change. For example, if
the plugin implements a storage engine, existing tables for the storage
engine become inaccessible, and attempts to create new tables for the
storage engine result in tables that use the default storage engine
unless the `NO_ENGINE_SUBSTITUTION' SQL mode has been enabled to cause
an error to occur instead.

Disabling a plugin may require adjustment to other options. For
example, if you start the server using `--skip-innodb' to disable *Note
`InnoDB': innodb-storage-engine, other `innodb_XXX' options likely will
need to be omitted from the startup command.  In addition, if the
server is configured to use *Note `InnoDB': innodb-storage-engine. as
the default storage engine, it will not start unless you specify
another available storage engine with `--default-storage-engine'.

*Uninstalling Plugins*

A plugin known to the server can be uninstalled to disable it at
runtime with the *Note `UNINSTALL PLUGIN': uninstall-plugin.
statement. The statement unloads the plugin and removes it from the
`mysql.plugin' table if it is registered there. For this reason, *Note
`UNINSTALL PLUGIN': uninstall-plugin. statement requires the `DELETE'
privilege for the `mysql.plugin' table. With the plugin no longer
registered in the table, the server will not load the plugin
automatically for subsequent restarts.

*Note `UNINSTALL PLUGIN': uninstall-plugin. can unload plugins
regardless of whether they were loaded with *Note `INSTALL PLUGIN':
install-plugin. or `--plugin-load'.

*Note `UNINSTALL PLUGIN': uninstall-plugin. cannot unload plugins that
are built in to the server. These can be identified as those that have
a library name of `NULL' in the output from *Note
`INFORMATION_SCHEMA.PLUGINS': plugins-table. or *Note `SHOW PLUGINS':
show-plugins.


File: manual.info,  Node: obtaining-plugin-information,  Prev: server-plugin-loading,  Up: server-plugins

5.1.8.2 Obtaining Server Plugin Information
...........................................

There are several ways to determine which plugins are installed in the
server:

   * The *Note `INFORMATION_SCHEMA.PLUGINS': plugins-table.  table
     contains a row for each loaded plugin. Any that have a
     `PLUGIN_LIBRARY' value of `NULL' are built in and cannot be
     unloaded.


          mysql> SELECT * FROM information_schema.PLUGINS\G
          *************************** 1. row ***************************
                     PLUGIN_NAME: binlog
                  PLUGIN_VERSION: 1.0
                   PLUGIN_STATUS: ACTIVE
                     PLUGIN_TYPE: STORAGE ENGINE
             PLUGIN_TYPE_VERSION: 50158.0
                  PLUGIN_LIBRARY: NULL
          PLUGIN_LIBRARY_VERSION: NULL
                   PLUGIN_AUTHOR: MySQL AB
              PLUGIN_DESCRIPTION: This is a pseudo storage engine to represent the binlog in a transaction
                  PLUGIN_LICENSE: GPL
          ...
          *************************** 10. row ***************************
                     PLUGIN_NAME: InnoDB
                  PLUGIN_VERSION: 1.0
                   PLUGIN_STATUS: ACTIVE
                     PLUGIN_TYPE: STORAGE ENGINE
             PLUGIN_TYPE_VERSION: 50158.0
                  PLUGIN_LIBRARY: ha_innodb_plugin.so
          PLUGIN_LIBRARY_VERSION: 1.0
                   PLUGIN_AUTHOR: Innobase Oy
              PLUGIN_DESCRIPTION: Supports transactions, row-level locking,
                                  and foreign keys
                  PLUGIN_LICENSE: GPL
          ...

   * The *Note `SHOW PLUGINS': show-plugins. statement displays a row
     for each loaded plugin. Any that have a `Library' value of `NULL'
     are built in and cannot be unloaded.


          mysql> SHOW PLUGINS\G
          *************************** 1. row ***************************
             Name: binlog
           Status: ACTIVE
             Type: STORAGE ENGINE
          Library: NULL
          License: GPL
          ...
          *************************** 10. row ***************************
             Name: InnoDB
           Status: ACTIVE
             Type: STORAGE ENGINE
          Library: ha_innodb_plugin.so
          License: GPL
          ...

   * The `mysql.plugin' table shows which plugins have been registered
     with *Note `INSTALL PLUGIN': install-plugin. The table contains
     only plugin names and library file names, so it does not provide
     as much information as the *Note `PLUGINS': plugins-table. table
     or the *Note `SHOW PLUGINS': show-plugins. statement.


File: manual.info,  Node: server-side-help-support,  Next: server-signal-response,  Prev: server-plugins,  Up: mysqld-server

5.1.9 Server-Side Help
----------------------

MySQL Server supports a *Note `HELP': help.  statement that returns
online information from the MySQL Reference manual (see *Note help::).
The proper operation of this statement requires that the help tables in
the `mysql' database be initialized with help topic information, which
is done by processing the contents of the `fill_help_tables.sql' script.

If you install MySQL using a binary or source distribution on Unix,
help table content initialization occurs when you run *Note
`mysql_install_db': mysql-install-db. For an RPM distribution on Linux
or binary distribution on Windows, content initialization occurs as
part of the MySQL installation process.

If you upgrade MySQL using a binary distribution, help table content is
not upgraded automatically, but you can upgrade it manually. Locate the
`fill_help_tables.sql' file in the `share' or `share/mysql' directory.
Change location into that directory and process the file with the *Note
`mysql': mysql. client as follows:


     shell> mysql -u root mysql < fill_help_tables.sql

You can also obtain the latest `fill_help_tables.sql' at any time to
upgrade your help tables. Download the proper file for your version of
MySQL from `http://dev.mysql.com/doc/index-other.html'. After
downloading and uncompressing the file, process it with *Note `mysql':
mysql. as described previously.

If you are working with Bazaar and a MySQL development source tree, you
must use a downloaded copy of the `fill_help_tables.sql' file because
the source tree contains only a `stub' version.

*Note*:

For a server that participates in replication, the help table content
upgrade process involves multiple servers. For details, see *Note
replication-features-server-side-help::.


File: manual.info,  Node: server-signal-response,  Next: server-shutdown,  Prev: server-side-help-support,  Up: mysqld-server

5.1.10 Server Response to Signals
---------------------------------

On Unix, signals can be sent to processes.  *Note `mysqld': mysqld.
responds to signals sent to it as follows:

   * `SIGTERM' causes the server to shut down.

   * `SIGHUP' causes the server to reload the grant tables and to flush
     tables, logs, the thread cache, and the host cache. These actions
     are like various forms of the *Note `FLUSH': flush. statement. The
     server also writes a status report to the error log that has this
     format:


          Status information:

          Current dir: /var/mysql/data/
          Running threads: 0  Stack size: 196608
          Current locks:

          Key caches:
          default
          Buffer_size:       8388600
          Block_size:           1024
          Division_limit:        100
          Age_limit:             300
          blocks used:             0
          not flushed:             0
          w_requests:              0
          writes:                  0
          r_requests:              0
          reads:                   0

          handler status:
          read_key:            0
          read_next:           0
          read_rnd             0
          read_first:          1
          write:               0
          delete               0
          update:              0

          Table status:
          Opened tables:          5
          Open tables:            0
          Open files:             7
          Open streams:           0

          Alarm status:
          Active alarms:   1
          Max used alarms: 2
          Next alarm time: 67

On some Mac OS X 10.3 versions, *Note `mysqld': mysqld. ignores
`SIGHUP' and `SIGQUIT'.


File: manual.info,  Node: server-shutdown,  Prev: server-signal-response,  Up: mysqld-server

5.1.11 The Shutdown Process
---------------------------

   * *Note sql-mode-setting::

   * *Note sql-mode-important::

   * *Note sql-mode-full::

   * *Note sql-mode-strict::

   * *Note sql-mode-combo::

The server shutdown process takes place as follows:

  1. The shutdown process is initiated.

     This can occur initiated several ways. For example, a user with
     the `SHUTDOWN' privilege can execute a *Note `mysqladmin
     shutdown': mysqladmin. command.  *Note `mysqladmin': mysqladmin.
     can be used on any platform supported by MySQL. Other operating
     system-specific shutdown initiation methods are possible as well:
     The server shuts down on Unix when it receives a `SIGTERM' signal.
     A server running as a service on Windows shuts down when the
     services manager tells it to.

  2. The server creates a shutdown thread if necessary.

     Depending on how shutdown was initiated, the server might create a
     thread to handle the shutdown process. If shutdown was requested
     by a client, a shutdown thread is created. If shutdown is the
     result of receiving a `SIGTERM' signal, the signal thread might
     handle shutdown itself, or it might create a separate thread to do
     so. If the server tries to create a shutdown thread and cannot
     (for example, if memory is exhausted), it issues a diagnostic
     message that appears in the error log:


          Error: Can't create thread to kill server

  3. The server stops accepting new connections.

     To prevent new activity from being initiated during shutdown, the
     server stops accepting new client connections by closing the
     handlers for the network interfaces to which it normally listens
     for connections: the TCP/IP port, the Unix socket file, the
     Windows named pipe, and shared memory on Windows.

  4. The server terminates current activity.

     For each thread associated with a client connection, the server
     breaks the connection to the client and marks the thread as
     killed. Threads die when they notice that they are so marked.
     Threads for idle connections die quickly. Threads that currently
     are processing statements check their state periodically and take
     longer to die. For additional information about thread
     termination, see *Note kill::, in particular for the instructions
     about killed *Note `REPAIR TABLE': repair-table. or *Note
     `OPTIMIZE TABLE': optimize-table. operations on `MyISAM' tables.

     For threads that have an open transaction, the transaction is
     rolled back. Note that if a thread is updating a nontransactional
     table, an operation such as a multiple-row *Note `UPDATE': update.
     or *Note `INSERT': insert. may leave the table partially updated
     because the operation can terminate before completion.

     If the server is a master replication server, it treats threads
     associated with currently connected slaves like other client
     threads. That is, each one is marked as killed and exits when it
     next checks its state.

     If the server is a slave replication server, it stops the I/O and
     SQL threads, if they are active, before marking client threads as
     killed. The SQL thread is permitted to finish its current
     statement (to avoid causing replication problems), and then stops.
     In MySQL 5.1.34 and earlier, if the SQL thread was in the middle
     of a transaction at this point, the transaction was rolled back;
     in MySQL 5.1.35 and later, the server waits until the current
     replication event group (if any) has finished executing, or until
     the user issues a *Note `KILL QUERY': kill. or *Note `KILL
     CONNECTION': kill. statement. See also *Note stop-slave::.

     If the slave is updating a nontransactional table when it is
     forcibly killed, the slave's data may become inconsistent with the
     master.

  5. The server shuts down or closes storage engines.

     At this stage, the server flushes the table cache and closes all
     open tables.

     Each storage engine performs any actions necessary for tables that
     it manages. For example, `MyISAM' flushes any pending index writes
     for a table.  `InnoDB' flushes its buffer pool to disk (unless
     `innodb_fast_shutdown' is 2), writes the current LSN to the
     tablespace, and terminates its own internal threads.

  6. The server exits.


File: manual.info,  Node: server-logs,  Next: multiple-servers,  Prev: mysqld-server,  Up: server-administration

5.2 MySQL Server Logs
=====================

* Menu:

* log-destinations::             Selecting General Query and Slow Query Log Output Destinations
* error-log::                    The Error Log
* query-log::                    The General Query Log
* binary-log::                   The Binary Log
* slow-query-log::               The Slow Query Log
* ddl-log::                      The DDL Log
* log-file-maintenance::         Server Log Maintenance

MySQL Server has several logs that can help you find out what activity
is taking place.

This table lists MySQL Server log types and describes the information
written to each log.

Log Type               Information Written to Log
Error log              Problems encountered starting, running, or
                       stopping *Note `mysqld': mysqld.
General query log      Established client connections and statements
                       received from clients
Binary log             Statements that change data (also used for
                       replication)
Relay log              Data changes received from a replication master
                       server
Slow query log         Queries that took more than `long_query_time'
                       seconds to execute
DDL log (metadata log) Metadata operations performed by DDL statements

By default, no logs are enabled, except the error log on Windows.  (The
DDL log is always created when required, and has no user-configurable
options; see *Note ddl-log::.) The following log-specific sections
provide information about the server options that enable logging.

By default, the server writes files for all enabled logs in the data
directory. You can force the server to close and reopen the log files
(or in some cases switch to a new log file) by flushing the logs. Log
flushing occurs when you issue a *Note `FLUSH LOGS': flush.  statement;
execute *Note `mysqladmin': mysqladmin. with a `flush-logs' or `refresh'
argument; or execute *Note `mysqldump': mysqldump. with a
`--flush-logs' or `--master-data' option. See *Note flush::, *Note
mysqladmin::, and *Note mysqldump::. In addition, the binary log is
flushed when its size reaches the value of the `max_binlog_size' system
variable.

You can control the general query and slow query logs during runtime.
You can enable or disable logging, or change the log file name. You can
tell the server to write general query and slow query entries to log
tables, log files, or both. For details, see *Note log-destinations::,
*Note query-log::, and *Note slow-query-log::.

The relay log is used only on slave replication servers, to hold data
changes from the master server that must also be made on the slave. For
discussion of relay log contents and configuration, see *Note
slave-logs-relaylog::.

For information about log maintenance operations such as expiration of
old log files, see *Note log-file-maintenance::.

For information about keeping logs secure, see *Note password-logging::.


File: manual.info,  Node: log-destinations,  Next: error-log,  Prev: server-logs,  Up: server-logs

5.2.1 Selecting General Query and Slow Query Log Output Destinations
--------------------------------------------------------------------

As of MySQL 5.1.6, MySQL Server provides flexible control over the
destination of output to the general query log and the slow query log,
if those logs are enabled. Possible destinations for log entries are
log files or the `general_log' and `slow_log' tables in the `mysql'
database. Either or both destinations can be selected. (Before MySQL
5.1.6, the server uses only log files as the destination for general
query log and slow query log entries.)

*Note*:

For new installations of MySQL 5.1.6 or higher, the log tables are
created during the installation procedure along with the other system
tables. If you upgrade MySQL from a release older than 5.1.6 to MySQL
5.1.6 or higher, you must upgrade the system tables after upgrading to
make sure that the log tables exist.  See *Note mysql-upgrade::.

Currently, logging to tables incurs significantly more server overhead
than logging to files. If you enable the general log or slow query log
and require highest performance, you should use file logging, not table
logging.

*Log control at server startup.* The `--log-output' option specifies
the destination for log output, if logging is enabled. This option does
not in itself enable the logs. Its syntax is `--log-output[=VALUE,...]':

   * If `--log-output' is given with a value, the value should be a
     comma-separated list of one or more of the words `TABLE' (log to
     tables), `FILE' (log to files), or `NONE' (do not log to tables or
     files).  `NONE', if present, takes precedence over any other
     specifiers.

   * If `--log-output' is omitted or given without a value, the default
     is `FILE'.  (For MySQL 5.1.6 through 5.1.20, the default logging
     destination is `TABLE'.)

The `general_log' system variable controls logging to the general query
log for the selected log destinations. If specified at server startup,
`general_log' takes an optional argument of 1 or 0 to enable or disable
the log. To specify a file name other than the default for file
logging, set the `general_log_file' variable.  Similarly, the
`slow_query_log' variable controls logging to the slow query log for
the selected destinations and setting `slow_query_log_file' specifies a
file name for file logging. If either log is enabled, the server opens
the corresponding log file and writes startup messages to it. However,
further logging of queries to the file does not occur unless the `FILE'
log destination is selected.  Prior to MySQL 5.1.29, the `--log' and
`--log-slow-queries' options enable the general query log and slow
query log. Either option may be given with a file name argument to
specify a log file name to override the default.

Examples:

   * To write general query log entries to the log table and the log
     file, use `--log-output=TABLE,FILE' to select both log
     destinations and `--general_log' to enable the general query log.

   * To write general and slow query log entries only to the log
     tables, use `--log-output=TABLE' to select tables as the log
     destination and `--general_log' and `--slow_query_log' to enable
     both logs.

   * To write slow query log entries only to the log file, use
     `--log-output=FILE' to select files as the log destination and
     `--slow_query_log' to enable the slow query log. (In this case,
     because the default log destination is `FILE', you could omit the
     `--log-output' option.)

*Log control at runtime.* The system variables associated with log
tables and files enable runtime control over logging:

   * The global `log_output' system variable indicates the current
     logging destination. It can be modified at runtime to change the
     destination.

   * The global `general_log' and `slow_query_log' variables indicate
     whether the general query log and slow query log are enabled
     (`ON') or disabled (`OFF'). You can set these variables at runtime
     to control whether the logs are enabled.

   * The global `general_log_file' and `slow_query_log_file' variables
     indicate the names of the general query log and slow query log
     files. As of MySQL 5.1.29, you can set these variables at server
     startup or at runtime to change the names of the log files. Before
     MySQL 5.1.29, you can set these variables only at runtime, but the
     `--log' and `--log-slow-queries' options can be given with a file
     name argument at startup to change the log file names from their
     default values.

   * To disable or enable general query logging for the current
     connection, set the session `sql_log_off' variable to `ON' or
     `OFF'.

The use of tables for log output offers the following benefits:

   * Log entries have a standard format. To display the current
     structure of the log tables, use these statements:


          SHOW CREATE TABLE mysql.general_log;
          SHOW CREATE TABLE mysql.slow_log;

   * Log contents are accessible through SQL statements. This enables
     the use of queries that select only those log entries that satisfy
     specific criteria. For example, to select log contents associated
     with a particular client (which can be useful for identifying
     problematic queries from that client), it is easier to do this
     using a log table than a log file.

   * Logs are accessible remotely through any client that can connect
     to the server and issue queries (if the client has the appropriate
     log table privileges). It is not necessary to log in to the server
     host and directly access the file system.

The log table implementation has the following characteristics:

   * In general, the primary purpose of log tables is to provide an
     interface for users to observe the runtime execution of the
     server, not to interfere with its runtime execution.

   * *Note `CREATE TABLE': create-table, *Note `ALTER TABLE':
     alter-table, and *Note `DROP TABLE': drop-table. are valid
     operations on a log table. For *Note `ALTER TABLE': alter-table.
     and *Note `DROP TABLE': drop-table, the log table cannot be in use
     and must be disabled, as described later.

   * By default, the log tables use the `CSV' storage engine that
     writes data in comma-separated values format. For users who have
     access to the `.CSV' files that contain log table data, the files
     are easy to import into other programs such as spreadsheets that
     can process CSV input.

     Beginning with MySQL 5.1.12, the log tables can be altered to use
     the `MyISAM' storage engine. You cannot use *Note `ALTER TABLE':
     alter-table. to alter a log table that is in use. The log must be
     disabled first. No engines other than `CSV' or `MyISAM' are legal
     for the log tables.

   * To disable logging so that you can alter (or drop) a log table,
     you can use the following strategy. The example uses the general
     query log; the procedure for the slow query log is similar but
     uses the `slow_log' table and `slow_query_log' system variable.


          SET @old_log_state = @@global.general_log;
          SET GLOBAL general_log = 'OFF';
          ALTER TABLE mysql.general_log ENGINE = MyISAM;
          SET GLOBAL general_log = @old_log_state;

   * *Note `TRUNCATE TABLE': truncate-table. is a valid operation on a
     log table. It can be used to expire log entries.

   * As of MySQL 5.1.13, *Note `RENAME TABLE': rename-table. is a valid
     operation on a log table. You can atomically rename a log table
     (to perform log rotation, for example) using the following
     strategy:


          USE mysql;
          DROP TABLE IF EXISTS general_log2;
          CREATE TABLE general_log2 LIKE general_log;
          RENAME TABLE general_log TO general_log_backup, general_log2 TO general_log;

   * *Note `LOCK TABLES': lock-tables. cannot be used on a log table.

   * *Note `INSERT': insert, *Note `DELETE': delete, and *Note
     `UPDATE': update. cannot be used on a log table. These operations
     are permitted only internally to the server itself.

   * *Note `FLUSH TABLES WITH READ LOCK': flush. and the state of the
     global `read_only' system variable have no effect on log tables.
     The server can always write to the log tables.

   * Entries written to the log tables are not written to the binary
     log and thus are not replicated to slave servers.

   * To flush the log tables or log files, use *Note `FLUSH TABLES':
     flush.  or *Note `FLUSH LOGS': flush, respectively. (From MySQL
     5.1.12 to 5.1.20, *Note `FLUSH TABLES': flush.  ignores log tables
     and *Note `FLUSH LOGS': flush.  flushes both the log tables and
     files.)

   * Partitioning of log tables is not permitted beginning with MySQL
     5.1.20, and not recommended before that.

   * Before MySQL 5.1.64, *Note `mysqldump': mysqldump. does not dump
     the `general_log' or `slow_query_log' tables for dumps of the
     `mysql' database. As of 5.1.64, the dump includes statements to
     recreate those tables so that they are not missing after reloading
     the dump file. Log table contents are not dumped.


File: manual.info,  Node: error-log,  Next: query-log,  Prev: log-destinations,  Up: server-logs

5.2.2 The Error Log
-------------------

The error log contains information indicating when *Note `mysqld':
mysqld. was started and stopped and also any critical errors that occur
while the server is running. If *Note `mysqld': mysqld. notices a table
that needs to be automatically checked or repaired, it writes a message
to the error log.

On some operating systems, the error log contains a stack trace if
*Note `mysqld': mysqld. dies. The trace can be used to determine where
*Note `mysqld': mysqld. died. See *Note porting::.

If *Note `mysqld_safe': mysqld-safe. is used to start *Note `mysqld':
mysqld. and *Note `mysqld': mysqld. dies unexpectedly, *Note
`mysqld_safe': mysqld-safe. notices this, restarts *Note `mysqld':
mysqld, and writes a `restarted mysqld' message to the error log.

In the following discussion, `console' means `stderr', the standard
error output; this is your terminal or console window unless the
standard error output has been redirected. (For example, if invoked
with the `--syslog' option, *Note `mysqld_safe': mysqld-safe. arranges
for the server's `stderr' to be sent to `syslog', as described later.)

On Windows, the `--log-error' and `--console' options both affect error
logging:

   * Without `--log-error', *Note `mysqld': mysqld. writes error
     messages to `HOST_NAME.err' in the data directory.

   * With `--log-error[=FILE_NAME]', *Note `mysqld': mysqld. writes
     error messages to an error log file. The server uses the named
     file if present, creating it in the data directory unless an
     absolute path name is given to specify a different directory. If
     no file is named, the default name is `HOST_NAME.err' in the data
     directory.

   * With `--console', *Note `mysqld': mysqld. writes error messages to
     the console, unless `--log-error' is also given. If both options
     are present, the last one takes precedence.

In addition, on Windows, the server writes events and error messages to
the Windows Event Log within the Application log.  Entries marked as
`Warning' and `Note' are written to the Event Log, but not
informational messages such as information statements from individual
storage engines. These log entries have a source of `MySQL'. You cannot
disable writing information to the Windows Event Log.

On Unix and Unix-like systems, *Note `mysqld': mysqld. writes error log
messages as follows:

   * Without `--log-error', *Note `mysqld': mysqld. writes error
     messages to the console.

   * With `--log-error[=`file_name']', *Note `mysqld': mysqld. writes
     error messages to an error log file. The server uses the named
     file if present, creating it in the data directory unless an
     absolute path name is given to specify a different directory. If
     no file is named, the default name is `HOST_NAME.err' in the data
     directory.

At runtime, `log_error' system variable indicates the error log file
name if error output is written to a file.

If you specify `--log-error' in an option file in a `[mysqld]',
`[server]', or `[mysqld_safe]' section, *Note `mysqld_safe':
mysqld-safe. will find and use the option.

If you flush the logs using *Note `FLUSH LOGS': flush. or *Note
`mysqladmin flush-logs': mysqladmin. and *Note `mysqld': mysqld. is
writing the error log to a file (for example, if it was started with the
`--log-error' option), the effect is version dependent:

   * As of MySQL 5.1.51, the server closes and reopens the log file. To
     rename the file, do so manually before flushing. Then flushing the
     logs reopens a new file with the original file name. For example,
     to rename the file and create a new one, use the following
     commands:


          shell> mv HOST_NAME.err HOST_NAME.err-old
          shell> mysqladmin flush-logs
          shell> mv HOST_NAME.err-old BACKUP-DIRECTORY

     On Windows, use `rename' rather than `mv'.

   * Prior to MySQL 5.1.51, the server renames the current log file
     with the suffix `-old', then creates a new empty log file. Be
     aware that a second log-flushing operation thus causes the
     original error log file to be lost unless you save it under a
     different name. On Windows, you cannot rename the error log while
     the server has it open before MySQL 5.1.51. To avoid a restart,
     flush the logs first to cause the server to rename the original
     file and create a new one, then save the renamed file. That also
     works on Unix, or you can use the commands shown earlier.

No error log renaming occurs when the logs are flushed in any case if
the server is not writing to a named file.

If you use *Note `mysqld_safe': mysqld-safe. to start *Note `mysqld':
mysqld, *Note `mysqld_safe': mysqld-safe. arranges for *Note `mysqld':
mysqld. to write error messages to a log file or (as of MySQL 5.1.20)
to `syslog':

   * Before 5.1.20, *Note `mysqld_safe': mysqld-safe. behavior is to
     log to a file, using the default error log file if the
     `--log-error' option is not given to *Note `mysqld_safe':
     mysqld-safe. Otherwise, *Note `mysqld_safe': mysqld-safe. uses the
     file name specified using `--log-error=FILE_NAME'.

   * From 5.1.20 on, *Note `mysqld_safe': mysqld-safe. has two
     additional error-logging options, `--syslog' and `--skip-syslog'.

     In 5.1.21 and up, the default with no logging options is
     `--skip-syslog', which is compatible with the default behavior of
     writing an error log file for releases prior to 5.1.20. To
     explicitly specify use of an error log file, specify
     `--log-error=FILE_NAME' to *Note `mysqld_safe': mysqld-safe, and
     *Note `mysqld_safe': mysqld-safe. will arrange for *Note `mysqld':
     mysqld. to write messages to a log file. To use `syslog' instead,
     specify the `--syslog' option.

     *In 5.1.20 _only_, the following conditions apply*: 1) The default
     is to use `syslog', which is not compatible with releases prior to
     5.1.20. 2) Logging to `syslog' may fail to operate correctly in
     some cases; if so, use `--skip-syslog' or `--log-error'.

     For logging to `syslog', messages from *Note `mysqld_safe':
     mysqld-safe. and *Note `mysqld': mysqld.  are written with a tag
     of `mysqld_safe' and `mysqld', respectively. As of MySQL 5.1.21,
     to specify a suffix for the tag, use `--syslog-tag=TAG', which
     modifies the tags to be `mysqld_safe-TAG' and `mysqld-TAG'.

The `--log-warnings' option or `log_warnings' system variable can be
used to control warning logging to the error log. The default value is
enabled (1). Warning logging can be disabled using a value of 0. If the
value is greater than 1, aborted connections are written to the error
log. See *Note communication-errors::.


File: manual.info,  Node: query-log,  Next: binary-log,  Prev: error-log,  Up: server-logs

5.2.3 The General Query Log
---------------------------

The general query log is a general record of what *Note `mysqld':
mysqld. is doing. The server writes information to this log when
clients connect or disconnect, and it logs each SQL statement received
from clients. The general query log can be very useful when you suspect
an error in a client and want to know exactly what the client sent to
*Note `mysqld': mysqld.

*Note `mysqld': mysqld. writes statements to the query log in the order
that it receives them, which might differ from the order in which they
are executed. This logging order is in contrast with that of the binary
log, for which statements are written after they are executed but
before any locks are released. In addition, the query log may contain
statements that only select data while such statements are never
written to the binary log.

When using statement-based logging all statements are written to the
query log, but when using row-based logging, updates are sent as row
changes rather than SQL statements, and thus these statements are never
written to the query log when `binlog_format' is `ROW'. A given update
also might not be written to the query log when this variable is set to
`MIXED', depending on the statement used. See *Note
replication-sbr-rbr::, for more information.

Control the general query log at server startup as follows:

   * Before 5.1.6, the general query log destination is always a file.
     To enable the log, start *Note `mysqld': mysqld. with the
     `--log[=FILE_NAME]' or `-l [FILE_NAME]' option.

   * As of MySQL 5.1.6, the destination can be a file or a table, or
     both. Start *Note `mysqld': mysqld. with the `--log[=FILE_NAME]'
     or `-l [FILE_NAME]' option to enable the general query log, and
     optionally use `--log-output' to specify the log destination (as
     described in *Note log-destinations::).

   * As of MySQL 5.1.12, as an alternative to `--log' or `-l', use
     `--general_log[={0|1}]' to specify the initial general query log
     state. In this case, the default general query log file name is
     used. With no argument or an argument of 1, `--general_log'
     enables the log.  With an argument of 0, this option disables the
     log.

   * As of MySQL 5.1.29, use `--general_log[={0|1}]' to enable or
     disable the general query log, and optionally
     `--general_log_file=FILE_NAME' to specify a log file name. The
     `--log' and `-l' options are deprecated.

If the general query log file is enabled but no name is specified, the
default name is `HOST_NAME.log' and the server creates the file in the
same directory where it creates the PID file. If a name is given, the
server creates the file in the data directory unless an absolute path
name is given to specify a different directory.

To disable or enable the general query log or change the log file name
at runtime, use the global `general_log' and `general_log_file' system
variables. Set `general_log' to 0 (or `OFF') to disable the log or to 1
(or `ON') to enable it. Set `general_log_file' to specify the name of
the log file. If a log file already is open, it is closed and the new
file is opened.

When the general query log is enabled, the server writes output to any
destinations specified by the `--log-output' option or `log_output'
system variable. If you enable the log, the server opens the log file
and writes startup messages to it. However, further logging of queries
to the file does not occur unless the `FILE' log destination is
selected. If the destination is `NONE', the server writes no queries
even if the general log is enabled. Setting the log file name has no
effect on logging if the log destination value does not contain `FILE'.

Server restarts and log flushing do not cause a new general query log
file to be generated (although flushing closes and reopens it). On
Unix, you can rename the file and create a new one by using the
following commands:


     shell> mv HOST_NAME.log HOST_NAME-old.log
     shell> mysqladmin flush-logs
     shell> mv HOST_NAME-old.log BACKUP-DIRECTORY

On Windows, you cannot rename the general query log file while the
server has it open before MySQL 5.1.3. You must stop the server, rename
the file, and then restart the server to create a new log file.

As of MySQL 5.1.12, you can rename the general query log file at
runtime by disabling the log:


     SET GLOBAL general_log = 'OFF';

With the log disabled, rename the log file externally; for example,
from the command line. Then enable the log again:


     SET GLOBAL general_log = 'ON';

This method works on any platform and does not require a server restart.

The session `sql_log_off' variable can be set to `ON' or `OFF' to
disable or enable general query logging for the current connection.

The general query log should be protected because logged statements
might contain passwords. See *Note password-logging::.


File: manual.info,  Node: binary-log,  Next: slow-query-log,  Prev: query-log,  Up: server-logs

5.2.4 The Binary Log
--------------------

* Menu:

* binary-log-formats::           Binary Logging Formats
* binary-log-setting::           Setting The Binary Log Format
* binary-log-mixed::             Mixed Binary Logging Format
* binary-log-mysql-database::    Logging Format for Changes to mysql Database Tables

The binary log contains `events' that describe database changes such as
table creation operations or changes to table data. It also contains
events for statements that potentially could have made changes (for
example, a *Note `DELETE': delete. which matched no rows), unless
row-based logging is used. The binary log also contains information
about how long each statement took that updated data.  The binary log
has two important purposes:

   * For replication, the binary log on a master replication server
     provides a record of the data changes to be sent to slave servers.
     The master server sends the events contained in its binary log to
     its slaves, which execute those events to make the same data
     changes that were made on the master. See *Note
     replication-implementation::.

   * Certain data recovery operations require use of the binary log.
     After a backup has been restored, the events in the binary log
     that were recorded after the backup was made are re-executed.
     These events bring databases up to date from the point of the
     backup. See *Note point-in-time-recovery::.

The binary log is not used for statements such as *Note `SELECT':
select. or *Note `SHOW': show. that do not modify data. To log all
statements (for example, to identify a problem query), use the general
query log. See *Note query-log::.

Running a server with binary logging enabled makes performance slightly
slower. However, the benefits of the binary log in enabling you to set
up replication and for restore operations generally outweigh this minor
performance decrement.

The binary log should be protected because logged statements might
contain passwords. See *Note password-logging::.

The following discussion describes some of the server options and
variables that affect the operation of binary logging. For a complete
list, see *Note replication-options-binary-log::.

To enable the binary log, start the server with the
`--log-bin[=BASE_NAME]' option. If no BASE_NAME value is given, the
default name is the value of the `pid-file' option (which by default is
the name of host machine) followed by `-bin'. If the basename is given,
the server writes the file in the data directory unless the basename is
given with a leading absolute path name to specify a different
directory. It is recommended that you specify a basename explicitly
rather than using the default of the host name; see *Note bugs::, for
the reason.

*Note*:

From MySQL 5.1.18 through 5.1.22, `mysql' was used when no BASE_NAME
was specified. Also in these versions, a path given as part of the
`--log-bin' options was treated as absolute rather than relative. The
previous behaviors were restored in MySQL 5.1.23. (See Bug #28603 and
Bug #28597.)

If you supply an extension in the log name (for example,
`--log-bin=BASE_NAME.EXTENSION'), the extension is silently removed and
ignored.

*Note `mysqld': mysqld. appends a numeric extension to the binary log
basename to generate binary log file names. The number increases each
time the server creates a new log file, thus creating an ordered series
of files. The server creates a new file in the series each time it
starts or flushes the logs. The server also creates a new binary log
file automatically after the current log's size reaches
`max_binlog_size'. A binary log file may become larger than
`max_binlog_size' if you are using large transactions because a
transaction is written to the file in one piece, never split between
files.

To keep track of which binary log files have been used, *Note `mysqld':
mysqld. also creates a binary log index file that contains the names of
all used binary log files. By default, this has the same basename as
the binary log file, with the extension `'.index''. You can change the
name of the binary log index file with the `--log-bin-index[=FILE_NAME]'
option. You should not manually edit this file while *Note `mysqld':
mysqld. is running; doing so would confuse *Note `mysqld': mysqld.

The term `binary log file' generally denotes an individual numbered
file containing database events. The term `binary log' collectively
denotes the set of numbered binary log files plus the index file.

A client that has the `SUPER' privilege can disable binary logging of
its own statements by using a `SET sql_log_bin=0' statement. See *Note
server-system-variables::.

The format of the events recorded in the binary log is dependent on the
binary logging format. Three format types are supported, row-based
logging, statement-based logging and mixed-base logging.  The binary
logging format used depends on the MySQL version. For general
descriptions of the logging formats, see *Note binary-log-formats::.
For detailed information about the format of the binary log, see MySQL
Internals: The Binary Log
(http://dev.mysql.com/doc/internals/en/binary-log.html).

The server evaluates the `--binlog-do-db' and `--binlog-ignore-db'
options in the same way as it does the `--replicate-do-db' and
`--replicate-ignore-db' options. For information about how this is
done, see *Note replication-rules-db-options::.

If you are replicating from a MySQL Cluster to a standalone MySQL
Server, you should be aware that the *Note `NDB': mysql-cluster.
storage engine uses default values for some binary logging options
(including options specific to `NDB' such as
`--ndb-log-update-as-write') that differ from those used by other
storage engines. If not corrected for, these differences can lead to
divergence of the master's and slave's binary logs. For more
information, see *Note mysql-cluster-replication-ndb-to-non-ndb::. In
particular, if you are using a nontransactional storage engine such as
*Note `MyISAM': myisam-storage-engine. on the slave, see *Note
mysql-cluster-replication-ndb-to-nontransactional::.

A replication slave server by default does not write to its own binary
log any data modifications that are received from the replication
master. To log these modifications, start the slave with the
`--log-slave-updates' option in addition to the `--log-bin' option (see
*Note replication-options-slave::). This is done when a slave is also
to act as a master to other slaves in chained replication.

You can delete all binary log files with the *Note `RESET MASTER':
reset-master. statement, or a subset of them with *Note `PURGE BINARY
LOGS': purge-binary-logs. See *Note reset::, and *Note
purge-binary-logs::.

If you are using replication, you should not delete old binary log
files on the master until you are sure that no slave still needs to use
them. For example, if your slaves never run more than three days
behind, once a day you can execute *Note `mysqladmin flush-logs':
mysqladmin. on the master and then remove any logs that are more than
three days old. You can remove the files manually, but it is preferable
to use *Note `PURGE BINARY LOGS': purge-binary-logs, which also safely
updates the binary log index file for you (and which can take a date
argument). See *Note purge-binary-logs::.

You can display the contents of binary log files with the *Note
`mysqlbinlog': mysqlbinlog. utility. This can be useful when you want
to reprocess statements in the log for a recovery operation. For
example, you can update a MySQL server from the binary log as follows:


     shell> mysqlbinlog LOG_FILE | mysql -h SERVER_NAME

*Note `mysqlbinlog': mysqlbinlog. also can be used to display
replication slave relay log file contents because they are written
using the same format as binary log files. For more information on the
*Note `mysqlbinlog': mysqlbinlog. utility and how to use it, see *Note
mysqlbinlog::. For more information about the binary log and recovery
operations, see *Note point-in-time-recovery::.

Binary logging is done immediately after a statement or transaction
completes but before any locks are released or any commit is done. This
ensures that the log is logged in commit order.

Updates to nontransactional tables are stored in the binary log
immediately after execution. In MySQL 5.1.22 and earlier versions of
MySQL 5.1, an *Note `UPDATE': update. statement using a stored function
that modified a nontransactional table was not logged if it failed, and
an *Note `INSERT ... ON DUPLICATE KEY UPDATE': insert-on-duplicate.
statement that encountered a duplicate key constraint--but did not
actually change any data--was not logged. Beginning with MySQL 5.1.23,
both of these statements are written to the binary log. (Bug #23333)

Within an uncommitted transaction, all updates (*Note `UPDATE': update,
*Note `DELETE': delete, or *Note `INSERT': insert.) that change
transactional tables such as `InnoDB' tables are cached until a *Note
`COMMIT': commit. statement is received by the server. At that point,
*Note `mysqld': mysqld. writes the entire transaction to the binary log
before the *Note `COMMIT': commit. is executed.

Modifications to nontransactional tables cannot be rolled back. If a
transaction that is rolled back includes modifications to
nontransactional tables, the entire transaction is logged with a *Note
`ROLLBACK': commit.  statement at the end to ensure that the
modifications to those tables are replicated.

When a thread that handles the transaction starts, it allocates a
buffer of `binlog_cache_size' to buffer statements. If a statement is
bigger than this, the thread opens a temporary file to store the
transaction. The temporary file is deleted when the thread ends.

The `Binlog_cache_use' status variable shows the number of transactions
that used this buffer (and possibly a temporary file) for storing
statements. The `Binlog_cache_disk_use' status variable shows how many
of those transactions actually had to use a temporary file. These two
variables can be used for tuning `binlog_cache_size' to a large enough
value that avoids the use of temporary files.

The `max_binlog_cache_size' system variable (default 4GB, which is also
the maximum) can be used to restrict the total size used to cache a
multiple-statement transaction. If a transaction is larger than this
many bytes, it fails and rolls back. The minimum value is 4096.

If you are using the binary log and row based logging, concurrent
inserts are converted to normal inserts for `CREATE ...  SELECT' or
*Note `INSERT ... SELECT': insert-select. statements. This is done to
ensure that you can re-create an exact copy of your tables by applying
the log during a backup operation. If you are using statement-based
logging, the original statement is written to the log.

The binary log format has some known limitations that can affect
recovery from backups. See *Note replication-features::.

Binary logging for stored programs is done as described in *Note
stored-programs-logging::.

Note that the binary log format differs in MySQL 5.1 from previous
versions of MySQL, due to enhancements in replication. See *Note
replication-compatibility::.

Writes to the binary log file and binary log index file are handled in
the same way as writes to `MyISAM' tables. See *Note full-disk::.

By default, the binary log is not synchronized to disk at each write.
So if the operating system or machine (not only the MySQL server)
crashes, there is a chance that the last statements of the binary log
are lost. To prevent this, you can make the binary log be synchronized
to disk after every N writes to the binary log, with the `sync_binlog'
system variable. See *Note server-system-variables::. 1 is the safest
value for `sync_binlog', but also the slowest. Even with `sync_binlog'
set to 1, there is still the chance of an inconsistency between the
table content and binary log content in case of a crash. For example,
if you are using `InnoDB' tables and the MySQL server processes a *Note
`COMMIT': commit.  statement, it writes the whole transaction to the
binary log and then commits this transaction into `InnoDB'. If the
server crashes between those two operations, the transaction is rolled
back by `InnoDB' at restart but still exists in the binary log. To
resolve this, you should set `--innodb_support_xa' to 1. Although this
option is related to the support of XA transactions in InnoDB, it also
ensures that the binary log and InnoDB data files are synchronized.

For this option to provide a greater degree of safety, the MySQL server
should also be configured to synchronize the binary log and the
`InnoDB' logs to disk at every transaction.  The `InnoDB' logs are
synchronized by default, and `sync_binlog=1' can be used to synchronize
the binary log. The effect of this option is that at restart after a
crash, after doing a rollback of transactions, the MySQL server cuts
rolled back `InnoDB' transactions from the binary log. This ensures
that the binary log reflects the exact data of `InnoDB' tables, and so,
that the slave remains in synchrony with the master (not receiving a
statement which has been rolled back).

If the MySQL server discovers at crash recovery that the binary log is
shorter than it should have been, it lacks at least one successfully
committed `InnoDB' transaction. This should not happen if
`sync_binlog=1' and the disk/file system do an actual sync when they
are requested to (some do not), so the server prints an error message
`The binary log FILE_NAME is shorter than its expected size'. In this
case, this binary log is not correct and replication should be
restarted from a fresh snapshot of the master's data.

For MySQL 5.1.20 and later (and MySQL 5.0.46 and later for backward
compatibility), the session values of the following system variables
are written to the binary log and honored by the replication slave when
parsing the binary log:

   * `sql_mode' (except that the `NO_DIR_IN_CREATE' mode is not
     replicated; see *Note replication-features-variables::)

   * `foreign_key_checks'

   * `unique_checks'

   * `character_set_client'

   * `collation_connection'

   * `collation_database'

   * `collation_server'

   * `sql_auto_is_null'


File: manual.info,  Node: binary-log-formats,  Next: binary-log-setting,  Prev: binary-log,  Up: binary-log

5.2.4.1 Binary Logging Formats
..............................

The server uses several logging formats to record information in the
binary log. The exact format employed depends on the version of MySQL
being used. There are three logging formats:

   * Replication capabilities in MySQL originally were based on
     propagation of SQL statements from master to slave. This is called
     _statement-based logging_. You can cause this format to be used by
     starting the server with `--binlog-format=STATEMENT'.

   * In _row-based logging_, the master writes events to the binary log
     that indicate how individual table rows are affected. You can
     cause the server to use row-based logging by starting it with
     `--binlog-format=ROW'.

   * A third option is also available: _mixed logging_. With mixed
     logging, statement-based logging is used by default, but the
     logging mode switches automatically to row-based in certain cases
     as described below. You can cause MySQL to use mixed logging
     explicitly by starting *Note `mysqld': mysqld. with the option
     `--binlog-format=MIXED'.

Support for row-based logging was added in MySQL 5.1.5. Mixed logging
is available beginning with MySQL 5.1.8. In MySQL 5.1.12, `MIXED'
become the default logging mode; in 5.1.29, the default was changed
back to `STATEMENT' for compatibility with MySQL 5.0.

Starting with MySQL 5.1.20, the logging format can also be set or
limited by the storage engine being used. This helps to eliminate
issues when replicating certain statements between a master and slave
that are using different storage engines.

With statement-based replication, there may be issues with replicating
nondeterministic statements. In deciding whether or not a given
statement is safe for statement-based replication, MySQL determines
whether it can guarantee that the statement can be replicated using
statement-based logging. If MySQL cannot make this guarantee, it marks
the statement as potentially unreliable and issues the warning,
`Statement may not be safe to log in statement format'.

Prior to MySQL 5.1.36, this warning read, `Statement is not safe to log
in statement format'. (Bug #42415)

You can avoid these issues by using MySQL's row-based replication
instead.


File: manual.info,  Node: binary-log-setting,  Next: binary-log-mixed,  Prev: binary-log-formats,  Up: binary-log

5.2.4.2 Setting The Binary Log Format
.....................................

You can select the binary logging format explicitly by starting the
MySQL server with `--binlog-format=TYPE'.  The supported values for
TYPE are:

   * `STATEMENT' causes logging to be statement based.

   * `ROW' causes logging to be row based.

   * `MIXED' causes logging to use mixed format.

The default binary logging format depends on the version of MySQL you
are using:

   * For MySQL 5.1.11 and earlier, and for MySQL 5.1.29 and later,
     statement-based logging is used by default.

   * For MySQL 5.1.12 through MySQL 5.1.28, mixed logging is used by
     default.

Exception

For all MySQL Cluster releases using version 6.1 or later of the *Note
`NDBCLUSTER': mysql-cluster. storage engine (even those releases based
on MySQL 5.1.29 and later), the default binary log format is `MIXED'.
See *Note mysql-cluster-replication::.

The logging format also can be switched at runtime. To specify the
format globally for all clients, set the global value of the
`binlog_format' system variable:


     mysql> SET GLOBAL binlog_format = 'STATEMENT';
     mysql> SET GLOBAL binlog_format = 'ROW';
     mysql> SET GLOBAL binlog_format = 'MIXED';

An individual client can control the logging format for its own
statements by setting the session value of `binlog_format':


     mysql> SET SESSION binlog_format = 'STATEMENT';
     mysql> SET SESSION binlog_format = 'ROW';
     mysql> SET SESSION binlog_format = 'MIXED';

*Note*:

Each MySQL Server can set its own and only its own binary logging
format (true whether `binlog_format' is set with global or session
scope). This means that changing the logging format on a replication
master does not cause a slave to change its logging format to match.
(When using `STATEMENT' mode, the `binlog_format' system variable is
not replicated; when using `MIXED' or `ROW' logging mode, it is
replicated but is ignored by the slave.) Changing the binary logging
format on the master while replication is ongoing, or without also
changing it on the slave can thus cause unexpected results, or even
cause replication to fail altogether.

To change the global `binlog_format' value, you must have the `SUPER'
privilege. This is also true for the session value as of MySQL 5.1.29.

In addition to switching the logging format manually, a slave server
may switch the format _automatically_.  This happens when the server is
running in either `STATEMENT' or `MIXED' format and encounters an event
in the binary log that is written in `ROW' logging format. In that
case, the slave switches to row-based replication temporarily for that
event, and switches back to the previous format afterward.

There are several reasons why a client might want to set binary logging
on a per-session basis:

   * A session that makes many small changes to the database might want
     to use row-based logging.

   * A session that performs updates that match many rows in the
     `WHERE' clause might want to use statement-based logging because
     it will be more efficient to log a few statements than many rows.

   * Some statements require a lot of execution time on the master, but
     result in just a few rows being modified. It might therefore be
     beneficial to replicate them using row-based logging.

There are exceptions when you cannot switch the replication format at
runtime:

   * From within a stored function or a trigger

   * If the *Note `NDBCLUSTER': mysql-cluster. storage engine is enabled

   * If the session is currently in row-based replication mode and has
     open temporary tables

Trying to switch the format in any of these cases results in an error.

If you are using *Note `InnoDB': innodb-storage-engine. tables and the
transaction isolation level is `READ COMMITTED' or `READ UNCOMMITTED',
only row-based logging can be used. It is _possible_ to change the
logging format to `STATEMENT', but doing so at runtime leads very
rapidly to errors because `InnoDB' can no longer perform inserts.

Switching the replication format at runtime is not recommended when any
temporary tables exist, because temporary tables are logged only when
using statement-based replication, whereas with row-based replication
they are not logged. With mixed replication, temporary tables are
usually logged; exceptions happen with user-defined functions (UDFs)
and with the `UUID()' function.

With the binary log format set to `ROW', many changes are written to
the binary log using the row-based format. Some changes, however, still
use the statement-based format. Examples include all DDL (data
definition language) statements such as *Note `CREATE TABLE':
create-table, *Note `ALTER TABLE': alter-table, or *Note `DROP TABLE':
drop-table.

The `--binlog-row-event-max-size' option is available for servers that
are capable of row-based replication. Rows are stored into the binary
log in chunks having a size in bytes not exceeding the value of this
option.  The value must be a multiple of 256. The default value is 1024.

*Warning*:

When using _statement-based logging_ for replication, it is possible
for the data on the master and slave to become different if a statement
is designed in such a way that the data modification is
_nondeterministic_; that is, it is left to the will of the query
optimizer. In general, this is not a good practice even outside of
replication. For a detailed explanation of this issue, see *Note bugs::.


File: manual.info,  Node: binary-log-mixed,  Next: binary-log-mysql-database,  Prev: binary-log-setting,  Up: binary-log

5.2.4.3 Mixed Binary Logging Format
...................................

When running in `MIXED' logging format, the server automatically
switches from statement-based to row-based logging under the following
conditions:

   * When a DML statement updates an *Note `NDBCLUSTER': mysql-cluster.
     table.

   * When a function contains `UUID()'.

   * Prior to MySQL 5.1.40, when two or more tables with
     `AUTO_INCREMENT' columns are updated. As of 5.1.40, when one or
     more tables with `AUTO_INCREMENT' columns are updated and a
     trigger or stored function is invoked. Unlike other unsafe
     statements, this does not generate a warning if `binlog_format =
     STATEMENT'.

     For more information, see *Note
     replication-features-auto-increment::.

   * When any *Note `INSERT DELAYED': insert-delayed. is executed.

   * When the body of a view requires row-based replication, the
     statement creating the view also uses it. For example, this occurs
     when the statement creating a view uses the `UUID()' function.

   * When a call to a UDF is involved.

   * If a statement is logged by row and the session that executed the
     statement has any temporary tables, logging by row is used for all
     subsequent statements (except for those accessing temporary
     tables) until all temporary tables in use by that session are
     dropped.

     This is true whether or not any temporary tables are actually
     logged.

     Temporary tables cannot be logged using row-based format; thus,
     once row-based logging is used, all subsequent statements using
     that table are unsafe. The server approximates this condition by
     treating all statements executed during the session as unsafe
     until the session no longer holds any temporary tables.

   * Beginning with MySQL 5.1.23:

        * When `FOUND_ROWS()' or `ROW_COUNT()' is used. (Bug #12092,
          Bug #30244)

        * When `USER()', `CURRENT_USER()', or `CURRENT_USER' is used.
          (Bug #28086)

   * Beginning with MySQL 5.1.24, when a statement refers to one or
     more system variables. (Bug #31168)

     Exception

     The following system variables, when used with session scope
     (only), do not cause the logging format to switch:

        * `auto_increment_increment'

        * `auto_increment_offset'

        * `character_set_client'

        * `character_set_connection'

        * `character_set_database'

        * `character_set_server'

        * `collation_connection'

        * `collation_database'

        * `collation_server'

        * `foreign_key_checks'

        * `identity'

        * `last_insert_id'

        * `lc_time_names'

        * `pseudo_thread_id'

        * `sql_auto_is_null'

        * `time_zone'

        * `timestamp'

        * `unique_checks'

     For information about determining system variable scope, see *Note
     using-system-variables::.

     For information about how replication treats `sql_mode', see *Note
     replication-features-variables::.

   * Beginning with MySQL 5.1.30, when one of the tables involved is a
     log table in the `mysql' database.

   * Beginning with MySQL 5.1.34, when the `LOAD_FILE()' function is
     used.  (Bug #39701)

*Note*:

Starting with MySQL 5.1.20, a warning is generated if you try to
execute a statement using statement-based logging that should be
written using row-based logging. The warning is shown both in the
client (in the output of *Note `SHOW WARNINGS': show-warnings.) and
through the *Note `mysqld': mysqld. error log. A warning is added to the
*Note `SHOW WARNINGS': show-warnings. table each time such a statement
is executed. However, only the first statement that generated the
warning for each client session is written to the error log to prevent
flooding the log.

Starting with MySQL 5.1.20, in addition to the decisions above,
individual engines can also determine the logging format used when
information in a table is updated. The logging capabilities of an
individual engine can be defined as follows:

   * If an engine supports row-based logging, the engine is said to be
     _row-logging capable_.

   * If an engine supports statement-based logging, the engine is said
     to be _statement-logging capable_.

A given storage engine can support either or both logging formats. The
following table lists the logging formats supported by each storage
engine.

This table lists the logging formats supported by each storage engine.

Storage Engine                       Row Logging        Statement Logging
                                     Supported          Supported
`ARCHIVE'                            Yes                Yes
`BLACKHOLE'                          Yes                Yes
`CSV'                                Yes                Yes
`EXAMPLE'                            Yes                No
`FEDERATED'                          Yes                Yes
`HEAP'                               Yes                Yes
`InnoDB'                             Yes                Yes when the
                                                        transaction
                                                        isolation level is
                                                        `REPEATABLE READ'
                                                        or
                                                        `SERIALIZABLE'; No
                                                        otherwise.
`MyISAM'                             Yes                Yes
`MERGE'                              Yes                Yes
*Note `NDBCLUSTER': mysql-cluster.   Yes                No

When determining the logging mode to be used, the capabilities of all
the tables affected by the event are combined. The set of affected
tables is then marked according to these rules:

   * A set of tables is defined as _row-logging restricted_ if the
     tables are row-logging capable but not statement-logging capable.

   * A set of tables is defined as _statement-logging restricted_ if
     the tables are statement-logging capable but not row-logging
     capable.

Once the determination of the possible logging formats required by the
statement is complete it is compared to the current `binlog_format'
setting. The following table is used to decide how the information is
recorded in the binary log or, if appropriate, whether an error is
raised. In the table, a safe operation is defined as one that is
deterministic.

Several rules decide whether the statement is deterministic, as shown
in the following table, where *SLR* stands for `statement-logging
restricted' and *RLR* stands for `row-logging restricted'. A statement
is _statement-logging restricted_ if one or more of the tables it
accesses is not row-logging capable.  Similarly, a statement is
_row-logging restricted_ if any table accessed by the statement is not
statement-logging capable.

The information in this table is used to determine how information is
recorded in the binary log or, if appropriate, whether an error is
raised. The table outlines conditions (Safe/unsafe, `binlog_format',
SLR, RLR) and corresponding actions.

ConditionAction                                            
Safe/unsafe`binlog_format'    SLR     RLR     Error/Warning  Logged as
Safe    `STATEMENT'        Yes     Yes     `Error: not    
                                           loggable'      
Safe    `STATEMENT'        Yes     No                     `STATEMENT'
Safe    `STATEMENT'        No      Yes     `Error: not    
                                           loggable'      
Safe    `STATEMENT'        No      No                     `STATEMENT'
Safe    `MIXED'            Yes     Yes     `Error: not    
                                           loggable'      
Safe    `MIXED'            Yes     No                     `STATEMENT'
Safe    `MIXED'            No      Yes                    `ROW'
Safe    `MIXED'            No      No                     `STATEMENT'
Safe    `ROW'              Yes     Yes     `Error: not    
                                           loggable'      
Safe    `ROW'              Yes     No      `Error: not    
                                           loggable'      
Safe    `ROW'              No      Yes                    `ROW'
Safe    `ROW'              No      No                     `ROW'
Unsafe  `STATEMENT'        Yes     Yes     `Error: not    
                                           loggable'      
Unsafe  `STATEMENT'        Yes     No      `Warning:      `STATEMENT'
                                           unsafe'        
Unsafe  `STATEMENT'        No      Yes     `Error: not    
                                           loggable'      
Unsafe  `STATEMENT'        No      No      `Warning:      `STATEMENT'
                                           unsafe'        
Unsafe  `MIXED'            Yes     Yes     `Error: not    
                                           loggable'      
Unsafe  `MIXED'            Yes     No      `Error: not    
                                           loggable'      
Unsafe  `MIXED'            No      Yes                    `ROW'
Unsafe  `MIXED'            No      No                     `ROW'
Unsafe  `ROW'              Yes     Yes     `Error: not    
                                           loggable'      
Unsafe  `ROW'              Yes     No      `Error: not    
                                           loggable'      
Unsafe  `ROW'              No      Yes                    `ROW'
Unsafe  `ROW'              No      No                     `ROW'

When a warning is produced by the determination, a standard MySQL
warning is produced (and is available using *Note `SHOW WARNINGS':
show-warnings.). The information is also written to the *Note `mysqld':
mysqld. error log. Only one error for each error instance per client
connection is logged to prevent flooding the log. The log message
includes the SQL statement that was attempted.

If a slave server was started with `--log-warnings' enabled, the slave
prints messages to the error log to provide information about its
status, such as the binary log and relay log coordinates where it
starts its job, when it is switching to another relay log, when it
reconnects after a disconnect, and so forth.


File: manual.info,  Node: binary-log-mysql-database,  Prev: binary-log-mixed,  Up: binary-log

5.2.4.4 Logging Format for Changes to mysql Database Tables
...........................................................

The contents of the grant tables in the `mysql' database can be
modified directly (for example, with *Note `INSERT': insert. or *Note
`DELETE': delete.) or indirectly (for example, with *Note `GRANT':
grant. or *Note `CREATE USER': create-user.). As of MySQL 5.1.17,
statements that affect `mysql' database tables are written to the
binary log using the following rules:

   * Data manipulation statements that change data in `mysql' database
     tables directly are logged according to the setting of the
     `binlog_format' system variable. This pertains to statements such
     as *Note `INSERT': insert, *Note `UPDATE': update, *Note `DELETE':
     delete, *Note `REPLACE': replace, *Note `DO': do, *Note `LOAD DATA
     INFILE': load-data, *Note `SELECT': select, and *Note `TRUNCATE
     TABLE': truncate-table.

   * Statements that change the `mysql' database indirectly are logged
     as statements regardless of the value of `binlog_format'. This
     pertains to statements such as *Note `GRANT': grant, *Note
     `REVOKE': revoke, *Note `SET PASSWORD': set-password, *Note
     `RENAME USER': rename-user, `CREATE' (all forms except *Note
     `CREATE TABLE ... SELECT': create-table.), `ALTER' (all forms),
     and `DROP' (all forms).

*Note `CREATE TABLE ... SELECT': create-table. is a combination of data
definition and data manipulation. The *Note `CREATE TABLE':
create-table.  part is logged using statement format and the *Note
`SELECT': select. part is logged according to the value of
`binlog_format'.


File: manual.info,  Node: slow-query-log,  Next: ddl-log,  Prev: binary-log,  Up: server-logs

5.2.5 The Slow Query Log
------------------------

The slow query log consists of SQL statements that took more than
`long_query_time' seconds to execute and (as of MySQL 5.1.21) required
at least `min_examined_row_limit' rows to be examined. The default
value of `long_query_time' is 10. Beginning with MySQL 5.1.21, the
minimum is 0, and the value can be specified to a resolution of
microseconds. For logging to a file, times are written including the
microseconds part. For logging to tables, only integer times are
written; the microseconds part is ignored. Prior to MySQL 5.1.21, the
minimum value is 1, and the value for this variable must be an integer.

By default, administrative statements are not logged, nor are queries
that do not use indexes for lookups. This behavior can be changed using
`--log-slow-admin-statements' and `--log-queries-not-using-indexes', as
described later.

The time to acquire the initial locks is not counted as execution time.
*Note `mysqld': mysqld. writes a statement to the slow query log after
it has been executed and after all locks have been released, so log
order might differ from execution order.

Control the slow query log at server startup as follows:

   * Before 5.1.6, the slow query log destination is always a file.  To
     enable the log, start *Note `mysqld': mysqld. with the
     `--log-slow-queries[=FILE_NAME]' option.

   * As of MySQL 5.1.6, the destination can be a file or a table, or
     both. Start *Note `mysqld': mysqld. with the
     `--log-slow-queries[=FILE_NAME]' option to enable the slow query
     log, and optionally use `--log-output' to specify the log
     destination (as described in *Note log-destinations::).

   * As of MySQL 5.1.12, as an alternative to `--log-slow-queries', use
     `--slow_query_log[={0|1}]' to specify the initial slow query log
     state. In this case, the default slow query log file name is used.
     With no argument or an argument of 1, `--slow_query_log' enables
     the log. With an argument of 0, this option disables the log.

   * As of MySQL 5.1.29, use `--slow_query_log[={0|1}]' to enable or
     disable the slow query log, and optionally
     `--slow_query_log_file=FILE_NAME' to specify a log file name. The
     `--log-slow-queries' option is deprecated.

If the slow query log file is enabled but no name is specified, the
default name is `HOST_NAME-slow.log' and the server creates the file in
the same directory where it creates the PID file. If a name is given,
the server creates the file in the data directory unless an absolute
path name is given to specify a different directory.

To disable or enable the slow query log or change the log file name at
runtime, use the global `slow_query_log' and `slow_query_log_file'
system variables. Set `slow_query_log' to 0 (or `OFF') to disable the
log or to 1 (or `ON') to enable it. Set `slow_query_log_file' to specify
the name of the log file. If a log file already is open, it is closed
and the new file is opened.

When the slow query log is enabled, the server writes output to any
destinations specified by the `--log-output' option or `log_output'
system variable. If you enable the log, the server opens the log file
and writes startup messages to it. However, further logging of queries
to the file does not occur unless the `FILE' log destination is
selected. If the destination is `NONE', the server writes no queries
even if the slow query log is enabled. Setting the log file name has no
effect on logging if the log destination value does not contain `FILE'.

The server writes less information to the slow query log (and binary
log) if you use the `--log-short-format' option.

To include slow administrative statements in the statements written to
the slow query log, use the `--log-slow-admin-statements' server
option. Administrative statements include *Note `ALTER TABLE':
alter-table, *Note `ANALYZE TABLE': analyze-table, *Note `CHECK TABLE':
check-table, *Note `CREATE INDEX': create-index, *Note `DROP INDEX':
drop-index, *Note `OPTIMIZE TABLE': optimize-table, and *Note `REPAIR
TABLE': repair-table.

To include queries that do not use indexes for row lookups in the
statements written to the slow query log, use the
`--log-queries-not-using-indexes' server option. See *Note
server-options::. When such queries are logged, the slow query log may
grow quickly.

The server uses the controlling parameters in the following order to
determine whether to write a query to the slow query log:

  1. The query must either not be an administrative statement, or
     `--log-slow-admin-statements' must have been specified.

  2. The query must have taken at least `long_query_time' seconds, or
     `--log-queries-not-using-indexes' must have been specified and the
     query used no indexes for row lookups.

  3. The query must have examined at least `min_examined_row_limit'
     rows.

The server does not write queries handled by the query cache to the
slow query log, nor queries that would not benefit from the presence of
an index because the table has zero rows or one row.

Prior to MySQL 5.1.45, replication slaves did not write replicated
queries to the slow query log, even if the same queries were written to
the slow query log on the master. (Bug #23300) In MySQL 5.1.45 and
later, this behavior can be overridden using the
`--log-slow-slave-statements' option.

The slow query log should be protected because logged statements might
contain passwords. See *Note password-logging::.

The slow query log can be used to find queries that take a long time to
execute and are therefore candidates for optimization.  However,
examining a long slow query log can become a difficult task. To make
this easier, you can process a slow query log file using the *Note
`mysqldumpslow': mysqldumpslow. command to summarize the queries that
appear in the log. See *Note mysqldumpslow::.


File: manual.info,  Node: ddl-log,  Next: log-file-maintenance,  Prev: slow-query-log,  Up: server-logs

5.2.6 The DDL Log
-----------------

In MySQL 5.1 and later, the DDL log, or metadata log, records metadata
operations generated by data definition statements such as *Note `DROP
TABLE': drop-table. and *Note `ALTER TABLE': alter-table. MySQL uses
this log to recover from crashes occurring in the middle of a metadata
operation. When executing the statement `DROP TABLE t1, t2', we need to
ensure that both `t1' and `t2' are dropped, and that each table drop is
complete. Another example of this type of SQL statement is *Note `ALTER
TABLE t3 DROP PARTITION p2': alter-table-partition-operations, where we
must make certain that the partition is completely dropped and that its
definition is removed from the list of partitions for table `t3'.

A record of metadata operations such as those just described are
written to the file `ddl_log.log', in the MySQL data directory. This is
a binary file; it is not intended to be human-readable, and you should
not attempt to modify it in any way.

`ddl_log.log' is not created until it is actually needed for recording
metadata statements, so it is possible for this file not to be present
on a MySQL server that is functioning in a completely normal manner.

There are no user-configurable server options or variables associated
with this file.


File: manual.info,  Node: log-file-maintenance,  Prev: ddl-log,  Up: server-logs

5.2.7 Server Log Maintenance
----------------------------

As described in *Note server-logs::, MySQL Server can create several
different log files to help you see what activity is taking place.
However, you must clean up these files regularly to ensure that the
logs do not take up too much disk space.

When using MySQL with logging enabled, you may want to back up and
remove old log files from time to time and tell MySQL to start logging
to new files. See *Note backup-methods::.

On a Linux (Red Hat) installation, you can use the `mysql-log-rotate'
script for this. If you installed MySQL from an RPM distribution, this
script should have been installed automatically. Be careful with this
script if you are using the binary log for replication. You should not
remove binary logs until you are certain that their contents have been
processed by all slaves.

On other systems, you must install a short script yourself that you
start from `cron' (or its equivalent) for handling log files.

For the binary log, you can set the `expire_logs_days' system variable
to expire binary log files automatically after a given number of days
(see *Note server-system-variables::). If you are using replication,
you should set the variable no lower than the maximum number of days
your slaves might lag behind the master. To remove binary logs on
demand, use the *Note `PURGE BINARY LOGS': purge-binary-logs. statement
(see *Note purge-binary-logs::).

You can force MySQL to start using new log files by flushing the logs.
Log flushing occurs when you issue a *Note `FLUSH LOGS': flush.
statement or execute a *Note `mysqladmin flush-logs': mysqladmin, *Note
`mysqladmin refresh': mysqladmin, *Note `mysqldump --flush-logs':
mysqldump, or *Note `mysqldump --master-data': mysqldump. command. See
*Note flush::, *Note mysqladmin::, and *Note mysqldump::. In addition,
the binary log is flushed when its size reaches the value of the
`max_binlog_size' system variable.

A log-flushing operation does the following:

   * If general query logging or slow query logging to a log file is
     enabled, the server closes and reopens the general query log file
     or slow query log file.

   * If binary logging is enabled, the server closes the current binary
     log file and opens a new log file with the next sequence number.

   * If the server was started with the `--log-error' option to cause
     the error log to be written to a file, the result of a
     log-flushing operation is version dependent:

        * As of MySQL 5.1.51, the server closes and reopens the log
          file.

        * Prior to MySQL 5.1.51, the server renames the current log
          file with the suffix `-old', then creates a new empty log
          file.

The server creates a new binary log file when you flush the logs.
However, it just closes and reopens the general and slow query log
files. To cause new files to be created on Unix, rename the current log
files before flushing them. At flush time, the server opens new log
files with the original names. For example, if the general and slow
query log files are named `mysql.log' and `mysql-slow.log', you can use
a series of commands like this:


     shell> cd MYSQL-DATA-DIRECTORY
     shell> mv mysql.log mysql.old
     shell> mv mysql-slow.log mysql-slow.old
     shell> mysqladmin flush-logs

On Windows, use `rename' rather than `mv'.

At this point, you can make a backup of `mysql.old' and
`mysql-slow.old' and then remove them from disk.

As of MySQL 5.1.12, you can rename the general query log or slow query
log at runtime by disabling the log:


     SET GLOBAL general_log = 'OFF';
     SET GLOBAL slow_query_log = 'OFF';

With the logs disabled, rename the log files externally; for example,
from the command line. Then enable the logs again:


     SET GLOBAL general_log = 'ON';
     SET GLOBAL slow_query_log = 'ON';

This method works on any platform and does not require a server restart.

For older versions of MySQL on Windows, you cannot rename certain log
files while the server has them open. Before MySQL 5.1.3, this
restriction applies to all log files. You must stop the server, rename
the file, then restart the server to create a new log file.  From 5.1.4
to 5.1.50, the restriction applies only to the error log file. To
rename the error log file, a stop and restart can be avoided by
flushing the logs to cause the server to rename the current log file
with the suffix `-old' and create a new empty error log file. For
further information, see *Note error-log::.


File: manual.info,  Node: multiple-servers,  Prev: server-logs,  Up: server-administration

5.3 Running Multiple MySQL Instances on One Machine
===================================================

* Menu:

* multiple-data-directories::    Setting Up Multiple Data Directories
* multiple-windows-servers::     Running Multiple MySQL Instances on Windows
* multiple-unix-servers::        Running Multiple MySQL Instances on Unix
* multiple-server-clients::      Using Client Programs in a Multiple-Server Environment

In some cases, you might want to run multiple instances of MySQL on a
single machine. You might want to test a new MySQL release while
leaving an existing production setup undisturbed. Or you might want to
give different users access to different *Note `mysqld': mysqld.
servers that they manage themselves. (For example, you might be an
Internet Service Provider that wants to provide independent MySQL
installations for different customers.)

It is possible to use a different MySQL server binary per instance, or
use the same binary for multiple instances, or any combination of the
two approaches. For example, you might run a server from MySQL 5.0 and
one from MySQL 5.1, to see how different versions handle a given
workload. Or you might run multiple instances of the current production
version, each managing a different set of databases.

Whether or not you use distinct server binaries, each instance that you
run must be configured with unique values for several operating
parameters. This eliminates the potential for conflict between
instances. Parameters can be set on the command line, in option files,
or by setting environment variables. See *Note program-options::. To
see the values used by a given instance, connect to it and execute a
*Note `SHOW VARIABLES': show-variables. statement.

The primary resource managed by a MySQL instance is the data directory.
Each instance should use a different data directory, the location of
which is specified using the `--datadir=PATH' option. For methods of
configuring each instance with its own data directory, and warnings
about the dangers of failing to do so, see *Note
multiple-data-directories::.

In addition to using different data directories, several other options
must have different values for each server instance:

   * `--port=PORT_NUM'

     `--port' controls the port number for TCP/IP connections.
     Alternatively, if the host has multiple network addresses, you can
     use `--bind-address' to cause each server to listen to a different
     address.

   * `--socket=PATH'

     `--socket' controls the Unix socket file path on Unix or the named
     pipe name on Windows. On Windows, it is necessary to specify
     distinct pipe names only for those servers configured to permit
     named-pipe connections.

   * `--shared-memory-base-name=NAME'

     This option is used only on Windows. It designates the
     shared-memory name used by a Windows server to permit clients to
     connect using shared memory. It is necessary to specify distinct
     shared-memory names only for those servers configured to permit
     shared-memory connections.

   * `--pid-file=FILE_NAME'

     This option indicates the path name of the file in which the
     server writes its process ID.

If you use the following log file options, their values must differ for
each server:

   * `--general_log_file=FILE_NAME'

   * `--log-bin[=FILE_NAME]'

   * `--slow_query_log_file=FILE_NAME'

   * `--log-error[=FILE_NAME]'

For further discussion of log file options, see *Note server-logs::.

To achieve better performance, you can specify the following option
differently for each server, to spread the load between several
physical disks:

   * `--tmpdir=PATH'

Having different temporary directories also makes it easier to
determine which MySQL server created any given temporary file.

If you have multiple MySQL installations in different locations, you
can specify the base directory for each installation with the
`--basedir=PATH' option. This causes each instance to automatically use
a different data directory, log files, and PID file because the default
for each of those parameters is relative to the base directory. In that
case, the only other options you need to specify are the `--socket' and
`--port' options. Suppose that you install different versions of MySQL
using `tar' file binary distributions. These install in different
locations, so you can start the server for each installation using the
command `bin/mysqld_safe' under its corresponding base directory. *Note
`mysqld_safe': mysqld-safe. determines the proper `--basedir' option to
pass to *Note `mysqld': mysqld, and you need specify only the
`--socket' and `--port' options to *Note `mysqld_safe': mysqld-safe.

As discussed in the following sections, it is possible to start
additional servers by specifying appropriate command options or by
setting environment variables. However, if you need to run multiple
servers on a more permanent basis, it is more convenient to use option
files to specify for each server those option values that must be
unique to it. The `--defaults-file' option is useful for this purpose.


File: manual.info,  Node: multiple-data-directories,  Next: multiple-windows-servers,  Prev: multiple-servers,  Up: multiple-servers

5.3.1 Setting Up Multiple Data Directories
------------------------------------------

Each MySQL Instance on a machine should have its own data directory.
The location is specified using the `--datadir=PATH' option.

There are different methods of setting up a data directory for a new
instance:

   * Create a new data directory.

   * Copy an existing data directory.

The following discussion provides more detail about each method.

*Warning*:

Normally, you should never have two servers that update data in the
same databases. This may lead to unpleasant surprises if your operating
system does not support fault-free system locking. If (despite this
warning) you run multiple servers using the same data directory and
they have logging enabled, you must use the appropriate options to
specify log file names that are unique to each server. Otherwise, the
servers try to log to the same files.

Even when the preceding precautions are observed, this kind of setup
works only with `MyISAM' and `MERGE' tables, and not with any of the
other storage engines. Also, this warning against sharing a data
directory among servers always applies in an NFS environment.
Permitting multiple MySQL servers to access a common data directory
over NFS is a _very bad idea_. The primary problem is that NFS is the
speed bottleneck. It is not meant for such use. Another risk with NFS
is that you must devise a way to ensure that two or more servers do not
interfere with each other. Usually NFS file locking is handled by the
`lockd' daemon, but at the moment there is no platform that performs
locking 100% reliably in every situation.

*Create a New Data Directory*

With this method, the data directory will be in the same state as when
you first install MySQL. It will have the default set of MySQL accounts
and no user data.

On Unix, initialize the data directory by running *Note
`mysql_install_db': mysql-install-db. See *Note unix-postinstallation::.

On Windows, the data directory is included in MySQL distributions.  If
you obtain a distribution in Windows Zip archive format, you can unpack
it into a temporary location, then copy the `data' directory from this
location to where you are setting up the new instance.

*Copy an Existing Data Directory*

With this method, any MySQL accounts or user data present in the data
directory are carried over to the new data directory.

  1. Stop the existing MySQL instance using the data directory.  This
     must be a clean shutdown so that the instance flushes any pending
     changes to disk.

  2. Copy the data directory to the location where the new data
     directory should be.

  3. Copy the `my.cnf' or `my.ini' option file used by the existing
     instance. This serves as a basis for the new instance.

  4. Modify the new option file so that any pathnames referring to the
     original data directory refer to the new data directory.  Also,
     modify any other options that must be unique per instance, such as
     the TCP/IP port number and the log files.  For a list of
     parameters that must be unique per instance, see *Note
     multiple-servers::.

  5. Start the new instance, telling it to use the new option file.


File: manual.info,  Node: multiple-windows-servers,  Next: multiple-unix-servers,  Prev: multiple-data-directories,  Up: multiple-servers

5.3.2 Running Multiple MySQL Instances on Windows
-------------------------------------------------

* Menu:

* multiple-windows-command-line-servers::  Starting Multiple MySQL Instances at the Windows Command Line
* multiple-windows-services::    Starting Multiple MySQL Instances as Windows Services

You can run multiple servers on Windows by starting them manually from
the command line, each with appropriate operating parameters, or by
installing several servers as Windows services and running them that
way. General instructions for running MySQL from the command line or as
a service are given in *Note windows-installation::. The following
sections describe how to start each server with different values for
those options that must be unique per server, such as the data
directory. These options are listed in *Note multiple-servers::.


File: manual.info,  Node: multiple-windows-command-line-servers,  Next: multiple-windows-services,  Prev: multiple-windows-servers,  Up: multiple-windows-servers

5.3.2.1 Starting Multiple MySQL Instances at the Windows Command Line
.....................................................................

The procedure for starting a single MySQL server manually from the
command line is described in *Note windows-start-command-line::. To
start multiple servers this way, you can specify the appropriate
options on the command line or in an option file. It is more convenient
to place the options in an option file, but it is necessary to make
sure that each server gets its own set of options. To do this, create
an option file for each server and tell the server the file name with a
`--defaults-file' option when you run it.

Suppose that you want to run *Note `mysqld': mysqld. on port 3307 with
a data directory of `C:\mydata1', and *Note `mysqld-debug': mysqld. on
port 3308 with a data directory of `C:\mydata2'. Use this procedure:

  1. Make sure that each data directory exists, including its own copy
     of the `mysql' database that contains the grant tables.

  2. Create two option files. For example, create one file named
     `C:\my-opts1.cnf' that looks like this:


          [mysqld]
          datadir = C:/mydata1
          port = 3307

     Create a second file named `C:\my-opts2.cnf' that looks like this:


          [mysqld]
          datadir = C:/mydata2
          port = 3308

  3. Use the `--defaults-file' option to start each server with its own
     option file:


          C:\> C:\mysql\bin\mysqld --defaults-file=C:\my-opts1.cnf
          C:\> C:\mysql\bin\mysqld-debug --defaults-file=C:\my-opts2.cnf

     Each server starts in the foreground (no new prompt appears until
     the server exits later), so you will need to issue those two
     commands in separate console windows.

To shut down the servers, connect to each using the appropriate port
number:


     C:\> C:\mysql\bin\mysqladmin --port=3307 shutdown
     C:\> C:\mysql\bin\mysqladmin --port=3308 shutdown

Servers configured as just described permit clients to connect over
TCP/IP. If your version of Windows supports named pipes and you also
want to permit named-pipe connections, use the *Note `mysqld-nt':
mysqld. (MySQL 5.1.20 and earlier), *Note `mysqld': mysqld. (MySQL
5.1.21 and later) or *Note `mysqld-debug': mysqld. server and specify
options that enable the named pipe and specify its name. Each server
that supports named-pipe connections must use a unique pipe name. For
example, the `C:\my-opts1.cnf' file might be written like this:


     [mysqld]
     datadir = C:/mydata1
     port = 3307
     enable-named-pipe
     socket = mypipe1

Modify `C:\my-opts2.cnf' similarly for use by the second server. Then
start the servers as described previously.

A similar procedure applies for servers that you want to permit
shared-memory connections. Enable such connections with the
`--shared-memory' option and specify a unique shared-memory name for
each server with the `--shared-memory-base-name' option.


File: manual.info,  Node: multiple-windows-services,  Prev: multiple-windows-command-line-servers,  Up: multiple-windows-servers

5.3.2.2 Starting Multiple MySQL Instances as Windows Services
.............................................................

On Windows, a MySQL server can run as a Windows service. The procedures
for installing, controlling, and removing a single MySQL service are
described in *Note windows-start-service::.

To set up multiple MySQL services, you must make sure that each
instance uses a different service name in addition to the other
parameters that must be unique per instance.

For the following instructions, suppose that you want to run the *Note
`mysqld': mysqld. server from two different versions of MySQL that are
installed at `C:\mysql-5.0.92' and `C:\mysql-5.1.73', respectively.
(This might be the case if you are running 5.0.92 as your production
server, but also want to conduct tests using 5.1.73.)

To install MySQL as a Windows service, use the `--install' or
`--install-manual' option. For information about these options, see
*Note windows-start-service::.

Based on the preceding information, you have several ways to set up
multiple services. The following instructions describe some examples.
Before trying any of them, shut down and remove any existing MySQL
services.

   * *Approach 1:* Specify the options for all services in one of the
     standard option files. To do this, use a different service name
     for each server. Suppose that you want to run the 5.0.92 *Note
     `mysqld': mysqld. using the service name of `mysqld1' and the
     5.1.73 *Note `mysqld': mysqld. using the service name `mysqld2'.
     In this case, you can use the `[mysqld1]' group for 5.0.92 and the
     `[mysqld2]' group for 5.1.73.  For example, you can set up
     `C:\my.cnf' like this:


          # options for mysqld1 service
          [mysqld1]
          basedir = C:/mysql-5.0.92
          port = 3307
          enable-named-pipe
          socket = mypipe1

          # options for mysqld2 service
          [mysqld2]
          basedir = C:/mysql-5.1.73
          port = 3308
          enable-named-pipe
          socket = mypipe2

     Install the services as follows, using the full server path names
     to ensure that Windows registers the correct executable program
     for each service:


          C:\> C:\mysql-5.0.92\bin\mysqld --install mysqld1
          C:\> C:\mysql-5.1.73\bin\mysqld --install mysqld2

     To start the services, use the services manager, or use `NET
     START' with the appropriate service names:


          C:\> NET START mysqld1
          C:\> NET START mysqld2

     To stop the services, use the services manager, or use `NET STOP'
     with the appropriate service names:


          C:\> NET STOP mysqld1
          C:\> NET STOP mysqld2

   * *Approach 2:* Specify options for each server in separate files
     and use `--defaults-file' when you install the services to tell
     each server what file to use.  In this case, each file should list
     options using a `[mysqld]' group.

     With this approach, to specify options for the 5.0.92 *Note
     `mysqld-nt': mysqld, create a file `C:\my-opts1.cnf' that looks
     like this:


          [mysqld]
          basedir = C:/mysql-5.0.92
          port = 3307
          enable-named-pipe
          socket = mypipe1

     For the 5.1.73 *Note `mysqld': mysqld, create a file
     `C:\my-opts2.cnf' that looks like this:


          [mysqld]
          basedir = C:/mysql-5.1.73
          port = 3308
          enable-named-pipe
          socket = mypipe2

     Install the services as follows (enter each command on a single
     line):


          C:\> C:\mysql-5.0.92\bin\mysqld --install mysqld1
                     --defaults-file=C:\my-opts1.cnf
          C:\> C:\mysql-5.1.73\bin\mysqld --install mysqld2
                     --defaults-file=C:\my-opts2.cnf

     When you install a MySQL server as a service and use a
     `--defaults-file' option, the service name must precede the option.

     After installing the services, start and stop them the same way as
     in the preceding example.

To remove multiple services, use *Note `mysqld --remove': mysqld. for
each one, specifying a service name following the `--remove' option. If
the service name is the default (`MySQL'), you can omit it.


File: manual.info,  Node: multiple-unix-servers,  Next: multiple-server-clients,  Prev: multiple-windows-servers,  Up: multiple-servers

5.3.3 Running Multiple MySQL Instances on Unix
----------------------------------------------

One way is to run multiple MySQL instances on Unix is to compile
different servers with different default TCP/IP ports and Unix socket
files so that each one listens on different network interfaces.
Compiling in different base directories for each installation also
results automatically in a separate, compiled-in data directory, log
file, and PID file location for each server.

Assume that an existing 5.0 server is configured for the default TCP/IP
port number (3306) and Unix socket file (`/tmp/mysql.sock'). To
configure a new 5.1.73 server to have different operating parameters,
use a `configure' command something like this:


     shell> ./configure --with-tcp-port=PORT_NUMBER \
                  --with-unix-socket-path=FILE_NAME \
                  --prefix=/usr/local/mysql-5.1.73

Here, PORT_NUMBER and FILE_NAME must be different from the default
TCP/IP port number and Unix socket file path name, and the `--prefix'
value should specify an installation directory different from the one
under which the existing MySQL installation is located.

If you have a MySQL server listening on a given port number, you can
use the following command to find out what operating parameters it is
using for several important configurable variables, including the base
directory and Unix socket file name:


     shell> mysqladmin --host=HOST_NAME --port=PORT_NUMBER variables

With the information displayed by that command, you can tell what
option values _not_ to use when configuring an additional server.

If you specify `localhost' as the host name, *Note `mysqladmin':
mysqladmin. defaults to using a Unix socket file connection rather than
TCP/IP. To explicitly specify the connection protocol, use the
`--protocol={TCP|SOCKET|PIPE|MEMORY}' option.

You need not compile a new MySQL server just to start with a different
Unix socket file and TCP/IP port number. It is also possible to use the
same server binary and start each invocation of it with different
parameter values at runtime. One way to do so is by using command-line
options:


     shell> mysqld_safe --socket=FILE_NAME --port=PORT_NUMBER

To start a second server, provide different `--socket' and `--port'
option values, and pass a `--datadir=PATH' option to *Note
`mysqld_safe': mysqld-safe. so that the server uses a different data
directory.

Alternatively, put the options for each server in a different option
file, then start each server using a `--defaults-file' option that
specifies the path to the appropriate option file. For example, if the
option files for two server instances are named
`/usr/local/mysql/my.cnf' and `/usr/local/mysql/my.cnf2', start the
servers like this: command:


     shell> mysqld_safe --defaults-file=/usr/local/mysql/my.cnf
     shell> mysqld_safe --defaults-file=/usr/local/mysql/my.cnf2

Another way to achieve a similar effect is to use environment variables
to set the Unix socket file name and TCP/IP port number:


     shell> MYSQL_UNIX_PORT=/tmp/mysqld-new.sock
     shell> MYSQL_TCP_PORT=3307
     shell> export MYSQL_UNIX_PORT MYSQL_TCP_PORT
     shell> mysql_install_db --user=mysql
     shell> mysqld_safe --datadir=/path/to/datadir &

This is a quick way of starting a second server to use for testing. The
nice thing about this method is that the environment variable settings
apply to any client programs that you invoke from the same shell. Thus,
connections for those clients are automatically directed to the second
server.

*Note environment-variables::, includes a list of other environment
variables you can use to affect MySQL programs.

On Unix, the *Note `mysqld_multi': mysqld-multi. script provides
another way to start multiple servers. See *Note mysqld-multi::.


File: manual.info,  Node: multiple-server-clients,  Prev: multiple-unix-servers,  Up: multiple-servers

5.3.4 Using Client Programs in a Multiple-Server Environment
------------------------------------------------------------

To connect with a client program to a MySQL server that is listening to
different network interfaces from those compiled into your client, you
can use one of the following methods:

   * Start the client with `--host=HOST_NAME' `--port=PORT_NUMBER' to
     connect using TCP/IP to a remote server, with `--host=127.0.0.1'
     `--port=PORT_NUMBER' to connect using TCP/IP to a local server, or
     with `--host=localhost' `--socket=FILE_NAME' to connect to a local
     server using a Unix socket file or a Windows named pipe.

   * Start the client with `--protocol=TCP' to connect using TCP/IP,
     `--protocol=SOCKET' to connect using a Unix socket file,
     `--protocol=PIPE' to connect using a named pipe, or
     `--protocol=MEMORY' to connect using shared memory. For TCP/IP
     connections, you may also need to specify `--host' and `--port'
     options. For the other types of connections, you may need to
     specify a `--socket' option to specify a Unix socket file or
     Windows named-pipe name, or a `--shared-memory-base-name' option
     to specify the shared-memory name. Shared-memory connections are
     supported only on Windows.

   * On Unix, set the `MYSQL_UNIX_PORT' and `MYSQL_TCP_PORT'
     environment variables to point to the Unix socket file and TCP/IP
     port number before you start your clients. If you normally use a
     specific socket file or port number, you can place commands to set
     these environment variables in your `.login' file so that they
     apply each time you log in. See *Note environment-variables::.

   * Specify the default Unix socket file and TCP/IP port number in the
     `[client]' group of an option file. For example, you can use
     `C:\my.cnf' on Windows, or the `.my.cnf' file in your home
     directory on Unix. See *Note option-files::.

   * In a C program, you can specify the socket file or port number
     arguments in the *Note `mysql_real_connect()': mysql-real-connect.
     call. You can also have the program read option files by calling
     *Note `mysql_options()': mysql-options. See *Note
     c-api-functions::.

   * If you are using the Perl `DBD::mysql' module, you can read
     options from MySQL option files. For example:


          $dsn = "DBI:mysql:test;mysql_read_default_group=client;"
                  . "mysql_read_default_file=/usr/local/mysql/data/my.cnf";
          $dbh = DBI->connect($dsn, $user, $password);

     See *Note apis-perl::.

     Other programming interfaces may provide similar capabilities for
     reading option files.


File: manual.info,  Node: security,  Next: backup-and-recovery,  Prev: server-administration,  Up: Top

6 Security
**********

* Menu:

* general-security-issues::      General Security Issues
* privilege-system::             The MySQL Access Privilege System
* user-account-management::      MySQL User Account Management

When thinking about security within a MySQL installation, you should
consider a wide range of possible topics and how they affect the
security of your MySQL server and related applications:

   * General factors that affect security. These include choosing good
     passwords, not granting unnecessary privileges to users, ensuring
     application security by preventing SQL injections and data
     corruption, and others. See *Note general-security-issues::.

   * Security of the installation itself. The data files, log files,
     and the all the application files of your installation should be
     protected to ensure that they are not readable or writable by
     unauthorized parties. For more information, see *Note
     postinstallation::.

   * Access control and security within the database system itself,
     including the users and databases granted with access to the
     databases, views and stored programs in use within the database.
     For more information, see *Note privilege-system::, and *Note
     user-account-management::.

   * Network security of MySQL and your system. The security is related
     to the grants for individual users, but you may also wish to
     restrict MySQL so that it is available only locally on the MySQL
     server host, or to a limited set of other hosts.

   * Ensure that you have adequate and appropriate backups of your
     database files, configuration and log files. Also be sure that you
     have a recovery solution in place and test that you are able to
     successfully recover the information from your backups. See *Note
     backup-and-recovery::.


File: manual.info,  Node: general-security-issues,  Next: privilege-system,  Prev: security,  Up: security

6.1 General Security Issues
===========================

* Menu:

* security-guidelines::          Security Guidelines
* password-security::            Keeping Passwords Secure
* security-against-attack::      Making MySQL Secure Against Attackers
* security-options::             Security-Related mysqld Options and Variables
* changing-mysql-user::          How to Run MySQL as a Normal User
* load-data-local::              Security Issues with LOAD DATA LOCAL
* secure-client-programming::    Client Programming Security Guidelines

This section describes general security issues to be aware of and what
you can do to make your MySQL installation more secure against attack
or misuse. For information specifically about the access control system
that MySQL uses for setting up user accounts and checking database
access, see *Note postinstallation::.

For answers to some questions that are often asked about MySQL Server
security issues, see *Note faqs-security::.


File: manual.info,  Node: security-guidelines,  Next: password-security,  Prev: general-security-issues,  Up: general-security-issues

6.1.1 Security Guidelines
-------------------------

Anyone using MySQL on a computer connected to the Internet should read
this section to avoid the most common security mistakes.

In discussing security, it is necessary to consider fully protecting
the entire server host (not just the MySQL server) against all types of
applicable attacks: eavesdropping, altering, playback, and denial of
service. We do not cover all aspects of availability and fault
tolerance here.

MySQL uses security based on Access Control Lists (ACLs) for all
connections, queries, and other operations that users can attempt to
perform. There is also support for SSL-encrypted connections between
MySQL clients and servers. Many of the concepts discussed here are not
specific to MySQL at all; the same general ideas apply to almost all
applications.

When running MySQL, follow these guidelines:

   * *Do not ever give anyone (except MySQL `root' accounts) access to
     the `user' table in the `mysql' database!* This is critical.

   * Learn how the MySQL access privilege system works (see *Note
     privilege-system::). Use the *Note `GRANT': grant. and *Note
     `REVOKE': revoke. statements to control access to MySQL. Do not
     grant more privileges than necessary.  Never grant privileges to
     all hosts.

     Checklist:

        * Try `mysql -u root'. If you are able to connect successfully
          to the server without being asked for a password, anyone can
          connect to your MySQL server as the MySQL `root' user with
          full privileges!  Review the MySQL installation instructions,
          paying particular attention to the information about setting a
          `root' password. See *Note default-privileges::.

        * Use the *Note `SHOW GRANTS': show-grants.  statement to check
          which accounts have access to what.  Then use the *Note
          `REVOKE': revoke.  statement to remove those privileges that
          are not necessary.

   * Do not store cleartext passwords in your database. If your
     computer becomes compromised, the intruder can take the full list
     of passwords and use them. Instead, use `SHA1()', `MD5()', or some
     other one-way hashing function and store the hash value.

     To prevent password recovery using rainbow tables, do not use
     these functions on a plain password; instead, choose some string
     to be used as a salt, and use hash(hash(password)+salt) values.

   * Do not choose passwords from dictionaries. Special programs exist
     to break passwords. Even passwords like `xfish98' are very bad.
     Much better is `duag98' which contains the same word `fish' but
     typed one key to the left on a standard QWERTY keyboard. Another
     method is to use a password that is taken from the first
     characters of each word in a sentence (for example, `Four score
     and seven years ago' results in a password of `Fsasya').  The
     password is easy to remember and type, but difficult to guess for
     someone who does not know the sentence. In this case, you can
     additionally substitute digits for the number words to obtain the
     phrase `4 score and 7 years ago', yielding the password `4sa7ya'
     which is even more difficult to guess.

   * Invest in a firewall. This protects you from at least 50% of all
     types of exploits in any software. Put MySQL behind the firewall
     or in a demilitarized zone (DMZ).

     Checklist:

        * Try to scan your ports from the Internet using a tool such as
          `nmap'. MySQL uses port 3306 by default. This port should not
          be accessible from untrusted hosts. As a simple way to check
          whether your MySQL port is open, try the following command
          from some remote machine, where SERVER_HOST is the host name
          or IP address of the host on which your MySQL server runs:


               shell> telnet SERVER_HOST 3306

          If `telnet' hangs or the connection is refused, the port is
          blocked, which is how you want it to be. If you get a
          connection and some garbage characters, the port is open, and
          should be closed on your firewall or router, unless you
          really have a good reason to keep it open.

   * Applications that access MySQL should not trust any data entered
     by users, and should be written using proper defensive programming
     techniques. See *Note secure-client-programming::.

   * Do not transmit plain (unencrypted) data over the Internet.  This
     information is accessible to everyone who has the time and ability
     to intercept it and use it for their own purposes.  Instead, use
     an encrypted protocol such as SSL or SSH. MySQL supports internal
     SSL connections. Another technique is to use SSH port-forwarding
     to create an encrypted (and compressed) tunnel for the
     communication.

   * Learn to use the `tcpdump' and `strings' utilities. In most cases,
     you can check whether MySQL data streams are unencrypted by
     issuing a command like the following:


          shell> tcpdump -l -i eth0 -w - src or dst port 3306 | strings

     This works under Linux and should work with small modifications
     under other systems.

     *Warning*:

     If you do not see cleartext data, this does not always mean that
     the information actually is encrypted. If you need high security,
     consult with a security expert.


File: manual.info,  Node: password-security,  Next: security-against-attack,  Prev: security-guidelines,  Up: general-security-issues

6.1.2 Keeping Passwords Secure
------------------------------

* Menu:

* password-security-user::       End-User Guidelines for Password Security
* password-security-admin::      Administrator Guidelines for Password Security
* password-logging::             Passwords and Logging
* password-hashing::             Password Hashing in MySQL
* application-password-use::     Implications of Password Hashing Changes in MySQL 4.1 for Application Programs

Passwords occur in several contexts within MySQL. The following
sections provide guidelines that enable end users and administrators to
keep these passwords secure and avoid exposing them. There is also a
discussion of how MySQL uses password hashing internally.


File: manual.info,  Node: password-security-user,  Next: password-security-admin,  Prev: password-security,  Up: password-security

6.1.2.1 End-User Guidelines for Password Security
.................................................

MySQL users should use the following guidelines to keep passwords
secure.

When you run a client program to connect to the MySQL server, it is
inadvisable to specify your password in a way that exposes it to
discovery by other users. The methods you can use to specify your
password when you run client programs are listed here, along with an
assessment of the risks of each method. In short, the safest methods
are to have the client program prompt for the password or to specify
the password in a properly protected option file.

   * Use a `-pYOUR_PASS' or `--password=YOUR_PASS' option on the
     command line. For example:


          shell> mysql -u francis -pfrank DB_NAME

     This is convenient _but insecure_. On some systems, your password
     becomes visible to system status programs such as `ps' that may be
     invoked by other users to display command lines. MySQL clients
     typically overwrite the command-line password argument with zeros
     during their initialization sequence. However, there is still a
     brief interval during which the value is visible.  Also, on some
     systems this overwriting strategy is ineffective and the password
     remains visible to `ps'. (SystemV Unix systems and perhaps others
     are subject to this problem.)

     If your operating environment is set up to display your current
     command in the title bar of your terminal window, the password
     remains visible as long as the command is running, even if the
     command has scrolled out of view in the window content area.

   * Use the `-p' or `--password' option on the command line with no
     password value specified.  In this case, the client program
     solicits the password interactively:


          shell> mysql -u francis -p DB_NAME
          Enter password: ********

     The ``*'' characters indicate where you enter your password. The
     password is not displayed as you enter it.

     It is more secure to enter your password this way than to specify
     it on the command line because it is not visible to other users.
     However, this method of entering a password is suitable only for
     programs that you run interactively. If you want to invoke a
     client from a script that runs noninteractively, there is no
     opportunity to enter the password from the keyboard. On some
     systems, you may even find that the first line of your script is
     read and interpreted (incorrectly) as your password.

   * Store your password in an option file. For example, on Unix, you
     can list your password in the `[client]' section of the `.my.cnf'
     file in your home directory:


          [client]
          password=your_pass

     To keep the password safe, the file should not be accessible to
     anyone but yourself. To ensure this, set the file access mode to
     `400' or `600'.  For example:


          shell> chmod 600 .my.cnf

     To name from the command line a specific option file containing
     the password, use the `--defaults-file=FILE_NAME' option, where
     `file_name' is the full path name to the file. For example:


          shell> mysql --defaults-file=/home/francis/mysql-opts

     *Note option-files::, discusses option files in more detail.

   * Store your password in the `MYSQL_PWD' environment variable. See
     *Note environment-variables::.

     This method of specifying your MySQL password must be considered
     _extremely insecure_ and should not be used. Some versions of `ps'
     include an option to display the environment of running processes.
     On some systems, if you set `MYSQL_PWD', your password is exposed
     to any other user who runs `ps'. Even on systems without such a
     version of `ps', it is unwise to assume that there are no other
     methods by which users can examine process environments.

On Unix, the *Note `mysql': mysql. client writes a record of executed
statements to a history file (see *Note mysql-logging::). By default,
this file is named `.mysql_history' and is created in your home
directory. Passwords can be written as plain text in SQL statements
such as *Note `CREATE USER': create-user, *Note `GRANT': grant, and
*Note `SET PASSWORD': set-password, so if you use these statements,
they are logged in the history file. To keep this file safe, use a
restrictive access mode, the same way as described earlier for the
`.my.cnf' file.

If your command interpreter is configured to maintain a history, any
file in which the commands are saved will contain MySQL passwords
entered on the command line. For example, `bash' uses
`~/.bash_history'. Any such file should have a restrictive access mode.


File: manual.info,  Node: password-security-admin,  Next: password-logging,  Prev: password-security-user,  Up: password-security

6.1.2.2 Administrator Guidelines for Password Security
......................................................

Database administrators should use the following guidelines to keep
passwords secure.

MySQL stores passwords for user accounts in the `mysql.user' table.
Access to this table should never be granted to any nonadministrative
accounts.

A user who has access to modify the plugin directory (the value of the
`plugin_dir' system variable) or the `my.cnf' file that specifies the
location of the plugin directory can replace plugins and modify the
capabilities provided by plugins.

Files such as log files to which passwords might be written should be
protected. See *Note password-logging::.


File: manual.info,  Node: password-logging,  Next: password-hashing,  Prev: password-security-admin,  Up: password-security

6.1.2.3 Passwords and Logging
.............................

Passwords can be written as plain text in SQL statements such as *Note
`CREATE USER': create-user, *Note `GRANT': grant, and *Note `SET
PASSWORD': set-password, or statements that invoke the `PASSWORD()'
function.  If these statements are logged by the MySQL server as
written, such passwords become available to anyone with access to the
logs. This applies to the general query log, the slow query log, and
the binary log (see *Note server-logs::). To guard against unwarranted
exposure to log files, they should be located in a directory that
restricts access to only the server and the database administrator. If
you log to tables in the `mysql' database, access to the tables should
never be granted to any nonadministrative accounts.

Replication slaves store the password for the replication master in the
`master.info' file. Restrict this file to be accessible only to the
database administrator.

Database backups that include tables or log files containing passwords
should be protected using a restricted access mode.


File: manual.info,  Node: password-hashing,  Next: application-password-use,  Prev: password-logging,  Up: password-security

6.1.2.4 Password Hashing in MySQL
.................................

MySQL lists user accounts in the `user' table of the `mysql' database.
Each MySQL account can be assigned a password, although the `user'
table does not store the cleartext version of the password, but a hash
value computed from it.

MySQL uses passwords in two phases of client/server communication:

   * When a client attempts to connect to the server, there is an
     initial authentication step in which the client must present a
     password that has a hash value matching the hash value stored in
     the `user' table for the account the client wants to use.

   * After the client connects, it can (if it has sufficient
     privileges) set or change the password hash for accounts listed in
     the `user' table. The client can do this by using the `PASSWORD()'
     function to generate a password hash, or by using a
     password-generating statement (*Note `CREATE USER': create-user,
     *Note `GRANT': grant, or *Note `SET PASSWORD': set-password.).

In other words, the server _checks_ hash values during authentication
when a client first attempts to connect. The server _generates_ hash
values if a connected client invokes the `PASSWORD()' function or uses a
password-generating statement to set or change a password.

Password hashing methods in MySQL have the history described following.
These changes are illustrated by changes in the result from the
`PASSWORD()' function that computes password hash values and in the
structure of the `user' table where passwords are stored.

*The Original (Pre-4.1) Hashing Method*

The original hashing method produced a 16-byte string. Such hashes look
like this:


     mysql> SELECT PASSWORD('mypass');
     +--------------------+
     | PASSWORD('mypass') |
     +--------------------+
     | 6f8c114b58f2ce9e   |
     +--------------------+

To store account passwords, the `Password' column of the `user' table
was at this point 16 bytes long.

*The 4.1 Hashing Method*

MySQL 4.1 introduced password hashing that provided better security and
reduced the risk of passwords being intercepted.  There were several
aspects to this change:

   * Different `PASSWORD()' function result format

   * Widening of the `Password' column

   * Control over the default hashing method

   * Control over the permitted hashing methods for clients attempting
     to connect to the server

The changes in MySQL 4.1 took place in two stages:

   * MySQL 4.1.0 used a preliminary version of the 4.1 hashing method.
     Because this method was so short lived, the following discussion
     says nothing more about it.

   * In MySQL 4.1.1, the hashing method was modified to produce a
     longer 41-byte hash value:


          mysql> SELECT PASSWORD('mypass');
          +-------------------------------------------+
          | PASSWORD('mypass')                        |
          +-------------------------------------------+
          | *6C8989366EAF75BB670AD8EA7A7FC1176A95CEF4 |
          +-------------------------------------------+

     The longer password hash format has better cryptographic
     properties, and client authentication based on long hashes is more
     secure than that based on the older short hashes.

     To accommodate longer password hashes, the `Password' column in the
     `user' table was changed at this point to be 41 bytes, its current
     length.

     A widened `Password' column can store password hashes in both the
     pre-4.1 and 4.1 formats. The format of any given hash value can be
     determined two ways:

        * The length: 4.1 and pre-4.1 hashes are 41 and 16 bytes,
          respectively.

        * Password hashes in the 4.1 format always begin with a ``*''
          character, whereas passwords in the pre-4.1 format never do.

     To permit explicit generation of pre-4.1 password hashes, two
     additional changes were made:

        * The `OLD_PASSWORD()' function was added, which returns hash
          values in the 16-byte format.

        * For compatibility purposes, the `old_passwords' system
          variable was added, to enable DBAs and applications control
          over the hashing method. The default `old_passwords' value of
          0 causes hashing to use the 4.1 method (41-byte hash values),
          but setting `old_passwords=1' causes hashing to use the
          pre-4.1 method. In this case, `PASSWORD()' produces 16-byte
          values and is equivalent to `OLD_PASSWORD()'

     To permit DBAs control over how clients are permitted to connect,
     the `secure_auth' system variable was added. Starting the server
     with this variable disabled or enabled permits or prohibits
     clients to connect using the older pre-4.1 password hashing method.
     Before MySQL 5.6.5, `secure_auth' is disabled by default. As of
     5.6.5, `secure_auth' is enabled by default to promote a more
     secure default configuration.  (DBAs can disable it at their
     discretion, but this is not recommended.)

     In addition, the *Note `mysql': mysql. client supports a
     `--secure-auth' option that is analogous to `secure_auth', but
     from the client side. It can be used to prevent connections to
     less secure accounts that use pre-4.1 password hashing. This
     option is disabled by default before MySQL 5.6.7, enabled
     thereafter.

*Compatibility Issues Related to Hashing Methods*

The widening of the `Password' column in MySQL 4.1 from 16 bytes to 41
bytes affects installation or upgrade operations as follows:

   * If you perform a new installation of MySQL, the `Password' column
     is made 41 bytes long automatically.

   * Upgrades from MySQL 4.1 or later to current versions of MySQL
     should not give rise to any issues in regard to the `Password'
     column because both versions use the same column length and
     password hashing method.

   * For upgrades from a pre-4.1 release to 4.1 or later, you must
     upgrade the system tables after upgrading. (See *Note
     mysql-upgrade::.)

The 4.1 hashing method is understood only by MySQL 4.1 (and newer)
servers and clients, which can result in some compatibility problems. A
4.1 or newer client can connect to a pre-4.1 server, because the client
understands both the pre-4.1 and 4.1 password hashing methods. However,
a pre-4.1 client that attempts to connect to a 4.1 or newer server may
run into difficulties. For example, a 4.0 *Note `mysql': mysql. client
may fail with the following error message:


     shell> mysql -h localhost -u root
     Client does not support authentication protocol requested
     by server; consider upgrading MySQL client

This phenomenon also occurs for attempts to use the older PHP `mysql'
extension after upgrading to MySQL 4.1 or newer. (See Common Problems
with MySQL and PHP
(http://dev.mysql.com/doc/apis-php/en/apis-php-problems.html).)

The following discussion describes the differences between the pre-4.1
and 4.1 hashing methods, and what you should do if you upgrade your
server but need to maintain backward compatibility with pre-4.1
clients. (However, permitting connections by old clients is not
recommended and should be avoided if possible.)  Additional information
can be found in *Note old-client::. This information is of particular
importance to PHP programmers migrating MySQL databases from versions
older than 4.1 to 4.1 or higher.

The differences between short and long password hashes are relevant
both for how the server uses passwords during authentication and for
how it generates password hashes for connected clients that perform
password-changing operations.

The way in which the server uses password hashes during authentication
is affected by the width of the `Password' column:

   * If the column is short, only short-hash authentication is used.

   * If the column is long, it can hold either short or long hashes,
     and the server can use either format:

        * Pre-4.1 clients can connect, but because they know only about
          the pre-4.1 hashing method, they can authenticate only using
          accounts that have short hashes.

        * 4.1 and later clients can authenticate using accounts that
          have short or long hashes.

Even for short-hash accounts, the authentication process is actually a
bit more secure for 4.1 and later clients than for older clients. In
terms of security, the gradient from least to most secure is:

   * Pre-4.1 client authenticating with short password hash

   * 4.1 or later client authenticating with short password hash

   * 4.1 or later client authenticating with long password hash

The way in which the server generates password hashes for connected
clients is affected by the width of the `Password' column and by the
`old_passwords' system variable.  A 4.1 or later server generates long
hashes only if certain conditions are met: The `Password' column must
be wide enough to hold long values and `old_passwords' must not be set
to 1.

Those conditions apply as follows:

   * The `Password' column must be wide enough to hold long hashes (41
     bytes). If the column has not been updated and still has the
     pre-4.1 width of 16 bytes, the server notices that long hashes
     cannot fit into it and generates only short hashes when a client
     performs password-changing operations using the `PASSWORD()'
     function or a password-generating statement. This is the behavior
     that occurs if you have upgraded from a version of MySQL older
     than 4.1 to 4.1 or later but have not yet run the *Note
     `mysql_upgrade': mysql-upgrade. program to widen the `Password'
     column.

   * If the `Password' column is wide, it can store either short or
     long password hashes. In this case, the `PASSWORD()' function and
     password-generating statements generate long hashes unless the
     server was started with the `old_passwords' system variable set to
     1 to force the server to generate short password hashes instead.

The purpose of the `old_passwords' system variable is to permit
backward compatibility with pre-4.1 clients under circumstances where
the server would otherwise generate long password hashes. The option
does not affect authentication (4.1 and later clients can still use
accounts that have long password hashes), but it does prevent creation
of a long password hash in the `user' table as the result of a
password-changing operation. Were that permitted to occur, the account
could no longer be used by pre-4.1 clients. With `old_passwords'
disabled, the following undesirable scenario is possible:

   * An old pre-4.1 client connects to an account that has a short
     password hash.

   * The client changes its own password. With `old_passwords' disabled,
     this results in the account having a long password hash.

   * The next time the old client attempts to connect to the account,
     it cannot, because the account has a long password hash that
     requires the 4.1 hashing method during authentication. (Once an
     account has a long password hash in the user table, only 4.1 and
     later clients can authenticate for it because pre-4.1 clients do
     not understand long hashes.)

This scenario illustrates that, if you must support older pre-4.1
clients, it is problematic to run a 4.1 or newer server without
`old_passwords' set to 1.  By running the server with `old_passwords=1',
password-changing operations do not generate long password hashes and
thus do not cause accounts to become inaccessible to older clients.
(Those clients cannot inadvertently lock themselves out by changing
their password and ending up with a long password hash.)

The downside of `old_passwords=1' is that any passwords created or
changed use short hashes, even for 4.1 or later clients. Thus, you lose
the additional security provided by long password hashes. To create an
account that has a long hash (for example, for use by 4.1 clients) or
to change an existing account to use a long password hash, an
administrator can set the session value of `old_passwords' set to 0
while leaving the global value set to 1:


     mysql> SET @@session.old_passwords = 0;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @@session.old_passwords, @@global.old_passwords;
     +-------------------------+------------------------+
     | @@session.old_passwords | @@global.old_passwords |
     +-------------------------+------------------------+
     |                       0 |                      1 |
     +-------------------------+------------------------+
     1 row in set (0.00 sec)

     mysql> CREATE USER 'newuser'@'localhost' IDENTIFIED BY 'newpass';
     Query OK, 0 rows affected (0.03 sec)

     mysql> SET PASSWORD FOR 'existinguser'@'localhost' = PASSWORD('existingpass');
     Query OK, 0 rows affected (0.00 sec)

The following scenarios are possible in MySQL 4.1 or later. The factors
are whether the `Password' column is short or long, and, if long,
whether the server is started with `old_passwords' enabled or disabled.

*Scenario 1:* Short `Password' column in user table:

   * Only short hashes can be stored in the `Password' column.

   * The server uses only short hashes during client authentication.

   * For connected clients, password hash-generating operations
     involving the `PASSWORD()' function or password-generating
     statements use short hashes exclusively. Any change to an
     account's password results in that account having a short password
     hash.

   * The value of `old_passwords' is irrelevant because with a short
     `Password' column, the server generates only short password hashes
     anyway.

This scenario occurs when a pre-4.1 MySQL installation has been
upgraded to 4.1 or later but *Note `mysql_upgrade': mysql-upgrade.  has
not been run to upgrade the system tables in the `mysql' database.
(This is not a recommended configuration because it does not permit use
of more secure 4.1 password hashing.)

*Scenario 2:* Long `Password' column; server started with
`old_passwords=1':

   * Short or long hashes can be stored in the `Password' column.

   * 4.1 and later clients can authenticate for accounts that have
     short or long hashes.

   * Pre-4.1 clients can authenticate only for accounts that have short
     hashes.

   * For connected clients, password hash-generating operations
     involving the `PASSWORD()' function or password-generating
     statements use short hashes exclusively. Any change to an
     account's password results in that account having a short password
     hash.

In this scenario, newly created accounts have short password hashes
because `old_passwords=1' prevents generation of long hashes. Also, if
you create an account with a long hash before setting `old_passwords'
to 1, changing the account's password while `old_passwords=1' results
in the account being given a short password, causing it to lose the
security benefits of a longer hash.

To create a new account that has a long password hash, or to change the
password of any existing account to use a long hash, first set the
session value of `old_passwords' set to 0 while leaving the global
value set to 1, as described previously.

In this scenario, the server has an up to date `Password' column, but
is running with the default password hashing method set to generate
pre-4.1 hash values. This is not a recommended configuration but may be
useful during a transitional period in which pre-4.1 clients and
passwords are upgraded to 4.1 or later. When that has been done, it is
preferable to run the server with `old_passwords=0' and `secure_auth=1'.

*Scenario 3:* Long `Password' column; server started with
`old_passwords=0':

   * Short or long hashes can be stored in the `Password' column.

   * 4.1 and later clients can authenticate using accounts that have
     short or long hashes.

   * Pre-4.1 clients can authenticate only using accounts that have
     short hashes.

   * For connected clients, password hash-generating operations
     involving the `PASSWORD()' function or password-generating
     statements use long hashes exclusively. A change to an account's
     password results in that account having a long password hash.

As indicated earlier, a danger in this scenario is that it is possible
for accounts that have a short password hash to become inaccessible to
pre-4.1 clients. A change to such an account's password made using the
`PASSWORD()' function or a password-generating statement results in the
account being given a long password hash. From that point on, no
pre-4.1 client can connect to the server using that account. The client
must upgrade to 4.1 or later.

If this is a problem, you can change a password in a special way. For
example, normally you use *Note `SET PASSWORD': set-password. as
follows to change an account password:


     SET PASSWORD FOR 'SOME_USER'@'SOME_HOST' = PASSWORD('mypass');

To change the password but create a short hash, use the
`OLD_PASSWORD()' function instead:


     SET PASSWORD FOR 'SOME_USER'@'SOME_HOST' = OLD_PASSWORD('mypass');

`OLD_PASSWORD()' is useful for situations in which you explicitly want
to generate a short hash.

The disadvantages for each of the preceding scenarios may be summarized
as follows:

In scenario 1, you cannot take advantage of longer hashes that provide
more secure authentication.

In scenario 2, `old_passwords=1' prevents accounts with short hashes
from becoming inaccessible, but password-changing operations cause
accounts with long hashes to revert to short hashes unless you take
care to change the session value of `old_passwords' to 0 first.

In scenario 3, accounts with short hashes become inaccessible to
pre-4.1 clients if you change their passwords without explicitly using
`OLD_PASSWORD()'.

The best way to avoid compatibility problems related to short password
hashes is to not use them:

   * Upgrade all client programs to MySQL 4.1 or later.

   * Run the server with `old_passwords=0'.

   * Reset the password for any account with a short password hash to
     use a long password hash.

   * For additional security, run the server with `secure_auth=1'.


File: manual.info,  Node: application-password-use,  Prev: password-hashing,  Up: password-security

6.1.2.5 Implications of Password Hashing Changes in MySQL 4.1 for Application Programs
......................................................................................

An upgrade to MySQL version 4.1 or later can cause compatibility issues
for applications that use `PASSWORD()' to generate passwords for their
own purposes. Applications really should not do this, because
`PASSWORD()' should be used only to manage passwords for MySQL
accounts. But some applications use `PASSWORD()' for their own purposes
anyway.

If you upgrade to 4.1 or later from a pre-4.1 version of MySQL and run
the server under conditions where it generates long password hashes, an
application using `PASSWORD()' for its own passwords breaks. The
recommended course of action in such cases is to modify the application
to use another function, such as `SHA1()' or `MD5()', to produce hashed
values.  If that is not possible, you can use the `OLD_PASSWORD()'
function, which is provided for generate short hashes in the old
format. However, you should note that `OLD_PASSWORD()' may one day no
longer be supported.

If the server is running with `old_passwords=1', it generates short
hashes and `OLD_PASSWORD()' is equivalent to `PASSWORD()'.

PHP programmers migrating their MySQL databases from version 4.0 or
lower to version 4.1 or higher should see MySQL and PHP
(http://dev.mysql.com/doc/apis-php/en/index.html).


File: manual.info,  Node: security-against-attack,  Next: security-options,  Prev: password-security,  Up: general-security-issues

6.1.3 Making MySQL Secure Against Attackers
-------------------------------------------

When you connect to a MySQL server, you should use a password. The
password is not transmitted in clear text over the connection.
Password handling during the client connection sequence was upgraded in
MySQL 4.1.1 to be very secure. If you are still using pre-4.1.1-style
passwords, the encryption algorithm is not as strong as the newer
algorithm. With some effort, a clever attacker who can sniff the
traffic between the client and the server can crack the password. (See
*Note password-hashing::, for a discussion of the different password
handling methods.)

All other information is transferred as text, and can be read by anyone
who is able to watch the connection. If the connection between the
client and the server goes through an untrusted network, and you are
concerned about this, you can use the compressed protocol to make
traffic much more difficult to decipher. You can also use MySQL's
internal SSL support to make the connection even more secure. See *Note
ssl-connections::. Alternatively, use SSH to get an encrypted TCP/IP
connection between a MySQL server and a MySQL client. You can find an
Open Source SSH client at `http://www.openssh.org/', and a comparison
of both Open Source and Commercial SSH clients at
`http://en.wikipedia.org/wiki/Comparison_of_SSH_clients'.

To make a MySQL system secure, you should strongly consider the
following suggestions:

   * Require all MySQL accounts to have a password. A client program
     does not necessarily know the identity of the person running it.
     It is common for client/server applications that the user can
     specify any user name to the client program. For example, anyone
     can use the *Note `mysql': mysql. program to connect as any other
     person simply by invoking it as `mysql -u OTHER_USER DB_NAME' if
     OTHER_USER has no password. If all accounts have a password,
     connecting using another user's account becomes much more
     difficult.

     For a discussion of methods for setting passwords, see *Note
     assigning-passwords::.

   * Make sure that the only Unix user account with read or write
     privileges in the database directories is the account that is used
     for running *Note `mysqld': mysqld.

   * Never run the MySQL server as the Unix `root' user. This is
     extremely dangerous, because any user with the `FILE' privilege is
     able to cause the server to create files as `root' (for example,
     `~root/.bashrc'). To prevent this, *Note `mysqld': mysqld. refuses
     to run as `root' unless that is specified explicitly using the
     `--user=root' option.

     *Note `mysqld': mysqld. can (and should) be run as an ordinary,
     unprivileged user instead. You can create a separate Unix account
     named `mysql' to make everything even more secure. Use this
     account only for administering MySQL. To start *Note `mysqld':
     mysqld. as a different Unix user, add a `user' option that
     specifies the user name in the `[mysqld]' group of the `my.cnf'
     option file where you specify server options. For example:


          [mysqld]
          user=mysql

     This causes the server to start as the designated user whether you
     start it manually or by using *Note `mysqld_safe': mysqld-safe. or
     *Note `mysql.server': mysql-server. For more details, see *Note
     changing-mysql-user::.

     Running *Note `mysqld': mysqld. as a Unix user other than `root'
     does not mean that you need to change the `root' user name in the
     `user' table. _User names for MySQL accounts have nothing to do
     with user names for Unix accounts_.

   * Do not grant the `FILE' privilege to nonadministrative users. Any
     user that has this privilege can write a file anywhere in the file
     system with the privileges of the *Note `mysqld': mysqld. daemon.
     This includes the server's data directory containing the files that
     implement the privilege tables. To make `FILE'-privilege
     operations a bit safer, files generated with *Note `SELECT ...
     INTO OUTFILE': select-into. do not overwrite existing files and are
     writable by everyone.

     The `FILE' privilege may also be used to read any file that is
     world-readable or accessible to the Unix user that the server runs
     as. With this privilege, you can read any file into a database
     table. This could be abused, for example, by using *Note `LOAD
     DATA': load-data. to load `/etc/passwd' into a table, which then
     can be displayed with *Note `SELECT': select.

     To limit the location in which files can be read and written, set
     the `secure_file_priv' system to a specific directory. See *Note
     server-system-variables::.

   * Do not grant the `PROCESS' or `SUPER' privilege to
     nonadministrative users. The output of *Note `mysqladmin
     processlist': mysqladmin. and *Note `SHOW PROCESSLIST':
     show-processlist. shows the text of any statements currently being
     executed, so any user who is permitted to see the server process
     list might be able to see statements issued by other users such as
     `UPDATE user SET password=PASSWORD('not_secure')'.

     *Note `mysqld': mysqld. reserves an extra connection for users who
     have the `SUPER' privilege, so that a MySQL `root' user can log in
     and check server activity even if all normal connections are in
     use.

     The `SUPER' privilege can be used to terminate client connections,
     change server operation by changing the value of system variables,
     and control replication servers.

   * Do not permit the use of symlinks to tables. (This capability can
     be disabled with the `--skip-symbolic-links' option.) This is
     especially important if you run *Note `mysqld': mysqld. as `root',
     because anyone that has write access to the server's data directory
     then could delete any file in the system! See *Note
     symbolic-links-to-tables::.

   * Stored programs and views should be written using the security
     guidelines discussed in *Note stored-programs-security::.

   * If you do not trust your DNS, you should use IP addresses rather
     than host names in the grant tables. In any case, you should be
     very careful about creating grant table entries using host name
     values that contain wildcards.

   * If you want to restrict the number of connections permitted to a
     single account, you can do so by setting the
     `max_user_connections' variable in *Note `mysqld': mysqld. The
     *Note `GRANT': grant. statement also supports resource control
     options for limiting the extent of server use permitted to an
     account. See *Note grant::.

   * If the plugin directory is writable by the server, it may be
     possible for a user to write executable code to a file in the
     directory using *Note `SELECT ... INTO DUMPFILE': select. This can
     be prevented by making `plugin_dir' read only to the server or by
     setting `--secure-file-priv' to a directory where *Note `SELECT':
     select. writes can be made safely.


File: manual.info,  Node: security-options,  Next: changing-mysql-user,  Prev: security-against-attack,  Up: general-security-issues

6.1.4 Security-Related mysqld Options and Variables
---------------------------------------------------

The following table shows *Note `mysqld': mysqld. options and system
variables that affect security. For descriptions of each of these, see
*Note server-options::, and *Note server-system-variables::.

*Security Option/Variable Summary*

Name           Cmd-Line    Option File System Var  Status Var  Var Scope   Dynamic
allow-suspicious-udfsYes         Yes                                             
automatic_sp_privileges                        Yes                     Global      Yes
chroot         Yes         Yes                                             
des-key-file   Yes         Yes                                             
local_infile                           Yes                     Global      Yes
old_passwords                          Yes                     Both        Yes
safe-show-databaseYes         Yes         Yes                     Global      Yes
safe-user-createYes         Yes                                             
secure-auth    Yes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
secure_auth                                                                
secure-file-privYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
secure_file_priv                                                            
skip-grant-tablesYes         Yes                                             
skip-name-resolveYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
skip_name_resolve                                                            
skip-networkingYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
skip_networking                                                            
skip-show-databaseYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
skip_show_database                                                            


File: manual.info,  Node: changing-mysql-user,  Next: load-data-local,  Prev: security-options,  Up: general-security-issues

6.1.5 How to Run MySQL as a Normal User
---------------------------------------

On Windows, you can run the server as a Windows service using a normal
user account.

On Unix, the MySQL server *Note `mysqld': mysqld. can be started and
run by any user. However, you should avoid running the server as the
Unix `root' user for security reasons. To change *Note `mysqld':
mysqld. to run as a normal unprivileged Unix user USER_NAME, you must
do the following:

  1. Stop the server if it is running (use *Note `mysqladmin shutdown':
     mysqladmin.).

  2. Change the database directories and files so that USER_NAME has
     privileges to read and write files in them (you might need to do
     this as the Unix `root' user):


          shell> chown -R USER_NAME /PATH/TO/MYSQL/DATADIR

     If you do not do this, the server will not be able to access
     databases or tables when it runs as USER_NAME.

     If directories or files within the MySQL data directory are
     symbolic links, `chown -R' might not follow symbolic links for
     you. If it does not, you will also need to follow those links and
     change the directories and files they point to.

  3. Start the server as user USER_NAME.  Another alternative is to
     start *Note `mysqld': mysqld. as the Unix `root' user and use the
     `--user=USER_NAME' option. *Note `mysqld': mysqld. starts up, then
     switches to run as the Unix user USER_NAME before accepting any
     connections.

  4. To start the server as the given user automatically at system
     startup time, specify the user name by adding a `user' option to
     the `[mysqld]' group of the `/etc/my.cnf' option file or the
     `my.cnf' option file in the server's data directory. For example:


          [mysqld]
          user=USER_NAME

If your Unix machine itself is not secured, you should assign passwords
to the MySQL `root' accounts in the grant tables. Otherwise, any user
with a login account on that machine can run the *Note `mysql': mysql.
client with a `--user=root' option and perform any operation. (It is a
good idea to assign passwords to MySQL accounts in any case, but
especially so when other login accounts exist on the server host.) See
*Note default-privileges::.


File: manual.info,  Node: load-data-local,  Next: secure-client-programming,  Prev: changing-mysql-user,  Up: general-security-issues

6.1.6 Security Issues with LOAD DATA LOCAL
------------------------------------------

The *Note `LOAD DATA': load-data. statement can load a file that is
located on the server host, or it can load a file that is located on
the client host when the `LOCAL' keyword is specified.

There are two potential security issues with supporting the `LOCAL'
version of *Note `LOAD DATA': load-data. statements:

   * The transfer of the file from the client host to the server host
     is initiated by the MySQL server. In theory, a patched server
     could be built that would tell the client program to transfer a
     file of the server's choosing rather than the file named by the
     client in the *Note `LOAD DATA': load-data. statement. Such a
     server could access any file on the client host to which the
     client user has read access.

   * In a Web environment where the clients are connecting from a Web
     server, a user could use *Note `LOAD DATA LOCAL': load-data. to
     read any files that the Web server process has read access to
     (assuming that a user could run any command against the SQL
     server). In this environment, the client with respect to the MySQL
     server actually is the Web server, not the remote program being
     run by the user who connects to the Web server.

To deal with these problems, we changed how *Note `LOAD DATA LOCAL':
load-data. is handled as of MySQL 3.23.49 and MySQL 4.0.2 (4.0.13 on
Windows):

   * By default, all MySQL clients and libraries in binary
     distributions are compiled with the `--enable-local-infile'
     option, to be compatible with MySQL 3.23.48 and before.

   * If you build MySQL from source but do not invoke `configure' with
     the `--enable-local-infile' option, *Note `LOAD DATA LOCAL':
     load-data. cannot be used by any client unless it is written
     explicitly to invoke *Note `mysql_options(...
     MYSQL_OPT_LOCAL_INFILE, 0)': mysql-options. See *Note
     mysql-options::.

   * You can disable all *Note `LOAD DATA LOCAL': load-data. statements
     from the server side by starting *Note `mysqld': mysqld. with the
     `--local-infile=0' option.

   * For the *Note `mysql': mysql. command-line client, enable *Note
     `LOAD DATA LOCAL': load-data. by specifying the
     `--local-infile[=1]' option, or disable it with the
     `--local-infile=0' option. For *Note `mysqlimport': mysqlimport,
     local data file loading is off by default; enable it with the
     `--local' or `-L' option. In any case, successful use of a local
     load operation requires that the server permits it.

   * If you use *Note `LOAD DATA LOCAL': load-data. in Perl scripts or
     other programs that read the `[client]' group from option files,
     you can add the `local-infile=1' option to that group. However, to
     keep this from causing problems for programs that do not understand
     `local-infile', specify it using the `loose-' prefix:


          [client]
          loose-local-infile=1

   * If *Note `LOAD DATA LOCAL': load-data. is disabled, either in the
     server or the client, a client that attempts to issue such a
     statement receives the following error message:


          ERROR 1148: The used command is not allowed with this MySQL version


File: manual.info,  Node: secure-client-programming,  Prev: load-data-local,  Up: general-security-issues

6.1.7 Client Programming Security Guidelines
--------------------------------------------

Applications that access MySQL should not trust any data entered by
users, who can try to trick your code by entering special or escaped
character sequences in Web forms, URLs, or whatever application you
have built. Be sure that your application remains secure if a user
enters something like ``; DROP DATABASE mysql;''. This is an extreme
example, but large security leaks and data loss might occur as a result
of hackers using similar techniques, if you do not prepare for them.

A common mistake is to protect only string data values. Remember to
check numeric data as well. If an application generates a query such as
`SELECT * FROM table WHERE ID=234' when a user enters the value `234',
the user can enter the value `234 OR 1=1' to cause the application to
generate the query `SELECT * FROM table WHERE ID=234 OR 1=1'. As a
result, the server retrieves every row in the table. This exposes every
row and causes excessive server load.  The simplest way to protect from
this type of attack is to use single quotation marks around the numeric
constants: `SELECT * FROM table WHERE ID='234''. If the user enters
extra information, it all becomes part of the string. In a numeric
context, MySQL automatically converts this string to a number and
strips any trailing nonnumeric characters from it.

Sometimes people think that if a database contains only publicly
available data, it need not be protected. This is incorrect. Even if it
is permissible to display any row in the database, you should still
protect against denial of service attacks (for example, those that are
based on the technique in the preceding paragraph that causes the
server to waste resources). Otherwise, your server becomes unresponsive
to legitimate users.

Checklist:

   * Enable strict SQL mode to tell the server to be more restrictive
     of what data values it accepts. See *Note sql-mode::.

   * Try to enter single and double quotation marks (``''' and ``"'')
     in all of your Web forms.  If you get any kind of MySQL error,
     investigate the problem right away.

   * Try to modify dynamic URLs by adding `%22' (``"''), `%23' (``#''),
     and `%27' (``''') to them.

   * Try to modify data types in dynamic URLs from numeric to character
     types using the characters shown in the previous examples. Your
     application should be safe against these and similar attacks.

   * Try to enter characters, spaces, and special symbols rather than
     numbers in numeric fields. Your application should remove them
     before passing them to MySQL or else generate an error.  Passing
     unchecked values to MySQL is very dangerous!

   * Check the size of data before passing it to MySQL.

   * Have your application connect to the database using a user name
     different from the one you use for administrative purposes. Do not
     give your applications any access privileges they do not need.

Many application programming interfaces provide a means of escaping
special characters in data values. Properly used, this prevents
application users from entering values that cause the application to
generate statements that have a different effect than you intend:

   * MySQL C API: Use the *Note `mysql_real_escape_string()':
     mysql-real-escape-string. API call.

   * MySQL++: Use the `escape' and `quote' modifiers for query streams.

   * PHP: Use either the `mysqli' or `pdo_mysql' extensions, and not
     the older `ext/mysql' extension. The preferred API's support the
     improved MySQL authentication protocol and passwords, as well as
     prepared statements with placeholders.  See also Choosing an API
     (http://dev.mysql.com/doc/apis-php/en/apis-php-mysqlinfo.api.choosing.html).

     If the older `ext/mysql' extension must be used, then for escaping
     use the *Note `mysql_real_escape_string()':
     mysql-real-escape-string.  function and not *Note
     `mysql_escape_string()': mysql-escape-string. or `addslashes()'
     because only *Note `mysql_real_escape_string()':
     mysql-real-escape-string. is character set-aware; the other
     functions can be `bypassed' when using (invalid) multibyte
     character sets.

   * Perl DBI: Use placeholders or the `quote()' method.

   * Ruby DBI: Use placeholders or the `quote()' method.

   * Java JDBC: Use a `PreparedStatement' object and placeholders.

Other programming interfaces might have similar capabilities.


File: manual.info,  Node: privilege-system,  Next: user-account-management,  Prev: general-security-issues,  Up: security

6.2 The MySQL Access Privilege System
=====================================

* Menu:

* privileges-provided::          Privileges Provided by MySQL
* grant-table-structure::        Privilege System Grant Tables
* account-names::                Specifying Account Names
* connection-access::            Access Control, Stage 1: Connection Verification
* request-access::               Access Control, Stage 2: Request Verification
* privilege-changes::            When Privilege Changes Take Effect
* access-denied::                Causes of Access-Denied Errors

The primary function of the MySQL privilege system is to authenticate a
user who connects from a given host and to associate that user with
privileges on a database such as *Note `SELECT': select, *Note
`INSERT': insert, *Note `UPDATE': update, and *Note `DELETE': delete.
Additional functionality includes the ability to have anonymous users
and to grant privileges for MySQL-specific functions such as *Note
`LOAD DATA INFILE': load-data. and administrative operations.

There are some things that you cannot do with the MySQL privilege
system:

   * You cannot explicitly specify that a given user should be denied
     access. That is, you cannot explicitly match a user and then
     refuse the connection.

   * You cannot specify that a user has privileges to create or drop
     tables in a database but not to create or drop the database itself.

   * A password applies globally to an account. You cannot associate a
     password with a specific object such as a database, table, or
     routine.

The user interface to the MySQL privilege system consists of SQL
statements such as *Note `CREATE USER': create-user, *Note `GRANT':
grant, and *Note `REVOKE': revoke. See *Note account-management-sql::.

Internally, the server stores privilege information in the grant tables
of the `mysql' database (that is, in the database named `mysql'). The
MySQL server reads the contents of these tables into memory when it
starts and bases access-control decisions on the in-memory copies of
the grant tables.

The MySQL privilege system ensures that all users may perform only the
operations permitted to them. As a user, when you connect to a MySQL
server, your identity is determined by _the host from which you
connect_ and _the user name you specify_. When you issue requests after
connecting, the system grants privileges according to your identity and
_what you want to do_.

MySQL considers both your host name and user name in identifying you
because there is no reason to assume that a given user name belongs to
the same person on all hosts. For example, the user `joe' who connects
from `office.example.com' need not be the same person as the user `joe'
who connects from `home.example.com'. MySQL handles this by enabling
you to distinguish users on different hosts that happen to have the
same name: You can grant one set of privileges for connections by `joe'
from `office.example.com', and a different set of privileges for
connections by `joe' from `home.example.com'. To see what privileges a
given account has, use the *Note `SHOW GRANTS': show-grants. statement.
For example:


     SHOW GRANTS FOR 'joe'@'office.example.com';
     SHOW GRANTS FOR 'joe'@'home.example.com';

MySQL access control involves two stages when you run a client program
that connects to the server:

*Stage 1:* The server accepts or rejects the connection based on your
identity and whether you can verify your identity by supplying the
correct password.

*Stage 2:* Assuming that you can connect, the server checks each
statement you issue to determine whether you have sufficient privileges
to perform it. For example, if you try to select rows from a table in a
database or drop a table from the database, the server verifies that
you have the `SELECT' privilege for the table or the `DROP' privilege
for the database.

For a more detailed description of what happens during each stage, see
*Note connection-access::, and *Note request-access::.

If your privileges are changed (either by yourself or someone else)
while you are connected, those changes do not necessarily take effect
immediately for the next statement that you issue. For details about
the conditions under which the server reloads the grant tables, see
*Note privilege-changes::.

For general security-related advice, see *Note
general-security-issues::. For help in diagnosing privilege-related
problems, see *Note access-denied::.


File: manual.info,  Node: privileges-provided,  Next: grant-table-structure,  Prev: privilege-system,  Up: privilege-system

6.2.1 Privileges Provided by MySQL
----------------------------------

MySQL provides privileges that apply in different contexts and at
different levels of operation:

   * Administrative privileges enable users to manage operation of the
     MySQL server. These privileges are global because they are not
     specific to a particular database.

   * Database privileges apply to a database and to all objects within
     it. These privileges can be granted for specific databases, or
     globally so that they apply to all databases.

   * Privileges for database objects such as tables, indexes, views,
     and stored routines can be granted for specific objects within a
     database, for all objects of a given type within a database (for
     example, all tables in a database), or globally for all objects of
     a given type in all databases).

Information about account privileges is stored in the `user', `db',
`host', `tables_priv', `columns_priv', and `procs_priv' tables in the
`mysql' database (see *Note grant-table-structure::). The MySQL server
reads the contents of these tables into memory when it starts and
reloads them under the circumstances indicated in *Note
privilege-changes::. Access-control decisions are based on the
in-memory copies of the grant tables.

Some releases of MySQL introduce changes to the structure of the grant
tables to add new privileges or features. To make sure that you can
take advantage of any new capabilities, update your grant tables to
have the current structure whenever you update to a new version of
MySQL. See *Note mysql-upgrade::.

The following table shows the privilege names used at the SQL level in
the *Note `GRANT': grant. and *Note `REVOKE': revoke. statements, along
with the column name associated with each privilege in the grant tables
and the context in which the privilege applies.

*Permissible Privileges for GRANT and REVOKE*

Privilege              Column                   Context
`CREATE'               `Create_priv'            databases, tables, or
                                                indexes
`DROP'                 `Drop_priv'              databases, tables, or views
`GRANT OPTION'         `Grant_priv'             databases, tables, or
                                                stored routines
`LOCK TABLES'          `Lock_tables_priv'       databases
`REFERENCES'           `References_priv'        databases or tables
`EVENT'                `Event_priv'             databases
`ALTER'                `Alter_priv'             tables
`DELETE'               `Delete_priv'            tables
`INDEX'                `Index_priv'             tables
`INSERT'               `Insert_priv'            tables or columns
`SELECT'               `Select_priv'            tables or columns
`UPDATE'               `Update_priv'            tables or columns
`CREATE TEMPORARY      `Create_tmp_table_priv'  tables
TABLES'                                         
`TRIGGER'              `Trigger_priv'           tables
`CREATE VIEW'          `Create_view_priv'       views
`SHOW VIEW'            `Show_view_priv'         views
`ALTER ROUTINE'        `Alter_routine_priv'     stored routines
`CREATE ROUTINE'       `Create_routine_priv'    stored routines
`EXECUTE'              `Execute_priv'           stored routines
`FILE'                 `File_priv'              file access on server host
`CREATE USER'          `Create_user_priv'       server administration
`PROCESS'              `Process_priv'           server administration
`RELOAD'               `Reload_priv'            server administration
`REPLICATION CLIENT'   `Repl_client_priv'       server administration
`REPLICATION SLAVE'    `Repl_slave_priv'        server administration
`SHOW DATABASES'       `Show_db_priv'           server administration
`SHUTDOWN'             `Shutdown_priv'          server administration
`SUPER'                `Super_priv'             server administration
`ALL [PRIVILEGES]'                              server administration
`USAGE'                                         server administration

The following list provides a general description of each privilege
available in MySQL. Particular SQL statements might have more specific
privilege requirements than indicated here. If so, the description for
the statement in question provides the details.

   * The `ALL' or `ALL PRIVILEGES' privilege specifier is shorthand. It
     stands for `all privileges available at a given privilege level'
     (except `GRANT OPTION'). For example, granting `ALL' at the global
     or table level grants all global privileges or all table-level
     privileges.

   * The `ALTER' privilege enables use of *Note `ALTER TABLE':
     alter-table. to change the structure of tables. *Note `ALTER
     TABLE': alter-table. also requires the `CREATE' and `INSERT'
     privileges. Renaming a table requires `ALTER' and `DROP' on the
     old table, `ALTER', `CREATE', and `INSERT' on the new table.

   * The `ALTER ROUTINE' privilege is needed to alter or drop stored
     routines (procedures and functions).

   * The `CREATE' privilege enables creation of new databases and
     tables.

   * The `CREATE ROUTINE' privilege is needed to create stored routines
     (procedures and functions).

   * The `CREATE TEMPORARY TABLES' privilege enables the creation of
     temporary tables using the *Note `CREATE TEMPORARY TABLE':
     create-table. statement.

     However, other operations on a temporary table, such as *Note
     `INSERT': insert, *Note `UPDATE': update, or *Note `SELECT':
     select, require additional privileges for those operations for the
     database containing the temporary table, or for the nontemporary
     table of the same name.

     To keep privileges for temporary and nontemporary tables separate,
     a common workaround for this situation is to create a database
     dedicated to the use of temporary tables. Then for that database,
     a user can be granted the `CREATE TEMPORARY TABLES' privilege,
     along with any other privileges required for temporary table
     operations done by that user.

   * The `CREATE USER' privilege enables use of *Note `CREATE USER':
     create-user, *Note `DROP USER': drop-user, *Note `RENAME USER':
     rename-user, and *Note `REVOKE ALL PRIVILEGES': revoke.

   * The `CREATE VIEW' privilege enables use of *Note `CREATE VIEW':
     create-view.

   * The `DELETE' privilege enables rows to be deleted from tables in a
     database.

   * The `DROP' privilege enables you to drop (remove) existing
     databases, tables, and views.  Beginning with MySQL 5.1.10, the
     `DROP' privilege is also required to use the statement `ALTER
     TABLE ... DROP PARTITION' on a partitioned table. Beginning with
     MySQL 5.1.16, the `DROP' privilege is required for *Note `TRUNCATE
     TABLE': truncate-table. (before that, *Note `TRUNCATE TABLE':
     truncate-table. requires the `DELETE' privilege). _If you grant
     the `DROP' privilege for the `mysql' database to a user, that user
     can drop the database in which the MySQL access privileges are
     stored._

   * The `EVENT' privilege is required to create, alter, drop, or see
     events for the Event Scheduler.  This privilege was added in MySQL
     5.1.6.

   * The `EXECUTE' privilege is required to execute stored routines
     (procedures and functions).

   * The `FILE' privilege gives you permission to read and write files
     on the server host using the *Note `LOAD DATA INFILE': load-data.
     and *Note `SELECT ... INTO OUTFILE': select-into. statements and
     the `LOAD_FILE()' function. A user who has the `FILE' privilege can
     read any file on the server host that is either world-readable or
     readable by the MySQL server. (This implies the user can read any
     file in any database directory, because the server can access any
     of those files.) The `FILE' privilege also enables the user to
     create new files in any directory where the MySQL server has write
     access. This includes the server's data directory containing the
     files that implement the privilege tables. As a security measure,
     the server will not overwrite existing files.

     To limit the location in which files can be read and written, set
     the `secure_file_priv' system to a specific directory. See *Note
     server-system-variables::.

   * The `GRANT OPTION' privilege enables you to give to other users or
     remove from other users those privileges that you yourself possess.

   * The `INDEX' privilege enables you to create or drop (remove)
     indexes.  `INDEX' applies to existing tables. If you have the
     `CREATE' privilege for a table, you can include index definitions
     in the *Note `CREATE TABLE': create-table. statement.

   * The `INSERT' privilege enables rows to be inserted into tables in
     a database.  `INSERT' is also required for the *Note `ANALYZE
     TABLE': analyze-table, *Note `OPTIMIZE TABLE': optimize-table, and
     *Note `REPAIR TABLE': repair-table. table-maintenance statements.

   * The `LOCK TABLES' privilege enables the use of explicit *Note
     `LOCK TABLES': lock-tables. statements to lock tables for which
     you have the `SELECT' privilege. This includes the use of write
     locks, which prevents other sessions from reading the locked table.

   * The `PROCESS' privilege pertains to display of information about
     the threads executing within the server (that is, information
     about the statements being executed by sessions). The privilege
     enables use of *Note `SHOW PROCESSLIST': show-processlist. or
     *Note `mysqladmin processlist': mysqladmin. to see threads
     belonging to other accounts; you can always see your own threads.
     The `PROCESS' privilege also enables use of *Note `SHOW ENGINE':
     show-engine.

   * The `REFERENCES' privilege currently is unused.

   * The `RELOAD' privilege enables use of the *Note `FLUSH': flush.
     statement. It also enables *Note `mysqladmin': mysqladmin.
     commands that are equivalent to *Note `FLUSH': flush. operations:
     `flush-hosts', `flush-logs', `flush-privileges', `flush-status',
     `flush-tables', `flush-threads', `refresh', and `reload'.

     The `reload' command tells the server to reload the grant tables
     into memory.  `flush-privileges' is a synonym for `reload'. The
     `refresh' command closes and reopens the log files and flushes all
     tables. The other `flush-XXX' commands perform functions similar to
     `refresh', but are more specific and may be preferable in some
     instances. For example, if you want to flush just the log files,
     `flush-logs' is a better choice than `refresh'.

   * The `REPLICATION CLIENT' privilege enables the use of *Note `SHOW
     MASTER STATUS': show-master-status. and *Note `SHOW SLAVE STATUS':
     show-slave-status. In MySQL 5.1.64 and later, it also enables the
     use of the *Note `SHOW BINARY LOGS': show-binary-logs.  statement.

   * The `REPLICATION SLAVE' privilege should be granted to accounts
     that are used by slave servers to connect to the current server as
     their master. Without this privilege, the slave cannot request
     updates that have been made to databases on the master server.

   * The `SELECT' privilege enables you to select rows from tables in a
     database.  *Note `SELECT': select. statements require the `SELECT'
     privilege only if they actually retrieve rows from a table. Some
     *Note `SELECT': select. statements do not access tables and can be
     executed without permission for any database. For example, you can
     use *Note `SELECT': select. as a simple calculator to evaluate
     expressions that make no reference to tables:


          SELECT 1+1;
          SELECT PI()*2;

     The `SELECT' privilege is also needed for other statements that
     read column values. For example, `SELECT' is needed for columns
     referenced on the right hand side of COL_NAME=EXPR assignment in
     *Note `UPDATE': update. statements or for columns named in the
     `WHERE' clause of *Note `DELETE': delete. or *Note `UPDATE':
     update. statements.

   * The `SHOW DATABASES' privilege enables the account to see database
     names by issuing the `SHOW DATABASE' statement. Accounts that do
     not have this privilege see only databases for which they have
     some privileges, and cannot use the statement at all if the server
     was started with the `--skip-show-database' option.  Note that
     _any_ global privilege is a privilege for the database.

   * The `SHOW VIEW' privilege enables use of *Note `SHOW CREATE VIEW':
     show-create-view.

   * The `SHUTDOWN' privilege enables use of the *Note `mysqladmin
     shutdown': mysqladmin. command.  There is no corresponding SQL
     statement.

   * The `SUPER' privilege enables an account to use *Note `CHANGE
     MASTER TO': change-master-to, *Note `KILL': kill. or *Note
     `mysqladmin kill': mysqladmin. to kill threads belonging to other
     accounts (you can always kill your own threads), *Note `PURGE
     BINARY LOGS': purge-binary-logs, configuration changes using *Note
     `SET GLOBAL': set-statement. to modify global system variables, the
     *Note `mysqladmin debug': mysqladmin. command, enabling or
     disabling logging, performing updates even if the `read_only'
     system variable is enabled, starting and stopping replication on
     slave servers, specification of any account in the `DEFINER'
     attribute of stored programs and views, and enables you to connect
     (once) even if the connection limit controlled by the
     `max_connections' system variable is reached.

     To create or alter stored functions if binary logging is enabled,
     you may also need the `SUPER' privilege, as described in *Note
     stored-programs-logging::.

   * The `TRIGGER' privilege enables trigger operations. You must have
     this privilege for a table to create, drop, or execute triggers
     for that table. This privilege was added in MySQL 5.1.6. (Prior to
     MySQL 5.1.6, trigger operations required the `SUPER' privilege.)

   * The `UPDATE' privilege enables rows to be updated in tables in a
     database.

   * The `USAGE' privilege specifier stands for `no privileges.' It is
     used at the global level with *Note `GRANT': grant. to modify
     account attributes such as resource limits or SSL characteristics
     without affecting existing account privileges.

It is a good idea to grant to an account only those privileges that it
needs. You should exercise particular caution in granting the `FILE'
and administrative privileges:

   * The `FILE' privilege can be abused to read into a database table
     any files that the MySQL server can read on the server host. This
     includes all world-readable files and files in the server's data
     directory.  The table can then be accessed using *Note `SELECT':
     select. to transfer its contents to the client host.

   * The `GRANT OPTION' privilege enables users to give their
     privileges to other users. Two users that have different
     privileges and with the `GRANT OPTION' privilege are able to
     combine privileges.

   * The `ALTER' privilege may be used to subvert the privilege system
     by renaming tables.

   * The `SHUTDOWN' privilege can be abused to deny service to other
     users entirely by terminating the server.

   * The `PROCESS' privilege can be used to view the plain text of
     currently executing statements, including statements that set or
     change passwords.

   * The `SUPER' privilege can be used to terminate other sessions or
     change how the server operates.

   * Privileges granted for the `mysql' database itself can be used to
     change passwords and other access privilege information. Passwords
     are stored encrypted, so a malicious user cannot simply read them
     to know the plain text password. However, a user with write access
     to the `user' table `Password' column can change an account's
     password, and then connect to the MySQL server using that account.


File: manual.info,  Node: grant-table-structure,  Next: account-names,  Prev: privileges-provided,  Up: privilege-system

6.2.2 Privilege System Grant Tables
-----------------------------------

Normally, you manipulate the contents of the grant tables in the
`mysql' database indirectly by using statements such as *Note `GRANT':
grant. and *Note `REVOKE': revoke. to set up accounts and control the
privileges available to each one. See *Note account-management-sql::.
The discussion here describes the underlying structure of the grant
tables and how the server uses their contents when interacting with
clients.

These `mysql' database tables contain grant information:

   * `user': Contains user accounts, global privileges, and other
     non-privilege columns.

   * `db': Contains database-level privileges.

   * `host': Obsolete.

   * `tables_priv': Contains table-level privileges.

   * `columns_priv': Contains column-level privileges.

   * `procs_priv': Contains stored procedure and function privileges.

Other tables in the `mysql' database do not hold grant information and
are discussed elsewhere:

   * `event': Contains information about Event Scheduler events: See
     *Note events::.

   * `func': Contains information about user-defined functions: See
     *Note adding-functions::.

   * `help_XXX': These tables are used for server-side help: See *Note
     server-side-help-support::.

   * `plugin': Contains information about server plugins: See *Note
     server-plugin-loading::, and *Note plugin-api::.

   * `proc': Contains information about stored procedures and
     functions: See *Note stored-routines::.

   * `servers': Used by the `FEDERATED' storage engine: See *Note
     federated-create-server::.

   * `time_zone_XXX': These tables contain time zone information: See
     *Note time-zone-support::.

   * Tables with `_log' in their name are used for logging: See *Note
     server-logs::.

*Note*:

Modifications to tables in the `mysql' database normally are made by
the server in response to statements such as *Note `CREATE USER':
create-user, *Note `GRANT': grant, or *Note `CREATE PROCEDURE':
create-procedure. Direct modification of these tables using statements
such as *Note `INSERT': insert, *Note `UPDATE': update, or *Note
`DELETE': delete. is not encouraged. The server is free to ignore rows
that become malformed as a result of such modifications.

Each grant table contains scope columns and privilege columns:

   * Scope columns determine the scope of each row (entry) in the
     tables; that is, the context in which the row applies. For
     example, a `user' table row with `Host' and `User' values of
     `'thomas.loc.gov'' and `'bob'' would be used for authenticating
     connections made to the server from the host `thomas.loc.gov' by a
     client that specifies a user name of `bob'. Similarly, a `db'
     table row with `Host', `User', and `Db' column values of
     `'thomas.loc.gov'', `'bob'' and `'reports'' would be used when
     `bob' connects from the host `thomas.loc.gov' to access the
     `reports' database. The `tables_priv' and `columns_priv' tables
     contain scope columns indicating tables or table/column
     combinations to which each row applies. The `procs_priv' scope
     columns indicate the stored routine to which each row applies.

   * Privilege columns indicate which privileges are granted by a table
     row; that is, what operations can be performed. The server
     combines the information in the various grant tables to form a
     complete description of a user's privileges.  *Note
     request-access::, describes the rules that are used to do this.

The server uses the grant tables in the following manner:

   * The `user' table scope columns determine whether to reject or
     permit incoming connections. For permitted connections, any
     privileges granted in the `user' table indicate the user's global
     privileges. Any privilege granted in this table applies to _all_
     databases on the server.

     *Note*:

     Because any global privilege is considered a privilege for all
     databases, any global privilege enables a user to see all database
     names with *Note `SHOW DATABASES': show-databases. or by examining
     the *Note `SCHEMATA': schemata-table. table of
     `INFORMATION_SCHEMA'.

   * The `db' table scope columns determine which users can access
     which databases from which hosts. The privilege columns determine
     which operations are permitted. A privilege granted at the
     database level applies to the database and to all objects in the
     database, such as tables and stored programs.

   * The `host' table is used in conjunction with the `db' table when
     you want a given `db' table row to apply to several hosts. For
     example, if you want a user to be able to use a database from
     several hosts in your network, leave the `Host' value empty in the
     user's `db' table row, then populate the `host' table with a row
     for each of those hosts. This mechanism is described more detail in
     *Note request-access::.

     *Note*:

     The `host' table must be modified directly with statements such as
     *Note `INSERT': insert, *Note `UPDATE': update, and *Note
     `DELETE': delete. It is not affected by statements such as *Note
     `GRANT': grant. and *Note `REVOKE': revoke. that modify the grant
     tables indirectly. Most MySQL installations need not use this
     table at all.

   * The `tables_priv' and `columns_priv' tables are similar to the
     `db' table, but are more fine-grained: They apply at the table and
     column levels rather than at the database level. A privilege
     granted at the table level applies to the table and to all its
     columns. A privilege granted at the column level applies only to a
     specific column.

   * The `procs_priv' table applies to stored routines. A privilege
     granted at the routine level applies only to a single routine.

The server uses the `user', `db', and `host' tables in the `mysql'
database at both the first and second stages of access control (see
*Note privilege-system::).  The columns in the `user' and `db' tables
are shown here. The `host' table is similar to the `db' table but has a
specialized use as described in *Note request-access::.

*user and db Table Columns*

Table Name                    `user'                 `db'
*Scope columns*               `Host'                 `Host'
                              `User'                 `Db'
                              `Password'             `User'
*Privilege columns*           `Select_priv'          `Select_priv'
                              `Insert_priv'          `Insert_priv'
                              `Update_priv'          `Update_priv'
                              `Delete_priv'          `Delete_priv'
                              `Index_priv'           `Index_priv'
                              `Alter_priv'           `Alter_priv'
                              `Create_priv'          `Create_priv'
                              `Drop_priv'            `Drop_priv'
                              `Grant_priv'           `Grant_priv'
                              `Create_view_priv'     `Create_view_priv'
                              `Show_view_priv'       `Show_view_priv'
                              `Create_routine_priv'  `Create_routine_priv'
                              `Alter_routine_priv'   `Alter_routine_priv'
                              `Execute_priv'         `Execute_priv'
                              `Trigger_priv'         `Trigger_priv'
                              `Event_priv'           `Event_priv'
                              `Create_tmp_table_priv'`Create_tmp_table_priv'
                              `Lock_tables_priv'     `Lock_tables_priv'
                              `References_priv'      `References_priv'
                              `Reload_priv'          
                              `Shutdown_priv'        
                              `Process_priv'         
                              `File_priv'            
                              `Show_db_priv'         
                              `Super_priv'           
                              `Repl_slave_priv'      
                              `Repl_client_priv'     
                              `Create_user_priv'     
*Security columns*            `ssl_type'             
                              `ssl_cipher'           
                              `x509_issuer'          
                              `x509_subject'         
*Resource control columns*    `max_questions'        
                              `max_updates'          
                              `max_connections'      
                              `max_user_connections' 

The `Event_priv' and `Trigger_priv' columns were added in MySQL 5.1.6.

During the second stage of access control, the server performs request
verification to make sure that each client has sufficient privileges
for each request that it issues. In addition to the `user', `db', and
`host' grant tables, the server may also consult the `tables_priv' and
`columns_priv' tables for requests that involve tables. The latter
tables provide finer privilege control at the table and column levels.
They have the columns shown in the following table.

*tables_priv and columns_priv Table Columns*

Table Name     `tables_priv'  `columns_priv'
*Scope         `Host'         `Host'
columns*                      
               `Db'           `Db'
               `User'         `User'
               `Table_name'   `Table_name'
                              `Column_name'
*Privilege     `Table_priv'   `Column_priv'
columns*                      
               `Column_priv'  
*Other         `Timestamp'    `Timestamp'
columns*                      
               `Grantor'      

The `Timestamp' and `Grantor' columns currently are unused and are
discussed no further here.

For verification of requests that involve stored routines, the server
may consult the `procs_priv' table, which has the columns shown in the
following table.

*procs_priv Table Columns*

Table Name     `procs_priv'
*Scope         `Host'
columns*       
               `Db'
               `User'
               `Routine_name'
               `Routine_type'
*Privilege     `Proc_priv'
columns*       
*Other         `Timestamp'
columns*       
               `Grantor'

The `Routine_type' column is an *Note `ENUM': enum. column with values
of `'FUNCTION'' or `'PROCEDURE'' to indicate the type of routine the
row refers to. This column enables privileges to be granted separately
for a function and a procedure with the same name.

The `Timestamp' and `Grantor' columns are set to the current timestamp
and the `CURRENT_USER' value, respectively.  However, they are unused
and are discussed no further here.

Scope columns in the grant tables contain strings. They are declared as
shown here; the default value for each is the empty string.

*Grant Table Scope Column Types*

Column Name    Type
`Host'         `CHAR(60)'
`User'         `CHAR(16)'
`Password'     `CHAR(41)'
`Db'           `CHAR(64)'
`Table_name'   `CHAR(64)'
`Column_name'  `CHAR(64)'
`Routine_name' `CHAR(64)'

For access-checking purposes, comparisons of `User', `Password', `Db',
and `Table_name' values are case sensitive. Comparisons of `Host',
`Column_name', and `Routine_name' values are not case sensitive.

In the `user', `db', and `host' tables, each privilege is listed in a
separate column that is declared as `ENUM('N','Y') DEFAULT 'N''. In
other words, each privilege can be disabled or enabled, with the
default being disabled.

In the `tables_priv', `columns_priv', and `procs_priv' tables, the
privilege columns are declared as *Note `SET': set. columns. Values in
these columns can contain any combination of the privileges controlled
by the table. Only those privileges listed in the column value are
enabled.

*Set-Type Privilege Column Values*

Table Name     Column Name        Possible Set Elements
`tables_priv'  `Table_priv'       `'Select', 'Insert', 'Update',
                                  'Delete', 'Create', 'Drop',
                                  'Grant', 'References', 'Index',
                                  'Alter', 'Create View', 'Show
                                  view', 'Trigger''
`tables_priv'  `Column_priv'      `'Select', 'Insert', 'Update',
                                  'References''
`columns_priv' `Column_priv'      `'Select', 'Insert', 'Update',
                                  'References''
`procs_priv'   `Proc_priv'        `'Execute', 'Alter Routine',
                                  'Grant''

Administrative privileges (such as `RELOAD' or `SHUTDOWN') are
specified only in the `user' table. Administrative operations are
operations on the server itself and are not database-specific, so there
is no reason to list these privileges in the other grant tables.
Consequently, to determine whether you can perform an administrative
operation, the server need consult only the `user' table.

The `FILE' privilege also is specified only in the `user' table. It is
not an administrative privilege as such, but your ability to read or
write files on the server host is independent of the database you are
accessing.

The *Note `mysqld': mysqld. server reads the contents of the grant
tables into memory when it starts. You can tell it to reload the tables
by issuing a *Note `FLUSH PRIVILEGES': flush.  statement or executing a
*Note `mysqladmin flush-privileges': mysqladmin. or *Note `mysqladmin
reload': mysqladmin.  command. Changes to the grant tables take effect
as indicated in *Note privilege-changes::.

When you modify an account's privileges, it is a good idea to verify
that the changes set up privileges the way you want. To check the
privileges for a given account, use the *Note `SHOW GRANTS':
show-grants. statement (see *Note show-grants::). For example, to
determine the privileges that are granted to an account with user name
and host name values of `bob' and `pc84.example.com', use this
statement:


     SHOW GRANTS FOR 'bob'@'pc84.example.com';


File: manual.info,  Node: account-names,  Next: connection-access,  Prev: grant-table-structure,  Up: privilege-system

6.2.3 Specifying Account Names
------------------------------

MySQL account names consist of a user name and a host name. This
enables creation of accounts for users with the same name who can
connect from different hosts. This section describes how to write
account names, including special values and wildcard rules.

In SQL statements such as *Note `CREATE USER': create-user, *Note
`GRANT': grant, and *Note `SET PASSWORD': set-password, write account
names using the following rules:

   * Syntax for account names is `'USER_NAME'@'HOST_NAME''.

   * An account name consisting only of a user name is equivalent to
     `'USER_NAME'@'%''.  For example, `'me'' is equivalent to
     `'me'@'%''.

   * The user name and host name need not be quoted if they are legal
     as unquoted identifiers. Quotes are necessary to specify a
     USER_NAME string containing special characters (such as ``-''), or
     a HOST_NAME string containing special characters or wildcard
     characters (such as ``%''); for example, `'test-user'@'%.com''.

   * Quote user names and host names as identifiers or as strings,
     using either backticks (```''), single quotation marks (``'''), or
     double quotation marks (``"'').

   * The user name and host name parts, if quoted, must be quoted
     separately. That is, write `'me'@'localhost'', not
     `'me@localhost''; the latter is interpreted as
     `'me@localhost'@'%''.

   * A reference to the `CURRENT_USER' or `CURRENT_USER()' function is
     equivalent to specifying the current client's user name and host
     name literally.

MySQL stores account names in grant tables in the `mysql' database
using separate columns for the user name and host name parts:

   * The `user' table contains one row for each account. The `User' and
     `Host' columns store the user name and host name. This table also
     indicates which global privileges the account has.

   * Other grant tables indicate privileges an account has for
     databases and objects within databases. These tables have `User'
     and `Host' columns to store the account name. Each row in these
     tables associates with the account in the `user' table that has
     the same `User' and `Host' values.

For additional detail about grant table structure, see *Note
grant-table-structure::.

User names and host names have certain special values or wildcard
conventions, as described following.

A user name is either a nonblank value that literally matches the user
name for incoming connection attempts, or a blank value (empty string)
that matches any user name. An account with a blank user name is an
anonymous user. To specify an anonymous user in SQL statements, use a
quoted empty user name part, such as `''@'localhost''.

The host name part of an account name can take many forms, and
wildcards are permitted:

   * A host value can be a host name or an IP address. The name
     `'localhost'' indicates the local host. The IP address
     `'127.0.0.1'' indicates the loopback interface.

   * You can use the wildcard characters ``%'' and ``_'' in host name
     or IP address values. These have the same meaning as for
     pattern-matching operations performed with the `LIKE' operator.
     For example, a host value of `'%'' matches any host name, whereas
     a value of `'%.mysql.com'' matches any host in the `mysql.com'
     domain.  `'192.168.1.%'' matches any host in the 192.168.1 class C
     network.

     Because you can use IP wildcard values in host values (for
     example, `'192.168.1.%'' to match every host on a subnet), someone
     could try to exploit this capability by naming a host
     `192.168.1.somewhere.com'. To foil such attempts, MySQL disallows
     matching on host names that start with digits and a dot. Thus, if
     you have a host named something like `1.2.example.com', its name
     never matches the host part of account names. An IP wildcard value
     can match only IP addresses, not host names.

   * For a host value specified as an IP address, you can specify a
     netmask indicating how many address bits to use for the network
     number. The syntax is `HOST_IP/NETMASK'.  For example:


          CREATE USER 'david'@'192.58.197.0/255.255.255.0';

     This enables `david' to connect from any client host having an IP
     address CLIENT_IP for which the following condition is true:


          CLIENT_IP & NETMASK = HOST_IP

     That is, for the *Note `CREATE USER': create-user.  statement just
     shown:


          CLIENT_IP & 255.255.255.0 = 192.58.197.0

     IP addresses that satisfy this condition and can connect to the
     MySQL server are those in the range from `192.58.197.0' to
     `192.58.197.255'.

     The netmask can only be used to tell the server to use 8, 16, 24,
     or 32 bits of the address. Examples:

        * `192.0.0.0/255.0.0.0': Any host on the 192 class A network

        * `192.168.0.0/255.255.0.0': Any host on the 192.168 class B
          network

        * `192.168.1.0/255.255.255.0': Any host on the 192.168.1 class
          C network

        * `192.168.1.1': Only the host with this specific IP address

     The following netmask will not work because it masks 28 bits, and
     28 is not a multiple of 8:


          192.168.0.1/255.255.255.240

The server performs matching of host values in account names against
the client host using the value returned by the system DNS resolver for
the client host name or IP address. Except in the case that the account
host value is specified using netmask notation, this comparison is
performed as a string match, even for an account host value given as an
IP address. This means that you should specify account host values in
the same format used by DNS.  Here are examples of problems to watch
out for:

   * Suppose that a host on the local network has a fully qualified
     name of `host1.example.com'. If DNS returns name lookups for this
     host as `host1.example.com', use that name in account host values.
     But if DNS returns just `host1', use `host1' instead.

   * If DNS returns the IP address for a given host as `192.168.1.2',
     that will match an account host value of `192.168.1.2' but not
     `192.168.01.2'. Similarly, it will match an account host pattern
     like `192.168.1.%' but not `192.168.01.%'.

To avoid problems like this, it is advisable to check the format in
which your DNS returns host names and addresses, and use values in the
same format in MySQL account names.


File: manual.info,  Node: connection-access,  Next: request-access,  Prev: account-names,  Up: privilege-system

6.2.4 Access Control, Stage 1: Connection Verification
------------------------------------------------------

When you attempt to connect to a MySQL server, the server accepts or
rejects the connection based on your identity and whether you can
verify your identity by supplying the correct password. If not, the
server denies access to you completely. Otherwise, the server accepts
the connection, and then enters Stage 2 and waits for requests.

Your identity is based on two pieces of information:

   * The client host from which you connect

   * Your MySQL user name

Identity checking is performed using the three `user' table scope
columns (`Host', `User', and `Password'). The server accepts the
connection only if the `Host' and `User' columns in some `user' table
row match the client host name and user name and the client supplies
the password specified in that row. The rules for permissible `Host'
and `User' values are given in *Note account-names::.

If the `User' column value is nonblank, the user name in an incoming
connection must match exactly. If the `User' value is blank, it matches
any user name.  If the `user' table row that matches an incoming
connection has a blank user name, the user is considered to be an
anonymous user with no name, not a user with the name that the client
actually specified. This means that a blank user name is used for all
further access checking for the duration of the connection (that is,
during Stage 2).

The `Password' column can be blank. This is not a wildcard and does not
mean that any password matches. It means that the user must connect
without specifying a password.

Nonblank `Password' values in the `user' table represent encrypted
passwords. MySQL does not store passwords in plaintext form for anyone
to see.  Rather, the password supplied by a user who is attempting to
connect is encrypted (using the `PASSWORD()' function). The encrypted
password then is used during the connection process when checking
whether the password is correct. This is done without the encrypted
password ever traveling over the connection. See *Note user-names::.

From MySQL's point of view, the encrypted password is the _real_
password, so you should never give anyone access to it. In particular,
_do not give nonadministrative users read access to tables in the
`mysql' database_.

The following table shows how various combinations of `Host' and `User'
values in the `user' table apply to incoming connections.

This table shows how various combinations of `Host' and `User' values in
the `user' table apply to incoming connections to a MySQL server.

`Host' Value              `User'      Permissible Connections
                          Value       
`'thomas.loc.gov''        `'fred''    `fred', connecting from
                                      `thomas.loc.gov'
`'thomas.loc.gov''        `'''        Any user, connecting from
                                      `thomas.loc.gov'
`'%''                     `'fred''    `fred', connecting from any host
`'%''                     `'''        Any user, connecting from any host
`'%.loc.gov''             `'fred''    `fred', connecting from any host in
                                      the `loc.gov' domain
`'x.y.%''                 `'fred''    `fred', connecting from `x.y.net',
                                      `x.y.com', `x.y.edu', and so on;
                                      this is probably not useful
`'144.155.166.177''       `'fred''    `fred', connecting from the host
                                      with IP address `144.155.166.177'
`'144.155.166.%''         `'fred''    `fred', connecting from any host in
                                      the `144.155.166' class C subnet
`'144.155.166.0/255.255.255.0''`'fred''    Same as previous example

It is possible for the client host name and user name of an incoming
connection to match more than one row in the `user' table. The
preceding set of examples demonstrates this: Several of the entries
shown match a connection from `thomas.loc.gov' by `fred'.

When multiple matches are possible, the server must determine which of
them to use. It resolves this issue as follows:

   * Whenever the server reads the `user' table into memory, it sorts
     the rows.

   * When a client attempts to connect, the server looks through the
     rows in sorted order.

   * The server uses the first row that matches the client host name
     and user name.

The server uses sorting rules that order rows with the most-specific
`Host' values first. Literal host names and IP addresses are the most
specific. (The specificity of a literal IP address is not affected by
whether it has a netmask, so `192.168.1.13' and
`192.168.1.0/255.255.255.0' are considered equally specific.) The
pattern `'%'' means `any host' and is least specific. The empty string
`''' also means `any host' but sorts after `'%''. Rows with the same
`Host' value are ordered with the most-specific `User' values first (a
blank `User' value means `any user' and is least specific). For rows
with equally-specific `Host' and `User' values, the order is
indeterminate.

To see how this works, suppose that the `user' table looks like this:


     +-----------+----------+-
     | Host      | User     | ...
     +-----------+----------+-
     | %         | root     | ...
     | %         | jeffrey  | ...
     | localhost | root     | ...
     | localhost |          | ...
     +-----------+----------+-

When the server reads the table into memory, it sorts the rows using
the rules just described. The result after sorting looks like this:


     +-----------+----------+-
     | Host      | User     | ...
     +-----------+----------+-
     | localhost | root     | ...
     | localhost |          | ...
     | %         | jeffrey  | ...
     | %         | root     | ...
     +-----------+----------+-

When a client attempts to connect, the server looks through the sorted
rows and uses the first match found. For a connection from `localhost'
by `jeffrey', two of the rows from the table match: the one with `Host'
and `User' values of `'localhost'' and `''', and the one with values of
`'%'' and `'jeffrey''. The `'localhost'' row appears first in sorted
order, so that is the one the server uses.

Here is another example. Suppose that the `user' table looks like this:


     +----------------+----------+-
     | Host           | User     | ...
     +----------------+----------+-
     | %              | jeffrey  | ...
     | thomas.loc.gov |          | ...
     +----------------+----------+-

The sorted table looks like this:


     +----------------+----------+-
     | Host           | User     | ...
     +----------------+----------+-
     | thomas.loc.gov |          | ...
     | %              | jeffrey  | ...
     +----------------+----------+-

A connection by `jeffrey' from `thomas.loc.gov' is matched by the first
row, whereas a connection by `jeffrey' from any host is matched by the
second.

*Note*:

It is a common misconception to think that, for a given user name, all
rows that explicitly name that user are used first when the server
attempts to find a match for the connection.  This is not true. The
preceding example illustrates this, where a connection from
`thomas.loc.gov' by `jeffrey' is first matched not by the row
containing `'jeffrey'' as the `User' column value, but by the row with
no user name. As a result, `jeffrey' is authenticated as an anonymous
user, even though he specified a user name when connecting.

If you are able to connect to the server, but your privileges are not
what you expect, you probably are being authenticated as some other
account. To find out what account the server used to authenticate you,
use the `CURRENT_USER()' function. (See *Note information-functions::.)
It returns a value in `USER_NAME@HOST_NAME' format that indicates the
`User' and `Host' values from the matching `user' table row. Suppose
that `jeffrey' connects and issues the following query:


     mysql> SELECT CURRENT_USER();
     +----------------+
     | CURRENT_USER() |
     +----------------+
     | @localhost     |
     +----------------+

The result shown here indicates that the matching `user' table row had
a blank `User' column value. In other words, the server is treating
`jeffrey' as an anonymous user.

Another way to diagnose authentication problems is to print out the
`user' table and sort it by hand to see where the first match is being
made.


File: manual.info,  Node: request-access,  Next: privilege-changes,  Prev: connection-access,  Up: privilege-system

6.2.5 Access Control, Stage 2: Request Verification
---------------------------------------------------

After you establish a connection, the server enters Stage 2 of access
control. For each request that you issue through that connection, the
server determines what operation you want to perform, then checks
whether you have sufficient privileges to do so. This is where the
privilege columns in the grant tables come into play. These privileges
can come from any of the `user', `db', `host', `tables_priv',
`columns_priv', or `procs_priv' tables. (You may find it helpful to
refer to *Note grant-table-structure::, which lists the columns present
in each of the grant tables.)

The `user' table grants privileges that are assigned to you on a global
basis and that apply no matter what the default database is. For
example, if the `user' table grants you the `DELETE' privilege, you can
delete rows from any table in any database on the server host! It is
wise to grant privileges in the `user' table only to people who need
them, such as database administrators. For other users, you should
leave all privileges in the `user' table set to `'N'' and grant
privileges at more specific levels only. You can grant privileges for
particular databases, tables, columns, or routines.

The `db' and `host' tables grant database-specific privileges. Values
in the scope columns of these tables can take the following forms:

   * A blank `User' value in the `db' table matches the anonymous user.
     A nonblank value matches literally; there are no wildcards in user
     names.

   * The wildcard characters ``%'' and ``_'' can be used in the `Host'
     and `Db' columns of either table. These have the same meaning as
     for pattern-matching operations performed with the `LIKE'
     operator. If you want to use either character literally when
     granting privileges, you must escape it with a backslash. For
     example, to include the underscore character (``_'') as part of a
     database name, specify it as ``\_'' in the *Note `GRANT': grant.
     statement.

   * A `'%'' `Host' value in the `db' table means `any host.' A blank
     `Host' value in the `db' table means `consult the `host' table for
     further information' (a process that is described later in this
     section).

   * A `'%'' or blank `Host' value in the `host' table means `any host.'

   * A `'%'' or blank `Db' value in either table means `any database.'

The server reads the `db' and `host' tables into memory and sorts them
at the same time that it reads the `user' table. The server sorts the
`db' table based on the `Host', `Db', and `User' scope columns, and
sorts the `host' table based on the `Host' and `Db' scope columns. As
with the `user' table, sorting puts the most-specific values first and
least-specific values last, and when the server looks for matching
entries, it uses the first match that it finds.

The `tables_priv', `columns_priv', and `procs_priv' tables grant
table-specific, column-specific, and routine-specific privileges.
Values in the scope columns of these tables can take the following
forms:

   * The wildcard characters ``%'' and ``_'' can be used in the `Host'
     column. These have the same meaning as for pattern-matching
     operations performed with the `LIKE' operator.

   * A `'%'' or blank `Host' value means `any host.'

   * The `Db', `Table_name', `Column_name', and `Routine_name' columns
     cannot contain wildcards or be blank.

The server sorts the `tables_priv', `columns_priv', and `procs_priv'
tables based on the `Host', `Db', and `User' columns. This is similar
to `db' table sorting, but simpler because only the `Host' column can
contain wildcards.

The server uses the sorted tables to verify each request that it
receives. For requests that require administrative privileges such as
`SHUTDOWN' or `RELOAD', the server checks only the `user' table row
because that is the only table that specifies administrative
privileges. The server grants access if the row permits the requested
operation and denies access otherwise. For example, if you want to
execute *Note `mysqladmin shutdown': mysqladmin. but your `user' table
row does not grant the `SHUTDOWN' privilege to you, the server denies
access without even checking the `db' or `host' tables. (They contain
no `Shutdown_priv' column, so there is no need to do so.)

For database-related requests (*Note `INSERT': insert, *Note `UPDATE':
update, and so on), the server first checks the user's global
privileges by looking in the `user' table row. If the row permits the
requested operation, access is granted. If the global privileges in the
`user' table are insufficient, the server determines the user's
database-specific privileges by checking the `db' and `host' tables:

  1. The server looks in the `db' table for a match on the `Host', `Db',
     and `User' columns. The `Host' and `User' columns are matched to
     the connecting user's host name and MySQL user name. The `Db'
     column is matched to the database that the user wants to access.
     If there is no row for the `Host' and `User', access is denied.

  2. If there is a matching `db' table row and its `Host' column is not
     blank, that row defines the user's database-specific privileges.

  3. If the matching `db' table row's `Host' column is blank, it
     signifies that the `host' table enumerates which hosts should be
     permitted access to the database. In this case, a further lookup
     is done in the `host' table to find a match on the `Host' and `Db'
     columns. If no `host' table row matches, access is denied. If
     there is a match, the user's database-specific privileges are
     computed as the intersection (_not_ the union!) of the privileges
     in the `db' and `host' table entries; that is, the privileges that
     are `'Y'' in both entries. (This way you can grant general
     privileges in the `db' table row and then selectively restrict
     them on a host-by-host basis using the `host' table entries.)

After determining the database-specific privileges granted by the `db'
and `host' table entries, the server adds them to the global privileges
granted by the `user' table. If the result permits the requested
operation, access is granted. Otherwise, the server successively checks
the user's table and column privileges in the `tables_priv' and
`columns_priv' tables, adds those to the user's privileges, and permits
or denies access based on the result. For stored-routine operations, the
server uses the `procs_priv' table rather than `tables_priv' and
`columns_priv'.

Expressed in boolean terms, the preceding description of how a user's
privileges are calculated may be summarized like this:


     global privileges
     OR (database privileges AND host privileges)
     OR table privileges
     OR column privileges
     OR routine privileges

It may not be apparent why, if the global `user' row privileges are
initially found to be insufficient for the requested operation, the
server adds those privileges to the database, table, and column
privileges later. The reason is that a request might require more than
one type of privilege. For example, if you execute an *Note `INSERT
INTO ... SELECT': insert-select. statement, you need both the `INSERT'
and the `SELECT' privileges. Your privileges might be such that the
`user' table row grants one privilege and the `db' table row grants the
other. In this case, you have the necessary privileges to perform the
request, but the server cannot tell that from either table by itself;
the privileges granted by the entries in both tables must be combined.

The `host' table is not affected by the *Note `GRANT': grant. or *Note
`REVOKE': revoke. statements, so it is unused in most MySQL
installations. If you modify it directly, you can use it for some
specialized purposes, such as to maintain a list of secure servers on
the local network that are granted all privileges.

You can also use the `host' table to indicate hosts that are _not_
secure. Suppose that you have a machine `public.your.domain' that is
located in a public area that you do not consider secure. You can
enable access to all hosts on your network except that machine by using
`host' table entries like this:


     +--------------------+----+-
     | Host               | Db | ...
     +--------------------+----+-
     | public.your.domain | %  | ... (all privileges set to 'N')
     | %.your.domain      | %  | ... (all privileges set to 'Y')
     +--------------------+----+-


File: manual.info,  Node: privilege-changes,  Next: access-denied,  Prev: request-access,  Up: privilege-system

6.2.6 When Privilege Changes Take Effect
----------------------------------------

When *Note `mysqld': mysqld. starts, it reads all grant table contents
into memory. The in-memory tables become effective for access control
at that point.

If you modify the grant tables indirectly using account-management
statements such as *Note `GRANT': grant, *Note `REVOKE': revoke, *Note
`SET PASSWORD': set-password, or *Note `RENAME USER': rename-user, the
server notices these changes and loads the grant tables into memory
again immediately.

If you modify the grant tables directly using statements such as *Note
`INSERT': insert, *Note `UPDATE': update, or *Note `DELETE': delete,
your changes have no effect on privilege checking until you either
restart the server or tell it to reload the tables. If you change the
grant tables directly but forget to reload them, your changes have _no
effect_ until you restart the server. This may leave you wondering why
your changes seem to make no difference!

To tell the server to reload the grant tables, perform a
flush-privileges operation. This can be done by issuing a *Note `FLUSH
PRIVILEGES': flush.  statement or by executing a *Note `mysqladmin
flush-privileges': mysqladmin. or *Note `mysqladmin reload': mysqladmin.
command.

A grant table reload affects privileges for each existing client
connection as follows:

   * Table and column privilege changes take effect with the client's
     next request.

   * Database privilege changes take effect the next time the client
     executes a `USE DB_NAME' statement.

     *Note*:

     Client applications may cache the database name; thus, this effect
     may not be visible to them without actually changing to a
     different database or flushing the privileges.

   * Global privileges and passwords are unaffected for a connected
     client. These changes take effect only for subsequent connections.

If the server is started with the `--skip-grant-tables' option, it does
not read the grant tables or implement any access control. Anyone can
connect and do anything, _which is insecure._ To cause a server thus
started to read the tables and enable access checking, flush the
privileges.


File: manual.info,  Node: access-denied,  Prev: privilege-changes,  Up: privilege-system

6.2.7 Causes of Access-Denied Errors
------------------------------------

If you encounter problems when you try to connect to the MySQL server,
the following items describe some courses of action you can take to
correct the problem.

   * Make sure that the server is running. If it is not, clients cannot
     connect to it. For example, if an attempt to connect to the server
     fails with a message such as one of those following, one cause
     might be that the server is not running:


          shell> mysql
          ERROR 2003: Can't connect to MySQL server on 'HOST_NAME' (111)
          shell> mysql
          ERROR 2002: Can't connect to local MySQL server through socket
          '/tmp/mysql.sock' (111)

   * It might be that the server is running, but you are trying to
     connect using a TCP/IP port, named pipe, or Unix socket file
     different from the one on which the server is listening. To
     correct this when you invoke a client program, specify a `--port'
     option to indicate the proper port number, or a `--socket' option
     to indicate the proper named pipe or Unix socket file. To find out
     where the socket file is, you can use this command:


          shell> netstat -ln | grep mysql

   * Make sure that the server has not been configured to ignore
     network connections or (if you are attempting to connect remotely)
     that it has not been configured to listen only locally on its
     network interfaces. If the server was started with
     `--skip-networking', it will not accept TCP/IP connections at all.
     If the server was started with `--bind-address=127.0.0.1', it will
     listen for TCP/IP connections only locally on the loopback
     interface and will not accept remote connections.

   * Check to make sure that there is no firewall blocking access to
     MySQL. Your firewall may be configured on the basis of the
     application being executed, or the port number used by MySQL for
     communication (3306 by default). Under Linux or Unix, check your
     IP tables (or similar) configuration to ensure that the port has
     not been blocked. Under Windows, applications such as ZoneAlarm or
     the Windows XP personal firewall may need to be configured not to
     block the MySQL port.

   * The grant tables must be properly set up so that the server can
     use them for access control. For some distribution types (such as
     binary distributions on Windows, or RPM distributions on Linux),
     the installation process initializes the `mysql' database
     containing the grant tables.  For distributions that do not do
     this, you must initialize the grant tables manually by running the
     *Note `mysql_install_db': mysql-install-db. program. For details,
     see *Note unix-postinstallation::.

     To determine whether you need to initialize the grant tables, look
     for a `mysql' directory under the data directory. (The data
     directory normally is named `data' or `var' and is located under
     your MySQL installation directory.) Make sure that you have a file
     named `user.MYD' in the `mysql' database directory. If not,
     execute the *Note `mysql_install_db': mysql-install-db. program.
     After running this program and starting the server, test the
     initial privileges by executing this command:


          shell> mysql -u root test

     The server should let you connect without error.

   * After a fresh installation, you should connect to the server and
     set up your users and their access permissions:


          shell> mysql -u root mysql

     The server should let you connect because the MySQL `root' user
     has no password initially. That is also a security risk, so
     setting the password for the `root' accounts is something you
     should do while you're setting up your other MySQL accounts. For
     instructions on setting the initial passwords, see *Note
     default-privileges::.

   * If you have updated an existing MySQL installation to a newer
     version, did you run the *Note `mysql_upgrade': mysql-upgrade.
     script? If not, do so. The structure of the grant tables changes
     occasionally when new capabilities are added, so after an upgrade
     you should always make sure that your tables have the current
     structure. For instructions, see *Note mysql-upgrade::.

   * If a client program receives the following error message when it
     tries to connect, it means that the server expects passwords in a
     newer format than the client is capable of generating:


          shell> mysql
          Client does not support authentication protocol requested
          by server; consider upgrading MySQL client

     For information on how to deal with this, see *Note
     password-hashing::, and *Note old-client::.

   * Remember that client programs use connection parameters specified
     in option files or environment variables. If a client program
     seems to be sending incorrect default connection parameters when
     you have not specified them on the command line, check any
     applicable option files and your environment. For example, if you
     get `Access denied' when you run a client without any options,
     make sure that you have not specified an old password in any of
     your option files!

     You can suppress the use of option files by a client program by
     invoking it with the `--no-defaults' option. For example:


          shell> mysqladmin --no-defaults -u root version

     The option files that clients use are listed in *Note
     option-files::. Environment variables are listed in *Note
     environment-variables::.

   * If you get the following error, it means that you are using an
     incorrect `root' password:


          shell> mysqladmin -u root -pXXXX ver
          Access denied for user 'root'@'localhost' (using password: YES)

     If the preceding error occurs even when you have not specified a
     password, it means that you have an incorrect password listed in
     some option file. Try the `--no-defaults' option as described in
     the previous item.

     For information on changing passwords, see *Note
     assigning-passwords::.

     If you have lost or forgotten the `root' password, see *Note
     resetting-permissions::.

   * If you change a password by using *Note `SET PASSWORD':
     set-password, *Note `INSERT': insert, or *Note `UPDATE': update,
     you must encrypt the password using the `PASSWORD()' function. If
     you do not use `PASSWORD()' for these statements, the password
     will not work. For example, the following statement assigns a
     password, but fails to encrypt it, so the user is not able to
     connect afterward:


          SET PASSWORD FOR 'abe'@'HOST_NAME' = 'eagle';

     Instead, set the password like this:


          SET PASSWORD FOR 'abe'@'HOST_NAME' = PASSWORD('eagle');

     The `PASSWORD()' function is unnecessary when you specify a
     password using the *Note `CREATE USER': create-user. or *Note
     `GRANT': grant. statements or the *Note `mysqladmin password':
     mysqladmin. command. Each of those automatically uses `PASSWORD()'
     to encrypt the password. See *Note assigning-passwords::, and
     *Note create-user::.

   * `localhost' is a synonym for your local host name, and is also the
     default host to which clients try to connect if you specify no
     host explicitly.

     To avoid this problem on such systems, you can use a
     `--host=127.0.0.1' option to name the server host explicitly. This
     will make a TCP/IP connection to the local *Note `mysqld': mysqld.
     server. You can also use TCP/IP by specifying a `--host' option
     that uses the actual host name of the local host. In this case,
     the host name must be specified in a `user' table row on the
     server host, even though you are running the client program on the
     same host as the server.

   * The `Access denied' error message tells you who you are trying to
     log in as, the client host from which you are trying to connect,
     and whether you were using a password. Normally, you should have
     one row in the `user' table that exactly matches the host name and
     user name that were given in the error message. For example, if
     you get an error message that contains `using password: NO', it
     means that you tried to log in without a password.

   * If you get an `Access denied' error when trying to connect to the
     database with `mysql -u USER_NAME', you may have a problem with
     the `user' table. Check this by executing `mysql -u root mysql'
     and issuing this SQL statement:


          SELECT * FROM user;

     The result should include a row with the `Host' and `User' columns
     matching your client's host name and your MySQL user name.

   * If the following error occurs when you try to connect from a host
     other than the one on which the MySQL server is running, it means
     that there is no row in the `user' table with a `Host' value that
     matches the client host:


          Host ... is not allowed to connect to this MySQL server

     You can fix this by setting up an account for the combination of
     client host name and user name that you are using when trying to
     connect.

     If you do not know the IP address or host name of the machine from
     which you are connecting, you should put a row with `'%'' as the
     `Host' column value in the `user' table. After trying to connect
     from the client machine, use a `SELECT USER()' query to see how
     you really did connect. Then change the `'%'' in the `user' table
     row to the actual host name that shows up in the log. Otherwise,
     your system is left insecure because it permits connections from
     any host for the given user name.

     On Linux, another reason that this error might occur is that you
     are using a binary MySQL version that is compiled with a different
     version of the `glibc' library than the one you are using. In this
     case, you should either upgrade your operating system or `glibc',
     or download a source distribution of MySQL version and compile it
     yourself. A source RPM is normally trivial to compile and install,
     so this is not a big problem.

   * If you specify a host name when trying to connect, but get an
     error message where the host name is not shown or is an IP
     address, it means that the MySQL server got an error when trying
     to resolve the IP address of the client host to a name:


          shell> mysqladmin -u root -pXXXX -h SOME_HOSTNAME ver
          Access denied for user 'root'@'' (using password: YES)

     If you try to connect as `root' and get the following error, it
     means that you do not have a row in the `user' table with a `User'
     column value of `'root'' and that *Note `mysqld': mysqld. cannot
     resolve the host name for your client:


          Access denied for user ''@'unknown'

     These errors indicate a DNS problem. To fix it, execute *Note
     `mysqladmin flush-hosts': mysqladmin. to reset the internal DNS
     host cache. See *Note host-cache::.

     Some permanent solutions are:

        * Determine what is wrong with your DNS server and fix it.

        * Specify IP addresses rather than host names in the MySQL
          grant tables.

        * Put an entry for the client machine name in `/etc/hosts' on
          Unix or `\windows\hosts' on Windows.

        * Start *Note `mysqld': mysqld. with the `--skip-name-resolve'
          option.

        * Start *Note `mysqld': mysqld. with the `--skip-host-cache'
          option.

        * On Unix, if you are running the server and the client on the
          same machine, connect to `localhost'.  Unix connections to
          `localhost' use a Unix socket file rather than TCP/IP.

        * On Windows, if you are running the server and the client on
          the same machine and the server supports named pipe
          connections, connect to the host name `.' (period).
          Connections to `.' use a named pipe rather than TCP/IP.

   * If `mysql -u root test' works but `mysql -h YOUR_HOSTNAME -u root
     test' results in `Access denied' (where YOUR_HOSTNAME is the
     actual host name of the local host), you may not have the correct
     name for your host in the `user' table. A common problem here is
     that the `Host' value in the `user' table row specifies an
     unqualified host name, but your system's name resolution routines
     return a fully qualified domain name (or vice versa). For example,
     if you have an entry with host `'pluto'' in the `user' table, but
     your DNS tells MySQL that your host name is `'pluto.example.com'',
     the entry does not work. Try adding an entry to the `user' table
     that contains the IP address of your host as the `Host' column
     value.  (Alternatively, you could add an entry to the `user' table
     with a `Host' value that contains a wildcard; for example,
     `'pluto.%''. However, use of `Host' values ending with ``%'' is
     _insecure_ and is _not_ recommended!)

   * If `mysql -u USER_NAME test' works but `mysql -u USER_NAME
     OTHER_DB' does not, you have not granted access to the given user
     for the database named OTHER_DB.

   * If `mysql -u USER_NAME' works when executed on the server host,
     but `mysql -h HOST_NAME -u USER_NAME' does not work when executed
     on a remote client host, you have not enabled access to the server
     for the given user name from the remote host.

   * If you cannot figure out why you get `Access denied', remove from
     the `user' table all entries that have `Host' values containing
     wildcards (entries that contain `'%'' or `'_'' characters).  A
     very common error is to insert a new entry with `Host'=`'%'' and
     `User'=`'SOME_USER'', thinking that this enables you to specify
     `localhost' to connect from the same machine.  The reason that
     this does not work is that the default privileges include an entry
     with `Host'=`'localhost'' and `User'=`'''. Because that entry has
     a `Host' value `'localhost'' that is more specific than `'%'', it
     is used in preference to the new entry when connecting from
     `localhost'! The correct procedure is to insert a second entry with
     `Host'=`'localhost'' and `User'=`'SOME_USER'', or to delete the
     entry with `Host'=`'localhost'' and `User'=`'''. After deleting
     the entry, remember to issue a *Note `FLUSH PRIVILEGES': flush.
     statement to reload the grant tables. See also *Note
     connection-access::.

   * If you are able to connect to the MySQL server, but get an `Access
     denied' message whenever you issue a *Note `SELECT ... INTO
     OUTFILE': select-into. or *Note `LOAD DATA INFILE': load-data.
     statement, your entry in the `user' table does not have the `FILE'
     privilege enabled.

   * If you change the grant tables directly (for example, by using
     *Note `INSERT': insert, *Note `UPDATE': update, or *Note `DELETE':
     delete. statements) and your changes seem to be ignored, remember
     that you must execute a *Note `FLUSH PRIVILEGES': flush. statement
     or a *Note `mysqladmin flush-privileges': mysqladmin. command to
     cause the server to reload the privilege tables. Otherwise, your
     changes have no effect until the next time the server is
     restarted. Remember that after you change the `root' password with
     an *Note `UPDATE': update. statement, you will not need to specify
     the new password until after you flush the privileges, because the
     server will not know you've changed the password yet!

   * If your privileges seem to have changed in the middle of a
     session, it may be that a MySQL administrator has changed them.
     Reloading the grant tables affects new client connections, but it
     also affects existing connections as indicated in *Note
     privilege-changes::.

   * If you have access problems with a Perl, PHP, Python, or ODBC
     program, try to connect to the server with `mysql -u USER_NAME
     DB_NAME' or `mysql -u USER_NAME -pYOUR_PASS DB_NAME'. If you are
     able to connect using the *Note `mysql': mysql. client, the
     problem lies with your program, not with the access privileges.
     (There is no space between `-p' and the password; you can also use
     the `--password=YOUR_PASS' syntax to specify the password. If you
     use the `-p' or `--password' option with no password value, MySQL
     prompts you for the password.)

   * For testing purposes, start the *Note `mysqld': mysqld.  server
     with the `--skip-grant-tables' option.  Then you can change the
     MySQL grant tables and use the *Note `mysqlaccess': mysqlaccess.
     script to check whether your modifications have the desired
     effect. When you are satisfied with your changes, execute *Note
     `mysqladmin flush-privileges': mysqladmin. to tell the *Note
     `mysqld': mysqld. server to reload the privileges.  This enables
     you to begin using the new grant table contents without stopping
     and restarting the server.

   * If you get the following error, you may have a problem with the
     `db' or `host' table:


          Access to database denied

     If the entry selected from the `db' table has an empty value in
     the `Host' column, make sure that there are one or more
     corresponding entries in the `host' table specifying which hosts
     the `db' table entry applies to. This problem occurs infrequently
     because the `host' table is rarely used.

   * If everything else fails, start the *Note `mysqld': mysqld.
     server with a debugging option (for example,
     `--debug=d,general,query'). This prints host and user information
     about attempted connections, as well as information about each
     command issued. See *Note dbug-package::.

   * If you have any other problems with the MySQL grant tables and
     feel you must post the problem to the mailing list, always provide
     a dump of the MySQL grant tables. You can dump the tables with the
     *Note `mysqldump mysql': mysqldump. command. To file a bug report,
     see the instructions at *Note bug-reports::. In some cases, you
     may need to restart *Note `mysqld': mysqld. with
     `--skip-grant-tables' to run *Note `mysqldump': mysqldump.


File: manual.info,  Node: user-account-management,  Prev: privilege-system,  Up: security

6.3 MySQL User Account Management
=================================

* Menu:

* user-names::                   User Names and Passwords
* adding-users::                 Adding User Accounts
* removing-users::               Removing User Accounts
* user-resources::               Setting Account Resource Limits
* assigning-passwords::          Assigning Account Passwords
* ssl-connections::              Using SSL for Secure Connections
* windows-and-ssh::              Connecting to MySQL Remotely from Windows with SSH
* account-activity-auditing::    SQL-Based MySQL Account Activity Auditing

This section describes how to set up accounts for clients of your MySQL
server. It discusses the following topics:

   * The meaning of account names and passwords as used in MySQL and
     how that compares to names and passwords used by your operating
     system

   * How to set up new accounts and remove existing accounts

   * How to change passwords

   * Guidelines for using passwords securely

   * How to use secure connections with SSL

See also *Note account-management-sql::, which describes the syntax and
use for all user-management SQL statements.


File: manual.info,  Node: user-names,  Next: adding-users,  Prev: user-account-management,  Up: user-account-management

6.3.1 User Names and Passwords
------------------------------

MySQL stores accounts in the `user' table of the `mysql' database. An
account is defined in terms of a user name and the client host or hosts
from which the user can connect to the server. The account may also
have a password.  For information about account representation in the
`user' table, see *Note grant-table-structure::.

There are several distinctions between the way user names and passwords
are used by MySQL and the way they are used by your operating system:

   * User names, as used by MySQL for authentication purposes, have
     nothing to do with user names (login names) as used by Windows or
     Unix. On Unix, most MySQL clients by default try to log in using
     the current Unix user name as the MySQL user name, but that is for
     convenience only. The default can be overridden easily, because
     client programs permit any user name to be specified with a `-u' or
     `--user' option. Because this means that anyone can attempt to
     connect to the server using any user name, you cannot make a
     database secure in any way unless all MySQL accounts have
     passwords. Anyone who specifies a user name for an account that
     has no password is able to connect successfully to the server.

   * MySQL user names can be up to 16 characters long. Operating system
     user names, because they are completely unrelated to MySQL user
     names, may be of a different maximum length. For example, Unix
     user names typically are limited to eight characters.

     *Warning*:

     The limit on MySQL user name length is hard-coded in the MySQL
     servers and clients, and trying to circumvent it by modifying the
     definitions of the tables in the `mysql' database _does not work_.

     You should never alter any of the tables in the `mysql' database
     in any manner whatsoever except by means of the procedure that is
     described in *Note mysql-upgrade::. Attempting to redefine MySQL's
     system tables in any other fashion results in undefined (and
     unsupported!) behavior.

   * The server uses MySQL passwords stored in the `user' table to
     authenticate client connections using MySQL built-in
     authentication. These passwords have nothing to do with passwords
     for logging in to your operating system. There is no necessary
     connection between the `external' password you use to log in to a
     Windows or Unix machine and the password you use to access the
     MySQL server on that machine.

   * MySQL encrypts passwords stored in the `user' table using its own
     algorithm. This encryption is the same as that implemented by the
     `PASSWORD()' SQL function but differs from that used during the
     Unix login process. Unix password encryption is the same as that
     implemented by the `ENCRYPT()' SQL function. See the descriptions
     of the `PASSWORD()' and `ENCRYPT()' functions in *Note
     encryption-functions::.

     From version 4.1 on, MySQL employs a stronger authentication
     method that has better password protection during the connection
     process than in earlier versions. It is secure even if TCP/IP
     packets are sniffed or the `mysql' database is captured. (In
     earlier versions, even though passwords are stored in encrypted
     form in the `user' table, knowledge of the encrypted password
     value could be used to connect to the MySQL server.)  *Note
     password-hashing::, discusses password encryption further.

   * It is possible to connect to the server regardless of character
     set settings if the user name and password contain only ASCII
     characters. To connect when the user name or password contain
     non-ASCII characters, the client should call the *Note
     `mysql_options()': mysql-options. C API function with the
     `MYSQL_SET_CHARSET_NAME' option and appropriate character set name
     as arguments. This causes authentication to take place using the
     specified character set. Otherwise, authentication will fail
     unless the server default character set is the same as the
     encoding in the authentication defaults.

     Standard MySQL client programs support a `--default-character-set'
     option that causes *Note `mysql_options()': mysql-options. to be
     called as just described. For programs that use a connector that is
     not based on the C API, the connector may provide an equivalent to
     *Note `mysql_options()': mysql-options.  that can be used instead.
     Check the connector documentation.

     The preceding notes do not apply for `ucs2', which is not
     permitted as a client character set.

When you install MySQL, the grant tables are populated with an initial
set of accounts. The names and access privileges for these accounts are
described in *Note default-privileges::, which also discusses how to
assign passwords to them. Thereafter, you normally set up, modify, and
remove MySQL accounts using statements such as *Note `CREATE USER':
create-user, *Note `GRANT': grant, and *Note `REVOKE': revoke. See
*Note account-management-sql::.

When you connect to a MySQL server with a command-line client, specify
the user name and password as necessary for the account that you want
to use:


     shell> mysql --user=monty --password=PASSWORD DB_NAME

If you prefer short options, the command looks like this:


     shell> mysql -u monty -pPASSWORD DB_NAME

There must be _no space_ between the `-p' option and the following
password value.

If you omit the PASSWORD value following the `--password' or `-p'
option on the command line, the client prompts for one.

Specifying a password on the command line should be considered
insecure. See *Note password-security-user::. You can use an option
file to avoid giving the password on the command line.

For additional information about specifying user names, passwords, and
other connection parameters, see *Note connecting::.


File: manual.info,  Node: adding-users,  Next: removing-users,  Prev: user-names,  Up: user-account-management

6.3.2 Adding User Accounts
--------------------------

You can create MySQL accounts in two ways:

   * By using statements intended for creating accounts, such as *Note
     `CREATE USER': create-user. or *Note `GRANT': grant. These
     statements cause the server to make appropriate modifications to
     the grant tables.

   * By manipulating the MySQL grant tables directly with statements
     such as *Note `INSERT': insert, *Note `UPDATE': update, or *Note
     `DELETE': delete.

The preferred method is to use account-creation statements because they
are more concise and less error-prone than manipulating the grant
tables directly. *Note `CREATE USER': create-user.  and *Note `GRANT':
grant. are described in *Note account-management-sql::.

Another option for creating accounts is to use the GUI tool MySQL
Workbench. Or one of several available third-party programs that offer
capabilities for MySQL account administration.  `phpMyAdmin' is one
such program.

The following examples show how to use the *Note `mysql': mysql. client
program to set up new accounts.  These examples assume that privileges
have been set up according to the defaults described in *Note
default-privileges::.  This means that to make changes, you must
connect to the MySQL server as the MySQL `root' user, and the `root'
account must have the `INSERT' privilege for the `mysql' database and
the `RELOAD' administrative privilege.

As noted in the examples where appropriate, some of the statements will
fail if the server's SQL mode has been set to enable certain
restrictions. In particular, strict mode (`STRICT_TRANS_TABLES',
`STRICT_ALL_TABLES') and `NO_AUTO_CREATE_USER' will prevent the server
from accepting some of the statements. Workarounds are indicated for
these cases. For more information about SQL modes and their effect on
grant table manipulation, see *Note sql-mode::, and *Note grant::.

First, use the *Note `mysql': mysql. program to connect to the server
as the MySQL `root' user:


     shell> mysql --user=root mysql

If you have assigned a password to the `root' account, you will also
need to supply a `--password' or `-p' option, both for this *Note
`mysql': mysql. command and for those later in this section.

After connecting to the server as `root', you can add new accounts. The
following statements use *Note `GRANT': grant. to set up four new
accounts:


     mysql> CREATE USER 'monty'@'localhost' IDENTIFIED BY 'some_pass';
     mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'localhost'
         ->     WITH GRANT OPTION;
     mysql> CREATE USER 'monty'@'%' IDENTIFIED BY 'some_pass';
     mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'%'
         ->     WITH GRANT OPTION;
     mysql> CREATE USER 'admin'@'localhost';
     mysql> GRANT RELOAD,PROCESS ON *.* TO 'admin'@'localhost';
     mysql> CREATE USER 'dummy'@'localhost';

The accounts created by these statements have the following properties:

   * Two of the accounts have a user name of `monty' and a password of
     `some_pass'. Both accounts are superuser accounts with full
     privileges to do anything. The `'monty'@'localhost'' account can
     be used only when connecting from the local host. The
     `'monty'@'%'' account uses the `'%'' wildcard for the host part,
     so it can be used to connect from any host.

     It is necessary to have both accounts for `monty' to be able to
     connect from anywhere as `monty'. Without the `localhost' account,
     the anonymous-user account for `localhost' that is created by
     *Note `mysql_install_db': mysql-install-db. would take precedence
     when `monty' connects from the local host. As a result, `monty'
     would be treated as an anonymous user. The reason for this is that
     the anonymous-user account has a more specific `Host' column value
     than the `'monty'@'%'' account and thus comes earlier in the
     `user' table sort order.  (`user' table sorting is discussed in
     *Note connection-access::.)

   * The `'admin'@'localhost'' account has no password. This account
     can be used only by `admin' to connect from the local host. It is
     granted the `RELOAD' and `PROCESS' administrative privileges.
     These privileges enable the `admin' user to execute the *Note
     `mysqladmin reload': mysqladmin, *Note `mysqladmin refresh':
     mysqladmin, and *Note `mysqladmin flush-XXX': mysqladmin.
     commands, as well as *Note `mysqladmin processlist': mysqladmin .
     No privileges are granted for accessing any databases. You could
     add such privileges later by issuing other *Note `GRANT': grant.
     statements.

   * The `'dummy'@'localhost'' account has no password. This account
     can be used only to connect from the local host. No privileges are
     granted. It is assumed that you will grant specific privileges to
     the account later.

The statements that create accounts with no password will fail if the
`NO_AUTO_CREATE_USER' SQL mode is enabled. To deal with this, use an
`IDENTIFIED BY' clause that specifies a nonempty password.

To check the privileges for an account, use *Note `SHOW GRANTS':
show-grants.:


     mysql> SHOW GRANTS FOR 'admin'@'localhost';
     +-----------------------------------------------------+
     | Grants for admin@localhost                          |
     +-----------------------------------------------------+
     | GRANT RELOAD, PROCESS ON *.* TO 'admin'@'localhost' |
     +-----------------------------------------------------+

As an alternative to *Note `CREATE USER': create-user.  and *Note
`GRANT': grant, you can create the same accounts directly by issuing
*Note `INSERT': insert.  statements and then telling the server to
reload the grant tables using *Note `FLUSH PRIVILEGES': flush.:


     shell> mysql --user=root mysql
     mysql> INSERT INTO user
         ->     VALUES('localhost','monty',PASSWORD('some_pass'),
         ->     'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y');
     mysql> INSERT INTO user
         ->     VALUES('%','monty',PASSWORD('some_pass'),
         ->     'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y',
         ->     'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y',
         ->     '','','','',0,0,0,0);
     mysql> INSERT INTO user SET Host='localhost',User='admin',
         ->     Reload_priv='Y', Process_priv='Y';
     mysql> INSERT INTO user (Host,User,Password)
         ->     VALUES('localhost','dummy','');
     mysql> FLUSH PRIVILEGES;

When you create accounts with *Note `INSERT': insert, it is necessary
to use *Note `FLUSH PRIVILEGES': flush.  to tell the server to reload
the grant tables. Otherwise, the changes go unnoticed until you restart
the server. With *Note `CREATE USER': create-user, *Note `FLUSH
PRIVILEGES': flush.  is unnecessary.

The reason for using the `PASSWORD()' function with *Note `INSERT':
insert. is to encrypt the password. The *Note `CREATE USER':
create-user.  statement encrypts the password for you, so `PASSWORD()'
is unnecessary.

The `'Y'' values enable privileges for the accounts. Depending on your
MySQL version, you may have to use a different number of `'Y'' values
in the first two *Note `INSERT': insert. statements. The *Note
`INSERT': insert. statement for the `admin' account employs the more
readable extended *Note `INSERT': insert. syntax using `SET'.

In the *Note `INSERT': insert. statement for the `dummy' account, only
the `Host', `User', and `Password' columns in the `user' table row are
assigned values. None of the privilege columns are set explicitly, so
MySQL assigns them all the default value of `'N''. This is equivalent
to what *Note `CREATE USER': create-user. does.

If strict SQL mode is enabled, all columns that have no default value
must have a value specified. In this case, *Note `INSERT': insert.
statements must explicitly specify values for the `ssl_cipher',
`x509_issuer', and `x509_subject' columns.

To set up a superuser account, it is necessary only to insert a `user'
table row with all privilege columns set to `'Y''. The `user' table
privileges are global, so no entries in any of the other grant tables
are needed.

The next examples create three accounts and give them access to
specific databases. Each of them has a user name of `custom' and
password of `obscure'.

To create the accounts with *Note `CREATE USER': create-user. and *Note
`GRANT': grant, use the following statements:


     shell> mysql --user=root mysql
     mysql> CREATE USER 'custom'@'localhost' IDENTIFIED BY 'obscure';
     mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
         ->     ON bankaccount.*
         ->     TO 'custom'@'localhost';
     mysql> CREATE USER 'custom'@'host47.example.com' IDENTIFIED BY 'obscure';
     mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
         ->     ON expenses.*
         ->     TO 'custom'@'host47.example.com';
     mysql> CREATE USER 'custom'@'server.domain' IDENTIFIED BY 'obscure';
     mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
         ->     ON customer.*
         ->     TO 'custom'@'server.domain';

The three accounts can be used as follows:

   * The first account can access the `bankaccount' database, but only
     from the local host.

   * The second account can access the `expenses' database, but only
     from the host `host47.example.com'.

   * The third account can access the `customer' database, but only
     from the host `server.domain'.

To set up the `custom' accounts without *Note `GRANT': grant, use *Note
`INSERT': insert. statements as follows to modify the grant tables
directly:


     shell> mysql --user=root mysql
     mysql> INSERT INTO user (Host,User,Password)
         ->     VALUES('localhost','custom',PASSWORD('obscure'));
     mysql> INSERT INTO user (Host,User,Password)
         ->     VALUES('host47.example.com','custom',PASSWORD('obscure'));
     mysql> INSERT INTO user (Host,User,Password)
         ->     VALUES('server.domain','custom',PASSWORD('obscure'));
     mysql> INSERT INTO db
         ->     (Host,Db,User,Select_priv,Insert_priv,
         ->     Update_priv,Delete_priv,Create_priv,Drop_priv)
         ->     VALUES('localhost','bankaccount','custom',
         ->     'Y','Y','Y','Y','Y','Y');
     mysql> INSERT INTO db
         ->     (Host,Db,User,Select_priv,Insert_priv,
         ->     Update_priv,Delete_priv,Create_priv,Drop_priv)
         ->     VALUES('host47.example.com','expenses','custom',
         ->     'Y','Y','Y','Y','Y','Y');
     mysql> INSERT INTO db
         ->     (Host,Db,User,Select_priv,Insert_priv,
         ->     Update_priv,Delete_priv,Create_priv,Drop_priv)
         ->     VALUES('server.domain','customer','custom',
         ->     'Y','Y','Y','Y','Y','Y');
     mysql> FLUSH PRIVILEGES;

The first three *Note `INSERT': insert. statements add `user' table
entries that permit the user `custom' to connect from the various hosts
with the given password, but grant no global privileges (all privileges
are set to the default value of `'N''). The next three *Note `INSERT':
insert. statements add `db' table entries that grant privileges to
`custom' for the `bankaccount', `expenses', and `customer' databases,
but only when accessed from the proper hosts. As usual when you modify
the grant tables directly, you must tell the server to reload them with
*Note `FLUSH PRIVILEGES': flush.  so that the privilege changes take
effect.

To create a user who has access from all machines in a given domain
(for example, `mydomain.com'), you can use the ``%'' wildcard character
in the host part of the account name:


     mysql> CREATE USER 'myname'@'%.mydomain.com' IDENTIFIED BY 'mypass';

To do the same thing by modifying the grant tables directly, do this:


     mysql> INSERT INTO user (Host,User,Password,...)
         ->     VALUES('%.mydomain.com','myname',PASSWORD('mypass'),...);
     mysql> FLUSH PRIVILEGES;


File: manual.info,  Node: removing-users,  Next: user-resources,  Prev: adding-users,  Up: user-account-management

6.3.3 Removing User Accounts
----------------------------

To remove an account, use the *Note `DROP USER': drop-user. statement,
which is described in *Note drop-user::.


File: manual.info,  Node: user-resources,  Next: assigning-passwords,  Prev: removing-users,  Up: user-account-management

6.3.4 Setting Account Resource Limits
-------------------------------------

One means of limiting use of MySQL server resources is to set the
global `max_user_connections' system variable to a nonzero value. This
limits the number of simultaneous connections that can be made by any
given account, but places no limits on what a client can do once
connected. In addition, setting `max_user_connections' does not enable
management of individual accounts. Both types of control are of
interest to many MySQL administrators, particularly those working for
Internet Service Providers.

In MySQL 5.1, you can limit use of the following server resources for
individual accounts:

   * The number of queries that an account can issue per hour

   * The number of updates that an account can issue per hour

   * The number of times an account can connect to the server per hour

   * The number of simultaneous connections to the server by an account

Any statement that a client can issue counts against the query limit
(unless its results are served from the query cache). Only statements
that modify databases or tables count against the update limit.

An `account' in this context corresponds to a row in the `mysql.user'
table. That is, a connection is assessed against the `User' and `Host'
values in the `user' table row that applies to the connection. For
example, an account `'usera'@'%.example.com'' corresponds to a row in
the `user' table that has `User' and `Host' values of `usera' and
`%.example.com', to permit `usera' to connect from any host in the
`example.com' domain. In this case, the server applies resource limits
in this row collectively to all connections by `usera' from any host in
the `example.com' domain because all such connections use the same
account.

Before MySQL 5.0.3, an `account' was assessed against the actual host
from which a user connects. This older method accounting may be
selected by starting the server with the `--old-style-user-limits'
option. In this case, if `usera' connects simultaneously from
`host1.example.com' and `host2.example.com', the server applies the
account resource limits separately to each connection. If `usera'
connects again from `host1.example.com', the server applies the limits
for that connection together with the existing connection from that
host.

To set resource limits for an account, use the *Note `GRANT': grant.
statement (see *Note grant::). Provide a `WITH' clause that names each
resource to be limited. The default value for each limit is zero (no
limit). For example, to create a new account that can access the
`customer' database, but only in a limited fashion, issue these
statements:


     mysql> CREATE USER 'francis'@'localhost' IDENTIFIED BY 'frank';
     mysql> GRANT ALL ON customer.* TO 'francis'@'localhost'
         ->     WITH MAX_QUERIES_PER_HOUR 20
         ->          MAX_UPDATES_PER_HOUR 10
         ->          MAX_CONNECTIONS_PER_HOUR 5
         ->          MAX_USER_CONNECTIONS 2;

The limit types need not all be named in the `WITH' clause, but those
named can be present in any order. The value for each per-hour limit
should be an integer representing a count per hour. For
`MAX_USER_CONNECTIONS', the limit is an integer representing the
maximum number of simultaneous connections by the account. If this
limit is set to zero, the global `max_user_connections' system variable
value determines the number of simultaneous connections.  If
`max_user_connections' is also zero, there is no limit for the account.

To modify existing limits for an account, use a *Note `GRANT USAGE':
grant.  statement at the global level (`ON *.*'). The following
statement changes the query limit for `francis' to 100:


     mysql> GRANT USAGE ON *.* TO 'francis'@'localhost'
         ->     WITH MAX_QUERIES_PER_HOUR 100;

The statement modifies only the limit value specified and leaves the
account otherwise unchanged.

To remove a limit, set its value to zero. For example, to remove the
limit on how many times per hour `francis' can connect, use this
statement:


     mysql> GRANT USAGE ON *.* TO 'francis'@'localhost'
         ->     WITH MAX_CONNECTIONS_PER_HOUR 0;

As mentioned previously, the simultaneous-connection limit for an
account is determined from the `MAX_USER_CONNECTIONS' limit and the
`max_user_connections' system variable. Suppose that the global
`max_user_connections' value is 10 and three accounts have resource
limits specified with *Note `GRANT': grant.:


     GRANT ... TO 'user1'@'localhost' WITH MAX_USER_CONNECTIONS 0;
     GRANT ... TO 'user2'@'localhost' WITH MAX_USER_CONNECTIONS 5;
     GRANT ... TO 'user3'@'localhost' WITH MAX_USER_CONNECTIONS 20;

`user1' has a connection limit of 10 (the global `max_user_connections'
value) because it has a zero `MAX_USER_CONNECTIONS' limit). `user2' and
`user3' have connection limits of 5 and 20, respectively, because they
have nonzero `MAX_USER_CONNECTIONS' limits.

The server stores resource limits for an account in the `user' table
row corresponding to the account.  The `max_questions', `max_updates',
and `max_connections' columns store the per-hour limits, and the
`max_user_connections' column stores the `MAX_USER_CONNECTIONS' limit.
(See *Note grant-table-structure::.) If your `user' table does not have
these columns, it must be upgraded; see *Note mysql-upgrade::.

Resource-use counting takes place when any account has a nonzero limit
placed on its use of any of the resources.

As the server runs, it counts the number of times each account uses
resources. If an account reaches its limit on number of connections
within the last hour, further connections for the account are rejected
until that hour is up. Similarly, if the account reaches its limit on
the number of queries or updates, further queries or updates are
rejected until the hour is up. In all such cases, an appropriate error
message is issued.

Resource counting is done per account, not per client. For example, if
your account has a query limit of 50, you cannot increase your limit to
100 by making two simultaneous client connections to the server.
Queries issued on both connections are counted together.

The current per-hour resource-use counts can be reset globally for all
accounts, or individually for a given account:

   * To reset the current counts to zero for all accounts, issue a
     *Note `FLUSH USER_RESOURCES': flush. statement. The counts also
     can be reset by reloading the grant tables (for example, with a
     *Note `FLUSH PRIVILEGES': flush. statement or a *Note `mysqladmin
     reload': mysqladmin. command).

   * The counts for an individual account can be set to zero by
     re-granting it any of its limits. To do this, use *Note `GRANT
     USAGE': grant.  as described earlier and specify a limit value
     equal to the value that the account currently has.

Counter resets do not affect the `MAX_USER_CONNECTIONS' limit.

All counts begin at zero when the server starts; counts are not carried
over through a restart.

For the `MAX_USER_CONNECTIONS' limit, an edge case can occur if the
account currently has open the maximum number of connections permitted
to it: A disconnect followed quickly by a connect can result in an error
(`ER_TOO_MANY_USER_CONNECTIONS' or `ER_USER_LIMIT_REACHED') if the
server has not fully processed the disconnect by the time the connect
occurs. When the server finishes disconnect processing, another
connection will once more be permitted.


File: manual.info,  Node: assigning-passwords,  Next: ssl-connections,  Prev: user-resources,  Up: user-account-management

6.3.5 Assigning Account Passwords
---------------------------------

Required credentials for clients that connect to the MySQL server can
include a password. This section describes how to assign passwords for
MySQL accounts.

To assign a password when you create a new account with *Note `CREATE
USER': create-user, include an `IDENTIFIED BY' clause:


     mysql> CREATE USER 'jeffrey'@'localhost'
         -> IDENTIFIED BY 'mypass';

To assign or change a password for an existing account, one way is to
issue a *Note `SET PASSWORD': set-password. statement:


     mysql> SET PASSWORD FOR
         -> 'jeffrey'@'localhost' = PASSWORD('mypass');

MySQL stores passwords in the `user' table in the `mysql' database.
Only users such as `root' that have the `UPDATE' privilege for the
`mysql' database can change the password for other users. If you are
not connected as an anonymous user, you can change your own password by
omitting the `FOR' clause:


     mysql> SET PASSWORD = PASSWORD('mypass');

The `old_passwords' system variable value determines the hashing method
used by `PASSWORD()'. If you specify the password using that function
and *Note `SET PASSWORD': set-password. rejects the password as not
being in the correct format, it may be necessary to set `old_passwords'
to change the hashing method. For descriptions of the permitted values,
see *Note server-system-variables::.

Enabling the `read_only' system variable prevents the use of the *Note
`SET PASSWORD': set-password. statement by any user not having the
`SUPER' privilege.

You can also use a *Note `GRANT USAGE': grant. statement at the global
level (`ON *.*') to assign a password to an account without affecting
the account's current privileges:


     mysql> GRANT USAGE ON *.* TO 'jeffrey'@'localhost'
         -> IDENTIFIED BY 'mypass';

To assign a password from the command line, use the *Note `mysqladmin':
mysqladmin. command:


     shell> mysqladmin -u USER_NAME -h HOST_NAME password "NEWPWD"

The account for which this command sets the password is the one with a
`user' table row that matches USER_NAME in the `User' column and the
client host _from which you connect_ in the `Host' column.

During authentication when a client connects to the server, MySQL
treats the password in the `user' table as an encrypted hash value (the
value that `PASSWORD()' would return for the password). When assigning
a password to an account, it is important to store an encrypted value,
not the plaintext password.  Use the following guidelines:

   * When you assign a password using *Note `CREATE USER': create-user,
     *Note `GRANT': grant. with an `IDENTIFIED BY' clause, or the *Note
     `mysqladmin password': mysqladmin. command, they encrypt the
     password for you. Specify the literal plaintext password:


          mysql> CREATE USER 'jeffrey'@'localhost'
              -> IDENTIFIED BY 'mypass';

   * For *Note `CREATE USER': create-user. or *Note `GRANT': grant, you
     can avoid sending the plaintext password if you know the hash
     value that `PASSWORD()' would return for the password. Specify the
     hash value preceded by the keyword `PASSWORD':


          mysql> CREATE USER 'jeffrey'@'localhost'
              -> IDENTIFIED BY PASSWORD '*90E462C37378CED12064BB3388827D2BA3A9B689';

   * When you assign an account a nonempty password using *Note `SET
     PASSWORD': set-password, you must use the `PASSWORD()' function to
     encrypt the password, otherwise the password is stored as
     plaintext.  Suppose that you assign a password like this:


          mysql> SET PASSWORD FOR
              -> 'jeffrey'@'localhost' = 'mypass';

     The result is that the literal value `'mypass'' is stored as the
     password in the `user' table, not the encrypted value. When
     `jeffrey' attempts to connect to the server using this password,
     the value is encrypted and compared to the value stored in the
     `user' table.  However, the stored value is the literal string
     `'mypass'', so the comparison fails and the server rejects the
     connection with an `Access denied' error.

*Note*:

`PASSWORD()' encryption differs from Unix password encryption. See
*Note user-names::.

It is preferable to assign passwords using *Note `SET PASSWORD':
set-password, *Note `GRANT': grant, or *Note `mysqladmin': mysqladmin,
but it is also possible to modify the `user' table directly. In this
case, you must also use *Note `FLUSH PRIVILEGES': flush. to cause the
server to reread the grant tables. Otherwise, the change remains
unnoticed by the server until you restart it.


File: manual.info,  Node: ssl-connections,  Next: windows-and-ssh,  Prev: assigning-passwords,  Up: user-account-management

6.3.6 Using SSL for Secure Connections
--------------------------------------

* Menu:

* ssl-basics::                   Basic SSL Concepts
* configuring-for-ssl::          Configuring MySQL for SSL
* using-ssl-connections::        Using SSL Connections
* ssl-options::                  SSL Command Options
* creating-ssl-certs::           Setting Up SSL Certificates and Keys for MySQL

MySQL supports secure (encrypted) connections between MySQL clients and
the server using the Secure Sockets Layer (SSL) protocol. This section
discusses how to use SSL connections. For information on how to require
users to use SSL connections, see the discussion of the `REQUIRE'
clause of the *Note `GRANT': grant. statement in *Note grant::.

The standard configuration of MySQL is intended to be as fast as
possible, so encrypted connections are not used by default. For
applications that require the security provided by encrypted
connections, the extra computation to encrypt the data is worthwhile.

MySQL enables encryption on a per-connection basis. You can choose an
unencrypted connection or a secure encrypted SSL connection according
the requirements of individual applications.

Secure connections are based on the OpenSSL API and are available
through the MySQL C API. Replication uses the C API, so secure
connections can be used between master and slave servers. See *Note
replication-solutions-ssl::.

Another way to connect securely is from within an SSH connection to the
MySQL server host. For an example, see *Note windows-and-ssh::.


File: manual.info,  Node: ssl-basics,  Next: configuring-for-ssl,  Prev: ssl-connections,  Up: ssl-connections

6.3.6.1 Basic SSL Concepts
..........................

To understand how MySQL uses SSL, it is necessary to explain some basic
SSL and X509 concepts. People who are familiar with these concepts can
skip this part of the discussion.

By default, MySQL uses unencrypted connections between the client and
the server. This means that someone with access to the network could
watch all your traffic and look at the data being sent or received.
They could even change the data while it is in transit between client
and server. To improve security a little, you can compress
client/server traffic by using the `--compress' option when invoking
client programs. However, this does not foil a determined attacker.

When you need to move information over a network in a secure fashion,
an unencrypted connection is unacceptable. Encryption is the way to
make any kind of data unreadable. Encryption algorithms must include
security elements to resist many kinds of known attacks such as
changing the order of encrypted messages or replaying data twice.

SSL is a protocol that uses different encryption algorithms to ensure
that data received over a public network can be trusted.  It has
mechanisms to detect any data change, loss, or replay.  SSL also
incorporates algorithms that provide identity verification using the
X509 standard.

X509 makes it possible to identify someone on the Internet. It is most
commonly used in e-commerce applications. In basic terms, there should
be some entity called a `Certificate Authority' (or CA) that assigns
electronic certificates to anyone who needs them. Certificates rely on
asymmetric encryption algorithms that have two encryption keys (a public
key and a secret key). A certificate owner can show the certificate to
another party as proof of identity. A certificate consists of its
owner's public key. Any data encrypted with this public key can be
decrypted only using the corresponding secret key, which is held by the
owner of the certificate.

For more information about SSL, X509, encryption, or public-key
cryptography, perform an Internet search for the keywords in which you
are interested.


File: manual.info,  Node: configuring-for-ssl,  Next: using-ssl-connections,  Prev: ssl-basics,  Up: ssl-connections

6.3.6.2 Configuring MySQL for SSL
.................................

To use SSL connections between the MySQL server and client programs,
your system must support either OpenSSL or yaSSL, and your version of
MySQL must be built with SSL support. To make it easier to use secure
connections, MySQL is bundled with yaSSL, which uses the same licensing
model as MySQL. (OpenSSL uses an Apache-style license.) yaSSL support
is available on all MySQL platforms supported by Oracle Corporation.

To get secure connections to work with MySQL and SSL, you must do the
following:

  1. If you are not using a binary (precompiled) version of MySQL that
     has been built with SSL support, and you are going to use OpenSSL
     rather than the bundled yaSSL library, install OpenSSL if it has
     not already been installed. We have tested MySQL with OpenSSL
     0.9.6. To obtain OpenSSL, visit `http://www.openssl.org'.

     Building MySQL using OpenSSL requires a shared OpenSSL library,
     otherwise linker errors occur. Alternatively, build MySQL using
     yaSSL.

  2. If you are not using a binary (precompiled) version of MySQL that
     has been built with SSL support, configure a MySQL source
     distribution to use SSL. When you configure MySQL, invoke the
     `configure' script like this:


          shell> ./configure --with-ssl

     That command configures the distribution to use the bundled yaSSL
     library. To use OpenSSL instead, specify the `--with-ssl' option
     with the path to the directory where the OpenSSL header files and
     libraries are located:


          shell> ./configure --with-ssl=PATH

     *Note*:

     On some platforms the full determination of the You may also need
     to explicitly add the SSL library and header directories. You can
     do this by setting the `LDFLAGS', `CFLAGS', `CPPFLAGS' and
     `CXXFLAGS' with the full directories. For example:

          shell> LDFLAGS="-L/usr/local/ssl/lib" CFLAGS="-I/usr/local/ssl/include" \
          CPPFLAGS="-I/usr/local/ssl/include" CXXFLAGS="-I/usr/local/ssl/include" \
          configure --with-ssl=/usr/local/ssl

     Before MySQL 5.1.11, you must use the appropriate option to select
     the SSL library that you want to use.

     For yaSSL:


          shell> ./configure --with-yassl

     For OpenSSL:


          shell> ./configure --with-openssl

     Then compile and install the distribution.

     On Unix platforms, yaSSL retrieves true random numbers from either
     `/dev/urandom' or `/dev/random'. Bug#13164 lists workarounds for
     some very old platforms which do not support these devices.

  3. To check whether a *Note `mysqld': mysqld. server supports SSL,
     examine the value of the `have_ssl' system variable:


          mysql> SHOW VARIABLES LIKE 'have_ssl';
          +---------------+-------+
          | Variable_name | Value |
          +---------------+-------+
          | have_ssl      | YES   |
          +---------------+-------+

     If the value is `YES', the server supports SSL connections. If the
     value is `DISABLED', the server is capable of supporting SSL
     connections but was not started with the appropriate `--ssl-XXX'
     options to enable them to be used; see *Note
     using-ssl-connections::.


File: manual.info,  Node: using-ssl-connections,  Next: ssl-options,  Prev: configuring-for-ssl,  Up: ssl-connections

6.3.6.3 Using SSL Connections
.............................

To enable SSL connections, your MySQL distribution must be built with
SSL support, as described in *Note configuring-for-ssl::. In addition,
the proper SSL-related options must be used to specify the appropriate
certificate and key files. For a complete list of SSL options, see
*Note ssl-options::.

To start the MySQL server so that it permits clients to connect using
SSL, use the options that identify the certificate and key files the
server uses when establishing a secure connection:

   * `--ssl-ca' identifies the Certificate Authority (CA) certificate.

   * `--ssl-cert' identifies the server public key certificate. This
     can be sent to the client and authenticated against the CA
     certificate that it has.

   * `--ssl-key' identifies the server private key.

For example, start the server like this:


     shell> mysqld --ssl-ca=CA-CERT.PEM \
              --ssl-cert=SERVER-CERT.PEM \
              --ssl-key=SERVER-KEY.PEM

Each option names a file in PEM format. For instructions on generating
the required SSL certificate and key files, see *Note
creating-ssl-certs::. If you have a MySQL source distribution, you can
also test your setup using the demonstration certificate and key files
in the `mysql-test/std_data' directory of the distribution.

Similar options are used on the client side, but `--ssl-cert' and
`--ssl-key' identify the client public and private key. The Certificate
Authority certificate, if specified, must be the same as used by the
server.

To establish a secure connection to a MySQL server with SSL support,
the options that a client must specify depend on the SSL requirements
of the MySQL account used by the client. (See the discussion of the
`REQUIRE' clause in *Note grant::.)

Suppose that you want to connect using an account that has no special
SSL requirements or was created using a *Note `GRANT': grant. statement
that includes the `REQUIRE SSL' option. As a recommended set of SSL
options, start the server with at least `--ssl-cert' and `--ssl-key',
and invoke the client with `--ssl-ca'. A client can connect securely
like this:


     shell> mysql --ssl-ca=CA-CERT.PEM

To require that a client certificate also be specified, create the
account using the `REQUIRE X509' option.  Then the client must also
specify the proper client key and certificate files or the server will
reject the connection:


     shell> mysql --ssl-ca=CA-CERT.PEM \
            --ssl-cert=CLIENT-CERT.PEM \
            --ssl-key=CLIENT-KEY.PEM

To prevent use of SSL and override other SSL options, invoke the client
program with `--ssl=0' or a synonym (`--skip-ssl', `--disable-ssl'):


     shell> mysql --ssl=0

A client can determine whether the current connection with the server
uses SSL by checking the value of the `Ssl_cipher' status variable.
The value is nonempty if SSL is used, and empty otherwise. For example:


     mysql> SHOW STATUS LIKE 'Ssl_cipher';
     +---------------+--------------------+
     | Variable_name | Value              |
     +---------------+--------------------+
     | Ssl_cipher    | DHE-RSA-AES256-SHA |
     +---------------+--------------------+

For the *Note `mysql': mysql. client, an alternative is to use the
`STATUS' or `\s' command and check the `SSL' line:


     mysql> \s
     ...
     SSL: Cipher in use is DHE-RSA-AES256-SHA
     ...

Or:


     mysql> \s
     ...
     SSL: Not in use
     ...

The C API enables application programs to use SSL:

   * To establish a secure connection, use the *Note `mysql_ssl_set()':
     mysql-ssl-set. C API function to set the appropriate certificate
     options before calling *Note `mysql_real_connect()':
     mysql-real-connect. See *Note mysql-ssl-set::.

   * To determine whether SSL is in use after the connection is
     established, use *Note `mysql_get_ssl_cipher()':
     mysql-get-ssl-cipher. A non-`NULL' return value indicates a secure
     connection and names the SSL cipher used for encryption. A `NULL'
     return value indicates that SSL is not being used. See *Note
     mysql-get-ssl-cipher::.

Replication uses the C API, so secure connections can be used between
master and slave servers. See *Note replication-solutions-ssl::.


File: manual.info,  Node: ssl-options,  Next: creating-ssl-certs,  Prev: using-ssl-connections,  Up: ssl-connections

6.3.6.4 SSL Command Options
...........................

This section describes options that specify whether to use SSL and the
names of SSL certificate and key files. These options can be given on
the command line or in an option file. They are not available unless
MySQL has been built with SSL support. See *Note configuring-for-ssl::.
For examples of suggested use and how to check whether a connection is
secure, see *Note using-ssl-connections::. (There are also
`--master-ssl*' options that can be used for setting up a secure
connection from a slave replication server to a master server; see
*Note replication-options::.)

*SSL Option/Variable Summary*

Name           Cmd-Line    Option File System Var  Status Var  Var Scope   Dynamic
have_openssl                           Yes                     Global      No
have_ssl                               Yes                     Global      No
skip-ssl       Yes         Yes                                             
ssl            Yes         Yes                                             
ssl-ca         Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_ca                                                                     
ssl-capath     Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_capath                                                                 
ssl-cert       Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_cert                                                                   
ssl-cipher     Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_cipher                                                                 
ssl-key        Yes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ssl_key                                                                    

   * `--ssl'

     For the server, this option specifies that the server permits but
     does not require SSL connections.

     For a client program, this option permits but does not require the
     client to connect to the server using SSL.  Therefore, this option
     is not sufficient in itself to cause an SSL connection to be used.
     For example, if you specify this option for a client program but
     the server has not been configured to permit SSL connections, an
     unencrypted connection is used.

     As a recommended set of options to enable SSL connections, use at
     least `--ssl-cert' and `--ssl-key' on the server side and
     `--ssl-ca' on the client side. See *Note using-ssl-connections::.

     `--ssl' may be implied by other `--ssl-XXX' options, as indicated
     in the descriptions for those options.

     The `--ssl' option can be given in its negated form to override
     other SSL options and indicate that SSL should _not_ be used.  To
     do this, specify the option as `--ssl=0' or a synonym
     (`--skip-ssl', `--disable-ssl').  For example, you might have SSL
     options specified in the `[client]' group of your option file to
     use SSL connections by default when you invoke MySQL client
     programs. To use an unencrypted connection instead, invoke the
     client program with `--skip-ssl' on the command line to override
     the options in the option file.

     To require use of an SSL connection for a MySQL account, issue a
     *Note `GRANT': grant. statement for the account that includes at
     least a `REQUIRE SSL' clause. Connections for the account will be
     rejected unless MySQL supports SSL connections and the server and
     client have been started with the proper SSL options.

     The `REQUIRE' clause permits other SSL-related options, which can
     be used to enforce stricter requirements than `REQUIRE SSL'. For
     additional details about which SSL command options may or must be
     specified by clients that connect using accounts configured using
     the various `REQUIRE' options, see the description of `REQUIRE' in
     *Note grant::.

   * `--ssl-ca=FILE_NAME'

     The path to a file in PEM format that contains a list of trusted
     SSL certificate authorities. This option implies `--ssl'.

     As of MySQL 5.1.18, if you use SSL when establishing a client
     connection, to tell the client not to authenticate the server
     certificate, specify neither `--ssl-ca' nor `--ssl-capath'. The
     server still verifies the client according to any applicable
     requirements established using *Note `GRANT': grant. statements
     for the client account, and it still uses any `--ssl-ca' or
     `--ssl-capath' option values specified at server startup.

   * `--ssl-capath=DIRECTORY_NAME'

     The path to a directory that contains trusted SSL certificate
     authority certificates in PEM format. This option implies `--ssl'.

     As of MySQL 5.1.18, if you use SSL when establishing a client
     connection, to tell the client not to authenticate the server
     certificate, specify neither `--ssl-ca' nor `--ssl-capath'. The
     server still verifies the client according to any applicable
     requirements established using *Note `GRANT': grant. statements
     for the client account, and it still uses any `--ssl-ca' or
     `--ssl-capath' option values specified at server startup.

     MySQL distributions built with OpenSSL support the `--ssl-capath'
     option.  Distributions built with yaSSL do not because yaSSL does
     not look in any directory and does not follow a chained
     certificate tree. yaSSL requires that all components of the CA
     certificate tree be contained within a single CA certificate tree
     and that each certificate in the file has a unique SubjectName
     value. To work around this yaSSL limitation, concatenate the
     individual certificate files comprising the certificate tree into
     a new file and specify that file as the value of the `--ssl-ca'
     option.

   * `--ssl-cert=FILE_NAME'

     The name of the SSL certificate file in PEM format to use for
     establishing a secure connection. This option implies `--ssl'.

   * `--ssl-cipher=CIPHER_LIST'

     A list of permissible ciphers to use for SSL encryption. If no
     cipher in the list is supported, SSL connections will not work.
     This option implies `--ssl'.

     For greatest portability, CIPHER_LIST should be a list of one or
     more cipher names, separated by colons. This format is understood
     both by OpenSSL and yaSSL. Examples:


          --ssl-cipher=AES128-SHA
          --ssl-cipher=DHE-RSA-AES256-SHA:AES128-SHA

     OpenSSL supports a more flexible syntax for specifying ciphers, as
     described in the OpenSSL documentation at
     `http://www.openssl.org/docs/apps/ciphers.html'.  However, yaSSL
     does not, so attempts to use that extended syntax fail for a MySQL
     distribution built with yaSSL.

     For OpenSSL, the supported ciphers may depend on which version
     your server is linked against. For example, the list might include
     these ciphers:


          AES256-GCM-SHA384
          AES256-SHA
          AES256-SHA256
          CAMELLIA256-SHA
          DES-CBC3-SHA
          DHE-DSS-AES256-GCM-SHA384
          DHE-DSS-AES256-SHA
          DHE-DSS-AES256-SHA256
          DHE-DSS-CAMELLIA256-SHA
          DHE-RSA-AES256-GCM-SHA384
          DHE-RSA-AES256-SHA
          DHE-RSA-AES256-SHA256
          DHE-RSA-CAMELLIA256-SHA
          ECDH-ECDSA-AES256-GCM-SHA384
          ECDH-ECDSA-AES256-SHA
          ECDH-ECDSA-AES256-SHA384
          ECDH-ECDSA-DES-CBC3-SHA
          ECDH-RSA-AES256-GCM-SHA384
          ECDH-RSA-AES256-SHA
          ECDH-RSA-AES256-SHA384
          ECDH-RSA-DES-CBC3-SHA
          ECDHE-ECDSA-AES128-GCM-SHA256
          ECDHE-ECDSA-AES128-SHA
          ECDHE-ECDSA-AES128-SHA256
          ECDHE-ECDSA-AES256-GCM-SHA384
          ECDHE-ECDSA-AES256-SHA
          ECDHE-ECDSA-AES256-SHA384
          ECDHE-ECDSA-DES-CBC3-SHA
          ECDHE-RSA-AES128-GCM-SHA256
          ECDHE-RSA-AES128-SHA
          ECDHE-RSA-AES128-SHA256
          ECDHE-RSA-AES256-GCM-SHA384
          ECDHE-RSA-AES256-SHA
          ECDHE-RSA-AES256-SHA384
          ECDHE-RSA-DES-CBC3-SHA
          EDH-DSS-DES-CBC3-SHA
          EDH-RSA-DES-CBC3-SHA
          PSK-3DES-EDE-CBC-SHA
          PSK-AES256-CBC-SHA
          SRP-DSS-3DES-EDE-CBC-SHA
          SRP-DSS-AES-128-CBC-SHA
          SRP-DSS-AES-256-CBC-SHA
          SRP-RSA-3DES-EDE-CBC-SHA
          SRP-RSA-AES-128-CBC-S
          SRP-RSA-AES-256-CBC-SHA

     yaSSL supports these ciphers:


          AES128-RMD
          AES128-SHA
          AES256-RMD
          AES256-SHA
          DES-CBC-SHA
          DES-CBC3-RMD
          DES-CBC3-SHA
          DHE-RSA-AES128-RMD
          DHE-RSA-AES128-SHA
          DHE-RSA-AES256-RMD
          DHE-RSA-AES256-SHA
          DHE-RSA-DES-CBC3-RMD
          EDH-RSA-DES-CBC-SHA
          EDH-RSA-DES-CBC3-SHA
          RC4-MD5
          RC4-SHA

     To verify exactly which ciphers a given server supports, check the
     value of the `Ssl_cipher_list' status variable using this query:


          SHOW STATUS LIKE 'Ssl_cipher_list';

   * `--ssl-key=FILE_NAME'

     The name of the SSL key file in PEM format to use for establishing
     a secure connection. This option implies `--ssl'.

     If the MySQL distribution was built using OpenSSL and the key file
     is protected by a passphrase, the program prompts the user for the
     passphrase. The password must be given interactively; it cannot be
     stored in a file. If the passphrase is incorrect, the program
     continues as if it could not read the key. If the MySQL
     distribution was built using yaSSL and the key file is protected
     by a passphrase, an error occurs.

   * `--ssl-verify-server-cert'

     This option is available for client programs only, not the server.
     It causes the client to check the server's Common Name value in
     the certificate that the server sends to the client. The client
     verifies that name against the host name the client uses for
     connecting to the server, and the connection fails if there is a
     mismatch. This feature can be used to prevent man-in-the-middle
     attacks. Verification is disabled by default. This option was
     added in MySQL 5.1.11.


File: manual.info,  Node: creating-ssl-certs,  Prev: ssl-options,  Up: ssl-connections

6.3.6.5 Setting Up SSL Certificates and Keys for MySQL
......................................................

This section demonstrates how to set up SSL certificate and key files
for use by MySQL servers and clients. The first example shows a
simplified procedure such as you might use from the command line. The
second shows a script that contains more detail. The first two examples
are intended for use on Unix and both use the `openssl' command that is
part of OpenSSL. The third example describes how to set up SSL files on
Windows.

*Important*:

Whatever method you use to generate the certificate and key files, the
Common Name value used for the server and client certificates/keys must
each differ from the Common Name value used for the CA certificate.
Otherwise, the certificate and key files will not work for servers
compiled using OpenSSL. A typical error in this case is:


     ERROR 2026 (HY000): SSL connection error:
     error:00000001:lib(0):func(0):reason(1)

*Example 1: Creating SSL Files from the Command Line on Unix*

The following example shows a set of commands to create MySQL server
and client certificate and key files. You will need to respond to
several prompts by the `openssl' commands. To generate test files, you
can press Enter to all prompts. To generate files for production use,
you should provide nonempty responses.


     # Create clean environment
     shell> rm -rf newcerts
     shell> mkdir newcerts && cd newcerts

     # Create CA certificate
     shell> openssl genrsa 2048 > ca-key.pem
     shell> openssl req -new -x509 -nodes -days 3600 \
              -key ca-key.pem -out ca-cert.pem

     # Create server certificate, remove passphrase, and sign it
     # server-cert.pem = public key, server-key.pem = private key
     shell> openssl req -newkey rsa:2048 -days 3600 \
              -nodes -keyout server-key.pem -out server-req.pem
     shell> openssl rsa -in server-key.pem -out server-key.pem
     shell> openssl x509 -req -in server-req.pem -days 3600 \
              -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out server-cert.pem

     # Create client certificate, remove passphrase, and sign it
     # client-cert.pem = public key, client-key.pem = private key
     shell> openssl req -newkey rsa:2048 -days 3600 \
              -nodes -keyout client-key.pem -out client-req.pem
     shell> openssl rsa -in client-key.pem -out client-key.pem
     shell> openssl x509 -req -in client-req.pem -days 3600 \
              -CA ca-cert.pem -CAkey ca-key.pem -set_serial 01 -out client-cert.pem

After generating the certificates, verify them:


     shell> openssl verify -CAfile ca-cert.pem server-cert.pem client-cert.pem
     server-cert.pem: OK
     client-cert.pem: OK

Now you have a set of files that can be used as follows:

   * `ca-cert.pem': Use this as the argument to `--ssl-ca' on the server
     and client sides. (The CA certificate, if used, must be the same
     on both sides.)

   * `server-cert.pem', `server-key.pem': Use these as the arguments to
     `--ssl-cert' and `--ssl-key' on the server side.

   * `client-cert.pem', `client-key.pem': Use these as the arguments to
     `--ssl-cert' and `--ssl-key' on the client side.

To use the files to test SSL connections, see *Note
using-ssl-connections::.

*Example 2: Creating SSL Files Using a Script on Unix*

Here is an example script that shows how to set up SSL certificate and
key files for MySQL. After executing the script, use the files to test
SSL connections as described in *Note using-ssl-connections::.


     DIR=`pwd`/openssl
     PRIV=$DIR/private

     mkdir $DIR $PRIV $DIR/newcerts
     cp /usr/share/ssl/openssl.cnf $DIR
     replace ./demoCA $DIR -- $DIR/openssl.cnf

     # Create necessary files: $database, $serial and $new_certs_dir
     # directory (optional)

     touch $DIR/index.txt
     echo "01" > $DIR/serial

     #
     # Generation of Certificate Authority(CA)
     #

     openssl req -new -x509 -keyout $PRIV/cakey.pem -out $DIR/ca-cert.pem \
         -days 3600 -config $DIR/openssl.cnf

     # Sample output:
     # Using configuration from /home/monty/openssl/openssl.cnf
     # Generating a 1024 bit RSA private key
     # ................++++++
     # .........++++++
     # writing new private key to '/home/monty/openssl/private/cakey.pem'
     # Enter PEM pass phrase:
     # Verifying password - Enter PEM pass phrase:
     # -----
     # You are about to be asked to enter information that will be
     # incorporated into your certificate request.
     # What you are about to enter is what is called a Distinguished Name
     # or a DN.
     # There are quite a few fields but you can leave some blank
     # For some fields there will be a default value,
     # If you enter '.', the field will be left blank.
     # -----
     # Country Name (2 letter code) [AU]:FI
     # State or Province Name (full name) [Some-State]:.
     # Locality Name (eg, city) []:
     # Organization Name (eg, company) [Internet Widgits Pty Ltd]:MySQL AB
     # Organizational Unit Name (eg, section) []:
     # Common Name (eg, YOUR name) []:MySQL admin
     # Email Address []:

     #
     # Create server request and key
     #
     openssl req -new -keyout $DIR/server-key.pem -out \
         $DIR/server-req.pem -days 3600 -config $DIR/openssl.cnf

     # Sample output:
     # Using configuration from /home/monty/openssl/openssl.cnf
     # Generating a 1024 bit RSA private key
     # ..++++++
     # ..........++++++
     # writing new private key to '/home/monty/openssl/server-key.pem'
     # Enter PEM pass phrase:
     # Verifying password - Enter PEM pass phrase:
     # -----
     # You are about to be asked to enter information that will be
     # incorporated into your certificate request.
     # What you are about to enter is what is called a Distinguished Name
     # or a DN.
     # There are quite a few fields but you can leave some blank
     # For some fields there will be a default value,
     # If you enter '.', the field will be left blank.
     # -----
     # Country Name (2 letter code) [AU]:FI
     # State or Province Name (full name) [Some-State]:.
     # Locality Name (eg, city) []:
     # Organization Name (eg, company) [Internet Widgits Pty Ltd]:MySQL AB
     # Organizational Unit Name (eg, section) []:
     # Common Name (eg, YOUR name) []:MySQL server
     # Email Address []:
     #
     # Please enter the following 'extra' attributes
     # to be sent with your certificate request
     # A challenge password []:
     # An optional company name []:

     #
     # Remove the passphrase from the key
     #
     openssl rsa -in $DIR/server-key.pem -out $DIR/server-key.pem

     #
     # Sign server cert
     #
     openssl ca -cert $DIR/ca-cert.pem -policy policy_anything \
         -out $DIR/server-cert.pem -config $DIR/openssl.cnf \
         -infiles $DIR/server-req.pem

     # Sample output:
     # Using configuration from /home/monty/openssl/openssl.cnf
     # Enter PEM pass phrase:
     # Check that the request matches the signature
     # Signature ok
     # The Subjects Distinguished Name is as follows
     # countryName           :PRINTABLE:'FI'
     # organizationName      :PRINTABLE:'MySQL AB'
     # commonName            :PRINTABLE:'MySQL admin'
     # Certificate is to be certified until Sep 13 14:22:46 2003 GMT
     # (365 days)
     # Sign the certificate? [y/n]:y
     #
     #
     # 1 out of 1 certificate requests certified, commit? [y/n]y
     # Write out database with 1 new entries
     # Data Base Updated

     #
     # Create client request and key
     #
     openssl req -new -keyout $DIR/client-key.pem -out \
         $DIR/client-req.pem -days 3600 -config $DIR/openssl.cnf

     # Sample output:
     # Using configuration from /home/monty/openssl/openssl.cnf
     # Generating a 1024 bit RSA private key
     # .....................................++++++
     # .............................................++++++
     # writing new private key to '/home/monty/openssl/client-key.pem'
     # Enter PEM pass phrase:
     # Verifying password - Enter PEM pass phrase:
     # -----
     # You are about to be asked to enter information that will be
     # incorporated into your certificate request.
     # What you are about to enter is what is called a Distinguished Name
     # or a DN.
     # There are quite a few fields but you can leave some blank
     # For some fields there will be a default value,
     # If you enter '.', the field will be left blank.
     # -----
     # Country Name (2 letter code) [AU]:FI
     # State or Province Name (full name) [Some-State]:.
     # Locality Name (eg, city) []:
     # Organization Name (eg, company) [Internet Widgits Pty Ltd]:MySQL AB
     # Organizational Unit Name (eg, section) []:
     # Common Name (eg, YOUR name) []:MySQL user
     # Email Address []:
     #
     # Please enter the following 'extra' attributes
     # to be sent with your certificate request
     # A challenge password []:
     # An optional company name []:

     #
     # Remove the passphrase from the key
     #
     openssl rsa -in $DIR/client-key.pem -out $DIR/client-key.pem

     #
     # Sign client cert
     #

     openssl ca -cert $DIR/ca-cert.pem -policy policy_anything \
         -out $DIR/client-cert.pem -config $DIR/openssl.cnf \
         -infiles $DIR/client-req.pem

     # Sample output:
     # Using configuration from /home/monty/openssl/openssl.cnf
     # Enter PEM pass phrase:
     # Check that the request matches the signature
     # Signature ok
     # The Subjects Distinguished Name is as follows
     # countryName           :PRINTABLE:'FI'
     # organizationName      :PRINTABLE:'MySQL AB'
     # commonName            :PRINTABLE:'MySQL user'
     # Certificate is to be certified until Sep 13 16:45:17 2003 GMT
     # (365 days)
     # Sign the certificate? [y/n]:y
     #
     #
     # 1 out of 1 certificate requests certified, commit? [y/n]y
     # Write out database with 1 new entries
     # Data Base Updated

     #
     # Create a my.cnf file that you can use to test the certificates
     #

     cat <<EOF > $DIR/my.cnf
     [client]
     ssl-ca=$DIR/ca-cert.pem
     ssl-cert=$DIR/client-cert.pem
     ssl-key=$DIR/client-key.pem
     [mysqld]
     ssl-ca=$DIR/ca-cert.pem
     ssl-cert=$DIR/server-cert.pem
     ssl-key=$DIR/server-key.pem
     EOF

*Example 3: Creating SSL Files on Windows*

Download OpenSSL for Windows if it is not installed on your system. An
overview of available packages can be seen here:


     `http://www.slproweb.com/products/Win32OpenSSL.html'

Choose the Win32 OpenSSL Light or Win64 OpenSSL Light package,
depending on your architecture (32-bit or 64-bit). The default
installation location will be `C:\OpenSSL-Win32' or `C:\OpenSSL-Win64',
depending on which package you downloaded. The following instructions
assume a default location of `C:\OpenSSL-Win32'. Modify this as
necessary if you are using the 64-bit package.

If a message occurs during setup indicating `'...critical component is
missing: Microsoft Visual C++ 2008 Redistributables'', cancel the setup
and download one of the following packages as well, again depending on
your architecture (32-bit or 64-bit):

   * Visual C++ 2008 Redistributables (x86), available at:


          `http://www.microsoft.com/downloads/details.aspx?familyid=9B2DA534-3E03-4391-8A4D-074B9F2BC1BF'

   * Visual C++ 2008 Redistributables (x64), available at:


          `http://www.microsoft.com/downloads/details.aspx?familyid=bd2a6171-e2d6-4230-b809-9a8d7548c1b6'

After installing the additional package, restart the OpenSSL setup
procedure.

During installation, leave the default `C:\OpenSSL-Win32' as the
install path, and also leave the default option `'Copy OpenSSL DLL files
to the Windows system directory'' selected.

When the installation has finished, add `C:\OpenSSL-Win32\bin' to the
Windows System Path variable of your server:

  1. On the Windows desktop, right-click the `My Computer' icon, and
     select `Properties'.

  2. Select the `Advanced' tab from the `System Properties' menu that
     appears, and click the `Environment Variables' button.

  3. Under `System Variables', select `Path', then click the `Edit'
     button. The `Edit System Variable' dialogue should appear.

  4. Add `';C:\OpenSSL-Win32\bin'' to the end (notice the semicolon).

  5. Press OK 3 times.

  6. Check that OpenSSL was correctly integrated into the Path variable
     by opening a new command console (`Start>Run>cmd.exe') and
     verifying that OpenSSL is available:


          Microsoft Windows [Version ...]
          Copyright (c) 2006 Microsoft Corporation. All rights reserved.

          C:\Windows\system32>cd \

          C:\>openssl
          OpenSSL> exit <<< If you see the OpenSSL prompt, installation was successful.

          C:\>

Depending on your version of Windows, the preceding path-setting
instructions might differ slightly.

After OpenSSL has been installed, use instructions similar to those
from Example 1 (shown earlier in this section), with the following
changes:

   * Change the following Unix commands:


          # Create clean environment
          shell> rm -rf newcerts
          shell> mkdir newcerts && cd newcerts

     On Windows, use these commands instead:


          # Create clean environment
          shell> md c:\newcerts
          shell> cd c:\newcerts

   * When a `'\'' character is shown at the end of a command line, this
     `'\'' character must be removed and the command lines entered all
     on a single line.

After generating the certificate and key files, to use them to test SSL
connections, see *Note using-ssl-connections::.


File: manual.info,  Node: windows-and-ssh,  Next: account-activity-auditing,  Prev: ssl-connections,  Up: user-account-management

6.3.7 Connecting to MySQL Remotely from Windows with SSH
--------------------------------------------------------

This section describes how to get a secure connection to a remote MySQL
server with SSH. The information was provided by David Carlson
<dcarlson@mplcomm.com>.

  1. Install an SSH client on your Windows machine. For a comparison of
     SSH clients, see
     `http://en.wikipedia.org/wiki/Comparison_of_SSH_clients'.

  2. Start your Windows SSH client. Set `Host_Name =
     YOURMYSQLSERVER_URL_OR_IP'.  Set `userid=YOUR_USERID' to log in to
     your server. This `userid' value might not be the same as the user
     name of your MySQL account.

  3. Set up port forwarding. Either do a remote forward (Set
     `local_port: 3306', `remote_host: YOURMYSQLSERVERNAME_OR_IP',
     `remote_port: 3306' ) or a local forward (Set `port: 3306', `host:
     localhost', `remote port: 3306').

  4. Save everything, otherwise you will have to redo it the next time.

  5. Log in to your server with the SSH session you just created.

  6. On your Windows machine, start some ODBC application (such as
     Access).

  7. Create a new file in Windows and link to MySQL using the ODBC
     driver the same way you normally do, except type in `localhost'
     for the MySQL host server, not YOURMYSQLSERVERNAME.

At this point, you should have an ODBC connection to MySQL, encrypted
using SSH.


File: manual.info,  Node: account-activity-auditing,  Prev: windows-and-ssh,  Up: user-account-management

6.3.8 SQL-Based MySQL Account Activity Auditing
-----------------------------------------------

Applications can use the following guidelines to perform SQL-based
auditing that ties database activity to MySQL accounts.

MySQL accounts correspond to rows in the `mysql.user' table. When a
client connects successfully, the server authenticates the client to a
particular row in this table. The `User' and `Host' column values in
this row uniquely identify the account and correspond to the
`'USER_NAME'@'HOST_NAME'' format in which account names are written in
SQL statements.

The account used to authenticate a client determines which privileges
the client has. Normally, the `CURRENT_USER()' function can be invoked
to determine which account this is for the client user.  Its value is
constructed from the `User' and `Host' columns of the `user' table row
for the account.

However, there are circumstances under which the `CURRENT_USER()' value
corresponds not to the client user but to a different account. This
occurs in contexts when privilege checking is not based the client's
account:

   * Stored routines (procedures and functions) defined with the `SQL
     SECURITY DEFINER' characteristic

   * Views defined with the `SQL SECURITY DEFINER' characteristic (as
     of MySQL 5.1.12)

   * Triggers and events

In those contexts, privilege checking is done against the `DEFINER'
account and `CURRENT_USER()' refers to that account, not to the account
for the client who invoked the stored routine or view or who caused the
trigger to activate. To determine the invoking user, you can call the
`USER()' function, which returns a value indicating the actual user
name provided by the client and the host from which the client
connected. However, this value does not necessarily correspond directly
to an account in the `user' table, because the `USER()' value never
contains wildcards, whereas account values (as returned by
`CURRENT_USER()') may contain user name and host name wildcards.

For example, a blank user name matches any user, so an account of
`''@'localhost'' enables clients to connect as an anonymous user from
the local host with any user name. If this case, if a client connects
as `user1' from the local host, `USER()' and `CURRENT_USER()' return
different values:


     mysql> SELECT USER(), CURRENT_USER();
     +-----------------+----------------+
     | USER()          | CURRENT_USER() |
     +-----------------+----------------+
     | user1@localhost | @localhost     |
     +-----------------+----------------+

The host name part of an account can contain wildcards, too. If the
host name contains a `'%'' or `'_'' pattern character or uses netmask
notation, the account can be used for clients connecting from multiple
hosts and the `CURRENT_USER()' value will not indicate which one. For
example, the account `'user2'@'%.example.com'' can be used by `user2'
to connect from any host in the `example.com' domain. If `user2'
connects from `remote.example.com', `USER()' and `CURRENT_USER()'
return different values:


     mysql> SELECT USER(), CURRENT_USER();
     +--------------------------+---------------------+
     | USER()                   | CURRENT_USER()      |
     +--------------------------+---------------------+
     | user2@remote.example.com | user2@%.example.com |
     +--------------------------+---------------------+

If an application must invoke `USER()' for user auditing (for example,
if it does auditing from within triggers) but must also be able to
associate the `USER()' value with an account in the `user' table, it is
necessary to avoid accounts that contain wildcards in the `User' or
`Host' column.  Specifically, do not permit `User' to be empty (which
creates an anonymous-user account), and do not permit pattern
characters or netmask notation in `Host' values. All accounts must have
a nonempty `User' value and literal `Host' value.

With respect to the previous examples, the `''@'localhost'' and
`'user2'@'%.example.com'' accounts should be changed not to use
wildcards:


     RENAME USER ''@'localhost' TO 'user1'@'localhost';
     RENAME USER 'user2'@'%.example.com' TO 'user2'@'remote.example.com';

If `user2' must be able to connect from several hosts in the
`example.com' domain, there should be a separate account for each host.

To extract the user name or host name part from a `CURRENT_USER()' or
`USER()' value, use the `SUBSTRING_INDEX()' function:


     mysql> SELECT SUBSTRING_INDEX(CURRENT_USER(),'@',1);
     +---------------------------------------+
     | SUBSTRING_INDEX(CURRENT_USER(),'@',1) |
     +---------------------------------------+
     | user1                                 |
     +---------------------------------------+

     mysql> SELECT SUBSTRING_INDEX(CURRENT_USER(),'@',-1);
     +----------------------------------------+
     | SUBSTRING_INDEX(CURRENT_USER(),'@',-1) |
     +----------------------------------------+
     | localhost                              |
     +----------------------------------------+


File: manual.info,  Node: backup-and-recovery,  Next: optimization,  Prev: security,  Up: Top

7 Backup and Recovery
*********************

* Menu:

* backup-types::                 Backup and Recovery Types
* backup-methods::               Database Backup Methods
* backup-strategy-example::      Example Backup and Recovery Strategy
* using-mysqldump::              Using mysqldump for Backups
* point-in-time-recovery::       Point-in-Time (Incremental) Recovery Using the Binary Log
* myisam-table-maintenance::     MyISAM Table Maintenance and Crash Recovery

It is important to back up your databases so that you can recover your
data and be up and running again in case problems occur, such as system
crashes, hardware failures, or users deleting data by mistake. Backups
are also essential as a safeguard before upgrading a MySQL
installation, and they can be used to transfer a MySQL installation to
another system or to set up replication slave servers.

MySQL offers a variety of backup strategies from which you can choose
the methods that best suit the requirements for your installation. This
chapter discusses several backup and recovery topics with which you
should be familiar:

   * Types of backups: Logical versus physical, full versus
     incremental, and so forth.

   * Methods for creating backups.

   * Recovery methods, including point-in-time recovery.

   * Backup scheduling, compression, and encryption.

   * Table maintenance, to enable recovery of corrupt tables.

*Additional Resources*

Resources related to backup or to maintaining data availability include
the following:

   * Customers of MySQL Enterprise Edition can use the MySQL Enterprise
     Backup product for backups. For an overview of the MySQL
     Enterprise Backup product, see *Note mysql-enterprise-backup::.

   * A forum dedicated to backup issues is available at
     `http://forums.mysql.com/list.php?28'.

   * Details for *Note `mysqldump': mysqldump, *Note `mysqlhotcopy':
     mysqlhotcopy, and other MySQL backup programs can be found in
     *Note programs::.

   * The syntax of the SQL statements described here is given in *Note
     sql-syntax::.

   * For additional information about `InnoDB' backup procedures, see
     *Note innodb-backup::.

   * Replication enables you to maintain identical data on multiple
     servers. This has several benefits, such as enabling client query
     load to be distributed over servers, availability of data even if
     a given server is taken offline or fails, and the ability to make
     backups with no impact on the master by using a slave server. See
     *Note replication::.

   * MySQL Cluster provides a high-availability, high-redundancy
     version of MySQL adapted for the distributed computing
     environment. See *Note mysql-cluster::. For information
     specifically about MySQL Cluster backup, see *Note
     mysql-cluster-backup::.

   * Distributed Replicated Block Device (DRBD) is another
     high-availability solution. It works by replicating a block device
     from a primary server to a secondary server at the block level.
     See *Note ha-overview::


File: manual.info,  Node: backup-types,  Next: backup-methods,  Prev: backup-and-recovery,  Up: backup-and-recovery

7.1 Backup and Recovery Types
=============================

This section describes the characteristics of different types of
backups.

*Physical (Raw) Versus Logical Backups*

Physical backups consist of raw copies of the directories and files
that store database contents. This type of backup is suitable for
large, important databases that need to be recovered quickly when
problems occur.

Logical backups save information represented as logical database
structure (*Note `CREATE DATABASE': create-database, *Note `CREATE
TABLE': create-table. statements) and content (*Note `INSERT': insert.
statements or delimited-text files). This type of backup is suitable
for smaller amounts of data where you might edit the data values or
table structure, or recreate the data on a different machine
architecture.

Logical backup methods have these characteristics:

   * The backup is done by querying the MySQL server to obtain database
     structure and content information.

   * Backup is slower than physical methods because the server must
     access database information and convert it to logical format.  If
     the output is written on the client side, the server must also
     send it to the backup program.

   * Output is larger than for physical backup, particularly when saved
     in text format.

   * Backup and restore granularity is available at the server level
     (all databases), database level (all tables in a particular
     database), or table level. This is true regardless of storage
     engine.

   * The backup does not include log or configuration files, or other
     database-related files that are not part of databases.

   * Backups stored in logical format are machine independent and
     highly portable.

   * Logical backups are performed with the MySQL server running.  The
     server is not taken offline.

   * Logical backup tools include the *Note `mysqldump': mysqldump.
     program and the *Note `SELECT ... INTO OUTFILE': select.
     statement. These work for any storage engine, even `MEMORY'.

   * To restore logical backups, SQL-format dump files can be processed
     using the *Note `mysql': mysql. client. To load delimited-text
     files, use the *Note `LOAD DATA INFILE': load-data. statement or
     the *Note `mysqlimport': mysqlimport. client.

Physical backup methods have these characteristics:

   * The backup consists of exact copies of database directories and
     files. Typically this is a copy of all or part of the MySQL data
     directory. Data from `MEMORY' tables cannot be backed up this way
     because their contents are not stored on disk.

   * Physical backup methods are faster than logical because they
     involve only file copying without conversion.

   * Output is more compact than for logical backup.

   * Backup and restore granularity ranges from the level of the entire
     data directory down to the level of individual files.  This may or
     may not provide for table-level granularity, depending on storage
     engine. (Each `MyISAM' table corresponds uniquely to a set of
     files, but an `InnoDB' table shares file storage with other
     `InnoDB' tables.)

   * In addition to databases, the backup can include any related files
     such as log or configuration files.

   * Backups are portable only to other machines that have identical or
     similar hardware characteristics.

   * Backups can be performed while the MySQL server is not running. If
     the server is running, it is necessary to perform appropriate
     locking so that the server does not change database contents
     during the backup.

   * Physical backup tools include file system-level commands (such as
     `cp', `scp', `tar', `rsync'), *Note `mysqlhotcopy': mysqlhotcopy.
     for `MyISAM' tables, `ibbackup' for `InnoDB' tables, or `START
     BACKUP' for *Note `NDB': mysql-cluster. tables.

   * For restore, files copied at the file system level or with *Note
     `mysqlhotcopy': mysqlhotcopy. can be copied back to their original
     locations with file system commands; `ibbackup' restores `InnoDB'
     tables, and *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. restores *Note `NDB':
     mysql-cluster. tables.

*Online Versus Offline Backups*

Online backups take place while the MySQL server is running so that the
database information can be obtained from the server.  Offline backups
take place while the server is stopped. This distinction can also be
described as `hot' versus `cold' backups; a `warm' backup is one where
the server remains running but locked against modifying data while you
access database files externally.

Online backup methods have these characteristics:

   * The backup is less intrusive to other clients, which can connect
     to the MySQL server during the backup and may be able to access
     data depending on what operations they need to perform.

   * Care must be taken to impose appropriate locking so that data
     modifications do not take place that would compromise backup
     integrity. The MySQL Enterprise Backup product does such locking
     automatically.

Offline backup methods have these characteristics:

   * Clients can be affected adversely because the server is
     unavailable during backup. For that reason, such backups are often
     taken from a replication slave server that can be taken offline
     without harming availability.

   * The backup procedure is simpler because there is no possibility of
     interference from client activity.

A similar distinction between online and offline applies for recovery
operations, and similar characteristics apply. However, it is more
likely that clients will be affected for online recovery than for
online backup because recovery requires stronger locking. During
backup, clients might be able to read data while it is being backed up.
Recovery modifies data and does not just read it, so clients must be
prevented from accessing data while it is being restored.

*Local Versus Remote Backups*

A local backup is performed on the same host where the MySQL server
runs, whereas a remote backup is done from a different host. For some
types of backups, the backup can be initiated from a remote host even
if the output is written locally on the server.  host.

   * *Note `mysqldump': mysqldump. can connect to local or remote
     servers. For SQL output (`CREATE' and *Note `INSERT': insert.
     statements), local or remote dumps can be done and generate output
     on the client.  For delimited-text output (with the `--tab'
     option), data files are created on the server host.

   * *Note `mysqlhotcopy': mysqlhotcopy. performs only local backups:
     It connects to the server to lock it against data modifications
     and then copies local table files.

   * *Note `SELECT ... INTO OUTFILE': select-into. can be initiated
     from a local or remote client host, but the output file is created
     on the server host.

   * Physical backup methods typically are initiated locally on the
     MySQL server host so that the server can be taken offline,
     although the destination for copied files might be remote.

*Snapshot Backups*

Some file system implementations enable `snapshots' to be taken. These
provide logical copies of the file system at a given point in time,
without requiring a physical copy of the entire file system. (For
example, the implementation may use copy-on-write techniques so that
only parts of the file system modified after the snapshot time need be
copied.) MySQL itself does not provide the capability for taking file
system snapshots.  It is available through third-party solutions such
as Veritas, LVM, or ZFS.

*Full Versus Incremental Backups*

A full backup includes all data managed by a MySQL server at a given
point in time. An incremental backup consists of the changes made to
the data during a given time span (from one point in time to another).
MySQL has different ways to perform full backups, such as those
described earlier in this section. Incremental backups are made
possible by enabling the server's binary log, which the server uses to
record data changes.

*Full Versus Point-in-Time (Incremental) Recovery*

A full recovery restores all data from a full backup. This restores the
server instance to the state that it had when the backup was made. If
that state is not sufficiently current, a full recovery can be followed
by recovery of incremental backups made since the full backup, to bring
the server to a more up-to-date state.

Incremental recovery is recovery of changes made during a given time
span. This is also called point-in-time recovery because it makes a
server's state current up to a given time. Point-in-time recovery is
based on the binary log and typically follows a full recovery from the
backup files that restores the server to its state when the backup was
made. Then the data changes written in the binary log files are applied
as incremental recovery to redo data modifications and bring the server
up to the desired point in time.

*Table Maintenance*

Data integrity can be compromised if tables become corrupt. For *Note
`InnoDB': innodb-storage-engine. tables, this is not a typical issue.
For programs to check *Note `MyISAM': myisam-storage-engine.  tables
and repair them if problems are found, see *Note
myisam-table-maintenance::.

*Backup Scheduling, Compression, and Encryption*

Backup scheduling is valuable for automating backup procedures.
Compression of backup output reduces space requirements, and encryption
of the output provides better security against unauthorized access of
backed-up data. MySQL itself does not provide these capabilities. The
MySQL Enterprise Backup product can compress `InnoDB' backups, and
compression or encryption of backup output can be achieved using file
system utilities. Other third-party solutions may be available.


File: manual.info,  Node: backup-methods,  Next: backup-strategy-example,  Prev: backup-types,  Up: backup-and-recovery

7.2 Database Backup Methods
===========================

This section summarizes some general methods for making backups.

*Making a Hot Backup with MySQL Enterprise Backup*

Customers of MySQL Enterprise Edition can use the MySQL Enterprise
Backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_mysql_enterprise_backup)
product to do physical
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_physical)
backups of entire instances or selected databases, tables, or both.
This product includes features for incremental
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_incremental_backup)
and compressed
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_compressed_backup)
backups.  Backing up the physical database files makes restore much
faster than logical techniques such as the `mysqldump' command.
`InnoDB' tables are copied using a hot backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_hot_backup)
mechanism.  (Ideally, the `InnoDB' tables should represent a
substantial majority of the data.) Tables from other storage engines
are copied using a warm backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_warm_backup)
mechanism. For an overview of the MySQL Enterprise Backup product, see
*Note mysql-enterprise-backup::.

*Making Backups with mysqldump or mysqlhotcopy*

The *Note `mysqldump': mysqldump. program and the *Note `mysqlhotcopy':
mysqlhotcopy. script can make backups.  *Note `mysqldump': mysqldump.
is more general because it can back up all kinds of tables. *Note
`mysqlhotcopy': mysqlhotcopy. works only with some storage engines.
(See *Note using-mysqldump::, and *Note mysqlhotcopy::.)

For `InnoDB' tables, it is possible to perform an online backup that
takes no locks on tables using the `--single-transaction' option to
*Note `mysqldump': mysqldump. See *Note backup-policy::.

*Making Backups by Copying Table Files*

For storage engines that represent each table using its own files,
tables can be backed up by copying those files. For example, `MyISAM'
tables are stored as files, so it is easy to do a backup by copying
files (`*.frm', `*.MYD', and `*.MYI' files).  To get a consistent
backup, stop the server or lock and flush the relevant tables:


     LOCK TABLES TBL_LIST READ;
     FLUSH TABLES TBL_LIST;

You need only a read lock; this enables other clients to continue to
query the tables while you are making a copy of the files in the
database directory. The *Note `FLUSH TABLES': flush.  statement is
needed to ensure that the all active index pages are written to disk
before you start the backup. See *Note lock-tables::, and *Note flush::.

You can also create a binary backup simply by copying all table files,
as long as the server isn't updating anything. The *Note
`mysqlhotcopy': mysqlhotcopy. script uses this method. (But note that
table file copying methods do not work if your database contains
`InnoDB' tables.  *Note `mysqlhotcopy': mysqlhotcopy. does not work for
`InnoDB' tables because `InnoDB' does not necessarily store table
contents in database directories.  Also, even if the server is not
actively updating data, `InnoDB' may still have modified data cached in
memory and not flushed to disk.)

*Making Delimited-Text File Backups*

To create a text file containing a table's data, you can use *Note
`SELECT * INTO OUTFILE 'FILE_NAME' FROM TBL_NAME': select-into. The
file is created on the MySQL server host, not the client host. For this
statement, the output file cannot already exist because permitting
files to be overwritten constitutes a security risk. See *Note
select::. This method works for any kind of data file, but saves only
table data, not the table structure.

Another way to create text data files (along with files containing
*Note `CREATE TABLE': create-table. statements for the backed up
tables) is to use *Note `mysqldump': mysqldump. with the `--tab'
option. See *Note mysqldump-delimited-text::.

To reload a delimited-text data file, use *Note `LOAD DATA INFILE':
load-data. or *Note `mysqlimport': mysqlimport.

*Making Incremental Backups by Enabling the Binary Log*

MySQL supports incremental backups: You must start the server with the
`--log-bin' option to enable binary logging; see *Note binary-log::.
The binary log files provide you with the information you need to
replicate changes to the database that are made subsequent to the point
at which you performed a backup. At the moment you want to make an
incremental backup (containing all changes that happened since the last
full or incremental backup), you should rotate the binary log by using
*Note `FLUSH LOGS': flush. This done, you need to copy to the backup
location all binary logs which range from the one of the moment of the
last full or incremental backup to the last but one. These binary logs
are the incremental backup; at restore time, you apply them as
explained in *Note point-in-time-recovery::. The next time you do a
full backup, you should also rotate the binary log using *Note `FLUSH
LOGS': flush, *Note `mysqldump --flush-logs': mysqldump, or *Note
`mysqlhotcopy --flushlog': mysqlhotcopy. See *Note mysqldump::, and
*Note mysqlhotcopy::.

*Making Backups Using Replication Slaves*

If you have performance problems with your master server while making
backups, one strategy that can help is to set up replication and
perform backups on the slave rather than on the master. See *Note
replication-solutions-backups::.

If you are backing up a slave replication server, you should back up
its `master.info' and `relay-log.info' files when you back up the
slave's databases, regardless of the backup method you choose.  These
information files are always needed to resume replication after you
restore the slave's data. If your slave is replicating *Note `LOAD DATA
INFILE': load-data. statements, you should also back up any
`SQL_LOAD-*' files that exist in the directory that the slave uses for
this purpose. The slave needs these files to resume replication of any
interrupted *Note `LOAD DATA INFILE': load-data. operations. The
location of this directory is the value of the `--slave-load-tmpdir'
option. If the server was not started with that option, the directory
location is the value of the `tmpdir' system variable.

*Recovering Corrupt Tables*

If you have to restore `MyISAM' tables that have become corrupt, try to
recover them using *Note `REPAIR TABLE': repair-table. or *Note
`myisamchk -r': myisamchk. first. That should work in 99.9% of all
cases. If *Note `myisamchk': myisamchk. fails, see *Note
myisam-table-maintenance::.

*Making Backups Using a File System Snapshot*

If you are using a Veritas file system, you can make a backup like this:

  1. From a client program, execute *Note `FLUSH TABLES WITH READ
     LOCK': flush.

  2. From another shell, execute `mount vxfs snapshot'.

  3. From the first client, execute *Note `UNLOCK TABLES': lock-tables.

  4. Copy files from the snapshot.

  5. Unmount the snapshot.

Similar snapshot capabilities may be available in other file systems,
such as LVM or ZFS.


File: manual.info,  Node: backup-strategy-example,  Next: using-mysqldump,  Prev: backup-methods,  Up: backup-and-recovery

7.3 Example Backup and Recovery Strategy
========================================

* Menu:

* backup-policy::                Establishing a Backup Policy
* recovery-from-backups::        Using Backups for Recovery
* backup-strategy-summary::      Backup Strategy Summary

This section discusses a procedure for performing backups that enables
you to recover data after several types of crashes:

   * Operating system crash

   * Power failure

   * File system crash

   * Hardware problem (hard drive, motherboard, and so forth)

The example commands do not include options such as `--user' and
`--password' for the *Note `mysqldump': mysqldump. and *Note `mysql':
mysql. client programs. You should include such options as necessary to
enable client programs to connect to the MySQL server.

Assume that data is stored in the `InnoDB' storage engine, which has
support for transactions and automatic crash recovery. Assume also that
the MySQL server is under load at the time of the crash. If it were
not, no recovery would ever be needed.

For cases of operating system crashes or power failures, we can assume
that MySQL's disk data is available after a restart. The `InnoDB' data
files might not contain consistent data due to the crash, but `InnoDB'
reads its logs and finds in them the list of pending committed and
noncommitted transactions that have not been flushed to the data files.
`InnoDB' automatically rolls back those transactions that were not
committed, and flushes to its data files those that were committed.
Information about this recovery process is conveyed to the user through
the MySQL error log. The following is an example log excerpt:


     InnoDB: Database was not shut down normally.
     InnoDB: Starting recovery from log files...
     InnoDB: Starting log scan based on checkpoint at
     InnoDB: log sequence number 0 13674004
     InnoDB: Doing recovery: scanned up to log sequence number 0 13739520
     InnoDB: Doing recovery: scanned up to log sequence number 0 13805056
     InnoDB: Doing recovery: scanned up to log sequence number 0 13870592
     InnoDB: Doing recovery: scanned up to log sequence number 0 13936128
     ...
     InnoDB: Doing recovery: scanned up to log sequence number 0 20555264
     InnoDB: Doing recovery: scanned up to log sequence number 0 20620800
     InnoDB: Doing recovery: scanned up to log sequence number 0 20664692
     InnoDB: 1 uncommitted transaction(s) which must be rolled back
     InnoDB: Starting rollback of uncommitted transactions
     InnoDB: Rolling back trx no 16745
     InnoDB: Rolling back of trx no 16745 completed
     InnoDB: Rollback of uncommitted transactions completed
     InnoDB: Starting an apply batch of log records to the database...
     InnoDB: Apply batch completed
     InnoDB: Started
     mysqld: ready for connections

For the cases of file system crashes or hardware problems, we can
assume that the MySQL disk data is _not_ available after a restart.
This means that MySQL fails to start successfully because some blocks
of disk data are no longer readable. In this case, it is necessary to
reformat the disk, install a new one, or otherwise correct the
underlying problem.  Then it is necessary to recover our MySQL data
from backups, which means that backups must already have been made. To
make sure that is the case, design and implement a backup policy.


File: manual.info,  Node: backup-policy,  Next: recovery-from-backups,  Prev: backup-strategy-example,  Up: backup-strategy-example

7.3.1 Establishing a Backup Policy
----------------------------------

To be useful, backups must be scheduled regularly. A full backup (a
snapshot of the data at a point in time) can be done in MySQL with
several tools. For example, *Note MySQL Enterprise Backup:
mysql-enterprise-backup. can perform a physical backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_physical_backup)
of an entire instance, with optimizations to minimize overhead and
avoid disruption when backing up `InnoDB' data files; *Note
`mysqldump': mysqldump. provides online logical backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_logical_backup).
This discussion uses *Note `mysqldump': mysqldump.

Assume that we make a full backup of all our `InnoDB' tables in all
databases using the following command on Sunday at 1 p.m., when load is
low:


     shell> mysqldump --single-transaction --all-databases > backup_sunday_1_PM.sql

The resulting `.sql' file produced by *Note `mysqldump': mysqldump.
contains a set of SQL *Note `INSERT': insert. statements that can be
used to reload the dumped tables at a later time.

This backup operation acquires a global read lock on all tables at the
beginning of the dump (using *Note `FLUSH TABLES WITH READ LOCK':
flush.). As soon as this lock has been acquired, the binary log
coordinates are read and the lock is released. If long updating
statements are running when the *Note `FLUSH': flush. statement is
issued, the backup operation may stall until those statements finish.
After that, the dump becomes lock-free and does not disturb reads and
writes on the tables.

It was assumed earlier that the tables to back up are `InnoDB' tables,
so `--single-transaction' uses a consistent read and guarantees that
data seen by *Note `mysqldump': mysqldump. does not change. (Changes
made by other clients to `InnoDB' tables are not seen by the *Note
`mysqldump': mysqldump. process.) If the backup operation includes
nontransactional tables, consistency requires that they do not change
during the backup. For example, for the `MyISAM' tables in the `mysql'
database, there must be no administrative changes to MySQL accounts
during the backup.

Full backups are necessary, but it is not always convenient to create
them. They produce large backup files and take time to generate. They
are not optimal in the sense that each successive full backup includes
all data, even that part that has not changed since the previous full
backup. It is more efficient to make an initial full backup, and then
to make incremental backups. The incremental backups are smaller and
take less time to produce. The tradeoff is that, at recovery time, you
cannot restore your data just by reloading the full backup. You must
also process the incremental backups to recover the incremental changes.

To make incremental backups, we need to save the incremental changes.
In MySQL, these changes are represented in the binary log, so the MySQL
server should always be started with the `--log-bin' option to enable
that log. With binary logging enabled, the server writes each data
change into a file while it updates data. Looking at the data directory
of a MySQL server that was started with the `--log-bin' option and that
has been running for some days, we find these MySQL binary log files:


     -rw-rw---- 1 guilhem  guilhem   1277324 Nov 10 23:59 gbichot2-bin.000001
     -rw-rw---- 1 guilhem  guilhem         4 Nov 10 23:59 gbichot2-bin.000002
     -rw-rw---- 1 guilhem  guilhem        79 Nov 11 11:06 gbichot2-bin.000003
     -rw-rw---- 1 guilhem  guilhem       508 Nov 11 11:08 gbichot2-bin.000004
     -rw-rw---- 1 guilhem  guilhem 220047446 Nov 12 16:47 gbichot2-bin.000005
     -rw-rw---- 1 guilhem  guilhem    998412 Nov 14 10:08 gbichot2-bin.000006
     -rw-rw---- 1 guilhem  guilhem       361 Nov 14 10:07 gbichot2-bin.index

Each time it restarts, the MySQL server creates a new binary log file
using the next number in the sequence. While the server is running, you
can also tell it to close the current binary log file and begin a new
one manually by issuing a *Note `FLUSH LOGS': flush. SQL statement or
with a *Note `mysqladmin flush-logs': mysqladmin.  command. *Note
`mysqldump': mysqldump. also has an option to flush the logs. The
`.index' file in the data directory contains the list of all MySQL
binary logs in the directory.

The MySQL binary logs are important for recovery because they form the
set of incremental backups. If you make sure to flush the logs when you
make your full backup, the binary log files created afterward contain
all the data changes made since the backup. Let's modify the previous
*Note `mysqldump': mysqldump.  command a bit so that it flushes the
MySQL binary logs at the moment of the full backup, and so that the
dump file contains the name of the new current binary log:


     shell> mysqldump --single-transaction --flush-logs --master-data=2 \
              --all-databases > backup_sunday_1_PM.sql

After executing this command, the data directory contains a new binary
log file, `gbichot2-bin.000007', because the `--flush-logs' option
causes the server to flush its logs. The `--master-data' option causes
*Note `mysqldump': mysqldump. to write binary log information to its
output, so the resulting `.sql' dump file includes these lines:


     -- Position to start replication or point-in-time recovery from
     -- CHANGE MASTER TO MASTER_LOG_FILE='gbichot2-bin.000007',MASTER_LOG_POS=4;

Because the *Note `mysqldump': mysqldump. command made a full backup,
those lines mean two things:

   * The dump file contains all changes made before any changes written
     to the `gbichot2-bin.000007' binary log file or newer.

   * All data changes logged after the backup are not present in the
     dump file, but are present in the `gbichot2-bin.000007' binary log
     file or newer.

On Monday at 1 p.m., we can create an incremental backup by flushing
the logs to begin a new binary log file. For example, executing a *Note
`mysqladmin flush-logs': mysqladmin. command creates
`gbichot2-bin.000008'. All changes between the Sunday 1 p.m. full
backup and Monday 1 p.m. will be in the `gbichot2-bin.000007' file. This
incremental backup is important, so it is a good idea to copy it to a
safe place. (For example, back it up on tape or DVD, or copy it to
another machine.) On Tuesday at 1 p.m., execute another *Note
`mysqladmin flush-logs': mysqladmin. command. All changes between
Monday 1 p.m. and Tuesday 1 p.m. will be in the `gbichot2-bin.000008'
file (which also should be copied somewhere safe).

The MySQL binary logs take up disk space. To free up space, purge them
from time to time. One way to do this is by deleting the binary logs
that are no longer needed, such as when we make a full backup:


     shell> mysqldump --single-transaction --flush-logs --master-data=2 \
              --all-databases --delete-master-logs > backup_sunday_1_PM.sql

*Note*:

Deleting the MySQL binary logs with *Note `mysqldump
--delete-master-logs': mysqldump. can be dangerous if your server is a
replication master server, because slave servers might not yet fully
have processed the contents of the binary log.  The description for the
*Note `PURGE BINARY LOGS': purge-binary-logs. statement explains what
should be verified before deleting the MySQL binary logs. See *Note
purge-binary-logs::.


File: manual.info,  Node: recovery-from-backups,  Next: backup-strategy-summary,  Prev: backup-policy,  Up: backup-strategy-example

7.3.2 Using Backups for Recovery
--------------------------------

Now, suppose that we have a catastrophic crash on Wednesday at 8 a.m.
that requires recovery from backups. To recover, first we restore the
last full backup we have (the one from Sunday 1 p.m.). The full backup
file is just a set of SQL statements, so restoring it is very easy:


     shell> mysql < backup_sunday_1_PM.sql

At this point, the data is restored to its state as of Sunday 1 p.m..
To restore the changes made since then, we must use the incremental
backups; that is, the `gbichot2-bin.000007' and `gbichot2-bin.000008'
binary log files. Fetch the files if necessary from where they were
backed up, and then process their contents like this:


     shell> mysqlbinlog gbichot2-bin.000007 gbichot2-bin.000008 | mysql

We now have recovered the data to its state as of Tuesday 1 p.m., but
still are missing the changes from that date to the date of the crash.
To not lose them, we would have needed to have the MySQL server store
its MySQL binary logs into a safe location (RAID disks, SAN, ...)
different from the place where it stores its data files, so that these
logs were not on the destroyed disk. (That is, we can start the server
with a `--log-bin' option that specifies a location on a different
physical device from the one on which the data directory resides. That
way, the logs are safe even if the device containing the directory is
lost.) If we had done this, we would have the `gbichot2-bin.000009'
file (and any subsequent files) at hand, and we could apply them using
*Note `mysqlbinlog': mysqlbinlog. and *Note `mysql': mysql. to restore
the most recent data changes with no loss up to the moment of the crash:


     shell> mysqlbinlog gbichot2-bin.000009 ... | mysql

For more information about using *Note `mysqlbinlog': mysqlbinlog.  to
process binary log files, see *Note point-in-time-recovery::.


File: manual.info,  Node: backup-strategy-summary,  Prev: recovery-from-backups,  Up: backup-strategy-example

7.3.3 Backup Strategy Summary
-----------------------------

In case of an operating system crash or power failure, `InnoDB' itself
does all the job of recovering data. But to make sure that you can
sleep well, observe the following guidelines:

   * Always run the MySQL server with the `--log-bin' option, or even
     `--log-bin=LOG_NAME', where the log file name is located on some
     safe media different from the drive on which the data directory is
     located. If you have such safe media, this technique can also be
     good for disk load balancing (which results in a performance
     improvement).

   * Make periodic full backups, using the *Note `mysqldump':
     mysqldump. command shown earlier in *Note backup-policy::, that
     makes an online, nonblocking backup.

   * Make periodic incremental backups by flushing the logs with *Note
     `FLUSH LOGS': flush.  or *Note `mysqladmin flush-logs': mysqladmin.


File: manual.info,  Node: using-mysqldump,  Next: point-in-time-recovery,  Prev: backup-strategy-example,  Up: backup-and-recovery

7.4 Using mysqldump for Backups
===============================

* Menu:

* mysqldump-sql-format::         Dumping Data in SQL Format with mysqldump
* reloading-sql-format-dumps::   Reloading SQL-Format Backups
* mysqldump-delimited-text::     Dumping Data in Delimited-Text Format with mysqldump
* reloading-delimited-text-dumps::  Reloading Delimited-Text Format Backups
* mysqldump-tips::               mysqldump Tips

This section describes how to use *Note `mysqldump': mysqldump. to
produce dump files, and how to reload dump files. A dump file can be
used in several ways:

   * As a backup to enable data recovery in case of data loss.

   * As a source of data for setting up replication slaves.

   * As a source of data for experimentation:

        * To make a copy of a database that you can use without
          changing the original data.

        * To test potential upgrade incompatibilities.

*Note `mysqldump': mysqldump. produces two types of output, depending
on whether the `--tab' option is given:

   * Without `--tab', *Note `mysqldump': mysqldump. writes SQL
     statements to the standard output. This output consists of
     `CREATE' statements to create dumped objects (databases, tables,
     stored routines, and so forth), and `INSERT' statements to load
     data into tables.  The output can be saved in a file and reloaded
     later using *Note `mysql': mysql. to recreate the dumped objects.
     Options are available to modify the format of the SQL statements,
     and to control which objects are dumped.

   * With `--tab', *Note `mysqldump': mysqldump. produces two output
     files for each dumped table. The server writes one file as
     tab-delimited text, one line per table row. This file is named
     `TBL_NAME.txt' in the output directory. The server also sends a
     *Note `CREATE TABLE': create-table. statement for the table to
     *Note `mysqldump': mysqldump, which writes it as a file named
     `TBL_NAME.sql' in the output directory.


File: manual.info,  Node: mysqldump-sql-format,  Next: reloading-sql-format-dumps,  Prev: using-mysqldump,  Up: using-mysqldump

7.4.1 Dumping Data in SQL Format with mysqldump
-----------------------------------------------

This section describes how to use *Note `mysqldump': mysqldump.  to
create SQL-format dump files. For information about reloading such dump
files, see *Note reloading-sql-format-dumps::.

By default, *Note `mysqldump': mysqldump. writes information as SQL
statements to the standard output. You can save the output in a file:


     shell> mysqldump [ARGUMENTS] > FILE_NAME

To dump all databases, invoke *Note `mysqldump': mysqldump. with the
`--all-databases' option:


     shell> mysqldump --all-databases > dump.sql

To dump only specific databases, name them on the command line and use
the `--databases' option:


     shell> mysqldump --databases db1 db2 db3 > dump.sql

The `--databases' option causes all names on the command line to be
treated as database names.  Without this option, *Note `mysqldump':
mysqldump. treats the first name as a database name and those following
as table names.

With `--all-databases' or `--databases', *Note `mysqldump': mysqldump.
writes *Note `CREATE DATABASE': create-database. and *Note `USE': use.
statements prior to the dump output for each database. This ensures
that when the dump file is reloaded, it creates each database if it
does not exist and makes it the default database so database contents
are loaded into the same database from which they came. If you want to
cause the dump file to force a drop of each database before recreating
it, use the `--add-drop-database' option as well. In this case, *Note
`mysqldump': mysqldump. writes a *Note `DROP DATABASE': drop-database.
statement preceding each *Note `CREATE DATABASE': create-database.
statement.

To dump a single database, name it on the command line:


     shell> mysqldump --databases test > dump.sql

In the single-database case, it is permissible to omit the
`--databases' option:


     shell> mysqldump test > dump.sql

The difference between the two preceding commands is that without
`--databases', the dump output contains no *Note `CREATE DATABASE':
create-database. or *Note `USE': use.  statements. This has several
implications:

   * When you reload the dump file, you must specify a default database
     name so that the server knows which database to reload.

   * For reloading, you can specify a database name different from the
     original name, which enables you to reload the data into a
     different database.

   * If the database to be reloaded does not exist, you must create it
     first.

   * Because the output will contain no *Note `CREATE DATABASE':
     create-database. statement, the `--add-drop-database' option has
     no effect. If you use it, it produces no *Note `DROP DATABASE':
     drop-database. statement.

To dump only specific tables from a database, name them on the command
line following the database name:


     shell> mysqldump test t1 t3 t7 > dump.sql


File: manual.info,  Node: reloading-sql-format-dumps,  Next: mysqldump-delimited-text,  Prev: mysqldump-sql-format,  Up: using-mysqldump

7.4.2 Reloading SQL-Format Backups
----------------------------------

To reload a dump file written by *Note `mysqldump': mysqldump.  that
consists of SQL statements, use it as input to the *Note `mysql':
mysql. client. If the dump file was created by *Note `mysqldump':
mysqldump. with the `--all-databases' or `--databases' option, it
contains *Note `CREATE DATABASE': create-database. and *Note `USE':
use. statements and it is not necessary to specify a default database
into which to load the data:


     shell> mysql < dump.sql

Alternatively, from within *Note `mysql': mysql, use a `source' command:


     mysql> source dump.sql

If the file is a single-database dump not containing *Note `CREATE
DATABASE': create-database. and *Note `USE': use. statements, create the
database first (if necessary):


     shell> mysqladmin create db1

Then specify the database name when you load the dump file:


     shell> mysql db1 < dump.sql

Alternatively, from within *Note `mysql': mysql, create the database,
select it as the default database, and load the dump file:


     mysql> CREATE DATABASE IF NOT EXISTS db1;
     mysql> USE db1;
     mysql> source dump.sql


File: manual.info,  Node: mysqldump-delimited-text,  Next: reloading-delimited-text-dumps,  Prev: reloading-sql-format-dumps,  Up: using-mysqldump

7.4.3 Dumping Data in Delimited-Text Format with mysqldump
----------------------------------------------------------

This section describes how to use *Note `mysqldump': mysqldump.  to
create delimited-text dump files. For information about reloading such
dump files, see *Note reloading-delimited-text-dumps::.

If you invoke *Note `mysqldump': mysqldump. with the `--tab=DIR_NAME'
option, it uses DIR_NAME as the output directory and dumps tables
individually in that directory using two files for each table. The
table name is the basename for these files. For a table named `t1', the
files are named `t1.sql' and `t1.txt'. The `.sql' file contains a *Note
`CREATE TABLE': create-table. statement for the table. The `.txt' file
contains the table data, one line per table row.

The following command dumps the contents of the `db1' database to files
in the `/tmp' database:


     shell> mysqldump --tab=/tmp db1

The `.txt' files containing table data are written by the server, so
they are owned by the system account used for running the server. The
server uses *Note `SELECT ... INTO OUTFILE': select-into. to write the
files, so you must have the `FILE' privilege to perform this operation,
and an error occurs if a given `.txt' file already exists.

The server sends the `CREATE' definitions for dumped tables to *Note
`mysqldump': mysqldump, which writes them to `.sql' files. These files
therefore are owned by the user who executes *Note `mysqldump':
mysqldump.

It is best that `--tab' be used only for dumping a local server. If you
use it with a remote server, the `--tab' directory must exist on both
the local and remote hosts, and the `.txt' files will be written by the
server in the remote directory (on the server host), whereas the `.sql'
files will be written by *Note `mysqldump': mysqldump. in the local
directory (on the client host).

For *Note `mysqldump --tab': mysqldump, the server by default writes
table data to `.txt' files one line per row with tabs between column
values, no quotation marks around column values, and newline as the
line terminator. (These are the same defaults as for *Note `SELECT ...
INTO OUTFILE': select-into.)

To enable data files to be written using a different format, *Note
`mysqldump': mysqldump. supports these options:

   * `--fields-terminated-by=STR'

     The string for separating column values (default: tab).

   * `--fields-enclosed-by=CHAR'

     The character within which to enclose column values (default: no
     character).

   * `--fields-optionally-enclosed-by=CHAR'

     The character within which to enclose non-numeric column values
     (default: no character).

   * `--fields-escaped-by=CHAR'

     The character for escaping special characters (default: no
     escaping).

   * `--lines-terminated-by=STR'

     The line-termination string (default: newline).

Depending on the value you specify for any of these options, it might
be necessary on the command line to quote or escape the value
appropriately for your command interpreter. Alternatively, specify the
value using hex notation. Suppose that you want *Note `mysqldump':
mysqldump. to quote column values within double quotation marks. To do
so, specify double quote as the value for the `--fields-enclosed-by'
option. But this character is often special to command interpreters and
must be treated specially. For example, on Unix, you can quote the
double quote like this:


     --fields-enclosed-by='"'

On any platform, you can specify the value in hex:


     --fields-enclosed-by=0x22

It is common to use several of the data-formatting options together.
For example, to dump tables in comma-separated values format with lines
terminated by carriage-return/newline pairs (`\r\n'), use this command
(enter it on a single line):


     shell> mysqldump --tab=/tmp --fields-terminated-by=,
              --fields-enclosed-by='"' --lines-terminated-by=0x0d0a db1

Should you use any of the data-formatting options to dump table data,
you will need to specify the same format when you reload data files
later, to ensure proper interpretation of the file contents.


File: manual.info,  Node: reloading-delimited-text-dumps,  Next: mysqldump-tips,  Prev: mysqldump-delimited-text,  Up: using-mysqldump

7.4.4 Reloading Delimited-Text Format Backups
---------------------------------------------

For backups produced with *Note `mysqldump --tab': mysqldump, each
table is represented in the output directory by an `.sql' file
containing the *Note `CREATE TABLE': create-table. statement for the
table, and a `.txt' file containing the table data. To reload a table,
first change location into the output directory. Then process the
`.sql' file with *Note `mysql': mysql. to create an empty table and
process the `.txt' file to load the data into the table:


     shell> mysql db1 < t1.sql
     shell> mysqlimport db1 t1.txt

An alternative to using *Note `mysqlimport': mysqlimport. to load the
data file is to use the *Note `LOAD DATA INFILE': load-data. statement
from within the *Note `mysql': mysql. client:


     mysql> USE db1;
     mysql> LOAD DATA INFILE 't1.txt' INTO TABLE t1;

If you used any data-formatting options with *Note `mysqldump':
mysqldump. when you initially dumped the table, you must use the same
options with *Note `mysqlimport': mysqlimport. or *Note `LOAD DATA
INFILE': load-data. to ensure proper interpretation of the data file
contents:


     shell> mysqlimport --fields-terminated-by=,
              --fields-enclosed-by='"' --lines-terminated-by=0x0d0a db1 t1.txt

Or:


     mysql> USE db1;
     mysql> LOAD DATA INFILE 't1.txt' INTO TABLE t1
         -> FIELDS TERMINATED BY ',' FIELDS ENCLOSED BY '"'
         -> LINES TERMINATED BY '\r\n';


File: manual.info,  Node: mysqldump-tips,  Prev: reloading-delimited-text-dumps,  Up: using-mysqldump

7.4.5 mysqldump Tips
--------------------

* Menu:

* mysqldump-copying-database::   Making a Copy of a Database
* mysqldump-copying-to-other-server::  Copy a Database from one Server to Another
* mysqldump-stored-programs::    Dumping Stored Programs
* mysqldump-definition-data-dumps::  Dumping Table Definitions and Content Separately
* mysqldump-upgrade-testing::    Using mysqldump to Test for Upgrade Incompatibilities

This section surveys techniques that enable you to use *Note
`mysqldump': mysqldump. to solve specific problems:

   * How to make a copy a database

   * How to copy a database from one server to another

   * How to dump stored programs (stored procedures and functions,
     triggers, and events)

   * How to dump definitions and data separately


File: manual.info,  Node: mysqldump-copying-database,  Next: mysqldump-copying-to-other-server,  Prev: mysqldump-tips,  Up: mysqldump-tips

7.4.5.1 Making a Copy of a Database
...................................


     shell> mysqldump db1 > dump.sql
     shell> mysqladmin create db2
     shell> mysql db2 < dump.sql

Do not use `--databases' on the *Note `mysqldump': mysqldump. command
line because that causes `USE db1' to be included in the dump file,
which overrides the effect of naming `db2' on the *Note `mysql': mysql.
command line.


File: manual.info,  Node: mysqldump-copying-to-other-server,  Next: mysqldump-stored-programs,  Prev: mysqldump-copying-database,  Up: mysqldump-tips

7.4.5.2 Copy a Database from one Server to Another
..................................................

On Server 1:


     shell> mysqldump --databases db1 > dump.sql

Copy the dump file from Server 1 to Server 2.

On Server 2:


     shell> mysql < dump.sql

Use of `--databases' with the *Note `mysqldump': mysqldump. command
line causes the dump file to include *Note `CREATE DATABASE':
create-database. and *Note `USE': use. statements that create the
database if it does exist and make it the default database for the
reloaded data.

Alternatively, you can omit `--databases' from the *Note `mysqldump':
mysqldump. command. Then you will need to create the database on Server
2 (if necessary) and specify it as the default database when you reload
the dump file.

On Server 1:


     shell> mysqldump db1 > dump.sql

On Server 2:


     shell> mysqladmin create db1
     shell> mysql db1 < dump.sql

You can specify a different database name in this case, so omitting
`--databases' from the *Note `mysqldump': mysqldump. command enables
you to dump data from one database and load it into another.


File: manual.info,  Node: mysqldump-stored-programs,  Next: mysqldump-definition-data-dumps,  Prev: mysqldump-copying-to-other-server,  Up: mysqldump-tips

7.4.5.3 Dumping Stored Programs
...............................

Several options control how *Note `mysqldump': mysqldump.  handles
stored programs (stored procedures and functions, triggers, and events):

   * `--events': Dump Event Scheduler events

   * `--routines': Dump stored procedures and functions

   * `--triggers': Dump triggers for tables

The `--triggers' option is enabled by default so that when tables are
dumped, they are accompanied by any triggers they have. The other
options are disabled by default and must be specified explicitly to dump
the corresponding objects. To disable any of these options explicitly,
use its skip form: `--skip-events', `--skip-routines', or
`--skip-triggers'.


File: manual.info,  Node: mysqldump-definition-data-dumps,  Next: mysqldump-upgrade-testing,  Prev: mysqldump-stored-programs,  Up: mysqldump-tips

7.4.5.4 Dumping Table Definitions and Content Separately
........................................................

The `--no-data' option tells *Note `mysqldump': mysqldump. not to dump
table data, resulting in the dump file containing only statements to
create the tables. Conversely, the `--no-create-info' option tells
*Note `mysqldump': mysqldump. to suppress `CREATE' statements from the
output, so that the dump file contains only table data.

For example, to dump table definitions and data separately for the
`test' database, use these commands:


     shell> mysqldump --no-data test > dump-defs.sql
     shell> mysqldump --no-create-info test > dump-data.sql

For a definition-only dump, add the `--routines' and `--events' options
to also include stored routine and event definitions:


     shell> mysqldump --no-data --routines --events test > dump-defs.sql


File: manual.info,  Node: mysqldump-upgrade-testing,  Prev: mysqldump-definition-data-dumps,  Up: mysqldump-tips

7.4.5.5 Using mysqldump to Test for Upgrade Incompatibilities
.............................................................

When contemplating a MySQL upgrade, it is prudent to install the newer
version separately from your current production version. Then you can
dump the database and database object definitions from the production
server and load them into the new server to verify that they are
handled properly. (This is also useful for testing downgrades.)

On the production server:


     shell> mysqldump --all-databases --no-data --routines --events > dump-defs.sql

On the upgraded server:


     shell> mysql < dump-defs.sql

Because the dump file does not contain table data, it can be processed
quickly. This enables you to spot potential incompatibilities without
waiting for lengthy data-loading operations. Look for warnings or
errors while the dump file is being processed.

After you have verified that the definitions are handled properly, dump
the data and try to load it into the upgraded server.

On the production server:


     shell> mysqldump --all-databases --no-create-info > dump-data.sql

On the upgraded server:


     shell> mysql < dump-data.sql

Now check the table contents and run some test queries.


File: manual.info,  Node: point-in-time-recovery,  Next: myisam-table-maintenance,  Prev: using-mysqldump,  Up: backup-and-recovery

7.5 Point-in-Time (Incremental) Recovery Using the Binary Log
=============================================================

* Menu:

* point-in-time-recovery-times::  Point-in-Time Recovery Using Event Times
* point-in-time-recovery-positions::  Point-in-Time Recovery Using Event Positions

Point-in-time recovery refers to recovery of data changes made since a
given point in time. Typically, this type of recovery is performed
after restoring a full backup that brings the server to its state as of
the time the backup was made. (The full backup can be made in several
ways, such as those listed in *Note backup-methods::.) Point-in-time
recovery then brings the server up to date incrementally from the time
of the full backup to a more recent time.

Point-in-time recovery is based on these principles:

   * The source of information for point-in-time recovery is the set of
     incremental backups represented by the binary log files generated
     subsequent to the full backup operation. Therefore, the server
     must be started with the `--log-bin' option to enable binary
     logging (see *Note binary-log::).

     To restore data from the binary log, you must know the name and
     location of the current binary log files. By default, the server
     creates binary log files in the data directory, but a path name
     can be specified with the `--log-bin' option to place the files in
     a different location. *Note binary-log::.

     To see a listing of all binary log files, use this statement:


          mysql> SHOW BINARY LOGS;

     To determine the name of the current binary log file, issue the
     following statement:


          mysql> SHOW MASTER STATUS;

   * The *Note `mysqlbinlog': mysqlbinlog. utility converts the events
     in the binary log files from binary format to text so that they
     can be executed or viewed. *Note `mysqlbinlog': mysqlbinlog.  has
     options for selecting sections of the binary log based on event
     times or position of events within the log. See *Note
     mysqlbinlog::.

   * Executing events from the binary log causes the data modifications
     they represent to be redone. This enables recovery of data changes
     for a given span of time. To execute events from the binary log,
     process *Note `mysqlbinlog': mysqlbinlog. output using the *Note
     `mysql': mysql. client:


          shell> mysqlbinlog BINLOG_FILES | mysql -u root -p

   * Viewing log contents can be useful when you need to determine
     event times or positions to select partial log contents prior to
     executing events. To view events from the log, send *Note
     `mysqlbinlog': mysqlbinlog. output into a paging program:


          shell> mysqlbinlog BINLOG_FILES | more

     Alternatively, save the output in a file and view the file in a
     text editor:


          shell> mysqlbinlog BINLOG_FILES > tmpfile
          shell> ... EDIT TMPFILE ...

   * Saving the output in a file is useful as a preliminary to
     executing the log contents with certain events removed, such as an
     accidental *Note `DROP DATABASE': drop-database.  You can delete
     from the file any statements not to be executed before executing
     its contents. After editing the file, execute the contents as
     follows:


          shell> mysql -u root -p < tmpfile

If you have more than one binary log to execute on the MySQL server,
the safe method is to process them all using a single connection to the
server. Here is an example that demonstrates what may be _unsafe_:


     shell> mysqlbinlog binlog.000001 | mysql -u root -p # DANGER!!
     shell> mysqlbinlog binlog.000002 | mysql -u root -p # DANGER!!

Processing binary logs this way using different connections to the
server causes problems if the first log file contains a *Note `CREATE
TEMPORARY TABLE': create-table. statement and the second log contains a
statement that uses the temporary table. When the first *Note `mysql':
mysql. process terminates, the server drops the temporary table. When
the second *Note `mysql': mysql. process attempts to use the table, the
server reports `unknown table.'

To avoid problems like this, use a _single_ connection to execute the
contents of all binary logs that you want to process. Here is one way
to do so:


     shell> mysqlbinlog binlog.000001 binlog.000002 | mysql -u root -p

Another approach is to write all the logs to a single file and then
process the file:


     shell> mysqlbinlog binlog.000001 >  /tmp/statements.sql
     shell> mysqlbinlog binlog.000002 >> /tmp/statements.sql
     shell> mysql -u root -p -e "source /tmp/statements.sql"


File: manual.info,  Node: point-in-time-recovery-times,  Next: point-in-time-recovery-positions,  Prev: point-in-time-recovery,  Up: point-in-time-recovery

7.5.1 Point-in-Time Recovery Using Event Times
----------------------------------------------

To indicate the start and end times for recovery, specify the
`--start-datetime' and `--stop-datetime' options for *Note
`mysqlbinlog': mysqlbinlog, in *Note `DATETIME': datetime. format. As
an example, suppose that exactly at 10:00 a.m. on April 20, 2005 an SQL
statement was executed that deleted a large table. To restore the table
and data, you could restore the previous night's backup, and then
execute the following command:


     shell> mysqlbinlog --stop-datetime="2005-04-20 9:59:59" \
              /var/log/mysql/bin.123456 | mysql -u root -p

This command recovers all of the data up until the date and time given
by the `--stop-datetime' option. If you did not detect the erroneous
SQL statement that was entered until hours later, you will probably
also want to recover the activity that occurred afterward. Based on
this, you could run *Note `mysqlbinlog': mysqlbinlog. again with a
start date and time, like so:


     shell> mysqlbinlog --start-datetime="2005-04-20 10:01:00" \
              /var/log/mysql/bin.123456 | mysql -u root -p

In this command, the SQL statements logged from 10:01 a.m. on will be
re-executed. The combination of restoring of the previous night's dump
file and the two *Note `mysqlbinlog': mysqlbinlog. commands restores
everything up until one second before 10:00 a.m. and everything from
10:01 a.m. on.

To use this method of point-in-time recovery, you should examine the
log to be sure of the exact times to specify for the commands. To
display the log file contents without executing them, use this command:


     shell> mysqlbinlog /var/log/mysql/bin.123456 > /tmp/mysql_restore.sql

Then open the `/tmp/mysql_restore.sql' file with a text editor to
examine it.

Excluding specific changes by specifying times for *Note `mysqlbinlog':
mysqlbinlog. does not work well if multiple statements executed at the
same time as the one to be excluded.


File: manual.info,  Node: point-in-time-recovery-positions,  Prev: point-in-time-recovery-times,  Up: point-in-time-recovery

7.5.2 Point-in-Time Recovery Using Event Positions
--------------------------------------------------

Instead of specifying dates and times, the `--start-position' and
`--stop-position' options for *Note `mysqlbinlog': mysqlbinlog. can be
used for specifying log positions. They work the same as the start and
stop date options, except that you specify log position numbers rather
than dates. Using positions may enable you to be more precise about
which part of the log to recover, especially if many transactions
occurred around the same time as a damaging SQL statement. To determine
the position numbers, run *Note `mysqlbinlog': mysqlbinlog. for a range
of times near the time when the unwanted transaction was executed, but
redirect the results to a text file for examination. This can be done
like so:


     shell> mysqlbinlog --start-datetime="2005-04-20 9:55:00" \
              --stop-datetime="2005-04-20 10:05:00" \
              /var/log/mysql/bin.123456 > /tmp/mysql_restore.sql

This command creates a small text file in the `/tmp' directory that
contains the SQL statements around the time that the deleterious SQL
statement was executed. Open this file with a text editor and look for
the statement that you do not want to repeat. Determine the positions
in the binary log for stopping and resuming the recovery and make note
of them. Positions are labeled as `log_pos' followed by a number. After
restoring the previous backup file, use the position numbers to process
the binary log file. For example, you would use commands something like
these:


     shell> mysqlbinlog --stop-position=368312 /var/log/mysql/bin.123456 \
              | mysql -u root -p

     shell> mysqlbinlog --start-position=368315 /var/log/mysql/bin.123456 \
              | mysql -u root -p

The first command recovers all the transactions up until the stop
position given. The second command recovers all transactions from the
starting position given until the end of the binary log. Because the
output of *Note `mysqlbinlog': mysqlbinlog. includes `SET TIMESTAMP'
statements before each SQL statement recorded, the recovered data and
related MySQL logs will reflect the original times at which the
transactions were executed.


File: manual.info,  Node: myisam-table-maintenance,  Prev: point-in-time-recovery,  Up: backup-and-recovery

7.6 MyISAM Table Maintenance and Crash Recovery
===============================================

* Menu:

* myisam-crash-recovery::        Using myisamchk for Crash Recovery
* myisam-check::                 How to Check MyISAM Tables for Errors
* myisam-repair::                How to Repair MyISAM Tables
* myisam-optimization::          MyISAM Table Optimization
* myisam-maintenance-schedule::  Setting Up a MyISAM Table Maintenance Schedule

This section discusses how to use *Note `myisamchk': myisamchk. to
check or repair `MyISAM' tables (tables that have `.MYD' and `.MYI'
files for storing data and indexes). For general *Note `myisamchk':
myisamchk. background, see *Note myisamchk::. Other table-repair
information can be found at *Note rebuilding-tables::.

You can use *Note `myisamchk': myisamchk. to check, repair, or optimize
database tables. The following sections describe how to perform these
operations and how to set up a table maintenance schedule. For
information about using *Note `myisamchk': myisamchk.  to get
information about your tables, see *Note myisamchk-table-info::.

Even though table repair with *Note `myisamchk': myisamchk. is quite
secure, it is always a good idea to make a backup _before_ doing a
repair or any maintenance operation that could make a lot of changes to
a table.

*Note `myisamchk': myisamchk. operations that affect indexes can cause
`FULLTEXT' indexes to be rebuilt with full-text parameters that are
incompatible with the values used by the MySQL server. To avoid this
problem, follow the guidelines in *Note myisamchk-general-options::.

`MyISAM' table maintenance can also be done using the SQL statements
that perform operations similar to what *Note `myisamchk': myisamchk.
can do:

   * To check `MyISAM' tables, use *Note `CHECK TABLE': check-table.

   * To repair `MyISAM' tables, use *Note `REPAIR TABLE': repair-table.

   * To optimize `MyISAM' tables, use *Note `OPTIMIZE TABLE':
     optimize-table.

   * To analyze `MyISAM' tables, use *Note `ANALYZE TABLE':
     analyze-table.

For additional information about these statements, see *Note
table-maintenance-sql::.

These statements can be used directly or by means of the *Note
`mysqlcheck': mysqlcheck. client program. One advantage of these
statements over *Note `myisamchk': myisamchk. is that the server does
all the work. With *Note `myisamchk': myisamchk, you must make sure
that the server does not use the tables at the same time so that there
is no unwanted interaction between *Note `myisamchk': myisamchk. and
the server.


File: manual.info,  Node: myisam-crash-recovery,  Next: myisam-check,  Prev: myisam-table-maintenance,  Up: myisam-table-maintenance

7.6.1 Using myisamchk for Crash Recovery
----------------------------------------

This section describes how to check for and deal with data corruption
in MySQL databases. If your tables become corrupted frequently, you
should try to find the reason why. See *Note crashing::.

For an explanation of how `MyISAM' tables can become corrupted, see
*Note myisam-table-problems::.

If you run *Note `mysqld': mysqld. with external locking disabled
(which is the default), you cannot reliably use *Note `myisamchk':
myisamchk. to check a table when *Note `mysqld': mysqld. is using the
same table. If you can be certain that no one will access the tables
through *Note `mysqld': mysqld. while you run *Note `myisamchk':
myisamchk, you only have to execute *Note `mysqladmin flush-tables':
mysqladmin. before you start checking the tables. If you cannot
guarantee this, you must stop *Note `mysqld': mysqld. while you check
the tables. If you run *Note `myisamchk': myisamchk. to check tables
that *Note `mysqld': mysqld. is updating at the same time, you may get
a warning that a table is corrupt even when it is not.

If the server is run with external locking enabled, you can use *Note
`myisamchk': myisamchk. to check tables at any time. In this case, if
the server tries to update a table that *Note `myisamchk': myisamchk.
is using, the server will wait for *Note `myisamchk': myisamchk. to
finish before it continues.

If you use *Note `myisamchk': myisamchk. to repair or optimize tables,
you _must_ always ensure that the *Note `mysqld': mysqld. server is not
using the table (this also applies if external locking is disabled). If
you do not stop *Note `mysqld': mysqld, you should at least do a *Note
`mysqladmin flush-tables': mysqladmin. before you run *Note
`myisamchk': myisamchk. Your tables _may become corrupted_ if the
server and *Note `myisamchk': myisamchk. access the tables
simultaneously.

When performing crash recovery, it is important to understand that each
`MyISAM' table TBL_NAME in a database corresponds to the three files in
the database directory shown in the following table.

This table lists the three files in the database directory that
correspond to each `MyISAM' table.

File           Purpose
`TBL_NAME.frm' Definition (format) file
`TBL_NAME.MYD' Data file
`TBL_NAME.MYI' Index file

Each of these three file types is subject to corruption in various
ways, but problems occur most often in data files and index files.

*Note `myisamchk': myisamchk. works by creating a copy of the `.MYD'
data file row by row. It ends the repair stage by removing the old
`.MYD' file and renaming the new file to the original file name. If you
use `--quick', *Note `myisamchk': myisamchk. does not create a temporary
`.MYD' file, but instead assumes that the `.MYD' file is correct and
generates only a new index file without touching the `.MYD' file. This
is safe, because *Note `myisamchk': myisamchk.  automatically detects
whether the `.MYD' file is corrupt and aborts the repair if it is. You
can also specify the `--quick' option twice to *Note `myisamchk':
myisamchk. In this case, *Note `myisamchk': myisamchk. does not abort
on some errors (such as duplicate-key errors) but instead tries to
resolve them by modifying the `.MYD' file. Normally the use of two
`--quick' options is useful only if you have too little free disk space
to perform a normal repair. In this case, you should at least make a
backup of the table before running *Note `myisamchk': myisamchk.


File: manual.info,  Node: myisam-check,  Next: myisam-repair,  Prev: myisam-crash-recovery,  Up: myisam-table-maintenance

7.6.2 How to Check MyISAM Tables for Errors
-------------------------------------------

To check a `MyISAM' table, use the following commands:

   * *Note `myisamchk TBL_NAME': myisamchk.

     This finds 99.99% of all errors. What it cannot find is corruption
     that involves _only_ the data file (which is very unusual). If you
     want to check a table, you should normally run *Note `myisamchk':
     myisamchk. without options or with the `-s' (silent) option.

   * *Note `myisamchk -m TBL_NAME': myisamchk.

     This finds 99.999% of all errors. It first checks all index
     entries for errors and then reads through all rows. It calculates
     a checksum for all key values in the rows and verifies that the
     checksum matches the checksum for the keys in the index tree.

   * *Note `myisamchk -e TBL_NAME': myisamchk.

     This does a complete and thorough check of all data (`-e' means
     `extended check').  It does a check-read of every key for each row
     to verify that they indeed point to the correct row. This may take
     a long time for a large table that has many indexes. Normally,
     *Note `myisamchk': myisamchk. stops after the first error it
     finds. If you want to obtain more information, you can add the
     `-v' (verbose) option. This causes *Note `myisamchk': myisamchk.
     to keep going, up through a maximum of 20 errors.

   * *Note `myisamchk -e -i TBL_NAME': myisamchk.

     This is like the previous command, but the `-i' option tells *Note
     `myisamchk': myisamchk. to print additional statistical
     information.

In most cases, a simple *Note `myisamchk': myisamchk. command with no
arguments other than the table name is sufficient to check a table.


File: manual.info,  Node: myisam-repair,  Next: myisam-optimization,  Prev: myisam-check,  Up: myisam-table-maintenance

7.6.3 How to Repair MyISAM Tables
---------------------------------

The discussion in this section describes how to use *Note `myisamchk':
myisamchk. on `MyISAM' tables (extensions `.MYI' and `.MYD').

You can also use the *Note `CHECK TABLE': check-table.  and *Note
`REPAIR TABLE': repair-table. statements to check and repair `MyISAM'
tables. See *Note check-table::, and *Note repair-table::.

Symptoms of corrupted tables include queries that abort unexpectedly
and observable errors such as these:

   * `TBL_NAME.frm' is locked against change

   * Can't find file `TBL_NAME.MYI' (Errcode: NNN)

   * Unexpected end of file

   * Record file is crashed

   * Got error NNN from table handler

To get more information about the error, run *Note `perror': perror.
NNN, where NNN is the error number. The following example shows how to
use *Note `perror': perror. to find the meanings for the most common
error numbers that indicate a problem with a table:


     shell> perror 126 127 132 134 135 136 141 144 145
     MySQL error code 126 = Index file is crashed
     MySQL error code 127 = Record-file is crashed
     MySQL error code 132 = Old database file
     MySQL error code 134 = Record was already deleted (or record file crashed)
     MySQL error code 135 = No more room in record file
     MySQL error code 136 = No more room in index file
     MySQL error code 141 = Duplicate unique key or constraint on write or update
     MySQL error code 144 = Table is crashed and last repair failed
     MySQL error code 145 = Table was marked as crashed and should be repaired

Note that error 135 (no more room in record file) and error 136 (no
more room in index file) are not errors that can be fixed by a simple
repair. In this case, you must use *Note `ALTER TABLE': alter-table. to
increase the `MAX_ROWS' and `AVG_ROW_LENGTH' table option values:


     ALTER TABLE TBL_NAME MAX_ROWS=XXX AVG_ROW_LENGTH=YYY;

If you do not know the current table option values, use *Note `SHOW
CREATE TABLE': show-create-table.

For the other errors, you must repair your tables.  *Note `myisamchk':
myisamchk. can usually detect and fix most problems that occur.

The repair process involves up to four stages, described here.  Before
you begin, you should change location to the database directory and
check the permissions of the table files. On Unix, make sure that they
are readable by the user that *Note `mysqld': mysqld. runs as (and to
you, because you need to access the files you are checking). If it
turns out you need to modify files, they must also be writable by you.

This section is for the cases where a table check fails (such as those
described in *Note myisam-check::), or you want to use the extended
features that *Note `myisamchk': myisamchk.  provides.

The *Note `myisamchk': myisamchk. options used for table maintenance
with are described in *Note myisamchk::.  *Note `myisamchk': myisamchk.
also has variables that you can set to control memory allocation that
may improve performance. See *Note myisamchk-memory::.

If you are going to repair a table from the command line, you must
first stop the *Note `mysqld': mysqld. server. Note that when you do
*Note `mysqladmin shutdown': mysqladmin. on a remote server, the *Note
`mysqld': mysqld. server is still available for a while after *Note
`mysqladmin': mysqladmin. returns, until all statement-processing has
stopped and all index changes have been flushed to disk.

*Stage 1: Checking your tables*

Run *Note `myisamchk *.MYI': myisamchk. or *Note `myisamchk -e *.MYI':
myisamchk. if you have more time. Use the `-s' (silent) option to
suppress unnecessary information.

If the *Note `mysqld': mysqld. server is stopped, you should use the
`--update-state' option to tell *Note `myisamchk': myisamchk. to mark
the table as `checked.'

You have to repair only those tables for which *Note `myisamchk':
myisamchk. announces an error. For such tables, proceed to Stage 2.

If you get unexpected errors when checking (such as `out of memory'
errors), or if *Note `myisamchk': myisamchk.  crashes, go to Stage 3.

*Stage 2: Easy safe repair*

First, try *Note `myisamchk -r -q TBL_NAME': myisamchk. (`-r -q' means
`quick recovery mode'). This attempts to repair the index file without
touching the data file. If the data file contains everything that it
should and the delete links point at the correct locations within the
data file, this should work, and the table is fixed. Start repairing
the next table. Otherwise, use the following procedure:

  1. Make a backup of the data file before continuing.

  2. Use *Note `myisamchk -r TBL_NAME': myisamchk.  (`-r' means
     `recovery mode').  This removes incorrect rows and deleted rows
     from the data file and reconstructs the index file.

  3. If the preceding step fails, use *Note `myisamchk --safe-recover
     TBL_NAME': myisamchk. Safe recovery mode uses an old recovery
     method that handles a few cases that regular recovery mode does
     not (but is slower).

*Note*:

If you want a repair operation to go much faster, you should set the
values of the `sort_buffer_size' and `key_buffer_size' variables each
to about 25% of your available memory when running *Note `myisamchk':
myisamchk.

If you get unexpected errors when repairing (such as `out of memory'
errors), or if *Note `myisamchk': myisamchk. crashes, go to Stage 3.

*Stage 3: Difficult repair*

You should reach this stage only if the first 16KB block in the index
file is destroyed or contains incorrect information, or if the index
file is missing. In this case, it is necessary to create a new index
file. Do so as follows:

  1. Move the data file to a safe place.

  2. Use the table description file to create new (empty) data and
     index files:


          shell> mysql DB_NAME
          mysql> SET autocommit=1;
          mysql> TRUNCATE TABLE TBL_NAME;
          mysql> quit

  3. Copy the old data file back onto the newly created data file. (Do
     not just move the old file back onto the new file.  You want to
     retain a copy in case something goes wrong.)

*Important*:

If you are using replication, you should stop it prior to performing
the above procedure, since it involves file system operations, and
these are not logged by MySQL.

Go back to Stage 2. *Note `myisamchk -r -q': myisamchk. should work.
(This should not be an endless loop.)

You can also use the `REPAIR TABLE TBL_NAME USE_FRM' SQL statement,
which performs the whole procedure automatically.  There is also no
possibility of unwanted interaction between a utility and the server,
because the server does all the work when you use *Note `REPAIR TABLE':
repair-table. See *Note repair-table::.

*Stage 4: Very difficult repair*

You should reach this stage only if the `.frm' description file has
also crashed.  That should never happen, because the description file
is not changed after the table is created:

  1. Restore the description file from a backup and go back to Stage 3.
     You can also restore the index file and go back to Stage 2. In the
     latter case, you should start with *Note `myisamchk -r': myisamchk.

  2. If you do not have a backup but know exactly how the table was
     created, create a copy of the table in another database.  Remove
     the new data file, and then move the `.frm' description and `.MYI'
     index files from the other database to your crashed database. This
     gives you new description and index files, but leaves the `.MYD'
     data file alone. Go back to Stage 2 and attempt to reconstruct the
     index file.


File: manual.info,  Node: myisam-optimization,  Next: myisam-maintenance-schedule,  Prev: myisam-repair,  Up: myisam-table-maintenance

7.6.4 MyISAM Table Optimization
-------------------------------

To coalesce fragmented rows and eliminate wasted space that results
from deleting or updating rows, run *Note `myisamchk': myisamchk. in
recovery mode:


     shell> myisamchk -r TBL_NAME

You can optimize a table in the same way by using the *Note `OPTIMIZE
TABLE': optimize-table. SQL statement.  *Note `OPTIMIZE TABLE':
optimize-table. does a table repair and a key analysis, and also sorts
the index tree so that key lookups are faster. There is also no
possibility of unwanted interaction between a utility and the server,
because the server does all the work when you use *Note `OPTIMIZE
TABLE': optimize-table. See *Note optimize-table::.

*Note `myisamchk': myisamchk. has a number of other options that you
can use to improve the performance of a table:

   * `--analyze' or `-a': Perform key distribution analysis. This
     improves join performance by enabling the join optimizer to better
     choose the order in which to join the tables and which indexes it
     should use.

   * `--sort-index' or `-S': Sort the index blocks. This optimizes
     seeks and makes table scans that use indexes faster.

   * `--sort-records=INDEX_NUM' or `-R INDEX_NUM': Sort data rows
     according to a given index. This makes your data much more
     localized and may speed up range-based *Note `SELECT': select. and
     `ORDER BY' operations that use this index.

For a full description of all available options, see *Note myisamchk::.


File: manual.info,  Node: myisam-maintenance-schedule,  Prev: myisam-optimization,  Up: myisam-table-maintenance

7.6.5 Setting Up a MyISAM Table Maintenance Schedule
----------------------------------------------------

It is a good idea to perform table checks on a regular basis rather
than waiting for problems to occur. One way to check and repair
`MyISAM' tables is with the *Note `CHECK TABLE': check-table. and *Note
`REPAIR TABLE': repair-table. statements. See *Note
table-maintenance-sql::.

Another way to check tables is to use *Note `myisamchk': myisamchk. For
maintenance purposes, you can use *Note `myisamchk -s': myisamchk. The
`-s' option (short for `--silent') causes *Note `myisamchk': myisamchk.
to run in silent mode, printing messages only when errors occur.

It is also a good idea to enable automatic `MyISAM' table checking. For
example, whenever the machine has done a restart in the middle of an
update, you usually need to check each table that could have been
affected before it is used further. (These are `expected crashed
tables.') To cause the server to check `MyISAM' tables automatically,
start it with the `--myisam-recover' option. See *Note server-options::.

You should also check your tables regularly during normal system
operation. For example, you can run a `cron' job to check important
tables once a week, using a line like this in a `crontab' file:


     35 0 * * 0 /PATH/TO/MYISAMCHK --fast --silent /PATH/TO/DATADIR/*/*.MYI

This prints out information about crashed tables so that you can
examine and repair them as necessary.

To start with, execute *Note `myisamchk -s': myisamchk. each night on
all tables that have been updated during the last 24 hours. As you see
that problems occur infrequently, you can back off the checking
frequency to once a week or so.

Normally, MySQL tables need little maintenance. If you are performing
many updates to `MyISAM' tables with dynamic-sized rows (tables with
*Note `VARCHAR': char, *Note `BLOB': blob, or *Note `TEXT': blob.
columns) or have tables with many deleted rows you may want to
defragment/reclaim space from the tables from time to time. You can do
this by using *Note `OPTIMIZE TABLE': optimize-table. on the tables in
question. Alternatively, if you can stop the *Note `mysqld': mysqld.
server for a while, change location into the data directory and use
this command while the server is stopped:


     shell> myisamchk -r -s --sort-index --myisam_sort_buffer_size=16M */*.MYI


File: manual.info,  Node: optimization,  Next: language-structure,  Prev: backup-and-recovery,  Up: Top

8 Optimization
**************

* Menu:

* optimize-overview::            Optimization Overview
* execution-plan-information::   Obtaining Query Execution Plan Information
* statement-optimization::       Optimizing SQL Statements
* controlling-optimizer::        Controlling the Query Optimizer
* optimization-indexes::         Optimization and Indexes
* buffering-caching::            Buffering and Caching
* locking-issues::               Locking Issues
* optimizing-database-structure::  Optimizing Database Structure
* optimizing-the-server::        Optimizing the MySQL Server
* thread-information::           Examining Thread Information

This chapter explains different ways to optimize MySQL and provides
examples. Optimization is a complex task because ultimately it requires
understanding of the entire system to be optimized.  Although it may be
possible to perform some local optimizations with little knowledge of
your system or application, the more optimal you want your system to
become, the more you must know about it.


File: manual.info,  Node: optimize-overview,  Next: execution-plan-information,  Prev: optimization,  Up: optimization

8.1 Optimization Overview
=========================

* Menu:

* design-limitations::           MySQL Design Limitations and Tradeoffs
* portability::                  Designing Applications for Portability
* mysql-benchmarks::             The MySQL Benchmark Suite
* custom-benchmarks::            Using Your Own Benchmarks

The most important factor in making a system fast is its basic design.
You must also know what kinds of processing your system is doing, and
what its bottlenecks are. In most cases, system bottlenecks arise from
these sources:

   * Disk seeks. It takes time for the disk to find a piece of data.
     With modern disks, the mean time for this is usually lower than
     10ms, so we can in theory do about 100 seeks a second. This time
     improves slowly with new disks and is very hard to optimize for a
     single table. The way to optimize seek time is to distribute the
     data onto more than one disk.

   * Disk reading and writing. When the disk is at the correct
     position, we need to read the data. With modern disks, one disk
     delivers at least 10-20MB/s throughput. This is easier to optimize
     than seeks because you can read in parallel from multiple disks.

   * CPU cycles. When we have the data in main memory, we need to
     process it to get our result. Having large tables compared to the
     amount of memory is the most common limiting factor. But with
     small tables, speed is usually not the problem.

   * Memory bandwidth. When the CPU needs more data than can fit in the
     CPU cache, main memory bandwidth becomes a bottleneck.  This is an
     uncommon bottleneck for most systems, but one to be aware of.


File: manual.info,  Node: design-limitations,  Next: portability,  Prev: optimize-overview,  Up: optimize-overview

8.1.1 MySQL Design Limitations and Tradeoffs
--------------------------------------------

When using the `MyISAM' storage engine, MySQL uses extremely fast table
locking that permits multiple readers or a single writer. The biggest
problem with this storage engine occurs when you have a steady stream
of mixed updates and slow selects on a single table. If this is a
problem for certain tables, you can use another storage engine for
them. See *Note storage-engines::.

MySQL can work with both transactional and nontransactional tables. To
make it easier to work smoothly with nontransactional tables (which
cannot roll back if something goes wrong), MySQL has the following
rules. Note that these rules apply _only_ when not running in strict
SQL mode or if you use the `IGNORE' specifier for *Note `INSERT':
insert. or *Note `UPDATE': update.

   * All columns have default values.

   * If you insert an inappropriate or out-of-range value into a
     column, MySQL sets the column to the `best possible value' instead
     of reporting an error. For numeric values, this is 0, the smallest
     possible value or the largest possible value. For strings, this is
     either the empty string or as much of the string as can be stored
     in the column.

   * All calculated expressions return a value that can be used instead
     of signaling an error condition. For example, 1/0 returns `NULL'.

To change the preceding behaviors, you can enable stricter data
handling by setting the server SQL mode appropriately. For more
information about data handling, see *Note constraints::, *Note
sql-mode::, and *Note insert::.


File: manual.info,  Node: portability,  Next: mysql-benchmarks,  Prev: design-limitations,  Up: optimize-overview

8.1.2 Designing Applications for Portability
--------------------------------------------

Because all SQL servers implement different parts of standard SQL, it
takes work to write portable database applications. It is very easy to
achieve portability for very simple selects and inserts, but becomes
more difficult the more capabilities you require. If you want an
application that is fast with many database systems, it becomes even
more difficult.

All database systems have some weak points. That is, they have
different design compromises that lead to different behavior.

To make a complex application portable, you need to determine which SQL
servers it must work with, and then determine what features those
servers support. You can use the MySQL `crash-me' program to find
functions, types, and limits that you can use with a selection of
database servers. `crash-me' does not check for every possible feature,
but it is still reasonably comprehensive, performing about 450 tests.
An example of the type of information `crash-me' can provide is that you
should not use column names that are longer than 18 characters if you
want to be able to use Informix or DB2.

The `crash-me' program and the MySQL benchmarks are all very database
independent. By taking a look at how they are written, you can get a
feeling for what you must do to make your own applications database
independent. The programs can be found in the `sql-bench' directory of
MySQL source distributions. They are written in Perl and use the DBI
database interface. Use of DBI in itself solves part of the portability
problem because it provides database-independent access methods. See
*Note mysql-benchmarks::.

If you strive for database independence, you need to get a good feeling
for each SQL server's bottlenecks. For example, MySQL is very fast in
retrieving and updating rows for `MyISAM' tables, but has a problem in
mixing slow readers and writers on the same table. Transactional
database systems in general are not very good at generating summary
tables from log tables, because in this case row locking is almost
useless.

To make your application _really_ database independent, you should
define an easily extendable interface through which you manipulate your
data. For example, C++ is available on most systems, so it makes sense
to use a C++ class-based interface to the databases.

If you use some feature that is specific to a given database system
(such as the *Note `REPLACE': replace.  statement, which is specific to
MySQL), you should implement the same feature for other SQL servers by
coding an alternative method. Although the alternative might be slower,
it enables the other servers to perform the same tasks.

With MySQL, you can use the `/*! */' syntax to add MySQL-specific
keywords to a statement. The code inside `/* */' is treated as a
comment (and ignored) by most other SQL servers. For information about
writing comments, see *Note comments::.

If high performance is more important than exactness, as for some Web
applications, it is possible to create an application layer that caches
all results to give you even higher performance. By letting old results
expire after a while, you can keep the cache reasonably fresh. This
provides a method to handle high load spikes, in which case you can
dynamically increase the cache size and set the expiration timeout
higher until things get back to normal.

In this case, the table creation information should contain information
about the initial cache size and how often the table should normally be
refreshed.

An attractive alternative to implementing an application cache is to
use the MySQL query cache. By enabling the query cache, the server
handles the details of determining whether a query result can be
reused. This simplifies your application. See *Note query-cache::.


File: manual.info,  Node: mysql-benchmarks,  Next: custom-benchmarks,  Prev: portability,  Up: optimize-overview

8.1.3 The MySQL Benchmark Suite
-------------------------------

This benchmark suite is meant to tell any user what operations a given
SQL implementation performs well or poorly. You can get a good idea for
how the benchmarks work by looking at the code and results in the
`sql-bench' directory in any MySQL source distribution.

Note that this benchmark is single-threaded, so it measures the minimum
time for the operations performed. We plan to add multi-threaded tests
to the benchmark suite in the future.

To use the benchmark suite, the following requirements must be
satisfied:

   * The benchmark suite is provided with MySQL source distributions.
     You can either download a released distribution from
     `http://dev.mysql.com/downloads/', or use the current development
     source tree. (See *Note installing-development-tree::.)

   * The benchmark scripts are written in Perl and use the Perl DBI
     module to access database servers, so DBI must be installed. You
     also need the server-specific DBD drivers for each of the servers
     you want to test. For example, to test MySQL, PostgreSQL, and DB2,
     you must have the `DBD::mysql', `DBD::Pg', and `DBD::DB2' modules
     installed. See *Note perl-support::.

After you obtain a MySQL source distribution, you can find the
benchmark suite located in its `sql-bench' directory. To run the
benchmark tests, build MySQL, and then change location into the
`sql-bench' directory and execute the `run-all-tests' script:


     shell> cd sql-bench
     shell> perl run-all-tests --server=SERVER_NAME

SERVER_NAME should be the name of one of the supported servers. To get
a list of all options and supported servers, invoke this command:


     shell> perl run-all-tests --help

The `crash-me' script also is located in the `sql-bench' directory.
`crash-me' tries to determine what features a database system supports
and what its capabilities and limitations are by actually running
queries. For example, it determines:

   * What data types are supported

   * How many indexes are supported

   * What functions are supported

   * How big a query can be

   * How big a *Note `VARCHAR': char. column can be

For more information about benchmark results, visit
http://www.mysql.com/why-mysql/benchmarks/.


File: manual.info,  Node: custom-benchmarks,  Prev: mysql-benchmarks,  Up: optimize-overview

8.1.4 Using Your Own Benchmarks
-------------------------------

You should definitely benchmark your application and database to find
out where the bottlenecks are. After fixing one bottleneck (or by
replacing it with a `dummy' module), you can proceed to identify the
next bottleneck. Even if the overall performance for your application
currently is acceptable, you should at least make a plan for each
bottleneck and decide how to solve it if someday you really need the
extra performance.

For examples of portable benchmark programs, look at those in the MySQL
benchmark suite. See *Note mysql-benchmarks::. You can take any program
from this suite and modify it for your own needs. By doing this, you
can try different solutions to your problem and test which really is
fastest for you.

Another free benchmark suite is the Open Source Database Benchmark,
available at `http://osdb.sourceforge.net/'.

It is very common for a problem to occur only when the system is very
heavily loaded. We have had many customers who contact us when they
have a (tested) system in production and have encountered load
problems. In most cases, performance problems turn out to be due to
issues of basic database design (for example, table scans are not good
under high load) or problems with the operating system or libraries.
Most of the time, these problems would be much easier to fix if the
systems were not already in production.

To avoid problems like this, you should put some effort into
benchmarking your whole application under the worst possible load:

   * The *Note `mysqlslap': mysqlslap. program can be helpful for
     simulating a high load produced by multiple clients issuing
     queries simultaneously. See *Note mysqlslap::.

   * You can also try benchmarking packages such as SysBench and DBT2,
     available at `http://sourceforge.net/projects/sysbench/', and
     `http://osdldbt.sourceforge.net/#dbt2'.

These programs or packages can bring a system to its knees, so be sure
to use them only on your development systems.


File: manual.info,  Node: execution-plan-information,  Next: statement-optimization,  Prev: optimize-overview,  Up: optimization

8.2 Obtaining Query Execution Plan Information
==============================================

* Menu:

* using-explain::                Optimizing Queries with EXPLAIN
* explain-output::               EXPLAIN Output Format
* explain-extended::             EXPLAIN EXTENDED Output Format
* estimating-performance::       Estimating Query Performance


File: manual.info,  Node: using-explain,  Next: explain-output,  Prev: execution-plan-information,  Up: execution-plan-information

8.2.1 Optimizing Queries with EXPLAIN
-------------------------------------

The *Note `EXPLAIN': explain. statement can be used to obtain
information about how MySQL executes a statement:

   * When you precede a *Note `SELECT': select.  statement with the
     keyword *Note `EXPLAIN': explain, MySQL displays information from
     the optimizer about the statement execution plan. That is, MySQL
     explains how it would process the statement, including information
     about how tables are joined and in which order. For information
     about using *Note `EXPLAIN': explain. to obtain execution plan
     information, see *Note explain-output::.

   * *Note `EXPLAIN EXTENDED': explain-extended. can be used to obtain
     additional execution plan information. See *Note
     explain-extended::.

   * As of MySQL 5.1.5, *Note `EXPLAIN PARTITIONS': explain. is useful
     for examining queries involving partitioned tables. See *Note
     partitioning-info::.

With the help of *Note `EXPLAIN': explain, you can see where you should
add indexes to tables so that the statement executes faster by using
indexes to find rows. You can also use *Note `EXPLAIN': explain. to
check whether the optimizer joins the tables in an optimal order. To
give a hint to the optimizer to use a join order corresponding to the
order in which the tables are named in a *Note `SELECT': select.
statement, begin the statement with `SELECT STRAIGHT_JOIN' rather than
just *Note `SELECT': select. (See *Note select::.)

If you have a problem with indexes not being used when you believe that
they should be, run *Note `ANALYZE TABLE': analyze-table. to update
table statistics, such as cardinality of keys, that can affect the
choices the optimizer makes. See *Note analyze-table::.

*Note*:

*Note `EXPLAIN': explain. can also be used to obtain information about
the columns in a table.  *Note `EXPLAIN TBL_NAME': explain. is
synonymous with `DESCRIBE TBL_NAME' and `SHOW COLUMNS FROM TBL_NAME'.
For more information, see *Note describe::, and *Note show-columns::.


File: manual.info,  Node: explain-output,  Next: explain-extended,  Prev: using-explain,  Up: execution-plan-information

8.2.2 EXPLAIN Output Format
---------------------------

The *Note `EXPLAIN': explain. statement provides information about the
execution plan for a *Note `SELECT': select. statement.

*Note `EXPLAIN': explain. returns a row of information for each table
used in the *Note `SELECT': select. statement. It lists the tables in
the output in the order that MySQL would read them while processing the
statement. MySQL resolves all joins using a nested-loop join method.
This means that MySQL reads a row from the first table, and then finds
a matching row in the second table, the third table, and so on. When
all tables are processed, MySQL outputs the selected columns and
backtracks through the table list until a table is found for which there
are more matching rows. The next row is read from this table and the
process continues with the next table.

When the `EXTENDED' keyword is used, *Note `EXPLAIN': explain. produces
extra information that can be viewed by issuing a *Note `SHOW
WARNINGS': show-warnings. statement following the *Note `EXPLAIN':
explain. statement.  *Note `EXPLAIN EXTENDED': explain-extended. also
displays the `filtered' column as of MySQL 5.1.12. See *Note
explain-extended::.

*Note*:

You cannot use the `EXTENDED' and `PARTITIONS' keywords together in the
same *Note `EXPLAIN': explain. statement.

   * `EXPLAIN' Output Columns

   * `EXPLAIN' Join Types

   * `EXPLAIN' Extra Information

   * `EXPLAIN' Output Interpretation

*EXPLAIN Output Columns*

This section describes the output columns produced by *Note `EXPLAIN':
explain. Later sections provide additional information about the `type'
and `Extra' columns.

Each output row from *Note `EXPLAIN': explain.  provides information
about one table. Each row contains the values summarized in *Note
explain-output-column-table::, and described in more detail following
the table.

*EXPLAIN Output Columns*

Column             Meaning
`id'               The `SELECT' identifier
`select_type'      The `SELECT' type
`table'            The table for the output row
`partitions'       The matching partitions
`type'             The join type
`possible_keys'    The possible indexes to choose
`key'              The index actually chosen
`key_len'          The length of the chosen key
`ref'              The columns compared to the index
`rows'             Estimate of rows to be examined
`filtered'         Percentage of rows filtered by table condition
`Extra'            Additional information

   * `id'

     The *Note `SELECT': select. identifier. This is the sequential
     number of the *Note `SELECT': select. within the query. The value
     can be `NULL' if the row refers to the union result of other rows.
     In this case, the `table' column shows a value like `<unionM,N>'
     to indicate that the row refers to the union of the rows with `id'
     values of M and N.

   * `select_type'

     The type of *Note `SELECT': select, which can be any of those
     shown in the following table.

     This table lists `select_type' values and describes the meaning of
     each.

     `select_type'     Meaning
     Value             
     `SIMPLE'          Simple *Note `SELECT': select. (not using *Note
                       `UNION': union. or subqueries)
     `PRIMARY'         Outermost *Note `SELECT': select.
     *Note `UNION':    Second or later *Note `SELECT': select. statement
     union.            in a *Note `UNION': union.
     `DEPENDENT UNION' Second or later *Note `SELECT': select. statement
                       in a *Note `UNION': union, dependent on outer
                       query
     `UNION RESULT'    Result of a *Note `UNION': union.
     `SUBQUERY'        First *Note `SELECT': select. in subquery
     `DEPENDENT        First *Note `SELECT': select. in subquery,
     SUBQUERY'         dependent on outer query
     `DERIVED'         Derived table *Note `SELECT': select. (subquery in
                       `FROM' clause)
     `UNCACHEABLE      A subquery for which the result cannot be cached
     SUBQUERY'         and must be re-evaluated for each row of the
                       outer query
     `UNCACHEABLE      The second or later select in a *Note `UNION':
     UNION'            union.  that belongs to an uncacheable subquery
                       (see `UNCACHEABLE SUBQUERY')

     `DEPENDENT' typically signifies the use of a correlated subquery.
     See *Note correlated-subqueries::.

     `DEPENDENT SUBQUERY' evaluation differs from `UNCACHEABLE
     SUBQUERY' evaluation. For `DEPENDENT SUBQUERY', the subquery is
     re-evaluated only once for each set of different values of the
     variables from its outer context. For `UNCACHEABLE SUBQUERY', the
     subquery is re-evaluated for each row of the outer context.

     Cacheability of subqueries differs from caching of query results
     in the query cache (which is described in *Note
     query-cache-operation::). Subquery caching occurs during query
     execution, whereas the query cache is used to store results only
     after query execution finishes.

   * `table'

     The name of the table to which the row of output refers.  This can
     also be one of the following values:

        * `<unionM,N>': The row refers to the union of the rows with
          `id' values of M and N.

        * `<derivedN>': The row refers to the derived table result for
          the row with an `id' value of N. A derived table may result,
          for example, from a subquery in the `FROM' clause.

   * `partitions'

     The partitions from which records would be matched by the query.
     This column is displayed only if the `PARTITIONS' keyword is used.
     The value is `NULL' for nonpartitioned tables. See *Note
     partitioning-info::.

   * `type'

     The join type. For descriptions of the different types, see
     `EXPLAIN' Join Types.

   * `possible_keys'

     The `possible_keys' column indicates which indexes MySQL can
     choose from use to find the rows in this table. Note that this
     column is totally independent of the order of the tables as
     displayed in the output from *Note `EXPLAIN': explain. That means
     that some of the keys in `possible_keys' might not be usable in
     practice with the generated table order.

     If this column is `NULL', there are no relevant indexes. In this
     case, you may be able to improve the performance of your query by
     examining the `WHERE' clause to check whether it refers to some
     column or columns that would be suitable for indexing. If so,
     create an appropriate index and check the query with *Note
     `EXPLAIN': explain. again. See *Note alter-table::.

     To see what indexes a table has, use `SHOW INDEX FROM TBL_NAME'.

   * `key'

     The `key' column indicates the key (index) that MySQL actually
     decided to use. If MySQL decides to use one of the `possible_keys'
     indexes to look up rows, that index is listed as the key value.

     It is possible that `key' will name an index that is not present
     in the `possible_keys' value. This can happen if none of the
     `possible_keys' indexes are suitable for looking up rows, but all
     the columns selected by the query are columns of some other index.
     That is, the named index covers the selected columns, so although
     it is not used to determine which rows to retrieve, an index scan
     is more efficient than a data row scan.

     For `InnoDB', a secondary index might cover the selected columns
     even if the query also selects the primary key because `InnoDB'
     stores the primary key value with each secondary index. If `key'
     is `NULL', MySQL found no index to use for executing the query more
     efficiently.

     To force MySQL to use or ignore an index listed in the
     `possible_keys' column, use `FORCE INDEX', `USE INDEX', or `IGNORE
     INDEX' in your query. See *Note index-hints::.

     For `MyISAM' and `NDB' tables, running *Note `ANALYZE TABLE':
     analyze-table.  helps the optimizer choose better indexes. For
     `MyISAM' tables, *Note `myisamchk --analyze': myisamchk. does the
     same as *Note `ANALYZE TABLE': analyze-table. See *Note
     myisam-table-maintenance::.

   * `key_len'

     The `key_len' column indicates the length of the key that MySQL
     decided to use. The length is `NULL' if the `key' column says
     `NULL'. Note that the value of `key_len' enables you to determine
     how many parts of a multiple-part key MySQL actually uses.

   * `ref'

     The `ref' column shows which columns or constants are compared to
     the index named in the `key' column to select rows from the table.

   * `rows'

     The `rows' column indicates the number of rows MySQL believes it
     must examine to execute the query.

     For *Note `InnoDB': innodb-storage-engine. tables, this number is
     an estimate, and may not always be exact.

   * `filtered'

     The `filtered' column indicates an estimated percentage of table
     rows that will be filtered by the table condition. That is, `rows'
     shows the estimated number of rows examined and `rows' x `filtered'
     / `100' shows the number of rows that will be joined with previous
     tables. This column is displayed if you use *Note `EXPLAIN
     EXTENDED': explain-extended.  (New in MySQL 5.1.12)

   * `Extra'

     This column contains additional information about how MySQL
     resolves the query. For descriptions of the different values, see
     `EXPLAIN' Extra Information.

*EXPLAIN Join Types*

The `type' column of *Note `EXPLAIN': explain. output describes how
tables are joined. The following list describes the join types, ordered
from the best type to the worst:

   * `system'

     The table has only one row (= system table). This is a special
     case of the `const' join type.

   * `const'

     The table has at most one matching row, which is read at the start
     of the query. Because there is only one row, values from the
     column in this row can be regarded as constants by the rest of the
     optimizer.  `const' tables are very fast because they are read
     only once.

     `const' is used when you compare all parts of a `PRIMARY KEY' or
     `UNIQUE' index to constant values. In the following queries,
     TBL_NAME can be used as a `const' table:


          SELECT * FROM TBL_NAME WHERE PRIMARY_KEY=1;

          SELECT * FROM TBL_NAME
            WHERE PRIMARY_KEY_PART1=1 AND PRIMARY_KEY_PART2=2;

   * `eq_ref'

     One row is read from this table for each combination of rows from
     the previous tables. Other than the `system' and `const' types,
     this is the best possible join type. It is used when all parts of
     an index are used by the join and the index is a `PRIMARY KEY' or
     `UNIQUE NOT NULL' index.

     `eq_ref' can be used for indexed columns that are compared using
     the `=' operator. The comparison value can be a constant or an
     expression that uses columns from tables that are read before this
     table. In the following examples, MySQL can use an `eq_ref' join to
     process REF_TABLE:


          SELECT * FROM REF_TABLE,OTHER_TABLE
            WHERE REF_TABLE.KEY_COLUMN=OTHER_TABLE.COLUMN;

          SELECT * FROM REF_TABLE,OTHER_TABLE
            WHERE REF_TABLE.KEY_COLUMN_PART1=OTHER_TABLE.COLUMN
            AND REF_TABLE.KEY_COLUMN_PART2=1;

   * `ref'

     All rows with matching index values are read from this table for
     each combination of rows from the previous tables.  `ref' is used
     if the join uses only a leftmost prefix of the key or if the key
     is not a `PRIMARY KEY' or `UNIQUE' index (in other words, if the
     join cannot select a single row based on the key value). If the
     key that is used matches only a few rows, this is a good join type.

     `ref' can be used for indexed columns that are compared using the
     `=' or `<=>' operator. In the following examples, MySQL can use a
     `ref' join to process REF_TABLE:


          SELECT * FROM REF_TABLE WHERE KEY_COLUMN=EXPR;

          SELECT * FROM REF_TABLE,OTHER_TABLE
            WHERE REF_TABLE.KEY_COLUMN=OTHER_TABLE.COLUMN;

          SELECT * FROM REF_TABLE,OTHER_TABLE
            WHERE REF_TABLE.KEY_COLUMN_PART1=OTHER_TABLE.COLUMN
            AND REF_TABLE.KEY_COLUMN_PART2=1;

   * `fulltext'

     The join is performed using a `FULLTEXT' index.

   * `ref_or_null'

     This join type is like `ref', but with the addition that MySQL
     does an extra search for rows that contain `NULL' values. This
     join type optimization is used most often in resolving subqueries.
     In the following examples, MySQL can use a `ref_or_null' join to
     process REF_TABLE:


          SELECT * FROM REF_TABLE
            WHERE KEY_COLUMN=EXPR OR KEY_COLUMN IS NULL;

     See *Note is-null-optimization::.

   * `index_merge'

     This join type indicates that the Index Merge optimization is
     used. In this case, the `key' column in the output row contains a
     list of indexes used, and `key_len' contains a list of the longest
     key parts for the indexes used. For more information, see *Note
     index-merge-optimization::.

   * `unique_subquery'

     This type replaces `ref' for some `IN' subqueries of the following
     form:


          VALUE IN (SELECT PRIMARY_KEY FROM SINGLE_TABLE WHERE SOME_EXPR)

     `unique_subquery' is just an index lookup function that replaces
     the subquery completely for better efficiency.

   * `index_subquery'

     This join type is similar to `unique_subquery'. It replaces `IN'
     subqueries, but it works for nonunique indexes in subqueries of
     the following form:


          VALUE IN (SELECT KEY_COLUMN FROM SINGLE_TABLE WHERE SOME_EXPR)

   * `range'

     Only rows that are in a given range are retrieved, using an index
     to select the rows. The `key' column in the output row indicates
     which index is used. The `key_len' contains the longest key part
     that was used. The `ref' column is `NULL' for this type.

     `range' can be used when a key column is compared to a constant
     using any of the `=', `<>', `>', `>=', `<', `<=', `IS NULL', `<=>',
     `BETWEEN', or `IN()' operators:


          SELECT * FROM TBL_NAME
            WHERE KEY_COLUMN = 10;

          SELECT * FROM TBL_NAME
            WHERE KEY_COLUMN BETWEEN 10 and 20;

          SELECT * FROM TBL_NAME
            WHERE KEY_COLUMN IN (10,20,30);

          SELECT * FROM TBL_NAME
            WHERE KEY_PART1= 10 AND KEY_PART2 IN (10,20,30);

   * `index'

     The `index' join type is the same as `ALL', except that the index
     tree is scanned. This occurs two ways:

        * If the index is a covering index for the queries and can be
          used to satisfy all data required from the table, only the
          index tree is scanned. In this case, the `Extra' column says
          `Using index'. An index-only scan usually is faster than
          `ALL' because the size of the index usually is smaller than
          the table data.

        * A full table scan is performed using reads from the index to
          look up data rows in index order. `Uses index' does not
          appear in the `Extra' column.

     MySQL can use this join type when the query uses only columns that
     are part of a single index.

   * `ALL'

     A full table scan is done for each combination of rows from the
     previous tables. This is normally not good if the table is the
     first table not marked `const', and usually _very_ bad in all
     other cases. Normally, you can avoid `ALL' by adding indexes that
     enable row retrieval from the table based on constant values or
     column values from earlier tables.

*EXPLAIN Extra Information*

The `Extra' column of *Note `EXPLAIN': explain. output contains
additional information about how MySQL resolves the query. The
following list explains the values that can appear in this column. If
you want to make your queries as fast as possible, look out for `Extra'
values of `Using filesort' and `Using temporary'.

   * `Child of 'TABLE' pushed join@1'

     This table is referenced as the child of TABLE in a join that can
     be pushed down to the NDB kernel. Applies only in MySQL Cluster
     NDB 7.2.0 and later, when pushed-down joins are enabled. See the
     description of the `ndb_join_pushdown' server system variable for
     more information and examples.

   * `const row not found'

     For a query such as `SELECT ... FROM TBL_NAME', the table was
     empty.

   * `Distinct'

     MySQL is looking for distinct values, so it stops searching for
     more rows for the current row combination after it has found the
     first matching row.

   * `Full scan on NULL key'

     This occurs for subquery optimization as a fallback strategy when
     the optimizer cannot use an index-lookup access method.

   * `Impossible HAVING'

     The `HAVING' clause is always false and cannot select any rows.

   * `Impossible WHERE'

     The `WHERE' clause is always false and cannot select any rows.

   * `Impossible WHERE noticed after reading const tables'

     MySQL has read all `const' (and `system') tables and notice that
     the `WHERE' clause is always false.

   * `No matching min/max row'

     No row satisfies the condition for a query such as `SELECT
     MIN(...) FROM ... WHERE CONDITION'.

   * `no matching row in const table'

     For a query with a join, there was an empty table or a table with
     no rows satisfying a unique index condition.

   * `No tables used'

     The query has no `FROM' clause, or has a `FROM DUAL' clause.

   * `Not exists'

     MySQL was able to do a `LEFT JOIN' optimization on the query and
     does not examine more rows in this table for the previous row
     combination after it finds one row that matches the `LEFT JOIN'
     criteria. Here is an example of the type of query that can be
     optimized this way:


          SELECT * FROM t1 LEFT JOIN t2 ON t1.id=t2.id
            WHERE t2.id IS NULL;

     Assume that `t2.id' is defined as `NOT NULL'. In this case, MySQL
     scans `t1' and looks up the rows in `t2' using the values of
     `t1.id'. If MySQL finds a matching row in `t2', it knows that
     `t2.id' can never be `NULL', and does not scan through the rest of
     the rows in `t2' that have the same `id' value. In other words,
     for each row in `t1', MySQL needs to do only a single lookup in
     `t2', regardless of how many rows actually match in `t2'.

   * `Parent of N pushed join@1'

     This table is referenced as the parent of the table in row N of
     the current *Note `EXPLAIN': explain. output in a join that can be
     pushed down to the NDB kernel. Applies only in MySQL Cluster NDB
     7.2.0 and later when pushed-down joins are enabled. See the
     description of the `ndb_join_pushdown' server system variable for
     more information and examples.

   * `Range checked for each record (index map: N)'

     MySQL found no good index to use, but found that some of indexes
     might be used after column values from preceding tables are known.
     For each row combination in the preceding tables, MySQL checks
     whether it is possible to use a `range' or `index_merge' access
     method to retrieve rows. This is not very fast, but is faster than
     performing a join with no index at all. The applicability criteria
     are as described in *Note range-optimization::, and *Note
     index-merge-optimization::, with the exception that all column
     values for the preceding table are known and considered to be
     constants.

     Indexes are numbered beginning with 1, in the same order as shown
     by *Note `SHOW INDEX': show-index. for the table. The index map
     value N is a bitmask value that indicates which indexes are
     candidates.  For example, a value of `0x19' (binary 11001) means
     that indexes 1, 4, and 5 will be considered.

   * `Scanned N databases'

     This indicates how many directory scans the server performs when
     processing a query for `INFORMATION_SCHEMA' tables, as described
     in *Note information-schema-optimization::. The value of N can be
     0, 1, or `all'.

   * `Select tables optimized away'

     The query contained only aggregate functions (`MIN()', `MAX()')
     that were all resolved using an index, or `COUNT(*)' for `MyISAM',
     and no `GROUP BY' clause. The optimizer determined that only one
     row should be returned.

   * `Skip_open_table', `Open_frm_only', `Open_trigger_only',
     `Open_full_table'

     These values indicate file-opening optimizations that apply to
     queries for `INFORMATION_SCHEMA' tables, as described in *Note
     information-schema-optimization::.

        * `Skip_open_table': Table files do not need to be opened. The
          information has already become available within the query by
          scanning the database directory.

        * `Open_frm_only': Only the table's `.frm' file need be opened.

        * `Open_trigger_only': Only the table's `.TRG' file need be
          opened.

        * `Open_full_table': The unoptimized information lookup. The
          `.frm', `.MYD', and `.MYI' files must be opened.

   * `unique row not found'

     For a query such as `SELECT ... FROM TBL_NAME', no rows satisfy
     the condition for a `UNIQUE' index or `PRIMARY KEY' on the table.

   * `Using filesort'

     MySQL must do an extra pass to find out how to retrieve the rows
     in sorted order. The sort is done by going through all rows
     according to the join type and storing the sort key and pointer to
     the row for all rows that match the `WHERE' clause. The keys then
     are sorted and the rows are retrieved in sorted order. See *Note
     order-by-optimization::.

   * `Using index'

     The column information is retrieved from the table using only
     information in the index tree without having to do an additional
     seek to read the actual row. This strategy can be used when the
     query uses only columns that are part of a single index.

     If the `Extra' column also says `Using where', it means the index
     is being used to perform lookups of key values. Without `Using
     where', the optimizer may be reading the index to avoid reading
     data rows but not using it for lookups. For example, if the index
     is a covering index for the query, the optimizer may scan it
     without using it for lookups.

     For `InnoDB' tables that have a user-defined clustered index, that
     index can be used even when `Using index' is absent from the
     `Extra' column. This is the case if `type' is `index' and `key' is
     `PRIMARY'.

   * `Using index for group-by'

     Similar to the `Using index' table access method, `Using index for
     group-by' indicates that MySQL found an index that can be used to
     retrieve all columns of a `GROUP BY' or `DISTINCT' query without
     any extra disk access to the actual table. Additionally, the index
     is used in the most efficient way so that for each group, only a
     few index entries are read. For details, see *Note
     group-by-optimization::.

   * `Using join buffer'

     Tables from earlier joins are read in portions into the join
     buffer, and then their rows are used from the buffer to perform
     the join with the current table.

   * `Using sort_union(...)', `Using union(...)', `Using intersect(...)'

     These indicate how index scans are merged for the `index_merge'
     join type.  See *Note index-merge-optimization::.

   * `Using temporary'

     To resolve the query, MySQL needs to create a temporary table to
     hold the result. This typically happens if the query contains
     `GROUP BY' and `ORDER BY' clauses that list columns differently.

   * `Using where'

     A `WHERE' clause is used to restrict which rows to match against
     the next table or send to the client.  Unless you specifically
     intend to fetch or examine all rows from the table, you may have
     something wrong in your query if the `Extra' value is not `Using
     where' and the table join type is `ALL' or `index'. Even if you are
     using an index for all parts of a `WHERE' clause, you may see
     `Using where' if the column can be `NULL'.

   * `Using where with pushed condition'

     This item applies to *Note `NDBCLUSTER': mysql-cluster.  tables
     _only_. It means that MySQL Cluster is using the Condition
     Pushdown optimization to improve the efficiency of a direct
     comparison between a nonindexed column and a constant. In such
     cases, the condition is `pushed down' to the cluster's data nodes
     and is evaluated on all data nodes simultaneously. This eliminates
     the need to send nonmatching rows over the network, and can speed
     up such queries by a factor of 5 to 10 times over cases where
     Condition Pushdown could be but is not used. For more information,
     see *Note condition-pushdown-optimization::.

*EXPLAIN Output Interpretation*

You can get a good indication of how good a join is by taking the
product of the values in the `rows' column of the *Note `EXPLAIN':
explain. output. This should tell you roughly how many rows MySQL must
examine to execute the query. If you restrict queries with the
`max_join_size' system variable, this row product also is used to
determine which multiple-table *Note `SELECT': select. statements to
execute and which to abort. See *Note server-parameters::.

The following example shows how a multiple-table join can be optimized
progressively based on the information provided by *Note `EXPLAIN':
explain.

Suppose that you have the *Note `SELECT': select.  statement shown here
and that you plan to examine it using *Note `EXPLAIN': explain.:


     EXPLAIN SELECT tt.TicketNumber, tt.TimeIn,
                    tt.ProjectReference, tt.EstimatedShipDate,
                    tt.ActualShipDate, tt.ClientID,
                    tt.ServiceCodes, tt.RepetitiveID,
                    tt.CurrentProcess, tt.CurrentDPPerson,
                    tt.RecordVolume, tt.DPPrinted, et.COUNTRY,
                    et_1.COUNTRY, do.CUSTNAME
             FROM tt, et, et AS et_1, do
             WHERE tt.SubmitTime IS NULL
               AND tt.ActualPC = et.EMPLOYID
               AND tt.AssignedPC = et_1.EMPLOYID
               AND tt.ClientID = do.CUSTNMBR;

For this example, make the following assumptions:

   * The columns being compared have been declared as follows.

     This table outlines table names, column names, and data types for
     the columns being compared in the `EXPLAIN' example described in
     the preceding text.

     Table   Column            Data Type
     `tt'    `ActualPC'        `CHAR(10)'
     `tt'    `AssignedPC'      `CHAR(10)'
     `tt'    `ClientID'        `CHAR(10)'
     `et'    `EMPLOYID'        `CHAR(15)'
     `do'    `CUSTNMBR'        `CHAR(15)'

   * The tables have the following indexes.

     This table lists indexes for each of the tables that are part of
     the `EXPLAIN' example described in the preceding text.

     Table   Index
     `tt'    `ActualPC'
     `tt'    `AssignedPC'
     `tt'    `ClientID'
     `et'    `EMPLOYID' (primary key)
     `do'    `CUSTNMBR' (primary key)

   * The `tt.ActualPC' values are not evenly distributed.

Initially, before any optimizations have been performed, the *Note
`EXPLAIN': explain. statement produces the following information:


     table type possible_keys key  key_len ref  rows  Extra
     et    ALL  PRIMARY       NULL NULL    NULL 74
     do    ALL  PRIMARY       NULL NULL    NULL 2135
     et_1  ALL  PRIMARY       NULL NULL    NULL 74
     tt    ALL  AssignedPC,   NULL NULL    NULL 3872
                ClientID,
                ActualPC
           Range checked for each record (index map: 0x23)

Because `type' is `ALL' for each table, this output indicates that
MySQL is generating a Cartesian product of all the tables; that is,
every combination of rows. This takes quite a long time, because the
product of the number of rows in each table must be examined. For the
case at hand, this product is 74 x 2135 x 74 x 3872 = 45,268,558,720
rows. If the tables were bigger, you can only imagine how long it would
take.

One problem here is that MySQL can use indexes on columns more
efficiently if they are declared as the same type and size. In this
context, *Note `VARCHAR': char. and *Note `CHAR': char. are considered
the same if they are declared as the same size.  `tt.ActualPC' is
declared as `CHAR(10)' and `et.EMPLOYID' is `CHAR(15)', so there is a
length mismatch.

To fix this disparity between column lengths, use *Note `ALTER TABLE':
alter-table. to lengthen `ActualPC' from 10 characters to 15 characters:


     mysql> ALTER TABLE tt MODIFY ActualPC VARCHAR(15);

Now `tt.ActualPC' and `et.EMPLOYID' are both `VARCHAR(15)'. Executing
the *Note `EXPLAIN': explain. statement again produces this result:


     table type   possible_keys key     key_len ref         rows    Extra
     tt    ALL    AssignedPC,   NULL    NULL    NULL        3872    Using
                  ClientID,                                         where
                  ActualPC
     do    ALL    PRIMARY       NULL    NULL    NULL        2135
           Range checked for each record (index map: 0x1)
     et_1  ALL    PRIMARY       NULL    NULL    NULL        74
           Range checked for each record (index map: 0x1)
     et    eq_ref PRIMARY       PRIMARY 15      tt.ActualPC 1

This is not perfect, but is much better: The product of the `rows'
values is less by a factor of 74. This version executes in a couple of
seconds.

A second alteration can be made to eliminate the column length
mismatches for the `tt.AssignedPC = et_1.EMPLOYID' and `tt.ClientID =
do.CUSTNMBR' comparisons:


     mysql> ALTER TABLE tt MODIFY AssignedPC VARCHAR(15),
         ->                MODIFY ClientID   VARCHAR(15);

After that modification, *Note `EXPLAIN': explain.  produces the output
shown here:


     table type   possible_keys key      key_len ref           rows Extra
     et    ALL    PRIMARY       NULL     NULL    NULL          74
     tt    ref    AssignedPC,   ActualPC 15      et.EMPLOYID   52   Using
                  ClientID,                                         where
                  ActualPC
     et_1  eq_ref PRIMARY       PRIMARY  15      tt.AssignedPC 1
     do    eq_ref PRIMARY       PRIMARY  15      tt.ClientID   1

At this point, the query is optimized almost as well as possible. The
remaining problem is that, by default, MySQL assumes that values in the
`tt.ActualPC' column are evenly distributed, and that is not the case
for the `tt' table. Fortunately, it is easy to tell MySQL to analyze
the key distribution:


     mysql> ANALYZE TABLE tt;

With the additional index information, the join is perfect and *Note
`EXPLAIN': explain. produces this result:


     table type   possible_keys key     key_len ref           rows Extra
     tt    ALL    AssignedPC    NULL    NULL    NULL          3872 Using
                  ClientID,                                        where
                  ActualPC
     et    eq_ref PRIMARY       PRIMARY 15      tt.ActualPC   1
     et_1  eq_ref PRIMARY       PRIMARY 15      tt.AssignedPC 1
     do    eq_ref PRIMARY       PRIMARY 15      tt.ClientID   1

Note that the `rows' column in the output from *Note `EXPLAIN':
explain. is an educated guess from the MySQL join optimizer. You should
check whether the numbers are even close to the truth by comparing the
`rows' product with the actual number of rows that the query returns.
If the numbers are quite different, you might get better performance by
using `STRAIGHT_JOIN' in your *Note `SELECT': select. statement and
trying to list the tables in a different order in the `FROM' clause.

It is possible in some cases to execute statements that modify data
when *Note `EXPLAIN SELECT': explain. is used with a subquery; for more
information, see *Note from-clause-subqueries::.


File: manual.info,  Node: explain-extended,  Next: estimating-performance,  Prev: explain-output,  Up: execution-plan-information

8.2.3 EXPLAIN EXTENDED Output Format
------------------------------------

When *Note `EXPLAIN': explain. is used with the `EXTENDED' keyword, the
output includes a `filtered' column not otherwise displayed. This
column indicates the estimated percentage of table rows that will be
filtered by the table condition. In addition, the statement produces
extra information that can be viewed by issuing a *Note `SHOW
WARNINGS': show-warnings. statement following the *Note `EXPLAIN':
explain. statement.  The `Message' value in *Note `SHOW WARNINGS':
show-warnings. output displays how the optimizer qualifies table and
column names in the *Note `SELECT': select. statement, what the *Note
`SELECT': select. looks like after the application of rewriting and
optimization rules, and possibly other notes about the optimization
process.

Here is an example of extended output:


     mysql> EXPLAIN EXTENDED
         -> SELECT t1.a, t1.a IN (SELECT t2.a FROM t2) FROM t1\G
     *************************** 1. row ***************************
                id: 1
       select_type: PRIMARY
             table: t1
              type: index
     possible_keys: NULL
               key: PRIMARY
           key_len: 4
               ref: NULL
              rows: 4
          filtered: 100.00
             Extra: Using index
     *************************** 2. row ***************************
                id: 2
       select_type: DEPENDENT SUBQUERY
             table: t2
              type: index_subquery
     possible_keys: a
               key: a
           key_len: 5
               ref: func
              rows: 2
          filtered: 100.00
             Extra: Using index
     2 rows in set, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS\G
     *************************** 1. row ***************************
       Level: Note
        Code: 1003
     Message: select `test`.`t1`.`a` AS `a`,
              <in_optimizer>(`test`.`t1`.`a`,
              <exists>(<index_lookup>(<cache>(`test`.`t1`.`a`)
              in t2 on a checking NULL having
              <is_not_null_test>(`test`.`t2`.`a`)))) AS `t1.a
              IN (SELECT t2.a FROM t2)` from `test`.`t1`
     1 row in set (0.00 sec)

Because the statement displayed by *Note `SHOW WARNINGS':
show-warnings. may contain special markers to provide information about
query rewriting or optimizer actions, the statement is not necessarily
valid SQL and is not intended to be executed. The output may also
include rows with `Message' values that provide additional non-SQL
explanatory notes about actions taken by the optimizer.

The following list describes special markers that can appear in
`EXTENDED' output displayed by *Note `SHOW WARNINGS': show-warnings.:

   * `<cache>(EXPR)'

     The expression (such as a scalar subquery) is executed once and
     the resulting value is saved in memory for later use.

   * `<exists>(QUERY FRAGMENT)'

     The subquery predicate is converted to an `EXISTS' predicate and
     the subquery is transformed so that it can be used together with
     the `EXISTS' predicate.

   * `<in_optimizer>(QUERY FRAGMENT)'

     This is an internal optimizer object with no user significance.

   * `<index_lookup>(QUERY FRAGMENT)'

     The query fragment is processed using an index lookup to find
     qualifying rows.

   * `<is_not_null_test>(EXPR)'

     A test to verify that the expression does not evaluate to `NULL'.

   * `<primary_index_lookup>(QUERY FRAGMENT)'

     The query fragment is processed using a primary key lookup to find
     qualifying rows.

   * `<ref_null_helper>(EXPR)'

     This is an internal optimizer object with no user significance.

When some tables are of `const' or `system' type, expressions involving
columns from these tables are evaluated early by the optimizer and are
not part of the displayed statement. However, with `FORMAT=JSON', some
`const' table accesses are displayed as a `ref' access that uses a
const value.


File: manual.info,  Node: estimating-performance,  Prev: explain-extended,  Up: execution-plan-information

8.2.4 Estimating Query Performance
----------------------------------

In most cases, you can estimate query performance by counting disk
seeks. For small tables, you can usually find a row in one disk seek
(because the index is probably cached). For bigger tables, you can
estimate that, using B-tree indexes, you need this many seeks to find a
row: `log(ROW_COUNT) / log(INDEX_BLOCK_LENGTH / 3 * 2 / (INDEX_LENGTH +
DATA_POINTER_LENGTH)) + 1'.

In MySQL, an index block is usually 1,024 bytes and the data pointer is
usually four bytes. For a 500,000-row table with a key value length of
three bytes (the size of *Note `MEDIUMINT': integer-types.), the
formula indicates `log(500,000)/log(1024/3*2/(3+4)) + 1' = `4' seeks.

This index would require storage of about 500,000 * 7 * 3/2 = 5.2MB
(assuming a typical index buffer fill ratio of 2/3), so you probably
have much of the index in memory and so need only one or two calls to
read data to find the row.

For writes, however, you need four seek requests to find where to place
a new index value and normally two seeks to update the index and write
the row.

Note that the preceding discussion does not mean that your application
performance slowly degenerates by log N. As long as everything is
cached by the OS or the MySQL server, things become only marginally
slower as the table gets bigger. After the data gets too big to be
cached, things start to go much slower until your applications are
bound only by disk seeks (which increase by log N). To avoid this,
increase the key cache size as the data grows. For `MyISAM' tables, the
key cache size is controlled by the `key_buffer_size' system variable.
See *Note server-parameters::.


File: manual.info,  Node: statement-optimization,  Next: controlling-optimizer,  Prev: execution-plan-information,  Up: optimization

8.3 Optimizing SQL Statements
=============================

* Menu:

* select-optimization::          Optimizing SELECT Statements
* non-select-optimization::      Optimizing Non-SELECT Statements
* information-schema-optimization::  INFORMATION_SCHEMA Optimization
* miscellaneous-optimization-tips::  Other Optimization Tips


File: manual.info,  Node: select-optimization,  Next: non-select-optimization,  Prev: statement-optimization,  Up: statement-optimization

8.3.1 Optimizing SELECT Statements
----------------------------------

* Menu:

* select-speed::                 Speed of SELECT Statements
* where-optimizations::          How MySQL Optimizes WHERE Clauses
* range-optimization::           Range Optimization
* index-merge-optimization::     Index Merge Optimization
* condition-pushdown-optimization::  Engine Condition Pushdown Optimization
* is-null-optimization::         IS NULL Optimization
* left-join-optimization::       LEFT JOIN and RIGHT JOIN Optimization
* nested-loop-joins::            Nested-Loop Join Algorithms
* nested-join-optimization::     Nested Join Optimization
* outer-join-simplification::    Outer Join Simplification
* order-by-optimization::        ORDER BY Optimization
* group-by-optimization::        GROUP BY Optimization
* distinct-optimization::        DISTINCT Optimization
* subquery-optimization-with-exists::  Optimizing Subqueries with EXISTS Strategy
* limit-optimization::           Optimizing LIMIT Queries
* how-to-avoid-table-scan::      How to Avoid Table Scans

First, one factor affects all statements: The more complex your
permissions setup, the more overhead you have. Using simpler
permissions when you issue *Note `GRANT': grant.  statements enables
MySQL to reduce permission-checking overhead when clients execute
statements. For example, if you do not grant any table-level or
column-level privileges, the server need not ever check the contents of
the `tables_priv' and `columns_priv' tables. Similarly, if you place no
resource limits on any accounts, the server does not have to perform
resource counting. If you have a very high statement-processing load,
it may be worth the time to use a simplified grant structure to reduce
permission-checking overhead.

If your problem is with a specific MySQL expression or function, you
can perform a timing test by invoking the `BENCHMARK()' function using
the *Note `mysql': mysql. client program. Its syntax is
`BENCHMARK(LOOP_COUNT,EXPRESSION)'.  The return value is always zero,
but *Note `mysql': mysql.  prints a line displaying approximately how
long the statement took to execute. For example:


     mysql> SELECT BENCHMARK(1000000,1+1);
     +------------------------+
     | BENCHMARK(1000000,1+1) |
     +------------------------+
     |                      0 |
     +------------------------+
     1 row in set (0.32 sec)

This result was obtained on a Pentium II 400MHz system. It shows that
MySQL can execute 1,000,000 simple addition expressions in 0.32 seconds
on that system.

All MySQL functions should be highly optimized, but there may be some
exceptions. `BENCHMARK()' is an excellent tool for finding out if some
function is a problem for your queries.


File: manual.info,  Node: select-speed,  Next: where-optimizations,  Prev: select-optimization,  Up: select-optimization

8.3.1.1 Speed of SELECT Statements
..................................

In general, when you want to make a slow `SELECT ...  WHERE' query
faster, the first thing to check is whether you can add an index. All
references between different tables should usually be done with
indexes. You can use the *Note `EXPLAIN': explain. statement to
determine which indexes are used for a *Note `SELECT': select. See
*Note using-explain::, and *Note mysql-indexes::.

Some general tips for speeding up queries on `MyISAM' tables:

   * To help MySQL better optimize queries, use *Note `ANALYZE TABLE':
     analyze-table. or run *Note `myisamchk --analyze': myisamchk. on a
     table after it has been loaded with data. This updates a value for
     each index part that indicates the average number of rows that
     have the same value. (For unique indexes, this is always 1.) MySQL
     uses this to decide which index to choose when you join two tables
     based on a nonconstant expression. You can check the result from
     the table analysis by using `SHOW INDEX FROM TBL_NAME' and
     examining the `Cardinality' value.  *Note `myisamchk --description
     --verbose': myisamchk. shows index distribution information.

   * To sort an index and data according to an index, use *Note
     `myisamchk --sort-index --sort-records=1': myisamchk.  (assuming
     that you want to sort on index 1). This is a good way to make
     queries faster if you have a unique index from which you want to
     read all rows in order according to the index. The first time you
     sort a large table this way, it may take a long time.


File: manual.info,  Node: where-optimizations,  Next: range-optimization,  Prev: select-speed,  Up: select-optimization

8.3.1.2 How MySQL Optimizes WHERE Clauses
.........................................

This section discusses optimizations that can be made for processing
`WHERE' clauses. The examples use *Note `SELECT': select. statements,
but the same optimizations apply for `WHERE' clauses in *Note `DELETE':
delete. and *Note `UPDATE': update. statements.

Work on the MySQL optimizer is ongoing, so this section is incomplete.
MySQL performs a great many optimizations, not all of which are
documented here.

Some of the optimizations performed by MySQL follow:

   * Removal of unnecessary parentheses:


             ((a AND b) AND c OR (((a AND b) AND (c AND d))))
          -> (a AND b AND c) OR (a AND b AND c AND d)

   * Constant folding:


             (a<b AND b=c) AND a=5
          -> b>5 AND b=c AND a=5

   * Constant condition removal (needed because of constant folding):


             (B>=5 AND B=5) OR (B=6 AND 5=5) OR (B=7 AND 5=6)
          -> B=5 OR B=6

   * Constant expressions used by indexes are evaluated only once.

   * `COUNT(*)' on a single table without a `WHERE' is retrieved
     directly from the table information for `MyISAM' and `MEMORY'
     tables. This is also done for any `NOT NULL' expression when used
     with only one table.

   * Early detection of invalid constant expressions. MySQL quickly
     detects that some *Note `SELECT': select. statements are
     impossible and returns no rows.

   * `HAVING' is merged with `WHERE' if you do not use `GROUP BY' or
     aggregate functions (`COUNT()', `MIN()', and so on).

   * For each table in a join, a simpler `WHERE' is constructed to get
     a fast `WHERE' evaluation for the table and also to skip rows as
     soon as possible.

   * All constant tables are read first before any other tables in the
     query. A constant table is any of the following:

        * An empty table or a table with one row.

        * A table that is used with a `WHERE' clause on a `PRIMARY KEY'
          or a `UNIQUE' index, where all index parts are compared to
          constant expressions and are defined as `NOT NULL'.

     All of the following tables are used as constant tables:


          SELECT * FROM t WHERE PRIMARY_KEY=1;
          SELECT * FROM t1,t2
            WHERE t1.PRIMARY_KEY=1 AND t2.PRIMARY_KEY=t1.id;

   * The best join combination for joining the tables is found by
     trying all possibilities. If all columns in `ORDER BY' and `GROUP
     BY' clauses come from the same table, that table is preferred
     first when joining.

   * If there is an `ORDER BY' clause and a different `GROUP BY'
     clause, or if the `ORDER BY' or `GROUP BY' contains columns from
     tables other than the first table in the join queue, a temporary
     table is created.

   * If you use the `SQL_SMALL_RESULT' option, MySQL uses an in-memory
     temporary table.

   * Each table index is queried, and the best index is used unless the
     optimizer believes that it is more efficient to use a table scan.
     At one time, a scan was used based on whether the best index
     spanned more than 30% of the table, but a fixed percentage no
     longer determines the choice between using an index or a scan. The
     optimizer now is more complex and bases its estimate on additional
     factors such as table size, number of rows, and I/O block size.

   * In some cases, MySQL can read rows from the index without even
     consulting the data file. If all columns used from the index are
     numeric, only the index tree is used to resolve the query.

   * Before each row is output, those that do not match the `HAVING'
     clause are skipped.

Some examples of queries that are very fast:


     SELECT COUNT(*) FROM TBL_NAME;

     SELECT MIN(KEY_PART1),MAX(KEY_PART1) FROM TBL_NAME;

     SELECT MAX(KEY_PART2) FROM TBL_NAME
       WHERE KEY_PART1=CONSTANT;

     SELECT ... FROM TBL_NAME
       ORDER BY KEY_PART1,KEY_PART2,... LIMIT 10;

     SELECT ... FROM TBL_NAME
       ORDER BY KEY_PART1 DESC, KEY_PART2 DESC, ... LIMIT 10;

MySQL resolves the following queries using only the index tree,
assuming that the indexed columns are numeric:


     SELECT KEY_PART1,KEY_PART2 FROM TBL_NAME WHERE KEY_PART1=VAL;

     SELECT COUNT(*) FROM TBL_NAME
       WHERE KEY_PART1=VAL1 AND KEY_PART2=VAL2;

     SELECT KEY_PART2 FROM TBL_NAME GROUP BY KEY_PART1;

The following queries use indexing to retrieve the rows in sorted order
without a separate sorting pass:


     SELECT ... FROM TBL_NAME
       ORDER BY KEY_PART1,KEY_PART2,... ;

     SELECT ... FROM TBL_NAME
       ORDER BY KEY_PART1 DESC, KEY_PART2 DESC, ... ;


File: manual.info,  Node: range-optimization,  Next: index-merge-optimization,  Prev: where-optimizations,  Up: select-optimization

8.3.1.3 Range Optimization
..........................

* Menu:

* range-access-single-part::     The Range Access Method for Single-Part Indexes
* range-access-multi-part::      The Range Access Method for Multiple-Part Indexes

The `range' access method uses a single index to retrieve a subset of
table rows that are contained within one or several index value
intervals. It can be used for a single-part or multiple-part index. The
following sections give a detailed description of how intervals are
extracted from the `WHERE' clause.


File: manual.info,  Node: range-access-single-part,  Next: range-access-multi-part,  Prev: range-optimization,  Up: range-optimization

8.3.1.4 The Range Access Method for Single-Part Indexes
.......................................................

For a single-part index, index value intervals can be conveniently
represented by corresponding conditions in the `WHERE' clause, so we
speak of _range conditions_ rather than `intervals.'

The definition of a range condition for a single-part index is as
follows:

   * For both `BTREE' and `HASH' indexes, comparison of a key part with
     a constant value is a range condition when using the `=', `<=>',
     `IN()', `IS NULL', or `IS NOT NULL' operators.

   * Additionally, for `BTREE' indexes, comparison of a key part with a
     constant value is a range condition when using the `>', `<', `>=',
     `<=', `BETWEEN', `!=', or `<>' operators, or `LIKE' comparisons if
     the argument to `LIKE' is a constant string that does not start
     with a wildcard character.

   * For all types of indexes, multiple range conditions combined with
     `OR' or `AND' form a range condition.

`Constant value' in the preceding descriptions means one of the
following:

   * A constant from the query string

   * A column of a `const' or `system' table from the same join

   * The result of an uncorrelated subquery

   * Any expression composed entirely from subexpressions of the
     preceding types

Here are some examples of queries with range conditions in the `WHERE'
clause:


     SELECT * FROM t1
       WHERE KEY_COL > 1
       AND KEY_COL < 10;

     SELECT * FROM t1
       WHERE KEY_COL = 1
       OR KEY_COL IN (15,18,20);

     SELECT * FROM t1
       WHERE KEY_COL LIKE 'ab%'
       OR KEY_COL BETWEEN 'bar' AND 'foo';

Note that some nonconstant values may be converted to constants during
the constant propagation phase.

MySQL tries to extract range conditions from the `WHERE' clause for
each of the possible indexes. During the extraction process, conditions
that cannot be used for constructing the range condition are dropped,
conditions that produce overlapping ranges are combined, and conditions
that produce empty ranges are removed.

Consider the following statement, where `key1' is an indexed column and
`nonkey' is not indexed:


     SELECT * FROM t1 WHERE
       (key1 < 'abc' AND (key1 LIKE 'abcde%' OR key1 LIKE '%b')) OR
       (key1 < 'bar' AND nonkey = 4) OR
       (key1 < 'uux' AND key1 > 'z');

The extraction process for key `key1' is as follows:

  1. Start with original `WHERE' clause:


          (key1 < 'abc' AND (key1 LIKE 'abcde%' OR key1 LIKE '%b')) OR
          (key1 < 'bar' AND nonkey = 4) OR
          (key1 < 'uux' AND key1 > 'z')

  2. Remove `nonkey = 4' and `key1 LIKE '%b'' because they cannot be
     used for a range scan. The correct way to remove them is to replace
     them with `TRUE', so that we do not miss any matching rows when
     doing the range scan. Having replaced them with `TRUE', we get:


          (key1 < 'abc' AND (key1 LIKE 'abcde%' OR TRUE)) OR
          (key1 < 'bar' AND TRUE) OR
          (key1 < 'uux' AND key1 > 'z')

  3. Collapse conditions that are always true or false:

        * `(key1 LIKE 'abcde%' OR TRUE)' is always true

        * `(key1 < 'uux' AND key1 > 'z')' is always false

     Replacing these conditions with constants, we get:


          (key1 < 'abc' AND TRUE) OR (key1 < 'bar' AND TRUE) OR (FALSE)

     Removing unnecessary `TRUE' and `FALSE' constants, we obtain:


          (key1 < 'abc') OR (key1 < 'bar')

  4. Combining overlapping intervals into one yields the final
     condition to be used for the range scan:


          (key1 < 'bar')

In general (and as demonstrated by the preceding example), the
condition used for a range scan is less restrictive than the `WHERE'
clause. MySQL performs an additional check to filter out rows that
satisfy the range condition but not the full `WHERE' clause.

The range condition extraction algorithm can handle nested `AND'/`OR'
constructs of arbitrary depth, and its output does not depend on the
order in which conditions appear in `WHERE' clause.

Currently, MySQL does not support merging multiple ranges for the
`range' access method for spatial indexes. To work around this
limitation, you can use a *Note `UNION': union. with identical *Note
`SELECT': select. statements, except that you put each spatial
predicate in a different *Note `SELECT': select.


File: manual.info,  Node: range-access-multi-part,  Prev: range-access-single-part,  Up: range-optimization

8.3.1.5 The Range Access Method for Multiple-Part Indexes
.........................................................

Range conditions on a multiple-part index are an extension of range
conditions for a single-part index. A range condition on a
multiple-part index restricts index rows to lie within one or several
key tuple intervals. Key tuple intervals are defined over a set of key
tuples, using ordering from the index.

For example, consider a multiple-part index defined as `key1(KEY_PART1,
KEY_PART2, KEY_PART3)', and the following set of key tuples listed in
key order:


     KEY_PART1  KEY_PART2  KEY_PART3
       NULL       1          'abc'
       NULL       1          'xyz'
       NULL       2          'foo'
        1         1          'abc'
        1         1          'xyz'
        1         2          'abc'
        2         1          'aaa'

The condition `KEY_PART1 = 1' defines this interval:


     (1,-inf,-inf) <= (KEY_PART1,KEY_PART2,KEY_PART3) < (1,+inf,+inf)

The interval covers the 4th, 5th, and 6th tuples in the preceding data
set and can be used by the range access method.

By contrast, the condition `KEY_PART3 = 'abc'' does not define a single
interval and cannot be used by the range access method.

The following descriptions indicate how range conditions work for
multiple-part indexes in greater detail.

   * For `HASH' indexes, each interval containing identical values can
     be used. This means that the interval can be produced only for
     conditions in the following form:


              KEY_PART1 CMP CONST1
          AND KEY_PART2 CMP CONST2
          AND ...
          AND KEY_PARTN CMP CONSTN;

     Here, CONST1, CONST2, ... are constants, CMP is one of the `=',
     `<=>', or `IS NULL' comparison operators, and the conditions cover
     all index parts.  (That is, there are N conditions, one for each
     part of an N-part index.) For example, the following is a range
     condition for a three-part `HASH' index:


          KEY_PART1 = 1 AND KEY_PART2 IS NULL AND KEY_PART3 = 'foo'

     For the definition of what is considered to be a constant, see
     *Note range-access-single-part::.

   * For a `BTREE' index, an interval might be usable for conditions
     combined with `AND', where each condition compares a key part with
     a constant value using `=', `<=>', `IS NULL', `>', `<', `>=', `<=',
     `!=', `<>', `BETWEEN', or `LIKE 'PATTERN'' (where `'PATTERN'' does
     not start with a wildcard). An interval can be used as long as it
     is possible to determine a single key tuple containing all rows
     that match the condition (or two intervals if `<>' or `!=' is
     used).

     The optimizer attempts to use additional key parts to determine
     the interval as long as the comparison operator is `=', `<=>', or
     `IS NULL'. If the operator is `>', `<', `>=', `<=', `!=', `<>',
     `BETWEEN', or `LIKE', the optimizer uses it but considers no more
     key parts. For the following expression, the optimizer uses `='
     from the first comparison. It also uses `>=' from the second
     comparison but considers no further key parts and does not use the
     third comparison for interval construction:


          KEY_PART1 = 'foo' AND KEY_PART2 >= 10 AND KEY_PART3 > 10

     The single interval is:


          ('foo',10,-inf) < (KEY_PART1,KEY_PART2,KEY_PART3) < ('foo',+inf,+inf)

     It is possible that the created interval contains more rows than
     the initial condition. For example, the preceding interval
     includes the value `('foo', 11, 0)', which does not satisfy the
     original condition.

   * If conditions that cover sets of rows contained within intervals
     are combined with `OR', they form a condition that covers a set of
     rows contained within the union of their intervals. If the
     conditions are combined with `AND', they form a condition that
     covers a set of rows contained within the intersection of their
     intervals. For example, for this condition on a two-part index:


          (KEY_PART1 = 1 AND KEY_PART2 < 2) OR (KEY_PART1 > 5)

     The intervals are:


          (1,-inf) < (KEY_PART1,KEY_PART2) < (1,2)
          (5,-inf) < (KEY_PART1,KEY_PART2)

     In this example, the interval on the first line uses one key part
     for the left bound and two key parts for the right bound. The
     interval on the second line uses only one key part. The `key_len'
     column in the *Note `EXPLAIN': explain. output indicates the
     maximum length of the key prefix used.

     In some cases, `key_len' may indicate that a key part was used,
     but that might be not what you would expect. Suppose that
     KEY_PART1 and KEY_PART2 can be `NULL'. Then the `key_len' column
     displays two key part lengths for the following condition:


          KEY_PART1 >= 1 AND KEY_PART2 < 2

     But, in fact, the condition is converted to this:


          KEY_PART1 >= 1 AND KEY_PART2 IS NOT NULL

*Note range-access-single-part::, describes how optimizations are
performed to combine or eliminate intervals for range conditions on a
single-part index.  Analogous steps are performed for range conditions
on multiple-part indexes.


File: manual.info,  Node: index-merge-optimization,  Next: condition-pushdown-optimization,  Prev: range-optimization,  Up: select-optimization

8.3.1.6 Index Merge Optimization
................................

* Menu:

* index-merge-intersection::     The Index Merge Intersection Access Algorithm
* index-merge-union::            The Index Merge Union Access Algorithm
* index-merge-sort-union::       The Index Merge Sort-Union Access Algorithm

The _Index Merge_ method is used to retrieve rows with several `range'
scans and to merge their results into one. The merge can produce unions,
intersections, or unions-of-intersections of its underlying scans. This
access method merges index scans from a single table; it does not merge
scans across multiple tables.

In *Note `EXPLAIN': explain. output, the Index Merge method appears as
`index_merge' in the `type' column. In this case, the `key' column
contains a list of indexes used, and `key_len' contains a list of the
longest key parts for those indexes.

Examples:


     SELECT * FROM TBL_NAME WHERE KEY1 = 10 OR KEY2 = 20;

     SELECT * FROM TBL_NAME
       WHERE (KEY1 = 10 OR KEY2 = 20) AND NON_KEY=30;

     SELECT * FROM t1, t2
       WHERE (t1.KEY1 IN (1,2) OR t1.KEY2 LIKE 'VALUE%')
       AND t2.KEY1=t1.SOME_COL;

     SELECT * FROM t1, t2
       WHERE t1.KEY1=1
       AND (t2.KEY1=t1.SOME_COL OR t2.KEY2=t1.SOME_COL2);

The Index Merge method has several access algorithms (seen in the
`Extra' field of *Note `EXPLAIN': explain. output):

   * `Using intersect(...)'

   * `Using union(...)'

   * `Using sort_union(...)'

The following sections describe these methods in greater detail.

*Note*:

The Index Merge optimization algorithm has the following known
deficiencies:

   * If your query has a complex `WHERE' clause with deep `AND'/`OR'
     nesting and MySQL doesn't choose the optimal plan, try
     distributing terms using the following identity laws:


          (X AND Y) OR Z = (X OR Z) AND (Y OR Z)
          (X OR Y) AND Z = (X AND Z) OR (Y AND Z)

   * Index Merge is not applicable to full-text indexes. We plan to
     extend it to cover these in a future MySQL release.

   * If a range scan is possible on some key, the optimizer will not
     consider using Index Merge Union or Index Merge Sort-Union
     algorithms. For example, consider this query:


          SELECT * FROM t1 WHERE (goodkey1 < 10 OR goodkey2 < 20) AND badkey < 30;

     For this query, two plans are possible:

        * An Index Merge scan using the `(goodkey1 < 10 OR goodkey2 <
          20)' condition.

        * A range scan using the `badkey < 30' condition.

     However, the optimizer considers only the second plan.

The choice between different possible variants of the Index Merge
access method and other access methods is based on cost estimates of
various available options.


File: manual.info,  Node: index-merge-intersection,  Next: index-merge-union,  Prev: index-merge-optimization,  Up: index-merge-optimization

8.3.1.7 The Index Merge Intersection Access Algorithm
.....................................................

This access algorithm can be employed when a `WHERE' clause was
converted to several range conditions on different keys combined with
`AND', and each condition is one of the following:

   * In this form, where the index has exactly N parts (that is, all
     index parts are covered):


          KEY_PART1=CONST1 AND KEY_PART2=CONST2 ... AND KEY_PARTN=CONSTN

   * Any range condition over a primary key of an `InnoDB' table.

Examples:


     SELECT * FROM INNODB_TABLE WHERE PRIMARY_KEY < 10 AND KEY_COL1=20;

     SELECT * FROM TBL_NAME
       WHERE (KEY1_PART1=1 AND KEY1_PART2=2) AND KEY2=2;

The Index Merge intersection algorithm performs simultaneous scans on
all used indexes and produces the intersection of row sequences that it
receives from the merged index scans.

If all columns used in the query are covered by the used indexes, full
table rows are not retrieved (*Note `EXPLAIN': explain. output contains
`Using index' in `Extra' field in this case). Here is an example of
such a query:


     SELECT COUNT(*) FROM t1 WHERE key1=1 AND key2=1;

If the used indexes don't cover all columns used in the query, full
rows are retrieved only when the range conditions for all used keys are
satisfied.

If one of the merged conditions is a condition over a primary key of an
`InnoDB' table, it is not used for row retrieval, but is used to filter
out rows retrieved using other conditions.


File: manual.info,  Node: index-merge-union,  Next: index-merge-sort-union,  Prev: index-merge-intersection,  Up: index-merge-optimization

8.3.1.8 The Index Merge Union Access Algorithm
..............................................

The applicability criteria for this algorithm are similar to those for
the Index Merge method intersection algorithm. The algorithm can be
employed when the table's `WHERE' clause was converted to several range
conditions on different keys combined with `OR', and each condition is
one of the following:

   * In this form, where the index has exactly N parts (that is, all
     index parts are covered):


          KEY_PART1=CONST1 AND KEY_PART2=CONST2 ... AND KEY_PARTN=CONSTN

   * Any range condition over a primary key of an `InnoDB' table.

   * A condition for which the Index Merge method intersection
     algorithm is applicable.

Examples:


     SELECT * FROM t1 WHERE KEY1=1 OR KEY2=2 OR KEY3=3;

     SELECT * FROM INNODB_TABLE WHERE (KEY1=1 AND KEY2=2) OR
       (KEY3='foo' AND KEY4='bar') AND KEY5=5;


File: manual.info,  Node: index-merge-sort-union,  Prev: index-merge-union,  Up: index-merge-optimization

8.3.1.9 The Index Merge Sort-Union Access Algorithm
...................................................

This access algorithm is employed when the `WHERE' clause was converted
to several range conditions combined by `OR', but for which the Index
Merge method union algorithm is not applicable.

Examples:


     SELECT * FROM TBL_NAME WHERE KEY_COL1 < 10 OR KEY_COL2 < 20;

     SELECT * FROM TBL_NAME
       WHERE (KEY_COL1 > 10 OR KEY_COL2 = 20) AND NONKEY_COL=30;

The difference between the sort-union algorithm and the union algorithm
is that the sort-union algorithm must first fetch row IDs for all rows
and sort them before returning any rows.


File: manual.info,  Node: condition-pushdown-optimization,  Next: is-null-optimization,  Prev: index-merge-optimization,  Up: select-optimization

8.3.1.10 Engine Condition Pushdown Optimization
...............................................

This optimization improves the efficiency of direct comparisons between
a nonindexed column and a constant. In such cases, the condition is
`pushed down' to the storage engine for evaluation. This optimization
can be used only by the *Note `NDBCLUSTER': mysql-cluster. storage
engine.

For MySQL Cluster, this optimization can eliminate the need to send
nonmatching rows over the network between the cluster's data nodes and
the MySQL Server that issued the query, and can speed up queries where
it is used by a factor of 5 to 10 times over cases where condition
pushdown could be but is not used.

Suppose that a MySQL Cluster table is defined as follows:


     CREATE TABLE t1 (
         a INT,
         b INT,
         KEY(a)
     ) ENGINE=NDBCLUSTER;

Condition pushdown can be used with queries such as the one shown here,
which includes a comparison between a nonindexed column and a constant:


     SELECT a, b FROM t1 WHERE b = 10;

The use of condition pushdown can be seen in the output of *Note
`EXPLAIN': explain.:


     mysql> EXPLAIN SELECT a,b FROM t1 WHERE b = 10\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: t1
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: 10
             Extra: Using where with pushed condition

However, condition pushdown _cannot_ be used with either of these two
queries:


     SELECT a,b FROM t1 WHERE a = 10;
     SELECT a,b FROM t1 WHERE b + 1 = 10;

Condition pushdown is not applicable to the first query because an
index exists on column `a'. (An index access method would be more
efficient and so would be chosen in preference to condition pushdown.)
Condition pushdown cannot be employed for the second query because the
comparison involving the nonindexed column `b' is indirect. (However,
condition pushdown could be applied if you were to reduce `b + 1 = 10'
to `b = 9' in the `WHERE' clause.)

Condition pushdown may also be employed when an indexed column is
compared with a constant using a `>' or `<' operator:


     mysql> EXPLAIN SELECT a, b FROM t1 WHERE a < 2\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: t1
              type: range
     possible_keys: a
               key: a
           key_len: 5
               ref: NULL
              rows: 2
             Extra: Using where with pushed condition

Other supported comparisons for condition pushdown include the
following:

   * `COLUMN [NOT] LIKE PATTERN'

     PATTERN must be a string literal containing the pattern to be
     matched; for syntax, see *Note string-comparison-functions::.

   * `COLUMN IS [NOT] NULL'

   * `COLUMN IN (VALUE_LIST)'

     Each item in the VALUE_LIST must be a constant, literal value.

   * `COLUMN BETWEEN CONSTANT1 AND CONSTANT2'

     CONSTANT1 and CONSTANT2 must each be a constant, literal value.

In all of the cases in the preceding list, it is possible for the
condition to be converted into the form of one or more direct
comparisons between a column and a constant.

Engine condition pushdown is enabled by default. To disable it at
server startup, set the `engine_condition_pushdown' system variable.
For example, in a `my.cnf' file, use these lines:


     [mysqld]
     engine_condition_pushdown=0

At runtime, disable condition pushdown with either of the following
statements:


     SET engine_condition_pushdown=OFF;


     SET engine_condition_pushdown=0;

Limitations

Engine condition pushdown is subject to the following limitations:

   * Condition pushdown is supported only by the *Note `NDBCLUSTER':
     mysql-cluster. storage engine.

   * Columns may be compared with constants only; however, this
     includes expressions which evaluate to constant values.

   * Columns used in comparisons cannot be of any of the *Note `BLOB':
     blob. or *Note `TEXT': blob. types.

   * A string value to be compared with a column must use the same
     collation as the column.

   * Joins are not directly supported; conditions involving multiple
     tables are pushed separately where possible. Use *Note `EXPLAIN
     EXTENDED': explain-extended. to determine which conditions are
     actually pushed down.


File: manual.info,  Node: is-null-optimization,  Next: left-join-optimization,  Prev: condition-pushdown-optimization,  Up: select-optimization

8.3.1.11 IS NULL Optimization
.............................

MySQL can perform the same optimization on COL_NAME `IS NULL' that it
can use for COL_NAME `=' CONSTANT_VALUE. For example, MySQL can use
indexes and ranges to search for `NULL' with `IS NULL'.

Examples:


     SELECT * FROM TBL_NAME WHERE KEY_COL IS NULL;

     SELECT * FROM TBL_NAME WHERE KEY_COL <=> NULL;

     SELECT * FROM TBL_NAME
       WHERE KEY_COL=CONST1 OR KEY_COL=CONST2 OR KEY_COL IS NULL;

If a `WHERE' clause includes a COL_NAME `IS NULL' condition for a
column that is declared as `NOT NULL', that expression is optimized
away. This optimization does not occur in cases when the column might
produce `NULL' anyway; for example, if it comes from a table on the
right side of a `LEFT JOIN'.

MySQL can also optimize the combination `COL_NAME = EXPR OR COL_NAME IS
NULL', a form that is common in resolved subqueries.  *Note `EXPLAIN':
explain. shows `ref_or_null' when this optimization is used.

This optimization can handle one `IS NULL' for any key part.

Some examples of queries that are optimized, assuming that there is an
index on columns `a' and `b' of table `t2':


     SELECT * FROM t1 WHERE t1.a=EXPR OR t1.a IS NULL;

     SELECT * FROM t1, t2 WHERE t1.a=t2.a OR t2.a IS NULL;

     SELECT * FROM t1, t2
       WHERE (t1.a=t2.a OR t2.a IS NULL) AND t2.b=t1.b;

     SELECT * FROM t1, t2
       WHERE t1.a=t2.a AND (t2.b=t1.b OR t2.b IS NULL);

     SELECT * FROM t1, t2
       WHERE (t1.a=t2.a AND t2.a IS NULL AND ...)
       OR (t1.a=t2.a AND t2.a IS NULL AND ...);

`ref_or_null' works by first doing a read on the reference key, and
then a separate search for rows with a `NULL' key value.

Note that the optimization can handle only one `IS NULL' level. In the
following query, MySQL uses key lookups only on the expression
`(t1.a=t2.a AND t2.a IS NULL)' and is not able to use the key part on
`b':


     SELECT * FROM t1, t2
       WHERE (t1.a=t2.a AND t2.a IS NULL)
       OR (t1.b=t2.b AND t2.b IS NULL);


File: manual.info,  Node: left-join-optimization,  Next: nested-loop-joins,  Prev: is-null-optimization,  Up: select-optimization

8.3.1.12 LEFT JOIN and RIGHT JOIN Optimization
..............................................

MySQL implements an `A LEFT JOIN B join_condition' as follows:

   * Table B is set to depend on table A and all tables on which A
     depends.

   * Table A is set to depend on all tables (except B) that are used in
     the `LEFT JOIN' condition.

   * The `LEFT JOIN' condition is used to decide how to retrieve rows
     from table B. (In other words, any condition in the `WHERE' clause
     is not used.)

   * All standard join optimizations are performed, with the exception
     that a table is always read after all tables on which it depends.
     If there is a circular dependence, MySQL issues an error.

   * All standard `WHERE' optimizations are performed.

   * If there is a row in A that matches the `WHERE' clause, but there
     is no row in B that matches the `ON' condition, an extra B row is
     generated with all columns set to `NULL'.

   * If you use `LEFT JOIN' to find rows that do not exist in some
     table and you have the following test: `COL_NAME IS NULL' in the
     `WHERE' part, where COL_NAME is a column that is declared as `NOT
     NULL', MySQL stops searching for more rows (for a particular key
     combination) after it has found one row that matches the `LEFT
     JOIN' condition.

The implementation of `RIGHT JOIN' is analogous to that of `LEFT JOIN'
with the roles of the tables reversed.

The join optimizer calculates the order in which tables should be
joined. The table read order forced by `LEFT JOIN' or `STRAIGHT_JOIN'
helps the join optimizer do its work much more quickly, because there
are fewer table permutations to check. Note that this means that if you
do a query of the following type, MySQL does a full scan on `b' because
the `LEFT JOIN' forces it to be read before `d':


     SELECT *
       FROM a JOIN b LEFT JOIN c ON (c.key=a.key)
       LEFT JOIN d ON (d.key=a.key)
       WHERE b.key=d.key;

The fix in this case is reverse the order in which `a' and `b' are
listed in the `FROM' clause:


     SELECT *
       FROM b JOIN a LEFT JOIN c ON (c.key=a.key)
       LEFT JOIN d ON (d.key=a.key)
       WHERE b.key=d.key;

For a `LEFT JOIN', if the `WHERE' condition is always false for the
generated `NULL' row, the `LEFT JOIN' is changed to a normal join. For
example, the `WHERE' clause would be false in the following query if
`t2.column1' were `NULL':


     SELECT * FROM t1 LEFT JOIN t2 ON (column1) WHERE t2.column2=5;

Therefore, it is safe to convert the query to a normal join:


     SELECT * FROM t1, t2 WHERE t2.column2=5 AND t1.column1=t2.column1;

This can be made faster because MySQL can use table `t2' before table
`t1' if doing so would result in a better query plan. To provide a hint
about the table join order, use `STRAIGHT_JOIN'. (See *Note select::.)


File: manual.info,  Node: nested-loop-joins,  Next: nested-join-optimization,  Prev: left-join-optimization,  Up: select-optimization

8.3.1.13 Nested-Loop Join Algorithms
....................................

MySQL executes joins between tables using a nested-loop algorithm or
variations on it.

*Nested-Loop Join Algorithm*

A simple nested-loop join (NLJ) algorithm reads rows from the first
table in a loop one at a time, passing each row to a nested loop that
processes the next table in the join. This process is repeated as many
times as there remain tables to be joined.

Assume that a join between three tables `t1', `t2', and `t3' is to be
executed using the following join types:


     Table   Join Type
     t1      range
     t2      ref
     t3      ALL

If a simple NLJ algorithm is used, the join is processed like this:


     for each row in t1 matching range {
       for each row in t2 matching reference key {
         for each row in t3 {
           if row satisfies join conditions,
           send to client
         }
       }
     }

Because the NLJ algorithm passes rows one at a time from outer loops to
inner loops, it typically reads tables processed in the inner loops
many times.

*Block Nested-Loop Join Algorithm*

A Block Nested-Loop (BNL) Join algorithm uses buffering of rows read in
outer loops to reduce the number of times that tables in inner loops
must be read. For example, if 10 rows are read into a buffer and the
buffer is passed to the next inner loop, each row read in the inner
loop can be compared against all 10 rows in the buffer. The reduces the
number of times the inner table must be read by an order of magnitude.

MySQL uses join buffering under these conditions:

   * The `join_buffer_size' system variable determines the size of each
     join buffer.

   * Join buffering can be used when the join is of type `ALL' or
     `index' (in other words, when no possible keys can be used, and a
     full scan is done, of either the data or index rows,
     respectively), or `range'.

   * One buffer is allocated for each join that can be buffered, so a
     given query might be processed using multiple join buffers.

   * A join buffer is never allocated for the first nonconst table,
     even if it would be of type `ALL' or `index'.

   * A join buffer is allocated prior to executing the join and freed
     after the query is done.

   * Only columns of interest to the join are stored in the join
     buffer, not whole rows.

For the example join described previously for the NLJ algorithm
(without buffering), the join is done as follow using join buffering:


     for each row in t1 matching range {
       for each row in t2 matching reference key {
         store used columns from t1, t2 in join buffer
         if buffer is full {
           for each row in t3 {
             for each t1, t2 combination in join buffer {
               if row satisfies join conditions,
               send to client
             }
           }
           empty buffer
         }
       }
     }

     if buffer is not empty {
       for each row in t3 {
         for each t1, t2 combination in join buffer {
           if row satisfies join conditions,
           send to client
         }
       }
     }

If S is the size of each stored `t1', `t2' combination is the join
buffer and C is the number of combinations in the buffer, the number of
times table `t3' is scanned is:


     (S * C)/join_buffer_size + 1

The number of `t3' scans decreases as the value of `join_buffer_size'
increases, up to the point when `join_buffer_size' is large enough to
hold all previous row combinations. At that point, there is no speed to
be gained by making it larger.


File: manual.info,  Node: nested-join-optimization,  Next: outer-join-simplification,  Prev: nested-loop-joins,  Up: select-optimization

8.3.1.14 Nested Join Optimization
.................................

The syntax for expressing joins permits nested joins. The following
discussion refers to the join syntax described in *Note join::.

The syntax of TABLE_FACTOR is extended in comparison with the SQL
Standard. The latter accepts only TABLE_REFERENCE, not a list of them
inside a pair of parentheses. This is a conservative extension if we
consider each comma in a list of TABLE_REFERENCE items as equivalent to
an inner join. For example:


     SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
                      ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

is equivalent to:


     SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)
                      ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

In MySQL, `CROSS JOIN' is a syntactic equivalent to `INNER JOIN' (they
can replace each other). In standard SQL, they are not equivalent.
`INNER JOIN' is used with an `ON' clause; `CROSS JOIN' is used
otherwise.

In general, parentheses can be ignored in join expressions containing
only inner join operations. After removing parentheses and grouping
operations to the left, the join expression:


     t1 LEFT JOIN (t2 LEFT JOIN t3 ON t2.b=t3.b OR t2.b IS NULL)
        ON t1.a=t2.a

transforms into the expression:


     (t1 LEFT JOIN t2 ON t1.a=t2.a) LEFT JOIN t3
         ON t2.b=t3.b OR t2.b IS NULL

Yet, the two expressions are not equivalent. To see this, suppose that
the tables `t1', `t2', and `t3' have the following state:

   * Table `t1' contains rows `(1)', `(2)'

   * Table `t2' contains row `(1,101)'

   * Table `t3' contains row `(101)'

In this case, the first expression returns a result set including the
rows `(1,1,101,101)', `(2,NULL,NULL,NULL)', whereas the second
expression returns the rows `(1,1,101,101)', `(2,NULL,NULL,101)':


     mysql> SELECT *
         -> FROM t1
         ->      LEFT JOIN
         ->      (t2 LEFT JOIN t3 ON t2.b=t3.b OR t2.b IS NULL)
         ->      ON t1.a=t2.a;
     +------+------+------+------+
     | a    | a    | b    | b    |
     +------+------+------+------+
     |    1 |    1 |  101 |  101 |
     |    2 | NULL | NULL | NULL |
     +------+------+------+------+

     mysql> SELECT *
         -> FROM (t1 LEFT JOIN t2 ON t1.a=t2.a)
         ->      LEFT JOIN t3
         ->      ON t2.b=t3.b OR t2.b IS NULL;
     +------+------+------+------+
     | a    | a    | b    | b    |
     +------+------+------+------+
     |    1 |    1 |  101 |  101 |
     |    2 | NULL | NULL |  101 |
     +------+------+------+------+

In the following example, an outer join operation is used together with
an inner join operation:


     t1 LEFT JOIN (t2, t3) ON t1.a=t2.a

That expression cannot be transformed into the following expression:


     t1 LEFT JOIN t2 ON t1.a=t2.a, t3.

For the given table states, the two expressions return different sets
of rows:


     mysql> SELECT *
         -> FROM t1 LEFT JOIN (t2, t3) ON t1.a=t2.a;
     +------+------+------+------+
     | a    | a    | b    | b    |
     +------+------+------+------+
     |    1 |    1 |  101 |  101 |
     |    2 | NULL | NULL | NULL |
     +------+------+------+------+

     mysql> SELECT *
         -> FROM t1 LEFT JOIN t2 ON t1.a=t2.a, t3;
     +------+------+------+------+
     | a    | a    | b    | b    |
     +------+------+------+------+
     |    1 |    1 |  101 |  101 |
     |    2 | NULL | NULL |  101 |
     +------+------+------+------+

Therefore, if we omit parentheses in a join expression with outer join
operators, we might change the result set for the original expression.

More exactly, we cannot ignore parentheses in the right operand of the
left outer join operation and in the left operand of a right join
operation. In other words, we cannot ignore parentheses for the inner
table expressions of outer join operations. Parentheses for the other
operand (operand for the outer table) can be ignored.

The following expression:


     (t1,t2) LEFT JOIN t3 ON P(t2.b,t3.b)

is equivalent to this expression:


     t1, t2 LEFT JOIN t3 ON P(t2.b,t3.b)

for any tables `t1,t2,t3' and any condition `P' over attributes `t2.b'
and `t3.b'.

Whenever the order of execution of the join operations in a join
expression (JOIN_TABLE) is not from left to right, we talk about nested
joins. Consider the following queries:


     SELECT * FROM t1 LEFT JOIN (t2 LEFT JOIN t3 ON t2.b=t3.b) ON t1.a=t2.a
       WHERE t1.a > 1

     SELECT * FROM t1 LEFT JOIN (t2, t3) ON t1.a=t2.a
       WHERE (t2.b=t3.b OR t2.b IS NULL) AND t1.a > 1

Those queries are considered to contain these nested joins:


     t2 LEFT JOIN t3 ON t2.b=t3.b
     t2, t3

The nested join is formed in the first query with a left join
operation, whereas in the second query it is formed with an inner join
operation.

In the first query, the parentheses can be omitted: The grammatical
structure of the join expression will dictate the same order of
execution for join operations. For the second query, the parentheses
cannot be omitted, although the join expression here can be interpreted
unambiguously without them.  (In our extended syntax the parentheses in
`(t2, t3)' of the second query are required, although theoretically the
query could be parsed without them: We still would have unambiguous
syntactical structure for the query because `LEFT JOIN' and `ON' would
play the role of the left and right delimiters for the expression
`(t2,t3)'.)

The preceding examples demonstrate these points:

   * For join expressions involving only inner joins (and not outer
     joins), parentheses can be removed. You can remove parentheses and
     evaluate left to right (or, in fact, you can evaluate the tables
     in any order).

   * The same is not true, in general, for outer joins or for outer
     joins mixed with inner joins. Removal of parentheses may change
     the result.

Queries with nested outer joins are executed in the same pipeline
manner as queries with inner joins. More exactly, a variation of the
nested-loop join algorithm is exploited.  Recall by what algorithmic
schema the nested-loop join executes a query. Suppose that we have a
join query over 3 tables `T1,T2,T3' of the form:


     SELECT * FROM T1 INNER JOIN T2 ON P1(T1,T2)
                      INNER JOIN T3 ON P2(T2,T3)
       WHERE P(T1,T2,T3).

Here, `P1(T1,T2)' and `P2(T3,T3)' are some join conditions (on
expressions), whereas `P(T1,T2,T3)' is a condition over columns of
tables `T1,T2,T3'.

The nested-loop join algorithm would execute this query in the
following manner:


     FOR each row t1 in T1 {
       FOR each row t2 in T2 such that P1(t1,t2) {
         FOR each row t3 in T3 such that P2(t2,t3) {
           IF P(t1,t2,t3) {
              t:=t1||t2||t3; OUTPUT t;
           }
         }
       }
     }

The notation `t1||t2||t3' means `a row constructed by concatenating the
columns of rows `t1', `t2', and `t3'.' In some of the following
examples, `NULL' where a row name appears means that `NULL' is used for
each column of that row. For example, `t1||t2||NULL' means `a row
constructed by concatenating the columns of rows `t1' and `t2', and
`NULL' for each column of `t3'.'

Now let's consider a query with nested outer joins:


     SELECT * FROM T1 LEFT JOIN
                   (T2 LEFT JOIN T3 ON P2(T2,T3))
                   ON P1(T1,T2)
       WHERE P(T1,T2,T3).

For this query, we modify the nested-loop pattern to get:


     FOR each row t1 in T1 {
       BOOL f1:=FALSE;
       FOR each row t2 in T2 such that P1(t1,t2) {
         BOOL f2:=FALSE;
         FOR each row t3 in T3 such that P2(t2,t3) {
           IF P(t1,t2,t3) {
             t:=t1||t2||t3; OUTPUT t;
           }
           f2=TRUE;
           f1=TRUE;
         }
         IF (!f2) {
           IF P(t1,t2,NULL) {
             t:=t1||t2||NULL; OUTPUT t;
           }
           f1=TRUE;
         }
       }
       IF (!f1) {
         IF P(t1,NULL,NULL) {
           t:=t1||NULL||NULL; OUTPUT t;
         }
       }
     }

In general, for any nested loop for the first inner table in an outer
join operation, a flag is introduced that is turned off before the loop
and is checked after the loop. The flag is turned on when for the
current row from the outer table a match from the table representing
the inner operand is found.  If at the end of the loop cycle the flag
is still off, no match has been found for the current row of the outer
table.  In this case, the row is complemented by `NULL' values for the
columns of the inner tables. The result row is passed to the final
check for the output or into the next nested loop, but only if the row
satisfies the join condition of all embedded outer joins.

In our example, the outer join table expressed by the following
expression is embedded:


     (T2 LEFT JOIN T3 ON P2(T2,T3))

Note that for the query with inner joins, the optimizer could choose a
different order of nested loops, such as this one:


     FOR each row t3 in T3 {
       FOR each row t2 in T2 such that P2(t2,t3) {
         FOR each row t1 in T1 such that P1(t1,t2) {
           IF P(t1,t2,t3) {
              t:=t1||t2||t3; OUTPUT t;
           }
         }
       }
     }

For the queries with outer joins, the optimizer can choose only such an
order where loops for outer tables precede loops for inner tables.
Thus, for our query with outer joins, only one nesting order is
possible. For the following query, the optimizer will evaluate two
different nestings:


     SELECT * T1 LEFT JOIN (T2,T3) ON P1(T1,T2) AND P2(T1,T3)
       WHERE P(T1,T2,T3)

The nestings are these:


     FOR each row t1 in T1 {
       BOOL f1:=FALSE;
       FOR each row t2 in T2 such that P1(t1,t2) {
         FOR each row t3 in T3 such that P2(t1,t3) {
           IF P(t1,t2,t3) {
             t:=t1||t2||t3; OUTPUT t;
           }
           f1:=TRUE
         }
       }
       IF (!f1) {
         IF P(t1,NULL,NULL) {
           t:=t1||NULL||NULL; OUTPUT t;
         }
       }
     }

and:


     FOR each row t1 in T1 {
       BOOL f1:=FALSE;
       FOR each row t3 in T3 such that P2(t1,t3) {
         FOR each row t2 in T2 such that P1(t1,t2) {
           IF P(t1,t2,t3) {
             t:=t1||t2||t3; OUTPUT t;
           }
           f1:=TRUE
         }
       }
       IF (!f1) {
         IF P(t1,NULL,NULL) {
           t:=t1||NULL||NULL; OUTPUT t;
         }
       }
     }

In both nestings, `T1' must be processed in the outer loop because it
is used in an outer join.  `T2' and `T3' are used in an inner join, so
that join must be processed in the inner loop.  However, because the
join is an inner join, `T2' and `T3' can be processed in either order.

When discussing the nested-loop algorithm for inner joins, we omitted
some details whose impact on the performance of query execution may be
huge. We did not mention so-called `pushed-down' conditions. Suppose
that our `WHERE' condition `P(T1,T2,T3)' can be represented by a
conjunctive formula:


     P(T1,T2,T2) = C1(T1) AND C2(T2) AND C3(T3).

In this case, MySQL actually uses the following nested-loop schema for
the execution of the query with inner joins:


     FOR each row t1 in T1 such that C1(t1) {
       FOR each row t2 in T2 such that P1(t1,t2) AND C2(t2)  {
         FOR each row t3 in T3 such that P2(t2,t3) AND C3(t3) {
           IF P(t1,t2,t3) {
              t:=t1||t2||t3; OUTPUT t;
           }
         }
       }
     }

You see that each of the conjuncts `C1(T1)', `C2(T2)', `C3(T3)' are
pushed out of the most inner loop to the most outer loop where it can
be evaluated. If `C1(T1)' is a very restrictive condition, this
condition pushdown may greatly reduce the number of rows from table `T1'
passed to the inner loops. As a result, the execution time for the
query may improve immensely.

For a query with outer joins, the `WHERE' condition is to be checked
only after it has been found that the current row from the outer table
has a match in the inner tables. Thus, the optimization of pushing
conditions out of the inner nested loops cannot be applied directly to
queries with outer joins. Here we have to introduce conditional
pushed-down predicates guarded by the flags that are turned on when a
match has been encountered.

For our example with outer joins with:


     P(T1,T2,T3)=C1(T1) AND C(T2) AND C3(T3)

the nested-loop schema using guarded pushed-down conditions looks like
this:


     FOR each row t1 in T1 such that C1(t1) {
       BOOL f1:=FALSE;
       FOR each row t2 in T2
           such that P1(t1,t2) AND (f1?C2(t2):TRUE) {
         BOOL f2:=FALSE;
         FOR each row t3 in T3
             such that P2(t2,t3) AND (f1&&f2?C3(t3):TRUE) {
           IF (f1&&f2?TRUE:(C2(t2) AND C3(t3))) {
             t:=t1||t2||t3; OUTPUT t;
           }
           f2=TRUE;
           f1=TRUE;
         }
         IF (!f2) {
           IF (f1?TRUE:C2(t2) && P(t1,t2,NULL)) {
             t:=t1||t2||NULL; OUTPUT t;
           }
           f1=TRUE;
         }
       }
       IF (!f1 && P(t1,NULL,NULL)) {
           t:=t1||NULL||NULL; OUTPUT t;
       }
     }

In general, pushed-down predicates can be extracted from join
conditions such as `P1(T1,T2)' and `P(T2,T3)'. In this case, a
pushed-down predicate is guarded also by a flag that prevents checking
the predicate for the `NULL'-complemented row generated by the
corresponding outer join operation.

Note that access by key from one inner table to another in the same
nested join is prohibited if it is induced by a predicate from the
`WHERE' condition. (We could use conditional key access in this case,
but this technique is not employed yet in MySQL 5.1.)


File: manual.info,  Node: outer-join-simplification,  Next: order-by-optimization,  Prev: nested-join-optimization,  Up: select-optimization

8.3.1.15 Outer Join Simplification
..................................

Table expressions in the `FROM' clause of a query are simplified in
many cases.

At the parser stage, queries with right outer joins operations are
converted to equivalent queries containing only left join operations.
In the general case, the conversion is performed according to the
following rule:


     (T1, ...) RIGHT JOIN (T2,...) ON P(T1,...,T2,...) =
     (T2, ...) LEFT JOIN (T1,...) ON P(T1,...,T2,...)

All inner join expressions of the form `T1 INNER JOIN T2 ON P(T1,T2)'
are replaced by the list `T1,T2', `P(T1,T2)' being joined as a conjunct
to the `WHERE' condition (or to the join condition of the embedding
join, if there is any).

When the optimizer evaluates plans for join queries with outer join
operation, it takes into consideration only the plans where, for each
such operation, the outer tables are accessed before the inner tables.
The optimizer options are limited because only such plans enables us to
execute queries with outer joins operations by the nested loop schema.

Suppose that we have a query of the form:


     SELECT * T1 LEFT JOIN T2 ON P1(T1,T2)
       WHERE P(T1,T2) AND R(T2)

with `R(T2)' narrowing greatly the number of matching rows from table
`T2'. If we executed the query as it is, the optimizer would have no
other choice besides to access table `T1' before table `T2' that may
lead to a very inefficient execution plan.

Fortunately, MySQL converts such a query into a query without an outer
join operation if the `WHERE' condition is null-rejected. A condition
is called null-rejected for an outer join operation if it evaluates to
`FALSE' or to `UNKNOWN' for any `NULL'-complemented row built for the
operation.

Thus, for this outer join:


     T1 LEFT JOIN T2 ON T1.A=T2.A

Conditions such as these are null-rejected:


     T2.B IS NOT NULL,
     T2.B > 3,
     T2.C <= T1.C,
     T2.B < 2 OR T2.C > 1

Conditions such as these are not null-rejected:


     T2.B IS NULL,
     T1.B < 3 OR T2.B IS NOT NULL,
     T1.B < 3 OR T2.B > 3

The general rules for checking whether a condition is null-rejected for
an outer join operation are simple. A condition is null-rejected in the
following cases:

   * If it is of the form `A IS NOT NULL', where `A' is an attribute of
     any of the inner tables

   * If it is a predicate containing a reference to an inner table that
     evaluates to `UNKNOWN' when one of its arguments is `NULL'

   * If it is a conjunction containing a null-rejected condition as a
     conjunct

   * If it is a disjunction of null-rejected conditions

A condition can be null-rejected for one outer join operation in a
query and not null-rejected for another. In the query:


     SELECT * FROM T1 LEFT JOIN T2 ON T2.A=T1.A
                      LEFT JOIN T3 ON T3.B=T1.B
       WHERE T3.C > 0

the `WHERE' condition is null-rejected for the second outer join
operation but is not null-rejected for the first one.

If the `WHERE' condition is null-rejected for an outer join operation
in a query, the outer join operation is replaced by an inner join
operation.

For example, the preceding query is replaced with the query:


     SELECT * FROM T1 LEFT JOIN T2 ON T2.A=T1.A
                      INNER JOIN T3 ON T3.B=T1.B
       WHERE T3.C > 0

For the original query, the optimizer would evaluate plans compatible
with only one access order `T1,T2,T3'. For the replacing query, it
additionally considers the access sequence `T3,T1,T2'.

A conversion of one outer join operation may trigger a conversion of
another. Thus, the query:


     SELECT * FROM T1 LEFT JOIN T2 ON T2.A=T1.A
                      LEFT JOIN T3 ON T3.B=T2.B
       WHERE T3.C > 0

will be first converted to the query:


     SELECT * FROM T1 LEFT JOIN T2 ON T2.A=T1.A
                      INNER JOIN T3 ON T3.B=T2.B
       WHERE T3.C > 0

which is equivalent to the query:


     SELECT * FROM (T1 LEFT JOIN T2 ON T2.A=T1.A), T3
       WHERE T3.C > 0 AND T3.B=T2.B

Now the remaining outer join operation can be replaced by an inner
join, too, because the condition `T3.B=T2.B' is null-rejected and we
get a query without outer joins at all:


     SELECT * FROM (T1 INNER JOIN T2 ON T2.A=T1.A), T3
       WHERE T3.C > 0 AND T3.B=T2.B

Sometimes we succeed in replacing an embedded outer join operation, but
cannot convert the embedding outer join. The following query:


     SELECT * FROM T1 LEFT JOIN
                   (T2 LEFT JOIN T3 ON T3.B=T2.B)
                   ON T2.A=T1.A
       WHERE T3.C > 0

is converted to:


     SELECT * FROM T1 LEFT JOIN
                   (T2 INNER JOIN T3 ON T3.B=T2.B)
                   ON T2.A=T1.A
       WHERE T3.C > 0,

That can be rewritten only to the form still containing the embedding
outer join operation:


     SELECT * FROM T1 LEFT JOIN
                   (T2,T3)
                   ON (T2.A=T1.A AND T3.B=T2.B)
       WHERE T3.C > 0.

When trying to convert an embedded outer join operation in a query, we
must take into account the join condition for the embedding outer join
together with the `WHERE' condition. In the query:


     SELECT * FROM T1 LEFT JOIN
                   (T2 LEFT JOIN T3 ON T3.B=T2.B)
                   ON T2.A=T1.A AND T3.C=T1.C
       WHERE T3.D > 0 OR T1.D > 0

the `WHERE' condition is not null-rejected for the embedded outer join,
but the join condition of the embedding outer join `T2.A=T1.A AND
T3.C=T1.C' is null-rejected. So the query can be converted to:


     SELECT * FROM T1 LEFT JOIN
                   (T2, T3)
                   ON T2.A=T1.A AND T3.C=T1.C AND T3.B=T2.B
       WHERE T3.D > 0 OR T1.D > 0


File: manual.info,  Node: order-by-optimization,  Next: group-by-optimization,  Prev: outer-join-simplification,  Up: select-optimization

8.3.1.16 ORDER BY Optimization
..............................

In some cases, MySQL can use an index to satisfy an `ORDER BY' clause
without doing any extra sorting.

The index can also be used even if the `ORDER BY' does not match the
index exactly, as long as all of the unused portions of the index and
all the extra `ORDER BY' columns are constants in the `WHERE' clause.
The following queries use the index to resolve the `ORDER BY' part:


     SELECT * FROM t1
       ORDER BY KEY_PART1,KEY_PART2,... ;

     SELECT * FROM t1
       WHERE KEY_PART1 = CONSTANT
       ORDER BY KEY_PART2;

     SELECT * FROM t1
       ORDER BY KEY_PART1 DESC, KEY_PART2 DESC;

     SELECT * FROM t1
       WHERE KEY_PART1 = 1
       ORDER BY KEY_PART1 DESC, KEY_PART2 DESC;

     SELECT * FROM t1
       WHERE KEY_PART1 > CONSTANT
       ORDER BY KEY_PART1 ASC;

     SELECT * FROM t1
       WHERE KEY_PART1 < CONSTANT
       ORDER BY KEY_PART1 DESC;

     SELECT * FROM t1
       WHERE KEY_PART1 = CONSTANT1 AND KEY_PART2 > CONSTANT2
       ORDER BY KEY_PART2;

In some cases, MySQL _cannot_ use indexes to resolve the `ORDER BY',
although it still uses indexes to find the rows that match the `WHERE'
clause. These cases include the following:

   * You use `ORDER BY' on different keys:


          SELECT * FROM t1 ORDER BY KEY1, KEY2;

   * You use `ORDER BY' on nonconsecutive parts of a key:


          SELECT * FROM t1 WHERE KEY2=CONSTANT ORDER BY KEY_PART2;

   * You mix `ASC' and `DESC':


          SELECT * FROM t1 ORDER BY KEY_PART1 DESC, KEY_PART2 ASC;

   * The key used to fetch the rows is not the same as the one used in
     the `ORDER BY':


          SELECT * FROM t1 WHERE KEY2=CONSTANT ORDER BY KEY1;

   * You use `ORDER BY' with an expression that includes terms other
     than the key column name:


          SELECT * FROM t1 ORDER BY ABS(KEY);
          SELECT * FROM t1 ORDER BY -KEY;

   * You are joining many tables, and the columns in the `ORDER BY' are
     not all from the first nonconstant table that is used to retrieve
     rows. (This is the first table in the *Note `EXPLAIN': explain.
     output that does not have a `const' join type.)

   * You have different `ORDER BY' and `GROUP BY' expressions.

   * You index only a prefix of a column named in the `ORDER BY'
     clause. In this case, the index cannot be used to fully resolve
     the sort order. For example, if you have a *Note `CHAR(20)': char.
     column, but index only the first 10 bytes, the index cannot
     distinguish values past the 10th byte and a `filesort' will be
     needed.

   * The type of table index used does not store rows in order.  For
     example, this is true for a `HASH' index in a `MEMORY' table.

Availability of an index for sorting may be affected by the use of
column aliases. Suppose that the column `t1.a' is indexed. In this
statement, the name of the column in the select list is `a'.  It refers
to `t1.a', so for the reference to `a' in the `ORDER BY', the index can
be used:


     SELECT a FROM t1 ORDER BY a;

In this statement, the name of the column in the select list is also
`a', but it is the alias name. It refers to `ABS(a)', so for the
reference to `a' in the `ORDER BY', the index cannot be used:


     SELECT ABS(a) AS a FROM t1 ORDER BY a;

In the following statement, the `ORDER BY' refers to a name that is not
the name of a column in the select list. But there is a column in `t1'
named `a', so the `ORDER BY' uses that, and the index can be used. (The
resulting sort order may be completely different from the order for
`ABS(a)', of course.)


     SELECT ABS(a) AS b FROM t1 ORDER BY a;

By default, MySQL sorts all `GROUP BY COL1, COL2, ...' queries as if
you specified `ORDER BY COL1, COL2, ...' in the query as well. If you
include an explicit `ORDER BY' clause that contains the same column
list, MySQL optimizes it away without any speed penalty, although the
sorting still occurs. If a query includes `GROUP BY' but you want to
avoid the overhead of sorting the result, you can suppress sorting by
specifying `ORDER BY NULL'. For example:


     INSERT INTO foo
     SELECT a, COUNT(*) FROM bar GROUP BY a ORDER BY NULL;

With *Note `EXPLAIN SELECT ... ORDER BY': explain, you can check
whether MySQL can use indexes to resolve the query. It cannot if you see
`Using filesort' in the `Extra' column. See *Note using-explain::.
Filesort uses a fixed-length row-storage format similar to that used by
the *Note `MEMORY': memory-storage-engine. storage engine.
Variable-length types such as *Note `VARCHAR': char. are stored using a
fixed length.

MySQL has two `filesort' algorithms for sorting and retrieving results.
The original method uses only the `ORDER BY' columns. The modified
method uses not just the `ORDER BY' columns, but all the columns
referenced by the query.

The optimizer selects which `filesort' algorithm to use. It normally
uses the modified algorithm except when *Note `BLOB': blob. or *Note
`TEXT': blob. columns are involved, in which case it uses the original
algorithm. For both algorithms, the sort buffer size is the
`sort_buffer_size' system variable value.

The original `filesort' algorithm works as follows:

  1. Read all rows according to key or by table scanning. Skip rows
     that do not match the `WHERE' clause.

  2. For each row, store a pair of values (the sort key value and the
     row ID) in the sort buffer.

  3. If all pairs fit into the sort buffer, no temporary file is
     created. Otherwise, when the sort buffer becomes full, run a qsort
     (quicksort) on it in memory and write it to a temporary file. Save
     a pointer to the sorted block.

  4. Repeat the preceding steps until all rows have been read.

  5. Do a multi-merge of up to `MERGEBUFF' (7) regions to one block in
     another temporary file. Repeat until all blocks from the first
     file are in the second file.

  6. Repeat the following until there are fewer than `MERGEBUFF2' (15)
     blocks left.

  7. On the last multi-merge, only the row ID (the last part of the
     value pair) is written to a result file.

  8. Read the rows in sorted order using the row IDs in the result
     file. To optimize this, read in a large block of row IDs, sort
     them, and use them to read the rows in sorted order into a row
     buffer. The row buffer size is the `read_rnd_buffer_size' system
     variable value. The code for this step is in the `sql/records.cc'
     source file.

One problem with this approach is that it reads rows twice: One time
during `WHERE' clause evaluation, and again after sorting the value
pairs. And even if the rows were accessed successively the first time
(for example, if a table scan is done), the second time they are
accessed randomly. (The sort keys are ordered, but the row positions
are not.)

The modified `filesort' algorithm incorporates an optimization to avoid
reading the rows twice: It records the sort key value, but instead of
the row ID, it records the columns referenced by the query. The modified
`filesort' algorithm works like this:

  1. Read the rows that match the `WHERE' clause.

  2. For each row, record a tuple of values consisting of the sort key
     value and the columns referenced by the query.

  3. When the sort buffer becomes full, sort the tuples by sort key
     value in memory and write it to a temporary file.

  4. After merge-sorting the temporary file, retrieve the rows in
     sorted order, but read the required columns directly from the
     sorted tuples rather than by accessing the table a second time.

Using the modified `filesort' algorithm, the tuples are longer than the
pairs used in the original method, and fewer of them fit in the sort
buffer. As a result, it is possible for the extra I/O to make the
modified approach slower, not faster. To avoid a slowdown, the
optimizer uses the modified algorithm only if the total size of the
extra columns in the sort tuple does not exceed the value of the
`max_length_for_sort_data' system variable. (A symptom of setting the
value of this variable too high is that you should see high disk
activity and low CPU activity.)

If a `filesort' is done, *Note `EXPLAIN': explain. output includes
`Using filesort' in the `Extra' column.

Suppose that a table `t1' has four `VARCHAR' columns `a', `b', `c', and
`d' and that the optimizer uses `filesort' for this query:


     SELECT * FROM t1 ORDER BY a, b;

The query sorts by `a' and `b', but returns all columns, so the columns
referenced by the query are `a', `b', `c', and `d'. Depending on which
`filesort' algorithm the optimizer chooses, the query executes as
follows:

For the original algorithm, sort buffer tuples have these contents:


     (fixed size a value, fixed size b value,
     row ID into t1)

The optimizer sorts on the fixed size values. After sorting, the
optimizer reads the tuples in order and uses the row ID in each tuple
to read rows from `t1' to obtain the select list column values.

For the modified algorithm, sort buffer tuples have these contents:


     (fixed size a value, fixed size b value,
     a value, b value, c value, d value)

The optimizer sorts on the fixed size values. After sorting, the
optimizer reads the tuples in order and uses the values for `a', `b',
`c', and `d' to obtain the select list column values without reading
`t1' again.

For slow queries for which `filesort' is not used, you might try
lowering `max_length_for_sort_data' to a value that is appropriate to
trigger a `filesort'.

To increase `ORDER BY' speed, check whether you can get MySQL to use
indexes rather than an extra sorting phase. If this is not possible,
you can try the following strategies:

   * Increase the `sort_buffer_size' variable value.

   * Increase the `read_rnd_buffer_size' variable value.

   * Use less RAM per row by declaring columns only as large as they
     need to be to hold the values stored in them. For example,
     `CHAR(16)' is better than `CHAR(200)' if values never exceed 16
     characters.

   * Change the `tmpdir' system variable to point to a dedicated file
     system with large amounts of free space. The variable value can
     list several paths that are used in round-robin fashion; you can
     use this feature to spread the load across several directories.
     Paths should be separated by colon characters (``:'') on Unix and
     semicolon characters (``;'') on Windows, NetWare, and OS/2. The
     paths should name directories in file systems located on different
     _physical_ disks, not different partitions on the same disk.


File: manual.info,  Node: group-by-optimization,  Next: distinct-optimization,  Prev: order-by-optimization,  Up: select-optimization

8.3.1.17 GROUP BY Optimization
..............................

* Menu:

* loose-index-scan::             Loose Index Scan
* tight-index-scan::             Tight Index Scan

The most general way to satisfy a `GROUP BY' clause is to scan the
whole table and create a new temporary table where all rows from each
group are consecutive, and then use this temporary table to discover
groups and apply aggregate functions (if any). In some cases, MySQL is
able to do much better than that and to avoid creation of temporary
tables by using index access.

The most important preconditions for using indexes for `GROUP BY' are
that all `GROUP BY' columns reference attributes from the same index,
and that the index stores its keys in order (for example, this is a
`BTREE' index and not a `HASH' index). Whether use of temporary tables
can be replaced by index access also depends on which parts of an index
are used in a query, the conditions specified for these parts, and the
selected aggregate functions.

There are two ways to execute a `GROUP BY' query through index access,
as detailed in the following sections. In the first method, the
grouping operation is applied together with all range predicates (if
any). The second method first performs a range scan, and then groups the
resulting tuples.

In MySQL, `GROUP BY' is used for sorting, so the server may also apply
`ORDER BY' optimizations to grouping. See *Note order-by-optimization::.


File: manual.info,  Node: loose-index-scan,  Next: tight-index-scan,  Prev: group-by-optimization,  Up: group-by-optimization

8.3.1.18 Loose Index Scan
.........................

The most efficient way to process `GROUP BY' is when an index is used
to directly retrieve the grouping columns. With this access method,
MySQL uses the property of some index types that the keys are ordered
(for example, `BTREE'). This property enables use of lookup groups in
an index without having to consider all keys in the index that satisfy
all `WHERE' conditions. This access method considers only a fraction of
the keys in an index, so it is called a _loose index scan_. When there
is no `WHERE' clause, a loose index scan reads as many keys as the
number of groups, which may be a much smaller number than that of all
keys. If the `WHERE' clause contains range predicates (see the
discussion of the `range' join type in *Note using-explain::), a loose
index scan looks up the first key of each group that satisfies the range
conditions, and again reads the least possible number of keys. This is
possible under the following conditions:

   * The query is over a single table.

   * The `GROUP BY' names only columns that form a leftmost prefix of
     the index and no other columns. (If, instead of `GROUP BY', the
     query has a `DISTINCT' clause, all distinct attributes refer to
     columns that form a leftmost prefix of the index.) For example, if
     a table `t1' has an index on `(c1,c2,c3)', loose index scan is
     applicable if the query has `GROUP BY c1, c2,'. It is not
     applicable if the query has `GROUP BY c2, c3' (the columns are not
     a leftmost prefix) or `GROUP BY c1, c2, c4' (`c4' is not in the
     index).

   * The only aggregate functions used in the select list (if any) are
     `MIN()' and `MAX()', and all of them refer to the same column. The
     column must be in the index and must follow the columns in the
     `GROUP BY'.

   * Any other parts of the index than those from the `GROUP BY'
     referenced in the query must be constants (that is, they must be
     referenced in equalities with constants), except for the argument
     of `MIN()' or `MAX()' functions.

   * For columns in the index, full column values must be indexed, not
     just a prefix. For example, with `c1 VARCHAR(20), INDEX (c1(10))',
     the index cannot be used for loose index scan.

If loose index scan is applicable to a query, the *Note `EXPLAIN':
explain. output shows `Using index for group-by' in the `Extra' column.

Assume that there is an index `idx(c1,c2,c3)' on table
`t1(c1,c2,c3,c4)'. The loose index scan access method can be used for
the following queries:


     SELECT c1, c2 FROM t1 GROUP BY c1, c2;
     SELECT DISTINCT c1, c2 FROM t1;
     SELECT c1, MIN(c2) FROM t1 GROUP BY c1;
     SELECT c1, c2 FROM t1 WHERE c1 < CONST GROUP BY c1, c2;
     SELECT MAX(c3), MIN(c3), c1, c2 FROM t1 WHERE c2 > CONST GROUP BY c1, c2;
     SELECT c2 FROM t1 WHERE c1 < CONST GROUP BY c1, c2;
     SELECT c1, c2 FROM t1 WHERE c3 = CONST GROUP BY c1, c2;

The following queries cannot be executed with this quick select method,
for the reasons given:

   * There are aggregate functions other than `MIN()' or `MAX()':


          SELECT c1, SUM(c2) FROM t1 GROUP BY c1;

   * The columns in the `GROUP BY' clause do not form a leftmost prefix
     of the index:


          SELECT c1, c2 FROM t1 GROUP BY c2, c3;

   * The query refers to a part of a key that comes after the `GROUP
     BY' part, and for which there is no equality with a constant:


          SELECT c1, c3 FROM t1 GROUP BY c1, c2;

     Were the query to include `WHERE c3 = CONST', loose index scan
     could be used.


File: manual.info,  Node: tight-index-scan,  Prev: loose-index-scan,  Up: group-by-optimization

8.3.1.19 Tight Index Scan
.........................

A tight index scan may be either a full index scan or a range index
scan, depending on the query conditions.

When the conditions for a loose index scan are not met, it still may be
possible to avoid creation of temporary tables for `GROUP BY' queries.
If there are range conditions in the `WHERE' clause, this method reads
only the keys that satisfy these conditions.  Otherwise, it performs an
index scan. Because this method reads all keys in each range defined by
the `WHERE' clause, or scans the whole index if there are no range
conditions, we term it a _tight index scan_. With a tight index scan,
the grouping operation is performed only after all keys that satisfy
the range conditions have been found.

For this method to work, it is sufficient that there is a constant
equality condition for all columns in a query referring to parts of the
key coming before or in between parts of the `GROUP BY' key. The
constants from the equality conditions fill in any `gaps' in the search
keys so that it is possible to form complete prefixes of the index.
These index prefixes then can be used for index lookups. If we require
sorting of the `GROUP BY' result, and it is possible to form search
keys that are prefixes of the index, MySQL also avoids extra sorting
operations because searching with prefixes in an ordered index already
retrieves all the keys in order.

Assume that there is an index `idx(c1,c2,c3)' on table
`t1(c1,c2,c3,c4)'. The following queries do not work with the loose
index scan access method described earlier, but still work with the
tight index scan access method.

   * There is a gap in the `GROUP BY', but it is covered by the
     condition `c2 = 'a'':


          SELECT c1, c2, c3 FROM t1 WHERE c2 = 'a' GROUP BY c1, c3;

   * The `GROUP BY' does not begin with the first part of the key, but
     there is a condition that provides a constant for that part:


          SELECT c1, c2, c3 FROM t1 WHERE c1 = 'a' GROUP BY c2, c3;


File: manual.info,  Node: distinct-optimization,  Next: subquery-optimization-with-exists,  Prev: group-by-optimization,  Up: select-optimization

8.3.1.20 DISTINCT Optimization
..............................

`DISTINCT' combined with `ORDER BY' needs a temporary table in many
cases.

Because `DISTINCT' may use `GROUP BY', you should be aware of how MySQL
works with columns in `ORDER BY' or `HAVING' clauses that are not part
of the selected columns. See *Note group-by-extensions::.

In most cases, a `DISTINCT' clause can be considered as a special case
of `GROUP BY'.  For example, the following two queries are equivalent:


     SELECT DISTINCT c1, c2, c3 FROM t1
     WHERE c1 > CONST;

     SELECT c1, c2, c3 FROM t1
     WHERE c1 > CONST GROUP BY c1, c2, c3;

Due to this equivalence, the optimizations applicable to `GROUP BY'
queries can be also applied to queries with a `DISTINCT' clause. Thus,
for more details on the optimization possibilities for `DISTINCT'
queries, see *Note group-by-optimization::.

When combining `LIMIT ROW_COUNT' with `DISTINCT', MySQL stops as soon
as it finds ROW_COUNT unique rows.

If you do not use columns from all tables named in a query, MySQL stops
scanning any unused tables as soon as it finds the first match. In the
following case, assuming that `t1' is used before `t2' (which you can
check with *Note `EXPLAIN': explain.), MySQL stops reading from `t2'
(for any particular row in `t1') when it finds the first row in `t2':


     SELECT DISTINCT t1.a FROM t1, t2 where t1.a=t2.a;


File: manual.info,  Node: subquery-optimization-with-exists,  Next: limit-optimization,  Prev: distinct-optimization,  Up: select-optimization

8.3.1.21 Optimizing Subqueries with EXISTS Strategy
...................................................

Certain optimizations are applicable to comparisons that use the `IN'
operator to test subquery results (or that use `=ANY', which is
equivalent).  This section discusses these optimizations, particularly
with regard to the challenges that `NULL' values present. Suggestions
on what you can do to help the optimizer are given at the end of the
discussion.

Consider the following subquery comparison:


     OUTER_EXPR IN (SELECT INNER_EXPR FROM ... WHERE SUBQUERY_WHERE)

MySQL evaluates queries `from outside to inside.' That is, it first
obtains the value of the outer expression OUTER_EXPR, and then runs the
subquery and captures the rows that it produces.

A very useful optimization is to `inform' the subquery that the only
rows of interest are those where the inner expression INNER_EXPR is
equal to OUTER_EXPR. This is done by pushing down an appropriate
equality into the subquery's `WHERE' clause. That is, the comparison is
converted to this:


     EXISTS (SELECT 1 FROM ... WHERE SUBQUERY_WHERE AND OUTER_EXPR=INNER_EXPR)

After the conversion, MySQL can use the pushed-down equality to limit
the number of rows that it must examine when evaluating the subquery.

More generally, a comparison of N values to a subquery that returns
N-value rows is subject to the same conversion. If OE_I and IE_I
represent corresponding outer and inner expression values, this
subquery comparison:


     (OE_1, ..., OE_N) IN
       (SELECT IE_1, ..., IE_N FROM ... WHERE SUBQUERY_WHERE)

Becomes:


     EXISTS (SELECT 1 FROM ... WHERE SUBQUERY_WHERE
                               AND OE_1 = IE_1
                               AND ...
                               AND OE_N = IE_N)

The following discussion assumes a single pair of outer and inner
expression values for simplicity.

The conversion just described has its limitations. It is valid only if
we ignore possible `NULL' values.  That is, the `pushdown' strategy
works as long as both of these two conditions are true:

   * OUTER_EXPR and INNER_EXPR cannot be `NULL'.

   * You do not need to distinguish `NULL' from `FALSE' subquery
     results. (If the subquery is a part of an `OR' or `AND' expression
     in the `WHERE' clause, MySQL assumes that you don't care.)

When either or both of those conditions do not hold, optimization is
more complex.

Suppose that OUTER_EXPR is known to be a non-`NULL' value but the
subquery does not produce a row such that OUTER_EXPR = INNER_EXPR. Then
`OUTER_EXPR IN (SELECT ...)' evaluates as follows:

   * `NULL', if the *Note `SELECT': select. produces any row where
     INNER_EXPR is `NULL'

   * `FALSE', if the *Note `SELECT': select. produces only non-`NULL'
     values or produces nothing

In this situation, the approach of looking for rows with `OUTER_EXPR =
INNER_EXPR' is no longer valid. It is necessary to look for such rows,
but if none are found, also look for rows where INNER_EXPR is `NULL'.
Roughly speaking, the subquery can be converted to:


     EXISTS (SELECT 1 FROM ... WHERE SUBQUERY_WHERE AND
             (OUTER_EXPR=INNER_EXPR OR INNER_EXPR IS NULL))

The need to evaluate the extra `IS NULL' condition is why MySQL has the
`ref_or_null' access method:


     mysql> EXPLAIN
         -> SELECT OUTER_EXPR IN (SELECT t2.maybe_null_key
         ->                       FROM t2, t3 WHERE ...)
         -> FROM t1;
     *************************** 1. row ***************************
                id: 1
       select_type: PRIMARY
             table: t1
     ...
     *************************** 2. row ***************************
                id: 2
       select_type: DEPENDENT SUBQUERY
             table: t2
              type: ref_or_null
     possible_keys: maybe_null_key
               key: maybe_null_key
           key_len: 5
               ref: func
              rows: 2
             Extra: Using where; Using index
     ...

The `unique_subquery' and `index_subquery' subquery-specific access
methods also have or-null variants.  However, they are not visible in
*Note `EXPLAIN': explain. output, so you must use *Note `EXPLAIN
EXTENDED': explain-extended. followed by *Note `SHOW WARNINGS':
show-warnings. (note the `checking NULL' in the warning message):


     mysql> EXPLAIN EXTENDED
         -> SELECT OUTER_EXPR IN (SELECT maybe_null_key FROM t2) FROM t1\G
     *************************** 1. row ***************************
                id: 1
       select_type: PRIMARY
             table: t1
     ...
     *************************** 2. row ***************************
                id: 2
       select_type: DEPENDENT SUBQUERY
             table: t2
              type: index_subquery
     possible_keys: maybe_null_key
               key: maybe_null_key
           key_len: 5
               ref: func
              rows: 2
             Extra: Using index

     mysql> SHOW WARNINGS\G
     *************************** 1. row ***************************
       Level: Note
        Code: 1003
     Message: select (`test`.`t1`.`outer_expr`,
              (((`test`.`t1`.`outer_expr`) in t2 on
              maybe_null_key checking NULL))) AS `outer_expr IN (SELECT
              maybe_null_key FROM t2)` from `test`.`t1`

The additional `OR ... IS NULL' condition makes query execution
slightly more complicated (and some optimizations within the subquery
become inapplicable), but generally this is tolerable.

The situation is much worse when OUTER_EXPR can be `NULL'. According to
the SQL interpretation of `NULL' as `unknown value,' `NULL IN (SELECT
INNER_EXPR ...)' should evaluate to:

   * `NULL', if the *Note `SELECT': select. produces any rows

   * `FALSE', if the *Note `SELECT': select. produces no rows

For proper evaluation, it is necessary to be able to check whether the
*Note `SELECT': select. has produced any rows at all, so `OUTER_EXPR =
INNER_EXPR' cannot be pushed down into the subquery. This is a problem,
because many real world subqueries become very slow unless the equality
can be pushed down.

Essentially, there must be different ways to execute the subquery
depending on the value of OUTER_EXPR. In MySQL 5.1 before 5.1.16, the
optimizer chose speed over distinguishing a `NULL' from `FALSE' result,
so for some queries, you might get a `FALSE' result rather than `NULL'.

As of MySQL 5.1.16, the optimizer chooses SQL compliance over speed, so
it accounts for the possibility that OUTER_EXPR might be `NULL'.

If OUTER_EXPR is `NULL', to evaluate the following expression, it is
necessary to run the *Note `SELECT': select. to determine whether it
produces any rows:


     NULL IN (SELECT INNER_EXPR FROM ... WHERE SUBQUERY_WHERE)

It is necessary to run the original *Note `SELECT': select. here,
without any pushed-down equalities of the kind mentioned earlier.

On the other hand, when OUTER_EXPR is not `NULL', it is absolutely
essential that this comparison:


     OUTER_EXPR IN (SELECT INNER_EXPR FROM ... WHERE SUBQUERY_WHERE)

be converted to this expression that uses a pushed-down condition:


     EXISTS (SELECT 1 FROM ... WHERE SUBQUERY_WHERE AND OUTER_EXPR=INNER_EXPR)

Without this conversion, subqueries will be slow. To solve the dilemma
of whether to push down or not push down conditions into the subquery,
the conditions are wrapped in `trigger' functions. Thus, an expression
of the following form:


     OUTER_EXPR IN (SELECT INNER_EXPR FROM ... WHERE SUBQUERY_WHERE)

is converted into:


     EXISTS (SELECT 1 FROM ... WHERE SUBQUERY_WHERE
                               AND trigcond(OUTER_EXPR=INNER_EXPR))

More generally, if the subquery comparison is based on several pairs of
outer and inner expressions, the conversion takes this comparison:


     (OE_1, ..., OE_N) IN (SELECT IE_1, ..., IE_N FROM ... WHERE SUBQUERY_WHERE)

and converts it to this expression:


     EXISTS (SELECT 1 FROM ... WHERE SUBQUERY_WHERE
                               AND trigcond(OE_1=IE_1)
                               AND ...
                               AND trigcond(OE_N=IE_N)
            )

Each `trigcond(X)' is a special function that evaluates to the
following values:

   * X when the `linked' outer expression OE_I is not `NULL'

   * `TRUE' when the `linked' outer expression OE_I is `NULL'

Note that trigger functions are _not_ triggers of the kind that you
create with *Note `CREATE TRIGGER': create-trigger.

Equalities that are wrapped into `trigcond()' functions are not first
class predicates for the query optimizer. Most optimizations cannot
deal with predicates that may be turned on and off at query execution
time, so they assume any `trigcond(X)' to be an unknown function and
ignore it. At the moment, triggered equalities can be used by those
optimizations:

   * Reference optimizations: `trigcond(X=Y [OR Y IS NULL])' can be
     used to construct `ref', `eq_ref', or `ref_or_null' table accesses.

   * Index lookup-based subquery execution engines: `trigcond(X=Y)' can
     be used to construct `unique_subquery' or `index_subquery'
     accesses.

   * Table-condition generator: If the subquery is a join of several
     tables, the triggered condition will be checked as soon as
     possible.

When the optimizer uses a triggered condition to create some kind of
index lookup-based access (as for the first two items of the preceding
list), it must have a fallback strategy for the case when the condition
is turned off. This fallback strategy is always the same: Do a full
table scan. In *Note `EXPLAIN': explain. output, the fallback shows up
as `Full scan on NULL key' in the `Extra' column:


     mysql> EXPLAIN SELECT t1.col1,
         -> t1.col1 IN (SELECT t2.key1 FROM t2 WHERE t2.col2=t1.col2) FROM t1\G
     *************************** 1. row ***************************
                id: 1
       select_type: PRIMARY
             table: t1
             ...
     *************************** 2. row ***************************
                id: 2
       select_type: DEPENDENT SUBQUERY
             table: t2
              type: index_subquery
     possible_keys: key1
               key: key1
           key_len: 5
               ref: func
              rows: 2
             Extra: Using where; Full scan on NULL key

If you run *Note `EXPLAIN EXTENDED': explain-extended.  followed by
*Note `SHOW WARNINGS': show-warnings, you can see the triggered
condition:


     *************************** 1. row ***************************
       Level: Note
        Code: 1003
     Message: select `test`.`t1`.`col1` AS `col1`,
              <in_optimizer>(`test`.`t1`.`col1`,
              <exists>(<index_lookup>(<cache>(`test`.`t1`.`col1`) in t2
              on key1 checking NULL
              where (`test`.`t2`.`col2` = `test`.`t1`.`col2`) having
              trigcond(<is_not_null_test>(`test`.`t2`.`key1`))))) AS
              `t1.col1 IN (select t2.key1 from t2 where t2.col2=t1.col2)`
              from `test`.`t1`

The use of triggered conditions has some performance implications. A
`NULL IN (SELECT ...)' expression now may cause a full table scan
(which is slow) when it previously did not. This is the price paid for
correct results (the goal of the trigger-condition strategy was to
improve compliance and not speed).

For multiple-table subqueries, execution of `NULL IN (SELECT ...)' will
be particularly slow because the join optimizer doesn't optimize for
the case where the outer expression is `NULL'. It assumes that subquery
evaluations with `NULL' on the left side are very rare, even if there
are statistics that indicate otherwise. On the other hand, if the outer
expression might be `NULL' but never actually is, there is no
performance penalty.

To help the query optimizer better execute your queries, use these tips:

   * A column must be declared as `NOT NULL' if it really is. (This
     also helps other aspects of the optimizer.)

   * If you don't need to distinguish a `NULL' from `FALSE' subquery
     result, you can easily avoid the slow execution path. Replace a
     comparison that looks like this:


          OUTER_EXPR IN (SELECT INNER_EXPR FROM ...)

     with this expression:


          (OUTER_EXPR IS NOT NULL) AND (OUTER_EXPR IN (SELECT INNER_EXPR FROM ...))

     Then `NULL IN (SELECT ...)' will never be evaluated because MySQL
     stops evaluating `AND' parts as soon as the expression result is
     clear.


File: manual.info,  Node: limit-optimization,  Next: how-to-avoid-table-scan,  Prev: subquery-optimization-with-exists,  Up: select-optimization

8.3.1.22 Optimizing LIMIT Queries
.................................

In some cases, MySQL handles a query differently when you are using
`LIMIT ROW_COUNT' and not using `HAVING':

   * If you are selecting only a few rows with `LIMIT', MySQL uses
     indexes in some cases when normally it would prefer to do a full
     table scan.

   * If you use `LIMIT ROW_COUNT' with `ORDER BY', MySQL ends the
     sorting as soon as it has found the first ROW_COUNT rows of the
     sorted result, rather than sorting the entire result. If ordering
     is done by using an index, this is very fast. If a filesort must
     be done, all rows that match the query without the `LIMIT' clause
     must be selected, and most or all of them must be sorted, before
     it can be ascertained that the first ROW_COUNT rows have been
     found.  In either case, after the initial rows have been found,
     there is no need to sort any remainder of the result set, and
     MySQL does not do so.

   * When combining `LIMIT ROW_COUNT' with `DISTINCT', MySQL stops as
     soon as it finds ROW_COUNT unique rows.

   * In some cases, a `GROUP BY' can be resolved by reading the key in
     order (or doing a sort on the key) and then calculating summaries
     until the key value changes. In this case, `LIMIT ROW_COUNT' does
     not calculate any unnecessary `GROUP BY' values.

   * As soon as MySQL has sent the required number of rows to the
     client, it aborts the query unless you are using
     `SQL_CALC_FOUND_ROWS'.

   * `LIMIT 0' quickly returns an empty set.  This can be useful for
     checking the validity of a query.  When using one of the MySQL
     APIs, it can also be employed for obtaining the types of the
     result columns. This technique does not work with the *Note
     `mysql': mysql.  client program, which merely displays `Empty set'
     in such cases. Instead, use *Note `SHOW COLUMNS': show-columns. or
     *Note `DESCRIBE': describe. for this purpose.

   * When the server uses temporary tables to resolve the query, it
     uses the `LIMIT ROW_COUNT' clause to calculate how much space is
     required.


File: manual.info,  Node: how-to-avoid-table-scan,  Prev: limit-optimization,  Up: select-optimization

8.3.1.23 How to Avoid Table Scans
.................................

The output from *Note `EXPLAIN': explain. shows `ALL' in the `type'
column when MySQL uses a table scan to resolve a query. This usually
happens under the following conditions:

   * The table is so small that it is faster to perform a table scan
     than to bother with a key lookup. This is common for tables with
     fewer than 10 rows and a short row length.

   * There are no usable restrictions in the `ON' or `WHERE' clause for
     indexed columns.

   * You are comparing indexed columns with constant values and MySQL
     has calculated (based on the index tree) that the constants cover
     too large a part of the table and that a table scan would be
     faster. See *Note where-optimizations::.

   * You are using a key with low cardinality (many rows match the key
     value) through another column. In this case, MySQL assumes that by
     using the key it probably will do many key lookups and that a
     table scan would be faster.

For small tables, a table scan often is appropriate and the performance
impact is negligible. For large tables, try the following techniques to
avoid having the optimizer incorrectly choose a table scan:

   * Use `ANALYZE TABLE TBL_NAME' to update the key distributions for
     the scanned table. See *Note analyze-table::.

   * Use `FORCE INDEX' for the scanned table to tell MySQL that table
     scans are very expensive compared to using the given index:


          SELECT * FROM t1, t2 FORCE INDEX (INDEX_FOR_COLUMN)
            WHERE t1.COL_NAME=t2.COL_NAME;

     See *Note index-hints::.

   * Start *Note `mysqld': mysqld. with the `--max-seeks-for-key=1000'
     option or use `SET max_seeks_for_key=1000' to tell the optimizer to
     assume that no key scan causes more than 1,000 key seeks.  See
     *Note server-system-variables::.


File: manual.info,  Node: non-select-optimization,  Next: information-schema-optimization,  Prev: select-optimization,  Up: statement-optimization

8.3.2 Optimizing Non-SELECT Statements
--------------------------------------

* Menu:

* insert-speed::                 Speed of INSERT Statements
* update-speed::                 Speed of UPDATE Statements
* delete-speed::                 Speed of DELETE Statements
* repair-table-speed::           Speed of REPAIR TABLE Statements


File: manual.info,  Node: insert-speed,  Next: update-speed,  Prev: non-select-optimization,  Up: non-select-optimization

8.3.2.1 Speed of INSERT Statements
..................................

The time required for inserting a row is determined by the following
factors, where the numbers indicate approximate proportions:

   * Connecting: (3)

   * Sending query to server: (2)

   * Parsing query: (2)

   * Inserting row: (1 x size of row)

   * Inserting indexes: (1 x number of indexes)

   * Closing: (1)

This does not take into consideration the initial overhead to open
tables, which is done once for each concurrently running query.

The size of the table slows down the insertion of indexes by log N,
assuming B-tree indexes.

You can use the following methods to speed up inserts:

   * If you are inserting many rows from the same client at the same
     time, use *Note `INSERT': insert.  statements with multiple
     `VALUES' lists to insert several rows at a time. This is
     considerably faster (many times faster in some cases) than using
     separate single-row *Note `INSERT': insert.  statements. If you
     are adding data to a nonempty table, you can tune the
     `bulk_insert_buffer_size' variable to make data insertion even
     faster. See *Note server-system-variables::.

   * If multiple clients are inserting a lot of rows, you can get
     higher speed by using the *Note `INSERT DELAYED': insert-delayed.
     statement. See *Note insert-delayed::.

   * For a `MyISAM' table, you can use concurrent inserts to add rows
     at the same time that *Note `SELECT': select. statements are
     running, if there are no deleted rows in middle of the data file.
     See *Note concurrent-inserts::.

   * When loading a table from a text file, use *Note `LOAD DATA
     INFILE': load-data. This is usually 20 times faster than using
     *Note `INSERT': insert. statements.  See *Note load-data::.

   * With some extra work, it is possible to make *Note `LOAD DATA
     INFILE': load-data. run even faster for a `MyISAM' table when the
     table has many indexes. Use the following procedure:

       1. Optionally create the table with *Note `CREATE TABLE':
          create-table.

       2. Execute a *Note `FLUSH TABLES': flush. statement or a *Note
          `mysqladmin flush-tables': mysqladmin. command.

       3. Use *Note `myisamchk --keys-used=0 -rq
          /PATH/TO/DB/TBL_NAME.': myisamchk.  This removes all use of
          indexes for the table.

       4. Insert data into the table with *Note `LOAD DATA INFILE':
          load-data. This does not update any indexes and therefore is
          very fast.

       5. If you intend only to read from the table in the future, use
          *Note `myisampack': myisampack. to compress it. See *Note
          compressed-format::.

       6. Re-create the indexes with *Note `myisamchk -rq
          /PATH/TO/DB/TBL_NAME': myisamchk.  This creates the index
          tree in memory before writing it to disk, which is much
          faster that updating the index during *Note `LOAD DATA
          INFILE': load-data. because it avoids lots of disk seeks.
          The resulting index tree is also perfectly balanced.

       7. Execute a *Note `FLUSH TABLES': flush. statement or a *Note
          `mysqladmin flush-tables': mysqladmin. command.

     *Note `LOAD DATA INFILE': load-data. performs the preceding
     optimization automatically if the `MyISAM' table into which you
     insert data is empty. The main difference between automatic
     optimization and using the procedure explicitly is that you can let
     *Note `myisamchk': myisamchk. allocate much more temporary memory
     for the index creation than you might want the server to allocate
     for index re-creation when it executes the *Note `LOAD DATA
     INFILE': load-data. statement.

     You can also disable or enable the nonunique indexes for a
     `MyISAM' table by using the following statements rather than *Note
     `myisamchk': myisamchk. If you use these statements, you can skip
     the *Note `FLUSH TABLE': flush. operations:


          ALTER TABLE TBL_NAME DISABLE KEYS;
          ALTER TABLE TBL_NAME ENABLE KEYS;

   * To speed up *Note `INSERT': insert.  operations that are performed
     with multiple statements for nontransactional tables, lock your
     tables:


          LOCK TABLES a WRITE;
          INSERT INTO a VALUES (1,23),(2,34),(4,33);
          INSERT INTO a VALUES (8,26),(6,29);
          ...
          UNLOCK TABLES;

     This benefits performance because the index buffer is flushed to
     disk only once, after all *Note `INSERT': insert. statements have
     completed. Normally, there would be as many index buffer flushes
     as there are *Note `INSERT': insert.  statements. Explicit locking
     statements are not needed if you can insert all rows with a single
     *Note `INSERT': insert.

     To obtain faster insertions for transactional tables, you should
     use *Note `START TRANSACTION': commit. and *Note `COMMIT': commit.
     instead of *Note `LOCK TABLES': lock-tables.

     Locking also lowers the total time for multiple-connection tests,
     although the maximum wait time for individual connections might go
     up because they wait for locks.  Suppose that five clients attempt
     to perform inserts simultaneously as follows:

        * Connection 1 does 1000 inserts

        * Connections 2, 3, and 4 do 1 insert

        * Connection 5 does 1000 inserts

     If you do not use locking, connections 2, 3, and 4 finish before 1
     and 5. If you use locking, connections 2, 3, and 4 probably do not
     finish before 1 or 5, but the total time should be about 40%
     faster.

     *Note `INSERT': insert, *Note `UPDATE': update, and *Note
     `DELETE': delete. operations are very fast in MySQL, but you can
     obtain better overall performance by adding locks around
     everything that does more than about five successive inserts or
     updates. If you do very many successive inserts, you could do a
     *Note `LOCK TABLES': lock-tables. followed by an *Note `UNLOCK
     TABLES': lock-tables. once in a while (each 1,000 rows or so) to
     permit other threads to access table. This would still result in a
     nice performance gain.

     *Note `INSERT': insert. is still much slower for loading data than
     *Note `LOAD DATA INFILE': load-data, even when using the
     strategies just outlined.

   * To increase performance for `MyISAM' tables, for both *Note `LOAD
     DATA INFILE': load-data. and *Note `INSERT': insert, enlarge the
     key cache by increasing the `key_buffer_size' system variable. See
     *Note server-parameters::.


File: manual.info,  Node: update-speed,  Next: delete-speed,  Prev: insert-speed,  Up: non-select-optimization

8.3.2.2 Speed of UPDATE Statements
..................................

An update statement is optimized like a *Note `SELECT': select. query
with the additional overhead of a write. The speed of the write depends
on the amount of data being updated and the number of indexes that are
updated. Indexes that are not changed do not get updated.

Another way to get fast updates is to delay updates and then do many
updates in a row later. Performing multiple updates together is much
quicker than doing one at a time if you lock the table.

For a `MyISAM' table that uses dynamic row format, updating a row to a
longer total length may split the row. If you do this often, it is very
important to use *Note `OPTIMIZE TABLE': optimize-table. occasionally.
See *Note optimize-table::.


File: manual.info,  Node: delete-speed,  Next: repair-table-speed,  Prev: update-speed,  Up: non-select-optimization

8.3.2.3 Speed of DELETE Statements
..................................

The time required to delete individual rows is exactly proportional to
the number of indexes. To delete rows more quickly, you can increase
the size of the key cache by increasing the `key_buffer_size' system
variable. See *Note server-parameters::.

To delete all rows from a table, `TRUNCATE TABLE TBL_NAME' is faster
than `DELETE FROM TBL_NAME'. Truncate operations are not
transaction-safe; an error occurs when attempting one in the course of
an active transaction or active table lock. See *Note truncate-table::.


File: manual.info,  Node: repair-table-speed,  Prev: delete-speed,  Up: non-select-optimization

8.3.2.4 Speed of REPAIR TABLE Statements
........................................

*Note `REPAIR TABLE': repair-table. for `MyISAM' tables is similar to
using *Note `myisamchk': myisamchk. for repair operations, and some of
the same performance optimizations apply:

   * *Note `myisamchk': myisamchk. has variables that control memory
     allocation. You may be able to its improve performance by setting
     these variables, as described in *Note myisamchk-memory::.

   * For *Note `REPAIR TABLE': repair-table, the same principle
     applies, but because the repair is done by the server, you set
     server system variables instead of *Note `myisamchk': myisamchk.
     variables. Also, In addition to setting memory-allocation
     variables, increasing the `myisam_max_sort_file_size' system
     variable increases the likelihood that the repair will use the
     faster filesort method and avoid the slower repair by key cache
     method. Set the variable to the maximum file size for your system,
     after checking to be sure that there is enough free space to hold
     a copy of the table files. The free space must be available in the
     file system containing the original table files.

Suppose that a *Note `myisamchk': myisamchk. table-repair operation is
done using the following options to set its memory-allocation variables:


     --key_buffer_size=128M --myisam_sort_buffer_size=256M
     --read_buffer_size=64M --write_buffer_size=64M

Some of those *Note `myisamchk': myisamchk. variables correspond to
server system variables:

This table lists *Note `myisamchk': myisamchk.  variables and
corresponding server system variables.

*Note `myisamchk': myisamchk.        System Variable
Variable                             
`key_buffer_size'                    `key_buffer_size'
`myisam_sort_buffer_size'            `myisam_sort_buffer_size'
`read_buffer_size'                   `read_buffer_size'
`write_buffer_size'                  none

Each of the server system variables can be set at runtime, and some of
them (`myisam_sort_buffer_size', `read_buffer_size') have a session
value in addition to a global value. Setting a session value limits the
effect of the change to your current session and does not affect other
users. Changing a global-only variable (`key_buffer_size',
`myisam_max_sort_file_size') affects other users as well. For
`key_buffer_size', you must take into account that the buffer is shared
with those users.  For example, if you set the *Note `myisamchk':
myisamchk.  `key_buffer_size' variable to 128MB, you could set the
corresponding `key_buffer_size' system variable larger than that (if it
is not already set larger), to permit key buffer use by activity in
other sessions.  However, changing the global key buffer size
invalidates the buffer, causing increased disk I/O and slowdown for
other sessions. An alternative that avoids this problem is to use a
separate key cache, assign to it the indexes from the table to be
repaired, and deallocate it when the repair is complete.  See *Note
multiple-key-caches::.

Based on the preceding remarks, a *Note `REPAIR TABLE': repair-table.
operation can be done as follows to use settings similar to the *Note
`myisamchk': myisamchk. command.  Here a separate 128MB key buffer is
allocated and the file system is assumed to permit a file size of at
least 100GB.


     SET SESSION myisam_sort_buffer_size = 256*1024*1024;
     SET SESSION read_buffer_size = 64*1024*1024;
     SET GLOBAL myisam_max_sort_file_size = 100*1024*1024*1024;
     SET GLOBAL repair_cache.key_buffer_size = 128*1024*1024;
     CACHE INDEX TBL_NAME IN repair_cache;
     LOAD INDEX INTO CACHE TBL_NAME;
     REPAIR TABLE TBL_NAME ;
     SET GLOBAL repair_cache.key_buffer_size = 0;

If you intend to change a global variable but want to do so only for
the duration of a *Note `REPAIR TABLE': repair-table. operation to
minimally affect other users, save its value in a user variable and
restore it afterward.  For example:


     SET @old_myisam_sort_buffer_size = @@global.myisam_max_sort_file_size;
     SET GLOBAL myisam_max_sort_file_size = 100*1024*1024*1024;
     REPAIR TABLE tbl_name ;
     SET GLOBAL myisam_max_sort_file_size = @old_myisam_max_sort_file_size;

The system variables that affect *Note `REPAIR TABLE': repair-table.
can be set globally at server startup if you want the values to be in
effect by default. For example, add these lines to the server `my.cnf'
file:


     [mysqld]
     myisam_sort_buffer_size=256M
     key_buffer_size=1G
     myisam_max_sort_file_size=100G

These settings do not include `read_buffer_size'. Setting
`read_buffer_size' globally to a large value does so for all sessions
and can cause performance to suffer due to excessive memory allocation
for a server with many simultaneous sessions.


File: manual.info,  Node: information-schema-optimization,  Next: miscellaneous-optimization-tips,  Prev: non-select-optimization,  Up: statement-optimization

8.3.3 INFORMATION_SCHEMA Optimization
-------------------------------------

As of MySQL 5.1.21, the implementation of `INFORMATION_SCHEMA' is such
that certain types of queries for `INFORMATION_SCHEMA' tables can be
optimized to execute more quickly. This section provides guidelines on
writing queries that take advantage of these optimizations. In general,
the strategies outlined here minimize the need for the server to access
the file system to obtain the information that makes up the contents of
`INFORMATION_SCHEMA' tables. By writing queries that enable the server
to avoid directory scans or opening table files, you will obtain better
performance. These optimizations do have an effect on how collations
are used for searches in `INFORMATION_SCHEMA' tables. For more
information, see *Note charset-collation-information-schema::.

*1) Try to use constant lookup values for database and table names in
the `WHERE' clause*

You can take advantage of this principle as follows:

   * To look up databases or tables, use expressions that evaluate to a
     constant, such as literal values, functions that return a
     constant, or scalar subqueries.

   * Avoid queries that use a nonconstant database name lookup value
     (or no lookup value) because they require a scan of the data
     directory to find matching database directory names.

   * Within a database, avoid queries that use a nonconstant table name
     lookup value (or no lookup value) because they require a scan of
     the database directory to find matching table files.

This principle applies to the `INFORMATION_SCHEMA' tables shown in the
following table, which shows the columns for which a constant lookup
value enables the server to avoid a directory scan. For example, if you
are selecting from *Note `TABLES': tables-table, using a constant lookup
value for `TABLE_SCHEMA' in the `WHERE' clause enables a data directory
scan to be avoided.

This table lists `INFORMATION_SCHEMA' tables and table columns for
which a constant lookup value enables the server to avoid directory
scans.

Table                    Column to specify to     Column to specify to
                         avoid data directory     avoid database
                         scan                     directory scan
*Note `COLUMNS':         `TABLE_SCHEMA'           `TABLE_NAME'
columns-table.                                    
*Note                    `TABLE_SCHEMA'           `TABLE_NAME'
`KEY_COLUMN_USAGE':                               
key-column-usage-table.                           
*Note `PARTITIONS':      `TABLE_SCHEMA'           `TABLE_NAME'
partitions-table.                                 
*Note                    `CONSTRAINT_SCHEMA'      `TABLE_NAME'
`REFERENTIAL_CONSTRAINTS':                         
referential-constraints-table.                         
*Note `STATISTICS':      `TABLE_SCHEMA'           `TABLE_NAME'
statistics-table.                                 
*Note `TABLES':          `TABLE_SCHEMA'           `TABLE_NAME'
tables-table.                                     
*Note                    `TABLE_SCHEMA'           `TABLE_NAME'
`TABLE_CONSTRAINTS':                              
table-constraints-table.                          
*Note `TRIGGERS':        `EVENT_OBJECT_SCHEMA'    `EVENT_OBJECT_TABLE'
triggers-table.                                   
*Note `VIEWS':           `TABLE_SCHEMA'           `TABLE_NAME'
views-table.                                      

The benefit of a query that is limited to a specific constant database
name is that checks need be made only for the named database directory.
Example:

     SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
     WHERE TABLE_SCHEMA = 'test';

Use of the literal database name `test' enables the server to check
only the `test' database directory, regardless of how many databases
there might be. By contrast, the following query is less efficient
because it requires a scan of the data directory to determine which
database names match the pattern `'test%'':

     SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
     WHERE TABLE_SCHEMA LIKE 'test%';

For a query that is limited to a specific constant table name, checks
need be made only for the named table within the corresponding database
directory. Example:

     SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
     WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME = 't1';

Use of the literal table name `t1' enables the server to check only the
files for the `t1' table, regardless of how many tables there might be
in the `test' database. By contrast, the following query requires a
scan of the `test' database directory to determine which table names
match the pattern `'t%'':

     SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
     WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME LIKE 't%';

The following query requires a scan of the database directory to
determine matching database names for the pattern `'test%'', and for
each matching database, it requires a scan of the database directory to
determine matching table names for the pattern `'t%'':

     SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
     WHERE TABLE_SCHEMA = 'test%' AND TABLE_NAME LIKE 't%';

*2) Write queries that minimize the number of table files that must be
opened*

For queries that refer to certain `INFORMATION_SCHEMA' table columns,
several optimizations are available that minimize the number of table
files that must be opened. Example:

     SELECT TABLE_NAME, ENGINE FROM INFORMATION_SCHEMA.TABLES
     WHERE TABLE_SCHEMA = 'test';

In this case, after the server has scanned the database directory to
determine the names of the tables in the database, those names become
available with no further file system lookups. Thus, `TABLE_NAME'
requires no files to be opened. The `ENGINE' (storage engine) value can
be determined by opening the table's `.frm' file, without touching
other table files such as the `.MYD' or `.MYI' file.

Some values, such as `INDEX_LENGTH' for `MyISAM' tables, require
opening the `.MYD' or `.MYI' file as well.

The file-opening optimization types are denoted thus:

   * `SKIP_OPEN_TABLE': Table files do not need to be opened. The
     information has already become available within the query by
     scanning the database directory.

   * `OPEN_FRM_ONLY': Only the table's `.frm' file need be opened.

   * `OPEN_TRIGGER_ONLY': Only the table's `.TRG' file need be opened.

   * `OPEN_FULL_TABLE': The unoptimized information lookup. The `.frm',
     `.MYD', and `.MYI' files must be opened.

The following list indicates how the preceding optimization types apply
to `INFORMATION_SCHEMA' table columns. For tables and columns not
named, none of the optimizations apply.

   * *Note `COLUMNS': columns-table.: `OPEN_FRM_ONLY' applies to all
     columns

   * *Note `KEY_COLUMN_USAGE': key-column-usage-table.:
     `OPEN_FULL_TABLE' applies to all columns

   * *Note `PARTITIONS': partitions-table.: `OPEN_FULL_TABLE' applies
     to all columns

   * *Note `REFERENTIAL_CONSTRAINTS': referential-constraints-table.:
     `OPEN_FULL_TABLE' applies to all columns

   * *Note `STATISTICS': statistics-table.:

     This table shows optimization types that apply to
     `INFORMATION_SCHEMA' *Note `STATISTICS': statistics-table. table
     columns.

     Column                             Optimization type
     `TABLE_CATALOG'                    `OPEN_FRM_ONLY'
     `TABLE_SCHEMA'                     `OPEN_FRM_ONLY'
     `TABLE_NAME'                       `OPEN_FRM_ONLY'
     `NON_UNIQUE'                       `OPEN_FRM_ONLY'
     `INDEX_SCHEMA'                     `OPEN_FRM_ONLY'
     `INDEX_NAME'                       `OPEN_FRM_ONLY'
     `SEQ_IN_INDEX'                     `OPEN_FRM_ONLY'
     `COLUMN_NAME'                      `OPEN_FRM_ONLY'
     `COLLATION'                        `OPEN_FRM_ONLY'
     `CARDINALITY'                      `OPEN_FULL_TABLE'
     `SUB_PART'                         `OPEN_FRM_ONLY'
     `PACKED'                           `OPEN_FRM_ONLY'
     `NULLABLE'                         `OPEN_FRM_ONLY'
     `INDEX_TYPE'                       `OPEN_FULL_TABLE'
     `COMMENT'                          `OPEN_FRM_ONLY'

   * *Note `TABLES': tables-table.:

     This table shows optimization types that apply to
     `INFORMATION_SCHEMA' *Note `TABLES': tables-table. table columns.

     Column                             Optimization type
     `TABLE_CATALOG'                    `SKIP_OPEN_TABLE'
     `TABLE_SCHEMA'                     `SKIP_OPEN_TABLE'
     `TABLE_NAME'                       `SKIP_OPEN_TABLE'
     `TABLE_TYPE'                       `OPEN_FRM_ONLY'
     `ENGINE'                           `OPEN_FRM_ONLY'
     `VERSION'                          `OPEN_FRM_ONLY'
     `ROW_FORMAT'                       `OPEN_FULL_TABLE'
     `TABLE_ROWS'                       `OPEN_FULL_TABLE'
     `AVG_ROW_LENGTH'                   `OPEN_FULL_TABLE'
     `DATA_LENGTH'                      `OPEN_FULL_TABLE'
     `MAX_DATA_LENGTH'                  `OPEN_FULL_TABLE'
     `INDEX_LENGTH'                     `OPEN_FULL_TABLE'
     `DATA_FREE'                        `OPEN_FULL_TABLE'
     `AUTO_INCREMENT'                   `OPEN_FULL_TABLE'
     `CREATE_TIME'                      `OPEN_FULL_TABLE'
     `UPDATE_TIME'                      `OPEN_FULL_TABLE'
     `CHECK_TIME'                       `OPEN_FULL_TABLE'
     `TABLE_COLLATION'                  `OPEN_FRM_ONLY'
     `CHECKSUM'                         `OPEN_FULL_TABLE'
     `CREATE_OPTIONS'                   `OPEN_FRM_ONLY'
     `TABLE_COMMENT'                    `OPEN_FRM_ONLY'

   * *Note `TABLE_CONSTRAINTS': table-constraints-table.:
     `OPEN_FULL_TABLE' applies to all columns

   * *Note `TRIGGERS': triggers-table.: `OPEN_FULL_TABLE' applies to
     all columns

   * *Note `VIEWS': views-table.:

     This table shows optimization types that apply to
     `INFORMATION_SCHEMA' *Note `VIEWS': views-table. table columns.

     Column                             Optimization type
     `TABLE_CATALOG'                    `OPEN_FRM_ONLY'
     `TABLE_SCHEMA'                     `OPEN_FRM_ONLY'
     `TABLE_NAME'                       `OPEN_FRM_ONLY'
     `VIEW_DEFINITION'                  `OPEN_FULL_TABLE'
     `CHECK_OPTION'                     `OPEN_FULL_TABLE'
     `IS_UPDATABLE'                     `OPEN_FULL_TABLE'
     `DEFINER'                          `OPEN_FULL_TABLE'
     `SECURITY_TYPE'                    `OPEN_FULL_TABLE'
     `CHARACTER_SET_CLIENT'             `OPEN_FULL_TABLE'
     `COLLATION_CONNECTION'             `OPEN_FULL_TABLE'

*3) Use *Note `EXPLAIN': explain. to determine whether the server can
use `INFORMATION_SCHEMA' optimizations for a query*

This applies particularly for `INFORMATION_SCHEMA' queries that search
for information from more than one database, which might take a long
time and impact performance. The `Extra' value in *Note `EXPLAIN':
explain. output indicates which, if any, of the optimizations described
earlier the server can use to evaluate `INFORMATION_SCHEMA' queries.
The following examples demonstrate the kinds of information you can
expect to see in the `Extra' value.

     mysql> EXPLAIN SELECT TABLE_NAME FROM INFORMATION_SCHEMA.VIEWS WHERE
         -> TABLE_SCHEMA = 'test' AND TABLE_NAME = 'v1'\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: VIEWS
              type: ALL
     possible_keys: NULL
               key: TABLE_SCHEMA,TABLE_NAME
           key_len: NULL
               ref: NULL
              rows: NULL
             Extra: Using where; Open_frm_only; Scanned 0 databases

Use of constant database and table lookup values enables the server to
avoid directory scans. For references to `VIEWS.TABLE_NAME', only the
`.frm' file need be opened.

     mysql> EXPLAIN SELECT TABLE_NAME, ROW_FORMAT FROM INFORMATION_SCHEMA.TABLES\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: TABLES
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: NULL
             Extra: Open_full_table; Scanned all databases

No lookup values are provided (there is no `WHERE' clause), so the
server must scan the data directory and each database directory. For
each table thus identified, the table name and row format are selected.
`TABLE_NAME' requires no further table files to be opened (the
`SKIP_OPEN_TABLE' optimization applies). `ROW_FORMAT' requires all
table files to be opened (`OPEN_FULL_TABLE' applies).  *Note `EXPLAIN':
explain. reports `OPEN_FULL_TABLE' because it is more expensive than
`SKIP_OPEN_TABLE'.

     mysql> EXPLAIN SELECT TABLE_NAME, TABLE_TYPE FROM INFORMATION_SCHEMA.TABLES
         -> WHERE TABLE_SCHEMA = 'test'\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: TABLES
              type: ALL
     possible_keys: NULL
               key: TABLE_SCHEMA
           key_len: NULL
               ref: NULL
              rows: NULL
             Extra: Using where; Open_frm_only; Scanned 1 database

No table name lookup value is provided, so the server must scan the
`test' database directory. For the `TABLE_NAME' and `TABLE_TYPE'
columns, the `SKIP_OPEN_TABLE' and `OPEN_FRM_ONLY' optimizations apply,
respectively. *Note `EXPLAIN': explain. reports `OPEN_FRM_ONLY' because
it is more expensive.

     mysql> EXPLAIN SELECT B.TABLE_NAME
         -> FROM INFORMATION_SCHEMA.TABLES AS A, INFORMATION_SCHEMA.COLUMNS AS B
         -> WHERE A.TABLE_SCHEMA = 'test'
         -> AND A.TABLE_NAME = 't1'
         -> AND B.TABLE_NAME = A.TABLE_NAME\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: A
              type: ALL
     possible_keys: NULL
               key: TABLE_SCHEMA,TABLE_NAME
           key_len: NULL
               ref: NULL
              rows: NULL
             Extra: Using where; Skip_open_table; Scanned 0 databases
     *************************** 2. row ***************************
                id: 1
       select_type: SIMPLE
             table: B
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: NULL
             Extra: Using where; Open_frm_only; Scanned all databases;
                    Using join buffer

For the first *Note `EXPLAIN': explain. output row: Constant database
and table lookup values enable the server to avoid directory scans for
`TABLES' values.  References to `TABLES.TABLE_NAME' require no further
table files.

For the second *Note `EXPLAIN': explain. output row: All *Note
`COLUMNS': columns-table. table values are `OPEN_FRM_ONLY' lookups, so
`COLUMNS.TABLE_NAME' requires the `.frm' file to be opened.

     mysql> EXPLAIN SELECT * FROM INFORMATION_SCHEMA.COLLATIONS\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: COLLATIONS
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: NULL
             Extra:

In this case, no optimizations apply because *Note `COLLATIONS':
collations-table. is not one of the `INFORMATION_SCHEMA' tables for
which optimizations are available.


File: manual.info,  Node: miscellaneous-optimization-tips,  Prev: information-schema-optimization,  Up: statement-optimization

8.3.4 Other Optimization Tips
-----------------------------

This section lists a number of miscellaneous tips for improving query
processing speed:

   * Use persistent connections to the database to avoid connection
     overhead. If you cannot use persistent connections and you are
     initiating many new connections to the database, you may want to
     change the value of the `thread_cache_size' variable.  See *Note
     server-parameters::.

   * Always check whether all your queries really use the indexes that
     you have created in the tables. In MySQL, you can do this with the
     *Note `EXPLAIN': explain.  statement. See *Note using-explain::.

   * Try to avoid complex *Note `SELECT': select.  queries on `MyISAM'
     tables that are updated frequently, to avoid problems with table
     locking that occur due to contention between readers and writers.

   * `MyISAM' supports concurrent inserts: If a table has no free
     blocks in the middle of the data file, you can *Note `INSERT':
     insert. new rows into it at the same time that other threads are
     reading from the table. If it is important to be able to do this,
     you should consider using the table in ways that avoid deleting
     rows.  Another possibility is to run *Note `OPTIMIZE TABLE':
     optimize-table. to defragment the table after you have deleted a
     lot of rows from it. This behavior is altered by setting the
     `concurrent_insert' variable.  You can force new rows to be
     appended (and therefore permit concurrent inserts), even in tables
     that have deleted rows.  See *Note concurrent-inserts::.

   * To fix any compression issues that may have occurred with
     `ARCHIVE' tables, you can use *Note `OPTIMIZE TABLE':
     optimize-table. See *Note archive-storage-engine::.

   * Use `ALTER TABLE ... ORDER BY EXPR1, EXPR2, ...' if you usually
     retrieve rows in `EXPR1, EXPR2, ...' order. By using this option
     after extensive changes to the table, you may be able to get
     higher performance.

   * In some cases, it may make sense to introduce a column that is
     `hashed' based on information from other columns. If this column
     is short, reasonably unique, and indexed, it may be much faster
     than a `wide' index on many columns. In MySQL, it is very easy to
     use this extra column:


          SELECT * FROM TBL_NAME
            WHERE HASH_COL=MD5(CONCAT(VAL1,VAL2))
            AND COL1=VAL1 AND COL2=VAL2;

   * For `MyISAM' tables that change frequently, you should try to
     avoid all variable-length columns (*Note `VARCHAR': char, *Note
     `BLOB': blob, and *Note `TEXT': blob.). The table uses dynamic row
     format if it includes even a single variable-length column. See
     *Note storage-engines::.

   * It is normally not useful to split a table into different tables
     just because the rows become large. In accessing a row, the
     biggest performance hit is the disk seek needed to find the first
     byte of the row. After finding the data, most modern disks can
     read the entire row fast enough for most applications. The only
     cases where splitting up a table makes an appreciable difference
     is if it is a `MyISAM' table using dynamic row format that you can
     change to a fixed row size, or if you very often need to scan the
     table but do not need most of the columns. See *Note
     storage-engines::.

   * If you often need to calculate results such as counts based on
     information from a lot of rows, it may be preferable to introduce
     a new table and update the counter in real time.  An update of the
     following form is very fast:


          UPDATE TBL_NAME SET COUNT_COL=COUNT_COL+1 WHERE KEY_COL=CONSTANT;

     This is very important when you use MySQL storage engines such as
     `MyISAM' that has only table-level locking (multiple readers with
     single writers). This also gives better performance with most
     database systems, because the row locking manager in this case has
     less to do.

   * If you need to collect statistics from large log tables, use
     summary tables instead of scanning the entire log table.
     Maintaining the summaries should be much faster than trying to
     calculate statistics `live.' Regenerating new summary tables from
     the logs when things change (depending on business decisions) is
     faster than changing the running application.

   * If possible, you should classify reports as `live' or as
     `statistical,' where data needed for statistical reports is
     created only from summary tables that are generated periodically
     from the live data.

   * Take advantage of the fact that columns have default values.
     Insert values explicitly only when the value to be inserted
     differs from the default. This reduces the parsing that MySQL must
     do and improves the insert speed.

   * In some cases, it is convenient to pack and store data into a
     *Note `BLOB': blob. column. In this case, you must provide code in
     your application to pack and unpack information, but this may save
     a lot of accesses at some stage. This is practical when you have
     data that does not conform well to a rows-and-columns table
     structure.

   * Normally, you should try to keep all data nonredundant (observing
     what is referred to in database theory as _third normal form_).
     However, there may be situations in which it can be advantageous to
     duplicate information or create summary tables to gain more speed.

   * Stored routines or UDFs (user-defined functions) may be a good way
     to gain performance for some tasks. See *Note stored-routines::,
     and *Note adding-functions::, for more information.

   * You can increase performance by caching queries or answers in your
     application and then executing many inserts or updates together.
     If your database system supports table locks, this should help to
     ensure that the index cache is only flushed once after all
     updates. You can also take advantage of MySQL's query cache to
     achieve similar results; see *Note query-cache::.

   * Use *Note `INSERT DELAYED': insert-delayed. when you do not need
     to know when your data is written. This reduces the overall
     insertion impact because many rows can be written with a single
     disk write.

   * Use `INSERT LOW_PRIORITY' when you want to give *Note `SELECT':
     select. statements higher priority than your inserts.

     Use `SELECT HIGH_PRIORITY' to get retrievals that jump the queue.
     That is, the *Note `SELECT': select. is executed even if there is
     another client waiting to do a write.

     `LOW_PRIORITY' and `HIGH_PRIORITY' have an effect only for storage
     engines that use only table-level locking (such as `MyISAM',
     `MEMORY', and `MERGE').

   * Use multiple-row *Note `INSERT': insert.  statements to store many
     rows with one SQL statement. Many SQL servers support this,
     including MySQL.

   * Use *Note `LOAD DATA INFILE': load-data. to load large amounts of
     data. This is faster than using *Note `INSERT': insert.
     statements.

   * Use `AUTO_INCREMENT' columns so that each row in a table can be
     identified by a single unique value.  unique values.

   * Use *Note `OPTIMIZE TABLE': optimize-table. once in a while to
     avoid fragmentation with dynamic-format `MyISAM' tables. See *Note
     myisam-table-formats::.

   * Use `MEMORY' tables when possible to get more speed. See *Note
     memory-storage-engine::.  `MEMORY' tables are useful for
     noncritical data that is accessed often, such as information about
     the last displayed banner for users who don't have cookies enabled
     in their Web browser. User sessions are another alternative
     available in many Web application environments for handling
     volatile state data.

   * With Web servers, images and other binary assets should normally
     be stored as files. That is, store only a reference to the file
     rather than the file itself in the database.  Most Web servers are
     better at caching files than database contents, so using files is
     generally faster.

   * Columns with identical information in different tables should be
     declared to have identical data types so that joins based on the
     corresponding columns will be faster.

   * Try to keep column names simple. For example, in a table named
     `customer', use a column name of `name' instead of
     `customer_name'. To make your names portable to other SQL servers,
     you should keep them shorter than 18 characters.

   * If you need really high speed, you should take a look at the
     low-level interfaces for data storage that the different SQL
     servers support. For example, by accessing the MySQL `MyISAM'
     storage engine directly, you could get a speed increase of two to
     five times compared to using the SQL interface. To be able to do
     this, the data must be on the same server as the application, and
     usually it should only be accessed by one process (because
     external file locking is really slow). One could eliminate these
     problems by introducing low-level `MyISAM' commands in the MySQL
     server (this could be one easy way to get more performance if
     needed). By carefully designing the database interface, it should
     be quite easy to support this type of optimization.

   * If you are using numeric data, it is faster in many cases to
     access information from a database (using a live connection) than
     to access a text file. Information in the database is likely to be
     stored in a more compact format than in the text file, so
     accessing it involves fewer disk accesses. You also save code in
     your application because you need not parse your text files to
     find line and column boundaries.

   * Replication can provide a performance benefit for some operations.
     You can distribute client retrievals among replication servers to
     split up the load. To avoid slowing down the master while making
     backups, you can make backups using a slave server. See *Note
     replication::.

   * Declaring a `MyISAM' table with the `DELAY_KEY_WRITE=1' table
     option makes index updates faster because they are not flushed to
     disk until the table is closed. The downside is that if something
     kills the server while such a table is open, you should ensure
     that the table is okay by running the server with the
     `--myisam-recover' option, or by running *Note `myisamchk':
     myisamchk. before restarting the server. (However, even in this
     case, you should not lose anything by using `DELAY_KEY_WRITE',
     because the key information can always be generated from the data
     rows.)


File: manual.info,  Node: controlling-optimizer,  Next: optimization-indexes,  Prev: statement-optimization,  Up: optimization

8.4 Controlling the Query Optimizer
===================================

* Menu:

* controlling-query-plan-evaluation::  Controlling Query Plan Evaluation
* switchable-optimizations::     Controlling Switchable Optimizations

MySQL provides optimizer control through system variables that affect
how query plans are evaluated and which switchable optimizations are
enabled.


File: manual.info,  Node: controlling-query-plan-evaluation,  Next: switchable-optimizations,  Prev: controlling-optimizer,  Up: controlling-optimizer

8.4.1 Controlling Query Plan Evaluation
---------------------------------------

The task of the query optimizer is to find an optimal plan for
executing an SQL query. Because the difference in performance between
`good' and `bad' plans can be orders of magnitude (that is, seconds
versus hours or even days), most query optimizers, including that of
MySQL, perform a more or less exhaustive search for an optimal plan
among all possible query evaluation plans. For join queries, the number
of possible plans investigated by the MySQL optimizer grows
exponentially with the number of tables referenced in a query.  For
small numbers of tables (typically less than 7 to 10) this is not a
problem. However, when larger queries are submitted, the time spent in
query optimization may easily become the major bottleneck in the
server's performance.

A more flexible method for query optimization enables the user to
control how exhaustive the optimizer is in its search for an optimal
query evaluation plan. The general idea is that the fewer plans that
are investigated by the optimizer, the less time it spends in compiling
a query. On the other hand, because the optimizer skips some plans, it
may miss finding an optimal plan.

The behavior of the optimizer with respect to the number of plans it
evaluates can be controlled using two system variables:

   * The `optimizer_prune_level' variable tells the optimizer to skip
     certain plans based on estimates of the number of rows accessed
     for each table. Our experience shows that this kind of `educated
     guess' rarely misses optimal plans, and may dramatically reduce
     query compilation times. That is why this option is on
     (`optimizer_prune_level=1') by default.  However, if you believe
     that the optimizer missed a better query plan, this option can be
     switched off (`optimizer_prune_level=0') with the risk that query
     compilation may take much longer. Note that, even with the use of
     this heuristic, the optimizer still explores a roughly exponential
     number of plans.

   * The `optimizer_search_depth' variable tells how far into the
     `future' of each incomplete plan the optimizer should look to
     evaluate whether it should be expanded further. Smaller values of
     `optimizer_search_depth' may result in orders of magnitude smaller
     query compilation times. For example, queries with 12, 13, or more
     tables may easily require hours and even days to compile if
     `optimizer_search_depth' is close to the number of tables in the
     query. At the same time, if compiled with `optimizer_search_depth'
     equal to 3 or 4, the optimizer may compile in less than a minute
     for the same query. If you are unsure of what a reasonable value
     is for `optimizer_search_depth', this variable can be set to 0 to
     tell the optimizer to determine the value automatically.


File: manual.info,  Node: switchable-optimizations,  Prev: controlling-query-plan-evaluation,  Up: controlling-optimizer

8.4.2 Controlling Switchable Optimizations
------------------------------------------

The `optimizer_switch' system variable enables control over optimizer
behavior. Its value is a set of flags, each of which has a value of `on'
or `off' to indicate whether the corresponding optimizer behavior is
enabled or disabled. This variable has global and session values and
can be changed at runtime. The global default can be set at server
startup.

To see the current set of optimizer flags, select the variable value:


     mysql> SELECT @@optimizer_switch\G
     *************************** 1. row ***************************
     @@optimizer_switch: index_merge=on,index_merge_union=on,
                         index_merge_sort_union=on,
                         index_merge_intersection=on

To change the value of `optimizer_switch', assign a value consisting of
a comma-separated list of one or more commands:


     SET [GLOBAL|SESSION] optimizer_switch='COMMAND[,COMMAND]...';

Each COMMAND value should have one of the forms shown in the following
table.

This table describes the syntax of the COMMAND value for SET
`optimizer_switch' commands.

Command Syntax     Meaning
`default'          Reset every optimization to its default value
`OPT_NAME=default' Set the named optimization to its default value
`OPT_NAME=off'     Disable the named optimization
`OPT_NAME=on'      Enable the named optimization

The order of the commands in the value does not matter, although the
`default' command is executed first if present. Setting an OPT_NAME
flag to `default' sets it to whichever of `on' or `off' is its default
value. Specifying any given OPT_NAME more than once in the value is not
permitted and causes an error. Any errors in the value cause the
assignment to fail with an error, leaving the value of
`optimizer_switch' unchanged.

The following table lists the permissible OPT_NAME flag names.

This table describes permissible OPT_NAME flag names for SET
`optimizer_switch' commands.

Flag Name                 Meaning
`index_merge'             Controls all Index Merge optimizations
`index_merge_intersection'Controls the Index Merge Intersection Access
                          optimization
`index_merge_sort_union'  Controls the Index Merge Sort-Union Access
                          optimization
`index_merge_union'       Controls the Index Merge Union Access
                          optimization

For information about Index Merge, see *Note index-merge-optimization::.

When you assign a value to `optimizer_switch', flags that are not
mentioned keep their current values. This makes it possible to enable
or disable specific optimizer behaviors in a single statement without
affecting other behaviors. The statement does not depend on what other
optimizer flags exist and what their values are. Suppose that all Index
Merge optimizations are enabled:


     mysql> SELECT @@optimizer_switch\G
     *************************** 1. row ***************************
     @@optimizer_switch: index_merge=on,index_merge_union=on,
                         index_merge_sort_union=on,
                         index_merge_intersection=on

If the server is using the Index Merge Union or Index Merge Sort-Union
access methods for certain queries and you want to check whether the
optimizer will perform better without them, set the variable value like
this:


     mysql> SET optimizer_switch='index_merge_union=off,index_merge_sort_union=off';

     mysql> SELECT @@optimizer_switch\G
     *************************** 1. row ***************************
     @@optimizer_switch: index_merge=on,index_merge_union=off,
                         index_merge_sort_union=off,
                         index_merge_intersection=on


File: manual.info,  Node: optimization-indexes,  Next: buffering-caching,  Prev: controlling-optimizer,  Up: optimization

8.5 Optimization and Indexes
============================

* Menu:

* column-indexes::               Column Indexes
* multiple-column-indexes::      Multiple-Column Indexes
* mysql-indexes::                How MySQL Uses Indexes
* myisam-index-statistics::      InnoDB and MyISAM Index Statistics Collection


File: manual.info,  Node: column-indexes,  Next: multiple-column-indexes,  Prev: optimization-indexes,  Up: optimization-indexes

8.5.1 Column Indexes
--------------------

All MySQL data types can be indexed. Use of indexes on the relevant
columns is the best way to improve the performance of *Note `SELECT':
select. operations.

The maximum number of indexes per table and the maximum index length is
defined per storage engine. See *Note storage-engines::. All storage
engines support at least 16 indexes per table and a total index length
of at least 256 bytes. Most storage engines have higher limits.

With `COL_NAME(N)' syntax in an index specification, you can create an
index that uses only the first N characters of a string column.
Indexing only a prefix of column values in this way can make the index
file much smaller. When you index a *Note `BLOB': blob. or *Note
`TEXT': blob. column, you _must_ specify a prefix length for the index.
For example:


     CREATE TABLE test (blob_col BLOB, INDEX(blob_col(10)));

Prefixes can be up to 1000 bytes long (767 bytes for `InnoDB' tables).

*Note*:

Prefix limits are measured in bytes, while the prefix length in *Note
`CREATE TABLE': create-table. statements is interpreted as number of
characters. _Take this into account when specifying a prefix length for
a column that uses a multibyte character set_.

You can also create `FULLTEXT' indexes. These are used for full-text
searches. Only the `MyISAM' storage engine supports `FULLTEXT' indexes
and only for *Note `CHAR': char, *Note `VARCHAR': char, and *Note
`TEXT': blob. columns. Indexing always takes place over the entire
column and column prefix indexing is not supported. For details, see
*Note fulltext-search::.

You can also create indexes on spatial data types. Currently, only
`MyISAM' supports R-tree indexes on spatial types. Other storage
engines use B-trees for indexing spatial types (except for `ARCHIVE' and
*Note `NDBCLUSTER': mysql-cluster, which do not support spatial type
indexing).

The `MEMORY' storage engine uses `HASH' indexes by default, but also
supports `BTREE' indexes.


File: manual.info,  Node: multiple-column-indexes,  Next: mysql-indexes,  Prev: column-indexes,  Up: optimization-indexes

8.5.2 Multiple-Column Indexes
-----------------------------

MySQL can create composite indexes (that is, indexes on multiple
columns). An index may consist of up to 16 columns. For certain data
types, you can index a prefix of the column (see *Note
column-indexes::).

MySQL can use multiple-column indexes for queries that test all the
columns in the index, or queries that test just the first column, the
first two columns, the first three columns, and so on. If you specify
the columns in the right order in the index definition, a single
composite index can speed up several kinds of queries on the same table.

A multiple-column index can be considered a sorted array, the rows of
which contain values that are created by concatenating the values of
the indexed columns.

*Note*:

As an alternative to a composite index, you can introduce a column that
is `hashed' based on information from other columns. If this column is
short, reasonably unique, and indexed, it might be faster than a `wide'
index on many columns. In MySQL, it is very easy to use this extra
column:


     SELECT * FROM TBL_NAME
       WHERE HASH_COL=MD5(CONCAT(VAL1,VAL2))
       AND COL1=VAL1 AND COL2=VAL2;

Suppose that a table has the following specification:


     CREATE TABLE test (
         id         INT NOT NULL,
         last_name  CHAR(30) NOT NULL,
         first_name CHAR(30) NOT NULL,
         PRIMARY KEY (id),
         INDEX name (last_name,first_name)
     );

The `name' index is an index over the `last_name' and `first_name'
columns. The index can be used for lookups in queries that specify
values in a known range for combinations of `last_name' and `first_name'
values. It can also be used for queries that specify just a `last_name'
value because that column is a leftmost prefix of the index (as
described later in this section). Therefore, the `name' index is used
for lookups in the following queries:


     SELECT * FROM test WHERE last_name='Widenius';

     SELECT * FROM test
       WHERE last_name='Widenius' AND first_name='Michael';

     SELECT * FROM test
       WHERE last_name='Widenius'
       AND (first_name='Michael' OR first_name='Monty');

     SELECT * FROM test
       WHERE last_name='Widenius'
       AND first_name >='M' AND first_name < 'N';

However, the `name' index is _not_ used for lookups in the following
queries:


     SELECT * FROM test WHERE first_name='Michael';

     SELECT * FROM test
       WHERE last_name='Widenius' OR first_name='Michael';

Suppose that you issue the following *Note `SELECT': select. statement:


     mysql> SELECT * FROM TBL_NAME WHERE col1=VAL1 AND col2=VAL2;

If a multiple-column index exists on `col1' and `col2', the appropriate
rows can be fetched directly. If separate single-column indexes exist on
`col1' and `col2', the optimizer attempts to use the Index Merge
optimization (see *Note index-merge-optimization::), or attempts to find
the most restrictive index by deciding which index excludes more rows
and using that index to fetch the rows.

If the table has a multiple-column index, any leftmost prefix of the
index can be used by the optimizer to find rows. For example, if you
have a three-column index on `(col1, col2, col3)', you have indexed
search capabilities on `(col1)', `(col1, col2)', and `(col1, col2,
col3)'.

MySQL cannot use the index to perform lookups if the columns do not
form a leftmost prefix of the index. Suppose that you have the *Note
`SELECT': select. statements shown here:


     SELECT * FROM TBL_NAME WHERE col1=VAL1;
     SELECT * FROM TBL_NAME WHERE col1=VAL1 AND col2=VAL2;

     SELECT * FROM TBL_NAME WHERE col2=VAL2;
     SELECT * FROM TBL_NAME WHERE col2=VAL2 AND col3=VAL3;

If an index exists on `(col1, col2, col3)', only the first two queries
use the index. The third and fourth queries do involve indexed columns,
but `(col2)' and `(col2, col3)' are not leftmost prefixes of `(col1,
col2, col3)'.


File: manual.info,  Node: mysql-indexes,  Next: myisam-index-statistics,  Prev: multiple-column-indexes,  Up: optimization-indexes

8.5.3 How MySQL Uses Indexes
----------------------------

Indexes are used to find rows with specific column values quickly.
Without an index, MySQL must begin with the first row and then read
through the entire table to find the relevant rows. The larger the
table, the more this costs. If the table has an index for the columns
in question, MySQL can quickly determine the position to seek to in the
middle of the data file without having to look at all the data. If a
table has 1,000 rows, this is at least 100 times faster than reading
sequentially. If you need to access most of the rows, it is faster to
read sequentially, because this minimizes disk seeks.

Most MySQL indexes (`PRIMARY KEY', `UNIQUE', `INDEX', and `FULLTEXT')
are stored in B-trees. Exceptions are that indexes on spatial data
types use R-trees, and that `MEMORY' tables also support hash indexes.

Strings are automatically prefix- and end-space compressed. See *Note
create-index::.

In general, indexes are used as described in the following discussion.
Characteristics specific to hash indexes (as used in `MEMORY' tables)
are described at the end of this section.

MySQL uses indexes for these operations:

   * To find the rows matching a `WHERE' clause quickly.

   * To eliminate rows from consideration. If there is a choice between
     multiple indexes, MySQL normally uses the index that finds the
     smallest number of rows.

   * To retrieve rows from other tables when performing joins.  MySQL
     can use indexes on columns more efficiently if they are declared
     as the same type and size. In this context, *Note `VARCHAR': char.
     and *Note `CHAR': char. are considered the same if they are
     declared as the same size. For example, `VARCHAR(10)' and
     `CHAR(10)' are the same size, but `VARCHAR(10)' and `CHAR(15)' are
     not.

     For comparisons between nonbinary string columns, both columns
     should use the same character set. For example, comparing a `utf8'
     column with a `latin1' column precludes use of an index.

     Comparison of dissimilar columns (comparing a string column to a
     temporal or numeric column, for example) may prevent use of
     indexes if values cannot be compared directly without conversion.
     For a given value such as `1' in the numeric column, it might
     compare equal to any number of values in the string column such as
     `'1'', `' 1'', `'00001'', or `'01.e1''.  This rules out use of any
     indexes for the string column.

   * To find the `MIN()' or `MAX()' value for a specific indexed column
     KEY_COL. This is optimized by a preprocessor that checks whether
     you are using `WHERE KEY_PART_N = CONSTANT' on all key parts that
     occur before KEY_COL in the index. In this case, MySQL does a
     single key lookup for each `MIN()' or `MAX()' expression and
     replaces it with a constant. If all expressions are replaced with
     constants, the query returns at once. For example:


          SELECT MIN(KEY_PART2),MAX(KEY_PART2)
            FROM TBL_NAME WHERE KEY_PART1=10;

   * To sort or group a table if the sorting or grouping is done on a
     leftmost prefix of a usable key (for example, `ORDER BY KEY_PART1,
     KEY_PART2'). If all key parts are followed by `DESC', the key is
     read in reverse order. See *Note order-by-optimization::, and
     *Note group-by-optimization::.

   * In some cases, a query can be optimized to retrieve values without
     consulting the data rows. If a query uses only columns from a
     table that are numeric and that form a leftmost prefix for some
     key, the selected values may be retrieved from the index tree for
     greater speed:


          SELECT KEY_PART3 FROM TBL_NAME
            WHERE KEY_PART1=1

Suppose that you issue the following *Note `SELECT': select. statement:


     mysql> SELECT * FROM TBL_NAME WHERE col1=VAL1 AND col2=VAL2;

If a multiple-column index exists on `col1' and `col2', the appropriate
rows can be fetched directly. If separate single-column indexes exist on
`col1' and `col2', the optimizer will attempt to use the Index Merge
optimization (see *Note index-merge-optimization::), or attempt to find
the most restrictive index by deciding which index finds fewer rows and
using that index to fetch the rows.

If the table has a multiple-column index, any leftmost prefix of the
index can be used by the optimizer to find rows. For example, if you
have a three-column index on `(col1, col2, col3)', you have indexed
search capabilities on `(col1)', `(col1, col2)', and `(col1, col2,
col3)'.

MySQL cannot use an index if the columns do not form a leftmost prefix
of the index. Suppose that you have the *Note `SELECT': select.
statements shown here:


     SELECT * FROM TBL_NAME WHERE col1=VAL1;
     SELECT * FROM TBL_NAME WHERE col1=VAL1 AND col2=VAL2;

     SELECT * FROM TBL_NAME WHERE col2=VAL2;
     SELECT * FROM TBL_NAME WHERE col2=VAL2 AND col3=VAL3;

If an index exists on `(col1, col2, col3)', only the first two queries
use the index. The third and fourth queries do involve indexed columns,
but `(col2)' and `(col2, col3)' are not leftmost prefixes of `(col1,
col2, col3)'.

*B-Tree Index Characteristics*

A B-tree index can be used for column comparisons in expressions that
use the `=', `>', `>=', `<', `<=', or `BETWEEN' operators. The index
also can be used for `LIKE' comparisons if the argument to `LIKE' is a
constant string that does not start with a wildcard character. For
example, the following *Note `SELECT': select. statements use indexes:


     SELECT * FROM TBL_NAME WHERE KEY_COL LIKE 'Patrick%';
     SELECT * FROM TBL_NAME WHERE KEY_COL LIKE 'Pat%_ck%';

In the first statement, only rows with `'Patrick' <= KEY_COL <
'Patricl'' are considered. In the second statement, only rows with
`'Pat' <= KEY_COL < 'Pau'' are considered.

The following *Note `SELECT': select. statements do not use indexes:


     SELECT * FROM TBL_NAME WHERE KEY_COL LIKE '%Patrick%';
     SELECT * FROM TBL_NAME WHERE KEY_COL LIKE OTHER_COL;

In the first statement, the `LIKE' value begins with a wildcard
character. In the second statement, the `LIKE' value is not a constant.

If you use `... LIKE '%STRING%'' and STRING is longer than three
characters, MySQL uses the _Turbo Boyer-Moore algorithm_ to initialize
the pattern for the string and then uses this pattern to perform the
search more quickly.

A search using `COL_NAME IS NULL' employs indexes if COL_NAME is
indexed.

Any index that does not span all `AND' levels in the `WHERE' clause is
not used to optimize the query. In other words, to be able to use an
index, a prefix of the index must be used in every `AND' group.

The following `WHERE' clauses use indexes:


     ... WHERE INDEX_PART1=1 AND INDEX_PART2=2 AND OTHER_COLUMN=3
         /* INDEX = 1 OR INDEX = 2 */
     ... WHERE INDEX=1 OR A=10 AND INDEX=2
         /* optimized like "INDEX_PART1='hello'" */
     ... WHERE INDEX_PART1='hello' AND INDEX_PART3=5
         /* Can use index on INDEX1 but not on INDEX2 or INDEX3 */
     ... WHERE INDEX1=1 AND INDEX2=2 OR INDEX1=3 AND INDEX3=3;

These `WHERE' clauses do _not_ use indexes:


         /* INDEX_PART1 is not used */
     ... WHERE INDEX_PART2=1 AND INDEX_PART3=2

         /*  Index is not used in both parts of the WHERE clause  */
     ... WHERE INDEX=1 OR A=10

         /* No index spans all rows  */
     ... WHERE INDEX_PART1=1 OR INDEX_PART2=10

Sometimes MySQL does not use an index, even if one is available.  One
circumstance under which this occurs is when the optimizer estimates
that using the index would require MySQL to access a very large
percentage of the rows in the table. (In this case, a table scan is
likely to be much faster because it requires fewer seeks.) However, if
such a query uses `LIMIT' to retrieve only some of the rows, MySQL uses
an index anyway, because it can much more quickly find the few rows to
return in the result.

*Hash Index Characteristics*

Hash indexes have somewhat different characteristics from those just
discussed:

   * They are used only for equality comparisons that use the `=' or
     `<=>' operators (but are _very_ fast). They are not used for
     comparison operators such as `<' that find a range of values.

   * The optimizer cannot use a hash index to speed up `ORDER BY'
     operations. (This type of index cannot be used to search for the
     next entry in order.)

   * MySQL cannot determine approximately how many rows there are
     between two values (this is used by the range optimizer to decide
     which index to use). This may affect some queries if you change a
     `MyISAM' table to a hash-indexed `MEMORY' table.

   * Only whole keys can be used to search for a row. (With a B-tree
     index, any leftmost prefix of the key can be used to find rows.)


File: manual.info,  Node: myisam-index-statistics,  Prev: mysql-indexes,  Up: optimization-indexes

8.5.4 InnoDB and MyISAM Index Statistics Collection
---------------------------------------------------

Storage engines collect statistics about tables for use by the
optimizer. Table statistics are based on value groups, where a value
group is a set of rows with the same key prefix value. For optimizer
purposes, an important statistic is the average value group size.

MySQL uses the average value group size in the following ways:

   * To estimate how may rows must be read for each `ref' access

   * To estimate how many row a partial join will produce; that is, the
     number of rows that an operation of this form will produce:


          (...) JOIN TBL_NAME ON TBL_NAME.KEY = EXPR

As the average value group size for an index increases, the index is
less useful for those two purposes because the average number of rows
per lookup increases: For the index to be good for optimization
purposes, it is best that each index value target a small number of
rows in the table. When a given index value yields a large number of
rows, the index is less useful and MySQL is less likely to use it.

The average value group size is related to table cardinality, which is
the number of value groups. The *Note `SHOW INDEX': show-index.
statement displays a cardinality value based on N/S, where N is the
number of rows in the table and S is the average value group size. That
ratio yields an approximate number of value groups in the table.

For a join based on the `<=>' comparison operator, `NULL' is not
treated differently from any other value: `NULL <=> NULL', just as `N
<=> N' for any other N.

However, for a join based on the `=' operator, `NULL' is different from
non-`NULL' values: `EXPR1 = EXPR2' is not true when EXPR1 or EXPR2 (or
both) are `NULL'. This affects `ref' accesses for comparisons of the
form `TBL_NAME.KEY = EXPR': MySQL will not access the table if the
current value of EXPR is `NULL', because the comparison cannot be true.

For `=' comparisons, it does not matter how many `NULL' values are in
the table. For optimization purposes, the relevant value is the average
size of the non-`NULL' value groups. However, MySQL does not currently
enable that average size to be collected or used.

For `InnoDB' and `MyISAM' tables, you have some control over collection
of table statistics by means of the `innodb_stats_method' and
`myisam_stats_method' system variables, respectively. These variables
have three possible values, which differ as follows:

   * When the variable is set to `nulls_equal', all `NULL' values are
     treated as identical (that is, they all form a single value group).

     If the `NULL' value group size is much higher than the average
     non-`NULL' value group size, this method skews the average value
     group size upward. This makes index appear to the optimizer to be
     less useful than it really is for joins that look for non-`NULL'
     values. Consequently, the `nulls_equal' method may cause the
     optimizer not to use the index for `ref' accesses when it should.

   * When the variable is set to `nulls_unequal', `NULL' values are not
     considered the same. Instead, each `NULL' value forms a separate
     value group of size 1.

     If you have many `NULL' values, this method skews the average
     value group size downward. If the average non-`NULL' value group
     size is large, counting `NULL' values each as a group of size 1
     causes the optimizer to overestimate the value of the index for
     joins that look for non-`NULL' values. Consequently, the
     `nulls_unequal' method may cause the optimizer to use this index
     for `ref' lookups when other methods may be better.

   * When the variable is set to `nulls_ignored', `NULL' values are
     ignored.

If you tend to use many joins that use `<=>' rather than `=', `NULL'
values are not special in comparisons and one `NULL' is equal to
another. In this case, `nulls_equal' is the appropriate statistics
method.

The `innodb_stats_method' system variable has a global value; the
`myisam_stats_method' system variable has both global and session
values. Setting the global value affects statistics collection for
tables from the corresponding storage engine. Setting the session value
affects statistics collection only for the current client connection.
This means that you can force a table's statistics to be regenerated
with a given method without affecting other clients by setting the
session value of `myisam_stats_method'.

To regenerate table statistics, you can use any of the following
methods:

   * Execute *Note `myisamchk --stats_method=METHOD_NAME --analyze':
     myisamchk.

   * Change the table to cause its statistics to go out of date (for
     example, insert a row and then delete it), and then set
     `myisam_stats_method' and issue an *Note `ANALYZE TABLE':
     analyze-table.  statement

Some caveats regarding the use of `innodb_stats_method' and
`myisam_stats_method':

   * You can force table statistics to be collected explicitly, as just
     described. However, MySQL may also collect statistics
     automatically. For example, if during the course of executing
     statements for a table, some of those statements modify the table,
     MySQL may collect statistics.  (This may occur for bulk inserts or
     deletes, or some *Note `ALTER TABLE': alter-table. statements, for
     example.) If this happens, the statistics are collected using
     whatever value `innodb_stats_method' or `myisam_stats_method' has
     at the time. Thus, if you collect statistics using one method, but
     the system variable is set to the other method when a table's
     statistics are collected automatically later, the other method
     will be used.

   * There is no way to tell which method was used to generate
     statistics for a given table.

   * These variables apply only to `InnoDB' and `MyISAM' tables. Other
     storage engines have only one method for collecting table
     statistics. Usually it is closer to the `nulls_equal' method.


File: manual.info,  Node: buffering-caching,  Next: locking-issues,  Prev: optimization-indexes,  Up: optimization

8.6 Buffering and Caching
=========================

* Menu:

* myisam-key-cache::             The MyISAM Key Cache
* innodb-buffer-pool::           The InnoDB Buffer Pool
* query-cache::                  The MySQL Query Cache

MySQL uses several strategies that cache information in memory buffers
to increase performance.


File: manual.info,  Node: myisam-key-cache,  Next: innodb-buffer-pool,  Prev: buffering-caching,  Up: buffering-caching

8.6.1 The MyISAM Key Cache
--------------------------

* Menu:

* shared-key-cache::             Shared Key Cache Access
* multiple-key-caches::          Multiple Key Caches
* midpoint-insertion::           Midpoint Insertion Strategy
* index-preloading::             Index Preloading
* key-cache-block-size::         Key Cache Block Size
* key-cache-restructuring::      Restructuring a Key Cache

To minimize disk I/O, the `MyISAM' storage engine exploits a strategy
that is used by many database management systems. It employs a cache
mechanism to keep the most frequently accessed table blocks in memory:

   * For index blocks, a special structure called the _key cache_ (or
     _key buffer_) is maintained. The structure contains a number of
     block buffers where the most-used index blocks are placed.

   * For data blocks, MySQL uses no special cache. Instead it relies on
     the native operating system file system cache.

This section first describes the basic operation of the `MyISAM' key
cache. Then it discusses features that improve key cache performance
and that enable you to better control cache operation:

   * Multiple sessions can access the cache concurrently.

   * You can set up multiple key caches and assign table indexes to
     specific caches.

To control the size of the key cache, use the `key_buffer_size' system
variable. If this variable is set equal to zero, no key cache is used.
The key cache also is not used if the `key_buffer_size' value is too
small to allocate the minimal number of block buffers (8).

When the key cache is not operational, index files are accessed using
only the native file system buffering provided by the operating system.
(In other words, table index blocks are accessed using the same
strategy as that employed for table data blocks.)

An index block is a contiguous unit of access to the `MyISAM' index
files. Usually the size of an index block is equal to the size of nodes
of the index B-tree.  (Indexes are represented on disk using a B-tree
data structure.  Nodes at the bottom of the tree are leaf nodes. Nodes
above the leaf nodes are nonleaf nodes.)

All block buffers in a key cache structure are the same size.  This
size can be equal to, greater than, or less than the size of a table
index block. Usually one these two values is a multiple of the other.

When data from any table index block must be accessed, the server first
checks whether it is available in some block buffer of the key cache.
If it is, the server accesses data in the key cache rather than on
disk. That is, it reads from the cache or writes into it rather than
reading from or writing to disk.  Otherwise, the server chooses a cache
block buffer containing a different table index block (or blocks) and
replaces the data there by a copy of required table index block. As
soon as the new index block is in the cache, the index data can be
accessed.

If it happens that a block selected for replacement has been modified,
the block is considered `dirty.' In this case, prior to being replaced,
its contents are flushed to the table index from which it came.

Usually the server follows an _LRU (Least Recently Used)_ strategy:
When choosing a block for replacement, it selects the least recently
used index block. To make this choice easier, the key cache module
maintains all used blocks in a special list (_LRU chain_) ordered by
time of use. When a block is accessed, it is the most recently used and
is placed at the end of the list. When blocks need to be replaced,
blocks at the beginning of the list are the least recently used and
become the first candidates for eviction.

The `InnoDB' storage engine also uses an LRU algorithm, to manage its
buffer pool. See *Note innodb-buffer-pool::.


File: manual.info,  Node: shared-key-cache,  Next: multiple-key-caches,  Prev: myisam-key-cache,  Up: myisam-key-cache

8.6.1.1 Shared Key Cache Access
...............................

Threads can access key cache buffers simultaneously, subject to the
following conditions:

   * A buffer that is not being updated can be accessed by multiple
     sessions.

   * A buffer that is being updated causes sessions that need to use it
     to wait until the update is complete.

   * Multiple sessions can initiate requests that result in cache block
     replacements, as long as they do not interfere with each other
     (that is, as long as they need different index blocks, and thus
     cause different cache blocks to be replaced).

Shared access to the key cache enables the server to improve throughput
significantly.


File: manual.info,  Node: multiple-key-caches,  Next: midpoint-insertion,  Prev: shared-key-cache,  Up: myisam-key-cache

8.6.1.2 Multiple Key Caches
...........................

Shared access to the key cache improves performance but does not
eliminate contention among sessions entirely. They still compete for
control structures that manage access to the key cache buffers. To
reduce key cache access contention further, MySQL also provides
multiple key caches. This feature enables you to assign different table
indexes to different key caches.

Where there are multiple key caches, the server must know which cache
to use when processing queries for a given `MyISAM' table. By default,
all `MyISAM' table indexes are cached in the default key cache. To
assign table indexes to a specific key cache, use the *Note `CACHE
INDEX': cache-index.  statement (see *Note cache-index::). For example,
the following statement assigns indexes from the tables `t1', `t2', and
`t3' to the key cache named `hot_cache':


     mysql> CACHE INDEX t1, t2, t3 IN hot_cache;
     +---------+--------------------+----------+----------+
     | Table   | Op                 | Msg_type | Msg_text |
     +---------+--------------------+----------+----------+
     | test.t1 | assign_to_keycache | status   | OK       |
     | test.t2 | assign_to_keycache | status   | OK       |
     | test.t3 | assign_to_keycache | status   | OK       |
     +---------+--------------------+----------+----------+

The key cache referred to in a *Note `CACHE INDEX': cache-index.
statement can be created by setting its size with a *Note `SET GLOBAL':
set-statement. parameter setting statement or by using server startup
options. For example:


     mysql> SET GLOBAL keycache1.key_buffer_size=128*1024;

To destroy a key cache, set its size to zero:


     mysql> SET GLOBAL keycache1.key_buffer_size=0;

Note that you cannot destroy the default key cache. Any attempt to do
this will be ignored:


     mysql> SET GLOBAL key_buffer_size = 0;

     mysql> SHOW VARIABLES LIKE 'key_buffer_size';
     +-----------------+---------+
     | Variable_name   | Value   |
     +-----------------+---------+
     | key_buffer_size | 8384512 |
     +-----------------+---------+

Key cache variables are structured system variables that have a name
and components. For `keycache1.key_buffer_size', `keycache1' is the
cache variable name and `key_buffer_size' is the cache component. See
*Note structured-system-variables::, for a description of the syntax
used for referring to structured key cache system variables.

By default, table indexes are assigned to the main (default) key cache
created at the server startup. When a key cache is destroyed, all
indexes assigned to it are reassigned to the default key cache.

For a busy server, you can use a strategy that involves three key
caches:

   * A `hot' key cache that takes up 20% of the space allocated for all
     key caches. Use this for tables that are heavily used for searches
     but that are not updated.

   * A `cold' key cache that takes up 20% of the space allocated for
     all key caches. Use this cache for medium-sized, intensively
     modified tables, such as temporary tables.

   * A `warm' key cache that takes up 60% of the key cache space.
     Employ this as the default key cache, to be used by default for
     all other tables.

One reason the use of three key caches is beneficial is that access to
one key cache structure does not block access to the others. Statements
that access tables assigned to one cache do not compete with statements
that access tables assigned to another cache. Performance gains occur
for other reasons as well:

   * The hot cache is used only for retrieval queries, so its contents
     are never modified. Consequently, whenever an index block needs to
     be pulled in from disk, the contents of the cache block chosen for
     replacement need not be flushed first.

   * For an index assigned to the hot cache, if there are no queries
     requiring an index scan, there is a high probability that the
     index blocks corresponding to nonleaf nodes of the index B-tree
     remain in the cache.

   * An update operation most frequently executed for temporary tables
     is performed much faster when the updated node is in the cache and
     need not be read in from disk first. If the size of the indexes of
     the temporary tables are comparable with the size of cold key
     cache, the probability is very high that the updated node is in the
     cache.

The *Note `CACHE INDEX': cache-index. statement sets up an association
between a table and a key cache, but the association is lost each time
the server restarts. If you want the association to take effect each
time the server starts, one way to accomplish this is to use an option
file: Include variable settings that configure your key caches, and an
`init-file' option that names a file containing *Note `CACHE INDEX':
cache-index.  statements to be executed. For example:


     key_buffer_size = 4G
     hot_cache.key_buffer_size = 2G
     cold_cache.key_buffer_size = 2G
     init_file=/PATH/TO/DATA-DIRECTORY/mysqld_init.sql

The statements in `mysqld_init.sql' are executed each time the server
starts. The file should contain one SQL statement per line. The
following example assigns several tables each to `hot_cache' and
`cold_cache':


     CACHE INDEX db1.t1, db1.t2, db2.t3 IN hot_cache
     CACHE INDEX db1.t4, db2.t5, db2.t6 IN cold_cache


File: manual.info,  Node: midpoint-insertion,  Next: index-preloading,  Prev: multiple-key-caches,  Up: myisam-key-cache

8.6.1.3 Midpoint Insertion Strategy
...................................

By default, the key cache management system uses a simple LRU strategy
for choosing key cache blocks to be evicted, but it also supports a
more sophisticated method called the _midpoint insertion strategy._

When using the midpoint insertion strategy, the LRU chain is divided
into two parts: a hot sublist and a warm sublist. The division point
between two parts is not fixed, but the key cache management system
takes care that the warm part is not `too short,' always containing at
least `key_cache_division_limit' percent of the key cache blocks.
`key_cache_division_limit' is a component of structured key cache
variables, so its value is a parameter that can be set per cache.

When an index block is read from a table into the key cache, it is
placed at the end of the warm sublist. After a certain number of hits
(accesses of the block), it is promoted to the hot sublist. At present,
the number of hits required to promote a block (3) is the same for all
index blocks.

A block promoted into the hot sublist is placed at the end of the list.
The block then circulates within this sublist. If the block stays at
the beginning of the sublist for a long enough time, it is demoted to
the warm sublist. This time is determined by the value of the
`key_cache_age_threshold' component of the key cache.

The threshold value prescribes that, for a key cache containing N
blocks, the block at the beginning of the hot sublist not accessed
within the last `N * key_cache_age_threshold / 100' hits is to be moved
to the beginning of the warm sublist. It then becomes the first
candidate for eviction, because blocks for replacement always are taken
from the beginning of the warm sublist.

The midpoint insertion strategy enables you to keep more-valued blocks
always in the cache. If you prefer to use the plain LRU strategy, leave
the `key_cache_division_limit' value set to its default of 100.

The midpoint insertion strategy helps to improve performance when
execution of a query that requires an index scan effectively pushes out
of the cache all the index blocks corresponding to valuable high-level
B-tree nodes. To avoid this, you must use a midpoint insertion strategy
with the `key_cache_division_limit' set to much less than 100. Then
valuable frequently hit nodes are preserved in the hot sublist during
an index scan operation as well.


File: manual.info,  Node: index-preloading,  Next: key-cache-block-size,  Prev: midpoint-insertion,  Up: myisam-key-cache

8.6.1.4 Index Preloading
........................

If there are enough blocks in a key cache to hold blocks of an entire
index, or at least the blocks corresponding to its nonleaf nodes, it
makes sense to preload the key cache with index blocks before starting
to use it. Preloading enables you to put the table index blocks into a
key cache buffer in the most efficient way: by reading the index blocks
from disk sequentially.

Without preloading, the blocks are still placed into the key cache as
needed by queries. Although the blocks will stay in the cache, because
there are enough buffers for all of them, they are fetched from disk in
random order, and not sequentially.

To preload an index into a cache, use the *Note `LOAD INDEX INTO
CACHE': load-index. statement. For example, the following statement
preloads nodes (index blocks) of indexes of the tables `t1' and `t2':


     mysql> LOAD INDEX INTO CACHE t1, t2 IGNORE LEAVES;
     +---------+--------------+----------+----------+
     | Table   | Op           | Msg_type | Msg_text |
     +---------+--------------+----------+----------+
     | test.t1 | preload_keys | status   | OK       |
     | test.t2 | preload_keys | status   | OK       |
     +---------+--------------+----------+----------+

The `IGNORE LEAVES' modifier causes only blocks for the nonleaf nodes
of the index to be preloaded.  Thus, the statement shown preloads all
index blocks from `t1', but only blocks for the nonleaf nodes from `t2'.

If an index has been assigned to a key cache using a *Note `CACHE
INDEX': cache-index. statement, preloading places index blocks into
that cache. Otherwise, the index is loaded into the default key cache.


File: manual.info,  Node: key-cache-block-size,  Next: key-cache-restructuring,  Prev: index-preloading,  Up: myisam-key-cache

8.6.1.5 Key Cache Block Size
............................

It is possible to specify the size of the block buffers for an
individual key cache using the `key_cache_block_size' variable. This
permits tuning of the performance of I/O operations for index files.

The best performance for I/O operations is achieved when the size of
read buffers is equal to the size of the native operating system I/O
buffers. But setting the size of key nodes equal to the size of the I/O
buffer does not always ensure the best overall performance. When
reading the big leaf nodes, the server pulls in a lot of unnecessary
data, effectively preventing reading other leaf nodes.

To control the size of blocks in the `.MYI' index file of `MyISAM'
tables, use the `--myisam-block-size' option at server startup.


File: manual.info,  Node: key-cache-restructuring,  Prev: key-cache-block-size,  Up: myisam-key-cache

8.6.1.6 Restructuring a Key Cache
.................................

A key cache can be restructured at any time by updating its parameter
values. For example:


     mysql> SET GLOBAL cold_cache.key_buffer_size=4*1024*1024;

If you assign to either the `key_buffer_size' or `key_cache_block_size'
key cache component a value that differs from the component's current
value, the server destroys the cache's old structure and creates a new
one based on the new values. If the cache contains any dirty blocks,
the server saves them to disk before destroying and re-creating the
cache. Restructuring does not occur if you change other key cache
parameters.

When restructuring a key cache, the server first flushes the contents
of any dirty buffers to disk. After that, the cache contents become
unavailable. However, restructuring does not block queries that need to
use indexes assigned to the cache.  Instead, the server directly
accesses the table indexes using native file system caching. File
system caching is not as efficient as using a key cache, so although
queries execute, a slowdown can be anticipated. After the cache has been
restructured, it becomes available again for caching indexes assigned
to it, and the use of file system caching for the indexes ceases.


File: manual.info,  Node: innodb-buffer-pool,  Next: query-cache,  Prev: myisam-key-cache,  Up: buffering-caching

8.6.2 The InnoDB Buffer Pool
----------------------------

*Note `InnoDB': innodb-storage-engine. maintains a buffer pool for
caching data and indexes in memory. `InnoDB' manages the pool as a
list, using a least recently used (LRU) algorithm incorporating a
midpoint insertion strategy. When room is needed to add a new block to
the pool, `InnoDB' evicts the least recently used block and adds the
new block to the middle of the list. The midpoint insertion strategy in
effect causes the list to be treated as two sublists:

   * At the head, a sublist of `new' (or `young') blocks that have been
     recently used.

   * At the tail, a sublist of `old' blocks that are less recently used.

As a result of the algorithm, the new sublist contains blocks that are
heavily used by queries. The old sublist contains less-used blocks, and
candidates for eviction are taken from this sublist.

The LRU algorithm operates as follows by default:

   * 3/8 of the buffer pool is devoted to the old sublist.

   * The midpoint of the list is the boundary where the tail of the new
     sublist meets the head of the old sublist.

   * When `InnoDB' reads a block into the buffer pool, it initially
     inserts it at the midpoint (the head of the old sublist). A block
     can be read in as a result of two types of read requests: Because
     it is required (for example, to satisfy query execution), or as
     part of read-ahead performed in anticipation that it will be
     required.

   * The first access to a block in the old sublist makes it `young',
     causing it to move to the head of the buffer pool (the head of the
     new sublist). If the block was read in because it was required,
     the first access occurs immediately and the block is made young.
     If the block was read in due to read-ahead, the first access does
     not occur immediately (and might not occur at all before the block
     is evicted).

   * As long as no accesses occur for a block in the pool, it `ages' by
     moving toward the tail of the list.  Blocks in both the new and
     old sublists age as other blocks are made new. Blocks in the old
     sublist also age as blocks are inserted at the midpoint.
     Eventually, a block that remains unused for long enough reaches
     the tail of the old sublist and is evicted.

In the default operation of the buffer pool, a block when read in is
loaded at the midpoint and then moved immediately to the head of the
new sublist as soon as an access occurs. In the case of a table scan
(such as performed for a *Note `mysqldump': mysqldump. operation), each
block read by the scan ends up moving to the head of the new sublist
because multiple rows are accessed from each block. This occurs even for
a one-time scan, where the blocks are not otherwise used by other
queries. Blocks may also be loaded by the read-ahead background thread
and then moved to the head of the new sublist by a single access. These
effects can be disadvantageous because they push blocks that are in
heavy use by other queries out of the new sublist to the old sublist
where they become subject to eviction.

Several `InnoDB' system variables control the size of the buffer pool
and let you tune the LRU algorithm:

   * `innodb_buffer_pool_size'

     Specifies the size of the buffer pool. If your buffer pool is
     small and you have sufficient memory, making the pool larger can
     improve performance by reducing the amount of disk I/O needed as
     queries access `InnoDB' tables.

   * `innodb_old_blocks_pct'

     Specifies the approximate percentage of the buffer pool that
     `InnoDB' uses for the old block sublist.  The range of values is 5
     to 95. The default value is 37 (that is, 3/8 of the pool).

   * `innodb_old_blocks_time'

     Specifies how long in milliseconds (ms) a block inserted into the
     old sublist must stay there after its first access before it can
     be moved to the new sublist. The default value is 0: A block
     inserted into the old sublist moves to the new sublist when Innodb
     has evicted 1/4 of the inserted block's pages from the buffer
     pool, no matter how soon after insertion the access occurs. If the
     value is greater than 0, blocks remain in the old sublist until an
     access occurs at least that many ms after the first access. For
     example, a value of 1000 causes blocks to stay in the old sublist
     for 1 second after the first access before they become eligible to
     move to the new sublist.

`innodb_old_blocks_pct' and `innodb_old_blocks_time' are available as
of MySQL 5.1.41, but only for `InnoDB Plugin', not the built-in version
of `InnoDB'.

By setting `innodb_old_blocks_time' greater than 0, you can prevent
one-time table scans from flooding the new sublist with blocks used
only for the scan. Rows in a block read in for a scan are accessed
rapidly many times in succession, but the block is unused after that. If
`innodb_old_blocks_time' is set to a value greater than the block scan
time, the block is not moved to the new sublist during the table scan.
Instead, it remains in the old sublist and ages to the tail of the list
to be evicted quickly. This way, blocks used only for a one-time scan
do not act to the detriment of heavily used blocks in the new sublist.

`innodb_old_blocks_time' can be set at runtime, so you can change it
temporarily while performing operations such as table scans and dumps
to prevent them from flooding the new sublist:


     SET GLOBAL innodb_old_blocks_time = 1000;
     ... PERFORM QUERIES THAT SCAN TABLES ...
     SET GLOBAL innodb_old_blocks_time = 0;

This strategy does not apply if your intent is to fill the buffer pool
with a table's content. For example, you might perform a table or index
scan at server startup or during benchmarking or testing specifically
to `warm up' the buffer pool. In this case, leaving
`innodb_old_blocks_time' set to 0 accomplishes the goal of loading the
scanned blocks into the new sublist.

The output from the InnoDB Standard Monitor contains several fields in
the `BUFFER POOL AND MEMORY' section that pertain to operation of the
buffer pool LRU algorithm:

   * `Old database pages': The number of pages in the old sublist of
     the buffer pool.

   * `Pages made young, not young': The number of old pages that were
     moved to the head of the buffer pool (the new sublist), and the
     number of pages that have remained in the old sublist without
     being made new.

   * `youngs/s non-youngs/s': The number of accesses to old pages that
     have resulted in making them young or not. This metric differs
     from that of the previous item in two ways. First, it relates only
     to old pages.  Second, it is based on number of accesses to pages
     and not the number of pages. (There can be multiple accesses to a
     given page, all of which are counted.)

   * `young-making rate': Hits that cause blocks to move to the head of
     the buffer pool.

   * `not': Hits that do not cause blocks to move to the head of the
     buffer pool (due to the delay not being met).

The `young-making' rate and `not' rate will not normally add up to the
overall buffer pool hit rate. Hits for blocks in the old sublist cause
them to move to the new sublist, but hits to blocks in the new sublist
cause them to move to the head of the list only if they are a certain
distance from the head.

The preceding information from the Monitor can help you make LRU tuning
decisions:

   * If you see very low `youngs/s' values when you do not have large
     scans going on, that indicates that you might need to either
     reduce the delay time, or increase the percentage of the buffer
     pool used for the old sublist.  Increasing the percentage makes
     the old sublist larger, so blocks in that sublist take longer to
     move to the tail and be evicted. This increases the likelihood
     that they will be accessed again and be made young.

   * If you do not see a lot of `non-youngs/s' when you are doing large
     table scans (and lots of `youngs/s'), you will want to tune your
     delay value to be larger.

For more information about InnoDB Monitors, see *Note innodb-monitors::.

The `MyISAM' storage engine also uses an LRU algorithm, to manage its
key cache. See *Note myisam-key-cache::.


File: manual.info,  Node: query-cache,  Prev: innodb-buffer-pool,  Up: buffering-caching

8.6.3 The MySQL Query Cache
---------------------------

* Menu:

* query-cache-operation::        How the Query Cache Operates
* query-cache-in-select::        Query Cache SELECT Options
* query-cache-configuration::    Query Cache Configuration
* query-cache-status-and-maintenance::  Query Cache Status and Maintenance

The query cache stores the text of a *Note `SELECT': select. statement
together with the corresponding result that was sent to the client. If
an identical statement is received later, the server retrieves the
results from the query cache rather than parsing and executing the
statement again. The query cache is shared among sessions, so a result
set generated by one client can be sent in response to the same query
issued by another client.

The query cache can be useful in an environment where you have tables
that do not change very often and for which the server receives many
identical queries. This is a typical situation for many Web servers
that generate many dynamic pages based on database content.

The query cache does not return stale data. When tables are modified,
any relevant entries in the query cache are flushed.

*Note*:

The query cache does not work in an environment where you have multiple
*Note `mysqld': mysqld. servers updating the same `MyISAM' tables.

*Note*:

As of MySQL 5.1.17, the query cache is used for prepared statements
under the conditions described in *Note query-cache-operation::. Before
5.1.17, the query cache is not used for prepared statements.

*Note*:

As of MySQL 5.1.63, the query cache is not supported for partitioned
tables, and is automatically disabled for queries involving partitioned
tables. The query cache cannot be enabled for such queries. (Bug #53775)

Some performance data for the query cache follows. These results were
generated by running the MySQL benchmark suite on a Linux Alpha
2x500MHz system with 2GB RAM and a 64MB query cache.

   * If all the queries you are performing are simple (such as
     selecting a row from a table with one row), but still differ so
     that the queries cannot be cached, the overhead for having the
     query cache active is 13%. This could be regarded as the worst
     case scenario. In real life, queries tend to be much more
     complicated, so the overhead normally is significantly lower.

   * Searches for a single row in a single-row table are 238% faster
     with the query cache than without it. This can be regarded as
     close to the minimum speedup to be expected for a query that is
     cached.

To disable the query cache at server startup, set the
`query_cache_size' system variable to 0. By disabling the query cache
code, there is no noticeable overhead. If you build MySQL from source,
query cache capabilities can be excluded from the server entirely by
invoking `configure' with the `--without-query-cache' option.

The query cache offers the potential for substantial performance
improvement, but you should not assume that it will do so under all
circumstances. With some query cache configurations or server
workloads, you might actually see a performance decrease:

   * Be cautious about sizing the query cache excessively large, which
     increases the overhead required to maintain the cache, possibly
     beyond the benefit of enabling it. Sizes in tens of megabytes are
     usually beneficial. Sizes in the hundreds of megabytes might not
     be.

   * Server workload has a significant effect on query cache
     efficiency. A query mix consisting almost entirely of a fixed set
     of *Note `SELECT': select.  statements is much more likely to
     benefit from enabling the cache than a mix in which frequent *Note
     `INSERT': insert. statements cause continual invalidation of
     results in the cache. In some cases, a workaround is to use the
     `SQL_NO_CACHE' option to prevent results from even entering the
     cache for *Note `SELECT': select. statements that use frequently
     modified tables. (See *Note query-cache-in-select::.)

To verify that enabling the query cache is beneficial, test the
operation of your MySQL server with the cache enabled and disabled.
Then retest periodically because query cache efficiency may change as
server workload changes.


File: manual.info,  Node: query-cache-operation,  Next: query-cache-in-select,  Prev: query-cache,  Up: query-cache

8.6.3.1 How the Query Cache Operates
....................................

This section describes how the query cache works when it is
operational. *Note query-cache-configuration::, describes how to
control whether it is operational.

Incoming queries are compared to those in the query cache before
parsing, so the following two queries are regarded as different by the
query cache:


     SELECT * FROM TBL_NAME
     Select * from TBL_NAME

Queries must be _exactly_ the same (byte for byte) to be seen as
identical. In addition, query strings that are identical may be treated
as different for other reasons. Queries that use different databases,
different protocol versions, or different default character sets are
considered different queries and are cached separately.

The cache is not used for queries of the following types:

   * Queries that are a subquery of an outer query

   * Queries executed within the body of a stored function, trigger, or
     event

Before a query result is fetched from the query cache, MySQL checks
whether the user has *Note `SELECT': select. privilege for all
databases and tables involved. If this is not the case, the cached
result is not used.

If a query result is returned from query cache, the server increments
the `Qcache_hits' status variable, not `Com_select'. See *Note
query-cache-status-and-maintenance::.

If a table changes, all cached queries that use the table become
invalid and are removed from the cache. This includes queries that use
`MERGE' tables that map to the changed table. A table can be changed by
many types of statements, such as *Note `INSERT': insert, *Note
`UPDATE': update, *Note `DELETE': delete, *Note `TRUNCATE TABLE':
truncate-table, *Note `ALTER TABLE': alter-table, *Note `DROP TABLE':
drop-table, or *Note `DROP DATABASE': drop-database.

The query cache also works within transactions when using `InnoDB'
tables.

In MySQL 5.1, the result from a *Note `SELECT': select. query on a view
is cached.

The query cache works for `SELECT SQL_CALC_FOUND_ROWS ...' queries and
stores a value that is returned by a following `SELECT FOUND_ROWS()'
query.  `FOUND_ROWS()' returns the correct value even if the preceding
query was fetched from the cache because the number of found rows is
also stored in the cache. The `SELECT FOUND_ROWS()' query itself cannot
be cached.

Before MySQL 5.1.17, prepared statements do not use the query cache.
Beginning with 5.1.17, prepared statements use the query cache under
certain conditions, which differ depending on the preparation method:

   * Statements that are issued using the binary protocol using *Note
     `mysql_stmt_prepare()': mysql-stmt-prepare. and *Note
     `mysql_stmt_execute()': mysql-stmt-execute. See *Note
     c-api-prepared-statements::.

     For a prepared statement executed using the binary protocol,
     comparison with statements in the query cache is based on the text
     of the statement after expansion of `?' parameter markers. The
     statement is compared only with other cached statements that were
     executed using the binary protocol. That is, for query cache
     purposes, statements issued using the binary protocol are distinct
     from statements issued using the text protocol.

   * Statements that are issued using the text (nonbinary) protocol
     using *Note `PREPARE': prepare. and *Note `EXECUTE': execute. See
     *Note sql-syntax-prepared-statements::. These are denoted SQL PS
     statements here.

     Before MySQL 5.1.21, for a prepared statement executed using *Note
     `PREPARE': prepare. and *Note `EXECUTE': execute, it is not cached
     if it contains any `?' parameter markers.  In that case, the
     statement after parameter expansion contains references to user
     variables, which prevents caching, even for nonprepared
     statements. If the statement contains no parameter markers, the
     statement is compared with statements in the query cache that were
     executed using the text protocol (that is, it is compared with
     other SQL PS statements and nonprepared statements). As of MySQL
     5.1.21, this limitation is lifted and prepared statements that
     contain parameter markers can be cached because expansion directly
     substitutes the user variable values.

A query cannot be cached if it contains any of the functions shown in
the following table.

This table lists functions that if used within a query, do not allow
the query to be cached.

`BENCHMARK()'            `CONNECTION_ID()'        `CONVERT_TZ()'
`CURDATE()'              `CURRENT_DATE()'         `CURRENT_TIME()'
`CURRENT_TIMESTAMP()'    `CURTIME()'              `DATABASE()'
`ENCRYPT()' with one     `FOUND_ROWS()'           `GET_LOCK()'
parameter                                         
`LAST_INSERT_ID()'       `LOAD_FILE()'            `MASTER_POS_WAIT()'
`NOW()'                  `RAND()'                 `RELEASE_LOCK()'
`SLEEP()'                `SYSDATE()'              `UNIX_TIMESTAMP()' with
                                                  no parameters
`USER()'                 `UUID()'                 `UUID_SHORT()'

A query also is not cached under these conditions:

   * It refers to user-defined functions (UDFs) or stored functions.

   * It refers to user variables or local stored program variables.

   * It refers to tables in the `mysql' or `INFORMATION_SCHEMA' system
     database.

   * (_MySQL 5.1.63 and later_:) It refers to any partitioned tables.

   * It is of any of the following forms:


          SELECT ... LOCK IN SHARE MODE
          SELECT ... FOR UPDATE
          SELECT ... INTO OUTFILE ...
          SELECT ... INTO DUMPFILE ...
          SELECT * FROM ... WHERE autoincrement_col IS NULL

     The last form is not cached because it is used as the ODBC
     workaround for obtaining the last insert ID value. See the
     Connector/ODBC section of *Note connectors-apis::.

     Statements within transactions that use `SERIALIZABLE' isolation
     level also cannot be cached because they use `LOCK IN SHARE MODE'
     locking.

   * It uses `TEMPORARY' tables.

   * It does not use any tables.

   * It generates warnings.

   * The user has a column-level privilege for any of the involved
     tables.


File: manual.info,  Node: query-cache-in-select,  Next: query-cache-configuration,  Prev: query-cache-operation,  Up: query-cache

8.6.3.2 Query Cache SELECT Options
..................................

Two query cache-related options may be specified in *Note `SELECT':
select. statements:

   * `SQL_CACHE'

     The query result is cached if it is cacheable and the value of the
     `query_cache_type' system variable is `ON' or `DEMAND'.

   * `SQL_NO_CACHE'

     The server does not use the query cache. It neither checks the
     query cache to see whether the result is already cached, nor does
     it cache the query result. (Due to a limitation in the parser, a
     space character must precede and follow the `SQL_NO_CACHE'
     keyword; a nonspace such as a newline causes the server to check
     the query cache to see whether the result is already cached.)

Examples:


     SELECT SQL_CACHE id, name FROM customer;
     SELECT SQL_NO_CACHE id, name FROM customer;


File: manual.info,  Node: query-cache-configuration,  Next: query-cache-status-and-maintenance,  Prev: query-cache-in-select,  Up: query-cache

8.6.3.3 Query Cache Configuration
.................................

The `have_query_cache' server system variable indicates whether the
query cache is available:


     mysql> SHOW VARIABLES LIKE 'have_query_cache';
     +------------------+-------+
     | Variable_name    | Value |
     +------------------+-------+
     | have_query_cache | YES   |
     +------------------+-------+

When using a standard MySQL binary, this value is always `YES', even if
query caching is disabled.

Several other system variables control query cache operation.  These
can be set in an option file or on the command line when starting *Note
`mysqld': mysqld. The query cache system variables all have names that
begin with `query_cache_'. They are described briefly in *Note
server-system-variables::, with additional configuration information
given here.

To set the size of the query cache, set the `query_cache_size' system
variable. Setting it to 0 disables the query cache. The default size is
0, so the query cache is disabled by default.

Be careful not to set the size of the cache too large. Due to the need
for threads to lock the cache during updates, you may see lock
contention issues with a very large cache.

*Note*:

When using the Windows Configuration Wizard to install or configure
MySQL, the default value for `query_cache_size' will be configured
automatically for you based on the different configuration types
available. When using the Windows Configuration Wizard, the query cache
may be enabled (that is, set to a nonzero value) due to the selected
configuration. The query cache is also controlled by the setting of the
`query_cache_type' variable.  You should check the values of these
variables as set in your `my.ini' file after configuration has taken
place.

When you set `query_cache_size' to a nonzero value, keep in mind that
the query cache needs a minimum size of about 40KB to allocate its
structures. (The exact size depends on system architecture.) If you set
the value too small, you'll get a warning, as in this example:


     mysql> SET GLOBAL query_cache_size = 40000;
     Query OK, 0 rows affected, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS\G
     *************************** 1. row ***************************
       Level: Warning
        Code: 1282
     Message: Query cache failed to set size 39936;
              new query cache size is 0

     mysql> SET GLOBAL query_cache_size = 41984;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SHOW VARIABLES LIKE 'query_cache_size';
     +------------------+-------+
     | Variable_name    | Value |
     +------------------+-------+
     | query_cache_size | 41984 |
     +------------------+-------+

For the query cache to actually be able to hold any query results, its
size must be set larger:


     mysql> SET GLOBAL query_cache_size = 1000000;
     Query OK, 0 rows affected (0.04 sec)

     mysql> SHOW VARIABLES LIKE 'query_cache_size';
     +------------------+--------+
     | Variable_name    | Value  |
     +------------------+--------+
     | query_cache_size | 999424 |
     +------------------+--------+
     1 row in set (0.00 sec)

The `query_cache_size' value is aligned to the nearest 1024 byte block.
The value reported may therefore be different from the value that you
assign.

If the query cache size is greater than 0, the `query_cache_type'
variable influences how it works. This variable can be set to the
following values:

   * A value of `0' or `OFF' prevents caching or retrieval of cached
     results.

   * A value of `1' or `ON' enables caching except of those statements
     that begin with `SELECT SQL_NO_CACHE'.

   * A value of `2' or `DEMAND' causes caching of only those statements
     that begin with `SELECT SQL_CACHE'.

Setting the `GLOBAL' `query_cache_type' value determines query cache
behavior for all clients that connect after the change is made.
Individual clients can control cache behavior for their own connection
by setting the `SESSION' `query_cache_type' value. For example, a
client can disable use of the query cache for its own queries like this:


     mysql> SET SESSION query_cache_type = OFF;

If you set `query_cache_type' at server startup (rather than at runtime
with a *Note `SET': set-statement.  statement), only the numeric values
are permitted.

To control the maximum size of individual query results that can be
cached, set the `query_cache_limit' system variable. The default value
is 1MB.

*Note*:

You can set the maximum size that can be specified for the query cache
at runtime with the *Note `SET': set-statement.  statement by using the
`--maximum-query_cache_size=32M' option on the command line or in the
configuration file.

When a query is to be cached, its result (the data sent to the client)
is stored in the query cache during result retrieval.  Therefore the
data usually is not handled in one big chunk.  The query cache
allocates blocks for storing this data on demand, so when one block is
filled, a new block is allocated.  Because memory allocation operation
is costly (timewise), the query cache allocates blocks with a minimum
size given by the `query_cache_min_res_unit' system variable. When a
query is executed, the last result block is trimmed to the actual data
size so that unused memory is freed. Depending on the types of queries
your server executes, you might find it helpful to tune the value of
`query_cache_min_res_unit':

   * The default value of `query_cache_min_res_unit' is 4KB. This
     should be adequate for most cases.

   * If you have a lot of queries with small results, the default block
     size may lead to memory fragmentation, as indicated by a large
     number of free blocks. Fragmentation can force the query cache to
     prune (delete) queries from the cache due to lack of memory. In
     this case, you should decrease the value of
     `query_cache_min_res_unit'.  The number of free blocks and queries
     removed due to pruning are given by the values of the
     `Qcache_free_blocks' and `Qcache_lowmem_prunes' status variables.

   * If most of your queries have large results (check the
     `Qcache_total_blocks' and `Qcache_queries_in_cache' status
     variables), you can increase performance by increasing
     `query_cache_min_res_unit'.  However, be careful to not make it
     too large (see the previous item).


File: manual.info,  Node: query-cache-status-and-maintenance,  Prev: query-cache-configuration,  Up: query-cache

8.6.3.4 Query Cache Status and Maintenance
..........................................

To check whether the query cache is present in your MySQL server, use
the following statement:


     mysql> SHOW VARIABLES LIKE 'have_query_cache';
     +------------------+-------+
     | Variable_name    | Value |
     +------------------+-------+
     | have_query_cache | YES   |
     +------------------+-------+

You can defragment the query cache to better utilize its memory with
the *Note `FLUSH QUERY CACHE': flush. statement. The statement does not
remove any queries from the cache.

The `RESET QUERY CACHE' statement removes all query results from the
query cache. The *Note `FLUSH TABLES': flush.  statement also does this.

To monitor query cache performance, use *Note `SHOW STATUS':
show-status. to view the cache status variables:


     mysql> SHOW STATUS LIKE 'Qcache%';
     +-------------------------+--------+
     | Variable_name           | Value  |
     +-------------------------+--------+
     | Qcache_free_blocks      | 36     |
     | Qcache_free_memory      | 138488 |
     | Qcache_hits             | 79570  |
     | Qcache_inserts          | 27087  |
     | Qcache_lowmem_prunes    | 3114   |
     | Qcache_not_cached       | 22989  |
     | Qcache_queries_in_cache | 415    |
     | Qcache_total_blocks     | 912    |
     +-------------------------+--------+

Descriptions of each of these variables are given in *Note
server-status-variables::. Some uses for them are described here.

The total number of *Note `SELECT': select.  queries is given by this
formula:


       Com_select
     + Qcache_hits
     + queries with errors found by parser

The `Com_select' value is given by this formula:


       Qcache_inserts
     + Qcache_not_cached
     + queries with errors found during the column-privileges check

The query cache uses variable-length blocks, so `Qcache_total_blocks'
and `Qcache_free_blocks' may indicate query cache memory fragmentation.
After *Note `FLUSH QUERY CACHE': flush, only a single free block
remains.

Every cached query requires a minimum of two blocks (one for the query
text and one or more for the query results). Also, every table that is
used by a query requires one block.  However, if two or more queries
use the same table, only one table block needs to be allocated.

The information provided by the `Qcache_lowmem_prunes' status variable
can help you tune the query cache size. It counts the number of queries
that have been removed from the cache to free up memory for caching new
queries. The query cache uses a least recently used (LRU) strategy to
decide which queries to remove from the cache. Tuning information is
given in *Note query-cache-configuration::.


File: manual.info,  Node: locking-issues,  Next: optimizing-database-structure,  Prev: buffering-caching,  Up: optimization

8.7 Locking Issues
==================

* Menu:

* internal-locking::             Internal Locking Methods
* table-locking::                Table Locking Issues
* concurrent-inserts::           Concurrent Inserts
* external-locking::             External Locking

MySQL manages contention for table contents using locking:

   * Internal locking is performed within the MySQL server itself to
     manage contention for table contents by multiple threads.  This
     type of locking is internal because it is performed entirely by
     the server and involves no other programs. See *Note
     internal-locking::.

   * External locking occurs when the server and other programs lock
     *Note `MyISAM': myisam-storage-engine. table files to coordinate
     among themselves which program can access the tables at which
     time. See *Note external-locking::.


File: manual.info,  Node: internal-locking,  Next: table-locking,  Prev: locking-issues,  Up: locking-issues

8.7.1 Internal Locking Methods
------------------------------

This section discusses internal locking; that is, locking performed
within the MySQL server itself to manage contention for table contents
by multiple sessions. This type of locking is internal because it is
performed entirely by the server and involves no other programs.
External locking occurs when the server and other programs lock *Note
`MyISAM': myisam-storage-engine. table files to coordinate among
themselves which program can access the tables at which time. See *Note
external-locking::.

MySQL uses row-level locking
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_row_lock)
for `InnoDB' tables to support simultaneous write access by multiple
sessions, making them suitable for multi-user, highly concurrent, and
OLTP applications. MySQL uses table-level locking
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_table_lock)
for `MyISAM', `MEMORY', and `MERGE' tables, allowing only one session to
update those tables at a time, making them more suitable for read-only,
read-mostly, or single-user applications.

*Considerations for Table Locking*

Table locking in MySQL is deadlock-free for storage engines that use
table-level locking. Deadlock avoidance is managed by always requesting
all needed locks at once at the beginning of a query and always locking
the tables in the same order.

MySQL grants table write locks as follows:

  1. If there are no locks on the table, put a write lock on it.

  2. Otherwise, put the lock request in the write lock queue.

MySQL grants table read locks as follows:

  1. If there are no write locks on the table, put a read lock on it.

  2. Otherwise, put the lock request in the read lock queue.

Table updates are given higher priority than table retrievals.
Therefore, when a lock is released, the lock is made available to the
requests in the write lock queue and then to the requests in the read
lock queue. This ensures that updates to a table are not `starved' even
if there is heavy *Note `SELECT': select. activity for the table.
However, if you have many updates for a table, *Note `SELECT': select.
statements wait until there are no more updates.

For information on altering the priority of reads and writes, see *Note
table-locking::.

You can analyze the table lock contention on your system by checking the
`Table_locks_immediate' and `Table_locks_waited' status variables,
which indicate the number of times that requests for table locks could
be granted immediately and the number that had to wait, respectively:


     mysql> SHOW STATUS LIKE 'Table%';
     +-----------------------+---------+
     | Variable_name         | Value   |
     +-----------------------+---------+
     | Table_locks_immediate | 1151552 |
     | Table_locks_waited    | 15324   |
     +-----------------------+---------+

The `MyISAM' storage engine supports concurrent inserts to reduce
contention between readers and writers for a given table: If a `MyISAM'
table has no free blocks in the middle of the data file, rows are
always inserted at the end of the data file. In this case, you can
freely mix concurrent *Note `INSERT': insert. and *Note `SELECT':
select. statements for a `MyISAM' table without locks. That is, you can
insert rows into a `MyISAM' table at the same time other clients are
reading from it. Holes can result from rows having been deleted from or
updated in the middle of the table. If there are holes, concurrent
inserts are disabled but are enabled again automatically when all holes
have been filled with new data. This behavior is altered by the
`concurrent_insert' system variable. See *Note concurrent-inserts::.

If you acquire a table lock explicitly with *Note `LOCK TABLES':
lock-tables, you can request a `READ LOCAL' lock rather than a `READ'
lock to enable other sessions to perform concurrent inserts while you
have the table locked.

To perform many *Note `INSERT': insert. and *Note `SELECT': select.
operations on a table `real_table' when concurrent inserts are not
possible, you can insert rows into a temporary table `temp_table' and
update the real table with the rows from the temporary table
periodically. This can be done with the following code:


     mysql> LOCK TABLES real_table WRITE, temp_table WRITE;
     mysql> INSERT INTO real_table SELECT * FROM temp_table;
     mysql> DELETE FROM temp_table;
     mysql> UNLOCK TABLES;

`InnoDB' uses row locks. Deadlocks are possible for `InnoDB' because it
automatically acquires locks during the processing of SQL statements,
not at the start of the transaction.

*Considerations for Row Locking*

Advantages of row-level locking:

   * Fewer lock conflicts when different sessions access different rows

   * Fewer changes for rollbacks

   * Possible to lock a single row for a long time

Disadvantages of row-level locking:

   * Requires more memory than table-level locks

   * Slower than table-level locks when used on a large part of the
     table because you must acquire many more locks

   * Slower than other locks if you often do `GROUP BY' operations on a
     large part of the data or if you must scan the entire table
     frequently

*Choosing the Type of Locking*

Generally, table locks are superior to row-level locks in the following
cases:

   * Most statements for the table are reads

   * Statements for the table are a mix of reads and writes, where
     writes are updates or deletes for a single row that can be fetched
     with one key read:


          UPDATE TBL_NAME SET COLUMN=VALUE WHERE UNIQUE_KEY_COL=KEY_VALUE;
          DELETE FROM TBL_NAME WHERE UNIQUE_KEY_COL=KEY_VALUE;

   * *Note `SELECT': select. combined with concurrent *Note `INSERT':
     insert. statements, and very few *Note `UPDATE': update. or *Note
     `DELETE': delete. statements

   * Many scans or `GROUP BY' operations on the entire table without
     any writers

With higher-level locks, you can more easily tune applications by
supporting locks of different types, because the lock overhead is less
than for row-level locks.

Options other than row-level locking:

   * Versioning (such as that used in MySQL for concurrent inserts)
     where it is possible to have one writer at the same time as many
     readers. This means that the database or table supports different
     views for the data depending on when access begins. Other common
     terms for this are `time travel,' `copy on write,' or `copy on
     demand.'

   * Copy on demand is in many cases superior to row-level locking.
     However, in the worst case, it can use much more memory than using
     normal locks.

   * Instead of using row-level locks, you can employ application-level
     locks, such as those provided by `GET_LOCK()' and `RELEASE_LOCK()'
     in MySQL.  These are advisory locks, so they work only with
     applications that cooperate with each other. See *Note
     miscellaneous-functions::.


File: manual.info,  Node: table-locking,  Next: concurrent-inserts,  Prev: internal-locking,  Up: locking-issues

8.7.2 Table Locking Issues
--------------------------

To achieve a very high lock speed, MySQL uses table locking (instead of
page, row, or column locking) for all storage engines except `InnoDB'
and *Note `NDBCLUSTER': mysql-cluster.

For `InnoDB' tables, MySQL uses table locking only if you explicitly
lock the table with *Note `LOCK TABLES': lock-tables. For this storage
engine, avoid using *Note `LOCK TABLES': lock-tables.  at all, because
`InnoDB' uses automatic row-level locking to ensure transaction
isolation.

For large tables, table locking is often better than row locking, but
there are some disadvantages:

   * Table locking enables many sessions to read from a table at the
     same time, but if a session wants to write to a table, it must
     first get exclusive access. During the update, all other sessions
     that want to access this particular table must wait until the
     update is done.

   * Table locking causes problems in cases such as when a session is
     waiting because the disk is full and free space needs to become
     available before the session can proceed. In this case, all
     sessions that want to access the problem table are also put in a
     waiting state until more disk space is made available.

Table locking is also disadvantageous under the following scenario:

   * A session issues a *Note `SELECT': select.  that takes a long time
     to run.

   * Another session then issues an *Note `UPDATE': update. on the same
     table.  This session waits until the *Note `SELECT': select. is
     finished.

   * Another session issues another *Note `SELECT': select. statement
     on the same table. Because *Note `UPDATE': update. has higher
     priority than *Note `SELECT': select, this *Note `SELECT': select.
     waits for the *Note `UPDATE': update. to finish, _after_ waiting
     for the first *Note `SELECT': select. to finish.

The following items describe some ways to avoid or reduce contention
caused by table locking:

   * Try to get the *Note `SELECT': select.  statements to run faster
     so that they lock tables for a shorter time. You might have to
     create some summary tables to do this.

   * Start *Note `mysqld': mysqld. with `--low-priority-updates'. For
     storage engines that use only table-level locking (such as
     `MyISAM', `MEMORY', and `MERGE'), this gives all statements that
     update (modify) a table lower priority than *Note `SELECT':
     select. statements. In this case, the second *Note `SELECT':
     select.  statement in the preceding scenario would execute before
     the *Note `UPDATE': update. statement, and would not need to wait
     for the first *Note `SELECT': select. to finish.

   * To specify that all updates issued in a specific connection should
     be done with low priority, set the `low_priority_updates' server
     system variable equal to 1.

   * To give a specific *Note `INSERT': insert, *Note `UPDATE': update,
     or *Note `DELETE': delete. statement lower priority, use the
     `LOW_PRIORITY' attribute.

   * To give a specific *Note `SELECT': select.  statement higher
     priority, use the `HIGH_PRIORITY' attribute. See *Note select::.

   * Start *Note `mysqld': mysqld. with a low value for the
     `max_write_lock_count' system variable to force MySQL to
     temporarily elevate the priority of all *Note `SELECT': select.
     statements that are waiting for a table after a specific number of
     inserts to the table occur. This permits `READ' locks after a
     certain number of `WRITE' locks.

   * If you have problems with *Note `INSERT': insert. combined with
     *Note `SELECT': select, consider switching to `MyISAM' tables,
     which support concurrent *Note `SELECT': select. and *Note
     `INSERT': insert. statements. (See *Note concurrent-inserts::.)

   * If you mix inserts and deletes on the same table, *Note `INSERT
     DELAYED': insert-delayed. may be of great help. See *Note
     insert-delayed::.

   * If you have problems with mixed *Note `SELECT': select. and *Note
     `DELETE': delete. statements, the `LIMIT' option to *Note
     `DELETE': delete. may help. See *Note delete::.

   * Using `SQL_BUFFER_RESULT' with *Note `SELECT': select. statements
     can help to make the duration of table locks shorter. See *Note
     select::.

   * You could change the locking code in `mysys/thr_lock.c' to use a
     single queue.  In this case, write locks and read locks would have
     the same priority, which might help some applications.

Here are some tips concerning table locks in MySQL:

   * Concurrent users are not a problem if you do not mix updates with
     selects that need to examine many rows in the same table.

   * You can use *Note `LOCK TABLES': lock-tables. to increase speed,
     because many updates within a single lock is much faster than
     updating without locks. Splitting table contents into separate
     tables may also help.

   * If you encounter speed problems with table locks in MySQL, you may
     be able to improve performance by converting some of your tables
     to `InnoDB'. See *Note innodb-storage-engine::.


File: manual.info,  Node: concurrent-inserts,  Next: external-locking,  Prev: table-locking,  Up: locking-issues

8.7.3 Concurrent Inserts
------------------------

The `MyISAM' storage engine supports concurrent inserts to reduce
contention between readers and writers for a given table: If a `MyISAM'
table has no holes in the data file (deleted rows in the middle), an
*Note `INSERT': insert. statement can be executed to add rows to the
end of the table at the same time that *Note `SELECT': select.
statements are reading rows from the table. If there are multiple *Note
`INSERT': insert. statements, they are queued and performed in
sequence, concurrently with the *Note `SELECT': select. statements. The
results of a concurrent *Note `INSERT': insert. may not be visible
immediately.

The `concurrent_insert' system variable can be set to modify the
concurrent-insert processing.  By default, the variable is set to 1 and
concurrent inserts are handled as just described. If
`concurrent_insert' is set to 0, concurrent inserts are disabled. If
the variable is set to 2, concurrent inserts at the end of the table
are permitted even for tables that have deleted rows. See also the
description of the `concurrent_insert' system variable.

Under circumstances where concurrent inserts can be used, there is
seldom any need to use the `DELAYED' modifier for *Note `INSERT':
insert. statements.  See *Note insert-delayed::.

If you are using the binary log, concurrent inserts are converted to
normal inserts for `CREATE ...  SELECT' or *Note `INSERT ... SELECT':
insert-select. statements. This is done to ensure that you can
re-create an exact copy of your tables by applying the log during a
backup operation. See *Note binary-log::. In addition, for those
statements a read lock is placed on the selected-from table such that
inserts into that table are blocked. The effect is that concurrent
inserts for that table must wait as well.

With *Note `LOAD DATA INFILE': load-data, if you specify `CONCURRENT'
with a `MyISAM' table that satisfies the condition for concurrent
inserts (that is, it contains no free blocks in the middle), other
sessions can retrieve data from the table while *Note `LOAD DATA':
load-data. is executing. Use of the `CONCURRENT' option affects the
performance of *Note `LOAD DATA': load-data. a bit, even if no other
session is using the table at the same time.

If you specify `HIGH_PRIORITY', it overrides the effect of the
`--low-priority-updates' option if the server was started with that
option. It also causes concurrent inserts not to be used.

For *Note `LOCK TABLE': lock-tables, the difference between `READ
LOCAL' and `READ' is that `READ LOCAL' permits nonconflicting *Note
`INSERT': insert. statements (concurrent inserts) to execute while the
lock is held. However, this cannot be used if you are going to
manipulate the database using processes external to the server while
you hold the lock.


File: manual.info,  Node: external-locking,  Prev: concurrent-inserts,  Up: locking-issues

8.7.4 External Locking
----------------------

External locking is the use of file system locking to manage contention
for *Note `MyISAM': myisam-storage-engine. database tables by multiple
processes. External locking is used in situations where a single
process such as the MySQL server cannot be assumed to be the only
process that requires access to tables. Here are some examples:

   * If you run multiple servers that use the same database directory
     (not recommended), each server must have external locking enabled.

   * If you use *Note `myisamchk': myisamchk. to perform table
     maintenance operations on *Note `MyISAM': myisam-storage-engine.
     tables, you must either ensure that the server is not running, or
     that the server has external locking enabled so that it locks
     table files as necessary to coordinate with *Note `myisamchk':
     myisamchk.  for access to the tables. The same is true for use of
     *Note `myisampack': myisampack. to pack *Note `MyISAM':
     myisam-storage-engine. tables.

     If the server is run with external locking enabled, you can use
     *Note `myisamchk': myisamchk. at any time for read operations such
     a checking tables. In this case, if the server tries to update a
     table that *Note `myisamchk': myisamchk. is using, the server will
     wait for *Note `myisamchk': myisamchk. to finish before it
     continues.

     If you use *Note `myisamchk': myisamchk. for write operations such
     as repairing or optimizing tables, or if you use *Note
     `myisampack': myisampack. to pack tables, you _must_ always ensure
     that the *Note `mysqld': mysqld. server is not using the table. If
     you don't stop *Note `mysqld': mysqld, you should at least do a
     *Note `mysqladmin flush-tables': mysqladmin. before you run *Note
     `myisamchk': myisamchk. Your tables _may become corrupted_ if the
     server and *Note `myisamchk': myisamchk. access the tables
     simultaneously.

With external locking in effect, each process that requires access to a
table acquires a file system lock for the table files before proceeding
to access the table. If all necessary locks cannot be acquired, the
process is blocked from accessing the table until the locks can be
obtained (after the process that currently holds the locks releases
them).

External locking affects server performance because the server must
sometimes wait for other processes before it can access tables.

External locking is unnecessary if you run a single server to access a
given data directory (which is the usual case) and if no other programs
such as *Note `myisamchk': myisamchk. need to modify tables while the
server is running. If you only _read_ tables with other programs,
external locking is not required, although *Note `myisamchk': myisamchk.
might report warnings if the server changes tables while *Note
`myisamchk': myisamchk. is reading them.

With external locking disabled, to use *Note `myisamchk': myisamchk,
you must either stop the server while *Note `myisamchk': myisamchk.
executes or else lock and flush the tables before running *Note
`myisamchk': myisamchk.  (See *Note system-optimization::.) To avoid
this requirement, use the *Note `CHECK TABLE': check-table.  and *Note
`REPAIR TABLE': repair-table. statements to check and repair *Note
`MyISAM': myisam-storage-engine. tables.

For *Note `mysqld': mysqld, external locking is controlled by the value
of the `skip_external_locking' system variable. When this variable is
enabled, external locking is disabled, and vice versa. From MySQL 4.0
on, external locking is disabled by default.

Use of external locking can be controlled at server startup by using
the `--external-locking' or `--skip-external-locking' option.

If you do use external locking option to enable updates to *Note
`MyISAM': myisam-storage-engine. tables from many MySQL processes, you
must ensure that the following conditions are satisfied:

   * You should not use the query cache for queries that use tables
     that are updated by another process.

   * You should not start the server with the `--delay-key-write=ALL'
     option or use the `DELAY_KEY_WRITE=1' table option for any shared
     tables. Otherwise, index corruption can occur.

The easiest way to satisfy these conditions is to always use
`--external-locking' together with `--delay-key-write=OFF' and
`--query-cache-size=0'. (This is not done by default because in many
setups it is useful to have a mixture of the preceding options.)


File: manual.info,  Node: optimizing-database-structure,  Next: optimizing-the-server,  Prev: locking-issues,  Up: optimization

8.8 Optimizing Database Structure
=================================

* Menu:

* data-size::                    Make Your Data as Small as Possible
* procedure-analyse::            Using PROCEDURE ANALYSE
* table-cache::                  How MySQL Opens and Closes Tables
* creating-many-tables::         Disadvantages of Creating Many Tables in the Same Database
* internal-temporary-tables::    How MySQL Uses Internal Temporary Tables


File: manual.info,  Node: data-size,  Next: procedure-analyse,  Prev: optimizing-database-structure,  Up: optimizing-database-structure

8.8.1 Make Your Data as Small as Possible
-----------------------------------------

Design your tables to minimize their space on the disk. This can result
in huge improvements by reducing the amount of data written to and read
from disk. Smaller tables normally require less main memory while their
contents are being actively processed during query execution. Any space
reduction for table data also results in smaller indexes that can be
processed faster.

MySQL supports many different storage engines (table types) and row
formats. For each table, you can decide which storage and indexing
method to use. Choosing the proper table format for your application
may give you a big performance gain. See *Note storage-engines::.

You can get better performance for a table and minimize storage space
by using the techniques listed here:

   * Use the most efficient (smallest) data types possible. MySQL has
     many specialized types that save disk space and memory.  For
     example, use the smaller integer types if possible to get smaller
     tables. *Note `MEDIUMINT': integer-types.  is often a better
     choice than *Note `INT': integer-types. because a *Note
     `MEDIUMINT': integer-types. column uses 25% less space.

   * Declare columns to be `NOT NULL' if possible. It makes everything
     faster and you save one bit per column. If you really need `NULL'
     in your application, you should definitely use it. Just avoid
     having it on all columns by default.

   * For `MyISAM' tables, if you do not have any variable-length columns
     (*Note `VARCHAR': char, *Note `TEXT': blob, or *Note `BLOB': blob.
     columns), a fixed-size row format is used. This is faster but may
     waste some space.  See *Note myisam-table-formats::. You can hint
     that you want to have fixed length rows even if you have *Note
     `VARCHAR': char. columns with the *Note `CREATE TABLE':
     create-table. option `ROW_FORMAT=FIXED'.

   * `InnoDB' tables use a compact storage format. In versions of MySQL
     earlier than 5.0.3, `InnoDB' rows contain some redundant
     information, such as the number of columns and the length of each
     column, even for fixed-size columns. By default, tables are
     created in the compact format (`ROW_FORMAT=COMPACT'). If you wish
     to downgrade to older versions of MySQL, you can request the old
     format with `ROW_FORMAT=REDUNDANT'.

     The presence of the compact row format decreases row storage space
     by about 20% at the cost of increasing CPU use for some
     operations. If your workload is a typical one that is limited by
     cache hit rates and disk speed it is likely to be faster. If it is
     a rare case that is limited by CPU speed, it might be slower.

     The compact `InnoDB' format also changes how *Note `CHAR': char.
     columns containing UTF-8 data are stored. With
     `ROW_FORMAT=REDUNDANT', a UTF-8 `CHAR(N)' occupies 3 x N bytes,
     given that the maximum length of a UTF-8 encoded character is
     three bytes. Many languages can be written primarily using
     single-byte UTF-8 characters, so a fixed storage length often
     wastes space. With `ROW_FORMAT=COMPACT' format, `InnoDB' allocates
     a variable amount of storage in the range from N to 3 x N bytes
     for these columns by stripping trailing spaces if necessary. The
     minimum storage length is kept as N bytes to facilitate in-place
     updates in typical cases.

   * The primary index of a table should be as short as possible.  This
     makes identification of each row easy and efficient.

   * Create only the indexes that you really need. Indexes are good for
     retrieval but bad when you need to store data quickly. If you
     access a table mostly by searching on a combination of columns,
     create an index on them. The first part of the index should be the
     column most used. If you _always_ use many columns when selecting
     from the table, the first column in the index should be the one
     with the most duplicates to obtain better compression of the index.

   * If it is very likely that a string column has a unique prefix on
     the first number of characters, it is better to index only this
     prefix, using MySQL's support for creating an index on the
     leftmost part of the column (see *Note create-index::). Shorter
     indexes are faster, not only because they require less disk space,
     but because they also give you more hits in the index cache, and
     thus fewer disk seeks. See *Note server-parameters::.

   * In some circumstances, it can be beneficial to split into two a
     table that is scanned very often. This is especially true if it is
     a dynamic-format table and it is possible to use a smaller static
     format table that can be used to find the relevant rows when
     scanning the table.


File: manual.info,  Node: procedure-analyse,  Next: table-cache,  Prev: data-size,  Up: optimizing-database-structure

8.8.2 Using PROCEDURE ANALYSE
-----------------------------

`ANALYSE([MAX_ELEMENTS[,MAX_MEMORY]])'

`ANALYSE()' examines the result from a query and returns an analysis of
the results that suggests optimal data types for each column that may
help reduce table sizes. To obtain this analysis, append `PROCEDURE
ANALYSE' to the end of a *Note `SELECT': select. statement:


     SELECT ... FROM ... WHERE ... PROCEDURE ANALYSE([MAX_ELEMENTS,[MAX_MEMORY]])

For example:


     SELECT col1, col2 FROM table1 PROCEDURE ANALYSE(10, 2000);

The results show some statistics for the values returned by the query,
and propose an optimal data type for the columns. This can be helpful
for checking your existing tables, or after importing new data. You may
need to try different settings for the arguments so that `PROCEDURE
ANALYSE()' does not suggest the *Note `ENUM': enum. data type when it
is not appropriate.

The arguments are optional and are used as follows:

   * MAX_ELEMENTS (default 256) is the maximum number of distinct
     values that `ANALYSE()' notices per column. This is used by
     `ANALYSE()' to check whether the optimal data type should be of
     type *Note `ENUM': enum.; if there are more than MAX_ELEMENTS
     distinct values, then *Note `ENUM': enum. is not a suggested type.

   * MAX_MEMORY (default 8192) is the maximum amount of memory that
     `ANALYSE()' should allocate per column while trying to find all
     distinct values.


File: manual.info,  Node: table-cache,  Next: creating-many-tables,  Prev: procedure-analyse,  Up: optimizing-database-structure

8.8.3 How MySQL Opens and Closes Tables
---------------------------------------

When you execute a *Note `mysqladmin status': mysqladmin. command, you
should see something like this:


     Uptime: 426 Running threads: 1 Questions: 11082
     Reloads: 1 Open tables: 12

The `Open tables' value of 12 can be somewhat puzzling if you have only
six tables.

MySQL is multi-threaded, so there may be many clients issuing queries
for a given table simultaneously. To minimize the problem with multiple
client sessions having different states on the same table, the table is
opened independently by each concurrent session. This uses additional
memory but normally increases performance. With `MyISAM' tables, one
extra file descriptor is required for the data file for each client
that has the table open. (By contrast, the index file descriptor is
shared between all sessions.)

*Note*:

`table_open_cache' was known as `table_cache' in MySQL 5.1.2 and
earlier.

The `table_open_cache' and `max_connections' system variables affect
the maximum number of files the server keeps open. If you increase one
or both of these values, you may run up against a limit imposed by your
operating system on the per-process number of open file descriptors.
Many operating systems permit you to increase the open-files limit,
although the method varies widely from system to system. Consult your
operating system documentation to determine whether it is possible to
increase the limit and how to do so.

`table_open_cache' is related to `max_connections'. For example, for
200 concurrent running connections, you should have a table cache size
of at least `200 * N', where N is the maximum number of tables per join
in any of the queries which you execute. You must also reserve some
extra file descriptors for temporary tables and files.

Make sure that your operating system can handle the number of open file
descriptors implied by the `table_open_cache' setting. If
`table_open_cache' is set too high, MySQL may run out of file
descriptors and refuse connections, fail to perform queries, and be
very unreliable.  You also have to take into account that the `MyISAM'
storage engine needs two file descriptors for each unique open table.
You can increase the number of file descriptors available to MySQL
using the `--open-files-limit' startup option to *Note `mysqld':
mysqld. See *Note not-enough-file-handles::.

The cache of open tables is kept at a level of `table_open_cache'
entries. The default value is 64; this can be changed with the
`--table_open_cache' option to *Note `mysqld': mysqld. Note that MySQL
may temporarily open more tables than this to execute queries.

MySQL closes an unused table and removes it from the table cache under
the following circumstances:

   * When the cache is full and a thread tries to open a table that is
     not in the cache.

   * When the cache contains more than `table_open_cache' entries and a
     table in the cache is no longer being used by any threads.

   * When a table flushing operation occurs. This happens when someone
     issues a *Note `FLUSH TABLES': flush. statement or executes a
     *Note `mysqladmin flush-tables': mysqladmin. or *Note `mysqladmin
     refresh': mysqladmin. command.

When the table cache fills up, the server uses the following procedure
to locate a cache entry to use:

   * Tables that are not currently in use are released, beginning with
     the table least recently used.

   * If a new table needs to be opened, but the cache is full and no
     tables can be released, the cache is temporarily extended as
     necessary. When the cache is in a temporarily extended state and a
     table goes from a used to unused state, the table is closed and
     released from the cache.

A `MyISAM' table is opened for each concurrent access. This means the
table needs to be opened twice if two threads access the same table or
if a thread accesses the table twice in the same query (for example, by
joining the table to itself). Each concurrent open requires an entry in
the table cache. The first open of any `MyISAM' table takes two file
descriptors: one for the data file and one for the index file. Each
additional use of the table takes only one file descriptor for the data
file. The index file descriptor is shared among all threads.

If you are opening a table with the `HANDLER TBL_NAME OPEN' statement, a
dedicated table object is allocated for the thread. This table object
is not shared by other threads and is not closed until the thread calls
`HANDLER TBL_NAME CLOSE' or the thread terminates. When this happens,
the table is put back in the table cache (if the cache is not full). See
*Note handler::.

You can determine whether your table cache is too small by checking the
*Note `mysqld': mysqld. status variable `Opened_tables', which indicates
the number of table-opening operations since the server started:


     mysql> SHOW GLOBAL STATUS LIKE 'Opened_tables';
     +---------------+-------+
     | Variable_name | Value |
     +---------------+-------+
     | Opened_tables | 2741  |
     +---------------+-------+

If the value is very large or increases rapidly, even when you have not
issued many *Note `FLUSH TABLES': flush.  statements, you should
increase the table cache size. See *Note server-system-variables::, and
*Note server-status-variables::.


File: manual.info,  Node: creating-many-tables,  Next: internal-temporary-tables,  Prev: table-cache,  Up: optimizing-database-structure

8.8.4 Disadvantages of Creating Many Tables in the Same Database
----------------------------------------------------------------

If you have many `MyISAM' tables in the same database directory, open,
close, and create operations are slow.  If you execute *Note `SELECT':
select. statements on many different tables, there is a little overhead
when the table cache is full, because for every table that has to be
opened, another must be closed. You can reduce this overhead by
increasing the number of entries permitted in the table cache.


File: manual.info,  Node: internal-temporary-tables,  Prev: creating-many-tables,  Up: optimizing-database-structure

8.8.5 How MySQL Uses Internal Temporary Tables
----------------------------------------------

In some cases, the server creates internal temporary tables while
processing queries. Such a table can be held in memory and processed by
the `MEMORY' storage engine, or stored on disk and processed by the
`MyISAM' storage engine. The server may create a temporary table
initially as an in-memory table, then convert it to an on-disk table if
it becomes too large. Users have no direct control over when the server
creates an internal temporary table or which storage engine the server
uses to manage it.

Temporary tables can be created under conditions such as these:

   * *Note `UNION': union. queries use temporary tables.

   * Some views require temporary tables, such those evaluated using
     the `TEMPTABLE' algorithm, or that use *Note `UNION': union. or
     aggregation.

   * If there is an `ORDER BY' clause and a different `GROUP BY'
     clause, or if the `ORDER BY' or `GROUP BY' contains columns from
     tables other than the first table in the join queue, a temporary
     table is created.

   * `DISTINCT' combined with `ORDER BY' may require a temporary table.

   * If you use the `SQL_SMALL_RESULT' option, MySQL uses an in-memory
     temporary table, unless the query also contains elements
     (described later) that require on-disk storage.

   * Multiple-table *Note `UPDATE': update.  statements.

   * `GROUP_CONCAT()' or `COUNT(DISTINCT)' evaluation.

To determine whether a query requires a temporary table, use *Note
`EXPLAIN': explain. and check the `Extra' column to see whether it says
`Using temporary' (see *Note using-explain::).

If an internal temporary table is created initially as an in-memory
table but becomes too large, MySQL automatically converts it to an
on-disk table. The maximum size for in-memory temporary tables is the
minimum of the `tmp_table_size' and `max_heap_table_size' values.  This
differs from `MEMORY' tables explicitly created with *Note `CREATE
TABLE': create-table.: For such tables, only the `max_heap_table_size'
system variable determines how large the table is permitted to grow and
there is no conversion to on-disk format.

When the server creates an internal temporary table (either in memory
or on disk), it increments the `Created_tmp_tables' status variable. If
the server creates the table on disk (either initially or by converting
an in-memory table) it increments the `Created_tmp_disk_tables' status
variable.

Some conditions prevent the use of an in-memory temporary table, in
which case the server uses an on-disk table instead:

   * Presence of a *Note `BLOB': blob. or *Note `TEXT': blob. column in
     the table

   * Presence of any string column in a `GROUP BY' or `DISTINCT' clause
     larger than 512 bytes

   * Presence of any string column with a maximum length larger than
     512 (bytes for binary strings, characters for nonbinary strings)
     in the *Note `SELECT': select. list, if *Note `UNION': union. or
     *Note `UNION ALL': union.  is used

   * The *Note `SHOW COLUMNS': show-columns. and The *Note `DESCRIBE':
     describe. statements use `BLOB' as the type for some columns, thus
     the temporary table used for the results is an on-disk table.


File: manual.info,  Node: optimizing-the-server,  Next: thread-information,  Prev: optimizing-database-structure,  Up: optimization

8.9 Optimizing the MySQL Server
===============================

* Menu:

* system-optimization::          System Factors and Startup Parameter Tuning
* server-parameters::            Tuning Server Parameters
* connection-threads::           How MySQL Uses Threads for Client Connections
* memory-use::                   How MySQL Uses Memory
* disk-issues::                  Disk Issues
* symbolic-links::               Using Symbolic Links
* large-page-support::           Enabling Large Page Support
* host-cache::                   DNS Lookup Optimization and the Host Cache


File: manual.info,  Node: system-optimization,  Next: server-parameters,  Prev: optimizing-the-server,  Up: optimizing-the-server

8.9.1 System Factors and Startup Parameter Tuning
-------------------------------------------------

We start with system-level factors, because some of these decisions
must be made very early to achieve large performance gains. In other
cases, a quick look at this section may suffice.  However, it is always
nice to have a sense of how much can be gained by changing factors that
apply at this level.

Before using MySQL in production, we advise you to test it on your
intended platform.

Other tips:

   * If you have enough RAM, you could remove all swap devices.  Some
     operating systems use a swap device in some contexts even if you
     have free memory.

   * Avoid external locking for *Note `MyISAM': myisam-storage-engine.
     tables. Since MySQL 4.0, the default has been for external locking
     to be disabled on all systems. The `--external-locking' and
     `--skip-external-locking' options explicitly enable and disable
     external locking.

     Note that disabling external locking does not affect MySQL's
     functionality as long as you run only one server. Just remember to
     take down the server (or lock and flush the relevant tables)
     before you run *Note `myisamchk': myisamchk. On some systems it is
     mandatory to disable external locking because it does not work,
     anyway.

     The only case in which you cannot disable external locking is when
     you run multiple MySQL _servers_ (not clients) on the same data,
     or if you run *Note `myisamchk': myisamchk. to check (not repair)
     a table without telling the server to flush and lock the tables
     first. Note that using multiple MySQL servers to access the same
     data concurrently is generally _not_ recommended, except when
     using MySQL Cluster.

     The *Note `LOCK TABLES': lock-tables. and *Note `UNLOCK TABLES':
     lock-tables. statements use internal locking, so you can use them
     even if external locking is disabled.


File: manual.info,  Node: server-parameters,  Next: connection-threads,  Prev: system-optimization,  Up: optimizing-the-server

8.9.2 Tuning Server Parameters
------------------------------

You can determine the default buffer sizes used by the *Note `mysqld':
mysqld. server using this command:


     shell> mysqld --verbose --help

This command produces a list of all *Note `mysqld': mysqld.  options
and configurable system variables. The output includes the default
variable values and looks something like this:


     abort-slave-event-count           0
     allow-suspicious-udfs             FALSE
     auto-increment-increment          1
     auto-increment-offset             1
     automatic-sp-privileges           TRUE
     back_log                          50
     basedir                           /home/jon/bin/mysql-5.1/
     bind-address                      (No default value)
     binlog-row-event-max-size         1024
     binlog_cache_size                 32768
     binlog_format                     (No default value)
     bulk_insert_buffer_size           8388608
     character-set-client-handshake    TRUE
     character-set-filesystem          binary
     character-set-server              latin1
     character-sets-dir                /home/jon/bin/mysql-5.1/share/mysql/charsets/
     chroot                            (No default value)
     collation-server                  latin1_swedish_ci
     completion-type                   0
     concurrent-insert                 1
     connect_timeout                   10
     console                           FALSE
     datadir                           .
     datetime_format                   %Y-%m-%d %H:%i:%s
     date_format                       %Y-%m-%d
     default-character-set             latin1
     default-collation                 latin1_swedish_ci
     default-storage-engine            MyISAM
     default-table-type                MyISAM
     default-time-zone                 (No default value)
     default_week_format               0
     delayed_insert_limit              100
     delayed_insert_timeout            300
     delayed_queue_size                1000
     disconnect-slave-event-count      0
     div_precision_increment           4
     enable-locking                    FALSE
     engine-condition-pushdown         TRUE
     expire_logs_days                  0
     external-locking                  FALSE
     flush_time                        0
     ft_max_word_len                   84
     ft_min_word_len                   4
     ft_query_expansion_limit          20
     ft_stopword_file                  (No default value)
     gdb                               FALSE
     general_log                       FALSE
     general_log_file                  (No default value)
     group_concat_max_len              1024
     help                              TRUE
     init-connect                      (No default value)
     init-file                         (No default value)
     init-slave                        (No default value)
     innodb                            TRUE
     innodb-adaptive-hash-index        TRUE
     innodb-additional-mem-pool-size   1048576
     innodb-autoextend-increment       8
     innodb-autoinc-lock-mode          1
     innodb-buffer-pool-size           8388608
     innodb-checksums                  TRUE
     innodb-commit-concurrency         0
     innodb-concurrency-tickets        500
     innodb-data-file-path             (No default value)
     innodb-data-home-dir              (No default value)
     innodb-doublewrite                TRUE
     innodb-fast-shutdown              1
     innodb-file-io-threads            4
     innodb-file-per-table             FALSE
     innodb-flush-log-at-trx-commit    1
     innodb-flush-method               (No default value)
     innodb-force-recovery             0
     innodb-lock-wait-timeout          50
     innodb-locks-unsafe-for-binlog    FALSE
     innodb-log-buffer-size            1048576
     innodb-log-file-size              5242880
     innodb-log-files-in-group         2
     innodb-log-group-home-dir         (No default value)
     innodb-max-dirty-pages-pct        90
     innodb-max-purge-lag              0
     innodb-mirrored-log-groups        1
     innodb-open-files                 300
     innodb-rollback-on-timeout        FALSE
     innodb-stats-on-metadata          TRUE
     innodb-status-file                FALSE
     innodb-support-xa                 TRUE
     innodb-sync-spin-loops            20
     innodb-table-locks                TRUE
     innodb-thread-concurrency         8
     innodb-thread-sleep-delay         10000
     interactive_timeout               28800
     join_buffer_size                  131072
     keep_files_on_create              FALSE
     key_buffer_size                   8384512
     key_cache_age_threshold           300
     key_cache_block_size              1024
     key_cache_division_limit          100
     language                          /home/jon/bin/mysql-5.1/share/mysql/english/
     large-pages                       FALSE
     lc-time-names                     en_US
     local-infile                      TRUE
     log                               (No default value)
     log-bin                           (No default value)
     log-bin-index                     (No default value)
     log-bin-trust-function-creators   FALSE
     log-bin-trust-routine-creators    FALSE
     log-error
     log-isam                          myisam.log
     log-output                        FILE
     log-queries-not-using-indexes     FALSE
     log-short-format                  FALSE
     log-slave-updates                 FALSE
     log-slow-admin-statements         FALSE
     log-slow-slave-statements         FALSE
     log-tc                            tc.log
     log-tc-size                       24576
     log-update                        (No default value)
     log-warnings                      1
     log_slow_queries                  (No default value)
     long_query_time                   10
     low-priority-updates              FALSE
     lower_case_table_names            0
     master-connect-retry              60
     master-host                       (No default value)
     master-info-file                  master.info
     master-password                   (No default value)
     master-port                       3306
     master-retry-count                86400
     master-ssl                        FALSE
     master-ssl-ca                     (No default value)
     master-ssl-capath                 (No default value)
     master-ssl-cert                   (No default value)
     master-ssl-cipher                 (No default value)
     master-ssl-key                    (No default value)
     master-user                       test
     max-binlog-dump-events            0
     max_allowed_packet                1048576
     max_binlog_cache_size             18446744073709547520
     max_binlog_size                   1073741824
     max_connections                   151
     max_connect_errors                10
     max_delayed_threads               20
     max_error_count                   64
     max_heap_table_size               16777216
     max_join_size                     18446744073709551615
     max_length_for_sort_data          1024
     max_prepared_stmt_count           16382
     max_relay_log_size                0
     max_seeks_for_key                 18446744073709551615
     max_sort_length                   1024
     max_sp_recursion_depth            0
     max_tmp_tables                    32
     max_user_connections              0
     max_write_lock_count              18446744073709551615
     memlock                           FALSE
     min_examined_row_limit            0
     multi_range_count                 256
     myisam-recover                    OFF
     myisam_block_size                 1024
     myisam_data_pointer_size          6
     myisam_max_extra_sort_file_size   2147483648
     myisam_max_sort_file_size         9223372036853727232
     myisam_repair_threads             1
     myisam_sort_buffer_size           8388608
     myisam_stats_method               nulls_unequal
     myisam_use_mmap                   FALSE
     ndb-autoincrement-prefetch-sz     1
     ndb-cache-check-time              0
     ndb-connectstring                 (No default value)
     ndb-extra-logging                 0
     ndb-force-send                    TRUE
     ndb-index-stat-enable             FALSE
     ndb-mgmd-host                     (No default value)
     ndb-nodeid                        0
     ndb-optimized-node-selection      TRUE
     ndb-report-thresh-binlog-epoch-slip 3
     ndb-report-thresh-binlog-mem-usage 10
     ndb-shm                           FALSE
     ndb-use-copying-alter-table       FALSE
     ndb-use-exact-count               TRUE
     ndb-use-transactions              TRUE
     ndb_force_send                    TRUE
     ndb_use_exact_count               TRUE
     ndb_use_transactions              TRUE
     net_buffer_length                 16384
     net_read_timeout                  30
     net_retry_count                   10
     net_write_timeout                 60
     new                               FALSE
     old                               FALSE
     old-alter-table                   FALSE
     old-passwords                     FALSE
     old-style-user-limits             FALSE
     open_files_limit                  1024
     optimizer_prune_level             1
     optimizer_search_depth            62
     pid-file                          /home/jon/bin/mysql-5.1/var/tonfisk.pid
     plugin-load                       (No default value)
     plugin_dir                        /home/jon/bin/mysql-5.1/lib/mysql/plugin
     port                              3306
     port-open-timeout                 0
     preload_buffer_size               32768
     profiling_history_size            15
     query_alloc_block_size            8192
     query_cache_limit                 1048576
     query_cache_min_res_unit          4096
     query_cache_size                  0
     query_cache_type                  1
     query_cache_wlock_invalidate      FALSE
     query_prealloc_size               8192
     range_alloc_block_size            4096
     read_buffer_size                  131072
     read_only                         FALSE
     read_rnd_buffer_size              262144
     record_buffer                     131072
     relay-log                         (No default value)
     relay-log-index                   (No default value)
     relay-log-info-file               relay-log.info
     relay_log_purge                   TRUE
     relay_log_space_limit             0
     replicate-same-server-id          FALSE
     report-host                       (No default value)
     report-password                   (No default value)
     report-port                       3306
     report-user                       (No default value)
     rpl-recovery-rank                 0
     safe-user-create                  FALSE
     secure-auth                       FALSE
     secure-file-priv                  (No default value)
     server-id                         0
     show-slave-auth-info              FALSE
     skip-grant-tables                 FALSE
     skip-slave-start                  FALSE
     slave-exec-mode                   STRICT
     slave-load-tmpdir                 /tmp
     slave_compressed_protocol         FALSE
     slave_net_timeout                 3600
     slave_transaction_retries         10
     slow-query-log                    FALSE
     slow_launch_time                  2
     slow_query_log_file               (No default value)
     socket                            /tmp/mysql.sock
     sort_buffer_size                  2097144
     sporadic-binlog-dump-fail         FALSE
     sql-mode                          OFF
     symbolic-links                    TRUE
     sync-binlog                       0
     sync-frm                          TRUE
     sysdate-is-now                    FALSE
     table_definition_cache            256
     table_lock_wait_timeout           50
     table_open_cache                  64
     tc-heuristic-recover              (No default value)
     temp-pool                         TRUE
     thread_cache_size                 0
     thread_concurrency                10
     thread_stack                      262144
     timed_mutexes                     FALSE
     time_format                       %H:%i:%s
     tmpdir                            (No default value)
     tmp_table_size                    16777216
     transaction_alloc_block_size      8192
     transaction_prealloc_size         4096
     updatable_views_with_limit        1
     use-symbolic-links                TRUE
     verbose                           TRUE
     wait_timeout                      28800
     warnings                          1

For a *Note `mysqld': mysqld. server that is currently running, you can
see the current values of its system variables by connecting to it and
issuing this statement:


     mysql> SHOW VARIABLES;

You can also see some statistical and status indicators for a running
server by issuing this statement:


     mysql> SHOW STATUS;

System variable and status information also can be obtained using *Note
`mysqladmin': mysqladmin.:


     shell> mysqladmin variables
     shell> mysqladmin extended-status

For a full description of all system and status variables, see *Note
server-system-variables::, and *Note server-status-variables::.

MySQL uses algorithms that are very scalable, so you can usually run
with very little memory. However, normally you get better performance
by giving MySQL more memory.

When tuning a MySQL server, the two most important variables to
configure are `key_buffer_size' and `table_open_cache'. You should
first feel confident that you have these set appropriately before
trying to change any other variables.

The following examples indicate some typical variable values for
different runtime configurations.

   * If you have at least 256MB of memory and many tables and want
     maximum performance with a moderate number of clients, you should
     use something like this:


          shell> mysqld_safe --key_buffer_size=64M --table_open_cache=256 \
                     --sort_buffer_size=4M --read_buffer_size=1M &

   * If you have only 128MB of memory and only a few tables, but you
     still do a lot of sorting, you can use something like this:


          shell> mysqld_safe --key_buffer_size=16M --sort_buffer_size=1M

     If there are very many simultaneous connections, swapping problems
     may occur unless *Note `mysqld': mysqld. has been configured to
     use very little memory for each connection.  *Note `mysqld':
     mysqld. performs better if you have enough memory for all
     connections.

   * With little memory and lots of connections, use something like
     this:


          shell> mysqld_safe --key_buffer_size=512K --sort_buffer_size=100K \
                     --read_buffer_size=100K &

     Or even this:


          shell> mysqld_safe --key_buffer_size=512K --sort_buffer_size=16K \
                     --table_open_cache=32 --read_buffer_size=8K \
                     --net_buffer_length=1K &

If you are performing `GROUP BY' or `ORDER BY' operations on tables
that are much larger than your available memory, you should increase
the value of `read_rnd_buffer_size' to speed up the reading of rows
following sorting operations.

You can make use of the example option files included with your MySQL
distribution; see *Note server-configuration-defaults::.

If you specify an option on the command line for *Note `mysqld':
mysqld. or *Note `mysqld_safe': mysqld-safe, it remains in effect only
for that invocation of the server. To use the option every time the
server runs, put it in an option file.

To see the effects of a parameter change, do something like this:


     shell> mysqld --key_buffer_size=32M --verbose --help

The variable values are listed near the end of the output. Make sure
that the `--verbose' and `--help' options are last.  Otherwise, the
effect of any options listed after them on the command line are not
reflected in the output.

For information on tuning the `InnoDB' storage engine, see *Note
innodb-tuning::.


File: manual.info,  Node: connection-threads,  Next: memory-use,  Prev: server-parameters,  Up: optimizing-the-server

8.9.3 How MySQL Uses Threads for Client Connections
---------------------------------------------------

Connection manager threads handle client connection requests on the
network interfaces that the server listens to. On all platforms, one
manager thread handles TCP/IP connection requests. On Unix, this
manager thread also handles Unix socket file connection requests. On
Windows, a manager thread handles shared-memory connection requests,
and another handles named-pipe connection requests. The server does not
create threads to handle interfaces that it does not listen to. For
example, a Windows server that does not have support for named-pipe
connections enabled does not create a thread to handle them.

Connection manager threads associate each client connection with a
thread dedicated to it that handles authentication and request
processing for that connection. Manager threads create a new thread
when necessary but try to avoid doing so by consulting the thread cache
first to see whether it contains a thread that can be used for the
connection. When a connection ends, its thread is returned to the
thread cache if the cache is not full.

In this connection thread model, there are as many threads as there are
clients currently connected, which has some disadvantages when server
workload must scale to handle large numbers of connections. For
example, thread creation and disposal becomes expensive. Also, each
thread requires server and kernel resources, such as stack space. To
accommodate a large number of simultaneous connections, the stack size
per thread must be kept small, leading to a situation where it is
either too small or the server consumes large amounts of memory.
Exhaustion of other resources can occur as well, and scheduling
overhead can become significant.

To control and monitor how the server manages threads that handle
client connections, several system and status variables are relevant.
(See *Note server-system-variables::, and *Note
server-status-variables::.)

The thread cache has a size determined by the `thread_cache_size' system
variable. The default value is 0 (no caching), which causes a thread to
be set up for each new connection and disposed of when the connection
terminates. Set `thread_cache_size' to N to enable N inactive
connection threads to be cached. `thread_cache_size' can be set at
server startup or changed while the server runs. A connection thread
becomes inactive when the client connection with which it was
associated terminates.

To monitor the number of threads in the cache and how many threads have
been created because a thread could not be taken from the cache,
monitor the `Threads_cached' and `Threads_created' status variables.

You can set `max_connections' at server startup or at runtime to
control the maximum number of clients that can connect simultaneously.

When the thread stack is too small, this limits the complexity of the
SQL statements which the server can handle, the recursion depth of
stored procedures, and other memory-consuming actions.  To set a stack
size of N bytes for each thread, start the server with
`--thread_stack=N'.


File: manual.info,  Node: memory-use,  Next: disk-issues,  Prev: connection-threads,  Up: optimizing-the-server

8.9.4 How MySQL Uses Memory
---------------------------

The following list indicates some of the ways that the *Note `mysqld':
mysqld. server uses memory. Where applicable, the name of the system
variable relevant to the memory use is given:

   * All threads share the *Note `MyISAM': myisam-storage-engine.  key
     buffer; its size is determined by the `key_buffer_size' variable.
     Other buffers used by the server are allocated as needed.  See
     *Note server-parameters::.

   * Each thread that is used to manage client connections uses some
     thread-specific space. The following list indicates these and
     which variables control their size:

        * A stack (variable `thread_stack')

        * A connection buffer (variable `net_buffer_length')

        * A result buffer (variable `net_buffer_length')

     The connection buffer and result buffer each begin with a size
     equal to `net_buffer_length' bytes, but are dynamically enlarged
     up to `max_allowed_packet' bytes as needed. The result buffer
     shrinks to `net_buffer_length' bytes after each SQL statement.
     While a statement is running, a copy of the current statement
     string is also allocated.

   * All threads share the same base memory.

   * When a thread is no longer needed, the memory allocated to it is
     released and returned to the system unless the thread goes back
     into the thread cache. In that case, the memory remains allocated.

   * Before MySQL 5.1.4, only compressed `MyISAM' tables are memory
     mapped. As of MySQL 5.1.4, the `myisam_use_mmap' system variable
     can be set to 1 to enable memory-mapping for all `MyISAM' tables.

   * Each request that performs a sequential scan of a table allocates
     a _read buffer_ (variable `read_buffer_size').

   * When reading rows in an arbitrary sequence (for example, following
     a sort), a _random-read buffer_ (variable `read_rnd_buffer_size')
     may be allocated to avoid disk seeks.

   * All joins are executed in a single pass, and most joins can be
     done without even using a temporary table. Most temporary tables
     are memory-based hash tables. Temporary tables with a large row
     length (calculated as the sum of all column lengths) or that
     contain *Note `BLOB': blob.  columns are stored on disk.

     If an internal in-memory temporary table becomes too large, MySQL
     handles this automatically by changing the table from in-memory to
     on-disk format, to be handled by the `MyISAM' storage engine. You
     can increase the permissible temporary table size as described in
     *Note internal-temporary-tables::.

   * Most requests that perform a sort allocate a sort buffer and zero
     to two temporary files depending on the result set size. See *Note
     temporary-files::.

   * Almost all parsing and calculating is done in thread-local and
     reusable memory pools. No memory overhead is needed for small
     items, so the normal slow memory allocation and freeing is
     avoided. Memory is allocated only for unexpectedly large strings.

   * For each `MyISAM' table that is opened, the index file is opened
     once; the data file is opened once for each concurrently running
     thread. For each concurrent thread, a table structure, column
     structures for each column, and a buffer of size `3 * N' are
     allocated (where N is the maximum row length, not counting *Note
     `BLOB': blob. columns). A *Note `BLOB': blob. column requires five
     to eight bytes plus the length of the *Note `BLOB': blob. data. The
     `MyISAM' storage engine maintains one extra row buffer for
     internal use.

   * For each table having *Note `BLOB': blob.  columns, a buffer is
     enlarged dynamically to read in larger *Note `BLOB': blob. values.
     If you scan a table, a buffer as large as the largest *Note
     `BLOB': blob. value is allocated.

   * Handler structures for all in-use tables are saved in a cache and
     managed as a FIFO. The initial cache size is taken from the value
     of the `table_open_cache' system variable. If a table has been
     used by two running threads at the same time, the cache contains
     two entries for the table.  See *Note table-cache::.

   * A *Note `FLUSH TABLES': flush. statement or *Note `mysqladmin
     flush-tables': mysqladmin. command closes all tables that are not
     in use at once and marks all in-use tables to be closed when the
     currently executing thread finishes. This effectively frees most
     in-use memory.  *Note `FLUSH TABLES': flush. does not return until
     all tables have been closed.

   * The server caches information in memory as a result of *Note
     `GRANT': grant, *Note `CREATE USER': create-user, *Note `CREATE
     SERVER': create-server, and *Note `INSTALL PLUGIN':
     install-plugin. statements.  This memory is not released by the
     corresponding *Note `REVOKE': revoke, *Note `DROP USER': drop-user,
     *Note `DROP SERVER': drop-server, and *Note `UNINSTALL PLUGIN':
     uninstall-plugin. statements, so for a server that executes many
     instances of the statements that cause caching, there will be an
     increase in memory use. This cached memory can be freed with *Note
     `FLUSH PRIVILEGES': flush.

`ps' and other system status programs may report that *Note `mysqld':
mysqld. uses a lot of memory. This may be caused by thread stacks on
different memory addresses.  For example, the Solaris version of `ps'
counts the unused memory between stacks as used memory. To verify this,
check available swap with `swap -s'. We test *Note `mysqld': mysqld.
with several memory-leakage detectors (both commercial and Open
Source), so there should be no memory leaks.


File: manual.info,  Node: disk-issues,  Next: symbolic-links,  Prev: memory-use,  Up: optimizing-the-server

8.9.5 Disk Issues
-----------------

   * Disk seeks are a huge performance bottleneck. This problem becomes
     more apparent when the amount of data starts to grow so large that
     effective caching becomes impossible. For large databases where
     you access data more or less randomly, you can be sure that you
     need at least one disk seek to read and a couple of disk seeks to
     write things. To minimize this problem, use disks with low seek
     times.

   * Increase the number of available disk spindles (and thereby reduce
     the seek overhead) by either symlinking files to different disks
     or striping the disks:

        * Using symbolic links

          This means that, for `MyISAM' tables, you symlink the index
          file and data files from their usual location in the data
          directory to another disk (that may also be striped). This
          makes both the seek and read times better, assuming that the
          disk is not used for other purposes as well. See *Note
          symbolic-links::.

        * Striping

          Striping means that you have many disks and put the first
          block on the first disk, the second block on the second disk,
          and the N-th block on the (`N MOD NUMBER_OF_DISKS') disk, and
          so on. This means if your normal data size is less than the
          stripe size (or perfectly aligned), you get much better
          performance. Striping is very dependent on the operating
          system and the stripe size, so benchmark your application
          with different stripe sizes.  See *Note custom-benchmarks::.

          The speed difference for striping is _very_ dependent on the
          parameters.  Depending on how you set the striping parameters
          and number of disks, you may get differences measured in
          orders of magnitude. You have to choose to optimize for
          random or sequential access.

   * For reliability, you may want to use RAID 0+1 (striping plus
     mirroring), but in this case, you need 2 x N drives to hold N
     drives of data. This is probably the best option if you have the
     money for it.  However, you may also have to invest in some
     volume-management software to handle it efficiently.

   * A good option is to vary the RAID level according to how critical
     a type of data is. For example, store semi-important data that can
     be regenerated on a RAID 0 disk, but store really important data
     such as host information and logs on a RAID 0+1 or RAID N disk.
     RAID N can be a problem if you have many writes, due to the time
     required to update the parity bits.

   * On Linux, you can get much better performance by using `hdparm' to
     configure your disk's interface. (Up to 100% under load is not
     uncommon.) The following `hdparm' options should be quite good for
     MySQL, and probably for many other applications:


          hdparm -m 16 -d 1

     Note that performance and reliability when using this command
     depend on your hardware, so we strongly suggest that you test your
     system thoroughly after using `hdparm'. Please consult the
     `hdparm' manual page for more information.  If `hdparm' is not
     used wisely, file system corruption may result, so back up
     everything before experimenting!

   * You can also set the parameters for the file system that the
     database uses:

     If you do not need to know when files were last accessed (which is
     not really useful on a database server), you can mount your file
     systems with the `-o noatime' option. That skips updates to the
     last access time in inodes on the file system, which avoids some
     disk seeks.

     On many operating systems, you can set a file system to be updated
     asynchronously by mounting it with the `-o async' option. If your
     computer is reasonably stable, this should give you better
     performance without sacrificing too much reliability. (This flag
     is on by default on Linux.)


File: manual.info,  Node: symbolic-links,  Next: large-page-support,  Prev: disk-issues,  Up: optimizing-the-server

8.9.6 Using Symbolic Links
--------------------------

* Menu:

* symbolic-links-to-databases::  Using Symbolic Links for Databases on Unix
* symbolic-links-to-tables::     Using Symbolic Links for MyISAM Tables on Unix
* windows-symbolic-links::       Using Symbolic Links for Databases on Windows

You can move databases or tables from the database directory to other
locations and replace them with symbolic links to the new locations.
You might want to do this, for example, to move a database to a file
system with more free space or increase the speed of your system by
spreading your tables to different disks.

The recommended way to do this is to symlink entire database
directories to a different disk. Symlink `MyISAM' tables only as a last
resort.

To determine the location of your data directory, use this statement:


     SHOW VARIABLES LIKE 'datadir';


File: manual.info,  Node: symbolic-links-to-databases,  Next: symbolic-links-to-tables,  Prev: symbolic-links,  Up: symbolic-links

8.9.6.1 Using Symbolic Links for Databases on Unix
..................................................

On Unix, the way to symlink a database is first to create a directory
on some disk where you have free space and then to create a soft link
to it from the MySQL data directory.


     shell> mkdir /dr1/databases/test
     shell> ln -s /dr1/databases/test /PATH/TO/DATADIR

MySQL does not support linking one directory to multiple databases.
Replacing a database directory with a symbolic link works as long as
you do not make a symbolic link between databases. Suppose that you
have a database `db1' under the MySQL data directory, and then make a
symlink `db2' that points to `db1':


     shell> cd /PATH/TO/DATADIR
     shell> ln -s db1 db2

The result is that, or any table `tbl_a' in `db1', there also appears
to be a table `tbl_a' in `db2'. If one client updates `db1.tbl_a' and
another client updates `db2.tbl_a', problems are likely to occur.


File: manual.info,  Node: symbolic-links-to-tables,  Next: windows-symbolic-links,  Prev: symbolic-links-to-databases,  Up: symbolic-links

8.9.6.2 Using Symbolic Links for MyISAM Tables on Unix
......................................................

Symlinks are fully supported only for `MyISAM' tables. For files used
by tables for other storage engines, you may get strange problems if
you try to use symbolic links.

Do not symlink tables on systems that do not have a fully operational
`realpath()' call. (Linux and Solaris support `realpath()'). To
determine whether your system supports symbolic links, check the value
of the `have_symlink' system variable using this statement:


     SHOW VARIABLES LIKE 'have_symlink';

The handling of symbolic links for `MyISAM' tables works as follows:

   * In the data directory, you always have the table format (`.frm')
     file, the data (`.MYD') file, and the index (`.MYI') file. The
     data file and index file can be moved elsewhere and replaced in
     the data directory by symlinks. The format file cannot.

   * You can symlink the data file and the index file independently to
     different directories.

   * To instruct a running MySQL server to perform the symlinking, use
     the `DATA DIRECTORY' and `INDEX DIRECTORY' options to *Note
     `CREATE TABLE': create-table. See *Note create-table::.
     Alternatively, if *Note `mysqld': mysqld. is not running,
     symlinking can be accomplished manually using `ln -s' from the
     command line.

     *Note*:

     Beginning with MySQL 5.1.24, the path used with either or both of
     the `DATA DIRECTORY' and `INDEX DIRECTORY' options may not include
     the MySQL `data' directory.  (Bug #32167)

   * *Note `myisamchk': myisamchk. does not replace a symlink with the
     data file or index file. It works directly on the file to which
     the symlink points. Any temporary files are created in the
     directory where the data file or index file is located. The same
     is true for the *Note `ALTER TABLE': alter-table, *Note `OPTIMIZE
     TABLE': optimize-table, and *Note `REPAIR TABLE': repair-table.
     statements.

   * *Note*:

     When you drop a table that is using symlinks, _both the symlink
     and the file to which the symlink points are dropped_. This is an
     extremely good reason _not_ to run *Note `mysqld': mysqld. as the
     system `root' or permit system users to have write access to MySQL
     database directories.

   * If you rename a table with *Note `ALTER TABLE ... RENAME':
     alter-table. or *Note `RENAME TABLE': rename-table. and you do not
     move the table to another database, the symlinks in the database
     directory are renamed to the new names and the data file and index
     file are renamed accordingly.

   * If you use *Note `ALTER TABLE ... RENAME': alter-table. or *Note
     `RENAME TABLE': rename-table. to move a table to another database,
     the table is moved to the other database directory. If the table
     name changed, the symlinks in the new database directory are
     renamed to the new names and the data file and index file are
     renamed accordingly.

   * If you are not using symlinks, start *Note `mysqld': mysqld. with
     the `--skip-symbolic-links' option to ensure that no one can use
     *Note `mysqld': mysqld. to drop or rename a file outside of the
     data directory.

These table symlink operations are not supported:

   * *Note `ALTER TABLE': alter-table. ignores the `DATA DIRECTORY' and
     `INDEX DIRECTORY' table options.

   * *Note `BACKUP TABLE': backup-table. and *Note `RESTORE TABLE':
     restore-table. do not respect symbolic links.

   * As indicated previously, only the data and index files can be
     symbolic links. The `.frm' file must _never_ be a symbolic link.
     Attempting to do this (for example, to make one table name a
     synonym for another) produces incorrect results. Suppose that you
     have a database `db1' under the MySQL data directory, a table
     `tbl1' in this database, and in the `db1' directory you make a
     symlink `tbl2' that points to `tbl1':


          shell> cd /PATH/TO/DATADIR/db1
          shell> ln -s tbl1.frm tbl2.frm
          shell> ln -s tbl1.MYD tbl2.MYD
          shell> ln -s tbl1.MYI tbl2.MYI

     Problems result if one thread reads `db1.tbl1' and another thread
     updates `db1.tbl2':

        * The query cache is `fooled' (it has no way of knowing that
          `tbl1' has not been updated, so it returns outdated results).

        * `ALTER' statements on `tbl2' fail.


File: manual.info,  Node: windows-symbolic-links,  Prev: symbolic-links-to-tables,  Up: symbolic-links

8.9.6.3 Using Symbolic Links for Databases on Windows
.....................................................

On Windows, symbolic links can be used for database directories. This
enables you to put a database directory at a different location (for
example, on a different disk) by setting up a symbolic link to it. Use
of database symlinks on Windows is similar to their use on Unix,
although the procedure for setting up the link differs.

Suppose that you want to place the database directory for a database
named `mydb' at `D:\data\mydb'. To do this, create a symbolic link in
the MySQL data directory that points to `D:\data\mydb'. However, before
creating the symbolic link, make sure that the `D:\data\mydb' directory
exists by creating it if necessary. If you already have a database
directory named `mydb' in the data directory, move it to `D:\data'.
Otherwise, the symbolic link will be ineffective. To avoid problems,
make sure that the server is not running when you move the database
directory.

On Windows, create a symbolic link to a MySQL database by creating a
`.sym' file in the data directory that contains the path to the
destination directory.  The file should be named `DB_NAME.sym', where
DB_NAME is the database name.

Support for database symbolic links on Windows using `.sym' files is
enabled by default. If you do not need `.sym' file symbolic links, you
can disable support for them by starting *Note `mysqld': mysqld. with
the `--skip-symbolic-links' option. To determine whether your system
supports `.sym' file symbolic links, check the value of the
`have_symlink' system variable using this statement:


     SHOW VARIABLES LIKE 'have_symlink';

To create a `.sym' file symlink, use this procedure:

  1. Change location into the data directory:


          C:\> cd \PATH\TO\DATADIR

  2. In the data directory, create a text file named `mydb.sym' that
     contains this path name: `D:\data\mydb\'

     *Note*:

     The path name to the new database and tables should be absolute.
     If you specify a relative path, the location will be relative to
     the `mydb.sym' file.

After this, all tables created in the database `mydb' are created in
`D:\data\mydb'.

The following limitations apply to the use of `.sym' files for database
symbolic linking on Windows:

   * The symbolic link is not used if a directory with the same name as
     the database exists in the MySQL data directory.

   * The `--innodb_file_per_table' option cannot be used.

   * If you run *Note `mysqld': mysqld. as a service, you cannot use a
     mapped drive to a remote server as the destination of the symbolic
     link. As a workaround, you can use the full path
     (`\\servername\path\').


File: manual.info,  Node: large-page-support,  Next: host-cache,  Prev: symbolic-links,  Up: optimizing-the-server

8.9.7 Enabling Large Page Support
---------------------------------

Some hardware/operating system architectures support memory pages
greater than the default (usually 4KB). The actual implementation of
this support depends on the underlying hardware and operating system.
Applications that perform a lot of memory accesses may obtain
performance improvements by using large pages due to reduced
Translation Lookaside Buffer (TLB) misses.

In MySQL, large pages can be used by InnoDB, to allocate memory for its
buffer pool and additional memory pool.

Currently, MySQL supports only the Linux implementation of large page
support (which is called HugeTLB in Linux).

Before large pages can be used on Linux, the kernel must be enabled to
support them and it is necessary to configure the HugeTLB memory pool.
For reference, the HugeTBL API is documented in the
`Documentation/vm/hugetlbpage.txt' file of your Linux sources.

The kernel for some recent systems such as Red Hat Enterprise Linux
appear to have the large pages feature enabled by default.  To check
whether this is true for your kernel, use the following command and
look for output lines containing `huge':


     shell> cat /proc/meminfo | grep -i huge
     HugePages_Total:       0
     HugePages_Free:        0
     HugePages_Rsvd:        0
     HugePages_Surp:        0
     Hugepagesize:       4096 kB

The nonempty command output indicates that large page support is
present, but the zero values indicate that no pages are configured for
use.

If your kernel needs to be reconfigured to support large pages, consult
the `hugetlbpage.txt' file for instructions.

Assuming that your Linux kernel has large page support enabled,
configure it for use by MySQL using the following commands.  Normally,
you put these in an `rc' file or equivalent startup file that is
executed during the system boot sequence, so that the commands execute
each time the system starts. The commands should execute early in the
boot sequence, before the MySQL server starts. Be sure to change the
allocation numbers and the group number as appropriate for your system.


     # Set the number of pages to be used.
     # Each page is normally 2MB, so a value of 20 = 40MB.
     # This command actually allocates memory, so this much
     # memory must be available.
     echo 20 > /proc/sys/vm/nr_hugepages

     # Set the group number that is permitted to access this
     # memory (102 in this case). The mysql user must be a
     # member of this group.
     echo 102 > /proc/sys/vm/hugetlb_shm_group

     # Increase the amount of shmem permitted per segment
     # (12G in this case).
     echo 1560281088 > /proc/sys/kernel/shmmax

     # Increase total amount of shared memory.  The value
     # is the number of pages. At 4KB/page, 4194304 = 16GB.
     echo 4194304 > /proc/sys/kernel/shmall

For MySQL usage, you normally want the value of `shmmax' to be close to
the value of `shmall'.

To verify the large page configuration, check `/proc/meminfo' again as
described previously. Now you should see some nonzero values:


     shell> cat /proc/meminfo | grep -i huge
     HugePages_Total:      20
     HugePages_Free:       20
     HugePages_Rsvd:        0
     HugePages_Surp:        0
     Hugepagesize:       4096 kB

The final step to make use of the `hugetlb_shm_group' is to give the
`mysql' user an `unlimited' value for the memlock limit. This can by
done either by editing `/etc/security/limits.conf' or by adding the
following command to your *Note `mysqld_safe': mysqld-safe. script:


     ulimit -l unlimited

Adding the `ulimit' command to *Note `mysqld_safe': mysqld-safe. causes
the `root' user to set the memlock limit to `unlimited' before
switching to the `mysql' user. (This assumes that *Note `mysqld_safe':
mysqld-safe. is started by `root'.)

Large page support in MySQL is disabled by default. To enable it, start
the server with the `--large-pages' option. For example, you can use
the following lines in your server's `my.cnf' file:


     [mysqld]
     large-pages

With this option, `InnoDB' uses large pages automatically for its
buffer pool and additional memory pool. If `InnoDB' cannot do this, it
falls back to use of traditional memory and writes a warning to the
error log: `Warning: Using conventional memory pool'

To verify that large pages are being used, check `/proc/meminfo' again:


     shell> cat /proc/meminfo | grep -i huge
     HugePages_Total:      20
     HugePages_Free:       20
     HugePages_Rsvd:        2
     HugePages_Surp:        0
     Hugepagesize:       4096 kB


File: manual.info,  Node: host-cache,  Prev: large-page-support,  Up: optimizing-the-server

8.9.8 DNS Lookup Optimization and the Host Cache
------------------------------------------------

The MySQL server maintains a host cache in memory that contains
information about clients: IP address, host name, and error
information. The server uses this cache for nonlocal TCP connections.
It does not use the cache for TCP connections established using the
loopback interface address (`127.0.0.1'), or for connections established
using a Unix socket file, named pipe, or shared memory.

For each new client connection, the server uses the client IP address
to check whether the client host name is in the host cache. If not, the
server attempts to resolve the host name.  First, it resolves the IP
address to a host name and resolves that host name back to an IP
address. Then it compares the result to the original IP address to
ensure that they are the same. The server stores information about the
result of this operation in the host cache. If the cache is full, the
least recently used entry is discarded.

The server performs host name resolution using the thread-safe
`gethostbyaddr_r()' and `gethostbyname_r()' calls if the operating
system supports them. Otherwise, the thread performing the lookup locks
a mutex and calls `gethostbyaddr()' and `gethostbyname()' instead. In
this case, no other thread can resolve host names that are not in the
host cache until the thread holding the mutex lock releases it.

The server uses the host cache for several purposes:

   * By caching the results of IP-to-host name lookups, the server
     avoids doing a DNS lookup for each client connection.  Instead,
     for a given host, it needs to perform a lookup only for the first
     connection from that host.

   * The cache contains information about errors that occur during the
     connection process. Some errors are considered `blocking.' If too
     many of these occur successively from a given host without a
     successful connection, the server blocks further connections from
     that host. The `max_connect_errors' system variable determines the
     number of permitted errors before blocking occurs. See *Note
     blocked-host::.

To unblock blocked hosts, flush the host cache by issuing a *Note
`FLUSH HOSTS': flush.  statement or executing a *Note `mysqladmin
flush-hosts': mysqladmin. command.

It is possible for a blocked host to become unblocked even without
*Note `FLUSH HOSTS': flush. if activity from other hosts has occurred
since the last connection attempt from the blocked host. This can occur
because the server discards the least recently used cache entry to make
room for a new entry if the cache is full when a connection arrives
from a client IP not in the cache. If the discarded entry is for a
blocked host, that host becomes unblocked.

The host cache is enabled by default. To disable it, start the server
with the `--skip-host-cache' option.

To disable DNS host name lookups, start the server with the
`--skip-name-resolve' option. In this case, the server uses only IP
addresses and not host names to match connecting hosts to rows in the
MySQL grant tables.  Only accounts specified in those tables using IP
addresses can be used.

If you have a very slow DNS and many hosts, you might be able to
improve performance either by disabling DNS lookups with
`--skip-name-resolve' or by increasing the `HOST_CACHE_SIZE' define
(default value: 128) and recompiling the server

To disallow TCP/IP connections entirely, start the server with the
`--skip-networking' option.

Some connection errors are not associated with TCP connections, occur
very early in the connection process (even before an IP address is
known), or are not specific to any particular IP address (such as
out-of-memory conditions).


File: manual.info,  Node: thread-information,  Prev: optimizing-the-server,  Up: optimization

8.10 Examining Thread Information
=================================

* Menu:

* thread-commands::              Thread Command Values
* general-thread-states::        General Thread States
* delayed-insert-thread-states::  Delayed-Insert Thread States
* query-cache-thread-states::    Query Cache Thread States
* master-thread-states::         Replication Master Thread States
* slave-io-thread-states::       Replication Slave I/O Thread States
* slave-sql-thread-states::      Replication Slave SQL Thread States
* slave-connection-thread-states::  Replication Slave Connection Thread States
* mysql-cluster-thread-states::  MySQL Cluster Thread States
* event-scheduler-thread-states::  Event Scheduler Thread States

When you are attempting to ascertain what your MySQL server is doing,
it can be helpful to examine the process list, which is the set of
threads currently executing within the server. Process list information
is available from these sources:

   * The `SHOW [FULL] PROCESSLIST' statement: *Note show-processlist::

   * The *Note `SHOW PROFILE': show-profile. statement: *Note
     show-profiles::

   * The `INFORMATION_SCHEMA' *Note `PROCESSLIST': processlist-table.
     table: *Note processlist-table::

   * The *Note `mysqladmin processlist': mysqladmin. command: *Note
     mysqladmin::

You can always view information about your own threads. To view
information about threads being executed for other accounts, you must
have the `PROCESS' privilege.

Each process list entry contains several pieces of information:

   * `Id' is the connection identifier for the client associated with
     the thread.

   * `User' and `Host' indicate the account associated with the thread.

   * `db' is the default database for the thread, or `NULL' if none is
     selected.

   * `Command' and `State' indicate what the thread is doing.

     Most states correspond to very quick operations. If a thread stays
     in a given state for many seconds, there might be a problem that
     needs to be investigated.

   * `Time' indicates how long the thread has been in its current
     state. The thread's notion of the current time may be altered in
     some cases: The thread can change the time with *Note `SET
     TIMESTAMP = VALUE': set-statement. For a thread running on a slave
     that is processing events from the master, the thread time is set
     to the time found in the events and thus reflects current time on
     the master and not the slave.

   * `Info' contains the text of the statement being executed by the
     thread, or `NULL' if it is not executing one. By default, this
     value contains only the first 100 characters of the statement. To
     see the complete statements, use *Note `SHOW FULL PROCESSLIST':
     show-processlist.

The following sections list the possible `Command' values, and `State'
values grouped by category. The meaning for some of these values is
self-evident. For others, additional description is provided.


File: manual.info,  Node: thread-commands,  Next: general-thread-states,  Prev: thread-information,  Up: thread-information

8.10.1 Thread Command Values
----------------------------

A thread can have any of the following `Command' values:

   * `Binlog Dump'

     This is a thread on a master server for sending binary log
     contents to a slave server.

   * `Change user'

     The thread is executing a change-user operation.

   * `Close stmt'

     The thread is closing a prepared statement.

   * `Connect'

     A replication slave is connected to its master.

   * `Connect Out'

     A replication slave is connecting to its master.

   * `Create DB'

     The thread is executing a create-database operation.

   * `Daemon'

     This thread is internal to the server, not a thread that services
     a client connection.

   * `Debug'

     The thread is generating debugging information.

   * `Delayed insert'

     The thread is a delayed-insert handler.

   * `Drop DB'

     The thread is executing a drop-database operation.

   * `Error'

   * `Execute'

     The thread is executing a prepared statement.

   * `Fetch'

     The thread is fetching the results from executing a prepared
     statement.

   * `Field List'

     The thread is retrieving information for table columns.

   * `Init DB'

     The thread is selecting a default database.

   * `Kill'

     The thread is killing another thread.

   * `Long Data'

     The thread is retrieving long data in the result of executing a
     prepared statement.

   * `Ping'

     The thread is handling a server-ping request.

   * `Prepare'

     The thread is preparing a prepared statement.

   * `Processlist'

     The thread is producing information about server threads.

   * `Query'

     The thread is executing a statement.

   * `Quit'

     The thread is terminating.

   * `Refresh'

     The thread is flushing table, logs, or caches, or resetting status
     variable or replication server information.

   * `Register Slave'

     The thread is registering a slave server.

   * `Reset stmt'

     The thread is resetting a prepared statement.

   * `Set option'

     The thread is setting or resetting a client statement-execution
     option.

   * `Shutdown'

     The thread is shutting down the server.

   * `Sleep'

     The thread is waiting for the client to send a new statement to it.

   * `Statistics'

     The thread is producing server-status information.

   * `Table Dump'

     The thread is sending table contents to a slave server.

   * `Time'

     Unused.


File: manual.info,  Node: general-thread-states,  Next: delayed-insert-thread-states,  Prev: thread-commands,  Up: thread-information

8.10.2 General Thread States
----------------------------

The following list describes thread `State' values that are associated
with general query processing and not more specialized activities such
as replication. Many of these are useful only for finding bugs in the
server.

   * `After create'

     This occurs when the thread creates a table (including internal
     temporary tables), at the end of the function that creates the
     table. This state is used even if the table could not be created
     due to some error.

   * `Analyzing'

     The thread is calculating a `MyISAM' table key distributions (for
     example, for *Note `ANALYZE TABLE': analyze-table.).

   * `checking permissions'

     The thread is checking whether the server has the required
     privileges to execute the statement.

   * `Checking table'

     The thread is performing a table check operation.

   * `cleaning up'

     The thread has processed one command and is preparing to free
     memory and reset certain state variables.

   * `closing tables'

     The thread is flushing the changed table data to disk and closing
     the used tables. This should be a fast operation. If not, you
     should verify that you do not have a full disk and that the disk
     is not in very heavy use.

   * `converting HEAP to MyISAM'

     The thread is converting an internal temporary table from a
     `MEMORY' table to an on-disk `MyISAM' table.

   * `copy to tmp table'

     The thread is processing an *Note `ALTER TABLE': alter-table.
     statement. This state occurs after the table with the new
     structure has been created but before rows are copied into it.

   * `Copying to group table'

     If a statement has different `ORDER BY' and `GROUP BY' criteria,
     the rows are sorted by group and copied to a temporary table.

   * `Copying to tmp table'

     The server is copying to a temporary table in memory.

   * `Copying to tmp table on disk'

     The server is copying to a temporary table on disk. The temporary
     result set has become too large (see *Note
     internal-temporary-tables::). Consequently, the thread is changing
     the temporary table from in-memory to disk-based format to save
     memory.

   * `Creating index'

     The thread is processing `ALTER TABLE ... ENABLE KEYS' for a
     `MyISAM' table.

   * `Creating sort index'

     The thread is processing a *Note `SELECT': select. that is
     resolved using an internal temporary table.

   * `creating table'

     The thread is creating a table. This includes creation of
     temporary tables.

   * `Creating tmp table'

     The thread is creating a temporary table in memory or on disk. If
     the table is created in memory but later is converted to an
     on-disk table, the state during that operation will be `Copying to
     tmp table on disk'.

   * `deleting from main table'

     The server is executing the first part of a multiple-table delete.
     It is deleting only from the first table, and saving columns and
     offsets to be used for deleting from the other (reference) tables.

   * `deleting from reference tables'

     The server is executing the second part of a multiple-table delete
     and deleting the matched rows from the other tables.

   * `discard_or_import_tablespace'

     The thread is processing an `ALTER TABLE ... DISCARD TABLESPACE'
     or `ALTER TABLE ... IMPORT TABLESPACE' statement.

   * `end'

     This occurs at the end but before the cleanup of *Note `ALTER
     TABLE': alter-table, *Note `CREATE VIEW': create-view, *Note
     `DELETE': delete, *Note `INSERT': insert, *Note `SELECT': select,
     or *Note `UPDATE': update. statements.

   * `executing'

     The thread has begun executing a statement.

   * `Execution of init_command'

     The thread is executing statements in the value of the
     `init_command' system variable.

   * `freeing items'

     The thread has executed a command. Some freeing of items done
     during this state involves the query cache. This state is usually
     followed by `cleaning up'.

   * `Flushing tables'

     The thread is executing *Note `FLUSH TABLES': flush. and is
     waiting for all threads to close their tables.

   * `FULLTEXT initialization'

     The server is preparing to perform a natural-language full-text
     search.

   * `init'

     This occurs before the initialization of *Note `ALTER TABLE':
     alter-table, *Note `DELETE': delete, *Note `INSERT': insert, *Note
     `SELECT': select, or *Note `UPDATE': update. statements. Actions
     taken by the server in this state include flushing the binary log,
     the `InnoDB' log, and some query cache cleanup operations.

     For the `end' state, the following operations could be happening:

        * Removing query cache entries after data in a table is changed

        * Writing an event to the binary log

        * Freeing memory buffers, including for blobs

   * `Killed'

     Someone has sent a *Note `KILL': kill.  statement to the thread
     and it should abort next time it checks the kill flag. The flag is
     checked in each major loop in MySQL, but in some cases it might
     still take a short time for the thread to die. If the thread is
     locked by some other thread, the kill takes effect as soon as the
     other thread releases its lock.

   * `Locked'

     The query is locked by another query.

   * `logging slow query'

     The thread is writing a statement to the slow-query log.

   * `NULL'

     This state is used for the *Note `SHOW PROCESSLIST':
     show-processlist. state.

   * `login'

     The initial state for a connection thread until the client has
     been authenticated successfully.

   * `manage keys'

     The server is enabling or disabling a table index.

   * `Opening tables', `Opening table'

     The thread is trying to open a table. This is should be very fast
     procedure, unless something prevents opening. For example, an
     *Note `ALTER TABLE': alter-table. or a *Note `LOCK TABLE':
     lock-tables. statement can prevent opening a table until the
     statement is finished. It is also worth checking that your
     `table_open_cache' value is large enough.

   * `optimizing'

     The server is performing initial optimizations for a query.

   * `preparing'

     This state occurs during query optimization.

   * `Purging old relay logs'

     The thread is removing unneeded relay log files.

   * `query end'

     This state occurs after processing a query but before the `freeing
     items' state.

   * `Reading from net'

     The server is reading a packet from the network.

   * `Removing duplicates'

     The query was using *Note `SELECT DISTINCT': select. in such a way
     that MySQL could not optimize away the distinct operation at an
     early stage.  Because of this, MySQL requires an extra stage to
     remove all duplicated rows before sending the result to the client.

   * `removing tmp table'

     The thread is removing an internal temporary table after
     processing a *Note `SELECT': select.  statement. This state is not
     used if no temporary table was created.

   * `rename'

     The thread is renaming a table.

   * `rename result table'

     The thread is processing an *Note `ALTER TABLE': alter-table.
     statement, has created the new table, and is renaming it to
     replace the original table.

   * `Reopen tables'

     The thread got a lock for the table, but noticed after getting the
     lock that the underlying table structure changed. It has freed the
     lock, closed the table, and is trying to reopen it.

   * `Repair by sorting'

     The repair code is using a sort to create indexes.

   * `Repair done'

     The thread has completed a multi-threaded repair for a `MyISAM'
     table.

   * `Repair with keycache'

     The repair code is using creating keys one by one through the key
     cache. This is much slower than `Repair by sorting'.

   * `Rolling back'

     The thread is rolling back a transaction.

   * `Saving state'

     For `MyISAM' table operations such as repair or analysis, the
     thread is saving the new table state to the `.MYI' file header.
     State includes information such as number of rows, the
     `AUTO_INCREMENT' counter, and key distributions.

   * `Searching rows for update'

     The thread is doing a first phase to find all matching rows before
     updating them. This has to be done if the *Note `UPDATE': update.
     is changing the index that is used to find the involved rows.

   * `Sending data'

     The thread is reading and processing rows for a *Note `SELECT':
     select. statement, and sending data to the client. Because
     operations occurring during this state tend to perform large
     amounts of disk access (reads), it is often the longest-running
     state over the lifetime of a given query.

   * `setup'

     The thread is beginning an *Note `ALTER TABLE': alter-table.
     operation.

   * `Sorting for group'

     The thread is doing a sort to satisfy a `GROUP BY'.

   * `Sorting for order'

     The thread is doing a sort to satisfy a `ORDER BY'.

   * `Sorting index'

     The thread is sorting index pages for more efficient access during
     a `MyISAM' table optimization operation.

   * `Sorting result'

     For a *Note `SELECT': select. statement, this is similar to
     `Creating sort index', but for nontemporary tables.

   * `statistics'

     The server is calculating statistics to develop a query execution
     plan. If a thread is in this state for a long time, the server is
     probably disk-bound performing other work.

   * `System lock'

     The thread is going to request or is waiting for an internal or
     external system lock for the table. If this state is being caused
     by requests for external locks and you are not using multiple
     *Note `mysqld': mysqld. servers that are accessing the same *Note
     `MyISAM': myisam-storage-engine.  tables, you can disable external
     system locks with the `--skip-external-locking' option. However,
     external locking is disabled by default, so it is likely that this
     option will have no effect.

   * `Table lock'

     The next thread state after `System lock'.  The thread has
     acquired an external lock and is going to request an internal
     table lock.

   * `update'

     The thread is getting ready to start updating the table.

   * `Updating'

     The thread is searching for rows to update and is updating them.

   * `updating main table'

     The server is executing the first part of a multiple-table update.
     It is updating only the first table, and saving columns and
     offsets to be used for updating the other (reference) tables.

   * `updating reference tables'

     The server is executing the second part of a multiple-table update
     and updating the matched rows from the other tables.

   * `User lock'

     The thread is going to request or is waiting for an advisory lock
     requested with a `GET_LOCK()' call. For *Note `SHOW PROFILE':
     show-profile, this state means the thread is requesting the lock
     (not waiting for it).

   * `User sleep'

     The thread has invoked a `SLEEP()' call.

   * `Waiting for release of readlock'

     The thread is waiting for a global read lock obtained by another
     thread (with *Note `FLUSH TABLES WITH READ LOCK': flush.) to be
     released.

   * `Waiting for tables', `Waiting for table'

     The thread got a notification that the underlying structure for a
     table has changed and it needs to reopen the table to get the new
     structure. However, to reopen the table, it must wait until all
     other threads have closed the table in question.

     This notification takes place if another thread has used *Note
     `FLUSH TABLES': flush. or one of the following statements on the
     table in question: `FLUSH TABLES TBL_NAME', *Note `ALTER TABLE':
     alter-table, *Note `RENAME TABLE': rename-table, *Note `REPAIR
     TABLE': repair-table, *Note `ANALYZE TABLE': analyze-table, or
     *Note `OPTIMIZE TABLE': optimize-table.

   * `Waiting on cond'

     A generic state in which the thread is waiting for a condition to
     become true. No specific state information is available.

   * `Waiting to get readlock'

     The thread has issued a *Note `FLUSH TABLES WITH READ LOCK':
     flush. statement to obtain a global read lock and is waiting to
     obtain the lock.

   * `Writing to net'

     The server is writing a packet to the network.


File: manual.info,  Node: delayed-insert-thread-states,  Next: query-cache-thread-states,  Prev: general-thread-states,  Up: thread-information

8.10.3 Delayed-Insert Thread States
-----------------------------------

These thread states are associated with processing for `DELAYED'
inserts (see *Note insert-delayed::). Some states are associated with
connection threads that process *Note `INSERT DELAYED': insert-delayed.
statements from clients. Other states are associated with
delayed-insert handler threads that insert the rows. There is a
delayed-insert handler thread for each table for which *Note `INSERT
DELAYED': insert-delayed.  statements are issued.

States associated with a connection thread that processes an *Note
`INSERT DELAYED': insert-delayed. statement from the client:

   * `allocating local table'

     The thread is preparing to feed rows to the delayed-insert handler
     thread.

   * `Creating delayed handler'

     The thread is creating a handler for `DELAYED' inserts.

   * `got handler lock'

     This occurs before the `allocating local table' state and after
     the `waiting for handler lock' state, when the connection thread
     gets access to the delayed-insert handler thread.

   * `got old table'

     This occurs after the `waiting for handler open' state. The
     delayed-insert handler thread has signaled that it has ended its
     initialization phase, which includes opening the table for delayed
     inserts.

   * `storing row into queue'

     The thread is adding a new row to the list of rows that the
     delayed-insert handler thread must insert.

   * `waiting for delay_list'

     This occurs during the initialization phase when the thread is
     trying to find the delayed-insert handler thread for the table,
     and before attempting to gain access to the list of delayed-insert
     threads.

   * `waiting for handler insert'

     An *Note `INSERT DELAYED': insert-delayed. handler has processed
     all pending inserts and is waiting for new ones.

   * `waiting for handler lock'

     This occurs before the `allocating local table' state when the
     connection thread waits for access to the delayed-insert handler
     thread.

   * `waiting for handler open'

     This occurs after the `Creating delayed handler' state and before
     the `got old table' state. The delayed-insert handler thread has
     just been started, and the connection thread is waiting for it to
     initialize.

States associated with a delayed-insert handler thread that inserts the
rows:

   * `insert'

     The state that occurs just before inserting rows into the table.

   * `reschedule'

     After inserting a number of rows, the delayed-insert thread sleeps
     to let other threads do work.

   * `upgrading lock'

     A delayed-insert handler is trying to get a lock for the table to
     insert rows.

   * `Waiting for INSERT'

     A delayed-insert handler is waiting for a connection thread to add
     rows to the queue (see `storing row into queue').


File: manual.info,  Node: query-cache-thread-states,  Next: master-thread-states,  Prev: delayed-insert-thread-states,  Up: thread-information

8.10.4 Query Cache Thread States
--------------------------------

These thread states are associated with the query cache (see *Note
query-cache::).

   * `checking privileges on cached query'

     The server is checking whether the user has privileges to access a
     cached query result.

   * `checking query cache for query'

     The server is checking whether the current query is present in the
     query cache.

   * `invalidating query cache entries'

     Query cache entries are being marked invalid because the
     underlying tables have changed.

   * `sending cached result to client'

     The server is taking the result of a query from the query cache
     and sending it to the client.

   * `storing result in query cache'

     The server is storing the result of a query in the query cache.


File: manual.info,  Node: master-thread-states,  Next: slave-io-thread-states,  Prev: query-cache-thread-states,  Up: thread-information

8.10.5 Replication Master Thread States
---------------------------------------

The following list shows the most common states you may see in the
`State' column for the master's `Binlog Dump' thread. If you see no
`Binlog Dump' threads on a master server, this means that replication
is not running--that is, that no slaves are currently connected.

   * `Sending binlog event to slave'

     Binary logs consist of _events_, where an event is usually an
     update plus some other information. The thread has read an event
     from the binary log and is now sending it to the slave.

   * `Finished reading one binlog; switching to next binlog'

     The thread has finished reading a binary log file and is opening
     the next one to send to the slave.

   * `Has sent all binlog to slave; waiting for binlog to be updated'

     The thread has read all outstanding updates from the binary logs
     and sent them to the slave. The thread is now idle, waiting for
     new events to appear in the binary log resulting from new updates
     occurring on the master.

   * `Waiting to finalize termination'

     A very brief state that occurs as the thread is stopping.


File: manual.info,  Node: slave-io-thread-states,  Next: slave-sql-thread-states,  Prev: master-thread-states,  Up: thread-information

8.10.6 Replication Slave I/O Thread States
------------------------------------------

The following list shows the most common states you see in the `State'
column for a slave server I/O thread.  This state also appears in the
`Slave_IO_State' column displayed by *Note `SHOW SLAVE STATUS':
show-slave-status, so you can get a good view of what is happening by
using that statement.

   * `Waiting for master update'

     The initial state before `Connecting to master'.

   * `Connecting to master'

     The thread is attempting to connect to the master.

   * `Checking master version'

     A state that occurs very briefly, after the connection to the
     master is established.

   * `Registering slave on master'

     A state that occurs very briefly after the connection to the
     master is established.

   * `Requesting binlog dump'

     A state that occurs very briefly, after the connection to the
     master is established. The thread sends to the master a request
     for the contents of its binary logs, starting from the requested
     binary log file name and position.

   * `Waiting to reconnect after a failed binlog dump request'

     If the binary log dump request failed (due to disconnection), the
     thread goes into this state while it sleeps, then tries to
     reconnect periodically. The interval between retries can be
     specified using the *Note `CHANGE MASTER TO': change-master-to.
     statement or the `--master-connect-retry' option.

   * `Reconnecting after a failed binlog dump request'

     The thread is trying to reconnect to the master.

   * `Waiting for master to send event'

     The thread has connected to the master and is waiting for binary
     log events to arrive. This can last for a long time if the master
     is idle. If the wait lasts for `slave_net_timeout' seconds, a
     timeout occurs. At that point, the thread considers the connection
     to be broken and makes an attempt to reconnect.

   * `Queueing master event to the relay log'

     The thread has read an event and is copying it to the relay log so
     that the SQL thread can process it.

   * `Waiting to reconnect after a failed master event read'

     An error occurred while reading (due to disconnection). The thread
     is sleeping for the number of seconds set by the *Note `CHANGE
     MASTER TO': change-master-to. statement or
     `--master-connect-retry' option (default 60) before attempting to
     reconnect.

   * `Reconnecting after a failed master event read'

     The thread is trying to reconnect to the master. When connection
     is established again, the state becomes `Waiting for master to
     send event'.

   * `Waiting for the slave SQL thread to free enough relay log space'

     You are using a nonzero `relay_log_space_limit' value, and the
     relay logs have grown large enough that their combined size
     exceeds this value. The I/O thread is waiting until the SQL thread
     frees enough space by processing relay log contents so that it can
     delete some relay log files.

   * `Waiting for slave mutex on exit'

     A state that occurs briefly as the thread is stopping.


File: manual.info,  Node: slave-sql-thread-states,  Next: slave-connection-thread-states,  Prev: slave-io-thread-states,  Up: thread-information

8.10.7 Replication Slave SQL Thread States
------------------------------------------

The following list shows the most common states you may see in the
`State' column for a slave server SQL thread:

   * `Waiting for the next event in relay log'

     The initial state before `Reading event from the relay log'.

   * `Reading event from the relay log'

     The thread has read an event from the relay log so that the event
     can be processed.

   * `Has read all relay log; waiting for the slave I/O thread to
     update it'

     The thread has processed all events in the relay log files, and is
     now waiting for the I/O thread to write new events to the relay
     log.

   * `Making temp file'

     The thread is executing a *Note `LOAD DATA INFILE': load-data.
     statement and is creating a temporary file containing the data
     from which the slave will read rows.

   * `Waiting for slave mutex on exit'

     A very brief state that occurs as the thread is stopping.

The `State' column for the I/O thread may also show the text of a
statement. This indicates that the thread has read an event from the
relay log, extracted the statement from it, and is executing it.


File: manual.info,  Node: slave-connection-thread-states,  Next: mysql-cluster-thread-states,  Prev: slave-sql-thread-states,  Up: thread-information

8.10.8 Replication Slave Connection Thread States
-------------------------------------------------

These thread states occur on a replication slave but are associated
with connection threads, not with the I/O or SQL threads.

   * `Changing master'

     The thread is processing a *Note `CHANGE MASTER TO':
     change-master-to. statement.

   * `Creating table from master dump'

     The slave is creating a table using the *Note `CREATE TABLE':
     create-table. statement contained in the dump from the master.
     Used for *Note `LOAD TABLE FROM MASTER': load-table-from-master.
     and *Note `LOAD DATA FROM MASTER': load-data-from-master.

   * `Killing slave'

     The thread is processing a `STOP SLAVE' statement.

   * `Opening master dump table'

     This state occurs after `Creating table from master dump'.

   * `Reading master dump table data'

     This state occurs after `Opening master dump table'.

   * `Rebuilding the index on master dump table'

     This state occurs after `Reading master dump table data'.

   * `starting slave'

     The thread is starting the slave threads after processing a
     successful *Note `LOAD DATA FROM MASTER': load-data-from-master.
     load operation.


File: manual.info,  Node: mysql-cluster-thread-states,  Next: event-scheduler-thread-states,  Prev: slave-connection-thread-states,  Up: thread-information

8.10.9 MySQL Cluster Thread States
----------------------------------

   * `Committing events to binlog'

   * `Opening mysql.ndb_apply_status'

   * `Processing events'

     The thread is processing events for binary logging.

   * `Processing events from schema table'

     The thread is doing the work of schema replication.

   * `Shutting down'

   * `Syncing ndb table schema operation and binlog'

     This is used to have a correct binary log of schema operations for
     NDB.

   * `Waiting for event from ndbcluster'

     The server is acting as an SQL node in a MySQL Cluster, and is
     connected to a cluster management node.

   * `Waiting for first event from ndbcluster'

   * `Waiting for ndbcluster binlog update to reach current position'

   * `Waiting for ndbcluster to start'

   * `Waiting for schema epoch'

     The thread is waiting for a schema epoch (that is, a global
     checkpoint).


File: manual.info,  Node: event-scheduler-thread-states,  Prev: mysql-cluster-thread-states,  Up: thread-information

8.10.10 Event Scheduler Thread States
-------------------------------------

These states occur for the Event Scheduler thread, threads that are
created to execute scheduled events, or threads that terminate the
scheduler.

   * `Clearing'

     The scheduler thread or a thread that was executing an event is
     terminating and is about to end.

   * `Initialized'

     The scheduler thread or a thread that will execute an event has
     been initialized.

   * `Waiting for next activation'

     The scheduler has a nonempty event queue but the next activation
     is in the future.

   * `Waiting for scheduler to stop'

     The thread issued `SET GLOBAL event_scheduler=OFF' and is waiting
     for the scheduler to stop.

   * `Waiting on empty queue'

     The scheduler's event queue is empty and it is sleeping.


File: manual.info,  Node: language-structure,  Next: globalization,  Prev: optimization,  Up: Top

9 Language Structure
********************

* Menu:

* literals::                     Literal Values
* identifiers::                  Schema Object Names
* reserved-words::               Reserved Words
* user-variables::               User-Defined Variables
* expressions::                  Expression Syntax
* comments::                     Comment Syntax

This chapter discusses the rules for writing the following elements of
SQL (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_sql)
statements when using MySQL:

   * Literal values such as strings and numbers

   * Identifiers such as database, table, and column names

   * Reserved words

   * User-defined and system variables

   * Comments


File: manual.info,  Node: literals,  Next: identifiers,  Prev: language-structure,  Up: language-structure

9.1 Literal Values
==================

* Menu:

* string-literals::              String Literals
* number-literals::              Number Literals
* date-and-time-literals::       Date and Time Literals
* hexadecimal-literals::         Hexadecimal Literals
* boolean-literals::             Boolean Literals
* bit-field-literals::           Bit-Field Literals
* null-values::                  NULL Values

This section describes how to write literal values in MySQL. These
include strings, numbers, hexadecimal values, boolean values, and
`NULL'. The section also covers the various nuances and `gotchas' that
you may run into when dealing with these basic types in MySQL.


File: manual.info,  Node: string-literals,  Next: number-literals,  Prev: literals,  Up: literals

9.1.1 String Literals
---------------------

A string is a sequence of bytes or characters, enclosed within either
single quote (``''') or double quote (``"'') characters.  Examples:


     'a string'
     "another string"

Quoted strings placed next to each other are concatenated to a single
string. The following lines are equivalent:


     'a string'
     'a' ' ' 'string'

If the `ANSI_QUOTES' SQL mode is enabled, string literals can be quoted
only within single quotation marks because a string quoted within
double quotation marks is interpreted as an identifier.

A _binary string_ is a string of bytes that has no character set or
collation. A _nonbinary string_ is a string of characters that has a
character set and collation. For both types of strings, comparisons are
based on the numeric values of the string unit.  For binary strings,
the unit is the byte. For nonbinary strings the unit is the character
and some character sets support multibyte characters. Character value
ordering is a function of the string collation.

String literals may have an optional character set introducer and
`COLLATE' clause:


     [_CHARSET_NAME]'STRING' [COLLATE COLLATION_NAME]

Examples:


     SELECT _latin1'STRING';
     SELECT _latin1'STRING' COLLATE latin1_danish_ci;

You can use `N'LITERAL'' (or `n'LITERAL'') to create a string in the
national character set. These statements are equivalent:


     SELECT N'some text';
     SELECT n'some text';
     SELECT _utf8'some text';

For more information about these forms of string syntax, see *Note
charset-literal::, and *Note charset-national::.

Within a string, certain sequences have special meaning unless the
`NO_BACKSLASH_ESCAPES' SQL mode is enabled. Each of these sequences
begins with a backslash (``\''), known as the _escape character_. MySQL
recognizes the escape sequences shown in *Note
character-escape-sequences::. For all other escape sequences, backslash
is ignored. That is, the escaped character is interpreted as if it was
not escaped. For example, ``\x'' is just ``x''. These sequences are case
sensitive. For example, ``\b'' is interpreted as a backspace, but
``\B'' is interpreted as ``B''. Escape processing is done according to
the character set indicated by the `character_set_connection' system
variable. This is true even for strings that are preceded by an
introducer that indicates a different character set, as discussed in
*Note charset-literal::.

*Special Character Escape Sequences*

Escape      Character Represented by Sequence
Sequence    
`\0'        An ASCII NUL (`0x00') character.
`\''        A single quote (``''') character.
`\"'        A double quote (``"'') character.
`\b'        A backspace character.
`\n'        A newline (linefeed) character.
`\r'        A carriage return character.
`\t'        A tab character.
`\Z'        ASCII 26 (Control+Z). See note following the table.
`\\'        A backslash (``\'') character.
`\%'        A ``%'' character. See note following the table.
`\_'        A ``_'' character. See note following the table.

The ASCII 26 character can be encoded as ``\Z'' to enable you to work
around the problem that ASCII 26 stands for END-OF-FILE on Windows.
ASCII 26 within a file causes problems if you try to use `mysql DB_NAME
< FILE_NAME'.

The ``\%'' and ``\_'' sequences are used to search for literal
instances of ``%'' and ``_'' in pattern-matching contexts where they
would otherwise be interpreted as wildcard characters. See the
description of the `LIKE' operator in *Note
string-comparison-functions::. If you use ``\%'' or ``\_'' outside of
pattern-matching contexts, they evaluate to the strings ``\%'' and
``\_'', not to ``%'' and ``_''.

There are several ways to include quote characters within a string:

   * A ``''' inside a string quoted with ``''' may be written as ``''''.

   * A ``"'' inside a string quoted with ``"'' may be written as ``""''.

   * Precede the quote character by an escape character (``\'').

   * A ``''' inside a string quoted with ``"'' needs no special
     treatment and need not be doubled or escaped. In the same way,
     ``"'' inside a string quoted with ``''' needs no special treatment.

The following *Note `SELECT': select. statements demonstrate how
quoting and escaping work:


     mysql> SELECT 'hello', '"hello"', '""hello""', 'hel''lo', '\'hello';
     +-------+---------+-----------+--------+--------+
     | hello | "hello" | ""hello"" | hel'lo | 'hello |
     +-------+---------+-----------+--------+--------+

     mysql> SELECT "hello", "'hello'", "''hello''", "hel""lo", "\"hello";
     +-------+---------+-----------+--------+--------+
     | hello | 'hello' | ''hello'' | hel"lo | "hello |
     +-------+---------+-----------+--------+--------+

     mysql> SELECT 'This\nIs\nFour\nLines';
     +--------------------+
     | This
     Is
     Four
     Lines |
     +--------------------+

     mysql> SELECT 'disappearing\ backslash';
     +------------------------+
     | disappearing backslash |
     +------------------------+

If you want to insert binary data into a string column (such as a *Note
`BLOB': blob. column), you should represent certain characters by
escape sequences. Backslash (``\'') and the quote character used to
quote the string must be escaped. In certain client environments, it
may also be necessary to escape `NUL' or Control+Z. The *Note `mysql':
mysql. client truncates quoted strings containing `NUL' characters if
they are not escaped, and Control+Z may be taken for END-OF-FILE on
Windows if not escaped. For the escape sequences that represent each of
these characters, see *Note character-escape-sequences::.

When writing application programs, any string that might contain any of
these special characters must be properly escaped before the string is
used as a data value in an SQL statement that is sent to the MySQL
server. You can do this in two ways:

   * Process the string with a function that escapes the special
     characters. In a C program, you can use the *Note
     `mysql_real_escape_string()': mysql-real-escape-string. C API
     function to escape characters. See *Note
     mysql-real-escape-string::. Within SQL statements that construct
     other SQL statements, you can use the `QUOTE()' function. The Perl
     DBI interface provides a `quote' method to convert special
     characters to the proper escape sequences. See *Note apis-perl::.
     Other language interfaces may provide a similar capability.

   * As an alternative to explicitly escaping special characters, many
     MySQL APIs provide a placeholder capability that enables you to
     insert special markers into a statement string, and then bind data
     values to them when you issue the statement. In this case, the API
     takes care of escaping special characters in the values for you.


File: manual.info,  Node: number-literals,  Next: date-and-time-literals,  Prev: string-literals,  Up: literals

9.1.2 Number Literals
---------------------

Number literals include exact-value (integer and *Note `DECIMAL':
fixed-point-types.) literals and approximate-value (floating-point)
literals.

Integers are represented as a sequence of digits. Numbers may include
``.'' as a decimal separator. Numbers may be preceded by ``-'' or ``+''
to indicate a negative or positive value, respectively. Numbers
represented in scientific notation with a mantissa and exponent are
approximate-value numbers.

Exact-value numeric literals have an integer part or fractional part,
or both. They may be signed. Examples: `1', `.2', `3.4', `-5', `-6.78',
`+9.10'.

Approximate-value numeric literals are represented in scientific
notation with a mantissa and exponent. Either or both parts may be
signed. Examples: `1.2E3', `1.2E-3', `-1.2E3', `-1.2E-3'.

Two numbers that look similar may be treated differently. For example,
`2.34' is an exact-value (fixed-point) number, whereas `2.34E0' is an
approximate-value (floating-point) number.

The *Note `DECIMAL': fixed-point-types. data type is a fixed-point type
and calculations are exact. In MySQL, the *Note `DECIMAL':
fixed-point-types. type has several synonyms: *Note `NUMERIC':
fixed-point-types, *Note `DEC': fixed-point-types, *Note `FIXED':
fixed-point-types. The integer types also are exact-value types. For
more information about exact-value calculations, see *Note
precision-math::.

The *Note `FLOAT': floating-point-types. and *Note `DOUBLE':
floating-point-types. data types are floating-point types and
calculations are approximate. In MySQL, types that are synonymous with
*Note `FLOAT': floating-point-types. or *Note `DOUBLE':
floating-point-types. are *Note `DOUBLE PRECISION':
floating-point-types. and *Note `REAL': floating-point-types.

An integer may be used in a floating-point context; it is interpreted
as the equivalent floating-point number.


File: manual.info,  Node: date-and-time-literals,  Next: hexadecimal-literals,  Prev: number-literals,  Up: literals

9.1.3 Date and Time Literals
----------------------------

Date and time values can be represented in several formats, such as
quoted strings or as numbers, depending on the exact type of the value
and other factors. For example, in contexts where MySQL expects a date,
it interprets any of `'2015-07-21'', `'20150721'', and `20150721' as a
date.

This section describes the acceptable formats for date and time
literals. For more information about the temporal data types, such as
the range of permitted values, consult these sections:

   * *Note date-and-time-type-overview::

   * *Note date-and-time-types::

Standard SQL and ODBC Date and Time Literals

Standard SQL permits temporal literals to be specified using a type
keyword and a string. The space between the keyword and string is
optional.


     DATE 'STR'
     TIME 'STR'
     TIMESTAMP 'STR'

MySQL recognizes those constructions and also the corresponding ODBC
syntax:


     { d 'STR' }
     { t 'STR' }
     { ts 'STR' }

However, MySQL ignores the type keyword and each of the preceding
constructions produces the string value `'STR'', with a type of *Note
`VARCHAR': char.

String and Numeric Literals in Date and Time Context

MySQL recognizes *Note `DATE': datetime. values in these formats:

   * As a string in either `'YYYY-MM-DD'' or `'YY-MM-DD'' format. A
     `relaxed' syntax is permitted: Any punctuation character may be
     used as the delimiter between date parts.  For example,
     `'2012-12-31'', `'2012/12/31'', `'2012^12^31'', and `'2012@12@31''
     are equivalent.

   * As a string with no delimiters in either `'YYYYMMDD'' or `'YYMMDD''
     format, provided that the string makes sense as a date. For
     example, `'20070523'' and `'070523'' are interpreted as
     `'2007-05-23'', but `'071332'' is illegal (it has nonsensical
     month and day parts) and becomes `'0000-00-00''.

   * As a number in either `YYYYMMDD' or `YYMMDD' format, provided that
     the number makes sense as a date. For example, `19830905' and
     `830905' are interpreted as `'1983-09-05''.

MySQL recognizes *Note `DATETIME': datetime. and *Note `TIMESTAMP':
datetime. values in these formats:

   * As a string in either `'YYYY-MM-DD HH:MM:SS'' or `'YY-MM-DD
     HH:MM:SS'' format. A `relaxed' syntax is permitted here, too: Any
     punctuation character may be used as the delimiter between date
     parts or time parts. For example, `'2012-12-31 11:30:45'',
     `'2012^12^31 11+30+45'', `'2012/12/31 11*30*45'', and `'2012@12@31
     11^30^45'' are equivalent.

     The date and time parts can be separated by `T' rather than a
     space. For example, `'2012-12-31 11:30:45''
     `'2012-12-31T11:30:45'' are equivalent.

   * As a string with no delimiters in either `'YYYYMMDDHHMMSS'' or
     `'YYMMDDHHMMSS'' format, provided that the string makes sense as a
     date. For example, `'20070523091528'' and `'070523091528'' are
     interpreted as `'2007-05-23 09:15:28'', but `'071122129015'' is
     illegal (it has a nonsensical minute part) and becomes `'0000-00-00
     00:00:00''.

   * As a number in either `YYYYMMDDHHMMSS' or `YYMMDDHHMMSS' format,
     provided that the number makes sense as a date. For example,
     `19830905132800' and `830905132800' are interpreted as
     `'1983-09-05 13:28:00''.

A *Note `DATETIME': datetime. or *Note `TIMESTAMP': datetime. value can
include a trailing fractional seconds part in up to microseconds (6
digits) precision. Although this fractional part is recognized, it is
discarded from values stored into *Note `DATETIME': datetime. or *Note
`TIMESTAMP': datetime. columns. For information about fractional
seconds support in MySQL, see *Note fractional-seconds::.

Dates containing two-digit year values are ambiguous because the
century is unknown. MySQL interprets two-digit year values using these
rules:

   * Year values in the range `70-99' are converted to `1970-1999'.

   * Year values in the range `00-69' are converted to `2000-2069'.

See also *Note two-digit-years::.

For values specified as strings that include date part delimiters, it
is unnecessary to specify two digits for month or day values that are
less than `10'.  `'2015-6-9'' is the same as `'2015-06-09''. Similarly,
for values specified as strings that include time part delimiters, it
is unnecessary to specify two digits for hour, minute, or second values
that are less than `10'. `'2015-10-30 1:2:3'' is the same as
`'2015-10-30 01:02:03''.

Values specified as numbers should be 6, 8, 12, or 14 digits long. If a
number is 8 or 14 digits long, it is assumed to be in `YYYYMMDD' or
`YYYYMMDDHHMMSS' format and that the year is given by the first 4
digits. If the number is 6 or 12 digits long, it is assumed to be in
`YYMMDD' or `YYMMDDHHMMSS' format and that the year is given by the
first 2 digits. Numbers that are not one of these lengths are
interpreted as though padded with leading zeros to the closest length.

Values specified as nondelimited strings are interpreted according
their length. For a string 8 or 14 characters long, the year is assumed
to be given by the first 4 characters.  Otherwise, the year is assumed
to be given by the first 2 characters. The string is interpreted from
left to right to find year, month, day, hour, minute, and second
values, for as many parts as are present in the string. This means you
should not use strings that have fewer than 6 characters. For example,
if you specify `'9903'', thinking that represents March, 1999, MySQL
converts it to the `zero' date value. This occurs because the year and
month values are `99' and `03', but the day part is completely missing.
However, you can explicitly specify a value of zero to represent
missing month or day parts. For example, to insert the value
`'1999-03-00'', use `'990300''.

MySQL recognizes *Note `TIME': time. values in these formats:

   * As a string in `'D HH:MM:SS'' format. You can also use one of the
     following `relaxed' syntaxes: `'HH:MM:SS'', `'HH:MM'', `'D HH:MM'',
     `'D HH'', or `'SS''. Here `D' represents days and can have a value
     from 0 to 34.

   * As a string with no delimiters in `'HHMMSS'' format, provided that
     it makes sense as a time. For example, `'101112'' is understood as
     `'10:11:12'', but `'109712'' is illegal (it has a nonsensical
     minute part) and becomes `'00:00:00''.

   * As a number in `HHMMSS' format, provided that it makes sense as a
     time. For example, `101112' is understood as `'10:11:12''. The
     following alternative formats are also understood: `SS', `MMSS',
     or `HHMMSS'.

A trailing fractional seconds part is recognized in the `'D
HH:MM:SS.fraction'', `'HH:MM:SS.fraction'', `'HHMMSS.fraction'', and
`HHMMSS.fraction' time formats, where `fraction' is the fractional part
in up to microseconds (6 digits) precision. Although this fractional
part is recognized, it is discarded from values stored into *Note
`TIME': time. columns. For information about fractional seconds support
in MySQL, see *Note fractional-seconds::.

For *Note `TIME': time. values specified as strings that include a time
part delimiter, it is unnecessary to specify two digits for hours,
minutes, or seconds values that are less than `10'. `'8:3:2'' is the
same as `'08:03:02''.


File: manual.info,  Node: hexadecimal-literals,  Next: boolean-literals,  Prev: date-and-time-literals,  Up: literals

9.1.4 Hexadecimal Literals
--------------------------

MySQL supports hexadecimal values, written using `X'VAL'', `x'VAL'', or
`0xVAL' format, where VAL contains hexadecimal digits (`0..9', `A..F').
Lettercase of the digits does not matter. For values written using
`X'VAL'' or `x'VAL'' format, VAL must contain an even number of digits.
For values written using `0xVAL syntax', values that contain an odd
number of digits are treated as having an extra leading `0'. For
example, `0x0a' and `0xaaa' are interpreted as `0x0a' and `0x0aaa'.

In numeric contexts, hexadecimal values act like integers (64-bit
precision). In string contexts, they act like binary strings, where
each pair of hex digits is converted to a character:


     mysql> SELECT X'4D7953514C';
             -> 'MySQL'
     mysql> SELECT 0x0a+0;
             -> 10
     mysql> SELECT 0x5061756c;
             -> 'Paul'

The default type of a hexadecimal value is a string. If you want to
ensure that the value is treated as a number, you can use `CAST(... AS
UNSIGNED)':


     mysql> SELECT 0x41, CAST(0x41 AS UNSIGNED);
             -> 'A', 65

The `X'HEXSTRING'' syntax is based on standard SQL. The `0x' syntax is
based on ODBC. Hexadecimal strings are often used by ODBC to supply
values for *Note `BLOB': blob.  columns.

You can convert a string or a number to a string in hexadecimal format
with the `HEX()' function:


     mysql> SELECT HEX('cat');
             -> '636174'
     mysql> SELECT 0x636174;
             -> 'cat'


File: manual.info,  Node: boolean-literals,  Next: bit-field-literals,  Prev: hexadecimal-literals,  Up: literals

9.1.5 Boolean Literals
----------------------

The constants `TRUE' and `FALSE' evaluate to `1' and `0', respectively.
The constant names can be written in any lettercase.


     mysql> SELECT TRUE, true, FALSE, false;
             -> 1, 1, 0, 0


File: manual.info,  Node: bit-field-literals,  Next: null-values,  Prev: boolean-literals,  Up: literals

9.1.6 Bit-Field Literals
------------------------

Bit-field values can be written using `b'VALUE'' or `0bVALUE' notation.
VALUE is a binary value written using zeros and ones.

Bit-field notation is convenient for specifying values to be assigned
to *Note `BIT': bit-type. columns:


     mysql> CREATE TABLE t (b BIT(8));
     mysql> INSERT INTO t SET b = b'11111111';
     mysql> INSERT INTO t SET b = b'1010';
     mysql> INSERT INTO t SET b = b'0101';

Bit values are returned as binary values. To display them in printable
form, add 0 or use a conversion function such as `BIN()'. High-order 0
bits are not displayed in the converted value.


     mysql> SELECT b+0, BIN(b+0), OCT(b+0), HEX(b+0) FROM t;
     +------+----------+----------+----------+
     | b+0  | BIN(b+0) | OCT(b+0) | HEX(b+0) |
     +------+----------+----------+----------+
     |  255 | 11111111 | 377      | FF       |
     |   10 | 1010     | 12       | A        |
     |    5 | 101      | 5        | 5        |
     +------+----------+----------+----------+

Bit values assigned to user variables are treated as binary strings. To
assign a bit value as a number to a user variable, use `CAST()' or `+0':


     mysql> SET @v1 = 0b1000001;
     mysql> SET @v2 = CAST(0b1000001 AS UNSIGNED), @v3 = 0b1000001+0;
     mysql> SELECT @v1, @v2, @v3;
     +------+------+------+
     | @v1  | @v2  | @v3  |
     +------+------+------+
     | A    |   65 |   65 |
     +------+------+------+


File: manual.info,  Node: null-values,  Prev: bit-field-literals,  Up: literals

9.1.7 NULL Values
-----------------

The `NULL' value means `no data.' `NULL' can be written in any
lettercase. A synonym is `\N' (case sensitive).

For text file import or export operations performed with *Note `LOAD
DATA INFILE': load-data. or *Note `SELECT ... INTO OUTFILE':
select-into, `NULL' is represented by the `\N' sequence. See *Note
load-data::.

Be aware that the `NULL' value is different from values such as `0' for
numeric types or the empty string for string types. For more
information, see *Note problems-with-null::.


File: manual.info,  Node: identifiers,  Next: reserved-words,  Prev: literals,  Up: language-structure

9.2 Schema Object Names
=======================

* Menu:

* identifier-qualifiers::        Identifier Qualifiers
* identifier-case-sensitivity::  Identifier Case Sensitivity
* identifier-mapping::           Mapping of Identifiers to File Names
* function-resolution::          Function Name Parsing and Resolution

Certain objects within MySQL, including database, table, index, column,
alias, view, stored procedure, partition, tablespace, and other object
names are known as identifiers. This section describes the permissible
syntax for identifiers in MySQL.  *Note identifier-case-sensitivity::,
describes which types of identifiers are case sensitive and under what
conditions.

An identifier may be quoted or unquoted. If an identifier contains
special characters or is a reserved word, you _must_ quote it whenever
you refer to it.  (Exception: A reserved word that follows a period in
a qualified name must be an identifier, so it need not be quoted.)
Reserved words are listed at *Note reserved-words::.

Identifiers are converted to Unicode internally. They may contain these
characters:

   * Permitted characters in unquoted identifiers:

        * ASCII: [0-9,a-z,A-Z$_] (basic Latin letters, digits 0-9,
          dollar, underscore)

        * Extended: U+0080 .. U+FFFF

   * Permitted characters in quoted identifiers include the full
     Unicode Basic Multilingual Plane (BMP), except U+0000:

        * ASCII: U+0001 .. U+007F

        * Extended: U+0080 .. U+FFFF

   * ASCII NUL (U+0000) and supplementary characters (U+10000 and
     higher) are not permitted in quoted or unquoted identifiers.

   * Identifiers may begin with a digit but unless quoted may not
     consist solely of digits.

   * Database, table, and column names cannot end with space characters.

   * Before MySQL 5.1.6, database and table names cannot contain ``/'',
     ``\'', ``.'', or characters that are not permitted in file names.

The identifier quote character is the backtick (```''):


     mysql> SELECT * FROM `select` WHERE `select`.id > 100;

If the `ANSI_QUOTES' SQL mode is enabled, it is also permissible to
quote identifiers within double quotation marks:


     mysql> CREATE TABLE "test" (col INT);
     ERROR 1064: You have an error in your SQL syntax...
     mysql> SET sql_mode='ANSI_QUOTES';
     mysql> CREATE TABLE "test" (col INT);
     Query OK, 0 rows affected (0.00 sec)

The `ANSI_QUOTES' mode causes the server to interpret double-quoted
strings as identifiers.  Consequently, when this mode is enabled,
string literals must be enclosed within single quotation marks. They
cannot be enclosed within double quotation marks. The server SQL mode
is controlled as described in *Note sql-mode::.

Identifier quote characters can be included within an identifier if you
quote the identifier. If the character to be included within the
identifier is the same as that used to quote the identifier itself,
then you need to double the character. The following statement creates
a table named `a`b' that contains a column named `c"d':


     mysql> CREATE TABLE `a``b` (`c"d` INT);

In the select list of a query, a quoted column alias can be specified
using identifier or string quoting characters:


     mysql> SELECT 1 AS `one`, 2 AS 'two';
     +-----+-----+
     | one | two |
     +-----+-----+
     |   1 |   2 |
     +-----+-----+

Elsewhere in the statement, quoted references to the alias must use
identifier quoting or the reference is treated as a string literal.

It is recommended that you do not use names that begin with `Me' or
`MeN', where M and N are integers. For example, avoid using `1e' as an
identifier, because an expression such as `1e+3' is ambiguous. Depending
on context, it might be interpreted as the expression `1e + 3' or as
the number `1e+3'.

Be careful when using `MD5()' to produce table names because it can
produce names in illegal or ambiguous formats such as those just
described.

A user variable cannot be used directly in an SQL statement as an
identifier or as part of an identifier. See *Note user-variables::, for
more information and examples of workarounds.

As of MySQL 5.1.6, special characters in database and table names are
encoded in the corresponding file system names as described in *Note
identifier-mapping::. If you have databases or tables from an older
version of MySQL that contain special characters and for which the
underlying directory names or file names have not been updated to use
the new encoding, the server displays their names with a prefix of
`#mysql50#'. For information about referring to such names or
converting them to the newer encoding, see that section.

The following table describes the maximum length for each type of
identifier.

This table describes the maximum length for each type of MySQL object
identifier.

Identifier  Maximum
            Length
            (characters)
Database    64
Table       64
Column      64
Index       64
Constraint  64
Stored      64
Program     
View        64
Tablespace  64
Server      64
Log File    64
Group       
Alias       256 (see
            exception
            following
            table)
Compound    16
Statement   
Label       

As of MySQL 5.1.23, aliases for column names in *Note `CREATE VIEW':
create-view. statements are checked against the maximum column length
of 64 characters (not the maximum alias length of 256 characters).

Identifiers are stored using Unicode (UTF-8). This applies to
identifiers in table definitions that are stored in `.frm' files and to
identifiers stored in the grant tables in the `mysql' database. The
sizes of the identifier string columns in the grant tables are measured
in characters. You can use multibyte characters without reducing the
number of characters permitted for values stored in these columns,
something not true prior to MySQL 4.1. As indicated earlier, the
permissible Unicode characters are those in the Basic Multilingual
Plane (BMP). Supplementary characters are not permitted.


File: manual.info,  Node: identifier-qualifiers,  Next: identifier-case-sensitivity,  Prev: identifiers,  Up: identifiers

9.2.1 Identifier Qualifiers
---------------------------

MySQL permits names that consist of a single identifier or multiple
identifiers. The components of a multiple-part name must be separated
by period (``.'') characters. The initial parts of a multiple-part name
act as qualifiers that affect the context within which the final
identifier is interpreted.

In MySQL, you can refer to a table column using any of the following
forms.

This table lists forms (column references) that can be used to refer to
table columns.

Column Reference       Meaning
COL_NAME               The column COL_NAME from whichever table used in
                       the statement contains a column of that name.
TBL_NAME.COL_NAME      The column COL_NAME from table TBL_NAME of the
                       default database.
DB_NAME.TBL_NAME.COL_NAMEThe column COL_NAME from table TBL_NAME of the
                       database DB_NAME.

The qualifier character is a separate token and need not be contiguous
with the associated identifiers. For example, TBL_NAME.COL_NAME and
TBL_NAME . COL_NAME are equivalent.

If any components of a multiple-part name require quoting, quote them
individually rather than quoting the name as a whole. For example,
write ``my-table`.`my-column`', not ``my-table.my-column`'.

A reserved word that follows a period in a qualified name must be an
identifier, so in that context it need not be quoted.

You need not specify a TBL_NAME or DB_NAME.TBL_NAME prefix for a column
reference in a statement unless the reference would be ambiguous.
Suppose that tables `t1' and `t2' each contain a column `c', and you
retrieve `c' in a *Note `SELECT': select. statement that uses both `t1'
and `t2'. In this case, `c' is ambiguous because it is not unique among
the tables used in the statement. You must qualify it with a table name
as `t1.c' or `t2.c' to indicate which table you mean. Similarly, to
retrieve from a table `t' in database `db1' and from a table `t' in
database `db2' in the same statement, you must refer to columns in
those tables as `db1.t.COL_NAME' and `db2.t.COL_NAME'.

The syntax `.TBL_NAME' means the table TBL_NAME in the default
database. This syntax is accepted for ODBC compatibility because some
ODBC programs prefix table names with a ``.'' character.


File: manual.info,  Node: identifier-case-sensitivity,  Next: identifier-mapping,  Prev: identifier-qualifiers,  Up: identifiers

9.2.2 Identifier Case Sensitivity
---------------------------------

In MySQL, databases correspond to directories within the data
directory. Each table within a database corresponds to at least one
file within the database directory (and possibly more, depending on the
storage engine). Triggers also correspond to files. Consequently, the
case sensitivity of the underlying operating system plays a part in the
case sensitivity of database, table, and trigger names. This means such
names are not case sensitive in Windows, but are case sensitive in most
varieties of Unix. One notable exception is Mac OS X, which is
Unix-based but uses a default file system type (HFS+) that is not case
sensitive. However, Mac OS X also supports UFS volumes, which are case
sensitive just as on any Unix. See *Note extensions-to-ansi::. The
`lower_case_table_names' system variable also affects how the server
handles identifier case sensitivity, as described later in this section.

*Note*:

Although database, table, and trigger names are not case sensitive on
some platforms, you should not refer to one of these using different
cases within the same statement. The following statement would not work
because it refers to a table both as `my_table' and as `MY_TABLE':


     mysql> SELECT * FROM my_table WHERE MY_TABLE.col=1;

Column, index, stored routine, and event names are not case sensitive
on any platform, nor are column aliases.

However, names of logfile groups are case sensitive. This differs from
standard SQL.

By default, table aliases are case sensitive on Unix, but not so on
Windows or Mac OS X. The following statement would not work on Unix,
because it refers to the alias both as `a' and as `A':


     mysql> SELECT COL_NAME FROM TBL_NAME AS a
         -> WHERE a.COL_NAME = 1 OR A.COL_NAME = 2;

However, this same statement is permitted on Windows. To avoid problems
caused by such differences, it is best to adopt a consistent
convention, such as always creating and referring to databases and
tables using lowercase names. This convention is recommended for
maximum portability and ease of use.

How table and database names are stored on disk and used in MySQL is
affected by the `lower_case_table_names' system variable, which you can
set when starting *Note `mysqld': mysqld.  `lower_case_table_names' can
take the values shown in the following table. This variable does _not_
affect case sensitivity of trigger identifiers. On Unix, the default
value of `lower_case_table_names' is 0. On Windows the default value is
1. On Mac OS X, the default value is 2.

This table describes values for the `lower_case_table_names' system
variable.

Value   Meaning
`0'     Table and database names are stored on disk using the lettercase
        specified in the *Note `CREATE TABLE': create-table. or *Note
        `CREATE DATABASE': create-database. statement. Name comparisons
        are case sensitive. You should _not_ set this variable to 0 if
        you are running MySQL on a system that has case-insensitive file
        names (such as Windows or Mac OS X). If you force this variable
        to 0 with `--lower-case-table-names=0' on a case-insensitive
        file system and access `MyISAM' tablenames using different
        lettercases, index corruption may result.
`1'     Table names are stored in lowercase on disk and name comparisons
        are not case sensitive. MySQL converts all table names to
        lowercase on storage and lookup. This behavior also applies to
        database names and table aliases.
`2'     Table and database names are stored on disk using the lettercase
        specified in the *Note `CREATE TABLE': create-table. or *Note
        `CREATE DATABASE': create-database. statement, but MySQL
        converts them to lowercase on lookup. Name comparisons are not
        case sensitive. This works _only_ on file systems that are not
        case sensitive!  `InnoDB' table names are stored in lowercase,
        as for `lower_case_table_names=1'.

If you are using MySQL on only one platform, you do not normally have
to change the `lower_case_table_names' variable from its default value.
However, you may encounter difficulties if you want to transfer tables
between platforms that differ in file system case sensitivity. For
example, on Unix, you can have two different tables named `my_table' and
`MY_TABLE', but on Windows these two names are considered identical. To
avoid data transfer problems arising from lettercase of database or
table names, you have two options:

   * Use `lower_case_table_names=1' on all systems. The main
     disadvantage with this is that when you use *Note `SHOW TABLES':
     show-tables. or *Note `SHOW DATABASES': show-databases, you do not
     see the names in their original lettercase.

   * Use `lower_case_table_names=0' on Unix and
     `lower_case_table_names=2' on Windows. This preserves the
     lettercase of database and table names. The disadvantage of this
     is that you must ensure that your statements always refer to your
     database and table names with the correct lettercase on Windows.
     If you transfer your statements to Unix, where lettercase is
     significant, they do not work if the lettercase is incorrect.

     *Exception*: If you are using `InnoDB' tables and you are trying
     to avoid these data transfer problems, you should set
     `lower_case_table_names' to 1 on all platforms to force names to
     be converted to lowercase.

If you plan to set the `lower_case_table_names' system variable to 1 on
Unix, you must first convert your old database and table names to
lowercase before stopping *Note `mysqld': mysqld. and restarting it
with the new variable setting. To do this for an individual table, use
*Note `RENAME TABLE': rename-table.:


     RENAME TABLE T1 TO t1;

To convert one or more entire databases, dump them before setting
`lower_case_table_names', then drop the databases, and reload them
after setting `lower_case_table_names':

  1. Use *Note `mysqldump': mysqldump. to dump each database:


          mysqldump --databases db1 > db1.sql
          mysqldump --databases db2 > db2.sql
          ...

     Do this for each database that must be recreated.

  2. Use `DROP DATABASE' to drop each database.

  3. Stop the server, set `lower_case_table_names', and restart the
     server.

  4. Reload the dump file for each database. Because
     `lower_case_table_names' is set, each database and table name will
     be converted to lowercase as it is recreated:


          mysql < db1.sql
          mysql < db2.sql
          ...

Object names may be considered duplicates if their uppercase forms are
equal according to a binary collation. That is true for names of
cursors, conditions, procedures, functions, savepoints, stored routine
parameters, stored program local variables, and plugins. It is not true
for names of columns, constraints, databases, partitions, statements
prepared with *Note `PREPARE': prepare, tables, triggers, users, and
user-defined variables.

File system case sensitivity can affect searches in string columns of
`INFORMATION_SCHEMA' tables. For more information, see *Note
charset-collation-information-schema::.


File: manual.info,  Node: identifier-mapping,  Next: function-resolution,  Prev: identifier-case-sensitivity,  Up: identifiers

9.2.3 Mapping of Identifiers to File Names
------------------------------------------

There is a correspondence between database and table identifiers and
names in the file system. For the basic structure, MySQL represents
each database as a directory in the data directory, and each table by
one or more files in the appropriate database directory. For the table
format files (`.FRM'), the data is always stored in this structure and
location.

For the data and index files, the exact representation on disk is
storage engine specific. These files may be stored in the same location
as the `FRM' files, or the information may be stored in a separate file.
`InnoDB' data is stored in the InnoDB data files. If you are using
tablespaces with `InnoDB', then the specific tablespace files you
create are used instead.

Before MySQL 5.1.6, there are some limitations on the characters that
can be used in identifiers for database objects that correspond to file
system objects. For example, path name separator characters are not
permitted, and ``.'' is not permitted because it begins the extension
for table files.

As of MySQL 5.1.6, any character is legal in database or table
identifiers except ASCII NUL (`0x00'). MySQL encodes any characters
that are problematic in the corresponding file system objects when it
creates database directories or table files:

   * Basic Latin letters (`a..zA..Z'), digits (`0..9') and underscore
     (`_') are encoded as is. Consequently, their case sensitivity
     directly depends on file system features.

   * All other national letters from alphabets that have
     uppercase/lowercase mapping are encoded as shown in the following
     table. Values in the Code Range column are UCS-2 values.

     This table shows the encoding for national letters from alphabets
     that have uppercase/lowercase mapping, excluding basic Latin
     letters (`a..zA..Z'), digits (`0..9') and underscore (`_'), which
     are encoded as is.

     Code Range Pattern    Number     Used       Unused     Blocks
     00C0..017F [@][0..4][g..z]5*20= 100  97         3          Latin-1
                                                            Supplement +
                                                            Latin Extended-A
     0370..03FF [@][5..9][g..z]5*20= 100  88         12         Greek and Coptic
     0400..052F [@][g..z][0..6]20*7= 140  137        3          Cyrillic +
                                                            Cyrillic
                                                            Supplement
     0530..058F [@][g..z][7..8]20*2= 40   38         2          Armenian
     2160..217F [@][g..z][9]20*1= 20   16         4          Number Forms
     0180..02AF [@][g..z][a..k]20*11=220  203        17         Latin Extended-B
                                                            + IPA Extensions
     1E00..1EFF [@][g..z][l..r]20*7= 140  136        4          Latin Extended
                                                            Additional
     1F00..1FFF [@][g..z][s..z]20*8= 160  144        16         Greek Extended
     .... ....  [@][a..f][g..z]6*20= 120  0          120        RESERVED
     24B6..24E9 [@][@][a..z]26         26         0          Enclosed
                                                            Alphanumerics
     FF21..FF5A [@][a..z][@]26         26         0          Halfwidth and
                                                            Fullwidth forms

     One of the bytes in the sequence encodes lettercase. For example:
     `LATIN CAPITAL LETTER A WITH GRAVE' is encoded as `@0G', whereas
     `LATIN SMALL LETTER A WITH GRAVE' is encoded as `@0g'. Here the
     third byte (`G' or `g') indicates lettercase. (On a
     case-insensitive file system, both letters will be treated as the
     same.)

     For some blocks, such as Cyrillic, the second byte determines
     lettercase. For other blocks, such as Latin1 Supplement, the third
     byte determines lettercase. If two bytes in the sequence are
     letters (as in Greek Extended), the leftmost letter character
     stands for lettercase. All other letter bytes must be in lowercase.

   * All nonletter characters except underscore (`_'), as well as
     letters from alphabets that do not have uppercase/lowercase
     mapping (such as Hebrew) are encoded using hexadecimal
     representation using lowercase letters for hex digits `a..f':


          0x003F -> @003f
          0xFFFF -> @ffff

     The hexadecimal values correspond to character values in the
     `ucs2' double-byte character set.

On Windows, some names such as `nul', `prn', and `aux' cannot be used
as file names because they are reserved as device names. As of MySQL
5.1.10, these are permissible names in MySQL. They are encoded by
appending `@@@' to the name when the server creates the corresponding
file or directory. This occurs on all platforms for portability of the
corresponding database object between platforms.

If you have databases or tables from a version of MySQL older than
5.1.6 that contain special characters and for which the underlying
directory names or file names have not been updated to use the new
encoding, the server displays their names with a prefix of `#mysql50#'
in the output from `INFORMATION_SCHEMA' tables or *Note `SHOW': show.
statements. For example, if you have a table named `a@b' and its name
encoding has not been updated, *Note `SHOW TABLES': show-tables.
displays it like this:


     mysql> SHOW TABLES;
     +----------------+
     | Tables_in_test |
     +----------------+
     | #mysql50#a@b   |
     +----------------+

To refer to such a name for which the encoding has not been updated,
you must supply the `#mysql50#' prefix:


     mysql> SHOW COLUMNS FROM `a@b`;
     ERROR 1146 (42S02): Table 'test.a@b' doesn't exist

     mysql> SHOW COLUMNS FROM `#mysql50#a@b`;
     +-------+---------+------+-----+---------+-------+
     | Field | Type    | Null | Key | Default | Extra |
     +-------+---------+------+-----+---------+-------+
     | i     | int(11) | YES  |     | NULL    |       |
     +-------+---------+------+-----+---------+-------+

To update old names to eliminate the need to use the special prefix to
refer to them, re-encode them with *Note `mysqlcheck': mysqlcheck. The
following command updates all names to the new encoding:


     shell> mysqlcheck --check-upgrade --fix-db-names --fix-table-names --all-databases

To check only specific databases or tables, omit `--all-databases' and
provide the appropriate database or table arguments. For information
about *Note `mysqlcheck': mysqlcheck. invocation syntax, see *Note
mysqlcheck::.

*Note*:

The `#mysql50#' prefix is intended only to be used internally by the
server. You should not create databases or tables with names that use
this prefix.

Also, *Note `mysqlcheck': mysqlcheck. cannot fix names that contain
literal instances of the `@' character that is used for encoding
special characters. If you have databases or tables that contain this
character, use *Note `mysqldump': mysqldump. to dump them before
upgrading to MySQL 5.1.6 or later, and then reload the dump file after
upgrading.


File: manual.info,  Node: function-resolution,  Prev: identifier-mapping,  Up: identifiers

9.2.4 Function Name Parsing and Resolution
------------------------------------------

MySQL 5.1 supports built-in (native) functions, user-defined functions
(UDFs), and stored functions. This section describes how the server
recognizes whether the name of a built-in function is used as a
function call or as an identifier, and how the server determines which
function to use in cases when functions of different types exist with a
given name.

*Built-In Function Name Parsing*

The parser uses default rules for parsing names of built-in functions.
These rules can be changed by enabling the `IGNORE_SPACE' SQL mode.

When the parser encounters a word that is the name of a built-in
function, it must determine whether the name signifies a function call
or is instead a nonexpression reference to an identifier such as a
table or column name. For example, in the following statements, the
first reference to `count' is a function call, whereas the second
reference is a table name:


     SELECT COUNT(*) FROM mytable;
     CREATE TABLE count (i INT);

The parser should recognize the name of a built-in function as
indicating a function call only when parsing what is expected to be an
expression. That is, in nonexpression context, function names are
permitted as identifiers.

However, some built-in functions have special parsing or implementation
considerations, so the parser uses the following rules by default to
distinguish whether their names are being used as function calls or as
identifiers in nonexpression context:

   * To use the name as a function call in an expression, there must be
     no whitespace between the name and the following ``('' parenthesis
     character.

   * Conversely, to use the function name as an identifier, it must not
     be followed immediately by a parenthesis.

The requirement that function calls be written with no whitespace
between the name and the parenthesis applies only to the built-in
functions that have special considerations.  `COUNT' is one such name.
The exact list of function names for which following whitespace
determines their interpretation are those listed in the
`sql_functions[]' array of the `sql/lex.h' source file. Before MySQL
5.1, these are rather numerous (about 200), so you may find it easiest
to treat the no-whitespace requirement as applying to all function
calls. In MySQL 5.1, parser improvements reduce to about 30 the number
of affected function names.

For functions not listed in the `sql_functions[]') array, whitespace
does not matter. They are interpreted as function calls only when used
in expression context and may be used freely as identifiers otherwise.
`ASCII' is one such name. However, for these nonaffected function
names, interpretation may vary in expression context: `FUNC_NAME ()' is
interpreted as a built-in function if there is one with the given name;
if not, `FUNC_NAME ()' is interpreted as a user-defined function or
stored function if one exists with that name.

The `IGNORE_SPACE' SQL mode can be used to modify how the parser treats
function names that are whitespace-sensitive:

   * With `IGNORE_SPACE' disabled, the parser interprets the name as a
     function call when there is no whitespace between the name and the
     following parenthesis. This occurs even when the function name is
     used in nonexpression context:


          mysql> CREATE TABLE count(i INT);
          ERROR 1064 (42000): You have an error in your SQL syntax ...
          near 'count(i INT)'

     To eliminate the error and cause the name to be treated as an
     identifier, either use whitespace following the name or write it
     as a quoted identifier (or both):


          CREATE TABLE count (i INT);
          CREATE TABLE `count`(i INT);
          CREATE TABLE `count` (i INT);

   * With `IGNORE_SPACE' enabled, the parser loosens the requirement
     that there be no whitespace between the function name and the
     following parenthesis. This provides more flexibility in writing
     function calls. For example, either of the following function
     calls are legal:


          SELECT COUNT(*) FROM mytable;
          SELECT COUNT (*) FROM mytable;

     However, enabling `IGNORE_SPACE' also has the side effect that the
     parser treats the affected function names as reserved words (see
     *Note reserved-words::). This means that a space following the
     name no longer signifies its use as an identifier. The name can be
     used in function calls with or without following whitespace, but
     causes a syntax error in nonexpression context unless it is
     quoted. For example, with `IGNORE_SPACE' enabled, both of the
     following statements fail with a syntax error because the parser
     interprets `count' as a reserved word:


          CREATE TABLE count(i INT);
          CREATE TABLE count (i INT);

     To use the function name in nonexpression context, write it as a
     quoted identifier:


          CREATE TABLE `count`(i INT);
          CREATE TABLE `count` (i INT);

To enable the `IGNORE_SPACE' SQL mode, use this statement:


     SET sql_mode = 'IGNORE_SPACE';

`IGNORE_SPACE' is also enabled by certain other composite modes such as
`ANSI' that include it in their value:


     SET sql_mode = 'ANSI';

Check *Note sql-mode::, to see which composite modes enable
`IGNORE_SPACE'.

To minimize the dependency of SQL code on the `IGNORE_SPACE' setting,
use these guidelines:

   * Avoid creating UDFs or stored functions that have the same name as
     a built-in function.

   * Avoid using function names in nonexpression context. For example,
     these statements use `count' (one of the affected function names
     affected by `IGNORE_SPACE'), so they fail with or without
     whitespace following the name if `IGNORE_SPACE' is enabled:


          CREATE TABLE count(i INT);
          CREATE TABLE count (i INT);

     If you must use a function name in nonexpression context, write it
     as a quoted identifier:


          CREATE TABLE `count`(i INT);
          CREATE TABLE `count` (i INT);

The number of function names affected by `IGNORE_SPACE' was reduced
significantly in MySQL 5.1.13, from about 200 to about 30. As of MySQL
5.1.13, only the following functions are still affected by the
`IGNORE_SPACE' setting.

This table lists functions that are still affected by the
`IGNORE_SPACE' setting as of MySQL 5.1.13.

`ADDDATE'          `BIT_AND'          `BIT_OR'           `BIT_XOR'
`CAST'             `COUNT'            `CURDATE'          `CURTIME'
`DATE_ADD'         `DATE_SUB'         `EXTRACT'          `GROUP_CONCAT'
`MAX'              `MID'              `MIN'              `NOW'
`POSITION'         `SESSION_USER'     `STD'              `STDDEV'
`STDDEV_POP'       `STDDEV_SAMP'      `SUBDATE'          `SUBSTR'
`SUBSTRING'        `SUM'              `SYSDATE'          `SYSTEM_USER'
`TRIM'             `VARIANCE'         `VAR_POP'          `VAR_SAMP'

For earlier versions of MySQL, check the contents of the
`sql_functions[]' array in the `sql/lex.h' source file to see which
functions are affected by `IGNORE_SPACE'.

*Incompatibility warning*: The change in MySQL 5.1.13 that reduces the
number of function names affected by `IGNORE_SPACE' improves the
consistency of parser operation. However, it also introduces the
possibility of incompatibility for old SQL code that relies on the
following conditions:

   * `IGNORE_SPACE' is disabled.

   * The presence or absence of whitespace following a function name is
     used to distinguish between a built-in function and stored
     function that have the same name, such as `PI()' versus `PI ()'.

For functions that are no longer affected by `IGNORE_SPACE' as of MySQL
5.1.13, that strategy no longer works. Either of the following
approaches can be used if you have code that is subject to the
preceding incompatibility:

   * If a stored function has a name that conflicts with a built-in
     function, refer to the stored function with a schema name
     qualifier, regardless of whether whitespace is present. For
     example, write `SCHEMA_NAME.PI()' or `SCHEMA_NAME.PI ()'.

   * Alternatively, rename the stored function to use a nonconflicting
     name and change invocations of the function to use the new name.

*Function Name Resolution*

The following rules describe how the server resolves references to
function names for function creation and invocation:

   * Built-in functions and user-defined functions

     As of MySQL 5.1.14, an error occurs if you try to create a UDF
     with the same name as a built-in function. Before 5.1.14, a UDF
     can be created with the same name as a built-in function but the
     UDF cannot be invoked because the parser resolves invocations of
     the function to refer to the built-in function. For example, if
     you create a UDF named `ABS', references to `ABS()' invoke the
     built-in function.

   * Built-in functions and stored functions

     It is possible to create a stored function with the same name as a
     built-in function, but to invoke the stored function it is
     necessary to qualify it with a schema name.  For example, if you
     create a stored function named `PI' in the `test' schema, you
     invoke it as `test.PI()' because the server resolves `PI()' as a
     reference to the built-in function. As of 5.1.14, the server
     creates a warning if the stored function name collides with a
     built-in function name. The warning can be displayed with *Note
     `SHOW WARNINGS': show-warnings.

   * User-defined functions and stored functions

     User-defined functions and stored functions share the same
     namespace, so you cannot create a UDF and a stored function with
     the same name.

The preceding function name resolution rules have implications for
upgrading to versions of MySQL that implement new built-in functions:

   * If you have already created a user-defined function with a given
     name and upgrade MySQL to a version that implements a new built-in
     function with the same name, the UDF becomes inaccessible. To
     correct this, use *Note `DROP FUNCTION': drop-function. to drop
     the UDF, and then use *Note `CREATE FUNCTION': create-function. to
     re-create the UDF with a different nonconflicting name.

   * If a new version of MySQL implements a built-in function with the
     same name as an existing stored function, you have two choices:
     Rename the stored function to use a nonconflicting name, or change
     calls to the function so that they use a schema qualifier (that
     is, use `SCHEMA_NAME.FUNC_NAME()' syntax).


File: manual.info,  Node: reserved-words,  Next: user-variables,  Prev: identifiers,  Up: language-structure

9.3 Reserved Words
==================

Certain words such as *Note `SELECT': select, *Note `DELETE': delete, or
*Note `BIGINT': integer-types. are reserved and require special
treatment for use as identifiers such as table and column names. This
may also be true for the names of built-in functions.

Reserved words are permitted as identifiers if you quote them as
described in *Note identifiers:::


     mysql> CREATE TABLE interval (begin INT, end INT);
     ERROR 1064 (42000): You have an error in your SQL syntax ...
     near 'interval (begin INT, end INT)'

     mysql> CREATE TABLE `interval` (begin INT, end INT);
     Query OK, 0 rows affected (0.01 sec)

Exception: A word that follows a period in a qualified name must be an
identifier, so it need not be quoted even if it is reserved:


     mysql> CREATE TABLE mydb.interval (begin INT, end INT);
     Query OK, 0 rows affected (0.01 sec)

Names of built-in functions are permitted as identifiers but may
require care to be used as such. For example, `COUNT' is acceptable as
a column name. However, by default, no whitespace is permitted in
function invocations between the function name and the following ``(''
character. This requirement enables the parser to distinguish whether
the name is used in a function call or in nonfunction context. For
further detail on recognition of function names, see *Note
function-resolution::.

The words in the following table are explicitly reserved in MySQL 5.1.
In addition, `_FILENAME' is reserved. At some point, you might upgrade
to a higher version, so it is a good idea to have a look at future
reserved words, too.  You can find these in the manuals that cover
higher versions of MySQL. Most of the words in the table are forbidden
by standard SQL as column or table names (for example, `GROUP'). A few
are reserved because MySQL needs them and uses a `yacc' parser. A
reserved word can be used as an identifier if you quote it.

For a more detailed list of reserved words, including differences
between versions, see Reserved Words in MySQL 5.1
(http://dev.mysql.com/doc/mysqld-version-reference/en/mysqld-version-reference-reservedwords-5-1.html).

*Reserved Words in MySQL 5.1.74*

`ACCESSIBLE'             `ADD'                    `ALL'
`ALTER'                  `ANALYZE'                `AND'
`AS'                     `ASC'                    `ASENSITIVE'
`BEFORE'                 `BETWEEN'                `BIGINT'
`BINARY'                 `BLOB'                   `BOTH'
`BY'                     `CALL'                   `CASCADE'
`CASE'                   `CHANGE'                 `CHAR'
`CHARACTER'              `CHECK'                  `COLLATE'
`COLUMN'                 `CONDITION'              `CONSTRAINT'
`CONTINUE'               `CONVERT'                `CREATE'
`CROSS'                  `CURRENT_DATE'           `CURRENT_TIME'
`CURRENT_TIMESTAMP'      `CURRENT_USER'           `CURSOR'
`DATABASE'               `DATABASES'              `DAY_HOUR'
`DAY_MICROSECOND'        `DAY_MINUTE'             `DAY_SECOND'
`DEC'                    `DECIMAL'                `DECLARE'
`DEFAULT'                `DELAYED'                `DELETE'
`DESC'                   `DESCRIBE'               `DETERMINISTIC'
`DISTINCT'               `DISTINCTROW'            `DIV'
`DOUBLE'                 `DROP'                   `DUAL'
`EACH'                   `ELSE'                   `ELSEIF'
`ENCLOSED'               `ESCAPED'                `EXISTS'
`EXIT'                   `EXPLAIN'                `FALSE'
`FETCH'                  `FLOAT'                  `FLOAT4'
`FLOAT8'                 `FOR'                    `FORCE'
`FOREIGN'                `FROM'                   `FULLTEXT'
`GRANT'                  `GROUP'                  `HAVING'
`HIGH_PRIORITY'          `HOUR_MICROSECOND'       `HOUR_MINUTE'
`HOUR_SECOND'            `IF'                     `IGNORE'
`IN'                     `INDEX'                  `INFILE'
`INNER'                  `INOUT'                  `INSENSITIVE'
`INSERT'                 `INT'                    `INT1'
`INT2'                   `INT3'                   `INT4'
`INT8'                   `INTEGER'                `INTERVAL'
`INTO'                   `IS'                     `ITERATE'
`JOIN'                   `KEY'                    `KEYS'
`KILL'                   `LEADING'                `LEAVE'
`LEFT'                   `LIKE'                   `LIMIT'
`LINEAR'                 `LINES'                  `LOAD'
`LOCALTIME'              `LOCALTIMESTAMP'         `LOCK'
`LONG'                   `LONGBLOB'               `LONGTEXT'
`LOOP'                   `LOW_PRIORITY'           `MASTER_SSL_VERIFY_SERVER_CERT'
`MATCH'                  `MEDIUMBLOB'             `MEDIUMINT'
`MEDIUMTEXT'             `MIDDLEINT'              `MINUTE_MICROSECOND'
`MINUTE_SECOND'          `MOD'                    `MODIFIES'
`NATURAL'                `NOT'                    `NO_WRITE_TO_BINLOG'
`NULL'                   `NUMERIC'                `ON'
`OPTIMIZE'               `OPTION'                 `OPTIONALLY'
`OR'                     `ORDER'                  `OUT'
`OUTER'                  `OUTFILE'                `PRECISION'
`PRIMARY'                `PROCEDURE'              `PURGE'
`RANGE'                  `READ'                   `READS'
`READ_WRITE'             `REAL'                   `REFERENCES'
`REGEXP'                 `RELEASE'                `RENAME'
`REPEAT'                 `REPLACE'                `REQUIRE'
`RESTRICT'               `RETURN'                 `REVOKE'
`RIGHT'                  `RLIKE'                  `SCHEMA'
`SCHEMAS'                `SECOND_MICROSECOND'     `SELECT'
`SENSITIVE'              `SEPARATOR'              `SET'
`SHOW'                   `SMALLINT'               `SPATIAL'
`SPECIFIC'               `SQL'                    `SQLEXCEPTION'
`SQLSTATE'               `SQLWARNING'             `SQL_BIG_RESULT'
`SQL_CALC_FOUND_ROWS'    `SQL_SMALL_RESULT'       `SSL'
`STARTING'               `STRAIGHT_JOIN'          `TABLE'
`TERMINATED'             `THEN'                   `TINYBLOB'
`TINYINT'                `TINYTEXT'               `TO'
`TRAILING'               `TRIGGER'                `TRUE'
`UNDO'                   `UNION'                  `UNIQUE'
`UNLOCK'                 `UNSIGNED'               `UPDATE'
`USAGE'                  `USE'                    `USING'
`UTC_DATE'               `UTC_TIME'               `UTC_TIMESTAMP'
`VALUES'                 `VARBINARY'              `VARCHAR'
`VARCHARACTER'           `VARYING'                `WHEN'
`WHERE'                  `WHILE'                  `WITH'
`WRITE'                  `XOR'                    `YEAR_MONTH'
`ZEROFILL'                                        

*New Reserved Words in MySQL 5.1*

`ACCESSIBLE'             `LINEAR'                 `MASTER_SSL_VERIFY_SERVER_CERT'
`RANGE'                  `READ_ONLY'              `READ_WRITE'

MySQL permits some keywords to be used as unquoted identifiers because
many people previously used them. Examples are those in the following
list:

   * `ACTION'

   * *Note `BIT': bit-type.

   * *Note `DATE': datetime.

   * *Note `ENUM': enum.

   * `NO'

   * *Note `TEXT': blob.

   * *Note `TIME': time.

   * *Note `TIMESTAMP': datetime.


File: manual.info,  Node: user-variables,  Next: expressions,  Prev: reserved-words,  Up: language-structure

9.4 User-Defined Variables
==========================

You can store a value in a user-defined variable in one statement and
then refer to it later in another statement. This enables you to pass
values from one statement to another.  _User-defined variables are
session-specific_.  That is, a user variable defined by one client
cannot be seen or used by other clients. All variables for a given
client session are automatically freed when that client exits.

User variables are written as `@VAR_NAME', where the variable name
VAR_NAME consists of alphanumeric characters, ``.'', ``_'', and ``$''.
A user variable name can contain other characters if you quote it as a
string or identifier (for example, `@'my-var'', `@"my-var"', or
`@`my-var`').

User variable names are not case sensitive in MySQL 5.0 and up.

One way to set a user-defined variable is by issuing a *Note `SET':
set-statement.  statement:


     SET @VAR_NAME = EXPR [, @VAR_NAME = EXPR] ...

For *Note `SET': set-statement, either `=' or `:=' can be used as the
assignment operator.

You can also assign a value to a user variable in statements other than
*Note `SET': set-statement.  In this case, the assignment operator must
be `:=' and not `=' because the latter is treated as the comparison
operator `=' in non-*Note `SET': set-statement.  statements:


     mysql> SET @t1=1, @t2=2, @t3:=4;
     mysql> SELECT @t1, @t2, @t3, @t4 := @t1+@t2+@t3;
     +------+------+------+--------------------+
     | @t1  | @t2  | @t3  | @t4 := @t1+@t2+@t3 |
     +------+------+------+--------------------+
     |    1 |    2 |    4 |                  7 |
     +------+------+------+--------------------+

User variables can be assigned a value from a limited set of data
types: integer, decimal, floating-point, binary or nonbinary string, or
`NULL' value. Assignment of decimal and real values does not preserve
the precision or scale of the value. A value of a type other than one
of the permissible types is converted to a permissible type. For
example, a value having a temporal or spatial data type is converted to
a binary string.

If a user variable is assigned a nonbinary (character) string value, it
has the same character set and collation as the string.  The
coercibility of user variables is implicit. (This is the same
coercibility as for table column values.)

Bit values assigned to user variables are treated as binary strings. To
assign a bit value as a number to a user variable, use `CAST()' or `+0':


     mysql> SET @v1 = b'1000001';
     mysql> SET @v2 = CAST(b'1000001' AS UNSIGNED), @v3 = b'1000001'+0;
     mysql> SELECT @v1, @v2, @v3;
     +------+------+------+
     | @v1  | @v2  | @v3  |
     +------+------+------+
     | A    |   65 |   65 |
     +------+------+------+

If the value of a user variable is selected in a result set, it is
returned to the client as a string.

If you refer to a variable that has not been initialized, it has a
value of `NULL' and a type of string.

User variables may be used in most contexts where expressions are
permitted. This does not currently include contexts that explicitly
require a literal value, such as in the `LIMIT' clause of a *Note
`SELECT': select. statement, or the `IGNORE N LINES' clause of a *Note
`LOAD DATA': load-data. statement.

As a general rule, other than in *Note `SET': set-statement.
statements, you should never assign a value to a user variable and read
the value within the same statement. For example, to increment a
variable, this is okay:


     SET @a = @a + 1;

For other statements, such as *Note `SELECT': select, you might get the
results you expect, but this is not guaranteed. In the following
statement, you might think that MySQL will evaluate `@a' first and then
do an assignment second:


     SELECT @a, @a:=@a+1, ...;

However, the order of evaluation for expressions involving user
variables is undefined.

Another issue with assigning a value to a variable and reading the
value within the same non-*Note `SET': set-statement.  statement is
that the default result type of a variable is based on its type at the
start of the statement. The following example illustrates this:


     mysql> SET @a='test';
     mysql> SELECT @a,(@a:=20) FROM TBL_NAME;

For this *Note `SELECT': select. statement, MySQL reports to the client
that column one is a string and converts all accesses of `@a' to
strings, even though @a is set to a number for the second row. After the
*Note `SELECT': select. statement executes, `@a' is regarded as a
number for the next statement.

To avoid problems with this behavior, either do not assign a value to
and read the value of the same variable within a single statement, or
else set the variable to `0', `0.0', or `''' to define its type before
you use it.

In a *Note `SELECT': select. statement, each select expression is
evaluated only when sent to the client. This means that in a `HAVING',
`GROUP BY', or `ORDER BY' clause, referring to a variable that is
assigned a value in the select expression list does _not_ work as
expected:


     mysql> SELECT (@aa:=id) AS a, (@aa+3) AS b FROM TBL_NAME HAVING b=5;

The reference to `b' in the `HAVING' clause refers to an alias for an
expression in the select list that uses `@aa'.  This does not work as
expected: `@aa' contains the value of `id' from the previous selected
row, not from the current row.

User variables are intended to provide data values. They cannot be used
directly in an SQL statement as an identifier or as part of an
identifier, such as in contexts where a table or database name is
expected, or as a reserved word such as *Note `SELECT': select. This is
true even if the variable is quoted, as shown in the following example:


     mysql> SELECT c1 FROM t;
     +----+
     | c1 |
     +----+
     |  0 |
     +----+
     |  1 |
     +----+
     2 rows in set (0.00 sec)

     mysql> SET @col = "c1";
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @col FROM t;
     +------+
     | @col |
     +------+
     | c1   |
     +------+
     1 row in set (0.00 sec)

     mysql> SELECT `@col` FROM t;
     `ERROR 1054 (42S22): Unknown column '@col' in 'field list''

     mysql> SET @col = "`c1`";
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @col FROM t;
     +------+
     | @col |
     +------+
     | `c1` |
     +------+
     1 row in set (0.00 sec)

An exception to this principle that user variables cannot be used to
provide identifiers, is when you are constructing a string for use as a
prepared statement to execute later. In this case, user variables can
be used to provide any part of the statement. The following example
illustrates how this can be done:


     mysql> SET @c = "c1";
     Query OK, 0 rows affected (0.00 sec)

     mysql> SET @s = CONCAT("SELECT ", @c, " FROM t");
     Query OK, 0 rows affected (0.00 sec)

     mysql> PREPARE stmt FROM @s;
     Query OK, 0 rows affected (0.04 sec)
     Statement prepared

     mysql> EXECUTE stmt;
     +----+
     | c1 |
     +----+
     |  0 |
     +----+
     |  1 |
     +----+
     2 rows in set (0.00 sec)

     mysql> DEALLOCATE PREPARE stmt;
     Query OK, 0 rows affected (0.00 sec)

See *Note sql-syntax-prepared-statements::, for more information.

A similar technique can be used in application programs to construct
SQL statements using program variables, as shown here using PHP 5:


     <?php
       $mysqli = new mysqli("localhost", "user", "pass", "test");

       if( mysqli_connect_errno() )
         die("Connection failed: %s\n", mysqli_connect_error());

       $col = "c1";

       $query = "SELECT $col FROM t";

       $result = $mysqli->query($query);

       while($row = $result->fetch_assoc())
       {
         echo "<p>" . $row["$col"] . "</p>\n";
       }

       $result->close();

       $mysqli->close();
     ?>

Assembling an SQL statement in this fashion is sometimes known as
`Dynamic SQL'.


File: manual.info,  Node: expressions,  Next: comments,  Prev: user-variables,  Up: language-structure

9.5 Expression Syntax
=====================

The following rules define expression syntax in MySQL. The grammar
shown here is based on that given in the `sql/sql_yacc.yy' file of
MySQL source distributions. See the notes after the grammar for
additional information about some of the terms.


     EXPR:
         EXPR OR EXPR
       | EXPR || EXPR
       | EXPR XOR EXPR
       | EXPR AND EXPR
       | EXPR && EXPR
       | NOT EXPR
       | ! EXPR
       | BOOLEAN_PRIMARY IS [NOT] {TRUE | FALSE | UNKNOWN}
       | BOOLEAN_PRIMARY

     BOOLEAN_PRIMARY:
         BOOLEAN_PRIMARY IS [NOT] NULL
       | BOOLEAN_PRIMARY <=> PREDICATE
       | BOOLEAN_PRIMARY COMPARISON_OPERATOR PREDICATE
       | BOOLEAN_PRIMARY COMPARISON_OPERATOR {ALL | ANY} (SUBQUERY)
       | PREDICATE

     COMPARISON_OPERATOR: = | >= | > | <= | < | <> | !=

     PREDICATE:
         BIT_EXPR [NOT] IN (SUBQUERY)
       | BIT_EXPR [NOT] IN (EXPR [, EXPR] ...)
       | BIT_EXPR [NOT] BETWEEN BIT_EXPR AND PREDICATE
       | BIT_EXPR SOUNDS LIKE BIT_EXPR
       | BIT_EXPR [NOT] LIKE SIMPLE_EXPR [ESCAPE SIMPLE_EXPR]
       | BIT_EXPR [NOT] REGEXP BIT_EXPR
       | BIT_EXPR

     BIT_EXPR:
         BIT_EXPR | BIT_EXPR
       | BIT_EXPR & BIT_EXPR
       | BIT_EXPR << BIT_EXPR
       | BIT_EXPR >> BIT_EXPR
       | BIT_EXPR + BIT_EXPR
       | BIT_EXPR - BIT_EXPR
       | BIT_EXPR * BIT_EXPR
       | BIT_EXPR / BIT_EXPR
       | BIT_EXPR DIV BIT_EXPR
       | BIT_EXPR MOD BIT_EXPR
       | BIT_EXPR % BIT_EXPR
       | BIT_EXPR ^ BIT_EXPR
       | BIT_EXPR + INTERVAL_EXPR
       | BIT_EXPR - INTERVAL_EXPR
       | SIMPLE_EXPR

     SIMPLE_EXPR:
         LITERAL
       | IDENTIFIER
       | FUNCTION_CALL
       | SIMPLE_EXPR COLLATE COLLATION_NAME
       | PARAM_MARKER
       | VARIABLE
       | SIMPLE_EXPR || SIMPLE_EXPR
       | + SIMPLE_EXPR
       | - SIMPLE_EXPR
       | ~ SIMPLE_EXPR
       | ! SIMPLE_EXPR
       | BINARY SIMPLE_EXPR
       | (EXPR [, EXPR] ...)
       | ROW (EXPR, EXPR [, EXPR] ...)
       | (SUBQUERY)
       | EXISTS (SUBQUERY)
       | {IDENTIFIER EXPR}
       | MATCH_EXPR
       | CASE_EXPR
       | INTERVAL_EXPR

Notes:

For operator precedence, see in *Note operator-precedence::.

For literal value syntax, see *Note literals::.

For identifier syntax, see *Note identifiers::.

Variables can be user variables, system variables, or stored program
local variables or parameters:

   * User variables: *Note user-variables::

   * System variables: *Note using-system-variables::

   * Local variables: *Note declare-local-variable::

   * Parameters: *Note create-procedure::

PARAM_MARKER is `?' as used in prepared statements for placeholders. See
*Note prepare::.

`(SUBQUERY)' indicates a subquery that returns a single value; that is,
a scalar subquery. See *Note scalar-subqueries::.

`{IDENTIFIER EXPR}' is ODBC escape syntax and is accepted for ODBC
compatibility. The value is EXPR. The curly braces in the syntax should
be written literally; they are not metasyntax as used elsewhere in
syntax descriptions.

MATCH_EXPR indicates a `MATCH' expression. See *Note fulltext-search::.

CASE_EXPR indicates a `CASE' expression. See *Note
control-flow-functions::.

INTERVAL_EXPR represents a time interval. The syntax is `INTERVAL EXPR
UNIT', where UNIT is a specifier such as `HOUR', `DAY', or `WEEK'. For
the full list of UNIT specifiers, see the description of the
`DATE_ADD()' function in *Note date-and-time-functions::.

The meaning of some operators depends on the SQL mode:

   * By default, `||' is a logical `OR' operator. With
     `PIPES_AS_CONCAT' enabled, `||' is string concatenation, with a
     precedence between `^' and the unary operators.

   * By default, `!' has a higher precedence than `NOT'. With
     `HIGH_NOT_PRECEDENCE' enabled, `!' and `NOT' have the same
     precedence.

See *Note sql-mode::.


File: manual.info,  Node: comments,  Prev: expressions,  Up: language-structure

9.6 Comment Syntax
==================

MySQL Server supports three comment styles:

   * From a ``#'' character to the end of the line.

   * From a ``-- '' sequence to the end of the line. In MySQL, the ``--
     '' (double-dash) comment style requires the second dash to be
     followed by at least one whitespace or control character (such as
     a space, tab, newline, and so on). This syntax differs slightly
     from standard SQL comment syntax, as discussed in *Note
     ansi-diff-comments::.

   * From a `/*' sequence to the following `*/' sequence, as in the C
     programming language. This syntax enables a comment to extend over
     multiple lines because the beginning and closing sequences need
     not be on the same line.

The following example demonstrates all three comment styles:


     mysql> SELECT 1+1;     # This comment continues to the end of line
     mysql> SELECT 1+1;     -- This comment continues to the end of line
     mysql> SELECT 1 /* this is an in-line comment */ + 1;
     mysql> SELECT 1+
     /*
     this is a
     multiple-line comment
     */
     1;

Nested comments are not supported. (Under some conditions, nested
comments might be permitted, but usually are not, and users should
avoid them.)

MySQL Server supports some variants of C-style comments. These enable
you to write code that includes MySQL extensions, but is still
portable, by using comments of the following form:


     /*! MYSQL-SPECIFIC CODE */

In this case, MySQL Server parses and executes the code within the
comment as it would any other SQL statement, but other SQL servers will
ignore the extensions. For example, MySQL Server recognizes the
`STRAIGHT_JOIN' keyword in the following statement, but other servers
will not:


     SELECT /*! STRAIGHT_JOIN */ col1 FROM table1,table2 WHERE ...

If you add a version number after the ``!'' character, the syntax within
the comment is executed only if the MySQL version is greater than or
equal to the specified version number. The `TEMPORARY' keyword in the
following comment is executed only by servers from MySQL 3.23.02 or
higher:


     CREATE /*!32302 TEMPORARY */ TABLE t (a INT);

The comment syntax just described applies to how the *Note `mysqld':
mysqld. server parses SQL statements. The *Note `mysql': mysql. client
program also performs some parsing of statements before sending them to
the server. (It does this to determine statement boundaries within a
multiple-statement input line.)

Comments in this format, `/*!12345 ... */', are not stored on the
server. If this format is used to comment stored routines, the comments
will not be retained on the server.

The use of short-form *Note `mysql': mysql. commands such as `\C'
within multi-line `/* ...  */' comments is not supported.


File: manual.info,  Node: globalization,  Next: data-types,  Prev: language-structure,  Up: Top

10 Globalization
****************

* Menu:

* charset::                      Character Set Support
* error-message-language::       Setting the Error Message Language
* adding-character-set::         Adding a Character Set
* adding-collation::             Adding a Collation to a Character Set
* charset-configuration::        Character Set Configuration
* time-zone-support::            MySQL Server Time Zone Support
* locale-support::               MySQL Server Locale Support

This chapter covers issues of globalization, which includes
internationalization (MySQL's capabilities for adapting to local use)
and localization (selecting particular local conventions):

   * MySQL support for character sets in SQL statements.

   * How to configure the server to support different character sets.

   * Selecting the language for error messages.

   * How to set the server's time zone and enable per-connection time
     zone support.

   * Selecting the locale for day and month names.


File: manual.info,  Node: charset,  Next: error-message-language,  Prev: globalization,  Up: globalization

10.1 Character Set Support
==========================

* Menu:

* charset-general::              Character Sets and Collations in General
* charset-mysql::                Character Sets and Collations in MySQL
* charset-syntax::               Specifying Character Sets and Collations
* charset-connection::           Connection Character Sets and Collations
* charset-applications::         Configuring the Character Set and Collation for Applications
* charset-errors::               Character Set for Error Messages
* charset-collations::           Collation Issues
* charset-repertoire::           String Repertoire
* charset-operations::           Operations Affected by Character Set Support
* charset-unicode::              Unicode Support
* charset-metadata::             UTF-8 for Metadata
* charset-conversion::           Column Character Set Conversion
* charset-charsets::             Character Sets and Collations That MySQL Supports

MySQL includes character set support that enables you to store data
using a variety of character sets and perform comparisons according to
a variety of collations. You can specify character sets at the server,
database, table, and column level. MySQL supports the use of character
sets for the `MyISAM', `MEMORY', *Note `NDBCLUSTER': mysql-cluster, and
`InnoDB' storage engines.

This chapter discusses the following topics:

   * What are character sets and collations?

   * The multiple-level default system for character set assignment.

   * Syntax for specifying character sets and collations.

   * Affected functions and operations.

   * Unicode support.

   * The character sets and collations that are available, with notes.

Character set issues affect not only data storage, but also
communication between client programs and the MySQL server. If you want
the client program to communicate with the server using a character set
different from the default, you'll need to indicate which one. For
example, to use the `utf8' Unicode character set, issue this statement
after connecting to the server:


     SET NAMES 'utf8';

For more information about configuring character sets for application
use and character set-related issues in client/server communication,
see *Note charset-applications::, and *Note charset-connection::.


File: manual.info,  Node: charset-general,  Next: charset-mysql,  Prev: charset,  Up: charset

10.1.1 Character Sets and Collations in General
-----------------------------------------------

A _character set_ is a set of symbols and encodings. A _collation_ is a
set of rules for comparing characters in a character set. Let's make the
distinction clear with an example of an imaginary character set.

Suppose that we have an alphabet with four letters: ``A'', ``B'', ``a'',
``b''. We give each letter a number: ``A'' = 0, ``B'' = 1, ``a'' = 2,
``b'' = 3. The letter ``A'' is a symbol, the number 0 is the *encoding*
for ``A'', and the combination of all four letters and their encodings
is a *character set*.

Suppose that we want to compare two string values, ``A'' and ``B''. The
simplest way to do this is to look at the encodings: 0 for ``A'' and 1
for ``B''. Because 0 is less than 1, we say ``A'' is less than ``B''.
What we've just done is apply a collation to our character set. The
collation is a set of rules (only one rule in this case): `compare the
encodings.' We call this simplest of all possible collations a _binary_
collation.

But what if we want to say that the lowercase and uppercase letters are
equivalent? Then we would have at least two rules: (1) treat the
lowercase letters ``a'' and ``b'' as equivalent to ``A'' and ``B''; (2)
then compare the encodings. We call this a _case-insensitive_
collation. It is a little more complex than a binary collation.

In real life, most character sets have many characters: not just ``A''
and ``B'' but whole alphabets, sometimes multiple alphabets or eastern
writing systems with thousands of characters, along with many special
symbols and punctuation marks. Also in real life, most collations have
many rules, not just for whether to distinguish lettercase, but also
for whether to distinguish accents (an `accent' is a mark attached to a
character as in German ``O"''), and for multiple-character mappings
(such as the rule that ``O"'' = ``OE'' in one of the two German
collations).

MySQL can do these things for you:

   * Store strings using a variety of character sets.

   * Compare strings using a variety of collations.

   * Mix strings with different character sets or collations in the
     same server, the same database, or even the same table.

   * Enable specification of character set and collation at any level.

In these respects, MySQL is far ahead of most other database management
systems. However, to use these features effectively, you need to know
what character sets and collations are available, how to change the
defaults, and how they affect the behavior of string operators and
functions.


File: manual.info,  Node: charset-mysql,  Next: charset-syntax,  Prev: charset-general,  Up: charset

10.1.2 Character Sets and Collations in MySQL
---------------------------------------------

The MySQL server can support multiple character sets. To list the
available character sets, use the *Note `SHOW CHARACTER SET':
show-character-set. statement. A partial listing follows.  For more
complete information, see *Note charset-charsets::.


     mysql> SHOW CHARACTER SET;
     +----------+-----------------------------+---------------------+--------+
     | Charset  | Description                 | Default collation   | Maxlen |
     +----------+-----------------------------+---------------------+--------+
     | big5     | Big5 Traditional Chinese    | big5_chinese_ci     |      2 |
     | dec8     | DEC West European           | dec8_swedish_ci     |      1 |
     | cp850    | DOS West European           | cp850_general_ci    |      1 |
     | hp8      | HP West European            | hp8_english_ci      |      1 |
     | koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |      1 |
     | latin1   | cp1252 West European        | latin1_swedish_ci   |      1 |
     | latin2   | ISO 8859-2 Central European | latin2_general_ci   |      1 |
     | swe7     | 7bit Swedish                | swe7_swedish_ci     |      1 |
     | ascii    | US ASCII                    | ascii_general_ci    |      1 |
     | ujis     | EUC-JP Japanese             | ujis_japanese_ci    |      3 |
     | sjis     | Shift-JIS Japanese          | sjis_japanese_ci    |      2 |
     | hebrew   | ISO 8859-8 Hebrew           | hebrew_general_ci   |      1 |
     | tis620   | TIS620 Thai                 | tis620_thai_ci      |      1 |
     | euckr    | EUC-KR Korean               | euckr_korean_ci     |      2 |
     | koi8u    | KOI8-U Ukrainian            | koi8u_general_ci    |      1 |
     | gb2312   | GB2312 Simplified Chinese   | gb2312_chinese_ci   |      2 |
     | greek    | ISO 8859-7 Greek            | greek_general_ci    |      1 |
     | cp1250   | Windows Central European    | cp1250_general_ci   |      1 |
     | gbk      | GBK Simplified Chinese      | gbk_chinese_ci      |      2 |
     | latin5   | ISO 8859-9 Turkish          | latin5_turkish_ci   |      1 |
     ...

Any given character set always has at least one collation. It may have
several collations. To list the collations for a character set, use the
*Note `SHOW COLLATION': show-collation. statement. For example, to see
the collations for the `latin1' (cp1252 West European) character set,
use this statement to find those collation names that begin with
`latin1':


     mysql> SHOW COLLATION LIKE 'latin1%';
     +---------------------+---------+----+---------+----------+---------+
     | Collation           | Charset | Id | Default | Compiled | Sortlen |
     +---------------------+---------+----+---------+----------+---------+
     | latin1_german1_ci   | latin1  |  5 |         |          |       0 |
     | latin1_swedish_ci   | latin1  |  8 | Yes     | Yes      |       1 |
     | latin1_danish_ci    | latin1  | 15 |         |          |       0 |
     | latin1_german2_ci   | latin1  | 31 |         | Yes      |       2 |
     | latin1_bin          | latin1  | 47 |         | Yes      |       1 |
     | latin1_general_ci   | latin1  | 48 |         |          |       0 |
     | latin1_general_cs   | latin1  | 49 |         |          |       0 |
     | latin1_spanish_ci   | latin1  | 94 |         |          |       0 |
     +---------------------+---------+----+---------+----------+---------+

The `latin1' collations have the following meanings.

This table lists `latin1' character set collations, as described in the
example above, and provides the meaning of each collation.

Collation                     Meaning
`latin1_german1_ci'           German DIN-1
`latin1_swedish_ci'           Swedish/Finnish
`latin1_danish_ci'            Danish/Norwegian
`latin1_german2_ci'           German DIN-2
`latin1_bin'                  Binary according to `latin1' encoding
`latin1_general_ci'           Multilingual (Western European)
`latin1_general_cs'           Multilingual (ISO Western European), case
                              sensitive
`latin1_spanish_ci'           Modern Spanish

Collations have these general characteristics:

   * Two different character sets cannot have the same collation.

   * Each character set has one collation that is the _default
     collation_. For example, the default collation for `latin1' is
     `latin1_swedish_ci'. The output for *Note `SHOW CHARACTER SET':
     show-character-set. indicates which collation is the default for
     each displayed character set.

   * There is a convention for collation names: They start with the
     name of the character set with which they are associated, they
     usually include a language name, and they end with `_ci' (case
     insensitive), `_cs' (case sensitive), or `_bin' (binary).

In cases where a character set has multiple collations, it might not be
clear which collation is most suitable for a given application. To
avoid choosing the wrong collation, it can be helpful to perform some
comparisons with representative data values to make sure that a given
collation sorts values the way you expect.

Collation-Charts.Org (http://www.collation-charts.org/) is a useful
site for information that shows how one collation compares to another.


File: manual.info,  Node: charset-syntax,  Next: charset-connection,  Prev: charset-mysql,  Up: charset

10.1.3 Specifying Character Sets and Collations
-----------------------------------------------

* Menu:

* charset-server::               Server Character Set and Collation
* charset-database::             Database Character Set and Collation
* charset-table::                Table Character Set and Collation
* charset-column::               Column Character Set and Collation
* charset-literal::              Character String Literal Character Set and Collation
* charset-national::             National Character Set
* charset-examples::             Examples of Character Set and Collation Assignment
* charset-compatibility::        Compatibility with Other DBMSs

There are default settings for character sets and collations at four
levels: server, database, table, and column. The description in the
following sections may appear complex, but it has been found in
practice that multiple-level defaulting leads to natural and obvious
results.

`CHARACTER SET' is used in clauses that specify a character set.
`CHARSET' can be used as a synonym for `CHARACTER SET'.

Character set issues affect not only data storage, but also
communication between client programs and the MySQL server. If you want
the client program to communicate with the server using a character set
different from the default, you'll need to indicate which one. For
example, to use the `utf8' Unicode character set, issue this statement
after connecting to the server:


     SET NAMES 'utf8';

For more information about character set-related issues in
client/server communication, see *Note charset-connection::.


File: manual.info,  Node: charset-server,  Next: charset-database,  Prev: charset-syntax,  Up: charset-syntax

10.1.3.1 Server Character Set and Collation
...........................................

MySQL Server has a server character set and a server collation. These
can be set at server startup on the command line or in an option file
and changed at runtime.

Initially, the server character set and collation depend on the options
that you use when you start *Note `mysqld': mysqld. You can use
`--character-set-server' for the character set. Along with it, you can
add `--collation-server' for the collation. If you don't specify a
character set, that is the same as saying
`--character-set-server=latin1'.  If you specify only a character set
(for example, `latin1') but not a collation, that is the same as saying
`--character-set-server=latin1' `--collation-server=latin1_swedish_ci'
because `latin1_swedish_ci' is the default collation for `latin1'.
Therefore, the following three commands all have the same effect:


     shell> mysqld
     shell> mysqld --character-set-server=latin1
     shell> mysqld --character-set-server=latin1 \
                --collation-server=latin1_swedish_ci

One way to change the settings is by recompiling. If you want to change
the default server character set and collation when building from
sources, use: `--with-charset' and `--with-collation' as arguments for
`configure'. For example:


     shell> ./configure --with-charset=latin1

Or:


     shell> ./configure --with-charset=latin1 \
                --with-collation=latin1_german1_ci

Both *Note `mysqld': mysqld. and `configure' verify that the character
set/collation combination is valid. If not, each program displays an
error message and terminates.

The server character set and collation are used as default values if
the database character set and collation are not specified in *Note
`CREATE DATABASE': create-database.  statements. They have no other
purpose.

The current server character set and collation can be determined from
the values of the `character_set_server' and `collation_server' system
variables. These variables can be changed at runtime.


File: manual.info,  Node: charset-database,  Next: charset-table,  Prev: charset-server,  Up: charset-syntax

10.1.3.2 Database Character Set and Collation
.............................................

Every database has a database character set and a database collation.
The *Note `CREATE DATABASE': create-database.  and *Note `ALTER
DATABASE': alter-database. statements have optional clauses for
specifying the database character set and collation:


     CREATE DATABASE DB_NAME
         [[DEFAULT] CHARACTER SET CHARSET_NAME]
         [[DEFAULT] COLLATE COLLATION_NAME]

     ALTER DATABASE DB_NAME
         [[DEFAULT] CHARACTER SET CHARSET_NAME]
         [[DEFAULT] COLLATE COLLATION_NAME]

The keyword `SCHEMA' can be used instead of `DATABASE'.

All database options are stored in a text file named `db.opt' that can
be found in the database directory.

The `CHARACTER SET' and `COLLATE' clauses make it possible to create
databases with different character sets and collations on the same
MySQL server.

Example:


     CREATE DATABASE DB_NAME CHARACTER SET latin1 COLLATE latin1_swedish_ci;

MySQL chooses the database character set and database collation in the
following manner:

   * If both `CHARACTER SET X' and `COLLATE Y' are specified, character
     set X and collation Y are used.

   * If `CHARACTER SET X' is specified without `COLLATE', character set
     X and its default collation are used. To see the default collation
     for each character set, use the *Note `SHOW COLLATION':
     show-collation.  statement.

   * If `COLLATE Y' is specified without `CHARACTER SET', the character
     set associated with Y and collation Y are used.

   * Otherwise, the server character set and server collation are used.

The database character set and collation are used as default values for
table definitions if the table character set and collation are not
specified in *Note `CREATE TABLE': create-table. statements. The
database character set also is used by *Note `LOAD DATA INFILE':
load-data. The character set and collation have no other purposes.

The character set and collation for the default database can be
determined from the values of the `character_set_database' and
`collation_database' system variables. The server sets these variables
whenever the default database changes. If there is no default database,
the variables have the same value as the corresponding server-level
system variables, `character_set_server' and `collation_server'.


File: manual.info,  Node: charset-table,  Next: charset-column,  Prev: charset-database,  Up: charset-syntax

10.1.3.3 Table Character Set and Collation
..........................................

Every table has a table character set and a table collation.  The *Note
`CREATE TABLE': create-table. and *Note `ALTER TABLE': alter-table.
statements have optional clauses for specifying the table character set
and collation:


     CREATE TABLE TBL_NAME (COLUMN_LIST)
         [[DEFAULT] CHARACTER SET CHARSET_NAME]
         [COLLATE COLLATION_NAME]]

     ALTER TABLE TBL_NAME
         [[DEFAULT] CHARACTER SET CHARSET_NAME]
         [COLLATE COLLATION_NAME]

Example:


     CREATE TABLE t1 ( ... )
     CHARACTER SET latin1 COLLATE latin1_danish_ci;

MySQL chooses the table character set and collation in the following
manner:

   * If both `CHARACTER SET X' and `COLLATE Y' are specified, character
     set X and collation Y are used.

   * If `CHARACTER SET X' is specified without `COLLATE', character set
     X and its default collation are used. To see the default collation
     for each character set, use the *Note `SHOW COLLATION':
     show-collation.  statement.

   * If `COLLATE Y' is specified without `CHARACTER SET', the character
     set associated with Y and collation Y are used.

   * Otherwise, the database character set and collation are used.

The table character set and collation are used as default values for
column definitions if the column character set and collation are not
specified in individual column definitions.  The table character set
and collation are MySQL extensions; there are no such things in
standard SQL.


File: manual.info,  Node: charset-column,  Next: charset-literal,  Prev: charset-table,  Up: charset-syntax

10.1.3.4 Column Character Set and Collation
...........................................

Every `character' column (that is, a column of type *Note `CHAR': char,
*Note `VARCHAR': char, or *Note `TEXT': blob.) has a column character
set and a column collation. Column definition syntax for *Note `CREATE
TABLE': create-table. and *Note `ALTER TABLE': alter-table. has optional
clauses for specifying the column character set and collation:


     COL_NAME {CHAR | VARCHAR | TEXT} (COL_LENGTH)
         [CHARACTER SET CHARSET_NAME]
         [COLLATE COLLATION_NAME]

These clauses can also be used for *Note `ENUM': enum. and *Note `SET':
set. columns:


     COL_NAME {ENUM | SET} (VAL_LIST)
         [CHARACTER SET CHARSET_NAME]
         [COLLATE COLLATION_NAME]

Examples:


     CREATE TABLE t1
     (
         col1 VARCHAR(5)
           CHARACTER SET latin1
           COLLATE latin1_german1_ci
     );

     ALTER TABLE t1 MODIFY
         col1 VARCHAR(5)
           CHARACTER SET latin1
           COLLATE latin1_swedish_ci;

MySQL chooses the column character set and collation in the following
manner:

   * If both `CHARACTER SET X' and `COLLATE Y' are specified, character
     set X and collation Y are used.


          CREATE TABLE t1
          (
              col1 CHAR(10) CHARACTER SET utf8 COLLATE utf8_unicode_ci
          ) CHARACTER SET latin1 COLLATE latin1_bin;

     The character set and collation are specified for the column, so
     they are used. The column has character set `utf8' and collation
     `utf8_unicode_ci'.

   * If `CHARACTER SET X' is specified without `COLLATE', character set
     X and its default collation are used.


          CREATE TABLE t1
          (
              col1 CHAR(10) CHARACTER SET utf8
          ) CHARACTER SET latin1 COLLATE latin1_bin;

     The character set is specified for the column, but the collation
     is not. The column has character set `utf8' and the default
     collation for `utf8', which is `utf8_general_ci'. To see the
     default collation for each character set, use the *Note `SHOW
     COLLATION': show-collation. statement.

   * If `COLLATE Y' is specified without `CHARACTER SET', the character
     set associated with Y and collation Y are used.


          CREATE TABLE t1
          (
              col1 CHAR(10) COLLATE utf8_polish_ci
          ) CHARACTER SET latin1 COLLATE latin1_bin;

     The collation is specified for the column, but the character set
     is not. The column has collation `utf8_polish_ci' and the
     character set is the one associated with the collation, which is
     `utf8'.

   * Otherwise, the table character set and collation are used.


          CREATE TABLE t1
          (
              col1 CHAR(10)
          ) CHARACTER SET latin1 COLLATE latin1_bin;

     Neither the character set nor collation are specified for the
     column, so the table defaults are used. The column has character
     set `latin1' and collation `latin1_bin'.

The `CHARACTER SET' and `COLLATE' clauses are standard SQL.

If you use *Note `ALTER TABLE': alter-table. to convert a column from
one character set to another, MySQL attempts to map the data values,
but if the character sets are incompatible, there may be data loss.


File: manual.info,  Node: charset-literal,  Next: charset-national,  Prev: charset-column,  Up: charset-syntax

10.1.3.5 Character String Literal Character Set and Collation
.............................................................

Every character string literal has a character set and a collation.

A character string literal may have an optional character set
introducer and `COLLATE' clause:


     [_CHARSET_NAME]'STRING' [COLLATE COLLATION_NAME]

Examples:


     SELECT 'STRING';
     SELECT _latin1'STRING';
     SELECT _latin1'STRING' COLLATE latin1_danish_ci;

For the simple statement `SELECT 'STRING'', the string has the
character set and collation defined by the `character_set_connection'
and `collation_connection' system variables.

The `_CHARSET_NAME' expression is formally called an _introducer_. It
tells the parser, `the string that is about to follow uses character set
X.' Because this has confused people in the past, we emphasize that an
introducer does not change the string to the introducer character set
like `CONVERT()' would do. It does not change the string's value,
although padding may occur. The introducer is just a signal. An
introducer is also legal before standard hex literal and numeric hex
literal notation (`x'LITERAL'' and `0xNNNN'), or before bit-field
literal notation (`b'LITERAL'' and `0bNNNN').

Examples:


     SELECT _latin1 x'AABBCC';
     SELECT _latin1 0xAABBCC;
     SELECT _latin1 b'1100011';
     SELECT _latin1 0b1100011;

MySQL determines a literal's character set and collation in the
following manner:

   * If both _X and `COLLATE Y' are specified, character set X and
     collation Y are used.

   * If _X is specified but `COLLATE' is not specified, character set X
     and its default collation are used. To see the default collation
     for each character set, use the *Note `SHOW COLLATION':
     show-collation.  statement.

   * Otherwise, the character set and collation given by the
     `character_set_connection' and `collation_connection' system
     variables are used.

Examples:

   * A string with `latin1' character set and `latin1_german1_ci'
     collation:


          SELECT _latin1'Mu"ller' COLLATE latin1_german1_ci;

   * A string with `latin1' character set and its default collation
     (that is, `latin1_swedish_ci'):


          SELECT _latin1'Mu"ller';

   * A string with the connection default character set and collation:


          SELECT 'Mu"ller';

Character set introducers and the `COLLATE' clause are implemented
according to standard SQL specifications.

An introducer indicates the character set for the following string, but
does not change now how the parser performs escape processing within
the string. Escapes are always interpreted by the parser according to
the character set given by `character_set_connection'.

The following examples show that escape processing occurs using
`character_set_connection' even in the presence of an introducer. The
examples use `SET NAMES' (which changes `character_set_connection', as
discussed in *Note charset-connection::), and display the resulting
strings using the `HEX()' function so that the exact string contents
can be seen.

Example 1:


     mysql> SET NAMES latin1;
     Query OK, 0 rows affected (0.01 sec)

     mysql> SELECT HEX('a`\n'), HEX(_sjis'a`\n');
     +------------+-----------------+
     | HEX('a`\n') | HEX(_sjis'a`\n') |
     +------------+-----------------+
     | E00A       | E00A            |
     +------------+-----------------+
     1 row in set (0.00 sec)

Here, ``a`'' (hex value `E0') is followed by ``\n'', the escape
sequence for newline. The escape sequence is interpreted using the
`character_set_connection' value of `latin1' to produce a literal
newline (hex value `0A'). This happens even for the second string. That
is, the introducer of `_sjis' does not affect the parser's escape
processing.

Example 2:


     mysql> SET NAMES sjis;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT HEX('a`\n'), HEX(_latin1'a`\n');
     +------------+-------------------+
     | HEX('a`\n') | HEX(_latin1'a`\n') |
     +------------+-------------------+
     | E05C6E     | E05C6E            |
     +------------+-------------------+
     1 row in set (0.04 sec)

Here, `character_set_connection' is `sjis', a character set in which
the sequence of ``a`'' followed by ``\'' (hex values `05' and `5C') is
a valid multibyte character. Hence, the first two bytes of the string
are interpreted as a single `sjis' character, and the ``\'' is not
interpreted as an escape character. The following ``n'' (hex value
`6E') is not interpreted as part of an escape sequence. This is true
even for the second string; the introducer of `_latin1' does not affect
escape processing.


File: manual.info,  Node: charset-national,  Next: charset-examples,  Prev: charset-literal,  Up: charset-syntax

10.1.3.6 National Character Set
...............................

Standard SQL defines *Note `NCHAR': char. or *Note `NATIONAL CHAR':
char. as a way to indicate that a *Note `CHAR': char. column should use
some predefined character set. MySQL 5.1 uses `utf8' as this predefined
character set. For example, these data type declarations are equivalent:


     CHAR(10) CHARACTER SET utf8
     NATIONAL CHARACTER(10)
     NCHAR(10)

As are these:


     VARCHAR(10) CHARACTER SET utf8
     NATIONAL VARCHAR(10)
     NCHAR VARCHAR(10)
     NATIONAL CHARACTER VARYING(10)
     NATIONAL CHAR VARYING(10)

You can use `N'LITERAL'' (or `n'LITERAL'') to create a string in the
national character set. These statements are equivalent:


     SELECT N'some text';
     SELECT n'some text';
     SELECT _utf8'some text';

For information on upgrading character sets to MySQL 5.1 from versions
prior to 4.1, see the `MySQL 3.23, 4.0, 4.1 Reference Manual'.


File: manual.info,  Node: charset-examples,  Next: charset-compatibility,  Prev: charset-national,  Up: charset-syntax

10.1.3.7 Examples of Character Set and Collation Assignment
...........................................................

The following examples show how MySQL determines default character set
and collation values.

*Example 1: Table and Column Definition*


     CREATE TABLE t1
     (
         c1 CHAR(10) CHARACTER SET latin1 COLLATE latin1_german1_ci
     ) DEFAULT CHARACTER SET latin2 COLLATE latin2_bin;

Here we have a column with a `latin1' character set and a
`latin1_german1_ci' collation. The definition is explicit, so that is
straightforward. Notice that there is no problem with storing a
`latin1' column in a `latin2' table.

*Example 2: Table and Column Definition*


     CREATE TABLE t1
     (
         c1 CHAR(10) CHARACTER SET latin1
     ) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;

This time we have a column with a `latin1' character set and a default
collation. Although it might seem natural, the default collation is not
taken from the table level. Instead, because the default collation for
`latin1' is always `latin1_swedish_ci', column `c1' has a collation of
`latin1_swedish_ci' (not `latin1_danish_ci').

*Example 3: Table and Column Definition*


     CREATE TABLE t1
     (
         c1 CHAR(10)
     ) DEFAULT CHARACTER SET latin1 COLLATE latin1_danish_ci;

We have a column with a default character set and a default collation.
In this circumstance, MySQL checks the table level to determine the
column character set and collation.  Consequently, the character set
for column `c1' is `latin1' and its collation is `latin1_danish_ci'.

*Example 4: Database, Table, and Column Definition*


     CREATE DATABASE d1
         DEFAULT CHARACTER SET latin2 COLLATE latin2_czech_ci;
     USE d1;
     CREATE TABLE t1
     (
         c1 CHAR(10)
     );

We create a column without specifying its character set and collation.
We're also not specifying a character set and a collation at the table
level. In this circumstance, MySQL checks the database level to
determine the table settings, which thereafter become the column
settings.) Consequently, the character set for column `c1' is `latin2'
and its collation is `latin2_czech_ci'.


File: manual.info,  Node: charset-compatibility,  Prev: charset-examples,  Up: charset-syntax

10.1.3.8 Compatibility with Other DBMSs
.......................................

For MaxDB compatibility these two statements are the same:


     CREATE TABLE t1 (f1 CHAR(N) UNICODE);
     CREATE TABLE t1 (f1 CHAR(N) CHARACTER SET ucs2);


File: manual.info,  Node: charset-connection,  Next: charset-applications,  Prev: charset-syntax,  Up: charset

10.1.4 Connection Character Sets and Collations
-----------------------------------------------

Several character set and collation system variables relate to a
client's interaction with the server. Some of these have been mentioned
in earlier sections:

   * The server character set and collation are the values of the
     `character_set_server' and `collation_server' system variables.

   * The character set and collation of the default database are the
     values of the `character_set_database' and `collation_database'
     system variables.

Additional character set and collation system variables are involved in
handling traffic for the connection between a client and the server.
Every client has connection-related character set and collation system
variables.

A `connection' is what you make when you connect to the server. The
client sends SQL statements, such as queries, over the connection to
the server. The server sends responses, such as result sets or error
messages, over the connection back to the client. This leads to several
questions about character set and collation handling for client
connections, each of which can be answered in terms of system variables:

   * What character set is the statement in when it leaves the client?

     The server takes the `character_set_client' system variable to be
     the character set in which statements are sent by the client.

   * What character set should the server translate a statement to
     after receiving it?

     For this, the server uses the `character_set_connection' and
     `collation_connection' system variables. It converts statements
     sent by the client from `character_set_client' to
     `character_set_connection' (except for string literals that have
     an introducer such as `_latin1' or `_utf8').
     `collation_connection' is important for comparisons of literal
     strings. For comparisons of strings with column values,
     `collation_connection' does not matter because columns have their
     own collation, which has a higher collation precedence.

   * What character set should the server translate to before shipping
     result sets back to the client?

     The `character_set_results' system variable indicates the
     character set in which the server returns query results to the
     client. This includes result data such as column values, and
     result metadata such as column names.

Clients can fine-tune the settings for these variables, or depend on
the defaults (in which case, you can skip the rest of this section). If
you do not use the defaults, you must change the character settings
_for each connection to the server._

Two statements affect the connection-related character set variables as
a group:

   * `SET NAMES 'CHARSET_NAME' [COLLATE 'COLLATION_NAME']'

     `SET NAMES' indicates what character set the client will use to
     send SQL statements to the server.  Thus, `SET NAMES 'cp1251''
     tells the server, `future incoming messages from this client are
     in character set `cp1251'.' It also specifies the character set
     that the server should use for sending results back to the client.
     (For example, it indicates what character set to use for column
     values if you use a *Note `SELECT': select. statement.)

     A `SET NAMES 'CHARSET_NAME'' statement is equivalent to these
     three statements:


          SET character_set_client = CHARSET_NAME;
          SET character_set_results = CHARSET_NAME;
          SET character_set_connection = CHARSET_NAME;

     Setting `character_set_connection' to CHARSET_NAME also implicitly
     sets `collation_connection' to the default collation for
     CHARSET_NAME. It is unnecessary to set that collation explicitly.
     To specify a particular collation, use the optional `COLLATE'
     clause:


          SET NAMES 'CHARSET_NAME' COLLATE 'COLLATION_NAME'

   * `SET CHARACTER SET CHARSET_NAME'

     `SET CHARACTER SET' is similar to `SET NAMES' but sets
     `character_set_connection' and `collation_connection' to
     `character_set_database' and `collation_database'. A `SET
     CHARACTER SET CHARSET_NAME' statement is equivalent to these three
     statements:


          SET character_set_client = CHARSET_NAME;
          SET character_set_results = CHARSET_NAME;
          SET collation_connection = @@collation_database;

     Setting `collation_connection' also implicitly sets
     `character_set_connection' to the character set associated with
     the collation (equivalent to executing `SET
     character_set_connection = @@character_set_database'). It is
     unnecessary to set `character_set_connection' explicitly.

*Note*:

`ucs2' cannot be used as a client character set, which means that it
does not work for `SET NAMES' or `SET CHARACTER SET'.

The MySQL client programs `mysql', `mysqladmin', `mysqlcheck',
`mysqlimport', and `mysqlshow' determine the default character set to
use as follows:

   * In the absence of other information, the programs use the
     compiled-in default character set, usually `latin1'.

   * The programs support a `--default-character-set' option, which
     enables users to specify the character set explicitly to override
     whatever default the client otherwise determines.

When a client connects to the server, it sends the name of the
character set that it wants to use. The server uses the name to set the
`character_set_client', `character_set_results', and
`character_set_connection' system variables. In effect, the server
performs a `SET NAMES' operation using the character set name.

With the *Note `mysql': mysql. client, to use a character set different
from the default, you could explicitly execute `SET NAMES' every time
you start up. To accomplish the same result more easily, add the
`--default-character-set' option setting to your *Note `mysql': mysql.
command line or in your option file. For example, the following option
file setting changes the three connection-related character set
variables set to `koi8r' each time you invoke *Note `mysql': mysql.:


     [mysql]
     default-character-set=koi8r

If you are using the *Note `mysql': mysql. client with auto-reconnect
enabled (which is not recommended), it is preferable to use the
`charset' command rather than `SET NAMES'. For example:


     mysql> charset utf8
     Charset changed

The `charset' command issues a `SET NAMES' statement, and also changes
the default character set that *Note `mysql': mysql. uses when it
reconnects after the connection has dropped.

Example: Suppose that `column1' is defined as `CHAR(5) CHARACTER SET
latin2'. If you do not say `SET NAMES' or `SET CHARACTER SET', then for
`SELECT column1 FROM t', the server sends back all the values for
`column1' using the character set that the client specified when it
connected. On the other hand, if you say `SET NAMES 'latin1'' or `SET
CHARACTER SET latin1' before issuing the *Note `SELECT': select.
statement, the server converts the `latin2' values to `latin1' just
before sending results back.  Conversion may be lossy if there are
characters that are not in both character sets.

If you want the server to perform no conversion of result sets or error
messages, set `character_set_results' to `NULL' or `binary':


     SET character_set_results = NULL;

To see the values of the character set and collation system variables
that apply to your connection, use these statements:


     SHOW VARIABLES LIKE 'character_set%';
     SHOW VARIABLES LIKE 'collation%';

You must also consider the environment within which your MySQL
applications execute. See *Note charset-applications::.

For more information about character sets and error messages, see *Note
charset-errors::.


File: manual.info,  Node: charset-applications,  Next: charset-errors,  Prev: charset-connection,  Up: charset

10.1.5 Configuring the Character Set and Collation for Applications
-------------------------------------------------------------------

For applications that store data using the default MySQL character set
and collation (`latin1', `latin1_swedish_ci'), no special configuration
should be needed. If applications require data storage using a
different character set or collation, you can configure character set
information several ways:

   * Specify character settings per database. For example, applications
     that use one database might require `utf8', whereas applications
     that use another database might require `sjis'.

   * Specify character settings at server startup. This causes the
     server to use the given settings for all applications that do not
     make other arrangements.

   * Specify character settings at configuration time, if you build
     MySQL from source. This causes the server to use the given
     settings for all applications, without having to specify them at
     server startup.

When different applications require different character settings, the
per-database technique provides a good deal of flexibility. If most or
all applications use the same character set, specifying character
settings at server startup or configuration time may be most convenient.

For the per-database or server-startup techniques, the settings control
the character set for data storage. Applications must also tell the
server which character set to use for client/server communications, as
described in the following instructions.

The examples shown here assume use of the `utf8' character set and
`utf8_general_ci' collation.

*Specify character settings per database.* To create a database such
that its tables will use a given default character set and collation
for data storage, use a *Note `CREATE DATABASE': create-database.
statement like this:


     CREATE DATABASE mydb
       DEFAULT CHARACTER SET utf8
       DEFAULT COLLATE utf8_general_ci;

Tables created in the database will use `utf8' and `utf8_general_ci' by
default for any character columns.

Applications that use the database should also configure their
connection to the server each time they connect. This can be done by
executing a `SET NAMES 'utf8'' statement after connecting. The
statement can be used regardless of connection method: The *Note
`mysql': mysql. client, PHP scripts, and so forth.

In some cases, it may be possible to configure the connection to use
the desired character set some other way. For example, for connections
made using *Note `mysql': mysql, you can specify the
`--default-character-set=utf8' command-line option to achieve the same
effect as `SET NAMES 'utf8''.

For more information about configuring client connections, see *Note
charset-connection::.

If you change the default character set or collation for a database,
stored routines that use the database defaults must be dropped and
recreated so that they use the new defaults. (In a stored routine,
variables with character data types use the database defaults if the
character set or collation are not specified explicitly. See *Note
create-procedure::.)

*Specify character settings at server startup.* To select a character
set and collation at server startup, use the `--character-set-server'
and `--collation-server' options. For example, to specify the options
in an option file, include these lines:


     [mysqld]
     character-set-server=utf8
     collation-server=utf8_general_ci

These settings apply server-wide and apply as the defaults for
databases created by any application, and for tables created in those
databases.

It is still necessary for applications to configure their connection
using `SET NAMES' or equivalent after they connect, as described
previously. You might be tempted to start the server with the
`--init_connect="SET NAMES 'utf8'"' option to cause `SET NAMES' to be
executed automatically for each client that connects. However, this will
yield inconsistent results because the `init_connect' value is not
executed for users who have the `SUPER' privilege.

*Specify character settings at MySQL configuration time.* To select a
character set and collation when you configure and build MySQL from
source, use the `--with-charset' and `--with-collation' options:


     shell> ./configure --with-charset=utf8 --with-collation=utf8_general_ci

The resulting server uses `utf8' and `utf8_general_ci' as the default
for databases and tables and for client connections. It is unnecessary
to use `--character-set-server' and `--collation-server' to specify
those defaults at server startup. It is also unnecessary for
applications to configure their connection using `SET NAMES' or
equivalent after they connect to the server.

Regardless of how you configure the MySQL character set for application
use, you must also consider the environment within which those
applications execute. If you will send statements using UTF-8 text
taken from a file that you create in an editor, you should edit the
file with the locale of your environment set to UTF-8 so that the file
encoding is correct and so that the operating system handles it
correctly. If you use the *Note `mysql': mysql. client from within a
terminal window, the window must be configured to use UTF-8 or
characters may not display properly. For a script that executes in a Web
environment, the script must handle character encoding properly for its
interaction with the MySQL server, and it must generate pages that
correctly indicate the encoding so that browsers know how to display
the content of the pages. For example, you can include this `<meta>'
tag within your `<head>' element:


     <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />


File: manual.info,  Node: charset-errors,  Next: charset-collations,  Prev: charset-applications,  Up: charset

10.1.6 Character Set for Error Messages
---------------------------------------

This section describes how the server uses character sets for
constructing error messages and returning them to clients. For
information about the language of error messages (rather than the
character set), see *Note error-message-language::.

In MySQL 5.1, the server constructs error messages and returns them to
clients as follows:

   * The message template has the character set associated with the
     error message language. For example, English, Korean, and Russian
     messages use `latin1', `euckr', and `koi8r', respectively.

   * Parameters in the message template are replaced with values that
     apply to a specific error occurrence. These parameters use their
     own character set. Identifiers such as table or column names use
     UTF-8. Data values retain their character set. For example, in the
     following duplicate-key message, `'XXX'' has the character set of
     the table column associated with key 1:


          Duplicate entry 'XXX' for key1

The preceding method of error-message construction can result in
messages that contain a mix of character sets unless all items involved
contain only ASCII characters. This issue is resolved in MySQL 5.5, in
which error messages are constructed internally within the server using
UTF-8 and returned to the client in the character set specified by the
`character_set_results' system variable.


File: manual.info,  Node: charset-collations,  Next: charset-repertoire,  Prev: charset-errors,  Up: charset

10.1.7 Collation Issues
-----------------------

* Menu:

* charset-collation-names::      Collation Names
* charset-collate::              Using COLLATE in SQL Statements
* charset-collate-precedence::   COLLATE Clause Precedence
* charset-collation-charset::    Collations Must Be for the Right Character Set
* charset-collation-expressions::  Collation of Expressions
* charset-binary-collations::    The _bin and binary Collations
* charset-binary-op::            The BINARY Operator
* charset-collation-effect::     Examples of the Effect of Collation
* charset-collation-information-schema::  Collation and INFORMATION_SCHEMA Searches

The following sections discuss various aspects of character set
collations.


File: manual.info,  Node: charset-collation-names,  Next: charset-collate,  Prev: charset-collations,  Up: charset-collations

10.1.7.1 Collation Names
........................

MySQL collation names follow these rules:

   * A name ending in `_ci' indicates a case-insensitive collation.

   * A name ending in `_cs' indicates a case-sensitive collation.

   * A name ending in `_bin' indicates a binary collation. Character
     comparisons are based on character binary code values.


File: manual.info,  Node: charset-collate,  Next: charset-collate-precedence,  Prev: charset-collation-names,  Up: charset-collations

10.1.7.2 Using COLLATE in SQL Statements
........................................

With the `COLLATE' clause, you can override whatever the default
collation is for a comparison.  `COLLATE' may be used in various parts
of SQL statements. Here are some examples:

   * With `ORDER BY':


          SELECT k
          FROM t1
          ORDER BY k COLLATE latin1_german2_ci;

   * With `AS':


          SELECT k COLLATE latin1_german2_ci AS k1
          FROM t1
          ORDER BY k1;

   * With `GROUP BY':


          SELECT k
          FROM t1
          GROUP BY k COLLATE latin1_german2_ci;

   * With aggregate functions:


          SELECT MAX(k COLLATE latin1_german2_ci)
          FROM t1;

   * With `DISTINCT':


          SELECT DISTINCT k COLLATE latin1_german2_ci
          FROM t1;

   * With `WHERE':


               SELECT *
               FROM t1
               WHERE _latin1 'Mu"ller' COLLATE latin1_german2_ci = k;


               SELECT *
               FROM t1
               WHERE k LIKE _latin1 'Mu"ller' COLLATE latin1_german2_ci;

   * With `HAVING':


          SELECT k
          FROM t1
          GROUP BY k
          HAVING k = _latin1 'Mu"ller' COLLATE latin1_german2_ci;


File: manual.info,  Node: charset-collate-precedence,  Next: charset-collation-charset,  Prev: charset-collate,  Up: charset-collations

10.1.7.3 COLLATE Clause Precedence
..................................

The `COLLATE' clause has high precedence (higher than `||'), so the
following two expressions are equivalent:


     x || y COLLATE z
     x || (y COLLATE z)


File: manual.info,  Node: charset-collation-charset,  Next: charset-collation-expressions,  Prev: charset-collate-precedence,  Up: charset-collations

10.1.7.4 Collations Must Be for the Right Character Set
.......................................................

Each character set has one or more collations, but each collation is
associated with one and only one character set.  Therefore, the
following statement causes an error message because the `latin2_bin'
collation is not legal with the `latin1' character set:


     mysql> SELECT _latin1 'x' COLLATE latin2_bin;
     ERROR 1253 (42000): COLLATION 'latin2_bin' is not valid
     for CHARACTER SET 'latin1'


File: manual.info,  Node: charset-collation-expressions,  Next: charset-binary-collations,  Prev: charset-collation-charset,  Up: charset-collations

10.1.7.5 Collation of Expressions
.................................

In the great majority of statements, it is obvious what collation MySQL
uses to resolve a comparison operation. For example, in the following
cases, it should be clear that the collation is the collation of column
`charset_name':


     SELECT x FROM T ORDER BY x;
     SELECT x FROM T WHERE x = x;
     SELECT DISTINCT x FROM T;

However, with multiple operands, there can be ambiguity. For example:


     SELECT x FROM T WHERE x = 'Y';

Should the comparison use the collation of the column `x', or of the
string literal `'Y''? Both `x' and `'Y'' have collations, so which
collation takes precedence?

Standard SQL resolves such questions using what used to be called
`coercibility' rules. MySQL assigns coercibility values as follows:

   * An explicit `COLLATE' clause has a coercibility of 0. (Not
     coercible at all.)

   * The concatenation of two strings with different collations has a
     coercibility of 1.

   * The collation of a column or a stored routine parameter or local
     variable has a coercibility of 2.

   * A `system constant' (the string returned by functions such as
     `USER()' or `VERSION()') has a coercibility of 3.

   * The collation of a literal has a coercibility of 4.

   * `NULL' or an expression that is derived from `NULL' has a
     coercibility of 5.

MySQL uses coercibility values with the following rules to resolve
ambiguities:

   * Use the collation with the lowest coercibility value.

   * If both sides have the same coercibility, then:

        * If both sides are Unicode, or both sides are not Unicode, it
          is an error.

        * If one of the sides has a Unicode character set, and another
          side has a non-Unicode character set, the side with Unicode
          character set wins, and automatic character set conversion is
          applied to the non-Unicode side. For example, the following
          statement does not return an error:


               SELECT CONCAT(utf8_column, latin1_column) FROM t1;

          It returns a result that has a character set of `utf8' and
          the same collation as `utf8_column'. Values of
          `latin1_column' are automatically converted to `utf8' before
          concatenating.

        * For an operation with operands from the same character set
          but that mix a `_bin' collation and a `_ci' or `_cs'
          collation, the `_bin' collation is used. This is similar to
          how operations that mix nonbinary and binary strings evaluate
          the operands as binary strings, except that it is for
          collations rather than data types.

Although automatic conversion is not in the SQL standard, the SQL
standard document does say that every character set is (in terms of
supported characters) a `subset' of Unicode. Because it is a well-known
principle that `what applies to a superset can apply to a subset,' we
believe that a collation for Unicode can apply for comparisons with
non-Unicode strings.

Examples:

This table lists comparisons and the collation used for each comparison.

Comparison                           Collation Used
`column1 = 'A''                      Use collation of `column1'
`column1 = 'A' COLLATE x'            Use collation of `'A' COLLATE x'
`column1 COLLATE x = 'A' COLLATE y'  Error

The `COERCIBILITY()' function can be used to determine the coercibility
of a string expression:


     mysql> SELECT COERCIBILITY('A' COLLATE latin1_swedish_ci);
             -> 0
     mysql> SELECT COERCIBILITY(VERSION());
             -> 3
     mysql> SELECT COERCIBILITY('A');
             -> 4

See *Note information-functions::.

For implicit conversion of a numeric or temporal value to a string,
such as occurs for the argument `1' in the expression `CONCAT(1,
'abc')', the result is a binary string for which the character set and
collation are `binary'. See *Note type-conversion::.


File: manual.info,  Node: charset-binary-collations,  Next: charset-binary-op,  Prev: charset-collation-expressions,  Up: charset-collations

10.1.7.6 The _bin and binary Collations
.......................................

This section describes how `_bin' collations for nonbinary strings
differ from the `binary' `collation' for binary strings.

Nonbinary strings (as stored in the *Note `CHAR': char, *Note
`VARCHAR': char, and *Note `TEXT': blob. data types) have a character
set and collation. A given character set can have several collations,
each of which defines a particular sorting and comparison order for the
characters in the set. One of these is the binary collation for the
character set, indicated by a `_bin' suffix in the collation name. For
example, `latin1' and `utf8' have binary collations named `latin1_bin'
and `utf8_bin'.

Binary strings (as stored in the *Note `BINARY': binary-varbinary,
*Note `VARBINARY': binary-varbinary, and *Note `BLOB': blob. data
types) have no character set or collation in the sense that nonbinary
strings do. (Applied to a binary string, the `CHARSET()' and
`COLLATION()' functions both return a value of `binary'.) Binary
strings are sequences of bytes and the numeric values of those bytes
determine sort order.

The `_bin' collations differ from the `binary' collation in several
respects.

*The unit for sorting and comparison.* Binary strings are sequences of
bytes.  Sorting and comparison is always based on numeric byte values.
Nonbinary strings are sequences of characters, which might be
multibyte. Collations for nonbinary strings define an ordering of the
character values for sorting and comparison. For the `_bin' collation,
this ordering is based solely on binary code values of the characters
(which is similar to ordering for binary strings except that a `_bin'
collation must take into account that a character might contain
multiple bytes). For other collations, character ordering might take
additional factors such as lettercase into account.

*Character set conversion.* A nonbinary string has a character set and
is converted to another character set in many cases, even when the
string has a `_bin' collation:

   * When assigning column values from another column that has a
     different character set:


          UPDATE t1 SET utf8_bin_column=latin1_column;
          INSERT INTO t1 (latin1_column) SELECT utf8_bin_column FROM t2;

   * When assigning column values for *Note `INSERT': insert. or *Note
     `UPDATE': update. using a string literal:


          SET NAMES latin1;
          INSERT INTO t1 (utf8_bin_column) VALUES ('string-in-latin1');

   * When sending results from the server to a client:


          SET NAMES latin1;
          SELECT utf8_bin_column FROM t2;

For binary string columns, no conversion occurs. For the preceding
cases, the string value is copied byte-wise.

*Lettercase conversion.* Collations provide information about
lettercase of characters, so characters in a nonbinary string can be
converted from one lettercase to another, even for `_bin' collations
that ignore lettercase for ordering:


     mysql> SET NAMES latin1 COLLATE latin1_bin;
     Query OK, 0 rows affected (0.02 sec)

     mysql> SELECT LOWER('aA'), UPPER('zZ');
     +-------------+-------------+
     | LOWER('aA') | UPPER('zZ') |
     +-------------+-------------+
     | aa          | ZZ          |
     +-------------+-------------+
     1 row in set (0.13 sec)

The concept of lettercase does not apply to bytes in a binary string.
To perform lettercase conversion, the string must be converted to a
nonbinary string:


     mysql> SET NAMES binary;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT LOWER('aA'), LOWER(CONVERT('aA' USING latin1));
     +-------------+-----------------------------------+
     | LOWER('aA') | LOWER(CONVERT('aA' USING latin1)) |
     +-------------+-----------------------------------+
     | aA          | aa                                |
     +-------------+-----------------------------------+
     1 row in set (0.00 sec)

*Trailing space handling in comparisons.* Nonbinary strings have
`PADSPACE' behavior for all collations, including `_bin' collations.
Trailing spaces are insignificant in comparisons:


     mysql> SET NAMES utf8 COLLATE utf8_bin;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT 'a ' = 'a';
     +------------+
     | 'a ' = 'a' |
     +------------+
     |          1 |
     +------------+
     1 row in set (0.00 sec)

For binary strings, all characters are significant in comparisons,
including trailing spaces:


     mysql> SET NAMES binary;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT 'a ' = 'a';
     +------------+
     | 'a ' = 'a' |
     +------------+
     |          0 |
     +------------+
     1 row in set (0.00 sec)

*Trailing space handling for inserts and retrievals.* `CHAR(N)' columns
store nonbinary strings. Values shorter than N characters are extended
with spaces on insertion. For retrieval, trailing spaces are removed.

`BINARY(N)' columns store binary strings. Values shorter than N bytes
are extended with `0x00' bytes on insertion. For retrieval, nothing is
removed; a value of the declared length is always returned.


     mysql> CREATE TABLE t1 (
         ->   a CHAR(10) CHARACTER SET utf8 COLLATE utf8_bin,
         ->   b BINARY(10)
         -> );
     Query OK, 0 rows affected (0.09 sec)

     mysql> INSERT INTO t1 VALUES ('a','a');
     Query OK, 1 row affected (0.01 sec)

     mysql> SELECT HEX(a), HEX(b) FROM t1;
     +--------+----------------------+
     | HEX(a) | HEX(b)               |
     +--------+----------------------+
     | 61     | 61000000000000000000 |
     +--------+----------------------+
     1 row in set (0.04 sec)


File: manual.info,  Node: charset-binary-op,  Next: charset-collation-effect,  Prev: charset-binary-collations,  Up: charset-collations

10.1.7.7 The BINARY Operator
............................

The `BINARY' operator casts the string following it to a binary string.
This is an easy way to force a comparison to be done byte by byte
rather than character by character. `BINARY' also causes trailing
spaces to be significant.


     mysql> SELECT 'a' = 'A';
             -> 1
     mysql> SELECT BINARY 'a' = 'A';
             -> 0
     mysql> SELECT 'a' = 'a ';
             -> 1
     mysql> SELECT BINARY 'a' = 'a ';
             -> 0

`BINARY STR' is shorthand for `CAST(STR AS BINARY)'.

The `BINARY' attribute in character column definitions has a different
effect. A character column defined with the `BINARY' attribute is
assigned the binary collation of the column character set. Every
character set has a binary collation. For example, the binary collation
for the `latin1' character set is `latin1_bin', so if the table default
character set is `latin1', these two column definitions are equivalent:


     CHAR(10) BINARY
     CHAR(10) CHARACTER SET latin1 COLLATE latin1_bin

The effect of `BINARY' as a column attribute differs from its effect
prior to MySQL 4.1. Formerly, `BINARY' resulted in a column that was
treated as a binary string. A binary string is a string of bytes that
has no character set or collation, which differs from a nonbinary
character string that has a binary collation.  For both types of
strings, comparisons are based on the numeric values of the string
unit, but for nonbinary strings the unit is the character and some
character sets support multibyte characters. *Note binary-varbinary::.

The use of `CHARACTER SET binary' in the definition of a *Note `CHAR':
char, *Note `VARCHAR': char, or *Note `TEXT': blob. column causes the
column to be treated as a binary data type. For example, the following
pairs of definitions are equivalent:


     CHAR(10) CHARACTER SET binary
     BINARY(10)

     VARCHAR(10) CHARACTER SET binary
     VARBINARY(10)

     TEXT CHARACTER SET binary
     BLOB


File: manual.info,  Node: charset-collation-effect,  Next: charset-collation-information-schema,  Prev: charset-binary-op,  Up: charset-collations

10.1.7.8 Examples of the Effect of Collation
............................................

*Example 1: Sorting German Umlauts*

Suppose that column `X' in table `T' has these `latin1' column values:


     Muffler
     Mu"ller
     MX Systems
     MySQL

Suppose also that the column values are retrieved using the following
statement:


     SELECT X FROM T ORDER BY X COLLATE COLLATION_NAME;

The following table shows the resulting order of the values if we use
`ORDER BY' with different collations.

This table illustrates an example of the effect of collation, as
described in the preceding text. The table shows the resulting order of
values for three collations (`latin1_swedish_ci', `latin1_german1_ci',
`latin1_german2_ci') when using `ORDER BY'.

`latin1_swedish_ci'    `latin1_german1_ci'    `latin1_german2_ci'
Muffler                Muffler                Mu"ller
MX Systems             Mu"ller                Muffler
Mu"ller                MX Systems             MX Systems
MySQL                  MySQL                  MySQL

The character that causes the different sort orders in this example is
the U with two dots over it (`u"'), which the Germans call `U-umlaut.'

   * The first column shows the result of the *Note `SELECT': select.
     using the Swedish/Finnish collating rule, which says that U-umlaut
     sorts with Y.

   * The second column shows the result of the *Note `SELECT': select.
     using the German DIN-1 rule, which says that U-umlaut sorts with U.

   * The third column shows the result of the *Note `SELECT': select.
     using the German DIN-2 rule, which says that U-umlaut sorts with
     UE.

*Example 2: Searching for German Umlauts*

Suppose that you have three tables that differ only by the character
set and collation used:


     mysql> SET NAMES utf8;
     mysql> CREATE TABLE german1 (
         ->   c CHAR(10)
         -> ) CHARACTER SET latin1 COLLATE latin1_german1_ci;
     mysql> CREATE TABLE german2 (
         ->   c CHAR(10)
         -> ) CHARACTER SET latin1 COLLATE latin1_german2_ci;
     mysql> CREATE TABLE germanutf8 (
         ->   c CHAR(10)
         -> ) CHARACTER SET utf8 COLLATE utf8_unicode_ci;

Each table contains two records:


     mysql> INSERT INTO german1 VALUES ('Bar'), ('Ba"r');
     mysql> INSERT INTO german2 VALUES ('Bar'), ('Ba"r');
     mysql> INSERT INTO germanutf8 VALUES ('Bar'), ('Ba"r');

Two of the above collations have an `A = A"' equality, and one has no
such equality (`latin1_german2_ci'). For that reason, you'll get these
results in comparisons:


     mysql> SELECT * FROM german1 WHERE c = 'Ba"r';
     +------+
     | c    |
     +------+
     | Bar  |
     | Ba"r  |
     +------+
     mysql> SELECT * FROM german2 WHERE c = 'Ba"r';
     +------+
     | c    |
     +------+
     | Ba"r  |
     +------+
     mysql> SELECT * FROM germanutf8 WHERE c = 'Ba"r';
     +------+
     | c    |
     +------+
     | Bar  |
     | Ba"r  |
     +------+

This is not a bug but rather a consequence of the sorting properties of
`latin1_german1_ci' and `utf8_unicode_ci' (the sorting shown is done
according to the German DIN 5007 standard).


File: manual.info,  Node: charset-collation-information-schema,  Prev: charset-collation-effect,  Up: charset-collations

10.1.7.9 Collation and INFORMATION_SCHEMA Searches
..................................................

String columns in `INFORMATION_SCHEMA' tables have a collation of
`utf8_general_ci', which is case insensitive. However, searches in
`INFORMATION_SCHEMA' string columns are also affected by file system
case sensitivity. For values that correspond to objects that are
represented in the file system, such as names of databases and tables,
searches may be case sensitive if the file system is case sensitive.
This section describes how to work around this issue if necessary; see
also Bug #34921.

Suppose that a query searches the `SCHEMATA.SCHEMA_NAME' column for the
`test' database. On Linux, file systems are case sensitive, so
comparisons of `SCHEMATA.SCHEMA_NAME' with `'test'' match, but
comparisons with `'TEST'' do not:


     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME = 'test';
     +-------------+
     | SCHEMA_NAME |
     +-------------+
     | test        |
     +-------------+
     1 row in set (0.01 sec)

     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME = 'TEST';
     Empty set (0.00 sec)

On Windows or Mac OS X where file systems are not case sensitive,
comparisons match both `'test'' and `'TEST'':


     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME = 'test';
     +-------------+
     | SCHEMA_NAME |
     +-------------+
     | test        |
     +-------------+
     1 row in set (0.00 sec)

     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME = 'TEST';
     +-------------+
     | SCHEMA_NAME |
     +-------------+
     | TEST        |
     +-------------+
     1 row in set (0.00 sec)

The value of the `lower_case_table_names' system variable makes no
difference in this context.

This behavior occurs because the `utf8_general_ci' collation is not
used for `INFORMATION_SCHEMA' queries when searching the file system
for database objects. It is a result of optimizations implemented for
`INFORMATION_SCHEMA' searches in MySQL 5.1.21 and thus does not occur
prior to 5.1.21. For information about these optimizations, see *Note
information-schema-optimization::.

Searches in `INFORMATION_SCHEMA' string columns for values that refer to
`INFORMATION_SCHEMA' itself do use the `utf8_general_ci' collation
because `INFORMATION_SCHEMA' is a `virtual' database and is not
represented in the file system. For example, comparisons with
`SCHEMATA.SCHEMA_NAME' match `'information_schema'' or
`'INFORMATION_SCHEMA'' regardless of platform:


     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME = 'information_schema';
     +--------------------+
     | SCHEMA_NAME        |
     +--------------------+
     | information_schema |
     +--------------------+
     1 row in set (0.00 sec)

     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME = 'INFORMATION_SCHEMA';
     +--------------------+
     | SCHEMA_NAME        |
     +--------------------+
     | information_schema |
     +--------------------+
     1 row in set (0.00 sec)

If the result of a string operation on an `INFORMATION_SCHEMA' column
differs from expectations, a workaround is to use an explicit `COLLATE'
clause to force a suitable collation (*Note charset-collate::). For
example, to perform a case-insensitive search, use `COLLATE' with the
`INFORMATION_SCHEMA' column name:


     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME COLLATE utf8_general_ci = 'test';
     +-------------+
     | SCHEMA_NAME |
     +-------------+
     | test        |
     +-------------+
     1 row in set (0.00 sec)

     mysql> SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA
         -> WHERE SCHEMA_NAME COLLATE utf8_general_ci = 'TEST';
     | SCHEMA_NAME |
     +-------------+
     | test        |
     +-------------+
     1 row in set (0.00 sec)

You can also use the `UPPER()' or `LOWER()' function:


     WHERE UPPER(SCHEMA_NAME) = 'TEST'
     WHERE LOWER(SCHEMA_NAME) = 'test'

Although a case-insensitive comparison can be performed even on
platforms with case-sensitive file systems, as just shown, it is not
necessarily always the right thing to do. On such platforms, it is
possible to have multiple objects with names that differ only in
lettercase. For example, tables named `city', `CITY', and `City' can
all exist simultaneously. Consider whether a search should match all
such names or just one and write queries accordingly:


     WHERE TABLE_NAME COLLATE utf8_bin = 'City'
     WHERE TABLE_NAME COLLATE utf8_general_ci = 'city'
     WHERE UPPER(TABLE_NAME) = 'CITY'
     WHERE LOWER(TABLE_NAME) = 'city'

The first of those comparisons (with `utf8_bin') is case sensitive; the
others are not.


File: manual.info,  Node: charset-repertoire,  Next: charset-operations,  Prev: charset-collations,  Up: charset

10.1.8 String Repertoire
------------------------

The _repertoire_ of a character set is the collection of characters in
the set.

As of MySQL 5.1.21, string expressions have a repertoire attribute,
which can have two values:

   * `ASCII': The expression can contain only characters in the Unicode
     range `U+0000' to `U+007F'.

   * `UNICODE': The expression can contain characters in the Unicode
     range `U+0000' to `U+FFFF'.

The `ASCII' range is a subset of `UNICODE' range, so a string with
`ASCII' repertoire can be converted safely without loss of information
to the character set of any string with `UNICODE' repertoire or to a
character set that is a superset of `ASCII'. (All MySQL character sets
are supersets of `ASCII' with the exception of `swe7', which reuses some
punctuation characters for Swedish accented characters.) The use of
repertoire enables character set conversion in expressions for many
cases where MySQL would otherwise return an `illegal mix of collations'
error.

The following discussion provides examples of expressions and their
repertoires, and describes how the use of repertoire changes string
expression evaluation:

   * The repertoire for string constants depends on string content:


          SET NAMES utf8; SELECT 'abc';
          SELECT _utf8'def';
          SELECT N'MySQL';

     Although the character set is `utf8' in each of the preceding
     cases, the strings do not actually contain any characters outside
     the ASCII range, so their repertoire is `ASCII' rather than
     `UNICODE'.

   * Columns having the `ascii' character set have `ASCII' repertoire
     because of their character set. In the following table, `c1' has
     `ASCII' repertoire:


          CREATE TABLE t1 (c1 CHAR(1) CHARACTER SET ascii);

     The following example illustrates how repertoire enables a result
     to be determined in a case where an error occurs without
     repertoire:


          CREATE TABLE t1 (
            c1 CHAR(1) CHARACTER SET latin1,
            c2 CHAR(1) CHARACTER SET ascii
          );
          INSERT INTO t1 VALUES ('a','b');
          SELECT CONCAT(c1,c2) FROM t1;

     Without repertoire, this error occurs:


          ERROR 1267 (HY000): Illegal mix of collations (latin1_swedish_ci,IMPLICIT)
          and (ascii_general_ci,IMPLICIT) for operation 'concat'

     Using repertoire, subset to superset (`ascii' to `latin1')
     conversion can occur and a result is returned:


          +---------------+
          | CONCAT(c1,c2) |
          +---------------+
          | ab            |
          +---------------+

   * Functions with one string argument inherit the repertoire of their
     argument. The result of `UPPER(_utf8'ABC')' has `ASCII'
     repertoire, because its argument has `ASCII' repertoire.

   * For functions that return a string but do not have string
     arguments and use `character_set_connection' as the result
     character set, the result repertoire is `ASCII' if
     `character_set_connection' is `ascii', and `UNICODE' otherwise:


          FORMAT(NUMERIC_COLUMN, 4);

     Use of repertoire changes how MySQL evaluates the following
     example:


          SET NAMES ascii;
          CREATE TABLE t1 (a INT, b VARCHAR(10) CHARACTER SET latin1);
          INSERT INTO t1 VALUES (1,'b');
          SELECT CONCAT(FORMAT(a, 4), b) FROM t1;

     Without repertoire, this error occurs:


          ERROR 1267 (HY000): Illegal mix of collations (ascii_general_ci,COERCIBLE)
          and (latin1_swedish_ci,IMPLICIT) for operation 'concat'

     With repertoire, a result is returned:


          +-------------------------+
          | CONCAT(FORMAT(a, 4), b) |
          +-------------------------+
          | 1.0000b                 |
          +-------------------------+

   * Functions with two or more string arguments use the `widest'
     argument repertoire for the result repertoire (`UNICODE' is wider
     than `ASCII'). Consider the following `CONCAT()' calls:


          CONCAT(_ucs2 0x0041, _ucs2 0x0042)
          CONCAT(_ucs2 0x0041, _ucs2 0x00C2)

     For the first call, the repertoire is `ASCII' because both
     arguments are within the range of the `ascii' character set. For
     the second call, the repertoire is `UNICODE' because the second
     argument is outside the `ascii' character set range.

   * The repertoire for function return values is determined based only
     on the repertoire of the arguments that affect the result's
     character set and collation.


          IF(column1 < column2, 'smaller', 'greater')

     The result repertoire is `ASCII' because the two string arguments
     (the second argument and the third argument) both have `ASCII'
     repertoire. The first argument does not matter for the result
     repertoire, even if the expression uses string values.


File: manual.info,  Node: charset-operations,  Next: charset-unicode,  Prev: charset-repertoire,  Up: charset

10.1.9 Operations Affected by Character Set Support
---------------------------------------------------

* Menu:

* charset-result::               Result Strings
* charset-convert::              CONVERT() and CAST()
* charset-show::                 SHOW Statements and INFORMATION_SCHEMA

This section describes operations that take character set information
into account.


File: manual.info,  Node: charset-result,  Next: charset-convert,  Prev: charset-operations,  Up: charset-operations

10.1.9.1 Result Strings
.......................

MySQL has many operators and functions that return a string.  This
section answers the question: What is the character set and collation
of such a string?

For simple functions that take string input and return a string result
as output, the output's character set and collation are the same as
those of the principal input value.  For example, `UPPER(X)' returns a
string whose character string and collation are the same as that of X.
The same applies for `INSTR()', `LCASE()', `LOWER()', `LTRIM()',
`MID()', `REPEAT()', `REPLACE()', `REVERSE()', `RIGHT()', `RPAD()',
`RTRIM()', `SOUNDEX()', `SUBSTRING()', `TRIM()', `UCASE()', and
`UPPER()'.

Note: The `REPLACE()' function, unlike all other functions, always
ignores the collation of the string input and performs a case-sensitive
comparison.

If a string input or function result is a binary string, the string has
no character set or collation. This can be checked by using the
`CHARSET()' and `COLLATION()' functions, both of which return `binary'
to indicate that their argument is a binary string:


     mysql> SELECT CHARSET(BINARY 'a'), COLLATION(BINARY 'a');
     +---------------------+-----------------------+
     | CHARSET(BINARY 'a') | COLLATION(BINARY 'a') |
     +---------------------+-----------------------+
     | binary              | binary                |
     +---------------------+-----------------------+

For operations that combine multiple string inputs and return a single
string output, the `aggregation rules' of standard SQL apply for
determining the collation of the result:

   * If an explicit `COLLATE X' occurs, use X.

   * If explicit `COLLATE X' and `COLLATE Y' occur, raise an error.

   * Otherwise, if all collations are X, use X.

   * Otherwise, the result has no collation.

For example, with `CASE ... WHEN a THEN b WHEN b THEN c COLLATE X END',
the resulting collation is X. The same applies for *Note `UNION': union,
`||', `CONCAT()', `ELT()', `GREATEST()', `IF()', and `LEAST()'.

For operations that convert to character data, the character set and
collation of the strings that result from the operations are defined by
the `character_set_connection' and `collation_connection' system
variables. This applies only to `CAST()', `CONV()', `FORMAT()',
`HEX()', and `SPACE()'.

If you are uncertain about the character set or collation of the result
returned by a string function, you can use the `CHARSET()' or
`COLLATION()' function to find out:


     mysql> SELECT USER(), CHARSET(USER()), COLLATION(USER());
     +----------------+-----------------+-------------------+
     | USER()         | CHARSET(USER()) | COLLATION(USER()) |
     +----------------+-----------------+-------------------+
     | test@localhost | utf8            | utf8_general_ci   |
     +----------------+-----------------+-------------------+


File: manual.info,  Node: charset-convert,  Next: charset-show,  Prev: charset-result,  Up: charset-operations

10.1.9.2 CONVERT() and CAST()
.............................

`CONVERT()' provides a way to convert data between different character
sets. The syntax is:


     CONVERT(EXPR USING TRANSCODING_NAME)

In MySQL, transcoding names are the same as the corresponding character
set names.

Examples:


     SELECT CONVERT(_latin1'Mu"ller' USING utf8);
     INSERT INTO utf8table (utf8column)
         SELECT CONVERT(latin1field USING utf8) FROM latin1table;

`CONVERT(... USING ...)' is implemented according to the standard SQL
specification.

You may also use `CAST()' to convert a string to a different character
set. The syntax is:


     CAST(CHARACTER_STRING AS CHARACTER_DATA_TYPE CHARACTER SET CHARSET_NAME)

Example:


     SELECT CAST(_latin1'test' AS CHAR CHARACTER SET utf8);

If you use `CAST()' without specifying `CHARACTER SET', the resulting
character set and collation are defined by the
`character_set_connection' and `collation_connection' system variables.
If you use `CAST()' with `CHARACTER SET X', the resulting character set
and collation are `X' and the default collation of `X'.

You may not use a `COLLATE' clause inside a `CONVERT()' or `CAST()'
call, but you may use it outside. For example, `CAST(... COLLATE ...)'
is illegal, but `CAST(...)  COLLATE ...' is legal:


     SELECT CAST(_latin1'test' AS CHAR CHARACTER SET utf8) COLLATE utf8_bin;


File: manual.info,  Node: charset-show,  Prev: charset-convert,  Up: charset-operations

10.1.9.3 SHOW Statements and INFORMATION_SCHEMA
...............................................

Several *Note `SHOW': show. statements provide additional character set
information. These include *Note `SHOW CHARACTER SET':
show-character-set, *Note `SHOW COLLATION': show-collation, *Note `SHOW
CREATE DATABASE': show-create-database, *Note `SHOW CREATE TABLE':
show-create-table. and *Note `SHOW COLUMNS': show-columns. These
statements are described here briefly. For more information, see *Note
show::.

`INFORMATION_SCHEMA' has several tables that contain information
similar to that displayed by the *Note `SHOW': show. statements. For
example, the *Note `CHARACTER_SETS': character-sets-table. and *Note
`COLLATIONS': collations-table. tables contain the information
displayed by *Note `SHOW CHARACTER SET': show-character-set. and *Note
`SHOW COLLATION': show-collation. See *Note information-schema::.

The *Note `SHOW CHARACTER SET': show-character-set.  statement shows
all available character sets. It takes an optional `LIKE' clause that
indicates which character set names to match. For example:


     mysql> SHOW CHARACTER SET LIKE 'latin%';
     +---------+-----------------------------+-------------------+--------+
     | Charset | Description                 | Default collation | Maxlen |
     +---------+-----------------------------+-------------------+--------+
     | latin1  | cp1252 West European        | latin1_swedish_ci |      1 |
     | latin2  | ISO 8859-2 Central European | latin2_general_ci |      1 |
     | latin5  | ISO 8859-9 Turkish          | latin5_turkish_ci |      1 |
     | latin7  | ISO 8859-13 Baltic          | latin7_general_ci |      1 |
     +---------+-----------------------------+-------------------+--------+

The output from *Note `SHOW COLLATION': show-collation.  includes all
available character sets. It takes an optional `LIKE' clause that
indicates which collation names to match. For example:


     mysql> SHOW COLLATION LIKE 'latin1%';
     +-------------------+---------+----+---------+----------+---------+
     | Collation         | Charset | Id | Default | Compiled | Sortlen |
     +-------------------+---------+----+---------+----------+---------+
     | latin1_german1_ci | latin1  |  5 |         |          |       0 |
     | latin1_swedish_ci | latin1  |  8 | Yes     | Yes      |       0 |
     | latin1_danish_ci  | latin1  | 15 |         |          |       0 |
     | latin1_german2_ci | latin1  | 31 |         | Yes      |       2 |
     | latin1_bin        | latin1  | 47 |         | Yes      |       0 |
     | latin1_general_ci | latin1  | 48 |         |          |       0 |
     | latin1_general_cs | latin1  | 49 |         |          |       0 |
     | latin1_spanish_ci | latin1  | 94 |         |          |       0 |
     +-------------------+---------+----+---------+----------+---------+

*Note `SHOW CREATE DATABASE': show-create-database. displays the *Note
`CREATE DATABASE': create-database. statement that creates a given
database:


     mysql> SHOW CREATE DATABASE test;
     +----------+-----------------------------------------------------------------+
     | Database | Create Database                                                 |
     +----------+-----------------------------------------------------------------+
     | test     | CREATE DATABASE `test` /*!40100 DEFAULT CHARACTER SET latin1 */ |
     +----------+-----------------------------------------------------------------+

If no `COLLATE' clause is shown, the default collation for the
character set applies.

*Note `SHOW CREATE TABLE': show-create-table. is similar, but displays
the *Note `CREATE TABLE': create-table.  statement to create a given
table. The column definitions indicate any character set
specifications, and the table options include character set information.

The *Note `SHOW COLUMNS': show-columns. statement displays the
collations of a table's columns when invoked as *Note `SHOW FULL
COLUMNS': show-columns. Columns with *Note `CHAR': char, *Note
`VARCHAR': char, or *Note `TEXT': blob. data types have collations.
Numeric and other noncharacter types have no collation (indicated by
`NULL' as the `Collation' value). For example:


     mysql> SHOW FULL COLUMNS FROM person\G
     *************************** 1. row ***************************
          Field: id
           Type: smallint(5) unsigned
      Collation: NULL
           Null: NO
            Key: PRI
        Default: NULL
          Extra: auto_increment
     Privileges: select,insert,update,references
        Comment:
     *************************** 2. row ***************************
          Field: name
           Type: char(60)
      Collation: latin1_swedish_ci
           Null: NO
            Key:
        Default:
          Extra:
     Privileges: select,insert,update,references
        Comment:

The character set is not part of the display but is implied by the
collation name.


File: manual.info,  Node: charset-unicode,  Next: charset-metadata,  Prev: charset-operations,  Up: charset

10.1.10 Unicode Support
-----------------------

* Menu:

* charset-unicode-ucs2::         The ucs2 Character Set (UCS-2 Unicode Encoding)
* charset-unicode-utf8::         The utf8 Character Set (3-Byte UTF-8 Unicode Encoding)

MySQL 5.1 supports two character sets for storing Unicode data:

   * `ucs2', the UCS-2 encoding of the Unicode character set using 16
     bits per character.

   * `utf8', a UTF-8 encoding of the Unicode character set using one to
     three bytes per character.

These two character sets support the characters from the Basic
Multilingual Plane (BMP) of Unicode Version 3.0. BMP characters have
these characteristics:

   * Their code values are between 0 and 65535 (or `U+0000' ..
     `U+FFFF').

   * They can be encoded with a fixed 16-bit word, as in `ucs2'.

   * They can be encoded with 8, 16, or 24 bits, as in `utf8'.

   * They are sufficient for almost all characters in major languages.

The `ucs2' and `utf8' character sets do not support supplementary
characters that lie outside the BMP. Characters outside the BMP compare
as REPLACEMENT CHARACTER and convert to `'?'' when converted to a
Unicode character set.

A similar set of collations is available for each Unicode character
set. For example, each has a Danish collation, the names of which are
`ucs2_danish_ci' and `utf8_danish_ci'. All Unicode collations are
listed at *Note charset-unicode-sets::.

The MySQL implementation of UCS-2 stores characters in big-endian byte
order and does not use a byte order mark (BOM) at the beginning of
values. Other database systems might use little-endian byte order or a
BOM. In such cases, conversion of values will need to be performed when
transferring data between those systems and MySQL.

MySQL uses no BOM for UTF-8 values.

Client applications that need to communicate with the server using
Unicode should set the client character set accordingly; for example,
by issuing a `SET NAMES 'utf8'' statement. `ucs2' cannot be used as a
client character set, which means that it does not work for `SET NAMES'
or `SET CHARACTER SET'. (See *Note charset-connection::.)

The following sections provide additional detail on the Unicode
character sets in MySQL.


File: manual.info,  Node: charset-unicode-ucs2,  Next: charset-unicode-utf8,  Prev: charset-unicode,  Up: charset-unicode

10.1.10.1 The ucs2 Character Set (UCS-2 Unicode Encoding)
.........................................................

In UCS-2, every character is represented by a 2-byte Unicode code with
the most significant byte first. For example: `LATIN CAPITAL LETTER A'
has the code `0x0041' and it is stored as a 2-byte sequence: `0x00
0x41'. `CYRILLIC SMALL LETTER YERU' (Unicode `0x044B') is stored as a
2-byte sequence: `0x04 0x4B'. For Unicode characters and their codes,
please refer to the Unicode Home Page (http://www.unicode.org/).

In MySQL, the `ucs2' character set is a fixed-length 16-bit encoding
for Unicode BMP characters.


File: manual.info,  Node: charset-unicode-utf8,  Prev: charset-unicode-ucs2,  Up: charset-unicode

10.1.10.2 The utf8 Character Set (3-Byte UTF-8 Unicode Encoding)
................................................................

UTF-8 (Unicode Transformation Format with 8-bit units) is an
alternative way to store Unicode data. It is implemented according to
RFC 3629, which describes encoding sequences that take from one to four
bytes. Currently, MySQL support for UTF-8 does not include 4-byte
sequences. (An older standard for UTF-8 encoding, RFC 2279, describes
UTF-8 sequences that take from one to six bytes. RFC 3629 renders RFC
2279 obsolete; for this reason, sequences with five and six bytes are
no longer used.)

The idea of UTF-8 is that various Unicode characters are encoded using
byte sequences of different lengths:

   * Basic Latin letters, digits, and punctuation signs use one byte.

   * Most European and Middle East script letters fit into a 2-byte
     sequence: extended Latin letters (with tilde, macron, acute, grave
     and other accents), Cyrillic, Greek, Armenian, Hebrew, Arabic,
     Syriac, and others.

   * Korean, Chinese, and Japanese ideographs use 3-byte sequences.

*Tip*: To save space with UTF-8, use *Note `VARCHAR': char. instead of
*Note `CHAR': char. Otherwise, MySQL must reserve three bytes for each
character in a `CHAR CHARACTER SET utf8' column because that is the
maximum possible length. For example, MySQL must reserve 30 bytes for a
`CHAR(10) CHARACTER SET utf8' column.

For additional information about data type storage, see *Note
storage-requirements::. For information about `InnoDB' physical row
storage, including how `InnoDB' tables that use `COMPACT' row format
handle UTF-8 `CHAR(N)' columns internally, see *Note
innodb-physical-record::.


File: manual.info,  Node: charset-metadata,  Next: charset-conversion,  Prev: charset-unicode,  Up: charset

10.1.11 UTF-8 for Metadata
--------------------------

_Metadata_ is `the data about the data.' Anything that _describes_ the
database--as opposed to being the _contents_ of the database--is
metadata.  Thus column names, database names, user names, version names,
and most of the string results from *Note `SHOW': show. are metadata.
This is also true of the contents of tables in `INFORMATION_SCHEMA'
because those tables by definition contain information about database
objects.

Representation of metadata must satisfy these requirements:

   * All metadata must be in the same character set. Otherwise, neither
     the *Note `SHOW': show. statements nor *Note `SELECT': select.
     statements for tables in `INFORMATION_SCHEMA' would work properly
     because different rows in the same column of the results of these
     operations would be in different character sets.

   * Metadata must include all characters in all languages.  Otherwise,
     users would not be able to name columns and tables using their own
     languages.

To satisfy both requirements, MySQL stores metadata in a Unicode
character set, namely UTF-8. This does not cause any disruption if you
never use accented or non-Latin characters. But if you do, you should
be aware that metadata is in UTF-8.

The metadata requirements mean that the return values of the `USER()',
`CURRENT_USER()', `SESSION_USER()', `SYSTEM_USER()', `DATABASE()', and
`VERSION()' functions have the UTF-8 character set by default.

The server sets the `character_set_system' system variable to the name
of the metadata character set:


     mysql> SHOW VARIABLES LIKE 'character_set_system';
     +----------------------+-------+
     | Variable_name        | Value |
     +----------------------+-------+
     | character_set_system | utf8  |
     +----------------------+-------+

Storage of metadata using Unicode does _not_ mean that the server
returns headers of columns and the results of *Note `DESCRIBE':
describe. functions in the `character_set_system' character set by
default. When you use `SELECT column1 FROM t', the name `column1'
itself is returned from the server to the client in the character set
determined by the value of the `character_set_results' system variable,
which has a default value of `latin1'. If you want the server to pass
metadata results back in a different character set, use the `SET NAMES'
statement to force the server to perform character set conversion. `SET
NAMES' sets the `character_set_results' and other related system
variables. (See *Note charset-connection::.) Alternatively, a client
program can perform the conversion after receiving the result from the
server. It is more efficient for the client to perform the conversion,
but this option is not always available for all clients.

If `character_set_results' is set to `NULL', no conversion is performed
and the server returns metadata using its original character set (the
set indicated by `character_set_system').

Error messages returned from the server to the client are converted to
the client character set automatically, as with metadata.

If you are using (for example) the `USER()' function for comparison or
assignment within a single statement, don't worry. MySQL performs some
automatic conversion for you.


     SELECT * FROM t1 WHERE USER() = latin1_column;

This works because the contents of `latin1_column' are automatically
converted to UTF-8 before the comparison.


     INSERT INTO t1 (latin1_column) SELECT USER();

This works because the contents of `USER()' are automatically converted
to `latin1' before the assignment.

Although automatic conversion is not in the SQL standard, the SQL
standard document does say that every character set is (in terms of
supported characters) a `subset' of Unicode. Because it is a well-known
principle that `what applies to a superset can apply to a subset,' we
believe that a collation for Unicode can apply for comparisons with
non-Unicode strings. For more information about coercion of strings,
see *Note charset-collation-expressions::.


File: manual.info,  Node: charset-conversion,  Next: charset-charsets,  Prev: charset-metadata,  Up: charset

10.1.12 Column Character Set Conversion
---------------------------------------

To convert a binary or nonbinary string column to use a particular
character set, use *Note `ALTER TABLE': alter-table. For successful
conversion to occur, one of the following conditions must apply:

   * If the column has a binary data type (*Note `BINARY':
     binary-varbinary, *Note `VARBINARY': binary-varbinary, *Note
     `BLOB': blob.), all the values that it contains must be encoded
     using a single character set (the character set you're converting
     the column to). If you use a binary column to store information in
     multiple character sets, MySQL has no way to know which values use
     which character set and cannot convert the data properly.

   * If the column has a nonbinary data type (*Note `CHAR': char, *Note
     `VARCHAR': char, *Note `TEXT': blob.), its contents should be
     encoded in the column character set, not some other character set.
     If the contents are encoded in a different character set, you can
     convert the column to use a binary data type first, and then to a
     nonbinary column with the desired character set.

Suppose that a table `t' has a binary column named `col1' defined as
`VARBINARY(50)'. Assuming that the information in the column is encoded
using a single character set, you can convert it to a nonbinary column
that has that character set.  For example, if `col1' contains binary
data representing characters in the `greek' character set, you can
convert it as follows:


     ALTER TABLE t MODIFY col1 VARCHAR(50) CHARACTER SET greek;

If your original column has a type of `BINARY(50)', you could convert
it to `CHAR(50)', but the resulting values will be padded with `0x00'
bytes at the end, which may be undesirable. To remove these bytes, use
the `TRIM()' function:


     UPDATE t SET col1 = TRIM(TRAILING 0x00 FROM col1);

Suppose that table `t' has a nonbinary column named `col1' defined as
`CHAR(50) CHARACTER SET latin1' but you want to convert it to use
`utf8' so that you can store values from many languages. The following
statement accomplishes this:


     ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET utf8;

Conversion may be lossy if the column contains characters that are not
in both character sets.

A special case occurs if you have old tables from before MySQL 4.1
where a nonbinary column contains values that actually are encoded in a
character set different from the server's default character set. For
example, an application might have stored `sjis' values in a column,
even though MySQL's default character set was `latin1'. It is possible
to convert the column to use the proper character set but an additional
step is required. Suppose that the server's default character set was
`latin1' and `col1' is defined as `CHAR(50)' but its contents are
`sjis' values. The first step is to convert the column to a binary data
type, which removes the existing character set information without
performing any character conversion:


     ALTER TABLE t MODIFY col1 BLOB;

The next step is to convert the column to a nonbinary data type with
the proper character set:


     ALTER TABLE t MODIFY col1 CHAR(50) CHARACTER SET sjis;

This procedure requires that the table not have been modified already
with statements such as *Note `INSERT': insert. or *Note `UPDATE':
update. after an upgrade to MySQL 4.1 or later. In that case, MySQL
would store new values in the column using `latin1', and the column will
contain a mix of `sjis' and `latin1' values and cannot be converted
properly.

If you specified attributes when creating a column initially, you
should also specify them when altering the table with *Note `ALTER
TABLE': alter-table. For example, if you specified `NOT NULL' and an
explicit `DEFAULT' value, you should also provide them in the *Note
`ALTER TABLE': alter-table. statement.  Otherwise, the resulting column
definition will not include those attributes.

To convert all character columns in a table, the `ALTER TABLE ...
CONVERT TO CHARACTER SET CHARSET' statement may be useful. See *Note
alter-table::.


File: manual.info,  Node: charset-charsets,  Prev: charset-conversion,  Up: charset

10.1.13 Character Sets and Collations That MySQL Supports
---------------------------------------------------------

* Menu:

* charset-unicode-sets::         Unicode Character Sets
* charset-we-sets::              West European Character Sets
* charset-ce-sets::              Central European Character Sets
* charset-se-me-sets::           South European and Middle East Character Sets
* charset-baltic-sets::          Baltic Character Sets
* charset-cyrillic-sets::        Cyrillic Character Sets
* charset-asian-sets::           Asian Character Sets

MySQL supports 70+ collations for 30+ character sets. This section
indicates which character sets MySQL supports. There is one subsection
for each group of related character sets. For each character set, the
permissible collations are listed.

You can always list the available character sets and their default
collations with the *Note `SHOW CHARACTER SET': show-character-set.
statement:


     mysql> SHOW CHARACTER SET;
     +----------+-----------------------------+---------------------+
     | Charset  | Description                 | Default collation   |
     +----------+-----------------------------+---------------------+
     | big5     | Big5 Traditional Chinese    | big5_chinese_ci     |
     | dec8     | DEC West European           | dec8_swedish_ci     |
     | cp850    | DOS West European           | cp850_general_ci    |
     | hp8      | HP West European            | hp8_english_ci      |
     | koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |
     | latin1   | cp1252 West European        | latin1_swedish_ci   |
     | latin2   | ISO 8859-2 Central European | latin2_general_ci   |
     | swe7     | 7bit Swedish                | swe7_swedish_ci     |
     | ascii    | US ASCII                    | ascii_general_ci    |
     | ujis     | EUC-JP Japanese             | ujis_japanese_ci    |
     | sjis     | Shift-JIS Japanese          | sjis_japanese_ci    |
     | hebrew   | ISO 8859-8 Hebrew           | hebrew_general_ci   |
     | tis620   | TIS620 Thai                 | tis620_thai_ci      |
     | euckr    | EUC-KR Korean               | euckr_korean_ci     |
     | koi8u    | KOI8-U Ukrainian            | koi8u_general_ci    |
     | gb2312   | GB2312 Simplified Chinese   | gb2312_chinese_ci   |
     | greek    | ISO 8859-7 Greek            | greek_general_ci    |
     | cp1250   | Windows Central European    | cp1250_general_ci   |
     | gbk      | GBK Simplified Chinese      | gbk_chinese_ci      |
     | latin5   | ISO 8859-9 Turkish          | latin5_turkish_ci   |
     | armscii8 | ARMSCII-8 Armenian          | armscii8_general_ci |
     | utf8     | UTF-8 Unicode               | utf8_general_ci     |
     | ucs2     | UCS-2 Unicode               | ucs2_general_ci     |
     | cp866    | DOS Russian                 | cp866_general_ci    |
     | keybcs2  | DOS Kamenicky Czech-Slovak  | keybcs2_general_ci  |
     | macce    | Mac Central European        | macce_general_ci    |
     | macroman | Mac West European           | macroman_general_ci |
     | cp852    | DOS Central European        | cp852_general_ci    |
     | latin7   | ISO 8859-13 Baltic          | latin7_general_ci   |
     | cp1251   | Windows Cyrillic            | cp1251_general_ci   |
     | cp1256   | Windows Arabic              | cp1256_general_ci   |
     | cp1257   | Windows Baltic              | cp1257_general_ci   |
     | binary   | Binary pseudo charset       | binary              |
     | geostd8  | GEOSTD8 Georgian            | geostd8_general_ci  |
     | cp932    | SJIS for Windows Japanese   | cp932_japanese_ci   |
     | eucjpms  | UJIS for Windows Japanese   | eucjpms_japanese_ci |
     +----------+-----------------------------+---------------------+

In cases where a character set has multiple collations, it might not be
clear which collation is most suitable for a given application. To
avoid choosing the wrong collation, it can be helpful to perform some
comparisons with representative data values to make sure that a given
collation sorts values the way you expect.

Collation-Charts.Org (http://www.collation-charts.org/) is a useful
site for information that shows how one collation compares to another.


File: manual.info,  Node: charset-unicode-sets,  Next: charset-we-sets,  Prev: charset-charsets,  Up: charset-charsets

10.1.13.1 Unicode Character Sets
................................

MySQL 5.1 has two Unicode character sets:

   * `ucs2', the UCS-2 encoding of the Unicode character set using 16
     bits per character.

   * `utf8', a UTF-8 encoding of the Unicode character set using one to
     three bytes per character.

You can store text in about 650 languages using these character sets.
This section lists the collations available for each Unicode character
set and describes their differentiating properties. For general
information about the character sets, see *Note charset-unicode::.

A similar set of collations is available for each Unicode character
set. These are shown in the following list, where XXX represents the
character set name. For example, `XXX_danish_ci' represents the Danish
collations, the specific names of which are `ucs2_danish_ci' and
`utf8_danish_ci'.

   * `XXX_bin'

   * `XXX_czech_ci'

   * `XXX_danish_ci'

   * `XXX_esperanto_ci'

   * `XXX_estonian_ci'

   * `XXX_general_ci' (default)

   * `XXX_general_mysql500_ci'

   * `XXX_hungarian_ci'

   * `XXX_icelandic_ci'

   * `XXX_latvian_ci'

   * `XXX_lithuanian_ci'

   * `XXX_persian_ci'

   * `XXX_polish_ci'

   * `XXX_roman_ci'

   * `XXX_romanian_ci'

   * `XXX_slovak_ci'

   * `XXX_slovenian_ci'

   * `XXX_spanish_ci'

   * `XXX_spanish2_ci'

   * `XXX_swedish_ci'

   * `XXX_turkish_ci'

   * `XXX_unicode_ci'

The `XXX_hungarian_ci' collations were added in MySQL 5.1.5.

MySQL implements the `XXX_unicode_ci' collations according to the
Unicode Collation Algorithm (UCA) described at
`http://www.unicode.org/reports/tr10/'. The collation uses the
version-4.0.0 UCA weight keys:
`http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt'.
Currently, the `XXX_unicode_ci' collations have only partial support
for the Unicode Collation Algorithm. Some characters are not supported
yet. Also, combining marks are not fully supported. This affects
primarily Vietnamese, Yoruba, and some smaller languages such as
Navajo. A combined character will be considered different from the same
character written with a single unicode character in string
comparisons, and the two characters are considered to have a different
length (for example, as returned by the `CHAR_LENGTH()' function or in
result set metadata).

MySQL implements language-specific Unicode collations only if the
ordering with `XXX_unicode_ci' does not work well for a language.
Language-specific collations are UCA-based. They are derived from
`XXX_unicode_ci' with additional language tailoring rules.

For any Unicode character set, operations performed using the
`XXX_general_ci' collation are faster than those for the
`XXX_unicode_ci' collation. For example, comparisons for the
`utf8_general_ci' collation are faster, but slightly less correct, than
comparisons for `utf8_unicode_ci'. The reason for this is that
`utf8_unicode_ci' supports mappings such as expansions; that is, when
one character compares as equal to combinations of other characters.
For example, in German and some other languages ``ss'' is equal to
``ss''.  `utf8_unicode_ci' also supports contractions and ignorable
characters. `utf8_general_ci' is a legacy collation that does not
support expansions, contractions, or ignorable characters. It can make
only one-to-one comparisons between characters.

To further illustrate, the following equalities hold in both
`utf8_general_ci' and `utf8_unicode_ci' (for the effect this has in
comparisons or when doing searches, see *Note
charset-collation-effect::):


     A" = A
     O" = O
     U" = U

A difference between the collations is that this is true for
`utf8_general_ci':


     ss = s

Whereas this is true for `utf8_unicode_ci', which supports the German
DIN-1 ordering (also known as dictionary order):


     ss = ss

MySQL implements language-specific collations for the `utf8' character
set only if the ordering with `utf8_unicode_ci' does not work well for
a language. For example, `utf8_unicode_ci' works fine for German
dictionary order and French, so there is no need to create special
`utf8' collations.

`utf8_general_ci' also is satisfactory for both German and French,
except that ``ss'' is equal to ``s'', and not to ``ss''. If this is
acceptable for your application, you should use `utf8_general_ci'
because it is faster.  Otherwise, use `utf8_unicode_ci' because it is
more accurate.

`XXX_swedish_ci' includes Swedish rules. For example, in Swedish, the
following relationship holds, which is not something expected by a
German or French speaker:


     U" = Y < O"

The `XXX_spanish_ci' and `XXX_spanish2_ci' collations correspond to
modern Spanish and traditional Spanish, respectively. In both
collations, ``ñ'' (n-tilde) is a separate letter between ``n'' and
``o''. In addition, for traditional Spanish, ``ch'' is a separate
letter between ``c'' and ``d'', and ``ll'' is a separate letter between
``l'' and ``m''

The `XXX_spanish2_ci' collations may also be used for Asturian and
Galician.

The `XXX_danich_ci' collations may also be used for Norwegian.

In the `XXX_roman_ci' collations, `I' and `J' compare as equal, and `U'
and `V' compare as equal.

The `XXX_general_mysql500_ci' collations were added in MySQL 5.1.62.
They preserve the pre-5.1.24 ordering of the original `XXX_general_ci'
collations and permit upgrades for tables created before MySQL 5.1.24.
For more information, see *Note checking-table-incompatibilities::, and
*Note rebuilding-tables::.

For additional information about Unicode collations in MySQL, see
Collation-Charts.Org (utf8
(http://www.collation-charts.org/mysql60/by-charset.html#utf8)).


File: manual.info,  Node: charset-we-sets,  Next: charset-ce-sets,  Prev: charset-unicode-sets,  Up: charset-charsets

10.1.13.2 West European Character Sets
......................................

Western European character sets cover most West European languages,
such as French, Spanish, Catalan, Basque, Portuguese, Italian,
Albanian, Dutch, German, Danish, Swedish, Norwegian, Finnish, Faroese,
Icelandic, Irish, Scottish, and English.

   * `ascii' (US ASCII) collations:

        * `ascii_bin'

        * `ascii_general_ci' (default)

   * `cp850' (DOS West European) collations:

        * `cp850_bin'

        * `cp850_general_ci' (default)

   * `dec8' (DEC Western European) collations:

        * `dec8_bin'

        * `dec8_swedish_ci' (default)

   * `hp8' (HP Western European) collations:

        * `hp8_bin'

        * `hp8_english_ci' (default)

   * `latin1' (cp1252 West European) collations:

        * `latin1_bin'

        * `latin1_danish_ci'

        * `latin1_general_ci'

        * `latin1_general_cs'

        * `latin1_german1_ci'

        * `latin1_german2_ci'

        * `latin1_spanish_ci'

        * `latin1_swedish_ci' (default)

     `latin1' is the default character set.  MySQL's `latin1' is the
     same as the Windows `cp1252' character set. This means it is the
     same as the official `ISO 8859-1' or IANA (Internet Assigned
     Numbers Authority) `latin1', except that IANA `latin1' treats the
     code points between `0x80' and `0x9f' as `undefined,' whereas
     `cp1252', and therefore MySQL's `latin1', assign characters for
     those positions. For example, `0x80' is the Euro sign. For the
     `undefined' entries in `cp1252', MySQL translates `0x81' to Unicode
     `0x0081', `0x8d' to `0x008d', `0x8f' to `0x008f', `0x90' to
     `0x0090', and `0x9d' to `0x009d'.

     The `latin1_swedish_ci' collation is the default that probably is
     used by the majority of MySQL customers. Although it is frequently
     said that it is based on the Swedish/Finnish collation rules,
     there are Swedes and Finns who disagree with this statement.

     The `latin1_german1_ci' and `latin1_german2_ci' collations are
     based on the DIN-1 and DIN-2 standards, where DIN stands for
     _Deutsches Institut fu"r Normung_ (the German equivalent of ANSI).
     DIN-1 is called the `dictionary collation' and DIN-2 is called the
     `phone book collation.' For an example of the effect this has in
     comparisons or when doing searches, see *Note
     charset-collation-effect::.

        * `latin1_german1_ci' (dictionary) rules:


               A" = A
               O" = O
               U" = U
               ss = s

        * `latin1_german2_ci' (phone-book) rules:


               A" = AE
               O" = OE
               U" = UE
               ss = ss

     In the `latin1_spanish_ci' collation, ``ñ'' (n-tilde) is a
     separate letter between ``n'' and ``o''.

   * `macroman' (Mac West European) collations:

        * `macroman_bin'

        * `macroman_general_ci' (default)

   * `swe7' (7bit Swedish) collations:

        * `swe7_bin'

        * `swe7_swedish_ci' (default)

For additional information about Western European collations in MySQL,
see Collation-Charts.Org (ascii
(http://www.collation-charts.org/mysql60/by-charset.html#ascii), cp850
(http://www.collation-charts.org/mysql60/by-charset.html#cp850), dec8
(http://www.collation-charts.org/mysql60/by-charset.html#dec8), hp8
(http://www.collation-charts.org/mysql60/by-charset.html#hp8), latin1
(http://www.collation-charts.org/mysql60/by-charset.html#latin1),
macroman
(http://www.collation-charts.org/mysql60/by-charset.html#macroman),
swe7 (http://www.collation-charts.org/mysql60/by-charset.html#swe7)).


File: manual.info,  Node: charset-ce-sets,  Next: charset-se-me-sets,  Prev: charset-we-sets,  Up: charset-charsets

10.1.13.3 Central European Character Sets
.........................................

MySQL provides some support for character sets used in the Czech
Republic, Slovakia, Hungary, Romania, Slovenia, Croatia, Poland, and
Serbia (Latin).

   * `cp1250' (Windows Central European) collations:

        * `cp1250_bin'

        * `cp1250_croatian_ci'

        * `cp1250_czech_cs'

        * `cp1250_general_ci' (default)

        * `cp1250_polish_ci'

   * `cp852' (DOS Central European) collations:

        * `cp852_bin'

        * `cp852_general_ci' (default)

   * `keybcs2' (DOS Kamenicky Czech-Slovak) collations:

        * `keybcs2_bin'

        * `keybcs2_general_ci' (default)

   * `latin2' (ISO 8859-2 Central European) collations:

        * `latin2_bin'

        * `latin2_croatian_ci'

        * `latin2_czech_cs'

        * `latin2_general_ci' (default)

        * `latin2_hungarian_ci'

   * `macce' (Mac Central European) collations:

        * `macce_bin'

        * `macce_general_ci' (default)

For additional information about Central European collations in MySQL,
see Collation-Charts.Org (cp1250
(http://www.collation-charts.org/mysql60/by-charset.html#cp1250), cp852
(http://www.collation-charts.org/mysql60/by-charset.html#cp852),
keybcs2
(http://www.collation-charts.org/mysql60/by-charset.html#keybcs2),
latin2 (http://www.collation-charts.org/mysql60/by-charset.html#latin2),
macce (http://www.collation-charts.org/mysql60/by-charset.html#macce)).


File: manual.info,  Node: charset-se-me-sets,  Next: charset-baltic-sets,  Prev: charset-ce-sets,  Up: charset-charsets

10.1.13.4 South European and Middle East Character Sets
.......................................................

South European and Middle Eastern character sets supported by MySQL
include Armenian, Arabic, Georgian, Greek, Hebrew, and Turkish.

   * `armscii8' (ARMSCII-8 Armenian) collations:

        * `armscii8_bin'

        * `armscii8_general_ci' (default)

   * `cp1256' (Windows Arabic) collations:

        * `cp1256_bin'

        * `cp1256_general_ci' (default)

   * `geostd8' (GEOSTD8 Georgian) collations:

        * `geostd8_bin'

        * `geostd8_general_ci' (default)

   * `greek' (ISO 8859-7 Greek) collations:

        * `greek_bin'

        * `greek_general_ci' (default)

   * `hebrew' (ISO 8859-8 Hebrew) collations:

        * `hebrew_bin'

        * `hebrew_general_ci' (default)

   * `latin5' (ISO 8859-9 Turkish) collations:

        * `latin5_bin'

        * `latin5_turkish_ci' (default)

For additional information about South European and Middle Eastern
collations in MySQL, see Collation-Charts.Org (armscii8
(http://www.collation-charts.org/mysql60/by-charset.html#armscii8),
cp1256 (http://www.collation-charts.org/mysql60/by-charset.html#cp1256),
geostd8
(http://www.collation-charts.org/mysql60/by-charset.html#geostd8),
greek (http://www.collation-charts.org/mysql60/by-charset.html#greek),
hebrew (http://www.collation-charts.org/mysql60/by-charset.html#hebrew),
latin5
(http://www.collation-charts.org/mysql60/by-charset.html#latin5)).


File: manual.info,  Node: charset-baltic-sets,  Next: charset-cyrillic-sets,  Prev: charset-se-me-sets,  Up: charset-charsets

10.1.13.5 Baltic Character Sets
...............................

The Baltic character sets cover Estonian, Latvian, and Lithuanian
languages.

   * `cp1257' (Windows Baltic) collations:

        * `cp1257_bin'

        * `cp1257_general_ci' (default)

        * `cp1257_lithuanian_ci'

   * `latin7' (ISO 8859-13 Baltic) collations:

        * `latin7_bin'

        * `latin7_estonian_cs'

        * `latin7_general_ci' (default)

        * `latin7_general_cs'

For additional information about Baltic collations in MySQL, see
Collation-Charts.Org (cp1257
(http://www.collation-charts.org/mysql60/by-charset.html#cp1257),
latin7
(http://www.collation-charts.org/mysql60/by-charset.html#latin7)).


File: manual.info,  Node: charset-cyrillic-sets,  Next: charset-asian-sets,  Prev: charset-baltic-sets,  Up: charset-charsets

10.1.13.6 Cyrillic Character Sets
.................................

The Cyrillic character sets and collations are for use with Belarusian,
Bulgarian, Russian, Ukrainian, and Serbian (Cyrillic) languages.

   * `cp1251' (Windows Cyrillic) collations:

        * `cp1251_bin'

        * `cp1251_bulgarian_ci'

        * `cp1251_general_ci' (default)

        * `cp1251_general_cs'

        * `cp1251_ukrainian_ci'

   * `cp866' (DOS Russian) collations:

        * `cp866_bin'

        * `cp866_general_ci' (default)

   * `koi8r' (KOI8-R Relcom Russian) collations:

        * `koi8r_bin'

        * `koi8r_general_ci' (default)

   * `koi8u' (KOI8-U Ukrainian) collations:

        * `koi8u_bin'

        * `koi8u_general_ci' (default)

For additional information about Cyrillic collations in MySQL, see
Collation-Charts.Org (cp1251
(http://www.collation-charts.org/mysql60/by-charset.html#cp1251), cp866
(http://www.collation-charts.org/mysql60/by-charset.html#cp866), koi8r
(http://www.collation-charts.org/mysql60/by-charset.html#koi8r), koi8u
(http://www.collation-charts.org/mysql60/by-charset.html#koi8u)).  ).


File: manual.info,  Node: charset-asian-sets,  Prev: charset-cyrillic-sets,  Up: charset-charsets

10.1.13.7 Asian Character Sets
..............................

* Menu:

* charset-cp932::                The cp932 Character Set

The Asian character sets that we support include Chinese, Japanese,
Korean, and Thai. These can be complicated. For example, the Chinese
sets must allow for thousands of different characters. See *Note
charset-cp932::, for additional information about the `cp932' and
`sjis' character sets.

For answers to some common questions and problems relating support for
Asian character sets in MySQL, see *Note faqs-cjk::.

   * `big5' (Big5 Traditional Chinese) collations:

        * `big5_bin'

        * `big5_chinese_ci' (default)

   * `cp932' (SJIS for Windows Japanese) collations:

        * `cp932_bin'

        * `cp932_japanese_ci' (default)

   * `eucjpms' (UJIS for Windows Japanese) collations:

        * `eucjpms_bin'

        * `eucjpms_japanese_ci' (default)

   * `euckr' (EUC-KR Korean) collations:

        * `euckr_bin'

        * `euckr_korean_ci' (default)

   * `gb2312' (GB2312 Simplified Chinese) collations:

        * `gb2312_bin'

        * `gb2312_chinese_ci' (default)

   * `gbk' (GBK Simplified Chinese) collations:

        * `gbk_bin'

        * `gbk_chinese_ci' (default)

   * `sjis' (Shift-JIS Japanese) collations:

        * `sjis_bin'

        * `sjis_japanese_ci' (default)

   * `tis620' (TIS620 Thai) collations:

        * `tis620_bin'

        * `tis620_thai_ci' (default)

   * `ujis' (EUC-JP Japanese) collations:

        * `ujis_bin'

        * `ujis_japanese_ci' (default)

The `big5_chinese_ci' collation sorts on number of strokes.

For additional information about Asian collations in MySQL, see
Collation-Charts.Org (big5
(http://www.collation-charts.org/mysql60/by-charset.html#big5), cp932
(http://www.collation-charts.org/mysql60/by-charset.html#cp932),
eucjpms
(http://www.collation-charts.org/mysql60/by-charset.html#eucjpms),
euckr (http://www.collation-charts.org/mysql60/by-charset.html#euckr),
gb2312 (http://www.collation-charts.org/mysql60/by-charset.html#gb2312),
gbk (http://www.collation-charts.org/mysql60/by-charset.html#gbk), sjis
(http://www.collation-charts.org/mysql60/by-charset.html#sjis), tis620
(http://www.collation-charts.org/mysql60/by-charset.html#tis620), ujis
(http://www.collation-charts.org/mysql60/by-charset.html#ujis)).


File: manual.info,  Node: charset-cp932,  Prev: charset-asian-sets,  Up: charset-asian-sets

10.1.13.8 The cp932 Character Set
.................................

*Why is `cp932' needed?*

In MySQL, the `sjis' character set corresponds to the `Shift_JIS'
character set defined by IANA, which supports JIS X0201 and JIS X0208
characters. (See `http://www.iana.org/assignments/character-sets'.)

However, the meaning of `SHIFT JIS' as a descriptive term has become
very vague and it often includes the extensions to `Shift_JIS' that are
defined by various vendors.

For example, `SHIFT JIS' used in Japanese Windows environments is a
Microsoft extension of `Shift_JIS' and its exact name is `Microsoft
Windows Codepage : 932' or `cp932'. In addition to the characters
supported by `Shift_JIS', `cp932' supports extension characters such as
NEC special characters, NEC selected--IBM extended characters, and IBM
selected characters.

Many Japanese users have experienced problems using these extension
characters. These problems stem from the following factors:

   * MySQL automatically converts character sets.

   * Character sets are converted using Unicode (`ucs2').

   * The `sjis' character set does not support the conversion of these
     extension characters.

   * There are several conversion rules from so-called `SHIFT JIS' to
     Unicode, and some characters are converted to Unicode differently
     depending on the conversion rule. MySQL supports only one of these
     rules (described later).

The MySQL `cp932' character set is designed to solve these problems.

Because MySQL supports character set conversion, it is important to
separate IANA `Shift_JIS' and `cp932' into two different character sets
because they provide different conversion rules.

*How does `cp932' differ from `sjis'?*

The `cp932' character set differs from `sjis' in the following ways:

   * `cp932' supports NEC special characters, NEC selected--IBM
     extended characters, and IBM selected characters.

   * Some `cp932' characters have two different code points, both of
     which convert to the same Unicode code point. When converting from
     Unicode back to `cp932', one of the code points must be selected.
     For this `round trip conversion,' the rule recommended by
     Microsoft is used. (See
     `http://support.microsoft.com/kb/170559/EN-US/'.)

     The conversion rule works like this:

        * If the character is in both JIS X 0208 and NEC special
          characters, use the code point of JIS X 0208.

        * If the character is in both NEC special characters and IBM
          selected characters, use the code point of NEC special
          characters.

        * If the character is in both IBM selected characters and NEC
          selected--IBM extended characters, use the code point of IBM
          extended characters.

     The table shown at
     `http://www.microsoft.com/globaldev/reference/dbcs/932.htm'
     provides information about the Unicode values of `cp932'
     characters. For `cp932' table entries with characters under which
     a four-digit number appears, the number represents the
     corresponding Unicode (`ucs2') encoding. For table entries with an
     underlined two-digit value appears, there is a range of `cp932'
     character values that begin with those two digits. Clicking such a
     table entry takes you to a page that displays the Unicode value for
     each of the `cp932' characters that begin with those digits.

     The following links are of special interest. They correspond to
     the encodings for the following sets of characters:

        * NEC special characters:


               `http://www.microsoft.com/globaldev/reference/dbcs/932/932_87.htm'

        * NEC selected--IBM extended characters:


               `http://www.microsoft.com/globaldev/reference/dbcs/932/932_ED.htm'
               `http://www.microsoft.com/globaldev/reference/dbcs/932/932_EE.htm'

        * IBM selected characters:


               `http://www.microsoft.com/globaldev/reference/dbcs/932/932_FA.htm'
               `http://www.microsoft.com/globaldev/reference/dbcs/932/932_FB.htm'
               `http://www.microsoft.com/globaldev/reference/dbcs/932/932_FC.htm'

   * `cp932' supports conversion of user-defined characters in
     combination with `eucjpms', and solves the problems with
     `sjis'/`ujis' conversion. For details, please refer to
     `http://www.sljfaq.org/afaq/encodings.html'.

For some characters, conversion to and from `ucs2' is different for
`sjis' and `cp932'. The following tables illustrate these differences.

Conversion to `ucs2':

This table lists `sjis'/`cp932' values and shows the difference between
`sjis' to `ucs2' conversion and `cp932' to `ucs2' conversion.

`sjis'/`cp932' Value     `sjis' -> `ucs2'         `cp932' -> `ucs2'
                         Conversion               Conversion
5C                       005C                     005C
7E                       007E                     007E
815C                     2015                     2015
815F                     005C                     FF3C
8160                     301C                     FF5E
8161                     2016                     2225
817C                     2212                     FF0D
8191                     00A2                     FFE0
8192                     00A3                     FFE1
81CA                     00AC                     FFE2

Conversion from `ucs2':

This table lists `ucs2' values and shows the difference between `ucs2'
to `sjis' conversion and `ucs2' to `cp932' conversion.

`ucs2' value             `ucs2' -> `sjis'         `ucs2' -> `cp932'
                         Conversion               Conversion
005C                     815F                     5C
007E                     7E                       7E
00A2                     8191                     3F
00A3                     8192                     3F
00AC                     81CA                     3F
2015                     815C                     815C
2016                     8161                     3F
2212                     817C                     3F
2225                     3F                       8161
301C                     8160                     3F
FF0D                     3F                       817C
FF3C                     3F                       815F
FF5E                     3F                       8160
FFE0                     3F                       8191
FFE1                     3F                       8192
FFE2                     3F                       81CA

Users of any Japanese character sets should be aware that using
`--character-set-client-handshake' (or
`--skip-character-set-client-handshake') has an important effect. See
*Note server-options::.


File: manual.info,  Node: error-message-language,  Next: adding-character-set,  Prev: charset,  Up: globalization

10.2 Setting the Error Message Language
=======================================

By default, *Note `mysqld': mysqld. produces error messages in English,
but they can also be displayed in any of several other languages:
Czech, Danish, Dutch, Estonian, French, German, Greek, Hungarian,
Italian, Japanese, Korean, Norwegian, Norwegian-ny, Polish, Portuguese,
Romanian, Russian, Slovak, Spanish, or Swedish.

You can select which language the server uses for error messages using
the instructions in this section.

To start *Note `mysqld': mysqld. with a particular language for error
messages, use the `--language' or `-L' option. The option value can be
a language name or the full path to the error message file. For example:


     shell> mysqld --language=swedish

Or:


     shell> mysqld --language=/usr/local/share/swedish

The language name should be specified in lowercase.

By default, the language files are located in the `share/mysql/LANGUAGE'
directory under the MySQL base directory.

For information about changing the character set for error messages
(rather than the language), see *Note charset-errors::.

You can change the content of the error messages produced by the server
using the instructions in the MySQL Internals manual, available at
MySQL Internals: Error Messages
(http://dev.mysql.com/doc/internals/en/error-messages.html). If you do
change the content of error messages, remember to repeat your changes
after each upgrade to a newer version of MySQL.


File: manual.info,  Node: adding-character-set,  Next: adding-collation,  Prev: error-message-language,  Up: globalization

10.3 Adding a Character Set
===========================

* Menu:

* character-arrays::             Character Definition Arrays
* string-collating::             String Collating Support for Complex Character Sets
* multibyte-characters::         Multi-Byte Character Support for Complex Character Sets

This section discusses the procedure for adding a character set to
MySQL. The proper procedure depends on whether the character set is
simple or complex:

   * If the character set does not need special string collating
     routines for sorting and does not need multibyte character
     support, it is simple.

   * If the character set needs either of those features, it is complex.

For example, `greek' and `swe7' are simple character sets, whereas
`big5' and `czech' are complex character sets.

To use the following instructions, you must have a MySQL source
distribution. In the instructions, MYSET represents the name of the
character set that you want to add.

  1. Add a `<charset>' element for MYSET to the
     `sql/share/charsets/Index.xml' file. Use the existing contents in
     the file as a guide to adding new contents. A partial listing for
     the `latin1' `<charset>' element follows:


          <charset name="latin1">
            <family>Western</family>
            <description>cp1252 West European</description>
            ...
            <collation name="latin1_swedish_ci" id="8" order="Finnish, Swedish">
              <flag>primary</flag>
              <flag>compiled</flag>
            </collation>
            <collation name="latin1_danish_ci" id="15" order="Danish"/>
            ...
            <collation name="latin1_bin" id="47" order="Binary">
              <flag>binary</flag>
              <flag>compiled</flag>
            </collation>
            ...
          </charset>

     The `<charset>' element must list all the collations for the
     character set. These must include at least a binary collation and
     a default (primary) collation.  The default collation is often
     named using a suffix of `general_ci' (general, case insensitive).
     It is possible for the binary collation to be the default
     collation, but usually they are different. The default collation
     should have a `primary' flag. The binary collation should have a
     `binary' flag.

     You must assign a unique ID number to each collation, chosen from
     the range 1 to 254. To find the maximum of the currently used
     collation IDs, use this query:


          SELECT MAX(ID) FROM INFORMATION_SCHEMA.COLLATIONS;

  2. This step depends on whether you are adding a simple or complex
     character set. A simple character set requires only a
     configuration file, whereas a complex character set requires C
     source file that defines collation functions, multibyte functions,
     or both.

     For a simple character set, create a configuration file,
     `MYSET.xml', that describes the character set properties. Create
     this file in the `sql/share/charsets' directory. You can use a
     copy of `latin1.xml' as the basis for this file. The syntax for
     the file is very simple:

        * Comments are written as ordinary XML comments (`<!-- TEXT
          -->').

        * Words within `<map>' array elements are separated by
          arbitrary amounts of whitespace.

        * Each word within `<map>' array elements must be a number in
          hexadecimal format.

        * The `<map>' array element for the `<ctype>' element has 257
          words.  The other `<map>' array elements after that have 256
          words. See *Note character-arrays::.

        * For each collation listed in the `<charset>' element for the
          character set in `Index.xml', `MYSET.xml' must contain a
          `<collation>' element that defines the character ordering.

     For a complex character set, create a C source file that describes
     the character set properties and defines the support routines
     necessary to properly perform operations on the character set:

        * Create the file `ctype-MYSET.c' in the `strings' directory.
          Look at one of the existing `ctype-*.c' files (such as
          `ctype-big5.c') to see what needs to be defined. The arrays
          in your file must have names like `ctype_MYSET',
          `to_lower_MYSET', and so on. These correspond to the arrays
          for a simple character set. See *Note character-arrays::.

        * For each `<collation>' element listed in the `<charset>'
          element for the character set in `Index.xml', the
          `ctype-MYSET.c' file must provide an implementation of the
          collation.

        * If the character set requires string collating functions, see
          *Note string-collating::.

        * If the character set requires multibyte character support,
          see *Note multibyte-characters::.

  3. Modify the configuration information. Use the existing
     configuration information as a guide to adding information for
     MYSYS. The example here assumes that the character set has default
     and binary collations, but more lines are needed if MYSET has
     additional collations.

       1. Edit `mysys/charset-def.c', and `register' the collations for
          the new character set.

          Add these lines to the `declaration' section:


               #ifdef HAVE_CHARSET_MYSET
               extern CHARSET_INFO my_charset_MYSET_general_ci;
               extern CHARSET_INFO my_charset_MYSET_bin;
               #endif

          Add these lines to the `registration' section:


               #ifdef HAVE_CHARSET_MYSET
                 add_compiled_collation(&my_charset_MYSET_general_ci);
                 add_compiled_collation(&my_charset_MYSET_bin);
               #endif

       2. If the character set uses `ctype-MYSET.c', edit
          `strings/Makefile.am' and add `ctype-MYSET.c' to each
          definition of the `CSRCS' variable, and to the `EXTRA_DIST'
          variable.

       3. If the character set uses `ctype-MYSET.c', edit
          `libmysql/Makefile.shared' and add `ctype-MYSET.lo' to the
          `mystringsobjects' definition.

       4. Edit `config/ac-macros/character_sets.m4':

            1. Add MYSET to one of the `define(CHARSETS_AVAILABLE...)'
               lines in alphabetic order.

            2. Add MYSET to `CHARSETS_COMPLEX'. This is needed even for
               simple character sets, or `configure' will not recognize
               `--with-charset=MYSET'.

            3. Add MYSET to the first `case' control structure. Omit the
               `USE_MB' and `USE_MB_IDENT' lines for 8-bit character
               sets.


                    MYSET)
                      AC_DEFINE(HAVE_CHARSET_MYSET, 1, [Define to enable charset MYSET])
                      AC_DEFINE([USE_MB], 1, [Use multi-byte character routines])
                      AC_DEFINE(USE_MB_IDENT, 1)
                      ;;

            4. Add MYSET to the second `case' control structure:


                    MYSET)
                      default_charset_default_collation="MYSET_general_ci"
                      default_charset_collations="MYSET_general_ci MYSET_bin"
                      ;;

  4. Reconfigure, recompile, and test.


File: manual.info,  Node: character-arrays,  Next: string-collating,  Prev: adding-character-set,  Up: adding-character-set

10.3.1 Character Definition Arrays
----------------------------------

Each simple character set has a configuration file located in the
`sql/share/charsets' directory. For a character set named MYSYS, the
file is named `MYSET.xml'. It uses `<map>' array elements to list
character set properties. `<map>' elements appear within these elements:

   * `<ctype>' defines attributes for each character.

   * `<lower>' and `<upper>' list the lowercase and uppercase
     characters.

   * `<unicode>' maps 8-bit character values to Unicode values.

   * `<collation>' elements indicate character ordering for comparisons
     and sorts, one element per collation. Binary collations need no
     `<map>' element because the character codes themselves provide the
     ordering.

For a complex character set as implemented in a `ctype-MYSET.c' file in
the `strings' directory, there are corresponding arrays:
`ctype_MYSET[]', `to_lower_MYSET[]', and so forth. Not every complex
character set has all of the arrays. See also the existing `ctype-*.c'
files for examples. See the `CHARSET_INFO.txt' file in the `strings'
directory for additional information.

Most of the arrays are indexed by character value and have 256
elements. The `<ctype>' array is indexed by character value + 1 and has
257 elements. This is a legacy convention for handling `EOF'.

`<ctype>' array elements are bit values.  Each element describes the
attributes of a single character in the character set. Each attribute
is associated with a bitmask, as defined in `include/m_ctype.h':


     #define _MY_U   01      /* Upper case */
     #define _MY_L   02      /* Lower case */
     #define _MY_NMR 04      /* Numeral (digit) */
     #define _MY_SPC 010     /* Spacing character */
     #define _MY_PNT 020     /* Punctuation */
     #define _MY_CTR 040     /* Control character */
     #define _MY_B   0100    /* Blank */
     #define _MY_X   0200    /* heXadecimal digit */

The `<ctype>' value for a given character should be the union of the
applicable bitmask values that describe the character. For example,
`'A'' is an uppercase character (`_MY_U') as well as a hexadecimal
digit (`_MY_X'), so its `ctype' value should be defined like this:


     ctype['A'+1] = _MY_U | _MY_X = 01 | 0200 = 0201

The bitmask values in `m_ctype.h' are octal values, but the elements of
the `<ctype>' array in `MYSET.xml' should be written as hexadecimal
values.

The `<lower>' and `<upper>' arrays hold the lowercase and uppercase
characters corresponding to each member of the character set. For
example:


     lower['A'] should contain 'a'
     upper['a'] should contain 'A'

Each `<collation>' array indicates how characters should be ordered for
comparison and sorting purposes. MySQL sorts characters based on the
values of this information. In some cases, this is the same as the
`<upper>' array, which means that sorting is case-insensitive. For more
complicated sorting rules (for complex character sets), see the
discussion of string collating in *Note string-collating::.


File: manual.info,  Node: string-collating,  Next: multibyte-characters,  Prev: character-arrays,  Up: adding-character-set

10.3.2 String Collating Support for Complex Character Sets
----------------------------------------------------------

For a simple character set named MYSET, sorting rules are specified in
the `MYSET.xml' configuration file using `<map>' array elements within
`<collation>' elements.  If the sorting rules for your language are too
complex to be handled with simple arrays, you must define string
collating functions in the `ctype-MYSET.c' source file in the `strings'
directory.

The existing character sets provide the best documentation and examples
to show how these functions are implemented. Look at the `ctype-*.c'
files in the `strings' directory, such as the files for the `big5',
`czech', `gbk', `sjis', and `tis160' character sets. Take a look at the
`MY_COLLATION_HANDLER' structures to see how they are used. See also the
`CHARSET_INFO.txt' file in the `strings' directory for additional
information.


File: manual.info,  Node: multibyte-characters,  Prev: string-collating,  Up: adding-character-set

10.3.3 Multi-Byte Character Support for Complex Character Sets
--------------------------------------------------------------

If you want to add support for a new character set named MYSET that
includes multibyte characters, you must use multibyte character
functions in the `ctype-MYSET.c' source file in the `strings' directory.

The existing character sets provide the best documentation and examples
to show how these functions are implemented. Look at the `ctype-*.c'
files in the `strings' directory, such as the files for the `euc_kr',
`gb2312', `gbk', `sjis', and `ujis' character sets. Take a look at the
`MY_CHARSET_HANDLER' structures to see how they are used. See also the
`CHARSET_INFO.txt' file in the `strings' directory for additional
information.


File: manual.info,  Node: adding-collation,  Next: charset-configuration,  Prev: adding-character-set,  Up: globalization

10.4 Adding a Collation to a Character Set
==========================================

* Menu:

* charset-collation-implementations::  Collation Implementation Types
* adding-collation-choosing-id::  Choosing a Collation ID
* adding-collation-simple-8bit::  Adding a Simple Collation to an 8-Bit Character Set
* adding-collation-unicode-uca::  Adding a UCA Collation to a Unicode Character Set

A collation is a set of rules that defines how to compare and sort
character strings. Each collation in MySQL belongs to a single
character set. Every character set has at least one collation, and most
have two or more collations.

A collation orders characters based on weights. Each character in a
character set maps to a weight. Characters with equal weights compare
as equal, and characters with unequal weights compare according to the
relative magnitude of their weights.

MySQL supports several collation implementations, as discussed in *Note
charset-collation-implementations::. Some of these can be added to
MySQL without recompiling:

   * Simple collations for 8-bit character sets.

   * UCA-based collations for Unicode character sets.

   * Binary (`XXX_bin') collations.

The following sections describe how to add collations of the first two
types to existing character sets. All existing character sets already
have a binary collation, so there is no need here to describe how to
add one.

Summary of the procedure for adding a new collation:

  1. Choose a collation ID.

  2. Add configuration information that names the collation and
     describes the character-ordering rules.

  3. Restart the server.

  4. Verify that the collation is present.

The instructions here cover only collations that can be added without
recompiling MySQL. To add a collation that does require recompiling (as
implemented by means of functions in a C source file), use the
instructions in *Note adding-character-set::. However, instead of adding
all the information required for a complete character set, just modify
the appropriate files for an existing character set. That is, based on
what is already present for the character set's current collations, add
data structures, functions, and configuration information for the new
collation.

*Note*:

If you modify an existing collation, that may affect the ordering of
rows for indexes on columns that use the collation.  In this case,
rebuild any such indexes to avoid problems such as incorrect query
results. For further information, see *Note
checking-table-incompatibilities::.

*Additional Resources*

   * The Unicode Collation Algorithm (UCA) specification:
     `http://www.unicode.org/reports/tr10/'

   * The Locale Data Markup Language (LDML) specification:
     `http://www.unicode.org/reports/tr35/'

   * MySQL Blog article `Instructions for adding a new Unicode
     collation':
     `http://blogs.mysql.com/peterg/2008/05/19/instructions-for-adding-a-new-unicode-collation/'


File: manual.info,  Node: charset-collation-implementations,  Next: adding-collation-choosing-id,  Prev: adding-collation,  Up: adding-collation

10.4.1 Collation Implementation Types
-------------------------------------

MySQL implements several types of collations:

*Simple collations for 8-bit character sets*

This kind of collation is implemented using an array of 256 weights
that defines a one-to-one mapping from character codes to weights.
`latin1_swedish_ci' is an example.  It is a case-insensitive collation,
so the uppercase and lowercase versions of a character have the same
weights and they compare as equal.


     mysql> SET NAMES 'latin1' COLLATE 'latin1_swedish_ci';
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT 'a' = 'A';
     +-----------+
     | 'a' = 'A' |
     +-----------+
     |         1 |
     +-----------+
     1 row in set (0.00 sec)

For implementation instructions, see *Note
adding-collation-simple-8bit::.

*Complex collations for 8-bit character sets*

This kind of collation is implemented using functions in a C source
file that define how to order characters, as described in *Note
adding-character-set::.

*Collations for non-Unicode multibyte character sets*

For this type of collation, 8-bit (single-byte) and multibyte
characters are handled differently. For 8-bit characters, character
codes map to weights in case-insensitive fashion. (For example, the
single-byte characters `'a'' and `'A'' both have a weight of `0x41'.)
For multibyte characters, there are two types of relationship between
character codes and weights:

   * Weights equal character codes.  `sjis_japanese_ci' is an example
     of this kind of collation. The multibyte character `'ぢ'' has a
     character code of `0x82C0', and the weight is also `0x82C0'.

   * Character codes map one-to-one to weights, but a code is not
     necessarily equal to the weight.  `gbk_chinese_ci' is an example
     of this kind of collation. The multibyte character `'膰'' has a
     character code of `0x81B0' but a weight of `0xC286'.

For implementation instructions, see *Note adding-character-set::.

*Collations for Unicode multibyte character sets*

Some of these collations are based on the Unicode Collation Algorithm
(UCA), others are not.

Non-UCA collations have a one-to-one mapping from character code to
weight. In MySQL, such collations are case insensitive and accent
insensitive. `utf8_general_ci' is an example: `'a'', `'A'', `'A`'', and
`'a''' each have different character codes but all have a weight of
`0x0041' and compare as equal.


     mysql> SET NAMES 'utf8' COLLATE 'utf8_general_ci';
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT 'a' = 'A', 'a' = 'A`', 'a' = 'a'';
     +-----------+-----------+-----------+
     | 'a' = 'A' | 'a' = 'A`' | 'a' = 'a'' |
     +-----------+-----------+-----------+
     |         1 |         1 |         1 |
     +-----------+-----------+-----------+
     1 row in set (0.06 sec)

UCA-based collations in MySQL have these properties:

   * If a character has weights, each weight uses 2 bytes (16 bits).

   * A character may have zero weights (or an empty weight). In this
     case, the character is ignorable. Example: "U+0000 NULL" does not
     have a weight and is ignorable.

   * A character may have one weight. Example: `'a'' has a weight of
     `0x0E33'.

   * A character may have many weights. This is an expansion.  Example:
     The German letter `'ss'' (SZ ligature, or SHARP S) has a weight of
     `0x0FEA0FEA'.

   * Many characters may have one weight. This is a contraction.
     Example: `'ch'' is a single letter in Czech and has a weight of
     `0x0EE2'.

A many-characters-to-many-weights mapping is also possible (this is
contraction with expansion), but is not supported by MySQL.

For implementation instructions, for a non-UCA collation, see *Note
adding-character-set::. For a UCA collation, see *Note
adding-collation-unicode-uca::.

*Miscellaneous collations*

There are also a few collations that do not fall into any of the
previous categories.


File: manual.info,  Node: adding-collation-choosing-id,  Next: adding-collation-simple-8bit,  Prev: charset-collation-implementations,  Up: adding-collation

10.4.2 Choosing a Collation ID
------------------------------

Each collation must have a unique ID. To add a collation, you must
choose an ID value that is not currently used. The value must be in the
range from 1 to 254. The collation ID that you choose will appear in
these contexts:

   * The `ID' column of the *Note `INFORMATION_SCHEMA.COLLATIONS':
     collations-table.  table.

   * The `Id' column of *Note `SHOW COLLATION': show-collation. output.

   * The `charsetnr' member of the `MYSQL_FIELD' C API data structure.

   * The `number' member of the `MY_CHARSET_INFO' data structure
     returned by the *Note `mysql_get_character_set_info()':
     mysql-get-character-set-info.  C API function.

To determine the largest currently used ID, issue the following
statement:


     mysql> SELECT MAX(ID) FROM INFORMATION_SCHEMA.COLLATIONS;
     +---------+
     | MAX(ID) |
     +---------+
     |     210 |
     +---------+

For the output just shown, you could choose an ID higher than 210 for
the new collation.

To display a list of all currently used IDs, issue this statement:


     mysql> SELECT ID FROM INFORMATION_SCHEMA.COLLATIONS ORDER BY ID;
     +-----+
     | ID  |
     +-----+
     |   1 |
     |   2 |
     | ... |
     |  52 |
     |  53 |
     |  57 |
     |  58 |
     | ... |
     |  98 |
     |  99 |
     | 128 |
     | 129 |
     | ... |
     | 210 |
     +-----+

In this case, you can either choose an unused ID from within the
current range of IDs, or choose an ID that is higher than the current
maximum ID. For example, in the output just shown, there are unused IDs
between 53 and 57, and between 99 and 128. Or you could choose an ID
higher than 210.

*Warning*:

If you upgrade MySQL, you may find that the collation ID you choose has
been assigned to a collation included in the new MySQL distribution. In
this case, you will need to choose a new value for your own collation.

In addition, before upgrading, you should save the configuration files
that you change. If you upgrade in place, the process will replace the
your modified files.


File: manual.info,  Node: adding-collation-simple-8bit,  Next: adding-collation-unicode-uca,  Prev: adding-collation-choosing-id,  Up: adding-collation

10.4.3 Adding a Simple Collation to an 8-Bit Character Set
----------------------------------------------------------

This section describes how to add a simple collation for an 8-bit
character set by writing the `<collation>' elements associated with a
`<charset>' character set description in the MySQL `Index.xml' file.
The procedure described here does not require recompiling MySQL. The
example adds a collation named `latin1_test_ci' to the `latin1'
character set.

  1. Choose a collation ID, as shown in *Note
     adding-collation-choosing-id::. The following steps use an ID of
     56.

  2. Modify the `Index.xml' and `latin1.xml' configuration files. These
     files will be located in the directory named by the
     `character_sets_dir' system variable. You can check the variable
     value as follows, although the path name might be different on
     your system:


          mysql> SHOW VARIABLES LIKE 'character_sets_dir';
          +--------------------+-----------------------------------------+
          | Variable_name      | Value                                   |
          +--------------------+-----------------------------------------+
          | character_sets_dir | /user/local/mysql/share/mysql/charsets/ |
          +--------------------+-----------------------------------------+

  3. Choose a name for the collation and list it in the `Index.xml'
     file. Find the `<charset>' element for the character set to which
     the collation is being added, and add a `<collation>' element that
     indicates the collation name and ID, to associate the name with the
     ID. For example:


          <charset name="latin1">
            ...
            <collation name="latin1_test_ci" id="56"/>
            ...
          </charset>

  4. In the `latin1.xml' configuration file, add a `<collation>'
     element that names the collation and that contains a `<map>'
     element that defines a character code-to-weight mapping table for
     character codes 0 to 255. Each value within the `<map>' element
     must be a number in hexadecimal format.


          <collation name="latin1_test_ci">
          <map>
           00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
           10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F
           20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F
           30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F
           40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
           50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F
           60 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
           50 51 52 53 54 55 56 57 58 59 5A 7B 7C 7D 7E 7F
           80 81 82 83 84 85 86 87 88 89 8A 8B 8C 8D 8E 8F
           90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F
           A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF
           B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF
           41 41 41 41 5B 5D 5B 43 45 45 45 45 49 49 49 49
           44 4E 4F 4F 4F 4F 5C D7 5C 55 55 55 59 59 DE DF
           41 41 41 41 5B 5D 5B 43 45 45 45 45 49 49 49 49
           44 4E 4F 4F 4F 4F 5C F7 5C 55 55 55 59 59 DE FF
          </map>
          </collation>

  5. Restart the server and use this statement to verify that the
     collation is present:


          mysql> SHOW COLLATION LIKE 'latin1_test_ci';
          +----------------+---------+----+---------+----------+---------+
          | Collation      | Charset | Id | Default | Compiled | Sortlen |
          +----------------+---------+----+---------+----------+---------+
          | latin1_test_ci | latin1  | 56 |         |          |       1 |
          +----------------+---------+----+---------+----------+---------+


File: manual.info,  Node: adding-collation-unicode-uca,  Prev: adding-collation-simple-8bit,  Up: adding-collation

10.4.4 Adding a UCA Collation to a Unicode Character Set
--------------------------------------------------------

* Menu:

* ldml-collation-example::       Defining a UCA Collation Using LDML Syntax
* ldml-rules::                   LDML Syntax Supported in MySQL

This section describes how to add a UCA collation for a Unicode
character set by writing the `<collation>' element within a `<charset>'
character set description in the MySQL `Index.xml' file. The procedure
described here does not require recompiling MySQL. It uses a subset of
the Locale Data Markup Language (LDML) specification, which is
available at `http://www.unicode.org/reports/tr35/'. In 5.1, this
method of adding collations is supported as of MySQL 5.1.20. With this
method, you need not define the entire collation. Instead, you begin
with an existing `base' collation and describe the new collation in
terms of how it differs from the base collation. The following table
lists the base collations of the Unicode character sets for which UCA
collations can be defined.

*MySQL Character Sets Available for User-Defined UCA Collations*

Character Set          Base Collation
`utf8'                 `utf8_unicode_ci'
`ucs2'                 `ucs2_unicode_ci'

The following sections show how to add a collation that is defined
using LDML syntax, and provide a summary of LDML rules supported in
MySQL.


File: manual.info,  Node: ldml-collation-example,  Next: ldml-rules,  Prev: adding-collation-unicode-uca,  Up: adding-collation-unicode-uca

10.4.4.1 Defining a UCA Collation Using LDML Syntax
...................................................

To add a UCA collation for a Unicode character set without recompiling
MySQL, use the following procedure. If you are unfamiliar with the LDML
rules used to describe the collation's sort characteristics, see *Note
ldml-rules::.

The example adds a collation named `utf8_phone_ci' to the `utf8'
character set. The collation is designed for a scenario involving a Web
application for which users post their names and phone numbers. Phone
numbers can be given in very different formats:


     +7-12345-67
     +7-12-345-67
     +7 12 345 67
     +7 (12) 345 67
     +71234567

The problem raised by dealing with these kinds of values is that the
varying permissible formats make searching for a specific phone number
very difficult. The solution is to define a new collation that reorders
punctuation characters, making them ignorable.

  1. Choose a collation ID, as shown in *Note
     adding-collation-choosing-id::. The following steps use an ID of
     252.

  2. To modify the `Index.xml' configuration file. This file will be
     located in the directory named by the `character_sets_dir' system
     variable. You can check the variable value as follows, although
     the path name might be different on your system:


          mysql> SHOW VARIABLES LIKE 'character_sets_dir';
          +--------------------+-----------------------------------------+
          | Variable_name      | Value                                   |
          +--------------------+-----------------------------------------+
          | character_sets_dir | /user/local/mysql/share/mysql/charsets/ |
          +--------------------+-----------------------------------------+

  3. Choose a name for the collation and list it in the `Index.xml'
     file. In addition, you'll need to provide the collation ordering
     rules. Find the `<charset>' element for the character set to which
     the collation is being added, and add a `<collation>' element that
     indicates the collation name and ID, to associate the name with
     the ID. Within the `<collation>' element, provide a `<rules>'
     element containing the ordering rules:


          <charset name="utf8">
            ...
            <collation name="utf8_phone_ci" id="252">
              <rules>
                <reset>\u0000</reset>
                <s>\u0020</s> <!-- space -->
                <s>\u0028</s> <!-- left parenthesis -->
                <s>\u0029</s> <!-- right parenthesis -->
                <s>\u002B</s> <!-- plus -->
                <s>\u002D</s> <!-- hyphen -->
              </rules>
            </collation>
            ...
          </charset>

  4. If you want a similar collation for other Unicode character sets,
     add other `<collation>' elements. For example, to define
     `ucs2_phone_ci', add a `<collation>' element to the `<charset
     name="ucs2">' element.  Remember that each collation must have its
     own unique ID.

  5. Restart the server and use this statement to verify that the
     collation is present:


          mysql> SHOW COLLATION LIKE 'utf8_phone_ci';
          +---------------+---------+-----+---------+----------+---------+
          | Collation     | Charset | Id  | Default | Compiled | Sortlen |
          +---------------+---------+-----+---------+----------+---------+
          | utf8_phone_ci | utf8    | 252 |         |          |       8 |
          +---------------+---------+-----+---------+----------+---------+

Now test the collation to make sure that it has the desired properties.

Create a table containing some sample phone numbers using the new
collation:


     mysql> CREATE TABLE phonebook (
         ->   name VARCHAR(64),
         ->   phone VARCHAR(64) CHARACTER SET utf8 COLLATE utf8_phone_ci
         -> );
     Query OK, 0 rows affected (0.09 sec)

     mysql> INSERT INTO phonebook VALUES ('Svoj','+7 912 800 80 02');
     Query OK, 1 row affected (0.00 sec)

     mysql> INSERT INTO phonebook VALUES ('Hf','+7 (912) 800 80 04');
     Query OK, 1 row affected (0.00 sec)

     mysql> INSERT INTO phonebook VALUES ('Bar','+7-912-800-80-01');
     Query OK, 1 row affected (0.00 sec)

     mysql> INSERT INTO phonebook VALUES ('Ramil','(7912) 800 80 03');
     Query OK, 1 row affected (0.00 sec)

     mysql> INSERT INTO phonebook VALUES ('Sanja','+380 (912) 8008005');
     Query OK, 1 row affected (0.00 sec)

Run some queries to see whether the ignored punctuation characters are
in fact ignored for sorting and comparisons:


     mysql> SELECT * FROM phonebook ORDER BY phone;
     +-------+--------------------+
     | name  | phone              |
     +-------+--------------------+
     | Sanja | +380 (912) 8008005 |
     | Bar   | +7-912-800-80-01   |
     | Svoj  | +7 912 800 80 02   |
     | Ramil | (7912) 800 80 03   |
     | Hf    | +7 (912) 800 80 04 |
     +-------+--------------------+
     5 rows in set (0.00 sec)

     mysql> SELECT * FROM phonebook WHERE phone='+7(912)800-80-01';
     +------+------------------+
     | name | phone            |
     +------+------------------+
     | Bar  | +7-912-800-80-01 |
     +------+------------------+
     1 row in set (0.00 sec)

     mysql> SELECT * FROM phonebook WHERE phone='79128008001';
     +------+------------------+
     | name | phone            |
     +------+------------------+
     | Bar  | +7-912-800-80-01 |
     +------+------------------+
     1 row in set (0.00 sec)

     mysql> SELECT * FROM phonebook WHERE phone='7 9 1 2 8 0 0 8 0 0 1';
     +------+------------------+
     | name | phone            |
     +------+------------------+
     | Bar  | +7-912-800-80-01 |
     +------+------------------+
     1 row in set (0.00 sec)


File: manual.info,  Node: ldml-rules,  Prev: ldml-collation-example,  Up: adding-collation-unicode-uca

10.4.4.2 LDML Syntax Supported in MySQL
.......................................

This section describes the LDML syntax that MySQL recognizes.  This is
a subset of the syntax described in the LDML specification available at
`http://www.unicode.org/reports/tr35/', which should be consulted for
further information. The rules described here are all supported except
that character sorting occurs only at the primary level. Rules that
specify differences at secondary or higher sort levels are recognized
(and thus can be included in collation definitions) but are treated as
equality at the primary level.

*Character Representation*

Characters named in LDML rules can be written in `\uNNNN' format, where
NNNN is the hexadecimal Unicode code point value. Within hexadecimal
values, the digits `A' through `F' are not case sensitive; `\u00E1' and
`\u00e1' are equivalent. Basic Latin letters `A-Z' and `a-z' can also be
written literally (this is a MySQL limitation; the LDML specification
permits literal non-Latin1 characters in the rules). Only characters in
the Basic Multilingual Plane can be specified. This notation does not
apply to characters outside the BMP range of `0000' to `FFFF'.

The `Index.xml' file itself should be written using ASCII encoding.

*Syntax Rules*

LDML has reset rules and shift rules to specify character ordering.
Orderings are given as a set of rules that begin with a reset rule that
establishes an anchor point, followed by shift rules that indicate how
characters sort relative to the anchor point.

   * A `<reset>' rule does not specify any ordering in and of itself.
     Instead, it `resets' the ordering for subsequent shift rules to
     cause them to be taken in relation to a given character. Either of
     the following rules resets subsequent shift rules to be taken in
     relation to the letter `'A'':


          <reset>A</reset>

          <reset>\u0041</reset>

   * The `<p>', `<s>', and `<t>' shift rules define primary, secondary,
     and tertiary differences of a character from another character:

        * Use primary differences to distinguish separate letters.

        * Use secondary differences to distinguish accent variations.

        * Use tertiary differences to distinguish lettercase variations.

     Either of these rules specifies a primary shift rule for the `'G''
     character:


          <p>G</p>

          <p>\u0047</p>


File: manual.info,  Node: charset-configuration,  Next: time-zone-support,  Prev: adding-collation,  Up: globalization

10.5 Character Set Configuration
================================

You can change the default server character set and collation with the
`--character-set-server' and `--collation-server' options when you
start the server. The collation must be a legal collation for the
default character set. (Use the *Note `SHOW COLLATION': show-collation.
statement to determine which collations are available for each
character set.) See *Note server-options::.

If you try to use a character set that is not compiled into your
binary, you might run into the following problems:

   * Your program uses an incorrect path to determine where the
     character sets are stored (which is typically the
     `share/mysql/charsets' or `share/charsets' directory under the
     MySQL installation directory). This can be fixed by using the
     `--character-sets-dir' option when you run the program in
     question. For example, to specify a directory to be used by MySQL
     client programs, list it in the `[client]' group of your option
     file. The examples given here show what the setting might look
     like for Unix or Windows, respectively:


          [client]
          character-sets-dir=/usr/local/mysql/share/mysql/charsets

          [client]
          character-sets-dir="C:/Program Files/MySQL/MySQL Server 5.1/share/charsets"

   * The character set is a complex character set that cannot be loaded
     dynamically. In this case, you must recompile the program with
     support for the character set.

     For Unicode character sets, you can define collations without
     recompiling by using LDML notation. See *Note
     adding-collation-unicode-uca::.

   * The character set is a dynamic character set, but you do not have
     a configuration file for it. In this case, you should install the
     configuration file for the character set from a new MySQL
     distribution.

   * If your character set index file does not contain the name for the
     character set, your program displays an error message. The file is
     named `Index.xml' and the message is:


          Character set 'CHARSET_NAME' is not a compiled character set and is not
          specified in the '/usr/share/mysql/charsets/Index.xml' file

     To solve this problem, you should either get a new index file or
     manually add the name of any missing character sets to the current
     file.

You can force client programs to use specific character set as follows:


     [client]
     default-character-set=CHARSET_NAME

This is normally unnecessary. However, when `character_set_system'
differs from `character_set_server' or `character_set_client', and you
input characters manually (as database object identifiers, column
values, or both), these may be displayed incorrectly in output from the
client or the output itself may be formatted incorrectly.  In such
cases, starting the mysql client with
`--default-character-set=SYSTEM_CHARACTER_SET'--that is, setting the
client character set to match the system character set--should fix the
problem.

For `MyISAM' tables, you can check the character set name and number
for a table with *Note `myisamchk -dvv TBL_NAME': myisamchk.


File: manual.info,  Node: time-zone-support,  Next: locale-support,  Prev: charset-configuration,  Up: globalization

10.6 MySQL Server Time Zone Support
===================================

* Menu:

* time-zone-upgrades::           Staying Current with Time Zone Changes
* time-zone-leap-seconds::       Time Zone Leap Second Support

The MySQL server maintains several time zone settings:

   * The system time zone. When the server starts, it attempts to
     determine the time zone of the host machine and uses it to set the
     `system_time_zone' system variable. The value does not change
     thereafter.

     You can set the system time zone for MySQL Server at startup with
     the `--timezone=TIMEZONE_NAME' option to *Note `mysqld_safe':
     mysqld-safe. You can also set it by setting the `TZ' environment
     variable before you start *Note `mysqld': mysqld. The permissible
     values for `--timezone' or `TZ' are system dependent. Consult your
     operating system documentation to see what values are acceptable.

   * The server's current time zone. The global `time_zone' system
     variable indicates the time zone the server currently is operating
     in.  The initial value for `time_zone' is `'SYSTEM'', which
     indicates that the server time zone is the same as the system time
     zone.

     The initial global server time zone value can be specified
     explicitly at startup with the `--default-time-zone=TIMEZONE'
     option on the command line, or you can use the following line in
     an option file:


          default-time-zone='TIMEZONE'

     If you have the `SUPER' privilege, you can set the global server
     time zone value at runtime with this statement:


          mysql> SET GLOBAL time_zone = TIMEZONE;

   * Per-connection time zones. Each client that connects has its own
     time zone setting, given by the session `time_zone' variable.
     Initially, the session variable takes its value from the global
     `time_zone' variable, but the client can change its own time zone
     with this statement:


          mysql> SET time_zone = TIMEZONE;

The current session time zone setting affects display and storage of
time values that are zone-sensitive. This includes the values displayed
by functions such as `NOW()' or `CURTIME()', and values stored in and
retrieved from *Note `TIMESTAMP': datetime. columns.  Values for *Note
`TIMESTAMP': datetime. columns are converted from the current time zone
to UTC for storage, and from UTC to the current time zone for retrieval.

The current time zone setting does not affect values displayed by
functions such as `UTC_TIMESTAMP()' or values in *Note `DATE': datetime,
*Note `TIME': time, or *Note `DATETIME': datetime. columns. Nor are
values in those data types stored in UTC; the time zone applies for them
only when converting from `TIMESTAMP' values. If you want
locale-specific arithmetic for *Note `DATE': datetime, *Note `TIME':
time, or *Note `DATETIME': datetime. values, convert them to UTC,
perform the arithmetic, and then convert back.

The current values of the global and client-specific time zones can be
retrieved like this:


     mysql> SELECT @@global.time_zone, @@session.time_zone;

TIMEZONE values can be given in several formats, none of which are case
sensitive:

   * The value `'SYSTEM'' indicates that the time zone should be the
     same as the system time zone.

   * The value can be given as a string indicating an offset from UTC,
     such as `'+10:00'' or `'-6:00''.

   * The value can be given as a named time zone, such as
     `'Europe/Helsinki'', `'US/Eastern'', or `'MET''.  Named time zones
     can be used only if the time zone information tables in the
     `mysql' database have been created and populated.

The MySQL installation procedure creates the time zone tables in the
`mysql' database, but does not load them. You must do so manually using
the following instructions. (If you are upgrading to MySQL 4.1.3 or
later from an earlier version, you can create the tables by upgrading
your `mysql' database. Use the instructions in *Note mysql-upgrade::.
After creating the tables, you can load them.)

*Note*:

Loading the time zone information is not necessarily a one-time
operation because the information changes occasionally. For example,
the rules for Daylight Saving Time in the United States, Mexico, and
parts of Canada changed in 2007. When such changes occur, applications
that use the old rules become out of date and you may find it necessary
to reload the time zone tables to keep the information used by your
MySQL server current. See the notes at the end of this section.

If your system has its own _zoneinfo_ database (the set of files
describing time zones), you should use the *Note `mysql_tzinfo_to_sql':
mysql-tzinfo-to-sql. program for filling the time zone tables. Examples
of such systems are Linux, FreeBSD, Solaris, and Mac OS X. One likely
location for these files is the `/usr/share/zoneinfo' directory. If
your system does not have a zoneinfo database, you can use the
downloadable package described later in this section.

The *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. program is used
to load the time zone tables. On the command line, pass the zoneinfo
directory path name to *Note `mysql_tzinfo_to_sql':
mysql-tzinfo-to-sql. and send the output into the *Note `mysql': mysql.
program. For example:


     shell> mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root mysql

*Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. reads your system's
time zone files and generates SQL statements from them.  *Note `mysql':
mysql. processes those statements to load the time zone tables.

*Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql. also can be used to
load a single time zone file or to generate leap second information:

   * To load a single time zone file TZ_FILE that corresponds to a time
     zone name TZ_NAME, invoke *Note `mysql_tzinfo_to_sql':
     mysql-tzinfo-to-sql. like this:


          shell> mysql_tzinfo_to_sql TZ_FILE TZ_NAME | mysql -u root mysql

     With this approach, you must execute a separate command to load
     the time zone file for each named zone that the server needs to
     know about.

   * If your time zone needs to account for leap seconds, initialize
     the leap second information like this, where TZ_FILE is the name
     of your time zone file:


          shell> mysql_tzinfo_to_sql --leap TZ_FILE | mysql -u root mysql

   * After running *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql, it
     is best to restart the server so that it does not continue to use
     any previously cached time zone data.

If your system is one that has no zoneinfo database (for example,
Windows or HP-UX), you can use the package of pre-built time zone
tables that is available for download at the MySQL Developer Zone:


     `http://dev.mysql.com/downloads/timezones.html'

This time zone package contains `.frm', `.MYD', and `.MYI' files for
the `MyISAM' time zone tables. These tables should be part of the
`mysql' database, so you should place the files in the `mysql'
subdirectory of your MySQL server's data directory. Stop the server
before doing this and restart it afterward.

*Warning*:

Do not use the downloadable package if your system has a zoneinfo
database. Use the *Note `mysql_tzinfo_to_sql': mysql-tzinfo-to-sql.
utility instead.  Otherwise, you may cause a difference in datetime
handling between MySQL and other applications on your system.

For information about time zone settings in replication setup, please
see *Note replication-features::.


File: manual.info,  Node: time-zone-upgrades,  Next: time-zone-leap-seconds,  Prev: time-zone-support,  Up: time-zone-support

10.6.1 Staying Current with Time Zone Changes
---------------------------------------------

As mentioned earlier, when the time zone rules change, applications
that use the old rules become out of date. To stay current, it is
necessary to make sure that your system uses current time zone
information is used. For MySQL, there are two factors to consider in
staying current:

   * The operating system time affects the value that the MySQL server
     uses for times if its time zone is set to `SYSTEM'. Make sure that
     your operating system is using the latest time zone information.
     For most operating systems, the latest update or service pack
     prepares your system for the time changes. Check the Web site for
     your operating system vendor for an update that addresses the time
     changes.

   * If you replace the system's `/etc/localtime' timezone file with a
     version that uses rules differing from those in effect at *Note
     `mysqld': mysqld. startup, you should restart *Note `mysqld':
     mysqld. so that it uses the updated rules.  Otherwise, *Note
     `mysqld': mysqld. might not notice when the system changes its
     time.

   * If you use named time zones with MySQL, make sure that the time
     zone tables in the `mysql' database are up to date. If your system
     has its own zoneinfo database, you should reload the MySQL time
     zone tables whenever the zoneinfo database is updated, using the
     instructions given earlier in this section. For systems that do
     not have their own zoneinfo database, check the MySQL Developer
     Zone for updates. When a new update is available, download it and
     use it to replace your current time zone tables. *Note `mysqld':
     mysqld. caches time zone information that it looks up, so after
     replacing the time zone tables, you should restart *Note `mysqld':
     mysqld. to make sure that it does not continue to serve outdated
     time zone data.

If you are uncertain whether named time zones are available, for use
either as the server's time zone setting or by clients that set their
own time zone, check whether your time zone tables are empty. The
following query determines whether the table that contains time zone
names has any rows:


     mysql> SELECT COUNT(*) FROM mysql.time_zone_name;
     +----------+
     | COUNT(*) |
     +----------+
     |        0 |
     +----------+

A count of zero indicates that the table is empty. In this case, no one
can be using named time zones, and you don't need to update the tables.
A count greater than zero indicates that the table is not empty and
that its contents are available to be used for named time zone support.
In this case, you should be sure to reload your time zone tables so
that anyone who uses named time zones will get correct query results.

To check whether your MySQL installation is updated properly for a
change in Daylight Saving Time rules, use a test like the one
following. The example uses values that are appropriate for the 2007
DST 1-hour change that occurs in the United States on March 11 at 2 a.m.

The test uses these two queries:


     SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');
     SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');

The two time values indicate the times at which the DST change occurs,
and the use of named time zones requires that the time zone tables be
used. The desired result is that both queries return the same result
(the input time, converted to the equivalent value in the 'US/Central'
time zone).

Before updating the time zone tables, you would see an incorrect result
like this:


     mysql> SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');
     +------------------------------------------------------------+
     | CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central') |
     +------------------------------------------------------------+
     | 2007-03-11 01:00:00                                        |
     +------------------------------------------------------------+

     mysql> SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');
     +------------------------------------------------------------+
     | CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central') |
     +------------------------------------------------------------+
     | 2007-03-11 02:00:00                                        |
     +------------------------------------------------------------+

After updating the tables, you should see the correct result:


     mysql> SELECT CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central');
     +------------------------------------------------------------+
     | CONVERT_TZ('2007-03-11 2:00:00','US/Eastern','US/Central') |
     +------------------------------------------------------------+
     | 2007-03-11 01:00:00                                        |
     +------------------------------------------------------------+

     mysql> SELECT CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central');
     +------------------------------------------------------------+
     | CONVERT_TZ('2007-03-11 3:00:00','US/Eastern','US/Central') |
     +------------------------------------------------------------+
     | 2007-03-11 01:00:00                                        |
     +------------------------------------------------------------+


File: manual.info,  Node: time-zone-leap-seconds,  Prev: time-zone-upgrades,  Up: time-zone-support

10.6.2 Time Zone Leap Second Support
------------------------------------

Before MySQL 5.1.31, if the operating system is configured to return
leap seconds from OS time calls or if the MySQL server uses a time zone
definition that has leap seconds, functions such as `NOW()' could
return a value having a time part that ends with `:59:60' or `:59:61'.
If such values are inserted into a table, they would be dumped as is by
*Note `mysqldump': mysqldump. but considered invalid when reloaded,
leading to backup/restore problems.

As of MySQL 5.1.31, leap second values are returned with a time part
that ends with `:59:59'. This means that a function such as `NOW()' can
return the same value for two or three consecutive seconds during the
leap second. It remains true that literal temporal values having a time
part that ends with `:59:60' or `:59:61' are considered invalid.

If it is necessary to search for *Note `TIMESTAMP': datetime. values
one second before the leap second, anomalous results may be obtained if
you use a comparison with `'YYYY-MM-DD hh:mm:ss'' values. The following
example demonstrates this. It changes the local time zone to UTC so
there is no difference between internal values (which are in UTC) and
displayed values (which have time zone correction applied).


     mysql> CREATE TABLE t1 (
         ->   a INT,
         ->   ts TIMESTAMP DEFAULT NOW(),
         ->   PRIMARY KEY (ts)
         -> );
     Query OK, 0 rows affected (0.01 sec)

     mysql> -- change to UTC
     mysql> SET time_zone = '+00:00';
     Query OK, 0 rows affected (0.00 sec)

     mysql> -- Simulate NOW() = '2008-12-31 23:59:59'
     mysql> SET timestamp = 1230767999;
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO t1 (a) VALUES (1);
     Query OK, 1 row affected (0.00 sec)

     mysql> -- Simulate NOW() = '2008-12-31 23:59:60'
     mysql> SET timestamp = 1230768000;
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO t1 (a) VALUES (2);
     Query OK, 1 row affected (0.00 sec)

     mysql> -- values differ internally but display the same
     mysql> SELECT a, ts, UNIX_TIMESTAMP(ts) FROM t1;
     +------+---------------------+--------------------+
     | a    | ts                  | UNIX_TIMESTAMP(ts) |
     +------+---------------------+--------------------+
     |    1 | 2008-12-31 23:59:59 |         1230767999 |
     |    2 | 2008-12-31 23:59:59 |         1230768000 |
     +------+---------------------+--------------------+
     2 rows in set (0.00 sec)

     mysql> -- only the non-leap value matches
     mysql> SELECT * FROM t1 WHERE ts = '2008-12-31 23:59:59';
     +------+---------------------+
     | a    | ts                  |
     +------+---------------------+
     |    1 | 2008-12-31 23:59:59 |
     +------+---------------------+
     1 row in set (0.00 sec)

     mysql> -- the leap value with seconds=60 is invalid
     mysql> SELECT * FROM t1 WHERE ts = '2008-12-31 23:59:60';
     Empty set, 2 warnings (0.00 sec)

To work around this, you can use a comparison based on the UTC value
actually stored in column, which has the leap second correction applied:


     mysql> -- selecting using UNIX_TIMESTAMP value return leap value
     mysql> SELECT * FROM t1 WHERE UNIX_TIMESTAMP(ts) = 1230768000;
     +------+---------------------+
     | a    | ts                  |
     +------+---------------------+
     |    2 | 2008-12-31 23:59:59 |
     +------+---------------------+
     1 row in set (0.00 sec)


File: manual.info,  Node: locale-support,  Prev: time-zone-support,  Up: globalization

10.7 MySQL Server Locale Support
================================

Beginning with MySQL 5.1.12, the locale indicated by the
`lc_time_names' system variable controls the language used to display
day and month names and abbreviations. This variable affects the output
from the `DATE_FORMAT()', `DAYNAME()', and `MONTHNAME()' functions.

`lc_time_names' does not affect the `STR_TO_DATE()' or `GET_FORMAT()'
function.

Locale names have language and region subtags listed by IANA
(`http://www.iana.org/assignments/language-subtag-registry') such as
`'ja_JP'' or `'pt_BR''.  The default value is `'en_US'' regardless of
your system's locale setting, but you can set the value at server
startup or set the `GLOBAL' value if you have the `SUPER' privilege.
Any client can examine the value of `lc_time_names' or set its
`SESSION' value to affect the locale for its own connection.


     mysql> SET NAMES 'utf8';
     Query OK, 0 rows affected (0.09 sec)

     mysql> SELECT @@lc_time_names;
     +-----------------+
     | @@lc_time_names |
     +-----------------+
     | en_US           |
     +-----------------+
     1 row in set (0.00 sec)

     mysql> SELECT DAYNAME('2010-01-01'), MONTHNAME('2010-01-01');
     +-----------------------+-------------------------+
     | DAYNAME('2010-01-01') | MONTHNAME('2010-01-01') |
     +-----------------------+-------------------------+
     | Friday                | January                 |
     +-----------------------+-------------------------+
     1 row in set (0.00 sec)

     mysql> SELECT DATE_FORMAT('2010-01-01','%W %a %M %b');
     +-----------------------------------------+
     | DATE_FORMAT('2010-01-01','%W %a %M %b') |
     +-----------------------------------------+
     | Friday Fri January Jan                  |
     +-----------------------------------------+
     1 row in set (0.00 sec)

     mysql> SET lc_time_names = 'es_MX';
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @@lc_time_names;
     +-----------------+
     | @@lc_time_names |
     +-----------------+
     | es_MX           |
     +-----------------+
     1 row in set (0.00 sec)

     mysql> SELECT DAYNAME('2010-01-01'), MONTHNAME('2010-01-01');
     +-----------------------+-------------------------+
     | DAYNAME('2010-01-01') | MONTHNAME('2010-01-01') |
     +-----------------------+-------------------------+
     | viernes               | enero                   |
     +-----------------------+-------------------------+
     1 row in set (0.00 sec)

     mysql> SELECT DATE_FORMAT('2010-01-01','%W %a %M %b');
     +-----------------------------------------+
     | DATE_FORMAT('2010-01-01','%W %a %M %b') |
     +-----------------------------------------+
     | viernes vie enero ene                   |
     +-----------------------------------------+
     1 row in set (0.00 sec)

The day or month name for each of the affected functions is converted
from `utf8' to the character set indicated by the
`character_set_connection' system variable.

`lc_time_names' may be set to any of the following locale values.

This table lists locale values to which `lc_time_names' may be set. The
locale values are presented in a two-column table and in alphabetical
order from left to right.

`ar_AE': Arabic - United Arab        `ar_BH': Arabic - Bahrain
Emirates                             
`ar_DZ': Arabic - Algeria            `ar_EG': Arabic - Egypt
`ar_IN': Arabic - India              `ar_IQ': Arabic - Iraq
`ar_JO': Arabic - Jordan             `ar_KW': Arabic - Kuwait
`ar_LB': Arabic - Lebanon            `ar_LY': Arabic - Libya
`ar_MA': Arabic - Morocco            `ar_OM': Arabic - Oman
`ar_QA': Arabic - Qatar              `ar_SA': Arabic - Saudi Arabia
`ar_SD': Arabic - Sudan              `ar_SY': Arabic - Syria
`ar_TN': Arabic - Tunisia            `ar_YE': Arabic - Yemen
`be_BY': Belarusian - Belarus        `bg_BG': Bulgarian - Bulgaria
`ca_ES': Catalan - Spain             `cs_CZ': Czech - Czech Republic
`da_DK': Danish - Denmark            `de_AT': German - Austria
`de_BE': German - Belgium            `de_CH': German - Switzerland
`de_DE': German - Germany            `de_LU': German - Luxembourg
`en_AU': English - Australia         `en_CA': English - Canada
`en_GB': English - United Kingdom    `en_IN': English - India
`en_NZ': English - New Zealand       `en_PH': English - Philippines
`en_US': English - United States     `en_ZA': English - South Africa
`en_ZW': English - Zimbabwe          `es_AR': Spanish - Argentina
`es_BO': Spanish - Bolivia           `es_CL': Spanish - Chile
`es_CO': Spanish - Columbia          `es_CR': Spanish - Costa Rica
`es_DO': Spanish - Dominican         `es_EC': Spanish - Ecuador
Republic                             
`es_ES': Spanish - Spain             `es_GT': Spanish - Guatemala
`es_HN': Spanish - Honduras          `es_MX': Spanish - Mexico
`es_NI': Spanish - Nicaragua         `es_PA': Spanish - Panama
`es_PE': Spanish - Peru              `es_PR': Spanish - Puerto Rico
`es_PY': Spanish - Paraguay          `es_SV': Spanish - El Salvador
`es_US': Spanish - United States     `es_UY': Spanish - Uruguay
`es_VE': Spanish - Venezuela         `et_EE': Estonian - Estonia
`eu_ES': Basque - Basque             `fi_FI': Finnish - Finland
`fo_FO': Faroese - Faroe Islands     `fr_BE': French - Belgium
`fr_CA': French - Canada             `fr_CH': French - Switzerland
`fr_FR': French - France             `fr_LU': French - Luxembourg
`gl_ES': Galician - Spain            `gu_IN': Gujarati - India
`he_IL': Hebrew - Israel             `hi_IN': Hindi - India
`hr_HR': Croatian - Croatia          `hu_HU': Hungarian - Hungary
`id_ID': Indonesian - Indonesia      `is_IS': Icelandic - Iceland
`it_CH': Italian - Switzerland       `it_IT': Italian - Italy
`ja_JP': Japanese - Japan            `ko_KR': Korean - Republic of Korea
`lt_LT': Lithuanian - Lithuania      `lv_LV': Latvian - Latvia
`mk_MK': Macedonian - FYROM          `mn_MN': Mongolia - Mongolian
`ms_MY': Malay - Malaysia            `nb_NO': Norwegian(Bokmaal) - Norway
`nl_BE': Dutch - Belgium             `nl_NL': Dutch - The Netherlands
`no_NO': Norwegian - Norway          `pl_PL': Polish - Poland
`pt_BR': Portugese - Brazil          `pt_PT': Portugese - Portugal
`ro_RO': Romanian - Romania          `ru_RU': Russian - Russia
`ru_UA': Russian - Ukraine           `sk_SK': Slovak - Slovakia
`sl_SI': Slovenian - Slovenia        `sq_AL': Albanian - Albania
`sr_YU': Serbian - Yugoslavia        `sv_FI': Swedish - Finland
`sv_SE': Swedish - Sweden            `ta_IN': Tamil - India
`te_IN': Telugu - India              `th_TH': Thai - Thailand
`tr_TR': Turkish - Turkey            `uk_UA': Ukrainian - Ukraine
`ur_PK': Urdu - Pakistan             `vi_VN': Vietnamese - Viet Nam
`zh_CN': Chinese - China             `zh_HK': Chinese - Hong Kong
`zh_TW': Chinese - Taiwan Province   
of China                             


File: manual.info,  Node: data-types,  Next: functions,  Prev: globalization,  Up: Top

11 Data Types
*************

* Menu:

* data-type-overview::           Data Type Overview
* numeric-types::                Numeric Types
* date-and-time-types::          Date and Time Types
* string-types::                 String Types
* spatial-extensions::           Extensions for Spatial Data
* data-type-defaults::           Data Type Default Values
* storage-requirements::         Data Type Storage Requirements
* choosing-types::               Choosing the Right Type for a Column
* other-vendor-data-types::      Using Data Types from Other Database Engines

MySQL supports a number of SQL
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_sql) data
types in several categories: numeric types, date and time types, string
(character and byte) types, and spatial types. This chapter provides an
overview of these data types, a more detailed description of the
properties of the types in each category, and a summary of the data
type storage requirements. The initial overview is intentionally brief.
The more detailed descriptions later in the chapter should be consulted
for additional information about particular data types, such as the
permissible formats in which you can specify values.

Data type descriptions use these conventions:

   * M indicates the maximum display width for integer types. For
     floating-point and fixed-point types, M is the total number of
     digits that can be stored (the precision). For string types, M is
     the maximum length. The maximum permissible value of M depends on
     the data type.

   * D applies to floating-point and fixed-point types and indicates
     the number of digits following the decimal point (the scale). The
     maximum possible value is 30, but should be no greater than M-2.

   * Square brackets (``['' and ``]'') indicate optional parts of type
     definitions.


File: manual.info,  Node: data-type-overview,  Next: numeric-types,  Prev: data-types,  Up: data-types

11.1 Data Type Overview
=======================

* Menu:

* numeric-type-overview::        Numeric Type Overview
* date-and-time-type-overview::  Date and Time Type Overview
* string-type-overview::         String Type Overview


File: manual.info,  Node: numeric-type-overview,  Next: date-and-time-type-overview,  Prev: data-type-overview,  Up: data-type-overview

11.1.1 Numeric Type Overview
----------------------------

A summary of the numeric data types follows. For additional information
about properties and storage requirements of the numeric types, see
*Note numeric-types::, and *Note storage-requirements::.

M indicates the maximum display width for integer types. The maximum
display width is 255. Display width is unrelated to the range of values
a type can contain, as described in *Note numeric-types::. For
floating-point and fixed-point types, M is the total number of digits
that can be stored.

If you specify `ZEROFILL' for a numeric column, MySQL automatically
adds the `UNSIGNED' attribute to the column.

Numeric data types that permit the `UNSIGNED' attribute also permit
`SIGNED'. However, these data types are signed by default, so the
`SIGNED' attribute has no effect.

`SERIAL' is an alias for `BIGINT UNSIGNED NOT NULL AUTO_INCREMENT
UNIQUE'.

`SERIAL DEFAULT VALUE' in the definition of an integer column is an
alias for `NOT NULL AUTO_INCREMENT UNIQUE'.

*Warning*:

When you use subtraction between integer values where one is of type
`UNSIGNED', the result is unsigned unless the `NO_UNSIGNED_SUBTRACTION'
SQL mode is enabled. See *Note cast-functions::.

   * *Note `BIT[(M)]': bit-type.

     A bit-field type. M indicates the number of bits per value, from 1
     to 64. The default is 1 if M is omitted.

   * *Note `TINYINT[(M)] [UNSIGNED] [ZEROFILL]': integer-types.

     A very small integer. The signed range is `-128' to `127'. The
     unsigned range is `0' to `255'.

   * *Note `BOOL': integer-types, *Note `BOOLEAN': integer-types.

     These types are synonyms for *Note `TINYINT(1)': integer-types. A
     value of zero is considered false. Nonzero values are considered
     true:


          mysql> SELECT IF(0, 'true', 'false');
          +------------------------+
          | IF(0, 'true', 'false') |
          +------------------------+
          | false                  |
          +------------------------+

          mysql> SELECT IF(1, 'true', 'false');
          +------------------------+
          | IF(1, 'true', 'false') |
          +------------------------+
          | true                   |
          +------------------------+

          mysql> SELECT IF(2, 'true', 'false');
          +------------------------+
          | IF(2, 'true', 'false') |
          +------------------------+
          | true                   |
          +------------------------+

     However, the values `TRUE' and `FALSE' are merely aliases for `1'
     and `0', respectively, as shown here:


          mysql> SELECT IF(0 = FALSE, 'true', 'false');
          +--------------------------------+
          | IF(0 = FALSE, 'true', 'false') |
          +--------------------------------+
          | true                           |
          +--------------------------------+

          mysql> SELECT IF(1 = TRUE, 'true', 'false');
          +-------------------------------+
          | IF(1 = TRUE, 'true', 'false') |
          +-------------------------------+
          | true                          |
          +-------------------------------+

          mysql> SELECT IF(2 = TRUE, 'true', 'false');
          +-------------------------------+
          | IF(2 = TRUE, 'true', 'false') |
          +-------------------------------+
          | false                         |
          +-------------------------------+

          mysql> SELECT IF(2 = FALSE, 'true', 'false');
          +--------------------------------+
          | IF(2 = FALSE, 'true', 'false') |
          +--------------------------------+
          | false                          |
          +--------------------------------+

     The last two statements display the results shown because `2' is
     equal to neither `1' nor `0'.

   * *Note `SMALLINT[(M)] [UNSIGNED] [ZEROFILL]': integer-types.

     A small integer. The signed range is `-32768' to `32767'. The
     unsigned range is `0' to `65535'.

   * *Note `MEDIUMINT[(M)] [UNSIGNED] [ZEROFILL]': integer-types.

     A medium-sized integer. The signed range is `-8388608' to
     `8388607'.  The unsigned range is `0' to `16777215'.

   * *Note `INT[(M)] [UNSIGNED] [ZEROFILL]': integer-types.

     A normal-size integer. The signed range is `-2147483648' to
     `2147483647'. The unsigned range is `0' to `4294967295'.

   * *Note `INTEGER[(M)] [UNSIGNED] [ZEROFILL]': integer-types.

     This type is a synonym for *Note `INT': integer-types.

   * *Note `BIGINT[(M)] [UNSIGNED] [ZEROFILL]': integer-types.

     A large integer. The signed range is `-9223372036854775808' to
     `9223372036854775807'. The unsigned range is `0' to
     `18446744073709551615'.

     `SERIAL' is an alias for `BIGINT UNSIGNED NOT NULL AUTO_INCREMENT
     UNIQUE'.

     Some things you should be aware of with respect to *Note `BIGINT':
     integer-types. columns:

        * All arithmetic is done using signed *Note `BIGINT':
          integer-types. or *Note `DOUBLE': floating-point-types.
          values, so you should not use unsigned big integers larger
          than `9223372036854775807' (63 bits) except with bit
          functions! If you do that, some of the last digits in the
          result may be wrong because of rounding errors when
          converting a *Note `BIGINT': integer-types. value to a *Note
          `DOUBLE': floating-point-types.

          MySQL can handle *Note `BIGINT': integer-types.  in the
          following cases:

             * When using integers to store large unsigned values in a
               *Note `BIGINT': integer-types. column.

             * In `MIN(COL_NAME)' or `MAX(COL_NAME)', where COL_NAME
               refers to a *Note `BIGINT': integer-types. column.

             * When using operators (`+', `-', `*', and so on) where
               both operands are integers.

        * You can always store an exact integer value in a *Note
          `BIGINT': integer-types. column by storing it using a string.
          In this case, MySQL performs a string-to-number conversion
          that involves no intermediate double-precision representation.

        * The `-', `+', and `*' operators use *Note `BIGINT':
          integer-types.  arithmetic when both operands are integer
          values. This means that if you multiply two big integers (or
          results from functions that return integers), you may get
          unexpected results when the result is larger than
          `9223372036854775807'.

   * *Note `DECIMAL[(M[,D])] [UNSIGNED] [ZEROFILL]': fixed-point-types.

     A packed `exact' fixed-point number.  M is the total number of
     digits (the precision) and D is the number of digits after the
     decimal point (the scale). The decimal point and (for negative
     numbers) the ``-'' sign are not counted in M. If D is 0, values
     have no decimal point or fractional part. The maximum number of
     digits (M) for *Note `DECIMAL': fixed-point-types. is 65. The
     maximum number of supported decimals (D) is 30. If D is omitted,
     the default is 0. If M is omitted, the default is 10.

     `UNSIGNED', if specified, disallows negative values.

     All basic calculations (`+, -, *, /') with *Note `DECIMAL':
     fixed-point-types. columns are done with a precision of 65 digits.

   * *Note `DEC[(M[,D])] [UNSIGNED] [ZEROFILL]': fixed-point-types,
     *Note `NUMERIC[(M[,D])] [UNSIGNED] [ZEROFILL]': fixed-point-types,
     *Note `FIXED[(M[,D])] [UNSIGNED] [ZEROFILL]': fixed-point-types.

     These types are synonyms for *Note `DECIMAL': fixed-point-types.
     The *Note `FIXED': fixed-point-types. synonym is available for
     compatibility with other database systems.

   * *Note `FLOAT[(M,D)] [UNSIGNED] [ZEROFILL]': floating-point-types.

     A small (single-precision) floating-point number.  Permissible
     values are `-3.402823466E+38' to `-1.175494351E-38', `0', and
     `1.175494351E-38' to `3.402823466E+38'. These are the theoretical
     limits, based on the IEEE standard. The actual range might be
     slightly smaller depending on your hardware or operating system.

     M is the total number of digits and D is the number of digits
     following the decimal point. If M and D are omitted, values are
     stored to the limits permitted by the hardware. A single-precision
     floating-point number is accurate to approximately 7 decimal
     places.

     `UNSIGNED', if specified, disallows negative values.

     Using *Note `FLOAT': floating-point-types. might give you some
     unexpected problems because all calculations in MySQL are done
     with double precision. See *Note no-matching-rows::.

   * *Note `DOUBLE[(M,D)] [UNSIGNED] [ZEROFILL]': floating-point-types.

     A normal-size (double-precision) floating-point number.
     Permissible values are `-1.7976931348623157E+308' to
     `-2.2250738585072014E-308', `0', and `2.2250738585072014E-308' to
     `1.7976931348623157E+308'. These are the theoretical limits, based
     on the IEEE standard. The actual range might be slightly smaller
     depending on your hardware or operating system.

     M is the total number of digits and D is the number of digits
     following the decimal point. If M and D are omitted, values are
     stored to the limits permitted by the hardware. A double-precision
     floating-point number is accurate to approximately 15 decimal
     places.

     `UNSIGNED', if specified, disallows negative values.

   * *Note `DOUBLE PRECISION[(M,D)] [UNSIGNED] [ZEROFILL]':
     floating-point-types, *Note `REAL[(M,D)] [UNSIGNED] [ZEROFILL]':
     floating-point-types.

     These types are synonyms for *Note `DOUBLE': floating-point-types.
     Exception: If the `REAL_AS_FLOAT' SQL mode is enabled, *Note
     `REAL': floating-point-types. is a synonym for *Note `FLOAT':
     floating-point-types. rather than *Note `DOUBLE':
     floating-point-types.

   * *Note `FLOAT(P) [UNSIGNED] [ZEROFILL]': floating-point-types.

     A floating-point number. P represents the precision in bits, but
     MySQL uses this value only to determine whether to use *Note
     `FLOAT': floating-point-types. or *Note `DOUBLE':
     floating-point-types. for the resulting data type. If P is from 0
     to 24, the data type becomes *Note `FLOAT': floating-point-types.
     with no M or D values. If P is from 25 to 53, the data type
     becomes *Note `DOUBLE': floating-point-types. with no M or D
     values. The range of the resulting column is the same as for the
     single-precision *Note `FLOAT': floating-point-types. or
     double-precision *Note `DOUBLE': floating-point-types. data types
     described earlier in this section.

     *Note `FLOAT(P)': floating-point-types.  syntax is provided for
     ODBC compatibility.


File: manual.info,  Node: date-and-time-type-overview,  Next: string-type-overview,  Prev: numeric-type-overview,  Up: data-type-overview

11.1.2 Date and Time Type Overview
----------------------------------

A summary of the temporal data types follows. For additional
information about properties and storage requirements of the temporal
types, see *Note date-and-time-types::, and *Note
storage-requirements::. For descriptions of functions that operate on
temporal values, see *Note date-and-time-functions::.

For the *Note `DATE': datetime. and *Note `DATETIME': datetime. range
descriptions, `supported' means that although earlier values might
work, there is no guarantee.

   * *Note `DATE': datetime.

     A date. The supported range is `'1000-01-01'' to `'9999-12-31''.
     MySQL displays *Note `DATE': datetime. values in `'YYYY-MM-DD''
     format, but permits assignment of values to *Note `DATE': datetime.
     columns using either strings or numbers.

   * *Note `DATETIME': datetime.

     A date and time combination. The supported range is `'1000-01-01
     00:00:00'' to `'9999-12-31 23:59:59''. MySQL displays *Note
     `DATETIME': datetime. values in `'YYYY-MM-DD HH:MM:SS'' format,
     but permits assignment of values to *Note `DATETIME': datetime.
     columns using either strings or numbers.

   * *Note `TIMESTAMP': datetime.

     A timestamp. The range is `'1970-01-01 00:00:01'' UTC to
     `'2038-01-19 03:14:07'' UTC.  *Note `TIMESTAMP': datetime. values
     are stored as the number of seconds since the epoch (`'1970-01-01
     00:00:00'' UTC). A *Note `TIMESTAMP': datetime. cannot represent
     the value `'1970-01-01 00:00:00'' because that is equivalent to 0
     seconds from the epoch and the value 0 is reserved for
     representing `'0000-00-00 00:00:00'', the `zero' *Note
     `TIMESTAMP': datetime. value.

     Unless specified otherwise, the first *Note `TIMESTAMP': datetime.
     column in a table is defined to be automatically set to the date
     and time of the most recent modification if not explicitly
     assigned a value. This makes *Note `TIMESTAMP': datetime.  useful
     for recording the timestamp of an *Note `INSERT': insert. or *Note
     `UPDATE': update. operation. You can also set any *Note
     `TIMESTAMP': datetime. column to the current date and time by
     assigning it a `NULL' value, unless it has been defined with the
     `NULL' attribute to permit `NULL' values. The automatic
     initialization and updating to the current date and time can be
     specified using `DEFAULT CURRENT_TIMESTAMP' and `ON UPDATE
     CURRENT_TIMESTAMP' clauses, as described in *Note
     timestamp-initialization::.

     *Note*:

     The *Note `TIMESTAMP': datetime. format that was used prior to
     MySQL 4.1 is not supported in MySQL 5.1; see `MySQL 3.23, 4.0, 4.1
     Reference Manual' for information regarding the old format.

   * *Note `TIME': time.

     A time. The range is `'-838:59:59'' to `'838:59:59''. MySQL
     displays *Note `TIME': time. values in `'HH:MM:SS'' format, but
     permits assignment of values to *Note `TIME': time. columns using
     either strings or numbers.

   * *Note `YEAR[(2|4)]': year.

     A year in two-digit or four-digit format. The default is
     four-digit format. `YEAR(2)' or `YEAR(4)' differ in display
     format, but have the same range of values. In four-digit format,
     values display as `1901' to `2155', and `0000'. In two-digit
     format, values display as `70' to `69', representing years from
     1970 to 2069.  MySQL displays *Note `YEAR': year. values in `YYYY'
     or `YY' format, but permits assignment of values to *Note `YEAR':
     year. columns using either strings or numbers.

     *Note*:

     The `YEAR(2)' data type has certain issues that you should
     consider before choosing to use it.  As of MySQL 5.1.65, `YEAR(2)'
     is deprecated. For more information, see *Note
     migrating-to-year4::.

     For additional information about `YEAR' display format and
     interpretation of input values, see *Note year::.

The `SUM()' and `AVG()' aggregate functions do not work with temporal
values. (They convert the values to numbers, losing everything after
the first nonnumeric character.) To work around this problem, convert
to numeric units, perform the aggregate operation, and convert back to
a temporal value.  Examples:


     SELECT SEC_TO_TIME(SUM(TIME_TO_SEC(TIME_COL))) FROM TBL_NAME;
     SELECT FROM_DAYS(SUM(TO_DAYS(DATE_COL))) FROM TBL_NAME;

*Note*:

The MySQL server can be run with the `MAXDB' SQL mode enabled. In this
case, *Note `TIMESTAMP': datetime. is identical with *Note `DATETIME':
datetime. If this mode is enabled at the time that a table is created,
*Note `TIMESTAMP': datetime. columns are created as *Note `DATETIME':
datetime. columns. As a result, such columns use *Note `DATETIME':
datetime. display format, have the same range of values, and there is
no automatic initialization or updating to the current date and time.
See *Note sql-mode::.


File: manual.info,  Node: string-type-overview,  Prev: date-and-time-type-overview,  Up: data-type-overview

11.1.3 String Type Overview
---------------------------

A summary of the string data types follows. For additional information
about properties and storage requirements of the string types, see
*Note string-types::, and *Note storage-requirements::.

In some cases, MySQL may change a string column to a type different
from that given in a *Note `CREATE TABLE': create-table. or *Note
`ALTER TABLE': alter-table.  statement. See *Note
silent-column-changes::.

MySQL interprets length specifications in character column definitions
in character units. This applies to *Note `CHAR': char, *Note
`VARCHAR': char, and the *Note `TEXT': blob. types.

Column definitions for many string data types can include attributes
that specify the character set or collation of the column. These
attributes apply to the *Note `CHAR': char, *Note `VARCHAR': char, the
*Note `TEXT': blob. types, *Note `ENUM': enum, and *Note `SET': set.
data types:

   * The `CHARACTER SET' attribute specifies the character set, and the
     `COLLATE' attribute specifies a collation for the character set.
     For example:


          CREATE TABLE t
          (
              c1 VARCHAR(20) CHARACTER SET utf8,
              c2 TEXT CHARACTER SET latin1 COLLATE latin1_general_cs
          );

     This table definition creates a column named `c1' that has a
     character set of `utf8' with the default collation for that
     character set, and a column named `c2' that has a character set of
     `latin1' and a case-sensitive collation.

     The rules for assigning the character set and collation when
     either or both of the `CHARACTER SET' and `COLLATE' attributes are
     missing are described in *Note charset-column::.

     `CHARSET' is a synonym for `CHARACTER SET'.

   * Specifying the `CHARACTER SET binary' attribute for a character
     data type causes the column to be created as the corresponding
     binary data type: *Note `CHAR': char. becomes *Note `BINARY':
     binary-varbinary, *Note `VARCHAR': char. becomes *Note
     `VARBINARY': binary-varbinary, and *Note `TEXT': blob. becomes
     *Note `BLOB': blob. For the *Note `ENUM': enum. and *Note `SET':
     set. data types, this does not occur; they are created as
     declared. Suppose that you specify a table using this definition:


          CREATE TABLE t
          (
            c1 VARCHAR(10) CHARACTER SET binary,
            c2 TEXT CHARACTER SET binary,
            c3 ENUM('a','b','c') CHARACTER SET binary
          );

     The resulting table has this definition:


          CREATE TABLE t
          (
            c1 VARBINARY(10),
            c2 BLOB,
            c3 ENUM('a','b','c') CHARACTER SET binary
          );

   * The `ASCII' attribute is shorthand for `CHARACTER SET latin1'.

   * The `UNICODE' attribute is shorthand for `CHARACTER SET ucs2'.

   * The `BINARY' attribute is shorthand for specifying the binary
     collation of the column character set.  In this case, sorting and
     comparison are based on numeric character values.

Character column sorting and comparison are based on the character set
assigned to the column. For the *Note `CHAR': char, *Note `VARCHAR':
char, *Note `TEXT': blob, *Note `ENUM': enum, and *Note `SET': set.
data types, you can declare a column with a binary collation or the
`BINARY' attribute to cause sorting and comparison to use the underlying
character code values rather than a lexical ordering.

*Note charset::, provides additional information about use of character
sets in MySQL.

   * `[NATIONAL] CHAR[(M)] [CHARACTER SET CHARSET_NAME] [COLLATE
     COLLATION_NAME]'

     A fixed-length string that is always right-padded with spaces to
     the specified length when stored.  M represents the column length
     in characters. The range of M is 0 to 255. If M is omitted, the
     length is 1.

     *Note*:

     Trailing spaces are removed when *Note `CHAR': char. values are
     retrieved unless the `PAD_CHAR_TO_FULL_LENGTH' SQL mode is enabled.

     *Note `CHAR': char. is shorthand for *Note `CHARACTER': char.
     *Note `NATIONAL CHAR': char. (or its equivalent short form, *Note
     `NCHAR': char.)  is the standard SQL way to define that a *Note
     `CHAR': char. column should use some predefined character set.
     MySQL 4.1 and up uses `utf8' as this predefined character set.
     *Note charset-national::.

     The *Note `CHAR BYTE': binary-varbinary. data type is an alias for
     the *Note `BINARY': binary-varbinary. data type. This is a
     compatibility feature.

     MySQL permits you to create a column of type `CHAR(0)'. This is
     useful primarily when you have to be compliant with old
     applications that depend on the existence of a column but that do
     not actually use its value. `CHAR(0)' is also quite nice when you
     need a column that can take only two values: A column that is
     defined as `CHAR(0) NULL' occupies only one bit and can take only
     the values `NULL' and `''' (the empty string).

   * `[NATIONAL] VARCHAR(M) [CHARACTER SET CHARSET_NAME] [COLLATE
     COLLATION_NAME]'

     A variable-length string. M represents the maximum column length
     in characters. The range of M is 0 to 65,535. The effective
     maximum length of a *Note `VARCHAR': char. is subject to the
     maximum row size (65,535 bytes, which is shared among all columns)
     and the character set used. For example, `utf8' characters can
     require up to three bytes per character, so a *Note `VARCHAR':
     char. column that uses the `utf8' character set can be declared to
     be a maximum of 21,844 characters. See *Note column-count-limit::.

     MySQL stores *Note `VARCHAR': char. values as a 1-byte or 2-byte
     length prefix plus data. The length prefix indicates the number of
     bytes in the value. A *Note `VARCHAR': char. column uses one
     length byte if values require no more than 255 bytes, two length
     bytes if values may require more than 255 bytes.

     *Note*:

     MySQL 5.1 follows the standard SQL specification, and does _not_
     remove trailing spaces from *Note `VARCHAR': char. values.

     *Note `VARCHAR': char. is shorthand for *Note `CHARACTER VARYING':
     char.  *Note `NATIONAL VARCHAR': char. is the standard SQL way to
     define that a *Note `VARCHAR': char. column should use some
     predefined character set. MySQL 4.1 and up uses `utf8' as this
     predefined character set.  *Note charset-national::.  *Note
     `NVARCHAR': char. is shorthand for *Note `NATIONAL VARCHAR': char.

   * *Note `BINARY(M)': binary-varbinary.

     The *Note `BINARY': binary-varbinary. type is similar to the *Note
     `CHAR': char. type, but stores binary byte strings rather than
     nonbinary character strings.  M represents the column length in
     bytes.

   * *Note `VARBINARY(M)': binary-varbinary.

     The *Note `VARBINARY': binary-varbinary. type is similar to the
     *Note `VARCHAR': char. type, but stores binary byte strings rather
     than nonbinary character strings. M represents the maximum column
     length in bytes.

   * *Note `TINYBLOB': blob.

     A *Note `BLOB': blob. column with a maximum length of 255 (2^8 - 1)
     bytes. Each *Note `TINYBLOB': blob. value is stored using a 1-byte
     length prefix that indicates the number of bytes in the value.

   * *Note `TINYTEXT [CHARACTER SET CHARSET_NAME] [COLLATE
     COLLATION_NAME]': blob.

     A *Note `TEXT': blob. column with a maximum length of 255 (2^8 - 1)
     characters. The effective maximum length is less if the value
     contains multibyte characters. Each *Note `TINYTEXT': blob. value
     is stored using a 1-byte length prefix that indicates the number of
     bytes in the value.

   * *Note `BLOB[(M)]': blob.

     A *Note `BLOB': blob. column with a maximum length of 65,535 (2^16
     - 1) bytes. Each *Note `BLOB': blob. value is stored using a
     2-byte length prefix that indicates the number of bytes in the
     value.

     An optional length M can be given for this type. If this is done,
     MySQL creates the column as the smallest *Note `BLOB': blob. type
     large enough to hold values M bytes long.

   * *Note `TEXT[(M)] [CHARACTER SET CHARSET_NAME] [COLLATE
     COLLATION_NAME]': blob.

     A *Note `TEXT': blob. column with a maximum length of 65,535 (2^16
     - 1) characters. The effective maximum length is less if the value
     contains multibyte characters. Each *Note `TEXT': blob. value is
     stored using a 2-byte length prefix that indicates the number of
     bytes in the value.

     An optional length M can be given for this type. If this is done,
     MySQL creates the column as the smallest *Note `TEXT': blob. type
     large enough to hold values M characters long.

   * *Note `MEDIUMBLOB': blob.

     A *Note `BLOB': blob. column with a maximum length of 16,777,215
     (2^24 - 1) bytes. Each *Note `MEDIUMBLOB': blob.  value is stored
     using a 3-byte length prefix that indicates the number of bytes in
     the value.

   * *Note `MEDIUMTEXT [CHARACTER SET CHARSET_NAME] [COLLATE
     COLLATION_NAME]': blob.

     A *Note `TEXT': blob. column with a maximum length of 16,777,215
     (2^24 - 1) characters. The effective maximum length is less if the
     value contains multibyte characters. Each *Note `MEDIUMTEXT':
     blob. value is stored using a 3-byte length prefix that indicates
     the number of bytes in the value.

   * *Note `LONGBLOB': blob.

     A *Note `BLOB': blob. column with a maximum length of
     4,294,967,295 or 4GB (2^32 - 1) bytes. The effective maximum
     length of *Note `LONGBLOB': blob. columns depends on the
     configured maximum packet size in the client/server protocol and
     available memory. Each *Note `LONGBLOB': blob. value is stored
     using a 4-byte length prefix that indicates the number of bytes in
     the value.

   * *Note `LONGTEXT [CHARACTER SET CHARSET_NAME] [COLLATE
     COLLATION_NAME]': blob.

     A *Note `TEXT': blob. column with a maximum length of
     4,294,967,295 or 4GB (2^32 - 1) characters. The effective maximum
     length is less if the value contains multibyte characters. The
     effective maximum length of *Note `LONGTEXT': blob.  columns also
     depends on the configured maximum packet size in the client/server
     protocol and available memory. Each *Note `LONGTEXT': blob.  value
     is stored using a 4-byte length prefix that indicates the number
     of bytes in the value.

   * *Note `ENUM('VALUE1','VALUE2',...) [CHARACTER SET CHARSET_NAME]
     [COLLATE COLLATION_NAME]': enum.

     An enumeration. A string object that can have only one value,
     chosen from the list of values `'VALUE1'', `'VALUE2'', `...',
     `NULL' or the special `''' error value.  *Note `ENUM': enum.
     values are represented internally as integers.

     An *Note `ENUM': enum. column can have a maximum of 65,535
     distinct elements. (The practical limit is less than 3000.) A
     table can have no more than 255 unique element list definitions
     among its *Note `ENUM': enum. and *Note `SET': set. columns
     considered as a group. For more information on these limits, see
     *Note limits-frm-file::.

   * *Note `SET('VALUE1','VALUE2',...) [CHARACTER SET CHARSET_NAME]
     [COLLATE COLLATION_NAME]': set.

     A set. A string object that can have zero or more values, each of
     which must be chosen from the list of values `'VALUE1'',
     `'VALUE2'', `...' *Note `SET': set.  values are represented
     internally as integers.

     A *Note `SET': set. column can have a maximum of 64 distinct
     members. A table can have no more than 255 unique element list
     definitions among its *Note `ENUM': enum. and *Note `SET': set.
     columns considered as a group. For more information on this limit,
     see *Note limits-frm-file::.


File: manual.info,  Node: numeric-types,  Next: date-and-time-types,  Prev: data-type-overview,  Up: data-types

11.2 Numeric Types
==================

* Menu:

* integer-types::                Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT
* fixed-point-types::            Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC
* floating-point-types::         Floating-Point Types (Approximate Value) - FLOAT, DOUBLE
* bit-type::                     Bit-Value Type - BIT
* numeric-type-attributes::      Numeric Type Attributes
* out-of-range-and-overflow::    Out-of-Range and Overflow Handling

MySQL supports all standard SQL numeric data types. These types include
the exact numeric data types (*Note `INTEGER': integer-types, *Note
`SMALLINT': integer-types, *Note `DECIMAL': fixed-point-types, and
*Note `NUMERIC': fixed-point-types.), as well as the approximate
numeric data types (*Note `FLOAT': floating-point-types, *Note `REAL':
floating-point-types, and *Note `DOUBLE PRECISION':
floating-point-types.). The keyword *Note `INT': integer-types. is a
synonym for *Note `INTEGER': integer-types, and the keywords *Note
`DEC': fixed-point-types. and *Note `FIXED': fixed-point-types. are
synonyms for *Note `DECIMAL': fixed-point-types. MySQL treats *Note
`DOUBLE': floating-point-types. as a synonym for *Note `DOUBLE
PRECISION': floating-point-types. (a nonstandard extension). MySQL also
treats *Note `REAL': floating-point-types.  as a synonym for *Note
`DOUBLE PRECISION': floating-point-types.  (a nonstandard variation),
unless the `REAL_AS_FLOAT' SQL mode is enabled.

The *Note `BIT': bit-type. data type stores bit-field values and is
supported for *Note `MyISAM': myisam-storage-engine, *Note `MEMORY':
memory-storage-engine, *Note `InnoDB': innodb-storage-engine, and *Note
`NDBCLUSTER': mysql-cluster. tables.

For information about how MySQL handles assignment of out-of-range
values to columns and overflow during expression evaluation, see *Note
out-of-range-and-overflow::.

For information about numeric type storage requirements, see *Note
storage-requirements::.

The data type used for the result of a calculation on numeric operands
depends on the types of the operands and the operations performed on
them. For more information, see *Note arithmetic-functions::.


File: manual.info,  Node: integer-types,  Next: fixed-point-types,  Prev: numeric-types,  Up: numeric-types

11.2.1 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT
---------------------------------------------------------------------------------------

MySQL supports the SQL standard integer types `INTEGER' (or `INT') and
`SMALLINT'. As an extension to the standard, MySQL also supports the
integer types `TINYINT', `MEDIUMINT', and `BIGINT'. The following table
shows the required storage and range for each integer type.

This table shows required storage and range for integer types supported
by MySQL.

Type        Storage     Minimum Value             Maximum Value
            (Bytes)     (Signed/Unsigned)         (Signed/Unsigned)
`TINYINT'   1           `-128'                    `127'
                        `0'                       `255'
`SMALLINT'  2           `-32768'                  `32767'
                        `0'                       `65535'
`MEDIUMINT' 3           `-8388608'                `8388607'
                        `0'                       `16777215'
`INT'       4           `-2147483648'             `2147483647'
                        `0'                       `4294967295'
`BIGINT'    8           `-9223372036854775808'    `9223372036854775807'
                        `0'                       `18446744073709551615'


File: manual.info,  Node: fixed-point-types,  Next: floating-point-types,  Prev: integer-types,  Up: numeric-types

11.2.2 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC
---------------------------------------------------------

The `DECIMAL' and `NUMERIC' types store exact numeric data values.
These types are used when it is important to preserve exact precision,
for example with monetary data. In MySQL, `NUMERIC' is implemented as
`DECIMAL', so the following remarks about `DECIMAL' apply equally to
`NUMERIC'.

MySQL 5.1 stores `DECIMAL' values in binary format. See *Note
precision-math::.

In a `DECIMAL' column declaration, the precision and scale can be (and
usually is) specified; for example:


     salary DECIMAL(5,2)

In this example, `5' is the precision and `2' is the scale. The
precision represents the number of significant digits that are stored
for values, and the scale represents the number of digits that can be
stored following the decimal point.

Standard SQL requires that `DECIMAL(5,2)' be able to store any value
with five digits and two decimals, so values that can be stored in the
`salary' column range from `-999.99' to `999.99'.

In standard SQL, the syntax `DECIMAL(M)' is equivalent to
`DECIMAL(M,0)'.  Similarly, the syntax `DECIMAL' is equivalent to
`DECIMAL(M,0)', where the implementation is permitted to decide the
value of M. MySQL supports both of these variant forms of `DECIMAL'
syntax. The default value of M is 10.

If the scale is 0, `DECIMAL' values contain no decimal point or
fractional part.

The maximum number of digits for `DECIMAL' is 65, but the actual range
for a given `DECIMAL' column can be constrained by the precision or
scale for a given column. When such a column is assigned a value with
more digits following the decimal point than are permitted by the
specified scale, the value is converted to that scale. (The precise
behavior is operating system-specific, but generally the effect is
truncation to the permissible number of digits.)


File: manual.info,  Node: floating-point-types,  Next: bit-type,  Prev: fixed-point-types,  Up: numeric-types

11.2.3 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE
---------------------------------------------------------------

The `FLOAT' and `DOUBLE' types represent approximate numeric data
values. MySQL uses four bytes for single-precision values and eight
bytes for double-precision values.

For `FLOAT', the SQL standard permits an optional specification of the
precision (but not the range of the exponent) in bits following the
keyword `FLOAT' in parentheses. MySQL also supports this optional
precision specification, but the precision value is used only to
determine storage size. A precision from 0 to 23 results in a 4-byte
single-precision `FLOAT' column. A precision from 24 to 53 results in
an 8-byte double-precision `DOUBLE' column.

MySQL permits a nonstandard syntax: `FLOAT(M,D)' or `REAL(M,D)' or
`DOUBLE PRECISION(M,D)'.  Here, ``(M,D)'' means than values can be
stored with up to M digits in total, of which D digits may be after the
decimal point. For example, a column defined as `FLOAT(7,4)' will look
like `-999.9999' when displayed. MySQL performs rounding when storing
values, so if you insert `999.00009' into a `FLOAT(7,4)' column, the
approximate result is `999.0001'.

Because floating-point values are approximate and not stored as exact
values, attempts to treat them as exact in comparisons may lead to
problems. They are also subject to platform or implementation
dependencies. For more information, see *Note problems-with-float::

For maximum portability, code requiring storage of approximate numeric
data values should use `FLOAT' or `DOUBLE PRECISION' with no
specification of precision or number of digits.


File: manual.info,  Node: bit-type,  Next: numeric-type-attributes,  Prev: floating-point-types,  Up: numeric-types

11.2.4 Bit-Value Type - BIT
---------------------------

The `BIT' data type is used to store bit-field values. A type of
`BIT(M)' enables storage of M-bit values.  M can range from 1 to 64.

To specify bit values, `b'VALUE'' notation can be used. VALUE is a
binary value written using zeros and ones. For example, `b'111'' and
`b'10000000'' represent 7 and 128, respectively. See *Note
bit-field-literals::.

If you assign a value to a `BIT(M)' column that is less than M bits
long, the value is padded on the left with zeros. For example,
assigning a value of `b'101'' to a `BIT(6)' column is, in effect, the
same as assigning `b'000101''.


File: manual.info,  Node: numeric-type-attributes,  Next: out-of-range-and-overflow,  Prev: bit-type,  Up: numeric-types

11.2.5 Numeric Type Attributes
------------------------------

MySQL supports an extension for optionally specifying the display width
of integer data types in parentheses following the base keyword for the
type. For example, *Note `INT(4)': integer-types. specifies an *Note
`INT': integer-types. with a display width of four digits. This
optional display width may be used by applications to display integer
values having a width less than the width specified for the column by
left-padding them with spaces. (That is, this width is present in the
metadata returned with result sets. Whether it is used or not is up to
the application.)

The display width does _not_ constrain the range of values that can be
stored in the column. Nor does it prevent values wider than the column
display width from being displayed correctly. For example, a column
specified as *Note `SMALLINT(3)': integer-types. has the usual *Note
`SMALLINT': integer-types. range of `-32768' to `32767', and values
outside the range permitted by three digits are displayed in full using
more than three digits.

When used in conjunction with the optional (nonstandard) attribute
`ZEROFILL', the default padding of spaces is replaced with zeros. For
example, for a column declared as *Note `INT(4) ZEROFILL':
integer-types, a value of `5' is retrieved as `0005'.

*Note*:

The `ZEROFILL' attribute is ignored when a column is involved in
expressions or *Note `UNION': union. queries.

If you store values larger than the display width in an integer column
that has the `ZEROFILL' attribute, you may experience problems when
MySQL generates temporary tables for some complicated joins. In these
cases, MySQL assumes that the data values fit within the column display
width.

All integer types can have an optional (nonstandard) attribute
`UNSIGNED'. Unsigned type can be used to permit only nonnegative
numbers in a column or when you need a larger upper numeric range for
the column. For example, if an *Note `INT': integer-types. column is
`UNSIGNED', the size of the column's range is the same but its
endpoints shift from `-2147483648' and `2147483647' up to `0' and
`4294967295'.

Floating-point and fixed-point types also can be `UNSIGNED'. As with
integer types, this attribute prevents negative values from being
stored in the column. Unlike the integer types, the upper range of
column values remains the same.

If you specify `ZEROFILL' for a numeric column, MySQL automatically
adds the `UNSIGNED' attribute to the column.

Integer or floating-point data types can have the additional attribute
`AUTO_INCREMENT'. When you insert a value of `NULL' (recommended) or
`0' into an indexed `AUTO_INCREMENT' column, the column is set to the
next sequence value. Typically this is `VALUE+1', where VALUE is the
largest value for the column currently in the table. `AUTO_INCREMENT'
sequences begin with `1'. (Inserting `NULL' to generate
`AUTO_INCREMENT' values requires that the column be declared `NOT
NULL'. If the column is declared `NULL', inserting `NULL' stores a
`NULL'.)

As of MySQL 5.1.67, negative values for `AUTO_INCREMENT' columns are
not supported.


File: manual.info,  Node: out-of-range-and-overflow,  Prev: numeric-type-attributes,  Up: numeric-types

11.2.6 Out-of-Range and Overflow Handling
-----------------------------------------

When MySQL stores a value in a numeric column that is outside the
permissible range of the column data type, the result depends on the
SQL mode in effect at the time:

   * If strict SQL mode is enabled, MySQL rejects the out-of-range
     value with an error, and the insert fails, in accordance with the
     SQL standard.

   * If no restrictive modes are enabled, MySQL clips the value to the
     appropriate endpoint of the range and stores the resulting value
     instead.

     When an out-of-range value is assigned to an integer column, MySQL
     stores the value representing the corresponding endpoint of the
     column data type range. If you store 256 into a *Note `TINYINT':
     integer-types. or `TINYINT UNSIGNED' column, MySQL stores 127 or
     255, respectively.

     When a floating-point or fixed-point column is assigned a value
     that exceeds the range implied by the specified (or default)
     precision and scale, MySQL stores the value representing the
     corresponding endpoint of that range.

Column-assignment conversions that occur due to clipping when MySQL is
not operating in strict mode are reported as warnings for *Note `ALTER
TABLE': alter-table, *Note `LOAD DATA INFILE': load-data, *Note
`UPDATE': update, and multiple-row *Note `INSERT': insert. statements.
In strict mode, these statements fail, and some or all the values will
not be inserted or changed, depending on whether the table is a
transactional table and other factors. For details, see *Note
sql-mode::.

In MySQL 5.1, overflow handling during numeric expression evaluation
depends on the types of the operands:

   * Integer overflow results in silent wraparound.

   * `DECIMAL' overflow results in a truncated result and a warning.

   * Floating-point overflow produces a `NULL' result. Before MySQL
     5.1.24, overflow for some operations results in `+INF', `-INF', or
     `NaN'.

For example, the largest signed *Note `BIGINT': integer-types. value is
9223372036854775807, so the following expression wraps around to the
minimum *Note `BIGINT': integer-types. value:


     mysql> SELECT 9223372036854775807 + 1;
     +-------------------------+
     | 9223372036854775807 + 1 |
     +-------------------------+
     |    -9223372036854775808 |
     +-------------------------+

To enable the operation to succeed in this case, convert the value to
unsigned;


     mysql> SELECT CAST(9223372036854775807 AS UNSIGNED) + 1;
     +-------------------------------------------+
     | CAST(9223372036854775807 AS UNSIGNED) + 1 |
     +-------------------------------------------+
     |                       9223372036854775808 |
     +-------------------------------------------+

Whether overflow occurs depends on the range of the operands, so
another way to handle the preceding expression is to use exact-value
arithmetic because *Note `DECIMAL': fixed-point-types. values have a
larger range than integers:


     mysql> SELECT 9223372036854775807.0 + 1;
     +---------------------------+
     | 9223372036854775807.0 + 1 |
     +---------------------------+
     |     9223372036854775808.0 |
     +---------------------------+

Subtraction between integer values, where one is of type `UNSIGNED',
produces an unsigned result by default. If the result would otherwise
have been negative, it becomes the maximum integer value. If the
`NO_UNSIGNED_SUBTRACTION' SQL mode is enabled, the result is negative.


     mysql> SET sql_mode = '';
     mysql> SELECT CAST(0 AS UNSIGNED) - 1;
     +-------------------------+
     | CAST(0 AS UNSIGNED) - 1 |
     +-------------------------+
     |    18446744073709551615 |
     +-------------------------+

     mysql> SET sql_mode = 'NO_UNSIGNED_SUBTRACTION';
     mysql> SELECT CAST(0 AS UNSIGNED) - 1;
     +-------------------------+
     | CAST(0 AS UNSIGNED) - 1 |
     +-------------------------+
     |                      -1 |
     +-------------------------+

If the result of such an operation is used to update an `UNSIGNED'
integer column, the result is clipped to the maximum value for the
column type, or clipped to 0 if `NO_UNSIGNED_SUBTRACTION' is enabled.
If strict SQL mode is enabled, an error occurs and the column remains
unchanged.


File: manual.info,  Node: date-and-time-types,  Next: string-types,  Prev: numeric-types,  Up: data-types

11.3 Date and Time Types
========================

* Menu:

* datetime::                     The DATE, DATETIME, and TIMESTAMP Types
* time::                         The TIME Type
* year::                         The YEAR Type
* migrating-to-year4::           YEAR(2) Limitations and Migrating to YEAR(4)
* timestamp-initialization::     Automatic Initialization and Updating for TIMESTAMP
* fractional-seconds::           Fractional Seconds in Time Values
* date-and-time-type-conversion::  Conversion Between Date and Time Types
* two-digit-years::              Two-Digit Years in Dates

The date and time types for representing temporal values are *Note
`DATE': datetime, *Note `TIME': time, *Note `DATETIME': datetime, *Note
`TIMESTAMP': datetime, and *Note `YEAR': year. Each temporal type has a
range of valid values, as well as a `zero' value that may be used when
you specify an invalid value that MySQL cannot represent. The *Note
`TIMESTAMP': datetime. type has special automatic updating behavior,
described later. For temporal type storage requirements, see *Note
storage-requirements::.

Keep in mind these general considerations when working with date and
time types:

   * MySQL retrieves values for a given date or time type in a standard
     output format, but it attempts to interpret a variety of formats
     for input values that you supply (for example, when you specify a
     value to be assigned to or compared to a date or time type). For a
     description of the permitted formats for date and time types, see
     *Note date-and-time-literals::. It is expected that you supply
     valid values. Unpredictable results may occur if you use values in
     other formats.

   * Although MySQL tries to interpret values in several formats, date
     parts must always be given in year-month-day order (for example,
     `'98-09-04''), rather than in the month-day-year or day-month-year
     orders commonly used elsewhere (for example, `'09-04-98'',
     `'04-09-98'').

   * Dates containing two-digit year values are ambiguous because the
     century is unknown. MySQL interprets two-digit year values using
     these rules:

        * Year values in the range `70-99' are converted to `1970-1999'.

        * Year values in the range `00-69' are converted to `2000-2069'.

     See also *Note two-digit-years::.

   * Conversion of values from one temporal type to another occurs
     according to the rules in *Note date-and-time-type-conversion::.

   * MySQL automatically converts a date or time value to a number if
     the value is used in a numeric context and vice versa.

   * By default, when MySQL encounters a value for a date or time type
     that is out of range or otherwise invalid for the type, it
     converts the value to the `zero' value for that type. The
     exception is that out-of-range *Note `TIME': time. values are
     clipped to the appropriate endpoint of the *Note `TIME': time.
     range.

   * By setting the SQL mode to the appropriate value, you can specify
     more exactly what kind of dates you want MySQL to support. (See
     *Note sql-mode::.) You can get MySQL to accept certain dates, such
     as `'2009-11-31'', by enabling the `ALLOW_INVALID_DATES' SQL mode.
     This is useful when you want to store a `possibly wrong' value
     which the user has specified (for example, in a web form) in the
     database for future processing. Under this mode, MySQL verifies
     only that the month is in the range from 1 to 12 and that the day
     is in the range from 1 to 31.

   * MySQL permits you to store dates where the day or month and day
     are zero in a *Note `DATE': datetime. or *Note `DATETIME':
     datetime. column. This is useful for applications that need to
     store birthdates for which you may not know the exact date. In
     this case, you simply store the date as `'2009-00-00'' or
     `'2009-01-00''. If you store dates such as these, you should not
     expect to get correct results for functions such as `DATE_SUB()' or
     `DATE_ADD()' that require complete dates. To disallow zero month
     or day parts in dates, enable the `NO_ZERO_IN_DATE' SQL mode.

   * MySQL permits you to store a `zero' value of `'0000-00-00'' as a
     `dummy date.' This is in some cases more convenient than using
     `NULL' values, and uses less data and index space. To disallow
     `'0000-00-00'', enable the `NO_ZERO_DATE' SQL mode.

   * `Zero' date or time values used through Connector/ODBC are
     converted automatically to `NULL' because ODBC cannot handle such
     values.

The following table shows the format of the `zero' value for each type.
The `zero' values are special, but you can store or refer to them
explicitly using the values shown in the table. You can also do this
using the values `'0'' or `0', which are easier to write. For temporal
types that include a date part (*Note `DATE': datetime, *Note
`DATETIME': datetime, and *Note `TIMESTAMP': datetime.), use of these
values produces warnings if the `NO_ZERO_DATE' SQL mode is enabled.

This table shows the format of the `zero' value for temporal data types.

Data Type              `Zero' Value
*Note `DATE':          `'0000-00-00''
datetime.              
*Note `TIME': time.    `'00:00:00''
*Note `DATETIME':      `'0000-00-00 00:00:00''
datetime.              
*Note `TIMESTAMP':     `'0000-00-00 00:00:00''
datetime.              
*Note `YEAR': year.    `0000'


File: manual.info,  Node: datetime,  Next: time,  Prev: date-and-time-types,  Up: date-and-time-types

11.3.1 The DATE, DATETIME, and TIMESTAMP Types
----------------------------------------------

The `DATE', `DATETIME', and `TIMESTAMP' types are related. This section
describes their characteristics, how they are similar, and how they
differ. MySQL recognizes `DATE', `DATETIME', and `TIMESTAMP' values in
several formats, described in *Note date-and-time-literals::. For the
`DATE' and `DATETIME' range descriptions, `supported' means that
although earlier values might work, there is no guarantee.

The `DATE' type is used for values with a date part but no time part.
MySQL retrieves and displays `DATE' values in `'YYYY-MM-DD'' format.
The supported range is `'1000-01-01'' to `'9999-12-31''.

The `DATETIME' type is used for values that contain both date and time
parts. MySQL retrieves and displays `DATETIME' values in `'YYYY-MM-DD
HH:MM:SS'' format. The supported range is `'1000-01-01 00:00:00'' to
`'9999-12-31 23:59:59''.

The `TIMESTAMP' data type is used for values that contain both date and
time parts.  `TIMESTAMP' has a range of `'1970-01-01 00:00:01'' UTC to
`'2038-01-19 03:14:07'' UTC.

MySQL converts `TIMESTAMP' values from the current time zone to UTC for
storage, and back from UTC to the current time zone for retrieval.
(This does not occur for other types such as `DATETIME'.) By default,
the current time zone for each connection is the server's time. The
time zone can be set on a per-connection basis. As long as the time
zone setting remains constant, you get back the same value you store.
If you store a `TIMESTAMP' value, and then change the time zone and
retrieve the value, the retrieved value is different from the value you
stored. This occurs because the same time zone was not used for
conversion in both directions. The current time zone is available as
the value of the `time_zone' system variable. For more information, see
*Note time-zone-support::.

The `TIMESTAMP' data type offers automatic initialization and updating
to the current date and time. For more information, see *Note
timestamp-initialization::.

A `DATETIME' or `TIMESTAMP' value can include a trailing fractional
seconds part in up to microseconds (6 digits) precision. Although this
fractional part is recognized, it is discarded from values stored into
`DATETIME' or `TIMESTAMP' columns. For information about fractional
seconds support in MySQL, see *Note fractional-seconds::.

Invalid `DATE', `DATETIME', or `TIMESTAMP' values are converted to the
`zero' value of the appropriate type (`'0000-00-00'' or `'0000-00-00
00:00:00'').

Be aware of certain properties of date value interpretation in MySQL:

   * MySQL permits a `relaxed' format for values specified as strings,
     in which any punctuation character may be used as the delimiter
     between date parts or time parts.  In some cases, this syntax can
     be deceiving. For example, a value such as `'10:11:12'' might look
     like a time value because of the ``:'' delimiter, but is
     interpreted as the year `'2010-11-12'' if used in a date context.
     The value `'10:45:15'' is converted to `'0000-00-00'' because
     `'45'' is not a valid month.

   * The server requires that month and day values be valid, and not
     merely in the range 1 to 12 and 1 to 31, respectively.  With
     strict mode disabled, invalid dates such as `'2004-04-31'' are
     converted to `'0000-00-00'' and a warning is generated.  With
     strict mode enabled, invalid dates generate an error.  To permit
     such dates, enable `ALLOW_INVALID_DATES'. See *Note sql-mode::,
     for more information.

   * MySQL does not accept `TIMESTAMP' values that include a zero in
     the day or month column or values that are not a valid date. The
     sole exception to this rule is the special `zero' value
     `'0000-00-00 00:00:00''.

   * In MySQL 5.1, `CAST()' treats a `TIMESTAMP' value as a string when
     not selecting from a table. (This is true even if you specify
     `FROM DUAL'.) See *Note cast-functions::.

   * Dates containing two-digit year values are ambiguous because the
     century is unknown. MySQL interprets two-digit year values using
     these rules:

        * Year values in the range `00-69' are converted to `2000-2069'.

        * Year values in the range `70-99' are converted to `1970-1999'.

     See also *Note two-digit-years::.

*Note*:

The MySQL server can be run with the `MAXDB' SQL mode enabled. In this
case, `TIMESTAMP' is identical with `DATETIME'. If this mode is enabled
at the time that a table is created, `TIMESTAMP' columns are created as
`DATETIME' columns. As a result, such columns use `DATETIME' display
format, have the same range of values, and there is no automatic
initialization or updating to the current date and time. See *Note
sql-mode::.


File: manual.info,  Node: time,  Next: year,  Prev: datetime,  Up: date-and-time-types

11.3.2 The TIME Type
--------------------

MySQL retrieves and displays `TIME' values in `'HH:MM:SS'' format (or
`'HHH:MM:SS'' format for large hours values).  `TIME' values may range
from `'-838:59:59'' to `'838:59:59''. The hours part may be so large
because the `TIME' type can be used not only to represent a time of day
(which must be less than 24 hours), but also elapsed time or a time
interval between two events (which may be much greater than 24 hours,
or even negative).

MySQL recognizes `TIME' values in several formats, described in *Note
date-and-time-literals::.  Some of these formats can include a trailing
fractional seconds part in up to microseconds (6 digits) precision.
Although this fractional part is recognized, it is discarded from values
stored into `TIME' columns. For information about fractional seconds
support in MySQL, see *Note fractional-seconds::.

Be careful about assigning abbreviated values to a `TIME' column. MySQL
interprets abbreviated `TIME' values with colons as time of the day.
That is, `'11:12'' means `'11:12:00'', not `'00:11:12''. MySQL
interprets abbreviated values without colons using the assumption that
the two rightmost digits represent seconds (that is, as elapsed time
rather than as time of day). For example, you might think of `'1112''
and `1112' as meaning `'11:12:00'' (12 minutes after 11 o'clock), but
MySQL interprets them as `'00:11:12'' (11 minutes, 12 seconds).
Similarly, `'12'' and `12' are interpreted as `'00:00:12''.

By default, values that lie outside the `TIME' range but are otherwise
valid are clipped to the closest endpoint of the range. For example,
`'-850:00:00'' and `'850:00:00'' are converted to `'-838:59:59'' and
`'838:59:59''. Invalid `TIME' values are converted to `'00:00:00''.
Note that because `'00:00:00'' is itself a valid `TIME' value, there is
no way to tell, from a value of `'00:00:00'' stored in a table, whether
the original value was specified as `'00:00:00'' or whether it was
invalid.

For more restrictive treatment of invalid `TIME' values, enable strict
SQL mode to cause errors to occur. See *Note sql-mode::.


File: manual.info,  Node: year,  Next: migrating-to-year4,  Prev: time,  Up: date-and-time-types

11.3.3 The YEAR Type
--------------------

The `YEAR' type is a 1-byte type used to represent year values. It can
be declared as `YEAR(4)' or `YEAR(2)' to specify a display width of
four or two characters. The default is four characters if no width is
given.

*Note*:

The `YEAR(2)' data type has certain issues that you should consider
before choosing to use it. As of MySQL 5.1.65, `YEAR(2)' is deprecated.
For more information, see *Note migrating-to-year4::.

`YEAR(4)' and `YEAR(2)' differ in display format, but have the same
range of values. For 4-digit format, MySQL displays `YEAR' values in
`YYYY' format, with a range of `1901' to `2155', or `0000'. For 2-digit
format, MySQL displays only the last two (least significant) digits;
for example, `70' (1970 or 2070) or `69' (2069).

You can specify input `YEAR' values in a variety of formats:

   * As a 4-digit number in the range `1901' to `2155'.

   * As a 4-digit string in the range `'1901'' to `'2155''.

   * As a 1- or 2-digit number in the range `1' to `99'. MySQL converts
     values in the ranges `1' to `69' and `70' to `99' to `YEAR' values
     in the ranges `2001' to `2069' and `1970' to `1999'.

   * As a 1- or 2-digit string in the range `'0'' to `'99''. MySQL
     converts values in the ranges `'0'' to `'69'' and `'70'' to `'99''
     to `YEAR' values in the ranges `2000' to `2069' and `1970' to
     `1999'.

   * Inserting a numeric `0' has a different effect for `YEAR(2)' and
     `YEAR(4)'. For `YEAR(2)', the result has a display value of `00'
     and an internal value of `2000'. For `YEAR(4)', the result has a
     display value of `0000' and an internal value of `0000'. To
     specify zero for `YEAR(4)' and have it be interpreted as `2000',
     specify it as a string `'0'' or `'00''.

   * As the result of a function that returns a value that is
     acceptable in a `YEAR' context, such as `NOW()'.

MySQL converts invalid `YEAR' values to `0000'.

See also *Note two-digit-years::.


File: manual.info,  Node: migrating-to-year4,  Next: timestamp-initialization,  Prev: year,  Up: date-and-time-types

11.3.4 YEAR(2) Limitations and Migrating to YEAR(4)
---------------------------------------------------

This section describes problems that can occur when using *Note
`YEAR(2)': year. and provides information about converting existing
*Note `YEAR(2)': year.  columns to *Note `YEAR(4)': year.

Although the internal range of values for *Note `YEAR(4)': year. and
*Note `YEAR(2)': year. is the same (`1901' to `2155', and `0000'), the
display width for *Note `YEAR(2)': year. makes that type inherently
ambiguous because displayed values indicate only the last two digits of
the internal values and omit the century digits. The result can be a
loss of information under certain circumstances. For this reason,
consider avoiding *Note `YEAR(2)': year. throughout your applications
and using *Note `YEAR(4)': year.  wherever you need a *Note `YEAR':
year. data type. Note that conversion will become necessary at some
point because support for *Note `YEAR': year. data types with display
values other than 4, most notably *Note `YEAR(2)': year, is reduced as
of MySQL 5.6.6 and will be removed entirely in a future release.

*YEAR(2) Limitations*

Issues with the *Note `YEAR(2)': year. data type include ambiguity of
displayed values, and possible loss of information when values are
dumped and reloaded or converted to strings.

   * Displayed *Note `YEAR(2)': year. values can be ambiguous. It is
     possible for up to three *Note `YEAR(2)': year. values that have
     different internal values to have the same displayed value, as the
     following example demonstrates:


          mysql> CREATE TABLE t (y2 YEAR(2), y4 YEAR(4));
          Query OK, 0 rows affected (0.01 sec)

          mysql> INSERT INTO t (y2) VALUES(1912),(2012),(2112);
          Query OK, 3 rows affected (0.00 sec)
          Records: 3  Duplicates: 0  Warnings: 0

          mysql> UPDATE t SET y4 = y2;
          Query OK, 3 rows affected (0.00 sec)
          Rows matched: 3  Changed: 3  Warnings: 0

          mysql> SELECT * FROM t;
          +------+------+
          | y2   | y4   |
          +------+------+
          |   12 | 1912 |
          |   12 | 2012 |
          |   12 | 2112 |
          +------+------+
          3 rows in set (0.00 sec)

   * If you use *Note `mysqldump': mysqldump. to dump the table created
     in the preceding item, the dump file represents all `y2' values
     using the same 2-digit representation (`12'). If you reload the
     table from the dump file, all resulting rows have internal value
     `2012' and display value `12', thus losing the distinctions among
     them.

   * Conversion of a *Note `YEAR(2)': year. or *Note `YEAR(4)': year.
     data value to string form uses the display width of the *Note
     `YEAR': year. type. Suppose that *Note `YEAR(2)': year. and *Note
     `YEAR(4)': year. columns both contain the value `1970'. Assigning
     each column to a string results in a value of `'70'' or `'1970'',
     respectively. That is, loss of information occurs for conversion
     from *Note `YEAR(2)': year. to string.

   * Values outside the range from `1970' to `2069' are stored
     incorrectly when inserted into a *Note `YEAR(2)': year. column in a
     *Note `CSV': csv-storage-engine. table. For example, inserting
     `2111' results in a display value of `11' but an internal value of
     `2011'.

To avoid these problems, use *Note `YEAR(4)': year. rather than *Note
`YEAR(2)': year. Suggestions regarding migration strategies appear
later in this section.

*Migrating from YEAR(2) to YEAR(4)*

To convert *Note `YEAR(2)': year. columns to *Note `YEAR(4)': year, use
*Note `ALTER TABLE': alter-table. Suppose that a table `t1' has this
definition:


     CREATE TABLE t1 (ycol YEAR(2) NOT NULL DEFAULT '70');

Modify the column using `ALTER TABLE' as follows. Remember to include
any column attributes such as `NOT NULL' or `DEFAULT':


     ALTER TABLE t1 MODIFY ycol YEAR(4) NOT NULL DEFAULT '1970';

The *Note `ALTER TABLE': alter-table. statement converts the table
without changing *Note `YEAR(2)': year. values. If the server is a
replication master, the *Note `ALTER TABLE': alter-table. statement
replicates to slaves and makes the corresponding table change on each
one.

One migration method should be avoided: Do not dump your data with
*Note `mysqldump': mysqldump. and reload the dump file after upgrading.
This has the potential to change *Note `YEAR(2)': year. values, as
described previously.

A migration from *Note `YEAR(2)': year. to *Note `YEAR(4)': year.
should also involve examining application code for the possibility of
changed behavior under conditions such as these:

   * Code that expects selecting a *Note `YEAR': year. column to produce
     exactly two digits.

   * Code that does not account for different handling for inserts of
     numeric `0': Inserting `0' into *Note `YEAR(2)': year. or *Note
     `YEAR(4)': year. results in an internal value of `2000' or `0000',
     respectively.


File: manual.info,  Node: timestamp-initialization,  Next: fractional-seconds,  Prev: migrating-to-year4,  Up: date-and-time-types

11.3.5 Automatic Initialization and Updating for TIMESTAMP
----------------------------------------------------------

*Note*:

In older versions of MySQL (prior to 4.1), the properties of the *Note
`TIMESTAMP': datetime. data type differed significantly in several ways
from what is described in this section (see the `MySQL 3.23, 4.0, 4.1
Reference Manual' for details); these include syntax extensions which
are deprecated in MySQL 5.1, and no longer supported in MySQL 5.5. This
has implications for performing a dump and restore or replicating
between MySQL Server versions. If you are using columns that are defined
using the old *Note `TIMESTAMP(N)': datetime.  syntax, see *Note
upgrading-from-previous-series::, prior to upgrading to MySQL 5.1 or
later.

The *Note `TIMESTAMP': datetime. data type offers automatic
initialization and updating to the current date and time (that is, the
current timestamp). You can choose whether to use these properties and
which column should have them:

   * One *Note `TIMESTAMP': datetime. column in a table can have the
     current timestamp as the default value for initializing the
     column, as the auto-update value, or both. It is not possible to
     have the current timestamp be the default value for one column and
     the auto-update value for another column.

   * If the column is auto-initialized, it is set to the current
     timestamp for inserted rows that specify no value for the column.

   * If the column is auto-updated, it is automatically updated to the
     current timestamp when the value of any other column in the row is
     changed from its current value. The column remains unchanged if
     all other columns are set to their current values. To prevent the
     column from updating when other columns change, explicitly set it
     to its current value. To update the column even when other columns
     do not change, explicitly set it to the value it should have (for
     example, set it to `CURRENT_TIMESTAMP').

In addition, you can initialize or update any *Note `TIMESTAMP':
datetime. column to the current date and time by assigning it a `NULL'
value, unless it has been defined with the `NULL' attribute to permit
`NULL' values.

To specify automatic properties, use the `DEFAULT CURRENT_TIMESTAMP'
and `ON UPDATE CURRENT_TIMESTAMP' clauses. The order of the clauses
does not matter. If both are present in a column definition, either can
occur first. Any of the synonyms for `CURRENT_TIMESTAMP' have the same
meaning as `CURRENT_TIMESTAMP'.  These are `CURRENT_TIMESTAMP()',
`NOW()', `LOCALTIME', `LOCALTIME()', `LOCALTIMESTAMP', and
`LOCALTIMESTAMP()'.

Use of `DEFAULT CURRENT_TIMESTAMP' and `ON UPDATE CURRENT_TIMESTAMP' is
specific to *Note `TIMESTAMP': datetime. The `DEFAULT' clause also can
be used to specify a constant (nonautomatic) default value; for example,
`DEFAULT 0' or `DEFAULT '2000-01-01 00:00:00''.

*Note*:

The following examples that use `DEFAULT 0' do not work if the
`NO_ZERO_DATE' SQL mode is enabled because that mode causes `zero' date
values (specified, for example, as `0' `'0000-00-00 00:00:00'') to be
rejected. Be aware that the `TRADITIONAL' SQL mode includes
`NO_ZERO_DATE'.

The following rules describe the possibilities for defining the first
*Note `TIMESTAMP': datetime. column in a table with the current
timestamp for both the default and auto-update values, for one but not
the other, or for neither:

   * With both `DEFAULT CURRENT_TIMESTAMP' and `ON UPDATE
     CURRENT_TIMESTAMP', the column has the current timestamp for its
     default value and is automatically updated to the current
     timestamp.


          CREATE TABLE t1 (
            ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
          );

   * With neither `DEFAULT CURRENT_TIMESTAMP' nor `ON UPDATE
     CURRENT_TIMESTAMP', it is the same as specifying both `DEFAULT
     CURRENT_TIMESTAMP' and `ON UPDATE CURRENT_TIMESTAMP'.


          CREATE TABLE t1 (
            ts TIMESTAMP
          );

   * With a `DEFAULT' clause but no `ON UPDATE CURRENT_TIMESTAMP'
     clause, the column has the given default value and is not
     automatically updated to the current timestamp.

     The default depends on whether the `DEFAULT' clause specifies
     `CURRENT_TIMESTAMP' or a constant value.  With
     `CURRENT_TIMESTAMP', the default is the current timestamp.


          CREATE TABLE t1 (
            ts TIMESTAMP DEFAULT CURRENT_TIMESTAMP
          );

     With a constant, the default is the given value. In this case, the
     column has no automatic properties at all.


          CREATE TABLE t1 (
            ts TIMESTAMP DEFAULT 0
          );

   * With an `ON UPDATE CURRENT_TIMESTAMP' clause and a constant
     `DEFAULT' clause, the column is automatically updated to the
     current timestamp and has the given constant default value.


          CREATE TABLE t1 (
            ts TIMESTAMP DEFAULT 0 ON UPDATE CURRENT_TIMESTAMP
          );

   * With an `ON UPDATE CURRENT_TIMESTAMP' clause but no `DEFAULT'
     clause, the column is automatically updated to the current
     timestamp. The default is 0 unless the column is defined with the
     `NULL' attribute, in which case the default is `NULL'.


          CREATE TABLE t1 (
            ts TIMESTAMP ON UPDATE CURRENT_TIMESTAMP      -- default 0
          );
          CREATE TABLE t2 (
            ts TIMESTAMP NULL ON UPDATE CURRENT_TIMESTAMP -- default NULL
          );

It need not be the first *Note `TIMESTAMP': datetime. column in a table
that is automatically initialized or updated to the current timestamp.
However, to specify automatic initialization or updating for a different
*Note `TIMESTAMP': datetime. column, you must suppress the automatic
properties for the first one. Then, for the other *Note `TIMESTAMP':
datetime. column, the rules for the `DEFAULT' and `ON UPDATE' clauses
are the same as for the first *Note `TIMESTAMP': datetime. column,
except that if you omit both clauses, no automatic initialization or
updating occurs.

To suppress automatic properties for the first *Note `TIMESTAMP':
datetime. column, do either of the following:

   * Define the column with a `DEFAULT' clause that specifies a
     constant default value.

   * Specify the `NULL' attribute. This also causes the column to
     permit `NULL' values, which means that you cannot assign the
     current timestamp by setting the column to `NULL'. Assigning
     `NULL' sets the column to `NULL'.

Consider these table definitions:


     CREATE TABLE t1 (
       ts1 TIMESTAMP DEFAULT 0,
       ts2 TIMESTAMP DEFAULT CURRENT_TIMESTAMP
                     ON UPDATE CURRENT_TIMESTAMP);
     CREATE TABLE t2 (
       ts1 TIMESTAMP NULL,
       ts2 TIMESTAMP DEFAULT CURRENT_TIMESTAMP
                     ON UPDATE CURRENT_TIMESTAMP);
     CREATE TABLE t3 (
       ts1 TIMESTAMP NULL DEFAULT 0,
       ts2 TIMESTAMP DEFAULT CURRENT_TIMESTAMP
                     ON UPDATE CURRENT_TIMESTAMP);

The tables have these properties:

   * In each table definition, the first *Note `TIMESTAMP': datetime.
     column has no automatic initialization or updating.

   * The tables differ in how the `ts1' column handles `NULL' values.
     For `t1', `ts1' is `NOT NULL' and assigning it a value of `NULL'
     sets it to the current timestamp.  For `t2' and `t3', `ts1'
     permits `NULL' and assigning it a value of `NULL' sets it to
     `NULL'.

   * `t2' and `t3' differ in the default value for `ts1'. For `t2',
     `ts1' is defined to permit `NULL', so the default is also `NULL'
     in the absence of an explicit `DEFAULT' clause. For `t3', `ts1'
     permits `NULL' but has an explicit default of 0.

*TIMESTAMP Initialization and the NULL Attribute*

By default, *Note `TIMESTAMP': datetime. columns are `NOT NULL', cannot
contain `NULL' values, and assigning `NULL' assigns the current
timestamp. To permit a *Note `TIMESTAMP': datetime. column to contain
`NULL', explicitly declare it with the `NULL' attribute. In this case,
the default value also becomes `NULL' unless overridden with a
`DEFAULT' clause that specifies a different default value. `DEFAULT
NULL' can be used to explicitly specify `NULL' as the default value.
(For a *Note `TIMESTAMP': datetime.  column not declared with the
`NULL' attribute, `DEFAULT NULL' is invalid.) If a *Note `TIMESTAMP':
datetime. column permits `NULL' values, assigning `NULL' sets it to
`NULL', not to the current timestamp.

The following table contains several *Note `TIMESTAMP': datetime.
columns that permit `NULL' values:


     CREATE TABLE t
     (
       ts1 TIMESTAMP NULL DEFAULT NULL,
       ts2 TIMESTAMP NULL DEFAULT 0,
       ts3 TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP
     );

A *Note `TIMESTAMP': datetime. column that permits `NULL' values does
_not_ take on the current timestamp at insert time except under one of
the following conditions:

   * Its default value is defined as `CURRENT_TIMESTAMP' and no value
     is specified for the column

   * `CURRENT_TIMESTAMP' or any of its synonyms such as `NOW()' is
     explicitly inserted into the column

In other words, a *Note `TIMESTAMP': datetime.  column defined to
permit `NULL' values auto-initializes only if its definition includes
`DEFAULT CURRENT_TIMESTAMP':


     CREATE TABLE t (ts TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP);

If the *Note `TIMESTAMP': datetime. column permits `NULL' values but
its definition does not include `DEFAULT CURRENT_TIMESTAMP', you must
explicitly insert a value corresponding to the current date and time.
Suppose that tables `t1' and `t2' have these definitions:


     CREATE TABLE t1 (ts TIMESTAMP NULL DEFAULT '0000-00-00 00:00:00');
     CREATE TABLE t2 (ts TIMESTAMP NULL DEFAULT NULL);

To set the *Note `TIMESTAMP': datetime. column in either table to the
current timestamp at insert time, explicitly assign it that value. For
example:


     INSERT INTO t1 VALUES (NOW());
     INSERT INTO t2 VALUES (CURRENT_TIMESTAMP);


File: manual.info,  Node: fractional-seconds,  Next: date-and-time-type-conversion,  Prev: timestamp-initialization,  Up: date-and-time-types

11.3.6 Fractional Seconds in Time Values
----------------------------------------

A trailing fractional seconds part is permissible for temporal values
in contexts such as literal values, and in the arguments to or return
values from some temporal functions. Example:


     mysql> SELECT MICROSECOND('2010-12-10 14:12:09.019473');
     +-------------------------------------------+
     | MICROSECOND('2010-12-10 14:12:09.019473') |
     +-------------------------------------------+
     |                                     19473 |
     +-------------------------------------------+

However, when MySQL stores a value into a column of any temporal data
type, it discards any fractional part and does not store it.


File: manual.info,  Node: date-and-time-type-conversion,  Next: two-digit-years,  Prev: fractional-seconds,  Up: date-and-time-types

11.3.7 Conversion Between Date and Time Types
---------------------------------------------

To some extent, you can convert a value from one temporal type to
another. However, there may be some alteration of the value or loss of
information. In all cases, conversion between temporal types is subject
to the range of valid values for the resulting type. For example,
although *Note `DATE': datetime, *Note `DATETIME': datetime, and *Note
`TIMESTAMP': datetime. values all can be specified using the same set
of formats, the types do not all have the same range of values.  *Note
`TIMESTAMP': datetime. values cannot be earlier than `1970' UTC or
later than `'2038-01-19 03:14:07'' UTC. This means that a date such as
`'1968-01-01'', while valid as a *Note `DATE': datetime. or *Note
`DATETIME': datetime. value, is not valid as a *Note `TIMESTAMP':
datetime. value and is converted to `0'.

Conversion of *Note `DATE': datetime. values:

   * Conversion to a *Note `DATETIME': datetime. or *Note `TIMESTAMP':
     datetime. value adds a time part of `'00:00:00'' because the *Note
     `DATE': datetime. value contains no time information.

   * Conversion to a *Note `TIME': time. value is not useful; the
     result is `'00:00:00''.

Conversion of *Note `DATETIME': datetime. and *Note `TIMESTAMP':
datetime. values:

   * Conversion to a *Note `DATE': datetime. value discards the time
     part because the *Note `DATE': datetime. type contains no time
     information.

   * Conversion to a *Note `TIME': time. value discards the date part
     because the *Note `TIME': time. type contains no date information.

Conversion of *Note `TIME': time. values:

MySQL converts a time value to a date or date-and-time value by parsing
the string value of the time as a date or date-and-time.  This is
unlikely to be useful. For example, `'23:12:31'' interpreted as a date
becomes `'2023-12-31''. Time values not valid as dates become
`'0000-00-00'' or `NULL'.

Prior to MySQL 5.1.18, when *Note `DATE': datetime.  values are
compared with *Note `DATETIME': datetime.  values, the time portion of
the *Note `DATETIME': datetime. value is ignored, or the comparison
could be performed as a string compare. Starting from MySQL 5.1.18, a
*Note `DATE': datetime. value is coerced to the *Note `DATETIME':
datetime. type by adding the time portion as `'00:00:00''. To mimic the
old behavior, use the `CAST()' function to cause the comparison
operands to be treated as previously. For example:


     DATE_COL = CAST(DATETIME_COL AS DATE)

Conversion of *Note `TIME': time. or *Note `DATETIME': datetime. values
to numeric form (for example, by adding `+0') results in a
double-precision value with a microseconds part of `.000000':


     mysql> SELECT CURTIME(), CURTIME()+0;
     +-----------+---------------+
     | CURTIME() | CURTIME()+0   |
     +-----------+---------------+
     | 10:41:36  | 104136.000000 |
     +-----------+---------------+
     mysql> SELECT NOW(), NOW()+0;
     +---------------------+-----------------------+
     | NOW()               | NOW()+0               |
     +---------------------+-----------------------+
     | 2007-11-30 10:41:47 | 20071130104147.000000 |
     +---------------------+-----------------------+


File: manual.info,  Node: two-digit-years,  Prev: date-and-time-type-conversion,  Up: date-and-time-types

11.3.8 Two-Digit Years in Dates
-------------------------------

Date values with two-digit years are ambiguous because the century is
unknown. Such values must be interpreted into four-digit form because
MySQL stores years internally using four digits.

For *Note `DATETIME': datetime, *Note `DATE': datetime, and *Note
`TIMESTAMP': datetime. types, MySQL interprets dates specified with
ambiguous year values using these rules:

   * Year values in the range `00-69' are converted to `2000-2069'.

   * Year values in the range `70-99' are converted to `1970-1999'.

For `YEAR', the rules are the same, with this exception: A numeric `00'
inserted into `YEAR(4)' results in `0000' rather than `2000'. To
specify zero for `YEAR(4)' and have it be interpreted as `2000',
specify it as a string `'0'' or `'00''.

Remember that these rules are only heuristics that provide reasonable
guesses as to what your data values mean. If the rules used by MySQL do
not produce the values you require, you must provide unambiguous input
containing four-digit year values.

`ORDER BY' properly sorts *Note `YEAR': year. values that have two-digit
years.

Some functions like `MIN()' and `MAX()' convert a *Note `YEAR': year.
to a number. This means that a value with a two-digit year does not
work properly with these functions. The fix in this case is to convert
the *Note `YEAR': year. to four-digit year format.


File: manual.info,  Node: string-types,  Next: spatial-extensions,  Prev: date-and-time-types,  Up: data-types

11.4 String Types
=================

* Menu:

* char::                         The CHAR and VARCHAR Types
* binary-varbinary::             The BINARY and VARBINARY Types
* blob::                         The BLOB and TEXT Types
* enum::                         The ENUM Type
* set::                          The SET Type

The string types are *Note `CHAR': char, *Note `VARCHAR': char, *Note
`BINARY': binary-varbinary, *Note `VARBINARY': binary-varbinary, *Note
`BLOB': blob, *Note `TEXT': blob, *Note `ENUM': enum, and *Note `SET':
set. This section describes how these types work and how to use them in
your queries. For string type storage requirements, see *Note
storage-requirements::.


File: manual.info,  Node: char,  Next: binary-varbinary,  Prev: string-types,  Up: string-types

11.4.1 The CHAR and VARCHAR Types
---------------------------------

The `CHAR' and `VARCHAR' types are similar, but differ in the way they
are stored and retrieved. They also differ in maximum length and in
whether trailing spaces are retained.

The `CHAR' and `VARCHAR' types are declared with a length that
indicates the maximum number of characters you want to store. For
example, `CHAR(30)' can hold up to 30 characters.

The length of a `CHAR' column is fixed to the length that you declare
when you create the table. The length can be any value from 0 to 255.
When `CHAR' values are stored, they are right-padded with spaces to the
specified length. When `CHAR' values are retrieved, trailing spaces are
removed unless the `PAD_CHAR_TO_FULL_LENGTH' SQL mode is enabled.

Values in `VARCHAR' columns are variable-length strings. The length can
be specified as a value from 0 to 65,535. The effective maximum length
of a `VARCHAR' is subject to the maximum row size (65,535 bytes, which
is shared among all columns) and the character set used. See *Note
column-count-limit::.

In contrast to `CHAR', `VARCHAR' values are stored as a 1-byte or
2-byte length prefix plus data. The length prefix indicates the number
of bytes in the value. A column uses one length byte if values require
no more than 255 bytes, two length bytes if values may require more
than 255 bytes.

If strict SQL mode is not enabled and you assign a value to a `CHAR' or
`VARCHAR' column that exceeds the column's maximum length, the value is
truncated to fit and a warning is generated. For truncation of nonspace
characters, you can cause an error to occur (rather than a warning) and
suppress insertion of the value by using strict SQL mode. See *Note
sql-mode::.

For `VARCHAR' columns, trailing spaces in excess of the column length
are truncated prior to insertion and a warning is generated, regardless
of the SQL mode in use. For `CHAR' columns, truncation of excess
trailing spaces from inserted values is performed silently regardless of
the SQL mode.

`VARCHAR' values are not padded when they are stored. Trailing spaces
are retained when values are stored and retrieved, in conformance with
standard SQL.

The following table illustrates the differences between `CHAR' and
`VARCHAR' by showing the result of storing various string values into
`CHAR(4)' and `VARCHAR(4)' columns (assuming that the column uses a
single-byte character set such as `latin1').

This table illustrates the difference between `CHAR' and `VARCHAR'
storage requirements by showing the required storage for various string
values in `CHAR(4)' and `VARCHAR(4)' columns.

Value       `CHAR(4)'   Storage        `VARCHAR(4)'Storage
                        Required                   Required
`'''        `'    ''    4 bytes        `'''        1 byte
`'ab''      `'ab  ''    4 bytes        `'ab''      3 bytes
`'abcd''    `'abcd''    4 bytes        `'abcd''    5 bytes
`'abcdefgh''`'abcd''    4 bytes        `'abcd''    5 bytes

The values shown as stored in the last row of the table apply _only
when not using strict mode_; if MySQL is running in strict mode, values
that exceed the column length are _not stored_, and an error results.

If a given value is stored into the `CHAR(4)' and `VARCHAR(4)' columns,
the values retrieved from the columns are not always the same because
trailing spaces are removed from `CHAR' columns upon retrieval.  The
following example illustrates this difference:


     mysql> CREATE TABLE vc (v VARCHAR(4), c CHAR(4));
     Query OK, 0 rows affected (0.01 sec)

     mysql> INSERT INTO vc VALUES ('ab  ', 'ab  ');
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT CONCAT('(', v, ')'), CONCAT('(', c, ')') FROM vc;
     +---------------------+---------------------+
     | CONCAT('(', v, ')') | CONCAT('(', c, ')') |
     +---------------------+---------------------+
     | (ab  )              | (ab)                |
     +---------------------+---------------------+
     1 row in set (0.06 sec)

Values in `CHAR' and `VARCHAR' columns are sorted and compared
according to the character set collation assigned to the column.

All MySQL collations are of type `PADSPACE'.  This means that all
`CHAR', `VARCHAR', and `TEXT' values in MySQL are compared without
regard to any trailing spaces.  `Comparison' in this context does not
include the `LIKE' pattern-matching operator, for which trailing spaces
are significant. For example:


     mysql> CREATE TABLE names (myname CHAR(10));
     Query OK, 0 rows affected (0.03 sec)

     mysql> INSERT INTO names VALUES ('Monty');
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT myname = 'Monty', myname = 'Monty  ' FROM names;
     +------------------+--------------------+
     | myname = 'Monty' | myname = 'Monty  ' |
     +------------------+--------------------+
     |                1 |                  1 |
     +------------------+--------------------+
     1 row in set (0.00 sec)

     mysql> SELECT myname LIKE 'Monty', myname LIKE 'Monty  ' FROM names;
     +---------------------+-----------------------+
     | myname LIKE 'Monty' | myname LIKE 'Monty  ' |
     +---------------------+-----------------------+
     |                   1 |                     0 |
     +---------------------+-----------------------+
     1 row in set (0.00 sec)

This is true for all MySQL versions, and is not affected by the server
SQL mode.

*Note*:

For more information about MySQL character sets and collations, see
*Note charset::. For additional information about storage requirements,
see *Note storage-requirements::.

For those cases where trailing pad characters are stripped or
comparisons ignore them, if a column has an index that requires unique
values, inserting into the column values that differ only in number of
trailing pad characters will result in a duplicate-key error. For
example, if a table contains `'a'', an attempt to store `'a '' causes a
duplicate-key error.


File: manual.info,  Node: binary-varbinary,  Next: blob,  Prev: char,  Up: string-types

11.4.2 The BINARY and VARBINARY Types
-------------------------------------

The `BINARY' and `VARBINARY' types are similar to *Note `CHAR': char.
and *Note `VARCHAR': char, except that they contain binary strings
rather than nonbinary strings. That is, they contain byte strings
rather than character strings. This means that they have no character
set, and sorting and comparison are based on the numeric values of the
bytes in the values.

The permissible maximum length is the same for `BINARY' and `VARBINARY'
as it is for *Note `CHAR': char. and *Note `VARCHAR': char, except that
the length for `BINARY' and `VARBINARY' is a length in bytes rather
than in characters.

The `BINARY' and `VARBINARY' data types are distinct from the `CHAR
BINARY' and `VARCHAR BINARY' data types. For the latter types, the
`BINARY' attribute does not cause the column to be treated as a binary
string column. Instead, it causes the binary collation for the column
character set to be used, and the column itself contains nonbinary
character strings rather than binary byte strings. For example, `CHAR(5)
BINARY' is treated as `CHAR(5) CHARACTER SET latin1 COLLATE
latin1_bin', assuming that the default character set is `latin1'. This
differs from `BINARY(5)', which stores 5-bytes binary strings that have
no character set or collation. For information about differences
between nonbinary string binary collations and binary strings, see
*Note charset-binary-collations::.

If strict SQL mode is not enabled and you assign a value to a `BINARY'
or `VARBINARY' column that exceeds the column's maximum length, the
value is truncated to fit and a warning is generated. For cases of
truncation, you can cause an error to occur (rather than a warning) and
suppress insertion of the value by using strict SQL mode. See *Note
sql-mode::.

When `BINARY' values are stored, they are right-padded with the pad
value to the specified length. The pad value is `0x00' (the zero byte).
Values are right-padded with `0x00' on insert, and no trailing bytes
are removed on select. All bytes are significant in comparisons,
including `ORDER BY' and `DISTINCT' operations. `0x00' bytes and spaces
are different in comparisons, with `0x00' < space.

Example: For a `BINARY(3)' column, `'a '' becomes `'a \0'' when
inserted.  `'a\0'' becomes `'a\0\0'' when inserted. Both inserted
values remain unchanged when selected.

For `VARBINARY', there is no padding on insert and no bytes are
stripped on select. All bytes are significant in comparisons, including
`ORDER BY' and `DISTINCT' operations. `0x00' bytes and spaces are
different in comparisons, with `0x00' < space.

For those cases where trailing pad bytes are stripped or comparisons
ignore them, if a column has an index that requires unique values,
inserting into the column values that differ only in number of trailing
pad bytes will result in a duplicate-key error. For example, if a table
contains `'a'', an attempt to store `'a\0'' causes a duplicate-key
error.

You should consider the preceding padding and stripping characteristics
carefully if you plan to use the `BINARY' data type for storing binary
data and you require that the value retrieved be exactly the same as the
value stored. The following example illustrates how `0x00'-padding of
`BINARY' values affects column value comparisons:


     mysql> CREATE TABLE t (c BINARY(3));
     Query OK, 0 rows affected (0.01 sec)

     mysql> INSERT INTO t SET c = 'a';
     Query OK, 1 row affected (0.01 sec)

     mysql> SELECT HEX(c), c = 'a', c = 'a\0\0' from t;
     +--------+---------+-------------+
     | HEX(c) | c = 'a' | c = 'a\0\0' |
     +--------+---------+-------------+
     | 610000 |       0 |           1 |
     +--------+---------+-------------+
     1 row in set (0.09 sec)

If the value retrieved must be the same as the value specified for
storage with no padding, it might be preferable to use `VARBINARY' or
one of the *Note `BLOB': blob. data types instead.


File: manual.info,  Node: blob,  Next: enum,  Prev: binary-varbinary,  Up: string-types

11.4.3 The BLOB and TEXT Types
------------------------------

A `BLOB' is a binary large object that can hold a variable amount of
data. The four `BLOB' types are `TINYBLOB', `BLOB', `MEDIUMBLOB', and
`LONGBLOB'.  These differ only in the maximum length of the values they
can hold. The four `TEXT' types are `TINYTEXT', `TEXT', `MEDIUMTEXT',
and `LONGTEXT'.  These correspond to the four `BLOB' types and have the
same maximum lengths and storage requirements. See *Note
storage-requirements::.

`BLOB' values are treated as binary strings (byte strings). They have
no character set, and sorting and comparison are based on the numeric
values of the bytes in column values. `TEXT' values are treated as
nonbinary strings (character strings). They have a character set, and
values are sorted and compared based on the collation of the character
set.

If strict SQL mode is not enabled and you assign a value to a `BLOB' or
`TEXT' column that exceeds the column's maximum length, the value is
truncated to fit and a warning is generated. For truncation of nonspace
characters, you can cause an error to occur (rather than a warning) and
suppress insertion of the value by using strict SQL mode. See *Note
sql-mode::.

Beginning with MySQL 5.1.24, truncation of excess trailing spaces from
values to be inserted into *Note `TEXT': blob. columns always generates
a warning, regardless of the SQL mode.

For `TEXT' and `BLOB' columns, there is no padding on insert and no
bytes are stripped on select.

If a `TEXT' column is indexed, index entry comparisons are space-padded
at the end. This means that, if the index requires unique values,
duplicate-key errors will occur for values that differ only in the
number of trailing spaces.  For example, if a table contains `'a'', an
attempt to store `'a '' causes a duplicate-key error. This is not true
for `BLOB' columns.

In most respects, you can regard a `BLOB' column as a *Note
`VARBINARY': binary-varbinary. column that can be as large as you like.
Similarly, you can regard a `TEXT' column as a *Note `VARCHAR': char.
column.  `BLOB' and `TEXT' differ from *Note `VARBINARY':
binary-varbinary. and *Note `VARCHAR': char. in the following ways:

   * For indexes on `BLOB' and `TEXT' columns, you must specify an index
     prefix length. For *Note `CHAR': char. and *Note `VARCHAR': char,
     a prefix length is optional. See *Note column-indexes::.

   * `BLOB' and `TEXT' columns cannot have `DEFAULT' values.

If you use the `BINARY' attribute with a `TEXT' data type, the column
is assigned the binary collation of the column character set.

`LONG' and `LONG VARCHAR' map to the `MEDIUMTEXT' data type. This is a
compatibility feature.

MySQL Connector/ODBC defines `BLOB' values as `LONGVARBINARY' and `TEXT'
values as `LONGVARCHAR'.

Because `BLOB' and `TEXT' values can be extremely long, you might
encounter some constraints in using them:

   * Only the first `max_sort_length' bytes of the column are used when
     sorting. The default value of `max_sort_length' is 1024.  You can
     make more bytes significant in sorting or grouping by increasing
     the value of `max_sort_length' at server startup or runtime. Any
     client can change the value of its session `max_sort_length'
     variable:


          mysql> SET max_sort_length = 2000;
          mysql> SELECT id, comment FROM t
              -> ORDER BY comment;

   * Instances of `BLOB' or `TEXT' columns in the result of a query
     that is processed using a temporary table causes the server to use
     a table on disk rather than in memory because the `MEMORY' storage
     engine does not support those data types (see *Note
     internal-temporary-tables::). Use of disk incurs a performance
     penalty, so include `BLOB' or `TEXT' columns in the query result
     only if they are really needed. For example, avoid using *Note
     `SELECT *': select, which selects all columns.

   * The maximum size of a `BLOB' or `TEXT' object is determined by its
     type, but the largest value you actually can transmit between the
     client and server is determined by the amount of available memory
     and the size of the communications buffers. You can change the
     message buffer size by changing the value of the
     `max_allowed_packet' variable, but you must do so for both the
     server and your client program. For example, both *Note `mysql':
     mysql.  and *Note `mysqldump': mysqldump. enable you to change the
     client-side `max_allowed_packet' value.  See *Note
     server-parameters::, *Note mysql::, and *Note mysqldump::.  You
     may also want to compare the packet sizes and the size of the data
     objects you are storing with the storage requirements, see *Note
     storage-requirements::

Each `BLOB' or `TEXT' value is represented internally by a separately
allocated object. This is in contrast to all other data types, for
which storage is allocated once per column when the table is opened.

In some cases, it may be desirable to store binary data such as media
files in `BLOB' or `TEXT' columns. You may find MySQL's string handling
functions useful for working with such data. See *Note
string-functions::. For security and other reasons, it is usually
preferable to do so using application code rather than giving
application users the `FILE' privilege. You can discuss specifics for
various languages and platforms in the MySQL Forums
(`http://forums.mysql.com/').


File: manual.info,  Node: enum,  Next: set,  Prev: blob,  Up: string-types

11.4.4 The ENUM Type
--------------------

An `ENUM' is a string object with a value chosen from a list of
permitted values that are enumerated explicitly in the column
specification at table creation time.  It has these advantages:

   * Compact data storage in situations where a column has a limited
     set of possible values. The strings you specify as input values
     are automatically encoded as numbers. See *Note
     storage-requirements:: for the storage requirements for `ENUM'
     types.

   * Readable queries and output. The numbers are translated back to
     the corresponding strings in query results.

and these potential issues to consider:

   * If you make enumeration values that look like numbers, it is easy
     to mix up the literal values with their internal index numbers, as
     explained in *Note enum-limits::.

   * Using `ENUM' columns in `ORDER BY' clauses requires extra care, as
     explained in *Note enum-sorting::.

*Creating and Using ENUM Columns*

An enumeration value must be a quoted string literal. For example, you
can create a table with an `ENUM' column like this:


     CREATE TABLE shirts (
         name VARCHAR(40),
         size ENUM('x-small', 'small', 'medium', 'large', 'x-large')
     );
     INSERT INTO shirts (name, size) VALUES ('dress shirt','large'), ('t-shirt','medium'),
       ('polo shirt','small');
     SELECT name, size FROM shirts WHERE size = 'medium';
     +---------+--------+
     | name    | size   |
     +---------+--------+
     | t-shirt | medium |
     +---------+--------+
     UPDATE shirts SET size = 'small' WHERE size = 'large';
     COMMIT;

Inserting 1 million rows into this table with a value of `'medium''
would require 1 million bytes of storage, as opposed to 6 million bytes
if you stored the actual string `'medium'' in a `VARCHAR' column.

*Index Values for Enumeration Literals*

Each enumeration value has an index:

   * The elements listed in the column specification are assigned index
     numbers, beginning with 1.

   * The index value of the empty string error value is 0. This means
     that you can use the following *Note `SELECT': select. statement
     to find rows into which invalid `ENUM' values were assigned:


          mysql> SELECT * FROM TBL_NAME WHERE ENUM_COL=0;

   * The index of the `NULL' value is `NULL'.

   * The term `index' here refers to a position within the list of
     enumeration values. It has nothing to do with table indexes.

For example, a column specified as `ENUM('Mercury', 'Venus', 'Earth')'
can have any of the values shown here. The index of each value is also
shown.

This table shows possible values for a column specified as
`ENUM('Mercury', 'Venus', 'Earth')'. The table also shows the index of
each value.

Value       Index
`NULL'      `NULL'
`'''        0
`'Mercury'' 1
`'Venus''   2
`'Earth''   3

An *Note `ENUM': enum. column can have a maximum of 65,535 distinct
elements. (The practical limit is less than 3000.) A table can have no
more than 255 unique element list definitions among its *Note `ENUM':
enum. and *Note `SET': set. columns considered as a group. For more
information on these limits, see *Note limits-frm-file::.

If you retrieve an `ENUM' value in a numeric context, the column
value's index is returned. For example, you can retrieve numeric values
from an `ENUM' column like this:


     mysql> SELECT ENUM_COL+0 FROM TBL_NAME;

Functions such as `SUM()' or `AVG()' that expect a numeric argument
cast the argument to a number if necessary. For `ENUM' values, the
index number is used in the calculation.

*Handling of Enumeration Literals*

Trailing spaces are automatically deleted from `ENUM' member values in
the table definition when a table is created.

When retrieved, values stored into an `ENUM' column are displayed using
the lettercase that was used in the column definition. Note that `ENUM'
columns can be assigned a character set and collation. For binary or
case-sensitive collations, lettercase is taken into account when
assigning values to the column.

If you store a number into an `ENUM' column, the number is treated as
the index into the possible values, and the value stored is the
enumeration member with that index.  (However, this does _not_ work with
*Note `LOAD DATA': load-data, which treats all input as strings.) If
the numeric value is quoted, it is still interpreted as an index if
there is no matching string in the list of enumeration values. For
these reasons, it is not advisable to define an `ENUM' column with
enumeration values that look like numbers, because this can easily
become confusing. For example, the following column has enumeration
members with string values of `'0'', `'1'', and `'2'', but numeric
index values of `1', `2', and `3':


     numbers ENUM('0','1','2')

If you store `2', it is interpreted as an index value, and becomes
`'1'' (the value with index 2). If you store `'2'', it matches an
enumeration value, so it is stored as `'2''. If you store `'3'', it
does not match any enumeration value, so it is treated as an index and
becomes `'2'' (the value with index 3).


     mysql> INSERT INTO t (numbers) VALUES(2),('2'),('3');
     mysql> SELECT * FROM t;
     +---------+
     | numbers |
     +---------+
     | 1       |
     | 2       |
     | 2       |
     +---------+

To determine all possible values for an `ENUM' column, use *Note `SHOW
COLUMNS FROM TBL_NAME LIKE 'ENUM_COL'': show-columns. and parse the
`ENUM' definition in the `Type' column of the output.

In the C API, `ENUM' values are returned as strings. For information
about using result set metadata to distinguish them from other strings,
see *Note c-api-data-structures::.

*Empty or NULL Enumeration Values*

An enumeration value can also be the empty string (`''') or `NULL'
under certain circumstances:

   * If you insert an invalid value into an `ENUM' (that is, a string
     not present in the list of permitted values), the empty string is
     inserted instead as a special error value. This string can be
     distinguished from a `normal' empty string by the fact that this
     string has the numeric value 0. See *Note enum-indexes:: for
     details about the numeric indexes for the enumeration values.

     If strict SQL mode is enabled, attempts to insert invalid `ENUM'
     values result in an error.

   * If an `ENUM' column is declared to permit `NULL', the `NULL' value
     is a valid value for the column, and the default value is `NULL'.
     If an `ENUM' column is declared `NOT NULL', its default value is
     the first element of the list of permitted values.

*Enumeration Sorting*

`ENUM' values are sorted based on their index numbers, which depend on
the order in which the enumeration members were listed in the column
specification. For example, `'b'' sorts before `'a'' for `ENUM('b',
'a')'. The empty string sorts before nonempty strings, and `NULL'
values sort before all other enumeration values.

To prevent unexpected results when using the `ORDER BY' clause on an
`ENUM' column, use one of these techniques:

   * Specify the `ENUM' list in alphabetic order.

   * Make sure that the column is sorted lexically rather than by index
     number by coding `ORDER BY CAST(COL AS CHAR)' or `ORDER BY
     CONCAT(COL)'.

*Enumeration Limitations*

An enumeration value cannot be an expression, even one that evaluates
to a string value.

For example, this *Note `CREATE TABLE': create-table.  statement does
_not_ work because the `CONCAT' function cannot be used to construct an
enumeration value:


     CREATE TABLE sizes (
         size ENUM('small', CONCAT('med','ium'), 'large')
     );

You also cannot employ a user variable as an enumeration value.  This
pair of statements do _not_ work:


     SET @mysize = 'medium';

     CREATE TABLE sizes (
         size ENUM('small', @mysize, 'large')
     );

We strongly recommend that you do _not_ use numbers as enumeration
values, because it does not save on storage over the appropriate *Note
`TINYINT': integer-types. or *Note `SMALLINT': integer-types. type, and
it is easy to mix up the strings and the underlying number values
(which might not be the same) if you quote the `ENUM' values
incorrectly. If you do use a number as an enumeration value, always
enclose it in quotation marks. If the quotation marks are omitted, the
number is regarded as an index. See *Note enum-literals:: to see how
even a quoted number could be mistakenly used as a numeric index value.

Duplicate values in the definition cause a warning, or an error if
strict SQL mode is enabled.


File: manual.info,  Node: set,  Prev: enum,  Up: string-types

11.4.5 The SET Type
-------------------

A `SET' is a string object that can have zero or more values, each of
which must be chosen from a list of permitted values specified when the
table is created.  `SET' column values that consist of multiple set
members are specified with members separated by commas (``,''). A
consequence of this is that `SET' member values should not themselves
contain commas.

For example, a column specified as `SET('one', 'two') NOT NULL' can
have any of these values:


     ''
     'one'
     'two'
     'one,two'

A *Note `SET': set. column can have a maximum of 64 distinct members. A
table can have no more than 255 unique element list definitions among
its *Note `ENUM': enum. and *Note `SET': set. columns considered as a
group. For more information on this limit, see *Note limits-frm-file::.

Duplicate values in the definition cause a warning, or an error if
strict SQL mode is enabled.

Trailing spaces are automatically deleted from `SET' member values in
the table definition when a table is created.

When retrieved, values stored in a `SET' column are displayed using the
lettercase that was used in the column definition. Note that `SET'
columns can be assigned a character set and collation. For binary or
case-sensitive collations, lettercase is taken into account when
assigning values to the column.

MySQL stores `SET' values numerically, with the low-order bit of the
stored value corresponding to the first set member. If you retrieve a
`SET' value in a numeric context, the value retrieved has bits set
corresponding to the set members that make up the column value. For
example, you can retrieve numeric values from a `SET' column like this:


     mysql> SELECT SET_COL+0 FROM TBL_NAME;

If a number is stored into a `SET' column, the bits that are set in the
binary representation of the number determine the set members in the
column value. For a column specified as `SET('a','b','c','d')', the
members have the following decimal and binary values.

This table shows decimal and binary values for members of a column
specified as `SET('a','b','c','d')'.

`SET'       Decimal Value  Binary Value
Member                     
`'a''       `1'            `0001'
`'b''       `2'            `0010'
`'c''       `4'            `0100'
`'d''       `8'            `1000'

If you assign a value of `9' to this column, that is `1001' in binary,
so the first and fourth `SET' value members `'a'' and `'d'' are selected
and the resulting value is `'a,d''.

For a value containing more than one `SET' element, it does not matter
what order the elements are listed in when you insert the value. It
also does not matter how many times a given element is listed in the
value. When the value is retrieved later, each element in the value
appears once, with elements listed according to the order in which they
were specified at table creation time. For example, suppose that a
column is specified as `SET('a','b','c','d')':


     mysql> CREATE TABLE myset (col SET('a', 'b', 'c', 'd'));

If you insert the values `'a,d'', `'d,a'', `'a,d,d'', `'a,d,a'', and
`'d,a,d'':


     mysql> INSERT INTO myset (col) VALUES
     -> ('a,d'), ('d,a'), ('a,d,a'), ('a,d,d'), ('d,a,d');
     Query OK, 5 rows affected (0.01 sec)
     Records: 5  Duplicates: 0  Warnings: 0

Then all these values appear as `'a,d'' when retrieved:


     mysql> SELECT col FROM myset;
     +------+
     | col  |
     +------+
     | a,d  |
     | a,d  |
     | a,d  |
     | a,d  |
     | a,d  |
     +------+
     5 rows in set (0.04 sec)

If you set a `SET' column to an unsupported value, the value is ignored
and a warning is issued:


     mysql> INSERT INTO myset (col) VALUES ('a,d,d,s');
     Query OK, 1 row affected, 1 warning (0.03 sec)

     mysql> SHOW WARNINGS;
     +---------+------+------------------------------------------+
     | Level   | Code | Message                                  |
     +---------+------+------------------------------------------+
     | Warning | 1265 | Data truncated for column 'col' at row 1 |
     +---------+------+------------------------------------------+
     1 row in set (0.04 sec)

     mysql> SELECT col FROM myset;
     +------+
     | col  |
     +------+
     | a,d  |
     | a,d  |
     | a,d  |
     | a,d  |
     | a,d  |
     | a,d  |
     +------+
     6 rows in set (0.01 sec)

If strict SQL mode is enabled, attempts to insert invalid `SET' values
result in an error.

`SET' values are sorted numerically.  `NULL' values sort before
non-`NULL' `SET' values.

Functions such as `SUM()' or `AVG()' that expect a numeric argument
cast the argument to a number if necessary. For `SET' values, the cast
operation causes the numeric value to be used.

Normally, you search for `SET' values using the `FIND_IN_SET()'
function or the `LIKE' operator:


     mysql> SELECT * FROM TBL_NAME WHERE FIND_IN_SET('VALUE',SET_COL)>0;
     mysql> SELECT * FROM TBL_NAME WHERE SET_COL LIKE '%VALUE%';

The first statement finds rows where SET_COL contains the VALUE set
member. The second is similar, but not the same: It finds rows where
SET_COL contains VALUE anywhere, even as a substring of another set
member.

The following statements also are permitted:


     mysql> SELECT * FROM TBL_NAME WHERE SET_COL & 1;
     mysql> SELECT * FROM TBL_NAME WHERE SET_COL = 'VAL1,VAL2';

The first of these statements looks for values containing the first set
member. The second looks for an exact match. Be careful with
comparisons of the second type. Comparing set values to `'VAL1,VAL2''
returns different results than comparing values to `'VAL2,VAL1''.  You
should specify the values in the same order they are listed in the
column definition.

To determine all possible values for a `SET' column, use `SHOW COLUMNS
FROM TBL_NAME LIKE SET_COL' and parse the `SET' definition in the `Type'
column of the output.

In the C API, `SET' values are returned as strings. For information
about using result set metadata to distinguish them from other strings,
see *Note c-api-data-structures::.


File: manual.info,  Node: spatial-extensions,  Next: data-type-defaults,  Prev: string-types,  Up: data-types

11.5 Extensions for Spatial Data
================================

* Menu:

* spatial-datatypes::            Spatial Data Types
* opengis-geometry-model::       The OpenGIS Geometry Model
* using-spatial-data::           Using Spatial Data

The Open Geospatial Consortium (OGC) is is an international consortium
of more than 250 companies, agencies, and universities participating in
the development of publicly available conceptual solutions that can be
useful with all kinds of applications that manage spatial data.

The Open Geospatial Consortium publishes the `OpenGIS(R) Implementation
Standard for Geographic information - Simple feature access - Part 2:
SQL option', a document that proposes several conceptual ways for
extending an SQL RDBMS to support spatial data. This specification is
available from the OGC Web site at
`http://www.opengeospatial.org/standards/sfs'.

Following the OGC specification, MySQL implements spatial extensions as
a subset of the *SQL with Geometry Types* environment. This term refers
to an SQL environment that has been extended with a set of geometry
types. A geometry-valued SQL column is implemented as a column that has
a geometry type. The specification describes a set of SQL geometry
types, as well as functions on those types to create and analyze
geometry values.

MySQL spatial extensions enable the generation, storage, and analysis
of geographic features:

   * Data types for representing spatial values

   * Functions for manipulating spatial values

   * Spatial indexing for improved access times to spatial columns

The data types and functions are available for *Note `MyISAM':
myisam-storage-engine, *Note `InnoDB': innodb-storage-engine, *Note
`NDB': mysql-cluster, and *Note `ARCHIVE': archive-storage-engine.
tables. For indexing spatial columns, `MyISAM' supports both `SPATIAL'
and non-`SPATIAL' indexes. The other storage engines support
non-`SPATIAL' indexes, as described in *Note create-index::.

A *geographic feature* is anything in the world that has a location. A
feature can be:

   * An entity. For example, a mountain, a pond, a city.

   * A space. For example, town district, the tropics.

   * A definable location. For example, a crossroad, as a particular
     place where two streets intersect.

Some documents use the term *geospatial feature* to refer to geographic
features.

*Geometry* is another word that denotes a geographic feature.
Originally the word *geometry* meant measurement of the earth. Another
meaning comes from cartography, referring to the geometric features
that cartographers use to map the world.

The discussion here considers these terms synonymous: *geographic
feature*, *geospatial feature*, *feature*, or *geometry*. The term most
commonly used is *geometry*, defined as _a point or an aggregate of
points representing anything in the world that has a location_.

The following material covers these topics:

   * The spatial data types implemented in MySQL model

   * The basis of the spatial extensions in the OpenGIS geometry model

   * Data formats for representing spatial data

   * How to use spatial data in MySQL

   * Use of indexing for spatial data

   * MySQL differences from the OpenGIS specification

For information about functions that operate on spatial data, see *Note
spatial-analysis-functions::.

*MySQL GIS Conformance and Compatibility*

MySQL does not implement the following GIS features:

   * Additional Metadata Views

     OpenGIS specifications propose several additional metadata views.
     For example, a system view named `GEOMETRY_COLUMNS' contains a
     description of geometry columns, one row for each geometry column
     in the database.

   * The OpenGIS function `Length()' on `LineString' and
     `MultiLineString' should be called in MySQL as `GLength()'

     The problem is that there is an existing SQL function `Length()'
     that calculates the length of string values, and sometimes it is
     not possible to distinguish whether the function is called in a
     textual or spatial context.

*Additional Resources*

   * The Open Geospatial Consortium publishes the `OpenGIS(R)
     Implementation Standard for Geographic information - Simple
     feature access - Part 2: SQL option', a document that proposes
     several conceptual ways for extending an SQL RDBMS to support
     spatial data. The Open Geospatial Consortium (OGC) maintains a Web
     site at `http://www.opengeospatial.org/'. The specification is
     available there at `http://www.opengeospatial.org/standards/sfs'.
     It contains additional information relevant to the material here.

   * If you have questions or concerns about the use of the spatial
     extensions to MySQL, you can discuss them in the GIS forum:
     `http://forums.mysql.com/list.php?23'.


File: manual.info,  Node: spatial-datatypes,  Next: opengis-geometry-model,  Prev: spatial-extensions,  Up: spatial-extensions

11.5.1 Spatial Data Types
-------------------------

MySQL has data types that correspond to OpenGIS classes. Some of these
types hold single geometry values:

   * `GEOMETRY'

   * `POINT'

   * `LINESTRING'

   * `POLYGON'

`GEOMETRY' can store geometry values of any type. The other
single-value types (`POINT', `LINESTRING', and `POLYGON') restrict
their values to a particular geometry type.

The other data types hold collections of values:

   * `MULTIPOINT'

   * `MULTILINESTRING'

   * `MULTIPOLYGON'

   * `GEOMETRYCOLLECTION'

`GEOMETRYCOLLECTION' can store a collection of objects of any type. The
other collection types (`MULTIPOINT', `MULTILINESTRING',
`MULTIPOLYGON', and `GEOMETRYCOLLECTION') restrict collection members
to those having a particular geometry type.

MySQL spatial data types have their basis in the OpenGIS geometry
model, described in *Note opengis-geometry-model::. For examples showing
how to use spatial data types in MySQL, see *Note using-spatial-data::.


File: manual.info,  Node: opengis-geometry-model,  Next: using-spatial-data,  Prev: spatial-datatypes,  Up: spatial-extensions

11.5.2 The OpenGIS Geometry Model
---------------------------------

* Menu:

* gis-geometry-class-hierarchy::  The Geometry Class Hierarchy
* gis-class-geometry::           Geometry Class
* gis-class-point::              Point Class
* gis-class-curve::              Curve Class
* gis-class-linestring::         LineString Class
* gis-class-surface::            Surface Class
* gis-class-polygon::            Polygon Class
* gis-class-geometrycollection::  GeometryCollection Class
* gis-class-multipoint::         MultiPoint Class
* gis-class-multicurve::         MultiCurve Class
* gis-class-multilinestring::    MultiLineString Class
* gis-class-multisurface::       MultiSurface Class
* gis-class-multipolygon::       MultiPolygon Class

The set of geometry types proposed by OGC's *SQL with Geometry Types*
environment is based on the *OpenGIS Geometry Model*. In this model,
each geometric object has the following general properties:

   * It is associated with a Spatial Reference System, which describes
     the coordinate space in which the object is defined.

   * It belongs to some geometry class.


File: manual.info,  Node: gis-geometry-class-hierarchy,  Next: gis-class-geometry,  Prev: opengis-geometry-model,  Up: opengis-geometry-model

11.5.2.1 The Geometry Class Hierarchy
.....................................

The geometry classes define a hierarchy as follows:

   * `Geometry' (noninstantiable)

        * `Point' (instantiable)

        * `Curve' (noninstantiable)

             * `LineString' (instantiable)

                  * `Line'

                  * `LinearRing'

        * `Surface' (noninstantiable)

             * `Polygon' (instantiable)

        * `GeometryCollection' (instantiable)

             * `MultiPoint' (instantiable)

             * `MultiCurve' (noninstantiable)

                  * `MultiLineString' (instantiable)

             * `MultiSurface' (noninstantiable)

                  * `MultiPolygon' (instantiable)

It is not possible to create objects in noninstantiable classes. It is
possible to create objects in instantiable classes. All classes have
properties, and instantiable classes may also have assertions (rules
that define valid class instances).

`Geometry' is the base class. It is an abstract class. The instantiable
subclasses of `Geometry' are restricted to zero-, one-, and
two-dimensional geometric objects that exist in two-dimensional
coordinate space. All instantiable geometry classes are defined so that
valid instances of a geometry class are topologically closed (that is,
all defined geometries include their boundary).

The base `Geometry' class has subclasses for `Point', `Curve',
`Surface', and `GeometryCollection':

   * `Point' represents zero-dimensional objects.

   * `Curve' represents one-dimensional objects, and has subclass
     `LineString', with sub-subclasses `Line' and `LinearRing'.

   * `Surface' is designed for two-dimensional objects and has subclass
     `Polygon'.

   * `GeometryCollection' has specialized zero-, one-, and
     two-dimensional collection classes named `MultiPoint',
     `MultiLineString', and `MultiPolygon' for modeling geometries
     corresponding to collections of `Points', `LineStrings', and
     `Polygons', respectively.  `MultiCurve' and `MultiSurface' are
     introduced as abstract superclasses that generalize the collection
     interfaces to handle `Curves' and `Surfaces'.

`Geometry', `Curve', `Surface', `MultiCurve', and `MultiSurface' are
defined as noninstantiable classes. They define a common set of methods
for their subclasses and are included for extensibility.

`Point', `LineString', `Polygon', `GeometryCollection', `MultiPoint',
`MultiLineString', and `MultiPolygon' are instantiable classes.


File: manual.info,  Node: gis-class-geometry,  Next: gis-class-point,  Prev: gis-geometry-class-hierarchy,  Up: opengis-geometry-model

11.5.2.2 Geometry Class
.......................

`Geometry' is the root class of the hierarchy. It is a noninstantiable
class but has a number of properties, described in the following list,
that are common to all geometry values created from any of the
`Geometry' subclasses. Particular subclasses have their own specific
properties, described later.

*Geometry Properties*

A geometry value has the following properties:

   * Its *type*. Each geometry belongs to one of the instantiable
     classes in the hierarchy.

   * Its *SRID*, or Spatial Reference Identifier. This value identifies
     the geometry's associated Spatial Reference System that describes
     the coordinate space in which the geometry object is defined.

     In MySQL, the SRID value is an integer associated with the
     geometry value. All calculations are done assuming Euclidean
     (planar) geometry. The maximum usable SRID value is 2^32-1. If a
     larger value is given, only the lower 32 bits are used.

   * Its *coordinates* in its Spatial Reference System, represented as
     double-precision (8-byte) numbers. All nonempty geometries include
     at least one pair of (X,Y) coordinates. Empty geometries contain no
     coordinates.

     Coordinates are related to the SRID. For example, in different
     coordinate systems, the distance between two objects may differ
     even when objects have the same coordinates, because the distance
     on the *planar* coordinate system and the distance on the
     *geocentric* system (coordinates on the Earth's surface) are
     different things.

   * Its *interior*, *boundary*, and *exterior*.

     Every geometry occupies some position in space. The exterior of a
     geometry is all space not occupied by the geometry. The interior
     is the space occupied by the geometry. The boundary is the
     interface between the geometry's interior and exterior.

   * Its *MBR* (minimum bounding rectangle), or envelope. This is the
     bounding geometry, formed by the minimum and maximum (X,Y)
     coordinates:


          ((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))

   * Whether the value is *simple* or *nonsimple*. Geometry values of
     types (`LineString', `MultiPoint', `MultiLineString') are either
     simple or nonsimple. Each type determines its own assertions for
     being simple or nonsimple.

   * Whether the value is *closed* or *not closed*. Geometry values of
     types (`LineString', `MultiString') are either closed or not
     closed. Each type determines its own assertions for being closed
     or not closed.

   * Whether the value is *empty* or *nonempty* A geometry is empty if
     it does not have any points. Exterior, interior, and boundary of
     an empty geometry are not defined (that is, they are represented
     by a `NULL' value). An empty geometry is defined to be always
     simple and has an area of 0.

   * Its *dimension*. A geometry can have a dimension of -1, 0, 1, or 2:

        * -1 for an empty geometry.

        * 0 for a geometry with no length and no area.

        * 1 for a geometry with nonzero length and zero area.

        * 2 for a geometry with nonzero area.

     `Point' objects have a dimension of zero.  `LineString' objects
     have a dimension of 1. `Polygon' objects have a dimension of 2.
     The dimensions of `MultiPoint', `MultiLineString', and
     `MultiPolygon' objects are the same as the dimensions of the
     elements they consist of.


File: manual.info,  Node: gis-class-point,  Next: gis-class-curve,  Prev: gis-class-geometry,  Up: opengis-geometry-model

11.5.2.3 Point Class
....................

A `Point' is a geometry that represents a single location in coordinate
space.

*`Point' Examples*

   * Imagine a large-scale map of the world with many cities. A `Point'
     object could represent each city.

   * On a city map, a `Point' object could represent a bus stop.

*`Point' Properties*

   * X-coordinate value.

   * Y-coordinate value.

   * `Point' is defined as a zero-dimensional geometry.

   * The boundary of a `Point' is the empty set.


File: manual.info,  Node: gis-class-curve,  Next: gis-class-linestring,  Prev: gis-class-point,  Up: opengis-geometry-model

11.5.2.4 Curve Class
....................

A `Curve' is a one-dimensional geometry, usually represented by a
sequence of points. Particular subclasses of `Curve' define the type of
interpolation between points. `Curve' is a noninstantiable class.

*`Curve' Properties*

   * A `Curve' has the coordinates of its points.

   * A `Curve' is defined as a one-dimensional geometry.

   * A `Curve' is simple if it does not pass through the same point
     twice.

   * A `Curve' is closed if its start point is equal to its endpoint.

   * The boundary of a closed `Curve' is empty.

   * The boundary of a nonclosed `Curve' consists of its two endpoints.

   * A `Curve' that is simple and closed is a `LinearRing'.


File: manual.info,  Node: gis-class-linestring,  Next: gis-class-surface,  Prev: gis-class-curve,  Up: opengis-geometry-model

11.5.2.5 LineString Class
.........................

A `LineString' is a `Curve' with linear interpolation between points.

*`LineString' Examples*

   * On a world map, `LineString' objects could represent rivers.

   * In a city map, `LineString' objects could represent streets.

*`LineString' Properties*

   * A `LineString' has coordinates of segments, defined by each
     consecutive pair of points.

   * A `LineString' is a `Line' if it consists of exactly two points.

   * A `LineString' is a `LinearRing' if it is both closed and simple.


File: manual.info,  Node: gis-class-surface,  Next: gis-class-polygon,  Prev: gis-class-linestring,  Up: opengis-geometry-model

11.5.2.6 Surface Class
......................

A `Surface' is a two-dimensional geometry. It is a noninstantiable
class. Its only instantiable subclass is `Polygon'.

*`Surface' Properties*

   * A `Surface' is defined as a two-dimensional geometry.

   * The OpenGIS specification defines a simple `Surface' as a geometry
     that consists of a single `patch' that is associated with a single
     exterior boundary and zero or more interior boundaries.

   * The boundary of a simple `Surface' is the set of closed curves
     corresponding to its exterior and interior boundaries.


File: manual.info,  Node: gis-class-polygon,  Next: gis-class-geometrycollection,  Prev: gis-class-surface,  Up: opengis-geometry-model

11.5.2.7 Polygon Class
......................

A `Polygon' is a planar `Surface' representing a multisided geometry.
It is defined by a single exterior boundary and zero or more interior
boundaries, where each interior boundary defines a hole in the
`Polygon'.

*`Polygon' Examples*

   * On a region map, `Polygon' objects could represent forests,
     districts, and so on.

*`Polygon' Assertions*

   * The boundary of a `Polygon' consists of a set of `LinearRing'
     objects (that is, `LineString' objects that are both simple and
     closed) that make up its exterior and interior boundaries.

   * A `Polygon' has no rings that cross. The rings in the boundary of
     a `Polygon' may intersect at a `Point', but only as a tangent.

   * A `Polygon' has no lines, spikes, or punctures.

   * A `Polygon' has an interior that is a connected point set.

   * A `Polygon' may have holes. The exterior of a `Polygon' with holes
     is not connected. Each hole defines a connected component of the
     exterior.

The preceding assertions make a `Polygon' a simple geometry.


File: manual.info,  Node: gis-class-geometrycollection,  Next: gis-class-multipoint,  Prev: gis-class-polygon,  Up: opengis-geometry-model

11.5.2.8 GeometryCollection Class
.................................

A `GeometryCollection' is a geometry that is a collection of one or
more geometries of any class.

All the elements in a `GeometryCollection' must be in the same Spatial
Reference System (that is, in the same coordinate system). There are no
other constraints on the elements of a `GeometryCollection', although
the subclasses of `GeometryCollection' described in the following
sections may restrict membership.  Restrictions may be based on:

   * Element type (for example, a `MultiPoint' may contain only `Point'
     elements)

   * Dimension

   * Constraints on the degree of spatial overlap between elements


File: manual.info,  Node: gis-class-multipoint,  Next: gis-class-multicurve,  Prev: gis-class-geometrycollection,  Up: opengis-geometry-model

11.5.2.9 MultiPoint Class
.........................

A `MultiPoint' is a geometry collection composed of `Point' elements.
The points are not connected or ordered in any way.

*`MultiPoint' Examples*

   * On a world map, a `MultiPoint' could represent a chain of small
     islands.

   * On a city map, a `MultiPoint' could represent the outlets for a
     ticket office.

*`MultiPoint' Properties*

   * A `MultiPoint' is a zero-dimensional geometry.

   * A `MultiPoint' is simple if no two of its `Point' values are equal
     (have identical coordinate values).

   * The boundary of a `MultiPoint' is the empty set.


File: manual.info,  Node: gis-class-multicurve,  Next: gis-class-multilinestring,  Prev: gis-class-multipoint,  Up: opengis-geometry-model

11.5.2.10 MultiCurve Class
..........................

A `MultiCurve' is a geometry collection composed of `Curve' elements.
`MultiCurve' is a noninstantiable class.

*`MultiCurve' Properties*

   * A `MultiCurve' is a one-dimensional geometry.

   * A `MultiCurve' is simple if and only if all of its elements are
     simple; the only intersections between any two elements occur at
     points that are on the boundaries of both elements.

   * A `MultiCurve' boundary is obtained by applying the `mod 2 union
     rule' (also known as the `odd-even rule'): A point is in the
     boundary of a `MultiCurve' if it is in the boundaries of an odd
     number of `MultiCurve' elements.

   * A `MultiCurve' is closed if all of its elements are closed.

   * The boundary of a closed `MultiCurve' is always empty.


File: manual.info,  Node: gis-class-multilinestring,  Next: gis-class-multisurface,  Prev: gis-class-multicurve,  Up: opengis-geometry-model

11.5.2.11 MultiLineString Class
...............................

A `MultiLineString' is a `MultiCurve' geometry collection composed of
`LineString' elements.

*`MultiLineString' Examples*

   * On a region map, a `MultiLineString' could represent a river
     system or a highway system.


File: manual.info,  Node: gis-class-multisurface,  Next: gis-class-multipolygon,  Prev: gis-class-multilinestring,  Up: opengis-geometry-model

11.5.2.12 MultiSurface Class
............................

A `MultiSurface' is a geometry collection composed of surface elements.
`MultiSurface' is a noninstantiable class. Its only instantiable
subclass is `MultiPolygon'.

*`MultiSurface' Assertions*

   * Two `MultiSurface' surfaces have no interiors that intersect.

   * Two `MultiSurface' elements have boundaries that intersect at most
     at a finite number of points.


File: manual.info,  Node: gis-class-multipolygon,  Prev: gis-class-multisurface,  Up: opengis-geometry-model

11.5.2.13 MultiPolygon Class
............................

A `MultiPolygon' is a `MultiSurface' object composed of `Polygon'
elements.

*`MultiPolygon' Examples*

   * On a region map, a `MultiPolygon' could represent a system of
     lakes.

*`MultiPolygon' Assertions*

   * A `MultiPolygon' has no two `Polygon' elements with interiors that
     intersect.

   * A `MultiPolygon' has no two `Polygon' elements that cross (crossing
     is also forbidden by the previous assertion), or that touch at an
     infinite number of points.

   * A `MultiPolygon' may not have cut lines, spikes, or punctures. A
     `MultiPolygon' is a regular, closed point set.

   * A `MultiPolygon' that has more than one `Polygon' has an interior
     that is not connected. The number of connected components of the
     interior of a `MultiPolygon' is equal to the number of `Polygon'
     values in the `MultiPolygon'.

*`MultiPolygon' Properties*

   * A `MultiPolygon' is a two-dimensional geometry.

   * A `MultiPolygon' boundary is a set of closed curves (`LineString'
     values) corresponding to the boundaries of its `Polygon' elements.

   * Each `Curve' in the boundary of the `MultiPolygon' is in the
     boundary of exactly one `Polygon' element.

   * Every `Curve' in the boundary of an `Polygon' element is in the
     boundary of the `MultiPolygon'.


File: manual.info,  Node: using-spatial-data,  Prev: opengis-geometry-model,  Up: spatial-extensions

11.5.3 Using Spatial Data
-------------------------

* Menu:

* gis-data-formats::             Supported Spatial Data Formats
* creating-spatial-columns::     Creating Spatial Columns
* populating-spatial-columns::   Populating Spatial Columns
* fetching-spatial-data::        Fetching Spatial Data
* optimizing-spatial-analysis::  Optimizing Spatial Analysis
* creating-spatial-indexes::     Creating Spatial Indexes
* using-spatial-indexes::        Using Spatial Indexes

This section describes how to create tables that include spatial data
type columns, and how to manipulate spatial information.


File: manual.info,  Node: gis-data-formats,  Next: creating-spatial-columns,  Prev: using-spatial-data,  Up: using-spatial-data

11.5.3.1 Supported Spatial Data Formats
.......................................

* Menu:

* gis-wkt-format::               Well-Known Text (WKT) Format
* gis-wkb-format::               Well-Known Binary (WKB) Format

Two standard spatial data formats are used to represent geometry
objects in queries:

   * Well-Known Text (WKT) format

   * Well-Known Binary (WKB) format

Internally, MySQL stores geometry values in a format that is not
identical to either WKT or WKB format.

There are functions available to convert between different data
formats; see *Note gis-format-conversion-functions::.


File: manual.info,  Node: gis-wkt-format,  Next: gis-wkb-format,  Prev: gis-data-formats,  Up: gis-data-formats

11.5.3.2 Well-Known Text (WKT) Format
.....................................

The Well-Known Text (WKT) representation of geometry values is designed
for exchanging geometry data in ASCII form. The OpenGIS specification
provides a Backus-Naur grammar that specifies the formal production
rules for writing WKT values (see *Note spatial-extensions::).

Examples of WKT representations of geometry objects:

   * A `Point':


          POINT(15 20)

     The point coordinates are specified with no separating comma. This
     differs from the syntax for the SQL `Point()' function, which
     requires a comma between the coordinates. Take care to use the
     syntax appropriate to the context of a given spatial operation.
     For example, the following statements both extract the
     X-coordinate from a `Point' object. The first produces the object
     directly using the `Point()' function. The second uses a WKT
     representation converted to a `Point' with `GeomFromText()'.


          mysql> SELECT X(POINT(15, 20));
          +------------------+
          | X(POINT(15, 20)) |
          +------------------+
          |               15 |
          +------------------+

          mysql> SELECT X(GeomFromText('POINT(15 20)'));
          +---------------------------------+
          | X(GeomFromText('POINT(15 20)')) |
          +---------------------------------+
          |                              15 |
          +---------------------------------+

   * A `LineString' with four points:


          LINESTRING(0 0, 10 10, 20 25, 50 60)

     The point coordinate pairs are separated by commas.

   * A `Polygon' with one exterior ring and one interior ring:


          POLYGON((0 0,10 0,10 10,0 10,0 0),(5 5,7 5,7 7,5 7, 5 5))

   * A `MultiPoint' with three `Point' values:


          MULTIPOINT(0 0, 20 20, 60 60)

   * A `MultiLineString' with two `LineString' values:


          MULTILINESTRING((10 10, 20 20), (15 15, 30 15))

   * A `MultiPolygon' with two `Polygon' values:


          MULTIPOLYGON(((0 0,10 0,10 10,0 10,0 0)),((5 5,7 5,7 7,5 7, 5 5)))

   * A `GeometryCollection' consisting of two `Point' values and one
     `LineString':


          GEOMETRYCOLLECTION(POINT(10 10), POINT(30 30), LINESTRING(15 15, 20 20))


File: manual.info,  Node: gis-wkb-format,  Prev: gis-wkt-format,  Up: gis-data-formats

11.5.3.3 Well-Known Binary (WKB) Format
.......................................

The Well-Known Binary (WKB) representation of geometric values is used
for exchanging geometry data as binary streams represented by *Note
`BLOB': blob.  values containing geometric WKB information. This format
is defined by the OpenGIS specification (see *Note
spatial-extensions::). It is also defined in the ISO `SQL/MM Part 3:
Spatial' standard.

WKB uses 1-byte unsigned integers, 4-byte unsigned integers, and 8-byte
double-precision numbers (IEEE 754 format). A byte is eight bits.

For example, a WKB value that corresponds to `POINT(1 1)' consists of
this sequence of 21 bytes, each represented by two hex digits:


     0101000000000000000000F03F000000000000F03F

The sequence consists of these components:


     Byte order:   01
     WKB type:     01000000
     X coordinate: 000000000000F03F
     Y coordinate: 000000000000F03F

Component representation is as follows:

   * The byte order is either 1 or 0 to indicate little-endian or
     big-endian storage. The little-endian and big-endian byte orders
     are also known as Network Data Representation (NDR) and External
     Data Representation (XDR), respectively.

   * The WKB type is a code that indicates the geometry type.  Values
     from 1 through 7 indicate `Point', `LineString', `Polygon',
     `MultiPoint', `MultiLineString', `MultiPolygon', and
     `GeometryCollection'.

   * A `Point' value has X and Y coordinates, each represented as a
     double-precision value.

WKB values for more complex geometry values have more complex data
structures, as detailed in the OpenGIS specification.


File: manual.info,  Node: creating-spatial-columns,  Next: populating-spatial-columns,  Prev: gis-data-formats,  Up: using-spatial-data

11.5.3.4 Creating Spatial Columns
.................................

MySQL provides a standard way of creating spatial columns for geometry
types, for example, with *Note `CREATE TABLE': create-table. or *Note
`ALTER TABLE': alter-table.  Spatial columns are supported for *Note
`MyISAM': myisam-storage-engine, *Note `InnoDB': innodb-storage-engine,
*Note `NDB': mysql-cluster, and *Note `ARCHIVE':
archive-storage-engine. tables. See also the notes about spatial
indexes under *Note creating-spatial-indexes::.

   * Use the *Note `CREATE TABLE': create-table.  statement to create a
     table with a spatial column:


          CREATE TABLE geom (g GEOMETRY);

   * Use the *Note `ALTER TABLE': alter-table.  statement to add or
     drop a spatial column to or from an existing table:


          ALTER TABLE geom ADD pt POINT;
          ALTER TABLE geom DROP pt;


File: manual.info,  Node: populating-spatial-columns,  Next: fetching-spatial-data,  Prev: creating-spatial-columns,  Up: using-spatial-data

11.5.3.5 Populating Spatial Columns
...................................

After you have created spatial columns, you can populate them with
spatial data.

Values should be stored in internal geometry format, but you can
convert them to that format from either Well-Known Text (WKT) or
Well-Known Binary (WKB) format. The following examples demonstrate how
to insert geometry values into a table by converting WKT values to
internal geometry format:

   * Perform the conversion directly in the *Note `INSERT': insert.
     statement:


          INSERT INTO geom VALUES (GeomFromText('POINT(1 1)'));

          SET @g = 'POINT(1 1)';
          INSERT INTO geom VALUES (GeomFromText(@g));

   * Perform the conversion prior to the *Note `INSERT': insert.:


          SET @g = GeomFromText('POINT(1 1)');
          INSERT INTO geom VALUES (@g);

The following examples insert more complex geometries into the table:


     SET @g = 'LINESTRING(0 0,1 1,2 2)';
     INSERT INTO geom VALUES (GeomFromText(@g));

     SET @g = 'POLYGON((0 0,10 0,10 10,0 10,0 0),(5 5,7 5,7 7,5 7, 5 5))';
     INSERT INTO geom VALUES (GeomFromText(@g));

     SET @g =
     'GEOMETRYCOLLECTION(POINT(1 1),LINESTRING(0 0,1 1,2 2,3 3,4 4))';
     INSERT INTO geom VALUES (GeomFromText(@g));

The preceding examples use `GeomFromText()' to create geometry values.
You can also use type-specific functions:


     SET @g = 'POINT(1 1)';
     INSERT INTO geom VALUES (PointFromText(@g));

     SET @g = 'LINESTRING(0 0,1 1,2 2)';
     INSERT INTO geom VALUES (LineStringFromText(@g));

     SET @g = 'POLYGON((0 0,10 0,10 10,0 10,0 0),(5 5,7 5,7 7,5 7, 5 5))';
     INSERT INTO geom VALUES (PolygonFromText(@g));

     SET @g =
     'GEOMETRYCOLLECTION(POINT(1 1),LINESTRING(0 0,1 1,2 2,3 3,4 4))';
     INSERT INTO geom VALUES (GeomCollFromText(@g));

A client application program that wants to use WKB representations of
geometry values is responsible for sending correctly formed WKB in
queries to the server. There are several ways to satisfy this
requirement. For example:

   * Inserting a `POINT(1 1)' value with hex literal syntax:


          mysql> INSERT INTO geom VALUES
              -> (GeomFromWKB(0x0101000000000000000000F03F000000000000F03F));

   * An ODBC application can send a WKB representation, binding it to a
     placeholder using an argument of *Note `BLOB': blob. type:


          INSERT INTO geom VALUES (GeomFromWKB(?))

     Other programming interfaces may support a similar placeholder
     mechanism.

   * In a C program, you can escape a binary value using *Note
     `mysql_real_escape_string()': mysql-real-escape-string.  and
     include the result in a query string that is sent to the server.
     See *Note mysql-real-escape-string::.


File: manual.info,  Node: fetching-spatial-data,  Next: optimizing-spatial-analysis,  Prev: populating-spatial-columns,  Up: using-spatial-data

11.5.3.6 Fetching Spatial Data
..............................

Geometry values stored in a table can be fetched in internal format.
You can also convert them to WKT or WKB format.

   * Fetching spatial data in internal format:

     Fetching geometry values using internal format can be useful in
     table-to-table transfers:


          CREATE TABLE geom2 (g GEOMETRY) SELECT g FROM geom;

   * Fetching spatial data in WKT format:

     The `AsText()' function converts a geometry from internal format
     to a WKT string.


          SELECT AsText(g) FROM geom;

   * Fetching spatial data in WKB format:

     The `AsBinary()' function converts a geometry from internal format
     to a *Note `BLOB': blob. containing the WKB value.


          SELECT AsBinary(g) FROM geom;


File: manual.info,  Node: optimizing-spatial-analysis,  Next: creating-spatial-indexes,  Prev: fetching-spatial-data,  Up: using-spatial-data

11.5.3.7 Optimizing Spatial Analysis
....................................

For *Note `MyISAM': myisam-storage-engine. tables, search operations in
columns containing spatial data can be optimized using `SPATIAL'
indexes. The most typical operations are:

   * Point queries that search for all objects that contain a given
     point

   * Region queries that search for all objects that overlap a given
     region

MySQL uses *R-Trees with quadratic splitting* for `SPATIAL' indexes on
spatial columns. A `SPATIAL' index is built using the minimum bounding
rectangle (MBR) of a geometry. For most geometries, the MBR is a
minimum rectangle that surrounds the geometries. For a horizontal or a
vertical linestring, the MBR is a rectangle degenerated into the
linestring. For a point, the MBR is a rectangle degenerated into the
point.

It is also possible to create normal indexes on spatial columns. In a
non-`SPATIAL' index, you must declare a prefix for any spatial column
except for `POINT' columns.

`MyISAM' supports both `SPATIAL' and non-`SPATIAL' indexes. Other
storage engines support non-`SPATIAL' indexes, as described in *Note
create-index::.


File: manual.info,  Node: creating-spatial-indexes,  Next: using-spatial-indexes,  Prev: optimizing-spatial-analysis,  Up: using-spatial-data

11.5.3.8 Creating Spatial Indexes
.................................

For *Note `MyISAM': myisam-storage-engine. tables, MySQL can create
spatial indexes using syntax similar to that for creating regular
indexes, but using the `SPATIAL' keyword. Columns in spatial indexes
must be declared `NOT NULL'. The following examples demonstrate how to
create spatial indexes:

   * With *Note `CREATE TABLE': create-table.:


          CREATE TABLE geom (g GEOMETRY NOT NULL, SPATIAL INDEX(g)) ENGINE=MyISAM;

   * With *Note `ALTER TABLE': alter-table.:


          ALTER TABLE geom ADD SPATIAL INDEX(g);

   * With *Note `CREATE INDEX': create-index.:


          CREATE SPATIAL INDEX sp_index ON geom (g);

`SPATIAL INDEX' creates an R-tree index. For storage engines that
support nonspatial indexing of spatial columns, the engine creates a
B-tree index. A B-tree index on spatial values is useful for
exact-value lookups, but not for range scans.

For more information on indexing spatial columns, see *Note
create-index::.

To drop spatial indexes, use *Note `ALTER TABLE': alter-table. or *Note
`DROP INDEX': drop-index.:

   * With *Note `ALTER TABLE': alter-table.:


          ALTER TABLE geom DROP INDEX g;

   * With *Note `DROP INDEX': drop-index.:


          DROP INDEX sp_index ON geom;

Example: Suppose that a table `geom' contains more than 32,000
geometries, which are stored in the column `g' of type `GEOMETRY'. The
table also has an `AUTO_INCREMENT' column `fid' for storing object ID
values.


     mysql> DESCRIBE geom;
     +-------+----------+------+-----+---------+----------------+
     | Field | Type     | Null | Key | Default | Extra          |
     +-------+----------+------+-----+---------+----------------+
     | fid   | int(11)  |      | PRI | NULL    | auto_increment |
     | g     | geometry |      |     |         |                |
     +-------+----------+------+-----+---------+----------------+
     2 rows in set (0.00 sec)

     mysql> SELECT COUNT(*) FROM geom;
     +----------+
     | count(*) |
     +----------+
     |    32376 |
     +----------+
     1 row in set (0.00 sec)

To add a spatial index on the column `g', use this statement:


     mysql> ALTER TABLE geom ADD SPATIAL INDEX(g) ENGINE=MyISAM;
     Query OK, 32376 rows affected (4.05 sec)
     Records: 32376  Duplicates: 0  Warnings: 0


File: manual.info,  Node: using-spatial-indexes,  Prev: creating-spatial-indexes,  Up: using-spatial-data

11.5.3.9 Using Spatial Indexes
..............................

The optimizer investigates whether available spatial indexes can be
involved in the search for queries that use a function such as
`MBRContains()' or `MBRWithin()' in the `WHERE' clause. The following
query finds all objects that are in the given rectangle:


     mysql> SET @poly =
         -> 'Polygon((30000 15000,
                      31000 15000,
                      31000 16000,
                      30000 16000,
                      30000 15000))';
     mysql> SELECT fid,AsText(g) FROM geom WHERE
         -> MBRContains(GeomFromText(@poly),g);
     +-----+---------------------------------------------------------------+
     | fid | AsText(g)                                                     |
     +-----+---------------------------------------------------------------+
     |  21 | LINESTRING(30350.4 15828.8,30350.6 15845,30333.8 15845,30 ... |
     |  22 | LINESTRING(30350.6 15871.4,30350.6 15887.8,30334 15887.8, ... |
     |  23 | LINESTRING(30350.6 15914.2,30350.6 15930.4,30334 15930.4, ... |
     |  24 | LINESTRING(30290.2 15823,30290.2 15839.4,30273.4 15839.4, ... |
     |  25 | LINESTRING(30291.4 15866.2,30291.6 15882.4,30274.8 15882. ... |
     |  26 | LINESTRING(30291.6 15918.2,30291.6 15934.4,30275 15934.4, ... |
     | 249 | LINESTRING(30337.8 15938.6,30337.8 15946.8,30320.4 15946. ... |
     |   1 | LINESTRING(30250.4 15129.2,30248.8 15138.4,30238.2 15136. ... |
     |   2 | LINESTRING(30220.2 15122.8,30217.2 15137.8,30207.6 15136, ... |
     |   3 | LINESTRING(30179 15114.4,30176.6 15129.4,30167 15128,3016 ... |
     |   4 | LINESTRING(30155.2 15121.4,30140.4 15118.6,30142 15109,30 ... |
     |   5 | LINESTRING(30192.4 15085,30177.6 15082.2,30179.2 15072.4, ... |
     |   6 | LINESTRING(30244 15087,30229 15086.2,30229.4 15076.4,3024 ... |
     |   7 | LINESTRING(30200.6 15059.4,30185.6 15058.6,30186 15048.8, ... |
     |  10 | LINESTRING(30179.6 15017.8,30181 15002.8,30190.8 15003.6, ... |
     |  11 | LINESTRING(30154.2 15000.4,30168.6 15004.8,30166 15014.2, ... |
     |  13 | LINESTRING(30105 15065.8,30108.4 15050.8,30118 15053,3011 ... |
     | 154 | LINESTRING(30276.2 15143.8,30261.4 15141,30263 15131.4,30 ... |
     | 155 | LINESTRING(30269.8 15084,30269.4 15093.4,30258.6 15093,30 ... |
     | 157 | LINESTRING(30128.2 15011,30113.2 15010.2,30113.6 15000.4, ... |
     +-----+---------------------------------------------------------------+
     20 rows in set (0.00 sec)

Use *Note `EXPLAIN': explain. to check the way this query is executed:


     mysql> SET @poly =
         -> 'Polygon((30000 15000,
                      31000 15000,
                      31000 16000,
                      30000 16000,
                      30000 15000))';
     mysql> EXPLAIN SELECT fid,AsText(g) FROM geom WHERE
         -> MBRContains(GeomFromText(@poly),g)\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: geom
              type: range
     possible_keys: g
               key: g
           key_len: 32
               ref: NULL
              rows: 50
             Extra: Using where
     1 row in set (0.00 sec)

Check what would happen without a spatial index:


     mysql> SET @poly =
         -> 'Polygon((30000 15000,
                      31000 15000,
                      31000 16000,
                      30000 16000,
                      30000 15000))';
     mysql> EXPLAIN SELECT fid,AsText(g) FROM g IGNORE INDEX (g) WHERE
         -> MBRContains(GeomFromText(@poly),g)\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: geom
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: 32376
             Extra: Using where
     1 row in set (0.00 sec)

Executing the *Note `SELECT': select. statement without the spatial
index yields the same result but causes the execution time to rise from
0.00 seconds to 0.46 seconds:


     mysql> SET @poly =
         -> 'Polygon((30000 15000,
                      31000 15000,
                      31000 16000,
                      30000 16000,
                      30000 15000))';
     mysql> SELECT fid,AsText(g) FROM geom IGNORE INDEX (g) WHERE
         -> MBRContains(GeomFromText(@poly),g);
     +-----+---------------------------------------------------------------+
     | fid | AsText(g)                                                     |
     +-----+---------------------------------------------------------------+
     |   1 | LINESTRING(30250.4 15129.2,30248.8 15138.4,30238.2 15136. ... |
     |   2 | LINESTRING(30220.2 15122.8,30217.2 15137.8,30207.6 15136, ... |
     |   3 | LINESTRING(30179 15114.4,30176.6 15129.4,30167 15128,3016 ... |
     |   4 | LINESTRING(30155.2 15121.4,30140.4 15118.6,30142 15109,30 ... |
     |   5 | LINESTRING(30192.4 15085,30177.6 15082.2,30179.2 15072.4, ... |
     |   6 | LINESTRING(30244 15087,30229 15086.2,30229.4 15076.4,3024 ... |
     |   7 | LINESTRING(30200.6 15059.4,30185.6 15058.6,30186 15048.8, ... |
     |  10 | LINESTRING(30179.6 15017.8,30181 15002.8,30190.8 15003.6, ... |
     |  11 | LINESTRING(30154.2 15000.4,30168.6 15004.8,30166 15014.2, ... |
     |  13 | LINESTRING(30105 15065.8,30108.4 15050.8,30118 15053,3011 ... |
     |  21 | LINESTRING(30350.4 15828.8,30350.6 15845,30333.8 15845,30 ... |
     |  22 | LINESTRING(30350.6 15871.4,30350.6 15887.8,30334 15887.8, ... |
     |  23 | LINESTRING(30350.6 15914.2,30350.6 15930.4,30334 15930.4, ... |
     |  24 | LINESTRING(30290.2 15823,30290.2 15839.4,30273.4 15839.4, ... |
     |  25 | LINESTRING(30291.4 15866.2,30291.6 15882.4,30274.8 15882. ... |
     |  26 | LINESTRING(30291.6 15918.2,30291.6 15934.4,30275 15934.4, ... |
     | 154 | LINESTRING(30276.2 15143.8,30261.4 15141,30263 15131.4,30 ... |
     | 155 | LINESTRING(30269.8 15084,30269.4 15093.4,30258.6 15093,30 ... |
     | 157 | LINESTRING(30128.2 15011,30113.2 15010.2,30113.6 15000.4, ... |
     | 249 | LINESTRING(30337.8 15938.6,30337.8 15946.8,30320.4 15946. ... |
     +-----+---------------------------------------------------------------+
     20 rows in set (0.46 sec)


File: manual.info,  Node: data-type-defaults,  Next: storage-requirements,  Prev: spatial-extensions,  Up: data-types

11.6 Data Type Default Values
=============================

The `DEFAULT VALUE' clause in a data type specification indicates a
default value for a column. With one exception, the default value must
be a constant; it cannot be a function or an expression. This means,
for example, that you cannot set the default for a date column to be
the value of a function such as `NOW()' or `CURRENT_DATE'. The
exception is that you can specify `CURRENT_TIMESTAMP' as the default
for a *Note `TIMESTAMP': datetime.  column. See *Note
timestamp-initialization::.

*Note `BLOB': blob. and *Note `TEXT': blob. columns cannot be assigned a
default value.

If a column definition includes no explicit `DEFAULT' value, MySQL
determines the default value as follows:

If the column can take `NULL' as a value, the column is defined with an
explicit `DEFAULT NULL' clause.

If the column cannot take `NULL' as the value, MySQL defines the column
with no explicit `DEFAULT' clause. Exception: If the column is defined
as part of a `PRIMARY KEY' but not explicitly as `NOT NULL', MySQL
creates it as a `NOT NULL' column (because `PRIMARY KEY' columns must
be `NOT NULL'), but also assigns it a `DEFAULT' clause using the
implicit default value. To prevent this, include an explicit `NOT NULL'
in the definition of any `PRIMARY KEY' column.

For data entry into a `NOT NULL' column that has no explicit `DEFAULT'
clause, if an *Note `INSERT': insert. or *Note `REPLACE': replace.
statement includes no value for the column, or an *Note `UPDATE':
update.  statement sets the column to `NULL', MySQL handles the column
according to the SQL mode in effect at the time:

   * If strict SQL mode is enabled, an error occurs for transactional
     tables and the statement is rolled back. For nontransactional
     tables, an error occurs, but if this happens for the second or
     subsequent row of a multiple-row statement, the preceding rows
     will have been inserted.

   * If strict mode is not enabled, MySQL sets the column to the
     implicit default value for the column data type.

Suppose that a table `t' is defined as follows:


     CREATE TABLE t (i INT NOT NULL);

In this case, `i' has no explicit default, so in strict mode each of
the following statements produce an error and no row is inserted. When
not using strict mode, only the third statement produces an error; the
implicit default is inserted for the first two statements, but the
third fails because `DEFAULT(i)' cannot produce a value:


     INSERT INTO t VALUES();
     INSERT INTO t VALUES(DEFAULT);
     INSERT INTO t VALUES(DEFAULT(i));

See *Note sql-mode::.

For a given table, you can use the *Note `SHOW CREATE TABLE':
show-create-table. statement to see which columns have an explicit
`DEFAULT' clause.

Implicit defaults are defined as follows:

   * For numeric types, the default is `0', with the exception that for
     integer or floating-point types declared with the `AUTO_INCREMENT'
     attribute, the default is the next value in the sequence.

   * For date and time types other than *Note `TIMESTAMP': datetime,
     the default is the appropriate `zero' value for the type. For the
     first *Note `TIMESTAMP': datetime. column in a table, the default
     value is the current date and time. See *Note
     date-and-time-types::.

   * For string types other than *Note `ENUM': enum, the default value
     is the empty string. For *Note `ENUM': enum, the default is the
     first enumeration value.

`SERIAL DEFAULT VALUE' in the definition of an integer column is an
alias for `NOT NULL AUTO_INCREMENT UNIQUE'.


File: manual.info,  Node: storage-requirements,  Next: choosing-types,  Prev: data-type-defaults,  Up: data-types

11.7 Data Type Storage Requirements
===================================

The storage requirements for data vary, according to the storage engine
being used for the table in question. Different storage engines use
different methods for recording the raw data and different data types.
In addition, some engines may compress the information in a given row,
either on a column or entire row basis, making calculation of the
storage requirements for a given table or column structure.

However, all storage engines must communicate and exchange information
on a given row within a table using the same structure, and this
information is consistent, irrespective of the storage engine used to
write the information to disk.

This sections includes some guideliness and information for the storage
requirements for each data type supported by MySQL, including details
for the internal format and the sizes used by storage engines that used
a fixed size representation for different types. Information is listed
by category or storage engine.

The internal representation of a table has a maximum row size of 65,535
bytes, even if the storage engine is capable of supporting larger rows.
This figure excludes *Note `BLOB': blob. or *Note `TEXT': blob.
columns, which contribute only 9 to 12 bytes toward this size. For
*Note `BLOB': blob. and `TEXT' data, the information is stored
internally in a different area of memory than the row buffer. Different
storage engines handle the allocation and storage of this data in
different ways, according to the method they use for handling the
corresponding types. For more information, see *Note storage-engines::,
and *Note column-count-limit::.

*Storage Requirements for InnoDB Tables*

See *Note innodb-physical-record:: for information about storage
requirements for `InnoDB' tables.

*Storage Requirements for NDBCLUSTER Tables*

*Important*:

For tables using the *Note `NDBCLUSTER': mysql-cluster.  storage
engine, there is the factor of _4-byte alignment_ to be taken into
account when calculating storage requirements. This means that all
*Note `NDB': mysql-cluster. data storage is done in multiples of 4
bytes. Thus, a column value that would take 15 bytes in a table using a
storage engine other than *Note `NDB': mysql-cluster. requires 16 bytes
in an *Note `NDB': mysql-cluster. table. This requirement applies in
addition to any other considerations that are discussed in this
section. For example, in *Note `NDBCLUSTER': mysql-cluster. tables, the
*Note `TINYINT': integer-types, *Note `SMALLINT': integer-types, *Note
`MEDIUMINT': integer-types, and *Note `INTEGER': integer-types.  (*Note
`INT': integer-types.) column types each require 4 bytes storage per
record due to the alignment factor.

An exception to this rule is the *Note `BIT': bit-type. type, which is
_not_ 4-byte aligned. In MySQL Cluster tables, a `BIT(M)' column takes
M bits of storage space.  However, if a table definition contains 1 or
more *Note `BIT': bit-type. columns (up to 32 *Note `BIT': bit-type.
columns), then *Note `NDBCLUSTER': mysql-cluster. reserves 4 bytes (32
bits) per row for these. If a table definition contains more than 32
*Note `BIT': bit-type. columns (up to 64 such columns), then *Note
`NDBCLUSTER': mysql-cluster.  reserves 8 bytes (that is, 64 bits) per
row.

In addition, while a `NULL' itself does not require any storage space,
*Note `NDBCLUSTER': mysql-cluster. reserves 4 bytes per row if the
table definition contains any columns defined as `NULL', up to 32 `NULL'
columns. (If a MySQL Cluster table is defined with more than 32 `NULL'
columns up to 64 `NULL' columns, then 8 bytes per row is reserved.)

When calculating storage requirements for MySQL Cluster tables, you
must also remember that every table using the *Note `NDBCLUSTER':
mysql-cluster. storage engine requires a primary key; if no primary key
is defined by the user, then a `hidden' primary key will be created by
*Note `NDB': mysql-cluster. This hidden primary key consumes 31-35
bytes per table record.

You may find the `ndb_size.pl' utility to be useful for estimating
*Note `NDB': mysql-cluster. storage requirements. This Perl script
connects to a current MySQL (non-Cluster) database and creates a report
on how much space that database would require if it used the *Note
`NDBCLUSTER': mysql-cluster. storage engine. See *Note
mysql-cluster-programs-ndb-size-pl::, for more information.

*Storage Requirements for Numeric Types*

This table shows storage required for numeric data types.

Data Type                     Storage Required
*Note `TINYINT':              1 byte
integer-types.                
*Note `SMALLINT':             2 bytes
integer-types.                
*Note `MEDIUMINT':            3 bytes
integer-types.                
*Note `INT': integer-types,   4 bytes
*Note `INTEGER':              
integer-types.                
*Note `BIGINT':               8 bytes
integer-types.                
`FLOAT(P)'                    4 bytes if 0 <= P <= 24, 8 bytes if 25 <=
                              P <= 53
*Note `FLOAT':                4 bytes
floating-point-types.         
`DOUBLE [PRECISION]', *Note   8 bytes
`REAL': floating-point-types. 
`DECIMAL(M,D)',               Varies; see following discussion
`NUMERIC(M,D)'                
`BIT(M)'                      approximately (M+7)/8 bytes

Values for *Note `DECIMAL': fixed-point-types. (and *Note `NUMERIC':
fixed-point-types.) columns are represented using a binary format that
packs nine decimal (base 10) digits into four bytes. Storage for the
integer and fractional parts of each value are determined separately.
Each multiple of nine digits requires four bytes, and the `leftover'
digits require some fraction of four bytes. The storage required for
excess digits is given by the following table.

This table shows storage required by excess/leftover digits.

Leftover Digits    Number of Bytes
0                  0
1                  1
2                  1
3                  2
4                  2
5                  3
6                  3
7                  4
8                  4

*Storage Requirements for Date and Time Types*

This table shows storage required for date and time types.

Data Type                     Storage Required
*Note `DATE': datetime.       3 bytes
*Note `TIME': time.           3 bytes
*Note `DATETIME': datetime.   8 bytes
*Note `TIMESTAMP': datetime.  4 bytes
*Note `YEAR': year.           1 byte

For details about internal representation of temporal values, see MySQL
Internals: Important Algorithms and Structures
(http://dev.mysql.com/doc/internals/en/algorithms.html).

*Storage Requirements for String Types*

In the following table, M represents the declared column length in
characters for nonbinary string types and bytes for binary string types.
L represents the actual length in bytes of a given string value.

This table shows storage required for string types.

Data Type                     Storage Required
`CHAR(M)'                     M x W bytes, 0 `<= M <=' 255, where W is
                              the number of bytes required for the
                              maximum-length character in the character
                              set. See *Note innodb-physical-record::
                              for information about `CHAR' data type
                              storage requirements for `InnoDB' tables.
`BINARY(M)'                   M bytes, 0 `<= M <=' 255
`VARCHAR(M)', `VARBINARY(M)'  L + 1 bytes if column values require 0 -
                              255 bytes, L + 2 bytes if values may
                              require more than 255 bytes
*Note `TINYBLOB': blob,       L + 1 bytes, where L < 2^8
*Note `TINYTEXT': blob.       
*Note `BLOB': blob, *Note     L + 2 bytes, where L < 2^16
`TEXT': blob.                 
*Note `MEDIUMBLOB': blob,     L + 3 bytes, where L < 2^24
*Note `MEDIUMTEXT': blob.     
*Note `LONGBLOB': blob,       L + 4 bytes, where L < 2^32
*Note `LONGTEXT': blob.       
`ENUM('VALUE1','VALUE2',...)' 1 or 2 bytes, depending on the number of
                              enumeration values (65,535 values maximum)
`SET('VALUE1','VALUE2',...)'  1, 2, 3, 4, or 8 bytes, depending on the
                              number of set members (64 members maximum)

Variable-length string types are stored using a length prefix plus
data. The length prefix requires from one to four bytes depending on
the data type, and the value of the prefix is L (the byte length of the
string). For example, storage for a *Note `MEDIUMTEXT': blob.  value
requires L bytes to store the value plus three bytes to store the
length of the value.

To calculate the number of bytes used to store a particular *Note
`CHAR': char, *Note `VARCHAR': char, or *Note `TEXT': blob. column
value, you must take into account the character set used for that
column and whether the value contains multibyte characters. In
particular, when using the `utf8' Unicode character set, you must keep
in mind that not all characters use the same number of bytes and can
require up to three bytes per character. For a breakdown of the storage
used for different categories of `utf8' characters, see *Note
charset-unicode::.

*Note `VARCHAR': char, *Note `VARBINARY': binary-varbinary, and the
*Note `BLOB': blob. and *Note `TEXT': blob. types are variable-length
types. For each, the storage requirements depend on these factors:

   * The actual length of the column value

   * The column's maximum possible length

   * The character set used for the column, because some character sets
     contain multibyte characters

For example, a `VARCHAR(255)' column can hold a string with a maximum
length of 255 characters. Assuming that the column uses the `latin1'
character set (one byte per character), the actual storage required is
the length of the string (L), plus one byte to record the length of the
string. For the string `'abcd'', L is 4 and the storage requirement is
five bytes. If the same column is instead declared to use the `ucs2'
double-byte character set, the storage requirement is 10 bytes: The
length of `'abcd'' is eight bytes and the column requires two bytes to
store lengths because the maximum length is greater than 255 (up to 510
bytes).

The effective maximum number of _bytes_ that can be stored in a *Note
`VARCHAR': char. or *Note `VARBINARY': binary-varbinary. column is
subject to the maximum row size of 65,535 bytes, which is shared among
all columns. For a *Note `VARCHAR': char. column that stores multibyte
characters, the effective maximum number of _characters_ is less. For
example, `utf8' characters can require up to three bytes per character,
so a *Note `VARCHAR': char. column that uses the `utf8' character set
can be declared to be a maximum of 21,844 characters. See *Note
column-count-limit::.

The *Note `NDBCLUSTER': mysql-cluster. storage engine in MySQL 5.1
supports variable-width columns. This means that a *Note `VARCHAR':
char. column in a MySQL Cluster table requires the same amount of
storage as it would using any other storage engine, with the exception
that such values are 4-byte aligned. Thus, the string `'abcd'' stored
in a `VARCHAR(50)' column using the `latin1' character set requires 8
bytes (rather than 6 bytes for the same column value in a `MyISAM'
table). This represents a change in behavior from earlier versions of
*Note `NDBCLUSTER': mysql-cluster, where a `VARCHAR(50)' column would
require 52 bytes storage per record regardless of the length of the
string being stored.

*Note `TEXT': blob. and *Note `BLOB': blob. columns are implemented
differently in the NDB Cluster storage engine, wherein each row in a
*Note `TEXT': blob. column is made up of two separate parts. One of
these is of fixed size (256 bytes), and is actually stored in the
original table. The other consists of any data in excess of 256 bytes,
which is stored in a hidden table.  The rows in this second table are
always 2,000 bytes long. This means that the size of a *Note `TEXT':
blob.  column is 256 if SIZE <= 256 (where SIZE represents the size of
the row); otherwise, the size is 256 + SIZE + (2000 - (SIZE - 256) %
2000).

The size of an *Note `ENUM': enum. object is determined by the number
of different enumeration values. One byte is used for enumerations with
up to 255 possible values. Two bytes are used for enumerations having
between 256 and 65,535 possible values. See *Note enum::.

The size of a *Note `SET': set. object is determined by the number of
different set members. If the set size is N, the object occupies
`(N+7)/8' bytes, rounded up to 1, 2, 3, 4, or 8 bytes. A *Note `SET':
set. can have a maximum of 64 members. See *Note set::.


File: manual.info,  Node: choosing-types,  Next: other-vendor-data-types,  Prev: storage-requirements,  Up: data-types

11.8 Choosing the Right Type for a Column
=========================================

For optimum storage, you should try to use the most precise type in all
cases. For example, if an integer column is used for values in the
range from `1' to `99999', `MEDIUMINT UNSIGNED' is the best type. Of
the types that represent all the required values, this type uses the
least amount of storage.

All basic calculations (`+', `-', `*', and `/') with *Note `DECIMAL':
fixed-point-types.  columns are done with precision of 65 decimal (base
10) digits.  See *Note numeric-type-overview::.

If accuracy is not too important or if speed is the highest priority,
the *Note `DOUBLE': floating-point-types. type may be good enough. For
high precision, you can always convert to a fixed-point type stored in a
*Note `BIGINT': integer-types. This enables you to do all calculations
with 64-bit integers and then convert results back to floating-point
values as necessary.

`PROCEDURE ANALYSE' can be used to obtain suggestions for optimal
column data types. For more information, see *Note procedure-analyse::.


File: manual.info,  Node: other-vendor-data-types,  Prev: choosing-types,  Up: data-types

11.9 Using Data Types from Other Database Engines
=================================================

To facilitate the use of code written for SQL implementations from
other vendors, MySQL maps data types as shown in the following table.
These mappings make it easier to import table definitions from other
database systems into MySQL.

This table provides a mapping of MySQL data types to data types from
other vendors.

Other Vendor Type         MySQL Type
*Note `BOOL':             *Note `TINYINT': integer-types.
integer-types.            
*Note `BOOLEAN':          *Note `TINYINT': integer-types.
integer-types.            
`CHARACTER VARYING(M)'    `VARCHAR(M)'
*Note `FIXED':            *Note `DECIMAL': fixed-point-types.
fixed-point-types.        
*Note `FLOAT4':           *Note `FLOAT': floating-point-types.
floating-point-types.     
*Note `FLOAT8':           *Note `DOUBLE': floating-point-types.
floating-point-types.     
*Note `INT1':             *Note `TINYINT': integer-types.
integer-types.            
*Note `INT2':             *Note `SMALLINT': integer-types.
integer-types.            
*Note `INT3':             *Note `MEDIUMINT': integer-types.
integer-types.            
*Note `INT4':             *Note `INT': integer-types.
integer-types.            
`INT8'                    *Note `BIGINT': integer-types.
`LONG VARBINARY'          *Note `MEDIUMBLOB': blob.
`LONG VARCHAR'            *Note `MEDIUMTEXT': blob.
`LONG'                    *Note `MEDIUMTEXT': blob.
*Note `MIDDLEINT':        *Note `MEDIUMINT': integer-types.
integer-types.            
*Note `NUMERIC':          *Note `DECIMAL': fixed-point-types.
fixed-point-types.        

Data type mapping occurs at table creation time, after which the
original type specifications are discarded. If you create a table with
types used by other vendors and then issue a `DESCRIBE TBL_NAME'
statement, MySQL reports the table structure using the equivalent MySQL
types. For example:


     mysql> CREATE TABLE t (a BOOL, b FLOAT8, c LONG VARCHAR, d NUMERIC);
     Query OK, 0 rows affected (0.00 sec)

     mysql> DESCRIBE t;
     +-------+---------------+------+-----+---------+-------+
     | Field | Type          | Null | Key | Default | Extra |
     +-------+---------------+------+-----+---------+-------+
     | a     | tinyint(1)    | YES  |     | NULL    |       |
     | b     | double        | YES  |     | NULL    |       |
     | c     | mediumtext    | YES  |     | NULL    |       |
     | d     | decimal(10,0) | YES  |     | NULL    |       |
     +-------+---------------+------+-----+---------+-------+
     4 rows in set (0.01 sec)


File: manual.info,  Node: functions,  Next: sql-syntax,  Prev: data-types,  Up: Top

12 Functions and Operators
**************************

* Menu:

* func-op-summary-ref::          Function and Operator Reference
* type-conversion::              Type Conversion in Expression Evaluation
* non-typed-operators::          Operators
* control-flow-functions::       Control Flow Functions
* string-functions::             String Functions
* numeric-functions::            Numeric Functions and Operators
* date-and-time-functions::      Date and Time Functions
* mysql-calendar::               What Calendar Is Used By MySQL?
* fulltext-search::              Full-Text Search Functions
* cast-functions::               Cast Functions and Operators
* xml-functions::                XML Functions
* bit-functions::                Bit Functions
* encryption-functions::         Encryption and Compression Functions
* information-functions::        Information Functions
* spatial-analysis-functions::   Spatial Analysis Functions
* miscellaneous-functions::      Miscellaneous Functions
* group-by-functions-and-modifiers::  Functions and Modifiers for Use with GROUP BY Clauses
* precision-math::               Precision Math

Expressions can be used at several points in SQL
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_sql)
statements, such as in the `ORDER BY' or `HAVING' clauses of *Note
`SELECT': select. statements, in the `WHERE' clause of a *Note
`SELECT': select, *Note `DELETE': delete, or *Note `UPDATE': update.
statement, or in *Note `SET': set-statement.  statements. Expressions
can be written using literal values, column values, `NULL', built-in
functions, stored functions, user-defined functions, and operators.
This chapter describes the functions and operators that are permitted
for writing expressions in MySQL. Instructions for writing stored
functions and user-defined functions are given in *Note
stored-routines::, and *Note adding-functions::. See *Note
function-resolution::, for the rules describing how the server
interprets references to different kinds of functions.

An expression that contains `NULL' always produces a `NULL' value
unless otherwise indicated in the documentation for a particular
function or operator.

*Note*:

By default, there must be no whitespace between a function name and the
parenthesis following it. This helps the MySQL parser distinguish
between function calls and references to tables or columns that happen
to have the same name as a function. However, spaces around function
arguments are permitted.

You can tell the MySQL server to accept spaces after function names by
starting it with the `--sql-mode=IGNORE_SPACE' option. (See *Note
sql-mode::.) Individual client programs can request this behavior by
using the `CLIENT_IGNORE_SPACE' option for *Note
`mysql_real_connect()': mysql-real-connect. In either case, all
function names become reserved words.

For the sake of brevity, most examples in this chapter display the
output from the *Note `mysql': mysql. program in abbreviated form.
Rather than showing examples in this format:


     mysql> SELECT MOD(29,9);
     +-----------+
     | mod(29,9) |
     +-----------+
     |         2 |
     +-----------+
     1 rows in set (0.00 sec)

This format is used instead:


     mysql> SELECT MOD(29,9);
             -> 2


File: manual.info,  Node: func-op-summary-ref,  Next: type-conversion,  Prev: functions,  Up: functions

12.1 Function and Operator Reference
====================================

*Functions/Operators*

Name                          Description
`ABS()'                       Return the absolute value
`ACOS()'                      Return the arc cosine
`ADDDATE()'                   Add time values (intervals) to a date value
`ADDTIME()'                   Add time
`AES_DECRYPT()'               Decrypt using AES
`AES_ENCRYPT()'               Encrypt using AES
`AND', `&&'                   Logical AND
`Area()'                      Return Polygon or MultiPolygon area
`AsBinary()', `AsWKB()'       Convert from internal geometry format to
                              WKB
`ASCII()'                     Return numeric value of left-most character
`ASIN()'                      Return the arc sine
`='                           Assign a value (as part of a  *Note `SET':
                              set-statement. statement, or  as part of
                              the `SET' clause in an  *Note `UPDATE':
                              update. statement)
`:='                          Assign a value
`AsText()', `AsWKT()'         Convert from internal geometry format to
                              WKT
`ATAN2()', `ATAN()'           Return the arc tangent of the two arguments
`ATAN()'                      Return the arc tangent
`AVG()'                       Return the average value of the argument
`BENCHMARK()'                 Repeatedly execute an expression
`BETWEEN ... AND ...'         Check whether a value is within a range of
                              values
`BIN()'                       Return a string containing binary
                              representation of a number
`BINARY'                      Cast a string to a binary string
`BIT_AND()'                   Return bitwise and
`BIT_COUNT()'                 Return the number of bits that are set
`BIT_LENGTH()'                Return length of argument in bits
`BIT_OR()'                    Return bitwise or
`BIT_XOR()'                   Return bitwise xor
`&'                           Bitwise AND
`~'                           Invert bits
`|'                           Bitwise OR
`^'                           Bitwise XOR
`Boundary()'                  Return geometry boundary
`CASE'                        Case operator
`CAST()'                      Cast a value as a certain type
`CEIL()'                      Return the smallest integer value not less
                              than the argument
`CEILING()'                   Return the smallest integer value not less
                              than the argument
`Centroid()'                  Return centroid as a point
`CHAR_LENGTH()'               Return number of characters in argument
`CHAR()'                      Return the character for each integer
                              passed
`CHARACTER_LENGTH()'          Synonym for CHAR_LENGTH()
`CHARSET()'                   Return the character set of the argument
`COALESCE()'                  Return the first non-NULL argument
`COERCIBILITY()'              Return the collation coercibility value of
                              the string argument
`COLLATION()'                 Return the collation of the string argument
`COMPRESS()'                  Return result as a binary string
`CONCAT_WS()'                 Return concatenate with separator
`CONCAT()'                    Return concatenated string
`CONNECTION_ID()'             Return the connection ID (thread ID) for
                              the connection
`Contains()'                  Whether one geometry contains another
`CONV()'                      Convert numbers between different number
                              bases
`CONVERT_TZ()'                Convert from one timezone to another
`CONVERT()'                   Cast a value as a certain type
`COS()'                       Return the cosine
`COT()'                       Return the cotangent
`COUNT(DISTINCT)'             Return the count of a number of different
                              values
`COUNT()'                     Return a count of the number of rows
                              returned
`CRC32()'                     Compute a cyclic redundancy check value
`Crosses()'                   Whether one geometry crosses another
`CURDATE()'                   Return the current date
`CURRENT_DATE()',             Synonyms for CURDATE()
`CURRENT_DATE'                
`CURRENT_TIME()',             Synonyms for CURTIME()
`CURRENT_TIME'                
`CURRENT_TIMESTAMP()',        Synonyms for NOW()
`CURRENT_TIMESTAMP'           
`CURRENT_USER()',             The authenticated user name and host name
`CURRENT_USER'                
`CURTIME()'                   Return the current time
`DATABASE()'                  Return the default (current) database name
`DATE_ADD()'                  Add time values (intervals) to a date value
`DATE_FORMAT()'               Format date as specified
`DATE_SUB()'                  Subtract a time value (interval) from a
                              date
`DATE()'                      Extract the date part of a date or
                              datetime expression
`DATEDIFF()'                  Subtract two dates
`DAY()'                       Synonym for DAYOFMONTH()
`DAYNAME()'                   Return the name of the weekday
`DAYOFMONTH()'                Return the day of the month (0-31)
`DAYOFWEEK()'                 Return the weekday index of the argument
`DAYOFYEAR()'                 Return the day of the year (1-366)
`DECODE()'                    Decodes a string encrypted using ENCODE()
`DEFAULT()'                   Return the default value for a table column
`DEGREES()'                   Convert radians to degrees
`DES_DECRYPT()'               Decrypt a string
`DES_ENCRYPT()'               Encrypt a string
`Dimension()'                 Dimension of geometry
`Disjoint()'                  Whether one geometry is disjoint from
                              another
`DIV'                         Integer division
`/'                           Division operator
`ELT()'                       Return string at index number
`ENCODE()'                    Encode a string
`ENCRYPT()'                   Encrypt a string
`EndPoint()'                  End Point of LineString
`Envelope()'                  Return MBR of geometry
`<=>'                         NULL-safe equal to operator
`='                           Equal operator
`Equals()'                    Whether one geometry is equal to another
`EXP()'                       Raise to the power of
`EXPORT_SET()'                Return a string such that for every bit
                              set in the value bits, you  get an on
                              string and for every unset bit, you get an
                              off string
`ExteriorRing()'              Return exterior ring of Polygon
`EXTRACT()'                   Extract part of a date
`ExtractValue()'              Extracts a value from an XML string using
                              XPath notation
`FIELD()'                     Return the index (position) of the first
                              argument in the  subsequent arguments
`FIND_IN_SET()'               Return the index position of the first
                              argument within the second  argument
`FLOOR()'                     Return the largest integer value not
                              greater than the argument
`FORMAT()'                    Return a number formatted to specified
                              number of decimal places
`FOUND_ROWS()'                For a SELECT with a LIMIT clause, the
                              number of rows that would be  returned
                              were there no LIMIT clause
`FROM_DAYS()'                 Convert a day number to a date
`FROM_UNIXTIME()'             Format UNIX timestamp as a date
`GeomCollFromText()',         Return geometry collection from WKT
`GeometryCollectionFromText()'
`GeomCollFromWKB()',          Return geometry collection from WKB
`GeometryCollectionFromWKB()' 
`GeometryCollection()'        Construct geometry collection from
                              geometries
`GeometryN()'                 Return N-th geometry from geometry
                              collection
`GeometryType()'              Return name of geometry type
`GeomFromText()',             Return geometry from WKT
`GeometryFromText()'          
`GeomFromWKB()'               Return geometry from WKB
`GET_FORMAT()'                Return a date format string
`GET_LOCK()'                  Get a named lock
`GLength()'                   Return length of LineString
`>='                          Greater than or equal operator
`>'                           Greater than operator
`GREATEST()'                  Return the largest argument
`GROUP_CONCAT()'              Return a concatenated string
`HEX()'                       Return a hexadecimal representation of a
                              decimal or string value
`HOUR()'                      Extract the hour
`IF()'                        If/else construct
`IFNULL()'                    Null if/else construct
`IN()'                        Check whether a value is within a set of
                              values
`INET_ATON()'                 Return the numeric value of an IP address
`INET_NTOA()'                 Return the IP address from a numeric value
`INSERT()'                    Insert a substring at the specified
                              position up to the specified  number of
                              characters
`INSTR()'                     Return the index of the first occurrence
                              of substring
`InteriorRingN()'             Return N-th interior ring of Polygon
`Intersects()'                Whether one geometry intersects another
`INTERVAL()'                  Return the index of the argument that is
                              less than the first  argument
`IS_FREE_LOCK()'              Checks whether the named lock is free
`IS NOT NULL'                 NOT NULL value test
`IS NOT'                      Test a value against a boolean
`IS NULL'                     NULL value test
`IS_USED_LOCK()'              Checks whether the named lock is in use.
                              Return connection  identifier if true.
`IS'                          Test a value against a boolean
`IsClosed()'                  Whether a geometry is closed and simple
`IsEmpty()'                   Placeholder function
`ISNULL()'                    Test whether the argument is NULL
`IsSimple()'                  Whether a geometry is simple
`LAST_DAY'                    Return the last day of the month for the
                              argument
`LAST_INSERT_ID()'            Value of the AUTOINCREMENT column for the
                              last INSERT
`LCASE()'                     Synonym for LOWER()
`LEAST()'                     Return the smallest argument
`<<'                          Left shift
`LEFT()'                      Return the leftmost number of characters
                              as specified
`LENGTH()'                    Return the length of a string in bytes
`<='                          Less than or equal operator
`<'                           Less than operator
`LIKE'                        Simple pattern matching
`LineFromText()'              Construct LineString from WKT
`LineFromWKB()',              Construct LineString from WKB
`LineStringFromWKB()'         
`LineString()'                Construct LineString from Point values
`LN()'                        Return the natural logarithm of the
                              argument
`LOAD_FILE()'                 Load the named file
`LOCALTIME()', `LOCALTIME'    Synonym for NOW()
`LOCALTIMESTAMP',             Synonym for NOW()
`LOCALTIMESTAMP()'            
`LOCATE()'                    Return the position of the first
                              occurrence of substring
`LOG10()'                     Return the base-10 logarithm of the
                              argument
`LOG2()'                      Return the base-2 logarithm of the argument
`LOG()'                       Return the natural logarithm of the first
                              argument
`LOWER()'                     Return the argument in lowercase
`LPAD()'                      Return the string argument, left-padded
                              with the specified string
`LTRIM()'                     Remove leading spaces
`MAKE_SET()'                  Return a set of comma-separated strings
                              that have the  corresponding bit in bits
                              set
`MAKEDATE()'                  Create a date from the year and day of year
`MAKETIME()'                  Create time from hour, minute, second
`MASTER_POS_WAIT()'           Block until the slave has read and applied
                              all updates up to the  specified position
`MATCH'                       Perform full-text search
`MAX()'                       Return the maximum value
`MBRContains()'               Whether MBR of one geometry contains MBR
                              of another
`MBRDisjoint()'               Whether MBRs of two geometries are disjoint
`MBREqual()'                  Whether MBRs of two geometries are equal
`MBRIntersects()'             Whether MBRs of two geometries intersect
`MBROverlaps()'               Whether MBRs of two geometries overlap
`MBRTouches()'                Whether MBRs of two geometries touch
`MBRWithin()'                 Whether MBR of one geometry is within MBR
                              of another
`MD5()'                       Calculate MD5 checksum
`MICROSECOND()'               Return the microseconds from argument
`MID()'                       Return a substring starting from the
                              specified position
`MIN()'                       Return the minimum value
`-'                           Minus operator
`MINUTE()'                    Return the minute from the argument
`MLineFromText()',            Construct MultiLineString from WKT
`MultiLineStringFromText()'   
`MLineFromWKB()',             Construct MultiLineString from WKB
`MultiLineStringFromWKB()'    
`MOD()'                       Return the remainder
`% or MOD'                    Modulo operator
`MONTH()'                     Return the month from the date passed
`MONTHNAME()'                 Return the name of the month
`MPointFromText()',           Construct MultiPoint from WKT
`MultiPointFromText()'        
`MPointFromWKB()',            Construct MultiPoint from WKB
`MultiPointFromWKB()'         
`MPolyFromText()',            Construct MultiPolygon from WKT
`MultiPolygonFromText()'      
`MPolyFromWKB()',             Construct MultiPolygon from WKB
`MultiPolygonFromWKB()'       
`MultiLineString()'           Contruct MultiLineString from LineString
                              values
`MultiPoint()'                Construct MultiPoint from Point values
`MultiPolygon()'              Construct MultiPolygon from Polygon values
`NAME_CONST()'                Causes the column to have the given name
`NOT BETWEEN ... AND ...'     Check whether a value is not within a
                              range of values
`!=', `<>'                    Not equal operator
`NOT IN()'                    Check whether a value is not within a set
                              of values
`NOT LIKE'                    Negation of simple pattern matching
`NOT REGEXP'                  Negation of REGEXP
`NOT', `!'                    Negates value
`NOW()'                       Return the current date and time
`NULLIF()'                    Return NULL if expr1 = expr2
`NumGeometries()'             Return number of geometries in geometry
                              collection
`NumInteriorRings()'          Return number of interior rings in Polygon
`NumPoints()'                 Return number of points in LineString
`OCT()'                       Return a string containing octal
                              representation of a number
`OCTET_LENGTH()'              Synonym for LENGTH()
`OLD_PASSWORD()'(deprecated   Return the value of the pre-4.1
5.6.5)                        implementation of PASSWORD
`||', `OR'                    Logical OR
`ORD()'                       Return character code for leftmost
                              character of the argument
`Overlaps()'                  Whether one geometry overlaps another
`PASSWORD()'                  Calculate and return a password string
`PERIOD_ADD()'                Add a period to a year-month
`PERIOD_DIFF()'               Return the number of months between periods
`PI()'                        Return the value of pi
`+'                           Addition operator
`Point()'                     Construct Point from coordinates
`PointFromText()'             Construct Point from WKT
`PointFromWKB()'              Construct Point from WKB
`PointN()'                    Return N-th point from LineString
`PolyFromText()',             Construct Polygon from WKT
`PolygonFromText()'           
`PolyFromWKB()',              Construct Polygon from WKB
`PolygonFromWKB()'            
`Polygon()'                   Construct Polygon from LineString arguments
`POSITION()'                  Synonym for LOCATE()
`POW()'                       Return the argument raised to the
                              specified power
`POWER()'                     Return the argument raised to the
                              specified power
*Note `PROCEDURE ANALYSE()':  Analyze the results of a query
procedure-analyse.            
`QUARTER()'                   Return the quarter from a date argument
`QUOTE()'                     Escape the argument for use in an SQL
                              statement
`RADIANS()'                   Return argument converted to radians
`RAND()'                      Return a random floating-point value
`REGEXP'                      Pattern matching using regular expressions
`RELEASE_LOCK()'              Releases the named lock
`REPEAT()'                    Repeat a string the specified number of
                              times
`REPLACE()'                   Replace occurrences of a specified string
`REVERSE()'                   Reverse the characters in a string
`>>'                          Right shift
`RIGHT()'                     Return the specified rightmost number of
                              characters
`RLIKE'                       Synonym for REGEXP
`ROUND()'                     Round the argument
`ROW_COUNT()'                 The number of rows updated
`RPAD()'                      Append string the specified number of times
`RTRIM()'                     Remove trailing spaces
`SCHEMA()'                    Synonym for DATABASE()
`SEC_TO_TIME()'               Converts seconds to 'HH:MM:SS' format
`SECOND()'                    Return the second (0-59)
`SESSION_USER()'              Synonym for USER()
`SHA1()', `SHA()'             Calculate an SHA-1 160-bit checksum
`SIGN()'                      Return the sign of the argument
`SIN()'                       Return the sine of the argument
`SLEEP()'                     Sleep for a number of seconds
`SOUNDEX()'                   Return a soundex string
`SOUNDS LIKE'                 Compare sounds
`SPACE()'                     Return a string of the specified number of
                              spaces
`SQRT()'                      Return the square root of the argument
`SRID()'                      Return spatial reference system ID for
                              geometry
`StartPoint()'                Start Point of LineString
`STD()'                       Return the population standard deviation
`STDDEV_POP()'                Return the population standard deviation
`STDDEV_SAMP()'               Return the sample standard deviation
`STDDEV()'                    Return the population standard deviation
`STR_TO_DATE()'               Convert a string to a date
`STRCMP()'                    Compare two strings
`SUBDATE()'                   Synonym for DATE_SUB() when invoked with
                              three arguments
`SUBSTR()'                    Return the substring as specified
`SUBSTRING_INDEX()'           Return a substring from a string before
                              the specified number of  occurrences of
                              the delimiter
`SUBSTRING()'                 Return the substring as specified
`SUBTIME()'                   Subtract times
`SUM()'                       Return the sum
`SYSDATE()'                   Return the time at which the function
                              executes
`SYSTEM_USER()'               Synonym for USER()
`TAN()'                       Return the tangent of the argument
`TIME_FORMAT()'               Format as time
`TIME_TO_SEC()'               Return the argument converted to seconds
`TIME()'                      Extract the time portion of the expression
                              passed
`TIMEDIFF()'                  Subtract time
`*'                           Multiplication operator
`TIMESTAMP()'                 With a single argument, this function
                              returns the date or datetime  expression;
                              with two arguments, the sum of the
                              arguments
`TIMESTAMPADD()'              Add an interval to a datetime expression
`TIMESTAMPDIFF()'             Subtract an interval from a datetime
                              expression
`TO_DAYS()'                   Return the date argument converted to days
`Touches()'                   Whether one geometry touches another
`TRIM()'                      Remove leading and trailing spaces
`TRUNCATE()'                  Truncate to specified number of decimal
                              places
`UCASE()'                     Synonym for UPPER()
`-'                           Change the sign of the argument
`UNCOMPRESS()'                Uncompress a string compressed
`UNCOMPRESSED_LENGTH()'       Return the length of a string before
                              compression
`UNHEX()'                     Return a string containing hex
                              representation of a number
`UNIX_TIMESTAMP()'            Return a UNIX timestamp
`UpdateXML()'                 Return replaced XML fragment
`UPPER()'                     Convert to uppercase
`USER()'                      The user name and host name provided by
                              the client
`UTC_DATE()'                  Return the current UTC date
`UTC_TIME()'                  Return the current UTC time
`UTC_TIMESTAMP()'             Return the current UTC date and time
`UUID_SHORT()'                Return an integer-valued universal
                              identifier
`UUID()'                      Return a Universal Unique Identifier (UUID)
`VALUES()'                    Defines the values to be used during an
                              INSERT
`VAR_POP()'                   Return the population standard variance
`VAR_SAMP()'                  Return the sample variance
`VARIANCE()'                  Return the population standard variance
`VERSION()'                   Return a string that indicates the MySQL
                              server version
`WEEK()'                      Return the week number
`WEEKDAY()'                   Return the weekday index
`WEEKOFYEAR()'                Return the calendar week of the date (0-53)
`Within()'                    Whether one geometry is within another
`X()'                         Return X coordinate of Point
`XOR'                         Logical XOR
`Y()'                         Return Y coordinate of Point
`YEAR()'                      Return the year
`YEARWEEK()'                  Return the year and week


File: manual.info,  Node: type-conversion,  Next: non-typed-operators,  Prev: func-op-summary-ref,  Up: functions

12.2 Type Conversion in Expression Evaluation
=============================================

When an operator is used with operands of different types, type
conversion occurs to make the operands compatible. Some conversions
occur implicitly. For example, MySQL automatically converts numbers to
strings as necessary, and vice versa.


     mysql> SELECT 1+'1';
             -> 2
     mysql> SELECT CONCAT(2,' test');
             -> '2 test'

It is also possible to convert a number to a string explicitly using
the `CAST()' function.  Conversion occurs implicitly with the
`CONCAT()' function because it expects string arguments.


     mysql> SELECT 38.8, CAST(38.8 AS CHAR);
             -> 38.8, '38.8'
     mysql> SELECT 38.8, CONCAT(38.8);
             -> 38.8, '38.8'

See later in this section for information about the character set of
implicit number-to-string conversions, and for modified rules that
apply to `CREATE TABLE ... SELECT' statements.

The following rules describe how conversion occurs for comparison
operations:

   * If one or both arguments are `NULL', the result of the comparison
     is `NULL', except for the `NULL'-safe `<=>' equality comparison
     operator. For `NULL <=> NULL', the result is true. No conversion
     is needed.

   * If both arguments in a comparison operation are strings, they are
     compared as strings.

   * If both arguments are integers, they are compared as integers.

   * Hexadecimal values are treated as binary strings if not compared
     to a number.

   * If one of the arguments is a *Note `TIMESTAMP': datetime. or *Note
     `DATETIME': datetime. column and the other argument is a constant,
     the constant is converted to a timestamp before the comparison is
     performed. This is done to be more ODBC-friendly. Note that this
     is not done for the arguments to `IN()'! To be safe, always use
     complete datetime, date, or time strings when doing comparisons.
     For example, to achieve best results when using `BETWEEN' with
     date or time values, use `CAST()' to explicitly convert the values
     to the desired data type.

   * If one of the arguments is a decimal value, comparison depends on
     the other argument. The arguments are compared as decimal values
     if the other argument is a decimal or integer value, or as
     floating-point values if the other argument is a floating-point
     value.

   * In all other cases, the arguments are compared as floating-point
     (real) numbers.

For information about conversion of values from one temporal type to
another, see *Note date-and-time-type-conversion::.

The following examples illustrate conversion of strings to numbers for
comparison operations:


     mysql> SELECT 1 > '6x';
             -> 0
     mysql> SELECT 7 > '6x';
             -> 1
     mysql> SELECT 0 > 'x6';
             -> 0
     mysql> SELECT 0 = 'x6';
             -> 1

For comparisons of a string column with a number, MySQL cannot use an
index on the column to look up the value quickly. If STR_COL is an
indexed string column, the index cannot be used when performing the
lookup in the following statement:


     SELECT * FROM TBL_NAME WHERE STR_COL=1;

The reason for this is that there are many different strings that may
convert to the value `1', such as `'1'', `' 1'', or `'1a''.

Comparisons that use floating-point numbers (or values that are
converted to floating-point numbers) are approximate because such
numbers are inexact. This might lead to results that appear
inconsistent:


     mysql> SELECT '18015376320243458' = 18015376320243458;
             -> 1
     mysql> SELECT '18015376320243459' = 18015376320243459;
             -> 0

Such results can occur because the values are converted to
floating-point numbers, which have only 53 bits of precision and are
subject to rounding:


     mysql> SELECT '18015376320243459'+0.0;
             -> 1.8015376320243e+16

Furthermore, the conversion from string to floating-point and from
integer to floating-point do not necessarily occur the same way.  The
integer may be converted to floating-point by the CPU, whereas the
string is converted digit by digit in an operation that involves
floating-point multiplications.

The results shown will vary on different systems, and can be affected
by factors such as computer architecture or the compiler version or
optimization level. One way to avoid such problems is to use `CAST()'
so that a value is not converted implicitly to a float-point number:


     mysql> SELECT CAST('18015376320243459' AS UNSIGNED) = 18015376320243459;
             -> 1

For more information about floating-point comparisons, see *Note
problems-with-float::.

Implicit conversion of a numeric or temporal value to a string produces
a binary string (a *Note `BINARY': binary-varbinary, *Note `VARBINARY':
binary-varbinary, or *Note `BLOB': blob. value). Such implicit
conversions to string typically occur for functions that are passed
numeric or temporal values when string values are more usual, and thus
can have effects beyond the type of the converted value. Consider the
expression `CONCAT(1, 'abc')'. The numeric argument `1' is converted to
the binary string `'1'' and the concatenation of that value with the
nonbinary string `'abc'' produces the binary string `'1abc''.

For integer expressions, the preceding remarks about expression
_evaluation_ apply somewhat differently for expression _assignment_;
for example, in a statement such as this:


     CREATE TABLE t SELECT INTEGER_EXPR;

In this case, the table in the column resulting from the expression has
type *Note `INT': integer-types. or *Note `BIGINT': integer-types.
depending on the length of the integer expression. If the maximum
length of the expression does no fit in an *Note `INT': integer-types,
*Note `BIGINT': integer-types. is used instead. The length is taken
from the `max_length' value of the *Note `SELECT': select. result set
metadata (see *Note c-api-data-structures::). This means that you can
force a *Note `BIGINT': integer-types. rather than *Note `INT':
integer-types. by use of a sufficiently long expression:


     CREATE TABLE t SELECT 000000000000000000000;


File: manual.info,  Node: non-typed-operators,  Next: control-flow-functions,  Prev: type-conversion,  Up: functions

12.3 Operators
==============

* Menu:

* operator-precedence::          Operator Precedence
* comparison-operators::         Comparison Functions and Operators
* logical-operators::            Logical Operators
* assignment-operators::         Assignment Operators

*Operators*

Name                          Description
`AND', `&&'                   Logical AND
`='                           Assign a value (as part of a  *Note `SET':
                              set-statement. statement, or  as part of
                              the `SET' clause in an  *Note `UPDATE':
                              update. statement)
`:='                          Assign a value
`BETWEEN ... AND ...'         Check whether a value is within a range of
                              values
`BINARY'                      Cast a string to a binary string
`&'                           Bitwise AND
`~'                           Invert bits
`|'                           Bitwise OR
`^'                           Bitwise XOR
`CASE'                        Case operator
`DIV'                         Integer division
`/'                           Division operator
`<=>'                         NULL-safe equal to operator
`='                           Equal operator
`>='                          Greater than or equal operator
`>'                           Greater than operator
`IS NOT NULL'                 NOT NULL value test
`IS NOT'                      Test a value against a boolean
`IS NULL'                     NULL value test
`IS'                          Test a value against a boolean
`<<'                          Left shift
`<='                          Less than or equal operator
`<'                           Less than operator
`LIKE'                        Simple pattern matching
`-'                           Minus operator
`% or MOD'                    Modulo operator
`NOT BETWEEN ... AND ...'     Check whether a value is not within a
                              range of values
`!=', `<>'                    Not equal operator
`NOT LIKE'                    Negation of simple pattern matching
`NOT REGEXP'                  Negation of REGEXP
`NOT', `!'                    Negates value
`||', `OR'                    Logical OR
`+'                           Addition operator
`REGEXP'                      Pattern matching using regular expressions
`>>'                          Right shift
`RLIKE'                       Synonym for REGEXP
`SOUNDS LIKE'                 Compare sounds
`*'                           Multiplication operator
`-'                           Change the sign of the argument
`XOR'                         Logical XOR


File: manual.info,  Node: operator-precedence,  Next: comparison-operators,  Prev: non-typed-operators,  Up: non-typed-operators

12.3.1 Operator Precedence
--------------------------

Operator precedences are shown in the following list, from highest
precedence to the lowest. Operators that are shown together on a line
have the same precedence.


     INTERVAL
     BINARY, COLLATE
     !
     - (unary minus), ~ (unary bit inversion)
     ^
     *, /, DIV, %, MOD
     -, +
     <<, >>
     &
     |
     = (comparison), <=>, >=, >, <=, <, <>, !=, IS, LIKE, REGEXP, IN
     BETWEEN, CASE, WHEN, THEN, ELSE
     NOT
     &&, AND
     XOR
     ||, OR
     = (assignment), :=

The precedence of `=' depends on whether it is used as a comparison
operator (`=') or as an assignment operator (`='). When used as a
comparison operator, it has the same precedence as `<=>', `>=', `>',
`<=', `<', `<>', `!=', `IS', `LIKE', `REGEXP', and `IN'. When used as
an assignment operator, it has the same precedence as `:='.  *Note
set-statement::, and *Note user-variables::, explain how MySQL
determines which interpretation of `=' should apply.

The meaning of some operators depends on the SQL mode:

   * By default, `||' is a logical `OR' operator. With
     `PIPES_AS_CONCAT' enabled, `||' is string concatenation, with a
     precedence between `^' and the unary operators.

   * By default, `!' has a higher precedence than `NOT'. With
     `HIGH_NOT_PRECEDENCE' enabled, `!' and `NOT' have the same
     precedence.

See *Note sql-mode::.

The precedence of operators determines the order of evaluation of terms
in an expression. To override this order and group terms explicitly,
use parentheses. For example:


     mysql> SELECT 1+2*3;
             -> 7
     mysql> SELECT (1+2)*3;
             -> 9


File: manual.info,  Node: comparison-operators,  Next: logical-operators,  Prev: operator-precedence,  Up: non-typed-operators

12.3.2 Comparison Functions and Operators
-----------------------------------------

*Comparison Operators*

Name                          Description
`BETWEEN ... AND ...'         Check whether a value is within a range of
                              values
`COALESCE()'                  Return the first non-NULL argument
`<=>'                         NULL-safe equal to operator
`='                           Equal operator
`>='                          Greater than or equal operator
`>'                           Greater than operator
`GREATEST()'                  Return the largest argument
`IN()'                        Check whether a value is within a set of
                              values
`INTERVAL()'                  Return the index of the argument that is
                              less than the first  argument
`IS NOT NULL'                 NOT NULL value test
`IS NOT'                      Test a value against a boolean
`IS NULL'                     NULL value test
`IS'                          Test a value against a boolean
`ISNULL()'                    Test whether the argument is NULL
`LEAST()'                     Return the smallest argument
`<='                          Less than or equal operator
`<'                           Less than operator
`LIKE'                        Simple pattern matching
`NOT BETWEEN ... AND ...'     Check whether a value is not within a
                              range of values
`!=', `<>'                    Not equal operator
`NOT IN()'                    Check whether a value is not within a set
                              of values
`NOT LIKE'                    Negation of simple pattern matching
`STRCMP()'                    Compare two strings

Comparison operations result in a value of `1' (`TRUE'), `0' (`FALSE'),
or `NULL'. These operations work for both numbers and strings. Strings
are automatically converted to numbers and numbers to strings as
necessary.

The following relational comparison operators can be used to compare
not only scalar operands, but row operands:


     =  >  <  >=  <=  <>  !=

For examples of row comparisons, see *Note row-subqueries::.

Some of the functions in this section return values other than `1'
(`TRUE'), `0' (`FALSE'), or `NULL'. For example, `LEAST()' and
`GREATEST()'. However, the value they return is based on comparison
operations performed according to the rules described in *Note
type-conversion::.

To convert a value to a specific type for comparison purposes, you can
use the `CAST()' function.  String values can be converted to a
different character set using `CONVERT()'. See *Note cast-functions::.

By default, string comparisons are not case sensitive and use the
current character set. The default is `latin1' (cp1252 West European),
which also works well for English.

   * `='

     Equal:


          mysql> SELECT 1 = 0;
                  -> 0
          mysql> SELECT '0' = 0;
                  -> 1
          mysql> SELECT '0.0' = 0;
                  -> 1
          mysql> SELECT '0.01' = 0;
                  -> 0
          mysql> SELECT '.01' = 0.01;
                  -> 1

   * `<=>'

     `NULL'-safe equal. This operator performs an equality comparison
     like the `=' operator, but returns `1' rather than `NULL' if both
     operands are `NULL', and `0' rather than `NULL' if one operand is
     `NULL'.


          mysql> SELECT 1 <=> 1, NULL <=> NULL, 1 <=> NULL;
                  -> 1, 1, 0
          mysql> SELECT 1 = 1, NULL = NULL, 1 = NULL;
                  -> 1, NULL, NULL

   * `<>', `!='

     Not equal:


          mysql> SELECT '.01' <> '0.01';
                  -> 1
          mysql> SELECT .01 <> '0.01';
                  -> 0
          mysql> SELECT 'zapp' <> 'zappp';
                  -> 1

   * `<='

     Less than or equal:


          mysql> SELECT 0.1 <= 2;
                  -> 1

   * `<'

     Less than:


          mysql> SELECT 2 < 2;
                  -> 0

   * `>='

     Greater than or equal:


          mysql> SELECT 2 >= 2;
                  -> 1

   * `>'

     Greater than:


          mysql> SELECT 2 > 2;
                  -> 0

   * `IS BOOLEAN_VALUE'

     Tests a value against a boolean value, where BOOLEAN_VALUE can be
     `TRUE', `FALSE', or `UNKNOWN'.


          mysql> SELECT 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN;
                  -> 1, 1, 1

   * `IS NOT BOOLEAN_VALUE'

     Tests a value against a boolean value, where BOOLEAN_VALUE can be
     `TRUE', `FALSE', or `UNKNOWN'.


          mysql> SELECT 1 IS NOT UNKNOWN, 0 IS NOT UNKNOWN, NULL IS NOT UNKNOWN;
                  -> 1, 1, 0

   * `IS NULL'

     Tests whether a value is `NULL'.


          mysql> SELECT 1 IS NULL, 0 IS NULL, NULL IS NULL;
                  -> 0, 0, 1

     To work well with ODBC programs, MySQL supports the following
     extra features when using `IS NULL':

        * If `sql_auto_is_null' variable is set to 1 (the default),
          then after a statement that successfully inserts an
          automatically generated `AUTO_INCREMENT' value, you can find
          that value by issuing a statement of the following form:


               SELECT * FROM TBL_NAME WHERE AUTO_COL IS NULL

          If the statement returns a row, the value returned is the
          same as if you invoked the `LAST_INSERT_ID()' function. For
          details, including the return value after a multiple-row
          insert, see *Note information-functions::. If no
          `AUTO_INCREMENT' value was successfully inserted, the *Note
          `SELECT': select.  statement returns no row.

          The behavior of retrieving an `AUTO_INCREMENT' value by using
          an `IS NULL' comparison can be disabled by setting
          `sql_auto_is_null = 0'.  See *Note server-system-variables::.

        * For *Note `DATE': datetime. and *Note `DATETIME': datetime.
          columns that are declared as `NOT NULL', you can find the
          special date `'0000-00-00'' by using a statement like this:


               SELECT * FROM TBL_NAME WHERE DATE_COLUMN IS NULL

          This is needed to get some ODBC applications to work because
          ODBC does not support a `'0000-00-00'' date value.

          See Obtaining Auto-Increment Values
          (http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-usagenotes-functionality-last-insert-id.html),
          and the description for the `FLAG_AUTO_IS_NULL' option at
          Connector/ODBC Connection Parameters
          (http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-configuration-connection-parameters.html).

   * `IS NOT NULL'

     Tests whether a value is not `NULL'.


          mysql> SELECT 1 IS NOT NULL, 0 IS NOT NULL, NULL IS NOT NULL;
                  -> 1, 1, 0

   * `EXPR BETWEEN MIN AND MAX'

     If EXPR is greater than or equal to MIN and EXPR is less than or
     equal to MAX, `BETWEEN' returns `1', otherwise it returns `0'.
     This is equivalent to the expression `(MIN <= EXPR AND EXPR <=
     MAX)' if all the arguments are of the same type. Otherwise type
     conversion takes place according to the rules described in *Note
     type-conversion::, but applied to all the three arguments.


          mysql> SELECT 2 BETWEEN 1 AND 3, 2 BETWEEN 3 and 1;
                  -> 1, 0
          mysql> SELECT 1 BETWEEN 2 AND 3;
                  -> 0
          mysql> SELECT 'b' BETWEEN 'a' AND 'c';
                  -> 1
          mysql> SELECT 2 BETWEEN 2 AND '3';
                  -> 1
          mysql> SELECT 2 BETWEEN 2 AND 'x-3';
                  -> 0

     For best results when using `BETWEEN' with date or time values,
     use `CAST()' to explicitly convert the values to the desired data
     type.  Examples: If you compare a *Note `DATETIME': datetime. to
     two *Note `DATE': datetime. values, convert the *Note `DATE':
     datetime. values to *Note `DATETIME': datetime. values. If you use
     a string constant such as `'2001-1-1'' in a comparison to a *Note
     `DATE': datetime, cast the string to a *Note `DATE': datetime.

   * `EXPR NOT BETWEEN MIN AND MAX'

     This is the same as `NOT (EXPR BETWEEN MIN AND MAX)'.

   * `COALESCE(VALUE,...)'

     Returns the first non-`NULL' value in the list, or `NULL' if there
     are no non-`NULL' values.


          mysql> SELECT COALESCE(NULL,1);
                  -> 1
          mysql> SELECT COALESCE(NULL,NULL,NULL);
                  -> NULL

   * `GREATEST(VALUE1,VALUE2,...)'

     With two or more arguments, returns the largest (maximum-valued)
     argument. The arguments are compared using the same rules as for
     `LEAST()'.


          mysql> SELECT GREATEST(2,0);
                  -> 2
          mysql> SELECT GREATEST(34.0,3.0,5.0,767.0);
                  -> 767.0
          mysql> SELECT GREATEST('B','A','C');
                  -> 'C'

     `GREATEST()' returns `NULL' if any argument is `NULL'.

   * `EXPR IN (VALUE,...)'

     Returns `1' if EXPR is equal to any of the values in the `IN'
     list, else returns `0'. If all values are constants, they are
     evaluated according to the type of EXPR and sorted. The search for
     the item then is done using a binary search. This means `IN' is
     very quick if the `IN' value list consists entirely of constants.
     Otherwise, type conversion takes place according to the rules
     described in *Note type-conversion::, but applied to all the
     arguments.


          mysql> SELECT 2 IN (0,3,5,7);
                  -> 0
          mysql> SELECT 'wefwf' IN ('wee','wefwf','weg');
                  -> 1

     You should never mix quoted and unquoted values in an `IN' list
     because the comparison rules for quoted values (such as strings)
     and unquoted values (such as numbers) differ. Mixing types may
     therefore lead to inconsistent results. For example, do not write
     an `IN' expression like this:


          SELECT val1 FROM tbl1 WHERE val1 IN (1,2,'a');

     Instead, write it like this:


          SELECT val1 FROM tbl1 WHERE val1 IN ('1','2','a');

     The number of values in the `IN' list is only limited by the
     `max_allowed_packet' value.

     To comply with the SQL standard, `IN' returns `NULL' not only if
     the expression on the left hand side is `NULL', but also if no
     match is found in the list and one of the expressions in the list
     is `NULL'.

     `IN()' syntax can also be used to write certain types of
     subqueries. See *Note any-in-some-subqueries::.

   * `EXPR NOT IN (VALUE,...)'

     This is the same as `NOT (EXPR IN (VALUE,...))'.

   * `ISNULL(EXPR)'

     If EXPR is `NULL', `ISNULL()' returns `1', otherwise it returns
     `0'.


          mysql> SELECT ISNULL(1+1);
                  -> 0
          mysql> SELECT ISNULL(1/0);
                  -> 1

     `ISNULL()' can be used instead of `=' to test whether a value is
     `NULL'. (Comparing a value to `NULL' using `=' always yields
     false.)

     The `ISNULL()' function shares some special behaviors with the `IS
     NULL' comparison operator. See the description of `IS NULL'.

   * `INTERVAL(N,N1,N2,N3,...)'

     Returns `0' if N < N1, `1' if N < N2 and so on or `-1' if N is
     `NULL'. All arguments are treated as integers. It is required that
     N1 < N2 < N3 < `...' < NN for this function to work correctly.
     This is because a binary search is used (very fast).


          mysql> SELECT INTERVAL(23, 1, 15, 17, 30, 44, 200);
                  -> 3
          mysql> SELECT INTERVAL(10, 1, 10, 100, 1000);
                  -> 2
          mysql> SELECT INTERVAL(22, 23, 30, 44, 200);
                  -> 0

   * `LEAST(VALUE1,VALUE2,...)'

     With two or more arguments, returns the smallest (minimum-valued)
     argument. The arguments are compared using the following rules:

        * If any argument is `NULL', the result is `NULL'. No
          comparison is needed.

        * If the return value is used in an *Note `INTEGER':
          integer-types. context or all arguments are integer-valued,
          they are compared as integers.

        * If the return value is used in a *Note `REAL':
          floating-point-types. context or all arguments are
          real-valued, they are compared as reals.

        * If the arguments comprise a mix of numbers and strings, they
          are compared as numbers.

        * If any argument is a nonbinary (character) string, the
          arguments are compared as nonbinary strings.

        * In all other cases, the arguments are compared as binary
          strings.


          mysql> SELECT LEAST(2,0);
                  -> 0
          mysql> SELECT LEAST(34.0,3.0,5.0,767.0);
                  -> 3.0
          mysql> SELECT LEAST('B','A','C');
                  -> 'A'

     Note that the preceding conversion rules can produce strange
     results in some borderline cases:


          mysql> SELECT CAST(LEAST(3600, 9223372036854775808.0) as SIGNED);
                  -> -9223372036854775808

     This happens because MySQL reads `9223372036854775808.0' in an
     integer context. The integer representation is not good enough to
     hold the value, so it wraps to a signed integer.


File: manual.info,  Node: logical-operators,  Next: assignment-operators,  Prev: comparison-operators,  Up: non-typed-operators

12.3.3 Logical Operators
------------------------

*Logical Operators*

Name                          Description
`AND', `&&'                   Logical AND
`NOT', `!'                    Negates value
`||', `OR'                    Logical OR
`XOR'                         Logical XOR

In SQL, all logical operators evaluate to `TRUE', `FALSE', or `NULL'
(`UNKNOWN'). In MySQL, these are implemented as 1 (`TRUE'), 0
(`FALSE'), and `NULL'. Most of this is common to different SQL database
servers, although some servers may return any nonzero value for `TRUE'.

MySQL evaluates any nonzero, non-`NULL' value to `TRUE'. For example,
the following statements all assess to `TRUE':


     mysql> SELECT 10 IS TRUE;
     -> 1
     mysql> SELECT -10 IS TRUE;
     -> 1
     mysql> SELECT 'string' IS NOT NULL;
     -> 1

   * `NOT', `!'

     Logical NOT. Evaluates to `1' if the operand is `0', to `0' if the
     operand is nonzero, and `NOT NULL' returns `NULL'.


          mysql> SELECT NOT 10;
                  -> 0
          mysql> SELECT NOT 0;
                  -> 1
          mysql> SELECT NOT NULL;
                  -> NULL
          mysql> SELECT ! (1+1);
                  -> 0
          mysql> SELECT ! 1+1;
                  -> 1

     The last example produces `1' because the expression evaluates the
     same way as `(!1)+1'.

   * `AND', `&&'

     Logical AND. Evaluates to `1' if all operands are nonzero and not
     `NULL', to `0' if one or more operands are `0', otherwise `NULL' is
     returned.


          mysql> SELECT 1 && 1;
                  -> 1
          mysql> SELECT 1 && 0;
                  -> 0
          mysql> SELECT 1 && NULL;
                  -> NULL
          mysql> SELECT 0 && NULL;
                  -> 0
          mysql> SELECT NULL && 0;
                  -> 0

   * `OR', `||'

     Logical OR. When both operands are non-`NULL', the result is `1'
     if any operand is nonzero, and `0' otherwise. With a `NULL'
     operand, the result is `1' if the other operand is nonzero, and
     `NULL' otherwise. If both operands are `NULL', the result is
     `NULL'.


          mysql> SELECT 1 || 1;
                  -> 1
          mysql> SELECT 1 || 0;
                  -> 1
          mysql> SELECT 0 || 0;
                  -> 0
          mysql> SELECT 0 || NULL;
                  -> NULL
          mysql> SELECT 1 || NULL;
                  -> 1

   * `XOR'

     Logical XOR. Returns `NULL' if either operand is `NULL'. For
     non-`NULL' operands, evaluates to `1' if an odd number of operands
     is nonzero, otherwise `0' is returned.


          mysql> SELECT 1 XOR 1;
                  -> 0
          mysql> SELECT 1 XOR 0;
                  -> 1
          mysql> SELECT 1 XOR NULL;
                  -> NULL
          mysql> SELECT 1 XOR 1 XOR 1;
                  -> 1

     `a XOR b' is mathematically equal to `(a AND (NOT b)) OR ((NOT a)
     and b)'.


File: manual.info,  Node: assignment-operators,  Prev: logical-operators,  Up: non-typed-operators

12.3.4 Assignment Operators
---------------------------

*Assignment Operators*

Name                          Description
`='                           Assign a value (as part of a  *Note `SET':
                              set-statement. statement, or  as part of
                              the `SET' clause in an  *Note `UPDATE':
                              update. statement)
`:='                          Assign a value

   * `:='

     Assignment operator. Causes the user variable on the left hand
     side of the operator to take on the value to its right.  The value
     on the right hand side may be a literal value, another variable
     storing a value, or any legal expression that yields a scalar
     value, including the result of a query (provided that this value
     is a scalar value). You can perform multiple assignments in the
     same *Note `SET': set-statement.  statement. You can perform
     multiple assignments in the same statement-

     Unlike `=', the `:=' operator is never interpreted as a comparison
     operator. This means you can use `:=' in any valid SQL statement
     (not just in *Note `SET': set-statement.  statements) to assign a
     value to a variable.


          mysql> SELECT @var1, @var2;
                  -> NULL, NULL
          mysql> SELECT @var1 := 1, @var2;
                  -> 1, NULL
          mysql> SELECT @var1, @var2;
                  -> 1, NULL
          mysql> SELECT @var1, @var2 := @var1;
                  -> 1, 1
          mysql> SELECT @var1, @var2;
                  -> 1, 1

          mysql> SELECT @var1:=COUNT(*) FROM t1;
                  -> 4
          mysql> SELECT @var1;
                  -> 4

     You can make value assignments using `:=' in other statements
     besides *Note `SELECT': select, such as *Note `UPDATE': update, as
     shown here:


          mysql> SELECT @var1;
                  -> 4
          mysql> SELECT * FROM t1;
                  -> 1, 3, 5, 7

          mysql> UPDATE t1 SET c1 = 2 WHERE c1 = @var1:= 1;
          Query OK, 1 row affected (0.00 sec)
          Rows matched: 1  Changed: 1  Warnings: 0

          mysql> SELECT @var1;
                  -> 1
          mysql> SELECT * FROM t1;
                  -> 2, 3, 5, 7

     While it is also possible both to set and to read the value of the
     same variable in a single SQL statement using the `:=' operator,
     this is not recommended.  *Note user-variables::, explains why you
     should avoid doing this.

   * `='

     This operator is used to perform value assignments in two cases,
     described in the next two paragraphs.

     Within a *Note `SET': set-statement.  statement, `=' is treated as
     an assignment operator that causes the user variable on the left
     hand side of the operator to take on the value to its right. (In
     other words, when used in a *Note `SET': set-statement.
     statement, `=' is treated identically to `:='.)  The value on the
     right hand side may be a literal value, another variable storing a
     value, or any legal expression that yields a scalar value,
     including the result of a query (provided that this value is a
     scalar value). You can perform multiple assignments in the same
     *Note `SET': set-statement.  statement.

     In the `SET' clause of an *Note `UPDATE': update. statement, `='
     also acts as an assignment operator; in this case, however, it
     causes the column named on the left hand side of the operator to
     assume the value given to the right, provided any `WHERE'
     conditions that are part of the *Note `UPDATE': update. are met.
     You can make multiple assignments in the same `SET' clause of an
     *Note `UPDATE': update. statement.

     In any other context, `=' is treated as a comparison operator.


          mysql> SELECT @var1, @var2;
                  -> NULL, NULL
          mysql> SELECT @var1 := 1, @var2;
                  -> 1, NULL
          mysql> SELECT @var1, @var2;
                  -> 1, NULL
          mysql> SELECT @var1, @var2 := @var1;
                  -> 1, 1
          mysql> SELECT @var1, @var2;
                  -> 1, 1

     For more information, see *Note set-statement::, *Note update::,
     and *Note subqueries::.


File: manual.info,  Node: control-flow-functions,  Next: string-functions,  Prev: non-typed-operators,  Up: functions

12.4 Control Flow Functions
===========================

*Flow Control Operators*

Name                          Description
`CASE'                        Case operator
`IF()'                        If/else construct
`IFNULL()'                    Null if/else construct
`NULLIF()'                    Return NULL if expr1 = expr2

   * `CASE VALUE WHEN [COMPARE_VALUE] THEN RESULT [WHEN [COMPARE_VALUE]
     THEN RESULT ...] [ELSE RESULT] END'

     `CASE WHEN [CONDITION] THEN RESULT [WHEN [CONDITION] THEN RESULT
     ...] [ELSE RESULT] END'

     The first version returns the RESULT where `VALUE=COMPARE_VALUE'.
     The second version returns the result for the first condition that
     is true. If there was no matching result value, the result after
     `ELSE' is returned, or `NULL' if there is no `ELSE' part.


          mysql> SELECT CASE 1 WHEN 1 THEN 'one'
              ->     WHEN 2 THEN 'two' ELSE 'more' END;
                  -> 'one'
          mysql> SELECT CASE WHEN 1>0 THEN 'true' ELSE 'false' END;
                  -> 'true'
          mysql> SELECT CASE BINARY 'B'
              ->     WHEN 'a' THEN 1 WHEN 'b' THEN 2 END;
                  -> NULL

     The return type of a `CASE' expression is the compatible
     aggregated type of all return values, but also depends on the
     context in which it is used.  If used in a string context, the
     result is returned as a string. If used in a numeric context, the
     result is returned as a decimal, real, or integer value.

     *Note*:

     The syntax of the `CASE' _expression_ shown here differs slightly
     from that of the SQL *Note `CASE': case.  _statement_ described in
     *Note case::, for use inside stored programs. The *Note `CASE':
     case. statement cannot have an `ELSE NULL' clause, and it is
     terminated with `END CASE' instead of `END'.

   * `IF(EXPR1,EXPR2,EXPR3)'

     If EXPR1 is `TRUE' (`EXPR1 <> 0' and `EXPR1 <> NULL') then `IF()'
     returns EXPR2; otherwise it returns EXPR3.  `IF()' returns a
     numeric or string value, depending on the context in which it is
     used.


          mysql> SELECT IF(1>2,2,3);
                  -> 3
          mysql> SELECT IF(1<2,'yes','no');
                  -> 'yes'
          mysql> SELECT IF(STRCMP('test','test1'),'no','yes');
                  -> 'no'

     If only one of EXPR2 or EXPR3 is explicitly `NULL', the result
     type of the `IF()' function is the type of the non-`NULL'
     expression.

     The default return type of `IF()' (which may matter when it is
     stored into a temporary table) is calculated as follows.

     This table lists expressions and corresponding return values which
     show how the default return type of `IF()' is calculated.

     Expression                         Return Value
     EXPR2 or EXPR3 returns a string    string
     EXPR2 or EXPR3 returns a           floating-point
     floating-point value               
     EXPR2 or EXPR3 returns an integer  integer

     If EXPR2 and EXPR3 are both strings, the result is case sensitive
     if either string is case sensitive.

     *Note*:

     There is also an *Note `IF': if.  _statement_, which differs from
     the `IF()' _function_ described here. See *Note if::.

   * `IFNULL(EXPR1,EXPR2)'

     If EXPR1 is not `NULL', `IFNULL()' returns EXPR1; otherwise it
     returns EXPR2.  `IFNULL()' returns a numeric or string value,
     depending on the context in which it is used.


          mysql> SELECT IFNULL(1,0);
                  -> 1
          mysql> SELECT IFNULL(NULL,10);
                  -> 10
          mysql> SELECT IFNULL(1/0,10);
                  -> 10
          mysql> SELECT IFNULL(1/0,'yes');
                  -> 'yes'

     The default result value of `IFNULL(EXPR1,EXPR2)' is the more
     `general' of the two expressions, in the order `STRING', *Note
     `REAL': floating-point-types, or *Note `INTEGER': integer-types.
     Consider the case of a table based on expressions or where MySQL
     must internally store a value returned by `IFNULL()' in a
     temporary table:


          mysql> CREATE TABLE tmp SELECT IFNULL(1,'test') AS test;
          mysql> DESCRIBE tmp;
          +-------+--------------+------+-----+---------+-------+
          | Field | Type         | Null | Key | Default | Extra |
          +-------+--------------+------+-----+---------+-------+
          | test  | varbinary(4) | NO   |     |         |       |
          +-------+--------------+------+-----+---------+-------+

     In this example, the type of the `test' column is *Note
     `VARBINARY(4)': binary-varbinary.

   * `NULLIF(EXPR1,EXPR2)'

     Returns `NULL' if `EXPR1 = EXPR2' is true, otherwise returns
     EXPR1. This is the same as `CASE WHEN EXPR1 = EXPR2 THEN NULL ELSE
     EXPR1 END'.


          mysql> SELECT NULLIF(1,1);
                  -> NULL
          mysql> SELECT NULLIF(1,2);
                  -> 1

     Note that MySQL evaluates EXPR1 twice if the arguments are not
     equal.


File: manual.info,  Node: string-functions,  Next: numeric-functions,  Prev: control-flow-functions,  Up: functions

12.5 String Functions
=====================

* Menu:

* string-comparison-functions::  String Comparison Functions
* regexp::                       Regular Expressions

*String Operators*

Name                          Description
`ASCII()'                     Return numeric value of left-most character
`BIN()'                       Return a string containing binary
                              representation of a number
`BIT_LENGTH()'                Return length of argument in bits
`CHAR_LENGTH()'               Return number of characters in argument
`CHAR()'                      Return the character for each integer
                              passed
`CHARACTER_LENGTH()'          Synonym for CHAR_LENGTH()
`CONCAT_WS()'                 Return concatenate with separator
`CONCAT()'                    Return concatenated string
`ELT()'                       Return string at index number
`EXPORT_SET()'                Return a string such that for every bit
                              set in the value bits, you  get an on
                              string and for every unset bit, you get an
                              off string
`FIELD()'                     Return the index (position) of the first
                              argument in the  subsequent arguments
`FIND_IN_SET()'               Return the index position of the first
                              argument within the second  argument
`FORMAT()'                    Return a number formatted to specified
                              number of decimal places
`HEX()'                       Return a hexadecimal representation of a
                              decimal or string value
`INSERT()'                    Insert a substring at the specified
                              position up to the specified  number of
                              characters
`INSTR()'                     Return the index of the first occurrence
                              of substring
`LCASE()'                     Synonym for LOWER()
`LEFT()'                      Return the leftmost number of characters
                              as specified
`LENGTH()'                    Return the length of a string in bytes
`LIKE'                        Simple pattern matching
`LOAD_FILE()'                 Load the named file
`LOCATE()'                    Return the position of the first
                              occurrence of substring
`LOWER()'                     Return the argument in lowercase
`LPAD()'                      Return the string argument, left-padded
                              with the specified string
`LTRIM()'                     Remove leading spaces
`MAKE_SET()'                  Return a set of comma-separated strings
                              that have the  corresponding bit in bits
                              set
`MATCH'                       Perform full-text search
`MID()'                       Return a substring starting from the
                              specified position
`NOT LIKE'                    Negation of simple pattern matching
`NOT REGEXP'                  Negation of REGEXP
`OCT()'                       Return a string containing octal
                              representation of a number
`OCTET_LENGTH()'              Synonym for LENGTH()
`ORD()'                       Return character code for leftmost
                              character of the argument
`POSITION()'                  Synonym for LOCATE()
`QUOTE()'                     Escape the argument for use in an SQL
                              statement
`REGEXP'                      Pattern matching using regular expressions
`REPEAT()'                    Repeat a string the specified number of
                              times
`REPLACE()'                   Replace occurrences of a specified string
`REVERSE()'                   Reverse the characters in a string
`RIGHT()'                     Return the specified rightmost number of
                              characters
`RLIKE'                       Synonym for REGEXP
`RPAD()'                      Append string the specified number of times
`RTRIM()'                     Remove trailing spaces
`SOUNDEX()'                   Return a soundex string
`SOUNDS LIKE'                 Compare sounds
`SPACE()'                     Return a string of the specified number of
                              spaces
`STRCMP()'                    Compare two strings
`SUBSTR()'                    Return the substring as specified
`SUBSTRING_INDEX()'           Return a substring from a string before
                              the specified number of  occurrences of
                              the delimiter
`SUBSTRING()'                 Return the substring as specified
`TRIM()'                      Remove leading and trailing spaces
`UCASE()'                     Synonym for UPPER()
`UNHEX()'                     Return a string containing hex
                              representation of a number
`UPPER()'                     Convert to uppercase

String-valued functions return `NULL' if the length of the result would
be greater than the value of the `max_allowed_packet' system variable.
See *Note server-parameters::.

For functions that operate on string positions, the first position is
numbered 1.

For functions that take length arguments, noninteger arguments are
rounded to the nearest integer.

   * `ASCII(STR)'

     Returns the numeric value of the leftmost character of the string
     STR. Returns `0' if STR is the empty string. Returns `NULL' if STR
     is `NULL'.  `ASCII()' works for 8-bit characters.


          mysql> SELECT ASCII('2');
                  -> 50
          mysql> SELECT ASCII(2);
                  -> 50
          mysql> SELECT ASCII('dx');
                  -> 100

     See also the `ORD()' function.

   * `BIN(N)'

     Returns a string representation of the binary value of N, where N
     is a longlong (*Note `BIGINT': integer-types.) number. This is
     equivalent to `CONV(N,10,2)'.  Returns `NULL' if N is `NULL'.


          mysql> SELECT BIN(12);
                  -> '1100'

   * `BIT_LENGTH(STR)'

     Returns the length of the string STR in bits.


          mysql> SELECT BIT_LENGTH('text');
                  -> 32

   * `CHAR(N,...  [USING CHARSET_NAME])'

     `CHAR()' interprets each argument N as an integer and returns a
     string consisting of the characters given by the code values of
     those integers. `NULL' values are skipped.


          mysql> SELECT CHAR(77,121,83,81,'76');
                  -> 'MySQL'
          mysql> SELECT CHAR(77,77.3,'77.3');
                  -> 'MMM'

     `CHAR()' arguments larger than 255 are converted into multiple
     result bytes. For example, `CHAR(256)' is equivalent to
     `CHAR(1,0)', and `CHAR(256*256)' is equivalent to `CHAR(1,0,0)':


          mysql> SELECT HEX(CHAR(1,0)), HEX(CHAR(256));
          +----------------+----------------+
          | HEX(CHAR(1,0)) | HEX(CHAR(256)) |
          +----------------+----------------+
          | 0100           | 0100           |
          +----------------+----------------+
          mysql> SELECT HEX(CHAR(1,0,0)), HEX(CHAR(256*256));
          +------------------+--------------------+
          | HEX(CHAR(1,0,0)) | HEX(CHAR(256*256)) |
          +------------------+--------------------+
          | 010000           | 010000             |
          +------------------+--------------------+

     By default, `CHAR()' returns a binary string. To produce a string
     in a given character set, use the optional `USING' clause:


          mysql> SELECT CHARSET(CHAR(0x65)), CHARSET(CHAR(0x65 USING utf8));
          +---------------------+--------------------------------+
          | CHARSET(CHAR(0x65)) | CHARSET(CHAR(0x65 USING utf8)) |
          +---------------------+--------------------------------+
          | binary              | utf8                           |
          +---------------------+--------------------------------+

     If `USING' is given and the result string is illegal for the given
     character set, a warning is issued.  Also, if strict SQL mode is
     enabled, the result from `CHAR()' becomes `NULL'.

   * `CHAR_LENGTH(STR)'

     Returns the length of the string STR, measured in characters. A
     multibyte character counts as a single character. This means that
     for a string containing five 2-byte characters, `LENGTH()' returns
     `10', whereas `CHAR_LENGTH()' returns `5'.

   * `CHARACTER_LENGTH(STR)'

     `CHARACTER_LENGTH()' is a synonym for `CHAR_LENGTH()'.

   * `CONCAT(STR1,STR2,...)'

     Returns the string that results from concatenating the arguments.
     May have one or more arguments. If all arguments are nonbinary
     strings, the result is a nonbinary string. If the arguments
     include any binary strings, the result is a binary string. A
     numeric argument is converted to its equivalent binary string
     form; if you want to avoid that, you can use an explicit type
     cast, as in this example:


          SELECT CONCAT(CAST(INT_COL AS CHAR), CHAR_COL);

     `CONCAT()' returns `NULL' if any argument is `NULL'.


          mysql> SELECT CONCAT('My', 'S', 'QL');
                  -> 'MySQL'
          mysql> SELECT CONCAT('My', NULL, 'QL');
                  -> NULL
          mysql> SELECT CONCAT(14.3);
                  -> '14.3'

     For quoted strings, concatenation can be performed by placing the
     strings next to each other:


          mysql> SELECT 'My' 'S' 'QL';
                  -> 'MySQL'

   * `CONCAT_WS(SEPARATOR,STR1,STR2,...)'

     `CONCAT_WS()' stands for Concatenate With Separator and is a
     special form of `CONCAT()'. The first argument is the separator
     for the rest of the arguments. The separator is added between the
     strings to be concatenated. The separator can be a string, as can
     the rest of the arguments. If the separator is `NULL', the result
     is `NULL'.


          mysql> SELECT CONCAT_WS(',','First name','Second name','Last Name');
                  -> 'First name,Second name,Last Name'
          mysql> SELECT CONCAT_WS(',','First name',NULL,'Last Name');
                  -> 'First name,Last Name'

     `CONCAT_WS()' does not skip empty strings. However, it does skip
     any `NULL' values after the separator argument.

   * `ELT(N,STR1,STR2,STR3,...)'

     `ELT()' returns the Nth element of the list of strings: STR1 if N
     = `1', STR2 if N = `2', and so on. Returns `NULL' if N is less
     than `1' or greater than the number of arguments.  `ELT()' is the
     complement of `FIELD()'.


          mysql> SELECT ELT(1, 'ej', 'Heja', 'hej', 'foo');
                  -> 'ej'
          mysql> SELECT ELT(4, 'ej', 'Heja', 'hej', 'foo');
                  -> 'foo'

   * `EXPORT_SET(BITS,ON,OFF[,SEPARATOR[,NUMBER_OF_BITS]])'

     Returns a string such that for every bit set in the value BITS,
     you get an ON string and for every bit not set in the value, you
     get an OFF string. Bits in BITS are examined from right to left
     (from low-order to high-order bits).  Strings are added to the
     result from left to right, separated by the SEPARATOR string (the
     default being the comma character ``,''). The number of bits
     examined is given by NUMBER_OF_BITS, which has a default of 64 if
     not specified.  NUMBER_OF_BITS is silently clipped to 64 if larger
     than 64. It is treated as an unsigned integer, so a value of -1 is
     effectively the same as 64.


          mysql> SELECT EXPORT_SET(5,'Y','N',',',4);
                  -> 'Y,N,Y,N'
          mysql> SELECT EXPORT_SET(6,'1','0',',',10);
                  -> '0,1,1,0,0,0,0,0,0,0'

   * `FIELD(STR,STR1,STR2,STR3,...)'

     Returns the index (position) of STR in the STR1, STR2, STR3, `...'
     list.  Returns `0' if STR is not found.

     If all arguments to `FIELD()' are strings, all arguments are
     compared as strings. If all arguments are numbers, they are
     compared as numbers.  Otherwise, the arguments are compared as
     double.

     If STR is `NULL', the return value is `0' because `NULL' fails
     equality comparison with any value. `FIELD()' is the complement of
     `ELT()'.


          mysql> SELECT FIELD('ej', 'Hej', 'ej', 'Heja', 'hej', 'foo');
                  -> 2
          mysql> SELECT FIELD('fo', 'Hej', 'ej', 'Heja', 'hej', 'foo');
                  -> 0

   * `FIND_IN_SET(STR,STRLIST)'

     Returns a value in the range of 1 to N if the string STR is in the
     string list STRLIST consisting of N substrings. A string list is a
     string composed of substrings separated by ``,'' characters. If
     the first argument is a constant string and the second is a column
     of type *Note `SET': set, the `FIND_IN_SET()' function is
     optimized to use bit arithmetic. Returns `0' if STR is not in
     STRLIST or if STRLIST is the empty string.  Returns `NULL' if
     either argument is `NULL'. This function does not work properly if
     the first argument contains a comma (``,'') character.


          mysql> SELECT FIND_IN_SET('b','a,b,c,d');
                  -> 2

   * `FORMAT(X,D)'

     Formats the number X to a format like `'#,###,###.##'', rounded to
     D decimal places, and returns the result as a string. If D is `0',
     the result has no decimal point or fractional part.


          mysql> SELECT FORMAT(12332.123456, 4);
                  -> '12,332.1235'
          mysql> SELECT FORMAT(12332.1,4);
                  -> '12,332.1000'
          mysql> SELECT FORMAT(12332.2,0);
                  -> '12,332'

   * `HEX(STR)', `HEX(N)'

     For a string argument STR, `HEX()' returns a hexadecimal string
     representation of STR where each byte of each character in STR is
     converted to two hexadecimal digits. (Multibyte characters
     therefore become more than two digits.) The inverse of this
     operation is performed by the `UNHEX()' function.

     For a numeric argument N, `HEX()' returns a hexadecimal string
     representation of the value of N treated as a longlong (*Note
     `BIGINT': integer-types.) number. This is equivalent to
     `CONV(N,10,16)'.  The inverse of this operation is performed by
     `CONV(HEX(N),16,10)'.


          mysql> SELECT 0x616263, HEX('abc'), UNHEX(HEX('abc'));
                  -> 'abc', 616263, 'abc'
          mysql> SELECT HEX(255), CONV(HEX(255),16,10);
                  -> 'FF', 255

   * `INSERT(STR,POS,LEN,NEWSTR)'

     Returns the string STR, with the substring beginning at position
     POS and LEN characters long replaced by the string NEWSTR. Returns
     the original string if POS is not within the length of the string.
     Replaces the rest of the string from position POS if LEN is not
     within the length of the rest of the string. Returns `NULL' if any
     argument is `NULL'.


          mysql> SELECT INSERT('Quadratic', 3, 4, 'What');
                  -> 'QuWhattic'
          mysql> SELECT INSERT('Quadratic', -1, 4, 'What');
                  -> 'Quadratic'
          mysql> SELECT INSERT('Quadratic', 3, 100, 'What');
                  -> 'QuWhat'

     This function is multibyte safe.

   * `INSTR(STR,SUBSTR)'

     Returns the position of the first occurrence of substring SUBSTR
     in string STR. This is the same as the two-argument form of
     `LOCATE()', except that the order of the arguments is reversed.


          mysql> SELECT INSTR('foobarbar', 'bar');
                  -> 4
          mysql> SELECT INSTR('xbar', 'foobar');
                  -> 0

     This function is multibyte safe, and is case sensitive only if at
     least one argument is a binary string.

   * `LCASE(STR)'

     `LCASE()' is a synonym for `LOWER()'.

   * `LEFT(STR,LEN)'

     Returns the leftmost LEN characters from the string STR, or `NULL'
     if any argument is `NULL'.


          mysql> SELECT LEFT('foobarbar', 5);
                  -> 'fooba'

     This function is multibyte safe.

   * `LENGTH(STR)'

     Returns the length of the string STR, measured in bytes. A
     multibyte character counts as multiple bytes. This means that for a
     string containing five 2-byte characters, `LENGTH()' returns `10',
     whereas `CHAR_LENGTH()' returns `5'.


          mysql> SELECT LENGTH('text');
                  -> 4

     *Note*:

     The `Length()' OpenGIS spatial function is named `GLength()' in
     MySQL.

   * `LOAD_FILE(FILE_NAME)'

     Reads the file and returns the file contents as a string. To use
     this function, the file must be located on the server host, you
     must specify the full path name to the file, and you must have the
     `FILE' privilege.  The file must be readable by all and its size
     less than `max_allowed_packet' bytes. If the `secure_file_priv'
     system variable is set to a nonempty directory name, the file to be
     loaded must be located in that directory.

     If the file does not exist or cannot be read because one of the
     preceding conditions is not satisfied, the function returns `NULL'.

     As of MySQL 5.1.6, the `character_set_filesystem' system variable
     controls interpretation of file names that are given as literal
     strings.


          mysql> UPDATE t
                      SET blob_col=LOAD_FILE('/tmp/picture')
                      WHERE id=1;

   * `LOCATE(SUBSTR,STR)', `LOCATE(SUBSTR,STR,POS)'

     The first syntax returns the position of the first occurrence of
     substring SUBSTR in string STR. The second syntax returns the
     position of the first occurrence of substring SUBSTR in string
     STR, starting at position POS. Returns `0' if SUBSTR is not in STR.


          mysql> SELECT LOCATE('bar', 'foobarbar');
                  -> 4
          mysql> SELECT LOCATE('xbar', 'foobar');
                  -> 0
          mysql> SELECT LOCATE('bar', 'foobarbar', 5);
                  -> 7

     This function is multibyte safe, and is case-sensitive only if at
     least one argument is a binary string.

   * `LOWER(STR)'

     Returns the string STR with all characters changed to lowercase
     according to the current character set mapping. The default is
     `latin1' (cp1252 West European).


          mysql> SELECT LOWER('QUADRATICALLY');
                  -> 'quadratically'

     `LOWER()' (and `UPPER()') are ineffective when applied to binary
     strings (*Note `BINARY': binary-varbinary, *Note `VARBINARY':
     binary-varbinary, *Note `BLOB': blob.). To perform lettercase
     conversion, convert the string to a nonbinary string:


          mysql> SET @str = BINARY 'New York';
          mysql> SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
          +-------------+-----------------------------------+
          | LOWER(@str) | LOWER(CONVERT(@str USING latin1)) |
          +-------------+-----------------------------------+
          | New York    | new york                          |
          +-------------+-----------------------------------+

     This function is multibyte safe.

   * `LPAD(STR,LEN,PADSTR)'

     Returns the string STR, left-padded with the string PADSTR to a
     length of LEN characters. If STR is longer than LEN, the return
     value is shortened to LEN characters.


          mysql> SELECT LPAD('hi',4,'??');
                  -> '??hi'
          mysql> SELECT LPAD('hi',1,'??');
                  -> 'h'

   * `LTRIM(STR)'

     Returns the string STR with leading space characters removed.


          mysql> SELECT LTRIM('  barbar');
                  -> 'barbar'

     This function is multibyte safe.

   * `MAKE_SET(BITS,STR1,STR2,...)'

     Returns a set value (a string containing substrings separated by
     ``,'' characters) consisting of the strings that have the
     corresponding bit in BITS set.  STR1 corresponds to bit 0, STR2 to
     bit 1, and so on.  `NULL' values in STR1, STR2, `...' are not
     appended to the result.


          mysql> SELECT MAKE_SET(1,'a','b','c');
                  -> 'a'
          mysql> SELECT MAKE_SET(1 | 4,'hello','nice','world');
                  -> 'hello,world'
          mysql> SELECT MAKE_SET(1 | 4,'hello','nice',NULL,'world');
                  -> 'hello'
          mysql> SELECT MAKE_SET(0,'a','b','c');
                  -> ''

   * `MID(STR,POS,LEN)'

     `MID(STR,POS,LEN)' is a synonym for `SUBSTRING(STR,POS,LEN)'.

   * `OCT(N)'

     Returns a string representation of the octal value of N, where N
     is a longlong (*Note `BIGINT': integer-types.) number. This is
     equivalent to `CONV(N,10,8)'.  Returns `NULL' if N is `NULL'.


          mysql> SELECT OCT(12);
                  -> '14'

   * `OCTET_LENGTH(STR)'

     `OCTET_LENGTH()' is a synonym for `LENGTH()'.

   * `ORD(STR)'

     If the leftmost character of the string STR is a multibyte
     character, returns the code for that character, calculated from the
     numeric values of its constituent bytes using this formula:


            (1st byte code)
          + (2nd byte code * 256)
          + (3rd byte code * 256^2) ...

     If the leftmost character is not a multibyte character, `ORD()'
     returns the same value as the `ASCII()' function.


          mysql> SELECT ORD('2');
                  -> 50

   * `POSITION(SUBSTR IN STR)'

     `POSITION(SUBSTR IN STR)' is a synonym for `LOCATE(SUBSTR,STR)'.

   * `QUOTE(STR)'

     Quotes a string to produce a result that can be used as a properly
     escaped data value in an SQL statement. The string is returned
     enclosed by single quotation marks and with each instance of
     backslash (``\''), single quote (``'''), ASCII `NUL', and
     Control+Z preceded by a backslash.  If the argument is `NULL', the
     return value is the word `NULL' without enclosing single quotation
     marks.


          mysql> SELECT QUOTE('Don\'t!');
                  -> 'Don\'t!'
          mysql> SELECT QUOTE(NULL);
                  -> NULL

     For comparison, see the quoting rules for literal strings and
     within the C API in *Note string-literals::, and *Note
     mysql-real-escape-string::.

   * `REPEAT(STR,COUNT)'

     Returns a string consisting of the string STR repeated COUNT
     times. If COUNT is less than 1, returns an empty string. Returns
     `NULL' if STR or COUNT are `NULL'.


          mysql> SELECT REPEAT('MySQL', 3);
                  -> 'MySQLMySQLMySQL'

   * `REPLACE(STR,FROM_STR,TO_STR)'

     Returns the string STR with all occurrences of the string FROM_STR
     replaced by the string TO_STR.  `REPLACE()' performs a
     case-sensitive match when searching for FROM_STR.


          mysql> SELECT REPLACE('www.mysql.com', 'w', 'Ww');
                  -> 'WwWwWw.mysql.com'

     This function is multibyte safe.

   * `REVERSE(STR)'

     Returns the string STR with the order of the characters reversed.


          mysql> SELECT REVERSE('abc');
                  -> 'cba'

     This function is multibyte safe.

   * `RIGHT(STR,LEN)'

     Returns the rightmost LEN characters from the string STR, or
     `NULL' if any argument is `NULL'.


          mysql> SELECT RIGHT('foobarbar', 4);
                  -> 'rbar'

     This function is multibyte safe.

   * `RPAD(STR,LEN,PADSTR)'

     Returns the string STR, right-padded with the string PADSTR to a
     length of LEN characters. If STR is longer than LEN, the return
     value is shortened to LEN characters.


          mysql> SELECT RPAD('hi',5,'?');
                  -> 'hi???'
          mysql> SELECT RPAD('hi',1,'?');
                  -> 'h'

     This function is multibyte safe.

   * `RTRIM(STR)'

     Returns the string STR with trailing space characters removed.


          mysql> SELECT RTRIM('barbar   ');
                  -> 'barbar'

     This function is multibyte safe.

   * `SOUNDEX(STR)'

     Returns a soundex string from STR.  Two strings that sound almost
     the same should have identical soundex strings. A standard soundex
     string is four characters long, but the `SOUNDEX()' function
     returns an arbitrarily long string. You can use `SUBSTRING()' on
     the result to get a standard soundex string. All nonalphabetic
     characters in STR are ignored. All international alphabetic
     characters outside the A-Z range are treated as vowels.

     *Important*:

     When using `SOUNDEX()', you should be aware of the following
     limitations:

        * This function, as currently implemented, is intended to work
          well with strings that are in the English language only.
          Strings in other languages may not produce reliable results.

        * This function is not guaranteed to provide consistent results
          with strings that use multibyte character sets, including
          `utf-8'.

          We hope to remove these limitations in a future release.  See
          Bug #22638 for more information.


          mysql> SELECT SOUNDEX('Hello');
                  -> 'H400'
          mysql> SELECT SOUNDEX('Quadratically');
                  -> 'Q36324'

     *Note*:

     This function implements the original Soundex algorithm, not the
     more popular enhanced version (also described by D.  Knuth). The
     difference is that original version discards vowels first and
     duplicates second, whereas the enhanced version discards
     duplicates first and vowels second.

   * `EXPR1 SOUNDS LIKE EXPR2'

     This is the same as `SOUNDEX(EXPR1) = SOUNDEX(EXPR2)'.

   * `SPACE(N)'

     Returns a string consisting of N space characters.


          mysql> SELECT SPACE(6);
                  -> '      '

   * `SUBSTR(STR,POS)', `SUBSTR(STR FROM POS)', `SUBSTR(STR,POS,LEN)',
     `SUBSTR(STR FROM POS FOR LEN)'

     `SUBSTR()' is a synonym for `SUBSTRING()'.

   * `SUBSTRING(STR,POS)', `SUBSTRING(STR FROM POS)',
     `SUBSTRING(STR,POS,LEN)', `SUBSTRING(STR FROM POS FOR LEN)'

     The forms without a LEN argument return a substring from string STR
     starting at position POS. The forms with a LEN argument return a
     substring LEN characters long from string STR, starting at position
     POS. The forms that use `FROM' are standard SQL syntax. It is also
     possible to use a negative value for POS. In this case, the
     beginning of the substring is POS characters from the end of the
     string, rather than the beginning. A negative value may be used
     for POS in any of the forms of this function.

     For all forms of `SUBSTRING()', the position of the first
     character in the string from which the substring is to be
     extracted is reckoned as `1'.


          mysql> SELECT SUBSTRING('Quadratically',5);
                  -> 'ratically'
          mysql> SELECT SUBSTRING('foobarbar' FROM 4);
                  -> 'barbar'
          mysql> SELECT SUBSTRING('Quadratically',5,6);
                  -> 'ratica'
          mysql> SELECT SUBSTRING('Sakila', -3);
                  -> 'ila'
          mysql> SELECT SUBSTRING('Sakila', -5, 3);
                  -> 'aki'
          mysql> SELECT SUBSTRING('Sakila' FROM -4 FOR 2);
                  -> 'ki'

     This function is multibyte safe.

     If LEN is less than 1, the result is the empty string.

   * `SUBSTRING_INDEX(STR,DELIM,COUNT)'

     Returns the substring from string STR before COUNT occurrences of
     the delimiter DELIM. If COUNT is positive, everything to the left
     of the final delimiter (counting from the left) is returned. If
     COUNT is negative, everything to the right of the final delimiter
     (counting from the right) is returned.  `SUBSTRING_INDEX()'
     performs a case-sensitive match when searching for DELIM.


          mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', 2);
                  -> 'www.mysql'
          mysql> SELECT SUBSTRING_INDEX('www.mysql.com', '.', -2);
                  -> 'mysql.com'

     This function is multibyte safe.

   * `TRIM([{BOTH | LEADING | TRAILING} [REMSTR] FROM] STR)',
     `TRIM([REMSTR FROM] STR)'

     Returns the string STR with all REMSTR prefixes or suffixes
     removed. If none of the specifiers `BOTH', `LEADING', or
     `TRAILING' is given, `BOTH' is assumed.  REMSTR is optional and,
     if not specified, spaces are removed.


          mysql> SELECT TRIM('  bar   ');
                  -> 'bar'
          mysql> SELECT TRIM(LEADING 'x' FROM 'xxxbarxxx');
                  -> 'barxxx'
          mysql> SELECT TRIM(BOTH 'x' FROM 'xxxbarxxx');
                  -> 'bar'
          mysql> SELECT TRIM(TRAILING 'xyz' FROM 'barxxyz');
                  -> 'barx'

     This function is multibyte safe.

   * `UCASE(STR)'

     `UCASE()' is a synonym for `UPPER()'.

   * `UNHEX(STR)'

     For a string argument STR, `UNHEX(STR)' interprets each pair of
     characters in the argument as a hexadecimal number and converts it
     to the byte represented by the number. The return value is a
     binary string.


          mysql> SELECT UNHEX('4D7953514C');
                  -> 'MySQL'
          mysql> SELECT 0x4D7953514C;
                  -> 'MySQL'
          mysql> SELECT UNHEX(HEX('string'));
                  -> 'string'
          mysql> SELECT HEX(UNHEX('1267'));
                  -> '1267'

     The characters in the argument string must be legal hexadecimal
     digits: `'0'' ..  `'9'', `'A'' ..  `'F'', `'a'' ..  `'f''. If the
     argument contains any nonhexadecimal digits, the result is `NULL':


          mysql> SELECT UNHEX('GG');
          +-------------+
          | UNHEX('GG') |
          +-------------+
          | NULL        |
          +-------------+

     A `NULL' result can occur if the argument to `UNHEX()' is a *Note
     `BINARY': binary-varbinary. column, because values are padded with
     0x00 bytes when stored but those bytes are not stripped on
     retrieval. For example, `'41'' is stored into a `CHAR(3)' column as
     `'41 '' and retrieved as `'41'' (with the trailing pad space
     stripped), so `UNHEX()' for the column value returns `'A''. By
     contrast `'41'' is stored into a `BINARY(3)' column as `'41\0''
     and retrieved as `'41\0'' (with the trailing pad `0x00' byte not
     stripped).  `'\0'' is not a legal hexadecimal digit, so `UNHEX()'
     for the column value returns `NULL'.

     For a numeric argument N, the inverse of `HEX(N)' is not performed
     by `UNHEX()'.  Use `CONV(HEX(N),16,10)' instead. See the
     description of `HEX()'.

   * `UPPER(STR)'

     Returns the string STR with all characters changed to uppercase
     according to the current character set mapping. The default is
     `latin1' (cp1252 West European).


          mysql> SELECT UPPER('Hej');
                  -> 'HEJ'

     See the description of `LOWER()' for information that also applies
     to `UPPER()', such as information about how to perform lettercase
     conversion of binary strings (*Note `BINARY': binary-varbinary,
     *Note `VARBINARY': binary-varbinary, *Note `BLOB': blob.) for
     which these functions are ineffective.

     This function is multibyte safe.


File: manual.info,  Node: string-comparison-functions,  Next: regexp,  Prev: string-functions,  Up: string-functions

12.5.1 String Comparison Functions
----------------------------------

*String Comparison Operators*

Name                          Description
`LIKE'                        Simple pattern matching
`NOT LIKE'                    Negation of simple pattern matching
`STRCMP()'                    Compare two strings

If a string function is given a binary string as an argument, the
resulting string is also a binary string. A number converted to a
string is treated as a binary string. This affects only comparisons.

Normally, if any expression in a string comparison is case sensitive,
the comparison is performed in case-sensitive fashion.

   * `EXPR LIKE PAT [ESCAPE 'ESCAPE_CHAR']'

     Pattern matching using SQL simple regular expression comparison.
     Returns `1' (`TRUE') or `0' (`FALSE'). If either EXPR or PAT is
     `NULL', the result is `NULL'.

     The pattern need not be a literal string. For example, it can be
     specified as a string expression or table column.

     Per the SQL standard, `LIKE' performs matching on a per-character
     basis, thus it can produce results different from the `='
     comparison operator:


          mysql> SELECT 'a"' LIKE 'ae' COLLATE latin1_german2_ci;
          +-----------------------------------------+
          | 'a"' LIKE 'ae' COLLATE latin1_german2_ci |
          +-----------------------------------------+
          |                                       0 |
          +-----------------------------------------+
          mysql> SELECT 'a"' = 'ae' COLLATE latin1_german2_ci;
          +--------------------------------------+
          | 'a"' = 'ae' COLLATE latin1_german2_ci |
          +--------------------------------------+
          |                                    1 |
          +--------------------------------------+

     In particular, trailing spaces are significant, which is not true
     for *Note `CHAR': char. or *Note `VARCHAR': char. comparisons
     performed with the `=' operator:


          mysql> SELECT 'a' = 'a ', 'a' LIKE 'a ';
          +------------+---------------+
          | 'a' = 'a ' | 'a' LIKE 'a ' |
          +------------+---------------+
          |          1 |             0 |
          +------------+---------------+
          1 row in set (0.00 sec)

     With `LIKE' you can use the following two wildcard characters in
     the pattern.

     This table lists wildcard characters that can be used with the
     `LIKE' string comparison function and provides a description of
     each character.

     Character     Description
     `%'           Matches any number of characters, even zero characters
     `_'           Matches exactly one character


          mysql> SELECT 'David!' LIKE 'David_';
                  -> 1
          mysql> SELECT 'David!' LIKE '%D%v%';
                  -> 1

     To test for literal instances of a wildcard character, precede it
     by the escape character. If you do not specify the `ESCAPE'
     character, ``\'' is assumed.

     This table lists strings that are assumed if you do not specify
     the `ESCAPE' character when testing for literal instances of
     wildcard characters.  A description of each string is provided.

     String        Description
     `\%'          Matches one ``%'' character
     `\_'          Matches one ``_'' character


          mysql> SELECT 'David!' LIKE 'David\_';
                  -> 0
          mysql> SELECT 'David_' LIKE 'David\_';
                  -> 1

     To specify a different escape character, use the `ESCAPE' clause:


          mysql> SELECT 'David_' LIKE 'David|_' ESCAPE '|';
                  -> 1

     The escape sequence should be empty or one character long.  The
     expression must evaluate as a constant at execution time. As of
     MySQL 5.1.2, if the `NO_BACKSLASH_ESCAPES' SQL mode is enabled,
     the sequence cannot be empty.

     The following two statements illustrate that string comparisons
     are not case sensitive unless one of the operands is a binary
     string:


          mysql> SELECT 'abc' LIKE 'ABC';
                  -> 1
          mysql> SELECT 'abc' LIKE BINARY 'ABC';
                  -> 0

     In MySQL, `LIKE' is permitted on numeric expressions. (This is an
     extension to the standard SQL `LIKE'.)


          mysql> SELECT 10 LIKE '1%';
                  -> 1

     *Note*:

     Because MySQL uses C escape syntax in strings (for example, ``\n''
     to represent a newline character), you must double any ``\'' that
     you use in `LIKE' strings. For example, to search for ``\n'',
     specify it as ``\\n''. To search for ``\'', specify it as
     ``\\\\''; this is because the backslashes are stripped once by the
     parser and again when the pattern match is made, leaving a single
     backslash to be matched against.

     Exception: At the end of the pattern string, backslash can be
     specified as ``\\''. At the end of the string, backslash stands
     for itself because there is nothing following to escape. Suppose
     that a table contains the following values:


          mysql> SELECT filename FROM t1;
          +--------------+
          | filename     |
          +--------------+
          | C:           |
          | C:\          |
          | C:\Programs  |
          | C:\Programs\ |
          +--------------+

     To test for values that end with backslash, you can match the
     values using either of the following patterns:


          mysql> SELECT filename, filename LIKE '%\\' FROM t1;
          +--------------+---------------------+
          | filename     | filename LIKE '%\\' |
          +--------------+---------------------+
          | C:           |                   0 |
          | C:\          |                   1 |
          | C:\Programs  |                   0 |
          | C:\Programs\ |                   1 |
          +--------------+---------------------+

          mysql> SELECT filename, filename LIKE '%\\\\' FROM t1;
          +--------------+-----------------------+
          | filename     | filename LIKE '%\\\\' |
          +--------------+-----------------------+
          | C:           |                     0 |
          | C:\          |                     1 |
          | C:\Programs  |                     0 |
          | C:\Programs\ |                     1 |
          +--------------+-----------------------+

   * `EXPR NOT LIKE PAT [ESCAPE 'ESCAPE_CHAR']'

     This is the same as `NOT (EXPR LIKE PAT [ESCAPE 'ESCAPE_CHAR'])'.

     *Note*:

     Aggregate queries involving `NOT LIKE' comparisons with columns
     containing `NULL' may yield unexpected results. For example,
     consider the following table and data:


          CREATE TABLE foo (bar VARCHAR(10));

          INSERT INTO foo VALUES (NULL), (NULL);

     The query `SELECT COUNT(*) FROM foo WHERE bar LIKE '%baz%';'
     returns `0'. You might assume that `SELECT COUNT(*) FROM foo WHERE
     bar NOT LIKE '%baz%';' would return `2'. However, this is not the
     case: The second query returns `0'. This is because `NULL NOT LIKE
     EXPR' always returns `NULL', regardless of the value of EXPR. The
     same is true for aggregate queries involving `NULL' and
     comparisons using `NOT RLIKE' or `NOT REGEXP'. In such cases, you
     must test explicitly for `NOT NULL' using `OR' (and not `AND'), as
     shown here:


          SELECT COUNT(*) FROM foo WHERE bar NOT LIKE '%baz%' OR bar IS NULL;

   * `STRCMP(EXPR1,EXPR2)'

     `STRCMP()' returns `0' if the strings are the same, `-1' if the
     first argument is smaller than the second according to the current
     sort order, and `1' otherwise.


          mysql> SELECT STRCMP('text', 'text2');
                  -> -1
          mysql> SELECT STRCMP('text2', 'text');
                  -> 1
          mysql> SELECT STRCMP('text', 'text');
                  -> 0

     `STRCMP()' performs the comparison using the collation of the
     arguments.


          mysql> SET @s1 = _latin1 'x' COLLATE latin1_general_ci;
          mysql> SET @s2 = _latin1 'X' COLLATE latin1_general_ci;
          mysql> SET @s3 = _latin1 'x' COLLATE latin1_general_cs;
          mysql> SET @s4 = _latin1 'X' COLLATE latin1_general_cs;
          mysql> SELECT STRCMP(@s1, @s2), STRCMP(@s3, @s4);
          +------------------+------------------+
          | STRCMP(@s1, @s2) | STRCMP(@s3, @s4) |
          +------------------+------------------+
          |                0 |                1 |
          +------------------+------------------+

     If the collations are incompatible, one of the arguments must be
     converted to be compatible with the other. See *Note
     charset-collation-expressions::.


          mysql> SELECT STRCMP(@s1, @s3);
          ERROR 1267 (HY000): Illegal mix of collations (latin1_general_ci,IMPLICIT) and (latin1_general_cs,IMPLICIT) for operation 'strcmp'
          mysql> SELECT STRCMP(@s1, @s3 COLLATE latin1_general_ci);
          +--------------------------------------------+
          | STRCMP(@s1, @s3 COLLATE latin1_general_ci) |
          +--------------------------------------------+
          |                                          0 |
          +--------------------------------------------+


File: manual.info,  Node: regexp,  Prev: string-comparison-functions,  Up: string-functions

12.5.2 Regular Expressions
--------------------------

*String Regular Expression Operators*

Name                          Description
`NOT REGEXP'                  Negation of REGEXP
`REGEXP'                      Pattern matching using regular expressions
`RLIKE'                       Synonym for REGEXP

A regular expression is a powerful way of specifying a pattern for a
complex search.

MySQL uses Henry Spencer's implementation of regular expressions, which
is aimed at conformance with POSIX 1003.2.  MySQL uses the extended
version to support pattern-matching operations performed with the
`REGEXP' operator in SQL statements.

This section summarizes, with examples, the special characters and
constructs that can be used in MySQL for `REGEXP' operations. It does
not contain all the details that can be found in Henry Spencer's
`regex(7)' manual page. That manual page is included in MySQL source
distributions, in the `regex.7' file under the `regex' directory. See
also *Note pattern-matching::.

*Regular Expression Operators*

   * `EXPR NOT REGEXP PAT', `EXPR NOT RLIKE PAT'

     This is the same as `NOT (EXPR REGEXP PAT)'.

   * `EXPR REGEXP PAT', `EXPR RLIKE PAT'

     Performs a pattern match of a string expression EXPR against a
     pattern PAT. The pattern can be an extended regular expression,
     the syntax for which is discussed later in this section. Returns
     `1' if EXPR matches PAT; otherwise it returns `0'. If either EXPR
     or PAT is `NULL', the result is `NULL'.  `RLIKE' is a synonym for
     `REGEXP', provided for `mSQL' compatibility.

     The pattern need not be a literal string. For example, it can be
     specified as a string expression or table column.

     *Note*:

     Because MySQL uses the C escape syntax in strings (for example,
     ``\n'' to represent the newline character), you must double any
     ``\'' that you use in your `REGEXP' strings.

     `REGEXP' is not case sensitive, except when used with binary
     strings.


          mysql> SELECT 'Monty!' REGEXP '.*';
                  -> 1
          mysql> SELECT 'new*\n*line' REGEXP 'new\\*.\\*line';
                  -> 1
          mysql> SELECT 'a' REGEXP 'A', 'a' REGEXP BINARY 'A';
                  -> 1  0
          mysql> SELECT 'a' REGEXP '^[a-d]';
                  -> 1

     `REGEXP' and `RLIKE' use the character set and collations of the
     arguments when deciding the type of a character and performing the
     comparison. If the arguments have different character sets or
     collations, coercibility rules apply as described in *Note
     charset-collation-expressions::.

     *Warning*:

     The `REGEXP' and `RLIKE' operators work in byte-wise fashion, so
     they are not multibyte safe and may produce unexpected results with
     multibyte character sets. In addition, these operators compare
     characters by their byte values and accented characters may not
     compare as equal even if a given collation treats them as equal.

*Syntax of Regular Expressions*

A regular expression describes a set of strings. The simplest regular
expression is one that has no special characters in it.  For example,
the regular expression `hello' matches `hello' and nothing else.

Nontrivial regular expressions use certain special constructs so that
they can match more than one string. For example, the regular
expression `hello|word' matches either the string `hello' or the string
`word'.

As a more complex example, the regular expression `B[an]*s' matches any
of the strings `Bananas', `Baaaaas', `Bs', and any other string
starting with a `B', ending with an `s', and containing any number of
`a' or `n' characters in between.

A regular expression for the `REGEXP' operator may use any of the
following special characters and constructs:

   * `^'

     Match the beginning of a string.


          mysql> SELECT 'fo\nfo' REGEXP '^fo$';                   -> 0
          mysql> SELECT 'fofo' REGEXP '^fo';                      -> 1

   * `$'

     Match the end of a string.


          mysql> SELECT 'fo\no' REGEXP '^fo\no$';                 -> 1
          mysql> SELECT 'fo\no' REGEXP '^fo$';                    -> 0

   * `.'

     Match any character (including carriage return and newline).


          mysql> SELECT 'fofo' REGEXP '^f.*$';                    -> 1
          mysql> SELECT 'fo\r\nfo' REGEXP '^f.*$';                -> 1

   * `a*'

     Match any sequence of zero or more `a' characters.


          mysql> SELECT 'Ban' REGEXP '^Ba*n';                     -> 1
          mysql> SELECT 'Baaan' REGEXP '^Ba*n';                   -> 1
          mysql> SELECT 'Bn' REGEXP '^Ba*n';                      -> 1

   * `a+'

     Match any sequence of one or more `a' characters.


          mysql> SELECT 'Ban' REGEXP '^Ba+n';                     -> 1
          mysql> SELECT 'Bn' REGEXP '^Ba+n';                      -> 0

   * `a?'

     Match either zero or one `a' character.


          mysql> SELECT 'Bn' REGEXP '^Ba?n';                      -> 1
          mysql> SELECT 'Ban' REGEXP '^Ba?n';                     -> 1
          mysql> SELECT 'Baan' REGEXP '^Ba?n';                    -> 0

   * `de|abc'

     Match either of the sequences `de' or `abc'.


          mysql> SELECT 'pi' REGEXP 'pi|apa';                     -> 1
          mysql> SELECT 'axe' REGEXP 'pi|apa';                    -> 0
          mysql> SELECT 'apa' REGEXP 'pi|apa';                    -> 1
          mysql> SELECT 'apa' REGEXP '^(pi|apa)$';                -> 1
          mysql> SELECT 'pi' REGEXP '^(pi|apa)$';                 -> 1
          mysql> SELECT 'pix' REGEXP '^(pi|apa)$';                -> 0

   * `(abc)*'

     Match zero or more instances of the sequence `abc'.


          mysql> SELECT 'pi' REGEXP '^(pi)*$';                    -> 1
          mysql> SELECT 'pip' REGEXP '^(pi)*$';                   -> 0
          mysql> SELECT 'pipi' REGEXP '^(pi)*$';                  -> 1

   * `{1}', `{2,3}'

     `{n}' or `{m,n}' notation provides a more general way of writing
     regular expressions that match many occurrences of the previous
     atom (or `piece') of the pattern. `m' and `n' are integers.

        * `a*'

          Can be written as `a{0,}'.

        * `a+'

          Can be written as `a{1,}'.

        * `a?'

          Can be written as `a{0,1}'.

     To be more precise, `a{n}' matches exactly `n' instances of `a'.
     `a{n,}' matches `n' or more instances of `a'.  `a{m,n}' matches `m'
     through `n' instances of `a', inclusive.

     `m' and `n' must be in the range from `0' to `RE_DUP_MAX' (default
     255), inclusive. If both `m' and `n' are given, `m' must be less
     than or equal to `n'.


          mysql> SELECT 'abcde' REGEXP 'a[bcd]{2}e';              -> 0
          mysql> SELECT 'abcde' REGEXP 'a[bcd]{3}e';              -> 1
          mysql> SELECT 'abcde' REGEXP 'a[bcd]{1,10}e';           -> 1

   * `[a-dX]', `[^a-dX]'

     Matches any character that is (or is not, if ^ is used) either
     `a', `b', `c', `d' or `X'. A `-' character between two other
     characters forms a range that matches all characters from the
     first character to the second. For example, `[0-9]' matches any
     decimal digit.  To include a literal `]' character, it must
     immediately follow the opening bracket `['.  To include a literal
     `-' character, it must be written first or last. Any character
     that does not have a defined special meaning inside a `[]' pair
     matches only itself.


          mysql> SELECT 'aXbc' REGEXP '[a-dXYZ]';                 -> 1
          mysql> SELECT 'aXbc' REGEXP '^[a-dXYZ]$';               -> 0
          mysql> SELECT 'aXbc' REGEXP '^[a-dXYZ]+$';              -> 1
          mysql> SELECT 'aXbc' REGEXP '^[^a-dXYZ]+$';             -> 0
          mysql> SELECT 'gheis' REGEXP '^[^a-dXYZ]+$';            -> 1
          mysql> SELECT 'gheisa' REGEXP '^[^a-dXYZ]+$';           -> 0

   * `[.characters.]'

     Within a bracket expression (written using `[' and `]'), matches
     the sequence of characters of that collating element.
     `characters' is either a single character or a character name like
     `newline'. The following table lists the permissible character
     names.

     The following table shows the permissible character names and the
     characters that they match. For characters given as numeric
     values, the values are represented in octal.

     This table shows permissible character names and matching
     characters. To save space, the column pairing of Name and
     Character are presented in a four column table format in this
     order: Name, Character, Name, Character.  For characters given as
     numeric values, the values are represented in octal.

     Name              Character         Name              Character
     `NUL'             `0'               `SOH'             `001'
     `STX'             `002'             `ETX'             `003'
     `EOT'             `004'             `ENQ'             `005'
     `ACK'             `006'             `BEL'             `007'
     `alert'           `007'             `BS'              `010'
     `backspace'       `'\b''            `HT'              `011'
     `tab'             `'\t''            `LF'              `012'
     `newline'         `'\n''            `VT'              `013'
     `vertical-tab'    `'\v''            `FF'              `014'
     `form-feed'       `'\f''            `CR'              `015'
     `carriage-return' `'\r''            `SO'              `016'
     `SI'              `017'             `DLE'             `020'
     `DC1'             `021'             `DC2'             `022'
     `DC3'             `023'             `DC4'             `024'
     `NAK'             `025'             `SYN'             `026'
     `ETB'             `027'             `CAN'             `030'
     `EM'              `031'             `SUB'             `032'
     `ESC'             `033'             `IS4'             `034'
     `FS'              `034'             `IS3'             `035'
     `GS'              `035'             `IS2'             `036'
     `RS'              `036'             `IS1'             `037'
     `US'              `037'             `space'           `' ''
     `exclamation-mark'`'!''             `quotation-mark'  `'"''
     `number-sign'     `'#''             `dollar-sign'     `'$''
     `percent-sign'    `'%''             `ampersand'       `'&''
     `apostrophe'      `'\'''            `left-parenthesis'`'(''
     `right-parenthesis'`')''             `asterisk'        `'*''
     `plus-sign'       `'+''             `comma'           `',''
     `hyphen'          `'-''             `hyphen-minus'    `'-''
     `period'          `'.''             `full-stop'       `'.''
     `slash'           `'/''             `solidus'         `'/''
     `zero'            `'0''             `one'             `'1''
     `two'             `'2''             `three'           `'3''
     `four'            `'4''             `five'            `'5''
     `six'             `'6''             `seven'           `'7''
     `eight'           `'8''             `nine'            `'9''
     `colon'           `':''             `semicolon'       `';''
     `less-than-sign'  `'<''             `equals-sign'     `'=''
     `greater-than-sign'`'>''             `question-mark'   `'?''
     `commercial-at'   `'@''             `left-square-bracket'`'[''
     `backslash'       `'\\''            `reverse-solidus' `'\\''
     `right-square-bracket'`']''             `circumflex'      `'^''
     `circumflex-accent'`'^''             `underscore'      `'_''
     `low-line'        `'_''             `grave-accent'    `'`''
     `left-brace'      `'{''             `left-curly-bracket'`'{''
     `vertical-line'   `'|''             `right-brace'     `'}''
     `right-curly-bracket'`'}''             `tilde'           `'~''
     `DEL'             `177'                               


          mysql> SELECT '~' REGEXP '[[.~.]]';                     -> 1
          mysql> SELECT '~' REGEXP '[[.tilde.]]';                 -> 1

   * `[=character_class=]'

     Within a bracket expression (written using `[' and `]'),
     `[=character_class=]' represents an equivalence class. It matches
     all characters with the same collation value, including itself.
     For example, if `o' and `(+)' are the members of an equivalence
     class, `[[=o=]]', `[[=(+)=]]', and `[o(+)]' are all synonymous. An
     equivalence class may not be used as an endpoint of a range.

   * `[:character_class:]'

     Within a bracket expression (written using `[' and `]'),
     `[:character_class:]' represents a character class that matches
     all characters belonging to that class. The following table lists
     the standard class names. These names stand for the character
     classes defined in the `ctype(3)' manual page. A particular locale
     may provide other class names. A character class may not be used
     as an endpoint of a range.

     This table lists character class names and describes the meaning
     of each.

     Character     Meaning
     Class Name    
     `alnum'       Alphanumeric characters
     `alpha'       Alphabetic characters
     `blank'       Whitespace characters
     `cntrl'       Control characters
     `digit'       Digit characters
     `graph'       Graphic characters
     `lower'       Lowercase alphabetic characters
     `print'       Graphic or space characters
     `punct'       Punctuation characters
     `space'       Space, tab, newline, and carriage return
     `upper'       Uppercase alphabetic characters
     `xdigit'      Hexadecimal digit characters


          mysql> SELECT 'justalnums' REGEXP '[[:alnum:]]+';       -> 1
          mysql> SELECT '!!' REGEXP '[[:alnum:]]+';               -> 0

   * `[[:<:]]', `[[:>:]]'

     These markers stand for word boundaries. They match the beginning
     and end of words, respectively. A word is a sequence of word
     characters that is not preceded by or followed by word characters.
     A word character is an alphanumeric character in the `alnum' class
     or an underscore (`_').


          mysql> SELECT 'a word a' REGEXP '[[:<:]]word[[:>:]]';   -> 1
          mysql> SELECT 'a xword a' REGEXP '[[:<:]]word[[:>:]]';  -> 0

To use a literal instance of a special character in a regular
expression, precede it by two backslash (\) characters. The MySQL
parser interprets one of the backslashes, and the regular expression
library interprets the other. For example, to match the string `1+2'
that contains the special `+' character, only the last of the following
regular expressions is the correct one:


     mysql> SELECT '1+2' REGEXP '1+2';                       -> 0
     mysql> SELECT '1+2' REGEXP '1\+2';                      -> 0
     mysql> SELECT '1+2' REGEXP '1\\+2';                     -> 1


File: manual.info,  Node: numeric-functions,  Next: date-and-time-functions,  Prev: string-functions,  Up: functions

12.6 Numeric Functions and Operators
====================================

* Menu:

* arithmetic-functions::         Arithmetic Operators
* mathematical-functions::       Mathematical Functions

*Numeric Functions and Operators*

Name                          Description
`ABS()'                       Return the absolute value
`ACOS()'                      Return the arc cosine
`ASIN()'                      Return the arc sine
`ATAN2()', `ATAN()'           Return the arc tangent of the two arguments
`ATAN()'                      Return the arc tangent
`CEIL()'                      Return the smallest integer value not less
                              than the argument
`CEILING()'                   Return the smallest integer value not less
                              than the argument
`CONV()'                      Convert numbers between different number
                              bases
`COS()'                       Return the cosine
`COT()'                       Return the cotangent
`CRC32()'                     Compute a cyclic redundancy check value
`DEGREES()'                   Convert radians to degrees
`DIV'                         Integer division
`/'                           Division operator
`EXP()'                       Raise to the power of
`FLOOR()'                     Return the largest integer value not
                              greater than the argument
`LN()'                        Return the natural logarithm of the
                              argument
`LOG10()'                     Return the base-10 logarithm of the
                              argument
`LOG2()'                      Return the base-2 logarithm of the argument
`LOG()'                       Return the natural logarithm of the first
                              argument
`-'                           Minus operator
`MOD()'                       Return the remainder
`% or MOD'                    Modulo operator
`PI()'                        Return the value of pi
`+'                           Addition operator
`POW()'                       Return the argument raised to the
                              specified power
`POWER()'                     Return the argument raised to the
                              specified power
`RADIANS()'                   Return argument converted to radians
`RAND()'                      Return a random floating-point value
`ROUND()'                     Round the argument
`SIGN()'                      Return the sign of the argument
`SIN()'                       Return the sine of the argument
`SQRT()'                      Return the square root of the argument
`TAN()'                       Return the tangent of the argument
`*'                           Multiplication operator
`TRUNCATE()'                  Truncate to specified number of decimal
                              places
`-'                           Change the sign of the argument


File: manual.info,  Node: arithmetic-functions,  Next: mathematical-functions,  Prev: numeric-functions,  Up: numeric-functions

12.6.1 Arithmetic Operators
---------------------------

*Arithmetic Operators*

Name                          Description
`DIV'                         Integer division
`/'                           Division operator
`-'                           Minus operator
`% or MOD'                    Modulo operator
`+'                           Addition operator
`*'                           Multiplication operator
`-'                           Change the sign of the argument

The usual arithmetic operators are available. The result is determined
according to the following rules:

   * In the case of `-', `+', and `*', the result is calculated with
     *Note `BIGINT': integer-types.  (64-bit) precision if both
     operands are integers.

   * If both operands are integers and any of them are unsigned, the
     result is an unsigned integer. For subtraction, if the
     `NO_UNSIGNED_SUBTRACTION' SQL mode is enabled, the result is
     signed even if any operand is unsigned.

   * If any of the operands of a `+', `-', `/', `*', `%' is a real or
     string value, the precision of the result is the precision of the
     operand with the maximum precision.

   * In division performed with `/', the scale of the result when using
     two exact-value operands is the scale of the first operand plus
     the value of the `div_precision_increment' system variable (which
     is 4 by default). For example, the result of the expression `5.05
     / 0.014' has a scale of six decimal places (`360.714286').

These rules are applied for each operation, such that nested
calculations imply the precision of each component. Hence, `(14620 /
9432456) / (24250 / 9432456)', resolves first to `(0.0014) / (0.0026)',
with the final result having 8 decimal places (`0.60288653').

Because of these rules and the way they are applied, care should be
taken to ensure that components and subcomponents of a calculation use
the appropriate level of precision. See *Note cast-functions::.

For information about handling of overflow in numeric expression
evaluation, see *Note out-of-range-and-overflow::.

Arithmetic operators apply to numbers. For other types of values,
alternative operations may be available. For example, to add date
values, use `DATE_ADD()'; see *Note date-and-time-functions::.

   * `+'

     Addition:


          mysql> SELECT 3+5;
                  -> 8

   * `-'

     Subtraction:


          mysql> SELECT 3-5;
                  -> -2

   * `-'

     Unary minus. This operator changes the sign of the operand.


          mysql> SELECT - 2;
                  -> -2

     *Note*:

     If this operator is used with a *Note `BIGINT': integer-types, the
     return value is also a *Note `BIGINT': integer-types. This means
     that you should avoid using `-' on integers that may have the
     value of -2^63.

   * `*'

     Multiplication:


          mysql> SELECT 3*5;
                  -> 15
          mysql> SELECT 18014398509481984*18014398509481984.0;
                  -> 324518553658426726783156020576256.0

   * `/'

     Division:


          mysql> SELECT 3/5;
                  -> 0.60

     Division by zero produces a `NULL' result:


          mysql> SELECT 102/(1-1);
                  -> NULL

     A division is calculated with *Note `BIGINT': integer-types.
     arithmetic only if performed in a context where its result is
     converted to an integer.

   * `DIV'

     Integer division. Similar to `FLOOR()', but is safe with *Note
     `BIGINT': integer-types. values. Incorrect results may occur for
     noninteger operands that exceed *Note `BIGINT': integer-types.
     range.


          mysql> SELECT 5 DIV 2;
                  -> 2

   * `N % M', `N MOD M'

     Modulo operation. Returns the remainder of N divided by M. For
     more information, see the description for the `MOD()' function in
     *Note mathematical-functions::.


File: manual.info,  Node: mathematical-functions,  Prev: arithmetic-functions,  Up: numeric-functions

12.6.2 Mathematical Functions
-----------------------------

*Mathematical Functions*

Name                          Description
`ABS()'                       Return the absolute value
`ACOS()'                      Return the arc cosine
`ASIN()'                      Return the arc sine
`ATAN2()', `ATAN()'           Return the arc tangent of the two arguments
`ATAN()'                      Return the arc tangent
`CEIL()'                      Return the smallest integer value not less
                              than the argument
`CEILING()'                   Return the smallest integer value not less
                              than the argument
`CONV()'                      Convert numbers between different number
                              bases
`COS()'                       Return the cosine
`COT()'                       Return the cotangent
`CRC32()'                     Compute a cyclic redundancy check value
`DEGREES()'                   Convert radians to degrees
`EXP()'                       Raise to the power of
`FLOOR()'                     Return the largest integer value not
                              greater than the argument
`LN()'                        Return the natural logarithm of the
                              argument
`LOG10()'                     Return the base-10 logarithm of the
                              argument
`LOG2()'                      Return the base-2 logarithm of the argument
`LOG()'                       Return the natural logarithm of the first
                              argument
`MOD()'                       Return the remainder
`PI()'                        Return the value of pi
`POW()'                       Return the argument raised to the
                              specified power
`POWER()'                     Return the argument raised to the
                              specified power
`RADIANS()'                   Return argument converted to radians
`RAND()'                      Return a random floating-point value
`ROUND()'                     Round the argument
`SIGN()'                      Return the sign of the argument
`SIN()'                       Return the sine of the argument
`SQRT()'                      Return the square root of the argument
`TAN()'                       Return the tangent of the argument
`TRUNCATE()'                  Truncate to specified number of decimal
                              places

All mathematical functions return `NULL' in the event of an error.

   * `ABS(X)'

     Returns the absolute value of X.


          mysql> SELECT ABS(2);
                  -> 2
          mysql> SELECT ABS(-32);
                  -> 32

     This function is safe to use with *Note `BIGINT': integer-types.
     values.

   * `ACOS(X)'

     Returns the arc cosine of X, that is, the value whose cosine is X.
     Returns `NULL' if X is not in the range `-1' to `1'.


          mysql> SELECT ACOS(1);
                  -> 0
          mysql> SELECT ACOS(1.0001);
                  -> NULL
          mysql> SELECT ACOS(0);
                  -> 1.5707963267949

   * `ASIN(X)'

     Returns the arc sine of X, that is, the value whose sine is X.
     Returns `NULL' if X is not in the range `-1' to `1'.


          mysql> SELECT ASIN(0.2);
                  -> 0.20135792079033
          mysql> SELECT ASIN('foo');

          +-------------+
          | ASIN('foo') |
          +-------------+
          |           0 |
          +-------------+
          1 row in set, 1 warning (0.00 sec)

          mysql> SHOW WARNINGS;
          +---------+------+-----------------------------------------+
          | Level   | Code | Message                                 |
          +---------+------+-----------------------------------------+
          | Warning | 1292 | Truncated incorrect DOUBLE value: 'foo' |
          +---------+------+-----------------------------------------+

   * `ATAN(X)'

     Returns the arc tangent of X, that is, the value whose tangent is
     X.


          mysql> SELECT ATAN(2);
                  -> 1.1071487177941
          mysql> SELECT ATAN(-2);
                  -> -1.1071487177941

   * `ATAN(Y,X)', `ATAN2(Y,X)'

     Returns the arc tangent of the two variables X and Y. It is
     similar to calculating the arc tangent of `Y / X', except that the
     signs of both arguments are used to determine the quadrant of the
     result.


          mysql> SELECT ATAN(-2,2);
                  -> -0.78539816339745
          mysql> SELECT ATAN2(PI(),0);
                  -> 1.5707963267949

   * `CEIL(X)'

     `CEIL()' is a synonym for `CEILING()'.

   * `CEILING(X)'

     Returns the smallest integer value not less than X.


          mysql> SELECT CEILING(1.23);
                  -> 2
          mysql> SELECT CEILING(-1.23);
                  -> -1

     For exact-value numeric arguments, the return value has an
     exact-value numeric type. For string or floating-point arguments,
     the return value has a floating-point type.

   * `CONV(N,FROM_BASE,TO_BASE)'

     Converts numbers between different number bases. Returns a string
     representation of the number N, converted from base FROM_BASE to
     base TO_BASE. Returns `NULL' if any argument is `NULL'. The
     argument N is interpreted as an integer, but may be specified as
     an integer or a string. The minimum base is `2' and the maximum
     base is `36'. If TO_BASE is a negative number, N is regarded as a
     signed number. Otherwise, N is treated as unsigned.  `CONV()'
     works with 64-bit precision.


          mysql> SELECT CONV('a',16,2);
                  -> '1010'
          mysql> SELECT CONV('6E',18,8);
                  -> '172'
          mysql> SELECT CONV(-17,10,-18);
                  -> '-H'
          mysql> SELECT CONV(10+'10'+'10'+0xa,10,10);
                  -> '40'

   * `COS(X)'

     Returns the cosine of X, where X is given in radians.


          mysql> SELECT COS(PI());
                  -> -1

   * `COT(X)'

     Returns the cotangent of X.


          mysql> SELECT COT(12);
                  -> -1.5726734063977
          mysql> SELECT COT(0);
                  -> NULL

   * `CRC32(EXPR)'

     Computes a cyclic redundancy check value and returns a 32-bit
     unsigned value. The result is `NULL' if the argument is `NULL'.
     The argument is expected to be a string and (if possible) is
     treated as one if it is not.


          mysql> SELECT CRC32('MySQL');
                  -> 3259397556
          mysql> SELECT CRC32('mysql');
                  -> 2501908538

   * `DEGREES(X)'

     Returns the argument X, converted from radians to degrees.


          mysql> SELECT DEGREES(PI());
                  -> 180
          mysql> SELECT DEGREES(PI() / 2);
                  -> 90

   * `EXP(X)'

     Returns the value of _e_ (the base of natural logarithms) raised
     to the power of X. The inverse of this function is `LOG()' (using
     a single argument only) or `LN()'.


          mysql> SELECT EXP(2);
                  -> 7.3890560989307
          mysql> SELECT EXP(-2);
                  -> 0.13533528323661
          mysql> SELECT EXP(0);
                  -> 1

   * `FLOOR(X)'

     Returns the largest integer value not greater than X.


          mysql> SELECT FLOOR(1.23);
                  -> 1
          mysql> SELECT FLOOR(-1.23);
                  -> -2

     For exact-value numeric arguments, the return value has an
     exact-value numeric type. For string or floating-point arguments,
     the return value has a floating-point type.

   * `FORMAT(X,D)'

     Formats the number X to a format like `'#,###,###.##'', rounded to
     D decimal places, and returns the result as a string. For details,
     see *Note string-functions::.

   * `HEX(N_or_S)'

     This function can be used to obtain a hexadecimal representation
     of a decimal number or a string; the manner in which it does so
     varies according to the argument's type. See this function's
     description in *Note string-functions::, for details.

   * `LN(X)'

     Returns the natural logarithm of X; that is, the base-_e_
     logarithm of X. If X is less than or equal to 0, then `NULL' is
     returned.


          mysql> SELECT LN(2);
                  -> 0.69314718055995
          mysql> SELECT LN(-2);
                  -> NULL

     This function is synonymous with `LOG(X)'.  The inverse of this
     function is the `EXP()' function.

   * `LOG(X)', `LOG(B,X)'

     If called with one parameter, this function returns the natural
     logarithm of X. If X is less than or equal to 0, then `NULL' is
     returned.

     The inverse of this function (when called with a single argument)
     is the `EXP()' function.


          mysql> SELECT LOG(2);
                  -> 0.69314718055995
          mysql> SELECT LOG(-2);
                  -> NULL

     If called with two parameters, this function returns the logarithm
     of X to the base B. If X is less than or equal to 0, or if B is
     less than or equal to 1, then `NULL' is returned.


          mysql> SELECT LOG(2,65536);
                  -> 16
          mysql> SELECT LOG(10,100);
                  -> 2
          mysql> SELECT LOG(1,100);
                  -> NULL

     `LOG(B,X)' is equivalent to `LOG(X) / LOG(B)'.

   * `LOG2(X)'

     Returns the base-2 logarithm of `X'.


          mysql> SELECT LOG2(65536);
                  -> 16
          mysql> SELECT LOG2(-100);
                  -> NULL

     `LOG2()' is useful for finding out how many bits a number requires
     for storage. This function is equivalent to the expression `LOG(X)
     / LOG(2)'.

   * `LOG10(X)'

     Returns the base-10 logarithm of X.


          mysql> SELECT LOG10(2);
                  -> 0.30102999566398
          mysql> SELECT LOG10(100);
                  -> 2
          mysql> SELECT LOG10(-100);
                  -> NULL

     `LOG10(X)' is equivalent to `LOG(10,X)'.

   * `MOD(N,M)', `N % M', `N MOD M'

     Modulo operation. Returns the remainder of N divided by M.


          mysql> SELECT MOD(234, 10);
                  -> 4
          mysql> SELECT 253 % 7;
                  -> 1
          mysql> SELECT MOD(29,9);
                  -> 2
          mysql> SELECT 29 MOD 9;
                  -> 2

     This function is safe to use with *Note `BIGINT': integer-types.
     values.

     `MOD()' also works on values that have a fractional part and
     returns the exact remainder after division:


          mysql> SELECT MOD(34.5,3);
                  -> 1.5

     `MOD(N,0)' returns `NULL'.

   * `PI()'

     Returns the value of π (pi). The default number of decimal places
     displayed is seven, but MySQL uses the full double-precision value
     internally.


          mysql> SELECT PI();
                  -> 3.141593
          mysql> SELECT PI()+0.000000000000000000;
                  -> 3.141592653589793116

   * `POW(X,Y)'

     Returns the value of X raised to the power of Y.


          mysql> SELECT POW(2,2);
                  -> 4
          mysql> SELECT POW(2,-2);
                  -> 0.25

   * `POWER(X,Y)'

     This is a synonym for `POW()'.

   * `RADIANS(X)'

     Returns the argument X, converted from degrees to radians. (Note
     that π radians equals 180 degrees.)


          mysql> SELECT RADIANS(90);
                  -> 1.5707963267949

   * `RAND()', `RAND(N)'

     Returns a random floating-point value V in the range `0' <= V <
     `1.0'. If a constant integer argument N is specified, it is used
     as the seed value, which produces a repeatable sequence of column
     values. In the following example, note that the sequences of
     values produced by `RAND(3)' is the same both places where it
     occurs.


          mysql> CREATE TABLE t (i INT);
          Query OK, 0 rows affected (0.42 sec)

          mysql> INSERT INTO t VALUES(1),(2),(3);
          Query OK, 3 rows affected (0.00 sec)
          Records: 3  Duplicates: 0  Warnings: 0

          mysql> SELECT i, RAND() FROM t;
          +------+------------------+
          | i    | RAND()           |
          +------+------------------+
          |    1 | 0.61914388706828 |
          |    2 | 0.93845168309142 |
          |    3 | 0.83482678498591 |
          +------+------------------+
          3 rows in set (0.00 sec)

          mysql> SELECT i, RAND(3) FROM t;
          +------+------------------+
          | i    | RAND(3)          |
          +------+------------------+
          |    1 | 0.90576975597606 |
          |    2 | 0.37307905813035 |
          |    3 | 0.14808605345719 |
          +------+------------------+
          3 rows in set (0.00 sec)

          mysql> SELECT i, RAND() FROM t;
          +------+------------------+
          | i    | RAND()           |
          +------+------------------+
          |    1 | 0.35877890638893 |
          |    2 | 0.28941420772058 |
          |    3 | 0.37073435016976 |
          +------+------------------+
          3 rows in set (0.00 sec)

          mysql> SELECT i, RAND(3) FROM t;
          +------+------------------+
          | i    | RAND(3)          |
          +------+------------------+
          |    1 | 0.90576975597606 |
          |    2 | 0.37307905813035 |
          |    3 | 0.14808605345719 |
          +------+------------------+
          3 rows in set (0.01 sec)

     With a constant initializer, the seed is initialized once when the
     statement is compiled, prior to execution. As of MySQL 5.1.16, if
     a nonconstant initializer (such as a column name) is used as the
     argument, the seed is initialized with the value for each
     invocation of `RAND()'. (One implication of this is that for equal
     argument values, `RAND()' will return the same value each time.)
     From MySQL 5.1.3 to 5.1.15, nonconstant arguments are not
     permitted. Before that, the effect of using a nonconstant argument
     is undefined.

     To obtain a random integer R in the range I <= R < J, use the
     expression `FLOOR(I + RAND() * (J' - `I))'.  For example, to
     obtain a random integer in the range the range `7' <= R < `12', you
     could use the following statement:


          SELECT FLOOR(7 + (RAND() * 5));

     `RAND()' in a `WHERE' clause is re-evaluated every time the
     `WHERE' is executed.

     You cannot use a column with `RAND()' values in an `ORDER BY'
     clause, because `ORDER BY' would evaluate the column multiple
     times.  However, you can retrieve rows in random order like this:


          mysql> SELECT * FROM TBL_NAME ORDER BY RAND();

     `ORDER BY RAND()' combined with `LIMIT' is useful for selecting a
     random sample from a set of rows:


          mysql> SELECT * FROM table1, table2 WHERE a=b AND c<d -> ORDER BY RAND() LIMIT 1000;

     `RAND()' is not meant to be a perfect random generator. It is a
     fast way to generate random numbers on demand that is portable
     between platforms for the same MySQL version.

     Beginning with MySQL 5.1.43, this function is flagged as unsafe
     for statement-based replication; use of this function causes a
     warning when using statement-based replication, and the statement
     is logged using the binary format when `binlog_format' is `MIXED'.
     (Bug #49222)

   * `ROUND(X)', `ROUND(X,D)'

     Rounds the argument X to D decimal places. The rounding algorithm
     depends on the data type of X. D defaults to 0 if not specified. D
     can be negative to cause D digits left of the decimal point of the
     value X to become zero.


          mysql> SELECT ROUND(-1.23);
                  -> -1
          mysql> SELECT ROUND(-1.58);
                  -> -2
          mysql> SELECT ROUND(1.58);
                  -> 2
          mysql> SELECT ROUND(1.298, 1);
                  -> 1.3
          mysql> SELECT ROUND(1.298, 0);
                  -> 1
          mysql> SELECT ROUND(23.298, -1);
                  -> 20

     The return type is the same type as that of the first argument
     (assuming that it is integer, double, or decimal).  This means
     that for an integer argument, the result is an integer (no decimal
     places):


          mysql> SELECT ROUND(150.000,2), ROUND(150,2);
          +------------------+--------------+
          | ROUND(150.000,2) | ROUND(150,2) |
          +------------------+--------------+
          |           150.00 |          150 |
          +------------------+--------------+

     `ROUND()' uses the following rules depending on the type of the
     first argument:

        * For exact-value numbers, `ROUND()' uses the `round half away
          from zero' or `round toward nearest' rule: A value with a
          fractional part of .5 or greater is rounded up to the next
          integer if positive or down to the next integer if negative.
          (In other words, it is rounded away from zero.) A value with
          a fractional part less than .5 is rounded down to the next
          integer if positive or up to the next integer if negative.

        * For approximate-value numbers, the result depends on the C
          library. On many systems, this means that `ROUND()' uses the
          "round to nearest even" rule: A value with any fractional part
          is rounded to the nearest even integer.

     The following example shows how rounding differs for exact and
     approximate values:


          mysql> SELECT ROUND(2.5), ROUND(25E-1);
          +------------+--------------+
          | ROUND(2.5) | ROUND(25E-1) |
          +------------+--------------+
          | 3          |            2 |
          +------------+--------------+

     For more information, see *Note precision-math::.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.43, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #49222)

   * `SIGN(X)'

     Returns the sign of the argument as `-1', `0', or `1', depending on
     whether X is negative, zero, or positive.


          mysql> SELECT SIGN(-32);
                  -> -1
          mysql> SELECT SIGN(0);
                  -> 0
          mysql> SELECT SIGN(234);
                  -> 1

   * `SIN(X)'

     Returns the sine of X, where X is given in radians.


          mysql> SELECT SIN(PI());
                  -> 1.2246063538224e-16
          mysql> SELECT ROUND(SIN(PI()));
                  -> 0

   * `SQRT(X)'

     Returns the square root of a nonnegative number X.


          mysql> SELECT SQRT(4);
                  -> 2
          mysql> SELECT SQRT(20);
                  -> 4.4721359549996
          mysql> SELECT SQRT(-16);
                  -> NULL

   * `TAN(X)'

     Returns the tangent of X, where X is given in radians.


          mysql> SELECT TAN(PI());
                  -> -1.2246063538224e-16
          mysql> SELECT TAN(PI()+1);
                  -> 1.5574077246549

   * `TRUNCATE(X,D)'

     Returns the number X, truncated to D decimal places. If D is `0',
     the result has no decimal point or fractional part.  D can be
     negative to cause D digits left of the decimal point of the value
     X to become zero.


          mysql> SELECT TRUNCATE(1.223,1);
                  -> 1.2
          mysql> SELECT TRUNCATE(1.999,1);
                  -> 1.9
          mysql> SELECT TRUNCATE(1.999,0);
                  -> 1
          mysql> SELECT TRUNCATE(-1.999,1);
                  -> -1.9
          mysql> SELECT TRUNCATE(122,-2);
                 -> 100
          mysql> SELECT TRUNCATE(10.28*100,0);
                 -> 1028

     All numbers are rounded toward zero.


File: manual.info,  Node: date-and-time-functions,  Next: mysql-calendar,  Prev: numeric-functions,  Up: functions

12.7 Date and Time Functions
============================

This section describes the functions that can be used to manipulate
temporal values. See *Note date-and-time-types::, for a description of
the range of values each date and time type has and the valid formats
in which values may be specified.

*Date/Time Functions*

Name                          Description
`ADDDATE()'                   Add time values (intervals) to a date value
`ADDTIME()'                   Add time
`CONVERT_TZ()'                Convert from one timezone to another
`CURDATE()'                   Return the current date
`CURRENT_DATE()',             Synonyms for CURDATE()
`CURRENT_DATE'                
`CURRENT_TIME()',             Synonyms for CURTIME()
`CURRENT_TIME'                
`CURRENT_TIMESTAMP()',        Synonyms for NOW()
`CURRENT_TIMESTAMP'           
`CURTIME()'                   Return the current time
`DATE_ADD()'                  Add time values (intervals) to a date value
`DATE_FORMAT()'               Format date as specified
`DATE_SUB()'                  Subtract a time value (interval) from a
                              date
`DATE()'                      Extract the date part of a date or
                              datetime expression
`DATEDIFF()'                  Subtract two dates
`DAY()'                       Synonym for DAYOFMONTH()
`DAYNAME()'                   Return the name of the weekday
`DAYOFMONTH()'                Return the day of the month (0-31)
`DAYOFWEEK()'                 Return the weekday index of the argument
`DAYOFYEAR()'                 Return the day of the year (1-366)
`EXTRACT()'                   Extract part of a date
`FROM_DAYS()'                 Convert a day number to a date
`FROM_UNIXTIME()'             Format UNIX timestamp as a date
`GET_FORMAT()'                Return a date format string
`HOUR()'                      Extract the hour
`LAST_DAY'                    Return the last day of the month for the
                              argument
`LOCALTIME()', `LOCALTIME'    Synonym for NOW()
`LOCALTIMESTAMP',             Synonym for NOW()
`LOCALTIMESTAMP()'            
`MAKEDATE()'                  Create a date from the year and day of year
`MAKETIME()'                  Create time from hour, minute, second
`MICROSECOND()'               Return the microseconds from argument
`MINUTE()'                    Return the minute from the argument
`MONTH()'                     Return the month from the date passed
`MONTHNAME()'                 Return the name of the month
`NOW()'                       Return the current date and time
`PERIOD_ADD()'                Add a period to a year-month
`PERIOD_DIFF()'               Return the number of months between periods
`QUARTER()'                   Return the quarter from a date argument
`SEC_TO_TIME()'               Converts seconds to 'HH:MM:SS' format
`SECOND()'                    Return the second (0-59)
`STR_TO_DATE()'               Convert a string to a date
`SUBDATE()'                   Synonym for DATE_SUB() when invoked with
                              three arguments
`SUBTIME()'                   Subtract times
`SYSDATE()'                   Return the time at which the function
                              executes
`TIME_FORMAT()'               Format as time
`TIME_TO_SEC()'               Return the argument converted to seconds
`TIME()'                      Extract the time portion of the expression
                              passed
`TIMEDIFF()'                  Subtract time
`TIMESTAMP()'                 With a single argument, this function
                              returns the date or datetime  expression;
                              with two arguments, the sum of the
                              arguments
`TIMESTAMPADD()'              Add an interval to a datetime expression
`TIMESTAMPDIFF()'             Subtract an interval from a datetime
                              expression
`TO_DAYS()'                   Return the date argument converted to days
`UNIX_TIMESTAMP()'            Return a UNIX timestamp
`UTC_DATE()'                  Return the current UTC date
`UTC_TIME()'                  Return the current UTC time
`UTC_TIMESTAMP()'             Return the current UTC date and time
`WEEK()'                      Return the week number
`WEEKDAY()'                   Return the weekday index
`WEEKOFYEAR()'                Return the calendar week of the date (0-53)
`YEAR()'                      Return the year
`YEARWEEK()'                  Return the year and week

Here is an example that uses date functions. The following query
selects all rows with a DATE_COL value from within the last 30 days:


     mysql> SELECT SOMETHING FROM TBL_NAME
         -> WHERE DATE_SUB(CURDATE(),INTERVAL 30 DAY) <= DATE_COL;

The query also selects rows with dates that lie in the future.

Functions that expect date values usually accept datetime values and
ignore the time part. Functions that expect time values usually accept
datetime values and ignore the date part.

Functions that return the current date or time each are evaluated only
once per query at the start of query execution. This means that
multiple references to a function such as `NOW()' within a single query
always produce the same result. (For our purposes, a single query also
includes a call to a stored program (stored routine, trigger, or event)
and all subprograms called by that program.) This principle also
applies to `CURDATE()', `CURTIME()', `UTC_DATE()', `UTC_TIME()',
`UTC_TIMESTAMP()', and to any of their synonyms.

The `CURRENT_TIMESTAMP()', `CURRENT_TIME()', `CURRENT_DATE()', and
`FROM_UNIXTIME()' functions return values in the connection's current
time zone, which is available as the value of the `time_zone' system
variable. In addition, `UNIX_TIMESTAMP()' assumes that its argument is
a datetime value in the current time zone. See *Note
time-zone-support::.

Some date functions can be used with `zero' dates or incomplete dates
such as `'2001-11-00'', whereas others cannot. Functions that extract
parts of dates typically work with incomplete dates and thus can return
0 when you might otherwise expect a nonzero value. For example:


     mysql> SELECT DAYOFMONTH('2001-11-00'), MONTH('2005-00-00');
             -> 0, 0

Other functions expect complete dates and return `NULL' for incomplete
dates. These include functions that perform date arithmetic or that map
parts of dates to names. For example:


     mysql> SELECT DATE_ADD('2006-05-00',INTERVAL 1 DAY);
             -> NULL
     mysql> SELECT DAYNAME('2006-05-00');
             -> NULL

*Note*:

From MySQL 5.1.59 to 5.1.61, a change in handling of a date-related
assertion caused several functions to become more strict when passed a
`DATE()' function value as their argument and reject incomplete dates
with a day part of zero. These functions are affected: `CONVERT_TZ()',
`DATE_ADD()', `DATE_SUB()', `DAYOFYEAR()', `LAST_DAY()',
`TIMESTAMPDIFF()', `TO_DAYS()', `TO_SECONDS()'
(http://dev.mysql.com/doc/refman/5.5/en/date-and-time-functions.html#function_to-seconds),
`WEEK()', `WEEKDAY()', `WEEKOFYEAR()', `YEARWEEK()'. Because this
changes date-handling behavior in General Availability-status series
MySQL 5.1, the change was reverted in 5.1.62.

   * `ADDDATE(DATE,INTERVAL EXPR UNIT)', `ADDDATE(EXPR,DAYS)'

     When invoked with the `INTERVAL' form of the second argument,
     `ADDDATE()' is a synonym for `DATE_ADD()'. The related function
     `SUBDATE()' is a synonym for `DATE_SUB()'. For information on the
     `INTERVAL' UNIT argument, see the discussion for `DATE_ADD()'.


          mysql> SELECT DATE_ADD('2008-01-02', INTERVAL 31 DAY);
                  -> '2008-02-02'
          mysql> SELECT ADDDATE('2008-01-02', INTERVAL 31 DAY);
                  -> '2008-02-02'

     When invoked with the DAYS form of the second argument, MySQL
     treats it as an integer number of days to be added to EXPR.


          mysql> SELECT ADDDATE('2008-01-02', 31);
                  -> '2008-02-02'

   * `ADDTIME(EXPR1,EXPR2)'

     `ADDTIME()' adds EXPR2 to EXPR1 and returns the result.  EXPR1 is
     a time or datetime expression, and EXPR2 is a time expression.


          mysql> SELECT ADDTIME('2007-12-31 23:59:59.999999', '1 1:1:1.000002');
                  -> '2008-01-02 01:01:01.000001'
          mysql> SELECT ADDTIME('01:00:00.999999', '02:00:00.999998');
                  -> '03:00:01.999997'

   * `CONVERT_TZ(DT,FROM_TZ,TO_TZ)'

     `CONVERT_TZ()' converts a datetime value DT from the time zone
     given by FROM_TZ to the time zone given by TO_TZ and returns the
     resulting value. Time zones are specified as described in *Note
     time-zone-support::. This function returns `NULL' if the arguments
     are invalid.

     If the value falls out of the supported range of the *Note
     `TIMESTAMP': datetime. type when converted from FROM_TZ to UTC, no
     conversion occurs. The *Note `TIMESTAMP': datetime. range is
     described in *Note date-and-time-type-overview::.


          mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','GMT','MET');
                  -> '2004-01-01 13:00:00'
          mysql> SELECT CONVERT_TZ('2004-01-01 12:00:00','+00:00','+10:00');
                  -> '2004-01-01 22:00:00'

     *Note*:

     To use named time zones such as `'MET'' or `'Europe/Moscow'', the
     time zone tables must be properly set up. See *Note
     time-zone-support::, for instructions.

     Before MySQL 5.1.17, if you intend to use `CONVERT_TZ()' while
     other tables are locked with *Note `LOCK TABLES': lock-tables, you
     must also lock the `mysql.time_zone_name' table. See *Note
     lock-tables::.

   * `CURDATE()'

     Returns the current date as a value in `'YYYY-MM-DD'' or `YYYYMMDD'
     format, depending on whether the function is used in a string or
     numeric context.


          mysql> SELECT CURDATE();
                  -> '2008-06-13'
          mysql> SELECT CURDATE() + 0;
                  -> 20080613

   * `CURRENT_DATE', `CURRENT_DATE()'

     `CURRENT_DATE' and `CURRENT_DATE()' are synonyms for `CURDATE()'.

   * `CURRENT_TIME', `CURRENT_TIME()'

     `CURRENT_TIME' and `CURRENT_TIME()' are synonyms for `CURTIME()'.

   * `CURRENT_TIMESTAMP', `CURRENT_TIMESTAMP()'

     `CURRENT_TIMESTAMP' and `CURRENT_TIMESTAMP()' are synonyms for
     `NOW()'.

   * `CURTIME()'

     Returns the current time as a value in `'HH:MM:SS'' or
     `HHMMSS.uuuuuu' format, depending on whether the function is used
     in a string or numeric context. The value is expressed in the
     current time zone.


          mysql> SELECT CURTIME();
                  -> '23:50:26'
          mysql> SELECT CURTIME() + 0;
                  -> 235026.000000

   * `DATE(EXPR)'

     Extracts the date part of the date or datetime expression EXPR.


          mysql> SELECT DATE('2003-12-31 01:02:03');
                  -> '2003-12-31'

   * `DATEDIFF(EXPR1,EXPR2)'

     `DATEDIFF()' returns EXPR1 - EXPR2 expressed as a value in days
     from one date to the other. EXPR1 and EXPR2 are date or
     date-and-time expressions. Only the date parts of the values are
     used in the calculation.


          mysql> SELECT DATEDIFF('2007-12-31 23:59:59','2007-12-30');
                  -> 1
          mysql> SELECT DATEDIFF('2010-11-30 23:59:59','2010-12-31');
                  -> -31

   * `DATE_ADD(DATE,INTERVAL EXPR UNIT)', `DATE_SUB(DATE,INTERVAL EXPR
     UNIT)'

     These functions perform date arithmetic. The DATE argument
     specifies the starting date or datetime value.  EXPR is an
     expression specifying the interval value to be added or subtracted
     from the starting date. EXPR is a string; it may start with a
     ``-'' for negative intervals. UNIT is a keyword indicating the
     units in which the expression should be interpreted.

     The `INTERVAL' keyword and the UNIT specifier are not case
     sensitive.

     The following table shows the expected form of the EXPR argument
     for each UNIT value.

     This table lists UNIT values and the expected EXPR argument for
     each.

     UNIT Value                         Expected EXPR Format
     `MICROSECOND'                      `MICROSECONDS'
     `SECOND'                           `SECONDS'
     `MINUTE'                           `MINUTES'
     `HOUR'                             `HOURS'
     `DAY'                              `DAYS'
     `WEEK'                             `WEEKS'
     `MONTH'                            `MONTHS'
     `QUARTER'                          `QUARTERS'
     `YEAR'                             `YEARS'
     `SECOND_MICROSECOND'               `'SECONDS.MICROSECONDS''
     `MINUTE_MICROSECOND'               `'MINUTES:SECONDS.MICROSECONDS''
     `MINUTE_SECOND'                    `'MINUTES:SECONDS''
     `HOUR_MICROSECOND'                 `'HOURS:MINUTES:SECONDS.MICROSECONDS''
     `HOUR_SECOND'                      `'HOURS:MINUTES:SECONDS''
     `HOUR_MINUTE'                      `'HOURS:MINUTES''
     `DAY_MICROSECOND'                  `'DAYS
                                        HOURS:MINUTES:SECONDS.MICROSECONDS''
     `DAY_SECOND'                       `'DAYS HOURS:MINUTES:SECONDS''
     `DAY_MINUTE'                       `'DAYS HOURS:MINUTES''
     `DAY_HOUR'                         `'DAYS HOURS''
     `YEAR_MONTH'                       `'YEARS-MONTHS''

     The return value depends on the arguments:

        * *Note `DATETIME': datetime. if the first argument is a *Note
          `DATETIME': datetime. (or *Note `TIMESTAMP': datetime.)
          value, or if the first argument is a *Note `DATE': datetime.
          and the UNIT value uses `HOURS', `MINUTES', or `SECONDS'.

        * String otherwise.

     To ensure that the result is *Note `DATETIME': datetime, you can
     use `CAST()' to convert the first argument to *Note `DATETIME':
     datetime.

     MySQL permits any punctuation delimiter in the EXPR format. Those
     shown in the table are the suggested delimiters. If the DATE
     argument is a *Note `DATE': datetime. value and your calculations
     involve only `YEAR', `MONTH', and `DAY' parts (that is, no time
     parts), the result is a *Note `DATE': datetime. value. Otherwise,
     the result is a *Note `DATETIME': datetime. value.

     Date arithmetic also can be performed using `INTERVAL' together
     with the `+' or `-' operator:


          `date' + INTERVAL EXPR UNIT
          `date' - INTERVAL EXPR UNIT

     `INTERVAL EXPR UNIT' is permitted on either side of the `+'
     operator if the expression on the other side is a date or datetime
     value.  For the `-' operator, `INTERVAL EXPR UNIT' is permitted
     only on the right side, because it makes no sense to subtract a
     date or datetime value from an interval.


          mysql> SELECT '2008-12-31 23:59:59' + INTERVAL 1 SECOND;
                  -> '2009-01-01 00:00:00'
          mysql> SELECT INTERVAL 1 DAY + '2008-12-31';
                  -> '2009-01-01'
          mysql> SELECT '2005-01-01' - INTERVAL 1 SECOND;
                  -> '2004-12-31 23:59:59'
          mysql> SELECT DATE_ADD('2000-12-31 23:59:59',
              ->                 INTERVAL 1 SECOND);
                  -> '2001-01-01 00:00:00'
          mysql> SELECT DATE_ADD('2010-12-31 23:59:59',
              ->                 INTERVAL 1 DAY);
                  -> '2011-01-01 23:59:59'
          mysql> SELECT DATE_ADD('2100-12-31 23:59:59',
              ->                 INTERVAL '1:1' MINUTE_SECOND);
                  -> '2101-01-01 00:01:00'
          mysql> SELECT DATE_SUB('2005-01-01 00:00:00',
              ->                 INTERVAL '1 1:1:1' DAY_SECOND);
                  -> '2004-12-30 22:58:59'
          mysql> SELECT DATE_ADD('1900-01-01 00:00:00',
              ->                 INTERVAL '-1 10' DAY_HOUR);
                  -> '1899-12-30 14:00:00'
          mysql> SELECT DATE_SUB('1998-01-02', INTERVAL 31 DAY);
                  -> '1997-12-02'
          mysql> SELECT DATE_ADD('1992-12-31 23:59:59.000002',
              ->            INTERVAL '1.999999' SECOND_MICROSECOND);
                  -> '1993-01-01 00:00:01.000001'

     If you specify an interval value that is too short (does not
     include all the interval parts that would be expected from the
     UNIT keyword), MySQL assumes that you have left out the leftmost
     parts of the interval value.  For example, if you specify a UNIT
     of `DAY_SECOND', the value of EXPR is expected to have days,
     hours, minutes, and seconds parts. If you specify a value like
     `'1:10'', MySQL assumes that the days and hours parts are missing
     and the value represents minutes and seconds. In other words,
     `'1:10' DAY_SECOND' is interpreted in such a way that it is
     equivalent to `'1:10' MINUTE_SECOND'. This is analogous to the way
     that MySQL interprets *Note `TIME': time. values as representing
     elapsed time rather than as a time of day.

     Because EXPR is treated as a string, be careful if you specify a
     nonstring value with `INTERVAL'. For example, with an interval
     specifier of `HOUR_MINUTE', `6/4' evaluates to `1.5000' and is
     treated as 1 hour, 5000 minutes:


          mysql> SELECT 6/4;
                  -> 1.5000
          mysql> SELECT DATE_ADD('2009-01-01', INTERVAL 6/4 HOUR_MINUTE);
                  -> '2009-01-04 12:20:00'

     To ensure interpretation of the interval value as you expect, a
     `CAST()' operation may be used.  To treat `6/4' as 1 hour, 5
     minutes, cast it to a *Note `DECIMAL': fixed-point-types. value
     with a single fractional digit:


          mysql> SELECT CAST(6/4 AS DECIMAL(3,1));
                  -> 1.5
          mysql> SELECT DATE_ADD('1970-01-01 12:00:00',
              ->                 INTERVAL CAST(6/4 AS DECIMAL(3,1)) HOUR_MINUTE);
                  -> '1970-01-01 13:05:00'

     If you add to or subtract from a date value something that
     contains a time part, the result is automatically converted to a
     datetime value:


          mysql> SELECT DATE_ADD('2013-01-01', INTERVAL 1 DAY);
                  -> '2013-01-02'
          mysql> SELECT DATE_ADD('2013-01-01', INTERVAL 1 HOUR);
                  -> '2013-01-01 01:00:00'

     If you add `MONTH', `YEAR_MONTH', or `YEAR' and the resulting date
     has a day that is larger than the maximum day for the new month,
     the day is adjusted to the maximum days in the new month:


          mysql> SELECT DATE_ADD('2009-01-30', INTERVAL 1 MONTH);
                  -> '2009-02-28'

     Date arithmetic operations require complete dates and do not work
     with incomplete dates such as `'2006-07-00'' or badly malformed
     dates:


          mysql> SELECT DATE_ADD('2006-07-00', INTERVAL 1 DAY);
                  -> NULL
          mysql> SELECT '2005-03-32' + INTERVAL 1 MONTH;
                  -> NULL

   * `DATE_FORMAT(DATE,FORMAT)'

     Formats the DATE value according to the FORMAT string.

     The following specifiers may be used in the FORMAT string. The
     ``%'' character is required before format specifier characters.

     This table lists specifier characters for the `DATE_FORMAT'
     function that may be used in the FORMAT string and provides a
     description of each specifier character.

     Specifier     Description
     `%a'          Abbreviated weekday name (`Sun'..`Sat')
     `%b'          Abbreviated month name (`Jan'..`Dec')
     `%c'          Month, numeric (`0'..`12')
     `%D'          Day of the month with English suffix (`0th',
                   `1st', `2nd', `3rd', ...)
     `%d'          Day of the month, numeric (`00'..`31')
     `%e'          Day of the month, numeric (`0'..`31')
     `%f'          Microseconds (`000000'..`999999')
     `%H'          Hour (`00'..`23')
     `%h'          Hour (`01'..`12')
     `%I'          Hour (`01'..`12')
     `%i'          Minutes, numeric (`00'..`59')
     `%j'          Day of year (`001'..`366')
     `%k'          Hour (`0'..`23')
     `%l'          Hour (`1'..`12')
     `%M'          Month name (`January'..`December')
     `%m'          Month, numeric (`00'..`12')
     `%p'          `AM' or `PM'
     `%r'          Time, 12-hour (`hh:mm:ss' followed by `AM' or
                   `PM')
     `%S'          Seconds (`00'..`59')
     `%s'          Seconds (`00'..`59')
     `%T'          Time, 24-hour (`hh:mm:ss')
     `%U'          Week (`00'..`53'), where Sunday is the first
                   day of the week; `WEEK()' mode 0
     `%u'          Week (`00'..`53'), where Monday is the first
                   day of the week; `WEEK()' mode 1
     `%V'          Week (`01'..`53'), where Sunday is the first
                   day of the week; `WEEK()' mode 2; used with
                   `%X'
     `%v'          Week (`01'..`53'), where Monday is the first
                   day of the week; `WEEK()' mode 3; used with
                   `%x'
     `%W'          Weekday name (`Sunday'..`Saturday')
     `%w'          Day of the week (`0'=Sunday..`6'=Saturday)
     `%X'          Year for the week where Sunday is the first
                   day of the week, numeric, four digits; used
                   with `%V'
     `%x'          Year for the week, where Monday is the first
                   day of the week, numeric, four digits; used
                   with `%v'
     `%Y'          Year, numeric, four digits
     `%y'          Year, numeric (two digits)
     `%%'          A literal ``%'' character
     `%X'          X, for any `X' not listed above

     Ranges for the month and day specifiers begin with zero due to the
     fact that MySQL permits the storing of incomplete dates such as
     `'2014-00-00''.

     As of MySQL 5.1.12, the language used for day and month names and
     abbreviations is controlled by the value of the `lc_time_names'
     system variable (*Note locale-support::).

     For the `%U', `%u', `%V', and `%v' specifiers, see the description
     of the `WEEK()' function for information about the mode values.
     The mode affects how week numbering occurs.

     As of MySQL 5.1.15, `DATE_FORMAT()' returns a string with a
     character set and collation given by `character_set_connection' and
     `collation_connection' so that it can return month and weekday
     names containing non-ASCII characters. Before 5.1.15, the return
     value is a binary string.


          mysql> SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y');
                  -> 'Sunday October 2009'
          mysql> SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s');
                  -> '22:23:00'
          mysql> SELECT DATE_FORMAT('1900-10-04 22:23:00',
              ->                 '%D %y %a %d %m %b %j');
                  -> '4th 00 Thu 04 10 Oct 277'
          mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00',
              ->                 '%H %k %I %r %T %S %w');
                  -> '22 22 10 10:23:00 PM 22:23:00 00 6'
          mysql> SELECT DATE_FORMAT('1999-01-01', '%X %V');
                  -> '1998 52'
          mysql> SELECT DATE_FORMAT('2006-06-00', '%d');
                  -> '00'

   * `DATE_SUB(DATE,INTERVAL EXPR UNIT)'

     See the description for `DATE_ADD()'.

   * `DAY(DATE)'

     `DAY()' is a synonym for `DAYOFMONTH()'.

   * `DAYNAME(DATE)'

     Returns the name of the weekday for DATE. As of MySQL 5.1.12, the
     language used for the name is controlled by the value of the
     `lc_time_names' system variable (*Note locale-support::).


          mysql> SELECT DAYNAME('2007-02-03');
                  -> 'Saturday'

   * `DAYOFMONTH(DATE)'

     Returns the day of the month for DATE, in the range `1' to `31', or
     `0' for dates such as `'0000-00-00'' or `'2008-00-00'' that have a
     zero day part.


          mysql> SELECT DAYOFMONTH('2007-02-03');
                  -> 3

   * `DAYOFWEEK(DATE)'

     Returns the weekday index for DATE (`1' = Sunday, `2' = Monday,
     ..., `7' = Saturday). These index values correspond to the ODBC
     standard.


          mysql> SELECT DAYOFWEEK('2007-02-03');
                  -> 7

   * `DAYOFYEAR(DATE)'

     Returns the day of the year for DATE, in the range `1' to `366'.


          mysql> SELECT DAYOFYEAR('2007-02-03');
                  -> 34

   * `EXTRACT(UNIT FROM DATE)'

     The `EXTRACT()' function uses the same kinds of unit specifiers as
     `DATE_ADD()' or `DATE_SUB()', but extracts parts from the date
     rather than performing date arithmetic.


          mysql> SELECT EXTRACT(YEAR FROM '2009-07-02');
                 -> 2009
          mysql> SELECT EXTRACT(YEAR_MONTH FROM '2009-07-02 01:02:03');
                 -> 200907
          mysql> SELECT EXTRACT(DAY_MINUTE FROM '2009-07-02 01:02:03');
                 -> 20102
          mysql> SELECT EXTRACT(MICROSECOND
              ->                FROM '2003-01-02 10:30:00.000123');
                  -> 123

   * `FROM_DAYS(N)'

     Given a day number N, returns a *Note `DATE': datetime. value.


          mysql> SELECT FROM_DAYS(730669);
                  -> '2007-07-03'

     Use `FROM_DAYS()' with caution on old dates. It is not intended
     for use with values that precede the advent of the Gregorian
     calendar (1582). See *Note mysql-calendar::.

   * `FROM_UNIXTIME(UNIX_TIMESTAMP)',
     `FROM_UNIXTIME(UNIX_TIMESTAMP,FORMAT)'

     Returns a representation of the UNIX_TIMESTAMP argument as a value
     in `'YYYY-MM-DD HH:MM:SS'' or `YYYYMMDDHHMMSS.uuuuuu' format,
     depending on whether the function is used in a string or numeric
     context.  The value is expressed in the current time zone.
     UNIX_TIMESTAMP is an internal timestamp value such as is produced
     by the `UNIX_TIMESTAMP()' function.

     If FORMAT is given, the result is formatted according to the FORMAT
     string, which is used the same way as listed in the entry for the
     `DATE_FORMAT()' function.


          mysql> SELECT FROM_UNIXTIME(1196440219);
                  -> '2007-11-30 10:30:19'
          mysql> SELECT FROM_UNIXTIME(1196440219) + 0;
                  -> 20071130103019.000000
          mysql> SELECT FROM_UNIXTIME(UNIX_TIMESTAMP(),
              ->                      '%Y %D %M %h:%i:%s %x');
                  -> '2007 30th November 10:30:59 2007'

     Note: If you use `UNIX_TIMESTAMP()' and `FROM_UNIXTIME()' to
     convert between *Note `TIMESTAMP': datetime. values and Unix
     timestamp values, the conversion is lossy because the mapping is
     not one-to-one in both directions. For details, see the
     description of the `UNIX_TIMESTAMP()' function.

   * `GET_FORMAT({DATE|TIME|DATETIME},
     {'EUR'|'USA'|'JIS'|'ISO'|'INTERNAL'})'

     Returns a format string. This function is useful in combination
     with the `DATE_FORMAT()' and the `STR_TO_DATE()' functions.

     The possible values for the first and second arguments result in
     several possible format strings (for the specifiers used, see the
     table in the `DATE_FORMAT()' function description). ISO format
     refers to ISO 9075, not ISO 8601.

     This table lists function calls for the `GET_FORMAT' function
     along with results for each function call.

     Function Call                            Result
     `GET_FORMAT(DATE,'USA')'                 `'%m.%d.%Y''
     `GET_FORMAT(DATE,'JIS')'                 `'%Y-%m-%d''
     `GET_FORMAT(DATE,'ISO')'                 `'%Y-%m-%d''
     `GET_FORMAT(DATE,'EUR')'                 `'%d.%m.%Y''
     `GET_FORMAT(DATE,'INTERNAL')'            `'%Y%m%d''
     `GET_FORMAT(DATETIME,'USA')'             `'%Y-%m-%d %H.%i.%s''
     `GET_FORMAT(DATETIME,'JIS')'             `'%Y-%m-%d %H:%i:%s''
     `GET_FORMAT(DATETIME,'ISO')'             `'%Y-%m-%d %H:%i:%s''
     `GET_FORMAT(DATETIME,'EUR')'             `'%Y-%m-%d %H.%i.%s''
     `GET_FORMAT(DATETIME,'INTERNAL')'        `'%Y%m%d%H%i%s''
     `GET_FORMAT(TIME,'USA')'                 `'%h:%i:%s %p''
     `GET_FORMAT(TIME,'JIS')'                 `'%H:%i:%s''
     `GET_FORMAT(TIME,'ISO')'                 `'%H:%i:%s''
     `GET_FORMAT(TIME,'EUR')'                 `'%H.%i.%s''
     `GET_FORMAT(TIME,'INTERNAL')'            `'%H%i%s''

     *Note `TIMESTAMP': datetime. can also be used as the first
     argument to `GET_FORMAT()', in which case the function returns the
     same values as for *Note `DATETIME': datetime.


          mysql> SELECT DATE_FORMAT('2003-10-03',GET_FORMAT(DATE,'EUR'));
                  -> '03.10.2003'
          mysql> SELECT STR_TO_DATE('10.31.2003',GET_FORMAT(DATE,'USA'));
                  -> '2003-10-31'

   * `HOUR(TIME)'

     Returns the hour for TIME. The range of the return value is `0' to
     `23' for time-of-day values. However, the range of *Note `TIME':
     time. values actually is much larger, so `HOUR' can return values
     greater than `23'.


          mysql> SELECT HOUR('10:05:03');
                  -> 10
          mysql> SELECT HOUR('272:59:59');
                  -> 272

   * `LAST_DAY(DATE)'

     Takes a date or datetime value and returns the corresponding value
     for the last day of the month. Returns `NULL' if the argument is
     invalid.


          mysql> SELECT LAST_DAY('2003-02-05');
                  -> '2003-02-28'
          mysql> SELECT LAST_DAY('2004-02-05');
                  -> '2004-02-29'
          mysql> SELECT LAST_DAY('2004-01-01 01:01:01');
                  -> '2004-01-31'
          mysql> SELECT LAST_DAY('2003-03-32');
                  -> NULL

   * `LOCALTIME', `LOCALTIME()'

     `LOCALTIME' and `LOCALTIME()' are synonyms for `NOW()'.

   * `LOCALTIMESTAMP', `LOCALTIMESTAMP()'

     `LOCALTIMESTAMP' and `LOCALTIMESTAMP()' are synonyms for `NOW()'.

   * `MAKEDATE(YEAR,DAYOFYEAR)'

     Returns a date, given year and day-of-year values.  DAYOFYEAR must
     be greater than 0 or the result is `NULL'.


          mysql> SELECT MAKEDATE(2011,31), MAKEDATE(2011,32);
                  -> '2011-01-31', '2011-02-01'
          mysql> SELECT MAKEDATE(2011,365), MAKEDATE(2014,365);
                  -> '2011-12-31', '2014-12-31'
          mysql> SELECT MAKEDATE(2011,0);
                  -> NULL

   * `MAKETIME(HOUR,MINUTE,SECOND)'

     Returns a time value calculated from the HOUR, MINUTE, and SECOND
     arguments.


          mysql> SELECT MAKETIME(12,15,30);
                  -> '12:15:30'

   * `MICROSECOND(EXPR)'

     Returns the microseconds from the time or datetime expression EXPR
     as a number in the range from `0' to `999999'.


          mysql> SELECT MICROSECOND('12:00:00.123456');
                  -> 123456
          mysql> SELECT MICROSECOND('2009-12-31 23:59:59.000010');
                  -> 10

   * `MINUTE(TIME)'

     Returns the minute for TIME, in the range `0' to `59'.


          mysql> SELECT MINUTE('2008-02-03 10:05:03');
                  -> 5

   * `MONTH(DATE)'

     Returns the month for DATE, in the range `1' to `12' for January
     to December, or `0' for dates such as `'0000-00-00'' or
     `'2008-00-00'' that have a zero month part.


          mysql> SELECT MONTH('2008-02-03');
                  -> 2

   * `MONTHNAME(DATE)'

     Returns the full name of the month for DATE. As of MySQL 5.1.12,
     the language used for the name is controlled by the value of the
     `lc_time_names' system variable (*Note locale-support::).


          mysql> SELECT MONTHNAME('2008-02-03');
                  -> 'February'

   * `NOW()'

     Returns the current date and time as a value in `'YYYY-MM-DD
     HH:MM:SS'' or `YYYYMMDDHHMMSS.uuuuuu' format, depending on whether
     the function is used in a string or numeric context.  The value is
     expressed in the current time zone.


          mysql> SELECT NOW();
                  -> '2007-12-15 23:50:26'
          mysql> SELECT NOW() + 0;
                  -> 20071215235026.000000

     `NOW()' returns a constant time that indicates the time at which
     the statement began to execute. (Within a stored function or
     trigger, `NOW()' returns the time at which the function or
     triggering statement began to execute.) This differs from the
     behavior for `SYSDATE()', which returns the exact time at which it
     executes.


          mysql> SELECT NOW(), SLEEP(2), NOW();
          +---------------------+----------+---------------------+
          | NOW()               | SLEEP(2) | NOW()               |
          +---------------------+----------+---------------------+
          | 2006-04-12 13:47:36 |        0 | 2006-04-12 13:47:36 |
          +---------------------+----------+---------------------+

          mysql> SELECT SYSDATE(), SLEEP(2), SYSDATE();
          +---------------------+----------+---------------------+
          | SYSDATE()           | SLEEP(2) | SYSDATE()           |
          +---------------------+----------+---------------------+
          | 2006-04-12 13:47:44 |        0 | 2006-04-12 13:47:46 |
          +---------------------+----------+---------------------+

     In addition, the `SET TIMESTAMP' statement affects the value
     returned by `NOW()' but not by `SYSDATE()'. This means that
     timestamp settings in the binary log have no effect on invocations
     of `SYSDATE()'.  Setting the timestamp to a nonzero value causes
     each subsequent invocation of `NOW()' to return that value.
     Setting the timestamp to zero cancels this effect so that `NOW()'
     once again returns the current date and time.

     See the description for `SYSDATE()' for additional information
     about the differences between the two functions.

   * `PERIOD_ADD(P,N)'

     Adds N months to period P (in the format `YYMM' or `YYYYMM').
     Returns a value in the format `YYYYMM'. Note that the period
     argument P is _not_ a date value.


          mysql> SELECT PERIOD_ADD(200801,2);
                  -> 200803

   * `PERIOD_DIFF(P1,P2)'

     Returns the number of months between periods P1 and P2. P1 and P2
     should be in the format `YYMM' or `YYYYMM'. Note that the period
     arguments P1 and P2 are _not_ date values.


          mysql> SELECT PERIOD_DIFF(200802,200703);
                  -> 11

   * `QUARTER(DATE)'

     Returns the quarter of the year for DATE, in the range `1' to `4'.


          mysql> SELECT QUARTER('2008-04-01');
                  -> 2

   * `SECOND(TIME)'

     Returns the second for TIME, in the range `0' to `59'.


          mysql> SELECT SECOND('10:05:03');
                  -> 3

   * `SEC_TO_TIME(SECONDS)'

     Returns the SECONDS argument, converted to hours, minutes, and
     seconds, as a *Note `TIME': time. value. The range of the result
     is constrained to that of the *Note `TIME': time. data type. A
     warning occurs if the argument corresponds to a value outside that
     range.


          mysql> SELECT SEC_TO_TIME(2378);
                  -> '00:39:38'
          mysql> SELECT SEC_TO_TIME(2378) + 0;
                  -> 3938

   * `STR_TO_DATE(STR,FORMAT)'

     This is the inverse of the `DATE_FORMAT()' function. It takes a
     string STR and a format string FORMAT.  `STR_TO_DATE()' returns a
     *Note `DATETIME': datetime. value if the format string contains
     both date and time parts, or a *Note `DATE': datetime. or *Note
     `TIME': time. value if the string contains only date or time
     parts. If the date, time, or datetime value extracted from STR is
     illegal, `STR_TO_DATE()' returns `NULL' and produces a warning.

     The server scans STR attempting to match FORMAT to it. The format
     string can contain literal characters and format specifiers
     beginning with `%'. Literal characters in FORMAT must match
     literally in STR. Format specifiers in FORMAT must match a date or
     time part in STR. For the specifiers that can be used in FORMAT,
     see the `DATE_FORMAT()' function description.


          mysql> SELECT STR_TO_DATE('01,5,2013','%d,%m,%Y');
                  -> '2013-05-01'
          mysql> SELECT STR_TO_DATE('May 1, 2013','%M %d,%Y');
                  -> '2013-05-01'

     Scanning starts at the beginning of STR and fails if FORMAT is
     found not to match. Extra characters at the end of STR are ignored.


          mysql> SELECT STR_TO_DATE('a09:30:17','a%h:%i:%s');
                  -> '09:30:17'
          mysql> SELECT STR_TO_DATE('a09:30:17','%h:%i:%s');
                  -> NULL
          mysql> SELECT STR_TO_DATE('09:30:17a','%h:%i:%s');
                  -> '09:30:17'

     Unspecified date or time parts have a value of 0, so incompletely
     specified values in STR produce a result with some or all parts
     set to 0:


          mysql> SELECT STR_TO_DATE('abc','abc');
                  -> '0000-00-00'
          mysql> SELECT STR_TO_DATE('9','%m');
                  -> '0000-09-00'
          mysql> SELECT STR_TO_DATE('9','%s');
                  -> '00:00:09'

     Range checking on the parts of date values is as described in
     *Note datetime::. This means, for example, that `zero' dates or
     dates with part values of 0 are permitted unless the SQL mode is
     set to disallow such values.


          mysql> SELECT STR_TO_DATE('00/00/0000', '%m/%d/%Y');
                  -> '0000-00-00'
          mysql> SELECT STR_TO_DATE('04/31/2004', '%m/%d/%Y');
                  -> '2004-04-31'

     *Note*:

     You cannot use format `"%X%V"' to convert a year-week string to a
     date because the combination of a year and week does not uniquely
     identify a year and month if the week crosses a month boundary. To
     convert a year-week to a date, you should also specify the weekday:


          mysql> SELECT STR_TO_DATE('200442 Monday', '%X%V %W');
                  -> '2004-10-18'

   * `SUBDATE(DATE,INTERVAL EXPR UNIT)', `SUBDATE(EXPR,DAYS)'

     When invoked with the `INTERVAL' form of the second argument,
     `SUBDATE()' is a synonym for `DATE_SUB()'. For information on the
     `INTERVAL' UNIT argument, see the discussion for `DATE_ADD()'.


          mysql> SELECT DATE_SUB('2008-01-02', INTERVAL 31 DAY);
                  -> '2007-12-02'
          mysql> SELECT SUBDATE('2008-01-02', INTERVAL 31 DAY);
                  -> '2007-12-02'

     The second form enables the use of an integer value for DAYS. In
     such cases, it is interpreted as the number of days to be
     subtracted from the date or datetime expression EXPR.


          mysql> SELECT SUBDATE('2008-01-02 12:00:00', 31);
                  -> '2007-12-02 12:00:00'

   * `SUBTIME(EXPR1,EXPR2)'

     `SUBTIME()' returns EXPR1 - EXPR2 expressed as a value in the same
     format as EXPR1.  EXPR1 is a time or datetime expression, and
     EXPR2 is a time expression.


          mysql> SELECT SUBTIME('2007-12-31 23:59:59.999999','1 1:1:1.000002');
                  -> '2007-12-30 22:58:58.999997'
          mysql> SELECT SUBTIME('01:00:00.999999', '02:00:00.999998');
                  -> '-00:59:59.999999'

   * `SYSDATE()'

     Returns the current date and time as a value in `'YYYY-MM-DD
     HH:MM:SS'' or `YYYYMMDDHHMMSS.uuuuuu' format, depending on whether
     the function is used in a string or numeric context.

     `SYSDATE()' returns the time at which it executes. This differs
     from the behavior for `NOW()', which returns a constant time that
     indicates the time at which the statement began to execute.
     (Within a stored function or trigger, `NOW()' returns the time at
     which the function or triggering statement began to execute.)


          mysql> SELECT NOW(), SLEEP(2), NOW();
          +---------------------+----------+---------------------+
          | NOW()               | SLEEP(2) | NOW()               |
          +---------------------+----------+---------------------+
          | 2006-04-12 13:47:36 |        0 | 2006-04-12 13:47:36 |
          +---------------------+----------+---------------------+

          mysql> SELECT SYSDATE(), SLEEP(2), SYSDATE();
          +---------------------+----------+---------------------+
          | SYSDATE()           | SLEEP(2) | SYSDATE()           |
          +---------------------+----------+---------------------+
          | 2006-04-12 13:47:44 |        0 | 2006-04-12 13:47:46 |
          +---------------------+----------+---------------------+

     In addition, the `SET TIMESTAMP' statement affects the value
     returned by `NOW()' but not by `SYSDATE()'. This means that
     timestamp settings in the binary log have no effect on invocations
     of `SYSDATE()'.

     Because `SYSDATE()' can return different values even within the
     same statement, and is not affected by `SET TIMESTAMP', it is
     nondeterministic and therefore unsafe for replication if
     statement-based binary logging is used. If that is a problem, you
     can use row-based logging.

     Alternatively, you can use the `--sysdate-is-now' option to cause
     `SYSDATE()' to be an alias for `NOW()'. This works if the option
     is used on both the master and the slave.

     The nondeterministic nature of `SYSDATE()' also means that indexes
     cannot be used for evaluating expressions that refer to it.

     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `TIME(EXPR)'

     Extracts the time part of the time or datetime expression EXPR and
     returns it as a string.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)


          mysql> SELECT TIME('2003-12-31 01:02:03');
                  -> '01:02:03'
          mysql> SELECT TIME('2003-12-31 01:02:03.000123');
                  -> '01:02:03.000123'

   * `TIMEDIFF(EXPR1,EXPR2)'

     `TIMEDIFF()' returns EXPR1 - EXPR2 expressed as a time value.
     EXPR1 and EXPR2 are time or date-and-time expressions, but both
     must be of the same type.

     The result returned by `TIMEDIFF()' is limited to the range
     allowed for *Note `TIME': time. values. Alternatively, you can use
     either of the functions `TIMESTAMPDIFF()' and `UNIX_TIMESTAMP()',
     both of which return integers.


          mysql> SELECT TIMEDIFF('2000:01:01 00:00:00',
              ->                 '2000:01:01 00:00:00.000001');
                  -> '-00:00:00.000001'
          mysql> SELECT TIMEDIFF('2008-12-31 23:59:59.000001',
              ->                 '2008-12-30 01:01:01.000002');
                  -> '46:58:57.999999'

   * `TIMESTAMP(EXPR)', `TIMESTAMP(EXPR1,EXPR2)'

     With a single argument, this function returns the date or datetime
     expression EXPR as a datetime value. With two arguments, it adds
     the time expression EXPR2 to the date or datetime expression EXPR1
     and returns the result as a datetime value.


          mysql> SELECT TIMESTAMP('2003-12-31');
                  -> '2003-12-31 00:00:00'
          mysql> SELECT TIMESTAMP('2003-12-31 12:00:00','12:00:00');
                  -> '2004-01-01 00:00:00'

   * `TIMESTAMPADD(UNIT,INTERVAL,DATETIME_EXPR)'

     Adds the integer expression INTERVAL to the date or datetime
     expression DATETIME_EXPR. The unit for INTERVAL is given by the
     UNIT argument, which should be one of the following values:
     `FRAC_SECOND' (microseconds), `SECOND', `MINUTE', `HOUR', `DAY',
     `WEEK', `MONTH', `QUARTER', or `YEAR'.

     Beginning with MySQL 5.1.24, it is possible to use `MICROSECOND'
     in place of `FRAC_SECOND' with this function, and `FRAC_SECOND' is
     deprecated.  `FRAC_SECOND' is removed in MySQL 5.5.

     The UNIT value may be specified using one of keywords as shown, or
     with a prefix of `SQL_TSI_'. For example, `DAY' and `SQL_TSI_DAY'
     both are legal.


          mysql> SELECT TIMESTAMPADD(MINUTE,1,'2003-01-02');
                  -> '2003-01-02 00:01:00'
          mysql> SELECT TIMESTAMPADD(WEEK,1,'2003-01-02');
                  -> '2003-01-09'

   * `TIMESTAMPDIFF(UNIT,DATETIME_EXPR1,DATETIME_EXPR2)'

     Returns DATETIME_EXPR2 - DATETIME_EXPR1, where DATETIME_EXPR1 and
     DATETIME_EXPR2 are date or datetime expressions. One expression
     may be a date and the other a datetime; a date value is treated as
     a datetime having the time part `'00:00:00'' where necessary. The
     unit for the result (an integer) is given by the UNIT argument.
     The legal values for UNIT are the same as those listed in the
     description of the `TIMESTAMPADD()' function.


          mysql> SELECT TIMESTAMPDIFF(MONTH,'2003-02-01','2003-05-01');
                  -> 3
          mysql> SELECT TIMESTAMPDIFF(YEAR,'2002-05-01','2001-01-01');
                  -> -1
          mysql> SELECT TIMESTAMPDIFF(MINUTE,'2003-02-01','2003-05-01 12:05:55');
                  -> 128885

     *Note*:

     The order of the date or datetime arguments for this function is
     the opposite of that used with the `TIMESTAMP()' function when
     invoked with 2 arguments.

   * `TIME_FORMAT(TIME,FORMAT)'

     This is used like the `DATE_FORMAT()' function, but the FORMAT
     string may contain format specifiers only for hours, minutes,
     seconds, and microseconds.  Other specifiers produce a `NULL'
     value or `0'.

     If the TIME value contains an hour part that is greater than `23',
     the `%H' and `%k' hour format specifiers produce a value larger
     than the usual range of `0..23'. The other hour format specifiers
     produce the hour value modulo 12.


          mysql> SELECT TIME_FORMAT('100:00:00', '%H %k %h %I %l');
                  -> '100 100 04 04 4'

   * `TIME_TO_SEC(TIME)'

     Returns the TIME argument, converted to seconds.


          mysql> SELECT TIME_TO_SEC('22:23:00');
                  -> 80580
          mysql> SELECT TIME_TO_SEC('00:39:38');
                  -> 2378

   * `TO_DAYS(DATE)'

     Given a date DATE, returns a day number (the number of days since
     year 0).


          mysql> SELECT TO_DAYS(950501);
                  -> 728779
          mysql> SELECT TO_DAYS('2007-10-07');
                  -> 733321

     `TO_DAYS()' is not intended for use with values that precede the
     advent of the Gregorian calendar (1582), because it does not take
     into account the days that were lost when the calendar was
     changed. For dates before 1582 (and possibly a later year in other
     locales), results from this function are not reliable. See *Note
     mysql-calendar::, for details.

     Remember that MySQL converts two-digit year values in dates to
     four-digit form using the rules in *Note date-and-time-types::.
     For example, `'2008-10-07'' and `'08-10-07'' are seen as identical
     dates:


          mysql> SELECT TO_DAYS('2008-10-07'), TO_DAYS('08-10-07');
                  -> 733687, 733687

     In MySQL, the zero date is defined as `'0000-00-00'', even though
     this date is itself considered invalid. This means that, for
     `'0000-00-00'' and `'0000-01-01'', `TO_DAYS()' returns the values
     shown here:


          mysql> SELECT TO_DAYS('0000-00-00');
          +-----------------------+
          | to_days('0000-00-00') |
          +-----------------------+
          |                  NULL |
          +-----------------------+
          1 row in set, 1 warning (0.00 sec)

          mysql> SHOW WARNINGS;
          +---------+------+----------------------------------------+
          | Level   | Code | Message                                |
          +---------+------+----------------------------------------+
          | Warning | 1292 | Incorrect datetime value: '0000-00-00' |
          +---------+------+----------------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT TO_DAYS('0000-01-01');
          +-----------------------+
          | to_days('0000-01-01') |
          +-----------------------+
          |                     1 |
          +-----------------------+
          1 row in set (0.00 sec)

     This is true whether or not the `ALLOW_INVALID_DATES' SQL server
     mode is enabled.

   * `UNIX_TIMESTAMP()', `UNIX_TIMESTAMP(DATE)'

     If called with no argument, returns a Unix timestamp (seconds
     since `'1970-01-01 00:00:00'' UTC) as an unsigned integer. If
     `UNIX_TIMESTAMP()' is called with a DATE argument, it returns the
     value of the argument as seconds since `'1970-01-01 00:00:00''
     UTC. DATE may be a *Note `DATE': datetime. string, a *Note
     `DATETIME': datetime. string, a *Note `TIMESTAMP': datetime, or a
     number in the format `YYMMDD' or `YYYYMMDD'. The server interprets
     DATE as a value in the current time zone and converts it to an
     internal value in UTC. Clients can set their time zone as
     described in *Note time-zone-support::.


          mysql> SELECT UNIX_TIMESTAMP();
                  -> 1196440210
          mysql> SELECT UNIX_TIMESTAMP('2007-11-30 10:30:19');
                  -> 1196440219

     When `UNIX_TIMESTAMP()' is used on a *Note `TIMESTAMP': datetime.
     column, the function returns the internal timestamp value
     directly, with no implicit `string-to-Unix-timestamp' conversion.
     If you pass an out-of-range date to `UNIX_TIMESTAMP()', it returns
     `0'.

     Note: If you use `UNIX_TIMESTAMP()' and `FROM_UNIXTIME()' to
     convert between *Note `TIMESTAMP': datetime. values and Unix
     timestamp values, the conversion is lossy because the mapping is
     not one-to-one in both directions. For example, due to conventions
     for local time zone changes, it is possible for two
     `UNIX_TIMESTAMP()' to map two *Note `TIMESTAMP': datetime. values
     to the same Unix timestamp value.  `FROM_UNIXTIME()' will map that
     value back to only one of the original *Note `TIMESTAMP':
     datetime. values. Here is an example, using *Note `TIMESTAMP':
     datetime. values in the `CET' time zone:


          mysql> SELECT UNIX_TIMESTAMP('2005-03-27 03:00:00');
          +---------------------------------------+
          | UNIX_TIMESTAMP('2005-03-27 03:00:00') |
          +---------------------------------------+
          |                            1111885200 |
          +---------------------------------------+
          mysql> SELECT UNIX_TIMESTAMP('2005-03-27 02:00:00');
          +---------------------------------------+
          | UNIX_TIMESTAMP('2005-03-27 02:00:00') |
          +---------------------------------------+
          |                            1111885200 |
          +---------------------------------------+
          mysql> SELECT FROM_UNIXTIME(1111885200);
          +---------------------------+
          | FROM_UNIXTIME(1111885200) |
          +---------------------------+
          | 2005-03-27 03:00:00       |
          +---------------------------+

     If you want to subtract `UNIX_TIMESTAMP()' columns, you might want
     to cast the result to signed integers. See *Note cast-functions::.

   * `UTC_DATE', `UTC_DATE()'

     Returns the current UTC date as a value in `'YYYY-MM-DD'' or
     `YYYYMMDD' format, depending on whether the function is used in a
     string or numeric context.


          mysql> SELECT UTC_DATE(), UTC_DATE() + 0;
                  -> '2003-08-14', 20030814

   * `UTC_TIME', `UTC_TIME()'

     Returns the current UTC time as a value in `'HH:MM:SS'' or
     `HHMMSS.uuuuuu' format, depending on whether the function is used
     in a string or numeric context.


          mysql> SELECT UTC_TIME(), UTC_TIME() + 0;
                  -> '18:07:53', 180753.000000

   * `UTC_TIMESTAMP', `UTC_TIMESTAMP()'

     Returns the current UTC date and time as a value in `'YYYY-MM-DD
     HH:MM:SS'' or `YYYYMMDDHHMMSS.uuuuuu' format, depending on whether
     the function is used in a string or numeric context.


          mysql> SELECT UTC_TIMESTAMP(), UTC_TIMESTAMP() + 0;
                  -> '2003-08-14 18:08:04', 20030814180804.000000

   * `WEEK(DATE[,MODE])'

     This function returns the week number for DATE. The two-argument
     form of `WEEK()' enables you to specify whether the week starts on
     Sunday or Monday and whether the return value should be in the
     range from `0' to `53' or from `1' to `53'. If the MODE argument
     is omitted, the value of the `default_week_format' system variable
     is used. See *Note server-system-variables::.

     The following table describes how the MODE argument works.

     This table describes how the MODE argument of the `WEEK' function
     works. For each mode value, the table lists the first day of the
     week, the range, and a description of week 1.

     Mode    First day of  Range         Week 1 is the first week ...
             week                        
     0       Sunday        0-53          with a Sunday in this year
     1       Monday        0-53          with 4 or more days this year
     2       Sunday        1-53          with a Sunday in this year
     3       Monday        1-53          with 4 or more days this year
     4       Sunday        0-53          with 4 or more days this year
     5       Monday        0-53          with a Monday in this year
     6       Sunday        1-53          with 4 or more days this year
     7       Monday        1-53          with a Monday in this year

     For MODE values with a meaning of `with 4 or more days this year,'
     weeks are numbered according to ISO 8601:1988:

        * If the week containing January 1 has 4 or more days in the
          new year, it is week 1.

        * Otherwise, it is the last week of the previous year, and the
          next week is week 1.


          mysql> SELECT WEEK('2008-02-20');
                  -> 7
          mysql> SELECT WEEK('2008-02-20',0);
                  -> 7
          mysql> SELECT WEEK('2008-02-20',1);
                  -> 8
          mysql> SELECT WEEK('2008-12-31',1);
                  -> 53

     Note that if a date falls in the last week of the previous year,
     MySQL returns `0' if you do not use `2', `3', `6', or `7' as the
     optional MODE argument:


          mysql> SELECT YEAR('2000-01-01'), WEEK('2000-01-01',0);
                  -> 2000, 0

     One might argue that `WEEK()' should return `52' because the given
     date actually occurs in the 52nd week of 1999.  `WEEK()' returns
     `0' instead so that the return value is `the week number in the
     given year.' This makes use of the `WEEK()' function reliable when
     combined with other functions that extract a date part from a date.

     If you prefer a result evaluated with respect to the year that
     contains the first day of the week for the given date, use `0',
     `2', `5', or `7' as the optional MODE argument.


          mysql> SELECT WEEK('2000-01-01',2);
                  -> 52

     Alternatively, use the `YEARWEEK()' function:


          mysql> SELECT YEARWEEK('2000-01-01');
                  -> 199952
          mysql> SELECT MID(YEARWEEK('2000-01-01'),5,2);
                  -> '52'

   * `WEEKDAY(DATE)'

     Returns the weekday index for DATE (`0' = Monday, `1' = Tuesday,
     ... `6' = Sunday).


          mysql> SELECT WEEKDAY('2008-02-03 22:23:00');
                  -> 6
          mysql> SELECT WEEKDAY('2007-11-06');
                  -> 1

   * `WEEKOFYEAR(DATE)'

     Returns the calendar week of the date as a number in the range
     from `1' to `53'.  `WEEKOFYEAR()' is a compatibility function that
     is equivalent to `WEEK(DATE,3)'.


          mysql> SELECT WEEKOFYEAR('2008-02-20');
                  -> 8

   * `YEAR(DATE)'

     Returns the year for DATE, in the range `1000' to `9999', or `0'
     for the `zero' date.


          mysql> SELECT YEAR('1987-01-01');
                  -> 1987

   * `YEARWEEK(DATE)', `YEARWEEK(DATE,MODE)'

     Returns year and week for a date. The MODE argument works exactly
     like the MODE argument to `WEEK()'. The year in the result may be
     different from the year in the date argument for the first and the
     last week of the year.


          mysql> SELECT YEARWEEK('1987-01-01');
                  -> 198653

     Note that the week number is different from what the `WEEK()'
     function would return (`0') for optional arguments `0' or `1', as
     `WEEK()' then returns the week in the context of the given year.


File: manual.info,  Node: mysql-calendar,  Next: fulltext-search,  Prev: date-and-time-functions,  Up: functions

12.8 What Calendar Is Used By MySQL?
====================================

MySQL uses what is known as a _proleptic Gregorian calendar_.

Every country that has switched from the Julian to the Gregorian
calendar has had to discard at least ten days during the switch.  To
see how this works, consider the month of October 1582, when the first
Julian-to-Gregorian switch occurred.

This table shows the month of October 1582, when the first
Julian-to-Gregorian switch occurred. Table headings are days of the
week and table rows list the dates for each day of the week. The table
is intended to illustrate that there are no dates between October 4 and
October 15.

Monday     Tuesday    Wednesday  Thursday   Friday     Saturday   Sunday
1          2          3          4          15         16         17
18         19         20         21         22         23         24
25         26         27         28         29         30         31

There are no dates between October 4 and October 15. This discontinuity
is called the _cutover_. Any dates before the cutover are Julian, and
any dates following the cutover are Gregorian. Dates during a cutover
are nonexistent.

A calendar applied to dates when it was not actually in use is called
_proleptic_. Thus, if we assume there was never a cutover and Gregorian
rules always rule, we have a proleptic Gregorian calendar. This is what
is used by MySQL, as is required by standard SQL. For this reason,
dates prior to the cutover stored as MySQL *Note `DATE': datetime. or
*Note `DATETIME': datetime. values must be adjusted to compensate for
the difference. It is important to realize that the cutover did not
occur at the same time in all countries, and that the later it
happened, the more days were lost. For example, in Great Britain, it
took place in 1752, when Wednesday September 2 was followed by Thursday
September 14. Russia remained on the Julian calendar until 1918, losing
13 days in the process, and what is popularly referred to as its
`October Revolution' occurred in November according to the Gregorian
calendar.


File: manual.info,  Node: fulltext-search,  Next: cast-functions,  Prev: mysql-calendar,  Up: functions

12.9 Full-Text Search Functions
===============================

* Menu:

* fulltext-natural-language::    Natural Language Full-Text Searches
* fulltext-boolean::             Boolean Full-Text Searches
* fulltext-query-expansion::     Full-Text Searches with Query Expansion
* fulltext-stopwords::           Full-Text Stopwords
* fulltext-restrictions::        Full-Text Restrictions
* fulltext-fine-tuning::         Fine-Tuning MySQL Full-Text Search
* full-text-adding-collation::   Adding a Collation for Full-Text Indexing

`MATCH (COL1,COL2,...)  AGAINST (EXPR [SEARCH_MODIFIER])'


     SEARCH_MODIFIER:
       {
            IN NATURAL LANGUAGE MODE
          | IN NATURAL LANGUAGE MODE WITH QUERY EXPANSION
          | IN BOOLEAN MODE
          | WITH QUERY EXPANSION
       }

MySQL has support for full-text indexing and searching:

   * A full-text index in MySQL is an index of type `FULLTEXT'.

   * Full-text indexes can be used only with `MyISAM' tables. (In MySQL
     5.6 and up, they can also be used with `InnoDB' tables.)
     Full-text indexes can be created only for *Note `CHAR': char,
     *Note `VARCHAR': char, or *Note `TEXT': blob. columns.

   * A `FULLTEXT' index definition can be given in the *Note `CREATE
     TABLE': create-table. statement when a table is created, or added
     later using *Note `ALTER TABLE': alter-table. or *Note `CREATE
     INDEX': create-index.

   * For large data sets, it is much faster to load your data into a
     table that has no `FULLTEXT' index and then create the index after
     that, than to load data into a table that has an existing
     `FULLTEXT' index.

Full-text searching is performed using `MATCH() ... AGAINST' syntax.
`MATCH()' takes a comma-separated list that names the columns to be
searched.  `AGAINST' takes a string to search for, and an optional
modifier that indicates what type of search to perform.  The search
string must be a string value that is constant during query evaluation.
This rules out, for example, a table column because that can differ for
each row.

There are three types of full-text searches:

   * A natural language search interprets the search string as a phrase
     in natural human language (a phrase in free text).  There are no
     special operators. The stopword list applies. In addition, words
     that are present in 50% or more of the rows are considered common
     and do not match.

     Full-text searches are natural language searches if the `IN
     NATURAL LANGUAGE MODE' modifier is given or if no modifier is
     given. For more information, see *Note fulltext-natural-language::.

   * A boolean search interprets the search string using the rules of a
     special query language. The string contains the words to search
     for. It can also contain operators that specify requirements such
     that a word must be present or absent in matching rows, or that it
     should be weighted higher or lower than usual. Common words such
     as `some' or `then' are stopwords and do not match if present in
     the search string. The `IN BOOLEAN MODE' modifier specifies a
     boolean search. For more information, see *Note fulltext-boolean::.

   * A query expansion search is a modification of a natural language
     search. The search string is used to perform a natural language
     search. Then words from the most relevant rows returned by the
     search are added to the search string and the search is done
     again. The query returns the rows from the second search. The `IN
     NATURAL LANGUAGE MODE WITH QUERY EXPANSION' or `WITH QUERY
     EXPANSION' modifier specifies a query expansion search. For more
     information, see *Note fulltext-query-expansion::.

The `IN NATURAL LANGUAGE MODE' and `IN NATURAL LANGUAGE MODE WITH QUERY
EXPANSION' modifiers were added in MySQL 5.1.7.

Constraints on full-text searching are listed in *Note
fulltext-restrictions::.

The *Note `myisam_ftdump': myisam-ftdump. utility can be used to dump
the contents of a full-text index. This may be helpful for debugging
full-text queries. See *Note myisam-ftdump::.


File: manual.info,  Node: fulltext-natural-language,  Next: fulltext-boolean,  Prev: fulltext-search,  Up: fulltext-search

12.9.1 Natural Language Full-Text Searches
------------------------------------------

By default or with the `IN NATURAL LANGUAGE MODE' modifier, the
`MATCH()' function performs a natural language search for a string
against a _text collection_. A collection is a set of one or more
columns included in a `FULLTEXT' index. The search string is given as
the argument to `AGAINST()'. For each row in the table, `MATCH()'
returns a relevance value; that is, a similarity measure between the
search string and the text in that row in the columns named in the
`MATCH()' list.


     mysql> CREATE TABLE articles (
         ->   id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
         ->   title VARCHAR(200),
         ->   body TEXT,
         ->   FULLTEXT (title,body)
         -> ) ENGINE=MyISAM;
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO articles (title,body) VALUES
         -> ('MySQL Tutorial','DBMS stands for DataBase ...'),
         -> ('How To Use MySQL Well','After you went through a ...'),
         -> ('Optimizing MySQL','In this tutorial we will show ...'),
         -> ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'),
         -> ('MySQL vs. YourSQL','In the following database comparison ...'),
         -> ('MySQL Security','When configured properly, MySQL ...');
     Query OK, 6 rows affected (0.00 sec)
     Records: 6  Duplicates: 0  Warnings: 0

     mysql> SELECT * FROM articles
         -> WHERE MATCH (title,body)
         -> AGAINST ('database' IN NATURAL LANGUAGE MODE);
     +----+-------------------+------------------------------------------+
     | id | title             | body                                     |
     +----+-------------------+------------------------------------------+
     |  5 | MySQL vs. YourSQL | In the following database comparison ... |
     |  1 | MySQL Tutorial    | DBMS stands for DataBase ...             |
     +----+-------------------+------------------------------------------+
     2 rows in set (0.00 sec)

By default, the search is performed in case-insensitive fashion.
However, you can perform a case-sensitive full-text search by using a
binary collation for the indexed columns. For example, a column that
uses the `latin1' character set of can be assigned a collation of
`latin1_bin' to make it case sensitive for full-text searches.

When `MATCH()' is used in a `WHERE' clause, as in the example shown
earlier, the rows returned are automatically sorted with the highest
relevance first. Relevance values are nonnegative floating-point
numbers. Zero relevance means no similarity.  Relevance is computed
based on the number of words in the row, the number of unique words in
that row, the total number of words in the collection, and the number
of documents (rows) that contain a particular word.

To simply count matches, you could use a query like this:


     mysql> SELECT COUNT(*) FROM articles
         -> WHERE MATCH (title,body)
         -> AGAINST ('database' IN NATURAL LANGUAGE MODE);
     +----------+
     | COUNT(*) |
     +----------+
     |        2 |
     +----------+
     1 row in set (0.00 sec)

However, you might find it quicker to rewrite the query as follows:


     mysql> SELECT
         -> COUNT(IF(MATCH (title,body) AGAINST ('database' IN NATURAL LANGUAGE MODE), 1, NULL))
         -> AS count
         -> FROM articles;
     +-------+
     | count |
     +-------+
     |     2 |
     +-------+
     1 row in set (0.03 sec)

The first query sorts the results by relevance whereas the second does
not. However, the second query performs a full table scan and the first
does not. The first may be faster if the search matches few rows;
otherwise, the second may be faster because it would read many rows
anyway.

For natural-language full-text searches, it is a requirement that the
columns named in the `MATCH()' function be the same columns included in
some `FULLTEXT' index in your table. For the preceding query, note that
the columns named in the `MATCH()' function (`title' and `body') are the
same as those named in the definition of the `article' table's
`FULLTEXT' index. If you wanted to search the `title' or `body'
separately, you would need to create separate `FULLTEXT' indexes for
each column.

It is also possible to perform a boolean search or a search with query
expansion. These search types are described in *Note
fulltext-boolean::, and *Note fulltext-query-expansion::.

A full-text search that uses an index can name columns only from a
single table in the `MATCH()' clause because an index cannot span
multiple tables. A boolean search can be done in the absence of an
index (albeit more slowly), in which case it is possible to name
columns from multiple tables.

The preceding example is a basic illustration that shows how to use the
`MATCH()' function where rows are returned in order of decreasing
relevance. The next example shows how to retrieve the relevance values
explicitly.  Returned rows are not ordered because the *Note `SELECT':
select. statement includes neither `WHERE' nor `ORDER BY' clauses:


     mysql> SELECT id, MATCH (title,body)
         -> AGAINST ('Tutorial' IN NATURAL LANGUAGE MODE) AS score
         -> FROM articles;
     +----+------------------+
     | id | score            |
     +----+------------------+
     |  1 | 0.65545833110809 |
     |  2 |                0 |
     |  3 | 0.66266459226608 |
     |  4 |                0 |
     |  5 |                0 |
     |  6 |                0 |
     +----+------------------+
     6 rows in set (0.00 sec)

The following example is more complex. The query returns the relevance
values and it also sorts the rows in order of decreasing relevance. To
achieve this result, specify `MATCH()' twice: once in the *Note
`SELECT': select. list and once in the `WHERE' clause. This causes no
additional overhead, because the MySQL optimizer notices that the two
`MATCH()' calls are identical and invokes the full-text search code
only once.


     mysql> SELECT id, body, MATCH (title,body) AGAINST
         -> ('Security implications of running MySQL as root'
         -> IN NATURAL LANGUAGE MODE) AS score
         -> FROM articles WHERE MATCH (title,body) AGAINST
         -> ('Security implications of running MySQL as root'
         -> IN NATURAL LANGUAGE MODE);
     +----+-------------------------------------+-----------------+
     | id | body                                | score           |
     +----+-------------------------------------+-----------------+
     |  4 | 1. Never run mysqld as root. 2. ... | 1.5219271183014 |
     |  6 | When configured properly, MySQL ... | 1.3114095926285 |
     +----+-------------------------------------+-----------------+
     2 rows in set (0.00 sec)

The MySQL `FULLTEXT' implementation regards any sequence of true word
characters (letters, digits, and underscores) as a word. That sequence
may also contain apostrophes (``'''), but not more than one in a row.
This means that `aaa'bbb' is regarded as one word, but `aaa''bbb' is
regarded as two words. Apostrophes at the beginning or the end of a
word are stripped by the `FULLTEXT' parser; `'aaa'bbb'' would be parsed
as `aaa'bbb'.

The `FULLTEXT' parser determines where words start and end by looking
for certain delimiter characters; for example, `` '' (space), ``,''
(comma), and ``.'' (period). If words are not separated by delimiters
(as in, for example, Chinese), the `FULLTEXT' parser cannot determine
where a word begins or ends. To be able to add words or other indexed
terms in such languages to a `FULLTEXT' index, you must preprocess them
so that they are separated by some arbitrary delimiter such as ``"''.

In MySQL 5.1, it is possible to write a plugin that replaces the
built-in full-text parser. For details, see *Note plugin-api::. For
example parser plugin source code, see the `plugin/fulltext' directory
of a MySQL source distribution.

Some words are ignored in full-text searches:

   * Any word that is too short is ignored. The default minimum length
     of words that are found by full-text searches is four characters.

   * Words in the stopword list are ignored. A stopword is a word such
     as `the' or `some' that is so common that it is considered to have
     zero semantic value.  There is a built-in stopword list, but it
     can be overwritten by a user-defined list.

The default stopword list is given in *Note fulltext-stopwords::. The
default minimum word length and stopword list can be changed as
described in *Note fulltext-fine-tuning::.

Every correct word in the collection and in the query is weighted
according to its significance in the collection or query. Consequently,
a word that is present in many documents has a lower weight (and may
even have a zero weight), because it has lower semantic value in this
particular collection.  Conversely, if the word is rare, it receives a
higher weight.  The weights of the words are combined to compute the
relevance of the row.

Such a technique works best with large collections (in fact, it was
carefully tuned this way). For very small tables, word distribution
does not adequately reflect their semantic value, and this model may
sometimes produce bizarre results. For example, although the word
`MySQL' is present in every row of the `articles' table shown earlier,
a search for the word produces no results:


     mysql> SELECT * FROM articles
         -> WHERE MATCH (title,body)
         -> AGAINST ('MySQL' IN NATURAL LANGUAGE MODE);
     Empty set (0.00 sec)

The search result is empty because the word `MySQL' is present in at
least 50% of the rows. As such, it is effectively treated as a
stopword. For large data sets, this is the most desirable behavior: A
natural language query should not return every second row from a 1GB
table. For small data sets, it may be less desirable.

A word that matches half of the rows in a table is less likely to
locate relevant documents. In fact, it most likely finds plenty of
irrelevant documents. We all know this happens far too often when we
are trying to find something on the Internet with a search engine. It
is with this reasoning that rows containing the word are assigned a low
semantic value for _the particular data set in which they occur_. A
given word may reach the 50% threshold in one data set but not another.

The 50% threshold has a significant implication when you first try
full-text searching to see how it works: If you create a table and
insert only one or two rows of text into it, every word in the text
occurs in at least 50% of the rows. As a result, no search returns any
results. Be sure to insert at least three rows, and preferably many
more. Users who need to bypass the 50% limitation can use the boolean
search mode; see *Note fulltext-boolean::.


File: manual.info,  Node: fulltext-boolean,  Next: fulltext-query-expansion,  Prev: fulltext-natural-language,  Up: fulltext-search

12.9.2 Boolean Full-Text Searches
---------------------------------

MySQL can perform boolean full-text searches using the `IN BOOLEAN
MODE' modifier. With this modifier, certain characters have special
meaning at the beginning or end of words in the search string. In the
following query, the `+' and `-' operators indicate that a word is
required to be present or absent, respectively, for a match to occur.
Thus, the query retrieves all the rows that contain the word `MySQL'
but that do _not_ contain the word `YourSQL':


     mysql> SELECT * FROM articles WHERE MATCH (title,body)
         -> AGAINST ('+MySQL -YourSQL' IN BOOLEAN MODE);
     +----+-----------------------+-------------------------------------+
     | id | title                 | body                                |
     +----+-----------------------+-------------------------------------+
     |  1 | MySQL Tutorial        | DBMS stands for DataBase ...        |
     |  2 | How To Use MySQL Well | After you went through a ...        |
     |  3 | Optimizing MySQL      | In this tutorial we will show ...   |
     |  4 | 1001 MySQL Tricks     | 1. Never run mysqld as root. 2. ... |
     |  6 | MySQL Security        | When configured properly, MySQL ... |
     +----+-----------------------+-------------------------------------+

*Note*:

In implementing this feature, MySQL uses what is sometimes referred to
as _implied Boolean logic_, in which

   * `+' stands for `AND'

   * `-' stands for `NOT'

   * [_no operator_] implies `OR'

Boolean full-text searches have these characteristics:

   * They do not use the 50% threshold.

   * They do not automatically sort rows in order of decreasing
     relevance. You can see this from the preceding query result: The
     row with the highest relevance is the one that contains `MySQL'
     twice, but it is listed last, not first.

   * They can work even without a `FULLTEXT' index, although a search
     executed in this fashion would be quite slow.

   * The minimum and maximum word length full-text parameters apply.

   * The stopword list applies.

The boolean full-text search capability supports the following
operators:

   * `+'

     A leading plus sign indicates that this word _must_ be present in
     each row that is returned.

   * `-'

     A leading minus sign indicates that this word must _not_ be
     present in any of the rows that are returned.

     Note: The `-' operator acts only to exclude rows that are
     otherwise matched by other search terms. Thus, a boolean-mode
     search that contains only terms preceded by `-' returns an empty
     result. It does not return `all rows except those containing any
     of the excluded terms.'

   * (no operator)

     By default (when neither `+' nor `-' is specified) the word is
     optional, but the rows that contain it are rated higher. This
     mimics the behavior of `MATCH() ...  AGAINST()' without the `IN
     BOOLEAN MODE' modifier.

   * `> <'

     These two operators are used to change a word's contribution to
     the relevance value that is assigned to a row. The `>' operator
     increases the contribution and the `<' operator decreases it. See
     the example following this list.

   * `( )'

     Parentheses group words into subexpressions. Parenthesized groups
     can be nested.

   * `~'

     A leading tilde acts as a negation operator, causing the word's
     contribution to the row's relevance to be negative.  This is
     useful for marking `noise' words. A row containing such a word is
     rated lower than others, but is not excluded altogether, as it
     would be with the `-' operator.

   * `*'

     The asterisk serves as the truncation (or wildcard) operator.
     Unlike the other operators, it should be _appended_ to the word to
     be affected.  Words match if they begin with the word preceding the
     `*' operator.

     If a word is specified with the truncation operator, it is not
     stripped from a boolean query, even if it is too short (as
     determined from the `ft_min_word_len' setting) or a stopword. This
     occurs because the word is not seen as too short or a stopword,
     but as a prefix that must be present in the document in the form
     of a word that begins with the prefix. Suppose that
     `ft_min_word_len=4'.  Then a search for `'+WORD +the*'' will
     likely return fewer rows than a search for `'+WORD +the'':

        * The former query remains as is and requires both WORD and
          `the*' (a word starting with `the') to be present in the
          document.

        * The latter query is transformed to `+WORD' (requiring only
          WORD to be present). `the' is both too short and a stopword,
          and either condition is enough to cause it to be ignored.

   * `"'

     A phrase that is enclosed within double quote (``"'') characters
     matches only rows that contain the phrase _literally, as it was
     typed_. The full-text engine splits the phrase into words and
     performs a search in the `FULLTEXT' index for the words. Nonword
     characters need not be matched exactly: Phrase searching requires
     only that matches contain exactly the same words as the phrase and
     in the same order. For example, `"test phrase"' matches `"test,
     phrase"'.

     If the phrase contains no words that are in the index, the result
     is empty. For example, if all words are either stopwords or
     shorter than the minimum length of indexed words, the result is
     empty.

The following examples demonstrate some search strings that use boolean
full-text operators:

   * `'apple banana''

     Find rows that contain at least one of the two words.

   * `'+apple +juice''

     Find rows that contain both words.

   * `'+apple macintosh''

     Find rows that contain the word `apple', but rank rows higher if
     they also contain `macintosh'.

   * `'+apple -macintosh''

     Find rows that contain the word `apple' but not `macintosh'.

   * `'+apple ~macintosh''

     Find rows that contain the word `apple', but if the row also
     contains the word `macintosh', rate it lower than if row does not.
     This is `softer' than a search for `'+apple -macintosh'', for
     which the presence of `macintosh' causes the row not to be returned
     at all.

   * `'+apple +(>turnover <strudel)''

     Find rows that contain the words `apple' and `turnover', or
     `apple' and `strudel' (in any order), but rank `apple turnover'
     higher than `apple strudel'.

   * `'apple*''

     Find rows that contain words such as `apple', `apples',
     `applesauce', or `applet'.

   * `'"some words"''

     Find rows that contain the exact phrase `some words' (for example,
     rows that contain `some words of wisdom' but not `some noise
     words'). Note that the ``"'' characters that enclose the phrase
     are operator characters that delimit the phrase.  They are not the
     quotation marks that enclose the search string itself.


File: manual.info,  Node: fulltext-query-expansion,  Next: fulltext-stopwords,  Prev: fulltext-boolean,  Up: fulltext-search

12.9.3 Full-Text Searches with Query Expansion
----------------------------------------------

Full-text search supports query expansion (and in particular, its
variant `blind query expansion'). This is generally useful when a
search phrase is too short, which often means that the user is relying
on implied knowledge that the full-text search engine lacks. For
example, a user searching for `database' may really mean that `MySQL',
`Oracle', `DB2', and `RDBMS' all are phrases that should match
`databases' and should be returned, too. This is implied knowledge.

Blind query expansion (also known as automatic relevance feedback) is
enabled by adding `WITH QUERY EXPANSION' or `IN NATURAL LANGUAGE MODE
WITH QUERY EXPANSION' following the search phrase. It works by
performing the search twice, where the search phrase for the second
search is the original search phrase concatenated with the few most
highly relevant documents from the first search.  Thus, if one of these
documents contains the word `databases' and the word `MySQL', the
second search finds the documents that contain the word `MySQL' even if
they do not contain the word `database'. The following example shows
this difference:


     mysql> SELECT * FROM articles
         -> WHERE MATCH (title,body)
         -> AGAINST ('database' IN NATURAL LANGUAGE MODE);
     +----+-------------------+------------------------------------------+
     | id | title             | body                                     |
     +----+-------------------+------------------------------------------+
     |  5 | MySQL vs. YourSQL | In the following database comparison ... |
     |  1 | MySQL Tutorial    | DBMS stands for DataBase ...             |
     +----+-------------------+------------------------------------------+
     2 rows in set (0.00 sec)

     mysql> SELECT * FROM articles
         -> WHERE MATCH (title,body)
         -> AGAINST ('database' WITH QUERY EXPANSION);
     +----+-------------------+------------------------------------------+
     | id | title             | body                                     |
     +----+-------------------+------------------------------------------+
     |  1 | MySQL Tutorial    | DBMS stands for DataBase ...             |
     |  5 | MySQL vs. YourSQL | In the following database comparison ... |
     |  3 | Optimizing MySQL  | In this tutorial we will show ...        |
     +----+-------------------+------------------------------------------+
     3 rows in set (0.00 sec)

Another example could be searching for books by Georges Simenon about
Maigret, when a user is not sure how to spell `Maigret'. A search for
`Megre and the reluctant witnesses' finds only `Maigret and the
Reluctant Witnesses' without query expansion. A search with query
expansion finds all books with the word `Maigret' on the second pass.

*Note*:

Because blind query expansion tends to increase noise significantly by
returning nonrelevant documents, it is meaningful to use only when a
search phrase is rather short.


File: manual.info,  Node: fulltext-stopwords,  Next: fulltext-restrictions,  Prev: fulltext-query-expansion,  Up: fulltext-search

12.9.4 Full-Text Stopwords
--------------------------

The stopword list is loaded and searched for full-text queries using
the server character set and collation (the values of the
`character_set_server' and `collation_server' system variables). False
hits or misses may occur for stopword lookups if the stopword file or
columns used for full-text indexing or searches have a character set or
collation different from `character_set_server' or `collation_server'.

Case sensitivity of stopword lookups depends on the server collation.
For example, lookups are case insensitive if the collation is
`latin1_swedish_ci', whereas lookups are case sensitive if the
collation is `latin1_general_cs' or `latin1_bin'.

The following table shows the default list of full-text stopwords. In a
MySQL source distribution, you can find this list in the
`storage/myisam/ft_static.c' file.

This table shows the default list of full-text stopwords. In a MySQL
source distribution, you can find this list in the `myisam/ft_static.c'
file. The table lists stopwords in alphabetical order when read from
left to right, row by row.

a's            able           about          above          according
accordingly    across         actually       after          afterwards
again          against        ain't          all            allow
allows         almost         alone          along          already
also           although       always         am             among
amongst        an             and            another        any
anybody        anyhow         anyone         anything       anyway
anyways        anywhere       apart          appear         appreciate
appropriate    are            aren't         around         as
aside          ask            asking         associated     at
available      away           awfully        be             became
because        become         becomes        becoming       been
before         beforehand     behind         being          believe
below          beside         besides        best           better
between        beyond         both           brief          but
by             c'mon          c's            came           can
can't          cannot         cant           cause          causes
certain        certainly      changes        clearly        co
com            come           comes          concerning     consequently
consider       considering    contain        containing     contains
corresponding  could          couldn't       course         currently
definitely     described      despite        did            didn't
different      do             does           doesn't        doing
don't          done           down           downwards      during
each           edu            eg             eight          either
else           elsewhere      enough         entirely       especially
et             etc            even           ever           every
everybody      everyone       everything     everywhere     ex
exactly        example        except         far            few
fifth          first          five           followed       following
follows        for            former         formerly       forth
four           from           further        furthermore    get
gets           getting        given          gives          go
goes           going          gone           got            gotten
greetings      had            hadn't         happens        hardly
has            hasn't         have           haven't        having
he             he's           hello          help           hence
her            here           here's         hereafter      hereby
herein         hereupon       hers           herself        hi
him            himself        his            hither         hopefully
how            howbeit        however        i'd            i'll
i'm            i've           ie             if             ignored
immediate      in             inasmuch       inc            indeed
indicate       indicated      indicates      inner          insofar
instead        into           inward         is             isn't
it             it'd           it'll          it's           its
itself         just           keep           keeps          kept
know           known          knows          last           lately
later          latter         latterly       least          less
lest           let            let's          like           liked
likely         little         look           looking        looks
ltd            mainly         many           may            maybe
me             mean           meanwhile      merely         might
more           moreover       most           mostly         much
must           my             myself         name           namely
nd             near           nearly         necessary      need
needs          neither        never          nevertheless   new
next           nine           no             nobody         non
none           noone          nor            normally       not
nothing        novel          now            nowhere        obviously
of             off            often          oh             ok
okay           old            on             once           one
ones           only           onto           or             other
others         otherwise      ought          our            ours
ourselves      out            outside        over           overall
own            particular     particularly   per            perhaps
placed         please         plus           possible       presumably
probably       provides       que            quite          qv
rather         rd             re             really         reasonably
regarding      regardless     regards        relatively     respectively
right          said           same           saw            say
saying         says           second         secondly       see
seeing         seem           seemed         seeming        seems
seen           self           selves         sensible       sent
serious        seriously      seven          several        shall
she            should         shouldn't      since          six
so             some           somebody       somehow        someone
something      sometime       sometimes      somewhat       somewhere
soon           sorry          specified      specify        specifying
still          sub            such           sup            sure
t's            take           taken          tell           tends
th             than           thank          thanks         thanx
that           that's         thats          the            their
theirs         them           themselves     then           thence
there          there's        thereafter     thereby        therefore
therein        theres         thereupon      these          they
they'd         they'll        they're        they've        think
third          this           thorough       thoroughly     those
though         three          through        throughout     thru
thus           to             together       too            took
toward         towards        tried          tries          truly
try            trying         twice          two            un
under          unfortunately  unless         unlikely       until
unto           up             upon           us             use
used           useful         uses           using          usually
value          various        very           via            viz
vs             want           wants          was            wasn't
way            we             we'd           we'll          we're
we've          welcome        well           went           were
weren't        what           what's         whatever       when
whence         whenever       where          where's        whereafter
whereas        whereby        wherein        whereupon      wherever
whether        which          while          whither        who
who's          whoever        whole          whom           whose
why            will           willing        wish           with
within         without        won't          wonder         would
wouldn't       yes            yet            you            you'd
you'll         you're         you've         your           yours
yourself       yourselves     zero                          


File: manual.info,  Node: fulltext-restrictions,  Next: fulltext-fine-tuning,  Prev: fulltext-stopwords,  Up: fulltext-search

12.9.5 Full-Text Restrictions
-----------------------------

   * Full-text searches are supported for `MyISAM' tables only. (In
     MySQL 5.6 and up, they can also be used with `InnoDB' tables.)

   * Full-text searches are not supported for partitioned tables.  See
     *Note partitioning-limitations::.

   * Full-text searches can be used with most multibyte character sets.
     The exception is that for Unicode, the `utf8' character set can be
     used, but not the `ucs2' character set. However, although
     `FULLTEXT' indexes on `ucs2' columns cannot be used, you can
     perform `IN BOOLEAN MODE' searches on a `ucs2' column that has no
     such index.

   * Ideographic languages such as Chinese and Japanese do not have
     word delimiters. Therefore, the `FULLTEXT' parser _cannot
     determine where words begin and end in these and other such
     languages_. The implications of this and some workarounds for the
     problem are described in *Note fulltext-search::.

   * Although the use of multiple character sets within a single table
     is supported, all columns in a `FULLTEXT' index must use the same
     character set and collation.

   * The `MATCH()' column list must match exactly the column list in
     some `FULLTEXT' index definition for the table, unless this
     `MATCH()' is `IN BOOLEAN MODE'. Boolean-mode searches can be done
     on nonindexed columns, although they are likely to be slow.

   * The argument to `AGAINST()' must be a string value that is
     constant during query evaluation. This rules out, for example, a
     table column because that can differ for each row.

   * Index hints are more limited for `FULLTEXT' searches than for
     non-`FULLTEXT' searches.  See *Note index-hints::.


File: manual.info,  Node: fulltext-fine-tuning,  Next: full-text-adding-collation,  Prev: fulltext-restrictions,  Up: fulltext-search

12.9.6 Fine-Tuning MySQL Full-Text Search
-----------------------------------------

MySQL's full-text search capability has few user-tunable parameters.
You can exert more control over full-text searching behavior if you
have a MySQL source distribution because some changes require source
code modifications. See *Note source-installation::.

Note that full-text search is carefully tuned for the most
effectiveness. Modifying the default behavior in most cases can
actually decrease effectiveness. _Do not alter the MySQL sources unless
you know what you are doing_.

Most full-text variables described in this section must be set at
server startup time. A server restart is required to change them; they
cannot be modified while the server is running.

Some variable changes require that you rebuild the `FULLTEXT' indexes
in your tables. Instructions for doing so are given later in this
section.

   * The minimum and maximum lengths of words to be indexed are defined
     by the `ft_min_word_len' and `ft_max_word_len' system variables.
     (See *Note server-system-variables::.)  The default minimum value
     is four characters; the default maximum is version dependent. If
     you change either value, you must rebuild your `FULLTEXT' indexes.
     For example, if you want three-character words to be searchable,
     you can set the `ft_min_word_len' variable by putting the
     following lines in an option file:


          [mysqld]
          ft_min_word_len=3

     Then restart the server and rebuild your `FULLTEXT' indexes. Note
     particularly the remarks regarding *Note `myisamchk': myisamchk.
     in the instructions following this list.

   * To override the default stopword list, set the `ft_stopword_file'
     system variable. (See *Note server-system-variables::.)  The
     variable value should be the path name of the file containing the
     stopword list, or the empty string to disable stopword filtering.
     The server looks for the file in the data directory unless an
     absolute path name is given to specify a different directory.
     After changing the value of this variable or the contents of the
     stopword file, restart the server and rebuild your `FULLTEXT'
     indexes.

     The stopword list is free-form. That is, you may use any
     nonalphanumeric character such as newline, space, or comma to
     separate stopwords. Exceptions are the underscore character
     (``_'') and a single apostrophe (``''') which are treated as part
     of a word. The character set of the stopword list is the server's
     default character set; see *Note charset-server::.

   * The 50% threshold for natural language searches is determined by
     the particular weighting scheme chosen. To disable it, look for
     the following line in `storage/myisam/ftdefs.h':


          #define GWS_IN_USE GWS_PROB

     Change that line to this:


          #define GWS_IN_USE GWS_FREQ

     Then recompile MySQL. There is no need to rebuild the indexes in
     this case.

     *Note*:

     By making this change, you _severely_ decrease MySQL's ability to
     provide adequate relevance values for the `MATCH()' function. If
     you really need to search for such common words, it would be
     better to search using `IN BOOLEAN MODE' instead, which does not
     observe the 50% threshold.

   * To change the operators used for boolean full-text searches, set
     the `ft_boolean_syntax' system variable. This variable can be
     changed while the server is running, but you must have the `SUPER'
     privilege to do so. No rebuilding of indexes is necessary in this
     case. See *Note server-system-variables::, which describes the
     rules governing how to set this variable.

   * If you want to change the set of characters that are considered
     word characters, you can do so in several ways, as described in
     the following list. After making the modification, you must
     rebuild the indexes for each table that contains any `FULLTEXT'
     indexes.  Suppose that you want to treat the hyphen character
     ('-') as a word character. Use one of these methods:

        * Modify the MySQL source: In `storage/myisam/ftdefs.h', see the
          `true_word_char()' and `misc_word_char()' macros. Add `'-''
          to one of those macros and recompile MySQL.

        * Modify a character set file: This requires no recompilation.
          The `true_word_char()' macro uses a `character type' table to
          distinguish letters and numbers from other characters. .  You
          can edit the contents of the `<ctype><map>' array in one of
          the character set XML files to specify that `'-'' is a
          `letter.' Then use the given character set for your
          `FULLTEXT' indexes. For information about the `<ctype><map>'
          array format, see *Note character-arrays::.

        * Add a new collation for the character set used by the indexed
          columns, and alter the columns to use that collation. For
          general information about adding collations, see *Note
          adding-collation::. For an example specific to full-text
          indexing, see *Note full-text-adding-collation::.

If you modify full-text variables that affect indexing
(`ft_min_word_len', `ft_max_word_len', or `ft_stopword_file'), or if you
change the stopword file itself, you must rebuild your `FULLTEXT'
indexes after making the changes and restarting the server. To rebuild
the indexes in this case, it is sufficient to do a `QUICK' repair
operation:


     mysql> REPAIR TABLE TBL_NAME QUICK;

Alternatively, use *Note `ALTER TABLE': alter-table.  with the `DROP
INDEX' and `ADD INDEX' options to drop and re-create each `FULLTEXT'
index. In some cases, this may be faster than a repair operation.

Each table that contains any `FULLTEXT' index must be repaired as just
shown. Otherwise, queries for the table may yield incorrect results,
and modifications to the table will cause the server to see the table
as corrupt and in need of repair.

Note that if you use *Note `myisamchk': myisamchk. to perform an
operation that modifies table indexes (such as repair or analyze), the
`FULLTEXT' indexes are rebuilt using the _default_ full-text parameter
values for minimum word length, maximum word length, and stopword file
unless you specify otherwise. This can result in queries failing.

The problem occurs because these parameters are known only by the
server. They are not stored in `MyISAM' index files. To avoid the
problem if you have modified the minimum or maximum word length or
stopword file values used by the server, specify the same
`ft_min_word_len', `ft_max_word_len', and `ft_stopword_file' values for
*Note `myisamchk': myisamchk. that you use for *Note `mysqld': mysqld.
For example, if you have set the minimum word length to 3, you can
repair a table with *Note `myisamchk': myisamchk. like this:


     shell> myisamchk --recover --ft_min_word_len=3 TBL_NAME.MYI

To ensure that *Note `myisamchk': myisamchk. and the server use the
same values for full-text parameters, place each one in both the
`[mysqld]' and `[myisamchk]' sections of an option file:


     [mysqld]
     ft_min_word_len=3

     [myisamchk]
     ft_min_word_len=3

An alternative to using *Note `myisamchk': myisamchk. for index
modification is to use the *Note `REPAIR TABLE': repair-table, *Note
`ANALYZE TABLE': analyze-table, *Note `OPTIMIZE TABLE': optimize-table,
or *Note `ALTER TABLE': alter-table. statements. These statements are
performed by the server, which knows the proper full-text parameter
values to use.


File: manual.info,  Node: full-text-adding-collation,  Prev: fulltext-fine-tuning,  Up: fulltext-search

12.9.7 Adding a Collation for Full-Text Indexing
------------------------------------------------

This section describes how to add a new collation for full-text
searches. The sample collation is like `latin1_swedish_ci' but treats
the `'-'' character as a letter rather than as a punctuation character
so that it can be indexed as a word character. General information
about adding collations is given in *Note adding-collation::; it is
assumed that you have read it and are familiar with the files involved.

To add a collation for full-text indexing, use this procedure:

  1. Add a collation to the `Index.xml' file.  The collation ID must be
     unused, so choose a value different from 62 if that ID is already
     taken on your system.


          <charset name="latin1">
          ...
          <collation name="latin1_fulltext_ci" id="62"/>
          </charset>

  2. Declare the sort order for the collation in the `latin1.xml' file.
     In this case, the order can be copied from `latin1_swedish_ci':


          <collation name="latin1_fulltext_ci">
          <map>
          00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
          10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F
          20 21 22 23 24 25 26 27 28 29 2A 2B 2C 2D 2E 2F
          30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F
          40 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
          50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F
          60 41 42 43 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F
          50 51 52 53 54 55 56 57 58 59 5A 7B 7C 7D 7E 7F
          80 81 82 83 84 85 86 87 88 89 8A 8B 8C 8D 8E 8F
          90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F
          A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF
          B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF
          41 41 41 41 5C 5B 5C 43 45 45 45 45 49 49 49 49
          44 4E 4F 4F 4F 4F 5D D7 D8 55 55 55 59 59 DE DF
          41 41 41 41 5C 5B 5C 43 45 45 45 45 49 49 49 49
          44 4E 4F 4F 4F 4F 5D F7 D8 55 55 55 59 59 DE FF
          </map>
          </collation>

  3. Modify the `ctype' array in `latin1.xml'. Change the value
     corresponding to 0x2D (which is the code for the `'-'' character)
     from 10 (punctuation) to 01 (small letter). In the following
     array, this is the element in the fourth row down, third value
     from the end.


          <ctype>
          <map>
          00
          20 20 20 20 20 20 20 20 20 28 28 28 28 28 20 20
          20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
          48 10 10 10 10 10 10 10 10 10 10 10 10 *01* 10 10
          84 84 84 84 84 84 84 84 84 84 10 10 10 10 10 10
          10 81 81 81 81 81 81 01 01 01 01 01 01 01 01 01
          01 01 01 01 01 01 01 01 01 01 01 10 10 10 10 10
          10 82 82 82 82 82 82 02 02 02 02 02 02 02 02 02
          02 02 02 02 02 02 02 02 02 02 02 10 10 10 10 20
          10 00 10 02 10 10 10 10 10 10 01 10 01 00 01 00
          00 10 10 10 10 10 10 10 10 10 02 10 02 00 02 01
          48 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10
          10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10
          01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
          01 01 01 01 01 01 01 10 01 01 01 01 01 01 01 02
          02 02 02 02 02 02 02 02 02 02 02 02 02 02 02 02
          02 02 02 02 02 02 02 10 02 02 02 02 02 02 02 02
          </map>
          </ctype>

  4. Restart the server.

  5. To employ the new collation, include it in the definition of
     columns that are to use it:


          mysql> DROP TABLE IF EXISTS t1;
          Query OK, 0 rows affected (0.13 sec)

          mysql> CREATE TABLE t1 (
              -> a TEXT CHARACTER SET latin1 COLLATE latin1_fulltext_ci,
              -> FULLTEXT INDEX(a)
              -> ) ENGINE=MyISAM;
          Query OK, 0 rows affected (0.47 sec)

  6. Test the collation to verify that hyphen is considered as a word
     character:


          mysql> INSERT INTO t1 VALUEs ('----'),('....'),('abcd');
          Query OK, 3 rows affected (0.22 sec)
          Records: 3  Duplicates: 0  Warnings: 0

          mysql> SELECT * FROM t1 WHERE MATCH a AGAINST ('----' IN BOOLEAN MODE);
          +------+
          | a    |
          +------+
          | ---- |
          +------+
          1 row in set (0.00 sec)


File: manual.info,  Node: cast-functions,  Next: xml-functions,  Prev: fulltext-search,  Up: functions

12.10 Cast Functions and Operators
==================================

*Cast Functions*

Name                          Description
`BINARY'                      Cast a string to a binary string
`CAST()'                      Cast a value as a certain type
`CONVERT()'                   Cast a value as a certain type

   * `BINARY'

     The `BINARY' operator casts the string following it to a binary
     string. This is an easy way to force a column comparison to be
     done byte by byte rather than character by character. This causes
     the comparison to be case sensitive even if the column is not
     defined as *Note `BINARY': binary-varbinary. or *Note `BLOB': blob.
     `BINARY' also causes trailing spaces to be significant.


          mysql> SELECT 'a' = 'A';
                  -> 1
          mysql> SELECT BINARY 'a' = 'A';
                  -> 0
          mysql> SELECT 'a' = 'a ';
                  -> 1
          mysql> SELECT BINARY 'a' = 'a ';
                  -> 0

     In a comparison, `BINARY' affects the entire operation; it can be
     given before either operand with the same result.

     `BINARY STR' is shorthand for `CAST(STR AS BINARY)'.

     Note that in some contexts, if you cast an indexed column to
     `BINARY', MySQL is not able to use the index efficiently.

   * `CAST(EXPR AS TYPE)'

     The `CAST()' function takes an expression of any type and produces
     a result value of a specified type, similar to `CONVERT()'. See
     the description of `CONVERT()' for more information.

   * `CONVERT(EXPR,TYPE)', `CONVERT(EXPR USING TRANSCODING_NAME)'

     The `CONVERT()' and `CAST()' functions take an expression of any
     type and produce a result value of a specified type.

     The TYPE for the result can be one of the following values:

        * `BINARY[(N)]'

        * `CHAR[(N)]'

        * *Note `DATE': datetime.

        * *Note `DATETIME': datetime.

        * `DECIMAL[(M[,D])]'

        * `SIGNED [INTEGER]'

        * *Note `TIME': time.

        * `UNSIGNED [INTEGER]'

     *Note `BINARY': binary-varbinary. produces a string with the *Note
     `BINARY': binary-varbinary. data type. See *Note
     binary-varbinary:: for a description of how this affects
     comparisons. If the optional length N is given, `BINARY(N)' causes
     the cast to use no more than N bytes of the argument. Values
     shorter than N bytes are padded with `0x00' bytes to a length of N.

     `CHAR(N)' causes the cast to use no more than N characters of the
     argument.

     `CAST()' and `CONVERT(... USING ...)' are standard SQL syntax. The
     non-`USING' form of `CONVERT()' is ODBC syntax.

     `CONVERT()' with `USING' is used to convert data between different
     character sets. In MySQL, transcoding names are the same as the
     corresponding character set names. For example, this statement
     converts the string `'abc'' in the default character set to the
     corresponding string in the `utf8' character set:


          SELECT CONVERT('abc' USING utf8);

Normally, you cannot compare a *Note `BLOB': blob.  value or other
binary string in case-insensitive fashion because binary strings have
no character set, and thus no concept of lettercase. To perform a
case-insensitive comparison, use the `CONVERT()' function to convert the
value to a nonbinary string. Comparisons of the result use the string
collation. For example, if the character set of the result has a
case-insensitive collation, a `LIKE' operation is not case sensitive:


     SELECT 'A' LIKE CONVERT(BLOB_COL USING latin1) FROM TBL_NAME;

To use a different character set, substitute its name for `latin1' in
the preceding statement. To specify a particular collation for the
converted string, use a `COLLATE' clause following the `CONVERT()'
call, as described in *Note charset-convert::. For example, to use
`latin1_german1_ci':


     SELECT 'A' LIKE CONVERT(BLOB_COL USING latin1) COLLATE latin1_german1_ci
       FROM TBL_NAME;

`CONVERT()' can be used more generally for comparing strings that are
represented in different character sets.

`LOWER()' (and `UPPER()') are ineffective when applied to binary
strings (*Note `BINARY': binary-varbinary, *Note `VARBINARY':
binary-varbinary, *Note `BLOB': blob.). To perform lettercase
conversion, convert the string to a nonbinary string:


     mysql> SET @str = BINARY 'New York';
     mysql> SELECT LOWER(@str), LOWER(CONVERT(@str USING latin1));
     +-------------+-----------------------------------+
     | LOWER(@str) | LOWER(CONVERT(@str USING latin1)) |
     +-------------+-----------------------------------+
     | New York    | new york                          |
     +-------------+-----------------------------------+

The cast functions are useful when you want to create a column with a
specific type in a *Note `CREATE TABLE ... SELECT': create-table.
statement:


     CREATE TABLE new_table SELECT CAST('2000-01-01' AS DATE);

The functions also can be useful for sorting *Note `ENUM': enum.
columns in lexical order.  Normally, sorting of *Note `ENUM': enum.
columns occurs using the internal numeric values. Casting the values to
*Note `CHAR': char. results in a lexical sort:


     SELECT ENUM_COL FROM TBL_NAME ORDER BY CAST(ENUM_COL AS CHAR);

`CAST(STR AS BINARY)' is the same thing as `BINARY STR'.  `CAST(EXPR AS
CHAR)' treats the expression as a string with the default character set.

`CAST()' also changes the result if you use it as part of a more
complex expression such as `CONCAT('Date: ',CAST(NOW() AS DATE))'.

You should not use `CAST()' to extract data in different formats but
instead use string functions like `LEFT()' or `EXTRACT()'. See *Note
date-and-time-functions::.

To cast a string to a numeric value in numeric context, you normally do
not have to do anything other than to use the string value as though it
were a number:


     mysql> SELECT 1+'1';
            -> 2

If you use a string in an arithmetic operation, it is converted to a
floating-point number during expression evaluation.

If you use a number in string context, the number automatically is
converted to a string:


     mysql> SELECT CONCAT('hello you ',2);
             -> 'hello you 2'

For information about implicit conversion of numbers to strings, see
*Note type-conversion::.

When using an explicit `CAST()' on a `TIMESTAMP' value in a statement
that does not select from any tables, the value is treated by MySQL 5.1
as a string prior to performing any conversion. This results in the
value being truncated when casting to a numeric type, as shown here:


     mysql> SELECT CAST(TIMESTAMP '2014-09-08 18:07:54' AS SIGNED);
     +-------------------------------------------------+
     | CAST(TIMESTAMP '2014-09-08 18:07:54' AS SIGNED) |
     +-------------------------------------------------+
     |                                            2014 |
     +-------------------------------------------------+
     1 row in set, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS;
     +---------+------+----------------------------------------------------------+
     | Level   | Code | Message                                                  |
     +---------+------+----------------------------------------------------------+
     | Warning | 1292 | Truncated incorrect INTEGER value: '2014-09-08 18:07:54' |
     +---------+------+----------------------------------------------------------+
     1 row in set (0.00 sec)

This does not apply when selecting rows from a table, as shown here:


     mysql> USE test;

     Database changed
     mysql> CREATE TABLE c_test (col TIMESTAMP);
     Query OK, 0 rows affected (0.07 sec)

     mysql> INSERT INTO c_test VALUES ('2014-09-08 18:07:54');
     Query OK, 1 row affected (0.05 sec)

     mysql> SELECT col, CAST(col AS UNSIGNED) AS c_col FROM c_test;
     +---------------------+----------------+
     | col                 | c_col          |
     +---------------------+----------------+
     | 2014-09-08 18:07:54 | 20140908180754 |
     +---------------------+----------------+
     1 row in set (0.00 sec)

This is a known issue which is resolved in MySQL 5.6.

MySQL supports arithmetic with both signed and unsigned 64-bit values.
If you are using numeric operators (such as `+' or `-') and one of the
operands is an unsigned integer, the result is unsigned by default (see
*Note arithmetic-functions::). You can override this by using the
`SIGNED' or `UNSIGNED' cast operator to cast a value to a signed or
unsigned 64-bit integer, respectively.


     mysql> SELECT CAST(1-2 AS UNSIGNED)
             -> 18446744073709551615
     mysql> SELECT CAST(CAST(1-2 AS UNSIGNED) AS SIGNED);
             -> -1

If either operand is a floating-point value, the result is a
floating-point value and is not affected by the preceding rule.  (In
this context, *Note `DECIMAL': fixed-point-types. column values are
regarded as floating-point values.)


     mysql> SELECT CAST(1 AS UNSIGNED) - 2.0;
             -> -1.0

The SQL mode affects the result of conversion operations.  Examples:

   * If you convert a `zero' date string to a date, `CONVERT()' and
     `CAST()' return `NULL' and produce a warning when the
     `NO_ZERO_DATE' SQL mode is enabled.

   * For integer subtraction, if the `NO_UNSIGNED_SUBTRACTION' SQL mode
     is enabled, the subtraction result is signed even if any operand
     is unsigned.

For more information, see *Note sql-mode::.


File: manual.info,  Node: xml-functions,  Next: bit-functions,  Prev: cast-functions,  Up: functions

12.11 XML Functions
===================

*XML Functions*

Name                          Description
`ExtractValue()'              Extracts a value from an XML string using
                              XPath notation
`UpdateXML()'                 Return replaced XML fragment

This section discusses XML and related functionality in MySQL.

*Note*:

It is possible to obtain XML-formatted output from MySQL in the *Note
`mysql': mysql. and *Note `mysqldump': mysqldump.  clients by invoking
them with the `--xml' option. See *Note mysql::, and *Note mysqldump::.

Beginning with MySQL 5.1.5, two functions providing basic XPath 1.0
(XML Path Language, version 1.0) capabilities are available.  Some
basic information about XPath syntax and usage is provided later in
this section; however, an in-depth discussion of these topics is beyond
the scope of this Manual, and you should refer to the XML Path Language
(XPath) 1.0 standard (http://www.w3.org/TR/xpath) for definitive
information. A useful resource for those new to XPath or who desire a
refresher in the basics is the Zvon.org XPath Tutorial
(http://www.zvon.org/xxl/XPathTutorial/), which is available in several
languages.

*Note*:

These functions remain under development. We continue to improve these
and other aspects of XML and XPath functionality in MySQL 5.1 and
onwards. You may discuss these, ask questions about them, and obtain
help from other users with them in the MySQL XML User Forum
(http://forums.mysql.com/list.php?44).

Beginning with MySQL 5.1.20, XPath expressions used with these
functions support user variables and local stored program variables.
User variables are weakly checked; variables local to stored programs
are strongly checked (see also Bug #26518):

   * User variables (weak checking)

     Variables using the syntax `$@VARIABLE_NAME' (that is, user
     variables) are not checked. No warnings or errors are issued by
     the server if a variable has the wrong type or has previously not
     been assigned a value. This also means the user is fully
     responsible for any typographical errors, since no warnings will
     be given if (for example) `$@myvariable' is used where
     `$@myvariable' was intended.

     Example:


          mysql> SET @xml = '<a><b>X</b><b>Y</b></a>';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SET @i =1, @j = 2;
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT @i, ExtractValue(@xml, '//b[$@i]');
          +------+--------------------------------+
          | @i   | ExtractValue(@xml, '//b[$@i]') |
          +------+--------------------------------+
          |    1 | X                              |
          +------+--------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT @j, ExtractValue(@xml, '//b[$@j]');
          +------+--------------------------------+
          | @j   | ExtractValue(@xml, '//b[$@j]') |
          +------+--------------------------------+
          |    2 | Y                              |
          +------+--------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT @k, ExtractValue(@xml, '//b[$@k]');
          +------+--------------------------------+
          | @k   | ExtractValue(@xml, '//b[$@k]') |
          +------+--------------------------------+
          | NULL |                                |
          +------+--------------------------------+
          1 row in set (0.00 sec)

   * Variables in stored programs (strong checking)

     Variables using the syntax `$VARIABLE_NAME' can be declared and
     used with these functions when they are called inside stored
     programs. Such variables are local to the stored program in which
     they are defined, and are strongly checked for type and value.

     Example:


          mysql> DELIMITER |

          mysql> CREATE PROCEDURE myproc ()
              -> BEGIN
              ->   DECLARE i INT DEFAULT 1;
              ->   DECLARE xml VARCHAR(25) DEFAULT '<a>X</a><a>Y</a><a>Z</a>';
              ->
              ->   WHILE i < 4 DO
              ->     SELECT xml, i, ExtractValue(xml, '//a[$i]');
              ->     SET i = i+1;
              ->   END WHILE;
              -> END |
          Query OK, 0 rows affected (0.01 sec)

          mysql> DELIMITER ;

          mysql> CALL myproc();
          +--------------------------+---+------------------------------+
          | xml                      | i | ExtractValue(xml, '//a[$i]') |
          +--------------------------+---+------------------------------+
          | <a>X</a><a>Y</a><a>Z</a> | 1 | X                            |
          +--------------------------+---+------------------------------+
          1 row in set (0.00 sec)

          +--------------------------+---+------------------------------+
          | xml                      | i | ExtractValue(xml, '//a[$i]') |
          +--------------------------+---+------------------------------+
          | <a>X</a><a>Y</a><a>Z</a> | 2 | Y                            |
          +--------------------------+---+------------------------------+
          1 row in set (0.01 sec)

          +--------------------------+---+------------------------------+
          | xml                      | i | ExtractValue(xml, '//a[$i]') |
          +--------------------------+---+------------------------------+
          | <a>X</a><a>Y</a><a>Z</a> | 3 | Z                            |
          +--------------------------+---+------------------------------+
          1 row in set (0.01 sec)

     Parameters

     Variables used in XPath expressions inside stored routines that
     are passed in as parameters are also subject to strong checking.

Expressions containing user variables or variables local to stored
programs must otherwise (except for notation) conform to the rules for
XPath expressions containing variables as given in the XPath 1.0
specification.

*Note*:

Currently, a user variable used to store an XPath expression is treated
as an empty string. Because of this, it is not possible to store an
XPath expression as a user variable. (Bug #32911)

   * `ExtractValue(XML_FRAG, XPATH_EXPR)'

     `ExtractValue()' takes two string arguments, a fragment of XML
     markup XML_FRAG and an XPath expression XPATH_EXPR (also known as a
     _locator_); it returns the text (`CDATA') of the first text node
     which is a child of the elements or elements matched by the XPath
     expression. In MySQL 5.1, the XPath expression can contain at most
     127 characters. (This limitation is lifted in MySQL 5.6.)

     Using this function is the equivalent of performing a match using
     the XPATH_EXPR after appending `/text()'. In other words,
     `ExtractValue('<a><b>Sakila</b></a>', '/a/b')' and
     `ExtractValue('<a><b>Sakila</b></a>', '/a/b/text()')' produce the
     same result.

     If multiple matches are found, the content of the first child text
     node of each matching element is returned (in the order matched)
     as a single, space-delimited string.

     If no matching text node is found for the expression (including
     the implicit `/text()')--for whatever reason, as long as
     XPATH_EXPR is valid, and XML_FRAG consists of elements which are
     properly nested and closed--an empty string is returned. No
     distinction is made between a match on an empty element and no
     match at all. This is by design.

     If you need to determine whether no matching element was found in
     XML_FRAG or such an element was found but contained no child text
     nodes, you should test the result of an expression that uses the
     XPath `count()' function. For example, both of these statements
     return an empty string, as shown here:


          mysql> SELECT ExtractValue('<a><b/></a>', '/a/b');
          +-------------------------------------+
          | ExtractValue('<a><b/></a>', '/a/b') |
          +-------------------------------------+
          |                                     |
          +-------------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue('<a><c/></a>', '/a/b');
          +-------------------------------------+
          | ExtractValue('<a><c/></a>', '/a/b') |
          +-------------------------------------+
          |                                     |
          +-------------------------------------+
          1 row in set (0.00 sec)

     However, you can determine whether there was actually a matching
     element using the following:


          mysql> SELECT ExtractValue('<a><b/></a>', 'count(/a/b)');
          +-------------------------------------+
          | ExtractValue('<a><b/></a>', 'count(/a/b)') |
          +-------------------------------------+
          | 1                                   |
          +-------------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue('<a><c/></a>', 'count(/a/b)');
          +-------------------------------------+
          | ExtractValue('<a><c/></a>', 'count(/a/b)') |
          +-------------------------------------+
          | 0                                   |
          +-------------------------------------+
          1 row in set (0.01 sec)

     *Important*:

     `ExtractValue()' returns only `CDATA', and does not return any
     tags that might be contained within a matching tag, nor any of
     their content (see the result returned as `val1' in the following
     example).


          mysql> SELECT
              ->   ExtractValue('<a>ccc<b>ddd</b></a>', '/a') AS val1,
              ->   ExtractValue('<a>ccc<b>ddd</b></a>', '/a/b') AS val2,
              ->   ExtractValue('<a>ccc<b>ddd</b></a>', '//b') AS val3,
              ->   ExtractValue('<a>ccc<b>ddd</b></a>', '/b') AS val4,
              ->   ExtractValue('<a>ccc<b>ddd</b><b>eee</b></a>', '//b') AS val5;

          +------+------+------+------+---------+
          | val1 | val2 | val3 | val4 | val5    |
          +------+------+------+------+---------+
          | ccc  | ddd  | ddd  |      | ddd eee |
          +------+------+------+------+---------+

     Beginning with MySQL 5.1.8, this function uses the current SQL
     collation for making comparisons with `contains()', performing the
     same collation aggregation as other string functions (such as
     `CONCAT()'), in taking into account the collation coercibility of
     their arguments; see *Note charset-collation-expressions::, for an
     explanation of the rules governing this behavior.

     (Previously, binary--that is, case-sensitive--comparison was
     always used.)

     Beginning with MySQL 5.1.12, `NULL' is returned if XML_FRAG
     contains elements which are not properly nested or closed, and a
     warning is generated, as shown in this example:


          mysql> SELECT ExtractValue('<a>c</a><b', '//a');
          +-----------------------------------+
          | ExtractValue('<a>c</a><b', '//a') |
          +-----------------------------------+
          | NULL                              |
          +-----------------------------------+
          1 row in set, 1 warning (0.00 sec)

          mysql> SHOW WARNINGS\G
          *************************** 1. row ***************************
            Level: Warning
             Code: 1525
          Message: Incorrect XML value: 'parse error at line 1 pos 11:
                   END-OF-INPUT unexpected ('>' wanted)'
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue('<a>c</a><b/>', '//a');
          +-------------------------------------+
          | ExtractValue('<a>c</a><b/>', '//a') |
          +-------------------------------------+
          | c                                   |
          +-------------------------------------+
          1 row in set (0.00 sec)

     Prior to MySQL 5.1.12, an empty string was returned in such cases.
     (Bug #18201)

   * `UpdateXML(XML_TARGET, XPATH_EXPR, NEW_XML)'

     This function replaces a single portion of a given fragment of XML
     markup XML_TARGET with a new XML fragment NEW_XML, and then
     returns the changed XML. The portion of XML_TARGET that is
     replaced matches an XPath expression XPATH_EXPR supplied by the
     user. In MySQL 5.1, the XPath expression can contain at most 127
     characters. (This limitation is lifted in MySQL 5.6.)

     If no expression matching XPATH_EXPR is found, or if multiple
     matches are found, the function returns the original XML_TARGET
     XML fragment. All three arguments should be strings.


          mysql> SELECT
              ->   UpdateXML('<a><b>ccc</b><d></d></a>', '/a', '<e>fff</e>') AS val1,
              ->   UpdateXML('<a><b>ccc</b><d></d></a>', '/b', '<e>fff</e>') AS val2,
              ->   UpdateXML('<a><b>ccc</b><d></d></a>', '//b', '<e>fff</e>') AS val3,
              ->   UpdateXML('<a><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val4,
              ->   UpdateXML('<a><d></d><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val5
              -> \G

          *************************** 1. row ***************************
          val1: <e>fff</e>
          val2: <a><b>ccc</b><d></d></a>
          val3: <a><e>fff</e><d></d></a>
          val4: <a><b>ccc</b><e>fff</e></a>
          val5: <a><d></d><b>ccc</b><d></d></a>

*Note*:

A discussion in depth of XPath syntax and usage are beyond the scope of
this Manual. Please see the XML Path Language (XPath) 1.0 specification
(http://www.w3.org/TR/xpath) for definitive information. A useful
resource for those new to XPath or who are wishing a refresher in the
basics is the Zvon.org XPath Tutorial
(http://www.zvon.org/xxl/XPathTutorial/), which is available in several
languages.

Descriptions and examples of some basic XPath expressions follow:

   * `/TAG'

     Matches `<TAG/>' if and only if `<TAG/>' is the root element.

     Example: `/a' has a match in `<a><b/></a>' because it matches the
     outermost (root) tag. It does not match the inner A element in
     `<b><a/></b>' because in this instance it is the child of another
     element.

   * `/TAG1/TAG2'

     Matches `<TAG2/>' if and only if it is a child of `<TAG1/>', and
     `<TAG1/>' is the root element.

     Example: `/a/b' matches the B element in the XML fragment
     `<a><b/></a>' because it is a child of the root element A. It does
     not have a match in `<b><a/></b>' because in this case, B is the
     root element (and hence the child of no other element). Nor does
     the XPath expression have a match in `<a><c><b/></c></a>'; here, B
     is a descendant of A, but not actually a child of A.

     This construct is extendable to three or more elements. For
     example, the XPath expression `/a/b/c' matches the C element in the
     fragment `<a><b><c/></b></a>'.

   * `//TAG'

     Matches any instance of `<TAG>'.

     Example: `//a' matches the A element in any of the following:
     `<a><b><c/></b></a>'; `<c><a><b/></a></b>'; `<c><b><a/></b></c>'.

     `//' can be combined with `/'. For example, `//a/b' matches the B
     element in either of the fragments `<a><b/></a>' or
     `<a><b><c/></b></a>'

     *Note*:

     `//TAG' is the equivalent of `/descendant-or-self::*/TAG'.  A
     common error is to confuse this with `/descendant-or-self::TAG',
     although the latter expression can actually lead to very different
     results, as can be seen here:


          mysql> SET @xml = '<a><b><c>w</c><b>x</b><d>y</d>z</b></a>';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT @xml;
          +-----------------------------------------+
          | @xml                                    |
          +-----------------------------------------+
          | <a><b><c>w</c><b>x</b><d>y</d>z</b></a> |
          +-----------------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue(@xml, '//b[1]');
          +------------------------------+
          | ExtractValue(@xml, '//b[1]') |
          +------------------------------+
          | x z                          |
          +------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue(@xml, '//b[2]');
          +------------------------------+
          | ExtractValue(@xml, '//b[2]') |
          +------------------------------+
          |                              |
          +------------------------------+
          1 row in set (0.01 sec)

          mysql> SELECT ExtractValue(@xml, '/descendant-or-self::*/b[1]');
          +---------------------------------------------------+
          | ExtractValue(@xml, '/descendant-or-self::*/b[1]') |
          +---------------------------------------------------+
          | x z                                               |
          +---------------------------------------------------+
          1 row in set (0.06 sec)

          mysql> SELECT ExtractValue(@xml, '/descendant-or-self::*/b[2]');
          +---------------------------------------------------+
          | ExtractValue(@xml, '/descendant-or-self::*/b[2]') |
          +---------------------------------------------------+
          |                                                   |
          +---------------------------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue(@xml, '/descendant-or-self::b[1]');
          +-------------------------------------------------+
          | ExtractValue(@xml, '/descendant-or-self::b[1]') |
          +-------------------------------------------------+
          | z                                               |
          +-------------------------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT ExtractValue(@xml, '/descendant-or-self::b[2]');
          +-------------------------------------------------+
          | ExtractValue(@xml, '/descendant-or-self::b[2]') |
          +-------------------------------------------------+
          | x                                               |
          +-------------------------------------------------+
          1 row in set (0.00 sec)

   * The `*' operator acts as a `wildcard' that matches any element.
     For example, the expression `/*/b' matches the B element in either
     of the XML fragments `<a><b/></a>' or `<c><b/></c>'. However, the
     expression does not produce a match in the fragment `<b><a/></b>'
     because B must be a child of some other element. The wildcard may
     be used in any position: The expression `/*/b/*' will match any
     child of a B element that is itself not the root element.

   * You can match any of several locators using the `|' (*Note
     `UNION': union.)  operator. For example, the expression `//b|//c'
     matches all B and C elements in the XML target.

   * It is also possible to match an element based on the value of one
     or more of its attributes. This done using the syntax
     `TAG[@ATTRIBUTE="VALUE"]'.  For example, the expression
     `//b[@id="idB"]' matches the second B element in the fragment
     `<a><b id="idA"/><c/><b id="idB"/></a>'. To match against _any_
     element having `ATTRIBUTE="VALUE"', use the XPath expression
     `//*[ATTRIBUTE="VALUE"]'.

     To filter multiple attribute values, simply use multiple
     attribute-comparison clauses in succession. For example, the
     expression `//b[@c="x"][@d="y"]' matches the element `<b c="x"
     d="y"/>' occurring anywhere in a given XML fragment.

     To find elements for which the same attribute matches any of
     several values, you can use multiple locators joined by the `|'
     operator. For example, to match all B elements whose C attributes
     have either of the values 23 or 17, use the expression
     `//b[@c="23"]|//b[@c="17"]'. You can also use the logical `or'
     operator for this purpose: `//b[@c="23" or @c="17"]'.

     *Note*:

     The difference between `or' and `|' is that `or' joins conditions,
     while `|' joins result sets.

XPath Limitations

The XPath syntax supported by these functions is currently subject to
the following limitations:

   * Nodeset-to-nodeset comparison (such as `'/a/b[@c=@d]'') is not
     supported.

   * Prior to MySQL 5.1.14, equality and inequality (`=' and `!=') were
     the only supported comparison operators. Beginning with MySQL
     5.1.14, all of the standard XPath comparison operators are
     supported.  (Bug #22823)

   * Relative locator expressions are resolved in the context of the
     root node. For example, consider the following query and result:


          mysql> SELECT ExtractValue(
              ->   '<a><b c="1">X</b><b c="2">Y</b></a>',
              ->    'a/b'
              -> ) AS result;
          +--------+
          | result |
          +--------+
          | X Y    |
          +--------+
          1 row in set (0.03 sec)

     In this case, the locator `a/b' resolves to `/a/b'.

     Relative locators are also supported within predicates. In the
     following example, `d[../@c="1"]' is resolved as `/a/b[@c="1"]/d':


          mysql> SELECT ExtractValue(
              ->      '<a>
              ->        <b c="1"><d>X</d></b>
              ->        <b c="2"><d>X</d></b>
              ->      </a>',
              ->      'a/b/d[../@c="1"]')
              -> AS result;
          +--------+
          | result |
          +--------+
          | X      |
          +--------+
          1 row in set (0.00 sec)

   * Locators prefixed with expressions that evaluate as scalar
     values--including variable references, literals, numbers, and
     scalar function calls--are not supported. Beginning with MySQL
     5.1.32, they are not permitted, and their use results in an error.
     (Bug #42495)

   * The `::' operator is not supported in combination with node types
     such as the following:

        * `AXIS::comment()'

        * `AXIS::text()'

        * `AXIS::processing-instructions()'

        * `AXIS::node()'

     However, name tests (such as `AXIS::NAME' and `AXIS::*') are
     supported, as shown in these examples:


          mysql> SELECT ExtractValue('<a><b>x</b><c>y</c></a>','/a/child::b');
          +-------------------------------------------------------+
          | ExtractValue('<a><b>x</b><c>y</c></a>','/a/child::b') |
          +-------------------------------------------------------+
          | x                                                     |
          +-------------------------------------------------------+
          1 row in set (0.02 sec)

          mysql> SELECT ExtractValue('<a><b>x</b><c>y</c></a>','/a/child::*');
          +-------------------------------------------------------+
          | ExtractValue('<a><b>x</b><c>y</c></a>','/a/child::*') |
          +-------------------------------------------------------+
          | x y                                                   |
          +-------------------------------------------------------+
          1 row in set (0.01 sec)

   * `Up-and-down' navigation is not supported in cases where the path
     would lead `above' the root element. That is, you cannot use
     expressions which match on descendants of ancestors of a given
     element, where one or more of the ancestors of the current element
     is also an ancestor of the root element (see Bug #16321).

   * The following XPath functions are not supported, or have known
     issues as indicated:

        * Prior to MySQL 5.1.24, the `boolean()' function did not
          produce correct results for some string and nodeset values,
          including the `NULL' string (see Bug #26051).

        * `id()'

        * `lang()'

        * Prior to MySQL 5.1.8, the `last()' function was not supported
          (see Bug #16318).

        * `local-name()'

        * `name()'

        * `namespace-uri()'

        * `normalize-space()'

        * `starts-with()'

        * `string()'

        * `substring-after()'

        * `substring-before()'

        * `translate()'

   * The following axes are not supported:

        * `following-sibling'

        * `following'

        * `preceding-sibling'

        * `preceding'

Beginning with MySQL 5.1.10, XPath expressions passed as arguments to
`ExtractValue()' and `UpdateXML()' may contain the colon character
(``:'') in element selectors, which enables their use with markup
employing XML namespaces notation. For example:


     mysql> SET @xml = '<a>111<b:c>222<d>333</d><e:f>444</e:f></b:c></a>';
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT ExtractValue(@xml, '//e:f');
     +-----------------------------+
     | ExtractValue(@xml, '//e:f') |
     +-----------------------------+
     | 444                         |
     +-----------------------------+
     1 row in set (0.00 sec)

     mysql> SELECT UpdateXML(@xml, '//b:c', '<g:h>555</g:h>');
     +--------------------------------------------+
     | UpdateXML(@xml, '//b:c', '<g:h>555</g:h>') |
     +--------------------------------------------+
     | <a>111<g:h>555</g:h></a>                   |
     +--------------------------------------------+
     1 row in set (0.00 sec)

This is similar in some respects to what is permitted by Apache Xalan
(http://xalan.apache.org/) and some other parsers, and is much simpler
than requiring namespace declarations or the use of the
`namespace-uri()' and `local-name()' functions.

Error handling

For both `ExtractValue()' and `UpdateXML()', the XPath locator used
must be valid and the XML to be searched must consist of elements which
are properly nested and closed. If the locator is invalid, an error is
generated:


     mysql> SELECT ExtractValue('<a>c</a><b/>', '/&a');
     `ERROR 1105 (HY000): XPATH syntax error: '&a''

If XML_FRAG does not consist of elements which are properly nested and
closed, `NULL' is returned and a warning is generated, as shown in this
example:


     mysql> SELECT ExtractValue('<a>c</a><b', '//a');
     +-----------------------------------+
     | ExtractValue('<a>c</a><b', '//a') |
     +-----------------------------------+
     | NULL                              |
     +-----------------------------------+
     1 row in set, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS\G
     *************************** 1. row ***************************
       Level: Warning
        Code: 1525
     Message: Incorrect XML value: 'parse error at line 1 pos 11:
              END-OF-INPUT unexpected ('>' wanted)'
     1 row in set (0.00 sec)

     mysql> SELECT ExtractValue('<a>c</a><b/>', '//a');
     +-------------------------------------+
     | ExtractValue('<a>c</a><b/>', '//a') |
     +-------------------------------------+
     | c                                   |
     +-------------------------------------+
     1 row in set (0.00 sec)

Prior to MySQL 5.1.12, an empty string was returned in such cases.
(Bug #18201)

*Important*:

The replacement XML used as the third argument to `UpdateXML()' is
_not_ checked to determine whether it consists solely of elements which
are properly nested and closed.

XPath Injection

_code injection_ occurs when malicious code is introduced into the
system to gain unauthorized access to privileges and data. It is based
on exploiting assumptions made by developers about the type and content
of data input from users. XPath is no exception in this regard.

A common scenario in which this can happen is the case of application
which handles authorization by matching the combination of a login name
and password with those found in an XML file, using an XPath expression
like this one:


     //user[login/text()='neapolitan' and password/text()='1c3cr34m']/attribute::id

This is the XPath equivalent of an SQL statement like this one:


     SELECT id FROM users WHERE login='neapolitan' AND password='1c3cr34m';

A PHP application employing XPath might handle the login process like
this:


     <?php

       $file     =   "users.xml";

       $login    =   $POST["login"];
       $password =   $POST["password"];

       $xpath = "//user[login/text()=$login and password/text()=$password]/attribute::id";

       if( file_exists($file) )
       {
         $xml = simplexml_load_file($file);

         if($result = $xml->xpath($xpath))
           echo "You are now logged in as user $result[0].";
         else
           echo "Invalid login name or password.";
       }
       else
         exit("Failed to open $file.");

     ?>

No checks are performed on the input. This means that a malevolent user
can `short-circuit' the test by entering `' or 1=1' for both the login
name and password, resulting in $xpath being evaluated as shown here:


     //user[login/text()='' or 1=1 and password/text()='' or 1=1]/attribute::id

Since the expression inside the square brackets always evaluates as
`true', it is effectively the same as this one, which matches the `id'
attribute of every `user' element in the XML document:


     //user/attribute::id

One way in which this particular attack can be circumvented is simply
by quoting the variable names to be interpolated in the definition of
`$xpath', forcing the values passed from a Web form to be converted to
strings:


     $xpath = "//user[login/text()='$login' and password/text()='$password']/attribute::id";

This is the same strategy that is often recommended for preventing SQL
injection attacks. In general, the practices you should follow for
preventing XPath injection attacks are the same as for preventing SQL
injection:

   * Never accepted untested data from users in your application.

   * Check all user-submitted data for type; reject or convert data
     that is of the wrong type

   * Test numeric data for out of range values; truncate, round, or
     reject values that are out of range. Test strings for illegal
     characters and either strip them out or reject input containing
     them.

   * Do not output explicit error messages that might provide an
     unauthorized user with clues that could be used to compromise the
     system; log these to a file or database table instead.

Just as SQL injection attacks can be used to obtain information about
database schemas, so can XPath injection be used to traverse XML files
to uncover their structure, as discussed in Amit Klein's paper Blind
XPath Injection
(http://www.packetstormsecurity.org/papers/bypass/Blind_XPath_Injection_20040518.pdf)
(PDF file, 46KB).

It is also important to check the output being sent back to the client.
Consider what can happen when we use the MySQL `ExtractValue()'
function:


     mysql> SELECT ExtractValue(
         ->     LOAD_FILE('users.xml'),
         ->     '//user[login/text()="" or 1=1 and password/text()="" or 1=1]/attribute::id'
         -> ) AS id;
     +-------------------------------+
     | id                            |
     +-------------------------------+
     | 00327 13579 02403 42354 28570 |
     +-------------------------------+
     1 row in set (0.01 sec)

Because `ExtractValue()' returns multiple matches as a single
space-delimited string, this injection attack provides every valid ID
contained within `users.xml' to the user as a single row of output. As
an extra safeguard, you should also test output before returning it to
the user. Here is a simple example:


     mysql> SELECT @id = ExtractValue(
         ->     LOAD_FILE('users.xml'),
         ->     '//user[login/text()="" or 1=1 and password/text()="" or 1=1]/attribute::id'
         -> );
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT IF(
         ->     INSTR(@id, ' ') = 0,
         ->     @id,
         ->     'Unable to retrieve user ID')
         -> AS singleID;
     +----------------------------+
     | singleID                   |
     +----------------------------+
     | Unable to retrieve user ID |
     +----------------------------+
     1 row in set (0.00 sec)

In general, the guidelines for returning data to users securely are the
same as for accepting user input. These can be summed up as:

   * Always test outgoing data for type and permissible values.

   * Never permit unauthorized users to view error messages that might
     provide information about the application that could be used to
     exploit it.


File: manual.info,  Node: bit-functions,  Next: encryption-functions,  Prev: xml-functions,  Up: functions

12.12 Bit Functions
===================

*Bitwise Functions*

Name                          Description
`BIT_COUNT()'                 Return the number of bits that are set
`&'                           Bitwise AND
`~'                           Invert bits
`|'                           Bitwise OR
`^'                           Bitwise XOR
`<<'                          Left shift
`>>'                          Right shift

MySQL uses *Note `BIGINT': integer-types. (64-bit) arithmetic for bit
operations, so these operators have a maximum range of 64 bits.

   * `|'

     Bitwise OR:


          mysql> SELECT 29 | 15;
                  -> 31

     The result is an unsigned 64-bit integer.

   * `&'

     Bitwise AND:


          mysql> SELECT 29 & 15;
                  -> 13

     The result is an unsigned 64-bit integer.

   * `^'

     Bitwise XOR:


          mysql> SELECT 1 ^ 1;
                  -> 0
          mysql> SELECT 1 ^ 0;
                  -> 1
          mysql> SELECT 11 ^ 3;
                  -> 8

     The result is an unsigned 64-bit integer.

   * `<<'

     Shifts a longlong (*Note `BIGINT': integer-types.)  number to the
     left.


          mysql> SELECT 1 << 2;
                  -> 4

     The result is an unsigned 64-bit integer. The value is truncated
     to 64 bits. In particular, if the shift count is greater or equal
     to the width of an unsigned 64-bit number, the result is zero.

   * `>>'

     Shifts a longlong (*Note `BIGINT': integer-types.)  number to the
     right.


          mysql> SELECT 4 >> 2;
                  -> 1

     The result is an unsigned 64-bit integer. The value is truncated
     to 64 bits. In particular, if the shift count is greater or equal
     to the width of an unsigned 64-bit number, the result is zero.

   * `~'

     Invert all bits.


          mysql> SELECT 5 & ~1;
                  -> 4

     The result is an unsigned 64-bit integer.

   * `BIT_COUNT(N)'

     Returns the number of bits that are set in the argument N.


          mysql> SELECT BIT_COUNT(29), BIT_COUNT(b'101010');
                  -> 4, 3


File: manual.info,  Node: encryption-functions,  Next: information-functions,  Prev: bit-functions,  Up: functions

12.13 Encryption and Compression Functions
==========================================

*Encryption Functions*

Name                          Description
`AES_DECRYPT()'               Decrypt using AES
`AES_ENCRYPT()'               Encrypt using AES
`COMPRESS()'                  Return result as a binary string
`DECODE()'                    Decodes a string encrypted using ENCODE()
`DES_DECRYPT()'               Decrypt a string
`DES_ENCRYPT()'               Encrypt a string
`ENCODE()'                    Encode a string
`ENCRYPT()'                   Encrypt a string
`MD5()'                       Calculate MD5 checksum
`OLD_PASSWORD()'(deprecated   Return the value of the pre-4.1
5.6.5)                        implementation of PASSWORD
`PASSWORD()'                  Calculate and return a password string
`SHA1()', `SHA()'             Calculate an SHA-1 160-bit checksum
`UNCOMPRESS()'                Uncompress a string compressed
`UNCOMPRESSED_LENGTH()'       Return the length of a string before
                              compression

Many encryption and compression functions return strings for which the
result might contain arbitrary byte values. If you want to store these
results, use a column with a *Note `VARBINARY': binary-varbinary. or
*Note `BLOB': blob. binary string data type. This will avoid potential
problems with trailing space removal or character set conversion that
would change data values, such as may occur if you use a nonbinary
string data type (*Note `CHAR': char, *Note `VARCHAR': char, *Note
`TEXT': blob.).

For functions such as `MD5()' or `SHA1()' that return a string of hex
digits, the return value cannot be converted to uppercase or compared in
case-insensitive fashion as is. You must convert the value to a
nonbinary string. See the discussion of binary string conversion in
*Note cast-functions::.

If an application stores values from a function such as `MD5()' or
`SHA1()' that returns a string of hex digits, more efficient storage
and comparisons can be obtained by converting the hex representation to
binary using `UNHEX()' and storing the result in a *Note `BINARY(N)':
binary-varbinary.  column. Each pair of hex digits requires one byte in
binary form, so the value of N depends on the length of the hex string.
N is 16 for an `MD5()' value and 20 for a `SHA1()' value.

The size penalty for storing the hex string in a *Note `CHAR': char.
column is at least two times, up to six times if the value is stored in
a column that uses the `utf8' character set (where each character uses 3
bytes). Storing the string also results in slower comparisons because
of the larger values and the need to take character set collation rules
into account.

Suppose that an application stores `MD5()' string values in a *Note
`CHAR(32)': char. column:


     CREATE TABLE md5_tbl (md5_val CHAR(32), ...);
     INSERT INTO md5_tbl (md5_val, ...) VALUES(MD5('abcdef'), ...);

To convert hex strings to more compact form, modify the application to
use `UNHEX()' and *Note `BINARY(16)': binary-varbinary. instead as
follows:


     CREATE TABLE md5_tbl (md5_val BINARY(16), ...);
     INSERT INTO md5_tbl (md5_val, ...) VALUES(UNHEX(MD5('abcdef')), ...);

Applications should be prepared to handle the very rare case that a
hashing function produces the same value for two different input
values. One way to make collisions detectable is to make the hash
column a primary key.

*Note*:

Exploits for the MD5 and SHA-1 algorithms have become known. You may
wish to consider using one of the other encryption functions described
in this section instead.

*Caution*:

Passwords or other sensitive values supplied as arguments to encryption
functions are sent in plaintext to the MySQL server unless an SSL
connection is used. Also, such values will appear in any MySQL logs to
which they are written. To avoid these types of exposure, applications
can encrypt sensitive values on the client side before sending them to
the server. The same considerations apply to encryption keys. To avoid
exposing these, applications can use stored procedures to encrypt and
decrypt values on the server side.

   * `AES_DECRYPT(CRYPT_STR,KEY_STR)'

     This function decrypts data using the official AES (Advanced
     Encryption Standard) algorithm. For more information, see the
     description of `AES_ENCRYPT()'.

   * `AES_ENCRYPT(STR,KEY_STR)'

     `AES_ENCRYPT()' and `AES_DECRYPT()' implement encryption and
     decryption of data using the official AES (Advanced Encryption
     Standard) algorithm, previously known as `Rijndael.' The AES
     standard permits various key lengths. These functions implement
     AES with a 128-bit key length, but you can extend them to 256 bits
     by modifying the source. The key length is a trade off between
     performance and security.

     `AES_ENCRYPT()' encrypts the string STR using the key string
     KEY_STR and returns a binary string containing the encrypted
     output.  `AES_DECRYPT()' decrypts the encrypted string CRYPT_STR
     using the key string KEY_STR and returns the original plaintext
     string. If either function argument is `NULL', the function returns
     `NULL'.

     The STR and CRYPT_STR arguments can be any length, and padding is
     automatically added to STR so it is a multiple of a block as
     required by block-based algorithms such as AES. This padding is
     automatically removed by the `AES_DECRYPT()' function. The length
     of CRYPT_STR can be calculated using this formula:


          16 * (trunc(STRING_LENGTH / 16) + 1)

     For a key length of 128 bits, the most secure way to pass a key to
     the KEY_STR argument is to create a truly random 128-bit value and
     pass it as a binary value. For example:


          INSERT INTO t
          VALUES (1,AES_ENCRYPT('text',UNHEX('F3229A0B371ED2D9441B830D21A390C3')));

     A passphrase can be used to generate an AES key by hashing the
     passphrase. For example:


          INSERT INTO t VALUES (1,AES_ENCRYPT('text', SHA1('My secret passphrase')));

     Do not pass a password or passphrase directly to CRYPT_STR, hash
     it first. Previous versions of this documentation suggested the
     former approach, but it is no longer recommended as the examples
     shown here are more secure.

     If `AES_DECRYPT()' detects invalid data or incorrect padding, it
     returns `NULL'. However, it is possible for `AES_DECRYPT()' to
     return a non-`NULL' value (possibly garbage) if the input data or
     the key is invalid.

   * `COMPRESS(STRING_TO_COMPRESS)'

     Compresses a string and returns the result as a binary string.
     This function requires MySQL to have been compiled with a
     compression library such as `zlib'.  Otherwise, the return value
     is always `NULL'.  The compressed string can be uncompressed with
     `UNCOMPRESS()'.


          mysql> SELECT LENGTH(COMPRESS(REPEAT('a',1000)));
                  -> 21
          mysql> SELECT LENGTH(COMPRESS(''));
                  -> 0
          mysql> SELECT LENGTH(COMPRESS('a'));
                  -> 13
          mysql> SELECT LENGTH(COMPRESS(REPEAT('a',16)));
                  -> 15

     The compressed string contents are stored the following way:

        * Empty strings are stored as empty strings.

        * Nonempty strings are stored as a 4-byte length of the
          uncompressed string (low byte first), followed by the
          compressed string. If the string ends with space, an extra
          ``.'' character is added to avoid problems with endspace
          trimming should the result be stored in a *Note `CHAR': char.
          or *Note `VARCHAR': char. column. (However, use of nonbinary
          string data types such as *Note `CHAR': char. or *Note
          `VARCHAR': char. to store compressed strings is not
          recommended anyway because character set conversion may
          occur. Use a *Note `VARBINARY': binary-varbinary. or *Note
          `BLOB': blob. binary string column instead.)

   * `DECODE(CRYPT_STR,PASS_STR)'

     Decrypts the encrypted string CRYPT_STR using PASS_STR as the
     password.  CRYPT_STR should be a string returned from `ENCODE()'.

   * `DES_DECRYPT(CRYPT_STR[,KEY_STR])'

     Decrypts a string encrypted with `DES_ENCRYPT()'. If an error
     occurs, this function returns `NULL'.

     This function works only if MySQL has been configured with SSL
     support. See *Note ssl-connections::.

     If no KEY_STR argument is given, `DES_DECRYPT()' examines the
     first byte of the encrypted string to determine the DES key number
     that was used to encrypt the original string, and then reads the
     key from the DES key file to decrypt the message.  For this to
     work, the user must have the `SUPER' privilege. The key file can
     be specified with the `--des-key-file' server option.

     If you pass this function a KEY_STR argument, that string is used
     as the key for decrypting the message.

     If the CRYPT_STR argument does not appear to be an encrypted
     string, MySQL returns the given CRYPT_STR.

   * `DES_ENCRYPT(STR[,{KEY_NUM|KEY_STR}])'

     Encrypts the string with the given key using the Triple-DES
     algorithm.

     This function works only if MySQL has been configured with SSL
     support. See *Note ssl-connections::.

     The encryption key to use is chosen based on the second argument
     to `DES_ENCRYPT()', if one was given. With no argument, the first
     key from the DES key file is used. With a KEY_NUM argument, the
     given key number (0 to 9) from the DES key file is used. With a
     KEY_STR argument, the given key string is used to encrypt STR.

     The key file can be specified with the `--des-key-file' server
     option.

     The return string is a binary string where the first character is
     `CHAR(128 | KEY_NUM)'. If an error occurs, `DES_ENCRYPT()' returns
     `NULL'.

     The 128 is added to make it easier to recognize an encrypted key.
     If you use a string key, KEY_NUM is 127.

     The string length for the result is given by this formula:


          NEW_LEN = ORIG_LEN + (8 - (ORIG_LEN % 8)) + 1

     Each line in the DES key file has the following format:


          KEY_NUM DES_KEY_STR

     Each KEY_NUM value must be a number in the range from `0' to `9'.
     Lines in the file may be in any order.  DES_KEY_STR is the string
     that is used to encrypt the message. There should be at least one
     space between the number and the key. The first key is the default
     key that is used if you do not specify any key argument to
     `DES_ENCRYPT()'.

     You can tell MySQL to read new key values from the key file with
     the *Note `FLUSH DES_KEY_FILE': flush. statement. This requires the
     `RELOAD' privilege.

     One benefit of having a set of default keys is that it gives
     applications a way to check for the existence of encrypted column
     values, without giving the end user the right to decrypt those
     values.


          mysql> SELECT customer_address FROM customer_table
               > WHERE crypted_credit_card = DES_ENCRYPT('credit_card_number');

   * `ENCODE(STR,PASS_STR)'

     Encrypt STR using PASS_STR as the password. The result is a binary
     string of the same length as STR. To decrypt the result, use
     `DECODE()'.

     The `ENCODE()' function should no longer be used. If you still
     need to use `ENCODE()', a salt value must be used with it to
     reduce risk. For example:


          ENCODE('plaintext', CONCAT('my_random_salt','my_secret_password'))

     A new random salt value must be used whenever a password is
     updated.

   * `ENCRYPT(STR[,SALT])'

     Encrypts STR using the Unix `crypt()' system call and returns a
     binary string. The SALT argument must be a string with at least
     two characters or the result will be `NULL'. If no SALT argument
     is given, a random value is used.


          mysql> SELECT ENCRYPT('hello');
                  -> 'VxuFAJXVARROc'

     `ENCRYPT()' ignores all but the first eight characters of STR, at
     least on some systems. This behavior is determined by the
     implementation of the underlying `crypt()' system call.

     The use of `ENCRYPT()' with the `ucs2' multibyte character set is
     not recommended because the system call expects a string
     terminated by a zero byte.

     If `crypt()' is not available on your system (as is the case with
     Windows), `ENCRYPT()' always returns `NULL'.

   * `MD5(STR)'

     Calculates an MD5 128-bit checksum for the string. The value is
     returned as a binary string of 32 hex digits, or `NULL' if the
     argument was `NULL'. The return value can, for example, be used as
     a hash key. See the notes at the beginning of this section about
     storing hash values efficiently.


          mysql> SELECT MD5('testing');
                  -> 'ae2b1fca515949e5d54fb22b8ed95575'

     This is the `RSA Data Security, Inc. MD5 Message-Digest Algorithm.'

     See the note regarding the MD5 algorithm at the beginning this
     section.

   * `OLD_PASSWORD(STR)'

     `OLD_PASSWORD()' was added when the implementation of `PASSWORD()'
     was changed in MySQL 4.1 to improve security.  `OLD_PASSWORD()'
     returns the value of the pre-4.1 implementation of `PASSWORD()' as
     a binary string, and is intended to permit you to reset passwords
     for any pre-4.1 clients that need to connect to your version 5.1
     MySQL server without locking them out. See *Note
     password-hashing::.

   * `PASSWORD(STR)'

     Returns a hashed password string calculated from the cleartext
     password STR. The return value is a binary string, or `NULL' if
     the argument is `NULL'. This function is the SQL interface to the
     algorithm used by the server to encrypt MySQL passwords for
     storage in the `mysql.user' grant table.

     The `old_passwords' system variable controls the password hashing
     method used by the `PASSWORD()' function. It also influences
     password hashing performed by *Note `CREATE USER': create-user. and
     *Note `GRANT': grant. statements that specify a password using an
     `IDENTIFIED BY' clause.

     The value determines whether or not to use `old' native MySQL
     password hashing. A value of 0 (or `OFF') causes passwords to be
     encrypted using the format available from MySQL 4.1 on. A value of
     1 (or `ON') causes password encryption to use the older pre-4.1
     format.

     If `old_passwords=1', `PASSWORD(STR)' returns the same value as
     `OLD_PASSWORD(STR)'.  The latter function is not affected by the
     value of `old_passwords'.


          mysql> SET old_passwords = 0;
          mysql> SELECT PASSWORD('mypass'), OLD_PASSWORD('mypass');
          +-------------------------------------------+------------------------+
          | PASSWORD('mypass')                        | OLD_PASSWORD('mypass') |
          +-------------------------------------------+------------------------+
          | *6C8989366EAF75BB670AD8EA7A7FC1176A95CEF4 | 6f8c114b58f2ce9e       |
          +-------------------------------------------+------------------------+

          mysql> SET old_passwords = 1;
          mysql> SELECT PASSWORD('mypass'), OLD_PASSWORD('mypass');
          +--------------------+------------------------+
          | PASSWORD('mypass') | OLD_PASSWORD('mypass') |
          +--------------------+------------------------+
          | 6f8c114b58f2ce9e   | 6f8c114b58f2ce9e       |
          +--------------------+------------------------+

     Encryption performed by `PASSWORD()' is one-way (not reversible).
     It is not the same type of encryption as used for Unix passwords;
     for that, use `ENCRYPT()'.

     *Note*:

     The `PASSWORD()' function is used by the authentication system in
     MySQL Server; you should _not_ use it in your own applications.
     For that purpose, consider `MD5()' or `SHA1()' instead. Also see
     section 2 (Challenge-Response Authentication Mechanism (CRAM)),
     for more information about handling passwords and authentication
     securely in your applications.

     *Caution*:

     Statements that invoke `PASSWORD()' may be recorded in server logs
     or on the client side in a history file such as
     `~/.mysql_history', which means that cleartext passwords may be
     read by anyone having read access to that information. For
     information about password logging in the server logs, see *Note
     password-logging::.  For similar information about client-side
     logging, see *Note mysql-logging::.

   * `SHA1(STR)', `SHA(STR)'

     Calculates an SHA-1 160-bit checksum for the string, as described
     in RFC 3174 (Secure Hash Algorithm). The value is returned as a
     binary string of 40 hex digits, or `NULL' if the argument was
     `NULL'. One of the possible uses for this function is as a hash
     key. See the notes at the beginning of this section about storing
     hash values efficiently. You can also use `SHA1()' as a
     cryptographic function for storing passwords.  `SHA()' is
     synonymous with `SHA1()'.


          mysql> SELECT SHA1('abc');
                  -> 'a9993e364706816aba3e25717850c26c9cd0d89d'

     `SHA1()' can be considered a cryptographically more secure
     equivalent of `MD5()'. However, see the note regarding the MD5 and
     SHA-1 algorithms at the beginning this section.

   * `UNCOMPRESS(STRING_TO_UNCOMPRESS)'

     Uncompresses a string compressed by the `COMPRESS()' function. If
     the argument is not a compressed value, the result is `NULL'. This
     function requires MySQL to have been compiled with a compression
     library such as `zlib'. Otherwise, the return value is always
     `NULL'.


          mysql> SELECT UNCOMPRESS(COMPRESS('any string'));
                  -> 'any string'
          mysql> SELECT UNCOMPRESS('any string');
                  -> NULL

   * `UNCOMPRESSED_LENGTH(COMPRESSED_STRING)'

     Returns the length that the compressed string had before being
     compressed.


          mysql> SELECT UNCOMPRESSED_LENGTH(COMPRESS(REPEAT('a',30)));
                  -> 30


File: manual.info,  Node: information-functions,  Next: spatial-analysis-functions,  Prev: encryption-functions,  Up: functions

12.14 Information Functions
===========================

*Information Functions*

Name                          Description
`BENCHMARK()'                 Repeatedly execute an expression
`CHARSET()'                   Return the character set of the argument
`COERCIBILITY()'              Return the collation coercibility value of
                              the string argument
`COLLATION()'                 Return the collation of the string argument
`CONNECTION_ID()'             Return the connection ID (thread ID) for
                              the connection
`CURRENT_USER()',             The authenticated user name and host name
`CURRENT_USER'                
`DATABASE()'                  Return the default (current) database name
`FOUND_ROWS()'                For a SELECT with a LIMIT clause, the
                              number of rows that would be  returned
                              were there no LIMIT clause
`LAST_INSERT_ID()'            Value of the AUTOINCREMENT column for the
                              last INSERT
`ROW_COUNT()'                 The number of rows updated
`SCHEMA()'                    Synonym for DATABASE()
`SESSION_USER()'              Synonym for USER()
`SYSTEM_USER()'               Synonym for USER()
`USER()'                      The user name and host name provided by
                              the client
`VERSION()'                   Return a string that indicates the MySQL
                              server version

   * `BENCHMARK(COUNT,EXPR)'

     The `BENCHMARK()' function executes the expression EXPR repeatedly
     COUNT times. It may be used to time how quickly MySQL processes
     the expression. The result value is always `0'. The intended use
     is from within the *Note `mysql': mysql. client, which reports
     query execution times:


          mysql> SELECT BENCHMARK(1000000,ENCODE('hello','goodbye'));
          +----------------------------------------------+
          | BENCHMARK(1000000,ENCODE('hello','goodbye')) |
          +----------------------------------------------+
          |                                            0 |
          +----------------------------------------------+
          1 row in set (4.74 sec)

     The time reported is elapsed time on the client end, not CPU time
     on the server end. It is advisable to execute `BENCHMARK()'
     several times, and to interpret the result with regard to how
     heavily loaded the server machine is.

     `BENCHMARK()' is intended for measuring the runtime performance of
     scalar expressions, which has some significant implications for
     the way that you use it and interpret the results:

        * Only scalar expressions can be used. Although the expression
          can be a subquery, it must return a single column and at most
          a single row. For example, `BENCHMARK(10, (SELECT * FROM t))'
          will fail if the table `t' has more than one column or more
          than one row.

        * Executing a `SELECT EXPR' statement N times differs from
          executing `SELECT BENCHMARK(N, EXPR)' in terms of the amount
          of overhead involved. The two have very different execution
          profiles and you should not expect them to take the same
          amount of time. The former involves the parser, optimizer,
          table locking, and runtime evaluation N times each. The latter
          involves only runtime evaluation N times, and all the other
          components just once. Memory structures already allocated are
          reused, and runtime optimizations such as local caching of
          results already evaluated for aggregate functions can alter
          the results. Use of `BENCHMARK()' thus measures performance
          of the runtime component by giving more weight to that
          component and removing the `noise' introduced by the network,
          parser, optimizer, and so forth.

   * `CHARSET(STR)'

     Returns the character set of the string argument.


          mysql> SELECT CHARSET('abc');
                  -> 'latin1'
          mysql> SELECT CHARSET(CONVERT('abc' USING utf8));
                  -> 'utf8'
          mysql> SELECT CHARSET(USER());
                  -> 'utf8'

   * `COERCIBILITY(STR)'

     Returns the collation coercibility value of the string argument.


          mysql> SELECT COERCIBILITY('abc' COLLATE latin1_swedish_ci);
                  -> 0
          mysql> SELECT COERCIBILITY(USER());
                  -> 3
          mysql> SELECT COERCIBILITY('abc');
                  -> 4

     The return values have the meanings shown in the following table.
     Lower values have higher precedence.

     This table lists collation coercibility return values, the meaning
     of each value, and provides an example of each.

     CoercibilityMeaning    Example
     `0'        Explicit   Value with `COLLATE' clause
                collation  
     `1'        No         Concatenation of strings with different
                collation  collations
     `2'        Implicit   Column value, stored routine parameter or
                collation  local variable
     `3'        System     `USER()' return value
                constant   
     `4'        Coercible  Literal string
     `5'        Ignorable  `NULL' or an expression derived from `NULL'

   * `COLLATION(STR)'

     Returns the collation of the string argument.


          mysql> SELECT COLLATION('abc');
                  -> 'latin1_swedish_ci'
          mysql> SELECT COLLATION(_utf8'abc');
                  -> 'utf8_general_ci'

   * `CONNECTION_ID()'

     Returns the connection ID (thread ID) for the connection.  Every
     connection has an ID that is unique among the set of currently
     connected clients.


          mysql> SELECT CONNECTION_ID();
                  -> 23786

   * `CURRENT_USER', `CURRENT_USER()'

     Returns the user name and host name combination for the MySQL
     account that the server used to authenticate the current client.
     This account determines your access privileges. The return value
     is a string in the `utf8' character set.

     The value of `CURRENT_USER()' can differ from the value of
     `USER()'.


          mysql> SELECT USER();
                  -> 'davida@localhost'
          mysql> SELECT * FROM mysql.user;
          ERROR 1044: Access denied for user ''@'localhost' to
          database 'mysql'
          mysql> SELECT CURRENT_USER();
                  -> '@localhost'

     The example illustrates that although the client specified a user
     name of `davida' (as indicated by the value of the `USER()'
     function), the server authenticated the client using an anonymous
     user account (as seen by the empty user name part of the
     `CURRENT_USER()' value). One way this might occur is that there is
     no account listed in the grant tables for `davida'.

     Within a stored program or view, `CURRENT_USER()' returns the
     account for the user who defined the object (as given by its
     `DEFINER' value) unless defined with the `SQL SECURITY INVOKER'
     characteristic. In the latter case, `CURRENT_USER()' returns the
     object's invoker.

     Triggers and events have no option to define the `SQL SECURITY'
     characteristic, so for these objects, `CURRENT_USER()' returns the
     account for the user who defined the object. To return the
     invoker, use `USER()' or `SESSION_USER()'.

     The following statements support use of the `CURRENT_USER()'
     function to take the place of the name of (and, possibly, a host
     for) an affected user or a definer; in such cases,
     `CURRENT_USER()' is expanded where and as needed:

        * *Note `DROP USER': drop-user.

        * *Note `RENAME USER': rename-user.

        * *Note `GRANT': grant.

        * *Note `REVOKE': revoke.

        * *Note `CREATE FUNCTION': create-function.

        * *Note `CREATE PROCEDURE': create-procedure.

        * *Note `CREATE TRIGGER': create-trigger.

        * *Note `CREATE EVENT': create-event.

        * *Note `CREATE VIEW': create-view.

        * *Note `ALTER EVENT': alter-event.

        * *Note `ALTER VIEW': alter-view.

        * *Note `SET PASSWORD': set-password.

     For information about the implications that this expansion of
     `CURRENT_USER()' has for replication in different releases of
     MySQL 5.1, see *Note replication-features-current-user::.

   * `DATABASE()'

     Returns the default (current) database name as a string in the
     `utf8' character set. If there is no default database,
     `DATABASE()' returns `NULL'. Within a stored routine, the default
     database is the database that the routine is associated with,
     which is not necessarily the same as the database that is the
     default in the calling context.


          mysql> SELECT DATABASE();
                  -> 'test'

     If there is no default database, `DATABASE()' returns `NULL'.

   * `FOUND_ROWS()'

     A *Note `SELECT': select. statement may include a `LIMIT' clause
     to restrict the number of rows the server returns to the client.
     In some cases, it is desirable to know how many rows the statement
     would have returned without the `LIMIT', but without running the
     statement again. To obtain this row count, include a
     `SQL_CALC_FOUND_ROWS' option in the *Note `SELECT': select.
     statement, and then invoke `FOUND_ROWS()' afterward:


          mysql> SELECT SQL_CALC_FOUND_ROWS * FROM TBL_NAME
              -> WHERE id > 100 LIMIT 10;
          mysql> SELECT FOUND_ROWS();

     The second *Note `SELECT': select. returns a number indicating how
     many rows the first *Note `SELECT': select. would have returned had
     it been written without the `LIMIT' clause.

     In the absence of the `SQL_CALC_FOUND_ROWS' option in the most
     recent successful *Note `SELECT': select. statement,
     `FOUND_ROWS()' returns the number of rows in the result set
     returned by that statement. If the statement includes a `LIMIT'
     clause, `FOUND_ROWS()' returns the number of rows up to the limit.
     For example, `FOUND_ROWS()' returns 10 or 60, respectively, if the
     statement includes `LIMIT 10' or `LIMIT 50, 10'.

     The row count available through `FOUND_ROWS()' is transient and
     not intended to be available past the statement following the
     `SELECT SQL_CALC_FOUND_ROWS' statement. If you need to refer to
     the value later, save it:


          mysql> SELECT SQL_CALC_FOUND_ROWS * FROM ... ;
          mysql> SET @rows = FOUND_ROWS();

     If you are using `SELECT SQL_CALC_FOUND_ROWS', MySQL must
     calculate how many rows are in the full result set. However, this
     is faster than running the query again without `LIMIT', because
     the result set need not be sent to the client.

     `SQL_CALC_FOUND_ROWS' and `FOUND_ROWS()' can be useful in
     situations when you want to restrict the number of rows that a
     query returns, but also determine the number of rows in the full
     result set without running the query again. An example is a Web
     script that presents a paged display containing links to the pages
     that show other sections of a search result. Using `FOUND_ROWS()'
     enables you to determine how many other pages are needed for the
     rest of the result.

     The use of `SQL_CALC_FOUND_ROWS' and `FOUND_ROWS()' is more complex
     for *Note `UNION': union. statements than for simple *Note
     `SELECT': select. statements, because `LIMIT' may occur at
     multiple places in a *Note `UNION': union. It may be applied to
     individual *Note `SELECT': select. statements in the *Note
     `UNION': union, or global to the *Note `UNION': union. result as a
     whole.

     The intent of `SQL_CALC_FOUND_ROWS' for *Note `UNION': union. is
     that it should return the row count that would be returned without
     a global `LIMIT'. The conditions for use of `SQL_CALC_FOUND_ROWS'
     with *Note `UNION': union. are:

        * The `SQL_CALC_FOUND_ROWS' keyword must appear in the first
          *Note `SELECT': select.  of the *Note `UNION': union.

        * The value of `FOUND_ROWS()' is exact only if *Note `UNION
          ALL': union.  is used. If *Note `UNION': union. without `ALL'
          is used, duplicate removal occurs and the value of
          `FOUND_ROWS()' is only approximate.

        * If no `LIMIT' is present in the *Note `UNION': union,
          `SQL_CALC_FOUND_ROWS' is ignored and returns the number of
          rows in the temporary table that is created to process the
          *Note `UNION': union.

     Beyond the cases described here, the behavior of `FOUND_ROWS()' is
     undefined (for example, its value following a *Note `SELECT':
     select. statement that fails with an error).

     *Important*:

     `FOUND_ROWS()' is not replicated reliably using statement-based
     replication.  Starting with MySQL 5.1.23, this function is
     automatically replicated using row-based replication.

   * `LAST_INSERT_ID()', `LAST_INSERT_ID(EXPR)'

     For MySQL 5.1.12 and later, with no argument, `LAST_INSERT_ID()'
     returns a 64-bit value representing the first automatically
     generated value successfully inserted for an `AUTO_INCREMENT'
     column as a result of the most recently executed *Note `INSERT':
     insert.  statement. The value has a type of `BIGINT UNSIGNED' as
     of MySQL 5.1.67, `BIGINT' (signed) before that. The value of
     `LAST_INSERT_ID()' remains unchanged if no rows are successfully
     inserted.

     With an argument, `LAST_INSERT_ID()' returns an unsigned integer
     as of MySQL 5.1.67, a signed integer before that.

     For example, after inserting a row that generates an
     `AUTO_INCREMENT' value, you can get the value like this:


          mysql> SELECT LAST_INSERT_ID();
                  -> 195

     In MySQL 5.1.11 and earlier, `LAST_INSERT_ID()' (with no argument)
     returns the first automatically generated value if any rows were
     successfully inserted or updated. This means that the returned
     value could be a value that was not successfully inserted into the
     table. If no rows were successfully inserted, `LAST_INSERT_ID()'
     returns 0.

     The value of `LAST_INSERT_ID()' will be consistent across all
     MySQL versions if all rows in the *Note `INSERT': insert. or *Note
     `UPDATE': update. statement were successful.

     if a table contains an `AUTO_INCREMENT' column and *Note `INSERT
     ... ON DUPLICATE KEY UPDATE': insert-on-duplicate. updates (rather
     than inserts) a row, the value of `LAST_INSERT_ID()' is not
     meaningful prior to MySQL 5.1.12. For a workaround, see *Note
     insert-on-duplicate::.

     The currently executing statement does not affect the value of
     `LAST_INSERT_ID()'. Suppose that you generate an `AUTO_INCREMENT'
     value with one statement, and then refer to `LAST_INSERT_ID()' in a
     multiple-row *Note `INSERT': insert. statement that inserts rows
     into a table with its own `AUTO_INCREMENT' column. The value of
     `LAST_INSERT_ID()' will remain stable in the second statement; its
     value for the second and later rows is not affected by the earlier
     row insertions.  (However, if you mix references to
     `LAST_INSERT_ID()' and `LAST_INSERT_ID(EXPR)', the effect is
     undefined.)

     If the previous statement returned an error, the value of
     `LAST_INSERT_ID()' is undefined.  For transactional tables, if the
     statement is rolled back due to an error, the value of
     `LAST_INSERT_ID()' is left undefined. For manual *Note `ROLLBACK':
     commit, the value of `LAST_INSERT_ID()' is not restored to that
     before the transaction; it remains as it was at the point of the
     *Note `ROLLBACK': commit.

     Prior to MySQL 5.1.73, this function was not replicated correctly
     if replication filtering rules were in use. (Bug #17234370, Bug
     #69861)

     Within the body of a stored routine (procedure or function) or a
     trigger, the value of `LAST_INSERT_ID()' changes the same way as
     for statements executed outside the body of these kinds of
     objects. The effect of a stored routine or trigger upon the value
     of `LAST_INSERT_ID()' that is seen by following statements depends
     on the kind of routine:

        * If a stored procedure executes statements that change the
          value of `LAST_INSERT_ID()', the changed value is seen by
          statements that follow the procedure call.

        * For stored functions and triggers that change the value, the
          value is restored when the function or trigger ends, so
          following statements will not see a changed value.

     The ID that was generated is maintained in the server on a
     _per-connection basis_. This means that the value returned by the
     function to a given client is the first `AUTO_INCREMENT' value
     generated for most recent statement affecting an `AUTO_INCREMENT'
     column _by that client_. This value cannot be affected by other
     clients, even if they generate `AUTO_INCREMENT' values of their
     own. This behavior ensures that each client can retrieve its own ID
     without concern for the activity of other clients, and without the
     need for locks or transactions.

     The value of `LAST_INSERT_ID()' is not changed if you set the
     `AUTO_INCREMENT' column of a row to a non-`magic' value (that is,
     a value that is not `NULL' and not `0').

     *Important*:

     If you insert multiple rows using a single *Note `INSERT': insert.
     statement, `LAST_INSERT_ID()' returns the value generated for the
     _first_ inserted row _only_. The reason for this is to make it
     possible to reproduce easily the same *Note `INSERT': insert.
     statement against some other server.

     For example:


          mysql> USE test;
          Database changed
          mysql> CREATE TABLE t (
              ->   id INT AUTO_INCREMENT NOT NULL PRIMARY KEY,
              ->   name VARCHAR(10) NOT NULL
              -> );
          Query OK, 0 rows affected (0.09 sec)

          mysql> INSERT INTO t VALUES (NULL, 'Bob');
          Query OK, 1 row affected (0.01 sec)

          mysql> SELECT * FROM t;
          +----+------+
          | id | name |
          +----+------+
          |  1 | Bob  |
          +----+------+
          1 row in set (0.01 sec)

          mysql> SELECT LAST_INSERT_ID();
          +------------------+
          | LAST_INSERT_ID() |
          +------------------+
          |                1 |
          +------------------+
          1 row in set (0.00 sec)

          mysql> INSERT INTO t VALUES
              -> (NULL, 'Mary'), (NULL, 'Jane'), (NULL, 'Lisa');
          Query OK, 3 rows affected (0.00 sec)
          Records: 3  Duplicates: 0  Warnings: 0

          mysql> SELECT * FROM t;
          +----+------+
          | id | name |
          +----+------+
          |  1 | Bob  |
          |  2 | Mary |
          |  3 | Jane |
          |  4 | Lisa |
          +----+------+
          4 rows in set (0.01 sec)

          mysql> SELECT LAST_INSERT_ID();
          +------------------+
          | LAST_INSERT_ID() |
          +------------------+
          |                2 |
          +------------------+
          1 row in set (0.00 sec)

     Although the second *Note `INSERT': insert.  statement inserted
     three new rows into `t', the ID generated for the first of these
     rows was `2', and it is this value that is returned by
     `LAST_INSERT_ID()' for the following *Note `SELECT': select.
     statement.

     If you use *Note `INSERT IGNORE': insert. and the row is ignored,
     the `LAST_INSERT_ID()' remains unchanged from the current value
     (or 0 is returned if the connection has not yet performed a
     successful `INSERT') and, for non-transactional tables, the
     `AUTO_INCREMENT' counter is not incremented. For `InnoDB' tables,
     the `AUTO_INCREMENT' counter is incremented if
     `innodb_autoinc_lock_mode' is set to `1' or `2', as demonstrated
     in the following example:

          mysql> USE test;
          Database changed

          mysql> SELECT @@innodb_autoinc_lock_mode;
          +----------------------------+
          | @@innodb_autoinc_lock_mode |
          +----------------------------+
          |                          1 |
          +----------------------------+
          1 row in set (0.00 sec)

          mysql> CREATE TABLE `t` (
          `id` INT(11) NOT NULL AUTO_INCREMENT,
          `val` INT(11) DEFAULT NULL,
          PRIMARY KEY (`id`),
          UNIQUE KEY `i1` (`val`)
          ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
          Query OK, 0 rows affected (0.02 sec)

          -- Insert two rows

          mysql> INSERT INTO t (val) VALUES (1),(2);
          Query OK, 2 rows affected (0.00 sec)
          Records: 2  Duplicates: 0  Warnings: 0

          -- With auto_increment_offset=1, the inserted rows
          -- result in an AUTO_INCREMENT value of 3

          mysql> SHOW CREATE TABLE t\G
          *************************** 1. row ***************************
                 Table: t
          Create Table: CREATE TABLE `t` (
            `id` int(11) NOT NULL AUTO_INCREMENT,
            `val` int(11) DEFAULT NULL,
            PRIMARY KEY (`id`),
            UNIQUE KEY `i1` (`val`)
          ) ENGINE=MyISAM AUTO_INCREMENT=3 DEFAULT CHARSET=latin1
          1 row in set (0.00 sec)

          -- LAST_INSERT_ID() returns the first automatically generated
          -- value that is successfully inserted for the AUTO_INCREMENT column

          mysql> SELECT LAST_INSERT_ID();
          +------------------+
          | LAST_INSERT_ID() |
          +------------------+
          |                1 |
          +------------------+
          1 row in set (0.00 sec)

          -- The attempted insertion of duplicate rows fail but errors are ignored

          mysql> INSERT IGNORE INTO t (val) VALUES (1),(2);
          Query OK, 0 rows affected (0.00 sec)
          Records: 2  Duplicates: 2  Warnings: 0

          -- With innodb_autoinc_lock_mode=1, the AUTO_INCREMENT counter
          -- is incremented for the ignored rows

          mysql> SHOW CREATE TABLE t\G
          *************************** 1. row ***************************
                 Table: t
          Create Table: CREATE TABLE `t` (
            `id` int(11) NOT NULL AUTO_INCREMENT,
            `val` int(11) DEFAULT NULL,
            PRIMARY KEY (`id`),
            UNIQUE KEY `i1` (`val`)
          ) ENGINE=MyISAM AUTO_INCREMENT=5 DEFAULT CHARSET=latin1
          1 row in set (0.00 sec)

          -- The LAST_INSERT_ID is unchanged becuase the previous insert was unsuccessful

          mysql> SELECT LAST_INSERT_ID();
          +------------------+
          | LAST_INSERT_ID() |
          +------------------+
          |                1 |
          +------------------+
          1 row in set (0.00 sec)

     See *Note innodb-auto-increment-handling:: for more information.

     If EXPR is given as an argument to `LAST_INSERT_ID()', the value of
     the argument is returned by the function and is remembered as the
     next value to be returned by `LAST_INSERT_ID()'. This can be used
     to simulate sequences:

       1. Create a table to hold the sequence counter and initialize it:


               mysql> CREATE TABLE sequence (id INT NOT NULL);
               mysql> INSERT INTO sequence VALUES (0);

       2. Use the table to generate sequence numbers like this:


               mysql> UPDATE sequence SET id=LAST_INSERT_ID(id+1);
               mysql> SELECT LAST_INSERT_ID();

          The *Note `UPDATE': update. statement increments the sequence
          counter and causes the next call to `LAST_INSERT_ID()' to
          return the updated value. The *Note `SELECT': select.
          statement retrieves that value. The *Note
          `mysql_insert_id()': mysql-insert-id. C API function can also
          be used to get the value. See *Note mysql-insert-id::.

     You can generate sequences without calling `LAST_INSERT_ID()', but
     the utility of using the function this way is that the ID value is
     maintained in the server as the last automatically generated
     value. It is multi-user safe because multiple clients can issue
     the *Note `UPDATE': update. statement and get their own sequence
     value with the *Note `SELECT': select. statement (or *Note
     `mysql_insert_id()': mysql-insert-id.), without affecting or being
     affected by other clients that generate their own sequence values.

     Note that *Note `mysql_insert_id()': mysql-insert-id. is only
     updated after *Note `INSERT': insert. and *Note `UPDATE': update.
     statements, so you cannot use the C API function to retrieve the
     value for `LAST_INSERT_ID(EXPR)' after executing other SQL
     statements like *Note `SELECT': select. or *Note `SET':
     set-statement.

   * `ROW_COUNT()'

     `ROW_COUNT()' returns the number of rows changed, deleted, or
     inserted by the last statement if it was an *Note `UPDATE': update,
     *Note `DELETE': delete, or *Note `INSERT': insert. For other
     statements, the value may not be meaningful.

     For *Note `UPDATE': update. statements, the affected-rows value by
     default is the number of rows actually changed. If you specify the
     `CLIENT_FOUND_ROWS' flag to *Note `mysql_real_connect()':
     mysql-real-connect. when connecting to *Note `mysqld': mysqld, the
     affected-rows value is the number of rows `found'; that is,
     matched by the `WHERE' clause.

     For *Note `REPLACE': replace. statements, the affected-rows value
     is 2 if the new row replaced an old row, because in this case, one
     row was inserted after the duplicate was deleted.

     For *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate. statements, the affected-rows value is 1 if
     the row is inserted as a new row and 2 if an existing row is
     updated.

     The `ROW_COUNT()' value is similar to the value from the *Note
     `mysql_affected_rows()': mysql-affected-rows. C API function and
     the row count that the *Note `mysql': mysql.  client displays
     following statement execution.


          mysql> INSERT INTO t VALUES(1),(2),(3);
          Query OK, 3 rows affected (0.00 sec)
          Records: 3  Duplicates: 0  Warnings: 0

          mysql> SELECT ROW_COUNT();
          +-------------+
          | ROW_COUNT() |
          +-------------+
          |           3 |
          +-------------+
          1 row in set (0.00 sec)

          mysql> DELETE FROM t WHERE i IN(1,2);
          Query OK, 2 rows affected (0.00 sec)

          mysql> SELECT ROW_COUNT();
          +-------------+
          | ROW_COUNT() |
          +-------------+
          |           2 |
          +-------------+
          1 row in set (0.00 sec)

     *Important*:

     `ROW_COUNT()' is not replicated reliably using statement-based
     replication. Beginning with MySQL 5.1.23, this function is
     automatically replicated using row-based replication. (Bug #30244)

   * `SCHEMA()'

     This function is a synonym for `DATABASE()'.

   * `SESSION_USER()'

     `SESSION_USER()' is a synonym for `USER()'.

   * `SYSTEM_USER()'

     `SYSTEM_USER()' is a synonym for `USER()'.

   * `USER()'

     Returns the current MySQL user name and host name as a string in
     the `utf8' character set.


          mysql> SELECT USER();
                  -> 'davida@localhost'

     The value indicates the user name you specified when connecting to
     the server, and the client host from which you connected. The
     value can be different from that of `CURRENT_USER()'.

     You can extract only the user name part like this:


          mysql> SELECT SUBSTRING_INDEX(USER(),'@',1);
                  -> 'davida'

   * `VERSION()'

     Returns a string that indicates the MySQL server version. The
     string uses the `utf8' character set. The value might have a
     suffix in addition to the version number.  See the description of
     the `version' system variable in *Note server-system-variables::.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)


          mysql> SELECT VERSION();
                  -> '5.1.73-standard'


File: manual.info,  Node: spatial-analysis-functions,  Next: miscellaneous-functions,  Prev: information-functions,  Up: functions

12.15 Spatial Analysis Functions
================================

* Menu:

* spatial-function-reference::   Spatial Function Reference
* gis-wkt-functions::            Functions That Create Geometry Values from WKT Values
* gis-wkb-functions::            Functions That Create Geometry Values from WKB Values
* gis-mysql-specific-functions::  MySQL-Specific Functions That Create Geometry Values
* gis-format-conversion-functions::  Geometry Format Conversion Functions
* gis-property-functions::       Geometry Property Functions
* spatial-operator-functions::   Spatial Operator Functions
* spatial-relation-functions::   Functions That Test Spatial Relations Between Geometry Objects

MySQL provides functions to perform various operations on spatial data.
These functions can be grouped into several major categories according
to the type of operation they perform:

   * Functions that create geometries in various formats (WKT, WKB,
     internal)

   * Functions that convert geometries between formats

   * Functions that access qualitative or quantitative properties of a
     geometry

   * Functions that describe relations between two geometries

   * Functions that create new geometries from existing ones

For general background about MySQL support for using spatial data, see
*Note spatial-extensions::.


File: manual.info,  Node: spatial-function-reference,  Next: gis-wkt-functions,  Prev: spatial-analysis-functions,  Up: spatial-analysis-functions

12.15.1 Spatial Function Reference
----------------------------------

*Spatial Functions*

Name                          Description
`Area()'                      Return Polygon or MultiPolygon area
`AsBinary()', `AsWKB()'       Convert from internal geometry format to
                              WKB
`AsText()', `AsWKT()'         Convert from internal geometry format to
                              WKT
`Boundary()'                  Return geometry boundary
`Centroid()'                  Return centroid as a point
`Contains()'                  Whether one geometry contains another
`Crosses()'                   Whether one geometry crosses another
`Dimension()'                 Dimension of geometry
`Disjoint()'                  Whether one geometry is disjoint from
                              another
`EndPoint()'                  End Point of LineString
`Envelope()'                  Return MBR of geometry
`Equals()'                    Whether one geometry is equal to another
`ExteriorRing()'              Return exterior ring of Polygon
`GeomCollFromText()',         Return geometry collection from WKT
`GeometryCollectionFromText()'
`GeomCollFromWKB()',          Return geometry collection from WKB
`GeometryCollectionFromWKB()' 
`GeometryCollection()'        Construct geometry collection from
                              geometries
`GeometryN()'                 Return N-th geometry from geometry
                              collection
`GeometryType()'              Return name of geometry type
`GeomFromText()',             Return geometry from WKT
`GeometryFromText()'          
`GeomFromWKB()'               Return geometry from WKB
`GLength()'                   Return length of LineString
`InteriorRingN()'             Return N-th interior ring of Polygon
`Intersects()'                Whether one geometry intersects another
`IsClosed()'                  Whether a geometry is closed and simple
`IsEmpty()'                   Placeholder function
`IsSimple()'                  Whether a geometry is simple
`LineFromText()'              Construct LineString from WKT
`LineFromWKB()',              Construct LineString from WKB
`LineStringFromWKB()'         
`LineString()'                Construct LineString from Point values
`MBRContains()'               Whether MBR of one geometry contains MBR
                              of another
`MBRDisjoint()'               Whether MBRs of two geometries are disjoint
`MBREqual()'                  Whether MBRs of two geometries are equal
`MBRIntersects()'             Whether MBRs of two geometries intersect
`MBROverlaps()'               Whether MBRs of two geometries overlap
`MBRTouches()'                Whether MBRs of two geometries touch
`MBRWithin()'                 Whether MBR of one geometry is within MBR
                              of another
`MLineFromText()',            Construct MultiLineString from WKT
`MultiLineStringFromText()'   
`MLineFromWKB()',             Construct MultiLineString from WKB
`MultiLineStringFromWKB()'    
`MPointFromText()',           Construct MultiPoint from WKT
`MultiPointFromText()'        
`MPointFromWKB()',            Construct MultiPoint from WKB
`MultiPointFromWKB()'         
`MPolyFromText()',            Construct MultiPolygon from WKT
`MultiPolygonFromText()'      
`MPolyFromWKB()',             Construct MultiPolygon from WKB
`MultiPolygonFromWKB()'       
`MultiLineString()'           Contruct MultiLineString from LineString
                              values
`MultiPoint()'                Construct MultiPoint from Point values
`MultiPolygon()'              Construct MultiPolygon from Polygon values
`NumGeometries()'             Return number of geometries in geometry
                              collection
`NumInteriorRings()'          Return number of interior rings in Polygon
`NumPoints()'                 Return number of points in LineString
`Overlaps()'                  Whether one geometry overlaps another
`Point()'                     Construct Point from coordinates
`PointFromText()'             Construct Point from WKT
`PointFromWKB()'              Construct Point from WKB
`PointN()'                    Return N-th point from LineString
`PolyFromText()',             Construct Polygon from WKT
`PolygonFromText()'           
`PolyFromWKB()',              Construct Polygon from WKB
`PolygonFromWKB()'            
`Polygon()'                   Construct Polygon from LineString arguments
`SRID()'                      Return spatial reference system ID for
                              geometry
`StartPoint()'                Start Point of LineString
`Touches()'                   Whether one geometry touches another
`Within()'                    Whether one geometry is within another
`X()'                         Return X coordinate of Point
`Y()'                         Return Y coordinate of Point


File: manual.info,  Node: gis-wkt-functions,  Next: gis-wkb-functions,  Prev: spatial-function-reference,  Up: spatial-analysis-functions

12.15.2 Functions That Create Geometry Values from WKT Values
-------------------------------------------------------------

These functions take as arguments a Well-Known Text (WKT)
representation and, optionally, a spatial reference system identifier
(SRID). They return the corresponding geometry.

`GeomFromText()' accepts a WKT value of any geometry type as its first
argument. Other functions provide type-specific construction functions
for construction of geometry values of each geometry type.

For a description of WKT format, see *Note gis-wkt-format::.

   * `GeomCollFromText(WKT[,SRID])',
     `GeometryCollectionFromText(WKT[,SRID])'

     Constructs a `GeometryCollection' value using its WKT
     representation and SRID.

   * `GeomFromText(WKT[,SRID])', `GeometryFromText(WKT[,SRID])'

     Constructs a geometry value of any type using its WKT
     representation and SRID.

   * `LineFromText(WKT[,SRID])', `LineStringFromText(WKT[,SRID])'

     Constructs a `LineString' value using its WKT representation and
     SRID.

   * `MLineFromText(WKT[,SRID])', `MultiLineStringFromText(WKT[,SRID])'

     Constructs a `MultiLineString' value using its WKT representation
     and SRID.

   * `MPointFromText(WKT[,SRID])', `MultiPointFromText(WKT[,SRID])'

     Constructs a `MultiPoint' value using its WKT representation and
     SRID.

   * `MPolyFromText(WKT[,SRID])', `MultiPolygonFromText(WKT[,SRID])'

     Constructs a `MultiPolygon' value using its WKT representation and
     SRID.

   * `PointFromText(WKT[,SRID])'

     Constructs a `Point' value using its WKT representation and SRID.

   * `PolyFromText(WKT[,SRID])', `PolygonFromText(WKT[,SRID])'

     Constructs a `Polygon' value using its WKT representation and SRID.


File: manual.info,  Node: gis-wkb-functions,  Next: gis-mysql-specific-functions,  Prev: gis-wkt-functions,  Up: spatial-analysis-functions

12.15.3 Functions That Create Geometry Values from WKB Values
-------------------------------------------------------------

These functions take as arguments a *Note `BLOB': blob. containing a
Well-Known Binary (WKB) representation and, optionally, a spatial
reference system identifier (SRID). They return the corresponding
geometry.

As of MySQL 5.1.35, these functions also accept geometry objects for
compatibility with the changes made in MySQL 5.1.35 to the return value
of the functions in *Note gis-mysql-specific-functions::. Thus, those
functions may continue to be used to provide the first argument to the
functions in this section.

`GeomFromWKB()' accepts a WKB value of any geometry type as its first
argument. Other functions provide type-specific construction functions
for construction of geometry values of each geometry type.

For a description of WKB format, see *Note gis-wkb-format::.

   * `GeomCollFromWKB(WKB[,SRID])',
     `GeometryCollectionFromWKB(WKB[,SRID])'

     Constructs a `GeometryCollection' value using its WKB
     representation and SRID.

   * `GeomFromWKB(WKB[,SRID])', `GeometryFromWKB(WKB[,SRID])'

     Constructs a geometry value of any type using its WKB
     representation and SRID.

   * `LineFromWKB(WKB[,SRID])', `LineStringFromWKB(WKB[,SRID])'

     Constructs a `LineString' value using its WKB representation and
     SRID.

   * `MLineFromWKB(WKB[,SRID])', `MultiLineStringFromWKB(WKB[,SRID])'

     Constructs a `MultiLineString' value using its WKB representation
     and SRID.

   * `MPointFromWKB(WKB[,SRID])', `MultiPointFromWKB(WKB[,SRID])'

     Constructs a `MultiPoint' value using its WKB representation and
     SRID.

   * `MPolyFromWKB(WKB[,SRID])', `MultiPolygonFromWKB(WKB[,SRID])'

     Constructs a `MultiPolygon' value using its WKB representation and
     SRID.

   * `PointFromWKB(WKB[,SRID])'

     Constructs a `Point' value using its WKB representation and SRID.

   * `PolyFromWKB(WKB[,SRID])', `PolygonFromWKB(WKB[,SRID])'

     Constructs a `Polygon' value using its WKB representation and SRID.


File: manual.info,  Node: gis-mysql-specific-functions,  Next: gis-format-conversion-functions,  Prev: gis-wkb-functions,  Up: spatial-analysis-functions

12.15.4 MySQL-Specific Functions That Create Geometry Values
------------------------------------------------------------

MySQL provides a set of useful nonstandard functions for creating
geometry values. The functions described in this section are MySQL
extensions to the OpenGIS specification.

As of MySQL 5.1.35, these functions produce geometry objects from
either WKB values or geometry objects as arguments. If any argument is
not a proper WKB or geometry representation of the proper object type,
the return value is `NULL'.

Before MySQL 5.1.35, these functions produce *Note `BLOB': blob. values
containing WKB representations of geometry values with no SRID from WKB
arguments. The WKB value returned from these functions can be converted
to geometry arguments by using them as the first argument to functions
in the `GeomFromWKB()' function family.

For example, as of MySQL 5.1.35, you can insert the geometry return
value from `Point()' directly into a `POINT' column:


     INSERT INTO t1 (pt_col) VALUES(Point(1,2));

Prior to MySQL 5.1.35, convert the WKB return value to a `Point' before
inserting it:


     INSERT INTO t1 (pt_col) VALUES(GeomFromWKB(Point(1,2)));

   * `GeometryCollection(G1,G2,...)'

     Constructs a `GeometryCollection'.

     If the argument contains a nonsupported geometry, the return value
     is `NULL'.

   * `LineString(PT1,PT2,...)'

     Constructs a `LineString' value from a number of `Point' or WKB
     `Point' arguments. If the number of arguments is less than two, the
     return value is `NULL'.

   * `MultiLineString(LS1,LS2,...)'

     Constructs a `MultiLineString' value using `LineString' or WKB
     `LineString' arguments.

   * `MultiPoint(PT1,PT2,...)'

     Constructs a `MultiPoint' value using `Point' or WKB `Point'
     arguments.

   * `MultiPolygon(POLY1,POLY2,...)'

     Constructs a `MultiPolygon' value from a set of `Polygon' or WKB
     `Polygon' arguments.

   * `Point(X,Y)'

     Constructs a `Point' using its coordinates.

   * `Polygon(LS1,LS2,...)'

     Constructs a `Polygon' value from a number of `LineString' or WKB
     `LineString' arguments. If any argument does not represent a
     `LinearRing' (that is, not a closed and simple `LineString'), the
     return value is `NULL'.


File: manual.info,  Node: gis-format-conversion-functions,  Next: gis-property-functions,  Prev: gis-mysql-specific-functions,  Up: spatial-analysis-functions

12.15.5 Geometry Format Conversion Functions
--------------------------------------------

MySQL supports the following functions for converting geometry values
between internal format and either WKT or WKB format:

   * `AsBinary(G)', `AsWKB(G)'

     Converts a value in internal geometry format to its WKB
     representation and returns the binary result.


          SELECT AsBinary(g) FROM geom;

   * `AsText(G)', `AsWKT(G)'

     Converts a value in internal geometry format to its WKT
     representation and returns the string result.


          mysql> SET @g = 'LineString(1 1,2 2,3 3)';
          mysql> SELECT AsText(GeomFromText(@g));
          +--------------------------+
          | AsText(GeomFromText(@g)) |
          +--------------------------+
          | LINESTRING(1 1,2 2,3 3)  |
          +--------------------------+

   * `GeomFromText(WKT[,SRID])'

     Converts a string value from its WKT representation to internal
     geometry format and returns the result. A number of type-specific
     functions are also supported, such as `PointFromText()' and
     `LineFromText()'. See *Note gis-wkt-functions::.

   * `GeomFromWKB(WKB[,SRID])'

     Converts a binary value from its WKB representation to internal
     geometry format and returns the result. A number of type-specific
     functions are also supported, such as `PointFromWKB()' and
     `LineFromWKB()'. See *Note gis-wkb-functions::.


File: manual.info,  Node: gis-property-functions,  Next: spatial-operator-functions,  Prev: gis-format-conversion-functions,  Up: spatial-analysis-functions

12.15.6 Geometry Property Functions
-----------------------------------

* Menu:

* gis-general-property-functions::  General Geometry Property Functions
* gis-point-property-functions::  Point Property Functions
* gis-linestring-property-functions::  LineString Property Functions
* gis-multilinestring-property-functions::  MultiLineString Property Functions
* gis-polygon-property-functions::  Polygon Property Functions
* gis-multipolygon-property-functions::  MultiPolygon Property Functions
* gis-geometrycollection-property-functions::  GeometryCollection Property Functions

Each function that belongs to this group takes a geometry value as its
argument and returns some quantitative or qualitative property of the
geometry. Some functions restrict their argument type. Such functions
return `NULL' if the argument is of an incorrect geometry type. For
example, the `Area()' polygon function returns `NULL' if the object
type is neither `Polygon' nor `MultiPolygon'.


File: manual.info,  Node: gis-general-property-functions,  Next: gis-point-property-functions,  Prev: gis-property-functions,  Up: gis-property-functions

12.15.6.1 General Geometry Property Functions
.............................................

The functions listed in this section do not restrict their argument and
accept a geometry value of any type.

   * `Dimension(G)'

     Returns the inherent dimension of the geometry value G. The result
     can be -1, 0, 1, or 2. The meaning of these values is given in
     *Note gis-class-geometry::.


          mysql> SELECT Dimension(GeomFromText('LineString(1 1,2 2)'));
          +------------------------------------------------+
          | Dimension(GeomFromText('LineString(1 1,2 2)')) |
          +------------------------------------------------+
          |                                              1 |
          +------------------------------------------------+

   * `Envelope(G)'

     Returns the minimum bounding rectangle (MBR) for the geometry
     value G. The result is returned as a `Polygon' value that is
     defined by the corner points of the bounding box:


          POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY))


          mysql> SELECT AsText(Envelope(GeomFromText('LineString(1 1,2 2)')));
          +-------------------------------------------------------+
          | AsText(Envelope(GeomFromText('LineString(1 1,2 2)'))) |
          +-------------------------------------------------------+
          | POLYGON((1 1,2 1,2 2,1 2,1 1))                        |
          +-------------------------------------------------------+

   * `GeometryType(G)'

     Returns a binary string indicating the name of the geometry type
     of which the geometry instance G is a member. The name corresponds
     to one of the instantiable `Geometry' subclasses.


          mysql> SELECT GeometryType(GeomFromText('POINT(1 1)'));
          +------------------------------------------+
          | GeometryType(GeomFromText('POINT(1 1)')) |
          +------------------------------------------+
          | POINT                                    |
          +------------------------------------------+

   * `IsSimple(G)'

     In MySQL 5.1, this function is a placeholder that always returns 0.

     The description of each instantiable geometric class given earlier
     in the chapter includes the specific conditions that cause an
     instance of that class to be classified as not simple. (See *Note
     gis-geometry-class-hierarchy::.)

   * `SRID(G)'

     Returns an integer indicating the Spatial Reference System ID for
     the geometry value G.

     In MySQL, the SRID value is just an integer associated with the
     geometry value. All calculations are done assuming Euclidean
     (planar) geometry.


          mysql> SELECT SRID(GeomFromText('LineString(1 1,2 2)',101));
          +-----------------------------------------------+
          | SRID(GeomFromText('LineString(1 1,2 2)',101)) |
          +-----------------------------------------------+
          |                                           101 |
          +-----------------------------------------------+

The OpenGIS specification also defines the following functions, which
MySQL does not implement:

   * `Boundary(G)'

     Returns a geometry that is the closure of the combinatorial
     boundary of the geometry value G.

   * `IsEmpty(G)'

     This function is a placeholder that returns 0 for any valid
     geometry value, 1 for any invalid geometry value or `NULL'.

     MySQL does not support GIS `EMPTY' values such as `POINT EMPTY'.


File: manual.info,  Node: gis-point-property-functions,  Next: gis-linestring-property-functions,  Prev: gis-general-property-functions,  Up: gis-property-functions

12.15.6.2 Point Property Functions
..................................

A `Point' consists of X and Y coordinates, which may be obtained using
the following functions:

   * `X(P)'

     Returns the X-coordinate value for the `Point' object P as a
     double-precision number.


          mysql> SELECT X(POINT(56.7, 53.34));
          +-----------------------+
          | X(POINT(56.7, 53.34)) |
          +-----------------------+
          |                  56.7 |
          +-----------------------+

   * `Y(P)'

     Returns the Y-coordinate value for the `Point' object P as a
     double-precision number.


          mysql> SELECT Y(POINT(56.7, 53.34));
          +-----------------------+
          | Y(POINT(56.7, 53.34)) |
          +-----------------------+
          |                 53.34 |
          +-----------------------+


File: manual.info,  Node: gis-linestring-property-functions,  Next: gis-multilinestring-property-functions,  Prev: gis-point-property-functions,  Up: gis-property-functions

12.15.6.3 LineString Property Functions
.......................................

A `LineString' consists of `Point' values. You can extract particular
points of a `LineString', count the number of points that it contains,
or obtain its length.

   * `EndPoint(LS)'

     Returns the `Point' that is the endpoint of the `LineString' value
     LS.


          mysql> SET @ls = 'LineString(1 1,2 2,3 3)';
          mysql> SELECT AsText(EndPoint(GeomFromText(@ls)));
          +-------------------------------------+
          | AsText(EndPoint(GeomFromText(@ls))) |
          +-------------------------------------+
          | POINT(3 3)                          |
          +-------------------------------------+

   * `GLength(LS)'

     Returns a double-precision number indicating the length of the
     `LineString' value LS in its associated spatial reference.


          mysql> SET @ls = 'LineString(1 1,2 2,3 3)';
          mysql> SELECT GLength(GeomFromText(@ls));
          +----------------------------+
          | GLength(GeomFromText(@ls)) |
          +----------------------------+
          |            2.8284271247462 |
          +----------------------------+

     `GLength()' is a nonstandard name. It corresponds to the OpenGIS
     `Length()' function. (There is an existing SQL function `Length()'
     that calculates the length of string values.)

   * `IsClosed(LS)'

     Returns 1 if the `LineString' value LS is closed (that is, its
     `StartPoint()' and `EndPoint()' values are the same) and is simple
     (does not pass through the same point more than once). Returns 0
     if LS is not closed, and -1 if it is `NULL'.


          mysql> SET @ls1 = '`LineString'(1 1,2 2,3 3,2 2)';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SET @ls2 = 'LineString(1 1,2 2,3 3,1 1)';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT IsClosed(`GeomFromText'(@ls1));
          +------------------------------+
          | IsClosed(GeomFromText(@ls1)) |
          +------------------------------+
          |                            0 |
          +------------------------------+
          1 row in set (0.00 sec)

          mysql> SELECT IsClosed(GeomFromText(@ls2));
          +------------------------------+
          | IsClosed(GeomFromText(@ls2)) |
          +------------------------------+
          |                            1 |
          +------------------------------+
          1 row in set (0.00 sec)

   * `NumPoints(LS)'

     Returns the number of `Point' objects in the `LineString' value LS.


          mysql> SET @ls = 'LineString(1 1,2 2,3 3)';
          mysql> SELECT NumPoints(GeomFromText(@ls));
          +------------------------------+
          | NumPoints(GeomFromText(@ls)) |
          +------------------------------+
          |                            3 |
          +------------------------------+

   * `PointN(LS,N)'

     Returns the N-th `Point' in the `Linestring' value LS. Points are
     numbered beginning with 1.


          mysql> SET @ls = 'LineString(1 1,2 2,3 3)';
          mysql> SELECT AsText(PointN(GeomFromText(@ls),2));
          +-------------------------------------+
          | AsText(PointN(GeomFromText(@ls),2)) |
          +-------------------------------------+
          | POINT(2 2)                          |
          +-------------------------------------+

   * `StartPoint(LS)'

     Returns the `Point' that is the start point of the `LineString'
     value LS.


          mysql> SET @ls = 'LineString(1 1,2 2,3 3)';
          mysql> SELECT AsText(StartPoint(GeomFromText(@ls)));
          +---------------------------------------+
          | AsText(StartPoint(GeomFromText(@ls))) |
          +---------------------------------------+
          | POINT(1 1)                            |
          +---------------------------------------+


File: manual.info,  Node: gis-multilinestring-property-functions,  Next: gis-polygon-property-functions,  Prev: gis-linestring-property-functions,  Up: gis-property-functions

12.15.6.4 MultiLineString Property Functions
............................................

These functions return properties of `MultiLineString' values.

   * `GLength(MLS)'

     Returns a double-precision number indicating the length of the
     `MultiLineString' value MLS. The length of MLS is equal to the sum
     of the lengths of its elements.


          mysql> SET @mls = 'MultiLineString((1 1,2 2,3 3),(4 4,5 5))';
          mysql> SELECT GLength(GeomFromText(@mls));
          +-----------------------------+
          | GLength(GeomFromText(@mls)) |
          +-----------------------------+
          |             4.2426406871193 |
          +-----------------------------+

     `GLength()' is a nonstandard name. It corresponds to the OpenGIS
     `Length()' function.

   * `IsClosed(MLS)'

     Returns 1 if the `MultiLineString' value MLS is closed (that is,
     the `StartPoint()' and `EndPoint()' values are the same for each
     `LineString' in MLS). Returns 0 if MLS is not closed, and -1 if it
     is `NULL'.


          mysql> SET @mls = 'MultiLineString((1 1,2 2,3 3),(4 4,5 5))';
          mysql> SELECT IsClosed(GeomFromText(@mls));
          +------------------------------+
          | IsClosed(GeomFromText(@mls)) |
          +------------------------------+
          |                            0 |
          +------------------------------+


File: manual.info,  Node: gis-polygon-property-functions,  Next: gis-multipolygon-property-functions,  Prev: gis-multilinestring-property-functions,  Up: gis-property-functions

12.15.6.5 Polygon Property Functions
....................................

These functions return properties of `Polygon' values.

   * `Area(POLY)'

     Returns a double-precision number indicating the area of the
     `Polygon' or `MultiPolygon' value POLY, as measured in its spatial
     reference system. The result is 0 for arguments of dimension 0 or
     1.


          mysql> SET @poly = 'Polygon((0 0,0 3,3 0,0 0),(1 1,1 2,2 1,1 1))';
          mysql> SELECT Area(GeomFromText(@poly));
          +---------------------------+
          | Area(GeomFromText(@poly)) |
          +---------------------------+
          |                         4 |
          +---------------------------+

          mysql> SET @mpoly =
              -> 'MultiPolygon(((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1)))';
          mysql> SELECT Area(GeomFromText(@mpoly));
          +----------------------------+
          | Area(GeomFromText(@mpoly)) |
          +----------------------------+
          |                          8 |
          +----------------------------+

   * `ExteriorRing(POLY)'

     Returns the exterior ring of the `Polygon' value POLY as a
     `LineString'.


          mysql> SET @poly =
              -> 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';
          mysql> SELECT AsText(ExteriorRing(GeomFromText(@poly)));
          +-------------------------------------------+
          | AsText(ExteriorRing(GeomFromText(@poly))) |
          +-------------------------------------------+
          | LINESTRING(0 0,0 3,3 3,3 0,0 0)           |
          +-------------------------------------------+

   * `InteriorRingN(POLY,N)'

     Returns the N-th interior ring for the `Polygon' value POLY as a
     `LineString'. Rings are numbered beginning with 1.


          mysql> SET @poly =
              -> 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';
          mysql> SELECT AsText(InteriorRingN(GeomFromText(@poly),1));
          +----------------------------------------------+
          | AsText(InteriorRingN(GeomFromText(@poly),1)) |
          +----------------------------------------------+
          | LINESTRING(1 1,1 2,2 2,2 1,1 1)              |
          +----------------------------------------------+

   * `NumInteriorRings(POLY)'

     Returns the number of interior rings in the `Polygon' value POLY.


          mysql> SET @poly =
              -> 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';
          mysql> SELECT NumInteriorRings(GeomFromText(@poly));
          +---------------------------------------+
          | NumInteriorRings(GeomFromText(@poly)) |
          +---------------------------------------+
          |                                     1 |
          +---------------------------------------+


File: manual.info,  Node: gis-multipolygon-property-functions,  Next: gis-geometrycollection-property-functions,  Prev: gis-polygon-property-functions,  Up: gis-property-functions

12.15.6.6 MultiPolygon Property Functions
.........................................

These functions return properties of `MultiPolygon' values.

   * `Area(MPOLY)'

     See the description of `Area()' in *Note
     gis-polygon-property-functions::.

   * `Centroid(MPOLY)'

     Returns the mathematical centroid for the `MultiPolygon' value
     MPOLY as a `Point'. The result is not guaranteed to be on the
     `MultiPolygon'.


          mysql> SET @poly =
              -> GeomFromText('POLYGON((0 0,10 0,10 10,0 10,0 0),(5 5,7 5,7 7,5 7,5 5))');
          mysql> SELECT GeometryType(@poly),AsText(Centroid(@poly));
          +---------------------+--------------------------------------------+
          | GeometryType(@poly) | AsText(Centroid(@poly))                    |
          +---------------------+--------------------------------------------+
          | POLYGON             | POINT(4.958333333333333 4.958333333333333) |
          +---------------------+--------------------------------------------+

The OpenGIS specification also defines the following function, which
MySQL does not implement:

   * `PointOnSurface(MPOLY)'

     Returns a `Point' value that is guaranteed to be on the
     `MultiPolygon' value MPOLY.


File: manual.info,  Node: gis-geometrycollection-property-functions,  Prev: gis-multipolygon-property-functions,  Up: gis-property-functions

12.15.6.7 GeometryCollection Property Functions
...............................................

These functions return properties of `GeometryCollection' values.

   * `GeometryN(GC,N)'

     Returns the N-th geometry in the `GeometryCollection' value GC.
     Geometries are numbered beginning with 1.


          mysql> SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3 3))';
          mysql> SELECT AsText(GeometryN(GeomFromText(@gc),1));
          +----------------------------------------+
          | AsText(GeometryN(GeomFromText(@gc),1)) |
          +----------------------------------------+
          | POINT(1 1)                             |
          +----------------------------------------+

   * `NumGeometries(GC)'

     Returns the number of geometries in the `GeometryCollection' value
     GC.


          mysql> SET @gc = 'GeometryCollection(Point(1 1),LineString(2 2, 3 3))';
          mysql> SELECT NumGeometries(GeomFromText(@gc));
          +----------------------------------+
          | NumGeometries(GeomFromText(@gc)) |
          +----------------------------------+
          |                                2 |
          +----------------------------------+


File: manual.info,  Node: spatial-operator-functions,  Next: spatial-relation-functions,  Prev: gis-property-functions,  Up: spatial-analysis-functions

12.15.7 Spatial Operator Functions
----------------------------------

OpenGIS proposes a number of functions that can produce geometries.
They are designed to implement spatial operators.

These functions are not implemented in MySQL.

   * `Buffer(G,D)'

     Returns a geometry that represents all points whose distance from
     the geometry value G is less than or equal to a distance of D.

   * `ConvexHull(G)'

     Returns a geometry that represents the convex hull of the geometry
     value G.

   * `Difference(G1,G2)'

     Returns a geometry that represents the point set difference of the
     geometry values G1 and G2.

   * `Intersection(G1,G2)'

     Returns a geometry that represents the point set intersection of
     the geometry values G1 and G2.

   * `SymDifference(G1,G2)'

     Returns a geometry that represents the point set symmetric
     difference of the geometry values G1 and G2.

   * `Union(G1,G2)'

     Returns a geometry that represents the point set union of the
     geometry values G1 and G2.

In addition, *Note gis-property-functions::, discusses several
functions that construct new geometries from existing ones. See that
section for descriptions of these functions:

   * `Envelope(G)'

   * `StartPoint(LS)'

   * `EndPoint(LS)'

   * `PointN(LS,N)'

   * `ExteriorRing(POLY)'

   * `InteriorRingN(POLY,N)'

   * `GeometryN(GC,N)'


File: manual.info,  Node: spatial-relation-functions,  Prev: spatial-operator-functions,  Up: spatial-analysis-functions

12.15.8 Functions That Test Spatial Relations Between Geometry Objects
----------------------------------------------------------------------

* Menu:

* spatial-relation-functions-mbr::  Spatial Relation Functions That Use Minimum Bounding Rectangles (MBRs)
* spatial-relation-functions-mysql-specific::  MySQL-Specific Spatial Relation Functions That Use Minimum Bounding Rectangles (MBRs)

The functions described in this section take two geometries as
arguments and return a qualitative or quantitative relation between
them.

   * The OpenGIS specification defines the a set of functions that test
     the relationship between two geometry values. MySQL originally
     implemented these functions such that they used object minimum
     bounding rectangles (MBRs) and returned the same result as the
     corresponding MBR-based functions. For example, `Contains()' and
     `MBRContains()' return the same result.  (Exception: `Crosses()'
     exists but `MBRCrosses()' does not.)

   * A MySQL-specific set of MBR-based functions is available to test
     the relationship between two geometry values.


File: manual.info,  Node: spatial-relation-functions-mbr,  Next: spatial-relation-functions-mysql-specific,  Prev: spatial-relation-functions,  Up: spatial-relation-functions

12.15.8.1 Spatial Relation Functions That Use Minimum Bounding Rectangles (MBRs)
................................................................................

The OpenGIS specification defines the following functions. They test
the relationship between two geometry values `g1' and `g2'. The MySQL
implementation uses minimum bounding rectangles, so these functions
return the same result as the corresponding MBR-based functions. The
return values 1 and 0 indicate true and false, respectively.

   * `Contains(G1,G2)'

     Returns 1 or 0 to indicate whether G1 completely contains G2. This
     tests the opposite relationship as `Within()'.

   * `Crosses(G1,G2)'

     Returns 1 if G1 spatially crosses G2. Returns `NULL' if `g1' is a
     `Polygon' or a `MultiPolygon', or if G2 is a `Point' or a
     `MultiPoint'. Otherwise, returns 0.

     The term _spatially crosses_ denotes a spatial relation between
     two given geometries that has the following properties:

        * The two geometries intersect

        * Their intersection results in a geometry that has a dimension
          that is one less than the maximum dimension of the two given
          geometries

        * Their intersection is not equal to either of the two given
          geometries

   * `Disjoint(G1,G2)'

     Returns 1 or 0 to indicate whether G1 is spatially disjoint from
     (does not intersect) G2.

   * `Equals(G1,G2)'

     Returns 1 or 0 to indicate whether G1 is spatially equal to G2.

   * `Intersects(G1,G2)'

     Returns 1 or 0 to indicate whether G1 spatially intersects G2.

   * `Overlaps(G1,G2)'

     Returns 1 or 0 to indicate whether G1 spatially overlaps G2. The
     term _spatially overlaps_ is used if two geometries intersect and
     their intersection results in a geometry of the same dimension but
     not equal to either of the given geometries.

   * `Touches(G1,G2)'

     Returns 1 or 0 to indicate whether G1 spatially touches G2. Two
     geometries _spatially touch_ if the interiors of the geometries do
     not intersect, but the boundary of one of the geometries
     intersects either the boundary or the interior of the other.

   * `Within(G1,G2)'

     Returns 1 or 0 to indicate whether G1 is spatially within G2. This
     tests the opposite relationship as `Contains()'.


File: manual.info,  Node: spatial-relation-functions-mysql-specific,  Prev: spatial-relation-functions-mbr,  Up: spatial-relation-functions

12.15.8.2 MySQL-Specific Spatial Relation Functions That Use Minimum Bounding Rectangles (MBRs)
...............................................................................................

MySQL provides several functions that test relations between minimum
bounding rectangles of two geometries `g1' and `g2'. The return values
1 and 0 indicate true and false, respectively.

   * `MBRContains(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangle
     of G1 contains the minimum bounding rectangle of G2.  This tests
     the opposite relationship as `MBRWithin()'.


          mysql> SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
          mysql> SET @g2 = GeomFromText('Point(1 1)');
          mysql> SELECT MBRContains(@g1,@g2), MBRWithin(@g2,@g1);
          +----------------------+--------------------+
          | MBRContains(@g1,@g2) | MBRWithin(@g2,@g1) |
          +----------------------+--------------------+
          |                    1 |                  1 |
          +----------------------+--------------------+

   * `MBRDisjoint(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangles
     of the two geometries G1 and G2 are disjoint (do not intersect).

   * `MBREqual(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangles
     of the two geometries G1 and G2 are the same.

   * `MBRIntersects(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangles
     of the two geometries G1 and G2 intersect.

   * `MBROverlaps(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangles
     of the two geometries G1 and G2 overlap. The term _spatially
     overlaps_ is used if two geometries intersect and their
     intersection results in a geometry of the same dimension but not
     equal to either of the given geometries.

   * `MBRTouches(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangles
     of the two geometries G1 and G2 touch. Two geometries _spatially
     touch_ if the interiors of the geometries do not intersect, but
     the boundary of one of the geometries intersects either the
     boundary or the interior of the other.

   * `MBRWithin(G1,G2)'

     Returns 1 or 0 to indicate whether the minimum bounding rectangle
     of G1 is within the minimum bounding rectangle of G2.  This tests
     the opposite relationship as `MBRContains()'.


          mysql> SET @g1 = GeomFromText('Polygon((0 0,0 3,3 3,3 0,0 0))');
          mysql> SET @g2 = GeomFromText('Polygon((0 0,0 5,5 5,5 0,0 0))');
          mysql> SELECT MBRWithin(@g1,@g2), MBRWithin(@g2,@g1);
          +--------------------+--------------------+
          | MBRWithin(@g1,@g2) | MBRWithin(@g2,@g1) |
          +--------------------+--------------------+
          |                  1 |                  0 |
          +--------------------+--------------------+


File: manual.info,  Node: miscellaneous-functions,  Next: group-by-functions-and-modifiers,  Prev: spatial-analysis-functions,  Up: functions

12.16 Miscellaneous Functions
=============================

*Miscellaneous Functions*

Name                          Description
`DEFAULT()'                   Return the default value for a table column
`GET_LOCK()'                  Get a named lock
`INET_ATON()'                 Return the numeric value of an IP address
`INET_NTOA()'                 Return the IP address from a numeric value
`IS_FREE_LOCK()'              Checks whether the named lock is free
`IS_USED_LOCK()'              Checks whether the named lock is in use.
                              Return connection  identifier if true.
`MASTER_POS_WAIT()'           Block until the slave has read and applied
                              all updates up to the  specified position
`NAME_CONST()'                Causes the column to have the given name
`RAND()'                      Return a random floating-point value
`RELEASE_LOCK()'              Releases the named lock
`SLEEP()'                     Sleep for a number of seconds
`UUID_SHORT()'                Return an integer-valued universal
                              identifier
`UUID()'                      Return a Universal Unique Identifier (UUID)
`VALUES()'                    Defines the values to be used during an
                              INSERT

   * `DEFAULT(COL_NAME)'

     Returns the default value for a table column. An error results if
     the column has no default value.


          mysql> UPDATE t SET i = DEFAULT(i)+1 WHERE id < 100;

   * `FORMAT(X,D)'

     Formats the number X to a format like `'#,###,###.##'', rounded to
     D decimal places, and returns the result as a string. For details,
     see *Note string-functions::.

   * `GET_LOCK(STR,TIMEOUT)'

     Tries to obtain a lock with a name given by the string STR, using
     a timeout of TIMEOUT seconds. Returns `1' if the lock was obtained
     successfully, `0' if the attempt timed out (for example, because
     another client has previously locked the name), or `NULL' if an
     error occurred (such as running out of memory or the thread was
     killed with *Note `mysqladmin kill': mysqladmin.). If you have a
     lock obtained with `GET_LOCK()', it is released when you execute
     `RELEASE_LOCK()', execute a new `GET_LOCK()', or your connection
     terminates (either normally or abnormally). Locks obtained with
     `GET_LOCK()' do not interact with transactions. That is,
     committing a transaction does not release any such locks obtained
     during the transaction.

     `GET_LOCK()' can be used to implement application locks or to
     simulate record locks. Names are locked on a server-wide basis. If
     a name has been locked within one session, `GET_LOCK()' blocks any
     request by another session for a lock with the same name. This
     enables clients that agree on a given lock name to use the name to
     perform cooperative advisory locking. But be aware that it also
     enables a client that is not among the set of cooperating clients
     to lock a name, either inadvertently or deliberately, and thus
     prevent any of the cooperating clients from locking that name. One
     way to reduce the likelihood of this is to use lock names that are
     database-specific or application-specific. For example, use lock
     names of the form DB_NAME.STR or APP_NAME.STR.


          mysql> SELECT GET_LOCK('lock1',10);
                  -> 1
          mysql> SELECT IS_FREE_LOCK('lock2');
                  -> 1
          mysql> SELECT GET_LOCK('lock2',10);
                  -> 1
          mysql> SELECT RELEASE_LOCK('lock2');
                  -> 1
          mysql> SELECT RELEASE_LOCK('lock1');
                  -> NULL

     The second `RELEASE_LOCK()' call returns `NULL' because the lock
     `'lock1'' was automatically released by the second `GET_LOCK()'
     call.

     If multiple clients are waiting for a lock, the order in which
     they will acquire it is undefined. Applications should not assume
     that clients will acquire the lock in the same order that they
     issued the lock requests.

     *Note*:

     If a client attempts to acquire a lock that is already held by
     another client, it blocks according to the TIMEOUT argument. If
     the blocked client terminates, its thread does not die until the
     lock request times out. This is a known bug (fixed in MySQL 5.5).

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `INET_ATON(EXPR)'

     Given the dotted-quad representation of an IPv4 network address as
     a string, returns an integer that represents the numeric value of
     the address in network byte order (big endian). `INET_ATON()'
     returns `NULL' if it does not understand its argument.


          mysql> SELECT INET_ATON('10.0.5.9');
                  -> 167773449

     For this example, the return value is calculated as 10x256^3 +
     0x256^2 + 5x256 + 9.

     `INET_ATON()' may or may not return a non-`NULL' result for
     short-form IP addresses (such as `'127.1'' as a representation of
     `'127.0.0.1''). Because of this, `INET_ATON()'a should not be used
     for such addresses.

     *Note*:

     To store values generated by `INET_ATON()', use an `INT UNSIGNED'
     column rather than *Note `INT': integer-types, which is signed. If
     you use a signed column, values corresponding to IP addresses for
     which the first octet is greater than 127 cannot be stored
     correctly. See *Note out-of-range-and-overflow::.

   * `INET_NTOA(EXPR)'

     Given a numeric IPv4 network address in network byte order,
     returns the dotted-quad representation of the address as a binary
     string. `INET_NTOA()' returns `NULL' if it does not understand its
     argument.


          mysql> SELECT INET_NTOA(167773449);
                  -> '10.0.5.9'

   * `IS_FREE_LOCK(STR)'

     Checks whether the lock named STR is free to use (that is, not
     locked). Returns `1' if the lock is free (no one is using the
     lock), `0' if the lock is in use, and `NULL' if an error occurs
     (such as an incorrect argument).

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `IS_USED_LOCK(STR)'

     Checks whether the lock named STR is in use (that is, locked). If
     so, it returns the connection identifier of the client that holds
     the lock. Otherwise, it returns `NULL'.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `MASTER_POS_WAIT(LOG_NAME,LOG_POS[,TIMEOUT])'

     This function is useful for control of master/slave
     synchronization. It blocks until the slave has read and applied
     all updates up to the specified position in the master log. The
     return value is the number of log events the slave had to wait for
     to advance to the specified position. The function returns `NULL'
     if the slave SQL thread is not started, the slave's master
     information is not initialized, the arguments are incorrect, or an
     error occurs.  It returns `-1' if the timeout has been exceeded.
     If the slave SQL thread stops while `MASTER_POS_WAIT()' is waiting,
     the function returns `NULL'. If the slave is past the specified
     position, the function returns immediately.

     If a TIMEOUT value is specified, `MASTER_POS_WAIT()' stops waiting
     when TIMEOUT seconds have elapsed.  TIMEOUT must be greater than
     0; a zero or negative TIMEOUT means no timeout.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `NAME_CONST(NAME,VALUE)'

     Returns the given value. When used to produce a result set column,
     `NAME_CONST()' causes the column to have the given name. The
     arguments should be constants.


          mysql> SELECT NAME_CONST('myname', 14);
          +--------+
          | myname |
          +--------+
          |     14 |
          +--------+

     This function is for internal use only. The server uses it when
     writing statements from stored programs that contain references to
     local program variables, as described in *Note
     stored-programs-logging::, You might see this function in the
     output from *Note `mysqlbinlog': mysqlbinlog.

     For your applications, you can obtain exactly the same result as
     in the example just shown by using simple aliasing, like this:


          mysql> SELECT 14 AS myname;
          +--------+
          | myname |
          +--------+
          |     14 |
          +--------+
          1 row in set (0.00 sec)

     See *Note select::, for more information about column aliases.

   * `RELEASE_LOCK(STR)'

     Releases the lock named by the string STR that was obtained with
     `GET_LOCK()'. Returns `1' if the lock was released, `0' if the
     lock was not established by this thread (in which case the lock is
     not released), and `NULL' if the named lock did not exist. The
     lock does not exist if it was never obtained by a call to
     `GET_LOCK()' or if it has previously been released.

     The *Note `DO': do. statement is convenient to use with
     `RELEASE_LOCK()'. See *Note do::.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `SLEEP(DURATION)'

     Sleeps (pauses) for the number of seconds given by the DURATION
     argument, then returns 0.  If `SLEEP()' is interrupted, it returns
     1. The duration may have a fractional part.

     This function is unsafe for statement-based replication.
     Beginning with MySQL 5.1.42, a warning is logged if you use this
     function when `binlog_format' is set to `STATEMENT'. (Bug #47995)

   * `UUID()'

     Returns a Universal Unique Identifier (UUID) generated according
     to `DCE 1.1: Remote Procedure Call' (Appendix A) CAE (Common
     Applications Environment) Specifications published by The Open
     Group in October 1997 (Document Number C706,
     `http://www.opengroup.org/public/pubs/catalog/c706.htm').

     A UUID is designed as a number that is globally unique in space
     and time. Two calls to `UUID()' are expected to generate two
     different values, even if these calls are performed on two
     separate computers that are not connected to each other.

     A UUID is a 128-bit number represented by a `utf8' string of five
     hexadecimal numbers in `aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee'
     format:

        * The first three numbers are generated from a timestamp.

        * The fourth number preserves temporal uniqueness in case the
          timestamp value loses monotonicity (for example, due to
          daylight saving time).

        * The fifth number is an IEEE 802 node number that provides
          spatial uniqueness. A random number is substituted if the
          latter is not available (for example, because the host
          computer has no Ethernet card, or we do not know how to find
          the hardware address of an interface on your operating
          system). In this case, spatial uniqueness cannot be
          guaranteed. Nevertheless, a collision should have _very_ low
          probability.

          Currently, the MAC address of an interface is taken into
          account only on FreeBSD and Linux. On other operating
          systems, MySQL uses a randomly generated 48-bit number.


          mysql> SELECT UUID();
                  -> '6ccd780c-baba-1026-9564-0040f4311e29'

     *Warning*:

     Although `UUID()' values are intended to be unique, they are not
     necessarily unguessable or unpredictable. If unpredictability is
     required, UUID values should be generated some other way.

     *Note*:

     `UUID()' does not work with statement-based replication.

   * `UUID_SHORT()'

     Returns a `short' universal identifier as a 64-bit unsigned
     integer (rather than a string-form 128-bit identifier as returned
     by the `UUID()' function).

     The value of `UUID_SHORT()' is guaranteed to be unique if the
     following conditions hold:

        * The `server_id' of the current host is unique among your set
          of master and slave servers

        * `server_id' is between 0 and 255

        * You do not set back your system time for your server between
          *Note `mysqld': mysqld. restarts

        * You do not invoke `UUID_SHORT()' on average more than 16
          million times per second between *Note `mysqld': mysqld.
          restarts

     The `UUID_SHORT()' return value is constructed this way:


            (server_id & 255) << 56
          + (server_startup_time_in_seconds << 24)
          + incremented_variable++;


          mysql> SELECT UUID_SHORT();
                  -> 92395783831158784

     Note that `UUID_SHORT()' does not work with statement-based
     replication.

     This function was added in MySQL 5.1.20.

   * `VALUES(COL_NAME)'

     In an *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate. statement, you can use the `VALUES(COL_NAME)'
     function in the *Note `UPDATE': update. clause to refer to column
     values from the *Note `INSERT': insert. portion of the statement.
     In other words, `VALUES(COL_NAME)' in the *Note `UPDATE': update.
     clause refers to the value of COL_NAME that would be inserted, had
     no duplicate-key conflict occurred. This function is especially
     useful in multiple-row inserts. The `VALUES()' function is
     meaningful only in the `ON DUPLICATE KEY UPDATE' clause of *Note
     `INSERT': insert. statements and returns `NULL' otherwise. See
     *Note insert-on-duplicate::.


          mysql> INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
              -> ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);


File: manual.info,  Node: group-by-functions-and-modifiers,  Next: precision-math,  Prev: miscellaneous-functions,  Up: functions

12.17 Functions and Modifiers for Use with GROUP BY Clauses
===========================================================

* Menu:

* group-by-functions::           GROUP BY (Aggregate) Functions
* group-by-modifiers::           GROUP BY Modifiers
* group-by-extensions::          MySQL Extensions to GROUP BY


File: manual.info,  Node: group-by-functions,  Next: group-by-modifiers,  Prev: group-by-functions-and-modifiers,  Up: group-by-functions-and-modifiers

12.17.1 GROUP BY (Aggregate) Functions
--------------------------------------

*Aggregate (`GROUP BY') Functions*

Name                          Description
`AVG()'                       Return the average value of the argument
`BIT_AND()'                   Return bitwise and
`BIT_OR()'                    Return bitwise or
`BIT_XOR()'                   Return bitwise xor
`COUNT(DISTINCT)'             Return the count of a number of different
                              values
`COUNT()'                     Return a count of the number of rows
                              returned
`GROUP_CONCAT()'              Return a concatenated string
`MAX()'                       Return the maximum value
`MIN()'                       Return the minimum value
`STD()'                       Return the population standard deviation
`STDDEV_POP()'                Return the population standard deviation
`STDDEV_SAMP()'               Return the sample standard deviation
`STDDEV()'                    Return the population standard deviation
`SUM()'                       Return the sum
`VAR_POP()'                   Return the population standard variance
`VAR_SAMP()'                  Return the sample variance
`VARIANCE()'                  Return the population standard variance

This section describes group (aggregate) functions that operate on sets
of values. Unless otherwise stated, group functions ignore `NULL'
values.

If you use a group function in a statement containing no `GROUP BY'
clause, it is equivalent to grouping on all rows. For more information,
see *Note group-by-extensions::.

For numeric arguments, the variance and standard deviation functions
return a *Note `DOUBLE': floating-point-types. value.  The `SUM()' and
`AVG()' functions return a *Note `DECIMAL': fixed-point-types. value
for exact-value arguments (integer or *Note `DECIMAL':
fixed-point-types.), and a *Note `DOUBLE': floating-point-types. value
for approximate-value arguments (*Note `FLOAT': floating-point-types. or
*Note `DOUBLE': floating-point-types.).

The `SUM()' and `AVG()' aggregate functions do not work with temporal
values. (They convert the values to numbers, losing everything after
the first nonnumeric character.) To work around this problem, convert
to numeric units, perform the aggregate operation, and convert back to
a temporal value.  Examples:


     SELECT SEC_TO_TIME(SUM(TIME_TO_SEC(TIME_COL))) FROM TBL_NAME;
     SELECT FROM_DAYS(SUM(TO_DAYS(DATE_COL))) FROM TBL_NAME;

Functions such as `SUM()' or `AVG()' that expect a numeric argument
cast the argument to a number if necessary. For *Note `SET': set. or
*Note `ENUM': enum. values, the cast operation causes the underlying
numeric value to be used.

   * `AVG([DISTINCT] EXPR)'

     Returns the average value of `EXPR'. The `DISTINCT' option can be
     used to return the average of the distinct values of EXPR.

     `AVG()' returns `NULL' if there were no matching rows.


          mysql> SELECT student_name, AVG(test_score)
              ->        FROM student
              ->        GROUP BY student_name;

   * `BIT_AND(EXPR)'

     Returns the bitwise `AND' of all bits in EXPR. The calculation is
     performed with 64-bit (*Note `BIGINT': integer-types.) precision.

     This function returns `18446744073709551615' if there were no
     matching rows. (This is the value of an unsigned *Note `BIGINT':
     integer-types. value with all bits set to 1.)

   * `BIT_OR(EXPR)'

     Returns the bitwise `OR' of all bits in EXPR. The calculation is
     performed with 64-bit (*Note `BIGINT': integer-types.) precision.

     This function returns `0' if there were no matching rows.

   * `BIT_XOR(EXPR)'

     Returns the bitwise `XOR' of all bits in EXPR. The calculation is
     performed with 64-bit (*Note `BIGINT': integer-types.) precision.

     This function returns `0' if there were no matching rows.

   * `COUNT(EXPR)'

     Returns a count of the number of non-`NULL' values of EXPR in the
     rows retrieved by a *Note `SELECT': select.  statement. The result
     is a *Note `BIGINT': integer-types. value.

     `COUNT()' returns `0' if there were no matching rows.


          mysql> SELECT student.student_name,COUNT(*)
              ->        FROM student,course
              ->        WHERE student.student_id=course.student_id
              ->        GROUP BY student_name;

     `COUNT(*)' is somewhat different in that it returns a count of the
     number of rows retrieved, whether or not they contain `NULL'
     values.

     `COUNT(*)' is optimized to return very quickly if the *Note
     `SELECT': select. retrieves from one table, no other columns are
     retrieved, and there is no `WHERE' clause. For example:


          mysql> SELECT COUNT(*) FROM student;

     This optimization applies only to `MyISAM' tables only, because an
     exact row count is stored for this storage engine and can be
     accessed very quickly. For transactional storage engines such as
     `InnoDB', storing an exact row count is more problematic because
     multiple transactions may be occurring, each of which may affect
     the count.

   * `COUNT(DISTINCT EXPR,[EXPR...])'

     Returns a count of the number of rows with different non-`NULL'
     EXPR values.

     `COUNT(DISTINCT)' returns `0' if there were no matching rows.


          mysql> SELECT COUNT(DISTINCT results) FROM student;

     In MySQL, you can obtain the number of distinct expression
     combinations that do not contain `NULL' by giving a list of
     expressions. In standard SQL, you would have to do a concatenation
     of all expressions inside `COUNT(DISTINCT ...)'.

   * `GROUP_CONCAT(EXPR)'

     This function returns a string result with the concatenated
     non-`NULL' values from a group. It returns `NULL' if there are no
     non-`NULL' values. The full syntax is as follows:


          GROUP_CONCAT([DISTINCT] EXPR [,EXPR ...]
                       [ORDER BY {UNSIGNED_INTEGER | COL_NAME | EXPR}
                           [ASC | DESC] [,COL_NAME ...]]
                       [SEPARATOR STR_VAL])


          mysql> SELECT student_name,
              ->     GROUP_CONCAT(test_score)
              ->     FROM student
              ->     GROUP BY student_name;

     Or:


          mysql> SELECT student_name,
              ->     GROUP_CONCAT(DISTINCT test_score
              ->               ORDER BY test_score DESC SEPARATOR ' ')
              ->     FROM student
              ->     GROUP BY student_name;

     In MySQL, you can get the concatenated values of expression
     combinations. To eliminate duplicate values, use the `DISTINCT'
     clause. To sort values in the result, use the `ORDER BY' clause.
     To sort in reverse order, add the `DESC' (descending) keyword to
     the name of the column you are sorting by in the `ORDER BY'
     clause. The default is ascending order; this may be specified
     explicitly using the `ASC' keyword. The default separator between
     values in a group is comma (``,''). To specify a separator
     explicitly, use `SEPARATOR' followed by the string literal value
     that should be inserted between group values. To eliminate the
     separator altogether, specify `SEPARATOR '''.

     The result is truncated to the maximum length that is given by the
     `group_concat_max_len' system variable, which has a default value
     of 1024. The value can be set higher, although the effective
     maximum length of the return value is constrained by the value of
     `max_allowed_packet'. The syntax to change the value of
     `group_concat_max_len' at runtime is as follows, where VAL is an
     unsigned integer:


          SET [GLOBAL | SESSION] group_concat_max_len = VAL;

     The return value is a nonbinary or binary string, depending on
     whether the arguments are nonbinary or binary strings.  The result
     type is *Note `TEXT': blob. or *Note `BLOB': blob. unless
     `group_concat_max_len' is less than or equal to 512, in which case
     the result type is *Note `VARCHAR': char. or *Note `VARBINARY':
     binary-varbinary.

     See also `CONCAT()' and `CONCAT_WS()': *Note string-functions::.

   * `MAX([DISTINCT] EXPR)'

     Returns the maximum value of EXPR.  `MAX()' may take a string
     argument; in such cases, it returns the maximum string value. See
     *Note mysql-indexes::. The `DISTINCT' keyword can be used to find
     the maximum of the distinct values of EXPR, however, this produces
     the same result as omitting `DISTINCT'.

     `MAX()' returns `NULL' if there were no matching rows.


          mysql> SELECT student_name, MIN(test_score), MAX(test_score)
              ->        FROM student
              ->        GROUP BY student_name;

     For `MAX()', MySQL currently compares *Note `ENUM': enum. and
     *Note `SET': set. columns by their string value rather than by the
     string's relative position in the set. This differs from how
     `ORDER BY' compares them. This is expected to be rectified in a
     future MySQL release.

   * `MIN([DISTINCT] EXPR)'

     Returns the minimum value of EXPR.  `MIN()' may take a string
     argument; in such cases, it returns the minimum string value. See
     *Note mysql-indexes::. The `DISTINCT' keyword can be used to find
     the minimum of the distinct values of EXPR, however, this produces
     the same result as omitting `DISTINCT'.

     `MIN()' returns `NULL' if there were no matching rows.


          mysql> SELECT student_name, MIN(test_score), MAX(test_score)
              ->        FROM student
              ->        GROUP BY student_name;

     For `MIN()', MySQL currently compares *Note `ENUM': enum. and
     *Note `SET': set. columns by their string value rather than by the
     string's relative position in the set. This differs from how
     `ORDER BY' compares them. This is expected to be rectified in a
     future MySQL release.

   * `STD(EXPR)'

     Returns the population standard deviation of EXPR. This is an
     extension to standard SQL. The standard SQL function
     `STDDEV_POP()' can be used instead.

     This function returns `NULL' if there were no matching rows.

   * `STDDEV(EXPR)'

     Returns the population standard deviation of EXPR. This function
     is provided for compatibility with Oracle. The standard SQL
     function `STDDEV_POP()' can be used instead.

     This function returns `NULL' if there were no matching rows.

   * `STDDEV_POP(EXPR)'

     Returns the population standard deviation of EXPR (the square root
     of `VAR_POP()'). You can also use `STD()' or `STDDEV()', which are
     equivalent but not standard SQL.

     `STDDEV_POP()' returns `NULL' if there were no matching rows.

   * `STDDEV_SAMP(EXPR)'

     Returns the sample standard deviation of EXPR (the square root of
     `VAR_SAMP()'.

     `STDDEV_SAMP()' returns `NULL' if there were no matching rows.

   * `SUM([DISTINCT] EXPR)'

     Returns the sum of EXPR. If the return set has no rows, `SUM()'
     returns `NULL'. The `DISTINCT' keyword can be used to sum only the
     distinct values of EXPR.

     `SUM()' returns `NULL' if there were no matching rows.

   * `VAR_POP(EXPR)'

     Returns the population standard variance of EXPR. It considers
     rows as the whole population, not as a sample, so it has the
     number of rows as the denominator. You can also use `VARIANCE()',
     which is equivalent but is not standard SQL.

     `VAR_POP()' returns `NULL' if there were no matching rows.

   * `VAR_SAMP(EXPR)'

     Returns the sample variance of EXPR. That is, the denominator is
     the number of rows minus one.

     `VAR_SAMP()' returns `NULL' if there were no matching rows.

   * `VARIANCE(EXPR)'

     Returns the population standard variance of EXPR. This is an
     extension to standard SQL. The standard SQL function `VAR_POP()'
     can be used instead.

     `VARIANCE()' returns `NULL' if there were no matching rows.


File: manual.info,  Node: group-by-modifiers,  Next: group-by-extensions,  Prev: group-by-functions,  Up: group-by-functions-and-modifiers

12.17.2 GROUP BY Modifiers
--------------------------

The `GROUP BY' clause permits a `WITH ROLLUP' modifier that causes
extra rows to be added to the summary output. These rows represent
higher-level (or super-aggregate) summary operations. `ROLLUP' thus
enables you to answer questions at multiple levels of analysis with a
single query. It can be used, for example, to provide support for OLAP
(Online Analytical Processing) operations.

Suppose that a table named `sales' has `year', `country', `product',
and `profit' columns for recording sales profitability:


     CREATE TABLE sales
     (
         year    INT NOT NULL,
         country VARCHAR(20) NOT NULL,
         product VARCHAR(32) NOT NULL,
         profit  INT
     );

The table's contents can be summarized per year with a simple `GROUP
BY' like this:


     mysql> SELECT year, SUM(profit) FROM sales GROUP BY year;
     +------+-------------+
     | year | SUM(profit) |
     +------+-------------+
     | 2000 |        4525 |
     | 2001 |        3010 |
     +------+-------------+

This output shows the total profit for each year, but if you also want
to determine the total profit summed over all years, you must add up
the individual values yourself or run an additional query.

Or you can use `ROLLUP', which provides both levels of analysis with a
single query. Adding a `WITH ROLLUP' modifier to the `GROUP BY' clause
causes the query to produce another row that shows the grand total over
all year values:


     mysql> SELECT year, SUM(profit) FROM sales GROUP BY year WITH ROLLUP;
     +------+-------------+
     | year | SUM(profit) |
     +------+-------------+
     | 2000 |        4525 |
     | 2001 |        3010 |
     | NULL |        7535 |
     +------+-------------+

The grand total super-aggregate line is identified by the value `NULL'
in the `year' column.

`ROLLUP' has a more complex effect when there are multiple `GROUP BY'
columns. In this case, each time there is a `break' (change in value) in
any but the last grouping column, the query produces an extra
super-aggregate summary row.

For example, without `ROLLUP', a summary on the `sales' table based on
`year', `country', and `product' might look like this:


     mysql> SELECT year, country, product, SUM(profit)
         -> FROM sales
         -> GROUP BY year, country, product;
     +------+---------+------------+-------------+
     | year | country | product    | SUM(profit) |
     +------+---------+------------+-------------+
     | 2000 | Finland | Computer   |        1500 |
     | 2000 | Finland | Phone      |         100 |
     | 2000 | India   | Calculator |         150 |
     | 2000 | India   | Computer   |        1200 |
     | 2000 | USA     | Calculator |          75 |
     | 2000 | USA     | Computer   |        1500 |
     | 2001 | Finland | Phone      |          10 |
     | 2001 | USA     | Calculator |          50 |
     | 2001 | USA     | Computer   |        2700 |
     | 2001 | USA     | TV         |         250 |
     +------+---------+------------+-------------+

The output indicates summary values only at the year/country/product
level of analysis. When `ROLLUP' is added, the query produces several
extra rows:


     mysql> SELECT year, country, product, SUM(profit)
         -> FROM sales
         -> GROUP BY year, country, product WITH ROLLUP;
     +------+---------+------------+-------------+
     | year | country | product    | SUM(profit) |
     +------+---------+------------+-------------+
     | 2000 | Finland | Computer   |        1500 |
     | 2000 | Finland | Phone      |         100 |
     | 2000 | Finland | NULL       |        1600 |
     | 2000 | India   | Calculator |         150 |
     | 2000 | India   | Computer   |        1200 |
     | 2000 | India   | NULL       |        1350 |
     | 2000 | USA     | Calculator |          75 |
     | 2000 | USA     | Computer   |        1500 |
     | 2000 | USA     | NULL       |        1575 |
     | 2000 | NULL    | NULL       |        4525 |
     | 2001 | Finland | Phone      |          10 |
     | 2001 | Finland | NULL       |          10 |
     | 2001 | USA     | Calculator |          50 |
     | 2001 | USA     | Computer   |        2700 |
     | 2001 | USA     | TV         |         250 |
     | 2001 | USA     | NULL       |        3000 |
     | 2001 | NULL    | NULL       |        3010 |
     | NULL | NULL    | NULL       |        7535 |
     +------+---------+------------+-------------+

For this query, adding `ROLLUP' causes the output to include summary
information at four levels of analysis, not just one. Here is how to
interpret the `ROLLUP' output:

   * Following each set of product rows for a given year and country,
     an extra summary row is produced showing the total for all
     products. These rows have the `product' column set to `NULL'.

   * Following each set of rows for a given year, an extra summary row
     is produced showing the total for all countries and products.
     These rows have the `country' and `products' columns set to `NULL'.

   * Finally, following all other rows, an extra summary row is
     produced showing the grand total for all years, countries, and
     products. This row has the `year', `country', and `products'
     columns set to `NULL'.

*Other Considerations When using ROLLUP*

The following items list some behaviors specific to the MySQL
implementation of `ROLLUP'.

When you use `ROLLUP', you cannot also use an `ORDER BY' clause to sort
the results. In other words, `ROLLUP' and `ORDER BY' are mutually
exclusive. However, you still have some control over sort order. `GROUP
BY' in MySQL sorts results, and you can use explicit `ASC' and `DESC'
keywords with columns named in the `GROUP BY' list to specify sort
order for individual columns. (The higher-level summary rows added by
`ROLLUP' still appear after the rows from which they are calculated,
regardless of the sort order.)

`LIMIT' can be used to restrict the number of rows returned to the
client. `LIMIT' is applied after `ROLLUP', so the limit applies against
the extra rows added by `ROLLUP'. For example:


     mysql> SELECT year, country, product, SUM(profit)
         -> FROM sales
         -> GROUP BY year, country, product WITH ROLLUP
         -> LIMIT 5;
     +------+---------+------------+-------------+
     | year | country | product    | SUM(profit) |
     +------+---------+------------+-------------+
     | 2000 | Finland | Computer   |        1500 |
     | 2000 | Finland | Phone      |         100 |
     | 2000 | Finland | NULL       |        1600 |
     | 2000 | India   | Calculator |         150 |
     | 2000 | India   | Computer   |        1200 |
     +------+---------+------------+-------------+

Using `LIMIT' with `ROLLUP' may produce results that are more difficult
to interpret, because you have less context for understanding the
super-aggregate rows.

The `NULL' indicators in each super-aggregate row are produced when the
row is sent to the client. The server looks at the columns named in the
`GROUP BY' clause following the leftmost one that has changed value. For
any column in the result set with a name that is a lexical match to any
of those names, its value is set to `NULL'. (If you specify grouping
columns by column number, the server identifies which columns to set to
`NULL' by number.)

Because the `NULL' values in the super-aggregate rows are placed into
the result set at such a late stage in query processing, you cannot
test them as `NULL' values within the query itself. For example, you
cannot add `HAVING product IS NULL' to the query to eliminate from the
output all but the super-aggregate rows.

On the other hand, the `NULL' values do appear as `NULL' on the client
side and can be tested as such using any MySQL client programming
interface.

MySQL permits a column that does not appear in the `GROUP BY' list to
be named in the select list.  In this case, the server is free to
choose any value from this nonaggregated column in summary rows, and
this includes the extra rows added by `WITH ROLLUP'. For example, in
the following query, `country' is a nonaggregated column that does not
appear in the `GROUP BY' list and values chosen for this column are
indeterminate:


     mysql> SELECT year, country, SUM(profit)
         -> FROM sales GROUP BY year WITH ROLLUP;
     +------+---------+-------------+
     | year | country | SUM(profit) |
     +------+---------+-------------+
     | 2000 | India   |        4525 |
     | 2001 | USA     |        3010 |
     | NULL | USA     |        7535 |
     +------+---------+-------------+

This behavior occurs if the `ONLY_FULL_GROUP_BY' SQL mode is not
enabled. If that mode is enabled, the server rejects the query as
illegal because `country' is not listed in the `GROUP BY' clause. For
more information about nonaggregated columns and `GROUP BY', see *Note
group-by-extensions::.


File: manual.info,  Node: group-by-extensions,  Prev: group-by-modifiers,  Up: group-by-functions-and-modifiers

12.17.3 MySQL Extensions to GROUP BY
------------------------------------

In standard SQL, a query that includes a `GROUP BY' clause cannot refer
to nonaggregated columns in the select list that are not named in the
`GROUP BY' clause. For example, this query is illegal in standard SQL
because the `name' column in the select list does not appear in the
`GROUP BY':


     SELECT o.custid, c.name, MAX(o.payment)
       FROM orders AS o, customers AS c
       WHERE o.custid = c.custid
       GROUP BY o.custid;

For the query to be legal, the `name' column must be omitted from the
select list or named in the `GROUP BY' clause.

MySQL extends the use of `GROUP BY' so that the select list can refer
to nonaggregated columns not named in the `GROUP BY' clause. This means
that the preceding query is legal in MySQL. You can use this feature to
get better performance by avoiding unnecessary column sorting and
grouping. However, this is useful primarily when all values in each
nonaggregated column not named in the `GROUP BY' are the same for each
group. The server is free to choose any value from each group, so
unless they are the same, the values chosen are indeterminate.
Furthermore, the selection of values from each group cannot be
influenced by adding an `ORDER BY' clause. Sorting of the result set
occurs after values have been chosen, and `ORDER BY' does not affect
which values within each group the server chooses.

A similar MySQL extension applies to the `HAVING' clause. In standard
SQL, a query that includes a `GROUP BY' clause cannot refer to
nonaggregated columns in the `HAVING' clause that are not named in the
`GROUP BY' clause. A MySQL extension permits references to such columns
to simplify calculations. This extension assumes that the nongrouped
columns will have the same group-wise values. Otherwise, the result is
indeterminate.

To disable the MySQL `GROUP BY' extension, enable the
`ONLY_FULL_GROUP_BY' SQL mode. This enables standard SQL behavior:
Columns not named in the `GROUP BY' clause cannot be used in the select
list or `HAVING' clause unless enclosed in an aggregate function.

`ONLY_FULL_GROUP_BY' also affects use of aliases in the `HAVING'
clauses.  For example, the following query returns `name' values that
occur only once in table `orders':


     SELECT name, COUNT(name) FROM orders
       GROUP BY name
       HAVING COUNT(name) = 1;

MySQL extends this behavior to permit the use of an alias in the
`HAVING' clause for the aggregated column:


     SELECT name, COUNT(name) AS c FROM orders
       GROUP BY name
       HAVING c = 1;

Enabling `ONLY_FULL_GROUP_BY' disables this MySQL extension and a
`non-grouping field 'c' is used in HAVING clause' error occurs because
the column `c' in the `HAVING' clause is not enclosed in an aggregate
function (instead, it _is_ an aggregate function).

The select list extension also applies to `ORDER BY'. That is, you can
refer to nonaggregated columns in the `ORDER BY' clause that do not
appear in the `GROUP BY' clause. (However, as mentioned previously,
`ORDER BY' does not affect which values are chosen from nonaggregated
columns; it only sorts them after they have been chosen.) This
extension does not apply if the `ONLY_FULL_GROUP_BY' SQL mode is
enabled.

In some cases, you can use `MIN()' and `MAX()' to obtain a specific
column value even if it is not unique. If the `sort' column contains
integers no larger than 6 digits, the following query gives the value of
`column' from the row containing the smallest `sort' value:


     SUBSTR(MIN(CONCAT(LPAD(sort,6,'0'),column)),7)

See *Note example-maximum-column-group-row::.

If you are trying to follow standard SQL, you cannot use expressions in
`GROUP BY' clauses. As a workaround, use an alias for the expression:


     SELECT id, FLOOR(value/100) AS val
       FROM TBL_NAME
       GROUP BY id, val;

MySQL permits expressions in `GROUP BY' clauses, so the alias is
unnecessary:


     SELECT id, FLOOR(value/100)
       FROM TBL_NAME
       GROUP BY id, FLOOR(value/100);


File: manual.info,  Node: precision-math,  Prev: group-by-functions-and-modifiers,  Up: functions

12.18 Precision Math
====================

* Menu:

* precision-math-numbers::       Types of Numeric Values
* precision-math-decimal-characteristics::  DECIMAL Data Type Characteristics
* precision-math-expressions::   Expression Handling
* precision-math-rounding::      Rounding Behavior
* precision-math-examples::      Precision Math Examples

MySQL 5.1 provides support for precision math: numeric value handling
that results in extremely accurate results and a high degree control
over invalid values. Precision math is based on these two features:

   * SQL modes that control how strict the server is about accepting or
     rejecting invalid data.

   * The MySQL library for fixed-point arithmetic.

These features have several implications for numeric operations and
provide a high degree of compliance with standard SQL:

   * *Precise calculations*: For exact-value numbers, calculations do
     not introduce floating-point errors. Instead, exact precision is
     used. For example, MySQL treats a number such as `.0001' as an
     exact value rather than as an approximation, and summing it 10,000
     times produces a result of exactly `1', not a value that is merely
     `close' to 1.

   * *Well-defined rounding behavior*: For exact-value numbers, the
     result of `ROUND()' depends on its argument, not on environmental
     factors such as how the underlying C library works.

   * *Platform independence*: Operations on exact numeric values are
     the same across different platforms such as Windows and Unix.

   * *Control over handling of invalid values*: Overflow and division
     by zero are detectable and can be treated as errors. For example,
     you can treat a value that is too large for a column as an error
     rather than having the value truncated to lie within the range of
     the column's data type. Similarly, you can treat division by zero
     as an error rather than as an operation that produces a result of
     `NULL'. The choice of which approach to take is determined by the
     setting of the server SQL mode.

The following discussion covers several aspects of how precision math
works, including possible incompatibilities with older applications. At
the end, some examples are given that demonstrate how MySQL 5.1 handles
numeric operations precisely. For information about controlling the SQL
mode, see *Note sql-mode::.


File: manual.info,  Node: precision-math-numbers,  Next: precision-math-decimal-characteristics,  Prev: precision-math,  Up: precision-math

12.18.1 Types of Numeric Values
-------------------------------

The scope of precision math for exact-value operations includes the
exact-value data types (integer and *Note `DECIMAL': fixed-point-types.
types) and exact-value numeric literals. Approximate-value data types
and numeric literals are handled as floating-point numbers.

Exact-value numeric literals have an integer part or fractional part,
or both. They may be signed. Examples: `1', `.2', `3.4', `-5', `-6.78',
`+9.10'.

Approximate-value numeric literals are represented in scientific
notation with a mantissa and exponent. Either or both parts may be
signed. Examples: `1.2E3', `1.2E-3', `-1.2E3', `-1.2E-3'.

Two numbers that look similar may be treated differently. For example,
`2.34' is an exact-value (fixed-point) number, whereas `2.34E0' is an
approximate-value (floating-point) number.

The *Note `DECIMAL': fixed-point-types. data type is a fixed-point type
and calculations are exact. In MySQL, the *Note `DECIMAL':
fixed-point-types. type has several synonyms: *Note `NUMERIC':
fixed-point-types, *Note `DEC': fixed-point-types, *Note `FIXED':
fixed-point-types. The integer types also are exact-value types.

The *Note `FLOAT': floating-point-types. and *Note `DOUBLE':
floating-point-types. data types are floating-point types and
calculations are approximate. In MySQL, types that are synonymous with
*Note `FLOAT': floating-point-types. or *Note `DOUBLE':
floating-point-types. are *Note `DOUBLE PRECISION':
floating-point-types. and *Note `REAL': floating-point-types.


File: manual.info,  Node: precision-math-decimal-characteristics,  Next: precision-math-expressions,  Prev: precision-math-numbers,  Up: precision-math

12.18.2 DECIMAL Data Type Characteristics
-----------------------------------------

This section discusses the characteristics of the *Note `DECIMAL':
fixed-point-types. data type (and its synonyms) in MySQL 5.1, with
particular regard to the following topics:

   * Maximum number of digits

   * Storage format

   * Storage requirements

   * The nonstandard MySQL extension to the upper range of *Note
     `DECIMAL': fixed-point-types. columns

Possible incompatibilities with applications that are written for older
versions of MySQL (prior to 5.0.3) are noted throughout this section.

The declaration syntax for a *Note `DECIMAL': fixed-point-types. column
is `DECIMAL(M,D)'.  The ranges of values for the arguments in MySQL 5.1
are as follows:

   * M is the maximum number of digits (the precision). It has a range
     of 1 to 65. (Older versions of MySQL permitted a range of 1 to
     254.)

   * D is the number of digits to the right of the decimal point (the
     scale). It has a range of 0 to 30 and must be no larger than M.

The maximum value of 65 for M means that calculations on *Note
`DECIMAL': fixed-point-types. values are accurate up to 65 digits. This
limit of 65 digits of precision also applies to exact-value numeric
literals, so the maximum range of such literals differs from before.
(In older versions of MySQL, decimal values could have up to 254
digits. However, calculations were done using floating-point and thus
were approximate, not exact.)

Values for *Note `DECIMAL': fixed-point-types. columns in MySQL 5.1 are
stored using a binary format that packs nine decimal digits into 4
bytes. The storage requirements for the integer and fractional parts of
each value are determined separately. Each multiple of nine digits
requires 4 bytes, and any remaining digits left over require some
fraction of 4 bytes. The storage required for remaining digits is given
by the following table.

This table lists the number of bytes required for remaining/leftover
digits.

Leftover Digits    Number of Bytes
0                  0
1-2                1
3-4                2
5-6                3
7-9                4

For example, a `DECIMAL(18,9)' column has nine digits on either side of
the decimal point, so the integer part and the fractional part each
require 4 bytes. A `DECIMAL(20,6)' column has fourteen integer digits
and six fractional digits. The integer digits require four bytes for
nine of the digits and 3 bytes for the remaining five digits. The six
fractional digits require 3 bytes.

Unlike some older versions of MySQL, *Note `DECIMAL':
fixed-point-types. columns in MySQL 5.1 do not store a leading `+'
character or `-' character or leading `0' digits. If you insert
`+0003.1' into a `DECIMAL(5,1)' column, it is stored as `3.1'. For
negative numbers, a literal `-' character is not stored.  Applications
that rely on the older behavior must be modified to account for this
change.

*Note `DECIMAL': fixed-point-types. columns in MySQL 5.1 do not permit
values larger than the range implied by the column definition. For
example, a `DECIMAL(3,0)' column supports a range of `-999' to `999'. A
`DECIMAL(M,D)' column permits at most M - D digits to the left of the
decimal point. This is not compatible with applications relying on older
versions of MySQL that permitted storing an extra digit in lieu of a
`+' sign.

The SQL standard requires that the precision of `NUMERIC(M,D)' be
_exactly_ M digits. For `DECIMAL(M,D)', the standard requires a
precision of at least M digits but permits more. In MySQL,
`DECIMAL(M,D)' and `NUMERIC(M,D)' are the same, and both have a
precision of exactly M digits.

For more detailed information about porting applications that rely on
the old treatment of the *Note `DECIMAL': fixed-point-types.  data
type, see the `MySQL 5.0 Reference Manual'.


File: manual.info,  Node: precision-math-expressions,  Next: precision-math-rounding,  Prev: precision-math-decimal-characteristics,  Up: precision-math

12.18.3 Expression Handling
---------------------------

With precision math, exact-value numbers are used as given whenever
possible. For example, numbers in comparisons are used exactly as given
without a change in value. In strict SQL mode, for *Note `INSERT':
insert. into a column with an exact data type (*Note `DECIMAL':
fixed-point-types. or integer), a number is inserted with its exact
value if it is within the column range. When retrieved, the value
should be the same as what was inserted. (If strict SQL mode is not
enabled, truncation for *Note `INSERT': insert. is permissible.)

Handling of a numeric expression depends on what kind of values the
expression contains:

   * If any approximate values are present, the expression is
     approximate and is evaluated using floating-point arithmetic.

   * If no approximate values are present, the expression contains only
     exact values. If any exact value contains a fractional part (a
     value following the decimal point), the expression is evaluated
     using *Note `DECIMAL': fixed-point-types. exact arithmetic and has
     a precision of 65 digits. The term `exact' is subject to the
     limits of what can be represented in binary. For example, `1.0/3.0'
     can be approximated in decimal notation as `.333...', but not
     written as an exact number, so `(1.0/3.0)*3.0' does not evaluate
     to exactly `1.0'.

   * Otherwise, the expression contains only integer values. The
     expression is exact and is evaluated using integer arithmetic and
     has a precision the same as *Note `BIGINT': integer-types. (64
     bits).

If a numeric expression contains any strings, they are converted to
double-precision floating-point values and the expression is
approximate.

Inserts into numeric columns are affected by the SQL mode, which is
controlled by the `sql_mode' system variable. (See *Note sql-mode::.)
The following discussion mentions strict mode (selected by the
`STRICT_ALL_TABLES' or `STRICT_TRANS_TABLES' mode values) and
`ERROR_FOR_DIVISION_BY_ZERO'.  To turn on all restrictions, you can
simply use `TRADITIONAL' mode, which includes both strict mode values
and `ERROR_FOR_DIVISION_BY_ZERO':


     mysql> SET sql_mode='TRADITIONAL';

If a number is inserted into an exact type column (*Note `DECIMAL':
fixed-point-types. or integer), it is inserted with its exact value if
it is within the column range.

If the value has too many digits in the fractional part, rounding
occurs and a warning is generated. Rounding is done as described in
*Note precision-math-rounding::.

If the value has too many digits in the integer part, it is too large
and is handled as follows:

   * If strict mode is not enabled, the value is truncated to the
     nearest legal value and a warning is generated.

   * If strict mode is enabled, an overflow error occurs.

Underflow is not detected, so underflow handling is undefined.

For inserts of strings into numeric columns, conversion from string to
number is handled as follows if the string has nonnumeric contents:

   * A string that does not begin with a number cannot be used as a
     number and produces an error in strict mode, or a warning
     otherwise. This includes the empty string.

   * A string that begins with a number can be converted, but the
     trailing nonnumeric portion is truncated. If the truncated portion
     contains anything other than spaces, this produces an error in
     strict mode, or a warning otherwise.

By default, division by zero produces a result of `NULL' and no
warning. By setting the SQL mode appropriately, division by zero can be
restricted.

With the `ERROR_FOR_DIVISION_BY_ZERO' SQL mode enabled, MySQL handles
division by zero differently:

   * If strict mode is not enabled, a warning occurs.

   * If strict mode is enabled, inserts and updates involving division
     by zero are prohibited, and an error occurs.

In other words, inserts and updates involving expressions that perform
division by zero can be treated as errors, but this requires
`ERROR_FOR_DIVISION_BY_ZERO' in addition to strict mode.

Suppose that we have this statement:


     INSERT INTO t SET i = 1/0;

This is what happens for combinations of strict and
`ERROR_FOR_DIVISION_BY_ZERO' modes.

This table shows what happens for combinations of strict and
`ERROR_FOR_DIVISION_BY_ZERO' modes.

`sql_mode' Value                     Result
`''' (Default)                       No warning, no error; `i' is set to
                                     `NULL'.
strict                               No warning, no error; `i' is set to
                                     `NULL'.
`ERROR_FOR_DIVISION_BY_ZERO'         Warning, no error; `i' is set to
                                     `NULL'.
strict,`ERROR_FOR_DIVISION_BY_ZERO'  Error condition; no row is inserted.


File: manual.info,  Node: precision-math-rounding,  Next: precision-math-examples,  Prev: precision-math-expressions,  Up: precision-math

12.18.4 Rounding Behavior
-------------------------

This section discusses precision math rounding for the `ROUND()'
function and for inserts into columns with exact-value types (*Note
`DECIMAL': fixed-point-types. and integer).

The `ROUND()' function rounds differently depending on whether its
argument is exact or approximate:

   * For exact-value numbers, `ROUND()' uses the `round half up' rule:
     A value with a fractional part of .5 or greater is rounded up to
     the next integer if positive or down to the next integer if
     negative. (In other words, it is rounded away from zero.) A value
     with a fractional part less than .5 is rounded down to the next
     integer if positive or up to the next integer if negative.

   * For approximate-value numbers, the result depends on the C
     library. On many systems, this means that `ROUND()' uses the `round
     to nearest even' rule: A value with any fractional part is rounded
     to the nearest even integer.

The following example shows how rounding differs for exact and
approximate values:


     mysql> SELECT ROUND(2.5), ROUND(25E-1);
     +------------+--------------+
     | ROUND(2.5) | ROUND(25E-1) |
     +------------+--------------+
     | 3          |            2 |
     +------------+--------------+

For inserts into a *Note `DECIMAL': fixed-point-types. or integer
column, the target is an exact data type, so rounding uses `round half
away from zero,' regardless of whether the value to be inserted is
exact or approximate:


     mysql> CREATE TABLE t (d DECIMAL(10,0));
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO t VALUES(2.5),(2.5E0);
     Query OK, 2 rows affected, 2 warnings (0.00 sec)
     Records: 2  Duplicates: 0  Warnings: 2

     mysql> SELECT d FROM t;
     +------+
     | d    |
     +------+
     | 3    |
     | 3    |
     +------+


File: manual.info,  Node: precision-math-examples,  Prev: precision-math-rounding,  Up: precision-math

12.18.5 Precision Math Examples
-------------------------------

This section provides some examples that show precision math query
results in MySQL 5.1. These examples demonstrate the principles
described in *Note precision-math-expressions::, and *Note
precision-math-rounding::.

*Example 1*. Numbers are used with their exact value as given when
possible:


     mysql> SELECT (.1 + .2) = .3;
     +----------------+
     | (.1 + .2) = .3 |
     +----------------+
     |              1 |
     +----------------+

For floating-point values, results are inexact:


     mysql> SELECT (.1E0 + .2E0) = .3E0;
     +----------------------+
     | (.1E0 + .2E0) = .3E0 |
     +----------------------+
     |                    0 |
     +----------------------+

Another way to see the difference in exact and approximate value
handling is to add a small number to a sum many times. Consider the
following stored procedure, which adds `.0001' to a variable 1,000
times.


     CREATE PROCEDURE p ()
     BEGIN
       DECLARE i INT DEFAULT 0;
       DECLARE d DECIMAL(10,4) DEFAULT 0;
       DECLARE f FLOAT DEFAULT 0;
       WHILE i < 10000 DO
         SET d = d + .0001;
         SET f = f + .0001E0;
         SET i = i + 1;
       END WHILE;
       SELECT d, f;
     END;

The sum for both `d' and `f' logically should be 1, but that is true
only for the decimal calculation. The floating-point calculation
introduces small errors:


     +--------+------------------+
     | d      | f                |
     +--------+------------------+
     | 1.0000 | 0.99999999999991 |
     +--------+------------------+

*Example 2*. Multiplication is performed with the scale required by
standard SQL. That is, for two numbers X1 and X2 that have scale S1 and
S2, the scale of the result is `S1 + S2':


     mysql> SELECT .01 * .01;
     +-----------+
     | .01 * .01 |
     +-----------+
     | 0.0001    |
     +-----------+

*Example 3*. Rounding behavior for exact-value numbers is well-defined:

Rounding behavior (for example, with the `ROUND()' function) is
independent of the implementation of the underlying C library, which
means that results are consistent from platform to platform.

   * Rounding for exact-value columns (*Note `DECIMAL':
     fixed-point-types. and integer) and exact-valued numbers uses the
     `round half away from zero' rule. Values with a fractional part of
     .5 or greater are rounded away from zero to the nearest integer, as
     shown here:


          mysql> SELECT ROUND(2.5), ROUND(-2.5);
          +------------+-------------+
          | ROUND(2.5) | ROUND(-2.5) |
          +------------+-------------+
          | 3          | -3          |
          +------------+-------------+

   * Rounding for floating-point values uses the C library, which on
     many systems uses the `round to nearest even' rule. Values with
     any fractional part on such systems are rounded to the nearest
     even integer:


          mysql> SELECT ROUND(2.5E0), ROUND(-2.5E0);
          +--------------+---------------+
          | ROUND(2.5E0) | ROUND(-2.5E0) |
          +--------------+---------------+
          |            2 |            -2 |
          +--------------+---------------+

*Example 4*. In strict mode, inserting a value that is out of range for
a column causes an error, rather than truncation to a legal value.

When MySQL is not running in strict mode, truncation to a legal value
occurs:


     mysql> SET sql_mode='';
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE TABLE t (i TINYINT);
     Query OK, 0 rows affected (0.01 sec)

     mysql> INSERT INTO t SET i = 128;
     Query OK, 1 row affected, 1 warning (0.00 sec)

     mysql> SELECT i FROM t;
     +------+
     | i    |
     +------+
     |  127 |
     +------+
     1 row in set (0.00 sec)

However, an error occurs if strict mode is in effect:


     mysql> SET sql_mode='STRICT_ALL_TABLES';
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE TABLE t (i TINYINT);
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO t SET i = 128;
     ERROR 1264 (22003): Out of range value adjusted for column 'i' at row 1

     mysql> SELECT i FROM t;
     Empty set (0.00 sec)

*Example 5*: In strict mode and with `ERROR_FOR_DIVISION_BY_ZERO' set,
division by zero causes an error, not a result of `NULL'.

In nonstrict mode, division by zero has a result of `NULL':


     mysql> SET sql_mode='';
     Query OK, 0 rows affected (0.01 sec)

     mysql> CREATE TABLE t (i TINYINT);
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO t SET i = 1 / 0;
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT i FROM t;
     +------+
     | i    |
     +------+
     | NULL |
     +------+
     1 row in set (0.03 sec)

However, division by zero is an error if the proper SQL modes are in
effect:


     mysql> SET sql_mode='STRICT_ALL_TABLES,ERROR_FOR_DIVISION_BY_ZERO';
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE TABLE t (i TINYINT);
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO t SET i = 1 / 0;
     ERROR 1365 (22012): Division by 0

     mysql> SELECT i FROM t;
     Empty set (0.01 sec)

*Example 6*. Exact-value literals are evaluated as exact values.

Prior to MySQL 5.0.3, exact-value and approximate-value literals both
are evaluated as double-precision floating-point values:


     mysql> SELECT VERSION();
     +------------+
     | VERSION()  |
     +------------+
     | 4.1.18-log |
     +------------+
     1 row in set (0.01 sec)

     mysql> CREATE TABLE t SELECT 2.5 AS a, 25E-1 AS b;
     Query OK, 1 row affected (0.07 sec)
     Records: 1  Duplicates: 0  Warnings: 0

     mysql> DESCRIBE t;
     +-------+-------------+------+-----+---------+-------+
     | Field | Type        | Null | Key | Default | Extra |
     +-------+-------------+------+-----+---------+-------+
     | a     | double(3,1) |      |     | 0.0     |       |
     | b     | double      |      |     | 0       |       |
     +-------+-------------+------+-----+---------+-------+
     2 rows in set (0.04 sec)

As of MySQL 5.0.3, the approximate-value literal is evaluated using
floating point, but the exact-value literal is handled as *Note
`DECIMAL': fixed-point-types.:


     mysql> SELECT VERSION();
     +-----------------+
     | VERSION()       |
     +-----------------+
     | 5.1.6-alpha-log |
     +-----------------+
     1 row in set (0.11 sec)

     mysql> CREATE TABLE t SELECT 2.5 AS a, 25E-1 AS b;
     Query OK, 1 row affected (0.01 sec)
     Records: 1  Duplicates: 0  Warnings: 0

     mysql> DESCRIBE t;
     +-------+-----------------------+------+-----+---------+-------+
     | Field | Type                  | Null | Key | Default | Extra |
     +-------+-----------------------+------+-----+---------+-------+
     | a     | decimal(2,1) unsigned | NO   |     | 0.0     |       |
     | b     | double                | NO   |     | 0       |       |
     +-------+-----------------------+------+-----+---------+-------+
     2 rows in set (0.01 sec)

*Example 7*. If the argument to an aggregate function is an exact
numeric type, the result is also an exact numeric type, with a scale at
least that of the argument.

Consider these statements:


     mysql> CREATE TABLE t (i INT, d DECIMAL, f FLOAT);
     mysql> INSERT INTO t VALUES(1,1,1);
     mysql> CREATE TABLE y SELECT AVG(i), AVG(d), AVG(f) FROM t;

Before MySQL 5.0.3, the result is a double no matter the argument type:


     mysql> DESCRIBE y;
     +--------+--------------+------+-----+---------+-------+
     | Field  | Type         | Null | Key | Default | Extra |
     +--------+--------------+------+-----+---------+-------+
     | AVG(i) | double(17,4) | YES  |     | NULL    |       |
     | AVG(d) | double(17,4) | YES  |     | NULL    |       |
     | AVG(f) | double       | YES  |     | NULL    |       |
     +--------+--------------+------+-----+---------+-------+

As of MySQL 5.0.3, the result is a double only for the floating-point
argument. For exact type arguments, the result is also an exact type:


     mysql> DESCRIBE y;
     +--------+---------------+------+-----+---------+-------+
     | Field  | Type          | Null | Key | Default | Extra |
     +--------+---------------+------+-----+---------+-------+
     | AVG(i) | decimal(14,4) | YES  |     | NULL    |       |
     | AVG(d) | decimal(14,4) | YES  |     | NULL    |       |
     | AVG(f) | double        | YES  |     | NULL    |       |
     +--------+---------------+------+-----+---------+-------+

The result is a double only for the floating-point argument. For exact
type arguments, the result is also an exact type.


File: manual.info,  Node: sql-syntax,  Next: storage-engines,  Prev: functions,  Up: Top

13 SQL Statement Syntax
***********************

* Menu:

* sql-syntax-data-definition::   Data Definition Statements
* sql-syntax-data-manipulation::  Data Manipulation Statements
* sql-syntax-transactions::      MySQL Transactional and Locking Statements
* sql-syntax-replication::       Replication Statements
* sql-syntax-prepared-statements::  SQL Syntax for Prepared Statements
* sql-syntax-compound-statements::  MySQL Compound-Statement Syntax
* sql-syntax-server-administration::  Database Administration Statements
* sql-syntax-utility::           MySQL Utility Statements

This chapter describes the syntax for the SQL
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_sql)
statements supported by MySQL.


File: manual.info,  Node: sql-syntax-data-definition,  Next: sql-syntax-data-manipulation,  Prev: sql-syntax,  Up: sql-syntax

13.1 Data Definition Statements
===============================

* Menu:

* alter-database::               ALTER DATABASE Syntax
* alter-event::                  ALTER EVENT Syntax
* alter-logfile-group::          ALTER LOGFILE GROUP Syntax
* alter-function::               ALTER FUNCTION Syntax
* alter-procedure::              ALTER PROCEDURE Syntax
* alter-server::                 ALTER SERVER Syntax
* alter-table::                  ALTER TABLE Syntax
* alter-tablespace::             ALTER TABLESPACE Syntax
* alter-view::                   ALTER VIEW Syntax
* create-database::              CREATE DATABASE Syntax
* create-event::                 CREATE EVENT Syntax
* create-function::              CREATE FUNCTION Syntax
* create-index::                 CREATE INDEX Syntax
* create-logfile-group::         CREATE LOGFILE GROUP Syntax
* create-procedure::             CREATE PROCEDURE and CREATE FUNCTION Syntax
* create-server::                CREATE SERVER Syntax
* create-table::                 CREATE TABLE Syntax
* create-tablespace::            CREATE TABLESPACE Syntax
* create-trigger::               CREATE TRIGGER Syntax
* create-view::                  CREATE VIEW Syntax
* drop-database::                DROP DATABASE Syntax
* drop-event::                   DROP EVENT Syntax
* drop-function::                DROP FUNCTION Syntax
* drop-index::                   DROP INDEX Syntax
* drop-logfile-group::           DROP LOGFILE GROUP Syntax
* drop-procedure::               DROP PROCEDURE and DROP FUNCTION Syntax
* drop-server::                  DROP SERVER Syntax
* drop-table::                   DROP TABLE Syntax
* drop-tablespace::              DROP TABLESPACE Syntax
* drop-trigger::                 DROP TRIGGER Syntax
* drop-view::                    DROP VIEW Syntax
* rename-database::              RENAME DATABASE Syntax
* rename-table::                 RENAME TABLE Syntax
* truncate-table::               TRUNCATE TABLE Syntax


File: manual.info,  Node: alter-database,  Next: alter-event,  Prev: sql-syntax-data-definition,  Up: sql-syntax-data-definition

13.1.1 ALTER DATABASE Syntax
----------------------------


     ALTER {DATABASE | SCHEMA} [DB_NAME]
         ALTER_SPECIFICATION ...
     ALTER {DATABASE | SCHEMA} DB_NAME
         UPGRADE DATA DIRECTORY NAME

     ALTER_SPECIFICATION:
         [DEFAULT] CHARACTER SET [=] CHARSET_NAME
       | [DEFAULT] COLLATE [=] COLLATION_NAME

*Note `ALTER DATABASE': alter-database. enables you to change the
overall characteristics of a database. These characteristics are stored
in the `db.opt' file in the database directory. To use *Note `ALTER
DATABASE': alter-database, you need the `ALTER' privilege on the
database.  *Note `ALTER SCHEMA': alter-database. is a synonym for *Note
`ALTER DATABASE': alter-database.

The database name can be omitted from the first syntax, in which case
the statement applies to the default database.

*National Language Characteristics*

The `CHARACTER SET' clause changes the default database character set.
The `COLLATE' clause changes the default database collation. *Note
charset::, discusses character set and collation names.

You can see what character sets and collations are available using,
respectively, the *Note `SHOW CHARACTER SET': show-character-set. and
*Note `SHOW COLLATION': show-collation.  statements. See *Note
show-character-set::, and *Note show-collation::, for more information.

If you change the default character set or collation for a database,
stored routines that use the database defaults must be dropped and
recreated so that they use the new defaults. (In a stored routine,
variables with character data types use the database defaults if the
character set or collation are not specified explicitly. See *Note
create-procedure::.)

*Upgrading from Versions Older than MySQL 5.1*

The syntax that includes the `UPGRADE DATA DIRECTORY NAME' clause was
added in MySQL 5.1.23. It updates the name of the directory associated
with the database to use the encoding implemented in MySQL 5.1 for
mapping database names to database directory names (see *Note
identifier-mapping::). This clause is for use under these conditions:

   * It is intended when upgrading MySQL to 5.1 or later from older
     versions.

   * It is intended to update a database directory name to the current
     encoding format if the name contains special characters that need
     encoding.

   * The statement is used by *Note `mysqlcheck': mysqlcheck. (as
     invoked by *Note `mysql_upgrade': mysql-upgrade.).

For example, if a database in MySQL 5.0 has the name `a-b-c', the name
contains instances of the `-' (dash) character. In MySQL 5.0, the
database directory is also named `a-b-c', which is not necessarily safe
for all file systems. In MySQL 5.1 and later, the same database name is
encoded as `a@002db@002dc' to produce a file system-neutral directory
name.

When a MySQL installation is upgraded to MySQL 5.1 or later from an
older version,the server displays a name such as `a-b-c' (which is in
the old format) as `#mysql50#a-b-c', and you must refer to the name
using the `#mysql50#' prefix. Use `UPGRADE DATA DIRECTORY NAME' in this
case to explicitly tell the server to re-encode the database directory
name to the current encoding format:


     ALTER DATABASE `#mysql50#a-b-c` UPGRADE DATA DIRECTORY NAME;

After executing this statement, you can refer to the database as
`a-b-c' without the special `#mysql50#' prefix.


File: manual.info,  Node: alter-event,  Next: alter-logfile-group,  Prev: alter-database,  Up: sql-syntax-data-definition

13.1.2 ALTER EVENT Syntax
-------------------------


     ALTER
         [DEFINER = { USER | CURRENT_USER }]
         EVENT EVENT_NAME
         [ON SCHEDULE SCHEDULE]
         [ON COMPLETION [NOT] PRESERVE]
         [RENAME TO NEW_EVENT_NAME]
         [ENABLE | DISABLE | DISABLE ON SLAVE]
         [COMMENT 'COMMENT']
         [DO EVENT_BODY]

The *Note `ALTER EVENT': alter-event. statement changes one or more of
the characteristics of an existing event without the need to drop and
recreate it. The syntax for each of the `DEFINER', `ON SCHEDULE', `ON
COMPLETION', `COMMENT', `ENABLE' / `DISABLE', and *Note `DO': do.
clauses is exactly the same as when used with *Note `CREATE EVENT':
create-event. (See *Note create-event::.)

Support for the `DEFINER' clause was added in MySQL 5.1.17.

Beginning with MySQL 5.1.12, this statement requires the `EVENT'
privilege. When a user executes a successful *Note `ALTER EVENT':
alter-event.  statement, that user becomes the definer for the affected
event.

(In MySQL 5.1.11 and earlier, an event could be altered only by its
definer, or by a user having the `SUPER' privilege.)

*Note `ALTER EVENT': alter-event. works only with an existing event:


     mysql> ALTER EVENT no_such_event
          >     ON SCHEDULE
          >       EVERY '2:3' DAY_HOUR;
     `ERROR 1517 (HY000): Unknown event 'no_such_event''

In each of the following examples, assume that the event named
`myevent' is defined as shown here:


     CREATE EVENT myevent
         ON SCHEDULE
           EVERY 6 HOUR
         COMMENT 'A sample comment.'
         DO
           UPDATE myschema.mytable SET mycol = mycol + 1;

The following statement changes the schedule for `myevent' from once
every six hours starting immediately to once every twelve hours,
starting four hours from the time the statement is run:


     ALTER EVENT myevent
         ON SCHEDULE
           EVERY 12 HOUR
         STARTS CURRENT_TIMESTAMP + INTERVAL 4 HOUR;

It is possible to change multiple characteristics of an event in a
single statement. This example changes the SQL statement executed by
`myevent' to one that deletes all records from `mytable'; it also
changes the schedule for the event such that it executes once, one day
after this *Note `ALTER EVENT': alter-event. statement is run.


     ALTER EVENT myevent
         ON SCHEDULE
           AT CURRENT_TIMESTAMP + INTERVAL 1 DAY
         DO
           TRUNCATE TABLE myschema.mytable;

Specify the options in an *Note `ALTER EVENT': alter-event. statement
only for those characteristics that you want to change; omitted options
keep their existing values. This includes any default values for *Note
`CREATE EVENT': create-event. such as `ENABLE'.

To disable `myevent', use this *Note `ALTER EVENT': alter-event.
statement:


     ALTER EVENT myevent
         DISABLE;

The `ON SCHEDULE' clause may use expressions involving built-in MySQL
functions and user variables to obtain any of the TIMESTAMP or INTERVAL
values which it contains. You cannot use stored routines or
user-defined functions in such expressions, and you cannot use any
table references; however, you can use `SELECT FROM DUAL'. This is true
for both *Note `ALTER EVENT': alter-event. and *Note `CREATE EVENT':
create-event. statements. Beginning with MySQL 5.1.13, references to
stored routines, user-defined functions, and tables in such cases are
specifically not permitted, and fail with an error (see Bug #22830).

Although an *Note `ALTER EVENT': alter-event. statement that contains
another *Note `ALTER EVENT': alter-event.  statement in its *Note `DO':
do. clause appears to succeed, when the server attempts to execute the
resulting scheduled event, the execution fails with an error.

To rename an event, use the *Note `ALTER EVENT': alter-event.
statement's `RENAME TO' clause.  This statement renames the event
`myevent' to `yourevent':


     ALTER EVENT myevent
         RENAME TO yourevent;

You can also move an event to a different database using `ALTER EVENT
... RENAME TO ...' and `DB_NAME.EVENT_NAME' notation, as shown here:


     ALTER EVENT olddb.myevent
         RENAME TO newdb.myevent;

To execute the previous statement, the user executing it must have the
`EVENT' privilege on both the `olddb' and `newdb' databases.

*Note*:

There is no `RENAME EVENT' statement.

Beginning with MySQL 5.1.18, a third value may also appear in place of
`ENABLE' or `DISABLE'; `DISABLE ON SLAVE' is used on a replication slave
to indicate an event which was created on the master and replicated to
the slave, but which is not executed on the slave.  Normally, `DISABLE
ON SLAVE' is set automatically as required; however, there are some
circumstances under which you may want or need to change it manually.
See *Note replication-features-invoked::, for more information.


File: manual.info,  Node: alter-logfile-group,  Next: alter-function,  Prev: alter-event,  Up: sql-syntax-data-definition

13.1.3 ALTER LOGFILE GROUP Syntax
---------------------------------


     ALTER LOGFILE GROUP LOGFILE_GROUP
         ADD UNDOFILE 'FILE_NAME'
         [INITIAL_SIZE [=] SIZE]
         [WAIT]
         ENGINE [=] ENGINE_NAME

This statement adds an `UNDO' file named 'FILE_NAME' to an existing log
file group LOGFILE_GROUP. An *Note `ALTER LOGFILE GROUP':
alter-logfile-group. statement has one and only one `ADD UNDOFILE'
clause. No `DROP UNDOFILE' clause is currently supported.

*Note*:

All MySQL Cluster Disk Data objects share the same namespace.  This
means that _each Disk Data object_ must be uniquely named (and not
merely each Disk Data object of a given type). For example, you cannot
have a tablespace and an undo log file with the same name, or an undo
log file and a data file with the same name.

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, path and file
names for undo log files could not be longer than 128 characters. (Bug
#31769)

The optional `INITIAL_SIZE' parameter sets the `UNDO' file's initial
size in bytes; if not specified, the initial size default to `128M'
(128 megabytes). You may optionally follow SIZE with a one-letter
abbreviation for an order of magnitude, similar to those used in
`my.cnf'. Generally, this is one of the letters `M' (for megabytes) or
`G' (for gigabytes).

On 32-bit systems, the maximum supported value for `INITIAL_SIZE' is
`4G'. (Bug #29186)

Beginning with MySQL Cluster NDB 6.2.18, 6.3.24, and 7.0.4, the minimum
permitted value for `INITIAL_SIZE' is `1M'. (Bug #29574)

*Note*:

`WAIT' is parsed but otherwise ignored. This keyword has no effect in
MySQL 5.1, MySQL Cluster NDB 6.x, or MySQL Cluster NDB 7.x, and is
intended for future expansion.

The `ENGINE' parameter (required) determines the storage engine which
is used by this log file group, with ENGINE_NAME being the name of the
storage engine. In MySQL 5.1, MySQL Cluster NDB 6.x, and MySQL Cluster
NDB 7.x, the only accepted values for ENGINE_NAME are `*Note
`NDBCLUSTER': mysql-cluster.' and `*Note `NDB': mysql-cluster.'. The
two values are equivalent.

Here is an example, which assumes that the log file group `lg_3' has
already been created using *Note `CREATE LOGFILE GROUP':
create-logfile-group. (see *Note create-logfile-group::):


     ALTER LOGFILE GROUP lg_3
         ADD UNDOFILE 'undo_10.dat'
         INITIAL_SIZE=32M
         ENGINE=NDBCLUSTER;

When *Note `ALTER LOGFILE GROUP': alter-logfile-group. is used with
`ENGINE = NDBCLUSTER' (alternatively, `ENGINE = NDB'), an `UNDO' log
file is created on each MySQL Cluster data node. You can verify that
the `UNDO' files were created and obtain information about them by
querying the *Note `INFORMATION_SCHEMA.FILES': files-table. table. For
example:


     mysql> SELECT FILE_NAME, LOGFILE_GROUP_NUMBER, EXTRA
         -> FROM INFORMATION_SCHEMA.FILES
         -> WHERE LOGFILE_GROUP_NAME = 'lg_3';
     +-------------+----------------------+----------------+
     | FILE_NAME   | LOGFILE_GROUP_NUMBER | EXTRA          |
     +-------------+----------------------+----------------+
     | newdata.dat |                    0 | CLUSTER_NODE=3 |
     | newdata.dat |                    0 | CLUSTER_NODE=4 |
     | undo_10.dat |                   11 | CLUSTER_NODE=3 |
     | undo_10.dat |                   11 | CLUSTER_NODE=4 |
     +-------------+----------------------+----------------+
     4 rows in set (0.01 sec)

(See *Note files-table::.)

Memory used for `UNDO_BUFFER_SIZE' comes from the global pool whose
size is determined by the value of the `SharedGlobalMemory' data node
configuration parameter. This includes any default value implied for
this option by the setting of the `InitialLogFileGroup' data node
configuration parameter.

*Note `ALTER LOGFILE GROUP': alter-logfile-group. was added in MySQL
5.1.6. It is useful only with Disk Data storage for MySQL Cluster. For
more information, see *Note mysql-cluster-disk-data::.


File: manual.info,  Node: alter-function,  Next: alter-procedure,  Prev: alter-logfile-group,  Up: sql-syntax-data-definition

13.1.4 ALTER FUNCTION Syntax
----------------------------


     ALTER FUNCTION FUNC_NAME [CHARACTERISTIC ...]

     CHARACTERISTIC:
         COMMENT 'STRING'
       | LANGUAGE SQL
       | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
       | SQL SECURITY { DEFINER | INVOKER }

This statement can be used to change the characteristics of a stored
function. More than one change may be specified in an *Note `ALTER
FUNCTION': alter-function. statement. However, you cannot change the
parameters or body of a stored function using this statement; to make
such changes, you must drop and re-create the function using *Note
`DROP FUNCTION': drop-function. and *Note `CREATE FUNCTION':
create-function.

You must have the `ALTER ROUTINE' privilege for the function. (That
privilege is granted automatically to the function creator.) If binary
logging is enabled, the *Note `ALTER FUNCTION': alter-function.
statement might also require the `SUPER' privilege, as described in
*Note stored-programs-logging::.


File: manual.info,  Node: alter-procedure,  Next: alter-server,  Prev: alter-function,  Up: sql-syntax-data-definition

13.1.5 ALTER PROCEDURE Syntax
-----------------------------


     ALTER PROCEDURE PROC_NAME [CHARACTERISTIC ...]

     CHARACTERISTIC:
         COMMENT 'STRING'
       | LANGUAGE SQL
       | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
       | SQL SECURITY { DEFINER | INVOKER }

This statement can be used to change the characteristics of a stored
procedure. More than one change may be specified in an *Note `ALTER
PROCEDURE': alter-procedure. statement. However, you cannot change the
parameters or body of a stored procedure using this statement; to make
such changes, you must drop and re-create the procedure using *Note
`DROP PROCEDURE': drop-procedure. and *Note `CREATE PROCEDURE':
create-procedure.

You must have the `ALTER ROUTINE' privilege for the procedure. By
default, that privilege is granted automatically to the procedure
creator. This behavior can be changed by disabling the
`automatic_sp_privileges' system variable. See *Note
stored-routines-privileges::.


File: manual.info,  Node: alter-server,  Next: alter-table,  Prev: alter-procedure,  Up: sql-syntax-data-definition

13.1.6 ALTER SERVER Syntax
--------------------------


     ALTER SERVER  SERVER_NAME
         OPTIONS (OPTION [, OPTION] ...)

Alters the server information for `SERVER_NAME', adjusting any of the
options permitted in the *Note `CREATE SERVER': create-server.
statement. The corresponding fields in the `mysql.servers' table are
updated accordingly. This statement requires the `SUPER' privilege.

For example, to update the `USER' option:

     ALTER SERVER s OPTIONS (USER 'sally');

`ALTER SERVER' does not cause an automatic commit.

In MySQL 5.1, `ALTER SERVER' is written to the binary log only when
using row-based logging. It is not logged when `binlog_format' is equal
to `STATEMENT' or `MIXED'.

`ALTER SERVER' was added in MySQL 5.1.15.


File: manual.info,  Node: alter-table,  Next: alter-tablespace,  Prev: alter-server,  Up: sql-syntax-data-definition

13.1.7 ALTER TABLE Syntax
-------------------------

* Menu:

* alter-table-partition-operations::  ALTER TABLE Partition Operations
* alter-table-online-operations::  ALTER TABLE Online Operations in MySQL Cluster
* alter-table-examples::         ALTER TABLE Examples


     ALTER [ONLINE | OFFLINE] [IGNORE] TABLE TBL_NAME
         [ALTER_SPECIFICATION [, ALTER_SPECIFICATION] ...]
         [PARTITION_OPTIONS]

     ALTER_SPECIFICATION:
         TABLE_OPTIONS
       | ADD [COLUMN] COL_NAME COLUMN_DEFINITION
             [FIRST | AFTER COL_NAME ]
       | ADD [COLUMN] (COL_NAME COLUMN_DEFINITION,...)
       | ADD {INDEX|KEY} [INDEX_NAME]
             [INDEX_TYPE] (INDEX_COL_NAME,...) [INDEX_OPTION] ...
       | ADD [CONSTRAINT [SYMBOL]] PRIMARY KEY
             [INDEX_TYPE] (INDEX_COL_NAME,...) [INDEX_OPTION] ...
       | ADD [CONSTRAINT [SYMBOL]]
             UNIQUE [INDEX|KEY] [INDEX_NAME]
             [INDEX_TYPE] (INDEX_COL_NAME,...) [INDEX_OPTION] ...
       | ADD FULLTEXT [INDEX|KEY] [INDEX_NAME]
             (INDEX_COL_NAME,...) [INDEX_OPTION] ...
       | ADD SPATIAL [INDEX|KEY] [INDEX_NAME]
             (INDEX_COL_NAME,...) [INDEX_OPTION] ...
       | ADD [CONSTRAINT [SYMBOL]]
             FOREIGN KEY [INDEX_NAME] (INDEX_COL_NAME,...)
             REFERENCE_DEFINITION
       | ALTER [COLUMN] COL_NAME {SET DEFAULT LITERAL | DROP DEFAULT}
       | CHANGE [COLUMN] OLD_COL_NAME NEW_COL_NAME COLUMN_DEFINITION
             [FIRST|AFTER COL_NAME]
       | MODIFY [COLUMN] COL_NAME COLUMN_DEFINITION
             [FIRST | AFTER COL_NAME]
       | DROP [COLUMN] COL_NAME
       | DROP PRIMARY KEY
       | DROP {INDEX|KEY} INDEX_NAME
       | DROP FOREIGN KEY FK_SYMBOL
       | DISABLE KEYS
       | ENABLE KEYS
       | RENAME [TO|AS] NEW_TBL_NAME
       | ORDER BY COL_NAME [, COL_NAME] ...
       | CONVERT TO CHARACTER SET CHARSET_NAME [COLLATE COLLATION_NAME]
       | [DEFAULT] CHARACTER SET [=] CHARSET_NAME [COLLATE [=] COLLATION_NAME]
       | DISCARD TABLESPACE
       | IMPORT TABLESPACE
       | ADD PARTITION (PARTITION_DEFINITION)
       | DROP PARTITION PARTITION_NAMES
       | COALESCE PARTITION NUMBER
       | REORGANIZE PARTITION [PARTITION_NAMES INTO (PARTITION_DEFINITIONS)]
       | ANALYZE PARTITION {PARTITION_NAMES | ALL}
       | CHECK PARTITION {PARTITION_NAMES | ALL}
       | OPTIMIZE PARTITION {PARTITION_NAMES | ALL}
       | REBUILD PARTITION {PARTITION_NAMES | ALL}
       | REPAIR PARTITION {PARTITION_NAMES | ALL}
       | PARTITION BY PARTITIONING_EXPRESSION
       | REMOVE PARTITIONING

     INDEX_COL_NAME:
         COL_NAME [(LENGTH)] [ASC | DESC]

     INDEX_TYPE:
         USING {BTREE | HASH}

     INDEX_OPTION:
         KEY_BLOCK_SIZE [=] VALUE
       | INDEX_TYPE
       | WITH PARSER PARSER_NAME

     TABLE_OPTIONS:
         TABLE_OPTION [[,] TABLE_OPTION] ...  (see *Note `CREATE TABLE': create-table. options)

     PARTITION_OPTIONS:
         (see *Note `CREATE TABLE': create-table. options)

*Note `ALTER TABLE': alter-table. changes the structure of a table. For
example, you can add or delete columns, create or destroy indexes,
change the type of existing columns, or rename columns or the table
itself. You can also change characteristics such as the storage engine
used for the table or the table comment.

Following the table name, specify the alterations to be made. If none
are given, *Note `ALTER TABLE': alter-table. does nothing.

The syntax for many of the permissible alterations is similar to
clauses of the *Note `CREATE TABLE': create-table.  statement. See
*Note create-table::, for more information.

TABLE_OPTIONS signifies table options of the kind that can be used in
the *Note `CREATE TABLE': create-table. statement, such as `ENGINE',
`AUTO_INCREMENT', `AVG_ROW_LENGTH', `MAX_ROWS', or `ROW_FORMAT'. For a
list of all table options and a description of each, see *Note
create-table::.  However, *Note `ALTER TABLE': alter-table. ignores the
`DATA DIRECTORY' and `INDEX DIRECTORY' table options.

PARTITION_OPTIONS signifies options that can be used with partitioned
tables. A number of partitioning-related extensions to *Note `ALTER
TABLE': alter-table. were added in MySQL 5.1.5. These can be used with
partitioned tables for repartitioning, for adding, dropping, merging,
and splitting partitions, and for performing partitioning maintenance.
It is possible for an *Note `ALTER TABLE': alter-table. statement to
contain a `PARTITION BY' or `REMOVE PARTITIONING' clause in an addition
to other alter specifications, but the `PARTITION BY' or `REMOVE
PARTITIONING' clause must be specified last after any other
specifications. The `ADD PARTITION', `DROP PARTITION', `COALESCE
PARTITION', `REORGANIZE PARTITION', `ANALYZE PARTITION', `CHECK
PARTITION', and `REPAIR PARTITION' options cannot be combined with
other alter specifications in a single `ALTER TABLE', since the options
just listed act on individual partitions. For a list of partition
options and a description of each, see *Note create-table::. For
additional information, see *Note alter-table-partition-operations::.

Some operations may result in warnings if attempted on a table for
which the storage engine does not support the operation. These warnings
can be displayed with *Note `SHOW WARNINGS': show-warnings. See *Note
show-warnings::.

For information on troubleshooting *Note `ALTER TABLE': alter-table,
see *Note alter-table-problems::.

*Storage, Performance, and Concurrency Considerations*

In most cases, *Note `ALTER TABLE': alter-table. makes a temporary copy
of the original table. MySQL waits for other operations that are
modifying the table, then proceeds. It incorporates the alteration into
the copy, deletes the original table, and renames the new one. While
*Note `ALTER TABLE': alter-table. is executing, the original table is
readable by other sessions. Updates and writes to the table that begin
after the *Note `ALTER TABLE': alter-table. operation begins are
stalled until the new table is ready, then are automatically redirected
to the new table without any failed updates. The temporary copy of the
original table is created in the database directory of the new table.
This can differ from the database directory of the original table for
*Note `ALTER TABLE': alter-table. operations that rename the table to a
different database.

For `MyISAM' tables, you can speed up index re-creation (the slowest
part of the alteration process) by setting the
`myisam_sort_buffer_size' system variable to a high value.

For some operations, an in-place *Note `ALTER TABLE': alter-table. is
possible that does not require a temporary table:

   * For `ALTER TABLE TBL_NAME RENAME TO NEW_TBL_NAME' without any
     other options, MySQL simply renames any files that correspond to
     the table TBL_NAME without making a copy. (You can also use the
     *Note `RENAME TABLE': rename-table. statement to rename tables.
     See *Note rename-table::.) Any privileges granted specifically for
     the renamed table are not migrated to the new name. They must be
     changed manually.

   * Alterations that modify only table metadata and not table data are
     immediate because the server only needs to alter the table `.frm'
     file, not touch table contents. The following changes are fast
     alterations that can be made this way:

        * Renaming a column, except for the *Note `InnoDB':
          innodb-storage-engine. storage engine.

        * Changing the default value of a column (except for *Note
          `NDB': mysql-cluster. tables; see Limitations of *Note
          `NDBCLUSTER': mysql-cluster. online operations).

        * Changing the definition of an *Note `ENUM': enum. or *Note
          `SET': set. column by adding new enumeration or set members
          to the _end_ of the list of valid member values, as long as
          the storage size of the data type does not change. For
          example, adding a member to a *Note `SET': set. column that
          has 8 members changes the required storage per value from 1
          byte to 2 bytes; this will require a table copy.  Adding
          members in the middle of the list causes renumbering of
          existing members, which requires a table copy.

   * `ALTER TABLE' with `ADD PARTITION', `DROP PARTITION', `COALESCE
     PARTITION', `REBUILD PARTITION', or `REORGANIZE PARTITION' does
     not create any temporary tables (except when used with *Note
     `NDB': mysql-cluster.  tables); however, these operations can and
     do create temporary partition files.

     `ADD' or `DROP' operations for `RANGE' or `LIST' partitions are
     immediate operations or nearly so.  `ADD' or `COALESCE' operations
     for `HASH' or `KEY' partitions copy data between all partitions,
     unless `LINEAR HASH' or `LINEAR KEY' was used; this is effectively
     the same as creating a new table, although the `ADD' or `COALESCE'
     operation is performed partition by partition.  `REORGANIZE'
     operations copy only changed partitions and do not touch unchanged
     ones.

   * Renaming an index, except for *Note `InnoDB':
     innodb-storage-engine.

   * Adding or dropping an index, for *Note `InnoDB':
     innodb-storage-engine. (if `InnoDB Plugin' is used) and *Note
     `NDB': mysql-cluster.

You can force an `ALTER TABLE' operation that would otherwise not
require a table copy to use the temporary table method (as supported in
MySQL 5.0) by setting the `old_alter_table' system variable to `ON'.

For *Note `NDBCLUSTER': mysql-cluster. tables, operations that add and
drop indexes on variable-width columns occur online, without any table
copying and without blocking concurrent DML actions for most of their
duration. See *Note alter-table-online-operations::.

*Usage Notes*

   * To use *Note `ALTER TABLE': alter-table, you need `ALTER',
     `CREATE', and `INSERT' privileges for the table. Renaming a table
     requires `ALTER' and `DROP' on the old table, `ALTER', `CREATE',
     and `INSERT' on the new table.

   * `IGNORE' is a MySQL extension to standard SQL. It controls how
     *Note `ALTER TABLE': alter-table. works if there are duplicates on
     unique keys in the new table or if warnings occur when strict mode
     is enabled. If `IGNORE' is not specified, the copy is aborted and
     rolled back if duplicate-key errors occur.  If `IGNORE' is
     specified, only one row is used of rows with duplicates on a
     unique key. The other conflicting rows are deleted. Incorrect
     values are truncated to the closest matching acceptable value.

   * Pending *Note `INSERT DELAYED': insert-delayed.  statements are
     lost if a table is write locked and *Note `ALTER TABLE':
     alter-table. is used to modify the table structure.

   * TABLE_OPTIONS signifies table options of the kind that can be used
     in the *Note `CREATE TABLE': create-table. statement, such as
     `ENGINE', `AUTO_INCREMENT', `AVG_ROW_LENGTH', `MAX_ROWS', or
     `ROW_FORMAT'.  For a list of all table options and a description
     of each, see *Note create-table::. However, *Note `ALTER TABLE':
     alter-table. ignores the `DATA DIRECTORY' and `INDEX DIRECTORY'
     table options.

     For example, to convert a table to be an `InnoDB' table, use this
     statement:


          ALTER TABLE t1 ENGINE = InnoDB;

     See *Note converting-tables-to-innodb:: for considerations when
     switching tables to the `InnoDB' storage engine.

     When you specify an `ENGINE' clause, *Note `ALTER TABLE':
     alter-table. rebuilds the table.  This is true even if the table
     already has the specified storage engine.

     The outcome of attempting to change a table's storage engine is
     affected by whether the desired storage engine is available and
     the setting of the `NO_ENGINE_SUBSTITUTION' SQL mode, as described
     in *Note sql-mode::.

     As of MySQL 5.1.11, to prevent inadvertent loss of data, *Note
     `ALTER TABLE': alter-table. cannot be used to change the storage
     engine of a table to `MERGE' or `BLACKHOLE'.

     To change the value of the `AUTO_INCREMENT' counter to be used for
     new rows, do this:


          ALTER TABLE t2 AUTO_INCREMENT = VALUE;

     You cannot reset the counter to a value less than or equal to any
     that have already been used. For `MyISAM', if the value is less
     than or equal to the maximum value currently in the
     `AUTO_INCREMENT' column, the value is reset to the current maximum
     plus one. For `InnoDB', _if the value is less than the current
     maximum value in the column, no error occurs and the current
     sequence value is not changed._

   * You can issue multiple `ADD', `ALTER', `DROP', and `CHANGE'
     clauses in a single *Note `ALTER TABLE': alter-table. statement,
     separated by commas. This is a MySQL extension to standard SQL,
     which permits only one of each clause per *Note `ALTER TABLE':
     alter-table. statement. For example, to drop multiple columns in a
     single statement, do this:


          ALTER TABLE t2 DROP COLUMN c, DROP COLUMN d;

   * `CHANGE COL_NAME', `DROP COL_NAME', and `DROP INDEX' are MySQL
     extensions to standard SQL.

   * The word `COLUMN' is optional and can be omitted.

   * COLUMN_DEFINITION clauses use the same syntax for `ADD' and
     `CHANGE' as for *Note `CREATE TABLE': create-table. See *Note
     create-table::.

   * You can rename a column using a `CHANGE OLD_COL_NAME NEW_COL_NAME
     COLUMN_DEFINITION' clause.  To do so, specify the old and new
     column names and the definition that the column currently has. For
     example, to rename an *Note `INTEGER': integer-types. column from
     `a' to `b', you can do this:


          ALTER TABLE t1 CHANGE a b INTEGER;

     To change a column's type but not the name, `CHANGE' syntax still
     requires an old and new column name, even if they are the same.
     For example:


          ALTER TABLE t1 CHANGE b b BIGINT NOT NULL;

     You can also use `MODIFY' to change a column's type without
     renaming it:


          ALTER TABLE t1 MODIFY b BIGINT NOT NULL;

     `MODIFY' is an extension to *Note `ALTER TABLE': alter-table. for
     Oracle compatibility.

     When you use `CHANGE' or `MODIFY', COLUMN_DEFINITION must include
     the data type and all attributes that should apply to the new
     column, other than index attributes such as `PRIMARY KEY' or
     `UNIQUE'. Attributes present in the original definition but not
     specified for the new definition are not carried forward. Suppose
     that a column `col1' is defined as `INT UNSIGNED DEFAULT 1 COMMENT
     'my column'' and you modify the column as follows:


          ALTER TABLE t1 MODIFY col1 BIGINT;

     The resulting column will be defined as `BIGINT', but will not
     include the attributes `UNSIGNED DEFAULT 1 COMMENT 'my column''. To
     retain them, the statement should be:


          ALTER TABLE t1 MODIFY col1 BIGINT UNSIGNED DEFAULT 1 COMMENT 'my column';

   * When you change a data type using `CHANGE' or `MODIFY', MySQL
     tries to convert existing column values to the new type as well as
     possible.

     *Warning*:

     This conversion may result in alteration of data. For example, if
     you shorten a string column, values may be truncated. To prevent
     the operation from succeeding if conversions to the new data type
     would result in loss of data, enable strict SQL mode before using
     *Note `ALTER TABLE': alter-table. (see *Note sql-mode::).

   * To add a column at a specific position within a table row, use
     `FIRST' or `AFTER COL_NAME'. The default is to add the column
     last. You can also use `FIRST' and `AFTER' in `CHANGE' or `MODIFY'
     operations to reorder columns within a table.

   * `ALTER ... SET DEFAULT' or `ALTER ...  DROP DEFAULT' specify a new
     default value for a column or remove the old default value,
     respectively. If the old default is removed and the column can be
     `NULL', the new default is `NULL'. If the column cannot be `NULL',
     MySQL assigns a default value as described in *Note
     data-type-defaults::.

   * *Note `DROP INDEX': drop-index. removes an index.  This is a MySQL
     extension to standard SQL. See *Note drop-index::. If you are
     unsure of the index name, use `SHOW INDEX FROM TBL_NAME'.

   * If columns are dropped from a table, the columns are also removed
     from any index of which they are a part. If all columns that make
     up an index are dropped, the index is dropped as well. If you use
     `CHANGE' or `MODIFY' to shorten a column for which an index exists
     on the column, and the resulting column length is less than the
     index length, MySQL shortens the index automatically.

   * If a table contains only one column, the column cannot be dropped.
     If what you intend is to remove the table, use *Note `DROP TABLE':
     drop-table. instead.

   * `DROP PRIMARY KEY' drops the primary key
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_primary_key).
     If there is no primary key, an error occurs. For information about
     the performance characteristics of primary keys, especially for
     `InnoDB' tables, see Using Primary Keys
     (http://dev.mysql.com/doc/refman/5.5/en/optimizing-primary-keys.html).

     If you add a `UNIQUE INDEX' or `PRIMARY KEY' to a table, MySQL
     stores it before any nonunique index to permit detection of
     duplicate keys as early as possible.

   * Some storage engines permit you to specify an index type when
     creating an index. The syntax for the INDEX_TYPE specifier is
     `USING TYPE_NAME'.  For details about `USING', see *Note
     create-index::. Before MySQL 5.1.10, `USING' can be given only
     before the index column list. As of 5.1.10, the preferred position
     is after the column list. Support for use of the option before the
     column list will be removed in a future MySQL release.

     INDEX_OPTION values specify additional options for an index.
     `USING' is one such option. For details about permissible
     INDEX_OPTION values, see *Note create-index::.

   * After an *Note `ALTER TABLE': alter-table. statement, it may be
     necessary to run *Note `ANALYZE TABLE': analyze-table. to update
     index cardinality information. See *Note show-index::.

   * `ORDER BY' enables you to create the new table with the rows in a
     specific order. Note that the table does not remain in this order
     after inserts and deletes. This option is useful primarily when
     you know that you are mostly to query the rows in a certain order
     most of the time. By using this option after major changes to the
     table, you might be able to get higher performance. In some cases,
     it might make sorting easier for MySQL if the table is in order by
     the column that you want to order it by later.

     `ORDER BY' syntax permits one or more column names to be specified
     for sorting, each of which optionally can be followed by `ASC' or
     `DESC' to indicate ascending or descending sort order,
     respectively. The default is ascending order. Only column names
     are permitted as sort criteria; arbitrary expressions are not
     permitted. This clause should be given last after any other
     clauses.

     `ORDER BY' does not make sense for `InnoDB' tables because
     `InnoDB' always orders table rows according to the clustered index
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_clustered_index).

     *Note*:

     When used on a partitioned table, `ALTER TABLE ...  ORDER BY'
     orders rows within each partition only.

   * If you use *Note `ALTER TABLE': alter-table. on a `MyISAM' table,
     all nonunique indexes are created in a separate batch (as for
     *Note `REPAIR TABLE': repair-table.). This should make *Note
     `ALTER TABLE': alter-table. much faster when you have many indexes.

     For `MyISAM' tables, key updating can be controlled explicitly.
     Use `ALTER TABLE ... DISABLE KEYS' to tell MySQL to stop updating
     nonunique indexes. Then use `ALTER TABLE ... ENABLE KEYS' to
     re-create missing indexes.  `MyISAM' does this with a special
     algorithm that is much faster than inserting keys one by one, so
     disabling keys before performing bulk insert operations should
     give a considerable speedup. Using `ALTER TABLE ...  DISABLE KEYS'
     requires the `INDEX' privilege in addition to the privileges
     mentioned earlier.

     While the nonunique indexes are disabled, they are ignored for
     statements such as *Note `SELECT': select. and *Note `EXPLAIN':
     explain. that otherwise would use them.

     `ENABLE KEYS' and `DISABLE KEYS' were not supported for
     partitioned tables prior to MySQL 5.1.11.

   * If *Note `ALTER TABLE': alter-table. for an `InnoDB' table results
     in changes to column values (for example, because a column is
     truncated), `InnoDB''s `FOREIGN KEY' constraint checks do not
     notice possible violations caused by changing the values.

   * The `FOREIGN KEY' and `REFERENCES' clauses are supported by the
     `InnoDB' storage engine, which implements `ADD [CONSTRAINT
     [SYMBOL]] FOREIGN KEY [INDEX_NAME] (...)  REFERENCES ... (...)'.
     See *Note innodb-foreign-key-constraints::. For other storage
     engines, the clauses are parsed but ignored. The `CHECK' clause is
     parsed but ignored by all storage engines. See *Note
     create-table::. The reason for accepting but ignoring syntax
     clauses is for compatibility, to make it easier to port code from
     other SQL servers, and to run applications that create tables with
     references. See *Note differences-from-ansi::.

     For *Note `ALTER TABLE': alter-table, unlike *Note `CREATE TABLE':
     create-table, `ADD FOREIGN KEY' ignores INDEX_NAME if given and
     uses an automatically generated foreign key name. As a workaround,
     include the `CONSTRAINT' clause to specify the foreign key name:


          ADD CONSTRAINT NAME FOREIGN KEY (....) ...

     *Important*:

     The inline `REFERENCES' specifications where the references are
     defined as part of the column specification are silently ignored by
     `InnoDB'. InnoDB only accepts `REFERENCES' clauses defined as part
     of a separate `FOREIGN KEY' specification.

     *Note*:

     Partitioned `InnoDB' tables do not support foreign keys. See *Note
     partitioning-limitations-storage-engines::, for more information.

   * `InnoDB' supports the use of *Note `ALTER TABLE': alter-table. to
     drop foreign keys:


          ALTER TABLE TBL_NAME DROP FOREIGN KEY FK_SYMBOL;

     For more information, see *Note innodb-foreign-key-constraints::.

   * Adding and dropping a foreign key in separate clauses of a single
     *Note `ALTER TABLE': alter-table. statement may be problematic in
     some cases and is therefore unsupported.  Use separate statements
     for each operation.

   * For an `InnoDB' table that is created with its own tablespace in
     an `.ibd' file, that file can be discarded and imported. To
     discard the `.ibd' file, use this statement:


          ALTER TABLE TBL_NAME DISCARD TABLESPACE;

     This deletes the current `.ibd' file, so be sure that you have a
     backup first. Attempting to access the table while the tablespace
     file is discarded results in an error.

     To import the backup `.ibd' file back into the table, copy it into
     the database directory, and then issue this statement:


          ALTER TABLE TBL_NAME IMPORT TABLESPACE;

     The tablespace file must have been created on the server into
     which it is imported later.

     *Note*:

     The *Note `ALTER TABLE ... IMPORT TABLESPACE': alter-table.
     feature does not enforce foreign key constraints on imported data.

     See *Note innodb-multiple-tablespaces::.

   * To change the table default character set and all character
     columns (*Note `CHAR': char, *Note `VARCHAR': char, *Note `TEXT':
     blob.) to a new character set, use a statement like this:


          ALTER TABLE TBL_NAME
          CONVERT TO CHARACTER SET CHARSET_NAME [COLLATE COLLATION_NAME];

     The statement also changes the collation of all character columns.
     If you specify no `COLLATE' clause to indicate which collation to
     use, the statement uses default collation for the character set.
     If this collation is inappropriate for the intended table use (for
     example, if it would change from a case-sensitive collation to a
     case-insensitive collation), specify a collation explicitly.

     For a column that has a data type of *Note `VARCHAR': char. or one
     of the *Note `TEXT': blob. types, `CONVERT TO CHARACTER SET' will
     change the data type as necessary to ensure that the new column is
     long enough to store as many characters as the original column.
     For example, a *Note `TEXT': blob. column has two length bytes,
     which store the byte-length of values in the column, up to a
     maximum of 65,535. For a `latin1' *Note `TEXT': blob. column, each
     character requires a single byte, so the column can store up to
     65,535 characters. If the column is converted to `utf8', each
     character might require up to three bytes, for a maximum possible
     length of 3 x 65,535 = 196,605 bytes. That length will not fit in a
     *Note `TEXT': blob. column's length bytes, so MySQL will convert
     the data type to *Note `MEDIUMTEXT': blob, which is the smallest
     string type for which the length bytes can record a value of
     196,605. Similarly, a *Note `VARCHAR': char. column might be
     converted to *Note `MEDIUMTEXT': blob.

     To avoid data type changes of the type just described, do not use
     `CONVERT TO CHARACTER SET'. Instead, use `MODIFY' to change
     individual columns. For example:


          ALTER TABLE t MODIFY latin1_text_col TEXT CHARACTER SET utf8;
          ALTER TABLE t MODIFY latin1_varchar_col VARCHAR(M) CHARACTER SET utf8;

     If you specify `CONVERT TO CHARACTER SET binary', the *Note
     `CHAR': char, *Note `VARCHAR': char, and *Note `TEXT': blob.
     columns are converted to their corresponding binary string types
     (*Note `BINARY': binary-varbinary, *Note `VARBINARY':
     binary-varbinary, *Note `BLOB': blob.). This means that the
     columns no longer will have a character set and a subsequent
     `CONVERT TO' operation will not apply to them.

     If CHARSET_NAME is `DEFAULT', the database character set is used.

     *Warning*:

     The `CONVERT TO' operation converts column values between the
     character sets. This is _not_ what you want if you have a column
     in one character set (like `latin1') but the stored values
     actually use some other, incompatible character set (like `utf8').
     In this case, you have to do the following for each such column:


          ALTER TABLE t1 CHANGE c1 c1 BLOB;
          ALTER TABLE t1 CHANGE c1 c1 TEXT CHARACTER SET utf8;

     The reason this works is that there is no conversion when you
     convert to or from *Note `BLOB': blob.  columns.

     To change only the _default_ character set for a table, use this
     statement:


          ALTER TABLE TBL_NAME DEFAULT CHARACTER SET CHARSET_NAME;

     The word `DEFAULT' is optional. The default character set is the
     character set that is used if you do not specify the character set
     for columns that you add to a table later (for example, with
     `ALTER TABLE ... ADD column').

With the *Note `mysql_info()': mysql-info. C API function, you can find
out how many rows were copied by *Note `ALTER TABLE': alter-table, and
(when `IGNORE' is used) how many rows were deleted due to duplication
of unique key values. See *Note mysql-info::.


File: manual.info,  Node: alter-table-partition-operations,  Next: alter-table-online-operations,  Prev: alter-table,  Up: alter-table

13.1.7.1 ALTER TABLE Partition Operations
.........................................

A number of partitioning-related extensions to *Note `ALTER TABLE':
alter-table. were added in MySQL 5.1.5. These can be used with
partitioned tables for repartitioning, for adding, dropping, merging,
and splitting partitions, and for performing partitioning maintenance.

It is possible for an *Note `ALTER TABLE': alter-table.  statement to
contain a `PARTITION BY' or `REMOVE PARTITIONING' clause in an addition
to other alter specifications, but the `PARTITION BY' or `REMOVE
PARTITIONING' clause must be specified last after any other
specifications. The `ADD PARTITION', `DROP PARTITION', `COALESCE
PARTITION', `REORGANIZE PARTITION', `ANALYZE PARTITION', `CHECK
PARTITION', and `REPAIR PARTITION' options cannot be combined with
other alter specifications in a single `ALTER TABLE', since the options
just listed act on individual partitions.

   * Simply using a PARTITION_OPTIONS clause with *Note `ALTER TABLE':
     alter-table. on a partitioned table repartitions the table
     according to the partitioning scheme defined by the
     PARTITION_OPTIONS. This clause always begins with `PARTITION BY',
     and follows the same syntax and other rules as apply to the
     PARTITION_OPTIONS clause for *Note `CREATE TABLE': create-table.
     (see *Note create-table::, for more detailed information), and can
     also be used to partition an existing table that is not already
     partitioned. For example, consider a (nonpartitioned) table
     defined as shown here:


          CREATE TABLE t1 (
              id INT,
              year_col INT
          );

     This table can be partitioned by `HASH', using the `id' column as
     the partitioning key, into 8 partitions by means of this statement:


          ALTER TABLE t1
              PARTITION BY HASH(id)
              PARTITIONS 8;

     The table that results from using an `ALTER TABLE ... PARTITION
     BY' statement must follow the same rules as one created using
     `CREATE TABLE ...  PARTITION BY'. This includes the rules governing
     the relationship between any unique keys (including any primary
     key) that the table might have, and the column or columns used in
     the partitioning expression, as discussed in *Note
     partitioning-limitations-partitioning-keys-unique-keys::.  The
     `CREATE TABLE ... PARTITION BY' rules for specifying the number of
     partitions also apply to `ALTER TABLE ... PARTITION BY'.

     `ALTER TABLE ... PARTITION BY' became available in MySQL 5.1.6.

     The PARTITION_DEFINITION clause for `ALTER TABLE ADD PARTITION'
     supports the same options as the clause of the same name for the
     *Note `CREATE TABLE': create-table. statement. (See *Note
     create-table::, for the syntax and description.) Suppose that you
     have the partitioned table created as shown here:


          CREATE TABLE t1 (
              id INT,
              year_col INT
          )
          PARTITION BY RANGE (year_col) (
              PARTITION p0 VALUES LESS THAN (1991),
              PARTITION p1 VALUES LESS THAN (1995),
              PARTITION p2 VALUES LESS THAN (1999)
          );

     You can add a new partition `p3' to this table for storing values
     less than `2002' as follows:


          ALTER TABLE t1 ADD PARTITION (PARTITION p3 VALUES LESS THAN (2002));

     `DROP PARTITION' can be used to drop one or more `RANGE' or `LIST'
     partitions. This statement cannot be used with `HASH' or `KEY'
     partitions; instead, use `COALESCE PARTITION' (see below). Any
     data that was stored in the dropped partitions named in the
     PARTITION_NAMES list is discarded. For example, given the table
     `t1' defined previously, you can drop the partitions named `p0' and
     `p1' as shown here:


          ALTER TABLE t1 DROP PARTITION p0, p1;

     *Note*:

     `DROP PARTITION' does not work with tables that use the *Note
     `NDBCLUSTER': mysql-cluster. storage engine.  See *Note
     partitioning-management-range-list::, and *Note
     mysql-cluster-limitations::.

     `ADD PARTITION' and `DROP PARTITION' do not currently support `IF
     [NOT] EXISTS'.

     Renames of partitioned table are supported. You can rename
     individual partitions indirectly using `ALTER TABLE ... REORGANIZE
     PARTITION'; however, this operation makes a copy of the
     partition's data..

     `COALESCE PARTITION' can be used with a table that is partitioned
     by `HASH' or `KEY' to reduce the number of partitions by NUMBER.
     Suppose that you have created table `t2' using the following
     definition:


          CREATE TABLE t2 (
              name VARCHAR (30),
              started DATE
          )
          PARTITION BY HASH( YEAR(started) )
          PARTITIONS 6;

     You can reduce the number of partitions used by `t2' from 6 to 4
     using the following statement:


          ALTER TABLE t2 COALESCE PARTITION 2;

     The data contained in the last NUMBER partitions will be merged
     into the remaining partitions. In this case, partitions 4 and 5
     will be merged into the first 4 partitions (the partitions
     numbered 0, 1, 2, and 3).

     To change some but not all the partitions used by a partitioned
     table, you can use `REORGANIZE PARTITION'. This statement can be
     used in several ways:

        * To merge a set of partitions into a single partition.  This
          can be done by naming several partitions in the
          PARTITION_NAMES list and supplying a single definition for
          PARTITION_DEFINITION.

        * To split an existing partition into several partitions.  You
          can accomplish this by naming a single partition for
          PARTITION_NAMES and providing multiple PARTITION_DEFINITIONS.

        * To change the ranges for a subset of partitions defined using
          `VALUES LESS THAN' or the value lists for a subset of
          partitions defined using `VALUES IN'.

        * This statement may also be used without the `PARTITION_NAMES
          INTO (PARTITION_DEFINITIONS)' option on tables that are
          automatically partitioned using `HASH' partitioning to force
          redistribution of data. (Currently, only *Note `NDBCLUSTER':
          mysql-cluster. tables are automatically partitioned in this
          way.) This is useful in MySQL Cluster NDB 7.0 and later
          where, after you have added new MySQL Cluster data nodes
          online to an existing MySQL Cluster, you wish to redistribute
          existing MySQL Cluster table data to the new data nodes. In
          such cases, you should invoke the statement with the `ONLINE'
          option; in other words, as shown here:


               ALTER ONLINE TABLE TABLE REORGANIZE PARTITION;

          You cannot perform other DDL concurrently with online table
          reorganization--that is, no other DDL statements can be
          issued while an `ALTER ONLINE TABLE ... REORGANIZE PARTITION'
          statement is executing. For more information about adding
          MySQL Cluster data nodes online, see *Note
          mysql-cluster-online-add-node::.

          `ALTER ONLINE TABLE ... REORGANIZE PARTITION' does not work
          with tables which were created using the `MAX_ROWS' option,
          because it uses the constant `MAX_ROWS' value specified in
          the original *Note `CREATE TABLE': create-table. statement to
          determine the number of partitions required, so no new
          partitions are created. Beginning with MySQL Cluster NDB
          7.0.32 and MySQL Cluster NDB 7.1.21, you can use `ALTER
          ONLINE TABLE ...  MAX_ROWS=ROWS' to increase the maximum
          number of rows for the table; after this, `ALTER ONLINE TABLE
          ... REORGANIZE PARTITION' can use this new, larger value to
          increase the number of partitions. The value of ROWS must be
          greater than the value specified for `MAX_ROWS' in the
          original `CREATE TABLE' statement for this to work.

          Attempting to use `REORGANIZE PARTITION' without the
          `PARTITION_NAMES INTO (PARTITION_DEFINITIONS)' option on
          explicitly partitioned tables results in the error
          `REORGANIZE PARTITION without parameters can only be used on
          auto-partitioned tables using HASH partitioning'.

     *Note*:

     For partitions that have not been explicitly named, MySQL
     automatically provides the default names `p0', `p1', `p2', and so
     on. As of MySQL 5.1.7, the same is true with regard to
     subpartitions.

     For more detailed information about and examples of `ALTER TABLE
     ... REORGANIZE PARTITION' statements, see *Note
     partitioning-management-range-list::.

   * Several additional options were introduced in MySQL 5.1.5 for
     providing partition maintenance and repair functionality analogous
     to that implemented for nonpartitioned tables by statements such
     as *Note `CHECK TABLE': check-table. and *Note `REPAIR TABLE':
     repair-table. (which are also supported for partitioned tables,
     beginning with MySQL 5.1.27--see note at the end of this item).
     These include `ANALYZE PARTITION', `CHECK PARTITION', `OPTIMIZE
     PARTITION', `REBUILD PARTITION', and `REPAIR PARTITION'. Each of
     these options takes a PARTITION_NAMES clause consisting of one or
     more names of partitions, separated by commas. The partitions must
     already exist in the table to be altered.  You can also use the
     `ALL' keyword in place of PARTITION_NAMES, in which case the
     statement acts on all partitions in the table. For more
     information and examples, see *Note partitioning-maintenance::.

     Prior to MySQL 5.1.68, it was not safe to execute multiple
     concurrent `REBUILD TABLE' operations on partitioned tables,
     whether on the same or different tables.  (Bug #14589559, Bug
     #66645)

     Some MySQL storage engines, such as *Note `InnoDB':
     innodb-storage-engine, do not support per-partition optimization.
     For a partitioned table using such a storage engine, `ALTER TABLE
     ... OPTIMIZE PARTITION' rebuilds the entire table. This is a known
     issue. Beginning with MySQL 5.1.68, running this statement on such
     a table causes the entire table to rebuilt and analyzed, and an
     appropriate warning to be issued. (Bug #11751825, Bug #42822)

     To work around this problem, use the statements `ALTER TABLE ...
     REBUILD PARTITION' and `ALTER TABLE ... ANALYZE PARTITION' instead.

     The `ANALYZE PARTITION', `CHECK PARTITION', `OPTIMIZE PARTITION',
     and `REPAIR PARTITION' options were disabled in MySQL 5.1.24, and
     re-enabled in MySQL 5.1.27.  (Bug #20129) They are not supported
     for tables which are not partitioned; beginning with MySQL 5.1.31,
     they are not permitted for such tables.

     Beginning with MySQL 5.1.27, you can use the statements *Note
     `ANALYZE TABLE': analyze-table, *Note `CHECK TABLE': check-table,
     *Note `OPTIMIZE TABLE': optimize-table, and *Note `REPAIR TABLE':
     repair-table. on partitioned tables. See *Note
     table-maintenance-sql::, for more information.

   * `REMOVE PARTITIONING' was introduced in MySQL 5.1.8 for the
     purpose of removing a table's partitioning without otherwise
     affecting the table or its data. (Previously, this was done using
     the `ENGINE' option.) This option can be combined with other *Note
     `ALTER TABLE': alter-table. options such as those used to add,
     drop, or rename columns or indexes.

   * In MySQL 5.1.7 and earlier, using the `ENGINE' option with *Note
     `ALTER TABLE': alter-table. caused any partitioning that a table
     might have had to be removed.  Beginning with MySQL 5.1.8, this
     option merely changes the storage engine used by the table and no
     longer affects partitioning in any way.

Only a single instance of any one of the following options can be used
in a given *Note `ALTER TABLE': alter-table.  statement: `PARTITION
BY', `ADD PARTITION', `DROP PARTITION', `TRUNCATE PARTITION',
`REORGANIZE PARTITION', or `COALESCE PARTITION', `ANALYZE PARTITION',
`CHECK PARTITION', `OPTIMIZE PARTITION', `REBUILD PARTITION', `REMOVE
PARTITIONING'.

For example, the following two statements are invalid:


     ALTER TABLE t1 ANALYZE PARTITION p1, ANALYZE PARTITION p2;

     ALTER TABLE t1 ANALYZE PARTITION p1, CHECK PARTITION p2;

In the first case, you can analyze partitions `p1' and `p2' of table
`t1' concurrently using a single statement with a single `ANALYZE
PARTITION' option that lists both of the partitions to be analyzed,
like this:


     ALTER TABLE t1 ANALYZE PARTITION p1, p2;

In the second case, it is not possible to perform `ANALYZE' and `CHECK'
operations on different partitions of the same table concurrently.
Instead, you must issue two separate statements, like this:


     ALTER TABLE t1 ANALYZE PARTITION p1;
     ALTER TABLE t1 CHECK PARTITION p2;

`ANALYZE', `CHECK', `OPTIMIZE', `REBUILD', `REPAIR', and `TRUNCATE'
operations are not allowed with subpartitions.


File: manual.info,  Node: alter-table-online-operations,  Next: alter-table-examples,  Prev: alter-table-partition-operations,  Up: alter-table

13.1.7.2 ALTER TABLE Online Operations in MySQL Cluster
.......................................................

Beginning with MySQL 5.1.17, operations that add and drop indexes on
variable-width columns of *Note `NDBCLUSTER': mysql-cluster. tables
occur online.  Online operations are noncopying; that is, they do not
require that indexes be re-created. They do not lock the table being
altered from access by other API nodes in a MySQL Cluster (but see
`Limitations' later in this section).  Such operations do not require
single user mode for *Note `NDBCLUSTER': mysql-cluster. table
alterations made in a cluster with multiple API nodes; transactions can
continue uninterrupted during online DDL operations.

The `ONLINE' keyword can be used to perform online `ADD COLUMN', `ADD
INDEX' (including `CREATE INDEX' statements), and `DROP INDEX'
operations on *Note `NDBCLUSTER': mysql-cluster. tables. Online renaming
of *Note `NDBCLUSTER': mysql-cluster. tables is also supported.

The `ONLINE' and `OFFLINE' keywords are supported only in MySQL Cluster
NDB 6.2 (beginning with 6.2.5) and 6.3 (beginning with 6.3.2) or later.
For earlier MySQL Cluster releases or standard MySQL 5.1 releases:

   * The server determines automatically whether an `ADD INDEX' or
     `DROP INDEX' operation can be (and is) performed online or
     offline; if the column is of a variable-width data type, the
     operation is performed online. It is not possible to override the
     server behavior in this regard.

   * Attempting to use the `ONLINE' or `OFFLINE' keyword in an *Note
     `ALTER TABLE': alter-table, *Note `CREATE INDEX': create-index, or
     *Note `DROP INDEX': drop-index. statement results in an error.

Currently you cannot add disk-based columns to *Note `NDBCLUSTER':
mysql-cluster. tables online. This means that, if you wish to add an
in-memory column to an *Note `NDBCLUSTER': mysql-cluster. table that
uses a table-level `STORAGE DISK' option, you must declare the new
column as using memory-based storage explicitly.  For example--assuming
that you have already created tablespace `ts1'--suppose that you create
table `t1' as follows:


     mysql> CREATE TABLE t1 (
          >     c1 INT NOT NULL PRIMARY KEY,
          >     c2 VARCHAR(30)
          >     )
          >     TABLESPACE ts1 STORAGE DISK
          >     ENGINE NDBCLUSTER;
     Query OK, 0 rows affected (1.73 sec)
     Records: 0  Duplicates: 0  Warnings: 0

You can add a new in-memory column to this table online as shown here:


     mysql> ALTER ONLINE TABLE t1 ADD COLUMN c3 INT COLUMN_FORMAT DYNAMIC STORAGE MEMORY;
     Query OK, 0 rows affected (1.25 sec)
     Records: 0  Duplicates: 0  Warnings: 0

This statement fails if the `STORAGE MEMORY' option is omitted:


     mysql> ALTER ONLINE TABLE t1 ADD COLUMN c3 INT COLUMN_FORMAT DYNAMIC;
     `ERROR 1235 (42000): This version of MySQL doesn't yet support
     'ALTER ONLINE TABLE t1 ADD COLUMN c3 INT COLUMN_FORMAT DYNAMIC''

If you omit the `COLUMN_FORMAT DYNAMIC' option, the dynamic column
format is employed automatically, but a warning is issued, as shown
here:


     mysql> ALTER ONLINE TABLE t1 ADD COLUMN c3 INT STORAGE MEMORY;
     Query OK, 0 rows affected, 1 warning (1.17 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     mysql> SHOW WARNINGS;
     +---------+------+---------------------------------------------------------------+
     | Level   | Code | Message                                                       |
     +---------+------+---------------------------------------------------------------+
     | Warning | 1478 | Converted FIXED field to DYNAMIC to enable on-line ADD COLUMN |
     +---------+------+---------------------------------------------------------------+
     1 row in set (0.00 sec)

     mysql> SHOW CREATE TABLE t1\G
     *************************** 1. row ***************************
            Table: t1
     Create Table: CREATE TABLE `t1` (
       `c1` int(11) NOT NULL,
       `c2` varchar(30) DEFAULT NULL,
       `c3` int(11) /*!50120 STORAGE MEMORY */ /*!50120 COLUMN_FORMAT DYNAMIC */ DEFAULT NULL,
       `t4` int(11) /*!50120 STORAGE MEMORY */ DEFAULT NULL,
       PRIMARY KEY (`c1`)
     ) /*!50100 TABLESPACE ts_1 STORAGE DISK */ ENGINE=ndbcluster DEFAULT CHARSET=latin1
     1 row in set (0.03 sec)

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, adding in-memory
columns to tables that were created using a table-level or column-level
`STORAGE DISK' option did not work correctly. (Bug #42549)

*Note*:

The `STORAGE' and `COLUMN_FORMAT' keywords are supported only in MySQL
Cluster; in any other version of MySQL, attempting to use either of
these keywords in a *Note `CREATE TABLE': create-table. or *Note `ALTER
TABLE': alter-table.  statement results in an error.

In MySQL Cluster NDB 7.0 and later, it is also possible to use the
statement `ALTER ONLINE TABLE ... REORGANIZE PARTITION' with no
`PARTITION_NAMES INTO (PARTITION_DEFINITIONS)' option on *Note
`NDBCLUSTER': mysql-cluster. tables. This can be used to redistribute
MySQL Cluster data among new data nodes that have been added to the
cluster online. For more information about this statement, see *Note
alter-table-partition-operations:: For more information about adding
data nodes online to a MySQL Cluster, see *Note
mysql-cluster-online-add-node::.

Prior to MySQL Cluster NDB 6.4.3, `ALTER ONLINE TABLE ... REORGANIZE
PARTITION' with no `PARTITION_NAMES INTO (PARTITION_DEFINITIONS)'
option did not work correctly with Disk Data tables or with in-memory
*Note `NDBCLUSTER': mysql-cluster. tables having one or more disk-based
columns. (Bug #42549)

*Limitations of NDBCLUSTER online operations*

Online `DROP COLUMN' operations are not supported.

Online *Note `ALTER TABLE': alter-table, *Note `CREATE INDEX':
create-index, or *Note `DROP INDEX': drop-index. statements that add
columns or add or drop indexes are subject to the following limitations:

   * A given online *Note `ALTER TABLE': alter-table.  can use only one
     of `ADD COLUMN', `ADD INDEX', or `DROP INDEX'. One or more columns
     can be added online in a single statement; only one index may be
     created or dropped online in a single statement.

   * An `ALTER TABLE' statement that performs a rename while using the
     `ONLINE' or `OFFLINE' keyword cannot perform any other operations,
     including but not limited to `ADD COLUMN', `ADD INDEX', or `DROP
     INDEX'. Beginning with MySQL Cluster NDB 6.3.52, MySQL Cluster NDB
     7.0.38, and MySQL Cluster NDB 7.1.27, such statements are
     specifically disallowed, and fail with ER_NOT_SUPPORTED_YET. (Bug
     #16021021)

   * The table being altered is not locked with respect to API nodes
     other than the one on which an online *Note `ALTER TABLE':
     alter-table. `ADD COLUMN', `ADD INDEX', or `DROP INDEX' operation
     (or *Note `CREATE INDEX': create-index. or *Note `DROP INDEX':
     drop-index. statement) is run.  However, the table is locked
     against any other operations originating on the _same_ API node
     while the online operation is being executed.

   * The table to be altered must have an explicit primary key; the
     hidden primary key created by the *Note `NDBCLUSTER':
     mysql-cluster. storage engine is not sufficient for this purpose.

   * The storage engine used by the table cannot be changed online.

   * When used with MySQL Cluster Disk Data tables, it is not possible
     to change the storage type (`DISK' or `MEMORY') of a column
     online. This means, that when you add or drop an index in such a
     way that the operation would be performed online, and you want the
     storage type of the column or columns to be changed, you must use
     the `OFFLINE' keyword in the statement that adds or drops the
     index.

Columns to be added online cannot use the *Note `BLOB': blob. or *Note
`TEXT': blob. type, and must meet the following criteria:

   * The columns must be dynamic; that is, it must be possible to
     create them using `COLUMN_FORMAT DYNAMIC'.  If you omit the
     `COLUMN_FORMAT DYNAMIC' option, the dynamic column format is
     employed automatically.

   * The columns must permit `NULL' values and not have any explicit
     default value other than `NULL'. Columns added online are
     automatically created as `DEFAULT NULL', as can be seen here:


          mysql> CREATE TABLE t1 (
               >     c1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY
               >     ) ENGINE=NDBCLUSTER;
          Query OK, 0 rows affected (1.44 sec)

          mysql> ALTER ONLINE TABLE t1
               >     ADD COLUMN c2 INT,
               >     ADD COLUMN c3 INT;
          Query OK, 0 rows affected, 2 warnings (0.93 sec)

          mysql> SHOW CREATE TABLE t1\G
          *************************** 1. row ***************************
                 Table: t1
          Create Table: CREATE TABLE `t1` (
            `c1` int(11) NOT NULL AUTO_INCREMENT,
            `c2` int(11) DEFAULT NULL,
            `c3` int(11) DEFAULT NULL,
            PRIMARY KEY (`c1`)
          ) ENGINE=ndbcluster DEFAULT CHARSET=latin1
          1 row in set (0.00 sec)

   * The columns must be added following any existing columns. If you
     attempt to add a column online before any existing columns or
     using the `FIRST' keyword, the statement fails with an error.

   * Existing table columns cannot be reordered online.

The preceding limitations do not apply to operations that merely rename
tables or columns.

For online *Note `ALTER TABLE': alter-table. operations on *Note
`NDBCLUSTER': mysql-cluster. tables, fixed-format columns are converted
to dynamic when they are added online, or when indexes are created or
dropped online, as shown here:


     mysql> CREATE TABLE t1 (
          >     c1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY
          >     ) ENGINE=NDBCLUSTER;
     Query OK, 0 rows affected (1.44 sec)

     mysql> ALTER ONLINE TABLE t1 ADD COLUMN c2 INT, ADD COLUMN c3 INT;
     Query OK, 0 rows affected, 2 warnings (0.93 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     mysql> SHOW WARNINGS;
     +---------+------+---------------------------------------------------------------+
     | Level   | Code | Message                                                       |
     +---------+------+---------------------------------------------------------------+
     | Warning | 1475 | Converted FIXED field to DYNAMIC to enable on-line ADD COLUMN |
     | Warning | 1475 | Converted FIXED field to DYNAMIC to enable on-line ADD COLUMN |
     +---------+------+---------------------------------------------------------------+
     2 rows in set (0.00 sec)

*Note*:

Existing columns, including the table's primary key, need not be
dynamic; only the column or columns to be added online must be dynamic.


     mysql> CREATE TABLE t2 (
          >     c1 INT NOT NULL AUTO_INCREMENT PRIMARY KEY COLUMN_FORMAT FIXED
          >     ) ENGINE=NDBCLUSTER;
     Query OK, 0 rows affected (2.10 sec)

     mysql> ALTER ONLINE TABLE t2 ADD COLUMN c2 INT;
     Query OK, 0 rows affected, 1 warning (0.78 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     mysql> SHOW WARNINGS;
     +---------+------+---------------------------------------------------------------+
     | Level   | Code | Message                                                       |
     +---------+------+---------------------------------------------------------------+
     | Warning | 1475 | Converted FIXED field to DYNAMIC to enable on-line ADD COLUMN |
     +---------+------+---------------------------------------------------------------+
     1 row in set (0.00 sec)

Columns are not converted from `FIXED' to `DYNAMIC' column format by
renaming operations.  For more information about `COLUMN_FORMAT', see
*Note create-table::.

The `KEY', `CONSTRAINT', and `IGNORE' keywords are supported in *Note
`ALTER TABLE': alter-table. statements using the `ONLINE' keyword.


File: manual.info,  Node: alter-table-examples,  Prev: alter-table-online-operations,  Up: alter-table

13.1.7.3 ALTER TABLE Examples
.............................

Begin with a table `t1' that is created as shown here:


     CREATE TABLE t1 (a INTEGER,b CHAR(10));

To rename the table from `t1' to `t2':


     ALTER TABLE t1 RENAME t2;

To change column `a' from *Note `INTEGER': integer-types. to `TINYINT
NOT NULL' (leaving the name the same), and to change column `b' from
`CHAR(10)' to `CHAR(20)' as well as renaming it from `b' to `c':


     ALTER TABLE t2 MODIFY a TINYINT NOT NULL, CHANGE b c CHAR(20);

To add a new *Note `TIMESTAMP': datetime. column named `d':


     ALTER TABLE t2 ADD d TIMESTAMP;

To add an index on column `d' and a `UNIQUE' index on column `a':


     ALTER TABLE t2 ADD INDEX (d), ADD UNIQUE (a);

To remove column `c':


     ALTER TABLE t2 DROP COLUMN c;

To add a new `AUTO_INCREMENT' integer column named `c':


     ALTER TABLE t2 ADD c INT UNSIGNED NOT NULL AUTO_INCREMENT,
       ADD PRIMARY KEY (c);

We indexed `c' (as a `PRIMARY KEY') because `AUTO_INCREMENT' columns
must be indexed, and we declare `c' as `NOT NULL' because primary key
columns cannot be `NULL'.

For *Note `NDB': mysql-cluster. tables, it is also possible to change
the storage type used for a table or column. For example, consider an
*Note `NDB': mysql-cluster. table created as shown here:


     mysql> CREATE TABLE t1 (c1 INT) TABLESPACE ts_1 ENGINE NDB;
     Query OK, 0 rows affected (1.27 sec)

To convert this table to disk-based storage, you can use the following
*Note `ALTER TABLE': alter-table. statement:


     mysql> ALTER TABLE t1 TABLESPACE ts_1 STORAGE DISK;
     Query OK, 0 rows affected (2.99 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     mysql> SHOW CREATE TABLE t1\G
     *************************** 1. row ***************************
            Table: t1
     Create Table: CREATE TABLE `t1` (
       `c1` int(11) DEFAULT NULL
     ) /*!50100 TABLESPACE ts_1 STORAGE DISK */
     ENGINE=ndbcluster DEFAULT CHARSET=latin1
     1 row in set (0.01 sec)

It is not necessary that the tablespace was referenced when the table
was originally created; however, the tablespace must be referenced by
the *Note `ALTER TABLE': alter-table.:


     mysql> CREATE TABLE t2 (c1 INT) ts_1 ENGINE NDB;
     Query OK, 0 rows affected (1.00 sec)

     mysql> ALTER TABLE t2 STORAGE DISK;
     `ERROR 1005 (HY000): Can't create table 'c.#sql-1750_3' (errno: 140)'
     mysql> ALTER TABLE t2 TABLESPACE ts_1 STORAGE DISK;
     Query OK, 0 rows affected (3.42 sec)
     Records: 0  Duplicates: 0  Warnings: 0
     mysql> SHOW CREATE TABLE t2\G
     *************************** 1. row ***************************
            Table: t1
     Create Table: CREATE TABLE `t2` (
       `c1` int(11) DEFAULT NULL
     ) /*!50100 TABLESPACE ts_1 STORAGE DISK */
     ENGINE=ndbcluster DEFAULT CHARSET=latin1
     1 row in set (0.01 sec)

To change the storage type of an individual column, you can use `ALTER
TABLE ... MODIFY [COLUMN]'. For example, suppose you create a MySQL
Cluster Disk Data table with two columns, using this *Note `CREATE
TABLE': create-table.  statement:


     mysql> CREATE TABLE t3 (c1 INT, c2 INT)
         ->     TABLESPACE ts_1 STORAGE DISK ENGINE NDB;
     Query OK, 0 rows affected (1.34 sec)

To change column `c2' from disk-based to in-memory storage, include a
STORAGE MEMORY clause in the column definition used by the ALTER TABLE
statement, as shown here:


     mysql> ALTER TABLE t3 MODIFY c2 INT STORAGE MEMORY;
     Query OK, 0 rows affected (3.14 sec)
     Records: 0  Duplicates: 0  Warnings: 0

You can make an in-memory column into a disk-based column by using
`STORAGE DISK' in a similar fashion.

Column `c1' uses disk-based storage, since this is the default for the
table (determined by the table-level `STORAGE DISK' clause in the *Note
`CREATE TABLE': create-table. statement). However, column `c2' uses
in-memory storage, as can be seen here in the output of SHOW *Note
`CREATE TABLE': create-table.:


     mysql> SHOW CREATE TABLE t3\G
     *************************** 1. row ***************************
            Table: t3
     Create Table: CREATE TABLE `t3` (
       `c1` int(11) DEFAULT NULL,
       `c2` int(11) /*!50120 STORAGE MEMORY */ DEFAULT NULL
     ) /*!50100 TABLESPACE ts_1 STORAGE DISK */ ENGINE=ndbcluster DEFAULT CHARSET=latin1
     1 row in set (0.02 sec)

When you add an `AUTO_INCREMENT' column, column values are filled in
with sequence numbers automatically. For `MyISAM' tables, you can set
the first sequence number by executing `SET INSERT_ID=VALUE' before
*Note `ALTER TABLE': alter-table. or by using the `AUTO_INCREMENT=VALUE'
table option. See *Note server-system-variables::.

With `MyISAM' tables, if you do not change the `AUTO_INCREMENT' column,
the sequence number is not affected. If you drop an `AUTO_INCREMENT'
column and then add another `AUTO_INCREMENT' column, the numbers are
resequenced beginning with 1.

When replication is used, adding an `AUTO_INCREMENT' column to a table
might not produce the same ordering of the rows on the slave and the
master. This occurs because the order in which the rows are numbered
depends on the specific storage engine used for the table and the order
in which the rows were inserted. If it is important to have the same
order on the master and slave, the rows must be ordered before
assigning an `AUTO_INCREMENT' number. Assuming that you want to add an
`AUTO_INCREMENT' column to the table `t1', the following statements
produce a new table `t2' identical to `t1' but with an `AUTO_INCREMENT'
column:


     CREATE TABLE t2 (id INT AUTO_INCREMENT PRIMARY KEY)
     SELECT * FROM t1 ORDER BY col1, col2;

This assumes that the table `t1' has columns `col1' and `col2'.

This set of statements will also produce a new table `t2' identical to
`t1', with the addition of an `AUTO_INCREMENT' column:


     CREATE TABLE t2 LIKE t1;
     ALTER TABLE t2 ADD id INT AUTO_INCREMENT PRIMARY KEY;
     INSERT INTO t2 SELECT * FROM t1 ORDER BY col1, col2;

*Important*:

To guarantee the same ordering on both master and slave, _all_ columns
of `t1' must be referenced in the `ORDER BY' clause.

Regardless of the method used to create and populate the copy having
the `AUTO_INCREMENT' column, the final step is to drop the original
table and then rename the copy:


     DROP TABLE t1;
     ALTER TABLE t2 RENAME t1;


File: manual.info,  Node: alter-tablespace,  Next: alter-view,  Prev: alter-table,  Up: sql-syntax-data-definition

13.1.8 ALTER TABLESPACE Syntax
------------------------------


     ALTER TABLESPACE TABLESPACE_NAME
         {ADD|DROP} DATAFILE 'FILE_NAME'
         [INITIAL_SIZE [=] SIZE]
         [WAIT]
         ENGINE [=] ENGINE_NAME

This statement can be used either to add a new data file, or to drop a
data file from a tablespace.

The `ADD DATAFILE' variant enables you to specify an initial size using
an `INITIAL_SIZE' clause, where SIZE is measured in bytes; the default
value is `128M' (128 megabytes). You may optionally follow this integer
value with a one-letter abbreviation for an order of magnitude, similar
to those used in `my.cnf'. Generally, this is one of the letters `M'
(for megabytes) or `G' (for gigabytes).

*Note*:

All MySQL Cluster Disk Data objects share the same namespace.  This
means that _each Disk Data object_ must be uniquely named (and not
merely each Disk Data object of a given type). For example, you cannot
have a tablespace and an data file with the same name, or an undo log
file and a with the same name.

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, path and file
names for data files could not be longer than 128 characters.  (Bug
#31770)

On 32-bit systems, the maximum supported value for `INITIAL_SIZE' is
`4G'. (Bug #29186)

`INITIAL_SIZE' is rounded as for *Note `CREATE TABLESPACE':
create-tablespace. Beginning with MySQL Cluster NDB 6.2.19, MySQL
Cluster NDB 6.3.32, MySQL Cluster NDB 7.0.13, and MySQL Cluster NDB
7.1.2, this rounding is done explicitly (also as with *Note `CREATE
TABLESPACE': create-tablespace.).

Once a data file has been created, its size cannot be changed; however,
you can add more data files to the tablespace using additional `ALTER
TABLESPACE ... ADD DATAFILE' statements.

Using `DROP DATAFILE' with *Note `ALTER TABLESPACE': alter-tablespace.
drops the data file 'FILE_NAME' from the tablespace.  You cannot drop a
data file from a tablespace which is in use by any table; in other
words, the data file must be empty (no extents used). See *Note
mysql-cluster-disk-data-objects::. In addition, any data file to be
dropped must previously have been added to the tablespace with *Note
`CREATE TABLESPACE': create-tablespace. or *Note `ALTER TABLESPACE':
alter-tablespace.

Both `ALTER TABLESPACE ... ADD DATAFILE' and `ALTER TABLESPACE ... DROP
DATAFILE' require an `ENGINE' clause which specifies the storage engine
used by the tablespace. In MySQL 5.1, the only accepted values for
ENGINE_NAME are *Note `NDB': mysql-cluster. and *Note `NDBCLUSTER':
mysql-cluster.

`WAIT' is parsed but otherwise ignored, and so has no effect in MySQL
5.1. It is intended for future expansion.

When `ALTER TABLESPACE ... ADD DATAFILE' is used with `ENGINE = NDB', a
data file is created on each Cluster data node. You can verify that the
data files were created and obtain information about them by querying
the *Note `INFORMATION_SCHEMA.FILES': files-table. table. For example,
the following query shows all data files belonging to the tablespace
named `newts':


     mysql> SELECT LOGFILE_GROUP_NAME, FILE_NAME, EXTRA
         -> FROM INFORMATION_SCHEMA.FILES
         -> WHERE TABLESPACE_NAME = 'newts' AND FILE_TYPE = 'DATAFILE';
     +--------------------+--------------+----------------+
     | LOGFILE_GROUP_NAME | FILE_NAME    | EXTRA          |
     +--------------------+--------------+----------------+
     | lg_3               | newdata.dat  | CLUSTER_NODE=3 |
     | lg_3               | newdata.dat  | CLUSTER_NODE=4 |
     | lg_3               | newdata2.dat | CLUSTER_NODE=3 |
     | lg_3               | newdata2.dat | CLUSTER_NODE=4 |
     +--------------------+--------------+----------------+
     2 rows in set (0.03 sec)

See *Note files-table::.

*Note `ALTER TABLESPACE': alter-tablespace. was added in MySQL 5.1.6.
In MySQL 5.1, it is useful only with Disk Data storage for MySQL
Cluster. See *Note mysql-cluster-disk-data::.


File: manual.info,  Node: alter-view,  Next: create-database,  Prev: alter-tablespace,  Up: sql-syntax-data-definition

13.1.9 ALTER VIEW Syntax
------------------------


     ALTER
         [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
         [DEFINER = { USER | CURRENT_USER }]
         [SQL SECURITY { DEFINER | INVOKER }]
         VIEW VIEW_NAME [(COLUMN_LIST)]
         AS SELECT_STATEMENT
         [WITH [CASCADED | LOCAL] CHECK OPTION]

This statement changes the definition of a view, which must exist.  The
syntax is similar to that for *Note `CREATE VIEW': create-view. and the
effect is the same as for *Note `CREATE OR REPLACE VIEW': create-view.
See *Note create-view::. This statement requires the `CREATE VIEW' and
`DROP' privileges for the view, and some privilege for each column
referred to in the *Note `SELECT': select. statement. As of MySQL
5.1.23, *Note `ALTER VIEW': alter-view. is permitted only to the
definer or users with the `SUPER' privilege.


File: manual.info,  Node: create-database,  Next: create-event,  Prev: alter-view,  Up: sql-syntax-data-definition

13.1.10 CREATE DATABASE Syntax
------------------------------


     CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] DB_NAME
         [CREATE_SPECIFICATION] ...

     CREATE_SPECIFICATION:
         [DEFAULT] CHARACTER SET [=] CHARSET_NAME
       | [DEFAULT] COLLATE [=] COLLATION_NAME

*Note `CREATE DATABASE': create-database. creates a database with the
given name. To use this statement, you need the `CREATE' privilege for
the database.  *Note `CREATE SCHEMA': create-database. is a synonym for
*Note `CREATE DATABASE': create-database.

An error occurs if the database exists and you did not specify `IF NOT
EXISTS'.

CREATE_SPECIFICATION options specify database characteristics. Database
characteristics are stored in the `db.opt' file in the database
directory.  The `CHARACTER SET' clause specifies the default database
character set. The `COLLATE' clause specifies the default database
collation.  *Note charset::, discusses character set and collation
names.

A database in MySQL is implemented as a directory containing files that
correspond to tables in the database. Because there are no tables in a
database when it is initially created, the *Note `CREATE DATABASE':
create-database. statement creates only a directory under the MySQL
data directory and the `db.opt' file. Rules for permissible database
names are given in *Note identifiers::. If a database name contains
special characters, the name for the database directory contains
encoded versions of those characters as described in *Note
identifier-mapping::.

If you manually create a directory under the data directory (for
example, with `mkdir'), the server considers it a database directory
and it shows up in the output of *Note `SHOW DATABASES': show-databases.

You can also use the *Note `mysqladmin': mysqladmin. program to create
databases. See *Note mysqladmin::.


File: manual.info,  Node: create-event,  Next: create-function,  Prev: create-database,  Up: sql-syntax-data-definition

13.1.11 CREATE EVENT Syntax
---------------------------


     CREATE
         [DEFINER = { USER | CURRENT_USER }]
         EVENT
         [IF NOT EXISTS]
         EVENT_NAME
         ON SCHEDULE SCHEDULE
         [ON COMPLETION [NOT] PRESERVE]
         [ENABLE | DISABLE | DISABLE ON SLAVE]
         [COMMENT 'COMMENT']
         DO EVENT_BODY;

     SCHEDULE:
         AT TIMESTAMP [+ INTERVAL INTERVAL] ...
       | EVERY INTERVAL
         [STARTS TIMESTAMP [+ INTERVAL INTERVAL] ...]
         [ENDS TIMESTAMP [+ INTERVAL INTERVAL] ...]

     INTERVAL:
         QUANTITY {YEAR | QUARTER | MONTH | DAY | HOUR | MINUTE |
                   WEEK | SECOND | YEAR_MONTH | DAY_HOUR | DAY_MINUTE |
                   DAY_SECOND | HOUR_MINUTE | HOUR_SECOND | MINUTE_SECOND}

This statement creates and schedules a new event. The event will not
run unless the Event Scheduler is enabled. For information about
checking Event Scheduler status and enabling it if necessary, see *Note
events-configuration::.

*Note `CREATE EVENT': create-event. requires the `EVENT' privilege for
the schema in which the event is to be created. It might also require
the `SUPER' privilege, depending on the `DEFINER' value, as described
later in this section.

The minimum requirements for a valid *Note `CREATE EVENT':
create-event. statement are as follows:

   * The keywords *Note `CREATE EVENT': create-event. plus an event
     name, which uniquely identifies the event within a database
     schema. (Prior to MySQL 5.1.12, the event name needed to be unique
     only among events created by the same user within a schema.)

   * An `ON SCHEDULE' clause, which determines when and how often the
     event executes.

   * A *Note `DO': do. clause, which contains the SQL statement to be
     executed by an event.

This is an example of a minimal *Note `CREATE EVENT': create-event.
statement:


     CREATE EVENT myevent
         ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
         DO
           UPDATE myschema.mytable SET mycol = mycol + 1;

The previous statement creates an event named `myevent'. This event
executes once--one hour following its creation--by running an SQL
statement that increments the value of the `myschema.mytable' table's
`mycol' column by 1.

The EVENT_NAME must be a valid MySQL identifier with a maximum length
of 64 characters. Event names are not case sensitive, so you cannot
have two events named `myevent' and `MyEvent' in the same schema. In
general, the rules governing event names are the same as those for
names of stored routines. See *Note identifiers::.

An event is associated with a schema. If no schema is indicated as part
of EVENT_NAME, the default (current) schema is assumed. To create an
event in a specific schema, qualify the event name with a schema using
`SCHEMA_NAME.EVENT_NAME' syntax.

The `DEFINER' clause specifies the MySQL account to be used when
checking access privileges at event execution time. If a USER value is
given, it should be a MySQL account specified as
`'USER_NAME'@'HOST_NAME'' (the same format used in the *Note `GRANT':
grant.  statement), `CURRENT_USER', or `CURRENT_USER()'. The default
`DEFINER' value is the user who executes the *Note `CREATE EVENT':
create-event. statement. This is the same as specifying `DEFINER =
CURRENT_USER' explicitly.

If you specify the `DEFINER' clause, these rules determine the valid
`DEFINER' user values:

   * If you do not have the `SUPER' privilege, the only permitted USER
     value is your own account, either specified literally or by using
     `CURRENT_USER'. You cannot set the definer to some other account.

   * If you have the `SUPER' privilege, you can specify any
     syntactically valid account name. If the account does not actually
     exist, a warning is generated.

   * Although it is possible to create an event with a nonexistent
     `DEFINER' account, an error occurs at event execution time if the
     account does not exist.

For more information about event security, see *Note
stored-programs-security::.

The `DEFINER' clause was added in MySQL 5.1.17.

Within an event, the `CURRENT_USER()' function returns the account used
to check privileges at event execution time, which is the `DEFINER'
user. For information about user auditing within events, see *Note
account-activity-auditing::.

`IF NOT EXISTS' has the same meaning for *Note `CREATE EVENT':
create-event. as for *Note `CREATE TABLE': create-table.: If an event
named EVENT_NAME already exists in the same schema, no action is taken,
and no error results. (However, a warning is generated in such cases.)

The `ON SCHEDULE' clause determines when, how often, and for how long
the EVENT_BODY defined for the event repeats. This clause takes one of
two forms:

   * `AT TIMESTAMP' is used for a one-time event. It specifies that the
     event executes one time only at the date and time given by
     TIMESTAMP, which must include both the date and time, or must be
     an expression that resolves to a datetime value. You may use a
     value of either the *Note `DATETIME': datetime. or *Note
     `TIMESTAMP': datetime. type for this purpose. If the date is in
     the past, a warning occurs, as shown here:


          mysql> SELECT NOW();
          +---------------------+
          | NOW()               |
          +---------------------+
          | 2006-02-10 23:59:01 |
          +---------------------+
          1 row in set (0.04 sec)

          mysql> CREATE EVENT e_totals
              ->     ON SCHEDULE AT '2006-02-10 23:59:00'
              ->     DO INSERT INTO test.totals VALUES (NOW());
          Query OK, 0 rows affected, 1 warning (0.00 sec)

          mysql> SHOW WARNINGS\G
          *************************** 1. row ***************************
            Level: Note
             Code: 1588
          Message: Event execution time is in the past and ON COMPLETION NOT
                   PRESERVE is set. The event was dropped immediately after
                   creation.

     *Note `CREATE EVENT': create-event. statements which are
     themselves invalid--for whatever reason--fail with an error.

     You may use `CURRENT_TIMESTAMP' to specify the current date and
     time. In such a case, the event acts as soon as it is created.

     To create an event which occurs at some point in the future
     relative to the current date and time--such as that expressed by
     the phrase `three weeks from now'--you can use the optional clause
     `+ INTERVAL INTERVAL'. The INTERVAL portion consists of two parts,
     a quantity and a unit of time, and follows the same syntax rules
     that govern intervals used in the `DATE_ADD()' function (see *Note
     date-and-time-functions::. The units keywords are also the same,
     except that you cannot use any units involving microseconds when
     defining an event. With some interval types, complex time units
     may be used. For example, `two minutes and ten seconds' can be
     expressed as `+ INTERVAL '2:10' MINUTE_SECOND'.

     You can also combine intervals. For example, `AT CURRENT_TIMESTAMP
     + INTERVAL 3 WEEK + INTERVAL 2 DAY' is equivalent to `three weeks
     and two days from now'. Each portion of such a clause must begin
     with `+ INTERVAL'.

   * To repeat actions at a regular interval, use an `EVERY' clause.
     The `EVERY' keyword is followed by an INTERVAL as described in the
     previous discussion of the `AT' keyword. (`+ INTERVAL' is _not_
     used with `EVERY'.) For example, `EVERY 6 WEEK' means `every six
     weeks'.

     Although `+ INTERVAL' clauses are not permitted in an `EVERY'
     clause, you can use the same complex time units permitted in a `+
     INTERVAL'.

     An `EVERY' clause may contain an optional `STARTS' clause.
     `STARTS' is followed by a TIMESTAMP value that indicates when the
     action should begin repeating, and may also use `+ INTERVAL
     INTERVAL' to specify an amount of time `from now'. For example,
     `EVERY 3 MONTH STARTS CURRENT_TIMESTAMP + INTERVAL 1 WEEK' means
     `every three months, beginning one week from now'. Similarly, you
     can express `every two weeks, beginning six hours and fifteen
     minutes from now' as `EVERY 2 WEEK STARTS CURRENT_TIMESTAMP +
     INTERVAL '6:15' HOUR_MINUTE'. Not specifying `STARTS' is the same
     as using `STARTS CURRENT_TIMESTAMP'--that is, the action specified
     for the event begins repeating immediately upon creation of the
     event.

     An `EVERY' clause may contain an optional `ENDS' clause. The `ENDS'
     keyword is followed by a TIMESTAMP value that tells MySQL when the
     event should stop repeating.  You may also use `+ INTERVAL
     INTERVAL' with `ENDS'; for instance, `EVERY 12 HOUR STARTS
     CURRENT_TIMESTAMP + INTERVAL 30 MINUTE ENDS CURRENT_TIMESTAMP +
     INTERVAL 4 WEEK' is equivalent to `every twelve hours, beginning
     thirty minutes from now, and ending four weeks from now'. Not using
     `ENDS' means that the event continues executing indefinitely.

     `ENDS' supports the same syntax for complex time units as `STARTS'
     does.

     You may use `STARTS', `ENDS', both, or neither in an `EVERY'
     clause.

     If a repeating event does not terminate within its scheduling
     interval, the result may be multiple instances of the event
     executing simultaneously. If this is undesirable, you should
     institute a mechanism to prevent simultaneous instances. For
     example, you could use the `GET_LOCK()' function, or row or table
     locking.

The `ON SCHEDULE' clause may use expressions involving built-in MySQL
functions and user variables to obtain any of the TIMESTAMP or INTERVAL
values which it contains. You may not use stored functions or
user-defined functions in such expressions, nor may you use any table
references; however, you may use `SELECT FROM DUAL'. This is true for
both *Note `CREATE EVENT': create-event. and *Note `ALTER EVENT':
alter-event. statements. Beginning with MySQL 5.1.13, references to
stored functions, user-defined functions, and tables in such cases are
specifically not permitted, and fail with an error (see Bug #22830).

Times in the `ON SCHEDULE' clause are interpreted using the current
session `time_zone' value. This becomes the event time zone; that is,
the time zone that is used for event scheduling and is in effect within
the event as it executes. These times are converted to UTC and stored
along with the event time zone in the `mysql.event' table. This enables
event execution to proceed as defined regardless of any subsequent
changes to the server time zone or daylight saving time effects.  For
additional information about representation of event times, see *Note
events-metadata::. See also *Note show-events::, and *Note
events-table::.

*Note*:

Prior to MySQL 5.1.17, the event time zone is not stored. The
`mysql.event' table must be updated before events created in earlier
releases can be created, altered, viewed, or used in MySQL 5.1.17 or
later. You can use *Note `mysql_upgrade': mysql-upgrade. for this (see
*Note mysql-upgrade::).

Normally, once an event has expired, it is immediately dropped.  You
can override this behavior by specifying `ON COMPLETION PRESERVE'.
Using `ON COMPLETION NOT PRESERVE' merely makes the default
nonpersistent behavior explicit.

You can create an event but prevent it from being active using the
`DISABLE' keyword. Alternatively, you can use `ENABLE' to make explicit
the default status, which is active. This is most useful in conjunction
with *Note `ALTER EVENT': alter-event. (see *Note alter-event::).

Beginning with MySQL 5.1.18, a third value may also appear in place of
`ENABLE' or `DISABLE'; `DISABLE ON SLAVE' is set for the status of an
event on a replication slave to indicate that the event was created on
the master and replicated to the slave, but is not executed on the
slave. See *Note replication-features-invoked::.

You may supply a comment for an event using a `COMMENT' clause.
COMMENT may be any string of up to 64 characters that you wish to use
for describing the event. The comment text, being a string literal,
must be surrounded by quotation marks.

The *Note `DO': do. clause specifies an action carried by the event,
and consists of an SQL statement. Nearly any valid MySQL statement that
can be used in a stored routine can also be used as the action
statement for a scheduled event. (See *Note
stored-program-restrictions::.) For example, the following event
`e_hourly' deletes all rows from the `sessions' table once per hour,
where this table is part of the `site_activity' schema:


     CREATE EVENT e_hourly
         ON SCHEDULE
           EVERY 1 HOUR
         COMMENT 'Clears out sessions table each hour.'
         DO
           DELETE FROM site_activity.sessions;

MySQL stores the `sql_mode' system variable setting in effect when an
event is created or altered, and always executes the event with this
setting in force, _regardless of the current server SQL mode when the
event begins executing_.

A *Note `CREATE EVENT': create-event. statement that contains an *Note
`ALTER EVENT': alter-event. statement in its *Note `DO': do. clause
appears to succeed; however, when the server attempts to execute the
resulting scheduled event, the execution fails with an error.

*Note*:

Statements such as *Note `SELECT': select. or *Note `SHOW': show. that
merely return a result set have no effect when used in an event; the
output from these is not sent to the MySQL Monitor, nor is it stored
anywhere.  However, you can use statements such as *Note `SELECT ...
INTO': select. and *Note `INSERT INTO ... SELECT': insert-select. that
store a result. (See the next example in this section for an instance
of the latter.)

The schema to which an event belongs is the default schema for table
references in the *Note `DO': do. clause.  Any references to tables in
other schemas must be qualified with the proper schema name. (In MySQL
5.1.6, all tables referenced in event *Note `DO': do. clauses had to
include a reference to the schema.)

As with stored routines, you can use compound-statement syntax in the
*Note `DO': do. clause by using the `BEGIN' and `END' keywords, as
shown here:


     delimiter |

     CREATE EVENT e_daily
         ON SCHEDULE
           EVERY 1 DAY
         COMMENT 'Saves total number of sessions then clears the table each day'
         DO
           BEGIN
             INSERT INTO site_activity.totals (time, total)
               SELECT CURRENT_TIMESTAMP, COUNT(*)
                 FROM site_activity.sessions;
             DELETE FROM site_activity.sessions;
           END |

     delimiter ;

This example uses the `delimiter' command to change the statement
delimiter. See *Note stored-programs-defining::.

More complex compound statements, such as those used in stored
routines, are possible in an event. This example uses local variables,
an error handler, and a flow control construct:


     delimiter |

     CREATE EVENT e
         ON SCHEDULE
           EVERY 5 SECOND
         DO
           BEGIN
             DECLARE v INTEGER;
             DECLARE CONTINUE HANDLER FOR SQLEXCEPTION BEGIN END;

             SET v = 0;

             WHILE v < 5 DO
               INSERT INTO t1 VALUES (0);
               UPDATE t2 SET s1 = s1 + 1;
               SET v = v + 1;
             END WHILE;
         END |

     delimiter ;

There is no way to pass parameters directly to or from events; however,
it is possible to invoke a stored routine with parameters within an
event:


     CREATE EVENT e_call_myproc
         ON SCHEDULE
           AT CURRENT_TIMESTAMP + INTERVAL 1 DAY
         DO CALL myproc(5, 27);

If an event's definer has the `SUPER' privilege, the event can read and
write global variables. As granting this privilege entails a potential
for abuse, extreme care must be taken in doing so.

Generally, any statements that are valid in stored routines may be used
for action statements executed by events. For more information about
statements permitted within stored routines, see *Note
stored-routines-syntax::. You can create an event as part of a stored
routine, but an event cannot be created by another event.


File: manual.info,  Node: create-function,  Next: create-index,  Prev: create-event,  Up: sql-syntax-data-definition

13.1.12 CREATE FUNCTION Syntax
------------------------------

The *Note `CREATE FUNCTION': create-function. statement is used to
create stored functions and user-defined functions (UDFs):

   * For information about creating stored functions, see *Note
     create-procedure::.

   * For information about creating user-defined functions, see *Note
     create-function-udf::.


File: manual.info,  Node: create-index,  Next: create-logfile-group,  Prev: create-function,  Up: sql-syntax-data-definition

13.1.13 CREATE INDEX Syntax
---------------------------


     CREATE [ONLINE|OFFLINE] [UNIQUE|FULLTEXT|SPATIAL] INDEX INDEX_NAME
         [INDEX_TYPE]
         ON TBL_NAME (INDEX_COL_NAME,...)
         [INDEX_OPTION] ...

     INDEX_COL_NAME:
         COL_NAME [(LENGTH)] [ASC | DESC]

     INDEX_TYPE:
         USING {BTREE | HASH}

     INDEX_OPTION:
         KEY_BLOCK_SIZE [=] VALUE
       | INDEX_TYPE
       | WITH PARSER PARSER_NAME

*Note `CREATE INDEX': create-index. is mapped to an *Note `ALTER
TABLE': alter-table. statement to create indexes. See *Note
alter-table::.  *Note `CREATE INDEX': create-index. cannot be used to
create a `PRIMARY KEY'; use *Note `ALTER TABLE': alter-table. instead.
For more information about indexes, see *Note mysql-indexes::.

Normally, you create all indexes on a table at the time the table
itself is created with *Note `CREATE TABLE': create-table. See *Note
create-table::. This guideline is especially important for `InnoDB'
tables, where the primary key determines the physical layout of rows in
the data file. *Note `CREATE INDEX': create-index.  enables you to add
indexes to existing tables.

A column list of the form `(col1,col2,...)' creates a multiple-column
index. Index key values are formed by concatenating the values of the
given columns.

Indexes can be created that use only the leading part of column values,
using `COL_NAME(LENGTH)' syntax to specify an index prefix length:

   * Prefixes can be specified for *Note `CHAR': char, *Note `VARCHAR':
     char, *Note `BINARY': binary-varbinary, and *Note `VARBINARY':
     binary-varbinary. columns.

   * *Note `BLOB': blob. and *Note `TEXT': blob. columns also can be
     indexed, but a prefix length _must_ be given.

   * Prefix lengths are given in characters for nonbinary string types
     and in bytes for binary string types. That is, index entries
     consist of the first LENGTH characters of each column value for
     *Note `CHAR': char, *Note `VARCHAR': char, and *Note `TEXT': blob.
     columns, and the first LENGTH bytes of each column value for *Note
     `BINARY': binary-varbinary, *Note `VARBINARY': binary-varbinary,
     and *Note `BLOB': blob. columns.

   * For spatial columns, prefix values cannot be given, as described
     later in this section.

The statement shown here creates an index using the first 10 characters
of the `name' column:


     CREATE INDEX part_of_name ON customer (name(10));

If names in the column usually differ in the first 10 characters, this
index should not be much slower than an index created from the entire
`name' column. Also, using column prefixes for indexes can make the
index file much smaller, which could save a lot of disk space and might
also speed up *Note `INSERT': insert. operations.

Prefix support and lengths of prefixes (where supported) are storage
engine dependent. For example, a prefix can be up to 1000 bytes long
for `MyISAM' tables, and 767 bytes for `InnoDB' tables. The
`NDBCLUSTER' storage engine does not support prefixes (see *Note
mysql-cluster-limitations-unsupported::).

*Note*:

Prefix limits are measured in bytes, whereas the prefix length in *Note
`CREATE INDEX': create-index. statements is interpreted as number of
characters for nonbinary data types (*Note `CHAR': char, *Note
`VARCHAR': char, *Note `TEXT': blob.). Take this into account when
specifying a prefix length for a column that uses a multibyte character
set.

Beginning with MySQL 5.1.17, indexes on variable-width columns of *Note
`NDBCLUSTER': mysql-cluster. tables are created online; that is,
without any table copying. The table is not locked against access from
other MySQL Cluster API nodes, although it is locked against other
operations on the _same_ API node for the duration of the operation.
This is done automatically by the server whenever it determines that it
is possible to do so; you do not have to use any special SQL syntax or
server options to cause it to happen.

In standard MySQL 5.1 releases, it is not possible to override the
server when it determines that an index is to be created without table
copying. In MySQL Cluster, you can create indexes offline (which causes
the table to be locked to all API nodes in the cluster) using the
`OFFLINE' keyword. The rules and limitations governing `CREATE OFFLINE
INDEX' and `CREATE ONLINE INDEX' are the same as for `ALTER OFFLINE
TABLE ... ADD INDEX' and `ALTER ONLINE TABLE ... ADD INDEX'. You cannot
cause the noncopying creation of an index that would normally be
created offline by using the `ONLINE' keyword: If it is not possible to
perform the *Note `CREATE INDEX': create-index. operation without table
copying, the server ignores the `ONLINE' keyword. For more information,
see *Note alter-table-online-operations::.

*Note*:

The `ONLINE' and `OFFLINE' keywords are available only in MySQL Cluster
NDB 6.2.5, 6.3.2, and later MySQL Cluster releases; attempting to use
these keywords in earlier MySQL Cluster releases or standard MySQL 5.1
releases results in a syntax error.

A `UNIQUE' index creates a constraint such that all values in the index
must be distinct. An error occurs if you try to add a new row with a
key value that matches an existing row. For all engines, a `UNIQUE'
index permits multiple `NULL' values for columns that can contain
`NULL'. If you specify a prefix value for a column in a `UNIQUE' index,
the column values must be unique within the prefix.

`FULLTEXT' indexes are supported only for `MyISAM' tables and can
include only *Note `CHAR': char, *Note `VARCHAR': char, and *Note
`TEXT': blob. columns. Indexing always happens over the entire column;
column prefix indexing is not supported and any prefix length is
ignored if specified. See *Note fulltext-search::, for details of
operation.

The `MyISAM', `InnoDB', *Note `NDB': mysql-cluster, and `ARCHIVE'
storage engines support spatial columns such as (`POINT' and `GEOMETRY'.
(*Note spatial-extensions::, describes the spatial data types.)
However, support for spatial column indexing varies among engines.
Spatial and nonspatial indexes are available according to the following
rules.

Spatial indexes (created using `SPATIAL INDEX') have these
characteristics:

   * Available only for `MyISAM' tables.  Specifying `SPATIAL INDEX'
     for other storage engines results in an error.

   * Indexed columns must be `NOT NULL'.

   * In MySQL 5.1, column prefix lengths are prohibited. The full width
     of each column is indexed.

Characteristics of nonspatial indexes (created with `INDEX', `UNIQUE',
or `PRIMARY KEY'):

   * Permitted for any storage engine that supports spatial columns
     except `ARCHIVE'.

   * Columns can be `NULL' unless the index is a primary key.

   * For each spatial column in a non-`SPATIAL' index except `POINT'
     columns, a column prefix length must be specified. (This is the
     same requirement as for indexed *Note `BLOB': blob. columns.) The
     prefix length is given in bytes.

   * The index type for a non-`SPATIAL' index depends on the storage
     engine. Currently, B-tree is used.

In MySQL 5.1:

   * You can add an index on a column that can have `NULL' values only
     if you are using the `MyISAM', `InnoDB', or `MEMORY' storage
     engine.

   * You can add an index on a *Note `BLOB': blob.  or *Note `TEXT':
     blob. column only if you are using the `MyISAM', or `InnoDB'
     storage engine.

An INDEX_COL_NAME specification can end with `ASC' or `DESC'. These
keywords are permitted for future extensions for specifying ascending
or descending index value storage. Currently, they are parsed but
ignored; index values are always stored in ascending order.

As of MySQL 5.1.10, index options can be given following the index
column list. An INDEX_OPTION value can be any of the following:

   * `KEY_BLOCK_SIZE [=] VALUE'

     Optionally specifies the size in bytes to use for index key
     blocks. The value is treated as a hint; a different size could be
     used if necessary.

     *Note*:

     `KEY_BLOCK_SIZE' is only supported at the table level for
     `InnoDB'. See *Note create-table::.

   * INDEX_TYPE

     Some storage engines permit you to specify an index type when
     creating an index. The permissible index type values supported by
     different storage engines are shown in the following table.  Where
     multiple index types are listed, the first one is the default when
     no index type specifier is given.

     This table lists permissible index types for each storage engine.

     Storage       Permissible Index Types
     Engine        
     `MyISAM'      `BTREE'
     `InnoDB'      `BTREE'
     `MEMORY'/`HEAP'`HASH', `BTREE'
     *Note `NDB':  `BTREE', `HASH' (see note in text)
     mysql-cluster.

     Example:


          CREATE TABLE lookup (id INT) ENGINE = MEMORY;
          CREATE INDEX id_index ON lookup (id) USING BTREE;

     `BTREE' indexes are implemented by the *Note `NDBCLUSTER':
     mysql-cluster. storage engine as T-tree indexes.

     *Note*:

     For indexes on *Note `NDB': mysql-cluster. table columns, the
     `USING' option can be specified only for a unique index or primary
     key.  `USING HASH' prevents the creation of an implicit ordered
     index; otherwise, creating a unique index or primary key on an
     *Note `NDB': mysql-cluster. table automatically results in the
     creation of both an ordered index and a hash index, each of which
     indexes the same set of columns.

     This means that a query using a unique index or primary key on a
     `NULL' column is always handled by *Note `NDB': mysql-cluster.
     with a full scan of the table. In particular, if you plan to use
     an `IS NULL' or `IS NOT NULL' condition involving a unique index
     or primary key column of an *Note `NDB': mysql-cluster. table, you
     should create any such index without `USING HASH'.

     The INDEX_TYPE clause cannot be used together with `SPATIAL INDEX'.

     If you specify an index type that is not valid for a given storage
     engine, but there is another index type available that the engine
     can use without affecting query results, the engine uses the
     available type. The parser recognizes `RTREE' as a type name, but
     currently this cannot be specified for any storage engine.

     Before MySQL 5.1.10, this option can be given only before the `ON
     TBL_NAME' clause. Use of the option in this position is deprecated
     as of 5.1.10 and support for it there will be removed in a future
     MySQL release. If an INDEX_TYPE option is given in both the
     earlier and later positions, the final option applies.

     `TYPE TYPE_NAME' is recognized as a synonym for `USING TYPE_NAME'.
     However, `USING' is the preferred form.

   * `WITH PARSER PARSER_NAME'

     This option can be used only with `FULLTEXT' indexes. It
     associates a parser plugin with the index if full-text indexing
     and searching operations need special handling. See *Note
     plugin-api::, for details on creating plugins.


File: manual.info,  Node: create-logfile-group,  Next: create-procedure,  Prev: create-index,  Up: sql-syntax-data-definition

13.1.14 CREATE LOGFILE GROUP Syntax
-----------------------------------


     CREATE LOGFILE GROUP LOGFILE_GROUP
         ADD UNDOFILE 'UNDO_FILE'
         [INITIAL_SIZE [=] INITIAL_SIZE]
         [UNDO_BUFFER_SIZE [=] UNDO_BUFFER_SIZE]
         [REDO_BUFFER_SIZE [=] REDO_BUFFER_SIZE]
         [NODEGROUP [=] NODEGROUP_ID]
         [WAIT]
         [COMMENT [=] COMMENT_TEXT]
         ENGINE [=] ENGINE_NAME

This statement creates a new log file group named LOGFILE_GROUP having
a single `UNDO' file named 'UNDO_FILE'. A *Note `CREATE LOGFILE GROUP':
create-logfile-group. statement has one and only one `ADD UNDOFILE'
clause. For rules covering the naming of log file groups, see *Note
identifiers::.

*Note*:

All MySQL Cluster Disk Data objects share the same namespace.  This
means that _each Disk Data object_ must be uniquely named (and not
merely each Disk Data object of a given type). For example, you cannot
have a tablespace and a log file group with the same name, or a
tablespace and a data file with the same name.

Beginning with MySQL 5.1.8, you can have only one log file group per
Cluster at any given time. (See Bug #16386)

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, path and file
names for undo log files could not be longer than 128 characters. (Bug
#31769)

The optional `INITIAL_SIZE' parameter sets the `UNDO' file's initial
size; if not specified, it defaults to `128M' (128 megabytes). The
optional `UNDO_BUFFER_SIZE' parameter sets the size used by the `UNDO'
buffer for the log file group; The default value for `UNDO_BUFFER_SIZE'
is `8M' (eight megabytes); this value cannot exceed the amount of
system memory available. Both of these parameters are specified in
bytes. You may optionally follow either or both of these with a
one-letter abbreviation for an order of magnitude, similar to those
used in `my.cnf'. Generally, this is one of the letters `M' (for
megabytes) or `G' (for gigabytes).

The memory used for both `INITIAL_SIZE' and `UNDO_BUFFER_SIZE' comes
from the global pool whose size is determined by the value of the
`SharedGlobalMemory' data node configuration parameter. This includes
any default value implied for these options by the setting of the
`InitialLogFileGroup' data node configuration parameter.

Beginning with MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, the maximum
permitted for `UNDO_BUFFER_SIZE' is `600M'; previously, it was `150M'.
(Bug #34102)

On 32-bit systems, the maximum supported value for `INITIAL_SIZE' is
`4G'. (Bug #29186)

Beginning with MySQL Cluster NDB 2.1.18, 6.3.24, and 7.0.4, the minimum
permitted value for `INITIAL_SIZE' is `1M'. (Bug #29574)

The `ENGINE' option determines the storage engine to be used by this
log file group, with ENGINE_NAME being the name of the storage engine.
In MySQL 5.1, this must be *Note `NDB': mysql-cluster. (or *Note
`NDBCLUSTER': mysql-cluster.). If `ENGINE' is not set, MySQL tries to
use the engine specified by the `storage_engine' server system
variable. In any case, if the engine is not specified as *Note `NDB':
mysql-cluster. or *Note `NDBCLUSTER': mysql-cluster, the `CREATE
LOGFILE GROUP' statement appears to succeed but actually fails to
create the log file group, as shown here:


     mysql> CREATE LOGFILE GROUP lg1
         ->     ADD UNDOFILE 'undo.dat' INITIAL_SIZE = 10M;
     Query OK, 0 rows affected, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS;
     +-------+------+------------------------------------------------------------------------------------------------+
     | Level | Code | Message                                                                                        |
     +-------+------+------------------------------------------------------------------------------------------------+
     | Error | 1478 | `Table storage engine 'MyISAM' does not support the create option 'TABLESPACE or LOGFILE GROUP'' |
     +-------+------+------------------------------------------------------------------------------------------------+
     1 row in set (0.00 sec)

     mysql> DROP LOGFILE GROUP lg1 ENGINE = NDB;
     `ERROR 1529 (HY000): Failed to drop LOGFILE GROUP'

     mysql> CREATE LOGFILE GROUP lg1
         ->     ADD UNDOFILE 'undo.dat' INITIAL_SIZE = 10M
         ->     ENGINE = NDB;
     Query OK, 0 rows affected (2.97 sec)

The fact that the `CREATE LOGFILE GROUP' statement does not actually
return an error when a non-`NDB' storage engine is named, but rather
appears to succeed, is a known issue which we hope to address in a
future release of MySQL Cluster.

REDO_BUFFER_SIZE, `NODEGROUP', `WAIT', and `COMMENT' are parsed but
ignored, and so have no effect in MySQL 5.1. These options are intended
for future expansion.

When used with `ENGINE [=] NDB', a log file group and associated `UNDO'
log file are created on each Cluster data node. You can verify that the
`UNDO' files were created and obtain information about them by querying
the *Note `INFORMATION_SCHEMA.FILES': files-table. table. For example:


     mysql> SELECT LOGFILE_GROUP_NAME, LOGFILE_GROUP_NUMBER, EXTRA
         -> FROM INFORMATION_SCHEMA.FILES
         -> WHERE FILE_NAME = 'undo_10.dat';
     +--------------------+----------------------+----------------+
     | LOGFILE_GROUP_NAME | LOGFILE_GROUP_NUMBER | EXTRA          |
     +--------------------+----------------------+----------------+
     | lg_3               |                   11 | CLUSTER_NODE=3 |
     | lg_3               |                   11 | CLUSTER_NODE=4 |
     +--------------------+----------------------+----------------+
     2 rows in set (0.06 sec)

*Note `CREATE LOGFILE GROUP': create-logfile-group. was added in MySQL
5.1.6. In MySQL 5.1, it is useful only with Disk Data storage for MySQL
Cluster. See *Note mysql-cluster-disk-data::.


File: manual.info,  Node: create-procedure,  Next: create-server,  Prev: create-logfile-group,  Up: sql-syntax-data-definition

13.1.15 CREATE PROCEDURE and CREATE FUNCTION Syntax
---------------------------------------------------


     CREATE
         [DEFINER = { USER | CURRENT_USER }]
         PROCEDURE SP_NAME ([PROC_PARAMETER[,...]])
         [CHARACTERISTIC ...] ROUTINE_BODY

     CREATE
         [DEFINER = { USER | CURRENT_USER }]
         FUNCTION SP_NAME ([FUNC_PARAMETER[,...]])
         RETURNS TYPE
         [CHARACTERISTIC ...] ROUTINE_BODY

     PROC_PARAMETER:
         [ IN | OUT | INOUT ] PARAM_NAME TYPE

     FUNC_PARAMETER:
         PARAM_NAME TYPE

     TYPE:
         ANY VALID MYSQL DATA TYPE

     CHARACTERISTIC:
         COMMENT 'STRING'
       | LANGUAGE SQL
       | [NOT] DETERMINISTIC
       | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
       | SQL SECURITY { DEFINER | INVOKER }

     ROUTINE_BODY:
         VALID SQL ROUTINE STATEMENT

These statements create stored routines. By default, a routine is
associated with the default database. To associate the routine
explicitly with a given database, specify the name as DB_NAME.SP_NAME
when you create it.

The *Note `CREATE FUNCTION': create-function. statement is also used in
MySQL to support UDFs (user-defined functions). See *Note
adding-functions::. A UDF can be regarded as an external stored
function. Stored functions share their namespace with UDFs. See *Note
function-resolution::, for the rules describing how the server
interprets references to different kinds of functions.

To invoke a stored procedure, use the *Note `CALL': call. statement (see
*Note call::). To invoke a stored function, refer to it in an
expression. The function returns a value during expression evaluation.

*Note `CREATE PROCEDURE': create-procedure. and *Note `CREATE
FUNCTION': create-function. require the `CREATE ROUTINE' privilege. They
might also require the `SUPER' privilege, depending on the `DEFINER'
value, as described later in this section. If binary logging is enabled,
*Note `CREATE FUNCTION': create-function. might require the `SUPER'
privilege, as described in *Note stored-programs-logging::.

By default, MySQL automatically grants the `ALTER ROUTINE' and
`EXECUTE' privileges to the routine creator. This behavior can be
changed by disabling the `automatic_sp_privileges' system variable. See
*Note stored-routines-privileges::.

The `DEFINER' and `SQL SECURITY' clauses specify the security context
to be used when checking access privileges at routine execution time,
as described later in this section.

If the routine name is the same as the name of a built-in SQL function,
a syntax error occurs unless you use a space between the name and the
following parenthesis when defining the routine or invoking it later.
For this reason, avoid using the names of existing SQL functions for
your own stored routines.

The `IGNORE_SPACE' SQL mode applies to built-in functions, not to
stored routines. It is always permissible to have spaces after a stored
routine name, regardless of whether `IGNORE_SPACE' is enabled.

The parameter list enclosed within parentheses must always be present.
If there are no parameters, an empty parameter list of `()' should be
used. Parameter names are not case sensitive.

Each parameter is an `IN' parameter by default.  To specify otherwise
for a parameter, use the keyword `OUT' or `INOUT' before the parameter
name.

*Note*:

Specifying a parameter as `IN', `OUT', or `INOUT' is valid only for a
`PROCEDURE'. For a `FUNCTION', parameters are always regarded as `IN'
parameters.

An `IN' parameter passes a value into a procedure. The procedure might
modify the value, but the modification is not visible to the caller
when the procedure returns. An `OUT' parameter passes a value from the
procedure back to the caller. Its initial value is `NULL' within the
procedure, and its value is visible to the caller when the procedure
returns. An `INOUT' parameter is initialized by the caller, can be
modified by the procedure, and any change made by the procedure is
visible to the caller when the procedure returns.

For each `OUT' or `INOUT' parameter, pass a user-defined variable in the
*Note `CALL': call. statement that invokes the procedure so that you
can obtain its value when the procedure returns. If you are calling the
procedure from within another stored procedure or function, you can
also pass a routine parameter or local routine variable as an `IN' or
`INOUT' parameter.

Routine parameters cannot be referenced in statements prepared within
the routine; see *Note stored-program-restrictions::.

The following example shows a simple stored procedure that uses an
`OUT' parameter:


     mysql> delimiter //

     mysql> CREATE PROCEDURE simpleproc (OUT param1 INT)
         -> BEGIN
         ->   SELECT COUNT(*) INTO param1 FROM t;
         -> END//
     Query OK, 0 rows affected (0.00 sec)

     mysql> delimiter ;

     mysql> CALL simpleproc(@a);
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @a;
     +------+
     | @a   |
     +------+
     | 3    |
     +------+
     1 row in set (0.00 sec)

The example uses the *Note `mysql': mysql. client `delimiter' command
to change the statement delimiter from `;' to `//' while the procedure
is being defined. This enables the `;' delimiter used in the procedure
body to be passed through to the server rather than being interpreted by
*Note `mysql': mysql. itself. See *Note stored-programs-defining::.

The `RETURNS' clause may be specified only for a `FUNCTION', for which
it is mandatory. It indicates the return type of the function, and the
function body must contain a `RETURN VALUE' statement. If the *Note
`RETURN': return. statement returns a value of a different type, the
value is coerced to the proper type. For example, if a function
specifies an *Note `ENUM': enum. or *Note `SET': set. value in the
`RETURNS' clause, but the *Note `RETURN': return. statement returns an
integer, the value returned from the function is the string for the
corresponding *Note `ENUM': enum. member of set of *Note `SET': set.
members.

The following example function takes a parameter, performs an operation
using an SQL function, and returns the result. In this case, it is
unnecessary to use `delimiter' because the function definition contains
no internal `;' statement delimiters:


     mysql> CREATE FUNCTION hello (s CHAR(20))
     mysql> RETURNS CHAR(50) DETERMINISTIC
         -> RETURN CONCAT('Hello, ',s,'!');
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT hello('world');
     +----------------+
     | hello('world') |
     +----------------+
     | Hello, world!  |
     +----------------+
     1 row in set (0.00 sec)

Parameter types and function return types can be declared to use any
valid data type, except that the `COLLATE' attribute cannot be used.

The ROUTINE_BODY consists of a valid SQL routine statement. This can be
a simple statement such as *Note `SELECT': select. or *Note `INSERT':
insert, or a compound statement written using `BEGIN' and `END'.
Compound statements can contain declarations, loops, and other control
structure statements. The syntax for these statements is described in
*Note sql-syntax-compound-statements::.

MySQL permits routines to contain DDL statements, such as `CREATE' and
`DROP'. MySQL also permits stored procedures (but not stored functions)
to contain SQL transaction statements such as *Note `COMMIT': commit.
Stored functions may not contain statements that perform explicit or
implicit commit or rollback. Support for these statements is not
required by the SQL standard, which states that each DBMS vendor may
decide whether to permit them.

Statements that return a result set can be used within a stored
procedure but not within a stored function. This prohibition includes
*Note `SELECT': select. statements that do not have an `INTO VAR_LIST'
clause and other statements such as *Note `SHOW': show, *Note
`EXPLAIN': explain, and *Note `CHECK TABLE': check-table. For
statements that can be determined at function definition time to return
a result set, a `Not allowed to return a result set from a function'
error occurs (`ER_SP_NO_RETSET'). For statements that can be determined
only at runtime to return a result set, a `PROCEDURE %s can't return a
result set in the given context' error occurs (`ER_SP_BADSELECT').

*Note `USE': use. statements within stored routines are not permitted.
When a routine is invoked, an implicit `USE DB_NAME' is performed (and
undone when the routine terminates). This causes the routine to have
the given default database while it executes.  References to objects in
databases other than the routine default database should be qualified
with the appropriate database name.

For additional information about statements that are not permitted in
stored routines, see *Note stored-program-restrictions::.

For information about invoking stored procedures from within programs
written in a language that has a MySQL interface, see *Note call::.

MySQL stores the `sql_mode' system variable setting in effect when a
routine is created or altered, and always executes the routine with
this setting in force, _regardless of the current server SQL mode when
the routine begins executing_.

The switch from the SQL mode of the invoker to that of the routine
occurs after evaluation of arguments and assignment of the resulting
values to routine parameters. If you define a routine in strict SQL
mode but invoke it in nonstrict mode, assignment of arguments to
routine parameters does not take place in strict mode. If you require
that expressions passed to a routine be assigned in strict SQL mode,
you should invoke the routine with strict mode in effect.

The `COMMENT' characteristic is a MySQL extension, and may be used to
describe the stored routine. This information is displayed by the *Note
`SHOW CREATE PROCEDURE': show-create-procedure. and *Note `SHOW CREATE
FUNCTION': show-create-function. statements.

The `LANGUAGE' characteristic indicates the language in which the
routine is written. The server ignores this characteristic; only SQL
routines are supported.

A routine is considered `deterministic' if it always produces the same
result for the same input parameters, and `not deterministic'
otherwise. If neither `DETERMINISTIC' nor `NOT DETERMINISTIC' is given
in the routine definition, the default is `NOT DETERMINISTIC'. To
declare that a function is deterministic, you must specify
`DETERMINISTIC' explicitly.

Assessment of the nature of a routine is based on the `honesty' of the
creator: MySQL does not check that a routine declared `DETERMINISTIC'
is free of statements that produce nondeterministic results. However,
misdeclaring a routine might affect results or affect performance.
Declaring a nondeterministic routine as `DETERMINISTIC' might lead to
unexpected results by causing the optimizer to make incorrect execution
plan choices.  Declaring a deterministic routine as `NONDETERMINISTIC'
might diminish performance by causing available optimizations not to be
used. Prior to MySQL 5.1.21, the `DETERMINISTIC' characteristic is
accepted, but not used by the optimizer.

If binary logging is enabled, the `DETERMINISTIC' characteristic
affects which routine definitions MySQL accepts.  See *Note
stored-programs-logging::.

A routine that contains the `NOW()' function (or its synonyms) or
`RAND()' is nondeterministic, but it might still be replication-safe.
For `NOW()', the binary log includes the timestamp and replicates
correctly.  `RAND()' also replicates correctly as long as it is called
only a single time during the execution of a routine. (You can consider
the routine execution timestamp and random number seed as implicit
inputs that are identical on the master and slave.)

Several characteristics provide information about the nature of data
use by the routine. In MySQL, these characteristics are advisory only.
The server does not use them to constrain what kinds of statements a
routine will be permitted to execute.

   * `CONTAINS SQL' indicates that the routine does not contain
     statements that read or write data. This is the default if none of
     these characteristics is given explicitly. Examples of such
     statements are `SET @x = 1' or `DO RELEASE_LOCK('abc')', which
     execute but neither read nor write data.

   * `NO SQL' indicates that the routine contains no SQL statements.

   * `READS SQL DATA' indicates that the routine contains statements
     that read data (for example, *Note `SELECT': select.), but not
     statements that write data.

   * `MODIFIES SQL DATA' indicates that the routine contains statements
     that may write data (for example, *Note `INSERT': insert. or *Note
     `DELETE': delete.).

The `SQL SECURITY' characteristic can be `DEFINER' or `INVOKER' to
specify the security context; that is, whether the routine executes
using the privileges of the account named in the routine `DEFINER'
clause or the user who invokes it. This account must have permission to
access the database with which the routine is associated. The default
value is `DEFINER'. The user who invokes the routine must have the
`EXECUTE' privilege for it, as must the `DEFINER' account if the routine
executes in definer security context.

The `DEFINER' clause specifies the MySQL account to be used when
checking access privileges at routine execution time for routines that
have the `SQL SECURITY DEFINER' characteristic. The `DEFINER' clause
was added in MySQL 5.1.8.

If a USER value is given for the `DEFINER' clause, it should be a MySQL
account specified as `'USER_NAME'@'HOST_NAME'' (the same format used in
the *Note `GRANT': grant.  statement), `CURRENT_USER', or
`CURRENT_USER()'. The default `DEFINER' value is the user who executes
the *Note `CREATE PROCEDURE': create-procedure. or *Note `CREATE
FUNCTION': create-function. or statement. This is the same as
specifying `DEFINER = CURRENT_USER' explicitly.

If you specify the `DEFINER' clause, these rules determine the valid
`DEFINER' user values:

   * If you do not have the `SUPER' privilege, the only permitted USER
     value is your own account, either specified literally or by using
     `CURRENT_USER'. You cannot set the definer to some other account.

   * If you have the `SUPER' privilege, you can specify any
     syntactically valid account name. If the account does not actually
     exist, a warning is generated.

   * Although it is possible to create a routine with a nonexistent
     `DEFINER' account, an error occurs at routine execution time if
     the `SQL SECURITY' value is `DEFINER' but the definer account does
     not exist.

For more information about stored routine security, see *Note
stored-programs-security::.

Within a stored routine that is defined with the `SQL SECURITY DEFINER'
characteristic, `CURRENT_USER' returns the routine's `DEFINER' value.
For information about user auditing within stored routines, see *Note
account-activity-auditing::.

Consider the following procedure, which displays a count of the number
of MySQL accounts listed in the `mysql.user' table:


     CREATE DEFINER = 'admin'@'localhost' PROCEDURE account_count()
     BEGIN
       SELECT 'Number of accounts:', COUNT(*) FROM mysql.user;
     END;

The procedure is assigned a `DEFINER' account of `'admin'@'localhost''
no matter which user defines it. It executes with the privileges of
that account no matter which user invokes it (because the default
security characteristic is `DEFINER'). The procedure succeeds or fails
depending on whether invoker has the `EXECUTE' privilege for it and
`'admin'@'localhost'' has the `SELECT' privilege for the `mysql.user'
table.

Now suppose that the procedure is defined with the `SQL SECURITY
INVOKER' characteristic:


     CREATE DEFINER = 'admin'@'localhost' PROCEDURE account_count()
     SQL SECURITY INVOKER
     BEGIN
       SELECT 'Number of accounts:', COUNT(*) FROM mysql.user;
     END;

The procedure still has a `DEFINER' of `'admin'@'localhost'', but in
this case, it executes with the privileges of the invoking user. Thus,
the procedure succeeds or fails depending on whether the invoker has
the `EXECUTE' privilege for it and the `SELECT' privilege for the
`mysql.user' table.

The server handles the data type of a routine parameter, local routine
variable created with *Note `DECLARE': declare, or function return value
as follows:

   * Assignments are checked for data type mismatches and overflow.
     Conversion and overflow problems result in warnings, or errors in
     strict SQL mode.

   * Only scalar values can be assigned. For example, a statement such
     as `SET x = (SELECT 1, 2)' is invalid.

   * For character data types, if there is a `CHARACTER SET' attribute
     in the declaration, the specified character set and its default
     collation are used. If there is no such attribute, the database
     character set in effect at routine creation time and its default
     collation are used. (The database character set is given by the
     value of the `character_set_database' system variable.) The
     `COLLATE' attribute is not supported. (This includes use of
     `BINARY', which in this context specifies the binary collation of
     the character set.)

     If you change the database default character set or collation,
     stored routines that use the database defaults must be dropped and
     recreated so that they use the new defaults.


File: manual.info,  Node: create-server,  Next: create-table,  Prev: create-procedure,  Up: sql-syntax-data-definition

13.1.16 CREATE SERVER Syntax
----------------------------


     CREATE SERVER SERVER_NAME
         FOREIGN DATA WRAPPER WRAPPER_NAME
         OPTIONS (OPTION [, OPTION] ...)

     OPTION:
       { HOST CHARACTER-LITERAL
       | DATABASE CHARACTER-LITERAL
       | USER CHARACTER-LITERAL
       | PASSWORD CHARACTER-LITERAL
       | SOCKET CHARACTER-LITERAL
       | OWNER CHARACTER-LITERAL
       | PORT NUMERIC-LITERAL }

This statement creates the definition of a server for use with the
`FEDERATED' storage engine. The `CREATE SERVER' statement creates a new
row in the `servers' table in the `mysql' database. This statement
requires the `SUPER' privilege.

The `SERVER_NAME' should be a unique reference to the server. Server
definitions are global within the scope of the server, it is not
possible to qualify the server definition to a specific database.
`SERVER_NAME' has a maximum length of 64 characters (names longer than
64 characters are silently truncated), and is case insensitive. You may
specify the name as a quoted string.

The `WRAPPER_NAME' should be `mysql', and may be quoted with single
quotation marks. Other values for `WRAPPER_NAME' are not currently
supported.

For each `OPTION' you must specify either a character literal or
numeric literal.  Character literals are UTF-8, support a maximum
length of 64 characters and default to a blank (empty) string. String
literals are silently truncated to 64 characters. Numeric literals must
be a number between 0 and 9999, default value is 0.

*Note*:

The `OWNER' option is currently not applied, and has no effect on the
ownership or operation of the server connection that is created.

The `CREATE SERVER' statement creates an entry in the `mysql.servers'
table that can later be used with the *Note `CREATE TABLE':
create-table. statement when creating a `FEDERATED' table. The options
that you specify will be used to populate the columns in the
`mysql.servers' table. The table columns are `Server_name', `Host',
`Db', `Username', `Password', `Port' and `Socket'.

For example:


     CREATE SERVER s
     FOREIGN DATA WRAPPER mysql
     OPTIONS (USER 'Remote', HOST '192.168.1.106', DATABASE 'test');

Be sure to specify all options necessary to establish a connection to
the server. The user name, host name, and database name are mandatory.
Other options might be required as well, such as password.

The data stored in the table can be used when creating a connection to
a `FEDERATED' table:

     CREATE TABLE t (s1 INT) ENGINE=FEDERATED CONNECTION='s';

For more information, see *Note federated-storage-engine::.

`CREATE SERVER' causes an implicit commit.

In MySQL 5.1, `CREATE SERVER' is written to the binary log only when
using row-based logging. It is not logged when `binlog_format' is equal
to `STATEMENT' or `MIXED'.

`CREATE SERVER' was added in MySQL 5.1.15.


File: manual.info,  Node: create-table,  Next: create-tablespace,  Prev: create-server,  Up: sql-syntax-data-definition

13.1.17 CREATE TABLE Syntax
---------------------------

* Menu:

* create-table-select::          CREATE TABLE ... SELECT Syntax
* create-table-foreign-keys::    Using FOREIGN KEY Constraints
* silent-column-changes::        Silent Column Specification Changes


     CREATE [TEMPORARY] TABLE [IF NOT EXISTS] TBL_NAME
         (CREATE_DEFINITION,...)
         [TABLE_OPTIONS]
         [PARTITION_OPTIONS]

Or:


     CREATE [TEMPORARY] TABLE [IF NOT EXISTS] TBL_NAME
         [(CREATE_DEFINITION,...)]
         [TABLE_OPTIONS]
         [PARTITION_OPTIONS]
         SELECT_STATEMENT

Or:


     CREATE [TEMPORARY] TABLE [IF NOT EXISTS] TBL_NAME
         { LIKE OLD_TBL_NAME | (LIKE OLD_TBL_NAME) }


     CREATE_DEFINITION:
         COL_NAME COLUMN_DEFINITION
       | [CONSTRAINT [SYMBOL]] PRIMARY KEY [INDEX_TYPE] (INDEX_COL_NAME,...)
           [INDEX_OPTION] ...
       | {INDEX|KEY} [INDEX_NAME] [INDEX_TYPE] (INDEX_COL_NAME,...)
           [INDEX_OPTION] ...
       | [CONSTRAINT [SYMBOL]] UNIQUE [INDEX|KEY]
           [INDEX_NAME] [INDEX_TYPE] (INDEX_COL_NAME,...)
           [INDEX_OPTION] ...
       | {FULLTEXT|SPATIAL} [INDEX|KEY] [INDEX_NAME] (INDEX_COL_NAME,...)
           [INDEX_OPTION] ...
       | [CONSTRAINT [SYMBOL]] FOREIGN KEY
           [INDEX_NAME] (INDEX_COL_NAME,...) REFERENCE_DEFINITION
       | CHECK (EXPR)

     COLUMN_DEFINITION:
         DATA_TYPE [NOT NULL | NULL] [DEFAULT DEFAULT_VALUE]
           [AUTO_INCREMENT] [UNIQUE [KEY] | [PRIMARY] KEY]
           [COMMENT 'STRING']
           [COLUMN_FORMAT {FIXED|DYNAMIC|DEFAULT}]
           [STORAGE {DISK|MEMORY|DEFAULT}]
           [REFERENCE_DEFINITION]

     DATA_TYPE:
         BIT[(LENGTH)]
       | TINYINT[(LENGTH)] [UNSIGNED] [ZEROFILL]
       | SMALLINT[(LENGTH)] [UNSIGNED] [ZEROFILL]
       | MEDIUMINT[(LENGTH)] [UNSIGNED] [ZEROFILL]
       | INT[(LENGTH)] [UNSIGNED] [ZEROFILL]
       | INTEGER[(LENGTH)] [UNSIGNED] [ZEROFILL]
       | BIGINT[(LENGTH)] [UNSIGNED] [ZEROFILL]
       | REAL[(LENGTH,DECIMALS)] [UNSIGNED] [ZEROFILL]
       | DOUBLE[(LENGTH,DECIMALS)] [UNSIGNED] [ZEROFILL]
       | FLOAT[(LENGTH,DECIMALS)] [UNSIGNED] [ZEROFILL]
       | DECIMAL[(LENGTH[,DECIMALS])] [UNSIGNED] [ZEROFILL]
       | NUMERIC[(LENGTH[,DECIMALS])] [UNSIGNED] [ZEROFILL]
       | DATE
       | TIME
       | TIMESTAMP
       | DATETIME
       | YEAR
       | CHAR[(LENGTH)]
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | VARCHAR(LENGTH)
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | BINARY[(LENGTH)]
       | VARBINARY(LENGTH)
       | TINYBLOB
       | BLOB
       | MEDIUMBLOB
       | LONGBLOB
       | TINYTEXT [BINARY]
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | TEXT [BINARY]
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | MEDIUMTEXT [BINARY]
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | LONGTEXT [BINARY]
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | ENUM(VALUE1,VALUE2,VALUE3,...)
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | SET(VALUE1,VALUE2,VALUE3,...)
           [CHARACTER SET CHARSET_NAME] [COLLATE COLLATION_NAME]
       | SPATIAL_TYPE

     INDEX_COL_NAME:
         COL_NAME [(LENGTH)] [ASC | DESC]

     INDEX_TYPE:
         USING {BTREE | HASH}

     INDEX_OPTION:
         KEY_BLOCK_SIZE [=] VALUE
       | INDEX_TYPE
       | WITH PARSER PARSER_NAME

     REFERENCE_DEFINITION:
         REFERENCES TBL_NAME (INDEX_COL_NAME,...)
           [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
           [ON DELETE REFERENCE_OPTION]
           [ON UPDATE REFERENCE_OPTION]

     REFERENCE_OPTION:
         RESTRICT | CASCADE | SET NULL | NO ACTION

     TABLE_OPTIONS:
         TABLE_OPTION [[,] TABLE_OPTION] ...

     TABLE_OPTION:
         ENGINE [=] ENGINE_NAME
       | AUTO_INCREMENT [=] VALUE
       | AVG_ROW_LENGTH [=] VALUE
       | [DEFAULT] CHARACTER SET [=] CHARSET_NAME
       | CHECKSUM [=] {0 | 1}
       | [DEFAULT] COLLATE [=] COLLATION_NAME
       | COMMENT [=] 'STRING'
       | CONNECTION [=] 'CONNECT_STRING'
       | DATA DIRECTORY [=] 'ABSOLUTE PATH TO DIRECTORY'
       | DELAY_KEY_WRITE [=] {0 | 1}
       | INDEX DIRECTORY [=] 'ABSOLUTE PATH TO DIRECTORY'
       | INSERT_METHOD [=] { NO | FIRST | LAST }
       | KEY_BLOCK_SIZE [=] VALUE
       | MAX_ROWS [=] VALUE
       | MIN_ROWS [=] VALUE
       | PACK_KEYS [=] {0 | 1 | DEFAULT}
       | PASSWORD [=] 'STRING'
       | ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT}
       | TABLESPACE TABLESPACE_NAME [STORAGE {DISK|MEMORY|DEFAULT}]
       | UNION [=] (TBL_NAME[,TBL_NAME]...)

     PARTITION_OPTIONS:
         PARTITION BY
             { [LINEAR] HASH(EXPR)
             | [LINEAR] KEY(COLUMN_LIST)
             | RANGE(EXPR)
             | LIST(EXPR) }
         [PARTITIONS NUM]
         [SUBPARTITION BY
             { [LINEAR] HASH(EXPR)
             | [LINEAR] KEY(COLUMN_LIST) }
           [SUBPARTITIONS NUM]
         ]
         [(PARTITION_DEFINITION [, PARTITION_DEFINITION] ...)]

     PARTITION_DEFINITION:
         PARTITION PARTITION_NAME
             [VALUES
                 {LESS THAN {(EXPR) | `MAXVALUE'}
                 |
                 IN (VALUE_LIST)}]
             [[STORAGE] ENGINE [=] ENGINE_NAME]
             [COMMENT [=] 'COMMENT_TEXT' ]
             [DATA DIRECTORY [=] '`DATA_DIR'']
             [INDEX DIRECTORY [=] '`INDEX_DIR'']
             [MAX_ROWS [=] MAX_NUMBER_OF_ROWS]
             [MIN_ROWS [=] MIN_NUMBER_OF_ROWS]
             [TABLESPACE [=] TABLESPACE_NAME]
             [NODEGROUP [=] NODE_GROUP_ID]
             [(SUBPARTITION_DEFINITION [, SUBPARTITION_DEFINITION] ...)]

     SUBPARTITION_DEFINITION:
         SUBPARTITION LOGICAL_NAME
             [[STORAGE] ENGINE [=] ENGINE_NAME]
             [COMMENT [=] 'COMMENT_TEXT' ]
             [DATA DIRECTORY [=] '`DATA_DIR'']
             [INDEX DIRECTORY [=] '`INDEX_DIR'']
             [MAX_ROWS [=] MAX_NUMBER_OF_ROWS]
             [MIN_ROWS [=] MIN_NUMBER_OF_ROWS]
             [TABLESPACE [=] TABLESPACE_NAME]
             [NODEGROUP [=] NODE_GROUP_ID]

     SELECT_STATEMENT:
         [IGNORE | REPLACE] [AS] SELECT ...   (SOME VALID SELECT STATEMENT)

*Note `CREATE TABLE': create-table. creates a table with the given
name. You must have the `CREATE' privilege for the table.

Rules for permissible table names are given in *Note identifiers::. By
default, the table is created in the default database. An error occurs
if the table exists, if there is no default database, or if the
database does not exist.

The table name can be specified as DB_NAME.TBL_NAME to create the table
in a specific database. This works regardless of whether there is a
default database, assuming that the database exists. If you use quoted
identifiers, quote the database and table names separately.  For
example, write ``mydb`.`mytbl`', not ``mydb.mytbl`'.

*Temporary Tables*

You can use the `TEMPORARY' keyword when creating a table. A
`TEMPORARY' table is visible only to the current session, and is
dropped automatically when the session is closed. This means that two
different sessions can use the same temporary table name without
conflicting with each other or with an existing non-`TEMPORARY' table
of the same name. (The existing table is hidden until the temporary
table is dropped.) To create temporary tables, you must have the
`CREATE TEMPORARY TABLES' privilege.

*Note*:

*Note `CREATE TABLE': create-table. does not automatically commit the
current active transaction if you use the `TEMPORARY' keyword.

*Note*:

`TEMPORARY' tables have a very loose relationship with databases
(schemas). Dropping a database does not automatically drop any
`TEMPORARY' tables created within that database. Also, you can create a
`TEMPORARY' table in a nonexistent database if you qualify the table
name with the database name in the `CREATE TABLE' statement. In this
case, all subsequent references to the table must be qualified with the
database name.

*Existing Table with Same Name*

The keywords `IF NOT EXISTS' prevent an error from occurring if the
table exists. However, there is no verification that the existing table
has a structure identical to that indicated by the *Note `CREATE
TABLE': create-table.  statement.

*Physical Representation*

MySQL represents each table by an `.frm' table format (definition) file
in the database directory. The storage engine for the table might
create other files as well.

For `InnoDB' tables, the file storage is controlled by the
`innodb_file_per_table' configuration option. When this option is
turned off, all `InnoDB' tables and indexes are stored in the system
tablespace
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_system_tablespace),
represented by one or more ibdata* files
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_ibdata_file).
For each `InnoDB' table created when this option is turned on, the
table data and all associated indexes are stored in a .ibd file
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_ibd_file)
located inside the database directory.

For `MyISAM' tables, the storage engine creates data and index files.
Thus, for each `MyISAM' table TBL_NAME, there are three disk files.

This table describes the purpose of `MyISAM' table TBL_NAME disk files.

File                   Purpose
`TBL_NAME.frm'         Table format (definition) file
`TBL_NAME.MYD'         Data file
`TBL_NAME.MYI'         Index file

*Note storage-engines::, describes what files each storage engine
creates to represent tables. If a table name contains special
characters, the names for the table files contain encoded versions of
those characters as described in *Note identifier-mapping::.

*Data Types and Attributes for Columns*

DATA_TYPE represents the data type in a column definition. SPATIAL_TYPE
represents a spatial data type. The data type syntax shown is
representative only. For a full description of the syntax available for
specifying column data types, as well as information about the
properties of each type, see *Note data-types::, and *Note
spatial-extensions::.

Some attributes do not apply to all data types.  `AUTO_INCREMENT'
applies only to integer and floating-point types. `DEFAULT' does not
apply to the *Note `BLOB': blob. or *Note `TEXT': blob. types.

   * If neither `NULL' nor `NOT NULL' is specified, the column is
     treated as though `NULL' had been specified.

   * An integer or floating-point column can have the additional
     attribute `AUTO_INCREMENT'. When you insert a value of `NULL'
     (recommended) or `0' into an indexed `AUTO_INCREMENT' column, the
     column is set to the next sequence value. Typically this is
     `VALUE+1', where VALUE is the largest value for the column
     currently in the table.  `AUTO_INCREMENT' sequences begin with `1'.

     To retrieve an `AUTO_INCREMENT' value after inserting a row, use
     the `LAST_INSERT_ID()' SQL function or the *Note
     `mysql_insert_id()': mysql-insert-id. C API function. See *Note
     information-functions::, and *Note mysql-insert-id::.

     If the `NO_AUTO_VALUE_ON_ZERO' SQL mode is enabled, you can store
     `0' in `AUTO_INCREMENT' columns as `0' without generating a new
     sequence value.  See *Note sql-mode::.

     *Note*:

     There can be only one `AUTO_INCREMENT' column per table, it must
     be indexed, and it cannot have a `DEFAULT' value. An
     `AUTO_INCREMENT' column works properly only if it contains only
     positive values. Inserting a negative number is regarded as
     inserting a very large positive number. This is done to avoid
     precision problems when numbers `wrap' over from positive to
     negative and also to ensure that you do not accidentally get an
     `AUTO_INCREMENT' column that contains `0'.

     For `MyISAM' tables, you can specify an `AUTO_INCREMENT' secondary
     column in a multiple-column key. See *Note
     example-auto-increment::.

     To make MySQL compatible with some ODBC applications, you can find
     the `AUTO_INCREMENT' value for the last inserted row with the
     following query:


          SELECT * FROM TBL_NAME WHERE AUTO_COL IS NULL

     For information about `InnoDB' and `AUTO_INCREMENT', see *Note
     innodb-auto-increment-handling::. For information about
     `AUTO_INCREMENT' and MySQL Replication, see *Note
     replication-features-auto-increment::.

   * Character data types (*Note `CHAR': char, *Note `VARCHAR': char,
     *Note `TEXT': blob.) can include `CHARACTER SET' and `COLLATE'
     attributes to specify the character set and collation for the
     column. For details, see *Note charset::. `CHARSET' is a synonym
     for `CHARACTER SET'. Example:


          CREATE TABLE t (c CHAR(20) CHARACTER SET utf8 COLLATE utf8_bin);

     MySQL 5.1 interprets length specifications in character column
     definitions in characters. (Versions before MySQL 4.1 interpreted
     them in bytes.) Lengths for *Note `BINARY': binary-varbinary. and
     *Note `VARBINARY': binary-varbinary. are in bytes.

   * The `DEFAULT' clause specifies a default value for a column. With
     one exception, the default value must be a constant; it cannot be
     a function or an expression. This means, for example, that you
     cannot set the default for a date column to be the value of a
     function such as `NOW()' or `CURRENT_DATE'. The exception is that
     you can specify `CURRENT_TIMESTAMP' as the default for a *Note
     `TIMESTAMP': datetime. column.  See *Note
     timestamp-initialization::.

     If a column definition includes no explicit `DEFAULT' value, MySQL
     determines the default value as described in *Note
     data-type-defaults::.

     *Note `BLOB': blob. and *Note `TEXT': blob. columns cannot be
     assigned a default value.

     *Note `CREATE TABLE': create-table. fails if a date-valued default
     is not correct according to the `NO_ZERO_IN_DATE' SQL mode, even
     if strict SQL mode is not enabled. For example, `c1 DATE DEFAULT
     '2010-00-00'' causes *Note `CREATE TABLE': create-table. to fail
     with `Invalid default value for 'c1''.

     Native default value handling in MySQL Cluster NDB 7.0.15, MySQL
     Cluster NDB 7.1.4, and later

     Starting with MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB
     7.1.4, default values for table columns are stored by *Note
     `NDBCLUSTER': mysql-cluster, rather than by the MySQL server as
     was previously the case. Because less data must be sent from an
     SQL node to the data nodes, inserts on tables having column value
     defaults can be performed more efficiently than before.

     Tables created using MySQL Cluster releases previous to the
     introduction of native default value support can still be used in
     MySQL Cluster NDB 7.0.15 and later, as well as well as MySQL
     Cluster NDB 7.1.4 and later. However, such tables continue to use
     defaults supplied by the MySQL server until they are upgraded.
     This upgrade can be done by means of an offline *Note `ALTER
     TABLE': alter-table. statement.

     *Important*:

     You cannot set or change a table column's default value using a
     noncopying *Note `ALTER TABLE': alter-table. operation.

     Tables created in versions of MySQL Cluster that support native
     default values cannot be used with versions of MySQL Cluster that
     lack this support.

     *Note `NDBCLUSTER': mysql-cluster. tables supporting native
     default values are still subject to the restrictions on default
     values imposed by the MySQL server. For more information, see
     *Note data-type-defaults::.

   * A comment for a column can be specified with the `COMMENT' option,
     up to 255 characters long.  The comment is displayed by the *Note
     `SHOW CREATE TABLE': show-create-table. and *Note `SHOW FULL
     COLUMNS': show-columns. statements.

   * In MySQL Cluster--beginning with MySQL Cluster NDB 6.2.5 and MySQL
     Cluster NDB 6.3.2--it is also possible to specify a data storage
     format for individual columns of *Note `NDB': mysql-cluster.
     tables using `COLUMN_FORMAT'. Permissible column formats are
     `FIXED', `DYNAMIC', and `DEFAULT'. `FIXED' is used to specify
     fixed-width storage, `DYNAMIC' permits the column to be
     variable-width, and `DEFAULT' causes the column to use fixed-width
     or variable-width storage as determined by the column's data type
     (possibly overridden by a `ROW_FORMAT' specifier).

     For *Note `NDB': mysql-cluster. tables, the default value for
     `COLUMN_FORMAT' is `DEFAULT'.

     `COLUMN_FORMAT' currently has no effect on columns of tables using
     storage engines other than *Note `NDB': mysql-cluster. The
     `COLUMN_FORMAT' keyword is supported only in the build of *Note
     `mysqld': mysqld. that is supplied with MySQL Cluster; it is not
     recognized in MySQL 5.1, where attempting to use `COLUMN_FORMAT'
     causes a syntax error.

   * For *Note `NDB': mysql-cluster. tables, beginning with MySQL
     Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.2, it is also possible
     to specify whether the column is stored on disk or in memory by
     using a `STORAGE' clause.  `STORAGE DISK' causes the column to be
     stored on disk, and `STORAGE MEMORY' causes in-memory storage to
     be used. The *Note `CREATE TABLE': create-table. statement used
     must still include a `TABLESPACE' clause:


          mysql> CREATE TABLE t1 (
              ->     c1 INT STORAGE DISK,
              ->     c2 INT STORAGE MEMORY
              -> ) ENGINE NDB;
          `ERROR 1005 (HY000): Can't create table 'c.t1' (errno: 140)'

          mysql> CREATE TABLE t1 (
              ->     c1 INT STORAGE DISK,
              ->     c2 INT STORAGE MEMORY
              -> ) TABLESPACE ts_1 ENGINE NDB;
          Query OK, 0 rows affected (1.06 sec)

     For *Note `NDB': mysql-cluster. tables, `STORAGE DEFAULT' is
     equivalent to `STORAGE MEMORY'.

     The `STORAGE' clause has no effect on tables using storage engines
     other than *Note `NDB': mysql-cluster. The `STORAGE' keyword is
     supported only in the build of *Note `mysqld': mysqld. that is
     supplied with MySQL Cluster; it is not recognized in any other
     version of MySQL, where any attempt to use the `STORAGE' keyword
     causes a syntax error.

   * `KEY' is normally a synonym for `INDEX'. The key attribute `PRIMARY
     KEY' can also be specified as just `KEY' when given in a column
     definition. This was implemented for compatibility with other
     database systems.

   * A `UNIQUE' index creates a constraint such that all values in the
     index must be distinct. An error occurs if you try to add a new
     row with a key value that matches an existing row. For all
     engines, a `UNIQUE' index permits multiple `NULL' values for
     columns that can contain `NULL'.

   * A `PRIMARY KEY' is a unique index where all key columns must be
     defined as `NOT NULL'. If they are not explicitly declared as `NOT
     NULL', MySQL declares them so implicitly (and silently). A table
     can have only one `PRIMARY KEY'. The name of a `PRIMARY KEY' is
     always `PRIMARY', which thus cannot be used as the name for any
     other kind of index.

     If you do not have a `PRIMARY KEY' and an application asks for the
     `PRIMARY KEY' in your tables, MySQL returns the first `UNIQUE'
     index that has no `NULL' columns as the `PRIMARY KEY'.

     In `InnoDB' tables, keep the `PRIMARY KEY' short to minimize
     storage overhead for secondary indexes. Each secondary index entry
     contains a copy of the primary key columns for the corresponding
     row. (See *Note innodb-table-and-index::.)

   * In the created table, a `PRIMARY KEY' is placed first, followed by
     all `UNIQUE' indexes, and then the nonunique indexes. This helps
     the MySQL optimizer to prioritize which index to use and also more
     quickly to detect duplicated `UNIQUE' keys.

   * A `PRIMARY KEY' can be a multiple-column index. However, you
     cannot create a multiple-column index using the `PRIMARY KEY' key
     attribute in a column specification. Doing so only marks that
     single column as primary. You must use a separate `PRIMARY
     KEY(INDEX_COL_NAME, ...)' clause.

   * If a `PRIMARY KEY' or `UNIQUE' index consists of only one column
     that has an integer type, you can also refer to the column as
     `_rowid' in *Note `SELECT': select. statements.

   * In MySQL, the name of a `PRIMARY KEY' is `PRIMARY'. For other
     indexes, if you do not assign a name, the index is assigned the
     same name as the first indexed column, with an optional suffix
     (`_2', `_3', `...') to make it unique. You can see index names for
     a table using `SHOW INDEX FROM TBL_NAME'. See *Note show-index::.

   * Some storage engines permit you to specify an index type when
     creating an index. The syntax for the INDEX_TYPE specifier is
     `USING TYPE_NAME'.

     Example:


          CREATE TABLE lookup
            (id INT, INDEX USING BTREE (id))
            ENGINE = MEMORY;

     Before MySQL 5.1.10, `USING' can be given only before the index
     column list. As of 5.1.10, the preferred position is after the
     column list. Support for use of the option before the column list
     will be removed in a future MySQL release.

     INDEX_OPTION values specify additional options for an index.
     `USING' is one such option. For details about permissible
     INDEX_OPTION values, see *Note create-index::.

     For more information about indexes, see *Note mysql-indexes::.

   * In MySQL 5.1, only the `InnoDB', `MyISAM', and `MEMORY' storage
     engines support indexes on columns that can have `NULL' values. In
     other cases, you must declare indexed columns as `NOT NULL' or an
     error results.

   * For *Note `CHAR': char, *Note `VARCHAR': char, *Note `BINARY':
     binary-varbinary, and *Note `VARBINARY': binary-varbinary.
     columns, indexes can be created that use only the leading part of
     column values, using `COL_NAME(LENGTH)' syntax to specify an index
     prefix length.  *Note `BLOB': blob. and *Note `TEXT': blob.
     columns also can be indexed, but a prefix length _must_ be given.
     Prefix lengths are given in characters for nonbinary string types
     and in bytes for binary string types. That is, index entries
     consist of the first LENGTH characters of each column value for
     *Note `CHAR': char, *Note `VARCHAR': char, and *Note `TEXT': blob.
     columns, and the first LENGTH bytes of each column value for *Note
     `BINARY': binary-varbinary, *Note `VARBINARY': binary-varbinary,
     and *Note `BLOB': blob. columns. Indexing only a prefix of column
     values like this can make the index file much smaller. See *Note
     column-indexes::.

     Only the `InnoDB' and `MyISAM' storage engines support indexing on
     *Note `BLOB': blob. and *Note `TEXT': blob. columns. For example:


          CREATE TABLE test (blob_col BLOB, INDEX(blob_col(10)));

     Prefixes can be up to 1000 bytes long (767 bytes for `InnoDB'
     tables). Note that prefix limits are measured in bytes, whereas
     the prefix length in *Note `CREATE TABLE': create-table.
     statements is interpreted as number of characters for nonbinary
     data types (*Note `CHAR': char, *Note `VARCHAR': char, *Note
     `TEXT': blob.). Take this into account when specifying a prefix
     length for a column that uses a multibyte character set.

   * An INDEX_COL_NAME specification can end with `ASC' or `DESC'.
     These keywords are permitted for future extensions for specifying
     ascending or descending index value storage.  Currently, they are
     parsed but ignored; index values are always stored in ascending
     order.

   * When you use `ORDER BY' or `GROUP BY' on a column in a *Note
     `SELECT': select, the server sorts values using only the initial
     number of bytes indicated by the `max_sort_length' system variable.

   * You can create special `FULLTEXT' indexes, which are used for
     full-text searches. Only the `MyISAM' storage engine supports
     `FULLTEXT' indexes. They can be created only from *Note `CHAR':
     char, *Note `VARCHAR': char, and *Note `TEXT': blob. columns.
     Indexing always happens over the entire column; column prefix
     indexing is not supported and any prefix length is ignored if
     specified. See *Note fulltext-search::, for details of operation. A
     `WITH PARSER' clause can be specified as an INDEX_OPTION value to
     associate a parser plugin with the index if full-text indexing and
     searching operations need special handling. This clause is valid
     only for `FULLTEXT' indexes. See *Note plugin-api::, for details
     on creating plugins.

   * You can create `SPATIAL' indexes on spatial data types. Spatial
     types are supported only for `MyISAM' tables and indexed columns
     must be declared as `NOT NULL'. See *Note spatial-extensions::.

   * *Note `InnoDB': innodb-storage-engine. tables support checking of
     foreign key constraints. The columns of the referenced table must
     always be explicitly named. Both `ON DELETE' and `ON UPDATE'
     actions on foreign keys. For more detailed information and
     examples, see *Note create-table-foreign-keys::. For information
     specific to foreign keys in `InnoDB', see *Note
     innodb-foreign-key-constraints::.

     For other storage engines, MySQL Server parses and ignores the
     `FOREIGN KEY' and `REFERENCES' syntax in *Note `CREATE TABLE':
     create-table. statements. The `CHECK' clause is parsed but ignored
     by all storage engines. See *Note ansi-diff-foreign-keys::.

     *Important*:

     For users familiar with the ANSI/ISO SQL Standard, please note
     that no storage engine, including `InnoDB', recognizes or enforces
     the `MATCH' clause used in referential integrity constraint
     definitions. Use of an explicit `MATCH' clause will not have the
     specified effect, and also causes `ON DELETE' and `ON UPDATE'
     clauses to be ignored. For these reasons, specifying `MATCH'
     should be avoided.

     The `MATCH' clause in the SQL standard controls how `NULL' values
     in a composite (multiple-column) foreign key are handled when
     comparing to a primary key. `InnoDB' essentially implements the
     semantics defined by `MATCH SIMPLE', which permit a foreign key to
     be all or partially `NULL'. In that case, the (child table) row
     containing such a foreign key is permitted to be inserted, and
     does not match any row in the referenced (parent) table. It is
     possible to implement other semantics using triggers.

     Additionally, MySQL requires that the referenced columns be
     indexed for performance. However, `InnoDB' does not enforce any
     requirement that the referenced columns be declared `UNIQUE' or
     `NOT NULL'. The handling of foreign key references to nonunique
     keys or keys that contain `NULL' values is not well defined for
     operations such as `UPDATE' or `DELETE CASCADE'. You are advised
     to use foreign keys that reference only keys that are both `UNIQUE'
     (or `PRIMARY') and `NOT NULL'.

     MySQL does not recognize or support `inline `REFERENCES'
     specifications' (as defined in the SQL standard) where the
     references are defined as part of the column specification. MySQL
     accepts `REFERENCES' clauses only when specified as part of a
     separate `FOREIGN KEY' specification.

     *Note*:

     Partitioned tables employing the *Note `InnoDB':
     innodb-storage-engine. storage engine do not support foreign keys.
     See *Note partitioning-limitations::, for more information.

   * There is a hard limit of 4096 columns per table, but the effective
     maximum may be less for a given table and depends on the factors
     discussed in *Note column-count-limit::.

The `TABLESPACE' and `STORAGE' table options were both introduced in
MySQL 5.1.6. In MySQL 5.1, they are employed only with *Note
`NDBCLUSTER': mysql-cluster. tables. The tablespace named
TABLESPACE_NAME must already have been created using *Note `CREATE
TABLESPACE': create-tablespace. `STORAGE' determines the type of
storage used (disk or memory), and can be one of `DISK', `MEMORY', or
`DEFAULT'.

`TABLESPACE ... STORAGE DISK' assigns a table to a MySQL Cluster Disk
Data tablespace. See *Note mysql-cluster-disk-data::, for more
information.

*Important*:

A `STORAGE' clause cannot be used in a *Note `CREATE TABLE':
create-table. statement without a `TABLESPACE' clause.

The `ENGINE' table option specifies the storage engine for the table.

*Storage Engines*

The `ENGINE' table option specifies the storage engine for the table,
using one of the names shown in the following table. The engine name
can be unquoted or quoted. The quoted name `'DEFAULT'' is equivalent to
specifying the default storage engine name.

This table lists storage engine names that are taken by the `ENGINE'
table option. A description is provided for each name.

Storage Engine     Description
`ARCHIVE'          The archiving storage engine. See *Note
                   archive-storage-engine::.
`CSV'              Tables that store rows in comma-separated values
                   format. See *Note csv-storage-engine::.
`EXAMPLE'          An example engine. See *Note
                   example-storage-engine::.
`FEDERATED'        Storage engine that accesses remote tables. See
                   *Note federated-storage-engine::.
`HEAP'             This is a synonym for `MEMORY'.
`InnoDB'           Transaction-safe tables with row locking and
                   foreign keys. See *Note innodb-storage-engine::.
`MEMORY'           The data for this storage engine is stored only
                   in memory. See *Note memory-storage-engine::.
`MERGE'            A collection of `MyISAM' tables used as one
                   table. Also known as `MRG_MyISAM'. See *Note
                   merge-storage-engine::.
`MyISAM'           The binary portable storage engine that is the
                   default storage engine used by MySQL. See *Note
                   myisam-storage-engine::.
*Note              Clustered, fault-tolerant, memory-based tables.
`NDBCLUSTER':      Also known as *Note `NDB': mysql-cluster. See
mysql-cluster.     *Note mysql-cluster::.

If a storage engine is specified that is not available, MySQL uses the
default engine instead. Normally, this is `MyISAM'. For example, if a
table definition includes the `ENGINE=INNODB' option but the MySQL
server does not support `INNODB' tables, the table is created as a
`MyISAM' table. This makes it possible to have a replication setup
where you have transactional tables on the master but tables created on
the slave are nontransactional (to get more speed). In MySQL 5.1, a
warning occurs if the storage engine specification is not honored.

Engine substitution can be controlled by the setting of the
`NO_ENGINE_SUBSTITUTION' SQL mode, as described in *Note sql-mode::.

*Note*:

The older `TYPE' option was synonymous with `ENGINE'. `TYPE' has been
deprecated since MySQL 4.0 but is still supported for backward
compatibility in MySQL 5.1 (excepting MySQL 5.1.7). Since MySQL 5.1.8,
it produces a warning. It is removed in MySQL 5.5.  _You should not use
`TYPE' in any new applications, and you should immediately begin
conversion of existing applications to use `ENGINE' instead_. (See the
Release Notes (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) for
MySQL 5.1.8.)

*Optimizing Performance*

The other table options are used to optimize the behavior of the table.
In most cases, you do not have to specify any of them.  These options
apply to all storage engines unless otherwise indicated. Options that
do not apply to a given storage engine may be accepted and remembered
as part of the table definition. Such options then apply if you later
use *Note `ALTER TABLE': alter-table. to convert the table to use a
different storage engine.

   * `AUTO_INCREMENT'

     The initial `AUTO_INCREMENT' value for the table. In MySQL 5.1,
     this works for `MyISAM', `MEMORY', and `InnoDB' tables. It also
     works for `ARCHIVE' tables as of MySQL 5.1.6. To set the first
     auto-increment value for engines that do not support the
     `AUTO_INCREMENT' table option, insert a `dummy' row with a value
     one less than the desired value after creating the table, and then
     delete the dummy row.

     For engines that support the `AUTO_INCREMENT' table option in
     *Note `CREATE TABLE': create-table.  statements, you can also use
     `ALTER TABLE TBL_NAME AUTO_INCREMENT = N' to reset the
     `AUTO_INCREMENT' value. The value cannot be set lower than the
     maximum value currently in the column.

   * `AVG_ROW_LENGTH'

     An approximation of the average row length for your table. You
     need to set this only for large tables with variable-size rows.

     When you create a `MyISAM' table, MySQL uses the product of the
     `MAX_ROWS' and `AVG_ROW_LENGTH' options to decide how big the
     resulting table is. If you don't specify either option, the
     maximum size for `MyISAM' data and index files is 256TB by
     default. (If your operating system does not support files that
     large, table sizes are constrained by the file size limit.) If you
     want to keep down the pointer sizes to make the index smaller and
     faster and you don't really need big files, you can decrease the
     default pointer size by setting the `myisam_data_pointer_size'
     system variable. (See *Note server-system-variables::.) If you
     want all your tables to be able to grow above the default limit
     and are willing to have your tables slightly slower and larger than
     necessary, you can increase the default pointer size by setting
     this variable. Setting the value to 7 permits table sizes up to
     65,536TB.

   * `[DEFAULT] CHARACTER SET'

     Specify a default character set for the table.  `CHARSET' is a
     synonym for `CHARACTER SET'. If the character set name is
     `DEFAULT', the database character set is used.

   * `CHECKSUM'

     Set this to 1 if you want MySQL to maintain a live checksum for
     all rows (that is, a checksum that MySQL updates automatically as
     the table changes). This makes the table a little slower to
     update, but also makes it easier to find corrupted tables. The
     *Note `CHECKSUM TABLE': checksum-table. statement reports the
     checksum.  (`MyISAM' only.)

   * `[DEFAULT] COLLATE'

     Specify a default collation for the table.

   * `COMMENT'

     A comment for the table, up to 60 characters long.

   * `CONNECTION'

     The connection string for a `FEDERATED' table.

     *Note*:

     Older versions of MySQL used a `COMMENT' option for the connection
     string.

   * `DATA DIRECTORY', `INDEX DIRECTORY'

     By using `DATA DIRECTORY='DIRECTORY'' or `INDEX
     DIRECTORY='DIRECTORY'' you can specify where the `MyISAM' storage
     engine should put a table's data file and index file. The directory
     must be the full path name to the directory, not a relative path.

     *Important*:

     Beginning with MySQL 5.1.23, table-level `DATA DIRECTORY' and
     `INDEX DIRECTORY' options are ignored for partitioned tables. (Bug
     #32091)

     These options work only when you are not using the
     `--skip-symbolic-links' option. Your operating system must also
     have a working, thread-safe `realpath()' call. See *Note
     symbolic-links-to-tables::, for more complete information.

     If a `MyISAM' table is created with no `DATA DIRECTORY' option, the
     `.MYD' file is created in the database directory. By default, if
     `MyISAM' finds an existing `.MYD' file in this case, it overwrites
     it. The same applies to `.MYI' files for tables created with no
     `INDEX DIRECTORY' option. As of MySQL 5.1.23, to suppress this
     behavior, start the server with the `--keep_files_on_create'
     option, in which case `MyISAM' will not overwrite existing files
     and returns an error instead.

     If a `MyISAM' table is created with a `DATA DIRECTORY' or `INDEX
     DIRECTORY' option and an existing `.MYD' or `.MYI' file is found,
     MyISAM always returns an error. It will not overwrite a file in
     the specified directory.

     *Important*:

     Beginning with MySQL 5.1.24, you cannot use path names that
     contain the MySQL data directory with `DATA DIRECTORY' or `INDEX
     DIRECTORY'.  This includes partitioned tables and individual table
     partitions. (See Bug #32167.)

   * `DELAY_KEY_WRITE'

     Set this to 1 if you want to delay key updates for the table until
     the table is closed. See the description of the `delay_key_write'
     system variable in *Note server-system-variables::.  (`MyISAM'
     only.)

   * `INSERT_METHOD'

     If you want to insert data into a `MERGE' table, you must specify
     with `INSERT_METHOD' the table into which the row should be
     inserted.  `INSERT_METHOD' is an option useful for `MERGE' tables
     only. Use a value of `FIRST' or `LAST' to have inserts go to the
     first or last table, or a value of `NO' to prevent inserts. See
     *Note merge-storage-engine::.

   * `KEY_BLOCK_SIZE'

     For compressed
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_compression)
     `InnoDB' tables, optionally specifies the size in kilobytes to use
     for pages
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_page).
     The value is treated as a hint; a different size could be used if
     necessary. A value of 0 represents that the default compressed
     page size.  See InnoDB Compressed Tables
     (http://dev.mysql.com/doc/refman/5.5/en/innodb-compression.html)
     for usage details.

     Individual index definitions can specify a `KEY_BLOCK_SIZE' value
     of their own to override the table value.

     `KEY_BLOCK_SIZE' was added in MySQL 5.1.10.

     *Note*:

     Oracle recommends enabling `innodb_strict_mode' when using the
     `KEY_BLOCK_SIZE' clause for `InnoDB' tables.

   * `MAX_ROWS'

     The maximum number of rows you plan to store in the table.  This
     is not a hard limit, but rather a hint to the storage engine that
     the table must be able to store at least this many rows.

     The *Note `NDB': mysql-cluster. storage engine treats this value
     as a maximum. If you plan to create very large MySQL Cluster
     tables (containing millions of rows), you should use this option
     to insure that *Note `NDB': mysql-cluster. allocates sufficient
     number of index slots in the hash table used for storing hashes of
     the table's primary keys by setting `MAX_ROWS = 2 * ROWS', where
     ROWS is the number of rows that you expect to insert into the
     table.

     *Note*:

     This option was incorrectly ignored by MySQL Cluster NDB 7.0 prior
     to version 7.0.20 and MySQL Cluster NDB 7.1 prior to version 7.1.9
     (see Bug #57360).

     The maximum `MAX_ROWS' value is 4294967295; larger values are
     truncated to this limit.

   * `MIN_ROWS'

     The minimum number of rows you plan to store in the table. The
     *Note `MEMORY': memory-storage-engine. storage engine uses this
     option as a hint about memory use.

   * `PACK_KEYS'

     `PACK_KEYS' takes effect only with `MyISAM' tables. Set this
     option to 1 if you want to have smaller indexes. This usually
     makes updates slower and reads faster. Setting the option to 0
     disables all packing of keys. Setting it to `DEFAULT' tells the
     storage engine to pack only long *Note `CHAR': char, *Note
     `VARCHAR': char, *Note `BINARY': binary-varbinary, or *Note
     `VARBINARY': binary-varbinary. columns.

     If you do not use `PACK_KEYS', the default is to pack strings, but
     not numbers. If you use `PACK_KEYS=1', numbers are packed as well.

     When packing binary number keys, MySQL uses prefix compression:

        * Every key needs one extra byte to indicate how many bytes of
          the previous key are the same for the next key.

        * The pointer to the row is stored in high-byte-first order
          directly after the key, to improve compression.

     This means that if you have many equal keys on two consecutive
     rows, all following `same' keys usually only take two bytes
     (including the pointer to the row). Compare this to the ordinary
     case where the following keys takes `storage_size_for_key +
     pointer_size' (where the pointer size is usually 4). Conversely,
     you get a significant benefit from prefix compression only if you
     have many numbers that are the same. If all keys are totally
     different, you use one byte more per key, if the key is not a key
     that can have `NULL' values. (In this case, the packed key length
     is stored in the same byte that is used to mark if a key is
     `NULL'.)

   * `PASSWORD'

     This option is unused. If you have a need to scramble your `.frm'
     files and make them unusable to any other MySQL server, please
     contact our sales department.

   * `ROW_FORMAT'

     Defines the physical format in which the rows are stored. The
     choices differ depending on the storage engine used for the table.

     For `InnoDB' tables:

        * Rows are stored in compact format (`ROW_FORMAT=COMPACT') by
          default.

        * The noncompact format used in older versions of MySQL can
          still be requested by specifying `ROW_FORMAT=REDUNDANT'.

        * To enable compression for `InnoDB' tables, specify
          `ROW_FORMAT=COMPRESSED' and follow the procedures in InnoDB
          Compressed Tables
          (http://dev.mysql.com/doc/refman/5.5/en/innodb-compression.html).
          This feature is available when you use the InnoDB Plugin for
          MySQL 5.1.

        * For more efficient `InnoDB' storage of data types, especially
          *Note `BLOB': blob.  types, specify `ROW_FORMAT=DYNAMIC' and
          follow the procedures in DYNAMIC and COMPRESSED Row Formats
          (http://dev.mysql.com/doc/refman/5.5/en/innodb-row-format-dynamic.html).
          This feature is available when you use the InnoDB Plugin for
          MySQL 5.1.  Both the `COMPRESSED' and `DYNAMIC' row formats
          require creating the table with the configuration settings
          `innodb_file_per_table=1' and `innodb_file_format=barracuda'.

        * When you specify a non-default `ROW_FORMAT' clause, consider
          also enabling the `innodb_strict_mode' configuration option.

     For `MyISAM' tables, the option value can be `FIXED' or `DYNAMIC'
     for static or variable-length row format.  *Note `myisampack':
     myisampack. sets the type to `COMPRESSED'. See *Note
     myisam-table-formats::.

     *Note*:

     When executing a *Note `CREATE TABLE': create-table.  statement,
     if you specify a row format which is not supported by the storage
     engine that is used for the table, the table is created using that
     storage engine's default row format. The information reported in
     this column in response to *Note `SHOW TABLE STATUS':
     show-table-status. is the actual row format used. This may differ
     from the value in the `Create_options' column because the original
     *Note `CREATE TABLE': create-table.  definition is retained during
     creation.

   * *Note `UNION': union.

     *Note `UNION': union. is used when you want to access a collection
     of identical `MyISAM' tables as one. This works only with `MERGE'
     tables. See *Note merge-storage-engine::.

     You must have `SELECT', `UPDATE', and `DELETE' privileges for the
     tables you map to a `MERGE' table.

     *Note*:

     Formerly, all tables used had to be in the same database as the
     `MERGE' table itself. This restriction no longer applies.

*Partitioning*

PARTITION_OPTIONS can be used to control partitioning of the table
created with *Note `CREATE TABLE': create-table.

*Important*:

Not all options shown in the syntax for PARTITION_OPTIONS at the
beginning of this section are available for all partitioning types.
Please see the listings for the following individual types for
information specific to each type, and see *Note partitioning::, for
more complete information about the workings of and uses for
partitioning in MySQL, as well as additional examples of table creation
and other statements relating to MySQL partitioning.

If used, a PARTITION_OPTIONS clause begins with `PARTITION BY'. This
clause contains the function that is used to determine the partition;
the function returns an integer value ranging from 1 to NUM, where NUM
is the number of partitions. (The maximum number of user-defined
partitions which a table may contain is 1024; the number of
subpartitions--discussed later in this section--is included in this
maximum.) The choices that are available for this function in MySQL 5.1
are shown in the following list:

   * `HASH(EXPR)': Hashes one or more columns to create a key for
     placing and locating rows. EXPR is an expression using one or more
     table columns. This can be any valid MySQL expression (including
     MySQL functions) that yields a single integer value. For example,
     these are both valid *Note `CREATE TABLE': create-table.
     statements using `PARTITION BY HASH':


          CREATE TABLE t1 (col1 INT, col2 CHAR(5))
              PARTITION BY HASH(col1);

          CREATE TABLE t1 (col1 INT, col2 CHAR(5), col3 DATETIME)
              PARTITION BY HASH ( YEAR(col3) );

     You may not use either `VALUES LESS THAN' or `VALUES IN' clauses
     with `PARTITION BY HASH'.

     `PARTITION BY HASH' uses the remainder of EXPR divided by the
     number of partitions (that is, the modulus). For examples and
     additional information, see *Note partitioning-hash::.

     The `LINEAR' keyword entails a somewhat different algorithm. In
     this case, the number of the partition in which a row is stored is
     calculated as the result of one or more logical `AND' operations.
     For discussion and examples of linear hashing, see *Note
     partitioning-linear-hash::.

   * `KEY(COLUMN_LIST)': This is similar to `HASH', except that MySQL
     supplies the hashing function so as to guarantee an even data
     distribution. The COLUMN_LIST argument is simply a list of table
     columns. This example shows a simple table partitioned by key,
     with 4 partitions:


          CREATE TABLE tk (col1 INT, col2 CHAR(5), col3 DATE)
              PARTITION BY KEY(col3)
              PARTITIONS 4;

     For tables that are partitioned by key, you can employ linear
     partitioning by using the `LINEAR' keyword.  This has the same
     effect as with tables that are partitioned by `HASH'. That is, the
     partition number is found using the `&' operator rather than the
     modulus (see *Note partitioning-linear-hash::, and *Note
     partitioning-key::, for details). This example uses linear
     partitioning by key to distribute data between 5 partitions:


          CREATE TABLE tk (col1 INT, col2 CHAR(5), col3 DATE)
              PARTITION BY LINEAR KEY(col3)
              PARTITIONS 5;

     You may not use either `VALUES LESS THAN' or `VALUES IN' clauses
     with `PARTITION BY KEY'.

   * `RANGE(EXPR)': In this case, EXPR shows a range of values using a
     set of `VALUES LESS THAN' operators. When using range
     partitioning, you must define at least one partition using `VALUES
     LESS THAN'.  You cannot use `VALUES IN' with range partitioning.

     `VALUES LESS THAN' can be used with either a literal value or an
     expression that evaluates to a single value.

     Suppose that you have a table that you wish to partition on a
     column containing year values, according to the following scheme.

     This table illustrates a table partitioning scheme based on a
     column containing year values, as described in the preceding text.
     The table lists partition numbers and corresponding range of years.

     Partition Number:           Years Range:
     0                           1990 and earlier
     1                           1991 to 1994
     2                           1995 to 1998
     3                           1999 to 2002
     4                           2003 to 2005
     5                           2006 and later

     A table implementing such a partitioning scheme can be realized by
     the *Note `CREATE TABLE': create-table.  statement shown here:


          CREATE TABLE t1 (
              year_col  INT,
              some_data INT
          )
          PARTITION BY RANGE (year_col) (
              PARTITION p0 VALUES LESS THAN (1991),
              PARTITION p1 VALUES LESS THAN (1995),
              PARTITION p2 VALUES LESS THAN (1999),
              PARTITION p3 VALUES LESS THAN (2002),
              PARTITION p4 VALUES LESS THAN (2006),
              PARTITION p5 VALUES LESS THAN MAXVALUE
          );

     `PARTITION ... VALUES LESS THAN ...' statements work in a
     consecutive fashion. `VALUES LESS THAN MAXVALUE' works to specify
     `leftover' values that are greater than the maximum value
     otherwise specified.

     Note that `VALUES LESS THAN' clauses work sequentially in a manner
     similar to that of the `case' portions of a `switch ...  case'
     block (as found in many programming languages such as C, Java, and
     PHP). That is, the clauses must be arranged in such a way that the
     upper limit specified in each successive `VALUES LESS THAN' is
     greater than that of the previous one, with the one referencing
     `MAXVALUE' coming last of all in the list.

   * `LIST(EXPR)': This is useful when assigning partitions based on a
     table column with a restricted set of possible values, such as a
     state or country code. In such a case, all rows pertaining to a
     certain state or country can be assigned to a single partition, or
     a partition can be reserved for a certain set of states or
     countries. It is similar to `RANGE', except that only `VALUES IN'
     may be used to specify permissible values for each partition.

     `VALUES IN' is used with a list of values to be matched. For
     instance, you could create a partitioning scheme such as the
     following:


          CREATE TABLE client_firms (
              id   INT,
              name VARCHAR(35)
          )
          PARTITION BY LIST (id) (
              PARTITION r0 VALUES IN (1, 5, 9, 13, 17, 21),
              PARTITION r1 VALUES IN (2, 6, 10, 14, 18, 22),
              PARTITION r2 VALUES IN (3, 7, 11, 15, 19, 23),
              PARTITION r3 VALUES IN (4, 8, 12, 16, 20, 24)
          );

     When using list partitioning, you must define at least one
     partition using `VALUES IN'. You cannot use `VALUES LESS THAN'
     with `PARTITION BY LIST'.

     *Note*:

     Currently, the value list used with `VALUES IN' must consist of
     integer values only.

   * The number of partitions may optionally be specified with a
     `PARTITIONS NUM' clause, where NUM is the number of partitions. If
     both this clause _and_ any `PARTITION' clauses are used, NUM must
     be equal to the total number of any partitions that are declared
     using `PARTITION' clauses.

     *Note*:

     Whether or not you use a `PARTITIONS' clause in creating a table
     that is partitioned by `RANGE' or `LIST', you must still include
     at least one `PARTITION VALUES' clause in the table definition
     (see below).

   * A partition may optionally be divided into a number of
     subpartitions. This can be indicated by using the optional
     `SUBPARTITION BY' clause. Subpartitioning may be done by `HASH' or
     `KEY'.  Either of these may be `LINEAR'. These work in the same
     way as previously described for the equivalent partitioning types.
     (It is not possible to subpartition by `LIST' or `RANGE'.)

     The number of subpartitions can be indicated using the
     `SUBPARTITIONS' keyword followed by an integer value.

   * MySQL 5.1.12 introduces rigorous checking of the value used in a
     `PARTITIONS' or `SUBPARTITIONS' clause. Beginning with this
     version, this value must adhere to the following rules:

        * The value must be a positive, nonzero integer.

        * No leading zeros are permitted.

        * The value must be an integer literal, and cannot not be an
          expression. For example, `PARTITIONS 0.2E+01' is not
          permitted, even though `0.2E+01' evaluates to `2'. (Bug
          #15890)

*Note*:

The expression (EXPR) used in a `PARTITION BY' clause cannot refer to
any columns not in the table being created; beginning with MySQL
5.1.23, such references are specifically not permitted and cause the
statement to fail with an error. (Bug #29444)

Each partition may be individually defined using a PARTITION_DEFINITION
clause. The individual parts making up this clause are as follows:

   * `PARTITION PARTITION_NAME': This specifies a logical name for the
     partition.

   * A `VALUES' clause: For range partitioning, each partition must
     include a `VALUES LESS THAN' clause; for list partitioning, you
     must specify a `VALUES IN' clause for each partition. This is used
     to determine which rows are to be stored in this partition. See
     the discussions of partitioning types in *Note partitioning::, for
     syntax examples.

   * An optional `COMMENT' clause may be used to specify a string that
     describes the partition. Example:


          COMMENT = 'Data for the years previous to 1999'

   * `DATA DIRECTORY' and `INDEX DIRECTORY' may be used to indicate the
     directory where, respectively, the data and indexes for this
     partition are to be stored. Both the `DATA_DIR' and the `INDEX_DIR'
     must be absolute system path names. Example:


          CREATE TABLE th (id INT, name VARCHAR(30), adate DATE)
          PARTITION BY LIST(YEAR(adate))
          (
            PARTITION p1999 VALUES IN (1995, 1999, 2003)
              DATA DIRECTORY = '`/var/appdata/95/data''
              INDEX DIRECTORY = '`/var/appdata/95/idx'',
            PARTITION p2000 VALUES IN (1996, 2000, 2004)
              DATA DIRECTORY = '`/var/appdata/96/data''
              INDEX DIRECTORY = '`/var/appdata/96/idx'',
            PARTITION p2001 VALUES IN (1997, 2001, 2005)
              DATA DIRECTORY = '`/var/appdata/97/data''
              INDEX DIRECTORY = '`/var/appdata/97/idx'',
            PARTITION p2002 VALUES IN (1998, 2002, 2006)
              DATA DIRECTORY = '`/var/appdata/98/data''
              INDEX DIRECTORY = '`/var/appdata/98/idx''
          );

     `DATA DIRECTORY' and `INDEX DIRECTORY' behave in the same way as
     in the *Note `CREATE TABLE': create-table. statement's
     TABLE_OPTION clause as used for `MyISAM' tables.

     One data directory and one index directory may be specified per
     partition. If left unspecified, the data and indexes are stored by
     default in the table's database directory.

     On Windows, the `DATA DIRECTORY' and `INDEX DIRECTORY' options are
     not supported for individual partitions or subpartitions.
     Beginning with MySQL 5.1.24, these options are ignored on Windows,
     except that a warning is generated. (Bug #30459)

     *Note*:

     Prior to MySQL 5.1.18, `DATA DIRECTORY' and `INDEX DIRECTORY' were
     permitted even if the `NO_DIR_IN_CREATE' server SQL mode was in
     effect at the time that a partitioned table was created. Beginning
     with MySQL 5.1.18, these options are ignored for creating
     partitioned tables if `NO_DIR_IN_CREATE' is in effect. (Bug #24633)

   * `MAX_ROWS' and `MIN_ROWS' may be used to specify, respectively,
     the maximum and minimum number of rows to be stored in the
     partition. The values for MAX_NUMBER_OF_ROWS and
     MIN_NUMBER_OF_ROWS must be positive integers. As with the
     table-level options with the same names, these act only as
     `suggestions' to the server and are not hard limits.

   * The optional `TABLESPACE' clause may be used to designate a
     tablespace for the partition. Used for MySQL Cluster only.

   * The partitioning handler accepts a `[STORAGE] ENGINE' option for
     both `PARTITION' and `SUBPARTITION'. Currently, the only way in
     which this can be used is to set all partitions or all
     subpartitions to the same storage engine, and an attempt to set
     different storage engines for partitions or subpartitions in the
     same table will give rise to the error `ERROR 1469 (HY000): The
     mix of handlers in the partitions is not permitted in this version
     of MySQL'. We expect to lift this restriction on partitioning in a
     future MySQL release.

   * The `NODEGROUP' option can be used to make this partition act as
     part of the node group identified by NODE_GROUP_ID. This option is
     applicable only to MySQL Cluster.

   * The partition definition may optionally contain one or more
     SUBPARTITION_DEFINITION clauses.  Each of these consists at a
     minimum of the `SUBPARTITION NAME', where NAME is an identifier
     for the subpartition. Except for the replacement of the
     `PARTITION' keyword with `SUBPARTITION', the syntax for a
     subpartition definition is identical to that for a partition
     definition.

     Subpartitioning must be done by `HASH' or `KEY', and can be done
     only on `RANGE' or `LIST' partitions. See *Note
     partitioning-subpartitions::.

Partitions can be modified, merged, added to tables, and dropped from
tables. For basic information about the MySQL statements to accomplish
these tasks, see *Note alter-table::. For more detailed descriptions
and examples, see *Note partitioning-management::.

*Important*:

The original *Note `CREATE TABLE': create-table.  statement, including
all specifications and table options are stored by MySQL when the table
is created. The information is retained so that if you change storage
engines, collations or other settings using an *Note `ALTER TABLE':
alter-table. statement, the original table options specified are
retained. This enables you to change between *Note `InnoDB':
innodb-storage-engine. and *Note `MyISAM': myisam-storage-engine. table
types even though the row formats supported by the two engines are
different.

Because the text of the original statement is retained, but due to the
way that certain values and options may be silently reconfigured (such
as the `ROW_FORMAT'), the active table definition (accessible through
*Note `DESCRIBE': describe. or with *Note `SHOW TABLE STATUS':
show-table-status.) and the table creation string (accessible through
*Note `SHOW CREATE TABLE': show-create-table.) will report different
values.

*Cloning or Copying a Table*

You can create one table from another by adding a *Note `SELECT':
select. statement at the end of the *Note `CREATE TABLE': create-table.
statement:


     CREATE TABLE NEW_TBL SELECT * FROM ORIG_TBL;

For more information, see *Note create-table-select::.

Use `LIKE' to create an empty table based on the definition of another
table, including any column attributes and indexes defined in the
original table:


     CREATE TABLE NEW_TBL LIKE ORIG_TBL;

The copy is created using the same version of the table storage format
as the original table. The `SELECT' privilege is required on the
original table.

`LIKE' works only for base tables, not for views.

`CREATE TABLE ... LIKE' does not preserve any `DATA DIRECTORY' or `INDEX
DIRECTORY' table options that were specified for the original table, or
any foreign key definitions.

If the original table is a `TEMPORARY' table, `CREATE TABLE ... LIKE'
does not preserve `TEMPORARY'. To create a `TEMPORARY' destination
table, use `CREATE TEMPORARY TABLE ... LIKE'.

In MySQL 5.1, changes to the SQL mode do not affect *Note `CREATE TABLE
... LIKE': create-table. If the current SQL mode is different from the
mode in effect when the original table was created, the statement
succeeds even if the table definition is invalid for the new mode.


File: manual.info,  Node: create-table-select,  Next: create-table-foreign-keys,  Prev: create-table,  Up: create-table

13.1.17.1 CREATE TABLE ... SELECT Syntax
........................................

You can create one table from another by adding a *Note `SELECT':
select. statement at the end of the *Note `CREATE TABLE': create-table.
statement:


     CREATE TABLE NEW_TBL [AS] SELECT * FROM ORIG_TBL;

MySQL creates new columns for all elements in the *Note `SELECT':
select. For example:


     mysql> CREATE TABLE test (a INT NOT NULL AUTO_INCREMENT,
         ->        PRIMARY KEY (a), KEY(b))
         ->        ENGINE=MyISAM SELECT b,c FROM test2;

This creates a *Note `MyISAM': myisam-storage-engine. table with three
columns, `a', `b', and `c'. The `ENGINE' option is part of the *Note
`CREATE TABLE': create-table.  statement, and should not be used
following the *Note `SELECT': select.; this would result in a syntax
error. The same is true for other *Note `CREATE TABLE': create-table.
options such as `CHARSET'.

Notice that the columns from the *Note `SELECT': select. statement are
appended to the right side of the table, not overlapped onto it. Take
the following example:


     mysql> SELECT * FROM foo;
     +---+
     | n |
     +---+
     | 1 |
     +---+

     mysql> CREATE TABLE bar (m INT) SELECT n FROM foo;
     Query OK, 1 row affected (0.02 sec)
     Records: 1  Duplicates: 0  Warnings: 0

     mysql> SELECT * FROM bar;
     +------+---+
     | m    | n |
     +------+---+
     | NULL | 1 |
     +------+---+
     1 row in set (0.00 sec)

For each row in table `foo', a row is inserted in `bar' with the values
from `foo' and default values for the new columns.

In a table resulting from *Note `CREATE TABLE ... SELECT':
create-table, columns named only in the *Note `CREATE TABLE':
create-table. part come first.  Columns named in both parts or only in
the *Note `SELECT': select. part come after that. The data type of
*Note `SELECT': select. columns can be overridden by also specifying
the column in the *Note `CREATE TABLE': create-table. part.

If any errors occur while copying the data to the table, it is
automatically dropped and not created.

You can precede the *Note `SELECT': select. by `IGNORE' or *Note
`REPLACE': replace. to indicate how to handle rows that duplicate
unique key values. With `IGNORE', rows that duplicate an existing row
on a unique key value are discarded. With *Note `REPLACE': replace, new
rows replace rows that have the same unique key value. If neither
`IGNORE' nor *Note `REPLACE': replace. is specified, duplicate unique
key values result in an error.

*Note `CREATE TABLE ... SELECT': create-table. does not automatically
create any indexes for you. This is done intentionally to make the
statement as flexible as possible. If you want to have indexes in the
created table, you should specify these before the *Note `SELECT':
select. statement:


     mysql> CREATE TABLE bar (UNIQUE (n)) SELECT n FROM foo;

Some conversion of data types might occur. For example, the
`AUTO_INCREMENT' attribute is not preserved, and *Note `VARCHAR': char.
columns can become *Note `CHAR': char. columns. Retrained attributes
are `NULL' (or `NOT NULL') and, for those columns that have them,
`CHARACTER SET', `COLLATION', `COMMENT', and the `DEFAULT' clause.

When creating a table with *Note `CREATE TABLE ... SELECT':
create-table-select, make sure to alias any function calls or
expressions in the query. If you do not, the `CREATE' statement might
fail or result in undesirable column names.


     CREATE TABLE artists_and_works
       SELECT artist.name, COUNT(work.artist_id) AS number_of_works
       FROM artist LEFT JOIN work ON artist.id = work.artist_id
       GROUP BY artist.id;

You can also explicitly specify the data type for a generated column:


     CREATE TABLE foo (a TINYINT NOT NULL) SELECT b+1 AS a FROM bar;

For *Note `CREATE TABLE ... SELECT': create-table, if `IF NOT EXISTS' is
given and the destination table already exists, the result is version
dependent. Before MySQL 5.5.6, MySQL handles the statement as follows:

   * The table definition given in the *Note `CREATE TABLE':
     create-table. part is ignored.  No error occurs, even if the
     definition does not match that of the existing table. MySQL
     attempts to insert the rows from the *Note `SELECT': select. part
     anyway.

   * If there is a mismatch between the number of columns in the table
     and the number of columns produced by the *Note `SELECT': select.
     part, the selected values are assigned to the rightmost columns.
     For example, if the table contains N columns and the *Note
     `SELECT': select. produces M columns, where M < N, the selected
     values are assigned to the M rightmost columns in the table. Each
     of the initial N - M columns is assigned its default value, either
     that specified explicitly in the column definition or the implicit
     column data type default if the definition contains no default. If
     the *Note `SELECT': select. part produces too many columns (M >
     N), an error occurs.

   * If strict SQL mode is enabled and any of these initial columns do
     not have an explicit default value, the statement fails with an
     error.

The following example illustrates `IF NOT EXISTS' handling:


     mysql> CREATE TABLE t1 (i1 INT DEFAULT 0, i2 INT, i3 INT, i4 INT);
     Query OK, 0 rows affected (0.05 sec)

     mysql> CREATE TABLE IF NOT EXISTS t1 (c1 CHAR(10)) SELECT 1, 2;
     Query OK, 1 row affected, 1 warning (0.01 sec)
     Records: 1  Duplicates: 0  Warnings: 0

     mysql> SELECT * FROM t1;
     +------+------+------+------+
     | i1   | i2   | i3   | i4   |
     +------+------+------+------+
     |    0 | NULL |    1 |    2 |
     +------+------+------+------+
     1 row in set (0.00 sec)

As of MySQL 5.5.6, handling of *Note `CREATE TABLE IF NOT EXISTS ...
SELECT': create-table-select. statements was changed for the case that
the destination table already exists. This change also involves a
change in MySQL 5.1 beginning with 5.1.51.

   * Previously, for *Note `CREATE TABLE IF NOT EXISTS ... SELECT':
     create-table-select, MySQL produced a warning that the table
     exists, but inserted the rows and wrote the statement to the
     binary log anyway. By contrast, *Note `CREATE TABLE ... SELECT':
     create-table-select. (without `IF NOT EXISTS') failed with an
     error, but MySQL inserted no rows and did not write the statement
     to the binary log.

   * MySQL now handles both statements the same way when the
     destination table exists, in that neither statement inserts rows
     or is written to the binary log. The difference between them is
     that MySQL produces a warning when `IF NOT EXISTS' is present and
     an error when it is not.

This change means that, for the preceding example, the *Note `CREATE
TABLE IF NOT EXISTS ... SELECT': create-table-select. statement inserts
nothing into the destination table as of MySQL 5.5.6.

This change in handling of `IF NOT EXISTS' results in an
incompatibility for statement-based replication from a MySQL 5.1 master
with the original behavior and a MySQL 5.5 slave with the new behavior.
Suppose that *Note `CREATE TABLE IF NOT EXISTS ... SELECT':
create-table-select. is executed on the master and the destination
table exists. The result is that rows are inserted on the master but
not on the slave. (Row-based replication does not have this problem.)

To address this issue, statement-based binary logging for *Note `CREATE
TABLE IF NOT EXISTS ... SELECT': create-table-select. is changed in
MySQL 5.1 as of 5.1.51:

   * If the destination table does not exist, there is no change: The
     statement is logged as is.

   * If the destination table does exist, the statement is logged as
     the equivalent pair of *Note `CREATE TABLE IF NOT EXISTS':
     create-table-select. and *Note `INSERT ... SELECT': insert-select.
     statements. (If the *Note `SELECT': select. in the original
     statement is preceded by `IGNORE' or *Note `REPLACE': replace, the
     *Note `INSERT': insert. becomes *Note `INSERT IGNORE': insert. or
     *Note `REPLACE': replace, respectively.)

This change provides forward compatibility for statement-based
replication from MySQL 5.1 to 5.5 because when the destination table
exists, the rows will be inserted on both the master and slave. To take
advantage of this compatibility measure, the 5.1 server must be at
least 5.1.51 and the 5.5 server must be at least 5.5.6.

To upgrade an existing 5.1-to-5.5 replication scenario, upgrade the
master first to 5.1.51 or higher. Note that this differs from the usual
replication upgrade advice of upgrading the slave first.

A workaround for applications that wish to achieve the original effect
(rows inserted regardless of whether the destination table exists) is
to use *Note `CREATE TABLE IF NOT EXISTS': create-table-select. and
*Note `INSERT ... SELECT': insert-select. statements rather than *Note
`CREATE TABLE IF NOT EXISTS ... SELECT': create-table-select.
statements.

Along with the change just described, the following related change was
made: Previously, if an existing view was named as the destination
table for *Note `CREATE TABLE IF NOT EXISTS ... SELECT':
create-table-select, rows were inserted into the underlying base table
and the statement was written to the binary log. As of MySQL 5.1.51 and
5.5.6, nothing is inserted or logged.

To ensure that the binary log can be used to re-create the original
tables, MySQL does not permit concurrent inserts during *Note `CREATE
TABLE ... SELECT': create-table.


File: manual.info,  Node: create-table-foreign-keys,  Next: silent-column-changes,  Prev: create-table-select,  Up: create-table

13.1.17.2 Using FOREIGN KEY Constraints
.......................................

MySQL supports foreign keys, which let you cross-reference related data
across tables, and foreign key constraints
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_foreign_key_constraint),
which help keep this spread-out data consistent. The essential syntax
for a foreign key constraint definition in a *Note `CREATE TABLE':
create-table. or *Note `ALTER TABLE': alter-table. statement looks like
this:


     [CONSTRAINT [SYMBOL]] FOREIGN KEY
         [INDEX_NAME] (INDEX_COL_NAME, ...)
         REFERENCES TBL_NAME (INDEX_COL_NAME,...)
         [ON DELETE REFERENCE_OPTION]
         [ON UPDATE REFERENCE_OPTION]

     REFERENCE_OPTION:
         RESTRICT | CASCADE | SET NULL | NO ACTION

INDEX_NAME represents a foreign key ID. If given, this is ignored if an
index for the foreign key is defined explicitly. Otherwise, if MySQL
creates an index for the foreign key, it uses INDEX_NAME for the index
name.

Foreign keys definitions are subject to the following conditions:

   * Foreign key relationships involve a parent table
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_parent_table)
     that holds the central data values, and a child table
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_child_table)
     with identical values pointing back to its parent. The `FOREIGN
     KEY' clause is specified in the child table. The parent and child
     tables must use the same storage engine. They must not be
     `TEMPORARY' tables.

   * Corresponding columns in the foreign key and the referenced key
     must have similar data types. _The size and sign of integer types
     must be the same_. The length of string types need not be the
     same. For nonbinary (character) string columns, the character set
     and collation must be the same.

   * MySQL requires indexes on foreign keys and referenced keys so that
     foreign key checks can be fast and not require a table scan. In
     the referencing table, there must be an index where the foreign
     key columns are listed as the _first_ columns in the same order.
     Such an index is created on the referencing table automatically if
     it does not exist. This index might be silently dropped later, if
     you create another index that can be used to enforce the foreign
     key constraint.  INDEX_NAME, if given, is used as described
     previously.

   * `InnoDB' permits a foreign key to reference any index column or
     group of columns. However, in the referenced table, there must be
     an index where the referenced columns are listed as the _first_
     columns in the same order.

   * Index prefixes on foreign key columns are not supported. One
     consequence of this is that *Note `BLOB': blob. and *Note `TEXT':
     blob. columns cannot be included in a foreign key because indexes
     on those columns must always include a prefix length.

   * If the `CONSTRAINT SYMBOL' clause is given, the SYMBOL value, if
     used, must be unique in the database. A duplicate SYMBOL will
     result in an error similar to: `ERROR 1005 (HY000): Can't create
     table 'test.#sql-211d_3' (errno: 121)'. If the clause is not
     given, or a SYMBOL is not included following the `CONSTRAINT'
     keyword, a name for the constraint is created automatically.

   * *Note `InnoDB': innodb-storage-engine. does not currently support
     foreign keys for tables with user-defined partitioning. This
     includes both parent and child tables.

*Referential Actions*

This section describes how foreign keys help guarantee referential
integrity
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_referential_integrity).

For storage engines supporting foreign keys, MySQL rejects any *Note
`INSERT': insert. or *Note `UPDATE': update. operation that attempts to
create a foreign key value in a child table if there is no a matching
candidate key value in the parent table.

When an *Note `UPDATE': update. or *Note `DELETE': delete. operation
affects a key value in the parent table that has matching rows in the
child table, the result depends on the _referential action_ specified
using `ON UPDATE' and `ON DELETE' subclauses of the `FOREIGN KEY'
clause. MySQL supports five options regarding the action to be taken,
listed here:

   * `CASCADE': Delete or update the row from the parent table, and
     automatically delete or update the matching rows in the child
     table. Both `ON DELETE CASCADE' and `ON UPDATE CASCADE' are
     supported. Between two tables, do not define several `ON UPDATE
     CASCADE' clauses that act on the same column in the parent table
     or in the child table.

     *Note*:

     Currently, cascaded foreign key actions do not activate triggers.

   * `SET NULL': Delete or update the row from the parent table, and
     set the foreign key column or columns in the child table to
     `NULL'. Both `ON DELETE SET NULL' and `ON UPDATE SET NULL' clauses
     are supported.

     If you specify a `SET NULL' action, _make sure that you have not
     declared the columns in the child table as `NOT NULL'_.

   * `RESTRICT': Rejects the delete or update operation for the parent
     table. Specifying `RESTRICT' (or `NO ACTION') is the same as
     omitting the `ON DELETE' or `ON UPDATE' clause.

   * `NO ACTION': A keyword from standard SQL.  In MySQL, equivalent to
     `RESTRICT'. The MySQL Server rejects the delete or update
     operation for the parent table if there is a related foreign key
     value in the referenced table. Some database systems have deferred
     checks, and `NO ACTION' is a deferred check. In MySQL, foreign key
     constraints are checked immediately, so `NO ACTION' is the same as
     `RESTRICT'.

   * `SET DEFAULT': This action is recognized by the MySQL parser, but
     *Note `InnoDB': innodb-storage-engine.  rejects table definitions
     containing `ON DELETE SET DEFAULT' or `ON UPDATE SET DEFAULT'
     clauses.

For an `ON DELETE' or `ON UPDATE' that is not specified, the default
action is always `RESTRICT'.

MySQL supports foreign key references between one column and another
within a table. (A column cannot have a foreign key reference to
itself.) In these cases, `child table records' really refers to
dependent records within the same table.

*Examples of Foreign Key Clauses*

Here is a simple example that relates `parent' and `child' tables
through a single-column foreign key:


     CREATE TABLE parent (
         id INT NOT NULL,
         PRIMARY KEY (id)
     ) ENGINE=INNODB;

     CREATE TABLE child (
         id INT,
         parent_id INT,
         INDEX par_ind (parent_id),
         FOREIGN KEY (parent_id)
             REFERENCES parent(id)
             ON DELETE CASCADE
     ) ENGINE=INNODB;

A more complex example in which a `product_order' table has foreign
keys for two other tables. One foreign key references a two-column
index in the `product' table. The other references a single-column
index in the `customer' table:


     CREATE TABLE product (
         category INT NOT NULL, id INT NOT NULL,
         price DECIMAL,
         PRIMARY KEY(category, id)
     )   ENGINE=INNODB;

     CREATE TABLE customer (
         id INT NOT NULL,
         PRIMARY KEY (id)
     )   ENGINE=INNODB;

     CREATE TABLE product_order (
         no INT NOT NULL AUTO_INCREMENT,
         product_category INT NOT NULL,
         product_id INT NOT NULL,
         customer_id INT NOT NULL,

         PRIMARY KEY(no),
         INDEX (product_category, product_id),
         INDEX (customer_id),

         FOREIGN KEY (product_category, product_id)
           REFERENCES product(category, id)
           ON UPDATE CASCADE ON DELETE RESTRICT,

         FOREIGN KEY (customer_id)
           REFERENCES customer(id)
     )   ENGINE=INNODB;

*Adding foreign keys*

You can add a new foreign key constraint to an existing table by using
*Note `ALTER TABLE': alter-table. The syntax relating to foreign keys
for this statement is shown here:


     ALTER TABLE TBL_NAME
         ADD [CONSTRAINT [SYMBOL]] FOREIGN KEY
         [INDEX_NAME] (INDEX_COL_NAME, ...)
         REFERENCES TBL_NAME (INDEX_COL_NAME,...)
         [ON DELETE REFERENCE_OPTION]
         [ON UPDATE REFERENCE_OPTION]

The foreign key can be self referential (referring to the same table).
When you add a foreign key constraint to a table using *Note `ALTER
TABLE': alter-table, _remember to create the required indexes first._

*Dropping Foreign Keys*

You can also use *Note `ALTER TABLE': alter-table. to drop foreign
keys, using the syntax shown here:


     ALTER TABLE TBL_NAME DROP FOREIGN KEY FK_SYMBOL;

If the `FOREIGN KEY' clause included a `CONSTRAINT' name when you
created the foreign key, you can refer to that name to drop the foreign
key.  Otherwise, the FK_SYMBOL value is generated internally when the
foreign key is created. To find out the symbol value when you want to
drop a foreign key, use a *Note `SHOW CREATE TABLE': show-create-table.
statement, as shown here:


     mysql> SHOW CREATE TABLE ibtest11c\G
     *************************** 1. row ***************************
            Table: ibtest11c
     Create Table: CREATE TABLE `ibtest11c` (
       `A` int(11) NOT NULL auto_increment,
       `D` int(11) NOT NULL default '0',
       `B` varchar(200) NOT NULL default '',
       `C` varchar(175) default NULL,
       PRIMARY KEY  (`A`,`D`,`B`),
       KEY `B` (`B`,`C`),
       KEY `C` (`C`),
       CONSTRAINT `0_38775` FOREIGN KEY (`A`, `D`)
     REFERENCES `ibtest11a` (`A`, `D`)
     ON DELETE CASCADE ON UPDATE CASCADE,
       CONSTRAINT `0_38776` FOREIGN KEY (`B`, `C`)
     REFERENCES `ibtest11a` (`B`, `C`)
     ON DELETE CASCADE ON UPDATE CASCADE
     ) ENGINE=INNODB CHARSET=latin1
     1 row in set (0.01 sec)

     mysql> ALTER TABLE ibtest11c DROP FOREIGN KEY `0_38775`;

Adding and dropping a foreign key in separate clauses of a single *Note
`ALTER TABLE': alter-table. statement may be problematic in some cases
and is therefore unsupported. Use separate statements for each
operation.

If an *Note `ALTER TABLE': alter-table. statement results in changes to
column values (for example, because a column is truncated), MySQL's
foreign key constraint checks do not notice possible violations caused
by changing the values.

*Foreign Keys and Other MySQL Statements*

Table and column identifiers in a `FOREIGN KEY ...  REFERENCES ...'
clause can be quoted within backticks (``'). Alternatively, double
quotation marks (`"') can be used if the `ANSI_QUOTES' SQL mode is
enabled. The setting of the `lower_case_table_names' system variable is
also taken into account.

You can view a child table's foreign key definitions as part of the
output of the *Note `SHOW CREATE TABLE': show-create-table. statement:


     SHOW CREATE TABLE TBL_NAME;

You can also obtain information about foreign keys by querying the
*Note `INFORMATION_SCHEMA.KEY_COLUMN_USAGE': key-column-usage-table.
table.

*Note `mysqldump': mysqldump. produces correct definitions of tables in
the dump file, including the foreign keys for child tables.

To make it easier to reload dump files for tables that have foreign key
relationships, *Note `mysqldump': mysqldump.  automatically includes a
statement in the dump output to set `foreign_key_checks' to 0. This
avoids problems with tables having to be reloaded in a particular order
when the dump is reloaded. It is also possible to set this variable
manually:


     mysql> SET foreign_key_checks = 0;
     mysql> SOURCE DUMP_FILE_NAME;
     mysql> SET foreign_key_checks = 1;

This enables you to import the tables in any order if the dump file
contains tables that are not correctly ordered for foreign keys. It
also speeds up the import operation. Setting `foreign_key_checks' to 0
can also be useful for ignoring foreign key constraints during *Note
`LOAD DATA': load-data. and *Note `ALTER TABLE': alter-table.
operations. However, even if `foreign_key_checks = 0', MySQL does not
permit the creation of a foreign key constraint where a column
references a nonmatching column type. Also, if a table has foreign key
constraints, *Note `ALTER TABLE': alter-table. cannot be used to alter
the table to use another storage engine. To change the storage engine,
you must drop any foreign key constraints first.

You cannot issue *Note `DROP TABLE': drop-table. for a table that is
referenced by a `FOREIGN KEY' constraint, unless you do `SET
foreign_key_checks = 0'. When you drop a table, any constraints that
were defined in the statement used to create that table are also
dropped.

If you re-create a table that was dropped, it must have a definition
that conforms to the foreign key constraints referencing it. It must
have the correct column names and types, and it must have indexes on
the referenced keys, as stated earlier. If these are not satisfied,
MySQL returns Error 1005 and refers to Error 150 in the error message,
which means that a foreign key constraint was not correctly formed.
Similarly, if an *Note `ALTER TABLE': alter-table. fails due to Error
150, this means that a foreign key definition would be incorrectly
formed for the altered table.

For `InnoDB' tables, you can obtain a detailed explanation of the most
recent `InnoDB' foreign key error in the MySQL Server, by checking the
output of *Note `SHOW ENGINE INNODB STATUS': show-engine.

*Important*:

For users familiar with the ANSI/ISO SQL Standard, please note that no
storage engine, including `InnoDB', recognizes or enforces the `MATCH'
clause used in referential-integrity constraint definitions. Use of an
explicit `MATCH' clause will not have the specified effect, and also
causes `ON DELETE' and `ON UPDATE' clauses to be ignored. For these
reasons, specifying `MATCH' should be avoided.

The `MATCH' clause in the SQL standard controls how `NULL' values in a
composite (multiple-column) foreign key are handled when comparing to a
primary key. MySQL essentially implements the semantics defined by
`MATCH SIMPLE', which permit a foreign key to be all or partially
`NULL'. In that case, the (child table) row containing such a foreign
key is permitted to be inserted, and does not match any row in the
referenced (parent) table. It is possible to implement other semantics
using triggers.

Additionally, MySQL requires that the referenced columns be indexed for
performance reasons. However, the system does not enforce a requirement
that the referenced columns be `UNIQUE' or be declared `NOT NULL'. The
handling of foreign key references to nonunique keys or keys that
contain `NULL' values is not well defined for operations such as *Note
`UPDATE': update. or `DELETE CASCADE'. You are advised to use foreign
keys that reference only `UNIQUE' (including `PRIMARY') and `NOT NULL'
keys.

Furthermore, MySQL does not recognize or support `inline `REFERENCES'
specifications' (as defined in the SQL standard) where the references
are defined as part of the column specification. MySQL accepts
`REFERENCES' clauses only when specified as part of a separate `FOREIGN
KEY' specification. For storage engines that do not support foreign
keys (such as *Note `MyISAM': myisam-storage-engine.), MySQL Server
parses and ignores foreign key specifications.


File: manual.info,  Node: silent-column-changes,  Prev: create-table-foreign-keys,  Up: create-table

13.1.17.3 Silent Column Specification Changes
.............................................

In some cases, MySQL silently changes column specifications from those
given in a *Note `CREATE TABLE': create-table. or *Note `ALTER TABLE':
alter-table. statement. These might be changes to a data type, to
attributes associated with a data type, or to an index specification.

All changes are subject to the internal row-size limit of 65,535 bytes,
which may cause some attempts at data type changes to fail. See *Note
column-count-limit::.

   * *Note `TIMESTAMP': datetime. display sizes are discarded.

     Also note that *Note `TIMESTAMP': datetime.  columns are `NOT
     NULL' by default.

   * Columns that are part of a `PRIMARY KEY' are made `NOT NULL' even
     if not declared that way.

   * Trailing spaces are automatically deleted from *Note `ENUM': enum.
     and *Note `SET': set. member values when the table is created.

   * MySQL maps certain data types used by other SQL database vendors
     to MySQL types. See *Note other-vendor-data-types::.

   * If you include a `USING' clause to specify an index type that is
     not permitted for a given storage engine, but there is another
     index type available that the engine can use without affecting
     query results, the engine uses the available type.

   * If strict SQL mode is not enabled, a *Note `VARCHAR': char. column
     with a length specification greater than 65535 is converted to
     *Note `TEXT': blob, and a *Note `VARBINARY': binary-varbinary.
     column with a length specification greater than 65535 is converted
     to *Note `BLOB': blob. Otherwise, an error occurs in either of
     these cases.

   * Specifying the `CHARACTER SET binary' attribute for a character
     data type causes the column to be created as the corresponding
     binary data type: *Note `CHAR': char. becomes *Note `BINARY':
     binary-varbinary, *Note `VARCHAR': char. becomes *Note
     `VARBINARY': binary-varbinary, and *Note `TEXT': blob. becomes
     *Note `BLOB': blob. For the *Note `ENUM': enum. and *Note `SET':
     set. data types, this does not occur; they are created as
     declared. Suppose that you specify a table using this definition:


          CREATE TABLE t
          (
            c1 VARCHAR(10) CHARACTER SET binary,
            c2 TEXT CHARACTER SET binary,
            c3 ENUM('a','b','c') CHARACTER SET binary
          );

     The resulting table has this definition:


          CREATE TABLE t
          (
            c1 VARBINARY(10),
            c2 BLOB,
            c3 ENUM('a','b','c') CHARACTER SET binary
          );

To see whether MySQL used a data type other than the one you specified,
issue a *Note `DESCRIBE': describe. or *Note `SHOW CREATE TABLE':
show-create-table. statement after creating or altering the table.

Certain other data type changes can occur if you compress a table using
*Note `myisampack': myisampack. See *Note compressed-format::.


File: manual.info,  Node: create-tablespace,  Next: create-trigger,  Prev: create-table,  Up: sql-syntax-data-definition

13.1.18 CREATE TABLESPACE Syntax
--------------------------------


     CREATE TABLESPACE TABLESPACE_NAME
         ADD DATAFILE 'FILE_NAME'
         USE LOGFILE GROUP LOGFILE_GROUP
         [EXTENT_SIZE [=] EXTENT_SIZE]
         [INITIAL_SIZE [=] INITIAL_SIZE]
         [AUTOEXTEND_SIZE [=] AUTOEXTEND_SIZE]
         [MAX_SIZE [=] MAX_SIZE]
         [NODEGROUP [=] NODEGROUP_ID]
         [WAIT]
         [COMMENT [=] COMMENT_TEXT]
         ENGINE [=] ENGINE_NAME

This statement is used to create a tablespace, which can contain one or
more data files, providing storage space for tables. One data file is
created and added to the tablespace using this statement. Additional
data files may be added to the tablespace by using the *Note `ALTER
TABLESPACE': alter-tablespace.  statement (see *Note
alter-tablespace::). For rules covering the naming of tablespaces, see
*Note identifiers::.

*Note*:

All MySQL Cluster Disk Data objects share the same namespace.  This
means that _each Disk Data object_ must be uniquely named (and not
merely each Disk Data object of a given type). For example, you cannot
have a tablespace and a log file group with the same name, or a
tablespace and a data file with the same name.

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, path and file
names for data files could not be longer than 128 characters.  (Bug
#31770)

A log file group of one or more `UNDO' log files must be assigned to
the tablespace to be created with the `USE LOGFILE GROUP' clause.
LOGFILE_GROUP must be an existing log file group created with *Note
`CREATE LOGFILE GROUP': create-logfile-group. (see *Note
create-logfile-group::).  Multiple tablespaces may use the same log
file group for `UNDO' logging.

The `EXTENT_SIZE' sets the size, in bytes, of the extents used by any
files belonging to the tablespace. The default value is 1M. The minimum
size is 32K, and theoretical maximum is 2G, although the practical
maximum size depends on a number of factors. In most cases, changing
the extent size does not have any measurable effect on performance, and
the default value is recommended for all but the most unusual
situations.

An _extent_ is a unit of disk space allocation. One extent is filled
with as much data as that extent can contain before another extent is
used. In theory, up to 65,535 (64K) extents may used per data file;
however, the recommended maximum is 32,768 (32K). The recommended
maximum size for a single data file is 32G--that is, 32K extents x 1 MB
per extent. In addition, once an extent is allocated to a given
partition, it cannot be used to store data from a different partition;
an extent cannot store data from more than one partition. This means,
for example that a tablespace having a single datafile whose
`INITIAL_SIZE' is 256 MB and whose `EXTENT_SIZE' is 128M has just two
extents, and so can be used to store data from at most two different
disk data table partitions.

You can see how many extents remain free in a given data file by
querying the *Note `INFORMATION_SCHEMA.FILES': files-table.  table, and
so derive an estimate for how much space remains free in the file. For
further discussion and examples, see *Note files-table::.

The `INITIAL_SIZE' parameter sets the data file's total size in bytes.
Once the file has been created, its size cannot be changed; however,
you can add more data files to the tablespace using `ALTER TABLESPACE
... ADD DATAFILE'. See *Note alter-tablespace::.

`INITIAL_SIZE' is optional; its default value is `128M'.

On 32-bit systems, the maximum supported value for `INITIAL_SIZE' is
`4G'. (Bug #29186)

When setting `EXTENT_SIZE' or `INITIAL_SIZE' (either or both), you may
optionally follow the number with a one-letter abbreviation for an
order of magnitude, similar to those used in `my.cnf'. Generally, this
is one of the letters `M' (for megabytes) or `G' (for gigabytes).

`INITIAL_SIZE', `EXTENT_SIZE', and `UNDO_BUFFER_SIZE' are subject to
rounding as follows:

   * `EXTENT_SIZE' and `UNDO_BUFFER_SIZE' are each rounded up to the
     nearest whole multiple of 32K.

   * `INITIAL_SIZE' is rounded _down_ to the nearest whole multiple of
     32K.

     For data files, _INITIAL_SIZE_ is subject to further rounding; the
     result just obtained is rounded up to the nearest whole multiple
     of `EXTENT_SIZE' (after any rounding).

The rounding just described has always (since Disk Data tablespaces
were introduced in MySQL 5.1.6) been performed implicitly, but
beginning with MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.32,
MySQL Cluster NDB 7.0.13, and MySQL Cluster NDB 7.1.2, this rounding is
done explicitly, and a warning is issued by the MySQL Server when any
such rounding is performed.  The rounded values are also used by the
NDB kernel for calculating *Note `INFORMATION_SCHEMA.FILES':
files-table. column values and other purposes. However, to avoid an
unexpected result, we suggest that you always use whole multiples of
32K in specifying these options.

`AUTOEXTEND_SIZE', `MAX_SIZE', `NODEGROUP', `WAIT', and `COMMENT' are
parsed but ignored, and so currently have no effect. These options are
intended for future expansion.

The `ENGINE' parameter determines the storage engine which uses this
tablespace, with ENGINE_NAME being the name of the storage engine. In
MySQL 5.1, ENGINE_NAME must be one of the values *Note `NDB':
mysql-cluster. or *Note `NDBCLUSTER': mysql-cluster.

When *Note `CREATE TABLESPACE': create-tablespace. is used with `ENGINE
= NDB', a tablespace and associated data file are created on each
Cluster data node. You can verify that the data files were created and
obtain information about them by querying the *Note
`INFORMATION_SCHEMA.FILES': files-table.  table. For example:


     mysql> SELECT LOGFILE_GROUP_NAME, FILE_NAME, EXTRA
         -> FROM INFORMATION_SCHEMA.FILES
         -> WHERE TABLESPACE_NAME = 'newts' AND FILE_TYPE = 'DATAFILE';
     +--------------------+-------------+----------------+
     | LOGFILE_GROUP_NAME | FILE_NAME   | EXTRA          |
     +--------------------+-------------+----------------+
     | lg_3               | newdata.dat | CLUSTER_NODE=3 |
     | lg_3               | newdata.dat | CLUSTER_NODE=4 |
     +--------------------+-------------+----------------+
     2 rows in set (0.01 sec)

(See *Note files-table::.)

*Note `CREATE TABLESPACE': create-tablespace. was added in MySQL 5.1.6.
In MySQL 5.1, it is useful only with Disk Data storage for MySQL
Cluster. See *Note mysql-cluster-disk-data::.


File: manual.info,  Node: create-trigger,  Next: create-view,  Prev: create-tablespace,  Up: sql-syntax-data-definition

13.1.19 CREATE TRIGGER Syntax
-----------------------------


     CREATE
         [DEFINER = { USER | CURRENT_USER }]
         TRIGGER TRIGGER_NAME
         TRIGGER_TIME TRIGGER_EVENT
         ON TBL_NAME FOR EACH ROW
         TRIGGER_BODY

     TRIGGER_TIME: { BEFORE | AFTER }

     TRIGGER_EVENT: { INSERT | UPDATE | DELETE }

This statement creates a new trigger. A trigger is a named database
object that is associated with a table, and that activates when a
particular event occurs for the table. The trigger becomes associated
with the table named TBL_NAME, which must refer to a permanent table.
You cannot associate a trigger with a `TEMPORARY' table or a view.

Trigger names exist in the schema namespace, meaning that all triggers
must have unique names within a schema. Triggers in different schemas
can have the same name.

This section describes *Note `CREATE TRIGGER': create-trigger. syntax.
For additional discussion, see *Note trigger-syntax::.

*Note `CREATE TRIGGER': create-trigger. requires the `TRIGGER'
privilege for the table associated with the trigger. The statement
might also require the `SUPER' privilege, depending on the `DEFINER'
value, as described later in this section. If binary logging is
enabled, *Note `CREATE TRIGGER': create-trigger. might require the
`SUPER' privilege, as described in *Note stored-programs-logging::.
(Before MySQL 5.1.6, there is no `TRIGGER' privilege and this statement
requires the `SUPER' privilege in all cases.)

The `DEFINER' clause determines the security context to be used when
checking access privileges at trigger activation time, as described
later in this section.

TRIGGER_TIME is the trigger action time. It can be `BEFORE' or `AFTER'
to indicate that the trigger activates before or after each row to be
modified.

TRIGGER_EVENT indicates the kind of operation that activates the
trigger. These TRIGGER_EVENT values are permitted:

   * *Note `INSERT': insert.: The trigger activates whenever a new row
     is inserted into the table; for example, through *Note `INSERT':
     insert, *Note `LOAD DATA': load-data, and *Note `REPLACE':
     replace. statements.

   * *Note `UPDATE': update.: The trigger activates whenever a row is
     modified; for example, through *Note `UPDATE': update. statements.

   * *Note `DELETE': delete.: The trigger activates whenever a row is
     deleted from the table; for example, through *Note `DELETE':
     delete. and *Note `REPLACE': replace. statements.  *Note `DROP
     TABLE': drop-table. and *Note `TRUNCATE TABLE': truncate-table.
     statements on the table do _not_ activate this trigger, because
     they do not use *Note `DELETE': delete.  Dropping a partition does
     not activate *Note `DELETE': delete. triggers, either.

The TRIGGER_EVENT does not represent a literal type of SQL statement
that activates the trigger so much as it represents a type of table
operation. For example, an *Note `INSERT': insert. trigger activates
not only for *Note `INSERT': insert. statements but also *Note `LOAD
DATA': load-data. statements because both statements insert rows into a
table.

A potentially confusing example of this is the `INSERT INTO ... ON
DUPLICATE KEY UPDATE ...' syntax: a `BEFORE INSERT' trigger activates
for every row, followed by either an `AFTER INSERT' trigger or both the
`BEFORE UPDATE' and `AFTER UPDATE' triggers, depending on whether there
was a duplicate key for the row.

*Note*:

Cascaded foreign key actions do not activate triggers.

There cannot be multiple triggers for a given table that have the same
trigger event and action time. For example, you cannot have two `BEFORE
UPDATE' triggers for a table. But you can have a `BEFORE UPDATE' and a
`BEFORE INSERT' trigger, or a `BEFORE UPDATE' and an `AFTER UPDATE'
trigger.

TRIGGER_BODY is the statement to execute when the trigger activates. To
execute multiple statements, use the *Note `BEGIN ... END': begin-end.
compound statement construct. This also enables you to use the same
statements that are permissible within stored routines. See *Note
begin-end::. Some statements are not permitted in triggers; see *Note
stored-program-restrictions::.

Within the trigger body, you can refer to columns in the subject table
(the table associated with the trigger) by using the aliases `OLD' and
`NEW'.  `OLD.COL_NAME' refers to a column of an existing row before it
is updated or deleted.  `NEW.COL_NAME' refers to the column of a new
row to be inserted or an existing row after it is updated.

MySQL stores the `sql_mode' system variable setting in effect when a
trigger is created, and always executes the trigger body with this
setting in force, _regardless of the current server SQL mode when the
trigger begins executing_.

The `DEFINER' clause specifies the MySQL account to be used when
checking access privileges at trigger activation time. If a USER value
is given, it should be a MySQL account specified as
`'USER_NAME'@'HOST_NAME'' (the same format used in the *Note `GRANT':
grant.  statement), `CURRENT_USER', or `CURRENT_USER()'. The default
`DEFINER' value is the user who executes the *Note `CREATE TRIGGER':
create-trigger. statement. This is the same as specifying `DEFINER =
CURRENT_USER' explicitly.

If you specify the `DEFINER' clause, these rules determine the valid
`DEFINER' user values:

   * If you do not have the `SUPER' privilege, the only permitted USER
     value is your own account, either specified literally or by using
     `CURRENT_USER'. You cannot set the definer to some other account.

   * If you have the `SUPER' privilege, you can specify any
     syntactically valid account name. If the account does not actually
     exist, a warning is generated.

   * Although it is possible to create a trigger with a nonexistent
     `DEFINER' account, it is not a good idea for such triggers to be
     activated until the account actually does exist. Otherwise, the
     behavior with respect to privilege checking is undefined.

Note: Prior to MySQL 5.1.6, *Note `CREATE TRIGGER': create-trigger.
always requires the `SUPER' privilege, so only the second of the
preceding rules applies.

MySQL takes the `DEFINER' user into account when checking trigger
privileges as follows:

   * At *Note `CREATE TRIGGER': create-trigger. time, the user who
     issues the statement must have the `TRIGGER' privilege.  (`SUPER'
     prior to MySQL 5.1.6.)

   * At trigger activation time, privileges are checked against the
     `DEFINER' user. This user must have these privileges:

        * The `TRIGGER' privilege.  (`SUPER' prior to MySQL 5.1.6.)

        * The `SELECT' privilege for the subject table if references to
          table columns occur using `OLD.COL_NAME' or `NEW.COL_NAME' in
          the trigger body.

        * The `UPDATE' privilege for the subject table if table columns
          are targets of `SET NEW.COL_NAME = VALUE' assignments in the
          trigger body.

        * Whatever other privileges normally are required for the
          statements executed by the trigger.

For more information about trigger security, see *Note
stored-programs-security::.

Within a trigger body, the `CURRENT_USER()' function returns the
account used to check privileges at trigger activation time. This is
the `DEFINER' user, not the user whose actions caused the trigger to be
activated. For information about user auditing within triggers, see
*Note account-activity-auditing::.

If you use *Note `LOCK TABLES': lock-tables. to lock a table that has
triggers, the tables used within the trigger are also locked, as
described in *Note lock-tables-and-triggers::.

For additional discussion of trigger use, see *Note trigger-syntax::.


File: manual.info,  Node: create-view,  Next: drop-database,  Prev: create-trigger,  Up: sql-syntax-data-definition

13.1.20 CREATE VIEW Syntax
--------------------------


     CREATE
         [OR REPLACE]
         [ALGORITHM = {UNDEFINED | MERGE | TEMPTABLE}]
         [DEFINER = { USER | CURRENT_USER }]
         [SQL SECURITY { DEFINER | INVOKER }]
         VIEW VIEW_NAME [(COLUMN_LIST)]
         AS SELECT_STATEMENT
         [WITH [CASCADED | LOCAL] CHECK OPTION]

The *Note `CREATE VIEW': create-view. statement creates a new view, or
replaces an existing one if the `OR REPLACE' clause is given. If the
view does not exist, *Note `CREATE OR REPLACE VIEW': create-view. is
the same as *Note `CREATE VIEW': create-view. If the view does exist,
*Note `CREATE OR REPLACE VIEW': create-view. is the same as *Note
`ALTER VIEW': alter-view.

The SELECT_STATEMENT is a *Note `SELECT': select. statement that
provides the definition of the view. (When you select from the view,
you select in effect using the *Note `SELECT': select.  statement.)
SELECT_STATEMENT can select from base tables or other views.

The view definition is `frozen' at creation time, so changes to the
underlying tables afterward do not affect the view definition. For
example, if a view is defined as `SELECT *' on a table, new columns
added to the table later do not become part of the view.

The `ALGORITHM' clause affects how MySQL processes the view. The
`DEFINER' and `SQL SECURITY' clauses specify the security context to be
used when checking access privileges at view invocation time. The `WITH
CHECK OPTION' clause can be given to constrain inserts or updates to
rows in tables referenced by the view. These clauses are described
later in this section.

The *Note `CREATE VIEW': create-view. statement requires the `CREATE
VIEW' privilege for the view, and some privilege for each column
selected by the *Note `SELECT': select. statement. For columns used
elsewhere in the *Note `SELECT': select. statement you must have the
`SELECT' privilege.  If the `OR REPLACE' clause is present, you must
also have the `DROP' privilege for the view. *Note `CREATE VIEW':
create-view. might also require the `SUPER' privilege, depending on the
`DEFINER' value, as described later in this section.

When a view is referenced, privilege checking occurs as described later
in this section.

A view belongs to a database. By default, a new view is created in the
default database. To create the view explicitly in a given database,
specify the name as DB_NAME.VIEW_NAME when you create it:


     mysql> CREATE VIEW test.v AS SELECT * FROM t;

Within a database, base tables and views share the same namespace, so a
base table and a view cannot have the same name.

Columns retrieved by the *Note `SELECT': select.  statement can be
simple references to table columns. They can also be expressions that
use functions, constant values, operators, and so forth.

Views must have unique column names with no duplicates, just like base
tables. By default, the names of the columns retrieved by the *Note
`SELECT': select. statement are used for the view column names. To
define explicit names for the view columns, the optional COLUMN_LIST
clause can be given as a list of comma-separated identifiers. The
number of names in COLUMN_LIST must be the same as the number of
columns retrieved by the *Note `SELECT': select. statement.

*Note*:

Prior to MySQL 5.1.29, when you modify an existing view, the server
saves a backup of the current view definition under the view database
directory, in a subdirectory named `arc'. The backup file for a view
`v' is named `v.frm-00001'.  If you alter the view again, the next
backup is named `v.frm-00002'. The three latest view backup definitions
are stored.

Backed up view definitions are not preserved by *Note `mysqldump':
mysqldump, or any other such programs, but you can retain them using a
file copy operation. However, they are not needed for anything but to
provide you with a backup of your previous view definition.

It is safe to remove these backup definitions, but only while *Note
`mysqld': mysqld. is not running. If you delete the `arc' subdirectory
or its files while *Note `mysqld': mysqld. is running, an error occurs
the next time you try to alter the view:

     mysql> ALTER VIEW v AS SELECT * FROM t;
     ERROR 6 (HY000): Error on delete of '.\test\arc/v.frm-0004' (Errcode:
     2)

Unqualified table or view names in the *Note `SELECT': select.
statement are interpreted with respect to the default database. A view
can refer to tables or views in other databases by qualifying the table
or view name with the proper database name.

A view can be created from many kinds of *Note `SELECT': select.
statements. It can refer to base tables or other views. It can use
joins, *Note `UNION': union, and subqueries. The *Note `SELECT':
select. need not even refer to any tables. The following example
defines a view that selects two columns from another table, as well as
an expression calculated from those columns:


     mysql> CREATE TABLE t (qty INT, price INT);
     mysql> INSERT INTO t VALUES(3, 50);
     mysql> CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;
     mysql> SELECT * FROM v;
     +------+-------+-------+
     | qty  | price | value |
     +------+-------+-------+
     |    3 |    50 |   150 |
     +------+-------+-------+

A view definition is subject to the following restrictions:

   * The *Note `SELECT': select. statement cannot contain a subquery in
     the `FROM' clause.

   * The *Note `SELECT': select. statement cannot refer to system or
     user variables.

   * Within a stored program, the definition cannot refer to program
     parameters or local variables.

   * The *Note `SELECT': select. statement cannot refer to prepared
     statement parameters.

   * Any table or view referred to in the definition must exist.
     However, after a view has been created, it is possible to drop a
     table or view that the definition refers to. In this case, use of
     the view results in an error. To check a view definition for
     problems of this kind, use the *Note `CHECK TABLE': check-table.
     statement.

   * The definition cannot refer to a `TEMPORARY' table, and you cannot
     create a `TEMPORARY' view.

   * Any tables named in the view definition must exist at definition
     time.

   * You cannot associate a trigger with a view.

   * As of MySQL 5.1.23, aliases for column names in the *Note
     `SELECT': select. statement are checked against the maximum column
     length of 64 characters (not the maximum alias length of 256
     characters).

`ORDER BY' is permitted in a view definition, but it is ignored if you
select from a view using a statement that has its own `ORDER BY'.

For other options or clauses in the definition, they are added to the
options or clauses of the statement that references the view, but the
effect is undefined. For example, if a view definition includes a
`LIMIT' clause, and you select from the view using a statement that has
its own `LIMIT' clause, it is undefined which limit applies. This same
principle applies to options such as `ALL', `DISTINCT', or
`SQL_SMALL_RESULT' that follow the *Note `SELECT': select. keyword, and
to clauses such as `INTO', `FOR UPDATE', `LOCK IN SHARE MODE', and
`PROCEDURE'.

If you create a view and then change the query processing environment
by changing system variables, that may affect the results that you get
from the view:


     mysql> CREATE VIEW v (mycol) AS SELECT 'abc';
     Query OK, 0 rows affected (0.01 sec)

     mysql> SET sql_mode = '';
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT "mycol" FROM v;
     +-------+
     | mycol |
     +-------+
     | mycol |
     +-------+
     1 row in set (0.01 sec)

     mysql> SET sql_mode = 'ANSI_QUOTES';
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT "mycol" FROM v;
     +-------+
     | mycol |
     +-------+
     | abc   |
     +-------+
     1 row in set (0.00 sec)

The `DEFINER' and `SQL SECURITY' clauses determine which MySQL account
to use when checking access privileges for the view when a statement is
executed that references the view. These clauses were added in MySQL
5.1.2. The valid `SQL SECURITY' characteristic values are `DEFINER' and
`INVOKER'. These indicate that the required privileges must be held by
the user who defined or invoked the view, respectively. The default
`SQL SECURITY' value is `DEFINER'.

If a USER value is given for the `DEFINER' clause, it should be a MySQL
account specified as `'USER_NAME'@'HOST_NAME'' (the same format used in
the *Note `GRANT': grant.  statement), `CURRENT_USER', or
`CURRENT_USER()'. The default `DEFINER' value is the user who executes
the *Note `CREATE VIEW': create-view. statement. This is the same as
specifying `DEFINER = CURRENT_USER' explicitly.

If you specify the `DEFINER' clause, these rules determine the valid
`DEFINER' user values:

   * If you do not have the `SUPER' privilege, the only valid USER
     value is your own account, either specified literally or by using
     `CURRENT_USER'. You cannot set the definer to some other account.

   * If you have the `SUPER' privilege, you can specify any
     syntactically valid account name. If the account does not actually
     exist, a warning is generated.

   * Although it is possible to create a view with a nonexistent
     `DEFINER' account, an error occurs when the view is referenced if
     the `SQL SECURITY' value is `DEFINER' but the definer account does
     not exist.

For more information about view security, see *Note
stored-programs-security::.

Within a view definition, `CURRENT_USER' returns the view's `DEFINER'
value by default as of MySQL 5.1.12.  For older versions, and for views
defined with the `SQL SECURITY INVOKER' characteristic, `CURRENT_USER'
returns the account for the view's invoker. For information about user
auditing within views, see *Note account-activity-auditing::.

Within a stored routine that is defined with the `SQL SECURITY DEFINER'
characteristic, `CURRENT_USER' returns the routine's `DEFINER' value.
This also affects a view defined within such a routine, if the view
definition contains a `DEFINER' value of `CURRENT_USER'.

As of MySQL 5.1.2 (when the `DEFINER' and `SQL SECURITY' clauses were
implemented), view privileges are checked like this:

   * At view definition time, the view creator must have the privileges
     needed to use the top-level objects accessed by the view. For
     example, if the view definition refers to table columns, the
     creator must have some privilege for each column in the select
     list of the definition, and the `SELECT' privilege for each column
     used elsewhere in the definition. If the definition refers to a
     stored function, only the privileges needed to invoke the function
     can be checked. The privileges required at function invocation
     time can be checked only as it executes: For different
     invocations, different execution paths within the function might
     be taken.

   * The user who references a view must have appropriate privileges to
     access it (`SELECT' to select from it, `INSERT' to insert into it,
     and so forth.)

   * When a view has been referenced, privileges for objects accessed
     by the view are checked against the privileges held by the view
     `DEFINER' account or invoker, depending on whether the `SQL
     SECURITY' characteristic is `DEFINER' or `INVOKER', respectively.

   * If reference to a view causes execution of a stored function,
     privilege checking for statements executed within the function
     depend on whether the function `SQL SECURITY' characteristic is
     `DEFINER' or `INVOKER'. If the security characteristic is
     `DEFINER', the function runs with the privileges of the `DEFINER'
     account. If the characteristic is `INVOKER', the function runs
     with the privileges determined by the view's `SQL SECURITY'
     characteristic.

Prior to MySQL 5.1.2 (before the `DEFINER' and `SQL SECURITY' clauses
were implemented), privileges required for objects used in a view are
checked at view creation time.

Example: A view might depend on a stored function, and that function
might invoke other stored routines. For example, the following view
invokes a stored function `f()':


     CREATE VIEW v AS SELECT * FROM t WHERE t.id = f(t.name);

Suppose that `f()' contains a statement such as this:


     IF name IS NULL then
       CALL p1();
     ELSE
       CALL p2();
     END IF;

The privileges required for executing statements within `f()' need to
be checked when `f()' executes. This might mean that privileges are
needed for `p1()' or `p2()', depending on the execution path within
`f()'.  Those privileges must be checked at runtime, and the user who
must possess the privileges is determined by the `SQL SECURITY' values
of the view `v' and the function `f()'.

The `DEFINER' and `SQL SECURITY' clauses for views are extensions to
standard SQL. In standard SQL, views are handled using the rules for
`SQL SECURITY DEFINER'. The standard says that the definer of the view,
which is the same as the owner of the view's schema, gets applicable
privileges on the view (for example, `SELECT') and may grant them. MySQL
has no concept of a schema `owner', so MySQL adds a clause to identify
the definer. The `DEFINER' clause is an extension where the intent is
to have what the standard has; that is, a permanent record of who
defined the view.  This is why the default `DEFINER' value is the
account of the view creator.

If you invoke a view that was created before MySQL 5.1.2, it is treated
as though it was created with a `SQL SECURITY DEFINER' characteristic
and with a `DEFINER' value that is the same as your account.  However,
because the actual definer is unknown, MySQL issues a warning. To
eliminate the warning, it is sufficient to re-create the view so that
the view definition includes a `DEFINER' clause.

The optional `ALGORITHM' clause is a MySQL extension to standard SQL.
It affects how MySQL processes the view. `ALGORITHM' takes three values:
`MERGE', `TEMPTABLE', or `UNDEFINED'. The default algorithm is
`UNDEFINED' if no `ALGORITHM' clause is present. For more information,
see *Note view-algorithms::.

Some views are updatable. That is, you can use them in statements such
as *Note `UPDATE': update, *Note `DELETE': delete, or *Note `INSERT':
insert. to update the contents of the underlying table. For a view to
be updatable, there must be a one-to-one relationship between the rows
in the view and the rows in the underlying table. There are also
certain other constructs that make a view nonupdatable.

The `WITH CHECK OPTION' clause can be given for an updatable view to
prevent inserts or updates to rows except those for which the `WHERE'
clause in the SELECT_STATEMENT is true.

In a `WITH CHECK OPTION' clause for an updatable view, the `LOCAL' and
`CASCADED' keywords determine the scope of check testing when the view
is defined in terms of another view. The `LOCAL' keyword restricts the
`CHECK OPTION' only to the view being defined. `CASCADED' causes the
checks for underlying views to be evaluated as well. When neither
keyword is given, the default is `CASCADED'.

For more information about updatable views and the `WITH CHECK OPTION'
clause, see *Note view-updatability::.


File: manual.info,  Node: drop-database,  Next: drop-event,  Prev: create-view,  Up: sql-syntax-data-definition

13.1.21 DROP DATABASE Syntax
----------------------------


     DROP {DATABASE | SCHEMA} [IF EXISTS] DB_NAME

*Note `DROP DATABASE': drop-database. drops all tables in the database
and deletes the database. Be _very_ careful with this statement! To use
*Note `DROP DATABASE': drop-database, you need the `DROP' privilege on
the database.  *Note `DROP SCHEMA': drop-database. is a synonym for
*Note `DROP DATABASE': drop-database.

*Important*:

When a database is dropped, user privileges on the database are _not_
automatically dropped. See *Note grant::.

`IF EXISTS' is used to prevent an error from occurring if the database
does not exist.

If the default database is dropped, the default database is unset (the
`DATABASE()' function returns `NULL').

If you use *Note `DROP DATABASE': drop-database. on a symbolically
linked database, both the link and the original database are deleted.

*Note `DROP DATABASE': drop-database. returns the number of tables that
were removed. This corresponds to the number of `.frm' files removed.

The *Note `DROP DATABASE': drop-database. statement removes from the
given database directory those files and directories that MySQL itself
may create during normal operation:

   * All files with the following extensions.

     The *Note `DROP DATABASE': drop-database.  statement removes files
     with extension types shown in this table. Extensions are listed in
     alphabetical order from left to right.

     `.BAK'  `.DAT'  `.HSH'  `.MRG'
     `.MYD'  `.MYI'  `.TRG'  `.TRN'
     `.db'   `.frm'  `.ibd'  `.ndb'
     `.par'                  

   * The `db.opt' file, if it exists.

If other files or directories remain in the database directory after
MySQL removes those just listed, the database directory cannot be
removed. In this case, you must remove any remaining files or
directories manually and issue the *Note `DROP DATABASE':
drop-database. statement again.

Dropping a database does not remove any `TEMPORARY' tables that were
created in that database. `TEMPORARY' tables are automatically removed
when the session that created them ends. See *Note
create-temporary-table::.

You can also drop databases with *Note `mysqladmin': mysqladmin.  See
*Note mysqladmin::.


File: manual.info,  Node: drop-event,  Next: drop-function,  Prev: drop-database,  Up: sql-syntax-data-definition

13.1.22 DROP EVENT Syntax
-------------------------


     DROP EVENT [IF EXISTS] EVENT_NAME

This statement drops the event named EVENT_NAME. The event immediately
ceases being active, and is deleted completely from the server.

If the event does not exist, the error `ERROR 1517 (HY000): Unknown
event 'EVENT_NAME'' results. You can override this and cause the
statement to generate a warning for nonexistent events instead using
`IF EXISTS'.

Beginning with MySQL 5.1.12, this statement requires the `EVENT'
privilege for the schema to which the event to be dropped belongs. (In
MySQL 5.1.11 and earlier, an event could be dropped only by its
definer, or by a user having the `SUPER' privilege.)


File: manual.info,  Node: drop-function,  Next: drop-index,  Prev: drop-event,  Up: sql-syntax-data-definition

13.1.23 DROP FUNCTION Syntax
----------------------------

The *Note `DROP FUNCTION': drop-function. statement is used to drop
stored functions and user-defined functions (UDFs):

   * For information about dropping stored functions, see *Note
     drop-procedure::.

   * For information about dropping user-defined functions, see *Note
     drop-function-udf::.


File: manual.info,  Node: drop-index,  Next: drop-logfile-group,  Prev: drop-function,  Up: sql-syntax-data-definition

13.1.24 DROP INDEX Syntax
-------------------------


     DROP [ONLINE|OFFLINE] INDEX INDEX_NAME ON TBL_NAME

*Note `DROP INDEX': drop-index. drops the index named INDEX_NAME from
the table TBL_NAME. This statement is mapped to an *Note `ALTER TABLE':
alter-table. statement to drop the index. See *Note alter-table::.

To drop a primary key, the index name is always `PRIMARY', which must
be specified as a quoted identifier because `PRIMARY' is a reserved
word:


     DROP INDEX `PRIMARY` ON t;

Beginning with MySQL 5.1.17, indexes on variable-width columns of *Note
`NDBCLUSTER': mysql-cluster. tables are dropped online; that is,
without any table copying. The table is not locked against access from
other MySQL Cluster API nodes, although it is locked against other
operations on the _same_ API node for the duration of the operation.
This is done automatically by the server whenever it determines that it
is possible to do so; you do not have to use any special SQL syntax or
server options to cause it to happen.

In standard MySQL 5.1 releases, it is not possible to override the
server when it determines that an index is to be dropped without table
copying. In MySQL Cluster, you can drop indexes offline (which causes
the table to be locked for all API nodes in the cluster) using the
`OFFLINE' keyword. The rules and limitations governing `DROP OFFLINE
INDEX' and `DROP ONLINE INDEX' are the same as for `ALTER OFFLINE TABLE
... DROP INDEX' and `ALTER ONLINE TABLE ... DROP INDEX'. You cannot
cause the noncopying dropping of an index that would normally be
dropped offline by using the `ONLINE' keyword: If it is not possible to
perform the `DROP' operation without table copying, the server ignores
the `ONLINE' keyword. For more information, see *Note
alter-table-online-operations::.

*Note*:

The `ONLINE' and `OFFLINE' keywords are available only in MySQL Cluster
NDB 6.2.5, 6.3.2, and later MySQL Cluster releases; attempting to use
these keywords in earlier MySQL Cluster releases or standard MySQL 5.1
releases results in a syntax error.


File: manual.info,  Node: drop-logfile-group,  Next: drop-procedure,  Prev: drop-index,  Up: sql-syntax-data-definition

13.1.25 DROP LOGFILE GROUP Syntax
---------------------------------


     DROP LOGFILE GROUP LOGFILE_GROUP
         ENGINE [=] ENGINE_NAME

This statement drops the log file group named LOGFILE_GROUP. The log
file group must already exist or an error results. (For information on
creating log file groups, see *Note create-logfile-group::.)

*Important*:

Before dropping a log file group, you must drop all tablespaces that
use that log file group for `UNDO' logging.

The required `ENGINE' clause provides the name of the storage engine
used by the log file group to be dropped. In MySQL 5.1, the only
permitted values for ENGINE_NAME are *Note `NDB': mysql-cluster. and
*Note `NDBCLUSTER': mysql-cluster.

*Note `DROP LOGFILE GROUP': drop-logfile-group. was added in MySQL
5.1.6. In MySQL 5.1, it is useful only with Disk Data storage for MySQL
Cluster. See *Note mysql-cluster-disk-data::.


File: manual.info,  Node: drop-procedure,  Next: drop-server,  Prev: drop-logfile-group,  Up: sql-syntax-data-definition

13.1.26 DROP PROCEDURE and DROP FUNCTION Syntax
-----------------------------------------------


     DROP {PROCEDURE | FUNCTION} [IF EXISTS] SP_NAME

This statement is used to drop a stored procedure or function.  That
is, the specified routine is removed from the server. You must have the
`ALTER ROUTINE' privilege for the routine. (If the
`automatic_sp_privileges' system variable is enabled, that privilege
and `EXECUTE' are granted automatically to the routine creator when the
routine is created and dropped from the creator when the routine is
dropped. See *Note stored-routines-privileges::.)

The `IF EXISTS' clause is a MySQL extension. It prevents an error from
occurring if the procedure or function does not exist. A warning is
produced that can be viewed with *Note `SHOW WARNINGS': show-warnings.

*Note `DROP FUNCTION': drop-function. is also used to drop user-defined
functions (see *Note drop-function-udf::).


File: manual.info,  Node: drop-server,  Next: drop-table,  Prev: drop-procedure,  Up: sql-syntax-data-definition

13.1.27 DROP SERVER Syntax
--------------------------


     DROP SERVER [ IF EXISTS ] SERVER_NAME

Drops the server definition for the server named `SERVER_NAME'. The
corresponding row in the `mysql.servers' table is deleted. This
statement requires the `SUPER' privilege.

Dropping a server for a table does not affect any `FEDERATED' tables
that used this connection information when they were created. See *Note
create-server::.

`DROP SERVER' does not cause an automatic commit.

In MySQL 5.1, `DROP SERVER' is written to the binary log only when
using row-based logging. It is not logged when `binlog_format' is equal
to `STATEMENT' or `MIXED'.

*Note `DROP SERVER': drop-server. was added in MySQL 5.1.15.


File: manual.info,  Node: drop-table,  Next: drop-tablespace,  Prev: drop-server,  Up: sql-syntax-data-definition

13.1.28 DROP TABLE Syntax
-------------------------


     DROP [TEMPORARY] TABLE [IF EXISTS]
         TBL_NAME [, TBL_NAME] ...
         [RESTRICT | CASCADE]

*Note `DROP TABLE': drop-table. removes one or more tables. You must
have the `DROP' privilege for each table. All table data and the table
definition are _removed_, so _be careful_ with this statement! If any
of the tables named in the argument list do not exist, MySQL returns an
error indicating by name which nonexisting tables it was unable to drop,
but it also drops all of the tables in the list that do exist.

*Important*:

When a table is dropped, user privileges on the table are _not_
automatically dropped. See *Note grant::.

Note that for a partitioned table, *Note `DROP TABLE': drop-table.
permanently removes the table definition, all of its partitions, and
all of the data which was stored in those partitions. It also removes
the partitioning definition (`.par') file associated with the dropped
table.

Use `IF EXISTS' to prevent an error from occurring for tables that do
not exist. A `NOTE' is generated for each nonexistent table when using
`IF EXISTS'. See *Note show-warnings::.

`RESTRICT' and `CASCADE' are permitted to make porting easier. In MySQL
5.1, they do nothing.

*Note*:

*Note `DROP TABLE': drop-table. automatically commits the current
active transaction, unless you use the `TEMPORARY' keyword.

The `TEMPORARY' keyword has the following effects:

   * The statement drops only `TEMPORARY' tables.

   * The statement does not end an ongoing transaction.

   * No access rights are checked. (A `TEMPORARY' table is visible only
     to the session that created it, so no check is necessary.)

Using `TEMPORARY' is a good way to ensure that you do not accidentally
drop a non-`TEMPORARY' table.


File: manual.info,  Node: drop-tablespace,  Next: drop-trigger,  Prev: drop-table,  Up: sql-syntax-data-definition

13.1.29 DROP TABLESPACE Syntax
------------------------------


     DROP TABLESPACE TABLESPACE_NAME
         ENGINE [=] ENGINE_NAME

This statement drops a tablespace that was previously created using
*Note `CREATE TABLESPACE': create-tablespace. (see *Note
create-tablespace::).

*Important*:

The tablespace to be dropped must not contain any data files; in other
words, before you can drop a tablespace, you must first drop each of
its data files using `ALTER TABLESPACE ...  DROP DATAFILE' (see *Note
alter-tablespace::).

The `ENGINE' clause (required) specifies the storage engine used by the
tablespace. In MySQL 5.1, the only accepted values for ENGINE_NAME are
*Note `NDB': mysql-cluster. and *Note `NDBCLUSTER': mysql-cluster.

*Note `DROP TABLESPACE': drop-tablespace. was added in MySQL 5.1.6. In
MySQL 5.1, it is useful only with Disk Data storage for MySQL Cluster.
See *Note mysql-cluster-disk-data::.


File: manual.info,  Node: drop-trigger,  Next: drop-view,  Prev: drop-tablespace,  Up: sql-syntax-data-definition

13.1.30 DROP TRIGGER Syntax
---------------------------


     DROP TRIGGER [IF EXISTS] [SCHEMA_NAME.]TRIGGER_NAME

This statement drops a trigger. The schema (database) name is optional.
If the schema is omitted, the trigger is dropped from the default
schema. *Note `DROP TRIGGER': drop-trigger.  requires the `TRIGGER'
privilege for the table associated with the trigger. (This statement
requires the `SUPER' privilege prior to MySQL 5.1.6.)

Use `IF EXISTS' to prevent an error from occurring for a trigger that
does not exist. A `NOTE' is generated for a nonexistent trigger when
using `IF EXISTS'. See *Note show-warnings::. The `IF EXISTS' clause
was added in MySQL 5.1.14.

Triggers for a table are also dropped if you drop the table.

*Note*:

When upgrading from a version of MySQL older than MySQL 5.0.10 to
5.0.10 or newer--including all MySQL 5.1 releases--you must drop all
triggers and re-create them.  Otherwise, *Note `DROP TRIGGER':
drop-trigger. does not work for older triggers after the upgrade. See
*Note upgrading-from-previous-series::, for a suggested upgrade
procedure.


File: manual.info,  Node: drop-view,  Next: rename-database,  Prev: drop-trigger,  Up: sql-syntax-data-definition

13.1.31 DROP VIEW Syntax
------------------------


     DROP VIEW [IF EXISTS]
         VIEW_NAME [, VIEW_NAME] ...
         [RESTRICT | CASCADE]

*Note `DROP VIEW': drop-view. removes one or more views. You must have
the `DROP' privilege for each view. If any of the views named in the
argument list do not exist, MySQL returns an error indicating by name
which nonexisting views it was unable to drop, but it also drops all of
the views in the list that do exist.

The `IF EXISTS' clause prevents an error from occurring for views that
don't exist. When this clause is given, a `NOTE' is generated for each
nonexistent view.  See *Note show-warnings::.

`RESTRICT' and `CASCADE', if given, are parsed and ignored.


File: manual.info,  Node: rename-database,  Next: rename-table,  Prev: drop-view,  Up: sql-syntax-data-definition

13.1.32 RENAME DATABASE Syntax
------------------------------


     RENAME {DATABASE | SCHEMA} DB_NAME TO NEW_DB_NAME;

This statement was added in MySQL 5.1.7 but was found to be dangerous
and was removed in MySQL 5.1.23. It was intended to enable upgrading
pre-5.1 databases to use the encoding implemented in 5.1 for mapping
database names to database directory names (see *Note
identifier-mapping::). However, use of this statement could result in
loss of database contents, which is why it was removed. Do not use
`RENAME DATABASE' in earlier versions in which it is present.

To perform the task of upgrading database names with the new encoding,
use `ALTER DATABASE DB_NAME UPGRADE DATA DIRECTORY NAME' instead (see
*Note alter-database::).


File: manual.info,  Node: rename-table,  Next: truncate-table,  Prev: rename-database,  Up: sql-syntax-data-definition

13.1.33 RENAME TABLE Syntax
---------------------------


     RENAME TABLE TBL_NAME TO NEW_TBL_NAME
         [, TBL_NAME2 TO NEW_TBL_NAME2] ...

This statement renames one or more tables.

The rename operation is done atomically, which means that no other
session can access any of the tables while the rename is running.  For
example, if you have an existing table `old_table', you can create
another table `new_table' that has the same structure but is empty, and
then replace the existing table with the empty one as follows (assuming
that `backup_table' does not already exist):


     CREATE TABLE new_table (...);
     RENAME TABLE old_table TO backup_table, new_table TO old_table;

If the statement renames more than one table, renaming operations are
done from left to right. If you want to swap two table names, you can
do so like this (assuming that `tmp_table' does not already exist):


     RENAME TABLE old_table TO tmp_table,
                  new_table TO old_table,
                  tmp_table TO new_table;

As long as two databases are on the same file system, you can use *Note
`RENAME TABLE': rename-table. to move a table from one database to
another:


     RENAME TABLE CURRENT_DB.TBL_NAME TO OTHER_DB.TBL_NAME;

If there are any triggers associated with a table which is moved to a
different database using *Note `RENAME TABLE': rename-table, then the
statement fails with the error `Trigger in wrong schema'.

*Note `RENAME TABLE': rename-table. also works for views, as long as
you do not try to rename a view into a different database.

Any privileges granted specifically for the renamed table or view are
not migrated to the new name. They must be changed manually.

When you execute `RENAME', you cannot have any locked tables or active
transactions. You must also have the `ALTER' and `DROP' privileges on
the original table, and the `CREATE' and `INSERT' privileges on the new
table.

If MySQL encounters any errors in a multiple-table rename, it does a
reverse rename for all renamed tables to return everything to its
original state.

You cannot use `RENAME' to rename a `TEMPORARY' table. However, you can
use *Note `ALTER TABLE': alter-table. instead:


     mysql> ALTER TABLE orig_name RENAME new_name;


File: manual.info,  Node: truncate-table,  Prev: rename-table,  Up: sql-syntax-data-definition

13.1.34 TRUNCATE TABLE Syntax
-----------------------------


     TRUNCATE [TABLE] TBL_NAME

*Note `TRUNCATE TABLE': truncate-table. empties a table completely. It
requires the `DROP' privilege as of MySQL 5.1.16. (Before 5.1.16, it
requires the `DELETE' privilege).

Logically, *Note `TRUNCATE TABLE': truncate-table. is equivalent to a
*Note `DELETE': delete. statement that deletes all rows, but there are
practical differences under some circumstances.

For an `InnoDB' table:

   * If there are no `FOREIGN KEY' constraints, `InnoDB' performs fast
     truncation by dropping the original table and creating an empty
     one with the same definition, which is much faster than deleting
     rows one by one.

   * When you use this fast truncation technique with the
     `innodb_file_per_table' option enabled, the operating system can
     reuse the freed disk space.  For users of the InnoDB Plugin, the
     space is reclaimed automatically, as described in Reclaiming Disk
     Space with TRUNCATE TABLE
     (http://dev.mysql.com/doc/refman/5.5/en/innodb-truncate-table-reclaim-space.html).
     If you do not have the InnoDB Plugin installed, issue the *Note
     `OPTIMIZE TABLE': optimize-table. statement to free the disk space
     for the table.

   * If there are any `FOREIGN KEY' constraints that reference the
     table, `InnoDB' processes *Note `TRUNCATE TABLE': truncate-table.
     by deleting rows one by one, processing the constraints as it
     proceeds. If the `FOREIGN KEY' constraint specifies `DELETE
     CASCADE', rows from the child (referenced) table are deleted, and
     the truncated table becomes empty. If the `FOREIGN KEY' constraint
     does _not_ specify `CASCADE', the *Note `TRUNCATE TABLE':
     truncate-table. statement deletes rows one by one and stops if it
     encounters a parent row that is referenced by the child, returning
     this error:


          ERROR 1451 (23000): Cannot delete or update a parent row: a foreign
          key constraint fails (`test`.`child`, CONSTRAINT `child_ibfk_1`
          FOREIGN KEY (`parent_id`) REFERENCES `parent` (`id`))

     *Note*:

     In MySQL 5.5 and higher, *Note `TRUNCATE TABLE': truncate-table.
     is not allowed for `InnoDB' tables referenced by foreign keys. For
     ease of upgrading, rewrite such statements to use `DELETE' instead.

   * The `AUTO_INCREMENT' counter is reset to zero by *Note `TRUNCATE
     TABLE': truncate-table, regardless of whether there is a `FOREIGN
     KEY' constraint.

This is the same as a *Note `DELETE': delete.  statement with no
`WHERE' clause.

The count of rows affected by *Note `TRUNCATE TABLE': truncate-table.
is accurate only when it is mapped to a *Note `DELETE': delete.
statement.

For other storage engines, *Note `TRUNCATE TABLE': truncate-table.
differs from *Note `DELETE': delete.  in the following ways in MySQL
5.1:

   * Truncate operations drop and re-create the table, which is much
     faster than deleting rows one by one, particularly for large
     tables.

   * Truncate operations cause an implicit commit.

   * Truncation operations cannot be performed if the session holds an
     active table lock.

   * Truncation operations do not return a meaningful value for the
     number of deleted rows. The usual result is `0 rows affected,'
     which should be interpreted as `no information.'

   * As long as the table format file `TBL_NAME.frm' is valid, the
     table can be re-created as an empty table with *Note `TRUNCATE
     TABLE': truncate-table, even if the data or index files have
     become corrupted.

   * The table handler does not remember the last used `AUTO_INCREMENT'
     value, but starts counting from the beginning. This is true even
     for `MyISAM' and `InnoDB', which normally do not reuse sequence
     values.

   * When used with partitioned tables, *Note `TRUNCATE TABLE':
     truncate-table. preserves the partitioning; that is, the data and
     index files are dropped and re-created, while the partition
     definitions (`.par') file is unaffected.

   * Since truncation of a table does not make any use of *Note
     `DELETE': delete, the *Note `TRUNCATE TABLE': truncate-table.
     statement does not invoke `ON DELETE' triggers.

As of MySQL 5.1.39, *Note `TRUNCATE TABLE': truncate-table.  for a
table closes all handlers for the table that were opened with *Note
`HANDLER OPEN': handler.

Beginning with MySQL 5.1.32, *Note `TRUNCATE TABLE': truncate-table. is
treated for purposes of binary logging and replication as *Note `DROP
TABLE': drop-table. followed by *Note `CREATE TABLE':
create-table.--that is, as DDL rather than DML. This is due to the fact
that, when using *Note `InnoDB': innodb-storage-engine. and other
transactional storage engines where the transaction isolation level
does not permit statement-based logging (`READ COMMITTED' or `READ
UNCOMMITTED'), the statement was not logged and replicated when using
`STATEMENT' or `MIXED' logging mode. (Bug #36763) However, it is still
applied on replication slaves using *Note `InnoDB':
innodb-storage-engine. in the manner described previously.


File: manual.info,  Node: sql-syntax-data-manipulation,  Next: sql-syntax-transactions,  Prev: sql-syntax-data-definition,  Up: sql-syntax

13.2 Data Manipulation Statements
=================================

* Menu:

* call::                         CALL Syntax
* delete::                       DELETE Syntax
* do::                           DO Syntax
* handler::                      HANDLER Syntax
* insert::                       INSERT Syntax
* load-data::                    LOAD DATA INFILE Syntax
* replace::                      REPLACE Syntax
* select::                       SELECT Syntax
* subqueries::                   Subquery Syntax
* update::                       UPDATE Syntax


File: manual.info,  Node: call,  Next: delete,  Prev: sql-syntax-data-manipulation,  Up: sql-syntax-data-manipulation

13.2.1 CALL Syntax
------------------


     CALL SP_NAME([PARAMETER[,...]])
     CALL SP_NAME[()]

The *Note `CALL': call. statement invokes a stored procedure that was
defined previously with *Note `CREATE PROCEDURE': create-procedure.

As of MySQL 5.1.13, stored procedures that take no arguments can be
invoked without parentheses. That is, `CALL p()' and `CALL p' are
equivalent.

*Note `CALL': call. can pass back values to its caller using parameters
that are declared as `OUT' or `INOUT' parameters.  When the procedure
returns, a client program can also obtain the number of rows affected
for the final statement executed within the routine: At the SQL level,
call the `ROW_COUNT()' function; from the C API, call the *Note
`mysql_affected_rows()': mysql-affected-rows. function.

To get back a value from a procedure using an `OUT' or `INOUT'
parameter, pass the parameter by means of a user variable, and then
check the value of the variable after the procedure returns. (If you are
calling the procedure from within another stored procedure or function,
you can also pass a routine parameter or local routine variable as an
`IN' or `INOUT' parameter.) For an `INOUT' parameter, initialize its
value before passing it to the procedure. The following procedure has
an `OUT' parameter that the procedure sets to the current server
version, and an `INOUT' value that the procedure increments by one from
its current value:


     CREATE PROCEDURE p (OUT ver_param VARCHAR(25), INOUT incr_param INT)
     BEGIN
       # Set value of OUT parameter
       SELECT VERSION() INTO ver_param;
       # Increment value of INOUT parameter
       SET incr_param = incr_param + 1;
     END;

Before calling the procedure, initialize the variable to be passed as
the `INOUT' parameter. After calling the procedure, the values of the
two variables will have been set or modified:


     mysql> SET @increment = 10;
     mysql> CALL p(@version, @increment);
     mysql> SELECT @version, @increment;
     +------------+------------+
     | @version   | @increment |
     +------------+------------+
     | 5.1.32-log | 11         |
     +------------+------------+

In prepared *Note `CALL': call. statements used with *Note `PREPARE':
prepare. and *Note `EXECUTE': execute, placeholder support is available
in MySQL 5.1 for `IN' parameters, but not for `OUT' or `INOUT'
parameters. To work around this limitation for `OUT' and `INOUT'
parameters, forego the use of placeholders; instead, refer to user
variables in the *Note `CALL': call. statement itself and do not
specify them in the *Note `EXECUTE': execute. statement:


     mysql> SET @increment = 10;
     mysql> PREPARE s FROM 'CALL p(@version, @increment)';
     mysql> EXECUTE s;
     mysql> SELECT @version, @increment;
     +------------+------------+
     | @version   | @increment |
     +------------+------------+
     | 5.1.32-log | 11         |
     +------------+------------+

To write C programs that use the *Note `CALL': call. SQL statement to
execute stored procedures that produce result sets, the
`CLIENT_MULTI_RESULTS' flag must be enabled. This is because each *Note
`CALL': call. returns a result to indicate the call status, in addition
to any result sets that might be returned by statements executed within
the procedure. `CLIENT_MULTI_RESULTS' must also be enabled if *Note
`CALL': call. is used to execute any stored procedure that contains
prepared statements. It cannot be determined when such a procedure is
loaded whether those statements will produce result sets, so it is
necessary to assume that they will.

`CLIENT_MULTI_RESULTS' can be enabled when you call *Note
`mysql_real_connect()': mysql-real-connect, either explicitly by
passing the `CLIENT_MULTI_RESULTS' flag itself, or implicitly by passing
`CLIENT_MULTI_STATEMENTS' (which also enables `CLIENT_MULTI_RESULTS').

To process the result of a *Note `CALL': call.  statement executed using
*Note `mysql_query()': mysql-query. or *Note `mysql_real_query()':
mysql-real-query, use a loop that calls *Note `mysql_next_result()':
mysql-next-result. to determine whether there are more results. For an
example, see *Note c-api-multiple-queries::.

For programs written in a language that provides a MySQL interface,
there is no native method for directly retrieving the results of `OUT'
or `INOUT' parameters from *Note `CALL': call. statements. To get the
parameter values, pass user-defined variables to the procedure in the
*Note `CALL': call. statement and then execute a *Note `SELECT':
select. statement to produce a result set containing the variable
values. To handle an `INOUT' parameter, execute a statement prior to
the *Note `CALL': call. that sets the corresponding user variable to
the value to be passed to the procedure.

The following example illustrates the technique (without error
checking) for the stored procedure `p' described earlier that has an
`OUT' parameter and an `INOUT' parameter:


     mysql_query(mysql, "SET @increment = 10");
     mysql_query(mysql, "CALL p(@version, @increment)");
     mysql_query(mysql, "SELECT @version, @increment");
     result = mysql_store_result(mysql);
     row = mysql_fetch_row(result);
     mysql_free_result(result);

After the preceding code executes, `row[0]' and `row[1]' contain the
values of `@version' and `@increment', respectively.


File: manual.info,  Node: delete,  Next: do,  Prev: call,  Up: sql-syntax-data-manipulation

13.2.2 DELETE Syntax
--------------------

Single-table syntax:


     DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM TBL_NAME
         [WHERE WHERE_CONDITION]
         [ORDER BY ...]
         [LIMIT ROW_COUNT]

Multiple-table syntax:


     DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
         TBL_NAME[.*] [, TBL_NAME[.*]] ...
         FROM TABLE_REFERENCES
         [WHERE WHERE_CONDITION]

Or:


     DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
         FROM TBL_NAME[.*] [, TBL_NAME[.*]] ...
         USING TABLE_REFERENCES
         [WHERE WHERE_CONDITION]

For the single-table syntax, the *Note `DELETE': delete. statement
deletes rows from TBL_NAME and returns a count of the number of deleted
rows. This count can be obtained by calling the `ROW_COUNT()' function
(see *Note information-functions::). The `WHERE' clause, if given,
specifies the conditions that identify which rows to delete. With no
`WHERE' clause, all rows are deleted. If the `ORDER BY' clause is
specified, the rows are deleted in the order that is specified. The
`LIMIT' clause places a limit on the number of rows that can be deleted.

For the multiple-table syntax, *Note `DELETE': delete. deletes from each
TBL_NAME the rows that satisfy the conditions. In this case, `ORDER BY'
and `LIMIT' cannot be used.

WHERE_CONDITION is an expression that evaluates to true for each row to
be deleted. It is specified as described in *Note select::.

Currently, you cannot delete from a table and select from the same
table in a subquery.

You need the `DELETE' privilege on a table to delete rows from it. You
need only the `SELECT' privilege for any columns that are only read,
such as those named in the `WHERE' clause.

As stated, a *Note `DELETE': delete. statement with no `WHERE' clause
deletes all rows. A faster way to do this, when you do not need to know
the number of deleted rows, is to use *Note `TRUNCATE TABLE':
truncate-table.  However, within a transaction or if you have a lock on
the table, *Note `TRUNCATE TABLE': truncate-table. cannot be used
whereas *Note `DELETE': delete. can. See *Note truncate-table::, and
*Note lock-tables::.

If you delete the row containing the maximum value for an
`AUTO_INCREMENT' column, the value is not reused for a `MyISAM' or
`InnoDB' table. If you delete all rows in the table with `DELETE FROM
TBL_NAME' (without a `WHERE' clause) in `autocommit' mode, the sequence
starts over for all storage engines except `InnoDB' and `MyISAM'. There
are some exceptions to this behavior for `InnoDB' tables, as discussed
in *Note innodb-auto-increment-handling::.

For `MyISAM' tables, you can specify an `AUTO_INCREMENT' secondary
column in a multiple-column key. In this case, reuse of values deleted
from the top of the sequence occurs even for `MyISAM' tables. See *Note
example-auto-increment::.

The *Note `DELETE': delete. statement supports the following modifiers:

   * If you specify `LOW_PRIORITY', the server delays execution of the
     *Note `DELETE': delete.  until no other clients are reading from
     the table. This affects only storage engines that use only
     table-level locking (such as `MyISAM', `MEMORY', and `MERGE').

   * For `MyISAM' tables, if you use the `QUICK' keyword, the storage
     engine does not merge index leaves during delete, which may speed
     up some kinds of delete operations.

   * The `IGNORE' keyword causes MySQL to ignore errors during the
     process of deleting rows. (Errors encountered during the parsing
     stage are processed in the usual manner.) Errors that are ignored
     due to the use of `IGNORE' are returned as warnings.

The speed of delete operations may also be affected by factors
discussed in *Note delete-speed::.

In `MyISAM' tables, deleted rows are maintained in a linked list and
subsequent *Note `INSERT': insert. operations reuse old row positions.
To reclaim unused space and reduce file sizes, use the *Note `OPTIMIZE
TABLE': optimize-table. statement or the *Note `myisamchk': myisamchk.
utility to reorganize tables.  *Note `OPTIMIZE TABLE': optimize-table.
is easier to use, but *Note `myisamchk': myisamchk. is faster. See
*Note optimize-table::, and *Note myisamchk::.

The `QUICK' modifier affects whether index leaves are merged for delete
operations. `DELETE QUICK' is most useful for applications where index
values for deleted rows are replaced by similar index values from rows
inserted later. In this case, the holes left by deleted values are
reused.

`DELETE QUICK' is not useful when deleted values lead to underfilled
index blocks spanning a range of index values for which new inserts
occur again. In this case, use of `QUICK' can lead to wasted space in
the index that remains unreclaimed. Here is an example of such a
scenario:

  1. Create a table that contains an indexed `AUTO_INCREMENT' column.

  2. Insert many rows into the table. Each insert results in an index
     value that is added to the high end of the index.

  3. Delete a block of rows at the low end of the column range using
     `DELETE QUICK'.

In this scenario, the index blocks associated with the deleted index
values become underfilled but are not merged with other index blocks
due to the use of `QUICK'. They remain underfilled when new inserts
occur, because new rows do not have index values in the deleted range.
Furthermore, they remain underfilled even if you later use *Note
`DELETE': delete. without `QUICK', unless some of the deleted index
values happen to lie in index blocks within or adjacent to the
underfilled blocks. To reclaim unused index space under these
circumstances, use *Note `OPTIMIZE TABLE': optimize-table.

If you are going to delete many rows from a table, it might be faster
to use `DELETE QUICK' followed by *Note `OPTIMIZE TABLE':
optimize-table. This rebuilds the index rather than performing many
index block merge operations.

The MySQL-specific `LIMIT ROW_COUNT' option to *Note `DELETE': delete.
tells the server the maximum number of rows to be deleted before
control is returned to the client. This can be used to ensure that a
given *Note `DELETE': delete. statement does not take too much time.
You can simply repeat the *Note `DELETE': delete. statement until the
number of affected rows is less than the `LIMIT' value.

If the *Note `DELETE': delete. statement includes an `ORDER BY' clause,
rows are deleted in the order specified by the clause. This is useful
primarily in conjunction with `LIMIT'. For example, the following
statement finds rows matching the `WHERE' clause, sorts them by
`timestamp_column', and deletes the first (oldest) one:


     DELETE FROM somelog WHERE user = 'jcole'
     ORDER BY timestamp_column LIMIT 1;

`ORDER BY' may also be useful in some cases to delete rows in an order
required to avoid referential integrity violations.

If you are deleting many rows from a large table, you may exceed the
lock table size for an `InnoDB' table. To avoid this problem, or simply
to minimize the time that the table remains locked, the following
strategy (which does not use *Note `DELETE': delete. at all) might be
helpful:

  1. Select the rows _not_ to be deleted into an empty table that has
     the same structure as the original table:


          INSERT INTO t_copy SELECT * FROM t WHERE ... ;

  2. Use *Note `RENAME TABLE': rename-table. to atomically move the
     original table out of the way and rename the copy to the original
     name:


          RENAME TABLE t TO t_old, t_copy TO t;

  3. Drop the original table:


          DROP TABLE t_old;

No other sessions can access the tables involved while *Note `RENAME
TABLE': rename-table. executes, so the rename operation is not subject
to concurrency problems. See *Note rename-table::.

You can specify multiple tables in a *Note `DELETE': delete. statement
to delete rows from one or more tables depending on the particular
condition in the `WHERE' clause. However, you cannot use `ORDER BY' or
`LIMIT' in a multiple-table *Note `DELETE': delete. The
TABLE_REFERENCES clause lists the tables involved in the join. Its
syntax is described in *Note join::.

For the first multiple-table syntax, only matching rows from the tables
listed before the `FROM' clause are deleted. For the second
multiple-table syntax, only matching rows from the tables listed in the
`FROM' clause (before the `USING' clause) are deleted. The effect is
that you can delete rows from many tables at the same time and have
additional tables that are used only for searching:


     DELETE t1, t2 FROM t1 INNER JOIN t2 INNER JOIN t3
     WHERE t1.id=t2.id AND t2.id=t3.id;

Or:


     DELETE FROM t1, t2 USING t1 INNER JOIN t2 INNER JOIN t3
     WHERE t1.id=t2.id AND t2.id=t3.id;

These statements use all three tables when searching for rows to
delete, but delete matching rows only from tables `t1' and `t2'.

The preceding examples use `INNER JOIN', but multiple-table *Note
`DELETE': delete. statements can use other types of join permitted in
*Note `SELECT': select. statements, such as `LEFT JOIN'. For example,
to delete rows that exist in `t1' that have no match in `t2', use a
`LEFT JOIN':


     DELETE t1 FROM t1 LEFT JOIN t2 ON t1.id=t2.id WHERE t2.id IS NULL;

The syntax permits `.*' after each TBL_NAME for compatibility with
`Access'.

If you use a multiple-table *Note `DELETE': delete.  statement
involving `InnoDB' tables for which there are foreign key constraints,
the MySQL optimizer might process tables in an order that differs from
that of their parent/child relationship. In this case, the statement
fails and rolls back. Instead, you should delete from a single table and
rely on the `ON DELETE' capabilities that `InnoDB' provides to cause
the other tables to be modified accordingly.

*Note*:

If you declare an alias for a table, you must use the alias when
referring to the table:


     DELETE t1 FROM test AS t1, test2 WHERE ...

Table aliases in a multiple-table *Note `DELETE': delete. should be
declared only in the TABLE_REFERENCES part of the statement.

Correct:


     DELETE a1, a2 FROM t1 AS a1 INNER JOIN t2 AS a2
     WHERE a1.id=a2.id;

     DELETE FROM a1, a2 USING t1 AS a1 INNER JOIN t2 AS a2
     WHERE a1.id=a2.id;

Incorrect:


     DELETE t1 AS a1, t2 AS a2 FROM t1 INNER JOIN t2
     WHERE a1.id=a2.id;

     DELETE FROM t1 AS a1, t2 AS a2 USING t1 INNER JOIN t2
     WHERE a1.id=a2.id;

Declaration of aliases other than in the TABLE_REFERENCES part of the
statement should be avoided because that can lead to ambiguous
statements that have unexpected results such as deleting rows from the
wrong table. This is such a statement:


     DELETE t1 AS a2 FROM t1 AS a1 INNER JOIN t2 AS a2;

As of MySQL 5.1.23, alias declarations outside the TABLE_REFERENCES
part of the statement are disallowed for the `USING' variant of
multiple-table *Note `DELETE': delete. syntax. (In MySQL 5.5, alias
declarations outside TABLE_REFERENCES are disallowed for all
multiple-table *Note `DELETE': delete. statements.)

For alias references in the list of tables from which to delete rows in
a multiple-table delete, the default database is used unless one is
specified explicitly. For example, if the default database is `db1',
the following statement does not work because the unqualified alias
reference `a2' is interpreted as having a database of `db1':


     DELETE a1, a2 FROM db1.t1 AS a1 INNER JOIN db2.t2 AS a2
     WHERE a1.id=a2.id;

To correctly match an alias that refers to a table outside the default
database, you must explicitly qualify the reference with the name of
the proper database:


     DELETE a1, db2.a2 FROM db1.t1 AS a1 INNER JOIN db2.t2 AS a2
     WHERE a1.id=a2.id;


File: manual.info,  Node: do,  Next: handler,  Prev: delete,  Up: sql-syntax-data-manipulation

13.2.3 DO Syntax
----------------


     DO EXPR [, EXPR] ...

*Note `DO': do. executes the expressions but does not return any
results. In most respects, *Note `DO': do. is shorthand for `SELECT
EXPR, ...', but has the advantage that it is slightly faster when you
do not care about the result.

*Note `DO': do. is useful primarily with functions that have side
effects, such as `RELEASE_LOCK()'.

Example: This *Note `SELECT': select. statement pauses, but also
produces a result set:


     mysql> SELECT SLEEP(5);
     +----------+
     | SLEEP(5) |
     +----------+
     |        0 |
     +----------+
     1 row in set (5.02 sec)

*Note `DO': do, on the other hand, pauses without producing a result
set.:


     mysql> DO SLEEP(5);
     Query OK, 0 rows affected (4.99 sec)

This could be useful, for example in a stored function or trigger,
which prohibit statements that produce result sets.

*Note `DO': do. only executes expressions. It cannot be used in all
cases where `SELECT' can be used. For example, `DO id FROM t1' is
invalid because it references a table.


File: manual.info,  Node: handler,  Next: insert,  Prev: do,  Up: sql-syntax-data-manipulation

13.2.4 HANDLER Syntax
---------------------


     HANDLER TBL_NAME OPEN [ [AS] ALIAS]

     HANDLER TBL_NAME READ INDEX_NAME { = | <= | >= | < | > } (VALUE1,VALUE2,...)
         [ WHERE WHERE_CONDITION ] [LIMIT ... ]
     HANDLER TBL_NAME READ INDEX_NAME { FIRST | NEXT | PREV | LAST }
         [ WHERE WHERE_CONDITION ] [LIMIT ... ]
     HANDLER TBL_NAME READ { FIRST | NEXT }
         [ WHERE WHERE_CONDITION ] [LIMIT ... ]

     HANDLER TBL_NAME CLOSE

The `HANDLER' statement provides direct access to table storage engine
interfaces. It is available for `InnoDB' and `MyISAM' tables.

The `HANDLER ... OPEN' statement opens a table, making it accessible
using subsequent `HANDLER ...  READ' statements. This table object is
not shared by other sessions and is not closed until the session calls
`HANDLER ... CLOSE' or the session terminates. If you open the table
using an alias, further references to the open table with other
`HANDLER' statements must use the alias rather than the table name.

The first `HANDLER ... READ' syntax fetches a row where the index
specified satisfies the given values and the `WHERE' condition is met.
If you have a multiple-column index, specify the index column values as
a comma-separated list. Either specify values for all the columns in
the index, or specify values for a leftmost prefix of the index
columns. Suppose that an index `my_idx' includes three columns named
`col_a', `col_b', and `col_c', in that order. The `HANDLER' statement
can specify values for all three columns in the index, or for the
columns in a leftmost prefix. For example:


     HANDLER ... READ my_idx = (col_a_val,col_b_val,col_c_val) ...
     HANDLER ... READ my_idx = (col_a_val,col_b_val) ...
     HANDLER ... READ my_idx = (col_a_val) ...

To employ the `HANDLER' interface to refer to a table's `PRIMARY KEY',
use the quoted identifier ``PRIMARY`':


     HANDLER TBL_NAME READ `PRIMARY` ...

The second `HANDLER ... READ' syntax fetches a row from the table in
index order that matches the `WHERE' condition.

The third `HANDLER ... READ' syntax fetches a row from the table in
natural row order that matches the `WHERE' condition. It is faster than
`HANDLER TBL_NAME READ INDEX_NAME' when a full table scan is desired.
Natural row order is the order in which rows are stored in a `MyISAM'
table data file. This statement works for `InnoDB' tables as well, but
there is no such concept because there is no separate data file.

Without a `LIMIT' clause, all forms of `HANDLER ... READ' fetch a
single row if one is available. To return a specific number of rows,
include a `LIMIT' clause. It has the same syntax as for the *Note
`SELECT': select. statement. See *Note select::.

`HANDLER ... CLOSE' closes a table that was opened with `HANDLER ...
OPEN'.

There are several reasons to use the `HANDLER' interface instead of
normal *Note `SELECT': select.  statements:

   * `HANDLER' is faster than *Note `SELECT': select.:

        * A designated storage engine handler object is allocated for
          the `HANDLER ... OPEN'. The object is reused for subsequent
          `HANDLER' statements for that table; it need not be
          reinitialized for each one.

        * There is less parsing involved.

        * There is no optimizer or query-checking overhead.

        * The handler interface does not have to provide a consistent
          look of the data (for example, dirty reads
          (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_dirty_read)
          are permitted), so the storage engine can use optimizations
          that *Note `SELECT': select. does not normally permit.

   * `HANDLER' makes it easier to port to MySQL applications that use a
     low-level `ISAM'-like interface.

   * `HANDLER' enables you to traverse a database in a manner that is
     difficult (or even impossible) to accomplish with *Note `SELECT':
     select. The `HANDLER' interface is a more natural way to look at
     data when working with applications that provide an interactive
     user interface to the database.

`HANDLER' is a somewhat low-level statement. For example, it does not
provide consistency. That is, `HANDLER ... OPEN' does _not_ take a
snapshot of the table, and does _not_ lock the table. This means that
after a `HANDLER ...  OPEN' statement is issued, table data can be
modified (by the current session or other sessions) and these
modifications might be only partially visible to `HANDLER ...  NEXT' or
`HANDLER ... PREV' scans.

An open handler can be closed and marked for reopen, in which case the
handler loses its position in the table. This occurs when both of the
following circumstances are true:

   * Any session executes *Note `FLUSH TABLES': flush.  or DDL
     statements on the handler's table.

   * The session in which the handler is open executes non-`HANDLER'
     statements that use tables.

As of MySQL 5.1.39, *Note `TRUNCATE TABLE': truncate-table.  for a
table closes all handlers for the table that were opened with *Note
`HANDLER OPEN': handler.

`HANDLER' is not supported with partitioned tables.


File: manual.info,  Node: insert,  Next: load-data,  Prev: handler,  Up: sql-syntax-data-manipulation

13.2.5 INSERT Syntax
--------------------

* Menu:

* insert-select::                INSERT ... SELECT Syntax
* insert-delayed::               INSERT DELAYED Syntax
* insert-on-duplicate::          INSERT ... ON DUPLICATE KEY UPDATE Syntax


     INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
         [INTO] TBL_NAME [(COL_NAME,...)]
         {VALUES | VALUE} ({EXPR | DEFAULT},...),(...),...
         [ ON DUPLICATE KEY UPDATE
           COL_NAME=EXPR
             [, COL_NAME=EXPR] ... ]

Or:


     INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
         [INTO] TBL_NAME
         SET COL_NAME={EXPR | DEFAULT}, ...
         [ ON DUPLICATE KEY UPDATE
           COL_NAME=EXPR
             [, COL_NAME=EXPR] ... ]

Or:


     INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
         [INTO] TBL_NAME [(COL_NAME,...)]
         SELECT ...
         [ ON DUPLICATE KEY UPDATE
           COL_NAME=EXPR
             [, COL_NAME=EXPR] ... ]

*Note `INSERT': insert. inserts new rows into an existing table. The
*Note `INSERT ... VALUES': insert. and *Note `INSERT ... SET': insert.
forms of the statement insert rows based on explicitly specified
values. The *Note `INSERT ... SELECT': insert-select. form inserts rows
selected from another table or tables. *Note `INSERT ... SELECT':
insert-select. is discussed further in *Note insert-select::.

You can use *Note `REPLACE': replace. instead of *Note `INSERT':
insert. to overwrite old rows.  *Note `REPLACE': replace. is the
counterpart to *Note `INSERT IGNORE': insert. in the treatment of new
rows that contain unique key values that duplicate old rows: The new
rows are used to replace the old rows rather than being discarded. See
*Note replace::.

TBL_NAME is the table into which rows should be inserted. The columns
for which the statement provides values can be specified as follows:

   * You can provide a comma-separated list of column names following
     the table name. In this case, a value for each named column must
     be provided by the `VALUES' list or the *Note `SELECT': select.
     statement.

   * If you do not specify a list of column names for *Note `INSERT ...
     VALUES': insert. or *Note `INSERT ... SELECT': insert-select,
     values for every column in the table must be provided by the
     `VALUES' list or the *Note `SELECT': select. statement. If you do
     not know the order of the columns in the table, use `DESCRIBE
     TBL_NAME' to find out.

   * The `SET' clause indicates the column names explicitly.

Column values can be given in several ways:

   * If you are not running in strict SQL mode, any column not
     explicitly given a value is set to its default (explicit or
     implicit) value. For example, if you specify a column list that
     does not name all the columns in the table, unnamed columns are
     set to their default values. Default value assignment is described
     in *Note data-type-defaults::. See also *Note
     constraint-invalid-data::.

     If you want an *Note `INSERT': insert. statement to generate an
     error unless you explicitly specify values for all columns that do
     not have a default value, you should use strict mode. See *Note
     sql-mode::.

   * Use the keyword `DEFAULT' to set a column explicitly to its
     default value. This makes it easier to write *Note `INSERT':
     insert. statements that assign values to all but a few columns,
     because it enables you to avoid writing an incomplete `VALUES' list
     that does not include a value for each column in the table.
     Otherwise, you would have to write out the list of column names
     corresponding to each value in the `VALUES' list.

     You can also use `DEFAULT(COL_NAME)' as a more general form that
     can be used in expressions to produce a given column's default
     value.

   * If both the column list and the `VALUES' list are empty, *Note
     `INSERT': insert. creates a row with each column set to its
     default value:


          INSERT INTO TBL_NAME () VALUES();

     In strict mode, an error occurs if any column doesn't have a
     default value. Otherwise, MySQL uses the implicit default value
     for any column that does not have an explicitly defined default.

   * You can specify an expression EXPR to provide a column value. This
     might involve type conversion if the type of the expression does
     not match the type of the column, and conversion of a given value
     can result in different inserted values depending on the data
     type. For example, inserting the string `'1999.0e-2'' into an
     *Note `INT': integer-types, *Note `FLOAT': floating-point-types,
     `DECIMAL(10,6)', or *Note `YEAR': year. column results in the
     values `1999', `19.9921', `19.992100', and `1999' being inserted,
     respectively. The reason the value stored in the *Note `INT':
     integer-types. and *Note `YEAR': year. columns is `1999' is that
     the string-to-integer conversion looks only at as much of the
     initial part of the string as may be considered a valid integer or
     year. For the floating-point and fixed-point columns, the
     string-to-floating-point conversion considers the entire string a
     valid floating-point value.

     An expression EXPR can refer to any column that was set earlier in
     a value list. For example, you can do this because the value for
     `col2' refers to `col1', which has previously been assigned:


          INSERT INTO TBL_NAME (col1,col2) VALUES(15,col1*2);

     But the following is not legal, because the value for `col1'
     refers to `col2', which is assigned after `col1':


          INSERT INTO TBL_NAME (col1,col2) VALUES(col2*2,15);

     One exception involves columns that contain `AUTO_INCREMENT'
     values. Because the `AUTO_INCREMENT' value is generated after
     other value assignments, any reference to an `AUTO_INCREMENT'
     column in the assignment returns a `0'.

*Note `INSERT': insert. statements that use `VALUES' syntax can insert
multiple rows. To do this, include multiple lists of column values,
each enclosed within parentheses and separated by commas. Example:


     INSERT INTO TBL_NAME (a,b,c) VALUES(1,2,3),(4,5,6),(7,8,9);

The values list for each row must be enclosed within parentheses.  The
following statement is illegal because the number of values in the list
does not match the number of column names:


     INSERT INTO TBL_NAME (a,b,c) VALUES(1,2,3,4,5,6,7,8,9);

`VALUE' is a synonym for `VALUES' in this context. Neither implies
anything about the number of values lists, and either may be used
whether there is a single values list or multiple lists.

The affected-rows value for an *Note `INSERT': insert. can be obtained
using the `ROW_COUNT()' function (see *Note information-functions::),
or the *Note `mysql_affected_rows()': mysql-affected-rows. C API
function (see *Note mysql-affected-rows::).

If you use an *Note `INSERT ... VALUES': insert. statement with
multiple value lists or *Note `INSERT ... SELECT': insert-select, the
statement returns an information string in this format:


     Records: 100 Duplicates: 0 Warnings: 0

`Records' indicates the number of rows processed by the statement.
(This is not necessarily the number of rows actually inserted because
`Duplicates' can be nonzero.) `Duplicates' indicates the number of rows
that could not be inserted because they would duplicate some existing
unique index value. `Warnings' indicates the number of attempts to
insert column values that were problematic in some way. Warnings can
occur under any of the following conditions:

   * Inserting `NULL' into a column that has been declared `NOT NULL'.
     For multiple-row *Note `INSERT': insert. statements or *Note
     `INSERT INTO ... SELECT': insert-select. statements, the column is
     set to the implicit default value for the column data type. This is
     `0' for numeric types, the empty string (`''') for string types,
     and the `zero' value for date and time types.  *Note `INSERT INTO
     ... SELECT': insert-select. statements are handled the same way as
     multiple-row inserts because the server does not examine the
     result set from the *Note `SELECT': select. to see whether it
     returns a single row. (For a single-row *Note `INSERT': insert, no
     warning occurs when `NULL' is inserted into a `NOT NULL' column.
     Instead, the statement fails with an error.)

   * Setting a numeric column to a value that lies outside the column's
     range. The value is clipped to the closest endpoint of the range.

   * Assigning a value such as `'10.34 a'' to a numeric column. The
     trailing nonnumeric text is stripped off and the remaining numeric
     part is inserted. If the string value has no leading numeric part,
     the column is set to `0'.

   * Inserting a string into a string column (*Note `CHAR': char, *Note
     `VARCHAR': char, *Note `TEXT': blob, or *Note `BLOB': blob.) that
     exceeds the column's maximum length. The value is truncated to the
     column's maximum length.

   * Inserting a value into a date or time column that is illegal for
     the data type. The column is set to the appropriate zero value for
     the type.

If you are using the C API, the information string can be obtained by
invoking the *Note `mysql_info()': mysql-info.  function. See *Note
mysql-info::.

If *Note `INSERT': insert. inserts a row into a table that has an
`AUTO_INCREMENT' column, you can find the value used for that column by
using the SQL `LAST_INSERT_ID()' function. From within the C API, use
the *Note `mysql_insert_id()': mysql-insert-id. function.  However, you
should note that the two functions do not always behave identically.
The behavior of *Note `INSERT': insert. statements with respect to
`AUTO_INCREMENT' columns is discussed further in *Note
information-functions::, and *Note mysql-insert-id::.

The *Note `INSERT': insert. statement supports the following modifiers:

   * If you use the `DELAYED' keyword, the server puts the row or rows
     to be inserted into a buffer, and the client issuing the *Note
     `INSERT DELAYED': insert-delayed. statement can then continue
     immediately. If the table is in use, the server holds the rows.
     When the table is free, the server begins inserting rows, checking
     periodically to see whether there are any new read requests for
     the table. If there are, the delayed row queue is suspended until
     the table becomes free again. See *Note insert-delayed::.

     `DELAYED' is ignored with *Note `INSERT ... SELECT':
     insert-select. or *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate.

     Beginning with MySQL 5.1.19, `DELAYED' is also disregarded for an
     *Note `INSERT': insert.  that uses functions accessing tables or
     triggers, or that is called from a function or a trigger.

   * If you use the `LOW_PRIORITY' keyword, execution of the *Note
     `INSERT': insert. is delayed until no other clients are reading
     from the table.  This includes other clients that began reading
     while existing clients are reading, and while the `INSERT
     LOW_PRIORITY' statement is waiting. It is possible, therefore, for
     a client that issues an `INSERT LOW_PRIORITY' statement to wait
     for a very long time (or even forever) in a read-heavy
     environment. (This is in contrast to *Note `INSERT DELAYED':
     insert-delayed, which lets the client continue at once.) Note that
     `LOW_PRIORITY' should normally not be used with `MyISAM' tables
     because doing so disables concurrent inserts. See *Note
     concurrent-inserts::.

     If you specify `HIGH_PRIORITY', it overrides the effect of the
     `--low-priority-updates' option if the server was started with
     that option. It also causes concurrent inserts not to be used. See
     *Note concurrent-inserts::.

     `LOW_PRIORITY' and `HIGH_PRIORITY' affect only storage engines
     that use only table-level locking (such as `MyISAM', `MEMORY', and
     `MERGE').

   * If you use the `IGNORE' keyword, errors that occur while executing
     the *Note `INSERT': insert. statement are ignored.  For example,
     without `IGNORE', a row that duplicates an existing `UNIQUE' index
     or `PRIMARY KEY' value in the table causes a duplicate-key error
     and the statement is aborted. With `IGNORE', the row is discarded
     and no error occurs. Ignored errors may generate warnings instead,
     although duplicate-key errors do not.

     `IGNORE' has a similar effect on inserts into partitioned tables
     where no partition matching a given value is found. Without
     `IGNORE', such *Note `INSERT': insert. statements are aborted with
     an error; however, when *Note `INSERT IGNORE': insert. is used,
     the insert operation fails silently for the row containing the
     unmatched value, but any rows that are matched are inserted. For
     an example, see *Note partitioning-list::.

     Data conversions that would trigger errors abort the statement if
     `IGNORE' is not specified. With `IGNORE', invalid values are
     adjusted to the closest values and inserted; warnings are produced
     but the statement does not abort. You can determine with the *Note
     `mysql_info()': mysql-info. C API function how many rows were
     actually inserted into the table.

   * If you specify `ON DUPLICATE KEY UPDATE', and a row is inserted
     that would cause a duplicate value in a `UNIQUE' index or `PRIMARY
     KEY', an *Note `UPDATE': update. of the old row is performed. The
     affected-rows value per row is 1 if the row is inserted as a new
     row and 2 if an existing row is updated. See *Note
     insert-on-duplicate::.

Inserting into a table requires the `INSERT' privilege for the table. If
the `ON DUPLICATE KEY UPDATE' clause is used and a duplicate key causes
an *Note `UPDATE': update. to be performed instead, the statement
requires the `UPDATE' privilege for the columns to be updated. For
columns that are read but not modified you need only the `SELECT'
privilege (such as for a column referenced only on the right hand side
of an COL_NAME=EXPR assignment in an `ON DUPLICATE KEY UPDATE' clause).

An `INSERT'statement that acts on a partitioned table using a storage
engine such as *Note `MyISAM': myisam-storage-engine. that employs
table-level locks locks all partitions of the table. This does not
occur with tables using storage engines such as *Note `InnoDB':
innodb-storage-engine.  that employ row-level locking. This issue is
resolved in MySQL 5.6. See *Note partitioning-limitations-locking::, for
more information.


File: manual.info,  Node: insert-select,  Next: insert-delayed,  Prev: insert,  Up: insert

13.2.5.1 INSERT ... SELECT Syntax
.................................


     INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
         [INTO] TBL_NAME [(COL_NAME,...)]
         SELECT ...
         [ ON DUPLICATE KEY UPDATE COL_NAME=EXPR, ... ]

With *Note `INSERT ... SELECT': insert-select, you can quickly insert
many rows into a table from one or many tables. For example:


     INSERT INTO tbl_temp2 (fld_id)
       SELECT tbl_temp1.fld_order_id
       FROM tbl_temp1 WHERE tbl_temp1.fld_order_id > 100;

The following conditions hold for a *Note `INSERT ... SELECT':
insert-select. statements:

   * Specify `IGNORE' to ignore rows that would cause duplicate-key
     violations.

   * `DELAYED' is ignored with *Note `INSERT ... SELECT': insert-select.

   * The target table of the *Note `INSERT': insert. statement may
     appear in the `FROM' clause of the *Note `SELECT': select. part of
     the query.  (This was not possible in some older versions of
     MySQL.)  However, you cannot insert into a table and select from
     the same table in a subquery.

     When selecting from and inserting into a table at the same time,
     MySQL creates a temporary table to hold the rows from the *Note
     `SELECT': select. and then inserts those rows into the target
     table. However, it remains true that you cannot use `INSERT INTO t
     ... SELECT ...  FROM t' when `t' is a `TEMPORARY' table, because
     `TEMPORARY' tables cannot be referred to twice in the same
     statement (see *Note temporary-table-problems::).

   * `AUTO_INCREMENT' columns work as usual.

   * To ensure that the binary log can be used to re-create the
     original tables, MySQL does not permit concurrent inserts for
     *Note `INSERT ... SELECT': insert-select. statements.

   * To avoid ambiguous column reference problems when the *Note
     `SELECT': select. and the *Note `INSERT': insert. refer to the same
     table, provide a unique alias for each table used in the *Note
     `SELECT': select. part, and qualify column names in that part with
     the appropriate alias.

In the values part of `ON DUPLICATE KEY UPDATE', you can refer to
columns in other tables, as long as you do not use `GROUP BY' in the
*Note `SELECT': select. part. One side effect is that you must qualify
nonunique column names in the values part.

The order in which rows are returned by a *Note `SELECT': select.
statement with no `ORDER BY' clause is not determined. This means that,
when using replication, there is no guarantee that such a `SELECT'
returns rows in the same order on the master and the slave; this can
lead to inconsistencies between them. To prevent this from occurring,
you should always write `INSERT ... SELECT' statements that are to be
replicated as `INSERT ... SELECT ... ORDER BY COLUMN'. The choice of
COLUMN does not matter as long as the same order for returning the rows
is enforced on both the master and the slave. See also *Note
replication-features-limit::.

An `INSERT ... SELECT' statement that acts on partitioned tables using
a storage engine such as *Note `MyISAM': myisam-storage-engine. that
employs table-level locks locks all partitions of the source and target
tables. This does not occur with tables using storage engines such as
*Note `InnoDB': innodb-storage-engine. that employ row-level locking.
This issue is resolved in MySQL 5.6. See *Note
partitioning-limitations-locking::, for more information.


File: manual.info,  Node: insert-delayed,  Next: insert-on-duplicate,  Prev: insert-select,  Up: insert

13.2.5.2 INSERT DELAYED Syntax
..............................


     INSERT DELAYED ...

The `DELAYED' option for the *Note `INSERT': insert. statement is a
MySQL extension to standard SQL that is very useful if you have clients
that cannot or need not wait for the *Note `INSERT': insert. to
complete. This is a common situation when you use MySQL for logging and
you also periodically run *Note `SELECT': select. and *Note `UPDATE':
update. statements that take a long time to complete.

When a client uses *Note `INSERT DELAYED': insert-delayed, it gets an
okay from the server at once, and the row is queued to be inserted when
the table is not in use by any other thread.

Another major benefit of using *Note `INSERT DELAYED': insert-delayed.
is that inserts from many clients are bundled together and written in
one block. This is much faster than performing many separate inserts.

Note that *Note `INSERT DELAYED': insert-delayed. is slower than a
normal *Note `INSERT': insert. if the table is not otherwise in use.
There is also the additional overhead for the server to handle a
separate thread for each table for which there are delayed rows. This
means that you should use *Note `INSERT DELAYED': insert-delayed. only
when you are really sure that you need it.

The queued rows are held only in memory until they are inserted into
the table. This means that if you terminate *Note `mysqld': mysqld.
forcibly (for example, with `kill -9') or if *Note `mysqld': mysqld.
dies unexpectedly, _any queued rows that have not been written to disk
are lost_.

There are some constraints on the use of `DELAYED':

   * *Note `INSERT DELAYED': insert-delayed. works only with `MyISAM',
     `MEMORY', `ARCHIVE', and (as of MySQL 5.1.19) `BLACKHOLE' tables.
     For engines that do not support `DELAYED', an error occurs.

   * An error occurs for *Note `INSERT DELAYED': insert-delayed. if
     used with a table that has been locked with `LOCK TABLES' because
     the insert must be handled by a separate thread, not by the
     session that holds the lock.

   * For `MyISAM' tables, if there are no free blocks in the middle of
     the data file, concurrent *Note `SELECT': select. and *Note
     `INSERT': insert. statements are supported. Under these
     circumstances, you very seldom need to use *Note `INSERT DELAYED':
     insert-delayed. with `MyISAM'.

   * *Note `INSERT DELAYED': insert-delayed. should be used only for
     *Note `INSERT': insert. statements that specify value lists. The
     server ignores `DELAYED' for *Note `INSERT ... SELECT':
     insert-select. or *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate. statements.

   * Because the *Note `INSERT DELAYED': insert-delayed.  statement
     returns immediately, before the rows are inserted, you cannot use
     `LAST_INSERT_ID()' to get the `AUTO_INCREMENT' value that the
     statement might generate.

   * `DELAYED' rows are not visible to *Note `SELECT': select.
     statements until they actually have been inserted.

   * *Note `INSERT DELAYED': insert-delayed. is treated as a normal
     *Note `INSERT': insert. if the statement inserts multiple rows and
     binary logging is enabled and the global logging format is to use
     statement-based logging (`binlog_format' is set to `STATEMENT').
     This restriction does not apply to row-based binary logging.

   * `DELAYED' is ignored on slave replication servers, so that *Note
     `INSERT DELAYED': insert-delayed. is treated as a normal *Note
     `INSERT': insert. on slaves. This is because `DELAYED' could cause
     the slave to have different data than the master.

   * Pending *Note `INSERT DELAYED': insert-delayed.  statements are
     lost if a table is write locked and *Note `ALTER TABLE':
     alter-table. is used to modify the table structure.

   * *Note `INSERT DELAYED': insert-delayed. is not supported for views.

   * *Note `INSERT DELAYED': insert-delayed. is not supported for
     partitioned tables.

The following describes in detail what happens when you use the
`DELAYED' option to *Note `INSERT': insert. or *Note `REPLACE':
replace. In this description, the `thread' is the thread that received
an *Note `INSERT DELAYED': insert-delayed. statement and `handler' is
the thread that handles all *Note `INSERT DELAYED': insert-delayed.
statements for a particular table.

   * When a thread executes a `DELAYED' statement for a table, a
     handler thread is created to process all `DELAYED' statements for
     the table, if no such handler already exists.

   * The thread checks whether the handler has previously acquired a
     `DELAYED' lock; if not, it tells the handler thread to do so. The
     `DELAYED' lock can be obtained even if other threads have a `READ'
     or `WRITE' lock on the table. However, the handler waits for all
     *Note `ALTER TABLE': alter-table. locks or *Note `FLUSH TABLES':
     flush. statements to finish, to ensure that the table structure is
     up to date.

   * The thread executes the *Note `INSERT': insert. statement, but
     instead of writing the row to the table, it puts a copy of the
     final row into a queue that is managed by the handler thread. Any
     syntax errors are noticed by the thread and reported to the client
     program.

   * The client cannot obtain from the server the number of duplicate
     rows or the `AUTO_INCREMENT' value for the resulting row, because
     the *Note `INSERT': insert. returns before the insert operation
     has been completed. (If you use the C API, the *Note
     `mysql_info()': mysql-info. function does not return anything
     meaningful, for the same reason.)

   * The binary log is updated by the handler thread when the row is
     inserted into the table. In case of multiple-row inserts, the
     binary log is updated when the first row is inserted.

   * Each time that `delayed_insert_limit' rows are written, the
     handler checks whether any *Note `SELECT': select. statements are
     still pending. If so, it permits these to execute before
     continuing.

   * When the handler has no more rows in its queue, the table is
     unlocked. If no new *Note `INSERT DELAYED': insert-delayed.
     statements are received within `delayed_insert_timeout' seconds,
     the handler terminates.

   * If more than `delayed_queue_size' rows are pending in a specific
     handler queue, the thread requesting *Note `INSERT DELAYED':
     insert-delayed. waits until there is room in the queue. This is
     done to ensure that *Note `mysqld': mysqld. does not use all
     memory for the delayed memory queue.

   * The handler thread shows up in the MySQL process list with
     `delayed_insert' in the `Command' column. It is killed if you
     execute a *Note `FLUSH TABLES': flush. statement or kill it with
     `KILL THREAD_ID'. However, before exiting, it first stores all
     queued rows into the table. During this time it does not accept
     any new *Note `INSERT': insert. statements from other threads. If
     you execute an *Note `INSERT DELAYED': insert-delayed. statement
     after this, a new handler thread is created.

     Note that this means that *Note `INSERT DELAYED': insert-delayed.
     statements have higher priority than normal *Note `INSERT':
     insert. statements if there is an *Note `INSERT DELAYED':
     insert-delayed.  handler running. Other update statements have to
     wait until the *Note `INSERT DELAYED': insert-delayed. queue is
     empty, someone terminates the handler thread (with `KILL
     THREAD_ID'), or someone executes a *Note `FLUSH TABLES': flush.

   * The following status variables provide information about *Note
     `INSERT DELAYED': insert-delayed. statements.

     This table lists status variables for *Note `INSERT DELAYED':
     insert-delayed. statements and describes the meaning of each.

     Status Variable                Meaning
     `Delayed_insert_threads'       Number of handler threads
     `Delayed_writes'               Number of rows written with *Note
                                    `INSERT DELAYED': insert-delayed.
     `Not_flushed_delayed_rows'     Number of rows waiting to be written

     You can view these variables by issuing a *Note `SHOW STATUS':
     show-status. statement or by executing a *Note `mysqladmin
     extended-status': mysqladmin.  command.


File: manual.info,  Node: insert-on-duplicate,  Prev: insert-delayed,  Up: insert

13.2.5.3 INSERT ... ON DUPLICATE KEY UPDATE Syntax
..................................................

If you specify `ON DUPLICATE KEY UPDATE', and a row is inserted that
would cause a duplicate value in a `UNIQUE' index or `PRIMARY KEY',
MySQL performs an *Note `UPDATE': update. of the old row. For example,
if column `a' is declared as `UNIQUE' and contains the value `1', the
following two statements have similar effect:


     INSERT INTO table (a,b,c) VALUES (1,2,3)
       ON DUPLICATE KEY UPDATE c=c+1;

     UPDATE table SET c=c+1 WHERE a=1;

(The effects are not identical for an `InnoDB' table where `a' is an
auto-increment column.  With an auto-increment column, an `INSERT'
statement increases the auto-increment value but `UPDATE' does not.)

The `ON DUPLICATE KEY UPDATE' clause can contain multiple column
assignments, separated by commas.

With `ON DUPLICATE KEY UPDATE', the affected-rows value per row is 1 if
the row is inserted as a new row, and 2 if an existing row is updated.

If column `b' is also unique, the *Note `INSERT': insert. is equivalent
to this *Note `UPDATE': update. statement instead:


     UPDATE table SET c=c+1 WHERE a=1 OR b=2 LIMIT 1;

If `a=1 OR b=2' matches several rows, only _one_ row is updated. In
general, you should try to avoid using an `ON DUPLICATE KEY UPDATE'
clause on tables with multiple unique indexes.

You can use the `VALUES(COL_NAME)' function in the *Note `UPDATE':
update. clause to refer to column values from the *Note `INSERT':
insert. portion of the *Note `INSERT ... ON DUPLICATE KEY UPDATE':
insert-on-duplicate. statement. In other words, `VALUES(COL_NAME)' in
the `ON DUPLICATE KEY UPDATE' clause refers to the value of COL_NAME
that would be inserted, had no duplicate-key conflict occurred. This
function is especially useful in multiple-row inserts. The `VALUES()'
function is meaningful only in `INSERT ... UPDATE' statements and
returns `NULL' otherwise. Example:


     INSERT INTO table (a,b,c) VALUES (1,2,3),(4,5,6)
       ON DUPLICATE KEY UPDATE c=VALUES(a)+VALUES(b);

That statement is identical to the following two statements:


     INSERT INTO table (a,b,c) VALUES (1,2,3)
       ON DUPLICATE KEY UPDATE c=3;
     INSERT INTO table (a,b,c) VALUES (4,5,6)
       ON DUPLICATE KEY UPDATE c=9;

If a table contains an `AUTO_INCREMENT' column and *Note `INSERT ... ON
DUPLICATE KEY UPDATE': insert-on-duplicate. inserts or updates a row,
the `LAST_INSERT_ID()' function returns the `AUTO_INCREMENT' value.
Exception: For updates, `LAST_INSERT_ID()' is not meaningful prior to
MySQL 5.1.12. However, you can work around this by using
`LAST_INSERT_ID(EXPR)'.  Suppose that `id' is the `AUTO_INCREMENT'
column. To make `LAST_INSERT_ID()' meaningful for updates, insert rows
as follows:


     INSERT INTO table (a,b,c) VALUES (1,2,3)
       ON DUPLICATE KEY UPDATE id=LAST_INSERT_ID(id), c=3;

The `DELAYED' option is ignored when you use `ON DUPLICATE KEY UPDATE'.

An `INSERT ... ON DUPLICATE KEY UPDATE' on a partitioned table using a
storage engine such as *Note `MyISAM': myisam-storage-engine. that
employs table-level locks locks all partitions of the table. This does
not occur with tables using storage engines such as *Note `InnoDB':
innodb-storage-engine. that employ row-level locking. This issue is
resolved in MySQL 5.6. See *Note partitioning-limitations-locking::,
for more information.


File: manual.info,  Node: load-data,  Next: replace,  Prev: insert,  Up: sql-syntax-data-manipulation

13.2.6 LOAD DATA INFILE Syntax
------------------------------


     LOAD DATA [LOW_PRIORITY | CONCURRENT] [LOCAL] INFILE 'FILE_NAME'
         [REPLACE | IGNORE]
         INTO TABLE TBL_NAME
         [CHARACTER SET CHARSET_NAME]
         [{FIELDS | COLUMNS}
             [TERMINATED BY 'STRING']
             [[OPTIONALLY] ENCLOSED BY 'CHAR']
             [ESCAPED BY 'CHAR']
         ]
         [LINES
             [STARTING BY 'STRING']
             [TERMINATED BY 'STRING']
         ]
         [IGNORE NUMBER LINES]
         [(COL_NAME_OR_USER_VAR,...)]
         [SET COL_NAME = EXPR,...]

The *Note `LOAD DATA INFILE': load-data. statement reads rows from a
text file into a table at a very high speed.  *Note `LOAD DATA INFILE':
load-data. is the complement of *Note `SELECT ... INTO OUTFILE':
select-into. (See *Note select-into::.) To write data from a table to a
file, use *Note `SELECT ... INTO OUTFILE': select-into. To read the
file back into a table, use *Note `LOAD DATA INFILE': load-data. The
syntax of the `FIELDS' and `LINES' clauses is the same for both
statements.  Both clauses are optional, but `FIELDS' must precede
`LINES' if both are specified.

You can also load data files by using the *Note `mysqlimport':
mysqlimport. utility; it operates by sending a *Note `LOAD DATA
INFILE': load-data. statement to the server. The `--local' option causes
*Note `mysqlimport': mysqlimport. to read data files from the client
host. You can specify the `--compress' option to get better performance
over slow networks if the client and server support the compressed
protocol. See *Note mysqlimport::.

For more information about the efficiency of *Note `INSERT': insert.
versus *Note `LOAD DATA INFILE': load-data. and speeding up *Note `LOAD
DATA INFILE': load-data, see *Note insert-speed::.

The file name must be given as a literal string. On Windows, specify
backslashes in path names as forward slashes or doubled backslashes. As
of MySQL 5.1.6, the `character_set_filesystem' system variable controls
the interpretation of the file name.

The character set indicated by the `character_set_database' system
variable is used to interpret the information in the file.  `SET NAMES'
and the setting of `character_set_client' do not affect interpretation
of input. If the contents of the input file use a character set that
differs from the default, it is usually preferable to specify the
character set of the file by using the `CHARACTER SET' clause, which is
available as of MySQL 5.1.17. A character set of `binary' specifies `no
conversion.'

*Note `LOAD DATA INFILE': load-data. interprets all fields in the file
as having the same character set, regardless of the data types of the
columns into which field values are loaded. For proper interpretation of
file contents, you must ensure that it was written with the correct
character set. For example, if you write a data file with *Note
`mysqldump -T': mysqldump. or by issuing a *Note `SELECT ... INTO
OUTFILE': select-into. statement in *Note `mysql': mysql, be sure to
use a `--default-character-set' option so that output is written in the
character set to be used when the file is loaded with *Note `LOAD DATA
INFILE': load-data.

*Note*:

It is not possible to load data files that use the `ucs2' character set.

If you use `LOW_PRIORITY', execution of the *Note `LOAD DATA':
load-data. statement is delayed until no other clients are reading from
the table. This affects only storage engines that use only table-level
locking (such as `MyISAM', `MEMORY', and `MERGE').

If you specify `CONCURRENT' with a `MyISAM' table that satisfies the
condition for concurrent inserts (that is, it contains no free blocks
in the middle), other threads can retrieve data from the table while
*Note `LOAD DATA': load-data. is executing. This option affects the
performance of *Note `LOAD DATA': load-data. a bit, even if no other
thread is using the table at the same time.

With row-based replication, `CONCURRENT' is replicated regardless of
MySQL version. With statement-based replication `CONCURRENT' is not
replicated prior to MySQL 5.1.43 (see Bug #34628). For more
information, see *Note replication-features-load-data::.

*Note*:

Prior to MySQL 5.1.23, *Note `LOAD DATA': load-data.  performed very
poorly when importing into partitioned tables.  The statement now uses
buffering to improve performance; however, the buffer uses 130KB memory
per partition to achieve this. (Bug #26527)

The `LOCAL' keyword affects expected location of the file and error
handling, as described later.  `LOCAL' works only if your server and
your client both have been configured to permit it. For example, if
*Note `mysqld': mysqld. was started with `--local-infile=0', `LOCAL'
does not work. See *Note load-data-local::.

The `LOCAL' keyword affects where the file is expected to be found:

   * If `LOCAL' is specified, the file is read by the client program on
     the client host and sent to the server.  The file can be given as
     a full path name to specify its exact location. If given as a
     relative path name, the name is interpreted relative to the
     directory in which the client program was started.

     When using `LOCAL' with *Note `LOAD DATA': load-data, a copy of
     the file is created in the server's temporary directory. This is
     _not_ the directory determined by the value of `tmpdir' or
     `slave_load_tmpdir', but rather the operating system's temporary
     directory, and is not configurable in the MySQL Server. (Typically
     the system temporary directory is `/tmp' on Linux systems and
     `C:\WINDOWS\TEMP' on Windows.)  Lack of sufficient space for the
     copy in this directory can cause the *Note `LOAD DATA LOCAL':
     load-data. statement to fail.

   * If `LOCAL' is not specified, the file must be located on the
     server host and is read directly by the server.  The server uses
     the following rules to locate the file:

        * If the file name is an absolute path name, the server uses it
          as given.

        * If the file name is a relative path name with one or more
          leading components, the server searches for the file relative
          to the server's data directory.

        * If a file name with no leading components is given, the
          server looks for the file in the database directory of the
          default database.

In the non-`LOCAL' case, these rules mean that a file named as
`./myfile.txt' is read from the server's data directory, whereas the
file named as `myfile.txt' is read from the database directory of the
default database. For example, if `db1' is the default database, the
following *Note `LOAD DATA': load-data. statement reads the file
`data.txt' from the database directory for `db1', even though the
statement explicitly loads the file into a table in the `db2' database:


     LOAD DATA INFILE 'data.txt' INTO TABLE db2.my_table;

*Note*:

A regression in MySQL 5.1.40 caused the database referenced in a fully
qualified table name to be ignored by *Note `LOAD DATA': load-data.
when using replication with either `STATEMENT' or `MIXED' as the binary
logging format; this could lead to problems if the table was not in the
current database. As a workaround, you can specify the correct database
with the *Note `USE': use. statement prior to executing *Note `LOAD
DATA': load-data. If necessary, you can reset the default database with
a second *Note `USE': use. statement following the *Note `LOAD DATA':
load-data. statement.

This issue was fixed in MySQL 5.1.41. (Bug #48297)

For security reasons, when reading text files located on the server,
the files must either reside in the database directory or be readable
by all. Also, to use *Note `LOAD DATA INFILE': load-data. on server
files, you must have the `FILE' privilege. See *Note
privileges-provided::. For non-`LOCAL' load operations, if the
`secure_file_priv' system variable is set to a nonempty directory name,
the file to be loaded must be located in that directory.

Using `LOCAL' is a bit slower than letting the server access the files
directly, because the contents of the file must be sent over the
connection by the client to the server. On the other hand, you do not
need the `FILE' privilege to load local files.

`LOCAL' also affects error handling:

   * With *Note `LOAD DATA INFILE': load-data, data-interpretation and
     duplicate-key errors terminate the operation.

   * With *Note `LOAD DATA LOCAL INFILE': load-data,
     data-interpretation and duplicate-key errors become warnings and
     the operation continues because the server has no way to stop
     transmission of the file in the middle of the operation. For
     duplicate-key errors, this is the same as if `IGNORE' is specified.
     `IGNORE' is explained further later in this section.

The `REPLACE' and `IGNORE' keywords control handling of input rows that
duplicate existing rows on unique key values:

   * If you specify `REPLACE', input rows replace existing rows. In
     other words, rows that have the same value for a primary key or
     unique index as an existing row. See *Note replace::.

   * If you specify `IGNORE', rows that duplicate an existing row on a
     unique key value are discarded.

   * If you do not specify either option, the behavior depends on
     whether the `LOCAL' keyword is specified.  Without `LOCAL', an
     error occurs when a duplicate key value is found, and the rest of
     the text file is ignored. With `LOCAL', the default behavior is
     the same as if `IGNORE' is specified; this is because the server
     has no way to stop transmission of the file in the middle of the
     operation.

To ignore foreign key constraints during the load operation, issue a
`SET foreign_key_checks = 0' statement before executing *Note `LOAD
DATA': load-data.

If you use *Note `LOAD DATA INFILE': load-data. on an empty `MyISAM'
table, all nonunique indexes are created in a separate batch (as for
*Note `REPAIR TABLE': repair-table.). Normally, this makes *Note `LOAD
DATA INFILE': load-data. much faster when you have many indexes. In some
extreme cases, you can create the indexes even faster by turning them
off with `ALTER TABLE ... DISABLE KEYS' before loading the file into
the table and using `ALTER TABLE ... ENABLE KEYS' to re-create the
indexes after loading the file. See *Note insert-speed::.

For both the *Note `LOAD DATA INFILE': load-data. and *Note `SELECT ...
INTO OUTFILE': select-into. statements, the syntax of the `FIELDS' and
`LINES' clauses is the same. Both clauses are optional, but `FIELDS'
must precede `LINES' if both are specified.

If you specify a `FIELDS' clause, each of its subclauses (`TERMINATED
BY', `[OPTIONALLY] ENCLOSED BY', and `ESCAPED BY') is also optional,
except that you must specify at least one of them.

If you specify no `FIELDS' or `LINES' clause, the defaults are the same
as if you had written this:


     FIELDS TERMINATED BY '\t' ENCLOSED BY '' ESCAPED BY '\\'
     LINES TERMINATED BY '\n' STARTING BY ''

(Backslash is the MySQL escape character within strings in SQL
statements, so to specify a literal backslash, you must specify two
backslashes for the value to be interpreted as a single backslash. The
escape sequences `'\t'' and `'\n'' specify tab and newline characters,
respectively.)

In other words, the defaults cause *Note `LOAD DATA INFILE': load-data.
to act as follows when reading input:

   * Look for line boundaries at newlines.

   * Do not skip over any line prefix.

   * Break lines into fields at tabs.

   * Do not expect fields to be enclosed within any quoting characters.

   * Interpret characters preceded by the escape character ``\'' as
     escape sequences. For example, ``\t'', ``\n'', and ``\\'' signify
     tab, newline, and backslash, respectively. See the discussion of
     `FIELDS ESCAPED BY' later for the full list of escape sequences.

Conversely, the defaults cause *Note `SELECT ... INTO OUTFILE':
select-into. to act as follows when writing output:

   * Write tabs between fields.

   * Do not enclose fields within any quoting characters.

   * Use ``\'' to escape instances of tab, newline, or ``\'' that occur
     within field values.

   * Write newlines at the ends of lines.

*Note*:

If you have generated the text file on a Windows system, you might have
to use `LINES TERMINATED BY '\r\n'' to read the file properly, because
Windows programs typically use two characters as a line terminator.
Some programs, such as `WordPad', might use `\r' as a line terminator
when writing files. To read such files, use `LINES TERMINATED BY '\r''.

If all the lines you want to read in have a common prefix that you want
to ignore, you can use `LINES STARTING BY 'PREFIX_STRING'' to skip over
the prefix, _and anything before it_. If a line does not include the
prefix, the entire line is skipped. Suppose that you issue the
following statement:


     LOAD DATA INFILE '/tmp/test.txt' INTO TABLE test
       FIELDS TERMINATED BY ','  LINES STARTING BY 'xxx';

If the data file looks like this:


     xxx"abc",1
     something xxx"def",2
     "ghi",3

The resulting rows will be `("abc",1)' and `("def",2)'. The third row
in the file is skipped because it does not contain the prefix.

The `IGNORE NUMBER LINES' option can be used to ignore lines at the
start of the file. For example, you can use `IGNORE 1 LINES' to skip
over an initial header line containing column names:


     LOAD DATA INFILE '/tmp/test.txt' INTO TABLE test IGNORE 1 LINES;

When you use *Note `SELECT ... INTO OUTFILE': select-into. in tandem
with *Note `LOAD DATA INFILE': load-data. to write data from a database
into a file and then read the file back into the database later, the
field- and line-handling options for both statements must match.
Otherwise, *Note `LOAD DATA INFILE': load-data. will not interpret the
contents of the file properly. Suppose that you use *Note `SELECT ...
INTO OUTFILE': select-into. to write a file with fields delimited by
commas:


     SELECT * INTO OUTFILE 'data.txt'
       FIELDS TERMINATED BY ','
       FROM table2;

To read the comma-delimited file back in, the correct statement would
be:


     LOAD DATA INFILE 'data.txt' INTO TABLE table2
       FIELDS TERMINATED BY ',';

If instead you tried to read in the file with the statement shown
following, it wouldn't work because it instructs *Note `LOAD DATA
INFILE': load-data. to look for tabs between fields:


     LOAD DATA INFILE 'data.txt' INTO TABLE table2
       FIELDS TERMINATED BY '\t';

The likely result is that each input line would be interpreted as a
single field.

*Note `LOAD DATA INFILE': load-data. can be used to read files obtained
from external sources. For example, many programs can export data in
comma-separated values (CSV) format, such that lines have fields
separated by commas and enclosed within double quotation marks, with an
initial line of column names. If the lines in such a file are
terminated by carriage return/newline pairs, the statement shown here
illustrates the field- and line-handling options you would use to load
the file:


     LOAD DATA INFILE 'data.txt' INTO TABLE TBL_NAME
       FIELDS TERMINATED BY ',' ENCLOSED BY '"'
       LINES TERMINATED BY '\r\n'
       IGNORE 1 LINES;

If the input values are not necessarily enclosed within quotation
marks, use `OPTIONALLY' before the `ENCLOSED BY' keywords.

Any of the field- or line-handling options can specify an empty string
(`'''). If not empty, the `FIELDS [OPTIONALLY] ENCLOSED BY' and `FIELDS
ESCAPED BY' values must be a single character. The `FIELDS TERMINATED
BY', `LINES STARTING BY', and `LINES TERMINATED BY' values can be more
than one character. For example, to write lines that are terminated by
carriage return/linefeed pairs, or to read a file containing such
lines, specify a `LINES TERMINATED BY '\r\n'' clause.

To read a file containing jokes that are separated by lines consisting
of `%%', you can do this


     CREATE TABLE jokes
       (a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
       joke TEXT NOT NULL);
     LOAD DATA INFILE '/tmp/jokes.txt' INTO TABLE jokes
       FIELDS TERMINATED BY ''
       LINES TERMINATED BY '\n%%\n' (joke);

`FIELDS [OPTIONALLY] ENCLOSED BY' controls quoting of fields. For output
(*Note `SELECT ... INTO OUTFILE': select-into.), if you omit the word
`OPTIONALLY', all fields are enclosed by the `ENCLOSED BY' character.
An example of such output (using a comma as the field delimiter) is
shown here:


     "1","a string","100.20"
     "2","a string containing a , comma","102.20"
     "3","a string containing a \" quote","102.20"
     "4","a string containing a \", quote and comma","102.20"

If you specify `OPTIONALLY', the `ENCLOSED BY' character is used only
to enclose values from columns that have a string data type (such as
*Note `CHAR': char, *Note `BINARY': binary-varbinary, *Note `TEXT':
blob, or *Note `ENUM': enum.):


     1,"a string",100.20
     2,"a string containing a , comma",102.20
     3,"a string containing a \" quote",102.20
     4,"a string containing a \", quote and comma",102.20

Note that occurrences of the `ENCLOSED BY' character within a field
value are escaped by prefixing them with the `ESCAPED BY' character.
Also note that if you specify an empty `ESCAPED BY' value, it is
possible to inadvertently generate output that cannot be read properly
by *Note `LOAD DATA INFILE': load-data. For example, the preceding
output just shown would appear as follows if the escape character is
empty. Observe that the second field in the fourth line contains a comma
following the quote, which (erroneously) appears to terminate the field:


     1,"a string",100.20
     2,"a string containing a , comma",102.20
     3,"a string containing a " quote",102.20
     4,"a string containing a ", quote and comma",102.20

For input, the `ENCLOSED BY' character, if present, is stripped from
the ends of field values. (This is true regardless of whether
`OPTIONALLY' is specified; `OPTIONALLY' has no effect on input
interpretation.) Occurrences of the `ENCLOSED BY' character preceded by
the `ESCAPED BY' character are interpreted as part of the current field
value.

If the field begins with the `ENCLOSED BY' character, instances of that
character are recognized as terminating a field value only if followed
by the field or line `TERMINATED BY' sequence. To avoid ambiguity,
occurrences of the `ENCLOSED BY' character within a field value can be
doubled and are interpreted as a single instance of the character. For
example, if `ENCLOSED BY '"'' is specified, quotation marks are handled
as shown here:


     "The ""BIG"" boss"  -> The "BIG" boss
     The "BIG" boss      -> The "BIG" boss
     The ""BIG"" boss    -> The ""BIG"" boss

`FIELDS ESCAPED BY' controls how to read or write special characters:

   * For input, if the `FIELDS ESCAPED BY' character is not empty,
     occurrences of that character are stripped and the following
     character is taken literally as part of a field value. Some
     two-character sequences that are exceptions, where the first
     character is the escape character.  These sequences are shown in
     the following table (using ``\'' for the escape character).  The
     rules for `NULL' handling are described later in this section.

     This table lists two-character sequences for which the first
     character (a ``\'') is the escape character.

     Character  Escape Sequence
     `\0'       An ASCII NUL (`0x00') character
     `\b'       A backspace character
     `\n'       A newline (linefeed) character
     `\r'       A carriage return character
     `\t'       A tab character.
     `\Z'       ASCII 26 (Control+Z)
     `\N'       NULL

     For more information about ``\''-escape syntax, see *Note
     string-literals::.

     If the `FIELDS ESCAPED BY' character is empty, escape-sequence
     interpretation does not occur.

   * For output, if the `FIELDS ESCAPED BY' character is not empty, it
     is used to prefix the following characters on output:

        * The `FIELDS ESCAPED BY' character

        * The `FIELDS [OPTIONALLY] ENCLOSED BY' character

        * The first character of the `FIELDS TERMINATED BY' and `LINES
          TERMINATED BY' values

        * ASCII `0' (what is actually written following the escape
          character is ASCII ``0'', not a zero-valued byte)

     If the `FIELDS ESCAPED BY' character is empty, no characters are
     escaped and `NULL' is output as `NULL', not `\N'. It is probably
     not a good idea to specify an empty escape character, particularly
     if field values in your data contain any of the characters in the
     list just given.

In certain cases, field- and line-handling options interact:

   * If `LINES TERMINATED BY' is an empty string and `FIELDS TERMINATED
     BY' is nonempty, lines are also terminated with `FIELDS TERMINATED
     BY'.

   * If the `FIELDS TERMINATED BY' and `FIELDS ENCLOSED BY' values are
     both empty (`'''), a fixed-row (nondelimited) format is used. With
     fixed-row format, no delimiters are used between fields (but you
     can still have a line terminator). Instead, column values are read
     and written using a field width wide enough to hold all values in
     the field. For *Note `TINYINT': integer-types, *Note `SMALLINT':
     integer-types, *Note `MEDIUMINT': integer-types, *Note `INT':
     integer-types, and *Note `BIGINT': integer-types, the field widths
     are 4, 6, 8, 11, and 20, respectively, no matter what the declared
     display width is.

     `LINES TERMINATED BY' is still used to separate lines. If a line
     does not contain all fields, the rest of the columns are set to
     their default values. If you do not have a line terminator, you
     should set this to `'''. In this case, the text file must contain
     all fields for each row.

     Fixed-row format also affects handling of `NULL' values, as
     described later. Note that fixed-size format does not work if you
     are using a multibyte character set.

Handling of `NULL' values varies according to the `FIELDS' and `LINES'
options in use:

   * For the default `FIELDS' and `LINES' values, `NULL' is written as
     a field value of `\N' for output, and a field value of `\N' is
     read as `NULL' for input (assuming that the `ESCAPED BY' character
     is ``\'').

   * If `FIELDS ENCLOSED BY' is not empty, a field containing the
     literal word `NULL' as its value is read as a `NULL' value. This
     differs from the word `NULL' enclosed within `FIELDS ENCLOSED BY'
     characters, which is read as the string `'NULL''.

   * If `FIELDS ESCAPED BY' is empty, `NULL' is written as the word
     `NULL'.

   * With fixed-row format (which is used when `FIELDS TERMINATED BY'
     and `FIELDS ENCLOSED BY' are both empty), `NULL' is written as an
     empty string. Note that this causes both `NULL' values and empty
     strings in the table to be indistinguishable when written to the
     file because both are written as empty strings. If you need to be
     able to tell the two apart when reading the file back in, you
     should not use fixed-row format.

An attempt to load `NULL' into a `NOT NULL' column causes assignment of
the implicit default value for the column's data type and a warning, or
an error in strict SQL mode. Implicit default values are discussed in
*Note data-type-defaults::.

Some cases are not supported by *Note `LOAD DATA INFILE': load-data.:

   * Fixed-size rows (`FIELDS TERMINATED BY' and `FIELDS ENCLOSED BY'
     both empty) and *Note `BLOB': blob. or *Note `TEXT': blob. columns.

   * If you specify one separator that is the same as or a prefix of
     another, *Note `LOAD DATA INFILE': load-data. cannot interpret the
     input properly. For example, the following `FIELDS' clause would
     cause problems:


          FIELDS TERMINATED BY '"' ENCLOSED BY '"'

   * If `FIELDS ESCAPED BY' is empty, a field value that contains an
     occurrence of `FIELDS ENCLOSED BY' or `LINES TERMINATED BY'
     followed by the `FIELDS TERMINATED BY' value causes *Note `LOAD
     DATA INFILE': load-data. to stop reading a field or line too early.
     This happens because *Note `LOAD DATA INFILE': load-data. cannot
     properly determine where the field or line value ends.

The following example loads all columns of the `persondata' table:


     LOAD DATA INFILE 'persondata.txt' INTO TABLE persondata;

By default, when no column list is provided at the end of the *Note
`LOAD DATA INFILE': load-data. statement, input lines are expected to
contain a field for each table column. If you want to load only some of
a table's columns, specify a column list:


     LOAD DATA INFILE 'persondata.txt' INTO TABLE persondata (col1,col2,...);

You must also specify a column list if the order of the fields in the
input file differs from the order of the columns in the table.
Otherwise, MySQL cannot tell how to match input fields with table
columns.

The column list can contain either column names or user variables.
With user variables, the `SET' clause enables you to perform
transformations on their values before assigning the result to columns.

User variables in the `SET' clause can be used in several ways. The
following example uses the first input column directly for the value of
`t1.column1', and assigns the second input column to a user variable
that is subjected to a division operation before being used for the
value of `t1.column2':


     LOAD DATA INFILE 'file.txt'
       INTO TABLE t1
       (column1, @var1)
       SET column2 = @var1/100;

The `SET' clause can be used to supply values not derived from the
input file. The following statement sets `column3' to the current date
and time:


     LOAD DATA INFILE 'file.txt'
       INTO TABLE t1
       (column1, column2)
       SET column3 = CURRENT_TIMESTAMP;

You can also discard an input value by assigning it to a user variable
and not assigning the variable to a table column:


     LOAD DATA INFILE 'file.txt'
       INTO TABLE t1
       (column1, @dummy, column2, @dummy, column3);

Use of the column/variable list and `SET' clause is subject to the
following restrictions:

   * Assignments in the `SET' clause should have only column names on
     the left hand side of assignment operators.

   * You can use subqueries in the right hand side of `SET'
     assignments. A subquery that returns a value to be assigned to a
     column may be a scalar subquery only. Also, you cannot use a
     subquery to select from the table that is being loaded.

   * Lines ignored by an `IGNORE' clause are not processed for the
     column/variable list or `SET' clause.

   * User variables cannot be used when loading data with fixed-row
     format because user variables do not have a display width.

When processing an input line, *Note `LOAD DATA': load-data. splits it
into fields and uses the values according to the column/variable list
and the `SET' clause, if they are present. Then the resulting row is
inserted into the table. If there are `BEFORE INSERT' or `AFTER INSERT'
triggers for the table, they are activated before or after inserting
the row, respectively.

If an input line has too many fields, the extra fields are ignored and
the number of warnings is incremented.

If an input line has too few fields, the table columns for which input
fields are missing are set to their default values. Default value
assignment is described in *Note data-type-defaults::.

An empty field value is interpreted different from a missing field:

   * For string types, the column is set to the empty string.

   * For numeric types, the column is set to `0'.

   * For date and time types, the column is set to the appropriate
     `zero' value for the type. See *Note date-and-time-types::.

These are the same values that result if you assign an empty string
explicitly to a string, numeric, or date or time type explicitly in an
*Note `INSERT': insert. or *Note `UPDATE': update. statement.

Treatment of empty or incorrect field values differs from that just
described if the SQL mode is set to a restrictive value. For example, if
`sql_mode='TRADITIONAL', conversion of an empty value or a value such
as `'x'' for a numeric column results in an error, not conversion to 0.
(With `LOCAL', warnings occur rather than errors, even with a
restrictive `sql_mode' value, because the server has no way to stop
transmission of the file in the middle of the operation.)

*Note `TIMESTAMP': datetime. columns are set to the current date and
time only if there is a `NULL' value for the column (that is, `\N') and
the column is not declared to permit `NULL' values, or if the *Note
`TIMESTAMP': datetime. column's default value is the current timestamp
and it is omitted from the field list when a field list is specified.

*Note `LOAD DATA INFILE': load-data. regards all input as strings, so
you cannot use numeric values for *Note `ENUM': enum. or *Note `SET':
set. columns the way you can with *Note `INSERT': insert. statements.
All *Note `ENUM': enum. and *Note `SET': set. values must be specified
as strings.

*Note `BIT': bit-type. values cannot be loaded using binary notation
(for example, `b'011010''). To work around this, specify the values as
regular integers and use the `SET' clause to convert them so that MySQL
performs a numeric type conversion and loads them into the *Note `BIT':
bit-type. column properly:


     shell> cat /tmp/bit_test.txt
     2
     127
     shell> mysql test
     mysql> LOAD DATA INFILE '/tmp/bit_test.txt'
         -> INTO TABLE bit_test (@var1) SET b = CAST(@var1 AS UNSIGNED);
     Query OK, 2 rows affected (0.00 sec)
     Records: 2  Deleted: 0  Skipped: 0  Warnings: 0

     mysql> SELECT BIN(b+0) FROM bit_test;
     +----------+
     | bin(b+0) |
     +----------+
     | 10       |
     | 1111111  |
     +----------+
     2 rows in set (0.00 sec)

On Unix, if you need *Note `LOAD DATA': load-data. to read from a pipe,
you can use the following technique (the example loads a listing of the
`/' directory into the table `db1.t1'):


     mkfifo /mysql/data/db1/ls.dat
     chmod 666 /mysql/data/db1/ls.dat
     find / -ls > /mysql/data/db1/ls.dat &
     mysql -e "LOAD DATA INFILE 'ls.dat' INTO TABLE t1" db1

Note that you must run the command that generates the data to be loaded
and the *Note `mysql': mysql. commands either on separate terminals, or
run the data generation process in the background (as shown in the
preceding example). If you do not do this, the pipe will block until
data is read by the *Note `mysql': mysql. process.

When the *Note `LOAD DATA INFILE': load-data. statement finishes, it
returns an information string in the following format:


     Records: 1  Deleted: 0  Skipped: 0  Warnings: 0

Warnings occur under the same circumstances as when values are inserted
using the *Note `INSERT': insert. statement (see *Note insert::),
except that *Note `LOAD DATA INFILE': load-data. also generates
warnings when there are too few or too many fields in the input row.

You can use *Note `SHOW WARNINGS': show-warnings. to get a list of the
first `max_error_count' warnings as information about what went wrong.
See *Note show-warnings::.

If you are using the C API, you can get information about the statement
by calling the *Note `mysql_info()': mysql-info. function. See *Note
mysql-info::.

For partitioned tables using storage engines that employ table locks,
such as *Note `MyISAM': myisam-storage-engine, any locks caused by
`LOAD DATA' perform locks on all partitions of the table. This does not
apply to tables using storage engines which employ row-level locking,
such as *Note `InnoDB': innodb-storage-engine. For more information, see
*Note partitioning-limitations-locking::.


File: manual.info,  Node: replace,  Next: select,  Prev: load-data,  Up: sql-syntax-data-manipulation

13.2.7 REPLACE Syntax
---------------------


     REPLACE [LOW_PRIORITY | DELAYED]
         [INTO] TBL_NAME [(COL_NAME,...)]
         {VALUES | VALUE} ({EXPR | DEFAULT},...),(...),...

Or:


     REPLACE [LOW_PRIORITY | DELAYED]
         [INTO] TBL_NAME
         SET COL_NAME={EXPR | DEFAULT}, ...

Or:


     REPLACE [LOW_PRIORITY | DELAYED]
         [INTO] TBL_NAME [(COL_NAME,...)]
         SELECT ...

*Note `REPLACE': replace. works exactly like *Note `INSERT': insert,
except that if an old row in the table has the same value as a new row
for a `PRIMARY KEY' or a `UNIQUE' index, the old row is deleted before
the new row is inserted. See *Note insert::.

*Note `REPLACE': replace. is a MySQL extension to the SQL standard. It
either inserts, or _deletes_ and inserts. For another MySQL extension
to standard SQL--that either inserts or _updates_--see *Note
insert-on-duplicate::.

Note that unless the table has a `PRIMARY KEY' or `UNIQUE' index, using
a *Note `REPLACE': replace. statement makes no sense.  It becomes
equivalent to *Note `INSERT': insert, because there is no index to be
used to determine whether a new row duplicates another.

Values for all columns are taken from the values specified in the *Note
`REPLACE': replace. statement. Any missing columns are set to their
default values, just as happens for *Note `INSERT': insert. You cannot
refer to values from the current row and use them in the new row. If
you use an assignment such as `SET COL_NAME = COL_NAME + 1', the
reference to the column name on the right hand side is treated as
`DEFAULT(COL_NAME)', so the assignment is equivalent to `SET COL_NAME =
DEFAULT(COL_NAME) + 1'.

To use *Note `REPLACE': replace, you must have both the `INSERT' and
`DELETE' privileges for the table.

The *Note `REPLACE': replace. statement returns a count to indicate the
number of rows affected. This is the sum of the rows deleted and
inserted. If the count is 1 for a single-row *Note `REPLACE': replace,
a row was inserted and no rows were deleted. If the count is greater
than 1, one or more old rows were deleted before the new row was
inserted. It is possible for a single row to replace more than one old
row if the table contains multiple unique indexes and the new row
duplicates values for different old rows in different unique indexes.

The affected-rows count makes it easy to determine whether *Note
`REPLACE': replace. only added a row or whether it also replaced any
rows: Check whether the count is 1 (added) or greater (replaced).

If you are using the C API, the affected-rows count can be obtained
using the *Note `mysql_affected_rows()': mysql-affected-rows. function.

Currently, you cannot replace into a table and select from the same
table in a subquery.

MySQL uses the following algorithm for *Note `REPLACE': replace. (and
`LOAD DATA ...  REPLACE'):

  1. Try to insert the new row into the table

  2. While the insertion fails because a duplicate-key error occurs for
     a primary key or unique index:

       1. Delete from the table the conflicting row that has the
          duplicate key value

       2. Try again to insert the new row into the table

It is possible that in the case of a duplicate-key error, a storage
engine may perform the `REPLACE' as an update rather than a delete plus
insert, but the semantics are the same. There are no user-visible
effects other than a possible difference in how the storage engine
increments `Handler_XXX' status variables.

When modifying an existing table that is not partitioned to accommodate
partitioning, or, when modifying the partitioning of an already
partitioned table, you may consider altering the table's primary key
(see *Note partitioning-limitations-partitioning-keys-unique-keys::).
You should be aware that, if you do this, the results of `REPLACE'
statements may be affected, just as they would be if you modified the
primary key of a nonpartitioned table. Consider the table created by
the following *Note `CREATE TABLE': create-table. statement:


     CREATE TABLE test (
       id INT UNSIGNED NOT NULL AUTO_INCREMENT,
       data VARCHAR(64) DEFAULT NULL,
       ts TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
       PRIMARY KEY (id)
     );

When we create this table and run the statements shown in the mysql
client, the result is as follows:


     mysql> REPLACE INTO test VALUES (1, 'Old', '2014-08-20 18:47:00');
     Query OK, 1 row affected (0.04 sec)

     mysql> REPLACE INTO test VALUES (1, 'New', '2014-08-20 18:47:42');
     Query OK, 2 rows affected (0.04 sec)

     mysql> SELECT * FROM test;
     +----+------+---------------------+
     | id | data | ts                  |
     +----+------+---------------------+
     |  1 | New  | 2014-08-20 18:47:42 |
     +----+------+---------------------+
     1 row in set (0.00 sec)

Now we create a second table almost identical to the first, except that
the primary key now covers 2 columns, as shown here (emphasized text):


     CREATE TABLE test2 (
       id INT UNSIGNED NOT NULL AUTO_INCREMENT,
       data VARCHAR(64) DEFAULT NULL,
       ts TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
       _PRIMARY KEY (id, ts)_
     );

When we run on `test2' the same two `REPLACE' statements as we did on
the original `test' table, we obtain a different result:


     mysql> REPLACE INTO test2 VALUES (1, 'Old', '2014-08-20 18:47:00');
     Query OK, 1 row affected (0.05 sec)

     mysql> REPLACE INTO test2 VALUES (1, 'New', '2014-08-20 18:47:42');
     Query OK, 1 row affected (0.06 sec)

     mysql> SELECT * FROM test2;
     +----+------+---------------------+
     | id | data | ts                  |
     +----+------+---------------------+
     |  1 | Old  | 2014-08-20 18:47:00 |
     |  1 | New  | 2014-08-20 18:47:42 |
     +----+------+---------------------+
     2 rows in set (0.00 sec)

This is due to the fact that, when run on `test2', both the `id' and
`ts' column values must match those of an existing row for the row to
be replaced; otherwise, a row is inserted.

A `REPLACE' statement that acts on a partitioned table using a storage
engine such as *Note `MyISAM': myisam-storage-engine. that employs
table-level locks locks all partitions of the table. This does not
occur with tables using storage engines such as *Note `InnoDB':
innodb-storage-engine.  that employ row-level locking. This issue is
resolved in MySQL 5.6. See *Note partitioning-limitations-locking::, for
more information.


File: manual.info,  Node: select,  Next: subqueries,  Prev: replace,  Up: sql-syntax-data-manipulation

13.2.8 SELECT Syntax
--------------------

* Menu:

* select-into::                  SELECT ... INTO Syntax
* join::                         JOIN Syntax
* index-hints::                  Index Hint Syntax
* union::                        UNION Syntax


     SELECT
         [ALL | DISTINCT | DISTINCTROW ]
           [HIGH_PRIORITY]
           [STRAIGHT_JOIN]
           [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
           [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
         SELECT_EXPR [, SELECT_EXPR ...]
         [FROM TABLE_REFERENCES
         [WHERE WHERE_CONDITION]
         [GROUP BY {COL_NAME | EXPR | POSITION}
           [ASC | DESC], ... [WITH ROLLUP]]
         [HAVING WHERE_CONDITION]
         [ORDER BY {COL_NAME | EXPR | POSITION}
           [ASC | DESC], ...]
         [LIMIT {[OFFSET,] ROW_COUNT | ROW_COUNT OFFSET OFFSET}]
         [PROCEDURE PROCEDURE_NAME(ARGUMENT_LIST)]
         [INTO OUTFILE 'FILE_NAME'
             [CHARACTER SET CHARSET_NAME]
             EXPORT_OPTIONS
           | INTO DUMPFILE 'FILE_NAME'
           | INTO VAR_NAME [, VAR_NAME]]
         [FOR UPDATE | LOCK IN SHARE MODE]]

*Note `SELECT': select. is used to retrieve rows selected from one or
more tables, and can include *Note `UNION': union. statements and
subqueries.  See *Note union::, and *Note subqueries::.

The most commonly used clauses of *Note `SELECT': select. statements
are these:

   * Each SELECT_EXPR indicates a column that you want to retrieve.
     There must be at least one SELECT_EXPR.

   * TABLE_REFERENCES indicates the table or tables from which to
     retrieve rows. Its syntax is described in *Note join::.

   * The `WHERE' clause, if given, indicates the condition or
     conditions that rows must satisfy to be selected.  WHERE_CONDITION
     is an expression that evaluates to true for each row to be
     selected. The statement selects all rows if there is no `WHERE'
     clause.

     In the `WHERE' expression, you can use any of the functions and
     operators that MySQL supports, except for aggregate (summary)
     functions. See *Note expressions::, and *Note functions::.

*Note `SELECT': select. can also be used to retrieve rows computed
without reference to any table.

For example:


     mysql> SELECT 1 + 1;
             -> 2

You are permitted to specify `DUAL' as a dummy table name in situations
where no tables are referenced:


     mysql> SELECT 1 + 1 FROM DUAL;
             -> 2

`DUAL' is purely for the convenience of people who require that all
*Note `SELECT': select.  statements should have `FROM' and possibly
other clauses. MySQL may ignore the clauses. MySQL does not require
`FROM DUAL' if no tables are referenced.

In general, clauses used must be given in exactly the order shown in
the syntax description. For example, a `HAVING' clause must come after
any `GROUP BY' clause and before any `ORDER BY' clause. The exception
is that the `INTO' clause can appear either as shown in the syntax
description or immediately following the SELECT_EXPR list. For more
information about `INTO', see *Note select-into::.

The list of SELECT_EXPR terms comprises the select list that indicates
which columns to retrieve. Terms specify a column or expression or can
use `*'-shorthand:

   * A select list consisting only of a single unqualified `*' can be
     used as shorthand to select all columns from all tables:


          SELECT * FROM t1 INNER JOIN t2 ...

   * `TBL_NAME.*' can be used as a qualified shorthand to select all
     columns from the named table:


          SELECT t1.*, t2.* FROM t1 INNER JOIN t2 ...

   * Use of an unqualified `*' with other items in the select list may
     produce a parse error. To avoid this problem, use a qualified
     `TBL_NAME.*' reference


          SELECT AVG(score), t1.* FROM t1 ...

The following list provides additional information about other `SELECT'
clauses:

   * A SELECT_EXPR can be given an alias using `AS ALIAS_NAME'. The
     alias is used as the expression's column name and can be used in
     `GROUP BY', `ORDER BY', or `HAVING' clauses. For example:


          SELECT CONCAT(last_name,', ',first_name) AS full_name
            FROM mytable ORDER BY full_name;

     The `AS' keyword is optional when aliasing a SELECT_EXPR with an
     identifier. The preceding example could have been written like
     this:


          SELECT CONCAT(last_name,', ',first_name) full_name
            FROM mytable ORDER BY full_name;

     However, because the `AS' is optional, a subtle problem can occur
     if you forget the comma between two SELECT_EXPR expressions: MySQL
     interprets the second as an alias name. For example, in the
     following statement, `columnb' is treated as an alias name:


          SELECT columna columnb FROM mytable;

     For this reason, it is good practice to be in the habit of using
     `AS' explicitly when specifying column aliases.

     It is not permissible to refer to a column alias in a `WHERE'
     clause, because the column value might not yet be determined when
     the `WHERE' clause is executed. See *Note problems-with-alias::.

   * The `FROM TABLE_REFERENCES' clause indicates the table or tables
     from which to retrieve rows. If you name more than one table, you
     are performing a join. For information on join syntax, see *Note
     join::. For each table specified, you can optionally specify an
     alias.


          TBL_NAME [[AS] ALIAS] [INDEX_HINT]

     The use of index hints provides the optimizer with information
     about how to choose indexes during query processing. For a
     description of the syntax for specifying these hints, see *Note
     index-hints::.

     You can use `SET max_seeks_for_key=VALUE' as an alternative way to
     force MySQL to prefer key scans instead of table scans. See *Note
     server-system-variables::.

   * You can refer to a table within the default database as TBL_NAME,
     or as DB_NAME.TBL_NAME to specify a database explicitly. You can
     refer to a column as COL_NAME, TBL_NAME.COL_NAME, or
     DB_NAME.TBL_NAME.COL_NAME.  You need not specify a TBL_NAME or
     DB_NAME.TBL_NAME prefix for a column reference unless the
     reference would be ambiguous. See *Note identifier-qualifiers::,
     for examples of ambiguity that require the more explicit column
     reference forms.

   * A table reference can be aliased using `TBL_NAME AS ALIAS_NAME' or
     TBL_NAME ALIAS_NAME:


          SELECT t1.name, t2.salary FROM employee AS t1, info AS t2
            WHERE t1.name = t2.name;

          SELECT t1.name, t2.salary FROM employee t1, info t2
            WHERE t1.name = t2.name;

   * Columns selected for output can be referred to in `ORDER BY' and
     `GROUP BY' clauses using column names, column aliases, or column
     positions. Column positions are integers and begin with 1:


          SELECT college, region, seed FROM tournament
            ORDER BY region, seed;

          SELECT college, region AS r, seed AS s FROM tournament
            ORDER BY r, s;

          SELECT college, region, seed FROM tournament
            ORDER BY 2, 3;

     To sort in reverse order, add the `DESC' (descending) keyword to
     the name of the column in the `ORDER BY' clause that you are
     sorting by.  The default is ascending order; this can be specified
     explicitly using the `ASC' keyword.

     If `ORDER BY' occurs within a subquery and also is applied in the
     outer query, the outermost `ORDER BY' takes precedence. For
     example, results for the following statement are sorted in
     descending order, not ascending order:


          (SELECT ... ORDER BY a) ORDER BY a DESC;

     Use of column positions is deprecated because the syntax has been
     removed from the SQL standard.

   * If you use `GROUP BY', output rows are sorted according to the
     `GROUP BY' columns as if you had an `ORDER BY' for the same
     columns. To avoid the overhead of sorting that `GROUP BY'
     produces, add `ORDER BY NULL':


          SELECT a, COUNT(b) FROM test_table GROUP BY a ORDER BY NULL;

   * MySQL extends the `GROUP BY' clause so that you can also specify
     `ASC' and `DESC' after columns named in the clause:


          SELECT a, COUNT(b) FROM test_table GROUP BY a DESC;

   * MySQL extends the use of `GROUP BY' to permit selecting fields
     that are not mentioned in the `GROUP BY' clause. If you are not
     getting the results that you expect from your query, please read
     the description of `GROUP BY' found in *Note
     group-by-functions-and-modifiers::.

   * `GROUP BY' permits a `WITH ROLLUP' modifier. See *Note
     group-by-modifiers::.

   * The `HAVING' clause is applied nearly last, just before items are
     sent to the client, with no optimization. (`LIMIT' is applied after
     `HAVING'.)

     The SQL standard requires that `HAVING' must reference only
     columns in the `GROUP BY' clause or columns used in aggregate
     functions. However, MySQL supports an extension to this behavior,
     and permits `HAVING' to refer to columns in the *Note `SELECT':
     select. list and columns in outer subqueries as well.

     If the `HAVING' clause refers to a column that is ambiguous, a
     warning occurs. In the following statement, `col2' is ambiguous
     because it is used as both an alias and a column name:


          SELECT COUNT(col1) AS col2 FROM t GROUP BY col2 HAVING col2 = 2;

     Preference is given to standard SQL behavior, so if a `HAVING'
     column name is used both in `GROUP BY' and as an aliased column in
     the output column list, preference is given to the column in the
     `GROUP BY' column.

   * Do not use `HAVING' for items that should be in the `WHERE'
     clause. For example, do not write the following:


          SELECT COL_NAME FROM TBL_NAME HAVING COL_NAME > 0;

     Write this instead:


          SELECT COL_NAME FROM TBL_NAME WHERE COL_NAME > 0;

   * The `HAVING' clause can refer to aggregate functions, which the
     `WHERE' clause cannot:


          SELECT user, MAX(salary) FROM users
            GROUP BY user HAVING MAX(salary) > 10;

     (This did not work in some older versions of MySQL.)

   * MySQL permits duplicate column names. That is, there can be more
     than one SELECT_EXPR with the same name. This is an extension to
     standard SQL. Because MySQL also permits `GROUP BY' and `HAVING'
     to refer to SELECT_EXPR values, this can result in an ambiguity:


          SELECT 12 AS a, a FROM t GROUP BY a;

     In that statement, both columns have the name `a'. To ensure that
     the correct column is used for grouping, use different names for
     each SELECT_EXPR.

   * MySQL resolves unqualified column or alias references in `ORDER
     BY' clauses by searching in the SELECT_EXPR values, then in the
     columns of the tables in the `FROM' clause.  For `GROUP BY' or
     `HAVING' clauses, it searches the `FROM' clause before searching
     in the SELECT_EXPR values. (For `GROUP BY' and `HAVING', this
     differs from the pre-MySQL 5.0 behavior that used the same rules
     as for `ORDER BY'.)

   * The `LIMIT' clause can be used to constrain the number of rows
     returned by the *Note `SELECT': select. statement.  `LIMIT' takes
     one or two numeric arguments, which must both be nonnegative
     integer constants (except when using prepared statements).

     With two arguments, the first argument specifies the offset of the
     first row to return, and the second specifies the maximum number
     of rows to return. The offset of the initial row is 0 (not 1):


          SELECT * FROM tbl LIMIT 5,10;  # Retrieve rows 6-15

     To retrieve all rows from a certain offset up to the end of the
     result set, you can use some large number for the second
     parameter. This statement retrieves all rows from the 96th row to
     the last:


          SELECT * FROM tbl LIMIT 95,18446744073709551615;

     With one argument, the value specifies the number of rows to
     return from the beginning of the result set:


          SELECT * FROM tbl LIMIT 5;     # Retrieve first 5 rows

     In other words, `LIMIT ROW_COUNT' is equivalent to `LIMIT 0,
     ROW_COUNT'.

     For prepared statements, you can use placeholders. The following
     statements will return one row from the `tbl' table:


          SET @a=1;
          PREPARE STMT FROM 'SELECT * FROM tbl LIMIT ?';
          EXECUTE STMT USING @a;

     The following statements will return the second to sixth row from
     the `tbl' table:


          SET @skip=1; SET @numrows=5;
          PREPARE STMT FROM 'SELECT * FROM tbl LIMIT ?, ?';
          EXECUTE STMT USING @skip, @numrows;

     For compatibility with PostgreSQL, MySQL also supports the `LIMIT
     ROW_COUNT OFFSET OFFSET' syntax.

     If `LIMIT' occurs within a subquery and also is applied in the
     outer query, the outermost `LIMIT' takes precedence. For example,
     the following statement produces two rows, not one:


          (SELECT ... LIMIT 1) LIMIT 2;

   * A `PROCEDURE' clause names a procedure that should process the
     data in the result set. For an example, see *Note
     procedure-analyse::, which describes `ANALYSE', a procedure that
     can be used to obtain suggestions for optimal column data types
     that may help reduce table sizes.

   * The *Note `SELECT ... INTO': select-into. form of *Note `SELECT':
     select.  enables the query result to be written to a file or
     stored in variables. For more information, see *Note select-into::.

   * If you use `FOR UPDATE' with a storage engine that uses page or
     row locks, rows examined by the query are write-locked until the
     end of the current transaction. Using `LOCK IN SHARE MODE' sets a
     shared lock that permits other transactions to read the examined
     rows but not to update or delete them. See *Note
     innodb-locking-reads::.

Following the *Note `SELECT': select. keyword, you can use a number of
options that affect the operation of the statement. `HIGH_PRIORITY',
`STRAIGHT_JOIN', and options beginning with `SQL_' are MySQL extensions
to standard SQL.

   * The `ALL' and `DISTINCT' options specify whether duplicate rows
     should be returned.  `ALL' (the default) specifies that all
     matching rows should be returned, including duplicates.
     `DISTINCT' specifies removal of duplicate rows from the result
     set. It is an error to specify both options. `DISTINCTROW' is a
     synonym for `DISTINCT'.

   * `HIGH_PRIORITY' gives the *Note `SELECT': select. higher priority
     than a statement that updates a table. You should use this only for
     queries that are very fast and must be done at once. A `SELECT
     HIGH_PRIORITY' query that is issued while the table is locked for
     reading runs even if there is an update statement waiting for the
     table to be free. This affects only storage engines that use only
     table-level locking (such as `MyISAM', `MEMORY', and `MERGE').

     `HIGH_PRIORITY' cannot be used with *Note `SELECT': select.
     statements that are part of a *Note `UNION': union.

   * `STRAIGHT_JOIN' forces the optimizer to join the tables in the
     order in which they are listed in the `FROM' clause. You can use
     this to speed up a query if the optimizer joins the tables in
     nonoptimal order.  `STRAIGHT_JOIN' also can be used in the
     TABLE_REFERENCES list. See *Note join::.

     `STRAIGHT_JOIN' does not apply to any table that the optimizer
     treats as a `const' or `system' table. Such a table produces a
     single row, is read during the optimization phase of query
     execution, and references to its columns are replaced with the
     appropriate column values before query execution proceeds. These
     tables will appear first in the query plan displayed by *Note
     `EXPLAIN': explain. See *Note using-explain::. This exception may
     not apply to `const' or `system' tables that are used on the
     `NULL'-complemented side of an outer join (that is, the right-side
     table of a `LEFT JOIN' or the left-side table of a `RIGHT JOIN'.

   * `SQL_BIG_RESULT' or `SQL_SMALL_RESULT' can be used with `GROUP BY'
     or `DISTINCT' to tell the optimizer that the result set has many
     rows or is small, respectively. For `SQL_BIG_RESULT', MySQL
     directly uses disk-based temporary tables if needed, and prefers
     sorting to using a temporary table with a key on the `GROUP BY'
     elements. For `SQL_SMALL_RESULT', MySQL uses fast temporary tables
     to store the resulting table instead of using sorting.  This
     should not normally be needed.

   * `SQL_BUFFER_RESULT' forces the result to be put into a temporary
     table. This helps MySQL free the table locks early and helps in
     cases where it takes a long time to send the result set to the
     client. This option can be used only for top-level *Note `SELECT':
     select.  statements, not for subqueries or following *Note
     `UNION': union.

   * `SQL_CALC_FOUND_ROWS' tells MySQL to calculate how many rows there
     would be in the result set, disregarding any `LIMIT' clause. The
     number of rows can then be retrieved with `SELECT FOUND_ROWS()'.
     See *Note information-functions::.

   * The `SQL_CACHE' and `SQL_NO_CACHE' options affect caching of query
     results in the query cache (see *Note query-cache::). `SQL_CACHE'
     tells MySQL to store the result in the query cache if it is
     cacheable and the value of the `query_cache_type' system variable
     is `2' or `DEMAND'.  With `SQL_NO_CACHE', the server does not use
     the query cache. It neither checks the query cache to see whether
     the result is already cached, nor does it cache the query result.
     (Due to a limitation in the parser, a space character must precede
     and follow the `SQL_NO_CACHE' keyword; a nonspace such as a
     newline causes the server to check the query cache to see whether
     the result is already cached.)

     For a query that uses *Note `UNION': union, subqueries, or views,
     the following rules apply:

        * `SQL_NO_CACHE' applies if it appears in any *Note `SELECT':
          select. in the query.

        * For a cacheable query, `SQL_CACHE' applies if it appears in
          the first *Note `SELECT': select. of the query, or in the
          first *Note `SELECT': select. of a view referred to by the
          query.

A `SELECT' from a partitioned table using a storage engine such as
*Note `MyISAM': myisam-storage-engine. that employs table-level locks
locks all partitions of the table. This does not occur with tables
using storage engines such as *Note `InnoDB': innodb-storage-engine.
that employ row-level locking.  This issue is resolved in MySQL 5.6. See
*Note partitioning-limitations-locking::, for more information.


File: manual.info,  Node: select-into,  Next: join,  Prev: select,  Up: select

13.2.8.1 SELECT ... INTO Syntax
...............................

The *Note `SELECT ... INTO': select-into. form of *Note `SELECT':
select.  enables a query result to be stored in variables or written to
a file:

   * `SELECT ... INTO VAR_LIST' selects column values and stores them
     into variables.

   * `SELECT ... INTO OUTFILE' writes the selected rows to a file.
     Column and line terminators can be specified to produce a specific
     output format.

   * `SELECT ... INTO DUMPFILE' writes a single row to a file without
     any formatting.

The *Note `SELECT': select. syntax description (see *Note select::)
shows the `INTO' clause near the end of the statement. It is also
possible to use `INTO' immediately following the SELECT_EXPR list.

An `INTO' clause should not be used in a nested *Note `SELECT': select.
because such a *Note `SELECT': select. must return its result to the
outer context.

The `INTO' clause can name a list of one or more variables, which can
be user-defined variables, stored procedure or function parameters, or
stored program local variables. (Within a prepared `SELECT ... INTO
OUTFILE' statement, only user-defined variables are permitted;see *Note
local-variable-scope::.)

The selected values are assigned to the variables. The number of
variables must match the number of columns. The query should return a
single row. If the query returns no rows, a warning with error code
1329 occurs (`No data'), and the variable values remain unchanged. If
the query returns multiple rows, error 1172 occurs (`Result consisted of
more than one row'). If it is possible that the statement may retrieve
multiple rows, you can use `LIMIT 1' to limit the result set to a
single row.


     SELECT id, data INTO @x, @y FROM test.t1 LIMIT 1;

User variable names are not case sensitive. See *Note user-variables::.

The *Note `SELECT ... INTO OUTFILE 'FILE_NAME'': select-into. form of
*Note `SELECT': select. writes the selected rows to a file. The file is
created on the server host, so you must have the `FILE' privilege to use
this syntax. FILE_NAME cannot be an existing file, which among other
things prevents files such as `/etc/passwd' and database tables from
being destroyed. As of MySQL 5.1.6, the `character_set_filesystem'
system variable controls the interpretation of the file name.

The *Note `SELECT ... INTO OUTFILE': select-into. statement is intended
primarily to let you very quickly dump a table to a text file on the
server machine.  If you want to create the resulting file on some other
host than the server host, you normally cannot use *Note `SELECT ...
INTO OUTFILE': select-into. since there is no way to write a path to the
file relative to the server host's file system.

However, if the MySQL client software is installed on the remote
machine, you can instead use a client command such as `mysql -e "SELECT
..." > FILE_NAME' to generate the file on the client host.

It is also possible to create the resulting file on a different host
other than the server host, if the location of the file on the remote
host can be accessed using a network-mapped path on the server's file
system. In this case, the presence of *Note `mysql': mysql. (or some
other MySQL client program) is not required on the target host.

*Note `SELECT ... INTO OUTFILE': select-into. is the complement of
*Note `LOAD DATA INFILE': load-data. Column values are written
converted to the character set specified in the `CHARACTER SET' clause,
which is available as of MySQL 5.1.38. Prior to 5.1.38 or if no such
clause is present, values are dumped using the `binary' character set.
In effect, there is no character set conversion. If a result set
contains columns in several character sets, the output data file will
as well and you may not be able to reload the file correctly.

The syntax for the EXPORT_OPTIONS part of the statement consists of the
same `FIELDS' and `LINES' clauses that are used with the *Note `LOAD
DATA INFILE': load-data. statement. See *Note load-data::, for
information about the `FIELDS' and `LINES' clauses, including their
default values and permissible values.

`FIELDS ESCAPED BY' controls how to write special characters. If the
`FIELDS ESCAPED BY' character is not empty, it is used when necessary
to avoid ambiguity as a prefix that precedes following characters on
output:

   * The `FIELDS ESCAPED BY' character

   * The `FIELDS [OPTIONALLY] ENCLOSED BY' character

   * The first character of the `FIELDS TERMINATED BY' and `LINES
     TERMINATED BY' values

   * ASCII `NUL' (the zero-valued byte; what is actually written
     following the escape character is ASCII ``0'', not a zero-valued
     byte)

The `FIELDS TERMINATED BY', `ENCLOSED BY', `ESCAPED BY', or `LINES
TERMINATED BY' characters _must_ be escaped so that you can read the
file back in reliably. ASCII `NUL' is escaped to make it easier to view
with some pagers.

The resulting file does not have to conform to SQL syntax, so nothing
else need be escaped.

If the `FIELDS ESCAPED BY' character is empty, no characters are
escaped and `NULL' is output as `NULL', not `\N'. It is probably not a
good idea to specify an empty escape character, particularly if field
values in your data contain any of the characters in the list just
given.

Here is an example that produces a file in the comma-separated values
(CSV) format used by many programs:


     SELECT a,b,a+b INTO OUTFILE '/tmp/result.txt'
       FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
       LINES TERMINATED BY '\n'
       FROM test_table;

If you use `INTO DUMPFILE' instead of `INTO OUTFILE', MySQL writes only
one row into the file, without any column or line termination and
without performing any escape processing. This is useful if you want to
store a *Note `BLOB': blob. value in a file.

*Note*:

Any file created by `INTO OUTFILE' or `INTO DUMPFILE' is writable by
all users on the server host. The reason for this is that the MySQL
server cannot create a file that is owned by anyone other than the user
under whose account it is running. (You should _never_ run *Note
`mysqld': mysqld. as `root' for this and other reasons.) The file thus
must be world-writable so that you can manipulate its contents.

If the `secure_file_priv' system variable is set to a nonempty
directory name, the file to be written must be located in that
directory.

In the context of *Note `SELECT ... INTO': select-into. statements that
occur as part of events executed by the Event Scheduler, diagnostics
messages (not only errors, but also warnings) are written to the error
log, and, on Windows, to the application event log. For additional
information, see *Note events-status-info::.


File: manual.info,  Node: join,  Next: index-hints,  Prev: select-into,  Up: select

13.2.8.2 JOIN Syntax
....................

MySQL supports the following `JOIN' syntaxes for the TABLE_REFERENCES
part of *Note `SELECT': select. statements and multiple-table *Note
`DELETE': delete. and *Note `UPDATE': update. statements:


     TABLE_REFERENCES:
         ESCAPED_TABLE_REFERENCE [, ESCAPED_TABLE_REFERENCE] ...

     ESCAPED_TABLE_REFERENCE:
         TABLE_REFERENCE
       | { OJ TABLE_REFERENCE }

     TABLE_REFERENCE:
         TABLE_FACTOR
       | JOIN_TABLE

     TABLE_FACTOR:
         TBL_NAME [[AS] ALIAS] [INDEX_HINT_LIST]
       | TABLE_SUBQUERY [AS] ALIAS
       | ( TABLE_REFERENCES )

     JOIN_TABLE:
         TABLE_REFERENCE [INNER | CROSS] JOIN TABLE_FACTOR [JOIN_CONDITION]
       | TABLE_REFERENCE STRAIGHT_JOIN TABLE_FACTOR
       | TABLE_REFERENCE STRAIGHT_JOIN TABLE_FACTOR ON CONDITIONAL_EXPR
       | TABLE_REFERENCE {LEFT|RIGHT} [OUTER] JOIN TABLE_REFERENCE JOIN_CONDITION
       | TABLE_REFERENCE NATURAL [{LEFT|RIGHT} [OUTER]] JOIN TABLE_FACTOR

     JOIN_CONDITION:
         ON CONDITIONAL_EXPR
       | USING (COLUMN_LIST)

     INDEX_HINT_LIST:
         INDEX_HINT [, INDEX_HINT] ...

     INDEX_HINT:
         USE {INDEX|KEY}
           [FOR {JOIN|ORDER BY|GROUP BY}] ([INDEX_LIST])
       | IGNORE {INDEX|KEY}
           [FOR {JOIN|ORDER BY|GROUP BY}] (INDEX_LIST)
       | FORCE {INDEX|KEY}
           [FOR {JOIN|ORDER BY|GROUP BY}] (INDEX_LIST)

     INDEX_LIST:
         INDEX_NAME [, INDEX_NAME] ...

A table reference is also known as a join expression.

The syntax of TABLE_FACTOR is extended in comparison with the SQL
Standard. The latter accepts only TABLE_REFERENCE, not a list of them
inside a pair of parentheses.

This is a conservative extension if we consider each comma in a list of
TABLE_REFERENCE items as equivalent to an inner join. For example:


     SELECT * FROM t1 LEFT JOIN (t2, t3, t4)
                      ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

is equivalent to:


     SELECT * FROM t1 LEFT JOIN (t2 CROSS JOIN t3 CROSS JOIN t4)
                      ON (t2.a=t1.a AND t3.b=t1.b AND t4.c=t1.c)

In MySQL, `JOIN', `CROSS JOIN', and `INNER JOIN' are syntactic
equivalents (they can replace each other). In standard SQL, they are
not equivalent. `INNER JOIN' is used with an `ON' clause, `CROSS JOIN'
is used otherwise.

In general, parentheses can be ignored in join expressions containing
only inner join operations. MySQL also supports nested joins (see *Note
nested-join-optimization::).

Index hints can be specified to affect how the MySQL optimizer makes
use of indexes. For more information, see *Note index-hints::.

The following list describes general factors to take into account when
writing joins.

   * A table reference can be aliased using `TBL_NAME AS ALIAS_NAME' or
     TBL_NAME ALIAS_NAME:


          SELECT t1.name, t2.salary
            FROM employee AS t1 INNER JOIN info AS t2 ON t1.name = t2.name;

          SELECT t1.name, t2.salary
            FROM employee t1 INNER JOIN info t2 ON t1.name = t2.name;

   * A TABLE_SUBQUERY is also known as a subquery in the `FROM' clause.
     Such subqueries _must_ include an alias to give the subquery
     result a table name. A trivial example follows; see also *Note
     from-clause-subqueries::.


          SELECT * FROM (SELECT 1, 2, 3) AS t1;

   * `INNER JOIN' and `,' (comma) are semantically equivalent in the
     absence of a join condition: both produce a Cartesian product
     between the specified tables (that is, each and every row in the
     first table is joined to each and every row in the second table).

     However, the precedence of the comma operator is less than of
     `INNER JOIN', `CROSS JOIN', `LEFT JOIN', and so on. If you mix
     comma joins with the other join types when there is a join
     condition, an error of the form `Unknown column 'COL_NAME' in 'on
     clause'' may occur. Information about dealing with this problem is
     given later in this section.

   * The CONDITIONAL_EXPR used with `ON' is any conditional expression
     of the form that can be used in a `WHERE' clause.  Generally, you
     should use the `ON' clause for conditions that specify how to join
     tables, and the `WHERE' clause to restrict which rows you want in
     the result set.

   * If there is no matching row for the right table in the `ON' or
     `USING' part in a `LEFT JOIN', a row with all columns set to
     `NULL' is used for the right table. You can use this fact to find
     rows in a table that have no counterpart in another table:


          SELECT left_tbl.*
            FROM left_tbl LEFT JOIN right_tbl ON left_tbl.id = right_tbl.id
            WHERE right_tbl.id IS NULL;

     This example finds all rows in `left_tbl' with an `id' value that
     is not present in `right_tbl' (that is, all rows in `left_tbl'
     with no corresponding row in `right_tbl'). This assumes that
     `right_tbl.id' is declared `NOT NULL'. See *Note
     left-join-optimization::.

   * The `USING(COLUMN_LIST)' clause names a list of columns that must
     exist in both tables. If tables `a' and `b' both contain columns
     `c1', `c2', and `c3', the following join compares corresponding
     columns from the two tables:


          a LEFT JOIN b USING (c1,c2,c3)

   * The `NATURAL [LEFT] JOIN' of two tables is defined to be
     semantically equivalent to an `INNER JOIN' or a `LEFT JOIN' with a
     `USING' clause that names all columns that exist in both tables.

   * `RIGHT JOIN' works analogously to `LEFT JOIN'. To keep code
     portable across databases, it is recommended that you use `LEFT
     JOIN' instead of `RIGHT JOIN'.

   * The `{ OJ ... }' syntax shown in the join syntax description
     exists only for compatibility with ODBC.  The curly braces in the
     syntax should be written literally; they are not metasyntax as
     used elsewhere in syntax descriptions.


          SELECT left_tbl.*
              FROM { OJ left_tbl LEFT OUTER JOIN right_tbl ON left_tbl.id = right_tbl.id }
              WHERE right_tbl.id IS NULL;

     As of MySQL 5.1.24, you can use other types of joins within `{ OJ
     ... }', such as `INNER JOIN' or `RIGHT OUTER JOIN'. This helps
     with compatibility with some third-party applications, but is not
     official ODBC syntax.

     A consequence of this change is that the parser does not permit
     nested `{ OJ ... }' constructs (which are not legal ODBC syntax,
     anyway). Queries that use such constructs should be rewritten. For
     example, this query is now produces an error:


          SELECT * FROM
             {OJ
                {OJ a LEFT OUTER JOIN b ON a.a1=b.a1}
                LEFT OUTER JOIN c ON b.b1 = c.b1};

     That can be replaced by any of the following rewrites:


          SELECT * FROM
              {OJ a LEFT OUTER JOIN b
                    LEFT OUTER JOIN c ON b.b1 = c.b1 ON a.a1=b.a1};

          SELECT * FROM
             {OJ a LEFT OUTER JOIN b ON a.a1=b.a1
                   LEFT OUTER JOIN c ON b.b1 = c.b1};

          SELECT * FROM
               a LEFT OUTER JOIN b ON a.a1=b.a1 LEFT OUTER JOIN c ON b.b1 = c.b1;

     The first two are legal according to ODBC, and you nest the joins
     inside a single `{ OJ ...}' clause.  The third is standard SQL
     syntax, without ODBC decoration.  It can be used with parentheses
     to emphasize the evaluation order:


          SELECT * FROM
               ((a LEFT OUTER JOIN b ON a.a1=b.a1)
                   LEFT OUTER JOIN c ON b.b1 = c.b1);

   * `STRAIGHT_JOIN' is similar to `JOIN', except that the left table is
     always read before the right table. This can be used for those
     (few) cases for which the join optimizer puts the tables in the
     wrong order.

Some join examples:


     SELECT * FROM table1, table2;

     SELECT * FROM table1 INNER JOIN table2 ON table1.id=table2.id;

     SELECT * FROM table1 LEFT JOIN table2 ON table1.id=table2.id;

     SELECT * FROM table1 LEFT JOIN table2 USING (id);

     SELECT * FROM table1 LEFT JOIN table2 ON table1.id=table2.id
       LEFT JOIN table3 ON table2.id=table3.id;

*Join Processing Changes in MySQL 5.0.12*

*Note*:

Natural joins and joins with `USING', including outer join variants,
are processed according to the SQL:2003 standard. The goal was to align
the syntax and semantics of MySQL with respect to `NATURAL JOIN' and
`JOIN ... USING' according to SQL:2003. However, these changes in join
processing can result in different output columns for some joins. Also,
some queries that appeared to work correctly in older versions (prior
to 5.0.12) must be rewritten to comply with the standard.

These changes have five main aspects:

   * The way that MySQL determines the result columns of `NATURAL' or
     `USING' join operations (and thus the result of the entire `FROM'
     clause).

   * Expansion of `SELECT *' and `SELECT TBL_NAME.*' into a list of
     selected columns.

   * Resolution of column names in `NATURAL' or `USING' joins.

   * Transformation of `NATURAL' or `USING' joins into `JOIN ...  ON'.

   * Resolution of column names in the `ON' condition of a `JOIN ...
     ON'.

The following list provides more detail about several effects of
current join processing versus join processing in older versions. The
term `previously' means `prior to MySQL 5.0.12.'

   * The columns of a `NATURAL' join or a `USING' join may be different
     from previously. Specifically, redundant output columns no longer
     appear, and the order of columns for `SELECT *' expansion may be
     different from before.

     Consider this set of statements:


          CREATE TABLE t1 (i INT, j INT);
          CREATE TABLE t2 (k INT, j INT);
          INSERT INTO t1 VALUES(1,1);
          INSERT INTO t2 VALUES(1,1);
          SELECT * FROM t1 NATURAL JOIN t2;
          SELECT * FROM t1 JOIN t2 USING (j);

     Previously, the statements produced this output:


          +------+------+------+------+
          | i    | j    | k    | j    |
          +------+------+------+------+
          |    1 |    1 |    1 |    1 |
          +------+------+------+------+
          +------+------+------+------+
          | i    | j    | k    | j    |
          +------+------+------+------+
          |    1 |    1 |    1 |    1 |
          +------+------+------+------+

     In the first *Note `SELECT': select.  statement, column `j'
     appears in both tables and thus becomes a join column, so,
     according to standard SQL, it should appear only once in the
     output, not twice. Similarly, in the second SELECT statement,
     column `j' is named in the `USING' clause and should appear only
     once in the output, not twice. But in both cases, the redundant
     column is not eliminated. Also, the order of the columns is not
     correct according to standard SQL.

     Now the statements produce this output:


          +------+------+------+
          | j    | i    | k    |
          +------+------+------+
          |    1 |    1 |    1 |
          +------+------+------+
          +------+------+------+
          | j    | i    | k    |
          +------+------+------+
          |    1 |    1 |    1 |
          +------+------+------+

     The redundant column is eliminated and the column order is correct
     according to standard SQL:

        * First, coalesced common columns of the two joined tables, in
          the order in which they occur in the first table

        * Second, columns unique to the first table, in order in which
          they occur in that table

        * Third, columns unique to the second table, in order in which
          they occur in that table

     The single result column that replaces two common columns is
     defined using the coalesce operation. That is, for two `t1.a' and
     `t2.a' the resulting single join column `a' is defined as `a =
     COALESCE(t1.a, t2.a)', where:


          COALESCE(x, y) = (CASE WHEN V1 IS NOT NULL THEN V1 ELSE V2 END)

     If the join operation is any other join, the result columns of the
     join consists of the concatenation of all columns of the joined
     tables. This is the same as previously.

     A consequence of the definition of coalesced columns is that, for
     outer joins, the coalesced column contains the value of the
     non-`NULL' column if one of the two columns is always `NULL'. If
     neither or both columns are `NULL', both common columns have the
     same value, so it doesn't matter which one is chosen as the value
     of the coalesced column. A simple way to interpret this is to
     consider that a coalesced column of an outer join is represented
     by the common column of the inner table of a `JOIN'. Suppose that
     the tables `t1(a,b)' and `t2(a,c)' have the following contents:


          t1    t2
          ----  ----
          1 x   2 z
          2 y   3 w

     Then:


          mysql> SELECT * FROM t1 NATURAL LEFT JOIN t2;
          +------+------+------+
          | a    | b    | c    |
          +------+------+------+
          |    1 | x    | NULL |
          |    2 | y    | z    |
          +------+------+------+

     Here column `a' contains the values of `t1.a'.


          mysql> SELECT * FROM t1 NATURAL RIGHT JOIN t2;
          +------+------+------+
          | a    | c    | b    |
          +------+------+------+
          |    2 | z    | y    |
          |    3 | w    | NULL |
          +------+------+------+

     Here column `a' contains the values of `t2.a'.

     Compare these results to the otherwise equivalent queries with
     `JOIN ... ON':


          mysql> SELECT * FROM t1 LEFT JOIN t2 ON (t1.a = t2.a);
          +------+------+------+------+
          | a    | b    | a    | c    |
          +------+------+------+------+
          |    1 | x    | NULL | NULL |
          |    2 | y    |    2 | z    |
          +------+------+------+------+


          mysql> SELECT * FROM t1 RIGHT JOIN t2 ON (t1.a = t2.a);
          +------+------+------+------+
          | a    | b    | a    | c    |
          +------+------+------+------+
          |    2 | y    |    2 | z    |
          | NULL | NULL |    3 | w    |
          +------+------+------+------+

   * Previously, a `USING' clause could be rewritten as an `ON' clause
     that compares corresponding columns. For example, the following two
     clauses were semantically identical:


          a LEFT JOIN b USING (c1,c2,c3)
          a LEFT JOIN b ON a.c1=b.c1 AND a.c2=b.c2 AND a.c3=b.c3

     Now the two clauses no longer are quite the same:

        * With respect to determining which rows satisfy the join
          condition, both joins remain semantically identical.

        * With respect to determining which columns to display for
          `SELECT *' expansion, the two joins are not semantically
          identical. The `USING' join selects the coalesced value of
          corresponding columns, whereas the `ON' join selects all
          columns from all tables. For the preceding `USING' join,
          `SELECT *' selects these values:


               COALESCE(a.c1,b.c1), COALESCE(a.c2,b.c2), COALESCE(a.c3,b.c3)

          For the `ON' join, `SELECT *' selects these values:


               a.c1, a.c2, a.c3, b.c1, b.c2, b.c3

          With an inner join, `COALESCE(a.c1,b.c1)' is the same as
          either `a.c1' or `b.c1' because both columns will have the
          same value. With an outer join (such as `LEFT JOIN'), one of
          the two columns can be `NULL'. That column will be omitted
          from the result.

   * The evaluation of multi-way natural joins differs in a very
     important way that affects the result of `NATURAL' or `USING' joins
     and that can require query rewriting. Suppose that you have three
     tables `t1(a,b)', `t2(c,b)', and `t3(a,c)' that each have one row:
     `t1(1,2)', `t2(10,2)', and `t3(7,10)'. Suppose also that you have
     this `NATURAL JOIN' on the three tables:


          SELECT ... FROM t1 NATURAL JOIN t2 NATURAL JOIN t3;

     Previously, the left operand of the second join was considered to
     be `t2', whereas it should be the nested join `(t1 NATURAL JOIN
     t2)'. As a result, the columns of `t3' are checked for common
     columns only in `t2', and, if `t3' has common columns with `t1',
     these columns are not used as equi-join columns. Thus, previously,
     the preceding query was transformed to the following equi-join:


          SELECT ... FROM t1, t2, t3
            WHERE t1.b = t2.b AND t2.c = t3.c;

     That join is missing one more equi-join predicate `(t1.a = t3.a)'.
     As a result, it produces one row, not the empty result that it
     should. The correct equivalent query is this:


          SELECT ... FROM t1, t2, t3
            WHERE t1.b = t2.b AND t2.c = t3.c AND t1.a = t3.a;

     If you require the same query result in current versions of MySQL
     as in older versions, rewrite the natural join as the first
     equi-join.

   * Previously, the comma operator (`,') and `JOIN' both had the same
     precedence, so the join expression `t1, t2 JOIN t3' was
     interpreted as `((t1, t2) JOIN t3)'. Now `JOIN' has higher
     precedence, so the expression is interpreted as `(t1, (t2 JOIN
     t3))'. This change affects statements that use an `ON' clause,
     because that clause can refer only to columns in the operands of
     the join, and the change in precedence changes interpretation of
     what those operands are.

     Example:


          CREATE TABLE t1 (i1 INT, j1 INT);
          CREATE TABLE t2 (i2 INT, j2 INT);
          CREATE TABLE t3 (i3 INT, j3 INT);
          INSERT INTO t1 VALUES(1,1);
          INSERT INTO t2 VALUES(1,1);
          INSERT INTO t3 VALUES(1,1);
          SELECT * FROM t1, t2 JOIN t3 ON (t1.i1 = t3.i3);

     Previously, the *Note `SELECT': select. was legal due to the
     implicit grouping of `t1,t2' as `(t1,t2)'. Now the `JOIN' takes
     precedence, so the operands for the `ON' clause are `t2' and `t3'.
     Because `t1.i1' is not a column in either of the operands, the
     result is an `Unknown column 't1.i1' in 'on clause'' error. To
     allow the join to be processed, group the first two tables
     explicitly with parentheses so that the operands for the `ON'
     clause are `(t1,t2)' and `t3':


          SELECT * FROM (t1, t2) JOIN t3 ON (t1.i1 = t3.i3);

     Alternatively, avoid the use of the comma operator and use `JOIN'
     instead:


          SELECT * FROM t1 JOIN t2 JOIN t3 ON (t1.i1 = t3.i3);

     This change also applies to statements that mix the comma operator
     with `INNER JOIN', `CROSS JOIN', `LEFT JOIN', and `RIGHT JOIN',
     all of which now have higher precedence than the comma operator.

   * Previously, the `ON' clause could refer to columns in tables named
     to its right. Now an `ON' clause can refer only to its operands.

     Example:


          CREATE TABLE t1 (i1 INT);
          CREATE TABLE t2 (i2 INT);
          CREATE TABLE t3 (i3 INT);
          SELECT * FROM t1 JOIN t2 ON (i1 = i3) JOIN t3;

     Previously, the *Note `SELECT': select.  statement was legal. Now
     the statement fails with an `Unknown column 'i3' in 'on clause''
     error because `i3' is a column in `t3', which is not an operand of
     the `ON' clause. The statement should be rewritten as follows:


          SELECT * FROM t1 JOIN t2 JOIN t3 ON (i1 = i3);

   * Resolution of column names in `NATURAL' or `USING' joins is
     different than previously.  For column names that are outside the
     `FROM' clause, MySQL now handles a superset of the queries
     compared to previously. That is, in cases when MySQL formerly
     issued an error that some column is ambiguous, the query now is
     handled correctly. This is due to the fact that MySQL now treats
     the common columns of `NATURAL' or `USING' joins as a single
     column, so when a query refers to such columns, the query compiler
     does not consider them as ambiguous.

     Example:


          SELECT * FROM t1 NATURAL JOIN t2 WHERE b > 1;

     Previously, this query would produce an error `ERROR 1052 (23000):
     Column 'b' in where clause is ambiguous'. Now the query produces
     the correct result:


          +------+------+------+
          | b    | c    | y    |
          +------+------+------+
          |    4 |    2 |    3 |
          +------+------+------+

     One extension of MySQL compared to the SQL:2003 standard is that
     MySQL enables you to qualify the common (coalesced) columns of
     `NATURAL' or `USING' joins (just as previously), while the
     standard disallows that.


File: manual.info,  Node: index-hints,  Next: union,  Prev: join,  Up: select

13.2.8.3 Index Hint Syntax
..........................

You can provide hints to give the optimizer information about how to
choose indexes during query processing.  *Note join::, describes the
general syntax for specifying tables in a *Note `SELECT': select.
statement. The syntax for an individual table, including that for index
hints, looks like this:


     TBL_NAME [[AS] ALIAS] [INDEX_HINT_LIST]

     INDEX_HINT_LIST:
         INDEX_HINT [, INDEX_HINT] ...

     INDEX_HINT:
         USE {INDEX|KEY}
           [FOR {JOIN|ORDER BY|GROUP BY}] ([INDEX_LIST])
       | IGNORE {INDEX|KEY}
           [FOR {JOIN|ORDER BY|GROUP BY}] (INDEX_LIST)
       | FORCE {INDEX|KEY}
           [FOR {JOIN|ORDER BY|GROUP BY}] (INDEX_LIST)

     INDEX_LIST:
         INDEX_NAME [, INDEX_NAME] ...

By specifying `USE INDEX (INDEX_LIST)', you can tell MySQL to use only
one of the named indexes to find rows in the table. The alternative
syntax `IGNORE INDEX (INDEX_LIST)' can be used to tell MySQL to not use
some particular index or indexes. These hints are useful if *Note
`EXPLAIN': explain. shows that MySQL is using the wrong index from the
list of possible indexes.

You can also use `FORCE INDEX', which acts like `USE INDEX
(INDEX_LIST)' but with the addition that a table scan is assumed to be
_very_ expensive. In other words, a table scan is used only if there is
no way to use one of the given indexes to find rows in the table.

Each hint requires the names of _indexes_, not the names of columns.
The name of a `PRIMARY KEY' is `PRIMARY'. To see the index names for a
table, use *Note `SHOW INDEX': show-index.

An INDEX_NAME value need not be a full index name. It can be an
unambiguous prefix of an index name. If a prefix is ambiguous, an error
occurs.

Prior to MySQL 5.1.17, `USE INDEX', `IGNORE INDEX', and `FORCE INDEX'
affect only which indexes are used when MySQL decides how to find rows
in the table and how to process joins.  They do not affect whether an
index is used when resolving an `ORDER BY' or `GROUP BY' clause.

Examples:


     SELECT * FROM table1 USE INDEX (col1_index,col2_index)
       WHERE col1=1 AND col2=2 AND col3=3;

     SELECT * FROM table1 IGNORE INDEX (col3_index)
       WHERE col1=1 AND col2=2 AND col3=3;

As of MySQL 5.1.17, the syntax for index hints is extended in the
following ways:

   * It is syntactically valid to specify an empty INDEX_LIST for `USE
     INDEX', which means `use no indexes.' Specifying an empty
     INDEX_LIST for `FORCE INDEX' or `IGNORE INDEX' is a syntax error.

   * You can specify the scope of a index hint by adding a `FOR' clause
     to the hint. This provides more fine-grained control over the
     optimizer's selection of an execution plan for various phases of
     query processing. To affect only the indexes used when MySQL
     decides how to find rows in the table and how to process joins,
     use `FOR JOIN'. To influence index usage for sorting or grouping
     rows, use `FOR ORDER BY' or `FOR GROUP BY'. (However, if there is a
     covering index for the table and it is used to access the table,
     the optimizer will ignore `IGNORE INDEX FOR {ORDER BY|GROUP BY}'
     hints that disable that index.)

   * You can specify multiple index hints:


          SELECT * FROM t1 USE INDEX (i1) IGNORE INDEX FOR ORDER BY (i2) ORDER BY a;

     It is not a error to name the same index in several hints (even
     within the same hint):


          SELECT * FROM t1 USE INDEX (i1) USE INDEX (i1,i1);

     However, it is an error to mix `USE INDEX' and `FORCE INDEX' for
     the same table:


          SELECT * FROM t1 USE INDEX FOR JOIN (i1) FORCE INDEX FOR JOIN (i2);

The default scope of index hints also is changed as of MySQL 5.1.17.
Formerly, index hints applied only to how indexes are used for
retrieval of records and not during resolution of `ORDER BY' or `GROUP
BY' clauses. As of 5.1.17, if you specify no `FOR' clause for an index
hint, the hint by default applies to all parts of the statement. For
example, this hint:


     IGNORE INDEX (i1)

is equivalent to this combination of hints:


     IGNORE INDEX FOR JOIN (i1)
     IGNORE INDEX FOR ORDER BY (i1)
     IGNORE INDEX FOR GROUP BY (i1)

To cause the server to use the older behavior for hint scope when no
`FOR' clause is present (so that hints apply only to row retrieval),
enable the `old' system variable at server startup. Take care about
enabling this variable in a replication setup. With statement-based
binary logging, having different modes for the master and slaves might
lead to replication errors.

When index hints are processed, they are collected in a single list by
type (*Note `USE': use, `FORCE', `IGNORE') and by scope (`FOR JOIN',
`FOR ORDER BY', `FOR GROUP BY'). For example:


     SELECT * FROM t1
       USE INDEX () IGNORE INDEX (i2) USE INDEX (i1) USE INDEX (i2);

is equivalent to:


     SELECT * FROM t1
        USE INDEX (i1,i2) IGNORE INDEX (i2);

The index hints then are applied for each scope in the following order:

  1. `{USE|FORCE} INDEX' is applied if present.  (If not, the
     optimizer-determined set of indexes is used.)

  2. `IGNORE INDEX' is applied over the result of the previous step.
     For example, the following two queries are equivalent:


          SELECT * FROM t1 USE INDEX (i1) IGNORE INDEX (i2) USE INDEX (i2);

          SELECT * FROM t1 USE INDEX (i1);

For `FULLTEXT' searches, index hints do not work before MySQL 5.1.31.
As of 5.1.31, index hints work as follows:

   * For natural language mode searches, index hints are silently
     ignored. For example, `IGNORE INDEX(i)' is ignored with no warning
     and the index is still used.

     For boolean mode searches, index hints with `FOR ORDER BY' or `FOR
     GROUP BY' are silently ignored. Index hints with `FOR JOIN' or no
     `FOR' modifier are honored. In contrast to how hints apply for
     non-`FULLTEXT' searches, the hint is used for all phases of query
     execution (finding rows and retrieval, grouping, and ordering).
     This is true even if the hint is given for a non-`FULLTEXT' index.

For example, the following two queries are equivalent:


     SELECT * FROM t
       USE INDEX (index1)
       IGNORE INDEX (index1) FOR ORDER BY
       IGNORE INDEX (index1) FOR GROUP BY
       WHERE ... IN BOOLEAN MODE ... ;

     SELECT * FROM t
       USE INDEX (index1)
       WHERE ... IN BOOLEAN MODE ... ;


File: manual.info,  Node: union,  Prev: index-hints,  Up: select

13.2.8.4 UNION Syntax
.....................


     SELECT ...
     UNION [ALL | DISTINCT] SELECT ...
     [UNION [ALL | DISTINCT] SELECT ...]

*Note `UNION': union. is used to combine the result from multiple *Note
`SELECT': select.  statements into a single result set.

The column names from the first *Note `SELECT': select. statement are
used as the column names for the results returned. Selected columns
listed in corresponding positions of each *Note `SELECT': select.
statement should have the same data type. (For example, the first
column selected by the first statement should have the same type as the
first column selected by the other statements.)

If the data types of corresponding *Note `SELECT': select. columns do
not match, the types and lengths of the columns in the *Note `UNION':
union. result take into account the values retrieved by all of the
*Note `SELECT': select. statements. For example, consider the following:


     mysql> SELECT REPEAT('a',1) UNION SELECT REPEAT('b',10);
     +---------------+
     | REPEAT('a',1) |
     +---------------+
     | a             |
     | bbbbbbbbbb    |
     +---------------+

(In some earlier versions of MySQL, only the type and length from the
first *Note `SELECT': select. would have been used and the second row
would have been truncated to a length of 1.)

The *Note `SELECT': select. statements are normal select statements,
but with the following restrictions:

   * Only the last *Note `SELECT': select.  statement can use `INTO
     OUTFILE'. (However, the entire *Note `UNION': union. result is
     written to the file.)

   * `HIGH_PRIORITY' cannot be used with *Note `SELECT': select.
     statements that are part of a *Note `UNION': union. If you specify
     it for the first *Note `SELECT': select, it has no effect. If you
     specify it for any subsequent *Note `SELECT': select. statements,
     a syntax error results.

The default behavior for *Note `UNION': union. is that duplicate rows
are removed from the result. The optional `DISTINCT' keyword has no
effect other than the default because it also specifies duplicate-row
removal. With the optional `ALL' keyword, duplicate-row removal does
not occur and the result includes all matching rows from all the *Note
`SELECT': select. statements.

You can mix *Note `UNION ALL': union. and *Note `UNION DISTINCT':
union. in the same query. Mixed *Note `UNION': union. types are treated
such that a `DISTINCT' union overrides any `ALL' union to its left. A
`DISTINCT' union can be produced explicitly by using *Note `UNION
DISTINCT': union. or implicitly by using *Note `UNION': union. with no
following `DISTINCT' or `ALL' keyword.

To apply `ORDER BY' or `LIMIT' to an individual *Note `SELECT': select,
place the clause inside the parentheses that enclose the *Note
`SELECT': select.:


     (SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10)
     UNION
     (SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);

However, use of `ORDER BY' for individual *Note `SELECT': select.
statements implies nothing about the order in which the rows appear in
the final result because *Note `UNION': union. by default produces an
unordered set of rows. Therefore, the use of `ORDER BY' in this context
is typically in conjunction with `LIMIT', so that it is used to
determine the subset of the selected rows to retrieve for the *Note
`SELECT': select, even though it does not necessarily affect the order
of those rows in the final *Note `UNION': union. result. If `ORDER BY'
appears without `LIMIT' in a *Note `SELECT': select, it is optimized
away because it will have no effect anyway.

To use an `ORDER BY' or `LIMIT' clause to sort or limit the entire
*Note `UNION': union. result, parenthesize the individual *Note
`SELECT': select. statements and place the `ORDER BY' or `LIMIT' after
the last one. The following example uses both clauses:


     (SELECT a FROM t1 WHERE a=10 AND B=1)
     UNION
     (SELECT a FROM t2 WHERE a=11 AND B=2)
     ORDER BY a LIMIT 10;

A statement without parentheses is equivalent to one parenthesized as
just shown.

This kind of `ORDER BY' cannot use column references that include a
table name (that is, names in TBL_NAME.COL_NAME format). Instead,
provide a column alias in the first *Note `SELECT': select. statement
and refer to the alias in the `ORDER BY'. (Alternatively, refer to the
column in the `ORDER BY' using its column position. However, use of
column positions is deprecated.)

Also, if a column to be sorted is aliased, the `ORDER BY' clause _must_
refer to the alias, not the column name. The first of the following
statements will work, but the second will fail with an `Unknown column
'a' in 'order clause'' error:


     (SELECT a AS b FROM t) UNION (SELECT ...) ORDER BY b;
     (SELECT a AS b FROM t) UNION (SELECT ...) ORDER BY a;

To cause rows in a *Note `UNION': union. result to consist of the sets
of rows retrieved by each *Note `SELECT': select. one after the other,
select an additional column in each *Note `SELECT': select. to use as a
sort column and add an `ORDER BY' following the last *Note `SELECT':
select.:


     (SELECT 1 AS sort_col, col1a, col1b, ... FROM t1)
     UNION
     (SELECT 2, col2a, col2b, ... FROM t2) ORDER BY sort_col;

To additionally maintain sort order within individual *Note `SELECT':
select. results, add a secondary column to the `ORDER BY' clause:


     (SELECT 1 AS sort_col, col1a, col1b, ... FROM t1)
     UNION
     (SELECT 2, col2a, col2b, ... FROM t2) ORDER BY sort_col, col1a;

Use of an additional column also enables you to determine which *Note
`SELECT': select. each row comes from. Extra columns can provide other
identifying information as well, such as a string that indicates a
table name.


File: manual.info,  Node: subqueries,  Next: update,  Prev: select,  Up: sql-syntax-data-manipulation

13.2.9 Subquery Syntax
----------------------

* Menu:

* scalar-subqueries::            The Subquery as Scalar Operand
* comparisons-using-subqueries::  Comparisons Using Subqueries
* any-in-some-subqueries::       Subqueries with ANY, IN, or SOME
* all-subqueries::               Subqueries with ALL
* row-subqueries::               Row Subqueries
* exists-and-not-exists-subqueries::  Subqueries with EXISTS or NOT EXISTS
* correlated-subqueries::        Correlated Subqueries
* from-clause-subqueries::       Subqueries in the FROM Clause
* subquery-errors::              Subquery Errors
* optimizing-subqueries::        Optimizing Subqueries
* rewriting-subqueries::         Rewriting Subqueries as Joins

A subquery is a *Note `SELECT': select. statement within another
statement.

Starting with MySQL 4.1, all subquery forms and operations that the SQL
standard requires are supported, as well as a few features that are
MySQL-specific.

Here is an example of a subquery:


     SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);

In this example, `SELECT * FROM t1 ...' is the _outer query_ (or _outer
statement_), and `(SELECT column1 FROM t2)' is the _subquery_. We say
that the subquery is _nested_ within the outer query, and in fact it is
possible to nest subqueries within other subqueries, to a considerable
depth. A subquery must always appear within parentheses.

The main advantages of subqueries are:

   * They allow queries that are _structured_ so that it is possible to
     isolate each part of a statement.

   * They provide alternative ways to perform operations that would
     otherwise require complex joins and unions.

   * Many people find subqueries more readable than complex joins or
     unions. Indeed, it was the innovation of subqueries that gave
     people the original idea of calling the early SQL `Structured
     Query Language.'

Here is an example statement that shows the major points about subquery
syntax as specified by the SQL standard and supported in MySQL:


     DELETE FROM t1
     WHERE s11 > ANY
      (SELECT COUNT(*) /* no hint */ FROM t2
       WHERE NOT EXISTS
        (SELECT * FROM t3
         WHERE ROW(5*t2.s1,77)=
          (SELECT 50,11*s1 FROM t4 UNION SELECT 50,77 FROM
           (SELECT * FROM t5) AS t5)));

A subquery can return a scalar (a single value), a single row, a single
column, or a table (one or more rows of one or more columns). These are
called scalar, column, row, and table subqueries. Subqueries that
return a particular kind of result often can be used only in certain
contexts, as described in the following sections.

There are few restrictions on the type of statements in which
subqueries can be used. A subquery can contain many of the keywords or
clauses that an ordinary *Note `SELECT': select. can contain:
`DISTINCT', `GROUP BY', `ORDER BY', `LIMIT', joins, index hints, *Note
`UNION': union. constructs, comments, functions, and so on.

A subquery's outer statement can be any one of: *Note `SELECT': select,
*Note `INSERT': insert, *Note `UPDATE': update, *Note `DELETE': delete,
*Note `SET': set-statement, or *Note `DO': do.

In MySQL, you cannot modify a table and select from the same table in a
subquery. This applies to statements such as *Note `DELETE': delete,
*Note `INSERT': insert, *Note `REPLACE': replace, *Note `UPDATE':
update, and (because subqueries can be used in the `SET' clause) *Note
`LOAD DATA INFILE': load-data.

For information about how the optimizer handles subqueries, see *Note
subquery-optimization-with-exists::. For a discussion of restrictions
on subquery use, including performance issues for certain forms of
subquery syntax, see *Note subquery-restrictions::.


File: manual.info,  Node: scalar-subqueries,  Next: comparisons-using-subqueries,  Prev: subqueries,  Up: subqueries

13.2.9.1 The Subquery as Scalar Operand
.......................................

In its simplest form, a subquery is a scalar subquery that returns a
single value. A scalar subquery is a simple operand, and you can use it
almost anywhere a single column value or literal is legal, and you can
expect it to have those characteristics that all operands have: a data
type, a length, an indication that it can be `NULL', and so on.  For
example:


     CREATE TABLE t1 (s1 INT, s2 CHAR(5) NOT NULL);
     INSERT INTO t1 VALUES(100, 'abcde');
     SELECT (SELECT s2 FROM t1);

The subquery in this *Note `SELECT': select.  returns a single value
(`'abcde'') that has a data type of *Note `CHAR': char, a length of 5,
a character set and collation equal to the defaults in effect at *Note
`CREATE TABLE': create-table. time, and an indication that the value in
the column can be `NULL'. Nullability of the value selected by a scalar
subquery is not copied because if the subquery result is empty, the
result is `NULL'. For the subquery just shown, if `t1' were empty, the
result would be `NULL' even though `s2' is `NOT NULL'.

There are a few contexts in which a scalar subquery cannot be used. If
a statement permits only a literal value, you cannot use a subquery.
For example, `LIMIT' requires literal integer arguments, and *Note
`LOAD DATA INFILE': load-data. requires a literal string file name. You
cannot use subqueries to supply these values.

When you see examples in the following sections that contain the rather
spartan construct `(SELECT column1 FROM t1)', imagine that your own
code contains much more diverse and complex constructions.

Suppose that we make two tables:


     CREATE TABLE t1 (s1 INT);
     INSERT INTO t1 VALUES (1);
     CREATE TABLE t2 (s1 INT);
     INSERT INTO t2 VALUES (2);

Then perform a *Note `SELECT': select.:


     SELECT (SELECT s1 FROM t2) FROM t1;

The result is `2' because there is a row in `t2' containing a column
`s1' that has a value of `2'.

A scalar subquery can be part of an expression, but remember the
parentheses, even if the subquery is an operand that provides an
argument for a function. For example:


     SELECT UPPER((SELECT s1 FROM t1)) FROM t2;


File: manual.info,  Node: comparisons-using-subqueries,  Next: any-in-some-subqueries,  Prev: scalar-subqueries,  Up: subqueries

13.2.9.2 Comparisons Using Subqueries
.....................................

The most common use of a subquery is in the form:


     NON_SUBQUERY_OPERAND COMPARISON_OPERATOR (SUBQUERY)

Where COMPARISON_OPERATOR is one of these operators:


     =  >  <  >=  <=  <>  !=  <=>

For example:


     ... WHERE 'a' = (SELECT column1 FROM t1)

MySQL also permits this construct:


     NON_SUBQUERY_OPERAND LIKE (SUBQUERY)

At one time the only legal place for a subquery was on the right side
of a comparison, and you might still find some old DBMSs that insist on
this.

Here is an example of a common-form subquery comparison that you cannot
do with a join. It finds all the rows in table `t1' for which the
`column1' value is equal to a maximum value in table `t2':


     SELECT * FROM t1
       WHERE column1 = (SELECT MAX(column2) FROM t2);

Here is another example, which again is impossible with a join because
it involves aggregating for one of the tables. It finds all rows in
table `t1' containing a value that occurs twice in a given column:


     SELECT * FROM t1 AS t
       WHERE 2 = (SELECT COUNT(*) FROM t1 WHERE t1.id = t.id);

For a comparison of the subquery to a scalar, the subquery must return
a scalar. For a comparison of the subquery to a row constructor, the
subquery must be a row subquery that returns a row with the same number
of values as the row constructor. See *Note row-subqueries::.


File: manual.info,  Node: any-in-some-subqueries,  Next: all-subqueries,  Prev: comparisons-using-subqueries,  Up: subqueries

13.2.9.3 Subqueries with ANY, IN, or SOME
.........................................

Syntax:


     OPERAND COMPARISON_OPERATOR ANY (SUBQUERY)
     OPERAND IN (SUBQUERY)
     OPERAND COMPARISON_OPERATOR SOME (SUBQUERY)

Where COMPARISON_OPERATOR is one of these operators:


     =  >  <  >=  <=  <>  !=

The `ANY' keyword, which must follow a comparison operator, means
`return `TRUE' if the comparison is `TRUE' for `ANY' of the values in
the column that the subquery returns.' For example:


     SELECT s1 FROM t1 WHERE s1 > ANY (SELECT s1 FROM t2);

Suppose that there is a row in table `t1' containing `(10)'. The
expression is `TRUE' if table `t2' contains `(21,14,7)' because there
is a value `7' in `t2' that is less than `10'. The expression is
`FALSE' if table `t2' contains `(20,10)', or if table `t2' is empty.
The expression is _unknown_ (that is, `NULL') if table `t2' contains
`(NULL,NULL,NULL)'.

When used with a subquery, the word `IN' is an alias for `= ANY'. Thus,
these two statements are the same:


     SELECT s1 FROM t1 WHERE s1 = ANY (SELECT s1 FROM t2);
     SELECT s1 FROM t1 WHERE s1 IN    (SELECT s1 FROM t2);

`IN' and `= ANY' are not synonyms when used with an expression list.
`IN' can take an expression list, but `= ANY' cannot. See *Note
comparison-operators::.

`NOT IN' is not an alias for `<> ANY', but for `<> ALL'. See *Note
all-subqueries::.

The word `SOME' is an alias for `ANY'. Thus, these two statements are
the same:


     SELECT s1 FROM t1 WHERE s1 <> ANY  (SELECT s1 FROM t2);
     SELECT s1 FROM t1 WHERE s1 <> SOME (SELECT s1 FROM t2);

Use of the word `SOME' is rare, but this example shows why it might be
useful. To most people, the English phrase `a is not equal to any b'
means `there is no b which is equal to a,' but that is not what is
meant by the SQL syntax. The syntax means `there is some b to which a
is not equal.' Using `<> SOME' instead helps ensure that everyone
understands the true meaning of the query.


File: manual.info,  Node: all-subqueries,  Next: row-subqueries,  Prev: any-in-some-subqueries,  Up: subqueries

13.2.9.4 Subqueries with ALL
............................

Syntax:


     OPERAND COMPARISON_OPERATOR ALL (SUBQUERY)

The word `ALL', which must follow a comparison operator, means `return
`TRUE' if the comparison is `TRUE' for `ALL' of the values in the
column that the subquery returns.' For example:


     SELECT s1 FROM t1 WHERE s1 > ALL (SELECT s1 FROM t2);

Suppose that there is a row in table `t1' containing `(10)'. The
expression is `TRUE' if table `t2' contains `(-5,0,+5)' because `10' is
greater than all three values in `t2'. The expression is `FALSE' if
table `t2' contains `(12,6,NULL,-100)' because there is a single value
`12' in table `t2' that is greater than `10'. The expression is
_unknown_ (that is, `NULL') if table `t2' contains `(0,NULL,1)'.

Finally, the expression is `TRUE' if table `t2' is empty. So, the
following expression is `TRUE' when table `t2' is empty:


     SELECT * FROM t1 WHERE 1 > ALL (SELECT s1 FROM t2);

But this expression is `NULL' when table `t2' is empty:


     SELECT * FROM t1 WHERE 1 > (SELECT s1 FROM t2);

In addition, the following expression is `NULL' when table `t2' is
empty:


     SELECT * FROM t1 WHERE 1 > ALL (SELECT MAX(s1) FROM t2);

In general, _tables containing `NULL' values_ and _empty tables_ are
`edge cases.' When writing subqueries, always consider whether you have
taken those two possibilities into account.

`NOT IN' is an alias for `<> ALL'. Thus, these two statements are the
same:


     SELECT s1 FROM t1 WHERE s1 <> ALL (SELECT s1 FROM t2);
     SELECT s1 FROM t1 WHERE s1 NOT IN (SELECT s1 FROM t2);


File: manual.info,  Node: row-subqueries,  Next: exists-and-not-exists-subqueries,  Prev: all-subqueries,  Up: subqueries

13.2.9.5 Row Subqueries
.......................

The discussion to this point has been of scalar or column subqueries;
that is, subqueries that return a single value or a column of values. A
_row subquery_ is a subquery variant that returns a single row and can
thus return more than one column value. Legal operators for row subquery
comparisons are:


     =  >  <  >=  <=  <>  !=  <=>

Here are two examples:


     SELECT * FROM t1
       WHERE (col1,col2) = (SELECT col3, col4 FROM t2 WHERE id = 10);
     SELECT * FROM t1
       WHERE ROW(col1,col2) = (SELECT col3, col4 FROM t2 WHERE id = 10);

For both queries, if the table `t2' contains a single row with `id =
10', the subquery returns a single row. If this row has `col3' and
`col4' values equal to the `col1' and `col2' values of any rows in
`t1', the `WHERE' expression is `TRUE' and each query returns those
`t1' rows. If the `t2' row `col3' and `col4' values are not equal the
`col1' and `col2' values of any `t1' row, the expression is `FALSE' and
the query returns an empty result set. The expression is _unknown_
(that is, `NULL') if the subquery produces no rows. An error occurs if
the subquery produces multiple rows because a row subquery can return
at most one row.

The expressions `(1,2)' and `ROW(1,2)' are sometimes called _row
constructors_. The two are equivalent. The row constructor and the row
returned by the subquery must contain the same number of values.

A row constructor is used for comparisons with subqueries that return
two or more columns. When a subquery returns a single column, this is
regarded as a scalar value and not as a row, so a row constructor
cannot be used with a subquery that does not return at least two
columns. Thus, the following query fails with a syntax error:


     SELECT * FROM t1 WHERE ROW(1) = (SELECT column1 FROM t2)

Row constructors are legal in other contexts. For example, the
following two statements are semantically equivalent:


     SELECT * FROM t1 WHERE (column1,column2) = (1,1);
     SELECT * FROM t1 WHERE column1 = 1 AND column2 = 1;

Prior to MySQL 5.1.12, only the second of the preceding two expressions
could be optimized.

The following query answers the request, `find all rows in table `t1'
that also exist in table `t2'':


     SELECT column1,column2,column3
       FROM t1
       WHERE (column1,column2,column3) IN
              (SELECT column1,column2,column3 FROM t2);


File: manual.info,  Node: exists-and-not-exists-subqueries,  Next: correlated-subqueries,  Prev: row-subqueries,  Up: subqueries

13.2.9.6 Subqueries with EXISTS or NOT EXISTS
.............................................

If a subquery returns any rows at all, `EXISTS SUBQUERY' is `TRUE', and
`NOT EXISTS SUBQUERY' is `FALSE'. For example:


     SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2);

Traditionally, an `EXISTS' subquery starts with `SELECT *', but it
could begin with `SELECT 5' or `SELECT column1' or anything at all.
MySQL ignores the *Note `SELECT': select. list in such a subquery, so
it makes no difference.

For the preceding example, if `t2' contains any rows, even rows with
nothing but `NULL' values, the `EXISTS' condition is `TRUE'. This is
actually an unlikely example because a `[NOT] EXISTS' subquery almost
always contains correlations. Here are some more realistic examples:

   * What kind of store is present in one or more cities?


          SELECT DISTINCT store_type FROM stores
            WHERE EXISTS (SELECT * FROM cities_stores
                          WHERE cities_stores.store_type = stores.store_type);

   * What kind of store is present in no cities?


          SELECT DISTINCT store_type FROM stores
            WHERE NOT EXISTS (SELECT * FROM cities_stores
                              WHERE cities_stores.store_type = stores.store_type);

   * What kind of store is present in all cities?


          SELECT DISTINCT store_type FROM stores s1
            WHERE NOT EXISTS (
              SELECT * FROM cities WHERE NOT EXISTS (
                SELECT * FROM cities_stores
                 WHERE cities_stores.city = cities.city
                 AND cities_stores.store_type = stores.store_type));

The last example is a double-nested `NOT EXISTS' query. That is, it has
a `NOT EXISTS' clause within a `NOT EXISTS' clause. Formally, it
answers the question `does a city exist with a store that is not in
`Stores''? But it is easier to say that a nested `NOT EXISTS' answers
the question `is X `TRUE' for all Y?'


File: manual.info,  Node: correlated-subqueries,  Next: from-clause-subqueries,  Prev: exists-and-not-exists-subqueries,  Up: subqueries

13.2.9.7 Correlated Subqueries
..............................

A _correlated subquery_ is a subquery that contains a reference to a
table that also appears in the outer query. For example:


     SELECT * FROM t1
       WHERE column1 = ANY (SELECT column1 FROM t2
                            WHERE t2.column2 = t1.column2);

Notice that the subquery contains a reference to a column of `t1', even
though the subquery's `FROM' clause does not mention a table `t1'. So,
MySQL looks outside the subquery, and finds `t1' in the outer query.

Suppose that table `t1' contains a row where `column1 = 5' and `column2
= 6'; meanwhile, table `t2' contains a row where `column1 = 5' and
`column2 = 7'. The simple expression `... WHERE column1 = ANY (SELECT
column1 FROM t2)' would be `TRUE', but in this example, the `WHERE'
clause within the subquery is `FALSE' (because `(5,6)' is not equal to
`(5,7)'), so the expression as a whole is `FALSE'.

*Scoping rule:* MySQL evaluates from inside to outside. For example:


     SELECT column1 FROM t1 AS x
       WHERE x.column1 = (SELECT column1 FROM t2 AS x
         WHERE x.column1 = (SELECT column1 FROM t3
           WHERE x.column2 = t3.column1));

In this statement, `x.column2' must be a column in table `t2' because
`SELECT column1 FROM t2 AS x ...' renames `t2'. It is not a column in
table `t1' because `SELECT column1 FROM t1 ...' is an outer query that
is _farther out_.

For subqueries in `HAVING' or `ORDER BY' clauses, MySQL also looks for
column names in the outer select list.

For certain cases, a correlated subquery is optimized. For example:


     VAL IN (SELECT KEY_VAL FROM TBL_NAME WHERE CORRELATED_CONDITION)

Otherwise, they are inefficient and likely to be slow. Rewriting the
query as a join might improve performance.

Aggregate functions in correlated subqueries may contain outer
references, provided the function contains nothing but outer
references, and provided the function is not contained in another
function or expression.


File: manual.info,  Node: from-clause-subqueries,  Next: subquery-errors,  Prev: correlated-subqueries,  Up: subqueries

13.2.9.8 Subqueries in the FROM Clause
......................................

Subqueries are legal in a *Note `SELECT': select.  statement's `FROM'
clause. The actual syntax is:


     SELECT ... FROM (SUBQUERY) [AS] NAME ...

The `[AS] NAME' clause is mandatory, because every table in a `FROM'
clause must have a name. Any columns in the SUBQUERY select list must
have unique names.

For the sake of illustration, assume that you have this table:


     CREATE TABLE t1 (s1 INT, s2 CHAR(5), s3 FLOAT);

Here is how to use a subquery in the `FROM' clause, using the example
table:


     INSERT INTO t1 VALUES (1,'1',1.0);
     INSERT INTO t1 VALUES (2,'2',2.0);
     SELECT sb1,sb2,sb3
       FROM (SELECT s1 AS sb1, s2 AS sb2, s3*2 AS sb3 FROM t1) AS sb
       WHERE sb1 > 1;

Result: `2, '2', 4.0'.

Here is another example: Suppose that you want to know the average of a
set of sums for a grouped table. This does not work:


     SELECT AVG(SUM(column1)) FROM t1 GROUP BY column1;

However, this query provides the desired information:


     SELECT AVG(sum_column1)
       FROM (SELECT SUM(column1) AS sum_column1
             FROM t1 GROUP BY column1) AS t1;

Notice that the column name used within the subquery (`sum_column1') is
recognized in the outer query.

Subqueries in the `FROM' clause can return a scalar, column, row, or
table. Subqueries in the `FROM' clause cannot be correlated subqueries,
unless used within the `ON' clause of a `JOIN' operation.

Subqueries in the `FROM' clause are executed even for the *Note
`EXPLAIN': explain. statement (that is, derived temporary tables are
materialized). This occurs because upper-level queries need information
about all tables during the optimization phase, and the table
represented by a subquery in the `FROM' clause is unavailable unless
the subquery is executed.

It is possible under certain circumstances to modify table data using
*Note `EXPLAIN SELECT': explain. This can occur if the outer query
accesses any tables and an inner query invokes a stored function that
changes one or more rows of a table. Suppose that there are two tables
`t1' and `t2' in database `d1', created as shown here:


     mysql> CREATE DATABASE d1;
     Query OK, 1 row affected (0.00 sec)

     mysql> USE d1;
     Database changed

     mysql> CREATE TABLE t1 (c1 INT);
     Query OK, 0 rows affected (0.15 sec)

     mysql> CREATE TABLE t2 (c1 INT);
     Query OK, 0 rows affected (0.08 sec)

Now we create a stored function `f1' which modifies `t2':


     mysql> DELIMITER //
     mysql> CREATE FUNCTION f1(p1 INT) RETURNS INT
     mysql>   BEGIN
     mysql>     INSERT INTO t2 VALUES (p1);
     mysql>     RETURN p1;
     mysql>   END //
     Query OK, 0 rows affected (0.01 sec)

     mysql> DELIMITER ;

Referencing the function directly in an *Note `EXPLAIN SELECT':
explain. does not have any effect on `t2', as shown here:


     mysql> SELECT * FROM t2;
     Empty set (0.00 sec)

     mysql> EXPLAIN SELECT f1(5);
     +----+-------------+-------+------+---------------+------+---------+------+------+----------------+
     | id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra          |
     +----+-------------+-------+------+---------------+------+---------+------+------+----------------+
     |  1 | SIMPLE      | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | No tables used |
     +----+-------------+-------+------+---------------+------+---------+------+------+----------------+
     1 row in set (0.00 sec)

     mysql> SELECT * FROM t2;
     Empty set (0.00 sec)

This is because the *Note `SELECT': select.  statement did not
reference any tables, as can be seen in the `table' and `Extra' columns
of the output. This is also true of the following nested *Note
`SELECT': select.:


     mysql> EXPLAIN SELECT NOW() AS a1, (SELECT f1(5)) AS a2;
     +----+-------------+-------+------+---------------+------+---------+------+------+----------------+
     | id | select_type | table | type | possible_keys | key  | key_len | ref  | rows | Extra          |
     +----+-------------+-------+------+---------------+------+---------+------+------+----------------+
     |  1 | PRIMARY     | NULL  | NULL | NULL          | NULL | NULL    | NULL | NULL | No tables used |
     +----+-------------+-------+------+---------------+------+---------+------+------+----------------+
     1 row in set, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS;
     +-------+------+------------------------------------------+
     | Level | Code | Message                                  |
     +-------+------+------------------------------------------+
     | Note  | 1249 | Select 2 was reduced during optimization |
     +-------+------+------------------------------------------+
     1 row in set (0.00 sec)

     mysql> SELECT * FROM t2;
     Empty set (0.00 sec)

However, if the outer *Note `SELECT': select.  references any tables,
the optimizer executes the statement in the subquery as well:


     mysql> EXPLAIN SELECT * FROM t1 AS a1, (SELECT f1(5)) AS a2;
     +----+-------------+------------+--------+---------------+------+---------+------+------+---------------------+
     | id | select_type | table      | type   | possible_keys | key  | key_len | ref  | rows | Extra               |
     +----+-------------+------------+--------+---------------+------+---------+------+------+---------------------+
     |  1 | PRIMARY     | a1         | system | NULL          | NULL | NULL    | NULL |    0 | const row not found |
     |  1 | PRIMARY     | <derived2> | system | NULL          | NULL | NULL    | NULL |    1 |                     |
     |  2 | DERIVED     | NULL       | NULL   | NULL          | NULL | NULL    | NULL | NULL | No tables used      |
     +----+-------------+------------+--------+---------------+------+---------+------+------+---------------------+
     3 rows in set (0.00 sec)

     mysql> SELECT * FROM t2;
     +------+
     | c1   |
     +------+
     |    5 |
     +------+
     1 row in set (0.00 sec)

This also means that an *Note `EXPLAIN SELECT': explain. statement such
as the one shown here may take a long time to execute because the
`BENCHMARK()' function is executed once for each row in `t1':


     EXPLAIN SELECT * FROM t1 AS a1, (SELECT BENCHMARK(1000000, MD5(NOW())));


File: manual.info,  Node: subquery-errors,  Next: optimizing-subqueries,  Prev: from-clause-subqueries,  Up: subqueries

13.2.9.9 Subquery Errors
........................

There are some errors that apply only to subqueries. This section
describes them.

   * Unsupported subquery syntax:


          ERROR 1235 (ER_NOT_SUPPORTED_YET)
          SQLSTATE = 42000
          Message = "This version of MySQL doesn't yet support
          'LIMIT & IN/ALL/ANY/SOME subquery'"

     This means that MySQL does not support statements of the following
     form:


          SELECT * FROM t1 WHERE s1 IN (SELECT s2 FROM t2 ORDER BY s1 LIMIT 1)

   * Incorrect number of columns from subquery:


          ERROR 1241 (ER_OPERAND_COL)
          SQLSTATE = 21000
          Message = "Operand should contain 1 column(s)"

     This error occurs in cases like this:


          SELECT (SELECT column1, column2 FROM t2) FROM t1;

     You may use a subquery that returns multiple columns, if the
     purpose is row comparison. In other contexts, the subquery must be
     a scalar operand. See *Note row-subqueries::.

   * Incorrect number of rows from subquery:


          ERROR 1242 (ER_SUBSELECT_NO_1_ROW)
          SQLSTATE = 21000
          Message = "Subquery returns more than 1 row"

     This error occurs for statements where the subquery must return at
     most one row but returns multiple rows. Consider the following
     example:


          SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);

     If `SELECT column1 FROM t2' returns just one row, the previous
     query will work. If the subquery returns more than one row, error
     1242 will occur. In that case, the query should be rewritten as:


          SELECT * FROM t1 WHERE column1 = ANY (SELECT column1 FROM t2);

   * Incorrectly used table in subquery:


          Error 1093 (ER_UPDATE_TABLE_USED)
          SQLSTATE = HY000
          Message = "You can't specify target table 'x'
          for update in FROM clause"

     This error occurs in cases such as the following, which attempts
     to modify a table and select from the same table in the subquery:


          UPDATE t1 SET column2 = (SELECT MAX(column1) FROM t1);

     You can use a subquery for assignment within an *Note `UPDATE':
     update. statement because subqueries are legal in *Note `UPDATE':
     update. and *Note `DELETE': delete. statements as well as in *Note
     `SELECT': select. statements.  However, you cannot use the same
     table (in this case, table `t1') for both the subquery `FROM'
     clause and the update target.

For transactional storage engines, the failure of a subquery causes the
entire statement to fail. For nontransactional storage engines, data
modifications made before the error was encountered are preserved.


File: manual.info,  Node: optimizing-subqueries,  Next: rewriting-subqueries,  Prev: subquery-errors,  Up: subqueries

13.2.9.10 Optimizing Subqueries
...............................

Development is ongoing, so no optimization tip is reliable for the long
term. The following list provides some interesting tricks that you
might want to play with:

   * Use subquery clauses that affect the number or order of the rows
     in the subquery. For example:


          SELECT * FROM t1 WHERE t1.column1 IN
            (SELECT column1 FROM t2 ORDER BY column1);
          SELECT * FROM t1 WHERE t1.column1 IN
            (SELECT DISTINCT column1 FROM t2);
          SELECT * FROM t1 WHERE EXISTS
            (SELECT * FROM t2 LIMIT 1);

   * Replace a join with a subquery. For example, try this:


          SELECT DISTINCT column1 FROM t1 WHERE t1.column1 IN (
            SELECT column1 FROM t2);

     Instead of this:


          SELECT DISTINCT t1.column1 FROM t1, t2
            WHERE t1.column1 = t2.column1;

   * Some subqueries can be transformed to joins for compatibility with
     older versions of MySQL that do not support subqueries. However,
     in some cases, converting a subquery to a join may improve
     performance. See *Note rewriting-subqueries::.

   * Move clauses from outside to inside the subquery. For example, use
     this query:


          SELECT * FROM t1
            WHERE s1 IN (SELECT s1 FROM t1 UNION ALL SELECT s1 FROM t2);

     Instead of this query:


          SELECT * FROM t1
            WHERE s1 IN (SELECT s1 FROM t1) OR s1 IN (SELECT s1 FROM t2);

     For another example, use this query:


          SELECT (SELECT column1 + 5 FROM t1) FROM t2;

     Instead of this query:


          SELECT (SELECT column1 FROM t1) + 5 FROM t2;

   * Use a row subquery instead of a correlated subquery. For example,
     use this query:


          SELECT * FROM t1
            WHERE (column1,column2) IN (SELECT column1,column2 FROM t2);

     Instead of this query:


          SELECT * FROM t1
            WHERE EXISTS (SELECT * FROM t2 WHERE t2.column1=t1.column1
                          AND t2.column2=t1.column2);

   * Use `NOT (a = ANY (...))' rather than `a <> ALL (...)'.

   * Use `x = ANY (TABLE CONTAINING (1,2))' rather than `x=1 OR x=2'.

   * Use `= ANY' rather than `EXISTS'.

   * For uncorrelated subqueries that always return one row, `IN' is
     always slower than `='. For example, use this query:


          SELECT * FROM t1
            WHERE t1.COL_NAME = (SELECT a FROM t2 WHERE b = SOME_CONST);

     Instead of this query:


          SELECT * FROM t1
            WHERE t1.COL_NAME IN (SELECT a FROM t2 WHERE b = SOME_CONST);

These tricks might cause programs to go faster or slower. Using MySQL
facilities like the `BENCHMARK()' function, you can get an idea about
what helps in your own situation. See *Note information-functions::.

Some optimizations that MySQL itself makes are:

   * MySQL executes uncorrelated subqueries only once. Use *Note
     `EXPLAIN': explain. to make sure that a given subquery really is
     uncorrelated.

   * MySQL rewrites `IN', `ALL', `ANY', and `SOME' subqueries in an
     attempt to take advantage of the possibility that the select-list
     columns in the subquery are indexed.

   * MySQL replaces subqueries of the following form with an
     index-lookup function, which *Note `EXPLAIN': explain. describes
     as a special join type (`unique_subquery' or `index_subquery'):


          ... IN (SELECT INDEXED_COLUMN FROM SINGLE_TABLE ...)

   * MySQL enhances expressions of the following form with an
     expression involving `MIN()' or `MAX()', unless `NULL' values or
     empty sets are involved:


          VALUE {ALL|ANY|SOME} {> | < | >= | <=} (UNCORRELATED SUBQUERY)

     For example, this `WHERE' clause:


          WHERE 5 > ALL (SELECT x FROM t)

     might be treated by the optimizer like this:


          WHERE 5 > (SELECT MAX(x) FROM t)

See also MySQL Internals: How MySQL Transforms Subqueries
(http://dev.mysql.com/doc/internals/en/transformations.html).


File: manual.info,  Node: rewriting-subqueries,  Prev: optimizing-subqueries,  Up: subqueries

13.2.9.11 Rewriting Subqueries as Joins
.......................................

Sometimes there are other ways to test membership in a set of values
than by using a subquery. Also, on some occasions, it is not only
possible to rewrite a query without a subquery, but it can be more
efficient to make use of some of these techniques rather than to use
subqueries. One of these is the `IN()' construct:

For example, this query:


     SELECT * FROM t1 WHERE id IN (SELECT id FROM t2);

Can be rewritten as:


     SELECT DISTINCT t1.* FROM t1, t2 WHERE t1.id=t2.id;

The queries:


     SELECT * FROM t1 WHERE id NOT IN (SELECT id FROM t2);
     SELECT * FROM t1 WHERE NOT EXISTS (SELECT id FROM t2 WHERE t1.id=t2.id);

Can be rewritten as:


     SELECT table1.*
       FROM table1 LEFT JOIN table2 ON table1.id=table2.id
       WHERE table2.id IS NULL;

A `LEFT [OUTER] JOIN' can be faster than an equivalent subquery because
the server might be able to optimize it better--a fact that is not
specific to MySQL Server alone. Prior to SQL-92, outer joins did not
exist, so subqueries were the only way to do certain things. Today,
MySQL Server and many other modern database systems offer a wide range
of outer join types.

MySQL Server supports multiple-table *Note `DELETE': delete. statements
that can be used to efficiently delete rows based on information from
one table or even from many tables at the same time. Multiple-table
*Note `UPDATE': update. statements are also supported. See *Note
delete::, and *Note update::.


File: manual.info,  Node: update,  Prev: subqueries,  Up: sql-syntax-data-manipulation

13.2.10 UPDATE Syntax
---------------------

Single-table syntax:


     UPDATE [LOW_PRIORITY] [IGNORE] TABLE_REFERENCE
         SET COL_NAME1={EXPR1|DEFAULT} [, COL_NAME2={EXPR2|DEFAULT}] ...
         [WHERE WHERE_CONDITION]
         [ORDER BY ...]
         [LIMIT ROW_COUNT]

Multiple-table syntax:


     UPDATE [LOW_PRIORITY] [IGNORE] TABLE_REFERENCES
         SET COL_NAME1={EXPR1|DEFAULT} [, COL_NAME2={EXPR2|DEFAULT}] ...
         [WHERE WHERE_CONDITION]

For the single-table syntax, the *Note `UPDATE': update. statement
updates columns of existing rows in the named table with new values. The
`SET' clause indicates which columns to modify and the values they
should be given. Each value can be given as an expression, or the
keyword `DEFAULT' to set a column explicitly to its default value. The
`WHERE' clause, if given, specifies the conditions that identify which
rows to update. With no `WHERE' clause, all rows are updated. If the
`ORDER BY' clause is specified, the rows are updated in the order that
is specified. The `LIMIT' clause places a limit on the number of rows
that can be updated.

For the multiple-table syntax, *Note `UPDATE': update. updates rows in
each table named in TABLE_REFERENCES that satisfy the conditions. Each
matching row is updated once, even if it matches the conditions
multiple times. For multiple-table syntax, `ORDER BY' and `LIMIT'
cannot be used.

WHERE_CONDITION is an expression that evaluates to true for each row to
be updated. For expression syntax, see *Note expressions::.

TABLE_REFERENCES and WHERE_CONDITION are specified as described in
*Note select::.

You need the `UPDATE' privilege only for columns referenced in an *Note
`UPDATE': update.  that are actually updated. You need only the
`SELECT' privilege for any columns that are read but not modified.

The *Note `UPDATE': update. statement supports the following modifiers:

   * With the `LOW_PRIORITY' keyword, execution of the *Note `UPDATE':
     update. is delayed until no other clients are reading from the
     table. This affects only storage engines that use only table-level
     locking (such as `MyISAM', `MEMORY', and `MERGE').

   * With the `IGNORE' keyword, the update statement does not abort
     even if errors occur during the update. Rows for which
     duplicate-key conflicts occur on a unique key value are not
     updated. Rows updated to values that would cause data conversion
     errors are updated to the closest valid values instead.

If you access a column from the table to be updated in an expression,
*Note `UPDATE': update. uses the current value of the column. For
example, the following statement sets `col1' to one more than its
current value:


     UPDATE t1 SET col1 = col1 + 1;

The second assignment in the following statement sets `col2' to the
current (updated) `col1' value, not the original `col1' value. The
result is that `col1' and `col2' have the same value. This behavior
differs from standard SQL.


     UPDATE t1 SET col1 = col1 + 1, col2 = col1;

Single-table *Note `UPDATE': update. assignments are generally
evaluated from left to right. For multiple-table updates, there is no
guarantee that assignments are carried out in any particular order.

If you set a column to the value it currently has, MySQL notices this
and does not update it.

If you update a column that has been declared `NOT NULL' by setting to
`NULL', an error occurs if strict SQL mode is enabled; otherwise, the
column is set to the implicit default value for the column data type
and the warning count is incremented. The implicit default value is `0'
for numeric types, the empty string (`''') for string types, and the
`zero' value for date and time types. See *Note data-type-defaults::.

*Note `UPDATE': update. returns the number of rows that were actually
changed. The *Note `mysql_info()': mysql-info. C API function returns
the number of rows that were matched and updated and the number of
warnings that occurred during the *Note `UPDATE': update.

You can use `LIMIT ROW_COUNT' to restrict the scope of the *Note
`UPDATE': update. A `LIMIT' clause is a rows-matched restriction. The
statement stops as soon as it has found ROW_COUNT rows that satisfy the
`WHERE' clause, whether or not they actually were changed.

If an *Note `UPDATE': update. statement includes an `ORDER BY' clause,
the rows are updated in the order specified by the clause. This can be
useful in certain situations that might otherwise result in an error.
Suppose that a table `t' contains a column `id' that has a unique
index. The following statement could fail with a duplicate-key error,
depending on the order in which rows are updated:


     UPDATE t SET id = id + 1;

For example, if the table contains 1 and 2 in the `id' column and 1 is
updated to 2 before 2 is updated to 3, an error occurs. To avoid this
problem, add an `ORDER BY' clause to cause the rows with larger `id'
values to be updated before those with smaller values:


     UPDATE t SET id = id + 1 ORDER BY id DESC;

You can also perform *Note `UPDATE': update.  operations covering
multiple tables. However, you cannot use `ORDER BY' or `LIMIT' with a
multiple-table *Note `UPDATE': update. The TABLE_REFERENCES clause
lists the tables involved in the join. Its syntax is described in *Note
join::. Here is an example:


     UPDATE items,month SET items.price=month.price
     WHERE items.id=month.id;

The preceding example shows an inner join that uses the comma operator,
but multiple-table *Note `UPDATE': update.  statements can use any type
of join permitted in *Note `SELECT': select. statements, such as `LEFT
JOIN'.

If you use a multiple-table *Note `UPDATE': update.  statement
involving `InnoDB' tables for which there are foreign key constraints,
the MySQL optimizer might process tables in an order that differs from
that of their parent/child relationship. In this case, the statement
fails and rolls back. Instead, update a single table and rely on the
`ON UPDATE' capabilities that `InnoDB' provides to cause the other
tables to be modified accordingly. See *Note
innodb-foreign-key-constraints::.

Currently, you cannot update a table and select from the same table in
a subquery.

Index hints (see *Note index-hints::) are accepted but ignored for
*Note `UPDATE': update. statements.

An `UPDATE' on a partitioned table using a storage engine such as *Note
`MyISAM': myisam-storage-engine. that employs table-level locks locks
all partitions of the table. This does not occur with tables using
storage engines such as *Note `InnoDB': innodb-storage-engine. that
employ row-level locking.  This issue is resolved in MySQL 5.6. See
*Note partitioning-limitations-locking::, for more information.


File: manual.info,  Node: sql-syntax-transactions,  Next: sql-syntax-replication,  Prev: sql-syntax-data-manipulation,  Up: sql-syntax

13.3 MySQL Transactional and Locking Statements
===============================================

* Menu:

* commit::                       START TRANSACTION, COMMIT, and ROLLBACK Syntax
* cannot-roll-back::             Statements That Cannot Be Rolled Back
* implicit-commit::              Statements That Cause an Implicit Commit
* savepoint::                    SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Syntax
* lock-tables::                  LOCK TABLES and UNLOCK TABLES Syntax
* set-transaction::              SET TRANSACTION Syntax
* xa::                           XA Transactions

MySQL supports local transactions (within a given client session)
through statements such as *Note `SET autocommit': commit, *Note `START
TRANSACTION': commit, *Note `COMMIT': commit, and *Note `ROLLBACK':
commit. See *Note commit::. XA transaction support enables MySQL to
participate in distributed transactions as well. See *Note xa::.


File: manual.info,  Node: commit,  Next: cannot-roll-back,  Prev: sql-syntax-transactions,  Up: sql-syntax-transactions

13.3.1 START TRANSACTION, COMMIT, and ROLLBACK Syntax
-----------------------------------------------------


     START TRANSACTION [WITH CONSISTENT SNAPSHOT]
     BEGIN [WORK]
     COMMIT [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
     ROLLBACK [WORK] [AND [NO] CHAIN] [[NO] RELEASE]
     SET autocommit = {0 | 1}

These statements provide control over use of transactions
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transaction):

   * `START TRANSACTION' or `BEGIN' start a new transaction.

   * `COMMIT' commits the current transaction, making its changes
     permanent.

   * `ROLLBACK' rolls back the current transaction, canceling its
     changes.

   * `SET autocommit' disables or enables the default autocommit mode
     for the current session.

By default, MySQL runs with autocommit
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_autocommit)
mode enabled.  This means that as soon as you execute a statement that
updates (modifies) a table, MySQL stores the update on disk to make it
permanent. The change cannot be rolled back.

To disable autocommit mode implicitly for a single series of
statements, use the `START TRANSACTION' statement:


     START TRANSACTION;
     SELECT @A:=SUM(salary) FROM table1 WHERE type=1;
     UPDATE table2 SET summary=@A WHERE type=1;
     COMMIT;

With `START TRANSACTION', autocommit remains disabled until you end the
transaction with `COMMIT' or `ROLLBACK'. The autocommit mode then
reverts to its previous state.

You can also begin a transaction like this:


     START TRANSACTION WITH CONSISTENT SNAPSHOT;

The `WITH CONSISTENT SNAPSHOT' option starts a consistent read
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_consistent_read)
for storage engines that are capable of it. This applies only to
`InnoDB'. The effect is the same as issuing a `START TRANSACTION'
followed by a *Note `SELECT': select. from any `InnoDB' table. See
*Note innodb-consistent-read::. The `WITH CONSISTENT SNAPSHOT' option
does not change the current transaction isolation level
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_isolation_level),
so it provides a consistent snapshot only if the current isolation
level is one that permits a consistent read. The only isolation level
that permits a consistent read is `REPEATABLE READ'. For all other
isolation levels, the `WITH CONSISTENT SNAPSHOT' clause is ignored.

*Important*:

Many APIs used for writing MySQL client applications (such as JDBC)
provide their own methods for starting transactions that can (and
sometimes should) be used instead of sending a `START TRANSACTION'
statement from the client.  See *Note connectors-apis::, or the
documentation for your API, for more information.

To disable autocommit mode explicitly, use the following statement:


     SET autocommit=0;

After disabling autocommit mode by setting the `autocommit' variable to
zero, changes to transaction-safe tables (such as those for *Note
`InnoDB': innodb-storage-engine. or *Note `NDBCLUSTER': mysql-cluster.)
are not made permanent immediately. You must use `COMMIT' to store your
changes to disk or `ROLLBACK' to ignore the changes.

`autocommit' is a session variable and must be set for each session. To
disable autocommit mode for each new connection, see the description of
the `autocommit' system variable at *Note server-system-variables::.

`BEGIN' and `BEGIN WORK' are supported as aliases of `START
TRANSACTION' for initiating a transaction. `START TRANSACTION' is
standard SQL syntax and is the recommended way to start an ad-hoc
transaction.

The *Note `BEGIN': commit.  statement differs from the use of the
`BEGIN' keyword that starts a *Note `BEGIN ... END': begin-end.
compound statement. The latter does not begin a transaction. See *Note
begin-end::.

*Note*:

Within all stored programs (stored procedures and functions, triggers,
and events), the parser treats `BEGIN [WORK]' as the beginning of a
*Note `BEGIN ... END': begin-end. block. Begin a transaction in this
context with `START TRANSACTION' instead.

The optional `WORK' keyword is supported for `COMMIT' and `ROLLBACK',
as are the `CHAIN' and `RELEASE' clauses. `CHAIN' and `RELEASE' can be
used for additional control over transaction completion.  The value of
the `completion_type' system variable determines the default completion
behavior. See *Note server-system-variables::.

The `AND CHAIN' clause causes a new transaction to begin as soon as the
current one ends, and the new transaction has the same isolation level
as the just-terminated transaction.  The `RELEASE' clause causes the
server to disconnect the current client session after terminating the
current transaction. Including the `NO' keyword suppresses `CHAIN' or
`RELEASE' completion, which can be useful if the `completion_type'
system variable is set to cause chaining or release completion by
default.

Beginning a transaction causes any pending transaction to be committed.
See *Note implicit-commit::, for more information.

Beginning a transaction also causes table locks acquired with *Note
`LOCK TABLES': lock-tables. to be released, as though you had executed
*Note `UNLOCK TABLES': lock-tables. Beginning a transaction does not
release a global read lock acquired with *Note `FLUSH TABLES WITH READ
LOCK': flush.

For best results, transactions should be performed using only tables
managed by a single transaction-safe storage engine.  Otherwise, the
following problems can occur:

   * If you use tables from more than one transaction-safe storage
     engine (such as `InnoDB'), and the transaction isolation level is
     not `SERIALIZABLE', it is possible that when one transaction
     commits, another ongoing transaction that uses the same tables
     will see only some of the changes made by the first transaction.
     That is, the atomicity of transactions is not guaranteed with
     mixed engines and inconsistencies can result. (If mixed-engine
     transactions are infrequent, you can use *Note `SET TRANSACTION
     ISOLATION LEVEL': set-transaction. to set the isolation level to
     `SERIALIZABLE' on a per-transaction basis as necessary.)

   * If you use tables that are not transaction-safe within a
     transaction, changes to those tables are stored at once,
     regardless of the status of autocommit mode.

   * If you issue a *Note `ROLLBACK': commit.  statement after updating
     a nontransactional table within a transaction, an
     `ER_WARNING_NOT_COMPLETE_ROLLBACK' warning occurs. Changes to
     transaction-safe tables are rolled back, but not changes to
     nontransaction-safe tables.

Each transaction is stored in the binary log in one chunk, upon *Note
`COMMIT': commit. Transactions that are rolled back are not logged.
(*Exception*: Modifications to nontransactional tables cannot be rolled
back. If a transaction that is rolled back includes modifications to
nontransactional tables, the entire transaction is logged with a *Note
`ROLLBACK': commit.  statement at the end to ensure that modifications
to the nontransactional tables are replicated.) See *Note binary-log::.

You can change the isolation level for transactions with the *Note `SET
TRANSACTION': set-transaction. statement. See *Note set-transaction::.

Rolling back can be a slow operation that may occur implicitly without
the user having explicitly asked for it (for example, when an error
occurs). Because of this, *Note `SHOW PROCESSLIST': show-processlist.
displays `Rolling back' in the `State' column for the session, not only
for explicit rollbacks performed with the *Note `ROLLBACK': commit.
statement but also for implicit rollbacks.

*Note*:

Beginning with MySQL 5.1.36, `BEGIN', `COMMIT', and `ROLLBACK' are no
longer affected by `--replicate-do-db' or `--replicate-ignore-db'
rules. (Bug #43263)


File: manual.info,  Node: cannot-roll-back,  Next: implicit-commit,  Prev: commit,  Up: sql-syntax-transactions

13.3.2 Statements That Cannot Be Rolled Back
--------------------------------------------

Some statements cannot be rolled back. In general, these include data
definition language (DDL) statements, such as those that create or drop
databases, those that create, drop, or alter tables or stored routines.

You should design your transactions not to include such statements. If
you issue a statement early in a transaction that cannot be rolled
back, and then another statement later fails, the full effect of the
transaction cannot be rolled back in such cases by issuing a *Note
`ROLLBACK': commit.  statement.


File: manual.info,  Node: implicit-commit,  Next: savepoint,  Prev: cannot-roll-back,  Up: sql-syntax-transactions

13.3.3 Statements That Cause an Implicit Commit
-----------------------------------------------

The statements listed in this section (and any synonyms for them)
implicitly end any transaction active in the current session, as if you
had done a *Note `COMMIT': commit. before executing the statement.

   * *Data definition language (DDL) statements that define or modify
     database objects.* `ALTER DATABASE ... UPGRADE DATA DIRECTORY
     NAME', *Note `ALTER EVENT': alter-event, *Note `ALTER PROCEDURE':
     alter-procedure, *Note `ALTER SERVER': alter-server, *Note `ALTER
     TABLE': alter-table, *Note `CREATE DATABASE': create-database,
     *Note `CREATE EVENT': create-event, *Note `CREATE INDEX':
     create-index, *Note `CREATE PROCEDURE': create-procedure, *Note
     `CREATE SERVER': create-server, *Note `CREATE TABLE': create-table,
     *Note `DROP DATABASE': drop-database, *Note `DROP EVENT':
     drop-event, *Note `DROP INDEX': drop-index, *Note `DROP
     PROCEDURE': drop-procedure, *Note `DROP SERVER': drop-server,
     *Note `DROP TABLE': drop-table, *Note `RENAME TABLE': rename-table,
     *Note `TRUNCATE TABLE': truncate-table.

     *Note `ALTER FUNCTION': alter-function, *Note `CREATE FUNCTION':
     create-function. and *Note `DROP FUNCTION': drop-function. also
     cause an implicit commit when used with stored functions, but not
     with UDFs. (*Note `ALTER FUNCTION': alter-function. can only be
     used with stored functions.)

     *Note `CREATE TABLE': create-table. and *Note `DROP TABLE':
     drop-table. statements do not commit a transaction if the
     `TEMPORARY' keyword is used. (This does not apply to other
     operations on temporary tables such as *Note `ALTER TABLE':
     alter-table. and *Note `CREATE INDEX': create-index, which do
     cause a commit.) However, although no implicit commit occurs,
     neither can the statement be rolled back, which means that the use
     of such statements causes transactional atomicity to be violated.
     For example, if you use *Note `CREATE TEMPORARY TABLE':
     create-table. and then roll back the transaction, the table
     remains in existence.

     The *Note `CREATE TABLE': create-table. statement in `InnoDB' is
     processed as a single transaction. This means that a *Note
     `ROLLBACK': commit.  from the user does not undo *Note `CREATE
     TABLE': create-table. statements the user made during that
     transaction.

     Beginning with MySQL 5.1.3, *Note `ALTER VIEW': alter-view, *Note
     `CREATE TRIGGER': create-trigger, *Note `CREATE VIEW': create-view,
     *Note `DROP TRIGGER': drop-trigger, and *Note `DROP VIEW':
     drop-view. cause an implicit commit.

     Beginning with MySQL 5.1.15, *Note `CREATE TABLE ... SELECT':
     create-table. causes an implicit commit before and after the
     statement is executed when you are creating nontemporary tables.
     (No commit occurs for `CREATE TEMPORARY TABLE ... SELECT'.) This
     is to prevent an issue during replication where the table could be
     created on the master after a rollback, but fail to be recorded in
     the binary log, and therefore not replicated to the slave. For more
     information, see Bug #22865.

   * *Statements that implicitly use or modify tables in the `mysql'
     database.* Beginning with MySQL 5.1.3, *Note `CREATE USER':
     create-user, *Note `DROP USER': drop-user, and *Note `RENAME
     USER': rename-user. cause an implicit commit. Beginning with MySQL
     5.1.23, *Note `GRANT': grant, *Note `REVOKE': revoke, and *Note
     `SET PASSWORD': set-password. statements cause an implicit commit.

   * *Transaction-control and locking statements.* *Note `BEGIN':
     commit, *Note `LOCK TABLES': lock-tables, `SET autocommit = 1' (if
     the value is not already 1), *Note `START TRANSACTION': commit,
     *Note `UNLOCK TABLES': lock-tables.

     *Note `UNLOCK TABLES': lock-tables. commits a transaction only if
     any tables currently have been locked with *Note `LOCK TABLES':
     lock-tables. This does not occur for *Note `UNLOCK TABLES':
     lock-tables. following *Note `FLUSH TABLES WITH READ LOCK': flush.
     because the latter statement does not acquire table-level locks.

     Transactions cannot be nested. This is a consequence of the
     implicit commit performed for any current transaction when you
     issue a *Note `START TRANSACTION': commit. statement or one of its
     synonyms.

     Statements that cause an implicit commit cannot be used in an XA
     transaction while the transaction is in an `ACTIVE' state.

     The *Note `BEGIN': commit.  statement differs from the use of the
     `BEGIN' keyword that starts a *Note `BEGIN ... END': begin-end.
     compound statement. The latter does not cause an implicit commit.
     See *Note begin-end::.

   * *Data loading statements.* *Note `LOAD DATA INFILE': load-data.
     Before MySQL 5.1.12, *Note `LOAD DATA INFILE': load-data. caused
     an implicit commit for all storage engines. As of MySQL 5.1.12, it
     causes an implicit commit only for tables using the *Note `NDB':
     mysql-cluster. storage engine. For more information, see Bug
     #11151.

   * *Administrative statements.* *Note `CACHE INDEX': cache-index,
     *Note `LOAD INDEX INTO CACHE': load-index. Beginning with MySQL
     5.1.10, *Note `ANALYZE TABLE': analyze-table, *Note `CHECK TABLE':
     check-table, *Note `OPTIMIZE TABLE': optimize-table, and *Note
     `REPAIR TABLE': repair-table. cause an implicit commit.


File: manual.info,  Node: savepoint,  Next: lock-tables,  Prev: implicit-commit,  Up: sql-syntax-transactions

13.3.4 SAVEPOINT, ROLLBACK TO SAVEPOINT, and RELEASE SAVEPOINT Syntax
---------------------------------------------------------------------


     SAVEPOINT IDENTIFIER
     ROLLBACK [WORK] TO [SAVEPOINT] IDENTIFIER
     RELEASE SAVEPOINT IDENTIFIER

`InnoDB' supports the SQL statements *Note `SAVEPOINT': savepoint,
*Note `ROLLBACK TO SAVEPOINT': savepoint, *Note `RELEASE SAVEPOINT':
savepoint. and the optional `WORK' keyword for *Note `ROLLBACK': commit.

The *Note `SAVEPOINT': savepoint. statement sets a named transaction
savepoint with a name of IDENTIFIER. If the current transaction has a
savepoint with the same name, the old savepoint is deleted and a new
one is set.

The *Note `ROLLBACK TO SAVEPOINT': savepoint. statement rolls back a
transaction to the named savepoint without terminating the transaction.
Modifications that the current transaction made to rows after the
savepoint was set are undone in the rollback, but `InnoDB' does _not_
release the row locks that were stored in memory after the savepoint.
(For a new inserted row, the lock information is carried by the
transaction ID stored in the row; the lock is not separately stored in
memory. In this case, the row lock is released in the undo.) Savepoints
that were set at a later time than the named savepoint are deleted.

If the *Note `ROLLBACK TO SAVEPOINT': savepoint. statement returns the
following error, it means that no savepoint with the specified name
exists:


     ERROR 1305 (42000): SAVEPOINT IDENTIFIER does not exist

The *Note `RELEASE SAVEPOINT': savepoint. statement removes the named
savepoint from the set of savepoints of the current transaction. No
commit or rollback occurs. It is an error if the savepoint does not
exist.

All savepoints of the current transaction are deleted if you execute a
*Note `COMMIT': commit, or a *Note `ROLLBACK': commit. that does not
name a savepoint.

A new savepoint level is created when a stored function is invoked or a
trigger is activated. The savepoints on previous levels become
unavailable and thus do not conflict with savepoints on the new level.
When the function or trigger terminates, any savepoints it created are
released and the previous savepoint level is restored.


File: manual.info,  Node: lock-tables,  Next: set-transaction,  Prev: savepoint,  Up: sql-syntax-transactions

13.3.5 LOCK TABLES and UNLOCK TABLES Syntax
-------------------------------------------

* Menu:

* lock-tables-and-transactions::  Interaction of Table Locking and Transactions
* lock-tables-and-triggers::     LOCK TABLES and Triggers
* lock-tables-restrictions::     Table-Locking Restrictions and Conditions


     LOCK TABLES
         TBL_NAME [[AS] ALIAS] LOCK_TYPE
         [, TBL_NAME [[AS] ALIAS] LOCK_TYPE] ...

     LOCK_TYPE:
         READ [LOCAL]
       | [LOW_PRIORITY] WRITE

     UNLOCK TABLES

MySQL enables client sessions to acquire table locks explicitly for the
purpose of cooperating with other sessions for access to tables, or to
prevent other sessions from modifying tables during periods when a
session requires exclusive access to them. A session can acquire or
release locks only for itself. One session cannot acquire locks for
another session or release locks held by another session.

Locks may be used to emulate transactions or to get more speed when
updating tables. This is explained in more detail later in this section.

*Note `LOCK TABLES': lock-tables. explicitly acquires table locks for
the current client session. Table locks can be acquired for base tables
or views. You must have the `LOCK TABLES' privilege, and the `SELECT'
privilege for each object to be locked.

For view locking, *Note `LOCK TABLES': lock-tables. adds all base
tables used in the view to the set of tables to be locked and locks
them automatically. If you lock a table explicitly with *Note `LOCK
TABLES': lock-tables, any tables used in triggers are also locked
implicitly, as described in *Note lock-tables-and-triggers::.

*Note `UNLOCK TABLES': lock-tables. explicitly releases any table locks
held by the current session. *Note `LOCK TABLES': lock-tables.
implicitly releases any table locks held by the current session before
acquiring new locks.

Another use for *Note `UNLOCK TABLES': lock-tables. is to release the
global read lock acquired with the *Note `FLUSH TABLES WITH READ LOCK':
flush. statement, which enables you to lock all tables in all
databases. See *Note flush::. (This is a very convenient way to get
backups if you have a file system such as Veritas that can take
snapshots in time.)

A table lock protects only against inappropriate reads or writes by
other sessions. The session holding the lock, even a read lock, can
perform table-level operations such as *Note `DROP TABLE': drop-table.
Truncate operations are not transaction-safe, so an error occurs if the
session attempts one during an active transaction or while holding a
table lock.

The following discussion applies only to non-`TEMPORARY' tables. *Note
`LOCK TABLES': lock-tables. is permitted (but ignored) for a
`TEMPORARY' table. The table can be accessed freely by the session
within which it was created, regardless of what other locking may be in
effect. No lock is necessary because no other session can see the table.

For information about other conditions on the use of *Note `LOCK
TABLES': lock-tables. and statements that cannot be used while *Note
`LOCK TABLES': lock-tables. is in effect, see *Note
lock-tables-restrictions::

*Rules for Lock Acquisition*

To acquire table locks within the current session, use the *Note `LOCK
TABLES': lock-tables. statement. The following lock types are available:

`READ [LOCAL]' lock:

   * The session that holds the lock can read the table (but not write
     it).

   * Multiple sessions can acquire a `READ' lock for the table at the
     same time.

   * Other sessions can read the table without explicitly acquiring a
     `READ' lock.

   * The `LOCAL' modifier enables nonconflicting *Note `INSERT':
     insert. statements (concurrent inserts) by other sessions to
     execute while the lock is held.  (See *Note concurrent-inserts::.)
     However, `READ LOCAL' cannot be used if you are going to
     manipulate the database using processes external to the server
     while you hold the lock. For `InnoDB' tables, `READ LOCAL' is the
     same as `READ'.

`[LOW_PRIORITY] WRITE' lock:

   * The session that holds the lock can read and write the table.

   * Only the session that holds the lock can access the table. No
     other session can access it until the lock is released.

   * Lock requests for the table by other sessions block while the
     `WRITE' lock is held.

   * The `LOW_PRIORITY' modifier affects lock scheduling if the `WRITE'
     lock request must wait, as described later.

If the *Note `LOCK TABLES': lock-tables. statement must wait due to
locks held by other sessions on any of the tables, it blocks until all
locks can be acquired.

A session that requires locks must acquire all the locks that it needs
in a single *Note `LOCK TABLES': lock-tables.  statement. While the
locks thus obtained are held, the session can access only the locked
tables. For example, in the following sequence of statements, an error
occurs for the attempt to access `t2' because it was not locked in the
*Note `LOCK TABLES': lock-tables. statement:


     mysql> LOCK TABLES t1 READ;
     mysql> SELECT COUNT(*) FROM t1;
     +----------+
     | COUNT(*) |
     +----------+
     |        3 |
     +----------+
     mysql> SELECT COUNT(*) FROM t2;
     ERROR 1100 (HY000): Table 't2' was not locked with LOCK TABLES

Tables in the `INFORMATION_SCHEMA' database are an exception. They can
be accessed without being locked explicitly even while a session holds
table locks obtained with *Note `LOCK TABLES': lock-tables.

You cannot refer to a locked table multiple times in a single query
using the same name. Use aliases instead, and obtain a separate lock
for the table and each alias:


     mysql> LOCK TABLE t WRITE, t AS t1 READ;
     mysql> INSERT INTO t SELECT * FROM t;
     ERROR 1100: Table 't' was not locked with LOCK TABLES
     mysql> INSERT INTO t SELECT * FROM t AS t1;

The error occurs for the first *Note `INSERT': insert. because there
are two references to the same name for a locked table. The second
*Note `INSERT': insert. succeeds because the references to the table
use different names.

If your statements refer to a table by means of an alias, you must lock
the table using that same alias. It does not work to lock the table
without specifying the alias:


     mysql> LOCK TABLE t READ;
     mysql> SELECT * FROM t AS myalias;
     ERROR 1100: Table 'myalias' was not locked with LOCK TABLES

Conversely, if you lock a table using an alias, you must refer to it in
your statements using that alias:


     mysql> LOCK TABLE t AS myalias READ;
     mysql> SELECT * FROM t;
     ERROR 1100: Table 't' was not locked with LOCK TABLES
     mysql> SELECT * FROM t AS myalias;

`WRITE' locks normally have higher priority than `READ' locks to ensure
that updates are processed as soon as possible. This means that if one
session obtains a `READ' lock and then another session requests a
`WRITE' lock, subsequent `READ' lock requests wait until the session
that requested the `WRITE' lock has obtained the lock and released it.
A request for a `LOW_PRIORITY WRITE' lock, by contrast, permits
subsequent `READ' lock requests by other sessions to be satisfied first
if they occur while the `LOW_PRIORITY WRITE' request is waiting. You
should use `LOW_PRIORITY WRITE' locks only if you are sure that
eventually there will be a time when no sessions have a `READ' lock.
For `InnoDB' tables in transactional mode (autocommit = 0), a waiting
`LOW_PRIORITY WRITE' lock acts like a regular `WRITE' lock and causes
subsequent `READ' lock requests to wait.

*Note `LOCK TABLES': lock-tables. acquires locks as follows:

  1. Sort all tables to be locked in an internally defined order.  From
     the user standpoint, this order is undefined.

  2. If a table is to be locked with a read and a write lock, put the
     write lock request before the read lock request.

  3. Lock one table at a time until the session gets all locks.

This policy ensures that table locking is deadlock free. There are,
however, other things you need to be aware of about this policy: If you
are using a `LOW_PRIORITY WRITE' lock for a table, it means only that
MySQL waits for this particular lock until there are no other sessions
that want a `READ' lock. When the session has gotten the `WRITE' lock
and is waiting to get the lock for the next table in the lock table
list, all other sessions wait for the `WRITE' lock to be released. If
this becomes a serious problem with your application, you should
consider converting some of your tables to transaction-safe tables.

*Note*:

`LOCK TABLES' or `UNLOCK TABLES', when applied to a partitioned table,
always locks or unlocks the entire table. See *Note
partitioning-limitations-locking::.

*Rules for Lock Release*

When the table locks held by a session are released, they are all
released at the same time. A session can release its locks explicitly,
or locks may be released implicitly under certain conditions.

   * A session can release its locks explicitly with *Note `UNLOCK
     TABLES': lock-tables.

   * If a session issues a *Note `LOCK TABLES': lock-tables. statement
     to acquire a lock while already holding locks, its existing locks
     are released implicitly before the new locks are granted.

   * If a session begins a transaction (for example, with *Note `START
     TRANSACTION': commit.), an implicit *Note `UNLOCK TABLES':
     lock-tables. is performed, which causes existing locks to be
     released. (For additional information about the interaction
     between table locking and transactions, see *Note
     lock-tables-and-transactions::.)

If the connection for a client session terminates, whether normally or
abnormally, the server implicitly releases all table locks held by the
session (transactional and nontransactional). If the client reconnects,
the locks will no longer be in effect. In addition, if the client had
an active transaction, the server rolls back the transaction upon
disconnect, and if reconnect occurs, the new session begins with
autocommit enabled. For this reason, clients may wish to disable
auto-reconnect. With auto-reconnect in effect, the client is not
notified if reconnect occurs but any table locks or current transaction
will have been lost. With auto-reconnect disabled, if the connection
drops, an error occurs for the next statement issued. The client can
detect the error and take appropriate action such as reacquiring the
locks or redoing the transaction. See *Note auto-reconnect::.

*Note*:

If you use *Note `ALTER TABLE': alter-table. on a locked table, it may
become unlocked. For example, if you attempt a second *Note `ALTER
TABLE': alter-table.  operation, the result may be an error `Table
'TBL_NAME' was not locked with LOCK TABLES'. To handle this, lock the
table again prior to the second alteration. See also *Note
alter-table-problems::.


File: manual.info,  Node: lock-tables-and-transactions,  Next: lock-tables-and-triggers,  Prev: lock-tables,  Up: lock-tables

13.3.5.1 Interaction of Table Locking and Transactions
......................................................

*Note `LOCK TABLES': lock-tables. and *Note `UNLOCK TABLES':
lock-tables. interact with the use of transactions as follows:

   * *Note `LOCK TABLES': lock-tables. is not transaction-safe and
     implicitly commits any active transaction before attempting to
     lock the tables.

   * *Note `UNLOCK TABLES': lock-tables. implicitly commits any active
     transaction, but only if *Note `LOCK TABLES': lock-tables. has
     been used to acquire table locks. For example, in the following
     set of statements, *Note `UNLOCK TABLES': lock-tables. releases
     the global read lock but does not commit the transaction because
     no table locks are in effect:


          FLUSH TABLES WITH READ LOCK;
          START TRANSACTION;
          SELECT ... ;
          UNLOCK TABLES;

   * Beginning a transaction (for example, with *Note `START
     TRANSACTION': commit.) implicitly commits any current transaction
     and releases existing table locks.

   * *Note `FLUSH TABLES WITH READ LOCK': flush. acquires a global read
     lock and not table locks, so it is not subject to the same
     behavior as *Note `LOCK TABLES': lock-tables. and *Note `UNLOCK
     TABLES': lock-tables. with respect to table locking and implicit
     commits. For example, *Note `START TRANSACTION': commit. does not
     release the global read lock.  See *Note flush::.

   * Other statements that implicitly cause transactions to be
     committed do not release existing table locks. For a list of such
     statements, see *Note implicit-commit::.

   * The correct way to use *Note `LOCK TABLES': lock-tables. and *Note
     `UNLOCK TABLES': lock-tables. with transactional tables, such as
     `InnoDB' tables, is to begin a transaction with `SET autocommit =
     0' (not *Note `START TRANSACTION': commit.) followed by *Note
     `LOCK TABLES': lock-tables, and to not call *Note `UNLOCK TABLES':
     lock-tables. until you commit the transaction explicitly. For
     example, if you need to write to table `t1' and read from table
     `t2', you can do this:


          SET autocommit=0;
          LOCK TABLES t1 WRITE, t2 READ, ...;
          ... DO SOMETHING WITH TABLES T1 AND T2 HERE ...
          COMMIT;
          UNLOCK TABLES;

     When you call *Note `LOCK TABLES': lock-tables, `InnoDB'
     internally takes its own table lock, and MySQL takes its own table
     lock.  `InnoDB' releases its internal table lock at the next
     commit, but for MySQL to release its table lock, you have to call
     *Note `UNLOCK TABLES': lock-tables. You should not have
     `autocommit = 1', because then `InnoDB' releases its internal table
     lock immediately after the call of *Note `LOCK TABLES':
     lock-tables, and deadlocks can very easily happen.  `InnoDB' does
     not acquire the internal table lock at all if `autocommit = 1', to
     help old applications avoid unnecessary deadlocks.

   * *Note `ROLLBACK': commit.  does not release table locks.


File: manual.info,  Node: lock-tables-and-triggers,  Next: lock-tables-restrictions,  Prev: lock-tables-and-transactions,  Up: lock-tables

13.3.5.2 LOCK TABLES and Triggers
.................................

If you lock a table explicitly with *Note `LOCK TABLES': lock-tables,
any tables used in triggers are also locked implicitly:

   * The locks are taken as the same time as those acquired explicitly
     with the *Note `LOCK TABLES': lock-tables. statement.

   * The lock on a table used in a trigger depends on whether the table
     is used only for reading. If so, a read lock suffices.  Otherwise,
     a write lock is used.

   * If a table is locked explicitly for reading with *Note `LOCK
     TABLES': lock-tables, but needs to be locked for writing because
     it might be modified within a trigger, a write lock is taken
     rather than a read lock.  (That is, an implicit write lock needed
     due to the table's appearance within a trigger causes an explicit
     read lock request for the table to be converted to a write lock
     request.)

Suppose that you lock two tables, `t1' and `t2', using this statement:


     LOCK TABLES t1 WRITE, t2 READ;

If `t1' or `t2' have any triggers, tables used within the triggers will
also be locked.  Suppose that `t1' has a trigger defined like this:


     CREATE TRIGGER t1_a_ins AFTER INSERT ON t1 FOR EACH ROW
     BEGIN
       UPDATE t4 SET count = count+1
           WHERE id = NEW.id AND EXISTS (SELECT a FROM t3);
       INSERT INTO t2 VALUES(1, 2);
     END;

The result of the *Note `LOCK TABLES': lock-tables.  statement is that
`t1' and `t2' are locked because they appear in the statement, and `t3'
and `t4' are locked because they are used within the trigger:

   * `t1' is locked for writing per the `WRITE' lock request.

   * `t2' is locked for writing, even though the request is for a
     `READ' lock. This occurs because `t2' is inserted into within the
     trigger, so the `READ' request is converted to a `WRITE' request.

   * `t3' is locked for reading because it is only read from within the
     trigger.

   * `t4' is locked for writing because it might be updated within the
     trigger.


File: manual.info,  Node: lock-tables-restrictions,  Prev: lock-tables-and-triggers,  Up: lock-tables

13.3.5.3 Table-Locking Restrictions and Conditions
..................................................

You can safely use *Note `KILL': kill. to terminate a session that is
waiting for a table lock. See *Note kill::.

You should _not_ lock any tables that you are using with *Note `INSERT
DELAYED': insert-delayed. An *Note `INSERT DELAYED': insert-delayed. in
this case results in an error because the insert must be handled by a
separate thread, not by the session which holds the lock.

*Note `LOCK TABLES': lock-tables. and *Note `UNLOCK TABLES':
lock-tables. cannot be used within stored programs.

For some operations, system tables in the `mysql' database must be
accessed. For example, the *Note `HELP': help. statement requires the
contents of the server-side help tables, and `CONVERT_TZ()' might need
to read the time zone tables. Before MySQL 5.1.17, to perform such
operations while a *Note `LOCK TABLES': lock-tables.  statement is in
effect, you must also lock the requisite system tables explicitly or a
lock error occurs. As of 5.1.17, the server implicitly locks the system
tables for reading as necessary so that you need not lock them
explicitly. These tables are treated as just described:


     mysql.help_category
     mysql.help_keyword
     mysql.help_relation
     mysql.help_topic
     mysql.proc
     mysql.time_zone
     mysql.time_zone_leap_second
     mysql.time_zone_name
     mysql.time_zone_transition
     mysql.time_zone_transition_type

If you want to explicitly place a `WRITE' lock on any of those tables
with a *Note `LOCK TABLES': lock-tables. statement, the table must be
the only one locked; no other table can be locked with the same
statement.

Normally, you do not need to lock tables, because all single *Note
`UPDATE': update. statements are atomic; no other session can interfere
with any other currently executing SQL statement. However, there are a
few cases when locking tables may provide an advantage:

   * If you are going to run many operations on a set of `MyISAM'
     tables, it is much faster to lock the tables you are going to use.
     Locking `MyISAM' tables speeds up inserting, updating, or deleting
     on them because MySQL does not flush the key cache for the locked
     tables until *Note `UNLOCK TABLES': lock-tables. is called.
     Normally, the key cache is flushed after each SQL statement.

     The downside to locking the tables is that no session can update a
     `READ'-locked table (including the one holding the lock) and no
     session can access a `WRITE'-locked table other than the one
     holding the lock.

   * If you are using tables for a nontransactional storage engine, you
     must use *Note `LOCK TABLES': lock-tables. if you want to ensure
     that no other session modifies the tables between a *Note
     `SELECT': select. and an *Note `UPDATE': update. The example shown
     here requires *Note `LOCK TABLES': lock-tables. to execute safely:


          LOCK TABLES trans READ, customer WRITE;
          SELECT SUM(value) FROM trans WHERE customer_id=SOME_ID;
          UPDATE customer
            SET total_value=SUM_FROM_PREVIOUS_STATEMENT
            WHERE customer_id=SOME_ID;
          UNLOCK TABLES;

     Without *Note `LOCK TABLES': lock-tables, it is possible that
     another session might insert a new row in the `trans' table
     between execution of the *Note `SELECT': select. and *Note
     `UPDATE': update. statements.

You can avoid using *Note `LOCK TABLES': lock-tables.  in many cases by
using relative updates (`UPDATE customer SET VALUE=VALUE+NEW_VALUE') or
the `LAST_INSERT_ID()' function.  See *Note ansi-diff-transactions::.

You can also avoid locking tables in some cases by using the user-level
advisory lock functions `GET_LOCK()' and `RELEASE_LOCK()'. These locks
are saved in a hash table in the server and implemented with
`pthread_mutex_lock()' and `pthread_mutex_unlock()' for high speed. See
*Note miscellaneous-functions::.

See *Note internal-locking::, for more information on locking policy.


File: manual.info,  Node: set-transaction,  Next: xa,  Prev: lock-tables,  Up: sql-syntax-transactions

13.3.6 SET TRANSACTION Syntax
-----------------------------


     SET [GLOBAL | SESSION] TRANSACTION ISOLATION LEVEL
       {
            REPEATABLE READ
          | READ COMMITTED
          | READ UNCOMMITTED
          | SERIALIZABLE
        }

This statement sets the transaction isolation level, used for
operations on *Note `InnoDB': innodb-storage-engine. tables.

*Scope of the Isolation Level*

You can set the isolation level globally, for the current session, or
for the next transaction:

   * With the `GLOBAL' keyword, the statement sets the default
     transaction level globally for all subsequent sessions. Existing
     sessions are unaffected.

   * With the `SESSION' keyword, the statement sets the default
     transaction level for all subsequent transactions performed within
     the current session.

   * Without any `SESSION' or `GLOBAL' keyword, the statement sets the
     isolation level for the next (not started) transaction performed
     within the current session.

A change to the global default isolation level requires the `SUPER'
privilege. Any session is free to change its session isolation level
(even in the middle of a transaction), or the isolation level for its
next transaction.

*Note `SET TRANSACTION ISOLATION LEVEL': set-transaction. without
`GLOBAL' or `SESSION' is not permitted while there is an active
transaction:


     mysql> START TRANSACTION;
     Query OK, 0 rows affected (0.02 sec)

     mysql> SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;
     ERROR 1568 (25001): Transaction isolation level can't be changed
     while a transaction is in progress

To set the global default isolation level at server startup, use the
`--transaction-isolation=LEVEL' option to *Note `mysqld': mysqld. on
the command line or in an option file. Values of LEVEL for this option
use dashes rather than spaces, so the permissible values are
`READ-UNCOMMITTED', `READ-COMMITTED', `REPEATABLE-READ', or
`SERIALIZABLE'. For example, to set the default isolation level to
`REPEATABLE READ', use these lines in the `[mysqld]' section of an
option file:


     [mysqld]
     transaction-isolation = REPEATABLE-READ

It is possible to check or set the global and session transaction
isolation levels at runtime by using the `tx_isolation' system variable:


     SELECT @@GLOBAL.tx_isolation, @@tx_isolation;
     SET GLOBAL tx_isolation='REPEATABLE-READ';
     SET SESSION tx_isolation='SERIALIZABLE';

*Details and Usage of Isolation Levels*

`InnoDB' supports each of the transaction isolation levels described
here using different locking strategies. You can enforce a high degree
of consistency with the default `REPEATABLE READ' level, for operations
on crucial data where ACID compliance is important.  Or you can relax
the consistency rules with `READ COMMITTED' or even `READ UNCOMMITTED',
in situations such as bulk reporting where precise consistency and
repeatable results are less important than minimizing the amount of
overhead for locking. `SERIALIZABLE' enforces even stricter rules than
`REPEATABLE READ', and is used mainly in specialized situations, such
as with XA transactions and for troubleshooting issues with concurrency
and deadlocks.

For full information about how these isolation levels work with
`InnoDB' transactions, see *Note innodb-transaction-model::. In
particular, for additional information about `InnoDB' record-level
locks and how it uses them to execute various types of statements, see
*Note innodb-record-level-locks:: and *Note innodb-locks-set::.

The following list describes how MySQL supports the different
transaction levels. The list goes from the most commonly used level to
the least used.

   * `REPEATABLE READ'

     This is the default isolation level for `InnoDB'. For consistent
     reads, there is an important difference from the `READ COMMITTED'
     isolation level: All consistent reads within the same transaction
     read the snapshot established by the first read. This convention
     means that if you issue several plain (nonlocking) *Note `SELECT':
     select. statements within the same transaction, these *Note
     `SELECT': select.  statements are consistent also with respect to
     each other. See *Note innodb-consistent-read::.

     For locking reads (*Note `SELECT': select. with `FOR UPDATE' or
     `LOCK IN SHARE MODE'), *Note `UPDATE': update, and *Note `DELETE':
     delete. statements, locking depends on whether the statement uses
     a unique index with a unique search condition, or a range-type
     search condition. For a unique index with a unique search
     condition, `InnoDB' locks only the index record found, not the gap
     before it. For other search conditions, `InnoDB' locks the index
     range scanned, using gap locks or next-key (gap plus index-record)
     locks to block insertions by other sessions into the gaps covered
     by the range.

   * `READ COMMITTED'

     A somewhat Oracle-like isolation level with respect to consistent
     (nonlocking) reads: Each consistent read, even within the same
     transaction, sets and reads its own fresh snapshot. See *Note
     innodb-consistent-read::.

     For locking reads (*Note `SELECT': select. with `FOR UPDATE' or
     `LOCK IN SHARE MODE'), *Note `UPDATE': update.  statements, and
     *Note `DELETE': delete.  statements, `InnoDB' locks only index
     records, not the gaps before them, and thus permits the free
     insertion of new records next to locked records.

     *Note*:

     In MySQL 5.1, when `READ COMMITTED' isolation level is used or the
     `innodb_locks_unsafe_for_binlog' system variable is enabled, there
     is no `InnoDB' gap locking except for foreign-key constraint
     checking and duplicate-key checking. Also, record locks for
     nonmatching rows are released after MySQL has evaluated the
     `WHERE' condition.

     As of MySQL 5.1, if you use `READ COMMITTED' or enable
     `innodb_locks_unsafe_for_binlog', you _must_ use row-based binary
     logging.

   * `READ UNCOMMITTED'

     *Note `SELECT': select. statements are performed in a nonlocking
     fashion, but a possible earlier version of a row might be used.
     Thus, using this isolation level, such reads are not consistent.
     This is also called a `dirty read.' Otherwise, this isolation
     level works like `READ COMMITTED'.

   * `SERIALIZABLE'

     This level is like `REPEATABLE READ', but `InnoDB' implicitly
     converts all plain *Note `SELECT': select.  statements to *Note
     `SELECT ... LOCK IN SHARE MODE': select. if autocommit is
     disabled. If autocommit is enabled, the *Note `SELECT': select. is
     its own transaction.  It therefore is known to be read only and
     can be serialized if performed as a consistent (nonlocking) read
     and need not block for other transactions. (To force a plain *Note
     `SELECT': select. to block if other transactions have modified the
     selected rows, disable autocommit.)


File: manual.info,  Node: xa,  Prev: set-transaction,  Up: sql-syntax-transactions

13.3.7 XA Transactions
----------------------

* Menu:

* xa-statements::                XA Transaction SQL Syntax
* xa-states::                    XA Transaction States

Support for XA transactions is available for the `InnoDB' storage
engine. The MySQL XA implementation is based on the X/Open CAE document
`Distributed Transaction Processing: The XA Specification'. This
document is published by The Open Group and available at
`http://www.opengroup.org/public/pubs/catalog/c193.htm'.  Limitations
of the current XA implementation are described in *Note
xa-restrictions::.

On the client side, there are no special requirements. The XA interface
to a MySQL server consists of SQL statements that begin with the `XA'
keyword. MySQL client programs must be able to send SQL statements and
to understand the semantics of the XA statement interface. They do not
need be linked against a recent client library. Older client libraries
also will work.

Currently, among the MySQL Connectors, MySQL Connector/J 5.0.0 supports
XA directly (by means of a class interface that handles the XA SQL
statement interface for you).

XA supports distributed transactions, that is, the ability to permit
multiple separate transactional resources to participate in a global
transaction. Transactional resources often are RDBMSs but may be other
kinds of resources.

A global transaction involves several actions that are transactional in
themselves, but that all must either complete successfully as a group,
or all be rolled back as a group. In essence, this extends ACID
properties `up a level' so that multiple ACID transactions can be
executed in concert as components of a global operation that also has
ACID properties.  (However, for a distributed transaction, you must use
the `SERIALIZABLE' isolation level to achieve ACID properties. It is
enough to use `REPEATABLE READ' for a nondistributed transaction, but
not for a distributed transaction.)

Some examples of distributed transactions:

   * An application may act as an integration tool that combines a
     messaging service with an RDBMS. The application makes sure that
     transactions dealing with message sending, retrieval, and
     processing that also involve a transactional database all happen
     in a global transaction. You can think of this as `transactional
     email.'

   * An application performs actions that involve different database
     servers, such as a MySQL server and an Oracle server (or multiple
     MySQL servers), where actions that involve multiple servers must
     happen as part of a global transaction, rather than as separate
     transactions local to each server.

   * A bank keeps account information in an RDBMS and distributes and
     receives money through automated teller machines (ATMs).  It is
     necessary to ensure that ATM actions are correctly reflected in
     the accounts, but this cannot be done with the RDBMS alone. A
     global transaction manager integrates the ATM and database
     resources to ensure overall consistency of financial transactions.

Applications that use global transactions involve one or more Resource
Managers and a Transaction Manager:

   * A Resource Manager (RM) provides access to transactional
     resources. A database server is one kind of resource manager.  It
     must be possible to either commit or roll back transactions
     managed by the RM.

   * A Transaction Manager (TM) coordinates the transactions that are
     part of a global transaction. It communicates with the RMs that
     handle each of these transactions. The individual transactions
     within a global transaction are `branches' of the global
     transaction. Global transactions and their branches are identified
     by a naming scheme described later.

The MySQL implementation of XA MySQL enables a MySQL server to act as a
Resource Manager that handles XA transactions within a global
transaction. A client program that connects to the MySQL server acts as
the Transaction Manager.

To carry out a global transaction, it is necessary to know which
components are involved, and bring each component to a point when it
can be committed or rolled back. Depending on what each component
reports about its ability to succeed, they must all commit or roll back
as an atomic group. That is, either all components must commit, or all
components must roll back. To manage a global transaction, it is
necessary to take into account that any component or the connecting
network might fail.

The process for executing a global transaction uses two-phase commit
(2PC). This takes place after the actions performed by the branches of
the global transaction have been executed.

  1. In the first phase, all branches are prepared. That is, they are
     told by the TM to get ready to commit. Typically, this means each
     RM that manages a branch records the actions for the branch in
     stable storage. The branches indicate whether they are able to do
     this, and these results are used for the second phase.

  2. In the second phase, the TM tells the RMs whether to commit or
     roll back. If all branches indicated when they were prepared that
     they will be able to commit, all branches are told to commit. If
     any branch indicated when it was prepared that it will not be able
     to commit, all branches are told to roll back.

In some cases, a global transaction might use one-phase commit (1PC).
For example, when a Transaction Manager finds that a global transaction
consists of only one transactional resource (that is, a single branch),
that resource can be told to prepare and commit at the same time.


File: manual.info,  Node: xa-statements,  Next: xa-states,  Prev: xa,  Up: xa

13.3.7.1 XA Transaction SQL Syntax
..................................

To perform XA transactions in MySQL, use the following statements:


     XA {START|BEGIN} XID [JOIN|RESUME]

     XA END XID [SUSPEND [FOR MIGRATE]]

     XA PREPARE XID

     XA COMMIT XID [ONE PHASE]

     XA ROLLBACK XID

     XA RECOVER

For *Note `XA START': xa-statements, the `JOIN' and `RESUME' clauses
are not supported.

For *Note `XA END': xa-statements. the `SUSPEND [FOR MIGRATE]' clause
is not supported.

Each XA statement begins with the `XA' keyword, and most of them
require an XID value. An XID is an XA transaction identifier. It
indicates which transaction the statement applies to. XID values are
supplied by the client, or generated by the MySQL server. An XID value
has from one to three parts:


     XID: GTRID [, BQUAL [, FORMATID ]]

GTRID is a global transaction identifier, BQUAL is a branch qualifier,
and FORMATID is a number that identifies the format used by the GTRID
and BQUAL values. As indicated by the syntax, BQUAL and FORMATID are
optional. The default BQUAL value is `''' if not given. The default
FORMATID value is 1 if not given.

GTRID and BQUAL must be string literals, each up to 64 bytes (not
characters) long.  GTRID and BQUAL can be specified in several ways.
You can use a quoted string (`'ab''), hex string (`0x6162', `X'ab''), or
bit value (`b'NNNN'').

FORMATID is an unsigned integer.

The GTRID and BQUAL values are interpreted in bytes by the MySQL
server's underlying XA support routines. However, while an SQL
statement containing an XA statement is being parsed, the server works
with some specific character set. To be safe, write GTRID and BQUAL as
hex strings.

XID values typically are generated by the Transaction Manager. Values
generated by one TM must be different from values generated by other
TMs. A given TM must be able to recognize its own XID values in a list
of values returned by the *Note `XA RECOVER': xa-statements. statement.

For *Note `XA START XID': xa-statements. starts an XA transaction with
the given XID value.  Each XA transaction must have a unique XID value,
so the value must not currently be used by another XA transaction.
Uniqueness is assessed using the GTRID and BQUAL values. All following
XA statements for the XA transaction must be specified using the same
XID value as that given in the *Note `XA START': xa-statements.
statement. If you use any of those statements but specify an XID value
that does not correspond to some existing XA transaction, an error
occurs.

One or more XA transactions can be part of the same global transaction.
All XA transactions within a given global transaction must use the same
GTRID value in the XID value. For this reason, GTRID values must be
globally unique so that there is no ambiguity about which global
transaction a given XA transaction is part of. The BQUAL part of the
XID value must be different for each XA transaction within a global
transaction. (The requirement that BQUAL values be different is a
limitation of the current MySQL XA implementation. It is not part of
the XA specification.)

The *Note `XA RECOVER': xa-statements. statement returns information
for those XA transactions on the MySQL server that are in the
`PREPARED' state. (See *Note xa-states::.) The output includes a row
for each such XA transaction on the server, regardless of which client
started it.

*Note `XA RECOVER': xa-statements. output rows look like this (for an
example XID value consisting of the parts `'abc'', `'def'', and `7'):


     mysql> XA RECOVER;
     +----------+--------------+--------------+--------+
     | formatID | gtrid_length | bqual_length | data   |
     +----------+--------------+--------------+--------+
     |        7 |            3 |            3 | abcdef |
     +----------+--------------+--------------+--------+

The output columns have the following meanings:

   * `formatID' is the FORMATID part of the transaction XID

   * `gtrid_length' is the length in bytes of the GTRID part of the XID

   * `bqual_length' is the length in bytes of the BQUAL part of the XID

   * `data' is the concatenation of the GTRID and BQUAL parts of the XID


File: manual.info,  Node: xa-states,  Prev: xa-statements,  Up: xa

13.3.7.2 XA Transaction States
..............................

An XA transaction progresses through the following states:

  1. Use *Note `XA START': xa-statements. to start an XA transaction
     and put it in the `ACTIVE' state.

  2. For an `ACTIVE' XA transaction, issue the SQL statements that make
     up the transaction, and then issue an *Note `XA END':
     xa-statements. statement.  *Note `XA END': xa-statements. puts the
     transaction in the `IDLE' state.

  3. For an `IDLE' XA transaction, you can issue either an *Note `XA
     PREPARE': xa-statements. statement or an `XA COMMIT ... ONE PHASE'
     statement:

        * *Note `XA PREPARE': xa-statements. puts the transaction in the
          `PREPARED' state. An *Note `XA RECOVER': xa-statements.
          statement at this point will include the transaction's XID
          value in its output, because *Note `XA RECOVER':
          xa-statements. lists all XA transactions that are in the
          `PREPARED' state.

        * `XA COMMIT ... ONE PHASE' prepares and commits the
          transaction. The XID value will not be listed by *Note `XA
          RECOVER': xa-statements. because the transaction terminates.

  4. For a `PREPARED' XA transaction, you can issue an *Note `XA
     COMMIT': xa-statements. statement to commit and terminate the
     transaction, or *Note `XA ROLLBACK': xa-statements. to roll back
     and terminate the transaction.

Here is a simple XA transaction that inserts a row into a table as part
of a global transaction:


     mysql> XA START 'xatest';
     Query OK, 0 rows affected (0.00 sec)

     mysql> INSERT INTO mytable (i) VALUES(10);
     Query OK, 1 row affected (0.04 sec)

     mysql> XA END 'xatest';
     Query OK, 0 rows affected (0.00 sec)

     mysql> XA PREPARE 'xatest';
     Query OK, 0 rows affected (0.00 sec)

     mysql> XA COMMIT 'xatest';
     Query OK, 0 rows affected (0.00 sec)

Within the context of a given client connection, XA transactions and
local (non-XA) transactions are mutually exclusive. For example, if
*Note `XA START': xa-statements. has been issued to begin an XA
transaction, a local transaction cannot be started until the XA
transaction has been committed or rolled back. Conversely, if a local
transaction has been started with *Note `START TRANSACTION': commit, no
XA statements can be used until the transaction has been committed or
rolled back.

Note that if an XA transaction is in the `ACTIVE' state, you cannot
issue any statements that cause an implicit commit. That would violate
the XA contract because you could not roll back the XA transaction. You
will receive the following error if you try to execute such a statement:


     ERROR 1399 (XAE07): XAER_RMFAIL: The command cannot be executed
     when global transaction is in the ACTIVE state

Statements to which the preceding remark applies are listed at *Note
implicit-commit::.


File: manual.info,  Node: sql-syntax-replication,  Next: sql-syntax-prepared-statements,  Prev: sql-syntax-transactions,  Up: sql-syntax

13.4 Replication Statements
===========================

* Menu:

* replication-master-sql::       SQL Statements for Controlling Master Servers
* replication-slave-sql::        SQL Statements for Controlling Slave Servers

Replication can be controlled through the SQL interface using the
statements described in this section. One group of statements controls
master servers, the other controls slave servers.


File: manual.info,  Node: replication-master-sql,  Next: replication-slave-sql,  Prev: sql-syntax-replication,  Up: sql-syntax-replication

13.4.1 SQL Statements for Controlling Master Servers
----------------------------------------------------

* Menu:

* purge-binary-logs::            PURGE BINARY LOGS Syntax
* reset-master::                 RESET MASTER Syntax
* set-sql-log-bin::              SET sql_log_bin Syntax

This section discusses statements for managing master replication
servers. *Note replication-slave-sql::, discusses statements for
managing slave servers.

In addition to the statements described here, the following *Note
`SHOW': show. statements are used with master servers in replication.
For information about these statements, see *Note show::.

   * *Note `SHOW BINARY LOGS': show-binary-logs.

   * *Note `SHOW BINLOG EVENTS': show-binlog-events.

   * *Note `SHOW MASTER STATUS': show-master-status.

   * *Note `SHOW SLAVE HOSTS': show-slave-hosts.


File: manual.info,  Node: purge-binary-logs,  Next: reset-master,  Prev: replication-master-sql,  Up: replication-master-sql

13.4.1.1 PURGE BINARY LOGS Syntax
.................................


     PURGE { BINARY | MASTER } LOGS
         { TO 'LOG_NAME' | BEFORE DATETIME_EXPR }

The binary log is a set of files that contain information about data
modifications made by the MySQL server. The log consists of a set of
binary log files, plus an index file (see *Note binary-log::).

The *Note `PURGE BINARY LOGS': purge-binary-logs. statement deletes all
the binary log files listed in the log index file prior to the
specified log file name or date.  `BINARY' and `MASTER' are synonyms.
Deleted log files also are removed from the list recorded in the index
file, so that the given log file becomes the first in the list.

This statement has no effect if the server was not started with the
`--log-bin' option to enable binary logging.

Examples:


     PURGE BINARY LOGS TO 'mysql-bin.010';
     PURGE BINARY LOGS BEFORE '2008-04-02 22:46:26';

The `BEFORE' variant's DATETIME_EXPR argument should evaluate to a
*Note `DATETIME': datetime. value (a value in `'YYYY-MM-DD hh:mm:ss''
format).

This statement is safe to run while slaves are replicating. You need
not stop them. If you have an active slave that currently is reading
one of the log files you are trying to delete, this statement does
nothing and fails with an error. However, if a slave is not connected
and you happen to purge one of the log files it has yet to read, the
slave will be unable to replicate after it reconnects.

To safely purge binary log files, follow this procedure:

  1. On each slave server, use *Note `SHOW SLAVE STATUS':
     show-slave-status. to check which log file it is reading.

  2. Obtain a listing of the binary log files on the master server with
     *Note `SHOW BINARY LOGS': show-binary-logs.

  3. Determine the earliest log file among all the slaves. This is the
     target file. If all the slaves are up to date, this is the last
     log file on the list.

  4. Make a backup of all the log files you are about to delete.  (This
     step is optional, but always advisable.)

  5. Purge all log files up to but not including the target file.

You can also set the `expire_logs_days' system variable to expire
binary log files automatically after a given number of days (see *Note
server-system-variables::).  If you are using replication, you should
set the variable no lower than the maximum number of days your slaves
might lag behind the master.

Prior to MySQL 5.1.24, `PURGE BINARY LOGS TO' and `PURGE BINARY LOGS
BEFORE' did not behave in the same way (and neither one behaved
correctly) when binary log files listed in the `.index' file had been
removed from the system by some other means (such as using `rm' on
Linux). Beginning with MySQL 5.1.24, both variants of the statement
fail with an error in such cases.  (Bug #18199, Bug #18453) To handle
such errors, edit the `.index' file (which is a simple text file)
manually to ensure that it lists only the binary log files that are
actually present, then run again the *Note `PURGE BINARY LOGS':
purge-binary-logs. statement that failed.


File: manual.info,  Node: reset-master,  Next: set-sql-log-bin,  Prev: purge-binary-logs,  Up: replication-master-sql

13.4.1.2 RESET MASTER Syntax
............................


     RESET MASTER

Deletes all binary log files listed in the index file, resets the
binary log index file to be empty, and creates a new binary log file.
This statement is intended to be used only when the master is started
for the first time.

*Important*:

The effects of *Note `RESET MASTER': reset-master.  differ from those
of *Note `PURGE BINARY LOGS': purge-binary-logs. in 2 key ways:

  1. *Note `RESET MASTER': reset-master. removes _all_ binary log files
     that are listed in the index file, leaving only a single, empty
     binary log file with a numeric suffix of `.000001', whereas the
     numbering is not reset by *Note `PURGE BINARY LOGS':
     purge-binary-logs.

  2. *Note `RESET MASTER': reset-master. is _not_ intended to be used
     while any replication slaves are running. The behavior of *Note
     `RESET MASTER': reset-master. when used while slaves are running
     is undefined (and thus unsupported), whereas *Note `PURGE BINARY
     LOGS': purge-binary-logs. may be safely used while replication
     slaves are running.

See also *Note purge-binary-logs::.

*Note `RESET MASTER': reset-master. can prove useful when you first set
up the master and the slave, so that you can verify the setup as
follows:

  1. Start the master and slave, and start replication (see *Note
     replication-howto::).

  2. Execute a few test queries on the master.

  3. Check that the queries were replicated to the slave.

  4. When replication is running correctly, issue *Note `STOP SLAVE':
     stop-slave. followed by *Note `RESET SLAVE': reset-slave. on the
     slave, then verify that any unwanted data no longer exists on the
     slave.

  5. Issue *Note `RESET MASTER': reset-master. on the master to clean
     up the test queries.

After verifying the setup and getting rid of any unwanted and log files
generated by testing, you can start the slave and begin replicating.


File: manual.info,  Node: set-sql-log-bin,  Prev: reset-master,  Up: replication-master-sql

13.4.1.3 SET sql_log_bin Syntax
...............................


     SET sql_log_bin = {0|1}

Disables or enables binary logging for the current session
(`sql_log_bin' is a session variable) if the client has the `SUPER'
privilege. The statement fails with an error if the client does not
have that privilege.


File: manual.info,  Node: replication-slave-sql,  Prev: replication-master-sql,  Up: sql-syntax-replication

13.4.2 SQL Statements for Controlling Slave Servers
---------------------------------------------------

* Menu:

* change-master-to::             CHANGE MASTER TO Syntax
* load-data-from-master::        LOAD DATA FROM MASTER Syntax
* load-table-from-master::       LOAD TABLE tbl_name FROM MASTER Syntax
* master-pos-wait::              MASTER_POS_WAIT() Syntax
* reset-slave::                  RESET SLAVE Syntax
* set-global-sql-slave-skip-counter::  SET GLOBAL sql_slave_skip_counter Syntax
* start-slave::                  START SLAVE Syntax
* stop-slave::                   STOP SLAVE Syntax

This section discusses statements for managing slave replication
servers. *Note replication-master-sql::, discusses statements for
managing master servers.

In addition to the statements described here, *Note `SHOW SLAVE
STATUS': show-slave-status. is also used with replication slaves. For
information about this statement, see *Note show-slave-status::.


File: manual.info,  Node: change-master-to,  Next: load-data-from-master,  Prev: replication-slave-sql,  Up: replication-slave-sql

13.4.2.1 CHANGE MASTER TO Syntax
................................


     CHANGE MASTER TO OPTION [, OPTION] ...

     OPTION:
         MASTER_BIND = 'INTERFACE_NAME'
       | MASTER_HOST = 'HOST_NAME'
       | MASTER_USER = 'USER_NAME'
       | MASTER_PASSWORD = 'PASSWORD'
       | MASTER_PORT = PORT_NUM
       | MASTER_CONNECT_RETRY = INTERVAL
       | MASTER_HEARTBEAT_PERIOD = INTERVAL
       | MASTER_LOG_FILE = 'MASTER_LOG_NAME'
       | MASTER_LOG_POS = MASTER_LOG_POS
       | RELAY_LOG_FILE = 'RELAY_LOG_NAME'
       | RELAY_LOG_POS = RELAY_LOG_POS
       | MASTER_SSL = {0|1}
       | MASTER_SSL_CA = 'CA_FILE_NAME'
       | MASTER_SSL_CAPATH = 'CA_DIRECTORY_NAME'
       | MASTER_SSL_CERT = 'CERT_FILE_NAME'
       | MASTER_SSL_KEY = 'KEY_FILE_NAME'
       | MASTER_SSL_CIPHER = 'CIPHER_LIST'
       | MASTER_SSL_VERIFY_SERVER_CERT = {0|1}
       | IGNORE_SERVER_IDS = (SERVER_ID_LIST)

     SERVER_ID_LIST:
         [SERVER_ID [, SERVER_ID] ... ]

*Note `CHANGE MASTER TO': change-master-to. changes the parameters that
the slave server uses for connecting to the master server, for reading
the master binary log, and reading the slave relay log. It also updates
the contents of the `master.info' and `relay-log.info' files. To use
*Note `CHANGE MASTER TO': change-master-to, the slave replication
threads must be stopped (use *Note `STOP SLAVE': stop-slave. if
necessary).

Options not specified retain their value, except as indicated in the
following discussion. Thus, in most cases, there is no need to specify
options that do not change. For example, if the password to connect to
your MySQL master has changed, you just need to issue these statements
to tell the slave about the new password:


     STOP SLAVE; -- if replication was running
     CHANGE MASTER TO MASTER_PASSWORD='new3cret';
     START SLAVE; -- if you want to restart replication

`MASTER_HOST', `MASTER_USER', `MASTER_PASSWORD', and `MASTER_PORT'
provide information to the slave about how to connect to its master:

   * `MASTER_HOST' and `MASTER_PORT' are the host name (or IP address)
     of the master host and its TCP/IP port.

     *Note*:

     Replication cannot use Unix socket files. You must be able to
     connect to the master MySQL server using TCP/IP.

     If you specify the `MASTER_HOST' or `MASTER_PORT' option, the
     slave assumes that the master server is different from before
     (even if the option value is the same as its current value.) In
     this case, the old values for the master binary log file name and
     position are considered no longer applicable, so if you do not
     specify `MASTER_LOG_FILE' and `MASTER_LOG_POS' in the statement,
     `MASTER_LOG_FILE=''' and `MASTER_LOG_POS=4' are silently appended
     to it.

     Setting `MASTER_HOST=''' (that is, setting its value explicitly to
     an empty string) is _not_ the same as not setting `MASTER_HOST' at
     all. Setting this option to an empty string causes *Note `START
     SLAVE': start-slave. subsequently to fail. This issue is addressed
     in MySQL 5.5. (Bug #28796)

   * `MASTER_USER' and `MASTER_PASSWORD' are the user name and password
     of the account to use for connecting to the master.

     The password used for a MySQL Replication slave account in a
     `CHANGE MASTER TO' statement is limited to 32 characters in
     length; if the password is longer, the statement succeeds, but any
     excess characters are silently truncated. This is an issue
     specific to MySQL Replication, which is fixed in MySQL 5.7. (Bug
     #11752299, Bug #43439)

     The text of a running *Note `CHANGE MASTER TO': change-master-to.
     statement, including values for `MASTER_USER' and
     `MASTER_PASSWORD', can be seen in the output of a concurrent *Note
     `SHOW PROCESSLIST': show-processlist. statement.

The `MASTER_SSL_XXX' options provide information about using SSL for
the connection.  They correspond to the `--ssl-XXX' options described
in *Note ssl-options::, and *Note replication-solutions-ssl::.
`MASTER_SSL_VERIFY_SERVER_CERT' was added in MySQL 5.1.18. These
options can be changed even on slaves that are compiled without SSL
support. They are saved to the `master.info' file, but are ignored if
the slave does not have SSL support enabled.

`MASTER_CONNECT_RETRY' specifies how many seconds to wait between
connect retries. The default is 60. The _number_ of reconnection
attempts is limited by the `--master-retry-count' server option; for
more information, see *Note replication-options::.

The next two options (`MASTER_BIND' and `MASTER_HEARTBEAT_PERIOD') are
available in MySQL Cluster NDB 6.3 and later, but are not supported in
mainline MySQL 5.1:

`MASTER_BIND' is for use on replication slaves having multiple network
interfaces, and determines which of the slave's network interfaces is
chosen for connecting to the master.

The ability to bind a replication slave to specific network interface
was added in MySQL Cluster NDB 6.3.4.

`MASTER_HEARTBEAT_PERIOD' sets the interval in seconds between
replication heartbeats. Whenever the master's binary log is updated
with an event, the waiting period for the next heartbeat is reset.
INTERVAL is a decimal value having the range 0 to 4294967 seconds and a
resolution in milliseconds; the smallest nonzero value is 0.001.
Heartbeats are sent by the master only if there are no unsent events in
the binary log file for a period longer than INTERVAL.

Setting INTERVAL to 0 disables heartbeats altogether. The default value
for INTERVAL is equal to the value of `slave_net_timeout' divided by 2.

Setting `@@global.slave_net_timeout' to a value less than that of the
current heartbeat interval results in a warning being issued. The
effect of issuing *Note `RESET SLAVE': reset-slave. on the heartbeat
interval is to reset it to the default value.

`MASTER_HEARTBEAT_PERIOD' was added in MySQL Cluster NDB 6.3.4.

`MASTER_LOG_FILE' and `MASTER_LOG_POS' are the coordinates at which the
slave I/O thread should begin reading from the master the next time the
thread starts. `RELAY_LOG_FILE' and `RELAY_LOG_POS' are the coordinates
at which the slave SQL thread should begin reading from the relay log
the next time the thread starts. If you specify either of
`MASTER_LOG_FILE' or `MASTER_LOG_POS', you cannot specify
`RELAY_LOG_FILE' or `RELAY_LOG_POS'. If neither of `MASTER_LOG_FILE' or
`MASTER_LOG_POS' is specified, the slave uses the last coordinates of
the _slave SQL thread_ before *Note `CHANGE MASTER TO':
change-master-to. was issued. This ensures that there is no
discontinuity in replication, even if the slave SQL thread was late
compared to the slave I/O thread, when you merely want to change, say,
the password to use.

*Note `CHANGE MASTER TO': change-master-to.  _deletes all relay log
files_ and starts a new one, unless you specify `RELAY_LOG_FILE' or
`RELAY_LOG_POS'. In that case, relay log files are kept; the
`relay_log_purge' global variable is set silently to 0.

`IGNORE_SERVER_IDS' was added in MySQL Cluster NDB 6.1.29, MySQL
Cluster NDB 6.3.31, MySQL Cluster NDB 7.0.11, and MySQL Cluster NDB
7.1.0 (see Bug #47037). This option takes a comma-separated list of 0
or more server IDs. Events originating from the corresponding servers
are ignored, with the exception of log rotation and deletion events,
which are still recorded in the relay log.

In circular replication, the originating server normally acts as the
terminator of its own events, so that they are not applied more than
once. Thus, this option is useful in circular replication when one of
the servers in the circle is removed.  Suppose that you have a circular
replication setup with 4 servers, having server IDs 1, 2, 3, and 4, and
server 3 fails.  When bridging the gap by starting replication from
server 2 to server 4, you can include `IGNORE_SERVER_IDS = (3)' in the
*Note `CHANGE MASTER TO': change-master-to. statement that you issue on
server 4 to tell it to use server 2 as its master instead of server 3.
Doing so causes it to ignore and not to propagate any statements that
originated with the server that is no longer in use.

If a *Note `CHANGE MASTER TO': change-master-to. statement is issued
without any `IGNORE_SERVER_IDS' option, any existing list is preserved;
*Note `RESET SLAVE': reset-slave. also has no effect on the server ID
list. To clear the list of ignored servers, it is necessary to use the
option with an empty list:


     CHANGE MASTER TO IGNORE_SERVER_IDS = ();

If `IGNORE_SERVER_IDS' contains the server's own ID and the server was
started with the `--replicate-same-server-id' option enabled, an error
results.

Beginning with MySQL 5.1.47, invoking *Note `CHANGE MASTER TO':
change-master-to. causes the previous values for `MASTER_HOST',
`MASTER_PORT', `MASTER_LOG_FILE', and `MASTER_LOG_POS' to be written to
the error log, along with other information about the slave's state
prior to execution.

*Note `CHANGE MASTER TO': change-master-to. is useful for setting up a
slave when you have the snapshot of the master and have recorded the
master binary log coordinates corresponding to the time of the
snapshot. After loading the snapshot into the slave to synchronize it
with the master, you can run `CHANGE MASTER TO
MASTER_LOG_FILE='LOG_NAME', MASTER_LOG_POS=LOG_POS' on the slave to
specify the coordinates at which the slave should begin reading the
master binary log.

The following example changes the master server the slave uses and
establishes the master binary log coordinates from which the slave
begins reading. This is used when you want to set up the slave to
replicate the master:


     CHANGE MASTER TO
       MASTER_HOST='master2.mycompany.com',
       MASTER_USER='replication',
       MASTER_PASSWORD='bigs3cret',
       MASTER_PORT=3306,
       MASTER_LOG_FILE='master2-bin.001',
       MASTER_LOG_POS=4,
       MASTER_CONNECT_RETRY=10;

The next example shows an operation that is less frequently employed.
It is used when the slave has relay log files that you want it to
execute again for some reason. To do this, the master need not be
reachable. You need only use *Note `CHANGE MASTER TO':
change-master-to. and start the SQL thread (`START SLAVE SQL_THREAD'):


     CHANGE MASTER TO
       RELAY_LOG_FILE='slave-relay-bin.006',
       RELAY_LOG_POS=4025;

You can even use the second operation in a nonreplication setup with a
standalone, nonslave server for recovery following a crash. Suppose
that your server has crashed and you have restored it from a backup.
You want to replay the server's own binary log files (not relay log
files, but regular binary log files), named (for example)
`myhost-bin.*'.  First, make a backup copy of these binary log files in
some safe place, in case you don't exactly follow the procedure below
and accidentally have the server purge the binary log. Use `SET GLOBAL
relay_log_purge=0' for additional safety. Then start the server without
the `--log-bin' option, Instead, use the `--replicate-same-server-id',
`--relay-log=myhost-bin' (to make the server believe that these regular
binary log files are relay log files) and `--skip-slave-start' options.
After the server starts, issue these statements:


     CHANGE MASTER TO
       RELAY_LOG_FILE='myhost-bin.153',
       RELAY_LOG_POS=410,
       MASTER_HOST='some_dummy_string';
     START SLAVE SQL_THREAD;

The server reads and executes its own binary log files, thus achieving
crash recovery. Once the recovery is finished, run *Note `STOP SLAVE':
stop-slave, shut down the server, delete the `master.info' and
`relay-log.info' files, and restart the server with its original
options.

Specifying the `MASTER_HOST' option (even with a dummy value) is
required to make the server think it is a slave.

The following table shows the maximum permissible length for the
string-valued options.

This table shows the maximum permissible length for `MASTER_POS_WAIT()'
string-valued options.

Option         Maximum Length
`MASTER_HOST'  60
`MASTER_USER'  16
`MASTER_PASSWORD'32
`MASTER_LOG_FILE'255
`RELAY_LOG_FILE'255
`MASTER_SSL_CA'255
`MASTER_SSL_CAPATH'255
`MASTER_SSL_CERT'255
`MASTER_SSL_KEY'255
`MASTER_SSL_CIPHER'511


File: manual.info,  Node: load-data-from-master,  Next: load-table-from-master,  Prev: change-master-to,  Up: replication-slave-sql

13.4.2.2 LOAD DATA FROM MASTER Syntax
.....................................


     LOAD DATA FROM MASTER

*Note*:

This feature is deprecated and should be avoided. It is subject to
removal in a future version of MySQL.

Since the current implementation of `LOAD DATA FROM MASTER' and `LOAD
TABLE FROM MASTER' is very limited, these statements are deprecated as
of MySQL 4.1 and removed in MySQL 5.5.

The recommended alternative solution to using `LOAD DATA FROM MASTER'
or `LOAD TABLE FROM MASTER' is using *Note `mysqldump': mysqldump. or
*Note `mysqlhotcopy': mysqlhotcopy. The latter requires Perl and two
Perl modules (`DBI' and `DBD:mysql') and works for `MyISAM' and
`ARCHIVE' tables only. With *Note `mysqldump': mysqldump, you can
create SQL dumps on the master and pipe (or copy) these to a *Note
`mysql': mysql. client on the slave. This has the advantage of working
for all storage engines, but can be quite slow, since it works using
*Note `SELECT': select.

This statement takes a snapshot of the master and copies it to the
slave. It updates the values of `MASTER_LOG_FILE' and `MASTER_LOG_POS'
so that the slave starts replicating from the correct position. Any
table and database exclusion rules specified with the
`--replicate-*-do-*' and `--replicate-*-ignore-*' options are honored.
`--replicate-rewrite-db' is _not_ taken into account because a user
could use this option to set up a nonunique mapping such as
`--replicate-rewrite-db="db1->db3"' and
`--replicate-rewrite-db="db2->db3"', which would confuse the slave when
loading tables from the master.

Use of this statement is subject to the following conditions:

   * It works only for `MyISAM' tables.  Attempting to load a
     non-`MyISAM' table results in the following error:


          ERROR 1189 (08S01): Net error reading from master

   * It acquires a global read lock on the master while taking the
     snapshot, which prevents updates on the master during the load
     operation.

If you are loading large tables, you might have to increase the values
of `net_read_timeout' and `net_write_timeout' on both the master and
slave servers. See *Note server-system-variables::.

Note that `LOAD DATA FROM MASTER' does _not_ copy any tables from the
`mysql' database. This makes it easy to have different users and
privileges on the master and the slave.

To use `LOAD DATA FROM MASTER', the replication account that is used to
connect to the master must have the `RELOAD' and `SUPER' privileges on
the master and the `SELECT' privilege for all master tables you want to
load. All master tables for which the user does not have the *Note
`SELECT': select.  privilege are ignored by `LOAD DATA FROM MASTER'.
This is because the master hides them from the user: `LOAD DATA FROM
MASTER' calls *Note `SHOW DATABASES': show-databases. to know the master
databases to load, but *Note `SHOW DATABASES': show-databases. returns
only databases for which the user has some privilege. See *Note
show-databases::. On the slave side, the user that issues `LOAD DATA
FROM MASTER' must have privileges for dropping and creating the
databases and tables that are copied.


File: manual.info,  Node: load-table-from-master,  Next: master-pos-wait,  Prev: load-data-from-master,  Up: replication-slave-sql

13.4.2.3 LOAD TABLE tbl_name FROM MASTER Syntax
...............................................


     LOAD TABLE TBL_NAME FROM MASTER

*Note*:

This feature is deprecated and should be avoided. It is subject to
removal in a future version of MySQL.

Since the current implementation of `LOAD DATA FROM MASTER' and `LOAD
TABLE FROM MASTER' is very limited, these statements are deprecated as
of MySQL 4.1 and removed in MySQL 5.5.

The recommended alternative solution to using `LOAD DATA FROM MASTER'
or `LOAD TABLE FROM MASTER' is using *Note `mysqldump': mysqldump. or
*Note `mysqlhotcopy': mysqlhotcopy. The latter requires Perl and two
Perl modules (`DBI' and `DBD:mysql') and works for `MyISAM' and
`ARCHIVE' tables only. With *Note `mysqldump': mysqldump, you can
create SQL dumps on the master and pipe (or copy) these to a *Note
`mysql': mysql. client on the slave. This has the advantage of working
for all storage engines, but can be quite slow, since it works using
*Note `SELECT': select.

Transfers a copy of the table from the master to the slave. This
statement is implemented mainly debugging `LOAD DATA FROM MASTER'
operations. To use `LOAD TABLE', the account used for connecting to the
master server must have the `RELOAD' and `SUPER' privileges on the
master and the `SELECT' privilege for the master table to load. On the
slave side, the user that issues `LOAD TABLE FROM MASTER' must have
privileges for dropping and creating the table.

The conditions for `LOAD DATA FROM MASTER' apply here as well. For
example, `LOAD TABLE FROM MASTER' works only for `MyISAM' tables. The
timeout notes for `LOAD DATA FROM MASTER' apply as well.


File: manual.info,  Node: master-pos-wait,  Next: reset-slave,  Prev: load-table-from-master,  Up: replication-slave-sql

13.4.2.4 MASTER_POS_WAIT() Syntax
.................................


     SELECT MASTER_POS_WAIT('MASTER_LOG_FILE', MASTER_LOG_POS [, TIMEOUT])

This is actually a function, not a statement. It is used to ensure that
the slave has read and executed events up to a given position in the
master's binary log. See *Note miscellaneous-functions::, for a full
description.


File: manual.info,  Node: reset-slave,  Next: set-global-sql-slave-skip-counter,  Prev: master-pos-wait,  Up: replication-slave-sql

13.4.2.5 RESET SLAVE Syntax
...........................


     RESET SLAVE

*Note `RESET SLAVE': reset-slave. makes the slave forget its
replication position in the master's binary log. This statement is
meant to be used for a clean start: It deletes the `master.info' and
`relay-log.info' files, all the relay log files, and starts a new relay
log file. To use *Note `RESET SLAVE': reset-slave, the slave
replication threads must be stopped (use *Note `STOP SLAVE':
stop-slave. if necessary).

*Note*:

All relay log files are deleted, even if they have not been completely
executed by the slave SQL thread. (This is a condition likely to exist
on a replication slave if you have issued a *Note `STOP SLAVE':
stop-slave. statement or if the slave is highly loaded.)

If any startup options for setting connection parameters (such as
master host, master port, master user, and master password) are in use,
then any corresponding connection information stored in the
`master.info' file is immediately reset using the values specified for
these options. Options for which values are not specified are cleared.
However, since these options are deprecated in MySQL 5.1 and removed
altogether from MySQL 5.5, you are encouraged to use a *Note `CHANGE
MASTER TO': change-master-to. statement instead to reset the connection
parameters. (If you do not use the startup options, you must issue
*Note `CHANGE MASTER TO': change-master-to. in such cases if you do not
want the connection settings to be cleared.)

If the slave SQL thread was in the middle of replicating temporary
tables when it was stopped, and *Note `RESET SLAVE': reset-slave. is
issued, these replicated temporary tables are deleted on the slave.


File: manual.info,  Node: set-global-sql-slave-skip-counter,  Next: start-slave,  Prev: reset-slave,  Up: replication-slave-sql

13.4.2.6 SET GLOBAL sql_slave_skip_counter Syntax
.................................................


     SET GLOBAL sql_slave_skip_counter = N

This statement skips the next N events from the master. This is useful
for recovering from replication stops caused by a statement.

This statement is valid only when the slave threads are not running.
Otherwise, it produces an error.

When using this statement, it is important to understand that the
binary log is actually organized as a sequence of groups known as
_event groups_. Each event group consists of a sequence of events.

   * For transactional tables, an event group corresponds to a
     transaction.

   * For nontransactional tables, an event group corresponds to a
     single SQL statement.

*Note*:

A single transaction can contain changes to both transactional and
nontransactional tables.

When you use *Note `SET GLOBAL sql_slave_skip_counter':
set-global-sql-slave-skip-counter. to skip events and the result is in
the middle of a group, the slave continues to skip events until it
reaches the end of the group. Execution then starts with the next event
group.

Beginning with MySQL 5.1.47, issuing this statement causes the previous
values of `RELAY_LOG_FILE', `RELAY_LOG_POS', and
`sql_slave_skip_counter' to be written to the error log.


File: manual.info,  Node: start-slave,  Next: stop-slave,  Prev: set-global-sql-slave-skip-counter,  Up: replication-slave-sql

13.4.2.7 START SLAVE Syntax
...........................


     START SLAVE [THREAD_TYPES]

     START SLAVE [SQL_THREAD] UNTIL
         MASTER_LOG_FILE = 'LOG_NAME', MASTER_LOG_POS = LOG_POS

     START SLAVE [SQL_THREAD] UNTIL
         RELAY_LOG_FILE = 'LOG_NAME', RELAY_LOG_POS = LOG_POS

     THREAD_TYPES:
         [THREAD_TYPE [, THREAD_TYPE] ... ]

     THREAD_TYPE: IO_THREAD | SQL_THREAD

*Note `START SLAVE': start-slave. with no THREAD_TYPE options starts
both of the slave threads. The I/O thread reads events from the master
server and stores them in the relay log. The SQL thread reads events
from the relay log and executes them.  *Note `START SLAVE':
start-slave. requires the `SUPER' privilege.

If *Note `START SLAVE': start-slave. succeeds in starting the slave
threads, it returns without any error.  However, even in that case, it
might be that the slave threads start and then later stop (for example,
because they do not manage to connect to the master or read its binary
log, or some other problem). *Note `START SLAVE': start-slave. does not
warn you about this. You must check the slave's error log for error
messages generated by the slave threads, or check that they are running
satisfactorily with *Note `SHOW SLAVE STATUS': show-slave-status.

*Note `START SLAVE': start-slave. sends an acknowledgment to the user
after both the I/O thread and the SQL thread have started. However, the
I/O thread may not yet have connected. For this reason, a successful
*Note `START SLAVE': start-slave. causes *Note `SHOW SLAVE STATUS':
show-slave-status. to show `Slave_SQL_Running=Yes', but this does not
guarantee that `Slave_IO_Running=Yes' (because `Slave_IO_Running=Yes'
only if the I/O thread is running _and connected_). For more
information, see *Note show-slave-status::, and *Note
replication-administration-status::.

You can add `IO_THREAD' and `SQL_THREAD' options to the statement to
name which of the threads to start.

An `UNTIL' clause may be added to specify that the slave should start
and run until the SQL thread reaches a given point in the master binary
log or in the slave relay log.  When the SQL thread reaches that point,
it stops. If the `SQL_THREAD' option is specified in the statement, it
starts only the SQL thread. Otherwise, it starts both slave threads. If
the SQL thread is running, the `UNTIL' clause is ignored and a warning
is issued.

For an `UNTIL' clause, you must specify both a log file name and
position. Do not mix master and relay log options.

Any `UNTIL' condition is reset by a subsequent *Note `STOP SLAVE':
stop-slave. statement, a *Note `START SLAVE': start-slave. statement
that includes no `UNTIL' clause, or a server restart.

The `UNTIL' clause can be useful for debugging replication, or to cause
replication to proceed until just before the point where you want to
avoid having the slave replicate an event. For example, if an unwise
*Note `DROP TABLE': drop-table. statement was executed on the master,
you can use `UNTIL' to tell the slave to execute up to that point but
no farther. To find what the event is, use *Note `mysqlbinlog':
mysqlbinlog. with the master binary log or slave relay log, or by using
a *Note `SHOW BINLOG EVENTS': show-binlog-events. statement.

If you are using `UNTIL' to have the slave process replicated queries
in sections, it is recommended that you start the slave with the
`--skip-slave-start' option to prevent the SQL thread from running when
the slave server starts. It is probably best to use this option in an
option file rather than on the command line, so that an unexpected
server restart does not cause it to be forgotten.

The *Note `SHOW SLAVE STATUS': show-slave-status. statement includes
output fields that display the current values of the `UNTIL' condition.

In old versions of MySQL (before 4.0.5), this statement was called
`SLAVE START'. This usage is still accepted in MySQL 5.1 for backward
compatibility, but is deprecated and is removed in MySQL 5.6.


File: manual.info,  Node: stop-slave,  Prev: start-slave,  Up: replication-slave-sql

13.4.2.8 STOP SLAVE Syntax
..........................


     STOP SLAVE [THREAD_TYPES]

     THREAD_TYPES:
         [THREAD_TYPE [, THREAD_TYPE] ... ]

     THREAD_TYPE: IO_THREAD | SQL_THREAD

Stops the slave threads. *Note `STOP SLAVE': stop-slave. requires the
`SUPER' privilege. Recommended best practice is to execute `STOP SLAVE'
on the slave before stopping the slave server (see *Note
server-shutdown::, for more information).

_When using the row-based logging format_: Prior to MySQL 5.1.35, you
should _always_ execute `STOP SLAVE' on the slave before stopping the
slave server to help avoid the possibility of an inconsistent slave; in
MySQL 5.1.35 and later, you should execute this statement on the slave
prior to shutting down the slave server if you are replicating any
tables that use a nontransactional storage engine (see the `Note' later
in this section). In MySQL 5.1.55 and later, you can also use `STOP
SLAVE SQL_THREAD' for this purpose.

Like *Note `START SLAVE': start-slave, this statement may be used with
the `IO_THREAD' and `SQL_THREAD' options to name the thread or threads
to be stopped.

*Note*:

The transactional behavior of *Note `STOP SLAVE': stop-slave. changed
in MySQL 5.1.35. Previously, it took effect immediately. Beginning with
MySQL 5.1.35, it waits until any current replication event group
affecting one or more nontransactional tables has finished executing
(if there is any such replication group), or until the user issues a
*Note `KILL QUERY': kill. or *Note `KILL CONNECTION': kill. statement.
(Bug #319, Bug #38205)

In old versions of MySQL (before 4.0.5), this statement was called
`SLAVE STOP'. This usage is still accepted in MySQL 5.1 for backward
compatibility, but is deprecated and is removed in MySQL 5.6.


File: manual.info,  Node: sql-syntax-prepared-statements,  Next: sql-syntax-compound-statements,  Prev: sql-syntax-replication,  Up: sql-syntax

13.5 SQL Syntax for Prepared Statements
=======================================

* Menu:

* prepare::                      PREPARE Syntax
* execute::                      EXECUTE Syntax
* deallocate-prepare::           DEALLOCATE PREPARE Syntax
* statement-repreparation::      Automatic Prepared Statement Repreparation

MySQL 5.1 provides support for server-side prepared statements. This
support takes advantage of the efficient client/server binary protocol
implemented in MySQL 4.1, provided that you use an appropriate client
programming interface. Candidate interfaces include the MySQL C API
client library (for C programs), MySQL Connector/J (for Java programs),
and MySQL Connector/Net. For example, the C API provides a set of
function calls that make up its prepared statement API. See *Note
c-api-prepared-statements::. Other language interfaces can provide
support for prepared statements that use the binary protocol by linking
in the C client library, one example being the `mysqli' extension
(http://php.net/mysqli), available in PHP 5.0 and later.

An alternative SQL interface to prepared statements is available.  This
interface is not as efficient as using the binary protocol through a
prepared statement API, but requires no programming because it is
available directly at the SQL level:

   * You can use it when no programming interface is available to you.

   * You can use it from any program that enables you to send SQL
     statements to the server to be executed, such as the *Note
     `mysql': mysql. client program.

   * You can use it even if the client is using an old version of the
     client library. The only requirement is that you be able to
     connect to a server that is recent enough to support SQL syntax
     for prepared statements.

SQL syntax for prepared statements is intended to be used for
situations such as these:

   * You want to test how prepared statements work in your application
     before coding it.

   * An application has problems executing prepared statements and you
     want to determine interactively what the problem is.

   * You want to create a test case that describes a problem you are
     having with prepared statements, so that you can file a bug report.

   * You need to use prepared statements but do not have access to a
     programming API that supports them.

SQL syntax for prepared statements is based on three SQL statements:

   * *Note `PREPARE': prepare. prepares a statement for execution (see
     *Note prepare::).

   * *Note `EXECUTE': execute. executes a prepared statement (see *Note
     execute::).

   * *Note `DEALLOCATE PREPARE': deallocate-prepare. releases a
     prepared statement (see *Note deallocate-prepare::).

The following examples show two equivalent ways of preparing a
statement that computes the hypotenuse of a triangle given the lengths
of the two sides.

The first example shows how to create a prepared statement by using a
string literal to supply the text of the statement:


     mysql> PREPARE stmt1 FROM 'SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse';
     mysql> SET @a = 3;
     mysql> SET @b = 4;
     mysql> EXECUTE stmt1 USING @a, @b;
     +------------+
     | hypotenuse |
     +------------+
     |          5 |
     +------------+
     mysql> DEALLOCATE PREPARE stmt1;

The second example is similar, but supplies the text of the statement
as a user variable:


     mysql> SET @s = 'SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse';
     mysql> PREPARE stmt2 FROM @s;
     mysql> SET @a = 6;
     mysql> SET @b = 8;
     mysql> EXECUTE stmt2 USING @a, @b;
     +------------+
     | hypotenuse |
     +------------+
     |         10 |
     +------------+
     mysql> DEALLOCATE PREPARE stmt2;

Here is an additional example that demonstrates how to choose the table
on which to perform a query at runtime, by storing the name of the
table as a user variable:


     mysql> USE test;
     mysql> CREATE TABLE t1 (a INT NOT NULL);
     mysql> INSERT INTO t1 VALUES (4), (8), (11), (32), (80);

     mysql> SET @table = 't1';
     mysql> SET @s = CONCAT('SELECT * FROM ', @table);

     mysql> PREPARE stmt3 FROM @s;
     mysql> EXECUTE stmt3;
     +----+
     | a  |
     +----+
     |  4 |
     |  8 |
     | 11 |
     | 32 |
     | 80 |
     +----+

     mysql> DEALLOCATE PREPARE stmt3;

A prepared statement is specific to the session in which it was
created. If you terminate a session without deallocating a previously
prepared statement, the server deallocates it automatically.

A prepared statement is also global to the session. If you create a
prepared statement within a stored routine, it is not deallocated when
the stored routine ends.

To guard against too many prepared statements being created
simultaneously, set the `max_prepared_stmt_count' system variable. To
prevent the use of prepared statements, set the value to 0.

The following SQL statements can be used in prepared statements:


     ALTER TABLE
     CALL
     COMMIT
     {CREATE | DROP} INDEX
     {CREATE | DROP} TABLE
     {CREATE | DROP} VIEW
     DELETE
     DO
     INSERT
     RENAME TABLE
     REPLACE
     SELECT
     SET
     SHOW (most variants)
     TRUNCATE TABLE
     UPDATE

As of MySQL 5.1.10, the following additional statements are supported:


     ANALYZE TABLE
     OPTIMIZE TABLE
     REPAIR TABLE

As of MySQL 5.1.12, the following additional statements are supported:


     CACHE INDEX
     CHANGE MASTER
     CHECKSUM {TABLE | TABLES}
     {CREATE | RENAME | DROP} DATABASE
     {CREATE | RENAME | DROP} USER
     FLUSH {TABLE | TABLES | TABLES WITH READ LOCK | HOSTS | PRIVILEGES
       | LOGS | STATUS | MASTER | SLAVE | DES_KEY_FILE | USER_RESOURCES}
     GRANT
     INSTALL PLUGIN
     KILL
     LOAD INDEX INTO CACHE
     RESET {MASTER | SLAVE | QUERY CACHE}
     REVOKE
     SHOW {AUTHORS | CONTRIBUTORS | WARNINGS | ERRORS}
     SHOW BINLOG EVENTS
     SHOW CREATE {PROCEDURE | FUNCTION | EVENT | TABLE | VIEW}
     SHOW {MASTER | BINARY} LOGS
     SHOW {MASTER | SLAVE} STATUS
     SLAVE {START | STOP}
     UNINSTALL PLUGIN

Other statements are not supported in MySQL 5.1.

Generally, statements not permitted in SQL prepared statements are also
not permitted in stored programs. Exceptions are noted in *Note
stored-program-restrictions::.

Metadata changes to tables or views referred to by prepared statements
are detected and cause automatic repreparation of the statement when it
is next executed. For more information, see *Note
statement-repreparation::.

Placeholders can be used for the arguments of the `LIMIT' clause when
using prepared statements. See *Note select::.

In prepared *Note `CALL': call. statements used with *Note `PREPARE':
prepare. and *Note `EXECUTE': execute, placeholder support for `OUT'
and `INOUT' parameters is not available in MySQL 5.1. See *Note call::,
for an example and a workaround. Placeholders can be used for `IN'
parameters regardless of version.

SQL syntax for prepared statements cannot be used in nested fashion.
That is, a statement passed to *Note `PREPARE': prepare. cannot itself
be a *Note `PREPARE': prepare, *Note `EXECUTE': execute, or *Note
`DEALLOCATE PREPARE': deallocate-prepare. statement.

SQL syntax for prepared statements is distinct from using prepared
statement API calls. For example, you cannot use the *Note
`mysql_stmt_prepare()': mysql-stmt-prepare. C API function to prepare a
*Note `PREPARE': prepare, *Note `EXECUTE': execute, or *Note
`DEALLOCATE PREPARE': deallocate-prepare. statement.

SQL syntax for prepared statements can be used within stored
procedures, but not in stored functions or triggers. However, a cursor
cannot be used for a dynamic statement that is prepared and executed
with *Note `PREPARE': prepare. and *Note `EXECUTE': execute. The
statement for a cursor is checked at cursor creation time, so the
statement cannot be dynamic.

SQL syntax for prepared statements does not support multi-statements
(that is, multiple statements within a single string separated by ``;''
characters).

Before MySQL 5.1.17, prepared statements do not use the query cache.
As of 5.1.17, prepared statements use the query cache under the
conditions described in *Note query-cache-operation::.

To write C programs that use the *Note `CALL': call.  SQL statement to
execute stored procedures that contain prepared statements, the
`CLIENT_MULTI_RESULTS' flag must be enabled. This is because each *Note
`CALL': call.  returns a result to indicate the call status, in
addition to any result sets that might be returned by statements
executed within the procedure.

`CLIENT_MULTI_RESULTS' can be enabled when you call *Note
`mysql_real_connect()': mysql-real-connect, either explicitly by
passing the `CLIENT_MULTI_RESULTS' flag itself, or implicitly by passing
`CLIENT_MULTI_STATEMENTS' (which also enables `CLIENT_MULTI_RESULTS').
For additional information, see *Note call::.


File: manual.info,  Node: prepare,  Next: execute,  Prev: sql-syntax-prepared-statements,  Up: sql-syntax-prepared-statements

13.5.1 PREPARE Syntax
---------------------


     PREPARE STMT_NAME FROM PREPARABLE_STMT

The *Note `PREPARE': prepare. statement prepares a SQL statement and
assigns it a name, STMT_NAME, by which to refer to the statement later.
The prepared statement is executed with *Note `EXECUTE': execute. and
released with *Note `DEALLOCATE PREPARE': deallocate-prepare. For
examples, see *Note sql-syntax-prepared-statements::.

Statement names are not case sensitive.  PREPARABLE_STMT is either a
string literal or a user variable that contains the text of the SQL
statement. The text must represent a single statement, not multiple
statements. Within the statement, `?' characters can be used as
parameter markers to indicate where data values are to be bound to the
query later when you execute it. The `?' characters should not be
enclosed within quotation marks, even if you intend to bind them to
string values.  Parameter markers can be used only where data values
should appear, not for SQL keywords, identifiers, and so forth.

If a prepared statement with the given name already exists, it is
deallocated implicitly before the new statement is prepared. This means
that if the new statement contains an error and cannot be prepared, an
error is returned and no statement with the given name exists.

The scope of a prepared statement is the session within which it is
created, which as several implications:

   * A prepared statement created in one session is not available to
     other sessions.

   * When a session ends, whether normally or abnormally, its prepared
     statements no longer exist. If auto-reconnect is enabled, the
     client is not notified that the connection was lost. For this
     reason, clients may wish to disable auto-reconnect. See *Note
     auto-reconnect::.

   * A prepared statement created within a stored program continues to
     exist after the program finishes executing and can be executed
     outside the program later.

   * A statement prepared in stored program context cannot refer to
     stored procedure or function parameters or local variables because
     they go out of scope when the program ends and would be
     unavailable were the statement to be executed later outside the
     program. As a workaround, refer instead to user-defined variables,
     which also have session scope; see *Note user-variables::.


File: manual.info,  Node: execute,  Next: deallocate-prepare,  Prev: prepare,  Up: sql-syntax-prepared-statements

13.5.2 EXECUTE Syntax
---------------------


     EXECUTE STMT_NAME
         [USING @VAR_NAME [, @VAR_NAME] ...]

After preparing a statement with *Note `PREPARE': prepare, you execute
it with an *Note `EXECUTE': execute. statement that refers to the
prepared statement name. If the prepared statement contains any
parameter markers, you must supply a `USING' clause that lists user
variables containing the values to be bound to the parameters.
Parameter values can be supplied only by user variables, and the
`USING' clause must name exactly as many variables as the number of
parameter markers in the statement.

You can execute a given prepared statement multiple times, passing
different variables to it or setting the variables to different values
before each execution.

For examples, see *Note sql-syntax-prepared-statements::.


File: manual.info,  Node: deallocate-prepare,  Next: statement-repreparation,  Prev: execute,  Up: sql-syntax-prepared-statements

13.5.3 DEALLOCATE PREPARE Syntax
--------------------------------


     {DEALLOCATE | DROP} PREPARE STMT_NAME

To deallocate a prepared statement produced with *Note `PREPARE':
prepare, use a *Note `DEALLOCATE PREPARE': deallocate-prepare.
statement that refers to the prepared statement name. Attempting to
execute a prepared statement after deallocating it results in an error.

For examples, see *Note sql-syntax-prepared-statements::.


File: manual.info,  Node: statement-repreparation,  Prev: deallocate-prepare,  Up: sql-syntax-prepared-statements

13.5.4 Automatic Prepared Statement Repreparation
-------------------------------------------------

As of MySQL 5.1.25, metadata changes to tables or views referred to by
prepared statements are detected and cause automatic repreparation of
the statement when it is next executed. This applies to prepared
statements processed at the SQL level (using the *Note `PREPARE':
prepare. statement) and those processed using the binary client/server
protocol (using the *Note `mysql_stmt_prepare()': mysql-stmt-prepare. C
API function).

The server attempts repreparation up to three times. An error occurs if
all attempts fail.

Metadata changes occur for DDL statements such as those that create,
drop, alter, rename, or truncate tables, or that analyze, optimize, or
repair tables. Repreparation also occurs after referenced tables or
views are flushed from the table definition cache, either implicitly to
make room for new entries in the cache, or explicitly due to *Note
`FLUSH TABLES': flush.

Table content changes (for example, with *Note `INSERT': insert. or
*Note `UPDATE': update.) do not cause repreparation, nor do *Note
`SELECT': select. statements.

Repreparation is automatic, but to the extent that it occurs,
diminishes prepared statement performance.

Repreparation uses the default database and SQL mode that were in
effect for the original preparation.

The `Com_stmt_reprepare' status variable tracks the number of
repreparations.

An incompatibility with older versions of MySQL (before 5.1.25) is that
a prepared statement may return a different set of columns or different
column types from one execution to the next. For example, if the
prepared statement is `SELECT * FROM t1', altering `t1' to contain a
different number of columns causes the next execution to return a
number of columns different from the previous execution.

Older versions of the client library cannot handle this change in
behavior. For applications that use prepared statements with a server
that performs automatic repreparation, an upgrade to the new client
library is strongly recommended.


File: manual.info,  Node: sql-syntax-compound-statements,  Next: sql-syntax-server-administration,  Prev: sql-syntax-prepared-statements,  Up: sql-syntax

13.6 MySQL Compound-Statement Syntax
====================================

* Menu:

* begin-end::                    BEGIN ... END Compound-Statement Syntax
* statement-labels::             Statement Label Syntax
* declare::                      DECLARE Syntax
* stored-program-variables::     Variables in Stored Programs
* flow-control-statements::      Flow Control Statements
* cursors::                      Cursors
* condition-handling::           Condition Handling

This section describes the syntax for the *Note `BEGIN ... END':
begin-end.  compound statement and other statements that can be used in
the body of stored programs: Stored procedures and functions, triggers,
and events. These objects are defined in terms of SQL code that is
stored on the server for later invocation (see *Note
stored-programs-views::).

A compound statement is a block that can contain other blocks;
declarations for variables, condition handlers, and cursors; and flow
control constructs such as loops and conditional tests.


File: manual.info,  Node: begin-end,  Next: statement-labels,  Prev: sql-syntax-compound-statements,  Up: sql-syntax-compound-statements

13.6.1 BEGIN ... END Compound-Statement Syntax
----------------------------------------------


     [BEGIN_LABEL:] BEGIN
         [STATEMENT_LIST]
     END [END_LABEL]

*Note `BEGIN ... END': begin-end.  syntax is used for writing compound
statements, which can appear within stored programs (stored procedures
and functions, triggers, and events). A compound statement can contain
multiple statements, enclosed by the `BEGIN' and `END' keywords.
STATEMENT_LIST represents a list of one or more statements, each
terminated by a semicolon (`;') statement delimiter. The STATEMENT_LIST
itself is optional, so the empty compound statement (`BEGIN END') is
legal.

*Note `BEGIN ... END': begin-end.  blocks can be nested.

Use of multiple statements requires that a client is able to send
statement strings containing the `;' statement delimiter. In the *Note
`mysql': mysql. command-line client, this is handled with the
`delimiter' command.  Changing the `;' end-of-statement delimiter (for
example, to `//') permit `;' to be used in a program body. For an
example, see *Note stored-programs-defining::.

A *Note `BEGIN ... END': begin-end. block can be labeled. See *Note
statement-labels::.

The optional `[NOT] ATOMIC' clause is not supported. This means that no
transactional savepoint is set at the start of the instruction block
and the `BEGIN' clause used in this context has no effect on the
current transaction.

*Note*:

Within all stored programs, the parser treats *Note `BEGIN [WORK]':
commit.  as the beginning of a *Note `BEGIN ... END': begin-end. block.
To begin a transaction in this context, use *Note `START TRANSACTION':
commit. instead.


File: manual.info,  Node: statement-labels,  Next: declare,  Prev: begin-end,  Up: sql-syntax-compound-statements

13.6.2 Statement Label Syntax
-----------------------------


     [BEGIN_LABEL:] BEGIN
         [STATEMENT_LIST]
     END [END_LABEL]

     [BEGIN_LABEL:] LOOP
         STATEMENT_LIST
     END LOOP [END_LABEL]

     [BEGIN_LABEL:] REPEAT
         STATEMENT_LIST
     UNTIL SEARCH_CONDITION
     END REPEAT [END_LABEL]

     [BEGIN_LABEL:] WHILE SEARCH_CONDITION DO
         STATEMENT_LIST
     END WHILE [END_LABEL]

Labels are permitted for *Note `BEGIN ... END': begin-end.  blocks and
for the *Note `LOOP': loop, *Note `REPEAT': repeat, and *Note `WHILE':
while. statements. Label use for those statements follows these rules:

   * BEGIN_LABEL must be followed by a colon.

   * BEGIN_LABEL can be given without END_LABEL. If END_LABEL is
     present, it must be the same as BEGIN_LABEL.

   * END_LABEL cannot be given without BEGIN_LABEL.

   * Labels at the same nesting level must be distinct.

   * Labels can be up to 16 characters long.

To refer to a label within the labeled construct, use an *Note
`ITERATE': iterate. or *Note `LEAVE': leave. statement. The following
example uses those statements to continue iterating or terminate the
loop:


     CREATE PROCEDURE doiterate(p1 INT)
     BEGIN
       label1: LOOP
         SET p1 = p1 + 1;
         IF p1 < 10 THEN ITERATE label1; END IF;
         LEAVE label1;
       END LOOP label1;
     END;

The scope of a block label does not include the code for handlers
declared within the block. For details, see *Note declare-handler::.


File: manual.info,  Node: declare,  Next: stored-program-variables,  Prev: statement-labels,  Up: sql-syntax-compound-statements

13.6.3 DECLARE Syntax
---------------------

The *Note `DECLARE': declare. statement is used to define various items
local to a program:

   * Local variables. See *Note stored-program-variables::.

   * Conditions and handlers. See *Note condition-handling::.

   * Cursors. See *Note cursors::.

*Note `DECLARE': declare. is permitted only inside a *Note `BEGIN ...
END': begin-end.  compound statement and must be at its start, before
any other statements.

Declarations must follow a certain order. Cursor declarations must
appear before handler declarations. Variable and condition declarations
must appear before cursor or handler declarations.


File: manual.info,  Node: stored-program-variables,  Next: flow-control-statements,  Prev: declare,  Up: sql-syntax-compound-statements

13.6.4 Variables in Stored Programs
-----------------------------------

* Menu:

* declare-local-variable::       Local Variable DECLARE Syntax
* local-variable-scope::         Local Variable Scope and Resolution

System variables and user-defined variables can be used in stored
programs, just as they can be used outside stored-program context.  In
addition, stored programs can use `DECLARE' to define local variables,
and stored routines (procedures and functions) can be declared to take
parameters that communicate values between the routine and its caller.

   * To declare local variables, use the *Note `DECLARE':
     declare-local-variable.  statement, as described in *Note
     declare-local-variable::.

   * Variables can be set directly with the *Note `SET': set-statement.
     statement. See *Note set-statement::.

   * Results from queries can be retrieved into local variables using
     *Note `SELECT ... INTO VAR_LIST': select-into. or by opening a
     cursor and using *Note `FETCH ... INTO VAR_LIST': fetch. See *Note
     select-into::, and *Note cursors::.

For information about the scope of local variables and how MySQL
resolves ambiguous names, see *Note local-variable-scope::.


File: manual.info,  Node: declare-local-variable,  Next: local-variable-scope,  Prev: stored-program-variables,  Up: stored-program-variables

13.6.4.1 Local Variable DECLARE Syntax
......................................


     DECLARE VAR_NAME [, VAR_NAME] ... TYPE [DEFAULT VALUE]

This statement declares local variables within stored programs.  To
provide a default value for a variable, include a `DEFAULT' clause. The
value can be specified as an expression; it need not be a constant. If
the `DEFAULT' clause is missing, the initial value is `NULL'.

Local variables are treated like stored routine parameters with respect
to data type and overflow checking. See *Note create-procedure::.

Variable declarations must appear before cursor or handler declarations.

Local variable names are not case sensitive. Permissible characters and
quoting rules are the same as for other identifiers, as described in
*Note identifiers::.

The scope of a local variable is the *Note `BEGIN ... END': begin-end.
block within which it is declared. The variable can be referred to in
blocks nested within the declaring block, except those blocks that
declare a variable with the same name.


File: manual.info,  Node: local-variable-scope,  Prev: declare-local-variable,  Up: stored-program-variables

13.6.4.2 Local Variable Scope and Resolution
............................................

The scope of a local variable is the *Note `BEGIN ... END': begin-end.
block within which it is declared. The variable can be referred to in
blocks nested within the declaring block, except those blocks that
declare a variable with the same name.

Because local variables are in scope only during stored program
execution, references to them are not permitted in prepared statements
created within a stored program. Prepared statement scope is the
current session, not the stored program, so the statement could be
executed after the program ends, at which point the variables would no
longer be in scope. For example, `SELECT ... INTO LOCAL_VAR' cannot be
used as a prepared statement. This restriction also applies to stored
procedure and function parameters. See *Note prepare::.

A local variable should not have the same name as a table column. If an
SQL statement, such as a *Note `SELECT ... INTO': select. statement,
contains a reference to a column and a declared local variable with the
same name, MySQL currently interprets the reference as the name of a
variable. Consider the following procedure definition:


     CREATE PROCEDURE sp1 (x VARCHAR(5))
     BEGIN
       DECLARE xname VARCHAR(5) DEFAULT 'bob';
       DECLARE newname VARCHAR(5);
       DECLARE xid INT;

       SELECT xname, id INTO newname, xid
         FROM table1 WHERE xname = xname;
       SELECT newname;
     END;

MySQL interprets `xname' in the *Note `SELECT': select. statement as a
reference to the `xname' _variable_ rather than the `xname' _column_.
Consequently, when the procedure `sp1()'is called, the `newname'
variable returns the value `'bob'' regardless of the value of the
`table1.xname' column.

Similarly, the cursor definition in the following procedure contains a
*Note `SELECT': select. statement that refers to `xname'. MySQL
interprets this as a reference to the variable of that name rather than
a column reference.


     CREATE PROCEDURE sp2 (x VARCHAR(5))
     BEGIN
       DECLARE xname VARCHAR(5) DEFAULT 'bob';
       DECLARE newname VARCHAR(5);
       DECLARE xid INT;
       DECLARE done TINYINT DEFAULT 0;
       DECLARE cur1 CURSOR FOR SELECT xname, id FROM table1;
       DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = 1;

       OPEN cur1;
       read_loop: LOOP
         FETCH FROM cur1 INTO newname, xid;
         IF done THEN LEAVE read_loop; END IF;
         SELECT newname;
       END LOOP;
       CLOSE cur1;
     END;

See also *Note stored-program-restrictions::.


File: manual.info,  Node: flow-control-statements,  Next: cursors,  Prev: stored-program-variables,  Up: sql-syntax-compound-statements

13.6.5 Flow Control Statements
------------------------------

* Menu:

* case::                         CASE Syntax
* if::                           IF Syntax
* iterate::                      ITERATE Syntax
* leave::                        LEAVE Syntax
* loop::                         LOOP Syntax
* repeat::                       REPEAT Syntax
* return::                       RETURN Syntax
* while::                        WHILE Syntax

MySQL supports the *Note `IF': if, *Note `CASE': case, *Note `ITERATE':
iterate, *Note `LEAVE': leave.  *Note `LOOP': loop, *Note `WHILE':
while, and *Note `REPEAT': repeat. constructs for flow control within
stored programs. It also supports *Note `RETURN': return. within stored
functions.

Many of these constructs contain other statements, as indicated by the
grammar specifications in the following sections. Such constructs may
be nested. For example, an *Note `IF': if. statement might contain a
*Note `WHILE': while. loop, which itself contains a *Note `CASE': case.
statement.

MySQL does not support `FOR' loops.


File: manual.info,  Node: case,  Next: if,  Prev: flow-control-statements,  Up: flow-control-statements

13.6.5.1 CASE Syntax
....................


     CASE CASE_VALUE
         WHEN WHEN_VALUE THEN STATEMENT_LIST
         [WHEN WHEN_VALUE THEN STATEMENT_LIST] ...
         [ELSE STATEMENT_LIST]
     END CASE

Or:


     CASE
         WHEN SEARCH_CONDITION THEN STATEMENT_LIST
         [WHEN SEARCH_CONDITION THEN STATEMENT_LIST] ...
         [ELSE STATEMENT_LIST]
     END CASE

The *Note `CASE': case. statement for stored programs implements a
complex conditional construct.

*Note*:

There is also a `CASE' _expression_, which differs from the *Note
`CASE': case.  _statement_ described here. See *Note
control-flow-functions::. The *Note `CASE': case. statement cannot have
an `ELSE NULL' clause, and it is terminated with `END CASE' instead of
`END'.

For the first syntax, CASE_VALUE is an expression. This value is
compared to the WHEN_VALUE expression in each `WHEN' clause until one
of them is equal. When an equal WHEN_VALUE is found, the corresponding
`THEN' clause STATEMENT_LIST executes. If no WHEN_VALUE is equal, the
`ELSE' clause STATEMENT_LIST executes, if there is one.

This syntax cannot be used to test for equality with `NULL' because
`NULL = NULL' is false. See *Note working-with-null::.

For the second syntax, each `WHEN' clause SEARCH_CONDITION expression is
evaluated until one is true, at which point its corresponding `THEN'
clause STATEMENT_LIST executes. If no SEARCH_CONDITION is equal, the
`ELSE' clause STATEMENT_LIST executes, if there is one.

If no WHEN_VALUE or SEARCH_CONDITION matches the value tested and the
*Note `CASE': case. statement contains no `ELSE' clause, a `Case not
found for CASE statement' error results.

Each STATEMENT_LIST consists of one or more SQL statements; an empty
STATEMENT_LIST is not permitted.

To handle situations where no value is matched by any `WHEN' clause,
use an `ELSE' containing an empty *Note `BEGIN ... END': begin-end.
block, as shown in this example. (The indentation used here in the
`ELSE' clause is for purposes of clarity only, and is not otherwise
significant.)


     DELIMITER |

     CREATE PROCEDURE p()
       BEGIN
         DECLARE v INT DEFAULT 1;

         CASE v
           WHEN 2 THEN SELECT v;
           WHEN 3 THEN SELECT 0;
           ELSE
             BEGIN
             END;
         END CASE;
       END;
       |


File: manual.info,  Node: if,  Next: iterate,  Prev: case,  Up: flow-control-statements

13.6.5.2 IF Syntax
..................


     IF SEARCH_CONDITION THEN STATEMENT_LIST
         [ELSEIF SEARCH_CONDITION THEN STATEMENT_LIST] ...
         [ELSE STATEMENT_LIST]
     END IF

The *Note `IF': if. statement for stored programs implements a basic
conditional construct.

*Note*:

There is also an `IF()' _function_, which differs from the *Note `IF':
if.  _statement_ described here. See *Note control-flow-functions::. The
*Note `IF': if. statement can have `THEN', `ELSE', and `ELSEIF'
clauses, and it is terminated with `END IF'.

If the SEARCH_CONDITION evaluates to true, the corresponding `THEN' or
`ELSEIF' clause STATEMENT_LIST executes. If no SEARCH_CONDITION
matches, the `ELSE' clause STATEMENT_LIST executes.

Each STATEMENT_LIST consists of one or more SQL statements; an empty
STATEMENT_LIST is not permitted.

An `IF ... END IF' block, like all other flow-control blocks used
within stored programs, must be terminated with a semicolon, as shown
in this example:


     DELIMITER //

     CREATE FUNCTION SimpleCompare(n INT, m INT)
       RETURNS VARCHAR(20)

       BEGIN
         DECLARE s VARCHAR(20);

         IF n > m THEN SET s = '>';
         ELSEIF n = m THEN SET s = '=';
         ELSE SET s = '<';
         END IF;

         SET s = CONCAT(n, ' ', s, ' ', m);

         RETURN s;
       END //

     DELIMITER ;

As with other flow-control constructs, `IF ... END IF' blocks may be
nested within other flow-control constructs, including other *Note
`IF': if.  statements. Each *Note `IF': if. must be terminated by its
own `END IF' followed by a semicolon. You can use indentation to make
nested flow-control blocks more easily readable by humans (although
this is not required by MySQL), as shown here:


     DELIMITER //

     CREATE FUNCTION VerboseCompare (n INT, m INT)
       RETURNS VARCHAR(50)

       BEGIN
         DECLARE s VARCHAR(50);

         IF n = m THEN SET s = 'equals';
         ELSE
           IF n > m THEN SET s = 'greater';
           ELSE SET s = 'less';
           END IF;

           SET s = CONCAT('is ', s, ' than');
         END IF;

         SET s = CONCAT(n, ' ', s, ' ', m, '.');

         RETURN s;
       END //

     DELIMITER ;

In this example, the inner *Note `IF': if. is evaluated only if `n' is
not equal to `m'.


File: manual.info,  Node: iterate,  Next: leave,  Prev: if,  Up: flow-control-statements

13.6.5.3 ITERATE Syntax
.......................


     ITERATE LABEL

*Note `ITERATE': iterate. can appear only within *Note `LOOP': loop,
*Note `REPEAT': repeat, and *Note `WHILE': while. statements.  *Note
`ITERATE': iterate. means `start the loop again.'

For an example, see *Note loop::.


File: manual.info,  Node: leave,  Next: loop,  Prev: iterate,  Up: flow-control-statements

13.6.5.4 LEAVE Syntax
.....................


     LEAVE LABEL

This statement is used to exit the flow control construct that has the
given label. If the label is for the outermost stored program block,
*Note `LEAVE': leave. exits the program.

*Note `LEAVE': leave. can be used within *Note `BEGIN ... END':
begin-end. or loop constructs (*Note `LOOP': loop, *Note `REPEAT':
repeat, *Note `WHILE': while.).

For an example, see *Note loop::.


File: manual.info,  Node: loop,  Next: repeat,  Prev: leave,  Up: flow-control-statements

13.6.5.5 LOOP Syntax
....................


     [BEGIN_LABEL:] LOOP
         STATEMENT_LIST
     END LOOP [END_LABEL]

*Note `LOOP': loop. implements a simple loop construct, enabling
repeated execution of the statement list, which consists of one or more
statements, each terminated by a semicolon (`;') statement delimiter.
The statements within the loop are repeated until the loop is
terminated. Usually, this is accomplished with a *Note `LEAVE': leave.
statement. Within a stored function, *Note `RETURN': return. can also be
used, which exits the function entirely.

Neglecting to include a loop-termination statement results in an
infinite loop.

A *Note `LOOP': loop. statement can be labeled.  For the rules
regarding label use, see *Note statement-labels::.

Example:


     CREATE PROCEDURE doiterate(p1 INT)
     BEGIN
       label1: LOOP
         SET p1 = p1 + 1;
         IF p1 < 10 THEN
           ITERATE label1;
         END IF;
         LEAVE label1;
       END LOOP label1;
       SET @x = p1;
     END;


File: manual.info,  Node: repeat,  Next: return,  Prev: loop,  Up: flow-control-statements

13.6.5.6 REPEAT Syntax
......................


     [BEGIN_LABEL:] REPEAT
         STATEMENT_LIST
     UNTIL SEARCH_CONDITION
     END REPEAT [END_LABEL]

The statement list within a *Note `REPEAT': repeat. statement is
repeated until the SEARCH_CONDITION expression is true. Thus, a *Note
`REPEAT': repeat. always enters the loop at least once.  STATEMENT_LIST
consists of one or more statements, each terminated by a semicolon
(`;') statement delimiter.

A *Note `REPEAT': repeat. statement can be labeled. For the rules
regarding label use, see *Note statement-labels::.

Example:


     mysql> delimiter //

     mysql> CREATE PROCEDURE dorepeat(p1 INT)
         -> BEGIN
         ->   SET @x = 0;
         ->   REPEAT
         ->     SET @x = @x + 1;
         ->   UNTIL @x > p1 END REPEAT;
         -> END
         -> //
     Query OK, 0 rows affected (0.00 sec)

     mysql> CALL dorepeat(1000)//
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @x//
     +------+
     | @x   |
     +------+
     | 1001 |
     +------+
     1 row in set (0.00 sec)


File: manual.info,  Node: return,  Next: while,  Prev: repeat,  Up: flow-control-statements

13.6.5.7 RETURN Syntax
......................


     RETURN EXPR

The *Note `RETURN': return. statement terminates execution of a stored
function and returns the value EXPR to the function caller. There must
be at least one *Note `RETURN': return.  statement in a stored
function. There may be more than one if the function has multiple exit
points.

This statement is not used in stored procedures, triggers, or events.
The *Note `LEAVE': leave. statement can be used to exit a stored
program of those types.


File: manual.info,  Node: while,  Prev: return,  Up: flow-control-statements

13.6.5.8 WHILE Syntax
.....................


     [BEGIN_LABEL:] WHILE SEARCH_CONDITION DO
         STATEMENT_LIST
     END WHILE [END_LABEL]

The statement list within a *Note `WHILE': while.  statement is
repeated as long as the SEARCH_CONDITION expression is true.
STATEMENT_LIST consists of one or more SQL statements, each terminated
by a semicolon (`;') statement delimiter.

A *Note `WHILE': while. statement can be labeled.  For the rules
regarding label use, see *Note statement-labels::.

Example:


     CREATE PROCEDURE dowhile()
     BEGIN
       DECLARE v1 INT DEFAULT 5;

       WHILE v1 > 0 DO
         ...
         SET v1 = v1 - 1;
       END WHILE;
     END;


File: manual.info,  Node: cursors,  Next: condition-handling,  Prev: flow-control-statements,  Up: sql-syntax-compound-statements

13.6.6 Cursors
--------------

* Menu:

* close::                        Cursor CLOSE Syntax
* declare-cursor::               Cursor DECLARE Syntax
* fetch::                        Cursor FETCH Syntax
* open::                         Cursor OPEN Syntax

MySQL supports cursors inside stored programs. The syntax is as in
embedded SQL. Cursors have these properties:

   * Asensitive: The server may or may not make a copy of its result
     table

   * Read only: Not updatable

   * Nonscrollable: Can be traversed only in one direction and cannot
     skip rows

Cursor declarations must appear before handler declarations and after
variable and condition declarations.

Example:


     CREATE PROCEDURE curdemo()
     BEGIN
       DECLARE done INT DEFAULT FALSE;
       DECLARE a CHAR(16);
       DECLARE b, c INT;
       DECLARE cur1 CURSOR FOR SELECT id,data FROM test.t1;
       DECLARE cur2 CURSOR FOR SELECT i FROM test.t2;
       DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

       OPEN cur1;
       OPEN cur2;

       read_loop: LOOP
         FETCH cur1 INTO a, b;
         FETCH cur2 INTO c;
         IF done THEN
           LEAVE read_loop;
         END IF;
         IF b < c THEN
           INSERT INTO test.t3 VALUES (a,b);
         ELSE
           INSERT INTO test.t3 VALUES (a,c);
         END IF;
       END LOOP;

       CLOSE cur1;
       CLOSE cur2;
     END;


File: manual.info,  Node: close,  Next: declare-cursor,  Prev: cursors,  Up: cursors

13.6.6.1 Cursor CLOSE Syntax
............................


     CLOSE CURSOR_NAME

This statement closes a previously opened cursor. For an example, see
*Note cursors::.

An error occurs if the cursor is not open.

If not closed explicitly, a cursor is closed at the end of the *Note
`BEGIN ... END': begin-end. block in which it was declared.


File: manual.info,  Node: declare-cursor,  Next: fetch,  Prev: close,  Up: cursors

13.6.6.2 Cursor DECLARE Syntax
..............................


     DECLARE CURSOR_NAME CURSOR FOR SELECT_STATEMENT

This statement declares a cursor and associates it with a *Note
`SELECT': select. statement that retrieves the rows to be traversed by
the cursor. To fetch the rows later, use a *Note `FETCH': fetch.
statement. The number of columns retrieved by the *Note `SELECT':
select. statement must match the number of output variables specified
in the *Note `FETCH': fetch. statement.

The *Note `SELECT': select. statement cannot have an `INTO' clause.

Cursor declarations must appear before handler declarations and after
variable and condition declarations.

A stored program may contain multiple cursor declarations, but each
cursor declared in a given block must have a unique name.  For an
example, see *Note cursors::.

For information available through *Note `SHOW': show. statements, it is
possible in many cases to obtain equivalent information by using a
cursor with an `INFORMATION_SCHEMA' table.


File: manual.info,  Node: fetch,  Next: open,  Prev: declare-cursor,  Up: cursors

13.6.6.3 Cursor FETCH Syntax
............................


     FETCH [[NEXT] FROM] CURSOR_NAME INTO VAR_NAME [, VAR_NAME] ...

This statement fetches the next row for the *Note `SELECT': select.
statement associated with the specified cursor (which must be open),
and advances the cursor pointer. If a row exists, the fetched columns
are stored in the named variables. The number of columns retrieved by
the *Note `SELECT': select. statement must match the number of output
variables specified in the *Note `FETCH': fetch. statement.

If no more rows are available, a No Data condition occurs with SQLSTATE
value `'02000''. To detect this condition, you can set up a handler for
it (or for a `NOT FOUND' condition). For an example, see *Note
cursors::.


File: manual.info,  Node: open,  Prev: fetch,  Up: cursors

13.6.6.4 Cursor OPEN Syntax
...........................


     OPEN CURSOR_NAME

This statement opens a previously declared cursor. For an example, see
*Note cursors::.


File: manual.info,  Node: condition-handling,  Prev: cursors,  Up: sql-syntax-compound-statements

13.6.7 Condition Handling
-------------------------

* Menu:

* declare-condition::            DECLARE ... CONDITION Syntax
* declare-handler::              DECLARE ... HANDLER Syntax

Conditions may arise during stored program execution that require
special handling, such as exiting the current program block or
continuing execution. Handlers can be defined for general conditions
such as warnings or exceptions, or for specific conditions such as a
particular error code. Specific conditions can be assigned names and
referred to that way in handlers.

To name a condition, use the *Note `DECLARE ... CONDITION':
declare-condition. statement. To declare a handler, use the *Note
`DECLARE ... HANDLER': declare-handler. statement. See *Note
declare-condition::, and *Note declare-handler::.

Other statements related to conditions are `SIGNAL', `RESIGNAL', and
`GET DIAGNOSTICS'. The `SIGNAL' and `RESIGNAL' statements are not
supported until MySQL 5.5. The `GET DIAGNOSTICS' statement is not
supported until MySQL 5.6.

Before MySQL 5.6.3, if a statement that generates a warning or error
causes a condition handler to be invoked, the handler may not clear the
diagnostic area. This might lead to the appearance that the handler was
not invoked. The following discussion demonstrates the issue and
provides a workaround.

Suppose that a table `t1' is empty. The following procedure selects
from it, raising a No Data condition:


     CREATE PROCEDURE p1()
     BEGIN
       DECLARE a INT;
       DECLARE CONTINUE HANDLER FOR NOT FOUND
         BEGIN
           SET @handler_invoked = 1;
         END;
       SELECT c1 INTO a FROM t1;
     END;

As can be seen from the following sequence of statements, the condition
is not cleared by handler invocation (otherwise, the *Note `SHOW
WARNINGS': show-warnings. output would be empty). But as can be seen by
the value of `@handler_invoked', the handler was indeed invoked
(otherwise its value would be 0).


     mysql> SET @handler_invoked = 0;
     Query OK, 0 rows affected (0.00 sec)

     mysql> CALL p1();
     Query OK, 0 rows affected, 1 warning (0.00 sec)

     mysql> SHOW WARNINGS;
     +---------+------+-----------------------------------------------------+
     | Level   | Code | Message                                             |
     +---------+------+-----------------------------------------------------+
     | Warning | 1329 | No data - zero rows fetched, selected, or processed |
     +---------+------+-----------------------------------------------------+
     1 row in set (0.00 sec)

     mysql> SELECT @handler_invoked;
     +------------------+
     | @handler_invoked |
     +------------------+
     |                1 |
     +------------------+
     1 row in set (0.00 sec)

There are two ways to work around this issue:

   * Add an extra dummy statement that clears warnings at the end of
     the condition handler:


          CREATE PROCEDURE p1()
          BEGIN
            DECLARE a INT;
            DECLARE CONTINUE HANDLER FOR NOT FOUND
              BEGIN
                SET @handler_invoked = 1;
                SELECT 1 FROM (SELECT 1) AS t;
              END;
            SELECT c1 INTO a FROM t1;
          END;

     This works for `CONTINUE' and `EXIT' handlers.

   * Put an extra dummy statement that clears warnings following the
     statement that causes handler activation:


          CREATE PROCEDURE p1()
          BEGIN
            DECLARE a INT;
            DECLARE CONTINUE HANDLER FOR NOT FOUND
              BEGIN
                SET @handler_invoked = 1;
                SELECT 1 FROM (SELECT 1) AS t;
              END;
            SELECT c1 INTO a FROM t1;
          END;

     This works only for `CONTINUE' handlers.

This issue is resolved as of MySQL 5.6.3 and no workaround is needed.


File: manual.info,  Node: declare-condition,  Next: declare-handler,  Prev: condition-handling,  Up: condition-handling

13.6.7.1 DECLARE ... CONDITION Syntax
.....................................


     DECLARE CONDITION_NAME CONDITION FOR CONDITION_VALUE

     CONDITION_VALUE:
         MYSQL_ERROR_CODE
       | SQLSTATE [VALUE] SQLSTATE_VALUE

The *Note `DECLARE ... CONDITION': declare-condition. statement
declares a named error condition, associating a name with a condition
that needs specific handling. The name can be referred to in a
subsequent *Note `DECLARE ... HANDLER': declare-handler. statement (see
*Note declare-handler::).

Condition declarations must appear before cursor or handler
declarations.

The CONDITION_VALUE for *Note `DECLARE ... CONDITION':
declare-condition. can be a MySQL error code (a number) or an SQLSTATE
value (a 5-character string literal). You should not use MySQL error
code 0 or SQLSTATE values that begin with `'00'', because those
indicate success rather than an error condition. For a list of MySQL
error codes and SQLSTATE values, see *Note error-messages-server::.

Using names for conditions can help make stored program code clearer.
For example, this handler applies to attempts to drop a nonexistent
table, but that is apparent only if you know the meaning of MySQL error
code 1051:


     DECLARE CONTINUE HANDLER FOR 1051
       BEGIN
         -- body of handler
       END;

By declaring a name for the condition, the purpose of the handler is
more readily seen:


     DECLARE no_such_table CONDITION FOR 1051;
     DECLARE CONTINUE HANDLER FOR no_such_table
       BEGIN
         -- body of handler
       END;

Here is a named condition for the same condition, but based on the
corresponding SQLSTATE value rather than the MySQL error code:


     DECLARE no_such_table CONDITION FOR SQLSTATE '42S02';
     DECLARE CONTINUE HANDLER FOR no_such_table
       BEGIN
         -- body of handler
       END;


File: manual.info,  Node: declare-handler,  Prev: declare-condition,  Up: condition-handling

13.6.7.2 DECLARE ... HANDLER Syntax
...................................


     DECLARE HANDLER_ACTION HANDLER
         FOR CONDITION_VALUE [, CONDITION_VALUE] ...
         STATEMENT

     HANDLER_ACTION:
         CONTINUE
       | EXIT
       | UNDO

     CONDITION_VALUE:
         MYSQL_ERROR_CODE
       | SQLSTATE [VALUE] SQLSTATE_VALUE
       | CONDITION_NAME
       | SQLWARNING
       | NOT FOUND
       | SQLEXCEPTION

The *Note `DECLARE ... HANDLER': declare-handler. statement specifies a
handler that deals with one or more conditions. If one of these
conditions occurs, the specified STATEMENT executes.  STATEMENT can be
a simple statement such as `SET VAR_NAME = VALUE', or a compound
statement written using `BEGIN' and `END' (see *Note begin-end::).

Handler declarations must appear after variable or condition
declarations.

The HANDLER_ACTION value indicates what action the handler takes after
execution of the handler statement:

   * `CONTINUE': Execution of the current program continues.

   * `EXIT': Execution terminates for the *Note `BEGIN ... END':
     begin-end. compound statement in which the handler is declared.
     This is true even if the condition occurs in an inner block.

   * `UNDO': Not supported.

The CONDITION_VALUE for *Note `DECLARE ... HANDLER': declare-handler.
indicates the specific condition or class of conditions that activates
the handler:

   * A MySQL error code (a number) or an SQLSTATE value (a 5-character
     string literal). You should not use MySQL error code 0 or SQLSTATE
     values that begin with `'00'', because those indicate success
     rather than an error condition. For a list of MySQL error codes
     and SQLSTATE values, see *Note error-messages-server::.

   * A condition name previously specified with *Note `DECLARE ...
     CONDITION': declare-condition. A condition name can be associated
     with a MySQL error code or SQLSTATE value. See *Note
     declare-condition::.

   * `SQLWARNING' is shorthand for the class of SQLSTATE values that
     begin with `'01''.

   * `NOT FOUND' is shorthand for the class of SQLSTATE values that
     begin with `'02''.  This is relevant within the context of cursors
     and is used to control what happens when a cursor reaches the end
     of a data set. If no more rows are available, a No Data condition
     occurs with SQLSTATE value `'02000''. To detect this condition,
     you can set up a handler for it (or for a `NOT FOUND' condition).
     For an example, see *Note cursors::. This condition also occurs
     for `SELECT ... INTO VAR_LIST' statements that retrieve no rows.

   * `SQLEXCEPTION' is shorthand for the class of SQLSTATE values that
     do not begin with `'00'', `'01'', or `'02''.

If a condition occurs for which no handler has been declared, the
action taken depends on the condition class:

   * For `SQLEXCEPTION' conditions, the stored program terminates at
     the statement that raised the condition, as if there were an `EXIT'
     handler. If the program was called by another stored program, the
     calling program handles the condition using the handler selection
     rules applied to its own handlers.

   * For `SQLWARNING' or `NOT FOUND' conditions, the program continues
     executing, as if there were a `CONTINUE' handler.

The following example uses a handler for `SQLSTATE '23000'', which
occurs for a duplicate-key error:


     mysql> CREATE TABLE test.t (s1 INT, PRIMARY KEY (s1));
     Query OK, 0 rows affected (0.00 sec)

     mysql> delimiter //

     mysql> CREATE PROCEDURE handlerdemo ()
         -> BEGIN
         ->   DECLARE CONTINUE HANDLER FOR SQLSTATE '23000' SET @x2 = 1;
         ->   SET @x = 1;
         ->   INSERT INTO test.t VALUES (1);
         ->   SET @x = 2;
         ->   INSERT INTO test.t VALUES (1);
         ->   SET @x = 3;
         -> END;
         -> //
     Query OK, 0 rows affected (0.00 sec)

     mysql> CALL handlerdemo()//
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @x//
         +------+
         | @x   |
         +------+
         | 3    |
         +------+
         1 row in set (0.00 sec)

Notice that `@x' is `3' after the procedure executes, which shows that
execution continued to the end of the procedure after the error
occurred. If the *Note `DECLARE ... HANDLER': declare-handler.
statement had not been present, MySQL would have taken the default
action (`EXIT') after the second *Note `INSERT': insert. failed due to
the `PRIMARY KEY' constraint, and `SELECT @x' would have returned `2'.

To ignore a condition, declare a `CONTINUE' handler for it and
associate it with an empty block. For example:


     DECLARE CONTINUE HANDLER FOR SQLWARNING BEGIN END;

The scope of a block label does not include the code for handlers
declared within the block. Therefore, the statement associated with a
handler cannot use *Note `ITERATE': iterate. or *Note `LEAVE': leave.
to refer to labels for blocks that enclose the handler declaration.
Consider the following example, where the *Note `REPEAT': repeat. block
has a label of `retry':


     CREATE PROCEDURE p ()
     BEGIN
       DECLARE i INT DEFAULT 3;
       retry:
         REPEAT
           BEGIN
             DECLARE CONTINUE HANDLER FOR SQLWARNING
               BEGIN
                 ITERATE retry;    # illegal
               END;
             IF i < 0 THEN
               LEAVE retry;        # legal
             END IF;
             SET i = i - 1;
           END;
         UNTIL FALSE END REPEAT;
     END;

The `retry' label is in scope for the *Note `IF': if. statement within
the block. It is not in scope for the `CONTINUE' handler, so the
reference there is invalid and results in an error:


     ERROR 1308 (42000): LEAVE with no matching label: retry

To avoid references to outer labels in handlers, use one of these
strategies:

   * To leave the block, use an `EXIT' handler.  If no block cleanup is
     required, the *Note `BEGIN ... END': begin-end. handler body can
     be empty:


          DECLARE EXIT HANDLER FOR SQLWARNING BEGIN END;

     Otherwise, put the cleanup statements in the handler body:


          DECLARE EXIT HANDLER FOR SQLWARNING
            BEGIN
              BLOCK CLEANUP STATEMENTS
            END;

   * To continue execution, set a status variable in a `CONTINUE'
     handler that can be checked in the enclosing block to determine
     whether the handler was invoked. The following example uses the
     variable `done' for this purpose:


          CREATE PROCEDURE p ()
          BEGIN
            DECLARE i INT DEFAULT 3;
            DECLARE done INT DEFAULT FALSE;
            retry:
              REPEAT
                BEGIN
                  DECLARE CONTINUE HANDLER FOR SQLWARNING
                    BEGIN
                      SET done = TRUE;
                    END;
                  IF done OR i < 0 THEN
                    LEAVE retry;
                  END IF;
                  SET i = i - 1;
                END;
              UNTIL FALSE END REPEAT;
          END;


File: manual.info,  Node: sql-syntax-server-administration,  Next: sql-syntax-utility,  Prev: sql-syntax-compound-statements,  Up: sql-syntax

13.7 Database Administration Statements
=======================================

* Menu:

* account-management-sql::       Account Management Statements
* table-maintenance-sql::        Table Maintenance Statements
* plugin-sql::                   Plugin and User-Defined Function Statements
* set-statement::                SET Syntax
* show::                         SHOW Syntax
* other-administrative-sql::     Other Administrative Statements


File: manual.info,  Node: account-management-sql,  Next: table-maintenance-sql,  Prev: sql-syntax-server-administration,  Up: sql-syntax-server-administration

13.7.1 Account Management Statements
------------------------------------

* Menu:

* create-user::                  CREATE USER Syntax
* drop-user::                    DROP USER Syntax
* grant::                        GRANT Syntax
* rename-user::                  RENAME USER Syntax
* revoke::                       REVOKE Syntax
* set-password::                 SET PASSWORD Syntax

MySQL account information is stored in the tables of the `mysql'
database. This database and the access control system are discussed
extensively in *Note server-administration::, which you should consult
for additional details.

*Important*:

Some releases of MySQL introduce changes to the structure of the grant
tables to add new privileges or features. To make sure that you can
take advantage of any new capabilities, update your grant tables to
have the current structure whenever you update to a new version of
MySQL. See *Note mysql-upgrade::.


File: manual.info,  Node: create-user,  Next: drop-user,  Prev: account-management-sql,  Up: account-management-sql

13.7.1.1 CREATE USER Syntax
...........................


     CREATE USER USER_SPECIFICATION [, USER_SPECIFICATION] ...

     USER_SPECIFICATION:
         USER [IDENTIFIED BY [PASSWORD] 'PASSWORD']

The *Note `CREATE USER': create-user. statement creates new MySQL
accounts. An error occurs for accounts that already exist. To use this
statement, you must have the global `CREATE USER' privilege or the
`INSERT' privilege for the `mysql' database. For each account, *Note
`CREATE USER': create-user. creates a new row in the `mysql.user' table
with no privileges.  Depending on the syntax used, *Note `CREATE USER':
create-user. may also assign the account a password.

Each USER_SPECIFICATION clause consists of an account name and
information about how authentication occurs for clients that use the
account. This part of *Note `CREATE USER': create-user. syntax is
shared with *Note `GRANT': grant, so the description here applies to
*Note `GRANT': grant.  as well.

Each account name uses the format described in *Note account-names::.
For example:


     CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass';

If you specify only the user name part of the account name, a host name
part of `'%'' is used.

*Note `CREATE USER': create-user. examples:

   * To enable the user to connect with no password, include no
     `IDENTIFIED BY' clause:


          CREATE USER 'jeffrey'@'localhost';

   * To assign a password, use `IDENTIFIED BY' with the literal
     plaintext password value:


          CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass';

   * To avoid specifying the plaintext password if you know its hash
     value (the value that `PASSWORD()' would return for the password),
     specify the hash value preceded by the keyword `PASSWORD':


          CREATE USER 'jeffrey'@'localhost'
          IDENTIFIED BY PASSWORD '*90E462C37378CED12064BB3388827D2BA3A9B689';

For additional information about setting passwords, see *Note
assigning-passwords::.

*Important*:

*Note `CREATE USER': create-user. may be recorded in server logs or on
the client side in a history file such as `~/.mysql_history', which
means that cleartext passwords may be read by anyone having read access
to that information. For information about password logging in the
server logs, see *Note password-logging::. For similar information
about client-side logging, see *Note mysql-logging::.

*Important*:

Some releases of MySQL introduce changes to the structure of the grant
tables to add new privileges or features. To make sure that you can
take advantage of any new capabilities, update your grant tables to
have the current structure whenever you update to a new version of
MySQL. See *Note mysql-upgrade::.


File: manual.info,  Node: drop-user,  Next: grant,  Prev: create-user,  Up: account-management-sql

13.7.1.2 DROP USER Syntax
.........................


     DROP USER USER [, USER] ...

The *Note `DROP USER': drop-user. statement removes one or more MySQL
accounts and their privileges. It removes privilege rows for the
account from all grant tables. An error occurs for accounts that do not
exist. To use this statement, you must have the global `CREATE USER'
privilege or the `DELETE' privilege for the `mysql' database.

Each account name uses the format described in *Note account-names::.
For example:


     DROP USER 'jeffrey'@'localhost';

If you specify only the user name part of the account name, a host name
part of `'%'' is used.

*Important*:

*Note `DROP USER': drop-user. does not automatically close any open
user sessions. Rather, in the event that a user with an open session is
dropped, the statement does not take effect until that user's session is
closed. Once the session is closed, the user is dropped, and that
user's next attempt to log in will fail. _This is by design_.

*Note `DROP USER': drop-user. does not automatically drop or invalidate
databases or objects within them that the old user created. This
includes stored programs or views for which the `DEFINER' attribute
names the dropped user.  Attempts to access such objects may produce an
error if they execute in definer security context. (For information
about security context, see *Note stored-programs-security::.)


File: manual.info,  Node: grant,  Next: rename-user,  Prev: drop-user,  Up: account-management-sql

13.7.1.3 GRANT Syntax
.....................


     GRANT
         PRIV_TYPE [(COLUMN_LIST)]
           [, PRIV_TYPE [(COLUMN_LIST)]] ...
         ON [OBJECT_TYPE] PRIV_LEVEL
         TO USER_SPECIFICATION [, USER_SPECIFICATION] ...
         [REQUIRE {NONE | SSL_OPTION [[AND] SSL_OPTION] ...}]
         [WITH WITH_OPTION ...]

     OBJECT_TYPE:
         TABLE
       | FUNCTION
       | PROCEDURE

     PRIV_LEVEL:
         *
       | *.*
       | DB_NAME.*
       | DB_NAME.TBL_NAME
       | TBL_NAME
       | DB_NAME.ROUTINE_NAME

     USER_SPECIFICATION:
         USER [IDENTIFIED BY [PASSWORD] 'PASSWORD']

     SSL_OPTION:
         SSL
       | X509
       | CIPHER 'CIPHER'
       | ISSUER 'ISSUER'
       | SUBJECT 'SUBJECT'

     WITH_OPTION:
         GRANT OPTION
       | MAX_QUERIES_PER_HOUR COUNT
       | MAX_UPDATES_PER_HOUR COUNT
       | MAX_CONNECTIONS_PER_HOUR COUNT
       | MAX_USER_CONNECTIONS COUNT

The *Note `GRANT': grant. statement grants privileges to MySQL user
accounts.  *Note `GRANT': grant. also serves to specify other account
characteristics such as use of secure connections and limits on access
to server resources. To use *Note `GRANT': grant, you must have the
`GRANT OPTION' privilege, and you must have the privileges that you are
granting.

Normally, a database administrator first uses *Note `CREATE USER':
create-user. to create an account, then *Note `GRANT': grant. to define
its privileges and characteristics. For example:


     CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'mypass';
     GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
     GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost';
     GRANT USAGE ON *.* TO 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 90;

However, if an account named in a *Note `GRANT': grant. statement does
not already exist, *Note `GRANT': grant. may create it under the
conditions described later in the discussion of the
`NO_AUTO_CREATE_USER' SQL mode.

The *Note `REVOKE': revoke. statement is related to *Note `GRANT':
grant. and enables administrators to remove account privileges. See
*Note revoke::.

When successfully executed from the *Note `mysql': mysql.  program,
*Note `GRANT': grant. responds with `Query OK, 0 rows affected'. To
determine what privileges result from the operation, use *Note `SHOW
GRANTS': show-grants. See *Note show-grants::.

There are several aspects to the `GRANT' statement, described under the
following topics in this section:

   * Privileges Supported by MySQL

     However, an account with no password is insecure. To avoid this,
     use *Note `SET PASSWORD': set-password. to set the account
     password.

   * Global Privileges

   * Database Privileges

   * Table Privileges

   * Column Privileges

   * Stored Routine Privileges

   * Account Names and Passwords

   * Other Account Characteristics

   * MySQL and Standard SQL Versions of *Note `GRANT': grant.

*Important*:

Some releases of MySQL introduce changes to the structure of the grant
tables to add new privileges or features. To make sure that you can
take advantage of any new capabilities, update your grant tables to
have the current structure whenever you update to a new version of
MySQL. See *Note mysql-upgrade::.

*Privileges Supported by MySQL*

The following table summarizes the permissible PRIV_TYPE privilege
types that can be specified for the *Note `GRANT': grant. and *Note
`REVOKE': revoke. statements, and the levels at which each privilege
can be granted. For additional information about these privileges, see
*Note privileges-provided::.

*Permissible Privileges for GRANT and REVOKE*

Privilege              Meaning and Grantable Levels
`ALL [PRIVILEGES]'     Grant all privileges at specified access level
                       except `GRANT OPTION'
`ALTER'                Enable use of *Note `ALTER TABLE': alter-table.
                       Levels: Global, database, table.
`ALTER ROUTINE'        Enable stored routines to be altered or dropped.
                       Levels: Global, database, procedure.
`CREATE'               Enable database and table creation. Levels:
                       Global, database, table.
`CREATE ROUTINE'       Enable stored routine creation. Levels: Global,
                       database.
`CREATE TEMPORARY      Enable use of *Note `CREATE TEMPORARY TABLE':
TABLES'                create-table. Levels: Global, database.
`CREATE USER'          Enable use of *Note `CREATE USER': create-user,
                       *Note `DROP USER': drop-user, *Note `RENAME
                       USER': rename-user, and *Note `REVOKE ALL
                       PRIVILEGES': revoke. Level: Global.
`CREATE VIEW'          Enable views to be created or altered. Levels:
                       Global, database, table.
`DELETE'               Enable use of *Note `DELETE': delete. Level:
                       Global, database, table.
`DROP'                 Enable databases, tables, and views to be
                       dropped. Levels: Global, database, table.
`EVENT'                Enable use of events for the Event Scheduler.
                       Levels: Global, database.
`EXECUTE'              Enable the user to execute stored routines.
                       Levels: Global, database, table.
`FILE'                 Enable the user to cause the server to read or
                       write files. Level: Global.
`GRANT OPTION'         Enable privileges to be granted to or removed
                       from other accounts.  Levels: Global, database,
                       table, procedure.
`INDEX'                Enable indexes to be created or dropped. Levels:
                       Global, database, table.
`INSERT'               Enable use of *Note `INSERT': insert. Levels:
                       Global, database, table, column.
`LOCK TABLES'          Enable use of *Note `LOCK TABLES': lock-tables.
                       on tables for which you have the *Note `SELECT':
                       select.  privilege. Levels: Global, database.
`PROCESS'              Enable the user to see all processes with *Note
                       `SHOW PROCESSLIST': show-processlist. Level:
                       Global.
`REFERENCES'           Not implemented
`RELOAD'               Enable use of *Note `FLUSH': flush. operations.
                       Level: Global.
`REPLICATION CLIENT'   Enable the user to ask where master or slave
                       servers are. Level: Global.
`REPLICATION SLAVE'    Enable replication slaves to read binary log
                       events from the master.  Level: Global.
`SELECT'               Enable use of *Note `SELECT': select. Levels:
                       Global, database, table, column.
`SHOW DATABASES'       Enable *Note `SHOW DATABASES': show-databases. to
                       show all databases. Level: Global.
`SHOW VIEW'            Enable use of *Note `SHOW CREATE VIEW':
                       show-create-view. Levels: Global, database, table.
`SHUTDOWN'             Enable use of *Note `mysqladmin shutdown':
                       mysqladmin. Level: Global.
`SUPER'                Enable use of other administrative operations
                       such as *Note `CHANGE MASTER TO':
                       change-master-to, *Note `KILL': kill, *Note
                       `PURGE BINARY LOGS': purge-binary-logs, *Note
                       `SET GLOBAL': set-statement, and *Note
                       `mysqladmin debug': mysqladmin. command. Level:
                       Global.
`TRIGGER'              Enable trigger operations. Levels: Global,
                       database, table.
`UPDATE'               Enable use of *Note `UPDATE': update. Levels:
                       Global, database, table, column.
`USAGE'                Synonym for `no privileges'

The `EVENT' and `TRIGGER' privileges were added in MySQL 5.1.6. A
trigger is associated with a table, so to create or drop a trigger, you
must have the `TRIGGER' privilege for the table, not the trigger.
(Before MySQL 5.1.6, the `SUPER' privilege was required to create or
drop triggers.)

In *Note `GRANT': grant. statements, the `ALL [PRIVILEGES]' privilege
is named by itself and cannot be specified along with other privileges.
It stands for all privileges available for the level at which
privileges are to be granted except for the `GRANT OPTION' privilege.

`USAGE' can be specified to create a user that has no privileges, or to
specify the `REQUIRE' or `WITH' clauses for an account without changing
its existing privileges.

MySQL account information is stored in the tables of the `mysql'
database. This database and the access control system are discussed
extensively in *Note privilege-system::, which you should consult for
additional details.

If the grant tables hold privilege rows that contain mixed-case
database or table names and the `lower_case_table_names' system
variable is set to a nonzero value, *Note `REVOKE': revoke. cannot be
used to revoke these privileges. It will be necessary to manipulate the
grant tables directly. (*Note `GRANT': grant. will not create such rows
when `lower_case_table_names' is set, but such rows might have been
created prior to setting that variable.)

Privileges can be granted at several levels, depending on the syntax
used for the `ON' clause. For *Note `REVOKE': revoke, the same `ON'
syntax specifies which privileges to take away. The examples shown here
include no `IDENTIFIED BY 'PASSWORD'' clause for brevity, but you
should include one if the account does not already exist, to avoid
creating an insecure account that has no password.

*Global Privileges*

Global privileges are administrative or apply to all databases on a
given server. To assign global privileges, use `ON *.*' syntax:


     GRANT ALL ON *.* TO 'someuser'@'somehost';
     GRANT SELECT, INSERT ON *.* TO 'someuser'@'somehost';

Before MySQL 5.1.12, privileges also are assigned at the global level
if you use `ON *' syntax and you have _not_ selected a default
database. As of 5.1.12, `ON *' requires a default database and produces
an error if there is none.

The `CREATE USER', `FILE', `PROCESS', `RELOAD', `REPLICATION CLIENT',
`REPLICATION SLAVE', `SHOW DATABASES', `SHUTDOWN', and `SUPER'
privileges are administrative and can only be granted globally.

Other privileges can be granted globally or at more specific levels.

MySQL stores global privileges in the `mysql.user' table.

*Database Privileges*

Database privileges apply to all objects in a given database. To assign
database-level privileges, use `ON DB_NAME.*' syntax:


     GRANT ALL ON mydb.* TO 'someuser'@'somehost';
     GRANT SELECT, INSERT ON mydb.* TO 'someuser'@'somehost';

If you use `ON *' syntax (rather than `ON *.*') and you have selected a
default database, privileges are assigned at the database level for the
default database. An error occurs if there is no default database.

The `CREATE', `DROP', `EVENT', `GRANT OPTION', and `LOCK TABLES'
privileges can be specified at the database level. Table or routine
privileges also can be specified at the database level, in which case
they apply to all tables or routines in the database.

MySQL stores database privileges in the `mysql.db' table.

*Table Privileges*

Table privileges apply to all columns in a given table. To assign
table-level privileges, use `ON DB_NAME.TBL_NAME' syntax:


     GRANT ALL ON mydb.mytbl TO 'someuser'@'somehost';
     GRANT SELECT, INSERT ON mydb.mytbl TO 'someuser'@'somehost';

If you specify TBL_NAME rather than DB_NAME.TBL_NAME, the statement
applies to TBL_NAME in the default database. An error occurs if there
is no default database.

The permissible PRIV_TYPE values at the table level are `ALTER',
`CREATE VIEW', `CREATE', `DELETE', `DROP', `GRANT OPTION', `INDEX',
`INSERT', `SELECT', `SHOW VIEW', `TRIGGER', and `UPDATE'.

MySQL stores table privileges in the `mysql.tables_priv' table.

*Column Privileges*

Column privileges apply to single columns in a given table. Each
privilege to be granted at the column level must be followed by the
column or columns, enclosed within parentheses.


     GRANT SELECT (col1), INSERT (col1,col2) ON mydb.mytbl TO 'someuser'@'somehost';

The permissible PRIV_TYPE values for a column (that is, when you use a
COLUMN_LIST clause) are `INSERT', `SELECT', and `UPDATE'.

MySQL stores column privileges in the `mysql.columns_priv' table.

*Stored Routine Privileges*

The `ALTER ROUTINE', `CREATE ROUTINE', `EXECUTE', and `GRANT OPTION'
privileges apply to stored routines (procedures and functions). They
can be granted at the global and database levels. Except for `CREATE
ROUTINE', these privileges can be granted at the routine level for
individual routines.


     GRANT CREATE ROUTINE ON mydb.* TO 'someuser'@'somehost';
     GRANT EXECUTE ON PROCEDURE mydb.myproc TO 'someuser'@'somehost';

The permissible PRIV_TYPE values at the routine level are `ALTER
ROUTINE', `EXECUTE', and `GRANT OPTION'.  `CREATE ROUTINE' is not a
routine-level privilege because you must have this privilege to create
a routine in the first place.

MySQL stores routine-level privileges in the `mysql.procs_priv' table.

For the global, database, table, and routine levels, *Note `GRANT ALL':
grant.  assigns only the privileges that exist at the level you are
granting. For example, `GRANT ALL ON DB_NAME.*' is a database-level
statement, so it does not grant any global-only privileges such as
`FILE'.

The OBJECT_TYPE clause, if present, should be specified as `TABLE',
`FUNCTION', or `PROCEDURE' when the following object is a table, a
stored function, or a stored procedure.

The privileges for a database, table, column, or routine are formed
additively as the logical `OR' of the privileges at each of the
privilege levels. For example, if a user has a global `SELECT'
privilege, the privilege cannot be denied by an absence of the
privilege at the database, table, or column level. Details of the
privilege-checking procedure are presented in *Note request-access::.

MySQL enables you to grant privileges on databases or tables that do
not exist. For tables, the privileges to be granted must include the
`CREATE' privilege.  _This behavior is by design_, and is intended to
enable the database administrator to prepare user accounts and
privileges for databases or tables that are to be created at a later
time.

*Important*:

_MySQL does not automatically revoke any privileges when you drop a
database or table_. However, if you drop a routine, any routine-level
privileges granted for that routine are revoked.

*Account Names and Passwords*

The USER value indicates the MySQL account to which the *Note `GRANT':
grant.  statement applies. To accommodate granting rights to users from
arbitrary hosts, MySQL supports specifying the USER value in the form
`USER_NAME@HOST_NAME'.  If a USER_NAME or HOST_NAME value is legal as an
unquoted identifier, you need not quote it. However, quotation marks
are necessary to specify a USER_NAME string containing special
characters (such as ``-''), or a HOST_NAME string containing special
characters or wildcard characters (such as ``%''); for example,
`'test-user'@'%.com''. Quote the user name and host name separately.

You can specify wildcards in the host name. For example,
`USER_NAME@'%.example.com'' applies to USER_NAME for any host in the
`example.com' domain, and `USER_NAME@'192.168.1.%'' applies to
USER_NAME for any host in the `192.168.1' class C subnet.

The simple form USER_NAME is a synonym for `USER_NAME@'%''.

_MySQL does not support wildcards in user names_. To refer to an
anonymous user, specify an account with an empty user name with the
*Note `GRANT': grant. statement:


     GRANT ALL ON test.* TO ''@'localhost' ...

In this case, any user who connects from the local host with the
correct password for the anonymous user will be permitted access, with
the privileges associated with the anonymous-user account.

For additional information about user name and host name values in
account names, see *Note account-names::.

To specify quoted values, quote database, table, column, and routine
names as identifiers. Quote user names and host names as identifiers or
as strings. Quote passwords as strings. For string-quoting and
identifier-quoting guidelines, see *Note string-literals::, and *Note
identifiers::.

The ``_'' and ``%'' wildcards are permitted when specifying database
names in *Note `GRANT': grant. statements that grant privileges at the
global or database levels. This means, for example, that if you want to
use a ``_'' character as part of a database name, you should specify it
as ``\_'' in the *Note `GRANT': grant. statement, to prevent the user
from being able to access additional databases matching the wildcard
pattern; for example, `GRANT ... ON `foo\_bar`.* TO ...'.

*Warning*:

If you permit anonymous users to connect to the MySQL server, you
should also grant privileges to all local users as
`USER_NAME@localhost'.  Otherwise, the anonymous user account for
`localhost' in the `mysql.user' table (created during MySQL
installation) is used when named users try to log in to the MySQL
server from the local machine. For details, see *Note
connection-access::.

To determine whether the preceding warning applies to you, execute the
following query, which lists any anonymous users:


     SELECT Host, User FROM mysql.user WHERE User='';

To avoid the problem just described, delete the local anonymous user
account using this statement:


     DROP USER ''@'localhost';

*Note `GRANT': grant. supports host names up to 60 characters long.
Database, table, column, and routine names can be up to 64 characters.
User names can be up to 16 characters.

*Warning*:

_The permissible length for user names cannot be changed by altering
the `mysql.user' table.  Attempting to do so results in unpredictable
behavior which may even make it impossible for users to log in to the
MySQL server_. You should never alter any of the tables in the `mysql'
database in any manner whatsoever except by means of the procedure
described in *Note mysql-upgrade::.

To indicate how the user should authenticate when connecting to the
server, the USER_SPECIFICATION clause may include `IDENTIFIED BY' to
specify a password. Syntax of the user specification is the same as for
the *Note `CREATE USER': create-user. statement. For details, see *Note
create-user::.

When `IDENTIFIED BY' is present and you have the global grant privilege
(`GRANT OPTION'), the password becomes the new password for the
account, even if the account exists and already has a password.
Without `IDENTIFIED BY', the account password remains unchanged.

If the `NO_AUTO_CREATE_USER' SQL mode is not enabled and the account
named in a *Note `GRANT': grant. statement does not exist in the
`mysql.user' table, *Note `GRANT': grant. creates it. If you specify no
`IDENTIFIED BY' clause or provide an empty password, the user has no
password. _This is very insecure._

If `NO_AUTO_CREATE_USER' is enabled and the account does not exist,
*Note `GRANT': grant. fails and does not create the account unless the
`IDENTIFIED BY' clause is given to provide a nonempty password.

*Important*:

*Note `GRANT': grant. may be recorded in server logs or on the client
side in a history file such as `~/.mysql_history', which means that
cleartext passwords may be read by anyone having read access to that
information. For information about password logging in the server logs,
see *Note password-logging::. For similar information about client-side
logging, see *Note mysql-logging::.

*Other Account Characteristics*

The `WITH' clause is used for several purposes:

   * To enable a user to grant privileges to other users

   * To specify resource limits for a user

   * To specify whether and how a user must use secure connections to
     the server

The `WITH GRANT OPTION' clause gives the user the ability to give to
other users any privileges the user has at the specified privilege
level. You should be careful to whom you give the `GRANT OPTION'
privilege because two users with different privileges may be able to
combine privileges!

You cannot grant another user a privilege which you yourself do not
have; the `GRANT OPTION' privilege enables you to assign only those
privileges which you yourself possess.

Be aware that when you grant a user the `GRANT OPTION' privilege at a
particular privilege level, any privileges the user possesses (or may
be given in the future) at that level can also be granted by that user
to other users. Suppose that you grant a user the `INSERT' privilege on
a database. If you then grant the `SELECT' privilege on the database
and specify `WITH GRANT OPTION', that user can give to other users not
only the `SELECT' privilege, but also `INSERT'. If you then grant the
`UPDATE' privilege to the user on the database, the user can grant
`INSERT', `SELECT', and `UPDATE'.

For a nonadministrative user, you should not grant the `ALTER'
privilege globally or for the `mysql' database. If you do that, the user
can try to subvert the privilege system by renaming tables!

For additional information about security risks associated with
particular privileges, see *Note privileges-provided::.

Several `WITH' clause options specify limits on use of server resources
by an account:

   * The `MAX_QUERIES_PER_HOUR COUNT', `MAX_UPDATES_PER_HOUR COUNT', and
     `MAX_CONNECTIONS_PER_HOUR COUNT' limits restrict the number of
     queries, updates, and connections to the server permitted to this
     account during any given one-hour period. (Queries for which
     results are served from the query cache do not count against the
     `MAX_QUERIES_PER_HOUR' limit.) If COUNT is `0' (the default), this
     means that there is no limitation for the account.

   * The `MAX_USER_CONNECTIONS COUNT' limit restricts the maximum
     number of simultaneous connections to the server by the account. A
     nonzero COUNT specifies the limit for the account explicitly. If
     COUNT is `0' (the default), the server determines the number of
     simultaneous connections for the account from the global value of
     the `max_user_connections' system variable. If
     `max_user_connections' is also zero, there is no limit for the
     account.

To specify resource limits for an existing user without affecting
existing privileges, use *Note `GRANT USAGE': grant. at the global
level (`ON *.*') and name the limits to be changed. For example:


     GRANT USAGE ON *.* TO ...
       WITH MAX_QUERIES_PER_HOUR 500 MAX_UPDATES_PER_HOUR 100;

Limits not specified retain their current values.

For more information on restricting access to server resources, see
*Note user-resources::.

MySQL can check X509 certificate attributes in addition to the usual
authentication that is based on the user name and password. To specify
SSL-related options for a MySQL account, use the `REQUIRE' clause of the
*Note `GRANT': grant. statement. (For background information on the use
of SSL with MySQL, see *Note ssl-connections::.)

There are a number of different possibilities for limiting connection
types for a given account:

   * `REQUIRE NONE' indicates that the account has no SSL or X509
     requirements. This is the default if no SSL-related `REQUIRE'
     options are specified. Unencrypted connections are permitted if
     the user name and password are valid. However, encrypted
     connections can also be used, at the client's option, if the
     client has the proper certificate and key files. That is, the
     client need not specify any SSL command options, in which case the
     connection will be unencrypted. To use an encrypted connection,
     the client must specify either the `--ssl-ca' option, or all three
     of the `--ssl-ca', `--ssl-key', and `--ssl-cert' options.

   * The `REQUIRE SSL' option tells the server to permit only
     SSL-encrypted connections for the account.


          GRANT ALL PRIVILEGES ON test.* TO 'root'@'localhost'
            IDENTIFIED BY 'goodsecret' REQUIRE SSL;

     To connect, the client must specify the `--ssl-ca' option to
     authenticate the server certificate, and may additionally specify
     the `--ssl-key' and `--ssl-cert' options. If neither `--ssl-ca'
     option nor `--ssl-capath' option is specified, the client does not
     authenticate the server certificate.

   * `REQUIRE X509' means that the client must have a valid certificate
     but that the exact certificate, issuer, and subject do not matter.
     The only requirement is that it should be possible to verify its
     signature with one of the CA certificates.


          GRANT ALL PRIVILEGES ON test.* TO 'root'@'localhost'
            IDENTIFIED BY 'goodsecret' REQUIRE X509;

     To connect, the client must specify the `--ssl-ca', `--ssl-key',
     and `--ssl-cert' options. This is also true for `ISSUER' and
     `SUBJECT' because those `REQUIRE' options imply `X509'.

   * `REQUIRE ISSUER 'ISSUER'' places the restriction on connection
     attempts that the client must present a valid X509 certificate
     issued by CA `'ISSUER''. If the client presents a certificate that
     is valid but has a different issuer, the server rejects the
     connection. Use of X509 certificates always implies encryption, so
     the `SSL' option is unnecessary in this case.


          GRANT ALL PRIVILEGES ON test.* TO 'root'@'localhost'
            IDENTIFIED BY 'goodsecret'
            REQUIRE ISSUER '/C=FI/ST=Some-State/L=Helsinki/
              O=MySQL Finland AB/CN=Tonu Samuel/emailAddress=tonu@example.com';

     The `'ISSUER'' value should be entered as a single string.

     *Note*:

     If MySQL is linked against a version of OpenSSL older than 0.9.6h,
     use `Email' rather than `emailAddress' in the `'ISSUER'' value.

   * `REQUIRE SUBJECT 'SUBJECT'' places the restriction on connection
     attempts that the client must present a valid X509 certificate
     containing the subject SUBJECT. If the client presents a
     certificate that is valid but has a different subject, the server
     rejects the connection.


          GRANT ALL PRIVILEGES ON test.* TO 'root'@'localhost'
            IDENTIFIED BY 'goodsecret'
            REQUIRE SUBJECT '/C=EE/ST=Some-State/L=Tallinn/
              O=MySQL demo client certificate/
              CN=Tonu Samuel/emailAddress=tonu@example.com';

     The `'SUBJECT'' value should be entered as a single string. MySQL
     does a simple string comparison of this value to the value in the
     certificate, so lettercase and component ordering must be given
     exactly as present in the certificate.

     *Note*:

     Regarding `emailAddress', see the note in the description of
     `REQUIRE ISSUER'.

   * `REQUIRE CIPHER 'CIPHER'' is needed to ensure that ciphers and key
     lengths of sufficient strength are used. SSL itself can be weak if
     old algorithms using short encryption keys are used. Using this
     option, you can ask that a specific cipher method is used for a
     connection.


          GRANT ALL PRIVILEGES ON test.* TO 'root'@'localhost'
            IDENTIFIED BY 'goodsecret'
            REQUIRE CIPHER 'EDH-RSA-DES-CBC3-SHA';

The `SUBJECT', `ISSUER', and `CIPHER' options can be combined in the
`REQUIRE' clause like this:


     GRANT ALL PRIVILEGES ON test.* TO 'root'@'localhost'
       IDENTIFIED BY 'goodsecret'
       REQUIRE SUBJECT '/C=EE/ST=Some-State/L=Tallinn/
         O=MySQL demo client certificate/
         CN=Tonu Samuel/emailAddress=tonu@example.com'
       AND ISSUER '/C=FI/ST=Some-State/L=Helsinki/
         O=MySQL Finland AB/CN=Tonu Samuel/emailAddress=tonu@example.com'
       AND CIPHER 'EDH-RSA-DES-CBC3-SHA';

The order of the options does not matter, but no option can be
specified twice. The `AND' keyword is optional between `REQUIRE'
options.

If you are using table, column, or routine privileges for even one
user, the server examines table, column, and routine privileges for all
users and this slows down MySQL a bit.  Similarly, if you limit the
number of queries, updates, or connections for any users, the server
must monitor these values.

*MySQL and Standard SQL Versions of GRANT*

The biggest differences between the MySQL and standard SQL versions of
*Note `GRANT': grant. are:

   * MySQL associates privileges with the combination of a host name
     and user name and not with only a user name.

   * Standard SQL does not have global or database-level privileges,
     nor does it support all the privilege types that MySQL supports.

   * MySQL does not support the standard SQL `UNDER' privilege.

   * Standard SQL privileges are structured in a hierarchical manner.
     If you remove a user, all privileges the user has been granted are
     revoked. This is also true in MySQL if you use *Note `DROP USER':
     drop-user. See *Note drop-user::.

   * In standard SQL, when you drop a table, all privileges for the
     table are revoked. In standard SQL, when you revoke a privilege,
     all privileges that were granted based on that privilege are also
     revoked. In MySQL, privileges can be dropped only with explicit
     *Note `DROP USER': drop-user. or *Note `REVOKE': revoke.
     statements or by manipulating the MySQL grant tables directly.

   * In MySQL, it is possible to have the `INSERT' privilege for only
     some of the columns in a table. In this case, you can still
     execute *Note `INSERT': insert. statements on the table, provided
     that you insert values only for those columns for which you have
     the `INSERT' privilege. The omitted columns are set to their
     implicit default values if strict SQL mode is not enabled. In
     strict mode, the statement is rejected if any of the omitted
     columns have no default value. (Standard SQL requires you to have
     the `INSERT' privilege on all columns.) *Note sql-mode::,
     discusses strict mode.  *Note data-type-defaults::, discusses
     implicit default values.


File: manual.info,  Node: rename-user,  Next: revoke,  Prev: grant,  Up: account-management-sql

13.7.1.4 RENAME USER Syntax
...........................


     RENAME USER OLD_USER TO NEW_USER
         [, OLD_USER TO NEW_USER] ...

The *Note `RENAME USER': rename-user. statement renames existing MySQL
accounts. An error occurs for old accounts that do not exist or new
accounts that already exist. To use this statement, you must have the
global `CREATE USER' privilege or the `UPDATE' privilege for the
`mysql' database.

Each account name uses the format described in *Note account-names::.
For example:


     RENAME USER 'jeffrey'@'localhost' TO 'jeff'@'127.0.0.1';

If you specify only the user name part of the account name, a host name
part of `'%'' is used.

*Note `RENAME USER': rename-user. causes the privileges held by the old
user to be those held by the new user. However, *Note `RENAME USER':
rename-user. does not automatically drop or invalidate databases or
objects within them that the old user created. This includes stored
programs or views for which the `DEFINER' attribute names the old user.
Attempts to access such objects may produce an error if they execute in
definer security context. (For information about security context, see
*Note stored-programs-security::.)

The privilege changes take effect as indicated in *Note
privilege-changes::.


File: manual.info,  Node: revoke,  Next: set-password,  Prev: rename-user,  Up: account-management-sql

13.7.1.5 REVOKE Syntax
......................


     REVOKE
         PRIV_TYPE [(COLUMN_LIST)]
           [, PRIV_TYPE [(COLUMN_LIST)]] ...
         ON [OBJECT_TYPE] PRIV_LEVEL
         FROM USER [, USER] ...

     REVOKE ALL PRIVILEGES, GRANT OPTION
         FROM USER [, USER] ...

The *Note `REVOKE': revoke. statement enables system administrators to
revoke privileges from MySQL accounts.  Each account name uses the
format described in *Note account-names::. For example:


     REVOKE INSERT ON *.* FROM 'jeffrey'@'localhost';

If you specify only the user name part of the account name, a host name
part of `'%'' is used.

For details on the levels at which privileges exist, the permissible
PRIV_TYPE and PRIV_LEVEL values, and the syntax for specifying users
and passwords, see *Note grant::

To use the first *Note `REVOKE': revoke. syntax, you must have the
`GRANT OPTION' privilege, and you must have the privileges that you are
revoking.

To revoke all privileges, use the second syntax, which drops all
global, database, table, column, and routine privileges for the named
user or users:


     REVOKE ALL PRIVILEGES, GRANT OPTION FROM USER [, USER] ...

To use this *Note `REVOKE': revoke. syntax, you must have the global
`CREATE USER' privilege or the `UPDATE' privilege for the `mysql'
database.

*Note `REVOKE': revoke. removes privileges, but does not drop
`mysql.user' table entries. To remove a user account entirely, use
*Note `DROP USER': drop-user. (see *Note drop-user::) or *Note
`DELETE': delete.

If the grant tables hold privilege rows that contain mixed-case
database or table names and the `lower_case_table_names' system
variable is set to a nonzero value, *Note `REVOKE': revoke. cannot be
used to revoke these privileges. It will be necessary to manipulate the
grant tables directly. (*Note `GRANT': grant. will not create such rows
when `lower_case_table_names' is set, but such rows might have been
created prior to setting the variable.)

When successfully executed from the *Note `mysql': mysql.  program,
*Note `REVOKE': revoke. responds with `Query OK, 0 rows affected'. To
determine what privileges result from the operation, use *Note `SHOW
GRANTS': show-grants. See *Note show-grants::.


File: manual.info,  Node: set-password,  Prev: revoke,  Up: account-management-sql

13.7.1.6 SET PASSWORD Syntax
............................


     SET PASSWORD [FOR USER] =
         {
             PASSWORD('CLEARTEXT PASSWORD')
           | OLD_PASSWORD('CLEARTEXT PASSWORD')
           | 'ENCRYPTED PASSWORD'
         }

The *Note `SET PASSWORD': set-password. statement assigns a password to
a MySQL user account:

   * With no `FOR USER' clause, this statement sets the password for
     the current user:


          SET PASSWORD = PASSWORD('CLEARTEXT PASSWORD');

     Any client who connects to the server using a nonanonymous account
     can change the password for that account. To see which account the
     server authenticated you for, invoke the `CURRENT_USER()' function:


          SELECT CURRENT_USER();

   * With a `FOR USER' clause, this statement sets the password for the
     named account, which must exist:


          SET PASSWORD FOR 'jeffrey'@'localhost' = PASSWORD('CLEARTEXT PASSWORD');

     In this case, you must have the *Note `UPDATE': update. privilege
     for the `mysql' database.

In MySQL 5.1 and later, when the `read_only' system variable is
enabled, *Note `SET PASSWORD': set-password. requires the `SUPER'
privilege, in addition to any other required privileges.

If a `FOR USER' clause is given, the account name uses the format
described in *Note account-names::. The USER value should be given as
`'USER_NAME'@'HOST_NAME'', where `'USER_NAME'' and `'HOST_NAME'' are
exactly as listed in the `User' and `Host' columns of the account's
`mysql.user' table row. (If you specify only a user name, a host name
of `'%'' is used.) For example, to set the password for an account with
`User' and `Host' column values of `'bob'' and `'%.example.org'', write
the statement like this:


     SET PASSWORD FOR 'bob'@'%.example.org' = PASSWORD('CLEARTEXT PASSWORD');

The password can be specified in these ways:

   * Using the `PASSWORD()' function

     The function argument is the cleartext (unencrypted) password.
     `PASSWORD()' hashes the password and returns the encrypted
     password string.

     The `old_passwords' system variable value determines the hashing
     method used by `PASSWORD()'. For descriptions of the permitted
     values, see *Note server-system-variables::.

   * Using the `OLD_PASSWORD()' function:

     The function argument is the cleartext (unencrypted) password.
     `OLD_PASSWORD()' hashes the password using pre-4.1 hashing and
     returns the encrypted password string.

   * Using an already encrypted password string

     The password is specified as a string literal. It must represent
     the already encrypted password value, in the hash format required
     by the authentication method used for the account.

For more information about setting passwords, see *Note
assigning-passwords::

*Important*:

*Note `SET PASSWORD': set-password. may be recorded in server logs or
on the client side in a history file such as `~/.mysql_history', which
means that cleartext passwords may be read by anyone having read access
to that information. For information about password logging in the
server logs, see *Note password-logging::. For similar information
about client-side logging, see *Note mysql-logging::.

*Caution*:

If you are connecting to a MySQL 4.1 or later server using a pre-4.1
client program, do not change your password without first reading *Note
password-hashing::. The default password hashing format changed in
MySQL 4.1, and if you change your password, it might be stored using a
hashing format that pre-4.1 clients cannot generate, thus preventing
you from connecting to the server afterward.

If you are using MySQL Replication, be aware that, currently, a
password used by a replication slave as part of a *Note `CHANGE MASTER
TO': change-master-to. statement is effectively limited to 32
characters in length; if the password is longer, any excess characters
are truncated. This is not due to any limit imposed by the MySQL Server
generally, but rather is an issue specific to MySQL Replication. (For
more information, see Bug #43439.)


File: manual.info,  Node: table-maintenance-sql,  Next: plugin-sql,  Prev: account-management-sql,  Up: sql-syntax-server-administration

13.7.2 Table Maintenance Statements
-----------------------------------

* Menu:

* analyze-table::                ANALYZE TABLE Syntax
* backup-table::                 BACKUP TABLE Syntax
* check-table::                  CHECK TABLE Syntax
* checksum-table::               CHECKSUM TABLE Syntax
* optimize-table::               OPTIMIZE TABLE Syntax
* repair-table::                 REPAIR TABLE Syntax
* restore-table::                RESTORE TABLE Syntax


File: manual.info,  Node: analyze-table,  Next: backup-table,  Prev: table-maintenance-sql,  Up: table-maintenance-sql

13.7.2.1 ANALYZE TABLE Syntax
.............................


     ANALYZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE
         TBL_NAME [, TBL_NAME] ...

`ANALYZE TABLE' analyzes and stores the key distribution for a table.
During the analysis, the table is locked with a read lock for `InnoDB'
and `MyISAM'. This statement works with `InnoDB', `NDB', and `MyISAM'
tables. For `MyISAM' tables, this statement is equivalent to using
*Note `myisamchk --analyze': myisamchk.

For more information on how the analysis works within `InnoDB', see
*Note innodb-restrictions::.

MySQL uses the stored key distribution to decide the order in which
tables should be joined when you perform a join on something other than
a constant. In addition, key distributions can be used when deciding
which indexes to use for a specific table within a query.

This statement requires `SELECT' and `INSERT' privileges for the table.

Beginning with MySQL 5.1.27, `ANALYZE TABLE' is also supported for
partitioned tables. Also beginning with MySQL 5.1.27, you can use
`ALTER TABLE ... ANALYZE PARTITION' to analyze one or more partitions;
for more information, see *Note alter-table::, and *Note
partitioning-maintenance::.

`ANALYZE TABLE' returns a result set with the following columns.

This table describes the columns of the *Note `ANALYZE TABLE':
analyze-table. result set.

Column      Value
`Table'     The table name
`Op'        Always `analyze'
`Msg_type'  `status', `error', `info', `note', or
            `warning'
`Msg_text'  An informational message

You can check the stored key distribution with the *Note `SHOW INDEX':
show-index. statement. See *Note show-index::.

If the table has not changed since the last `ANALYZE TABLE' statement,
the table is not analyzed again.

By default, the server writes *Note `ANALYZE TABLE': analyze-table.
statements to the binary log so that they replicate to replication
slaves. To suppress logging, specify the optional `NO_WRITE_TO_BINLOG'
keyword or its alias `LOCAL'.


File: manual.info,  Node: backup-table,  Next: check-table,  Prev: analyze-table,  Up: table-maintenance-sql

13.7.2.2 BACKUP TABLE Syntax
............................


     BACKUP TABLE TBL_NAME [, TBL_NAME] ... TO '/PATH/TO/BACKUP/DIRECTORY'

*Note*:

This statement is deprecated and is removed in MySQL 5.5. As an
alternative, *Note `mysqldump': mysqldump. or *Note `mysqlhotcopy':
mysqlhotcopy. can be used instead.

*Note `BACKUP TABLE': backup-table. copies to the backup directory the
minimum number of table files needed to restore the table, after
flushing any buffered changes to disk. The statement works only for
`MyISAM' tables. It copies the `.frm' definition and `.MYD' data files.
The `.MYI' index file can be rebuilt from those two files. The
directory should be specified as a full path name. To restore the
table, use *Note `RESTORE TABLE': restore-table.

During the backup, a read lock is held for each table, one at time, as
they are being backed up. If you want to back up several tables as a
snapshot (preventing any of them from being changed during the backup
operation), issue a *Note `LOCK TABLES': lock-tables. statement first,
to obtain a read lock for all tables in the group.

*Note `BACKUP TABLE': backup-table. returns a result set with the
following columns.

This table describes the columns of the *Note `BACKUP TABLE':
backup-table. result set.

Column      Value
`Table'     The table name
`Op'        Always `backup'
`Msg_type'  `status', `error', `info', `note', or
            `warning'
`Msg_text'  An informational message


File: manual.info,  Node: check-table,  Next: checksum-table,  Prev: backup-table,  Up: table-maintenance-sql

13.7.2.3 CHECK TABLE Syntax
...........................


     CHECK TABLE TBL_NAME [, TBL_NAME] ... [OPTION] ...

     OPTION = {FOR UPGRADE | QUICK | FAST | MEDIUM | EXTENDED | CHANGED}

*Note `CHECK TABLE': check-table. checks a table or tables for errors.
*Note `CHECK TABLE': check-table.  works for *Note `InnoDB':
innodb-storage-engine, *Note `MyISAM': myisam-storage-engine, and *Note
`ARCHIVE': archive-storage-engine. tables. Starting with MySQL 5.1.9,
*Note `CHECK TABLE': check-table. is also valid for *Note `CSV':
csv-storage-engine. tables, see *Note csv-storage-engine::. For
`MyISAM' tables, the key statistics are updated as well.

*Note `CHECK TABLE': check-table. can also check views for problems,
such as tables that are referenced in the view definition that no
longer exist.

Beginning with MySQL 5.1.27, *Note `CHECK TABLE': check-table. is also
supported for partitioned tables. Also beginning with MySQL 5.1.27, you
can use `ALTER TABLE ... CHECK PARTITION' to check one or more
partitions; for more information, see *Note alter-table::, and *Note
partitioning-maintenance::.

*Output*

*Note `CHECK TABLE': check-table. returns a result set with the
following columns.

This table describes the columns of the *Note `CHECK TABLE':
check-table. result set.

Column      Value
`Table'     The table name
`Op'        Always `check'
`Msg_type'  `status', `error', `info', `note', or
            `warning'
`Msg_text'  An informational message

Note that the statement might produce many rows of information for each
checked table. The last row has a `Msg_type' value of `status' and the
`Msg_text' normally should be `OK'. If you don't get `OK', or `Table is
already up to date' you should normally run a repair of the table. See
*Note myisam-table-maintenance::. `Table is already up to date' means
that the storage engine for the table indicated that there was no need
to check the table.

*Checking Version Compatibility*

The `FOR UPGRADE' option checks whether the named tables are compatible
with the current version of MySQL.  This option was added in MySQL
5.1.7. With `FOR UPGRADE', the server checks each table to determine
whether there have been any incompatible changes in any of the table's
data types or indexes since the table was created. If not, the check
succeeds. Otherwise, if there is a possible incompatibility, the server
runs a full check on the table (which might take some time). If the
full check succeeds, the server marks the table's `.frm' file with the
current MySQL version number. Marking the `.frm' file ensures that
further checks for the table with the same version of the server will
be fast.

Incompatibilities might occur because the storage format for a data
type has changed or because its sort order has changed. Our aim is to
avoid these changes, but occasionally they are necessary to correct
problems that would be worse than an incompatibility between releases.

Currently, `FOR UPGRADE' discovers these incompatibilities:

   * The indexing order for end-space in *Note `TEXT': blob. columns for
     `InnoDB' and `MyISAM' tables changed between MySQL 4.1 and 5.0.

   * The storage method of the new *Note `DECIMAL': fixed-point-types.
     data type changed between MySQL 5.0.3 and 5.0.5.

   * As of MySQL 5.1.25, if your table was created by a different
     version of the MySQL server than the one you are currently
     running, `FOR UPGRADE' indicates that the table has an `.frm' file
     with an incompatible version. In this case, the result set returned
     by *Note `CHECK TABLE': check-table. contains a line with a
     `Msg_type' value of `error' and a `Msg_text' value of `Table
     upgrade required. Please do "REPAIR TABLE `TBL_NAME`" to fix it!'

   * Changes are sometimes made to character sets or collations that
     require table indexes to be rebuilt. For details about these
     changes and when `FOR UPGRADE' detects them, see *Note
     checking-table-incompatibilities::.

*Checking Data Consistency*

The other check options that can be given are shown in the following
table. These options are passed to the storage engine, which may use
them or not.

This table describes other *Note `CHECK TABLE': check-table. options.

Type        Meaning
`QUICK'     Do not scan the rows to check for incorrect links. Applies to
            `InnoDB' and `MyISAM' tables and views.
`FAST'      Check only tables that have not been closed properly.
            Applies only to `MyISAM' tables and views; ignored for
            `InnoDB'.
`CHANGED'   Check only tables that have been changed since the last
            check or that have not been closed properly. Applies only to
            `MyISAM' tables and views; ignored for `InnoDB'.
`MEDIUM'    Scan rows to verify that deleted links are valid. This also
            calculates a key checksum for the rows and verifies this
            with a calculated checksum for the keys. Applies only to
            `MyISAM' tables and views; ignored for `InnoDB'.
`EXTENDED'  Do a full key lookup for all keys for each row. This ensures
            that the table is 100% consistent, but takes a long time.
            Applies only to `MyISAM' tables and views; ignored for
            `InnoDB'.

If none of the options `QUICK', `MEDIUM', or `EXTENDED' are specified,
the default check type for dynamic-format `MyISAM' tables is `MEDIUM'.
This has the same result as running *Note `myisamchk --medium-check
TBL_NAME': myisamchk. on the table. The default check type also is
`MEDIUM' for static-format `MyISAM' tables, unless `CHANGED' or `FAST'
is specified. In that case, the default is `QUICK'. The row scan is
skipped for `CHANGED' and `FAST' because the rows are very seldom
corrupted.

You can combine check options, as in the following example that does a
quick check on the table to determine whether it was closed properly:


     CHECK TABLE test_table FAST QUICK;

*Note*:

In some cases, *Note `CHECK TABLE': check-table.  changes the table.
This happens if the table is marked as `corrupted' or `not closed
properly' but *Note `CHECK TABLE': check-table. does not find any
problems in the table. In this case, *Note `CHECK TABLE': check-table.
marks the table as okay.

If a table is corrupted, it is most likely that the problem is in the
indexes and not in the data part. All of the preceding check types
check the indexes thoroughly and should thus find most errors.

If you just want to check a table that you assume is okay, you should
use no check options or the `QUICK' option. The latter should be used
when you are in a hurry and can take the very small risk that `QUICK'
does not find an error in the data file. (In most cases, under normal
usage, MySQL should find any error in the data file. If this happens,
the table is marked as `corrupted' and cannot be used until it is
repaired.)

`FAST' and `CHANGED' are mostly intended to be used from a script (for
example, to be executed from `cron') if you want to check tables from
time to time. In most cases, `FAST' is to be preferred over `CHANGED'.
(The only case when it is not preferred is when you suspect that you
have found a bug in the `MyISAM' code.)

`EXTENDED' is to be used only after you have run a normal check but
still get strange errors from a table when MySQL tries to update a row
or find a row by key. This is very unlikely if a normal check has
succeeded.

Use of *Note `CHECK TABLE ... EXTENDED': check-table. might influence
the execution plan generated by the query optimizer.

Some problems reported by *Note `CHECK TABLE': check-table. cannot be
corrected automatically:

   * `Found row where the auto_increment column has the value 0'.

     This means that you have a row in the table where the
     `AUTO_INCREMENT' index column contains the value 0. (It is
     possible to create a row where the `AUTO_INCREMENT' column is 0 by
     explicitly setting the column to 0 with an *Note `UPDATE': update.
     statement.)

     This is not an error in itself, but could cause trouble if you
     decide to dump the table and restore it or do an *Note `ALTER
     TABLE': alter-table. on the table. In this case, the
     `AUTO_INCREMENT' column changes value according to the rules of
     `AUTO_INCREMENT' columns, which could cause problems such as a
     duplicate-key error.

     To get rid of the warning, simply execute an *Note `UPDATE':
     update. statement to set the column to some value other than 0.

*InnoDB Tables*

The following notes apply to *Note `InnoDB': innodb-storage-engine.
tables:

   * If *Note `CHECK TABLE': check-table. finds a problem for an
     `InnoDB' table, the server may shut down to prevent error
     propagation. Details of the error will be written to the error log.

   * If *Note `CHECK TABLE': check-table. encounters corruptions or
     errors in `InnoDB' tables or indexes, it reports an error. It does
     not shut down the server. Starting with MySQL 5.5, *Note `CHECK
     TABLE': check-table. usually marks the index and sometimes marks
     the table as corrupted, preventing further use of the index or
     table.

   * If *Note `CHECK TABLE': check-table. finds the wrong number of
     entries in a secondary index, it will report an error but will not
     shut down the server or prevent access to the file.

   * *Note `CHECK TABLE': check-table. surveys the index page
     structure, then surveys each key entry. It does not validate the
     key pointer to a clustered record or follow the path for *Note
     `BLOB': blob. pointers.

   * When an `InnoDB' table is stored in its own .ibd file
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_ibd_file)
     in file-per-table
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_file_per_table)
     mode, the first 3 pages
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_page) of
     the `.ibd' contain header information rather than table or index
     data. The `CHECK TABLE' statement does not detect inconsistencies
     that only affect the header data. To verify the entire contents of
     an `InnoDB' `.ibd' file, use the *Note `innochecksum':
     innochecksum. command.

   * When running `CHECK TABLE' on large `InnoDB' tables, other threads
     may be blocked during `CHECK TABLE' execution. To avoid timeouts,
     the semaphore wait threshold (600 seconds) is extended by 2 hours
     (7200 seconds) for `CHECK TABLE' operations. If `InnoDB' detects
     semaphore waits of 240 seconds or more it starts printing `InnoDB'
     monitor output to the error log. If a lock request extends beyond
     the semaphore wait threshold, `InnoDB' will abort the process. To
     avoid the possibility of a semaphore wait timeout entirely, you
     can run `CHECK TABLE QUICK' instead of `CHECK TABLE'.


File: manual.info,  Node: checksum-table,  Next: optimize-table,  Prev: check-table,  Up: table-maintenance-sql

13.7.2.4 CHECKSUM TABLE Syntax
..............................


     CHECKSUM TABLE TBL_NAME [, TBL_NAME] ... [ QUICK | EXTENDED ]

*Note `CHECKSUM TABLE': checksum-table. reports a table checksum.

With `QUICK', the live table checksum is reported if it is available,
or `NULL' otherwise. This is very fast. A live checksum is enabled by
specifying the `CHECKSUM=1' table option when you create the table;
currently, this is supported only for `MyISAM' tables. See *Note
create-table::.

With `EXTENDED', the entire table is read row by row and the checksum
is calculated. This can be very slow for large tables.

If neither `QUICK' nor `EXTENDED' is specified, MySQL returns a live
checksum if the table storage engine supports it and scans the table
otherwise.

For a nonexistent table, *Note `CHECKSUM TABLE': checksum-table.
returns `NULL' and generates a warning.

In MySQL 5.1, *Note `CHECKSUM TABLE': checksum-table. returns 0 for
partitioned tables unless you include the `EXTENDED' option. This issue
is resolved in MySQL 5.6. (Bug #11933226, Bug #60681)

The checksum value depends on the table row format. If the row format
changes, the checksum also changes. For example, the storage format for
*Note `VARCHAR': char.  changed between MySQL 4.1 and 5.0, so if a 4.1
table is upgraded to MySQL 5.0, the checksum value may change.

*Important*:

If the checksums for two tables are different, then it is almost
certain that the tables are different in some way.  However, because
the hashing function used by *Note `CHECKSUM TABLE': checksum-table. is
not guaranteed to be collision-free, there is a slight chance that two
tables which are not identical can produce the same checksum.


File: manual.info,  Node: optimize-table,  Next: repair-table,  Prev: checksum-table,  Up: table-maintenance-sql

13.7.2.5 OPTIMIZE TABLE Syntax
..............................


     OPTIMIZE [NO_WRITE_TO_BINLOG | LOCAL] TABLE
         TBL_NAME [, TBL_NAME] ...

Reorganizes the physical storage of table data and associated index
data, to reduce storage space and improve I/O efficiency when accessing
the table. The exact changes made to each table depend on the storage
engine
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_storage_engine)
used by that table.

Use *Note `OPTIMIZE TABLE': optimize-table. in these cases, depending
on the type of table:

   * After doing substantial insert, update, or delete operations on an
     `InnoDB' table that has its own .ibd file
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_ibd_file)
     because it was created with the `innodb_file_per_table' option
     enabled. The table and indexes are reorganized, and disk space can
     be reclaimed for use by the operating system.

   * After deleting a large part of a `MyISAM' or `ARCHIVE' table, or
     making many changes to a `MyISAM' or `ARCHIVE 'table with
     variable-length rows (tables that have *Note `VARCHAR': char,
     *Note `VARBINARY': binary-varbinary, *Note `BLOB': blob, or *Note
     `TEXT': blob. columns). Deleted rows are maintained in a linked
     list and subsequent *Note `INSERT': insert. operations reuse old
     row positions. You can use *Note `OPTIMIZE TABLE': optimize-table.
     to reclaim the unused space and to defragment the data file. After
     extensive changes to a table, this statement may also improve
     performance of statements that use the table, sometimes
     significantly.

This statement requires `SELECT' and `INSERT' privileges for the table.

Beginning with MySQL 5.1.27, *Note `OPTIMIZE TABLE': optimize-table. is
also supported for partitioned tables. For information about using this
statement with partitioned tables and table partitions, see *Note
partitioning-maintenance::.

*Note `OPTIMIZE TABLE': optimize-table. works for *Note `MyISAM':
myisam-storage-engine, *Note `InnoDB': innodb-storage-engine, and *Note
`ARCHIVE': archive-storage-engine. tables. Beginning with MySQL Cluster
NDB 6.3.7, *Note `OPTIMIZE TABLE': optimize-table. is also supported
for dynamic columns of in-memory *Note `NDB': mysql-cluster. tables. It
does not work for Disk Data tables. The performance of `OPTIMIZE' on
Cluster tables can be tuned by adjusting the value of the
`ndb_optimization_delay' system variable, which controls the number of
milliseconds to wait between processing batches of rows by *Note
`OPTIMIZE TABLE': optimize-table. For more information, see *Note
mysql-cluster-limitations-resolved::.

Beginning with MySQL Cluster NDB 6.3.8, *Note `OPTIMIZE TABLE':
optimize-table. can be interrupted by (for example) killing the SQL
thread performing the `OPTIMIZE' operation.

By default, *Note `OPTIMIZE TABLE': optimize-table. does _not_ work for
tables created using any other storage engine and returns a result
indicating this lack of support. You can make *Note `OPTIMIZE TABLE':
optimize-table. work for other storage engines by starting *Note
`mysqld': mysqld. with the `--skip-new' option. In this case, *Note
`OPTIMIZE TABLE': optimize-table. is just mapped to *Note `ALTER
TABLE': alter-table.

For `MyISAM' tables, *Note `OPTIMIZE TABLE': optimize-table. works as
follows:

  1. If the table has deleted or split rows, repair the table.

  2. If the index pages are not sorted, sort them.

  3. If the table's statistics are not up to date (and the repair could
     not be accomplished by sorting the index), update them.

For `InnoDB' tables, *Note `OPTIMIZE TABLE': optimize-table. is mapped
to *Note `ALTER TABLE': alter-table, which rebuilds the table to update
index statistics and free unused space in the clustered index.
Beginning with MySQL 5.1.27, this is displayed in the output of *Note
`OPTIMIZE TABLE': optimize-table.  when you run it on an `InnoDB'
table, as shown here:


     mysql> OPTIMIZE TABLE foo;
     +----------+----------+----------+-------------------------------------------------------------------+
     | Table    | Op       | Msg_type | Msg_text                                                          |
     +----------+----------+----------+-------------------------------------------------------------------+
     | test.foo | optimize | note     | Table does not support optimize, doing recreate + analyze instead |
     | test.foo | optimize | status   | OK                                                                |
     +----------+----------+----------+-------------------------------------------------------------------+

You can make *Note `OPTIMIZE TABLE': optimize-table. work on other
storage engines by starting *Note `mysqld': mysqld.  `--skip-new'
option. In this case, *Note `OPTIMIZE TABLE': optimize-table. is just
mapped to *Note `ALTER TABLE': alter-table.

*Note `OPTIMIZE TABLE': optimize-table. returns a result set with the
following columns.

This table describes columns of the *Note `OPTIMIZE TABLE':
optimize-table. result set.

Column      Value
`Table'     The table name
`Op'        Always `optimize'
`Msg_type'  `status', `error', `info', `note', or
            `warning'
`Msg_text'  An informational message

Note that MySQL locks the table during the time *Note `OPTIMIZE TABLE':
optimize-table. is running.

By default, the server writes *Note `OPTIMIZE TABLE': optimize-table.
statements to the binary log so that they replicate to replication
slaves. To suppress logging, specify the optional `NO_WRITE_TO_BINLOG'
keyword or its alias `LOCAL'.

*Note `OPTIMIZE TABLE': optimize-table. does not sort R-tree indexes,
such as spatial indexes on `POINT' columns. (Bug #23578)

As of MySQL 5.1.50, *Note `OPTIMIZE TABLE': optimize-table. table
catches and throws any errors that occur while copying table statistics
from the old file to the newly created file. For example. if the user
ID of the owner of the `.frm', `.MYD', or `.MYI' file is different from
the user ID of the *Note `mysqld': mysqld. process, *Note `OPTIMIZE
TABLE': optimize-table. generates a "cannot change ownership of the
file" error unless *Note `mysqld': mysqld. is started by the `root'
user.


File: manual.info,  Node: repair-table,  Next: restore-table,  Prev: optimize-table,  Up: table-maintenance-sql

13.7.2.6 REPAIR TABLE Syntax
............................


     REPAIR [NO_WRITE_TO_BINLOG | LOCAL] TABLE
         TBL_NAME [, TBL_NAME] ...
         [QUICK] [EXTENDED] [USE_FRM]

*Note `REPAIR TABLE': repair-table. repairs a possibly corrupted table.
By default, it has the same effect as *Note `myisamchk --recover
TBL_NAME': myisamchk.  *Note `REPAIR TABLE': repair-table. works for
`MyISAM' and for `ARCHIVE' tables. Starting with MySQL 5.1.9, `REPAIR'
is also valid for `CSV' tables. See *Note myisam-storage-engine::, and
*Note archive-storage-engine::, and *Note csv-storage-engine::

This statement requires `SELECT' and `INSERT' privileges for the table.

Beginning with MySQL 5.1.27, *Note `REPAIR TABLE': repair-table. is
also supported for partitioned tables.  However, the `USE_FRM' option
cannot be used with this statement on a partitioned table.

Also beginning with MySQL 5.1.27, you can use `ALTER TABLE ... REPAIR
PARTITION' to repair one or more partitions; for more information, see
*Note alter-table::, and *Note partitioning-maintenance::.

Normally, you should never have to run *Note `REPAIR TABLE':
repair-table. However, if disaster strikes, this statement is very
likely to get back all your data from a `MyISAM' table. If your tables
become corrupted often, you should try to find the reason for it, to
eliminate the need to use *Note `REPAIR TABLE': repair-table. See *Note
crashing::, and *Note myisam-table-problems::.

*Caution*:

It is best to make a backup of a table before performing a table repair
operation; under some circumstances the operation might cause data
loss. Possible causes include but are not limited to file system
errors. See *Note backup-and-recovery::.

*Warning*:

If the server crashes during a *Note `REPAIR TABLE': repair-table.
operation, it is essential after restarting it that you immediately
execute another *Note `REPAIR TABLE': repair-table. statement for the
table before performing any other operations on it. In the worst case,
you might have a new clean index file without information about the
data file, and then the next operation you perform could overwrite the
data file. This is an unlikely but possible scenario that underscores
the value of making a backup first.

*Note `REPAIR TABLE': repair-table. returns a result set with the
following columns.

This table describes columns of the *Note `REPAIR TABLE': repair-table.
result set.

Column      Value
`Table'     The table name
`Op'        Always `repair'
`Msg_type'  `status', `error', `info', `note', or
            `warning'
`Msg_text'  An informational message

The *Note `REPAIR TABLE': repair-table. statement might produce many
rows of information for each repaired table. The last row has a
`Msg_type' value of `status' and `Msg_test' normally should be `OK'. If
you do not get `OK' for a `MyISAM' table, you should try repairing it
with *Note `myisamchk --safe-recover': myisamchk. (*Note `REPAIR
TABLE': repair-table. does not implement all the options of *Note
`myisamchk': myisamchk.) With *Note `myisamchk --safe-recover':
myisamchk, you can also use options that *Note `REPAIR TABLE':
repair-table. does not support, such as `--max-record-length'.

If you use the `QUICK' option, *Note `REPAIR TABLE': repair-table.
tries to repair only the index file, and not the data file. This type
of repair is like that done by *Note `myisamchk --recover --quick':
myisamchk.

If you use the `EXTENDED' option, MySQL creates the index row by row
instead of creating one index at a time with sorting. This type of
repair is like that done by *Note `myisamchk --safe-recover': myisamchk.

The `USE_FRM' option is available for use if the `.MYI' index file is
missing or if its header is corrupted. This option tells MySQL not to
trust the information in the `.MYI' file header and to re-create it
using information from the `.frm' file. This kind of repair cannot be
done with *Note `myisamchk': myisamchk.

*Note*:

Use the `USE_FRM' option _only_ if you cannot use regular `REPAIR'
modes! Telling the server to ignore the `.MYI' file makes important
table metadata stored in the `.MYI' unavailable to the repair process,
which can have deleterious consequences:

   * The current `AUTO_INCREMENT' value is lost.

   * The link to deleted records in the table is lost, which means that
     free space for deleted records will remain unoccupied thereafter.

   * The `.MYI' header indicates whether the table is compressed. If
     the server ignores this information, it cannot tell that a table
     is compressed and repair can cause change or loss of table
     contents. This means that `USE_FRM' should not be used with
     compressed tables. That should not be necessary, anyway:
     Compressed tables are read only, so they should not become corrupt.

*Caution*:

As of MySQL 5.1.25, if you use `USE_FRM' for a table that was created
by a different version of the MySQL server than the one you are
currently running, *Note `REPAIR TABLE': repair-table. will not attempt
to repair the table. In this case, the result set returned by *Note
`REPAIR TABLE': repair-table. contains a line with a `Msg_type' value of
`error' and a `Msg_text' value of `Failed repairing incompatible .FRM
file'.

Prior to MySQL 5.1.25, _do not use_ `USE_FRM' if your table was created
by a different version of the MySQL server. Doing so risks the loss of
all rows in the table. It is particularly dangerous to use `USE_FRM'
after the server returns this message:


     Table upgrade required. Please do
     "REPAIR TABLE `TBL_NAME`"
     or dump/reload to fix it!

If `USE_FRM' is _not_ used, *Note `REPAIR TABLE': repair-table. checks
the table to see whether an upgrade is required. If so, it performs the
upgrade, following the same rules as *Note `CHECK TABLE ... FOR
UPGRADE': check-table. See *Note check-table::, for more information.
As of MySQL 5.1.25, *Note `REPAIR TABLE': repair-table. without
`USE_FRM' upgrades the `.frm' file to the current version.

By default, the server writes *Note `REPAIR TABLE': repair-table.
statements to the binary log so that they replicate to replication
slaves. To suppress logging, specify the optional `NO_WRITE_TO_BINLOG'
keyword or its alias `LOCAL'.

*Important*:

In the event that a table on the master becomes corrupted and you run
*Note `REPAIR TABLE': repair-table. on it, any resulting changes to the
original table are _not_ propagated to slaves.

You may be able to increase *Note `REPAIR TABLE': repair-table.
performance by setting certain system variables.  See *Note
repair-table-speed::.

As of MySQL 5.1.50, *Note `REPAIR TABLE': repair-table.  table catches
and throws any errors that occur while copying table statistics from
the old corrupted file to the newly created file. For example. if the
user ID of the owner of the `.frm', `.MYD', or `.MYI' file is different
from the user ID of the *Note `mysqld': mysqld. process, *Note `REPAIR
TABLE': repair-table. generates a "cannot change ownership of the file"
error unless *Note `mysqld': mysqld. is started by the `root' user.


File: manual.info,  Node: restore-table,  Prev: repair-table,  Up: table-maintenance-sql

13.7.2.7 RESTORE TABLE Syntax
.............................


     RESTORE TABLE TBL_NAME [, TBL_NAME] ... FROM '/PATH/TO/BACKUP/DIRECTORY'

*Note*:

This statement is deprecated and is removed in MySQL 5.5.

*Note `RESTORE TABLE': restore-table. restores the table or tables from
a backup that was made with *Note `BACKUP TABLE': backup-table. The
directory should be specified as a full path name.

Existing tables are not overwritten; if you try to restore over an
existing table, an error occurs. Just as for *Note `BACKUP TABLE':
backup-table, *Note `RESTORE TABLE': restore-table. currently works
only for `MyISAM' tables. Restored tables are not replicated from
master to slave.

The backup for each table consists of its `.frm' format file and `.MYD'
data file. The restore operation restores those files, and then uses
them to rebuild the `.MYI' index file. Restoring takes longer than
backing up due to the need to rebuild the indexes. The more indexes the
table has, the longer it takes.

*Note `RESTORE TABLE': restore-table. returns a result set with the
following columns.

This table describes columns of the *Note `RESTORE TABLE':
restore-table. result set.

Column      Value
`Table'     The table name
`Op'        Always `restore'
`Msg_type'  `status', `error', `info', `note', or
            `warning'
`Msg_text'  An informational message


File: manual.info,  Node: plugin-sql,  Next: set-statement,  Prev: table-maintenance-sql,  Up: sql-syntax-server-administration

13.7.3 Plugin and User-Defined Function Statements
--------------------------------------------------

* Menu:

* create-function-udf::          CREATE FUNCTION Syntax for User-Defined Functions
* drop-function-udf::            DROP FUNCTION Syntax
* install-plugin::               INSTALL PLUGIN Syntax
* uninstall-plugin::             UNINSTALL PLUGIN Syntax


File: manual.info,  Node: create-function-udf,  Next: drop-function-udf,  Prev: plugin-sql,  Up: plugin-sql

13.7.3.1 CREATE FUNCTION Syntax for User-Defined Functions
..........................................................


     CREATE [AGGREGATE] FUNCTION FUNCTION_NAME RETURNS {STRING|INTEGER|REAL|DECIMAL}
         SONAME SHARED_LIBRARY_NAME

A user-defined function (UDF) is a way to extend MySQL with a new
function that works like a native (built-in) MySQL function such as
`ABS()' or `CONCAT()'.

FUNCTION_NAME is the name that should be used in SQL statements to
invoke the function. The `RETURNS' clause indicates the type of the
function's return value. *Note `DECIMAL': fixed-point-types.  is a
legal value after `RETURNS', but currently *Note `DECIMAL':
fixed-point-types. functions return string values and should be written
like `STRING' functions.

SHARED_LIBRARY_NAME is the basename of the shared object file that
contains the code that implements the function. The file must be
located in the plugin directory.  This directory is given by the value
of the `plugin_dir' system variable.

*Note*:

This is a change in MySQL 5.1. For earlier versions of MySQL, the
shared object can be located in any directory that is searched by your
system's dynamic linker. For more information, see *Note
udf-compiling::.

To create a function, you must have the `INSERT' privilege for the
`mysql' database. This is necessary because *Note `CREATE FUNCTION':
create-function. adds a row to the `mysql.func' system table that
records the function's name, type, and shared library name. If you do
not have this table, you should run the *Note `mysql_upgrade':
mysql-upgrade. command to create it. See *Note mysql-upgrade::.

An active function is one that has been loaded with *Note `CREATE
FUNCTION': create-function. and not removed with *Note `DROP FUNCTION':
drop-function. All active functions are reloaded each time the server
starts, unless you start *Note `mysqld': mysqld. with the
`--skip-grant-tables' option. In this case, UDF initialization is
skipped and UDFs are unavailable.

For instructions on writing user-defined functions, see *Note
adding-udf::. For the UDF mechanism to work, functions must be written
in C or C++ (or another language that can use C calling conventions),
your operating system must support dynamic loading and you must have
compiled *Note `mysqld': mysqld. dynamically (not statically).

An `AGGREGATE' function works exactly like a native MySQL aggregate
(summary) function such as `SUM' or `COUNT()'. For `AGGREGATE' to work,
your `mysql.func' table must contain a `type' column. If your
`mysql.func' table does not have this column, you should run the *Note
`mysql_upgrade': mysql-upgrade. program to create it (see *Note
mysql-upgrade::).

*Note*:

To upgrade the shared library associated with a UDF, issue a *Note
`DROP FUNCTION': drop-function. statement, upgrade the shared library,
and then issue a *Note `CREATE FUNCTION': create-function. statement. If
you upgrade the shared library first and then use *Note `DROP
FUNCTION': drop-function, the server may crash.


File: manual.info,  Node: drop-function-udf,  Next: install-plugin,  Prev: create-function-udf,  Up: plugin-sql

13.7.3.2 DROP FUNCTION Syntax
.............................


     DROP FUNCTION FUNCTION_NAME

This statement drops the user-defined function (UDF) named
FUNCTION_NAME.

To drop a function, you must have the `DELETE' privilege for the
`mysql' database. This is because *Note `DROP FUNCTION': drop-function.
removes a row from the `mysql.func' system table that records the
function's name, type, and shared library name.

*Note*:

To upgrade the shared library associated with a UDF, issue a *Note
`DROP FUNCTION': drop-function. statement, upgrade the shared library,
and then issue a *Note `CREATE FUNCTION': create-function. statement. If
you upgrade the shared library first and then use *Note `DROP
FUNCTION': drop-function, the server may crash.

*Note `DROP FUNCTION': drop-function. is also used to drop stored
functions (see *Note drop-procedure::).


File: manual.info,  Node: install-plugin,  Next: uninstall-plugin,  Prev: drop-function-udf,  Up: plugin-sql

13.7.3.3 INSTALL PLUGIN Syntax
..............................


     INSTALL PLUGIN PLUGIN_NAME SONAME 'SHARED_LIBRARY_NAME'

This statement installs a server plugin. It requires the `INSERT'
privilege for the `mysql.plugin' table.

PLUGIN_NAME is the name of the plugin as defined in the plugin
descriptor structure contained in the library file (see *Note
plugin-data-structures::).  Plugin names are not case sensitive. For
maximal compatibility, plugin names should be limited to ASCII letters,
digits, and underscore because they are used in C source files, shell
command lines, M4 and Bourne shell scripts, and SQL environments.

SHARED_LIBRARY_NAME is the name of the shared library that contains the
plugin code. The name includes the file name extension (for example,
`libmyplugin.so', `libmyplugin.dll', or `libmyplugin.dylib').

The shared library must be located in the plugin directory (the
directory named by the `plugin_dir' system variable).  The library must
be in the plugin directory itself, not in a subdirectory. By default,
`plugin_dir' is the `plugin' directory under the directory named by the
`pkglibdir' configuration variable, but it can be changed by setting
the value of `plugin_dir' at server startup.  For example, set its
value in a `my.cnf' file:


     [mysqld]
     plugin_dir=/PATH/TO/PLUGIN/DIRECTORY

If the value of `plugin_dir' is a relative path name, it is taken to be
relative to the MySQL base directory (the value of the `basedir' system
variable).

*Note `INSTALL PLUGIN': install-plugin. loads and initializes the
plugin code to make the plugin available for use. A plugin is
initialized by executing its initialization function, which handles any
setup that the plugin must perform before it can be used. When the
server shuts down, it executes the deinitialization function for each
plugin that is loaded so that the plugin has a change to perform any
final cleanup.

*Note `INSTALL PLUGIN': install-plugin. also registers the plugin by
adding a line that indicates the plugin name and library file name to
the `mysql.plugin' table.  At server startup, the server loads and
initializes any plugin that is listed in the `mysql.plugin' table.
This means that a plugin is installed with *Note `INSTALL PLUGIN':
install-plugin. only once, not every time the server starts. Plugin
loading at startup does not occur if the server is started with the
`--skip-grant-tables' option.

A plugin library can contain multiple plugins. For each of them to be
installed, use a separate *Note `INSTALL PLUGIN': install-plugin.
statement. Each statement names a different plugin, but all of them
specify the same library name.

As of MySQL 5.1.33, *Note `INSTALL PLUGIN': install-plugin. causes the
server to read option (`my.cnf') files just as during server startup.
This enables the plugin to pick up any relevant options from those
files. It is possible to add plugin options to an option file even
before loading a plugin (if the `loose' prefix is used). It is also
possible to uninstall a plugin, edit `my.cnf', and install the plugin
again. Restarting the plugin this way enables it to the new option
values without a server restart.

Before MySQL 5.1.33, a plugin is started with each option set to its
default value.

For options that control individual plugin loading at server startup,
see *Note server-plugin-loading::. If you need to load plugins for a
single server startup when the `--skip-grant-tables' option is given
(which tells the server not to read system tables), use the
`--plugin-load' option. See *Note server-options::.

To remove a plugin, use the *Note `UNINSTALL PLUGIN': uninstall-plugin.
statement.

For additional information about plugin loading, see *Note
server-plugin-loading::.

To see what plugins are installed, use the *Note `SHOW PLUGINS':
show-plugins. statement or query the *Note
`INFORMATION_SCHEMA.PLUGINS': plugins-table.  table.

If you recompile a plugin library and need to reinstall it, you can use
either of the following methods:

   * Use *Note `UNINSTALL PLUGIN': uninstall-plugin. to uninstall all
     plugins in the library, install the new plugin library file in the
     plugin directory, and then use *Note `INSTALL PLUGIN':
     install-plugin. to install all plugins in the library. This
     procedure has the advantage that it can be used without stopping
     the server. However, if the plugin library contains many plugins,
     you must issue many *Note `INSTALL PLUGIN': install-plugin. and
     *Note `UNINSTALL PLUGIN': uninstall-plugin. statements.

   * Stop the server, install the new plugin library file in the plugin
     directory, and restart the server.


File: manual.info,  Node: uninstall-plugin,  Prev: install-plugin,  Up: plugin-sql

13.7.3.4 UNINSTALL PLUGIN Syntax
................................


     UNINSTALL PLUGIN PLUGIN_NAME

This statement removes an installed server plugin. It requires the
`DELETE' privilege for the `mysql.plugin' table.

PLUGIN_NAME must be the name of some plugin that is listed in the
`mysql.plugin' table. The server executes the plugin's deinitialization
function and removes the row for the plugin from the `mysql.plugin'
table, so that subsequent server restarts will not load and initialize
the plugin.  *Note `UNINSTALL PLUGIN': uninstall-plugin. does not remove
the plugin's shared library file.

You cannot uninstall a plugin if any table that uses it is open.

Plugin removal has implications for the use of associated tables. For
example, if a full-text parser plugin is associated with a `FULLTEXT'
index on the table, uninstalling the plugin makes the table unusable.
Any attempt to access the table results in an error. The table cannot
even be opened, so you cannot drop an index for which the plugin is
used. This means that uninstalling a plugin is something to do with
care unless you do not care about the table contents. If you are
uninstalling a plugin with no intention of reinstalling it later and
you care about the table contents, you should dump the table with *Note
`mysqldump': mysqldump. and remove the `WITH PARSER' clause from the
dumped *Note `CREATE TABLE': create-table. statement so that you can
reload the table later. If you do not care about the table, *Note `DROP
TABLE': drop-table. can be used even if any plugins associated with the
table are missing.

For additional information about plugin loading, see *Note
server-plugin-loading::.


File: manual.info,  Node: set-statement,  Next: show,  Prev: plugin-sql,  Up: sql-syntax-server-administration

13.7.4 SET Syntax
-----------------


     SET VARIABLE_ASSIGNMENT [, VARIABLE_ASSIGNMENT] ...

     VARIABLE_ASSIGNMENT:
           USER_VAR_NAME = EXPR
         | [GLOBAL | SESSION] SYSTEM_VAR_NAME = EXPR
         | [@@global. | @@session. | @@]SYSTEM_VAR_NAME = EXPR

The *Note `SET': set-statement.  statement assigns values to different
types of variables that affect the operation of the server or your
client. Older versions of MySQL employed `SET OPTION', but this syntax
is deprecated in favor of *Note `SET': set-statement.  without `OPTION'.

This section describes use of *Note `SET': set-statement. for assigning
values to variables. The *Note `SET': set-statement.  statement can be
used to assign values to these types of variables:

   * System variables. See *Note server-system-variables::. System
     variables also can be set at server startup, as described in *Note
     using-system-variables::.

     User-defined variables. See *Note user-variables::.

   * Stored procedure and function parameters, and stored program local
     variables. See *Note stored-program-variables::.

Some variants of *Note `SET': set-statement.  syntax are used in other
contexts:

   * `SET CHARACTER SET' and `SET NAMES' assign values to character set
     and collation variables associated with the connection to the
     server.  `SET ONE_SHOT' is used for replication. These variants
     are described later in this section.

   * *Note `SET PASSWORD': set-password. assigns account passwords. See
     *Note set-password::.

   * *Note `SET TRANSACTION ISOLATION LEVEL': set-transaction. sets the
     isolation level for transaction processing. See *Note
     set-transaction::.

The following discussion shows the different *Note `SET': set-statement.
syntaxes that you can use to set variables. The examples use the `='
assignment operator, but you can also use the `:=' assignment operator
for this purpose.

A user variable is written as `@VAR_NAME' and can be set as follows:


     SET @VAR_NAME = EXPR;

Many system variables are dynamic and can be changed while the server
runs by using the *Note `SET': set-statement.  statement. For a list,
see *Note dynamic-system-variables::. To change a system variable with
*Note `SET': set-statement, refer to it as VAR_NAME, optionally
preceded by a modifier:

   * To indicate explicitly that a variable is a global variable,
     precede its name by `GLOBAL' or `@@global.'. The `SUPER' privilege
     is required to set global variables.

   * To indicate explicitly that a variable is a session variable,
     precede its name by `SESSION', `@@session.', or `@@'.  Setting a
     session variable normally requires no special privilege, although
     there are exceptions (such as `sql_log_bin'.) A client can change
     its own session variables, but not those of any other client.

   * `LOCAL' and `@@local.' are synonyms for `SESSION' and `@@session.'.

   * If no modifier is present, *Note `SET': set-statement.  changes
     the session variable.

A *Note `SET': set-statement.  statement can contain multiple variable
assignments, separated by commas. For example, the statement can assign
values to a user-defined variable and a system variable. If you set
several system variables, the most recent `GLOBAL' or `SESSION'
modifier in the statement is used for following variables that have no
modifier specified.

Examples:


     SET sort_buffer_size=10000;
     SET @@local.sort_buffer_size=10000;
     SET GLOBAL sort_buffer_size=1000000, SESSION sort_buffer_size=1000000;
     SET @@sort_buffer_size=1000000;
     SET @@global.sort_buffer_size=1000000, @@local.sort_buffer_size=1000000;

The `@@VAR_NAME' syntax for system variables is supported for
compatibility with some other database systems.

If you change a session system variable, the value remains in effect
until your session ends or until you change the variable to a different
value. The change is not visible to other clients.

If you change a global system variable, the value is remembered and
used for new connections until the server restarts. (To make a global
system variable setting permanent, you should set it in an option
file.) The change is visible to any client that accesses that global
variable. However, the change affects the corresponding session
variable only for clients that connect after the change. The global
variable change does not affect the session variable for any client
that is currently connected (not even that of the client that issues the
*Note `SET GLOBAL': set-statement. statement).

To prevent incorrect usage, MySQL produces an error if you use *Note
`SET GLOBAL': set-statement. with a variable that can only be used with
*Note `SET SESSION': set-statement. or if you do not specify `GLOBAL'
(or `@@global.') when setting a global variable.

To set a `SESSION' variable to the `GLOBAL' value or a `GLOBAL' value
to the compiled-in MySQL default value, use the `DEFAULT' keyword. For
example, the following two statements are identical in setting the
session value of `max_join_size' to the global value:


     SET max_join_size=DEFAULT;
     SET @@session.max_join_size=@@global.max_join_size;

Not all system variables can be set to `DEFAULT'.  In such cases, use
of `DEFAULT' results in an error.

It is not permitted to assign the value `DEFAULT' to user-defined
variables, and not supported for stored procedure or function
parameters or stored program local variables. This results in a syntax
error for user-defined variables, and the results are undefined for
parameters or local variables.

You can refer to the values of specific global or session system
variables in expressions by using one of the `@@'-modifiers. For
example, you can retrieve values in a *Note `SELECT': select. statement
like this:


     SELECT @@global.sql_mode, @@session.sql_mode, @@sql_mode;

When you refer to a system variable in an expression as `@@VAR_NAME'
(that is, when you do not specify `@@global.' or `@@session.'), MySQL
returns the session value if it exists and the global value otherwise.
(This differs from `SET @@VAR_NAME = VALUE', which always refers to the
session value.)

*Note*:

Some variables displayed by `SHOW VARIABLES' may not be available using
`SELECT @@VAR_NAME' syntax; an `Unknown system variable' occurs. As a
workaround in such cases, you can use `SHOW VARIABLES LIKE 'VAR_NAME''.

Suffixes for specifying a value multiplier can be used when setting a
variable at server startup, but not to set the value with *Note `SET':
set-statement.  at runtime. On the other hand, with *Note `SET':
set-statement. you can assign a variable's value using an expression,
which is not true when you set a variable at server startup. For
example, the first of the following lines is legal at server startup,
but the second is not:


     shell> mysql --max_allowed_packet=16M
     shell> mysql --max_allowed_packet=16*1024*1024

Conversely, the second of the following lines is legal at runtime, but
the first is not:


     mysql> SET GLOBAL max_allowed_packet=16M;
     mysql> SET GLOBAL max_allowed_packet=16*1024*1024;

To display system variables names and values, use the *Note `SHOW
VARIABLES': show-variables. statement. (See *Note show-variables::.)

The following list describes *Note `SET': set-statement.  options that
have nonstandard syntax (that is, options that are not set with `NAME =
VALUE' syntax).

   * `CHARACTER SET {CHARSET_NAME | DEFAULT}'

     This maps all strings from and to the client with the given
     mapping. You can add new mappings by editing `sql/convert.cc' in
     the MySQL source distribution. `SET CHARACTER SET' sets three
     session system variables: `character_set_client' and
     `character_set_results' are set to the given character set, and
     `character_set_connection' to the value of
     `character_set_database'. See *Note charset-connection::.

     The default mapping can be restored by using the value `DEFAULT'.
     The default depends on the server configuration.

     `ucs2' cannot be used as a client character set, which means that
     it does not work for `SET CHARACTER SET'.

   * `NAMES {'CHARSET_NAME' [COLLATE 'COLLATION_NAME'] | DEFAULT}'

     `SET NAMES' sets the three session system variables
     `character_set_client', `character_set_connection', and
     `character_set_results' to the given character set. Setting
     `character_set_connection' to `charset_name' also sets
     `collation_connection' to the default collation for
     `charset_name'. The optional `COLLATE' clause may be used to
     specify a collation explicitly. See *Note charset-connection::.

     The default mapping can be restored by using a value of `DEFAULT'.
     The default depends on the server configuration.

     `ucs2' cannot be used as a client character set, which means that
     it does not work for `SET NAMES'.

   * `ONE_SHOT'

     This option is a modifier, not a variable. It is _only_ for
     internal use for replication: *Note `mysqlbinlog': mysqlbinlog.
     uses `SET ONE_SHOT' to modify temporarily the values of character
     set, collation, and time zone variables to reflect at rollforward
     what they were originally.  `ONE_SHOT' is for internal use only
     and is deprecated for MySQL 5.0 and up.

     `ONE_SHOT' is intended for use only with the permitted set of
     variables. With other variables, an error occurs:


          mysql> SET ONE_SHOT max_allowed_packet = 1;
          ERROR 1382 (HY000): The 'SET ONE_SHOT' syntax is reserved for purposes
          internal to the MySQL server

     If `ONE_SHOT' is used with the permitted variables, it changes the
     variables as requested, but only for the next non-*Note `SET':
     set-statement.  statement. After that, the server resets all
     character set, collation, and time zone-related system variables
     to their previous values. Example:


          mysql> SET ONE_SHOT character_set_connection = latin5;

          mysql> SET ONE_SHOT collation_connection = latin5_turkish_ci;

          mysql> SHOW VARIABLES LIKE '%_connection';
          +--------------------------+-------------------+
          | Variable_name            | Value             |
          +--------------------------+-------------------+
          | character_set_connection | latin5            |
          | collation_connection     | latin5_turkish_ci |
          +--------------------------+-------------------+

          mysql> SHOW VARIABLES LIKE '%_connection';
          +--------------------------+-------------------+
          | Variable_name            | Value             |
          +--------------------------+-------------------+
          | character_set_connection | latin1            |
          | collation_connection     | latin1_swedish_ci |
          +--------------------------+-------------------+


File: manual.info,  Node: show,  Next: other-administrative-sql,  Prev: set-statement,  Up: sql-syntax-server-administration

13.7.5 SHOW Syntax
------------------

* Menu:

* show-authors::                 SHOW AUTHORS Syntax
* show-binary-logs::             SHOW BINARY LOGS Syntax
* show-binlog-events::           SHOW BINLOG EVENTS Syntax
* show-character-set::           SHOW CHARACTER SET Syntax
* show-collation::               SHOW COLLATION Syntax
* show-columns::                 SHOW COLUMNS Syntax
* show-contributors::            SHOW CONTRIBUTORS Syntax
* show-create-database::         SHOW CREATE DATABASE Syntax
* show-create-event::            SHOW CREATE EVENT Syntax
* show-create-function::         SHOW CREATE FUNCTION Syntax
* show-create-procedure::        SHOW CREATE PROCEDURE Syntax
* show-create-table::            SHOW CREATE TABLE Syntax
* show-create-trigger::          SHOW CREATE TRIGGER Syntax
* show-create-view::             SHOW CREATE VIEW Syntax
* show-databases::               SHOW DATABASES Syntax
* show-engine::                  SHOW ENGINE Syntax
* show-engines::                 SHOW ENGINES Syntax
* show-errors::                  SHOW ERRORS Syntax
* show-events::                  SHOW EVENTS Syntax
* show-function-code::           SHOW FUNCTION CODE Syntax
* show-function-status::         SHOW FUNCTION STATUS Syntax
* show-grants::                  SHOW GRANTS Syntax
* show-index::                   SHOW INDEX Syntax
* show-innodb-status::           SHOW INNODB STATUS Syntax
* show-master-status::           SHOW MASTER STATUS Syntax
* show-open-tables::             SHOW OPEN TABLES Syntax
* show-plugins::                 SHOW PLUGINS Syntax
* show-privileges::              SHOW PRIVILEGES Syntax
* show-procedure-code::          SHOW PROCEDURE CODE Syntax
* show-procedure-status::        SHOW PROCEDURE STATUS Syntax
* show-processlist::             SHOW PROCESSLIST Syntax
* show-profile::                 SHOW PROFILE Syntax
* show-profiles::                SHOW PROFILES Syntax
* show-scheduler-status::        SHOW SCHEDULER STATUS Syntax
* show-slave-hosts::             SHOW SLAVE HOSTS Syntax
* show-slave-status::            SHOW SLAVE STATUS Syntax
* show-status::                  SHOW STATUS Syntax
* show-table-status::            SHOW TABLE STATUS Syntax
* show-tables::                  SHOW TABLES Syntax
* show-triggers::                SHOW TRIGGERS Syntax
* show-variables::               SHOW VARIABLES Syntax
* show-warnings::                SHOW WARNINGS Syntax

*Note `SHOW': show. has many forms that provide information about
databases, tables, columns, or status information about the server.
This section describes those following:


     SHOW AUTHORS
     SHOW {BINARY | MASTER} LOGS
     SHOW BINLOG EVENTS [IN 'LOG_NAME'] [FROM POS] [LIMIT [OFFSET,] ROW_COUNT]
     SHOW CHARACTER SET [LIKE_OR_WHERE]
     SHOW COLLATION [LIKE_OR_WHERE]
     SHOW [FULL] COLUMNS FROM TBL_NAME [FROM DB_NAME] [LIKE_OR_WHERE]
     SHOW CONTRIBUTORS
     SHOW CREATE DATABASE DB_NAME
     SHOW CREATE EVENT EVENT_NAME
     SHOW CREATE FUNCTION FUNC_NAME
     SHOW CREATE PROCEDURE PROC_NAME
     SHOW CREATE TABLE TBL_NAME
     SHOW CREATE TRIGGER TRIGGER_NAME
     SHOW CREATE VIEW VIEW_NAME
     SHOW DATABASES [LIKE_OR_WHERE]
     SHOW ENGINE ENGINE_NAME {STATUS | MUTEX}
     SHOW [STORAGE] ENGINES
     SHOW ERRORS [LIMIT [OFFSET,] ROW_COUNT]
     SHOW EVENTS
     SHOW FUNCTION CODE FUNC_NAME
     SHOW FUNCTION STATUS [LIKE_OR_WHERE]
     SHOW GRANTS FOR USER
     SHOW INDEX FROM TBL_NAME [FROM DB_NAME]
     SHOW INNODB STATUS
     SHOW MASTER STATUS
     SHOW OPEN TABLES [FROM DB_NAME] [LIKE_OR_WHERE]
     SHOW PLUGINS
     SHOW PROCEDURE CODE PROC_NAME
     SHOW PROCEDURE STATUS [LIKE_OR_WHERE]
     SHOW PRIVILEGES
     SHOW [FULL] PROCESSLIST
     SHOW PROFILE [TYPES] [FOR QUERY N] [OFFSET N] [LIMIT N]
     SHOW PROFILES
     SHOW SCHEDULER STATUS
     SHOW SLAVE HOSTS
     SHOW SLAVE STATUS
     SHOW [GLOBAL | SESSION] STATUS [LIKE_OR_WHERE]
     SHOW TABLE STATUS [FROM DB_NAME] [LIKE_OR_WHERE]
     SHOW [FULL] TABLES [FROM DB_NAME] [LIKE_OR_WHERE]
     SHOW TRIGGERS [FROM DB_NAME] [LIKE_OR_WHERE]
     SHOW [GLOBAL | SESSION] VARIABLES [LIKE_OR_WHERE]
     SHOW WARNINGS [LIMIT [OFFSET,] ROW_COUNT]

     LIKE_OR_WHERE:
         LIKE 'PATTERN'
       | WHERE EXPR

If the syntax for a given *Note `SHOW': show.  statement includes a
`LIKE 'PATTERN'' part, `'PATTERN'' is a string that can contain the SQL
``%'' and ``_'' wildcard characters. The pattern is useful for
restricting statement output to matching values.

Several *Note `SHOW': show. statements also accept a `WHERE' clause
that provides more flexibility in specifying which rows to display. See
*Note extended-show::.

Many MySQL APIs (such as PHP) enable you to treat the result returned
from a *Note `SHOW': show. statement as you would a result set from a
*Note `SELECT': select.; see *Note connectors-apis::, or your API
documentation for more information. In addition, you can work in SQL
with results from queries on tables in the `INFORMATION_SCHEMA'
database, which you cannot easily do with results from *Note `SHOW':
show.  statements. See *Note information-schema::.


File: manual.info,  Node: show-authors,  Next: show-binary-logs,  Prev: show,  Up: show

13.7.5.1 SHOW AUTHORS Syntax
............................


     SHOW AUTHORS

The *Note `SHOW AUTHORS': show-authors. statement displays information
about the people who work on MySQL. For each author, it displays `Name',
`Location', and `Comment' values.

This statement was added in MySQL 5.1.3.


File: manual.info,  Node: show-binary-logs,  Next: show-binlog-events,  Prev: show-authors,  Up: show

13.7.5.2 SHOW BINARY LOGS Syntax
................................


     SHOW BINARY LOGS
     SHOW MASTER LOGS

Lists the binary log files on the server. This statement is used as
part of the procedure described in *Note purge-binary-logs::, that
shows how to determine which logs can be purged.


     mysql> SHOW BINARY LOGS;
     +---------------+-----------+
     | Log_name      | File_size |
     +---------------+-----------+
     | binlog.000015 |    724935 |
     | binlog.000016 |    733481 |
     +---------------+-----------+

*Note `SHOW MASTER LOGS': show-binary-logs. is equivalent to *Note
`SHOW BINARY LOGS': show-binary-logs.

In MySQL 5.1.63 and earlier, the `SUPER' privilege was required to use
this statement. Starting with MySQL 5.1.64, a user with the
`REPLICATION CLIENT' privilege may also execute this statement.


File: manual.info,  Node: show-binlog-events,  Next: show-character-set,  Prev: show-binary-logs,  Up: show

13.7.5.3 SHOW BINLOG EVENTS Syntax
..................................


     SHOW BINLOG EVENTS
        [IN 'LOG_NAME'] [FROM POS] [LIMIT [OFFSET,] ROW_COUNT]

Shows the events in the binary log. If you do not specify `'LOG_NAME'',
the first binary log is displayed.

The `LIMIT' clause has the same syntax as for the *Note `SELECT':
select. statement. See *Note select::.

*Note*:

Issuing a *Note `SHOW BINLOG EVENTS': show-binlog-events.  with no
`LIMIT' clause could start a very time- and resource-consuming process
because the server returns to the client the complete contents of the
binary log (which includes all statements executed by the server that
modify data). As an alternative to *Note `SHOW BINLOG EVENTS':
show-binlog-events, use the *Note `mysqlbinlog': mysqlbinlog. utility
to save the binary log to a text file for later examination and
analysis. See *Note mysqlbinlog::.

*Note*:

Some events relating to the setting of user and system variables are
not included in the output from *Note `SHOW BINLOG EVENTS':
show-binlog-events. To get complete coverage of events within a binary
log, use *Note `mysqlbinlog': mysqlbinlog.


File: manual.info,  Node: show-character-set,  Next: show-collation,  Prev: show-binlog-events,  Up: show

13.7.5.4 SHOW CHARACTER SET Syntax
..................................


     SHOW CHARACTER SET
         [LIKE 'PATTERN' | WHERE EXPR]

The *Note `SHOW CHARACTER SET': show-character-set. statement shows all
available character sets. The `LIKE' clause, if present, indicates
which character set names to match. The `WHERE' clause can be given to
select rows using more general conditions, as discussed in *Note
extended-show::. For example:


     mysql> SHOW CHARACTER SET LIKE 'latin%';
     +---------+-----------------------------+-------------------+--------+
     | Charset | Description                 | Default collation | Maxlen |
     +---------+-----------------------------+-------------------+--------+
     | latin1  | cp1252 West European        | latin1_swedish_ci |      1 |
     | latin2  | ISO 8859-2 Central European | latin2_general_ci |      1 |
     | latin5  | ISO 8859-9 Turkish          | latin5_turkish_ci |      1 |
     | latin7  | ISO 8859-13 Baltic          | latin7_general_ci |      1 |
     +---------+-----------------------------+-------------------+--------+

The `Maxlen' column shows the maximum number of bytes required to store
one character.

The `filename' character set is for internal use only; consequently,
*Note `SHOW CHARACTER SET': show-character-set. does not display it.


File: manual.info,  Node: show-collation,  Next: show-columns,  Prev: show-character-set,  Up: show

13.7.5.5 SHOW COLLATION Syntax
..............................


     SHOW COLLATION
         [LIKE 'PATTERN' | WHERE EXPR]

This statement lists collations supported by the server. By default,
the output from *Note `SHOW COLLATION': show-collation. includes all
available collations. The `LIKE' clause, if present, indicates which
collation names to match. The `WHERE' clause can be given to select
rows using more general conditions, as discussed in *Note
extended-show::. For example:


     mysql> SHOW COLLATION LIKE 'latin1%';
     +-------------------+---------+----+---------+----------+---------+
     | Collation         | Charset | Id | Default | Compiled | Sortlen |
     +-------------------+---------+----+---------+----------+---------+
     | latin1_german1_ci | latin1  |  5 |         |          |       0 |
     | latin1_swedish_ci | latin1  |  8 | Yes     | Yes      |       0 |
     | latin1_danish_ci  | latin1  | 15 |         |          |       0 |
     | latin1_german2_ci | latin1  | 31 |         | Yes      |       2 |
     | latin1_bin        | latin1  | 47 |         | Yes      |       0 |
     | latin1_general_ci | latin1  | 48 |         |          |       0 |
     | latin1_general_cs | latin1  | 49 |         |          |       0 |
     | latin1_spanish_ci | latin1  | 94 |         |          |       0 |
     +-------------------+---------+----+---------+----------+---------+

The `Collation' and `Charset' columns indicate the names of the
collation and the character set with which it is associated. `Id' is the
collation ID. `Default' indicates whether the collation is the default
for its character set.  `Compiled' indicates whether the character set
is compiled into the server. `Sortlen' is related to the amount of
memory required to sort strings expressed in the character set.

To see the default collation for each character set, use the following
statement. `Default' is a reserved word, so to use it as an identifier,
it must be quoted as such:


     mysql> SHOW COLLATION WHERE `Default` = 'Yes';
     +---------------------+----------+----+---------+----------+---------+
     | Collation           | Charset  | Id | Default | Compiled | Sortlen |
     +---------------------+----------+----+---------+----------+---------+
     | big5_chinese_ci     | big5     |  1 | Yes     | Yes      |       1 |
     | dec8_swedish_ci     | dec8     |  3 | Yes     | Yes      |       1 |
     | cp850_general_ci    | cp850    |  4 | Yes     | Yes      |       1 |
     | hp8_english_ci      | hp8      |  6 | Yes     | Yes      |       1 |
     | koi8r_general_ci    | koi8r    |  7 | Yes     | Yes      |       1 |
     | latin1_swedish_ci   | latin1   |  8 | Yes     | Yes      |       1 |
     ...


File: manual.info,  Node: show-columns,  Next: show-contributors,  Prev: show-collation,  Up: show

13.7.5.6 SHOW COLUMNS Syntax
............................


     SHOW [FULL] COLUMNS {FROM | IN} TBL_NAME [{FROM | IN} DB_NAME]
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW COLUMNS': show-columns. displays information about the
columns in a given table. It also works for views. The `LIKE' clause,
if present, indicates which column names to match. The `WHERE' clause
can be given to select rows using more general conditions, as discussed
in *Note extended-show::.


     mysql> SHOW COLUMNS FROM City;
     +------------+----------+------+-----+---------+----------------+
     | Field      | Type     | Null | Key | Default | Extra          |
     +------------+----------+------+-----+---------+----------------+
     | Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
     | Name       | char(35) | NO   |     |         |                |
     | Country    | char(3)  | NO   | UNI |         |                |
     | District   | char(20) | YES  | MUL |         |                |
     | Population | int(11)  | NO   |     | 0       |                |
     +------------+----------+------+-----+---------+----------------+
     5 rows in set (0.00 sec)

If the data types differ from what you expect them to be based on a
*Note `CREATE TABLE': create-table. statement, note that MySQL
sometimes changes data types when you create or alter a table. The
conditions under which this occurs are described in *Note
silent-column-changes::.

The `FULL' keyword causes the output to include the column collation
and comments, as well as the privileges you have for each column.

You can use DB_NAME.TBL_NAME as an alternative to the `TBL_NAME FROM
DB_NAME' syntax. In other words, these two statements are equivalent:


     mysql> SHOW COLUMNS FROM mytable FROM mydb;
     mysql> SHOW COLUMNS FROM mydb.mytable;

*Note `SHOW COLUMNS': show-columns. displays the following values for
each table column:

`Field' indicates the column name.

`Type' indicates the column data type.

`Collation' indicates the collation for nonbinary string columns, or
`NULL' for other columns. This value is displayed only if you use the
`FULL' keyword.

The `Null' field contains `YES' if `NULL' values can be stored in the
column, `NO' if not.

The `Key' field indicates whether the column is indexed:

   * If `Key' is empty, the column either is not indexed or is indexed
     only as a secondary column in a multiple-column, nonunique index.

   * If `Key' is `PRI', the column is a `PRIMARY KEY' or is one of the
     columns in a multiple-column `PRIMARY KEY'.

   * If `Key' is `UNI', the column is the first column of a `UNIQUE'
     index. (A `UNIQUE' index permits multiple `NULL' values, but you
     can tell whether the column permits `NULL' by checking the `Null'
     field.)

   * If `Key' is `MUL', the column is the first column of a nonunique
     index in which multiple occurrences of a given value are permitted
     within the column.

If more than one of the `Key' values applies to a given column of a
table, `Key' displays the one with the highest priority, in the order
`PRI', `UNI', `MUL'.

A `UNIQUE' index may be displayed as `PRI' if it cannot contain `NULL'
values and there is no `PRIMARY KEY' in the table. A `UNIQUE' index may
display as `MUL' if several columns form a composite `UNIQUE' index;
although the combination of the columns is unique, each column can
still hold multiple occurrences of a given value.

The `Default' field indicates the default value that is assigned to the
column. This is `NULL' if the column has an explicit default of `NULL'.
As of MySQL 5.1.23, `Default' is also `NULL' if the column definition
has no `DEFAULT' clause.

The `Extra' field contains any additional information that is available
about a given column. The value is nonempty in these cases:
`auto_increment' for columns that have the `AUTO_INCREMENT' attribute;
as of MySQL 5.1.23, `on update CURRENT_TIMESTAMP' for *Note
`TIMESTAMP': datetime. columns that have the `ON UPDATE
CURRENT_TIMESTAMP' attribute.

`Privileges' indicates the privileges you have for the column. This
value is displayed only if you use the `FULL' keyword.

`Comment' indicates any comment the column has.  This value is
displayed only if you use the `FULL' keyword.

`SHOW FIELDS' is a synonym for *Note `SHOW COLUMNS': show-columns. You
can also list a table's columns with the *Note `mysqlshow DB_NAME
TBL_NAME': mysqlshow. command.

The *Note `DESCRIBE': describe. statement provides information similar
to *Note `SHOW COLUMNS': show-columns. See *Note describe::.

The *Note `SHOW CREATE TABLE': show-create-table, *Note `SHOW TABLE
STATUS': show-table-status, and *Note `SHOW INDEX': show-index.
statements also provide information about tables. See *Note show::.


File: manual.info,  Node: show-contributors,  Next: show-create-database,  Prev: show-columns,  Up: show

13.7.5.7 SHOW CONTRIBUTORS Syntax
.................................


     SHOW CONTRIBUTORS

The *Note `SHOW CONTRIBUTORS': show-contributors. statement displays
information about the people who contribute to MySQL source or to
causes that we support. For each contributor, it displays `Name',
`Location', and `Comment' values.

This statement was added in MySQL 5.1.12.


File: manual.info,  Node: show-create-database,  Next: show-create-event,  Prev: show-contributors,  Up: show

13.7.5.8 SHOW CREATE DATABASE Syntax
....................................


     SHOW CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] DB_NAME

Shows the *Note `CREATE DATABASE': create-database.  statement that
creates the named database. If the `SHOW' statement includes an `IF NOT
EXISTS' clause, the output too includes such a clause.  *Note `SHOW
CREATE SCHEMA': show-create-database. is a synonym for *Note `SHOW
CREATE DATABASE': show-create-database.


     mysql> SHOW CREATE DATABASE test\G
     *************************** 1. row ***************************
            Database: test
     Create Database: CREATE DATABASE `test`
                      /*!40100 DEFAULT CHARACTER SET latin1 */

     mysql> SHOW CREATE SCHEMA test\G
     *************************** 1. row ***************************
            Database: test
     Create Database: CREATE DATABASE `test`
                      /*!40100 DEFAULT CHARACTER SET latin1 */

*Note `SHOW CREATE DATABASE': show-create-database. quotes table and
column names according to the value of the `sql_quote_show_create'
option.  See *Note server-system-variables::.


File: manual.info,  Node: show-create-event,  Next: show-create-function,  Prev: show-create-database,  Up: show

13.7.5.9 SHOW CREATE EVENT Syntax
.................................


     SHOW CREATE EVENT EVENT_NAME

This statement displays the *Note `CREATE EVENT': create-event.
statement needed to re-create a given event. It requires the `EVENT'
privilege for the database from which the event is to be shown. For
example (using the same event `e_daily' defined and then altered in
*Note show-events::):


     mysql> SHOW CREATE EVENT test.e_daily\G
     *************************** 1. row ***************************
                    Event: e_daily
                 sql_mode:
                time_zone: SYSTEM
             Create Event: CREATE EVENT `e_daily`
                             ON SCHEDULE EVERY 1 DAY
                             STARTS CURRENT_TIMESTAMP + INTERVAL 6 HOUR
                             ON COMPLETION NOT PRESERVE
                             ENABLE
                             COMMENT 'Saves total number of sessions then
                                     clears the table each day'
                             DO BEGIN
                               INSERT INTO site_activity.totals (time, total)
                                 SELECT CURRENT_TIMESTAMP, COUNT(*)
                                 FROM site_activity.sessions;
                               DELETE FROM site_activity.sessions;
                             END
     character_set_client: latin1
     collation_connection: latin1_swedish_ci
       Database Collation: latin1_swedish_ci

`character_set_client' is the session value of the
`character_set_client' system variable when the event was created.
`collation_connection' is the session value of the
`collation_connection' system variable when the event was created.
`Database Collation' is the collation of the database with which the
event is associated. These columns were added in MySQL 5.1.21.

Note that the output reflects the current status of the event
(`ENABLE') rather than the status with which it was created.

This statement was implemented in MySQL 5.1.6.


File: manual.info,  Node: show-create-function,  Next: show-create-procedure,  Prev: show-create-event,  Up: show

13.7.5.10 SHOW CREATE FUNCTION Syntax
.....................................


     SHOW CREATE FUNCTION FUNC_NAME

This statement is similar to *Note `SHOW CREATE PROCEDURE':
show-create-procedure. but for stored functions. See *Note
show-create-procedure::.


File: manual.info,  Node: show-create-procedure,  Next: show-create-table,  Prev: show-create-function,  Up: show

13.7.5.11 SHOW CREATE PROCEDURE Syntax
......................................


     SHOW CREATE PROCEDURE PROC_NAME

This statement is a MySQL extension. It returns the exact string that
can be used to re-create the named stored procedure. A similar
statement, *Note `SHOW CREATE FUNCTION': show-create-function, displays
information about stored functions (see *Note show-create-function::).

To use either statement, you must be the owner of the routine or have
*Note `SELECT': select. access to the `mysql.proc' table. If you do not
have privileges for the routine itself, the value displayed for the
`Create Procedure' or `Create Function' field will be `NULL'.


     mysql> SHOW CREATE PROCEDURE test.simpleproc\G
     *************************** 1. row ***************************
                Procedure: simpleproc
                 sql_mode:
         Create Procedure: CREATE PROCEDURE `simpleproc`(OUT param1 INT)
                           BEGIN
                           SELECT COUNT(*) INTO param1 FROM t;
                           END
     character_set_client: latin1
     collation_connection: latin1_swedish_ci
       Database Collation: latin1_swedish_ci

     mysql> SHOW CREATE FUNCTION test.hello\G
     *************************** 1. row ***************************
                 Function: hello
                 sql_mode:
          Create Function: CREATE FUNCTION `hello`(s CHAR(20))
                           RETURNS CHAR(50)
                           RETURN CONCAT('Hello, ',s,'!')
     character_set_client: latin1
     collation_connection: latin1_swedish_ci
       Database Collation: latin1_swedish_ci

`character_set_client' is the session value of the
`character_set_client' system variable when the routine was created.
`collation_connection' is the session value of the
`collation_connection' system variable when the routine was created.
`Database Collation' is the collation of the database with which the
routine is associated. These columns were added in MySQL 5.1.21.


File: manual.info,  Node: show-create-table,  Next: show-create-trigger,  Prev: show-create-procedure,  Up: show

13.7.5.12 SHOW CREATE TABLE Syntax
..................................


     SHOW CREATE TABLE TBL_NAME

Shows the *Note `CREATE TABLE': create-table. statement that creates
the named table. To use this statement, you must have some privilege
for the table. This statement also works with views.


     mysql> SHOW CREATE TABLE t\G
     *************************** 1. row ***************************
            Table: t
     Create Table: CREATE TABLE t (
       id INT(11) default NULL auto_increment,
       s char(60) default NULL,
       PRIMARY KEY (id)
     ) ENGINE=MyISAM

*Note `SHOW CREATE TABLE': show-create-table. quotes table and column
names according to the value of the `sql_quote_show_create' option.
See *Note server-system-variables::.


File: manual.info,  Node: show-create-trigger,  Next: show-create-view,  Prev: show-create-table,  Up: show

13.7.5.13 SHOW CREATE TRIGGER Syntax
....................................


     SHOW CREATE TRIGGER TRIGGER_NAME

This statement shows the *Note `CREATE TRIGGER': create-trigger.
statement that creates the named trigger.


     mysql> SHOW CREATE TRIGGER ins_sum\G
     *************************** 1. row ***************************
                    Trigger: ins_sum
                   sql_mode:
     SQL Original Statement: CREATE DEFINER=`me`@`localhost` TRIGGER ins_sum
                             BEFORE INSERT ON account
                             FOR EACH ROW SET @sum = @sum + NEW.amount
       character_set_client: latin1
       collation_connection: latin1_swedish_ci
         Database Collation: latin1_swedish_ci

*Note `SHOW CREATE TRIGGER': show-create-trigger. output has the
following columns:

   * `Trigger': The trigger name.

   * `sql_mode': The SQL mode in effect when the trigger executes.

   * `SQL Original Statement': The *Note `CREATE TRIGGER':
     create-trigger. statement that defines the trigger.

   * `character_set_client': The session value of the
     `character_set_client' system variable when the trigger was
     created.

   * `collation_connection': The session value of the
     `collation_connection' system variable when the trigger was
     created.

   * `Database Collation': The collation of the database with which the
     trigger is associated.

*Note `SHOW CREATE TRIGGER': show-create-trigger. output has the
following columns:

   * `Trigger': The trigger name.

   * `sql_mode': The SQL mode in effect when the trigger executes.

   * `SQL Original Statement': The statement to be executed when the
     trigger activates.

   * `character_set_client': The session value of the
     `character_set_client' system variable when the trigger was
     created.

   * `collation_connection': The session value of the
     `collation_connection' system variable when the trigger was
     created.

   * `Database Collation': The collation of the database with which the
     trigger is associated.

*Note `SHOW CREATE TRIGGER': show-create-trigger. was added in MySQL
5.1.21.

You can also obtain information about trigger objects from
`INFORMATION_SCHEMA', which contains a *Note `TRIGGERS':
triggers-table. table. See *Note triggers-table::.


File: manual.info,  Node: show-create-view,  Next: show-databases,  Prev: show-create-trigger,  Up: show

13.7.5.14 SHOW CREATE VIEW Syntax
.................................


     SHOW CREATE VIEW VIEW_NAME

This statement shows the *Note `CREATE VIEW': create-view. statement
that creates the named view.


     mysql> SHOW CREATE VIEW v\G
     *************************** 1. row ***************************
                     View: v
              Create View: CREATE ALGORITHM=UNDEFINED
                           DEFINER=`bob`@`localhost`
                           SQL SECURITY DEFINER VIEW
                           `v` AS select 1 AS `a`,2 AS `b`
     character_set_client: latin1
     collation_connection: latin1_swedish_ci

`character_set_client' is the session value of the
`character_set_client' system variable when the view was created.
`collation_connection' is the session value of the
`collation_connection' system variable when the view was created. These
columns were added in MySQL 5.1.21.

Use of *Note `SHOW CREATE VIEW': show-create-view. requires the `SHOW
VIEW' privilege and the `SELECT' privilege for the view in question.

You can also obtain information about view objects from
`INFORMATION_SCHEMA', which contains a *Note `VIEWS': views-table.
table. See *Note views-table::.

MySQL lets you use different `sql_mode' settings to tell the server the
type of SQL syntax to support. For example, you might use the `ANSI'
SQL mode to ensure MySQL correctly interprets the standard SQL
concatenation operator, the double bar (`||'), in your queries. If you
then create a view that concatenates items, you might worry that
changing the `sql_mode' setting to a value different from `ANSI' could
cause the view to become invalid. But this is not the case. No matter
how you write out a view definition, MySQL always stores it the same
way, in a canonical form. Here is an example that shows how the server
changes a double bar concatenation operator to a `CONCAT()' function:


     mysql> SET sql_mode = 'ANSI';
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE VIEW test.v AS SELECT 'a' || 'b' as col1;
     Query OK, 0 rows affected (0.01 sec)

     mysql> SHOW CREATE VIEW test.v\G
     *************************** 1. row ***************************
                     View: v
              Create View: CREATE VIEW "v" AS select concat('a','b') AS "col1"
     ...
     1 row in set (0.00 sec)

The advantage of storing a view definition in canonical form is that
changes made later to the value of `sql_mode' will not affect the
results from the view. However an additional consequence is that
comments prior to *Note `SELECT': select. are stripped from the
definition by the server.


File: manual.info,  Node: show-databases,  Next: show-engine,  Prev: show-create-view,  Up: show

13.7.5.15 SHOW DATABASES Syntax
...............................


     SHOW {DATABASES | SCHEMAS}
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW DATABASES': show-databases. lists the databases on the
MySQL server host.  *Note `SHOW SCHEMAS': show-databases. is a synonym
for *Note `SHOW DATABASES': show-databases. The `LIKE' clause, if
present, indicates which database names to match. The `WHERE' clause
can be given to select rows using more general conditions, as discussed
in *Note extended-show::.

You see only those databases for which you have some kind of privilege,
unless you have the global *Note `SHOW DATABASES': show-databases.
privilege. You can also get this list using the *Note `mysqlshow':
mysqlshow. command.

If the server was started with the `--skip-show-database' option, you
cannot use this statement at all unless you have the `SHOW DATABASES'
privilege.

MySQL implements databases as directories in the data directory, so
this statement simply lists directories in that location.  However, the
output may include names of directories that do not correspond to
actual databases.


File: manual.info,  Node: show-engine,  Next: show-engines,  Prev: show-databases,  Up: show

13.7.5.16 SHOW ENGINE Syntax
............................


     SHOW ENGINE ENGINE_NAME {STATUS | MUTEX}

*Note `SHOW ENGINE': show-engine. displays operational information
about a storage engine. It requires the `PROCESS' privilege. The
statement has these variants:


     SHOW ENGINE INNODB STATUS
     SHOW ENGINE INNODB MUTEX
     SHOW ENGINE {NDB | NDBCLUSTER} STATUS

Older (and now deprecated) synonyms are *Note `SHOW INNODB STATUS':
show-innodb-status. for *Note `SHOW ENGINE INNODB STATUS': show-engine.
and `SHOW MUTEX STATUS' for *Note `SHOW ENGINE INNODB MUTEX':
show-engine. *Note `SHOW INNODB STATUS': show-innodb-status. and `SHOW
MUTEX STATUS' are removed in MySQL 5.5.

In MySQL 5.0, *Note `SHOW ENGINE INNODB MUTEX': show-engine. is invoked
as `SHOW MUTEX STATUS'. The latter statement displays similar
information but in a somewhat different output format.

*Note `SHOW ENGINE BDB LOGS': show-engine. formerly displayed status
information about `BDB' log files. As of MySQL 5.1.12, the `BDB'
storage engine is not supported, and this statement produces a warning.

*Note `SHOW ENGINE INNODB STATUS': show-engine. displays extensive
information from the standard `InnoDB' Monitor about the state of the
`InnoDB' storage engine. For information about the standard monitor and
other `InnoDB' Monitors that provide information about `InnoDB'
processing, see *Note innodb-monitors::.

*Note `SHOW ENGINE INNODB MUTEX': show-engine. displays `InnoDB' mutex
statistics. From MySQL 5.1.2 to 5.1.14, the statement displays the
following output fields:

   * `Type'

     Always `InnoDB'.

   * `Name'

     The mutex name and the source file where it is implemented.
     Example: `&pool->mutex:mem0pool.c'

     The mutex name indicates its purpose. For example, the `log_sys'
     mutex is used by the `InnoDB' logging subsystem and indicates how
     intensive logging activity is. The `buf_pool' mutex protects the
     `InnoDB' buffer pool.

   * `Status'

     The mutex status. The fields contains several values:

        * `count' indicates how many times the mutex was requested.

        * `spin_waits' indicates how many times the spinlock had to run.

        * `spin_rounds' indicates the number of spinlock rounds.
          (`spin_rounds' divided by `spin_waits' provides the average
          round count.)

        * `os_waits' indicates the number of operating system waits.
          This occurs when the spinlock did not work (the mutex was not
          locked during the spinlock and it was necessary to yield to
          the operating system and wait).

        * `os_yields' indicates the number of times a thread trying to
          lock a mutex gave up its timeslice and yielded to the
          operating system (on the presumption that permitting other
          threads to run will free the mutex so that it can be locked).

        * `os_wait_times' indicates the amount of time (in ms) spent in
          operating system waits, if the `timed_mutexes' system
          variable is 1 (`ON'). If `timed_mutexes' is 0 (`OFF'), timing
          is disabled, so `os_wait_times' is 0.  `timed_mutexes' is off
          by default.

From MySQL 5.1.15 on, the statement displays the following output
fields:

   * `Type'

     Always `InnoDB'.

   * `Name'

     The source file where the mutex is implemented, and the line
     number in the file where the mutex is created. The line number is
     specific to your version of MySQL.

   * `Status'

     This field displays the same values as previously described
     (`count', `spin_waits', `spin_rounds', `os_waits', `os_yields',
     `os_wait_times'), but only if `UNIV_DEBUG' was defined at MySQL
     compilation time (for example, in `include/univ.i' in the `InnoDB'
     part of the MySQL source tree). If `UNIV_DEBUG' was not defined,
     the statement displays only the `os_waits' value. In the latter
     case (without `UNIV_DEBUG'), the information on which the output
     is based is insufficient to distinguish regular mutexes and
     mutexes that protect rw-locks (which permit multiple readers or a
     single writer).  Consequently, the output may appear to contain
     multiple rows for the same mutex.

Information from this statement can be used to diagnose system
problems. For example, large values of `spin_waits' and `spin_rounds'
may indicate scalability problems.

If the server has the *Note `NDBCLUSTER': mysql-cluster.  storage
engine enabled, *Note `SHOW ENGINE NDB STATUS': show-engine. displays
cluster status information such as the number of connected data nodes,
the cluster connectstring, and cluster binlog epochs, as well as counts
of various Cluster API objects created by the MySQL Server when
connected to the cluster. Sample output from this statement is shown
here:


     mysql> SHOW ENGINE NDB STATUS;
     +------------+-----------------------+--------------------------------------------------+
     | Type       | Name                  | Status                                           |
     +------------+-----------------------+--------------------------------------------------+
     | ndbcluster | connection            | cluster_node_id=7,
       connected_host=192.168.0.103, connected_port=1186, number_of_data_nodes=4,
       number_of_ready_data_nodes=3, connect_count=0                                         |
     | ndbcluster | NdbTransaction        | created=6, free=0, sizeof=212                    |
     | ndbcluster | NdbOperation          | created=8, free=8, sizeof=660                    |
     | ndbcluster | NdbIndexScanOperation | created=1, free=1, sizeof=744                    |
     | ndbcluster | NdbIndexOperation     | created=0, free=0, sizeof=664                    |
     | ndbcluster | NdbRecAttr            | created=1285, free=1285, sizeof=60               |
     | ndbcluster | NdbApiSignal          | created=16, free=16, sizeof=136                  |
     | ndbcluster | NdbLabel              | created=0, free=0, sizeof=196                    |
     | ndbcluster | NdbBranch             | created=0, free=0, sizeof=24                     |
     | ndbcluster | NdbSubroutine         | created=0, free=0, sizeof=68                     |
     | ndbcluster | NdbCall               | created=0, free=0, sizeof=16                     |
     | ndbcluster | NdbBlob               | created=1, free=1, sizeof=264                    |
     | ndbcluster | NdbReceiver           | created=4, free=0, sizeof=68                     |
     | ndbcluster | binlog                | latest_epoch=155467, latest_trans_epoch=148126,
       latest_received_binlog_epoch=0, latest_handled_binlog_epoch=0,
       latest_applied_binlog_epoch=0                                                         |
     +------------+-----------------------+--------------------------------------------------+

The rows with `connection' and `binlog' in the `Name' column were added
to the output of this statement in MySQL 5.1. The `Status' column in
each of these rows provides information about the MySQL server's
connection to the cluster and about the cluster binary log's status,
respectively. The `Status' information is in the form of
comma-delimited set of name/value pairs.

The `connection' row's `Status' column contains the name/value pairs
described in the following table.

This table describes name and value pairs found in the `connection' row
`Status' column in the output of the *Note `SHOW ENGINE NDB STATUS':
show-engine. command.

Name                          Value
`cluster_node_id'             The node ID of the MySQL server in the
                              cluster
`connected_host'              The host name or IP address of the cluster
                              management server to which the MySQL
                              server is connected
`connected_port'              The port used by the MySQL server to
                              connect to the management server
                              (`connected_host')
`number_of_data_nodes'        The number of data nodes configured for
                              the cluster (that is, the number of
                              `[ndbd]' sections in the cluster
                              `config.ini' file)
`number_of_ready_data_nodes'  The number of data nodes in the cluster
                              that are actually running
`connect_count'               The number of times this *Note `mysqld':
                              mysqld. has connected or reconnected to
                              cluster data nodes

The `binlog' row's `Status' column contains information relating to
MySQL Cluster Replication. The name/value pairs it contains are
described in the following table.

This table describes name and value pairs found in the binlog row
Status column in the output of the SHOW ENGINE NDB STATUS command.

Name                          Value
`latest_epoch'                The most recent epoch most recently run on
                              this MySQL server (that is, the sequence
                              number of the most recent transaction run
                              on the server)
`latest_trans_epoch'          The most recent epoch processed by the
                              cluster's data nodes
`latest_received_binlog_epoch'The most recent epoch received by the
                              binlog thread
`latest_handled_binlog_epoch' The most recent epoch processed by the
                              binlog thread (for writing to the binlog)
`latest_applied_binlog_epoch' The most recent epoch actually written to
                              the binlog

See *Note mysql-cluster-replication::, for more information.

The remaining rows from the output of *Note `SHOW ENGINE NDB STATUS':
show-engine. which are most likely to prove useful in monitoring the
cluster are listed here by `Name':

   * `NdbTransaction': The number and size of `NdbTransaction' objects
     that have been created. An `NdbTransaction' is created each time a
     table schema operation (such as *Note `CREATE TABLE':
     create-table. or *Note `ALTER TABLE': alter-table.) is performed on
     an *Note `NDB': mysql-cluster. table.

   * `NdbOperation': The number and size of `NdbOperation' objects that
     have been created.

   * `NdbIndexScanOperation': The number and size of
     `NdbIndexScanOperation' objects that have been created.

   * `NdbIndexOperation': The number and size of `NdbIndexOperation'
     objects that have been created.

   * `NdbRecAttr': The number and size of `NdbRecAttr' objects that
     have been created. In general, one of these is created each time a
     data manipulation statement is performed by an SQL node.

   * `NdbBlob': The number and size of `NdbBlob' objects that have been
     created.  An `NdbBlob' is created for each new operation involving
     a *Note `BLOB': blob.  column in an *Note `NDB': mysql-cluster.
     table.

   * `NdbReceiver': The number and size of any `NdbReceiver' object
     that have been created. The number in the `created' column is the
     same as the number of data nodes in the cluster to which the MySQL
     server has connected.

*Note*:

*Note `SHOW ENGINE NDB STATUS': show-engine. returns an empty result if
no operations involving *Note `NDB': mysql-cluster. tables have been
performed during the current session by the MySQL client accessing the
SQL node on which this statement is run.


File: manual.info,  Node: show-engines,  Next: show-errors,  Prev: show-engine,  Up: show

13.7.5.17 SHOW ENGINES Syntax
.............................


     SHOW [STORAGE] ENGINES

*Note `SHOW ENGINES': show-engines. displays status information about
the server's storage engines. This is particularly useful for checking
whether a storage engine is supported, or to see what the default
engine is. This information can also be obtained from the
`INFORMATION_SCHEMA' *Note `ENGINES': engines-table. table. See *Note
engines-table::.

`SHOW TABLE TYPES' is a synonym, but is deprecated and is removed in
MySQL 5.5.


     mysql> SHOW ENGINES\G
     *************************** 1. row ***************************
           Engine: MEMORY
          Support: YES
          Comment: Hash based, stored in memory, useful for temporary tables
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 2. row ***************************
           Engine: MyISAM
          Support: DEFAULT
          Comment: Default engine as of MySQL 3.23 with great performance
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 3. row ***************************
           Engine: InnoDB
          Support: YES
          Comment: Supports transactions, row-level locking, and foreign keys
     Transactions: YES
               XA: YES
       Savepoints: YES
     *************************** 4. row ***************************
           Engine: EXAMPLE
          Support: YES
          Comment: Example storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 5. row ***************************
           Engine: ARCHIVE
          Support: YES
          Comment: Archive storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 6. row ***************************
           Engine: CSV
          Support: YES
          Comment: CSV storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 7. row ***************************
           Engine: BLACKHOLE
          Support: YES
          Comment: /dev/null storage engine (anything you write »
                   to it disappears)
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 8. row ***************************
           Engine: FEDERATED
          Support: YES
          Comment: Federated MySQL storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 9. row ***************************
           Engine: MRG_MYISAM
          Support: YES
          Comment: Collection of identical MyISAM tables
     Transactions: NO
               XA: NO
       Savepoints: NO

The output from *Note `SHOW ENGINES': show-engines. may vary according
to the MySQL version used and other factors. The values shown in the
`Support' column indicate the server's level of support for the storage
engine, as shown in the following table.

This table describes values for the `Support' column in the output of
the *Note `SHOW ENGINES': show-engines. command.

Value       Meaning
`YES'       The engine is supported and is active
`DEFAULT'   Like `YES', plus this is the default engine
`NO'        The engine is not supported
`DISABLED'  The engine is supported but has been disabled

A value of `NO' means that the server was compiled without support for
the engine, so it cannot be enabled at runtime.

A value of `DISABLED' occurs either because the server was started with
an option that disables the engine, or because not all options required
to enable it were given. In the latter case, the error log file should
contain a reason indicating why the option is disabled. See *Note
error-log::.

You might also see `DISABLED' for a storage engine if the server was
compiled to support it, but was started with a `--skip-ENGINE_NAME'
option. For the *Note `NDBCLUSTER': mysql-cluster. storage engine,
`DISABLED' means the server was compiled with support for MySQL
Cluster, but was not started with the `--ndbcluster' option.

All MySQL servers support `MyISAM' tables, because `MyISAM' is the
default storage engine.  It is not possible to disable `MyISAM'.

The `Transactions', `XA', and `Savepoints' columns were added in MySQL
5.1.2.  They indicate whether the storage engine supports transactions,
XA transactions, and savepoints, respectively.


File: manual.info,  Node: show-errors,  Next: show-events,  Prev: show-engines,  Up: show

13.7.5.18 SHOW ERRORS Syntax
............................


     SHOW ERRORS [LIMIT [OFFSET,] ROW_COUNT]
     SHOW COUNT(*) ERRORS

*Note `SHOW ERRORS': show-errors. is a diagnostic statement that is
similar to *Note `SHOW WARNINGS': show-warnings, except that it
displays information only for errors, rather than for errors, warnings,
and notes.

The `LIMIT' clause has the same syntax as for the *Note `SELECT':
select. statement. See *Note select::.

The *Note `SHOW COUNT(*) ERRORS': show-errors. statement displays the
number of errors. You can also retrieve this number from the
`error_count' variable:


     SHOW COUNT(*) ERRORS;
     SELECT @@error_count;

*Note `SHOW ERRORS': show-errors. and `error_count' apply only to
errors, not warnings or notes. In other respects, they are similar to
*Note `SHOW WARNINGS': show-warnings. and `warning_count'. In
particular, *Note `SHOW ERRORS': show-errors. cannot display
information for more than `max_error_count' messages, and `error_count'
can exceed the value of `max_error_count' if the number of errors
exceeds `max_error_count'.

For more information, see *Note show-warnings::.


File: manual.info,  Node: show-events,  Next: show-function-code,  Prev: show-errors,  Up: show

13.7.5.19 SHOW EVENTS Syntax
............................


     SHOW EVENTS [{FROM | IN} SCHEMA_NAME]
         [LIKE 'PATTERN' | WHERE EXPR]

This statement displays information about Event Manager events.  It
requires the `EVENT' privilege for the database from which the events
are to be shown.

In its simplest form, *Note `SHOW EVENTS': show-events.  lists all of
the events in the current schema:


     mysql> SELECT CURRENT_USER(), SCHEMA();
     +----------------+----------+
     | CURRENT_USER() | SCHEMA() |
     +----------------+----------+
     | jon@ghidora    | myschema |
     +----------------+----------+
     1 row in set (0.00 sec)

     mysql> SHOW EVENTS\G
     *************************** 1. row ***************************
                       Db: myschema
                     Name: e_daily
                  Definer: jon@ghidora
                Time zone: SYSTEM
                     Type: RECURRING
               Execute at: NULL
           Interval value: 10
           Interval field: SECOND
                   Starts: 2006-02-09 10:41:23
                     Ends: NULL
                   Status: ENABLED
               Originator: 0
     character_set_client: latin1
     collation_connection: latin1_swedish_ci
       Database Collation: latin1_swedish_ci

To see events for a specific schema, use the `FROM' clause. For
example, to see events for the `test' schema, use the following
statement:


     SHOW EVENTS FROM test;

The `LIKE' clause, if present, indicates which event names to match. The
`WHERE' clause can be given to select rows using more general
conditions, as discussed in *Note extended-show::.

*Note `SHOW EVENTS': show-events. output has the following columns:

   * `Db': The schema (database) on which the event is defined.

   * `Name': The name of the event.

   * `Time zone': The event time zone, which is the time zone used for
     scheduling the event and that is in effect within the event as it
     executes. The default value is `SYSTEM'.

     This column was added in MySQL 5.1.17. See the Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) for MySQL 5.1.17
     for important information if you are using the Event Scheduler and
     are upgrading to MySQL 5.1.17 or later from an earlier version.

   * `Definer': The account of the user who created the event, in
     `'USER_NAME'@'HOST_NAME'' format.

   * `Type': The event repetition type, either `ONE TIME' (transient) or
     `RECURRING' (repeating).

   * `Execute At': The date and time when a transient event is set to
     execute. Shown as a *Note `DATETIME': datetime. value.

     For a recurring event, the value of this column is always `NULL'.

   * `Interval Value': For a recurring event, the number of intervals
     to wait between event executions.

     For a transient event, the value of this column is always `NULL'.

   * `Interval Field': The time units used for the interval which a
     recurring event waits before repeating.

     For a transient event, the value of this column is always `NULL'.

   * `Starts': The start date and time for a recurring event. This is
     displayed as a *Note `DATETIME': datetime. value, and is `NULL' if
     no start date and time are defined for the event. (Prior to MySQL
     5.1.8, it defaulted to `'0000-00-00 00:00:00'' in such cases.)

     For a transient event, this column is always `NULL'.

   * `Ends': The end date and time for a recurring event. This is
     displayed as a *Note `DATETIME': datetime. value, and defaults to
     `NULL' if no end date and time is defined for the event.

     For a transient event, this column is always `NULL'.

   * `Status': The event status. One of `ENABLED', `DISABLED', or
     `SLAVESIDE_DISABLED'.

     `SLAVESIDE_DISABLED' was added in MySQL 5.1.18. This value
     indicates that the creation of the event occurred on another MySQL
     server acting as a replication master and replicated to the
     current MySQL server which is acting as a slave, but the event is
     not presently being executed on the slave.

   * `Originator': The server ID of the MySQL server on which the event
     was created. Defaults to 0. This column was added in MySQL 5.1.18.

   * `character_set_client' is the session value of the
     `character_set_client' system variable when the routine was
     created.  `collation_connection' is the session value of the
     `collation_connection' system variable when the routine was
     created.  `Database Collation' is the collation of the database
     with which the routine is associated. These columns were added in
     MySQL 5.1.21.

For more information about `SLAVE_DISABLED' and the `Originator'
column, see *Note replication-features-invoked::.

The event action statement is not shown in the output of *Note `SHOW
EVENTS': show-events. Use *Note `SHOW CREATE EVENT': show-create-event.
or the *Note `INFORMATION_SCHEMA.EVENTS': events-table. table.

Times displayed by *Note `SHOW EVENTS': show-events.  are given in the
event time zone (or UTC prior to MySQL 5.1.17), as discussed in *Note
events-metadata::.

The columns in the output of *Note `SHOW EVENTS': show-events. are
similar to, but not identical to the columns in the *Note
`INFORMATION_SCHEMA.EVENTS': events-table. table.  See *Note
events-table::.

*Note `SHOW EVENTS': show-events. was added in MySQL 5.1.6.

*Note*:

In MySQL 5.1.11 and earlier, *Note `SHOW EVENTS': show-events.
displayed only those events for which the current user was the definer,
and the *Note `SHOW FULL EVENTS': show-events. statement was used for
viewing events defined by all users on a given schema.  *Note `SHOW
FULL EVENTS': show-events. was removed in MySQL 5.1.12.


File: manual.info,  Node: show-function-code,  Next: show-function-status,  Prev: show-events,  Up: show

13.7.5.20 SHOW FUNCTION CODE Syntax
...................................


     SHOW FUNCTION CODE FUNC_NAME

This statement is similar to *Note `SHOW PROCEDURE CODE':
show-procedure-code. but for stored functions. See *Note
show-procedure-code::.


File: manual.info,  Node: show-function-status,  Next: show-grants,  Prev: show-function-code,  Up: show

13.7.5.21 SHOW FUNCTION STATUS Syntax
.....................................


     SHOW FUNCTION STATUS
         [LIKE 'PATTERN' | WHERE EXPR]

This statement is similar to *Note `SHOW PROCEDURE STATUS':
show-procedure-status. but for stored functions. See *Note
show-procedure-status::.


File: manual.info,  Node: show-grants,  Next: show-index,  Prev: show-function-status,  Up: show

13.7.5.22 SHOW GRANTS Syntax
............................


     SHOW GRANTS [FOR USER]

This statement lists the *Note `GRANT': grant.  statement or statements
that must be issued to duplicate the privileges that are granted to a
MySQL user account. The account is named using the same format as for
the *Note `GRANT': grant. statement; for example,
`'jeffrey'@'localhost''. If you specify only the user name part of the
account name, a host name part of `'%'' is used. For additional
information about specifying account names, see *Note grant::.


     mysql> SHOW GRANTS FOR 'root'@'localhost';
     +---------------------------------------------------------------------+
     | Grants for root@localhost                                           |
     +---------------------------------------------------------------------+
     | GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION |
     +---------------------------------------------------------------------+

To list the privileges granted to the account that you are using to
connect to the server, you can use any of the following statements:


     SHOW GRANTS;
     SHOW GRANTS FOR CURRENT_USER;
     SHOW GRANTS FOR CURRENT_USER();

As of MySQL 5.1.12, if `SHOW GRANTS FOR CURRENT_USER' (or any of the
equivalent syntaxes) is used in `DEFINER' context, such as within a
stored procedure that is defined with `SQL SECURITY DEFINER'), the
grants displayed are those of the definer and not the invoker.

*Note `SHOW GRANTS': show-grants. displays only the privileges granted
explicitly to the named account. Other privileges might be available to
the account, but they are not displayed. For example, if an anonymous
account exists, the named account might be able to use its privileges,
but *Note `SHOW GRANTS': show-grants. will not display them.

*Note `SHOW GRANTS': show-grants. requires the `SELECT' privilege for
the `mysql' database, except to see the privileges for the current user.


File: manual.info,  Node: show-index,  Next: show-innodb-status,  Prev: show-grants,  Up: show

13.7.5.23 SHOW INDEX Syntax
...........................


     SHOW {INDEX | INDEXES | KEYS}
         {FROM | IN} TBL_NAME
         [{FROM | IN} DB_NAME]
         [WHERE EXPR]

*Note `SHOW INDEX': show-index. returns table index information. The
format resembles that of the `SQLStatistics' call in ODBC.

*Note `SHOW INDEX': show-index. returns the following fields:

   * `Table'

     The name of the table.

   * `Non_unique'

     0 if the index cannot contain duplicates, 1 if it can.

   * `Key_name'

     The name of the index. If the index is the primary key, the name
     is always `PRIMARY'.

   * `Seq_in_index'

     The column sequence number in the index, starting with 1.

   * `Column_name'

     The column name.

   * `Collation'

     How the column is sorted in the index. In MySQL, this can have
     values ``A'' (Ascending) or `NULL' (Not sorted).

   * `Cardinality'

     An estimate of the number of unique values in the index.  This is
     updated by running *Note `ANALYZE TABLE': analyze-table. or *Note
     `myisamchk -a': myisamchk.  `Cardinality' is counted based on
     statistics stored as integers, so the value is not necessarily
     exact even for small tables. The higher the cardinality, the
     greater the chance that MySQL uses the index when doing joins.

   * `Sub_part'

     The number of indexed characters if the column is only partly
     indexed, `NULL' if the entire column is indexed.

   * `Packed'

     Indicates how the key is packed. `NULL' if it is not.

   * `Null'

     Contains `YES' if the column may contain `NULL' values and `''' if
     not.

   * `Index_type'

     The index method used (`BTREE', `FULLTEXT', `HASH', `RTREE').

   * `Comment'

     Information about the index not described in its own column, such
     as `disabled' if the index is disabled.

You can use DB_NAME.TBL_NAME as an alternative to the `TBL_NAME FROM
DB_NAME' syntax. These two statements are equivalent:


     SHOW INDEX FROM mytable FROM mydb;
     SHOW INDEX FROM mydb.mytable;

The `WHERE' clause can be given to select rows using more general
conditions, as discussed in *Note extended-show::.

You can also list a table's indexes with the *Note `mysqlshow -k
DB_NAME TBL_NAME': mysqlshow. command.


File: manual.info,  Node: show-innodb-status,  Next: show-master-status,  Prev: show-index,  Up: show

13.7.5.24 SHOW INNODB STATUS Syntax
...................................


     SHOW INNODB STATUS

In MySQL 5.1, this is a deprecated synonym for *Note `SHOW ENGINE
INNODB STATUS': show-engine. See *Note show-engine::.  *Note `SHOW
INNODB STATUS': show-innodb-status. is removed in MySQL 5.5.


File: manual.info,  Node: show-master-status,  Next: show-open-tables,  Prev: show-innodb-status,  Up: show

13.7.5.25 SHOW MASTER STATUS Syntax
...................................


     SHOW MASTER STATUS

This statement provides status information about the binary log files
of the master. It requires either the `SUPER' or `REPLICATION CLIENT'
privilege.

Example:


     mysql> SHOW MASTER STATUS;
     +---------------+----------+--------------+------------------+
     | File          | Position | Binlog_Do_DB | Binlog_Ignore_DB |
     +---------------+----------+--------------+------------------+
     | mysql-bin.003 | 73       | test         | manual,mysql     |
     +---------------+----------+--------------+------------------+


File: manual.info,  Node: show-open-tables,  Next: show-plugins,  Prev: show-master-status,  Up: show

13.7.5.26 SHOW OPEN TABLES Syntax
.................................


     SHOW OPEN TABLES [{FROM | IN} DB_NAME]
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW OPEN TABLES': show-open-tables. lists the non-`TEMPORARY'
tables that are currently open in the table cache. See *Note
table-cache::. The `WHERE' clause can be given to select rows using
more general conditions, as discussed in *Note extended-show::.

The `FROM' and `LIKE' clauses may be used beginning with MySQL 5.1.24.
The `LIKE' clause, if present, indicates which table names to match. The
`FROM' clause, if present, restricts the tables shown to those present
in the DB_NAME database.

*Note `SHOW OPEN TABLES': show-open-tables. output has the following
columns:

   * `Database'

     The database containing the table.

   * `Table'

     The table name.

   * `In_use'

     The number of table locks or lock requests there are for the
     table. For example, if one client acquires a lock for a table
     using `LOCK TABLE t1 WRITE', `In_use' will be 1. If another client
     issues `LOCK TABLE t1 WRITE' while the table remains locked, the
     client will block waiting for the lock, but the lock request
     causes `In_use' to be 2. If the count is zero, the table is open
     but not currently being used. `In_use' is also increased by the
     *Note `HANDLER ... OPEN': handler. statement and decreased by
     *Note `HANDLER ... CLOSE': handler.

   * `Name_locked'

     Whether the table name is locked. Name locking is used for
     operations such as dropping or renaming tables.


File: manual.info,  Node: show-plugins,  Next: show-privileges,  Prev: show-open-tables,  Up: show

13.7.5.27 SHOW PLUGINS Syntax
.............................


     SHOW PLUGINS

*Note `SHOW PLUGINS': show-plugins. displays information about server
plugins. Plugin information is also available in the
`INFORMATION_SCHEMA.PLUGINS' table. See *Note plugins-table::.

Example of *Note `SHOW PLUGINS': show-plugins. output:


     mysql> SHOW PLUGINS\G
     *************************** 1. row ***************************
        Name: binlog
      Status: ACTIVE
        Type: STORAGE ENGINE
     Library: NULL
     License: GPL
     *************************** 2. row ***************************
        Name: CSV
      Status: ACTIVE
        Type: STORAGE ENGINE
     Library: NULL
     License: GPL
     *************************** 3. row ***************************
        Name: MEMORY
      Status: ACTIVE
        Type: STORAGE ENGINE
     Library: NULL
     License: GPL
     *************************** 4. row ***************************
        Name: MyISAM
      Status: ACTIVE
        Type: STORAGE ENGINE
     Library: NULL
     License: GPL
     ...

*Note `SHOW PLUGINS': show-plugins. output has the following columns:

   * `Name': The name used to refer to the plugin in statements such as
     *Note `INSTALL PLUGIN': install-plugin. and *Note `UNINSTALL
     PLUGIN': uninstall-plugin.

   * `Status': The plugin status, one of `ACTIVE', `INACTIVE',
     `DISABLED', or `DELETED'.

   * `Type': The type of plugin, such as `STORAGE ENGINE' or
     `INFORMATION_SCHEMA'.

   * `Library': The name of the plugin shared object file. This is the
     name used to refer to the plugin file in statements such as *Note
     `INSTALL PLUGIN': install-plugin. and *Note `UNINSTALL PLUGIN':
     uninstall-plugin. This file is located in the directory named by
     the `plugin_dir' system variable. If the library name is `NULL',
     the plugin is compiled in and cannot be uninstalled with *Note
     `UNINSTALL PLUGIN': uninstall-plugin.

   * `License': How the plugin is licensed; for example, `GPL'.

For plugins installed with *Note `INSTALL PLUGIN': install-plugin, the
`Name' and `Library' values are also registered in the `mysql.plugin'
table.

For information about plugin data structures that form the basis of the
information displayed by *Note `SHOW PLUGINS': show-plugins, see *Note
plugin-api::.

`SHOW PLUGIN' was added in MySQL 5.1.5 and renamed to *Note `SHOW
PLUGINS': show-plugins. in 5.1.9.  `SHOW PLUGIN' is deprecated as of
5.1.9 and generates a warning, and is removed in MySQL 5.5.)


File: manual.info,  Node: show-privileges,  Next: show-procedure-code,  Prev: show-plugins,  Up: show

13.7.5.28 SHOW PRIVILEGES Syntax
................................


     SHOW PRIVILEGES

*Note `SHOW PRIVILEGES': show-privileges. shows the list of system
privileges that the MySQL server supports. The exact list of privileges
depends on the version of your server.


     mysql> SHOW PRIVILEGES\G
     *************************** 1. row ***************************
     Privilege: Alter
       Context: Tables
       Comment: To alter the table
     *************************** 2. row ***************************
     Privilege: Alter routine
       Context: Functions,Procedures
       Comment: To alter or drop stored functions/procedures
     *************************** 3. row ***************************
     Privilege: Create
       Context: Databases,Tables,Indexes
       Comment: To create new databases and tables
     *************************** 4. row ***************************
     Privilege: Create routine
       Context: Databases
       Comment: To use CREATE FUNCTION/PROCEDURE
     *************************** 5. row ***************************
     Privilege: Create temporary tables
       Context: Databases
       Comment: To use CREATE TEMPORARY TABLE
     ...

Privileges belonging to a specific user are displayed by the *Note
`SHOW GRANTS': show-grants. statement. See *Note show-grants::, for
more information.


File: manual.info,  Node: show-procedure-code,  Next: show-procedure-status,  Prev: show-privileges,  Up: show

13.7.5.29 SHOW PROCEDURE CODE Syntax
....................................


     SHOW PROCEDURE CODE PROC_NAME

This statement is a MySQL extension that is available only for servers
that have been built with debugging support. It displays a
representation of the internal implementation of the named stored
procedure. A similar statement, *Note `SHOW FUNCTION CODE':
show-function-code, displays information about stored functions (see
*Note show-function-code::).

To use either statement, you must be the owner of the routine or have
*Note `SELECT': select. access to the `mysql.proc' table.

If the named routine is available, each statement produces a result
set. Each row in the result set corresponds to one `instruction' in the
routine. The first column is `Pos', which is an ordinal number beginning
with 0. The second column is `Instruction', which contains an SQL
statement (usually changed from the original source), or a directive
which has meaning only to the stored-routine handler.


     mysql> DELIMITER //
     mysql> CREATE PROCEDURE p1 ()
         -> BEGIN
         ->   DECLARE fanta INT DEFAULT 55;
         ->   DROP TABLE t2;
         ->   LOOP
         ->     INSERT INTO t3 VALUES (fanta);
         ->     END LOOP;
         ->   END//
     Query OK, 0 rows affected (0.00 sec)

     mysql> SHOW PROCEDURE CODE p1//
     +-----+----------------------------------------+
     | Pos | Instruction                            |
     +-----+----------------------------------------+
     |   0 | set fanta@0 55                         |
     |   1 | stmt 9 "DROP TABLE t2"                 |
     |   2 | stmt 5 "INSERT INTO t3 VALUES (fanta)" |
     |   3 | jump 2                                 |
     +-----+----------------------------------------+
     4 rows in set (0.00 sec)

In this example, the nonexecutable `BEGIN' and `END' statements have
disappeared, and for the `DECLARE VARIABLE_NAME' statement, only the
executable part appears (the part where the default is assigned). For
each statement that is taken from source, there is a code word `stmt'
followed by a type (9 means `DROP', 5 means *Note `INSERT': insert, and
so on). The final row contains an instruction `jump 2', meaning `GOTO
instruction #2'.

These statements were added in MySQL 5.1.3.


File: manual.info,  Node: show-procedure-status,  Next: show-processlist,  Prev: show-procedure-code,  Up: show

13.7.5.30 SHOW PROCEDURE STATUS Syntax
......................................


     SHOW PROCEDURE STATUS
         [LIKE 'PATTERN' | WHERE EXPR]

This statement is a MySQL extension. It returns characteristics of a
stored procedure, such as the database, name, type, creator, creation
and modification dates, and character set information. A similar
statement, *Note `SHOW FUNCTION STATUS': show-function-status, displays
information about stored functions (see *Note show-function-status::).

The `LIKE' clause, if present, indicates which procedure or function
names to match. The `WHERE' clause can be given to select rows using
more general conditions, as discussed in *Note extended-show::.


     mysql> SHOW PROCEDURE STATUS LIKE 'sp1'\G
     *************************** 1. row ***************************
                       Db: test
                     Name: sp1
                     Type: PROCEDURE
                  Definer: testuser@localhost
                 Modified: 2004-08-03 15:29:37
                  Created: 2004-08-03 15:29:37
            Security_type: DEFINER
                  Comment:
     character_set_client: latin1
     collation_connection: latin1_swedish_ci
       Database Collation: latin1_swedish_ci

`character_set_client' is the session value of the
`character_set_client' system variable when the routine was created.
`collation_connection' is the session value of the
`collation_connection' system variable when the routine was created.
`Database Collation' is the collation of the database with which the
routine is associated. These columns were added in MySQL 5.1.21.

You can also get information about stored routines from the *Note
`ROUTINES': routines-table. table in `INFORMATION_SCHEMA'. See *Note
routines-table::.


File: manual.info,  Node: show-processlist,  Next: show-profile,  Prev: show-procedure-status,  Up: show

13.7.5.31 SHOW PROCESSLIST Syntax
.................................


     SHOW [FULL] PROCESSLIST

*Note `SHOW PROCESSLIST': show-processlist. shows you which threads are
running. You can also get this information from the `INFORMATION_SCHEMA'
*Note `PROCESSLIST': processlist-table. table or the *Note `mysqladmin
processlist': mysqladmin. command. If you have the `PROCESS' privilege,
you can see all threads. Otherwise, you can see only your own threads
(that is, threads associated with the MySQL account that you are
using). If you do not use the `FULL' keyword, only the first 100
characters of each statement are shown in the `Info' field.

This statement is very useful if you get the `too many connections'
error message and want to find out what is going on. MySQL reserves one
extra connection to be used by accounts that have the `SUPER'
privilege, to ensure that administrators should always be able to
connect and check the system (assuming that you are not giving this
privilege to all your users).

Threads can be killed with the *Note `KILL': kill. statement. See *Note
kill::.

Here is an example of *Note `SHOW PROCESSLIST': show-processlist.
output:


     mysql> SHOW FULL PROCESSLIST\G
     *************************** 1. row ***************************
     Id: 1
     User: system user
     Host:
     db: NULL
     Command: Connect
     Time: 1030455
     State: Waiting for master to send event
     Info: NULL
     *************************** 2. row ***************************
     Id: 2
     User: system user
     Host:
     db: NULL
     Command: Connect
     Time: 1004
     State: Has read all relay log; waiting for the slave
            I/O thread to update it
     Info: NULL
     *************************** 3. row ***************************
     Id: 3112
     User: replikator
     Host: artemis:2204
     db: NULL
     Command: Binlog Dump
     Time: 2144
     State: Has sent all binlog to slave; waiting for binlog to be updated
     Info: NULL
     *************************** 4. row ***************************
     Id: 3113
     User: replikator
     Host: iconnect2:45781
     db: NULL
     Command: Binlog Dump
     Time: 2086
     State: Has sent all binlog to slave; waiting for binlog to be updated
     Info: NULL
     *************************** 5. row ***************************
     Id: 3123
     User: stefan
     Host: localhost
     db: apollon
     Command: Query
     Time: 0
     State: NULL
     Info: SHOW FULL PROCESSLIST
     5 rows in set (0.00 sec)

The columns produced by *Note `SHOW PROCESSLIST': show-processlist.
have the following meanings:

   * `Id'

     The connection identifier.

   * `User'

     The MySQL user who issued the statement. If this is `system user',
     it refers to a nonclient thread spawned by the server to handle
     tasks internally.  This could be the I/O or SQL thread used on
     replication slaves or a delayed-row handler. `unauthenticated
     user' refers to a thread that has become associated with a client
     connection but for which authentication of the client user has not
     yet been done.  `event_scheduler' refers to the thread that
     monitors scheduled events. For `system user', there is no host
     specified in the `Host' column.

   * `Host'

     The host name of the client issuing the statement (except for
     `system user' where there is no host).  *Note `SHOW PROCESSLIST':
     show-processlist. reports the host name for TCP/IP connections in
     `HOST_NAME:CLIENT_PORT' format to make it easier to determine
     which client is doing what.

   * `db'

     The default database, if one is selected, otherwise `NULL'.

   * `Command'

     The type of command the thread is executing. For descriptions for
     thread commands, see *Note thread-information::. The value of this
     column corresponds to the `COM_XXX' commands of the client/server
     protocol and `Com_XXX' status variables. See *Note
     server-status-variables::

   * `Time'

     The time in seconds that the thread has been in its current state.
     For a slave SQL thread, the value is the number of seconds between
     the timestamp of the last replicated event and the real time of
     the slave machine. See *Note replication-implementation-details::.

   * `State'

     An action, event, or state that indicates what the thread is
     doing. Descriptions for `State' values can be found at *Note
     thread-information::.

     Most states correspond to very quick operations. If a thread stays
     in a given state for many seconds, there might be a problem that
     needs to be investigated.

     For the *Note `SHOW PROCESSLIST': show-processlist.  statement,
     the value of `State' is `NULL'.

   * `Info'

     The statement the thread is executing, or `NULL' if it is not
     executing any statement. The statement might be the one sent to the
     server, or an innermost statement if the statement executes other
     statements. For example, if a `CALL' statement executes a stored
     procedure that is executing a *Note `SELECT': select. statement,
     the `Info' value shows the *Note `SELECT': select. statement.


File: manual.info,  Node: show-profile,  Next: show-profiles,  Prev: show-processlist,  Up: show

13.7.5.32 SHOW PROFILE Syntax
.............................


     SHOW PROFILE [TYPE [, TYPE] ... ]
         [FOR QUERY N]
         [LIMIT ROW_COUNT [OFFSET OFFSET]]

     TYPE:
         ALL
       | BLOCK IO
       | CONTEXT SWITCHES
       | CPU
       | IPC
       | MEMORY
       | PAGE FAULTS
       | SOURCE
       | SWAPS

The *Note `SHOW PROFILE': show-profile. and *Note `SHOW PROFILES':
show-profiles. statements display profiling information that indicates
resource usage for statements executed during the course of the current
session.

Profiling is controlled by the `profiling' session variable, which has
a default value of 0 (`OFF').  Profiling is enabled by setting
`profiling' to 1 or `ON':


     mysql> SET profiling = 1;

*Note `SHOW PROFILES': show-profiles. displays a list of the most
recent statements sent to the server. The size of the list is
controlled by the `profiling_history_size' session variable, which has
a default value of 15. The maximum value is 100. Setting the value to 0
has the practical effect of disabling profiling.

All statements are profiled except *Note `SHOW PROFILE': show-profile.
and *Note `SHOW PROFILES': show-profiles, so you will find neither of
those statements in the profile list. Malformed statements are
profiled. For example, `SHOW PROFILING' is an illegal statement, and a
syntax error occurs if you try to execute it, but it will show up in
the profiling list.

*Note `SHOW PROFILE': show-profile. displays detailed information about
a single statement. Without the `FOR QUERY N' clause, the output
pertains to the most recently executed statement. If `FOR QUERY N' is
included, *Note `SHOW PROFILE': show-profile. displays information for
statement N. The values of N correspond to the `Query_ID' values
displayed by *Note `SHOW PROFILES': show-profiles.

The `LIMIT ROW_COUNT' clause may be given to limit the output to
ROW_COUNT rows. If `LIMIT' is given, `OFFSET OFFSET' may be added to
begin the output OFFSET rows into the full set of rows.

By default, *Note `SHOW PROFILE': show-profile. displays `Status' and
`Duration' columns. The `Status' values are like the `State' values
displayed by *Note `SHOW PROCESSLIST': show-processlist, although there
might be some minor differences in interpretion for the two statements
for some status values (see *Note thread-information::).

Optional TYPE values may be specified to display specific additional
types of information:

   * `ALL' displays all information

   * `BLOCK IO' displays counts for block input and output operations

   * `CONTEXT SWITCHES' displays counts for voluntary and involuntary
     context switches

   * `CPU' displays user and system CPU usage times

   * `IPC' displays counts for messages sent and received

   * `MEMORY' is not currently implemented

   * `PAGE FAULTS' displays counts for major and minor page faults

   * `SOURCE' displays the names of functions from the source code,
     together with the name and line number of the file in which the
     function occurs

   * `SWAPS' displays swap counts

Profiling is enabled per session. When a session ends, its profiling
information is lost.


     mysql> SELECT @@profiling;
     +-------------+
     | @@profiling |
     +-------------+
     |           0 |
     +-------------+
     1 row in set (0.00 sec)

     mysql> SET profiling = 1;
     Query OK, 0 rows affected (0.00 sec)

     mysql> DROP TABLE IF EXISTS t1;
     Query OK, 0 rows affected, 1 warning (0.00 sec)

     mysql> CREATE TABLE T1 (id INT);
     Query OK, 0 rows affected (0.01 sec)

     mysql> SHOW PROFILES;
     +----------+----------+--------------------------+
     | Query_ID | Duration | Query                    |
     +----------+----------+--------------------------+
     |        0 | 0.000088 | SET PROFILING = 1        |
     |        1 | 0.000136 | DROP TABLE IF EXISTS t1  |
     |        2 | 0.011947 | CREATE TABLE t1 (id INT) |
     +----------+----------+--------------------------+
     3 rows in set (0.00 sec)

     mysql> SHOW PROFILE;
     +----------------------+----------+
     | Status               | Duration |
     +----------------------+----------+
     | checking permissions | 0.000040 |
     | creating table       | 0.000056 |
     | After create         | 0.011363 |
     | query end            | 0.000375 |
     | freeing items        | 0.000089 |
     | logging slow query   | 0.000019 |
     | cleaning up          | 0.000005 |
     +----------------------+----------+
     7 rows in set (0.00 sec)

     mysql> SHOW PROFILE FOR QUERY 1;
     +--------------------+----------+
     | Status             | Duration |
     +--------------------+----------+
     | query end          | 0.000107 |
     | freeing items      | 0.000008 |
     | logging slow query | 0.000015 |
     | cleaning up        | 0.000006 |
     +--------------------+----------+
     4 rows in set (0.00 sec)

     mysql> SHOW PROFILE CPU FOR QUERY 2;
     +----------------------+----------+----------+------------+
     | Status               | Duration | CPU_user | CPU_system |
     +----------------------+----------+----------+------------+
     | checking permissions | 0.000040 | 0.000038 |   0.000002 |
     | creating table       | 0.000056 | 0.000028 |   0.000028 |
     | After create         | 0.011363 | 0.000217 |   0.001571 |
     | query end            | 0.000375 | 0.000013 |   0.000028 |
     | freeing items        | 0.000089 | 0.000010 |   0.000014 |
     | logging slow query   | 0.000019 | 0.000009 |   0.000010 |
     | cleaning up          | 0.000005 | 0.000003 |   0.000002 |
     +----------------------+----------+----------+------------+
     7 rows in set (0.00 sec)

*Note*:

Profiling is only partially functional on some architectures.  For
values that depend on the `getrusage()' system call, `NULL' is returned
on systems such as Windows that do not support the call. In addition,
profiling is per process and not per thread. This means that activity
on threads within the server other than your own may affect the timing
information that you see.

*Note `SHOW PROFILES': show-profiles. and *Note `SHOW PROFILE':
show-profile. were added in MySQL 5.1.24 (but were not added to binary
distributions by default until 5.1.28).

You can also get profiling information from the *Note `PROFILING':
profiling-table. table in `INFORMATION_SCHEMA'. See *Note
profiling-table::. For example, the following queries produce the same
result:


     SHOW PROFILE FOR QUERY 2;

     SELECT STATE, FORMAT(DURATION, 6) AS DURATION
     FROM INFORMATION_SCHEMA.PROFILING
     WHERE QUERY_ID = 2 ORDER BY SEQ;


File: manual.info,  Node: show-profiles,  Next: show-scheduler-status,  Prev: show-profile,  Up: show

13.7.5.33 SHOW PROFILES Syntax
..............................


     SHOW PROFILES

The *Note `SHOW PROFILES': show-profiles. statement, together with
*Note `SHOW PROFILE': show-profile, displays profiling information that
indicates resource usage for statements executed during the course of
the current session.  For more information, see *Note show-profile::.


File: manual.info,  Node: show-scheduler-status,  Next: show-slave-hosts,  Prev: show-profiles,  Up: show

13.7.5.34 SHOW SCHEDULER STATUS Syntax
......................................


     SHOW SCHEDULER STATUS

This statement provides debugging information regarding the Event
Scheduler's state. It is supported only in `-debug' builds of MySQL
5.1.11, and was removed in 5.1.12 and subsequent releases.

Sample output is shown here:


     +--------------------------------+---------------------+
     | Name                           | Value               |
     +--------------------------------+---------------------+
     | scheduler state                | INITIALIZED         |
     | thread_id                      | NULL                |
     | scheduler last locked at       | init_scheduler::313 |
     | scheduler last unlocked at     | init_scheduler::318 |
     | scheduler waiting on condition | 0                   |
     | scheduler workers count        | 0                   |
     | scheduler executed events      | 0                   |
     | scheduler data locked          | 0                   |
     | queue element count            | 1                   |
     | queue data locked              | 0                   |
     | queue data attempting lock     | 0                   |
     | queue last locked at           | create_event::218   |
     | queue last unlocked at         | create_event::222   |
     | queue last attempted lock at   | ::0                 |
     | queue waiting on condition     | 0                   |
     | next activation at             |    0-00-00 00:00:00 |
     +--------------------------------+---------------------+

In MySQL 5.1.12 and later, this information can be obtained using *Note
`mysqladmin debug': mysqladmin. (See *Note mysqladmin::.) For more
information about obtaining Event Scheduler status information, see
*Note events-status-info::.


File: manual.info,  Node: show-slave-hosts,  Next: show-slave-status,  Prev: show-scheduler-status,  Up: show

13.7.5.35 SHOW SLAVE HOSTS Syntax
.................................


     SHOW SLAVE HOSTS

Displays a list of replication slaves currently registered with the
master. Only slaves started with the `--report-host=HOST_NAME' option
are visible in this list.

`SHOW SLAVE HOSTS' should be executed on a server that acts as a
replication master. The statement displays information about servers
that are or have been connected as replication slaves, with each row of
the result corresponding to one slave server, as shown here:


     mysql> SHOW SLAVE HOSTS;
     +------------+-----------+------+-----------+
     | Server_id  | Host      | Port | Master_id |
     +------------+-----------+------+-----------+
     |  192168010 | iconnect2 | 3306 | 192168011 |
     | 1921680101 | athena    | 3306 | 192168011 |
     +------------+-----------+------+-----------+

   * `Server_id': The unique server ID of the slave server, as
     configured in the slave server's option file, or on the command
     line with `--server-id=VALUE'.

   * `Host': The host name of the slave server, as configured in the
     slave server's option file, or on the command line with
     `--report-host=HOST_NAME'.  Note that this can differ from the
     machine name as configured in the operating system.

   * `Port': The port on the master to which the slave server is
     listening.

   * `Master_id': The unique server ID of the master server that the
     slave server is replicating from.  This is the server ID of the
     server on which `SHOW SLAVE HOSTS' is executed, so this same value
     is listed for each row in the result.

Some MySQL versions report another variable, `Rpl_recovery_rank'. This
variable was never used, and was eventually removed. (Bug #13963)


File: manual.info,  Node: show-slave-status,  Next: show-status,  Prev: show-slave-hosts,  Up: show

13.7.5.36 SHOW SLAVE STATUS Syntax
..................................


     SHOW SLAVE STATUS

This statement provides status information on essential parameters of
the slave threads. It requires either the `SUPER' or `REPLICATION
CLIENT' privilege.

If you issue this statement using the *Note `mysql': mysql.  client,
you can use a `\G' statement terminator rather than a semicolon to
obtain a more readable vertical layout:


     mysql> SHOW SLAVE STATUS\G
     *************************** 1. row ***************************
                    Slave_IO_State: Waiting for master to send event
                       Master_Host: localhost
                       Master_User: root
                       Master_Port: 3306
                     Connect_Retry: 3
                   Master_Log_File: gbichot-bin.005
               Read_Master_Log_Pos: 79
                    Relay_Log_File: gbichot-relay-bin.005
                     Relay_Log_Pos: 548
             Relay_Master_Log_File: gbichot-bin.005
                  Slave_IO_Running: Yes
                 Slave_SQL_Running: Yes
                   Replicate_Do_DB:
               Replicate_Ignore_DB:
                Replicate_Do_Table:
            Replicate_Ignore_Table:
           Replicate_Wild_Do_Table:
       Replicate_Wild_Ignore_Table:
                        Last_Errno: 0
                        Last_Error:
                      Skip_Counter: 0
               Exec_Master_Log_Pos: 79
                   Relay_Log_Space: 552
                   Until_Condition: None
                    Until_Log_File:
                     Until_Log_Pos: 0
                Master_SSL_Allowed: No
                Master_SSL_CA_File:
                Master_SSL_CA_Path:
                   Master_SSL_Cert:
                 Master_SSL_Cipher:
                    Master_SSL_Key:
             Seconds_Behind_Master: 8
     Master_SSL_Verify_Server_Cert: No
                     Last_IO_Errno: 0
                     Last_IO_Error:
                    Last_SQL_Errno: 0
                    Last_SQL_Error:

The following list describes the fields returned by *Note `SHOW SLAVE
STATUS': show-slave-status. For additional information about
interpreting their meanings, see *Note
replication-administration-status::.

   * `Slave_IO_State'

     A copy of the `State' field of the *Note `SHOW PROCESSLIST':
     show-processlist. output for the slave I/O thread. This tells you
     what the thread is doing: trying to connect to the master, waiting
     for events from the master, reconnecting to the master, and so on.
     For a listing of possible states, see *Note
     slave-io-thread-states::.

   * `Master_Host'

     The master host that the slave is connected to.

   * `Master_User'

     The user name of the account used to connect to the master.

   * `Master_Port'

     The port used to connect to the master.

   * `Connect_Retry'

     The number of seconds between connect retries (default 60).  This
     can be set with the *Note `CHANGE MASTER TO': change-master-to.
     statement or `--master-connect-retry' option.

   * `Master_Log_File'

     The name of the master binary log file from which the I/O thread
     is currently reading.

   * `Read_Master_Log_Pos'

     The position in the current master binary log file up to which the
     I/O thread has read.

   * `Relay_Log_File'

     The name of the relay log file from which the SQL thread is
     currently reading and executing.

   * `Relay_Log_Pos'

     The position in the current relay log file up to which the SQL
     thread has read and executed.

   * `Relay_Master_Log_File'

     The name of the master binary log file containing the most recent
     event executed by the SQL thread.

   * `Slave_IO_Running'

     Whether the I/O thread is started and has connected successfully
     to the master. Internally, the state of this thread is represented
     by one of the following three values:

        * MYSQL_SLAVE_NOT_RUN

          The slave I/O thread is not running. For this state,
          `Slave_IO_Running' is `No'.

        * MYSQL_SLAVE_RUN_NOT_CONNECT

          The slave I/O thread is running, but is not connected to a
          replication master. For this state, `Slave_IO_Running'
          depends on the server version as shown in the following table.

          For the `MYSQL_SLAVE_RUN_NOT_CONNECT' state,
          `Slave_IO_Running' depends on the MySQL server version. This
          table shows MySQL version dependency for `Slave_IO_Running'.

          MySQL Version                   `Slave_IO_Running'
          4.1 (4.1.13 and earlier); 5.0   `Yes'
          (5.0.11 and earlier)            
          4.1 (4.1.14 and later); 5.0     `No'
          (5.0.12 and later)              
          5.1 (5.1.45 and earlier)        `No'
          5.1 (5.1.46 and later); 5.5     `Connecting'

        * MYSQL_SLAVE_RUN_CONNECT

          The slave I/O thread is running, and is connected to a
          replication master. For this state, `Slave_IO_Running' is
          `Yes'.

     Beginning with MySQL 5.1.46, the value of the `Slave_running'
     system status variable corresponds with this value. (Bug #30703)

   * `Slave_SQL_Running'

     Whether the SQL thread is started.

   * `Replicate_Do_DB', `Replicate_Ignore_DB'

     The lists of databases that were specified with the
     `--replicate-do-db' and `--replicate-ignore-db' options, if any.

   * `Replicate_Do_Table', `Replicate_Ignore_Table',
     `Replicate_Wild_Do_Table', `Replicate_Wild_Ignore_Table'

     The lists of tables that were specified with the
     `--replicate-do-table', `--replicate-ignore-table',
     `--replicate-wild-do-table', and `--replicate-wild-ignore-table'
     options, if any.

   * `Last_Errno', `Last_Error'

     As of MySQL 5.1.20, these columns are aliases for `Last_SQL_Errno'
     and `Last_SQL_Error'. Before 5.1.20, they indicate the error
     number and error message returned by the most recently executed
     statement. An error number of 0 and message of the empty string
     mean `no error.' If the `Last_Error' value is not empty, the error
     values also appear in the slave's error log.

     Beginning with MySQL 5.1.37, and with MySQL Cluster NDB 6.2.17,
     MySQL Cluster NDB 6.3.23, and MySQL Cluster NDB 6.4.3: Issuing
     *Note `RESET MASTER': reset-master.  or *Note `RESET SLAVE':
     reset-slave. resets the values shown in these columns. (Bug
     #34654, Bug #44270)

     *Note*:

     When the slave SQL thread receives an error, it reports the error
     first, then stops the SQL thread. This means that there is a small
     window of time during which *Note `SHOW SLAVE STATUS':
     show-slave-status. shows a nonzero value for `Last_SQL_Errno' even
     though `Slave_SQL_Running' still displays `Yes'.

   * `Skip_Counter'

     The current value of the `sql_slave_skip_counter' system variable.
     See *Note set-global-sql-slave-skip-counter::.

   * `Exec_Master_Log_Pos'

     The position in the current master binary log file to which the
     SQL thread has read and executed, marking the start of the next
     transaction or event to be processed. You can use this value with
     the *Note `CHANGE MASTER TO': change-master-to. statement's
     `MASTER_LOG_POS' option when starting a new slave from an existing
     slave, so that the new slave reads from this point. The
     coordinates given by (`Relay_Master_Log_File',
     `Exec_Master_Log_Pos') in the master's binary log correspond to
     the coordinates given by (`Relay_Log_File', `Relay_Log_Pos') in
     the relay log.

   * `Relay_Log_Space'

     The total combined size of all existing relay log files.

   * `Until_Condition', `Until_Log_File', `Until_Log_Pos'

     The values specified in the `UNTIL' clause of the *Note `START
     SLAVE': start-slave. statement.

     `Until_Condition' has these values:

        * `None' if no `UNTIL' clause was specified

        * `Master' if the slave is reading until a given position in
          the master's binary log

        * `Relay' if the slave is reading until a given position in its
          relay log

     `Until_Log_File' and `Until_Log_Pos' indicate the log file name
     and position that define the coordinates at which the SQL thread
     stops executing.

   * `Master_SSL_Allowed', `Master_SSL_CA_File', `Master_SSL_CA_Path',
     `Master_SSL_Cert', `Master_SSL_Cipher', `Master_SSL_Key',
     `Master_SSL_Verify_Server_Cert'

     These fields show the SSL parameters used by the slave to connect
     to the master, if any.

     `Master_SSL_Allowed' has these values:

        * `Yes' if an SSL connection to the master is permitted

        * `No' if an SSL connection to the master is not permitted

        * `Ignored' if an SSL connection is permitted but the slave
          server does not have SSL support enabled

     The values of the other SSL-related fields correspond to the
     values of the `MASTER_SSL_CA', `MASTER_SSL_CAPATH',
     `MASTER_SSL_CERT', `MASTER_SSL_CIPHER', `MASTER_SSL_KEY', and
     `MASTER_SSL_VERIFY_SERVER_CERT' options to the *Note `CHANGE
     MASTER TO': change-master-to.  statement. See *Note
     change-master-to::.  `MASTER_SSL_VERIFY_SERVER_CERT' was added in
     MySQL 5.1.18.

   * `Seconds_Behind_Master'

     This field is an indication of how `late' the slave is:

        * When the slave is actively processing updates, this field
          shows the difference between the current timestamp on the
          slave and the original timestamp logged on the master for the
          most event currently being processed on the slave.

        * When no event is currently being processed on the slave, this
          value is 0.

     In essence, this field measures the time difference in seconds
     between the slave SQL thread and the slave I/O thread. If the
     network connection between master and slave is fast, the slave I/O
     thread is very close to the master, so this field is a good
     approximation of how late the slave SQL thread is compared to the
     master. If the network is slow, this is _not_ a good approximation;
     the slave SQL thread may quite often be caught up with the
     slow-reading slave I/O thread, so `Seconds_Behind_Master' often
     shows a value of 0, even if the I/O thread is late compared to the
     master.  In other words, _this column is useful only for fast
     networks_.

     This time difference computation works even if the master and
     slave do not have identical clock times, provided that the
     difference, computed when the slave I/O thread starts, remains
     constant from then on. Any changes--including NTP updates--can
     lead to clock skews that can make calculation of
     `Seconds_Behind_Master' less reliable.

     This field is `NULL' (undefined or unknown) if the slave SQL
     thread is not running, or if the slave I/O thread is not running
     or is not connected to the master. For example, if the slave I/O
     thread is running but is not connected to the master and is
     sleeping for the number of seconds given by the *Note `CHANGE
     MASTER TO': change-master-to. statement or
     `--master-connect-retry' option (default 60) before reconnecting,
     the value is `NULL'. This is because the slave cannot know what
     the master is doing, and so cannot say reliably how late it is.

     The value of `Seconds_Behind_Master' is based on the timestamps
     stored in events, which are preserved through replication. This
     means that if a master M1 is itself a slave of M0, any event from
     M1's binary log that originates from M0's binary log has M0's
     timestamp for that event. This enables MySQL to replicate *Note
     `TIMESTAMP': datetime. successfully.  However, the problem for
     `Seconds_Behind_Master' is that if M1 also receives direct updates
     from clients, the `Seconds_Behind_Master' value randomly
     fluctuates because sometimes the last event from M1 originates
     from M0 and sometimes is the result of a direct update on M1.

   * `Last_IO_Errno', `Last_IO_Error'

     The error number and error message of the most recent error that
     caused the I/O thread to stop. An error number of 0 and message of
     the empty string mean `no error.' If the `Last_IO_Error' value is
     not empty, the error values also appear in the slave's error log.
     These columns were added in MySQL 5.1.20.

     MySQL Cluster

     Beginning with MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3:
     Issuing *Note `RESET MASTER': reset-master.  or *Note `RESET
     SLAVE': reset-slave. resets the values shown in these columns.
     This applies to MySQL Cluster only. (Bug #34654)

   * `Last_SQL_Errno', `Last_SQL_Error'

     The error number and error message of the most recent error that
     caused the SQL thread to stop. An error number of 0 and message of
     the empty string mean `no error.' If the `Last_SQL_Error' value is
     not empty, the error values also appear in the slave's error log.
     These columns were added in MySQL 5.1.20.

     Example:


          Last_SQL_Errno: 1051
          Last_SQL_Error: error 'Unknown table 'z'' on query 'drop table z'

     The message indicates that the table `z' existed on the master and
     was dropped there, but it did not exist on the slave, so *Note
     `DROP TABLE': drop-table. failed on the slave. (This might occur,
     for example, if you forget to copy the table to the slave when
     setting up replication.)

     MySQL Cluster

     Beginning with MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3:
     Issuing *Note `RESET MASTER': reset-master.  or *Note `RESET
     SLAVE': reset-slave. resets the values shown in these columns.
     This applies to MySQL Cluster only. (Bug #34654)

   * `Replicate_Ignore_Server_Ids' (MySQL Cluster only)

     Beginning with MySQL Cluster NDB 6.1.29, MySQL Cluster NDB 6.3.31,
     MySQL Cluster NDB 7.0.11, and MySQL Cluster NDB 7.1.0, you can
     tell a slave to ignore events from 0 or more masters using the
     `IGNORE_SERVER_IDS' option in a *Note `CHANGE MASTER TO':
     change-master-to.  statement. (See Bug #47037.) This is normally
     of interest only when using a circular or other multi-master
     replication setup.

     The message shown for `Replicate_Ignore_Server_Ids' consists of a
     space-delimited list of one or more numbers, the first value
     indicating the number of servers to be ignored; if not 0 (the
     default), this server-count value is followed by the actual server
     IDs. For example, if a *Note `CHANGE MASTER TO': change-master-to.
     statement containing the `IGNORE_SERVER_IDS = (2,6,9)' option has
     been issued to tell a slave to ignore masters having the server ID
     2, 6, or 9, that information appears as shown here:


            Replicate_Ignore_Server_Ids: 3 2 6 9

     `Replicate_Ignore_Server_Ids' filtering is performed by the I/O
     thread, rather than by the SQL thread, which means that events
     which are filtered out are not written to the relay log. This
     differs from the filtering actions taken by server options such
     `--replicate-do-table', which apply to the SQL thread.


File: manual.info,  Node: show-status,  Next: show-table-status,  Prev: show-slave-status,  Up: show

13.7.5.37 SHOW STATUS Syntax
............................


     SHOW [GLOBAL | SESSION] STATUS
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW STATUS': show-status. provides server status information.
This information also can be obtained using the *Note `mysqladmin
extended-status': mysqladmin. command. The `LIKE' clause, if present,
indicates which variable names to match. The `WHERE' clause can be
given to select rows using more general conditions, as discussed in
*Note extended-show::.  This statement does not require any privilege.
It requires only the ability to connect to the server.

Partial output is shown here. The list of names and values may be
different for your server. The meaning of each variable is given in
*Note server-status-variables::.


     mysql> SHOW STATUS;
     +--------------------------+------------+
     | Variable_name            | Value      |
     +--------------------------+------------+
     | Aborted_clients          | 0          |
     | Aborted_connects         | 0          |
     | Bytes_received           | 155372598  |
     | Bytes_sent               | 1176560426 |
     | Connections              | 30023      |
     | Created_tmp_disk_tables  | 0          |
     | Created_tmp_tables       | 8340       |
     | Created_tmp_files        | 60         |
     ...
     | Open_tables              | 1          |
     | Open_files               | 2          |
     | Open_streams             | 0          |
     | Opened_tables            | 44600      |
     | Questions                | 2026873    |
     ...
     | Table_locks_immediate    | 1920382    |
     | Table_locks_waited       | 0          |
     | Threads_cached           | 0          |
     | Threads_created          | 30022      |
     | Threads_connected        | 1          |
     | Threads_running          | 1          |
     | Uptime                   | 80380      |
     +--------------------------+------------+

With a `LIKE' clause, the statement displays only rows for those
variables with names that match the pattern:


     mysql> SHOW STATUS LIKE 'Key%';
     +--------------------+----------+
     | Variable_name      | Value    |
     +--------------------+----------+
     | Key_blocks_used    | 14955    |
     | Key_read_requests  | 96854827 |
     | Key_reads          | 162040   |
     | Key_write_requests | 7589728  |
     | Key_writes         | 3813196  |
     +--------------------+----------+

With the `GLOBAL' modifier, *Note `SHOW STATUS': show-status. displays
the status values for all connections to MySQL. With `SESSION', it
displays the status values for the current connection. If no modifier
is present, the default is `SESSION'. `LOCAL' is a synonym for
`SESSION'.

Some status variables have only a global value. For these, you get the
same value for both `GLOBAL' and `SESSION'. The scope for each status
variable is listed at *Note server-status-variables::.

Each invocation of the *Note `SHOW STATUS': show-status. statement uses
an internal temporary table and increments the global
`Created_tmp_tables' value.


File: manual.info,  Node: show-table-status,  Next: show-tables,  Prev: show-status,  Up: show

13.7.5.38 SHOW TABLE STATUS Syntax
..................................


     SHOW TABLE STATUS [{FROM | IN} DB_NAME]
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW TABLE STATUS': show-table-status. works likes *Note `SHOW
TABLES': show-tables, but provides a lot of information about each
non-`TEMPORARY' table. You can also get this list using the *Note
`mysqlshow --status DB_NAME': mysqlshow. command.  The `LIKE' clause,
if present, indicates which table names to match. The `WHERE' clause
can be given to select rows using more general conditions, as discussed
in *Note extended-show::.

This statement also displays information about views.

*Note `SHOW TABLE STATUS': show-table-status. output has the following
columns:

   * `Name'

     The name of the table.

   * `Engine'

     The storage engine for the table. See *Note storage-engines::.

   * `Version'

     The version number of the table's `.frm' file.

   * `Row_format'

     The row-storage format (`Fixed', `Dynamic', `Compressed',
     `Redundant', `Compact').  For `MyISAM' tables, (`Dynamic'
     corresponds to what *Note `myisamchk -dvv': myisamchk. reports as
     `Packed'. The format of `InnoDB' tables is reported as `Redundant'
     or `Compact'.  For the `Barracuda' file format of the `InnoDB
     Plugin', the format may be `Compressed' or `Dynamic'.

   * `Rows'

     The number of rows. Some storage engines, such as `MyISAM', store
     the exact count. For other storage engines, such as `InnoDB', this
     value is an approximation, and may vary from the actual value by
     as much as 40 to 50%. In such cases, use `SELECT COUNT(*)' to
     obtain an accurate count.

     The `Rows' value is `NULL' for tables in the `INFORMATION_SCHEMA'
     database.

   * `Avg_row_length'

     The average row length.

   * `Data_length'

     The length of the data file.

   * `Max_data_length'

     The maximum length of the data file. This is the total number of
     bytes of data that can be stored in the table, given the data
     pointer size used.

   * `Index_length'

     The length of the index file.

   * `Data_free'

     The number of allocated but unused bytes.

     Beginning with MySQL 5.1.24, this information is also shown for
     `InnoDB' tables (previously, it was in the `Comment' value).
     `InnoDB' tables report the free space of the tablespace to which
     the table belongs. For a table located in the shared tablespace,
     this is the free space of the shared tablespace. If you are using
     multiple tablespaces and the table has its own tablespace, the
     free space is for only that table. Free space means the number of
     completely free 1MB extents minus a safety margin. Even if free
     space displays as 0, it may be possible to insert rows as long as
     new extents need not be allocated.

     For partitioned tables, this value is only an estimate and may not
     be absolutely correct. A more accurate method of obtaining this
     information in such cases is to query the
     `INFORMATION_SCHEMA.PARTITIONS' table, as shown in this example:


          SELECT    SUM(DATA_FREE)
              FROM  INFORMATION_SCHEMA.PARTITIONS
              WHERE TABLE_SCHEMA = 'mydb'
              AND   TABLE_NAME   = 'mytable';

     For more information, see *Note partitions-table::.

   * `Auto_increment'

     The next `AUTO_INCREMENT' value.

   * `Create_time'

     When the table was created.

   * `Update_time'

     When the data file was last updated. For some storage engines,
     this value is `NULL'. For example, `InnoDB' stores multiple tables
     in its system tablespace
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_system_tablespace)
     and the data file timestamp does not apply. Even with
     file-per-table
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_file_per_table)
     mode with each `InnoDB' table in a separate `.ibd' file, change
     buffering
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_change_buffering)
     can delay the write to the data file, so the file modification
     time is different from the time of the last insert, update, or
     delete. For `MyISAM', the data file timestamp is used; however, on
     Windows the timestamp is not updated by updates so the value is
     inaccurate.

   * `Check_time'

     When the table was last checked. Not all storage engines update
     this time, in which case the value is always `NULL'.

   * `Collation'

     The table's character set and collation.

   * `Checksum'

     The live checksum value (if any).

   * `Create_options'

     Extra options used with *Note `CREATE TABLE': create-table. The
     original options supplied when *Note `CREATE TABLE': create-table.
     is called are retained and the options reported here may differ
     from the active table settings and options.

   * `Comment'

     The comment used when creating the table (or information as to why
     MySQL could not access the table information).

     Before MySQL 5.1.24, free space for `InnoDB' tables is reported in
     the comment.  As of 5.1.24, it is reported in the `Data_free'
     column.

For `MEMORY' tables, the `Data_length', `Max_data_length', and
`Index_length' values approximate the actual amount of allocated
memory. The allocation algorithm reserves memory in large amounts to
reduce the number of allocation operations.

For *Note `NDBCLUSTER': mysql-cluster. tables, the output of this
statement shows appropriate values for the `Avg_row_length' and
`Data_length' columns, with the exception that *Note `BLOB': blob.
columns are not taken into account. Prior to MySQL 5.1.21, the number
of MySQL Cluster replicas was shown in the `Comment' column as
`number_of_replicas' (Bug #11379).

For views, all the fields displayed by *Note `SHOW TABLE STATUS':
show-table-status. are `NULL' except that `Name' indicates the view
name and `Comment' says `view'.


File: manual.info,  Node: show-tables,  Next: show-triggers,  Prev: show-table-status,  Up: show

13.7.5.39 SHOW TABLES Syntax
............................


     SHOW [FULL] TABLES [{FROM | IN} DB_NAME]
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW TABLES': show-tables. lists the non-`TEMPORARY' tables in a
given database. You can also get this list using the *Note `mysqlshow
DB_NAME': mysqlshow. command. The `LIKE' clause, if present, indicates
which table names to match. The `WHERE' clause can be given to select
rows using more general conditions, as discussed in *Note
extended-show::.

Matching performed by the `LIKE' clause is dependent on the setting of
the `lower_case_table_names' system variable.

This statement also lists any views in the database. The `FULL'
modifier is supported such that *Note `SHOW FULL TABLES': show-tables.
displays a second output column. Values for the second column are `BASE
TABLE' for a table and `VIEW' for a view.

If you have no privileges for a base table or view, it does not show up
in the output from *Note `SHOW TABLES': show-tables. or *Note
`mysqlshow db_name': mysqlshow.


File: manual.info,  Node: show-triggers,  Next: show-variables,  Prev: show-tables,  Up: show

13.7.5.40 SHOW TRIGGERS Syntax
..............................


     SHOW TRIGGERS [{FROM | IN} DB_NAME]
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW TRIGGERS': show-triggers. lists the triggers currently
defined for tables in a database (the default database unless a `FROM'
clause is given). This statement returns results only for databases and
tables for which you have the `TRIGGER' privilege, or (prior to MySQL
5.1.23) if you have the `SUPER' privilege). The `LIKE' clause, if
present, indicates which table names to match (not trigger names) and
causes the statement to display triggers for those tables. The `WHERE'
clause can be given to select rows using more general conditions, as
discussed in *Note extended-show::.

For the trigger `ins_sum' as defined in *Note triggers::, the output of
this statement is as shown here:


     mysql> SHOW TRIGGERS LIKE 'acc%'\G
     *************************** 1. row ***************************
                  Trigger: ins_sum
                    Event: INSERT
                    Table: account
                Statement: SET @sum = @sum + NEW.amount
                   Timing: BEFORE
                  Created: NULL
                 sql_mode:
                  Definer: me@localhost
     character_set_client: latin1
     collation_connection: latin1_swedish_ci
       Database Collation: latin1_swedish_ci

*Note `SHOW TRIGGERS': show-triggers. output has the following columns:

   * `Trigger': The trigger name.

   * `Event': The type of operation that causes trigger activation. The
     value is `'INSERT'', `'UPDATE'', or `'DELETE''.

   * `Table': The table for which the trigger is defined.

   * `Statement': The trigger body; that is, the statement executed
     when the trigger activates.

   * `Timing': Whether the trigger activates before or after the
     triggering event. The value is `'BEFORE'' or `'AFTER''.

   * `Created': Currently, the value of this column is always `NULL'.

   * `sql_mode': The SQL mode in effect when the trigger executes.

   * `Definer': The account of the user who created the trigger, in
     `'USER_NAME'@'HOST_NAME'' format.

   * `character_set_client': The session value of the
     `character_set_client' system variable when the trigger was
     created. This column was added in MySQL 5.1.21.

   * `collation_connection': The session value of the
     `collation_connection' system variable when the trigger was
     created. This column was added in MySQL 5.1.21.

   * `Database Collation': The collation of the database with which the
     trigger is associated. This column was added in MySQL 5.1.21.

You can also obtain information about trigger objects from
`INFORMATION_SCHEMA', which contains a *Note `TRIGGERS':
triggers-table. table. See *Note triggers-table::.


File: manual.info,  Node: show-variables,  Next: show-warnings,  Prev: show-triggers,  Up: show

13.7.5.41 SHOW VARIABLES Syntax
...............................


     SHOW [GLOBAL | SESSION] VARIABLES
         [LIKE 'PATTERN' | WHERE EXPR]

*Note `SHOW VARIABLES': show-variables. shows the values of MySQL
system variables. This information also can be obtained using the *Note
`mysqladmin variables': mysqladmin. command. The `LIKE' clause, if
present, indicates which variable names to match. The `WHERE' clause
can be given to select rows using more general conditions, as discussed
in *Note extended-show::.  This statement does not require any
privilege. It requires only the ability to connect to the server.

With the `GLOBAL' modifier, *Note `SHOW VARIABLES': show-variables.
displays the values that are used for new connections to MySQL. If a
variable has no global value, the session value is displayed. With
`SESSION', *Note `SHOW VARIABLES': show-variables. displays the values
that are in effect for the current connection. If no modifier is
present, the default is `SESSION'. `LOCAL' is a synonym for `SESSION'.

*Note `SHOW VARIABLES': show-variables. is subject to a
version-dependent display-width limit. For variables with very long
values that are not completely displayed, use *Note `SELECT': select.
as a workaround. For example:


     SELECT @@GLOBAL.innodb_data_file_path;

If the default system variable values are unsuitable, you can set them
using command options when *Note `mysqld': mysqld.  starts, and most
can be changed at runtime with the *Note `SET': set-statement.
statement. See *Note using-system-variables::, and *Note
set-statement::.

Partial output is shown here. The list of names and values may be
different for your server.  *Note server-system-variables::, describes
the meaning of each variable, and *Note server-parameters::, provides
information about tuning them.


     mysql> SHOW VARIABLES;
     +---------------------------------+---------------------------+
     | Variable_name                   | Value                     |
     +---------------------------------+---------------------------+
     | auto_increment_increment        | 1                         |
     | auto_increment_offset           | 1                         |
     | automatic_sp_privileges         | ON                        |
     | back_log                        | 50                        |
     | basedir                         | /home/jon/bin/mysql-5.1/  |
     | binlog_cache_size               | 32768                     |
     | bulk_insert_buffer_size         | 8388608                   |
     | character_set_client            | latin1                    |
     | character_set_connection        | latin1                    |
     ...
     | max_user_connections            | 0                         |
     | max_write_lock_count            | 4294967295                |
     | multi_range_count               | 256                       |
     | myisam_data_pointer_size        | 6                         |
     | myisam_max_sort_file_size       | 2147483647                |
     | myisam_recover_options          | OFF                       |
     | myisam_repair_threads           | 1                         |
     | myisam_sort_buffer_size         | 8388608                   |
     | ndb_autoincrement_prefetch_sz   | 32                        |
     | ndb_cache_check_time            | 0                         |
     | ndb_force_send                  | ON                        |
     ...
     | time_zone                       | SYSTEM                    |
     | timed_mutexes                   | OFF                       |
     | tmp_table_size                  | 33554432                  |
     | tmpdir                          |                           |
     | transaction_alloc_block_size    | 8192                      |
     | transaction_prealloc_size       | 4096                      |
     | tx_isolation                    | REPEATABLE-READ           |
     | updatable_views_with_limit      | YES                       |
     | version                         | 5.1.6-alpha-log           |
     | version_comment                 | Source distribution       |
     | version_compile_machine         | i686                      |
     | version_compile_os              | suse-linux                |
     | wait_timeout                    | 28800                     |
     +---------------------------------+---------------------------+

With a `LIKE' clause, the statement displays only rows for those
variables with names that match the pattern. To obtain the row for a
specific variable, use a `LIKE' clause as shown:


     SHOW VARIABLES LIKE 'max_join_size';
     SHOW SESSION VARIABLES LIKE 'max_join_size';

To get a list of variables whose name match a pattern, use the ``%''
wildcard character in a `LIKE' clause:


     SHOW VARIABLES LIKE '%size%';
     SHOW GLOBAL VARIABLES LIKE '%size%';

Wildcard characters can be used in any position within the pattern to
be matched. Strictly speaking, because ``_'' is a wildcard that matches
any single character, you should escape it as ``\_'' to match it
literally. In practice, this is rarely necessary.


File: manual.info,  Node: show-warnings,  Prev: show-variables,  Up: show

13.7.5.42 SHOW WARNINGS Syntax
..............................


     SHOW WARNINGS [LIMIT [OFFSET,] ROW_COUNT]
     SHOW COUNT(*) WARNINGS

*Note `SHOW WARNINGS': show-warnings. is a diagnostic statement that
displays information about the conditions (errors, warnings, and notes)
resulting from executing a statement in the current session. Warnings
are generated for DML statements such as *Note `INSERT': insert, *Note
`UPDATE': update, and *Note `LOAD DATA INFILE': load-data. as well as
DDL statements such as *Note `CREATE TABLE': create-table. and *Note
`ALTER TABLE': alter-table.

The `LIMIT' clause has the same syntax as for the *Note `SELECT':
select. statement. See *Note select::.

*Note `SHOW WARNINGS': show-warnings. is also used following *Note
`EXPLAIN EXTENDED': explain-extended, to display the extra information
generated by *Note `EXPLAIN': explain. when the `EXTENDED' keyword is
used. See *Note explain-extended::.

*Note `SHOW WARNINGS': show-warnings. displays information about the
conditions resulting from the most recent statement in the current
session that generated messages. It shows nothing if the most recent
statement used a table and generated no messages. (That is, statements
that use a table but generate no messages clear the message list.)
Statements that do not use tables and do not generate messages have no
effect on the message list.

The *Note `SHOW COUNT(*) WARNINGS': show-warnings. diagnostic statement
displays the total number of errors, warnings, and notes. You can also
retrieve this number from the `warning_count' system variable:


     SHOW COUNT(*) WARNINGS;
     SELECT @@warning_count;

A related diagnostic statement, *Note `SHOW ERRORS': show-errors, shows
only error conditions (it excludes warnings and notes), and *Note `SHOW
COUNT(*) ERRORS': show-warnings. statement displays the total number of
errors.  See *Note show-errors::.

Here is a simple example that shows data-conversion warnings for *Note
`INSERT': insert.:


     mysql> CREATE TABLE t1 (a TINYINT NOT NULL, b CHAR(4));
     Query OK, 0 rows affected (0.05 sec)

     mysql> INSERT INTO t1 VALUES(10,'mysql'), (NULL,'test'), (300,'xyz');
     Query OK, 3 rows affected, 3 warnings (0.00 sec)
     Records: 3  Duplicates: 0  Warnings: 3

     mysql> SHOW WARNINGS\G
     *************************** 1. row ***************************
       Level: Warning
        Code: 1265
     Message: Data truncated for column 'b' at row 1
     *************************** 2. row ***************************
       Level: Warning
        Code: 1048
     Message: Column 'a' cannot be null
     *************************** 3. row ***************************
       Level: Warning
        Code: 1264
     Message: Out of range value for column 'a' at row 3
     3 rows in set (0.00 sec)

The `max_error_count' system variable controls the maximum number of
error, warning, and note messages for which the server stores
information, and thus the number of messages that *Note `SHOW
WARNINGS': show-warnings. displays. To change the number of messages
the server can store, change the value of `max_error_count'. The
default is 64.

`max_error_count' controls only how many messages are stored, not how
many are counted. The value of `warning_count' is not limited by
`max_error_count', even if the number of messages generated exceeds
`max_error_count'. The following example demonstrates this. The *Note
`ALTER TABLE': alter-table. statement produces three warning messages
(strict SQL mode is disabled for the example to prevent an error from
occuring after a single conversion issue). Only one message is stored
and displayed because `max_error_count' has been set to 1, but all
three are counted (as shown by the value of `warning_count'):


     mysql> SHOW VARIABLES LIKE 'max_error_count';
     +-----------------+-------+
     | Variable_name   | Value |
     +-----------------+-------+
     | max_error_count | 64    |
     +-----------------+-------+
     1 row in set (0.00 sec)

     mysql> SET max_error_count=1, sql_mode = '';
     Query OK, 0 rows affected (0.00 sec)

     mysql> ALTER TABLE t1 MODIFY b CHAR;
     Query OK, 3 rows affected, 3 warnings (0.00 sec)
     Records: 3  Duplicates: 0  Warnings: 3

     mysql> SHOW WARNINGS;
     +---------+------+----------------------------------------+
     | Level   | Code | Message                                |
     +---------+------+----------------------------------------+
     | Warning | 1263 | Data truncated for column 'b' at row 1 |
     +---------+------+----------------------------------------+
     1 row in set (0.00 sec)

     mysql> SELECT @@warning_count;
     +-----------------+
     | @@warning_count |
     +-----------------+
     |               3 |
     +-----------------+
     1 row in set (0.01 sec)

To disable message storage, set `max_error_count' to 0. In this case,
`warning_count' still indicates how many warnings occurred, but
messages are not stored and cannot be displayed.

The `sql_notes' system variable controls whether note messages increment
`warning_count' and whether the server stores them. By default,
`sql_notes' is 1, but if set to 0, notes do not increment
`warning_count' and the server does not store them:


     mysql> SET sql_notes = 1;
     mysql> DROP TABLE IF EXISTS test.no_such_table;
     Query OK, 0 rows affected, 1 warning (0.00 sec)
     mysql> SHOW WARNINGS;
     +-------+------+-------------------------------+
     | Level | Code | Message                       |
     +-------+------+-------------------------------+
     | Note  | 1051 | Unknown table 'no_such_table' |
     +-------+------+-------------------------------+
     1 row in set (0.00 sec)

     mysql> SET sql_notes = 0;
     mysql> DROP TABLE IF EXISTS test.no_such_table;
     Query OK, 0 rows affected (0.00 sec)
     mysql> SHOW WARNINGS;
     Empty set (0.00 sec)

The MySQL server sends to each client a count indicating the total
number of errors, warnings, and notes resulting from the most recent
statement executed by that client. From the C API, this value can be
obtained by calling *Note `mysql_warning_count()': mysql-warning-count.
See *Note mysql-warning-count::.


File: manual.info,  Node: other-administrative-sql,  Prev: show,  Up: sql-syntax-server-administration

13.7.6 Other Administrative Statements
--------------------------------------

* Menu:

* binlog::                       BINLOG Syntax
* cache-index::                  CACHE INDEX Syntax
* flush::                        FLUSH Syntax
* kill::                         KILL Syntax
* load-index::                   LOAD INDEX INTO CACHE Syntax
* reset::                        RESET Syntax


File: manual.info,  Node: binlog,  Next: cache-index,  Prev: other-administrative-sql,  Up: other-administrative-sql

13.7.6.1 BINLOG Syntax
......................


     BINLOG 'STR'

*Note `BINLOG': binlog. is an internal-use statement. It is generated
by the *Note `mysqlbinlog': mysqlbinlog.  program as the printable
representation of certain events in binary log files. (See *Note
mysqlbinlog::.) The `'STR'' value is a base 64-encoded string the that
server decodes to determine the data change indicated by the
corresponding event. This statement requires the `SUPER' privilege. It
was added in MySQL 5.1.5.


File: manual.info,  Node: cache-index,  Next: flush,  Prev: binlog,  Up: other-administrative-sql

13.7.6.2 CACHE INDEX Syntax
...........................


     CACHE INDEX
       TBL_INDEX_LIST [, TBL_INDEX_LIST] ...
       IN KEY_CACHE_NAME

     TBL_INDEX_LIST:
       TBL_NAME [[INDEX|KEY] (INDEX_NAME[, INDEX_NAME] ...)]

The *Note `CACHE INDEX': cache-index. statement assigns table indexes
to a specific key cache. It is used only for `MyISAM' tables. After the
indexes have been assigned, they can be preloaded into the cache if
desired with *Note `LOAD INDEX INTO CACHE': load-index.

The following statement assigns indexes from the tables `t1', `t2', and
`t3' to the key cache named `hot_cache':


     mysql> CACHE INDEX t1, t2, t3 IN hot_cache;
     +---------+--------------------+----------+----------+
     | Table   | Op                 | Msg_type | Msg_text |
     +---------+--------------------+----------+----------+
     | test.t1 | assign_to_keycache | status   | OK       |
     | test.t2 | assign_to_keycache | status   | OK       |
     | test.t3 | assign_to_keycache | status   | OK       |
     +---------+--------------------+----------+----------+

The syntax of *Note `CACHE INDEX': cache-index. enables you to specify
that only particular indexes from a table should be assigned to the
cache. The current implementation assigns all the table's indexes to
the cache, so there is no reason to specify anything other than the
table name.

The key cache referred to in a *Note `CACHE INDEX': cache-index.
statement can be created by setting its size with a parameter setting
statement or in the server parameter settings. For example:


     mysql> SET GLOBAL keycache1.key_buffer_size=128*1024;

Key cache parameters can be accessed as members of a structured system
variable. See *Note structured-system-variables::.

A key cache must exist before you can assign indexes to it:


     mysql> CACHE INDEX t1 IN non_existent_cache;
     ERROR 1284 (HY000): Unknown key cache 'non_existent_cache'

By default, table indexes are assigned to the main (default) key cache
created at the server startup. When a key cache is destroyed, all
indexes assigned to it become assigned to the default key cache again.

Index assignment affects the server globally: If one client assigns an
index to a given cache, this cache is used for all queries involving
the index, no matter which client issues the queries.


File: manual.info,  Node: flush,  Next: kill,  Prev: cache-index,  Up: other-administrative-sql

13.7.6.3 FLUSH Syntax
.....................


     FLUSH [NO_WRITE_TO_BINLOG | LOCAL]
         FLUSH_OPTION [, FLUSH_OPTION] ...

The *Note `FLUSH': flush. statement has several variant forms that
clear or reload various internal caches, flush tables, or acquire
locks. To execute *Note `FLUSH': flush, you must have the `RELOAD'
privilege.

By default, the server writes *Note `FLUSH': flush. statements to the
binary log so that they replicate to replication slaves. To suppress
logging, specify the optional `NO_WRITE_TO_BINLOG' keyword or its alias
`LOCAL'.

*Note*:

*Note `FLUSH LOGS': flush, *Note `FLUSH MASTER': flush, *Note `FLUSH
SLAVE': flush, and *Note `FLUSH TABLES WITH READ LOCK': flush. are not
written to the binary log in any case because they would cause problems
if replicated to a slave.

Sending a `SIGHUP' signal to the server causes several flush operations
to occur that are similar to various forms of the *Note `FLUSH': flush.
statement. See *Note server-signal-response::.

The *Note `FLUSH': flush. statement causes an implicit commit. See
*Note implicit-commit::.

The *Note `RESET': reset. statement is similar to *Note `FLUSH': flush.
See *Note reset::, for information about using the *Note `RESET':
reset. statement with replication.

FLUSH_OPTION can be any of the following items:

   * `DES_KEY_FILE'

     Reloads the DES keys from the file that was specified with the
     `--des-key-file' option at server startup time.

   * `HOSTS'

     Empties the host cache. You should flush the host cache if some of
     your hosts change IP address or if the error message `Host
     'HOST_NAME' is blocked' occurs. (See *Note blocked-host::.) When
     more than `max_connect_errors' errors occur successively for a
     given host while connecting to the MySQL server, MySQL assumes
     that something is wrong and blocks the host from further
     connection requests. Flushing the host cache enables further
     connection attempts from the host. The default value of
     `max_connect_errors' is 10.  To avoid this error message, start
     the server with `max_connect_errors' set to a large value.

   * `LOGS'

     Closes and reopens all log files. If binary logging is enabled,
     the sequence number of the binary log file is incremented by one
     relative to the previous file.

     Prior to MySQL 5.1.51, if you flush the logs using *Note `FLUSH
     LOGS': flush.  and *Note `mysqld': mysqld. is writing the error
     log to a file (for example, if it was started with the
     `--log-error' option), log file renaming may occur, as described in
     *Note error-log::.

   * `MASTER'

     Deletes all binary logs, resets the binary log index file and
     creates a new binary log.  *Note `FLUSH MASTER': flush. is
     deprecated in favor of *Note `RESET MASTER': reset-master.  *Note
     `FLUSH MASTER': flush. is still accepted in MySQL 5.1 for backward
     compatibility, but is removed in MySQL 5.6. See *Note
     reset-master::.

   * `PRIVILEGES'

     Reloads the privileges from the grant tables in the `mysql'
     database.

     The server caches information in memory as a result of *Note
     `GRANT': grant, *Note `CREATE USER': create-user, *Note `CREATE
     SERVER': create-server, and *Note `INSTALL PLUGIN':
     install-plugin. statements.  This memory is not released by the
     corresponding *Note `REVOKE': revoke, *Note `DROP USER': drop-user,
     *Note `DROP SERVER': drop-server, and *Note `UNINSTALL PLUGIN':
     uninstall-plugin. statements, so for a server that executes many
     instances of the statements that cause caching, there will be an
     increase in memory use. This cached memory can be freed with *Note
     `FLUSH PRIVILEGES': flush.

   * `QUERY CACHE'

     Defragment the query cache to better utilize its memory.  *Note
     `FLUSH QUERY CACHE': flush. does not remove any queries from the
     cache, unlike *Note `FLUSH TABLES': flush. or `RESET QUERY CACHE'.

   * `SLAVE'

     Resets all replication slave parameters, including relay log files
     and replication position in the master's binary logs.  *Note
     `FLUSH SLAVE': flush.  is deprecated in favor of *Note `RESET
     SLAVE': reset-slave.  *Note `FLUSH SLAVE': flush.  is still
     accepted in MySQL 5.1 for backward compatibility, but is removed
     in MySQL 5.6. See *Note reset-slave::.

   * `STATUS'

     This option adds the current thread's session status variable
     values to the global values and resets the session values to zero.
     Some global variables may be reset to zero as well. It also resets
     the counters for key caches (default and named) to zero and sets
     `Max_used_connections' to the current number of open connections.
     This is something you should use only when debugging a query. See
     *Note bug-reports::.

   * `TABLES'

     *Note `FLUSH TABLES': flush. flushes tables, and, depending on the
     variant used, acquires locks. The permitted syntax is discussed
     later in this section.

   * `USER_RESOURCES'

     Resets all per-hour user resources to zero. This enables clients
     that have reached their hourly connection, query, or update limits
     to resume activity immediately.  *Note `FLUSH USER_RESOURCES':
     flush. does not apply to the limit on maximum simultaneous
     connections. See *Note user-resources::.

The *Note `mysqladmin': mysqladmin. utility provides a command-line
interface to some flush operations, using commands such as
`flush-hosts', `flush-logs', `flush-privileges', `flush-status', and
`flush-tables'. See *Note mysqladmin::.

*Note*:

It is not possible to issue *Note `FLUSH': flush. statements within
stored functions or triggers. However, you may use *Note `FLUSH':
flush. in stored procedures, so long as these are not called from
stored functions or triggers. See *Note stored-program-restrictions::.

*FLUSH TABLES Syntax*

*Note `FLUSH TABLES': flush.  has several forms, described following.
*Note `FLUSH TABLE': flush. is a synonym for *Note `FLUSH TABLES':
flush, except that `TABLE' does not work with the `WITH READ LOCK'
variant.

   * `FLUSH TABLES'

     Closes all open tables, forces all tables in use to be closed, and
     flushes the query cache.  *Note `FLUSH TABLES': flush. also
     removes all query results from the query cache, like the `RESET
     QUERY CACHE' statement.

   * `FLUSH TABLES TBL_NAME [, TBL_NAME] ...'

     With a list of one or more comma-separated table names, this
     statement is like *Note `FLUSH TABLES': flush. with no names
     except that the server flushes only the named tables. No error
     occurs if a named table does not exist.

   * `FLUSH TABLES WITH READ LOCK'

     Closes all open tables and locks all tables for all databases with
     a global read lock. This is a very convenient way to get backups
     if you have a file system such as Veritas or ZFS that can take
     snapshots in time. Use *Note `UNLOCK TABLES': lock-tables. to
     release the lock.

     *Note `FLUSH TABLES WITH READ LOCK': flush. acquires a global read
     lock and not table locks, so it is not subject to the same
     behavior as *Note `LOCK TABLES': lock-tables. and *Note `UNLOCK
     TABLES': lock-tables. with respect to table locking and implicit
     commits:

        * *Note `UNLOCK TABLES': lock-tables. implicitly commits any
          active transaction only if any tables currently have been
          locked with *Note `LOCK TABLES': lock-tables.  The commit
          does not occur for *Note `UNLOCK TABLES': lock-tables.
          following *Note `FLUSH TABLES WITH READ LOCK': flush. because
          the latter statement does not acquire table locks.

        * Beginning a transaction causes table locks acquired with
          *Note `LOCK TABLES': lock-tables. to be released, as though
          you had executed *Note `UNLOCK TABLES': lock-tables.
          Beginning a transaction does not release a global read lock
          acquired with *Note `FLUSH TABLES WITH READ LOCK': flush.

     *Note `FLUSH TABLES WITH READ LOCK': flush. does not prevent the
     server from inserting rows into the log tables (see *Note
     log-destinations::).


File: manual.info,  Node: kill,  Next: load-index,  Prev: flush,  Up: other-administrative-sql

13.7.6.4 KILL Syntax
....................


     KILL [CONNECTION | QUERY] THREAD_ID

Each connection to *Note `mysqld': mysqld. runs in a separate thread.
You can see which threads are running with the *Note `SHOW
PROCESSLIST': show-processlist. statement and kill a thread with the
`KILL THREAD_ID' statement.

*Note `KILL': kill. permits an optional `CONNECTION' or `QUERY'
modifier:

   * *Note `KILL CONNECTION': kill. is the same as *Note `KILL': kill.
     with no modifier: It terminates the connection associated with the
     given THREAD_ID.

   * *Note `KILL QUERY': kill.  terminates the statement that the
     connection is currently executing, but leaves the connection
     itself intact.

If you have the `PROCESS' privilege, you can see all threads. If you
have the `SUPER' privilege, you can kill all threads and statements.
Otherwise, you can see and kill only your own threads and statements.

You can also use the *Note `mysqladmin processlist': mysqladmin.  and
*Note `mysqladmin kill': mysqladmin. commands to examine and kill
threads.

*Note*:

You cannot use *Note `KILL': kill. with the Embedded MySQL Server
library because the embedded server merely runs inside the threads of
the host application. It does not create any connection threads of its
own.

When you use *Note `KILL': kill, a thread-specific kill flag is set for
the thread. In most cases, it might take some time for the thread to
die because the kill flag is checked only at specific intervals:

   * In *Note `SELECT': select, `ORDER BY' and `GROUP BY' loops, the
     flag is checked after reading a block of rows. If the kill flag is
     set, the statement is aborted.

   * During *Note `ALTER TABLE': alter-table, the kill flag is checked
     before each block of rows are read from the original table. If the
     kill flag was set, the statement is aborted and the temporary
     table is deleted.

   * During *Note `UPDATE': update. or *Note `DELETE': delete.
     operations, the kill flag is checked after each block read and
     after each updated or deleted row. If the kill flag is set, the
     statement is aborted. Note that if you are not using transactions,
     the changes are not rolled back.

   * `GET_LOCK()' aborts and returns `NULL'.

   * An *Note `INSERT DELAYED': insert-delayed. thread quickly flushes
     (inserts) all rows it has in memory and then terminates.

   * If the thread is in the table lock handler (state: `Locked'), the
     table lock is quickly aborted.

   * If the thread is waiting for free disk space in a write call, the
     write is aborted with a `disk full' error message.

   * *Warning*:

     Killing a *Note `REPAIR TABLE': repair-table. or *Note `OPTIMIZE
     TABLE': optimize-table. operation on a `MyISAM' table results in a
     table that is corrupted and unusable. Any reads or writes to such a
     table fail until you optimize or repair it again (without
     interruption).


File: manual.info,  Node: load-index,  Next: reset,  Prev: kill,  Up: other-administrative-sql

13.7.6.5 LOAD INDEX INTO CACHE Syntax
.....................................


     LOAD INDEX INTO CACHE
       TBL_INDEX_LIST [, TBL_INDEX_LIST] ...

     TBL_INDEX_LIST:
       TBL_NAME
         [[INDEX|KEY] (INDEX_NAME[, INDEX_NAME] ...)]
         [IGNORE LEAVES]

The *Note `LOAD INDEX INTO CACHE': load-index. statement preloads a
table index into the key cache to which it has been assigned by an
explicit *Note `CACHE INDEX': cache-index. statement, or into the
default key cache otherwise.  *Note `LOAD INDEX INTO CACHE':
load-index. is used only for `MyISAM' tables. It is not supported for
tables having user-defined partitioning (see *Note
partitioning-limitations::.)

The `IGNORE LEAVES' modifier causes only blocks for the nonleaf nodes
of the index to be preloaded.

The following statement preloads nodes (index blocks) of indexes for
the tables `t1' and `t2':


     mysql> LOAD INDEX INTO CACHE t1, t2 IGNORE LEAVES;
     +---------+--------------+----------+----------+
     | Table   | Op           | Msg_type | Msg_text |
     +---------+--------------+----------+----------+
     | test.t1 | preload_keys | status   | OK       |
     | test.t2 | preload_keys | status   | OK       |
     +---------+--------------+----------+----------+

This statement preloads all index blocks from `t1'. It preloads only
blocks for the nonleaf nodes from `t2'.

The syntax of *Note `LOAD INDEX INTO CACHE': load-index. enables you to
specify that only particular indexes from a table should be preloaded.
The current implementation preloads all the table's indexes into the
cache, so there is no reason to specify anything other than the table
name.

*Note `LOAD INDEX INTO CACHE ... IGNORE LEAVES': load-index. fails
unless all indexes in a table have the same block size. (Prior to MySQL
5.1.19, it fails even without `IGNORE LEAVES'.) You can determine index
block sizes for a table by using *Note `myisamchk -dv': myisamchk. and
checking the `Blocksize' column.


File: manual.info,  Node: reset,  Prev: load-index,  Up: other-administrative-sql

13.7.6.6 RESET Syntax
.....................


     RESET RESET_OPTION [, RESET_OPTION] ...

The *Note `RESET': reset. statement is used to clear the state of
various server operations. You must have the `RELOAD' privilege to
execute *Note `RESET': reset.

*Note `RESET': reset. acts as a stronger version of the *Note `FLUSH':
flush. statement. See *Note flush::.

The *Note `RESET': reset. statement causes an implicit commit. See
*Note implicit-commit::.

RESET_OPTION can be any of the following:

   * `MASTER'

     Deletes all binary logs listed in the index file, resets the
     binary log index file to be empty, and creates a new binary log
     file.

   * `QUERY CACHE'

     Removes all query results from the query cache.

   * `SLAVE'

     Makes the slave forget its replication position in the master
     binary logs. Also resets the relay log by deleting any existing
     relay log files and beginning a new one.


File: manual.info,  Node: sql-syntax-utility,  Prev: sql-syntax-server-administration,  Up: sql-syntax

13.8 MySQL Utility Statements
=============================

* Menu:

* describe::                     DESCRIBE Syntax
* explain::                      EXPLAIN Syntax
* help::                         HELP Syntax
* use::                          USE Syntax


File: manual.info,  Node: describe,  Next: explain,  Prev: sql-syntax-utility,  Up: sql-syntax-utility

13.8.1 DESCRIBE Syntax
----------------------

The *Note `DESCRIBE': describe. and *Note `EXPLAIN': explain.
statements are synonyms, used either to obtain information about table
structure or query execution plans. For more information, see *Note
show-columns::, and *Note explain::.


File: manual.info,  Node: explain,  Next: help,  Prev: describe,  Up: sql-syntax-utility

13.8.2 EXPLAIN Syntax
---------------------


     {EXPLAIN | DESCRIBE | DESC}
         TBL_NAME [COL_NAME | WILD]

     {EXPLAIN | DESCRIBE | DESC}
         [EXPLAIN_TYPE] SELECT SELECT_OPTIONS

     EXPLAIN_TYPE: {EXTENDED | PARTITIONS}

The *Note `DESCRIBE': describe. and *Note `EXPLAIN': explain.
statements are synonyms. In practice, the *Note `DESCRIBE': describe.
keyword is more often used to obtain information about table structure,
whereas *Note `EXPLAIN': explain. is used to obtain a query execution
plan (that is, an explanation of how MySQL would execute a query). The
following discussion uses the *Note `DESCRIBE': describe. and *Note
`EXPLAIN': explain. keywords in accordance with those uses, but the
MySQL parser treats them as completely synonymous.

*Obtaining Table Structure Information*

*Note `DESCRIBE': describe. provides information about the columns in a
table:


     mysql> DESCRIBE City;
     +------------+----------+------+-----+---------+----------------+
     | Field      | Type     | Null | Key | Default | Extra          |
     +------------+----------+------+-----+---------+----------------+
     | Id         | int(11)  | NO   | PRI | NULL    | auto_increment |
     | Name       | char(35) | NO   |     |         |                |
     | Country    | char(3)  | NO   | UNI |         |                |
     | District   | char(20) | YES  | MUL |         |                |
     | Population | int(11)  | NO   |     | 0       |                |
     +------------+----------+------+-----+---------+----------------+

*Note `DESCRIBE': describe. is a shortcut for *Note `SHOW COLUMNS':
show-columns. These statements also display information for views. The
description for *Note `SHOW COLUMNS': show-columns. provides more
information about the output columns. See *Note show-columns::.

By default, *Note `DESCRIBE': describe. displays information about all
columns in the table.  COL_NAME, if given, is the name of a column in
the table. In this case, the statement displays information only for
the named column.  WILD, if given, is a pattern string. It can contain
the SQL ``%'' and ``_'' wildcard characters. In this case, the
statement displays output only for the columns with names matching the
string. There is no need to enclose the string within quotation marks
unless it contains spaces or other special characters.

The *Note `DESCRIBE': describe. statement is provided for compatibility
with Oracle.

The *Note `SHOW CREATE TABLE': show-create-table, *Note `SHOW TABLE
STATUS': show-table-status, and *Note `SHOW INDEX': show-index.
statements also provide information about tables. See *Note show::.

*Obtaining Execution Plan Information*

The *Note `EXPLAIN': explain. statement provides information about how
MySQL executes statements:

   * When you precede a *Note `SELECT': select.  statement with the
     keyword *Note `EXPLAIN': explain, MySQL displays information from
     the optimizer about the statement execution plan. That is, MySQL
     explains how it would process the statement, including information
     about how tables are joined and in which order. For information
     about using *Note `EXPLAIN': explain. to obtain execution plan
     information, see *Note explain-output::.

   * *Note `EXPLAIN EXTENDED': explain-extended. can be used to obtain
     additional execution plan information. See *Note
     explain-extended::.

   * As of MySQL 5.1.5, *Note `EXPLAIN PARTITIONS': explain. is useful
     for examining queries involving partitioned tables. See *Note
     partitioning-info::.

With the help of *Note `EXPLAIN': explain, you can see where you should
add indexes to tables so that the statement executes faster by using
indexes to find rows. You can also use *Note `EXPLAIN': explain. to
check whether the optimizer joins the tables in an optimal order. To
give a hint to the optimizer to use a join order corresponding to the
order in which the tables are named in a *Note `SELECT': select.
statement, begin the statement with `SELECT STRAIGHT_JOIN' rather than
just *Note `SELECT': select. (See *Note select::.)

If you have a problem with indexes not being used when you believe that
they should be, run *Note `ANALYZE TABLE': analyze-table. to update
table statistics, such as cardinality of keys, that can affect the
choices the optimizer makes. See *Note analyze-table::.


File: manual.info,  Node: help,  Next: use,  Prev: explain,  Up: sql-syntax-utility

13.8.3 HELP Syntax
------------------


     HELP 'SEARCH_STRING'

The *Note `HELP': help. statement returns online information from the
MySQL Reference manual. Its proper operation requires that the help
tables in the `mysql' database be initialized with help topic
information (see *Note server-side-help-support::).

The *Note `HELP': help. statement searches the help tables for the
given search string and displays the result of the search. The search
string is not case sensitive.

The search string can contain the wildcard characters ``%'' and ``_''.
These have the same meaning as for pattern-matching operations
performed with the `LIKE' operator. For example, `HELP 'rep%'' returns
a list of topics that begin with `rep'.

The HELP statement understands several types of search strings:

   * At the most general level, use `contents' to retrieve a list of
     the top-level help categories:


          HELP 'contents'

   * For a list of topics in a given help category, such as `Data
     Types', use the category name:


          HELP 'data types'

   * For help on a specific help topic, such as the `ASCII()' function
     or the *Note `CREATE TABLE': create-table. statement, use the
     associated keyword or keywords:


          HELP 'ascii'
          HELP 'create table'

In other words, the search string matches a category, many topics, or a
single topic. You cannot necessarily tell in advance whether a given
search string will return a list of items or the help information for a
single help topic. However, you can tell what kind of response *Note
`HELP': help. returned by examining the number of rows and columns in
the result set.

The following descriptions indicate the forms that the result set can
take. Output for the example statements is shown using the familiar
`tabular' or `vertical' format that you see when using the *Note
`mysql': mysql. client, but note that *Note `mysql': mysql. itself
reformats *Note `HELP': help. result sets in a different way.

   * Empty result set

     No match could be found for the search string.

   * Result set containing a single row with three columns

     This means that the search string yielded a hit for the help
     topic. The result has three columns:

        * `name': The topic name.

        * `description': Descriptive help text for the topic.

        * `example': Usage example or examples.  This column might be
          blank.

     Example: `HELP 'replace''

     Yields:


          name: REPLACE
          description: Syntax:
          REPLACE(str,from_str,to_str)

          Returns the string str with all occurrences of the string from_str
          replaced by the string to_str. REPLACE() performs a case-sensitive
          match when searching for from_str.
          example: mysql> SELECT REPLACE('www.mysql.com', 'w', 'Ww');
                  -> 'WwWwWw.mysql.com'

   * Result set containing multiple rows with two columns

     This means that the search string matched many help topics.  The
     result set indicates the help topic names:

        * `name': The help topic name.

        * `is_it_category': `Y' if the name represents a help category,
          `N' if it does not. If it does not, the `name' value when
          specified as the argument to the *Note `HELP': help.
          statement should yield a single-row result set containing a
          description for the named item.

     Example: `HELP 'status''

     Yields:


          +-----------------------+----------------+
          | name                  | is_it_category |
          +-----------------------+----------------+
          | SHOW                  | N              |
          | SHOW ENGINE           | N              |
          | SHOW INNODB STATUS    | N              |
          | SHOW MASTER STATUS    | N              |
          | SHOW PROCEDURE STATUS | N              |
          | SHOW SLAVE STATUS     | N              |
          | SHOW STATUS           | N              |
          | SHOW TABLE STATUS     | N              |
          +-----------------------+----------------+

   * Result set containing multiple rows with three columns

     This means the search string matches a category. The result set
     contains category entries:

        * `source_category_name': The help category name.

        * `name': The category or topic name

        * `is_it_category': `Y' if the name represents a help category,
          `N' if it does not. If it does not, the `name' value when
          specified as the argument to the *Note `HELP': help.
          statement should yield a single-row result set containing a
          description for the named item.

     Example: `HELP 'functions''

     Yields:


          +----------------------+-------------------------+----------------+
          | source_category_name | name                    | is_it_category |
          +----------------------+-------------------------+----------------+
          | Functions            | CREATE FUNCTION         | N              |
          | Functions            | DROP FUNCTION           | N              |
          | Functions            | Bit Functions           | Y              |
          | Functions            | Comparison operators    | Y              |
          | Functions            | Control flow functions  | Y              |
          | Functions            | Date and Time Functions | Y              |
          | Functions            | Encryption Functions    | Y              |
          | Functions            | Information Functions   | Y              |
          | Functions            | Logical operators       | Y              |
          | Functions            | Miscellaneous Functions | Y              |
          | Functions            | Numeric Functions       | Y              |
          | Functions            | String Functions        | Y              |
          +----------------------+-------------------------+----------------+

Before MySQL 5.1.17, if you intend to use the *Note `HELP': help.
statement while other tables are locked with *Note `LOCK TABLES':
lock-tables, you must also lock the required `mysql.help_XXX' tables.
See *Note lock-tables::.


File: manual.info,  Node: use,  Prev: help,  Up: sql-syntax-utility

13.8.4 USE Syntax
-----------------


     USE DB_NAME

The `USE DB_NAME' statement tells MySQL to use the DB_NAME database as
the default (current) database for subsequent statements. The database
remains the default until the end of the session or another *Note
`USE': use. statement is issued:


     USE db1;
     SELECT COUNT(*) FROM mytable;   # selects from db1.mytable
     USE db2;
     SELECT COUNT(*) FROM mytable;   # selects from db2.mytable

Making a particular database the default by means of the *Note `USE':
use. statement does not preclude you from accessing tables in other
databases. The following example accesses the `author' table from the
`db1' database and the `editor' table from the `db2' database:


     USE db1;
     SELECT author_name,editor_name FROM author,db2.editor
       WHERE author.editor_id = db2.editor.editor_id;


File: manual.info,  Node: storage-engines,  Next: ha-overview,  Prev: sql-syntax,  Up: Top

14 Storage Engines
******************

* Menu:

* storage-engine-compare-transactions::  Comparing Transaction and Nontransaction Engines
* storage-engines-other::        Other Storage Engines
* storage-engine-setting::       Setting the Storage Engine
* pluggable-storage-overview::   Overview of MySQL Storage Engine Architecture
* myisam-storage-engine::        The MyISAM Storage Engine
* innodb-storage-engine::        The InnoDB Storage Engine
* se-db2::                       The IBMDB2I Storage Engine
* merge-storage-engine::         The MERGE Storage Engine
* memory-storage-engine::        The MEMORY Storage Engine
* example-storage-engine::       The EXAMPLE Storage Engine
* federated-storage-engine::     The FEDERATED Storage Engine
* archive-storage-engine::       The ARCHIVE Storage Engine
* csv-storage-engine::           The CSV Storage Engine
* blackhole-storage-engine::     The BLACKHOLE Storage Engine

MySQL supports several storage engines that act as handlers for
different table types. MySQL storage engines include both those that
handle transaction-safe tables and those that handle
nontransaction-safe tables.

As of MySQL 5.1, MySQL Server uses a pluggable storage engine
architecture that enables storage engines to be loaded into and
unloaded from a running MySQL server.

*Note*:

Prior to MySQL 5.1.38, the pluggable storage engine architecture is
supported on Unix platforms only and pluggable storage engines are not
supported on Windows.

To determine which storage engines your server supports by using the
*Note `SHOW ENGINES': show-engines. statement. The value in the
`Support' column indicates whether an engine can be used. A value of
`YES', `NO', or `DEFAULT' indicates that an engine is available, not
available, or available and currently set as the default storage engine.


     mysql> SHOW ENGINES\G
     *************************** 1. row ***************************
           Engine: FEDERATED
          Support: NO
          Comment: Federated MySQL storage engine
     Transactions: NULL
               XA: NULL
       Savepoints: NULL
     *************************** 2. row ***************************
           Engine: MRG_MYISAM
          Support: YES
          Comment: Collection of identical MyISAM tables
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 3. row ***************************
           Engine: MyISAM
          Support: DEFAULT
          Comment: Default engine as of MySQL 3.23 with great performance
     Transactions: NO
               XA: NO
       Savepoints: NO
     ...

This chapter describes each of the MySQL storage engines except for
*Note `NDBCLUSTER': mysql-cluster, which is covered in *Note
mysql-cluster::. It also contains a description of the pluggable
storage engine architecture (see *Note pluggable-storage-overview::).

For information about storage engine support offered in commercial
MySQL Server binaries, see `MySQL Enterprise Server 5.1'
(http://www.mysql.com/products/enterprise/server.html), on the MySQL
Web site.  The storage engines available might depend on which edition
of Enterprise Server you are using.

For answers to some commonly asked questions about MySQL storage
engines, see *Note faqs-storage-engines::.

*MySQL 5.1 supported storage engines*

   * *Note `MyISAM': myisam-storage-engine.: The default MySQL storage
     engine and the one that is used the most in Web, data warehousing,
     and other application environments. `MyISAM' is supported in all
     MySQL configurations, and is the default storage engine unless you
     have configured MySQL to use a different one by default.

   * *Note `InnoDB': innodb-storage-engine.: A transaction-safe (ACID
     compliant) storage engine for MySQL that has commit, rollback, and
     crash-recovery capabilities to protect user data. `InnoDB'
     row-level locking (without escalation to coarser granularity
     locks) and Oracle-style consistent nonlocking reads increase
     multi-user concurrency and performance. `InnoDB' stores user data
     in clustered indexes to reduce I/O for common queries based on
     primary keys. To maintain data integrity, `InnoDB' also supports
     `FOREIGN KEY' referential-integrity constraints.

   * *Note `Memory': memory-storage-engine.: Stores all data in RAM for
     extremely fast access in environments that require quick lookups
     of reference and other like data.  This engine was formerly known
     as the `HEAP' engine.

   * *Note `Merge': merge-storage-engine.: Enables a MySQL DBA or
     developer to logically group a series of identical `MyISAM' tables
     and reference them as one object. Good for VLDB environments such
     as data warehousing.

   * *Note `Archive': archive-storage-engine.: Provides the perfect
     solution for storing and retrieving large amounts of
     seldom-referenced historical, archived, or security audit
     information.

   * *Note `Federated': federated-storage-engine.: Offers the ability
     to link separate MySQL servers to create one logical database from
     many physical servers. Very good for distributed or data mart
     environments.

   * *Note `NDB': mysql-cluster. (also known as *Note `NDBCLUSTER':
     mysql-cluster.)--This clustered database engine is particularly
     suited for applications that require the highest possible degree
     of uptime and availability.

     *Note*:

     The *Note `NDB': mysql-cluster. storage engine is not supported in
     standard MySQL 5.1 releases.  Currently supported MySQL Cluster
     releases include MySQL Cluster NDB 7.0 and MySQL Cluster NDB 7.1,
     which are based on MySQL 5.1, and MySQL Cluster NDB 7.2, which is
     based on MySQL 5.5. While based on MySQL Server, these releases
     also contain support for *Note `NDB': mysql-cluster.

   * *Note `CSV': csv-storage-engine.: The CSV storage engine stores
     data in text files using comma-separated values format. You can
     use the CSV engine to easily exchange data between other software
     and applications that can import and export in CSV format.

   * *Note `Blackhole': blackhole-storage-engine.: The Blackhole
     storage engine accepts but does not store data and retrievals
     always return an empty set. The functionality can be used in
     distributed database design where data is automatically
     replicated, but not stored locally.

   * *Note `Example': example-storage-engine.: The Example storage
     engine is `stub' engine that does nothing. You can create tables
     with this engine, but no data can be stored in them or retrieved
     from them. The purpose of this engine is to serve as an example in
     the MySQL source code that illustrates how to begin writing new
     storage engines.  As such, it is primarily of interest to
     developers.

It is important to remember that you are not restricted to using the
same storage engine for an entire server or schema: you can use a
different storage engine for each table in your schema.

*Choosing a Storage Engine*

The various storage engines provided with MySQL are designed with
different use cases in mind. To use the pluggable storage architecture
effectively, it is good to have an idea of the advantages and
disadvantages of the various storage engines. The following table
provides an overview of some storage engines provided with MySQL:

*Storage Engine Features*

Feature MyISAM       Memory       InnoDB       Archive      NDB
Storage 256TB        RAM          64TB         None         384EB
limits                                                      
TransactionsNo           No           Yes          No           Yes
Locking Table        Table        Row          Table        Row
granularity                                                    
MVCC    No           No           Yes          No           No
GeospatialYes          No           Yes          Yes          Yes
data                                                        
type                                                        
support                                                     
GeospatialYes          No           Yes InnoDB   No           No
indexing                          support for               
support                           geospatial                
                                  indexing is               
                                  available                 
                                  in MySQL                  
                                  5.7.5 and                 
                                  higher.                   
B-tree  Yes          Yes          Yes          No           No
indexes                                                     
T-tree  No           No           No           No           Yes
indexes                                                     
Hash    No           Yes          No InnoDB    No           Yes
indexes                           utilizes                  
                                  hash                      
                                  indexes                   
                                  internally                
                                  for its                   
                                  Adaptive                  
                                  Hash Index                
                                  feature.                  
Full-textYes          No           Yes InnoDB   No           No
search                            support for               
indexes                           FULLTEXT                  
                                  indexes is                
                                  available                 
                                  in MySQL                  
                                  5.6.4 and                 
                                  higher.                   
ClusteredNo           No           Yes          No           No
indexes                                                     
Data    No           N/A          Yes          No           Yes
caches                                                      
Index   Yes          N/A          Yes          No           Yes
caches                                                      
CompressedYes          No           Yes          Yes          No
data    Compressed                Compressed                
        MyISAM                    InnoDB                    
        tables are                tables                    
        supported                 require the               
        only when                 InnoDB                    
        using the                 Barracuda                 
        compressed                file format.              
        row format.                                         
        Tables                                              
        using the                                           
        compressed                                          
        row format                                          
        with MyISAM                                         
        are read                                            
        only.                                               
EncryptedYes          Yes          Yes          Yes          Yes
data                                                        
Implemented                                                    
in the                                                      
server                                                      
(via                                                        
encryption                                                    
functions),                                                    
rather                                                      
than                                                        
in the                                                      
storage                                                     
engine.                                                     
Cluster No           No           No           No           Yes
database                                                    
support                                                     
ReplicationYes          Yes          Yes          Yes          Yes
support                                                     
Implemented                                                    
in the                                                      
server,                                                     
rather                                                      
than                                                        
in the                                                      
storage                                                     
engine.                                                     
Foreign No           No           Yes          No           No
key                                                         
support                                                     
Backup  Yes          Yes          Yes          Yes          Yes
/                                                           
point-in-time                                                    
recovery                                                    
Implemented                                                    
in the                                                      
server,                                                     
rather                                                      
than                                                        
in the                                                      
storage                                                     
engine.                                                     
Query   Yes          Yes          Yes          Yes          Yes
cache                                                       
support                                                     
Update  Yes          Yes          Yes          Yes          Yes
statistics                                                    
for                                                         
data                                                        
dictionary                                                    


File: manual.info,  Node: storage-engine-compare-transactions,  Next: storage-engines-other,  Prev: storage-engines,  Up: storage-engines

14.1 Comparing Transaction and Nontransaction Engines
=====================================================

Transaction-safe tables (TSTs) have several advantages over
nontransaction-safe tables (NTSTs):

   * They are safer. Even if MySQL crashes or you get hardware
     problems, you can get your data back, either by automatic recovery
     or from a backup plus the transaction log.

   * You can combine many statements and accept them all at the same
     time with the *Note `COMMIT': commit.  statement (if autocommit is
     disabled).

   * You can execute *Note `ROLLBACK': commit. to ignore your changes
     (if autocommit is disabled).

   * If an update fails, all of your changes are reverted. (With
     nontransaction-safe tables, all changes that have taken place are
     permanent.)

   * Transaction-safe storage engines can provide better concurrency
     for tables that get many updates concurrently with reads.

You can combine transaction-safe and nontransaction-safe tables in the
same statements to get the best of both worlds. However, although MySQL
supports several transaction-safe storage engines, for best results,
you should not mix different storage engines within a transaction with
autocommit disabled. For example, if you do this, changes to
nontransaction-safe tables still are committed immediately and cannot
be rolled back. For information about this and other problems that can
occur in transactions that use mixed storage engines, see *Note
commit::.

Nontransaction-safe tables have several advantages of their own, all of
which occur because there is no transaction overhead:

   * Much faster

   * Lower disk space requirements

   * Less memory required to perform updates


File: manual.info,  Node: storage-engines-other,  Next: storage-engine-setting,  Prev: storage-engine-compare-transactions,  Up: storage-engines

14.2 Other Storage Engines
==========================

Other storage engines may be available from third parties and community
members that have used the Custom Storage Engine interface.

Third party engines are not supported by MySQL. For further
information, documentation, installation guides, bug reporting or for
any help or assistance with these engines, please contact the developer
of the engine directly.

For more information on developing a customer storage engine that can
be used with the Pluggable Storage Engine Architecture, see MySQL
Internals: Writing a Custom Storage Engine
(http://dev.mysql.com/doc/internals/en/custom-engine.html).


File: manual.info,  Node: storage-engine-setting,  Next: pluggable-storage-overview,  Prev: storage-engines-other,  Up: storage-engines

14.3 Setting the Storage Engine
===============================

When you create a new table, you can specify which storage engine to
use by adding an `ENGINE' table option to the *Note `CREATE TABLE':
create-table. statement:

     CREATE TABLE t (i INT) ENGINE = INNODB;

If you omit the `ENGINE' option, the default storage engine is used.
Normally, this is `MyISAM', but you can change it by using the
`--default-storage-engine' server startup option, or by setting the
`default-storage-engine' option in the `my.cnf' configuration file.

You can set the default storage engine to be used during the current
session by setting the `storage_engine' variable:


     SET storage_engine=MYISAM;

When MySQL is installed on Windows using the MySQL Configuration
Wizard, the `InnoDB' or `MyISAM' storage engine can be selected as the
default. See *Note mysql-config-wizard-database-usage::.

To convert a table from one storage engine to another, use an *Note
`ALTER TABLE': alter-table. statement that indicates the new engine:


     ALTER TABLE t ENGINE = MYISAM;

See *Note create-table::, and *Note alter-table::.

If you try to use a storage engine that is not compiled in or that is
compiled in but deactivated, MySQL instead creates a table using the
default storage engine. This behavior is convenient when you want to
copy tables between MySQL servers that support different storage
engines. (For example, in a replication setup, perhaps your master
server supports transactional storage engines for increased safety, but
the slave servers use only nontransactional storage engines for greater
speed.)

This automatic substitution of the default storage engine for
unavailable engines can be confusing for new MySQL users. A warning is
generated whenever a storage engine is automatically changed. To
prevent this from happening if the desired engine is unavailable,
enable the `NO_ENGINE_SUBSTITUTION' SQL mode.  In this case, an error
occurs instead of a warning and the table is not created or altered if
the desired engine is unavailable.  See *Note sql-mode::.

For new tables, MySQL always creates an `.frm' file to hold the table
and column definitions. The table's index and data may be stored in one
or more other files, depending on the storage engine. The server
creates the `.frm' file above the storage engine level.  Individual
storage engines create any additional files required for the tables
that they manage. If a table name contains special characters, the
names for the table files contain encoded versions of those characters
as described in *Note identifier-mapping::.

A database may contain tables of different types. That is, tables need
not all be created with the same storage engine.


File: manual.info,  Node: pluggable-storage-overview,  Next: myisam-storage-engine,  Prev: storage-engine-setting,  Up: storage-engines

14.4 Overview of MySQL Storage Engine Architecture
==================================================

* Menu:

* pluggable-storage::            Pluggable Storage Engine Architecture
* pluggable-storage-common-layer::  The Common Database Server Layer

The MySQL pluggable storage engine architecture enables a database
professional to select a specialized storage engine for a particular
application need while being completely shielded from the need to
manage any specific application coding requirements.  The MySQL server
architecture isolates the application programmer and DBA from all of
the low-level implementation details at the storage level, providing a
consistent and easy application model and API. Thus, although there are
different capabilities across different storage engines, the
application is shielded from these differences.

The pluggable storage engine architecture provides a standard set of
management and support services that are common among all underlying
storage engines. The storage engines themselves are the components of
the database server that actually perform actions on the underlying
data that is maintained at the physical server level.

This efficient and modular architecture provides huge benefits for
those wishing to specifically target a particular application
need--such as data warehousing, transaction processing, or high
availability situations--while enjoying the advantage of utilizing a
set of interfaces and services that are independent of any one storage
engine.

The application programmer and DBA interact with the MySQL database
through Connector APIs and service layers that are above the storage
engines. If application changes bring about requirements that demand
the underlying storage engine change, or that one or more storage
engines be added to support new needs, no significant coding or process
changes are required to make things work. The MySQL server architecture
shields the application from the underlying complexity of the storage
engine by presenting a consistent and easy-to-use API that applies
across storage engines.


File: manual.info,  Node: pluggable-storage,  Next: pluggable-storage-common-layer,  Prev: pluggable-storage-overview,  Up: pluggable-storage-overview

14.4.1 Pluggable Storage Engine Architecture
--------------------------------------------

As of MySQL 5.1, MySQL Server uses a pluggable storage engine
architecture that enables storage engines to be loaded into and
unloaded from a running MySQL server.

*Note*:

Prior to MySQL 5.1.38, the pluggable storage engine architecture is
supported on Unix platforms only and pluggable storage engines are not
supported on Windows.

*Plugging in a Storage Engine*

Before a storage engine can be used, the storage engine plugin shared
library must be loaded into MySQL using the *Note `INSTALL PLUGIN':
install-plugin. statement. For example, if the `EXAMPLE' engine plugin
is named `example' and the shared library is named `ha_example.so', you
load it with the following statement:


     mysql> INSTALL PLUGIN example SONAME 'ha_example.so';

To install a pluggable storage engine, the plugin file must be located
in the MySQL plugin directory, and the user issuing the *Note `INSTALL
PLUGIN': install-plugin. statement must have `INSERT' privilege for the
`mysql.plugin' table.

The shared library must be located in the MySQL server plugin
directory, the location of which is given by the `plugin_dir' system
variable.

*Unplugging a Storage Engine*

To unplug a storage engine, use the *Note `UNINSTALL PLUGIN':
uninstall-plugin. statement:


     mysql> UNINSTALL PLUGIN example;

If you unplug a storage engine that is needed by existing tables, those
tables become inaccessible, but will still be present on disk (where
applicable). Ensure that there are no tables using a storage engine
before you unplug the storage engine.


File: manual.info,  Node: pluggable-storage-common-layer,  Prev: pluggable-storage,  Up: pluggable-storage-overview

14.4.2 The Common Database Server Layer
---------------------------------------

A MySQL pluggable storage engine is the component in the MySQL database
server that is responsible for performing the actual data I/O
operations for a database as well as enabling and enforcing certain
feature sets that target a specific application need. A major benefit
of using specific storage engines is that you are only delivered the
features needed for a particular application, and therefore you have
less system overhead in the database, with the end result being more
efficient and higher database performance. This is one of the reasons
that MySQL has always been known to have such high performance,
matching or beating proprietary monolithic databases in industry
standard benchmarks.

From a technical perspective, what are some of the unique supporting
infrastructure components that are in a storage engine? Some of the key
feature differentiations include:

   * _Concurrency_: Some applications have more granular lock
     requirements (such as row-level locks) than others. Choosing the
     right locking strategy can reduce overhead and therefore improve
     overall performance. This area also includes support for
     capabilities such as multi-version concurrency control or
     `snapshot' read.

   * _Transaction Support_: Not every application needs transactions,
     but for those that do, there are very well defined requirements
     such as ACID compliance and more.

   * _Referential Integrity_: The need to have the server enforce
     relational database referential integrity through DDL defined
     foreign keys.

   * _Physical Storage_: This involves everything from the overall page
     size for tables and indexes as well as the format used for storing
     data to physical disk.

   * _Index Support_: Different application scenarios tend to benefit
     from different index strategies.  Each storage engine generally
     has its own indexing methods, although some (such as B-tree
     indexes) are common to nearly all engines.

   * _Memory Caches_: Different applications respond better to some
     memory caching strategies than others, so although some memory
     caches are common to all storage engines (such as those used for
     user connections or MySQL's high-speed Query Cache), others are
     uniquely defined only when a particular storage engine is put in
     play.

   * _Performance Aids_: This includes multiple I/O threads for
     parallel operations, thread concurrency, database checkpointing,
     bulk insert handling, and more.

   * _Miscellaneous Target Features_: This may include support for
     geospatial operations, security restrictions for certain data
     manipulation operations, and other similar features.

Each set of the pluggable storage engine infrastructure components are
designed to offer a selective set of benefits for a particular
application. Conversely, avoiding a set of component features helps
reduce unnecessary overhead. It stands to reason that understanding a
particular application's set of requirements and selecting the proper
MySQL storage engine can have a dramatic impact on overall system
efficiency and performance.


File: manual.info,  Node: myisam-storage-engine,  Next: innodb-storage-engine,  Prev: pluggable-storage-overview,  Up: storage-engines

14.5 The MyISAM Storage Engine
==============================

* Menu:

* myisam-start::                 MyISAM Startup Options
* key-space::                    Space Needed for Keys
* myisam-table-formats::         MyISAM Table Storage Formats
* myisam-table-problems::        MyISAM Table Problems

`MyISAM' is the default storage engine. It is based on the older (and
no longer available) `ISAM' storage engine but has many useful
extensions.

*`MyISAM' Storage Engine Features*

*Storage limits* 256TB    *Transactions*   No       *Locking         Table
                                                    granularity*     
*MVCC*           No       *Geospatial      Yes      *Geospatial      Yes
                          data type                 indexing         
                          support*                  support*         
*B-tree indexes* Yes      *T-tree indexes* No       *Hash indexes*   No
*Full-text       Yes      *Clustered       No       *Data caches*    No
search indexes*           indexes*                                   
*Index caches*   Yes      *Compressed      Yes      *Encrypted data  Yes
                          data*            CompressedImplemented in   
                                           MyISAM   the server (via  
                                           tables   encryption       
                                           are      functions),      
                                           supportedrather than in   
                                           only     the storage      
                                           when     engine.*         
                                           using                     
                                           the                       
                                           compressed                 
                                           row                       
                                           format.                   
                                           Tables                    
                                           using                     
                                           the                       
                                           compressed                 
                                           row                       
                                           format                    
                                           with                      
                                           MyISAM                    
                                           are                       
                                           read                      
                                           only.                     
*Cluster         No       *Replication     Yes      *Foreign key     No
database                  support                   support*         
support*                  Implemented in                             
                          the server,                                
                          rather than in                             
                          the storage                                
                          engine.*                                   
*Backup /        Yes      *Query cache     Yes      *Update          Yes
point-in-time             support*                  statistics for   
recovery                                            data dictionary* 
Implemented in                                                       
the server,                                                          
rather than in                                                       
the storage                                                          
engine.*                                                             

Each `MyISAM' table is stored on disk in three files. The files have
names that begin with the table name and have an extension to indicate
the file type. An `.frm' file stores the table format. The data file
has an `.MYD' (`MYData') extension. The index file has an `.MYI'
(`MYIndex') extension.

To specify explicitly that you want a `MyISAM' table, indicate that
with an `ENGINE' table option:


     CREATE TABLE t (i INT) ENGINE = MYISAM;

Normally, it is unnecessary to use `ENGINE' to specify the `MyISAM'
storage engine.  `MyISAM' is the default engine unless the default has
been changed. To ensure that `MyISAM' is used in situations where the
default might have been changed, include the `ENGINE' option explicitly.

You can check or repair `MyISAM' tables with the *Note `mysqlcheck':
mysqlcheck. client or *Note `myisamchk': myisamchk.  utility. You can
also compress `MyISAM' tables with *Note `myisampack': myisampack. to
take up much less space. See *Note mysqlcheck::, *Note myisamchk::, and
*Note myisampack::.

`MyISAM' tables have the following characteristics:

   * All data values are stored with the low byte first. This makes the
     data machine and operating system independent. The only
     requirements for binary portability are that the machine uses
     two's-complement signed integers and IEEE floating-point format.
     These requirements are widely used among mainstream machines.
     Binary compatibility might not be applicable to embedded systems,
     which sometimes have peculiar processors.

     There is no significant speed penalty for storing data low byte
     first; the bytes in a table row normally are unaligned and it
     takes little more processing to read an unaligned byte in order
     than in reverse order. Also, the code in the server that fetches
     column values is not time critical compared to other code.

   * All numeric key values are stored with the high byte first to
     permit better index compression.

   * Large files (up to 63-bit file length) are supported on file
     systems and operating systems that support large files.

   * There is a limit of 2^32 (~4.295E+09) rows in a `MyISAM' table. If
     you build MySQL with the `--with-big-tables' option, the row
     limitation is increased to (2^32)^2 (1.844E+19) rows. See *Note
     source-configuration-options::. Binary distributions for Unix and
     Linux are built with this option.

   * The maximum number of indexes per `MyISAM' table is 64. This can
     be changed by recompiling. Beginning with MySQL 5.1.4, you can
     configure the build by invoking `configure' with the
     `--with-max-indexes=N' option, where N is the maximum number of
     indexes to permit per `MyISAM' table.  N must be less than or
     equal to 128.  Before MySQL 5.1.4, you must change the source.

     The maximum number of columns per index is 16.

   * The maximum key length is 1000 bytes. This can also be changed by
     changing the source and recompiling. For the case of a key longer
     than 250 bytes, a larger key block size than the default of 1024
     bytes is used.

   * When rows are inserted in sorted order (as when you are using an
     `AUTO_INCREMENT' column), the index tree is split so that the high
     node only contains one key. This improves space utilization in the
     index tree.

   * Internal handling of one `AUTO_INCREMENT' column per table is
     supported. `MyISAM' automatically updates this column for *Note
     `INSERT': insert. and *Note `UPDATE': update. operations. This
     makes `AUTO_INCREMENT' columns faster (at least 10%).  Values at
     the top of the sequence are not reused after being deleted. (When
     an `AUTO_INCREMENT' column is defined as the last column of a
     multiple-column index, reuse of values deleted from the top of a
     sequence does occur.) The `AUTO_INCREMENT' value can be reset with
     *Note `ALTER TABLE': alter-table. or *Note `myisamchk': myisamchk.

   * Dynamic-sized rows are much less fragmented when mixing deletes
     with updates and inserts. This is done by automatically combining
     adjacent deleted blocks and by extending blocks if the next block
     is deleted.

   * `MyISAM' supports concurrent inserts: If a table has no free
     blocks in the middle of the data file, you can *Note `INSERT':
     insert. new rows into it at the same time that other threads are
     reading from the table. A free block can occur as a result of
     deleting rows or an update of a dynamic length row with more data
     than its current contents.  When all free blocks are used up
     (filled in), future inserts become concurrent again. See *Note
     concurrent-inserts::.

   * You can put the data file and index file in different directories
     on different physical devices to get more speed with the `DATA
     DIRECTORY' and `INDEX DIRECTORY' table options to *Note `CREATE
     TABLE': create-table. See *Note create-table::.

   * *Note `BLOB': blob. and *Note `TEXT': blob. columns can be indexed.

   * `NULL' values are permitted in indexed columns.  This takes 0 to 1
     bytes per key.

   * Each character column can have a different character set. See
     *Note charset::.

   * There is a flag in the `MyISAM' index file that indicates whether
     the table was closed correctly. If *Note `mysqld': mysqld. is
     started with the `--myisam-recover' option, `MyISAM' tables are
     automatically checked when opened, and are repaired if the table
     wasn't closed properly.

   * *Note `myisamchk': myisamchk. marks tables as checked if you run
     it with the `--update-state' option. *Note `myisamchk --fast':
     myisamchk. checks only those tables that don't have this mark.

   * *Note `myisamchk --analyze': myisamchk. stores statistics for
     portions of keys, as well as for entire keys.

   * *Note `myisampack': myisampack. can pack *Note `BLOB': blob. and
     *Note `VARCHAR': char. columns.

`MyISAM' also supports the following features:

   * Support for a true *Note `VARCHAR': char. type; a *Note `VARCHAR':
     char. column starts with a length stored in one or two bytes.

   * Tables with *Note `VARCHAR': char. columns may have fixed or
     dynamic row length.

   * The sum of the lengths of the *Note `VARCHAR': char. and *Note
     `CHAR': char. columns in a table may be up to 64KB.

   * Arbitrary length `UNIQUE' constraints.

*Additional Resources*

   * A forum dedicated to the `MyISAM' storage engine is available at
     `http://forums.mysql.com/list.php?21'.


File: manual.info,  Node: myisam-start,  Next: key-space,  Prev: myisam-storage-engine,  Up: myisam-storage-engine

14.5.1 MyISAM Startup Options
-----------------------------

The following options to *Note `mysqld': mysqld. can be used to change
the behavior of `MyISAM' tables. For additional information, see *Note
server-options::.

*MyISAM Option/Variable Reference*

Name           Cmd-Line    Option File System Var  Status Var  Var Scope   Dynamic
bulk_insert_buffer_sizeYes         Yes         Yes                     Both        Yes
concurrent_insertYes         Yes         Yes                     Global      Yes
delay-key-writeYes         Yes                                 Global      Yes
- _Variable_:                          Yes                     Global      Yes
delay_key_write                                                            
have_rtree_keys                        Yes                     Global      No
key_buffer_sizeYes         Yes         Yes                     Global      Yes
log-isam       Yes         Yes                                             
myisam-block-sizeYes         Yes                                             
myisam_data_pointer_sizeYes         Yes         Yes                     Global      Yes
myisam_max_sort_file_sizeYes         Yes         Yes                     Global      Yes
myisam_mmap_sizeYes         Yes         Yes                     Global      No
myisam-recover Yes         Yes                                             
- _Variable_:                                                              
myisam_recover_options                                                            
myisam_recover_options                        Yes                     Global      No
myisam_repair_threadsYes         Yes         Yes                     Both        Yes
myisam_sort_buffer_sizeYes         Yes         Yes                     Both        Yes
myisam_stats_methodYes         Yes         Yes                     Both        Yes
myisam_use_mmapYes         Yes         Yes                     Global      Yes
skip-concurrent-insertYes         Yes                                             
- _Variable_:                                                              
concurrent_insert                                                            
tmp_table_size Yes         Yes         Yes                     Both        Yes

   * `--myisam-recover=MODE'

     Set the mode for automatic recovery of crashed `MyISAM' tables.

   * `--delay-key-write=ALL'

     Don't flush key buffers between writes for any `MyISAM' table.

     *Note*:

     If you do this, you should not access `MyISAM' tables from another
     program (such as from another MySQL server or with *Note
     `myisamchk': myisamchk.) when the tables are in use.  Doing so
     risks index corruption. Using `--external-locking' does not
     eliminate this risk.

The following system variables affect the behavior of `MyISAM' tables.
For additional information, see *Note server-system-variables::.

   * `bulk_insert_buffer_size'

     The size of the tree cache used in bulk insert optimization.

     *Note*:

     This is a limit _per thread_!

   * `myisam_max_sort_file_size'

     The maximum size of the temporary file that MySQL is permitted to
     use while re-creating a `MyISAM' index (during *Note `REPAIR
     TABLE': repair-table, *Note `ALTER TABLE': alter-table, or *Note
     `LOAD DATA INFILE': load-data.). If the file size would be larger
     than this value, the index is created using the key cache instead,
     which is slower. The value is given in bytes.

   * `myisam_sort_buffer_size'

     Set the size of the buffer used when recovering tables.

Automatic recovery is activated if you start *Note `mysqld': mysqld.
with the `--myisam-recover' option. In this case, when the server opens
a `MyISAM' table, it checks whether the table is marked as crashed or
whether the open count variable for the table is not 0 and you are
running the server with external locking disabled. If either of these
conditions is true, the following happens:

   * The server checks the table for errors.

   * If the server finds an error, it tries to do a fast table repair
     (with sorting and without re-creating the data file).

   * If the repair fails because of an error in the data file (for
     example, a duplicate-key error), the server tries again, this time
     re-creating the data file.

   * If the repair still fails, the server tries once more with the old
     repair option method (write row by row without sorting).  This
     method should be able to repair any type of error and has low disk
     space requirements.

If the recovery wouldn't be able to recover all rows from previously
completed statements and you didn't specify `FORCE' in the value of the
`--myisam-recover' option, automatic repair aborts with an error
message in the error log:


     Error: Couldn't repair table: test.g00pages

If you specify `FORCE', a warning like this is written instead:


     Warning: Found 344 of 354 rows when repairing ./test/g00pages

Note that if the automatic recovery value includes `BACKUP', the
recovery process creates files with names of the form
`TBL_NAME-DATETIME.BAK'.  You should have a `cron' script that
automatically moves these files from the database directories to backup
media.


File: manual.info,  Node: key-space,  Next: myisam-table-formats,  Prev: myisam-start,  Up: myisam-storage-engine

14.5.2 Space Needed for Keys
----------------------------

`MyISAM' tables use B-tree indexes. You can roughly calculate the size
for the index file as `(key_length+4)/0.67', summed over all keys. This
is for the worst case when all keys are inserted in sorted order and
the table doesn't have any compressed keys.

String indexes are space compressed. If the first index part is a
string, it is also prefix compressed. Space compression makes the index
file smaller than the worst-case figure if a string column has a lot of
trailing space or is a *Note `VARCHAR': char. column that is not always
used to the full length. Prefix compression is used on keys that start
with a string. Prefix compression helps if there are many strings with
an identical prefix.

In `MyISAM' tables, you can also prefix compress numbers by specifying
the `PACK_KEYS=1' table option when you create the table. Numbers are
stored with the high byte first, so this helps when you have many
integer keys that have an identical prefix.


File: manual.info,  Node: myisam-table-formats,  Next: myisam-table-problems,  Prev: key-space,  Up: myisam-storage-engine

14.5.3 MyISAM Table Storage Formats
-----------------------------------

* Menu:

* static-format::                Static (Fixed-Length) Table Characteristics
* dynamic-format::               Dynamic Table Characteristics
* compressed-format::            Compressed Table Characteristics

`MyISAM' supports three different storage formats. Two of them, fixed
and dynamic format, are chosen automatically depending on the type of
columns you are using. The third, compressed format, can be created
only with the *Note `myisampack': myisampack. utility (see *Note
myisampack::).

When you use *Note `CREATE TABLE': create-table. or *Note `ALTER
TABLE': alter-table. for a table that has no *Note `BLOB': blob. or
*Note `TEXT': blob. columns, you can force the table format to `FIXED'
or `DYNAMIC' with the `ROW_FORMAT' table option.

See *Note create-table::, for information about `ROW_FORMAT'.

You can decompress (unpack) compressed `MyISAM' tables using *Note
`myisamchk `--unpack'': myisamchk.; see *Note myisamchk::, for more
information.


File: manual.info,  Node: static-format,  Next: dynamic-format,  Prev: myisam-table-formats,  Up: myisam-table-formats

14.5.3.1 Static (Fixed-Length) Table Characteristics
....................................................

Static format is the default for `MyISAM' tables. It is used when the
table contains no variable-length columns (*Note `VARCHAR': char, *Note
`VARBINARY': binary-varbinary, *Note `BLOB': blob, or *Note `TEXT':
blob.). Each row is stored using a fixed number of bytes.

Of the three `MyISAM' storage formats, static format is the simplest
and most secure (least subject to corruption). It is also the fastest
of the on-disk formats due to the ease with which rows in the data file
can be found on disk: To look up a row based on a row number in the
index, multiply the row number by the row length to calculate the row
position. Also, when scanning a table, it is very easy to read a
constant number of rows with each disk read operation.

The security is evidenced if your computer crashes while the MySQL
server is writing to a fixed-format `MyISAM' file. In this case, *Note
`myisamchk': myisamchk. can easily determine where each row starts and
ends, so it can usually reclaim all rows except the partially written
one. Note that `MyISAM' table indexes can always be reconstructed based
on the data rows.

*Note*:

Fixed-length row format is only available for tables without *Note
`BLOB': blob. or *Note `TEXT': blob. columns. Creating a table with
these columns with an explicit `ROW_FORMAT' clause will not raise an
error or warning; the format specification will be ignored.

Static-format tables have these characteristics:

   * *Note `CHAR': char. and *Note `VARCHAR': char. columns are
     space-padded to the specified column width, although the column
     type is not altered.  *Note `BINARY': binary-varbinary. and *Note
     `VARBINARY': binary-varbinary. columns are padded with `0x00'
     bytes to the column width.

   * Very quick.

   * Easy to cache.

   * Easy to reconstruct after a crash, because rows are located in
     fixed positions.

   * Reorganization is unnecessary unless you delete a huge number of
     rows and want to return free disk space to the operating system.
     To do this, use *Note `OPTIMIZE TABLE': optimize-table. or *Note
     `myisamchk -r': myisamchk.

   * Usually require more disk space than dynamic-format tables.


File: manual.info,  Node: dynamic-format,  Next: compressed-format,  Prev: static-format,  Up: myisam-table-formats

14.5.3.2 Dynamic Table Characteristics
......................................

Dynamic storage format is used if a `MyISAM' table contains any
variable-length columns (*Note `VARCHAR': char, *Note `VARBINARY':
binary-varbinary, *Note `BLOB': blob, or *Note `TEXT': blob.), or if
the table was created with the `ROW_FORMAT=DYNAMIC' table option.

Dynamic format is a little more complex than static format because each
row has a header that indicates how long it is. A row can become
fragmented (stored in noncontiguous pieces) when it is made longer as a
result of an update.

You can use *Note `OPTIMIZE TABLE': optimize-table. or *Note `myisamchk
-r': myisamchk. to defragment a table. If you have fixed-length columns
that you access or change frequently in a table that also contains some
variable-length columns, it might be a good idea to move the
variable-length columns to other tables just to avoid fragmentation.

Dynamic-format tables have these characteristics:

   * All string columns are dynamic except those with a length less
     than four.

   * Each row is preceded by a bitmap that indicates which columns
     contain the empty string (for string columns) or zero (for numeric
     columns). Note that this does not include columns that contain
     `NULL' values. If a string column has a length of zero after
     trailing space removal, or a numeric column has a value of zero,
     it is marked in the bitmap and not saved to disk. Nonempty strings
     are saved as a length byte plus the string contents.

   * Much less disk space usually is required than for fixed-length
     tables.

   * Each row uses only as much space as is required. However, if a row
     becomes larger, it is split into as many pieces as are required,
     resulting in row fragmentation. For example, if you update a row
     with information that extends the row length, the row becomes
     fragmented. In this case, you may have to run *Note `OPTIMIZE
     TABLE': optimize-table. or *Note `myisamchk -r': myisamchk. from
     time to time to improve performance. Use *Note `myisamchk -ei':
     myisamchk. to obtain table statistics.

   * More difficult than static-format tables to reconstruct after a
     crash, because rows may be fragmented into many pieces and links
     (fragments) may be missing.

   * The expected row length for dynamic-sized rows is calculated using
     the following expression:


          3
          + (NUMBER OF COLUMNS + 7) / 8
          + (NUMBER OF CHAR COLUMNS)
          + (PACKED SIZE OF NUMERIC COLUMNS)
          + (LENGTH OF STRINGS)
          + (NUMBER OF NULL COLUMNS + 7) / 8

     There is a penalty of 6 bytes for each link. A dynamic row is
     linked whenever an update causes an enlargement of the row. Each
     new link is at least 20 bytes, so the next enlargement probably
     goes in the same link. If not, another link is created. You can
     find the number of links using *Note `myisamchk -ed': myisamchk.
     All links may be removed with *Note `OPTIMIZE TABLE':
     optimize-table. or *Note `myisamchk -r': myisamchk.


File: manual.info,  Node: compressed-format,  Prev: dynamic-format,  Up: myisam-table-formats

14.5.3.3 Compressed Table Characteristics
.........................................

Compressed storage format is a read-only format that is generated with
the *Note `myisampack': myisampack. tool.  Compressed tables can be
uncompressed with *Note `myisamchk': myisamchk.

Compressed tables have the following characteristics:

   * Compressed tables take very little disk space. This minimizes disk
     usage, which is helpful when using slow disks (such as CD-ROMs).

   * Each row is compressed separately, so there is very little access
     overhead. The header for a row takes up one to three bytes
     depending on the biggest row in the table. Each column is
     compressed differently. There is usually a different Huffman tree
     for each column. Some of the compression types are:

        * Suffix space compression.

        * Prefix space compression.

        * Numbers with a value of zero are stored using one bit.

        * If values in an integer column have a small range, the column
          is stored using the smallest possible type. For example, a
          *Note `BIGINT': integer-types. column (eight bytes) can be
          stored as a *Note `TINYINT': integer-types. column (one byte)
          if all its values are in the range from `-128' to `127'.

        * If a column has only a small set of possible values, the data
          type is converted to *Note `ENUM': enum.

        * A column may use any combination of the preceding compression
          types.

   * Can be used for fixed-length or dynamic-length rows.

*Note*:

While a compressed table is read only, and you cannot therefore update
or add rows in the table, DDL (Data Definition Language) operations are
still valid. For example, you may still use `DROP' to drop the table,
and *Note `TRUNCATE TABLE': truncate-table. to empty the table.


File: manual.info,  Node: myisam-table-problems,  Prev: myisam-table-formats,  Up: myisam-storage-engine

14.5.4 MyISAM Table Problems
----------------------------

* Menu:

* corrupted-myisam-tables::      Corrupted MyISAM Tables
* myisam-table-close::           Problems from Tables Not Being Closed Properly

The file format that MySQL uses to store data has been extensively
tested, but there are always circumstances that may cause database
tables to become corrupted. The following discussion describes how this
can happen and how to handle it.


File: manual.info,  Node: corrupted-myisam-tables,  Next: myisam-table-close,  Prev: myisam-table-problems,  Up: myisam-table-problems

14.5.4.1 Corrupted MyISAM Tables
................................

Even though the `MyISAM' table format is very reliable (all changes to
a table made by an SQL statement are written before the statement
returns), you can still get corrupted tables if any of the following
events occur:

   * The *Note `mysqld': mysqld. process is killed in the middle of a
     write.

   * An unexpected computer shutdown occurs (for example, the computer
     is turned off).

   * Hardware failures.

   * You are using an external program (such as *Note `myisamchk':
     myisamchk.) to modify a table that is being modified by the server
     at the same time.

   * A software bug in the MySQL or `MyISAM' code.

Typical symptoms of a corrupt table are:

   * You get the following error while selecting data from the table:


          Incorrect key file for table: '...'. Try to repair it

   * Queries don't find rows in the table or return incomplete results.

You can check the health of a `MyISAM' table using the *Note `CHECK
TABLE': check-table. statement, and repair a corrupted `MyISAM' table
with *Note `REPAIR TABLE': repair-table. When *Note `mysqld': mysqld.
is not running, you can also check or repair a table with the *Note
`myisamchk': myisamchk. command.  See *Note check-table::, *Note
repair-table::, and *Note myisamchk::.

If your tables become corrupted frequently, you should try to determine
why this is happening. The most important thing to know is whether the
table became corrupted as a result of a server crash. You can verify
this easily by looking for a recent `restarted mysqld' message in the
error log. If there is such a message, it is likely that table
corruption is a result of the server dying. Otherwise, corruption may
have occurred during normal operation. This is a bug. You should try to
create a reproducible test case that demonstrates the problem. See
*Note crashing::, and *Note porting::.


File: manual.info,  Node: myisam-table-close,  Prev: corrupted-myisam-tables,  Up: myisam-table-problems

14.5.4.2 Problems from Tables Not Being Closed Properly
.......................................................

Each `MyISAM' index file (`.MYI' file) has a counter in the header that
can be used to check whether a table has been closed properly. If you
get the following warning from *Note `CHECK TABLE': check-table. or
*Note `myisamchk': myisamchk, it means that this counter has gone out
of sync:


     clients are using or haven't closed the table properly

This warning doesn't necessarily mean that the table is corrupted, but
you should at least check the table.

The counter works as follows:

   * The first time a table is updated in MySQL, a counter in the
     header of the index files is incremented.

   * The counter is not changed during further updates.

   * When the last instance of a table is closed (because a *Note
     `FLUSH TABLES': flush. operation was performed or because there is
     no room in the table cache), the counter is decremented if the
     table has been updated at any point.

   * When you repair the table or check the table and it is found to be
     okay, the counter is reset to zero.

   * To avoid problems with interaction with other processes that might
     check the table, the counter is not decremented on close if it was
     zero.

In other words, the counter can become incorrect only under these
conditions:

   * A `MyISAM' table is copied without first issuing *Note `LOCK
     TABLES': lock-tables. and *Note `FLUSH TABLES': flush.

   * MySQL has crashed between an update and the final close.  (Note
     that the table may still be okay, because MySQL always issues
     writes for everything between each statement.)

   * A table was modified by *Note `myisamchk --recover': myisamchk. or
     *Note `myisamchk --update-state': myisamchk. at the same time that
     it was in use by *Note `mysqld': mysqld.

   * Multiple *Note `mysqld': mysqld. servers are using the table and
     one server performed a *Note `REPAIR TABLE': repair-table. or
     *Note `CHECK TABLE': check-table. on the table while it was in use
     by another server. In this setup, it is safe to use *Note `CHECK
     TABLE': check-table, although you might get the warning from other
     servers. However, *Note `REPAIR TABLE': repair-table. should be
     avoided because when one server replaces the data file with a new
     one, this is not known to the other servers.

     In general, it is a bad idea to share a data directory among
     multiple servers. See *Note multiple-servers::, for additional
     discussion.


File: manual.info,  Node: innodb-storage-engine,  Next: se-db2,  Prev: myisam-storage-engine,  Up: storage-engines

14.6 The InnoDB Storage Engine
==============================

* Menu:

* innodb-introduction::          Introduction to InnoDB
* innodb-configuration::         InnoDB Configuration
* innodb-concepts::              InnoDB Concepts and Architecture
* innodb-tablespace::            InnoDB Tablespace Management
* innodb-tables::                InnoDB Table Management
* innodb-disk-management::       InnoDB Disk I/O and File Space Management
* innodb-parameters::            InnoDB Startup Options and System Variables
* innodb-tuning::                InnoDB Performance Tuning Tips
* innodb-monitors::              InnoDB Monitors
* innodb-backup::                InnoDB Backup and Recovery
* innodb-and-mysql-replication::  InnoDB and MySQL Replication
* innodb-troubleshooting::       InnoDB Troubleshooting


File: manual.info,  Node: innodb-introduction,  Next: innodb-configuration,  Prev: innodb-storage-engine,  Up: innodb-storage-engine

14.6.1 Introduction to InnoDB
-----------------------------

*Key Advantages of InnoDB*

`InnoDB' is a high-reliability and high-performance storage engine for
MySQL. Key advantages of `InnoDB' include:

   * Its design follows the ACID
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_acid)
     model, with transactions
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transaction)
     featuring commit
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_commit),
     rollback
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_rollback),
     and crash-recovery
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_crash_recovery)
     capabilities to protect user data.

   * Row-level locking
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_locking)
     (without escalation to coarser granularity locks) and Oracle-style
     consistent reads
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_consistent_read)
     increase multi-user concurrency and performance.

   * `InnoDB' tables arrange your data on disk to optimize common
     queries based on primary keys
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_primary_key).
     Each `InnoDB' table has a primary key index called the clustered
     index
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_clustered_index)
     that organizes the data to minimize I/O for primary key lookups.

   * To maintain data integrity, `InnoDB' also supports `FOREIGN KEY'
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_foreign_key)
     referential-integrity constraints.

   * You can freely mix `InnoDB' tables with tables from other MySQL
     storage engines, even within the same statement. For example, you
     can use a join operation to combine data from `InnoDB' and *Note
     `MEMORY': memory-storage-engine. tables in a single query.

   * `InnoDB' has been designed for CPU efficiency and maximum
     performance when processing large data volumes.

To determine whether your server supports `InnoDB' use the *Note `SHOW
ENGINES': show-engines. statement. See *Note show-engines::.

*InnoDB Storage Engine Features*

*Storage limits* 64TB     *Transactions*   Yes      *Locking         Row
                                                    granularity*     
*MVCC*           Yes      *Geospatial      Yes      *Geospatial      Yes
                          data type                 indexing         InnoDB
                          support*                  support*         support
                                                                     for
                                                                     geospatial
                                                                     indexing
                                                                     is
                                                                     available
                                                                     in
                                                                     MySQL
                                                                     5.7.5
                                                                     and
                                                                     higher.
*B-tree indexes* Yes      *T-tree indexes* No       *Hash indexes*   No
                                                                     InnoDB
                                                                     utilizes
                                                                     hash
                                                                     indexes
                                                                     internally
                                                                     for its
                                                                     Adaptive
                                                                     Hash
                                                                     Index
                                                                     feature.
*Full-text       Yes      *Clustered       Yes      *Data caches*    Yes
search indexes*  InnoDB   indexes*                                   
                 support                                             
                 for                                                 
                 FULLTEXT                                            
                 indexes                                             
                 is                                                  
                 available                                           
                 in                                                  
                 MySQL                                               
                 5.6.4                                               
                 and                                                 
                 higher.                                             
*Index caches*   Yes      *Compressed      Yes      *Encrypted data  Yes
                          data*            CompressedImplemented in   
                                           InnoDB   the server (via  
                                           tables   encryption       
                                           require  functions),      
                                           the      rather than in   
                                           InnoDB   the storage      
                                           Barracudaengine.*         
                                           file                      
                                           format.                   
*Cluster         No       *Replication     Yes      *Foreign key     Yes
database                  support                   support*         
support*                  Implemented in                             
                          the server,                                
                          rather than in                             
                          the storage                                
                          engine.*                                   
*Backup /        Yes      *Query cache     Yes      *Update          Yes
point-in-time             support*                  statistics for   
recovery                                            data dictionary* 
Implemented in                                                       
the server,                                                          
rather than in                                                       
the storage                                                          
engine.*                                                             

The `InnoDB' storage engine maintains its own buffer pool for caching
data and indexes in main memory.  `InnoDB' stores its tables and
indexes in a tablespace, which may consist of several files (or raw disk
partitions). This is different from, for example, `MyISAM' tables where
each table is stored using separate files. `InnoDB' tables can be very
large even on operating systems where file size is limited to 2GB.

The Windows Essentials installer makes `InnoDB' the MySQL default
storage engine on Windows, if the server being installed supports
`InnoDB'.

To compare the features of `InnoDB' with other storage engines provided
with MySQL, see the _Storage Engine Features_ table in *Note
storage-engines::.

*The InnoDB Plugin for MySQL*

   * At the 2008 MySQL User Conference, Innobase announced availability
     of an `InnoDB' Plugin for MySQL.  This plugin for MySQL exploits
     the `pluggable storage engine' architecture of MySQL, to permit
     users to replace the `built-in' version of `InnoDB' in MySQL 5.1.

   * As of MySQL 5.1.38, the `InnoDB Plugin' is included in MySQL 5.1
     releases, in addition to the built-in version of `InnoDB' that has
     been included in previous releases. MySQL 5.1.42 through 5.1.45
     include `InnoDB Plugin' 1.0.6, which is considered of Release
     Candidate (RC) quality. MySQL 5.1.46 and up include `InnoDB
     Plugin' 1.0.7 or higher, which is considered of General
     Availability (GA) quality.

   * Prior to MySQL Cluster NDB 7.1.11, MySQL Cluster was not
     compatible with the `InnoDB Plugin'.

   * The `InnoDB Plugin' offers new features, improved performance and
     scalability, enhanced reliability and new capabilities for
     flexibility and ease of use. Among the features of the `InnoDB
     Plugin' are `Fast index creation,' table and index compression,
     file format management, new `INFORMATION_SCHEMA' tables, capacity
     tuning, multiple background I/O threads, and group commit.

   * The `InnoDB Plugin' is included in source and binary
     distributions, except RHEL3, RHEL4, SuSE 9 (x86, x86_64, ia64),
     and generic Linux RPM packages.

   * For instructions on replacing the built-in version of `InnoDB'
     with `InnoDB Plugin', see *Note replacing-builtin-innodb::.

*MySQL Enterprise Backup and InnoDB*

The MySQL Enterprise Backup product lets you back up a running MySQL
database, including `InnoDB' and `MyISAM' tables, with minimal
disruption to operations while producing a consistent snapshot of the
database.  When MySQL Enterprise Backup is copying `InnoDB' tables,
reads and writes to both `InnoDB' and `MyISAM' tables can continue.
During the copying of `MyISAM' and other non-InnoDB tables, reads (but
not writes) to those tables are permitted. In addition, MySQL
Enterprise Backup can create compressed backup files, and back up
subsets of `InnoDB' tables. In conjunction with the MySQL binary log,
you can perform point-in-time recovery. MySQL Enterprise Backup is
included as part of the MySQL Enterprise subscription.

For a more complete description of MySQL Enterprise Backup, see *Note
mysql-enterprise-backup::.

*Additional Resources*

   * For `InnoDB'-related terms and definitions, see MySQL Glossary
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html).

   * A forum dedicated to the `InnoDB' storage engine is available here:
     MySQL Forums::InnoDB (http://forums.mysql.com/list.php?22).

   * `InnoDB' is published under the same GNU GPL License Version 2 (of
     June 1991) as MySQL. For more information on MySQL licensing, see
     `http://www.mysql.com/company/legal/licensing/'.


File: manual.info,  Node: innodb-configuration,  Next: innodb-concepts,  Prev: innodb-introduction,  Up: innodb-storage-engine

14.6.2 InnoDB Configuration
---------------------------

* Menu:

* replacing-builtin-innodb::     Using InnoDB Plugin Instead of the Built-In InnoDB

The first decisions to make about InnoDB configuration involve how to
lay out InnoDB data files, and how much memory to allocate for the
InnoDB storage engine. You record these choices either by recording
them in a configuration file that MySQL reads at startup, or by
specifying them as command-line options in a startup script.  The full
list of options, descriptions, and allowed parameter values is at *Note
innodb-parameters::.

*Overview of InnoDB Tablespace and Log Files*

Two important disk-based resources managed by the `InnoDB' storage
engine are its tablespace data files and its log files. If you specify
no `InnoDB' configuration options, MySQL creates an auto-extending data
file, slightly larger than 10MB, named `ibdata1' and two log files
named `ib_logfile0' and `ib_logfile1' in the MySQL data directory. Their
size is given by the size of the `innodb_log_file_size' system
variable. To get good performance, explicitly provide `InnoDB'
parameters as discussed in the following examples. Naturally, edit the
settings to suit your hardware and requirements.

The examples shown here are representative. See *Note
innodb-parameters:: for additional information about `InnoDB'-related
configuration parameters.

*Considerations for Storage Devices*

In some cases, database performance improves if the data is not all
placed on the same physical disk. Putting log files on a different disk
from data is very often beneficial for performance. The example
illustrates how to do this. It places the two data files on different
disks and places the log files on the third disk.  `InnoDB' fills the
tablespace beginning with the first data file. You can also use raw
disk partitions (raw devices) as `InnoDB' data files, which may speed
up I/O. See *Note innodb-raw-devices::.

*Caution*:

`InnoDB' is a transaction-safe (ACID compliant) storage engine for
MySQL that has commit, rollback, and crash-recovery capabilities to
protect user data.  *However, it cannot do so* if the underlying
operating system or hardware does not work as advertised. Many
operating systems or disk subsystems may delay or reorder write
operations to improve performance. On some operating systems, the very
`fsync()' system call that should wait until all unwritten data for a
file has been flushed might actually return before the data has been
flushed to stable storage. Because of this, an operating system crash
or a power outage may destroy recently committed data, or in the worst
case, even corrupt the database because of write operations having been
reordered. If data integrity is important to you, perform some
`pull-the-plug' tests before using anything in production. On Mac OS X
10.3 and up, `InnoDB' uses a special `fcntl()' file flush method. Under
Linux, it is advisable to *disable the write-back cache*.

On ATA/SATA disk drives, a command such `hdparm -W0 /dev/hda' may work
to disable the write-back cache.  *Beware that some drives or disk
controllers may be unable to disable the write-back cache.*

*Caution*:

If reliability is a consideration for your data, do not configure
`InnoDB' to use data files or log files on NFS volumes. Potential
problems vary according to OS and version of NFS, and include such
issues as lack of protection from conflicting writes, and limitations
on maximum file sizes.

*Specifying the Location and Size for InnoDB Tablespace Files*

To set up the `InnoDB' tablespace files, use the
`innodb_data_file_path' option in the `[mysqld]' section of the
`my.cnf' option file. On Windows, you can use `my.ini' instead. The
value of `innodb_data_file_path' should be a list of one or more data
file specifications. If you name more than one data file, separate them
by semicolon (``;'') characters:


     innodb_data_file_path=DATAFILE_SPEC1[;DATAFILE_SPEC2]...

For example, the following setting explicitly creates a tablespace
having the same characteristics as the default:


     [mysqld]
     innodb_data_file_path=ibdata1:10M:autoextend

This setting configures a single 10MB data file named `ibdata1' that is
auto-extending. No location for the file is given, so by default,
`InnoDB' creates it in the MySQL data directory.

Sizes are specified using `K', `M', or `G' suffix letters to indicate
units of KB, MB, or GB.

A tablespace containing a fixed-size 50MB data file named `ibdata1' and
a 50MB auto-extending file named `ibdata2' in the data directory can be
configured like this:


     [mysqld]
     innodb_data_file_path=ibdata1:50M;ibdata2:50M:autoextend

The full syntax for a data file specification includes the file name,
its size, and several optional attributes:


     FILE_NAME:FILE_SIZE[:autoextend[:max:MAX_FILE_SIZE]]

The `autoextend' and `max' attributes can be used only for the last
data file in the `innodb_data_file_path' line.

If you specify the `autoextend' option for the last data file, `InnoDB'
extends the data file if it runs out of free space in the tablespace.
The increment is 8MB at a time by default. To modify the increment,
change the `innodb_autoextend_increment' system variable.

If the disk becomes full, you might want to add another data file on
another disk. For tablespace reconfiguration instructions, see *Note
innodb-data-log-reconfiguration::.

`InnoDB' is not aware of the file system maximum file size, so be
cautious on file systems where the maximum file size is a small value
such as 2GB. To specify a maximum size for an auto-extending data file,
use the `max' attribute following the `autoextend' attribute. Use the
`max' attribute only in cases where constraining disk usage is of
critical importance, because exceeding the maximum size causes a fatal
error, possibly including a crash. The following configuration permits
`ibdata1' to grow up to a limit of 500MB:


     [mysqld]
     innodb_data_file_path=ibdata1:10M:autoextend:max:500M

`InnoDB' creates tablespace files in the MySQL data directory by
default. To specify a location explicitly, use the
`innodb_data_home_dir' option. For example, to use two files named
`ibdata1' and `ibdata2' but create them in the `/ibdata' directory,
configure `InnoDB' like this:


     [mysqld]
     innodb_data_home_dir = /ibdata
     innodb_data_file_path=ibdata1:50M;ibdata2:50M:autoextend

*Note*:

`InnoDB' does not create directories, so make sure that the `/ibdata'
directory exists before you start the server. This is also true of any
log file directories that you configure. Use the Unix or DOS `mkdir'
command to create any necessary directories.

Make sure that the MySQL server has the proper access rights to create
files in the data directory. More generally, the server must have
access rights in any directory where it needs to create data files or
log files.

`InnoDB' forms the directory path for each data file by textually
concatenating the value of `innodb_data_home_dir' to the data file
name, adding a path name separator (slash or backslash) between values
if necessary. If the `innodb_data_home_dir' option is not specified in
`my.cnf' at all, the default value is the `dot' directory `./', which
means the MySQL data directory. (The MySQL server changes its current
working directory to its data directory when it begins executing.)

If you specify `innodb_data_home_dir' as an empty string, you can
specify absolute paths for the data files listed in the
`innodb_data_file_path' value. The following example is equivalent to
the preceding one:


     [mysqld]
     innodb_data_home_dir =
     innodb_data_file_path=/ibdata/ibdata1:50M;/ibdata/ibdata2:50M:autoextend

*Specifying InnoDB Configuration Options*

*Sample `my.cnf' file for small systems.* Suppose that you have a
computer with 512MB RAM and one hard disk. The following example shows
possible configuration parameters in `my.cnf' or `my.ini' for `InnoDB',
including the `autoextend' attribute. The example suits most users,
both on Unix and Windows, who do not want to distribute `InnoDB' data
files and log files onto several disks. It creates an auto-extending
data file `ibdata1' and two `InnoDB' log files `ib_logfile0' and
`ib_logfile1' in the MySQL data directory.


     [mysqld]
     # You can write your other MySQL server options here
     # ...
     # Data files must be able to hold your data and indexes.
     # Make sure that you have enough free disk space.
     innodb_data_file_path = ibdata1:10M:autoextend
     #
     # Set buffer pool size to 50-80% of your computer's memory
     innodb_buffer_pool_size=256M
     innodb_additional_mem_pool_size=20M
     #
     # Set the log file size to about 25% of the buffer pool size
     innodb_log_file_size=64M
     innodb_log_buffer_size=8M
     #
     innodb_flush_log_at_trx_commit=1

Note that data files must be less than 2GB in some file systems. The
combined size of the log files must be less than 4GB. The combined size
of data files must be at least slightly larger than 10MB.

*Setting Up the InnoDB System Tablespace*

When you create an `InnoDB' system tablespace for the first time, it is
best that you start the MySQL server from the command prompt. `InnoDB'
then prints the information about the database creation to the screen,
so you can see what is happening. For example, on Windows, if *Note
`mysqld': mysqld. is located in `C:\Program Files\MySQL\MySQL Server
5.1\bin', you can start it like this:


     C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld" --console

If you do not send server output to the screen, check the server's
error log to see what `InnoDB' prints during the startup process.

For an example of what the information displayed by `InnoDB' should
look like, see *Note innodb-init::.

*Editing the MySQL Configuration File*

You can place `InnoDB' options in the `[mysqld]' group of any option
file that your server reads when it starts. The locations for option
files are described in *Note option-files::.

If you installed MySQL on Windows using the installation and
configuration wizards, the option file will be the `my.ini' file
located in your MySQL installation directory. See *Note
mysql-config-wizard-starting::.

If your PC uses a boot loader where the `C:' drive is not the boot
drive, your only option is to use the `my.ini' file in your Windows
directory (typically `C:\WINDOWS'). You can use the `SET' command at
the command prompt in a console window to print the value of `WINDIR':


     C:\> SET WINDIR
     windir=C:\WINDOWS

To make sure that *Note `mysqld': mysqld. reads options only from a
specific file, use the `--defaults-file' option as the first option on
the command line when starting the server:


     mysqld --defaults-file=YOUR_PATH_TO_MY_CNF

*Sample `my.cnf' file for large systems.* Suppose that you have a Linux
computer with 2GB RAM and three 60GB hard disks at directory paths `/',
`/dr2' and `/dr3'. The following example shows possible configuration
parameters in `my.cnf' for `InnoDB'.


     [mysqld]
     # You can write your other MySQL server options here
     # ...
     innodb_data_home_dir =
     #
     # Data files must be able to hold your data and indexes
     innodb_data_file_path = /db/ibdata1:2000M;/dr2/db/ibdata2:2000M:autoextend
     #
     # Set buffer pool size to 50-80% of your computer's memory,
     # but make sure on Linux x86 total memory usage is < 2GB
     innodb_buffer_pool_size=1G
     innodb_additional_mem_pool_size=20M
     innodb_log_group_home_dir = /dr3/iblogs
     #
     # Set the log file size to about 25% of the buffer pool size
     innodb_log_file_size=250M
     innodb_log_buffer_size=8M
     #
     innodb_flush_log_at_trx_commit=1
     innodb_lock_wait_timeout=50
     #
     # Uncomment the next line if you want to use it
     #innodb_thread_concurrency=5

*Determining the Maximum Memory Allocation for InnoDB*

*Warning*:

On 32-bit GNU/Linux x86, be careful not to set memory usage too high.
`glibc' may permit the process heap to grow over thread stacks, which
crashes your server. It is a risk if the value of the following
expression is close to or exceeds 2GB:


     innodb_buffer_pool_size
     + key_buffer_size
     + max_connections*(sort_buffer_size+read_buffer_size+binlog_cache_size)
     + max_connections*2MB

Each thread uses a stack (often 2MB, but only 256KB in MySQL binaries
provided by Oracle Corporation.) and in the worst case also uses
`sort_buffer_size + read_buffer_size' additional memory.

*Tuning other *Note `mysqld': mysqld. server parameters.* The following
values are typical and suit most users:


     [mysqld]
     skip-external-locking
     max_connections=200
     read_buffer_size=1M
     sort_buffer_size=1M
     #
     # Set key_buffer to 5 - 50% of your RAM depending on how much
     # you use MyISAM tables, but keep key_buffer_size + InnoDB
     # buffer pool size < 80% of your RAM
     key_buffer_size=VALUE

On Linux, if the kernel is enabled for large page support, `InnoDB' can
use large pages to allocate memory for its buffer pool and additional
memory pool. See *Note large-page-support::.

*Enabling the InnoDB Plugin*

If you want to use `InnoDB Plugin' rather than the built-in version of
`InnoDB', to get the latest performance improvements and new features
such as table compression and fast index creation, see *Note
replacing-builtin-innodb::.

*Turning Off InnoDB*

If you do not want to use `InnoDB' tables, start the server with the
`--innodb=OFF' or `--skip-innodb' option to disable the `InnoDB'
storage engine. In this case, the server will not start if the default
storage engine is set to *Note `InnoDB': innodb-storage-engine. Use
`--default-storage-engine' to set the default to some other engine if
necessary.


File: manual.info,  Node: replacing-builtin-innodb,  Prev: innodb-configuration,  Up: innodb-configuration

14.6.2.1 Using InnoDB Plugin Instead of the Built-In InnoDB
...........................................................

To use `InnoDB Plugin' in MySQL 5.1, you must disable the built-in
version of `InnoDB' that is also included and instruct the server to use
`InnoDB Plugin' instead. To accomplish this, use the following lines in
your `my.cnf' file:


     [mysqld]
     ignore-builtin-innodb
     plugin-load=innodb=ha_innodb_plugin.so

For the `plugin-load' option, `innodb' is the name to associate with
the plugin and `ha_innodb_plugin.so' is the name of the shared object
library that contains the plugin code. The extension of `.so' applies
for Unix (and similar) systems. For HP-UX on HPPA (11.11) or Windows,
the extension should be `.sl' or `.dll', respectively, rather than
`.so'.

If the server has problems finding the plugin when it starts up,
specify the pathname to the plugin directory. For example, if plugins
are located in the `lib/mysql/plugin' directory under the MySQL
installation directory and you have installed MySQL at
`/usr/local/mysql', use these lines in your `my.cnf' file:


     [mysqld]
     ignore-builtin-innodb
     plugin-load=innodb=ha_innodb_plugin.so
     plugin_dir=/usr/local/mysql/lib/mysql/plugin

The previous examples show how to activate the storage engine part of
`InnoDB Plugin,' but the plugin also implements several InnoDB-related
`INFORMATION_SCHEMA' tables. (For information about these tables, see
InnoDB INFORMATION_SCHEMA Tables
(http://dev.mysql.com/doc/refman/5.5/en/innodb-information-schema.html).)
To enable these tables, include additional `NAME=LIBRARY' pairs in the
value of the `plugin-load' option:


     [mysqld]
     ignore-builtin-innodb
     plugin-load=innodb=ha_innodb_plugin.so
       ;innodb_trx=ha_innodb_plugin.so
       ;innodb_locks=ha_innodb_plugin.so
       ;innodb_lock_waits=ha_innodb_plugin.so
       ;innodb_cmp=ha_innodb_plugin.so
       ;innodb_cmp_reset=ha_innodb_plugin.so
       ;innodb_cmpmem=ha_innodb_plugin.so
       ;innodb_cmpmem_reset=ha_innodb_plugin.so

The `plugin-load' option value as shown here is formatted on multiple
lines for display purposes but should be written in `my.cnf' using a
single line without spaces in the option value. On Windows, substitute
`.dll' for each instance of the `.so' extension.

After the server starts, verify that `InnoDB Plugin' has been loaded by
using the *Note `SHOW PLUGINS': show-plugins. statement. For example,
if you have loaded the storage engine and the `INFORMATION_SCHEMA'
tables, the output should include lines similar to these:


     mysql> SHOW PLUGINS;
     +---------------------+--------+--------------------+...
     | Name                | Status | Type               |...
     +---------------------+--------+--------------------+...
     ...
     | InnoDB              | ACTIVE | STORAGE ENGINE     |...
     | INNODB_TRX          | ACTIVE | INFORMATION SCHEMA |...
     | INNODB_LOCKS        | ACTIVE | INFORMATION SCHEMA |...
     | INNODB_LOCK_WAITS   | ACTIVE | INFORMATION SCHEMA |...
     | INNODB_CMP          | ACTIVE | INFORMATION SCHEMA |...
     | INNODB_CMP_RESET    | ACTIVE | INFORMATION SCHEMA |...
     | INNODB_CMPMEM       | ACTIVE | INFORMATION SCHEMA |...
     | INNODB_CMPMEM_RESET | ACTIVE | INFORMATION SCHEMA |...
     +---------------------+--------+--------------------+...

An alternative to using the `plugin-load' option at server startup is
to use the *Note `INSTALL PLUGIN': install-plugin. statement at
runtime. First start the server with the `ignore-builtin-innodb' option
to disable the built-in version of `InnoDB':


     [mysqld]
     ignore-builtin-innodb

Then issue an *Note `INSTALL PLUGIN': install-plugin.  statement for
each plugin that you want to load:


     mysql> INSTALL PLUGIN InnoDB SONAME 'ha_innodb_plugin.so';
     mysql> INSTALL PLUGIN INNODB_TRX SONAME 'ha_innodb_plugin.so';
     mysql> INSTALL PLUGIN INNODB_LOCKS SONAME 'ha_innodb_plugin.so';
     ...

*Note `INSTALL PLUGIN': install-plugin. need be issued only once for
each plugin. Installed plugins will be loaded automatically on
subsequent server restarts.

If you build MySQL from a source distribution, `InnoDB Plugin' is one
of the storage engines that is built by default. Build MySQL the way
you normally do; for example, by using the instructions at *Note
source-installation::.  After the build completes, you should find the
plugin shared object file under the `storage/innodb_plugin' directory,
and `make install' should install it in the plugin directory. Configure
MySQL to use `InnoDB Plugin' as described earlier for binary
distributions.

If you use `gcc', `InnoDB Plugin' cannot be compiled with `gcc' 3.x;
you must use `gcc' 4.x instead.

*Note*:

In MySQL 5.5, the `InnoDB Plugin' is also included, but it becomes the
built-in version of `InnoDB' in MySQL Server, replacing the version
previously included as the built-in `InnoDB' engine. This means that if
you use `InnoDB Plugin' in MySQL 5.1 using the instructions just given,
you will need to remove `ignore-builtin-innodb' and `plugin-load' from
your startup options after an upgrade to MySQL 5.5 or the server will
fail to start.


File: manual.info,  Node: innodb-concepts,  Next: innodb-tablespace,  Prev: innodb-configuration,  Up: innodb-storage-engine

14.6.3 InnoDB Concepts and Architecture
---------------------------------------

* Menu:

* innodb-transaction-model::     The InnoDB Transaction Model and Locking
* innodb-lock-modes::            InnoDB Lock Modes
* innodb-consistent-read::       Consistent Nonlocking Reads
* innodb-locking-reads::         SELECT ... FOR UPDATE and SELECT ... LOCK IN SHARE MODE Locking Reads
* innodb-record-level-locks::    InnoDB Record, Gap, and Next-Key Locks
* innodb-next-key-locking::      Avoiding the Phantom Problem Using Next-Key Locking
* innodb-locks-set::             Locks Set by Different SQL Statements in InnoDB
* innodb-implicit-commit::       Implicit Transaction Commit and Rollback
* innodb-deadlock-detection::    Deadlock Detection and Rollback
* innodb-deadlocks::             How to Cope with Deadlocks
* innodb-multi-versioning::      InnoDB Multi-Versioning
* innodb-table-and-index::       InnoDB Table and Index Structures


File: manual.info,  Node: innodb-transaction-model,  Next: innodb-lock-modes,  Prev: innodb-concepts,  Up: innodb-concepts

14.6.3.1 The InnoDB Transaction Model and Locking
.................................................

To implement a large-scale, busy, or highly reliable database
application, to port substantial code from a different database system,
or to tune MySQL performance, you must understand the notions of
transactions
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transaction)
and locking
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_locking) as
they relate to the InnoDB storage engine.

In the `InnoDB' transaction model, the goal is to combine the best
properties of a multi-versioning database with traditional two-phase
locking. `InnoDB' does locking on the row level and runs queries as
nonlocking consistent reads by default, in the style of Oracle. The
lock information in `InnoDB' is stored so space-efficiently that lock
escalation is not needed: Typically, several users are permitted to
lock every row in `InnoDB' tables, or any random subset of the rows,
without causing `InnoDB' memory exhaustion.

In `InnoDB', all user activity occurs inside a transaction. If
autocommit mode is enabled, each SQL statement forms a single
transaction on its own. By default, MySQL starts the session for each
new connection with autocommit enabled, so MySQL does a commit after
each SQL statement if that statement did not return an error. If a
statement returns an error, the commit or rollback behavior depends on
the error. See *Note innodb-error-handling::.

A session that has autocommit enabled can perform a multiple-statement
transaction by starting it with an explicit *Note `START TRANSACTION':
commit. or *Note `BEGIN': commit. statement and ending it with a *Note
`COMMIT': commit. or *Note `ROLLBACK': commit.  statement. See *Note
commit::.

If autocommit mode is disabled within a session with `SET autocommit =
0', the session always has a transaction open. A *Note `COMMIT':
commit. or *Note `ROLLBACK': commit.  statement ends the current
transaction and a new one starts.

A *Note `COMMIT': commit. means that the changes made in the current
transaction are made permanent and become visible to other sessions. A
*Note `ROLLBACK': commit.  statement, on the other hand, cancels all
modifications made by the current transaction. Both *Note `COMMIT':
commit. and *Note `ROLLBACK': commit. release all `InnoDB' locks that
were set during the current transaction.

In terms of the SQL:1992 transaction isolation levels, the default
`InnoDB' level is `REPEATABLE READ'.  `InnoDB' offers all four
transaction isolation levels described by the SQL standard: `READ
UNCOMMITTED', `READ COMMITTED', `REPEATABLE READ', and `SERIALIZABLE'.

A user can change the isolation level for a single session or for all
subsequent connections with the *Note `SET TRANSACTION':
set-transaction. statement. To set the server's default isolation level
for all connections, use the `--transaction-isolation' option on the
command line or in an option file. For detailed information about
isolation levels and level-setting syntax, see *Note set-transaction::.

In row-level locking, `InnoDB' normally uses next-key locking. That
means that besides index records, `InnoDB' can also lock the `gap'
preceding an index record to block insertions by other sessions in the
gap immediately before the index record. A next-key lock refers to a
lock that locks an index record and the gap before it.  A gap lock
refers to a lock that locks only the gap before some index record.

For more information about row-level locking, and the circumstances
under which gap locking is disabled, see *Note
innodb-record-level-locks::.


File: manual.info,  Node: innodb-lock-modes,  Next: innodb-consistent-read,  Prev: innodb-transaction-model,  Up: innodb-concepts

14.6.3.2 InnoDB Lock Modes
..........................

`InnoDB' implements standard row-level locking where there are two
types of locks, shared (S) locks
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_shared_lock)
and exclusive (X) locks
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_exclusive_lock).
For information about record, gap, and next-key lock types, see *Note
innodb-record-level-locks::.

   * A shared (S) lock permits a transaction to read a row.

   * An exclusive (X) lock permits a transaction to update or delete a
     row.

If transaction `T1' holds a shared (S) lock on row `r', then requests
from some distinct transaction `T2' for a lock on row `r' are handled
as follows:

   * A request by `T2' for an S lock can be granted immediately.  As a
     result, both `T1' and `T2' hold an S lock on `r'.

   * A request by `T2' for an X lock cannot be granted immediately.

If a transaction `T1' holds an exclusive (X) lock on row `r', a request
from some distinct transaction `T2' for a lock of either type on `r'
cannot be granted immediately. Instead, transaction `T2' has to wait
for transaction `T1' to release its lock on row `r'.

*Intention Locks*

Additionally, `InnoDB' supports _multiple granularity locking_ which
permits coexistence of record locks and locks on entire tables. To make
locking at multiple granularity levels practical, additional types of
locks called _intention locks_ are used.  Intention locks are table
locks in `InnoDB'. The idea behind intention locks is for a transaction
to indicate which type of lock (shared or exclusive) it will require
later for a row in that table. There are two types of intention locks
used in `InnoDB' (assume that transaction `T' has requested a lock of
the indicated type on table `t'):

   * Intention shared (IS): Transaction `T' intends to set S locks on
     individual rows in table `t'.

   * Intention exclusive (IX): Transaction `T' intends to set X locks
     on those rows.

For example, *Note `SELECT ... LOCK IN SHARE MODE': select. sets an IS
lock and *Note `SELECT ... FOR UPDATE': select. sets an IX lock.

The intention locking protocol is as follows:

   * Before a transaction can acquire an S lock on a row in table `t',
     it must first acquire an IS or stronger lock on `t'.

   * Before a transaction can acquire an X lock on a row, it must first
     acquire an IX lock on `t'.

These rules can be conveniently summarized by means of the following
_lock type compatibility matrix_.

Compatibility matrix showing which combinations of lock types X, IX, S,
and IS are allowed. Each cell in the matrix is marked as either
"Compatible" or "Conflict".

               X              IX             S              IS
X              Conflict       Conflict       Conflict       Conflict
IX             Conflict       Compatible     Conflict       Compatible
S              Conflict       Conflict       Compatible     Compatible
IS             Conflict       Compatible     Compatible     Compatible

A lock is granted to a requesting transaction if it is compatible with
existing locks, but not if it conflicts with existing locks.  A
transaction waits until the conflicting existing lock is released. If a
lock request conflicts with an existing lock and cannot be granted
because it would cause deadlock, an error occurs.

Thus, intention locks do not block anything except full table requests
(for example, `LOCK TABLES ... WRITE').  The main purpose of IX and IS
locks is to show that someone is locking a row, or going to lock a row
in the table.

*Deadlock Example*

The following example illustrates how an error can occur when a lock
request would cause a deadlock. The example involves two clients, A and
B.

First, client A creates a table containing one row, and then begins a
transaction. Within the transaction, A obtains an S lock on the row by
selecting it in share mode:


     mysql> CREATE TABLE t (i INT) ENGINE = InnoDB;
     Query OK, 0 rows affected (1.07 sec)

     mysql> INSERT INTO t (i) VALUES(1);
     Query OK, 1 row affected (0.09 sec)

     mysql> START TRANSACTION;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT * FROM t WHERE i = 1 LOCK IN SHARE MODE;
     +------+
     | i    |
     +------+
     |    1 |
     +------+
     1 row in set (0.10 sec)

Next, client B begins a transaction and attempts to delete the row from
the table:


     mysql> START TRANSACTION;
     Query OK, 0 rows affected (0.00 sec)

     mysql> DELETE FROM t WHERE i = 1;

The delete operation requires an X lock. The lock cannot be granted
because it is incompatible with the S lock that client A holds, so the
request goes on the queue of lock requests for the row and client B
blocks.

Finally, client A also attempts to delete the row from the table:


     mysql> DELETE FROM t WHERE i = 1;
     ERROR 1213 (40001): Deadlock found when trying to get lock;
     try restarting transaction

Deadlock occurs here because client A needs an X lock to delete the
row. However, that lock request cannot be granted because client B
already has a request for an X lock and is waiting for client A to
release its S lock. Nor can the S lock held by A be upgraded to an X
lock because of the prior request by B for an X lock. As a result,
`InnoDB' generates an error for one of the clients and releases its
locks. The client returns this error:


     ERROR 1213 (40001): Deadlock found when trying to get lock;
     try restarting transaction

At that point, the lock request for the other client can be granted and
it deletes the row from the table.

*Note*:

If the `LATEST DETECTED DEADLOCK' section of InnoDB Monitor output
includes a message stating, ``TOO DEEP OR LONG SEARCH IN THE LOCK TABLE
WAITS-FOR GRAPH, WE WILL ROLL BACK FOLLOWING TRANSACTION',' this
indicates that the number of transactions on the wait-for list has
reached a limit of 200, which is defined by
`LOCK_MAX_DEPTH_IN_DEADLOCK_CHECK'. A wait-for list that exceeds 200
transactions is treated as a deadlock and the transaction attempting to
check the wait-for list is rolled back.

The same error may also occur if the locking thread must look at more
than 1,000,000 locks owned by the transactions on the wait-for list.
The limit of 1,000,000 locks is defined by
`LOCK_MAX_N_STEPS_IN_DEADLOCK_CHECK'.


File: manual.info,  Node: innodb-consistent-read,  Next: innodb-locking-reads,  Prev: innodb-lock-modes,  Up: innodb-concepts

14.6.3.3 Consistent Nonlocking Reads
....................................

A consistent read means that `InnoDB' uses multi-versioning to present
to a query a snapshot of the database at a point in time. The query
sees the changes made by transactions that committed before that point
of time, and no changes made by later or uncommitted transactions. The
exception to this rule is that the query sees the changes made by
earlier statements within the same transaction. This exception causes
the following anomaly: If you update some rows in a table, a *Note
`SELECT': select. sees the latest version of the updated rows, but it
might also see older versions of any rows. If other sessions
simultaneously update the same table, the anomaly means that you might
see the table in a state that never existed in the database.

If the transaction isolation level is `REPEATABLE READ' (the default
level), all consistent reads within the same transaction read the
snapshot established by the first such read in that transaction.  You
can get a fresher snapshot for your queries by committing the current
transaction and after that issuing new queries.

With `READ COMMITTED' isolation level, each consistent read within a
transaction sets and reads its own fresh snapshot.

Consistent read is the default mode in which `InnoDB' processes *Note
`SELECT': select. statements in `READ COMMITTED' and `REPEATABLE READ'
isolation levels. A consistent read does not set any locks on the
tables it accesses, and therefore other sessions are free to modify
those tables at the same time a consistent read is being performed on
the table.

Suppose that you are running in the default `REPEATABLE READ' isolation
level. When you issue a consistent read (that is, an ordinary *Note
`SELECT': select. statement), `InnoDB' gives your transaction a
timepoint according to which your query sees the database. If another
transaction deletes a row and commits after your timepoint was
assigned, you do not see the row as having been deleted. Inserts and
updates are treated similarly.

*Note*:

The snapshot of the database state applies to *Note `SELECT': select.
statements within a transaction, not necessarily to DML
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_dml)
statements. If you insert or modify some rows and then commit that
transaction, a *Note `DELETE': delete. or *Note `UPDATE': update.
statement issued from another concurrent `REPEATABLE READ' transaction
could affect those just-committed rows, even though the session could
not query them. If a transaction does update or delete rows committed
by a different transaction, those changes do become visible to the
current transaction. For example, you might encounter a situation like
the following:


     SELECT COUNT(c1) FROM t1 WHERE c1 = 'xyz'; -- Returns 0: no rows match.
     DELETE FROM t1 WHERE c1 = 'xyz'; -- Deletes several rows recently committed by other transaction.

     SELECT COUNT(c2) FROM t1 WHERE c2 = 'abc'; -- Returns 0: no rows match.
     UPDATE t1 SET c2 = 'cba' WHERE c2 = 'abc'; -- Affects 10 rows: another txn just committed 10 rows with 'abc' values.
     SELECT COUNT(c2) FROM t1 WHERE c2 = 'cba'; -- Returns 10: this txn can now see the rows it just updated.

You can advance your timepoint by committing your transaction and then
doing another *Note `SELECT': select. or *Note `START TRANSACTION WITH
CONSISTENT SNAPSHOT': commit.

This is called _multi-versioned concurrency control_.

In the following example, session A sees the row inserted by B only
when B has committed the insert and A has committed as well, so that
the timepoint is advanced past the commit of B.


                  Session A              Session B

                SET autocommit=0;      SET autocommit=0;
     time
     |          SELECT * FROM t;
     |          empty set
     |                                 INSERT INTO t VALUES (1, 2);
     |
     v          SELECT * FROM t;
                empty set
                                       COMMIT;

                SELECT * FROM t;
                empty set

                COMMIT;

                SELECT * FROM t;
                ---------------------
                |    1    |    2    |
                ---------------------
                1 row in set

If you want to see the `freshest' state of the database, use either the
`READ COMMITTED' isolation level or a locking read:


     SELECT * FROM t LOCK IN SHARE MODE;

With `READ COMMITTED' isolation level, each consistent read within a
transaction sets and reads its own fresh snapshot. With `LOCK IN SHARE
MODE', a locking read occurs instead: A `SELECT' blocks until the
transaction containing the freshest rows ends (see *Note
innodb-locking-reads::).

Consistent read does not work over certain DDL statements:

   * Consistent read does not work over *Note `DROP TABLE': drop-table,
     because MySQL cannot use a table that has been dropped and
     `InnoDB' destroys the table.

   * Consistent read does not work over *Note `ALTER TABLE':
     alter-table, because that statement makes a temporary copy of the
     original table and deletes the original table when the temporary
     copy is built. When you reissue a consistent read within a
     transaction, rows in the new table are not visible because those
     rows did not exist when the transaction's snapshot was taken.

The type of read varies for selects in clauses like *Note `INSERT INTO
... SELECT': insert, *Note `UPDATE ... (SELECT)': update, and *Note
`CREATE TABLE ... SELECT': create-table. that do not specify `FOR
UPDATE' or `LOCK IN SHARE MODE':

   * By default, `InnoDB' uses stronger locks and the *Note `SELECT':
     select. part acts like `READ COMMITTED', where each consistent
     read, even within the same transaction, sets and reads its own
     fresh snapshot.

   * To use a consistent read in such cases, enable the
     `innodb_locks_unsafe_for_binlog' option and set the isolation
     level of the transaction to `READ UNCOMMITTED', `READ COMMITTED',
     or `REPEATABLE READ' (that is, anything other than
     `SERIALIZABLE'). In this case, no locks are set on rows read from
     the selected table.


File: manual.info,  Node: innodb-locking-reads,  Next: innodb-record-level-locks,  Prev: innodb-consistent-read,  Up: innodb-concepts

14.6.3.4 SELECT ... FOR UPDATE and SELECT ... LOCK IN SHARE MODE Locking Reads
..............................................................................

If you query data and then insert or update related data within the
same transaction, the regular `SELECT' statement does not give enough
protection. Other transactions can update or delete the same rows you
just queried.  `InnoDB' supports two types of locking reads that offer
extra safety:

   * *Note `SELECT ... LOCK IN SHARE MODE': select. sets a shared mode
     lock on any rows that are read. Other sessions can read the rows,
     but cannot modify them until your transaction commits. If any of
     these rows were changed by another transaction that has not yet
     committed, your query waits until that transaction ends and then
     uses the latest values.

   * *Note `SELECT ... FOR UPDATE': select. locks the rows and any
     associated index entries, the same as if you issued an `UPDATE'
     statement for those rows. Other transactions are blocked from
     updating those rows, from doing *Note `SELECT ... LOCK IN SHARE
     MODE': select, or from reading the data in certain transaction
     isolation levels. Consistent reads ignore any locks set on the
     records that exist in the read view. (Old versions of a record
     cannot be locked; they are reconstructed by applying undo logs on
     an in-memory copy of the record.)

These clauses are primarily useful when dealing with tree-structured or
graph-structured data, either in a single table or split across
multiple tables.

All locks set by `LOCK IN SHARE MODE' and `FOR UPDATE' queries are
released when the transaction is committed or rolled back.

*Note*:

Locking of rows for update using `SELECT FOR UPDATE' only applies when
autocommit is disabled (either by beginning transaction with *Note
`START TRANSACTION': commit. or by setting `autocommit' to 0. If
autocommit is enabled, the rows matching the specification are not
locked.

*Usage Examples*

Suppose that you want to insert a new row into a table `child', and
make sure that the child row has a parent row in table `parent'. Your
application code can ensure referential integrity throughout this
sequence of operations.

First, use a consistent read to query the table `PARENT' and verify
that the parent row exists.  Can you safely insert the child row to
table `CHILD'? No, because some other session could delete the parent
row in the moment between your `SELECT' and your `INSERT', without you
being aware of it.

To avoid this potential issue, perform the *Note `SELECT': select.
using `LOCK IN SHARE MODE':


     SELECT * FROM parent WHERE NAME = 'Jones' LOCK IN SHARE MODE;

After the `LOCK IN SHARE MODE' query returns the parent `'Jones'', you
can safely add the child record to the `CHILD' table and commit the
transaction. Any transaction that tries to read or write to the
applicable row in the `PARENT' table waits until you are finished, that
is, the data in all tables is in a consistent state.

For another example, consider an integer counter field in a table
`CHILD_CODES', used to assign a unique identifier to each child added
to table `CHILD'. Do not use either consistent read or a shared mode
read to read the present value of the counter, because two users of the
database could see the same value for the counter, and a duplicate-key
error occurs if two transactions attempt to add rows with the same
identifier to the `CHILD' table.

Here, `LOCK IN SHARE MODE' is not a good solution because if two users
read the counter at the same time, at least one of them ends up in
deadlock when it attempts to update the counter.

To implement reading and incrementing the counter, first perform a
locking read of the counter using `FOR UPDATE', and then increment the
counter. For example:


     SELECT counter_field FROM child_codes FOR UPDATE;
     UPDATE child_codes SET counter_field = counter_field + 1;

A *Note `SELECT ... FOR UPDATE': select. reads the latest available
data, setting exclusive locks on each row it reads. Thus, it sets the
same locks a searched SQL *Note `UPDATE': update. would set on the rows.

The preceding description is merely an example of how *Note `SELECT ...
FOR UPDATE': select. works. In MySQL, the specific task of generating a
unique identifier actually can be accomplished using only a single
access to the table:


     UPDATE child_codes SET counter_field = LAST_INSERT_ID(counter_field + 1);
     SELECT LAST_INSERT_ID();

The *Note `SELECT': select. statement merely retrieves the identifier
information (specific to the current connection). It does not access
any table.


File: manual.info,  Node: innodb-record-level-locks,  Next: innodb-next-key-locking,  Prev: innodb-locking-reads,  Up: innodb-concepts

14.6.3.5 InnoDB Record, Gap, and Next-Key Locks
...............................................

`InnoDB' has several types of record-level locks including record
locks, gap locks, and next-key locks. For information about shared
locks, exclusive locks, and intention locks, see *Note
innodb-lock-modes::.

   * Record lock: This is a lock on an index record.

   * Gap lock: This is a lock on a gap between index records, or a lock
     on the gap before the first or after the last index record.

   * Next-key lock: This is a combination of a record lock on the index
     record and a gap lock on the gap before the index record.

*Record Locks*

Record locks always lock index records, even if a table is defined with
no indexes. For such cases, `InnoDB' creates a hidden clustered index
and uses this index for record locking.  See *Note innodb-index-types::.

*Next-key Locks*

By default, `InnoDB' operates in `REPEATABLE READ' transaction
isolation level and with the `innodb_locks_unsafe_for_binlog' system
variable disabled. In this case, `InnoDB' uses next-key locks for
searches and index scans, which prevents phantom rows (see *Note
innodb-next-key-locking::).

Next-key locking combines index-row locking with gap locking.  `InnoDB'
performs row-level locking in such a way that when it searches or scans
a table index, it sets shared or exclusive locks on the index records
it encounters. Thus, the row-level locks are actually index-record
locks. In addition, a next-key lock on an index record also affects the
`gap' before that index record. That is, a next-key lock is an
index-record lock plus a gap lock on the gap preceding the index
record. If one session has a shared or exclusive lock on record `R' in
an index, another session cannot insert a new index record in the gap
immediately before `R' in the index order.

Suppose that an index contains the values 10, 11, 13, and 20. The
possible next-key locks for this index cover the following intervals,
where `(' or `)' denote exclusion of the interval endpoint and `[' or
`]' denote inclusion of the endpoint:


     (negative infinity, 10]
     (10, 11]
     (11, 13]
     (13, 20]
     (20, positive infinity)

For the last interval, the next-key lock locks the gap above the
largest value in the index and the `supremum' pseudo-record having a
value higher than any value actually in the index. The supremum is not
a real index record, so, in effect, this next-key lock locks only the
gap following the largest index value.

*Gap Locks*

The next-key locking example in the previous section shows that a gap
might span a single index value, multiple index values, or even be
empty.

Gap locking is not needed for statements that lock rows using a unique
index to search for a unique row. (This does not include the case that
the search condition includes only some columns of a multiple-column
unique index; in that case, gap locking does occur.) For example, if
the `id' column has a unique index, the following statement uses only
an index-record lock for the row having `id' value 100 and it does not
matter whether other sessions insert rows in the preceding gap:


     SELECT * FROM child WHERE id = 100;

If `id' is not indexed or has a nonunique index, the statement does
lock the preceding gap.

A type of gap lock called an insertion intention gap lock is set by
*Note `INSERT': insert. operations prior to row insertion. This lock
signals the intent to insert in such a way that multiple transactions
inserting into the same index gap need not wait for each other if they
are not inserting at the same position within the gap. Suppose that
there are index records with values of 4 and 7. Separate transactions
that attempt to insert values of 5 and 6 each lock the gap between 4
and 7 with insert intention locks prior to obtaining the exclusive lock
on the inserted row, but do not block each other because the rows are
nonconflicting. For more information about intention locks, see *Note
innodb-lock-modes::.

It is also worth noting here that conflicting locks can be held on a
gap by different transactions. For example, transaction A can hold a
shared gap lock (gap S-lock) on a gap while transaction B holds an
exclusive gap lock (gap X-lock) on the same gap. The reason conflicting
gap locks are allowed is that if a record is purged from an index, the
gap locks held on the record by different transactions must be merged.

Gap locks in `InnoDB' are `purely inhibitive', which means they only
stop other transactions from inserting to the gap. Thus, a gap X-lock
has the same effect as a gap S-lock.

*Disabling Gap Locking*

Gap locking can be disabled explicitly. This occurs if you change the
transaction isolation level to `READ COMMITTED' or enable the
`innodb_locks_unsafe_for_binlog' system variable. Under these
circumstances, gap locking is disabled for searches and index scans and
is used only for foreign-key constraint checking and duplicate-key
checking.

There are also other effects of using the `READ COMMITTED' isolation
level or enabling `innodb_locks_unsafe_for_binlog': Record locks for
nonmatching rows are released after MySQL has evaluated the `WHERE'
condition. For `UPDATE' statements, `InnoDB' does a `semi-consistent'
read, such that it returns the latest committed version to MySQL so
that MySQL can determine whether the row matches the `WHERE' condition
of the *Note `UPDATE': update.


File: manual.info,  Node: innodb-next-key-locking,  Next: innodb-locks-set,  Prev: innodb-record-level-locks,  Up: innodb-concepts

14.6.3.6 Avoiding the Phantom Problem Using Next-Key Locking
............................................................

The so-called _phantom_ problem occurs within a transaction when the
same query produces different sets of rows at different times. For
example, if a *Note `SELECT': select. is executed twice, but returns a
row the second time that was not returned the first time, the row is a
`phantom' row.

Suppose that there is an index on the `id' column of the `child' table
and that you want to read and lock all rows from the table having an
identifier value larger than 100, with the intention of updating some
column in the selected rows later:


     SELECT * FROM child WHERE id > 100 FOR UPDATE;

The query scans the index starting from the first record where `id' is
bigger than 100. Let the table contain rows having `id' values of 90
and 102. If the locks set on the index records in the scanned range do
not lock out inserts made in the gaps (in this case, the gap between 90
and 102), another session can insert a new row into the table with an
`id' of 101. If you were to execute the same *Note `SELECT': select.
within the same transaction, you would see a new row with an `id' of
101 (a `phantom') in the result set returned by the query.  If we
regard a set of rows as a data item, the new phantom child would
violate the isolation principle of transactions that a transaction
should be able to run so that the data it has read does not change
during the transaction.

To prevent phantoms, `InnoDB' uses an algorithm called _next-key
locking_ that combines index-row locking with gap locking. `InnoDB'
performs row-level locking in such a way that when it searches or scans
a table index, it sets shared or exclusive locks on the index records
it encounters. Thus, the row-level locks are actually index-record
locks. In addition, a next-key lock on an index record also affects the
`gap' before that index record. That is, a next-key lock is an
index-record lock plus a gap lock on the gap preceding the index
record. If one session has a shared or exclusive lock on record `R' in
an index, another session cannot insert a new index record in the gap
immediately before `R' in the index order.

When `InnoDB' scans an index, it can also lock the gap after the last
record in the index. Just that happens in the preceding example: To
prevent any insert into the table where `id' would be bigger than 100,
the locks set by `InnoDB' include a lock on the gap following `id'
value 102.

You can use next-key locking to implement a uniqueness check in your
application: If you read your data in share mode and do not see a
duplicate for a row you are going to insert, then you can safely insert
your row and know that the next-key lock set on the successor of your
row during the read prevents anyone meanwhile inserting a duplicate for
your row. Thus, the next-key locking enables you to `lock' the
nonexistence of something in your table.

Gap locking can be disabled as discussed in *Note
innodb-record-level-locks::. This may cause phantom problems because
other sessions can insert new rows into the gaps when gap locking is
disabled.


File: manual.info,  Node: innodb-locks-set,  Next: innodb-implicit-commit,  Prev: innodb-next-key-locking,  Up: innodb-concepts

14.6.3.7 Locks Set by Different SQL Statements in InnoDB
........................................................

A locking read, an *Note `UPDATE': update, or a *Note `DELETE': delete.
generally set record locks on every index record that is scanned in the
processing of the SQL statement. It does not matter whether there are
`WHERE' conditions in the statement that would exclude the row.
`InnoDB' does not remember the exact `WHERE' condition, but only knows
which index ranges were scanned. The locks are normally next-key locks
that also block inserts into the `gap' immediately before the record.
However, gap locking can be disabled explicitly, which causes next-key
locking not to be used. For more information, see *Note
innodb-record-level-locks::. The transaction isolation level also can
affect which locks are set; see *Note set-transaction::.

If a secondary index is used in a search and index record locks to be
set are exclusive, `InnoDB' also retrieves the corresponding clustered
index records and sets locks on them.

Differences between shared and exclusive locks are described in *Note
innodb-lock-modes::.

If you have no indexes suitable for your statement and MySQL must scan
the entire table to process the statement, every row of the table
becomes locked, which in turn blocks all inserts by other users to the
table. It is important to create good indexes so that your queries do
not unnecessarily scan many rows.

For *Note `SELECT ... FOR UPDATE': select. or *Note `SELECT ... LOCK IN
SHARE MODE': select, locks are acquired for scanned rows, and expected
to be released for rows that do not qualify for inclusion in the result
set (for example, if they do not meet the criteria given in the `WHERE'
clause). However, in some cases, rows might not be unlocked immediately
because the relationship between a result row and its original source
is lost during query execution. For example, in a *Note `UNION': union,
scanned (and locked) rows from a table might be inserted into a
temporary table before evaluation whether they qualify for the result
set. In this circumstance, the relationship of the rows in the
temporary table to the rows in the original table is lost and the
latter rows are not unlocked until the end of query execution.

`InnoDB' sets specific types of locks as follows.

   * *Note `SELECT ... FROM': select. is a consistent read, reading a
     snapshot of the database and setting no locks unless the
     transaction isolation level is set to `SERIALIZABLE'. For
     `SERIALIZABLE' level, the search sets shared next-key locks on the
     index records it encounters.

   * *Note `SELECT ... FROM ... LOCK IN SHARE MODE': select. sets
     shared next-key locks on all index records the search encounters.

   * For index records the search encounters, *Note `SELECT ... FROM
     ... FOR UPDATE': select. blocks other sessions from doing *Note
     `SELECT ... FROM ... LOCK IN SHARE MODE': select. or from reading
     in certain transaction isolation levels. Consistent reads will
     ignore any locks set on the records that exist in the read view.

   * *Note `UPDATE ... WHERE ...': update. sets an exclusive next-key
     lock on every record the search encounters.

   * *Note `DELETE FROM ... WHERE ...': delete. sets an exclusive
     next-key lock on every record the search encounters.

   * *Note `INSERT': insert. sets an exclusive lock on the inserted
     row. This lock is an index-record lock, not a next-key lock (that
     is, there is no gap lock) and does not prevent other sessions from
     inserting into the gap before the inserted row.

     Prior to inserting the row, a type of gap lock called an insertion
     intention gap lock is set. This lock signals the intent to insert
     in such a way that multiple transactions inserting into the same
     index gap need not wait for each other if they are not inserting
     at the same position within the gap.  Suppose that there are index
     records with values of 4 and 7.  Separate transactions that
     attempt to insert values of 5 and 6 each lock the gap between 4
     and 7 with insert intention locks prior to obtaining the exclusive
     lock on the inserted row, but do not block each other because the
     rows are nonconflicting.

     If a duplicate-key error occurs, a shared lock on the duplicate
     index record is set. This use of a shared lock can result in
     deadlock should there be multiple sessions trying to insert the
     same row if another session already has an exclusive lock. This
     can occur if another session deletes the row. Suppose that an
     `InnoDB' table `t1' has the following structure:


          CREATE TABLE t1 (i INT, PRIMARY KEY (i)) ENGINE = InnoDB;

     Now suppose that three sessions perform the following operations
     in order:

     Session 1:


          START TRANSACTION;
          INSERT INTO t1 VALUES(1);

     Session 2:


          START TRANSACTION;
          INSERT INTO t1 VALUES(1);

     Session 3:


          START TRANSACTION;
          INSERT INTO t1 VALUES(1);

     Session 1:


          ROLLBACK;

     The first operation by session 1 acquires an exclusive lock for
     the row. The operations by sessions 2 and 3 both result in a
     duplicate-key error and they both request a shared lock for the
     row. When session 1 rolls back, it releases its exclusive lock on
     the row and the queued shared lock requests for sessions 2 and 3
     are granted. At this point, sessions 2 and 3 deadlock: Neither can
     acquire an exclusive lock for the row because of the shared lock
     held by the other.

     A similar situation occurs if the table already contains a row
     with key value 1 and three sessions perform the following
     operations in order:

     Session 1:


          START TRANSACTION;
          DELETE FROM t1 WHERE i = 1;

     Session 2:


          START TRANSACTION;
          INSERT INTO t1 VALUES(1);

     Session 3:


          START TRANSACTION;
          INSERT INTO t1 VALUES(1);

     Session 1:


          COMMIT;

     The first operation by session 1 acquires an exclusive lock for
     the row. The operations by sessions 2 and 3 both result in a
     duplicate-key error and they both request a shared lock for the
     row. When session 1 commits, it releases its exclusive lock on the
     row and the queued shared lock requests for sessions 2 and 3 are
     granted. At this point, sessions 2 and 3 deadlock: Neither can
     acquire an exclusive lock for the row because of the shared lock
     held by the other.

   * *Note `INSERT ... ON DUPLICATE KEY UPDATE': insert-on-duplicate.
     differs from a simple *Note `INSERT': insert. in that an exclusive
     next-key lock rather than a shared lock is placed on the row to be
     updated when a duplicate-key error occurs.

   * *Note `REPLACE': replace. is done like an *Note `INSERT': insert.
     if there is no collision on a unique key. Otherwise, an exclusive
     next-key lock is placed on the row to be replaced.

   * `INSERT INTO T SELECT ... FROM S WHERE ...' sets an exclusive
     index record without a gap lock on each row inserted into `T'. If
     the transaction isolation level is `READ COMMITTED' or
     `innodb_locks_unsafe_for_binlog' is enabled, and the transaction
     isolation level is not `SERIALIZABLE', `InnoDB' does the search on
     `S' as a consistent read (no locks).  Otherwise, `InnoDB' sets
     shared next-key locks on rows from `S'.  `InnoDB' has to set locks
     in the latter case: In roll-forward recovery from a backup, every
     SQL statement must be executed in exactly the same way it was done
     originally.

     *Note `CREATE TABLE ... SELECT ...': create-table. performs the
     *Note `SELECT': select. with shared next-key locks or as a
     consistent read, as for *Note `INSERT ... SELECT': insert-select.

     When a `SELECT' is used in the constructs `REPLACE INTO t SELECT
     ... FROM s WHERE ...' or `UPDATE t ... WHERE col IN (SELECT ...
     FROM s ...)', `InnoDB' sets shared next-key locks on rows from
     table `s'.

   * While initializing a previously specified `AUTO_INCREMENT' column
     on a table, `InnoDB' sets an exclusive lock on the end of the
     index associated with the `AUTO_INCREMENT' column. In accessing the
     auto-increment counter, `InnoDB' uses a specific `AUTO-INC' table
     lock mode where the lock lasts only to the end of the current SQL
     statement, not to the end of the entire transaction. Other
     sessions cannot insert into the table while the `AUTO-INC' table
     lock is held; see *Note innodb-transaction-model::.

     `InnoDB' fetches the value of a previously initialized
     `AUTO_INCREMENT' column without setting any locks.

   * If a `FOREIGN KEY' constraint is defined on a table, any insert,
     update, or delete that requires the constraint condition to be
     checked sets shared record-level locks on the records that it
     looks at to check the constraint.  `InnoDB' also sets these locks
     in the case where the constraint fails.

   * *Note `LOCK TABLES': lock-tables. sets table locks, but it is the
     higher MySQL layer above the `InnoDB' layer that sets these locks.
     `InnoDB' is aware of table locks if `innodb_table_locks = 1' (the
     default) and `autocommit = 0', and the MySQL layer above `InnoDB'
     knows about row-level locks.

     Otherwise, `InnoDB''s automatic deadlock detection cannot detect
     deadlocks where such table locks are involved. Also, because in
     this case the higher MySQL layer does not know about row-level
     locks, it is possible to get a table lock on a table where another
     session currently has row-level locks. However, this does not
     endanger transaction integrity, as discussed in *Note
     innodb-deadlock-detection::. See also *Note innodb-restrictions::.


File: manual.info,  Node: innodb-implicit-commit,  Next: innodb-deadlock-detection,  Prev: innodb-locks-set,  Up: innodb-concepts

14.6.3.8 Implicit Transaction Commit and Rollback
.................................................

By default, MySQL starts the session for each new connection with
autocommit mode enabled, so MySQL does a commit after each SQL
statement if that statement did not return an error. If a statement
returns an error, the commit or rollback behavior depends on the error.
See *Note innodb-error-handling::.

If a session that has autocommit disabled ends without explicitly
committing the final transaction, MySQL rolls back that transaction.

Some statements implicitly end a transaction, as if you had done a
*Note `COMMIT': commit. before executing the statement. For details,
see *Note implicit-commit::.


File: manual.info,  Node: innodb-deadlock-detection,  Next: innodb-deadlocks,  Prev: innodb-implicit-commit,  Up: innodb-concepts

14.6.3.9 Deadlock Detection and Rollback
........................................

`InnoDB' automatically detects transaction deadlocks
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_deadlock)
and rolls back a transaction or transactions to break the deadlock.
`InnoDB' tries to pick small transactions to roll back, where the size
of a transaction is determined by the number of rows inserted, updated,
or deleted.

`InnoDB' is aware of table locks if `innodb_table_locks = 1' (the
default) and `autocommit = 0', and the MySQL layer above it knows about
row-level locks. Otherwise, `InnoDB' cannot detect deadlocks where a
table lock set by a MySQL *Note `LOCK TABLES': lock-tables.  statement
or a lock set by a storage engine other than `InnoDB' is involved.
Resolve these situations by setting the value of the
`innodb_lock_wait_timeout' system variable.

When `InnoDB' performs a complete rollback of a transaction, all locks
set by the transaction are released.  However, if just a single SQL
statement is rolled back as a result of an error, some of the locks set
by the statement may be preserved. This happens because `InnoDB' stores
row locks in a format such that it cannot know afterward which lock was
set by which statement.

As of MySQL 5.1.24, if a *Note `SELECT': select.  calls a stored
function in a transaction, and a statement within the function fails,
that statement rolls back. Furthermore, if *Note `ROLLBACK': commit. is
executed after that, the entire transaction rolls back. Before 5.1.24,
the failed statement did not roll back when it failed (even though it
might ultimately get rolled back by a *Note `ROLLBACK': commit. later
that rolls back the entire transaction).

For techniques to organize database operations to avoid deadlocks, see
*Note innodb-deadlocks::.


File: manual.info,  Node: innodb-deadlocks,  Next: innodb-multi-versioning,  Prev: innodb-deadlock-detection,  Up: innodb-concepts

14.6.3.10 How to Cope with Deadlocks
....................................

This section builds on the conceptual information about deadlocks in
*Note innodb-deadlock-detection::. It explains how to organize database
operations to minimize deadlocks and the subsequent error handling
required in applications.

Deadlocks
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_deadlock)
are a classic problem in transactional databases, but they are not
dangerous unless they are so frequent that you cannot run certain
transactions at all. Normally, you must write your applications so that
they are always prepared to re-issue a transaction if it gets rolled
back because of a deadlock.

`InnoDB' uses automatic row-level locking. You can get deadlocks even
in the case of transactions that just insert or delete a single row.
That is because these operations are not really `atomic'; they
automatically set locks on the (possibly several) index records of the
row inserted or deleted.

You can cope with deadlocks and reduce the likelihood of their
occurrence with the following techniques:

   * Use *Note `SHOW ENGINE INNODB STATUS': show-engine. to determine
     the cause of the latest deadlock. That can help you to tune your
     application to avoid deadlocks.

   * Always be prepared to re-issue a transaction if it fails due to
     deadlock. Deadlocks are not dangerous. Just try again.

   * Keep transactions small and short in duration to make them less
     prone to collision.

   * Commit transactions immediately after making a set of related
     changes to make them less prone to collision. In particular, do
     not leave an interactive *Note `mysql': mysql. session open for a
     long time with an uncommitted transaction.

   * If you are using locking reads (*Note `SELECT ... FOR UPDATE':
     select. or `SELECT ...  LOCK IN SHARE MODE'), try using a lower
     isolation level such as `READ COMMITTED'.

   * When modifying multiple tables within a transaction, or different
     sets of rows in the same table, do those operations in a
     consistent order each time. Then transactions form well-defined
     queues and do not deadlock. For example, organize database
     operations into functions within your application, or call stored
     routines, rather than coding multiple similar sequences of
     `INSERT', `UPDATE', and `DELETE' statements in different places.

   * Add well-chosen indexes to your tables. Then your queries need to
     scan fewer index records and consequently set fewer locks.  Use
     *Note `EXPLAIN SELECT': explain. to determine which indexes the
     MySQL server regards as the most appropriate for your queries.

   * Use less locking. If you can afford to permit a *Note `SELECT':
     select. to return data from an old snapshot, do not add the clause
     `FOR UPDATE' or `LOCK IN SHARE MODE' to it. Using the `READ
     COMMITTED' isolation level is good here, because each consistent
     read within the same transaction reads from its own fresh snapshot.

   * If nothing else helps, serialize your transactions with
     table-level locks. The correct way to use *Note `LOCK TABLES':
     lock-tables. with transactional tables, such as `InnoDB' tables,
     is to begin a transaction with `SET autocommit = 0' (not *Note
     `START TRANSACTION': commit.) followed by *Note `LOCK TABLES':
     lock-tables, and to not call *Note `UNLOCK TABLES': lock-tables.
     until you commit the transaction explicitly.  For example, if you
     need to write to table `t1' and read from table `t2', you can do
     this:


          SET autocommit=0;
          LOCK TABLES t1 WRITE, t2 READ, ...;
          ... DO SOMETHING WITH TABLES T1 AND T2 HERE ...
          COMMIT;
          UNLOCK TABLES;

     Table-level locks prevent concurrent updates to the table,
     avoiding deadlocks at the expense of less responsiveness for a
     busy system.

   * Another way to serialize transactions is to create an auxiliary
     `semaphore' table that contains just a single row. Have each
     transaction update that row before accessing other tables. In that
     way, all transactions happen in a serial fashion. Note that the
     `InnoDB' instant deadlock detection algorithm also works in this
     case, because the serializing lock is a row-level lock. With MySQL
     table-level locks, the timeout method must be used to resolve
     deadlocks.


File: manual.info,  Node: innodb-multi-versioning,  Next: innodb-table-and-index,  Prev: innodb-deadlocks,  Up: innodb-concepts

14.6.3.11 InnoDB Multi-Versioning
.................................

`InnoDB' is a multi-versioned storage engine: it keeps information
about old versions of changed rows, to support transactional features
such as concurrency and rollback. This information is stored in the
tablespace in a data structure called a rollback segment
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_rollback_segment)
(after an analogous data structure in Oracle).  `InnoDB' uses the
information in the rollback segment to perform the undo operations
needed in a transaction rollback. It also uses the information to build
earlier versions of a row for a consistent read.

*Internal Details of Multi-Versioning*

Internally, `InnoDB' adds three fields to each row stored in the
database. A 6-byte `DB_TRX_ID' field indicates the transaction
identifier for the last transaction that inserted or updated the row.
Also, a deletion is treated internally as an update where a special bit
in the row is set to mark it as deleted. Each row also contains a 7-byte
`DB_ROLL_PTR' field called the roll pointer. The roll pointer points to
an undo log record written to the rollback segment. If the row was
updated, the undo log record contains the information necessary to
rebuild the content of the row before it was updated. A 6-byte
`DB_ROW_ID' field contains a row ID that increases monotonically as new
rows are inserted. If `InnoDB' generates a clustered index
automatically, the index contains row ID values. Otherwise, the
`DB_ROW_ID' column does not appear in any index.

Undo logs in the rollback segment are divided into insert and update
undo logs. Insert undo logs are needed only in transaction rollback and
can be discarded as soon as the transaction commits.  Update undo logs
are used also in consistent reads, but they can be discarded only after
there is no transaction present for which `InnoDB' has assigned a
snapshot that in a consistent read could need the information in the
update undo log to build an earlier version of a database row.

*Guidelines for Managing Rollback Segments*

Commit your transactions regularly, including those transactions that
issue only consistent reads. Otherwise, `InnoDB' cannot discard data
from the update undo logs, and the rollback segment may grow too big,
filling up your tablespace.

The physical size of an undo log record in the rollback segment is
typically smaller than the corresponding inserted or updated row.  You
can use this information to calculate the space needed for your
rollback segment.

In the `InnoDB' multi-versioning scheme, a row is not physically
removed from the database immediately when you delete it with an SQL
statement. `InnoDB' only physically removes the corresponding row and
its index records when it discards the update undo log record written
for the deletion. This removal operation is called a purge
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_purge), and
it is quite fast, usually taking the same order of time as the SQL
statement that did the deletion.

If you insert and delete rows in smallish batches at about the same
rate in the table, the purge thread can start to lag behind and the
table can grow bigger and bigger because of all the `dead' rows, making
everything disk-bound and very slow. In such a case, throttle new row
operations, and allocate more resources to the purge thread by tuning
the `innodb_max_purge_lag' system variable. See *Note
innodb-parameters:: for more information.


File: manual.info,  Node: innodb-table-and-index,  Prev: innodb-multi-versioning,  Up: innodb-concepts

14.6.3.12 InnoDB Table and Index Structures
...........................................

* Menu:

* innodb-index-types::           Clustered and Secondary Indexes
* innodb-physical-structure::    Physical Structure of an InnoDB Index
* innodb-insert-buffering::      Insert Buffering
* innodb-adaptive-hash::         Adaptive Hash Indexes
* innodb-physical-record::       Physical Row Structure

*Role of the .frm File*

MySQL stores its data dictionary information for tables in `.frm' files
in database directories. This is true for all MySQL storage engines,
but every `InnoDB' table also has its own entry in the `InnoDB'
internal data dictionary inside the tablespace. When MySQL drops a
table or a database, it has to delete one or more `.frm' files as well
as the corresponding entries inside the `InnoDB' data dictionary.
Consequently, you cannot move `InnoDB' tables between databases simply
by moving the `.frm' files.


File: manual.info,  Node: innodb-index-types,  Next: innodb-physical-structure,  Prev: innodb-table-and-index,  Up: innodb-table-and-index

14.6.3.13 Clustered and Secondary Indexes
.........................................

Every `InnoDB' table has a special index called the clustered index
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_clustered_index)
where the data for the rows is stored. Typically, the clustered index
is synonymous with the primary key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_primary_key).
To get the best performance from queries, inserts, and other database
operations, you must understand how InnoDB uses the clustered index to
optimize the most common lookup and DML operations for each table.

   * If you define a `PRIMARY KEY' on your table, `InnoDB' uses it as
     the clustered index.

   * If you do not define a `PRIMARY KEY' for your table, MySQL picks
     the first `UNIQUE' index that has only `NOT NULL' columns as the
     primary key and `InnoDB' uses it as the clustered index.

   * If the table has no `PRIMARY KEY' or suitable `UNIQUE' index,
     `InnoDB' internally generates a hidden clustered index on a
     synthetic column containing row ID values. The rows are ordered by
     the ID that `InnoDB' assigns to the rows in such a table. The row
     ID is a 6-byte field that increases monotonically as new rows are
     inserted. Thus, the rows ordered by the row ID are physically in
     insertion order.

*How the Clustered Index Speeds Up Queries*

Accessing a row through the clustered index is fast because the row
data is on the same page where the index search leads. If a table is
large, the clustered index architecture often saves a disk I/O
operation when compared to storage organizations that store row data
using a different page from the index record.  (For example, `MyISAM'
uses one file for data rows and another for index records.)

*How Secondary Indexes Relate to the Clustered Index*

All indexes other than the clustered index are known as secondary
indexes
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_secondary_index).
In `InnoDB', each record in a secondary index contains the primary key
columns for the row, as well as the columns specified for the secondary
index.  `InnoDB' uses this primary key value to search for the row in
the clustered index.

If the primary key is long, the secondary indexes use more space, so it
is advantageous to have a short primary key.


File: manual.info,  Node: innodb-physical-structure,  Next: innodb-insert-buffering,  Prev: innodb-index-types,  Up: innodb-table-and-index

14.6.3.14 Physical Structure of an InnoDB Index
...............................................

All `InnoDB' indexes are B-trees where the index records are stored in
the leaf pages of the tree. The default size of an index page is 16KB.
When new records are inserted, `InnoDB' tries to leave 1/16 of the page
free for future insertions and updates of the index records.

If index records are inserted in a sequential order (ascending or
descending), the resulting index pages are about 15/16 full.  If
records are inserted in a random order, the pages are from 1/2 to 15/16
full. If the fill factor
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_fill_factor)
of an index page drops below 1/2, `InnoDB' tries to contract the index
tree to free the page.

*Note*:

Changing the page size is not a supported operation and there is no
guarantee that `InnoDB' will function normally with a page size other
than 16KB. Problems compiling or running InnoDB may occur. In
particular, `ROW_FORMAT=COMPRESSED' in the `InnoDB Plugin' assumes that
the page size is at most 16KB and uses 14-bit pointers.

A version of `InnoDB' built for one page size cannot use data files or
log files from a version built for a different page size.


File: manual.info,  Node: innodb-insert-buffering,  Next: innodb-adaptive-hash,  Prev: innodb-physical-structure,  Up: innodb-table-and-index

14.6.3.15 Insert Buffering
..........................

It is a common situation in database applications that the primary key
is a unique identifier and new rows are inserted in the ascending order
of the primary key. Thus, insertions into the clustered index do not
require random reads from a disk.

On the other hand, secondary indexes are usually nonunique, and
insertions into secondary indexes happen in a relatively random order.
This would cause a lot of random disk I/O operations without a special
mechanism used in `InnoDB'.

If an index record should be inserted into a nonunique secondary index,
`InnoDB' checks whether the secondary index page is in the buffer pool.
If that is the case, `InnoDB' does the insertion directly to the index
page. If the index page is not found in the buffer pool, `InnoDB'
inserts the record to a special insert buffer structure. The insert
buffer is kept so small that it fits entirely in the buffer pool, and
insertions can be done very fast.

*Disk I/O for Flushing the Insert Buffer*

Periodically, the insert buffer is merged into the secondary index
trees in the database. Often, it is possible to merge several changes
into the same page of the index tree, saving disk I/O operations. It
has been measured that the insert buffer can speed up insertions into a
table up to 15 times.

The insert buffer merging may continue to happen _after_ the
transaction has been committed.  In fact, it may continue to happen
after a server shutdown and restart (see *Note
forcing-innodb-recovery::).

Insert buffer merging may take many hours when many secondary indexes
must be updated and many rows have been inserted. During this time,
disk I/O will be increased, which can cause significant slowdown on
disk-bound queries. Another significant background I/O operation is the
purge thread (see *Note innodb-multi-versioning::).


File: manual.info,  Node: innodb-adaptive-hash,  Next: innodb-physical-record,  Prev: innodb-insert-buffering,  Up: innodb-table-and-index

14.6.3.16 Adaptive Hash Indexes
...............................

If a table fits almost entirely in main memory, the fastest way to
perform queries on it is to use hash indexes.  `InnoDB' has a mechanism
that monitors index searches made to the indexes defined for a table. If
`InnoDB' notices that queries could benefit from building a hash index,
it does so automatically.

The hash index is always built based on an existing B-tree index on the
table. `InnoDB' can build a hash index on a prefix of any length of the
key defined for the B-tree, depending on the pattern of searches that
`InnoDB' observes for the B-tree index. A hash index can be partial: It
is not required that the whole B-tree index is cached in the buffer
pool. `InnoDB' builds hash indexes on demand for those pages of the
index that are often accessed.

In a sense, `InnoDB' tailors itself through the adaptive hash index
mechanism to ample main memory, coming closer to the architecture of
main-memory databases.


File: manual.info,  Node: innodb-physical-record,  Prev: innodb-adaptive-hash,  Up: innodb-table-and-index

14.6.3.17 Physical Row Structure
................................

The physical row structure for an `InnoDB' table depends on the row
format specified when the table was created. For MySQL 5.1, `InnoDB'
uses the `COMPACT' format by default, but the `REDUNDANT' format is
available to retain compatibility with older versions of MySQL. To
check the row format of an `InnoDB' table, use *Note `SHOW TABLE
STATUS': show-table-status.

The compact row format decreases row storage space by about 20% at the
cost of increasing CPU use for some operations. If your workload is a
typical one that is limited by cache hit rates and disk speed, compact
format is likely to be faster. If the workload is a rare case that is
limited by CPU speed, compact format might be slower.

Rows in `InnoDB' tables that use `REDUNDANT' row format have the
following characteristics:

   * Each index record contains a 6-byte header. The header is used to
     link together consecutive records, and also in row-level locking.

   * Records in the clustered index contain fields for all user-defined
     columns. In addition, there is a 6-byte transaction ID field and a
     7-byte roll pointer field.

   * If no primary key was defined for a table, each clustered index
     record also contains a 6-byte row ID field.

   * Each secondary index record also contains all the primary key
     fields defined for the clustered index key that are not in the
     secondary index.

   * A record contains a pointer to each field of the record. If the
     total length of the fields in a record is less than 128 bytes, the
     pointer is one byte; otherwise, two bytes. The array of these
     pointers is called the record directory. The area where these
     pointers point is called the data part of the record.

   * Internally, `InnoDB' stores fixed-length character columns such as
     *Note `CHAR(10)': char. in a fixed-length format. `InnoDB' does
     not truncate trailing spaces from *Note `VARCHAR': char. columns.

   * An SQL `NULL' value reserves one or two bytes in the record
     directory. Besides that, an SQL `NULL' value reserves zero bytes
     in the data part of the record if stored in a variable length
     column. In a fixed-length column, it reserves the fixed length of
     the column in the data part of the record.  Reserving the fixed
     space for `NULL' values enables an update of the column from `NULL'
     to a non-`NULL' value to be done in place without causing
     fragmentation of the index page.

Rows in `InnoDB' tables that use `COMPACT' row format have the following
characteristics:

   * Each index record contains a 5-byte header that may be preceded by
     a variable-length header. The header is used to link together
     consecutive records, and also in row-level locking.

   * The variable-length part of the record header contains a bit
     vector for indicating `NULL' columns. If the number of columns in
     the index that can be `NULL' is N, the bit vector occupies
     `CEILING(N/8)' bytes. (For example, if there are anywhere from 9
     to 15 columns that can be `NULL', the bit vector uses two bytes.)
     Columns that are `NULL' do not occupy space other than the bit in
     this vector. The variable-length part of the header also contains
     the lengths of variable-length columns. Each length takes one or
     two bytes, depending on the maximum length of the column. If all
     columns in the index are `NOT NULL' and have a fixed length, the
     record header has no variable-length part.

   * For each non-`NULL' variable-length field, the record header
     contains the length of the column in one or two bytes. Two bytes
     will only be needed if part of the column is stored externally in
     overflow pages or the maximum length exceeds 255 bytes and the
     actual length exceeds 127 bytes. For an externally stored column,
     the 2-byte length indicates the length of the internally stored
     part plus the 20-byte pointer to the externally stored part. The
     internal part is 768 bytes, so the length is 768+20. The 20-byte
     pointer stores the true length of the column.

   * The record header is followed by the data contents of the
     non-`NULL' columns.

   * Records in the clustered index contain fields for all user-defined
     columns. In addition, there is a 6-byte transaction ID field and a
     7-byte roll pointer field.

   * If no primary key was defined for a table, each clustered index
     record also contains a 6-byte row ID field.

   * Each secondary index record also contains all the primary key
     fields defined for the clustered index key that are not in the
     secondary index. If any of these primary key fields are variable
     length, the record header for each secondary index will have a
     variable-length part to record their lengths, even if the
     secondary index is defined on fixed-length columns.

   * Internally, `InnoDB' stores fixed-length, fixed-width character
     columns such as *Note `CHAR(10)': char. in a fixed-length format.
     `InnoDB' does not truncate trailing spaces from *Note `VARCHAR':
     char. columns.

   * Internally, `InnoDB' attempts to store UTF-8 *Note `CHAR(N)': char.
     columns in N bytes by trimming trailing spaces. (With `REDUNDANT'
     row format, such columns occupy 3 x N bytes.) Reserving the minimum
     space N in many cases enables column updates to be done in place
     without causing fragmentation of the index page.


File: manual.info,  Node: innodb-tablespace,  Next: innodb-tables,  Prev: innodb-concepts,  Up: innodb-storage-engine

14.6.4 InnoDB Tablespace Management
-----------------------------------

* Menu:

* innodb-init::                  Creating the InnoDB Tablespace
* innodb-multiple-tablespaces::  Using Per-Table Tablespaces
* innodb-data-log-reconfiguration::  Changing the Number or Size of InnoDB Log Files and Resizing the InnoDB Tablespace
* innodb-raw-devices::           Using Raw Disk Partitions for the Shared Tablespace


File: manual.info,  Node: innodb-init,  Next: innodb-multiple-tablespaces,  Prev: innodb-tablespace,  Up: innodb-tablespace

14.6.4.1 Creating the InnoDB Tablespace
.......................................

Suppose that you have installed MySQL and have edited your option file
so that it contains the necessary `InnoDB' configuration parameters.
Before starting MySQL, verify that the directories you have specified
for `InnoDB' data files and log files exist and that the MySQL server
has access rights to those directories. `InnoDB' does not create
directories, only files. Check also that you have enough disk space for
the data and log files.

It is best to run the MySQL server *Note `mysqld': mysqld. from the
command prompt when you first start the server with `InnoDB' enabled,
not from *Note `mysqld_safe': mysqld-safe. or as a Windows service.
When you run from a command prompt you see what *Note `mysqld': mysqld.
prints and what is happening. On Unix, just invoke *Note `mysqld':
mysqld. On Windows, start *Note `mysqld': mysqld. with the `--console'
option to direct the output to the console window.

When you start the MySQL server after initially configuring `InnoDB' in
your option file, `InnoDB' creates your data files and log files, and
prints something like this:


     InnoDB: The first specified datafile /home/heikki/data/ibdata1
     did not exist:
     InnoDB: a new database to be created!
     InnoDB: Setting file /home/heikki/data/ibdata1 size to 134217728
     InnoDB: Database physically writes the file full: wait...
     InnoDB: datafile /home/heikki/data/ibdata2 did not exist:
     new to be created
     InnoDB: Setting file /home/heikki/data/ibdata2 size to 262144000
     InnoDB: Database physically writes the file full: wait...
     InnoDB: Log file /home/heikki/data/logs/ib_logfile0 did not exist:
     new to be created
     InnoDB: Setting log file /home/heikki/data/logs/ib_logfile0 size
     to 5242880
     InnoDB: Log file /home/heikki/data/logs/ib_logfile1 did not exist:
     new to be created
     InnoDB: Setting log file /home/heikki/data/logs/ib_logfile1 size
     to 5242880
     InnoDB: Doublewrite buffer not found: creating new
     InnoDB: Doublewrite buffer created
     InnoDB: Creating foreign key constraint system tables
     InnoDB: Foreign key constraint system tables created
     InnoDB: Started
     mysqld: ready for connections

At this point `InnoDB' has initialized its tablespace and log files.
You can connect to the MySQL server with the usual MySQL client
programs like *Note `mysql': mysql. When you shut down the MySQL server
with *Note `mysqladmin shutdown': mysqladmin, the output is like this:


     010321 18:33:34  mysqld: Normal shutdown
     010321 18:33:34  mysqld: Shutdown Complete
     InnoDB: Starting shutdown...
     InnoDB: Shutdown completed

You can look at the data file and log directories and you see the files
created there. When MySQL is started again, the data files and log
files have been created already, so the output is much briefer:


     InnoDB: Started
     mysqld: ready for connections

If you add the `innodb_file_per_table' option to `my.cnf', `InnoDB'
stores each table in its own `.ibd' file in the same MySQL database
directory where the `.frm' file is created. See *Note
innodb-multiple-tablespaces::.


File: manual.info,  Node: innodb-multiple-tablespaces,  Next: innodb-data-log-reconfiguration,  Prev: innodb-init,  Up: innodb-tablespace

14.6.4.2 Using Per-Table Tablespaces
....................................

You can store each `InnoDB' table and its indexes in its own file. This
feature is called `multiple tablespaces' because in effect each table
has its own tablespace.

*Advantages of Per-Table Tablespaces*

   * You can reclaim disk space when truncating or dropping a table.
     For tables created when file-per-table mode is turned off,
     truncating or dropping them creates free space internally in the
     ibdata files
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_ibdata_file).
     That free space can only be used for new `InnoDB' data.

   * The *Note `TRUNCATE TABLE': truncate-table. operation is faster
     when run on individual `.ibd' files.

   * You can store specific tables on separate storage devices, for I/O
     optimization, space management, or backup purposes.

   * You can run *Note `OPTIMIZE TABLE': optimize-table. to compact or
     recreate a tablespace. When you run an *Note `OPTIMIZE TABLE':
     optimize-table, `InnoDB' will create a new `.ibd' file with a
     temporary name, using only the space required to store actual
     data. When the optimization is complete, `InnoDB' removes the old
     `.ibd' file and replaces it with the new `.ibd' file. If the
     previous `.ibd' file had grown significantly but actual data only
     accounted for a portion of its size, running *Note `OPTIMIZE
     TABLE': optimize-table. allows you to reclaim the unused space.

   * You can move individual `InnoDB' tables rather than entire
     databases.

   * You can enable compression
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_compression)
     for table and index data, using the compressed row format
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_compressed_row_format).

   * You can enable more efficient storage for tables with large BLOB
     or text columns using the dynamic row format
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_dynamic_row_format).

   * Using `innodb_file_per_table' may improve chances for a successful
     recovery and save time if a corruption occurs, a server cannot be
     restarted, or backup and binary logs are unavailable.

   * You can back up or restore a single table quickly, without
     interrupting the use of other `InnoDB' tables, using the MySQL
     Enterprise Backup product. See Backing Up and Restoring a Single
     .ibd File
     (http://dev.mysql.com/doc/mysql-enterprise-backup/3.10/en/partial.restoring.single.html)
     for the procedure and restrictions.

   * File-per-table mode allows you to excluded tables from a backup.
     This is beneficial if you have tables that require backup less
     frequently or on a different schedule.

   * File-per-table mode is convenient for per-table status reporting
     when copying or backing up tables.

   * File-per-table mode allows you to monitor table size at a file
     system level, without accessing MySQL.

   * Common Linux file systems do not permit concurrent writes to a
     single file when `innodb_flush_method' is set to `O_DIRECT'. As a
     result, there are possible performance improvements when using
     `innodb_file_per_table' in conjunction with `innodb_flush_method'.

   * If `innodb_file_per_table' is disabled, there is one shared
     tablespace (the system tablespace) for tables, the data
     dictionary, and undo logs.  This single tablespace has a 64TB size
     limit. If `innodb_file_per_table' is enabled, each table has its
     own tablespace, each with a 64TB size limit. See *Note
     table-size-limit:: for related information.

*Potential Disadvantages of Per-Table Tablespaces*

   * With `innodb_file_per_table', each table may have unused table
     space, which can only be utilized by rows of the same table. This
     could lead to more rather than less wasted table space if not
     properly managed.

   * `fsync' operations must run on each open table rather than on a
     single file. Because there is a separate `fsync' operation for
     each file, write operations on multiple tables cannot be combined
     into a single I/O operation. This may require `InnoDB' to perform
     a higher total number of `fsync' operations.

   * *Note `mysqld': mysqld. must keep 1 open file handle per table,
     which may impact performance if you have numerous tables.

   * More file descriptors are used.

   * If backward compatibility with MySQL 5.1 is a concern, be aware
     that enabling `innodb_file_per_table' means that *Note `ALTER
     TABLE': alter-table. will move `InnoDB' tables from the system
     tablespace to individual `.ibd' files.

   * If many tables are growing there is potential for more
     fragmentation which can impede *Note `DROP TABLE': drop-table. and
     table scan performance. However, when fragmentation is managed,
     having files in their own tablespace can improve performance.

   * The buffer pool is scanned when dropping a per-table tablespace,
     which can take several seconds for buffer pools that are tens of
     gigabytes in size. The scan is performed with a broad internal
     lock, which may delay other operations.  Tables in the shared
     tablespace are not affected.

   * The `innodb_autoextend_increment' variable, which defines
     increment size (in MB) for extending the size of an auto-extending
     shared tablespace file when it becomes full, does not apply to
     per-table tablespace files.  Per-table tablespace files are
     auto-extending regardless of the value of
     `innodb_autoextend_increment'.  The initial extensions are by
     small amounts, after which extensions occur in increments of 4MB.

*Enabling and Disabling Multiple Tablespaces*

To enable multiple tablespaces, start the server with the
`--innodb_file_per_table' option. For example, add a line to the
`[mysqld]' section of `my.cnf':


     [mysqld]
     innodb_file_per_table

With multiple tablespaces enabled, `InnoDB' stores each newly created
table into its own `TBL_NAME.ibd' file in the database directory where
the table belongs. This is similar to what the `MyISAM' storage engine
does, but `MyISAM' divides the table into a `TBL_NAME.MYD' data file
and an `TBL_NAME.MYI' index file. For `InnoDB', the data and the
indexes are stored together in the `.ibd' file. The `TBL_NAME.frm' file
is still created as usual.

You cannot freely move `.ibd' files between database directories as you
can with `MyISAM' table files. This is because the table definition
that is stored in the `InnoDB' shared tablespace includes the database
name, and because `InnoDB' must preserve the consistency of transaction
IDs and log sequence numbers.

If you remove the `innodb_file_per_table' line from `my.cnf' and
restart the server, `InnoDB' creates tables inside the shared
tablespace files again.

The `--innodb_file_per_table' option affects only table creation, not
access to existing tables. If you start the server with this option,
new tables are created using `.ibd' files, but you can still access
tables that exist in the shared tablespace. If you start the server
without this option, new tables are created in the shared tablespace,
but you can still access any tables that were created using multiple
tablespaces.

*Note*:

`InnoDB' always needs the shared tablespace because it puts its
internal data dictionary and undo logs there. The `.ibd' files are not
sufficient for `InnoDB' to operate.

To move an `.ibd' file and the associated table from one database to
another, use a *Note `RENAME TABLE': rename-table. statement:


     RENAME TABLE DB1.TBL_NAME TO DB2.TBL_NAME;

If you have a `clean' backup of an `.ibd' file, you can restore it to
the MySQL installation from which it originated as follows:

  1. Issue this *Note `ALTER TABLE': alter-table.  statement to delete
     the current `.ibd' file:


          ALTER TABLE TBL_NAME DISCARD TABLESPACE;

  2. Copy the backup `.ibd' file to the proper database directory.

  3. Issue this *Note `ALTER TABLE': alter-table.  statement to tell
     `InnoDB' to use the new `.ibd' file for the table:


          ALTER TABLE TBL_NAME IMPORT TABLESPACE;

In this context, a `clean' `.ibd' file backup is one for which the
following requirements are satisfied:

   * There are no uncommitted modifications by transactions in the
     `.ibd' file.

   * There are no unmerged insert buffer entries in the `.ibd' file.

   * Purge has removed all delete-marked index records from the `.ibd'
     file.

   * *Note `mysqld': mysqld. has flushed all modified pages of the
     `.ibd' file from the buffer pool to the file.

You can make a clean backup `.ibd' file using the following method:

  1. Stop all activity from the *Note `mysqld': mysqld. server and
     commit all transactions.

  2. Wait until *Note `SHOW ENGINE INNODB STATUS': show-engine. shows
     that there are no active transactions in the database, and the
     main thread status of `InnoDB' is `Waiting for server activity'.
     Then you can make a copy of the `.ibd' file.

Another method for making a clean copy of an `.ibd' file is to use the
commercial `InnoDB Hot Backup' tool:

  1. Use `InnoDB Hot Backup' to back up the `InnoDB' installation.

  2. Start a second *Note `mysqld': mysqld. server on the backup and
     let it clean up the `.ibd' files in the backup.


File: manual.info,  Node: innodb-data-log-reconfiguration,  Next: innodb-raw-devices,  Prev: innodb-multiple-tablespaces,  Up: innodb-tablespace

14.6.4.3 Changing the Number or Size of InnoDB Log Files and Resizing the InnoDB Tablespace
...........................................................................................

This section describes how to change the number or size of `InnoDB'
redo log
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_redo_log)
files and how to increase or decrease `InnoDB' system tablespace
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_system_tablespace)
size.

*Changing the Number or Size of InnoDB Log Files*

To change the number or the size of your `InnoDB' redo log files,
perform the following steps:

  1. If `innodb_fast_shutdown' is set to 2, set `innodb_fast_shutdown'
     to 1:


          mysql> SET GLOBAL innodb_fast_shutdown = 1;

  2. After ensuring that `innodb_fast_shutdown' is not set to 2, stop
     the MySQL server and make sure that it shuts down without errors
     (to ensure that there is no information for outstanding
     transactions in the log).

  3. Copy the old log files into a safe place in case something went
     wrong during the shutdown and you need them to recover the
     tablespace.

  4. Delete the old log files from the log file directory.

  5. Edit `my.cnf' to change the log file configuration.

  6. Start the MySQL server again. *Note `mysqld': mysqld. sees that no
     *Note `InnoDB': innodb-storage-engine. log files exist at startup
     and creates new ones.

*Increasing the Size of the InnoDB Tablespace*

The easiest way to increase the size of the `InnoDB' system tablespace
is to configure it from the beginning to be auto-extending. Specify the
`autoextend' attribute for the last data file in the tablespace
definition. Then `InnoDB' increases the size of that file automatically
in 8MB increments when it runs out of space. The increment size can be
changed by setting the value of the `innodb_autoextend_increment'
system variable, which is measured in megabytes.

You can expand the system tablespace by a defined amount by adding
another data file:

  1. Shut down the MySQL server.

  2. If the previous last data file is defined with the keyword
     `autoextend', change its definition to use a fixed size, based on
     how large it has actually grown. Check the size of the data file,
     round it down to the closest multiple of 1024 x 1024 bytes (=
     1MB), and specify this rounded size explicitly in
     `innodb_data_file_path'.

  3. Add a new data file to the end of `innodb_data_file_path',
     optionally making that file auto-extending. Only the last data
     file in the `innodb_data_file_path' can be specified as
     auto-extending.

  4. Start the MySQL server again.

For example, this tablespace has just one auto-extending data file
`ibdata1':


     innodb_data_home_dir =
     innodb_data_file_path = /ibdata/ibdata1:10M:autoextend

Suppose that this data file, over time, has grown to 988MB. Here is the
configuration line after modifying the original data file to use a
fixed size and adding a new auto-extending data file:


     innodb_data_home_dir =
     innodb_data_file_path = /ibdata/ibdata1:988M;/disk2/ibdata2:50M:autoextend

When you add a new data file to the system tablespace configuration,
make sure that the filename does not refer to an existing file.
`InnoDB' creates and initializes the file when you restart the server.

*Decreasing the Size of the InnoDB Tablespace*

Currently, you cannot remove a data file from the tablespace. To
decrease the size of your tablespace, use this procedure:

  1. Use *Note `mysqldump': mysqldump. to dump all your `InnoDB' tables.

  2. Stop the server.

  3. Remove all the existing tablespace files, including the `ibdata'
     and `ib_log' files. If you want to keep a backup copy of the
     information, then copy all the `ib*' files to another location
     before the removing the files in your MySQL installation.

  4. Remove any `.frm' files for `InnoDB' tables.

  5. Configure a new tablespace.

  6. Restart the server.

  7. Import the dump files.


File: manual.info,  Node: innodb-raw-devices,  Prev: innodb-data-log-reconfiguration,  Up: innodb-tablespace

14.6.4.4 Using Raw Disk Partitions for the Shared Tablespace
............................................................

You can use raw disk partitions as data files in the `InnoDB' system
tablespace
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_system_tablespace).
This technique enables nonbuffered I/O on Windows and on some Linux and
Unix systems without file system overhead. Perform tests with and
without raw partitions to verify whether this change actually improves
performance on your system.

When you use a raw disk partition, ensure that the user ID that runs
the MySQL server has read and write privileges for that partition.  For
example, if you run the server as the `mysql' user, the partition must
be readable and writeable by `mysql'. If you run the server with the
`--memlock' option, the server must be run as `root', so the partition
must be readable and writeable by `root'.

The procedures described below involve option file modification. For
additional information, see *Note option-files::.

*Allocating a Raw Disk Partition on Linux and Unix Systems*

  1. When you create a new data file, specify the keyword `newraw'
     immediately after the data file size for the
     `innodb_data_file_path' option. The partition must be at least as
     large as the size that you specify. Note that 1MB in `InnoDB' is
     1024 x 1024 bytes, whereas 1MB in disk specifications usually
     means 1,000,000 bytes.


          [mysqld]
          innodb_data_home_dir=
          innodb_data_file_path=/dev/hdd1:3Gnewraw;/dev/hdd2:2Gnewraw

  2. Restart the server. `InnoDB' notices the `newraw' keyword and
     initializes the new partition. However, do not create or change any
     `InnoDB' tables yet. Otherwise, when you next restart the server,
     `InnoDB' reinitializes the partition and your changes are lost.
     (As a safety measure `InnoDB' prevents users from modifying data
     when any partition with `newraw' is specified.)

  3. After `InnoDB' has initialized the new partition, stop the server,
     change `newraw' in the data file specification to `raw':


          [mysqld]
          innodb_data_home_dir=
          innodb_data_file_path=/dev/hdd1:3Graw;/dev/hdd2:2Graw

  4. Restart the server. `InnoDB' now permits changes to be made.

*Allocating a Raw Disk Partition on Windows*

On Windows systems, the same steps and accompanying guidelines
described for Linux and Unix systems apply except that the
`innodb_data_file_path' setting differs slightly on Windows.

  1. When you create a new data file, specify the keyword `newraw'
     immediately after the data file size for the
     `innodb_data_file_path' option:


          [mysqld]
          innodb_data_home_dir=
          innodb_data_file_path=//./D::10Gnewraw

     The `//./' corresponds to the Windows syntax of `\\.\' for
     accessing physical drives. In the example above, `D:' is the drive
     letter of the partition.

  2. Restart the server. `InnoDB' notices the `newraw' keyword and
     initializes the new partition.

  3. After `InnoDB' has initialized the new partition, stop the server,
     change `newraw' in the data file specification to `raw':


          [mysqld]
          innodb_data_home_dir=
          innodb_data_file_path=//./D::10Graw

  4. Restart the server. `InnoDB' now permits changes to be made.


File: manual.info,  Node: innodb-tables,  Next: innodb-disk-management,  Prev: innodb-tablespace,  Up: innodb-storage-engine

14.6.5 InnoDB Table Management
------------------------------

* Menu:

* using-innodb-tables::          Creating InnoDB Tables
* innodb-transactions-with-different-apis::  Using InnoDB with Different APIs
* innodb-migration::             Moving or Copying InnoDB Tables to Another Machine
* converting-tables-to-innodb::  Converting Tables from MyISAM to InnoDB
* innodb-auto-increment-handling::  AUTO_INCREMENT Handling in InnoDB
* innodb-foreign-key-constraints::  InnoDB and FOREIGN KEY Constraints
* innodb-restrictions::          Limits on InnoDB Tables


File: manual.info,  Node: using-innodb-tables,  Next: innodb-transactions-with-different-apis,  Prev: innodb-tables,  Up: innodb-tables

14.6.5.1 Creating InnoDB Tables
...............................

To create an `InnoDB' table, specify an `ENGINE=InnoDB' option in the
*Note `CREATE TABLE': create-table. statement:


     CREATE TABLE customers (a INT, b CHAR (20), INDEX (a)) ENGINE=InnoDB;

The statement creates a table and an index on column `a' in the
`InnoDB' tablespace that consists of the data files that you specified
in `my.cnf'. In addition, MySQL creates a file `customers.frm' in the
`test' directory under the MySQL database directory. Internally,
`InnoDB' adds an entry for the table to its own data dictionary. The
entry includes the database name. For example, if `test' is the
database in which the `customers' table is created, the entry is for
`'test/customers''.  This means you can create a table of the same name
`customers' in some other database, and the table names do not collide
inside `InnoDB'.

You can query the amount of free space in the `InnoDB' tablespace by
issuing a *Note `SHOW TABLE STATUS': show-table-status. statement for
any `InnoDB' table. The amount of free space in the tablespace appears
in the `Data_free' section in the output of *Note `SHOW TABLE STATUS':
show-table-status. (or the `Comment' section prior to MySQL 5.1.24). For
example:


     SHOW TABLE STATUS FROM test LIKE 'customers'

The statistics
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_statistics)
*Note `SHOW': show. displays for `InnoDB' tables are only approximate.
They are used in SQL optimization. Table and index reserved sizes in
bytes are accurate, though.


File: manual.info,  Node: innodb-transactions-with-different-apis,  Next: innodb-migration,  Prev: using-innodb-tables,  Up: innodb-tables

14.6.5.2 Using InnoDB with Different APIs
.........................................

*Transactions in SQL*

By default, each client that connects to the MySQL server begins with
autocommit
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_autocommit)
mode enabled, which automatically commits every SQL statement as you
execute it. To use multiple-statement transactions, you can switch
autocommit off with the SQL statement `SET autocommit = 0' and end each
transaction with either *Note `COMMIT': commit. or *Note `ROLLBACK':
commit. If you want to leave autocommit on, you can begin your
transactions within *Note `START TRANSACTION': commit. and end them with
*Note `COMMIT': commit. or *Note `ROLLBACK': commit. The following
example shows two transactions. The first is committed; the second is
rolled back.


     shell> mysql test

     mysql> CREATE TABLE customer (a INT, b CHAR (20), INDEX (a))
         -> ENGINE=InnoDB;
     Query OK, 0 rows affected (0.00 sec)
     mysql> START TRANSACTION;
     Query OK, 0 rows affected (0.00 sec)
     mysql> INSERT INTO customer VALUES (10, 'Heikki');
     Query OK, 1 row affected (0.00 sec)
     mysql> COMMIT;
     Query OK, 0 rows affected (0.00 sec)
     mysql> SET autocommit=0;
     Query OK, 0 rows affected (0.00 sec)
     mysql> INSERT INTO customer VALUES (15, 'John');
     Query OK, 1 row affected (0.00 sec)
     mysql> ROLLBACK;
     Query OK, 0 rows affected (0.00 sec)
     mysql> SELECT * FROM customer;
     +------+--------+
     | a    | b      |
     +------+--------+
     |   10 | Heikki |
     +------+--------+
     1 row in set (0.00 sec)
     mysql>

*Transactions in Client-Side Languages*

In APIs such as PHP, Perl DBI, JDBC, ODBC, or the standard C call
interface of MySQL, you can send transaction control statements such as
*Note `COMMIT': commit. to the MySQL server as strings just like any
other SQL statements such as *Note `SELECT': select. or *Note `INSERT':
insert. Some APIs also offer separate special transaction commit and
rollback functions or methods.


File: manual.info,  Node: innodb-migration,  Next: converting-tables-to-innodb,  Prev: innodb-transactions-with-different-apis,  Up: innodb-tables

14.6.5.3 Moving or Copying InnoDB Tables to Another Machine
...........................................................

This section explains various techniques for moving or copying some or
all `InnoDB' tables to a different server. For example, you might move
an entire MySQL instance to a larger, faster server; you might clone an
entire MySQL instance to a new replication slave server; you might copy
individual tables to another server to development and test an
application, or to a data warehouse server to produce reports.

On Windows, `InnoDB' always stores database and table names internally
in lowercase. To move databases in a binary format from Unix to Windows
or from Windows to Unix, create all databases and tables using
lowercase names. A convenient way to accomplish this is to add the
following line to the `[mysqld]' section of your `my.cnf' or `my.ini'
file before creating any databases or tables:


     [mysqld]
     lower_case_table_names=1

Like `MyISAM' data files, `InnoDB' data and log files are
binary-compatible on all platforms having the same floating-point
number format. You can move an `InnoDB' database simply by copying all
the relevant files listed in *Note innodb-backup::. If the
floating-point formats differ but you have not used *Note `FLOAT':
floating-point-types. or *Note `DOUBLE': floating-point-types. data
types in your tables, then the procedure is the same: simply copy the
relevant files. If you use *Note `mysqldump': mysqldump. to dump your
tables on one machine and then import the dump files on the other
machine, it does not matter whether the formats differ or your tables
contain floating-point data.

One way to increase performance is to switch off autocommit mode when
importing data, assuming that the tablespace has enough space for the
big rollback segment that the import transactions generate.  Do the
commit only after importing a whole table or a segment of a table.


File: manual.info,  Node: converting-tables-to-innodb,  Next: innodb-auto-increment-handling,  Prev: innodb-migration,  Up: innodb-tables

14.6.5.4 Converting Tables from MyISAM to InnoDB
................................................

To convert a non-`InnoDB' table to use `InnoDB' use *Note `ALTER
TABLE': alter-table.:


     ALTER TABLE TABLE_NAME ENGINE=InnoDB;

*Important*:

Do not convert MySQL system tables in the `mysql' database (such as
`user' or `host') to the `InnoDB' type.  This is an unsupported
operation. The system tables must always be of the `MyISAM' type.

`InnoDB' does not have a special optimization for separate index
creation the way the `MyISAM' storage engine does. Therefore, it does
not pay to export and import the table and create indexes afterward.
The fastest way to alter a table to `InnoDB' is to do the inserts
directly to an `InnoDB' table. That is, use `ALTER TABLE ...
ENGINE=INNODB', or create an empty `InnoDB' table with identical
definitions and insert the rows with `INSERT INTO ... SELECT * FROM
...'.

If you have `UNIQUE' constraints on secondary keys, you can speed up a
table import by turning off the uniqueness checks temporarily during
the import operation:


     SET unique_checks=0;
     ... IMPORT OPERATION ...
     SET unique_checks=1;

For big tables, this saves disk I/O because `InnoDB' can use its insert
buffer
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_insert_buffer)
to write secondary index records as a batch. Be certain that the data
contains no duplicate keys.  `unique_checks' permits but does not
require storage engines to ignore duplicate keys.

To get better control over the insertion process, you might insert big
tables in pieces:


     INSERT INTO newtable SELECT * FROM oldtable
        WHERE yourkey > SOMETHING AND yourkey <= SOMETHINGELSE;

After all records have been inserted, you can rename the tables.

During the conversion of big tables, increase the size of the `InnoDB'
buffer pool to reduce disk I/O, to a maximum of 80% of physical memory.
You can also increase the sizes of the `InnoDB' log files.

Make sure that you do not fill up the tablespace: `InnoDB' tables
require a lot more disk space than `MyISAM' tables. If an *Note `ALTER
TABLE': alter-table. operation runs out of space, it starts a rollback,
and that can take hours if it is disk-bound. For inserts, `InnoDB' uses
the insert buffer to merge secondary index records to indexes in
batches. That saves a lot of disk I/O.  For rollback, no such mechanism
is used, and the rollback can take 30 times longer than the insertion.

In the case of a runaway rollback, if you do not have valuable data in
your database, it may be advisable to kill the database process rather
than wait for millions of disk I/O operations to complete.  For the
complete procedure, see *Note forcing-innodb-recovery::.

If you want all new user-created tables to use the `InnoDB' storage
engine, add the line `default-storage-engine=innodb' to the `[mysqld]'
section of your server option file.


File: manual.info,  Node: innodb-auto-increment-handling,  Next: innodb-foreign-key-constraints,  Prev: converting-tables-to-innodb,  Up: innodb-tables

14.6.5.5 AUTO_INCREMENT Handling in InnoDB
..........................................

* Menu:

* innodb-auto-increment-traditional::  Traditional InnoDB Auto-Increment Locking
* innodb-auto-increment-configurable::  Configurable InnoDB Auto-Increment Locking

Beginning with MySQL 5.1.22, `InnoDB' provides a locking strategy that
significantly improves scalability and performance of SQL statements
that add rows to tables with `AUTO_INCREMENT' columns. To use the
`AUTO_INCREMENT' mechanism with an `InnoDB' table, an `AUTO_INCREMENT'
column AI_COL must be defined as part of an index such that it is
possible to perform the equivalent of an indexed `SELECT MAX(AI_COL)'
lookup on the table to obtain the maximum column value. Typically, this
is achieved by making the column the first column of some table index.

This section provides background information on the original
(`traditional') implementation of auto-increment locking in `InnoDB',
explains the configurable locking mechanism, documents the parameter
for configuring the mechanism, and describes its behavior and
interaction with replication.


File: manual.info,  Node: innodb-auto-increment-traditional,  Next: innodb-auto-increment-configurable,  Prev: innodb-auto-increment-handling,  Up: innodb-auto-increment-handling

14.6.5.6 Traditional InnoDB Auto-Increment Locking
..................................................

The original implementation of auto-increment handling in `InnoDB' uses
the following strategy to prevent problems when using the binary log
for statement-based replication or for certain recovery scenarios.

If you specify an `AUTO_INCREMENT' column for an `InnoDB' table, the
table handle in the `InnoDB' data dictionary contains a special counter
called the auto-increment counter that is used in assigning new values
for the column. This counter is stored only in main memory, not on disk.

`InnoDB' uses the following algorithm to initialize the auto-increment
counter for a table `t' that contains an `AUTO_INCREMENT' column named
`ai_col': After a server startup, for the first insert into a table `t',
`InnoDB' executes the equivalent of this statement:


     SELECT MAX(ai_col) FROM t FOR UPDATE;

`InnoDB' increments the value retrieved by the statement and assigns it
to the column and to the auto-increment counter for the table. By
default, the value is incremented by one. This default can be
overridden by the `auto_increment_increment' configuration setting.

If the table is empty, `InnoDB' uses the value `1'. This default can be
overridden by the `auto_increment_offset' configuration setting.

If a *Note `SHOW TABLE STATUS': show-table-status. statement examines
the table `t' before the auto-increment counter is initialized, `InnoDB'
initializes but does not increment the value and stores it for use by
later inserts. This initialization uses a normal exclusive-locking read
on the table and the lock lasts to the end of the transaction.

`InnoDB' follows the same procedure for initializing the auto-increment
counter for a freshly created table.

After the auto-increment counter has been initialized, if you do not
explicitly specify a value for an `AUTO_INCREMENT' column, `InnoDB'
increments the counter and assigns the new value to the column. If you
insert a row that explicitly specifies the column value, and the value
is bigger than the current counter value, the counter is set to the
specified column value.

If a user specifies `NULL' or `0' for the `AUTO_INCREMENT' column in an
*Note `INSERT': insert, `InnoDB' treats the row as if the value was not
specified and generates a new value for it.

The behavior of the auto-increment mechanism is not defined if you
assign a negative value to the column, or if the value becomes bigger
than the maximum integer that can be stored in the specified integer
type.

When accessing the auto-increment counter, `InnoDB' uses a special
table-level `AUTO-INC' lock that it keeps to the end of the current SQL
statement, not to the end of the transaction. The special lock release
strategy was introduced to improve concurrency for inserts into a table
containing an `AUTO_INCREMENT' column. Nevertheless, two transactions
cannot have the `AUTO-INC' lock on the same table simultaneously, which
can have a performance impact if the `AUTO-INC' lock is held for a long
time. That might be the case for a statement such as `INSERT INTO t1
... SELECT ... FROM t2' that inserts all rows from one table into
another.

`InnoDB' uses the in-memory auto-increment counter as long as the
server runs. When the server is stopped and restarted, `InnoDB'
reinitializes the counter for each table for the first *Note `INSERT':
insert. to the table, as described earlier.

A server restart also cancels the effect of the `AUTO_INCREMENT = N'
table option in *Note `CREATE TABLE': create-table. and *Note `ALTER
TABLE': alter-table. statements, which you can use with `InnoDB' tables
to set the initial counter value or alter the current counter value.

You may see gaps in the sequence of values assigned to the
`AUTO_INCREMENT' column if you roll back transactions that have
generated numbers using the counter.


File: manual.info,  Node: innodb-auto-increment-configurable,  Prev: innodb-auto-increment-traditional,  Up: innodb-auto-increment-handling

14.6.5.7 Configurable InnoDB Auto-Increment Locking
...................................................

As described in the previous section, `InnoDB' uses a special lock
called the table-level `AUTO-INC' lock for inserts into tables with
`AUTO_INCREMENT' columns. This lock is normally held to the end of the
statement (not to the end of the transaction), to ensure that
auto-increment numbers are assigned in a predictable and repeatable
order for a given sequence of *Note `INSERT': insert. statements.

In the case of statement-based replication, this means that when an SQL
statement is replicated on a slave server, the same values are used for
the auto-increment column as on the master server. The result of
execution of multiple *Note `INSERT': insert. statements is
deterministic, and the slave reproduces the same data as on the master.
If auto-increment values generated by multiple *Note `INSERT': insert.
statements were interleaved, the result of two concurrent *Note
`INSERT': insert. statements would be nondeterministic, and could not
reliably be propagated to a slave server using statement-based
replication.

To make this clear, consider an example that uses this table:


     CREATE TABLE t1 (
       c1 INT(11) NOT NULL AUTO_INCREMENT,
       c2 VARCHAR(10) DEFAULT NULL,
       PRIMARY KEY (c1)
     ) ENGINE=InnoDB;

Suppose that there are two transactions running, each inserting rows
into a table with an `AUTO_INCREMENT' column. One transaction is using
an *Note `INSERT ... SELECT': insert-select. statement that inserts
1000 rows, and another is using a simple *Note `INSERT': insert.
statement that inserts one row:


     Tx1: INSERT INTO t1 (c2) SELECT 1000 rows from another table ...
     Tx2: INSERT INTO t1 (c2) VALUES ('xxx');

`InnoDB' cannot tell in advance how many rows will be retrieved from
the *Note `SELECT': select.  in the *Note `INSERT': insert. statement
in Tx1, and it assigns the auto-increment values one at a time as the
statement proceeds. With a table-level lock, held to the end of the
statement, only one *Note `INSERT': insert.  statement referring to
table `t1' can execute at a time, and the generation of auto-increment
numbers by different statements is not interleaved. The auto-increment
value generated by the Tx1 *Note `INSERT ... SELECT': insert-select.
statement will be consecutive, and the (single) auto-increment value
used by the *Note `INSERT': insert. statement in Tx2 will either be
smaller or larger than all those used for Tx1, depending on which
statement executes first.

As long as the SQL statements execute in the same order when replayed
from the binary log (when using statement-based replication, or in
recovery scenarios), the results will be the same as they were when Tx1
and Tx2 first ran. Thus, table-level locks held until the end of a
statement make *Note `INSERT': insert. statements using auto-increment
safe for use with statement-based replication.  However, those locks
limit concurrency and scalability when multiple transactions are
executing insert statements at the same time.

In the preceding example, if there were no table-level lock, the value
of the auto-increment column used for the *Note `INSERT': insert. in
Tx2 depends on precisely when the statement executes. If the *Note
`INSERT': insert. of Tx2 executes while the *Note `INSERT': insert. of
Tx1 is running (rather than before it starts or after it completes),
the specific auto-increment values assigned by the two *Note `INSERT':
insert. statements are nondeterministic, and may vary from run to run.

As of MySQL 5.1.22, `InnoDB' can avoid using the table-level `AUTO-INC'
lock for a class of *Note `INSERT': insert. statements where the number
of rows is known in advance, and still preserve deterministic execution
and safety for statement-based replication. Further, if you are not
using the binary log to replay SQL statements as part of recovery or
replication, you can entirely eliminate use of the table-level
`AUTO-INC' lock for even greater concurrency and performance, at the
cost of permitting gaps in auto-increment numbers assigned by a
statement and potentially having the numbers assigned by concurrently
executing statements interleaved.

For *Note `INSERT': insert. statements where the number of rows to be
inserted is known at the beginning of processing the statement,
`InnoDB' quickly allocates the required number of auto-increment values
without taking any lock, but only if there is no concurrent session
already holding the table-level `AUTO-INC' lock (because that other
statement will be allocating auto-increment values one-by-one as it
proceeds). More precisely, such an *Note `INSERT': insert. statement
obtains auto-increment values under the control of a mutex (a
light-weight lock) that is _not_ held until the statement completes,
but only for the duration of the allocation process.

This new locking scheme enables much greater scalability, but it does
introduce some subtle differences in how auto-increment values are
assigned compared to the original mechanism. To describe the way
auto-increment works in `InnoDB', the following discussion defines some
terms, and explains how `InnoDB' behaves using different settings of the
`innodb_autoinc_lock_mode' configuration parameter, which you can set
at server startup as of MySQL 5.1.22. Additional considerations are
described following the explanation of auto-increment locking behavior.

First, some definitions:

   * `*Note `INSERT': insert.-like' statements

     All statements that generate new rows in a table, including *Note
     `INSERT': insert, *Note `INSERT ... SELECT': insert-select, *Note
     `REPLACE': replace, *Note `REPLACE ... SELECT': replace, and *Note
     `LOAD DATA': load-data.

   * `Simple inserts'

     Statements for which the number of rows to be inserted can be
     determined in advance (when the statement is initially processed).
     This includes single-row and multiple-row *Note `INSERT': insert.
     and *Note `REPLACE': replace. statements that do not have a nested
     subquery, but not *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate.

   * `Bulk inserts'

     Statements for which the number of rows to be inserted (and the
     number of required auto-increment values) is not known in advance.
     This includes *Note `INSERT ... SELECT': insert-select, *Note
     `REPLACE ... SELECT': replace, and *Note `LOAD DATA': load-data.
     statements, but not plain `INSERT'. `InnoDB' will assign new
     values for the `AUTO_INCREMENT' column one at a time as each row
     is processed.

   * `Mixed-mode inserts'

     These are `simple insert' statements that specify the
     auto-increment value for some (but not all) of the new rows. An
     example follows, where `c1' is an `AUTO_INCREMENT' column of table
     `t1':


          INSERT INTO t1 (c1,c2) VALUES (1,'a'), (NULL,'b'), (5,'c'), (NULL,'d');

     Another type of `mixed-mode insert' is *Note `INSERT ... ON
     DUPLICATE KEY UPDATE': insert-on-duplicate, which in the worst
     case is in effect an *Note `INSERT': insert.  followed by a *Note
     `UPDATE': update, where the allocated value for the
     `AUTO_INCREMENT' column may or may not be used during the update
     phase.

There are three possible settings for the `innodb_autoinc_lock_mode'
parameter:

   * `innodb_autoinc_lock_mode = 0' (`traditional' lock mode)

     This lock mode provides the same behavior as before
     `innodb_autoinc_lock_mode' existed. For all `*Note `INSERT':
     insert.-like' statements, a special table-level `AUTO-INC' lock is
     obtained and held to the end of the statement. This assures that
     the auto-increment values assigned by any given statement are
     consecutive.

     This lock mode is provided for:

        * Backward compatibility.

        * Performance testing.

        * Working around issues with `mixed-mode inserts', due to the
          possible differences in semantics described later.

   * `innodb_autoinc_lock_mode = 1' (`consecutive' lock mode)

     This is the default lock mode. In this mode, `bulk inserts' use
     the special `AUTO-INC' table-level lock and hold it until the end
     of the statement.  This applies to all *Note `INSERT ... SELECT':
     insert-select, *Note `REPLACE ... SELECT': replace, and *Note
     `LOAD DATA': load-data. statements. Only one statement holding the
     `AUTO-INC' lock can execute at a time.

     With this lock mode, `simple inserts' (only) use a new locking
     model where a light-weight mutex is used during the allocation of
     auto-increment values, and no table-level `AUTO-INC' lock is used,
     unless an `AUTO-INC' lock is held by another transaction. If
     another transaction does hold an `AUTO-INC' lock, a `simple
     insert' waits for the `AUTO-INC' lock, as if it too were a `bulk
     insert'.

     This lock mode ensures that, in the presence of *Note `INSERT':
     insert. statements where the number of rows is not known in
     advance (and where auto-increment numbers are assigned as the
     statement progresses), all auto-increment values assigned by any
     `*Note `INSERT': insert.-like' statement are consecutive, and
     operations are safe for statement-based replication.

     Simply put, the important impact of this lock mode is
     significantly better scalability. This mode is safe for use with
     statement-based replication. Further, as with `traditional' lock
     mode, auto-increment numbers assigned by any given statement are
     _consecutive_. In this mode, there is _no change_ in semantics
     compared to `traditional' mode for any statement that uses
     auto-increment, with one important exception.

     The exception is for `mixed-mode inserts', where the user provides
     explicit values for an `AUTO_INCREMENT' column for some, but not
     all, rows in a multiple-row `simple insert'.  For such inserts,
     `InnoDB' will allocate more auto-increment values than the number
     of rows to be inserted. However, all values automatically assigned
     are consecutively generated (and thus higher than) the
     auto-increment value generated by the most recently executed
     previous statement. `Excess' numbers are lost.

   * `innodb_autoinc_lock_mode = 2' (`interleaved' lock mode)

     In this lock mode, no `*Note `INSERT': insert.-like' statements
     use the table-level `AUTO-INC' lock, and multiple statements can
     execute at the same time.  This is the fastest and most scalable
     lock mode, but it is _not safe_ when using statement-based
     replication or recovery scenarios when SQL statements are replayed
     from the binary log.

     In this lock mode, auto-increment values are guaranteed to be
     unique and monotonically increasing across all concurrently
     executing `*Note `INSERT': insert.-like' statements. However,
     because multiple statements can be generating numbers at the same
     time (that is, allocation of numbers is _interleaved_ across
     statements), the values generated for the rows inserted by any
     given statement may not be consecutive.

     If the only statements executing are `simple inserts' where the
     number of rows to be inserted is known ahead of time, there will
     be no gaps in the numbers generated for a single statement, except
     for `mixed-mode inserts'. However, when `bulk inserts' are
     executed, there may be gaps in the auto-increment values assigned
     by any given statement.

The auto-increment locking modes provided by `innodb_autoinc_lock_mode'
have several usage implications:

   * Using auto-increment with replication

     If you are using statement-based replication, set
     `innodb_autoinc_lock_mode' to 0 or 1 and use the same value on the
     master and its slaves.  Auto-increment values are not ensured to
     be the same on the slaves as on the master if you use
     `innodb_autoinc_lock_mode' = 2 (`interleaved') or configurations
     where the master and slaves do not use the same lock mode.

     If you are using row-based or mixed-format replication, all of the
     auto-increment lock modes are safe, since row-based replication is
     not sensitive to the order of execution of the SQL statements (and
     the mixed format uses row-based replication for any statements
     that are unsafe for statement-based replication).

   * `Lost' auto-increment values and sequence gaps

     In all lock modes (0, 1, and 2), if a transaction that generated
     auto-increment values rolls back, those auto-increment values are
     `lost'. Once a value is generated for an auto-increment column, it
     cannot be rolled back, whether or not the `*Note `INSERT':
     insert.-like' statement is completed, and whether or not the
     containing transaction is rolled back. Such lost values are not
     reused.  Thus, there may be gaps in the values stored in an
     `AUTO_INCREMENT' column of a table.

   * Gaps in auto-increment values for `bulk inserts'

     With `innodb_autoinc_lock_mode' set to 0 (`traditional') or 1
     (`consecutive'), the auto-increment values generated by any given
     statement will be consecutive, without gaps, because the
     table-level `AUTO-INC' lock is held until the end of the
     statement, and only one such statement can execute at a time.

     With `innodb_autoinc_lock_mode' set to 2 (`interleaved'), there
     may be gaps in the auto-increment values generated by `bulk
     inserts,' but only if there are concurrently executing `*Note
     `INSERT': insert.-like' statements.

     For lock modes 1 or 2, gaps may occur between successive
     statements because for bulk inserts the exact number of
     auto-increment values required by each statement may not be known
     and overestimation is possible.

   * Auto-increment values assigned by `mixed-mode inserts'

     Consider a `mixed-mode insert,' where a `simple insert' specifies
     the auto-increment value for some (but not all) resulting rows.
     Such a statement will behave differently in lock modes 0, 1, and 2.
     For example, assume `c1' is an `AUTO_INCREMENT' column of table
     `t1', and that the most recent automatically generated sequence
     number is 100. Consider the following `mixed-mode insert'
     statement:


          INSERT INTO t1 (c1,c2) VALUES (1,'a'), (NULL,'b'), (5,'c'), (NULL,'d');

     With `innodb_autoinc_lock_mode' set to 0 (`traditional'), the four
     new rows will be:


          +-----+------+
          | c1  | c2   |
          +-----+------+
          |   1 | a    |
          | 101 | b    |
          |   5 | c    |
          | 102 | d    |
          +-----+------+

     The next available auto-increment value will be 103 because the
     auto-increment values are allocated one at a time, not all at once
     at the beginning of statement execution. This result is true
     whether or not there are concurrently executing `*Note `INSERT':
     insert.-like' statements (of any type).

     With `innodb_autoinc_lock_mode' set to 1 (`consecutive'), the four
     new rows will also be:


          +-----+------+
          | c1  | c2   |
          +-----+------+
          |   1 | a    |
          | 101 | b    |
          |   5 | c    |
          | 102 | d    |
          +-----+------+

     However, in this case, the next available auto-increment value
     will be 105, not 103 because four auto-increment values are
     allocated at the time the statement is processed, but only two are
     used. This result is true whether or not there are concurrently
     executing `*Note `INSERT': insert.-like' statements (of any type).

     With `innodb_autoinc_lock_mode' set to mode 2 (`interleaved'), the
     four new rows will be:


          +-----+------+
          | c1  | c2   |
          +-----+------+
          |   1 | a    |
          |   X | b    |
          |   5 | c    |
          |   Y | d    |
          +-----+------+

     The values of X and Y will be unique and larger than any
     previously generated rows. However, the specific values of X and Y
     will depend on the number of auto-increment values generated by
     concurrently executing statements.

     Finally, consider the following statement, issued when the
     most-recently generated sequence number was the value 4:


          INSERT INTO t1 (c1,c2) VALUES (1,'a'), (NULL,'b'), (5,'c'), (NULL,'d');

     With any `innodb_autoinc_lock_mode' setting, this statement will
     generate a duplicate-key error 23000 (`Can't write; duplicate key
     in table') because 5 will be allocated for the row `(NULL, 'b')'
     and insertion of the row `(5, 'c')' will fail.


File: manual.info,  Node: innodb-foreign-key-constraints,  Next: innodb-restrictions,  Prev: innodb-auto-increment-handling,  Up: innodb-tables

14.6.5.8 InnoDB and FOREIGN KEY Constraints
...........................................

This section describes differences in the InnoDB storage engine's
handling of foreign keys as compared with that of the MySQL Server.

*Foreign Key Definitions*

Foreign key definitions for `InnoDB' tables are subject to the
following conditions:

   * `InnoDB' permits a foreign key to reference any index column or
     group of columns. However, in the referenced table, there must be
     an index where the referenced columns are listed as the _first_
     columns in the same order.

   * *Note `InnoDB': innodb-storage-engine. does not currently support
     foreign keys for tables with user-defined partitioning. This means
     that no user-partitioned `InnoDB' table may contain foreign key
     references or columns referenced by foreign keys.

   * `InnoDB' allows a foreign key constraint to reference a non-unique
     key. _This is an `InnoDB' extension to standard SQL._

*Referential Actions*

Referential actions for foreign keys of `InnoDB' tables are subject to
the following conditions:

   * While `SET DEFAULT' is allowed by the MySQL Server, it is rejected
     as invalid by `InnoDB'. *Note `CREATE TABLE': create-table. and
     *Note `ALTER TABLE': alter-table.  statements using this clause
     are not allowed for InnoDB tables.

   * If there are several rows in the parent table that have the same
     referenced key value, `InnoDB' acts in foreign key checks as if
     the other parent rows with the same key value do not exist. For
     example, if you have defined a `RESTRICT' type constraint, and
     there is a child row with several parent rows, `InnoDB' does not
     permit the deletion of any of those parent rows.

   * `InnoDB' performs cascading operations through a depth-first
     algorithm, based on records in the indexes corresponding to the
     foreign key constraints.

   * If `ON UPDATE CASCADE' or `ON UPDATE SET NULL' recurses to update
     the _same table_ it has previously updated during the cascade, it
     acts like `RESTRICT'. This means that you cannot use
     self-referential `ON UPDATE CASCADE' or `ON UPDATE SET NULL'
     operations. This is to prevent infinite loops resulting from
     cascaded updates. A self-referential `ON DELETE SET NULL', on the
     other hand, is possible, as is a self-referential `ON DELETE
     CASCADE'.  Cascading operations may not be nested more than 15
     levels deep.

   * Like MySQL in general, in an SQL statement that inserts, deletes,
     or updates many rows, `InnoDB' checks `UNIQUE' and `FOREIGN KEY'
     constraints row-by-row. When performing foreign key checks,
     `InnoDB' sets shared row-level locks on child or parent records it
     has to look at.  `InnoDB' checks foreign key constraints
     immediately; the check is not deferred to transaction commit.
     According to the SQL standard, the default behavior should be
     deferred checking. That is, constraints are only checked after the
     _entire SQL statement_ has been processed. Until `InnoDB'
     implements deferred constraint checking, some things will be
     impossible, such as deleting a record that refers to itself using
     a foreign key.

*Foreign Key Usage and Error Information*

You can obtain general information about foreign keys and their usage
from querying the *Note `INFORMATION_SCHEMA.KEY_COLUMN_USAGE':
key-column-usage-table.  table, and more information more specific to
`InnoDB' tables can be found in the `INNODB_SYS_FOREIGN'
(http://dev.mysql.com/doc/refman/5.6/en/innodb-sys-foreign-table.html)
and `INNODB_SYS_FOREIGN_COLS'
(http://dev.mysql.com/doc/refman/5.6/en/innodb-sys-foreign-cols-table.html)
tables, also in the `INFORMATION_SCHEMA' database. See also *Note
create-table-foreign-keys::.

In addition to *Note `SHOW ERRORS': show-errors, in the event of a
foreign key error involving `InnoDB' tables (usually Error 150 in the
MySQL Server), you can obtain a detailed explanation of the most recent
`InnoDB' foreign key error by checking the output of *Note `SHOW ENGINE
INNODB STATUS': show-engine.


File: manual.info,  Node: innodb-restrictions,  Prev: innodb-foreign-key-constraints,  Up: innodb-tables

14.6.5.9 Limits on InnoDB Tables
................................

*Warning*:

Do _not_ convert MySQL system tables in the `mysql' database from
`MyISAM' to `InnoDB' tables! This is an unsupported operation. If you
do this, MySQL does not restart until you restore the old system tables
from a backup or re-generate them with the *Note `mysql_install_db':
mysql-install-db. program.

*Warning*:

It is not a good idea to configure `InnoDB' to use data files or log
files on NFS volumes. Otherwise, the files might be locked by other
processes and become unavailable for use by MySQL.

*Maximums and Minimums*

   * A table can contain a maximum of 1000 columns.

   * A table can contain a maximum of 64 secondary indexes
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_secondary_index).

   * An index key for a single-column index can be up to 767 bytes.
     The same length limit applies to any index key prefix. See *Note
     create-index::.

   * The `InnoDB' internal maximum key length is 3500 bytes, but MySQL
     itself restricts this to 3072 bytes.  This limit applies to the
     length of the combined index key in a multi-column index.

   * The maximum row length, except for variable-length columns (*Note
     `VARBINARY': binary-varbinary, *Note `VARCHAR': char, *Note
     `BLOB': blob. and *Note `TEXT': blob.), is slightly less than half
     of a database page. That is, the maximum row length is about 8000
     bytes. *Note `LONGBLOB': blob. and *Note `LONGTEXT': blob.
     columns must be less than 4GB, and the total row length, including
     *Note `BLOB': blob. and *Note `TEXT': blob. columns, must be less
     than 4GB.

     If a row is less than half a page long, all of it is stored
     locally within the page. If it exceeds half a page,
     variable-length columns are chosen for external off-page storage
     until the row fits within half a page, as described in *Note
     innodb-file-space::.

     The row size for *Note `BLOB': blob. columns that are chosen for
     external off-page storage should not exceed 10% of the combined
     redo log
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_redo_log)
     file size. If the row size exceeds 10% of the combined redo log
     file size, `InnoDB' could overwrite the most recent checkpoint
     which may result in lost data during crash recovery. (Bug#69477).

   * Although `InnoDB' supports row sizes larger than 65,535 bytes
     internally, MySQL itself imposes a row-size limit of 65,535 for
     the combined size of all columns:


          mysql> CREATE TABLE t (a VARCHAR(8000), b VARCHAR(10000),
              -> c VARCHAR(10000), d VARCHAR(10000), e VARCHAR(10000),
              -> f VARCHAR(10000), g VARCHAR(10000)) ENGINE=InnoDB;
          ERROR 1118 (42000): Row size too large. The maximum row size for the
          used table type, not counting BLOBs, is 65535. You have to change some
          columns to TEXT or BLOBs

     See *Note column-count-limit::.

   * On some older operating systems, files must be less than 2GB.
     This is not a limitation of `InnoDB' itself, but if you require a
     large tablespace, you will need to configure it using several
     smaller data files rather than one or a file large data files.

   * The combined size of the `InnoDB' log files must be less than 4GB.

   * The minimum tablespace size is 10MB. The maximum tablespace size
     is four billion database pages (64TB). This is also the maximum
     size for a table.

   * The default database page size in `InnoDB' is 16KB.

     *Note*:

     Changing the page size is not a supported operation and there is
     no guarantee that *Note `InnoDB': innodb-storage-engine. will
     function normally with a page size other than 16KB. Problems
     compiling or running InnoDB may occur. In particular,
     `ROW_FORMAT=COMPRESSED' in the `InnoDB Plugin' assumes that the
     page size is at most 16KB and uses 14-bit pointers.

     A version of *Note `InnoDB': innodb-storage-engine. built for one
     page size cannot use data files or log files from a version built
     for a different page size. This limitation could affect restore or
     downgrade operations using data from MySQL 5.6, which does support
     page sizes other than 16KB.

*Index Types*

   * `InnoDB' tables do not support `FULLTEXT' indexes.

   * `InnoDB' tables support spatial data types, but not indexes on
     them.

*Restrictions on InnoDB Tables*

   * *Note `ANALYZE TABLE': analyze-table. determines index cardinality
     (as displayed in the `Cardinality' column of *Note `SHOW INDEX':
     show-index. output) by doing eight random dives to each of the
     index trees and updating index cardinality estimates accordingly.
     Because these are only estimates, repeated runs of *Note `ANALYZE
     TABLE': analyze-table. may produce different numbers. This makes
     *Note `ANALYZE TABLE': analyze-table. fast on `InnoDB' tables but
     not 100% accurate because it does not take all rows into account.

     For `InnoDB Plugin', you can change the number of random dives by
     modifying the `innodb_stats_sample_pages' system variable.

     MySQL uses index cardinality estimates only in join optimization.
     If some join is not optimized in the right way, you can try using
     *Note `ANALYZE TABLE': analyze-table. In the few cases that *Note
     `ANALYZE TABLE': analyze-table. does not produce values good
     enough for your particular tables, you can use `FORCE INDEX' with
     your queries to force the use of a particular index, or set the
     `max_seeks_for_key' system variable to ensure that MySQL prefers
     index lookups over table scans. See *Note
     server-system-variables::, and *Note optimizer-issues::.

   * If statements or transactions are running on a table and *Note
     `ANALYZE TABLE': analyze-table. is run on the same table followed
     by a second *Note `ANALYZE TABLE': analyze-table. operation, the
     second *Note `ANALYZE TABLE': analyze-table. operation is blocked
     until the statements or transactions are completed.  This
     behaviour occurs because *Note `ANALYZE TABLE': analyze-table.
     marks the currently loaded table definition as obsolete when *Note
     `ANALYZE TABLE': analyze-table. is finished running. New
     statements or transactions (including a second *Note `ANALYZE
     TABLE': analyze-table. statement) must load the new table
     definition into the table cache, which cannot occur until
     currently running statements or transactions are completed and the
     old table definition is purged. Loading multiple concurrent table
     definitions is not supported.

   * *Note `SHOW TABLE STATUS': show-table-status. does not give
     accurate statistics
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_statistics)
     on `InnoDB' tables, except for the physical size reserved by the
     table. The row count is only a rough estimate used in SQL
     optimization.

   * `InnoDB' does not keep an internal count of rows in a table
     because concurrent transactions might `see' different numbers of
     rows at the same time.  To process a `SELECT COUNT(*) FROM t'
     statement, `InnoDB' scans an index of the table, which takes some
     time if the index is not entirely in the buffer pool. If your
     table does not change often, using the MySQL query cache is a good
     solution. To get a fast count, you have to use a counter table you
     create yourself and let your application update it according to
     the inserts and deletes it does. If an approximate row count is
     sufficient, *Note `SHOW TABLE STATUS': show-table-status. can be
     used.  See *Note innodb-tuning::.

   * On Windows, `InnoDB' always stores database and table names
     internally in lowercase. To move databases in a binary format from
     Unix to Windows or from Windows to Unix, create all databases and
     tables using lowercase names.

   * An `AUTO_INCREMENT' column AI_COL must be defined as part of an
     index such that it is possible to perform the equivalent of an
     indexed `SELECT MAX(AI_COL)' lookup on the table to obtain the
     maximum column value. Typically, this is achieved by making the
     column the first column of some table index.

   * While initializing a previously specified `AUTO_INCREMENT' column
     on a table, `InnoDB' sets an exclusive lock on the end of the
     index associated with the `AUTO_INCREMENT' column. While accessing
     the auto-increment counter, `InnoDB' uses a specific `AUTO-INC'
     table lock mode where the lock lasts only to the end of the
     current SQL statement, not to the end of the entire transaction.
     Other clients cannot insert into the table while the `AUTO-INC'
     table lock is held. See *Note innodb-auto-increment-handling::.

   * When you restart the MySQL server, `InnoDB' may reuse an old value
     that was generated for an `AUTO_INCREMENT' column but never stored
     (that is, a value that was generated during an old transaction
     that was rolled back).

   * When an `AUTO_INCREMENT' integer column runs out of values, a
     subsequent `INSERT' operation returns a duplicate-key error. This
     is general MySQL behavior, similar to how `MyISAM' works.

   * `DELETE FROM TBL_NAME' does not regenerate the table but instead
     deletes all rows, one by one.

   * Under some conditions, `TRUNCATE TBL_NAME' for an `InnoDB' table
     is mapped to `DELETE FROM TBL_NAME'. See *Note truncate-table::.

   * The *Note `LOAD TABLE FROM MASTER': load-table-from-master.
     statement for setting up replication slave servers does not work
     for `InnoDB' tables. A workaround is to alter the table to
     `MyISAM' on the master, then do the load, and after that alter the
     master table back to `InnoDB'. Do not do this if the tables use
     `InnoDB'-specific features such as foreign keys.

   * Currently, cascaded foreign key actions do not activate triggers.

   * You cannot create a table with a column name that matches the name
     of an internal InnoDB column (including `DB_ROW_ID', `DB_TRX_ID',
     `DB_ROLL_PTR', and `DB_MIX_ID'). In versions of MySQL before
     5.1.10 this would cause a crash, since 5.1.10 the server will
     report error 1005 and refers to error -1 in the error message.
     This restriction applies only to use of the names in uppercase.

*Locking and Transactions*

   * *Note `LOCK TABLES': lock-tables. acquires two locks on each table
     if `innodb_table_locks=1' (the default). In addition to a table
     lock on the MySQL layer, it also acquires an `InnoDB' table lock.
     Versions of MySQL before 4.1.2 did not acquire `InnoDB' table
     locks; the old behavior can be selected by setting
     `innodb_table_locks=0'.  If no `InnoDB' table lock is acquired,
     *Note `LOCK TABLES': lock-tables. completes even if some records
     of the tables are being locked by other transactions.

   * All `InnoDB' locks held by a transaction are released when the
     transaction is committed or aborted. Thus, it does not make much
     sense to invoke *Note `LOCK TABLES': lock-tables. on `InnoDB'
     tables in `autocommit=1' mode because the acquired `InnoDB' table
     locks would be released immediately.

   * You cannot lock additional tables in the middle of a transaction
     because *Note `LOCK TABLES': lock-tables.  performs an implicit
     *Note `COMMIT': commit. and *Note `UNLOCK TABLES': lock-tables.

   * `InnoDB' has a limit of 1023 concurrent transactions that have
     created undo records by modifying data.  Workarounds include
     keeping transactions as small and fast as possible, delaying
     changes until near the end of the transaction, and using stored
     routines to reduce client/server latency delays. Applications
     should commit transactions before doing time-consuming client-side
     operations.


File: manual.info,  Node: innodb-disk-management,  Next: innodb-parameters,  Prev: innodb-tables,  Up: innodb-storage-engine

14.6.6 InnoDB Disk I/O and File Space Management
------------------------------------------------

* Menu:

* innodb-disk-io::               InnoDB Disk I/O
* innodb-file-space::            File Space Management
* innodb-file-defragmenting::    Defragmenting a Table


File: manual.info,  Node: innodb-disk-io,  Next: innodb-file-space,  Prev: innodb-disk-management,  Up: innodb-disk-management

14.6.6.1 InnoDB Disk I/O
........................

`InnoDB' uses simulated asynchronous disk I/O: `InnoDB' creates a
number of threads to take care of I/O operations, such as read-ahead.

There are two read-ahead heuristics in `InnoDB':

   * In sequential read-ahead, if `InnoDB' notices that the access
     pattern to a segment in the tablespace is sequential, it posts in
     advance a batch of reads of database pages to the I/O system.

   * In random read-ahead, if `InnoDB' notices that some area in a
     tablespace seems to be in the process of being fully read into the
     buffer pool, it posts the remaining reads to the I/O system.

`InnoDB' uses a novel file flush technique called _doublewrite_. It
adds safety to recovery following an operating system crash or a power
outage, and improves performance on most varieties of Unix by reducing
the need for `fsync()' operations.

Doublewrite means that before writing pages to a data file, `InnoDB'
first writes them to a contiguous tablespace area called the
doublewrite buffer. Only after the write and the flush to the
doublewrite buffer has completed does `InnoDB' write the pages to their
proper positions in the data file. If the operating system crashes in
the middle of a page write, `InnoDB' can later find a good copy of the
page from the doublewrite buffer during recovery.


File: manual.info,  Node: innodb-file-space,  Next: innodb-file-defragmenting,  Prev: innodb-disk-io,  Up: innodb-disk-management

14.6.6.2 File Space Management
..............................

The data files that you define in the configuration file form the
`InnoDB' tablespace. The files are logically concatenated to form the
tablespace. There is no striping in use.  Currently, you cannot define
where within the tablespace your tables are allocated. However, in a
newly created tablespace, `InnoDB' allocates space starting from the
first data file.

The tablespace consists of database pages with a default size of 16KB.
The pages are grouped into extents of size 1MB (64 consecutive pages).
The `files' inside a tablespace are called _segments_ in `InnoDB'. The
term `rollback segment' is somewhat confusing because it actually
contains many tablespace segments.

When a segment grows inside the tablespace, `InnoDB' allocates the
first 32 pages to it individually. After that, `InnoDB' starts to
allocate whole extents to the segment. `InnoDB' can add up to 4 extents
at a time to a large segment to ensure good sequentiality of data.

Two segments are allocated for each index in `InnoDB'. One is for
nonleaf nodes of the B-tree, the other is for the leaf nodes. The idea
here is to achieve better sequentiality for the leaf nodes, which
contain the data.

Some pages in the tablespace contain bitmaps of other pages, and
therefore a few extents in an `InnoDB' tablespace cannot be allocated
to segments as a whole, but only as individual pages.

When you ask for available free space in the tablespace by issuing a
*Note `SHOW TABLE STATUS': show-table-status. statement, `InnoDB'
reports the extents that are definitely free in the tablespace.
`InnoDB' always reserves some extents for cleanup and other internal
purposes; these reserved extents are not included in the free space.

When you delete data from a table, `InnoDB' contracts the corresponding
B-tree indexes. Whether the freed space becomes available for other
users depends on whether the pattern of deletes frees individual pages
or extents to the tablespace. Dropping a table or deleting all rows
from it is guaranteed to release the space to other users, but remember
that deleted rows are physically removed only in an (automatic) purge
operation after they are no longer needed for transaction rollbacks or
consistent reads. (See *Note innodb-multi-versioning::.)

To see information about the tablespace, use the Tablespace Monitor.
See *Note innodb-monitors::.

The maximum row length, except for variable-length columns (*Note
`VARBINARY': binary-varbinary, *Note `VARCHAR': char, *Note `BLOB':
blob. and *Note `TEXT': blob.), is slightly less than half of a
database page. That is, the maximum row length is about 8000 bytes.
*Note `LONGBLOB': blob. and *Note `LONGTEXT': blob. columns must be
less than 4GB, and the total row length, including *Note `BLOB': blob.
and *Note `TEXT': blob. columns, must be less than 4GB.

If a row is less than half a page long, all of it is stored locally
within the page. If it exceeds half a page, variable-length columns are
chosen for external off-page storage until the row fits within half a
page. For a column chosen for off-page storage, `InnoDB' stores the
first 768 bytes locally in the row, and the rest externally into
overflow pages. Each such column has its own list of overflow pages. The
768-byte prefix is accompanied by a 20-byte value that stores the true
length of the column and points into the overflow list where the rest
of the value is stored.


File: manual.info,  Node: innodb-file-defragmenting,  Prev: innodb-file-space,  Up: innodb-disk-management

14.6.6.3 Defragmenting a Table
..............................

If there are random insertions into or deletions from the indexes of a
table, the indexes may become fragmented. Fragmentation means that the
physical ordering of the index pages on the disk is not close to the
index ordering of the records on the pages, or that there are many
unused pages in the 64-page blocks that were allocated to the index.

One symptom of fragmentation is that a table takes more space than it
`should' take. How much that is exactly, is difficult to determine. All
`InnoDB' data and indexes are stored in B-trees, and their fill factor
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_fill_factor)
may vary from 50% to 100%. Another symptom of fragmentation is that a
table scan such as this takes more time than it `should' take:


     SELECT COUNT(*) FROM t WHERE a_non_indexed_column <> 12345;

The preceding query requires MySQL to perform a full table scan, the
slowest type of query for a large table.

It can speed up index scans if you periodically perform a `null' *Note
`ALTER TABLE': alter-table.  operation, which causes MySQL to rebuild
the table:


     ALTER TABLE TBL_NAME ENGINE=INNODB

Another way to perform a defragmentation operation is to use *Note
`mysqldump': mysqldump. to dump the table to a text file, drop the
table, and reload it from the dump file.

If the insertions into an index are always ascending and records are
deleted only from the end, the `InnoDB' filespace management algorithm
guarantees that fragmentation in the index does not occur.


File: manual.info,  Node: innodb-parameters,  Next: innodb-tuning,  Prev: innodb-disk-management,  Up: innodb-storage-engine

14.6.7 InnoDB Startup Options and System Variables
--------------------------------------------------

This section describes the `InnoDB'-related command options and system
variables.

   * System variables that are true or false can be enabled at server
     startup by naming them, or disabled by using a `--skip-' prefix.
     For example, to enable or disable `InnoDB' checksums, you can use
     `--innodb_checksums' or `--skip-innodb_checksums' on the command
     line, or `innodb_checksums' or `skip-innodb_checksums' in an
     option file.

   * System variables that take a numeric value can be specified as
     `--VAR_NAME=VALUE' on the command line or as `VAR_NAME=VALUE' in
     option files.

   * Many system variables can be changed at runtime (see *Note
     dynamic-system-variables::).

   * For information about `GLOBAL' and `SESSION' variable scope
     modifiers, refer to the *Note `SET': set-statement.  statement
     documentation.

   * For more information on specifying options and system variables,
     see *Note program-options::.

*`InnoDB' Option/Variable Reference*

Name           Cmd-Line    Option File System Var  Status Var  Var Scope   Dynamic
foreign_key_checks                        Yes                     Session     Yes
have_innodb                            Yes                     Global      No
ignore-builtin-innodbYes         Yes                                 Global      No
- _Variable_:                          Yes                     Global      No
ignore_builtin_innodb                                                            
innodb         Yes         Yes                                             
innodb_adaptive_flushingYes         Yes         Yes                     Global      Yes
innodb_adaptive_hash_indexYes         Yes         Yes                     Global      No
innodb_additional_mem_pool_sizeYes         Yes         Yes                     Global      No
innodb_autoextend_incrementYes         Yes         Yes                     Global      Yes
innodb_autoinc_lock_modeYes         Yes         Yes                     Global      No
innodb_buffer_pool_awe_mem_mbYes         Yes         Yes                     Global      No
Innodb_buffer_pool_pages_data                                    Yes         Global      No
Innodb_buffer_pool_pages_dirty                                    Yes         Global      No
Innodb_buffer_pool_pages_flushed                                    Yes         Global      No
Innodb_buffer_pool_pages_free                                    Yes         Global      No
Innodb_buffer_pool_pages_latched                                    Yes         Global      No
Innodb_buffer_pool_pages_misc                                    Yes         Global      No
Innodb_buffer_pool_pages_total                                    Yes         Global      No
Innodb_buffer_pool_read_ahead                                    Yes         Global      No
Innodb_buffer_pool_read_ahead_evicted                                    Yes         Global      No
Innodb_buffer_pool_read_ahead_rnd                                    Yes         Global      No
Innodb_buffer_pool_read_ahead_seq                                    Yes         Global      No
Innodb_buffer_pool_read_requests                                    Yes         Global      No
Innodb_buffer_pool_reads                                    Yes         Global      No
innodb_buffer_pool_sizeYes         Yes         Yes                     Global      No
Innodb_buffer_pool_wait_free                                    Yes         Global      No
Innodb_buffer_pool_write_requests                                    Yes         Global      No
innodb_change_bufferingYes         Yes         Yes                     Global      Yes
innodb_checksumsYes         Yes         Yes                     Global      No
innodb_commit_concurrencyYes         Yes         Yes                     Global      Yes
innodb_concurrency_ticketsYes         Yes         Yes                     Global      Yes
innodb_data_file_pathYes         Yes         Yes                     Global      No
Innodb_data_fsyncs                                    Yes         Global      No
innodb_data_home_dirYes         Yes         Yes                     Global      No
Innodb_data_pending_fsyncs                                    Yes         Global      No
Innodb_data_pending_reads                                    Yes         Global      No
Innodb_data_pending_writes                                    Yes         Global      No
Innodb_data_read                                    Yes         Global      No
Innodb_data_reads                                    Yes         Global      No
Innodb_data_writes                                    Yes         Global      No
Innodb_data_written                                    Yes         Global      No
Innodb_dblwr_pages_written                                    Yes         Global      No
Innodb_dblwr_writes                                    Yes         Global      No
innodb_doublewriteYes         Yes         Yes                     Global      No
innodb_fast_shutdownYes         Yes         Yes                     Global      Yes
innodb_file_formatYes         Yes         Yes                     Global      Yes
innodb_file_format_checkYes         Yes         Yes                     Global      Yes
innodb_file_io_threadsYes         Yes         Yes                     Global      No
innodb_file_per_tableYes         Yes         Yes                     Global      No
innodb_flush_log_at_trx_commitYes         Yes         Yes                     Global      Yes
innodb_flush_methodYes         Yes         Yes                     Global      No
innodb_force_recoveryYes         Yes         Yes                     Global      No
Innodb_have_atomic_builtins                                    Yes         Global      No
innodb_io_capacityYes         Yes         Yes                     Global      No
innodb_lock_wait_timeoutYes         Yes         Yes                     Both        No
innodb_locks_unsafe_for_binlogYes         Yes         Yes                     Global      No
innodb_log_arch_dirYes         Yes         Yes                     Global      No
innodb_log_archiveYes         Yes         Yes                     Global      No
innodb_log_buffer_sizeYes         Yes         Yes                     Global      No
innodb_log_file_sizeYes         Yes         Yes                     Global      No
innodb_log_files_in_groupYes         Yes         Yes                     Global      No
innodb_log_group_home_dirYes         Yes         Yes                     Global      No
Innodb_log_waits                                    Yes         Global      No
Innodb_log_write_requests                                    Yes         Global      No
Innodb_log_writes                                    Yes         Global      No
innodb_max_dirty_pages_pctYes         Yes         Yes                     Global      Yes
innodb_max_purge_lagYes         Yes         Yes                     Global      Yes
innodb_mirrored_log_groupsYes         Yes         Yes                     Global      No
innodb_old_blocks_pctYes         Yes         Yes                     Global      Yes
innodb_old_blocks_timeYes         Yes         Yes                     Global      Yes
innodb_open_filesYes         Yes         Yes                     Global      No
Innodb_os_log_fsyncs                                    Yes         Global      No
Innodb_os_log_pending_fsyncs                                    Yes         Global      No
Innodb_os_log_pending_writes                                    Yes         Global      No
Innodb_os_log_written                                    Yes         Global      No
Innodb_page_size                                    Yes         Global      No
Innodb_pages_created                                    Yes         Global      No
Innodb_pages_read                                    Yes         Global      No
Innodb_pages_written                                    Yes         Global      No
innodb_random_read_aheadYes         Yes         Yes                     Global      Yes
innodb_read_ahead_thresholdYes         Yes         Yes                     Global      Yes
innodb_read_io_threadsYes         Yes         Yes                     Global      No
innodb_replication_delayYes         Yes         Yes                     Global      Yes
innodb_rollback_on_timeoutYes         Yes         Yes                     Global      No
Innodb_row_lock_current_waits                                    Yes         Global      No
Innodb_row_lock_time                                    Yes         Global      No
Innodb_row_lock_time_avg                                    Yes         Global      No
Innodb_row_lock_time_max                                    Yes         Global      No
Innodb_row_lock_waits                                    Yes         Global      No
Innodb_rows_deleted                                    Yes         Global      No
Innodb_rows_inserted                                    Yes         Global      No
Innodb_rows_read                                    Yes         Global      No
Innodb_rows_updated                                    Yes         Global      No
innodb_spin_wait_delayYes         Yes         Yes                     Global      Yes
innodb_stats_methodYes         Yes         Yes                     Global      Yes
innodb_stats_on_metadataYes         Yes         Yes                     Global      Yes
innodb_stats_sample_pagesYes         Yes         Yes                     Global      Yes
innodb-status-fileYes         Yes                                             
innodb_strict_modeYes         Yes         Yes                     Both        Yes
innodb_support_xaYes         Yes         Yes                     Both        Yes
innodb_sync_spin_loopsYes         Yes         Yes                     Global      Yes
innodb_table_locksYes         Yes         Yes                     Both        Yes
innodb_thread_concurrencyYes         Yes         Yes                     Global      Yes
innodb_thread_sleep_delayYes         Yes         Yes                     Global      Yes
innodb_use_legacy_cardinality_algorithmYes         Yes         Yes                     Global      Yes
innodb_use_sys_mallocYes         Yes         Yes                     Global      No
innodb_version                         Yes                     Global      No
innodb_write_io_threadsYes         Yes         Yes                     Global      No
timed_mutexes  Yes         Yes         Yes                     Global      Yes
unique_checks                          Yes                     Session     Yes

*InnoDB Command Options*

   * `--ignore-builtin-innodb'

     Options for ignore-builtin-innodb

     *Introduced*         5.1.33          
     *Command-Line        `--ignore-builtin-innodb'        
     Format*                              
     *System Variable     `ignore_builtin_innodb'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     This option causes the server to behave as if the built-in
     `InnoDB' is not present, which enables `InnoDB Plugin' to be used
     instead. See *Note replacing-builtin-innodb::.

     If this option is given but `InnoDB Plugin' is not used in place
     of the built-in `InnoDB', it has the following effects:

        * Other *Note `InnoDB': innodb-storage-engine. options
          (including `--innodb' and `--skip-innodb') will not be
          recognized and should not be used.

        * The server will not start if the default storage engine is
          set to *Note `InnoDB': innodb-storage-engine. Use
          `--default-storage-engine' to set the default to some other
          engine if necessary.

        * *Note `InnoDB': innodb-storage-engine. will not appear in the
          output of *Note `SHOW ENGINES': show-engines.

     This option was added in MySQL 5.1.33.

   * `--innodb[=VALUE]'

     Controls loading of the `InnoDB' storage engine, if the server was
     compiled with `InnoDB' support. As of MySQL 5.1.36, this option
     has a tristate format, with possible values of `OFF', `ON', or
     `FORCE'. Before MySQL 5.1.36, this is a boolean option. See *Note
     server-plugin-loading::.

     To disable `InnoDB', use `--innodb=OFF' or `--skip-innodb'.  In
     this case, the server will not start if the default storage engine
     is set to *Note `InnoDB': innodb-storage-engine. Use
     `--default-storage-engine' to set the default to some other engine
     if necessary.

   * `--innodb-status-file'

     Options for innodb-status-file

     *Command-Line        `--innodb-status-file'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Controls whether `InnoDB' creates a file named
     `innodb_status.<PID>' in the MySQL data directory. If enabled,
     `InnoDB' periodically writes the output of *Note `SHOW ENGINE
     INNODB STATUS': show-engine. to this file.

     By default, the file is not created. To create it, start *Note
     `mysqld': mysqld. with the `--innodb-status-file=1' option.  The
     file is deleted during normal shutdown.

   * `--skip-innodb'

     Disable the `InnoDB' storage engine. See the description of
     `--innodb'.

*InnoDB System Variables*

   * `ignore_builtin_innodb'

     Options for ignore-builtin-innodb

     *Introduced*         5.1.33          
     *Command-Line        `--ignore-builtin-innodb'        
     Format*                              
     *System Variable     `ignore_builtin_innodb'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     Whether the server was started with the `--ignore-builtin-innodb'
     option, which causes the server to behave as if the built-in
     `InnoDB' is not present. For more information, see the description
     of `--ignore-builtin-innodb' under ``InnoDB' Command Options'
     earlier in this section. This variable was added in MySQL 5.1.33.

   * `innodb_adaptive_flushing'

     Options for innodb_adaptive_flushing

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_adaptive_flushing=#'        
     Format*                              
     *System Variable     `innodb_adaptive_flushing'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     (`InnoDB Plugin' only) `InnoDB Plugin' 1.0.4 and up uses a
     heuristic to determine when to flush dirty pages
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_dirty_page)
     in the buffer pool
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_buffer_pool).
     This heuristic is designed to avoid bursts of I/O activity and is
     used when `innodb_adaptive_flushing' is enabled (which is the
     default).

   * `innodb_adaptive_hash_index'

     Options for innodb_adaptive_hash_index

     *Introduced*         5.1.24          
     *Command-Line        `--innodb_adaptive_hash_index=#'        
     Format*                              
     *System Variable     `innodb_adaptive_hash_index'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     Whether the `InnoDB' adaptive hash index
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_adaptive_hash_index)
     is enabled or disabled. The adaptive hash index feature is useful
     for some workloads, and not for others; conduct benchmarks with it
     both enabled and disabled, using realistic workloads. See *Note
     innodb-adaptive-hash:: for details. This variable is enabled by
     default. Use `--skip-innodb_adaptive_hash_index' at server startup
     to disable it. This variable was added in MySQL 5.1.24.

   * `innodb_additional_mem_pool_size'

     Options for innodb_additional_mem_pool_size

     *Command-Line        `--innodb_additional_mem_pool_size=#'        
     Format*                              
     *System Variable     `innodb_additional_mem_pool_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1048576'        
     *Min Value*          `524288'        
     *Max Value*          `4294967295'        

     The size in bytes of a memory pool `InnoDB' uses to store data
     dictionary information and other internal data structures. The
     more tables you have in your application, the more memory you need
     to allocate here. If `InnoDB' runs out of memory in this pool, it
     starts to allocate memory from the operating system and writes
     warning messages to the MySQL error log. The default value is 1MB
     for the built-in *Note `InnoDB': innodb-storage-engine, 8MB for
     `InnoDB Plugin'.

     This variable relates to the `InnoDB' internal memory allocator,
     which is unused if `innodb_use_sys_malloc' is enabled.

   * `innodb_autoextend_increment'

     Options for innodb_autoextend_increment

     *Command-Line        `--innodb_autoextend_increment=#'        
     Format*                              
     *System Variable     `innodb_autoextend_increment'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `8'             
     *Min Value*          `1'             
     *Max Value*          `1000'          

     The increment size (in MB) for extending the size of an
     auto-extending shared tablespace file when it becomes full.  The
     default value is 8. This variable does not affect the per-table
     tablespace files that are created if you use
     `innodb_file_per_table=1'.  Those files are auto-extending
     regardless of the value of `innodb_autoextend_increment'.  The
     initial extensions are by small amounts, after which extensions
     occur in increments of 4MB.

   * `innodb_buffer_pool_awe_mem_mb'

     Options for innodb_buffer_pool_awe_mem_mb

     *Removed*            5.1.13          
     *Command-Line        `--innodb_buffer_pool_awe_mem_mb=#'        
     Format*                              
     *System Variable     `innodb_buffer_pool_awe_mem_mb'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
     *Platform Specific*  Windows         
                          *Permitted        
                          Values*         
     *Type* (Windows)     `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `63000'         

     The size of the buffer pool (in MB), if it is placed in the AWE
     memory. If it is greater than 0, `innodb_buffer_pool_size' is the
     window in the 32-bit address space of *Note `mysqld': mysqld.
     where `InnoDB' maps that AWE memory. A good value for
     `innodb_buffer_pool_size' is 500MB. The maximum possible value is
     63000.

     To take advantage of AWE memory, you will need to recompile MySQL
     yourself. The current project settings needed for doing this can
     be found in the `storage/innobase/os/os0proc.c' source file.

     This variable was removed in MySQL 5.1.13. Before that, it is
     relevant only in 32-bit Windows. If your 32-bit Windows operating
     system supports more than 4GB memory, using so-called `Address
     Windowing Extensions,' you can allocate the `InnoDB' buffer pool
     into the AWE physical memory using this variable.

   * `innodb_autoinc_lock_mode'

     Options for innodb_autoinc_lock_mode

     *Introduced*         5.1.22          
     *Command-Line        `--innodb_autoinc_lock_mode=#'        
     Format*                              
     *System Variable     `innodb_autoinc_lock_mode'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1'             
     *Valid Values*       `0'             
     `1'                                  
     `2'                                  

     The locking mode to use for generating auto-increment values.  The
     permissible values are 0, 1, or 2, for `traditional',
     `consecutive', or `interleaved' lock mode, respectively.  *Note
     innodb-auto-increment-handling::, describes the characteristics of
     these modes.

     This variable was added in MySQL 5.1.22 with a default of 1
     (`consecutive' lock mode). Before 5.1.22, `InnoDB' uses
     `traditional' lock mode.

   * `innodb_buffer_pool_size'

     Options for innodb_buffer_pool_size

     *Command-Line        `--innodb_buffer_pool_size=#'        
     Format*                              
     *System Variable     `innodb_buffer_pool_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values          
                          (<=             
                          5.1.27)*        
     *Type*               `numeric'        
     *Default*            `8388608'        
     *Min Value*          `1048576'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.28)*        
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `134217728'        
     *Min Value*          `1048576'        
     *Max Value*          `2**32-1'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.28)*        
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `134217728'        
     *Min Value*          `1048576'        
     *Max Value*          `2**64-1'        

     The size in bytes of the memory buffer `InnoDB' uses to cache data
     and indexes of its tables. The default value is 128MB, increased
     from a historical default of 8MB. In MySQL 5.1.28 and later, the
     maximum value depends on the CPU architecture; the maximum is
     4294967295 (2^32-1) on 32-bit systems and 18446744073709551615
     (2^64-1) on 64-bit systems. On 32-bit systems, the CPU
     architecture and operating system may impose a lower practical
     maximum size than the stated maximum.

     The larger you set this value, the less disk I/O is needed to
     access data in tables. On a dedicated database server, you may set
     this to up to 80% of the machine physical memory size. Be prepared
     to scale back this value if these other issues occur:

        * Competition for physical memory might cause paging in the
          operating system.

        * InnoDB reserves additional memory for buffers and control
          structures, so that the total allocated space is
          approximately 10% greater than the specified size.

        * The address space must be contiguous, which can be an issue
          on Windows systems with DLLs that load at specific addresses.

        * The time to initialize the buffer pool is roughly
          proportional to its size. On large installations, this
          initialization time may be significant. For example, on a
          modern Linux x86_64 server, initialization of a 10GB buffer
          pool takes approximately 6 seconds. See *Note
          innodb-buffer-pool::.

   * `innodb_change_buffering'

     Options for innodb_change_buffering

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_change_buffering=#'        
     Format*                              
     *System Variable     `innodb_change_buffering'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `inserts'        
     *Valid Values*       `inserts'        
     `none'                               

     (`InnoDB Plugin' only) Whether *Note `InnoDB':
     innodb-storage-engine. performs insert buffering.  The permitted
     values `none' (do not buffer any operations) and `inserts' (buffer
     insert operations). The default is `inserts'. For details, see
     Configuring InnoDB Change Buffering
     (http://dev.mysql.com/doc/refman/5.5/en/innodb-performance-change_buffering.html).

   * `innodb_checksums'

     Options for innodb_checksums

     *Command-Line        `--innodb_checksums'        
     Format*                              
     *System Variable     `innodb_checksums'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     `InnoDB' can use checksum validation on all pages read from the
     disk to ensure extra fault tolerance against broken hardware or
     data files. This validation is enabled by default. However, under
     some rare circumstances (such as when running benchmarks) this
     extra safety feature is unneeded and can be disabled with
     `--skip-innodb-checksums'.

   * `innodb_commit_concurrency'

     Options for innodb_commit_concurrency

     *Command-Line        `--innodb_commit_concurrency=#'        
     Format*                              
     *System Variable     `innodb_commit_concurrency'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `1000'          

     The number of threads that can commit at the same time. A value of
     0 (the default) permits any number of transactions to commit
     simultaneously.

     As of MySQL 5.1.36, the value of `innodb_commit_concurrency'
     cannot be changed at runtime from zero to nonzero or vice versa.
     The value can still be changed from one nonzero value to another.

   * `innodb_concurrency_tickets'

     Options for innodb_concurrency_tickets

     *Command-Line        `--innodb_concurrency_tickets=#'        
     Format*                              
     *System Variable     `innodb_concurrency_tickets'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `500'           
     *Min Value*          `1'             
     *Max Value*          `4294967295'        

     The number of threads that can enter `InnoDB' concurrently is
     determined by the `innodb_thread_concurrency' variable. A thread
     is placed in a queue when it tries to enter `InnoDB' if the number
     of threads has already reached the concurrency limit. When a
     thread is permitted to enter `InnoDB', it is given a number of
     `free tickets' equal to the value of `innodb_concurrency_tickets',
     and the thread can enter and leave `InnoDB' freely until it has
     used up its tickets. After that point, the thread again becomes
     subject to the concurrency check (and possible queuing) the next
     time it tries to enter `InnoDB'. The default value is 500.

   * `innodb_data_file_path'

     Options for innodb_data_file_path

     *Command-Line        `--innodb_data_file_path=name'        
     Format*                              
     *System Variable     `innodb_data_file_path'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `ibdata1:10M:autoextend'        

     The paths to individual data files and their sizes. The full
     directory path to each data file is formed by concatenating
     `innodb_data_home_dir' to each path specified here. The file sizes
     are specified MB or GB (1024MB) by appending `M' or `G' to the
     size value. The sum of the sizes of the files must be at least
     slightly larger than 10MB. If you do not specify
     `innodb_data_file_path', the default behavior is to create a
     single auto-extending data file, slightly larger than 10MB, named
     `ibdata1'. The size limit of individual files is determined by
     your operating system. You can set the file size to more than 4GB
     on those operating systems that support big files. You can also
     use raw disk partitions as data files. For detailed information on
     configuring `InnoDB' tablespace files, see *Note
     innodb-configuration::.

   * `innodb_data_home_dir'

     Options for innodb_data_home_dir

     *Command-Line        `--innodb_data_home_dir=path'        
     Format*                              
     *System Variable     `innodb_data_home_dir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The common part of the directory path for all `InnoDB' data files
     in the shared tablespace.  This setting does not affect the
     location of per-file tablespaces when `innodb_file_per_table' is
     enabled. The default value is the MySQL data directory. If you
     specify the value as an empty string, you can use absolute file
     paths in `innodb_data_file_path'.

   * `innodb_doublewrite'

     Options for innodb_doublewrite

     *Command-Line        `--innodb-doublewrite'        
     Format*                              
     *System Variable     `innodb_doublewrite'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        

     If this variable is enabled (the default), `InnoDB' stores all
     data twice, first to the doublewrite buffer, and then to the
     actual data files. This variable can be turned off with
     `--skip-innodb_doublewrite' for benchmarks or cases when top
     performance is needed rather than concern for data integrity or
     possible failures.

   * `innodb_fast_shutdown'

     Options for innodb_fast_shutdown

     *Command-Line        `--innodb_fast_shutdown[=#]'        
     Format*                              
     *System Variable     `innodb_fast_shutdown'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1'             
     *Valid Values*       `0'             
     `1'                                  
     `2'                                  

     The `InnoDB' shutdown mode. By default, the value is 1, which
     causes a `fast' shutdown (the normal type of shutdown). If the
     value is 0, `InnoDB' does a full purge and an insert buffer merge
     before a shutdown. These operations can take minutes, or even
     hours in extreme cases. If the value is 1, `InnoDB' skips these
     operations at shutdown.  If the value is 2, `InnoDB' will just
     flush its logs and then shut down cold, as if MySQL had crashed; no
     committed transaction will be lost, but crash recovery will be
     done at the next startup. A value of 2 cannot be used on NetWare.

   * `innodb_file_format'

     Options for innodb_file_format

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_file_format=#'        
     Format*                              
     *System Variable     `innodb_file_format'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (>=             
                          5.1.38)*        
     *Type*               `string'        
     *Default*            `Antelope'        

     (`InnoDB Plugin' only) The file format to use for new *Note
     `InnoDB': innodb-storage-engine. tables. Currently `Antelope' and
     `Barracuda' are supported. This applies only for tables that have
     their own tablespace, so for it to have an effect
     `innodb_file_per_table' must be enabled. The Barracuda
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_barracuda)
     file format is required for certain InnoDB features such as table
     compression.

   * `innodb_file_format_check'

     Options for innodb_file_format_check

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_file_format_check=#'        
     Format*                              
     *System Variable     `innodb_file_format_check'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.41)*        
     *Type*               `string'        
     *Default*            `Antelope'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.42)*        
     *Type*               `string'        
     *Default*            `Barracuda'        

     (`InnoDB Plugin' only) This variable can be set to 1 or 0 at
     server startup to enable or disable whether `InnoDB' checks the
     file format tag in the shared tablespace (for example, `Antelope'
     or `Barracuda'). If the tag is checked and is higher than that
     supported by the current version of `InnoDB', an error occurs and
     `InnoDB' does not start. If the tag is not higher, `InnoDB' sets
     the value of `innodb_file_format_check' to the file format tag,
     which is the value seen at runtime.

   * `innodb_file_io_threads'

     Options for innodb_file_io_threads

     *Command-Line        `--innodb_file_io_threads=#'        
     Format*                              
     *System Variable     `innodb_file_io_threads'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `4'             
     *Min Value*          `4'             
     *Max Value*          `64'            

     The number of file I/O threads in `InnoDB'.  Normally, this should
     be left at the default value of 4, but disk I/O on Windows may
     benefit from a larger number. On Unix, increasing the number has
     no effect; `InnoDB' always uses the default value.

     With `InnoDB Plugin', this variable is unused. Use
     `innodb_read_io_threads' and `innodb_write_io_threads' instead.

   * `innodb_file_per_table'

     Options for innodb_file_per_table

     *Command-Line        `--innodb_file_per_table'        
     Format*                              
     *System Variable     `innodb_file_per_table'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     If `innodb_file_per_table' is disabled (the default), `InnoDB'
     creates tables in the system tablespace
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_system_tablespace).
     If `innodb_file_per_table' is enabled, `InnoDB' creates each new
     table using its own `.ibd' file
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_ibd_file)
     for storing data and indexes, rather than in the system
     tablespace. See *Note innodb-multiple-tablespaces:: for information
     about advantages, disadvantages, and features, such as `InnoDB'
     table compression, that only work for tables stored in separate
     tablespaces.

   * `innodb_flush_log_at_trx_commit'

     Options for innodb_flush_log_at_trx_commit

     *Command-Line        `--innodb_flush_log_at_trx_commit[=#]'        
     Format*                              
     *System Variable     `innodb_flush_log_at_trx_commit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `1'             
     *Valid Values*       `0'             
     `1'                                  
     `2'                                  

     If the value of `innodb_flush_log_at_trx_commit' is 0, the log
     buffer is written out to the log file once per second and the
     flush to disk operation is performed on the log file, but nothing
     is done at a transaction commit. When the value is 1 (the
     default), the log buffer is written out to the log file at each
     transaction commit and the flush to disk operation is performed on
     the log file. When the value is 2, the log buffer is written out
     to the file at each commit, but the flush to disk operation is not
     performed on it. However, the flushing on the log file takes place
     once per second also when the value is 2. Note that the
     once-per-second flushing is not 100% guaranteed to happen every
     second, due to process scheduling issues.

     The default value of 1 is required for full ACID compliance.  You
     can achieve better performance by setting the value different from
     1, but then you can lose up to one second worth of transactions in
     a crash. With a value of 0, any *Note `mysqld': mysqld. process
     crash can erase the last second of transactions. With a value of
     2, only an operating system crash or a power outage can erase the
     last second of transactions. `InnoDB''s crash recovery
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_crash_recovery)
     works regardless of the value.

     For the greatest possible durability and consistency in a
     replication setup using `InnoDB' with transactions, use
     `innodb_flush_log_at_trx_commit=1' and `sync_binlog=1' in your
     master server `my.cnf' file.

     *Caution*:

     Many operating systems and some disk hardware fool the
     flush-to-disk operation. They may tell *Note `mysqld': mysqld.
     that the flush has taken place, even though it has not. Then the
     durability of transactions is not guaranteed even with the setting
     1, and in the worst case a power outage can even corrupt the
     `InnoDB' database. Using a battery-backed disk cache in the SCSI
     disk controller or in the disk itself speeds up file flushes, and
     makes the operation safer. You can also try using the Unix command
     `hdparm' to disable the caching of disk writes in hardware caches,
     or use some other command specific to the hardware vendor.

   * `innodb_flush_method'

     Options for innodb_flush_method

     *Command-Line        `--innodb_flush_method=name'        
     Format*                              
     *System Variable     `innodb_flush_method'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type* (Windows)     `string'        
     *Default*            `async_unbuffered'        
                          *Permitted        
                          Values          
                          (<=             
                          5.1.23)*        
     *Type* (Unix)        `string'        
     *Default*            `fdatasync'        
     *Valid Values*       `fdatasync'        
     `O_DSYNC'                            
     `O_DIRECT'                           
                          *Permitted        
                          Values          
                          (>=             
                          5.1.24)*        
     *Type* (Unix)        `string'        
     *Default*            `fsync'         
     *Valid Values*       `fsync'         
     `O_DSYNC'                            
     `O_DIRECT'                           

     Defines the method used to flush
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_flush)
     data to the `InnoDB' data files
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_data_files)
     and log files
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_log_file),
     which can affect I/O throughput. This variable is only
     configurable on Unix and Linux systems. On Windows systems, the
     flush method is always `async_unbuffered' and cannot be changed.

     The `innodb_flush_method' options include:

        * `fsync': `InnoDB' uses the `fsync()' system call to flush both
          the data and log files. `fsync' is the default setting.

        * `O_DSYNC': `InnoDB' uses `O_SYNC' to open and flush the log
          files, and `fsync()' to flush the data files.  `InnoDB' does
          not use `O_DSYNC' directly because there have been problems
          with it on many varieties of Unix.

        * `O_DIRECT': `InnoDB' uses `O_DIRECT' (or `directio()' on
          Solaris) to open the data files, and uses `fsync()' to flush
          both the data and log files. This option is available on some
          GNU/Linux versions, FreeBSD, and Solaris.

     How each settings affects performance depends on hardware
     configuration and workload. Benchmark your particular
     configuration to decide which setting to use, or whether to keep
     the default setting. Examine the `Innodb_data_fsyncs' status
     variable to see the overall number of `fsync()' calls for each
     setting. The mix of read and write operations in your workload can
     affect how a setting performs. For example, on a system with a
     hardware RAID controller and battery-backed write cache,
     `O_DIRECT' can help to avoid double buffering between the `InnoDB'
     buffer pool and the operating system's file system cache. On some
     systems where `InnoDB' data and log files are located on a SAN,
     the default value or `O_DSYNC' might be faster for a read-heavy
     workload with mostly `SELECT' statements. Always test this
     parameter with hardware and workload that reflect your production
     environment.

     Prior to MySQL 5.1.24, the default `innodb_flush_method' option
     was named `fdatasync'. When `fdatasync' was `' specified, `InnoDB'
     used the `fsync()' system call to flush both the data and log
     files. To avoid confusing the `fdatasync' option name with the
     `fdatasync()' system call, the option name was changed to `fsync'
     in MySQL 5.1.24.

   * `innodb_force_recovery'

     Options for innodb_force_recovery

     *Command-Line        `--innodb_force_recovery=#'        
     Format*                              
     *System Variable     `innodb_force_recovery'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `6'             

     The crash recovery mode. Possible values are from 0 to 6. For the
     meanings of these values and important information about
     `innodb_force_recovery', see *Note forcing-innodb-recovery::.

     *Warning*:

     Only set this variable to a value greater than 0 in an emergency
     situation, so that you can start `InnoDB' and dump your tables. As
     a safety measure, `InnoDB' prevents *Note `INSERT': insert, *Note
     `UPDATE': update, or *Note `DELETE': delete. operations when
     `innodb_force_recovery' is greater than 0.

   * `innodb_io_capacity'

     Options for innodb_io_capacity

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_io_capacity=#'        
     Format*                              
     *System Variable     `innodb_io_capacity'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `200'           
     *Min Value*          `100'           
     *Max Value*          `2**32-1'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `200'           
     *Min Value*          `100'           
     *Max Value*          `2**64-1'        

     (`InnoDB Plugin' only) An upper limit on the I/O activity
     performed by the `InnoDB' background tasks, such as flushing pages
     from the buffer pool
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_buffer_pool)
     and merging data from the insert buffer
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_insert_buffer).
     The default value is 200. For busy systems capable of higher I/O
     rates, you can set a higher value at server startup, to help the
     server handle the background maintenance work associated with a
     high rate of row changes. For systems with individual 5400 RPM or
     7200 RPM drives, you might lower the value to the former default
     of `100'.

     This parameter should be set to approximately the number of I/O
     operations that the system can perform per second.  Ideally, keep
     this setting as low as practical, but not so low that these
     background activities fall behind. If the value is too high, data
     is removed from the buffer pool and insert buffer too quickly to
     provide significant benefit from the caching.

     The value represents an estimated proportion of the I/O operations
     per second (IOPS) available to older-generation disk drives that
     could perform about 100 IOPS. The current default of 200 reflects
     that modern storage devices are capable of much higher I/O rates.

     In general, you can increase the value as a function of the number
     of drives used for *Note `InnoDB': innodb-storage-engine.  I/O,
     particularly fast drives capable of high numbers of IOPS.  For
     example, systems that use multiple disks or solid-state disks for
     *Note `InnoDB': innodb-storage-engine. are likely to benefit from
     the ability to control this parameter.

     Although you can specify a very high number, in practice such
     large values have little if any benefit; for example, a value of
     one million would be considered very high.

     You can set the `innodb_io_capacity' value to any number 100 or
     greater, and the default value is `200'. You can set the value of
     this parameter in the MySQL option file (`my.cnf' or `my.ini') or
     change it dynamically with the `SET GLOBAL' command, which
     requires the `SUPER' privilege.

     See Configuring the InnoDB Master Thread I/O Rate
     (http://dev.mysql.com/doc/refman/5.5/en/innodb-performance-thread_io_rate.html)
     for more guidelines about this option. For general information
     about InnoDB I/O performance, see Optimizing InnoDB Disk I/O
     (http://dev.mysql.com/doc/refman/5.5/en/optimizing-innodb-diskio.html).

     This variable was added in MySQL 5.1.38.

   * `innodb_lock_wait_timeout'

     Options for innodb_lock_wait_timeout

     *Command-Line        `--innodb_lock_wait_timeout=#'        
     Format*                              
     *System Variable     `innodb_lock_wait_timeout'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `50'            
     *Min Value*          `1'             
     *Max Value*          `1073741824'        

     The timeout in seconds an `InnoDB' transaction waits for a row
     lock before giving up. The default value is 50 seconds. A
     transaction that tries to access a row that is locked by another
     `InnoDB' transaction waits at most this many seconds for write
     access to the row before issuing the following error:


          ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

     When a lock wait timeout occurs, the current statement is rolled
     back (not the entire transaction). To have the entire transaction
     roll back, start the server with the `--innodb_rollback_on_timeout'
     option. See also *Note innodb-error-handling::.

     You might decrease this value for highly interactive applications
     or OLTP
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_oltp)
     systems, to display user feedback quickly or put the update into a
     queue for processing later. You might increase this value for
     long-running back-end operations, such as a transform step in a
     data warehouse that waits for other large insert or update
     operations to finish.

     `innodb_lock_wait_timeout' applies to `InnoDB' row locks only. A
     MySQL table lock does not happen inside `InnoDB' and this timeout
     does not apply to waits for table locks.

     `InnoDB' does detect transaction deadlocks in its own lock table
     immediately and rolls back one transaction.  The lock wait timeout
     value does not apply to such a wait.

     For the built-in `InnoDB', this variable can be set only at server
     startup. For `InnoDB Plugin', it can be set at startup or changed
     at runtime, and has both global and session values.

   * `innodb_locks_unsafe_for_binlog'

     Options for innodb_locks_unsafe_for_binlog

     *Command-Line        `--innodb_locks_unsafe_for_binlog'        
     Format*                              
     *System Variable     `innodb_locks_unsafe_for_binlog'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     This variable affects how `InnoDB' uses gap locking for searches
     and index scans. Normally, `InnoDB' uses an algorithm called
     _next-key locking_ that combines index-row locking with gap
     locking. `InnoDB' performs row-level locking in such a way that
     when it searches or scans a table index, it sets shared or
     exclusive locks on the index records it encounters. Thus, the
     row-level locks are actually index-record locks. In addition, a
     next-key lock on an index record also affects the `gap' before
     that index record. That is, a next-key lock is an index-record
     lock plus a gap lock on the gap preceding the index record. If one
     session has a shared or exclusive lock on record `R' in an index,
     another session cannot insert a new index record in the gap
     immediately before `R' in the index order. See *Note
     innodb-record-level-locks::.

     By default, the value of `innodb_locks_unsafe_for_binlog' is 0
     (disabled), which means that gap locking is enabled: `InnoDB' uses
     next-key locks for searches and index scans. To enable the
     variable, set it to 1. This causes gap locking to be disabled:
     `InnoDB' uses only index-record locks for searches and index scans.

     Enabling `innodb_locks_unsafe_for_binlog' does not disable the use
     of gap locking for foreign-key constraint checking or
     duplicate-key checking.

     The effect of enabling `innodb_locks_unsafe_for_binlog' is similar
     to but not identical to setting the transaction isolation level to
     `READ COMMITTED':

        * Enabling `innodb_locks_unsafe_for_binlog' is a global setting
          and affects all sessions, whereas the isolation level can be
          set globally for all sessions, or individually per session.

        * `innodb_locks_unsafe_for_binlog' can be set only at server
          startup, whereas the isolation level can be set at startup or
          changed at runtime.

     `READ COMMITTED' therefore offers finer and more flexible control
     than `innodb_locks_unsafe_for_binlog'.  For additional details
     about the effect of isolation level on gap locking, see *Note
     set-transaction::.

     Enabling `innodb_locks_unsafe_for_binlog' may cause phantom
     problems because other sessions can insert new rows into the gaps
     when gap locking is disabled. Suppose that there is an index on
     the `id' column of the `child' table and that you want to read and
     lock all rows from the table having an identifier value larger
     than 100, with the intention of updating some column in the
     selected rows later:


          SELECT * FROM child WHERE id > 100 FOR UPDATE;

     The query scans the index starting from the first record where
     `id' is greater than 100. If the locks set on the index records in
     that range do not lock out inserts made in the gaps, another
     session can insert a new row into the table. Consequently, if you
     were to execute the same *Note `SELECT': select. again within the
     same transaction, you would see a new row in the result set
     returned by the query. This also means that if new items are added
     to the database, `InnoDB' does not guarantee serializability.
     Therefore, if `innodb_locks_unsafe_for_binlog' is enabled,
     `InnoDB' guarantees at most an isolation level of `READ
     COMMITTED'. (Conflict serializability is still guaranteed.) For
     additional information about phantoms, see *Note
     innodb-next-key-locking::.

     Enabling `innodb_locks_unsafe_for_binlog' has additional effects:

        * For *Note `UPDATE': update. or *Note `DELETE': delete.
          statements, `InnoDB' holds locks only for rows that it
          updates or deletes. Record locks for nonmatching rows are
          released after MySQL has evaluated the `WHERE' condition.
          This greatly reduces the probability of deadlocks, but they
          can still happen.

        * For *Note `UPDATE': update. statements, if a row is already
          locked, `InnoDB' performs a `semi-consistent' read, returning
          the latest committed version to MySQL so that MySQL can
          determine whether the row matches the `WHERE' condition of the
          *Note `UPDATE': update. If the row matches (must be updated),
          MySQL reads the row again and this time `InnoDB' either locks
          it or waits for a lock on it.

     Consider the following example, beginning with this table:


          CREATE TABLE t (a INT NOT NULL, b INT) ENGINE = InnoDB;
          INSERT INTO t VALUES (1,2),(2,3),(3,2),(4,3),(5,2);
          COMMIT;

     In this case, table has no indexes, so searches and index scans
     use the hidden clustered index for record locking (see *Note
     innodb-index-types::).

     Suppose that one client performs an *Note `UPDATE': update. using
     these statements:


          SET autocommit = 0;
          UPDATE t SET b = 5 WHERE b = 3;

     Suppose also that a second client performs an *Note `UPDATE':
     update. by executing these statements following those of the first
     client:


          SET autocommit = 0;
          UPDATE t SET b = 4 WHERE b = 2;

     As *Note `InnoDB': innodb-storage-engine. executes each *Note
     `UPDATE': update, it first acquires an exclusive lock for each
     row, and then determines whether to modify it. If *Note `InnoDB':
     innodb-storage-engine. does not modify the row and
     `innodb_locks_unsafe_for_binlog' is enabled, it releases the lock.
     Otherwise, *Note `InnoDB': innodb-storage-engine. retains the lock
     until the end of the transaction. This affects transaction
     processing as follows.

     If `innodb_locks_unsafe_for_binlog' is disabled, the first *Note
     `UPDATE': update.  acquires x-locks and does not release any of
     them:


          x-lock(1,2); retain x-lock
          x-lock(2,3); update(2,3) to (2,5); retain x-lock
          x-lock(3,2); retain x-lock
          x-lock(4,3); update(4,3) to (4,5); retain x-lock
          x-lock(5,2); retain x-lock

     The second *Note `UPDATE': update. blocks as soon as it tries to
     acquire any locks (because first update has retained locks on all
     rows), and does not proceed until the first *Note `UPDATE':
     update. commits or rolls back:


          x-lock(1,2); block and wait for first UPDATE to commit or roll back

     If `innodb_locks_unsafe_for_binlog' is enabled, the first *Note
     `UPDATE': update.  acquires x-locks and releases those for rows
     that it does not modify:


          x-lock(1,2); unlock(1,2)
          x-lock(2,3); update(2,3) to (2,5); retain x-lock
          x-lock(3,2); unlock(3,2)
          x-lock(4,3); update(4,3) to (4,5); retain x-lock
          x-lock(5,2); unlock(5,2)

     For the second `UPDATE', `InnoDB' does a `semi-consistent' read,
     returning the latest committed version of each row to MySQL so
     that MySQL can determine whether the row matches the `WHERE'
     condition of the *Note `UPDATE': update.:


          x-lock(1,2); update(1,2) to (1,4); retain x-lock
          x-lock(2,3); unlock(2,3)
          x-lock(3,2); update(3,2) to (3,4); retain x-lock
          x-lock(4,3); unlock(4,3)
          x-lock(5,2); update(5,2) to (5,4); retain x-lock

     Semi-consistent read is available as of MySQL 5.1.5. Before 5.1.5,
     the second *Note `UPDATE': update.  proceeds part way before it
     blocks. It begins acquiring x-locks, and blocks when it tries to
     acquire one for a row still locked by first *Note `UPDATE': update.
     The second *Note `UPDATE': update. does not proceed until the
     first *Note `UPDATE': update.  commits or rolls back:


          x-lock(1,2); update(1,2) to (1,4); retain x-lock
          x-lock(2,3); block and wait for first UPDATE to commit or roll back

     In this case, the second *Note `UPDATE': update.  must wait for a
     commit or rollback of the first *Note `UPDATE': update, even
     though it affects different rows. The first *Note `UPDATE':
     update. has an exclusive lock on row (2,3) that it has not
     released. As the second *Note `UPDATE': update. scans rows, it
     tries to acquire an exclusive lock for that same row, which it
     cannot have. Thus, before MySQL 5.1.5, enabling
     `innodb_locks_unsafe_for_binlog' still does not permit operations
     such as *Note `UPDATE': update. to overtake other similar
     operations (such as another *Note `UPDATE': update.) even when
     they affect different rows.

   * `innodb_log_arch_dir'

     This variable is deprecated, and was removed in MySQL 5.1.21.

   * `innodb_log_archive'

     This variable is deprecated, and was removed in MySQL 5.1.18.

   * `innodb_log_buffer_size'

     Options for innodb_log_buffer_size

     *Command-Line        `--innodb_log_buffer_size=#'        
     Format*                              
     *System Variable     `innodb_log_buffer_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1048576'        
     *Min Value*          `1048576'        
     *Max Value*          `4294967295'        

     The size in bytes of the buffer that `InnoDB' uses to write to the
     log files on disk. The default value is 1MB for the built-in *Note
     `InnoDB': innodb-storage-engine, 8MB for `InnoDB Plugin'. Sensible
     values range from 1MB to 8MB. A large log buffer enables large
     transactions to run without a need to write the log to disk before
     the transactions commit. Thus, if you have big transactions,
     making the log buffer larger saves disk I/O.

   * `innodb_log_file_size'

     Options for innodb_log_file_size

     *Command-Line        `--innodb_log_file_size=#'        
     Format*                              
     *System Variable     `innodb_log_file_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `5242880'        
     *Min Value*          `1048576'        
     *Max Value*          `4GB /          
                          innodb_log_files_in_group'        

     The size in bytes of each log file
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_log_file)
     in a log group
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_log_group).
     The combined size of log files (`innodb_log_file_size' *
     `innodb_log_files_in_group') cannot exceed a maximum value that is
     slightly less than 4GB.  A pair of 2047 MB log files, for example,
     would allow you to approach the range limit but not exceed it. The
     default value is 5MB. Sensible values range from 1MB to 1/N-th of
     the size of the buffer pool, where N is the number of log files in
     the group. The larger the value, the less checkpoint flush
     activity is needed in the buffer pool, saving disk I/O.  But
     larger log files also mean that recovery is slower in case of a
     crash.

   * `innodb_log_files_in_group'

     Options for innodb_log_files_in_group

     *Command-Line        `--innodb_log_files_in_group=#'        
     Format*                              
     *System Variable     `innodb_log_files_in_group'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `2'             
     *Min Value*          `2'             
     *Max Value*          `100'           

     The number of log files in the log group.  `InnoDB' writes to the
     files in a circular fashion. The default (and recommended) value
     is 2.

   * `innodb_log_group_home_dir'

     Options for innodb_log_group_home_dir

     *Command-Line        `--innodb_log_group_home_dir=path'        
     Format*                              
     *System Variable     `innodb_log_group_home_dir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The directory path to the `InnoDB' log files.  If you do not
     specify any `InnoDB' log variables, the default is to create two
     files named `ib_logfile0' and `ib_logfile1' in the MySQL data
     directory.  Their size is given by the size of the
     `innodb_log_file_size' system variable.

   * `innodb_max_dirty_pages_pct'

     Options for innodb_max_dirty_pages_pct

     *Command-Line        `--innodb_max_dirty_pages_pct=#'        
     Format*                              
     *System Variable     `innodb_max_dirty_pages_pct'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `90'            
     *Min Value*          `0'             
     *Max Value*          `100'           

     This is an integer in the range from 0 to 100. The default value
     is 90 for the built-in *Note `InnoDB': innodb-storage-engine, 75
     for `InnoDB Plugin'. The main thread in `InnoDB' tries to write
     pages from the buffer pool so that the percentage of dirty (not
     yet written) pages will not exceed this value.

   * `innodb_max_purge_lag'

     Options for innodb_max_purge_lag

     *Command-Line        `--innodb_max_purge_lag=#'        
     Format*                              
     *System Variable     `innodb_max_purge_lag'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     This variable controls how to delay *Note `INSERT': insert, *Note
     `UPDATE': update, and *Note `DELETE': delete. operations when purge
     operations are lagging (see *Note innodb-multi-versioning::). The
     default value 0 (no delays).

     The `InnoDB' transaction system maintains a list of transactions
     that have index records delete-marked by *Note `UPDATE': update. or
     *Note `DELETE': delete. operations. Let the length of this list be
     PURGE_LAG.  When PURGE_LAG exceeds `innodb_max_purge_lag', each
     *Note `INSERT': insert, *Note `UPDATE': update, and *Note
     `DELETE': delete. operation is delayed by
     ((PURGE_LAG/`innodb_max_purge_lag')x10)-5 milliseconds. The delay
     is computed in the beginning of a purge batch, every ten seconds.
     The operations are not delayed if purge cannot run because of an
     old consistent read view that could see the rows to be purged.

     A typical setting for a problematic workload might be 1 million,
     assuming that transactions are small, only 100 bytes in size, and
     it is permissible to have 100MB of unpurged `InnoDB' table rows.

     The lag value is displayed as the history list length in the
     `TRANSACTIONS' section of InnoDB Monitor output. For example, if
     the output includes the following lines, the lag value is 20:


          ------------
          TRANSACTIONS
          ------------
          Trx id counter 0 290328385
          Purge done for trx's n:o < 0 290315608 undo n:o < 0 17
          History list length 20

   * `innodb_mirrored_log_groups'

     Has no effect.

   * `innodb_old_blocks_pct'

     Options for innodb_old_blocks_pct

     *Introduced*         5.1.41          
     *Command-Line        `--innodb_old_blocks_pct=#'        
     Format*                              
     *System Variable     `innodb_old_blocks_pct'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `37'            
     *Min Value*          `5'             
     *Max Value*          `95'            

     (`InnoDB Plugin' only) Specifies the approximate percentage of the
     `InnoDB' buffer pool
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_buffer_pool)
     used for the old block sublist
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_sublist).
     The range of values is 5 to 95. The default value is 37 (that is,
     3/8 of the pool). See *Note innodb-buffer-pool:: for information
     about buffer pool management, such as the LRU
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_lru)
     algorithm and eviction
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_eviction)
     policies.

     This variable was added in MySQL 5.1.41.

   * `innodb_old_blocks_time'

     Options for innodb_old_blocks_time

     *Introduced*         5.1.41          
     *Command-Line        `--innodb_old_blocks_time=#'        
     Format*                              
     *System Variable     `innodb_old_blocks_time'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `2**32-1'        

     (`InnoDB Plugin' only) Specifies how long in milliseconds (ms) a
     block inserted into the old sublist
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_sublist)
     must stay there after its first access before it can be moved to
     the new sublist. The default value is 0: A block inserted into the
     old sublist moves immediately to the new sublist the first time it
     is accessed, no matter how soon after insertion the access occurs.
     If the value is greater than 0, blocks remain in the old sublist
     until an access occurs at least that many ms after the first
     access. For example, a value of 1000 causes blocks to stay in the
     old sublist for 1 second after the first access before they become
     eligible to move to the new sublist.

     This variable is often used in combination with
     `innodb_old_blocks_pct'. See *Note innodb-buffer-pool:: for
     information about buffer pool management, such as the LRU
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_lru)
     algorithm and eviction
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_eviction)
     policies.

     This variable was added in MySQL 5.1.41.

   * `innodb_open_files'

     Options for innodb_open_files

     *Command-Line        `--innodb_open_files=#'        
     Format*                              
     *System Variable     `innodb_open_files'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `300'           
     *Min Value*          `10'            
     *Max Value*          `4294967295'        

     This variable is relevant only if you use multiple `InnoDB'
     tablespaces. It specifies the maximum number of `.ibd' files that
     MySQL can keep open at one time. The minimum value is 10. The
     default value is 300.

     The file descriptors used for `.ibd' files are for `InnoDB' tables
     only. They are independent of those specified by the
     `--open-files-limit' server option, and do not affect the
     operation of the table cache.

   * `innodb_random_read_ahead'

     Options for innodb_random_read_ahead

     *Introduced*         5.1.59          
     *Command-Line        `--innodb_random_read_ahead=#'        
     Format*                              
     *System Variable     `innodb_random_read_ahead'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Enables the random read-ahead
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_read_ahead)
     technique for optimizing `InnoDB' I/O. Random read-ahead
     functionality was removed from the `InnoDB Plugin' (version 1.0.4)
     and was therefore not included in MySQL 5.5.0 when `InnoDB Plugin'
     became the `built-in' version of `InnoDB'. Random read-ahead was
     reintroduced in MySQL 5.1.59 and 5.5.16 and higher along with the
     `innodb_random_read_ahead' configuration option, which is disabled
     by default.

     See Configuring InnoDB Buffer Pool Prefetching (Read-Ahead)
     (http://dev.mysql.com/doc/refman/5.5/en/innodb-performance-read_ahead.html)
     for details about the performance considerations for the different
     types of read-ahead requests. For general I/O tuning advice, see
     Optimizing InnoDB Disk I/O
     (http://dev.mysql.com/doc/refman/5.5/en/optimizing-innodb-diskio.html).

   * `innodb_read_ahead_threshold'

     Options for innodb_read_ahead_threshold

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_read_ahead_threshold=#'        
     Format*                              
     *System Variable     `innodb_read_ahead_threshold'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `56'            
     *Min Value*          `0'             
     *Max Value*          `64'            

     (`InnoDB Plugin' only) Controls the sensitivity of linear
     read-ahead
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_read_ahead)
     that `InnoDB' uses to prefetch pages into the buffer pool. If
     `InnoDB' reads at least `innodb_read_ahead_threshold' pages
     sequentially from an extent
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_extent)
     (64 pages), it initiates an asynchronous read for the entire
     following extent. The permissible range of values is 0 to 64. The
     default is 56: `InnoDB' must read at least 56 pages sequentially
     from an extent to initiate an asynchronous read for the following
     extent.

     This variable was added in MySQL 5.1.38.

   * `innodb_read_io_threads'

     Options for innodb_read_io_threads

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_read_io_threads=#'        
     Format*                              
     *System Variable     `innodb_read_io_threads'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `4'             
     *Min Value*          `1'             
     *Max Value*          `64'            

     (`InnoDB Plugin' only) The number of I/O threads for read
     operations in `InnoDB'. The default value is 4.

     *Note*:

     On Linux systems, running multiple MySQL servers (typically more
     than 12) with default settings for `innodb_read_io_threads',
     `innodb_write_io_threads', and the Linux `aio-max-nr' setting can
     exceed system limits. Ideally, increase the `aio-max-nr' setting;
     as a workaround, you might reduce the settings for one or both of
     the MySQL configuration options.

     This variable was added in MySQL 5.1.38.

   * `innodb_replication_delay'

     Options for innodb_replication_delay

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_replication_delay=#'        
     Format*                              
     *System Variable     `innodb_replication_delay'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     (`InnoDB Plugin' only) The replication thread delay (in ms) on a
     slave server if `innodb_thread_concurrency' is reached.

     This variable was added in MySQL 5.1.38.

   * `innodb_rollback_on_timeout'

     Options for innodb_rollback_on_timeout

     *Introduced*         5.1.15          
     *Command-Line        `--innodb_rollback_on_timeout'        
     Format*                              
     *System Variable     `innodb_rollback_on_timeout'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     In MySQL 5.1, `InnoDB' rolls back
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_rollback)
     only the last statement on a transaction timeout by default. If
     `--innodb_rollback_on_timeout' is specified, a transaction timeout
     causes `InnoDB' to abort and roll back the entire transaction (the
     same behavior as in MySQL 4.1). This variable was added in MySQL
     5.1.15.

   * `innodb_spin_wait_delay'

     Options for innodb_spin_wait_delay

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_spin_wait_delay=#'        
     Format*                              
     *System Variable     `innodb_spin_wait_delay'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `6'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     (`InnoDB Plugin' only) The maximum delay between polls for a spin
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_spin)
     lock. The low-level implementation of this mechanism varies
     depending on the combination of hardware and operating system, so
     the delay does not correspond to a fixed time interval. The
     default value is 6.

     This variable was added in MySQL 5.1.38.

   * `innodb_stats_method'

     Options for innodb_stats_method

     *Introduced*         5.1.56          
     *Command-Line        `--innodb_stats_method=name'        
     Format*                              
     *System Variable     `innodb_stats_method'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `nulls_equal'        
     *Valid Values*       `nulls_equal'        
     `nulls_unequal'                      
     `nulls_ignored'                      

     How the server treats `NULL' values when collecting statistics
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_statistics)
     about the distribution of index values for `InnoDB' tables. This
     variable has three possible values, `nulls_equal',
     `nulls_unequal', and `nulls_ignored'. For `nulls_equal', all `NULL'
     index values are considered equal and form a single value group
     that has a size equal to the number of `NULL' values. For
     `nulls_unequal', `NULL' values are considered unequal, and each
     `NULL' forms a distinct value group of size 1. For `nulls_ignored',
     `NULL' values are ignored.

     The method that is used for generating table statistics influences
     how the optimizer chooses indexes for query execution, as
     described in *Note myisam-index-statistics::.

   * `innodb_stats_on_metadata'

     Options for innodb_stats_on_metadata

     *Introduced*         5.1.17          
     *Command-Line        `--innodb_stats_on_metadata'        
     Format*                              
     *System Variable     `innodb_stats_on_metadata'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     When this variable is enabled (which is the default, as before the
     variable was created), `InnoDB' updates statistics
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_statistics)
     during metadata statements such as *Note `SHOW TABLE STATUS':
     show-table-status. or *Note `SHOW INDEX': show-index, or when
     accessing the `INFORMATION_SCHEMA' tables *Note `TABLES':
     tables-table. or *Note `STATISTICS': statistics-table. (These
     updates are similar to what happens for *Note `ANALYZE TABLE':
     analyze-table.) When disabled, `InnoDB' does not update statistics
     during these operations. Disabling this variable can improve
     access speed for schemas that have a large number of tables or
     indexes. It can also improve the stability of execution plans for
     queries that involve `InnoDB' tables.

     This variable was added in MySQL 5.1.17.

   * `innodb_stats_sample_pages'

     Options for innodb_stats_sample_pages

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_stats_sample_pages=#'        
     Format*                              
     *System Variable     `innodb_stats_sample_pages'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `8'             
     *Min Value*          `1'             
     *Max Value*          `2**64-1'        

     (`InnoDB Plugin' only) The number of index pages to sample for
     index distribution statistics
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_statistics)
     such as are calculated by *Note `ANALYZE TABLE': analyze-table.
     The default value is 8.

     This variable was added in MySQL 5.1.38.

   * `innodb_strict_mode'

     Options for innodb_strict_mode

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_strict_mode=#'        
     Format*                              
     *System Variable     `innodb_strict_mode'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     When `innodb_strict_mode' is `ON', `InnoDB' returns errors rather
     than warnings for certain conditions. The default value is `OFF'.

     Strict mode
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_strict_mode)
     helps guard against ignored typos and syntax errors in SQL, or
     other unintended consequences of various combinations of
     operational modes and SQL statements. When `innodb_strict_mode' is
     `ON', `InnoDB' raises error conditions in certain cases, rather
     than issuing a warning and processing the specified statement
     (perhaps with unintended behavior). This is analogous to *Note
     `sql_mode': sql-mode. in MySQL, which controls what SQL syntax
     MySQL accepts, and determines whether it silently ignores errors,
     or validates input syntax and data values.

     The `innodb_strict_mode' setting affects the handling of syntax
     errors for *Note `CREATE TABLE': create-table, *Note `ALTER
     TABLE': alter-table.  and *Note `CREATE INDEX': create-index.
     statements.  `innodb_strict_mode' also enables a record size
     check, so that an `INSERT' or `UPDATE' never fails due to the
     record being too large for the selected page size.

     Oracle recommends enabling `innodb_strict_mode' when using
     `ROW_FORMAT' and `KEY_BLOCK_SIZE' clauses on *Note `CREATE TABLE':
     create-table, *Note `ALTER TABLE': alter-table, and *Note `CREATE
     INDEX': create-index. statements. When `innodb_strict_mode' is
     `OFF', `InnoDB' ignores conflicting clauses and creates the table
     or index, with only a warning in the message log. The resulting
     table might have different behavior than you intended, such as
     having no compression when you tried to create a compressed table.
     When `innodb_strict_mode' is `ON', such problems generate an
     immediate error and the table or index is not created, avoiding a
     troubleshooting session later.

     You can turn `innodb_strict_mode' `ON' or `OFF' on the command
     line when you start `mysqld', or in the configuration file
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_configuration_file)
     `my.cnf' or `my.ini'. You can also enable or disable
     `innodb_strict_mode' at runtime with the statement `SET
     [GLOBAL|SESSION] innodb_strict_mode=MODE', where `MODE' is either
     `ON' or `OFF'.  Changing the `GLOBAL' setting requires the `SUPER'
     privilege and affects the operation of all clients that
     subsequently connect. Any client can change the `SESSION' setting
     for `innodb_strict_mode', and the setting affects only that client.

   * `innodb_support_xa'

     Options for innodb_support_xa

     *Command-Line        `--innodb_support_xa'        
     Format*                              
     *System Variable     `innodb_support_xa'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Enables `InnoDB' support for two-phase commit in XA
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_xa)
     transactions, causing an extra disk flush for transaction
     preparation. This setting is the default. The XA mechanism is used
     internally and is essential for any server that has its binary log
     turned on and is accepting changes to its data from more than one
     thread. If you turn it off, transactions can be written to the
     binary log in a different order from the one in which the live
     database is committing them. This can produce different data when
     the binary log is replayed in disaster recovery or on a
     replication slave. Do not turn it off on a replication master
     server unless you have an unusual setup where only one thread is
     able to change data.

     For a server that is accepting data changes from only one thread,
     it is safe and recommended to turn off this option to improve
     performance for *Note `InnoDB': innodb-storage-engine.  tables.
     For example, you can turn it off on replication slaves where only
     the replication SQL thread is changing data.

     You can also turn off this option if you do not need it for safe
     binary logging or replication, and you also do not use an external
     XA transaction manager.

   * `innodb_sync_spin_loops'

     Options for innodb_sync_spin_loops

     *Command-Line        `--innodb_sync_spin_loops=#'        
     Format*                              
     *System Variable     `innodb_sync_spin_loops'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `20'            
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     The number of times a thread waits for an `InnoDB' mutex to be
     freed before the thread is suspended. The default value is 20 for
     the built-in *Note `InnoDB': innodb-storage-engine, 30 for `InnoDB
     Plugin'.

   * `innodb_table_locks'

     Options for innodb_table_locks

     *Command-Line        `--innodb_table_locks'        
     Format*                              
     *System Variable     `innodb_table_locks'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     If `autocommit = 0', `InnoDB' honors *Note `LOCK TABLES':
     lock-tables.; MySQL does not return from `LOCK TABLES ... WRITE'
     until all other threads have released all their locks to the
     table. The default value of `innodb_table_locks' is 1, which means
     that *Note `LOCK TABLES': lock-tables.  causes InnoDB to lock a
     table internally if `autocommit = 0'.

   * `innodb_thread_concurrency'

     Options for innodb_thread_concurrency

     *Command-Line        `--innodb_thread_concurrency=#'        
     Format*                              
     *System Variable     `innodb_thread_concurrency'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `8'             
     *Min Value*          `0'             
     *Max Value*          `1000'          

     `InnoDB' tries to keep the number of operating system threads
     concurrently inside `InnoDB' less than or equal to the limit given
     by this variable. Once the number of threads reaches this limit,
     additional threads are placed into a wait state within a FIFO
     queue for execution. Threads waiting for locks are not counted in
     the number of concurrently executing threads.

     The correct value for this variable is dependent on environment
     and workload. You will need to try a range of different values to
     determine what value works for your applications. A recommended
     value is 2 times the number of CPUs plus the number of disks.

     The range of this variable is 0 to 1000. A value of 20 or higher
     is interpreted as infinite concurrency before MySQL 5.1.12. From
     5.1.12 on, you can disable thread concurrency checking by setting
     the value to 0. Disabling thread concurrency checking enables
     InnoDB to create as many threads as it needs. A value of 0 also
     disables the `queries inside InnoDB' and `queries in queue
     counters' in the `ROW OPERATIONS' section of `SHOW ENGINE INNODB
     STATUS' output.

     The default value for the built-in *Note `InnoDB':
     innodb-storage-engine. is 20 before MySQL 5.1.11 and 8 from 5.1.11
     on. The default for the `InnoDB Plugin' is 0.

   * `innodb_thread_sleep_delay'

     Options for innodb_thread_sleep_delay

     *Command-Line        `--innodb_thread_sleep_delay=#'        
     Format*                              
     *System Variable     `innodb_thread_sleep_delay'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `10000'         
     *Min Value*          `0'             
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `10000'         
     *Min Value*          `0'             
     *Max Value*          `18446744073709551615'        

     How long `InnoDB' threads sleep before joining the `InnoDB' queue,
     in microseconds.  The default value is 10,000. A value of 0
     disables sleep.

   * `innodb_use_legacy_cardinality_algorithm'

     Options for innodb_use_legacy_cardinality_algorithm

     *Introduced*         5.1.35          
     *Command-Line        `--innodb_use_legacy_cardinality_algorithm=#'        
     Format*                              
     *System Variable     `innodb_use_legacy_cardinality_algorithm'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     *Note `InnoDB': innodb-storage-engine. uses random numbers to
     generate dives into indexes for calculating index cardinality.
     However, under certain conditions, the algorithm does not generate
     random numbers, so *Note `ANALYZE TABLE': analyze-table. sometimes
     does not update cardinality estimates properly. An alternative
     algorithm was introduced in MySQL 5.1.35 with better randomization
     properties, and the `innodb_use_legacy_cardinality_algorithm',
     system variable which algorithm to use. The default value of the
     variable is 1 (`ON'), to use the original algorithm for
     compatibility with existing applications. The variable can be set
     to 0 (`OFF') to use the new algorithm with improved randomness.

     This variable is not used in `InnoDB Plugin' because the improved
     algorithm is used by default. Also, the number of random dives can
     be changed by modifying the `innodb_stats_sample_pages' system
     variable.

   * `innodb_use_sys_malloc'

     Options for innodb_use_sys_malloc

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_use_sys_malloc=#'        
     Format*                              
     *System Variable     `innodb_use_sys_malloc'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `ON'            

     (`InnoDB Plugin' only) Whether `InnoDB' uses the operating system
     memory allocator (`ON') or its own (`OFF'). The default value is
     `ON'.

     This variable was added in MySQL 5.1.38.

   * `innodb_version'

     (`InnoDB Plugin' only) The *Note `InnoDB': innodb-storage-engine.
     version number. Starting in 5.1.68, the separate numbering for
     `InnoDB' is discontinued and this value is the same as for the
     `version' variable.

     This variable was added in MySQL 5.1.38.

   * `innodb_write_io_threads'

     Options for innodb_write_io_threads

     *Introduced*         5.1.38          
     *Command-Line        `--innodb_write_io_threads=#'        
     Format*                              
     *System Variable     `innodb_write_io_threads'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `4'             
     *Min Value*          `1'             
     *Max Value*          `64'            

     (`InnoDB Plugin' only) The number of I/O threads for write
     operations in `InnoDB'. The default value is 4.

     *Note*:

     On Linux systems, running multiple MySQL servers (typically more
     than 12) with default settings for `innodb_read_io_threads',
     `innodb_write_io_threads', and the Linux `aio-max-nr' setting can
     exceed system limits. Ideally, increase the `aio-max-nr' setting;
     as a workaround, you might reduce the settings for one or both of
     the MySQL configuration options.

     This variable was added in MySQL 5.1.38.

You should also take into consideration the value of `sync_binlog',
which controls synchronization of the binary log to disk.


File: manual.info,  Node: innodb-tuning,  Next: innodb-monitors,  Prev: innodb-parameters,  Up: innodb-storage-engine

14.6.8 InnoDB Performance Tuning Tips
-------------------------------------

The followings tips are grouped by category. Some of them can apply in
multiple categories, so it is useful to read them all.

*Storage Layout Tips*

   * In `InnoDB', having a long `PRIMARY KEY' wastes a lot of disk
     space because its value must be stored with every secondary index
     record. (See *Note innodb-table-and-index::.) Create an
     `AUTO_INCREMENT' column as the primary key if your primary key is
     long.

   * Use the *Note `VARCHAR': char. data type instead of *Note `CHAR':
     char. if you are storing variable-length strings or if the column
     may contain many `NULL' values. A *Note `CHAR(N)': char.  column
     always takes N characters to store data, even if the string is
     shorter or its value is `NULL'. Smaller tables fit better in the
     buffer pool and reduce disk I/O.

     When using `COMPACT' row format (the default `InnoDB' format in
     MySQL 5.1) and variable-length character sets, such as `utf8' or
     `sjis', *Note `CHAR(N)': char.  will occupy a variable amount of
     space, at least N bytes.

*Transaction Management Tips*

   * Wrap several modifications into a single transaction to reduce the
     number of flush operations. `InnoDB' must flush the log to disk at
     each transaction commit if that transaction made modifications to
     the database. The rotation speed of a disk is typically at most
     167 revolutions/second (for a 10,000RPM disk), which constrains
     the number of commits to the same 167^th of a second if the disk
     does not `fool' the operating system.

   * If you can afford the loss of some of the latest committed
     transactions if a crash occurs, you can set the
     `innodb_flush_log_at_trx_commit' parameter to 0. `InnoDB' tries to
     flush the log once per second anyway, although the flush is not
     guaranteed.  Also, set the value of `innodb_support_xa' to 0, which
     will reduce the number of disk flushes due to synchronizing on
     disk data and the binary log.

*Disk I/O Tips*

   * `innodb_buffer_pool_size' specifies the size of the buffer pool.
     If your buffer pool is small and you have sufficient memory,
     making the pool larger can improve performance by reducing the
     amount of disk I/O needed as queries access *Note `InnoDB':
     innodb-storage-engine. tables. For more information about the
     pool, see *Note innodb-buffer-pool::.

   * Beware of big rollbacks of mass inserts: `InnoDB' uses the insert
     buffer to save disk I/O in inserts, but no such mechanism is used
     in a corresponding rollback. A disk-bound rollback can take 30
     times as long to perform as the corresponding insert. Killing the
     database process does not help because the rollback starts again on
     server startup. The only way to get rid of a runaway rollback is
     to increase the buffer pool so that the rollback becomes CPU-bound
     and runs fast, or to use a special procedure. See *Note
     forcing-innodb-recovery::.

   * Beware also of other big disk-bound operations. Use *Note `DROP
     TABLE': drop-table. and *Note `CREATE TABLE': create-table. to
     empty a table, not `DELETE FROM TBL_NAME'.

   * In some versions of GNU/Linux and Unix, flushing files to disk
     with the Unix `fsync()' call (which `InnoDB' uses by default) and
     other similar methods is surprisingly slow. If you are
     dissatisfied with database write performance, you might try
     setting the `innodb_flush_method' parameter to `O_DSYNC'. The
     `O_DSYNC' flush method seems to perform slower on most systems,
     but yours might not be one of them.

   * When using the `InnoDB' storage engine on Solaris 10 for x86_64
     architecture (AMD Opteron), it is important to use direct I/O for
     `InnoDB'-related files. Failure to do so may cause degradation of
     `InnoDB''s speed and performance on this platform. To use direct
     I/O for an entire UFS file system used for storing
     `InnoDB'-related files, mount it with the `forcedirectio' option;
     see `mount_ufs(1M)'. (The default on Solaris 10/x86_64 is _not_ to
     use this option.)  Alternatively, as of MySQL 5.1.18 you can set
     `innodb_flush_method = O_DIRECT' if you do not want to affect the
     entire file system. This causes `InnoDB' to call `directio()'
     instead of `fcntl()'. However, setting `innodb_flush_method' to
     `O_DIRECT' causes `InnoDB' to use direct I/O only for data files,
     not the log files.

     When using the `InnoDB' storage engine with a large
     `innodb_buffer_pool_size' value on any release of Solaris 2.6 and
     up and any platform (sparc/x86/x64/amd64), a significant
     performance gain might be achieved by placing `InnoDB' data files
     and log files on raw devices or on a separate direct I/O UFS file
     system using the `forcedirectio' mount option as described earlier
     (it is necessary to use the mount option rather than setting
     `innodb_flush_method' if you want direct I/O for the log files).
     Users of the Veritas file system VxFS should use the
     `convosync=direct' mount option. You are advised to perform tests
     with and without raw partitions or direct I/O file systems to
     verify whether performance is improved on your system.

     Other MySQL data files, such as those for `MyISAM' tables, should
     not be placed on a direct I/O file system. Executables or
     libraries _must not_ be placed on a direct I/O file system.

   * If the Unix `top' tool or the Windows Task Manager shows that the
     CPU usage percentage with your workload is less than 70%, your
     workload is probably disk-bound. Maybe you are making too many
     transaction commits, or the buffer pool is too small. Making the
     buffer pool bigger can help, but do not set it equal to more than
     80% of physical memory.

*Logging Tips*

   * Make your log files big, even as big as the buffer pool. When
     `InnoDB' has written the log files full, it must write the
     modified contents of the buffer pool to disk in a checkpoint.
     Small log files cause many unnecessary disk writes.  The
     disadvantage of big log files is that the recovery time is longer.

   * Make the log buffer quite large as well (on the order of 8MB).

*Bulk Data Loading Tips*

   * When importing data into `InnoDB', make sure that MySQL does not
     have autocommit mode enabled because that requires a log flush to
     disk for every insert. To disable autocommit during your import
     operation, surround it with *Note `SET autocommit': commit.  and
     *Note `COMMIT': commit. statements:


          SET autocommit=0;
          ... SQL IMPORT STATEMENTS ...
          COMMIT;

     If you use the *Note `mysqldump': mysqldump. option `--opt', you
     get dump files that are fast to import into an `InnoDB' table, even
     without wrapping them with the *Note `SET autocommit': commit.
     and *Note `COMMIT': commit. statements.

   * If you have `UNIQUE' constraints on secondary keys, you can speed
     up table imports by temporarily turning off the uniqueness checks
     during the import session:


          SET unique_checks=0;
          ... SQL IMPORT STATEMENTS ...
          SET unique_checks=1;

     For big tables, this saves a lot of disk I/O because `InnoDB' can
     use its insert buffer to write secondary index records in a batch.
     Be certain that the data contains no duplicate keys.

   * If you have `FOREIGN KEY' constraints in your tables, you can
     speed up table imports by turning the foreign key checks off for
     the duration of the import session:


          SET foreign_key_checks=0;
          ... SQL IMPORT STATEMENTS ...
          SET foreign_key_checks=1;

     For big tables, this can save a lot of disk I/O.

*Other Tips*

   * Unlike `MyISAM', `InnoDB' does not store an index cardinality
     value in its tables. Instead, `InnoDB' computes a cardinality for
     a table the first time it accesses it after startup. With a large
     number of tables, this might take significant time. It is the
     initial table open operation that is important, so to `warm up' a
     table for later use, access it immediately after startup by
     issuing a statement such as `SELECT 1 FROM TBL_NAME LIMIT 1'.

   * Use the multiple-row *Note `INSERT': insert.  syntax to reduce
     communication overhead between the client and the server if you
     need to insert many rows:


          INSERT INTO yourtable VALUES (1,2), (5,5), ...;

     This tip is valid for inserts into any table, not just `InnoDB'
     tables.

   * If you often have recurring queries for tables that are not
     updated frequently, enable the query cache:


          [mysqld]
          query_cache_type = 1
          query_cache_size = 10M


File: manual.info,  Node: innodb-monitors,  Next: innodb-backup,  Prev: innodb-tuning,  Up: innodb-storage-engine

14.6.9 InnoDB Monitors
----------------------

* Menu:

* innodb-standard-monitor::      InnoDB Standard Monitor and Lock Monitor Output
* innodb-tablespace-monitor::    InnoDB Tablespace Monitor Output
* innodb-table-monitor::         InnoDB Table Monitor Output

`InnoDB' Monitors provide information about the `InnoDB' internal
state. This information is useful for performance tuning. Each Monitor
can be enabled by creating a table with a special name, which causes
`InnoDB' to write Monitor output periodically. Output for the standard
`InnoDB' Monitor is also available on demand through the *Note `SHOW
ENGINE INNODB STATUS': show-engine. SQL statement. Additionally, to
assist with troubleshooting, `InnoDB' temporarily enables standard
`InnoDB' Monitor output under certain conditions. For more information,
see *Note innodb-troubleshooting::.

There are several types of `InnoDB' Monitors:

   * The standard `InnoDB' Monitor displays the following types of
     information:

        * Table and record locks held by each active transaction.

        * Lock waits of a transaction.

        * Semaphore waits of threads.

        * Pending file I/O requests.

        * Buffer pool statistics.

        * Purge and insert buffer merge activity of the main `InnoDB'
          thread.

     For a discussion of `InnoDB' lock modes, see *Note
     innodb-lock-modes::.

     To enable the standard `InnoDB' Monitor for periodic output,
     create a table named `innodb_monitor'. To obtain Monitor output on
     demand, use the *Note `SHOW ENGINE INNODB STATUS': show-engine.
     SQL statement to fetch the output to your client program. If you
     are using the *Note `mysql': mysql.  interactive client, the
     output is more readable if you replace the usual semicolon
     statement terminator with `\G':


          mysql> SHOW ENGINE INNODB STATUS\G

   * The `InnoDB' Lock Monitor is like the standard Monitor but also
     provides extensive lock information. To enable this Monitor for
     periodic output, create a table named `innodb_lock_monitor'.

   * The `InnoDB' Tablespace Monitor prints a list of file segments in
     the shared tablespace and validates the tablespace allocation data
     structures. To enable this Monitor for periodic output, create a
     table named `innodb_tablespace_monitor'.

   * The `InnoDB' Table Monitor prints the contents of the `InnoDB'
     internal data dictionary. To enable this Monitor for periodic
     output, create a table named `innodb_table_monitor'.

To enable an `InnoDB' Monitor for periodic output, use a `CREATE TABLE'
statement to create the table associated with the Monitor. For example,
to enable the standard `InnoDB' Monitor, create the `innodb_monitor'
table:


     CREATE TABLE innodb_monitor (a INT) ENGINE=INNODB;

To stop the Monitor, drop the table:


     DROP TABLE innodb_monitor;

The *Note `CREATE TABLE': create-table. syntax is just a way to pass a
command to the `InnoDB' engine through MySQL's SQL parser: The only
things that matter are the table name `innodb_monitor' and that it be an
`InnoDB' table. The structure of the table is not relevant at all for
the `InnoDB' Monitor. If you shut down the server, the Monitor does not
restart automatically when you restart the server. Drop the Monitor
table and issue a new *Note `CREATE TABLE': create-table. statement to
start the Monitor. (This syntax may change in a future release.)

As of MySQL 5.1.24, the `PROCESS' privilege is required to start or
stop the `InnoDB' Monitor tables.

When you enable `InnoDB' Monitors for periodic output, `InnoDB' writes
their output to the *Note `mysqld': mysqld. server standard error output
(`stderr'). In this case, no output is sent to clients. When switched
on, `InnoDB' Monitors print data about every 15 seconds. Server output
usually is directed to the error log (see *Note error-log::). This data
is useful in performance tuning. On Windows, start the server from a
command prompt in a console window with the `--console' option if you
want to direct the output to the window rather than to the error log.

`InnoDB' sends diagnostic output to `stderr' or to files rather than to
`stdout' or fixed-size memory buffers, to avoid potential buffer
overflows. As a side effect, the output of *Note `SHOW ENGINE INNODB
STATUS': show-engine. is written to a status file in the MySQL data
directory every fifteen seconds. The name of the file is
`innodb_status.PID', where PID is the server process ID.  `InnoDB'
removes the file for a normal shutdown. If abnormal shutdowns have
occurred, instances of these status files may be present and must be
removed manually. Before removing them, you might want to examine them
to see whether they contain useful information about the cause of
abnormal shutdowns. The `innodb_status.PID' file is created only if the
configuration option `innodb-status-file=1' is set.

`InnoDB' Monitors should be enabled only when you actually want to see
Monitor information because output generation does result in some
performance decrement. Also, if you enable monitor output by creating
the associated table, your error log may become quite large if you
forget to remove the table later.

For additional information about `InnoDB' monitors, see:

   * Mark Leith: InnoDB Table and Tablespace Monitors
     (http://www.markleith.co.uk/?p=25)

Each monitor begins with a header containing a timestamp and the
monitor name. For example:


     ================================================
     090407 12:06:19 INNODB TABLESPACE MONITOR OUTPUT
     ================================================

The header for the standard Monitor (`INNODB MONITOR OUTPUT') is also
used for the Lock Monitor because the latter produces the same output
with the addition of extra lock information.

The following sections describe the output for each Monitor.


File: manual.info,  Node: innodb-standard-monitor,  Next: innodb-tablespace-monitor,  Prev: innodb-monitors,  Up: innodb-monitors

14.6.9.1 InnoDB Standard Monitor and Lock Monitor Output
........................................................

The Lock Monitor is the same as the standard Monitor except that it
includes additional lock information. Enabling either monitor for
periodic output by creating the associated `InnoDB' table turns on the
same output stream, but the stream includes the extra information if
the Lock Monitor is enabled. For example, if you create the
`innodb_monitor' and `innodb_lock_monitor' tables, that turns on a
single output stream. The stream includes extra lock information until
you disable the Lock Monitor by removing the `innodb_lock_monitor'
table.

Example `InnoDB' Monitor output:


     mysql> SHOW ENGINE INNODB STATUS\G
     *************************** 1. row ***************************
     Status:
     =====================================
     030709 13:00:59 INNODB MONITOR OUTPUT
     =====================================
     Per second averages calculated from the last 18 seconds
     ----------
     BACKGROUND THREAD
     ----------
     srv_master_thread loops: 53 1_second, 44 sleeps, 5 10_second, 7 background,
       7 flush
     srv_master_thread log flush and writes: 48
     ----------
     SEMAPHORES
     ----------
     OS WAIT ARRAY INFO: reservation count 413452, signal count 378357
     --Thread 32782 has waited at btr0sea.c line 1477 for 0.00 seconds the
     semaphore: X-lock on RW-latch at 41a28668 created in file btr0sea.c line 135
     a writer (thread id 32782) has reserved it in mode wait exclusive
     number of readers 1, waiters flag 1
     Last time read locked in file btr0sea.c line 731
     Last time write locked in file btr0sea.c line 1347
     Mutex spin waits 0, rounds 0, OS waits 0
     RW-shared spins 108462, OS waits 37964; RW-excl spins 681824, OS waits
     375485
     Spin rounds per wait: 0.00 mutex, 20.00 RW-shared, 0.00 RW-excl
     ------------------------
     LATEST FOREIGN KEY ERROR
     ------------------------
     030709 13:00:59 Transaction:
     TRANSACTION 0 290328284, ACTIVE 0 sec, process no 3195, OS thread id 34831
     inserting
     15 lock struct(s), heap size 2496, undo log entries 9
     MySQL thread id 25, query id 4668733 localhost heikki update
     insert into ibtest11a (D, B, C) values (5, 'khDk' ,'khDk')
     Foreign key constraint fails for table test/ibtest11a:
     ,
       CONSTRAINT `0_219242` FOREIGN KEY (`A`, `D`) REFERENCES `ibtest11b` (`A`,
       `D`) ON DELETE CASCADE ON UPDATE CASCADE
     Trying to add in child table, in index PRIMARY tuple:
      0: len 4; hex 80000101; asc ....;; 1: len 4; hex 80000005; asc ....;; 2:
      len 4; hex 6b68446b; asc khDk;; 3: len 6; hex 0000114e0edc; asc ...N..;; 4:
      len 7; hex 00000000c3e0a7; asc .......;; 5: len 4; hex 6b68446b; asc khDk;;
     But in parent table test/ibtest11b, in index PRIMARY,
     the closest match we can find is record:
     RECORD: info bits 0 0: len 4; hex 8000015b; asc ...[;; 1: len 4; hex
     80000005; asc ....;; 2: len 3; hex 6b6864; asc khd;; 3: len 6; hex
     0000111ef3eb; asc ......;; 4: len 7; hex 800001001e0084; asc .......;; 5:
     len 3; hex 6b6864; asc khd;;
     ------------------------
     LATEST DETECTED DEADLOCK
     ------------------------
     030709 12:59:58
     *** (1) TRANSACTION:
     TRANSACTION 0 290252780, ACTIVE 1 sec, process no 3185, OS thread id 30733
     inserting
     LOCK WAIT 3 lock struct(s), heap size 320, undo log entries 146
     MySQL thread id 21, query id 4553379 localhost heikki update
     INSERT INTO alex1 VALUES(86, 86, 794,'aA35818','bb','c79166','d4766t',
     'e187358f','g84586','h794',date_format('2001-04-03 12:54:22','%Y-%m-%d
     %H:%i'),7
     *** (1) WAITING FOR THIS LOCK TO BE GRANTED:
     RECORD LOCKS space id 0 page no 48310 n bits 568 table test/alex1 index
     symbole trx id 0 290252780 lock mode S waiting
     Record lock, heap no 324 RECORD: info bits 0 0: len 7; hex 61613335383138;
     asc aa35818;; 1:
     *** (2) TRANSACTION:
     TRANSACTION 0 290251546, ACTIVE 2 sec, process no 3190, OS thread id 32782
     inserting
     130 lock struct(s), heap size 11584, undo log entries 437
     MySQL thread id 23, query id 4554396 localhost heikki update
     REPLACE INTO alex1 VALUES(NULL, 32, NULL,'aa3572','','c3572','d6012t','',
     NULL,'h396', NULL, NULL, 7.31,7.31,7.31,200)
     *** (2) HOLDS THE LOCK(S):
     RECORD LOCKS space id 0 page no 48310 n bits 568 table test/alex1 index
     symbole trx id 0 290251546 lock_mode X locks rec but not gap
     Record lock, heap no 324 RECORD: info bits 0 0: len 7; hex 61613335383138;
     asc aa35818;; 1:
     *** (2) WAITING FOR THIS LOCK TO BE GRANTED:
     RECORD LOCKS space id 0 page no 48310 n bits 568 table test/alex1 index
     symbole trx id 0 290251546 lock_mode X locks gap before rec insert intention
     waiting
     Record lock, heap no 82 RECORD: info bits 0 0: len 7; hex 61613335373230;
     asc aa35720;; 1:
     *** WE ROLL BACK TRANSACTION (1)
     ------------
     TRANSACTIONS
     ------------
     Trx id counter 0 290328385
     Purge done for trx's n:o < 0 290315608 undo n:o < 0 17
     History list length 20
     Total number of lock structs in row lock hash table 70
     LIST OF TRANSACTIONS FOR EACH SESSION:
     ---TRANSACTION 0 0, not started, process no 3491, OS thread id 42002
     MySQL thread id 32, query id 4668737 localhost heikki
     show innodb status
     ---TRANSACTION 0 290328384, ACTIVE 0 sec, process no 3205, OS thread id
     38929 inserting
     1 lock struct(s), heap size 320
     MySQL thread id 29, query id 4668736 localhost heikki update
     insert into speedc values (1519229,1, 'hgjhjgghggjgjgjgjgjggjgjgjgjgjgggjgjg
     jlhhgghggggghhjhghgggggghjhghghghghghhhhghghghjhhjghjghjkghjghjghjghjfhjfh
     ---TRANSACTION 0 290328383, ACTIVE 0 sec, process no 3180, OS thread id
     28684 committing
     1 lock struct(s), heap size 320, undo log entries 1
     MySQL thread id 19, query id 4668734 localhost heikki update
     insert into speedcm values (1603393,1, 'hgjhjgghggjgjgjgjgjggjgjgjgjgjgggjgj
     gjlhhgghggggghhjhghgggggghjhghghghghghhhhghghghjhhjghjghjkghjghjghjghjfhjf
     ---TRANSACTION 0 290328327, ACTIVE 0 sec, process no 3200, OS thread id
     36880 starting index read
     LOCK WAIT 2 lock struct(s), heap size 320
     MySQL thread id 27, query id 4668644 localhost heikki Searching rows for
     update
     update ibtest11a set B = 'kHdkkkk' where A = 89572
     ------- TRX HAS BEEN WAITING 0 SEC FOR THIS LOCK TO BE GRANTED:
     RECORD LOCKS space id 0 page no 65556 n bits 232 table test/ibtest11a index
     PRIMARY trx id 0 290328327 lock_mode X waiting
     Record lock, heap no 1 RECORD: info bits 0 0: len 9; hex 73757072656d756d00;
     asc supremum.;;
     ------------------
     ---TRANSACTION 0 290328284, ACTIVE 0 sec, process no 3195, OS thread id
     34831 rollback of SQL statement
     ROLLING BACK 14 lock struct(s), heap size 2496, undo log entries 9
     MySQL thread id 25, query id 4668733 localhost heikki update
     insert into ibtest11a (D, B, C) values (5, 'khDk' ,'khDk')
     ---TRANSACTION 0 290327208, ACTIVE 1 sec, process no 3190, OS thread id
     32782
     58 lock struct(s), heap size 5504, undo log entries 159
     MySQL thread id 23, query id 4668732 localhost heikki update
     REPLACE INTO alex1 VALUES(86, 46, 538,'aa95666','bb','c95666','d9486t',
     'e200498f','g86814','h538',date_format('2001-04-03 12:54:22','%Y-%m-%d
     %H:%i'),
     ---TRANSACTION 0 290323325, ACTIVE 3 sec, process no 3185, OS thread id
     30733 inserting
     4 lock struct(s), heap size 1024, undo log entries 165
     MySQL thread id 21, query id 4668735 localhost heikki update
     INSERT INTO alex1 VALUES(NULL, 49, NULL,'aa42837','','c56319','d1719t','',
     NULL,'h321', NULL, NULL, 7.31,7.31,7.31,200)
     --------
     FILE I/O
     --------
     I/O thread 0 state: waiting for i/o request (insert buffer thread)
     I/O thread 1 state: waiting for i/o request (log thread)
     I/O thread 2 state: waiting for i/o request (read thread)
     I/O thread 3 state: waiting for i/o request (write thread)
     Pending normal aio reads: 0, aio writes: 0,
      ibuf aio reads: 0, log i/o's: 0, sync i/o's: 0
     Pending flushes (fsync) log: 0; buffer pool: 0
     151671 OS file reads, 94747 OS file writes, 8750 OS fsyncs
     25.44 reads/s, 18494 avg bytes/read, 17.55 writes/s, 2.33 fsyncs/s
     -------------------------------------
     INSERT BUFFER AND ADAPTIVE HASH INDEX
     -------------------------------------
     Ibuf for space 0: size 1, free list len 19, seg size 21,
     85004 inserts, 85004 merged recs, 26669 merges
     Hash table size 207619, used cells 14461, node heap has 16 buffer(s)
     1877.67 hash searches/s, 5121.10 non-hash searches/s
     ---
     LOG
     ---
     Log sequence number 18 1212842764
     Log flushed up to   18 1212665295
     Last checkpoint at  18 1135877290
     0 pending log writes, 0 pending chkp writes
     4341 log i/o's done, 1.22 log i/o's/second
     ----------------------
     BUFFER POOL AND MEMORY
     ----------------------
     Total memory allocated 84966343; in additional pool allocated 1402624
     Buffer pool size   3200
     Free buffers       110
     Database pages     3074
     Modified db pages  2674
     Pending reads 0
     Pending writes: LRU 0, flush list 0, single page 0
     Pages read 171380, created 51968, written 194688
     28.72 reads/s, 20.72 creates/s, 47.55 writes/s
     Buffer pool hit rate 999 / 1000
     --------------
     ROW OPERATIONS
     --------------
     0 queries inside InnoDB, 0 queries in queue
     Main thread process no. 3004, id 7176, state: purging
     Number of rows inserted 3738558, updated 127415, deleted 33707, read 755779
     1586.13 inserts/s, 50.89 updates/s, 28.44 deletes/s, 107.88 reads/s
     ----------------------------
     END OF INNODB MONITOR OUTPUT
     ============================

`InnoDB' Monitor output is limited to 64,000 bytes when produced using
the *Note `SHOW ENGINE INNODB STATUS': show-engine. statement. This
limit does not apply to output written to the server's error output.

Some notes on the output sections:

*`Status'*

This section shows the timestamp, the monitor name, and the number of
seconds that per-second averages are based on. The number of seconds is
the elapsed time between the current time and the last time `InnoDB'
Monitor output was printed.

*`BACKGROUND THREAD'*

The `srv_master_thread' lines shows work done by the main background
thread. This section is displayed only by `InnoDB Plugin'.

*`SEMAPHORES'*

This section reports threads waiting for a semaphore and statistics on
how many times threads have needed a spin or a wait on a mutex or a
rw-lock semaphore. A large number of threads waiting for semaphores may
be a result of disk I/O, or contention problems inside `InnoDB'.
Contention can be due to heavy parallelism of queries or problems in
operating system thread scheduling. Setting the
`innodb_thread_concurrency' system variable smaller than the default
value might help in such situations. The `Spin rounds per wait' line
(`InnoDB Plugin' only) shows the number of spinlock rounds per OS wait
for a mutex.

*`LATEST FOREIGN KEY ERROR'*

This section provides information about the most recent foreign key
constraint error. It is not present if no such error has occurred. The
contents include the statement that failed as well as information about
the constraint that failed and the referenced and referencing tables.

*`LATEST DETECTED DEADLOCK'*

This section provides information about the most recent deadlock.  It
is not present if no deadlock has occurred. The contents show which
transactions are involved, the statement each was attempting to
execute, the locks they have and need, and which transaction `InnoDB'
decided to roll back to break the deadlock. The lock modes reported in
this section are explained in *Note innodb-lock-modes::.

*`TRANSACTIONS'*

If this section reports lock waits, your applications might have lock
contention. The output can also help to trace the reasons for
transaction deadlocks.

*`FILE I/O'*

This section provides information about threads that `InnoDB' uses to
perform various types of I/O.  The first few of these are dedicated to
general `InnoDB' processing. The contents also display information for
pending I/O operations and statistics for I/O performance.

On Unix, the number of threads is always 4. On Windows, the number
depends on the setting of the `innodb_file_io_threads' system variable.

*`INSERT BUFFER AND ADAPTIVE HASH INDEX'*

This section shows the status of the `InnoDB' insert buffer and
adaptive hash index. (See *Note innodb-insert-buffering::, and *Note
innodb-adaptive-hash::.) The contents include the number of operations
performed for each, plus statistics for hash index performance.

*`LOG'*

This section displays information about the `InnoDB' log. The contents
include the current log sequence number, how far the log has been
flushed to disk, and the position at which `InnoDB' last took a
checkpoint. (See *Note innodb-checkpoints::.) The section also displays
information about pending writes and write performance statistics.

*`BUFFER POOL AND MEMORY'*

This section gives you statistics on pages read and written. You can
calculate from these numbers how many data file I/O operations your
queries currently are doing.

For additional information about the operation of the buffer pool, see
*Note innodb-buffer-pool::.

*`ROW OPERATIONS'*

This section shows what the main thread is doing, including the number
and performance rate for each type of row operation.


File: manual.info,  Node: innodb-tablespace-monitor,  Next: innodb-table-monitor,  Prev: innodb-standard-monitor,  Up: innodb-monitors

14.6.9.2 InnoDB Tablespace Monitor Output
.........................................

The `InnoDB' Tablespace Monitor prints information about the file
segments in the shared tablespace and validates the tablespace
allocation data structures. If you use individual tablespaces by
enabling `innodb_file_per_table', the Tablespace Monitor does not
describe those tablespaces.

Example `InnoDB' Tablespace Monitor output:


     ================================================
     090408 21:28:09 INNODB TABLESPACE MONITOR OUTPUT
     ================================================
     FILE SPACE INFO: id 0
     size 13440, free limit 3136, free extents 28
     not full frag extents 2: used pages 78, full frag extents 3
     first seg id not used 0 23845
     SEGMENT id 0 1 space 0; page 2; res 96 used 46; full ext 0
     fragm pages 32; free extents 0; not full extents 1: pages 14
     SEGMENT id 0 2 space 0; page 2; res 1 used 1; full ext 0
     fragm pages 1; free extents 0; not full extents 0: pages 0
     SEGMENT id 0 3 space 0; page 2; res 1 used 1; full ext 0
     fragm pages 1; free extents 0; not full extents 0: pages 0
     ...
     SEGMENT id 0 15 space 0; page 2; res 160 used 160; full ext 2
     fragm pages 32; free extents 0; not full extents 0: pages 0
     SEGMENT id 0 488 space 0; page 2; res 1 used 1; full ext 0
     fragm pages 1; free extents 0; not full extents 0: pages 0
     SEGMENT id 0 17 space 0; page 2; res 1 used 1; full ext 0
     fragm pages 1; free extents 0; not full extents 0: pages 0
     ...
     SEGMENT id 0 171 space 0; page 2; res 592 used 481; full ext 7
     fragm pages 16; free extents 0; not full extents 2: pages 17
     SEGMENT id 0 172 space 0; page 2; res 1 used 1; full ext 0
     fragm pages 1; free extents 0; not full extents 0: pages 0
     SEGMENT id 0 173 space 0; page 2; res 96 used 44; full ext 0
     fragm pages 32; free extents 0; not full extents 1: pages 12
     ...
     SEGMENT id 0 601 space 0; page 2; res 1 used 1; full ext 0
     fragm pages 1; free extents 0; not full extents 0: pages 0
     NUMBER of file segments: 73
     Validating tablespace
     Validation ok
     ---------------------------------------
     END OF INNODB TABLESPACE MONITOR OUTPUT
     =======================================

The Tablespace Monitor output includes information about the shared
tablespace as a whole, followed by a list containing a breakdown for
each segment within the tablespace.

The tablespace consists of database pages with a default size of 16KB.
The pages are grouped into extents of size 1MB (64 consecutive pages).

The initial part of the output that displays overall tablespace
information has this format:


     FILE SPACE INFO: id 0
     size 13440, free limit 3136, free extents 28
     not full frag extents 2: used pages 78, full frag extents 3
     first seg id not used 0 23845

Overall tablespace information includes these values:

   * `id': The tablespace ID. A value of 0 refers to the shared
     tablespace.

   * `size': The current tablespace size in pages.

   * `free limit': The minimum page number for which the free list has
     not been initialized. Pages at or above this limit are free.

   * `free extents': The number of free extents.

   * `not full frag extents', `used pages': The number of fragment
     extents that are not completely filled, and the number of pages in
     those extents that have been allocated.

   * `full frag extents': The number of completely full fragment
     extents.

   * `first seg id not used': The first unused segment ID.

Individual segment information has this format:


     SEGMENT id 0 15 space 0; page 2; res 160 used 160; full ext 2
     fragm pages 32; free extents 0; not full extents 0: pages 0

Segment information includes these values:

`id': The segment ID.

`space', `page': The tablespace number and page within the tablespace
where the segment `inode' is located. A tablespace number of 0
indicates the shared tablespace. `InnoDB' uses inodes to keep track of
segments in the tablespace. The other fields displayed for a segment
(`id', `res', and so forth) are derived from information in the inode.

`res': The number of pages allocated (reserved) for the segment.

`used': The number of allocated pages in use by the segment.

`full ext': The number of extents allocated for the segment that are
completely used.

`fragm pages': The number of initial pages that have been allocated to
the segment.

`free extents': The number of extents allocated for the segment that
are completely unused.

`not full extents': The number of extents allocated for the segment
that are partially used.

`pages': The number of pages used within the not-full extents.

When a segment grows, it starts as a single page, and `InnoDB'
allocates the first pages for it individually, up to 32 pages (this is
the `fragm pages' value). After that, `InnoDB' allocates complete
64-page extents. `InnoDB' can add up to 4 extents at a time to a large
segment to ensure good sequentiality of data.

For the example segment shown earlier, it has 32 fragment pages, plus 2
full extents (64 pages each), for a total of 160 pages used out of 160
pages allocated. The following segment has 32 fragment pages and one
partially full extent using 14 pages for a total of 46 pages used out
of 96 pages allocated:


     SEGMENT id 0 1 space 0; page 2; res 96 used 46; full ext 0
     fragm pages 32; free extents 0; not full extents 1: pages 14

It is possible for a segment that has extents allocated to it to have a
`fragm pages' value less than 32 if some of the individual pages have
been deallocated subsequent to extent allocation.


File: manual.info,  Node: innodb-table-monitor,  Prev: innodb-tablespace-monitor,  Up: innodb-monitors

14.6.9.3 InnoDB Table Monitor Output
....................................

The `InnoDB' Table Monitor prints the contents of the `InnoDB' internal
data dictionary.

The output contains one section per table. The `SYS_FOREIGN' and
`SYS_FOREIGN_COLS' sections are for internal data dictionary tables
that maintain information about foreign keys.  There are also sections
for the Table Monitor table and each user-created `InnoDB' table.
Suppose that the following two tables have been created in the `test'
database:


     CREATE TABLE parent
     (
       par_id    INT NOT NULL,
       fname      CHAR(20),
       lname      CHAR(20),
       PRIMARY KEY (par_id),
       UNIQUE INDEX (lname, fname)
     ) ENGINE = INNODB;

     CREATE TABLE child
     (
       par_id      INT NOT NULL,
       child_id    INT NOT NULL,
       name        VARCHAR(40),
       birth       DATE,
       weight      DECIMAL(10,2),
       misc_info   VARCHAR(255),
       last_update TIMESTAMP,
       PRIMARY KEY (par_id, child_id),
       INDEX (name),
       FOREIGN KEY (par_id) REFERENCES parent (par_id)
         ON DELETE CASCADE
         ON UPDATE CASCADE
     ) ENGINE = INNODB;

Then the Table Monitor output will look something like this
(reformatted slightly):


     ===========================================
     090420 12:09:32 INNODB TABLE MONITOR OUTPUT
     ===========================================
     --------------------------------------
     TABLE: name SYS_FOREIGN, id 0 11, columns 7, indexes 3, appr.rows 1
       COLUMNS: ID: DATA_VARCHAR DATA_ENGLISH len 0;
                FOR_NAME: DATA_VARCHAR DATA_ENGLISH len 0;
                REF_NAME: DATA_VARCHAR DATA_ENGLISH len 0;
                N_COLS: DATA_INT len 4;
                DB_ROW_ID: DATA_SYS prtype 256 len 6;
                DB_TRX_ID: DATA_SYS prtype 257 len 6;
       INDEX: name ID_IND, id 0 11, fields 1/6, uniq 1, type 3
        root page 46, appr.key vals 1, leaf pages 1, size pages 1
        FIELDS:  ID DB_TRX_ID DB_ROLL_PTR FOR_NAME REF_NAME N_COLS
       INDEX: name FOR_IND, id 0 12, fields 1/2, uniq 2, type 0
        root page 47, appr.key vals 1, leaf pages 1, size pages 1
        FIELDS:  FOR_NAME ID
       INDEX: name REF_IND, id 0 13, fields 1/2, uniq 2, type 0
        root page 48, appr.key vals 1, leaf pages 1, size pages 1
        FIELDS:  REF_NAME ID
     --------------------------------------
     TABLE: name SYS_FOREIGN_COLS, id 0 12, columns 7, indexes 1, appr.rows 1
       COLUMNS: ID: DATA_VARCHAR DATA_ENGLISH len 0;
                POS: DATA_INT len 4;
                FOR_COL_NAME: DATA_VARCHAR DATA_ENGLISH len 0;
                REF_COL_NAME: DATA_VARCHAR DATA_ENGLISH len 0;
                DB_ROW_ID: DATA_SYS prtype 256 len 6;
                DB_TRX_ID: DATA_SYS prtype 257 len 6;
       INDEX: name ID_IND, id 0 14, fields 2/6, uniq 2, type 3
        root page 49, appr.key vals 1, leaf pages 1, size pages 1
        FIELDS:  ID POS DB_TRX_ID DB_ROLL_PTR FOR_COL_NAME REF_COL_NAME
     --------------------------------------
     TABLE: name test/child, id 0 14, columns 10, indexes 2, appr.rows 201
       COLUMNS: par_id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4;
                child_id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4;
                name: DATA_VARCHAR prtype 524303 len 40;
                birth: DATA_INT DATA_BINARY_TYPE len 3;
                weight: DATA_FIXBINARY DATA_BINARY_TYPE len 5;
                misc_info: DATA_VARCHAR prtype 524303 len 255;
                last_update: DATA_INT DATA_UNSIGNED DATA_BINARY_TYPE DATA_NOT_NULL len 4;
                DB_ROW_ID: DATA_SYS prtype 256 len 6;
                DB_TRX_ID: DATA_SYS prtype 257 len 6;
       INDEX: name PRIMARY, id 0 17, fields 2/9, uniq 2, type 3
        root page 52, appr.key vals 201, leaf pages 5, size pages 6
        FIELDS:  par_id child_id DB_TRX_ID DB_ROLL_PTR name birth weight misc_info last_update
       INDEX: name name, id 0 18, fields 1/3, uniq 3, type 0
        root page 53, appr.key vals 210, leaf pages 1, size pages 1
        FIELDS:  name par_id child_id
       FOREIGN KEY CONSTRAINT test/child_ibfk_1: test/child ( par_id )
                  REFERENCES test/parent ( par_id )
     --------------------------------------
     TABLE: name test/innodb_table_monitor, id 0 15, columns 4, indexes 1, appr.rows 0
       COLUMNS: i: DATA_INT DATA_BINARY_TYPE len 4;
                DB_ROW_ID: DATA_SYS prtype 256 len 6;
                DB_TRX_ID: DATA_SYS prtype 257 len 6;
       INDEX: name GEN_CLUST_INDEX, id 0 19, fields 0/4, uniq 1, type 1
        root page 193, appr.key vals 0, leaf pages 1, size pages 1
        FIELDS:  DB_ROW_ID DB_TRX_ID DB_ROLL_PTR i
     --------------------------------------
     TABLE: name test/parent, id 0 13, columns 6, indexes 2, appr.rows 299
       COLUMNS: par_id: DATA_INT DATA_BINARY_TYPE DATA_NOT_NULL len 4;
                fname: DATA_CHAR prtype 524542 len 20;
                lname: DATA_CHAR prtype 524542 len 20;
                DB_ROW_ID: DATA_SYS prtype 256 len 6;
                DB_TRX_ID: DATA_SYS prtype 257 len 6;
       INDEX: name PRIMARY, id 0 15, fields 1/5, uniq 1, type 3
        root page 50, appr.key vals 299, leaf pages 2, size pages 3
        FIELDS:  par_id DB_TRX_ID DB_ROLL_PTR fname lname
       INDEX: name lname, id 0 16, fields 2/3, uniq 2, type 2
        root page 51, appr.key vals 300, leaf pages 1, size pages 1
        FIELDS:  lname fname par_id
       FOREIGN KEY CONSTRAINT test/child_ibfk_1: test/child ( par_id )
                  REFERENCES test/parent ( par_id )
     -----------------------------------
     END OF INNODB TABLE MONITOR OUTPUT
     ==================================

For each table, Table Monitor output contains a section that displays
general information about the table and specific information about its
columns, indexes, and foreign keys.

The general information for each table includes the table name (in
`DB_NAME/TBL_NAME' format except for internal tables), its ID, the
number of columns and indexes, and an approximate row count.

The `COLUMNS' part of a table section lists each column in the table.
Information for each column indicates its name and data type
characteristics. Some internal columns are added by `InnoDB', such as
`DB_ROW_ID' (row ID), `DB_TRX_ID' (transaction ID), and `DB_ROLL_PTR'
(a pointer to the rollback/undo data).

   * `DATA_XXX': These symbols indicate the data type. There may be
     multiple `DATA_XXX' symbols for a given column.

   * `prtype': The column's `precise' type. This field includes
     information such as the column data type, character set code,
     nullability, signedness, and whether it is a binary string. This
     field is described in the `innobase/include/data0type.h' source
     file.

   * `len': The column length in bytes.

Each `INDEX' part of the table section provides the name and
characteristics of one table index:

   * `name': The index name. If the name is `PRIMARY', the index is a
     primary key. If the name is `GEN_CLUST_INDEX', the index is the
     clustered index that is created automatically if the table
     definition doesn't include a primary key or non-`NULL' unique
     index. See *Note innodb-index-types::.

   * `id': The index ID.

   * `fields': The number of fields in the index, as a value in `M/N'
     format:

        * M is the number of user-defined columns; that is, the number
          of columns you would see in the index definition in a `CREATE
          TABLE' statement.

        * N is the total number of index columns, including those added
          internally. For the clustered index, the total includes the
          other columns in the table definition, plus any columns added
          internally.  For a secondary index, the total includes the
          columns from the primary key that are not part of the
          secondary index.

   * `uniq': The number of leading fields that are enough to determine
     index values uniquely.

   * `type': The index type. This is a bit field.  For example, 1
     indicates a clustered index and 2 indicates a unique index, so a
     clustered index (which always contains unique values), will have a
     `type' value of 3. An index with a `type' value of 0 is neither
     clustered nor unique. The flag values are defined in the
     `innobase/include/dict0mem.h' source file.

   * `root page': The index root page number.

   * `appr. key vals': The approximate index cardinality.

   * `leaf pages': The approximate number of leaf pages in the index.

   * `size pages': The approximate total number of pages in the index.

   * `FIELDS': The names of the fields in the index. For a clustered
     index that was generated automatically, the field list begins with
     the internal `DB_ROW_ID' (row ID) field.  `DB_TRX_ID' and
     `DB_ROLL_PTR' are always added internally to the clustered index,
     following the fields that comprise the primary key. For a
     secondary index, the final fields are those from the primary key
     that are not part of the secondary index.

The end of the table section lists the `FOREIGN KEY' definitions that
apply to the table. This information appears whether the table is a
referencing or referenced table.


File: manual.info,  Node: innodb-backup,  Next: innodb-and-mysql-replication,  Prev: innodb-monitors,  Up: innodb-storage-engine

14.6.10 InnoDB Backup and Recovery
----------------------------------

* Menu:

* innodb-recovery::              The InnoDB Recovery Process
* innodb-checkpoints::           InnoDB Checkpoints

The key to safe database management is making regular backups.
Depending on your data volume, number of MySQL servers, and database
workload, you can use these techniques, alone or in combination: hot
backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_hot_backup)
with MySQL Enterprise Backup; cold backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_cold_backup)
by copying files while the MySQL server is shut down; physical backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_physical_backup)
for fast operation (especially for restore); logical backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_logical_backup)
with *Note `mysqldump': mysqldump. for smaller data volumes or to record
the structure of schema objects.

*Hot Backups*

The `mysqlbackup' command, part of the MySQL Enterprise Backup
component, lets you back up a running MySQL instance, including
`InnoDB' and *Note `MyISAM': myisam-storage-engine. tables, with
minimal disruption to operations while producing a consistent snapshot
of the database.  When `mysqlbackup' is copying `InnoDB' tables, reads
and writes to both `InnoDB' and `MyISAM' tables can continue. During
the copying of `MyISAM' tables, reads (but not writes) to those tables
are permitted. MySQL Enterprise Backup can also create compressed
backup files, and back up subsets of tables and databases. In
conjunction with MySQL's binary log, users can perform point-in-time
recovery. MySQL Enterprise Backup is part of the MySQL Enterprise
subscription. For more details, see *Note mysql-enterprise-backup::.

*Cold Backups*

If you can shut down your MySQL server, you can make a binary backup
that consists of all files used by `InnoDB' to manage its tables. Use
the following procedure:

  1. Do a slow shutdown
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_slow_shutdown)
     of the MySQL server and make sure that it stops without errors.

  2. Copy all `InnoDB' data files (`ibdata' files and `.ibd' files)
     into a safe place.

  3. Copy all the `.frm' files for `InnoDB' tables to a safe place.

  4. Copy all `InnoDB' log files (`ib_logfile' files) to a safe place.

  5. Copy your `my.cnf' configuration file or files to a safe place.

*Alternative Backup Types*

In addition to making binary backups as just described, regularly make
dumps of your tables with *Note `mysqldump': mysqldump. A binary file
might be corrupted without you noticing it. Dumped tables are stored
into text files that are human-readable, so spotting table corruption
becomes easier. Also, because the format is simpler, the chance for
serious data corruption is smaller.  *Note `mysqldump': mysqldump. also
has a `--single-transaction' option for making a consistent snapshot
without locking out other clients. See *Note backup-policy::.

Replication works with *Note `InnoDB': innodb-storage-engine. tables,
so you can use MySQL replication capabilities to keep a copy of your
database at database sites requiring high availability.

*Performing Recovery*

To recover your `InnoDB' database to the present from the time at which
the binary backup was made, you must run your MySQL server with binary
logging turned on, even before taking the backup. To achieve
point-in-time recovery after restoring a backup, you can apply changes
from the binary log that occurred after the backup was made. See *Note
point-in-time-recovery::.

To recover from a crash of your MySQL server, the only requirement is
to restart it. `InnoDB' automatically checks the logs and performs a
roll-forward of the database to the present.  `InnoDB' automatically
rolls back uncommitted transactions that were present at the time of
the crash. During recovery, *Note `mysqld': mysqld. displays output
something like this:


     InnoDB: Database was not shut down normally.
     InnoDB: Starting recovery from log files...
     InnoDB: Starting log scan based on checkpoint at
     InnoDB: log sequence number 0 13674004
     InnoDB: Doing recovery: scanned up to log sequence number 0 13739520
     InnoDB: Doing recovery: scanned up to log sequence number 0 13805056
     InnoDB: Doing recovery: scanned up to log sequence number 0 13870592
     InnoDB: Doing recovery: scanned up to log sequence number 0 13936128
     ...
     InnoDB: Doing recovery: scanned up to log sequence number 0 20555264
     InnoDB: Doing recovery: scanned up to log sequence number 0 20620800
     InnoDB: Doing recovery: scanned up to log sequence number 0 20664692
     InnoDB: 1 uncommitted transaction(s) which must be rolled back
     InnoDB: Starting rollback of uncommitted transactions
     InnoDB: Rolling back trx no 16745
     InnoDB: Rolling back of trx no 16745 completed
     InnoDB: Rollback of uncommitted transactions completed
     InnoDB: Starting an apply batch of log records to the database...
     InnoDB: Apply batch completed
     InnoDB: Started
     mysqld: ready for connections

If your database becomes corrupted or disk failure occurs, you must
perform the recovery using a backup. In the case of corruption, first
find a backup that is not corrupted. After restoring the base backup,
do a point-in-time recovery from the binary log files using *Note
`mysqlbinlog': mysqlbinlog. and *Note `mysql': mysql. to restore the
changes that occurred after the backup was made.

In some cases of database corruption, it is enough just to dump, drop,
and re-create one or a few corrupt tables. You can use the *Note `CHECK
TABLE': check-table. SQL statement to check whether a table is corrupt,
although *Note `CHECK TABLE': check-table. naturally cannot detect
every possible kind of corruption. You can use the Tablespace Monitor
to check the integrity of the file space management inside the
tablespace files.

In some cases, apparent database page corruption is actually due to the
operating system corrupting its own file cache, and the data on disk
may be okay. It is best first to try restarting your computer.  Doing
so may eliminate errors that appeared to be database page corruption.
If MySQL still has trouble starting because of `InnoDB' consistency
problems, see *Note forcing-innodb-recovery:: for steps to start the
instance in a diagnostic mode where you can dump the data.


File: manual.info,  Node: innodb-recovery,  Next: innodb-checkpoints,  Prev: innodb-backup,  Up: innodb-backup

14.6.10.1 The InnoDB Recovery Process
.....................................

`InnoDB' crash recovery consists of several steps. The first step, redo
log application, is performed during the initialization, before
accepting any connections. If all changes were flushed from the buffer
pool to the tablespaces (`ibdata*' and `*.ibd' files) at the time of
the shutdown or crash, the redo log application can be skipped. If the
redo log files are missing at startup, `InnoDB' skips the redo log
application.

The remaining steps after redo log application do not depend on the
redo log (other than for logging the writes) and are performed in
parallel with normal processing. These include:

   * Rolling back incomplete transactions: Any transactions that were
     active at the time of crash or fast shutdown.

   * Insert buffer merge: Applying changes from the insert buffer tree
     (from the shared tablespace) to leaf pages of secondary indexes as
     the index pages are read to the buffer pool.

   * Purge: Deleting delete-marked records that are no longer visible
     for any active transaction.

Of these, only rollback of incomplete transactions is special to crash
recovery. The insert buffer merge and the purge are performed during
normal processing.


File: manual.info,  Node: innodb-checkpoints,  Prev: innodb-recovery,  Up: innodb-backup

14.6.10.2 InnoDB Checkpoints
............................

`InnoDB' implements a checkpoint mechanism known as `fuzzy'
checkpointing. `InnoDB' flushes modified database pages from the buffer
pool in small batches. There is no need to flush the buffer pool in one
single batch, which would in practice stop processing of user SQL
statements during the checkpointing process.

During crash recovery, `InnoDB' looks for a checkpoint label written to
the log files. It knows that all modifications to the database before
the label are present in the disk image of the database. Then `InnoDB'
scans the log files forward from the checkpoint, applying the logged
modifications to the database.

`InnoDB' writes to its log files on a rotating basis. It also writes
checkpoint information to the first log file at each checkpoint. All
committed modifications that make the database pages in the buffer pool
different from the images on disk must be available in the log files in
case `InnoDB' has to do a recovery. This means that when `InnoDB'
starts to reuse a log file, it has to make sure that the database page
images on disk contain the modifications logged in the log file that
`InnoDB' is going to reuse. In other words, `InnoDB' must create a
checkpoint and this often involves flushing of modified database pages
to disk.

The preceding description explains why making your log files very large
may reduce disk I/O in checkpointing. It often makes sense to set the
total size of the log files as large as the buffer pool or even larger.
The disadvantage of using large log files is that crash recovery can
take longer because there is more logged information to apply to the
database.


File: manual.info,  Node: innodb-and-mysql-replication,  Next: innodb-troubleshooting,  Prev: innodb-backup,  Up: innodb-storage-engine

14.6.11 InnoDB and MySQL Replication
------------------------------------

MySQL replication works for `InnoDB' tables as it does for `MyISAM'
tables. It is also possible to use replication in a way where the
storage engine on the slave is not the same as the original storage
engine on the master. For example, you can replicate modifications to an
`InnoDB' table on the master to a `MyISAM' table on the slave.

To set up a new slave for a master, make a copy of the `InnoDB'
tablespace and the log files, as well as the `.frm' files of the
`InnoDB' tables, and move the copies to the slave. If the
`innodb_file_per_table' option is enabled, copy the `.ibd' files as
well. For the proper procedure to do this, see *Note innodb-backup::.

To make a new slave without taking down the master or an existing
slave, use the *Note MySQL Enterprise Backup: mysql-enterprise-backup.
product. If you can shut down the master or an existing slave, take a
cold backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_cold_backup)
of the `InnoDB' tablespaces and log files and use that to set up a
slave.

You cannot set up replication for `InnoDB' using the *Note `LOAD TABLE
FROM MASTER': load-table-from-master. statement, which works only for
`MyISAM' tables. There are two possible workarounds:

   * Dump the table on the master and import the dump file into the
     slave.

   * Use `ALTER TABLE TBL_NAME ENGINE=MyISAM' on the master before
     setting up replication with `LOAD TABLE TBL_NAME FROM MASTER', and
     then use *Note `ALTER TABLE': alter-table. to convert the master
     table back to `InnoDB' afterward.  However, this should not be
     done for tables that have foreign key definitions because the
     definitions will be lost.

Transactions that fail on the master do not affect replication at all.
MySQL replication is based on the binary log where MySQL writes SQL
statements that modify data. A transaction that fails (for example,
because of a foreign key violation, or because it is rolled back) is
not written to the binary log, so it is not sent to slaves.  See *Note
commit::.

Replication and CASCADE

Cascading actions for `InnoDB' tables on the master are replicated on
the slave _only_ if the tables sharing the foreign key relation use
`InnoDB' on both the master and slave. This is true whether you are
using statement-based or row-based replication. Suppose that you have
started replication, and then create two tables on the master using the
following *Note `CREATE TABLE': create-table. statements:


     CREATE TABLE fc1 (
         i INT PRIMARY KEY,
         j INT
     ) ENGINE = InnoDB;

     CREATE TABLE fc2 (
         m INT PRIMARY KEY,
         n INT,
         FOREIGN KEY ni (n) REFERENCES fc1 (i)
             ON DELETE CASCADE
     ) ENGINE = InnoDB;

Suppose that the slave does not have `InnoDB' support enabled. If this
is the case, then the tables on the slave are created, but they use the
`MyISAM' storage engine, and the `FOREIGN KEY' option is ignored.  Now
we insert some rows into the tables on the master:


     master> INSERT INTO fc1 VALUES (1, 1), (2, 2);
     Query OK, 2 rows affected (0.09 sec)
     Records: 2  Duplicates: 0  Warnings: 0

     master> INSERT INTO fc2 VALUES (1, 1), (2, 2), (3, 1);
     Query OK, 3 rows affected (0.19 sec)
     Records: 3  Duplicates: 0  Warnings: 0

At this point, on both the master and the slave, table `fc1' contains 2
rows, and table `fc2' contains 3 rows, as shown here:


     master> SELECT * FROM fc1;
     +---+------+
     | i | j    |
     +---+------+
     | 1 |    1 |
     | 2 |    2 |
     +---+------+
     2 rows in set (0.00 sec)

     master> SELECT * FROM fc2;
     +---+------+
     | m | n    |
     +---+------+
     | 1 |    1 |
     | 2 |    2 |
     | 3 |    1 |
     +---+------+
     3 rows in set (0.00 sec)

     slave> SELECT * FROM fc1;
     +---+------+
     | i | j    |
     +---+------+
     | 1 |    1 |
     | 2 |    2 |
     +---+------+
     2 rows in set (0.00 sec)

     slave> SELECT * FROM fc2;
     +---+------+
     | m | n    |
     +---+------+
     | 1 |    1 |
     | 2 |    2 |
     | 3 |    1 |
     +---+------+
     3 rows in set (0.00 sec)

Now suppose that you perform the following *Note `DELETE': delete.
statement on the master:


     master> DELETE FROM fc1 WHERE i=1;
     Query OK, 1 row affected (0.09 sec)

Due to the cascade, table `fc2' on the master now contains only 1 row:


     master> SELECT * FROM fc2;
     +---+---+
     | m | n |
     +---+---+
     | 2 | 2 |
     +---+---+
     1 row in set (0.00 sec)

However, the cascade does not propagate on the slave because on the
slave the *Note `DELETE': delete. for `fc1' deletes no rows from `fc2'.
The slave's copy of `fc2' still contains all of the rows that were
originally inserted:


     slave> SELECT * FROM fc2;
     +---+---+
     | m | n |
     +---+---+
     | 1 | 1 |
     | 3 | 1 |
     | 2 | 2 |
     +---+---+
     3 rows in set (0.00 sec)

This difference is due to the fact that the cascading deletes are
handled internally by the `InnoDB' storage engine, which means that
none of the changes are logged.


File: manual.info,  Node: innodb-troubleshooting,  Prev: innodb-and-mysql-replication,  Up: innodb-storage-engine

14.6.12 InnoDB Troubleshooting
------------------------------

* Menu:

* error-creating-innodb::        Dealing with InnoDB Initialization Problems
* forcing-innodb-recovery::      Forcing InnoDB Recovery
* innodb-troubleshooting-datadict::  Troubleshooting InnoDB Data Dictionary Operations
* innodb-error-handling::        InnoDB Error Handling
* innodb-error-codes::           InnoDB Error Codes
* operating-system-error-codes::  Operating System Error Codes

The following general guidelines apply to troubleshooting `InnoDB'
problems:

   * When an operation fails or you suspect a bug, look at the MySQL
     server error log (see *Note error-log::).

   * Issues relating to the `InnoDB' data dictionary include failed
     *Note `CREATE TABLE': create-table.  statements (orphaned table
     files), inability to open `.InnoDB' files, and `system cannot find
     the path specified' errors. For information about these sorts of
     problems and errors, see *Note innodb-troubleshooting-datadict::.

   * When troubleshooting, it is usually best to run the MySQL server
     from the command prompt, rather than through *Note `mysqld_safe':
     mysqld-safe. or as a Windows service. You can then see what *Note
     `mysqld': mysqld. prints to the console, and so have a better
     grasp of what is going on. On Windows, start *Note `mysqld':
     mysqld. with the `--console' option to direct the output to the
     console window.

   * Enable the `InnoDB' Monitors to obtain information about a problem
     (see *Note innodb-monitors::). If the problem is
     performance-related, or your server appears to be hung, you should
     enable the standard Monitor to print information about the
     internal state of `InnoDB'. If the problem is with locks, enable
     the Lock Monitor. If the problem is in creation of tables or other
     data dictionary operations, enable the Table Monitor to print the
     contents of the `InnoDB' internal data dictionary. To see
     tablespace information enable the Tablespace Monitor.

     `InnoDB' temporarily enables standard `InnoDB' Monitor output
     under the following conditions:

        * A long semaphore wait

        * `InnoDB' cannot find free blocks in the buffer pool

        * Over 67% of the buffer pool is occupied by lock heaps or the
          adaptive hash index

   * If you suspect that a table is corrupt, run *Note `CHECK TABLE':
     check-table. on that table.


File: manual.info,  Node: error-creating-innodb,  Next: forcing-innodb-recovery,  Prev: innodb-troubleshooting,  Up: innodb-troubleshooting

14.6.12.1 Dealing with InnoDB Initialization Problems
.....................................................

If `InnoDB' prints an operating system error during a file operation,
usually the problem has one of the following causes:

   * You did not create the `InnoDB' data file directory or the
     `InnoDB' log directory.

   * *Note `mysqld': mysqld. does not have access rights to create
     files in those directories.

   * *Note `mysqld': mysqld. cannot read the proper `my.cnf' or `my.ini'
     option file, and consequently does not see the options that you
     specified.

   * The disk is full or a disk quota is exceeded.

   * You have created a subdirectory whose name is equal to a data file
     that you specified, so the name cannot be used as a file name.

   * There is a syntax error in the `innodb_data_home_dir' or
     `innodb_data_file_path' value.

If something goes wrong when `InnoDB' attempts to initialize its
tablespace or its log files, delete all files created by `InnoDB'. This
means all `ibdata' files and all `ib_logfile' files. In case you have
already created some `InnoDB' tables, delete the corresponding `.frm'
files for these tables (and any `.ibd' files if you are using multiple
tablespaces) from the MySQL database directories as well. Then you can
try the `InnoDB' database creation again. It is best to start the MySQL
server from a command prompt so that you see what is happening.


File: manual.info,  Node: forcing-innodb-recovery,  Next: innodb-troubleshooting-datadict,  Prev: error-creating-innodb,  Up: innodb-troubleshooting

14.6.12.2 Forcing InnoDB Recovery
.................................

If there is database page corruption, you may want to dump your tables
from the database with *Note `SELECT ... INTO OUTFILE': select-into.
Usually, most of the data obtained in this way is intact. However, it
is possible that the corruption might cause `SELECT * FROM TBL_NAME'
statements or `InnoDB' background operations to crash or assert, or
even cause `InnoDB' roll-forward recovery to crash. In such cases, you
can use the `innodb_force_recovery' option to force the `InnoDB'
storage engine to start up while preventing background operations from
running, so that you can dump your tables. For example, you can add the
following line to the `[mysqld]' section of your option file before
restarting the server:


     [mysqld]
     innodb_force_recovery = 1

*Warning*:

Only set `innodb_force_recovery' to a value greater than 0 in an
emergency situation, so that you can start `InnoDB' and dump your
tables. Before doing so, ensure that you have a backup copy of your
database in case you need to recreate it. Values of 4 or greater can
permanently corrupt data files. Only use an `innodb_force_recovery'
setting of 4 or greater on a production server instance after you have
successfully tested the setting on separate physical copy of your
database. When forcing `InnoDB' recovery, you should always start with
`innodb_force_recovery=1' and only increase the value incrementally, as
necessary.

`innodb_force_recovery' is 0 by default (normal startup without forced
recovery). The permissible nonzero values for `innodb_force_recovery'
are 1 to 6.  A larger value includes the functionality of lesser
values. For example, a value of 3 includes all of the functionality of
values 1 and 2.

If you are able to dump your tables with an `innodb_force_recovery'
value of 3 or less, then you are relatively safe that only some data on
corrupt individual pages is lost. A value of 4 or greater is considered
dangerous because data files can be permanently corrupted. A value of 6
is considered drastic because database pages are left in an obsolete
state, which in turn may introduce more corruption into B-trees and
other database structures.

As a safety measure, `InnoDB' prevents users from performing *Note
`INSERT': insert, *Note `UPDATE': update, or *Note `DELETE': delete.
operations when `innodb_force_recovery' is greater than 0.

   * `1' (`SRV_FORCE_IGNORE_CORRUPT')

     Let the server run even if it detects a corrupt page
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_page).
     Try to make `SELECT * FROM TBL_NAME' jump over corrupt index
     records and pages, which helps in dumping tables.

   * `2' (`SRV_FORCE_NO_BACKGROUND')

     Prevent the master thread
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_master_thread)
     from running. If a crash would occur during the purge
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_purge)
     operation, this recovery value prevents it.

   * `3' (`SRV_FORCE_NO_TRX_UNDO')

     Do not run transaction rollbacks
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_rollback)
     after crash recovery
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_crash_recovery).

   * `4' (`SRV_FORCE_NO_IBUF_MERGE')

     Prevent insert buffer
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_insert_buffer)
     merge operations. If they would cause a crash, do not do them. Do
     not calculate table statistics
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_statistics).
     This value can permanently corrupt data files. After using this
     value, be prepared to drop and recreate all secondary indexes.

   * `5' (`SRV_FORCE_NO_UNDO_LOG_SCAN')

     Do not look at undo logs
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_undo_log)
     when starting the database: `InnoDB' treats even incomplete
     transactions as committed. This value can permanently corrupt data
     files.

   * `6' (`SRV_FORCE_NO_LOG_REDO')

     Do not do the redo log
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_redo_log)
     roll-forward in connection with recovery. This value can
     permanently corrupt data files. Leaves database pages in an
     obsolete state, which in turn may introduce more corruption into
     B-trees and other database structures.

You can *Note `SELECT': select. from tables to dump them, or `DROP' or
`CREATE' tables even if forced recovery is used. If you know that a
given table is causing a crash on rollback, you can drop it. You can
also use this to stop a runaway rollback caused by a failing mass
import or *Note `ALTER TABLE': alter-table. You can kill the *Note
`mysqld': mysqld. process and set `innodb_force_recovery' to `3' to
bring the database up without the rollback, then `DROP' the table that
is causing the runaway rollback.

If corruption within the table data prevents you from dumping the
entire table contents, a query with an `ORDER BY PRIMARY_KEY DESC'
clause might be able to dump the portion of the table after the
corrupted part.

If a high `innodb_force_recovery' value is required to start `InnoDB',
there may be corrupted data structures that could cause complex queries
(queries containing `WHERE', `ORDER BY', or other clauses) to fail. In
this case, you may only be able to run basic `SELECT * FROM t' queries.


File: manual.info,  Node: innodb-troubleshooting-datadict,  Next: innodb-error-handling,  Prev: forcing-innodb-recovery,  Up: innodb-troubleshooting

14.6.12.3 Troubleshooting InnoDB Data Dictionary Operations
...........................................................

A specific issue with tables is that the MySQL server keeps data
dictionary information in `.frm' files it stores in the database
directories, whereas `InnoDB' also stores the information into its own
data dictionary inside the tablespace files. If you move `.frm' files
around, or if the server crashes in the middle of a data dictionary
operation, the locations of the `.frm' files may end up out of
synchrony with the locations recorded in the `InnoDB' internal data
dictionary.

If a data dictionary corruption or consistency issue prevents you from
starting `InnoDB', see *Note forcing-innodb-recovery:: for information
about manual recovery.

*Problem with CREATE TABLE*

A symptom of an out-of-sync data dictionary is that a *Note `CREATE
TABLE': create-table. statement fails. If this occurs, look in the
server's error log. If the log says that the table already exists
inside the `InnoDB' internal data dictionary, you have an orphaned
table inside the `InnoDB' tablespace files that has no corresponding
`.frm' file. The error message looks like this:


     InnoDB: Error: table test/parent already exists in InnoDB internal
     InnoDB: data dictionary. Have you deleted the .frm file
     InnoDB: and not used DROP TABLE? Have you used DROP DATABASE
     InnoDB: for InnoDB tables in MySQL version <= 3.23.43?
     InnoDB: See the Restrictions section of the InnoDB manual.
     InnoDB: You can drop the orphaned table inside InnoDB by
     InnoDB: creating an InnoDB table with the same name in another
     InnoDB: database and moving the .frm file to the current database.
     InnoDB: Then MySQL thinks the table exists, and DROP TABLE will
     InnoDB: succeed.

You can drop the orphaned table by following the instructions given in
the error message. If you are still unable to use *Note `DROP TABLE':
drop-table. successfully, the problem may be due to name completion in
the *Note `mysql': mysql. client. To work around this problem, start
the *Note `mysql': mysql. client with the `--skip-auto-rehash' option
and try *Note `DROP TABLE': drop-table. again.  (With name completion
on, *Note `mysql': mysql. tries to construct a list of table names,
which fails when a problem such as just described exists.)

*Problem Opening Table*

Another symptom of an out-of-sync data dictionary is that MySQL prints
an error that it cannot open a `.InnoDB' file:


     ERROR 1016: Can't open file: 'child2.InnoDB'. (errno: 1)

In the error log you can find a message like this:


     InnoDB: Cannot find table test/child2 from the internal data dictionary
     InnoDB: of InnoDB though the .frm file for the table exists. Maybe you
     InnoDB: have deleted and recreated InnoDB data files but have forgotten
     InnoDB: to delete the corresponding .frm files of InnoDB tables?

This means that there is an orphaned `.frm' file without a
corresponding table inside `InnoDB'. You can drop the orphaned `.frm'
file by deleting it manually.

*Orphaned Intermediate Tables*

If MySQL crashes in the middle of an *Note `ALTER TABLE': alter-table.
operation, you may be left with an orphaned intermediate table.
Intermediate table names begin with `#sql-'. In your data directory you
will see an `#sql-*.ibd' file and an accompanying `#sql-*.frm' file
with the same name. The intermediate table is also listed in *Note
Table Monitor: innodb-monitors. output.

If both the `#sql-*.ibd' and `#sql-*.frm' files appear in your data
directory, drop the intermediate table by issuing a `DROP TABLE'
statement, prefixing the name of the table with `#mysql50#' and
enclosing the table name in backticks. For example:

     mysql> DROP TABLE `#mysql50##sql-1291_3`;
     Query OK, 0 rows affected (0.01 sec)

The `#mysql50#' prefix tells MySQL to ignore `file name safe encoding'
introduced in MySQL 5.1. Enclosing the table name in backticks is
required to perform SQL statements on table names with special
characters such as `#'.

If there is no table format file (`#sql-*.frm' file) in your data
directory or the *Note `DROP TABLE': drop-table. operation fails,
create a new `.frm' file that matches the table schema of the
`#sql-*.ibd' file (it must have the same columns and indexes defined).
To do this, perform the following steps:

  1. Determine if the `#sql-*.ibd' file has a pre-`ALTER' or
     post-`ALTER' schema definition. You can view the columns and
     indexes of the intermediate table using the *Note Table Monitor:
     innodb-monitors.

  2. Once you have determined if the `#sql-*.ibd' file has a
     pre-`ALTER' or post-`ALTER' schema definition, create a matching
     `#sql-*.frm' file in a different database directory. For example,
     if an intermediate table has a post-`ALTER' schema definition,
     create an `.frm' file that matches the altered schema definition:

          mysql> CREATE TABLE tmp LIKE employees.salaries; ALTER TABLE tmp DROP COLUMN to_date;
          Query OK, 0 rows affected (0.02 sec)

          Query OK, 0 rows affected (0.06 sec)
          Records: 0  Duplicates: 0  Warnings: 0

  3. Copy the `.frm' file to the database directory where the orphaned
     table is located and rename it to match the name of the
     `#sql-*.ibd' file

          shell> cp tmp.frm employees/#sql-sql-1291_3.frm

  4. Drop the intermediate table by issuing a *Note `DROP TABLE':
     drop-table. statement, prefixing the name of the table with
     `#mysql50#' and enclosing the table name in backticks. For example:

          mysql> DROP TABLE `#mysql50##sql-1291_3`;
          Query OK, 0 rows affected (0.01 sec)


File: manual.info,  Node: innodb-error-handling,  Next: innodb-error-codes,  Prev: innodb-troubleshooting-datadict,  Up: innodb-troubleshooting

14.6.12.4 InnoDB Error Handling
...............................

Error handling in `InnoDB' is not always the same as specified in the
SQL standard. According to the standard, any error during an SQL
statement should cause rollback of that statement. `InnoDB' sometimes
rolls back only part of the statement, or the whole transaction. The
following items describe how `InnoDB' performs error handling:

   * If you run out of file space in the tablespace, a MySQL `Table is
     full' error occurs and `InnoDB' rolls back the SQL statement.

   * A transaction deadlock causes `InnoDB' to roll back the entire
     transaction. Retry the whole transaction when this happens.

     A lock wait timeout causes `InnoDB' to roll back only the single
     statement that was waiting for the lock and encountered the
     timeout. (To have the entire transaction roll back, start the
     server with the `--innodb_rollback_on_timeout' option, available
     as of MySQL 5.1.15.) Retry the statement if using the current
     behavior, or the entire transaction if using
     `--innodb_rollback_on_timeout'.

     Both deadlocks and lock wait timeouts are normal on busy servers
     and it is necessary for applications to be aware that they may
     happen and handle them by retrying. You can make them less likely
     by doing as little work as possible between the first change to
     data during a transaction and the commit, so the locks are held
     for the shortest possible time and for the smallest possible
     number of rows. Sometimes splitting work between different
     transactions may be practical and helpful.

     When a transaction rollback occurs due to a deadlock or lock wait
     timeout, it cancels the effect of the statements within the
     transaction. But if the start-transaction statement was *Note
     `START TRANSACTION': commit. or *Note `BEGIN': commit.  statement,
     rollback does not cancel that statement. Further SQL statements
     become part of the transaction until the occurrence of *Note
     `COMMIT': commit, *Note `ROLLBACK': commit, or some SQL statement
     that causes an implicit commit.

   * A duplicate-key error rolls back the SQL statement, if you have
     not specified the `IGNORE' option in your statement.

   * A `row too long error' rolls back the SQL statement.

   * Other errors are mostly detected by the MySQL layer of code (above
     the `InnoDB' storage engine level), and they roll back the
     corresponding SQL statement. Locks are not released in a rollback
     of a single SQL statement.

During implicit rollbacks, as well as during the execution of an
explicit *Note `ROLLBACK': commit. SQL statement, *Note `SHOW
PROCESSLIST': show-processlist.  displays `Rolling back' in the `State'
column for the relevant connection.


File: manual.info,  Node: innodb-error-codes,  Next: operating-system-error-codes,  Prev: innodb-error-handling,  Up: innodb-troubleshooting

14.6.12.5 InnoDB Error Codes
............................

The following is a nonexhaustive list of common `InnoDB'-specific
errors that you may encounter, with information about why each occurs
and how to resolve the problem.

   * `1005 (ER_CANT_CREATE_TABLE)'

     Cannot create table. If the error message refers to error 150,
     table creation failed because a foreign key constraint was not
     correctly formed. If the error message refers to error -1, table
     creation probably failed because the table includes a column name
     that matched the name of an internal `InnoDB' table.

   * `1016 (ER_CANT_OPEN_FILE)'

     Cannot find the `InnoDB' table from the `InnoDB' data files,
     although the `.frm' file for the table exists. See *Note
     innodb-troubleshooting-datadict::.

   * `1114 (ER_RECORD_FILE_FULL)'

     `InnoDB' has run out of free space in the tablespace. Reconfigure
     the tablespace to add a new data file.

   * `1205 (ER_LOCK_WAIT_TIMEOUT)'

     Lock wait timeout expired. The statement that waited too long was
     rolled back
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_rollback)
     (not the entire transaction
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transaction)).
     You can increase the value of the `innodb_lock_wait_timeout'
     configuration option if SQL statements should wait longer for
     other transactions to complete, or decrease it if too many
     long-running transactions are causing locking
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_locking)
     problems and reducing concurrency
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_concurrency)
     on a busy system.

   * `1206 (ER_LOCK_TABLE_FULL)'

     The total number of locks exceeds the lock table size. To avoid
     this error, increase the value of `innodb_buffer_pool_size'.
     Within an individual application, a workaround may be to break a
     large operation into smaller pieces. For example, if the error
     occurs for a large *Note `INSERT': insert, perform several smaller
     *Note `INSERT': insert. operations.

   * `1213 (ER_LOCK_DEADLOCK)'

     The transaction
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_transaction)
     encountered a deadlock
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_deadlock)
     and was automatically rolled back
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_rollback)
     so that your application could take corrective action. To recover
     from this error, run all the operations in this transaction again.
     A deadlock occurs when requests for locks arrive in inconsistent
     order between transactions. The transaction that was rolled back
     released all its locks, and the other transaction can now get all
     the locks it requested.  Thus when you re-run the transaction that
     was rolled back, it might have to wait for other transactions to
     complete, but typically the deadlock does not recur. If you
     encounter frequent deadlocks, make the sequence of locking
     operations (`LOCK TABLES', `SELECT ... FOR UPDATE', and so on)
     consistent between the different transactions or applications that
     experience the issue. See *Note innodb-deadlocks:: for details.

   * `1216 (ER_NO_REFERENCED_ROW)'

     You are trying to add a row but there is no parent row, and a
     foreign key constraint fails. Add the parent row first.

   * `1217 (ER_ROW_IS_REFERENCED)'

     You are trying to delete a parent row that has children, and a
     foreign key constraint fails. Delete the children first.


File: manual.info,  Node: operating-system-error-codes,  Prev: innodb-error-codes,  Up: innodb-troubleshooting

14.6.12.6 Operating System Error Codes
......................................

To print the meaning of an operating system error number, use the *Note
`perror': perror. program that comes with the MySQL distribution.

   * *Linux System Error Codes*

     The following table provides a list of some common Linux system
     error codes. For a more complete list, see Linux source code
     (http://www.finalcog.com/c-error-codes-include-errno).

     Linux error codes associated with InnoDB file operations and other
     system calls.

     Number  Macro         Description
     1       `EPERM'       Operation not permitted
     2       `ENOENT'      No such file or directory
     3       `ESRCH'       No such process
     4       `EINTR'       Interrupted system call
     5       `EIO'         I/O error
     6       `ENXIO'       No such device or address
     7       `E2BIG'       Arg list too long
     8       `ENOEXEC'     Exec format error
     9       `EBADF'       Bad file number
     10      `ECHILD'      No child processes
     11      `EAGAIN'      Try again
     12      `ENOMEM'      Out of memory
     13      `EACCES'      Permission denied
     14      `EFAULT'      Bad address
     15      `ENOTBLK'     Block device required
     16      `EBUSY'       Device or resource busy
     17      `EEXIST'      File exists
     18      `EXDEV'       Cross-device link
     19      `ENODEV'      No such device
     20      `ENOTDIR'     Not a directory
     21      `EISDIR'      Is a directory
     22      `EINVAL'      Invalid argument
     23      `ENFILE'      File table overflow
     24      `EMFILE'      Too many open files
     25      `ENOTTY'      Inappropriate ioctl for device
     26      `ETXTBSY'     Text file busy
     27      `EFBIG'       File too large
     28      `ENOSPC'      No space left on device
     29      `ESPIPE'      File descriptor does not allow seeking
     30      `EROFS'       Read-only file system
     31      `EMLINK'      Too many links

   * *Windows System Error Codes*

     The following table provides a list of some common Windows system
     error codes. For a complete list, see the Microsoft Web site
     (http://msdn.microsoft.com/en-us/library/ms681381.aspx).

     Windows error codes associated with InnoDB file operations and
     other system calls.

     Number  Macro         Description
     1       `ERROR_INVALID_FUNCTION'Incorrect function.
     2       `ERROR_FILE_NOT_FOUND'The system cannot find the file specified.
     3       `ERROR_PATH_NOT_FOUND'The system cannot find the path specified.
     4       `ERROR_TOO_MANY_OPEN_FILES'The system cannot open the file.
     5       `ERROR_ACCESS_DENIED'Access is denied.
     6       `ERROR_INVALID_HANDLE'The handle is invalid.
     7       `ERROR_ARENA_TRASHED'The storage control blocks were destroyed.
     8       `ERROR_NOT_ENOUGH_MEMORY'Not enough storage is available to process
                           this command.
     9       `ERROR_INVALID_BLOCK'The storage control block address is invalid.
     10      `ERROR_BAD_ENVIRONMENT'The environment is incorrect.
     11      `ERROR_BAD_FORMAT'An attempt was made to load a program with an
                           incorrect format.
     12      `ERROR_INVALID_ACCESS'The access code is invalid.
     13      `ERROR_INVALID_DATA'The data is invalid.
     14      `ERROR_OUTOFMEMORY'Not enough storage is available to complete
                           this operation.
     15      `ERROR_INVALID_DRIVE'The system cannot find the drive specified.
     16      `ERROR_CURRENT_DIRECTORY'The directory cannot be removed.
     17      `ERROR_NOT_SAME_DEVICE'The system cannot move the file to a different
                           disk drive.
     18      `ERROR_NO_MORE_FILES'There are no more files.
     19      `ERROR_WRITE_PROTECT'The media is write protected.
     20      `ERROR_BAD_UNIT'The system cannot find the device specified.
     21      `ERROR_NOT_READY'The device is not ready.
     22      `ERROR_BAD_COMMAND'The device does not recognize the command.
     23      `ERROR_CRC'   Data error (cyclic redundancy check).
     24      `ERROR_BAD_LENGTH'The program issued a command but the command
                           length is incorrect.
     25      `ERROR_SEEK'  The drive cannot locate a specific area or
                           track on the disk.
     26      `ERROR_NOT_DOS_DISK'The specified disk or diskette cannot be
                           accessed.
     27      `ERROR_SECTOR_NOT_FOUND'The drive cannot find the sector requested.
     28      `ERROR_OUT_OF_PAPER'The printer is out of paper.
     29      `ERROR_WRITE_FAULT'The system cannot write to the specified
                           device.
     30      `ERROR_READ_FAULT'The system cannot read from the specified
                           device.
     31      `ERROR_GEN_FAILURE'A device attached to the system is not
                           functioning.
     32      `ERROR_SHARING_VIOLATION'The process cannot access the file because it
                           is being used by another process.
     33      `ERROR_LOCK_VIOLATION'The process cannot access the file because
                           another process has locked a portion of the
                           file.
     34      `ERROR_WRONG_DISK'The wrong diskette is in the drive. Insert %2
                           (Volume Serial Number: %3) into drive %1.
     36      `ERROR_SHARING_BUFFER_EXCEEDED'Too many files opened for sharing.
     38      `ERROR_HANDLE_EOF'Reached the end of the file.
     39      `ERROR_HANDLE_DISK_FULL'The disk is full.
     87      `ERROR_INVALID_PARAMETER'The parameter is incorrect.
     112     `ERROR_DISK_FULL'The disk is full.
     123     `ERROR_INVALID_NAME'The file name, directory name, or volume label
                           syntax is incorrect.
     1450    `ERROR_NO_SYSTEM_RESOURCES'Insufficient system resources exist to
                           complete the requested service.


File: manual.info,  Node: se-db2,  Next: merge-storage-engine,  Prev: innodb-storage-engine,  Up: storage-engines

14.7 The IBMDB2I Storage Engine
===============================

* Menu:

* se-db2-installation::          Installation
* se-db2-configuration::         Configuration Options
* se-db2-creating-tables::       Creating schemas and tables
* se-db2-metadata::              Database/metadata management
* se-db2-transactions::          Transaction behavior
* se-db2-terms::                 Principles and Terminology
* se-db2-notes::                 Notes and Limitations
* se-db2-collations::            Character sets and collations
* se-db2-errors::                Error codes and trouble-shooting information

The `IBMDB2I' storage engine is designed as a fully featured
transaction-capable storage engine that enables MySQL to store its data
in DB2 tables running on IBM i. With the `IBMDB2I' storage engine, data
can be shared between MySQL applications and applications coded for
native DB2 for i interfaces.

`IBMDB2I' provides ACID-compliant transactions, support for foreign key
constraints, full crash recovery, radix-tree-based indexes, and the
unique ability to enable DB2 for i applications to see and update table
data in real time.

More information about the storage engine and its interaction with DB2
for i can be found in IBM's _Using DB2 for i as a Storage Engine for
MySQL_ Redbook publication, at IBM DB2 for i a Storage Engine for MySQL
Redbook (http://www.redbooks.ibm.com/abstracts/sg247705.html).

*Note*:

The `IBMDB2I' storage engine was introduced in MySQL 5.1.33 and
considered GA in MySQL 5.1.35. It was removed in MySQL 5.1.54.


File: manual.info,  Node: se-db2-installation,  Next: se-db2-configuration,  Prev: se-db2,  Up: se-db2

14.7.1 Installation
-------------------

Because it relies on features specific to the IBM i operating system
running on IBM Power systems, the `IBMDB2I' storage engine is only
available on builds of MySQL specifically created for the IBM i
operating system.

IBM i 5.4 or later is required to run ``IBMDB2I''. Some features may
require IBM i 6.1 or later versions. As well, a set of program
temporary fixes (PTFs) must be installed. Information about the
specific PTF numbers can be obtained from
http://www-912.ibm.com/n_dir/nas4apar.nsf/c79815e083182fec862564c00079d117/67d12878076e4827862574e2003c6d4a?OpenDocument
(http://www-912.ibm.com/n_dir/nas4apar.nsf/c79815e083182fec862564c00079d117/67d12878076e4827862574e2003c6d4a?OpenDocument).

The engine is built as a dynamic plugin and so must be installed by
using the following command:

     mysql> INSTALL PLUGIN ibmdb2i SONAME ha_ibmdb2i.so;


File: manual.info,  Node: se-db2-configuration,  Next: se-db2-creating-tables,  Prev: se-db2-installation,  Up: se-db2

14.7.2 Configuration Options
----------------------------

*`IBMDB2I' Storage Engine Features*

Name           Cmd-Line    Option File System Var  Status Var  Var Scope   Dynamic
ibmdb2i_assume_exclusive_useYes         Yes         Yes                     Global      Yes
ibmdb2i_async_enabledYes         Yes         Yes                     Both        Yes
ibmdb2i_compat_opt_allow_zero_date_valsYes         Yes         Yes                     Both        Yes
ibmdb2i_compat_opt_blob_colsYes         Yes         Yes                     Both        Yes
ibmdb2i_compat_opt_time_as_durationYes         Yes         Yes                     Both        Yes
ibmdb2i_compat_opt_year_as_intYes         Yes         Yes                     Both        Yes
ibmdb2i_create_index_optionYes         Yes         Yes                     Both        Yes
ibmdb2i_lob_alloc_sizeYes         Yes         Yes                     Both        Yes
ibmdb2i_max_read_buffer_sizeYes         Yes         Yes                     Both        Yes
ibmdb2i_max_write_buffer_sizeYes         Yes         Yes                     Both        Yes
ibmdb2i_propogate_default_col_valsYes         Yes         Yes                     Both        Yes
ibmdb2i_rdb_nameYes         Yes         Yes                     Global      No
ibmdb2i_system_trace_levelYes         Yes         Yes                     Global      Yes
ibmdb2i_transaction_unsafeYes         Yes         Yes                     Both        Yes

   * `ibmdb2i_assume_exclusive_use'

     Options for ibmdb2i_assume_exclusive_use

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_assume_exclusive_use'        
     Format*                              
     *System Variable     `ibmdb2i_assume_exclusive_use'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `off'           

     Specifies whether an external interface (such as DB2 for i) may be
     altering the data accessible by the `IBMDB2I' engine. This is an
     advisory value that may improve performance when correctly set to
     ON. When the value is ON, `IBMDB2I' may perform some internal
     caching of table statistics. When the value is set to OFF,
     `IBMDB2I' must assume that the table rows could be inserted and
     deleted without its direct knowledge and must call DB2 to obtain
     accurate statistics before each operation.

     Default Value: OFF

   * `ibmdb2i_async_enabled'

     Options for ibmdb2i_async_enabled

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_async_enabled'        
     Format*                              
     *System Variable     `ibmdb2i_async_enabled'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `on'            

     Specifies whether buffering between `IBMDB2I' and the QSQSRVR jobs
     responsible for fetching row data should be done in an
     asynchronous manner. Asynchronous reads are enabled by default and
     provide optimal performance.Under normal circumstances, this value
     will never need to be modified.

     Default Value: ON

   * `ibmdb2i_create_index_option'

     Options for ibmdb2i_create_index_option

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_create_index_option'        
     Format*                              
     *System Variable     `ibmdb2i_create_index_option'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `numeric'        
     i)                                   
     *Default*            `0'             

     Controls whether additional indexes are created for use by
     traditional DB2 for i interfaces. When the value is 0, no
     additional indexes will be created. When the value is 1 and the
     index created on behalf of MySQL is ASCII-based, an additional
     index is created based on EBCDIC hexadecimal sorting. The
     additional index may be useful for traditional DB2 for i
     interfaces which expect indexes to use EBCDIC-based sort sequences.

     Default Value: 0

   * `ibmdb2i_compat_opt_time_as_duration'

     Options for ibmdb2i_compat_opt_time_as_duration

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_compat_opt_time_as_duration'        
     Format*                              
     *System Variable     `ibmdb2i_compat_opt_time_as_duration'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `off'           

     Controls how MySQL TIME columns are mapped to DB2 data types when
     creating or altering an `IBMDB2I' table.  When the value is `ON',
     the column is mapped to an `INTEGER' type in DB2 and supports the
     full range of values defined by MySQL for `TIME' types. When the
     value is `OFF', the column is mapped to a DB2 `TIME' type and
     supports values in the range of '00:00:00' to '23:59:59'. This
     option is provided to provide enhanced interoperability with DB2
     for i interfaces.

     Default Value: OFF

   * `ibmdb2i_system_trace_level'

     Options for ibmdb2i_system_trace_level

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_system_trace_level'        
     Format*                              
     *System Variable     `ibmdb2i_system_trace_level'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `0'             

     Specifies what kind of debugging information is to be gathered for
     `QSQSRVR' jobs servicing MySQL connections. Multiple sources of
     information may be specified by summing the respective values.
     Changes to this option only affect new connections. Valid values
     include

        * `0': No information (Default)

        * `2': `STRDBMON'

        * `4': `STRDBG'

        * `8': `DSPJOBLOG'

        * `16': `STRTRC'

        * `32': `PRTSQLINF'

     The most useful sources of information are `DSPJOBLOG', which will
     capture the job log for each `QSQSRVR' job in a spoolfile, and
     `STRDBG', which will increase the diagnostic information in each
     job log.

     Default Value: 0

   * `ibmdb2i_compat_opt_allow_zero_date_vals'

     Options for ibmdb2i_compat_opt_allow_zero_date_vals

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_compat_opt_allow_zero_date_vals'        
     Format*                              
     *System Variable     `ibmdb2i_compat_opt_allow_zero_date_vals'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `0'             

     Specifies whether the storage engine should permit the
     `0000-00-00' date in `DATETIME', `TIMESTAMP' and `DATE' columns.
     When the option is 0, attempts to insert a row containing this
     zero date into an `IBMDB2I' table will fail. As well, a warning
     will be generated when creating a column with this zero value as
     the default value. When this option is 1, the zero value will be
     substituted with `0001-01-01' when stored in DB2, and a
     `0001-01-01' value will be translated to `0000-00-00' when read
     from DB2. Similarly, when a column with a default zero value is
     created, the DB2 default value will be '0001-01-01'. Users must be
     aware that, when this option is 1, all values of `0001-01-01' in
     DB2 will be interpreted as `0000-00-00'. This option is primarily
     added for compatibility with applications which rely on the zero
     date.

     Default Value: 0

   * `ibmdb2i_propagate_default_col_vals'

     Options for ibmdb2i_propogate_default_col_vals

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_propogate_default_col_vals'        
     Format*                              
     *System Variable     `ibmdb2i_propogate_default_col_vals'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `on'            

     Specifies whether `DEFAULT' value associated with each column
     should be propagated to the DB2 definition of the table when a
     table is created or altered. The default value is ON. This ensures
     that rows inserted from a standard DB2 interface will use the same
     default values as when inserted from MySQL.

     Default Value: ON

   * `ibmdb2i_compat_opt_year_as_int'

     Options for ibmdb2i_compat_opt_year_as_int

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_compat_opt_year_as_int'        
     Format*                              
     *System Variable     `ibmdb2i_compat_opt_year_as_int'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `0'             

     Controls how YEAR columns are stored in DB2. The default is 0 and
     causes `YEAR' columns to be created as `CHAR(4) CCSID 1208'
     columns in DB2. Setting this option to 1 causes the YEAR columns
     to be created as `SMALLINT' columns. This provides a slight
     performance increase and enables indexes that combine a `YEAR'
     column with a character column.

     Default Value: 0

   * `ibmdb2i_lob_alloc_size'

     Options for ibmdb2i_lob_alloc_size

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_lob_alloc_size'        
     Format*                              
     *System Variable     `ibmdb2i_lob_alloc_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `numeric'        
     i)                                   
     *Default*            `2MB'           

     Controls how much space is allocated by default for reading data
     from a `BLOB' or `TEXT' field. If an application consistently uses
     `BLOB' or `TEXT' fields that contain more than 2 MB of data, read
     performance may be improved if this value is increased.
     Conversely, an application which uses smaller `BLOB' or `TEXT'
     fields may find that the MySQL memory footprint is reduced if a
     smaller value is specified for this option.

     Default Value: 2 MB

   * `ibmdb2i_compat_opt_blob_cols'

     Options for ibmdb2i_compat_opt_blob_cols

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_compat_opt_blob_cols'        
     Format*                              
     *System Variable     `ibmdb2i_compat_opt_blob_cols'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `numeric'        
     i)                                   
     *Default*            `0'             

     Specifies how MySQL `TEXT' and `BLOB' columns larger than 255
     characters are mapped when creating `IBMDB2I' tables. When the
     value is 0, `TEXT' columns are mapped to `CLOB' or `DBCLOB' columns
     for DB2 for i. This enables the column to contain the maximum size
     documented for `TEXT' columns (64K characters), but the column can
     not be included in an index.  When the value is 1, `TEXT' columns
     are mapped to `LONG VARCHAR'/`VARGRAPHIC' columns, and `BLOB'
     columns are mapped to `LONG VARBINARY'. This permits indexes to be
     created over the column, but it reduces the amount of storage
     available to the column below the documented maximum for `TEXT'
     columns. This option was provided to enable applications which
     relied on the ability to create prefix indexes over `TEXT' columns.

     Default Value: 0

   * `ibmdb2i_max_read_buffer_size'

     Options for ibmdb2i_max_read_buffer_size

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_max_read_buffer_size'        
     Format*                              
     *System Variable     `ibmdb2i_max_read_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `numeric'        
     i)                                   
     *Default*            `1MB'           

     Controls the maximum amount of memory allocated for buffering row
     data when doing reads from an `IBMDB2I' table. This buffering is
     done independently of any row buffering done within MySQL proper.
     Setting this value too low may reduce read performance, while
     setting it too high may increase memory usage and may also reduce
     read performance.

     Default Value: 1 MB

   * `ibmdb2i_max_write_buffer_size'

     Options for ibmdb2i_max_write_buffer_size

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_max_write_buffer_size'        
     Format*                              
     *System Variable     `ibmdb2i_max_write_buffer_size'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `numeric'        
     i)                                   
     *Default*            `8MB'           

     Controls the maximum amount of memory allocated for buffering row
     data when inserting multiple rows into an `IBMDB2I' table. This
     buffering is done independently of any row buffering done within
     MySQL proper.  Setting this value too low may reduce write
     performance, while setting it too high may increase memory usage.

     Default Value: 8 MB

   * `ibmdb2i_rdb_name'

     Options for ibmdb2i_rdb_name

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_rdb_name'        
     Format*                              
     *System Variable     `ibmdb2i_rdb_name'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type* (IBM System   `string'        
     i)                                   
     *Default*            `'              

     The name of a local DB2 for i relational database that will act as
     a container for all `IBMDB2I' tables.  This enables an independent
     auxiliary storage pool (IASP) to be selected for usage. If no
     value is specified, the system database (*SYSBAS) is used.

     Default Value: <blank>

   * `ibmdb2i_transaction_unsafe'

     Options for ibmdb2i_transaction_unsafe

     *Introduced*         5.1.33          
     *Command-Line        `ibmdb2i_transaction_unsafe'        
     Format*                              
     *System Variable     `ibmdb2i_transaction_unsafe'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type* (IBM System   `boolean'        
     i)                                   
     *Default*            `off'           

     Controls whether `IBMDB2I' honors the transactional commands and
     isolation levels specified for MySQL. If the value is OFF,
     transactions are fully supported.  If the value is ON,
     transactional behavior is not implemented.  This may provide a
     moderate performance increase for applications that do not rely on
     transactional guarantees.

     Default Value: OFF

The values specified for `ibmdb2i_create_index_option',
`ibmdb2i_create_time_columns_as_tod', `ibmdb2i_map_blob_to_varchar',
`ibmdb2i_compat_opt_allow_zero_date_vals',
`ibmdb2i_propagate_default_col_vals', and
`ibmdb2i_propagate_default_col_val' will be applied whenever an
`IBMDB2I' table is created. Tables are implicitly destroyed and
re-created when an `offline' `ALTER TABLE' is performed on an `IBMDB2I'
table. Therefore it is highly recommended that the values of these
variables be consistent across the lifetime of a table to prevent an
`ALTER TABLE' from running under a different set of options than were
used to originally create the table. If this recommendation is not
followed, the `ALTER TABLE' may fail upon encountering incompatible
data when re-creating the table.


File: manual.info,  Node: se-db2-creating-tables,  Next: se-db2-metadata,  Prev: se-db2-configuration,  Up: se-db2

14.7.3 Creating schemas and tables
----------------------------------

* Menu:

* se-db2-creating-tables-identifiers::  Identifier names
* se-db2-creating-tables-indexnames::  Index names

`IBMDB2I' tables are created by specifying the `ENGINE=IBMDB2I' option
on a `CREATE TABLE' or `ALTER TABLE' statement. These tables are stored
as DB2 for i objects in the QSYS.LIB file system. Therefore, in
contrast to the behavior of other storage engines, `IBMDB2I' table and
index data does not reside beneath the datadir directory with other
MySQL table data.

When the first `IBMDB2I' table is created in a MySQL schema, the
corresponding DB2 schema will be created (if it does not already exist).

Note that if the user profile running MySQL has sufficient authority
dropping a MySQL schema will drop a DB2 schema of the same name even if
the schema never contained any `IBMDB2I' tables and contains objects
not related to MySQL. Therefore, it is recommended that extreme caution
be used when dropping MySQL schemas when the `IBMDB2I' plugin is
installed.


File: manual.info,  Node: se-db2-creating-tables-identifiers,  Next: se-db2-creating-tables-indexnames,  Prev: se-db2-creating-tables,  Up: se-db2-creating-tables

14.7.3.1 Identifier names
.........................

DB2 for i file objects have both a short (10-character) system name and
an SQL name. The DB2 for i SQL name is always the same as the MySQL
name. However, because MySQL's sensitivity to the lettercase of schema
and table names depends on the file system containing the datadir,
mapping the MySQL name to the system name of the corresponding DB2 for
i object must account for several factors, described below.

When MySQL is operating in a case-sensitive mode (that is, datadir is
in a case-sensitive file-system like (/QOpenSys), the case of the
system name of the `IBMDB2I' object reflects the case of the name
specified to MySQL. If the object has all uppercase characters and is
equal to or less than 10 characters in length, the system name will be
undelimited and in uppercase.If the object name has mixed or lower-case
letters, the IBM i system name will contain up to 8 characters of the
name in the specified case and will be delimited by surrounding
quotation marks. If the MySQL name has more characters than can fit in
the delimited system name, the system name will be generated as a
mangled name delimited by surrounding quotation marks.

Examples of this naming behavior are given below:

*Naming Behavior in DB2 Storage Engine*

MySQL name               DB2 for i SQL name       IBM i System name
mytable                  mytable                  "mytable"
mylongertable            mylongertable            "mylo0001"
UPPERTABLE               UPPERTABLE               UPPERTABLE
UPPERLONGTABLE           UPPERLONGTABLE           UPPER00001
MixedTab                 MixedTab                 "MixedTab"
MixedlongerTab           MixedlongerTab           "Mixe0001"

If MySQL is operating in a case-insensitive mode, the IBM i system name
will contain up to 8 characters of the name in lower case and will be
delimited by surrounding quotation marks. If the MySQL name has more
characters than can fit in the delimited system name, the system name
will be generated as a mangled name delimited by surrounding quotation
marks.

Note that IBM i system names are not changed when a RENAME TABLE
command is executed. Only the DB2 for i SQL name changes.


File: manual.info,  Node: se-db2-creating-tables-indexnames,  Prev: se-db2-creating-tables-identifiers,  Up: se-db2-creating-tables

14.7.3.2 Index names
....................

* Menu:

* se-db2-data-type-mapping::     Data type mapping

Unlike MySQL, DB2 for i requires that index names be unique to an
entire schema. To support MySQL indexes, `IBMDB2I' creates the DB2 for
i indexes with modified file names. The generated name is a
concatenation of the index name, three underscores (_), and the table
name. For example, `CREATE INDEX idx1 ON tab1 (a, b)' would create a
DB2 index named `idx___tab1'. If the ibmdb2i_create_index_option value
is set to 1, an additional index may be created which is named with an
additional `H_' marker between the index and table names (for example,
idx___H_tab1). These generated names are then mangled to create the an
IBM i system name, as described above.

If a table is renamed, the indexes will also be renamed.

This index name generation scheme also has implications for the length
of index and table names; to permit the generated name and allow for
delimiting quotation marks, the combined length of the index and table
names must be less than or equal to 121 characters.


File: manual.info,  Node: se-db2-data-type-mapping,  Prev: se-db2-creating-tables-indexnames,  Up: se-db2-creating-tables-indexnames

14.7.3.3 Data type mapping
..........................

When creating a table, `IBMDB2I' may map the MySQL types specified on a
`CREATE TABLE' statement into a corresponding or compatible DB2 for i
type.  Examples include the `BIT' type, which is stored as a `BINARY'
field, or the `MEDIUMINT' type, which is stored as an `INTEGER' field.
For most data types, this mapping is transparent. Data types which have
restrictions unique to `IBMDB2I' are documented in *Note se-db2-notes::.


File: manual.info,  Node: se-db2-metadata,  Next: se-db2-transactions,  Prev: se-db2-creating-tables,  Up: se-db2

14.7.4 Database/metadata management
-----------------------------------

When an `IBMDB2I' table is created, a File Level ID (FID) file is
created in the database directory. This file has an extension .FID and
contains the last known FID of the associated DB2 for i physical file.
The `IBMDB2I' engine uses this FID value to determine whether
incompatible changes have been made to the table by an external
(non-MySQL) interface. If the physical file is altered, DB2 for i
automatically generates a new FID. The next time `IBMDB2I' attempts to
access the file, it will detect that the new FID does not match the
known FID, and it will prevent MySQL from using the table.

In some cases, the changes to the physical file that cause the FID to
be updated may not adversely affect access through MySQL and `IBMDB2I'.
In this case, a user may wish to override the FID check that `IBMDB2I'
performs. A user with appropriate permissions may do so simply by
deleting the `.FID' file associated with the table and performing a
`FLUSH TABLE' statement against the table. `IBMDB2I' will then
regenerate the file with the new FID the next time the table is
accessed from MySQL.

If triggers or constraints are applied to the table from a native DB2
interface, they will be respected when accessing the table from MySQL,
but MySQL will have no knowledge of the triggers or constraints.
Likewise, views and indexes can be created over the tables from a DB2
interface, but the indexes will not be accessible from MySQL.


File: manual.info,  Node: se-db2-transactions,  Next: se-db2-terms,  Prev: se-db2-metadata,  Up: se-db2

14.7.5 Transaction behavior
---------------------------

The `IBMDB2I' storage engine supports row-level transaction management.
All MySQL isolation levels are supported by the engine, and where
highest performance is required, transaction support can be disabled
globally or per session by modifying the ibmdb2i_transaction_unsafe
configuration option.

`IBMDB2I' uses the underlying DB2 for i transaction support to
implement MySQL isolation levels. DB2 for i uses table and row locks to
implement the various isolation levels, as described below:

*IBMDB2I Isolation Levels*

Isolation   Read-only        Read-write                      
level       (SELECT)         (UPDATE,                        
                             DELETE)                         
            Lock enforcement Visibility of   Lock            Visibility of
                             uncommitted     enforcement     uncommitted
                             work on behalf                  work on behalf
                             of other                        of other
                             connections                     connections
SERIALIZABLETable is locked  N/A             Table is        N/A
            until end of                     locked until    
            transaction.Other                end of          
            connections may                  transaction.Other
            read rows while                  connections     
            locked.                          may read rows   
                                             while locked.   
REPEATABLE  Rows that have   Rows cannot be  Rows that have  Rows cannot be
READ        been read are    read until      been read are   read until
            locked until     work is         locked until    work is
            end of           committed.      end of          committed.
            transaction.Other                transaction.Other
            connections may                  connections     
            read and insert                  may read and    
            rows while                       insert rows     
            locked.                          while locked.   
READ        Row is locked    Rows cannot be  Row is locked   Rows cannot be
COMMITTED   while cursor is  read until      while cursor    read until
            positioned on    work is         is positioned   work is
            that row.Other   committed.      on that         committed.
            connections may                  row.Other       
            read and insert                  connections     
            rows while                       may read and    
            locked.                          insert rows     
                                             while locked.   
READ        Row is locked    Rows can be     Row is locked   Rows can be
UNCOMMITTED while cursor is  read before     while cursor    read before
            positioned on    work is         is positioned   work is
            that row.Other   committed.      on that         committed.
            connections may                  row.Other       
            read and insert                  connections     
            rows while                       may read and    
            locked.                          insert rows     
                                             while locked.   
transaction_unsafeNo locks         Full access     Table is        Unrestricted
                                             locked until    access
                                             end of          
                                             transaction.Other
                                             connections     
                                             may read rows   
                                             while locked.   

Attempts to access locked rows time out according to the timeout value
associated with the underlying DB2 physical file. This timeout wait is
30 seconds by default. Refer to
http://publib.boulder.ibm.com/infocenter/iseries/v5r4/index.jsp?topic=/dbp/rbafoconcrec.htm
(http://publib.boulder.ibm.com/infocenter/iseries/v5r4/index.jsp?topic=/dbp/rbafoconcrec.htm)
for more information.

Because `IBMDB2I' does not multi-version rows under commitment control,
row lock contention may occur under certain scenarios. In particular,
when multiple connections attempt to read overlapping ranges of rows
while performing a statement that does updates, the connections may
contend for the same row locks. This may lead to delays until the row
lock timeout expires. Creating appropriate indexes and increasing query
selectivity to reduce range overlap may help to alleviate this
contention.


File: manual.info,  Node: se-db2-terms,  Next: se-db2-notes,  Prev: se-db2-transactions,  Up: se-db2

14.7.6 Principles and Terminology
---------------------------------

`AUTO_INCREMENT'

The MySQL auto_increment column attribute can be used to generate a
unique identity for new rows.The `IBMDB2I' storage engine maps the
MySQL auto_increment attribute to the DB2 for i identity attribute

For most MySQL storage engines, the auto_increment value is determined
by adding one to the maximum value stored in the table for the
column.For the `IBMDB2I' storage engine, DB2 for i generates the
identity value by adding one to the last generated value. Following are
some example MySQL statements to illustrate the point.


     create table t1 (a int auto increment, primary key(a)) engine = ibmdb2i;
     insert into t1 values(3);
     insert into t1 values(null),(null);

For the first INSERT statement, an explicit value of 3 is specified for
the auto_increment column, so the value 3 is stored in the inserted
row.For the second INSERT statement null is specified, so generated
values 1 and 2 will be stored in the rows.

Duplicate key failures can occur in DB2 for i if a MySQL application
mixes explicit auto_increment values with generated values within a
table. For the example above, if one more record is inserted into the
table for which an auto_increment value is generated, a duplicate key
error will occur because the value 3 (that is, the last generated value
plus one) already exists in the table.To effect the MySQL behavior for
auto_increment columns, the `IBMDB2I' storage engine will detect a
duplicate key error, alter the restart value for the DB2 identity
column to the maximum value plus one, and retry the failed insert, but
only if the following conditions are true:

   * The duplicate key error occurred on an index for which the
     auto_increment column is a key field

   * An exclusive (LENR) lock can be acquired on the table

   * The error occurred on the first or only row of the `INSERT'
     statement.

The `IBMDB2I' storage engine does not support the following usage of
auto_increment columns:

  1. Any MySQL global or session variable that affects the start,
     increment, or offset for generated auto_increment values.

  2. Any MySQL feature that returns the _next value to be used_ for an
     auto_increment column.

  3. An auto_increment column on a MySQL partitioned table.


File: manual.info,  Node: se-db2-notes,  Next: se-db2-collations,  Prev: se-db2-terms,  Up: se-db2

14.7.7 Notes and Limitations
----------------------------

   * When using multiples instances of MySQL on a single i5 host you
     should be aware that the two independent instances will access the
     same database within the DB2 environment. This can lead to
     namespace collisions and issues. To get round this limitation, you
     should configure different IBM i independent auxiliary storage
     pools (ISAPs) for each MySQL server, and then use the
     `ibmdb2i_rdb_name' option to MySQL to configure which IASP should
     be used for each MySQL instance.

   * Indexes over `VARBINARY' columns may not provide accurate
     estimates the optimizer. Queries over such indexes may produce
     error 2027 in the error log but will succeed. This affects only
     the performance of these queries, not the correctness of the
     results.

   * Setting `ibmdb2i_system_trace_level = 16 (STRTRC)' may cause
     unpredictable failures including error 2088 on some operations.
     This is unlikely to affect any users, as this value is recommended
     only for serviceability purposes.

   * `IBMDB2I' honors the `CASCADE'/`RESTRICT' option on the `DROP
     TABLE' statement.

   * The use of `FLUSH TABLES WITH READ LOCK' is discouraged when using
     `IBMDB2I' tables. Due to differences in internal locking
     implementations, `FLUSH TABLES WITH READ LOCK' may produce
     deadlocks on `IBMDB2I' tables.

   * Row-based replication is supported by `IBMDB2I'. Statement-based
     replication is not supported.

   * Schema name lengths are limited to 10 characters in IBM i 5.4 and
     30 characters in IBM i 6.1. If the schema name is mixed- or
     lower-case, two characters must be subtracted from the limit to
     account for surrounding quotation marks.

   * The RENAME TABLE command cannot be used to move `IBMDB2I' tables
     from one database to another.

   * The maximum length of the internal row format for `IBMDB2I' is
     32767 bytes. Because the internal row format may differ from the
     MySQL row format due to data mapping differences (see Creating
     schemas and tables section), anticipating this limit may be
     difficult.

   * The combined length of the index and table names must be less than
     or equal to 121 characters.

   * Indexes over TEXT or BLOB columns with a maximum length greater
     than 255 characters are not supported. The
     ibmdb2i_map_blob_to_varchar option can be used to work around this
     limitation for TEXT fields up to 64K characters.

   * Specific restrictions apply to certain data types as described in
     the following chart:

     *Data Type Restrictions in IBMDB2I*

     MySQL data    Restriction
     type          
     `LONGBLOB'    The maximum length of a DB2 BLOB data type is 2GB.
     or `LONGTEXT' 
     `DATE'        `IBMDB2I' does not support the special date value of
                   '0000-00-00'. The restrictions on `DATE' and
                   `DATETIME' columns can be removed by setting the
                   value of `ibmdb2i_compat_opt_allow_zero_date_vals' to
                   1.
     `DATETIME'    `IBMDB2I' does not support the special datetime value
                   of '0000-00-00 00:00:00'. The restrictions on `DATE'
                   and `DATETIME' columns can be removed by setting the
                   value of `ibmdb2i_compat_opt_allow_zero_date_vals' to
                   1.
     `DECIMAL(p,   If p is greater than 63 and s is greater than (p-63),
     s)' or        the field definition is truncated to `DECIMAL(63,
     `NUMERIC(p,   s-(p-63))'. If p is greater than 63 and s is less
     s)'           than or equal to (p-63), the definition is not
                   supported.
     `TIME'        By default, `IBMDB2I' only supports times in the range
                   '00:00:00' to '23:59:59.' See the
                   ibmdb2i_create_time_columns_as_tod option for more
                   information.

   * These MySQL statements are not supported by the `IBMDB2I' Engine:

        * `CACHE INDEX' and `LOAD INDEX INTO CACHE'

        * `HANDLER'

        * `CHECK TABLE'

        * `REPAIR TABLE'

        * ` BACKUP-RESTORE TABLE'

   * The `ucs2_spanish2_ci' and `utf8_spanish2_ci' collations are not
     supported by `IBMDB2I'. There are no plans to support these
     collations.

   * The `ucs2_swedish_ci' and `utf8_swedish_ci' collations were added
     in MySQL 5.1.35. supported by `IBMDB2I'. As with other
     language-specific unicode collations, the support will be only be
     available on IBM i 6.1 and later releases.


File: manual.info,  Node: se-db2-collations,  Next: se-db2-errors,  Prev: se-db2-notes,  Up: se-db2

14.7.8 Character sets and collations
------------------------------------

DB2 for i only supports a single collation per index or foreign key
constraint. A foreign key constraint must have the same collation as a
primary key constraint, if one exists..

Character sets and collations supported by `IBMDB2I' are described in
the list below. IBM i 6.1 is required for the most comprehensive
collation support. Note that Chinese, Japanese, and Korean character
sets are converted to UTF-16 for storage in DB2 for i;
`utf8_general_ci' is converted to `UCS2' for storage in DB2 for i.

*Collation Compatibility in IBMDB2I and MySQL*

MySQL          SupportedSupported
Collation      in IBM  in IBM
               i 5.4   i 6.1
`armscii8_general_ci'        
`armscii8_bin'         
`ascii_general_ci'        Yes
`ascii_bin'            Yes
`big5_chinese_ci'Yes     Yes
`big5_bin'     Yes     Yes
`cp1250_croatian_ci'        Yes
`cp1250_czech_cs'        Yes
`cp1250_general_ci'        Yes
`cp1250_polish_ci'        Yes
`cp1250_bin'           Yes
`cp1251_bulgarian_ci'        Yes
`cp1251_general_ci'        Yes
`cp1251_general_cs'        Yes
`cp1251_ukrainian_ci'        
`cp1251_bin'           Yes
`cp1256_general_ci'        Yes
`cp1256_bin'           Yes
`cp1257_general_ci'        
`cp1257_lithuanian_ci'        
`cp1257_bin'           
`cp850_general_ci'Yes     Yes
`cp850_bin'    Yes     Yes
`cp852_general_ci'        Yes
`cp852_bin'            Yes
`cp866_general_ci'        
`cp866_bin'            
`cp932_japanese_ci'Yes     Yes
`cp932_bin'    Yes     Yes
`dec8_swedish_ci'        
`dec8_bin'             
`eucjpms_japanese_ci'        
`eucjpms_bin'          
`euckr_korean_ci'Yes     Yes
`euckr_bin'    Yes     Yes
`gb2312_chinese_ci'Yes     Yes
`gb2312_bin'   Yes     Yes
`gbk_chinese_ci'Yes     Yes
`gbk_bin'      Yes     Yes
`geostd8_general_ci'        
`geostd8_bin'          
`greek_general_ci'Yes     Yes
`greek_bin'    Yes     Yes
`hebrew_general_ci'Yes     Yes
`hebrew_bin'   Yes     Yes
`hp8_english_ci'        
`hp8_bin'              
`keybcs2_general_ci'        
`keybcs2_bin'          
`koi8r_general_ci'        
`koi8r_bin'            
`koi8u_general_ci'        
`koi8u_bin'            
`latin1_danish_ci'Yes     Yes
`latin1_general_ci'Yes     Yes
`latin1_general_cs'Yes     Yes
`latin1_german1_ci'Yes     Yes
`latin1_german2_ci'        
`latin1_spanish_ci'Yes     Yes
`latin1_swedish_ci'Yes     Yes
`latin1_bin'   Yes     Yes
`latin2_croatian_ci'Yes     Yes
`latin2_czech_cs'Yes     Yes
`latin2_general_ci'Yes     Yes
`latin2_hungarian_ci'Yes     Yes
`latin2_bin'   Yes     Yes
`latin5_turkish_ci'Yes     Yes
`latin5_bin'   Yes     Yes
`latin7_estonian_cs'        
`latin7_general_ci'        
`latin7_general_cs'        
`latin7_bin'           
`macce_general_ci'        Yes
`macce_bin'            Yes
`macroman_general_ci'        
`macroman_bin'         
`sjis_japanese_ci'Yes     Yes
`sjis_bin'     Yes     Yes
`swe7_swedish_ci'        
`swe7_bin'             
`tis620_thai_ci'Yes     Yes
`tis620_bin'   Yes     Yes
`ucs2_czech_ci'        Yes
`ucs2_danish_ci'        Yes
`ucs2_esperanto_ci'        Yes
`ucs2_estonian_ci'        Yes
`ucs2_general_ci'Yes     Yes
`ucs2_hungarian_ci'        Yes
`ucs2_icelandic_ci'        Yes
`ucs2_latvian_ci'        Yes
`ucs2_lithuanian_ci'        Yes
`ucs2_persian_ci'        Yes
`ucs2_polish_ci'        Yes
`ucs2_roman_ci'        
`ucs2_romanian_ci'        Yes
`ucs2_slovak_ci'        Yes
`ucs2_slovenian_ci'        Yes
`ucs2_spanish_ci'        Yes
`ucs2_spanish2_ci'        Yes
`ucs2_turkish_ci'        Yes
`ucs2_unicode_ci'Yes     Yes
`ucs2_bin'     Yes     Yes
`ujis_japanese_ci'Yes     Yes
`ujis_bin'     Yes     Yes
`utf8_czech_ci'        Yes
`utf8_danish_ci'        Yes
`utf8_esperanto_ci'        Yes
`utf8_estonian_ci'        Yes
`utf8_general_ci'Yes     Yes
`utf8_hungarian_ci'        Yes
`utf8_icelandic_ci'        Yes
`utf8_latvian_ci'        Yes
`utf8_lithuanian_ci'        Yes
`utf8_persian_ci'        Yes
`utf8_polish_ci'        Yes
`utf8_roman_ci'        
`utf8_romanian_ci'        Yes
`utf8_slovak_ci'        Yes
`utf8_slovenian_ci'        Yes
`utf8_spanish_ci'        Yes
`utf8_spanish2_ci'        Yes
`utf8_turkish_ci'        Yes
`utf8_unicode_ci'        Yes
`utf8_bin'     Yes     Yes


File: manual.info,  Node: se-db2-errors,  Prev: se-db2-collations,  Up: se-db2

14.7.9 Error codes and trouble-shooting information
---------------------------------------------------

Errors reported by the `IBMDB2I' engine may originate from two
locations. Error values under 2500 originate in DB2 for i. Error values
over 2500 originate in the storage engine itself. Occasionally, errors
are reported by `IBMDB2I' but, due to the architecture of MySQL, cannot
be directly exposed to MySQL client interfaces. In these cases, issuing
a `SHOW ERRORS' statement or referring to the MySQL error log may be
necessary to determine the cause of a failure. Errors which originate
in DB2 for i are usually encountered in the DB2 for i SQL Server Mode
job (QSQSRVR) which services the MySQL client connection; additional
information about failures can often be found by looking in the job log
of the associated QSQSRVR job.

Following is the list of codes and messages for errors that occur in
DB2 for i that are reported by the `IBMDB2I' engine. %d and %s
represent numbers and strings, respectively, that are replaced when the
message is displayed.

*Error Codes from IBMDB2I*

Error   Error Message Text
Code    
Number  
0       Successful
2016    Thread ID is too long
2017    Error creating a SPACE memory object
2018    Error creating a FILE memory object
2019    Error creating a SPACE synchronization token
2020    Error creating a FILE synchronization token
2021    See message %-.7s in joblog for job %-.6s/%-.10s/%-.10s.
2022    Error unlocking a synchronization token when closing a connection
2023    Invalid action specified for an 'object lock' request
2024    Invalid action specified for a savepoint request
2025    Partial keys are not supported with an ICU sort sequence
2026    Error retrieving an ICU sort key
2027    Error converting single-byte sort sequence to UCS-2
2028    An unsupported collation was specified
2029    Validation failed for referenced table of foreign key constraint
2030    Error extracting table for constraint information
2031    Error extracting referenced table for constraint information
2032    Invalid action specified for a 'commitment control' request
2033    Invalid commitment control isolation level specified on 'open'
        request
2034    Invalid file handle
2036    Invalid option specified for returning data on 'read' request
2037    Invalid orientation specified for 'read' request
2038    Invalid option type specified for 'read' request
2039    Invalid isolation level for starting commitment control
2040    Error unlocking a synchronization token in module QMYALC
2041    Length of space for returned format is not long enough
2042    SQL XA transactions are currently unsupported by this interface
2043    The associated QSQSRVR job was killed or ended unexpectedly.
2044    Error unlocking a synchronization token in module QMYSEI
2045    Error unlocking a synchronization token in module QMYSPO
2046    Error converting input CCSID from short form to long form
2048    Error getting associated CCSID for CCSID conversion
2049    Error converting a string from one CCSID to another
2050    Error unlocking a synchronization token
2051    Error destroying a synchronization token
2052    Error locking a synchronization token
2053    Error recreating a synchronization token
2054    A space handle was not specified for a constraint request
2055    An SQL cursor was specified for a delete request
2057    Error on delete request because current UFCB for connection is
        not open
2058    An SQL cursor was specified for an object initialization request
2059    An SQL cursor was specified for an object override request
2060    A space handle was not specified for an object override request
2061    An SQL cursor was specified for an information request
2062    An SQL cursor was specified for an object lock request
2063    An SQL cursor was specified for an optimize request
2064    A data handle was not specified for a read request
2065    A row number handle was not specified for a read request
2066    A key handle was not specified for a read request
2067    An SQL cursor was specified for an row estimation request
2068    A space handle was not specified for a row estimation request
2069    An SQL cursor was specified for a release record request
2070    A statement handle was not specified for an 'execute immediate'
        request
2071    A statement handle was not specified for a 'prepare open' request
2072    An SQL cursor was specified for an update request
2073    The UFCB was not open for read
2074    Error on update request because current UFCB for connection is
        not open
2075    A data handle was not specified for an update request
2076    An SQL cursor was specified for a write request
2077    A data handle was not specified for a write request
2078    An unknown function was specified on a process request
2079    A share definition was not specified for an 'allocate share'
        request
2080    A share handle was not specified for an 'allocate share' request
2081    A use count handle was not specified for an 'allocate share'
        request
2082    A 'records per key' handle was not specified for an information
        request
2083    Error resolving LOB address
2084    Length of a LOB space is too small
2085    An unknown function was specified for a server request
2086    Object authorization failed. See message %-.7s in joblog for job
        %-.6s/%-.10s/%-.10s. for more information.
2088    Error locking mutex on server
2089    Error unlocking mutex on server
2090    Error checking for RDB name in RDB Directory
2091    Error creating mutex on server
2094    Error unlocking mutex
2095    Error connecting to server job
2096    Error connecting to server job
2098    Function check occurred while registering parameter spaces. See
        job log.
2101    End of block
2102    The file has changed and might not be compatible with the MySQL
        table definition
2103    Error giving pipe to server job
2104    There are open object locks when attempting to deallocate
2105    There is no open lock
2108    The maximum value for the auto_increment data type was exceeded
2109    Error occurred closing the pipe
2110    Error occurred taking a descriptor for the pipe
2111    Error writing to pipe
2112    Server was interrupted
2113    No pipe descriptor exists for reuse
2114    Error occurred during an SQL prepare statement
2115    Error occurred during an SQL open
2122    An unspecified error was returned from the system.



Following is the list of error codes and messages that occur within the
`IBMDB2I' storage engine.

*Error Codes and Messages in IBMDB2I*

Error   Error Message Text
Code    
Number  
2501    Error opening codeset conversion from %.64s to %.64s (errno =
        %d).  * Resolution:* Alter the table definition to specify a
        character set that is supported by the `IBMDB2I' engine.
2502    Invalid %-.10s name '%-.128s. * Resolution:* If a field name,
        ensure that it is less than the maximum length of 126
        characters.If an index name, ensure that the length of the index
        name plus the length of the table name is less than 121
        characters.
2503    Unsupported move from '%-.128s' to '%-.128s' on RENAME TABLE
        statement.  * Resolution:* Moving a table from one schema to
        another is not supported by the `IBMDB2I' engine. Create a new
        table in the 'to' schema, copy the data to the new table, and
        then drop the old table.
2504    The %-.64s character set is not supported. * Resolution:* Try
        using another character set.
2505    Auto_increment is not allowed for a partitioned table.  *
        Resolution:* Remove the auto_increment attribute from the table
        or do not partition the table.
2506    Character set conversion error due to unknown encoding scheme %d.
        * Resolution:* Alter the table definition to ensure that
        character sets assigned to columns are supported by the `IBMDB2I'
        engine.
2508    Table '%-.128s' was not found by the storage engine.  *
        Resolution:* A table definition exists in MySQL, but the
        correspondingtable in DB2 for i is not found. Delete the MySQL
        table or restore the DB2 table.
2509    Could not resolve to %-.128s in library %-.10s type %-.10s
        (errno = %d).  * Resolution:* Restore the missing IBM i object
        to the system.
2510    Error on _PGMCALL for program %-.10s in library %-.10s (error =
        %d).  * Resolution:* This is an internal error.
2511    Error on _ILECALL for API '%.128s' (error = %d).  *Resolution:*
        This is an internal error.
2512    Error in iconv() function during character set conversion (errno
        = %d).  *Resolution:* Ensure the text being inserted contains
        only valid code points for the associated character set. This
        may be caused by using ENCRYPT or COMPRESS on a text field,
        resulting in binary data containing invalid characters.
2513    Error from Get Encoding Scheme (QTQGESP) API: %d, %d, %d
        *Resolution:* This is an internal error.
2514    Error from Get Related Default CCSID (QTQGRDC) API: %d, %d, %d.
        * Resolution:* This is an internal error.
2515    Data out of range for column '%.192s'. * Resolution:* DB2 for i
        does not support a zero value for DATE and DATETIME data types.
        Specify a new value for the column.
2516    Schema name '%.128s' exceeds maximum length of %d characters.  *
        Resolution:* Change the schema name so that its length does not
        exceed the maximum. For mixed case or lowercase names, permit 2
        characters for outer quotation marks.
2517    Multiple collations not supported in a single index.  *
        Resolution:* DB2 for i only supports sort sequences at the table
        or index level, so all character-based columns in the primary
        key or index must be using the same collation. Alter the table
        definition so that all columns use the same collation.
2518    Sort sequence was not found. * Resolution:* Alter the table to
        use a collation that is supported by the `IBMDB2I' engine.
2519    One or more characters in column %.128s were substituted during
        conversion. * Resolution:* This is a warning that during the
        conversion of data from MySQL to DB2 some characters were
        replaced with substitute characters.
2520    A decimal column exceeded the maximum precision. Data may be
        truncated.  * Resolution:* A decimal column specified on a
        CREATE TABLE or ALTER TABLE command has greater precision than
        DB2 permits. Data stored in this column may be truncated. Change
        the column specification to have a precision less than or equal
        to 63.
2521    Some data returned by DB2 for table %s could not be converted
        for MySQL.  * Resolution:* This is a warning that some data
        could not be converted from DB2 to MySQL. Data was likely
        inserted into the table using DB2 interfaces that is valid data
        for DB2 but is invalid for MySQL.
2523    Column %.128s contains characters that cannot be converted.  *
        Resolution:* An error occurred converting data from the MySQL
        character set to the associated DB2 coded character set
        identifier (CCSID).Omit the incompatible characters or alter the
        table to specify a different character set for the column.
2524    An invalid name was specified for ibmdb2i_rdb_name.  *
        Resolution:* Specify a valid relational database (RDB) name.
2525    A duplicate key was encountered for index '%.128s'.
        *Resolution:* : Specify a unique key value for the row.
        Generally, this error occurs if a unique constraint or index has
        been applied to the table from a non-MySQL interface.
2528    Some attribute(s) defined for column '%.128s' may not be honored
        by accesses from DB2.


File: manual.info,  Node: merge-storage-engine,  Next: memory-storage-engine,  Prev: se-db2,  Up: storage-engines

14.8 The MERGE Storage Engine
=============================

* Menu:

* merge-table-advantages::       MERGE Table Advantages and Disadvantages
* merge-table-problems::         MERGE Table Problems

The `MERGE' storage engine, also known as the `MRG_MyISAM' engine, is a
collection of identical `MyISAM' tables that can be used as one.
`Identical' means that all tables have identical column and index
information. You cannot merge `MyISAM' tables in which the columns are
listed in a different order, do not have exactly the same columns, or
have the indexes in different order. However, any or all of the
`MyISAM' tables can be compressed with *Note `myisampack': myisampack.
See *Note myisampack::. Differences in table options such as
`AVG_ROW_LENGTH', `MAX_ROWS', or `PACK_KEYS' do not matter.

An alternative to a `MERGE' table is a partitioned table, which stores
partitions of a single table in separate files.  Partitioning enables
some operations to be performed more efficiently and is not limited to
the `MyISAM' storage engine. For more information, see *Note
partitioning::.

When you create a `MERGE' table, MySQL creates two files on disk. The
files have names that begin with the table name and have an extension
to indicate the file type. An `.frm' file stores the table format, and
an `.MRG' file contains the names of the underlying `MyISAM' tables
that should be used as one. The tables do not have to be in the same
database as the `MERGE' table.

You can use *Note `SELECT': select, *Note `DELETE': delete, *Note
`UPDATE': update, and *Note `INSERT': insert. on `MERGE' tables. You
must have `SELECT', `DELETE', and `UPDATE' privileges on the `MyISAM'
tables that you map to a `MERGE' table.

*Note*:

The use of `MERGE' tables entails the following security issue: If a
user has access to `MyISAM' table T, that user can create a `MERGE'
table M that accesses T. However, if the user's privileges on T are
subsequently revoked, the user can continue to access T by doing so
through M.

Use of *Note `DROP TABLE': drop-table. with a `MERGE' table drops only
the `MERGE' specification. The underlying tables are not affected.

To create a `MERGE' table, you must specify a `UNION=(LIST-OF-TABLES)'
option that indicates which `MyISAM' tables to use.  You can optionally
specify an `INSERT_METHOD' option to control how inserts into the
`MERGE' table take place. Use a value of `FIRST' or `LAST' to cause
inserts to be made in the first or last underlying table, respectively.
If you specify no `INSERT_METHOD' option or if you specify it with a
value of `NO', inserts into the `MERGE' table are not permitted and
attempts to do so result in an error.

The following example shows how to create a `MERGE' table:


     mysql> CREATE TABLE t1 (
         ->    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         ->    message CHAR(20)) ENGINE=MyISAM;
     mysql> CREATE TABLE t2 (
         ->    a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         ->    message CHAR(20)) ENGINE=MyISAM;
     mysql> INSERT INTO t1 (message) VALUES ('Testing'),('table'),('t1');
     mysql> INSERT INTO t2 (message) VALUES ('Testing'),('table'),('t2');
     mysql> CREATE TABLE total (
         ->    a INT NOT NULL AUTO_INCREMENT,
         ->    message CHAR(20), INDEX(a))
         ->    ENGINE=MERGE UNION=(t1,t2) INSERT_METHOD=LAST;

Note that column `a' is indexed as a `PRIMARY KEY' in the underlying
`MyISAM' tables, but not in the `MERGE' table. There it is indexed but
not as a `PRIMARY KEY' because a `MERGE' table cannot enforce
uniqueness over the set of underlying tables.  (Similarly, a column
with a `UNIQUE' index in the underlying tables should be indexed in the
`MERGE' table but not as a `UNIQUE' index.)

After creating the `MERGE' table, you can use it to issue queries that
operate on the group of tables as a whole:


     mysql> SELECT * FROM total;
     +---+---------+
     | a | message |
     +---+---------+
     | 1 | Testing |
     | 2 | table   |
     | 3 | t1      |
     | 1 | Testing |
     | 2 | table   |
     | 3 | t2      |
     +---+---------+

To remap a `MERGE' table to a different collection of `MyISAM' tables,
you can use one of the following methods:

   * `DROP' the `MERGE' table and re-create it.

   * Use `ALTER TABLE TBL_NAME UNION=(...)' to change the list of
     underlying tables.

     Beginning with MySQL 5.1.24, it is also possible to use `ALTER
     TABLE ... UNION=()' (that is, with an empty *Note `UNION': union.
     clause) to remove all of the underlying tables. However, in this
     case, the table is effectively empty and inserts fail because
     there is no underlying table to take new rows. Such a table might
     be useful as a template for creating new `MERGE' tables with
     `CREATE TABLE ... LIKE'.

As of MySQL 5.1.15, the underlying table definitions and indexes must
conform more closely than previously to the definition of the `MERGE'
table. Conformance is checked when a table that is part of a `MERGE'
table is opened, not when the `MERGE' table is created. If any table
fails the conformance checks, the operation that triggered the opening
of the table fails. This means that changes to the definitions of
tables within a `MERGE' may cause a failure when the `MERGE' table is
accessed. The conformance checks applied to each table are:

   * The underlying table and the `MERGE' table must have the same
     number of columns.

   * The column order in the underlying table and the `MERGE' table
     must match.

   * Additionally, the specification for each corresponding column in
     the parent `MERGE' table and the underlying tables are compared
     and must satisfy these checks:

        * The column type in the underlying table and the `MERGE' table
          must be equal.

        * The column length in the underlying table and the `MERGE'
          table must be equal.

        * The column of the underlying table and the `MERGE' table can
          be `NULL'.

   * The underlying table must have at least as many indexes as the
     `MERGE' table. The underlying table may have more indexes than the
     `MERGE' table, but cannot have fewer.

     *Note*:

     A known issue exists where indexes on the same columns must be in
     identical order, in both the `MERGE' table and the underlying
     `MyISAM' table. See Bug #33653.

     Each index must satisfy these checks:

        * The index type of the underlying table and the `MERGE' table
          must be the same.

        * The number of index parts (that is, multiple columns within a
          compound index) in the index definition for the underlying
          table and the `MERGE' table must be the same.

        * For each index part:

             * Index part lengths must be equal.

             * Index part types must be equal.

             * Index part languages must be equal.

             * Check whether index parts can be `NULL'.

For information about the table checks applied prior to MySQL 5.1.15,
see *Note merge-table-problems::.

As of MySQL 5.1.20, if a `MERGE' table cannot be opened or used because
of a problem with an underlying table, *Note `CHECK TABLE':
check-table. displays information about which table caused the problem.

*Additional Resources*

   * A forum dedicated to the `MERGE' storage engine is available at
     `http://forums.mysql.com/list.php?93'.


File: manual.info,  Node: merge-table-advantages,  Next: merge-table-problems,  Prev: merge-storage-engine,  Up: merge-storage-engine

14.8.1 MERGE Table Advantages and Disadvantages
-----------------------------------------------

`MERGE' tables can help you solve the following problems:

   * Easily manage a set of log tables. For example, you can put data
     from different months into separate tables, compress some of them
     with *Note `myisampack': myisampack, and then create a `MERGE'
     table to use them as one.

   * Obtain more speed. You can split a large read-only table based on
     some criteria, and then put individual tables on different disks.
     A `MERGE' table structured this way could be much faster than
     using a single large table.

   * Perform more efficient searches. If you know exactly what you are
     looking for, you can search in just one of the underlying tables
     for some queries and use a `MERGE' table for others. You can even
     have many different `MERGE' tables that use overlapping sets of
     tables.

   * Perform more efficient repairs. It is easier to repair individual
     smaller tables that are mapped to a `MERGE' table than to repair a
     single large table.

   * Instantly map many tables as one. A `MERGE' table need not
     maintain an index of its own because it uses the indexes of the
     individual tables. As a result, `MERGE' table collections are
     _very_ fast to create or remap. (You must still specify the index
     definitions when you create a `MERGE' table, even though no
     indexes are created.)

   * If you have a set of tables from which you create a large table on
     demand, you can instead create a `MERGE' table from them on
     demand. This is much faster and saves a lot of disk space.

   * Exceed the file size limit for the operating system. Each `MyISAM'
     table is bound by this limit, but a collection of `MyISAM' tables
     is not.

   * You can create an alias or synonym for a `MyISAM' table by
     defining a `MERGE' table that maps to that single table.  There
     should be no really notable performance impact from doing this
     (only a couple of indirect calls and `memcpy()' calls for each
     read).

The disadvantages of `MERGE' tables are:

   * You can use only identical `MyISAM' tables for a `MERGE' table.

   * Some `MyISAM' features are unavailable in `MERGE' tables. For
     example, you cannot create `FULLTEXT' indexes on `MERGE' tables.
     (You can create `FULLTEXT' indexes on the underlying `MyISAM'
     tables, but you cannot search the `MERGE' table with a full-text
     search.)

   * If the `MERGE' table is nontemporary, all underlying `MyISAM'
     tables must be nontemporary. If the `MERGE' table is temporary,
     the `MyISAM' tables can be any mix of temporary and nontemporary.

   * `MERGE' tables use more file descriptors than `MyISAM' tables. If
     10 clients are using a `MERGE' table that maps to 10 tables, the
     server uses (10 x 10) + 10 file descriptors. (10 data file
     descriptors for each of the 10 clients, and 10 index file
     descriptors shared among the clients.)

   * Index reads are slower. When you read an index, the `MERGE'
     storage engine needs to issue a read on all underlying tables to
     check which one most closely matches a given index value. To read
     the next index value, the `MERGE' storage engine needs to search
     the read buffers to find the next value. Only when one index
     buffer is used up does the storage engine need to read the next
     index block. This makes `MERGE' indexes much slower on `eq_ref'
     searches, but not much slower on `ref' searches. For more
     information about `eq_ref' and `ref', see *Note explain::.


File: manual.info,  Node: merge-table-problems,  Prev: merge-table-advantages,  Up: merge-storage-engine

14.8.2 MERGE Table Problems
---------------------------

The following are known problems with `MERGE' tables:

   * In versions of MySQL Server prior to 5.1.23, it was possible to
     create temporary merge tables with nontemporary child MyISAM
     tables.

     From versions 5.1.23, MERGE children were locked through the
     parent table. If the parent was temporary, it was not locked and
     so the children were not locked either. Parallel use of the MyISAM
     tables corrupted them.

   * If you use *Note `ALTER TABLE': alter-table. to change a `MERGE'
     table to another storage engine, the mapping to the underlying
     tables is lost. Instead, the rows from the underlying `MyISAM'
     tables are copied into the altered table, which then uses the
     specified storage engine.

   * The `INSERT_METHOD' table option for a `MERGE' table indicates
     which underlying `MyISAM' table to use for inserts into the
     `MERGE' table. However, use of the `AUTO_INCREMENT' table option
     for that `MyISAM' table has no effect for inserts into the `MERGE'
     table until at least one row has been inserted directly into the
     `MyISAM' table.

   * A `MERGE' table cannot maintain uniqueness constraints over the
     entire table. When you perform an *Note `INSERT': insert, the data
     goes into the first or last `MyISAM' table (as determined by the
     `INSERT_METHOD' option). MySQL ensures that unique key values
     remain unique within that `MyISAM' table, but not over all the
     underlying tables in the collection.

   * Because the `MERGE' engine cannot enforce uniqueness over the set
     of underlying tables, *Note `REPLACE': replace. does not work as
     expected. The two key facts are:

        * *Note `REPLACE': replace. can detect unique key violations
          only in the underlying table to which it is going to write
          (which is determined by the `INSERT_METHOD' option). This
          differs from violations in the `MERGE' table itself.

        * If *Note `REPLACE': replace. detects a unique key violation,
          it will change only the corresponding row in the underlying
          table it is writing to; that is, the first or last table, as
          determined by the `INSERT_METHOD' option.

     Similar considerations apply for *Note `INSERT ... ON DUPLICATE
     KEY UPDATE': insert-on-duplicate.

   * `MERGE' tables do not support partitioning.  That is, you cannot
     partition a `MERGE' table, nor can any of a `MERGE' table's
     underlying `MyISAM' tables be partitioned.

   * You should not use *Note `ANALYZE TABLE': analyze-table, *Note
     `REPAIR TABLE': repair-table, *Note `OPTIMIZE TABLE':
     optimize-table, *Note `ALTER TABLE': alter-table, *Note `DROP
     TABLE': drop-table, *Note `DELETE': delete. without a `WHERE'
     clause, or *Note `TRUNCATE TABLE': truncate-table. on any of the
     tables that are mapped into an open `MERGE' table. If you do so,
     the `MERGE' table may still refer to the original table and yield
     unexpected results. To work around this problem, ensure that no
     `MERGE' tables remain open by issuing a *Note `FLUSH TABLES':
     flush.  statement prior to performing any of the named operations.

     The unexpected results include the possibility that the operation
     on the `MERGE' table will report table corruption. If this occurs
     after one of the named operations on the underlying `MyISAM'
     tables, the corruption message is spurious. To deal with this,
     issue a *Note `FLUSH TABLES': flush.  statement after modifying
     the `MyISAM' tables.

   * *Note `DROP TABLE': drop-table. on a table that is in use by a
     `MERGE' table does not work on Windows because the `MERGE' storage
     engine's table mapping is hidden from the upper layer of MySQL.
     Windows does not permit open files to be deleted, so you first must
     flush all `MERGE' tables (with *Note `FLUSH TABLES': flush.)  or
     drop the `MERGE' table before dropping the table.

   * As of MySQL 5.1.15, the definition of the `MyISAM' tables and the
     `MERGE' table are checked when the tables are accessed (for
     example, as part of a *Note `SELECT': select. or *Note `INSERT':
     insert. statement). The checks ensure that the definitions of the
     tables and the parent `MERGE' table definition match by comparing
     column order, types, sizes and associated indexes. If there is a
     difference between the tables, an error is returned and the
     statement fails. Because these checks take place when the tables
     are opened, any changes to the definition of a single table,
     including column changes, column ordering, and engine alterations
     will cause the statement to fail.

     Prior to MySQL 5.1.15, table checks are applied as follows:

        * When you create or alter `MERGE' table, there is no check to
          ensure that the underlying tables are existing `MyISAM'
          tables and have identical structures. When the `MERGE' table
          is used, MySQL checks that the row length for all mapped
          tables is equal, but this is not foolproof. If you create a
          `MERGE' table from dissimilar `MyISAM' tables, you are very
          likely to run into strange problems.

        * Similarly, if you create a `MERGE' table from non-`MyISAM'
          tables, or if you drop an underlying table or alter it to be a
          non-`MyISAM' table, no error for the `MERGE' table occurs
          until later when you attempt to use it.

        * Because the underlying `MyISAM' tables need not exist when
          the `MERGE' table is created, you can create the tables in
          any order, as long as you do not use the `MERGE' table until
          all of its underlying tables are in place. Also, if you can
          ensure that a `MERGE' table will not be used during a given
          period, you can perform maintenance operations on the
          underlying tables, such as backing up or restoring them,
          altering them, or dropping and recreating them. It is not
          necessary to redefine the `MERGE' table temporarily to
          exclude the underlying tables while you are operating on them.

   * The order of indexes in the `MERGE' table and its underlying
     tables should be the same. If you use *Note `ALTER TABLE':
     alter-table. to add a `UNIQUE' index to a table used in a `MERGE'
     table, and then use *Note `ALTER TABLE': alter-table. to add a
     nonunique index on the `MERGE' table, the index ordering is
     different for the tables if there was already a nonunique index in
     the underlying table. (This happens because *Note `ALTER TABLE':
     alter-table. puts `UNIQUE' indexes before nonunique indexes to
     facilitate rapid detection of duplicate keys.) Consequently,
     queries on tables with such indexes may return unexpected results.

   * If you encounter an error message similar to `ERROR 1017 (HY000):
     Can't find file: 'TBL_NAME.MRG' (errno: 2)', it generally
     indicates that some of the underlying tables do not use the
     `MyISAM' storage engine. Confirm that all of these tables are
     `MyISAM'.

   * The maximum number of rows in a `MERGE' table is 2^64 (~1.844E+19;
     the same as for a `MyISAM' table), provided that the server was
     built using the `--with-big-tables' option.  (All standard MySQL
     5.1 standard binaries are built with this option; for more
     information, see *Note source-configuration-options::.) It is not
     possible to merge multiple `MyISAM' tables into a single `MERGE'
     table that would have more than this number of rows.

   * The `MERGE' storage engine does not support *Note `INSERT
     DELAYED': insert-delayed. statements.

   * Use of underlying `MyISAM' tables of differing row formats with a
     parent `MERGE' table is currently known to fail. See Bug #32364.

   * As of MySQL 5.1.23, you cannot change the union list of a
     nontemporary `MERGE' table when *Note `LOCK TABLES': lock-tables.
     is in effect. The following does _not_ work:


          CREATE TABLE m1 ... ENGINE=MRG_MYISAM ...;
          LOCK TABLES t1 WRITE, t2 WRITE, m1 WRITE;
          ALTER TABLE m1 ... UNION=(t1,t2) ...;

     However, you can do this with a temporary `MERGE' table.

   * As of MySQL 5.1.23, you cannot create a `MERGE' table with `CREATE
     ...  SELECT', neither as a temporary `MERGE' table, nor as a
     nontemporary `MERGE' table. For example:

          CREATE TABLE m1 ... ENGINE=MRG_MYISAM ... SELECT ...;

     Attempts to do this result in an error: TBL_NAME is not `BASE
     TABLE'.

   * In some cases, differing `PACK_KEYS' table option values among the
     `MERGE' and underlying tables cause unexpected results if the
     underlying tables contain `CHAR' or `BINARY' columns. As a
     workaround, use `ALTER TABLE' to ensure that all involved tables
     have the same `PACK_KEYS' value. (Bug #50646)


File: manual.info,  Node: memory-storage-engine,  Next: example-storage-engine,  Prev: merge-storage-engine,  Up: storage-engines

14.9 The MEMORY Storage Engine
==============================

The `MEMORY' storage engine (formerly known as `HEAP') creates
special-purpose tables with contents that are stored in memory. Because
the data is vulnerable to crashes, hardware issues, or power outages,
only use these tables as temporary work areas or read-only caches for
data pulled from other tables.

*`MEMORY' Storage Engine Features*

*Storage limits* RAM      *Transactions*   No       *Locking         Table
                                                    granularity*     
*MVCC*           No       *Geospatial      No       *Geospatial      No
                          data type                 indexing         
                          support*                  support*         
*B-tree indexes* Yes      *T-tree indexes* No       *Hash indexes*   Yes
*Full-text       No       *Clustered       No       *Data caches*    N/A
search indexes*           indexes*                                   
*Index caches*   N/A      *Compressed      No       *Encrypted data  Yes
                          data*                     Implemented in   
                                                    the server (via  
                                                    encryption       
                                                    functions),      
                                                    rather than in   
                                                    the storage      
                                                    engine.*         
*Cluster         No       *Replication     Yes      *Foreign key     No
database                  support                   support*         
support*                  Implemented in                             
                          the server,                                
                          rather than in                             
                          the storage                                
                          engine.*                                   
*Backup /        Yes      *Query cache     Yes      *Update          Yes
point-in-time             support*                  statistics for   
recovery                                            data dictionary* 
Implemented in                                                       
the server,                                                          
rather than in                                                       
the storage                                                          
engine.*                                                             

When to Use MEMORY or MySQL Cluster

Developers looking to deploy applications that use the `MEMORY' storage
engine for important, highly available, or frequently updated data
should consider whether MySQL Cluster is a better choice. A typical use
case for the `MEMORY' engine involves these characteristics:

   * Operations involving transient, non-critical data such as session
     management or caching. When the MySQL server halts or restarts,
     the data in `MEMORY' tables is lost.

   * In-memory storage for fast access and low latency. Data volume can
     fit entirely in memory without causing the operating system to
     swap out virtual memory pages.

   * A read-only or read-mostly data access pattern (limited updates).

MySQL Cluster offers the same features as the `MEMORY' engine with
higher performance levels, and provides additional features not
available with `MEMORY':

   * Row-level locking and multiple-thread operation for low contention
     between clients.

   * Scalability even with statement mixes that include writes.

   * Optional disk-backed operation for data durability.

   * Shared-nothing architecture and multiple-host operation with no
     single point of failure, enabling 99.999% availability.

   * Automatic data distribution across nodes; application developers
     need not craft custom sharding or partitioning solutions.

   * Support for variable-length data types (including *Note `BLOB':
     blob. and *Note `TEXT': blob.) not supported by `MEMORY'.

For a white paper with more detailed comparison of the `MEMORY' storage
engine and MySQL Cluster, see Scaling Web Services with MySQL Cluster:
An Alternative to the MySQL Memory Storage Engine
(http://www.mysql.com/why-mysql/white-papers/mysql-wp_cluster-7.0_Cluster_MEMORY.php).
This white paper includes a performance study of the two technologies
and a step-by-step guide describing how existing `MEMORY' users can
migrate to MySQL Cluster.

*Performance Characteristics*

`MEMORY' performance is constrained by contention resulting from
single-thread execution and table lock overhead when processing
updates. This limits scalability when load increases, particularly for
statement mixes that include writes.

Despite the in-memory processing for `MEMORY' tables, they are not
necessarily faster than *Note `InnoDB': innodb-storage-engine. tables
on a busy server, for general-purpose queries, or under a read/write
workload. In particular, the table locking involved with performing
updates can slow down concurrent usage of `MEMORY' tables from multiple
sessions.

Depending on the kinds of queries performed on a `MEMORY' table, you
might create indexes as either the default hash data structure (for
looking up single values based on a unique key), or a general-purpose
B-tree data structure (for all kinds of queries involving equality,
inequality, or range operators such as less than or greater than). The
following sections illustrate the syntax for creating both kinds of
indexes. A common performance issue is using the default hash indexes
in workloads where B-tree indexes are more efficient.

*Physical Characteristics of MEMORY Tables*

The `MEMORY' storage engine associates each table with one disk file,
which stores the table definition (not the data). The file name begins
with the table name and has an extension of `.frm'.

`MEMORY' tables have the following characteristics:

   * Space for `MEMORY' tables is allocated in small blocks. Tables use
     100% dynamic hashing for inserts. No overflow area or extra key
     space is needed. No extra space is needed for free lists. Deleted
     rows are put in a linked list and are reused when you insert new
     data into the table.  `MEMORY' tables also have none of the
     problems commonly associated with deletes plus inserts in hashed
     tables.

   * `MEMORY' tables use a fixed-length row-storage format.
     Variable-length types such as *Note `VARCHAR': char. are stored
     using a fixed length.

   * `MEMORY' tables cannot contain *Note `BLOB': blob. or *Note
     `TEXT': blob. columns.

   * `MEMORY' includes support for `AUTO_INCREMENT' columns.

   * Non-`TEMPORARY' `MEMORY' tables are shared among all clients, just
     like any other non-`TEMPORARY' table.

*DDL Operations for MEMORY Tables*

To create a `MEMORY' table, specify the clause `ENGINE=MEMORY' on the
*Note `CREATE TABLE': create-table. statement.


     CREATE TABLE t (i INT) ENGINE = MEMORY;

As indicated by the engine name, `MEMORY' tables are stored in memory.
They use hash indexes by default, which makes them very fast for
single-value lookups, and very useful for creating temporary tables.
However, when the server shuts down, all rows stored in `MEMORY' tables
are lost. The tables themselves continue to exist because their
definitions are stored in `.frm' files on disk, but they are empty when
the server restarts.

This example shows how you might create, use, and remove a `MEMORY'
table:


     mysql> CREATE TABLE test ENGINE=MEMORY
         ->     SELECT ip,SUM(downloads) AS down
         ->     FROM log_table GROUP BY ip;
     mysql> SELECT COUNT(ip),AVG(down) FROM test;
     mysql> DROP TABLE test;

The maximum size of `MEMORY' tables is limited by the
`max_heap_table_size' system variable, which has a default value of
16MB. To enforce different size limits for `MEMORY' tables, change the
value of this variable. The value in effect for *Note `CREATE TABLE':
create-table, or a subsequent *Note `ALTER TABLE': alter-table. or
*Note `TRUNCATE TABLE': truncate-table, is the value used for the life
of the table. A server restart also sets the maximum size of existing
`MEMORY' tables to the global `max_heap_table_size' value. You can set
the size for individual tables as described later in this section.

*Indexes*

The `MEMORY' storage engine supports both `HASH' and `BTREE' indexes.
You can specify one or the other for a given index by adding a `USING'
clause as shown here:


     CREATE TABLE lookup
         (id INT, INDEX USING HASH (id))
         ENGINE = MEMORY;
     CREATE TABLE lookup
         (id INT, INDEX USING BTREE (id))
         ENGINE = MEMORY;

For general characteristics of B-tree and hash indexes, see *Note
mysql-indexes::.

`MEMORY' tables can have up to 64 indexes per table, 16 columns per
index and a maximum key length of 3072 bytes.

If a `MEMORY' table hash index has a high degree of key duplication
(many index entries containing the same value), updates to the table
that affect key values and all deletes are significantly slower. The
degree of this slowdown is proportional to the degree of duplication
(or, inversely proportional to the index cardinality). You can use a
`BTREE' index to avoid this problem.

`MEMORY' tables can have nonunique keys. (This is an uncommon feature
for implementations of hash indexes.)

Columns that are indexed can contain `NULL' values.

*User-Created and Temporary Tables*

`MEMORY' table contents are stored in memory, which is a property that
`MEMORY' tables share with internal temporary tables that the server
creates on the fly while processing queries. However, the two types of
tables differ in that `MEMORY' tables are not subject to storage
conversion, whereas internal temporary tables are:

   * If an internal temporary table becomes too large, the server
     automatically converts it to on-disk storage, as described in
     *Note internal-temporary-tables::.

   * User-created `MEMORY' tables are never converted to disk tables.

*Loading Data*

To populate a `MEMORY' table when the MySQL server starts, you can use
the `--init-file' option. For example, you can put statements such as
*Note `INSERT INTO ... SELECT': insert-select. or *Note `LOAD DATA
INFILE': load-data. into this file to load the table from a persistent
data source. See *Note server-options::, and *Note load-data::.

For loading data into `MEMORY' tables accessed by other sessions
concurrently, `MEMORY' supports *Note `INSERT DELAYED': insert-delayed.
See *Note insert-delayed::.

*MEMORY Tables and Replication*

A server's `MEMORY' tables become empty when it is shut down and
restarted. If the server is a replication master, its slaves are not
aware that these tables have become empty, so you see out-of-date
content if you select data from the tables on the slaves. To
synchronize master and slave `MEMORY' tables, when a `MEMORY' table is
used on a master for the first time since it was started, a *Note
`DELETE': delete. statement is written to the master's binary log, to
empty the table on the slaves also. The slave still has outdated data
in the table during the interval between the master's restart and its
first use of the table. To avoid this interval when a direct query to
the slave could return stale data, use the `--init-file' option to
populate the `MEMORY' table on the master at startup.

*Managing Memory Use*

The server needs sufficient memory to maintain all `MEMORY' tables that
are in use at the same time.

Memory is not reclaimed if you delete individual rows from a `MEMORY'
table. Memory is reclaimed only when the entire table is deleted.
Memory that was previously used for deleted rows is re-used for new
rows within the same table. To free all the memory used by a `MEMORY'
table when you no longer require its contents, execute *Note `DELETE':
delete.  or *Note `TRUNCATE TABLE': truncate-table. to remove all rows,
or remove the table altogether using *Note `DROP TABLE': drop-table. To
free up the memory used by deleted rows, use `ALTER TABLE
ENGINE=MEMORY' to force a table rebuild.

The memory needed for one row in a `MEMORY' table is calculated using
the following expression:


     SUM_OVER_ALL_BTREE_KEYS(MAX_LENGTH_OF_KEY + sizeof(char*) * 4)
     + SUM_OVER_ALL_HASH_KEYS(sizeof(char*) * 2)
     + ALIGN(LENGTH_OF_ROW+1, sizeof(char*))

`ALIGN()' represents a round-up factor to cause the row length to be an
exact multiple of the `char' pointer size. `sizeof(char*)' is 4 on
32-bit machines and 8 on 64-bit machines.

As mentioned earlier, the `max_heap_table_size' system variable sets
the limit on the maximum size of `MEMORY' tables. To control the
maximum size for individual tables, set the session value of this
variable before creating each table. (Do not change the global
`max_heap_table_size' value unless you intend the value to be used for
`MEMORY' tables created by all clients.) The following example creates
two `MEMORY' tables, with a maximum size of 1MB and 2MB, respectively:


     mysql> SET max_heap_table_size = 1024*1024;
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE TABLE t1 (id INT, UNIQUE(id)) ENGINE = MEMORY;
     Query OK, 0 rows affected (0.01 sec)

     mysql> SET max_heap_table_size = 1024*1024*2;
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE TABLE t2 (id INT, UNIQUE(id)) ENGINE = MEMORY;
     Query OK, 0 rows affected (0.00 sec)

Both tables revert to the server's global `max_heap_table_size' value
if the server restarts.

You can also specify a `MAX_ROWS' table option in *Note `CREATE TABLE':
create-table. statements for `MEMORY' tables to provide a hint about
the number of rows you plan to store in them. This does not enable the
table to grow beyond the `max_heap_table_size' value, which still acts
as a constraint on maximum table size. For maximum flexibility in being
able to use `MAX_ROWS', set `max_heap_table_size' at least as high as
the value to which you want each `MEMORY' table to be able to grow.

*Additional Resources*

A forum dedicated to the `MEMORY' storage engine is available at
`http://forums.mysql.com/list.php?92'.


File: manual.info,  Node: example-storage-engine,  Next: federated-storage-engine,  Prev: memory-storage-engine,  Up: storage-engines

14.10 The EXAMPLE Storage Engine
================================

The `EXAMPLE' storage engine is a stub engine that does nothing. Its
purpose is to serve as an example in the MySQL source code that
illustrates how to begin writing new storage engines. As such, it is
primarily of interest to developers.

To enable the `EXAMPLE' storage engine if you build MySQL from source,
invoke `configure' with the `--with-example-storage-engine' option.

To examine the source for the `EXAMPLE' engine, look in the
`storage/example' directory of a MySQL source distribution.

When you create an `EXAMPLE' table, the server creates a table format
file in the database directory. The file begins with the table name and
has an `.frm' extension. No other files are created. No data can be
stored into the table. Retrievals return an empty result.


     mysql> CREATE TABLE test (i INT) ENGINE = EXAMPLE;
     Query OK, 0 rows affected (0.78 sec)

     mysql> INSERT INTO test VALUES(1),(2),(3);
     ERROR 1031 (HY000): Table storage engine for 'test' doesn't »
                         have this option

     mysql> SELECT * FROM test;
     Empty set (0.31 sec)

The `EXAMPLE' storage engine does not support indexing.


File: manual.info,  Node: federated-storage-engine,  Next: archive-storage-engine,  Prev: example-storage-engine,  Up: storage-engines

14.11 The FEDERATED Storage Engine
==================================

* Menu:

* federated-description::        FEDERATED Storage Engine Overview
* federated-create::             How to Create FEDERATED Tables
* federated-usagenotes::         FEDERATED Storage Engine Notes and Tips
* federated-storage-engine-resources::  FEDERATED Storage Engine Resources

The `FEDERATED' storage engine lets you access data from a remote MySQL
database without using replication or cluster technology. Querying a
local `FEDERATED' table automatically pulls the data from the remote
(federated) tables. No data is stored on the local tables.

To include the `FEDERATED' storage engine if you build MySQL from
source, invoke `configure' with the `--with-federated-storage-engine'
option.

Beginning with MySQL 5.1.26, the `FEDERATED' storage engine is not
enabled by default in the running server; to enable `FEDERATED', you
must start the MySQL server binary using the `--federated' option.

To examine the source for the `FEDERATED' engine, look in the
`storage/federated' directory of a MySQL source distribution.


File: manual.info,  Node: federated-description,  Next: federated-create,  Prev: federated-storage-engine,  Up: federated-storage-engine

14.11.1 FEDERATED Storage Engine Overview
-----------------------------------------

When you create a table using one of the standard storage engines (such
as `MyISAM', `CSV' or `InnoDB'), the table consists of the table
definition and the associated data. When you create a `FEDERATED'
table, the table definition is the same, but the physical storage of
the data is handled on a remote server.

A `FEDERATED' table consists of two elements:

   * A _remote server_ with a database table, which in turn consists of
     the table definition (stored in the `.frm' file) and the
     associated table. The table type of the remote table may be any
     type supported by the remote `mysqld' server, including `MyISAM'
     or `InnoDB'.

   * A _local server_ with a database table, where the table definition
     matches that of the corresponding table on the remote server. The
     table definition is stored within the `.frm' file. However, there
     is no data file on the local server. Instead, the table definition
     includes a connection string that points to the remote table.

When executing queries and statements on a `FEDERATED' table on the
local server, the operations that would normally insert, update or
delete information from a local data file are instead sent to the remote
server for execution, where they update the data file on the remote
server or return matching rows from the remote server.

The basic structure of a `FEDERATED' table setup is shown in *Note
figure-se-federated-structure::.

FIGURE GOES HERE: FEDERATED Table Structure

When a client issues an SQL statement that refers to a `FEDERATED'
table, the flow of information between the local server (where the SQL
statement is executed) and the remote server (where the data is
physically stored) is as follows:

  1. The storage engine looks through each column that the `FEDERATED'
     table has and constructs an appropriate SQL statement that refers
     to the remote table.

  2. The statement is sent to the remote server using the MySQL client
     API.

  3. The remote server processes the statement and the local server
     retrieves any result that the statement produces (an affected-rows
     count or a result set).

  4. If the statement produces a result set, each column is converted
     to internal storage engine format that the `FEDERATED' engine
     expects and can use to display the result to the client that
     issued the original statement.

The local server communicates with the remote server using MySQL client
C API functions. It invokes *Note `mysql_real_query()':
mysql-real-query. to send the statement. To read a result set, it uses
*Note `mysql_store_result()': mysql-store-result. and fetches rows one
at a time using *Note `mysql_fetch_row()': mysql-fetch-row.


File: manual.info,  Node: federated-create,  Next: federated-usagenotes,  Prev: federated-description,  Up: federated-storage-engine

14.11.2 How to Create FEDERATED Tables
--------------------------------------

* Menu:

* federated-create-connection::  Creating a FEDERATED Table Using CONNECTION
* federated-create-server::      Creating a FEDERATED Table Using CREATE SERVER

To create a `FEDERATED' table you should follow these steps:

  1. Create the table on the remote server. Alternatively, make a note
     of the table definition of an existing table, perhaps using the
     *Note `SHOW CREATE TABLE': show-create-table.  statement.

  2. Create the table on the local server with an identical table
     definition, but adding the connection information that links the
     local table to the remote table.

For example, you could create the following table on the remote server:


     CREATE TABLE test_table (
         id     INT(20) NOT NULL AUTO_INCREMENT,
         name   VARCHAR(32) NOT NULL DEFAULT '',
         other  INT(20) NOT NULL DEFAULT '0',
         PRIMARY KEY  (id),
         INDEX name (name),
         INDEX other_key (other)
     )
     ENGINE=MyISAM
     DEFAULT CHARSET=latin1;

To create the local table that will be federated to the remote table,
there are two options available. You can either create the local table
and specify the connection string (containing the server name, login,
password) to be used to connect to the remote table using the
`CONNECTION', or you can use an existing connection that you have
previously created using the *Note `CREATE SERVER': create-server.
statement.

*Important*:

When you create the local table it _must_ have an identical field
definition to the remote table.

*Note*:

You can improve the performance of a `FEDERATED' table by adding
indexes to the table on the host. The optimization will occur because
the query sent to the remote server will include the contents of the
`WHERE' clause and will be sent to the remote server and subsequently
executed locally. This reduces the network traffic that would otherwise
request the entire table from the server for local processing.


File: manual.info,  Node: federated-create-connection,  Next: federated-create-server,  Prev: federated-create,  Up: federated-create

14.11.2.1 Creating a FEDERATED Table Using CONNECTION
.....................................................

To use the first method, you must specify the `CONNECTION' string after
the engine type in a *Note `CREATE TABLE': create-table. statement. For
example:


     CREATE TABLE federated_table (
         id     INT(20) NOT NULL AUTO_INCREMENT,
         name   VARCHAR(32) NOT NULL DEFAULT '',
         other  INT(20) NOT NULL DEFAULT '0',
         PRIMARY KEY  (id),
         INDEX name (name),
         INDEX other_key (other)
     )
     ENGINE=FEDERATED
     DEFAULT CHARSET=latin1
     CONNECTION='mysql://fed_user@remote_host:9306/federated/test_table';

*Note*:

`CONNECTION' replaces the `COMMENT' used in some previous versions of
MySQL.

The `CONNECTION' string contains the information required to connect to
the remote server containing the table that will be used to physically
store the data. The connection string specifies the server name, login
credentials, port number and database/table information. In the
example, the remote table is on the server `remote_host', using port
9306. The name and port number should match the host name (or IP
address) and port number of the remote MySQL server instance you want
to use as your remote table.

The format of the connection string is as follows:


     SCHEME://USER_NAME[:PASSWORD]@HOST_NAME[:PORT_NUM]/DB_NAME/TBL_NAME

Where:

   * SCHEME: A recognized connection protocol. Only `mysql' is
     supported as the SCHEME value at this point.

   * USER_NAME: The user name for the connection. This user must have
     been created on the remote server, and must have suitable
     privileges to perform the required actions (*Note `SELECT': select,
     *Note `INSERT': insert, *Note `UPDATE': update, and so forth) on
     the remote table.

   * PASSWORD: (Optional) The corresponding password for USER_NAME.

   * HOST_NAME: The host name or IP address of the remote server.

   * PORT_NUM: (Optional) The port number for the remote server. The
     default is 3306.

   * DB_NAME: The name of the database holding the remote table.

   * TBL_NAME: The name of the remote table. The name of the local and
     the remote table do not have to match.

Sample connection strings:


     CONNECTION='mysql://username:password@hostname:port/database/tablename'
     CONNECTION='mysql://username@hostname/database/tablename'
     CONNECTION='mysql://username:password@hostname/database/tablename'


File: manual.info,  Node: federated-create-server,  Prev: federated-create-connection,  Up: federated-create

14.11.2.2 Creating a FEDERATED Table Using CREATE SERVER
........................................................

If you are creating a number of `FEDERATED' tables on the same server,
or if you want to simplify the process of creating `FEDERATED' tables,
you can use the *Note `CREATE SERVER': create-server. statement to
define the server connection parameters, just as you would with the
`CONNECTION' string.

The format of the *Note `CREATE SERVER': create-server.  statement is:

     CREATE SERVER
     SERVER_NAME
     FOREIGN DATA WRAPPER WRAPPER_NAME
     OPTIONS (OPTION [, OPTION] ...)

The SERVER_NAME is used in the connection string when creating a new
`FEDERATED' table.

For example, to create a server connection identical to the
`CONNECTION' string:

     CONNECTION='mysql://fed_user@remote_host:9306/federated/test_table';

You would use the following statement:

     CREATE SERVER fedlink
     FOREIGN DATA WRAPPER mysql
     OPTIONS (USER 'fed_user', HOST 'remote_host', PORT 9306, DATABASE 'federated');

To create a `FEDERATED' table that uses this connection, you still use
the `CONNECTION' keyword, but specify the name you used in the *Note
`CREATE SERVER': create-server. statement.

     CREATE TABLE test_table (
         id     INT(20) NOT NULL AUTO_INCREMENT,
         name   VARCHAR(32) NOT NULL DEFAULT '',
         other  INT(20) NOT NULL DEFAULT '0',
         PRIMARY KEY  (id),
         INDEX name (name),
         INDEX other_key (other)
     )
     ENGINE=FEDERATED
     DEFAULT CHARSET=latin1
     CONNECTION='fedlink/test_table';

The connection name in this example contains the name of the connection
(`fedlink') and the name of the table (`test_table') to link to,
separated by a slash. If you specify only the connection name without a
table name, the table name of the local table is used instead.

For more information on *Note `CREATE SERVER': create-server, see *Note
create-server::.

The *Note `CREATE SERVER': create-server. statement accepts the same
arguments as the `CONNECTION' string. The *Note `CREATE SERVER':
create-server.  statement updates the rows in the `mysql.servers'
table. See the following table for information on the correspondence
between parameters in a connection string, options in the *Note `CREATE
SERVER': create-server. statement, and the columns in the
`mysql.servers' table. For reference, the format of the `CONNECTION'
string is as follows:


     SCHEME://USER_NAME[:PASSWORD]@HOST_NAME[:PORT_NUM]/DB_NAME/TBL_NAME

This table describes the correspondence between parameters in a
connection string, options in the *Note `CREATE SERVER': create-server.
statement, and the columns in the `mysql.servers' table.

Description        `CONNECTION'       *Note `CREATE      `mysql.servers'
                   string             SERVER':           column
                                      create-server.     
                                      option             
Connection scheme  SCHEME             `wrapper_name'     `Wrapper'
Remote user        USER_NAME          `USER'             `Username'
Remote password    PASSWORD           `PASSWORD'         `Password'
Remote host        HOST_NAME          `HOST'             `Host'
Remote port        PORT_NUM           `PORT'             `Port'
Remote database    DB_NAME            `DATABASE'         `Db'


File: manual.info,  Node: federated-usagenotes,  Next: federated-storage-engine-resources,  Prev: federated-create,  Up: federated-storage-engine

14.11.3 FEDERATED Storage Engine Notes and Tips
-----------------------------------------------

You should be aware of the following points when using the `FEDERATED'
storage engine:

   * `FEDERATED' tables may be replicated to other slaves, but you must
     ensure that the slave servers are able to use the user/password
     combination that is defined in the `CONNECTION' string (or the row
     in the `mysql.servers' table) to connect to the remote server.

The following items indicate features that the `FEDERATED' storage
engine does and does not support:

   * The remote server must be a MySQL server.

   * The remote table that a `FEDERATED' table points to _must_ exist
     before you try to access the table through the `FEDERATED' table.

   * It is possible for one `FEDERATED' table to point to another, but
     you must be careful not to create a loop.

   * A `FEDERATED' table does not support indexes per se. Because
     access to the table is handled remotely, it is the remote table
     that supports the indexes. Care should be taken when creating a
     `FEDERATED' table since the index definition from an equivalent
     `MyISAM' or other table may not be supported.  For example,
     creating a `FEDERATED' table with an index prefix on *Note
     `VARCHAR': char, *Note `TEXT': blob. or *Note `BLOB': blob.
     columns will fail. The following definition in `MyISAM' is valid:

          CREATE TABLE `T1`(`A` VARCHAR(100),UNIQUE KEY(`A`(30))) ENGINE=MYISAM;

     The key prefix in this example is incompatible with the
     `FEDERATED' engine, and the equivalent statement will fail:

          CREATE TABLE `T1`(`A` VARCHAR(100),UNIQUE KEY(`A`(30))) ENGINE=FEDERATED
            CONNECTION='MYSQL://127.0.0.1:3306/TEST/T1';

     If possible, you should try to separate the column and index
     definition when creating tables on both the remote server and the
     local server to avoid these index issues.

   * Internally, the implementation uses *Note `SELECT': select, *Note
     `INSERT': insert, *Note `UPDATE': update, and *Note `DELETE':
     delete, but not *Note `HANDLER': handler.

   * The `FEDERATED' storage engine supports *Note `SELECT': select,
     *Note `INSERT': insert, *Note `UPDATE': update, *Note `DELETE':
     delete, *Note `TRUNCATE TABLE': truncate-table, and indexes. It
     does not support *Note `ALTER TABLE': alter-table, or any Data
     Definition Language statements that directly affect the structure
     of the table, other than *Note `DROP TABLE': drop-table. The
     current implementation does not use prepared statements.

   * `FEDERATED' accepts *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate. statements, but if a duplicate-key violation
     occurs, the statement fails with an error.

   * Performance on a `FEDERATED' table when performing bulk inserts
     (for example, on a *Note `INSERT INTO ... SELECT ...':
     insert-select. statement) is slower than with other table types
     because each selected row is treated as an individual *Note
     `INSERT': insert. statement on the `FEDERATED' table.

   * Transactions are not supported.

   * Before MySQL 5.1.21, for a multiple-row insert into a `FEDERATED'
     table that refers to a remote transactional table, if the insert
     failed for a row due to constraint failure, the remote table would
     contain a partial commit (the rows preceding the failed one)
     instead of rolling back the statement completely. This occurred
     because the rows were treated as individual inserts.

     As of MySQL 5.1.21, `FEDERATED' performs bulk-insert handling such
     that multiple rows are sent to the remote table in a batch. This
     provides a performance improvement and enables the remote table to
     perform improvement. Also, if the remote table is transactional, it
     enables the remote storage engine to perform statement rollback
     properly should an error occur. This capability has the following
     limitations:

        * The size of the insert cannot exceed the maximum packet size
          between servers. If the insert exceeds this size, it is
          broken into multiple packets and the rollback problem can
          occur.

        * Bulk-insert handling does not occur for *Note `INSERT ... ON
          DUPLICATE KEY UPDATE': insert-on-duplicate.

   * There is no way for the `FEDERATED' engine to know if the remote
     table has changed. The reason for this is that this table must
     work like a data file that would never be written to by anything
     other than the database system. The integrity of the data in the
     local table could be breached if there was any change to the
     remote database.

   * When using a `CONNECTION' string, you cannot use an '@' character
     in the password. You can get round this limitation by using the
     *Note `CREATE SERVER': create-server. statement to create a server
     connection.

   * The `insert_id' and `timestamp' options are not propagated to the
     data provider.

   * Any *Note `DROP TABLE': drop-table. statement issued against a
     `FEDERATED' table drops only the local table, not the remote table.

   * `FEDERATED' tables do not work with the query cache.

   * User-defined partitioning is not supported for `FEDERATED' tables.
     Beginning with MySQL 5.1.15, it is no longer possible to create
     such tables at all.


File: manual.info,  Node: federated-storage-engine-resources,  Prev: federated-usagenotes,  Up: federated-storage-engine

14.11.4 FEDERATED Storage Engine Resources
------------------------------------------

The following additional resources are available for the `FEDERATED'
storage engine:

   * A forum dedicated to the `FEDERATED' storage engine is available at
     `http://forums.mysql.com/list.php?105'.


File: manual.info,  Node: archive-storage-engine,  Next: csv-storage-engine,  Prev: federated-storage-engine,  Up: storage-engines

14.12 The ARCHIVE Storage Engine
================================

The `ARCHIVE' storage engine is used for storing large amounts of data
without indexes in a very small footprint.

*`ARCHIVE' Storage Engine Features*

*Storage limits* None     *Transactions*   No       *Locking         Table
                                                    granularity*     
*MVCC*           No       *Geospatial      Yes      *Geospatial      No
                          data type                 indexing         
                          support*                  support*         
*B-tree indexes* No       *T-tree indexes* No       *Hash indexes*   No
*Full-text       No       *Clustered       No       *Data caches*    No
search indexes*           indexes*                                   
*Index caches*   No       *Compressed      Yes      *Encrypted data  Yes
                          data*                     Implemented in   
                                                    the server (via  
                                                    encryption       
                                                    functions),      
                                                    rather than in   
                                                    the storage      
                                                    engine.*         
*Cluster         No       *Replication     Yes      *Foreign key     No
database                  support                   support*         
support*                  Implemented in                             
                          the server,                                
                          rather than in                             
                          the storage                                
                          engine.*                                   
*Backup /        Yes      *Query cache     Yes      *Update          Yes
point-in-time             support*                  statistics for   
recovery                                            data dictionary* 
Implemented in                                                       
the server,                                                          
rather than in                                                       
the storage                                                          
engine.*                                                             

The `ARCHIVE' storage engine is included in MySQL binary distributions.
To enable this storage engine if you build MySQL from source, invoke
`configure' with the `--with-archive-storage-engine' option.

To examine the source for the `ARCHIVE' engine, look in the
`storage/archive' directory of a MySQL source distribution.

You can check whether the `ARCHIVE' storage engine is available with
the *Note `SHOW ENGINES': show-engines.  statement.

When you create an `ARCHIVE' table, the server creates a table format
file in the database directory. The file begins with the table name and
has an `.frm' extension. The storage engine creates other files, all
having names beginning with the table name. The data file has an
extension of `.ARZ'. (Prior to MySQL 5.1.15, a metadata file with an
extension of `.ARM' is created as well.)  An `.ARN' file may appear
during optimization operations.

The `ARCHIVE' engine supports *Note `INSERT': insert. and *Note
`SELECT': select, but not *Note `DELETE': delete, *Note `REPLACE':
replace, or *Note `UPDATE': update. It does support `ORDER BY'
operations, *Note `BLOB': blob. columns, and basically all but spatial
data types (see *Note spatial-datatypes::). The `ARCHIVE' engine uses
row-level locking.

As of MySQL 5.1.6, the `ARCHIVE' engine supports the `AUTO_INCREMENT'
column attribute. The `AUTO_INCREMENT' column can have either a unique
or nonunique index. Attempting to create an index on any other column
results in an error. The `ARCHIVE' engine also supports the
`AUTO_INCREMENT' table option in *Note `CREATE TABLE': create-table.
statements to specify the initial sequence value for a new table or
reset the sequence value for an existing table, respectively.

`ARCHIVE' does not support inserting a value into an `AUTO_INCREMENT'
column less than the current maximum column value. Attempts to do so
result in an `ER_DUP_KEY' error.

As of MySQL 5.1.6, the `ARCHIVE' engine ignores *Note `BLOB': blob.
columns if they are not requested and scans past them while reading.
Formerly, the following two statements had the same cost, but as of
5.1.6, the second is much more efficient than the first:


     SELECT a, b, blob_col FROM archive_table;
     SELECT a, b FROM archive_table;

*Storage:* Rows are compressed as they are inserted. The `ARCHIVE'
engine uses `zlib' lossless data compression (see
`http://www.zlib.net/'). You can use *Note `OPTIMIZE TABLE':
optimize-table. to analyze the table and pack it into a smaller format
(for a reason to use *Note `OPTIMIZE TABLE': optimize-table, see later
in this section). The engine also supports *Note `CHECK TABLE':
check-table. There are several types of insertions that are used:

   * An *Note `INSERT': insert. statement just pushes rows into a
     compression buffer, and that buffer flushes as necessary. The
     insertion into the buffer is protected by a lock.  A *Note
     `SELECT': select. forces a flush to occur, unless the only
     insertions that have come in were *Note `INSERT DELAYED':
     insert-delayed. (those flush as necessary). See *Note
     insert-delayed::.

   * A bulk insert is visible only after it completes, unless other
     inserts occur at the same time, in which case it can be seen
     partially. A *Note `SELECT': select. never causes a flush of a
     bulk insert unless a normal insert occurs while it is loading.

*Retrieval*: On retrieval, rows are uncompressed on demand; there is no
row cache. A *Note `SELECT': select. operation performs a complete
table scan: When a *Note `SELECT': select. occurs, it finds out how
many rows are currently available and reads that number of rows. *Note
`SELECT': select. is performed as a consistent read. Note that lots of
*Note `SELECT': select. statements during insertion can deteriorate the
compression, unless only bulk or delayed inserts are used. To achieve
better compression, you can use *Note `OPTIMIZE TABLE': optimize-table.
or *Note `REPAIR TABLE': repair-table. The number of rows in `ARCHIVE'
tables reported by *Note `SHOW TABLE STATUS': show-table-status. is
always accurate.  See *Note optimize-table::, *Note repair-table::, and
*Note show-table-status::.

*Warning*:

*Known issue*: After a binary upgrade to MySQL 5.1 from a MySQL 5.0
installation that contains *Note `ARCHIVE': archive-storage-engine.
tables:

   * Before MySQL 5.1.42, accessing those tables will cause the server
     to crash, even if you have run *Note `mysql_upgrade':
     mysql-upgrade. or *Note `CHECK TABLE ... FOR UPGRADE': check-table.

   * As of MySQL 5.1.42, the server will not open 5.0 *Note `ARCHIVE':
     archive-storage-engine. tables at all.

In either case, the solution is to use *Note `mysqldump': mysqldump. to
dump all 5.0 *Note `ARCHIVE': archive-storage-engine. tables before
upgrading, and reload them into MySQL 5.1 after upgrading. This problem
is fixed in MySQL 5.6.4: The server can open *Note `ARCHIVE':
archive-storage-engine. tables created in MySQL 5.0.  However, it
remains the recommended upgrade procedure to dump 5.0 *Note `ARCHIVE':
archive-storage-engine. tables before upgrading and reload after
upgrading.

*Additional Resources*

   * A forum dedicated to the `ARCHIVE' storage engine is available at
     `http://forums.mysql.com/list.php?112'.


File: manual.info,  Node: csv-storage-engine,  Next: blackhole-storage-engine,  Prev: archive-storage-engine,  Up: storage-engines

14.13 The CSV Storage Engine
============================

* Menu:

* se-csv-repair::                Repairing and Checking CSV Tables
* se-csv-limitations::           CSV Limitations

The `CSV' storage engine stores data in text files using
comma-separated values format.

To enable the `CSV' storage engine if you build MySQL from source,
invoke `configure' with the `--with-csv-storage-engine' option.

To examine the source for the `CSV' engine, look in the `storage/csv'
directory of a MySQL source distribution.

When you create a `CSV' table, the server creates a table format file
in the database directory. The file begins with the table name and has
an `.frm' extension. The storage engine also creates a data file. Its
name begins with the table name and has a `.CSV' extension. The data
file is a plain text file. When you store data into the table, the
storage engine saves it into the data file in comma-separated values
format.


     mysql> CREATE TABLE test (i INT NOT NULL, c CHAR(10) NOT NULL)
         -> ENGINE = CSV;
     Query OK, 0 rows affected (0.12 sec)

     mysql> INSERT INTO test VALUES(1,'record one'),(2,'record two');
     Query OK, 2 rows affected (0.00 sec)
     Records: 2  Duplicates: 0  Warnings: 0

     mysql> SELECT * FROM test;
     +------+------------+
     | i    | c          |
     +------+------------+
     |    1 | record one |
     |    2 | record two |
     +------+------------+
     2 rows in set (0.00 sec)

Starting with MySQL 5.1.9, creating a CSV table also creates a
corresponding Metafile that stores the state of the table and the
number of rows that exist in the table. The name of this file is the
same as the name of the table with the extension `CSM'.

If you examine the `test.CSV' file in the database directory created by
executing the preceding statements, its contents should look like this:


     "1","record one"
     "2","record two"

This format can be read, and even written, by spreadsheet applications
such as Microsoft Excel or StarOffice Calc.


File: manual.info,  Node: se-csv-repair,  Next: se-csv-limitations,  Prev: csv-storage-engine,  Up: csv-storage-engine

14.13.1 Repairing and Checking CSV Tables
-----------------------------------------

*Functionality introduced in version 5.1.9*

The CSV storage engines supports the `CHECK' and `REPAIR' statements to
verify and if possible repair a damaged CSV table.

When running the `CHECK' statement, the CSV file will be checked for
validity by looking for the correct field separators, escaped fields
(matching or missing quotation marks), the correct number of fields
compared to the table definition and the existence of a corresponding
CSV metafile. The first invalid row discovered will report an error.
Checking a valid table produces output like that shown below:

     mysql> check table csvtest;
     +--------------+-------+----------+----------+
     | Table        | Op    | Msg_type | Msg_text |
     +--------------+-------+----------+----------+
     | test.csvtest | check | status   | OK       |
     +--------------+-------+----------+----------+
     1 row in set (0.00 sec)

A check on a corrupted table returns a fault:

     mysql> check table csvtest;
     +--------------+-------+----------+----------+
     | Table        | Op    | Msg_type | Msg_text |
     +--------------+-------+----------+----------+
     | test.csvtest | check | error    | Corrupt  |
     +--------------+-------+----------+----------+
     1 row in set (0.01 sec)

If the check fails, the table is marked as crashed (corrupt). Once a
table has been marked as corrupt, it is automatically repaired when you
next run `CHECK' or execute a *Note `SELECT': select. statement. The
corresponding corrupt status and new status will be displayed when
running `CHECK':

     mysql> check table csvtest;
     +--------------+-------+----------+----------------------------+
     | Table        | Op    | Msg_type | Msg_text                   |
     +--------------+-------+----------+----------------------------+
     | test.csvtest | check | warning  | Table is marked as crashed |
     | test.csvtest | check | status   | OK                         |
     +--------------+-------+----------+----------------------------+
     2 rows in set (0.08 sec)

To repair a table you can use `REPAIR', this copies as many valid rows
from the existing CSV data as possible, and then replaces the existing
CSV file with the recovered rows.  Any rows beyond the corrupted data
are lost.

     mysql> repair table csvtest;
     +--------------+--------+----------+----------+
     | Table        | Op     | Msg_type | Msg_text |
     +--------------+--------+----------+----------+
     | test.csvtest | repair | status   | OK       |
     +--------------+--------+----------+----------+
     1 row in set (0.02 sec)

*Warning*:

Note that during repair, only the rows from the CSV file up to the
first damaged row are copied to the new table. All other rows from the
first damaged row to the end of the table are removed, even valid rows.


File: manual.info,  Node: se-csv-limitations,  Prev: se-csv-repair,  Up: csv-storage-engine

14.13.2 CSV Limitations
-----------------------

The `CSV' storage engine does not support indexing.

Partitioning is not supported for tables using the `CSV' storage
engine. Beginning with MySQL 5.1.12, it is no longer possible to create
partitioned `CSV' tables. (See Bug #19307)

Beginning with MySQL 5.1.23, all tables that you create using the `CSV'
storage engine must have the `NOT NULL' attribute on all columns.
However, for backward compatibility, you can continue to use tables
with nullable columns that were created in previous MySQL releases.
(Bug #32050)


File: manual.info,  Node: blackhole-storage-engine,  Prev: csv-storage-engine,  Up: storage-engines

14.14 The BLACKHOLE Storage Engine
==================================

The `BLACKHOLE' storage engine acts as a `black hole' that accepts data
but throws it away and does not store it. Retrievals always return an
empty result:


     mysql> CREATE TABLE test(i INT, c CHAR(10)) ENGINE = BLACKHOLE;
     Query OK, 0 rows affected (0.03 sec)

     mysql> INSERT INTO test VALUES(1,'record one'),(2,'record two');
     Query OK, 2 rows affected (0.00 sec)
     Records: 2  Duplicates: 0  Warnings: 0

     mysql> SELECT * FROM test;
     Empty set (0.00 sec)

To enable the `BLACKHOLE' storage engine if you build MySQL from
source, invoke `configure' with the `--with-blackhole-storage-engine'
option.

To examine the source for the `BLACKHOLE' engine, look in the `sql'
directory of a MySQL source distribution.

When you create a `BLACKHOLE' table, the server creates a table format
file in the database directory. The file begins with the table name and
has an `.frm' extension. There are no other files associated with the
table.

The `BLACKHOLE' storage engine supports all kinds of indexes. That is,
you can include index declarations in the table definition.

You can check whether the `BLACKHOLE' storage engine is available with
the *Note `SHOW ENGINES': show-engines. statement.

Inserts into a `BLACKHOLE' table do not store any data, but if
statement based binary logging is enabled, the SQL statements are
logged and replicated to slave servers. This can be useful as a
repeater or filter mechanism.

*Note*:

When using the row based format for the binary log, updates and deletes
are skipped, and neither logged nor applied. For this reason, you
should use STATEMENT for the binary logging format, and not ROW or
MIXED.

Suppose that your application requires slave-side filtering rules, but
transferring all binary log data to the slave first results in too much
traffic. In such a case, it is possible to set up on the master host a
`dummy' slave process whose default storage engine is `BLACKHOLE',
depicted as follows:

Replication using `BLACKHOLE' for filtering

The master writes to its binary log. The `dummy' *Note `mysqld':
mysqld. process acts as a slave, applying the desired combination of
`replicate-do-*' and `replicate-ignore-*' rules, and writes a new,
filtered binary log of its own. (See *Note replication-options::.) This
filtered log is provided to the slave.

The dummy process does not actually store any data, so there is little
processing overhead incurred by running the additional *Note `mysqld':
mysqld. process on the replication master host.  This type of setup can
be repeated with additional replication slaves.

*Note `INSERT': insert. triggers for `BLACKHOLE' tables work as
expected. However, because the `BLACKHOLE' table does not actually
store any data, *Note `UPDATE': update. and *Note `DELETE': delete.
triggers are not activated: The `FOR EACH ROW' clause in the trigger
definition does not apply because there are no rows.

Other possible uses for the `BLACKHOLE' storage engine include:

   * Verification of dump file syntax.

   * Measurement of the overhead from binary logging, by comparing
     performance using `BLACKHOLE' with and without binary logging
     enabled.

   * `BLACKHOLE' is essentially a `no-op' storage engine, so it could
     be used for finding performance bottlenecks not related to the
     storage engine itself.

The `BLACKHOLE' storage engine does not support *Note `INSERT DELAYED':
insert-delayed, *Note `LOCK TABLES': lock-tables, or *Note `UNLOCK
TABLES': lock-tables.  statements prior to MySQL 5.1.19.

As of MySQL 5.1.4, the `BLACKHOLE' engine is transaction-aware, in the
sense that committed transactions are written to the binary log and
rolled-back transactions are not.

*Blackhole Engine and Auto Increment Columns*

The Blackhole engine is a no-op engine. Any operations performed on a
table using Blackhole will have no effect. This should be born in mind
when considering the behavior of primary key columns that auto
increment. The engine will not automatically increment field values,
and does not retain auto increment field state. This has important
implications in replication.

Consider the following replication scenario where all three of the
following conditions apply:

  1. On a master server there is a blackhole table with an auto
     increment field that is a primary key.

  2. On a slave the same table exists but using the MyISAM engine.

  3. Inserts are performed into the master's table without explicitly
     setting the auto increment value in the `INSERT' statement itself
     or through using a `SET INSERT_ID' statement.

In this scenario replication will fail with a duplicate entry error on
the primary key column.

In statement based replication, the value of `INSERT_ID' in the context
event will always be the same. Replication will therefore fail due to
trying insert a row with a duplicate value for a primary key column.

In row based replication, the value that the engine returns for the row
always be the same for each insert. This will result in the slave
attempting to replay two insert log entries using the same value for
the primary key column, and so replication will fail.

*Column Filtering*

When using row-based replication, (`binlog_format=ROW'), a slave where
the last columns are missing from a table is supported, as described in
the section *Note replication-features-differing-tables::.

This filtering works on the slave side, that is, the columns are copied
to the slave before they are filtered out. There are at least two cases
where it is not desirable to copy the columns to the slave:

  1. If the data is confidential, so the slave server should not have
     access to it.

  2. If the master has many slaves, filtering before sending to the
     slaves may reduce network traffic.

Master column filtering can be achieved using the `BLACKHOLE' engine.
This is carried out in a way similar to how master table filtering is
achieved - by using the `BLACKHOLE' engine and the
`--replicate-do-table' or `--replicate-ignore-table' option.

The setup for the master is:


     CREATE TABLE t1 (public_col_1, ..., public_col_N,
                      secret_col_1, ..., secret_col_M) ENGINE=MyISAM;

The setup for the trusted slave is:


     CREATE TABLE t1 (public_col_1, ..., public_col_N) ENGINE=BLACKHOLE;

The setup for the untrusted slave is:

     CREATE TABLE t1 (public_col_1, ..., public_col_N) ENGINE=MyISAM;


File: manual.info,  Node: ha-overview,  Next: replication,  Prev: storage-engines,  Up: Top

15 High Availability and Scalability
************************************

* Menu:

* ha-ovm-template::              Oracle VM Template for MySQL Enterprise Edition
* ha-drbd::                      Overview of MySQL with DRBD/Pacemaker/Corosync/Oracle Linux
* ha-wfc::                       Overview of MySQL with Windows Failover Clustering
* ha-vm::                        Using MySQL within an Amazon EC2 Instance
* ha-zfs-replication::           Using ZFS Replication
* ha-memcached::                 Using MySQL with `memcached'
* mysql-proxy::                  MySQL Proxy

Data is the currency of today's web, mobile, social, enterprise and
cloud applications. Ensuring data is always available is a top priority
for any organization. Minutes of downtime can result in significant
loss of revenue and reputation.

There is no `one size fits all' approach to delivering High
Availability (HA). Unique application attributes, business
requirements, operational capabilities and legacy infrastructure can
all influence HA technology selection. And technology is only one
element in delivering HA: people and processes are just as critical as
the technology itself.

MySQL is deployed into many applications demanding availability and
scalability. *Availability* refers to the ability to cope with, and if
necessary recover from, failures on the host, including failures of
MySQL, the operating system, or the hardware and maintenance activity
that may otherwise cause downtime.  Scalability
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_scalability)
refers to the ability to spread both the database and the load of your
application queries across multiple MySQL servers.

Because each application has different operational and availability
requirements, MySQL offers a range of certified and supported
solutions, delivering the appropriate levels of High Availability (HA)
and scalability to meet service level requirements. Such solutions
extend from replication, through virtualization and geographically
redundant, multi-data center solutions delivering 99.999% uptime.

Selecting the right high availability solution for an application
largely depends on:

   * The level of availability required.

   * The type of application being deployed.

   * Accepted best practices within your own environment.

The primary solutions supported by MySQL include:

   * MySQL Replication. Learn more: *Note replication::

   * MySQL Cluster. Learn more: *Note mysql-cluster::

   * Oracle VM Template for MySQL. Learn more: *Note ha-ovm-template::.

   * MySQL with DRBD with Corosync and Pacemaker. Learn more: *Note
     ha-drbd::.

   * MySQL with Windows Failover Clustering. Learn more: *Note ha-wfc::.

   * MySQL with Solaris Cluster.  Learn more about Solaris Cluster.
     (http://www.oracle.com/technetwork/server-storage/solaris-cluster/overview/index.html)

Further options are available using third-party solutions.

Each architecture used to achieve highly available database services is
differentiated by the levels of uptime it offers. These architectures
can be grouped into three main categories:

   * Data Replication.

   * Clustered & Virtualized Systems.

   * Shared-Nothing, Geographically-Replicated Clusters.

As illustrated in the following figure, each of these architectures
offers progressively higher levels of uptime, which must be balanced
against potentially greater levels of cost and complexity that each can
incur. Simply deploying a high availability architecture is not a
guarantee of actually delivering HA. In fact, a poorly implemented and
maintained shared-nothing cluster could easily deliver lower levels of
availability than a simple data replication solution.

FIGURE GOES HERE: Tradeoffs: Cost and Complexity versus Availability

The following table compares the HA and Scalability capabilities of the
various MySQL solutions:

*Feature Comparison of MySQL HA Solutions*

Requirement    MySQL          DRBD           Oracle VM      MySQL Cluster
               Replication                   Template       
*Availability*                                              
Platform       All Supported  Linux          Oracle Linux   All Supported
Support        by MySQL                                     by MySQL
               Server                                       Cluster
               (`http://www.mysql.com/support/supportedplatforms/database.html')                              (`http://www.mysql.com/support/supportedplatforms/cluster.html')
Automated IP   No             Yes            Yes            Depends on
Failover                                                    Connector and
                                                            Configuration
Automated      No             Yes            Yes            Yes
Database                                                    
Failover                                                    
Automatic      No             Yes            N/A - Shared   Yes
Data                                         Storage        
Resynchronization                                             
Typical        User / Script  Configuration  Configuration  1 Second and
Failover Time  Dependent      Dependent, 60  Dependent, 60  Less
                              seconds and    seconds and    
                              Above          Above          
Synchronous    No,            Yes            N/A - Shared   Yes
Replication    Asynchronous                  Storage        
               and                                          
               Semisynchronous                              
Shared Storage No,            No,            Yes            No,
               Distributed    Distributed                   Distributed
Geographic     Yes            Yes, via       Yes, via       Yes, via
redundancy                    MySQL          MySQL          MySQL
support                       Replication    Replication    Replication
Update Schema  No             No             No             Yes
On-Line                                                     
*Scalability*                                               
Number of      One Master,    One Active     One Active     255
Nodes          Multiple       (primary),     (primary),     
               Slaves         one Passive    one Passive    
                              (secondary)    (secondary)    
                              Node           Node           
Built-in Load  Reads, via     Reads, via     Reads, via     Yes, Reads
Balancing      MySQL          MySQL          MySQL          and Writes
               Replication    Replication    Replication &  
                                             During         
                                             Failover       
Supports       Yes            Yes            Yes            Yes
Read-Intensive                                              
Workloads                                                   
Supports       Yes, via       Yes, via       Yes, via       Yes, via
Write-IntensiveApplication-LevelApplication-LevelApplication-LevelAuto-Sharding
Workloads      Sharding       Sharding to    Sharding to    
                              Multiple       Multiple       
                              Active/Passive Active/Passive 
                              Pairs          Pairs          
Scale On-Line  No             No             No             Yes
(add nodes,                                                 
repartition,                                                
etc.)                                                       


File: manual.info,  Node: ha-ovm-template,  Next: ha-drbd,  Prev: ha-overview,  Up: ha-overview

15.1 Oracle VM Template for MySQL Enterprise Edition
====================================================

Virtualization is a key technology to enable data center efficiency and
high availability while providing the foundation for cloud computing.
Integrating MySQL Enterprise Edition with Oracle Linux, the Oracle VM
Template is the fastest, easiest, and most reliable way to provision
virtualized MySQL instances, enabling users to meet the explosive
demand for highly available services.

The Oracle VM Template enables rapid deployment and eliminates manual
configuration efforts. It provides a preinstalled and pre-configured
virtualized MySQL 5.5 Enterprise Edition software image running on
Oracle Linux and Oracle VM, certified for production use. The MySQL
software image has undergone extensive integration and quality
assurance testing as part of the development process.

In addition to rapid provisioning, MySQL users also benefit from the
integrated high availability features of Oracle VM which are designed
to enable organizations to meet stringent SLA (Service Level Agreement)
demands through a combination of:

   * *Automatic recovery from failures*, with Oracle VM automatically
     restarting failed instances on available servers in the server
     pool after outages of the physical server, VM or MySQL database.

   * *Live Migration*, enabling operations staff to move running
     instances of MySQL to alternative hosts within a server pool
     during maintenance operations.

Instructions for the creation, deployment and use of the Oracle VM
Template for MySQL Enterprise Edition are available from:

   * The Oracle VM Template for MySQL Enterprise Edition whitepaper:
     `http://www.mysql.com/why-mysql/white-papers/mysql_wp_oracle-vm-template-for-mee.php'.

   * The README file accompanying the download of the Template.

To download the Oracle VM Template for MySQL Enterprise, go to
`https://edelivery.oracle.com/oraclevm' and follow these instructions:

   * Complete your registration information (Name, Company Name, Email
     Address and Country) and click on the download agreement.

   * Select "Oracle VM Templates" from the "Select a Product Pack"
     pull-down menu and click "Go".

   * Select MySQL Enterprise from the list of Oracle VM Templates.

   * Download and unzip the files and refer to the README for further
     instructions.


File: manual.info,  Node: ha-drbd,  Next: ha-wfc,  Prev: ha-ovm-template,  Up: ha-overview

15.2 Overview of MySQL with DRBD/Pacemaker/Corosync/Oracle Linux
================================================================

DRBD (Distributed Replication Block Device) is one of the leading
solutions for MySQL HA (High Availability). When combined with
Pacemaker and Corosync, users have:

   * An end-to-end, integrated stack of mature and proven open source
     technologies, fully supported by Oracle (as part of MySQL
     Enterprise Edition).

   * Automatic failover and recovery for service continuity.

   * Mirroring, via synchronous replication, to ensure failover between
     nodes without the risk of losing committed transactions.

   * Building of HA clusters from commodity hardware, without the
     requirement for shared-storage.

The following figure illustrates the stack that can be used to deliver
a level of High Availability for the MySQL service.

At the lowest level, 2 hosts are required in order to provide physical
redundancy; if using a virtual environment, those 2 hosts should be on
different physical machines. It is an important feature that no shared
storage is required. At any point in time, the services will be active
on one host and in standby mode on the other.

Pacemaker and Corosync combine to provide the clustering layer that
sits between the services and the underlying hosts and operating
systems. Pacemaker is responsible for starting and stopping services,
ensuring that they are running on exactly one host, thus delivering
high availability and avoiding data corruption. Corosync provides the
underlying messaging infrastructure between the nodes that enables
Pacemaker to do its job; it also handles the nodes membership within
the cluster and informs Pacemaker of any changes.

FIGURE GOES HERE: MySQL, DRBD, Pacemaker, and Corosync Stack

The core Pacemaker process does not have built-in knowledge of the
specific services to be managed; instead, it uses agents that provide a
wrapper for the service-specific actions. For example, in this solution
we use agents for Virtual IP Addresses, MySQL and DRBD: these are all
existing agents and come packaged with Pacemaker.

The essential services managed by Pacemaker in this configuration are
DRBD, MySQL and the Virtual IP Address that applications use to connect
to the active MySQL service.

DRBD synchronizes data at the block device (typically a spinning or
solid state disk) - transparent to the application, database and even
the file system. DRBD requires the use of a journaling file system such
as `ext3' or `ext4'.  For this solution, it acts in an active-standby
mode: at any point in time, the directories being managed by DRBD are
accessible for reads and writes on exactly one of the two hosts and
inaccessible (even for reads) on the other. Any changes made on the
active host are synchronously replicated to the standby host by DRBD.

Download the following guide for detailed instructions on installing,
configuring, provisioning and testing the complete MySQL and DRBD
stack, including:

   * MySQL Database.

   * DRBD kernel module and userland utilities.

   * Pacemaker and Corosync cluster messaging and management processes.

   * Oracle Linux operating system.

Download the guide at:
`http://www.mysql.com/why-mysql/white-papers/mysql-high-availability-drbd-configuration-deployment-guide/'.

*Support for DRBD*

The complete DRBD stack for MySQL has been certified by Oracle.
Commercial support, which provides a single point of contact for the
entire stack, whether issues relate to the operating system, DRBD,
clustering software or MySQL, is available to those who have both MySQL
Enterprise Edition (http://www.mysql.com/products/enterprise/) and
Oracle Linux Premier Support
(http://www.oracle.com/us/technologies/linux/support/overview/index.html)
contracts.


File: manual.info,  Node: ha-wfc,  Next: ha-vm,  Prev: ha-drbd,  Up: ha-overview

15.3 Overview of MySQL with Windows Failover Clustering
=======================================================

Microsoft Windows is consistently ranked as the top development
platform for MySQL, based on surveys of the MySQL user community.

MySQL Enterprise Edition is certified and supported with Windows Server
2008 R2 Failover Clustering (WSFC), enabling organizations to safely
deploy business-critical applications demanding high levels of
availability using Microsoft's native Windows clustering services.

The following figure illustrates the integration of MySQL with Windows
Server Failover Clustering to provide a highly available service:

FIGURE GOES HERE: Typical MySQL HA Configuration with Windows Server
Failover Clustering

In this architecture, MySQL is deployed in an Active / Passive
configuration. Failures of either MySQL or the underlying server are
automatically detected and the MySQL instance is restarted on the
Passive node. Applications accessing the database, as well as any MySQL
replication slaves, can automatically reconnect to the new MySQL
process using the same Virtual IP address once MySQL recovery has
completed and it starts accepting connections.

MySQL with Windows Failover Clustering requires at least 2 servers
within the cluster together with shared storage (for example, FC-AL SAN
or iSCSI disks).

The MySQL binaries and data files are stored in the shared storage and
Windows Failover Clustering ensures that only one of the cluster nodes
will access those files at any point in time.

Clients connect to the MySQL service through a Virtual IP Address
(VIP). In the event of failover they experience a brief loss of
connection, but otherwise do not need to be aware that the failover has
happened, other than to handle the failure of any transactions that
were active when the failover occurred.

You can learn more about configuring MySQL with Windows Server Failover
Clustering from the whitepaper posted here:
`http://www.mysql.com/why-mysql/white-papers/mysql_wp_windows_failover_clustering.php'

For background and usage information about Windows Server Failover
Clustering, see these pages on the Microsoft Technet site:

   * Failover Clustering
     (http://technet.microsoft.com/en-us/library/cc725923(v=ws.10).aspx)

   * Failover Clusters in Windows Server 2008 R2
     (http://technet.microsoft.com/en-us/library/ff182338(v=ws.10).aspx)


File: manual.info,  Node: ha-vm,  Next: ha-zfs-replication,  Prev: ha-wfc,  Up: ha-overview

15.4 Using MySQL within an Amazon EC2 Instance
==============================================

* Menu:

* ha-vm-aws-setup::              Setting Up MySQL on an EC2 AMI
* ha-vm-aws-instance::           EC2 Instance Limitations
* ha-vm-aws-deploy::             Deploying a MySQL Database Using EC2

The Amazon Elastic Compute Cloud (EC2) service provides virtual servers
that you can build and deploy to run a variety of different
applications and services, including MySQL. The EC2 service is based
around the Xen framework, supporting x86, Linux based, platforms with
individual instances of a virtual machine referred to as an Amazon
Machine Image (AMI). You have complete (root) access to the AMI
instance that you create, enabling you to configure and install your
AMI in any way you choose.

To use EC2, you create an AMI based on the configuration and
applications that you intend to use, and upload the AMI to the Amazon
Simple Storage Service (S3). From the S3 resource, you can deploy one
or more copies of the AMI to run as an instance within the EC2
environment. The EC2 environment provides management and control of the
instance and contextual information about the instance while it is
running.

Because you can create and control the AMI, the configuration, and the
applications, you can deploy and create any environment you choose.
This includes a basic MySQL server in addition to more extensive
replication, HA and scalability scenarios that enable you to take
advantage of the EC2 environment, and the ability to deploy additional
instances as the demand for your MySQL services and applications grow.

To aid the deployment and distribution of work, three different Amazon
EC2 instances are available, small (identified as `m1.small'), large
(`m1.large') and extra large (`m1.xlarge'). The different types provide
different levels of computing power measured in EC2 computer units
(ECU). A summary of the different instance configurations is shown in
the following table.

This table lists EC2 instance attributes and outlines attribute
configuration settings for Small, Large, and Extra Large EC2 instances.

EC2 Attribute      Small              Large              Extra Large
Platform           32-bit             64-bit             64-bit
CPU cores          1                  2                  4
ECUs               1                  4                  8
RAM                1.7GB              7.5GB              15GB
Storage            150GB              840GB              1680GB
I/O Performance    Medium             High               High

The typical model for deploying and using MySQL within the EC2
environment is to create a basic AMI that you can use to hold your
database data and application. Once the basic environment for your
database and application has been created you can then choose to deploy
the AMI to a suitable instance. Here the flexibility of having an AMI
that can be re-deployed from the small to the large or extra large EC2
instance makes it easy to upgrade the hardware environment without
rebuilding your application or database stack.

To get started with MySQL on EC2, including information on how to set
up and install MySQL within an EC2 installation and how to port and
migrate your data to the running instance, see *Note ha-vm-aws-setup::.

For tips and advice on how to create a scalable EC2 environment using
MySQL, including guides on setting up replication, see *Note
ha-vm-aws-deploy::.


File: manual.info,  Node: ha-vm-aws-setup,  Next: ha-vm-aws-instance,  Prev: ha-vm,  Up: ha-vm

15.4.1 Setting Up MySQL on an EC2 AMI
-------------------------------------

There are many different ways of setting up an EC2 AMI with MySQL,
including using any of the pre-configured AMIs supplied by Amazon.

The default _Getting Started_ AMI provided by Amazon uses Fedora Core
4, and you can install MySQL by using `yum':


     shell> yum install mysql

This installs both the MySQL server and the Perl DBD::mysql driver for
the Perl DBI API.

Alternatively, you can use one of the AMIs that include MySQL within
the standard installation.

Finally, you can also install a standard version of MySQL downloaded
from the MySQL Web site. The installation process and instructions are
identical to any other installation of MySQL on Linux. See *Note
installing::.

The standard configuration for MySQL places the data files in the
default location, `/var/lib/mysql'. The default data directory on an
EC2 instance is `/mnt' (although on the large and extra large instance
you can alter this configuration). You must edit `/etc/my.cnf' to set
the `datadir' option to point to the larger storage area.

*Important*:

The first time you use the main storage location within an EC2 instance
it needs to be initialized. The initialization process starts
automatically the first time you write to the device. You can start
using the device right away, but the write performance of the new
device is significantly lower on the initial writes until the
initialization process has finished.

To avoid this problem when setting up a new instance, you should start
the initialization process before populating your MySQL database. One
way to do this is to use `dd' to write to the file system:


     root-shell> dd if=/dev/zero of=initialize bs=1024M count=50

The preceding creates a 50GB on the file system and starts the
initialization process. Delete the file once the process has finished.

The initialization process can be time-consuming. On the small
instance, initialization takes between two and three hours. For the
large and extra large drives, the initialization can be 10 or 20 hours,
respectively.

In addition to configuring the correct storage location for your MySQL
data files, also consider setting the following other settings in your
instance before you save the instance configuration for deployment:

   * Set the MySQL server ID, so that when you use it for replication,
     the ID information is set correctly.

   * Enabling binary logging, so that replication can be initialized
     without starting and stopping the server.

   * Set the caching and memory parameters for your storage engines.
     There are no limitations or restrictions on what storage engines
     you use in your EC2 environment. Choose a configuration, possibly
     using one of the standard configurations provided with MySQL
     appropriate for the instance on which you expect to deploy. The
     large and extra large instances have RAM that can be dedicated to
     caching. Be aware that if you choose to install `memcached' on the
     servers as part of your application stack you must ensure there is
     enough memory for both MySQL and `memcached'.

Once you have configured your AMI with MySQL and the rest of your
application stack, save the AMI so that you can deploy and reuse the
instance.

Once you have your application stack configured in an AMI, populating
your MySQL database with data should be performed by creating a dump of
your database using `mysqldump', transferring the dump to the EC2
instance, and then reloading the information into the EC2 instance
database.

Before using your instance with your application in a production
situation, be aware of the limitations of the EC2 instance environment.
See *Note ha-vm-aws-instance::. To begin using your MySQL AMI, consult
the notes on deployment. See *Note ha-vm-aws-deploy::.


File: manual.info,  Node: ha-vm-aws-instance,  Next: ha-vm-aws-deploy,  Prev: ha-vm-aws-setup,  Up: ha-vm

15.4.2 EC2 Instance Limitations
-------------------------------

Be aware of the following limitations of the EC2 instances before
deploying your applications. Although these shouldn't affect your
ability to deploy within the Amazon EC2 environment, they may alter the
way you setup and configure your environment to support your
application.

   * Data stored within instances is not persistent. If you create an
     instance and populate the instance with data, then the data only
     remains in place while the machine is running, and does not
     survive a reboot. If you shut down the instance, any data it
     contained is lost.

     To ensure that you do not lose information, take regular backups
     using *Note `mysqldump': mysqldump. If the data being stored is
     critical, consider using replication to keep a `live' backup of
     your data in the event of a failure. When creating a backup, write
     the data to the Amazon S3 service to avoid the transfer charges
     applied when copying data offsite.

   * EC2 instances are not persistent. If the hardware on which an
     instance is running fails, the instance is shut down. This can
     lead to loss of data or service.

     However, if you use EBS, you can attach an EBS storage volume to
     an EC2 instance, and that EBS volume is persistent. Like a disk,
     an EBS volume can fail, but it is possible to create point-in-time
     snapshots of the volume. Snapshots are persisted to Amazon S3 and
     can be used to restore data in the event of volume failure.

   * To replicate your EC2 instances to a non-EC2 environment, be aware
     of the transfer costs to and from the EC2 service. Data transfer
     between different EC2 instances is free, so using replication
     within the EC2 environment does not incur additional charges.

   * Certain HA features are either not directly supported, or have
     limiting factors or problems that could reduce their utility.  For
     example, using DRBD or MySQL Cluster might not work. The default
     storage configuration is also not redundant. You can use
     software-based RAID to improve redundancy, but this implies a
     further performance hit.


File: manual.info,  Node: ha-vm-aws-deploy,  Prev: ha-vm-aws-instance,  Up: ha-vm

15.4.3 Deploying a MySQL Database Using EC2
-------------------------------------------

Because you cannot guarantee the uptime and availability of your EC2
instances, when deploying MySQL within the EC2 environment, use an
approach that enables you to easily distribute work among your EC2
instances. There are a number of ways of doing this.  Using sharding
techniques, where you split the application across multiple servers
dedicating specific blocks of your dataset and users to different
servers is an effective way of doing this. As a general rule, it is
easier to create more EC2 instances to support more users than to
upgrade the instance to a larger machine.

The EC2 architecture works best when you treat the EC2 instances as
temporary, cache-based solutions, rather than as a long-term, high
availability solution. In addition to using multiple machines, take
advantage of other services, such as `memcached' to provide additional
caching for your application to help reduce the load on the MySQL
server so that it can concentrate on writes. On the large and extra
large instances within EC2, the RAM available can provide a large memory
cache for data.

Most types of scale-out topology that you would use with your own
hardware can be used and applied within the EC2 environment.  However,
use the limitations and advice already given to ensure that any
potential failures do not lose you any data. Also, because the relative
power of each EC2 instance is so low, be prepared to alter your
application to use sharding and add further EC2 instances to improve
the performance of your application.

For example, take the typical scale-out environment shown following,
where a single master replicates to one or more slaves (three in this
example), with a web server running on each replication slave.

Typical standard scale-out structure

You can reproduce this structure completely within the EC2 environment,
using an EC2 instance for the master, and one instance for each of the
web and MySQL slave servers.

*Note*:

Within the EC2 environment, internal (private) IP addresses used by the
EC2 instances are constant. Always use these internal addresses and
names when communicating between instances. Only use public IP
addresses when communicating with the outside world - for example, when
publicizing your application.

To ensure reliability of your database, add at least one replication
slave dedicated to providing an active backup and storage to the Amazon
S3 facility. You can see an example of this in the following topology.

Typical standard scale-out structure with backup using EC2

*Using `memcached'* within your EC2 instances should provide better
performance. The large and extra large instances have a significant
amount of RAM. To use `memcached' in your application, when loading
information from the database, first check whether the item exists in
the cache. If the data you are looking for exists in the cache, use it.
If not, reload the data from the database and populate the cache.

*Sharding* divides up data in your entire database by allocating
individual machines or machine groups to provide a unique set of data
according to an appropriate group. For example, you might put all users
with a surname ending in the letters A-D onto a single server. When a
user connects to the application and their surname is known, queries
can be redirected to the appropriate MySQL server.

When using sharding with EC2, separate the web server and MySQL server
into separate EC2 instances, and then apply the sharding decision logic
into your application. Once you know which MySQL server you should be
using for accessing the data you then distribute queries to the
appropriate server. You can see a sample of this in the following
illustration.

Using sharding in EC2 to spread the load

*Warning*:

With sharding and EC2, be careful that the potential for failure of an
instance does not affect your application. If the EC2 instance that
provides the MySQL server for a particular shard fails, then all of the
data on that shard becomes unavailable.


File: manual.info,  Node: ha-zfs-replication,  Next: ha-memcached,  Prev: ha-vm,  Up: ha-overview

15.5 Using ZFS Replication
==========================

* Menu:

* ha-zfs-config::                Using ZFS for File System Replication
* ha-zfs-mysql::                 Configuring MySQL for ZFS Replication
* ha-zfs-mysql-recovery::        Handling MySQL Recovery with ZFS

To support high availability environments, providing an instant copy of
the information on both the currently active machine and the hot backup
is a critical part of the HA solution. There are many solutions to this
problem, including *Note replication:: and *Note ha-drbd::.

The ZFS file system provides functionality to create a snapshot of the
file system contents, transfer the snapshot to another machine, and
extract the snapshot to recreate the file system. You can create a
snapshot at any time, and you can create as many snapshots as you like.
By continually creating, transferring, and restoring snapshots, you can
provide synchronization between one or more machines in a fashion
similar to DRBD.

The following example shows a simple Solaris system running with a
single ZFS pool, mounted at `/scratchpool':


     Filesystem             size   used  avail capacity  Mounted on
     /dev/dsk/c0d0s0        4.6G   3.7G   886M    82%    /
     /devices                 0K     0K     0K     0%    /devices
     ctfs                     0K     0K     0K     0%    /system/contract
     proc                     0K     0K     0K     0%    /proc
     mnttab                   0K     0K     0K     0%    /etc/mnttab
     swap                   1.4G   892K   1.4G     1%    /etc/svc/volatile
     objfs                    0K     0K     0K     0%    /system/object
     /usr/lib/libc/libc_hwcap1.so.1
                            4.6G   3.7G   886M    82%    /lib/libc.so.1
     fd                       0K     0K     0K     0%    /dev/fd
     swap                   1.4G    40K   1.4G     1%    /tmp
     swap                   1.4G    28K   1.4G     1%    /var/run
     /dev/dsk/c0d0s7         26G   913M    25G     4%    /export/home
     scratchpool             16G    24K    16G     1%    /scratchpool

The MySQL data is stored in a directory on `/scratchpool'. To help
demonstrate some of the basic replication functionality, there are also
other items stored in `/scratchpool' as well:


     total 17
     drwxr-xr-x  31 root     bin           50 Jul 21 07:32 DTT/
     drwxr-xr-x   4 root     bin            5 Jul 21 07:32 SUNWmlib/
     drwxr-xr-x  14 root     sys           16 Nov  5 09:56 SUNWspro/
     drwxrwxrwx  19 1000     1000          40 Nov  6 19:16 emacs-22.1/

To create a snapshot of the file system, you use `zfs snapshot',
specifying the pool and the snapshot name:


     root-shell> zfs snapshot scratchpool@snap1

To list the snapshots already taken:


     root-shell> zfs list -t snapshot
     NAME                USED  AVAIL  REFER  MOUNTPOINT
     scratchpool@snap1      0      -  24.5K  -
     scratchpool@snap2      0      -  24.5K  -

The snapshots themselves are stored within the file system metadata,
and the space required to keep them varies as time goes on because of
the way the snapshots are created. The initial creation of a snapshot
is very quick, because instead of taking an entire copy of the data and
metadata required to hold the entire snapshot, ZFS records only the
point in time and metadata of when the snapshot was created.

As more changes to the original file system are made, the size of the
snapshot increases because more space is required to keep the record of
the old blocks. If you create lots of snapshots, say one per day, and
then delete the snapshots from earlier in the week, the size of the
newer snapshots might also increase, as the changes that make up the
newer state have to be included in the more recent snapshots, rather
than being spread over the seven snapshots that make up the week.

You cannot directly back up the snapshots because they exist within the
file system metadata rather than as regular files. To get the snapshot
into a format that you can copy to another file system, tape, and so
on, you use the `zfs send' command to create a stream version of the
snapshot.

For example, to write the snapshot out to a file:


     root-shell> zfs send scratchpool@snap1 >/backup/scratchpool-snap1

Or tape:


     root-shell> zfs send scratchpool@snap1 >/dev/rmt/0

You can also write out the incremental changes between two snapshots
using `zfs send':


     root-shell> zfs send scratchpool@snap1 scratchpool@snap2 >/backup/scratchpool-changes

To recover a snapshot, you use `zfs recv', which applies the snapshot
information either to a new file system, or to an existing one.


File: manual.info,  Node: ha-zfs-config,  Next: ha-zfs-mysql,  Prev: ha-zfs-replication,  Up: ha-zfs-replication

15.5.1 Using ZFS for File System Replication
--------------------------------------------

Because `zfs send' and `zfs recv' use streams to exchange data, you can
use them to replicate information from one system to another by
combining `zfs send', `ssh', and `zfs recv'.

For example, to copy a snapshot of the `scratchpool' file system to a
new file system called `slavepool' on a new server, you would use the
following command. This sequence combines the snapshot of
`scratchpool', the transmission to the slave machine (using `ssh' with
login credentials), and the recovery of the snapshot on the slave using
`zfs recv':


     root-shell> zfs send scratchpool@snap1 |ssh ID@HOST pfexec zfs recv -F slavepool

The first part of the pipeline, `zfs send scratchpool@snap1', streams
the snapshot. The `ssh' command, and the command that it executes on
the other server, `pfexec zfs recv -F slavepool', receives the streamed
snapshot data and writes it to slavepool. In this instance, I've
specified the `-F' option which forces the snapshot data to be applied,
and is therefore destructive. This is fine, as I'm creating the first
version of my replicated file system.

On the slave machine, the replicated file system contains the exact
same content:


     root-shell> ls -al /slavepool/
     total 23
     drwxr-xr-x   6 root     root           7 Nov  8 09:13 ./
     drwxr-xr-x  29 root     root          34 Nov  9 07:06 ../
     drwxr-xr-x  31 root     bin           50 Jul 21 07:32 DTT/
     drwxr-xr-x   4 root     bin            5 Jul 21 07:32 SUNWmlib/
     drwxr-xr-x  14 root     sys           16 Nov  5 09:56 SUNWspro/
     drwxrwxrwx  19 1000     1000          40 Nov  6 19:16 emacs-22.1/

Once a snapshot has been created, to synchronize the file system again,
you create a new snapshot and then use the incremental snapshot feature
of `zfs send' to send the changes between the two snapshots to the
slave machine again:


     root-shell> zfs send -i scratchpool@snapshot1 scratchpool@snapshot2 |ssh ID@HOST pfexec zfs recv slavepool

This operation only succeeds if the file system on the slave machine
has not been modified at all. You cannot apply the incremental changes
to a destination file system that has changed.  In the example above,
the `ls' command would cause problems by changing the metadata, such as
the last access time for files or directories.

To prevent changes on the slave file system, set the file system on the
slave to be read-only:


     root-shell> zfs set readonly=on slavepool

Setting `readonly' means that you cannot change the file system on the
slave by normal means, including the file system metadata. Operations
that would normally update metadata (like our `ls') silently perform
their function without attempting to update the file system state.

In essence, the slave file system is nothing but a static copy of the
original file system. However, even when configured to be read-only, a
file system can have snapshots applied to it. With the file system set
to read only, re-run the initial copy:


     root-shell> zfs send scratchpool@snap1 |ssh ID@HOST pfexec zfs recv -F slavepool

Now you can make changes to the original file system and replicate them
to the slave.


File: manual.info,  Node: ha-zfs-mysql,  Next: ha-zfs-mysql-recovery,  Prev: ha-zfs-config,  Up: ha-zfs-replication

15.5.2 Configuring MySQL for ZFS Replication
--------------------------------------------

Configuring MySQL on the source file system is a case of creating the
data on the file system that you intend to replicate. The configuration
file in the example below has been updated to use
`/scratchpool/mysql-data' as the data directory, and now you can
initialize the tables:


     root-shell> mysql_install_db --defaults-file=/etc/mysql/5.5/my.cnf --user=mysql

To synchronize the initial information, perform a new snapshot and then
send an incremental snapshot to the slave using `zfs send':


     root-shell> zfs snapshot scratchpool@snap2
     root-shell> zfs send -i scratchpool@snap1 scratchpool@snap2|ssh ID@HOST pfexec zfs recv slavepool

Doublecheck that the slave has the data by looking at the MySQL data
directory on the `slavepool':


     root-shell> ls -al /slavepool/mysql-data/

Now you can start up MySQL, create some data, and then replicate the
changes using `zfs send'/` zfs recv' to the slave to synchronize the
changes.

The rate at which you perform the synchronization depends on your
application and environment. The limitation is the speed required to
perform the snapshot and then to send the changes over the network.

To automate the process, create a script that performs the snapshot,
send, and receive operation, and use `cron' to synchronize the changes
at set times or intervals.


File: manual.info,  Node: ha-zfs-mysql-recovery,  Prev: ha-zfs-mysql,  Up: ha-zfs-replication

15.5.3 Handling MySQL Recovery with ZFS
---------------------------------------

When using ZFS replication to provide a constant copy of your data,
ensure that you can recover your tables, either manually or
automatically, in the event of a failure of the original system.

In the event of a failure, follow this sequence:

  1. Stop the script on the master, if it is still up and running.

  2. Set the slave file system to be read/write:


          root-shell> zfs set readonly=off slavepool

  3. Start up *Note `mysqld': mysqld. on the slave. If you are using
     `InnoDB', you get auto-recovery, if it is needed, to make sure the
     table data is correct, as shown here when I started up from our
     mid-INSERT snapshot:


          InnoDB: The log sequence number in ibdata files does not match
          InnoDB: the log sequence number in the ib_logfiles!
          081109 15:59:59  InnoDB: Database was not shut down normally!
          InnoDB: Starting crash recovery.
          InnoDB: Reading tablespace information from the .ibd files...
          InnoDB: Restoring possible half-written data pages from the doublewrite
          InnoDB: buffer...
          081109 16:00:03  InnoDB: Started; log sequence number 0 1142807951
          081109 16:00:03 [Note] /slavepool/mysql-5.0.67-solaris10-i386/bin/mysqld: ready for connections.
          Version: '5.0.67'  socket: '/tmp/mysql.sock'  port: 3306  MySQL Community Server (GPL)

Use *Note `InnoDB': innodb-storage-engine. tables and a regular
synchronization schedule to reduce the risk for significant data loss.
On MyISAM tables, you might need to run *Note `REPAIR TABLE':
repair-table, and you might even have lost some information.


File: manual.info,  Node: ha-memcached,  Next: mysql-proxy,  Prev: ha-zfs-replication,  Up: ha-overview

15.6 Using MySQL with `memcached'
=================================

* Menu:

* ha-memcached-install::         Installing `memcached'
* ha-memcached-using::           Using `memcached'
* ha-memcached-interfaces::      Developing a `memcached' Application
* ha-memcached-stats::           Getting `memcached' Statistics
* ha-memcached-faq::             `memcached' FAQ

`memcached' is a simple, highly scalable key-based cache that stores
data and objects wherever dedicated or spare RAM is available for quick
access by applications, without going through layers of parsing or disk
I/O. To use, you run the `memcached' command on one or more hosts and
then use the shared cache to store objects. For more usage instructions,
see *Note ha-memcached-using::

Benefits of using `memcached' include:

   * Because all information is stored in RAM, the access speed is
     faster than loading the information each time from disk.

   * Because the `value' portion of the key-value pair does not have
     any data type restrictions, you can cache data such as complex
     structures, documents, images, or a mixture of such things.

   * If you use the in-memory cache to hold transient information, or
     as a read-only cache for information also stored in a database,
     the failure of any `memcached' server is not critical. For
     persistent data, you can fall back to an alternative lookup method
     using database queries, and reload the data into RAM on a
     different server.

The typical usage environment is to modify your application so that
information is read from the cache provided by `memcached'. If the
information is not in `memcached', then the data is loaded from the
MySQL database and written into the cache so that future requests for
the same object benefit from the cached data.

For a typical deployment layout, see *Note ha-memcached-fig-overview::.

FIGURE GOES HERE: `memcached' Architecture Overview

In the example structure, any of the clients can contact one of the
`memcached' servers to request a given key. Each client is configured
to talk to all of the servers shown in the illustration. Within the
client, when the request is made to store the information, the key used
to reference the data is hashed and this hash is then used to select
one of the `memcached' servers. The selection of the `memcached' server
takes place on the client before the server is contacted, keeping the
process lightweight.

The same algorithm is used again when a client requests the same key.
The same key generates the same hash, and the same `memcached' server
is selected as the source for the data. Using this method, the cached
data is spread among all of the `memcached' servers, and the cached
information is accessible from any client. The result is a distributed,
memory-based, cache that can return information, particularly complex
data and structures, much faster than natively reading the information
from the database.

The data held within a traditional `memcached' server is never stored
on disk (only in RAM, which means there is no persistence of data), and
the RAM cache is always populated from the backing store (a MySQL
database). If a `memcached' server fails, the data can always be
recovered from the MySQL database.


File: manual.info,  Node: ha-memcached-install,  Next: ha-memcached-using,  Prev: ha-memcached,  Up: ha-memcached

15.6.1 Installing `memcached'
-----------------------------

You can build and install `memcached' from the source code directly, or
you can use an existing operating system package or installation.

*Installing `memcached' from a Binary Distribution*

To install `memcached' on a Red Hat, or Fedora host, use `yum':


     root-shell> yum install memcached

*Note*:

On CentOS, you may be able to obtain a suitable RPM from another
source, or use the source tarball.

To install `memcached' on a Debian or Ubuntu host, use `apt-get':


     root-shell> apt-get install memcached

To install `memcached' on a Gentoo host, use `emerge':


     root-shell> emerge install memcached

*Building `memcached' from Source*

On other Unix-based platforms, including Solaris, AIX, HP-UX and Mac OS
X, and Linux distributions not mentioned already, you must install from
source. For Linux, make sure you have a 2.6-based kernel, which
includes the improved `epoll' interface. For all platforms, ensure that
you have `libevent' 1.1 or higher installed. You can obtain `libevent'
from `libevent' web page (http://www.monkey.org/~provos/libevent/).

You can obtain the source for `memcached' from `memcached' Web site
(http://www.danga.com/memcached).

To build `memcached', follow these steps:

  1. Extract the `memcached' source package:


          shell> gunzip -c memcached-1.2.5.tar.gz | tar xf -

  2. Change to the `memcached-1.2.5 directory:'


          shell> cd memcached-1.2.5

  3. Run `configure'


          shell> ./configure

     Some additional options you might specify to the `configure':

        * `--prefix'

          To specify a different installation directory, use the
          `--prefix' option:


               shell> ./configure --prefix=/opt

          The default is to use the `/usr/local' directory.

        * `--with-libevent'

          If you have installed `libevent' and `configure' cannot find
          the library, use the `--with-libevent' option to specify the
          location of the installed library.

        * `--enable-64bit'

          To build a 64-bit version of `memcached' (which enables you
          to use a single instance with a large RAM allocation), use
          `--enable-64bit'.

        * `--enable-threads'

          To enable multi-threading support in `memcached', which
          improves the response times on servers with a heavy load, use
          `--enable-threads'. You must have support for the POSIX
          threads within your operating system to enable thread
          support. For more information on the threading support, see
          *Note ha-memcached-using-threads::.

        * `--enable-dtrace'

          `memcached' includes a range of DTrace threads that can be
          used to monitor and benchmark a `memcached' instance. For more
          information, see *Note ha-memcached-using-dtrace::.

  4. Run `make' to build `memcached':


          shell> make

  5. Run `make install' to install `memcached':


          shell> make install


File: manual.info,  Node: ha-memcached-using,  Next: ha-memcached-interfaces,  Prev: ha-memcached-install,  Up: ha-memcached

15.6.2 Using `memcached'
------------------------

* Menu:

* ha-memcached-using-deployment::  `memcached' Deployment
* ha-memcached-using-namespaces::  Using Namespaces
* ha-memcached-using-expiry::    Data Expiry
* ha-memcached-using-hashtypes::  `memcached' Hashing/Distribution Types
* ha-memcached-using-dtrace::    Using `memcached' and DTrace
* ha-memcached-using-memory::    Memory Allocation within `memcached'
* ha-memcached-using-threads::   `memcached' Thread Support
* ha-memcached-using-logs::      `memcached' Logs

To start using `memcached', start the `memcached' service on one or
more servers.  Running `memcached' sets up the server, allocates the
memory and starts listening for connections from clients.

*Note*:

You do not need to be a privileged user (`root') to run `memcached'
except to listen on one of the privileged TCP/IP ports (below 1024).
You must, however, use a user that has not had their memory limits
restricted using `setrlimit' or similar.

To start the server, run `memcached' as a nonprivileged (that is,
non-`root') user:


     shell> memcached

By default, `memcached' uses the following settings:

   * Memory allocation of 64MB

   * Listens for connections on all network interfaces, using port 11211

   * Supports a maximum of 1024 simultaneous connections

Typically, you would specify the full combination of options that you
want when starting `memcached', and normally provide a startup script
to handle the initialization of `memcached'. For example, the following
line starts `memcached' with a maximum of 1024MB RAM for the cache,
listening on port 11211 on the IP address 192.168.0.110, running as a
background daemon:


     shell> memcached -d -m 1024 -p 11211 -l 192.168.0.110

To ensure that `memcached' is started up on boot, check the init script
and configuration parameters.

`memcached' supports the following options:

   * `-u user'

     If you start `memcached' as `root', use the `-u' option to specify
     the user for executing `memcached':


          shell> memcached -u memcache

   * `-m memory'

     Set the amount of memory allocated to `memcached' for object
     storage. Default is 64MB.

     To increase the amount of memory allocated for the cache, use the
     `-m' option to specify the amount of RAM to be allocated (in
     megabytes). The more RAM you allocate, the more data you can store
     and therefore the more effective your cache is.

     *Warning*:

     Do not specify a memory allocation larger than your available RAM.
     If you specify too large a value, then some RAM allocated for
     `memcached' uses swap space, and not physical RAM. This may lead
     to delays when storing and retrieving values, because data is
     swapped to disk, instead of storing the data directly in RAM.

     You can use the output of the `vmstat' command to get the free
     memory, as shown in `free' column:


          shell> vmstat
          kthr      memory            page            disk          faults      cpu
          r b w   swap  free  re  mf pi po fr de sr s1 s2 -- --   in   sy   cs us sy id
          0 0 0 5170504 3450392 2  7  2  0  0  0  4  0  0  0  0  296   54  199  0  0 100

     For example, to allocate 3GB of RAM:


          shell> memcached -m 3072

     On 32-bit x86 systems where you are using PAE to access memory
     above the 4GB limit, you cannot allocate RAM beyond the maximum
     process size. You can get around this by running multiple
     instances of `memcached', each listening on a different port:


          shell> memcached -m 1024 -p11211
          shell> memcached -m 1024 -p11212
          shell> memcached -m 1024 -p11213

     *Note*:

     On all systems, particularly 32-bit, ensure that you leave enough
     room for both `memcached' application in addition to the memory
     setting. For example, if you have a dedicated `memcached' host
     with 4GB of RAM, do not set the memory size above 3500MB.  Failure
     to do this may cause either a crash or severe performance issues.

   * `-l interface'

     Specify a network interface/address to listen for connections.
     The default is to listen on all available address (`INADDR_ANY').


          shell> memcached -l 192.168.0.110

     Support for IPv6 address support was added in `memcached' 1.2.5.

   * `-p port'

     Specify the TCP port to use for connections. Default is 18080.


          shell> memcached -p 18080

   * `-U port'

     Specify the UDP port to use for connections. Default is 11211, 0
     switches UDP off.


          shell> memcached -U 18080

   * `-s socket'

     Specify a Unix socket to listen on.

     If you are running `memcached' on the same server as the clients,
     you can disable the network interface and use a local Unix socket
     using the `-s' option:


          shell> memcached -s /tmp/memcached

     Using a Unix socket automatically disables network support, and
     saves network ports (allowing more ports to be used by your web
     server or other process).

   * `-a mask'

     Specify the access mask to be used for the Unix socket, in octal.
     Default is 0700.

   * `-c connections'

     Specify the maximum number of simultaneous connections to the
     `memcached' service. The default is 1024.


          shell> memcached -c 2048

     Use this option, either to reduce the number of connections (to
     prevent overloading `memcached' service) or to increase the number
     to make more effective use of the server running `memcached'
     server.

   * `-t threads'

     Specify the number of threads to use when processing incoming
     requests.

     By default, `memcached' is configured to use 4 concurrent threads.
     The threading improves the performance of storing and retrieving
     data in the cache, using a locking system to prevent different
     threads overwriting or updating the same values. To increase or
     decrease the number of threads, use the `-t' option:


          shell> memcached -t 8

   * `-d'

     Run `memcached' as a daemon (background) process:


          shell> memcached -d

   * `-r'

     Maximize the size of the core file limit. In the event of a
     failure, this attempts to dump the entire memory space to disk as
     a core file, up to any limits imposed by `setrlimit'.

   * `-M'

     Return an error to the client when the memory has been exhausted.
     This replaces the normal behavior of removing older items from the
     cache to make way for new items.

   * `-k'

     Lock down all paged memory. This reserves the memory before use,
     instead of allocating new slabs of memory as new items are stored
     in the cache.

     *Note*:

     There is a user-level limit on how much memory you can lock.
     Trying to allocate more than the available memory fails. You can
     set the limit for the user you started the daemon with (not for
     the `-u user' user) within the shell by using `ulimit -S -l NUM_KB'

   * `-v'

     Verbose mode. Prints errors and warnings while executing the main
     event loop.

   * `-vv'

     Very verbose mode. In addition to information printed by `-v',
     also prints each client command and the response.

   * `-vvv'

     Extremely verbose mode. In addition to information printed by
     `-vv', also show the internal state transitions.

   * `-h'

     Print the help message and exit.

   * `-i'

     Print the `memcached' and `libevent' license.

   * `-I mem'

     Specify the maximum size permitted for storing an object within
     the `memcached' instance. The size supports a unit postfix (`k'
     for kilobytes, `m' for megabytes). For example, to increase the
     maximum supported object size to 32MB:


          shell> memcached -I 32m

     The maximum object size you can specify is 128MB, the default
     remains at 1MB.

     This option was added in 1.4.2.

   * `-b'

     Set the backlog queue limit. The backlog queue configures how many
     network connections can be waiting to be processed by `memcached'.
     Increasing this limit may reduce errors received by the client
     that it is not able to connect to the `memcached' instance, but
     does not improve the performance of the server. The default is
     1024.

   * `-P pidfile'

     Save the process ID of the `memcached' instance into `file'.

   * `-f'

     Set the chunk size growth factor. When allocating new memory
     chunks, the allocated size of new chunks is determined by
     multiplying the default slab size by this factor.

     To see the effects of this option without extensive testing, use
     the `-vv' command-line option to show the calculated slab sizes.
     For more information, see *Note ha-memcached-using-logs::.

   * `-n bytes'

     The minimum space allocated for the key+value+flags information.
     The default is 48 bytes.

   * `-L'

     On systems that support large memory pages, enables large memory
     page use. Using large memory pages enables `memcached' to allocate
     the item cache in one large chunk, which can improve the
     performance by reducing the number misses when accessing memory.

   * `-C'

     Disable the use of compare and swap (CAS) operations.

     This option was added in `memcached' 1.3.x.

   * `-D char'

     Set the default character to be used as a delimiter between the
     key prefixes and IDs. This is used for the per-prefix statistics
     reporting (see *Note ha-memcached-stats::). The default is the
     colon (`:'). If this option is used, statistics collection is
     turned on automatically. If not used, you can enable stats
     collection by sending the `stats detail on' command to the server.

     This option was added in `memcached' 1.3.x.

   * `-R num'

     Sets the maximum number of requests per event process. The default
     is 20.

   * `-B protocol'

     Set the binding protocol, that is, the default `memcached'
     protocol support for client connections. Options are `ascii',
     `binary' or `auto'.  Automatic (`auto') is the default.

     This option was added in `memcached' 1.4.0.


File: manual.info,  Node: ha-memcached-using-deployment,  Next: ha-memcached-using-namespaces,  Prev: ha-memcached-using,  Up: ha-memcached-using

15.6.2.1 `memcached' Deployment
...............................

When using `memcached' you can use a number of different potential
deployment strategies and topologies. The exact strategy to use depends
on your application and environment. When developing a system for
deploying `memcached' within your system, keep in mind the following
points:

   * `memcached' is only a caching mechanism. It shouldn't be used to
     store information that you cannot otherwise afford to lose and
     then load from a different location.

   * There is no security built into the `memcached' protocol. At a
     minimum, make sure that the servers running `memcached' are only
     accessible from inside your network, and that the network ports
     being used are blocked (using a firewall or similar). If the
     information on the `memcached' servers that is being stored is any
     sensitive, then encrypt the information before storing it in
     `memcached'.

   * `memcached' does not provide any sort of failover. Because there
     is no communication between different `memcached' instances. If an
     instance fails, your application must capable of removing it from
     the list, reloading the data and then writing data to another
     `memcached' instance.

   * Latency between the clients and the `memcached' can be a problem
     if you are using different physical machines for these tasks. If
     you find that the latency is a problem, move the `memcached'
     instances to be on the clients.

   * Key length is determined by the `memcached' server. The default
     maximum key size is 250 bytes.

   * Try to use at least two `memcached' instances, especially for
     multiple clients, to avoid having a single point of failure.
     Ideally, create as many `memcached' nodes as possible. When adding
     and removing `memcached' instances from a pool, the hashing and
     distribution of key/value pairs may be affected. For information
     on how to avoid problems, see *Note ha-memcached-using-hashtypes::.


File: manual.info,  Node: ha-memcached-using-namespaces,  Next: ha-memcached-using-expiry,  Prev: ha-memcached-using-deployment,  Up: ha-memcached-using

15.6.2.2 Using Namespaces
.........................

The `memcached' cache is a very simple massive key/value storage
system, and as such there is no way of compartmentalizing data
automatically into different sections.  For example, if you are storing
information by the unique ID returned from a MySQL database, then
storing the data from two different tables could run into issues
because the same ID might be valid in both tables.

Some interfaces provide an automated mechanism for creating
_namespaces_ when storing information into the cache. In practice,
these namespaces are merely a prefix before a given ID that is applied
every time a value is stored or retrieve from the cache.

You can implement the same basic principle by using keys that describe
the object and the unique identifier within the key that you supply
when the object is stored. For example, when storing user data, prefix
the ID of the user with `user:' or `user-'.

*Note*:

Using namespaces or prefixes only controls the keys stored/retrieved.
There is no security within `memcached', and therefore no way to enforce
that a particular client only accesses keys with a particular
namespace. Namespaces are only useful as a method of identifying data
and preventing corruption of key/value pairs.


File: manual.info,  Node: ha-memcached-using-expiry,  Next: ha-memcached-using-hashtypes,  Prev: ha-memcached-using-namespaces,  Up: ha-memcached-using

15.6.2.3 Data Expiry
....................

There are two types of data expiry within a `memcached' instance. The
first type is applied at the point when you store a new key/value pair
into the `memcached' instance. If there is not enough space within a
suitable slab to store the value, then an existing least recently used
(LRU) object is removed (evicted) from the cache to make room for the
new item.

The LRU algorithm ensures that the object that is removed is one that
is either no longer in active use or that was used so long ago that its
data is potentially out of date or of little value.  However, in a
system where the memory allocated to `memcached' is smaller than the
number of regularly used objects required in the cache, a lot of expired
items could be removed from the cache even though they are in active
use. You use the statistics mechanism to get a better idea of the level
of evictions (expired objects). For more information, see *Note
ha-memcached-stats::.

You can change this eviction behavior by setting the `-M' command-line
option when starting `memcached'. This option forces an error to be
returned when the memory has been exhausted, instead of automatically
evicting older data.

The second type of expiry system is an explicit mechanism that you can
set when a key/value pair is inserted into the cache, or when deleting
an item from the cache. Using an expiration time can be a useful way of
ensuring that the data in the cache is up to date and in line with your
application needs and requirements.

A typical scenario for explicitly setting the expiry time might include
caching session data for a user when accessing a Web site. `memcached'
uses a lazy expiry mechanism where the explicit expiry time that has
been set is compared with the current time when the object is
requested. Only objects that have not expired are returned.

You can also set the expiry time when explicitly deleting an object
from the cache. In this case, the expiry time is really a timeout and
indicates the period when any attempts to set the value for a given key
are rejected.


File: manual.info,  Node: ha-memcached-using-hashtypes,  Next: ha-memcached-using-dtrace,  Prev: ha-memcached-using-expiry,  Up: ha-memcached-using

15.6.2.4 `memcached' Hashing/Distribution Types
...............................................

The `memcached' client interface supports a number of different
distribution algorithms that are used in multi-server configurations to
determine which host should be used when setting or getting data from a
given `memcached' instance. When you get or set a value, a hash is
constructed from the supplied key and then used to select a host from
the list of configured servers. Because the hashing mechanism uses the
supplied key as the basis for the hash, the same server is selected
during both set and get operations.

You can think of this process as follows. Given an array of servers (a,
b, and c), the client uses a hashing algorithm that returns an integer
based on the key being stored or retrieved.  The resulting value is
then used to select a server from the list of servers configured in the
client. Most standard client hashing within `memcache' clients uses a
simple modulus calculation on the value against the number of
configured `memcached' servers. You can summarize the process in
pseudocode as:


     @memcservers = ['a.memc','b.memc','c.memc'];
     $value = hash($key);
     $chosen = $value % length(@memcservers);

Replacing the above with values:


     @memcservers = ['a.memc','b.memc','c.memc'];
     $value = hash('myid');
     $chosen = 7009 % 3;

In the above example, the client hashing algorithm chooses the server
at index 1 (`7009 % 3 = 1'), and store or retrieve the key and value
with that server.

*Note*:

This selection and hashing process is handled automatically by the
`memcached' client you are using; you need only provide the list of
`memcached' servers to use.

You can see a graphical representation of this below in *Note
ha-memcached-using-hashtypes-fig-selection::.

FIGURE GOES HERE: `memcached' Hash Selection

The same hashing and selection process takes place during any operation
on the specified key within the `memcached' client.

Using this method provides a number of advantages:

   * The hashing and selection of the server to contact is handled
     entirely within the client. This eliminates the need to perform
     network communication to determine the right machine to contact.

   * Because the determination of the `memcached' server occurs
     entirely within the client, the server can be selected
     automatically regardless of the operation being executed (set, get,
     increment, etc.).

   * Because the determination is handled within the client, the
     hashing algorithm returns the same value for a given key; values
     are not affected or reset by differences in the server environment.

   * Selection is very fast. The hashing algorithm on the key value is
     quick and the resulting selection of the server is from a simple
     array of available machines.

   * Using client-side hashing simplifies the distribution of data over
     each `memcached' server. Natural distribution of the values
     returned by the hashing algorithm means that keys are
     automatically spread over the available servers.

Providing that the list of servers configured within the client remains
the same, the same stored key returns the same value, and therefore
selects the same server.

However, if you do not use the same hashing mechanism then the same
data may be recorded on different servers by different interfaces, both
wasting space on your `memcached' and leading to potential differences
in the information.

*Note*:

One way to use a multi-interface compatible hashing mechanism is to use
the `libmemcached' library and the associated interfaces. Because the
interfaces for the different languages (including C, Ruby, Perl and
Python) use the same client library interface, they always generate the
same hash code from the ID.

The problem with client-side selection of the server is that the list
of the servers (including their sequential order) _must_ remain
consistent on each client using the `memcached' servers, and the
servers must be available. If you try to perform an operation on a key
when:

   * A new `memcached' instance has been added to the list of available
     instances

   * A `memcached' instance has been removed from the list of available
     instances

   * The order of the `memcached' instances has changed

When the hashing algorithm is used on the given key, but with a
different list of servers, the hash calculation may choose a different
server from the list.

If a new `memcached' instance is added into the list of servers, as
`new.memc' is in the example below, then a GET operation using the same
key, `myid', can result in a cache-miss. This is because the same value
is computed from the key, which selects the same index from the array
of servers, but index 2 now points to the new server, not the server
`c.memc' where the data was originally stored. This would result in a
cache miss, even though the key exists within the cache on another
`memcached' instance.

FIGURE GOES HERE: `memcached' Hash Selection with New `memcached'
instance

This means that servers `c.memc' and `new.memc ' both contain the
information for key `myid', but the information stored against the key
in eachs server may be different in each instance. A more significant
problem is a much higher number of cache-misses when retrieving data,
as the addition of a new server changes the distribution of keys, and
this in turn requires rebuilding the cached data on the `memcached'
instances, causing an increase in database reads.

The same effect can occur if you actively manage the list of servers
configured in your clients, adding and removing the configured
`memcached' instances as each instance is identified as being
available. For example, removing a `memcached' instance when the client
notices that the instance can no longer be contacted can cause the
server selection to fail as described here.

To prevent this causing significant problems and invalidating your
cache, you can select the hashing algorithm used to select the server.
There are two common types of hashing algorithm, _consistent_ and
_modula_.

With _consistent_ hashing algorithms, the same key when applied to a
list of servers always uses the same server to store or retrieve the
keys, even if the list of configured servers changes. This means that
you can add and remove servers from the configure list and always use
the same server for a given key. There are two types of consistent
hashing algorithms available, Ketama and Wheel. Both types are
supported by `libmemcached', and implementations are available for PHP
and Java.

Any consistent hashing algorithm has some limitations. When you add
servers to an existing list of configured servers, keys are distributed
to the new servers as part of the normal distribution. When you remove
servers from the list, the keys are re-allocated to another server
within the list, meaning that the cache needs to be re-populated with
the information. Also, a consistent hashing algorithm does not resolve
the issue where you want consistent selection of a server across
multiple clients, but where each client contains a different list of
servers. The consistency is enforced only within a single client.

With a _modula_ hashing algorithm, the client selects a server by first
computing the hash and then choosing a server from the list of
configured servers. As the list of servers changes, so the server
selected when using a modula hashing algorithm also changes. The result
is the behavior described above; changes to the list of servers mean
that different servers are selected when retrieving data, leading to
cache misses and increase in database load as the cache is re-seeded
with information.

If you use only a single `memcached' instance for each client, or your
list of `memcached' servers configured for a client never changes, then
the selection of a hashing algorithm is irrelevant, as it has no
noticeable effect.

If you change your servers regularly, or you use a common set of
servers that are shared among a large number of clients, then using a
consistent hashing algorithm should help to ensure that your cache data
is not duplicated and the data is evenly distributed.


File: manual.info,  Node: ha-memcached-using-dtrace,  Next: ha-memcached-using-memory,  Prev: ha-memcached-using-hashtypes,  Up: ha-memcached-using

15.6.2.5 Using `memcached' and DTrace
.....................................

`memcached' includes a number of different DTrace probes that can be
used to monitor the operation of the server. The probes included can
monitor individual connections, slab allocations, and modifications to
the hash table when a key/value pair is added, updated, or removed.

For more information on DTrace and writing DTrace scripts, read the
DTrace User Guide (http://docs.oracle.com/cd/E19253-01/819-5488/).

Support for DTrace probes was added to `memcached' 1.2.6 includes a
number of DTrace probes that can be used to help monitor your
application. DTrace is supported on Solaris 10, OpenSolaris, Mac OS X
10.5 and FreeBSD. To enable the DTrace probes in `memcached', build
from source and use the `--enable-dtrace' option. For more information,
see *Note ha-memcached-install::.

The probes supported by `memcached' are:

   * `conn-allocate(connid)'

     Fired when a connection object is allocated from the connection
     pool.

        * `connid': The connection ID.

   * `conn-release(connid)'

     Fired when a connection object is released back to the connection
     pool.

     Arguments:

        * `connid': The connection ID.

   * `conn-create(ptr)'

     Fired when a new connection object is being created (that is,
     there are no free connection objects in the connection pool).

     Arguments:

        * `ptr': A pointer to the connection.  object

   * `conn-destroy(ptr)'

     Fired when a connection object is being destroyed.

     Arguments:

        * `ptr': A pointer to the connection object.

   * `conn-dispatch(connid, threadid)'

     Fired when a connection is dispatched from the main or
     connection-management thread to a worker thread.

     Arguments:

        * `connid': The connection ID.

        * `threadid': The thread ID.

   * `slabs-allocate(size, slabclass, slabsize, ptr)'

     Allocate memory from the slab allocator.

     Arguments:

        * `size': The requested size.

        * `slabclass': The allocation is fulfilled in this class.

        * `slabsize': The size of each item in this class.

        * `ptr': A pointer to allocated memory.

   * `slabs-allocate-failed(size, slabclass)'

     Failed to allocate memory (out of memory).

     Arguments:

        * `size': The requested size.

        * `slabclass': The class that failed to fulfill the request.

   * `slabs-slabclass-allocate(slabclass)'

     Fired when a slab class needs more space.

     Arguments:

        * `slabclass': The class that needs more memory.

   * `slabs-slabclass-allocate-failed(slabclass)'

     Failed to allocate memory (out of memory).

     Arguments:

        * `slabclass': The class that failed to grab more memory.

   * `slabs-free(size, slabclass, ptr)'

     Release memory.

     Arguments:

        * `size': The amount of memory to release, in bytes.

        * `slabclass': The class the memory belongs to.

        * `ptr': A pointer to the memory to release.

   * `assoc-find(key, depth)'

     Fired when we have searched the hash table for a named key.  These
     two elements provide an insight into how well the hash function
     operates. Traversals are a sign of a less optimal function,
     wasting CPU capacity.

     Arguments:

        * `key': The key searched for.

        * `depth': The depth in the list of hash table.

   * `assoc-insert(key, nokeys)'

     Fired when a new item has been inserted.

     Arguments:

        * `key': The key just inserted.

        * `nokeys': The total number of keys currently being stored,
          including the key for which insert was called.

   * `assoc-delete(key, nokeys)'

     Fired when a new item has been removed.

     Arguments:

        * `key': The key just deleted.

        * `nokeys': The total number of keys currently being stored,
          excluding the key for which delete was called.

   * `item-link(key, size)'

     Fired when an item is being linked in the cache.

     Arguments:

        * `key': The items key.

        * `size': The size of the data.

   * `item-unlink(key, size)'

     Fired when an item is being deleted.

     Arguments:

        * `key': The items key.

        * `size': The size of the data.

   * `item-remove(key, size)'

     Fired when the refcount for an item is reduced.

     Arguments:

        * `key': The item's key.

        * `size': The size of the data.

   * `item-update(key, size)'

     Fired when the "last referenced" time is updated.

     Arguments:

        * `key': The item's key.

        * `size': The size of the data.

   * `item-replace(oldkey, oldsize, newkey, newsize)'

     Fired when an item is being replaced with another item.

     Arguments:

        * `oldkey': The key of the item to replace.

        * `oldsize': The size of the old item.

        * `newkey': The key of the new item.

        * `newsize': The size of the new item.

   * `process-command-start(connid, request, size)'

     Fired when the processing of a command starts.

     Arguments:

        * `connid': The connection ID.

        * `request': The incoming request.

        * `size': The size of the request.

   * `process-command-end(connid, response, size)'

     Fired when the processing of a command is done.

     Arguments:

        * `connid': The connection ID.

        * `response': The response to send back to the client.

        * `size': The size of the response.

   * `command-get(connid, key, size)'

     Fired for a `get' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The size of the key's data (or -1 if not found).

   * `command-gets(connid, key, size, casid)'

     Fired for a `gets' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The size of the key's data (or -1 if not found).

        * `casid': The casid for the item.

   * `command-add(connid, key, size)'

     Fired for a `add' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The new size of the key's data (or -1 if not found).

   * `command-set(connid, key, size)'

     Fired for a `set' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The new size of the key's data (or -1 if not found).

   * `command-replace(connid, key, size)'

     Fired for a `replace' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The new size of the key's data (or -1 if not found).

   * `command-prepend(connid, key, size)'

     Fired for a `prepend' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The new size of the key's data (or -1 if not found).

   * `command-append(connid, key, size)'

     Fired for a `append' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The new size of the key's data (or -1 if not found).

   * `command-cas(connid, key, size, casid)'

     Fired for a `cas' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `size': The size of the key's data (or -1 if not found).

        * `casid': The cas ID requested.

   * `command-incr(connid, key, val)'

     Fired for `incr' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `val': The new value.

   * `command-decr(connid, key, val)'

     Fired for `decr' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `val': The new value.

   * `command-delete(connid, key, exptime)'

     Fired for a `delete' command.

     Arguments:

        * `connid': The connection ID.

        * `key': The requested key.

        * `exptime': The expiry time.


File: manual.info,  Node: ha-memcached-using-memory,  Next: ha-memcached-using-threads,  Prev: ha-memcached-using-dtrace,  Up: ha-memcached-using

15.6.2.6 Memory Allocation within `memcached'
.............................................

When you first start `memcached', the memory that you have configured
is not automatically allocated.  Instead, `memcached' only starts
allocating and reserving physical memory once you start saving
information into the cache.

When you start to store data into the cache, `memcached' does not
allocate the memory for the data on an item by item basis. Instead, a
slab allocation is used to optimize memory usage and prevent memory
fragmentation when information expires from the cache.

With slab allocation, memory is reserved in blocks of 1MB. The slab is
divided up into a number of blocks of equal size. When you try to store
a value into the cache, `memcached' checks the size of the value that
you are adding to the cache and determines which slab contains the
right size allocation for the item. If a slab with the item size
already exists, the item is written to the block within the slab.

If the new item is bigger than the size of any existing blocks, then a
new slab is created, divided up into blocks of a suitable size. If an
existing slab with the right block size already exists, but there are
no free blocks, a new slab is created. If you update an existing item
with data that is larger than the existing block allocation for that
key, then the key is re-allocated into a suitable slab.

For example, the default size for the smallest block is 88 bytes (40
bytes of value, and the default 48 bytes for the key and flag data). If
the size of the first item you store into the cache is less than 40
bytes, then a slab with a block size of 88 bytes is created and the
value stored.

If the size of the data that you intend to store is larger than this
value, then the block size is increased by the chunk size factor until
a block size large enough to hold the value is determined. The block
size is always a function of the scale factor, rounded up to a block
size which is exactly divisible into the chunk size.

For a sample of the structure, see *Note ha-memcached-fig-slabs::.

FIGURE GOES HERE: Memory Allocation in `memcached'

The result is that you have multiple pages allocated within the range
of memory allocated to `memcached'. Each page is 1MB in size (by
default), and is split into a different number of chunks, according to
the chunk size required to store the key/value pairs. Each instance has
multiple pages allocated, and a page is always created when a new item
needs to be created requiring a chunk of a particular size. A slab may
consist of multiple pages, and each page within a slab contains an equal
number of chunks.

The chunk size of a new slab is determined by the base chunk size
combined with the chunk size growth factor. For example, if the initial
chunks are 104 bytes in size, and the default chunk size growth factor
is used (1.25), then the next chunk size allocated would be the best
power of 2 fit for 104*1.25, or 136 bytes.

Allocating the pages in this way ensures that memory does not get
fragmented. However, depending on the distribution of the objects that
you store, it may lead to an inefficient distribution of the slabs and
chunks if you have significantly different sized items. For example,
having a relatively small number of items within each chunk size may
waste a lot of memory with just few chunks in each allocated page.

You can tune the growth factor to reduce this effect by using the `-f'
command line option, which adapts the growth factor applied to make
more effective use of the chunks and slabs allocated. For information
on how to determine the current slab allocation statistics, see *Note
ha-memcached-stats-slabs::.

If your operating system supports it, you can also start `memcached'
with the `-L' command line option. This option preallocates all the
memory during startup using large memory pages. This can improve
performance by reducing the number of misses in the CPU memory cache.


File: manual.info,  Node: ha-memcached-using-threads,  Next: ha-memcached-using-logs,  Prev: ha-memcached-using-memory,  Up: ha-memcached-using

15.6.2.7 `memcached' Thread Support
...................................

If you enable the thread implementation within when building
`memcached' from source, then `memcached' uses multiple threads in
addition to the `libevent' system to handle requests.

When enabled, the threading implementation operates as follows:

   * Threading is handled by wrapping functions within the code to
     provide basic protection from updating the same global structures
     at the same time.

   * Each thread uses its own instance of the `libevent' to help
     improve performance.

   * TCP/IP connections are handled with a single thread listening on
     the TCP/IP socket. Each connection is then distributed to one of
     the active threads on a simple round-robin basis. Each connection
     then operates solely within this thread while the connection
     remains open.

   * For UDP connections, all the threads listen to a single UDP socket
     for incoming requests. Threads that are not currently dealing with
     another request ignore the incoming packet. One of the remaining,
     nonbusy, threads reads the request and sends the response. This
     implementation can lead to increased CPU load as threads wake from
     sleep to potentially process the request.

Using threads can increase the performance on servers that have
multiple CPU cores available, as the requests to update the hash table
can be spread between the individual threads. To minimize overhead from
the locking mechanism employed, experiment with different thread values
to achieve the best performance based on the number and type of
requests within your given workload.


File: manual.info,  Node: ha-memcached-using-logs,  Prev: ha-memcached-using-threads,  Up: ha-memcached-using

15.6.2.8 `memcached' Logs
.........................

If you enable verbose mode, using the `-v', `-vv', or `-vvv' options,
then the information output by `memcached' includes details of the
operations being performed.

Without the verbose options, `memcached' normally produces no output
during normal operating.

   * *Output when using `-v'*

     The lowest verbosity level shows you:

        * Errors and warnings

        * Transient errors

        * Protocol and socket errors, including exhausting available
          connections

        * Each registered client connection, including the socket
          descriptor number and the protocol used.

          For example:


               32: Client using the ascii protocol
               33: Client using the ascii protocol

          Note that the socket descriptor is only valid while the
          client remains connected. Non-persistent connections may not
          be effectively represented.

     Examples of the error messages output at this level include:


          <%d send buffer was %d, now %d
          Can't listen for events on fd %d
          Can't read from libevent pipe
          Catastrophic: event fd doesn't match conn fd!
          Couldn't build response
          Couldn't realloc input buffer
          Couldn't update event
          Failed to build UDP headers
          Failed to read, and not due to blocking
          Too many open connections
          Unexpected state %d

   * *Output when using `-vv'*

     When using the second level of verbosity, you get more detailed
     information about protocol operations, keys updated, chunk and
     network operatings and details.

     During the initial start-up of `memcached' with this level of
     verbosity, you are shown the sizes of the individual slab classes,
     the chunk sizes, and the number of entries per slab. These do not
     show the allocation of the slabs, just the slabs that would be
     created when data is added. You are also given information about
     the listen queues and buffers used to send information. A sample
     of the output generated for a TCP/IP based system with the default
     memory and growth factors is given below:


          shell> memcached -vv
          slab class   1: chunk size     80 perslab 13107
          slab class   2: chunk size    104 perslab 10082
          slab class   3: chunk size    136 perslab  7710
          slab class   4: chunk size    176 perslab  5957
          slab class   5: chunk size    224 perslab  4681
          slab class   6: chunk size    280 perslab  3744
          slab class   7: chunk size    352 perslab  2978
          slab class   8: chunk size    440 perslab  2383
          slab class   9: chunk size    552 perslab  1899
          slab class  10: chunk size    696 perslab  1506
          slab class  11: chunk size    872 perslab  1202
          slab class  12: chunk size   1096 perslab   956
          slab class  13: chunk size   1376 perslab   762
          slab class  14: chunk size   1720 perslab   609
          slab class  15: chunk size   2152 perslab   487
          slab class  16: chunk size   2696 perslab   388
          slab class  17: chunk size   3376 perslab   310
          slab class  18: chunk size   4224 perslab   248
          slab class  19: chunk size   5280 perslab   198
          slab class  20: chunk size   6600 perslab   158
          slab class  21: chunk size   8256 perslab   127
          slab class  22: chunk size  10320 perslab   101
          slab class  23: chunk size  12904 perslab    81
          slab class  24: chunk size  16136 perslab    64
          slab class  25: chunk size  20176 perslab    51
          slab class  26: chunk size  25224 perslab    41
          slab class  27: chunk size  31536 perslab    33
          slab class  28: chunk size  39424 perslab    26
          slab class  29: chunk size  49280 perslab    21
          slab class  30: chunk size  61600 perslab    17
          slab class  31: chunk size  77000 perslab    13
          slab class  32: chunk size  96256 perslab    10
          slab class  33: chunk size 120320 perslab     8
          slab class  34: chunk size 150400 perslab     6
          slab class  35: chunk size 188000 perslab     5
          slab class  36: chunk size 235000 perslab     4
          slab class  37: chunk size 293752 perslab     3
          slab class  38: chunk size 367192 perslab     2
          slab class  39: chunk size 458992 perslab     2
          <26 server listening (auto-negotiate)
          <29 server listening (auto-negotiate)
          <30 send buffer was 57344, now 2097152
          <31 send buffer was 57344, now 2097152
          <30 server listening (udp)
          <30 server listening (udp)
          <31 server listening (udp)
          <30 server listening (udp)
          <30 server listening (udp)
          <31 server listening (udp)
          <31 server listening (udp)
          <31 server listening (udp)

     Using this verbosity level can be a useful way to check the
     effects of the growth factor used on slabs with different memory
     allocations, which in turn can be used to better tune the growth
     factor to suit the data you are storing in the cache. For example,
     if you set the growth factor to 4 (quadrupling the size of each
     slab):


          shell> memcached -f 4 -m 1g -vv
          slab class   1: chunk size     80 perslab 13107
          slab class   2: chunk size    320 perslab  3276
          slab class   3: chunk size   1280 perslab   819
          slab class   4: chunk size   5120 perslab   204
          slab class   5: chunk size  20480 perslab    51
          slab class   6: chunk size  81920 perslab    12
          slab class   7: chunk size 327680 perslab     3
          ...

     During use of the cache, this verbosity level also prints out
     detailed information on the storage and recovery of keys and other
     information. An example of the output during a typical set/get and
     increment/decrement operation is shown below.


          32: Client using the ascii protocol
          <32 set my_key 0 0 10
          >32 STORED
          <32 set object_key 1 0 36
          >32 STORED
          <32 get my_key
          >32 sending key my_key
          >32 END
          <32 get object_key
          >32 sending key object_key
          >32 END
          <32 set key 0 0 6
          >32 STORED
          <32 incr key 1
          >32 789544
          <32 decr key 1
          >32 789543
          <32 incr key 2
          >32 789545
          <32 set my_key 0 0 10
          >32 STORED
          <32 set object_key 1 0 36
          >32 STORED
          <32 get my_key
          >32 sending key my_key
          >32 END
          <32 get object_key
          >32 sending key object_key1 1 36

          >32 END
          <32 set key 0 0 6
          >32 STORED
          <32 incr key 1
          >32 789544
          <32 decr key 1
          >32 789543
          <32 incr key 2
          >32 789545

     During client communication, for each line, the initial character
     shows the direction of flow of the information.  The < for
     communication from the client to the `memcached' server and > for
     communication back to the client. The number is the numeric socket
     descriptor for the connection.

   * *Output when using `-vvv'*

     This level of verbosity includes the transitions of connections
     between different states in the event library while reading and
     writing content to/from the clients. It should be used to diagnose
     and identify issues in client communication. For example, you can
     use this information to determine if `memcached' is taking a long
     time to return information to the client, during the read of the
     client operation or before returning and completing the operation.
     An example of the typical sequence for a set operation is provided
     below:


          <32 new auto-negotiating client connection
          32: going from conn_new_cmd to conn_waiting
          32: going from conn_waiting to conn_read
          32: going from conn_read to conn_parse_cmd
          32: Client using the ascii protocol
          <32 set my_key 0 0 10
          32: going from conn_parse_cmd to conn_nread
          > NOT FOUND my_key
          >32 STORED
          32: going from conn_nread to conn_write
          32: going from conn_write to conn_new_cmd
          32: going from conn_new_cmd to conn_waiting
          32: going from conn_waiting to conn_read
          32: going from conn_read to conn_closing
          <32 connection closed.

All of the verbosity levels in `memcached' are designed to be used
during debugging or examination of issues.  The quantity of information
generated, particularly when using `-vvv', is significant, particularly
on a busy server. Also be aware that writing the error information out,
especially to disk, may negate some of the performance gains you
achieve by using `memcached'. Therefore, use in production or
deployment environments is not recommended.


File: manual.info,  Node: ha-memcached-interfaces,  Next: ha-memcached-stats,  Prev: ha-memcached-using,  Up: ha-memcached

15.6.3 Developing a `memcached' Application
-------------------------------------------

* Menu:

* ha-memcached-operations::      Basic `memcached' Operations
* ha-memcached-mysql-frontend::  Using `memcached' as a MySQL Caching Layer
* ha-memcached-interfaces-libmemcached::  Using `libmemcached' with C and C++
* ha-memcached-interfaces-perl::  Using MySQL and `memcached' with Perl
* ha-memcached-interfaces-python::  Using MySQL and `memcached' with Python
* ha-memcached-interfaces-php::  Using MySQL and `memcached' with PHP
* ha-memcached-interfaces-ruby::  Using MySQL and `memcached' with Ruby
* ha-memcached-interfaces-java::  Using MySQL and `memcached' with Java
* ha-memcached-interfaces-protocol::  Using the `memcached' TCP Text Protocol

A number of language interfaces let applications store and retrieve
information with `memcached' servers.  You can write `memcached'
applications in popular languages such as Perl, PHP, Python, Ruby, C,
and Java.

Data stored into a `memcached' server is referred to by a single string
(the key), with storage into the cache and retrieval from the cache
using the key as the reference. The cache therefore operates like a
large associative array or hash table.  It is not possible to structure
or otherwise organize the information stored in the cache. To emulate
database notions such as multiple tables or composite key values, you
must encode the extra information into the strings used as keys. For
example, to store or look up the address corresponding to a specific
latitude and longitude, you might turn those two numeric values into a
single comma-separated string to use as a key.


File: manual.info,  Node: ha-memcached-operations,  Next: ha-memcached-mysql-frontend,  Prev: ha-memcached-interfaces,  Up: ha-memcached-interfaces

15.6.3.1 Basic `memcached' Operations
.....................................

The interface to `memcached' supports the following methods for storing
and retrieving information in the cache, and these are consistent
across all the different APIs, although the language specific mechanics
might be different:

   * `get(KEY)': Retrieves information from the cache. Returns the value
     associated with the key if the specified key exists. Returns
     `NULL', `nil', `undefined', or the closest equivalent in the
     corresponding language, if the specified key does not exist.

   * `set(KEY, VALUE [, EXPIRY])': Sets the item associated with a key
     in the cache to the specified value. Note that this either updates
     an existing item if the key already exists, or adds a new
     key/value pair if the key doesn't exist. If the expiry time is
     specified, then the item expires (and is deleted) when the expiry
     time is reached. The time is specified in seconds, and is taken as
     a relative time if the value is less than 30 days (30*24*60*60),
     or an absolute time (epoch) if larger than this value.

   * `add(KEY, VALUE [, EXPIRY])': Adds the key and associated value to
     the cache, if the specified key does not already exist.

   * `replace(KEY, VALUE [, EXPIRY])': Replaces the item associated
     with the specified `key', only if the key already exists. The new
     value is given by the `value' parameter.

   * `delete(KEY [, TIME])': Deletes the `key' and its associated item
     from the cache. If you supply a `time', then adding another item
     with the specified `key' is blocked for the specified period.

   * `incr(KEY , VALUE)': Increments the item associated with the `key'
     by the specified `value'.

   * `decr(KEY , VALUE)': Decrements the item associated with the `key'
     by the specified `value'.

   * `flush_all': Invalidates (or expires) all the current items in the
     cache. Technically they still exist (they are not deleted), but
     they are silently destroyed the next time you try to access them.

In all implementations, most or all of these functions are duplicated
through the corresponding native language interface.

When practical, use `memcached' to store full items, rather than
caching a single column value from the database. For example, when
displaying a record about an object (invoice, user history, or blog
post), load all the data for the associated entry from the database,
and compile it into the internal structure that would normally be
required by the application. Save the complete object in the cache.

Complex data structures cannot be stored directly. Most interfaces
serialize the data for you, that is, put it in a textual form that can
reconstruct the original pointers and nesting. Perl uses `Storable',
PHP uses `serialize', Python uses `cPickle' (or `Pickle') and Java uses
the `Serializable' interface. In most cases, the serialization
interface used is customizable. To share data stored in `memcached'
instances between different language interfaces, consider using a common
serialization solution such as JSON (Javascript Object Notation).


File: manual.info,  Node: ha-memcached-mysql-frontend,  Next: ha-memcached-interfaces-libmemcached,  Prev: ha-memcached-operations,  Up: ha-memcached-interfaces

15.6.3.2 Using `memcached' as a MySQL Caching Layer
...................................................

When using `memcached' to cache MySQL data, your application must
retrieve data from the database and load the appropriate key-value
pairs into the cache. Then, subsequent lookups can be done directly
from the cache.

Because MySQL has its own in-memory caching mechanisms for queried
data, such as the `InnoDB' buffer pool
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_buffer_pool)
and the MySQL query cache, look for opportunities beyond loading
individual column values or rows into the cache. Prefer to cache
composite values, such as those retrieved from multiple tables through
a join query, or result sets assembled from multiple rows.

*Caution*:

Limit the information in the cache to non-sensitive data, because there
is no security required to access or update the information within a
`memcached' instance.  Anybody with access to the machine has the
ability to read, view and potentially update the information. To keep
the data secure, encrypt the information before caching it. To restrict
the users capable of connecting to the server, either disable network
access, or use IPTables or similar techniques to restrict access to the
`memcached' ports to a select set of hosts.

You can introduce `memcached' to an existing application, even if
caching was not part of the original design. In many languages and
environments the changes to the application will be just a few lines,
first to attempt to read from the cache when loading data, fall back to
the old method if the information is not cached, and to update the
cache with information once the data has been read.

The general sequence for using `memcached' in any language as a caching
solution for MySQL is as follows:

  1. Request the item from the cache.

  2. If the item exists, use the item data.

  3. If the item does not exist, load the data from MySQL, and store
     the value into the cache. This means the value is available to the
     next client that requests it from the cache.

For a flow diagram of this sequence, see *Note
ha-memcached-fig-basicflow::.

FIGURE GOES HERE: Typical `memcached' Application Flowchart

*Adapting Database Best Practices to `memcached' Applications*

The most direct way to cache MySQL data is to use a 2-column table,
where the first column is a primary key
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_primary_key).
Because of the uniqueness requirements for `memcached' keys, make sure
your database schema makes appropriate use of primary keys and unique
constraints
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_unique_constraint).

If you combine multiple column values into a single `memcached' item
value, choose data types to make it easy to parse the value back into
its components, for example by using a separator character between
numeric values.

The queries that map most easily to `memcached' lookups are those with
a single `WHERE' clause, using an `=' or `IN' operator.  For
complicated `WHERE' clauses, or those using operators such as `<', `>',
`BETWEEN', or `LIKE', `memcached' does not provide a simple or
efficient way to scan through or filter the keys or associated values,
so typically you perform those operations as SQL queries on the
underlying database.


File: manual.info,  Node: ha-memcached-interfaces-libmemcached,  Next: ha-memcached-interfaces-perl,  Prev: ha-memcached-mysql-frontend,  Up: ha-memcached-interfaces

15.6.3.3 Using `libmemcached' with C and C++
............................................

* Menu:

* ha-memcached-interfaces-libmemcached-base::  `libmemcached' Base Functions
* ha-memcached-interfaces-libmemcached-servers::  `libmemcached' Server Functions
* ha-memcached-interfaces-libmemcached-set::  `libmemcached' Set Functions
* ha-memcached-interfaces-libmemcached-get::  `libmemcached' Get Functions
* ha-memcached-interfaces-libmemcached-behaviors::  Controlling `libmemcached' Behaviors
* ha-memcached-interfaces-libmemcached-utilities::  `libmemcached' Command-Line Utilities

The `libmemcached' library provides both C and C++ interfaces to
`memcached' and is also the basis for a number of different additional
API implementations, including Perl, Python and Ruby. Understanding the
core `libmemcached' functions can help when using these other
interfaces.

The C library is the most comprehensive interface library for
`memcached' and provides functions and operational systems not always
exposed in interfaces not based on the `libmemcached' library.

The different functions can be divided up according to their basic
operation. In addition to functions that interface to the core API, a
number of utility functions provide extended functionality, such as
appending and prepending data.

To build and install `libmemcached', download the `libmemcached'
package, run `configure', and then build and install:


     shell> tar xjf libmemcached-0.21.tar.gz
     shell> cd libmemcached-0.21
     shell> ./configure
     shell> make
     shell> make install

On many Linux operating systems, you can install the corresponding
`libmemcached' package through the usual `yum', `apt-get', or similar
commands.

To build an application that uses the library, first set the list of
servers. Either directly manipulate the servers configured within the
main `memcached_st' structure, or separately populate a list of
servers, and then add this list to the `memcached_st' structure.  The
latter method is used in the following example. Once the server list
has been set, you can call the functions to store or retrieve data. A
simple application for setting a preset value to `localhost' is
provided here:


     #include <stdio.h>
     #include <string.h>
     #include <unistd.h>
     #include <libmemcached/memcached.h>

     int main(int argc, char *argv[])
     {
       memcached_server_st *servers = NULL;
       memcached_st *memc;
       memcached_return rc;
       char *key= "keystring";
       char *value= "keyvalue";

       memcached_server_st *memcached_servers_parse (char *server_strings);
       memc= memcached_create(NULL);

       servers= memcached_server_list_append(servers, "localhost", 11211, &rc);
       rc= memcached_server_push(memc, servers);

       if (rc == MEMCACHED_SUCCESS)
         fprintf(stderr,"Added server successfully\n");
       else
         fprintf(stderr,"Couldn't add server: %s\n",memcached_strerror(memc, rc));

       rc= memcached_set(memc, key, strlen(key), value, strlen(value), (time_t)0, (uint32_t)0);

       if (rc == MEMCACHED_SUCCESS)
         fprintf(stderr,"Key stored successfully\n");
       else
         fprintf(stderr,"Couldn't store key: %s\n",memcached_strerror(memc, rc));

       return 0;
     }

To test the success of an operation, use the return value, or populated
result code, for a given function. The value is always set to
`MEMCACHED_SUCCESS' if the operation succeeded. In the event of a
failure, use the `memcached_strerror()' function to translate the
result code into a printable string.

To build the application, specify the `memcached' library:


     shell> gcc -o memc_basic memc_basic.c -lmemcached

Running the above sample application, after starting a `memcached'
server, should return a success message:


     shell> memc_basic
     Added server successfully
     Key stored successfully


File: manual.info,  Node: ha-memcached-interfaces-libmemcached-base,  Next: ha-memcached-interfaces-libmemcached-servers,  Prev: ha-memcached-interfaces-libmemcached,  Up: ha-memcached-interfaces-libmemcached

15.6.3.4 `libmemcached' Base Functions
......................................

The base `libmemcached' functions let you create, destroy and clone the
main `memcached_st' structure that is used to interface with the
`memcached' servers. The main functions are defined below:


     memcached_st *memcached_create (memcached_st *ptr);

Creates a new `memcached_st' structure for use with the other
`libmemcached' API functions. You can supply an existing, static,
`memcached_st' structure, or `NULL' to have a new structured allocated.
Returns a pointer to the created structure, or `NULL' on failure.


     void memcached_free (memcached_st *ptr);

Frees the structure and memory allocated to a previously created
`memcached_st' structure.


     memcached_st *memcached_clone(memcached_st *clone, memcached_st *source);

Clones an existing `memcached' structure from the specified `source',
copying the defaults and list of servers defined in the structure.


File: manual.info,  Node: ha-memcached-interfaces-libmemcached-servers,  Next: ha-memcached-interfaces-libmemcached-set,  Prev: ha-memcached-interfaces-libmemcached-base,  Up: ha-memcached-interfaces-libmemcached

15.6.3.5 `libmemcached' Server Functions
........................................

The `libmemcached' API uses a list of servers, stored within the
`memcached_server_st' structure, to act as the list of servers used by
the rest of the functions. To use `memcached', you first create the
server list, and then apply the list of servers to a valid
`libmemcached' object.

Because the list of servers, and the list of servers within an active
`libmemcached' object can be manipulated separately, you can update and
manage server lists while an active `libmemcached' interface is running.

The functions for manipulating the list of servers within a
`memcached_st' structure are:


     memcached_return
        memcached_server_add (memcached_st *ptr,
                              char *hostname,
                              unsigned int port);

Adds a server, using the given `hostname' and `port' into the
`memcached_st' structure given in `ptr'.


     memcached_return
        memcached_server_add_unix_socket (memcached_st *ptr,
                                          char *socket);

Adds a Unix socket to the list of servers configured in the
`memcached_st' structure.


     unsigned int memcached_server_count (memcached_st *ptr);

Returns a count of the number of configured servers within the
`memcached_st' structure.


     memcached_server_st *
        memcached_server_list (memcached_st *ptr);

Returns an array of all the defined hosts within a `memcached_st'
structure.


     memcached_return
        memcached_server_push (memcached_st *ptr,
                               memcached_server_st *list);

Pushes an existing list of servers onto list of servers configured for
a current `memcached_st' structure. This adds servers to the end of the
existing list, and duplicates are not checked.

The `memcached_server_st' structure can be used to create a list of
`memcached' servers which can then be applied individually to
`memcached_st' structures.


     memcached_server_st *
        memcached_server_list_append (memcached_server_st *ptr,
                                      char *hostname,
                                      unsigned int port,
                                      memcached_return *error);

Adds a server, with `hostname' and `port', to the server list in `ptr'.
The result code is handled by the `error' argument, which should point
to an existing `memcached_return' variable. The function returns a
pointer to the returned list.


     unsigned int memcached_server_list_count (memcached_server_st *ptr);

Returns the number of the servers in the server list.


     void memcached_server_list_free (memcached_server_st *ptr);

Frees the memory associated with a server list.


     memcached_server_st *memcached_servers_parse (char *server_strings);

Parses a string containing a list of servers, where individual servers
are separated by a comma, space, or both, and where individual servers
are of the form `SERVER[:PORT]'.  The return value is a server list
structure.


File: manual.info,  Node: ha-memcached-interfaces-libmemcached-set,  Next: ha-memcached-interfaces-libmemcached-get,  Prev: ha-memcached-interfaces-libmemcached-servers,  Up: ha-memcached-interfaces-libmemcached

15.6.3.6 `libmemcached' Set Functions
.....................................

The set-related functions within `libmemcached' provide the same
functionality as the core functions supported by the `memcached'
protocol. The full definition for the different functions is the same
for all the base functions (`add', `replace', `prepend', `append'). For
example, the function definition for `memcached_set()' is:


     memcached_return
        memcached_set (memcached_st *ptr,
                       const char *key,
                       size_t key_length,
                       const char *value,
                       size_t value_length,
                       time_t expiration,
                       uint32_t flags);

The `ptr' is the `memcached_st' structure. The `key' and `key_length'
define the key name and length, and `value' and `value_length' the
corresponding value and length. You can also set the expiration and
optional flags. For more information, see *Note
ha-memcached-interfaces-libmemcached-behaviors::.

This table outlines the remainder of the set-related `libmemcached'
functions and the equivalent core functions supported by the `memcached'
protocol.

This table outlines the remainder of the set-related `libmemcached'
functions and the equivalent core functions supported by the `memcached'
protocol.

`libmemcached' Function              Equivalent Core Function
`memcached_set(memc, key,            Generic `set()' operation.
key_length, value, value_length,     
expiration, flags)'                  
`memcached_add(memc, key,            Generic `add()' function.
key_length, value, value_length,     
expiration, flags)'                  
`memcached_replace(memc, key,        Generic `replace()'.
key_length, value, value_length,     
expiration, flags)'                  
`memcached_prepend(memc, key,        Prepends the specified `value'
key_length, value, value_length,     before the current value of the
expiration, flags)'                  specified `key'.
`memcached_append(memc, key,         Appends the specified `value' after
key_length, value, value_length,     the current value of the specified
expiration, flags)'                  `key'.
`memcached_cas(memc, key,            Overwrites the data for a given key
key_length, value, value_length,     as long as the corresponding `cas'
expiration, flags, cas)'             value is still the same within the
                                     server.
`memcached_set_by_key(memc,          Similar to the generic `set()', but
master_key, master_key_length, key,  has the option of an additional
key_length, value, value_length,     master key that can be used to
expiration, flags)'                  identify an individual server.
`memcached_add_by_key(memc,          Similar to the generic `add()', but
master_key, master_key_length, key,  has the option of an additional
key_length, value, value_length,     master key that can be used to
expiration, flags)'                  identify an individual server.
`memcached_replace_by_key(memc,      Similar to the generic `replace()',
master_key, master_key_length, key,  but has the option of an additional
key_length, value, value_length,     master key that can be used to
expiration, flags)'                  identify an individual server.
`memcached_prepend_by_key(memc,      Similar to the
master_key, master_key_length, key,  `memcached_prepend()', but has the
key_length, value, value_length,     option of an additional master key
expiration, flags)'                  that can be used to identify an
                                     individual server.
`memcached_append_by_key(memc,       Similar to the
master_key, master_key_length, key,  `memcached_append()', but has the
key_length, value, value_length,     option of an additional master key
expiration, flags)'                  that can be used to identify an
                                     individual server.
`memcached_cas_by_key(memc,          Similar to the `memcached_cas()',
master_key, master_key_length, key,  but has the option of an additional
key_length, value, value_length,     master key that can be used to
expiration, flags)'                  identify an individual server.

The `by_key' methods add two further arguments that define the master
key, to be used and applied during the hashing stage for selecting the
servers. You can see this in the following definition:


     memcached_return
        memcached_set_by_key(memcached_st *ptr,
                             const char *master_key,
                             size_t master_key_length,
                             const char *key,
                             size_t key_length,
                             const char *value,
                             size_t value_length,
                             time_t expiration,
                             uint32_t flags);

All the functions return a value of type `memcached_return', which you
can compare against the `MEMCACHED_SUCCESS' constant.


File: manual.info,  Node: ha-memcached-interfaces-libmemcached-get,  Next: ha-memcached-interfaces-libmemcached-behaviors,  Prev: ha-memcached-interfaces-libmemcached-set,  Up: ha-memcached-interfaces-libmemcached

15.6.3.7 `libmemcached' Get Functions
.....................................

The `libmemcached' functions provide both direct access to a single
item, and a multiple-key request mechanism that provides much faster
responses when fetching a large number of keys simultaneously.

The main get-style function, which is equivalent to the generic `get()'
is `memcached_get()'. This function returns a string pointer, pointing
to the value associated with the specified key.


     char *memcached_get (memcached_st *ptr,
                          const char *key, size_t key_length,
                          size_t *value_length,
                          uint32_t *flags,
                          memcached_return *error);

A multi-key get, `memcached_mget()', is also available. Using a
multiple key get operation is much quicker to do in one block than
retrieving the key values with individual calls to `memcached_get()'. To
start the multi-key get, call `memcached_mget()':


     memcached_return
         memcached_mget (memcached_st *ptr,
                         char **keys, size_t *key_length,
                         unsigned int number_of_keys);

The return value is the success of the operation. The `keys' parameter
should be an array of strings containing the keys, and `key_length' an
array containing the length of each corresponding key.
`number_of_keys' is the number of keys supplied in the array.

To fetch the individual values, use `memcached_fetch()' to get each
corresponding value.


     char *memcached_fetch (memcached_st *ptr,
                            const char *key, size_t *key_length,
                            size_t *value_length,
                            uint32_t *flags,
                            memcached_return *error);

The function returns the key value, with the `key', `key_length' and
`value_length' parameters being populated with the corresponding key
and length information. The function returns `NULL' when there are no
more values to be returned. A full example, including the populating of
the key data and the return of the information is provided here.


     #include <stdio.h>
     #include <sstring.h>
     #include <unistd.h>
     #include <libmemcached/memcached.h>

     int main(int argc, char *argv[])
     {
       memcached_server_st *servers = NULL;
       memcached_st *memc;
       memcached_return rc;
       char *keys[]= {"huey", "dewey", "louie"};
       size_t key_length[3];
       char *values[]= {"red", "blue", "green"};
       size_t value_length[3];
       unsigned int x;
       uint32_t flags;

       char return_key[MEMCACHED_MAX_KEY];
       size_t return_key_length;
       char *return_value;
       size_t return_value_length;

       memc= memcached_create(NULL);

       servers= memcached_server_list_append(servers, "localhost", 11211, &rc);
       rc= memcached_server_push(memc, servers);

       if (rc == MEMCACHED_SUCCESS)
         fprintf(stderr,"Added server successfully\n");
       else
         fprintf(stderr,"Couldn't add server: %s\n",memcached_strerror(memc, rc));

       for(x= 0; x < 3; x++)
         {
           key_length[x] = strlen(keys[x]);
           value_length[x] = strlen(values[x]);

           rc= memcached_set(memc, keys[x], key_length[x], values[x],
                             value_length[x], (time_t)0, (uint32_t)0);
           if (rc == MEMCACHED_SUCCESS)
             fprintf(stderr,"Key %s stored successfully\n",keys[x]);
           else
             fprintf(stderr,"Couldn't store key: %s\n",memcached_strerror(memc, rc));
         }

       rc= memcached_mget(memc, keys, key_length, 3);

       if (rc == MEMCACHED_SUCCESS)
         {
           while ((return_value= memcached_fetch(memc, return_key, &return_key_length,
                                                 &return_value_length, &flags, &rc)) != NULL)
             {
               if (rc == MEMCACHED_SUCCESS)
                 {
                   fprintf(stderr,"Key %s returned %s\n",return_key, return_value);
                 }
             }
         }

       return 0;
     }

Running the above application produces the following output:


     shell> memc_multi_fetch
     Added server successfully
     Key huey stored successfully
     Key dewey stored successfully
     Key louie stored successfully
     Key huey returned red
     Key dewey returned blue
     Key louie returned green


File: manual.info,  Node: ha-memcached-interfaces-libmemcached-behaviors,  Next: ha-memcached-interfaces-libmemcached-utilities,  Prev: ha-memcached-interfaces-libmemcached-get,  Up: ha-memcached-interfaces-libmemcached

15.6.3.8 Controlling `libmemcached' Behaviors
.............................................

The behavior of `libmemcached' can be modified by setting one or more
behavior flags. These can either be set globally, or they can be
applied during the call to individual functions. Some behaviors also
accept an additional setting, such as the hashing mechanism used when
selecting servers.

To set global behaviors:


     memcached_return
        memcached_behavior_set (memcached_st *ptr,
                                memcached_behavior flag,
                                uint64_t data);

To get the current behavior setting:


     uint64_t
        memcached_behavior_get (memcached_st *ptr,
                                memcached_behavior flag);

The following table describes `libmemcached' behavior flags.

This table lists `libmemcached' behavior flags and provides a
description of each.

Behavior                      Description
`MEMCACHED_BEHAVIOR_NO_BLOCK' Caused `libmemcached' to use asynchronous
                              I/O.
`MEMCACHED_BEHAVIOR_TCP_NODELAY'Turns on no-delay for network sockets.
`MEMCACHED_BEHAVIOR_HASH'     Without a value, sets the default hashing
                              algorithm for keys to use MD5.  Other
                              valid values include
                              `MEMCACHED_HASH_DEFAULT',
                              `MEMCACHED_HASH_MD5', `MEMCACHED_HASH_CRC',
                              `MEMCACHED_HASH_FNV1_64',
                              `MEMCACHED_HASH_FNV1A_64',
                              `MEMCACHED_HASH_FNV1_32', and
                              `MEMCACHED_HASH_FNV1A_32'.
`MEMCACHED_BEHAVIOR_DISTRIBUTION'Changes the method of selecting the server
                              used to store a given value.  The default
                              method is `MEMCACHED_DISTRIBUTION_MODULA'.
                              You can enable consistent hashing by
                              setting
                              `MEMCACHED_DISTRIBUTION_CONSISTENT'.
                              `MEMCACHED_DISTRIBUTION_CONSISTENT' is an
                              alias for the value
                              `MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA'.
`MEMCACHED_BEHAVIOR_CACHE_LOOKUPS'Cache the lookups made to the DNS service.
                              This can improve the performance if you
                              are using names instead of IP addresses
                              for individual hosts.
`MEMCACHED_BEHAVIOR_SUPPORT_CAS'Support CAS operations. By default, this
                              is disabled because it imposes a
                              performance penalty.
`MEMCACHED_BEHAVIOR_KETAMA'   Sets the default distribution to
                              `MEMCACHED_DISTRIBUTION_CONSISTENT_KETAMA'
                              and the hash to `MEMCACHED_HASH_MD5'.
`MEMCACHED_BEHAVIOR_POLL_TIMEOUT'Modify the timeout value used by `poll()'.
                              Supply a `signed int' pointer for the
                              timeout value.
`MEMCACHED_BEHAVIOR_BUFFER_REQUESTS'Buffers IO requests instead of them being
                              sent. A get operation, or closing the
                              connection causes the data to be flushed.
`MEMCACHED_BEHAVIOR_VERIFY_KEY'Forces `libmemcached' to verify that a
                              specified key is valid.
`MEMCACHED_BEHAVIOR_SORT_HOSTS'If set, hosts added to the list of
                              configured hosts for a `memcached_st'
                              structure are placed into the host list in
                              sorted order. This breaks consistent
                              hashing if that behavior has been enabled.
`MEMCACHED_BEHAVIOR_CONNECT_TIMEOUT'In nonblocking mode this changes the value
                              of the timeout during socket connection.


File: manual.info,  Node: ha-memcached-interfaces-libmemcached-utilities,  Prev: ha-memcached-interfaces-libmemcached-behaviors,  Up: ha-memcached-interfaces-libmemcached

15.6.3.9 `libmemcached' Command-Line Utilities
..............................................

In addition to the main C library interface, `libmemcached' also
includes a number of command-line utilities that can be useful when
working with and debugging `memcached' applications.

All of the command-line tools accept a number of arguments, the most
critical of which is `servers', which specifies the list of servers to
connect to when returning information.

The main tools are:

   * `memcat': Display the value for each ID given on the command line:


          shell> memcat --servers=localhost hwkey
          Hello world

   * `memcp': Copy the contents of a file into the cache, using the
     file name as the key:


          shell> echo "Hello World" > hwkey
          shell> memcp --servers=localhost hwkey
          shell> memcat --servers=localhost hwkey
          Hello world

   * `memrm': Remove an item from the cache:


          shell> memcat --servers=localhost hwkey
          Hello world
          shell> memrm --servers=localhost hwkey
          shell> memcat --servers=localhost hwkey

   * `memslap': Test the load on one or more `memcached' servers,
     simulating get/set and multiple client operations. For example,
     you can simulate the load of 100 clients performing get operations:


          shell> memslap --servers=localhost --concurrency=100 --flush --test=get
          memslap --servers=localhost --concurrency=100 --flush --test=get	Threads connecting to servers 100
          	Took 13.571 seconds to read data

   * `memflush': Flush (empty) the contents of the `memcached' cache.


          shell> memflush --servers=localhost


File: manual.info,  Node: ha-memcached-interfaces-perl,  Next: ha-memcached-interfaces-python,  Prev: ha-memcached-interfaces-libmemcached,  Up: ha-memcached-interfaces

15.6.3.10 Using MySQL and `memcached' with Perl
...............................................

The `Cache::Memcached' module provides a native interface to the
Memcache protocol, and provides support for the core functions offered
by `memcached'. Install the module using your operating system's
package management system, or using `CPAN':


     root-shell> perl -MCPAN -e 'install Cache::Memcached'

To use `memcached' from Perl through the `Cache::Memcached' module,
first create a new `Cache::Memcached' object that defines the list of
servers and other parameters for the connection. The only argument is a
hash containing the options for the cache interface. For example, to
create a new instance that uses three `memcached' servers:


     use Cache::Memcached;

     my $cache = new Cache::Memcached {
         'servers' => [
             '192.168.0.100:11211',
             '192.168.0.101:11211',
             '192.168.0.102:11211',
     	],
     };

*Note*:

When using the `Cache::Memcached' interface with multiple servers, the
API automatically performs certain operations across all the servers in
the group. For example, getting statistical information through
`Cache::Memcached' returns a hash that contains data on a host-by-host
basis, as well as generalized statistics for all the servers in the
group.

You can set additional properties on the cache object instance when it
is created by specifying the option as part of the option hash.
Alternatively, you can use a corresponding method on the instance:

   * `servers' or method `set_servers()': Specifies the list of the
     servers to be used. The servers list should be a reference to an
     array of servers, with each element as the address and port number
     combination (separated by a colon). You can also specify a local
     connection through a Unix socket (for example
     `/tmp/sock/memcached'). To specify the server with a weight
     (indicating how much more frequently the server should be used
     during hashing), specify an array reference with the `memcached'
     server instance and a weight number. Higher numbers give higher
     priority.

   * `compress_threshold' or method `set_compress_threshold()':
     Specifies the threshold when values are compressed. Values larger
     than the specified number are automatically compressed (using
     `zlib') during storage and retrieval.

   * `no_rehash' or method `set_norehash()': Disables finding a new
     server if the original choice is unavailable.

   * `readonly' or method `set_readonly()': Disables writes to the
     `memcached' servers.

Once the `Cache::Memcached' object instance has been configured, you
can use the `set()' and `get()' methods to store and retrieve
information from the `memcached' servers.  Objects stored in the cache
are automatically serialized and deserialized using the `Storable'
module.

The `Cache::Memcached' interface supports the following methods for
storing/retrieving data, and relate to the generic methods as shown in
the table.

This table lists `memcached' functions used with Perl and the
equivalent generic methods in the `memcached' interface specification.

`Cache::Memcached' Function          Equivalent Generic Method
`get()'                              Generic `get()'.
`get_multi(keys)'                    Gets multiple `keys' from memcache
                                     using just one query. Returns a
                                     hash reference of key/value pairs.
`set()'                              Generic `set()'.
`add()'                              Generic `add()'.
`replace()'                          Generic `replace()'.
`delete()'                           Generic `delete()'.
`incr()'                             Generic `incr()'.
`decr()'                             Generic `decr()'.

Below is a complete example for using `memcached' with Perl and the
`Cache::Memcached' module:


     #!/usr/bin/perl

     use Cache::Memcached;
     use DBI;
     use Data::Dumper;

     # Configure the memcached server

     my $cache = new Cache::Memcached {
         'servers' => [
                        'localhost:11211',
                        ],
         };

     # Get the film name from the command line
     # memcached keys must not contain spaces, so create
     # a key name by replacing spaces with underscores

     my $filmname = shift or die "Must specify the film name\n";
     my $filmkey = $filmname;
     $filmkey =~ s/ /_/;

     # Load the data from the cache

     my $filmdata = $cache->get($filmkey);

     # If the data wasn't in the cache, then we load it from the database

     if (!defined($filmdata))
     {
         $filmdata = load_filmdata($filmname);

         if (defined($filmdata))
         {

     # Set the data into the cache, using the key

     	if ($cache->set($filmkey,$filmdata))
             {
                 print STDERR "Film data loaded from database and cached\n";
             }
             else
             {
                 print STDERR "Couldn't store to cache\n";
     	}
         }
         else
         {
          	die "Couldn't find $filmname\n";
         }
     }
     else
     {
         print STDERR "Film data loaded from Memcached\n";
     }

     sub load_filmdata
     {
         my ($filmname) = @_;

         my $dsn = "DBI:mysql:database=sakila;host=localhost;port=3306";

         $dbh = DBI->connect($dsn, 'sakila','password');

         my ($filmbase) = $dbh->selectrow_hashref(sprintf('select * from film where title = %s',
                                                          $dbh->quote($filmname)));

         if (!defined($filmname))
         {
          	return (undef);
         }

         $filmbase->{stars} =
     	$dbh->selectall_arrayref(sprintf('select concat(first_name," ",last_name) ' .
                                              'from film_actor left join (actor) ' .
                                              'on (film_actor.actor_id = actor.actor_id) ' .
                                              ' where film_id=%s',
                                              $dbh->quote($filmbase->{film_id})));

         return($filmbase);
     }

The example uses the Sakila database, obtaining film data from the
database and writing a composite record of the film and actors to
`memcached'. When calling it for a film does not exist, you get this
result:


     shell> memcached-sakila.pl "ROCK INSTINCT"
     Film data loaded from database and cached

When accessing a film that has already been added to the cache:


     shell> memcached-sakila.pl "ROCK INSTINCT"
     Film data loaded from Memcached


File: manual.info,  Node: ha-memcached-interfaces-python,  Next: ha-memcached-interfaces-php,  Prev: ha-memcached-interfaces-perl,  Up: ha-memcached-interfaces

15.6.3.11 Using MySQL and `memcached' with Python
.................................................

The Python `memcache' module interfaces to `memcached' servers, and is
written in pure Python (that is, without using one of the C APIs). You
can download and install a copy from Python Memcached
(http://www.tummy.com/Community/software/python-memcached/).

To install, download the package and then run the Python installer:


     python setup.py install
     running install
     running bdist_egg
     running egg_info
     creating python_memcached.egg-info
     ...
     removing 'build/bdist.linux-x86_64/egg' (and everything under it)
     Processing python_memcached-1.43-py2.4.egg
     creating /usr/lib64/python2.4/site-packages/python_memcached-1.43-py2.4.egg
     Extracting python_memcached-1.43-py2.4.egg to /usr/lib64/python2.4/site-packages
     Adding python-memcached 1.43 to easy-install.pth file

     Installed /usr/lib64/python2.4/site-packages/python_memcached-1.43-py2.4.egg
     Processing dependencies for python-memcached==1.43
     Finished processing dependencies for python-memcached==1.43

Once installed, the `memcache' module provides a class-based interface
to your `memcached' servers. When you store Python data structures as
`memcached' items, they are automatically serialized (turned into
string values) using the Python `cPickle' or `pickle' modules.

To create a new `memcache' interface, import the `memcache' module and
create a new instance of the `memcache.Client' class. For example, if
the `memcached' daemon is running on localhost using the default port:


     import memcache
     memc = memcache.Client(['127.0.0.1:11211'])

The first argument is an array of strings containing the server and
port number for each `memcached' instance to use. To enable debugging,
set the optional `debug' parameter to 1.

By default, the hashing mechanism used to divide the items among
multiple servers is `crc32'. To change the function used, set the value
of `memcache.serverHashFunction' to the alternate function to use. For
example:


     from zlib import adler32
     memcache.serverHashFunction = adler32

Once you have defined the servers to use within the `memcache'
instance, the core functions provide the same functionality as in the
generic interface specification. The following table provides a summary
of the supported functions:

This table lists Python `memcached' functions and the equivalent
generic functions in the `memcached' interface specification.

Python `memcache' Function           Equivalent Generic Function
`get()'                              Generic `get()'.
`get_multi(keys)'                    Gets multiple values from the
                                     supplied array of `keys'.  Returns
                                     a hash reference of key/value pairs.
`set()'                              Generic `set()'.
`set_multi(dict [, expiry [,         Sets multiple key/value pairs from
key_prefix]])'                       the supplied `dict'.
`add()'                              Generic `add()'.
`replace()'                          Generic `replace()'.
`prepend(key, value [, expiry])'     Prepends the supplied `value' to
                                     the value of the existing `key'.
`append(key, value [, expiry[)'      Appends the supplied `value' to the
                                     value of the existing `key'.
`delete()'                           Generic `delete()'.
`delete_multi(keys [, expiry [,      Deletes all the keys from the hash
key_prefix]] )'                      matching each string in the array
                                     `keys'.
`incr()'                             Generic `incr()'.
`decr()'                             Generic `decr()'.

*Note*:

Within the Python `memcache' module, all the `*_multi()'functions
support an optional `key_prefix' parameter. If supplied, then the
string is used as a prefix to all key lookups. For example, if you call:


     memc.get_multi(['a','b'], key_prefix='users:')

The function retrieves the keys `users:a' and `users:b' from the
servers.

Here is an example showing the storage and retrieval of information to
a `memcache' instance, loading the raw data from MySQL:


     import sys
     import MySQLdb
     import memcache

     memc = memcache.Client(['127.0.0.1:11211'], debug=1);

     try:
         conn = MySQLdb.connect (host = "localhost",
                                 user = "sakila",
                                 passwd = "password",
                                 db = "sakila")
     except MySQLdb.Error, e:
          print "Error %d: %s" % (e.args[0], e.args[1])
          sys.exit (1)

     popularfilms = memc.get('top5films')

     if not popularfilms:
         cursor = conn.cursor()
         cursor.execute('select film_id,title from film order by rental_rate desc limit 5')
         rows = cursor.fetchall()
         memc.set('top5films',rows,60)
         print "Updated memcached with MySQL data"
     else:
         print "Loaded data from memcached"
         for row in popularfilms:
             print "%s, %s" % (row[0], row[1])

When executed for the first time, the data is loaded from the MySQL
database and stored to the `memcached' server.


     shell> python memc_python.py
     Updated memcached with MySQL data

Because the data is automatically serialized using `cPickle'/`pickle',
when you load the data back from `memcached', you can use the object
directly. In the example above, the information stored to `memcached'
is in the form of rows from a Python DB cursor. When accessing the
information (within the 60 second expiry time), the data is loaded from
`memcached' and dumped:


     shell> python memc_python.py
     Loaded data from memcached
     2, ACE GOLDFINGER
     7, AIRPLANE SIERRA
     8, AIRPORT POLLOCK
     10, ALADDIN CALENDAR
     13, ALI FOREVER

The serialization and deserialization happens automatically.  Because
serialization of Python data may be incompatible with other interfaces
and languages, you can change the serialization module used during
initialization. For example, you might use JSON format when you store
complex data structures using a script written in one language, and
access them in a script written in a different language.


File: manual.info,  Node: ha-memcached-interfaces-php,  Next: ha-memcached-interfaces-ruby,  Prev: ha-memcached-interfaces-python,  Up: ha-memcached-interfaces

15.6.3.12 Using MySQL and `memcached' with PHP
..............................................

PHP provides support for the Memcache functions through a PECL
extension. To enable the PHP `memcache' extensions, build PHP using the
`--enable-memcache' option to `configure' when building from source.

If you are installing on a Red Hat-based server, you can install the
`php-pecl-memcache' RPM:


     root-shell> yum --install php-pecl-memcache

On Debian-based distributions, use the `php-memcache' package.

To set global runtime configuration options, specify the configuration
option values within your `php.ini' file. The following table provides
the name, default value, and a description for each global runtime
configuration option.

This table lists global runtime configuration options for the PECL
`Memcache' extension. The table provides configuration option names,
default values, and descriptions.

Configuration option      Default        Description
`memcache.allow_failover' 1              Specifies whether another
                                         server in the list should be
                                         queried if the first server
                                         selected fails.
`memcache.max_failover_attempts'20             Specifies the number of servers
                                         to try before returning a
                                         failure.
`memcache.chunk_size'     8192           Defines the size of network
                                         chunks used to exchange data
                                         with the `memcached' server.
`memcache.default_port'   11211          Defines the default port to use
                                         when communicating with the
                                         `memcached' servers.
`memcache.hash_strategy'  standard       Specifies which hash strategy
                                         to use. Set to `consistent' to
                                         enable servers to be added or
                                         removed from the pool without
                                         causing the keys to be remapped
                                         to other servers. When set to
                                         `standard', an older (modula)
                                         strategy is used that
                                         potentially uses different
                                         servers for storage.
`memcache.hash_function'  crc32          Specifies which function to use
                                         when mapping keys to servers.
                                         `crc32' uses the standard CRC32
                                         hash.  `fnv' uses the FNV-1a
                                         hashing algorithm.

To create a connection to a `memcached' server, create a new `Memcache'
object and then specify the connection options. For example:


     <?php

     $cache = new Memcache;
     $cache->connect('localhost',11211);
     ?>

This opens an immediate connection to the specified server.

To use multiple `memcached' servers, you need to add servers to the
memcache object using `addServer()':


     bool Memcache::addServer ( string $host [, int $port [, bool $persistent
                      [, int $weight [, int $timeout [, int $retry_interval
                      [, bool $status [, callback $failure_callback
                      ]]]]]]] )

The server management mechanism within the `php-memcache' module is a
critical part of the interface as it controls the main interface to the
`memcached' instances and how the different instances are selected
through the hashing mechanism.

To create a simple connection to two `memcached' instances:


     <?php

     $cache = new Memcache;
     $cache->addServer('192.168.0.100',11211);
     $cache->addServer('192.168.0.101',11211);
     ?>

In this scenario, the instance connection is not explicitly opened, but
only opened when you try to store or retrieve a value. To enable
persistent connections to `memcached' instances, set the `$persistent'
argument to true. This is the default setting, and causes the
connections to remain open.

To help control the distribution of keys to different instances, use
the global `memcache.hash_strategy' setting. This sets the hashing
mechanism used to select. You can also add another weight to each
server, which effectively increases the number of times the instance
entry appears in the instance list, therefore increasing the likelihood
of the instance being chosen over other instances. To set the weight,
set the value of the `$weight' argument to more than one.

The functions for setting and retrieving information are identical to
the generic functional interface offered by `memcached', as shown in
this table:

This table lists PECL `memcached' functions and the equivalent generic
functions in the `memcached' interface specification.

PECL `memcache' Function             Generic Function
`get()'                              Generic `get()'.
`set()'                              Generic `set()'.
`add()'                              Generic `add()'.
`replace()'                          Generic `replace()'.
`delete()'                           Generic `delete()'.
`increment()'                        Generic `incr()'.
`decrement()'                        Generic `decr()'.

A full example of the PECL `memcache' interface is provided below. The
code loads film data from the Sakila database when the user provides a
film name. The data stored into the `memcached' instance is recorded as
a `mysqli' result row, and the API automatically serializes the
information for you.


     <?php

     $memc = new Memcache;
     $memc->addServer('localhost','11211');

     if(empty($_POST['film'])) {
     ?>
       <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
         <head>
           <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
           <title>Simple Memcache Lookup</title>
         </head>
         <body>
           <form method="post">
             <p><b>Film</b>: <input type="text" size="20" name="film"></p>
             <input type="submit">
           </form>
           <hr/>
     <?php

     } else {

         echo "Loading data...\n";

         $film   = htmlspecialchars($_POST['film'], ENT_QUOTES, 'UTF-8');
         $mfilms = $memc->get($film);

         if ($mfilms) {

             printf("<p>Film data for %s loaded from memcache</p>", $mfilms['title']);

             foreach (array_keys($mfilms) as $key) {
                 printf("<p><b>%s</b>: %s</p>", $key, $mfilms[$key]);
             }

         } else {

             $mysqli = mysqli('localhost','sakila','password','sakila');

             if (mysqli_connect_error()) {
                 sprintf("Database error: (%d) %s", mysqli_connect_errno(), mysqli_connect_error());
                 exit;
             }

             $sql = sprintf('SELECT * FROM film WHERE title="%s"', $mysqli->real_escape_string($film));

             $result = $mysqli->query($sql);

             if (!$result) {
                 sprintf("Database error: (%d) %s", $mysqli->errno, $mysqli->error);
                 exit;
             }

             $row = $result->fetch_assoc();

             $memc->set($row['title'], $row);

             printf("<p>Loaded (%s) from MySQL</p>", htmlspecialchars($row['title'], ENT_QUOTES, 'UTF-8');
         }
     }
     ?>
       </body>
     </html>

With PHP, the connections to the `memcached' instances are kept open as
long as the PHP and associated Apache instance remain running. When
adding or removing servers from the list in a running instance (for
example, when starting another script that mentions additional
servers), the connections are shared, but the script only selects among
the instances explicitly configured within the script.

To ensure that changes to the server list within a script do not cause
problems, make sure to use the consistent hashing mechanism.


File: manual.info,  Node: ha-memcached-interfaces-ruby,  Next: ha-memcached-interfaces-java,  Prev: ha-memcached-interfaces-php,  Up: ha-memcached-interfaces

15.6.3.13 Using MySQL and `memcached' with Ruby
...............................................

There are a number of different modules for interfacing to `memcached'
within Ruby. The `Ruby-MemCache' client library provides a native
interface to `memcached' that does not require any external libraries,
such as `libmemcached'. You can obtain the installer package from
`http://www.deveiate.org/projects/RMemCache'.

To install, extract the package and then run `install.rb':


     shell> install.rb

If you have RubyGems, you can install the `Ruby-MemCache' gem:


     shell> gem install Ruby-MemCache
     Bulk updating Gem source index for: http://gems.rubyforge.org
     Install required dependency io-reactor? [Yn]  y
     Successfully installed Ruby-MemCache-0.0.1
     Successfully installed io-reactor-0.05
     Installing ri documentation for io-reactor-0.05...
     Installing RDoc documentation for io-reactor-0.05...

To use a `memcached' instance from within Ruby, create a new instance
of the `MemCache' object.


     require 'memcache'
     memc = MemCache::new '192.168.0.100:11211'

You can add a weight to each server to increase the likelihood of the
server being selected during hashing by appending the weight count to
the server host name/port string:


     require 'memcache'
     memc = MemCache::new '192.168.0.100:11211:3'

To add servers to an existing list, you can append them directly to the
`MemCache' object:


     memc += ["192.168.0.101:11211"]

To set data into the cache, you can just assign a value to a key within
the new cache object, which works just like a standard Ruby hash object:


     memc["key"] = "value"

Or to retrieve the value:


     print memc["key"]

For more explicit actions, you can use the method interface, which
mimics the main `memcached' API functions, as summarized in the
following table:

This table lists `memcached' methods for Ruby and the equivalent
`memcached' API functions.

Ruby `MemCache' Method               Equivalent `memcached' API Functions
`get()'                              Generic `get()'.
`get_hash(keys)'                     Get the values of multiple `keys',
                                     returning the information as a hash
                                     of the keys and their values.
`set()'                              Generic `set()'.
`set_many(pairs)'                    Set the values of the keys and
                                     values in the hash `pairs'.
`add()'                              Generic `add()'.
`replace()'                          Generic `replace()'.
`delete()'                           Generic `delete()'.
`incr()'                             Generic `incr()'.
`decr()'                             Generic `decr()'.


File: manual.info,  Node: ha-memcached-interfaces-java,  Next: ha-memcached-interfaces-protocol,  Prev: ha-memcached-interfaces-ruby,  Up: ha-memcached-interfaces

15.6.3.14 Using MySQL and `memcached' with Java
...............................................

The `com.danga.MemCached' class within Java provides a native interface
to `memcached' instances. You can obtain the client from
`https://github.com/gwhalin/Memcached-Java-Client/downloads'.  The Java
class uses hashes that are compatible with `libmemcached', so you can
mix and match Java and `libmemcached' applications accessing the same
`memcached' instances. The serialization between Java and other
interfaces are not compatible. If this is a problem, use JSON or a
similar nonbinary serialization format.

On most systems, you can download the package and use the `jar'
directly.

To use the `com.danga.MemCached' interface, you create a
`MemCachedClient' instance and then configure the list of servers by
configuring the `SockIOPool'. Through the pool specification you set up
the server list, weighting, and the connection parameters to optimized
the connections between your client and the `memcached' instances that
you configure.

Generally, you can configure the `memcached' interface once within a
single class, then use this interface throughout the rest of your
application.

For example, to create a basic interface, first configure the
`MemCachedClient' and base `SockIOPool' settings:


     public class MyClass {

         protected static MemCachedClient mcc = new MemCachedClient();

         static {

             String[] servers =
                 {
                     "localhost:11211",
                 };

             Integer[] weights = { 1 };

             SockIOPool pool = SockIOPool.getInstance();

             pool.setServers( servers );
             pool.setWeights( weights );

In the above sample, the list of servers is configured by creating an
array of the `memcached' instances to use. You can then configure
individual weights for each server.

The remainder of the properties for the connection are optional, but
you can set the connection numbers (initial connections, minimum
connections, maximum connections, and the idle timeout) by setting the
pool parameters:


     pool.setInitConn( 5 );
     pool.setMinConn( 5 );
     pool.setMaxConn( 250 );
     pool.setMaxIdle( 1000 * 60 * 60 * 6

Once the parameters have been configured, initialize the connection
pool:


     pool.initialize();

The pool, and the connection to your `memcached' instances should now
be ready to use.

To set the hashing algorithm used to select the server used when
storing a given key, use `pool.setHashingAlg()':


     pool.setHashingAlg( SockIOPool.NEW_COMPAT_HASH );

Valid values are `NEW_COMPAT_HASH', `OLD_COMPAT_HASH' and `NATIVE_HASH'
are also basic modula hashing algorithms. For a consistent hashing
algorithm, use `CONSISTENT_HASH'. These constants are equivalent to the
corresponding hash settings within `libmemcached'.

The following table outlines the Java `com.danga.MemCached' methods and
the equivalent generic methods in the `memcached' interface
specification.

This table lists Java `com.danga.MemCached' methods and the equivalent
generic methods in the `memcached' interface specification.

Java `com.danga.MemCached' Method    Equivalent Generic Method
`get()'                              Generic `get()'.
`getMulti(keys)'                     Get the values of multiple `keys',
                                     returning the information as Hash
                                     map using `java.lang.String' for
                                     the keys and `java.lang.Object' for
                                     the corresponding values.
`set()'                              Generic `set()'.
`add()'                              Generic `add()'.
`replace()'                          Generic `replace()'.
`delete()'                           Generic `delete()'.
`incr()'                             Generic `incr()'.
`decr()'                             Generic `decr()'.


File: manual.info,  Node: ha-memcached-interfaces-protocol,  Prev: ha-memcached-interfaces-java,  Up: ha-memcached-interfaces

15.6.3.15 Using the `memcached' TCP Text Protocol
.................................................

Communicating with a `memcached' server can be achieved through either
the TCP or UDP protocols. When using the TCP protocol, you can use a
simple text based interface for the exchange of information.

When communicating with `memcached', you can connect to the server
using the port configured for the server.  You can open a connection
with the server without requiring authorization or login. As soon as
you have connected, you can start to send commands to the server. When
you have finished, you can terminate the connection without sending any
specific disconnection command. Clients are encouraged to keep their
connections open to decrease latency and improve performance.

Data is sent to the `memcached' server in two forms:

   * Text lines, which are used to send commands to the server, and
     receive responses from the server.

   * Unstructured data, which is used to receive or send the value
     information for a given key. Data is returned to the client in
     exactly the format it was provided.

Both text lines (commands and responses) and unstructured data are
always terminated with the string `\r\n'.  Because the data being
stored may contain this sequence, the length of the data (returned by
the client before the unstructured data is transmitted should be used
to determine the end of the data.

Commands to the server are structured according to their operation:

   * *Storage commands*: `set', `add', `replace', `append', `prepend',
     `cas'

     Storage commands to the server take the form:


          command key [flags] [exptime] length [noreply]

     Or when using compare and swap (cas):


          cas key [flags] [exptime] length [casunique] [noreply]

     Where:

        * `command': The command name.

             * `set': Store value against key

             * `add': Store this value against key if the key does not
               already exist

             * `replace': Store this value against key if the key
               already exists

             * `append': Append the supplied value to the end of the
               value for the specified key. The `flags' and `exptime'
               arguments should not be used.

             * `prepend': Append value currently in the cache to the
               end of the supplied value for the specified key. The
               `flags' and `exptime' arguments should not be used.

             * `cas': Set the specified key to the supplied value, only
               if the supplied `casunique' matches. This is effectively
               the equivalent of change the information if nobody has
               updated it since I last fetched it.

        * `key': The key. All data is stored using a the specific key.
          The key cannot contain control characters or whitespace, and
          can be up to 250 characters in size.

        * `flags': The flags for the operation (as an integer). Flags
          in `memcached' are transparent. The `memcached' server
          ignores the contents of the flags. They can be used by the
          client to indicate any type of information. In `memcached'
          1.2.0 and lower the value is a 16-bit integer value. In
          `memcached' 1.2.1 and higher the value is a 32-bit integer.

        * `exptime': The expiry time, or zero for no expiry.

        * `length': The length of the supplied value block in bytes,
          excluding the terminating `\r\n' characters.

        * `casunique': A unique 64-bit value of an existing entry. This
          is used to compare against the existing value. Use the value
          returned by the `gets' command when issuing `cas' updates.

        * `noreply': Tells the server not to reply to the command.

     For example, to store the value `abcdef' into the key `xyzkey',
     you would use:


          set xyzkey 0 0 6\r\nabcdef\r\n

     The return value from the server is one line, specifying the
     status or error information. For more information, see *Note
     ha-memcached-interfaces-protocol-responses::.

   * *Retrieval commands*: `get', `gets'

     Retrieval commands take the form:


          get key1 [key2 .... keyn]
          gets key1 [key2 ... keyn]

     You can supply multiple keys to the commands, with each requested
     key separated by whitespace.

     The server responds with an information line of the form:


          VALUE key flags bytes [casunique]

     Where:

        * `key': The key name.

        * `flags': The value of the flag integer supplied to the
          `memcached' server when the value was stored.

        * `bytes': The size (excluding the terminating `\r\n' character
          sequence) of the stored value.

        * `casunique': The unique 64-bit integer that identifies the
          item.

     The information line is immediately followed by the value data
     block. For example:


          get xyzkey\r\n
          VALUE xyzkey 0 6\r\n
          abcdef\r\n

     If you have requested multiple keys, an information line and data
     block is returned for each key found. If a requested key does not
     exist in the cache, no information is returned.

   * *Delete commands*: `delete'

     Deletion commands take the form:


          delete key [time] [noreply]

     Where:

        * `key': The key name.

        * `time': The time in seconds (or a specific Unix time) for
          which the client wishes the server to refuse `add' or
          `replace' commands on this key. All `add', `replace', `get',
          and `gets' commands fail during this period. `set' operations
          succeed. After this period, the key is deleted permanently
          and all commands are accepted.

          If not supplied, the value is assumed to be zero (delete
          immediately).

        * `noreply': Tells the server not to reply to the command.

     Responses to the command are either `DELETED' to indicate that the
     key was successfully removed, or `NOT_FOUND' to indicate that the
     specified key could not be found.

   * *Increment/Decrement*: `incr', `decr'

     The increment and decrement commands change the value of a key
     within the server without performing a separate get/set sequence.
     The operations assume that the currently stored value is a 64-bit
     integer. If the stored value is not a 64-bit integer, then the
     value is assumed to be zero before the increment or decrement
     operation is applied.

     Increment and decrement commands take the form:


          incr key value [noreply]
          decr key value [noreply]

     Where:

        * `key': The key name.

        * `value': An integer to be used as the increment or decrement
          value.

        * `noreply': Tells the server not to reply to the command.

     The response is:

        * `NOT_FOUND': The specified key could not be located.

        * `value': The new value associated with the specified key.

     Values are assumed to be unsigned. For `decr' operations, the
     value is never decremented below 0. For `incr' operations, the
     value wraps around the 64-bit maximum.

   * *Statistics commands*: `stats'

     The `stats' command provides detailed statistical information
     about the current status of the `memcached' instance and the data
     it is storing.

     Statistics commands take the form:


          STAT [name] [value]

     Where:

        * `name': The optional name of the statistics to return. If not
          specified, the general statistics are returned.

        * `value': A specific value to be used when performing certain
          statistics operations.

     The return value is a list of statistics data, formatted as
     follows:


          STAT name value

     The statistics are terminated with a single line, `END'.

     For more information, see *Note ha-memcached-stats::.

For reference, a list of the different commands supported and their
formats is provided below.

*`memcached' Command Reference*

Command            Command Formats
`set'              `set key flags exptime length', `set key flags
                   exptime length noreply'
`add'              `add key flags exptime length', `add key flags
                   exptime length noreply'
`replace'          `replace key flags exptime length', `replace key
                   flags exptime length noreply'
`append'           `append key length', `append key length noreply'
`prepend'          `prepend key length', `prepend key length noreply'
`cas'              `cas key flags exptime length casunique', `cas key
                   flags exptime length casunique noreply'
`get'              `get key1 [key2 ... keyn]'
`gets'             `'
`delete'           `delete key', `delete key noreply', `delete key
                   expiry', `delete key expiry noreply'
`incr'             `incr key', `incr key noreply', `incr key value',
                   `incr key value noreply'
`decr'             `decr key', `decr key noreply', `decr key value',
                   `decr key value noreply'
`stat'             `stat', `stat name', `stat name value'

When sending a command to the server, the response from the server is
one of the settings in the following table. All response values from
the server are terminated by `\r\n':

*`memcached' Protocol Responses*

String             Description
`STORED'           Value has successfully been stored.
`NOT_STORED'       The value was not stored, but not because of an
                   error. For commands where you are adding a or
                   updating a value if it exists (such as `add' and
                   `replace'), or where the item has already been set to
                   be deleted.
`EXISTS'           When using a `cas' command, the item you are trying to
                   store already exists and has been modified since you
                   last checked it.
`NOT_FOUND'        The item you are trying to store, update or delete
                   does not exist or has already been deleted.
`ERROR'            You submitted a nonexistent command name.
`CLIENT_ERROR      There was an error in the input line, the detail is
errorstring'       contained in `errorstring'.
`SERVER_ERROR      There was an error in the server that prevents it
errorstring'       from returning the information. In extreme
                   conditions, the server may disconnect the client
                   after this error occurs.
`VALUE keys flags  The requested key has been found, and the stored
length'            `key', `flags' and data block are returned, of the
                   specified `length'.
`DELETED'          The requested key was deleted from the server.
`STAT name value'  A line of statistics data.
`END'              The end of the statistics data.


File: manual.info,  Node: ha-memcached-stats,  Next: ha-memcached-faq,  Prev: ha-memcached-interfaces,  Up: ha-memcached

15.6.4 Getting `memcached' Statistics
-------------------------------------

* Menu:

* ha-memcached-stats-general::   `memcached' General Statistics
* ha-memcached-stats-slabs::     `memcached' Slabs Statistics
* ha-memcached-stats-items::     `memcached' Item Statistics
* ha-memcached-stats-sizes::     `memcached' Size Statistics
* ha-memcached-stats-detail::    `memcached' Detail Statistics
* ha-memcached-stats-memcached-tool::  Using `memcached-tool'

The `memcached' system has a built-in statistics system that collects
information about the data being stored into the cache, cache hit
ratios, and detailed information on the memory usage and distribution
of information through the slab allocation used to store individual
items. Statistics are provided at both a basic level that provide the
core statistics, and more specific statistics for specific areas of the
`memcached' server.

This information can be useful to ensure that you are getting the
correct level of cache and memory usage, and that your slab allocation
and configuration properties are set at an optimal level.

The stats interface is available through the standard `memcached'
protocol, so the reports can be accessed by using `telnet' to connect
to the `memcached'. The supplied `memcached-tool' includes support for
obtaining the *Note ha-memcached-stats-slabs:: and *Note
ha-memcached-stats-general:: information. For more information, see
*Note ha-memcached-stats-memcached-tool::.

Alternatively, most of the language API interfaces provide a function
for obtaining the statistics from the server.

For example, to get the basic stats using `telnet':


     shell> telnet localhost 11211
     Trying ::1...
     Connected to localhost.
     Escape character is '^]'.
     stats
     STAT pid 23599
     STAT uptime 675
     STAT time 1211439587
     STAT version 1.2.5
     STAT pointer_size 32
     STAT rusage_user 1.404992
     STAT rusage_system 4.694685
     STAT curr_items 32
     STAT total_items 56361
     STAT bytes 2642
     STAT curr_connections 53
     STAT total_connections 438
     STAT connection_structures 55
     STAT cmd_get 113482
     STAT cmd_set 80519
     STAT get_hits 78926
     STAT get_misses 34556
     STAT evictions 0
     STAT bytes_read 6379783
     STAT bytes_written 4860179
     STAT limit_maxbytes 67108864
     STAT threads 1
     END

When using Perl and the `Cache::Memcached' module, the `stats()'
function returns information about all the servers currently configured
in the connection object, and total statistics for all the `memcached'
servers as a whole.

For example, the following Perl script obtains the stats and dumps the
hash reference that is returned:


     use Cache::Memcached;
     use Data::Dumper;

     my $memc = new Cache::Memcached;
     $memc->set_servers(\@ARGV);

     print Dumper($memc->stats());

When executed on the same `memcached' as used in the `Telnet' example
above we get a hash reference with the host by host and total
statistics:


     $VAR1 = {
         'hosts' => {
                'localhost:11211' => {
                           'misc' => {
                                 'bytes' => '2421',
                                 'curr_connections' => '3',
                                 'connection_structures' => '56',
                                 'pointer_size' => '32',
                                 'time' => '1211440166',
                                 'total_items' => '410956',
                                 'cmd_set' => '588167',
                                 'bytes_written' => '35715151',
                                 'evictions' => '0',
                                 'curr_items' => '31',
                                 'pid' => '23599',
                                 'limit_maxbytes' => '67108864',
                                 'uptime' => '1254',
                                 'rusage_user' => '9.857805',
                                 'cmd_get' => '838451',
                                 'rusage_system' => '34.096988',
                                 'version' => '1.2.5',
                                 'get_hits' => '581511',
                                 'bytes_read' => '46665716',
                                 'threads' => '1',
                                 'total_connections' => '3104',
                                 'get_misses' => '256940'
                               },
                           'sizes' => {
                                  '128' => '16',
                                  '64' => '15'
                                }
                         }
              },
         'self' => {},
         'total' => {
                'cmd_get' => 838451,
                'bytes' => 2421,
                'get_hits' => 581511,
                'connection_structures' => 56,
                'bytes_read' => 46665716,
                'total_items' => 410956,
                'total_connections' => 3104,
                'cmd_set' => 588167,
                'bytes_written' => 35715151,
                'curr_items' => 31,
                'get_misses' => 256940
              }
             };

The statistics are divided up into a number of distinct sections, and
then can be requested by adding the type to the `stats' command. Each
statistics output is covered in more detail in the following sections.

   * General statistics, see *Note ha-memcached-stats-general::.

   * Slab statistics (`slabs'), see *Note ha-memcached-stats-slabs::.

   * Item statistics (`items'), see *Note ha-memcached-stats-items::.

   * Size statistics (`sizes'), see *Note ha-memcached-stats-sizes::.

   * Detailed status (`detail'), see *Note ha-memcached-stats-detail::.


File: manual.info,  Node: ha-memcached-stats-general,  Next: ha-memcached-stats-slabs,  Prev: ha-memcached-stats,  Up: ha-memcached-stats

15.6.4.1 `memcached' General Statistics
.......................................

The output of the general statistics provides an overview of the
performance and use of the `memcached' instance. The statistics
returned by the command and their meaning is shown in the following
table.

The following terms are used to define the value type for each
statistics value:

   * `32u': 32-bit unsigned integer

   * `64u': 64-bit unsigned integer

   * `32u:32u': Two 32-bit unsigned integers separated by a colon

   * `String': Character string

This table lists `memcached' general statistics and provides the data
type and a description for each statistic.

Statistic      Data type   Description                              Version
`pid'          32u         Process ID of the `memcached' instance.  
`uptime'       32u         Uptime (in seconds) for this             
                           `memcached' instance.                    
`time'         32u         Current time (as epoch).                 
`version'      string      Version string of this instance.         
`pointer_size' string      Size of pointers for this host           
                           specified in bits (32 or 64).            
`rusage_user'  32u:32u     Total user time for this instance        
                           (seconds:microseconds).                  
`rusage_system'32u:32u     Total system time for this instance      
                           (seconds:microseconds).                  
`curr_items'   32u         Current number of items stored by this   
                           instance.                                
`total_items'  32u         Total number of items stored during the  
                           life of this instance.                   
`bytes'        64u         Current number of bytes used by this     
                           server to store items.                   
`curr_connections'32u         Current number of open connections.      
`total_connections'32u         Total number of connections opened       
                           since the server started running.        
`connection_structures'32u         Number of connection structures          
                           allocated by the server.                 
`cmd_get'      64u         Total number of retrieval requests       
                           (`get' operations).                      
`cmd_set'      64u         Total number of storage requests (`set'  
                           operations).                             
`get_hits'     64u         Number of keys that have been requested  
                           and found present.                       
`get_misses'   64u         Number of items that have been           
                           requested and not found.                 
`delete_hits'  64u         Number of keys that have been deleted    1.3.x
                           and found present.                       
`delete_misses'64u         Number of items that have been delete    1.3.x
                           and not found.                           
`incr_hits'    64u         Number of keys that have been            1.3.x
                           incremented and found present.           
`incr_misses'  64u         Number of items that have been           1.3.x
                           incremented and not found.               
`decr_hits'    64u         Number of keys that have been            1.3.x
                           decremented and found present.           
`decr_misses'  64u         Number of items that have been           1.3.x
                           decremented and not found.               
`cas_hits'     64u         Number of keys that have been compared   1.3.x
                           and swapped and found present.           
`cas_misses'   64u         Number of items that have been compared  1.3.x
                           and swapped and not found.               
`cas_badvalue' 64u         Number of keys that have been compared   1.3.x
                           and swapped, but the comparison          
                           (original) value did not match the       
                           supplied value.                          
`evictions'    64u         Number of valid items removed from       
                           cache to free memory for new items.      
`bytes_read'   64u         Total number of bytes read by this       
                           server from network.                     
`bytes_written'64u         Total number of bytes sent by this       
                           server to network.                       
`limit_maxbytes'32u         Number of bytes this server is           
                           permitted to use for storage.            
`threads'      32u         Number of worker threads requested.      
`conn_yields'  64u         Number of yields for connections         1.4.0
                           (related to the `-R' option).            

The most useful statistics from those given here are the number of
cache hits, misses, and evictions.

A large number of `get_misses' may just be an indication that the cache
is still being populated with information. The number should, over
time, decrease in comparison to the number of cache `get_hits'.  If,
however, you have a large number of cache misses compared to cache hits
after an extended period of execution, it may be an indication that the
size of the cache is too small and you either need to increase the
total memory size, or increase the number of the `memcached' instances
to improve the hit ratio.

A large number of `evictions' from the cache, particularly in
comparison to the number of items stored is a sign that your cache is
too small to hold the amount of information that you regularly want to
keep cached. Instead of items being retained in the cache, items are
being evicted to make way for new items keeping the turnover of items
in the cache high, reducing the efficiency of the cache.


File: manual.info,  Node: ha-memcached-stats-slabs,  Next: ha-memcached-stats-items,  Prev: ha-memcached-stats-general,  Up: ha-memcached-stats

15.6.4.2 `memcached' Slabs Statistics
.....................................

To get the `slabs' statistics, use the `stats slabs' command, or the
API equivalent.

The slab statistics provide you with information about the slabs that
have created and allocated for storing information within the cache.
You get information both on each individual slab-class and total
statistics for the whole slab.


     STAT 1:chunk_size 104
     STAT 1:chunks_per_page 10082
     STAT 1:total_pages 1
     STAT 1:total_chunks 10082
     STAT 1:used_chunks 10081
     STAT 1:free_chunks 1
     STAT 1:free_chunks_end 10079
     STAT 9:chunk_size 696
     STAT 9:chunks_per_page 1506
     STAT 9:total_pages 63
     STAT 9:total_chunks 94878
     STAT 9:used_chunks 94878
     STAT 9:free_chunks 0
     STAT 9:free_chunks_end 0
     STAT active_slabs 2
     STAT total_malloced 67083616
     END

Individual stats for each slab class are prefixed with the slab ID. A
unique ID is given to each allocated slab from the smallest size up to
the largest. The prefix number indicates the slab class number in
relation to the calculated chunk from the specified growth factor.
Hence in the example, 1 is the first chunk size and 9 is the 9th chunk
allocated size.

The parameters returned for each chunk size and a description of each
parameter are provided in the following table.

This table lists `memcached' slabs statistics parameters that are
returned for each chunk size.  The table provides the statistic name,
description, and the `memcached' version in which the statistic was
introduced (if applicable).

Statistic          Description                              Version
`chunk_size'       Space allocated to each chunk within     
                   this slab class.                         
`chunks_per_page'  Number of chunks within a single page    
                   for this slab class.                     
`total_pages'      Number of pages allocated to this slab   
                   class.                                   
`total_chunks'     Number of chunks allocated to the slab   
                   class.                                   
`used_chunks'      Number of chunks allocated to an item..  
`free_chunks'      Number of chunks not yet allocated to    
                   items.                                   
`free_chunks_end'  Number of free chunks at the end of the  
                   last allocated page.                     
`get_hits'         Number of get hits to this chunk         1.3.x
`cmd_set'          Number of set commands on this chunk     1.3.x
`delete_hits'      Number of delete hits to this chunk      1.3.x
`incr_hits'        Number of increment hits to this chunk   1.3.x
`decr_hits'        Number of decrement hits to this chunk   1.3.x
`cas_hits'         Number of CAS hits to this chunk         1.3.x
`cas_badval'       Number of CAS hits on this chunk where   1.3.x
                   the existing value did not match         
`mem_requested'    The true amount of memory of memory      1.4.1
                   requested within this chunk              

The following additional statistics cover the information for the
entire server, rather than on a chunk by chunk basis:

This table lists `memcached' slab statistics that provide information
for the entire server rather than for a single chunk. The table
provides the statistic name, description, and version (if applicable).

Statistic          Description                              Version
`active_slabs'     Total number of slab classes allocated.  
`total_malloced'   Total amount of memory allocated to      
                   slab pages.                              

The key values in the slab statistics are the `chunk_size', and the
corresponding `total_chunks' and `used_chunks' parameters. These given
an indication of the size usage of the chunks within the system.
Remember that one key/value pair is placed into a chunk of a suitable
size.

From these stats, you can get an idea of your size and chunk allocation
and distribution. If you store many items with a number of largely
different sizes, consider adjusting the chunk size growth factor to
increase in larger steps to prevent chunk and memory wastage. A good
indication of a bad growth factor is a high number of different slab
classes, but with relatively few chunks actually in use within each
slab. Increasing the growth factor creates fewer slab classes and
therefore makes better use of the allocated pages.


File: manual.info,  Node: ha-memcached-stats-items,  Next: ha-memcached-stats-sizes,  Prev: ha-memcached-stats-slabs,  Up: ha-memcached-stats

15.6.4.3 `memcached' Item Statistics
....................................

To get the `items' statistics, use the `stats items' command, or the
API equivalent.

The `items' statistics give information about the individual items
allocated within a given slab class.


     STAT items:2:number 1
     STAT items:2:age 452
     STAT items:2:evicted 0
     STAT items:2:evicted_nonzero 0
     STAT items:2:evicted_time 2
     STAT items:2:outofmemory 0
     STAT items:2:tailrepairs 0
     ...
     STAT items:27:number 1
     STAT items:27:age 452
     STAT items:27:evicted 0
     STAT items:27:evicted_nonzero 0
     STAT items:27:evicted_time 2
     STAT items:27:outofmemory 0
     STAT items:27:tailrepairs 0

The prefix number against each statistics relates to the corresponding
chunk size, as returned by the `stats slabs' statistics. The result is
a display of the number of items stored within each chunk within each
slab size, and specific statistics about their age, eviction counts, and
out of memory counts. A summary of the statistics is given in the
following table.

This table lists `memcached' item statistics and provides a description
of each.

Statistic          Description                                     
`number'           The number of items currently stored in this    
                   slab class.                                     
`age'              The age of the oldest item within the slab      
                   class, in seconds.                              
`evicted'          The number of items evicted to make way for     
                   new entries.                                    
`evicted_time'     The time of the last evicted entry              
`evicted_nonzero'  The time of the last evicted non-zero entry     1.4.0
`outofmemory'      The number of items for this slab class that    
                   have triggered an out of memory error (only     
                   value when the `-M' command line option is in   
                   effect).                                        
`tailrepairs'      Number of times the entries for a particular    
                   ID need repairing                               

Item level statistics can be used to determine how many items are
stored within a given slab and their freshness and recycle rate. You
can use this to help identify whether there are certain slab classes
that are triggering a much larger number of evictions that others.


File: manual.info,  Node: ha-memcached-stats-sizes,  Next: ha-memcached-stats-detail,  Prev: ha-memcached-stats-items,  Up: ha-memcached-stats

15.6.4.4 `memcached' Size Statistics
....................................

To get size statistics, use the `stats sizes' command, or the API
equivalent.

The size statistics provide information about the sizes and number of
items of each size within the cache. The information is returned as two
columns, the first column is the size of the item (rounded up to the
nearest 32 byte boundary), and the second column is the count of the
number of items of that size within the cache:


     96 35
     128 38
     160 807
     192 804
     224 410
     256 222
     288 83
     320 39
     352 53
     384 33
     416 64
     448 51
     480 30
     512 54
     544 39
     576 10065

*Caution*:

Running this statistic locks up your cache as each item is read from
the cache and its size calculated. On a large cache, this may take some
time and prevent any set or get operations until the process completes.

The item size statistics are useful only to determine the sizes of the
objects you are storing. Since the actual memory allocation is relevant
only in terms of the chunk size and page size, the information is only
useful during a careful debugging or diagnostic session.


File: manual.info,  Node: ha-memcached-stats-detail,  Next: ha-memcached-stats-memcached-tool,  Prev: ha-memcached-stats-sizes,  Up: ha-memcached-stats

15.6.4.5 `memcached' Detail Statistics
......................................

For `memcached' 1.3.x and higher, you can enable and obtain detailed
statistics about the get, set, and del operations on theindividual keys
stored in the cache, and determine whether the attempts hit (found) a
particular key.  These operations are only recorded while the detailed
stats analysis is turned on.

To enable detailed statistics, you must send the `stats detail on'
command to the `memcached' server:


     $ telnet localhost 11211
     Trying 127.0.0.1...
     Connected to tiger.
     Escape character is '^]'.
     stats detail on
     OK

Individual statistics are recorded for every `get', `set' and `del'
operation on a key, including keys that are not currently stored in the
server. For example, if an attempt is made to obtain the value of key
`abckey' and it does not exist, the `get' operating on the specified
key are recorded while detailed statistics are in effect, even if the
key is not currently stored. The `hits', that is, the number of `get' or
`del' operations for a key that exists in the server are also counted.

To turn detailed statistics off, send the `stats detail off' command to
the `memcached' server:


     $ telnet localhost 11211
     Trying 127.0.0.1...
     Connected to tiger.
     Escape character is '^]'.
     stats detail on
     OK

To obtain the detailed statistics recorded during the process, send the
`stats detail dump' command to the `memcached' server:


     stats detail dump
     PREFIX hykkey get 0 hit 0 set 1 del 0
     PREFIX xyzkey get 0 hit 0 set 1 del 0
     PREFIX yukkey get 1 hit 0 set 0 del 0
     PREFIX abckey get 3 hit 3 set 1 del 0
     END

You can use the detailed statistics information to determine whether
your `memcached' clients are using a large number of keys that do not
exist in the server by comparing the `hit' and `get' or `del' counts.
Because the information is recorded by key, you can also determine
whether the failures or operations are clustered around specific keys.


File: manual.info,  Node: ha-memcached-stats-memcached-tool,  Prev: ha-memcached-stats-detail,  Up: ha-memcached-stats

15.6.4.6 Using `memcached-tool'
...............................

The `memcached-tool', located within the `scripts' directory within the
`memcached' source directory. The tool provides convenient access to
some reports and statistics from any `memcached' instance.

The basic format of the command is:


     shell> ./memcached-tool hostname:port [command]

The default output produces a list of the slab allocations and usage.
For example:


     shell> memcached-tool localhost:11211 display
       #  Item_Size  Max_age   Pages   Count   Full?  Evicted Evict_Time OOM
       1      80B        93s       1      20      no        0        0    0
       2     104B        93s       1      16      no        0        0    0
       3     136B      1335s       1      28      no        0        0    0
       4     176B      1335s       1      24      no        0        0    0
       5     224B      1335s       1      32      no        0        0    0
       6     280B      1335s       1      34      no        0        0    0
       7     352B      1335s       1      36      no        0        0    0
       8     440B      1335s       1      46      no        0        0    0
       9     552B      1335s       1      58      no        0        0    0
      10     696B      1335s       1      66      no        0        0    0
      11     872B      1335s       1      89      no        0        0    0
      12     1.1K      1335s       1     112      no        0        0    0
      13     1.3K      1335s       1     145      no        0        0    0
      14     1.7K      1335s       1     123      no        0        0    0
      15     2.1K      1335s       1     198      no        0        0    0
      16     2.6K      1335s       1     199      no        0        0    0
      17     3.3K      1335s       1     229      no        0        0    0
      18     4.1K      1335s       1     248     yes       36        2    0
      19     5.2K      1335s       2     328      no        0        0    0
      20     6.4K      1335s       2     316     yes      387        1    0
      21     8.1K      1335s       3     381     yes      492        1    0
      22    10.1K      1335s       3     303     yes      598        2    0
      23    12.6K      1335s       5     405     yes      605        1    0
      24    15.8K      1335s       6     384     yes      766        2    0
      25    19.7K      1335s       7     357     yes      908      170    0
      26    24.6K      1336s       7     287     yes     1012        1    0
      27    30.8K      1336s       7     231     yes     1193      169    0
      28    38.5K      1336s       4     104     yes     1323      169    0
      29    48.1K      1336s       1      21     yes     1287        1    0
      30    60.2K      1336s       1      17     yes     1093      169    0
      31    75.2K      1337s       1      13     yes      713      168    0
      32    94.0K      1337s       1      10     yes      278      168    0
      33   117.5K      1336s       1       3      no        0        0    0

This output is the same if you specify the `command' as `display':


     shell> memcached-tool localhost:11211 display
       #  Item_Size  Max_age   Pages   Count   Full?  Evicted Evict_Time OOM
       1      80B        93s       1      20      no        0        0    0
       2     104B        93s       1      16      no        0        0    0
     ...

The output shows a summarized version of the output from the `slabs'
statistics. The columns provided in the output are shown below:

   * `#': The slab number

   * `Item_Size': The size of the slab

   * `Max_age': The age of the oldest item in the slab

   * `Pages': The number of pages allocated to the slab

   * `Count': The number of items in this slab

   * `Full?': Whether the slab is fully populated

   * `Evicted': The number of objects evicted from this slab

   * `Evict_Time': The time (in seconds) since the last eviction

   * `OOM': The number of items that have triggered an out of memory
     error

You can also obtain a dump of the general statistics for the server
using the `stats' command:


     shell> memcached-tool localhost:11211 stats
     #localhost:11211   Field       Value
              accepting_conns           1
                        bytes         162
                   bytes_read         485
                bytes_written        6820
                   cas_badval           0
                     cas_hits           0
                   cas_misses           0
                    cmd_flush           0
                      cmd_get           4
                      cmd_set           2
                  conn_yields           0
        connection_structures          11
             curr_connections          10
                   curr_items           2
                    decr_hits           0
                  decr_misses           1
                  delete_hits           0
                delete_misses           0
                    evictions           0
                     get_hits           4
                   get_misses           0
                    incr_hits           0
                  incr_misses           2
               limit_maxbytes    67108864
          listen_disabled_num           0
                          pid       12981
                 pointer_size          32
                rusage_system    0.013911
                  rusage_user    0.011876
                      threads           4
                         time  1255518565
            total_connections          20
                  total_items           2
                       uptime         880
                      version       1.4.2


File: manual.info,  Node: ha-memcached-faq,  Prev: ha-memcached-stats,  Up: ha-memcached

15.6.5 `memcached' FAQ
----------------------

*Questions*
   * 16.6.5.1: Can memcached be run on a Windows environment?

   * 16.6.5.2: What is the maximum size of an object you can store in
     memcached? Is that configurable?

   * 16.6.5.3: Is it true `memcached' will be much more effective with
     db-read-intensive applications than with db-write-intensive
     applications?

   * 16.6.5.4: Is there any overhead in not using persistent
     connections? If persistent is always recommended, what are the
     downsides (for example, locking up)?

   * 16.6.5.5: How is an event such as a crash of one of the
     `memcached' servers handled by the `memcached' client?

   * 16.6.5.6: What is a recommended hardware configuration for a
     memcached server?

   * 16.6.5.7: Is memcached more effective for video and audio as
     opposed to textual read/writes?

   * 16.6.5.8: Can `memcached' work with ASPX?

   * 16.6.5.9: How expensive is it to establish a memcache connection?
     Should those connections be pooled?

   * 16.6.5.10: How is the data handled when the `memcached' server is
     down?

   * 16.6.5.11: How are auto-increment columns in the MySQL database
     coordinated across multiple instances of memcached?

   * 16.6.5.12: Is compression available?

   * 16.6.5.13: Can we implement different types of `memcached' as
     different nodes in the same server, so can there be deterministic
     and non-deterministic in the same server?

   * 16.6.5.14: What are best practices for testing an implementation,
     to ensure that it improves performance, and to measure the impact
     of `memcached' configuration changes? And would you recommend
     keeping the configuration very simple to start?

*Questions and Answers* *16.6.5.1: ** Can memcached be run on a Windows
environment?  *

No. Currently `memcached' is available only on the Unix/Linux platform.
There is an unofficial port available, see
`http://www.codeplex.com/memcachedproviders'.

*16.6.5.2: ** What is the maximum size of an object you can store in
memcached? Is that configurable?  *

The default maximum object size is 1MB. In `memcached' 1.4.2 and later,
you can change the maximum size of an object using the `-I' command
line option.

For versions before this, to increase this size, you have to re-compile
`memcached'. You can modify the value of the `POWER_BLOCK' within the
`slabs.c' file within the source.

In `memcached' 1.4.2 and higher, you can configure the maximum
supported object size by using the `-I' command-line option. For
example, to increase the maximum object size to 5MB:


     $ memcached -I 5m

If an object is larger than the maximum object size, you must manually
split it. `memcached' is very simple: you give it a key and some data,
it tries to cache it in RAM. If you try to store more than the default
maximum size, the value is just truncated for speed reasons.

*16.6.5.3: ** Is it true `memcached' will be much more effective with
db-read-intensive applications than with db-write-intensive
applications?  *

Yes. `memcached' plays no role in database writes, it is a method of
caching data already read from the database in RAM.

*16.6.5.4: ** Is there any overhead in not using persistent
connections? If persistent is always recommended, what are the
downsides (for example, locking up)?  *

If you don't use persistent connections when communicating with
`memcached', there will be a small increase in the latency of opening
the connection each time. The effect is comparable to use nonpersistent
connections with MySQL.

In general, the chance of locking or other issues with persistent
connections is minimal, because there is very little locking within
`memcached'. If there is a problem, eventually your request will time
out and return no result, so your application will need to load from
MySQL again.

*16.6.5.5: ** How is an event such as a crash of one of the `memcached'
servers handled by the `memcached' client?  *

There is no automatic handling of this. If your client fails to get a
response from a server, code a fallback mechanism to load the data from
the MySQL database.

The client APIs all provide the ability to add and remove `memcached'
instances on the fly. If within your application you notice that
`memcached' server is no longer responding, you can remove the server
from the list of servers, and keys will automatically be redistributed
to another `memcached' server in the list. If retaining the cache
content on all your servers is important, make sure you use an API that
supports a consistent hashing algorithm. For more information, see
*Note ha-memcached-using-hashtypes::.

*16.6.5.6: ** What is a recommended hardware configuration for a
memcached server?  *

`memcached' has a very low processing overhead.  All that is required
is spare physical RAM capacity. A `memcached' server does not require a
dedicated machine. If you have web, application, or database servers
that have spare RAM capacity, then use them with `memcached'.

To build and deploy a dedicated `memcached' server, use a relatively
low-power CPU, lots of RAM, and one or more Gigabit Ethernet interfaces.

*16.6.5.7: ** Is memcached more effective for video and audio as
opposed to textual read/writes?  *

`memcached' works equally well for all kinds of data. To `memcached',
any value you store is just a stream of data. Remember, though, that
the maximum size of an object you can store in `memcached' is 1MB, but
can be configured to be larger by using the `-I' option in `memcached'
1.4.2 and later, or by modifying the source in versions before 1.4.2.
If you plan on using `memcached' with audio and video content, you will
probably want to increase the maximum object size. Also remember that
`memcached' is a solution for caching information for reading. It
shouldn't be used for writes, except when updating the information in
the cache.

*16.6.5.8: ** Can `memcached' work with ASPX?  *

There are ports and interfaces for many languages and environments.
ASPX relies on an underlying language such as C# or VisualBasic, and if
you are using ASP.NET then there is a C# `memcached' library. For more
information, see `https://sourceforge.net/projects/memcacheddotnet/'.

*16.6.5.9: ** How expensive is it to establish a memcache connection?
Should those connections be pooled?  *

Opening the connection is relatively inexpensive, because there is no
security, authentication or other handshake taking place before you can
start sending requests and getting results. Most APIs support a
persistent connection to a `memcached' instance to reduce the latency.
Connection pooling would depend on the API you are using, but if you
are communicating directly over TCP/IP, then connection pooling would
provide some small performance benefit.

*16.6.5.10: ** How is the data handled when the `memcached' server is
down?  *

The behavior is entirely application dependent. Most applications fall
back to loading the data from the database (just as if they were
updating the `memcached' information). If you are using multiple
`memcached' servers, you might also remove a downed server from the
list to prevent it from affecting performance. Otherwise, the client
will still attempt to communicate with the `memcached' server that
corresponds to the key you are trying to load.

*16.6.5.11: ** How are auto-increment columns in the MySQL database
coordinated across multiple instances of memcached?  *

They aren't. There is no relationship between MySQL and `memcached'
unless your application (or, if you are using the MySQL UDFs for
`memcached', your database definition) creates one.

If you are storing information based on an auto-increment key into
multiple instances of `memcached', the information is only stored on
one of the `memcached' instances anyway. The client uses the key value
to determine which `memcached' instance to store the information. It
doesn't store the same information across all the instances, as that
would be a waste of cache memory.

*16.6.5.12: ** Is compression available?  *

Yes. Most of the client APIs support some sort of compression, and some
even allow you to specify the threshold at which a value is deemed
appropriate for compression during storage.

*16.6.5.13: ** Can we implement different types of `memcached' as
different nodes in the same server, so can there be deterministic and
non-deterministic in the same server?  *

Yes. You can run multiple instances of `memcached' on a single server,
and in your client configuration you choose the list of servers you
want to use.

*16.6.5.14: ** What are best practices for testing an implementation,
to ensure that it improves performance, and to measure the impact of
`memcached' configuration changes? And would you recommend keeping the
configuration very simple to start?  *

The best way to test the performance is to start up a `memcached'
instance. First, modify your application so that it stores the data
just before the data is about to be used or displayed into `memcached'.
Since the APIs handle the serialization of the data, it should just be
a one-line modification to your code. Then, modify the start of the
process that would normally load that information from MySQL with the
code that requests the data from `memcached'. If the data cannot be
loaded from `memcached', default to the MySQL process.

All of the changes required will probably amount to just a few lines of
code. To get the best benefit, make sure you cache entire objects (for
example, all the components of a web page, blog post, discussion
thread, and so on), rather than using `memcached' as a simple cache of
individual rows of MySQL tables.

Keeping the configuration simple at the start, or even over the long
term, is easy with `memcached'. Once you have the basic structure up
and running, often the only ongoing change is to add more servers into
the list of servers used by your applications. You don't need to manage
the `memcached' servers, and there is no complex configuration; just
add more servers to the list and let the client API and the `memcached'
servers make the decisions.


File: manual.info,  Node: mysql-proxy,  Prev: ha-memcached,  Up: ha-overview

15.7 MySQL Proxy
================

* Menu:

* mysql-proxy-platforms::        MySQL Proxy Supported Platforms
* mysql-proxy-install::          Installing MySQL Proxy
* mysql-proxy-configuration::    MySQL Proxy Command Options
* mysql-proxy-scripting::        MySQL Proxy Scripting
* mysql-proxy-using::            Using MySQL Proxy
* mysql-proxy-faq::              MySQL Proxy FAQ

The MySQL Proxy is an application that communicates over the network
using the MySQL client/server protocol and provides communication
between one or more MySQL servers and one or more MySQL clients.
Because MySQL Proxy uses the MySQL network protocol, it can be used
without modification with any MySQL-compatible client that uses the
protocol. This includes the *Note `mysql': mysql. command-line client,
any clients that uses the MySQL client libraries, and any connector
that supports the MySQL network protocol.

In the most basic configuration, MySQL Proxy simply interposes itself
between the server and clients, passing queries from the clients to the
MySQL Server and returning the responses from the MySQL Server to the
appropriate client. In more advanced configurations, the MySQL Proxy
can also monitor and alter the communication between the client and the
server. Query interception enables you to add profiling, and
interception of the exchanges is scriptable using the Lua scripting
language.

By intercepting the queries from the client, the proxy can insert
additional queries into the list of queries sent to the server, and
remove the additional results when they are returned by the server.
Using this functionality you can return the results from the original
query to the client while adding informational statements to each
query, for example, to monitor their execution time or progress, and
separately log the results.

The proxy enables you to perform additional monitoring, filtering, or
manipulation of queries without requiring you to make any modifications
to the client and without the client even being aware that it is
communicating with anything but a genuine MySQL server.

This documentation covers MySQL Proxy 0.8.5.  And MySQL Proxy contains
third-party code. For license information on third-party code, see
*Note licenses-third-party::.

*Warning*:

MySQL Proxy is currently an Alpha release and should not be used within
production environments.

*Important*:

MySQL Proxy is compatible with MySQL 5.0 or later. Testing has not been
performed with Version 4.1. Please provide feedback on your experiences
using the MySQL Proxy Forum (http://forums.mysql.com/list.php?146).

For notes detailing the changes in each release of MySQL Proxy, see
MySQL Proxy Release Notes
(http://dev.mysql.com/doc/relnotes/mysql-proxy/en/).


File: manual.info,  Node: mysql-proxy-platforms,  Next: mysql-proxy-install,  Prev: mysql-proxy,  Up: mysql-proxy

15.7.1 MySQL Proxy Supported Platforms
--------------------------------------

MySQL Proxy is currently available as a precompiled binary for the
following platforms:

   * Linux (including Red Hat, Fedora, Debian, SuSE) and derivatives

   * Mac OS X

   * FreeBSD

   * IBM AIX

   * Sun Solaris

   * Microsoft Windows (including Microsoft Windows XP, Microsoft
     Windows Vista, Microsoft Windows Server 2003, Microsoft Windows
     Server 2008)

Other Unix/Linux platforms not listed should be compatible by using the
source package and building MySQL Proxy locally.

System requirements for the MySQL Proxy application are the same as the
main MySQL server. Currently MySQL Proxy is compatible only with MySQL
5.0.1 and later. MySQL Proxy is provided as a standalone binary. It is
not necessary to have MySQL or Lua installed.


File: manual.info,  Node: mysql-proxy-install,  Next: mysql-proxy-configuration,  Prev: mysql-proxy-platforms,  Up: mysql-proxy

15.7.2 Installing MySQL Proxy
-----------------------------

* Menu:

* mysql-proxy-install-binary::   Installing MySQL Proxy from a Binary Distribution
* mysql-proxy-install-source::   Installing MySQL Proxy from a Source Distribution
* mysql-proxy-install-cvs::      Installing MySQL Proxy from the Bazaar Repository
* mysql-proxy-configuration-windows::  Setting Up MySQL Proxy as a Windows Service

You have three choices for installing MySQL Proxy:

   * Precompiled binaries are available for a number of different
     platforms. See *Note mysql-proxy-install-binary::.

   * You can install from the source code to build on an environment
     not supported by the binary distributions. See *Note
     mysql-proxy-install-source::.

   * The latest version of the MySQL Proxy source code is available
     through a development repository. This is the best way to stay up
     to date with the latest fixes and revisions. See *Note
     mysql-proxy-install-cvs::.


File: manual.info,  Node: mysql-proxy-install-binary,  Next: mysql-proxy-install-source,  Prev: mysql-proxy-install,  Up: mysql-proxy-install

15.7.2.1 Installing MySQL Proxy from a Binary Distribution
..........................................................

If you download a binary package, you must extract and copy the package
contents to your desired installation directory. The package contains
files required by MySQL Proxy, including additional Lua scripts and
other components required for execution.

To install, unpack the archive into the desired directory, then modify
your `PATH' environment variable so that you can use the *Note
`mysql-proxy': mysql-proxy. command directly:


     shell> cd /usr/local
     shell> tar zxf mysql-proxy-0.8.5-PLATFORM.tar.gz
     shell> PATH=$PATH:/usr/local/mysql-proxy-0.8.5-PLATFORM/bin

To update the path globally on a system, you might need administrator
privileges to modify the appropriate `/etc/profile', `/etc/bashrc', or
other system configuration file.

On Windows, you can update the `PATH' environment variable using this
procedure:

  1. On the Windows desktop, right-click the `My Computer' icon, and
     select `Properties'.

  2. Next select the `Advanced' tab from the `System Properties' menu
     that appears, and click the `Environment Variables' button.

  3. Under `System Variables', select `Path', then click the `Edit'
     button. The `Edit System Variable' dialogue should appear.

The Microsoft Visual C++ runtime libraries are a requirement for
running MySQL Proxy as of version 0.8.2. Users that do not have these
libraries must download and install the Microsoft Visual C++ 2008
Service Pack 1 Redistributable Package MFC Security Update. Use the
following link to obtain the package:

*Note*:

This is not required on Windows 8 or higher as the Visual C++ runtime
libraries are bundled with that version of Windows.


     `http://www.microsoft.com/download/en/details.aspx?id=26368'


File: manual.info,  Node: mysql-proxy-install-source,  Next: mysql-proxy-install-cvs,  Prev: mysql-proxy-install-binary,  Up: mysql-proxy-install

15.7.2.2 Installing MySQL Proxy from a Source Distribution
..........................................................

You can download a source package and compile the MySQL Proxy yourself.
To build from source, you must have the following prerequisite
components installed:

   * `libevent' 1.4 or higher.

   * `lua' 5.1.x only. lua 5.2.x is not currently supported.

   * `glib2' 2.16.0 or higher.

   * `pkg-config'.

   * `libtool' 1.5.x or higher.

   * `autoconf' 2.56 or higher.

   * `automake' 1.10 or higher, up to 1.12.x. It is not possible to use
     version 1.13 or higher.

   * `flex' 2.5.37.

   * `gtk-doc' 1.18.

   * MySQL 5.0.x or higher developer files.

*Note*:

On some operating systems, you might need to manually build the
required components to get the latest version. If you have trouble
compiling MySQL Proxy, consider using a binary distributions instead.

After verifying that the prerequisite components are installed,
configure and build MySQL Proxy:


     shell> tar zxf mysql-proxy-0.8.5.tar.gz
     shell> cd mysql-proxy-0.8.5
     shell> ./configure
     shell> make

To test the build, use the `check' target to `make':


     shell> make check

You can install using the `install' target:


     shell> make install

By default, *Note `mysql-proxy': mysql-proxy. is installed into
`/usr/local/sbin/mysql-proxy'. The Lua example scripts are installed
into `/usr/local/share'.


File: manual.info,  Node: mysql-proxy-install-cvs,  Next: mysql-proxy-configuration-windows,  Prev: mysql-proxy-install-source,  Up: mysql-proxy-install

15.7.2.3 Installing MySQL Proxy from the Bazaar Repository
..........................................................

The MySQL Proxy source is available through a public Bazaar repository
and is the quickest way to get the latest releases and fixes.

A build from the Bazaar repository requires that the following
prerequisite components be installed:

   * Bazaar 1.10.0 or later.

   * `libevent' 1.4 or higher.

   * `lua' 5.1.x only. lua 5.2.x is not currently supported.

   * `glib2' 2.16.0 or higher.

   * `pkg-config'.

   * `libtool' 1.5.x only. Version 1.6 or higher is not currently
     supported.

   * `autoconf' 2.56 or higher.

   * `automake' 1.9 or higher.

   * `flex' 2.5.37.

   * `gtk-doc' 1.18.

   * MySQL 5.0.x or higher developer files.

The *Note `mysql-proxy': mysql-proxy. source is hosted on Launchpad. To
check out a local copy of the Bazaar repository, use `bzr':


     shell> bzr branch lp:mysql-proxy

The preceding command downloads a complete version of the Bazaar
repository for *Note `mysql-proxy': mysql-proxy. The main source files
are located within the `trunk' subdirectory. The configuration scripts
must be generated before you can configure and build *Note
`mysql-proxy': mysql-proxy. The `autogen.sh' script generates the
required configuration scripts for you:


     shell> sh ./autogen.sh

The `autogen.sh' script creates the standard `configure' script, which
you then use to configure and build with `make':


     shell> ./configure
     shell> make
     shell> make install

To create a standalone source distribution, identical to the source
distribution available for download, use this command:


     shell> make distcheck

The preceding command creates the file `mysql-proxy-0.8.5.tar.gz' (with
the corresponding current version) within the current directory.


File: manual.info,  Node: mysql-proxy-configuration-windows,  Prev: mysql-proxy-install-cvs,  Up: mysql-proxy-install

15.7.2.4 Setting Up MySQL Proxy as a Windows Service
....................................................

The MySQL distribution on Windows includes the `mysql-proxy-svc.exe'
command that enables a MySQL Proxy instance to be managed by the
Windows service control manager. You can control the service, including
automatically starting and stopping it during boot, reboot and
shutdown, without separately running the MySQL Proxy application.

To set up a MySQL Proxy service, use the `sc' command to create a new
service using the MySQL Proxy service command. Specify the MySQL Proxy
options on the `sc' command line, and identify the service with a
unique name. For example, to configure a new MySQL Proxy instance that
will automatically start when your system boots, redirecting queries to
the local MySQL server:


     C:\> sc create "Proxy" DisplayName= "MySQL Proxy" start= "auto" »
       binPath= "C:\Program Files\MySQL\mysql-proxy-0.8.5\bin\mysql-proxy-svc.exe »
       --proxy-backend-addresses=127.0.0.1:3306"

*Note*:

The space following the equal sign after each property is required;
failure to include it results in an error.

The preceding command creates a new service called `Proxy'. You can
start and stop the service using the `net start|stop' command with the
service name. The service is not automatically started after it is
created. To start the service:


     C:\> net start proxy
     The MySQL Proxy service is starting.
     The MySQL Proxy service was started successfully.

You can specify additional command-line options to the `sc' command.
You can also set up multiple MySQL Proxy services on the same machine
(providing they are configured to listen on different ports and/or IP
addresses.

You can delete a service that you have created:


     C:\> sc delete proxy

For more information on creating services using `sc', see How to create
a Windows service by using Sc.exe
(http://support.microsoft.com/kb/251192).


File: manual.info,  Node: mysql-proxy-configuration,  Next: mysql-proxy-scripting,  Prev: mysql-proxy-install,  Up: mysql-proxy

15.7.3 MySQL Proxy Command Options
----------------------------------

To start MySQL Proxy, you can run it directly from the command line:


     shell> mysql-proxy

For most situations, you specify at least the host name or address and
the port number of the backend MySQL server to which the MySQL Proxy
should pass queries.

You can specify options to *Note `mysql-proxy': mysql-proxy. either on
the command line, or by using a configuration file and the
`--defaults-file' command-line option to specify the file location.

If you use a configuration file, format it as follows:

   * Specify the options within a `[mysql-proxy]' configuration group.
     For example:


          [mysql-proxy]
          admin-address = HOST:PORT

   * Specify all configuration options in the form of a configuration
     name and the value to set.

   * For options that are a simple toggle on the command line (for
     example, `--proxy-skip-profiling'), use `true' or `false'. For
     example, the following is invalid:


          [mysql-proxy]
          proxy-skip-profiling

     But this is valid:


          [mysql-proxy]
          proxy-skip-profiling = true

   * Give the configuration file Unix permissions of `0660' (readable
     and writable by user and group, no access for others).

Failure to adhere to any of these requirements causes *Note
`mysql-proxy': mysql-proxy. to generate an error during startup.

The following tables list the supported configuration file and
command-line options.

*`mysql-proxy' Help Options*

Format             Description
-help              Show help options
-help-admin        Show admin module options
-help-all          Show all help options
-help-proxy        Show proxy module options

*`mysql-proxy' Admin Options*

Format             Description
-admin-address=host:portThe admin module listening host
                   and port
-admin-lua-script=file_nameScript to execute by the admin
                   module
-admin-password=passwordAuthentication password for
                   admin module
-admin-username=user_nameAuthentication user name for
                   admin module
-proxy-address=host:portThe listening proxy server host
                   and port

*`mysql-proxy' Proxy Options*

Format             Description                      Removed
-no-proxy          Do not start the proxy module    
-proxy-backend-addresses=host:portThe MySQL server host and port   
-proxy-fix-bug-25371Enable the fix for Bug #25371    0.8.1
                   for older libmysql versions      
-proxy-lua-script=file_nameFilename for Lua script for      
                   proxy operations                 
-proxy-pool-no-change-userDo not use the protocol          
                   CHANGE_USER command to reset     
                   the connection when coming from  
                   the connection pool              
-proxy-read-only-backend-addresses=host:portThe MySQL server host and port   
                   (read only)                      
-proxy-skip-profilingDisable query profiling          

*`mysql-proxy' Applications Options*

Format             Description
-basedir=dir_name  The base directory prefix for
                   paths in the configuration
-daemon            Start in daemon mode
-defaults-file=file_nameRead only named option file
-event-threads=countNumber of event-handling threads
-keepalive         Try to restart the proxy if a
                   crash occurs
-log-backtrace-on-crashTry to invoke the debugger and
                   generate a backtrace on crash
-log-file=file_nameThe file where error messages
                   are logged
-log-level=level   The logging level
-log-use-syslog    Log errors to syslog
-lua-cpath=dir_nameSet the LUA_CPATH
-lua-path=dir_name Set the LUA_PATH
-max-open-files=countThe maximum number of open
                   files to support
-pid-file=file_nameFile in which to store process
                   ID
-plugin-dir=dir_nameDirectory containing plugin
                   files
-plugins=plugin,...List of plugins to load
-user=user_name    The user to use when running
                   mysql-proxy
-version           Show version information

Except as noted in the following details, all of the options can be
used within the configuration file by supplying the option and the
corresponding value. For example:


     [mysql-proxy]
     log-file = /var/log/mysql-proxy.log
     log-level = message

   * `--help', `-h'

     Options for help

     *Command-Line        `--help'        
     Format*                              
                          `-h'            

     Show available help options.

   * `--help-admin'

     Options for help-admin

     *Command-Line        `--help-admin'        
     Format*                              

     Show options for the admin module.

   * `--help-all'

     Options for help-all

     *Command-Line        `--help-all'        
     Format*                              

     Show all help options.

   * `--help-proxy'

     Options for help-proxy

     *Command-Line        `--help-proxy'        
     Format*                              

     Show options for the proxy module.

   * `--admin-address=HOST:PORT'

     Options for admin-address

     *Command-Line        `--admin-address=host:port'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `:4041'         

     The host name (or IP address) and port for the administration
     port. The default is `localhost:4041'.

   * `--admin-lua-script=FILE_NAME'

     Options for admin-lua-script

     *Command-Line        `--admin-lua-script=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `'              

     The script to use for the proxy administration module.

   * `--admin-password=PASSWORD'

     Options for admin-password

     *Command-Line        `--admin-password=password'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     The password to use to authenticate users wanting to connect to
     the MySQL Proxy administration module. This module uses the MySQL
     protocol to request a user name and password for connections.

   * `--admin-username=USER_NAME'

     Options for admin-username

     *Command-Line        `--admin-username=user_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `root'          

     The user name to use to authenticate users wanting to connect to
     the MySQL Proxy administration module. This module uses the MySQL
     protocol to request a user name and password for connections. The
     default user name is `root'.

   * `--basedir=DIR_NAME'

     Options for basedir

     *Command-Line        `--basedir=dir_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The base directory to use as a prefix for all other file name
     configuration options. The base name should be an absolute (not
     relative) directory. If you specify a relative directory, *Note
     `mysql-proxy': mysql-proxy. generates an error during startup.

   * `--daemon'

     Options for daemon

     *Command-Line        `--daemon'        
     Format*                              

     Starts the proxy in daemon mode.

   * `--defaults-file=FILE_NAME'

     Options for defaults-file

     *Command-Line        `--defaults-file=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The file to read for configuration options. If not specified,
     MySQL Proxy takes options only from the command line.

   * `--event-threads=COUNT'

     Options for event-threads

     *Command-Line        `--event-threads=count'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1'             

     The number of event threads to reserve to handle incoming requests.

   * `--keepalive'

     Options for keepalive

     *Command-Line        `--keepalive'        
     Format*                              

     Create a process surrounding the main *Note `mysql-proxy':
     mysql-proxy. process that attempts to restart the main *Note
     `mysql-proxy': mysql-proxy. process in the event of a crash or
     other failure.

     *Note*:

     The `--keepalive' option is not available on Microsoft Windows.
     When running as a service, *Note `mysql-proxy': mysql-proxy.
     automatically restarts.

   * `--log-backtrace-on-crash'

     Options for log-backtrace-on-crash

     *Command-Line        `--log-backtrace-on-crash'        
     Format*                              

     Log a backtrace to the error log and try to initialize the
     debugger in the event of a failure.

   * `--log-file=FILE_NAME'

     Options for log-file

     *Command-Line        `--log-file=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The file to use to record log information. If this option is not
     given, *Note `mysql-proxy': mysql-proxy. logs to the standard
     error output.

   * `--log-level=LEVEL'

     Options for log-level

     *Command-Line        `--log-level=level'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `critical'        
     *Valid Values*       `critical'        
     `error'                              
     `warning'                            
     `info'                               
     `message'                            
     `debug'                              

     The log level to use when outputting error messages. Messages with
     that level (or lower) are output. For example, `message' level
     also outputs message with `info', `warning', and `error' levels.

   * `--log-use-syslog'

     Options for log-use-syslog

     *Command-Line        `--log-use-syslog'        
     Format*                              

     Log errors to the syslog (Unix/Linux only).

   * `--lua-cpath=DIR_NAME'

     Options for lua-cpath

     *Command-Line        `--lua-cpath=dir_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The `LUA_CPATH' to use when loading compiled modules or libraries
     for Lua scripts.

   * `--lua-path=DIR_NAME'

     Options for lua-path

     *Command-Line        `--lua-path=dir_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The `LUA_CPATH' to use when loading modules for Lua.

   * `--max-open-files=COUNT'

     Options for max-open-files

     *Command-Line        `--max-open-files=count'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     The maximum number of open files and sockets supported by the
     *Note `mysql-proxy': mysql-proxy. process. Certain scripts might
     require a higher value.

   * `--no-proxy'

     Options for no-proxy

     *Command-Line        `--no-proxy'        
     Format*                              

     Disable the proxy module.

   * `--plugin-dir=DIR_NAME'

     Options for plugin-dir

     *Command-Line        `--plugin-dir=dir_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           

     The directory to use when loading plugins for *Note `mysql-proxy':
     mysql-proxy.

   * `--plugins=PLUGIN'

     Options for plugins

     *Command-Line        `--plugins=plugin,...'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Loads a plugin.

     When using this option on the command line, you can specify the
     option multiple times to specify multiple plugins. For example:


          shell> mysql-proxy --plugins=proxy --plugins=admin

     When using the option within the configuration file, you should
     separate multiple plugins by commas. The equivalent of the
     preceding example would be:


          ...
          plugins=proxy,admin

   * `--proxy-address=HOST:PORT', `-P HOST:PORT'

     Options for proxy-address

     *Command-Line        `--proxy-address=host:port'        
     Format*                              
                          `-P             
                          host:port'        
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `:4040'         

     The listening host name (or IP address) and port of the proxy
     server. The default is `:4040' (all IPs on port 4040).

   * `--proxy-read-only-backend-addresses=HOST:PORT', `-r HOST:PORT'

     Options for proxy-read-only-backend-addresses

     *Command-Line        `--proxy-read-only-backend-addresses=host:port'        
     Format*                              
                          `-r             
                          host:port'        
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The listening host name (or IP address) and port of the proxy
     server for read-only connections. The default is for this
     information not to be set.

     *Note*:

     Setting this value only configures the servers within the
     corresponding internal structure (see `proxy.global.backends').
     You can determine the backend type by checking the `type' field
     for each connection.

     You should therefore only use this option in combination with a
     script designed to make use of the different backend types.

     When using this option on the command line, you can specify the
     option and the server multiple times to specify multiple backends.
     For example:


          shell> mysql-proxy --proxy-read-only-backend-addresses=192.168.0.1:3306 --proxy-read-only-backend-addresses=192.168.0.2:3306

     When using the option within the configuration file, you should
     separate multiple servers by commas. The equivalent of the
     preceding example would be:


          ...
          proxy-read-only-backend-addresses = 192.168.0.1:3306,192.168.0.2:3306

   * `--proxy-backend-addresses=HOST:PORT', `-b HOST:PORT'

     Options for proxy-backend-addresses

     *Command-Line        `--proxy-backend-addresses=host:port'        
     Format*                              
                          `-b             
                          host:port'        
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `127.0.0.1:3306'        

     The host name (or IP address) and port of the MySQL server to
     connect to. You can specify multiple backend servers by supplying
     multiple options. Clients are connected to each backend server in
     round-robin fashion. For example, if you specify two servers A and
     B, the first client connection will go to server A; the second
     client connection to server B and the third client connection to
     server A.

     When using this option on the command line, you can specify the
     option and the server multiple times to specify multiple backends.
     For example:


          shell> mysql-proxy --proxy-backend-addresses 192.168.0.1:3306 --proxy-backend-addresses 192.168.0.2:3306

     When using the option within the configuration file, you should
     separate multiple servers by commas. The equivalent of the
     preceding example would be:


          ...
          proxy-backend-addresses = 192.168.0.1:3306,192.168.0.2:3306

   * `--proxy-pool-no-change-user'

     Options for proxy-pool-no-change-user

     *Command-Line        `--proxy-pool-no-change-user'        
     Format*                              

     Disable use of the MySQL protocol `CHANGE_USER' command when
     reusing a connection from the pool of connections specified by the
     `proxy-backend-addresses' list.

   * `--proxy-skip-profiling'

     Options for proxy-skip-profiling

     *Command-Line        `--proxy-skip-profiling'        
     Format*                              

     Disable query profiling (statistics time tracking). The default is
     for tracking to be enabled.

   * `--proxy-fix-bug-25371'

     Options for proxy-fix-bug-25371

     *Removed*            0.8.1           
     *Command-Line        `--proxy-fix-bug-25371'        
     Format*                              

     Enable a workaround for an issue when connecting to a MySQL server
     later than 5.1.12 when using a MySQL client library of any earlier
     version.

     This option was removed in *Note `mysql-proxy': mysql-proxy.
     0.8.1. Now, *Note `mysql-proxy': mysql-proxy. returns an error
     message at the protocol level if it sees a `COM_CHANGE_USER' being
     sent to a server that has a version from 5.1.14 to 5.1.17.

   * `--proxy-lua-script=FILE_NAME', `-s FILE_NAME'

     Options for proxy-lua-script

     *Command-Line        `--proxy-lua-script=file_name'        
     Format*                              
                          `-s             
                          file_name'        
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The Lua script file to be loaded. Note that the script file is not
     physically loaded and parsed until a connection is made.  Also
     note that the specified Lua script is reloaded for each
     connection; if the content of the Lua script changes while *Note
     `mysql-proxy': mysql-proxy. is running, the updated content is
     automatically used when a new connection is made.

   * `--pid-file=FILE_NAME'

     Options for pid-file

     *Command-Line        `--pid-file=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The name of the file in which to store the process ID.

   * `--user=USER_NAME'

     Options for user

     *Command-Line        `--user=user_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Run *Note `mysql-proxy': mysql-proxy. as the specified `user'.

   * `--version', `-V'

     Options for version

     *Command-Line        `--version'        
     Format*                              
                          `-V'            

     Show the version number.

The most common usage is as a simple proxy service (that is, without
additional scripting). For basic proxy operation, you must specify at
least one `proxy-backend-addresses' option to specify the MySQL server
to connect to by default:


     shell> mysql-proxy --proxy-backend-addresses=MySQL.example.com:3306

The default proxy port is `4040', so you can connect to your MySQL
server through the proxy by specifying the host name and port details:


     shell> mysql --host=localhost --port=4040

If your server requires authentication information, this will be passed
through natively without alteration by *Note `mysql-proxy':
mysql-proxy, so you must also specify the required authentication
information:


     shell> mysql --host=localhost --port=4040 \
        --user=user_name --password=password

You can also connect to a read-only port (which filters out *Note
`UPDATE': update. and *Note `INSERT': insert. queries) by connecting to
the read-only port. By default the host name is the default, and the
port is `4042', but you can alter the host/port information by using the
`--proxy-read-only-backend-addresses' command-line option.

For more detailed information on how to use these command-line options,
and *Note `mysql-proxy': mysql-proxy. in general in combination with
Lua scripts, see *Note mysql-proxy-using::.


File: manual.info,  Node: mysql-proxy-scripting,  Next: mysql-proxy-using,  Prev: mysql-proxy-configuration,  Up: mysql-proxy

15.7.4 MySQL Proxy Scripting
----------------------------

* Menu:

* mysql-proxy-scripting-injection::  Proxy Scripting Sequence During Query Injection
* mysql-proxy-scripting-structures::  Internal Structures
* mysql-proxy-scripting-connect-server::  Capturing a Connection with `connect_server()'
* mysql-proxy-scripting-read-handshake::  Examining the Handshake with `read_handshake()'
* mysql-proxy-scripting-read-auth::  Examining the Authentication Credentials with `read_auth()'
* mysql-proxy-scripting-read-auth-result::  Accessing Authentication Information with `read_auth_result()'
* mysql-proxy-scripting-read-query::  Manipulating Queries with `read_query()'
* mysql-proxy-scripting-read-query-result::  Manipulating Results with `read_query_result()'

You can control how MySQL Proxy manipulates and works with the queries
and results that are passed on to the MySQL server through the use of
the embedded Lua scripting language. You can find out more about the
Lua programming language from the Lua Web site (http://www.lua.org).

The following diagram shows an overview of the classes exposed by MySQL
Proxy.

MySQL Proxy architecture

The primary interaction between MySQL Proxy and the server is provided
by defining one or more functions through an Lua script.  A number of
functions are supported, according to different events and operations
in the communication sequence between a client and one or more backend
MySQL servers:

   * `connect_server()': This function is called each time a connection
     is made to MySQL Proxy from a client.  You can use this function
     during load-balancing to intercept the original connection and
     decide which server the client should ultimately be attached to.
     If you do not define a special solution, a simple round-robin
     style distribution is used by default.

   * `read_handshake()': This function is called when the initial
     handshake information is returned by the server. You can capture
     the handshake information returned and provide additional checks
     before the authorization exchange takes place.

   * `read_auth()': This function is called when the authorization
     packet (user name, password, default database) are submitted by
     the client to the server for authentication.

   * `read_auth_result()': This function is called when the server
     returns an authorization packet to the client indicating whether
     the authorization succeeded.

   * `read_query()': This function is called each time a query is sent
     by the client to the server. You can use this to edit and
     manipulate the original query, including adding new queries before
     and after the original statement.  You can also use this function
     to return information directly to the client, bypassing the
     server, which can be useful to filter unwanted queries or queries
     that exceed known limits.

   * `read_query_result()': This function is called each time a result
     is returned from the server, providing you have manually injected
     queries into the query queue. If you have not explicitly injected
     queries within the `read_query()' function, this function is not
     triggered. You can use this to edit the result set, or to remove
     or filter the result sets generated from additional queries you
     injected into the queue when using `read_query()'.

The following table lists MySQL proxy and server communication
functions, the supplied information, and the direction of information
flow when the function is triggered.

This table lists MySQL proxy and server communication functions, the
supplied information, and the direction of information flow when the
function is triggered.

Function               Supplied Information   Direction
`connect_server()'     None                   Client to Server
`read_handshake()'     None                   Server to Client
`read_auth()'          None                   Client to Server
`read_auth_result()'   None                   Server to Client
`read_query()'         Query                  Client to Server
`read_query_result()'  Query result           Server to Client

By default, all functions return a result that indicates whether the
data should be passed on to the client or server (depending on the
direction of the information being transferred). This return value can
be overridden by explicitly returning a constant indicating that a
particular response should be sent. For example, it is possible to
construct result set information by hand within `read_query()' and to
return the result set directly to the client without ever sending the
original query to the server.

In addition to these functions, a number of built-in structures provide
control over how MySQL Proxy forwards queries and returns the results
by providing a simplified interface to elements such as the list of
queries and the groups of result sets that are returned.


File: manual.info,  Node: mysql-proxy-scripting-injection,  Next: mysql-proxy-scripting-structures,  Prev: mysql-proxy-scripting,  Up: mysql-proxy-scripting

15.7.4.1 Proxy Scripting Sequence During Query Injection
........................................................

The following figure gives an example of how the proxy might be used
when injecting queries into the query queue. Because the proxy sits
between the client and MySQL server, what the proxy sends to the
server, and the information that the proxy ultimately returns to the
client, need not match or correlate.  Once the client has connected to
the proxy, the sequence shown in the following diagram occurs for each
individual query sent by the client.

MySQL Proxy architecture

  1. When the client submits one query to the proxy, the `read_query()'
     function within the proxy is triggered. The function adds the
     query to the query queue.

  2. Once manipulation by `read_query()' has completed, the queries are
     submitted, sequentially, to the MySQL server.

  3. The MySQL server returns the results from each query, one result
     set for each query submitted. The `read_query_result()' function is
     triggered for each result set, and each invocation can decide
     which result set to return to the client

For example, you can queue additional queries into the global query
queue to be processed by the server. This can be used to add
statistical information by adding queries before and after the original
query, changing the original query:


     SELECT * FROM City;

Into a sequence of queries:


     SELECT NOW();
     SELECT * FROM City;
     SELECT NOW();

You can also modify the original statement; for example, to add *Note
`EXPLAIN': explain. to each statement executed to get information on
how the statement was processed, again altering our original SQL
statement into a number of statements:


     SELECT * FROM City;
     EXPLAIN SELECT * FROM City;

In both of these examples, the client would have received more result
sets than expected. Regardless of how you manipulate the incoming query
and the returned result, the number of queries returned by the proxy
must match the number of original queries sent by the client.

You could adjust the client to handle the multiple result sets sent by
the proxy, but in most cases you will want the existence of the proxy
to remain transparent. To ensure that the number of queries and result
sets match, you can use the MySQL Proxy `read_query_result()' to
extract the additional result set information and return only the
result set the client originally requested back to the client. You can
achieve this by giving each query that you add to the query queue a
unique ID, then filter out queries that do not match the original query
ID when processing them with `read_query_result()'.


File: manual.info,  Node: mysql-proxy-scripting-structures,  Next: mysql-proxy-scripting-connect-server,  Prev: mysql-proxy-scripting-injection,  Up: mysql-proxy-scripting

15.7.4.2 Internal Structures
............................

There are a number of internal structures within the scripting element
of MySQL Proxy. The primary structure is `proxy' and this provides an
interface to the many common structures used throughout the script,
such as connection lists and configured backend servers. Other
structures, such as the incoming packet from the client and result sets
are only available within the context of one of the scriptable
functions.

The following table describes common attributes of the MySQL `proxy'
scripting element.

This table describes common attributes of the MySQL `proxy' scripting
element.

Attribute              Description
`connection'           A structure containing the active client
                       connections. For a list of attributes, see
                       `proxy.connection'.
`servers'              A structure containing the list of configured
                       backend servers. For a list of attributes, see
                       `proxy.global.backends'.
`queries'              A structure containing the queue of queries that
                       will be sent to the server during a single client
                       query. For a list of attributes, see
                       `proxy.queries'.
`PROXY_VERSION'        The version number of MySQL Proxy, encoded in
                       hex. You can use this to check that the version
                       number supports a particular option from within
                       the Lua script. Note that the value is encoded as
                       a hex value, so to check the version is at least
                       0.5.1 you compare against `0x00501'.

*`proxy.connection'*

The `proxy.connection' object is read only, and provides information
about the current connection, and is split into a `client' and `server'
tables. This enables you to examine information about both the incoming
client connections to the proxy (`client'), and to the backend servers
(`server').

The following table describes the client and server attributes of the
`proxy.connection' object.

This table describes the client and server attributes of the
`proxy.connection' object.

Attribute              Description
`client.default_db'    Default database requested by the client
`client.username'      User name used to authenticate
`client.scrambled_password'The scrambled version of the password used to
                       authenticate
`client.dst.name'      The combined `address:port' of the Proxy port
                       used by this client (should match the
                       `--proxy-address' configuration parameter)
`client.dst.address'   The IP address of the of the Proxy port used by
                       this client
`client.dst.port'      The port number of the of the Proxy port used by
                       this client
`client.src.name'      The combined `address:port' of the client
                       (originating) TCP/IP endpoint
`client.src.address'   The IP address of the client (originating) TCP/IP
                       port
`client.src.port'      The port of the client (originating) TCP/IP
                       endpoint
`server.scramble_buffer'The scramble buffer used to scramble the password
`server.mysqld_version'The MySQL version number of the server
`server.thread_id'     The ID of the thread handling the connection to
                       the current server
`server.dst.name'      The combined `address:port' for the backend
                       server for the current connection (i.e. the
                       connection to the MySQL server)
`server.dst.address'   The address for the backend server
`server.dst.port'      The port for the backend server
`server.src.name'      The combined `address:port' for the TCP/IP
                       endpoint used by the Proxy to connect to the
                       backend server
`server.src.address'   The address of the endpoint for the proxy-side
                       connection to the MySQL server
`server.src.port'      The port of the endpoint for the proxy-side
                       connection to the MySQL server

*`proxy.global.backends'*

The `proxy.global.backends' table is partially writable and contains an
array of all the configured backend servers and the server metadata (IP
address, status, etc.). You can determine the array index of the
current connection using `proxy.connection["backend_ndx"]' which is the
index into this table of the backend server being used by the active
connection.

The attributes for each entry within the `proxy.global.backends' table
are shown in the following table.

This table describes the attributes for each entry within the
`proxy.global.backends' table.

Attribute              Description
`dst.name'             The combined `address:port' of the backend server.
`dst.address'          The IP address of the backend server.
`dst.port'             The port of the backend server.
`connected_clients'    The number of clients currently connected.
`state'                The status of the backend server. See *Note
                       mysql-proxy-scripting-structures-backend-states::.
`type'                 The type of the backend server. You can use this
                       to identify whether the backed was configured as
                       a standard read/write backend, or a read-only
                       backend. You can compare this value to the
                       `proxy.BACKEND_TYPE_RW' and
                       `proxy.BACKEND_TYPE_RO'.

*`proxy.queries'*

The `proxy.queries' object is a queue representing the list of queries
to be sent to the server. The queue is not populated automatically, but
if you do not explicitly populate the queue, queries are passed on to
the backend server verbatim. Also, if you do not populate the query
queue by hand, the `read_query_result()' function is not triggered.

The following functions are supported for populating the
`proxy.queries' object.

This table describes the functions that are supported for populating
the `proxy.queries' object.

Function               Description
`append(id,packet,[options])'Appends a query to the end of the query queue.
                       The `id' is an integer identifier that you can
                       use to recognize the query results when they are
                       returned by the server.  The packet should be a
                       properly formatted query packet.  The optional
                       `options' should be a table containing the
                       options specific to this packet.
`prepend(id,packet)'   Prepends a query to the query queue. The `id' is
                       an identifier that you can use to recognize the
                       query results when they are returned by the
                       server. The packet should be a properly formatted
                       query packet.
`reset()'              Empties the query queue.
`len()'                Returns the number of query packets in the queue.

For example, you could append a query packet to the `proxy.queries'
queue by using the `append()':


     proxy.queries:append(1,packet)

The optional third argument to `append()' should contain the options
for the packet. To have access to the result set through the
`read_query_result()' function, set the `resultset_is_needed' flag to
`true':


     proxy.queries:append( 1, packet, { resultset_is_needed = true } )

If that flag is `false' (the default), proxy will:

   * Send the result set to the client as soon as it is received

   * Reduce memory usage (because the result set is not stored
     internally for processing)

   * Reduce latency of returning results to the client

   * Pass data from server to client unaltered

The default mode is therefore quicker and useful if you only want to
monitor the queries sent, and the basic statistics.

To perform any kind of manipulation on the returned data, you must set
the flag to `true', which will:

   * Store the result set so that it can be processed.

   * Enable modification of the result set before it is returned to the
     client.

   * Enable you to discard the result set instead of returning it to
     the client.

*`proxy.response'*

The `proxy.response' structure is used when you want to return your own
MySQL response, instead of forwarding a packet that you have received a
backend server. The structure holds the response type information, an
optional error message, and the result set (rows/columns) to return.

The following table describes the attributes of the `proxy.response'
structure.

This table describes the attributes of the `proxy.response' structure.

Attribute              Description
`type'                 The type of the response. The type must be either
                       `MYSQLD_PACKET_OK' or `MYSQLD_PACKET_ERR'. If the
                       `MYSQLD_PACKET_ERR', you should set the value of
                       the `mysql.response.errmsg' with a suitable error
                       message.
`errmsg'               A string containing the error message that will
                       be returned to the client.
`resultset'            A structure containing the result set information
                       (columns and rows), identical to what would be
                       returned when returning a results from a *Note
                       `SELECT': select.  query.

When using `proxy.response' you either set `proxy.response.type' to
`proxy.MYSQLD_PACKET_OK' and then build `resultset' to contain the
results to return, or set `proxy.response.type' to
`proxy.MYSQLD_PACKET_ERR' and set the `proxy.response.errmsg' to a
string with the error message. To send the completed result set or error
message, you should return the `proxy.PROXY_SEND_RESULT' to trigger the
return of the packet information.

An example of this can be seen in the `tutorial-resultset.lua' script
within the MySQL Proxy package:


     if string.lower(command) == "show" and string.lower(option) == "querycounter" then
             ---
             -- proxy.PROXY_SEND_RESULT requires
             --
             -- proxy.response.type to be either
             -- * proxy.MYSQLD_PACKET_OK or
             -- * proxy.MYSQLD_PACKET_ERR
             --
             -- for proxy.MYSQLD_PACKET_OK you need a resultset
             -- * fields
             -- * rows
             --
             -- for proxy.MYSQLD_PACKET_ERR
             -- * errmsg
             proxy.response.type = proxy.MYSQLD_PACKET_OK
             proxy.response.resultset = {
                     fields = {
                             { type = proxy.MYSQL_TYPE_LONG, name = "global_query_counter", },
                             { type = proxy.MYSQL_TYPE_LONG, name = "query_counter", },
                     },
                     rows = {
                             { proxy.global.query_counter, query_counter }
                     }
             }

             -- we have our result, send it back
             return proxy.PROXY_SEND_RESULT
     elseif string.lower(command) == "show" and string.lower(option) == "myerror" then
             proxy.response.type = proxy.MYSQLD_PACKET_ERR
             proxy.response.errmsg = "my first error"

             return proxy.PROXY_SEND_RESULT

*`proxy.response.resultset'*

The `proxy.response.resultset' structure should be populated with the
rows and columns of data to return. The structure contains the
information about the entire result set, with the individual elements
of the data shown in the following table.

The following table describes the attributes of the
`proxy.response.resultset' structure.

This table describes the attributes of the `proxy.response.resultset'
structure.

Attribute              Description
`fields'               The definition of the columns being returned.
                       This should be a dictionary structure with the
                       `type' specifying the MySQL data type, and the
                       `name' specifying the column name.  Columns
                       should be listed in the order of the column data
                       that will be returned.
`flags'                A number of flags related to the result set.
                       Valid flags include `auto_commit' (whether an
                       automatic commit was triggered),
                       `no_good_index_used' (the query executed without
                       using an appropriate index), and `no_index_used'
                       (the query executed without using any index).
`rows'                 The actual row data. The information should be
                       returned as an array of arrays. Each inner array
                       should contain the column data, with the outer
                       array making up the entire result set.
`warning_count'        The number of warnings for this result set.
`affected_rows'        The number of rows affected by the original
                       statement.
`insert_id'            The last insert ID for an auto-incremented column
                       in a table.
`query_status'         The status of the query operation. You can use the
                       `MYSQLD_PACKET_OK' or `MYSQLD_PACKET_ERR'
                       constants to populate this parameter.

For an example showing how to use this structure, see `proxy.response'.

*Proxy Return State Constants*

The following constants are used internally by the proxy to specify the
response to send to the client or server. All constants are exposed as
values within the main `proxy' table.

This table describes proxy return state constants, which are used
internally by the proxy to specify the response to send to the client
or server.

Constant               Description
`PROXY_SEND_QUERY'     Causes the proxy to send the current contents of
                       the queries queue to the server.
`PROXY_SEND_RESULT'    Causes the proxy to send a result set back to the
                       client.
`PROXY_IGNORE_RESULT'  Causes the proxy to drop the result set (nothing
                       is returned to the client).

As constants, these entities are available without qualification in the
Lua scripts. For example, at the end of the `read_query_result()' you
might return `PROXY_IGNORE_RESULT:'


     return proxy.PROXY_IGNORE_RESULT

*Packet State Constants*

The following states describe the status of a network packet.  These
items are entries within the main `proxy' table.

This table describes packet state constants, which define the status of
a network packet.

Constant               Description
`MYSQLD_PACKET_OK'     The packet is OK
`MYSQLD_PACKET_ERR'    The packet contains error information
`MYSQLD_PACKET_RAW'    The packet contains raw data

*Backend State/Type Constants*

The following constants are used either to define the status or type of
the backend MySQL server to which the proxy is connected. These items
are entries within the main `proxy' table.

This table describes backend state/type constants, which are used to
define the status or type of the backend MySQL server to which the
proxy is connected.

Constant               Description
`BACKEND_STATE_UNKNOWN'The current status is unknown
`BACKEND_STATE_UP'     The backend is known to be up (available)
`BACKEND_STATE_DOWN'   The backend is known to be down (unavailable)
`BACKEND_TYPE_UNKNOWN' Backend type is unknown
`BACKEND_TYPE_RW'      Backend is available for read/write
`BACKEND_TYPE_RO'      Backend is available only for read-only use

*Server Command Constants*

The values described in the table below are used in the packets
exchanged between the client and server to identify the information in
the rest of the packet. These items are entries within the main `proxy'
table. The packet type is defined as the first character in the sent
packet. For example, when intercepting packets from the client to edit
or monitor a query, you would check that the first byte of the packet
was of type `proxy.COM_QUERY'.

This table describes server command constants, which are used in the
packets exchanged between the client and server to identify the
information in the rest of the packet.

Constant               Description
`COM_SLEEP'            Sleep
`COM_QUIT'             Quit
`COM_INIT_DB'          Initialize database
`COM_QUERY'            Query
`COM_FIELD_LIST'       Field List
`COM_CREATE_DB'        Create database
`COM_DROP_DB'          Drop database
`COM_REFRESH'          Refresh
`COM_SHUTDOWN'         Shutdown
`COM_STATISTICS'       Statistics
`COM_PROCESS_INFO'     Process List
`COM_CONNECT'          Connect
`COM_PROCESS_KILL'     Kill
`COM_DEBUG'            Debug
`COM_PING'             Ping
`COM_TIME'             Time
`COM_DELAYED_INSERT'   Delayed insert
`COM_CHANGE_USER'      Change user
`COM_BINLOG_DUMP'      Binlog dump
`COM_TABLE_DUMP'       Table dump
`COM_CONNECT_OUT'      Connect out
`COM_REGISTER_SLAVE'   Register slave
`COM_STMT_PREPARE'     Prepare server-side statement
`COM_STMT_EXECUTE'     Execute server-side statement
`COM_STMT_SEND_LONG_DATA'Long data
`COM_STMT_CLOSE'       Close server-side statement
`COM_STMT_RESET'       Reset statement
`COM_SET_OPTION'       Set option
`COM_STMT_FETCH'       Fetch statement
`COM_DAEMON'           Daemon (MySQL 5.1 only)
`COM_ERROR'            Error

*MySQL Type Constants*

These constants are used to identify the field types in the query
result data returned to clients from the result of a query. These items
are entries within the main `proxy' table.

This table describes MySQL type constants and associated field types.
The constants are used to identify the field types in the query result
data returned to clients from the result of a query.

Constant               Field Type
`MYSQL_TYPE_DECIMAL'   Decimal
`MYSQL_TYPE_NEWDECIMAL'Decimal (MySQL 5.0 or later)
`MYSQL_TYPE_TINY'      Tiny
`MYSQL_TYPE_SHORT'     Short
`MYSQL_TYPE_LONG'      Long
`MYSQL_TYPE_FLOAT'     Float
`MYSQL_TYPE_DOUBLE'    Double
`MYSQL_TYPE_NULL'      Null
`MYSQL_TYPE_TIMESTAMP' Timestamp
`MYSQL_TYPE_LONGLONG'  Long long
`MYSQL_TYPE_INT24'     Integer
`MYSQL_TYPE_DATE'      Date
`MYSQL_TYPE_TIME'      Time
`MYSQL_TYPE_DATETIME'  Datetime
`MYSQL_TYPE_YEAR'      Year
`MYSQL_TYPE_NEWDATE'   Date (MySQL 5.0 or later)
`MYSQL_TYPE_ENUM'      Enumeration
`MYSQL_TYPE_SET'       Set
`MYSQL_TYPE_TINY_BLOB' Tiny Blob
`MYSQL_TYPE_MEDIUM_BLOB'Medium Blob
`MYSQL_TYPE_LONG_BLOB' Long Blob
`MYSQL_TYPE_BLOB'      Blob
`MYSQL_TYPE_VAR_STRING'Varstring
`MYSQL_TYPE_STRING'    String
`MYSQL_TYPE_TINY'      Tiny (compatible with `MYSQL_TYPE_CHAR)'
`MYSQL_TYPE_ENUM'      Enumeration (compatible with
                       `MYSQL_TYPE_INTERVAL')
`MYSQL_TYPE_GEOMETRY'  Geometry
`MYSQL_TYPE_BIT'       Bit


File: manual.info,  Node: mysql-proxy-scripting-connect-server,  Next: mysql-proxy-scripting-read-handshake,  Prev: mysql-proxy-scripting-structures,  Up: mysql-proxy-scripting

15.7.4.3 Capturing a Connection with `connect_server()'
.......................................................

When the proxy accepts a connection from a MySQL client, the
`connect_server()' function is called.

There are no arguments to the function, but you can use and if
necessary manipulate the information in the `proxy.connection' table,
which is unique to each client session.

For example, if you have multiple backend servers, you can specify
which server that connection should use by setting the value of
`proxy.connection.backend_ndx' to a valid server number. The following
code chooses between two servers based on whether the current time in
minutes is odd or even:


     function connect_server()
             print("--> a client really wants to talk to a server")
             if (tonumber(os.date("%M")) % 2 == 0) then
                     proxy.connection.backend_ndx = 2
                     print("Choosing backend 2")
             else
                     proxy.connection.backend_ndx = 1
                     print("Choosing backend 1")
             end
             print("Using " .. proxy.global.backends[proxy.connection.backend_ndx].dst.name)
     end

This example also displays the IP address/port combination by accessing
the information from the internal `proxy.global.backends' table.


File: manual.info,  Node: mysql-proxy-scripting-read-handshake,  Next: mysql-proxy-scripting-read-auth,  Prev: mysql-proxy-scripting-connect-server,  Up: mysql-proxy-scripting

15.7.4.4 Examining the Handshake with `read_handshake()'
........................................................

Handshake information is sent by the server to the client after the
initial connection (through `connect_server()') has been made. The
handshake information contains details about the MySQL version, the ID
of the thread that will handle the connection information, and the IP
address of the client and server. This information is exposed through
the `proxy.connection' structure.

   * `proxy.connection.server.mysqld_version': The version of the MySQL
     server.

   * `proxy.connection.server.thread_id': The thread ID.

   * `proxy.connection.server.scramble_buffer': The password scramble
     buffer.

   * `proxy.connection.server.dst.name': The IP address of the server.

   * `proxy.connection.client.src.name': The IP address of the client.

For example, you can print out the handshake data and refuse clients by
IP address with the following function:


     function read_handshake()
             print("<-- let's send him some information about us")
             print("    mysqld-version: " .. proxy.connection.server.mysqld_version)
             print("    thread-id     : " .. proxy.connection.server.thread_id)
             print("    scramble-buf  : " .. string.format("%q",proxy.connection.server.scramble_buffer))
             print("    server-addr   : " .. proxy.connection.server.dst.name)
             print("    client-addr   : " .. proxy.connection.client.dst.name)

             if not proxy.connection.client.src.name:match("^127.0.0.1:") then
                     proxy.response.type = proxy.MYSQLD_PACKET_ERR
                     proxy.response.errmsg = "only local connects are allowed"

                     print("we don't like this client");

                     return proxy.PROXY_SEND_RESULT
             end
     end

Note that you must return an error packet to the client by using
`proxy.PROXY_SEND_RESULT'.


File: manual.info,  Node: mysql-proxy-scripting-read-auth,  Next: mysql-proxy-scripting-read-auth-result,  Prev: mysql-proxy-scripting-read-handshake,  Up: mysql-proxy-scripting

15.7.4.5 Examining the Authentication Credentials with `read_auth()'
....................................................................

The `read_auth()' function is triggered when an authentication
handshake is initiated by the client. In the execution sequence,
`read_auth()' occurs immediately after `read_handshake()', so the
server selection has already been made, but the connection and
authorization information has not yet been provided to the backend
server.

You can obtain the authentication information by examining the
`proxy.connection.client' structure. For more information, see
`proxy.connection'.

For example, you can print the user name and password supplied during
authorization using:


     function read_auth()
             print("    username      : " .. proxy.connection.client.username)
             print("    password      : " .. string.format("%q", proxy.connection.client.scrambled_password))
     end

You can interrupt the authentication process within this function and
return an error packet back to the client by constructing a new packet
and returning `proxy.PROXY_SEND_RESULT':


     proxy.response.type = proxy.MYSQLD_PACKET_ERR
     proxy.response.errmsg = "Logins are not allowed"
     return proxy.PROXY_SEND_RESULT


File: manual.info,  Node: mysql-proxy-scripting-read-auth-result,  Next: mysql-proxy-scripting-read-query,  Prev: mysql-proxy-scripting-read-auth,  Up: mysql-proxy-scripting

15.7.4.6 Accessing Authentication Information with `read_auth_result()'
.......................................................................

The return packet from the server during authentication is captured by
`read_auth_result()'. The only argument to this function is the
authentication packet returned by the server. As the packet is a raw
MySQL network protocol packet, you must access the first byte to
identify the packet type and contents. The `MYSQLD_PACKET_ERR' and
`MYSQLD_PACKET_OK' constants can be used to identify whether the
authentication was successful:


     function read_auth_result(auth)
             local state = auth.packet:byte()

             if state == proxy.MYSQLD_PACKET_OK then
                     print("<-- auth ok");
             elseif state == proxy.MYSQLD_PACKET_ERR then
                     print("<-- auth failed");
             else
                     print("<-- auth ... don't know: " .. string.format("%q", auth.packet));
             end
     end

If a long-password capable client tries to authenticate to a server
that supports long passwords, but the user password provided is
actually short, `read_auth_result()' will be called twice. The first
time, `auth.packet:byte()' will equal 254, indicating that the client
should try again using the old password protocol. The second time
`read_auth_result()/' is called, `auth.packet:byte()' will indicate
whether the authentication actually succeeded.


File: manual.info,  Node: mysql-proxy-scripting-read-query,  Next: mysql-proxy-scripting-read-query-result,  Prev: mysql-proxy-scripting-read-auth-result,  Up: mysql-proxy-scripting

15.7.4.7 Manipulating Queries with `read_query()'
.................................................

The `read_query()' function is called once for each query submitted by
the client and accepts a single argument, the query packet that was
provided. To access the content of the packet, you must parse the
packet contents manually.

For example, you can intercept a query packet and print out the
contents using the following function definition:


     function read_query( packet )
             if packet:byte() == proxy.COM_QUERY then
                     print("we got a normal query: " .. packet:sub(2))
             end
     end

This example checks the first byte of the packet to determine the type.
If the type is `COM_QUERY' (see *Note
mysql-proxy-scripting-structures-command-constants::), we extract the
query from the packet and print it. The structure of the packet type
supplied is important. In the case of a `COM_QUERY' packet, the
remaining contents of the packet are the text of the query string. In
this example, no changes have been made to the query or the list of
queries that will ultimately be sent to the MySQL server.

To modify a query, or add new queries, you must populate the query
queue (`proxy.queries'), then execute the queries that you have placed
into the queue. If you do not modify the original query or the queue,
the query received from the client is sent to the MySQL server verbatim.

When adding queries to the queue, you should follow these guidelines:

   * The packets inserted into the queue must be valid query packets.
     For each packet, you must set the initial byte to the packet type.
     If you are appending a query, you can append the query statement
     to the rest of the packet.

   * Once you add a query to the queue, the queue is used as the source
     for queries sent to the server. If you add a query to the queue to
     add more information, you must also add the original query to the
     queue or it will not be executed.

   * Once the queue has been populated, you must set the return value
     from `read_query()' to indicate whether the query queue should be
     sent to the server.

   * When you add queries to the queue, you should add an ID. The ID
     you specify is returned with the result set so that you identify
     each query and corresponding result set. The ID has no other
     purpose than as an identifier for correlating the query and result
     set. When operating in a passive mode, during profiling for
     example, you identify the original query and the corresponding
     result set so that the results expected by the client can be
     returned correctly.

   * Unless your client is designed to cope with more result sets than
     queries, you should ensure that the number of queries from the
     client match the number of results sets returned to the client.
     Using the unique ID and removing result sets you inserted will
     help.

Normally, the `read_query()' and `read_query_result()' function are
used in conjunction with each other to inject additional queries and
remove the additional result sets. However, `read_query_result()' is
only called if you populate the query queue within `read_query()'.


File: manual.info,  Node: mysql-proxy-scripting-read-query-result,  Prev: mysql-proxy-scripting-read-query,  Up: mysql-proxy-scripting

15.7.4.8 Manipulating Results with `read_query_result()'
........................................................

The `read_query_result()' is called for each result set returned by the
server only if you have manually injected queries into the query queue.
If you have not manipulated the query queue, this function is not
called. The function supports a single argument, the result packet,
which provides a number of properties:

   * `id': The ID of the result set, which corresponds to the ID that
     was set when the query packet was submitted to the server when
     using `append(id)' on the query queue. You must have set the
     `resultset_is_needed' flag to `append' to intercept the result set
     before it is returned to the client. See *Note
     mysql-proxy-scripting-structures-queries::.

   * `query': The text of the original query.

   * `query_time': The number of microseconds required to receive the
     first row of a result set since the query was sent to the server.

   * `response_time': The number of microseconds required to receive
     the last row of the result set since the query was sent to the
     server.

   * `resultset': The content of the result set data.

By accessing the result information from the MySQL server, you can
extract the results that match the queries that you injected, return
different result sets (for example, from a modified query), and even
create your own result sets.

The following Lua script, for example, will output the query, followed
by the query time and response time (that is, the time to execute the
query and the time to return the data for the query) for each query
sent to the server:


     function read_query( packet )
             if packet:byte() == proxy.COM_QUERY then
                     print("we got a normal query: " .. packet:sub(2))

                     proxy.queries:append(1, packet )

                     return proxy.PROXY_SEND_QUERY
             end
     end

     function read_query_result(inj)
             print("query-time: " .. (inj.query_time / 1000) .. "ms")
             print("response-time: " .. (inj.response_time / 1000) .. "ms")
     end

You can access the rows of returned results from the result set by
accessing the `rows' property of the `resultset' property of the result
that is exposed through `read_query_result()'. For example, you can
iterate over the results showing the first column from each row using
this Lua fragment:


     for row in inj.resultset.rows do
             print("injected query returned: " .. row[1])
     end

Just like `read_query()', `read_query_result()' can return different
values for each result according to the result returned. If you have
injected additional queries into the query queue, for example, remove
the results returned from those additional queries and return only the
results from the query originally submitted by the client.

The following example injects additional `SELECT NOW()' statements into
the query queue, giving them a different ID to the ID of the original
query. Within `read_query_result()', if the ID for the injected queries
is identified, we display the result row, and return the
`proxy.PROXY_IGNORE_RESULT' from the function so that the result is not
returned to the client. If the result is from any other query, we print
out the query time information for the query and return the default,
which passes on the result set unchanged. We could also have explicitly
returned `proxy.PROXY_IGNORE_RESULT' to the MySQL client.


     function read_query( packet )
             if packet:byte() == proxy.COM_QUERY then
                     proxy.queries:append(2, string.char(proxy.COM_QUERY) .. "SELECT NOW()", {resultset_is_needed = true} )
                     proxy.queries:append(1, packet, {resultset_is_needed = true})
                     proxy.queries:append(2, string.char(proxy.COM_QUERY) .. "SELECT NOW()", {resultset_is_needed = true} )

                     return proxy.PROXY_SEND_QUERY
             end
     end

     function read_query_result(inj)
             if inj.id == 2 then
                     for row in inj.resultset.rows do
                             print("injected query returned: " .. row[1])
                     end
                     return proxy.PROXY_IGNORE_RESULT
             else
                     print("query-time: " .. (inj.query_time / 1000) .. "ms")
                     print("response-time: " .. (inj.response_time / 1000) .. "ms")
             end
     end

For further examples, see *Note mysql-proxy-using::.


File: manual.info,  Node: mysql-proxy-using,  Next: mysql-proxy-faq,  Prev: mysql-proxy-scripting,  Up: mysql-proxy

15.7.5 Using MySQL Proxy
------------------------

* Menu:

* mysql-proxy-using-admin::      Using the Administration Interface

There are a number of different ways to use MySQL Proxy. At the most
basic level, you can allow MySQL Proxy to pass queries from clients to
a single server. To use MySQL Proxy in this mode, you just have to
specify on the command line the backend server to which the proxy
should connect:


     shell> mysql-proxy --proxy-backend-addresses=sakila:3306

If you specify multiple backend MySQL servers, the proxy connects each
client to each server in a round-robin fashion. Suppose that you have
two MySQL servers, A and B. The first client to connect is connected to
server A, the second to server B, the third to server A. For example:


     shell> mysql-proxy \
          --proxy-backend-addresses=narcissus:3306 \
          --proxy-backend-addresses=nostromo:3306

When you specify multiple servers in this way, the proxy automatically
identifies when a MySQL server has become unavailable and marks it
accordingly. New connections are automatically attached to a server
that is available, and a warning is reported to the standard output from
*Note `mysql-proxy': mysql-proxy.:


     network-mysqld.c.367: connect(nostromo:3306) failed: Connection refused
     network-mysqld-proxy.c.2405: connecting to backend (nostromo:3306) failed, marking it as down for ...

Lua scripts enable a finer level of control, both over the connections
and their distribution and how queries and result sets are processed.
When using an Lua script, you must specify the name of the script on
the command line using the `--proxy-lua-script' option:


     shell> mysql-proxy --proxy-lua-script=mc.lua --proxy-backend-addresses=sakila:3306

When you specify a script, the script is not executed until a
connection is made. This means that faults with the script are not
raised until the script is executed. Script faults will not affect the
distribution of queries to backend MySQL servers.

*Note*:

Because a script is not read until the connection is made, you can
modify the contents of the Lua script file while the proxy is still
running and the modified script is automatically used for the next
connection. This ensures that MySQL Proxy remains available because it
need not be restarted for the changes to take effect.


File: manual.info,  Node: mysql-proxy-using-admin,  Prev: mysql-proxy-using,  Up: mysql-proxy-using

15.7.5.1 Using the Administration Interface
...........................................

The *Note `mysql-proxy': mysql-proxy. administration interface can be
accessed using any MySQL client using the standard protocols.  You can
use the administration interface to gain information about the proxy
server as a whole - standard connections to the proxy are isolated to
operate as if you were connected directly to the backend MySQL server.

In *Note `mysql-proxy': mysql-proxy. 0.8.0 and earlier, a rudimentary
interface was built into the proxy. In later versions this was replaced
so that you must specify an administration script to be used when users
connect to the administration interface.

To use the administration interface, specify the user name and password
required to connect to the admin service, using the `--admin-username'
and `--admin-password' options.  You must also specify the Lua script
to be used as the interface to the administration service by using the
`admin-lua-script' script option to point to a Lua script.

For example, you can create a basic interface to the internal
components of the *Note `mysql-proxy': mysql-proxy. system using the
following script, written by Diego Medina:


     --[[

        Copyright 2008, 2010, Oracle and/or its affiliates. All rights reserved.

        This program is free software; you can redistribute it and/or modify
        it under the terms of the GNU General Public License as published by
        the Free Software Foundation; version 2 of the License.

        This program is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with this program; if not, write to the Free Software
        Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

     --]]

     -- admin.lua

     --[[

         See http://www.chriscalender.com/?p=41
         (Thanks to Chris Calender)
         See http://datacharmer.blogspot.com/2009/01/mysql-proxy-is-back.html
         (Thanks Giuseppe Maxia)

     --]]

     function set_error(errmsg)
         proxy.response = {
             type = proxy.MYSQLD_PACKET_ERR,
             errmsg = errmsg or "error"
         }
     end

     function read_query(packet)
         if packet:byte() ~= proxy.COM_QUERY then
             set_error("[admin] we only handle text-based queries (COM_QUERY)")
             return proxy.PROXY_SEND_RESULT
         end

         local query = packet:sub(2)
         local rows = { }
         local fields = { }

         -- try to match the string up to the first non-alphanum
         local f_s, f_e, command = string.find(packet, "^%s*(%w+)", 2)
         local option

         if f_e then
                 -- if that match, take the next sub-string as option
                 f_s, f_e, option = string.find(packet, "^%s+(%w+)", f_e + 1)
         end

         -- we got our commands, execute it
         if command == "show" and option == "querycounter" then
                 ---
                 -- proxy.PROXY_SEND_RESULT requires
                 --
                 -- proxy.response.type to be either
                 -- * proxy.MYSQLD_PACKET_OK or
                 -- * proxy.MYSQLD_PACKET_ERR
                 --
                 -- for proxy.MYSQLD_PACKET_OK you need a resultset
                 -- * fields
                 -- * rows
                 --
                 -- for proxy.MYSQLD_PACKET_ERR
                 -- * errmsg
                 proxy.response.type = proxy.MYSQLD_PACKET_OK
                 proxy.response.resultset = {
                         fields = {
                                 { type = proxy.MYSQL_TYPE_LONG, name = "query_counter", },
                         },
                         rows = {
                                 { proxy.global.query_counter }
                         }
                 }

                 -- we have our result, send it back
                 return proxy.PROXY_SEND_RESULT
         elseif command == "show" and option == "myerror" then
                 proxy.response.type = proxy.MYSQLD_PACKET_ERR
                 proxy.response.errmsg = "my first error"

                 return proxy.PROXY_SEND_RESULT

         elseif string.sub(packet, 2):lower() == 'select help' then
                 return show_process_help()

         elseif string.sub(packet, 2):lower() == 'show proxy processlist' then
                 return show_process_table()

         elseif query == "SELECT * FROM backends" then
             fields = {
                 { name = "backend_ndx",
                   type = proxy.MYSQL_TYPE_LONG },

                 { name = "address",
                   type = proxy.MYSQL_TYPE_STRING },
                 { name = "state",
                   type = proxy.MYSQL_TYPE_STRING },
                 { name = "type",
                   type = proxy.MYSQL_TYPE_STRING },
             }

             for i = 1, #proxy.global.backends do
                 local b = proxy.global.backends[i]

                 rows[#rows + 1] = {
                     i, b.dst.name, b.state, b.type
                 }
             end
         else
             set_error()
             return proxy.PROXY_SEND_RESULT
         end

         proxy.response = {
             type = proxy.MYSQLD_PACKET_OK,
             resultset = {
                 fields = fields,
                 rows = rows
             }
         }
         return proxy.PROXY_SEND_RESULT
     end

     function make_dataset (header, dataset)
         proxy.response.type = proxy.MYSQLD_PACKET_OK

         proxy.response.resultset = {
             fields = {},
             rows = {}
         }
         for i,v in pairs (header) do
             table.insert(proxy.response.resultset.fields, {type = proxy.MYSQL_TYPE_STRING, name = v})
         end
         for i,v in pairs (dataset) do
             table.insert(proxy.response.resultset.rows, v )
         end
         return proxy.PROXY_SEND_RESULT
     end

     function show_process_table()
         local dataset = {}
         local header = { 'Id', 'IP Address', 'Time' }
         local rows = {}
         for t_i, t_v in pairs (proxy.global.process) do
             for s_i, s_v in pairs ( t_v ) do
                 table.insert(rows, { t_i, s_v.ip, os.date('%c',s_v.ts) })
             end
         end
         return make_dataset(header,rows)
     end

     function show_process_help()
         local dataset = {}
         local header = { 'command',  'description' }
         local rows = {
             {'SELECT HELP',                 'This command.'},
             {'SHOW PROXY PROCESSLIST',      'Show all connections and their true IP Address.'},
         }
         return make_dataset(header,rows)
     end

     function dump_process_table()
         proxy.global.initialize_process_table()
         print('current contents of process table')
         for t_i, t_v in pairs (proxy.global.process) do
             print ('session id: ', t_i)
             for s_i, s_v in pairs ( t_v ) do
                 print ( '\t', s_i, s_v.ip, s_v.ts )
             end
         end
         print ('---END PROCESS TABLE---')
     end

     --[[    Help

     we use a simple string-match to split commands are word-boundaries

     mysql> show querycounter

     is split into
     command = "show"
     option  = "querycounter"

     spaces are ignored, the case has to be as is.

     mysql> show myerror

     returns a error-packet

     --]]

The script works in combination with a main proxy script,
`reporter.lua':


     --[[

        Copyright 2008, 2010, Oracle and/or its affiliates. All rights reserved.

        This program is free software; you can redistribute it and/or modify
        it under the terms of the GNU General Public License as published by
        the Free Software Foundation; version 2 of the License.

        This program is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
        GNU General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with this program; if not, write to the Free Software
        Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

     --]]

     -- reporter.lua

     --[[

         See http://www.chriscalender.com/?p=41
         (Thanks to Chris Calender)
         See http://datacharmer.blogspot.com/2009/01/mysql-proxy-is-back.html
         (Thanks Giuseppe Maxia)

     --]]

     proxy.global.query_counter = proxy.global.query_counter or 0

     function proxy.global.initialize_process_table()
         if proxy.global.process == nil then
             proxy.global.process = {}
         end
         if proxy.global.process[proxy.connection.server.thread_id] == nil then
             proxy.global.process[proxy.connection.server.thread_id] = {}
         end
     end

     function read_auth_result( auth )
         local state = auth.packet:byte()
         if state == proxy.MYSQLD_PACKET_OK then
             proxy.global.initialize_process_table()
             table.insert( proxy.global.process[proxy.connection.server.thread_id],
                 { ip = proxy.connection.client.src.name, ts = os.time() } )
         end
     end

     function disconnect_client()
         local connection_id = proxy.connection.server.thread_id
         if connection_id then
             -- client has disconnected, set this to nil
             proxy.global.process[connection_id] = nil
         end
     end

     ---
     -- read_query() can return a resultset
     --
     -- You can use read_query() to return a result-set.
     --
     -- @param packet the mysql-packet sent by the client
     --
     -- @return
     --   * nothing to pass on the packet as is,
     --   * proxy.PROXY_SEND_QUERY to send the queries from the proxy.queries queue
     --   * proxy.PROXY_SEND_RESULT to send your own result-set
     --
     function read_query( packet )
             -- a new query came in this connection
             -- using proxy.global.* to make it available to the admin plugin
             proxy.global.query_counter = proxy.global.query_counter + 1

     end

To use the script, save the first script to a file (`admin.lua' in the
following example) and the other to `reporter.lua', then run *Note
`mysql-proxy': mysql-proxy. specifying the admin script and a backend
MySQL server:


     shell> mysql-proxy --admin-lua-script=admin.lua --admin-password=password \ »
          --admin-username=root --proxy-backend-addresses=127.0.0.1:3306 -proxy-lua-script=reporter.lua

In a different window, connect to the MySQL server through the proxy:


     shell> mysql --user=root --password=password --port=4040
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 1798669
     Server version: 5.0.70-log Gentoo Linux mysql-5.0.70-r1

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql>

In another different window, connect to the *Note `mysql-proxy':
mysql-proxy. admin service using the specified user name and password:


     shell> mysql --user=root --password=password --port=4041 --host=localhost
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 1
     Server version: 5.0.99-agent-admin

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql>

To monitor the status of the proxy, ask for a list of the current
active processes:


     mysql> show proxy processlist;
     +---------+---------------------+--------------------------+
     | Id      | IP Address          | Time                     |
     +---------+---------------------+--------------------------+
     | 1798669 | 192.168.0.112:52592 | Wed Jan 20 16:58:00 2010 |
     +---------+---------------------+--------------------------+
     1 row in set (0.00 sec)

     mysql>

For more information on the example, see MySQL Proxy Admin Example
(http://fmpwizard.blogspot.com/2009/04/how-do-i-use-mysql-proxy-admin-plugin.html).


File: manual.info,  Node: mysql-proxy-faq,  Prev: mysql-proxy-using,  Up: mysql-proxy

15.7.6 MySQL Proxy FAQ
----------------------

*Questions*
   * 16.7.6.1: In load balancing, how can I separate reads from writes?

   * 16.7.6.2: How do I use a socket with MySQL Proxy? Proxy change logs
     mention that support for UNIX sockets has been added.

   * 16.7.6.3: Can I use MySQL Proxy with all versions of MySQL?

   * 16.7.6.4: Can I run MySQL Proxy as a daemon?

   * 16.7.6.5: Do proxy applications run on a separate server? If not,
     what is the overhead incurred by Proxy on the DB server side?

   * 16.7.6.6: With load balancing, what happens to transactions? Are
     all queries sent to the same server?

   * 16.7.6.7: Is it possible to use MySQL Proxy with updating a Lucene
     index (or Solr) by making TCP calls to that server to update?

   * 16.7.6.8: Is the system context switch expensive, how much
     overhead does the Lua script add?

   * 16.7.6.9: How much latency does a proxy add to a connection?

   * 16.7.6.10: Do you have to make one large script and call it at
     proxy startup, can I change scripts without stopping and restarting
     (interrupting) the proxy?

   * 16.7.6.11: If MySQL Proxy has to live on same machine as MySQL,
     are there any tuning considerations to ensure both perform
     optimally?

   * 16.7.6.12: I currently use SQL Relay for efficient connection
     pooling with a number of Apache processes connecting to a MySQL
     server. Can MySQL Proxy currently accomplish this? My goal is to
     minimize connection latency while keeping temporary tables
     available.

   * 16.7.6.13: Are these reserved function names (for example,
     `error_result()') that get automatically called?

   * 16.7.6.14: As the script is re-read by MySQL Proxy, does it cache
     this or is it looking at the file system with each request?

   * 16.7.6.15: Given that there is a `connect_server()' function, can
     a Lua script link up with multiple servers?

   * 16.7.6.16: Is the MySQL Proxy an API?

   * 16.7.6.17: The global namespace variable example with quotas does
     not persist after a reboot, is that correct?

   * 16.7.6.18: Can MySQL Proxy handle SSL connections?

   * 16.7.6.19: Could MySQL Proxy be used to capture passwords?

   * 16.7.6.20: Are there tools for isolating problems? How can someone
     figure out whether a problem is in the client, the database, or the
     proxy?

   * 16.7.6.21: Is MySQL Proxy similar to what is provided by Java
     connection pools?

   * 16.7.6.22: So authentication with connection pooling has to be
     done at every connection? What is the authentication latency?

   * 16.7.6.23: If you have multiple databases on the same box, can you
     use proxy to connect to databases on default port 3306?

   * 16.7.6.24: What about caching the authorization information so
     clients connecting are given back-end connections that were
     established with identical authorization information, thus saving
     a few more round trips?

   * 16.7.6.25: Is there any big web site using MySQL Proxy? For what
     purpose and what transaction rate have they achieved?

   * 16.7.6.26: How does MySQL Proxy compare to DBSlayer?

   * 16.7.6.27: I tried using MySQL Proxy without any Lua script to try
     a round-robin type load balancing. In this case, if the first
     database in the list is down, MySQL Proxy would not connect the
     client to the second database in the list.

   * 16.7.6.28: Is it `safe' to use `LuaSocket' with proxy scripts?

   * 16.7.6.29: How different is MySQL Proxy from DBCP (Database
     connection pooling) for Apache in terms of connection pooling?

   * 16.7.6.30: MySQL Proxy can handle about 5000 connections, what is
     the limit on a MySQL server?

   * 16.7.6.31: Would the Java-only connection pooling solution work for
     multiple web servers? With this, I would assume that you can pool
     across many web servers at once?

*Questions and Answers* *16.7.6.1: ** In load balancing, how can I
separate reads from writes?  *

There is no automatic separation of queries that perform reads or
writes to the different backend servers. However, you can specify to
*Note `mysql-proxy': mysql-proxy. that one or more of the `backend'
MySQL servers are read only.


     shell> mysql-proxy \
     --proxy-backend-addresses=10.0.1.2:3306 \
     --proxy-read-only-backend-addresses=10.0.1.3:3306 &

*16.7.6.2: ** How do I use a socket with MySQL Proxy? Proxy change logs
mention that support for UNIX sockets has been added.  *

Specify the path to the socket:


     --proxy-backend-addresses=/PATH/TO/SOCKET

*16.7.6.3: ** Can I use MySQL Proxy with all versions of MySQL?  *

MySQL Proxy is designed to work with MySQL 5.0 or higher, and supports
the MySQL network protocol for 5.0 and higher.

*16.7.6.4: ** Can I run MySQL Proxy as a daemon?  *

Use the `--daemon' option. To keep track of the process ID, the daemon
can be started with the `--pid-file=file' option to save the PID to a
known file name. On version 0.5.x, the Proxy cannot be started natively
as a daemon.

*16.7.6.5: ** Do proxy applications run on a separate server? If not,
what is the overhead incurred by Proxy on the DB server side?  *

You can run the proxy on the application server, on its own box, or on
the DB-server depending on the use case.

*16.7.6.6: ** With load balancing, what happens to transactions? Are all
queries sent to the same server?  *

Without any special customization the whole connection is sent to the
same server. That keeps the whole connection state intact.

*16.7.6.7: ** Is it possible to use MySQL Proxy with updating a Lucene
index (or Solr) by making TCP calls to that server to update?  *

Yes, but it is not advised for now.

*16.7.6.8: ** Is the system context switch expensive, how much overhead
does the Lua script add?  *

Lua is fast and the overhead should be small enough for most
applications. The raw packet overhead is around 400 microseconds.

*16.7.6.9: ** How much latency does a proxy add to a connection?  *

In the range of 400 microseconds per request.

*16.7.6.10: ** Do you have to make one large script and call it at proxy
startup, can I change scripts without stopping and restarting
(interrupting) the proxy?  *

You can just change the script and the proxy will reload it when a
client connects.

*16.7.6.11: ** If MySQL Proxy has to live on same machine as MySQL, are
there any tuning considerations to ensure both perform optimally?  *

MySQL Proxy can live on any box: application, database, or its own box.
MySQL Proxy uses comparatively little CPU or RAM, with negligible
additional requirements or overhead.

*16.7.6.12: ** I currently use SQL Relay for efficient connection
pooling with a number of Apache processes connecting to a MySQL server.
Can MySQL Proxy currently accomplish this? My goal is to minimize
connection latency while keeping temporary tables available.  *

Yes.

*16.7.6.13: ** Are these reserved function names (for example,
`error_result()') that get automatically called?  *

Only functions and values starting with `proxy.*' are provided by the
proxy. All others are user provided.

*16.7.6.14: ** As the script is re-read by MySQL Proxy, does it cache
this or is it looking at the file system with each request?  *

It looks for the script at client-connect and reads it if it has
changed, otherwise it uses the cached version.

*16.7.6.15: ** Given that there is a `connect_server()' function, can a
Lua script link up with multiple servers?  *

MySQL Proxy provides some tutorials in the source package; one is
`examples/tutorial-keepalive.lua'.

*16.7.6.16: ** Is the MySQL Proxy an API?  *

No, MySQL Proxy is an application that forwards packets from a client
to a server using the MySQL network protocol. The MySQL Proxy provides
a API allowing you to change its behavior.

*16.7.6.17: ** The global namespace variable example with quotas does
not persist after a reboot, is that correct?  *

Yes. If you restart the proxy, you lose the results, unless you save
them in a file.

*16.7.6.18: ** Can MySQL Proxy handle SSL connections?  *

No, being the man-in-the-middle, Proxy cannot handle encrypted sessions
because it cannot share the SSL information.

*16.7.6.19: ** Could MySQL Proxy be used to capture passwords?  *

The MySQL network protocol does not allow passwords to be sent in
cleartext, all you could capture is the encrypted version.

*16.7.6.20: ** Are there tools for isolating problems? How can someone
figure out whether a problem is in the client, the database, or the
proxy?  *

You can set a debug script in the proxy, which is an exceptionally good
tool for this purpose. You can see very clearly which component is
causing the problem, if you set the right breakpoints.

*16.7.6.21: ** Is MySQL Proxy similar to what is provided by Java
connection pools?  *

Yes and no. Java connection pools are specific to Java applications,
MySQL Proxy works with any client API that talks the MySQL network
protocol. Also, connection pools do not provide any functionality for
intelligently examining the network packets and modifying the contents.

*16.7.6.22: ** So authentication with connection pooling has to be done
at every connection? What is the authentication latency?  *

You can skip the round-trip and use the connection as it was added to
the pool. As long as the application cleans up the temporary tables it
used. The overhead is (as always) around 400 microseconds.

*16.7.6.23: ** If you have multiple databases on the same box, can you
use proxy to connect to databases on default port 3306?  *

Yes, MySQL Proxy can listen on any port, provided that none of the
MySQL servers are listening on the same port.

*16.7.6.24: ** What about caching the authorization information so
clients connecting are given back-end connections that were established
with identical authorization information, thus saving a few more round
trips?  *

There is an `--proxy-pool-no-change-user' option that provides this
functionality.

*16.7.6.25: ** Is there any big web site using MySQL Proxy? For what
purpose and what transaction rate have they achieved?  *

Yes, gaiaonline (http://gaiaonline.com/).  They have tested MySQL Proxy
and seen it handle 2400 queries per second through the proxy.

*16.7.6.26: ** How does MySQL Proxy compare to DBSlayer?  *

DBSlayer is a REST->MySQL tool, MySQL Proxy is transparent to your
application. No change to the application is needed.

*16.7.6.27: ** I tried using MySQL Proxy without any Lua script to try a
round-robin type load balancing. In this case, if the first database in
the list is down, MySQL Proxy would not connect the client to the
second database in the list.  *

This issue is fixed in version 0.7.0.

*16.7.6.28: ** Is it `safe' to use `LuaSocket' with proxy scripts?  *

You can, but it is not advised because it may block.

*16.7.6.29: ** How different is MySQL Proxy from DBCP (Database
connection pooling) for Apache in terms of connection pooling?  *

Connection Pooling is just one use case of the MySQL Proxy. You can use
it for a lot more and it works in cases where you cannot use DBCP (for
example, if you do not have Java).

*16.7.6.30: ** MySQL Proxy can handle about 5000 connections, what is
the limit on a MySQL server?  *

The server limit is given by the value of the `max_connections' system
variable. The default value is version dependent.

*16.7.6.31: ** Would the Java-only connection pooling solution work for
multiple web servers? With this, I would assume that you can pool
across many web servers at once?  *

Yes. But you can also start one proxy on each application server to get
a similar behavior as you have it already.


File: manual.info,  Node: replication,  Next: mysql-cluster,  Prev: ha-overview,  Up: Top

16 Replication
**************

* Menu:

* replication-configuration::    Replication Configuration
* replication-implementation::   Replication Implementation
* replication-solutions::        Replication Solutions
* replication-notes::            Replication Notes and Tips

Replication enables data from one MySQL database server (the master) to
be replicated to one or more MySQL database servers (the slaves).
Replication is asynchronous - slaves need not be connected permanently
to receive updates from the master. This means that updates can occur
over long-distance connections and even over temporary or intermittent
connections such as a dial-up service.  Depending on the configuration,
you can replicate all databases, selected databases, or even selected
tables within a database.

For answers to some questions often asked by those who are new to MySQL
Replication, see *Note faqs-replication::.

The target uses for replication in MySQL include:

   * Scale-out solutions - spreading the load among multiple slaves to
     improve performance. In this environment, all writes and updates
     must take place on the master server. Reads, however, may take
     place on one or more slaves. This model can improve the
     performance of writes (since the master is dedicated to updates),
     while dramatically increasing read speed across an increasing
     number of slaves.

   * Data security - because data is replicated to the slave, and the
     slave can pause the replication process, it is possible to run
     backup services on the slave without corrupting the corresponding
     master data.

   * Analytics - live data can be created on the master, while the
     analysis of the information can take place on the slave without
     affecting the performance of the master.

   * Long-distance data distribution - if a branch office would like to
     work with a copy of your main data, you can use replication to
     create a local copy of the data for their use without requiring
     permanent access to the master.

Replication in MySQL features support for one-way, asynchronous
replication, in which one server acts as the master, while one or more
other servers act as slaves. This is in contrast to the _synchronous_
replication which is a characteristic of MySQL Cluster (see *Note
mysql-cluster::).

There are a number of solutions available for setting up replication
between two servers, but the best method to use depends on the presence
of data and the engine types you are using. For more information on the
available options, see *Note replication-howto::.

There are two core types of replication format, Statement Based
Replication (SBR), which replicates entire SQL statements, and Row
Based Replication (RBR), which replicates only the changed rows. You
may also use a third variety, Mixed Based Replication (MBR). For more
information on the different replication formats, see *Note
replication-formats::. From MySQL 5.1.12 to MySQL 5.1.28, mixed format
is the default. Beginning with MySQL 5.1.29, statement-based format is
the default.

Replication is controlled through a number of different options and
variables. These control the core operation of the replication,
timeouts, and the databases and filters that can be applied on
databases and tables. For more information on the available options,
see *Note replication-options::.

You can use replication to solve a number of different problems,
including problems with performance, supporting the backup of different
databases, and as part of a larger solution to alleviate system
failures. For information on how to address these issues, see *Note
replication-solutions::.

For notes and tips on how different data types and statements are
treated during replication, including details of replication features,
version compatibility, upgrades, and problems and their resolution,
including an FAQ, see *Note replication-notes::.

For detailed information on the implementation of replication, how
replication works, the process and contents of the binary log,
background threads and the rules used to decide how statements are
recorded and replication, see *Note replication-implementation::.


File: manual.info,  Node: replication-configuration,  Next: replication-implementation,  Prev: replication,  Up: replication

16.1 Replication Configuration
==============================

* Menu:

* replication-howto::            How to Set Up Replication
* replication-formats::          Replication Formats
* replication-options::          Replication and Binary Logging Options and Variables
* replication-administration::   Common Replication Administration Tasks

Replication between servers in MySQL is based on the binary logging
mechanism. The MySQL instance operating as the master (the source of
the database changes) writes updates and changes as `events' to the
binary log. The information in the binary log is stored in different
logging formats according to the database changes being recorded.
Slaves are configured to read the binary log from the master and to
execute the events in the binary log on the slave's local database.

The master is `dumb' in this scenario. Once binary logging has been
enabled, all statements are recorded in the binary log. Each slave
receives a copy of the entire contents of the binary log. It is the
responsibility of the slave to decide which statements in the binary
log should be executed; you cannot configure the master to log only
certain events. If you do not specify otherwise, all events in the
master binary log are executed on the slave. If required, you can
configure the slave to process only events that apply to particular
databases or tables.

Each slave keeps a record of the binary log coordinates: The file name
and position within the file that it has read and processed from the
master. This means that multiple slaves can be connected to the master
and executing different parts of the same binary log.  Because the
slaves control this process, individual slaves can be connected and
disconnected from the server without affecting the master's operation.
Also, because each slave remembers the position within the binary log,
it is possible for slaves to be disconnected, reconnect and then `catch
up' by continuing from the recorded position.

Both the master and each slave must be configured with a unique ID
(using the `server-id' option). In addition, each slave must be
configured with information about the master host name, log file name,
and position within that file.  These details can be controlled from
within a MySQL session using the *Note `CHANGE MASTER TO':
change-master-to. statement on the slave. The details are stored within
the slave's `master.info' file.

This section describes the setup and configuration required for a
replication environment, including step-by-step instructions for
creating a new replication environment. The major components of this
section are:

   * For a guide to setting up two or more servers for replication,
     *Note replication-howto::, deals with the configuration of the
     systems and provides methods for copying data between the master
     and slaves.

   * Events in the binary log are recorded using a number of formats.
     These are referred to as statement-based replication (SBR) or
     row-based replication (RBR). A third type, mixed-format
     replication (MIXED), uses SBR or RBR replication automatically to
     take advantage of the benefits of both SBR and RBR formats when
     appropriate. The different formats are discussed in *Note
     replication-formats::.

   * Detailed information on the different configuration options and
     variables that apply to replication is provided in *Note
     replication-options::.

   * Once started, the replication process should require little
     administration or monitoring. However, for advice on common tasks
     that you may want to execute, see *Note
     replication-administration::.


File: manual.info,  Node: replication-howto,  Next: replication-formats,  Prev: replication-configuration,  Up: replication-configuration

16.1.1 How to Set Up Replication
--------------------------------

* Menu:

* replication-howto-masterbaseconfig::  Setting the Replication Master Configuration
* replication-howto-slavebaseconfig::  Setting the Replication Slave Configuration
* replication-howto-repuser::    Creating a User for Replication
* replication-howto-masterstatus::  Obtaining the Replication Master Binary Log Coordinates
* replication-howto-mysqldump::  Creating a Data Snapshot Using mysqldump
* replication-howto-rawdata::    Creating a Data Snapshot Using Raw Data Files
* replication-howto-newservers::  Setting Up Replication with New Master and Slaves
* replication-howto-existingdata::  Setting Up Replication with Existing Data
* replication-howto-additionalslaves::  Introducing Additional Slaves to an Existing Replication Environment
* replication-howto-slaveinit::  Setting the Master Configuration on the Slave

This section describes how to set up complete replication of a MySQL
server. There are a number of different methods for setting up
replication, and the exact method to use depends on how you are setting
up replication, and whether you already have data within your master
database.

There are some generic tasks that are common to all replication setups:

   * On the master, you must enable binary logging and configure a
     unique server ID. This might require a server restart. See *Note
     replication-howto-masterbaseconfig::.

   * On each slave that you want to connect to the master, you must
     configure a unique server ID. This might require a server restart.
     See *Note replication-howto-slavebaseconfig::.

   * You may want to create a separate user that will be used by your
     slaves to authenticate with the master to read the binary log for
     replication. The step is optional. See *Note
     replication-howto-repuser::.

   * Before creating a data snapshot or starting the replication
     process, you should record the position of the binary log on the
     master. You will need this information when configuring the slave
     so that the slave knows where within the binary log to start
     executing events. See *Note replication-howto-masterstatus::.

   * If you already have data on your master and you want to use it to
     synchronize your slave, you will need to create a data snapshot.
     You can create a snapshot using *Note `mysqldump': mysqldump. (see
     *Note replication-howto-mysqldump::) or by copying the data files
     directly (see *Note replication-howto-rawdata::).

   * You will need to configure the slave with settings for connecting
     to the master, such as the host name, login credentials, and
     binary log file name and position. See *Note
     replication-howto-slaveinit::.

Once you have configured the basic options, you will need to follow the
instructions for your replication setup. A number of alternatives are
provided:

   * If you are establishing a new MySQL master and one or more slaves,
     you need only set up the configuration, as you have no data to
     exchange. For guidance on setting up replication in this
     situation, see *Note replication-howto-newservers::.

   * If you are already running a MySQL server, and therefore already
     have data that must be transferred to your slaves before
     replication starts, have not previously configured the binary log
     and are able to shut down your MySQL server for a short period
     during the process, see *Note replication-howto-existingdata::.

   * If you are adding slaves to an existing replication environment,
     you can set up the slaves without affecting the master. See *Note
     replication-howto-additionalslaves::.

If you will be administering MySQL replication servers, we suggest that
you read this entire chapter through and try all statements mentioned
in *Note replication-master-sql::, and *Note replication-slave-sql::.
You should also familiarize yourself with the replication startup
options described in *Note replication-options::.

*Note*:

Note that certain steps within the setup process require the `SUPER'
privilege. If you do not have this privilege, it might not be possible
to enable replication.


File: manual.info,  Node: replication-howto-masterbaseconfig,  Next: replication-howto-slavebaseconfig,  Prev: replication-howto,  Up: replication-howto

16.1.1.1 Setting the Replication Master Configuration
.....................................................

On a replication master, you must enable binary logging and establish a
unique server ID. If this has not already been done, this part of
master setup requires a server restart.

Binary logging _must_ be enabled on the master because the binary log
is the basis for sending data changes from the master to its slaves. If
binary logging is not enabled, replication will not be possible.

Each server within a replication group must be configured with a unique
server ID. This ID is used to identify individual servers within the
group, and must be a positive integer between 1 and (2^32)-1. How you
organize and select the numbers is entirely up to you.

To configure the binary log and server ID options, you will need to
shut down your MySQL server and edit the `my.cnf' or `my.ini' file.
Add the following options to the configuration file within the
`[mysqld]' section. If these options already exist, but are commented
out, uncomment the options and alter them according to your needs. For
example, to enable binary logging using a log file name prefix of
`mysql-bin', and configure a server ID of 1, use these lines:


     [mysqld]
     log-bin=mysql-bin
     server-id=1

After making the changes, restart the server.

*Note*:

If you omit `server-id' (or set it explicitly to its default value of
0), a master refuses connections from all slaves.

*Note*:

For the greatest possible durability and consistency in a replication
setup using `InnoDB' with transactions, you should use
`innodb_flush_log_at_trx_commit=1' and `sync_binlog=1' in the master
`my.cnf' file.

*Note*:

Ensure that the `skip-networking' option is not enabled on your
replication master. If networking has been disabled, your slave will
not able to communicate with the master and replication will fail.


File: manual.info,  Node: replication-howto-slavebaseconfig,  Next: replication-howto-repuser,  Prev: replication-howto-masterbaseconfig,  Up: replication-howto

16.1.1.2 Setting the Replication Slave Configuration
....................................................

On a replication slave, you must establish a unique server ID.  If this
has not already been done, this part of slave setup requires a server
restart.

If the slave server ID is not already set, or the current value
conflicts with the value that you have chosen for the master server,
you should shut down your slave server and edit the configuration to
specify a unique server ID. For example:


     [mysqld]
     server-id=2

After making the changes, restart the server.

If you are setting up multiple slaves, each one must have a unique
`server-id' value that differs from that of the master and from each of
the other slaves. Think of `server-id' values as something similar to
IP addresses: These IDs uniquely identify each server instance in the
community of replication partners.

*Note*:

If you omit `server-id' (or set it explicitly to its default value of
0), a slave refuses to connect to a master.

You do not have to enable binary logging on the slave for replication
to be enabled. However, if you enable binary logging on the slave, you
can use the binary log for data backups and crash recovery on the
slave, and also use the slave as part of a more complex replication
topology (for example, where the slave acts as a master to other
slaves).


File: manual.info,  Node: replication-howto-repuser,  Next: replication-howto-masterstatus,  Prev: replication-howto-slavebaseconfig,  Up: replication-howto

16.1.1.3 Creating a User for Replication
........................................

Each slave must connect to the master using a MySQL user name and
password, so there must be a user account on the master that the slave
can use to connect. Any account can be used for this operation,
providing it has been granted the `REPLICATION SLAVE' privilege. You
may wish to create a different account for each slave, or connect to
the master using the same account for each slave.

You need not create an account specifically for replication.  However,
you should be aware that the user name and password will be stored in
plain text within the `master.info' file (see *Note
slave-logs-status::). Therefore, you may want to create a separate
account that has privileges only for the replication process, to
minimize the possibility of compromise to other accounts.

To create a new account, use *Note `CREATE USER': create-user. To grant
this account the privileges required for replication, use the *Note
`GRANT': grant.  statement. If you create an account solely for the
purposes of replication, that account needs only the `REPLICATION
SLAVE' privilege. For example, to set up a new user, `repl', that can
connect for replication from any host within the `mydomain.com' domain,
issue these statements on the master:


     mysql> CREATE USER 'repl'@'%.mydomain.com' IDENTIFIED BY 'slavepass';
     mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'%.mydomain.com';

See *Note account-management-sql::, for more information on statements
for manipulation of user accounts.


File: manual.info,  Node: replication-howto-masterstatus,  Next: replication-howto-mysqldump,  Prev: replication-howto-repuser,  Up: replication-howto

16.1.1.4 Obtaining the Replication Master Binary Log Coordinates
................................................................

To configure replication on the slave you must determine the master's
current coordinates within its binary log. You will need this
information so that when the slave starts the replication process, it
is able to start processing events from the binary log at the correct
point.

If you have existing data on your master that you want to synchronize
on your slaves before starting the replication process, you must stop
processing statements on the master, and then obtain its current binary
log coordinates and dump its data, before permitting the master to
continue executing statements. If you do not stop the execution of
statements, the data dump and the master status information that you
use will not match and you will end up with inconsistent or corrupted
databases on the slaves.

To obtain the master binary log coordinates, follow these steps:

  1. Start a session on the master by connecting to it with the
     command-line client, and flush all tables and block write
     statements by executing the *Note `FLUSH TABLES WITH READ LOCK':
     flush. statement:


          mysql> FLUSH TABLES WITH READ LOCK;

     For `InnoDB' tables, note that *Note `FLUSH TABLES WITH READ
     LOCK': flush. also blocks *Note `COMMIT': commit. operations.

     *Warning*:

     Leave the client from which you issued the *Note `FLUSH TABLES':
     flush. statement running so that the read lock remains in effect.
     If you exit the client, the lock is released.

  2. In a different session on the master, use the *Note `SHOW MASTER
     STATUS': show-master-status. statement to determine the current
     binary log file name and position:


          mysql > SHOW MASTER STATUS;
          +------------------+----------+--------------+------------------+
          | File             | Position | Binlog_Do_DB | Binlog_Ignore_DB |
          +------------------+----------+--------------+------------------+
          | mysql-bin.000003 | 73       | test         | manual,mysql     |
          +------------------+----------+--------------+------------------+

     The `File' column shows the name of the log file and `Position'
     shows the position within the file. In this example, the binary
     log file is `mysql-bin.000003' and the position is 73.  Record
     these values. You need them later when you are setting up the
     slave. They represent the replication coordinates at which the
     slave should begin processing new updates from the master.

     If the master has been running previously without binary logging
     enabled, the log file name and position values displayed by *Note
     `SHOW MASTER STATUS': show-master-status. or *Note `mysqldump
     --master-data': mysqldump. will be empty. In that case, the values
     that you need to use later when specifying the slave's log file
     and position are the empty string (`''') and `4'.

You now have the information you need to enable the slave to start
reading from the binary log in the correct place to start replication.

If you have existing data that needs be to synchronized with the slave
before you start replication, leave the client running so that the lock
remains in place and then proceed to *Note
replication-howto-mysqldump::, or *Note replication-howto-rawdata::.
The idea here is to prevent any further changes so that the data copied
to the slaves is in synchrony with the master.

If you are setting up a brand new master and slave replication group,
you can exit the first session to release the read lock.


File: manual.info,  Node: replication-howto-mysqldump,  Next: replication-howto-rawdata,  Prev: replication-howto-masterstatus,  Up: replication-howto

16.1.1.5 Creating a Data Snapshot Using mysqldump
.................................................

One way to create a snapshot of the data in an existing master database
is to use the *Note `mysqldump': mysqldump. tool to create a dump of
all the databases you want to replicate. Once the data dump has been
completed, you then import this data into the slave before starting the
replication process.

The example shown here dumps all databases to a file named `dbdump.db',
and includes the `--master-data' option which automatically appends the
*Note `CHANGE MASTER TO': change-master-to. statement required on the
slave to start the replication process:


     shell> mysqldump --all-databases --master-data > dbdump.db

If you do not use `--master-data', then it is necessary to lock all
tables in a separate session manually (using *Note `FLUSH TABLES WITH
READ LOCK': flush.) prior to running *Note `mysqldump': mysqldump, then
exiting or running UNLOCK TABLES from the second session to release the
locks. You must also obtain binary log position information matching the
snapshot, using *Note `SHOW MASTER STATUS': show-master-status, and use
this to issue the appropriate *Note `CHANGE MASTER TO':
change-master-to. statement when starting the slave.

When choosing databases to include in the dump, remember that you need
to filter out databases on each slave that you do not want to include
in the replication process.

To import the data, either copy the dump file to the slave, or access
the file from the master when connecting remotely to the slave.


File: manual.info,  Node: replication-howto-rawdata,  Next: replication-howto-newservers,  Prev: replication-howto-mysqldump,  Up: replication-howto

16.1.1.6 Creating a Data Snapshot Using Raw Data Files
......................................................

If your database is large, copying the raw data files can be more
efficient than using *Note `mysqldump': mysqldump. and importing the
file on each slave. This technique skips the overhead of updating
indexes as the `INSERT' statements are replayed.

Using this method with tables in storage engines with complex caching
or logging algorithms requires extra steps to produce a perfect `point
in time' snapshot: the initial copy command might leave out cache
information and logging updates, even if you have acquired a global
read lock. How the storage engine responds to this depends on its crash
recovery abilities.

This method also does not work reliably if the master and slave have
different values for `ft_stopword_file', `ft_min_word_len', or
`ft_max_word_len' and you are copying tables having full-text indexes.

If you use *Note `InnoDB': innodb-storage-engine. tables, you can use
the `mysqlbackup' command from the MySQL Enterprise Backup component to
produce a consistent snapshot.  This command records the log name and
offset corresponding to the snapshot to be later used on the slave.
MySQL Enterprise Backup is a commercial product that is included as
part of a MySQL Enterprise subscription. See *Note
mysql-enterprise-backup:: for detailed information.

Otherwise, use the cold backup
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_cold_backup)
technique to obtain a reliable binary snapshot of `InnoDB' tables: copy
all data files after doing a slow shutdown
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_slow_shutdown)
of the MySQL Server.

To create a raw data snapshot of `MyISAM' tables, you can use standard
copy tools such as `cp' or `copy', a remote copy tool such as `scp' or
`rsync', an archiving tool such as `zip' or `tar', or a file system
snapshot tool such as `dump', providing that your MySQL data files
exist on a single file system. If you are replicating only certain
databases, copy only those files that relate to those tables. (For
`InnoDB', all tables in all databases are stored in the system
tablespace
(http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_system_tablespace)
files, unless you have the `innodb_file_per_table' option enabled.)

You might want to specifically exclude the following files from your
archive:

   * Files relating to the `mysql' database.

   * The `master.info' file.

   * The master's binary log files.

   * Any relay log files.

To get the most consistent results with a raw data snapshot, shut down
the master server during the process, as follows:

  1. Acquire a read lock and get the master's status. See *Note
     replication-howto-masterstatus::.

  2. In a separate session, shut down the master server:


          shell> mysqladmin shutdown

  3. Make a copy of the MySQL data files. The following examples show
     common ways to do this. You need to choose only one of them:


          shell> tar cf /TMP/DB.TAR ./DATA
          shell> zip -r /TMP/DB.ZIP ./DATA
          shell> rsync --recursive ./DATA /TMP/DBDATA

  4. Restart the master server.

If you are not using `InnoDB' tables, you can get a snapshot of the
system from a master without shutting down the server as described in
the following steps:

  1. Acquire a read lock and get the master's status. See *Note
     replication-howto-masterstatus::.

  2. Make a copy of the MySQL data files. The following examples show
     common ways to do this. You need to choose only one of them:


          shell> tar cf /TMP/DB.TAR ./DATA
          shell> zip -r /TMP/DB.ZIP ./DATA
          shell> rsync --recursive ./DATA /TMP/DBDATA

  3. In the client where you acquired the read lock, release the lock:


          mysql> UNLOCK TABLES;

Once you have created the archive or copy of the database, copy the
files to each slave before starting the slave replication process.


File: manual.info,  Node: replication-howto-newservers,  Next: replication-howto-existingdata,  Prev: replication-howto-rawdata,  Up: replication-howto

16.1.1.7 Setting Up Replication with New Master and Slaves
..........................................................

The easiest and most straightforward method for setting up replication
is to use new master and slave servers.

You can also use this method if you are setting up new servers but have
an existing dump of the databases from a different server that you want
to load into your replication configuration. By loading the data into a
new master, the data will be automatically replicated to the slaves.

To set up replication between a new master and slave:

  1. Configure the MySQL master with the necessary configuration
     properties. See *Note replication-howto-masterbaseconfig::.

  2. Start up the MySQL master.

  3. Set up a user. See *Note replication-howto-repuser::.

  4. Obtain the master status information. See *Note
     replication-howto-masterstatus::.

  5. On the master, release the read lock:


          mysql> UNLOCK TABLES;

  6. On the slave, edit the MySQL configuration. See *Note
     replication-howto-slavebaseconfig::.

  7. Start up the MySQL slave.

  8. Execute a *Note `CHANGE MASTER TO': change-master-to.  statement
     to set the master replication server configuration. See *Note
     replication-howto-slaveinit::.

Perform the slave setup steps on each slave.

Because there is no data to load or exchange on a new server
configuration you do not need to copy or import any information.

If you are setting up a new replication environment using the data from
a different existing database server, you will now need to run the dump
file generated from that server on the new master. The database updates
will automatically be propagated to the slaves:


     shell> mysql -h master < fulldb.dump


File: manual.info,  Node: replication-howto-existingdata,  Next: replication-howto-additionalslaves,  Prev: replication-howto-newservers,  Up: replication-howto

16.1.1.8 Setting Up Replication with Existing Data
..................................................

When setting up replication with existing data, you will need to decide
how best to get the data from the master to the slave before starting
the replication service.

The basic process for setting up replication with existing data is as
follows:

  1. With the MySQL master running, create a user to be used by the
     slave when connecting to the master during replication.  See *Note
     replication-howto-repuser::.

  2. If you have not already configured the `server-id' and enabled
     binary logging on the master server, you will need to shut it down
     to configure these options. See *Note
     replication-howto-masterbaseconfig::.

     If you have to shut down your master server, this is a good
     opportunity to take a snapshot of its databases. You should obtain
     the master status (see *Note replication-howto-masterstatus::)
     before taking down the master, updating the configuration and
     taking a snapshot. For information on how to create a snapshot
     using raw data files, see *Note replication-howto-rawdata::.

  3. If your master server is already correctly configured, obtain its
     status (see *Note replication-howto-masterstatus::) and then use
     *Note `mysqldump': mysqldump. to take a snapshot (see *Note
     replication-howto-mysqldump::) or take a raw snapshot of the live
     server using the guide in *Note replication-howto-rawdata::.

  4. Update the configuration of the slave. See *Note
     replication-howto-slavebaseconfig::.

  5. The next step depends on how you created the snapshot of data on
     the master.

     If you used *Note `mysqldump': mysqldump.:

       1. Start the slave, using the `--skip-slave-start' option so
          that replication does not start.

       2. Import the dump file:


               shell> mysql < fulldb.dump

     If you created a snapshot using the raw data files:

       1. Extract the data files into your slave data directory.  For
          example:


               shell> tar xvf dbdump.tar

          You may need to set permissions and ownership on the files so
          that the slave server can access and modify them.

       2. Start the slave, using the `--skip-slave-start' option so
          that replication does not start.

  6. Configure the slave with the replication coordinates from the
     master. This tells the slave the binary log file and position
     within the file where replication needs to start.  Also, configure
     the slave with the login credentials and host name of the master.
     For more information on the *Note `CHANGE MASTER TO':
     change-master-to. statement required, see *Note
     replication-howto-slaveinit::.

  7. Start the slave threads:


          mysql> START SLAVE;

After you have performed this procedure, the slave should connect to
the master and catch up on any updates that have occurred since the
snapshot was taken.

If you have forgotten to set the `server-id' option for the master,
slaves cannot connect to it.

If you have forgotten to set the `server-id' option for the slave, you
get the following error in the slave's error log:


     Warning: You should set server-id to a non-0 value if master_host
     is set; we will force server id to 2, but this MySQL server will
     not act as a slave.

You also find error messages in the slave's error log if it is not able
to replicate for any other reason.

Once a slave is replicating, you can find in its data directory one
file named `master.info' and another named `relay-log.info'. The slave
uses these two files to keep track of how much of the master's binary
log it has processed. Do _not_ remove or edit these files unless you
know exactly what you are doing and fully understand the implications.
Even in that case, it is preferred that you use the *Note `CHANGE
MASTER TO': change-master-to.  statement to change replication
parameters. The slave will use the values specified in the statement to
update the status files automatically.

*Note*:

The content of `master.info' overrides some of the server options
specified on the command line or in `my.cnf'. See *Note
replication-options::, for more details.

A single snapshot of the master suffices for multiple slaves. To set up
additional slaves, use the same master snapshot and follow the slave
portion of the procedure just described.


File: manual.info,  Node: replication-howto-additionalslaves,  Next: replication-howto-slaveinit,  Prev: replication-howto-existingdata,  Up: replication-howto

16.1.1.9 Introducing Additional Slaves to an Existing Replication Environment
.............................................................................

To add another slave to an existing replication configuration, you can
do so without stopping the master. Instead, set up the new slave by
making a copy of an existing slave, except that you configure the new
slave with a different `server-id' value.

To duplicate an existing slave:

  1. Shut down the existing slave:


          shell> mysqladmin shutdown

  2. Copy the data directory from the existing slave to the new slave.
     You can do this by creating an archive using `tar' or `WinZip', or
     by performing a direct copy using a tool such as `cp' or `rsync'.
     Ensure that you also copy the log files and relay log files.

     A common problem that is encountered when adding new replication
     slaves is that the new slave fails with a series of warning and
     error messages like these:


          071118 16:44:10 [Warning] Neither --relay-log nor --relay-log-index were used; so
          replication may break when this MySQL server acts as a slave and has his hostname
          changed!! Please use '--relay-log=NEW_SLAVE_HOSTNAME-relay-bin' to avoid this problem.
          `071118 16:44:10 [ERROR] Failed to open the relay log './OLD_SLAVE_HOSTNAME-relay-bin.003525'
          (relay_log_pos 22940879)'
          071118 16:44:10 `[ERROR] Could not find target log during relay log initialization'
          071118 16:44:10 `[ERROR] Failed to initialize the master info structure'

     This is due to the fact that, if the `--relay-log' option is not
     specified, the relay log files contain the host name as part of
     their file names. (This is also true of the relay log index file
     if the `--relay-log-index' option is not used. See *Note
     replication-options::, for more information about these options.)

     To avoid this problem, use the same value for `--relay-log' on the
     new slave that was used on the existing slave. (If this option was
     not set explicitly on the existing slave, use
     `EXISTING_SLAVE_HOSTNAME-relay-bin'.)  If this is not feasible,
     copy the existing slave's relay log index file to the new slave
     and set the `--relay-log-index' option on the new slave to match
     what was used on the existing slave.  (If this option was not set
     explicitly on the existing slave, use
     `EXISTING_SLAVE_HOSTNAME-relay-bin.index'.)  Alternatively--if you
     have already tried to start the new slave (after following the
     remaining steps in this section) and have encountered errors like
     those described previously--then perform the following steps:

       1. If you have not already done so, issue a *Note `STOP SLAVE':
          stop-slave. on the new slave.

          If you have already started the existing slave again, issue a
          *Note `STOP SLAVE': stop-slave. on the existing slave as well.

       2. Copy the contents of the existing slave's relay log index
          file into the new slave's relay log index file, making sure
          to overwrite any content already in the file.

       3. Proceed with the remaining steps in this section.

  3. Copy the `master.info' and `relay-log.info' files from the existing
     slave to the new slave if they were not located in the data
     directory. These files hold the current log coordinates for the
     master's binary log and the slave's relay log.

  4. Start the existing slave.

  5. On the new slave, edit the configuration and give the new slave a
     unique `server-id' not used by the master or any of the existing
     slaves.

  6. Start the new slave. The slave will use the information in its
     `master.info' file to start the replication process.


File: manual.info,  Node: replication-howto-slaveinit,  Prev: replication-howto-additionalslaves,  Up: replication-howto

16.1.1.10 Setting the Master Configuration on the Slave
.......................................................

To set up the slave to communicate with the master for replication, you
must tell the slave the necessary connection information. To do this,
execute the following statement on the slave, replacing the option
values with the actual values relevant to your system:


     mysql> CHANGE MASTER TO
         ->     MASTER_HOST='MASTER_HOST_NAME',
         ->     MASTER_USER='REPLICATION_USER_NAME',
         ->     MASTER_PASSWORD='REPLICATION_PASSWORD',
         ->     MASTER_LOG_FILE='RECORDED_LOG_FILE_NAME',
         ->     MASTER_LOG_POS=RECORDED_LOG_POSITION;

*Note*:

Replication cannot use Unix socket files. You must be able to connect
to the master MySQL server using TCP/IP.

The *Note `CHANGE MASTER TO': change-master-to. statement has other
options as well. For example, it is possible to set up secure
replication using SSL. For a full list of options, and information
about the maximum permissible length for the string-valued options, see
*Note change-master-to::.


File: manual.info,  Node: replication-formats,  Next: replication-options,  Prev: replication-howto,  Up: replication-configuration

16.1.2 Replication Formats
--------------------------

* Menu:

* replication-sbr-rbr::          Advantages and Disadvantages of Statement-Based and Row-Based Replication
* replication-rbr-usage::        Usage of Row-Based Logging and Replication
* replication-rbr-safe-unsafe::  Determination of Safe and Unsafe Statements in Binary Logging

Replication works because events written to the binary log are read
from the master and then processed on the slave. The events are
recorded within the binary log in different formats according to the
type of event. The different replication formats used correspond to the
binary logging format used when the events were recorded in the
master's binary log. The correlation between binary logging formats and
the terms used during replication are:

   * Replication capabilities in MySQL originally were based on
     propagation of SQL statements from master to slave. This is called
     _statement-based replication_ (often abbreviated as _SBR_), which
     corresponds to the standard statement-based binary logging format.
     In MySQL 5.1.4 and earlier, binary logging and replication used
     this format exclusively.

   * Row-based binary logging logs changes in individual table rows.
     When used with MySQL replication, this is known as _row-based
     replication_ (often abbreviated as _RBR_). In row-based
     replication, the master writes _events_ to the binary log that
     indicate how individual table rows are changed.

   * As of MySQL 5.1.8, the server can change the binary logging format
     in real time according to the type of event using _mixed-format
     logging_.

     When the mixed format is in effect, statement-based logging is
     used by default, but automatically switches to row-based logging
     in particular cases as described later. Replication using the
     mixed format is often referred to as _mixed-based replication_ or
     _mixed-format replication_. For more information, see *Note
     binary-log-mixed::.

From MySQL 5.1.12 to MySQL 5.1.28, mixed format is the default.
Beginning with MySQL 5.1.29, statement-based format is the default.

MySQL Cluster

The default binary logging format in all MySQL Cluster NDB 6.x and 7.x
releases is `ROW'. MySQL Cluster Replication always uses row-based
replication, and the *Note `NDBCLUSTER': mysql-cluster. storage engine
is incompatible with statement-based replication. Using *Note
`NDBCLUSTER': mysql-cluster. sets row-based logging format
automatically. See *Note mysql-cluster-replication-general::, for more
information.

Starting with MySQL 5.1.20, when using `MIXED' format, the binary
logging format is determined in part by the storage engine being used
and the statement being executed. For more information on mixed-format
logging and the rules governing the support of different logging
formats, see *Note binary-log-mixed::.

The logging format in a running MySQL server is controlled by setting
the `binlog_format' server system variable. This variable can be set
with session or global scope. The rules governing when and how the new
setting takes effect are the same as for other MySQL server system
variables--setting the variable for the current session lasts only
until the end of that session, and the change is not visible to other
sessions; setting the variable globally requires a restart of the
server to take effect. For more information, see *Note set-statement::.

There are conditions under which you cannot change the binary logging
format at runtime or doing so causes replication to fail.  See *Note
binary-log-setting::.

You must have the `SUPER' privilege to set the global `binlog_format'
value. Starting with MySQL 5.1.29, you must have the `SUPER' privilege
to set either the global or session `binlog_format' value. (Bug #39106)

The statement-based and row-based replication formats have different
issues and limitations. For a comparison of their relative advantages
and disadvantages, see *Note replication-sbr-rbr::.

With statement-based replication, you may encounter issues with
replicating stored routines or triggers. You can avoid these issues by
using row-based replication instead. For more information, see *Note
stored-programs-logging::.


File: manual.info,  Node: replication-sbr-rbr,  Next: replication-rbr-usage,  Prev: replication-formats,  Up: replication-formats

16.1.2.1 Advantages and Disadvantages of Statement-Based and Row-Based Replication
..................................................................................

Each binary logging format has advantages and disadvantages. For most
users, the mixed replication format should provide the best combination
of data integrity and performance. If, however, you want to take
advantage of the features specific to the statement-based or row-based
replication format when performing certain tasks, you can use the
information in this section, which provides a summary of their relative
advantages and disadvantages, to determine which is best for your needs.

   * Advantages of statement-based replication

   * Disadvantages of statement-based replication

   * Advantages of row-based replication

   * Disadvantages of row-based replication

*Advantages of statement-based replication*

   * Proven technology that has existed in MySQL since 3.23.

   * Less data written to log files. When updates or deletes affect
     many rows, this results in _much_ less storage space required for
     log files. This also means that taking and restoring from backups
     can be accomplished more quickly.

   * Log files contain all statements that made any changes, so they
     can be used to audit the database.

*Disadvantages of statement-based replication*

   * Statements that are unsafe for SBR

     Not all statements which modify data (such as *Note `INSERT':
     insert.  *Note `DELETE': delete, *Note `UPDATE': update, and
     `REPLACE' statements) can be replicated using statement-based
     replication. Any nondeterministic behavior is difficult to
     replicate when using statement-based replication. Examples of such
     DML (Data Modification Language) statements include the following:

        * A statement that depends on a UDF or stored program that is
          nondeterministic, since the value returned by such a UDF or
          stored program or depends on factors other than the
          parameters supplied to it. (Row-based replication, however,
          simply replicates the value returned by the UDF or stored
          program, so its effect on table rows and data is the same on
          both the master and slave.) See *Note
          replication-features-invoked::, for more information.

        * *Note `DELETE': delete. and *Note `UPDATE': update.
          statements that use a `LIMIT' clause without an `ORDER BY'
          are nondeterministic. See *Note replication-features-limit::.

        * Statements using any of the following functions cannot be
          replicated properly using statement-based replication:

             * `LOAD_FILE()'

             * `UUID()', `UUID_SHORT()'

             * `USER()'

             * `FOUND_ROWS()'

             * `SYSDATE()' (unless both the master and the slave are
               started with the `--sysdate-is-now' option)

             * `GET_LOCK()'

             * `IS_FREE_LOCK()'

             * `IS_USED_LOCK()'

             * `MASTER_POS_WAIT()'

             * `RAND()'

             * `RELEASE_LOCK()'

             * `SLEEP()'

             * `VERSION()'

          However, all other functions are replicated correctly using
          statement-based replication, including `NOW()' and so forth.

          For more information, see *Note
          replication-features-functions::.

     Statements that cannot be replicated correctly using
     statement-based replication are logged with a warning like the one
     shown here:


          [Warning] Statement is not safe to log in statement format.

     A similar warning is also issued to the client in such cases. The
     client can display it using *Note `SHOW WARNINGS': show-warnings.

   * *Note `INSERT ... SELECT': insert. requires a greater number of
     row-level locks than with row-based replication.

   * *Note `UPDATE': update. statements that require a table scan
     (because no index is used in the `WHERE' clause) must lock a
     greater number of rows than with row-based replication.

   * For *Note `InnoDB': innodb-storage-engine.: An *Note `INSERT':
     insert. statement that uses `AUTO_INCREMENT' blocks other
     nonconflicting *Note `INSERT': insert.  statements.

   * For complex statements, the statement must be evaluated and
     executed on the slave before the rows are updated or inserted.
     With row-based replication, the slave only has to modify the
     affected rows, not execute the full statement.

   * If there is an error in evaluation on the slave, particularly when
     executing complex statements, statement-based replication may
     slowly increase the margin of error across the affected rows over
     time. See *Note replication-features-slaveerrors::.

   * Stored functions execute with the same `NOW()' value as the calling
     statement. However, this is not true of stored procedures.

   * Deterministic UDFs must be applied on the slaves.

   * Table definitions must be (nearly) identical on master and slave.
     See *Note replication-features-differing-tables::, for more
     information.

*Advantages of Row-Based Replication*

   * All changes can be replicated. This is the safest form of
     replication.

     For MySQL versions earlier than 5.1.14, DDL (Data Definition
     Language) statements such as *Note `CREATE TABLE': create-table.
     are replicated using statement-based replication, while DML
     statements, as well as *Note `GRANT': grant. and *Note `REVOKE':
     revoke. statements, are replicated using row-based replication.

     In MySQL 5.1.14 and later, the `mysql' database is not replicated.
     The `mysql' database is instead seen as a node-specific database.
     Row-based replication is not supported on tables in this database.
     Instead, statements that would normally update this
     information--such as *Note `GRANT': grant, *Note `REVOKE': revoke.
     and the manipulation of triggers, stored routines (including
     stored procedures), and views--are all replicated to slaves using
     statement-based replication.

     For statements such as *Note `CREATE TABLE ... SELECT':
     create-table, a `CREATE' statement is generated from the table
     definition and replicated using statement-based format, while the
     row insertions are replicated using row-based format.

   * The technology is the same as in most other database management
     systems; knowledge about other systems transfers to MySQL.

   * Fewer row locks are required on the master, which thus achieves
     higher concurrency, for the following types of statements:

        * *Note `INSERT ... SELECT': insert-select.

        * *Note `INSERT': insert. statements with `AUTO_INCREMENT'

        * *Note `UPDATE': update. or *Note `DELETE': delete. statements
          with `WHERE' clauses that do not use keys or do not change
          most of the examined rows.

   * Fewer row locks are required on the slave for any *Note `INSERT':
     insert, *Note `UPDATE': update, or *Note `DELETE': delete.
     statement.

*Disadvantages of Row-Based Replication*

   * RBR tends to generate more data that must be logged. To replicate
     a DML statement (such as an *Note `UPDATE': update. or *Note
     `DELETE': delete. statement), statement-based replication writes
     only the statement to the binary log. By contrast, row-based
     replication writes each changed row to the binary log. If the
     statement changes many rows, row-based replication may write
     significantly more data to the binary log; this is true even for
     statements that are rolled back. This also means that taking and
     restoring from backup can require more time. In addition, the
     binary log is locked for a longer time to write the data, which
     may cause concurrency problems.

   * Deterministic UDFs that generate large *Note `BLOB': blob. values
     take longer to replicate with row-based replication than with
     statement-based replication. This is because the *Note `BLOB':
     blob. column value is logged, rather than the statement generating
     the data.

   * You cannot examine the logs to see what statements were executed,
     nor can you see on the slave what statements were received from
     the master and executed.

     However, beginning with MySQL 5.1.29, you can see what data was
     changed using *Note `mysqlbinlog': mysqlbinlog. with the options
     `--base64-output=DECODE-ROWS' and `--verbose'.

   * For tables using the *Note `MyISAM': myisam-storage-engine.
     storage engine, a stronger lock is required on the slave for *Note
     `INSERT': insert. statements when applying them as row-based
     events to the binary log than when applying them as statements.
     This means that concurrent inserts on *Note `MyISAM':
     myisam-storage-engine. tables are not supported when using
     row-based replication.

   * Formerly, when performing a bulk operation that includes
     nontransactional storage engines, changes were applied as the
     statement executed. With row-based logging, this meant that the
     binary log was written while the statement was running. On the
     master, this does not cause problems with concurrency, because
     tables are locked until the bulk operation terminates. On the
     slave server, tables were not locked while the slave applied
     changes, because the slave did not know that those changes were
     part of a bulk operation.

     In such cases, if you retrieved data from a table on the master
     (for example, using `SELECT * FROM table_name'), the server waited
     for the bulk operation to complete before executing the *Note
     `SELECT': select. statement, because the table was read-locked. On
     the slave, the server did not wait (because there was no lock).
     This meant that, until the bulk operation on the slave completed,
     different results were obtained for the same *Note `SELECT':
     select.  query on the master and on the slave.

     This issue was resolved in MySQL 5.1.24. (Bug #29020)


File: manual.info,  Node: replication-rbr-usage,  Next: replication-rbr-safe-unsafe,  Prev: replication-sbr-rbr,  Up: replication-formats

16.1.2.2 Usage of Row-Based Logging and Replication
...................................................

Major changes in the replication environment and in the behavior of
applications can result from using row-based logging (RBL) or row-based
replication (RBR) rather than statement-based logging or replication.
This section describes a number of issues known to exist when using
row-based logging or replication, and discusses some best practices for
taking advantage of row-based logging and replication.

For additional information, see *Note replication-formats::, and *Note
replication-sbr-rbr::.

For information about issues specific to MySQL Cluster Replication
(which depends on row-based replication), see *Note
mysql-cluster-replication-issues::.

   * RBL, RBR, and temporary tables

     As noted in *Note replication-features-temptables::, temporary
     tables are not replicated when using row-based format. When mixed
     format is in effect, `safe' statements involving temporary tables
     are logged using statement-based format. For more information, see
     *Note replication-sbr-rbr::.

     Temporary tables are not replicated when using row-based format
     because there is no need. In addition, because temporary tables
     can be read only from the thread which created them, there is
     seldom if ever any benefit obtained from replicating them, even
     when using statement-based format.

   * RBL and the BLACKHOLE storage engine

     Prior to MySQL 5.1.29, *Note `DELETE': delete. and *Note `UPDATE':
     update. statements for `BLACKHOLE' tables did not work with RBL.
     (Bug #38360)

   * RBL and synchronization of nontransactional tables

     When many rows are affected, the set of changes is split into
     several events; when the statement commits, all of these events
     are written to the binary log if the statement is an initial
     nontransactional statement (occurring in the transaction before
     any transactional statements). When executing on the slave, a
     table lock is taken on all tables involved, and then the rows are
     applied in batch mode. (This may or may not be effective,
     depending on the engine used for the slave's copy of the table.)

   * Latency and binary log size

     Because RBL writes changes for each row to the binary log, its
     size can increase quite rapidly. In a replication environment,
     this can significantly increase the time required to make changes
     on the slave that match those on the master. You should be aware
     of the potential for this delay in your applications.

   * Reading the binary log

     *Note `mysqlbinlog': mysqlbinlog. displays row-based events in the
     binary log using the `BINLOG' statement (see *Note binlog::). This
     statement displays an event in printable form, but as a base
     64-encoded string the meaning of which is not evident. As of MySQL
     5.1.28, when invoked with the `--base64-output=DECODE-ROWS' and
     `--verbose' options, *Note `mysqlbinlog': mysqlbinlog. formats the
     contents of the binary log in a manner that is easily human
     readable. This is helpful when binary log events were written in
     row-based format if you want to read or recover from a replication
     or database failure using the contents of the binary log. For more
     information, see *Note mysqlbinlog-row-events::.

   * Binary log execution errors and slave_exec_mode

     If `slave_exec_mode' is `IDEMPOTENT', a failure to apply changes
     from RBL because the original row cannot be found does not trigger
     an error or cause replication to fail. This means that it is
     possible that updates are not applied on the slave, so that the
     master and slave are no longer synchronized. Latency issues and
     use of nontransactional tables with RBR when `slave_exec_mode' is
     `IDEMPOTENT' can cause the master and slave to diverge even
     further. For more information about `slave_exec_mode', see *Note
     server-system-variables::.

     *Note*:

     `slave_exec_mode=IDEMPOTENT' is generally useful only for circular
     replication or multi-master replication with MySQL Cluster, for
     which `IDEMPOTENT' is the default value (see *Note
     mysql-cluster-replication::).

     For other scenarios, setting `slave_exec_mode' to `STRICT' is
     normally sufficient; this is the default value for storage engines
     other than *Note `NDB': mysql-cluster.

   * Lack of binary log checksums

     RBL uses no checksums. This means that network, disk, and other
     errors may not be identified when processing the binary log. To
     ensure that data is transmitted without network corruption, you
     may want to consider using SSL, which adds another layer of
     checksumming, for replication connections. The *Note `CHANGE
     MASTER TO': change-master-to. statement has options to enable
     replication over SSL. See also *Note change-master-to::, for
     general information about setting up MySQL with SSL.

   * Filtering based on server ID not supported

     A common practice is to filter out changes on some slaves by using
     a `WHERE' clause that includes the relation `@@server_id <>
     ID_VALUE' clause with *Note `UPDATE': update. and *Note `DELETE':
     delete. statements, a simple example of such a clause being `WHERE
     @@server_id <> 1'. However, this does not work correctly with
     row-based logging. If you must use the `server_id' system variable
     for statement filtering, you must also use
     `--binlog_format=STATEMENT'.

   * Database-level replication options

     The effects of the `--replicate-do-db', `--replicate-ignore-db',
     and `--replicate-rewrite-db' options differ considerably depending
     on whether row-based or statement-based logging is used. Because
     of this, it is recommended to avoid database-level options and
     instead use table-level options such as `--replicate-do-table' and
     `--replicate-ignore-table'.  For more information about these
     options and the impact that your choice of replication format has
     on how they operate, see *Note replication-options::.

   * RBL, nontransactional tables, and stopped slaves

     When using row-based logging, if the slave server is stopped while
     a slave thread is updating a nontransactional table, the slave
     database may reaches an inconsistent state. For this reason, it is
     recommended that you use a transactional storage engine such as
     *Note `InnoDB': innodb-storage-engine. for all tables replicated
     using the row-based format.

     Use of *Note `STOP SLAVE': stop-slave. (or *Note `STOP SLAVE
     SQL_THREAD': stop-slave. in MySQL 5.1.55 and later) prior to
     shutting down the slave MySQL server helps prevent such issues
     from occurring, and is always recommended regardless of the
     logging format or storage engines employed.


File: manual.info,  Node: replication-rbr-safe-unsafe,  Prev: replication-rbr-usage,  Up: replication-formats

16.1.2.3 Determination of Safe and Unsafe Statements in Binary Logging
......................................................................

When speaking of the `safeness' of a statement in MySQL Replication, we
are referring to whether a statement and its effects can be replicated
correctly using statement-based format. If this is true of the
statement, we refer to the statement as _safe_; otherwise, we refer to
it as _unsafe_.

In general, a statement is safe if it deterministic, and unsafe if it
is not. However, certain nondeterministic functions are _not_
considered unsafe (see *Note replication-rbr-safe-unsafe-not::, later
in this section). In addition, statements using results from
floating-point math functions--which are hardware-dependent--are always
considered unsafe (see *Note replication-features-floatvalues::).

Handling of safe and unsafe statements

A statement is treated differently depending on whether the statement
is considered safe, and with respect to the binary logging format (that
is, the current value of `binlog_format').

   * No distinction is made in the treatment of safe and unsafe
     statements when the binary logging mode is `ROW'.

   * If the binary logging format is `MIXED', statements flagged as
     unsafe are logged using the row-based format; statements regarded
     as safe are logged using the statement-based format.

   * If the binary logging format is `STATEMENT', statements flagged as
     being unsafe generate a warning to this effect. (Safe statements
     are logged normally.)

For more information, see *Note replication-formats::.

Statements considered unsafe

Statements having the following characteristics are considered unsafe:

   * Statements containing system functions that may return a different
     value on slave.

     These functions include `FOUND_ROWS()', `GET_LOCK()',
     `IS_FREE_LOCK()', `IS_USED_LOCK()', `LOAD_FILE()',
     `MASTER_POS_WAIT()', `RELEASE_LOCK()', `ROW_COUNT()',
     `SESSION_USER()', `SLEEP()', `SYSDATE()', `SYSTEM_USER()',
     `USER()', `UUID()', and `UUID_SHORT()'.

     In MySQL 5.1.43 and later, `RAND()' is also treated as unsafe.
     (Bug #11757207, Bug #49222)

     Nondeterministic functions not considered unsafe

     Although these functions are not deterministic, they are treated
     as safe for purposes of logging and replication: `CONNECTION_ID()',
     `CURDATE()', `CURRENT_DATE()', `CURRENT_TIME()',
     `CURRENT_TIMESTAMP()', `CURTIME()', `LOCALTIME()',
     `LOCALTIMESTAMP()', `NOW()', `UNIX_TIMESTAMP()', `UTC_DATE()',
     `UTC_TIME()', `UTC_TIMESTAMP()', and `LAST_INSERT_ID()'

     For more information, see *Note replication-features-functions::.

   * References to system variables

     Most system variables are not replicated correctly using the
     statement-based format. For exceptions, see *Note
     binary-log-mixed::.

     See *Note replication-features-variables::.

   * UDFs

     Since we have no control over what a UDF does, we must assume that
     it is executing unsafe statements.

   * Updates a table having an AUTO_INCREMENT column

     This is unsafe because the order in which the rows are updated may
     differ on the master and the slave.

     In addition, an *Note `INSERT': insert. into a table that has a
     composite primary key containing an `AUTO_INCREMENT' column that
     is not the first column of this composite key is unsafe.

     For more information, see *Note
     replication-features-auto-increment::.

   * INSERT DELAYED statement

     This statement is considered unsafe because the insertion of the
     rows may interleave with concurrently executing statements.

   * INSERT ... ON DUPLICATE KEY UPDATE statements on tables with
     multiple primary or unique keys

     When executed against a table that contains more than one primary
     or unique key, this statement is considered unsafe, being
     sensitive to the order in which the storage engine checks the
     keys, which is not deterministic, and on which the choice of rows
     updated by the MySQL Server depends.

     Thus, such statements are considered unsafe.

   * Updates using LIMIT

     The order in which rows are retrieved is not specified.

     See *Note replication-features-limit::.

   * Accesses or references log tables

     The contents of the system log table may differ between master and
     slave.

   * Nontransactional operations after transactional operations

     Within a transaction, allowing any nontransactional reads or
     writes to execute after any transactional reads or writes is
     considered unsafe.

     For more information, see *Note
     replication-features-transactions::.

   * Accesses or references self-logging tables

     All reads and writes to self-logging tables are considered unsafe.
     Within a transaction, any statement following a read or write to
     self-logging tables is also considered unsafe.

   * LOAD DATA INFILE statements

     Beginning with MySQL 5.1.50, *Note `LOAD DATA INFILE': load-data.
     is considered unsafe, it causes a warning in statement-based mode,
     and a switch to row-based format when using mixed-format logging.
     See *Note replication-features-load-data::.

For additional information, see *Note replication-features::.


File: manual.info,  Node: replication-options,  Next: replication-administration,  Prev: replication-formats,  Up: replication-configuration

16.1.3 Replication and Binary Logging Options and Variables
-----------------------------------------------------------

* Menu:

* replication-options-table::    Replication and Binary Logging Option and Variable Reference
* replication-options-master::   Replication Master Options and Variables
* replication-options-slave::    Replication Slave Options and Variables
* replication-options-binary-log::  Binary Log Options and Variables

The next few sections contain information about *Note `mysqld': mysqld.
options and server variables that are used in replication and for
controlling the binary log. Options and variables for use on
replication masters and replication slaves are covered separately, as
are options and variables relating to binary logging. A set of
quick-reference tables providing basic information about these options
and variables is also included (in the next section following this one).

Of particular importance is the `--server-id' option.

Options for server-id

*Command-Line Format*  `--server-id=#'        
*System Variable Name* `server_id'        
*Variable Scope*       Global          
*Dynamic Variable*     Yes             
                       *Permitted        
                       Values*         
*Type*                 `numeric'        
*Default*              `0'             
*Min Value*            `0'             
*Max Value*            `4294967295'        

This option is common to both master and slave replication servers, and
is used in replication to enable master and slave servers to identify
themselves uniquely. For additional information, see *Note
replication-options-master::, and *Note replication-options-slave::.

On the master and each slave, you _must_ use the `--server-id' option
to establish a unique replication ID in the range from 1 to 2^32 - 1.
`Unique', means that each ID must be different from every other ID in
use by any other replication master or slave. Example: `server-id=3'.

If you omit `--server-id', the default ID is 0, in which case the
master refuses connections from all slaves, and slaves refuse to
connect to the master. In MySQL 5.1, whether the server ID is set to 0
explicitly or the default is allowed to be used, the server sets the
`server_id' system variable to 1; this is a known issue that is fixed
in MySQL 5.7.

For more information, see *Note replication-howto-slavebaseconfig::.


File: manual.info,  Node: replication-options-table,  Next: replication-options-master,  Prev: replication-options,  Up: replication-options

16.1.3.1 Replication and Binary Logging Option and Variable Reference
.....................................................................

The following tables list basic information about the MySQL
command-line options and system variables applicable to replication and
the binary log.

Summary of Replication options and variables in MySQL 5.1

Option or Variable Name

Command Line System Variable Status Variable

Option File Scope Dynamic

Notes

`Com_change_master'

No No Yes

No Both No

DESCRIPTION: Count of CHANGE MASTER statements

`Com_show_master_status'

No No Yes

No Both No

DESCRIPTION: Count of SHOW MASTER STATUS statements

`Com_show_new_master'

No No Yes

No Both No

DESCRIPTION: Count of SHOW NEW MASTER statements

`Com_show_slave_hosts'

No No Yes

No Both No

DESCRIPTION: Count of SHOW SLAVE HOSTS statements

`Com_show_slave_status'

No No Yes

No Both No

DESCRIPTION: Count of SHOW SLAVE STATUS statements

`Com_slave_start'

No No Yes

No Both No

DESCRIPTION: Count of START SLAVE statements

`Com_slave_stop'

No No Yes

No Both No

DESCRIPTION: Count of STOP SLAVE statements

`Rpl_status'

No No Yes

No Global No

DESCRIPTION: The status of fail-safe replication (not implemented)

`slave_exec_mode'

Yes Yes No

Yes Global Yes

DESCRIPTION: Allows for switching between idempotent mode (key and some
other errors suppressed) and strict mode; strict mode is the default,
except for MySQL Cluster, where idempotent is always used

`Slave_open_temp_tables'

No No Yes

No Global No

DESCRIPTION: Number of temporary tables that the slave SQL thread
currently has open

`Slave_retried_transactions'

No No Yes

No Global No

DESCRIPTION: The total number of times since startup that the
replication slave SQL thread has retried transactions

`Slave_running'

No No Yes

No Global No

DESCRIPTION: The state of this server as a replication slave (slave I/O
thread status)

`abort-slave-event-count'

Yes No No

Yes

No

DESCRIPTION: Option used by mysql-test for debugging and testing of
replication

`disconnect-slave-event-count'

Yes No No

Yes

No

DESCRIPTION: Option used by mysql-test for debugging and testing of
replication

`init_slave'

Yes Yes No

Yes Global Yes

DESCRIPTION: Statements that are executed when a slave connects to a
master

`log-slave-updates'

Yes Yes No

Yes Global No

DESCRIPTION: This option tells the slave to log the updates performed
by its SQL thread to its own binary log

`log_slave_updates'

Yes Yes No

Yes Global No

DESCRIPTION: Tells whether the slave should log the updates performed
by its SQL thread to its own binary log. Read-only; set using the
-log-slave-updates server option.

`master-connect-retry'

Yes No No

Yes

No

DESCRIPTION: Number of seconds the slave thread will sleep before
retrying to connect to the master in case the master goes down or the
connection is lost

`master-host'

Yes No No

Yes

No

DESCRIPTION: Master host name or IP address for replication

`master-info-file'

Yes No No

Yes

No

DESCRIPTION: The location and name of the file that remembers the
master and where the I/O replication thread is in the master's binary
logs

`master-password'

Yes No No

Yes

No

DESCRIPTION: The password the slave thread will authenticate with when
connecting to master

`master-port'

Yes No No

Yes

No

DESCRIPTION: The port the master is listening on

`master-retry-count'

Yes No No

Yes

No

DESCRIPTION: Number of tries the slave will make to connect to the
master before giving up

`master-ssl'

Yes No No

Yes

No

DESCRIPTION: Enable the slave to connect to the master using SSL

`master-ssl-ca'

Yes No No

Yes

No

DESCRIPTION: Master SSL CA file; applies only if master-ssl is enabled

`master-ssl-capath'

Yes No No

Yes

No

DESCRIPTION: Master SSL CA path; applies only if master-ssl is enabled

`master-ssl-cert'

Yes No No

Yes

No

DESCRIPTION: Master SSL certificate file name; applies only if
master-ssl is enabled

`master-ssl-cipher'

Yes No No

Yes

No

DESCRIPTION: Master SSL cipher; applies only if master-ssl is enabled

`master-ssl-key'

Yes No No

Yes

No

DESCRIPTION: Master SSL key file name; applies only if master-ssl is
enabled

`master-user'

Yes No No

Yes

No

DESCRIPTION: The user name the slave thread will use for authentication
when connecting to master. The user must have FILE privilege. If the
master user is not set, user test is assumed. The value in master.info
will take precedence if it can be read

`relay-log'

Yes Yes No

Yes Global No

DESCRIPTION: The location and base name to use for relay logs

`relay-log-index'

Yes Yes No

Yes Global No

DESCRIPTION: The location and name to use for the file that keeps a
list of the last relay logs

`relay-log-info-file'

Yes No No

Yes

No

DESCRIPTION: The location and name of the file that remembers where the
SQL replication thread is in the relay logs

`relay_log_info_file'

Yes Yes No

Yes Global No

DESCRIPTION: The name of the file in which the slave records
information about the relay logs.

`relay_log_index'

Yes Yes No

Yes Global No

DESCRIPTION: The name of the relay log index file.

`relay_log_purge'

Yes Yes No

Yes Global Yes

DESCRIPTION: Determines whether relay logs are purged

`relay_log_space_limit'

Yes Yes No

Yes Global No

DESCRIPTION: Maximum space to use for all relay logs

`replicate-do-db'

Yes No No

Yes

No

DESCRIPTION: Tells the slave SQL thread to restrict replication to the
specified database

`replicate-do-table'

Yes No No

Yes

No

DESCRIPTION: Tells the slave SQL thread to restrict replication to the
specified table

`replicate-ignore-db'

Yes No No

Yes

No

DESCRIPTION: Tells the slave SQL thread not to replicate to the
specified database

`replicate-ignore-table'

Yes No No

Yes

No

DESCRIPTION: Tells the slave SQL thread not to replicate to the
specified table

`replicate-rewrite-db'

Yes No No

Yes

No

DESCRIPTION: Updates to a database with a different name than the
original

`replicate-same-server-id'

Yes No No

Yes

No

DESCRIPTION: In replication, if set to 1, do not skip events having our
server id

`replicate-wild-do-table'

Yes No No

Yes

No

DESCRIPTION: Tells the slave thread to restrict replication to the
tables that match the specified wildcard pattern

`replicate-wild-ignore-table'

Yes No No

Yes

No

DESCRIPTION: Tells the slave thread not to replicate to the tables that
match the given wildcard pattern

`report-host'

Yes Yes No

Yes Global No

DESCRIPTION: Host name or IP of the slave to be reported to the master
during slave registration

`report-password'

Yes Yes No

Yes Global No

DESCRIPTION: An arbitrary password that the slave server should report
to the master. Not the same as the password for the MySQL replication
user account

`report-port'

Yes Yes No

Yes Global No

DESCRIPTION: Port for connecting to slave reported to the master during
slave registration

`report-user'

Yes Yes No

Yes Global No

DESCRIPTION: An arbitrary user name that a slave server should report
to the master. Not the same as the name used with the MySQL replication
user account.

`rpl_recovery_rank'

No Yes No

No Global Yes

DESCRIPTION: Not used; removed in later versions

`show-slave-auth-info'

Yes No No

Yes

No

DESCRIPTION: Show user name and password in SHOW SLAVE HOSTS on this
master

`skip-slave-start'

Yes No No

Yes

No

DESCRIPTION: If set, slave is not autostarted

`slave-load-tmpdir'

Yes Yes No

Yes Global No

DESCRIPTION: The location where the slave should put its temporary
files when replicating a LOAD DATA INFILE statement

`slave-skip-errors'

Yes Yes No

Yes Global No

DESCRIPTION: Tells the slave thread to continue replication when a
query returns an error from the provided list

`slave_compressed_protocol'

Yes Yes No

Yes Global Yes

DESCRIPTION: Use compression on master/slave protocol

`slave-max-allowed-packet'

Yes No No

Yes

No

DESCRIPTION: Maximum size, in bytes, of a packet that can be sent from
a replication master to a slave; overrides max_allowed_packet.

`slave_max_allowed_packet'

No Yes No

No Global Yes

DESCRIPTION: Maximum size, in bytes, of a packet that can be sent from
a replication master to a slave; overrides max_allowed_packet.

`slave_net_timeout'

Yes Yes No

Yes Global Yes

DESCRIPTION: Number of seconds to wait for more data from a
master/slave connection before aborting the read

`slave_transaction_retries'

Yes Yes No

Yes Global Yes

DESCRIPTION: Number of times the slave SQL thread will retry a
transaction in case it failed with a deadlock or elapsed lock wait
timeout, before giving up and stopping

`slave_type_conversions'

Yes Yes No

Yes Global No

DESCRIPTION: Controls type conversion mode on replication slave. Value
is a list of zero or more elements from the list: ALL_LOSSY,
ALL_NON_LOSSY. Set to an empty string to disallow type conversions
between master and slave.

`sql_slave_skip_counter'

No Yes No

No Global Yes

DESCRIPTION: Number of events from the master that a slave server
should skip. Not compatible with GTID replication.

`sync_binlog'

Yes Yes No

Yes Global Yes

DESCRIPTION: Synchronously flush binary log to disk after every #th
event

`have_row_based_replication'

No Yes No

No Global No

DESCRIPTION: Shows whether row-based replication is supported 


*Note replication-options-master::, provides more detailed information
about options and variables relating to replication master servers. For
more information about options and variables relating to replication
slaves, see *Note replication-options-slave::.

Summary of Binary Logging options and variables in MySQL 5.1

Option or Variable Name

Command Line System Variable Status Variable

Option File Scope Dynamic

Notes

`Binlog_cache_disk_use'

No No Yes

No Global No

DESCRIPTION: Number of transactions that used a temporary file instead
of the binary log cache

`Binlog_cache_use'

No No Yes

No Global No

DESCRIPTION: Number of transactions that used the temporary binary log
cache

`Com_show_binlog_events'

No No Yes

No Both No

DESCRIPTION: Count of SHOW BINLOG EVENTS statements

`Com_show_binlogs'

No No Yes

No Both No

DESCRIPTION: Count of SHOW BINLOGS statements

`binlog-do-db'

Yes No No

Yes

No

DESCRIPTION: Limits binary logging to specific databases

`binlog-ignore-db'

Yes No No

Yes

No

DESCRIPTION: Tells the master that updates to the given database should
not be logged to the binary log

`binlog-row-event-max-size'

Yes No No

Yes

No

DESCRIPTION: Binary log max event size

`binlog_cache_size'

Yes Yes No

Yes Global Yes

DESCRIPTION: Size of the cache to hold the SQL statements for the
binary log during a transaction

`binlog_format'

Yes Yes No

Yes Both Yes

DESCRIPTION: Specifies the format of the binary log

`binlog_direct_non_transactional_updates'

Yes Yes No

Yes Both Yes

DESCRIPTION: Causes updates using statement format to nontransactional
engines to be written directly to binary log.  See documentation before
using.

`log-bin-use-v1-row-events'

Yes Yes No

Yes Global No

DESCRIPTION: Use version 1 binary log row events

`log_bin_use_v1_row_events'

Yes Yes No

Yes Global No

DESCRIPTION: Shows whether server is using version 1 binary log row
events

`max-binlog-dump-events'

Yes No No

Yes

No

DESCRIPTION: Option used by mysql-test for debugging and testing of
replication

`max_binlog_cache_size'

Yes Yes No

Yes Global Yes

DESCRIPTION: Can be used to restrict the total size used to cache a
multi-statement transaction

`max_binlog_size'

Yes Yes No

Yes Global Yes

DESCRIPTION: Binary log will be rotated automatically when size exceeds
this value

`sporadic-binlog-dump-fail'

Yes No No

Yes

No

DESCRIPTION: Option used by mysql-test for debugging and testing of
replication 


*Note replication-options-binary-log::, provides more detailed
information about options and variables relating to binary logging. For
additional general information about the binary log, see *Note
binary-log::.

For information about the `sql_log_bin' and `sql_log_off' variables, see
*Note server-system-variables::.

For a table showing _all_ command-line options, system and status
variables used with *Note `mysqld': mysqld, see *Note
mysqld-option-tables::.


File: manual.info,  Node: replication-options-master,  Next: replication-options-slave,  Prev: replication-options-table,  Up: replication-options

16.1.3.2 Replication Master Options and Variables
.................................................

This section describes the server options and system variables that you
can use on replication master servers. You can specify the options
either on the *Note command line: command-line-options. or in an *Note
option file: option-files. You can specify system variable values using
*Note `SET': set-statement.

On the master and each slave, you must use the `server-id' option to
establish a unique replication ID. For each server, you should pick a
unique positive integer in the range from 1 to 2^32 - 1, and each ID
must be different from every other ID in use by any other replication
master or slave. Example: `server-id=3'.

For options used on the master for controlling binary logging, see
*Note replication-options-binary-log::.

*System Variables Used on Replication Masters*

The following system variables are used in controlling replication
masters:

   * `auto_increment_increment'

     Options for auto_increment_increment

     *System Variable     `auto_increment_increment'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `1'             
     *Max Value*          `65535'         

     `auto_increment_increment' and `auto_increment_offset' are
     intended for use with master-to-master replication, and can be
     used to control the operation of `AUTO_INCREMENT' columns. Both
     variables have global and session values, and each can assume an
     integer value between 1 and 65,535 inclusive. Setting the value of
     either of these two variables to 0 causes its value to be set to 1
     instead. Attempting to set the value of either of these two
     variables to an integer greater than 65,535 or less than 0 causes
     its value to be set to 65,535 instead. Attempting to set the value
     of `auto_increment_increment' or `auto_increment_offset' to a
     noninteger value gives rise to an error, and the actual value of
     the variable remains unchanged.

     *Note*:

     `auto_increment_increment' is supported for use with *Note `NDB':
     mysql-cluster.  tables beginning with MySQL 5.1.20, MySQL Cluster
     NDB 6.2.5, and MySQL Cluster NDB 6.3.2. Previously, setting it
     when using MySQL Cluster tables or MySQL Cluster Replication
     produced unpredictable results.

     These two variables affect `AUTO_INCREMENT' column behavior as
     follows:

        * `auto_increment_increment' controls the interval between
          successive column values.  For example:


               mysql> SHOW VARIABLES LIKE 'auto_inc%';
               +--------------------------+-------+
               | Variable_name            | Value |
               +--------------------------+-------+
               | auto_increment_increment | 1     |
               | auto_increment_offset    | 1     |
               +--------------------------+-------+
               2 rows in set (0.00 sec)

               mysql> CREATE TABLE autoinc1
                   -> (col INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
                 Query OK, 0 rows affected (0.04 sec)

               mysql> SET @@auto_increment_increment=10;
               Query OK, 0 rows affected (0.00 sec)

               mysql> SHOW VARIABLES LIKE 'auto_inc%';
               +--------------------------+-------+
               | Variable_name            | Value |
               +--------------------------+-------+
               | auto_increment_increment | 10    |
               | auto_increment_offset    | 1     |
               +--------------------------+-------+
               2 rows in set (0.01 sec)

               mysql> INSERT INTO autoinc1 VALUES (NULL), (NULL), (NULL), (NULL);
               Query OK, 4 rows affected (0.00 sec)
               Records: 4  Duplicates: 0  Warnings: 0

               mysql> SELECT col FROM autoinc1;
               +-----+
               | col |
               +-----+
               |   1 |
               |  11 |
               |  21 |
               |  31 |
               +-----+
               4 rows in set (0.00 sec)

        * `auto_increment_offset' determines the starting point for the
          `AUTO_INCREMENT' column value. Consider the following,
          assuming that these statements are executed during the same
          session as the example given in the description for
          `auto_increment_increment':


               mysql> SET @@auto_increment_offset=5;
               Query OK, 0 rows affected (0.00 sec)

               mysql> SHOW VARIABLES LIKE 'auto_inc%';
               +--------------------------+-------+
               | Variable_name            | Value |
               +--------------------------+-------+
               | auto_increment_increment | 10    |
               | auto_increment_offset    | 5     |
               +--------------------------+-------+
               2 rows in set (0.00 sec)

               mysql> CREATE TABLE autoinc2
                   -> (col INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
               Query OK, 0 rows affected (0.06 sec)

               mysql> INSERT INTO autoinc2 VALUES (NULL), (NULL), (NULL), (NULL);
               Query OK, 4 rows affected (0.00 sec)
               Records: 4  Duplicates: 0  Warnings: 0

               mysql> SELECT col FROM autoinc2;
               +-----+
               | col |
               +-----+
               |   5 |
               |  15 |
               |  25 |
               |  35 |
               +-----+
               4 rows in set (0.02 sec)

          If the value of `auto_increment_offset' is greater than that
          of `auto_increment_increment', the value of
          `auto_increment_offset' is ignored.

     Should one or both of these variables be changed and then new rows
     inserted into a table containing an `AUTO_INCREMENT' column, the
     results may seem counterintuitive because the series of
     `AUTO_INCREMENT' values is calculated without regard to any values
     already present in the column, and the next value inserted is the
     least value in the series that is greater than the maximum
     existing value in the `AUTO_INCREMENT' column. In other words, the
     series is calculated like so:

     `auto_increment_offset' + N x `auto_increment_increment'

     where N is a positive integer value in the series [1, 2, 3, ...].
     For example:


          mysql> SHOW VARIABLES LIKE 'auto_inc%';
          +--------------------------+-------+
          | Variable_name            | Value |
          +--------------------------+-------+
          | auto_increment_increment | 10    |
          | auto_increment_offset    | 5     |
          +--------------------------+-------+
          2 rows in set (0.00 sec)

          mysql> SELECT col FROM autoinc1;
          +-----+
          | col |
          +-----+
          |   1 |
          |  11 |
          |  21 |
          |  31 |
          +-----+
          4 rows in set (0.00 sec)

          mysql> INSERT INTO autoinc1 VALUES (NULL), (NULL), (NULL), (NULL);
          Query OK, 4 rows affected (0.00 sec)
          Records: 4  Duplicates: 0  Warnings: 0

          mysql> SELECT col FROM autoinc1;
          +-----+
          | col |
          +-----+
          |   1 |
          |  11 |
          |  21 |
          |  31 |
          |  35 |
          |  45 |
          |  55 |
          |  65 |
          +-----+
          8 rows in set (0.00 sec)

     The values shown for `auto_increment_increment' and
     `auto_increment_offset' generate the series 5 + N x 10, that is,
     [5, 15, 25, 35, 45, ...]. The greatest value present in the `col'
     column prior to the *Note `INSERT': insert. is 31, and the next
     available value in the `AUTO_INCREMENT' series is 35, so the
     inserted values for `col' begin at that point and the results are
     as shown for the *Note `SELECT': select.  query.

     It is not possible to confine the effects of these two variables
     to a single table, and thus they do not take the place of the
     sequences offered by some other database management systems; these
     variables control the behavior of all `AUTO_INCREMENT' columns in
     _all_ tables on the MySQL server. If the global value of either
     variable is set, its effects persist until the global value is
     changed or overridden by setting the session value, or until *Note
     `mysqld': mysqld. is restarted. If the local value is set, the new
     value affects `AUTO_INCREMENT' columns for all tables into which
     new rows are inserted by the current user for the duration of the
     session, unless the values are changed during that session.

     The default value of `auto_increment_increment' is 1. See *Note
     replication-features-auto-increment::.

   * `auto_increment_offset'

     Options for auto_increment_offset

     *System Variable     `auto_increment_offset'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `1'             
     *Max Value*          `65535'         

     This variable has a default value of 1. For particulars, see the
     description for `auto_increment_increment'.

     *Note*:

     `auto_increment_offset' is supported for use with *Note `NDB':
     mysql-cluster.  tables beginning with MySQL 5.1.20, MySQL Cluster
     NDB 6.2.5, and MySQL Cluster NDB 6.3.2. Previously, setting it
     when using MySQL Cluster tables or MySQL Cluster Replication
     produced unpredictable results.


File: manual.info,  Node: replication-options-slave,  Next: replication-options-binary-log,  Prev: replication-options-master,  Up: replication-options

16.1.3.3 Replication Slave Options and Variables
................................................

*Note replication-optvars-slaves::

*Note replication-sysvars-slaves::

This section describes the server options and system variables that
apply to slave replication servers. You can specify the options either
on the *Note command line: command-line-options. or in an *Note option
file: option-files. Many of the options can be set while the server is
running by using the *Note `CHANGE MASTER TO': change-master-to.
statement. You can specify system variable values using *Note `SET':
set-statement.

Server ID

On the master and each slave, you must use the `server-id' option to
establish a unique replication ID in the range from 1 to 2^32 - 1.
`Unique' means that each ID must be different from every other ID in use
by any other replication master or slave. Example `my.cnf' file:


     [mysqld]
     server-id=3

*Important*:

Certain `--master-XXX' options are handled in a special way to ensure
that the active replication configuration is not inadvertently altered
or affected:

   * `--master-host'

   * `--master-user'

   * `--master-password'

   * `--master-port'

   * `--master-connect-retry'

   * `--master-ssl'

   * `--master-ssl-ca'

   * `--master-ssl-capath'

   * `--master-ssl-cert'

   * `--master-ssl-cipher'

   * `--master-ssl-key'

Before MySQL 5.1.17, these options are silently ignored if given unless
there is no `master.info' file. If that file exists, the MySQL server
has already previously been configured for replication, so the
information in the file is used instead. Because the server gives an
existing `master.info' file precedence over the startup options just
described, you might elect not to use startup options for these values
at all, and instead to specify the replication parameters associated
with them by using the *Note `CHANGE MASTER TO': change-master-to.
statement. See *Note change-master-to::.

Beginning with MySQL 5.1.17, these options are deprecated and have no
effect when *Note `mysqld': mysqld. is started. If they are used, an
appropriate warning is written to the error log. Instead, you _must_ use
*Note `CHANGE MASTER TO': change-master-to. to set the values
corresponding to the deprecated options. These options are removed in
MySQL 5.5.

The `master.info' file format in MySQL 5.1 includes as its first line
the number of lines in the file. (See *Note slave-logs::.) If you
upgrade an older server (before MySQL 4.1.1) to a newer version, the new
server upgrades the `master.info' file to the new format automatically
when it starts. However, if you downgrade a newer server to an older
version, you should remove the first line manually before starting the
older server for the first time.

If no `master.info' file exists when the slave server starts, it uses
the values for those options that are specified in option files or on
the command line. This occurs when you start the server as a
replication slave for the very first time, when you use *Note `CHANGE
MASTER TO': change-master-to, or when you have run *Note `RESET SLAVE':
reset-slave. and then have shut down and restarted the slave.

Because the server uses `master.info' file contents and ignores any
startup options that correspond to the values listed in the file, if
you start the slave server with different values of the startup options
that correspond to values in the file, the different values have no
effect. To use different values, the preferred method is to use the
*Note `CHANGE MASTER TO': change-master-to. statement to reset the
values while the slave is running. Alternatively, you can stop the
server, remove the `master.info' file, and restart the server with
different option values.

Suppose that you specify this option in your `my.cnf' file to configure
a pre-5.1.17 slave server:


     [mysqld]
     master-host=SOME_HOST

The first time you start the server as a replication slave, it reads
and uses that option from the `my.cnf' file. The server then records
the value in the `master.info' file. The next time you start the
server, it reads the master host value from the `master.info' file only
and ignores the value in the option file. If you modify the `my.cnf'
file to specify a different master host value of SOME_OTHER_HOST, the
change has no effect. Instead, use *Note `CHANGE MASTER TO':
change-master-to. to change the value.

This example shows a more extensive use of startup options to configure
a pre-5.1.17 slave server:


     [mysqld]
     server-id=2
     master-host=db-master.mycompany.com
     master-port=3306
     master-user=pertinax
     master-password=freitag
     master-connect-retry=60
     report-host=db-slave.mycompany.com

As of 5.1.17, the `master-XXX' options are ignored and result in
warnings in the error log.

*Startup Options for Replication Slaves*

The following list describes startup options for controlling
replication slave servers. Many of these options can be set while the
server is running by using the *Note `CHANGE MASTER TO':
change-master-to. statement.  Others, such as the `--replicate-*'
options, can be set only when the slave server starts.
Replication-related system variables are discussed later in this
section.

   * `--abort-slave-event-count'

     Options for abort-slave-event-count

     *Command-Line        `--abort-slave-event-count=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             

     When this option is set to some positive integer VALUE other than
     0 (the default) it affects replication behavior as follows: After
     the slave SQL thread has started, VALUE log events are permitted
     to be executed; after that, the slave SQL thread does not receive
     any more events, just as if the network connection from the master
     were cut. The slave thread continues to run, and the output from
     *Note `SHOW SLAVE STATUS': show-slave-status. displays `Yes' in
     both the `Slave_IO_Running' and the `Slave_SQL_Running' columns,
     but no further events are read from the relay log.

     This option is used internally by the MySQL test suite for
     replication testing and debugging. It is not intended for use in a
     production setting.

   * `--disconnect-slave-event-count'

     Options for disconnect-slave-event-count

     *Command-Line        `--disconnect-slave-event-count=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             

     This option is used internally by the MySQL test suite for
     replication testing and debugging.

   * `--log-slave-updates'

     Options for log-slave-updates

     *Command-Line        `--log-slave-updates'        
     Format*                              
     *System Variable     `log_slave_updates'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Normally, a slave does not log to its own binary log any updates
     that are received from a master server. This option tells the
     slave to log the updates performed by its SQL thread to its own
     binary log. For this option to have any effect, the slave must
     also be started with the `--log-bin' option to enable binary
     logging.  `--log-slave-updates' is used when you want to chain
     replication servers. For example, you might want to set up
     replication servers using this arrangement:


          A -> B -> C

     Here, `A' serves as the master for the slave `B', and `B' serves
     as the master for the slave `C'. For this to work, `B' must be
     both a master _and_ a slave. You must start both `A' and `B' with
     `--log-bin' to enable binary logging, and `B' with the
     `--log-slave-updates' option so that updates received from `A' are
     logged by `B' to its binary log.

     When using MySQL Cluster Replication prior to MySQL Cluster NDB
     6.2.16 and MySQL Cluster NDB 6.3.13, records for `empty'
     epochs--that is, epochs in which no changes to *Note `NDBCLUSTER':
     mysql-cluster. data or tables took place--were inserted into the
     `ndb_apply_status' and `ndb_binlog_index' tables on the slave even
     when `--log-slave-updates' was disabled (Bug #37472). Beginning
     with MySQL Cluster NDB 6.3.33, MySQL Cluster NDB 7.0.14, and MySQL
     Cluster NDB 7.1.3, it is possible to re-enable the older behavior
     by using the `--ndb-log-empty-epochs' option.

     *Note*:

     The `--ndb-log-empty-epochs' option was first implemented in MySQL
     Cluster NDB 6.3.21 and MySQL Cluster NDB 6.4.1, but did not work
     correctly before the versions cited previously.

   * `--log-slow-slave-statements'

     Options for log-slow-slave-statements

     *Introduced*         5.1.21          
     *Command-Line        `--log-slow-slave-statements'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     When the slow query log is enabled, this option enables logging
     for queries that have taken more than `long_query_time' seconds to
     execute on the slave.

     This option was added in MySQL 5.1.21.

   * `--log-warnings[=LEVEL]'

     Options for log-warnings

     *Command-Line        `--log-warnings[=#]'        
     Format*                              
                          `-W             
                          [#]'            
     *System Variable     `log_warnings'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `0'             
     *Max Value*          `18446744073709547520'        

     This option causes a server to print more messages to the error
     log about what it is doing. With respect to replication, the
     server generates warnings that it succeeded in reconnecting after
     a network/connection failure, and informs you as to how each slave
     thread started. This option is enabled (1) by default; to disable
     it, use `--log-warnings=0'. Aborted connections are not logged to
     the error log unless the value is greater than 1.

     Note that the effects of this option are not limited to
     replication. It produces warnings across a spectrum of server
     activities.

   * `--master-connect-retry=SECONDS'

     Options for master-connect-retry

     *Deprecated*         5.1.17          
     *Command-Line        `--master-connect-retry=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `60'            

     The number of seconds that the slave thread sleeps before trying
     to reconnect to the master in case the master goes down or the
     connection is lost. The value in the `master.info' file takes
     precedence if it can be read. If not set, the default is 60.
     Connection retries are not invoked until the slave times out
     reading data from the master according to the value of
     `--slave-net-timeout'. The number of reconnection attempts is
     limited by the `--master-retry-count' option.

     This option is deprecated as of MySQL 5.1.17 and is removed in
     MySQL 5.5.

   * `slave-max-allowed-packet=BYTES'

     Options for slave-max-allowed-packet

     *Introduced*         5.1.64          
     *Command-Line        `--slave-max-allowed-packet=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1073741824'        
     *Min Value*          `1024'          
     *Max Value*          `1073741824'        

     In MySQL 5.1.64 and later, this option sets the maximum packet
     size in bytes for the slave SQL and I/O threads, so that large
     updates using row-based replication do not cause replication to
     fail because an update exceeded `max_allowed_packet'. (Bug
     #12400221, Bug #60926)

     The corresponding server variable `slave_max_allowed_packet'
     always has a value that is a positive integer multiple of 1024; if
     you set it to some value that is not such a multiple, the value is
     automatically rounded down to the next highest multiple of 1024.
     (For example, if you start the server with
     `--slave-max-allowed-packet=10000', the value used is 9216;
     setting 0 as the value causes 1024 to be used.) A truncation
     warning is issued in such cases.

     The maximum (and default) value is 1073741824 (1 GB); the minimum
     is 1024.

   * `--master-host=HOST_NAME'

     Options for master-host

     *Deprecated*         5.1.17          
     *Command-Line        `--master-host=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The host name or IP address of the master replication server. The
     value in `master.info' takes precedence if it can be read. If no
     master host is specified, the slave thread does not start.

     This option is deprecated as of MySQL 5.1.17 and is removed in
     MySQL 5.5.

   * `--master-info-file=FILE_NAME'

     Options for master-info-file

     *Command-Line        `--master-info-file=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `master.info'        

     The name to use for the file in which the slave records
     information about the master. The default name is `master.info' in
     the data directory. For information about the format of this file,
     see *Note slave-logs-status::.

   * `--master-password=PASSWORD'

     Options for master-password

     *Deprecated*         5.1.17          
     *Command-Line        `--master-password=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The password of the account that the slave thread uses for
     authentication when it connects to the master. The value in the
     `master.info' file takes precedence if it can be read. If not set,
     an empty password is assumed.

     This option is deprecated as of MySQL 5.1.17 and is removed in
     MySQL 5.5.

   * `--master-port=PORT_NUMBER'

     Options for master-port

     *Deprecated*         5.1.17          
     *Command-Line        `--master-port=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3306'          

     The TCP/IP port number that the master is listening on. The value
     in the `master.info' file takes precedence if it can be read. If
     not set, the compiled-in setting is assumed (normally 3306).

     This option is deprecated as of MySQL 5.1.17 and is removed in
     MySQL 5.5.

   * `--master-retry-count=COUNT'

     Options for master-retry-count

     *Command-Line        `--master-retry-count=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `86400'         
     *Min Value*          `0'             
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `86400'         
     *Min Value*          `0'             
     *Max Value*          `18446744073709551615'        

     The number of times that the slave tries to connect to the master
     before giving up. Reconnects are attempted at intervals set by the
     `--master-connect-retry' option (or the `MASTER_CONNECT_RETRY'
     option of the *Note `CHANGE MASTER TO': change-master-to.
     statement) and reconnects are triggered when data reads by the
     slave time out according to the `--slave-net-timeout' option.  The
     default value is 86400. A value of 0 means `infinite'; the slave
     attempts to connect forever.

   * `--master-ssl', `--master-ssl-ca=FILE_NAME',
     `--master-ssl-capath=DIRECTORY_NAME',
     `--master-ssl-cert=FILE_NAME', `--master-ssl-cipher=CIPHER_LIST',
     `--master-ssl-key=FILE_NAME'

     These options are used for setting up a secure replication
     connection to the master server using SSL. Their meanings are the
     same as the corresponding `--ssl', `--ssl-ca', `--ssl-capath',
     `--ssl-cert', `--ssl-cipher', `--ssl-key' options that are
     described in *Note ssl-options::. The values in the `master.info'
     file take precedence if they can be read.

     These options are deprecated as of MySQL 5.1.17 and are removed in
     MySQL 5.5.

   * `--master-user=USER_NAME'

     Options for master-user

     *Deprecated*         5.1.17          
     *Command-Line        `--master-user=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `test'          

     The user name of the account that the slave thread uses for
     authentication when it connects to the master. This account must
     have the `REPLICATION SLAVE' privilege. The value in the
     `master.info' file takes precedence if it can be read. If the
     master user name is not set, the name `test' is assumed.

     This option is deprecated as of MySQL 5.1.17 and is removed in
     MySQL 5.5.

   * `--max-relay-log-size=SIZE'

     Options for max_relay_log_size

     *Command-Line        `--max_relay_log_size=#'        
     Format*                              
     *System Variable     `max_relay_log_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `1073741824'        

     The size at which the server rotates relay log files
     automatically. If this value is nonzero, the relay log is rotated
     automatically when its size exceeds this value. If this value is
     zero (the default), the size at which relay log rotation occurs is
     determined by the value of `max_binlog_size'. For more
     information, see *Note slave-logs-relaylog::.

   * `--read-only'

     Options for read_only

     *Command-Line        `--read-only'        
     Format*                              
     *System Variable     `read_only'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `false'         

     Cause the slave to permit no updates except from slave threads or
     from users having the `SUPER' privilege. On a slave server, this
     can be useful to ensure that the slave accepts updates only from
     its master server and not from clients.  This variable does not
     apply to `TEMPORARY' tables.

   * `--relay-log=FILE_NAME'

     Options for relay-log

     *Command-Line        `--relay-log=file_name'        
     Format*                              
     *System Variable     `relay_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The basename for the relay log. The default basename is
     `HOST_NAME-relay-bin'.  The server writes the file in the data
     directory unless the basename is given with a leading absolute
     path name to specify a different directory. The server creates
     relay log files in sequence by adding a numeric suffix to the
     basename.

     Due to the manner in which MySQL parses server options, if you
     specify this option, you must supply a value; _the default
     basename is used only if the option is not actually specified_. If
     you use the `--relay-log' option without specifying a value,
     unexpected behavior is likely to result; this behavior depends on
     the other options used, the order in which they are specified, and
     whether they are specified on the command line or in an option
     file. For more information about how MySQL handles server options,
     see *Note program-options::.

     If you specify this option, the value specified is also used as
     the basename for the relay log index file. You can override this
     behavior by specifying a different relay log index file basename
     using the `--relay-log-index' option.

     You may find the `--relay-log' option useful in performing the
     following tasks:

        * Creating relay logs whose names are independent of host names.

        * If you need to put the relay logs in some area other than the
          data directory because your relay logs tend to be very large
          and you do not want to decrease `max_relay_log_size'.

        * To increase speed by using load-balancing between disks.

   * `--relay-log-index=FILE_NAME'

     Options for relay-log-index

     *Command-Line        `--relay-log-index=file_name'        
     Format*                              
     *System Variable     `relay_log_index'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The name to use for the relay log index file. The default name is
     `HOST_NAME-relay-bin.index' in the data directory, where HOST_NAME
     is the name of the slave server.

     Due to the manner in which MySQL parses server options, if you
     specify this option, you must supply a value; _the default
     basename is used only if the option is not actually specified_. If
     you use the `--relay-log-index' option without specifying a value,
     unexpected behavior is likely to result; this behavior depends on
     the other options used, the order in which they are specified, and
     whether they are specified on the command line or in an option
     file. For more information about how MySQL handles server options,
     see *Note program-options::.

     If you specify this option, the value specified is also used as
     the basename for the relay logs. You can override this behavior by
     specifying a different relay log file basename using the
     `--relay-log' option.

   * `--relay-log-info-file=FILE_NAME'

     Options for relay-log-info-file

     *Command-Line        `--relay-log-info-file=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `relay-log.info'        

     The name to use for the file in which the slave records
     information about the relay logs. The default name is
     `relay-log.info' in the data directory.  For information about the
     format of this file, see *Note slave-logs-status::.

   * `--relay-log-purge={0|1}'

     Options for relay_log_purge

     *Command-Line        `--relay_log_purge'        
     Format*                              
     *System Variable     `relay_log_purge'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Disable or enable automatic purging of relay logs as soon as they
     are no longer needed. The default value is 1 (enabled).  This is a
     global variable that can be changed dynamically with `SET GLOBAL
     relay_log_purge = N'.

   * `--relay-log-space-limit=SIZE'

     Options for relay_log_space_limit

     *Command-Line        `--relay_log_space_limit=#'        
     Format*                              
     *System Variable     `relay_log_space_limit'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     This option places an upper limit on the total size in bytes of
     all relay logs on the slave. A value of 0 means `no limit.' This
     is useful for a slave server host that has limited disk space.
     When the limit is reached, the I/O thread stops reading binary log
     events from the master server until the SQL thread has caught up
     and deleted some unused relay logs. Note that this limit is not
     absolute: There are cases where the SQL thread needs more events
     before it can delete relay logs. In that case, the I/O thread
     exceeds the limit until it becomes possible for the SQL thread to
     delete some relay logs because not doing so would cause a
     deadlock. You should not set `--relay-log-space-limit' to less
     than twice the value of `--max-relay-log-size' (or
     `--max-binlog-size' if `--max-relay-log-size' is 0).  In that
     case, there is a chance that the I/O thread waits for free space
     because `--relay-log-space-limit' is exceeded, but the SQL thread
     has no relay log to purge and is unable to satisfy the I/O thread.
     This forces the I/O thread to ignore `--relay-log-space-limit'
     temporarily.

   * `--replicate-do-db=DB_NAME'

     Options for replicate-do-db

     *Command-Line        `--replicate-do-db=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The effects of this option depend on whether statement-based or
     row-based replication is in use.

     Statement-based replication

     Tell the slave SQL thread to restrict replication to statements
     where the default database (that is, the one selected by *Note
     `USE': use.) is DB_NAME. To specify more than one database, use
     this option multiple times, once for each database; however, doing
     so does _not_ replicate cross-database statements such as `UPDATE
     SOME_DB.SOME_TABLE SET foo='bar'' while a different database (or no
     database) is selected.

     *Warning*:

     To specify multiple databases you _must_ use multiple instances of
     this option. Because database names can contain commas, if you
     supply a comma separated list then the list will be treated as the
     name of a single database.

     An example of what does not work as you might expect when using
     statement-based replication: If the slave is started with
     `--replicate-do-db=sales' and you issue the following statements
     on the master, the *Note `UPDATE': update. statement is _not_
     replicated:


          USE prices;
          UPDATE sales.january SET amount=amount+1000;

     The main reason for this `check just the default database'
     behavior is that it is difficult from the statement alone to know
     whether it should be replicated (for example, if you are using
     multiple-table *Note `DELETE': delete. statements or
     multiple-table *Note `UPDATE': update.  statements that act across
     multiple databases). It is also faster to check only the default
     database rather than all databases if there is no need.

     Row-based replication

     Tells the slave SQL thread to restrict replication to database
     DB_NAME. Only tables belonging to DB_NAME are changed; the current
     database has no effect on this.  Suppose that the slave is started
     with `--replicate-do-db=sales' and row-based replication is in
     effect, and then the following statements are run on the master:


          USE prices;
          UPDATE sales.february SET amount=amount+100;

     The `february' table in the `sales' database on the slave is
     changed in accordance with the *Note `UPDATE': update.  statement;
     this occurs whether or not the *Note `USE': use. statement was
     issued.  However, issuing the following statements on the master
     has no effect on the slave when using row-based replication and
     `--replicate-do-db=sales':


          USE prices;
          UPDATE prices.march SET amount=amount-25;

     Even if the statement `USE prices' were changed to `USE sales', the
     *Note `UPDATE': update. statement's effects would still not be
     replicated.

     Another important difference in how `--replicate-do-db' is handled
     in statement-based replication as opposed to row-based replication
     occurs with regard to statements that refer to multiple databases.
     Suppose that the slave is started with `--replicate-do-db=db1', and
     the following statements are executed on the master:


          USE db1;
          UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

     If you are using statement-based replication, then both tables are
     updated on the slave. However, when using row-based replication,
     only `table1' is affected on the slave; since `table2' is in a
     different database, `table2' on the slave is not changed by the
     *Note `UPDATE': update.  Now suppose that, instead of the `USE db1'
     statement, a `USE db4' statement had been used:


          USE db4;
          UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

     In this case, the *Note `UPDATE': update.  statement would have no
     effect on the slave when using statement-based replication.
     However, if you are using row-based replication, the *Note
     `UPDATE': update. would change `table1' on the slave, but not
     `table2'--in other words, only tables in the database named by
     `--replicate-do-db' are changed, and the choice of default
     database has no effect on this behavior.

     If you need cross-database updates to work, use
     `--replicate-wild-do-table=DB_NAME.%' instead. See *Note
     replication-rules::.

     *Note*:

     This option affects replication in the same manner that
     `--binlog-do-db' affects binary logging, and the effects of the
     replication format on how `--replicate-do-db' affects replication
     behavior are the same as those of the logging format on the
     behavior of `--binlog-do-db'.

     Beginning with MySQL 5.1.35, this option has no effect on *Note
     `BEGIN': commit, *Note `COMMIT': commit, or *Note `ROLLBACK':
     commit.  statements. (Bug #43263)

   * `--replicate-ignore-db=DB_NAME'

     Options for replicate-ignore-db

     *Command-Line        `--replicate-ignore-db=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     As with `--replicate-do-db', the effects of this option depend on
     whether statement-based or row-based replication is in use.

     Statement-based replication

     Tells the slave SQL thread not to replicate any statement where
     the default database (that is, the one selected by *Note `USE':
     use.) is DB_NAME.

     Row-based replication

     Tells the slave SQL thread not to update any tables in the
     database DB_NAME. The default database has no effect.

     When using statement-based replication, the following example does
     not work as you might expect. Suppose that the slave is started
     with `--replicate-ignore-db=sales' and you issue the following
     statements on the master:


          USE prices;
          UPDATE sales.january SET amount=amount+1000;

     The *Note `UPDATE': update. statement _is_ replicated in such a
     case because `--replicate-ignore-db' applies only to the default
     database (determined by the *Note `USE': use. statement). Because
     the `sales' database was specified explicitly in the statement,
     the statement has not been filtered.  However, when using
     row-based replication, the *Note `UPDATE': update. statement's
     effects are _not_ propagated to the slave, and the slave's copy of
     the `sales.january' table is unchanged; in this instance,
     `--replicate-ignore-db=sales' causes _all_ changes made to tables
     in the master's copy of the `sales' database to be ignored by the
     slave.

     To specify more than one database to ignore, use this option
     multiple times, once for each database. Because database names can
     contain commas, if you supply a comma separated list then the list
     will be treated as the name of a single database.

     You should not use this option if you are using cross-database
     updates and you do not want these updates to be replicated. See
     *Note replication-rules::.

     If you need cross-database updates to work, use
     `--replicate-wild-ignore-table=DB_NAME.%' instead. See *Note
     replication-rules::.

     *Note*:

     This option affects replication in the same manner that
     `--binlog-ignore-db' affects binary logging, and the effects of
     the replication format on how `--replicate-ignore-db' affects
     replication behavior are the same as those of the logging format
     on the behavior of `--binlog-ignore-db'.

     Beginning with MySQL 5.1.35, this option has no effect on *Note
     `BEGIN': commit, *Note `COMMIT': commit, or *Note `ROLLBACK':
     commit.  statements. (Bug #43263)

   * `--replicate-do-table=DB_NAME.TBL_NAME'

     Options for replicate-do-table

     *Command-Line        `--replicate-do-table=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Tells the slave SQL thread to restrict replication to the
     specified table. To specify more than one table, use this option
     multiple times, once for each table. This works for both
     cross-database updates and default database updates, in contrast to
     `--replicate-do-db'. See *Note replication-rules::.

     This option affects only statements that apply to tables. It does
     not affect statements that apply only to other database objects,
     such as stored routines. To filter statements operating on stored
     routines, use one or more of the `--replicate-*-db' options.

   * `--replicate-ignore-table=DB_NAME.TBL_NAME'

     Options for replicate-ignore-table

     *Command-Line        `--replicate-ignore-table=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Tells the slave SQL thread not to replicate any statement that
     updates the specified table, even if any other tables might be
     updated by the same statement. To specify more than one table to
     ignore, use this option multiple times, once for each table. This
     works for cross-database updates, in contrast to
     `--replicate-ignore-db'. See *Note replication-rules::.

     This option affects only statements that apply to tables. It does
     not affect statements that apply only to other database objects,
     such as stored routines. To filter statements operating on stored
     routines, use one or more of the `--replicate-*-db' options.

   * `--replicate-rewrite-db=FROM_NAME->TO_NAME'

     Options for replicate-rewrite-db

     *Command-Line        `--replicate-rewrite-db=old_name->new_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Tells the slave to translate the default database (that is, the
     one selected by *Note `USE': use.) to TO_NAME if it was FROM_NAME
     on the master. Only statements involving tables are affected (not
     statements such as *Note `CREATE DATABASE': create-database, *Note
     `DROP DATABASE': drop-database, and *Note `ALTER DATABASE':
     alter-database.), and only if FROM_NAME is the default database on
     the master. To specify multiple rewrites, use this option multiple
     times. The server uses the first one with a FROM_NAME value that
     matches. The database name translation is done _before_ the
     `--replicate-*' rules are tested.

     Statements in which table names are qualified with database names
     when using this option do not work with table-level replication
     filtering options such as `--replicate-do-table'. Suppose we have
     a database named `a' on the master, one named `b' on the slave,
     each containing a table `t', and have started the master with
     `--replicate-rewrite-db='a->b''. At a later point in time, we
     execute *Note `DELETE FROM a.t': delete. In this case, no relevant
     filtering rule works, for the reasons shown here:

       1. `--replicate-do-table=a.t' does not work because the slave
          has table `t' in database `b'.

       2. `--replicate-do-table=b.t' does not match the original
          statement and so is ignored.

       3. `--replicate-do-table=*.t' is handled identically to
          `--replicate-do-table=a.t', and thus does not work, either.

     Similarly, the `--replication-rewrite-db' option does not work
     with cross-database updates.

     If you use this option on the command line and the ``>'' character
     is special to your command interpreter, quote the option value. For
     example:


          shell> mysqld --replicate-rewrite-db="OLDDB->NEWDB"

   * `--replicate-same-server-id'

     Options for replicate-same-server-id

     *Command-Line        `--replicate-same-server-id'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     To be used on slave servers. Usually you should use the default
     setting of 0, to prevent infinite loops caused by circular
     replication. If set to 1, the slave does not skip events having
     its own server ID. Normally, this is useful only in rare
     configurations. Cannot be set to 1 if `--log-slave-updates' is
     used.  By default, the slave I/O thread does not write binary log
     events to the relay log if they have the slave's server ID (this
     optimization helps save disk usage). If you want to use
     `--replicate-same-server-id', be sure to start the slave with this
     option before you make the slave read its own events that you want
     the slave SQL thread to execute.

   * `--replicate-wild-do-table=DB_NAME.TBL_NAME'

     Options for replicate-wild-do-table

     *Command-Line        `--replicate-wild-do-table=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Tells the slave thread to restrict replication to statements where
     any of the updated tables match the specified database and table
     name patterns. Patterns can contain the ``%'' and ``_'' wildcard
     characters, which have the same meaning as for the `LIKE'
     pattern-matching operator.  To specify more than one table, use
     this option multiple times, once for each table. This works for
     cross-database updates. See *Note replication-rules::.

     This option applies to tables, views, and triggers. It does not
     apply to stored procedures and functions, or events. To filter
     statements operating on the latter objects, use one or more of the
     `--replicate-*-db' options.

     Example: `--replicate-wild-do-table=foo%.bar%' replicates only
     updates that use a table where the database name starts with `foo'
     and the table name starts with `bar'.

     If the table name pattern is `%', it matches any table name and
     the option also applies to database-level statements (*Note
     `CREATE DATABASE': create-database, *Note `DROP DATABASE':
     drop-database, and *Note `ALTER DATABASE': alter-database.). For
     example, if you use `--replicate-wild-do-table=foo%.%',
     database-level statements are replicated if the database name
     matches the pattern `foo%'.

     To include literal wildcard characters in the database or table
     name patterns, escape them with a backslash. For example, to
     replicate all tables of a database that is named `my_own%db', but
     not replicate tables from the `my1ownAABCdb' database, you should
     escape the ``_'' and ``%'' characters like this:
     `--replicate-wild-do-table=my\_own\%db'.  If you use the option on
     the command line, you might need to double the backslashes or
     quote the option value, depending on your command interpreter. For
     example, with the `bash' shell, you would need to type
     `--replicate-wild-do-table=my\\_own\\%db'.

   * `--replicate-wild-ignore-table=DB_NAME.TBL_NAME'

     Options for replicate-wild-ignore-table

     *Command-Line        `--replicate-wild-ignore-table=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     Tells the slave thread not to replicate a statement where any
     table matches the given wildcard pattern. To specify more than one
     table to ignore, use this option multiple times, once for each
     table. This works for cross-database updates. See *Note
     replication-rules::.

     Example: `--replicate-wild-ignore-table=foo%.bar%' does not
     replicate updates that use a table where the database name starts
     with `foo' and the table name starts with `bar'.

     For information about how matching works, see the description of
     the `--replicate-wild-do-table' option. The rules for including
     literal wildcard characters in the option value are the same as for
     `--replicate-wild-ignore-table' as well.

   * `--report-host=HOST_NAME'

     Options for report-host

     *Command-Line        `--report-host=host_name'        
     Format*                              
     *System Variable     `report_host'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The host name or IP address of the slave to be reported to the
     master during slave registration. This value appears in the output
     of *Note `SHOW SLAVE HOSTS': show-slave-hosts. on the master
     server. Leave the value unset if you do not want the slave to
     register itself with the master. Note that it is not sufficient
     for the master to simply read the IP address of the slave from the
     TCP/IP socket after the slave connects. Due to NAT and other
     routing issues, that IP may not be valid for connecting to the
     slave from the master or other hosts.

   * `--report-password=PASSWORD'

     Options for report-password

     *Command-Line        `--report-password=name'        
     Format*                              
     *System Variable     `report_password'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     An arbitrary account password to be reported by the slave to the
     master during slave registration. This value appears in the output
     of *Note `SHOW SLAVE HOSTS': show-slave-hosts. on the master
     server if the `--show-slave-auth-info' option is given.

     Although the name of this option might imply otherwise,
     `--report-password' is not connected to the MySQL user privilege
     system and so is not necessarily (or even likely to be) the same
     as the password for the MySQL replication user account.

   * `--report-port=SLAVE_PORT_NUM'

     Options for report-port

     *Command-Line        `--report-port=#'        
     Format*                              
     *System Variable     `report_port'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3306'          
     *Min Value*          `0'             
     *Max Value*          `65535'         

     The TCP/IP port number for connecting to the slave, to be reported
     to the master during slave registration. Set this only if the
     slave is listening on a nondefault port or if you have a special
     tunnel from the master or other clients to the slave. If you are
     not sure, do not use this option.

   * `--report-user=USER_NAME'

     Options for report-user

     *Command-Line        `--report-user=name'        
     Format*                              
     *System Variable     `report_user'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     The account user name of the slave to be reported to the master
     during slave registration. This value appears in the output of
     *Note `SHOW SLAVE HOSTS': show-slave-hosts. on the master server
     if the `--show-slave-auth-info' option is given.

     Although the name of this option might imply otherwise,
     `--report-user' is not connected to the MySQL user privilege
     system and so is not necessarily (or even likely to be) the same
     as the name of the MySQL replication user account.

   * `--show-slave-auth-info'

     Options for show-slave-auth-info

     *Command-Line        `--show-slave-auth-info'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Display slave user names and passwords in the output of *Note
     `SHOW SLAVE HOSTS': show-slave-hosts. on the master server for
     slaves started with the `--report-user' and `--report-password'
     options.

   * `--skip-slave-start'

     Options for skip-slave-start

     *Command-Line        `--skip-slave-start'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Tells the slave server not to start the slave threads when the
     server starts. To start the threads later, use a *Note `START
     SLAVE': start-slave. statement.

   * `--slave_compressed_protocol={0|1}'

     Options for slave_compressed_protocol

     *Command-Line        `--slave_compressed_protocol'        
     Format*                              
     *System Variable     `slave_compressed_protocol'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     If this option is set to 1, use compression for the slave/master
     protocol if both the slave and the master support it. The default
     is 0 (no compression).

   * `--slave-load-tmpdir=FILE_NAME'

     Options for slave-load-tmpdir

     *Command-Line        `--slave-load-tmpdir=path'        
     Format*                              
     *System Variable     `slave_load_tmpdir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           
     *Default*            `/tmp'          

     The name of the directory where the slave creates temporary files.
     This option is by default equal to the value of the `tmpdir'
     system variable.  When the slave SQL thread replicates a *Note
     `LOAD DATA INFILE': load-data. statement, it extracts the file to
     be loaded from the relay log into temporary files, and then loads
     these into the table. If the file loaded on the master is huge,
     the temporary files on the slave are huge, too.  Therefore, it
     might be advisable to use this option to tell the slave to put
     temporary files in a directory located in some file system that
     has a lot of available space. In that case, the relay logs are
     huge as well, so you might also want to use the `--relay-log'
     option to place the relay logs in that file system.

     The directory specified by this option should be located in a
     disk-based file system (not a memory-based file system) because
     the temporary files used to replicate *Note `LOAD DATA INFILE':
     load-data. must survive machine restarts. The directory also
     should not be one that is cleared by the operating system during
     the system startup process.

   * `--slave-net-timeout=SECONDS'

     Options for slave-net-timeout

     *Command-Line        `--slave-net-timeout=#'        
     Format*                              
     *System Variable     `slave_net_timeout'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3600'          
     *Min Value*          `1'             

     The number of seconds to wait for more data from the master before
     the slave considers the connection broken, aborts the read, and
     tries to reconnect. The first retry occurs immediately after the
     timeout. The interval between retries is controlled by the
     `MASTER_CONNECT_RETRY' option for the *Note `CHANGE MASTER TO':
     change-master-to. statement or `--master-connect-retry' option,
     and the number of reconnection attempts is limited by the
     `--master-retry-count' option. The default is 3600 seconds (one
     hour).

   * `--slave-skip-errors=[ERR_CODE1,ERR_CODE2,...|all]'

     _(MySQL Cluster NDB 7.0.33 and later; MySQL Cluster NDB 7.1.22 and
     later:)_
     `--slave-skip-errors=[ERR_CODE1,ERR_CODE2,...|all|ddl_exist_errors]'

     Options for slave-skip-errors

     *Command-Line        `--slave-skip-errors=name'        
     Format*                              
     *System Variable     `slave_skip_errors'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.61-ndb-7.0.33,5.1.61-ndb-7.1.22)*        
     *Type*               `string'        
     *Default*            `OFF'           
     *Valid Values*       `OFF'           
     `[list of error                      
     codes]'                              
     `all'                                
     `ddl_exist_errors'                   

     Normally, replication stops when an error occurs on the slave.
     This gives you the opportunity to resolve the inconsistency in the
     data manually. This option tells the slave SQL thread to continue
     replication when a statement returns any of the errors listed in
     the option value.

     Do not use this option unless you fully understand why you are
     getting errors. If there are no bugs in your replication setup and
     client programs, and no bugs in MySQL itself, an error that stops
     replication should never occur.  Indiscriminate use of this option
     results in slaves becoming hopelessly out of synchrony with the
     master, with you having no idea why this has occurred.

     *Note*:

     Prior to MySQL 5.1.35, this option had no effect with row-based
     logging. (Bug #39393)

     For error codes, you should use the numbers provided by the error
     message in your slave error log and in the output of *Note `SHOW
     SLAVE STATUS': show-slave-status.  *Note error-handling::, lists
     server error codes.

     You can also (but should not) use the very nonrecommended value of
     `all' to cause the slave to ignore all error messages and keeps
     going regardless of what happens. Needless to say, if you use
     `all', there are no guarantees regarding the integrity of your
     data. Please do not complain (or file bug reports) in this case if
     the slave's data is not anywhere close to what it is on the
     master. _You have been warned_.

     For MySQL Cluster Replication in MySQL Cluster NDB 7.0 beginning
     with version 7.0.33 and MySQL Cluster NDB 7.1 beginning with
     version 7.1.22, an additional shorthand value `ddl_exist_errors'
     is supported for use with the enhanced failover mechanism which is
     implemented in that and later version of MySQL Cluster NDB 7.2.
     This value is equivalent to the error code list
     `1007,1008,1050,1051,1054,1060,1061,1068,1094,1146'.  _This value
     is not supported by the *Note `mysqld': mysqld. binary included
     with the MySQL Server 5.1 distribution_. (Bug #11762277, Bug
     #54854) For more information, see *Note
     mysql-cluster-replication-failover::.

     Examples:


          --slave-skip-errors=1062,1053
          --slave-skip-errors=all
          --slave-skip-errors=ddl_exist_errors

*System Variables Used on Replication Slaves*

The following list describes system variables for controlling
replication slave servers. They can be set at server startup and some
of them can be changed at runtime using *Note `SET': set-statement.
Server options used with replication slaves are listed earlier in this
section.

   * `init_slave'

     Options for init_slave

     *Command-Line        `--init-slave=name'        
     Format*                              
     *System Variable     `init_slave'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This variable is similar to `init_connect', but is a string to be
     executed by a slave server each time the SQL thread starts. The
     format of the string is the same as for the `init_connect'
     variable.

     *Note*:

     The SQL thread sends an acknowledgment to the client before it
     executes `init_slave'. Therefore, it is not guaranteed that
     `init_slave' has been executed when *Note `START SLAVE':
     start-slave.  returns. See *Note start-slave::, for more
     information.

   * `relay_log'

     Options for relay-log

     *Command-Line        `--relay-log=file_name'        
     Format*                              
     *System Variable     `relay_log'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The name of the relay log file.

   * `relay_log_index'

     Options for relay_log_index

     *Command-Line        `--relay-log-index'        
     Format*                              
     *System Variable     `relay_log_index'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `*host_name*-relay-bin.index'        

     The name of the relay log index file. The default name is
     `HOST_NAME-relay-bin.index' in the data directory, where HOST_NAME
     is the name of the slave server.

   * `relay_log_info_file'

     Options for relay_log_info_file

     *Command-Line        `--relay-log-info-file=file_name'        
     Format*                              
     *System Variable     `relay_log_info_file'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `relay-log.info'        

     The name of the file in which the slave records information about
     the relay logs. The default name is `relay-log.info' in the data
     directory.

   * `rpl_recovery_rank'

     This variable is unused, and is removed in MySQL 5.6.

   * `slave_compressed_protocol'

     Options for slave_compressed_protocol

     *Command-Line        `--slave_compressed_protocol'        
     Format*                              
     *System Variable     `slave_compressed_protocol'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Whether to use compression of the slave/master protocol if both
     the slave and the master support it.

   * `slave_exec_mode'

     Options for slave_exec_mode

     *Introduced*         5.1.23-ndb-6.2.14,        
                          5.1.23-ndb-6.3.11,        
                          5.1.24          
     *Command-Line        `--slave-exec-mode=mode'        
     Format*                              
     *System Variable     `slave_exec_mode'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `STRICT'        
                          (ALL)           
     *Default*            `IDEMPOTENT'        
                          (NDB)           
     *Valid Values*       `IDEMPOTENT'        
     `STRICT'                             

     Controls whether `IDEMPOTENT' or `STRICT' mode is used in
     replication conflict resolution and error checking.  `IDEMPOTENT'
     mode causes suppression of duplicate-key and no-key-found errors.

     This mode is needed for multi-master replication, circular
     replication, and some other special replication scenarios for
     MySQL Cluster Replication. (See *Note
     mysql-cluster-replication-multi-master::, and *Note
     mysql-cluster-replication-conflict-resolution::, for more
     information.) The *Note `mysqld': mysqld.  supplied with MySQL
     Cluster ignores any value explicitly set for `slave_exec_mode', and
     always treats it as `IDEMPOTENT'.

     In MySQL Server 5.1, `STRICT' mode is the default value. This
     should not be changed; currently, `IDEMPOTENT' mode is supported
     only by *Note `NDB': mysql-cluster.

   * `slave_max_allowed_packet'

     Options for slave_max_allowed_packet

     *Introduced*         5.1.64          
     *System Variable     `slave_max_allowed_packet'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1073741824'        
     *Min Value*          `1024'          
     *Max Value*          `1073741824'        

     In MySQL 5.1.64 and later, this variable sets the maximum packet
     size for the slave SQL and I/O threads, so that large updates
     using row-based replication do not cause replication to fail
     because an update exceeded `max_allowed_packet'.

     This global variable always has a value that is a positive integer
     multiple of 1024; if you set it to some value that is not, the
     value is rounded down to the next highest multiple of 1024 for it
     is stored or used; setting `slave_max_allowed_packet' to 0 causes
     1024 to be used. (A truncation warning is issued in all such
     cases.) The default and maximum value is 1073741824 (1 GB); the
     minimum is 1024.

     `slave_max_allowed_packet' can also be set at startup, using the
     `--slave-max-allowed-packet' option.

   * `slave_load_tmpdir'

     Options for slave-load-tmpdir

     *Command-Line        `--slave-load-tmpdir=path'        
     Format*                              
     *System Variable     `slave_load_tmpdir'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `directory        
                          name'           
     *Default*            `/tmp'          

     The name of the directory where the slave creates temporary files
     for replicating *Note `LOAD DATA INFILE': load-data. statements.

   * `slave_net_timeout'

     Options for slave-net-timeout

     *Command-Line        `--slave-net-timeout=#'        
     Format*                              
     *System Variable     `slave_net_timeout'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `3600'          
     *Min Value*          `1'             

     The number of seconds to wait for more data from a master/slave
     connection before aborting the read. Before MySQL 5.1.41, this
     timeout applies only to TCP/IP connections, not to connections
     made through Unix socket files, named pipes, or shared memory.

   * `slave_skip_errors'

     Options for slave-skip-errors

     *Command-Line        `--slave-skip-errors=name'        
     Format*                              
     *System Variable     `slave_skip_errors'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.61-ndb-7.0.33,5.1.61-ndb-7.1.22)*        
     *Type*               `string'        
     *Default*            `OFF'           
     *Valid Values*       `OFF'           
     `[list of error                      
     codes]'                              
     `all'                                
     `ddl_exist_errors'                   

     Normally, replication stops when an error occurs on the slave.
     This gives you the opportunity to resolve the inconsistency in the
     data manually. This variable tells the slave SQL thread to
     continue replication when a statement returns any of the errors
     listed in the variable value.

   * `slave_transaction_retries'

     Options for slave_transaction_retries

     *Command-Line        `--slave_transaction_retries=#'        
     Format*                              
     *System Variable     `slave_transaction_retries'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `10'            
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     If a replication slave SQL thread fails to execute a transaction
     because of an *Note `InnoDB': innodb-storage-engine. deadlock or
     because the transaction's execution time exceeded *Note `InnoDB':
     innodb-storage-engine.'s `innodb_lock_wait_timeout' or *Note
     `NDBCLUSTER': mysql-cluster.'s
     `TransactionDeadlockDetectionTimeout' or
     `TransactionInactiveTimeout', it automatically retries
     `slave_transaction_retries' times before stopping with an error.
     The default value is 10.

   * `slave_type_conversions'

     Options for slave_type_conversions

     *Introduced*         5.1.44-ndb-6.3.33,        
                          5.1.44-ndb-7.0.14,        
                          5.1.44-ndb-7.1.3        
     *Command-Line        `--slave_type_conversions=set'        
     Format*                              
     *System Variable     `slave_type_conversions'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `set'           
     *Default*            `'              
     *Valid Values*       `ALL_LOSSY'        
     `ALL_NON_LOSSY'                      

     Controls the type conversion mode in effect on the slave when
     using MySQL Cluster Replication. Its value is a comma-delimited
     set of zero or more elements from the list: `ALL_LOSSY',
     `ALL_NON_LOSSY'. Set this variable to an empty string to disallow
     type conversions between the master and the slave. Changes require
     a restart of the slave to take effect.

     For additional information on type conversion modes applicable to
     MySQL Cluster replication attribute promotion and demotion, see
     *Note replication-features-attribute-promotion::.

     This variable was added in MySQL Cluster NDB 6.3.33, 7.0.14, and
     7.1.3.

   * `sql_slave_skip_counter'

     Options for sql_slave_skip_counter

     *System Variable     `sql_slave_skip_counter'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        

     The number of events from the master that a slave server should
     skip.

     *Important*:

     If skipping the number of events specified by setting this
     variable would cause the slave to begin in the middle of an event
     group, the slave continues to skip until it finds the beginning of
     the next event group and begins from that point. For more
     information, see *Note set-global-sql-slave-skip-counter::.


File: manual.info,  Node: replication-options-binary-log,  Prev: replication-options-slave,  Up: replication-options

16.1.3.4 Binary Log Options and Variables
.........................................

*Note replication-optvars-binlog::

*Note replication-sysvars-binlog::

You can use the *Note `mysqld': mysqld. options and system variables
that are described in this section to affect the operation of the
binary log as well as to control which statements are written to the
binary log. For additional information about the binary log, see *Note
binary-log::. For additional information about using MySQL server
options and system variables, see *Note server-options::, and *Note
server-system-variables::.

*Startup Options Used with Binary Logging*

The following list describes startup options for enabling and
configuring the binary log. System variables used with binary logging
are discussed later in this section.

   * `--binlog-row-event-max-size=N'

     Options for binlog-row-event-max-size

     *Introduced*         5.1.5           
     *Command-Line        `--binlog-row-event-max-size=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `1024'          
     *Min Value*          `256'           
     *Max Value*          `18446744073709547520'        

     Specify the maximum size of a row-based binary log event, in
     bytes. Rows are grouped into events smaller than this size if
     possible. The value should be a multiple of 256. The default is
     1024. See *Note replication-formats::.  This option was added in
     MySQL 5.1.5.

   * `--log-bin[=BASE_NAME]'

     Options for log-bin

     *Command-Line        `--log-bin'        
     Format*                              
     *System Variable     `log_bin'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     Enable binary logging. The server logs all statements that change
     data to the binary log, which is used for backup and replication.
     See *Note binary-log::.

     The option value, if given, is the basename for the log sequence.
     The server creates binary log files in sequence by adding a
     numeric suffix to the basename. It is recommended that you specify
     a basename (see *Note bugs::, for the reason). Otherwise, MySQL
     uses `HOST_NAME-bin' as the basename.

     Setting this option causes the `log_bin' system variable to be set
     to `ON' (or `1'), and not to the basename. This is a known issue;
     see Bug #19614 for more information.

   * `--log-bin-index[=FILE_NAME]'

     Options for log-bin-index

     *Command-Line        `--log-bin-index=file_name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           

     The index file for binary log file names. See *Note binary-log::.
     If you omit the file name, and if you did not specify one with
     `--log-bin', MySQL uses `HOST_NAME-bin.index' as the file name.

   * `--log-bin-trust-function-creators[={0|1}]'

     Options for log-bin-trust-function-creators

     *Command-Line        `--log-bin-trust-function-creators'        
     Format*                              
     *System Variable     `log_bin_trust_function_creators'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This option sets the corresponding
     `log_bin_trust_function_creators' system variable. If no argument
     is given, the option sets the variable to 1.
     `log_bin_trust_function_creators' affects how MySQL enforces
     restrictions on stored function and trigger creation. See *Note
     stored-programs-logging::.

     *Note*:

     Previously, this option was known as
     `--log-bin-trust-routine-creators', which is now deprecated.

   * `--log-bin-use-v1-row-events[={0|1}]'

     Options for log-bin-use-v1-row-events

     *Introduced*         5.1.56-ndb-7-0-27,        
                          5.1.56-ndb-7.1.16        
     *Command-Line        `--log-bin-use-v1-row-events[={0|1}]'        
     Format*                              
     *System Variable     `log_bin_use_v1_row_events'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `0'             

     Version 2 binary log row events are available beginning with MySQL
     Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16; however, Version
     2 events cannot be read by previous MySQL Cluster releases. Setting
     `--log-bin-use-v1-row-events' to 0 causes *Note `mysqld': mysqld.
     to use Version 2 binary log events. Setting this option to 1 (the
     default) causes *Note `mysqld': mysqld. to write the binary log
     using Version 1 logging events, which is the only version of
     binary log events used in previous releases, and thus produce
     binary logs that can be read by older slaves.

     The value used for this option can be obtained from the read-only
     `log_bin_use_v1_row_events' system variable.

     `--log-bin-use-v1-row-events' is chiefly of interest when setting
     up replication conflict detection and resolution using
     `NDB$EPOCH_TRANS()' as the conflict detection function, which
     requires Version 2 binary log row events. Thus, this option and
     `--ndb-log-transaction-id' are not compatible.

     *Note*:

     MySQL Cluster NDB 7.2.1 and later use Version 2 binary log events
     by default (and so the default value for this option changes to 0
     in those versions). You should keep this mind when planning
     upgrades for setups using MySQL Cluster Replication.

     `--log-bin-use-v1-row-events' is not supported in mainline MySQL
     Server 5.1 releases.

     For more information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `--log-short-format'

     Options for log-short-format

     *Command-Line        `--log-short-format'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Log less information to the binary log and slow query log, if they
     have been activated.

Statement selection options

The options in the following list affect which statements are written
to the binary log, and thus sent by a replication master server to its
slaves. There are also options for slave servers that control which
statements received from the master should be executed or ignored. For
details, see *Note replication-options-slave::.

   * `--binlog-do-db=DB_NAME'

     Options for binlog-do-db

     *Command-Line        `--binlog-do-db=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This option affects binary logging in a manner similar to the way
     that `--replicate-do-db' affects replication.

     The effects of this option depend on whether the statement-based
     or row-based logging format is in use, in the same way that the
     effects of `--replicate-do-db' depend on whether statement-based
     or row-based replication is in use.  You should keep in mind that
     the format used to log a given statement may not necessarily be
     the same as that indicated by the value of `binlog_format'. For
     example, DDL statements such as *Note `CREATE TABLE':
     create-table. and *Note `ALTER TABLE': alter-table. are always
     logged as statements, without regard to the logging format in
     effect, so the following statement-based rules for `--binlog-do-db'
     always apply in determining whether or not the statement is logged.

     Statement-based logging

     Only those statements are written to the binary log where the
     default database (that is, the one selected by *Note `USE': use.)
     is DB_NAME. To specify more than one database, use this option
     multiple times, once for each database; however, doing so does
     _not_ cause cross-database statements such as `UPDATE
     SOME_DB.SOME_TABLE SET foo='bar'' to be logged while a different
     database (or no database) is selected.

     *Warning*:

     To specify multiple databases you _must_ use multiple instances of
     this option. Because database names can contain commas, the list
     will be treated as the name of a single database if you supply a
     comma-separated list.

     An example of what does not work as you might expect when using
     statement-based logging: If the server is started with
     `--binlog-do-db=sales' and you issue the following statements, the
     *Note `UPDATE': update. statement is _not_ logged:


          USE prices;
          UPDATE sales.january SET amount=amount+1000;

     The main reason for this `just check the default database'
     behavior is that it is difficult from the statement alone to know
     whether it should be replicated (for example, if you are using
     multiple-table *Note `DELETE': delete. statements or
     multiple-table *Note `UPDATE': update.  statements that act across
     multiple databases). It is also faster to check only the default
     database rather than all databases if there is no need.

     Another case which may not be self-evident occurs when a given
     database is replicated even though it was not specified when
     setting the option. If the server is started with
     `--binlog-do-db=sales', the following *Note `UPDATE': update.
     statement is logged even though `prices' was not included when
     setting `--binlog-do-db':


          USE sales;
          UPDATE prices.discounts SET percentage = percentage + 10;

     Because `sales' is the default database when the *Note `UPDATE':
     update. statement is issued, the *Note `UPDATE': update. is logged.

     Row-based logging

     Logging is restricted to database DB_NAME. Only changes to tables
     belonging to DB_NAME are logged; the default database has no
     effect on this.  Suppose that the server is started with
     `--binlog-do-db=sales' and row-based logging is in effect, and
     then the following statements are executed:


          USE prices;
          UPDATE sales.february SET amount=amount+100;

     The changes to the `february' table in the `sales' database are
     logged in accordance with the *Note `UPDATE': update. statement;
     this occurs whether or not the *Note `USE': use. statement was
     issued.  However, when using the row-based logging format and
     `--binlog-do-db=sales', changes made by the following *Note
     `UPDATE': update.  are not logged:


          USE prices;
          UPDATE prices.march SET amount=amount-25;

     Even if the `USE prices' statement were changed to `USE sales', the
     *Note `UPDATE': update. statement's effects would still not be
     written to the binary log.

     Another important difference in `--binlog-do-db' handling for
     statement-based logging as opposed to the row-based logging occurs
     with regard to statements that refer to multiple databases.
     Suppose that the server is started with `--binlog-do-db=db1', and
     the following statements are executed:


          USE db1;
          UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

     If you are using statement-based logging, the updates to both
     tables are written to the binary log. However, when using the
     row-based format, only the changes to `table1' are logged;
     `table2' is in a different database, so it is not changed by the
     *Note `UPDATE': update.  Now suppose that, instead of the `USE db1'
     statement, a `USE db4' statement had been used:


          USE db4;
          UPDATE db1.table1 SET col1 = 10, db2.table2 SET col2 = 20;

     In this case, the *Note `UPDATE': update.  statement is not
     written to the binary log when using statement-based logging.
     However, when using row-based logging, the change to `table1' is
     logged, but not that to `table2'--in other words, only changes to
     tables in the database named by `--binlog-do-db' are logged, and
     the choice of default database has no effect on this behavior.

   * `--binlog-ignore-db=DB_NAME'

     Options for binlog-ignore-db

     *Command-Line        `--binlog-ignore-db=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        

     This option affects binary logging in a manner similar to the way
     that `--replicate-ignore-db' affects replication.

     The effects of this option depend on whether the statement-based
     or row-based logging format is in use, in the same way that the
     effects of `--replicate-ignore-db' depend on whether
     statement-based or row-based replication is in use. You should
     keep in mind that the format used to log a given statement may not
     necessarily be the same as that indicated by the value of
     `binlog_format'. For example, DDL statements such as *Note `CREATE
     TABLE': create-table. and *Note `ALTER TABLE': alter-table. are
     always logged as statements, without regard to the logging format
     in effect, so the following statement-based rules for
     `--binlog-ignore-db' always apply in determining whether or not
     the statement is logged.

     Statement-based logging

     Tells the server to not log any statement where the default
     database (that is, the one selected by *Note `USE': use.) is
     DB_NAME.

     Prior to MySQL 5.1.70, this option caused any statements
     containing fully qualified table names not to be logged if there
     was no default database specified (that is, when *Note `SELECT':
     select.  `DATABASE()' returned `NULL'). In MySQL 5.1.70 and later,
     when there is no default database, no `--binlog-ignore-db' options
     are applied, and such statements are always logged. (Bug
     #11829838, Bug #60188)

     Row-based format

     Tells the server not to log updates to any tables in the database
     DB_NAME. The current database has no effect.

     When using statement-based logging, the following example does not
     work as you might expect. Suppose that the server is started with
     `--binlog-ignore-db=sales' and you issue the following statements:


          USE prices;
          UPDATE sales.january SET amount=amount+1000;

     The *Note `UPDATE': update. statement _is_ logged in such a case
     because `--binlog-ignore-db' applies only to the default database
     (determined by the *Note `USE': use. statement). Because the
     `sales' database was specified explicitly in the statement, the
     statement has not been filtered.  However, when using row-based
     logging, the *Note `UPDATE': update. statement's effects are _not_
     written to the binary log, which means that no changes to the
     `sales.january' table are logged; in this instance,
     `--binlog-ignore-db=sales' causes _all_ changes made to tables in
     the master's copy of the `sales' database to be ignored for
     purposes of binary logging.

     To specify more than one database to ignore, use this option
     multiple times, once for each database. Because database names can
     contain commas, the list will be treated as the name of a single
     database if you supply a comma-separated list.

     You should not use this option if you are using cross-database
     updates and you do not want these updates to be logged.

Testing and debugging options

The following binary log options are used in replication testing and
debugging. They are not intended for use in normal operations.

   * `--max-binlog-dump-events=N'

     Options for max-binlog-dump-events

     *Command-Line        `--max-binlog-dump-events=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             

     This option is used internally by the MySQL test suite for
     replication testing and debugging.

   * `--sporadic-binlog-dump-fail'

     Options for sporadic-binlog-dump-fail

     *Command-Line        `--sporadic-binlog-dump-fail'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This option is used internally by the MySQL test suite for
     replication testing and debugging.

*System Variables Used with Binary Logging*

The following list describes system variables for controlling binary
logging. They can be set at server startup and some of them can be
changed at runtime using *Note `SET': set-statement.  Server options
used to control binary logging are listed earlier in this section. For
information about the `sql_log_bin' and `sql_log_off' variables, see
*Note server-system-variables::.

   * `binlog_cache_size'

     Options for binlog_cache_size

     *Command-Line        `--binlog_cache_size=#'        
     Format*                              
     *System Variable     `binlog_cache_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `32768'         
     *Min Value*          `4096'          
     *Max Value*          `4294967295'        

     The size of the cache to hold the SQL statements for the binary
     log during a transaction. A binary log cache is allocated for each
     client if the server supports any transactional storage engines
     and if the server has the binary log enabled (`--log-bin' option).
     If you often use large, multiple-statement transactions, you can
     increase this cache size to get better performance. The
     `Binlog_cache_use' and `Binlog_cache_disk_use' status variables
     can be useful for tuning the size of this variable. See *Note
     binary-log::.

   * `binlog_direct_non_transactional_updates'

     Options for binlog_direct_non_transactional_updates

     *Introduced*         5.1.44          
     *Command-Line        `--binlog_direct_non_transactional_updates[=value]'        
     Format*                              
     *System Variable     `binlog_direct_non_transactional_updates'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `OFF'           

     Due to concurrency issues, a slave can become inconsistent when a
     transaction contains updates to both transactional and
     nontransactional tables. MySQL tries to preserve causality among
     these statements by writing nontransactional statements to the
     transaction cache, which is flushed upon commit. However, problems
     arise when modifications done to nontransactional tables on behalf
     of a transaction become immediately visible to other connections
     because these changes may not be written immediately into the
     binary log.

     Beginning with MySQL 5.1.44, the
     `binlog_direct_non_transactional_updates' variable offers one
     possible workaround to this issue. By default, this variable is
     disabled. Enabling `binlog_direct_non_transactional_updates'
     causes updates to nontransactional tables to be written directly
     to the binary log, rather than to the transaction cache.

     _`binlog_direct_non_transactional_updates' works only for
     statements that are replicated using the statement-based binary
     logging format_; that is, it works only when the value of
     `binlog_format' is `STATEMENT', or when `binlog_format' is `MIXED'
     and a given statement is being replicated using the
     statement-based format. This variable has no effect when the
     binary log format is `ROW', or when `binlog_format' is set to
     `MIXED' and a given statement is replicated using the row-based
     format.

     *Important*:

     Before enabling this variable, you must make certain that there
     are no dependencies between transactional and nontransactional
     tables; an example of such a dependency would be the statement
     `INSERT INTO myisam_table SELECT * FROM innodb_table'. Otherwise,
     such statements are likely to cause the slave to diverge from the
     master.

   * `binlog_format'

     Options for binlog-format

     *Introduced*         5.1.5           
     *Command-Line        `--binlog-format=format'        
     Format*                              
     *System Variable     `binlog_format'        
     Name*                                
     *Variable Scope*     Global,         
                          Session         
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (>=             
                          5.1.5,          
                          <=              
                          5.1.7)*         
     *Type*               `enumeration'        
     *Default*            `STATEMENT'        
     *Valid Values*       `ROW'           
     `STATEMENT'                          
                          *Permitted        
                          Values          
                          (>=             
                          5.1.8,          
                          <=              
                          5.1.11)*        
     *Type*               `enumeration'        
     *Default*            `STATEMENT'        
     *Valid Values*       `ROW'           
     `STATEMENT'                          
     `MIXED'                              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.12,         
                          <=              
                          5.1.28)*        
     *Type*               `enumeration'        
     *Default*            `MIXED'         
     *Valid Values*       `ROW'           
     `STATEMENT'                          
     `MIXED'                              
                          *Permitted        
                          Values          
                          (>=             
                          5.1.29)*        
     *Type*               `enumeration'        
     *Default*            `STATEMENT'        
     *Valid Values*       `ROW'           
     `STATEMENT'                          
     `MIXED'                              

     This variable sets the binary logging format, and can be any one
     of `STATEMENT', `ROW', or `MIXED'. See *Note replication-formats::.
     `binlog_format' is set by the `--binlog-format' option at startup,
     or by the `binlog_format' variable at runtime.

     *Note*:

     While you can change the logging format at runtime, it is _not_
     recommended that you change it while replication is ongoing. This
     is due in part to the fact that slaves do not honor the master's
     `binlog_format' setting; a given MySQL Server can change only its
     own logging format.

     The startup variable was added in MySQL 5.1.5, and the runtime
     variable in MySQL 5.1.8. `MIXED' was added in MySQL 5.1.8.

     `STATEMENT' was used by default prior to MySQL 5.1.12; in MySQL
     5.1.12, the default was changed to `MIXED'. In MySQL 5.1.29, the
     default was changed back to `STATEMENT'.

     You must have the `SUPER' privilege to set the global
     `binlog_format' value.  Starting with MySQL 5.1.29, you must have
     the `SUPER' privilege to set either the global or session
     `binlog_format' value. (Bug #39106)

     The rules governing when changes to this variable take effect and
     how long the effect lasts are the same as for other MySQL server
     system variables. See *Note set-statement::, for more information.

     When `MIXED' is specified, statement-based replication is used,
     except for cases where only row-based replication is guaranteed to
     lead to proper results. For example, this happens when statements
     contain user-defined functions (UDF) or the `UUID()' function. An
     exception to this rule is that `MIXED' always uses statement-based
     replication for stored functions and triggers.

     There are exceptions when you cannot switch the replication format
     at runtime:

        * From within a stored function or a trigger.

        * If the *Note `NDBCLUSTER': mysql-cluster. storage engine is
          enabled.

        * If the session is currently in row-based replication mode and
          has open temporary tables.

     Trying to switch the format in those cases results in an error.

     Before MySQL 5.1.8, switching to row-based replication format
     would implicitly set `--log-bin-trust-function-creators=1' and
     `--innodb_locks_unsafe_for_binlog'.  This does not occur for MySQL
     5.1.8 and later.

     The binary log format affects the behavior of the following server
     options:

        * `--replicate-do-db'

        * `--replicate-ignore-db'

        * `--binlog-do-db'

        * `--binlog-ignore-db'

     These effects are discussed in detail in the descriptions of the
     individual options.

   * `log_bin'

     Options for log_bin

     *System Variable     `log_bin'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              

     Whether the binary log is enabled. If the `--log-bin' option is
     used, then the value of this variable is `ON'; otherwise it is
     `OFF'. This variable reports only on the status of binary logging
     (enabled or disabled); it does not actually report the value to
     which `--log-bin' is set.

     See *Note binary-log::.

   * `log_bin_use_v1_row_events'

     Options for log_bin_use_v1_row_events

     *Introduced*         5.1.56-ndb-7-0-27,        
                          5.1.56-ndb-7.1.16        
     *Command-Line        `--log-bin-use-v1-row-events[={0|1}]'        
     Format*                              
     *System Variable     `log_bin_use_v1_row_events'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `0'             

     Shows whether Version 2 binary logging, available beginning with
     MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16, is in use.
     A value of 1 shows that the server is writing the binary log using
     Version 1 logging events (the only version of binary log events
     used in previous releases), and thus producing a binary log that
     can be read by older slaves. 0 indicates that Version 2 binary log
     events are in use.

     This variable is read-only. To switch between Version 1 and
     Version 2 binary event binary logging, it is necessary to restart
     *Note `mysqld': mysqld. with the `--log-bin-use-v1-row-events'
     option.

     Other than when performing upgrades of MySQL Cluster Replication,
     `--log-bin-use-v1-events' is chiefly of interest when setting up
     replication conflict detection and resolution using
     `NDB$EPOCH_TRANS()', which requires Version 2 binary row event
     logging. Thus, this option and `--ndb-log-transaction-id' are not
     compatible.

     *Note*:

     MySQL Cluster NDB 7.2.1 and later use Version 2 binary log row
     events by default (and so the default value for this variable
     changes to 0 in those versions). You should keep this mind when
     planning upgrades for setups using MySQL Cluster Replication.

     This variable is not supported in mainline MySQL Server 5.1.

     For more information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `log_slave_updates'

     Options for log_slave_updates

     *Command-Line        `--log-slave-updates'        
     Format*                              
     *System Variable     `log_slave_updates'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   No              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Whether updates received by a slave server from a master server
     should be logged to the slave's own binary log.  Binary logging
     must be enabled on the slave for this variable to have any effect.
     See *Note replication-options::.

   * `max_binlog_cache_size'

     Options for max_binlog_cache_size

     *Command-Line        `--max_binlog_cache_size=#'        
     Format*                              
     *System Variable     `max_binlog_cache_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values          
                          (<=             
                          5.1.35)*        
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `4294967295'        
     *Min Value*          `4096'          
     *Max Value*          `4294967295'        
                          *Permitted        
                          Values          
                          (<=             
                          5.1.35)*        
     *Platform Bit Size*  `64'            
     *Type*               `numeric'        
     *Default*            `18446744073709547520'        
     *Min Value*          `4096'          
     *Max Value*          `18446744073709547520'        
                          *Permitted        
                          Values          
                          (>=             
                          5.1.36)*        
     *Type*               `numeric'        
     *Default*            `18446744073709547520'        
     *Min Value*          `4096'          
     *Max Value*          `18446744073709547520'        

     If a multiple-statement transaction requires more than this many
     bytes of memory, the server generates a `Multi-statement
     transaction required more than 'max_binlog_cache_size' bytes of
     storage' error.  The minimum value is 4096. The maximum and
     default values are 4GB on 32-bit platforms and 16EB (exabytes) on
     64-bit platforms. As of MySQL 5.1.36, the maximum value is 16EB
     (exabytes) on all platforms. The maximum recommended value is 4GB;
     this is due to the fact that MySQL currently cannot work with
     binary log positions greater than 4GB.

     In MySQL 5.1, a change in `max_binlog_cache_size' takes immediate
     effect for all active sessions.

   * `max_binlog_size'

     Options for max_binlog_size

     *Command-Line        `--max_binlog_size=#'        
     Format*                              
     *System Variable     `max_binlog_size'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1073741824'        
     *Min Value*          `4096'          
     *Max Value*          `1073741824'        

     If a write to the binary log causes the current log file size to
     exceed the value of this variable, the server rotates the binary
     logs (closes the current file and opens the next one). The minimum
     value is 4096 bytes. The maximum and default value is 1GB.

     A transaction is written in one chunk to the binary log, so it is
     never split between several binary logs. Therefore, if you have
     big transactions, you might see binary log files larger than
     `max_binlog_size'.

     If `max_relay_log_size' is 0, the value of `max_binlog_size'
     applies to relay logs as well.

   * `sync_binlog'

     Options for sync_binlog

     *Command-Line        `--sync-binlog=#'        
     Format*                              
     *System Variable     `sync_binlog'        
     Name*                                
     *Variable Scope*     Global          
     *Dynamic Variable*   Yes             
                          *Permitted        
                          Values*         
     *Platform Bit Size*  `32'            
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `4294967295'        

     If the value of this variable is greater than 0, the MySQL server
     synchronizes its binary log to disk (using `fdatasync()') after
     every `sync_binlog' writes to the binary log. There is one write
     to the binary log per statement if autocommit is enabled, and one
     write per transaction otherwise. The default value of
     `sync_binlog' is 0, which does no synchronizing to disk--in this
     case, the server relies on the operating system to flush the binary
     log's contents from time to time as for any other file.  A value
     of 1 is the safest choice because in the event of a crash you lose
     at most one statement or transaction from the binary log. However,
     it is also the slowest choice (unless the disk has a
     battery-backed cache, which makes synchronization very fast).


File: manual.info,  Node: replication-administration,  Prev: replication-options,  Up: replication-configuration

16.1.4 Common Replication Administration Tasks
----------------------------------------------

* Menu:

* replication-administration-status::  Checking Replication Status
* replication-administration-pausing::  Pausing Replication on the Slave

Once replication has been started it should execute without requiring
much regular administration. Depending on your replication environment,
you will want to check the replication status of each slave
periodically, daily, or even more frequently.


File: manual.info,  Node: replication-administration-status,  Next: replication-administration-pausing,  Prev: replication-administration,  Up: replication-administration

16.1.4.1 Checking Replication Status
....................................

The most common task when managing a replication process is to ensure
that replication is taking place and that there have been no errors
between the slave and the master. The primary statement for this is
*Note `SHOW SLAVE STATUS': show-slave-status, which you must execute on
each slave:


     mysql> SHOW SLAVE STATUS\G
     *************************** 1. row ***************************
                    Slave_IO_State: Waiting for master to send event
                       Master_Host: master1
                       Master_User: root
                       Master_Port: 3306
                     Connect_Retry: 60
                   Master_Log_File: mysql-bin.000004
               Read_Master_Log_Pos: 931
                    Relay_Log_File: slave1-relay-bin.000056
                     Relay_Log_Pos: 950
             Relay_Master_Log_File: mysql-bin.000004
                  Slave_IO_Running: Yes
                 Slave_SQL_Running: Yes
                   Replicate_Do_DB:
               Replicate_Ignore_DB:
                Replicate_Do_Table:
            Replicate_Ignore_Table:
           Replicate_Wild_Do_Table:
       Replicate_Wild_Ignore_Table:
                        Last_Errno: 0
                        Last_Error:
                      Skip_Counter: 0
               Exec_Master_Log_Pos: 931
                   Relay_Log_Space: 1365
                   Until_Condition: None
                    Until_Log_File:
                     Until_Log_Pos: 0
                Master_SSL_Allowed: No
                Master_SSL_CA_File:
                Master_SSL_CA_Path:
                   Master_SSL_Cert:
                 Master_SSL_Cipher:
                    Master_SSL_Key:
             Seconds_Behind_Master: 0
     Master_SSL_Verify_Server_Cert: No
                     Last_IO_Errno: 0
                     Last_IO_Error:
                    Last_SQL_Errno: 0
                    Last_SQL_Error:

The key fields from the status report to examine are:

   * `Slave_IO_State': The current status of the slave. See *Note
     slave-io-thread-states::, and *Note slave-sql-thread-states::, for
     more information.

   * `Slave_IO_Running': Whether the I/O thread for reading the
     master's binary log is running. Normally, you want this to be
     `Yes' unless you have not yet started replication or have
     explicitly stopped it with *Note `STOP SLAVE': stop-slave.

   * `Slave_SQL_Running': Whether the SQL thread for executing events
     in the relay log is running. As with the I/O thread, this should
     normally be `Yes'.

   * `Last_IO_Error', `Last_SQL_Error': The last errors registered by
     the I/O and SQL threads when processing the relay log. Ideally
     these should be blank, indicating no errors.

   * `Seconds_Behind_Master': The number of seconds that the slave SQL
     thread is behind processing the master binary log. A high number
     (or an increasing one) can indicate that the slave is unable to
     handle events from the master in a timely fashion.

     A value of 0 for `Seconds_Behind_Master' can usually be
     interpreted as meaning that the slave has caught up with the
     master, but there are some cases where this is not strictly true.
     For example, this can occur if the network connection between
     master and slave is broken but the slave I/O thread has not yet
     noticed this--that is, `slave_net_timeout' has not yet elapsed.

     It is also possible that transient values for
     `Seconds_Behind_Master' may not reflect the situation accurately.
     When the slave SQL thread has caught up on I/O,
     `Seconds_Behind_Master' displays 0; but when the slave I/O thread
     is still queuing up a new event, `Seconds_Behind_Master' may show a
     large value until the SQL thread finishes executing the new event.
     This is especially likely when the events have old timestamps; in
     such cases, if you execute *Note `SHOW SLAVE STATUS':
     show-slave-status. several times in a relatively short period, you
     may see this value change back and forth repeatedly between 0 and
     a relatively large value.

Several pairs of fields provide information about the progress of the
slave in reading events from the master binary log and processing them
in the relay log:

   * (`Master_Log_file', `Read_Master_Log_Pos'): Coordinates in the
     master binary log indicating how far the slave I/O thread has read
     events from that log.

   * (`Relay_Master_Log_File', `Exec_Master_Log_Pos'): Coordinates in
     the master binary log indicating how far the slave SQL thread has
     executed events received from that log.

   * (`Relay_Log_File', `Relay_Log_Pos'): Coordinates in the slave
     relay log indicating how far the slave SQL thread has executed the
     relay log. These correspond to the preceding coordinates, but are
     expressed in slave relay log coordinates rather than master binary
     log coordinates.

On the master, you can check the status of connected slaves using *Note
`SHOW PROCESSLIST': show-processlist. to examine the list of running
processes. Slave connections have `Binlog Dump' in the `Command' field:


     mysql> SHOW PROCESSLIST \G;
     *************************** 4. row ***************************
          Id: 10
        User: root
        Host: slave1:58371
          db: NULL
     Command: Binlog Dump
        Time: 777
       State: Has sent all binlog to slave; waiting for binlog to be updated
        Info: NULL

Because it is the slave that drives the replication process, very
little information is available in this report.

For slaves that were started with the `--report-host' option and are
connected to the master, the *Note `SHOW SLAVE HOSTS':
show-slave-hosts. statement on the master shows basic information about
the slaves. The output includes the ID of the slave server, the value
of the `--report-host' option, the connecting port, and master ID:


     mysql> SHOW SLAVE HOSTS;
     +-----------+--------+------+-------------------+-----------+
     | Server_id | Host   | Port | Rpl_recovery_rank | Master_id |
     +-----------+--------+------+-------------------+-----------+
     |        10 | slave1 | 3306 |                 0 |         1 |
     +-----------+--------+------+-------------------+-----------+
     1 row in set (0.00 sec)


File: manual.info,  Node: replication-administration-pausing,  Prev: replication-administration-status,  Up: replication-administration

16.1.4.2 Pausing Replication on the Slave
.........................................

You can stop and start the replication of statements on the slave using
the *Note `STOP SLAVE': stop-slave. and *Note `START SLAVE':
start-slave. statements.

To stop processing of the binary log from the master, use *Note `STOP
SLAVE': stop-slave.:


     mysql> STOP SLAVE;

When replication is stopped, the slave I/O thread stops reading events
from the master binary log and writing them to the relay log, and the
SQL thread stops reading events from the relay log and executing them.
You can pause the I/O or SQL thread individually by specifying the
thread type:


     mysql> STOP SLAVE IO_THREAD;
     mysql> STOP SLAVE SQL_THREAD;

To start execution again, use the *Note `START SLAVE': start-slave.
statement:


     mysql> START SLAVE;

To start a particular thread, specify the thread type:


     mysql> START SLAVE IO_THREAD;
     mysql> START SLAVE SQL_THREAD;

For a slave that performs updates only by processing events from the
master, stopping only the SQL thread can be useful if you want to
perform a backup or other task. The I/O thread will continue to read
events from the master but they are not executed. This makes it easier
for the slave to catch up when you restart the SQL thread.

Stopping only the I/O thread enables the events in the relay log to be
executed by the SQL thread up to the point where the relay log ends.
This can be useful when you want to pause execution to catch up with
events already received from the master, when you want to perform
administration on the slave but also ensure that it has processed all
updates to a specific point. This method can also be used to pause
event receipt on the slave while you conduct administration on the
master. Stopping the I/O thread but permitting the SQL thread to run
helps ensure that there is not a massive backlog of events to be
executed when replication is started again.


File: manual.info,  Node: replication-implementation,  Next: replication-solutions,  Prev: replication-configuration,  Up: replication

16.2 Replication Implementation
===============================

* Menu:

* replication-implementation-details::  Replication Implementation Details
* slave-logs::                   Replication Relay and Status Logs
* replication-rules::            How Servers Evaluate Replication Filtering Rules

Replication is based on the master server keeping track of all changes
to its databases (updates, deletes, and so on) in its binary log. The
binary log serves as a written record of all events that modify
database structure or content (data) from the moment the server was
started. Typically, *Note `SELECT': select.  statements are not
recorded because they modify neither database structure nor content.

Each slave that connects to the master requests a copy of the binary
log. That is, it pulls the data from the master, rather than the master
pushing the data to the slave. The slave also executes the events from
the binary log that it receives. This has the effect of repeating the
original changes just as they were made on the master.  Tables are
created or their structure modified, and data is inserted, deleted, and
updated according to the changes that were originally made on the
master.

Because each slave is independent, the replaying of the changes from
the master's binary log occurs independently on each slave that is
connected to the master. In addition, because each slave receives a
copy of the binary log only by requesting it from the master, the slave
is able to read and update the copy of the database at its own pace and
can start and stop the replication process at will without affecting
the ability to update to the latest database status on either the
master or slave side.

For more information on the specifics of the replication
implementation, see *Note replication-implementation-details::.

Masters and slaves report their status in respect of the replication
process regularly so that you can monitor them. See *Note
thread-information::, for descriptions of all replicated-related states.

The master binary log is written to a local relay log on the slave
before it is processed. The slave also records information about the
current position with the master's binary log and the local relay log.
See *Note slave-logs::.

Database changes are filtered on the slave according to a set of rules
that are applied according to the various configuration options and
variables that control event evaluation. For details on how these rules
are applied, see *Note replication-rules::.


File: manual.info,  Node: replication-implementation-details,  Next: slave-logs,  Prev: replication-implementation,  Up: replication-implementation

16.2.1 Replication Implementation Details
-----------------------------------------

MySQL replication capabilities are implemented using three threads, one
on the master server and two on the slave:

   * Binlog dump thread

     The master creates a thread to send the binary log contents to a
     slave when the slave connects. This thread can be identified in
     the output of *Note `SHOW PROCESSLIST': show-processlist. on the
     master as the `Binlog Dump' thread.

     The binlog dump thread acquires a lock on the master's binary log
     for reading each event that is to be sent to the slave. As soon as
     the event has been read, the lock is released, even before the
     event is sent to the slave.

   * Slave I/O thread

     When a *Note `START SLAVE': start-slave. statement is issued on a
     slave server, the slave creates an I/O thread, which connects to
     the master and asks it to send the updates recorded in its binary
     logs.

     The slave I/O thread reads the updates that the master's `Binlog
     Dump' thread sends (see previous item) and copies them to local
     files that comprise the slave's relay log.

     The state of this thread is shown as `Slave_IO_running' in the
     output of *Note `SHOW SLAVE STATUS': show-slave-status. or as
     `Slave_running' in the output of *Note `SHOW STATUS': show-status.

   * Slave SQL thread

     The slave creates an SQL thread to read the relay log that is
     written by the slave I/O thread and execute the events contained
     therein.

In the preceding description, there are three threads per master/slave
connection. A master that has multiple slaves creates one binlog dump
thread for each currently connected slave, and each slave has its own
I/O and SQL threads.

A slave uses two threads to separate reading updates from the master
and executing them into independent tasks. Thus, the task of reading
statements is not slowed down if statement execution is slow. For
example, if the slave server has not been running for a while, its I/O
thread can quickly fetch all the binary log contents from the master
when the slave starts, even if the SQL thread lags far behind. If the
slave stops before the SQL thread has executed all the fetched
statements, the I/O thread has at least fetched everything so that a
safe copy of the statements is stored locally in the slave's relay
logs, ready for execution the next time that the slave starts. This
enables the master server to purge its binary logs sooner because it no
longer needs to wait for the slave to fetch their contents.

The *Note `SHOW PROCESSLIST': show-processlist. statement provides
information that tells you what is happening on the master and on the
slave regarding replication. For information on master states, see
*Note master-thread-states::. For slave states, see *Note
slave-io-thread-states::, and *Note slave-sql-thread-states::.

The following example illustrates how the three threads show up in the
output from *Note `SHOW PROCESSLIST': show-processlist.

On the master server, the output from *Note `SHOW PROCESSLIST':
show-processlist. looks like this:


     mysql> SHOW PROCESSLIST\G
     *************************** 1. row ***************************
          Id: 2
        User: root
        Host: localhost:32931
          db: NULL
     Command: Binlog Dump
        Time: 94
       State: Has sent all binlog to slave; waiting for binlog to
              be updated
        Info: NULL

Here, thread 2 is a `Binlog Dump' replication thread that services a
connected slave. The `State' information indicates that all outstanding
updates have been sent to the slave and that the master is waiting for
more updates to occur. If you see no `Binlog Dump' threads on a master
server, this means that replication is not running; that is, no slaves
are currently connected.

On a slave server, the output from *Note `SHOW PROCESSLIST':
show-processlist. looks like this:


     mysql> SHOW PROCESSLIST\G
     *************************** 1. row ***************************
          Id: 10
        User: system user
        Host:
          db: NULL
     Command: Connect
        Time: 11
       State: Waiting for master to send event
        Info: NULL
     *************************** 2. row ***************************
          Id: 11
        User: system user
        Host:
          db: NULL
     Command: Connect
        Time: 11
       State: Has read all relay log; waiting for the slave I/O
              thread to update it
        Info: NULL

The `State' information indicates that thread 10 is the I/O thread that
is communicating with the master server, and thread 11 is the SQL
thread that is processing the updates stored in the relay logs. At the
time that *Note `SHOW PROCESSLIST': show-processlist. was run, both
threads were idle, waiting for further updates.

The value in the `Time' column can show how late the slave is compared
to the master. See *Note faqs-replication::. If sufficient time elapses
on the master side without activity on the `Binlog Dump' thread, the
master determines that the slave is no longer connected. As for any
other client connection, the timeouts for this depend on the values of
`net_write_timeout' and `net_retry_count'; for more information about
these, see *Note server-system-variables::.

The *Note `SHOW SLAVE STATUS': show-slave-status. statement provides
additional information about replication processing on a slave server.
See *Note replication-administration-status::.


File: manual.info,  Node: slave-logs,  Next: replication-rules,  Prev: replication-implementation-details,  Up: replication-implementation

16.2.2 Replication Relay and Status Logs
----------------------------------------

* Menu:

* slave-logs-relaylog::          The Slave Relay Log
* slave-logs-status::            Slave Status Logs

During replication, a slave server creates several logs that hold the
binary log events relayed from the master to the slave, and to record
information about the current status and location within the relay log.
There are three types of logs used in the process, listed here:

   * The _relay log_ consists of the events read from the binary log of
     the master and written by the slave I/O thread. Events in the
     relay log are executed on the slave as part of the SQL thread.

   * The _master info log_ contains status and current configuration
     information for the slave's connection to the master. This log
     holds information on the master host name, login credentials, and
     coordinates indicating how far the slave has read from the
     master's binary log.

   * The _relay log info log_ holds status information about the
     execution point within the slave's relay log.


File: manual.info,  Node: slave-logs-relaylog,  Next: slave-logs-status,  Prev: slave-logs,  Up: slave-logs

16.2.2.1 The Slave Relay Log
............................

The relay log, like the binary log, consists of a set of numbered files
containing events that describe database changes, and an index file
that contains the names of all used relay log files.

The term `relay log file' generally denotes an individual numbered file
containing database events. The term `relay log' collectively denotes
the set of numbered relay log files plus the index file.

Relay log files have the same format as binary log files and can be
read using *Note `mysqlbinlog': mysqlbinlog. (see *Note mysqlbinlog::).

By default, relay log file names have the form
`HOST_NAME-relay-bin.NNNNNN' in the data directory, where HOST_NAME is
the name of the slave server host and NNNNNN is a sequence number.
Successive relay log files are created using successive sequence
numbers, beginning with `000001'. The slave uses an index file to track
the relay log files currently in use. The default relay log index file
name is `HOST_NAME-relay-bin.index' in the data directory.

The default relay log file and relay log index file names can be
overridden with, respectively, the `--relay-log' and
`--relay-log-index' server options (see *Note replication-options::).

If a slave uses the default host-based relay log file names, changing a
slave's host name after replication has been set up can cause
replication to fail with the errors `Failed to open the relay log' and
`Could not find target log during relay log initialization'. This is a
known issue (see Bug #2122). If you anticipate that a slave's host name
might change in the future (for example, if networking is set up on the
slave such that its host name can be modified using DHCP), you can
avoid this issue entirely by using the `--relay-log' and
`--relay-log-index' options to specify relay log file names explicitly
when you initially set up the slave. This will make the names
independent of server host name changes.

If you encounter the issue after replication has already begun, one way
to work around it is to stop the slave server, prepend the contents of
the old relay log index file to the new one, and then restart the
slave. On a Unix system, this can be done as shown here:


     shell> cat NEW_RELAY_LOG_NAME.index >> OLD_RELAY_LOG_NAME.index
     shell> mv OLD_RELAY_LOG_NAME.index NEW_RELAY_LOG_NAME.index

A slave server creates a new relay log file under the following
conditions:

   * Each time the I/O thread starts.

   * When the logs are flushed; for example, with *Note `FLUSH LOGS':
     flush.  or *Note `mysqladmin flush-logs': mysqladmin.

   * When the size of the current relay log file becomes `too large,'
     determined as follows:

        * If the value of `max_relay_log_size' is greater than 0, that
          is the maximum relay log file size.

        * If the value of `max_relay_log_size' is 0, `max_binlog_size'
          determines the maximum relay log file size.

The SQL thread automatically deletes each relay log file as soon as it
has executed all events in the file and no longer needs it. There is no
explicit mechanism for deleting relay logs because the SQL thread takes
care of doing so. However, *Note `FLUSH LOGS': flush.  rotates relay
logs, which influences when the SQL thread deletes them.


File: manual.info,  Node: slave-logs-status,  Prev: slave-logs-relaylog,  Up: slave-logs

16.2.2.2 Slave Status Logs
..........................

A replication slave server creates two logs. By default, these logs are
files named `master.info' and `relay-log.info' and created in the data
directory. The names and locations of these files can be changed by
using the `--master-info-file' and `--relay-log-info-file' options,
respectively. See *Note replication-options::.

The two status logs contain information like that shown in the output
of the *Note `SHOW SLAVE STATUS': show-slave-status.  statement, which
is discussed in *Note replication-slave-sql::. Because the status logs
are stored on disk, they survive a slave server's shutdown.  The next
time the slave starts up, it reads the two logs to determine how far it
has proceeded in reading binary logs from the master and in processing
its own relay logs.

The master info log should be protected because it contains the
password for connecting to the master. See *Note password-logging::.

The slave I/O thread updates the master info log. The following table
shows the correspondence between the lines in the `master.info' file
and the columns displayed by *Note `SHOW SLAVE STATUS':
show-slave-status.

This table shows the correspondence between the lines in the
`master.info' file and the columns displayed by *Note `SHOW SLAVE
STATUS': show-slave-status.

Line in     `SHOW SLAVE STATUS' Column    Description
`master.info'                              
1                                         Number of lines in the file
2           `Master_Log_File'             The name of the master binary
                                          log currently being read from
                                          the master
3           `Read_Master_Log_Pos'         The current position within the
                                          master binary log that have
                                          been read from the master
4           `Master_Host'                 The host name of the master
5           `Master_User'                 The user name used to connect
                                          to the master
6           Password (not shown by *Note  The password used to connect to
            `SHOW SLAVE STATUS':          the master
            show-slave-status.)           
7           `Master_Port'                 The network port used to
                                          connect to the master
8           `Connect_Retry'               The period (in seconds) that
                                          the slave will wait before
                                          trying to reconnect to the
                                          master
9           `Master_SSL_Allowed'          Indicates whether the server
                                          supports SSL connections
10          `Master_SSL_CA_File'          The file used for the
                                          Certificate Authority (CA)
                                          certificate
11          `Master_SSL_CA_Path'          The path to the Certificate
                                          Authority (CA) certificates
12          `Master_SSL_Cert'             The name of the SSL certificate
                                          file
13          `Master_SSL_Cipher'           The list of possible ciphers
                                          used in the handshake for the
                                          SSL connection
14          `Master_SSL_Key'              The name of the SSL key file
15          `Master_SSL_Verify_Server_Cert'Whether to verify the server
                                          certificate (added in MySQL
                                          5.1.18)

The slave SQL thread updates the relay log info log. The following
table shows the correspondence between the lines in the
`relay-log.info' file and the columns displayed by *Note `SHOW SLAVE
STATUS': show-slave-status.

This table shows the correspondence between the lines in the
`relay-log.info' file and the columns displayed by *Note `SHOW SLAVE
STATUS': show-slave-status.

Line in     `SHOW SLAVE STATUS'       Description
`relay-log.info'Column                    
1           `Relay_Log_File'          The name of the current relay log
                                      file
2           `Relay_Log_Pos'           The current position within the
                                      relay log file; events up to this
                                      position have been executed on the
                                      slave database
3           `Relay_Master_Log_File'   The name of the master binary log
                                      file from which the events in the
                                      relay log file were read
4           `Exec_Master_Log_Pos'     The equivalent position within the
                                      master's binary log file of events
                                      that have already been executed

The contents of the `relay-log.info' file and the states shown by the
*Note `SHOW SLAVE STATUS': show-slave-status. statement might not match
if the `relay-log.info' file has not been flushed to disk. Ideally, you
should only view `relay-log.info' on a slave that is offline (that is,
`mysqld' is not running). For a running system, *Note `SHOW SLAVE
STATUS': show-slave-status.  should be used.

When you back up the slave's data, you should back up these two status
logs, along with the relay log files. The status logs are needed to
resume replication after you restore the data from the slave. If you
lose the relay logs but still have the relay log info log, you can
check it to determine how far the SQL thread has executed in the master
binary logs. Then you can use *Note `CHANGE MASTER TO':
change-master-to. with the `MASTER_LOG_FILE' and `MASTER_LOG_POS'
options to tell the slave to re-read the binary logs from that point.
Of course, this requires that the binary logs still exist on the master.


File: manual.info,  Node: replication-rules,  Prev: slave-logs,  Up: replication-implementation

16.2.3 How Servers Evaluate Replication Filtering Rules
-------------------------------------------------------

* Menu:

* replication-rules-db-options::  Evaluation of Database-Level Replication and Binary Logging Options
* replication-rules-table-options::  Evaluation of Table-Level Replication Options
* replication-rules-examples::   Replication Rule Application

If a master server does not write a statement to its binary log, the
statement is not replicated. If the server does log the statement, the
statement is sent to all slaves and each slave determines whether to
execute it or ignore it.

On the master, you can control which databases to log changes for by
using the `--binlog-do-db' and `--binlog-ignore-db' options to control
binary logging. For a description of the rules that servers use in
evaluating these options, see *Note replication-rules-db-options::. You
should not use these options to control which databases and tables are
replicated. Instead, use filtering on the slave to control the events
that are executed on the slave.

On the slave side, decisions about whether to execute or ignore
statements received from the master are made according to the
`--replicate-*' options that the slave was started with. (See *Note
replication-options::.)

In the simplest case, when there are no `--replicate-*' options, the
slave executes all statements that it receives from the master.
Otherwise, the result depends on the particular options given.

Database-level options (`--replicate-do-db', `--replicate-ignore-db')
are checked first; see *Note replication-rules-db-options::, for a
description of this process. If no database-level options are used,
option checking proceeds to any table-level options that may be in use
(see *Note replication-rules-table-options::, for a discussion of
these). If one or more database-level options are used but none are
matched, the statement is not replicated.

To make it easier to determine what effect an option set will have, it
is recommended that you avoid mixing `do' and `ignore' options, or
wildcard and nonwildcard options. An example of the latter that may
have unintended effects is the use of `--replicate-do-db' and
`--replicate-wild-do-table' together, where `--replicate-wild-do-table'
uses a pattern for the database name that matches the name given for
`--replicate-do-db'. Suppose a replication slave is started with
`--replicate-do-db=dbx' `--replicate-wild-do-table=db%.t1'.  Then,
suppose that on the master, you issue the statement *Note `CREATE
DATABASE dbx': create-database. Although you might expect it, this
statement is not replicated because it does not reference a table named
`t1'.

If any `--replicate-rewrite-db' options were specified, they are
applied before the `--replicate-*' filtering rules are tested.

*Note*:

In MySQL 5.1, database-level filtering options are case-sensitive on
platforms supporting case sensitivity in filenames, whereas table-level
filtering options are not (regardless of platform). This is true
regardless of the value of the `lower_case_table_names' system
variable. These are known issues which are fixed in MySQL 5.5.


File: manual.info,  Node: replication-rules-db-options,  Next: replication-rules-table-options,  Prev: replication-rules,  Up: replication-rules

16.2.3.1 Evaluation of Database-Level Replication and Binary Logging Options
............................................................................

When evaluating replication options, the slave begins by checking to
see whether there are any `--replicate-do-db' or
`--replicate-ignore-db' options that apply. When using `--binlog-do-db'
or `--binlog-ignore-db', the process is similar, but the options are
checked on the master.

With statement-based replication, the default database is checked for a
match. With row-based replication, the database where data is to be
changed is the database that is checked.  Regardless of the binary
logging format, checking of database-level options proceeds as shown in
the following diagram.

Evaluation of Database-Level Filtering Rules in Replication

The steps involved are listed here:

  1. Are there any `--replicate-do-db' options?

        * Yes

          Do any of them match the database?

             * Yes

               Execute the statement and exit.

             * No

               Ignore the statement and exit.

        * No

          Continue to step 2.

  2. Are there any `--replicate-ignore-db' options?

        * Yes

          Do any of them match the database?

             * Yes

               Ignore the statement and exit.

             * No

               Continue to step 3.

        * No

          Continue to step 3.

  3. Proceed to checking the table-level replication options, if there
     are any. For a description of how these options are checked, see
     *Note replication-rules-table-options::.

     *Important*:

     A statement that is still permitted at this stage is not yet
     actually executed. The statement is not executed until all
     table-level options (if any) have also been checked, and the
     outcome of that process permits execution of the statement.

For binary logging, the steps involved are listed here:

  1. Are there any `--binlog-do-db' or `--binlog-ignore-db' options?

        * Yes

          Continue to step 2.

        * No

          Log the statement and exit.

  2. Is there a default database (has any database been selected by
     *Note `USE': use.)?

        * Yes

          Continue to step 3.

        * No

          Ignore the statement and exit.

  3. There is a default database. Are there any `--binlog-do-db'
     options?

        * Yes

          Do any of them match the database?

             * Yes

               Log the statement and exit.

             * No

               Ignore the statement and exit.

        * No

          Continue to step 4.

  4. Do any of the `--binlog-ignore-db' options match the database?

        * Yes

          Ignore the statement and exit.

        * No

          Log the statement and exit.

*Important*:

For statement-based logging, an exception is made in the rules just
given for the *Note `CREATE DATABASE': create-database, *Note `ALTER
DATABASE': alter-database, and *Note `DROP DATABASE': drop-database.
statements. In those cases, the database being _created, altered, or
dropped_ replaces the default database when determining whether to log
or ignore updates.

`--binlog-do-db' can sometimes mean `ignore other databases'. For
example, when using statement-based logging, a server running with only
`--binlog-do-db=sales' does not write to the binary log statements for
which the default database differs from `sales'. When using row-based
logging with the same option, the server logs only those updates that
change data in `sales'.


File: manual.info,  Node: replication-rules-table-options,  Next: replication-rules-examples,  Prev: replication-rules-db-options,  Up: replication-rules

16.2.3.2 Evaluation of Table-Level Replication Options
......................................................

The slave checks for and evaluates table options only if either of the
following two conditions is true:

   * No matching database options were found.

   * One or more database options were found, and were evaluated to
     arrive at an `execute' condition according to the rules described
     in the previous section (see *Note replication-rules-db-options::).

First, as a preliminary condition, the slave checks whether
statement-based replication is enabled. If so, and the statement occurs
within a stored function, the slave executes the statement and exits.
If row-based replication is enabled, the slave does not know whether a
statement occurred within a stored function on the master, so this
condition does not apply.

*Note*:

For statement-based replication, replication events represent
statements (all changes making up a given event are associated with a
single SQL statement); for row-based replication, each event represents
a change in a single table row (thus a single statement such as `UPDATE
mytable SET mycol = 1' may yield many row-based events). When viewed in
terms of events, the process of checking table options is the same for
both row-based and statement-based replication.

Having reached this point, if there are no table options, the slave
simply executes all events. If there are any `--replicate-do-table' or
`--replicate-wild-do-table' options, the event must match one of these
if it is to be executed; otherwise, it is ignored. If there are any
`--replicate-ignore-table' or `--replicate-wild-ignore-table' options,
all events are executed except those that match any of these options.
This process is illustrated in the following diagram.

Evaluation of Table-Level Filtering Rules in Replication

The following steps describe this evaluation in more detail:

  1. Are there any table options?

        * Yes

          Continue to step 2.

        * No

          Execute the event and exit.

  2. Are there any `--replicate-do-table' options?

        * Yes

          Does the table match any of them?

             * Yes

               Execute the event and exit.

             * No

               Continue to step 3.

        * No

          Continue to step 3.

  3. Are there any `--replicate-ignore-table' options?

        * Yes

          Does the table match any of them?

             * Yes

               Ignore the event and exit.

             * No

               Continue to step 4.

        * No

          Continue to step 4.

  4. Are there any `--replicate-wild-do-table' options?

        * Yes

          Does the table match any of them?

             * Yes

               Execute the event and exit.

             * No

               Continue to step 5.

        * No

          Continue to step 5.

  5. Are there any `--replicate-wild-ignore-table' options?

        * Yes

          Does the table match any of them?

             * Yes

               Ignore the event and exit.

             * No

               Continue to step 6.

        * No

          Continue to step 6.

  6. Are there any `--replicate-do-table' or `--replicate-wild-do-table'
     options?

        * Yes

          Ignore the event and exit.

        * No

          Execute the event and exit.


File: manual.info,  Node: replication-rules-examples,  Prev: replication-rules-table-options,  Up: replication-rules

16.2.3.3 Replication Rule Application
.....................................

This section provides additional explanation and examples of usage for
different combinations of replication filtering options.

Some typical combinations of replication filter rule types are given in
the following table:

This table shows typical combinations of replication filter rule types
and describes the outcome of each.

Condition (Types of Options)  Outcome
No `--replicate-*' options    The slave executes all events that it
at all:                       receives from the master.
`--replicate-*-db' options,   The slave accepts or ignores events using
but no table options:         the database options. It executes all
                              events permitted by those options because
                              there are no table restrictions.
`--replicate-*-table'         All events are accepted at the
options, but no database      database-checking stage because there are
options:                      no database conditions. The slave executes
                              or ignores events based solely on the
                              table options.
A combination of database     The slave accepts or ignores events using
and table options:            the database options. Then it evaluates
                              all events permitted by those options
                              according to the table options. This can
                              sometimes lead to results that seem
                              counterintuitive, and that may be
                              different depending on whether you are
                              using statement-based or row-based
                              replication; see the text for an example.

A more complex example follows, in which we examine the outcomes for
both statement-based and row-based settings.

Suppose that we have two tables `mytbl1' in database `db1' and `mytbl2'
in database `db2' on the master, and the slave is running with the
following options (and no other replication filtering options):


     replicate-ignore-db = db1
     replicate-do-table  = db2.tbl2

Now we execute the following statements on the master:


     USE db1;
     INSERT INTO db2.tbl2 VALUES (1);

The results on the slave vary considerably depending on the binary log
format, and may not match initial expectations in either case.

Statement-based replication

The `USE' statement causes `db1' to be the default database. Thus the
`--replicate-ignore-db' option matches, _and the *Note `INSERT':
insert. statement is ignored_. The table options are not checked.

Row-based replication

The default database has no effect on how the slave reads database
options when using row-based replication. Thus, the *Note `USE': use.
statement makes no difference in how the `--replicate-ignore-db' option
is handled: the database specified by this option does not match the
database where the *Note `INSERT': insert.  statement changes data, so
the slave proceeds to check the table options. The table specified by
`--replicate-do-table' matches the table to be updated, _and the row is
inserted_.


File: manual.info,  Node: replication-solutions,  Next: replication-notes,  Prev: replication-implementation,  Up: replication

16.3 Replication Solutions
==========================

* Menu:

* replication-solutions-backups::  Using Replication for Backups
* replication-solutions-diffengines::  Using Replication with Different Master and Slave Storage Engines
* replication-solutions-scaleout::  Using Replication for Scale-Out
* replication-solutions-partitioning::  Replicating Different Databases to Different Slaves
* replication-solutions-performance::  Improving Replication Performance
* replication-solutions-switch::  Switching Masters During Failover
* replication-solutions-ssl::    Setting Up Replication Using SSL

Replication can be used in many different environments for a range of
purposes. This section provides general notes and advice on using
replication for specific solution types.

For information on using replication in a backup environment, including
notes on the setup, backup procedure, and files to back up, see *Note
replication-solutions-backups::.

For advice and tips on using different storage engines on the master
and slaves, see *Note replication-solutions-diffengines::.

Using replication as a scale-out solution requires some changes in the
logic and operation of applications that use the solution. See *Note
replication-solutions-scaleout::.

For performance or data distribution reasons, you may want to replicate
different databases to different replication slaves. See *Note
replication-solutions-partitioning::

As the number of replication slaves increases, the load on the master
can increase and lead to reduced performance (because of the need to
replicate the binary log to each slave). For tips on improving your
replication performance, including using a single secondary server as
an replication master, see *Note replication-solutions-performance::.

For guidance on switching masters, or converting slaves into masters as
part of an emergency failover solution, see *Note
replication-solutions-switch::.

To secure your replication communication, you can use SSL to encrypt
the communication channel. For step-by-step instructions, see *Note
replication-solutions-ssl::.


File: manual.info,  Node: replication-solutions-backups,  Next: replication-solutions-diffengines,  Prev: replication-solutions,  Up: replication-solutions

16.3.1 Using Replication for Backups
------------------------------------

* Menu:

* replication-solutions-backups-mysqldump::  Backing Up a Slave Using mysqldump
* replication-solutions-backups-rawdata::  Backing Up Raw Data from a Slave
* replication-solutions-backups-read-only::  Backing Up a Master or Slave by Making It Read Only

To use replication as a backup solution, replicate data from the master
to a slave, and then back up the data slave. The slave can be paused
and shut down without affecting the running operation of the master, so
you can produce an effective snapshot of `live' data that would
otherwise require the master to be shut down.

How you back up a database depends on its size and whether you are
backing up only the data, or the data and the replication slave state
so that you can rebuild the slave in the event of failure.  There are
therefore two choices:

   * If you are using replication as a solution to enable you to back
     up the data on the master, and the size of your database is not
     too large, the *Note `mysqldump': mysqldump. tool may be suitable.
     See *Note replication-solutions-backups-mysqldump::.

   * For larger databases, where *Note `mysqldump': mysqldump. would be
     impractical or inefficient, you can back up the raw data files
     instead. Using the raw data files option also means that you can
     back up the binary and relay logs that will enable you to recreate
     the slave in the event of a slave failure. For more information,
     see *Note replication-solutions-backups-rawdata::.

Another backup strategy, which can be used for either master or slave
servers, is to put the server in a read-only state. The backup is
performed against the read-only server, which then is changed back to
its usual read/write operational status. See *Note
replication-solutions-backups-read-only::.


File: manual.info,  Node: replication-solutions-backups-mysqldump,  Next: replication-solutions-backups-rawdata,  Prev: replication-solutions-backups,  Up: replication-solutions-backups

16.3.1.1 Backing Up a Slave Using mysqldump
...........................................

Using *Note `mysqldump': mysqldump. to create a copy of a database
enables you to capture all of the data in the database in a format that
enables the information to be imported into another instance of MySQL
Server (see *Note mysqldump::). Because the format of the information
is SQL statements, the file can easily be distributed and applied to
running servers in the event that you need access to the data in an
emergency. However, if the size of your data set is very large, *Note
`mysqldump': mysqldump. may be impractical.

When using *Note `mysqldump': mysqldump, you should stop replication on
the slave before starting the dump process to ensure that the dump
contains a consistent set of data:

  1. Stop the slave from processing requests. You can stop replication
     completely on the slave using *Note `mysqladmin': mysqladmin.:

          shell> mysqladmin stop-slave

     Alternatively, you can stop only the slave SQL thread to pause
     event execution:

          shell> mysql -e 'STOP SLAVE SQL_THREAD;'

     This enables the slave to continue to receive data change events
     from the master's binary log and store them in the relay logs
     using the I/O thread, but prevents the slave from executing these
     events and changing its data. Within busy replication
     environments, permitting the I/O thread to run during backup may
     speed up the catch-up process when you restart the slave SQL
     thread.

  2. Run *Note `mysqldump': mysqldump. to dump your databases. You may
     either dump all databases or select databases to be dumped. For
     example, to dump all databases:

          shell> mysqldump --all-databases > fulldb.dump

  3. Once the dump has completed, start slave operations again:

          shell> mysqladmin start-slave

In the preceding example, you may want to add login credentials (user
name, password) to the commands, and bundle the process up into a
script that you can run automatically each day.

If you use this approach, make sure you monitor the slave replication
process to ensure that the time taken to run the backup does not affect
the slave's ability to keep up with events from the master. See *Note
replication-administration-status::. If the slave is unable to keep up,
you may want to add another slave and distribute the backup process.
For an example of how to configure this scenario, see *Note
replication-solutions-partitioning::.


File: manual.info,  Node: replication-solutions-backups-rawdata,  Next: replication-solutions-backups-read-only,  Prev: replication-solutions-backups-mysqldump,  Up: replication-solutions-backups

16.3.1.2 Backing Up Raw Data from a Slave
.........................................

To guarantee the integrity of the files that are copied, backing up the
raw data files on your MySQL replication slave should take place while
your slave server is shut down. If the MySQL server is still running,
background tasks may still be updating the database files, particularly
those involving storage engines with background processes such as
`InnoDB'.  With `InnoDB', these problems should be resolved during
crash recovery, but since the slave server can be shut down during the
backup process without affecting the execution of the master it makes
sense to take advantage of this capability.

To shut down the server and back up the files:

  1. Shut down the slave MySQL server:

          shell> mysqladmin shutdown

  2. Copy the data files. You can use any suitable copying or archive
     utility, including `cp', `tar' or `WinZip'. For example, assuming
     that the data directory is located under the current directory,
     you can archive the entire directory as follows:

          shell> tar cf /tmp/dbbackup.tar ./data

  3. Start the MySQL server again. Under Unix:

          shell> mysqld_safe &

     Under Windows:

          C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld"

Normally you should back up the entire data directory for the slave
MySQL server. If you want to be able to restore the data and operate as
a slave (for example, in the event of failure of the slave), then in
addition to the slave's data, you should also back up the slave status
files, `master.info' and `relay-log.info', along with the relay log
files. These files are needed to resume replication after you restore
the slave's data.

If you lose the relay logs but still have the `relay-log.info' file,
you can check it to determine how far the SQL thread has executed in
the master binary logs. Then you can use *Note `CHANGE MASTER TO':
change-master-to. with the `MASTER_LOG_FILE' and `MASTER_LOG_POS'
options to tell the slave to re-read the binary logs from that point.
This requires that the binary logs still exist on the master server.

If your slave is replicating *Note `LOAD DATA INFILE': load-data.
statements, you should also back up any `SQL_LOAD-*' files that exist
in the directory that the slave uses for this purpose. The slave needs
these files to resume replication of any interrupted *Note `LOAD DATA
INFILE': load-data. operations. The location of this directory is the
value of the `--slave-load-tmpdir' option. If the server was not
started with that option, the directory location is the value of the
`tmpdir' system variable.


File: manual.info,  Node: replication-solutions-backups-read-only,  Prev: replication-solutions-backups-rawdata,  Up: replication-solutions-backups

16.3.1.3 Backing Up a Master or Slave by Making It Read Only
............................................................

It is possible to back up either master or slave servers in a
replication setup by acquiring a global read lock and manipulating the
`read_only' system variable to change the read-only state of the server
to be backed up:

  1. Make the server read-only, so that it processes only retrievals
     and blocks updates.

  2. Perform the backup.

  3. Change the server back to its normal read/write state.

*Note*:

The instructions in this section place the server to be backed up in a
state that is safe for backup methods that get the data from the
server, such as *Note `mysqldump': mysqldump.  (see *Note mysqldump::).
You should not attempt to use these instructions to make a binary
backup by copying files directly because the server may still have
modified data cached in memory and not flushed to disk.

These instructions also require MySQL 5.1.15 or higher. For earlier
versions, setting `read_only' does not block while table locks or
outstanding transactions are pending, so data changes can still occur
during the backup operation and produce inconsistent backup results.

The following instructions describe how to do this for a master server
and for a slave server. For both scenarios discussed here, suppose that
you have the following replication setup:

   * A master server M1

   * A slave server S1 that has M1 as its master

   * A client C1 connected to M1

   * A client C2 connected to S1

In either scenario, the statements to acquire the global read lock and
manipulate the `read_only' variable are performed on the server to be
backed up and do not propagate to any slaves of that server.

*Scenario 1: Backup with a Read-Only Master*

Put the master M1 in a read-only state by executing these statements on
it:


     mysql> FLUSH TABLES WITH READ LOCK;
     mysql> SET GLOBAL read_only = ON;

While M1 is in a read-only state, the following properties are true:

   * Requests for updates sent by C1 to M1 will block because the
     server is in read-only mode.

   * Requests for query results sent by C1 to M1 will succeed.

   * Making a backup on M1 is safe.

   * Making a backup on S1 is not safe. This server is still running,
     and might be processing the binary log or update requests coming
     from client C2

While M1 is read only, perform the backup. For example, you can use
*Note `mysqldump': mysqldump.

After the backup operation on M1 completes, restore M1 to its normal
operational state by executing these statements:


     mysql> SET GLOBAL read_only = OFF;
     mysql> UNLOCK TABLES;

Although performing the backup on M1 is safe (as far as the backup is
concerned), it is not optimal for performance because clients of M1 are
blocked from executing updates.

This strategy applies to backing up a master server in a replication
setup, but can also be used for a single server in a nonreplication
setting.

*Scenario 2: Backup with a Read-Only Slave*

Put the slave S1 in a read-only state by executing these statements on
it:


     mysql> FLUSH TABLES WITH READ LOCK;
     mysql> SET GLOBAL read_only = ON;

While S1 is in a read-only state, the following properties are true:

   * The master M1 will continue to operate, so making a backup on the
     master is not safe.

   * The slave S1 is stopped, so making a backup on the slave S1 is
     safe.

These properties provide the basis for a popular backup scenario:
Having one slave busy performing a backup for a while is not a problem
because it does not affect the entire network, and the system is still
running during the backup. In particular, clients can still perform
updates on the master server, which remains unaffected by backup
activity on the slave.

While S1 is read only, perform the backup. For example, you can use
*Note `mysqldump': mysqldump.

After the backup operation on S1 completes, restore S1 to its normal
operational state by executing these statements:


     mysql> SET GLOBAL read_only = OFF;
     mysql> UNLOCK TABLES;

After the slave is restored to normal operation, it again synchronizes
to the master by catching up with any outstanding updates from the
binary log of the master.


File: manual.info,  Node: replication-solutions-diffengines,  Next: replication-solutions-scaleout,  Prev: replication-solutions-backups,  Up: replication-solutions

16.3.2 Using Replication with Different Master and Slave Storage Engines
------------------------------------------------------------------------

It does not matter for the replication process whether the source table
on the master and the replicated table on the slave use different
engine types. In fact, the system variables `storage_engine' and
`table_type' are not replicated.

This provides a number of benefits in the replication process in that
you can take advantage of different engine types for different
replication scenarios. For example, in a typical scale-out scenario (see
*Note replication-solutions-scaleout::), you want to use `InnoDB'
tables on the master to take advantage of the transactional
functionality, but use `MyISAM' on the slaves where transaction support
is not required because the data is only read. When using replication
in a data-logging environment you may want to use the `Archive' storage
engine on the slave.

Configuring different engines on the master and slave depends on how
you set up the initial replication process:

   * If you used *Note `mysqldump': mysqldump. to create the database
     snapshot on your master, you could edit the dump file text to
     change the engine type used on each table.

     Another alternative for *Note `mysqldump': mysqldump. is to
     disable engine types that you do not want to use on the slave
     before using the dump to build the data on the slave. For example,
     you can add the `--skip-innodb' option on your slave to disable
     the `InnoDB' engine. If a specific engine does not exist for a
     table to be created, MySQL will use the default engine type,
     usually `MyISAM'. (This requires that the `NO_ENGINE_SUBSTITUTION'
     SQL mode is not enabled.) If you want to disable additional
     engines in this way, you may want to consider building a special
     binary to be used on the slave that only supports the engines you
     want.

   * If you are using raw data files (a binary backup) to set up the
     slave, you will be unable to change the initial table format.
     Instead, use *Note `ALTER TABLE': alter-table. to change the table
     types after the slave has been started.

   * For new master/slave replication setups where there are currently
     no tables on the master, avoid specifying the engine type when
     creating new tables.

If you are already running a replication solution and want to convert
your existing tables to another engine type, follow these steps:

  1. Stop the slave from running replication updates:


          mysql> STOP SLAVE;

     This will enable you to change engine types without interruptions.

  2. Execute an `ALTER TABLE ...  ENGINE='ENGINE_TYPE'' for each table
     to be changed.

  3. Start the slave replication process again:


          mysql> START SLAVE;

Although the `storage_engine' and `table_type' variables are not
replicated, be aware that *Note `CREATE TABLE': create-table. and *Note
`ALTER TABLE': alter-table.  statements that include the engine
specification will be correctly replicated to the slave. For example,
if you have a CSV table and you execute:


     mysql> ALTER TABLE csvtable Engine='MyISAM';

The above statement will be replicated to the slave and the engine type
on the slave will be converted to `MyISAM', even if you have previously
changed the table type on the slave to an engine other than CSV. If you
want to retain engine differences on the master and slave, you should
be careful to use the `storage_engine' variable on the master when
creating a new table. For example, instead of:


     mysql> CREATE TABLE tablea (columna int) Engine=MyISAM;

Use this format:


     mysql> SET storage_engine=MyISAM;
     mysql> CREATE TABLE tablea (columna int);

When replicated, the `storage_engine' variable will be ignored, and the
*Note `CREATE TABLE': create-table.  statement will execute on the
slave using the slave's default engine.


File: manual.info,  Node: replication-solutions-scaleout,  Next: replication-solutions-partitioning,  Prev: replication-solutions-diffengines,  Up: replication-solutions

16.3.3 Using Replication for Scale-Out
--------------------------------------

You can use replication as a scale-out solution; that is, where you
want to split up the load of database queries across multiple database
servers, within some reasonable limitations.

Because replication works from the distribution of one master to one or
more slaves, using replication for scale-out works best in an
environment where you have a high number of reads and low number of
writes/updates. Most Web sites fit into this category, where users are
browsing the Web site, reading articles, posts, or viewing products.
Updates only occur during session management, or when making a purchase
or adding a comment/message to a forum.

Replication in this situation enables you to distribute the reads over
the replication slaves, while still enabling your web servers to
communicate with the replication master when a write is required. You
can see a sample replication layout for this scenario in *Note
figure_replication-scaleout::.

FIGURE GOES HERE: Using Replication to Improve Performance During
Scale-Out

If the part of your code that is responsible for database access has
been properly abstracted/modularized, converting it to run with a
replicated setup should be very smooth and easy. Change the
implementation of your database access to send all writes to the
master, and to send reads to either the master or a slave. If your code
does not have this level of abstraction, setting up a replicated system
gives you the opportunity and motivation to clean it up. Start by
creating a wrapper library or module that implements the following
functions:

   * `safe_writer_connect()'

   * `safe_reader_connect()'

   * `safe_reader_statement()'

   * `safe_writer_statement()'

`safe_' in each function name means that the function takes care of
handling all error conditions. You can use different names for the
functions. The important thing is to have a unified interface for
connecting for reads, connecting for writes, doing a read, and doing a
write.

Then convert your client code to use the wrapper library. This may be a
painful and scary process at first, but it pays off in the long run.
All applications that use the approach just described are able to take
advantage of a master/slave configuration, even one involving multiple
slaves. The code is much easier to maintain, and adding troubleshooting
options is trivial. You need modify only one or two functions; for
example, to log how long each statement took, or which statement among
those issued gave you an error.

If you have written a lot of code, you may want to automate the
conversion task by using the *Note `replace': replace-utility. utility
that comes with standard MySQL distributions, or write your own
conversion script. Ideally, your code uses consistent programming style
conventions. If not, then you are probably better off rewriting it
anyway, or at least going through and manually regularizing it to use a
consistent style.


File: manual.info,  Node: replication-solutions-partitioning,  Next: replication-solutions-performance,  Prev: replication-solutions-scaleout,  Up: replication-solutions

16.3.4 Replicating Different Databases to Different Slaves
----------------------------------------------------------

There may be situations where you have a single master and want to
replicate different databases to different slaves. For example, you may
want to distribute different sales data to different departments to
help spread the load during data analysis. A sample of this layout is
shown in *Note figure_replication-multi-db::.

FIGURE GOES HERE: Using Replication to Replicate Databases to Separate
Replication Slaves

You can achieve this separation by configuring the master and slaves as
normal, and then limiting the binary log statements that each slave
processes by using the `--replicate-wild-do-table' configuration option
on each slave.

*Important*:

You should _not_ use `--replicate-do-db' for this purpose when using
statement-based replication, since statement-based replication causes
this option's affects to vary according to the database that is
currently selected. This applies to mixed-format replication as well,
since this enables some updates to be replicated using the
statement-based format.

However, it should be safe to use `--replicate-do-db' for this purpose
if you are using row-based replication only, since in this case the
currently selected database has no effect on the option's operation.

For example, to support the separation as shown in *Note
figure_replication-multi-db::, you should configure each replication
slave as follows, before executing *Note `START SLAVE': start-slave.:

   * Replication slave 1 should use
     `--replicate-wild-do-table=databaseA.%'.

   * Replication slave 2 should use
     `--replicate-wild-do-table=databaseB.%'.

   * Replication slave 3 should use
     `--replicate-wild-do-table=databaseC.%'.

Each slave in this configuration receives the entire binary log from
the master, but executes only those events from the binary log that
apply to the databases and tables included by the
`--replicate-wild-do-table' option in effect on that slave.

If you have data that must be synchronized to the slaves before
replication starts, you have a number of choices:

   * Synchronize all the data to each slave, and delete the databases,
     tables, or both that you do not want to keep.

   * Use *Note `mysqldump': mysqldump. to create a separate dump file
     for each database and load the appropriate dump file on each slave.

   * Use a raw data file dump and include only the specific files and
     databases that you need for each slave.

     *Note*:

     This does not work with *Note `InnoDB': innodb-storage-engine.
     databases unless you use `innodb_file_per_table'.


File: manual.info,  Node: replication-solutions-performance,  Next: replication-solutions-switch,  Prev: replication-solutions-partitioning,  Up: replication-solutions

16.3.5 Improving Replication Performance
----------------------------------------

As the number of slaves connecting to a master increases, the load,
although minimal, also increases, as each slave uses a client
connection to the master. Also, as each slave must receive a full copy
of the master binary log, the network load on the master may also
increase and create a bottleneck.

If you are using a large number of slaves connected to one master, and
that master is also busy processing requests (for example, as part of a
scale-out solution), then you may want to improve the performance of
the replication process.

One way to improve the performance of the replication process is to
create a deeper replication structure that enables the master to
replicate to only one slave, and for the remaining slaves to connect to
this primary slave for their individual replication requirements. A
sample of this structure is shown in *Note
figure_replication-performance::.

FIGURE GOES HERE: Using an Additional Replication Host to Improve
Performance

For this to work, you must configure the MySQL instances as follows:

   * Master 1 is the primary master where all changes and updates are
     written to the database. Binary logging should be enabled on this
     machine.

   * Master 2 is the slave to the Master 1 that provides the
     replication functionality to the remainder of the slaves in the
     replication structure. Master 2 is the only machine permitted to
     connect to Master 1. Master 2 also has binary logging enabled, and
     the `--log-slave-updates' option so that replication instructions
     from Master 1 are also written to Master 2's binary log so that
     they can then be replicated to the true slaves.

   * Slave 1, Slave 2, and Slave 3 act as slaves to Master 2, and
     replicate the information from Master 2, which actually consists
     of the upgrades logged on Master 1.

The above solution reduces the client load and the network interface
load on the primary master, which should improve the overall
performance of the primary master when used as a direct database
solution.

If your slaves are having trouble keeping up with the replication
process on the master, there are a number of options available:

   * If possible, put the relay logs and the data files on different
     physical drives. To do this, use the `--relay-log' option to
     specify the location of the relay log.

   * If the slaves are significantly slower than the master, you may
     want to divide up the responsibility for replicating different
     databases to different slaves. See *Note
     replication-solutions-partitioning::.

   * If your master makes use of transactions and you are not concerned
     about transaction support on your slaves, use `MyISAM' or another
     nontransactional engine on the slaves. See *Note
     replication-solutions-diffengines::.

   * If your slaves are not acting as masters, and you have a potential
     solution in place to ensure that you can bring up a master in the
     event of failure, then you can switch off `--log-slave-updates'.
     This prevents `dumb' slaves from also logging events they have
     executed into their own binary log.


File: manual.info,  Node: replication-solutions-switch,  Next: replication-solutions-ssl,  Prev: replication-solutions-performance,  Up: replication-solutions

16.3.6 Switching Masters During Failover
----------------------------------------

There is in MySQL 5.1 no official solution for providing failover
between master and slaves in the event of a failure. Instead, you must
set up a master and one or more slaves; then, you need to write an
application or script that monitors the master to check whether it is
up, and instructs the slaves and applications to change master in case
of failure. This section discusses some of the issues encountered when
setting up failover in this fashion.

*Note*:

The MySQL Utilities include a `mysqlfailover' tool that provides
failover capability using GTIDs, support for which requires MySQL 5.6
or later. For more information, see `mysqlfailover' -- Automatic
replication health monitoring and failover
(http://dev.mysql.com/doc/mysql-utilities/1.4/en/mysqlfailover.html),
and Replication with Global Transaction Identifiers
(http://dev.mysql.com/doc/refman/5.6/en/replication-gtids.html).

You can tell a slave to change to a new master using the *Note `CHANGE
MASTER TO': change-master-to. statement. The slave does not check
whether the databases on the master are compatible with those on the
slave; it simply begins reading and executing events from the specified
coordinates in the new master's binary log. In a failover situation,
all the servers in the group are typically executing the same events
from the same binary log file, so changing the source of the events
should not affect the structure or integrity of the database, provided
that you exercise care in making the change.

Slaves should be run with the `--log-bin' option and without
`--log-slave-updates'. In this way, the slave is ready to become a
master without restarting the slave *Note `mysqld': mysqld. Assume that
you have the structure shown in *Note
figure_replication-redundancy-before::.

FIGURE GOES HERE: Redundancy Using Replication, Initial Structure

In this diagram, the `MySQL Master' holds the master database, the
`MySQL Slave' hosts are replication slaves, and the `Web Client'
machines are issuing database reads and writes. Web clients that issue
only reads (and would normally be connected to the slaves) are not
shown, as they do not need to switch to a new server in the event of
failure. For a more detailed example of a read/write scale-out
replication structure, see *Note replication-solutions-scaleout::.

Each MySQL Slave (`Slave 1', `Slave 2', and `Slave 3') is a slave
running with `--log-bin' and without `--log-slave-updates'. Because
updates received by a slave from the master are not logged in the
binary log unless `--log-slave-updates' is specified, the binary log on
each slave is empty initially. If for some reason `MySQL Master'
becomes unavailable, you can pick one of the slaves to become the new
master. For example, if you pick `Slave 1', all `Web Clients' should be
redirected to `Slave 1', which writes the updates to its binary log.
`Slave 2' and `Slave 3' should then replicate from `Slave 1'.

The reason for running the slave without `--log-slave-updates' is to
prevent slaves from receiving updates twice in case you cause one of the
slaves to become the new master. If `Slave 1' has `--log-slave-updates'
enabled, it writes any updates that it receives from `Master' in its
own binary log. This means that, when `Slave 2' changes from `Master' to
`Slave 1' as its master, it may receive updates from `Slave 1' that it
has already received from `Master'.

Make sure that all slaves have processed any statements in their relay
log. On each slave, issue `STOP SLAVE IO_THREAD', then check the output
of *Note `SHOW PROCESSLIST': show-processlist. until you see `Has read
all relay log'. When this is true for all slaves, they can be
reconfigured to the new setup. On the slave `Slave 1' being promoted to
become the master, issue *Note `STOP SLAVE': stop-slave. and *Note
`RESET MASTER': reset-master.

On the other slaves `Slave 2' and `Slave 3', use *Note `STOP SLAVE':
stop-slave. and `CHANGE MASTER TO MASTER_HOST='Slave1'' (where
`'Slave1'' represents the real host name of `Slave 1'). To use `CHANGE
MASTER TO', add all information about how to connect to `Slave 1' from
`Slave 2' or `Slave 3' (USER, PASSWORD, PORT). When issuing the `CHANGE
MASTER TO' statement in this, there is no need to specify the name of
the `Slave 1' binary log file or log position to read from, since the
first binary log file and position 4, are the defaults. Finally, execute
*Note `START SLAVE': start-slave. on `Slave 2' and `Slave 3'.

Once the new replication setup is in place, you need to tell each `Web
Client' to direct its statements to `Slave 1'. From that point on, all
updates statements sent by `Web Client' to `Slave 1' are written to the
binary log of `Slave 1', which then contains every update statement
sent to `Slave 1' since `Master' died.

The resulting server structure is shown in *Note
figure_replication-redundancy-after::.

FIGURE GOES HERE: Redundancy Using Replication, After Master Failure

When `Master' becomes available again, you should make it a slave of
`Slave 1'. To do this, issue on `Master' the same *Note `CHANGE MASTER
TO': change-master-to. statement as that issued on `Slave 2' and `Slave
3' previously.  `Master' then becomes a slave of `S1ave 1' and picks up
the `Web Client' writes that it missed while it was offline.

To make `Master' a master again (for example, because it is the most
powerful machine), use the preceding procedure as if `Slave 1' was
unavailable and `Master' was to be the new master. During this
procedure, do not forget to run *Note `RESET MASTER': reset-master. on
`Master' before making `Slave 1', `Slave 2', and `Slave 3' slaves of
`Master'. If you fail to do this, the slaves may pick up stale writes
from the `Web Client' applications dating from before the point at
which `Master' became unavailable.

You should be aware that there is no synchronization between slaves,
even when they share the same master, and thus some slaves might be
considerably ahead of others. This means that in some cases the
procedure outlined in the previous example might not work as expected.
In practice, however, relay logs on all slaves should be relatively
close together.

One way to keep applications informed about the location of the master
is to have a dynamic DNS entry for the master. With `bind' you can use
`nsupdate' to update the DNS dynamically.


File: manual.info,  Node: replication-solutions-ssl,  Prev: replication-solutions-switch,  Up: replication-solutions

16.3.7 Setting Up Replication Using SSL
---------------------------------------

To use SSL for encrypting the transfer of the binary log required
during replication, both the master and the slave must support SSL
network connections. If either host does not support SSL connections
(because it has not been compiled or configured for SSL), replication
through an SSL connection is not possible.

Setting up replication using an SSL connection is similar to setting up
a server and client using SSL. You must obtain (or create) a suitable
security certificate that you can use on the master, and a similar
certificate (from the same certificate authority) on each slave.

For more information on setting up a server and client for SSL
connectivity, see *Note configuring-for-ssl::.

To enable SSL on the master you must create or obtain suitable
certificates, and then add the following configuration options to the
master's configuration within the `[mysqld]' section of the master's
`my.cnf' file:


     [mysqld]
     ssl-ca=CACERT.PEM
     ssl-cert=SERVER-CERT.PEM
     ssl-key=SERVER-KEY.PEM

The paths to the certificates may be relative or absolute; we recommend
that you always use complete paths for this purpose.

The options are as follows:

   * `ssl-ca' identifies the Certificate Authority (CA) certificate.

   * `ssl-cert' identifies the server public key.  This can be sent to
     the client and authenticated against the CA certificate that it
     has.

   * `ssl-key' identifies the server private key.

On the slave, you have two options available for setting the SSL
information. You can either add the slave certificates to the
`[client]' section of the slave's `my.cnf' file, or you can explicitly
specify the SSL information using the *Note `CHANGE MASTER TO':
change-master-to. statement:

   * To add the slave certificates using an option file, add the
     following lines to the `[client]' section of the slave's `my.cnf'
     file:

          [client]
          ssl-ca=CACERT.PEM
          ssl-cert=CLIENT-CERT.PEM
          ssl-key=CLIENT-KEY.PEM

     Restart the slave server, using the `--skip-slave-start' option to
     prevent the slave from connecting to the master. Use *Note `CHANGE
     MASTER TO': change-master-to. to specify the master configuration,
     using the `MASTER_SSL' option to enable SSL connectivity:


          mysql> CHANGE MASTER TO
              -> MASTER_HOST='master_hostname',
              -> MASTER_USER='replicate',
              -> MASTER_PASSWORD='password',
              -> MASTER_SSL=1;

   * To specify the SSL certificate options using the *Note `CHANGE
     MASTER TO': change-master-to. statement, append the SSL options:


          mysql> CHANGE MASTER TO
              -> MASTER_HOST='master_hostname',
              -> MASTER_USER='replicate',
              -> MASTER_PASSWORD='password',
              -> MASTER_SSL=1,
              -> MASTER_SSL_CA = 'ca_file_name',
              -> MASTER_SSL_CAPATH = 'ca_directory_name',
              -> MASTER_SSL_CERT = 'cert_file_name',
              -> MASTER_SSL_KEY = 'key_file_name';

After the master information has been updated, start the slave
replication process:


     mysql> START SLAVE;

You can use the *Note `SHOW SLAVE STATUS': show-slave-status.
statement to confirm that the SSL connection was established
successfully.

For more information on the *Note `CHANGE MASTER TO': change-master-to.
statement, see *Note change-master-to::.

If you want to enforce the use of SSL connections during replication,
then create a user with the `REPLICATION SLAVE' privilege and use the
`REQUIRE SSL' option for that user. For example:


     mysql> CREATE USER 'repl'@'%.mydomain.com' IDENTIFIED BY 'slavepass';
     mysql> GRANT REPLICATION SLAVE ON *.*
         -> TO 'repl'@'%.mydomain.com' REQUIRE SSL;

If the account already exists, you can add `REQUIRE SSL' to it with
this statement:


     mysql> GRANT USAGE ON *.*
         -> TO 'repl'@'%.mydomain.com' REQUIRE SSL;


File: manual.info,  Node: replication-notes,  Prev: replication-solutions,  Up: replication

16.4 Replication Notes and Tips
===============================

* Menu:

* replication-features::         Replication Features and Issues
* replication-compatibility::    Replication Compatibility Between MySQL Versions
* replication-upgrade::          Upgrading a Replication Setup
* replication-problems::         Troubleshooting Replication
* replication-bugs::             How to Report Replication Bugs or Problems


File: manual.info,  Node: replication-features,  Next: replication-compatibility,  Prev: replication-notes,  Up: replication-notes

16.4.1 Replication Features and Issues
--------------------------------------

* Menu:

* replication-features-auto-increment::  Replication and AUTO_INCREMENT
* replication-features-blackhole::  Replication and BLACKHOLE Tables
* replication-features-charset::  Replication and Character Sets
* replication-features-create-if-not-exists::  Replication of CREATE ... IF NOT EXISTS Statements
* replication-features-create-select::  Replication of CREATE TABLE ... SELECT Statements
* replication-features-current-user::  Replication of CURRENT_USER()
* replication-features-create-alter-drop-server::  Replication of CREATE SERVER, ALTER SERVER, and DROP SERVER
* replication-features-drop-if-exists::  Replication of DROP ... IF EXISTS Statements
* replication-features-differing-tables::  Replication with Differing Table Definitions on Master and Slave
* replication-features-directory::  Replication and DIRECTORY Table Options
* replication-features-invoked::  Replication of Invoked Features
* replication-features-floatvalues::  Replication and Floating-Point Values
* replication-features-flush::   Replication and FLUSH
* replication-features-functions::  Replication and System Functions
* replication-features-limit::   Replication and LIMIT
* replication-features-load-data::  Replication and LOAD DATA INFILE
* replication-features-logging::  Replication and the Slow Query Log
* replication-features-repair-table::  Replication and REPAIR TABLE
* replication-features-shutdowns::  Replication and Master or Slave Shutdowns
* replication-features-max-allowed-packet::  Replication and max_allowed_packet
* replication-features-memory::  Replication and MEMORY Tables
* replication-features-temptables::  Replication and Temporary Tables
* replication-features-mysqldb::  Replication of the mysql System Database
* replication-features-optimizer::  Replication and the Query Optimizer
* replication-features-reserved-words::  Replication and Reserved Words
* replication-features-set-password::  SET PASSWORD and Row-Based Replication
* replication-features-slaveerrors::  Slave Errors During Replication
* replication-features-server-side-help::  Replication of Server-Side Help Tables
* replication-features-sql-mode::  Replication and Server SQL Mode
* replication-features-timeout::  Replication Retries and Timeouts
* replication-features-timestamp::  Replication and TIMESTAMP
* replication-features-timezone::  Replication and Time Zones
* replication-features-transactions::  Replication and Transactions
* replication-features-triggers::  Replication and Triggers
* replication-features-truncate::  Replication and TRUNCATE TABLE
* replication-features-variables::  Replication and Variables
* replication-features-views::   Replication and Views

The following sections provide information about what is supported and
what is not in MySQL replication, and about specific issues and
situations that may occur when replicating certain statements.

Statement-based replication depends on compatibility at the SQL level
between the master and slave. In others, successful SBR requires that
any SQL features used be supported by both the master and the slave
servers. For example, if you use a feature on the master server that is
available only in MySQL 5.1 (or later), you cannot replicate to a slave
that uses MySQL 5.0 (or earlier).

Such incompatibilities also can occur within a release series when
using pre-production releases of MySQL. For example, the `SLEEP()'
function is available beginning with MySQL 5.0.12. If you use this
function on the master, you cannot replicate to a slave that uses MySQL
5.0.11 or earlier.

For this reason, use Generally Available (GA) releases of MySQL for
statement-based replication in a production setting, since we do not
introduce new SQL statements or change their behavior within a given
release series once that series reaches GA release status.

If you are planning to use statement-based replication between MySQL
5.1 and a previous MySQL release series, it is also a good idea to
consult the edition of the `MySQL Reference Manual' corresponding to
the earlier release series for information regarding the replication
characteristics of that series.

With MySQL's statement-based replication, there may be issues with
replicating stored routines or triggers. You can avoid these issues by
using MySQL's row-based replication instead. For a detailed list of
issues, see *Note stored-programs-logging::. For more information about
row-based logging and row-based replication, see *Note
binary-log-formats::, and *Note replication-formats::.

For additional information specific to replication and `InnoDB', see
*Note innodb-and-mysql-replication::. For information relating to
replication with MySQL Cluster, see *Note mysql-cluster-replication::.


File: manual.info,  Node: replication-features-auto-increment,  Next: replication-features-blackhole,  Prev: replication-features,  Up: replication-features

16.4.1.1 Replication and AUTO_INCREMENT
.......................................

Statement-based replication of `AUTO_INCREMENT', `LAST_INSERT_ID()', and
*Note `TIMESTAMP': datetime. values is done correctly, subject to the
following exceptions:

   * When using statement-based replication, `AUTO_INCREMENT' columns
     in tables on the slave must match the same columns on the master;
     that is, `AUTO_INCREMENT' columns must be replicated to
     `AUTO_INCREMENT' columns.

     This is a known issue which is fixed in MySQL 5.5. (Bug #12669186)

   * Prior to MySQL 5.1.12, a stored procedure that uses
     `LAST_INSERT_ID()' does not replicate properly using
     statement-based binary logging.

   * Prior to MySQL 5.1.12, when a stored routine or trigger caused an
     *Note `INSERT': insert. into an `AUTO_INCREMENT' column, the
     generated `AUTO_INCREMENT' value was not written into the binary
     log, so a different value could in some cases be inserted on the
     slave.

   * An insert into an `AUTO_INCREMENT' column caused by a stored
     routine or trigger running on a master that uses MySQL 5.0.60 or
     earlier does not replicate correctly to a slave running MySQL
     5.1.12 through 5.1.23 (inclusive). (Bug #33029)

     A statement invoking a trigger or function that causes an update
     to an `AUTO_INCREMENT' column is not replicated correctly using
     statement-based replication.  Beginning with MySQL 5.1.40, such
     statements are marked as unsafe. (Bug #45677)

   * The `AUTO_INCREMENT' table option was not replicated correctly
     prior to MySQL 5.1.31. (Bug #41986)

   * An *Note `INSERT': insert. into a table that has a composite
     primary key that includes an `AUTO_INCREMENT' column that is not
     the first column of this composite key is not safe for
     statement-based logging or replication. Beginning with MySQL
     5.1.64, such statements are marked as unsafe. (Bug #11754117, Bug
     #45670)

     This issue does not affect tables using the *Note `InnoDB':
     innodb-storage-engine. storage engine, since an `InnoDB' table
     with an AUTO_INCREMENT
     (http://dev.mysql.com/doc/refman/5.5/en/glossary.html#glos_auto_increment)
     column requires at least one key where the auto-increment column
     is the only or leftmost column.

   * Adding an `AUTO_INCREMENT' column to a table with *Note `ALTER
     TABLE': alter-table. might not produce the same ordering of the
     rows on the slave and the master. This occurs because the order in
     which the rows are numbered depends on the specific storage engine
     used for the table and the order in which the rows were inserted.
     If it is important to have the same order on the master and slave,
     the rows must be ordered before assigning an `AUTO_INCREMENT'
     number. Assuming that you want to add an `AUTO_INCREMENT' column
     to a table `t1' that has columns `col1' and `col2', the following
     statements produce a new table `t2' identical to `t1' but with an
     `AUTO_INCREMENT' column:


          CREATE TABLE t2 LIKE t1;
          ALTER TABLE t2 ADD id INT AUTO_INCREMENT PRIMARY KEY;
          INSERT INTO t2 SELECT * FROM t1 ORDER BY col1, col2;

     *Important*:

     To guarantee the same ordering on both master and slave, the
     `ORDER BY' clause must name _all_ columns of `t1'.

     The instructions just given are subject to the limitations of
     `CREATE TABLE ... LIKE': Foreign key definitions are ignored, as
     are the `DATA DIRECTORY' and `INDEX DIRECTORY' table options. If a
     table definition includes any of those characteristics, create
     `t2' using a *Note `CREATE TABLE': create-table. statement that is
     identical to the one used to create `t1', but with the addition of
     the `AUTO_INCREMENT' column.

     Regardless of the method used to create and populate the copy
     having the `AUTO_INCREMENT' column, the final step is to drop the
     original table and then rename the copy:


          DROP t1;
          ALTER TABLE t2 RENAME t1;

     See also *Note alter-table-problems::.


File: manual.info,  Node: replication-features-blackhole,  Next: replication-features-charset,  Prev: replication-features-auto-increment,  Up: replication-features

16.4.1.2 Replication and BLACKHOLE Tables
.........................................

The *Note `BLACKHOLE': blackhole-storage-engine. storage engine accepts
data but discards it and does not store it. When performing binary
logging, all inserts to such tables are always logged, regardless of
the logging format in use. Updates and deletes are handled differently
depending on whether statement based or row based logging is in use.
With the statement based logging format, all statements affecting
`BLACKHOLE' tables are logged, but their effects ignored. When using
row-based logging, updates and deletes to such tables are simply
skipped--they are not written to the binary log.

For this reason we recommend when you replicate to tables using the
*Note `BLACKHOLE': blackhole-storage-engine. storage engine that you
have the `binlog_format' server variable set to `STATEMENT', and not to
either `ROW' or `MIXED'.


File: manual.info,  Node: replication-features-charset,  Next: replication-features-create-if-not-exists,  Prev: replication-features-blackhole,  Up: replication-features

16.4.1.3 Replication and Character Sets
.......................................

The following applies to replication between MySQL servers that use
different character sets:

   * If the master uses MySQL 4.1, you must _always_ use the same
     _global_ character set and collation on the master and the slave,
     regardless of the slave MySQL version. (These are controlled by the
     `--character-set-server' and `--collation-server' options.)
     Otherwise, you may get duplicate-key errors on the slave, because
     a key that is unique in the master character set might not be
     unique in the slave character set. Note that this is not a cause
     for concern when master and slave are both MySQL 5.0 or later.

   * If the master is older than MySQL 4.1.3, the character set of any
     client should never be made different from its global value
     because this character set change is not known to the slave. In
     other words, clients should not use `SET NAMES', `SET CHARACTER
     SET', and so forth. If both the master and the slave are 4.1.3 or
     newer, clients can freely set session values for character set
     variables because these settings are written to the binary log and
     so are known to the slave. That is, clients can use `SET NAMES' or
     `SET CHARACTER SET' or can set variables such as
     `collation_client' or `collation_server'. However, clients are
     prevented from changing the _global_ value of these variables; as
     stated previously, the master and slave must always have identical
     global character set values. This is true whether you are using
     statement-based or row-based replication.

   * If the master has databases with a character set different from
     the global `character_set_server' value, you should design your
     *Note `CREATE TABLE': create-table. statements so that they do not
     implicitly rely on the database default character set. A good
     workaround is to state the character set and collation explicitly
     in *Note `CREATE TABLE': create-table.  statements.


File: manual.info,  Node: replication-features-create-if-not-exists,  Next: replication-features-create-select,  Prev: replication-features-charset,  Up: replication-features

16.4.1.4 Replication of CREATE ... IF NOT EXISTS Statements
...........................................................

This section discusses the rules that are applied when various `CREATE
... IF NOT EXISTS' statements are replicated.

Previous to MySQL 5.1.38

*Note `CREATE DATABASE IF NOT EXISTS': create-database. was replicated
only if the database named in the statement did not exist on the master.
*Note `CREATE TABLE IF NOT EXISTS': create-table. was replicated only
if the table named in the statement did not exist on the master.

MySQL 5.1.39 and later

Every *Note `CREATE DATABASE IF NOT EXISTS': create-database. statement
is replicated, whether or not the database already exists on the master.
Similarly, every *Note `CREATE TABLE IF NOT EXISTS': create-table.
statement is replicated, whether or not the table already exists on the
master. This includes *Note `CREATE TABLE IF NOT EXISTS ... LIKE':
create-table. However, replication of *Note `CREATE TABLE IF NOT EXISTS
... SELECT': create-table. follows somewhat different rules; see *Note
replication-features-create-select::, for more information.

Replication of CREATE EVENT IF NOT EXISTS

*Note `CREATE EVENT IF NOT EXISTS': create-event. is always replicated,
whether or not the event named in the statement already exists on the
master.  This is true for all MySQL 5.1 releases beginning with MySQL
5.1.6, when this statement was introduced.

See also Bug #45574.


File: manual.info,  Node: replication-features-create-select,  Next: replication-features-current-user,  Prev: replication-features-create-if-not-exists,  Up: replication-features

16.4.1.5 Replication of CREATE TABLE ... SELECT Statements
..........................................................

This section discusses how MySQL replicates *Note `CREATE TABLE ...
SELECT': create-table-select. statements.

These behaviors are not dependent on MySQL version:

   * *Note `CREATE TABLE ... SELECT': create-table-select. always
     performs an implicit commit (*Note implicit-commit::).

   * If destination table does not exist, logging occurs as follows. It
     does not matter whether `IF NOT EXISTS' is present.

        * `STATEMENT' or `MIXED' format: The statement is logged as
          written.

        * `ROW' format: The statement is logged as a *Note `CREATE
          TABLE': create-table.  statement followed by a series of
          insert-row events.

   * If the statement fails, nothing is logged. This includes the case
     that the destination table exists and `IF NOT EXISTS' is not given.

When the destination table exists and `IF NOT EXISTS' is given, MySQL
handles the statement in a version-dependent way.

In MySQL 5.1 before 5.1.51 and in MySQL 5.5 before 5.5.6 (this is the
original behavior):

   * `STATEMENT' or `MIXED' format: The statement is logged as written.

   * `ROW' format: The statement is logged as a *Note `CREATE TABLE':
     create-table. statement followed by a series of insert-row events.

In MySQL 5.1 as of 5.1.51:

   * `STATEMENT' or `MIXED' format: The statement is logged as the
     equivalent pair of *Note `CREATE TABLE': create-table. and *Note
     `INSERT INTO ... SELECT': insert-select. statements.

   * `ROW' format: The statement is logged as a *Note `CREATE TABLE':
     create-table. statement followed by a series of insert-row events.

In MySQL 5.5 as of 5.5.6:

   * Nothing is inserted or logged.

These version dependencies arise due to a change in MySQL 5.5.6 in
handling of *Note `CREATE TABLE ... SELECT': create-table-select. not
to insert rows if the destination table already exists, and a change
made in MySQL 5.1.51 to preserve forward compatibility in replication
of such statements from a 5.1 master to a 5.5 slave. For details, see
*Note create-table-select::.


File: manual.info,  Node: replication-features-current-user,  Next: replication-features-create-alter-drop-server,  Prev: replication-features-create-select,  Up: replication-features

16.4.1.6 Replication of CURRENT_USER()
......................................

The following statements support use of the `CURRENT_USER()' function
to take the place of the name of (and, possibly, the host for) an
affected user or a definer; in such cases, `CURRENT_USER()' is expanded
where and as needed:

   * *Note `DROP USER': drop-user.

   * *Note `RENAME USER': rename-user.

   * *Note `GRANT': grant.

   * *Note `REVOKE': revoke.

   * *Note `CREATE FUNCTION': create-function.

   * *Note `CREATE PROCEDURE': create-procedure.

   * *Note `CREATE TRIGGER': create-trigger.

   * *Note `CREATE EVENT': create-event.

   * *Note `CREATE VIEW': create-view.

   * *Note `ALTER EVENT': alter-event.

   * *Note `ALTER VIEW': alter-view.

   * *Note `SET PASSWORD': set-password.

In all MySQL 5.1 releases, when `CURRENT_USER()' or `CURRENT_USER' is
used as the definer in any of the statements *Note `CREATE FUNCTION':
create-function, *Note `CREATE PROCEDURE': create-procedure, *Note
`CREATE TRIGGER': create-trigger, *Note `CREATE EVENT': create-event,
*Note `CREATE VIEW': create-view, or *Note `ALTER VIEW': alter-view.
when binary logging is enabled, the function reference is expanded
before it is written to the binary log, so that the statement refers to
the same user on both the master and the slave when the statement is
replicated. Beginning with MySQL 5.1.49, `CURRENT_USER()' or
`CURRENT_USER' is also expanded prior to being written to the binary
log when used in *Note `DROP USER': drop-user, *Note `RENAME USER':
rename-user, *Note `GRANT': grant, *Note `REVOKE': revoke, or *Note
`ALTER EVENT': alter-event. (Bug #48321)


File: manual.info,  Node: replication-features-create-alter-drop-server,  Next: replication-features-drop-if-exists,  Prev: replication-features-current-user,  Up: replication-features

16.4.1.7 Replication of CREATE SERVER, ALTER SERVER, and DROP SERVER
....................................................................

In MySQL 5.1, the statements *Note `CREATE SERVER': create-server,
*Note `ALTER SERVER': alter-server, and *Note `DROP SERVER':
drop-server. are logged only when `binlog_format' is equal to `ROW'.
These statements are not written to the binary log when using either
the statement-based or mixed logging format.


File: manual.info,  Node: replication-features-drop-if-exists,  Next: replication-features-differing-tables,  Prev: replication-features-create-alter-drop-server,  Up: replication-features

16.4.1.8 Replication of DROP ... IF EXISTS Statements
.....................................................

The *Note `DROP DATABASE IF EXISTS': drop-database, *Note `DROP TABLE
IF EXISTS': drop-table, and *Note `DROP VIEW IF EXISTS': drop-view.
statements are always replicated, even if the database, table, or view
to be dropped does not exist on the master. This is to ensure that the
object to be dropped no longer exists on either the master or the
slave, once the slave has caught up with the master.

Beginning with MySQL 5.1.33, `DROP ... IF EXISTS' statements for stored
programs (stored procedures and functions, triggers, and events) are
also replicated, even if the stored program to be dropped does not
exist on the master. (Bug #13684)


File: manual.info,  Node: replication-features-differing-tables,  Next: replication-features-directory,  Prev: replication-features-drop-if-exists,  Up: replication-features

16.4.1.9 Replication with Differing Table Definitions on Master and Slave
.........................................................................

* Menu:

* replication-features-more-columns::  Replication with More Columns on Master or Slave
* replication-features-different-data-types::  Replication of Columns Having Different Data Types

Starting with MySQL 5.1.21, source and target tables for replication do
not have to be identical. A table on the master can have more or fewer
columns than the slave's copy of the table. In addition, corresponding
table columns on the master and the slave can use different data types,
subject to certain conditions.

In all cases where the source and target tables do not have identical
definitions, the database and table names must be the same on both the
master and the slave. Additional conditions are discussed, with
examples, in the following two sections.


File: manual.info,  Node: replication-features-more-columns,  Next: replication-features-different-data-types,  Prev: replication-features-differing-tables,  Up: replication-features-differing-tables

16.4.1.10 Replication with More Columns on Master or Slave
..........................................................

Starting with MySQL 5.1.21, you can replicate a table from the master
to the slave such that the master and slave copies of the table have
differing numbers of columns, subject to the following conditions:

   * Columns common to both versions of the table must be defined in
     the same order on the master and the slave.

     (This is true even if both tables have the same number of columns.)

   * Columns common to both versions of the table must be defined
     before any additional columns.

     This means that executing an *Note `ALTER TABLE': alter-table.
     statement on the slave where a new column is inserted into the
     table within the range of columns common to both tables causes
     replication to fail, as shown in the following example:

     Suppose that a table `t', existing on the master and the slave, is
     defined by the following *Note `CREATE TABLE': create-table.
     statement:


          CREATE TABLE t (
              c1 INT,
              c2 INT,
              c3 INT
          );

     Suppose that the *Note `ALTER TABLE': alter-table. statement shown
     here is executed on the slave:


          ALTER TABLE t ADD COLUMN cnew1 INT AFTER c3;

     The previous *Note `ALTER TABLE': alter-table. is permitted on the
     slave because the columns `c1', `c2', and `c3' that are common to
     both versions of table `t' remain grouped together in both
     versions of the table, before any columns that differ.

     However, the following *Note `ALTER TABLE': alter-table. statement
     cannot be executed on the slave without causing replication to
     break:


          ALTER TABLE t ADD COLUMN cnew2 INT AFTER c2;

     Replication fails after execution on the slave of the *Note `ALTER
     TABLE': alter-table. statement just shown, because the new column
     `cnew2' comes between columns common to both versions of `t'.

   * Each `extra' column in the version of the table having more
     columns must have a default value.

     *Note*:

     A column's default value is determined by a number of factors,
     including its type, whether it is defined with a `DEFAULT' option,
     whether it is declared as `NULL', and the server SQL mode in
     effect at the time of its creation; for more information, see
     *Note data-type-defaults::).

In addition, when the slave's copy of the table has more columns than
the master's copy, each column common to the tables must use the same
data type in both tables.

Examples

The following examples illustrate some valid and invalid table
definitions:

More columns on the master

The following table definitions are valid and replicate correctly:


     master> CREATE TABLE t1 (c1 INT, c2 INT, c3 INT);
     slave>  CREATE TABLE t1 (c1 INT, c2 INT);

The following table definitions would raise Error 1532
(`ER_BINLOG_ROW_RBR_TO_SBR') because the definitions of the columns
common to both versions of the table are in a different order on the
slave than they are on the master:


     master> CREATE TABLE t1 (c1 INT, c2 INT, c3 INT);
     slave>  CREATE TABLE t1 (c2 INT, c1 INT);

The following table definitions would also raise Error 1532 because the
definition of the extra column on the master appears before the
definitions of the columns common to both versions of the table:


     master> CREATE TABLE t1 (c3 INT, c1 INT, c2 INT);
     slave>  CREATE TABLE t1 (c1 INT, c2 INT);

More columns on the slave

The following table definitions are valid and replicate correctly:


     master> CREATE TABLE t1 (c1 INT, c2 INT);
     slave>  CREATE TABLE t1 (c1 INT, c2 INT, c3 INT);

The following definitions raise Error 1532 because the columns common
to both versions of the table are not defined in the same order on both
the master and the slave:


     master> CREATE TABLE t1 (c1 INT, c2 INT);
     slave>  CREATE TABLE t1 (c2 INT, c1 INT, c3 INT);

The following table definitions also raise Error 1532 because the
definition for the extra column in the slave's version of the table
appears before the definitions for the columns which are common to both
versions of the table:


     master> CREATE TABLE t1 (c1 INT, c2 INT);
     slave>  CREATE TABLE t1 (c3 INT, c1 INT, c2 INT);

The following table definitions fail because the slave's version of the
table has additional columns compared to the master's version, and the
two versions of the table use different data types for the common column
`c2':


     master> CREATE TABLE t1 (c1 INT, c2 BIGINT);
     slave>  CREATE TABLE t1 (c1 INT, c2 INT, c3 INT);


File: manual.info,  Node: replication-features-different-data-types,  Prev: replication-features-more-columns,  Up: replication-features-differing-tables

16.4.1.11 Replication of Columns Having Different Data Types
............................................................

Corresponding columns on the master's and the slave's copies of the
same table ideally should have the same data type. However, beginning
with MySQL 5.1.21, this is not always strictly enforced, as long as
certain conditions are met.

All other things being equal, it is always possible to replicate from a
column of a given data type to another column of the same type and same
size or width, where applicable, or larger. For example, you can
replicate from a `CHAR(10)' column to another `CHAR(10)', or from a
`CHAR(10)' column to a `CHAR(25)' column without any problems. In
certain cases, it also possible to replicate from a column having one
data type (on the master) to a column having a different data type (on
the slave); when the data type of the master's version of the column is
promoted to a type that is the same size or larger on the slave, this
is known as _attribute promotion_.

Attribute promotion can be used with both statement-based and row-based
replication, and is not dependent on the storage engine used by either
the master or the slave. However, the choice of logging format does
have an effect on the type conversions that are permitted; the
particulars are discussed later in this section.

*Important*:

Whether you use statement-based or row-based replication, the slave's
copy of the table cannot contain more columns than the master's copy if
you wish to employ attribute promotion.

Statement-based replication

When using statement-based replication, a simple rule of thumb to
follow is, `If the statement run on the master would also execute
successfully on the slave, it should also replicate successfully'. In
other words, if the statement uses a value that is compatible with the
type of a given column on the slave, the statement can be replicated.
For example, you can insert any value that fits in a `TINYINT' column
into a `BIGINT' column as well; it follows that, even if you change the
type of a `TINYINT' column in the slave's copy of a table to `BIGINT',
any insert into that column on the master that succeeds should also
succeed on the slave, since it is impossible to have a legal `TINYINT'
value that is large enough to exceed a `BIGINT' column.

When using statement-based replication, `AUTO_INCREMENT' columns must
be the same on both the master and the slave; otherwise, updates may be
applied to the wrong table on the slave. This is a known issue which is
fixed in MySQL 5.5. (Bug #12669186)

*Note*:

The restrictions described in the next few paragraphs do not apply to
MySQL Cluster Replication, beginning with MySQL Cluster NDB 6.3.33,
7.0.14, and 7.1.3. These and later versions of MySQL Cluster support
attribute promotion and demotion (such as *Note `TINYINT':
integer-types. to *Note `BIGINT': integer-types, and *Note
`VARCHAR(50)': char. to *Note `CHAR(25)': char, respectively) in
replication; see *Note replication-features-attribute-promotion::, for
more information.

Row-based replication

For row-based replication, the case is not so simple, due to the fact
that changes rather than statements are replicated, and these changes
are transmitted from master to slave using formats that do not always
map directly to MySQL server column data types. For example, with
row-based binary logging, you cannot replicate between different `INT'
subtypes, such as from `TINYINT' to `BIGINT', because changes to
columns of these types are represented differently from one another in
the binary log when using row-based logging. However, you can replicate
from `BLOB' to `TEXT' using row-based replication because changes to
`BLOB' and `TEXT' columns are represented using the same format in the
binary log.

Supported conversions for attribute promotion when using row-based
replication are shown in the following table:

This table shows supported conversions for attribute promotion when
using row-based replication.

From (Master)                        To (Slave)
*Note `BINARY': binary-varbinary.    *Note `CHAR': char.
*Note `BLOB': blob.                  *Note `TEXT': blob.
*Note `CHAR': char.                  *Note `BINARY': binary-varbinary.
*Note `DECIMAL': fixed-point-types.  *Note `NUMERIC': fixed-point-types.
*Note `NUMERIC': fixed-point-types.  *Note `DECIMAL': fixed-point-types.
*Note `TEXT': blob.                  *Note `BLOB': blob.
*Note `VARBINARY': binary-varbinary. *Note `VARCHAR': char.
*Note `VARCHAR': char.               *Note `VARBINARY': binary-varbinary.

*Note*:

In all cases, the size or width of the column on the slave must be
equal to or greater than that of the column on the master. For example,
you can replicate from a `CHAR(10)' column on the master to a column
that uses `BINARY(10)' or `BINARY(25)' on the slave, but you cannot
replicate from a `CHAR(10)' column on the master to `BINARY(5)' column
on the slave.

Any unique index (including primary keys) having a prefix must use a
prefix of the same length on both master and slave; in such cases,
differing prefix lengths are disallowed. It is possible to use a
nonunique index whose prefix length differs between master and slave,
but this can cause serious performance issues, particularly when the
prefix used on the master is longer. This is due to the fact that 2
unique prefixes of a given length may no longer be unique at a shorter
length; for example, the words _catalogue_ and _catamount_ have the
5-character prefixes _catal_ and _catam_, respectively, but share the
same 4-character prefix (_cata_). This can lead to queries that use
such indexes executing less efficiently on the slave, when a shorter
prefix is employed in the slave' definition of the same index than on
the master.

For *Note `DECIMAL': fixed-point-types. and *Note `NUMERIC':
fixed-point-types. columns, both the mantissa (_M_) and the number of
decimals (_D_) must be the same size or larger on the slave as compared
with the master. For example, replication from a `NUMERIC(5,4)' to a
`DECIMAL(6,4)' works, but not from a `NUMERIC(5,4)' to a `DECIMAL(5,3)'.

MySQL (except for MySQL Cluster) does _not_ support attribute promotion
of any of the following data types to or from any other data type when
using row-based replication:

   * *Note `INT': integer-types. (including `TINYINT', `SMALLINT',
     `MEDIUMINT', `BIGINT').

     Promotion between *Note `INT': integer-types.  subtypes--for
     example, from `SMALLINT' to `BIGINT'--is also not supported.

   * *Note `SET': set. or *Note `ENUM': enum.

   * *Note `FLOAT': floating-point-types. or *Note `DOUBLE':
     floating-point-types.

   * All of the data types relating to dates, times, or both: *Note
     `DATE': datetime, *Note `TIME': time, *Note `DATETIME': datetime,
     *Note `TIMESTAMP': datetime, and *Note `YEAR': year.

Attribute promotion and demotion (MySQL Cluster)

Beginning with MySQL Cluster NDB 6.3.33, 7.0.14, and 7.1.3, MySQL
Cluster Replication supports attribute promotion and demotion between
smaller data types and larger types. It is also possible to specify
whether or not to permit lossy (truncated) or non-lossy conversions of
demoted column values, as explained later in this section.

Lossy and non-lossy conversions

In the event that the target type cannot represent the value being
inserted, a decision must be made on how to handle the conversion. If
we permit the conversion but truncate (or otherwise modify) the source
value to achieve a `fit' in the target column, we make what is known as
a _lossy conversion_. A conversion which does not require truncation or
similar modifications to fit the source column value in the target
column is a _non-lossy_ conversion.

Type conversion modes (slave_type_conversions variable)

The setting of the `slave_type_conversions' global server variable
controls the type conversion mode used on the slave. This variable
takes a set of values from the following table, which shows the effects
of each mode on the slave's type-conversion behavior:

This table shows type conversion modes for the `slave_type_conversions'
global server variable and describes the effects of each mode on the
slave's type-conversion behavior.

Mode                      Effect
`ALL_LOSSY'               In this mode, type conversions that would mean
                          loss of information are permitted.
                          
                          This does not imply that non-lossy conversions
                          are permitted, merely that only cases
                          requiring either lossy conversions or no
                          conversion at all are permitted; for example,
                          enabling _only_ this mode permits an `INT'
                          column to be converted to `TINYINT' (a lossy
                          conversion), but not a `TINYINT' column to an
                          `INT' column (non-lossy).  Attempting the
                          latter conversion in this case would cause
                          replication to stop with an error on the slave.
`ALL_NON_LOSSY'           This mode permits conversions that do not
                          require truncation or other special handling
                          of the source value; that is, it permits
                          conversions where the target type has a wider
                          range than the source type.
                          
                          Setting this mode has no bearing on whether
                          lossy conversions are permitted; this is
                          controlled with the `ALL_LOSSY' mode. If only
                          `ALL_NON_LOSSY' is set, but not `ALL_LOSSY',
                          then attempting a conversion that would result
                          in the loss of data (such as `INT' to
                          `TINYINT', or `CHAR(25)' to `VARCHAR(20)')
                          causes the slave to stop with an error.
`ALL_LOSSY,ALL_NON_LOSSY' When this mode is set, all supported type
                          conversions are permitted, whether or not they
                          are lossy conversions.
[_empty_]                 When `slave_type_conversions' is not set, no
                          attribute promotion or demotion is permitted;
                          this means that all columns in the source and
                          target tables must be of the same types.
                          
                          This mode is the default.

Changing the type conversion mode requires restarting the slave with
the new `slave_type_conversions' setting.

Supported conversions

Supported conversions between different but similar data types are
shown in the following list:

   * Between any of the integer types *Note `TINYINT': integer-types,
     *Note `SMALLINT': integer-types, *Note `MEDIUMINT': integer-types,
     *Note `INT': integer-types, and *Note `BIGINT': integer-types.

     This includes conversions between the signed and unsigned versions
     of these types.

     Lossy conversions are made by truncating the source value to the
     maximum (or minimum) permitted by the target column. For insuring
     non-lossy conversions when going from unsigned to signed types,
     the target column must be large enough to accommodate the range of
     values in the source column. For example, you can demote `TINYINT
     UNSIGNED' non-lossily to `SMALLINT', but not to `TINYINT'.

   * Between any of the decimal types *Note `DECIMAL':
     fixed-point-types, *Note `FLOAT': floating-point-types, *Note
     `DOUBLE': floating-point-types, and *Note `NUMERIC':
     fixed-point-types.

     `FLOAT' to `DOUBLE' is a non-lossy conversion; `DOUBLE' to `FLOAT'
     can only be handled lossily. A conversion from `DECIMAL(M,D)' to
     `DECIMAL(M',D')' where `D' >= D' and `(M'-D') >= (M'-D) are
     non-lossy; for any case where `M' < M', `D' < D', or both, only a
     lossy conversion can be made.

     For any of the decimal types, if a value to be stored cannot be
     fit in the target type, the value is rounded down according to the
     rounding rules defined for the server elsewhere in the
     documentation. See *Note precision-math-rounding::, for information
     about how this is done for decimal types.

   * Between any of the string types *Note `CHAR': char, *Note
     `VARCHAR': char, and *Note `TEXT': blob, including conversions
     between different widths.

     Conversion of a `CHAR', `VARCHAR', or `TEXT' to a `CHAR',
     `VARCHAR', or `TEXT' column the same size or larger is never
     lossy. Lossy conversion is handled by inserting only the first N
     characters of the string on the slave, where N is the width of the
     target column.

     *Important*:

     Replication between columns using different character sets is not
     supported.

   * Between any of the binary data types *Note `BINARY':
     binary-varbinary, *Note `VARBINARY': binary-varbinary, and *Note
     `BLOB': blob, including conversions between different widths.

     Conversion of a `BINARY', `VARBINARY', or `BLOB' to a `BINARY',
     `VARBINARY', or `BLOB' column the same size or larger is never
     lossy. Lossy conversion is handled by inserting only the first N
     bytes of the string on the slave, where N is the width of the
     target column.

   * Between any 2 *Note `BIT': bit-type. columns of any 2 sizes.

     When inserting a value from a `BIT(M)' column into a `BIT(M')'
     column, where `M' > M', the most significant bits of the `BIT(M')'
     columns are cleared (set to zero) and the M bits of the `BIT(M)'
     value are set as the least significant bits of the `BIT(M')'
     column.

     When inserting a value from a source `BIT(M)' column into a target
     `BIT(M')' column, where `M' < M', the maximum possible value for
     the `BIT(M')' column is assigned; in other words, an `all-set'
     value is assigned to the target column.

Conversions between types not in the previous list are not permitted.


File: manual.info,  Node: replication-features-directory,  Next: replication-features-invoked,  Prev: replication-features-differing-tables,  Up: replication-features

16.4.1.12 Replication and DIRECTORY Table Options
.................................................

If a `DATA DIRECTORY' or `INDEX DIRECTORY' table option is used in a
*Note `CREATE TABLE': create-table. statement on the master server, the
table option is also used on the slave. This can cause problems if no
corresponding directory exists in the slave host file system or if it
exists but is not accessible to the slave server. This can be
overridden by using the `NO_DIR_IN_CREATE' server SQL mode on the
slave, which causes the slave to ignore the `DATA DIRECTORY' and `INDEX
DIRECTORY' table options when replicating *Note `CREATE TABLE':
create-table. statements. The result is that `MyISAM' data and index
files are created in the table's database directory.

For more information, see *Note sql-mode::.


File: manual.info,  Node: replication-features-invoked,  Next: replication-features-floatvalues,  Prev: replication-features-directory,  Up: replication-features

16.4.1.13 Replication of Invoked Features
.........................................

Replication of invoked features such as user-defined functions (UDFs)
and stored programs (stored procedures and functions, triggers, and
events) was re-implemented in MySQL 5.1.18 to provide the following
characteristics:

   * The effects of the feature are always replicated.

   * The following statements are replicated using statement-based
     replication:

        * *Note `CREATE EVENT': create-event.

        * *Note `ALTER EVENT': alter-event.

        * *Note `DROP EVENT': drop-event.

        * *Note `CREATE PROCEDURE': create-procedure.

        * *Note `DROP PROCEDURE': drop-procedure.

        * *Note `CREATE FUNCTION': create-function.

        * *Note `DROP FUNCTION': drop-function.

        * *Note `CREATE TRIGGER': create-trigger.

        * *Note `DROP TRIGGER': drop-trigger.

     However, the _effects_ of features created, modified, or dropped
     using these statements are replicated using row-based replication.

     *Note*:

     Attempting to replicate invoked features using statement-based
     replication produces the warning `Statement may not be safe to log
     in statement format'. (Prior to MySQL 5.1.36, this was `Statement
     is not safe to log in statement format'; see Bug #42415.) For
     example, trying to replicate a UDF with statement-based replication
     generates this warning because it currently cannot be determined
     by the MySQL server whether the UDF is deterministic. If you are
     absolutely certain that the invoked feature's effects are
     deterministic, you can safely disregard such warnings.

   * In the case of *Note `CREATE EVENT': create-event.  and *Note
     `ALTER EVENT': alter-event.:

        * The status of the event is set to `SLAVESIDE_DISABLED' on the
          slave regardless of the state specified (this does not apply
          to *Note `DROP EVENT': drop-event.).

        * The master on which the event was created is identified on
          the slave by its server ID. The `ORIGINATOR' column in *Note
          `INFORMATION_SCHEMA.EVENTS': events-table.  and the
          `originator' column in `mysql.event' were added to these
          tables in MySQL 5.1.18 to store this information. See *Note
          events-table::, and *Note show-events::, for more information.

   * The feature implementation resides on the slave in a renewable
     state so that if the master fails, the slave can be used as the
     master without loss of event processing.

To determine whether there are any scheduled events on a MySQL server
that were created on a different server (that was acting as a
replication master), query the *Note `INFORMATION_SCHEMA.EVENTS':
events-table. table in a manner similar to what is shown here:


     SELECT EVENT_SCHEMA, EVENT_NAME
         FROM INFORMATION_SCHEMA.EVENTS
         WHERE STATUS = 'SLAVESIDE_DISABLED';

Alternatively, you can use the *Note `SHOW EVENTS': show-events.
statement, like this:


     SHOW EVENTS
         WHERE STATUS = 'SLAVESIDE_DISABLED';

When promoting a replication slave having such events to a replication
master, you must enable each event using *Note `ALTER EVENT EVENT_NAME
ENABLED': alter-event, where EVENT_NAME is the name of the event.

If more than one master was involved in creating events on this slave,
and you wish to identify events that were created only on a given
master having the server ID MASTER_ID, modify the previous query on the
*Note `EVENTS': events-table. table to include the `ORIGINATOR' column,
as shown here:


     SELECT EVENT_SCHEMA, EVENT_NAME, ORIGINATOR
         FROM INFORMATION_SCHEMA.EVENTS
         WHERE STATUS = 'SLAVESIDE_DISABLED'
         AND   ORIGINATOR = 'MASTER_ID'

You can employ `ORIGINATOR' with the *Note `SHOW EVENTS': show-events.
statement in a similar fashion:


     SHOW EVENTS
         WHERE STATUS = 'SLAVESIDE_DISABLED'
         AND   ORIGINATOR = 'MASTER_ID'

Before enabling events that were replicated from the master, you should
disable the MySQL Event Scheduler on the slave (using a statement such
as `SET GLOBAL event_scheduler = OFF;'), run any necessary *Note `ALTER
EVENT': alter-event. statements, restart the server, then re-enable the
Event Scheduler on the slave afterward (using a statement such as `SET
GLOBAL event_scheduler = ON;')-

If you later demote the new master back to being a replication slave,
you must disable manually all events enabled by the *Note `ALTER
EVENT': alter-event. statements. You can do this by storing in a
separate table the event names from the *Note `SELECT': select.
statement shown previously, or using *Note `ALTER EVENT': alter-event.
statements to rename the events with a common prefix such as
`replicated_' to identify them.

If you rename the events, then when demoting this server back to being
a replication slave, you can identify the events by querying the *Note
`EVENTS': events-table. table, as shown here:


     SELECT CONCAT(EVENT_SCHEMA, '.', EVENT_NAME) AS 'Db.Event'
           FROM INFORMATION_SCHEMA.EVENTS
           WHERE INSTR(EVENT_NAME, 'replicated_') = 1;


File: manual.info,  Node: replication-features-floatvalues,  Next: replication-features-flush,  Prev: replication-features-invoked,  Up: replication-features

16.4.1.14 Replication and Floating-Point Values
...............................................

With statement-based replication, values are converted from decimal to
binary. Because conversions between decimal and binary representations
of them may be approximate, comparisons involving floating-point values
are inexact. This is true for operations that use floating-point values
explicitly, or that use values that are converted to floating-point
implicitly.  Comparisons of floating-point values might yield different
results on master and slave servers due to differences in computer
architecture, the compiler used to build MySQL, and so forth. See *Note
type-conversion::, and *Note problems-with-float::.


File: manual.info,  Node: replication-features-flush,  Next: replication-features-functions,  Prev: replication-features-floatvalues,  Up: replication-features

16.4.1.15 Replication and FLUSH
...............................

Some forms of the *Note `FLUSH': flush. statement are not logged
because they could cause problems if replicated to a slave: *Note
`FLUSH LOGS': flush, *Note `FLUSH MASTER': flush, *Note `FLUSH SLAVE':
flush, and *Note `FLUSH TABLES WITH READ LOCK': flush. For a syntax
example, see *Note flush::. The *Note `FLUSH TABLES': flush, *Note
`ANALYZE TABLE': analyze-table, *Note `OPTIMIZE TABLE': optimize-table,
and *Note `REPAIR TABLE': repair-table. statements are written to the
binary log and thus replicated to slaves. This is not normally a
problem because these statements do not modify table data.

However, this behavior can cause difficulties under certain
circumstances. If you replicate the privilege tables in the `mysql'
database and update those tables directly without using *Note `GRANT':
grant, you must issue a *Note `FLUSH PRIVILEGES': flush. on the slaves
to put the new privileges into effect. In addition, if you use *Note
`FLUSH TABLES': flush.  when renaming a `MyISAM' table that is part of
a `MERGE' table, you must issue *Note `FLUSH TABLES': flush.  manually
on the slaves. These statements are written to the binary log unless
you specify `NO_WRITE_TO_BINLOG' or its alias `LOCAL'.


File: manual.info,  Node: replication-features-functions,  Next: replication-features-limit,  Prev: replication-features-flush,  Up: replication-features

16.4.1.16 Replication and System Functions
..........................................

Certain functions do not replicate well under some conditions:

   * The `USER()', `CURRENT_USER()' (or `CURRENT_USER'), `UUID()',
     `VERSION()', `LOAD_FILE()', and `RAND()' functions are replicated
     without change and thus do not work reliably on the slave unless
     row-based replication is enabled. (See *Note
     replication-formats::.)

     For early implementations of mixed-format logging, stored
     functions, triggers, and views that use these functions in their
     body do not replicate reliably in mixed-format logging mode
     because the logging did not switch from statement-based to
     row-based format. For example, `INSERT INTO t SELECT FROM v',
     where `v' is a view that selects `UUID()' could cause problems.
     This limitation is lifted in MySQL 5.1.12.

     Beginning with MySQL 5.1.23, `USER()' and `CURRENT_USER()' are
     automatically replicated using row-based replication when using
     `MIXED' mode, and generate a warning in `STATEMENT' mode. (Bug
     #28086) (See also *Note replication-features-current-user::.)

     Beginning with MySQL 5.1.42, `VERSION()' is also automatically
     replicated using row-based replication when using `MIXED' mode,
     and generates a warning in `STATEMENT' mode. (Bug #47995) Beginning
     with MySQL 5.1.43, this is also true with regard to the `RAND()'
     function. (Bug #49222)

   * For `NOW()', the binary log includes the timestamp. This means
     that the value _as returned by the call to this function on the
     master_ is replicated to the slave. This can lead to a possibly
     unexpected result when replicating between MySQL servers in
     different time zones. Suppose that the master is located in New
     York, the slave is located in Stockholm, and both servers are
     using local time. Suppose further that, on the master, you create
     a table `mytable', perform an *Note `INSERT': insert. statement on
     this table, and then select from the table, as shown here:


          mysql> CREATE TABLE mytable (mycol TEXT);
          Query OK, 0 rows affected (0.06 sec)

          mysql> INSERT INTO mytable VALUES ( NOW() );
          Query OK, 1 row affected (0.00 sec)

          mysql> SELECT * FROM mytable;
          +---------------------+
          | mycol               |
          +---------------------+
          | 2009-09-01 12:00:00 |
          +---------------------+
          1 row in set (0.00 sec)

     Local time in Stockholm is 6 hours later than in New York; so, if
     you issue `SELECT NOW()' on the slave at that exact same instant,
     the value `2009-09-01 18:00:00' is returned. For this reason, if
     you select from the slave's copy of `mytable' after the *Note
     `CREATE TABLE': create-table. and *Note `INSERT': insert.
     statements just shown have been replicated, you might expect
     `mycol' to contain the value `2009-09-01 18:00:00'. However, this
     is not the case; when you select from the slave's copy of
     `mytable', you obtain exactly the same result as on the master:


          mysql> SELECT * FROM mytable;
          +---------------------+
          | mycol               |
          +---------------------+
          | 2009-09-01 12:00:00 |
          +---------------------+
          1 row in set (0.00 sec)

     Unlike `NOW()', the `SYSDATE()' function is not replication-safe
     because it is not affected by `SET TIMESTAMP' statements in the
     binary log and is nondeterministic if statement-based logging is
     used. This is not a problem if row-based logging is used.

     An alternative is to use the `--sysdate-is-now' option to cause
     `SYSDATE()' to be an alias for `NOW()'. This must be done on the
     master and the slave to work correctly. In such cases, a warning
     is still issued by this function, but can safely be ignored as
     long as `--sysdate-is-now' is used on both the master and the
     slave.

     Beginning with MySQL 5.1.42, `SYSDATE()' is automatically
     replicated using row-based replication when using `MIXED' mode,
     and generates a warning in `STATEMENT' mode. (Bug #47995)

     See also *Note replication-features-timezone::.

   * _The following restriction applies to statement-based replication
     only, not to row-based replication._ The `GET_LOCK()',
     `RELEASE_LOCK()', `IS_FREE_LOCK()', and `IS_USED_LOCK()' functions
     that handle user-level locks are replicated without the slave
     knowing the concurrency context on the master. Therefore, these
     functions should not be used to insert into a master table because
     the content on the slave would differ. For example, do not issue a
     statement such as `INSERT INTO mytable VALUES(GET_LOCK(...))'.

     Beginning with MySQL 5.1.42, these functions are automatically
     replicated using row-based replication when using `MIXED' mode,
     and generate a warning in `STATEMENT' mode. (Bug #47995)

As a workaround for the preceding limitations when statement-based
replication is in effect, you can use the strategy of saving the
problematic function result in a user variable and referring to the
variable in a later statement. For example, the following single-row
*Note `INSERT': insert. is problematic due to the reference to the
`UUID()' function:


     INSERT INTO t VALUES(UUID());

To work around the problem, do this instead:


     SET @my_uuid = UUID();
     INSERT INTO t VALUES(@my_uuid);

That sequence of statements replicates because the value of `@my_uuid'
is stored in the binary log as a user-variable event prior to the *Note
`INSERT': insert. statement and is available for use in the *Note
`INSERT': insert.

The same idea applies to multiple-row inserts, but is more cumbersome
to use. For a two-row insert, you can do this:


     SET @my_uuid1 = UUID(); @my_uuid2 = UUID();
     INSERT INTO t VALUES(@my_uuid1),(@my_uuid2);

However, if the number of rows is large or unknown, the workaround is
difficult or impracticable. For example, you cannot convert the
following statement to one in which a given individual user variable is
associated with each row:


     INSERT INTO t2 SELECT UUID(), * FROM t1;

Within a stored function, `RAND()' replicates correctly as long as it
is invoked only once during the execution of the function. (You can
consider the function execution timestamp and random number seed as
implicit inputs that are identical on the master and slave.)

The `FOUND_ROWS()' and `ROW_COUNT()' functions are not replicated
reliably using statement-based replication. A workaround is to store
the result of the function call in a user variable, and then use that
in the *Note `INSERT': insert. statement. For example, if you wish to
store the result in a table named `mytable', you might normally do so
like this:


     SELECT SQL_CALC_FOUND_ROWS FROM mytable LIMIT 1;
     INSERT INTO mytable VALUES( FOUND_ROWS() );

However, if you are replicating `mytable', you should use *Note `SELECT
... INTO': select-into, and then store the variable in the table, like
this:


     SELECT SQL_CALC_FOUND_ROWS INTO @found_rows FROM mytable LIMIT 1;
     INSERT INTO mytable VALUES(@found_rows);

In this way, the user variable is replicated as part of the context,
and applied on the slave correctly.

Beginning with MySQL 5.1.23, these functions are automatically
replicated using row-based replication when using `MIXED' mode, and
generate a warning in `STATEMENT' mode. (Bug #12092, Bug #30244)

Prior to MySQL 5.1.73, the value of `LAST_INSERT_ID()' was not
replicated correctly if any filtering options such as
`--replicate-ignore-db' and `--replicate-do-table' were enabled on the
slave. (Bug #17234370, BUG# 69861)


File: manual.info,  Node: replication-features-limit,  Next: replication-features-load-data,  Prev: replication-features-functions,  Up: replication-features

16.4.1.17 Replication and LIMIT
...............................

Statement-based replication of `LIMIT' clauses in *Note `DELETE':
delete, *Note `UPDATE': update, and *Note `INSERT ... SELECT':
insert-select. statements is unsafe since the order of the rows
affected is not defined. (Such statements can be replicated correctly
with statement-based replication only if they also contain an `ORDER
BY' clause.) Beginning with MySQL 5.1.24, when such a statement is
encountered:

   * When using `STATEMENT' mode, a warning that the statement is not
     safe for statement-based replication is now issued.

     Currently, when using `STATEMENT' mode, warnings are issued for
     DML statements containing `LIMIT' even when they also have an
     `ORDER BY' clause (and so are made deterministic). This is a known
     issue. (Bug #42851)

   * When using `MIXED' mode, the statement is now automatically
     replicated using row-based mode.


File: manual.info,  Node: replication-features-load-data,  Next: replication-features-logging,  Prev: replication-features-limit,  Up: replication-features

16.4.1.18 Replication and LOAD DATA INFILE
..........................................

The *Note `LOAD DATA INFILE': load-data. statement was not always
replicated correctly to a slave running MySQL 5.1.42 or earlier from a
master running MySQL 4.0 or earlier. When using statement-based
replication, the *Note `LOAD DATA INFILE': load-data. statement
`CONCURRENT' option was not replicated. This issue was fixed in MySQL
5.1.43. This issue does not have any impact on `CONCURRENT' option
handling when using row-based replication in MySQL 5.1 or later. (Bug
#34628)

In MySQL 5.1.52 and later, *Note `LOAD DATA INFILE': load-data. is
considered unsafe (see *Note replication-rbr-safe-unsafe::). It causes a
warning when using statement-based logging format, and is logged using
row-based format when using mixed-format logging.


File: manual.info,  Node: replication-features-logging,  Next: replication-features-repair-table,  Prev: replication-features-load-data,  Up: replication-features

16.4.1.19 Replication and the Slow Query Log
............................................

Prior to MySQL 5.1.45, replication slaves did not write replicated
queries to the slow query log, even if the same queries were written to
the slow query log on the master. (Bug #23300)


File: manual.info,  Node: replication-features-repair-table,  Next: replication-features-shutdowns,  Prev: replication-features-logging,  Up: replication-features

16.4.1.20 Replication and REPAIR TABLE
......................................

When used on a corrupted or otherwise damaged table, it is possible for
the *Note `REPAIR TABLE': repair-table.  statement to delete rows that
cannot be recovered. However, any such modifications of table data
performed by this statement are not replicated, which can cause master
and slave to lose synchronization. For this reason, in the event that a
table on the master becomes damaged and you use *Note `REPAIR TABLE':
repair-table. to repair it, you should first stop replication (if it is
still running) before using *Note `REPAIR TABLE': repair-table, then
afterward compare the master's and slave's copies of the table and be
prepared to correct any discrepancies manually, before restarting
replication.


File: manual.info,  Node: replication-features-shutdowns,  Next: replication-features-max-allowed-packet,  Prev: replication-features-repair-table,  Up: replication-features

16.4.1.21 Replication and Master or Slave Shutdowns
...................................................

It is safe to shut down a master server and restart it later.  When a
slave loses its connection to the master, the slave tries to reconnect
immediately and retries periodically if that fails.  The default is to
retry every 60 seconds. This may be changed with the *Note `CHANGE
MASTER TO': change-master-to.  statement or `--master-connect-retry'
option. A slave also is able to deal with network connectivity outages.
However, the slave notices the network outage only after receiving no
data from the master for `slave_net_timeout' seconds. If your outages
are short, you may want to decrease `slave_net_timeout'. See *Note
server-system-variables::.

An unclean shutdown (for example, a crash) on the master side can
result in the master binary log having a final position less than the
most recent position read by the slave, due to the master binary log
file not being flushed. This can cause the slave not to be able to
replicate when the master comes back up.  Setting `sync_binlog=1' in the
master `my.cnf' file helps to minimize this problem because it causes
the master to flush its binary log more frequently.

Shutting down a slave cleanly is safe because it keeps track of where
it left off. However, be careful that the slave does not have temporary
tables open; see *Note replication-features-temptables::. Unclean
shutdowns might produce problems, especially if the disk cache was not
flushed to disk before the problem occurred:

   * For transactions, the slave commits and then updates
     `relay-log.info'. If a crash occurs between these two operations,
     relay log processing will have proceeded further than the
     information file indicates and the slave will re-execute the
     events from the last transaction in the relay log after it has
     been restarted.

   * A similar problem can occur if the slave updates `relay-log.info'
     but the server host crashes before the write has been flushed to
     disk. Writes are not forced to disk because the server relies on
     the operating system to flush the file from time to time.

The fault tolerance of your system for these types of problems is
greatly increased if you have a good uninterruptible power supply.


File: manual.info,  Node: replication-features-max-allowed-packet,  Next: replication-features-memory,  Prev: replication-features-shutdowns,  Up: replication-features

16.4.1.22 Replication and max_allowed_packet
............................................

`max_allowed_packet' sets an upper limit on the size of any single
message between the MySQL server and clients, including replication
slaves. If you are replicating large column values (such as might be
found in *Note `TEXT': blob. or *Note `BLOB': blob. columns) and
`max_allowed_packet' is too small on the master, the master fails with
an error, and the slave shuts down the I/O thread. If
`max_allowed_packet' is too small on the slave, this also causes the
slave to stop the I/O thread.

Prior to MySQL 5.1.40, `Last_IO_Error' and `Last_IO_Errno' in the
output of *Note `SHOW SLAVE STATUS': show-slave-status. were not set in
the event that replication failed due to exceeding `max_allowed_packet'
(Bug #42914).

Row-based replication currently sends all columns and column values for
updated rows from the master to the slave, including values of columns
that were not actually changed by the update.  This means that, when
you are replicating large column values using row-based replication,
you must take care to set `max_allowed_packet' large enough to
accommodate the largest row in any table to be replicated, even if you
are replicating updates only, or you are inserting only relatively
small values.


File: manual.info,  Node: replication-features-memory,  Next: replication-features-temptables,  Prev: replication-features-max-allowed-packet,  Up: replication-features

16.4.1.23 Replication and MEMORY Tables
.......................................

When a master server shuts down and restarts, its *Note `MEMORY':
memory-storage-engine. tables become empty. To replicate this effect to
slaves, the first time that the master uses a given *Note `MEMORY':
memory-storage-engine. table after startup, it logs an event that
notifies slaves that the table must to be emptied by writing a *Note
`DELETE': delete. statement for that table to the binary log.

When a slave server shuts down and restarts, its *Note `MEMORY':
memory-storage-engine. tables become empty. This causes the slave to be
out of synchrony with the master and may lead to other failures or
cause the slave to stop:

   * Row-format updates and deletes received from the master may fail
     with `Can't find record in 'MEMORY_TABLE''.

   * Statements such as *Note `INSERT INTO ... SELECT FROM
     MEMORY_TABLE': insert-select. may insert a different set of rows
     on the master and slave.

The safe way to restart a slave that is replicating *Note `MEMORY':
memory-storage-engine. tables is to first drop or delete all rows from
the *Note `MEMORY': memory-storage-engine.  tables on the master and
wait until those changes have replicated to the slave. Then it is safe
to restart the slave.

An alternative restart method may apply in some cases. When
`binlog_format=ROW', you can prevent the slave from stopping if you set
`slave_exec_mode=IDEMPOTENT' before you start the slave again. This
allows the slave to continue to replicate, but its *Note `MEMORY':
memory-storage-engine. tables will still be different from those on the
master. This can be okay if the application logic is such that the
contents of *Note `MEMORY': memory-storage-engine. tables can be safely
lost (for example, if the *Note `MEMORY': memory-storage-engine. tables
are used for caching).  `slave_exec_mode=IDEMPOTENT' applies globally
to all tables, so it may hide other replication errors in non-*Note
`MEMORY': memory-storage-engine. tables.

(The method just described is not applicable in MySQL Cluster, where
`slave_exec_mode' is always `IDEMPOTENT', and cannot be changed.)

The size of *Note `MEMORY': memory-storage-engine. tables is limited by
the value of the `max_heap_table_size' system variable, which is not
replicated (see *Note replication-features-variables::). A change in
`max_heap_table_size' takes effect for `MEMORY' tables that are created
or updated using *Note `ALTER TABLE ... ENGINE = MEMORY': alter-table.
or *Note `TRUNCATE TABLE': truncate-table. following the change, or for
all *Note `MEMORY': memory-storage-engine. tables following a server
restart. If you increase the value of this variable on the master
without doing so on the slave, it becomes possible for a table on the
master to grow larger than its counterpart on the slave, leading to
inserts that succeed on the master but fail on the slave with `Table is
full' errors. This is a known issue (Bug #48666). In such cases, you
must set the global value of `max_heap_table_size' on the slave as well
as on the master, then restart replication. It is also recommended that
you restart both the master and slave MySQL servers, to insure that the
new value takes complete (global) effect on each of them.

See *Note memory-storage-engine::, for more information about *Note
`MEMORY': memory-storage-engine. tables.


File: manual.info,  Node: replication-features-temptables,  Next: replication-features-mysqldb,  Prev: replication-features-memory,  Up: replication-features

16.4.1.24 Replication and Temporary Tables
..........................................

The discussion in the following paragraphs does not apply when
`binlog_format=ROW' because, in that case, temporary tables are not
replicated; this means that there are never any temporary tables on the
slave to be lost in the event of an unplanned shutdown by the slave.
The remainder of this section applies only when using statement-based or
mixed-format replication. Loss of replicated temporary tables on the
slave can be an issue, whenever `binlog_format' is `STATEMENT' or
`MIXED', for statements involving temporary tables that can be logged
safely using statement-based format. For more information about
row-based replication and temporary tables, see RBR and temporary
tables.

Safe slave shutdown when using temporary tables

Temporary tables are replicated except in the case where you stop the
slave server (not just the slave threads) and you have replicated
temporary tables that are open for use in updates that have not yet
been executed on the slave. If you stop the slave server, the temporary
tables needed by those updates are no longer available when the slave
is restarted.  To avoid this problem, do not shut down the slave while
it has temporary tables open. Instead, use the following procedure:

  1. Issue a `STOP SLAVE SQL_THREAD' statement.

  2. Use *Note `SHOW STATUS': show-status. to check the value of the
     `Slave_open_temp_tables' variable.

  3. If the value is not 0, restart the slave SQL thread with `START
     SLAVE SQL_THREAD' and repeat the procedure later.

  4. When the value is 0, issue a *Note `mysqladmin shutdown':
     mysqladmin. command to stop the slave.

Temporary tables and replication options

By default, all temporary tables are replicated; this happens whether
or not there are any matching `--replicate-do-db',
`--replicate-do-table', or `--replicate-wild-do-table' options in
effect. However, the `--replicate-ignore-table' and
`--replicate-wild-ignore-table' options are honored for temporary
tables.

A recommended practice when using statement-based or mixed-format
replication is to designate a prefix for exclusive use in naming
temporary tables that you do not want replicated, then employ a
`--replicate-wild-ignore-table' option to match that prefix. For
example, you might give all such tables names beginning with `norep'
(such as `norepmytable', `norepyourtable', and so on), then use
`--replicate-wild-ignore-table=norep%' to prevent them from being
replicated.


File: manual.info,  Node: replication-features-mysqldb,  Next: replication-features-optimizer,  Prev: replication-features-temptables,  Up: replication-features

16.4.1.25 Replication of the mysql System Database
..................................................

MySQL 5.1.14 and later

Data modification statements made to tables in the `mysql' database are
replicated according to the value of `binlog_format'; if this value is
`MIXED', these statement are replicated using the row-based format.
However, statements that would normally update this information
indirectly--such *Note `GRANT': grant, *Note `REVOKE': revoke, and
statements manipulating triggers, stored routines, and views--are
replicated to slaves using statement-based replication.

MySQL 5.1.13 and earlier

User privileges are replicated only if the `mysql' database is
replicated. That is, the *Note `GRANT': grant, *Note `REVOKE': revoke,
*Note `SET PASSWORD': set-password, *Note `CREATE USER': create-user,
and *Note `DROP USER': drop-user. statements take effect on the slave
only if the replication setup includes the `mysql' database.


File: manual.info,  Node: replication-features-optimizer,  Next: replication-features-reserved-words,  Prev: replication-features-mysqldb,  Up: replication-features

16.4.1.26 Replication and the Query Optimizer
.............................................

It is possible for the data on the master and slave to become different
if a statement is written in such a way that the data modification is
nondeterministic; that is, left up the query optimizer. (In general,
this is not a good practice, even outside of replication.) Examples of
nondeterministic statements include *Note `DELETE': delete. or *Note
`UPDATE': update. statements that use `LIMIT' with no `ORDER BY'
clause; see *Note replication-features-limit::, for a detailed
discussion of these.


File: manual.info,  Node: replication-features-reserved-words,  Next: replication-features-set-password,  Prev: replication-features-optimizer,  Up: replication-features

16.4.1.27 Replication and Reserved Words
........................................

You can encounter problems when you attempt to replicate from an older
master to a newer slave and you make use of identifiers on the master
that are reserved words in the newer MySQL version running on the
slave. An example of this is using a table column named `current_user'
on a 4.0 master that is replicating to a 4.1 or higher slave because
`CURRENT_USER' is a reserved word beginning in MySQL 4.1. Replication
can fail in such cases with Error 1064 `You have an error in your SQL
syntax...', _even if a database or table named using the reserved word
or a table having a column named using the reserved word is excluded
from replication_. This is due to the fact that each SQL event must be
parsed by the slave prior to execution, so that the slave knows which
database object or objects would be affected; only after the event is
parsed can the slave apply any filtering rules defined by
`--replicate-do-db', `--replicate-do-table', `--replicate-ignore-db',
and `--replicate-ignore-table'.

To work around the problem of database, table, or column names on the
master which would be regarded as reserved words by the slave, do one
of the following:

   * Use one or more *Note `ALTER TABLE': alter-table.  statements on
     the master to change the names of any database objects where these
     names would be considered reserved words on the slave, and change
     any SQL statements that use the old names to use the new names
     instead.

   * In any SQL statements using these database object names, write the
     names as quoted identifiers using backtick characters (``').

For listings of reserved words by MySQL version, see Reserved Words
(http://dev.mysql.com/doc/mysqld-version-reference/en/mysqld-version-reference-optvar.html),
in the `MySQL Server Version Reference'. For identifier quoting rules,
see *Note identifiers::.


File: manual.info,  Node: replication-features-set-password,  Next: replication-features-slaveerrors,  Prev: replication-features-reserved-words,  Up: replication-features

16.4.1.28 SET PASSWORD and Row-Based Replication
................................................

Row-based replication of *Note `SET PASSWORD': set-password. statements
from a MySQL 5.1 master to a MySQL 5.5 slave did not work correctly
prior to MySQL 5.1.53 on the master and MySQL 5.5.7 on the slave (see
Bug #57098, Bug #57357).


File: manual.info,  Node: replication-features-slaveerrors,  Next: replication-features-server-side-help,  Prev: replication-features-set-password,  Up: replication-features

16.4.1.29 Slave Errors During Replication
.........................................

If a statement produces the same error (identical error code) on both
the master and the slave, the error is logged, but replication
continues.

If a statement produces different errors on the master and the slave,
the slave SQL thread terminates, and the slave writes a message to its
error log and waits for the database administrator to decide what to do
about the error. This includes the case that a statement produces an
error on the master or the slave, but not both. To address the issue,
connect to the slave manually and determine the cause of the problem.
*Note `SHOW SLAVE STATUS': show-slave-status. is useful for this. Then
fix the problem and run *Note `START SLAVE': start-slave. For example,
you might need to create a nonexistent table before you can start the
slave again.

If this error code validation behavior is not desirable, some or all
errors can be masked out (ignored) with the `--slave-skip-errors'
option.

For nontransactional storage engines such as `MyISAM', it is possible
to have a statement that only partially updates a table and returns an
error code.  This can happen, for example, on a multiple-row insert
that has one row violating a key constraint, or if a long update
statement is killed after updating some of the rows. If that happens on
the master, the slave expects execution of the statement to result in
the same error code. If it does not, the slave SQL thread stops as
described previously.

If you are replicating between tables that use different storage
engines on the master and slave, keep in mind that the same statement
might produce a different error when run against one version of the
table, but not the other, or might cause an error for one version of
the table, but not the other. For example, since `MyISAM' ignores
foreign key constraints, an *Note `INSERT': insert. or *Note `UPDATE':
update. statement accessing an `InnoDB' table on the master might cause
a foreign key violation but the same statement performed on a `MyISAM'
version of the same table on the slave would produce no such error,
causing replication to stop.


File: manual.info,  Node: replication-features-server-side-help,  Next: replication-features-sql-mode,  Prev: replication-features-slaveerrors,  Up: replication-features

16.4.1.30 Replication of Server-Side Help Tables
................................................

The server maintains tables in the `mysql' database that store
information for the *Note `HELP': help. statement (see *Note help::.
These tables can be loaded manually as described at *Note
server-side-help-support::.

Help table content is derived from the MySQL Reference Manual.  There
are versions of the manual specific to each MySQL release series, so
help content is specific to each series as well.  Normally, you load a
version of help content that matches the server version. This has
implications for replication. For example, you would load MySQL 5.5
help content into a MySQL 5.5 master server, but not necessarily
replicate that content to a MySQL 5.6 slave server for which 5.6 help
content is more appropriate.

This section describes how to manage help table content upgrades when
your servers participate in replication. Server versions are one factor
in this task. Another is that help table structure may differ between
the master and the slave.

Assume that help content is stored in a file named
`fill_help_tables.sql'. In MySQL distributions, this file is located
under the `share' or `share/mysql' directory, and the most recent
version is always available for download from
`http://dev.mysql.com/doc/index-other.html'.

To upgrade help tables, using the following procedure.  Connection
parameters are not shown for the *Note `mysql': mysql. commands
discussed here; in all cases, connect to the server using an account
such as `root' that has privileges for modifying tables in the `mysql'
database.

  1. Upgrade your servers by running *Note `mysql_upgrade':
     mysql-upgrade, first on the slaves and then on the master. This is
     the usual principle of upgrading slaves first.

  2. Decide whether you want to replicate help table content from the
     master to its slaves. If not, load the content on the master and
     each slave individually. Otherwise, check for and resolve any
     incompatibilities between help table structure on the master and
     its slaves, then load the content into the master and let it
     replicate to the slaves.

     More detail about these two methods of loading help table content
     follows.

*Loading Help Table Content Without Replication to Slaves*

To load help table content without replication, run this command on the
master and each slave individually, using a `fill_help_tables.sql' file
containing content appropriate to the server version (enter the command
on one line):


     mysql --init-command="SET sql_log_bin=0"
       mysql < fill_help_tables.sql

Use the `--init-command'
(http://dev.mysql.com/doc/refman/5.5/en/mysql-command-options.html#option_mysql_init-command)
option on each server, including the slaves, in case a slave also acts
as a master to other slaves in your replication topology. The `SET'
statement suppresses binary logging.  After the command has been run on
each server to be upgraded, you are done.

*Loading Help Table Content With Replication to Slaves*

If you do want to replicate help table content, check for help table
incompatibilities between your master and its slaves. The `url' column
in the `help_category' and `help_topic' tables was originally
`CHAR(128)', but is `TEXT' in newer MySQL versions to accommodate
longer URLs. To check help table structure, use this statement:


     SELECT TABLE_NAME, COLUMN_NAME, COLUMN_TYPE
     FROM INFORMATION_SCHEMA.COLUMNS
     WHERE TABLE_SCHEMA = 'mysql'
     AND COLUMN_NAME = 'url';

For tables with the old structure, the statement produces this result:


     +---------------+-------------+-------------+
     | TABLE_NAME    | COLUMN_NAME | COLUMN_TYPE |
     +---------------+-------------+-------------+
     | help_category | url         | char(128)   |
     | help_topic    | url         | char(128)   |
     +---------------+-------------+-------------+

For tables with the new structure, the statement produces this result:


     +---------------+-------------+-------------+
     | TABLE_NAME    | COLUMN_NAME | COLUMN_TYPE |
     +---------------+-------------+-------------+
     | help_category | url         | text        |
     | help_topic    | url         | text        |
     +---------------+-------------+-------------+

If the master and slave both have the old structure or both have the
new structure, they are compatible and you can replicate help table
content by executing this command on the master:


     mysql mysql < fill_help_tables.sql

The table content will load into the master, then replicate to the
slaves.

If the master and slave have incompatible help tables (one server has
the old structure and the other has the new), you have a choice between
not replicating help table content after all, or making the table
structures compatible so that you can replicate the content.

   * If you decide not to replicate the content after all, upgrade the
     master and slaves individually using *Note `mysql': mysql. with the
     `--init-command'
     (http://dev.mysql.com/doc/refman/5.5/en/mysql-command-options.html#option_mysql_init-command)
     option, as described previously.

   * If instead you decide to make the table structures compatible,
     upgrade the tables on the server that has the old structure.
     Suppose that your master server has the old table structure.
     Upgrade its tables to the new structure manually by executing
     these statements (binary logging is disabled here to prevent
     replication of the changes to the slaves, which already have the
     new structure):


          SET sql_log_bin=0;
          ALTER TABLE mysql.help_category ALTER COLUMN url TEXT;
          ALTER TABLE mysql.help_topic ALTER COLUMN url TEXT;

     Then run this command on the master:


          mysql mysql < fill_help_tables.sql

     The table content will load into the master, then replicate to the
     slaves.


File: manual.info,  Node: replication-features-sql-mode,  Next: replication-features-timeout,  Prev: replication-features-server-side-help,  Up: replication-features

16.4.1.31 Replication and Server SQL Mode
.........................................

Using different server SQL mode settings on the master and the slave
may cause the same *Note `INSERT': insert.  statements to be handled
differently on the master and the slave, leading the master and slave
to diverge. For best results, you should always use the same server SQL
mode on the master and on the slave. This advice applies whether you are
using statement-based or row-based replication.

If you are replicating partitioned tables, using different SQL modes on
the master and the slave is likely to cause issues. At a minimum, this
is likely to cause the distribution of data among partitions to be
different in the master's and slave's copies of a given table. It may
also cause inserts into partitioned tables that succeed on the master
to fail on the slave.

For more information, see *Note sql-mode::.


File: manual.info,  Node: replication-features-timeout,  Next: replication-features-timestamp,  Prev: replication-features-sql-mode,  Up: replication-features

16.4.1.32 Replication Retries and Timeouts
..........................................

The global system variable `slave_transaction_retries' affects
replication as follows: If the slave SQL thread fails to execute a
transaction because of an `InnoDB' deadlock or because it exceeded the
`InnoDB' `innodb_lock_wait_timeout' value, or the *Note `NDBCLUSTER':
mysql-cluster.  `TransactionDeadlockDetectionTimeout' or
`TransactionInactiveTimeout' value, the slave automatically retries the
transaction `slave_transaction_retries' times before stopping with an
error. The default value is 10. The total retry count can be seen in
the output of *Note `SHOW STATUS': show-status.; see *Note
server-status-variables::.


File: manual.info,  Node: replication-features-timestamp,  Next: replication-features-timezone,  Prev: replication-features-timeout,  Up: replication-features

16.4.1.33 Replication and TIMESTAMP
...................................

Older versions of MySQL (prior to 4.1) differed significantly in
several ways in their handling of the *Note `TIMESTAMP': datetime. data
type from what is supported in MySQL versions 5.1 and newer; these
include syntax extensions which are deprecated in MySQL 5.1, and that
no longer supported in MySQL 5.5. This can cause problems (including
replication failures) when replicating between MySQL Server versions,
if you are using columns that are defined using the old *Note
`TIMESTAMP(N)': datetime. syntax. See *Note
upgrading-from-previous-series::, for more information about the
differences, how they can impact MySQL replication, and what you can do
if you encounter such problems.


File: manual.info,  Node: replication-features-timezone,  Next: replication-features-transactions,  Prev: replication-features-timestamp,  Up: replication-features

16.4.1.34 Replication and Time Zones
....................................

The same system time zone should be set for both master and slave.
Otherwise, statements depending on the local time on the master are not
replicated properly, such as statements that use the `NOW()' or
`FROM_UNIXTIME()' functions. You can set the time zone in which MySQL
server runs by using the `--timezone=TIMEZONE_NAME' option of the
`mysqld_safe' script or by setting the `TZ' environment variable. See
also *Note replication-features-functions::.

If the master is MySQL 4.1 or earlier, both master and slave should
also use the same default connection time zone. That is, the
`--default-time-zone' parameter should have the same value for both
master and slave.

`CONVERT_TZ(...,...,@@session.time_zone)' is properly replicated only
if both master and slave are running MySQL 5.0.4 or newer.


File: manual.info,  Node: replication-features-transactions,  Next: replication-features-triggers,  Prev: replication-features-timezone,  Up: replication-features

16.4.1.35 Replication and Transactions
......................................

Mixing transactional and nontransactional statements within the same
transaction

In general, you should avoid transactions that update both
transactional and nontransactional tables in a replication environment.
You should also avoid using any statement that accesses both
transactional (or temporary) and nontransactional tables and writes to
any of them.

As of MySQL 5.1.44, the server uses these rules for binary logging:

   * If the initial statements in a transaction are nontransactional,
     they are written to the binary log immediately. The remaining
     statements in the transaction are cached and not written to the
     binary log until the transaction is committed. (If the transaction
     is rolled back, the cached statements are written to the binary log
     only if they make nontransactional changes that cannot be rolled
     back. Otherwise, they are discarded.)

   * For statement-based logging, logging of nontransactional
     statements is affected by the
     `binlog_direct_non_transactional_updates' system variable. When
     this variable is `OFF' (the default), logging is as just
     described. When this variable is `ON', logging occurs immediately
     for nontransactional statements occurring anywhere in the
     transaction (not just initial nontransactional statements). Other
     statements are kept in the transaction cache and logged when the
     transaction commits.  `binlog_direct_non_transactional_updates'
     has no effect for row-format or mixed-format binary logging.

Transactional, nontransactional, and mixed statements

To apply those rules, the server considers a statement nontransactional
if it changes only nontransactional tables, and transactional if it
changes only transactional tables. A statement that changes both
nontransactional and transactional tables is considered `mixed'. Mixed
statements, like transactional statements, are cached and logged when
the transaction commits.

*Note*:

A mixed statement is unrelated to mixed binary logging format.

Before MySQL 5.1.44, the rules for binary logging are similar to those
just described, except that there is no
`binlog_direct_non_transactional_updates' system variable to affect
logging of transactional statements.  Thus, the server immediately logs
only the initial nontransactional statements in a transaction and
caches the rest until commit time.

Before MySQL 5.1.31, the _effect_ of the rules differs because the
definition of transactional statement is different: In these earlier
versions, a statement is nontransactional if the first changes it makes
change nontransactional tables, transactional if the first changes it
makes change transactional tables. `First' applies in the sense that a
statement may have several effects if it involves such things as
triggers, stored functions, or multiple-table updates. A mixed
statement that changes both nontransactional and transactional tables
is handled as nontransactional or transactional depending on the type of
changes it makes first.

In situations where transactions mix updates to transactional and
nontransactional tables, the order of statements in the binary log is
correct, and all needed statements are written to the binary log even
in case of a *Note `ROLLBACK': commit.  However, when a second
connection updates the nontransactional table before the first
connection transaction is complete, statements can be logged out of
order because the second connection update is written immediately after
it is performed, regardless of the state of the transaction being
performed by the first connection.

Using different storage engines on master and slave

It is possible to replicate transactional tables on the master using
nontransactional tables on the slave. For example, you can replicate an
`InnoDB' master table as a `MyISAM' slave table. However, if you do
this, there are problems if the slave is stopped in the middle of a
*Note `BEGIN': commit ... *Note `COMMIT': commit. block because the
slave restarts at the beginning of the *Note `BEGIN': commit. block.

Beginning with MySQL 5.1.48, it is also safe to replicate transactions
from *Note `MyISAM': myisam-storage-engine. tables on the master to
transactional tables--such as tables that use the *Note `InnoDB':
innodb-storage-engine. storage engine--on the slave. In such cases
(beginning with MySQL 5.1.48), an `AUTOCOMMIT=1' statement issued on
the master is replicated, thus enforcing `AUTOCOMMIT' mode on the slave.

When the storage engine type of the slave is nontransactional,
transactions on the master that mix updates of transactional and
nontransactional tables should be avoided because they can cause
inconsistency of the data between the master transactional table and
the slave nontransactional table. That is, such transactions can lead
to master storage engine-specific behavior with the possible effect of
replication going out of synchrony. MySQL does not issue a warning
about this currently, so extra care should be taken when replicating
transactional tables from the master to nontransactional tables on the
slaves.

Beginning with MySQL Cluster NDB 6.2.14 and MySQL 5.1.24, every
transaction (including `autocommit' transactions) is recorded in the
binary log as though it starts with a *Note `BEGIN': commit.
statement, and ends with either a *Note `COMMIT': commit. or a *Note
`ROLLBACK': commit.  statement. However, this does _not_ apply to
nontransactional changes; any statements affecting tables using a
nontransactional storage engine such as *Note `MyISAM':
myisam-storage-engine. are regarded for this purpose as
nontransactional, even when `autocommit' is enabled. (Bug #26395)


File: manual.info,  Node: replication-features-triggers,  Next: replication-features-truncate,  Prev: replication-features-transactions,  Up: replication-features

16.4.1.36 Replication and Triggers
..................................

With statement-based replication, triggers executed on the master also
execute on the slave. With row-based replication, triggers executed on
the master do not execute on the slave.  Instead, the row changes on
the master resulting from trigger execution are replicated and applied
on the slave.

This behavior is by design. If under row-based replication the slave
applied the triggers as well as the row changes caused by them, the
changes would in effect be applied twice on the slave, leading to
different data on the master and the slave.

If you want triggers to execute on both the master and the
slave--perhaps because you have different triggers on the master and
slave--you must use statement-based replication.  However, to enable
slave-side triggers, it is not necessary to use statement-based
replication exclusively. It is sufficient to switch to statement-based
replication only for those statements where you want this effect, and
to use row-based replication the rest of the time.

Before MySQL 5.1.31, a trigger that was defined on a transactional
table but that updated a nontransactional table could cause updates on
the transactional table to be replicated before they were actually
committed on the master, and not be rolled back correctly on the slave
if they were rolled back on the master. (Bug #40116) See also *Note
replication-features-transactions::.

A statement invoking a trigger (or function) that causes an update to
an `AUTO_INCREMENT' column is not replicated correctly using
statement-based replication.  Beginning with MySQL 5.1.40, such
statements are marked as unsafe. (Bug #45677)


File: manual.info,  Node: replication-features-truncate,  Next: replication-features-variables,  Prev: replication-features-triggers,  Up: replication-features

16.4.1.37 Replication and TRUNCATE TABLE
........................................

*Note `TRUNCATE TABLE': truncate-table. is normally regarded as a DML
statement, and so would be expected to be logged and replicated using
row-based format when the binary logging mode is `ROW' or `MIXED'.
However this caused issues when logging or replicating, in `STATEMENT'
or `MIXED' mode, tables that used transactional storage engines such as
*Note `InnoDB': innodb-storage-engine. when the transaction isolation
level was `READ COMMITTED' or `READ UNCOMMITTED', which precludes
statement-based logging.

Beginning with MySQL 5.1.32, *Note `TRUNCATE TABLE': truncate-table. is
treated for purposes of logging and replication as DDL rather than DML
so that it can be logged and replicated as a statement. However, the
effects of the statement as applicable to *Note `InnoDB':
innodb-storage-engine. and other transactional tables on replication
slaves still follow the rules described in *Note truncate-table::
governing such tables. (Bug #36763)


File: manual.info,  Node: replication-features-variables,  Next: replication-features-views,  Prev: replication-features-truncate,  Up: replication-features

16.4.1.38 Replication and Variables
...................................

System variables are not replicated correctly when using `STATEMENT'
mode, except for the following variables when they are used with
session scope:

   * `auto_increment_increment'

   * `auto_increment_offset'

   * `character_set_client'

   * `character_set_connection'

   * `character_set_database'

   * `character_set_server'

   * `collation_connection'

   * `collation_database'

   * `collation_server'

   * `foreign_key_checks'

   * `identity'

   * `last_insert_id'

   * `lc_time_names'

   * `pseudo_thread_id'

   * `sql_auto_is_null'

   * `time_zone'

   * `timestamp'

   * `unique_checks'

When `MIXED' mode is used, the variables in the preceding list, when
used with session scope, cause a switch from statement-based to
row-based logging. See *Note binary-log-mixed::.

`sql_mode' is also replicated except for the `NO_DIR_IN_CREATE' mode;
the slave always preserves its own value for `NO_DIR_IN_CREATE',
regardless of changes to it on the master. This is true for all
replication formats.

However, when *Note `mysqlbinlog': mysqlbinlog. parses a `SET
@@sql_mode = MODE' statement, the full MODE value, including
`NO_DIR_IN_CREATE', is passed to the receiving server. For this reason,
replication of such a statement may not be safe when `STATEMENT' mode
is in use.

The `storage_engine' system variable is not replicated, regardless of
the logging mode; this is intended to facilitate replication between
different storage engines.

The `read_only' system variable is not replicated. In addition, the
enabling this variable has different effects with regard to temporary
tables, table locking, and the *Note `SET PASSWORD': set-password.
statement in different MySQL versions.

The `max_heap_table_size' system variable is not replicated. Increasing
the value of this variable on the master without doing so on the slave
can lead eventually to `Table is full' errors on the slave when trying
to execute *Note `INSERT': insert. statements on a *Note `MEMORY':
memory-storage-engine. table on the master that is thus permitted to
grow larger than its counterpart on the slave.  For more information,
see *Note replication-features-memory::.

In statement-based replication, session variables are not replicated
properly when used in statements that update tables.  For example, the
following sequence of statements will not insert the same data on the
master and the slave:


     SET max_join_size=1000;
     INSERT INTO mytable VALUES(@@max_join_size);

This does not apply to the common sequence:


     SET time_zone=...;
     INSERT INTO mytable VALUES(CONVERT_TZ(..., ..., @@time_zone));

Replication of session variables is not a problem when row-based
replication is being used, in which case, session variables are always
replicated safely. See *Note replication-formats::.

In MySQL 5.1.20 and later (and in MySQL 5.0.46 and later in MySQL 5.0,
for backward compatibility), the following session variables are
written to the binary log and honored by the replication slave when
parsing the binary log, regardless of the logging format:

   * `sql_mode'

   * `foreign_key_checks'

   * `unique_checks'

   * `character_set_client'

   * `collation_connection'

   * `collation_database'

   * `collation_server'

   * `sql_auto_is_null'

*Important*:

Even though session variables relating to character sets and collations
are written to the binary log, replication between different character
sets is not supported.

It is strongly recommended that you always use the same setting for the
`lower_case_table_names' system variable on both master and slave. In
particular, when a case-sensitive file system is used, setting this
variable to 1 on the slave, but to a different value on the master, can
cause two types of problems: Names of databases are not converted to
lowercase; in addition, when using row-based replication names of
tables are also not converted. Either of these problems can cause
replication to fail. This is a known issue, which is fixed in MySQL 5.6.


File: manual.info,  Node: replication-features-views,  Prev: replication-features-variables,  Up: replication-features

16.4.1.39 Replication and Views
...............................

Views are always replicated to slaves. Views are filtered by their own
name, not by the tables they refer to. This means that a view can be
replicated to the slave even if the view contains a table that would
normally be filtered out by `replication-ignore-table' rules. Care
should therefore be taken to ensure that views do not replicate table
data that would normally be filtered for security reasons.

Replication from a table to a samed-named view is supported using
statement-based logging, but not when using row-based logging. In MySQL
5.1.69 and later, trying to do so when row-based logging is in effect
causes an error. (Bug #11752707, Bug #43975)


File: manual.info,  Node: replication-compatibility,  Next: replication-upgrade,  Prev: replication-features,  Up: replication-notes

16.4.2 Replication Compatibility Between MySQL Versions
-------------------------------------------------------

MySQL supports replication from one major version to the next higher
major version. For example, you can replicate from a master running
MySQL 4.1 to a slave running MySQL 5.0, from a master running MySQL 5.0
to a slave running MySQL 5.1, and so on.

However, one may encounter difficulties when replicating from an older
master to a newer slave if the master uses statements or relies on
behavior no longer supported in the version of MySQL used on the slave.

The use of more than 2 MySQL Server versions is not supported in
replication setups involving multiple masters, regardless of the number
of master or slave MySQL servers. This restriction applies not only to
major versions, but to minor versions within the same major version as
well. For example, if you are using a chained or circular replication
setup, you cannot use MySQL 5.1.31, MySQL 5.1.32, and MySQL 5.1.34
concurrently, although you could use any 2 of these releases together.

In some cases, it is also possible to replicate between a master and a
slave that is more than one major version newer than the master.
However, there are known issues with trying to replicate from a master
running MySQL 4.1 or earlier to a slave running MySQL 5.1 or later. To
work around such problems, you can insert a MySQL server running an
intermediate version between the two; for example, rather than
replicating directly from a MySQL 4.1 master to a MySQL 5.1 slave, it
is possible to replicate from a MySQL 4.1 server to a MySQL 5.0 server,
and then from the MySQL 5.0 server to a MySQL 5.1 server.

*Important*:

It is strongly recommended to use the most recent release available
within a given MySQL major version because replication (and other)
capabilities are continually being improved. It is also recommended to
upgrade masters and slaves that use early releases of a major version
of MySQL to GA (production) releases when the latter become available
for that major version.

Replication from newer masters to older slaves may be possible, but is
generally not supported. This is due to a number of factors:

   * Binary log format changes

     The binary log format can change between major releases.  While we
     attempt to maintain backward compatibility, this is not always
     possible. For example, the binary log format implemented in MySQL
     5.0 changed considerably from that used in previous versions,
     especially with regard to handling of character sets, *Note `LOAD
     DATA INFILE': load-data, and time zones. This means that
     replication from a MySQL 5.0 (or later) master to a MySQL 4.1 (or
     earlier) slave is generally not supported.

     This also has significant implications for upgrading replication
     servers; see *Note replication-upgrade::, for more information.

   * Use of row-based replication

     Row-based replication was implemented in MySQL 5.1.5, so you
     cannot replicate using row-based replication from any MySQL 5.1 or
     later master to a slave older than MySQL 5.1.5.

     For more information about row-based replication, see *Note
     replication-formats::.

   * SQL incompatibilities

     You cannot replicate from a newer master to an older slave using
     statement-based replication if the statements to be replicated use
     SQL features available on the master but not on the slave.

     However, if both the master and the slave support row-based
     replication, and there are no data definition statements to be
     replicated that depend on SQL features found on the master but not
     on the slave, you can use row-based replication to replicate the
     effects of data modification statements even if the DDL run on the
     master is not supported on the slave.

For more information on potential replication issues, see *Note
replication-features::.


File: manual.info,  Node: replication-upgrade,  Next: replication-problems,  Prev: replication-compatibility,  Up: replication-notes

16.4.3 Upgrading a Replication Setup
------------------------------------

When you upgrade servers that participate in a replication setup, the
procedure for upgrading depends on the current server versions and the
version to which you are upgrading.

This section applies to upgrading replication from older versions of
MySQL to MySQL 5.1. A 4.0 server should be 4.0.3 or newer.

When you upgrade a master to 5.1 from an earlier MySQL release series,
you should first ensure that all the slaves of this master are using
the same 5.1.x release. If this is not the case, you should first
upgrade the slaves. To upgrade each slave, shut it down, upgrade it to
the appropriate 5.1.x version, restart it, and restart replication.
The 5.1 slave is able to read the old relay logs written prior to the
upgrade and to execute the statements they contain. Relay logs created
by the slave after the upgrade are in 5.1 format.

After the slaves have been upgraded, shut down the master, upgrade it
to the same 5.1.x release as the slaves, and restart it. The 5.1 master
is able to read the old binary logs written prior to the upgrade and to
send them to the 5.1 slaves. The slaves recognize the old format and
handle it properly. Binary logs created by the master subsequent to the
upgrade are in 5.1 format. These too are recognized by the 5.1 slaves.

In other words, when upgrading to MySQL 5.1, the slaves must be MySQL
5.1 before you can upgrade the master to 5.1. Note that downgrading from
5.1 to older versions does not work so simply: You must ensure that any
5.1 binary log or relay log has been fully processed, so that you can
remove it before proceeding with the downgrade.

Downgrading a replication setup to a previous version cannot be done
once you have switched from statement-based to row-based replication,
and after the first row-based statement has been written to the binlog.
See *Note replication-formats::.

Some upgrades may require that you drop and re-create database objects
when you move from one MySQL series to the next. For example, collation
changes might require that table indexes be rebuilt. Such operations,
if necessary, will be detailed at *Note
upgrading-from-previous-series::. It is safest to perform these
operations separately on the slaves and the master, and to disable
replication of these operations from the master to the slave. To
achieve this, use the following procedure:

  1. Stop all the slaves and upgrade them. Restart them with the
     `--skip-slave-start' option so that they do not connect to the
     master. Perform any table repair or rebuilding operations needed
     to re-create database objects, such as use of `REPAIR TABLE' or
     `ALTER TABLE', or dumping and reloading tables or triggers.

  2. Disable the binary log on the master. To do this without
     restarting the master, execute a `SET sql_log_bin = 0' statement.
     Alternatively, stop the master and restart it without the
     `--log-bin' option. If you restart the master, you might also want
     to disallow client connections. For example, if all clients
     connect using TCP/IP, use the `--skip-networking' option when you
     restart the master.

  3. With the binary log disabled, perform any table repair or
     rebuilding operations needed to re-create database objects.  The
     binary log must be disabled during this step to prevent these
     operations from being logged and sent to the slaves later.

  4. Re-enable the binary log on the master. If you set `sql_log_bin'
     to 0 earlier, execute a `SET sql_log_bin = 1' statement. If you
     restarted the master to disable the binary log, restart it with
     `--log-bin', and without `--skip-networking' so that clients and
     slaves can connect.

  5. Restart the slaves, this time without the `--skip-slave-start'
     option.


File: manual.info,  Node: replication-problems,  Next: replication-bugs,  Prev: replication-upgrade,  Up: replication-notes

16.4.4 Troubleshooting Replication
----------------------------------

If you have followed the instructions but your replication setup is not
working, the first thing to do is _check the error log for messages_.
Many users have lost time by not doing this soon enough after
encountering problems.

If you cannot tell from the error log what the problem was, try the
following techniques:

   * Verify that the master has binary logging enabled by issuing a
     *Note `SHOW MASTER STATUS': show-master-status. statement.  If
     logging is enabled, `Position' is nonzero.  If binary logging is
     not enabled, verify that you are running the master with the
     `--log-bin' option.

   * Verify that the master and slave both were started with the
     `--server-id' option and that the ID value is unique on each
     server.

   * Verify that the slave is running. Use *Note `SHOW SLAVE STATUS':
     show-slave-status. to check whether the `Slave_IO_Running' and
     `Slave_SQL_Running' values are both `Yes'. If not, verify the
     options that were used when starting the slave server. For example,
     `--skip-slave-start' prevents the slave threads from starting
     until you issue a *Note `START SLAVE': start-slave. statement.

   * If the slave is running, check whether it established a connection
     to the master. Use *Note `SHOW PROCESSLIST': show-processlist,
     find the I/O and SQL threads and check their `State' column to see
     what they display. See *Note replication-implementation-details::.
     If the I/O thread state says `Connecting to master', check the
     following:

        * Verify the privileges for the user being used for replication
          on the master.

        * Check that the host name of the master is correct and that
          you are using the correct port to connect to the master.  The
          port used for replication is the same as used for client
          network communication (the default is `3306'). For the host
          name, ensure that the name resolves to the correct IP address.

        * Check that networking has not been disabled on the master or
          slave. Look for the `skip-networking' option in the
          configuration file. If present, comment it out or remove it.

        * If the master has a firewall or IP filtering configuration,
          ensure that the network port being used for MySQL is not
          being filtered.

        * Check that you can reach the master by using `ping' or
          `traceroute'/`tracert' to reach the host.

   * If the slave was running previously but has stopped, the reason
     usually is that some statement that succeeded on the master failed
     on the slave. This should never happen if you have taken a proper
     snapshot of the master, and never modified the data on the slave
     outside of the slave thread. If the slave stops unexpectedly, it
     is a bug or you have encountered one of the known replication
     limitations described in *Note replication-features::. If it is a
     bug, see *Note replication-bugs::, for instructions on how to
     report it.

   * If a statement that succeeded on the master refuses to run on the
     slave, try the following procedure if it is not feasible to do a
     full database resynchronization by deleting the slave's databases
     and copying a new snapshot from the master:

       1. Determine whether the affected table on the slave is
          different from the master table. Try to understand how this
          happened. Then make the slave's table identical to the
          master's and run *Note `START SLAVE': start-slave.

       2. If the preceding step does not work or does not apply, try to
          understand whether it would be safe to make the update
          manually (if needed) and then ignore the next statement from
          the master.

       3. If you decide that the slave can skip the next statement from
          the master, issue the following statements:


               mysql> SET GLOBAL sql_slave_skip_counter = N;
               mysql> START SLAVE;

          The value of N should be 1 if the next statement from the
          master does not use `AUTO_INCREMENT' or `LAST_INSERT_ID()'.
          Otherwise, the value should be 2. The reason for using a
          value of 2 for statements that use `AUTO_INCREMENT' or
          `LAST_INSERT_ID()' is that they take two events in the binary
          log of the master.

          See also *Note set-global-sql-slave-skip-counter::.

       4. If you are sure that the slave started out perfectly
          synchronized with the master, and that no one has updated the
          tables involved outside of the slave thread, then presumably
          the discrepancy is the result of a bug. If you are running
          the most recent version of MySQL, please report the problem.
          If you are running an older version, try upgrading to the
          latest production release to determine whether the problem
          persists.


File: manual.info,  Node: replication-bugs,  Prev: replication-problems,  Up: replication-notes

16.4.5 How to Report Replication Bugs or Problems
-------------------------------------------------

When you have determined that there is no user error involved, and
replication still either does not work at all or is unstable, it is
time to send us a bug report. We need to obtain as much information as
possible from you to be able to track down the bug.  Please spend some
time and effort in preparing a good bug report.

If you have a repeatable test case that demonstrates the bug, please
enter it into our bugs database using the instructions given in *Note
bug-reports::. If you have a `phantom' problem (one that you cannot
duplicate at will), use the following procedure:

  1. Verify that no user error is involved. For example, if you update
     the slave outside of the slave thread, the data goes out of
     synchrony, and you can have unique key violations on updates. In
     this case, the slave thread stops and waits for you to clean up
     the tables manually to bring them into synchrony. _This is not a
     replication problem. It is a problem of outside interference
     causing replication to fail._

  2. Run the slave with the `--log-slave-updates' and `--log-bin'
     options. These options cause the slave to log the updates that it
     receives from the master into its own binary logs.

  3. Save all evidence before resetting the replication state. If we
     have no information or only sketchy information, it becomes
     difficult or impossible for us to track down the problem. The
     evidence you should collect is:

        * All binary log files from the master

        * All binary log files from the slave

        * The output of *Note `SHOW MASTER STATUS': show-master-status.
          from the master at the time you discovered the problem

        * The output of *Note `SHOW SLAVE STATUS': show-slave-status.
          from the slave at the time you discovered the problem

        * Error logs from the master and the slave

  4. Use *Note `mysqlbinlog': mysqlbinlog. to examine the binary logs.
     The following should be helpful to find the problem statement.
     LOG_FILE and LOG_POS are the `Master_Log_File' and
     `Read_Master_Log_Pos' values from *Note `SHOW SLAVE STATUS':
     show-slave-status.


          shell> mysqlbinlog --start-position=LOG_POS LOG_FILE | head

After you have collected the evidence for the problem, try to isolate
it as a separate test case first. Then enter the problem with as much
information as possible into our bugs database using the instructions
at *Note bug-reports::.


File: manual.info,  Node: mysql-cluster,  Next: partitioning,  Prev: replication,  Up: Top

17 MySQL Cluster NDB 6.1 - 7.1
******************************

* Menu:

* mysql-cluster-overview::       MySQL Cluster Overview
* mysql-cluster-installation::   MySQL Cluster Installation and Upgrades
* mysql-cluster-configuration::  Configuration of MySQL Cluster NDB 6.1-7.1
* mysql-cluster-programs::       MySQL Cluster Programs
* mysql-cluster-management::     Management of MySQL Cluster
* mysql-cluster-replication::    MySQL Cluster Replication
* mysql-cluster-news::           MySQL Cluster NDB 6.1 - 7.1 Release Notes

This chapter contains information about _MySQL Cluster_, which is a
high-availability, high-redundancy version of MySQL adapted for the
distributed computing environment.  Current releases of MySQL Cluster
use versions 6 and 7 of the *Note `NDB': mysql-cluster. storage engine
(also known as *Note `NDBCLUSTER': mysql-cluster.) to enable running
several computers with MySQL servers and other software in a cluster.

Beginning with MySQL 5.1.24, support for the *Note `NDBCLUSTER':
mysql-cluster. storage engine was removed from the standard MySQL
server binaries built by MySQL. Instead, users of MySQL Cluster
binaries built by MySQL should upgrade to the most recent binary
release of MySQL Cluster NDB 7.0 or MySQL Cluster 7.1 for supported
platforms--these include RPMs that should work with most Linux
distributions. MySQL Cluster users who build from source should be
aware that, also beginning with MySQL 5.1.24, *Note `NDBCLUSTER':
mysql-cluster. sources in the standard MySQL 5.1 tree are no longer
maintained; these users should use the sources provided for MySQL
Cluster NDB 7.0 or later. (Locations where the sources can be obtained
are listed later in this section.)

*Note*:

MySQL Cluster NDB 6.1, 6.2, and 6.3 were formerly known as `MySQL
Cluster Carrier Grade Edition'. Beginning with MySQL Cluster NDB 6.2.15
and MySQL Cluster NDB 6.3.14, this term is no longer applied to the
MySQL Cluster software--which is now known simply as `MySQL
Cluster'--but rather to a commercial licensing and support package. You
can learn more about available options for commercial licensing of
MySQL Cluster from
`http://mysql.com/products/database/cluster/features.html', on the
MySQL web site.

This chapter contains information about MySQL Cluster in MySQL 5.1
mainline releases through MySQL 5.1.23, MySQL Cluster NDB 6.2 releases
through 5.1.51-ndb-6.2.19, MySQL Cluster NDB 6.3 releases through
5.1.73-ndb-6.3.55, MySQL Cluster NDB 7.0 releases through
5.1.73-ndb-7.0.42 and MySQL Cluster NDB 7.1 releases through
5.1.73-ndb-7.1.34. Currently, the MySQL Cluster NDB 7.2 release series
is Generally Available (GA), as is MySQL Cluster NDB 7.1. MySQL Cluster
NDB 7.0 and MySQL Cluster NDB 6.3 are previous GA release series;
although they are still supported, we recommend that new deployments
use MySQL Cluster NDB 7.2. For information about MySQL Cluster NDB 7.2,
see MySQL Cluster NDB 7.2
(http://dev.mysql.com/doc/refman/5.5/en/mysql-cluster.html), in the
`MySQL 5.5 Manual'.

This chapter also contains historical information about MySQL Cluster
NDB 6.1 and MySQL Cluster NDB 6,2, although these release series are no
longer in active development, and no longer supported for new
deployments. You should upgrade to a MySQL Cluster NDB 7.1 or later
release series as soon as possible.

Release notes for the changes in each release of MySQL Cluster are
located at MySQL Cluster 7.1 Release Notes
(http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/).

Supported Platforms

MySQL Cluster is currently available and supported on a number of
platforms. For exact levels of support available for on specific
combinations of operating system versions, operating system
distributions, and hardware platforms, please refer to
`http://www.mysql.com/support/supportedplatforms/cluster.html'.

Availability

MySQL Cluster binary and source packages are available for supported
platforms from `http://dev.mysql.com/downloads/cluster/'.

*Note*:

Binary releases and RPMs were not available for MySQL Cluster NDB 6.2
prior to MySQL Cluster NDB 6.2.15.

MySQL Cluster release numbers

Starting with MySQL Cluster NDB 6.1 and MySQL Cluster NDB 6.2, MySQL
Cluster follows a somewhat different release pattern from the mainline
MySQL 5.1 Cluster series of releases. In this `Manual' and other MySQL
documentation, we identify these and later MySQL Cluster releases
employing a version number that begins with `NDB'. This version number
is that of the *Note `NDBCLUSTER': mysql-cluster.  storage engine used
in the release, and not of the MySQL server version on which the MySQL
Cluster release is based.

Version strings used in MySQL Cluster NDB 6.x and 7.x software

The version string displayed by MySQL Cluster NDB 6.x and 7.x software
uses this format:


     mysql-MYSQL_SERVER_VERSION-ndb-NDB_ENGINE_VERSION

MYSQL_SERVER_VERSION represents the version of the MySQL Server on
which the MySQL Cluster release is based. For all MySQL Cluster NDB 6.x
and 7.x releases, this is `5.1'. NDB_ENGINE_VERSION is the version of
the *Note `NDB': mysql-cluster. storage engine used by this release of
the MySQL Cluster software. You can see this format used in the *Note
`mysql': mysql. client, as shown here:


     shell> mysql
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 2
     Server version: 5.1.73-ndb-7.1.34 Source distribution

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql> SELECT VERSION()\G
     *************************** 1. row ***************************
     VERSION(): 5.1.73-ndb-7.1.34
     1 row in set (0.00 sec)

This version string is also displayed in the output of the `SHOW'
command in the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.  client:


     ndb_mgm> SHOW
     Connected to Management Server at: localhost:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=1    @10.0.10.6  (5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=2    @10.0.10.8  (5.1.73-ndb-7.1.34, Nodegroup: 0)

     [ndb_mgmd(MGM)] 1 node(s)
     id=3    @10.0.10.2  (5.1.73-ndb-7.1.34)

     [mysqld(API)]   2 node(s)
     id=4    @10.0.10.10  (5.1.73-ndb-7.1.34)
     id=5 (not connected, accepting connect from any host)

The version string identifies the mainline MySQL version from which the
MySQL Cluster release was branched and the version of the *Note
`NDBCLUSTER': mysql-cluster. storage engine used. For example, the full
version string for MySQL Cluster NDB 7.0.5 (the first GA MySQL Cluster
NDB 7.0 binary release) was `mysql-5.1.32-ndb-7.0.5'. From this we can
determine the following:

   * Since the portion of the version string preceding ``-ndb-'' is the
     base MySQL Server version, this means that MySQL Cluster NDB 7.0.5
     derives from the MySQL 5.1.32, and contains all feature
     enhancements and bugfixes from MySQL 5.1 up to and including MySQL
     5.1.32.

   * Since the portion of the version string following ``-ndb-''
     represents the version number of the *Note `NDB': mysql-cluster.
     (or *Note `NDBCLUSTER': mysql-cluster.) storage engine, MySQL
     Cluster NDB 7.0.5 uses version 7.0.5 of the *Note `NDBCLUSTER':
     mysql-cluster. storage engine.

New MySQL Cluster releases are numbered according to updates in the
`NDB' storage engine, and do not necessarily correspond in a linear
fashion with mainline MySQL Server releases.  For example, MySQL
Cluster NDB 7.0.5 (as previously noted) is based on MySQL 5.1.32, and
MySQL Cluster NDB 7.0.6 is based on MySQL 5.1.34 (version string:
`mysql-5.1.34-ndb-7.0.6').

Compatibility with standard MySQL 5.1 releases

While many standard MySQL schemas and applications can work using MySQL
Cluster, it is also true that unmodified applications and database
schemas may be slightly incompatible or have suboptimal performance
when run using MySQL Cluster (see *Note mysql-cluster-limitations::).
Most of these issues can be overcome, but this also means that you are
very unlikely to be able to switch an existing application
datastore--that currently uses, for example, *Note `MyISAM':
myisam-storage-engine.  or *Note `InnoDB': innodb-storage-engine.--to
use the *Note `NDB': mysql-cluster. storage engine without allowing for
the possibility of changes in schemas, queries, and applications.
Moreover, from MySQL 5.1.24 onwards, the MySQL Server and MySQL Cluster
codebases diverge considerably (and *Note `NDB': mysql-cluster. storage
engine support dropped from subsequent MySQL Server releases), so that
the standard *Note `mysqld': mysqld. cannot function as a dropin
replacement for the version of *Note `mysqld': mysqld. that is supplied
with MySQL Cluster.

MySQL Cluster development source trees

MySQL Cluster development trees can also be accessed from
`https://code.launchpad.net/~mysql/':

The MySQL Cluster development sources maintained at
`https://code.launchpad.net/~mysql/' are licensed under the GPL. For
information about obtaining MySQL sources using Bazaar and building
them yourself, see *Note installing-development-tree::.

Currently, MySQL Cluster NDB 7.0, MySQL Cluster NDB 7.1, and MySQL
Cluster NDB 7.2 releases are all Generally Available (GA), although we
recommend that new deployments use MySQL Cluster NDB 7.2. MySQL Cluster
NDB 6.1, MySQL Cluster NDB 6.2, and MySQL Cluster NDB 6.3, are no
longer in active development. For an overview of major features added
in MySQL Cluster NDB 6.x and 7.x releases, see *Note
mysql-cluster-development::. For an overview of major features added in
MySQL Cluster NDB 7.2, see MySQL Cluster Development History
(http://dev.mysql.com/doc/refman/5.5/en/mysql-cluster-development.html).

This chapter represents a work in progress, and its contents are
subject to revision as MySQL Cluster continues to evolve. Additional
information regarding MySQL Cluster can be found on the MySQL Web site
at `http://www.mysql.com/products/cluster/'.

Additional Resources

More information about MySQL Cluster can be found in the following
places:

   * For answers to some commonly asked questions about MySQL Cluster,
     see *Note faqs-mysql-cluster::.

   * The MySQL Cluster mailing list: `http://lists.mysql.com/cluster'.

   * The MySQL Cluster Forum: `http://forums.mysql.com/list.php?25'.

   * Many MySQL Cluster users and developers blog about their
     experiences with MySQL Cluster, and make feeds of these available
     through PlanetMySQL (http://www.planetmysql.org/).


File: manual.info,  Node: mysql-cluster-overview,  Next: mysql-cluster-installation,  Prev: mysql-cluster,  Up: mysql-cluster

17.1 MySQL Cluster Overview
===========================

* Menu:

* mysql-cluster-basics::         MySQL Cluster Core Concepts
* mysql-cluster-nodes-groups::   MySQL Cluster Nodes, Node Groups, Replicas, and Partitions
* mysql-cluster-overview-requirements::  MySQL Cluster Hardware, Software, and Networking Requirements
* mysql-cluster-development::    MySQL Cluster Development History
* mysql-cluster-compared::       MySQL Server Using InnoDB Compared with MySQL Cluster
* mysql-cluster-limitations::    Known Limitations of MySQL Cluster

_MySQL Cluster_ is a technology that enables clustering of in-memory
databases in a shared-nothing system. The shared-nothing architecture
enables the system to work with very inexpensive hardware, and with a
minimum of specific requirements for hardware or software.

MySQL Cluster is designed not to have any single point of failure.  In
a shared-nothing system, each component is expected to have its own
memory and disk, and the use of shared storage mechanisms such as
network shares, network file systems, and SANs is not recommended or
supported.

MySQL Cluster integrates the standard MySQL server with an in-memory
clustered storage engine called *Note `NDB': mysql-cluster.  (which
stands for `_N_etwork _D_ata_B_ase'). In our documentation, the term
*Note `NDB': mysql-cluster. refers to the part of the setup that is
specific to the storage engine, whereas `MySQL Cluster' refers to the
combination of one or more MySQL servers with the *Note `NDB':
mysql-cluster.  storage engine.

A MySQL Cluster consists of a set of computers, known as _hosts_, each
running one or more processes.  These processes, known as _nodes_, may
include MySQL servers (for access to NDB data), data nodes (for storage
of the data), one or more management servers, and possibly other
specialized data access programs. The relationship of these components
in a MySQL Cluster is shown here:

MySQL Cluster Components

All these programs work together to form a MySQL Cluster (see *Note
mysql-cluster-programs::. When data is stored by the *Note `NDB':
mysql-cluster. storage engine, the tables (and table data) are stored
in the data nodes. Such tables are directly accessible from all other
MySQL servers (SQL nodes) in the cluster.  Thus, in a payroll
application storing data in a cluster, if one application updates the
salary of an employee, all other MySQL servers that query this data can
see this change immediately.

Although a MySQL Cluster SQL node uses the *Note `mysqld': mysqld.
server daemon, it differs in a number of critical respects from the
*Note `mysqld': mysqld. binary supplied with the MySQL 5.1
distributions, and the two versions of *Note `mysqld': mysqld. are not
interchangeable.

In addition, a MySQL server that is not connected to a MySQL Cluster
cannot use the *Note `NDB': mysql-cluster. storage engine and cannot
access any MySQL Cluster data.

The data stored in the data nodes for MySQL Cluster can be mirrored;
the cluster can handle failures of individual data nodes with no other
impact than that a small number of transactions are aborted due to
losing the transaction state. Because transactional applications are
expected to handle transaction failure, this should not be a source of
problems.

Individual nodes can be stopped and restarted, and can then rejoin the
system (cluster). Rolling restarts (in which all nodes are restarted in
turn) are used in making configuration changes and software upgrades
(see *Note mysql-cluster-rolling-restart::). In MySQL Cluster NDB 7.0
and later, rolling restarts are also used as part of the process of
adding new data nodes online (see *Note
mysql-cluster-online-add-node::). For more information about data
nodes, how they are organized in a MySQL Cluster, and how they handle
and store MySQL Cluster data, see *Note mysql-cluster-nodes-groups::.

Backing up and restoring MySQL Cluster databases can be done using the
`NDB'-native functionality found in the MySQL Cluster management client
and the *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
program included in the MySQL Cluster distribution. For more
information, see *Note mysql-cluster-backup::, and *Note
mysql-cluster-programs-ndb-restore::. You can also use the standard
MySQL functionality provided for this purpose in *Note `mysqldump':
mysqldump. and the MySQL server. See *Note mysqldump::, for more
information.

MySQL Cluster nodes can use a number of different transport mechanisms
for inter-node communications, including TCP/IP using standard 100 Mbps
or faster Ethernet hardware. It is also possible to use the high-speed
_Scalable Coherent Interface_ (SCI) protocol with MySQL Cluster,
although this is not required to use MySQL Cluster. SCI requires special
hardware and software; see *Note mysql-cluster-interconnects::, for
more about SCI and using it with MySQL Cluster.


File: manual.info,  Node: mysql-cluster-basics,  Next: mysql-cluster-nodes-groups,  Prev: mysql-cluster-overview,  Up: mysql-cluster-overview

17.1.1 MySQL Cluster Core Concepts
----------------------------------

_*Note `NDBCLUSTER': mysql-cluster._ (also known as *Note `NDB':
mysql-cluster.) is an in-memory storage engine offering
high-availability and data-persistence features.

The *Note `NDBCLUSTER': mysql-cluster. storage engine can be configured
with a range of failover and load-balancing options, but it is easiest
to start with the storage engine at the cluster level. MySQL Cluster's
*Note `NDB': mysql-cluster. storage engine contains a complete set of
data, dependent only on other data within the cluster itself.

The `Cluster' portion of MySQL Cluster is configured independently of
the MySQL servers. In a MySQL Cluster, each part of the cluster is
considered to be a _node_.

*Note*:

In many contexts, the term `node' is used to indicate a computer, but
when discussing MySQL Cluster it means a _process_. It is possible to
run multiple nodes on a single computer; for a computer on which one or
more cluster nodes are being run we use the term _cluster host_.

There are three types of cluster nodes, and in a minimal MySQL Cluster
configuration, there will be at least three nodes, one of each of these
types:

   * _Management node_: The role of this type of node is to manage the
     other nodes within the MySQL Cluster, performing such functions as
     providing configuration data, starting and stopping nodes, running
     backup, and so forth.  Because this node type manages the
     configuration of the other nodes, a node of this type should be
     started first, before any other node. An MGM node is started with
     the command *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.

   * _Data node_: This type of node stores cluster data. There are as
     many data nodes as there are replicas, times the number of
     fragments (see *Note mysql-cluster-nodes-groups::). For example,
     with two replicas, each having two fragments, you need four data
     nodes. One replica is sufficient for data storage, but provides no
     redundancy; therefore, it is recommended to have 2 (or more)
     replicas to provide redundancy, and thus high availability. A data
     node is started with the command *Note `ndbd':
     mysql-cluster-programs-ndbd. (see *Note
     mysql-cluster-programs-ndbd::). In MySQL Cluster NDB 7.0 and
     later, *Note `ndbmtd': mysql-cluster-programs-ndbmtd. can also be
     used for the data node process; see *Note
     mysql-cluster-programs-ndbmtd::, for more information.

     MySQL Cluster tables are normally stored completely in memory
     rather than on disk (this is why we refer to MySQL Cluster as an
     _in-memory_ database). In MySQL 5.1, MySQL Cluster NDB 6.X, and
     later, some MySQL Cluster data can be stored on disk; see *Note
     mysql-cluster-disk-data::, for more information.

   * _SQL node_: This is a node that accesses the cluster data. In the
     case of MySQL Cluster, an SQL node is a traditional MySQL server
     that uses the *Note `NDBCLUSTER': mysql-cluster. storage engine.
     An SQL node is a *Note `mysqld': mysqld. process started with the
     `--ndbcluster' and `--ndb-connectstring' options, which are
     explained elsewhere in this chapter, possibly with additional
     MySQL server options as well.

     An SQL node is actually just a specialized type of _API node_,
     which designates any application which accesses MySQL Cluster
     data. Another example of an API node is the *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. utility that is used to
     restore a cluster backup. It is possible to write such
     applications using the NDB API. For basic information about the
     NDB API, see Getting Started with the NDB API
     (http://dev.mysql.com/doc/ndbapi/en/ndb-getting-started.html).

*Important*:

It is not realistic to expect to employ a three-node setup in a
production environment. Such a configuration provides no redundancy; to
benefit from MySQL Cluster's high-availability features, you must use
multiple data and SQL nodes. The use of multiple management nodes is
also highly recommended.

For a brief introduction to the relationships between nodes, node
groups, replicas, and partitions in MySQL Cluster, see *Note
mysql-cluster-nodes-groups::.

Configuration of a cluster involves configuring each individual node in
the cluster and setting up individual communication links between
nodes. MySQL Cluster is currently designed with the intention that data
nodes are homogeneous in terms of processor power, memory space, and
bandwidth. In addition, to provide a single point of configuration, all
configuration data for the cluster as a whole is located in one
configuration file.

The management server manages the cluster configuration file and the
cluster log. Each node in the cluster retrieves the configuration data
from the management server, and so requires a way to determine where
the management server resides. When interesting events occur in the
data nodes, the nodes transfer information about these events to the
management server, which then writes the information to the cluster log.

In addition, there can be any number of cluster client processes or
applications. These include standard MySQL clients, `NDB'-specific API
programs, and management clients. These are described in the next few
paragraphs.

Standard MySQL clients

MySQL Cluster can be used with existing MySQL applications written in
PHP, Perl, C, C++, Java, Python, Ruby, and so on.  Such client
applications send SQL statements to and receive responses from MySQL
servers acting as MySQL Cluster SQL nodes in much the same way that
they interact with standalone MySQL servers.

MySQL clients using a MySQL Cluster as a data source can be modified to
take advantage of the ability to connect with multiple MySQL servers to
achieve load balancing and failover. For example, Java clients using
Connector/J 5.0.6 and later can use `jdbc:mysql:loadbalance://' URLs
(improved in Connector/J 5.1.7) to achieve load balancing
transparently; for more information about using Connector/J with MySQL
Cluster, see Using Connector/J with MySQL Cluster
(http://dev.mysql.com/doc/ndbapi/en/mccj-using-connectorj.html).

NDB client programs

Client programs can be written that access MySQL Cluster data directly
from the `NDBCLUSTER' storage engine, bypassing any MySQL Servers that
may connected to the cluster, using the _NDB API_, a high-level C++ API.
Such applications may be useful for specialized purposes where an SQL
interface to the data is not needed. For more information, see The NDB
API (http://dev.mysql.com/doc/ndbapi/en/ndbapi.html).

Beginning with MySQL Cluster NDB 7.1, `NDB'-specific Java applications
can also be written for MySQL Cluster, using the _MySQL Cluster
Connector for Java_. This MySQL Cluster Connector includes _ClusterJ_,
a high-level database API similar to object-relational mapping
persistence frameworks such as Hibernate and JPA that connect directly
to `NDBCLUSTER', and so does not require access to a MySQL Server.
Support is also provided in MySQL Cluster NDB 7.1 and later for
_ClusterJPA_, an OpenJPA implementation for MySQL Cluster that
leverages the strengths of ClusterJ and JDBC; ID lookups and other fast
operations are performed using ClusterJ (bypassing the MySQL Server),
while more complex queries that can benefit from MySQL's query optimizer
are sent through the MySQL Server, using JDBC. See Java and MySQL
Cluster (http://dev.mysql.com/doc/ndbapi/en/mccj-overview-java.html),
and The ClusterJ API and Data Object Model
(http://dev.mysql.com/doc/ndbapi/en/mccj-overview-clusterj-object-models.html),
for more information.

Management clients

These clients connect to the management server and provide commands for
starting and stopping nodes gracefully, starting and stopping message
tracing (debug versions only), showing node versions and status,
starting and stopping backups, and so on.  An example of this type of
program is the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.
management client supplied with MySQL Cluster (see *Note
mysql-cluster-programs-ndb-mgm::).  Such applications can be written
using the _MGM API_, a C-language API that communicates directly with
one or more MySQL Cluster management servers. For more information, see
The MGM API (http://dev.mysql.com/doc/ndbapi/en/mgm-api.html).

Oracle also makes available MySQL Cluster Manager, which provides an
advanced command-line interface simplifying many complex MySQL Cluster
management tasks, such restarting a MySQL Cluster with a large number
of nodes. The MySQL Cluster Manager client also supports commands for
getting and setting the values of most node configuration parameters as
well as *Note `mysqld': mysqld. server options and variables relating
to MySQL Cluster. See MySQL(tm) Cluster Manager 1.3.2 User Manual
(http://dev.mysql.com/doc/mysql-cluster-manager/1.3/en/index.html), for
more information.

Event logs

MySQL Cluster logs events by category (startup, shutdown, errors,
checkpoints, and so on), priority, and severity. A complete listing of
all reportable events may be found in *Note
mysql-cluster-event-reports::. Event logs are of the two types listed
here:

   * _Cluster log_: Keeps a record of all desired reportable events for
     the cluster as a whole.

   * _Node log_: A separate log which is also kept for each individual
     node.

*Note*:

Under normal circumstances, it is necessary and sufficient to keep and
examine only the cluster log. The node logs need be consulted only for
application development and debugging purposes.

Checkpoint

Generally speaking, when data is saved to disk, it is said that a
_checkpoint_ has been reached. More specific to MySQL Cluster, a
checkpoint is a point in time where all committed transactions are
stored on disk. With regard to the *Note `NDB': mysql-cluster. storage
engine, there are two types of checkpoints which work together to
ensure that a consistent view of the cluster's data is maintained.
These are shown in the following list:

   * _Local Checkpoint (LCP)_: This is a checkpoint that is specific to
     a single node; however, LCPs take place for all nodes in the
     cluster more or less concurrently. An LCP involves saving all of a
     node's data to disk, and so usually occurs every few minutes. The
     precise interval varies, and depends upon the amount of data
     stored by the node, the level of cluster activity, and other
     factors.

   * _Global Checkpoint (GCP)_: A GCP occurs every few seconds, when
     transactions for all nodes are synchronized and the redo-log is
     flushed to disk.

For more information about the files and directories created by local
checkpoints and global checkpoints, see MySQL Cluster Data Node
`FileSystemDir' Files
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-ndbd-filesystemdir-files.html).


File: manual.info,  Node: mysql-cluster-nodes-groups,  Next: mysql-cluster-overview-requirements,  Prev: mysql-cluster-basics,  Up: mysql-cluster-overview

17.1.2 MySQL Cluster Nodes, Node Groups, Replicas, and Partitions
-----------------------------------------------------------------

This section discusses the manner in which MySQL Cluster divides and
duplicates data for storage.

A number of concepts central to an understanding of this topic are
discussed in the next few paragraphs.

(Data) Node

An *Note `ndbd': mysql-cluster-programs-ndbd. process, which stores a
_replica_ --that is, a copy of the _partition_ (see below) assigned to
the node group of which the node is a member.

Each data node should be located on a separate computer. While it is
also possible to host multiple *Note `ndbd':
mysql-cluster-programs-ndbd.  processes on a single computer, such a
configuration is not supported.

It is common for the terms `node' and `data node' to be used
interchangeably when referring to an *Note `ndbd':
mysql-cluster-programs-ndbd. process; where mentioned, management nodes
(*Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. processes) and SQL
nodes (*Note `mysqld': mysqld. processes) are specified as such in this
discussion.

Node Group

A node group consists of one or more nodes, and stores partitions, or
sets of _replicas_ (see next item).

The number of node groups in a MySQL Cluster is not directly
configurable; it is a function of the number of data nodes and of the
number of replicas (`NoOfReplicas' configuration parameter), as shown
here:


     [NUMBER_OF_NODE_GROUPS] = NUMBER_OF_DATA_NODES / `NoOfReplicas'

Thus, a MySQL Cluster with 4 data nodes has 4 node groups if
`NoOfReplicas' is set to 1 in the `config.ini' file, 2 node groups if
`NoOfReplicas' is set to 2, and 1 node group if `NoOfReplicas' is set
to 4.  Replicas are discussed later in this section; for more
information about `NoOfReplicas', see *Note
mysql-cluster-ndbd-definition::.

*Note*:

All node groups in a MySQL Cluster must have the same number of data
nodes.

Prior to MySQL Cluster NDB 7.0, it was not possible to add new data
nodes to a MySQL Cluster without shutting down the cluster completely
and reloading all of its data. In MySQL Cluster NDB 7.0 (beginning with
MySQL Cluster version NDB 6.4.0), you can add new node groups (and thus
new data nodes) to a running MySQL Cluster--see *Note
mysql-cluster-online-add-node::, for information about how this can be
done.

Partition

This is a portion of the data stored by the cluster. There are as many
cluster partitions as nodes participating in the cluster. Each node is
responsible for keeping at least one copy of any partitions assigned to
it (that is, at least one replica) available to the cluster.

A replica belongs entirely to a single node; a node can (and usually
does) store several replicas.

NDB and user-defined partitioning

MySQL Cluster normally partitions *Note `NDBCLUSTER': mysql-cluster.
tables automatically.  However, in MySQL 5.1 and later MySQL Cluster
releases, it is possible to employ user-defined partitioning with *Note
`NDBCLUSTER': mysql-cluster. tables. This is subject to the following
limitations:

  1. Only `KEY' and `LINEAR KEY' partitioning schemes can be used with
     *Note `NDB': mysql-cluster. tables.

  2. When using *Note `ndbd': mysql-cluster-programs-ndbd, the maximum
     number of partitions that may be defined explicitly for any *Note
     `NDB': mysql-cluster. table is `8 * [NUMBER OF NODE GROUPS]'.
     (The number of node groups in a MySQL Cluster is determined as
     discussed previously in this section.)

     When using *Note `ndbmtd': mysql-cluster-programs-ndbmtd, this
     maximum is also affected by the number of local query handler
     threads, which is determined by the value of the
     `MaxNoOfExecutionThreads' configuration parameter. In such cases,
     the maximum number of partitions that may be defined explicitly
     for an *Note `NDB': mysql-cluster. table is equal to `4 *
     MaxNoOfExecutionThreads * [NUMBER OF NODE GROUPS]'.

     See *Note mysql-cluster-programs-ndbmtd::, for more information.

For more information relating to MySQL Cluster and user-defined
partitioning, see *Note mysql-cluster-limitations::, and *Note
partitioning-limitations-storage-engines::.

Replica

This is a copy of a cluster partition. Each node in a node group stores
a replica. Also sometimes known as a _partition replica_. The number of
replicas is equal to the number of nodes per node group.

The following diagram illustrates a MySQL Cluster with four data nodes,
arranged in two node groups of two nodes each; nodes 1 and 2 belong to
node group 0, and nodes 3 and 4 belong to node group 1. Note that only
data (*Note `ndbd': mysql-cluster-programs-ndbd.) nodes are shown here;
although a working cluster requires an *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. process for cluster management and at
least one SQL node to access the data stored by the cluster, these have
been omitted in the figure for clarity.

A MySQL Cluster, with 2 node groups having 2 nodes each

The data stored by the cluster is divided into four partitions,
numbered 0, 1, 2, and 3. Each partition is stored--in multiple
copies--on the same node group. Partitions are stored on alternate node
groups as follows:

   * Partition 0 is stored on node group 0; a _primary replica_
     (primary copy) is stored on node 1, and a _backup replica_ (backup
     copy of the partition) is stored on node 2.

   * Partition 1 is stored on the other node group (node group 1); this
     partition's primary replica is on node 3, and its backup replica
     is on node 4.

   * Partition 2 is stored on node group 0. However, the placing of its
     two replicas is reversed from that of Partition 0; for Partition
     2, the primary replica is stored on node 2, and the backup on node
     1.

   * Partition 3 is stored on node group 1, and the placement of its
     two replicas are reversed from those of partition 1. That is, its
     primary replica is located on node 4, with the backup on node 3.

What this means regarding the continued operation of a MySQL Cluster is
this: so long as each node group participating in the cluster has at
least one node operating, the cluster has a complete copy of all data
and remains viable. This is illustrated in the next diagram.

Nodes required to keep a 2x2 cluster viable

In this example, where the cluster consists of two node groups of two
nodes each, any combination of at least one node in node group 0 and at
least one node in node group 1 is sufficient to keep the cluster
`alive' (indicated by arrows in the diagram).  However, if _both_ nodes
from _either_ node group fail, the remaining two nodes are not
sufficient (shown by the arrows marked out with an *X*); in either
case, the cluster has lost an entire partition and so can no longer
provide access to a complete set of all cluster data.


File: manual.info,  Node: mysql-cluster-overview-requirements,  Next: mysql-cluster-development,  Prev: mysql-cluster-nodes-groups,  Up: mysql-cluster-overview

17.1.3 MySQL Cluster Hardware, Software, and Networking Requirements
--------------------------------------------------------------------

One of the strengths of MySQL Cluster is that it can be run on
commodity hardware and has no unusual requirements in this regard,
other than for large amounts of RAM, due to the fact that all live data
storage is done in memory. (It is possible to reduce this requirement
using Disk Data tables--see *Note mysql-cluster-disk-data::, for more
information about these.) Naturally, multiple and faster CPUs can
enhance performance. Memory requirements for other MySQL Cluster
processes are relatively small.

The software requirements for MySQL Cluster are also modest. Host
operating systems do not require any unusual modules, services,
applications, or configuration to support MySQL Cluster. For supported
operating systems, a standard installation should be sufficient. The
MySQL software requirements are simple: all that is needed is a
production release of MySQL Cluster. It is not strictly necessary to
compile MySQL yourself merely to be able to use MySQL Cluster. We
assume that you are using the binaries appropriate to your platform,
available from the MySQL Cluster software downloads page at
`http://dev.mysql.com/downloads/cluster/'.

For communication between nodes, MySQL Cluster supports TCP/IP
networking in any standard topology, and the minimum expected for each
host is a standard 100 Mbps Ethernet card, plus a switch, hub, or
router to provide network connectivity for the cluster as a whole. We
strongly recommend that a MySQL Cluster be run on its own subnet which
is not shared with machines not forming part of the cluster for the
following reasons:

   * Security

     Communications between MySQL Cluster nodes are not encrypted or
     shielded in any way. The only means of protecting transmissions
     within a MySQL Cluster is to run your MySQL Cluster on a protected
     network. If you intend to use MySQL Cluster for Web applications,
     the cluster should definitely reside behind your firewall and not
     in your network's De-Militarized Zone (DMZ
     (http://compnetworking.about.com/cs/networksecurity/g/bldef_dmz.htm))
     or elsewhere.

     See *Note mysql-cluster-security-networking-issues::, for more
     information.

   * Efficiency

     Setting up a MySQL Cluster on a private or protected network
     enables the cluster to make exclusive use of bandwidth between
     cluster hosts. Using a separate switch for your MySQL Cluster not
     only helps protect against unauthorized access to MySQL Cluster
     data, it also ensures that MySQL Cluster nodes are shielded from
     interference caused by transmissions between other computers on
     the network. For enhanced reliability, you can use dual switches
     and dual cards to remove the network as a single point of failure;
     many device drivers support failover for such communication links.

Network communication and latency

MySQL Cluster requires communication between data nodes and API nodes
(including SQL nodes), as well as between data nodes and other data
nodes, to execute queries and updates. Communication latency between
these processes can directly affect the observed performance and
latency of user queries. In addition, to maintain consistency and
service despite the silent failure of nodes, MySQL Cluster uses
heartbeating and timeout mechanisms which treat an extended loss of
communication from a node as node failure. This can lead to reduced
redundancy. Recall that, to maintain data consistency, a MySQL Cluster
shuts down when the last node in a node group fails. Thus, to avoid
increasing the risk of a forced shutdown, breaks in communication
between nodes should be avoided wherever possible.

The failure of a data or API node results in the abort of all
uncommitted transactions involving the failed node. Data node recovery
requires synchronization of the failed node's data from a surviving
data node, and re-establishment of disk-based redo and checkpoint logs,
before the data node returns to service.  This recovery can take some
time, during which the Cluster operates with reduced redundancy.

Heartbeating relies on timely generation of heartbeat signals by all
nodes. This may not be possible if the node is overloaded, has
insufficient machine CPU due to sharing with other programs, or is
experiencing delays due to swapping. If heartbeat generation is
sufficiently delayed, other nodes treat the node that is slow to
respond as failed.

This treatment of a slow node as a failed one may or may not be
desirable in some circumstances, depending on the impact of the node's
slowed operation on the rest of the cluster. When setting timeout
values such as `HeartbeatIntervalDbDb' and `HeartbeatIntervalDbApi' for
MySQL Cluster, care must be taken care to achieve quick detection,
failover, and return to service, while avoiding potentially expensive
false positives.

Where communication latencies between data nodes are expected to be
higher than would be expected in a LAN environment (on the order of 100
µs), timeout parameters must be increased to ensure that any allowed
periods of latency periods are well within configured timeouts.
Increasing timeouts in this way has a corresponding effect on the
worst-case time to detect failure and therefore time to service
recovery.

LAN environments can typically be configured with stable low latency,
and such that they can provide redundancy with fast failover.
Individual link failures can be recovered from with minimal and
controlled latency visible at the TCP level (where MySQL Cluster
normally operates). WAN environments may offer a range of latencies, as
well as redundancy with slower failover times. Individual link failures
may require route changes to propagate before end-to-end connectivity
is restored. At the TCP level this can appear as large latencies on
individual channels.  The worst-case observed TCP latency in these
scenarios is related to the worst-case time for the IP layer to reroute
around the failures.

SCI support

It is also possible to use the high-speed Scalable Coherent Interface
(SCI) with MySQL Cluster, but this is not a requirement. See *Note
mysql-cluster-interconnects::, for more about this protocol and its use
with MySQL Cluster.


File: manual.info,  Node: mysql-cluster-development,  Next: mysql-cluster-compared,  Prev: mysql-cluster-overview-requirements,  Up: mysql-cluster-overview

17.1.4 MySQL Cluster Development History
----------------------------------------

* Menu:

* mysql-cluster-development-5-1-ndb-7-2::  MySQL Cluster Development in MySQL Cluster NDB 7.2.0
* mysql-cluster-development-5-1-ndb-7-1::  MySQL Cluster Development in MySQL Cluster NDB 7.1
* mysql-cluster-development-5-1-ndb-7-0::  MySQL Cluster Development in MySQL Cluster NDB 7.0
* mysql-cluster-development-5-1-ndb-6-3::  MySQL Cluster Development in MySQL Cluster NDB 6.3
* mysql-cluster-development-5-1-ndb-6-2::  MySQL Cluster Development in MySQL Cluster NDB 6.2
* mysql-cluster-development-5-1-ndb-6-1::  MySQL Cluster Development in MySQL Cluster NDB 6.1
* mysql-cluster-development-5-1::  Development History of MySQL Cluster in MySQL 5.1

In this section, we discuss changes in the implementation of MySQL
Cluster in MySQL 5.1, MySQL Cluster NDB 6.x, and MySQL Cluster NDB 7.x,
as compared to earlier MySQL Cluster releases.

There are a number of significant changes in the implementation of the
*Note `NDBCLUSTER': mysql-cluster. storage engine in mainline MySQL 5.1
releases up to and including MySQL 5.1.23 as compared to that in MySQL
5.0; MySQL Cluster NDB 6.x and 7.x make further changes and
improvements in MySQL Cluster in addition to these. The changes and
features most likely to be of interest are shown in the following
tables:

This table lists changes and features in MySQL Cluster NDB 7.2 that are
most likely to be of interest.

*Note MySQL Cluster NDB 7.2:
mysql-cluster-development-5-1-ndb-7-2.
Distribution of MySQL users and
privileges across MySQL Cluster SQL
nodes
Distributed pushed-down joins, with
greatly improved performance for
many joins that can thus be pushed
down and executed in parallel on
the data nodes.
Improved default values for data
node configuration parameters.

This table lists changes and features in MySQL Cluster NDB 7.1 that are
most likely to be of interest.

*Note MySQL Cluster NDB 7.1:
mysql-cluster-development-5-1-ndb-7-1.
Production-level support for MySQL
Cluster on Microsoft Windows
platforms.
*Note `ndbinfo':
mysql-cluster-ndbinfo.
meta-information database
MySQL Cluster Connector for Java,
including ClusterJ and OpenJPA
(ClusterJPA) support
Native support for default column
values

This table lists changes and features in MySQL Cluster NDB 7.0 that are
most likely to be of interest.

*Note MySQL Cluster NDB 7.0:
mysql-cluster-development-5-1-ndb-7-0.
Multi-threaded data nodes (*Note
`ndbmtd':
mysql-cluster-programs-ndbmtd. data
node daemon)
Online addition of data nodes;
online data redistribution
MySQL on Windows (alpha; source
releases only)
Configuration cache
Backup snapshots (`START BACKUP ...
SNAPSHOTSTART', `START BACKUP ...
SNAPSHOTEND' commands)
IPv6 support for geo-replication
Protected DDL operations
Dynamic buffering for NDB
transporters
Increased flexibility in
determining arbitration handling,
using a new `Arbitration' data node
configuration parameter
NDB API counters and associated
status variables, which make it
possible to observe the API-level
effects of SQL statements on *Note
`NDB': mysql-cluster. tables from
the *Note `mysql': mysql. client.

This table lists changes and features in MySQL Cluster NDB 6.3 that are
most likely to be of interest.

*Note MySQL Cluster NDB 6.3:
mysql-cluster-development-5-1-ndb-6-3.
Conflict detection and resolution
for multi-master replication
Compressed backups and local
checkpoints
Support for *Note `OPTIMIZE TABLE':
optimize-table.
Parallel data node recovery
Enhanced transaction coordinator
selection
Improved SQL statement performance
metrics
Transaction batching
*Note `ndb_restore':
mysql-cluster-programs-ndb-restore.
attribute promotion
Support for `epoll' (Linux only)
Distribution awareness
*Note `NDB': mysql-cluster. thread
locks; realtime extensions for
multiple CPUs

This table lists changes and features in MySQL Cluster NDB 6.2 that are
most likely to be of interest.

*Note MySQL Cluster NDB 6.2:
mysql-cluster-development-5-1-ndb-6-2.
Improved backup status reporting
(`BackupReportFrequency', `REPORT
BackupStatus')
Multiple connections per SQL node
Data access with `NdbRecord' (NDB
API)
`REPORT MemoryUsage' command
Memory allocation improvements
Management client connection control
Micro-GCPs
Online `ADD COLUMN'; improved
online index creation

This table lists changes and features in MySQL Cluster NDB 6.1 that are
most likely to be of interest.

*Note MySQL Cluster NDB 6.1:
mysql-cluster-development-5-1-ndb-6-1.
Greater number of cluster nodes
Disabling of arbitration
Additional `DUMP' commands
Faster Disk Data backups
Batched slave updates

This table lists changes and features in MySQL Cluster NDB 5.1 through
to 5.1.23 that are most likely to be of interest.

*Note MySQL 5.1 (through 5.1.23):
mysql-cluster-development-5-1.
MySQL Cluster Replication
Disk Data storage
Variable-size columns
User-defined partitioning
Autodiscovery of table schema
changes
Online adding and dropping of
indexes


File: manual.info,  Node: mysql-cluster-development-5-1-ndb-7-2,  Next: mysql-cluster-development-5-1-ndb-7-1,  Prev: mysql-cluster-development,  Up: mysql-cluster-development

17.1.4.1 MySQL Cluster Development in MySQL Cluster NDB 7.2.0
.............................................................

The following improvements to MySQL Cluster were made in MySQL Cluster
NDB 7.2.0.

   * Distribution of MySQL users and privileges

     Automatic distribution of MySQL users and privileges across all
     SQL nodes in a given MySQL Cluster is now supported. To enable
     this support, you must first import an SQL script
     `share/mysql/ndb_dist_priv.sql' that is included with the MySQL
     Cluster NDB 7.2 distribution. This script creates several stored
     procedures which you can use to enable privilege distribution and
     perform related tasks.

     When a new MySQL Server joins a MySQL Cluster where privilege
     distribution is in effect, it also participates in the privilege
     distribution automatically.

     Once privilege distribution is enabled, all changes to the grant
     tables made on any *Note `mysqld': mysqld. attached to the cluster
     are immediately available on any other attached MySQL Servers.
     This is true whether the changes are made using *Note `CREATE
     USER': create-user, *Note `GRANT': grant, or any of the other
     statements described elsewhere in this Manual (see *Note
     account-management-sql::.) This includes privileges relating to
     stored routines and views; however, automatic distribution of the
     views or stored routines themselves is not currently supported.

     For more information, see *Note
     mysql-cluster-privilege-distribution::.

   * Distributed pushed-down joins

     Many joins can now be pushed down to the NDB kernel for processing
     on MySQL Cluster data nodes. Previously, a join was handled in
     MySQL Cluster by means of repeated accesses of *Note `NDB':
     mysql-cluster. by the SQL node; however, when pushed-down joins
     are enabled, a pushable join is sent in its entirety to the data
     nodes, where it can be distributed among the data nodes and
     executed in parallel on multiple copies of the data, with a single,
     merged result being returned to *Note `mysqld': mysqld.  This can
     reduce greatly the number of round trips between an SQL node and
     the data nodes required to handle such a join, leading to greatly
     improved performance of join processing.

     It is possible to determine when joins can be pushed down to the
     data nodes by examining the join with *Note `EXPLAIN': explain. A
     number of new system status variables
     (`Ndb_pushed_queries_defined', `Ndb_pushed_queries_dropped',
     `Ndb_pushed_queries_executed', and `Ndb_pushed_reads') and
     additions to the *Note `counters': mysql-cluster-ndbinfo-counters.
     table (in the *Note `ndbinfo': mysql-cluster-ndbinfo.  information
     database) can also be helpful in determining when and how well
     joins are being pushed down.

     More information and examples are available in the description of
     the `ndb_join_pushdown' server system variable. See also the
     description of the status variables referenced in the previous
     paragraph, as well as *Note mysql-cluster-ndbinfo-counters::.

   * Improved default values for data node configuration parameters

     In order to provide more resiliency to environmental issues and
     better handling of some potential failure scenarios, and to
     perform more reliably with increases in memory and other resource
     requirements brought about by recent improvements in join handling
     by *Note `NDB': mysql-cluster, the default values for a number of
     MySQL Cluster data node configuration parameters have been
     changed. The parameters and changes are described in the following
     list:

        * `HeartbeatIntervalDbDb': Default increased from 1500 ms to
          5000 ms.

        * `ArbitrationTimeout': Default increased from 3000 ms to 7500
          ms.

        * `TimeBetweenEpochsTimeout': Now effectively disabled by
          default (default changed from 4000 ms to 0).

        * `SharedGlobalMemory': Default increased from 20 MB to 128 MB.

        * `MaxParallelScansPerFragment': Default increased from 32 to
          256.

     In addition, the value computed for `MaxNoOfLocalScans' when this
     parameter is not set in `config.ini' has been increased by a
     factor of 4.

MySQL Cluster NDB 7.2.1 and later MySQL Cluster NDB 7.2 releases are
based on MySQL Server 5.5 and are not covered here. See MySQL Cluster
NDB 7.2 (http://dev.mysql.com/doc/refman/5.5/en/mysql-cluster.html).


File: manual.info,  Node: mysql-cluster-development-5-1-ndb-7-1,  Next: mysql-cluster-development-5-1-ndb-7-0,  Prev: mysql-cluster-development-5-1-ndb-7-2,  Up: mysql-cluster-development

17.1.4.2 MySQL Cluster Development in MySQL Cluster NDB 7.1
...........................................................

The following improvements to MySQL Cluster have been made in MySQL
Cluster NDB 7.1.

   * MySQL Cluster information database (ndbinfo)

     The *Note `ndbinfo': mysql-cluster-ndbinfo. information database
     makes it possible to obtain real-time characteristics of a MySQL
     Cluster by issuing queries from the *Note `mysql': mysql. client
     or other MySQL client applications. *Note `ndbinfo':
     mysql-cluster-ndbinfo.  provides metadata specific to MySQL
     Cluster similarly to how the `INFORMATION_SCHEMA' database
     provides metadata for the standard MySQL Server. This eliminates
     much of the need to read log files, issue `REPORT' or `DUMP'
     commands in the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.
     client, or parse the output of *Note `ndb_config':
     mysql-cluster-programs-ndb-config. in order to get configuration
     and status information from a running MySQL Cluster.

     For more information, see *Note mysql-cluster-ndbinfo::.

   * Java connectors for MySQL Cluster

     The MySQL Cluster distribution now includes 2 new Java user APIs,
     ClusterJ and ClusterJPA. ClusterJ is an object-relational
     interface in a manner similar to that of Java persistence
     frameworks such as Hibernate. Cluster JPA is a reimplementation of
     OpenJPA. ClusterJ uses a backend library (NdbJTie) that provides
     access to the *Note `NDB': mysql-cluster. storage engine without
     using a MySQL Server connection or JDBC. ClusterJPA also uses
     NdbJTie when it improves performance, but can also process complex
     queries using JDBC and a MySQL Server connection, where it can
     take advantage of the MySQL query optimizer.

     ClusterJ and Cluster JPA can also be made to work with recent
     MySQL Cluster NDB 7.0 releases although the necessary library and
     JAR files are included only in MySQL Cluster NDB 7.1.1 and later.

     For more information about using ClusterJ and ClusterJPA, see
     MySQL Cluster Connector for Java
     (http://dev.mysql.com/doc/ndbapi/en/mccj.html).

   * New CHANGE MASTER TO option for circular replication

     Beginning with MySQL Cluster NDB 7.1.0, the *Note `CHANGE MASTER
     TO': change-master-to. statement supports an `IGNORE_SERVER_IDS'
     option which takes a comma-separated list of server IDs and causes
     events originating from the corresponding servers to be ignored.
     (Log rotation and log deletion events are preserved.)

     See *Note change-master-to::, as well as *Note
     show-slave-status::, for more information.

   * Native support for default column values

     Starting with MySQL Cluster NDB 7.1.4, default values for table
     columns are stored in the NDB kernel rather than by the MySQL
     server as was done previously. This means that inserts on tables
     having column value defaults can be smaller and faster than
     before, because less data must be sent from SQL nodes to
     `NDBCLUSTER'.

     Tables created using previous MySQL Cluster releases can still be
     used in MySQL Cluster 7.1.4 and later; however, they do not
     support native default values until they are upgraded. You can
     upgrade a table with non-native default values to support native
     default values using an offline *Note `ALTER TABLE': alter-table.
     statement.

   * MySQL Cluster on Windows (Production)

     Beginning with MySQL Cluster NDB 7.1.3, MySQL Cluster is available
     for production use on Microsoft Windows operating systems; MySQL
     Cluster NDB 7.1 binaries for Windows can be obtained from
     http://dev.mysql.com/downloads/cluster/
     (http://dev.mysql.com/downloads/cluster/).

     Features and behavior are generally comparable to those found on
     previously supported platforms such as Linux and Solaris. However,
     you must install the binaries manually.

     Beginning with MySQL Cluster NDB 7.1.5, MySQL Cluster processes
     can be run as Windows services.

     If you wish to build MySQL Cluster from source on Windows, you
     must configure the build using the
     `WITH_NDBCLUSTER_STORAGE_ENGINE' option.  For more information, see
     *Note windows-source-build::.

   * -nowait-nodes option for management servers

     It is now possible to configure a cluster with two management
     servers, but to start the cluster using only one of them by
     starting the management node daemon with the `--nowait-nodes'
     option. The other management server can then be started at a later
     time to join the running MySQL Cluster.

   * Improved lock handling for primary key lookups on BLOB tables

     A MySQL Cluster table stores all but the first 256 bytes of any
     *Note `BLOB': blob. or *Note `TEXT': blob. column values in a
     separate *Note `BLOB': blob. table; when executing queries against
     such tables, a shared lock is obtained. Prior to MySQL Cluster NDB
     7.1.1, when the query used a primary key lookup and took place
     within a transaction, the lock was held for the duration of the
     transaction, even after no more data was being read from the *Note
     `NDB': mysql-cluster. table. Now in such cases, the lock is
     released when all *Note `BLOB': blob. data associated with the
     table has been read. (Bug #49190)

     *Note*:

     A shared lock is also taken for unique key lookups; it is still
     the case that this lock is held for the duration of the
     transaction.

   * Heartbeat thread policy and priority

     Beginning with MySQL Cluster NDB 7.1.2, a new configuration
     parameter `HeartbeatThreadPriority' makes it possible to set the
     policy and the priority for the heartbeat thread on management and
     API nodes.

   * Improved access to partitioning information

     The *Note `ndb_desc': mysql-cluster-programs-ndb-desc. utility now
     provides additional information about the partitioning of data
     stored in MySQL Cluster. Beginning with MySQL Cluster NDB 7.1.2,
     the `--blob-info' option causes this program to include partition
     information for *Note `BLOB': blob. tables in its output. Also
     beginning with MySQL Cluster NDB 7.1.2, the `--extra-node-info'
     option causes *Note `ndb_desc': mysql-cluster-programs-ndb-desc.
     to include information about data distribution (that is, which
     table fragments are stored on which data nodes). Each of these
     options also requires the use of the `--extra-partition-info'
     option.

     Information about partition-to-node mappings can also be obtained
     using the `Table::getFragmentNodes()' method, also added in MySQL
     Cluster NDB 7.1.2.

   * Replication attribute promotion and demotion

     Beginning with MySQL Cluster NDB 7.1.3, MySQL Cluster Replication
     supports attribute promotion and demotion when replicating between
     columns of different but similar types on the master and the
     slave. For example, it is possible to promote an *Note `INT':
     integer-types. column on the master to a *Note `BIGINT':
     integer-types.  column on the slave, and to demote a *Note `TEXT':
     blob. column to a *Note `VARCHAR': char. column.

     The implementation of type demotion distinguishes between lossy
     and non-lossy type conversions, and their use on the slave can be
     controlled by setting the `slave_type_conversions' global server
     system variable.

     For more information, see *Note
     replication-features-attribute-promotion::.

   * Change in ndbinfo database

     The experimental *Note `pools': mysql-cluster-ndbinfo-pools.
     table was removed from *Note `ndbinfo': mysql-cluster-ndbinfo. in
     MySQL Cluster NDB 7.1.3. Applications which used this table can and
     should be rewritten to use other *Note `ndbinfo':
     mysql-cluster-ndbinfo. tables.

   * Configuration caching control

     Beginning with MySQL Cluster NDB 7.1.4, it is possible to disable
     the management server's configuration cache using the
     `--config-cache' option, which forces *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. to read its configuration data
     from the `config.ini' configuration file every time it starts. For
     more information about configuration caching and this option, see
     *Note mysql-cluster-config-file::. See also *Note
     mysql-cluster-programs-ndb-mgmd::.

   * Incompatible change in NDB API event reporting

     Beginning with MySQL Cluster NDB 7.1.4, DDL events are no longer
     reported on `Event' objects by default. Instead the desired level
     of event reporting (`EventReport' value) must be set explicitly
     using `Event::setReport()'.

   * Number of table attributes

     Beginning with MySQL Cluster NDB 7.1.4, the maximum number of
     attributes (columns plus indexes) per table has been increased
     from 128 to 512.

   * InnoDB support in commercial binaries

     Beginning with MySQL Cluster NDB 7.1.4b, all commercial binary
     releases of MySQL Cluster provide support for the *Note `InnoDB':
     innodb-storage-engine. storage engine.

   * Heartbeat ordering

     Beginning with MySQL Cluster NDB 7.1.5, it is possible to set a
     specific order for transmission of heartbeats between data nodes,
     using the `HeartbeatOrder' data node configuration parameter
     introduced in this version. This parameter can be useful in
     situations where multiple data nodes are running on the same host
     and a temporary disruption in connectivity between hosts would
     otherwise cause the loss of a node group (and thus failure of the
     cluster).

   * Relaxed ndb_restore column comparison rules

     When restoring data, ndb_restore compares the attributes of a
     column for equality with the definition of the column in the
     target table. However, not all of these attributes need to be the
     same for *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
     to be meaningful, safe and useful. Beginning with MySQL Cluster
     NDB 7.1.5, *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
     automatically ignores differences in certain column attributes
     which do not necessarily have to match between the version of the
     column in a backup and the version of that column in the MySQL
     Cluster to which the column data is being restored. These
     attributes include the following:

        * `COLUMN_FORMAT' setting (`FIXED', `DYNAMIC', or `DEFAULT')

        * `STORAGE' setting (`MEMORY' or `DISK')

        * The default value

        * The distribution key

     In such cases, *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. reports any such differences
     to minimize any chance of user error.

   * Storage of user data in anyValue

     When writing NDB events to the binary log, MySQL Cluster uses
     `OperationOptions::anyValue'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-operationoptions.html) to
     store the server ID. Beginning with MySQL Cluster NDB 7.1.6, it is
     possible to store user data from an NDB API application in part of
     the `anyValue' when *Note `mysqld': mysqld. has been started with
     the `--server-id-bits' option set to a nondefault value. Also
     beginning with MySQL Cluster NDB 7.1.6, it is possible to view
     this data in the output of mysqlbinlog, for which its own
     `--server-id-bits' option is added.

   * -add-drop-trigger option for mysqldump

     Beginning with MySQL Cluster NDB 7.1.8, this option can be used to
     force all *Note `CREATE TRIGGER': create-trigger. statements in
     *Note `mysqldump': mysqldump. output to be preceded by a *Note
     `DROP TRIGGER IF EXISTS': drop-trigger. statement.

   * Forcing node shutdown and restart

     In MySQL Cluster NDB 7.1.8 and later, it is possible using the
     *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. management client
     or the MGM API to force a data node shutdown or restart even if
     this would force the shutdown or restart of the entire cluster. In
     the management client, this is implemented through the addition of
     the `-f' (force) option to the `STOP' and `RESTART' commands. For
     more information, see *Note mysql-cluster-mgm-client-commands::.
     The MGM API also adds two new methods for forcing such a node
     shutdown or restart; see `ndb_mgm_stop4()'
     (http://dev.mysql.com/doc/ndbapi/en/mgm-ndb-mgm-stop4.html), and
     `ndb_mgm_restart4()'
     (http://dev.mysql.com/doc/ndbapi/en/mgm-ndb-mgm-restart4.html),
     for more information about these methods.

   * Disk Data usage statistics (diskpagebuffer table)

     MySQL Cluster 7.1.9 introduces a new table in the *Note `ndbinfo':
     mysql-cluster-ndbinfo. information database. The *Note
     `diskpagebuffer': mysql-cluster-ndbinfo-diskpagebuffer. table
     provides real-time data on disk page buffer usage. These
     statistics can be used to monitor performance of MySQL Cluster
     Disk Data read and write operations, and can prove useful in the
     tuning of Disk Data parameters such as `DiskPageBufferMemory'.

   * InnoDB Plugin support

     Beginning with MySQL Cluster NDB 7.1.9, the MySQL Server supplied
     with MySQL Cluster supports the *Note `InnoDB':
     innodb-storage-engine. Plugin. For more information about enabling
     the plugin if you are building MySQL Cluster from source, see
     *Note mysql-cluster-installation::.

     *Note*:

     Due to a packaging issue, the *Note `InnoDB':
     innodb-storage-engine. plugin was not included in RPMs for MySQL
     Cluster NDB 7.1.9; this issue was corrected in MySQL Cluster NDB
     7.1.9a. (Bug #58283)

   * TimeBetweenEpochsTimeout and GCP stop control

     Beginning with MySQL Cluster NDB 7.1.10, it is possible to disable
     GCP stops by setting `TimeBetweenEpochsTimeout' to 0. In addition,
     a warning is written to the cluster log whenever the time required
     for a GCP save exceeds 60 seconds or the time required for a GCP
     commit exceeds 10 seconds. This warning includes a report of the
     current value of `TimeBetweenEpochsTimeout'.  For more
     information, see *Note
     mysql-cluster-ndbd-definition-gcp-stop-errors::.

   * Skipping corrupted tables in NDB native backups

     Beginning with MySQL Cluster NDB 7.1.10, you can cause *Note
     `ndb_restore': mysql-cluster-programs-ndb-restore. to ignore
     tables that are corrupted due to missing blob parts tables by
     using the `--skip-broken-objects' option. When this option is
     used, such tables are skipped, and the restoration of any
     remaining uncorrupted tables in the backup continues.

   * BLOB read and write batching

     Beginning with MySQL Cluster NDB 7.1.10, it possible to control
     batching of *Note `BLOB': blob.  read and write operations. For
     SQL nodes, this can be done using the `--ndb-blob-read-batch-bytes'
     and `--ndb-blob-write-batch-bytes' options for *Note `mysqld':
     mysqld. In NDB API applications, you can control batching of *Note
     `BLOB': blob. reads and writes using the `NdbTransaction'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction.html)
     methods `setMaxPendingBlobReadBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-setmaxpendingblobreadbytes),
     `getMaxPendingBlobReadBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-getmaxpendingblobreadbytes),
     `setMaxPendingBlobWriteBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-setmaxpendingblobwritebytes),
     and `getMaxPendingBlobWriteBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-getmaxpendingblobwritebytes).

   * Restoring from a NDB native backup to a differently-named database

     MySQL Cluster NDB 7.1.11 adds a new `--rewrite-database' option to
     *Note `ndb_restore': mysql-cluster-programs-ndb-restore, which
     makes it possible to restore to a database having a different name
     from that of the database in the backup. The option can be used
     multiple times, and it is possible to restore from more than one
     source database in the backup to a single target database
     (although no protection against table or other object name
     collision is provided).

     See *Note mysql-cluster-programs-ndb-restore::, for more
     information.

   * Selective over-commit handling

     Beginning with MySQL Cluster NDB 7.1.10, it is possible to
     exercise more direct control over uncommitted operations from
     transactions aborted due to timeouts flushing redo logs to disk.
     This is implemented using three configuration parameters added in
     this version of MySQL Cluster: the data node configuration
     parameters `RedoOverCommitCounter' and `RedoOverCommitLimit', and
     the API node configuration parameter
     `DefaultOperationRedoProblemAction'.

     When an attempt to flush a given redo log takes longer than
     `RedoOverCommitLimit' seconds, and this occurs
     `RedoOverCommitLimit' times or more, the transactions contained
     within the redo log are aborted. Any operations left uncommitted
     as a result are either aborted or re-tried, according to the value
     of `DefaultOperationRedoProblemAction'.

     For more information, see *Note
     mysql-cluster-redo-over-commit-handling::

   * INFORMATION_SCHEMA improvements

     Beginning with MySQL Cluster NDB 7.1.11, Beginning with MySQL
     Cluster NDB 7.0.22, `INFORMATION_SCHEMA' provides disk usage
     information for MySQL Cluster Disk Data tables.  Previously, *Note
     `INFORMATION_SCHEMA.TABLES': tables-table.  showed only the space
     usage for the in-memory data part of the table. Now, it also shows
     the space allocated for and used by the disk_part data of that
     table as well.

     In addition, the *Note `INFORMATION_SCHEMA.PARTITIONS':
     partitions-table.  table (which did not show any statistics for
     *Note `NDB': mysql-cluster. tables) now shows correct values in
     this table's `TABLE_ROWS', `AVG_ROW_LENGTH', `DATA_LENGTH',
     `MAX_DATA_LENGTH', and `DATA_FREE' columns, for each partition.

   * ndb_restore attribute demotion

     Beginning with MySQL Cluster NDB 7.1.11, it is possible to enable
     attribute demotion when restoring a MySQL Cluster from a native
     backup running *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. with a new
     `--lossy-conversions' option.

     In general,the rules governing demotion are the same as for MySQL
     replication, although there are some exceptions that you may need
     to take into account being employing this option. See *Note
     replication-features-different-data-types::, for information about
     type conversions currently supported by attribute promotion and
     demotion in MySQL Cluster.

   * Improved multi-threaded order index building

     Previously, it was not possible to enable multi-threaded building
     of ordered indexes during initial restarts. In MySQL Cluster NDB
     7.1.11, this can now be done, using the new
     `TwoPassInitialNodeRestartCopy' data node configuration parameter.

   * Configuration version information in ndbinfo.nodes

     You can see which version or versions of the MySQL Cluster
     configuration file are in effect on the data nodes by checking the
     `config_generation' column which is added to the *Note `nodes':
     mysql-cluster-ndbinfo-nodes. table in MySQL Cluster NDB 7.1.13.

   * Configuration version information in ndbinfo.nodes

     You can see which version or versions of the MySQL Cluster
     configuration file are in effect on the data nodes by checking the
     `config_generation' column which is added to the *Note `nodes':
     mysql-cluster-ndbinfo-nodes. table in MySQL Cluster NDB 7.1.13.

   * Improvements in adding data nodes online

     Begining with MySQL Cluster NDB 7.0.24, it is possible to add data
     nodes online to a running MySQL Cluster without performing a
     rolling restart of the cluster or starting data node processes
     with the `--nowait-nodes' option. This can be done by setting
     `Nodegroup = 65536' in the `config.ini' file for any data nodes
     that should be started at a later time, when first starting the
     cluster. The amount of time the cluster waits before doing this
     can be controlled using the `StartNoNodeGroupTimeout' data node
     configuration parameter.

   * Unique key updates in replication

     It is possible in MySQL Cluster NDB 7.1.14 and later to employ
     operations that update unique keys when replicating *Note `NDB':
     mysql-cluster. tables. Previously this could lead to duplicate key
     errors when trying to execute the binary log (due to the fact that
     row events in the binary log were ordered according to the
     partitioning of the base table, and could differ in order within
     the epoch for that in which they were executed).

     *Important*:

     Master and slave tables must both be using the *Note `NDB':
     mysql-cluster. storage engine for this to work.

   * Starting with MySQL Cluster NDB 7.1.17, the NDB kernel implements
     a number of statistical counters relating to actions performed by
     or affecting `Ndb'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects. Such
     events include starting, closing, and aborting transactions;
     operations using primary keys or unique keys; table, range, and
     pruned scans; blocking of threads by incompleted operations; and
     data and events sent and received by MySQL Cluster nodes. NDB API
     statistics counters are incremented inside the NDB kernel whenever
     NDB API calls are made or data is sent to or received by the data
     nodes. A MySQL Server running as an SQL node in the cluster can
     access the values of these counters as system status variables, as
     seen in the output of *Note `SHOW STATUS': show-status, or in the
     results of queries against the *Note `SESSION_STATUS':
     status-table.  or *Note `GLOBAL_STATUS': status-table.  table in
     the `INFORMATION_SCHEMA' database.  By comparing the values of
     these status variables before and after the execution of
     statements affecting *Note `NDB': mysql-cluster. tables, you can
     observe the corresponding actions taken on the NDB API level. This
     can be highly useful when monitoring and tuning MySQL Cluster.

     For more information, see *Note
     mysql-cluster-ndb-api-statistics::. See also *Note
     mysql-cluster-status-variables::, for information about the
     individual status variables.

   * Version 2 binary log row events

     New versions of the `WRITE_ROW', `UPDATE_ROW', and `DELETE_ROW'
     events have been implemented in MySQL Cluster NDB 7.1.16,
     extending them with additional information intended to support
     future enhancements; these are referred to as `Version 2' binary
     log events.

     Version 2 log events are not backward compatible, and cannot be
     read by older slaves. A new *Note `mysqld': mysqld.  option
     `--log-bin-use-v1-row-events' can be employed to force use of
     Version 1 events when writing the binary log. This can be used
     during upgrades to make a newer *Note `mysqld': mysqld. generate
     Version 1 binary log row events that can be read by older slaves.

   * Circular replication: Primary wins first conflict detection

     Two new conflict detection functions `NDB$EPOCH()' and
     `NDB$EPOCH_TRANS()' can be useful in `active-active' circular
     replication scenarios with two MySQL Clusters. For each case, we
     designate one cluster as primary and one as secondary, and
     implement a `primary always wins' rule for determining whether to
     accept conflicting changes. When using `NDB$EPOCH()', conflicting
     rows on the secondary are realigned with those on the primary;
     when using `NDB$EPOCH_TRANS()', it is transactions containing rows
     in conflict (and any transactions which depend on them) on the
     secondary that are realigned.

     When using `NDB$EPOCH_TRANS()' as the conflict detection function,
     the binary log must be written using Version 2 binary logging row
     events; that is, the *Note `mysqld': mysqld. processes on both the
     primary and the secondary must be started with
     `--log-bin-use-v1-row-events=0'.  In addition, the secondary's
     binary log must include transaction IDs for all rows, that is, by
     setting `--ndb-log-transaction-id=1'.

     You can monitor conflict detection and resolution performed using
     these functions by reading a number of related server status
     variables, including `Ndb_conflict_fn_epoch',
     `Ndb_conflict_fn_epoch_trans', and
     `Ndb_conflict_trans_row_conflict_count' (among others). See *Note
     mysql-cluster-status-variables::.

     For more information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * Fail-fast data node capability

     Beginning with MySQL Cluster NDB 7.1.17, it is possible to enable
     fail-fast behavior for data nodes by enabling the
     `CrashOnCorruptedTuple' configuration parameter introduced in this
     version (disabled by default). Doing so causes data nodes to fail
     whenever they detect a corrupted tuple.

   * Rows per partition limit removed

     Previously it was possible to store a maximum of 46137488 rows in
     a single MySQL Cluster partition--that is, per data node.
     Beginning with MySQL Cluster NDB 7.0.36 and MySQL Cluster NDB
     7.1.25, this limitation has been lifted, and there is no longer
     any practical upper limit to this number. (Bug #13844405, Bug
     #14000373)

MySQL Cluster NDB 7.1 is also supported by MySQL Cluster Manager, which
provides an advanced command-line interface that can simplify many
complex MySQL Cluster management tasks. See MySQL(tm) Cluster Manager
1.3.2 User Manual
(http://dev.mysql.com/doc/mysql-cluster-manager/1.3/en/index.html), for
more information.


File: manual.info,  Node: mysql-cluster-development-5-1-ndb-7-0,  Next: mysql-cluster-development-5-1-ndb-6-3,  Prev: mysql-cluster-development-5-1-ndb-7-1,  Up: mysql-cluster-development

17.1.4.3 MySQL Cluster Development in MySQL Cluster NDB 7.0
...........................................................

The following list provides an overview of significant feature
additions and changes made in MySQL Cluster NDB 7.0. For more detailed
information about all feature changes and bugfixes made in MySQL
Cluster NDB 7.0, see
`http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-7-0.html'.

*Important*:

Early development versions of MySQL Cluster NDB 7.0 were known as
`MySQL Cluster NDB 6.4', and the first four releases in this series
were identified as MySQL Cluster NDB 6.4.0 through 6.4.3. Any
information relating to these MySQL Cluster NDB 6.4.x releases
appearing in this documentation apply to MySQL Cluster NDB 7.0.

MySQL Cluster NDB 7.0.4 is the fifth MySQL Cluster NDB 7.0 release; it
is the successor to MySQL Cluster NDB 6.4.3.

   * MySQL Cluster on Windows (alpha)

     MySQL Cluster NDB 7.0 is available on an experimental basis for
     Windows operating systems (for production use on Windows, you
     should use MySQL Cluster NDB 7.1.3 or later).  Features and
     behavior comparable to those found on platforms that are already
     supported--such as Linux and Solaris--are planned for MySQL
     Cluster on Windows. In MySQL Cluster NDB 7.0, you must build from
     source (Windows binaries are available for MySQL Cluster NDB 7.1
     releases). To enable MySQL Cluster support on Windows when
     building from source, you must configure the build using the
     `WITH_NDBCLUSTER_STORAGE_ENGINE' option.  For more information, see
     *Note windows-source-build::.

   * Ability to add nodes and node groups online

     Beginning with MySQL Cluster NDB 6.4.0, it is possible to add new
     node groups (and thus new data nodes) to a running MySQL Cluster
     without shutting down and reloading the cluster. As part of
     enabling this feature, a new command `CREATE NODEGROUP' has been
     added to the cluster management client and the functionality of the
     *Note `ALTER ONLINE TABLE ... REORGANIZE PARTITION': alter-table.
     SQL statement has been extended. For more information, see *Note
     mysql-cluster-online-add-node::.

   * Data node multi-threading support

     Beginning with MySQL Cluster NDB 6.4.0, a multi-threaded version
     of the data node daemon, named *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd, is available for use on data node
     hosts with multiple CPU cores. This binary is built automatically
     when compiling with MySQL Cluster support; no additional options
     other than those needed to provide MySQL Cluster support are
     needed when configuring the build. In most respects, *Note
     `ndbmtd': mysql-cluster-programs-ndbmtd.  functions in the same
     way as *Note `ndbd': mysql-cluster-programs-ndbd, and can use the
     same command-line options and configuration parameters. In
     addition, the new `MaxNoOfExecutionThreads' configuration
     parameter can be used to determine the number of data node process
     threads for *Note `ndbmtd': mysql-cluster-programs-ndbmtd. For
     more information, see *Note mysql-cluster-programs-ndbmtd::.

     *Note*:

     Disk Data tables are not yet supported for use with *Note
     `ndbmtd': mysql-cluster-programs-ndbmtd.

   * Configuration cache

     Formerly, MySQL Cluster configuration was stateless--that is,
     configuration information was reloaded from the cluster's global
     configuration file (usually `config.ini') each time *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. was started.
     Beginning with MySQL Cluster NDB 6.4.0, the cluster's configuration
     is cached internally, and the global configuration file is no
     longer automatically re-read when the management server is
     restarted. This behavior can be controlled using the management
     server options `--configdir', `--initial', and `--reload'.  In
     MySQL Cluster NDB 7.0.15 and later, the configuration cache can be
     disabled using the `--config-cache' option. For more information
     about these changes, see *Note mysql-cluster-config-file::. For
     more information about the new management server options, see
     *Note mysql-cluster-programs-ndb-mgmd::.

   * Detection of NDB API client connection errors

     In MySQL Cluster NDB 7.0 (6.4.0 and later releases), the NDB API's
     `Ndb_cluster_connection' class adds the `get_latest_error()' and
     `get_latest_error_msg()' methods for catching and diagnosing
     problems with NDB API client connections.

   * Snapshot options for backups

     Beginning with MySQL Cluster NDB 6.4.0, you can determine when
     performing a cluster backup whether the backup matches the state
     of the data when the backup was started or when it was completed,
     using the new options `SNAPSHOTSTART' and `SNAPSHOTEND' for the
     management client's `START BACKUP' command. See *Note
     mysql-cluster-backup-using-management-client::, for more
     information.

   * Dynamic NDB transporter send buffer memory allocation

     Previously, the NDB kernel used a fixed-size send buffer for every
     data node in the cluster, which was allocated when the node
     started. Because the size of this buffer could not be changed
     after the cluster was started, it was necessary to make it large
     enough in advance to accommodate the maximum possible load on any
     transporter socket. However, this was an inefficient use of memory,
     since much of it often went unused. Beginning with MySQL Cluster
     NDB 6.4.0, send buffer memory is allocated dynamically from a
     memory pool shared between all transporters, which means that the
     size of the send buffer can be adjusted as necessary. This change
     is reflected by the addition of the configuration parameters
     `TotalSendBufferMemory', `ReservedSendBufferMemory', and
     `OverLoadLimit', as well as a change in how the existing
     `SendBufferMemory' configuration parameter is used. For more
     information, see *Note mysql-cluster-config-send-buffers::.

   * Robust DDL operations

     Beginning with MySQL Cluster NDB 6.4.0, DDL operations (such as
     *Note `CREATE TABLE': create-table. or *Note `ALTER TABLE':
     alter-table.) are protected from data node failures; in the event
     of a data node failure, such operations are now rolled back
     gracefully.  Previously, if a data node failed while trying to
     perform a DDL operation, the MySQL Cluster data dictionary became
     locked and no further DDL statements could be executed without
     restarting the cluster.

   * IPv6 support in MySQL Cluster Replication

     Beginning with MySQL Cluster NDB 6.4.1, IPv6 networking is
     supported between MySQL Cluster SQL nodes, which makes it possible
     to replicate between instances of MySQL Cluster using IPv6
     addresses. However, IPv6 is supported only for direct connections
     between MySQL servers; all connections _within_ an individual
     MySQL Cluster must use IPv4. For more information, see *Note
     mysql-cluster-replication-issues::.

   * Restoring specific databases, tables, or columns from a MySQL
     Cluster backup

     It is now possible to exercise more fine-grained control when
     restoring a MySQL Cluster from backup using *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. Beginning with MySQL Cluster
     NDB 6.4.3, you can choose to restore only specified tables or
     databases, or exclude specific tables or databases from being
     restored, using the new *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. options `--include-tables',
     `--include-databases', `--exclude-tables', and
     `--exclude-databases'. Beginning with MySQL Cluster NDB 7.0.7, it
     is also possible to restore to a table having fewer columns than
     the original using the `--exclude-missing-columns' option. For
     more information about all of these options, see *Note
     mysql-cluster-programs-ndb-restore::.

   * Improved Disk Data file system configuration

     As of MySQL Cluster NDB 6.4.3, you can specify default locations
     for MySQL Cluster Disk Data data files and undo log files using
     the data node configuration parameters `FileSystemPathDD',
     `FileSystemPathDataFiles', and `FileSystemPathUndoFiles'.  This
     eliminates the need to use symbolic links to place Disk Data files
     separately from other files in data node file systems to improve
     Disk Data performance. For more information, see *Note
     mysql-cluster-ndbd-disk-data-filesystem-parameters::.

   * Automatic creation of Disk Data log file groups and tablespaces

     Beginning with MySQL Cluster NDB 6.4.3, using the data node
     configuration parameters `InitialLogFileGroup' and
     `InitialTablespace', you can cause the creation of a MySQL Cluster
     Disk Data log file group, tablespace, or both, when the cluster is
     first started. When using these parameters, no SQL statements are
     required to create these Disk Data objects.  For more information,
     see `Disk Data object creation parameters'.

   * Improved internal message passing and record handling

     MySQL Cluster NDB 7.0 contains 2 changes that optimize the use of
     network connections by addressing the size and number of messages
     passed between data nodes, and between data nodes and API nodes,
     which can increase MySQL Cluster and application performance:

        * Packed reads

          Formerly, each read request signal contained a list of
          columns to be retrieved, each of these column identifiers
          using 4 bytes within the message. This meant that the message
          size increased as the number of columns being fetched
          increased. In addition, in the response from the data node,
          each column result was packed to a 4-byte boundary, which
          resulted in wasted space. In MySQL Cluster NDB 7.0, messaging
          for read operations is optimized in both directions, using a
          bitmap in the read request to specify the columns to be
          fetched. Where many fields are requested, this can result in
          a significant message size reduction as compared with the old
          method. In addition, the 4-byte packing in responses is no
          longer used, which means that smaller fields consume less
          space.

        * Long signal transactions

          This enhancement reduces the number of messages and signals
          that are sent to data nodes for complex requests. Prior to
          MySQL Cluster NDB 7.0, there was a 100 byte limit on the size
          of the request signal, which meant that complex requests had
          to be split up between multiple messages prior to
          transmission, then reassembled on the receiving end. In
          addition to actual payload data, each message required its own
          operating system and protocol overhead such as header
          information. This often wasted network bandwidth and data
          node CPU. The maximum size of the message is now 32 KB, which
          is sufficient to accommodate most queries.

     Both of these optimizations are internal to the NDB API, and so is
     transparent to applications; this is true whether an application
     uses the NDB API directly or does so indirectly through an SQL
     node.

   * Configuration parameter data dumps

     Starting with MySQL Cluster NDB 7.0.6, the *Note `ndb_config':
     mysql-cluster-programs-ndb-config. utility supports a
     `--configinfo' option that causes it to dump a list of all
     configuration parameters supported by the cluster, along with
     brief descriptions, information about the parameters' default and
     permitted values, and the sections of the `config.ini' file in
     which the parameters apply. An additional `--xml' switch causes
     *Note `ndb_config': mysql-cluster-programs-ndb-config. to use XML
     rather than plaintext output. Using *Note `ndb_config
     `--configinfo'': mysql-cluster-programs-ndb-config. or *Note
     `ndb_config `--configinfo --xml'':
     mysql-cluster-programs-ndb-config. requires no access to a running
     MySQL Cluster, any other programs, or any files. For more
     information and examples, see *Note
     mysql-cluster-programs-ndb-config::.

   * Per-table reporting of free space on disk

     The *Note `INFORMATION_SCHEMA.FILES': files-table.  table shows
     information about used and free space in MySQL Cluster Disk Data
     data files, but this information is not applicable to individual
     tables. In MySQL Cluster NDB 7.0.8 and later, the *Note
     `ndb_desc': mysql-cluster-programs-ndb-desc. utility provides two
     additional columns in its output that show the amount of space
     allocated on disk for a given *Note `NDB': mysql-cluster. table as
     well the amount of space that remains available for additional
     storage of disk-based column data for that table. For more
     information, see *Note mysql-cluster-programs-ndb-desc::.

   * Improved restart times

     Optimizations in redo log handling and other file system
     operations introduced in MySQL Cluster NDB 7.0.9 have the
     potential to reduce considerably the time required for restarts.
     While actual performance benefits observed in production setups
     will naturally vary depending on database size, hardware, and
     other conditions, our own preliminary testing has shown that these
     improvements can yield startup times that are faster than those
     typical of previous MySQL Cluster NDB 7.0 releases by a factor of
     50 or more.

   * Native support for default column values

     Starting with MySQL Cluster NDB 7.0.15, default values for table
     columns are stored in the NDB kernel rather than by the MySQL
     server as was done previously. This means that inserts on tables
     having column value defaults can be smaller and faster than
     before, because less data must be sent from SQL nodes to
     `NDBCLUSTER'.

     Tables created using previous MySQL Cluster releases can still be
     used in MySQL Cluster 7.0.15 and later; however, they do not
     support native default values until they are upgraded. You can
     upgrade a table with non-native default values to support native
     default values using an offline *Note `ALTER TABLE': alter-table.
     statement.

   * -nowait-nodes option for management servers

     Starting with MySQL Cluster NDB 7.0.10, it is possible to
     configure a cluster with two management servers, but to start the
     cluster using only one of them by starting the management node
     daemon with the `--nowait-nodes' option.  The other management
     server can then be started at a later time to join the running
     MySQL Cluster.

   * Increased flexibility in online upgrade procedure

     Previously, when performing an upgrade of a running MySQL cluster,
     the order in which the types of cluster nodes had to be upgraded
     was very strict. However, beginning with MySQL Cluster NDB 7.0.10,
     MySQL Cluster supports online upgrading of API nodes (including
     MySQL servers running as SQL nodes) online upgrading management
     nodes, data nodes, or both.

     *Important*:

     Before attempting to use this new upgrade functionality, see *Note
     mysql-cluster-rolling-restart::, for additional information,
     especially if you are planning an online upgrade to MySQL Cluster
     NDB 7.0 from MySQL Cluster NDB 6.3.

   * New CHANGE MASTER TO option for circular replication

     Beginning with MySQL Cluster NDB 7.0.11, the *Note `CHANGE MASTER
     TO': change-master-to. statement supports an `IGNORE_SERVER_IDS'
     option which takes a comma-separated list of server IDs and causes
     events originating from the corresponding servers to be ignored.
     (Log rotation and log deletion events are preserved.)

     See *Note change-master-to::, as well as *Note
     show-slave-status::, for more information.

   * New replication conflict resolution strategy

     Beginning with MySQL Cluster NDB 7.0.11, the function
     `NDB$MAX_DELETE_WIN()' is available to implement `greatest
     timestamp, delete wins' conflict resolution. See *Note
     mysql-cluster-replication-ndb-max-delete-win::, for more
     information.

   * Improved lock handling for primary key lookups on BLOB tables

     A MySQL Cluster table stores all but the first 256 bytes of any
     *Note `BLOB': blob. or *Note `TEXT': blob. column values in a
     separate *Note `BLOB': blob. table; when executing queries against
     such tables, a shared lock is obtained. Prior to MySQL Cluster NDB
     7.0.12, when the query used a primary key lookup and took place
     within a transaction, the lock was held for the duration of the
     transaction, even after no more data was being read from the *Note
     `NDB': mysql-cluster. table. Now in such cases, the lock is
     released when all *Note `BLOB': blob. data associated with the
     table has been read. (Bug #49190)

     *Note*:

     A shared lock is also taken for unique key lookups; it is still
     the case that this lock is held for the duration of the
     transaction.

   * Heartbeat thread policy and priority

     Beginning with MySQL Cluster NDB 7.0.13, a new configuration
     parameter `HeartbeatThreadPriority' makes it possible to set the
     policy and the priority for the heartbeat thread on management and
     API nodes.

   * Improved access to partitioning information

     The *Note `ndb_desc': mysql-cluster-programs-ndb-desc. utility now
     provides additional information about the partitioning of data
     stored in MySQL Cluster. Beginning with MySQL Cluster NDB 7.0.13,
     the `--blob-info' option causes this program to include partition
     information for *Note `BLOB': blob. tables in its output.
     Beginning with MySQL Cluster NDB 7.0.14, the `--extra-node-info'
     option causes *Note `ndb_desc': mysql-cluster-programs-ndb-desc.
     to include information about data distribution (that is, which
     table fragments are stored on which data nodes). Each of these
     options also requires the use of the `--extra-partition-info'
     option.

     Information about partition-to-node mappings can also be obtained
     using the `Table::getFragmentNodes()' method, also added in MySQL
     Cluster NDB 7.0.14.

   * Replication attribute promotion and demotion

     Beginning with MySQL Cluster NDB 7.0.14, MySQL Cluster Replication
     supports attribute promotion and demotion when replicating between
     columns of different but similar types on the master and the
     slave. For example, it is possible to promote an *Note `INT':
     integer-types. column on the master to a *Note `BIGINT':
     integer-types.  column on the slave, and to demote a *Note `TEXT':
     blob. column to a *Note `VARCHAR': char. column.

     The implementation of type demotion distinguishes between lossy
     and non-lossy type conversions, and their use on the slave can be
     controlled by setting the `slave_type_conversions' global server
     system variable.

     For more information, see *Note
     replication-features-attribute-promotion::.

   * Incompatible change in NDB API event reporting

     Beginning with MySQL Cluster NDB 7.0.15, DDL events are no longer
     reported on `Event' objects by default. Instead such event
     reporting must be enabled explicitly using the `Event::setReport()'
     method. For more information, see `Event::setReport()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-event-methods.html#ndb-event-setreport),
     and The `Event::EventReport' Type
     (http://dev.mysql.com/doc/ndbapi/en/ndb-event-types.html#ndb-event-eventreport).

   * Number of table attributes

     Beginning with MySQL Cluster NDB 7.0.15, the maximum number of
     attributes (columns plus indexes) per table has been increased
     from 128 to 512.

   * Heartbeat ordering

     Beginning with MySQL Cluster NDB 7.0.16, it is possible to set a
     specific order for transmission of heartbeats between data nodes,
     using the `HeartbeatOrder' data node configuration parameter
     introduced in this version. This parameter can be useful in
     situations where multiple data nodes are running on the same host
     and a temporary disruption in connectivity between hosts would
     otherwise cause the loss of a node group (and thus failure of the
     cluster).

   * Relaxed ndb_restore column comparison rules

     When restoring data, ndb_restore compares the attributes of a
     column for equality with the definition of the column in the
     target table. However, not all of these attributes need to be the
     same for *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
     to be meaningful, safe and useful. Beginning with MySQL Cluster
     NDB 7.0.16, *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore.  automatically ignores
     differences in certain column attributes which do not necessarily
     have to match between the version of the column in a backup and
     the version of that column in the MySQL Cluster to which the
     column data is being restored. These attributes include the
     following:

        * `COLUMN_FORMAT' setting (`FIXED', `DYNAMIC', or `DEFAULT')

        * `STORAGE' setting (`MEMORY' or `DISK')

        * The default value

        * The distribution key

     In such cases, *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. reports any such differences
     to minimize any chance of user error.

   * Storage of user data in anyValue

     When writing NDB events to the binary log, MySQL Cluster uses
     `OperationOptions::anyValue'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-operationoptions.html) to
     store the server ID. Beginning with MySQL Cluster NDB 7.0.17, it
     is possible to store user data from an NDB API application in part
     of the `anyValue' when *Note `mysqld': mysqld. has been started
     with the `--server-id-bits' option set to a nondefault value. Also
     beginning with MySQL Cluster NDB 7.0.17, it is possible to view
     this data in the output of mysqlbinlog, for which its own
     `--server-id-bits' option is added.

   * -add-drop-trigger option for mysqldump

     Beginning with MySQL Cluster NDB 7.0.19, this option can be used
     to force all *Note `CREATE TRIGGER': create-trigger. statements in
     *Note `mysqldump': mysqldump. output to be preceded by a *Note
     `DROP TRIGGER IF EXISTS': drop-trigger. statement.

   * Forcing node shutdown and restart

     In MySQL Cluster NDB 7.0.19 and later, it is possible using the
     *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. management client
     or the MGM API to force a data node shutdown or restart even if
     this would force the shutdown or restart of the entire cluster. In
     the management client, this is implemented through the addition of
     the `-f' (force) option to the `STOP' and `RESTART' commands. For
     more information, see *Note mysql-cluster-mgm-client-commands::.
     The MGM API also adds two new methods for forcing such a node
     shutdown or restart; see `ndb_mgm_stop4()'
     (http://dev.mysql.com/doc/ndbapi/en/mgm-ndb-mgm-stop4.html), and
     `ndb_mgm_restart4()'
     (http://dev.mysql.com/doc/ndbapi/en/mgm-ndb-mgm-restart4.html),
     for more information about these methods.

   * TimeBetweenEpochsTimeout and GCP stop control

     Beginning with MySQL Cluster NDB 7.0.21, it is possible to disable
     GCP stops by setting `TimeBetweenEpochsTimeout' to 0. In addition,
     a warning is written to the cluster log whenever the time required
     for a GCP save exceeds 60 seconds or the time required for a GCP
     commit exceeds 10 seconds. This warning includes a report of the
     current value of `TimeBetweenEpochsTimeout'.  For more
     information, see *Note
     mysql-cluster-ndbd-definition-gcp-stop-errors::.

   * Skipping corrupted tables in NDB native backups

     Beginning with MySQL Cluster NDB 7.0.21, you can cause *Note
     `ndb_restore': mysql-cluster-programs-ndb-restore. to ignore
     tables that are corrupted due to missing blob parts tables by
     using the `--skip-broken-objects' option. When this option is
     used, such tables are skipped, and the restoration of any
     remaining uncorrupted tables in the backup continues.

   * BLOB read and write batching

     Beginning with MySQL Cluster NDB 7.0.21, it possible to control
     batching of *Note `BLOB': blob.  read and write operations. For
     SQL nodes, this can be done using the `--ndb-blob-read-batch-bytes'
     and `--ndb-blob-write-batch-bytes' options for *Note `mysqld':
     mysqld. In NDB API applications, you can control batching of *Note
     `BLOB': blob. reads and writes using the `NdbTransaction'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction.html)
     methods `setMaxPendingBlobReadBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-setmaxpendingblobreadbytes),
     `getMaxPendingBlobReadBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-getmaxpendingblobreadbytes),
     `setMaxPendingBlobWriteBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-setmaxpendingblobwritebytes),
     and `getMaxPendingBlobWriteBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-getmaxpendingblobwritebytes).

   * Restoring from a NDB native backup to a differently-named database

     MySQL Cluster NDB 7.0.22 adds a new `--rewrite-database' option to
     *Note `ndb_restore': mysql-cluster-programs-ndb-restore, which
     makes it possible to restore to a database having a different name
     from that of the database in the backup. The option can be used
     multiple times, and it is possible to restore from more than one
     source database in the backup to a single target database
     (although no protection against table or other object name
     collision is provided).

     See *Note mysql-cluster-programs-ndb-restore::, for more
     information.

   * INFORMATION_SCHEMA inprovements

     Beginning with MySQL Cluster NDB 7.0.22, `INFORMATION_SCHEMA'
     provides disk usage information for MySQL Cluster Disk Data tables.
     Previously, *Note `INFORMATION_SCHEMA.TABLES': tables-table.
     showed only the space usage for the in-memory data part of the
     table. Now, it also shows the space allocated for and used by the
     disk_part data of that table as well.

     In addition, the *Note `INFORMATION_SCHEMA.PARTITIONS':
     partitions-table.  table (which did not show any statistics for
     *Note `NDB': mysql-cluster. tables) now shows correct values in
     this table's `TABLE_ROWS', `AVG_ROW_LENGTH', `DATA_LENGTH',
     `MAX_DATA_LENGTH', and `DATA_FREE' columns, for each partition.

   * Configuration version information in ndbinfo.nodes

     You can see which version or versions of the MySQL Cluster
     configuration file are in effect on the data nodes by checking the
     `config_generation' column which is added to the *Note `nodes':
     mysql-cluster-ndbinfo-nodes. table in MySQL Cluster NDB 7.0.24.

   * Improvements in adding data nodes online

     Beginning with MySQL Cluster NDB 7.0.24, it is possible to add
     data nodes online to a running MySQL Cluster without performing a
     rolling restart of the cluster or starting data node processes
     with the `--nowait-nodes' option. This can be done by setting
     `Nodegroup = 65536' in the `config.ini' file for any data nodes
     that should be started at a later time, when first starting the
     cluster. The amount of time the cluster waits before doing this
     can be controlled using the `StartNoNodeGroupTimeout' data node
     configuration parameter.

   * Unique key updates in replication

     It is possible in MySQL Cluster NDB 7.0.25 and later to employ
     operations that update unique keys when replicating *Note `NDB':
     mysql-cluster. tables. Previously this could lead to duplicate key
     errors when trying to execute the binary log (due to the fact that
     row events in the binary log were ordered according to the
     partitioning of the base table, and could differ in order within
     the epoch for that in which they were executed).

     *Important*:

     Master and slave tables must both be using the *Note `NDB':
     mysql-cluster. storage engine for this to work.

   * Starting with MySQL Cluster NDB 7.0.22, the NDB kernel implements
     a number of statistical counters relating to actions performed by
     or affecting `Ndb'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects. Such
     events include starting, closing, and aborting transactions;
     operations using primary keys or unique keys; table, range, and
     pruned scans; blocking of threads by incompleted operations; and
     data and events sent and received by MySQL Cluster nodes. NDB API
     statistics counters are incremented inside the NDB kernel whenever
     NDB API calls are made or data is sent to or received by the data
     nodes. A MySQL Server running as an SQL node in the cluster can
     access the values of these counters as system status variables, as
     seen in the output of *Note `SHOW STATUS': show-status, or in the
     results of queries against the *Note `SESSION_STATUS':
     status-table.  or *Note `GLOBAL_STATUS': status-table.  table in
     the `INFORMATION_SCHEMA' database.  By comparing the values of
     these status variables before and after the execution of
     statements affecting *Note `NDB': mysql-cluster. tables, you can
     observe the corresponding actions taken on the NDB API level. This
     can be highly useful when monitoring and tuning MySQL Cluster.

     For more information, see *Note
     mysql-cluster-ndb-api-statistics::. See also *Note
     mysql-cluster-status-variables::, for information about the
     individual status variables.

   * Version 2 binary log row events

     New versions of the `WRITE_ROW', `UPDATE_ROW', and `DELETE_ROW'
     events have been implemented in MySQL Cluster NDB 7.0.27,
     extending them with additional information intended to support
     future enhancements; these are referred to as `Version 2' binary
     log events.

     Version 2 log events are not backward compatible, and cannot be
     read by older slaves. A new *Note `mysqld': mysqld.  option
     `--log-bin-use-v1-row-events' can be employed to force use of
     Version 1 events when writing the binary log. This can be used
     during upgrades to make a newer *Note `mysqld': mysqld. generate
     Version 1 binary log row events that can be read by older slaves.

   * Fail-fast data node capability

     Beginning with MySQL Cluster NDB 7.0.28, it is possible to enable
     fail-fast behavior for data nodes by enabling the
     `CrashOnCorruptedTuple' configuration parameter introduced in this
     version (disabled by default). Doing so causes data nodes to fail
     whenever they detect a corrupted tuple.

   * Rows per partition limit removed

     Previously it was possible to store a maximum of 46137488 rows in
     a single MySQL Cluster partition--that is, per data node.
     Beginning with MySQL Cluster NDB 7.0.36, this limitation has been
     lifted, and there is no longer any practical upper limit to this
     number.


File: manual.info,  Node: mysql-cluster-development-5-1-ndb-6-3,  Next: mysql-cluster-development-5-1-ndb-6-2,  Prev: mysql-cluster-development-5-1-ndb-7-0,  Up: mysql-cluster-development

17.1.4.4 MySQL Cluster Development in MySQL Cluster NDB 6.3
...........................................................

The following list provides an overview of significant feature
additions and changes first made in MySQL Cluster NDB 6.3. For more
detailed information about all feature changes and bugfixes made in
MySQL Cluster NDB 6.3, see
`http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-6-3.html'.

   * Conflict detection and resolution

     It is now possible to detect and resolve conflicts that arise in
     multi-master replication scenarios, such as circular replication,
     when different masters may try to update the same row on the slave
     with different data. Both `greatest timestamp wins' and `same
     timestamp wins' scenarios are supported. For more information, see
     *Note mysql-cluster-replication-conflict-resolution::.

   * Recovery of one master, many slaves replication setups

     Recovery of multi-way replication setups (`one master, many
     slaves') is now supported using the `--ndb-log-orig' server option
     and changes in the `mysql.ndb_binlog_index' table.  See *Note
     mysql-cluster-replication-schema::, for more information.

   * Enhanced selection options for transaction coordinator

     New values and behaviors are introduced for
     `--ndb_optimized_node_selection', enabling greater flexibility
     when an SQL node chooses a transaction coordinator. For more
     information, see the description of `ndb_optimized_node_selection'
     in *Note mysql-cluster-system-variables::.

   * Replication heartbeats

     Replication heartbeats facilitate the task of monitoring and
     detecting failures in master-slave connections in real time. This
     feature is implemented using a new `MASTER_HEARTBEAT_PERIOD =
     VALUE' clause for the *Note `CHANGE MASTER TO': change-master-to.
     statement and the addition of two status variables
     `Slave_heartbeat_period' and `Slave_received_heartbeats'.  For
     more information, see *Note change-master-to::.

   * NDB thread locks

     It is possible to lock *Note `NDB': mysql-cluster.  execution
     threads and maintenance threads (such as file system and other
     operating system threads) to specific CPUs on multiprocessor data
     node hosts, and to leverage real-time scheduling.

   * Improved performance of updates using primary keys or unique keys

     The number of unnecessary reads when performing a primary key or
     unique key update has been greatly reduced. Since it is seldom
     necessary to read a record prior to an update, this can yield a
     considerable improvement in performance. In addition, primary key
     columns are no longer written to when not needed during update
     operations.

   * Batching improvements

     Support of batched *Note `DELETE': delete.  and *Note `UPDATE':
     update. operations has been significantly improved. Batching of
     `UPDATE WHERE...' and multiple *Note `DELETE': delete. operations
     is also now implemented.

   * Improved SQL statement performance metrics

     The `Ndb_execute_count' system status variable measures the number
     of round trips made by SQL statements to the *Note `NDB':
     mysql-cluster. kernel, providing an improved metric for
     determining efficiency with which statements are executed. For
     more information, see `MySQL Cluster Status Variables:
     `Ndb_execute_count''.

   * Compressed LCPs and backups

     Compressed local checkpoints and backups can save 50% or more of
     the disk space used by uncompressed LCPs and backups. These can be
     enabled using the two new data node configuration parameters
     `CompressedLCP' and `CompressedBackup', respectively.

   * OPTIMIZE TABLE support with NDBCLUSTER tables

     *Note `OPTIMIZE TABLE': optimize-table. is supported for dynamic
     columns of in-memory *Note `NDB': mysql-cluster. tables. In such
     cases, it is no longer necessary to drop (and possibly to
     re-create) a table, or to perform a rolling restart, in order to
     recover memory from deleted rows for general re-use by Cluster.
     The performance of `OPTIMIZE' on Cluster tables can be tuned by
     adjusting the value of the `ndb_optimization_delay' system
     variable, which controls the number of milliseconds to wait between
     processing batches of rows by *Note `OPTIMIZE TABLE':
     optimize-table. In addition, *Note `OPTIMIZE TABLE':
     optimize-table. on an *Note `NDBCLUSTER': mysql-cluster. table can
     be interrupted by, for example, killing the SQL thread performing
     the `OPTIMIZE' operation.

   * Batching of transactions

     It is possible to cause statements occurring within the same
     transaction to be run as a batch by setting the session variable
     `transaction_allow_batching' to `1' or `ON'. To use this feature,
     `autocommit' must be set to `0' or `OFF'. Batch sizes can be
     controlled using the `--ndb-batch-size' option for *Note `mysqld':
     mysqld. For additional information, see *Note
     mysql-cluster-program-options-mysqld::, and *Note
     mysql-cluster-system-variables::.

   * Attribute promotion with ndb_restore

     It is possible using *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. to restore data reliably from
     a column of a given type to a column that uses a `larger' type.
     This is sometimes referred to as _attribute promotion_. For
     example, MySQL Cluster backup data that originated in a *Note
     `SMALLINT': integer-types. column can be restored to a *Note
     `MEDIUMINT': integer-types, *Note `INT': integer-types, or *Note
     `BIGINT': integer-types. column. See *Note
     mysql-cluster-programs-ndb-restore::, for more information.

   * Parallel data node recovery

     Recovery of multiple data nodes can now be done in parallel,
     rather than sequentially. In other words, several data nodes can
     be restored concurrently, which can often result in much faster
     recovery times than when they are restored one at a time.

   * Increased local checkpoint efficiency

     Only 2 local checkpoints are stored, rather than 3, lowering disk
     space requirements and the size and number of redo log files.

   * NDBCLUSTER table persistence control

     Persistence of *Note `NDB': mysql-cluster. tables can be
     controlled using the session variables `ndb_table_temporary' and
     `ndb_table_no_logging'.  `ndb_table_no_logging' causes *Note
     `NDB': mysql-cluster. tables not to be checkpointed to disk;
     `ndb_table_temporary' does the same, and in addition, no schema
     files are created. See *Note mysql-cluster-option-tables::.

   * Epoll support (Linux only)

     _Epoll_ is an improved method for handling file descriptors, which
     is more efficient than scanning to determine whether a file
     descriptor has data to be read. (The term _epoll_ is specific to
     Linux and equivalent functionality is known by other names on
     other platforms such as Solaris and FreeBSD.) Currently, MySQL
     Cluster supports this functionality on Linux only.

   * Distribution awareness (SQL nodes)

     In MySQL Cluster NDB 6.3, SQL nodes can take advantage of
     distribution awareness. Here we provide a brief example showing
     how to design a table to make a given class of queries
     distrubtion-aware. Suppose an *Note `NDBCLUSTER': mysql-cluster.
     table `t1' has the following schema:


          CREATE TABLE t1 (
              userid INT NOT NULL,
              serviceid INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
              data VARCHAR(255)
          )   ENGINE=NDBCLUSTER;

     Suppose further that most of the queries to be used in our
     application test values of the `userid' column of this table. The
     form of such a query looks something like this:


          SELECT COLUMNS FROM t1
              WHERE userid RELATION VALUE;

     In this query, RELATION represents some relational operator, such
     as `=', `<', `>', and so on. Queries using `IN' and a list of
     values can also be used:


          SELECT COLUMNS FROM t1
              WHERE userid IN VALUE_LIST;

     To make use of distribution awareness, we need to make the
     `userid' column part of the table's primary key, then explicitly
     partition the table with this column being used as the
     partitioning key. (Recall that for a partitioned table having one
     or more unique keys, all columns of the table's partitioning key
     must also be part of all of the unique keys--for more information
     and examples, see *Note
     partitioning-limitations-partitioning-keys-unique-keys::.)  In
     other words, the table schema should be equivalent to the
     following *Note `CREATE TABLE': create-table.  statement:


          CREATE TABLE t1 (
              userid INT NOT NULL,
              serviceid INT NOT NULL AUTO_INCREMENT,
              data VARCHAR(255),
              PRIMARY KEY p (userid,serviceid)
          )   ENGINE=NDBCLUSTER
              PARTITION BY KEY(userid);

     When the table is partitioned in this way, all rows having the
     same `userid' value are found on the same node group, and the
     MySQL Server can immediately select the optimal node to use as the
     transaction coordinator.

   * Realtime extensions for multiple CPUs

     When running MySQL Cluster data nodes on hosts with multiple
     processors, the realtime extensions make it possible to give
     priority to the data node process and control on which CPU cores
     it should operate. This can be done using the data node
     configuration parameters `RealtimeScheduler',
     `SchedulerExecutionTimer', and `SchedulerSpinTimer'.  Doing so
     properly can significantly lower response times and make them much
     more predictable response. For more information about using these
     parameters, see Defining Data Nodes: Realtime Performance
     Parameters

   * Fully automatic database discovery

     It is no longer a requirement for database autodiscovery that an
     SQL node already be connected to the cluster at the time that a
     database is created on another SQL node, or for a *Note `CREATE
     DATABASE': create-database. or *Note `CREATE SCHEMA':
     create-database. statement to be issued on the new SQL node after
     it joins the cluster.

   * Detection of NDB API client connection errors

     Beginning with MySQL Cluster NDB 6.3.20, the NDB API's
     `Ndb_cluster_connection' class adds the `get_latest_error()' and
     `get_latest_error_msg()' methods for catching and diagnosing
     problems with NDB API client connections.

   * Restoring specific databases, tables, or columns from a MySQL
     Cluster backup

     It is now possible to exercise more fine-grained control when
     restoring a MySQL Cluster from backup using *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. Beginning with MySQL Cluster
     NDB 6.3.22, you can choose to restore only specified tables or
     databases, or exclude specific tables or databases from being
     restored, using the new *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. options `--include-tables',
     `--include-databases', `--exclude-tables', and
     `--exclude-databases'. Beginning with MySQL Cluster NDB 6.3.26, it
     is also possible to restore to a table having fewer columns than
     the original using the `--exclude-missing-columns' option. For
     more information about all of these options, see *Note
     mysql-cluster-programs-ndb-restore::.

   * Improved Disk Data file system configuration

     As of MySQL Cluster NDB 6.3.22, you can specify default locations
     for MySQL Cluster Disk Data data files and undo log files using
     the data node configuration parameters `FileSystemPathDD',
     `FileSystemPathDataFiles', and `FileSystemPathUndoFiles'.  This
     eliminates the need to use symbolic links to place Disk Data files
     separately from other files in data node file systems to improve
     Disk Data performance. For more information, see *Note
     mysql-cluster-ndbd-disk-data-filesystem-parameters::.

   * Automatic creation of Disk Data log file groups and tablespaces

     Beginning with MySQL Cluster NDB 6.3.22, using the data node
     configuration parameters `InitialLogFileGroup' and
     `InitialTablespace', you can cause the creation of a MySQL Cluster
     Disk Data log file group, tablespace, or both, when the cluster is
     first started. When using these parameters, no SQL statements are
     required to create these Disk Data objects.  For more information,
     see `Disk Data object creation parameters'.

   * Configuration parameter data dumps

     Starting with MySQL Cluster NDB 6.3.25, the *Note `ndb_config':
     mysql-cluster-programs-ndb-config. utility supports a
     `--configinfo' option that causes it to dump a list of all
     configuration parameters supported by the cluster, along with
     brief descriptions, information about the parameters' default and
     permitted values, and the sections of the `config.ini' file in
     which the parameters apply. An additional `--xml' switch causes
     *Note `ndb_config': mysql-cluster-programs-ndb-config. to use XML
     rather than plaintext output. Using *Note `ndb_config
     `--configinfo'': mysql-cluster-programs-ndb-config. or *Note
     `ndb_config `--configinfo --xml'':
     mysql-cluster-programs-ndb-config. requires no access to a running
     MySQL Cluster, any other programs, or any files. For more
     information and examples, see *Note
     mysql-cluster-programs-ndb-config::.

   * Per-table reporting of free space on disk

     The *Note `INFORMATION_SCHEMA.FILES': files-table.  table shows
     information about used and free space in MySQL Cluster Disk Data
     data files, but this information is not applicable to individual
     tables. In MySQL Cluster NDB 6.3.27 and later, the *Note
     `ndb_desc': mysql-cluster-programs-ndb-desc. utility provides two
     additional columns in its output that show the amount of space
     allocated on disk for a given *Note `NDB': mysql-cluster. table as
     well the amount of space that remains available for additional
     storage of disk-based column data for that table. For more
     information, see *Note mysql-cluster-programs-ndb-desc::.

   * Improved restart times

     Optimizations in redo log handling and other file system
     operations introduced in MySQL Cluster NDB 6.3.28 have the
     potential to reduce considerably the time required for restarts.
     While actual performance benefits observed in production setups
     will naturally vary depending on database size, hardware, and
     other conditions, our own preliminary testing has shown that these
     improvements can yield startup times that are faster than those
     typical of previous MySQL Cluster NDB 6.3 releases by a factor of
     50 or more.

   * Increased flexibility in online upgrade procedure

     Previously, when performing an upgrade of a running MySQL cluster,
     the order in which the types of cluster nodes had to be upgraded
     was very strict. However, beginning with MySQL Cluster NDB 6.3.29,
     MySQL Cluster supports online upgrading of API nodes (including
     MySQL servers running as SQL nodes) before upgrading management
     nodes, data nodes, or both.

     *Important*:

     Before attempting to use this new upgrade functionality, see *Note
     mysql-cluster-rolling-restart::, for additional information,
     especially if you are planning an online upgrade from MySQL
     Cluster NDB 6.3 to MySQL Cluster NDB 7.0.

   * New replication conflict resolution strategy

     Beginning with MySQL Cluster NDB 6.3.31, the function
     `NDB$MAX_DELETE_WIN()' is available to implement `greatest
     timestamp, delete wins' conflict resolution. See *Note
     mysql-cluster-replication-ndb-max-delete-win::, for more
     information.

   * New CHANGE MASTER TO option for circular replication

     Beginning with MySQL Cluster NDB 6.3.31, the *Note `CHANGE MASTER
     TO': change-master-to. statement supports an `IGNORE_SERVER_IDS'
     option which takes a comma-separated list of server IDs and causes
     events originating from the corresponding servers to be ignored.
     (Log rotation and log deletion events are preserved.)

     See *Note change-master-to::, as well as *Note
     show-slave-status::, for more information.

   * Heartbeat thread policy and priority

     Beginning with MySQL Cluster NDB 6.3.32, a new configuration
     parameter `HeartbeatThreadPriority' makes it possible to set the
     policy and the priority for the heartbeat thread on management and
     API nodes.

   * Improved access to partitioning information

     The *Note `ndb_desc': mysql-cluster-programs-ndb-desc. utility now
     provides additional information about the partitioning of data
     stored in MySQL Cluster. Beginning with MySQL Cluster NDB 6.3.32,
     the `--blob-info' option causes this program to include partition
     information for *Note `BLOB': blob. tables in its output.
     Beginning with MySQL Cluster NDB 6.3.33, the `--extra-node-info'
     option causes *Note `ndb_desc': mysql-cluster-programs-ndb-desc.
     to include information about data distribution (that is, which
     table fragments are stored on which data nodes). Each of these
     options also requires the use of the `--extra-partition-info'
     option.

     Information about partition-to-node mappings can also be obtained
     using the `Table::getFragmentNodes()' method, also added in MySQL
     Cluster NDB 6.3.33.

   * Replication attribute promotion and demotion

     Beginning with MySQL Cluster NDB 6.3.33, MySQL Cluster Replication
     supports attribute promotion and demotion when replicating between
     columns of different but similar types on the master and the
     slave. For example, it is possible to promote an *Note `INT':
     integer-types. column on the master to a *Note `BIGINT':
     integer-types.  column on the slave, and to demote a *Note `TEXT':
     blob. column to a *Note `VARCHAR': char. column.

     The implementation of type demotion distinguishes between lossy
     and non-lossy type conversions, and their use on the slave can be
     controlled by setting the `slave_type_conversions' global server
     system variable.

     For more information, see *Note
     replication-features-attribute-promotion::.

   * Incompatible change in NDB API event reporting

     Beginning with MySQL Cluster NDB 6.3.34, DDL events are no longer
     reported on `Event' objects by default. Instead such event
     reporting must be enabled explicitly using the `Event::setReport()'
     method. For more information, see `Event::setReport()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-event-methods.html#ndb-event-setreport),
     and The `Event::EventReport' Type
     (http://dev.mysql.com/doc/ndbapi/en/ndb-event-types.html#ndb-event-eventreport).

   * Heartbeat ordering

     Beginning with MySQL Cluster NDB 6.3.35, it is possible to set a
     specific order for transmission of heartbeats between data nodes,
     using the `HeartbeatOrder' data node configuration parameter
     introduced in this version. This parameter can be useful in
     situations where multiple data nodes are running on the same host
     and a temporary disruption in connectivity between hosts would
     otherwise cause the loss of a node group (and thus failure of the
     cluster).

   * Relaxed ndb_restore column comparison rules

     When restoring data, ndb_restore compares the attributes of a
     column for equality with the definition of the column in the
     target table. However, not all of these attributes need to be the
     same for *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
     to be meaningful, safe and useful. Beginning with MySQL Cluster
     NDB 6.3.35, *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore.  automatically ignores
     differences in certain column attributes which do not necessarily
     have to match between the version of the column in a backup and
     the version of that column in the MySQL Cluster to which the
     column data is being restored. These attributes include the
     following:

        * `COLUMN_FORMAT' setting (`FIXED', `DYNAMIC', or `DEFAULT')

        * `STORAGE' setting (`MEMORY' or `DISK')

        * The default value

        * The distribution key

     In such cases, *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. reports any such differences
     to minimize any chance of user error.

   * -add-drop-trigger option for mysqldump

     Beginning with MySQL Cluster NDB 6.3.38, this option can be used
     to force all *Note `CREATE TRIGGER': create-trigger. statements in
     *Note `mysqldump': mysqldump. output to be preceded by a *Note
     `DROP TRIGGER IF EXISTS': drop-trigger. statement.

   * Skipping corrupted tables in NDB native backups

     Beginning with MySQL Cluster NDB 6.3.40, you can cause *Note
     `ndb_restore': mysql-cluster-programs-ndb-restore. to ignore
     tables that are corrupted due to missing blob parts tables by
     using the `--skip-broken-objects' option. When this option is
     used, such tables are skipped, and the restoration of any
     remaining uncorrupted tables in the backup continues.

   * Restoring from a NDB native backup to a differently-named database

     MySQL Cluster NDB 6.3.41 adds a new `--rewrite-database' option to
     *Note `ndb_restore': mysql-cluster-programs-ndb-restore, which
     makes it possible to restore to a database having a different name
     from that of the database in the backup. The option can be used
     multiple times, and it is possible to restore from more than one
     source database in the backup to a single target database
     (although no protection against table or other object name
     collision is provided).

     See *Note mysql-cluster-programs-ndb-restore::, for more
     information.


File: manual.info,  Node: mysql-cluster-development-5-1-ndb-6-2,  Next: mysql-cluster-development-5-1-ndb-6-1,  Prev: mysql-cluster-development-5-1-ndb-6-3,  Up: mysql-cluster-development

17.1.4.5 MySQL Cluster Development in MySQL Cluster NDB 6.2
...........................................................

The following list provides an overview of significant feature
additions and changes made in MySQL Cluster NDB 6.2. All of the changes
in this list are also available in MySQL Cluster NDB 6.3 . For more
detailed information about all feature changes and bugfixes made in
MySQL Cluster NDB 6.2, see
`http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-6-2.html'.

   * Enhanced backup status reporting

     Backup status reporting has been improved, aided in part by the
     introduction of a `BackupReportFrequency' configuration parameter.

   * Multiple cluster connections per SQL node

     A single MySQL server acting as a MySQL Cluster SQL node can
     employ multiple connections to the cluster using the
     `--ndb-cluster-connection-pool' startup option for *Note `mysqld':
     mysqld. This option is described in `MySQL Cluster-Related Command
     Options for *Note `mysqld': mysqld.:
     `--ndb-cluster-connection-pool' option'.

   * New data access interface

     The `NdbRecord' interface provides a new and simplified data
     handler for use in NDB API applications.

   * New reporting commands

     The new management client `REPORT BackupStatus' and `REPORT
     MemoryUsage' commands provide better access to information about
     the status of MySQL Cluster backups and how much memory is being
     used by MySQL Cluster for data and index storage. See *Note
     mysql-cluster-mgm-client-commands::, for more information about
     the `REPORT' commands. In addition, in-progress status reporting is
     provided by the *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. utility; see *Note
     mysql-cluster-programs-ndb-restore::.

   * Improved memory allocation and configuration

     Memory is now allocated by the *Note `NDB': mysql-cluster. kernel
     to tables on a page-by-page basis, which significantly reduces the
     memory overhead required for maintaining *Note `NDBCLUSTER':
     mysql-cluster. tables. In addition, the `MaxAllocate'
     configuration parameter now makes it possible to set the maximum
     size of the allocation unit used for table memory.

   * Choice of fixed-width or variable-width columns

     You can control whether fixed-width or variable-width storage is
     used for a given column of an *Note `NDB': mysql-cluster. table by
     employing of the `COLUMN_FORMAT' specifier as part of the column's
     definition in a *Note `CREATE TABLE': create-table. or *Note
     `ALTER TABLE': alter-table. statement. In addition, the ability to
     control whether a given column of an *Note `NDB': mysql-cluster.
     table is stored in memory or on disk, using the `STORAGE' specifier
     as part of the column's definition in a *Note `CREATE TABLE':
     create-table. or *Note `ALTER TABLE': alter-table. statement. For
     more information, see *Note create-table::, and *Note
     alter-table::.

   * Controlling management client connections

     The `--bind-address' cluster management server startup option
     makes it possible to restrict management client connections to
     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. to a single
     host (IP address or host name) and port, which can make MySQL
     Cluster management operations more secure. For more information
     about this option, see *Note mysql-cluster-programs-ndb-mgmd::.

   * Micro-GCPs

     Due to a change in the protocol for handling of global checkpoints
     (GCPs handled in this manner sometimes being referred to as
     `micro-GCPs'), it is now possible to control how often the GCI
     number is updated, and how often global checkpoints are written to
     disk, using the `TimeBetweenEpochs' and `TimeBetweenEpochsTimeout'
     configuration parameters. This improves the reliability and
     performance of MySQL Cluster Replication.

   * Core online schema change support

     Support for the online *Note `ALTER TABLE': alter-table.
     operations `ADD COLUMN', `ADD INDEX', and `DROP INDEX' is
     available. When the `ONLINE' keyword is used, the *Note `ALTER
     TABLE': alter-table. is noncopying, which means that indexes do
     not have to be re-created, which provides these benefits:

        * Single user mode is no longer required for *Note `ALTER
          TABLE': alter-table. operations that can be performed online.

        * Transactions can continue during *Note `ALTER TABLE':
          alter-table. operations that can be performed online.

        * Tables being altered online are not locked against access by
          other SQL nodes.

          However, such tables are locked against other operations on
          the _same_ SQL node for the duration of the *Note `ALTER
          TABLE': alter-table. We are working to overcome this
          limitation in a future MySQL Cluster release.

     Online *Note `CREATE INDEX': create-index. and *Note `DROP INDEX':
     drop-index. statements are also supported. Online changes can be
     suppressed using the `OFFLINE' key word. See *Note
     alter-table-online-operations::, *Note create-index::, and *Note
     drop-index::, for more detailed information.

   * mysql.ndb_binlog_index improvements

     More information has been added to the `mysql.ndb_binlog_index'
     table so that it is possible to determine which originating epochs
     have been applied inside an epoch. This is particularly useful for
     3-way replication. See *Note mysql-cluster-replication-schema::,
     for more information.

   * Epoch lag control

     The `MaxBufferedEpochs' data node configuration parameter provides
     a means to control the maximum number of unprocessed epochs by
     which a subscribing node can lag. Subscribers which exceed this
     number are disconnected and forced to reconnect.

   * Fully automatic database discovery

     It is no longer a requirement for database autodiscovery that an
     SQL node already be connected to the cluster at the time that a
     database is created on another SQL node, or for a *Note `CREATE
     DATABASE': create-database. or *Note `CREATE SCHEMA':
     create-database. statement to be issued on the new SQL node after
     it joins the cluster.

   * Multiple data node processes per host

     In earlier MySQL Cluster release series, we did not support MySQL
     Cluster deployments in production where more than one *Note
     `ndbd': mysql-cluster-programs-ndbd. process was run on a single
     physical machine. However, beginning with MySQL Cluster NDB 6.2.0,
     you can use multiple data node processes on a single host.

     *Note*:

     A multi-threaded version of *Note `ndbd':
     mysql-cluster-programs-ndbd.  tailored for use on hosts with
     multiple CPUs or cores was introduced in MySQL Cluster NDB 7.0. See
     *Note mysql-cluster-development-5-1-ndb-7-0::, and *Note
     mysql-cluster-programs-ndbmtd::, for more information.

   * Improved Disk Data file system configuration

     As of MySQL Cluster NDB 6.2.17, you can specify default locations
     for MySQL Cluster Disk Data data files and undo log files using
     the data node configuration parameters `FileSystemPathDD',
     `FileSystemPathDataFiles', and `FileSystemPathUndoFiles'.  This
     eliminates the need to use symbolic links to place Disk Data files
     separately from other files in data node file systems to improve
     Disk Data performance. For more information, see *Note
     mysql-cluster-ndbd-disk-data-filesystem-parameters::.

   * Automatic creation of Disk Data log file groups and tablespaces

     Beginning with MySQL Cluster NDB 6.2.17, using the data node
     configuration parameters `InitialLogFileGroup' and
     `InitialTablespace', you can cause the creation of a MySQL Cluster
     Disk Data log file group, tablespace, or both, when the cluster is
     first started. When using these parameters, no SQL statements are
     required to create these Disk Data objects.

   * Improved access to partitioning information

     The *Note `ndb_desc': mysql-cluster-programs-ndb-desc. utility now
     provides additional information about the partitioning of data
     stored in MySQL Cluster. Beginning with MySQL Cluster NDB 6.2.19,
     the `--extra-node-info' option causes *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc. to include information about data
     distribution (that is, which table fragments are stored on which
     data nodes). This option also requires the use of the
     `--extra-partition-info' option.

     Information about partition-to-node mappings can also be obtained
     using the `Table::getFragmentNodes()' method, also added in MySQL
     Cluster NDB 6.2.19.

   * New CHANGE MASTER TO option for circular replication

     Beginning with MySQL Cluster NDB 6.2.19, the *Note `CHANGE MASTER
     TO': change-master-to. statement supports an `IGNORE_SERVER_IDS'
     option which takes a comma-separated list of server IDs and causes
     events originating from the corresponding servers to be ignored.
     (Log rotation and log deletion events are preserved.)

     See *Note change-master-to::, as well as *Note
     show-slave-status::, for more information.


File: manual.info,  Node: mysql-cluster-development-5-1-ndb-6-1,  Next: mysql-cluster-development-5-1,  Prev: mysql-cluster-development-5-1-ndb-6-2,  Up: mysql-cluster-development

17.1.4.6 MySQL Cluster Development in MySQL Cluster NDB 6.1
...........................................................

The following list provides an overview of significant feature
additions and changes made in MySQL Cluster NDB 6.1. All of the changes
in this list are also available in MySQL Cluster NDB 6.2 and 6.3
releases. For detailed information about all changes made in MySQL
Cluster NDB 6.1, see
`http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-6-1.html'.

   * Increased number of cluster nodes

     The maximum number of all nodes in a MySQL Cluster has been
     increased to 255. For more information, see *Note
     mysql-cluster-limitations-multiple-nodes::.

   * Disabling arbitration

     It is now possible to disable arbitration by setting
     `ArbitrationRank=0' on all cluster management and SQL nodes. For
     more information, see `Defining the Management Server:
     `ArbitrationRank'' and `Defining SQL and Other API Nodes:
     `ArbitrationRank''.

   * Additional DUMP commands

     New management client `DUMP' commands provide help with tracking
     transactions, scan operations, and locks. See *Note
     mysql-cluster-mgm-client-commands::, and `DUMP' Commands
     (http://dev.mysql.com/doc/ndbapi/en/ndb-internals-dump-commands.html),
     for more information.

   * Faster Disk Data backups

     Improvements in backups of Disk Data tables can yield a 10 to 15%
     increase in backup speed of Disk Data tables.

   * Batched slave updates

     Batching of updates on cluster replication slaves, enabled using
     the `--slave-allow-batching' option for *Note `mysqld': mysqld,
     increases replication efficiency. For more information, see *Note
     mysql-cluster-replication-starting::.


File: manual.info,  Node: mysql-cluster-development-5-1,  Prev: mysql-cluster-development-5-1-ndb-6-1,  Up: mysql-cluster-development

17.1.4.7 Development History of MySQL Cluster in MySQL 5.1
..........................................................

A number of features for MySQL Cluster were implemented in MySQL 5.1
through MySQL 5.1.23, when support for MySQL Cluster was moved to MySQL
Cluster NDB. All of the features in the following list are also
available in all MySQL Cluster NDB (6.1 and later) releases.

   * Integration of MySQL Cluster into MySQL Replication

     MySQL Cluster Replication makes it possible to replicate from one
     MySQL Cluster to another. Updates on any SQL node (MySQL server)
     in the cluster acting as the master are replicated to the slave
     cluster; the state of the slave side remains consistent with the
     cluster acting as the master. This is sometimes referred to as
     _asynchronous replication_ between clusters, providing _geographic
     redundancy_. It is also possible to replicate from a MySQL Cluster
     acting as the master to a standalone MySQL server acting as the
     slave, or from a standalone MySQL master server to a slave
     cluster; in either of these cases, the standalone MySQL server
     uses a storage engine other than *Note `NDBCLUSTER': mysql-cluster.
     Multi-master replication setups such as circular replication are
     also supported.

     See *Note mysql-cluster-replication::.

   * Support for storage of rows on disk

     Storage of *Note `NDBCLUSTER': mysql-cluster. table data on disk
     is now supported. Indexed columns, including the primary key hash
     index, must still be stored in RAM; however, all other columns can
     be stored on disk.

     See *Note mysql-cluster-disk-data::.

   * Variable-size columns

     In MySQL 5.0, an *Note `NDBCLUSTER': mysql-cluster.  table column
     defined as `VARCHAR(255)' used 260 bytes of storage independent of
     what was stored in any particular record. In MySQL 5.1 Cluster
     tables, only the portion of the column actually taken up by the
     record is stored. This makes possible a significant reduction in
     space requirements for such columns as compared to previous
     release series--by a factor of up to 5 in many cases.

   * User-defined partitioning

     Users can define partitions based on columns that are part of the
     primary key. It is possible to partition *Note `NDB':
     mysql-cluster. tables based on `KEY' and `LINEAR KEY' schemes.
     This feature is also available for many other MySQL storage
     engines, which support additional partitioning types that are not
     available with *Note `NDBCLUSTER': mysql-cluster. tables.

     For additional general information about user-defined partitioning
     in MySQL 5.1, see *Note partitioning::. Specifics of partitioning
     types are discussed in *Note partitioning-types::.

     The MySQL Server can also determine whether it is possible to
     `prune away' some of the partitions from the `WHERE' clause, which
     can greatly speed up some queries. See *Note
     partitioning-pruning::, for information about designing tables and
     queries to take advantage of partition pruning.

   * Autodiscovery of table schema changes

     In MySQL 5.0, it was necessary to issue a *Note `FLUSH TABLES':
     flush. statement or a `dummy' *Note `SELECT': select. for new
     *Note `NDBCLUSTER': mysql-cluster. tables or changes made to
     schemas of existing *Note `NDBCLUSTER': mysql-cluster. tables on
     one SQL node to be visible on the cluster's other SQL nodes.  In
     MySQL 5.1, this is no longer necessary; new Cluster tables and
     changes in the definitions of existing *Note `NDBCLUSTER':
     mysql-cluster. tables made on one SQL node are immediately visible
     to all SQL nodes connected to the cluster.

     *Note*:

     When creating a new database, it is still necessary in MySQL 5.1
     to issue a *Note `CREATE DATABASE': create-database. or *Note
     `CREATE SCHEMA': create-database. statement on each SQL node in the
     cluster.

   * Distribution awareness (NDB API)

     _Distribution awareness_ is a mechanism by which the best data
     node is automatically selected to be queried for information.
     (Conceptually, it is similar in some ways to partition pruning (see
     *Note partitioning-pruning::). To take advantage of distribution
     awareness, you should do the following:

       1. Determine which table column is most likely to be used for
          finding matching records.

       2. Make this column part of the table's primary key.

       3. Explicitly partition the table by `KEY', using this column as
          the table' partitioning key.

     Following these steps causes records with the same value for the
     partitioning column to be stored on the same partition (that is,
     in the same node group). When reading data, transactions are begun
     on the data node actually having the desired rows instead of this
     node being determined by the usual round-robin mechanism.

     *Important*:

     To see a measureable impact on performance, the cluster must have
     at least four data nodes, since, with only two data nodes, both
     data nodes have exactly the same data.

     Using distribution awareness can yield performance increase of as
     great as 45% when using four data nodes, and possibly more when
     using a greater number of data nodes.

     *Note*:

     In mainline MySQL 5.1 releases, distribution awareness was
     supported only when using the NDB API; support was added for SQL
     and API nodes in MySQL Cluster NDB 6.3 (see *Note
     mysql-cluster-development-5-1-ndb-6-3::, which includes an example
     showing how to create a table to take advantage of distribution
     awareness).

   * Online adding and dropping of indexes

     For *Note `ALTER TABLE': alter-table. statements, `ADD INDEX' and
     `DROP INDEX' operations for dynamic (variable-width) columns on
     *Note `NDB': mysql-cluster. tables are now performed as online
     operations (no table copying). This is also true for *Note `CREATE
     INDEX': create-index.  and *Note `DROP INDEX': drop-index. As a
     result, these operations are now performed much more quickly than
     previously.

     For more information, see *Note alter-table-online-operations::,
     *Note create-index::, and *Note drop-index::.

See *Note mysql-cluster-limitations-resolved::, for more information.


File: manual.info,  Node: mysql-cluster-compared,  Next: mysql-cluster-limitations,  Prev: mysql-cluster-development,  Up: mysql-cluster-overview

17.1.5 MySQL Server Using InnoDB Compared with MySQL Cluster
------------------------------------------------------------

* Menu:

* mysql-cluster-ndb-innodb-engines::  Differences Between the NDB and InnoDB Storage Engines
* mysql-cluster-ndb-innodb-workloads::  NDB and InnoDB Workloads
* mysql-cluster-ndb-innodb-usage::  NDB and InnoDB Feature Usage Summary

MySQL Server offers a number of choices in storage engines. Since both
*Note `NDBCLUSTER': mysql-cluster. and *Note `InnoDB':
innodb-storage-engine. can serve as transactional MySQL storage
engines, users of MySQL Server sometimes become interested in MySQL
Cluster. They see *Note `NDB': mysql-cluster. as a possible alternative
or upgrade to the default *Note `InnoDB': innodb-storage-engine. storage
engine in MySQL 5.5. While *Note `NDB': mysql-cluster. and *Note
`InnoDB': innodb-storage-engine. share common characteristics, there
are differences in architecture and implementation, so that some
existing MySQL Server applications and usage scenarios can be a good
fit for MySQL Cluster, but not all of them.

In this section, we discuss and compare some characteristics of the
*Note `NDB': mysql-cluster. storage engine used by MySQL Cluster with
*Note `InnoDB': innodb-storage-engine. used in MySQL 5.1 and MySQL 5.5.
The next few sections provide a technical comparison. In many
instances, decisions about when and where to use MySQL Cluster must be
made on a case-by-case basis, taking all factors into consideration.
While it is beyond the scope of this documentation to provide specifics
for every conceivable usage scenario, we also attempt to offer some
very general guidance on the relative suitability of some common types
of applications for *Note `NDB': mysql-cluster. as opposed to *Note
`InnoDB': innodb-storage-engine. backends.

While it is possible to use *Note `InnoDB': innodb-storage-engine.
tables with MySQL Cluster, such tables are not clustered. MySQL Cluster
NDB 7.1 releases use a *Note `mysqld': mysqld. based on MySQL 5.1 which
includes `InnoDB' 1.0; MySQL Cluster NDB 7.2.1 and later are based on
MySQL Server 5.5, which includes support for `InnoDB' 1.1. It is also
not possible to use programs or libraries from a MySQL Cluster NDB 6.x
or MySQL Cluster NDB 7.x distribution with MySQL Server 5.1 or MySQL
Server 5.5, or the reverse.

While it is also true that some types of common business applications
can be run either on MySQL Cluster or on MySQL Server (most likely
using the *Note `InnoDB': innodb-storage-engine. storage engine), there
are some important architectural and implementation differences. *Note
mysql-cluster-ndb-innodb-engines::, provides a summary of the these
differences. Due to the differences, some usage scenarios are clearly
more suitable for one engine or the other; see *Note
mysql-cluster-ndb-innodb-workloads::. This in turn has an impact on the
types of applications that better suited for use with *Note `NDB':
mysql-cluster. or *Note `InnoDB': innodb-storage-engine. See *Note
mysql-cluster-ndb-innodb-usage::, for a comparison of the relative
suitability of each for use in common types of database applications.

For information about the relative characteristics of the *Note `NDB':
mysql-cluster. and *Note `MEMORY': memory-storage-engine. storage
engines, see *Note memory-compared-cluster::.

See *Note storage-engines::, for additional information about MySQL
storage engines.


File: manual.info,  Node: mysql-cluster-ndb-innodb-engines,  Next: mysql-cluster-ndb-innodb-workloads,  Prev: mysql-cluster-compared,  Up: mysql-cluster-compared

17.1.5.1 Differences Between the NDB and InnoDB Storage Engines
...............................................................

The MySQL Cluster *Note `NDB': mysql-cluster. storage engine is
implemented using a distributed, shared-nothing architecture, which
causes it to behave differently from *Note `InnoDB':
innodb-storage-engine. in a number of ways. For those unaccustomed to
working with *Note `NDB': mysql-cluster, unexpected behaviors can arise
due to its distributed nature with regard to transactions, foreign
keys, joins, and other characteristics. These are shown in the
following table:

This table lists feature differences between *Note `InnoDB':
innodb-storage-engine. and *Note `NDB': mysql-cluster. storage engines.

Feature                  *Note `InnoDB':          MySQL Cluster
                         innodb-storage-engine.   
_MySQL Server Version_   `InnoDB' 1.1: 5.5        MySQL Cluster NDB 6.3,
                                                  7.0, 7.1: 5.1
                         `InnoDB' 1.0: 5.1        
                                                  MySQL Cluster NDB 7.2:
                                                  5.5
                                                  
                                                  MySQL Cluster NDB 7.3:
                                                  5.6
_`InnoDB' Availability _ *Note `InnoDB':          _NDB 6.3, 7.0_: *Note
                         innodb-storage-engine.   `InnoDB':
                         1.1 plugin               innodb-storage-engine.
                                                  storage engine
                                                  
                                                  _NDB 7.1_: *Note
                                                  `InnoDB':
                                                  innodb-storage-engine.
                                                  1.0 plugin support
                                                  (MySQL Cluster NDB
                                                  7.1.9a and later)
                                                  
                                                  _NDB 7.2_: *Note
                                                  `InnoDB':
                                                  innodb-storage-engine.
                                                  1.1 (MySQL Cluster NDB
                                                  7.2.1 and later)
_Storage Limits_         64TB                     3TB
                                                  
                                                  (Practical upper limit
                                                  based on 48 data nodes
                                                  with 64GB RAM each; can
                                                  be increased with
                                                  disk-based data and
                                                  BLOBs)
_Foreign Keys_           Yes                      Prior to MySQL Cluster
                                                  NDB 7.3: No. (Ignored,
                                                  as with *Note `MyISAM':
                                                  myisam-storage-engine.)
                                                  
                                                  Available in MySQL
                                                  Cluster NDB 7.3 and
                                                  later.
_Transactions_           All standard types       `READ COMMITTED'
_MVCC_                   Yes                      No
_Data Compression_       Yes                      No
                                                  
                                                  (MySQL Cluster
                                                  checkpoint and backup
                                                  files can be compressed)
_Large Row Support (>    Supported for *Note      Supported for *Note
14K)_                    `VARBINARY':             `BLOB': blob. and *Note
                         binary-varbinary,        `TEXT': blob. columns
                         `VARCHAR', *Note         only
                         `BLOB': blob, and *Note  
                         `TEXT': blob. columns    (Using these types to
                                                  store very large
                                                  amounts of data can
                                                  lower MySQL Cluster
                                                  performance)
_Replication Support_    Asynchronous and         Automatic synchronous
                         semisynchronous          replication within a
                         replication using MySQL  MySQL Cluster.
                         Replication              
                                                  Asynchronous
                                                  replication between
                                                  MySQL Clusters, using
                                                  MySQL Replication
_Scaleout for Read       Yes (MySQL Replication)  Yes (Automatic
Operations_                                       partitioning in MySQL
                                                  Cluster; MySQL
                                                  Replication)
_Scaleout for Write      Requires                 Yes (Automatic
Operations_              application-level        partitioning in MySQL
                         partitioning (sharding)  Cluster is transparent
                                                  to applications)
_High Availability (HA)_ Requires additional      Yes (Designed for
                         software                 99.999% uptime)
_Node Failure Recovery   Requires additional      Automatic
and Failover_            software                 
                                                  (Key element in MySQL
                                                  Cluster architecture)
_Time for Node Failure   30 seconds or longer     Typically < 1 second
Recovery_                                         
_Real-Time Performance_  No                       Yes
_In-Memory Tables_       No                       Yes
                                                  
                                                  (Some data can
                                                  optionally be stored on
                                                  disk; both in-memory
                                                  and disk data storage
                                                  are durable)
_NoSQL Access to         Native memcached         Yes
Storage Engine _         interface in             
                         development (see the     Multiple APIs,
                         MySQL Dev Zone article   including C++,
                         `MySQL Cluster 7.2       HTTP/REST, Java and JPA
                         (DMR2): NoSQL,           (MySQL Cluster NDB 7.1
                         Key/Value, Memcached'    and later); Memcached
                         (http://dev.mysql.com/tech-resources/articles/mysql-cluster-7.2.html))(MySQL Cluster NDB 7.2
                                                  and later); Node.js
                                                  under development
                                                  (MySQL Cluster NDB 7.3)
_Concurrent and          Not supported            Up to 48 writers,
Parallel Writes_                                  optimized for
                                                  concurrent writes
_Conflict Detection and  No                       Yes
Resolution (Multiple                              
Replication Masters)_                             
_Hash Indexes_           No                       Yes
_Online Addition of      Read-only replicas       Yes (all node types)
Nodes_                   using MySQL Replication  
_Online Upgrades_        No                       Yes
_Online Schema           No.                      Yes.
Modifications_                                    


File: manual.info,  Node: mysql-cluster-ndb-innodb-workloads,  Next: mysql-cluster-ndb-innodb-usage,  Prev: mysql-cluster-ndb-innodb-engines,  Up: mysql-cluster-compared

17.1.5.2 NDB and InnoDB Workloads
.................................

MySQL Cluster has a range of unique attributes that make it ideal to
serve applications requiring high availability, fast failover, high
throughput, and low latency. Due to its distributed architecture and
multi-node implementation, MySQL Cluster also has specific constraints
that may keep some workloads from performing well. A number of major
differences in behavior between the *Note `NDB': mysql-cluster. and
*Note `InnoDB': innodb-storage-engine. storage engines with regard to
some common types of database-driven application workloads are shown in
the following table::

This table lists major differences in behavior between the *Note
`InnoDB': innodb-storage-engine. and *Note `NDB': mysql-cluster.
storage engines with regard to common types of database-driven
application workloads.

Workload                 *Note `InnoDB':          MySQL Cluster (*Note
                         innodb-storage-engine.   `NDB': mysql-cluster.)
_High-Volume OLTP        Yes                      Yes
Applications_                                     
_DSS Applications (data  Yes                      Limited (Join
marts, analytics)_                                operations across OLTP
                                                  datasets not exceeding
                                                  3TB in size)
_Custom Applications_    Yes                      Yes
_Packaged Applications_  Yes                      Limited (should be
                                                  mostly primary key
                                                  access).
                                                  
                                                  *Note*:
                                                  
                                                  MySQL Cluster NDB 7.3
                                                  supports foreign keys.
_In-Network Telecoms     No                       Yes
Applications (HLR, HSS,                           
SDP)_                                             
_Session Management and  Yes                      Yes
Caching_                                          
_E-Commerce              Yes                      Yes
Applications_                                     
_User Profile            Yes                      Yes
Management, AAA                                   
Protocol_                                         


File: manual.info,  Node: mysql-cluster-ndb-innodb-usage,  Prev: mysql-cluster-ndb-innodb-workloads,  Up: mysql-cluster-compared

17.1.5.3 NDB and InnoDB Feature Usage Summary
.............................................

When comparing application feature requirements to the capabilities of
*Note `InnoDB': innodb-storage-engine. with *Note `NDB': mysql-cluster,
some are clearly more compatible with one storage engine than the other.

The following table lists supported application features according to
the storage engine to which each feature is typically better suited.

This table lists supported application features according to the
storage engine to which each feature is typically better suited.

Preferred application requirements   Preferred application requirements
for *Note `InnoDB':                  for *Note `NDB': mysql-cluster.
innodb-storage-engine.               
   * Foreign keys                       * Write scaling
                                     
     *Note*:                            * 99.999% uptime
                                     
     MySQL Cluster NDB 7.3 supports     * Online addition of nodes and
     foreign keys.                        online schema operations
                                     
   * Full table scans                   * Multiple SQL and NoSQL APIs
                                          (see MySQL Cluster APIs:
   * Very large databases, rows, or       Overview and Concepts
     transactions                         (http://dev.mysql.com/doc/ndbapi/en/mysql-cluster-api-overview.html))
                                     
   * Transactions other than `READ      * Real-time performance
     COMMITTED'                      
                                        * Limited use of *Note `BLOB':
                                          blob.  columns

File: manual.info,  Node: mysql-cluster-limitations,  Prev: mysql-cluster-compared,  Up: mysql-cluster-overview

17.1.6 Known Limitations of MySQL Cluster
-----------------------------------------

* Menu:

* mysql-cluster-limitations-syntax::  Noncompliance with SQL Syntax in MySQL Cluster
* mysql-cluster-limitations-limits::  Limits and Differences of MySQL Cluster from Standard MySQL Limits
* mysql-cluster-limitations-transactions::  Limits Relating to Transaction Handling in MySQL Cluster
* mysql-cluster-limitations-error-handling::  MySQL Cluster Error Handling
* mysql-cluster-limitations-database-objects::  Limits Associated with Database Objects in MySQL Cluster
* mysql-cluster-limitations-unsupported::  Unsupported or Missing Features in MySQL Cluster
* mysql-cluster-limitations-performance::  Limitations Relating to Performance in MySQL Cluster
* mysql-cluster-limitations-exclusive-to-cluster::  Issues Exclusive to MySQL Cluster
* mysql-cluster-limitations-disk-data::  Limitations Relating to MySQL Cluster Disk Data Storage
* mysql-cluster-limitations-multiple-nodes::  Limitations Relating to Multiple MySQL Cluster Nodes
* mysql-cluster-limitations-resolved::  Previous MySQL Cluster Issues Resolved in MySQL 5.1, MySQL Cluster NDB 6.x, and MySQL Cluster NDB 7.x

In the sections that follow, we discuss known limitations in current
releases of MySQL Cluster as compared with the features available when
using the `MyISAM' and `InnoDB' storage engines. If you check the
`Cluster' category in the MySQL bugs database at
`http://bugs.mysql.com', you can find known bugs in the following
categories under `MySQL Server:' in the MySQL bugs database at
`http://bugs.mysql.com', which we intend to correct in upcoming
releases of MySQL Cluster:

   * MySQL Cluster

   * Cluster Direct API (NDBAPI)

   * Cluster Disk Data

   * Cluster Replication

   * ClusterJ

This information is intended to be complete with respect to the
conditions just set forth. You can report any discrepancies that you
encounter to the MySQL bugs database using the instructions given in
*Note bug-reports::. If we do not plan to fix the problem in MySQL
Cluster NDB 7.1, we will add it to the list.

See *Note mysql-cluster-limitations-resolved:: for a list of issues in
MySQL Cluster in MySQL 5.0 that have been resolved in the current
version.

*Note*:

Limitations and other issues specific to MySQL Cluster Replication are
described in *Note mysql-cluster-replication-issues::.


File: manual.info,  Node: mysql-cluster-limitations-syntax,  Next: mysql-cluster-limitations-limits,  Prev: mysql-cluster-limitations,  Up: mysql-cluster-limitations

17.1.6.1 Noncompliance with SQL Syntax in MySQL Cluster
.......................................................

Some SQL statements relating to certain MySQL features produce errors
when used with *Note `NDB': mysql-cluster. tables, as described in the
following list:

   * Temporary tables

     Temporary tables are not supported. Trying either to create a
     temporary table that uses the *Note `NDB': mysql-cluster. storage
     engine or to alter an existing temporary table to use *Note `NDB':
     mysql-cluster. fails with the error `Table storage engine
     'ndbcluster' does not support the create option 'TEMPORARY''.

   * Indexes and keys in NDB tables

     Keys and indexes on MySQL Cluster tables are subject to the
     following limitations:

        * Column width

          Attempting to create an index on an `NDB' table column whose
          width is greater than 3072 bytes succeeds, but only the first
          3072 bytes are actually used for the index. In such cases, a
          warning `Specified key was too long; max key length is 3072
          bytes' is issued, and a *Note `SHOW CREATE TABLE':
          show-create-table. statement shows the length of the index as
          3072.

        * TEXT and BLOB columns

          You cannot create indexes on *Note `NDB': mysql-cluster.
          table columns that use any of the *Note `TEXT': blob. or
          *Note `BLOB': blob. data types.

        * FULLTEXT indexes

          The *Note `NDB': mysql-cluster. storage engine does not
          support `FULLTEXT' indexes, which are possible for `MyISAM'
          tables only.

          However, you can create indexes on *Note `VARCHAR': char.
          columns of *Note `NDB': mysql-cluster. tables.

        * USING HASH keys and NULL

          Using nullable columns in unique keys and primary keys means
          that queries using these columns are handled as full table
          scans. To work around this issue, make the column `NOT NULL',
          or re-create the index without the `USING HASH' option.

        * Prefixes

          There are no prefix indexes; only entire columns can be
          indexed. (The size of an `NDB' column index is always the
          same as the width of the column in bytes, up to and including
          3072 bytes, as described earlier in this section. Also see
          *Note mysql-cluster-limitations-unsupported::, for additional
          information.)

        * BIT columns

          A *Note `BIT': bit-type. column cannot be a primary key,
          unique key, or index, nor can it be part of a composite
          primary key, unique key, or index.

        * AUTO_INCREMENT columns

          Like other MySQL storage engines, the *Note `NDB':
          mysql-cluster. storage engine can handle a maximum of one
          `AUTO_INCREMENT' column per table.  However, in the case of a
          Cluster table with no explicit primary key, an
          `AUTO_INCREMENT' column is automatically defined and used as a
          `hidden' primary key. For this reason, you cannot define a
          table that has an explicit `AUTO_INCREMENT' column unless that
          column is also declared using the `PRIMARY KEY' option.
          Attempting to create a table with an `AUTO_INCREMENT' column
          that is not the table's primary key, and using the *Note
          `NDB': mysql-cluster. storage engine, fails with an error.

   * MySQL Cluster and geometry data types

     Geometry data types (`WKT' and `WKB') are supported in *Note
     `NDB': mysql-cluster. tables in MySQL 5.1 (including MySQL Cluster
     NDB 6.X and 7.X through 7.1).  However, spatial indexes are not
     supported.

   * Character sets and binary log files

     Currently, the `ndb_apply_status' and `ndb_binlog_index' tables
     are created using the `latin1' (ASCII) character set.  Because
     names of binary logs are recorded in this table, binary log files
     named using non-Latin characters are not referenced correctly in
     these tables. This is a known issue, which we are working to fix.
     (Bug #50226)

     To work around this problem, use only Latin-1 characters when
     naming binary log files or setting any the `--basedir',
     `--log-bin', or `--log-bin-index' options.

   * Creating NDBCLUSTER tables with user-defined partitioning

     Support for user-defined partitioning for MySQL Cluster is
     restricted to [`LINEAR'] `KEY' partitioning. Beginning with MySQL
     5.1.12, using any other partitioning type with `ENGINE=NDB' or
     `ENGINE=NDBCLUSTER' in a *Note `CREATE TABLE': create-table.
     statement results in an error.

     Default partitioning scheme

     As of MySQL 5.1.6, all MySQL Cluster tables are by default
     partitioned by `KEY' using the table's primary key as the
     partitioning key. If no primary key is explicitly set for the
     table, the `hidden' primary key automatically created by the *Note
     `NDBCLUSTER': mysql-cluster. storage engine is used instead. For
     additional discussion of these and related issues, see *Note
     partitioning-key::.

     Beginning with MySQL Cluster NDB 6.2.18, MySQL Cluster NDB 6.3.25,
     and MySQL Cluster NDB 7.0.6, *Note `CREATE TABLE': create-table.
     and *Note `ALTER TABLE': alter-table. statements that would cause
     a user-partitioned *Note `NDBCLUSTER': mysql-cluster. table not to
     meet either or both of the following two requirements are not
     permitted, and fail with an error (Bug #40709):

       1. The table must have an explicit primary key.

       2. All columns listed in the table's partitioning expression
          must be part of the primary key.

     Exception

     If a user-partitioned *Note `NDBCLUSTER': mysql-cluster. table is
     created using an empty column-list (that is, using `PARTITION BY
     [LINEAR] KEY()'), then no explicit primary key is required.

     Maximum number of partitions for NDBCLUSTER tables

     The maximum number of partitions that can defined for a *Note
     `NDBCLUSTER': mysql-cluster. table when employing user-defined
     partitioning is 8 per node group.  (See *Note
     mysql-cluster-nodes-groups::, for more information about MySQL
     Cluster node groups.

     DROP PARTITION not supported

     It is not possible to drop partitions from *Note `NDB':
     mysql-cluster. tables using `ALTER TABLE ... DROP PARTITION'. The
     other partitioning extensions to *Note `ALTER TABLE':
     alter-table.--`ADD PARTITION', `REORGANIZE PARTITION', and
     `COALESCE PARTITION'--are supported for Cluster tables, but use
     copying and so are not optimized. See *Note
     partitioning-management-range-list:: and *Note alter-table::.

   * Row-based replication

     When using row-based replication with MySQL Cluster, binary
     logging cannot be disabled. That is, the *Note `NDB':
     mysql-cluster. storage engine ignores the value of `sql_log_bin'.
     (Bug #16680)


File: manual.info,  Node: mysql-cluster-limitations-limits,  Next: mysql-cluster-limitations-transactions,  Prev: mysql-cluster-limitations-syntax,  Up: mysql-cluster-limitations

17.1.6.2 Limits and Differences of MySQL Cluster from Standard MySQL Limits
...........................................................................

In this section, we list limits found in MySQL Cluster that either
differ from limits found in, or that are not found in, standard MySQL.

Memory usage and recovery

Memory consumed when data is inserted into an *Note `NDB':
mysql-cluster. table is not automatically recovered when deleted, as it
is with other storage engines.  Instead, the following rules hold true:

   * A *Note `DELETE': delete. statement on an *Note `NDB':
     mysql-cluster. table makes the memory formerly used by the deleted
     rows available for re-use by inserts on the same table only.
     However, this memory can be made available for general re-use by
     performing a rolling restart of the cluster. See *Note
     mysql-cluster-rolling-restart::.

     Beginning with MySQL Cluster NDB 6.3.7, this limitation can be
     overcome using *Note `OPTIMIZE TABLE': optimize-table. See *Note
     mysql-cluster-limitations-resolved::, for more information.

   * A *Note `DROP TABLE': drop-table. or *Note `TRUNCATE TABLE':
     truncate-table. operation on an *Note `NDB': mysql-cluster. table
     frees the memory that was used by this table for re-use by any
     *Note `NDB': mysql-cluster. table, either by the same table or by
     another *Note `NDB': mysql-cluster. table.

     *Note*:

     Recall that *Note `TRUNCATE TABLE': truncate-table.  drops and
     re-creates the table. See *Note truncate-table::.

   * Limits imposed by the cluster's configuration

     A number of hard limits exist which are configurable, but
     available main memory in the cluster sets limits. See the complete
     list of configuration parameters in *Note
     mysql-cluster-config-file::. Most configuration parameters can be
     upgraded online. These hard limits include:

        * Database memory size and index memory size (`DataMemory' and
          `IndexMemory', respectively).

          `DataMemory' is allocated as 32KB pages. As each `DataMemory'
          page is used, it is assigned to a specific table; once
          allocated, this memory cannot be freed except by dropping the
          table.

          See *Note mysql-cluster-ndbd-definition::, for more
          information.

        * The maximum number of operations that can be performed per
          transaction is set using the configuration parameters
          `MaxNoOfConcurrentOperations' and `MaxNoOfLocalOperations'.

          *Note*:

          Bulk loading, *Note `TRUNCATE TABLE': truncate-table, and
          *Note `ALTER TABLE': alter-table. are handled as special
          cases by running multiple transactions, and so are not subject
          to this limitation.

        * Different limits related to tables and indexes. For example,
          the maximum number of ordered indexes in the cluster is
          determined by `MaxNoOfOrderedIndexes', and the maximum number
          of ordered indexes per table is 16.

   * Node and data object maximums

     The following limits apply to numbers of cluster nodes and
     metadata objects:

        * The maximum number of data nodes is 48.

          A data node must have a node ID in the range of 1 to 48,
          inclusive. (Previous to MySQL Cluster NDB 6.1.1, management
          and API nodes were restricted to the range 1 to 63 inclusive
          as a node ID; starting with MySQL Cluster NDB 6.1.1,
          management and API nodes may use node IDs in the range 1 to
          255, inclusive.)

        * Prior to MySQL Cluster NDB 6.1.1, the total maximum number of
          nodes in a MySQL Cluster was 63. Beginning with MySQL Cluster
          NDB 6.1.1, the total maximum number of nodes in a MySQL
          Cluster is 255. In either case, this number includes all SQL
          nodes (MySQL Servers), API nodes (applications accessing the
          cluster other than MySQL servers), data nodes, and management
          servers.

        * The maximum number of metadata objects in current versions of
          MySQL Cluster is 20320. This limit is hard-coded.

     See *Note mysql-cluster-limitations-resolved::, for more
     information.


File: manual.info,  Node: mysql-cluster-limitations-transactions,  Next: mysql-cluster-limitations-error-handling,  Prev: mysql-cluster-limitations-limits,  Up: mysql-cluster-limitations

17.1.6.3 Limits Relating to Transaction Handling in MySQL Cluster
.................................................................

A number of limitations exist in MySQL Cluster with regard to the
handling of transactions. These include the following:

   * Transaction isolation level

     The *Note `NDBCLUSTER': mysql-cluster. storage engine supports
     only the `READ COMMITTED' transaction isolation level.  (`InnoDB',
     for example, supports `READ COMMITTED', `READ UNCOMMITTED',
     `REPEATABLE READ', and `SERIALIZABLE'.) See *Note
     mysql-cluster-backup-troubleshooting::, for information on how
     this can affect backing up and restoring Cluster databases.)

   * Transactions and BLOB or TEXT columns

     *Note `NDBCLUSTER': mysql-cluster. stores only part of a column
     value that uses any of MySQL's *Note `BLOB': blob. or *Note
     `TEXT': blob. data types in the table visible to MySQL; the
     remainder of the *Note `BLOB': blob. or *Note `TEXT': blob. is
     stored in a separate internal table that is not accessible to
     MySQL.  This gives rise to two related issues of which you should
     be aware whenever executing *Note `SELECT': select. statements on
     tables that contain columns of these types:

       1. For any *Note `SELECT': select. from a MySQL Cluster table:
          If the *Note `SELECT': select. includes a *Note `BLOB': blob.
          or *Note `TEXT': blob. column, the `READ COMMITTED'
          transaction isolation level is converted to a read with read
          lock. This is done to guarantee consistency.

       2. Prior to MySQL Cluster NDB 7.0.12, for any *Note `SELECT':
          select. which used a primary key lookup or unique key lookup
          to retrieve any columns that used any of the *Note `BLOB':
          blob. or *Note `TEXT': blob. data types and that was executed
          within a transaction, a shared read lock was held on the
          table for the duration of the transaction--that is, until the
          transaction was either committed or aborted.

          In MySQL Cluster NDB 7.0.12 and later, for primary key
          lookups, the lock is released as soon as all *Note `BLOB':
          blob. or *Note `TEXT': blob. data has been read.  (Bug
          #49190) However, for unique key lookups, the shared lock
          continues to be held for the lifetime of the transaction.

          This issue does not occur for queries that use index or table
          scans, even against *Note `NDB': mysql-cluster. tables having
          *Note `BLOB': blob. or *Note `TEXT': blob. columns.

          For example, consider the table `t' defined by the following
          *Note `CREATE TABLE': create-table. statement:


               CREATE TABLE t (
                   a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
                   b INT NOT NULL,
                   c INT NOT NULL,
                   d TEXT,
                   INDEX i(b),
                   UNIQUE KEY u(c)
               ) ENGINE = NDB,

          Either of the following queries on `t' causes a shared read
          lock, because the first query uses a primary key lookup and
          the second uses a unique key lookup:


               SELECT * FROM t WHERE a = 1;

               SELECT * FROM t WHERE c = 1;

          However, none of the four queries shown here causes a shared
          read lock:


               SELECT * FROM t WHERE b 1;

               SELECT * FROM t WHERE d = '1';

               SELECT * FROM t;

               SELECT b,c WHERE a = 1;

          This is because, of these four queries, the first uses an
          index scan, the second and third use table scans, and the
          fourth, while using a primary key lookup, does not retrieve
          the value of any *Note `BLOB': blob. or *Note `TEXT': blob.
          columns.

          You can help minimize issues with shared read locks by
          avoiding queries that use unique key lookups (or primary key
          lookups in MySQL Cluster NDB 7.0.11 and earlier) that
          retrieve *Note `BLOB': blob. or *Note `TEXT': blob. columns,
          or, in cases where such queries are not avoidable, by
          committing transactions as soon as possible afterward.

   * Rollbacks

     There are no partial transactions, and no partial rollbacks of
     transactions. A duplicate key or similar error causes the entire
     transaction to be rolled back.

     This behavior differs from that of other transactional storage
     engines such as *Note `InnoDB': innodb-storage-engine.  that may
     roll back individual statements.

   * Transactions and memory usage

     As noted elsewhere in this chapter, MySQL Cluster does not handle
     large transactions well; it is better to perform a number of small
     transactions with a few operations each than to attempt a single
     large transaction containing a great many operations. Among other
     considerations, large transactions require very large amounts of
     memory. Because of this, the transactional behavior of a number of
     MySQL statements is effected as described in the following list:

        * *Note `TRUNCATE TABLE': truncate-table. is not transactional
          when used on *Note `NDB': mysql-cluster. tables. If a *Note
          `TRUNCATE TABLE': truncate-table. fails to empty the table,
          then it must be re-run until it is successful.

        * `DELETE FROM' (even with no `WHERE' clause) _is_
          transactional. For tables containing a great many rows, you
          may find that performance is improved by using several
          `DELETE FROM ... LIMIT ...' statements to `chunk' the delete
          operation.  If your objective is to empty the table, then you
          may wish to use *Note `TRUNCATE TABLE': truncate-table.
          instead.

        * LOAD DATA statements

          *Note `LOAD DATA INFILE': load-data. is not transactional
          when used on *Note `NDB': mysql-cluster. tables.

          *Important*:

          When executing a *Note `LOAD DATA INFILE': load-data.
          statement, the *Note `NDB': mysql-cluster. engine performs
          commits at irregular intervals that enable better utilization
          of the communication network. It is not possible to know
          ahead of time when such commits take place.

          *Note `LOAD DATA FROM MASTER': load-data-from-master. is not
          supported in MySQL Cluster.

        * ALTER TABLE and transactions

          When copying an *Note `NDB': mysql-cluster. table as part of
          an *Note `ALTER TABLE': alter-table, the creation of the copy
          is nontransactional. (In any case, this operation is rolled
          back when the copy is deleted.)

   * Transactions and the COUNT() function

     When using MySQL Cluster Replication, it is not possible to
     guarantee the transactional consistency of the `COUNT()' function
     on the slave. In other words, when performing on the master a
     series of statements (*Note `INSERT': insert, *Note `DELETE':
     delete, or both) that changes the number of rows in a table within
     a single transaction, executing `SELECT COUNT(*) FROM TABLE'
     queries on the slave may yield intermediate results. This is due
     to the fact that `SELECT COUNT(...)' may perform dirty reads, and
     is not a bug in the *Note `NDB': mysql-cluster. storage engine.
     (See Bug #31321 for more information.)


File: manual.info,  Node: mysql-cluster-limitations-error-handling,  Next: mysql-cluster-limitations-database-objects,  Prev: mysql-cluster-limitations-transactions,  Up: mysql-cluster-limitations

17.1.6.4 MySQL Cluster Error Handling
.....................................

Starting, stopping, or restarting a node may give rise to temporary
errors causing some transactions to fail. These include the following
cases:

   * Temporary errors

     When first starting a node, it is possible that you may see Error
     1204 `Temporary failure, distribution changed' and similar
     temporary errors.

   * Errors due to node failure

     The stopping or failure of any data node can result in a number of
     different node failure errors. (However, there should be no
     aborted transactions when performing a planned shutdown of the
     cluster.)

In either of these cases, any errors that are generated must be handled
within the application. This should be done by retrying the transaction.

See also *Note mysql-cluster-limitations-limits::.


File: manual.info,  Node: mysql-cluster-limitations-database-objects,  Next: mysql-cluster-limitations-unsupported,  Prev: mysql-cluster-limitations-error-handling,  Up: mysql-cluster-limitations

17.1.6.5 Limits Associated with Database Objects in MySQL Cluster
.................................................................

Some database objects such as tables and indexes have different
limitations when using the *Note `NDBCLUSTER': mysql-cluster. storage
engine:

   * Table names containing special characters

     *Note `NDB': mysql-cluster. tables whose names contain characters
     other than letters, numbers, dashes, and underscores and which are
     created on one SQL node were not always discovered correctly by
     other SQL nodes. (Bug #31470)

     *Note*:

     This issue was fixed in MySQL 5.1.23, MySQL Cluster NDB 6.2.7, and
     MySQL Cluster NDB 6.3.4.

   * Number of database objects

     The maximum number of _all_ *Note `NDB': mysql-cluster. database
     objects in a single MySQL Cluster--including databases, tables,
     and indexes--is limited to 20320.

   * Attributes per table

     Prior to MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB 7.1.4, the
     maximum number of attributes (that is, columns and indexes) per
     table is limited to 128.

     Beginning with MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB
     7.1.4, this limit is increased to 512.

   * Attributes per key

     The maximum number of attributes per key is 32.

   * Row size

     Prior to MySQL Cluster NDB 7.0, the maximum permitted size of any
     one row was 8052 bytes; in MySQL Cluster NDB 7.0 and later, this
     is 14000 bytes. Each *Note `BLOB': blob. or *Note `TEXT': blob.
     column contributes 256 + 8 = 264 bytes to this total.


File: manual.info,  Node: mysql-cluster-limitations-unsupported,  Next: mysql-cluster-limitations-performance,  Prev: mysql-cluster-limitations-database-objects,  Up: mysql-cluster-limitations

17.1.6.6 Unsupported or Missing Features in MySQL Cluster
.........................................................

A number of features supported by other storage engines are not
supported for *Note `NDB': mysql-cluster. tables. Trying to use any of
these features in MySQL Cluster does not cause errors in or of itself;
however, errors may occur in applications that expects the features to
be supported or enforced:

   * Foreign key constraints

     Prior to MySQL Cluster NDB 7.3, the foreign key construct is
     ignored, just as it is by `MyISAM' tables. Foreign keys are
     supported in MySQL Cluster NDB 7.3 and later.

   * Index prefixes

     Prefixes on indexes are not supported for `NDBCLUSTER' tables. If
     a prefix is used as part of an index specification in a statement
     such as *Note `CREATE TABLE': create-table, *Note `ALTER TABLE':
     alter-table, or *Note `CREATE INDEX': create-index, the prefix is
     ignored.

   * OPTIMIZE operations

     `OPTIMIZE' operations are not supported.

     Beginning with MySQL Cluster NDB 6.3.7, this limitation has been
     lifted. See *Note mysql-cluster-limitations-resolved::, for more
     information.

   * LOAD TABLE ... FROM MASTER

     *Note `LOAD TABLE FROM MASTER': load-table-from-master. is not
     supported.

   * Savepoints and rollbacks

     Savepoints and rollbacks to savepoints are ignored as in `MyISAM'.

   * Durability of commits

     There are no durable commits on disk. Commits are replicated, but
     there is no guarantee that logs are flushed to disk on commit.

   * Replication

     Statement-based replication is not supported. Use
     `--binlog-format=ROW' (or `--binlog-format=MIXED') when setting up
     cluster replication. See *Note mysql-cluster-replication::, for
     more information.

*Note*:

See *Note mysql-cluster-limitations-transactions::, for more
information relating to limitations on transaction handling in *Note
`NDB': mysql-cluster.


File: manual.info,  Node: mysql-cluster-limitations-performance,  Next: mysql-cluster-limitations-exclusive-to-cluster,  Prev: mysql-cluster-limitations-unsupported,  Up: mysql-cluster-limitations

17.1.6.7 Limitations Relating to Performance in MySQL Cluster
.............................................................

The following performance issues are specific to or especially
pronounced in MySQL Cluster:

   * Range scans

     There are query performance issues due to sequential access to the
     *Note `NDB': mysql-cluster. storage engine; it is also relatively
     more expensive to do many range scans than it is with either
     `MyISAM' or `InnoDB'.

   * Reliability of Records in range

     The `Records in range' statistic is available but is not
     completely tested or officially supported. This may result in
     nonoptimal query plans in some cases. If necessary, you can employ
     `USE INDEX' or `FORCE INDEX' to alter the execution plan. See
     *Note index-hints::, for more information on how to do this.

   * Unique hash indexes

     Unique hash indexes created with `USING HASH' cannot be used for
     accessing a table if `NULL' is given as part of the key.


File: manual.info,  Node: mysql-cluster-limitations-exclusive-to-cluster,  Next: mysql-cluster-limitations-disk-data,  Prev: mysql-cluster-limitations-performance,  Up: mysql-cluster-limitations

17.1.6.8 Issues Exclusive to MySQL Cluster
..........................................

The following are limitations specific to the *Note `NDBCLUSTER':
mysql-cluster. storage engine:

   * Machine architecture

     All machines used in the cluster must have the same architecture.
     That is, all machines hosting nodes must be either big-endian or
     little-endian, and you cannot use a mixture of both. For example,
     you cannot have a management node running on a PowerPC which
     directs a data node that is running on an x86 machine. This
     restriction does not apply to machines simply running *Note
     `mysql': mysql.  or other clients that may be accessing the
     cluster's SQL nodes.

   * Binary logging

     MySQL Cluster has the following limitations or restrictions with
     regard to binary logging:

        * `sql_log_bin' has no effect on data operations; however, it
          is supported for schema operations.

        * MySQL Cluster cannot produce a binary log for tables having
          *Note `BLOB': blob. columns but no primary key.

        * Only the following schema operations are logged in a cluster
          binary log which is _not_ on the *Note `mysqld': mysqld.
          executing the statement:

             * *Note `CREATE TABLE': create-table.

             * *Note `ALTER TABLE': alter-table.

             * *Note `DROP TABLE': drop-table.

             * *Note `CREATE DATABASE': create-database. / *Note
               `CREATE SCHEMA': create-database.

             * *Note `DROP DATABASE': drop-database. / *Note `DROP
               SCHEMA': drop-database.

             * *Note `CREATE TABLESPACE': create-tablespace.

             * *Note `ALTER TABLESPACE': alter-tablespace.

             * *Note `DROP TABLESPACE': drop-tablespace.

             * *Note `CREATE LOGFILE GROUP': create-logfile-group.

             * *Note `ALTER LOGFILE GROUP': alter-logfile-group.

             * *Note `DROP LOGFILE GROUP': drop-logfile-group.

See also *Note mysql-cluster-limitations-multiple-nodes::.


File: manual.info,  Node: mysql-cluster-limitations-disk-data,  Next: mysql-cluster-limitations-multiple-nodes,  Prev: mysql-cluster-limitations-exclusive-to-cluster,  Up: mysql-cluster-limitations

17.1.6.9 Limitations Relating to MySQL Cluster Disk Data Storage
................................................................

Disk Data object maximums and minimums

Disk data objects are subject to the following maximums and minimums:

   * Maximum number of tablespaces: 2^32 (4294967296)

   * Maximum number of data files per tablespace: 2^16 (65536)

   * Maximum data file size: The theoretical limit is 64G; however, in
     MySQL 5.1 (including MySQL Cluster NDB 6.X and 7.X through 7.1),
     the practical upper limit is 32G. This is equivalent to 32768
     extents of 1M each.

     Since a MySQL Cluster Disk Data table can use at most 1
     tablespace, this means that the theoretical upper limit to the
     amount of data (in bytes) that can be stored on disk by a single
     `NDB' table is 32G * 65536 = 2251799813685248, or approximately 2
     petabytes.

   * The theoretical maximum number of extents per tablespace data file
     is 2^16 (65536); however, for practical purposes, the recommended
     maximum number of extents per data file is 2^15 (32768).

     The minimum and maximum possible sizes of extents for tablespace
     data files are 32K and 2G, respectively. See *Note
     create-tablespace::, for more information.

Disk Data tables and diskless mode

Use of Disk Data tables is not supported when running the cluster in
diskless mode. Beginning with MySQL 5.1.12, it is prohibited
altogether. (Bug #20008)


File: manual.info,  Node: mysql-cluster-limitations-multiple-nodes,  Next: mysql-cluster-limitations-resolved,  Prev: mysql-cluster-limitations-disk-data,  Up: mysql-cluster-limitations

17.1.6.10 Limitations Relating to Multiple MySQL Cluster Nodes
..............................................................

Multiple SQL nodes

The following are issues relating to the use of multiple MySQL servers
as MySQL Cluster SQL nodes, and are specific to the *Note `NDBCLUSTER':
mysql-cluster. storage engine:

   * No distributed table locks

     A *Note `LOCK TABLES': lock-tables. works only for the SQL node on
     which the lock is issued; no other SQL node in the cluster `sees'
     this lock. This is also true for a lock issued by any statement
     that locks tables as part of its operations. (See next item for an
     example.)

   * ALTER TABLE operations

     *Note `ALTER TABLE': alter-table. is not fully locking when
     running multiple MySQL servers (SQL nodes).  (As discussed in the
     previous item, MySQL Cluster does not support distributed table
     locks.)

Multiple management nodes

When using multiple management servers:

   * You must give nodes explicit IDs in connect strings because
     automatic allocation of node IDs does not work across multiple
     management servers.

   * In MySQL Cluster NDB 7.0.7 and earlier, you must take extreme care
     to have the same configurations for all management servers; no
     special checks for consistency are performed.

     Beginning with MySQL Cluster NDB 7.0.8, a management server when
     first starting checks for any other management server in the same
     MySQL Cluster, and upon successful connection to the other
     management server uses its configuration data.  This means that
     the management server `--reload' and `--initial' startup options
     are ignored unless the management server is the only one running.
     It also means that, when performing a rolling restart of a MySQL
     Cluster with multiple management nodes, the management server
     reads its own configuration file if (and only if) it is the only
     management server running in this MySQL Cluster. See *Note
     mysql-cluster-rolling-restart::, for more information.

Multiple network addresses

Multiple network addresses per data node are not supported.  Use of
these is liable to cause problems: In the event of a data node failure,
an SQL node waits for confirmation that the data node went down but
never receives it because another route to that data node remains open.
This can effectively make the cluster inoperable.

*Note*:

It is possible to use multiple network hardware _interfaces_ (such as
Ethernet cards) for a single data node, but these must be bound to the
same address.  This also means that it not possible to use more than one
`[tcp]' section per connection in the `config.ini' file. See *Note
mysql-cluster-tcp-definition::, for more information.


File: manual.info,  Node: mysql-cluster-limitations-resolved,  Prev: mysql-cluster-limitations-multiple-nodes,  Up: mysql-cluster-limitations

17.1.6.11 Previous MySQL Cluster Issues Resolved in MySQL 5.1, MySQL Cluster NDB 6.x, and MySQL Cluster NDB 7.x
...............................................................................................................

A number of limitations and related issues existing in earlier versions
of MySQL Cluster have been resolved:

   * Variable-length column support

     The *Note `NDBCLUSTER': mysql-cluster. storage engine now supports
     variable-length column types for in-memory tables.

     Previously, for example, any Cluster table having one or more
     *Note `VARCHAR': char. fields which contained only relatively
     small values, much more memory and disk space were required when
     using the *Note `NDBCLUSTER': mysql-cluster. storage engine than
     would have been the case for the same table and data using the
     `MyISAM' engine. In other words, in the case of a *Note `VARCHAR':
     char. column, such a column required the same amount of storage as
     a *Note `CHAR': char. column of the same size.  In MySQL 5.1, this
     is no longer the case for in-memory tables, where storage
     requirements for variable-length column types such as *Note
     `VARCHAR': char.  and `BINARY' are comparable to those for these
     column types when used in `MyISAM' tables (see *Note
     storage-requirements::).

     *Important*:

     For MySQL Cluster Disk Data tables, the fixed-width limitation
     continues to apply. See *Note mysql-cluster-disk-data::.

   * Replication with MySQL Cluster

     It is now possible to use MySQL replication with Cluster
     databases. For details, see *Note mysql-cluster-replication::.

     Circular Replication

     Circular replication is also supported with MySQL Cluster,
     beginning with MySQL 5.1.18. See *Note
     mysql-cluster-replication-multi-master::.

   * auto_increment_increment and auto_increment_offset

     The `auto_increment_increment' and `auto_increment_offset' server
     system variables are supported for Cluster replication beginning
     with MySQL 5.1.20, MySQL Cluster NDB 6.2.5, and MySQL Cluster
     6.3.2.

   * Database autodiscovery and online schema changes

     Autodiscovery of databases is now supported for multiple MySQL
     servers accessing the same MySQL Cluster. Formerly, autodiscovery
     in MySQL Cluster 5.1 and MySQL Cluster NDB 6.x releases required
     that a given *Note `mysqld': mysqld. was already running and
     connected to the cluster at the time that the database was created
     on a different *Note `mysqld': mysqld.--in other words, when a
     *Note `mysqld': mysqld. process connected to the cluster after a
     database named DB_NAME was created, it was necessary to issue a
     `CREATE DATABASE DB_NAME' or `CREATE SCHEMA DB_NAME' statement on
     the `new' MySQL server when it first accessed that MySQL Cluster.
     Beginning with MySQL Cluster NDB 6.2.16 and MySQL Cluster NDB
     6.3.18, such a `CREATE' statement is no longer required.  (Bug
     #39612)

     This also means that online schema changes in *Note `NDB':
     mysql-cluster. tables are now possible.  That is, the result of
     operations such as *Note `ALTER TABLE': alter-table. and *Note
     `CREATE INDEX': create-index. performed on one SQL node in the
     cluster are now visible to the cluster's other SQL nodes without
     any additional action being taken.

   * Backup and restore between architectures

     Beginning with MySQL 5.1.10, it is possible to perform a Cluster
     backup and restore between different architectures.
     Previously--for example--you could not back up a cluster running
     on a big-endian platform and then restore from that backup to a
     cluster running on a little-endian system. (Bug #19255)

   * Character set directory

     Beginning with MySQL 5.1.10, it is possible to install MySQL with
     Cluster support to a nondefault location and change the search
     path for font description files using either the `--basedir' or
     `--character-sets-dir' options. (Previously, *Note `ndbd':
     mysql-cluster-programs-ndbd. in MySQL 5.1 searched only the
     default path--typically
     `/usr/local/mysql/share/mysql/charsets'--for character sets.)

   * Multiple management servers

     In MySQL 5.1 (including all MySQL Cluster NDB 6.x and later
     versions), it is no longer necessary, when running multiple
     management servers, to restart all the cluster's data nodes to
     enable the management nodes to see one another.

     Also, when using multiple management servers and starting
     concurrently several API nodes (possibly including one or more SQL
     nodes) whose connection strings listed the management servers in
     different order, it was possible for 2 API nodes to be assigned
     the same node ID. This issue is resolved in MySQL Cluster NDB
     6.2.17, 6.3.23, and 6.4.3.  (Bug #42973)

   * Multiple data node processes per host

     Beginning with MySQL Cluster NDB 6.2.0, you can use multiple data
     node processes on a single host. (In MySQL Cluster NDB 6.1, MySQL
     5.1, and earlier release series, we did not support production
     MySQL Cluster deployments in which more than one *Note `ndbd':
     mysql-cluster-programs-ndbd. process was run on a single physical
     machine.)

     In addition, MySQL Cluster NDB 7.0 introduces support for
     multi-threaded data nodes (*Note `ndbmtd':
     mysql-cluster-programs-ndbmtd.). See *Note
     mysql-cluster-development-5-1-ndb-7-0::, and *Note
     mysql-cluster-programs-ndbmtd::, for more information.

   * Identifiers

     Formerly (in MySQL 5.0 and earlier), database names, table names
     and attribute names could not be as long for *Note `NDB':
     mysql-cluster. tables as tables using other storage engines,
     because attribute names were truncated internally. In MySQL 5.1
     and later, names of MySQL Cluster databases, tables, and table
     columns follow the same rules regarding length as they do for any
     other storage engine.

   * Length of CREATE TABLE statements

     *Note `CREATE TABLE': create-table. statements may be no more than
     4096 characters in length. _This limitation affects MySQL 5.1.6,
     5.1.7, and 5.1.8 only_. (See Bug #17813)

   * IGNORE and REPLACE functionality

     In MySQL 5.1.7 and earlier, *Note `INSERT IGNORE': insert, *Note
     `UPDATE IGNORE': update, and *Note `REPLACE': replace. were
     supported only for primary keys, but not for unique keys. It was
     possible to work around this issue by removing the constraint, then
     dropping the unique index, performing any inserts, and then adding
     the unique index again.

     This limitation was removed for *Note `INSERT IGNORE': insert. and
     *Note `REPLACE': replace.  in MySQL 5.1.8. (See Bug #17431.)

   * AUTO_INCREMENT columns

     In MySQL 5.1.10 and earlier versions, the maximum number of tables
     having `AUTO_INCREMENT' columns--including those belonging to
     hidden primary keys--was 2048.

     This limitation was lifted in MySQL 5.1.11.

   * Maximum number of cluster nodes

     Prior to MySQL Cluster NDB 6.1.1, the total maximum number of
     nodes in a MySQL Cluster was 63, including all SQL nodes (MySQL
     Servers), API nodes (applications accessing the cluster other than
     MySQL servers), data nodes, and management servers.

     Starting with MySQL Cluster NDB 6.1.1, the total maximum number of
     nodes in a MySQL Cluster is 255, including all SQL nodes (MySQL
     Servers), API nodes (applications accessing the cluster other than
     MySQL servers), data nodes, and management servers. The total
     number of data nodes and management nodes beginning with this
     version is 63, of which up to 48 can be data nodes.

     *Note*:

     The limitation that a data node cannot have a node ID greater than
     49 continues to apply.

   * Recovery of memory from deleted rows

     Beginning with MySQL Cluster NDB 6.3.7, memory can be reclaimed
     from an *Note `NDB': mysql-cluster. table for reuse with any *Note
     `NDB': mysql-cluster. table by employing *Note `OPTIMIZE TABLE':
     optimize-table, subject to the following limitations:

        * Only in-memory tables are supported; the *Note `OPTIMIZE
          TABLE': optimize-table. statement still has no effect on
          MySQL Cluster Disk Data tables.

        * Only variable-length columns (such as those declared as *Note
          `VARCHAR': char, *Note `TEXT': blob, or *Note `BLOB': blob.)
          are supported.

          However, you can force columns defined using fixed-length
          data types (such as *Note `CHAR': char.) to be dynamic using
          the `ROW_FORMAT' or `COLUMN_FORMAT' option with a *Note
          `CREATE TABLE': create-table. or *Note `ALTER TABLE':
          alter-table. statement.

          See *Note create-table::, and *Note alter-table::, for
          information on these options.

     You can regulate the effects of `OPTIMIZE' on performance by
     adjusting the value of the global system variable
     `ndb_optimization_delay', which sets the number of milliseconds to
     wait between batches of rows being processed by `OPTIMIZE'. The
     default value is 10 milliseconds. It is possible to set a lower
     value (to a minimum of `0'), but not recommended. The maximum is
     100000 milliseconds (that is, 100 seconds).

   * Implicit Rollbacks

     Prior to MySQL Cluster NDB 6.2.17 and MySQL Cluster NDB 6.3.19,
     MySQL Cluster did not automatically roll back a transaction that
     was aborted by a duplicate key or similar error, and subsequent
     statements raised `ERROR 1296 (HY000): Got error 4350 'Transaction
     already aborted' from NDBCLUSTER'. In such cases, it was necessary
     to issue an explicit *Note `ROLLBACK': commit.  statement first,
     and then to retry the entire transaction.

     Beginning with MySQL Cluster NDB 6.2.17 and MySQL Cluster NDB
     6.3.19, this limitation has been removed; now, an error which
     causes a transaction to be aborted generates an implicit rollback
     of the entire transaction. This is logged with the warning
     `Storage engine NDB does not support rollback for this statement.
     Transaction rolled back and must be restarted'. A statement
     subsequent to this starts a new transaction. (Bug #32656)

     *Note*:

     The *Note `NDBCLUSTER': mysql-cluster. storage engine does not
     support partial transactions or partial rollbacks of transactions
     in any version of MySQL Cluster.

   * Number of tables

     Previously, the maximum number of *Note `NDBCLUSTER':
     mysql-cluster. tables in a single MySQL Cluster was 1792, but this
     is no longer the case in MySQL 5.1 and later MySQL Cluster
     releases. However, the number of tables is still included in the
     total maximum number of *Note `NDBCLUSTER': mysql-cluster. database
     objects (20320). (See *Note
     mysql-cluster-limitations-database-objects::.)

   * DDL operations

     Beginning with MySQL Cluster NDB 6.4.0, DDL operations (such as
     *Note `CREATE TABLE': create-table. or *Note `ALTER TABLE':
     alter-table.) are protected from data node failures. Previously,
     if a data node failed while trying to perform one of these, the
     data dictionary became locked and no further DDL statements could
     be executed without restarting the cluster (Bug #36718).

   * Adding and dropping of data nodes

     In MySQL Cluster NDB 6.3 and previous versions of MySQL Cluster,
     the online adding or dropping of data nodes was not possible; such
     operations required a complete shutdown and restart of the entire
     cluster. In MySQL Cluster NDB 7.0 (beginning with MySQL Cluster
     NDB 6.4.0) and later MySQL Cluster release series, it is possible
     to add new data nodes to a running MySQL Cluster by performing a
     rolling restart, so that the cluster and the data stored in it
     remain available to applications.

     When planning to increase the number of data nodes in the cluster
     online in MySQL Cluster NDB 7.0 or MySQL Cluster NDB 7.1, you
     should be aware of and take into account the following issues:

        * New data nodes can be added online to a MySQL Cluster only as
          part of a new node group.

        * New data nodes can be added online, but cannot yet be dropped
          online. Reducing the number of data nodes still requires a
          system restart of the cluster.

        * As in previous MySQL Cluster releases, it is not possible to
          change online either the number of replicas (`NoOfReplicas'
          configuration parameter) or the number of data nodes per node
          group. These changes require a system restart.

        * Redistribution of existing cluster data using the new data
          nodes is not automatic; however, this can be accomplished
          using simple SQL statements in the *Note `mysql': mysql.
          client or other MySQL client application once the nodes have
          been added. During this procedure, it is not possible to
          perform DDL operations, although DML operations can continue
          as normal.

          The distribution of new cluster data (that is, data stored in
          the cluster _after_ the new nodes have been added) uses the
          new nodes without manual intervention.

     For more information, see *Note mysql-cluster-online-add-node::.

   * Native support for default column values

     Starting with MySQL Cluster NDB 7.1.0, default values for table
     columns are stored by *Note `NDBCLUSTER': mysql-cluster, rather
     than by the MySQL server as was previously the case. Because less
     data must be sent from an SQL node to the data nodes, inserts on
     tables having column value defaults can be performed more
     efficiently than before.

     Tables created using previous MySQL Cluster releases can still be
     used in MySQL Cluster 7.1.0 and later, although they do not
     support native default values and continue to use defaults
     supplied by the MySQL server until they are upgraded. This can be
     done by means of an offline *Note `ALTER TABLE': alter-table.
     statement.

     *Important*:

     You cannot set or change a table column's default value using an
     online *Note `ALTER TABLE': alter-table. operation

   * InnoDB plugin support

     Previously, *Note `InnoDB': innodb-storage-engine. support in
     MySQL Cluster was limited to the version built in to the MySQl
     Server. Beginning with MySQL Cluster NDB 7.1.9, MySQL Cluster also
     provides support for the *Note `InnoDB': innodb-storage-engine.
     Plugin. See *Note mysql-cluster-installation::, for information
     about enabling *Note `InnoDB': innodb-storage-engine. storage
     engine and plugin support with MySQL Cluster.

   * Distribution of MySQL users and privileges

     Previously, MySQL users and privileges created on one SQL node
     were unique to that SQL node, due to the fact that the MySQL grant
     tables were restricted to using the *Note `MyISAM':
     myisam-storage-engine. storage engine.  Beginning with MySQL
     Cluster NDB 7.2.0, it is possible, following installation of the
     MySQL Cluster software and setup of the desired users and
     privileges on one SQL node, to convert the grant tables to use
     *Note `NDB': mysql-cluster. and thus to distribute the users and
     privileges across all SQL nodes connected to the cluster. You can
     do this by loading and making use of a set of stored procedures
     defined in an SQL script supplied with the MySQL Cluster
     distribution. For more information, see *Note
     mysql-cluster-privilege-distribution::.

   * Number of rows per partition

     Previously, a single MySQL Cluster partition could hold a maximum
     of 46137488 rows. This limitation was removed in MySQL Cluster NDB
     7.0.36 and MySQL Cluster NDB 7.1.25.  (Bug #13844405, Bug
     #14000373)

     If you are still using a previous MySQL Cluster release, you can
     work around this limitation by taking advantage of the fact that
     the number of partitions is the same as the number of data nodes
     in the cluster (see *Note mysql-cluster-nodes-groups::). This means
     that, by increasing the number of data nodes, you can increase the
     available space for storing data.

     In MySQL Cluster NDB 7.0 and later, you can increase the number of
     data nodes in the cluster while the cluster remains in operation.
     See *Note mysql-cluster-online-add-node::, for more information.

     It is also possible to increase the number of partitions for *Note
     `NDB': mysql-cluster. tables by using explicit `KEY' or `LINEAR
     KEY' partitioning (see *Note partitioning-key::).


File: manual.info,  Node: mysql-cluster-installation,  Next: mysql-cluster-configuration,  Prev: mysql-cluster-overview,  Up: mysql-cluster

17.2 MySQL Cluster Installation and Upgrades
============================================

* Menu:

* mysql-cluster-install-linux::  Installing MySQL Cluster on Linux
* mysql-cluster-install-windows::  Installing MySQL Cluster on Windows
* mysql-cluster-install-configuration::  Initial Configuration of MySQL Cluster
* mysql-cluster-install-first-start::  Initial Startup of MySQL Cluster
* mysql-cluster-install-example-data::  MySQL Cluster Example with Tables and Data
* mysql-cluster-install-shutdown-restart::  Safe Shutdown and Restart of MySQL Cluster
* mysql-cluster-upgrade-downgrade::  Upgrading and Downgrading MySQL Cluster

This section describes the basics for planning, installing,
configuring, and running a MySQL Cluster. Whereas the examples in *Note
mysql-cluster-configuration:: provide more in-depth information on a
variety of clustering options and configuration, the result of
following the guidelines and procedures outlined here should be a
usable MySQL Cluster which meets the _minimum_ requirements for
availability and safeguarding of data.

For information about upgrading or downgrading a MySQL Cluster between
release versions, see *Note mysql-cluster-upgrade-downgrade::.

This section covers hardware and software requirements; networking
issues; installation of MySQL Cluster; configuration issues; starting,
stopping, and restarting the cluster; loading of a sample database; and
performing queries.

Assumptions

The following sections make a number of assumptions regarding the
cluster's physical and network configuration. These assumptions are
discussed in the next few paragraphs.

Cluster nodes and host computers

The cluster consists of four nodes, each on a separate host computer,
and each with a fixed network address on a typical Ethernet network as
shown here:

This table lists cluster nodes for an example configuration and
provides the IP address of each node.

Node                                 IP Address
Management node (`mgmd')             192.168.0.10
SQL node (*Note `mysqld': mysqld.)   192.168.0.20
Data node "A" (*Note `ndbd':         192.168.0.30
mysql-cluster-programs-ndbd.)        
Data node "B" (*Note `ndbd':         192.168.0.40
mysql-cluster-programs-ndbd.)        

This may be made clearer by the following diagram:

MySQL Cluster Multi-Computer Setup

Network addressing

In the interest of simplicity (and reliability), this `How-To' uses
only numeric IP addresses.  However, if DNS resolution is available on
your network, it is possible to use host names in lieu of IP addresses
in configuring Cluster. Alternatively, you can use the `hosts' file
(typically `/etc/hosts' for Linux and other Unix-like operating systems,
`C:\WINDOWS\system32\drivers\etc\hosts' on Windows, or your operating
system's equivalent) for providing a means to do host lookup if such is
available.

Potential hosts file issues

A common problem when trying to use host names for Cluster nodes arises
because of the way in which some operating systems (including some
Linux distributions) set up the system's own host name in the
`/etc/hosts' during installation. Consider two machines with the host
names `ndb1' and `ndb2', both in the `cluster' network domain. Red Hat
Linux (including some derivatives such as CentOS and Fedora) places the
following entries in these machines' `/etc/hosts' files:


     #  ndb1 `/etc/hosts':
     127.0.0.1   ndb1.cluster ndb1 localhost.localdomain localhost


     #  ndb2 `/etc/hosts':
     127.0.0.1   ndb2.cluster ndb2 localhost.localdomain localhost

SUSE Linux (including OpenSUSE) places these entries in the machines'
`/etc/hosts' files:


     #  ndb1 `/etc/hosts':
     127.0.0.1       localhost
     127.0.0.2       ndb1.cluster ndb1


     #  ndb2 `/etc/hosts':
     127.0.0.1       localhost
     127.0.0.2       ndb2.cluster ndb2

In both instances, `ndb1' routes `ndb1.cluster' to a loopback IP
address, but gets a public IP address from DNS for `ndb2.cluster',
while `ndb2' routes `ndb2.cluster' to a loopback address and obtains a
public address for `ndb1.cluster'. The result is that each data node
connects to the management server, but cannot tell when any other data
nodes have connected, and so the data nodes appear to hang while
starting.

*Caution*:

You cannot mix `localhost' and other host names or IP addresses in
`config.ini'. For these reasons, the solution in such cases (other than
to use IP addresses for _all_ `config.ini' `HostName' entries) is to
remove the fully qualified host names from `/etc/hosts' and use these in
`config.ini' for all cluster hosts.

Host computer type

Each host computer in our installation scenario is an Intel-based
desktop PC running a supported operating system installed to disk in a
standard configuration, and running no unnecessary services.  The core
operating system with standard TCP/IP networking capabilities should be
sufficient. Also for the sake of simplicity, we also assume that the
file systems on all hosts are set up identically. In the event that
they are not, you should adapt these instructions accordingly.

Network hardware

Standard 100 Mbps or 1 gigabit Ethernet cards are installed on each
machine, along with the proper drivers for the cards, and that all four
hosts are connected through a standard-issue Ethernet networking
appliance such as a switch. (All machines should use network cards with
the same throughout. That is, all four machines in the cluster should
have 100 Mbps cards _or_ all four machines should have 1 Gbps cards.)
MySQL Cluster works in a 100 Mbps network; however, gigabit Ethernet
provides better performance.

*Important*:

MySQL Cluster is _not_ intended for use in a network for which
throughput is less than 100 Mbps or which experiences a high degree of
latency. For this reason (among others), attempting to run a MySQL
Cluster over a wide area network such as the Internet is not likely to
be successful, and is not supported in production.

Sample data

We use the `world' database which is available for download from the
MySQL Web site (see `http://dev.mysql.com/doc/index-other.html'). We
assume that each machine has sufficient memory for running the operating
system, required MySQL Cluster processes, and (on the data nodes)
storing the database.

For general information about installing MySQL, see *Note installing::.
For information about installation of MySQL Cluster on Linux and other
Unix-like operating systems, see *Note mysql-cluster-install-linux::.
For information about installation of MySQL Cluster on Windows
operating systems, see *Note mysql-cluster-install-windows::.

For general information about MySQL Cluster hardware, software, and
networking requirements, see *Note
mysql-cluster-overview-requirements::.


File: manual.info,  Node: mysql-cluster-install-linux,  Next: mysql-cluster-install-windows,  Prev: mysql-cluster-installation,  Up: mysql-cluster-installation

17.2.1 Installing MySQL Cluster on Linux
----------------------------------------

* Menu:

* mysql-cluster-install-linux-binary::  Installing a MySQL Cluster Binary Release on Linux
* mysql-cluster-install-linux-rpm::  Installing MySQL Cluster from RPM
* mysql-cluster-install-linux-source::  Building MySQL Cluster from Source on Linux

This section covers installation of MySQL Cluster on Linux and other
Unix-like operating systems. While the next few sections refer to a
Linux operating system, the instructions and procedures given there
should be easily adaptable to other supported Unix-like platforms.

Beginning with MySQL Cluster NDB 7.1.3, MySQL Cluster is also supported
for production use on Windows operating systems; for installation and
setup instructions specific to Windows, see *Note
mysql-cluster-install-windows::.

Each MySQL Cluster host computer must have the correct executable
programs installed. A host running an SQL node must have installed on
it a MySQL Server binary (*Note `mysqld': mysqld.).  Management nodes
require the management server daemon (*Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.); data nodes require the data node
daemon (*Note `ndbd': mysql-cluster-programs-ndbd.; in MySQL Cluster
NDB 7.0 and later, you can use *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. instead. It is not necessary to install
the MySQL Server binary on management node hosts and data node hosts.
It is recommended that you also install the management client (*Note
`ndb_mgm': mysql-cluster-programs-ndb-mgm.) on the management server
host.

Installation of MySQL Cluster on Linux can be done using precompiled
binaries from Oracle (downloaded as a .tar.gz archive), with RPM
packages (also available from Oracle), or from source code. All three
of these installation methods are described in the section that follow.

Regardless of the method used, it is still necessary following
installation of the MySQL Cluster binaries to create configuration
files for all cluster nodes, before you can start the cluster. See
*Note mysql-cluster-install-configuration::.


File: manual.info,  Node: mysql-cluster-install-linux-binary,  Next: mysql-cluster-install-linux-rpm,  Prev: mysql-cluster-install-linux,  Up: mysql-cluster-install-linux

17.2.1.1 Installing a MySQL Cluster Binary Release on Linux
...........................................................

This section covers the steps necessary to install the correct
executables for each type of Cluster node from precompiled binaries
supplied by Oracle.

For setting up a cluster using precompiled binaries, the first step in
the installation process for each cluster host is to download the
latest MySQL Cluster NDB 6.3, MySQL Cluster NDB 7.0, or MySQL Cluster
NDB 7.1 binary archive
(`mysql-cluster-gpl-6.3.55-linux-i686-glibc23.tar.gz',
`mysql-cluster-gpl-7.0.42-linux-i686-glibc23.tar.gz', or
`mysql-cluster-gpl-7.1.34-linux-i686-glibc23.tar.gz', respectively)
from the MySQL Cluster downloads area
(http://dev.mysql.com/downloads/cluster/). We assume that you have
placed this file in each machine's `/var/tmp' directory. (If you do
require a custom binary, see *Note installing-development-tree::.)

*Note*:

After completing the installation, do not yet start any of the
binaries. We show you how to do so following the configuration of the
nodes (see *Note mysql-cluster-install-configuration::).

SQL nodes

On each of the machines designated to host SQL nodes, perform the
following steps as the system `root' user:

  1. Check your `/etc/passwd' and `/etc/group' files (or use whatever
     tools are provided by your operating system for managing users and
     groups) to see whether there is already a `mysql' group and `mysql'
     user on the system. Some OS distributions create these as part of
     the operating system installation process. If they are not already
     present, create a new `mysql' user group, and then add a `mysql'
     user to this group:


          shell> groupadd mysql
          shell> useradd -g mysql mysql

     The syntax for `useradd' and `groupadd' may differ slightly on
     different versions of Unix, or they may have different names such
     as `adduser' and `addgroup'.

  2. Change location to the directory containing the downloaded file,
     unpack the archive, and create a symbolic link named `mysql' to
     the `mysql' directory. Note that the actual file and directory
     names vary according to the MySQL Cluster version number.


          shell> cd /var/tmp
          shell> tar -C /usr/local -xzvf mysql-cluster-gpl-7.1.34-linux-i686-glibc23.tar.gz
          shell> ln -s /usr/local/mysql-cluster-gpl-7.1.34-linux-i686-glibc23 /usr/local/mysql

  3. Change location to the `mysql' directory and run the supplied
     script for creating the system databases:


          shell> cd mysql
          shell> scripts/mysql_install_db --user=mysql

  4. Set the necessary permissions for the MySQL server and data
     directories:


          shell> chown -R root .
          shell> chown -R mysql data
          shell> chgrp -R mysql .

  5. Copy the MySQL startup script to the appropriate directory, make
     it executable, and set it to start when the operating system is
     booted up:


          shell> cp support-files/mysql.server /etc/rc.d/init.d/
          shell> chmod +x /etc/rc.d/init.d/mysql.server
          shell> chkconfig --add mysql.server

     (The startup scripts directory may vary depending on your
     operating system and version--for example, in some Linux
     distributions, it is `/etc/init.d'.)

     Here we use Red Hat's `chkconfig' for creating links to the
     startup scripts; use whatever means is appropriate for this
     purpose on your platform, such as `update-rc.d' on Debian.

Remember that the preceding steps must be repeated on each machine
where an SQL node is to reside.

Data nodes

Installation of the data nodes does not require the *Note `mysqld':
mysqld. binary. Only the MySQL Cluster data node executable *Note
`ndbd': mysql-cluster-programs-ndbd. (single-threaded) or *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. (multi-threaded) is required.
These binaries can also be found in the `.tar.gz' archive. Again, we
assume that you have placed this archive in `/var/tmp'.

As system `root' (that is, after using `sudo', `su root', or your
system's equivalent for temporarily assuming the system administrator
account's privileges), perform the following steps to install the data
node binaries on the data node hosts:

  1. Change location to the `/var/tmp' directory, and extract the *Note
     `ndbd': mysql-cluster-programs-ndbd. and *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. binaries from the archive into a
     suitable directory such as `/usr/local/bin':


          shell> cd /var/tmp
          shell> tar -zxvf mysql-5.1.73-ndb-7.1.34-linux-i686-glibc23.tar.gz
          shell> cd mysql-5.1.73-ndb-7.1.34-linux-i686-glibc23
          shell> cp bin/ndbd /usr/local/bin/ndbd
          shell> cp bin/ndbmtd /usr/local/bin/ndbmtd

     (You can safely delete the directory created by unpacking the
     downloaded archive, and the files it contains, from `/var/tmp' once
     *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. and *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.  have been copied to
     the executables directory.)

  2. Change location to the directory into which you copied the files,
     and then make both of them executable:


          shell> cd /usr/local/bin
          shell> chmod +x ndb*

The preceding steps should be repeated on each data node host.

Although only one of the data node executables is required to run a
MySQL Cluster data node, we have shown you how to install both *Note
`ndbd': mysql-cluster-programs-ndbd. and *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. in the preceding instructions. We
recommend that you do this when installing or upgrading MySQL Cluster,
even if you plan to use only one of them, since this will save time and
trouble in the event that you later decide to change from one to the
other.

*Note*:

The data directory on each machine hosting a data node is
`/usr/local/mysql/data'. This piece of information is essential when
configuring the management node.  (See *Note
mysql-cluster-install-configuration::.)

Management nodes

Installation of the management node does not require the *Note
`mysqld': mysqld. binary. Only the MySQL Cluster management server
(*Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.) is required; you
most likely want to install the management client (*Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm.) as well. Both of these binaries also
be found in the `.tar.gz' archive.  Again, we assume that you have
placed this archive in `/var/tmp'.

As system `root', perform the following steps to install *Note
`ndb_mgmd': mysql-cluster-programs-ndb-mgmd. and *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. on the management node host:

  1. Change location to the `/var/tmp' directory, and extract the *Note
     `ndb_mgm': mysql-cluster-programs-ndb-mgm. and *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. from the archive into a suitable
     directory such as `/usr/local/bin':


          shell> cd /var/tmp
          shell> tar -zxvf mysql-5.1.73-ndb-7.1.34-linux-i686-glibc23.tar.gz
          shell> cd mysql-5.1.73-ndb-7.1.34-linux-i686-glibc23
          shell> cp bin/ndb_mgm* /usr/local/bin

     (You can safely delete the directory created by unpacking the
     downloaded archive, and the files it contains, from `/var/tmp' once
     *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. and *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.  have been copied to
     the executables directory.)

  2. Change location to the directory into which you copied the files,
     and then make both of them executable:


          shell> cd /usr/local/bin
          shell> chmod +x ndb_mgm*

In *Note mysql-cluster-install-configuration::, we create configuration
files for all of the nodes in our example MySQL Cluster.


File: manual.info,  Node: mysql-cluster-install-linux-rpm,  Next: mysql-cluster-install-linux-source,  Prev: mysql-cluster-install-linux-binary,  Up: mysql-cluster-install-linux

17.2.1.2 Installing MySQL Cluster from RPM
..........................................

This section covers the steps necessary to install the correct
executables for each type of MySQL Cluster node using RPM packages
supplied by Oracle.

RPMs are available for both 32-bit and 64-bit Linux platforms.  For a
MySQL Cluster, three RPMs are required:

   * The *Server* RPM (for example,
     `MySQL-Cluster-gpl-server-6.3.55-0.sles10.i586.rpm',
     `MySQL-Cluster-gpl-server-7.0.42-0.sles10.i586.rpm', or
     `MySQL-Cluster-gpl-server-7.1.34-0.sles10.i586.rpm'), which
     supplies the core files needed to run a MySQL Server with *Note
     `NDBCLUSTER': mysql-cluster. storage engine support (that is, as a
     MySQL Cluster SQL node).

     If you do not have your own client application capable of
     administering a MySQL server, you should also obtain and install
     the *Client* RPM (for example,
     `MySQL-Cluster-gpl-client-6.3.55-0.sles10.i586.rpm',
     `MySQL-Cluster-gpl-client-7.0.42-0.sles10.i586.rpm', or
     `MySQL-Cluster-gpl-client-7.1.34-0.sles10.i586.rpm').

   * The *Cluster storage engine* RPM (for example,
     `MySQL-Cluster-gpl-storage-6.3.55-0.sles10.i586.rpm',
     `MySQL-Cluster-gpl-storage-7.0.42-0.sles10.i586.rpm', or
     `MySQL-Cluster-gpl-storage-7.1.34-0.sles10.i586.rpm'), which
     supplies the MySQL Cluster data node binary (*Note `ndbd':
     mysql-cluster-programs-ndbd.).

   * The *Cluster storage engine management RPM* (for example,
     `MySQL-Cluster-gpl-management-6.3.55-0.sles10.i586.rpm',
     `MySQL-Cluster-gpl-management-7.0.42-0.sles10.i586.rpm', or
     `MySQL-Cluster-gpl-management-7.1.34-0.sles10.i586.rpm') which
     provides the MySQL Cluster management server binary (*Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.).

In addition, you should also obtain the *NDB Cluster - Storage engine
basic tools* RPM (for example,
`MySQL-Cluster-gpl-tools-6.3.55-0.sles10.i586.rpm',
`MySQL-Cluster-gpl-tools-7.0.42-0.sles10.i586.rpm', or
`MySQL-Cluster-gpl-tools-7.1.34-0.sles10.i586.rpm'), which supplies
several useful applications for working with a MySQL Cluster. The most
important of these is the MySQL Cluster management client (*Note
`ndb_mgm': mysql-cluster-programs-ndb-mgm.). The *NDB Cluster - Storage
engine extra tools* RPM (for example,
`MySQL-Cluster-gpl-extra-6.3.55-0.sles10.i586.rpm',
`MySQL-Cluster-gpl-extra-7.0.42-0.sles10.i586.rpm', or
`MySQL-Cluster-gpl-extra-7.1.34-0.sles10.i586.rpm') contains some
additional testing and monitoring programs, but is not required to
install a MySQL Cluster. (For more information about these additional
programs, see *Note mysql-cluster-programs::.)

The MySQL Cluster version number in the RPM file names (shown here as
`6.3.55', `7.0.42', or `7.1.34') can vary according to the version
which you are actually using. _It is very important that all of the
Cluster RPMs to be installed have the same version number_. The `glibc'
version number (if present), and architecture designation (shown here
as `i586') should be appropriate to the machine on which the RPM is to
be installed.

Data nodes

On a computer that is to host a cluster data node it is necessary to
install only the *NDB Cluster - Storage engine* RPM. To do so, copy this
RPM to the data node host, and run the following command as the system
root user, replacing the name shown for the RPM as necessary to match
that of the RPM downloaded from the MySQL web site:


     shell> rpm -Uhv MySQL-Cluster-gpl-storage-7.1.34-0.sles10.i586.rpm

The previous command installs the MySQL Cluster data node binary (*Note
`ndbd': mysql-cluster-programs-ndbd.) in the `/usr/sbin' directory.

SQL nodes

On each machine to be used for hosting a cluster SQL node, install the
*Server* RPM by executing the following command as the system root user,
replacing the name shown for the RPM as necessary to match the name of
the RPM downloaded from the MySQL web site:


     shell> rpm -Uhv MySQL-Cluster-gpl-server-7.1.34-0.sles10.i586.rpm

This installs the MySQL server binary (*Note `mysqld': mysqld.) in the
`/usr/sbin' directory, as well as all needed MySQL Server support
files. It also installs the *Note `mysql.server': mysql-server. and
*Note `mysqld_safe': mysqld-safe. startup scripts in `/usr/share/mysql'
and `/usr/bin', respectively. The RPM installer should take care of
general configuration issues (such as creating the `mysql' user and
group, if needed) automatically.

*Note*:

To administer the SQL node (MySQL server), you should also install the
*Client* RPM, as shown here:


     shell> rpm -Uhv MySQL-Cluster-gpl-client-7.1.34-0.sles10.i586.rpm

This installs the *Note `mysql': mysql. client program.

Management nodes

To install the MySQL Cluster management server, it is necessary only to
use the *NDB Cluster - Storage engine management* RPM. Copy this RPM to
the computer intended to host the management node, and then install it
by running the following command as the system root user (replace the
name shown for the RPM as necessary to match that of the *Storage engine
management* RPM downloaded from the MySQL web site):


     shell> rpm -Uhv MySQL-Cluster-gpl-management-7.1.34-0.sles10.i586.rpm

This installs the management server binary (*Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.) to the `/usr/sbin' directory.

You should also install the *Note `NDB': mysql-cluster.  management
client, which is supplied by the *Storage engine basic tools* RPM.
Copy this RPM to the same computer as the management node, and then
install it by running the following command as the system root user
(again, replace the name shown for the RPM as necessary to match that
of the *Storage engine basic tools* RPM downloaded from the MySQL web
site):


     shell> rpm -Uhv MySQL-Cluster-gpl-tools-7.1.34-0.sles10.i586.rpm

The *Storage engine basic tools* RPM installs the MySQL Cluster
management client (*Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.) to
the `/usr/bin' directory.

*Note*:

You can also install the *Cluster storage engine extra tools* RPM, if
you wish, as shown here:


     shell> rpm -Uhv MySQL-Cluster-gpl-extra-7.1.34-0.sles10.i586.rpm

You may find the extra tools useful; however the *Cluster storage
engine extra tools* RPM is _not_ required to install a working MySQL
Cluster.

See *Note linux-installation-rpm::, for general information about
installing MySQL using RPMs supplied by Oracle.

After installing from RPM, you still need to configure the cluster as
discussed in *Note mysql-cluster-install-configuration::.


File: manual.info,  Node: mysql-cluster-install-linux-source,  Prev: mysql-cluster-install-linux-rpm,  Up: mysql-cluster-install-linux

17.2.1.3 Building MySQL Cluster from Source on Linux
....................................................

This section provides information about compiling MySQL Cluster on
Linux and other Unix-like platforms. Building MySQL Cluster from source
is similar to building the standard MySQL Server, although it differs
in a few key respects discussed here. For general information about
building MySQL from source, see *Note source-installation::. Beginning
with MySQL Cluster NDB 7.1.3, MySQL Cluster is also supported on Windows
platforms, and can be built on Windows from source. For information
about compiling MySQL Cluster on Windows platforms, see *Note
mysql-cluster-install-windows-source::.

Building MySQL Cluster requires using the MySQL Cluster sources.  These
are available from the MySQL Cluster downloads page at
`http://dev.mysql.com/downloads/cluster/'. The archived source file
should have a name similar to `mysql-cluster-gpl-6.3.55.tar.gz',
`mysql-cluster-gpl-7.0.42.tar.gz', or `mysql-cluster-gpl-7.1.34.tar.gz'.
You can also obtain MySQL development sources from launchpad.net.
Attempting to build MySQL Cluster from standard MySQL 5.1 sources is
not supported.

In addition to any other `configure' options you wish to use, be sure
to include `--with-plugins=ndbcluster', `--with-plugins=max', or , or
`--with-plugins=max-no-innodb'.  Either of these options causes the
binaries for the management nodes, data nodes, and other MySQL Cluster
programs to be built; it also causes *Note `mysqld': mysqld. to be
compiled with *Note `NDB': mysql-cluster. storage engine support.

After you have run `make && make install' (or your system's
equivalent), the result is similar to what is obtained by unpacking a
precompiled binary to the same location. However, the layout can
differ. These differences are covered in the next few paragraphs.

Prior to MySQL Cluster NDB 7.1.9, MySQL Cluster was not compatible with
the *Note `InnoDB': innodb-storage-engine. Plugin; in earlier MySQL
Cluster releases, only the version of *Note `InnoDB':
innodb-storage-engine. supplied with the MySQL Server could be used.
Beginning with MySQL Cluster NDB 7.1.9, you can build MySQL Cluster with
*Note `InnoDB': innodb-storage-engine. storage engine or plugin support
using the appropriate `--with-plugins' option for `configure'.

Management nodes

When building from source and running the default `make install', the
management server binary (*Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.) is placed in
`/usr/local/mysql/libexec', while the management client binary (*Note
`ndb_mgm': mysql-cluster-programs-ndb-mgm.) can be found in
`/usr/local/mysql/bin'. Only *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. is required to be present on a
management node host; however, it is also a good idea to have *Note
`ndb_mgm': mysql-cluster-programs-ndb-mgm. present on the same host
machine.  Neither of these executables requires a specific location on
the host machine's file system.

Data nodes

The only executable required on a data node host is *Note `ndbd':
mysql-cluster-programs-ndbd. (*Note `mysqld': mysqld, for example, does
not have to be present on the host machine). By default when doing a
source build, this file is placed in the directory
`/usr/local/mysql/libexec'. For installing on multiple data node hosts,
only *Note `ndbd': mysql-cluster-programs-ndbd. need be copied to the
other host machine or machines. (This assumes that all data node hosts
use the same architecture and operating system; otherwise you may need
to compile separately for each different platform.)  *Note `ndbd':
mysql-cluster-programs-ndbd. need not be in any particular location on
the host's file system, as long as the location is known.

When compiling MySQL Cluster NDB 7.0 or later from source, no special
options are required for building multi-threaded data node binaries. On
Unix platforms, configuring the build with any of the options
`--with-plugins=ndbcluster', `--with-plugins=max', or
`--with-plugins=max-no-innodb' causes *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. to be built automatically; `make
install' places the *Note `ndbmtd': mysql-cluster-programs-ndbmtd.
binary in the `libexec' directory along with *Note `mysqld': mysqld,
*Note `ndbd': mysql-cluster-programs-ndbd, and *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm.

SQL nodes

If you compile MySQL with clustering support, and perform the default
installation (using `make install' as the system `root' user), *Note
`mysqld': mysqld. is placed in `/usr/local/mysql/bin'. Follow the steps
given in *Note source-installation:: to make *Note `mysqld': mysqld.
ready for use. If you want to run multiple SQL nodes, you can use a
copy of the same *Note `mysqld': mysqld. executable and its associated
support files on several machines. The easiest way to do this is to
copy the entire `/usr/local/mysql' directory and all directories and
files contained within it to the other SQL node host or hosts, then
repeat the steps from *Note source-installation:: on each machine. If
you configure the build with a nondefault `--prefix', you need to adjust
the directory accordingly.

In *Note mysql-cluster-install-configuration::, we create configuration
files for all of the nodes in our example MySQL Cluster.


File: manual.info,  Node: mysql-cluster-install-windows,  Next: mysql-cluster-install-configuration,  Prev: mysql-cluster-install-linux,  Up: mysql-cluster-installation

17.2.2 Installing MySQL Cluster on Windows
------------------------------------------

* Menu:

* mysql-cluster-install-windows-binary::  Installing MySQL Cluster on Windows from a Binary Release
* mysql-cluster-install-windows-source::  Compiling and Installing MySQL Cluster from Source on Windows
* mysql-cluster-install-windows-initial-start::  Initial Startup of MySQL Cluster on Windows
* mysql-cluster-install-windows-service::  Installing MySQL Cluster Processes as Windows Services

Experimental support for MySQL Cluster on Microsoft Windows operating
systems was introduced in MySQL Cluster NDB 7.0.  Beginning with MySQL
Cluster NDB 7.1.3, production support is provided for MySQL Cluster on
Windows, and MySQL Cluster binaries for Windows can be obtained from
`http://dev.mysql.com/downloads/cluster/'. For information about
installing MySQL Cluster on Windows from a binary release provided by
Oracle, see *Note mysql-cluster-install-windows-binary::.

It is also possible to compile and install MySQL Cluster from source on
Windows using Microsoft Visual Studio. For more information, see *Note
mysql-cluster-install-windows-source::.


File: manual.info,  Node: mysql-cluster-install-windows-binary,  Next: mysql-cluster-install-windows-source,  Prev: mysql-cluster-install-windows,  Up: mysql-cluster-install-windows

17.2.2.1 Installing MySQL Cluster on Windows from a Binary Release
..................................................................

This section describes a basic installation of MySQL Cluster on Windows
using a binary `no-install' MySQL Cluster release provided by Oracle,
using the same 4-node setup outlined in the beginning of this section
(see *Note mysql-cluster-installation::), as shown in the following
table:

This table illustrates the same 4-node MySQL cluster configuration
outlined in the beginning of this section. The table lists the cluster
nodes and the IP address of each node.

Node                                 IP Address
Management (MGMD) node               192.168.0.10
MySQL server (SQL) node              192.168.0.20
Data (NDBD) node "A"                 192.168.0.30
Data (NDBD) node "B"                 192.168.0.40

As on other platforms, the MySQL Cluster host computer running an SQL
node must have installed on it a MySQL Server binary (*Note
`mysqld.exe': mysqld.). You should also have the MySQL client (*Note
`mysql.exe': mysql.) on this host. For management nodes and data nodes,
it is not necessary to install the MySQL Server binary; however, each
management node requires the management server daemon (*Note
`ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd.); each data node
requires the data node daemon (*Note `ndbd.exe':
mysql-cluster-programs-ndbd. or *Note `ndbmtd.exe':
mysql-cluster-programs-ndbmtd.).  For this example, we refer to *Note
`ndbd.exe': mysql-cluster-programs-ndbd. as the data node executable,
but you can install *Note `ndbmtd.exe': mysql-cluster-programs-ndbmtd,
the multi-threaded version of this program, instead, in exactly the
same way. You should also install the management client (*Note
`ndb_mgm.exe': mysql-cluster-programs-ndb-mgm.)  on the management
server host. This section covers the steps necessary to install the
correct Windows binaries for each type of MySQL Cluster node.

*Note `ndbmtd.exe': mysql-cluster-programs-ndbmtd. was not included in
MySQL Cluster NDB 7.1.3 binary releases for Windows, due to a problem
with *Note `make_win_bin_dist': make-win-bin-dist. This issue was
corrected in MySQL Cluster NDB 7.1.5.

*Note*:

As with other Windows programs, MySQL Cluster executables are named
with the `.exe' file extension.  However, it is not necessary to
include the `.exe' extension when invoking these programs from the
command line. Therefore, we often simply refer to these programs in
this documentation as *Note `mysqld': mysqld, *Note `mysql': mysql,
*Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd, and so on. You
should understand that, whether we refer (for example) to *Note
`mysqld': mysqld. or *Note `mysqld.exe': mysqld, either name means the
same thing (the MySQL Server program).

For setting up a MySQL Cluster using Oracles's `no-install' binaries,
the first step in the installation process is to download the latest
MySQL Cluster Windows binary archive from
`http://dev.mysql.com/downloads/cluster/'. This archive has a filename
of the form `mysql-cluster-gpl-noinstall-VER-winARCH.zip', where VER is
the `NDB' storage engine version (such as `7.1.3'), and ARCH is the
architecture (`32' for 32-bit binaries, and `64' for 64-bit binaries).
For example, the MySQL Cluster NDB 7.1.3 `no-install' archive for
32-bit Windows systems is named
`mysql-cluster-gpl-noinstall-7.1.3-win32.zip'.

You can run 32-bit MySQL Cluster binaries on both 32-bit and 64-bit
versions of Windows; however, 64-bit MySQL Cluster binaries can be used
only on 64-bit versions of Windows. If you are using a 32-bit version
of Windows on a computer that has a 64-bit CPU, then you must use the
32-bit MySQL Cluster binaries.

To minimize the number of files that need to be downloaded from the
Internet or copied between machines, we start with the computer where
you intend to run the SQL node.

SQL node

We assume that you have placed a copy of the `no-install' archive in
the directory `C:\Documents and Settings\USERNAME\My
Documents\Downloads' on the computer having the IP address
192.168.0.20, where USERNAME is the name of the current user. (You can
obtain this name using `ECHO %USERNAME%' on the command line.) To
install and run MySQL Cluster executables as Windows services, this user
should be a member of the `Administrators' group.

Extract all the files from the archive. The Extraction Wizard
integrated with Windows Explorer is adequate for this task. (If you use
a different archive program, be sure that it extracts all files and
directories from the archive, and that it preserves the archive's
directory structure.) When you are asked for a destination directory,
enter `C:\', which causes the Extraction Wizard to extract the archive
to the directory `C:\mysql-cluster-gpl-noinstall-VER-winARCH'.  Rename
this directory to `C:\mysql'.

It is possible to install the MySQL Cluster binaries to directories
other than `C:\mysql\bin'; however, if you do so, you must modify the
paths shown in this procedure accordingly. In particular, if the MySQL
Server (SQL node) binary is installed to a location other than
`C:\mysql' or `C:\Program Files\MySQL\MySQL Server 5.1', or if the SQL
node's data directory is in a location other than `C:\mysql\data' or
`C:\Program Files\MySQL\MySQL Server 5.1\data', extra configuration
options must be used on the command line or added to the `my.ini' or
`my.cnf' file when starting the SQL node. For more information about
configuring a MySQL Server to run in a nonstandard location, see *Note
windows-install-archive::.

For a MySQL Server with MySQL Cluster support to run as part of a MySQL
Cluster, it must be started with the options `--ndbcluster' and
`--ndb-connectstring'. While you can specify these options on the
command line, it is usually more convenient to place them in an option
file. To do this, create a new text file in Notepad or another text
editor. Enter the following configuration information into this file:


     [mysqld]
     # Options for mysqld process:
     ndbcluster                      # run NDB storage engine
     ndb-connectstring=192.168.0.10  # location of management server

You can add other options used by this MySQL Server if desired (see
*Note windows-create-option-file::), but the file must contain the
options shown, at a minimum. Save this file as `C:\mysql\my.ini'. This
completes the installation and setup for the SQL node.

Data nodes

A MySQL Cluster data node on a Windows host requires only a single
executable, one of either *Note `ndbd.exe': mysql-cluster-programs-ndbd.
or *Note `ndbmtd.exe': mysql-cluster-programs-ndbmtd. For this example,
we assume that you are using *Note `ndbd.exe':
mysql-cluster-programs-ndbd, but the same instructions apply when using
*Note `ndbmtd.exe': mysql-cluster-programs-ndbmtd.  On each computer
where you wish to run a data node (the computers having the IP
addresses 192.168.0.30 and 192.168.0.40), create the directories
`C:\mysql', `C:\mysql\bin', and `C:\mysql\cluster-data'; then, on the
computer where you downloaded and extracted the `no-install' archive,
locate `ndbd.exe' in the `C:\mysql\bin' directory. Copy this file to
the `C:\mysql\bin' directory on each of the two data node hosts.

To function as part of a MySQL Cluster, each data node must be given
the address or hostname of the management server. You can supply this
information on the command line using the `--ndb-connectstring' or `-c'
option when starting each data node process.  However, it is usually
preferable to put this information in an option file. To do this,
create a new text file in Notepad or another text editor and enter the
following text:


     [mysql_cluster]
     # Options for data node process:
     ndb-connectstring=192.168.0.10  # location of management server

Save this file as `C:\mysql\my.ini' on the data node host. Create
another text file containing the same information and save it on as
`C:mysql\my.ini' on the other data node host, or copy the my.ini file
from the first data node host to the second one, making sure to place
the copy in the second data node's `C:\mysql' directory. Both data node
hosts are now ready to be used in the MySQL Cluster, which leaves only
the management node to be installed and configured.

Management node

The only executable program required on a computer used for hosting a
MySQL Cluster management node is the management server program *Note
`ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd. However, in order to
administer the MySQL Cluster once it has been started, you should also
install the MySQL Cluster management client program *Note
`ndb_mgm.exe': mysql-cluster-programs-ndb-mgm. on the same machine as
the management server. Locate these two programs on the machine where
you downloaded and extracted the `no-install' archive; this should be
the directory `C:\mysql\bin' on the SQL node host. Create the directory
`C:\mysql\bin' on the computer having the IP address 192.168.0.10, then
copy both programs to this directory.

You should now create two configuration files for use by `ndb_mgmd.exe':

  1. A local configuration file to supply configuration data specific
     to the management node itself. Typically, this file needs only to
     supply the location of the MySQL Cluster global configuration file
     (see item 2).

     To create this file, start a new text file in Notepad or another
     text editor, and enter the following information:


          [mysql_cluster]
          # Options for management node process
          config-file=C:/mysql/bin/config.ini

     Save this file as the plaintext file `C:\mysql\bin\my.ini'.

  2. A global configuration file from which the management node can
     obtain configuration information governing the MySQL Cluster as a
     whole. At a minimum, this file must contain a section for each
     node in the MySQL Cluster, and the IP addresses or hostnames for
     the management node and all data nodes (`HostName' configuration
     parameter).  It is also advisable to include the following
     additional information:

        * The IP address or hostname of any SQL nodes

        * The data memory and index memory allocated to each data node
          (`DataMemory' and `IndexMemory' configuration parameters)

        * The number of replicas, using the `NoOfReplicas'
          configuration parameter (see *Note
          mysql-cluster-nodes-groups::)

        * The directory where each data node stores it data and log
          file, and the directory where the management node keeps its
          log files (in both cases, the `DataDir' configuration
          parameter)

     Create a new text file using a text editor such as Notepad, and
     input the following information:


          [ndbd default]
          # Options affecting ndbd processes on all data nodes:
          NoOfReplicas=2                      # Number of replicas
          DataDir=C:/mysql/bin/cluster-data   # Directory for each data node's data files
                                              # Forward slashes used in directory path,
                                              # rather than backslashes. This is correct;
                                              # see *Important* note in text
          DataMemory=80M    # Memory allocated to data storage
          IndexMemory=18M   # Memory allocated to index storage
                            # For DataMemory and IndexMemory, we have used the
                            # default values. Since the "world" database takes up
                            # only about 500KB, this should be more than enough for
                            # this example Cluster setup.

          [ndb_mgmd]
          # Management process options:
          HostName=192.168.0.10               # Hostname or IP address of management node
          DataDir=C:/mysql/bin/cluster-logs   # Directory for management node log files

          [ndbd]
          # Options for data node "A":
                                          # (one [ndbd] section per data node)
          HostName=192.168.0.30           # Hostname or IP address

          [ndbd]
          # Options for data node "B":
          HostName=192.168.0.40           # Hostname or IP address

          [mysqld]
          # SQL node options:
          HostName=192.168.0.20           # Hostname or IP address

     Save this file as the plaintext file `C:\mysql\bin\config.ini'.

*Important*:

A single backslash character (`\') cannot be used when specifying
directory paths in program options or configuration files used by MySQL
Cluster on Windows. Instead, you must either escape each backslash
character with a second backslash (`\\'), or replace the backslash with
a forward slash character (`/'). For example, the following line from
the `[ndb_mgmd]' section of a MySQL Cluster `config.ini' file does not
work:


     DataDir=C:\mysql\bin\cluster-logs

Instead, you may use either of the following:


     DataDir=C:\\mysql\\bin\\cluster-logs  # Escaped backslashes


     DataDir=C:/mysql/bin/cluster-logs     # Forward slashes

For reasons of brevity and legibility, we recommend that you use
forward slashes in directory paths used in MySQL Cluster program
options and configuration files on Windows.


File: manual.info,  Node: mysql-cluster-install-windows-source,  Next: mysql-cluster-install-windows-initial-start,  Prev: mysql-cluster-install-windows-binary,  Up: mysql-cluster-install-windows

17.2.2.2 Compiling and Installing MySQL Cluster from Source on Windows
......................................................................

Oracle provides precompiled MySQL Cluster binaries for Windows which
should be adequate for most users. However, if you wish, it is also
possible to compile MySQL Cluster for Windows from source code. The
procedure for doing this is almost identical to the procedure used to
compile the standard MySQL Server binaries for Windows, and uses the
same tools. However, there are two major differences:

   * To build MySQL Cluster, you must use the MySQL Cluster sources,
     which you can obtain from
     `http://dev.mysql.com/downloads/cluster/'.

     Attempting to build MySQL Cluster from the source code for the
     standard MySQL Server is likely not to be successful, and is not
     supported by Oracle.

   * You must configure the build using the
     `WITH_NDBCLUSTER_STORAGE_ENGINE' option in addition to any other
     build options you wish to use before creating the Visual Studio
     project files. Once you have run `configure.js' with the desired
     options, you can create the project files and build from them in
     the same manner as you do when compiling the standard MySQL
     Server. For more information, see *Note windows-source-build::.

Prior to MySQL Cluster NDB 7.1.9, MySQL Cluster was not compatible with
the *Note `InnoDB': innodb-storage-engine. Plugin; in earlier MySQL
Cluster releases, only the version of *Note `InnoDB':
innodb-storage-engine. supplied with the MySQL Server could be used.
Beginning with MySQL Cluster NDB 7.1.9, you can build MySQL Cluster with
*Note `InnoDB': innodb-storage-engine. storage engine or plugin support
on Windows using `WITH_INNOBASE_STORAGE_ENGINE' with `configure.js'-

Once the build process is complete, you can create a Zip archive
containing the compiled binaries by running *Note `make_win_bin_dist':
make-win-bin-dist. The MySQL Cluster binaries can be found in the `bin'
directory of the resulting archive, which is equivalent to the
`no-install' archive, and which can be installed and configured in the
same manner. For basic information about how to accomplish these tasks,
see *Note mysql-cluster-install-windows-binary::.

On Windows, beginning with MySQL Cluster NDB 7.0.11, using
`WITH_NDBCLUSTER_STORAGE_ENGINE' with `configure.js' causes *Note
`ndbmtd.exe': mysql-cluster-programs-ndbmtd. to be built automatically,
and to be found in the `bin' directory of the archive created by *Note
`make_win_bin_dist': make-win-bin-dist. (It was not possible to build
*Note `ndbmtd.exe': mysql-cluster-programs-ndbmtd. on Windows prior to
MySQL Cluster NDB 7.0.11.)


File: manual.info,  Node: mysql-cluster-install-windows-initial-start,  Next: mysql-cluster-install-windows-service,  Prev: mysql-cluster-install-windows-source,  Up: mysql-cluster-install-windows

17.2.2.3 Initial Startup of MySQL Cluster on Windows
....................................................

Once the MySQL Cluster executables and needed configuration files are
in place, performing an initial start of the cluster is simply a matter
of starting the MySQL Cluster executables for all nodes in the cluster.
Each cluster node process must be started separately, and on the host
computer where it resides.  The management node should be started
first, followed by the data nodes, and then finally by any SQL nodes.

  1. On the management node host, issue the following command from the
     command line to start the management node process:


          C:\mysql\bin> ndb_mgmd
          2010-06-23 07:53:34 [MgmtSrvr] INFO -- NDB Cluster Management Server. mysql-5.1.73-ndb-7.1.34
          2010-06-23 07:53:34 [MgmtSrvr] INFO -- Reading cluster configuration from 'config.ini'

     The management node process continues to print logging output to
     the console. This is normal, because the management node is not
     running as a Windows service. (If you have used MySQL Cluster on a
     Unix-like platform such as Linux, you may notice that the
     management node's default behavior in this regard on Windows is
     effectively the opposite of its behavior on Unix systems, where it
     runs by default as a Unix daemon process. This behavior is also
     true of MySQL Cluster data node processes running on Windows.) For
     this reason, do not close the window in which *Note
     `ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd. is running; doing
     so kills the management node process. (See *Note
     mysql-cluster-install-windows-service::, where we show how to
     install and run MySQL Cluster processes as Windows services.)

     The required `-f' option tells the management node where to find
     the global configuration file (`config.ini'). The long form of this
     option is `--config-file'.

     *Important*:

     A MySQL Cluster management node caches the configuration data that
     it reads from `config.ini'; once it has created a configuration
     cache, it ignores the `config.ini' file on subsequent starts
     unless forced to do otherwise. This means that, if the management
     node fails to start due to an error in this file, you must make
     the management node re-read `config.ini' after you have corrected
     any errors in it. You can do this by starting *Note
     `ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd. with the
     `--reload' or `--initial' option on the command line. Either of
     these options works to refresh the configuration cache.

     It is not necessary or advisable to use either of these options in
     the management node's `my.ini' file.

     For additional information about options which can be used with
     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd, see *Note
     mysql-cluster-programs-ndb-mgmd::, as well as *Note
     mysql-cluster-program-options-common::.

  2. On each of the data node hosts, run the command shown here to
     start the data node processes:


          C:\mysql\bin> ndbd
          2010-06-23 07:53:46 [ndbd] INFO -- Configuration fetched from 'localhost:1186', generation: 1

     In each case, the first line of output from the data node process
     should resemble what is shown in the preceding example, and is
     followed by additional lines of logging output. As with the
     management node process, this is normal, because the data node is
     not running as a Windows service.  For this reason, do not close
     the console window in which the data node process is running;
     doing so kills *Note `ndbd.exe': mysql-cluster-programs-ndbd. (For
     more information, see *Note
     mysql-cluster-install-windows-service::.)

  3. Do not start the SQL node yet; it cannot connect to the cluster
     until the data nodes have finished starting, which may take some
     time. Instead, in a new console window on the management node
     host, start the MySQL Cluster management client *Note
     `ndb_mgm.exe': mysql-cluster-programs-ndb-mgm, which should be in
     `C:\mysql\bin' on the management node host. (Do not try to re-use
     the console window where *Note `ndb_mgmd.exe':
     mysql-cluster-programs-ndb-mgmd. is running by typing `CTRL'+`C',
     as this kills the management node.) The resulting output should
     look like this:


          C:\mysql\bin> ndb_mgm
          -- NDB Cluster -- Management Client --
          ndb_mgm>

     When the prompt `ndb_mgm>' appears, this indicates that the
     management client is ready to receive MySQL Cluster management
     commands. You can observe the status of the data nodes as they
     start by entering `ALL STATUS' at the management client prompt.
     This command causes a running report of the data nodes's startup
     sequence, which should look something like this:


          ndb_mgm> ALL STATUS
          Connected to Management Server at: localhost:1186
          Node 2: starting (Last completed phase 3) (mysql-5.1.73-ndb-7.1.34)
          Node 3: starting (Last completed phase 3) (mysql-5.1.73-ndb-7.1.34)

          Node 2: starting (Last completed phase 4) (mysql-5.1.73-ndb-7.1.34)
          Node 3: starting (Last completed phase 4) (mysql-5.1.73-ndb-7.1.34)

          Node 2: Started (version 7.1.34)
          Node 3: Started (version 7.1.34)

          ndb_mgm>

     *Note*:

     Commands issued in the management client are not case-sensitive;
     we use uppercase as the canonical form of these commands, but you
     are not required to observe this convention when inputting them
     into the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. client.
     For more information, see *Note
     mysql-cluster-mgm-client-commands::.

     The output produced by `ALL STATUS' is likely to vary from what is
     shown here, according to the speed at which the data nodes are
     able to start, the release version number of the MySQL Cluster
     software you are using, and other factors. What is significant is
     that, when you see that both data nodes have started, you are
     ready to start the SQL node.

     You can leave *Note `ndb_mgm.exe': mysql-cluster-programs-ndb-mgm.
     running; it has no negative impact on the performance of the MySQL
     Cluster, and we use it in the next step to verify that the SQL node
     is connected to the cluster after you have started it.

  4. On the computer designated as the SQL node host, open a console
     window and navigate to the directory where you unpacked the MySQL
     Cluster binaries (if you are following our example, this is
     `C:\mysql\bin').

     Start the SQL node by invoking *Note `mysqld.exe': mysqld.  from
     the command line, as shown here:


          C:\mysql\bin> mysqld --console

     The `--console' option causes logging information to be written to
     the console, which can be helpful in the event of problems. (Once
     you are satisfied that the SQL node is running in a satisfactory
     manner, you can stop it and restart it out without the `--console'
     option, so that logging is performed normally.)

     In the console window where the management client (*Note
     `ndb_mgm.exe': mysql-cluster-programs-ndb-mgm.) is running on the
     management node host, enter the `SHOW' command, which should
     produce output similar to what is shown here:


          ndb_mgm> SHOW
          Connected to Management Server at: localhost:1186
          Cluster Configuration
          ---------------------
          [ndbd(NDB)]     2 node(s)
          id=2    @192.168.0.30  (Version: 5.1.73-ndb-7.1.34, Nodegroup: 0, *)
          id=3    @192.168.0.40  (Version: 5.1.73-ndb-7.1.34, Nodegroup: 0)

          [ndb_mgmd(MGM)] 1 node(s)
          id=1    @192.168.0.10  (Version: 5.1.73-ndb-7.1.34)

          [mysqld(API)]   1 node(s)
          id=4    @192.168.0.20  (Version: 5.1.73-ndb-7.1.34)

     You can also verify that the SQL node is connected to the MySQL
     Cluster in the *Note `mysql': mysql. client (*Note `mysql.exe':
     mysql.) using the `SHOW ENGINE NDB STATUS' statement.

You should now be ready to work with database objects and data using
MySQL Cluster's *Note `NDBCLUSTER': mysql-cluster. storage engine. See
*Note mysql-cluster-install-example-data::, for more information and
examples.

Beginning with MySQL Cluster NDB 7.0.16 and MySQL Cluster NDB 7.1.5,
you can install *Note `ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd,
*Note `ndbd.exe': mysql-cluster-programs-ndbd, and *Note `ndbmtd.exe':
mysql-cluster-programs-ndbmtd.  as Windows services. For information on
how to do this, see *Note mysql-cluster-install-windows-service::).


File: manual.info,  Node: mysql-cluster-install-windows-service,  Prev: mysql-cluster-install-windows-initial-start,  Up: mysql-cluster-install-windows

17.2.2.4 Installing MySQL Cluster Processes as Windows Services
...............................................................

Once you are satisfied that MySQL Cluster is running as desired, you
can--beginning with MySQL Cluster NDB 7.0.16 and MySQL Cluster NDB
7.1.5--install the management nodes and data nodes as Windows services,
so that these processes are started and stopped automatically whenever
Windows is started or stopped. This also makes it possible to control
these processes from the command line with the appropriate `NET START'
or `NET STOP' command, or using the Windows graphical `Services'
utility.

Installing programs as Windows services usually must be done using an
account that has Administrator rights on the system.

To install the management node as a service on Windows, invoke *Note
`ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd. from the command line
on the machine hosting the management node, using the `--install'
option, as shown here:


     C:\> C:\mysql\bin\ndb_mgmd.exe --install
     Installing service 'MySQL Cluster Management Server'
       as '"C:\mysql\bin\ndbd.exe" "--service=ndb_mgmd"'
     Service successfully installed.

*Important*:

When installing a MySQL Cluster program as a Windows service, you
should always specify the complete path; otherwise the service
installation may fail with the error `The system cannot find the file
specified'.

The `--install' option must be used first, ahead of any other options
that might be specified for *Note `ndb_mgmd.exe':
mysql-cluster-programs-ndb-mgmd. However, it is preferable to specify
such options in an options file instead. If your options file is not in
one of the default locations as shown in the output of *Note
`ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd.  `--help', you can
specify the location using the `--config-file' option.

Now you should be able to start and stop the management server like
this:


     C:\> NET START ndb_mgmd
     The MySQL Cluster Management Server service is starting.
     The MySQL Cluster Management Server service was started successfully.

     C:\> NET STOP ndb_mgmd
     The MySQL Cluster Management Server service is stopping..
     The MySQL Cluster Management Server service was stopped successfully.

You can also start or stop the management server as a Windows service
using the descriptive name, as shown here:


     C:\> NET START 'MySQL Cluster Management Server'
     The MySQL Cluster Management Server service is starting.
     The MySQL Cluster Management Server service was started successfully.

     C:\> NET STOP  'MySQL Cluster Management Server'
     The MySQL Cluster Management Server service is stopping..
     The MySQL Cluster Management Server service was stopped successfully.

However, it is usually simpler to specify a short service name or to
permit the default service name to be used when installing the service,
and then reference that name when starting or stopping the service. To
specify a service name other than `ndb_mgmd', append it to the
`--install' option, as shown in this example:


     C:\> C:\mysql\bin\ndb_mgmd.exe --install=mgmd1
     Installing service 'MySQL Cluster Management Server'
           as '"C:\mysql\bin\ndb_mgmd.exe" "--service=mgmd1"'
     Service successfully installed.

Now you should be able to start or stop the service using the name you
have specified, like this:


     C:\> NET START mgmd1
     The MySQL Cluster Management Server service is starting.
     The MySQL Cluster Management Server service was started successfully.

     C:\> NET STOP mgmd1
     The MySQL Cluster Management Server service is stopping..
     The MySQL Cluster Management Server service was stopped successfully.

To remove the management node service, invoke *Note `ndb_mgmd.exe':
mysql-cluster-programs-ndb-mgmd. with the `--remove' option, as shown
here:


     C:\> C:\mysql\bin\ndb_mgmd.exe --remove
     Removing service 'MySQL Cluster Management Server'
     Service successfully removed.

If you installed the service using a service name other than the
default, you can remove the service by passing this name as the value
of the `--remove' option, like this:


     C:\> C:\mysql\bin\ndb_mgmd.exe --remove=mgmd1
     Removing service 'mgmd1'
     Service successfully removed.

Installation of a MySQL Cluster data node process as a Windows service
can be done in a similar fashion, using the `--install' option for
*Note `ndbd.exe': mysql-cluster-programs-ndbd. (or *Note `ndbmtd.exe':
mysql-cluster-programs-ndbmtd.), as shown here:


     C:\> C:\mysql\bin\ndbd.exe --install
     Installing service 'MySQL Cluster Data Node Daemon' as '"C:\mysql\bin\ndbd.exe" "--service=ndbd"'
     Service successfully installed.

Now you can start or stop the data node using either the default
service name or the descriptive name with `net start' or `net stop', as
shown in the following example:


     C:\> NET START ndbd
     The MySQL Cluster Data Node Daemon service is starting.
     The MySQL Cluster Data Node Daemon service was started successfully.

     C:\> NET STOP ndbd
     The MySQL Cluster Data Node Daemon service is stopping..
     The MySQL Cluster Data Node Daemon service was stopped successfully.

     C:\> NET START 'MySQL Cluster Data Node Daemon'
     The MySQL Cluster Data Node Daemon service is starting.
     The MySQL Cluster Data Node Daemon service was started successfully.

     C:\> NET STOP 'MySQL Cluster Data Node Daemon'
     The MySQL Cluster Data Node Daemon service is stopping..
     The MySQL Cluster Data Node Daemon service was stopped successfully.

To remove the data node service, invoke *Note `ndbd.exe':
mysql-cluster-programs-ndbd. with the `--remove' option, as shown here:


     C:\> C:\mysql\bin\ndbd.exe --remove
     Removing service 'MySQL Cluster Data Node Daemon'
     Service successfully removed.

As with *Note `ndb_mgmd.exe': mysql-cluster-programs-ndb-mgmd. (and
*Note `mysqld.exe': mysqld.), when installing *Note `ndbd.exe':
mysql-cluster-programs-ndbd. as a Windows service, you can also specify
a name for the service as the value of `--install', and then use it when
starting or stopping the service, like this:


     C:\> C:\mysql\bin\ndbd.exe --install=dnode1
     Installing service 'dnode1' as '"C:\mysql\bin\ndbd.exe" "--service=dnode1"'
     Service successfully installed.

     C:\> NET START dnode1
     The MySQL Cluster Data Node Daemon service is starting.
     The MySQL Cluster Data Node Daemon service was started successfully.

     C:\> NET STOP dnode1
     The MySQL Cluster Data Node Daemon service is stopping..
     The MySQL Cluster Data Node Daemon service was stopped successfully.

If you specified a service name when installing the data node service,
you can use this name when removing it as well, by passing it as the
value of the `--remove' option, as shown here:


     C:\> C:\mysql\bin\ndbd.exe --remove=dnode1
     Removing service 'dnode1'
     Service successfully removed.

Installation of the SQL node as a Windows service, starting the
service, stopping the service, and removing the service are done in a
similar fashion, using *Note `mysqld': mysqld.  `--install', `NET
START', `NET STOP', and *Note `mysqld': mysqld.  `--remove'. For
additional information, see *Note windows-start-service::.


File: manual.info,  Node: mysql-cluster-install-configuration,  Next: mysql-cluster-install-first-start,  Prev: mysql-cluster-install-windows,  Up: mysql-cluster-installation

17.2.3 Initial Configuration of MySQL Cluster
---------------------------------------------

For our four-node, four-host MySQL Cluster, it is necessary to write
four configuration files, one per node host.

   * Each data node or SQL node requires a `my.cnf' file that provides
     two pieces of information: a _connection string_ that tells the
     node where to find the management node, and a line telling the
     MySQL server on this host (the machine hosting the data node) to
     enable the *Note `NDBCLUSTER': mysql-cluster. storage engine.

     For more information on connection strings, see *Note
     mysql-cluster-connection-strings::.

   * The management node needs a `config.ini' file telling it how many
     replicas to maintain, how much memory to allocate for data and
     indexes on each data node, where to find the data nodes, where to
     save data to disk on each data node, and where to find any SQL
     nodes.

Configuring the data nodes and SQL nodes

The `my.cnf' file needed for the data nodes is fairly simple. The
configuration file should be located in the `/etc' directory and can be
edited using any text editor. (Create the file if it does not exist.)
For example:


     shell> vi /etc/my.cnf

*Note*:

We show `vi' being used here to create the file, but any text editor
should work just as well.

For each data node and SQL node in our example setup, `my.cnf' should
look like this:


     [mysqld]
     # Options for mysqld process:
     ndbcluster                      # run NDB storage engine

     [mysql_cluster]
     # Options for MySQL Cluster processes:
     ndb-connectstring=192.168.0.10  # location of management server

After entering the preceding information, save this file and exit the
text editor. Do this for the machines hosting data node `A', data node
`B', and the SQL node.

*Important*:

Once you have started a *Note `mysqld': mysqld. process with the
`ndbcluster' and `ndb-connectstring' parameters in the `[mysqld]' and
`[mysql_cluster]' sections of the `my.cnf' file as shown previously,
you cannot execute any *Note `CREATE TABLE': create-table. or *Note
`ALTER TABLE': alter-table. statements without having actually started
the cluster. Otherwise, these statements will fail with an error. This
is by design.

Configuring the management node

The first step in configuring the management node is to create the
directory in which the configuration file can be found and then to
create the file itself. For example (running as `root'):


     shell> mkdir /var/lib/mysql-cluster
     shell> cd /var/lib/mysql-cluster
     shell> vi config.ini

For our representative setup, the `config.ini' file should read as
follows:


     [ndbd default]
     # Options affecting ndbd processes on all data nodes:
     NoOfReplicas=2    # Number of replicas
     DataMemory=80M    # How much memory to allocate for data storage
     IndexMemory=18M   # How much memory to allocate for index storage
                       # For DataMemory and IndexMemory, we have used the
                       # default values. Since the "world" database takes up
                       # only about 500KB, this should be more than enough for
                       # this example Cluster setup.

     [tcp default]
     # TCP/IP options:
     portnumber=2202   # This the default; however, you can use any
                       # port that is free for all the hosts in the cluster
                       # Note: It is recommended that you do not specify the port
                       # number at all and simply allow the default value to be used
                       # instead

     [ndb_mgmd]
     # Management process options:
     hostname=192.168.0.10           # Hostname or IP address of MGM node
     datadir=/var/lib/mysql-cluster  # Directory for MGM node log files

     [ndbd]
     # Options for data node "A":
                                     # (one [ndbd] section per data node)
     hostname=192.168.0.30           # Hostname or IP address
     datadir=/usr/local/mysql/data   # Directory for this data node's data files

     [ndbd]
     # Options for data node "B":
     hostname=192.168.0.40           # Hostname or IP address
     datadir=/usr/local/mysql/data   # Directory for this data node's data files

     [mysqld]
     # SQL node options:
     hostname=192.168.0.20           # Hostname or IP address
                                     # (additional mysqld connections can be
                                     # specified for this node for various
                                     # purposes such as running ndb_restore)

*Note*:

The `world' database can be downloaded from
`http://dev.mysql.com/doc/', where it can be found listed under
`Examples'.

After all the configuration files have been created and these minimal
options have been specified, you are ready to proceed with starting the
cluster and verifying that all processes are running.  We discuss how
this is done in *Note mysql-cluster-install-first-start::.

For more detailed information about the available MySQL Cluster
configuration parameters and their uses, see *Note
mysql-cluster-config-file::, and *Note mysql-cluster-configuration::.
For configuration of MySQL Cluster as relates to making backups, see
*Note mysql-cluster-backup-configuration::.

*Note*:

The default port for Cluster management nodes is 1186; the default port
for data nodes is 2202. However, the cluster can automatically allocate
ports for data nodes from those that are already free.


File: manual.info,  Node: mysql-cluster-install-first-start,  Next: mysql-cluster-install-example-data,  Prev: mysql-cluster-install-configuration,  Up: mysql-cluster-installation

17.2.4 Initial Startup of MySQL Cluster
---------------------------------------

Starting the cluster is not very difficult after it has been
configured. Each cluster node process must be started separately, and
on the host where it resides. The management node should be started
first, followed by the data nodes, and then finally by any SQL nodes:

  1. On the management host, issue the following command from the
     system shell to start the management node process:


          shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini

     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. must be told
     where to find its configuration file, using the `-f' or
     `--config-file' option. (See *Note
     mysql-cluster-programs-ndb-mgmd::, for details.)

     For additional options which can be used with *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd, see *Note
     mysql-cluster-program-options-common::.

  2. On each of the data node hosts, run this command to start the
     *Note `ndbd': mysql-cluster-programs-ndbd. process:


          shell> ndbd

  3. If you used RPM files to install MySQL on the cluster host where
     the SQL node is to reside, you can (and should) use the supplied
     startup script to start the MySQL server process on the SQL node.

If all has gone well, and the cluster has been set up correctly, the
cluster should now be operational. You can test this by invoking the
*Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. management node client.
The output should look like that shown here, although you might see
some slight differences in the output depending upon the exact version
of MySQL that you are using:


     shell> ndb_mgm
     -- NDB Cluster -- Management Client --
     ndb_mgm> SHOW
     Connected to Management Server at: localhost:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=2    @192.168.0.30  (Version: 5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=3    @192.168.0.40  (Version: 5.1.73-ndb-7.1.34, Nodegroup: 0)

     [ndb_mgmd(MGM)] 1 node(s)
     id=1    @192.168.0.10  (Version: 5.1.73-ndb-7.1.34)

     [mysqld(API)]   1 node(s)
     id=4    @192.168.0.20  (Version: 5.1.73-ndb-7.1.34)

The SQL node is referenced here as `[mysqld(API)]', which reflects the
fact that the *Note `mysqld': mysqld. process is acting as a MySQL
Cluster API node.

*Note*:

The IP address shown for a given MySQL Cluster SQL or other API node in
the output of `SHOW' is the address used by the SQL or API node to
connect to the cluster data nodes, and not to any management node.

You should now be ready to work with databases, tables, and data in
MySQL Cluster. See *Note mysql-cluster-install-example-data::, for a
brief discussion.


File: manual.info,  Node: mysql-cluster-install-example-data,  Next: mysql-cluster-install-shutdown-restart,  Prev: mysql-cluster-install-first-start,  Up: mysql-cluster-installation

17.2.5 MySQL Cluster Example with Tables and Data
-------------------------------------------------

*Note*:

The information in this section applies to MySQL Cluster running on
both Unix and Windows platforms.

Working with database tables and data in MySQL Cluster is not much
different from doing so in standard MySQL. There are two key points to
keep in mind:

   * For a table to be replicated in the cluster, it must use the *Note
     `NDBCLUSTER': mysql-cluster. storage engine. To specify this, use
     the `ENGINE=NDBCLUSTER' or `ENGINE=NDB' option when creating the
     table:


          CREATE TABLE TBL_NAME (COL_NAME COLUMN_DEFINITIONS) ENGINE=NDBCLUSTER;

     Alternatively, for an existing table that uses a different storage
     engine, use *Note `ALTER TABLE': alter-table.  to change the table
     to use *Note `NDBCLUSTER': mysql-cluster.:


          ALTER TABLE TBL_NAME ENGINE=NDBCLUSTER;

   * Every *Note `NDBCLUSTER': mysql-cluster. table has a primary key.
     If no primary key is defined by the user when a table is created,
     the *Note `NDBCLUSTER': mysql-cluster.  storage engine
     automatically generates a hidden one. Such a key takes up space
     just as does any other table index. (It is not uncommon to
     encounter problems due to insufficient memory for accommodating
     these automatically created indexes.)

If you are importing tables from an existing database using the output
of *Note `mysqldump': mysqldump, you can open the SQL script in a text
editor and add the `ENGINE' option to any table creation statements, or
replace any existing `ENGINE' options. Suppose that you have the
`world' sample database on another MySQL server that does not support
MySQL Cluster, and you want to export the `City' table:


     shell> mysqldump --add-drop-table world City > city_table.sql

The resulting `city_table.sql' file will contain this table creation
statement (and the *Note `INSERT': insert. statements necessary to
import the table data):


     DROP TABLE IF EXISTS `City`;
     CREATE TABLE `City` (
       `ID` int(11) NOT NULL auto_increment,
       `Name` char(35) NOT NULL default '',
       `CountryCode` char(3) NOT NULL default '',
       `District` char(20) NOT NULL default '',
       `Population` int(11) NOT NULL default '0',
       PRIMARY KEY  (`ID`)
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1;

     INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);
     INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);
     INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);
     (REMAINING INSERT STATEMENTS OMITTED)

You need to make sure that MySQL uses the *Note `NDBCLUSTER':
mysql-cluster. storage engine for this table. There are two ways that
this can be accomplished. One of these is to modify the table definition
_before_ importing it into the Cluster database. Using the `City' table
as an example, modify the `ENGINE' option of the definition as follows:


     DROP TABLE IF EXISTS `City`;
     CREATE TABLE `City` (
       `ID` int(11) NOT NULL auto_increment,
       `Name` char(35) NOT NULL default '',
       `CountryCode` char(3) NOT NULL default '',
       `District` char(20) NOT NULL default '',
       `Population` int(11) NOT NULL default '0',
       PRIMARY KEY  (`ID`)
     ) *ENGINE=NDBCLUSTER* DEFAULT CHARSET=latin1;

     INSERT INTO `City` VALUES (1,'Kabul','AFG','Kabol',1780000);
     INSERT INTO `City` VALUES (2,'Qandahar','AFG','Qandahar',237500);
     INSERT INTO `City` VALUES (3,'Herat','AFG','Herat',186800);
     (REMAINING INSERT STATEMENTS OMITTED)

This must be done for the definition of each table that is to be part
of the clustered database. The easiest way to accomplish this is to do
a search-and-replace on the file that contains the definitions and
replace all instances of `TYPE=ENGINE_NAME' or `ENGINE=ENGINE_NAME'
with `ENGINE=NDBCLUSTER'. If you do not want to modify the file, you
can use the unmodified file to create the tables, and then use *Note
`ALTER TABLE': alter-table. to change their storage engine. The
particulars are given later in this section.

Assuming that you have already created a database named `world' on the
SQL node of the cluster, you can then use the *Note `mysql': mysql.
command-line client to read `city_table.sql', and create and populate
the corresponding table in the usual manner:


     shell> mysql world < city_table.sql

It is very important to keep in mind that the preceding command must be
executed on the host where the SQL node is running (in this case, on
the machine with the IP address `192.168.0.20').

To create a copy of the entire `world' database on the SQL node, use
*Note `mysqldump': mysqldump. on the noncluster server to export the
database to a file named `world.sql'; for example, in the `/tmp'
directory. Then modify the table definitions as just described and
import the file into the SQL node of the cluster like this:


     shell> mysql world < /tmp/world.sql

If you save the file to a different location, adjust the preceding
instructions accordingly.

Running *Note `SELECT': select. queries on the SQL node is no different
from running them on any other instance of a MySQL server. To run
queries from the command line, you first need to log in to the MySQL
Monitor in the usual way (specify the `root' password at the `Enter
password:' prompt):


     shell> mysql -u root -p
     Enter password:
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 1 to server version: 5.1.73-ndb-7.1.34

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql>

We simply use the MySQL server's `root' account and assume that you
have followed the standard security precautions for installing a MySQL
server, including setting a strong `root' password. For more
information, see *Note default-privileges::.

It is worth taking into account that Cluster nodes do _not_ make use of
the MySQL privilege system when accessing one another. Setting or
changing MySQL user accounts (including the `root' account) effects
only applications that access the SQL node, not interaction between
nodes. See *Note mysql-cluster-security-mysql-privileges::, for more
information.

If you did not modify the `ENGINE' clauses in the table definitions
prior to importing the SQL script, you should run the following
statements at this point:


     mysql> USE world;
     mysql> ALTER TABLE City ENGINE=NDBCLUSTER;
     mysql> ALTER TABLE Country ENGINE=NDBCLUSTER;
     mysql> ALTER TABLE CountryLanguage ENGINE=NDBCLUSTER;

Selecting a database and running a `SELECT' query against a table in
that database is also accomplished in the usual manner, as is exiting
the MySQL Monitor:


     mysql> USE world;
     mysql> SELECT Name, Population FROM City ORDER BY Population DESC LIMIT 5;
     +-----------+------------+
     | Name      | Population |
     +-----------+------------+
     | Bombay    |   10500000 |
     | Seoul     |    9981619 |
     | Sa~o Paulo |    9968485 |
     | Shanghai  |    9696300 |
     | Jakarta   |    9604900 |
     +-----------+------------+
     5 rows in set (0.34 sec)

     mysql> \q
     Bye

     shell>

Applications that use MySQL can employ standard APIs to access *Note
`NDB': mysql-cluster. tables. It is important to remember that your
application must access the SQL node, and not the management or data
nodes. This brief example shows how we might execute the *Note
`SELECT': select. statement just shown by using the PHP 5.X `mysqli'
extension running on a Web server elsewhere on the network:


     <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
       "http://www.w3.org/TR/html4/loose.dtd">
     <html>
     <head>
       <meta http-equiv="Content-Type"
                content="text/html; charset=iso-8859-1">
       <title>SIMPLE mysqli SELECT</title>
     </head>
     <body>
     <?php
       # connect to SQL node:
       $link = new mysqli('192.168.0.20', 'root', 'ROOT_PASSWORD', 'world');
       # parameters for mysqli constructor are:
       #   host, user, password, database

       if( mysqli_connect_errno() )
         die("Connect failed: " . mysqli_connect_error());

       $query = "SELECT Name, Population
                 FROM City
                 ORDER BY Population DESC
                 LIMIT 5";

       # if no errors...
       if( $result = $link->query($query) )
       {
     ?>
     <table border="1" width="40%" cellpadding="4" cellspacing ="1">
       <tbody>
       <tr>
         <th width="10%">City</th>
         <th>Population</th>
       </tr>
     <?
         # then display the results...
         while($row = $result->fetch_object())
           printf("<tr>\n  <td align=\"center\">%s</td><td>%d</td>\n</tr>\n",
                   $row->Name, $row->Population);
     ?>
       </tbody
     </table>
     <?
       # ...and verify the number of rows that were retrieved
         printf("<p>Affected rows: %d</p>\n", $link->affected_rows);
       }
       else
         # otherwise, tell us what went wrong
         echo mysqli_error();

       # free the result set and the mysqli connection object
       $result->close();
       $link->close();
     ?>
     </body>
     </html>

We assume that the process running on the Web server can reach the IP
address of the SQL node.

In a similar fashion, you can use the MySQL C API, Perl-DBI,
Python-mysql, or MySQL Connectors to perform the tasks of data
definition and manipulation just as you would normally with MySQL.


File: manual.info,  Node: mysql-cluster-install-shutdown-restart,  Next: mysql-cluster-upgrade-downgrade,  Prev: mysql-cluster-install-example-data,  Up: mysql-cluster-installation

17.2.6 Safe Shutdown and Restart of MySQL Cluster
-------------------------------------------------

To shut down the cluster, enter the following command in a shell on the
machine hosting the management node:


     shell> ndb_mgm -e shutdown

The `-e' option here is used to pass a command to the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. client from the shell. (See *Note
mysql-cluster-program-options-common::, for more information about this
option.) The command causes the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm, *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd, and any *Note `ndbd':
mysql-cluster-programs-ndbd. or *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. processes to terminate gracefully. Any
SQL nodes can be terminated using *Note `mysqladmin shutdown':
mysqladmin. and other means. On Windows platforms, assuming that you
have installed the SQL node as a Windows service, you can use `NET STOP
MYSQL'.

To restart the cluster on Unix platforms, run these commands:

   * On the management host (`192.168.0.10' in our example setup):


          shell> ndb_mgmd -f /var/lib/mysql-cluster/config.ini

   * On each of the data node hosts (`192.168.0.30' and `192.168.0.40'):


          shell> ndbd

   * Use the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. client to
     verify that both data nodes have started successfully.

   * On the SQL host (`192.168.0.20'):


          shell> mysqld_safe &

On Windows platforms, assuming that you have installed all MySQL
Cluster processes as Windows services using the default service names
(see *Note mysql-cluster-install-windows-service::), you can restart
the cluster as follows:

   * On the management host (`192.168.0.10' in our example setup),
     execute the following command:


          C:\> NET START ndb_mgmd

   * On each of the data node hosts (`192.168.0.30' and
     `192.168.0.40'), execute the following command:


          C:\> NET START ndbd

   * On the management node host, use the *Note `ndb_mgm':
     mysql-cluster-programs-ndb-mgm. client to verify that the
     management node and both data nodes have started successfully (see
     *Note mysql-cluster-install-windows-initial-start::).

   * On the SQL node host (`192.168.0.20'), execute the following
     command:


          C:\> NET START mysql

In a production setting, it is usually not desirable to shut down the
cluster completely. In many cases, even when making configuration
changes, or performing upgrades to the cluster hardware or software (or
both), which require shutting down individual host machines, it is
possible to do so without shutting down the cluster as a whole by
performing a _rolling restart_ of the cluster. For more information
about doing this, see *Note mysql-cluster-rolling-restart::.


File: manual.info,  Node: mysql-cluster-upgrade-downgrade,  Prev: mysql-cluster-install-shutdown-restart,  Up: mysql-cluster-installation

17.2.7 Upgrading and Downgrading MySQL Cluster
----------------------------------------------

* Menu:

* mysql-cluster-upgrade-downgrade-compatibility-7.x::  Upgrade and downgrade compatibility: MySQL Cluster NDB 7.x
* mysql-cluster-upgrade-downgrade-compatibility-6.x::  Upgrade and Downgrade Compatibility: MySQL Cluster NDB 6.x
* mysql-cluster-upgrade-downgrade-compatibility-5.1::  Upgrade and downgrade compatibility: MySQL 5.1

This section provides information about MySQL Cluster software and
table file compatibility between MySQL 5.1.23 and earlier, MySQL
Cluster NDB 6.x, and MySQL Cluster NDB 7.x releases with regard to
performing upgrades and downgrades as well as compatibility matrices
and notes. You are expected already to be familiar with installing and
configuring a MySQL Cluster prior to attempting an upgrade or
downgrade. See *Note mysql-cluster-configuration::.

For information regarding the rolling restart procedure used to perform
an online upgrade, see *Note mysql-cluster-rolling-restart::.

*Important*:

Only compatibility between MySQL versions with regard to *Note
`NDBCLUSTER': mysql-cluster. is taken into account in this section, and
there are likely other issues to be considered. _As with any other
MySQL software upgrade or downgrade, you are strongly encouraged to
review the relevant portions of the MySQL Manual for the MySQL versions
from which and to which you intend to migrate, before attempting an
upgrade or downgrade of the MySQL Cluster software_. See *Note
upgrading::.

For information about upgrades and downgrades to, from, and between
different releases of MySQL Cluster NDB 7.0 and MySQL Cluster NDB 7.1,
see *Note mysql-cluster-upgrade-downgrade-compatibility-7.x::.

For information about upgrades and downgrades to, from, and between
different releases of MySQL Cluster NDB 6.1, MySQL Cluster NDB 6.2, and
MySQL Cluster NDB 6.3, see *Note
mysql-cluster-upgrade-downgrade-compatibility-6.x::.

For information about upgrades and downgrades to, from, and between
different releases of MySQL Cluster NDB 7.2, see Upgrading and
Downgrading MySQL Cluster NDB 7.2
(http://dev.mysql.com/doc/refman/5.5/en/mysql-cluster-upgrade-downgrade.html).

For information about upgrades and downgrades to, from, and between
different editions of MySQL Cluster as found in standard MySQL 5.1.23
and earlier releases, see *Note
mysql-cluster-upgrade-downgrade-compatibility-5.1::.

*Important*:

Only compatibility between MySQL versions with regard to *Note
`NDBCLUSTER': mysql-cluster. is taken into account in this section, and
there are likely other issues to be considered. _As with any other
MySQL software upgrade or downgrade, you are strongly encouraged to
review the relevant portions of the MySQL Manual for the MySQL versions
from which and to which you intend to migrate, before attempting an
upgrade or downgrade of the MySQL Cluster software_. See *Note
upgrading::.


File: manual.info,  Node: mysql-cluster-upgrade-downgrade-compatibility-7.x,  Next: mysql-cluster-upgrade-downgrade-compatibility-6.x,  Prev: mysql-cluster-upgrade-downgrade,  Up: mysql-cluster-upgrade-downgrade

17.2.7.1 Upgrade and downgrade compatibility: MySQL Cluster NDB 7.x
...................................................................

The table shown here provides information on MySQL Cluster upgrade and
downgrade compatibility among different releases of MySQL Cluster NDB
7.0 and 7.1. Additional notes about upgrades and downgrades to, from,
or within the MySQL Cluster NDB 7.x release series can be found
immediately following the table.

MySQL Cluster upgrade/downgrade compatibility, MySQL Cluster NDB 7.x

*Notes: MySQL Cluster NDB 7.x*

Versions supported

Online upgrades from any MySQL Cluster NDB 7.0 release up to and
including MySQL Cluster NDB 7.0.4 (as well as all early releases
numbered NDB 6.4.x) to MySQL Cluster NDB 7.0.5 or later are not
possible. Upgrades to MySQL Cluster NDB 7.0.6 or later from MySQL
Cluster NDB 6.3.8 or a later MySQL Cluster NDB 6.3 release, or from
MySQL Cluster NDB 7.0.5 or later, are supported. (Bug #44294)

Upgrading ndbd to ndbmtd

When upgrading online from a MySQL Cluster NDB 6.3 release to a MySQL
Cluster NDB 7.0 (or later) release, you should not try to upgrade the
data nodes from *Note `ndbd': mysql-cluster-programs-ndbd. to *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. at the same time. Instead,
perform the upgrade using the new *Note `ndbd':
mysql-cluster-programs-ndbd. executable (from the MySQL Cluster NDB 7.0
or later distribution to which you are upgrading) to replace the one in
use on the data nodes. Once the version upgrade is complete, you can
perform a second (online) upgrade to replace the data node executables
with *Note `ndbmtd': mysql-cluster-programs-ndbmtd. from the newer
distribution.  Changing the data node binary type should not be an
issue when upgrading from MySQL Cluster NDB 7.0 or later version.

Changes in default values

In MySQL Cluster NDB 7.0.4, the default values for a number of MySQL
Cluster configuration parameters relating to memory usage and buffering
changed (see
`http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-5-1-32-ndb-7-0-4.html',
for a list of the parameters whose defaults changed). For this reason,
you may encounter issues if you try to use a configuration that does
not explicitly define each of these buffers (because it was developed
for a previous version of MySQL Cluster), `SendBufferMemory' and
`ReceiveBufferMemory' in particular.

Other known issues include the following:

   * Prior to MySQL Cluster NDB 7.0.7, DML statements failed if
     executed while performing an online upgrade from a MySQL Cluster
     NDB 6.3 release. (Bug #45917)

   * Following an upgrade from any MySQL Cluster NDB 6.3.x release to
     MySQL Cluster NDB 7.0.6, DDL and backup operations failed. This
     issue was resolved in MySQL Cluster NDB 7.0.7. (Bug #46494, Bug
     #46563)

   * In some cases, there could be problems with online upgrades from
     MySQL Cluster NDB 6.3 releases to MySQL Cluster NDB 7.0 releases
     due to a previous change in the signalling format used between
     nodes. This issue was corrected in MySQL Cluster NDB 7.0.9.

   * Once an *Note `NDB': mysql-cluster. table had an *Note `ALTER
     ONLINE TABLE': alter-table. operation performed on it using a MySQL
     Cluster NDB 6.3.x release, it could not be upgraded online to
     MySQL Cluster NDB 7.0. This issue was resolved in MySQL Cluster
     NDB 7.0.8. (See Bug #47542.)

   * Following an upgrade from MySQL Cluster NDB 6.3 to MySQL Cluster
     NDB 7.0, if there were any tables having unique indexes prior to
     the upgrade, attempts to create unique indexes failed. This could
     also occur when performing offline *Note `ALTER TABLE':
     alter-table.  operations on tables having indexes that were not
     dropped as a result of the *Note `ALTER TABLE': alter-table.  This
     issue was due to a change in the way that *Note `NDB':
     mysql-cluster. tracked unique indexes internally, and was resolved
     in MySQL Cluster NDB 7.0.9.  (Bug #48416)

     For upgrades to MySQL Cluster NDB 7.0 releases prior to version
     7.0.9, a workaround is available: Following the upgrade, execute a
     _second_ rolling restart of the cluster before performing any
     *Note `ALTER TABLE': alter-table. operations involving indexes.

   * Due to an issue discovered after the release of MySQL Cluster NDB
     7.0.10 (Bug #50433), it is not possible to perform an online
     upgrade from MySQL Cluster NDB 7.0.9b and earlier MySQL Cluster
     NDB 7.0 releases to MySQL Cluster NDB 7.0.10. Instead, you should
     upgrade your MySQL Cluster NDB 7.0 installation directly to MySQL
     Cluster NDB 7.0.11 or later.

     This issue did not appear to affect MySQL Cluster NDB 6.3, and it
     should be possible to upgrade online from MySQL Cluster NDB 6.3 to
     MySQL Cluster NDB 7.0.10 without any problems other than those
     noted previously.

   * It was not possible to perform an online upgrade from a MySQL
     Cluster NDB 6.3 or 7.0 release to MySQL Cluster NDB 7.1.0 or
     7.1.1. This issue was fixed in MySQL Cluster NDB 7.1.2 (see Bug
     #51429).

   * Following an upgrade to MySQL Cluster NDB 7.0.15 or later (MySQL
     Cluster NDB 7.0), or to MySQL Cluster NDB 7.1.4 or later (MySQL
     Cluster NDB 7.1), a table created in a previous version of MySQL
     Cluster does _not_ automatically support *Note `NDB':
     mysql-cluster.-native default values. Such a table continues to
     use default values supplied by the MySQL server until it is
     upgraded by performing an offline *Note `ALTER TABLE':
     alter-table. on it.

     When upgrading to a MySQL Cluster release that supports native
     default values from a MySQL Cluster release that does not, you
     should not attempt to create any new tables until all data nodes
     are using the new *Note `ndbd': mysql-cluster-programs-ndbd. or
     *Note `ndbmtd': mysql-cluster-programs-ndbmtd. binaries. This is
     because the older binaries do not provide support for native
     default values.

     *Important*:

     Tables created with native default value support cannot be used
     with versions of MySQL Cluster that do not support native default
     values.

   * NDB API changes in MySQL Cluster NDB 7.1.16 and MySQL Cluster NDB
     7.0.27 are not backward compatible. Due to these changes the
     version of the included NDB client library was increased from
     4.0.0 to 5.0.0; NDB API applications must be recompiled as part of
     any upgrade to these or later MySQL Cluster releases.

     In addition, NDB API programs should be updated as part of such an
     upgrade, in order to take into account changes in the default
     behavior and values for the `Ndb_cluster_connection::connect()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection-methods.html#ndb-ndb-cluster-connection-connect)
     method.

   * Due to issues discovered shortly after release, MySQL Cluster NDB
     7.0.20 was withdrawn and replaced with MySQL Cluster NDB 7.0.20a.
     Users of MySQL Cluster NDB 7.0.19 and previous MySQL Cluster NDB
     7.0 releases should upgrade to MySQL Cluster NDB 7.0.20a, or to a
     later MySQL Cluster NDB 7.0 release. See
     `http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-5-1-51-ndb-7-0-20a.html',
     for more information.

     Due to issues discovered following release, MySQL Cluster NDB
     7.1.15 was withdrawn and replaced with MySQL Cluster NDB 7.1.15a.
     Users of MySQL Cluster NDB 7.1.14 and previous MySQL Cluster NDB
     7.1 releases should upgrade to MySQL Cluster NDB 7.1.15a, or to a
     later MySQL Cluster NDB 7.1 release. See
     `http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-5-1-56-ndb-7-1-15a.html',
     for more information.

     Due to issues discovered shortly after release, MySQL Cluster NDB
     7.1.9 was withdrawn and replaced with MySQL Cluster NDB 7.1.9a.
     Users of MySQL Cluster NDB 7.1.8 and previous MySQL Cluster NDB
     7.1 releases should upgrade to MySQL Cluster NDB 7.1.14 (the last
     release directly upgrade-compatible with MySQL Cluster 7.1.18 and
     earlier) before upgrading to MySQL Cluster 7.1.15a or later. See
     `http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-5-1-51-ndb-7-1-9a.html',
     for more information.

   * When performing an online upgrade or downgrade between MySQL
     Cluster NDB 7.1.8 or earlier and a later release up to and
     including MySQL Cluster NDB 7.1.14, you must upgrade or downgrade
     the data nodes before upgrading or downgrading any SQL nodes;
     otherwise *Note `mysql_upgrade': mysql-upgrade. fails on the SQL
     nodes due to differences between *Note `ndbinfo':
     mysql-cluster-ndbinfo. tables used in the `old' and `new' versions
     of the MySQL Cluster software. You should also upgrade or downgrade
     the data nodes prior to the SQL nodes when performing an online
     upgrade or downgrade between MySQL Cluster NDB 7.1 releases where
     either of the versions involved is MySQL Cluster NDB 7.1.14 or
     earlier, and where one or more *Note `ndbinfo':
     mysql-cluster-ndbinfo. tables has more, fewer, or differing
     columns between the two versions.

     This issue is resolved in MySQL Cluster NDB 7.1.15. (Bug #11885602)

   * It was not possible to downgrade online to MySQL Cluster NDB 7.1
     from some later versions of MySQL Cluster due to a change in the
     size used for table hash maps by *Note `NDB': mysql-cluster. (Bug
     #14645319) This issue was resolved in MySQL Cluster NDB 7.1.26,
     where the size is made configurable using the `DefaultHashMapSize'
     parameter. (Bug #14800539) See the description of this parameter
     for more information.


File: manual.info,  Node: mysql-cluster-upgrade-downgrade-compatibility-6.x,  Next: mysql-cluster-upgrade-downgrade-compatibility-5.1,  Prev: mysql-cluster-upgrade-downgrade-compatibility-7.x,  Up: mysql-cluster-upgrade-downgrade

17.2.7.2 Upgrade and Downgrade Compatibility: MySQL Cluster NDB 6.x
...................................................................

The table shown here provides information on MySQL Cluster upgrade and
downgrade compatibility among different releases of MySQL Cluster NDB
6.1, 6.2, and 6.3. Additional notes about upgrades and downgrades to,
from, or within the MySQL Cluster NDB 6.x release series can be found
immediately following the table.

MySQL Cluster upgrade/downgrade compatibility, MySQL Cluster NDB 6.x

*Notes: MySQL Cluster NDB 6.1*

Availability of older releases

MySQL Cluster NDB 6.1 is no longer in production; information about
this series of releases is of historical interest only.  MySQL Cluster
NDB 6.2 is still available, but is no longer supported in new
deployments. If you are still using a MySQL Cluster NDB 6.1 or MySQL
Cluster NDB 6.2 release, you should upgrade to the most recent MySQL
Cluster NDB 7.0 or MySQL Cluster NDB 7.1 release as soon as possible.

   * It is not possible to upgrade from MySQL Cluster NDB 6.1.2 (or an
     older 6.1 release) directly to 6.1.4 or a newer NDB 6.1 release,
     or to downgrade from 6.1.4 (or a newer 6.1 release) directly to
     6.1.2 or an older NDB 6.1 release; in either case, you must
     upgrade or downgrade to MySQL Cluster NDB 6.1.3 first.

   * It is not possible to perform an online downgrade from MySQL
     Cluster NDB 6.1.8 (or a newer 6.1 release) to MySQL Cluster NDB
     6.1.7 (or an older 6.1 release).

   * MySQL Cluster NDB 6.1.6 and 6.1.18 were not released.

   * It is not possible to perform an online upgrade or downgrade
     between MySQL Cluster NDB 6.2 and any previous release series
     (including mainline MySQL 5.1 and MySQL Cluster NDB 6.1); it is
     necessary to perform a dump and reload. However, it should be
     possible to perform online upgrades or downgrades between any
     MySQL Cluster NDB 6.2 release and any MySQL Cluster NDB 6.3
     release up to and including 6.3.7.

*Notes: MySQL Cluster NDB 6.2 and MySQL Cluster NDB 6.3*

Internal column specification changes

The internal specifications for columns in *Note `NDB': mysql-cluster.
tables changed in MySQL Cluster NDB 6.1.17 and 6.2.1 to enable
compatibility with later MySQL Cluster releases implementing online
adding and dropping of columns (MySQL 5.1.17 through MySQL 5.1.23; MySQL
Cluster NDB 6.2.3 and later; MySQL Cluster NDB 6.3.2 and later). This
change is not backward-compatible with earlier MySQL Server or MySQL
Cluster releases.

To make tables created in earlier versions compatible with online
adding and dropping of columns in later versions, it is necessary to
force MySQL Cluster to convert the tables to the new format by
following this procedure following an upgrade:

  1. Upgrade the MySQL Cluster software on all data, management, and
     SQL nodes

  2. Back up all *Note `NDB': mysql-cluster. tables

  3. Shut down the cluster (all data, management, and SQL nodes)

  4. Restart the cluster, starting all data nodes with the `--initial'
     option (to clear and rebuild the data node file systems)

  5. Restore the tables from backup

To minimize possible later difficulties, it is strongly advised that
the procedure outlined above be followed as soon as possible after to
upgrading between the versions indicated. The procedure is _not_
necessary for *Note `NDBCLUSTER': mysql-cluster. tables created in any
of the following versions:

   * MySQL Cluster NDB 6.1.8 or a later MySQL Cluster NDB 6.1 release

   * MySQL Cluster 6.2.1 or a later MySQL Cluster NDB 6.2 release

   * Any MySQL Cluster NDB 6.3 release (or later MySQL Cluster release
     series)

Tables created in the versions listed previously (or later versions, as
indicated) are already compatible with adding and dropping of columns
online (as implemented beginning with MySQL Cluster NDB 6.2.5 and MySQL
Cluster NDB 6.3.2).

Additional issues encountered when upgrading or downgrading to or from
MySQL Cluster NDB 6.2 and MySQL Cluster NDB 6.3 releases are listed
here:

   * It was not possible to perform an online upgrade between any MySQL
     Cluster NDB 6.2 release and MySQL Cluster NDB 6.3.8 and later
     MySQL Cluster 6.3 releases. This issue was fixed in MySQL Cluster
     NDB 6.3.21. (Bug #41435)

   * Online downgrades between MySQL Cluster NDB 6.2.5 and earlier
     releases are not supported.

   * Online downgrades between MySQL Cluster NDB 6.3.8 and earlier
     releases are not supported.


File: manual.info,  Node: mysql-cluster-upgrade-downgrade-compatibility-5.1,  Prev: mysql-cluster-upgrade-downgrade-compatibility-6.x,  Up: mysql-cluster-upgrade-downgrade

17.2.7.3 Upgrade and downgrade compatibility: MySQL 5.1
.......................................................

The table shown here provides information on MySQL Cluster upgrade and
downgrade compatibility among different releases of MySQL 5.1 prior to
MySQL 5.1.24. Additional notes about upgrades and downgrades to, from,
or within the MySQL 5.1 release series can be found immediately
following the table.

MySQL Cluster upgrade/downgrade compatibility, MySQL 5.1

*Notes: MySQL 5.1*

   * MySQL 5.1.3 was the first public release in this series.

   * Direct upgrades or downgrades between MySQL Cluster 5.0 and 5.1
     are not supported; you must dump all *Note `NDBCLUSTER':
     mysql-cluster. tables using *Note `mysqldump': mysqldump, install
     the new version of the software, and then reload the tables from
     the dump.

   * You cannot downgrade a MySQL Cluster based on MySQL 5.1.6 or later
     and using Disk Data tables to MySQL 5.1.5 or earlier unless you
     convert all such tables to in-memory *Note `NDB': mysql-cluster.
     tables first.

   * MySQL 5.1.8, MySQL 5.1.10, and MySQL 5.1.13 were not released.

   * Online cluster upgrades and downgrades between MySQL 5.1.11 (or an
     earlier version) and 5.1.12 (or a later version) are not possible
     due to major changes in the cluster file system. In such cases,
     you must perform a backup or dump, upgrade (or downgrade) the
     software, start each data node with `--initial', and then restore
     from the backup or dump. You can use native *Note `NDB':
     mysql-cluster. backup and restore, or *Note `mysqldump':
     mysqldump. and *Note `LOAD DATA INFILE': load-data. for this
     purpose.

   * Online downgrades from MySQL 5.1.14 or later to versions previous
     to 5.1.14 are not supported due to incompatible changes in the
     cluster system tables.

MySQL Cluster Replication: changes in ndb_apply_status

Online upgrades from MySQL 5.1.17 and earlier to 5.1.18 and later MySQL
5.1.x releases are not supported for clusters using replication due to
incompatible changes in the `mysql.ndb_apply_status' table. (Online
upgrades from MySQL 5.1 to MySQL Cluster NDB 6.2 and later are not
supported, as discussed elsewhere in this section.)  However, it should
not be necessary to shut down the cluster entirely, if you follow this
modified rolling restart procedure:

  1. Stop the management server, update the management server software,
     then start the management server again. For multiple management
     servers, repeat this step for each management server in turn.

  2. For each data node in turn: Stop the data node, update the data
     node daemon (in MySQL Cluster NDB 7.0 and later, this can be
     either *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
     `ndbmtd': mysql-cluster-programs-ndbmtd.) with the new version,
     then restart the data node. It should not be necessary to use
     `--initial' when restarting any of the data nodes after updating
     the software.

  3. Stop _all_ SQL nodes. Upgrade the existing MySQL server
     installations to the new version on all SQL nodes, then restart
     them. It is not necessary to start them one at a time after
     upgrading the MySQL server software, but _there must be a time
     when none of them is running before starting any of them again
     using the 5.1.18 (or later) *Note `mysqld': mysqld._.
     Otherwise--due to the fact that `mysql.ndb_apply_status' uses the
     *Note `NDB': mysql-cluster. storage engine and is thus shared
     between all SQL nodes--there may be conflicts between the old and
     new versions of the table on different SQL nodes.

     You can find more information about the changes to
     `ndb_apply_status' in *Note mysql-cluster-replication-schema::.

*Note*:

You should upgrade the MySQL Cluster software on each node using the
same method by which it was originally installed.  See *Note
mysql-cluster-installation::, for more information.

As with any other MySQL Cluster version upgrade, you should also update
the MySQL Cluster management client (*Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm.) and other MySQL Cluster client
programs such as *Note `ndb_config': mysql-cluster-programs-ndb-config.
and *Note `ndb_error_reporter':
mysql-cluster-programs-ndb-error-reporter.; however, this does not have
to be done in any particular order.

Internal column specification changes

The internal specifications for columns in *Note `NDBCLUSTER':
mysql-cluster. tables changed in MySQL 5.1.18 to enable compatibility
with later MySQL Cluster releases that permit online adding and
dropping of columns.  _This change is not backward-compatible with
earlier MySQL versions_.

To make tables created in MySQL 5.1.17 and earlier compatible with
online adding and dropping of columns (available beginning with
beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB 6.3.2--see
*Note alter-table::, for more information), it is necessary to force
MySQL 5.1.18 and later to convert the tables to the new format by
following this procedure:

  1. Back up all *Note `NDBCLUSTER': mysql-cluster. tables.

  2. Upgrade the MySQL Cluster software on all data, management, and
     SQL nodes.

  3. Shut down the cluster completely (this includes all data,
     management, and API or SQL nodes).

  4. Restart the cluster, starting all data nodes with the `--initial'
     option (to clear and rebuild the data node file systems).

  5. Restore the *Note `NDBCLUSTER': mysql-cluster. tables from backup.

It is not necessary to follow this procedure for *Note `NDBCLUSTER':
mysql-cluster. tables created in MySQL 5.1.18 and later; such tables
are already compatible with online adding and dropping of columns (as
implemented beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster
NDB 6.3.2).

To minimize possible later difficulties, it is strongly advised that
the procedure outlined above be followed as soon as possible after to
upgrading from MySQL 5.1.17 or earlier to MySQL 5.1.18 or later.

Information about how this change effects users of MySQL Cluster NDB
6.x and 7.x is provided later in this section.

MySQL Cluster not supported in MySQL Server 5.1.24 and later

MySQL Cluster is not supported in standard MySQL 5.1 releases beginning
with MySQL 5.1.24. If you are using MySQL Cluster in a standard MySQL
5.1 release, you should upgrade to the most recent MySQL Cluster NDB
7.0 or MySQL Cluster NDB 7.1 release.


File: manual.info,  Node: mysql-cluster-configuration,  Next: mysql-cluster-programs,  Prev: mysql-cluster-installation,  Up: mysql-cluster

17.3 Configuration of MySQL Cluster NDB 6.1-7.1
===============================================

* Menu:

* mysql-cluster-quick::          Quick Test Setup of MySQL Cluster
* mysql-cluster-config-file::    MySQL Cluster Configuration Files
* mysql-cluster-params-overview::  Overview of MySQL Cluster Configuration Parameters
* mysql-cluster-options-variables::  MySQL Server Options and Variables for MySQL Cluster
* mysql-cluster-interconnects::  Using High-Speed Interconnects with MySQL Cluster

A MySQL server that is part of a MySQL Cluster differs in one chief
respect from a normal (nonclustered) MySQL server, in that it employs
the *Note `NDB': mysql-cluster. storage engine. This engine is also
referred to sometimes as *Note `NDBCLUSTER': mysql-cluster, although
`NDB' is preferred.

To avoid unnecessary allocation of resources, the server is configured
by default with the *Note `NDB': mysql-cluster.  storage engine
disabled. To enable *Note `NDB': mysql-cluster, you must modify the
server's `my.cnf' configuration file, or start the server with the
`--ndbcluster' option.

This MySQL server is a part of the cluster, so it also must know how to
access an management node to obtain the cluster configuration data. The
default behavior is to look for the management node on `localhost'.
However, should you need to specify that its location is elsewhere,
this can be done in `my.cnf', or with the *Note `mysql': mysql.
client. Before the *Note `NDB': mysql-cluster. storage engine can be
used, at least one management node must be operational, as well as any
desired data nodes.

For more information about `--ndbcluster' and other *Note `mysqld':
mysqld. options specific to MySQL Cluster, see *Note
mysql-cluster-program-options-mysqld::.

For information about installing MySQL Cluster, see *Note
mysql-cluster-installation::.


File: manual.info,  Node: mysql-cluster-quick,  Next: mysql-cluster-config-file,  Prev: mysql-cluster-configuration,  Up: mysql-cluster-configuration

17.3.1 Quick Test Setup of MySQL Cluster
----------------------------------------

To familiarize you with the basics, we will describe the simplest
possible configuration for a functional MySQL Cluster. After this, you
should be able to design your desired setup from the information
provided in the other relevant sections of this chapter.

First, you need to create a configuration directory such as
`/var/lib/mysql-cluster', by executing the following command as the
system `root' user:


     shell> mkdir /var/lib/mysql-cluster

In this directory, create a file named `config.ini' that contains the
following information. Substitute appropriate values for `HostName' and
`DataDir' as necessary for your system.


     # file "config.ini" - showing minimal setup consisting of 1 data node,
     # 1 management server, and 3 SQL nodes.
     # The empty default sections are not required, and are shown only for
     # the sake of completeness.
     # Data nodes must provide a hostname but SQL nodes are not required
     # to do so.
     # If you do not know the hostname for your machine, use localhost.
     # The DataDir parameter also has a default value, but it is recommended to
     # set it explicitly.
     # Note: [db], [api], and [mgm] are aliases for [ndbd], [mysqld], and [ndb_mgmd],
     # respectively. _[db] is deprecated and should not be used in new installations._

     [ndbd default]
     NoOfReplicas= 1

     [mysqld  default]
     [ndb_mgmd default]
     [tcp default]

     [ndb_mgmd]
     HostName= myhost.example.com

     [ndbd]
     HostName= myhost.example.com
     DataDir= /var/lib/mysql-cluster

     [mysqld]
     [mysqld]
     [mysqld]

You can now start the *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. management server. By default, it
attempts to read the `config.ini' file in its current working
directory, so change location into the directory where the file is
located and then invoke *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.:


     shell> cd /var/lib/mysql-cluster
     shell> ndb_mgmd

Then start a single data node by running *Note `ndbd':
mysql-cluster-programs-ndbd.:


     shell> ndbd

For command-line options which can be used when starting *Note `ndbd':
mysql-cluster-programs-ndbd, see *Note
mysql-cluster-program-options-common::.

By default, *Note `ndbd': mysql-cluster-programs-ndbd. looks for the
management server at `localhost' on port 1186.

*Note*:

If you have installed MySQL from a binary tarball, you will need to
specify the path of the *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. and *Note `ndbd':
mysql-cluster-programs-ndbd. servers explicitly. (Normally, these will
be found in `/usr/local/mysql/bin'.)

Finally, change location to the MySQL data directory (usually
`/var/lib/mysql' or `/usr/local/mysql/data'), and make sure that the
`my.cnf' file contains the option necessary to enable the NDB storage
engine:


     [mysqld]
     ndbcluster

You can now start the MySQL server as usual:


     shell> mysqld_safe --user=mysql &

Wait a moment to make sure the MySQL server is running properly.  If
you see the notice `mysql ended', check the server's `.err' file to
find out what went wrong.

If all has gone well so far, you now can start using the cluster.
Connect to the server and verify that the *Note `NDB': mysql-cluster.
storage engine is enabled:


     shell> mysql
     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 1 to server version: 5.1.73

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql> SHOW ENGINES\G
     ...
     *************************** 12. row ***************************
     Engine: NDBCLUSTER
     Support: YES
     Comment: Clustered, fault-tolerant, memory-based tables
     *************************** 13. row ***************************
     Engine: NDB
     Support: YES
     Comment: Alias for NDBCLUSTER
     ...

The row numbers shown in the preceding example output may be different
from those shown on your system, depending upon how your server is
configured.

Try to create an *Note `NDB': mysql-cluster. table:


     shell> mysql
     mysql> USE test;
     Database changed

     mysql> CREATE TABLE ctest (i INT) ENGINE=NDBCLUSTER;
     Query OK, 0 rows affected (0.09 sec)

     mysql> SHOW CREATE TABLE ctest \G
     *************************** 1. row ***************************
            Table: ctest
     Create Table: CREATE TABLE `ctest` (
       `i` int(11) default NULL
     ) ENGINE=ndbcluster DEFAULT CHARSET=latin1
     1 row in set (0.00 sec)

To check that your nodes were set up properly, start the management
client:


     shell> ndb_mgm

Use the `SHOW' command from within the management client to obtain a
report on the cluster's status:


     ndb_mgm> SHOW
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     1 node(s)
     id=2    @127.0.0.1  (Version: 5.1.73-ndb-7.1.34, Nodegroup: 0, *)

     [ndb_mgmd(MGM)] 1 node(s)
     id=1    @127.0.0.1  (Version: 5.1.73-ndb-7.1.34)

     [mysqld(API)]   3 node(s)
     id=3    @127.0.0.1  (Version: 5.1.73-ndb-7.1.34)
     id=4 (not connected, accepting connect from any host)
     id=5 (not connected, accepting connect from any host)

At this point, you have successfully set up a working MySQL Cluster.
You can now store data in the cluster by using any table created with
`ENGINE=NDBCLUSTER' or its alias `ENGINE=NDB'.


File: manual.info,  Node: mysql-cluster-config-file,  Next: mysql-cluster-params-overview,  Prev: mysql-cluster-quick,  Up: mysql-cluster-configuration

17.3.2 MySQL Cluster Configuration Files
----------------------------------------

* Menu:

* mysql-cluster-config-example::  MySQL Cluster Configuration: Basic Example
* mysql-cluster-config-starting::  Recommended Starting Configurations for MySQL Cluster NDB 6.2 and Later
* mysql-cluster-connection-strings::  MySQL Cluster Connection Strings
* mysql-cluster-computer-definition::  Defining Computers in a MySQL Cluster
* mysql-cluster-mgm-definition::  Defining a MySQL Cluster Management Server
* mysql-cluster-ndbd-definition::  Defining MySQL Cluster Data Nodes
* mysql-cluster-api-definition::  Defining SQL and Other API Nodes in a MySQL Cluster
* mysql-cluster-tcp-definition::  MySQL Cluster TCP/IP Connections
* mysql-cluster-tcp-definition-direct::  MySQL Cluster TCP/IP Connections Using Direct Connections
* mysql-cluster-shm-definition::  MySQL Cluster Shared-Memory Connections
* mysql-cluster-sci-definition::  SCI Transport Connections in MySQL Cluster
* mysql-cluster-config-lcp-params::  Configuring MySQL Cluster Parameters for Local Checkpoints
* mysql-cluster-config-send-buffers::  Configuring MySQL Cluster Send Buffer Parameters

Configuring MySQL Cluster requires working with two files:

   * `my.cnf': Specifies options for all MySQL Cluster executables.
     This file, with which you should be familiar with from previous
     work with MySQL, must be accessible by each executable running in
     the cluster.

   * `config.ini': This file, sometimes known as the _global
     configuration file_, is read only by the MySQL Cluster management
     server, which then distributes the information contained therein
     to all processes participating in the cluster. `config.ini'
     contains a description of each node involved in the cluster.  This
     includes configuration parameters for data nodes and configuration
     parameters for connections between all nodes in the cluster. For a
     quick reference to the sections that can appear in this file, and
     what sorts of configuration parameters may be placed in each
     section, see Sections of the `config.ini' File.

Caching of configuration data

Beginning with MySQL Cluster NDB 6.4.0, MySQL Cluster uses _stateful
configuration_. The global configuration file is no longer read every
time the management server is restarted. Instead, the management server
caches the configuration the first time it is started, and thereafter,
the global configuration file is read only when one of the following
items is true:

   * The management server is started using the -initial option

     In this case, the global configuration file is re-read, any
     existing cache files are deleted, and the management server
     creates a new configuration cache.

   * The management server is started using the -reload option

     In this case, the management server compares its cache with the
     global configuration file. If they differ, the management server
     creates a new configuration cache; any existing configuration
     cache is preserved, but not used. If the management server's cache
     and the global configuration file contain the same configuration
     data, then the existing cache is used, and no new cache is created.

   * The management server is started using a -config-cache option

     Beginning with MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB
     7.1.4, this option can be used to force the management server to
     bypass configuration caching altogether. In this case, the
     management server ignores any configuration files that may be
     present, always reading its configuration data from the
     `config.ini' file instead.

   * No configuration cache is found

     In this case, the management server reads the global configuration
     file and creates a cache containing the same configuration data as
     found in the file.

Configuration cache files

Beginning with MySQL Cluster 6.4.0, the management server by default
creates configuration cache files in a directory named `mysql-cluster'
in the MySQL installation directory. (If you build MySQL Cluster from
source on a Unix system, the default location is
`/usr/local/mysql-cluster'.) This can be overridden at runtime by
starting the management server with the `--configdir' option.
Configuration cache files are binary files named according to the
pattern `ndb_NODE_ID_config.bin.SEQ_ID', where NODE_ID is the management
server's node ID in the cluster, and SEQ_ID is a cache idenitifer. Cache
files are numbered sequentially using SEQ_ID, in the order in which they
are created. The management server uses the latest cache file as
determined by the SEQ_ID.

*Note*:

It is possible to roll back to a previous configuration by deleting
later configuration cache files, or by renaming an earlier cache file
so that it has a higher SEQ_ID. However, since configuration cache
files are written in a binary format, you should not attempt to edit
their contents by hand.

For more information about the `--configdir', `--config-cache',
`--initial', and `--reload' options for the MySQL Cluster management
server, see *Note mysql-cluster-programs-ndb-mgmd::.

We are continuously making improvements in Cluster configuration and
attempting to simplify this process. Although we strive to maintain
backward compatibility, there may be times when introduce an
incompatible change. In such cases we will try to let Cluster users
know in advance if a change is not backward compatible. If you find
such a change and we have not documented it, please report it in the
MySQL bugs database using the instructions given in *Note bug-reports::.


File: manual.info,  Node: mysql-cluster-config-example,  Next: mysql-cluster-config-starting,  Prev: mysql-cluster-config-file,  Up: mysql-cluster-config-file

17.3.2.1 MySQL Cluster Configuration: Basic Example
...................................................

To support MySQL Cluster, you will need to update `my.cnf' as shown in
the following example.  You may also specify these parameters on the
command line when invoking the executables.

*Note*:

The options shown here should not be confused with those that are used
in `config.ini' global configuration files. Global configuration
options are discussed later in this section.


     # my.cnf
     # example additions to my.cnf for MySQL Cluster
     # (valid in MySQL 5.1)

     # enable ndbcluster storage engine, and provide connection string for
     # management server host (default port is 1186)
     [mysqld]
     ndbcluster
     ndb-connectstring=ndb_mgmd.mysql.com

     # provide connection string for management server host (default port: 1186)
     [ndbd]
     connect-string=ndb_mgmd.mysql.com

     # provide connection string for management server host (default port: 1186)
     [ndb_mgm]
     connect-string=ndb_mgmd.mysql.com

     # provide location of cluster configuration file
     [ndb_mgmd]
     config-file=/etc/config.ini

(For more information on connection strings, see *Note
mysql-cluster-connection-strings::.)


     # my.cnf
     # example additions to my.cnf for MySQL Cluster
     # (will work on all versions)

     # enable ndbcluster storage engine, and provide connection string for management
     # server host to the default port 1186
     [mysqld]
     ndbcluster
     ndb-connectstring=ndb_mgmd.mysql.com:1186

*Important*:

Once you have started a *Note `mysqld': mysqld. process with the *Note
`NDBCLUSTER': mysql-cluster. and `ndb-connectstring' parameters in the
`[mysqld]' in the `my.cnf' file as shown previously, you cannot execute
any *Note `CREATE TABLE': create-table. or *Note `ALTER TABLE':
alter-table. statements without having actually started the cluster.
Otherwise, these statements will fail with an error. _This is by
design_.

You may also use a separate `[mysql_cluster]' section in the cluster
`my.cnf' file for settings to be read and used by all executables:


     # cluster-specific settings
     [mysql_cluster]
     ndb-connectstring=ndb_mgmd.mysql.com:1186

For additional *Note `NDB': mysql-cluster. variables that can be set in
the `my.cnf' file, see *Note mysql-cluster-system-variables::.

The MySQL Cluster global configuration file is by convention named
`config.ini' (but this is not required). It is read by *Note
`ndb_mgmd': mysql-cluster-programs-ndb-mgmd. at startup and can be
placed in any location that can be read by it. The location and name of
the configuration are specified using `--config-file=PATH_NAME' with
*Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. on the command line.
Beginning with MySQL Cluster NDB 6.4.0, this option has no default
value, and is ignored if *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. uses the configuration cache.

The global configuration file for MySQL Cluster uses INI format, which
consists of sections preceded by section headings (surrounded by square
brackets), followed by the appropriate parameter names and values. One
deviation from the standard INI format is that the parameter name and
value can be separated by a colon (``:'') as well as the equal sign
(``=''); however, the equal sign is preferred. Another deviation is
that sections are not uniquely identified by section name. Instead,
unique sections (such as two different nodes of the same type) are
identified by a unique ID specified as a parameter within the section.

Default values are defined for most parameters, and can also be
specified in `config.ini'. (Prior to MySQL Cluster NDB 6.3.25 and MySQL
Cluster NDB 7.0.6, there was no default value for `NoOfReplicas', which
always had to be specified explicitly in the `[ndbd default]' section.
Beginning with versions just stated, the default value is 2, which is
the recommended setting in most common usage scenarios.) To create a
default value section, simply add the word `default' to the section
name. For example, an `[ndbd]' section contains parameters that apply
to a particular data node, whereas an `[ndbd default]' section contains
parameters that apply to all data nodes. Suppose that all data nodes
should use the same data memory size. To configure them all, create an
`[ndbd default]' section that contains a `DataMemory' line to specify
the data memory size.

The global configuration file must define the computers and nodes
involved in the cluster and on which computers these nodes are located.
An example of a simple configuration file for a cluster consisting of
one management server, two data nodes and two SQL nodes is shown here:


     # file "config.ini" - 2 data nodes and 2 SQL nodes
     # This file is placed in the startup directory of ndb_mgmd (the
     # management server)
     # The first SQL node can be started from any host. The second
     # can be started only on the host mysqld_5.mysql.com

     [ndbd default]
     NoOfReplicas= 2
     DataDir= /var/lib/mysql-cluster

     [ndb_mgmd]
     Hostname= ndb_mgmd.mysql.com
     DataDir= /var/lib/mysql-cluster

     [ndbd]
     HostName= ndbd_2.mysql.com

     [ndbd]
     HostName= ndbd_3.mysql.com

     [mysqld]
     [mysqld]
     HostName= mysqld_5.mysql.com

*Note*:

The preceding example is intended as a minimal starting configuration
for purposes of familiarization with MySQL Cluster, and is almost
certain not to be sufficient for production settings. See *Note
mysql-cluster-config-starting::, which provides more complete example
starting configurations for use with MySQL Cluster NDB 6.2 and newer
versions of MySQL Cluster.

Each node has its own section in the `config.ini' file. For example,
this cluster has two data nodes, so the preceding configuration file
contains two `[ndbd]' sections defining these nodes.

*Note*:

Do not place comments on the same line as a section heading in the
`config.ini' file; this causes the management server not to start
because it cannot parse the configuration file in such cases.

*Sections of the config.ini File*

There are six different sections that you can use in the `config.ini'
configuration file, as described in the following list:

   * `[computer]': Defines cluster hosts. This is not required to
     configure a viable MySQL Cluster, but be may used as a convenience
     when setting up a large cluster.  See *Note
     mysql-cluster-computer-definition::, for more information.

   * `[ndbd]': Defines a cluster data node (*Note `ndbd':
     mysql-cluster-programs-ndbd. process). See *Note
     mysql-cluster-ndbd-definition::, for details.

   * `[mysqld]': Defines the cluster's MySQL server nodes (also called
     SQL or API nodes). For a discussion of SQL node configuration, see
     *Note mysql-cluster-api-definition::.

   * `[mgm]' or `[ndb_mgmd]': Defines a cluster management server (MGM)
     node. For information concerning the configuration of management
     nodes, see *Note mysql-cluster-mgm-definition::.

   * `[tcp]': Defines a TCP/IP connection between cluster nodes, with
     TCP/IP being the default connection protocol. Normally, `[tcp]' or
     `[tcp default]' sections are not required to set up a MySQL
     Cluster, as the cluster handles this automatically; however, it
     may be necessary in some situations to override the defaults
     provided by the cluster.  See *Note
     mysql-cluster-tcp-definition::, for information about available
     TCP/IP configuration parameters and how to use them. (You may also
     find *Note mysql-cluster-tcp-definition-direct:: to be of interest
     in some cases.)

   * `[shm]': Defines shared-memory connections between nodes. In MySQL
     5.1, it is enabled by default, but should still be considered
     experimental. For a discussion of SHM interconnects, see *Note
     mysql-cluster-shm-definition::.

   * `[sci]':Defines _Scalable Coherent Interface_ connections between
     cluster data nodes. Such connections require software which, while
     freely available, is not part of the MySQL Cluster distribution,
     as well as specialized hardware. See *Note
     mysql-cluster-sci-definition:: for detailed information about SCI
     interconnects.

You can define `default' values for each section. All Cluster parameter
names are case-insensitive, which differs from parameters specified in
`my.cnf' or `my.ini' files.


File: manual.info,  Node: mysql-cluster-config-starting,  Next: mysql-cluster-connection-strings,  Prev: mysql-cluster-config-example,  Up: mysql-cluster-config-file

17.3.2.2 Recommended Starting Configurations for MySQL Cluster NDB 6.2 and Later
................................................................................

Achieving the best performance from a MySQL Cluster depends on a number
of factors including the following:

   * MySQL Cluster software version

   * Numbers of data nodes and SQL nodes

   * Hardware

   * Operating system

   * Amount of data to be stored

   * Size and type of load under which the cluster is to operate

Therefore, obtaining an optimum configuration is likely to be an
iterative process, the outcome of which can vary widely with the
specifics of each MySQL Cluster deployment. Changes in configuration
are also likely to be indicated when changes are made in the platform
on which the cluster is run, or in applications that use the MySQL
Cluster's data. For these reasons, it is not possible to offer a single
configuration that is ideal for all usage scenarios. However, in this
section, we provide recommended base configurations for MySQL Cluster
NDB 6.2 and 6.3 that can serve as reasonable starting points.

Starting configuration for MySQL Cluster NDB 6.2

The following is a recommended starting point for configuring a cluster
running MySQL Cluster NDB 6.2.


     # TCP PARAMETERS

     [tcp default]
     `SendBufferMemory'=2M
     `ReceiveBufferMemory'=2M

     # Increasing the sizes of these 2 buffers beyond the default values
     # helps prevent bottlenecks due to slow disk I/O.

     # MANAGEMENT NODE PARAMETERS

     [ndb_mgmd default]
     `DataDir'=PATH/TO/MANAGEMENT/SERVER/DATA/DIRECTORY

     # It is possible to use a different data directory for each management
     # server, but for ease of administration it is preferable to be
     # consistent.

     [ndb_mgmd]
     `HostName'=MANAGEMENT-SERVER-1-HOSTNAME
     # `NodeId'=MANAGEMENT-SERVER-1-NODEID

     [ndb_mgmd]
     `HostName'=MANAGEMENT-SERVER-2-HOSTNAME

     # Using 2 management servers helps guarantee that there is always an
     # arbitrator in the event of network partitioning, and so is
     # recommended for high availability. Each management server must be
     # identified by a HostName. You may for the sake of convenience specify
     # a node ID for any management server, although one will be allocated
     # for it automatically; if you do so, it must be in the range 1-255
     # inclusive and must be unique among all IDs specified for cluster
     # nodes.

     # DATA NODE PARAMETERS

     [ndbd default]
     `NoOfReplicas'=2

     # Using 2 replicas is recommended to guarantee availability of data;
     # using only 1 replica does not provide any redundancy, which means
     # that the failure of a single data node causes the entire cluster to
     # shut down. We do not recommend using more than 2 replicas, since 2 is
     # sufficient to provide high availability, and we do not currently test
     # with greater values for this parameter.

     `LockPagesInMainMemory'=1

     # On Linux and Solaris systems, setting this parameter locks data node
     # processes into memory. Doing so prevents them from swapping to disk,
     # which can severely degrade cluster performance.

     `DataMemory'=3072M
     `IndexMemory'=384M

     # The values provided for DataMemory and IndexMemory assume 4 GB RAM
     # per data node. However, for best results, you should first calculate
     # the memory that would be used based on the data you actually plan to
     # store (you may find the *Note ndb_size.pl: mysql-cluster-programs-ndb-size-pl. utility helpful in estimating
     # this), then allow an extra 20% over the calculated values. Naturally,
     # you should ensure that each data node host has at least as much
     # physical memory as the sum of these two values.

     # `ODirect'=1

     # Enabling this parameter causes NDBCLUSTER to try using O_DIRECT
     # writes for local checkpoints and redo logs; this can reduce load on
     # CPUs. We recommend doing so when using MySQL Cluster NDB 6.2.3 or
     # newer on systems running Linux kernel 2.6 or later.

     `NoOfFragmentLogFiles'=300
     `DataDir'=PATH/TO/DATA/NODE/DATA/DIRECTORY
     `MaxNoOfConcurrentOperations'=100000
     `TimeBetweenGlobalCheckpoints'=1000
     `TimeBetweenEpochs'=200
     `DiskCheckpointSpeed'=10M
     `DiskCheckpointSpeedInRestart'=100M
     `RedoBuffer'=32M
     # `MaxNoOfLocalScans'=64
     `MaxNoOfTables'=1024
     `MaxNoOfOrderedIndexes'=256

     [ndbd]
     `HostName'=DATA-NODE-A-HOSTNAME
     # `NodeId'=DATA-NODE-A-NODEID

     [ndbd]
     `HostName'=DATA-NODE-B-HOSTNAME
     # `NodeId'=DATA-NODE-B-NODEID

     # You must have an [ndbd] section for every data node in the cluster;
     # each of these sections must include a HostName. Each section may
     # optionally include an Id for convenience, but in most cases, it is
     # sufficient to allow the cluster to allocate node IDs dynamically. If
     # you do specify the node ID for a data node, it must be in the range 1
     # to 48 inclusive and must be unique among all IDs specified for
     # cluster nodes.

     # SQL NODE / API NODE PARAMETERS

     [mysqld]
     # `HostName'=SQL-NODE-1-HOSTNAME
     # `NodeId'=SQL-NODE-A-NODEID

     [mysqld]

     [mysqld]

     # Each API or SQL node that connects to the cluster requires a [mysqld]
     # or [api] section of its own. Each such section defines a connection
     # `slot'; you should have at least as many of these sections in the
     # config.ini file as the total number of API nodes and SQL nodes that
     # you wish to have connected to the cluster at any given time. There is
     # no performance or other penalty for having extra slots available in
     # case you find later that you want or need more API or SQL nodes to
     # connect to the cluster at the same time.
     # If no HostName is specified for a given [mysqld] or [api] section,
     # then _any_ API or SQL node may use that slot to connect to the
     # cluster. You may wish to use an explicit HostName for one connection slot
     # to guarantee that an API or SQL node from that host can always
     # connect to the cluster. If you wish to prevent API or SQL nodes from
     # connecting from other than a desired host or hosts, then use a
     # HostName for every [mysqld] or [api] section in the config.ini file.
     # You can if you wish define a node ID (Id parameter) for any API or
     # SQL node, but this is not necessary; if you do so, it must be in the
     # range 1 to 255 inclusive and must be unique among all IDs specified
     # for cluster nodes.

Starting configuration for MySQL Cluster NDB 6.3

The following is a recommended starting point for configuring a cluster
running MySQL Cluster NDB 6.3. It is similar to the recommendation for
MySQL Cluster NDB 6.2, with the addition of parameters for better
control of *Note `NDBCLUSTER': mysql-cluster. process threads.


     # TCP PARAMETERS

     [tcp default]
     `SendBufferMemory'=2M
     `ReceiveBufferMemory'=2M

     # Increasing the sizes of these 2 buffers beyond the default values
     # helps prevent bottlenecks due to slow disk I/O.

     # MANAGEMENT NODE PARAMETERS

     [ndb_mgmd default]
     `DataDir'=PATH/TO/MANAGEMENT/SERVER/DATA/DIRECTORY

     # It is possible to use a different data directory for each management
     # server, but for ease of administration it is preferable to be
     # consistent.

     [ndb_mgmd]
     `HostName'=MANAGEMENT-SERVER-A-HOSTNAME
     # `NodeId'=MANAGEMENT-SERVER-A-NODEID

     [ndb_mgmd]
     `HostName'=MANAGEMENT-SERVER-B-HOSTNAME
     # `NodeId'=MANAGEMENT-SERVER-B-NODEID

     # Using 2 management servers helps guarantee that there is always an
     # arbitrator in the event of network partitioning, and so is
     # recommended for high availability. Each management server must be
     # identified by a HostName. You may for the sake of convenience specify
     # a NodeId for any management server, although one will be allocated
     # for it automatically; if you do so, it must be in the range 1-255
     # inclusive and must be unique among all IDs specified for cluster
     # nodes.

     # DATA NODE PARAMETERS

     [ndbd default]
     `NoOfReplicas'=2

     # Using 2 replicas is recommended to guarantee availability of data;
     # using only 1 replica does not provide any redundancy, which means
     # that the failure of a single data node causes the entire cluster to
     # shut down. We do not recommend using more than 2 replicas, since 2 is
     # sufficient to provide high availability, and we do not currently test
     # with greater values for this parameter.

     `LockPagesInMainMemory'=1

     # On Linux and Solaris systems, setting this parameter locks data node
     # processes into memory. Doing so prevents them from swapping to disk,
     # which can severely degrade cluster performance.

     `DataMemory'=3072M
     `IndexMemory'=384M

     # The values provided for DataMemory and IndexMemory assume 4 GB RAM
     # per data node. However, for best results, you should first calculate
     # the memory that would be used based on the data you actually plan to
     # store (you may find the *Note ndb_size.pl: mysql-cluster-programs-ndb-size-pl. utility helpful in estimating
     # this), then allow an extra 20% over the calculated values. Naturally,
     # you should ensure that each data node host has at least as much
     # physical memory as the sum of these two values.

     # `ODirect'=1

     # Enabling this parameter causes NDBCLUSTER to try using O_DIRECT
     # writes for local checkpoints and redo logs; this can reduce load on
     # CPUs. We recommend doing so when using MySQL Cluster NDB 6.2.3 or
     # newer on systems running Linux kernel 2.6 or later.

     `NoOfFragmentLogFiles'=300
     `DataDir'=PATH/TO/DATA/NODE/DATA/DIRECTORY
     `MaxNoOfConcurrentOperations'=100000

     `SchedulerSpinTimer'=400
     `SchedulerExecutionTimer'=100
     `RealTimeScheduler'=1
     # Setting these parameters allows you to take advantage of real-time scheduling
     # of NDB threads (introduced in MySQL Cluster NDB 6.3.4) to achieve increased
     # throughput when using *Note `ndbd': mysql-cluster-programs-ndbd. They are not needed when using *Note `ndbmtd': mysql-cluster-programs-ndbmtd.; in
     # particular, you should not set `RealTimeScheduler' for *Note `ndbmtd': mysql-cluster-programs-ndbmtd. data nodes.

     `TimeBetweenGlobalCheckpoints'=1000
     `TimeBetweenEpochs'=200
     `DiskCheckpointSpeed'=10M
     `DiskCheckpointSpeedInRestart'=100M
     `RedoBuffer'=32M

     # `CompressedLCP'=1
     # `CompressedBackup'=1
     # Enabling CompressedLCP and CompressedBackup causes, respectively, local
     checkpoint files and backup files to be compressed, which can result in a space
     savings of up to 50% over noncompressed LCPs and backups.

     # `MaxNoOfLocalScans'=64
     `MaxNoOfTables'=1024
     `MaxNoOfOrderedIndexes'=256

     [ndbd]
     `HostName'=DATA-NODE-A-HOSTNAME
     # `NodeId'=DATA-NODE-A-NODEID

     `LockExecuteThreadToCPU'=1
     `LockMaintThreadsToCPU'=0
     # On systems with multiple CPUs, these parameters can be used to lock NDBCLUSTER
     # threads to specific CPUs

     [ndbd]
     `HostName'=DATA-NODE-B-HOSTNAME
     # `NodeId'=DATA-NODE-B-NODEID

     `LockExecuteThreadToCPU'=1
     `LockMaintThreadsToCPU'=0

     # You must have an [ndbd] section for every data node in the cluster;
     # each of these sections must include a HostName. Each section may
     # optionally include a NodeId for convenience, but in most cases, it is
     # sufficient to allow the cluster to allocate node IDs dynamically. If
     # you do specify the node ID for a data node, it must be in the range 1
     # to 48 inclusive and must be unique among all IDs specified for
     # cluster nodes.

     # SQL NODE / API NODE PARAMETERS

     [mysqld]
     # `HostName'=SQL-NODE-A-HOSTNAME
     # `NodeId'=SQL-NODE-A-NODEID

     [mysqld]

     [mysqld]

     # Each API or SQL node that connects to the cluster requires a [mysqld]
     # or [api] section of its own. Each such section defines a connection
     # `slot'; you should have at least as many of these sections in the
     # config.ini file as the total number of API nodes and SQL nodes that
     # you wish to have connected to the cluster at any given time. There is
     # no performance or other penalty for having extra slots available in
     # case you find later that you want or need more API or SQL nodes to
     # connect to the cluster at the same time.
     # If no HostName is specified for a given [mysqld] or [api] section,
     # then _any_ API or SQL node may use that slot to connect to the
     # cluster. You may wish to use an explicit HostName for one connection slot
     # to guarantee that an API or SQL node from that host can always
     # connect to the cluster. If you wish to prevent API or SQL nodes from
     # connecting from other than a desired host or hosts, then use a
     # HostName for every [mysqld] or [api] section in the config.ini file.
     # You can if you wish define a node ID (NodeId parameter) for any API or
     # SQL node, but this is not necessary; if you do so, it must be in the
     # range 1 to 255 inclusive and must be unique among all IDs specified
     # for cluster nodes.

Recommended my.cnf options for SQL nodes

MySQL Servers acting as MySQL Cluster SQL nodes must always be started
with the `--ndbcluster' and `--ndb-connectstring' options, either on
the command line or in `my.cnf'. In addition, set the following options
for all *Note `mysqld': mysqld. processes in the cluster, unless your
setup requires otherwise:

   * `--ndb-use-exact-count=0'

   * `--ndb-index-stat-enable=0'

   * `--ndb-force-send=1'

   * `--engine-condition-pushdown=1'


File: manual.info,  Node: mysql-cluster-connection-strings,  Next: mysql-cluster-computer-definition,  Prev: mysql-cluster-config-starting,  Up: mysql-cluster-config-file

17.3.2.3 MySQL Cluster Connection Strings
.........................................

With the exception of the MySQL Cluster management server (*Note
`ndb_mgmd': mysql-cluster-programs-ndb-mgmd.), each node that is part
of a MySQL Cluster requires a _connection string_ that points to the
management server's location. This connection string is used in
establishing a connection to the management server as well as in
performing other tasks depending on the node's role in the cluster. The
syntax for a connection string is as follows:


     [nodeid=NODE_ID, ]HOST-DEFINITION[, HOST-DEFINITION[, ...]]

     HOST-DEFINITION:
         HOST_NAME[:PORT_NUMBER]

`node_id' is an integer greater than or equal to 1 which identifies a
node in `config.ini'.  HOST_NAME is a string representing a valid
Internet host name or IP address.  PORT_NUMBER is an integer referring
to a TCP/IP port number.


     example 1 (long):    "nodeid=2,myhost1:1100,myhost2:1100,192.168.0.3:1200"
     example 2 (short):   "myhost1"

`localhost:1186' is used as the default connection string value if none
is provided. If PORT_NUM is omitted from the connection string, the
default port is 1186. This port should always be available on the
network because it has been assigned by IANA for this purpose (see
`http://www.iana.org/assignments/port-numbers' for details).

By listing multiple host definitions, it is possible to designate
several redundant management servers. A MySQL Cluster data or API node
attempts to contact successive management servers on each host in the
order specified, until a successful connection has been established.

Beginning with MySQL Cluster NDB 6.3.19, it is also possible in a
connection string to specify one or more bind addresses to be used by
nodes having multiple network interfaces for connecting to management
servers. A bind address consists of a hostname or network address and
an optional port number. This enhanced syntax for connection strings is
shown here:


     [nodeid=NODE_ID, ]
         [bind-address=HOST-DEFINITION, ]
         HOST-DEFINITION[; bind-address=HOST-DEFINITION]
         HOST-DEFINITION[; bind-address=HOST-DEFINITION]
         [, ...]]

     HOST-DEFINITION:
         HOST_NAME[:PORT_NUMBER]

If a single bind address is used in the connection string _prior_ to
specifying any management hosts, then this address is used as the
default for connecting to any of them (unless overridden for a given
management server; see later in this section for an example). For
example, the following connection string causes the node to use
`192.168.178.242' regardless of the management server to which it
connects:


     bind-address=192.168.178.242, poseidon:1186, perch:1186

If a bind address is specified _following_ a management host
definition, then it is used only for connecting to that management
node. Consider the following connection string:


     poseidon:1186;bind-address=localhost, perch:1186;bind-address=192.168.178.242

In this case, the node uses `localhost' to connect to the management
server running on the host named `poseidon' and `192.168.178.242' to
connect to the management server running on the host named `perch'.

You can specify a default bind address and then override this default
for one or more specific management hosts. In the following example,
`localhost' is used for connecting to the management server running on
host `poseidon'; since `192.168.178.242' is specified first (before any
management server definitions), it is the default bind address and so
is used for connecting to the management servers on hosts `perch' and
`orca':


     bind-address=192.168.178.242,poseidon:1186;bind-address=localhost,perch:1186,orca:2200

There are a number of different ways to specify the connection string:

   * Each executable has its own command-line option which enables
     specifying the management server at startup. (See the
     documentation for the respective executable.)

   * It is also possible to set the connection string for all nodes in
     the cluster at once by placing it in a `[mysql_cluster]' section
     in the management server's `my.cnf' file.

   * For backward compatibility, two other options are available, using
     the same syntax:

       1. Set the `NDB_CONNECTSTRING' environment variable to contain
          the connection string.

       2. Write the connection string for each executable into a text
          file named `Ndb.cfg' and place this file in the executable's
          startup directory.

     However, these are now deprecated and should not be used for new
     installations.

The recommended method for specifying the connection string is to set
it on the command line or in the `my.cnf' file for each executable.

Previous to MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB 7.1.4, the
maximum length of a connection string was 1024 characters.


File: manual.info,  Node: mysql-cluster-computer-definition,  Next: mysql-cluster-mgm-definition,  Prev: mysql-cluster-connection-strings,  Up: mysql-cluster-config-file

17.3.2.4 Defining Computers in a MySQL Cluster
..............................................

The `[computer]' section has no real significance other than serving as
a way to avoid the need of defining host names for each node in the
system. All parameters mentioned here are required.

   * `Id'

     This table provides type and value information for the Id computer
     configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   string        [none]        ...           IS

     This is a unique identifier, used to refer to the host computer
     elsewhere in the configuration file.

     *Important*:

     The computer ID is _not_ the same as the node ID used for a
     management, API, or data node.  Unlike the case with node IDs, you
     cannot use `NodeId' in place of `Id' in the `[computer]' section
     of the `config.ini' file.

   * `HostName'

     This table provides type and value information for the HostName
     computer configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     This is the computer's hostname or IP address.


File: manual.info,  Node: mysql-cluster-mgm-definition,  Next: mysql-cluster-ndbd-definition,  Prev: mysql-cluster-computer-definition,  Up: mysql-cluster-config-file

17.3.2.5 Defining a MySQL Cluster Management Server
...................................................

The `[ndb_mgmd]' section is used to configure the behavior of the
management server. If multiple management servers are employed, you can
specify parameters common to all of them in an `[ndb_mgmd default]'
section.  `[mgm]' and `[mgm default]' are older aliases for these,
supported for backward compatibility.

All parameters in the following list are optional and assume their
default values if omitted.

*Note*:

If neither the `ExecuteOnComputer' nor the `HostName' parameter is
present, the default value `localhost' will be assumed for both.

   * `Id'

     This table provides type and value information for the Id
     management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   unsigned      [none]        1 - 63        IS
     NDB 6.1.1     unsigned      [none]        1 - 255       IS

     Each node in the cluster has a unique identity. For a management
     node, this is represented by an integer value in the range 1 to 63
     inclusive (previous to MySQL Cluster NDB 6.1.1), or in the range 1
     to 255 inclusive (MySQL Cluster NDB 6.1.1 and later). This ID is
     used by all internal cluster messages for addressing the node, and
     so must be unique for each MySQL Cluster node, regardless of the
     type of node.

     *Note*:

     Data node IDs must be less than 49, regardless of the MySQL
     Cluster version used. If you plan to deploy a large number of data
     nodes, it is a good idea to limit the node IDs for management
     nodes (and API nodes) to values greater than 48.

     The use of the `Id' parameter for identifying management nodes is
     deprecated in favor of `NodeId' beginning with MySQL Cluster NDB
     6.2.19, MySQL Cluster NDB 6.3.39, MySQL Cluster NDB 7.0.20, and
     MySQL Cluster NDB 7.1.9.  Although `Id' continues to be supported
     for backward compatibility, it now generates a warning.

   * `NodeId'

     This table provides type and value information for the NodeId
     management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   unsigned      [none]        1 - 63        IS
     NDB 6.1.1     unsigned      [none]        1 - 255       IS

     Each node in the cluster has a unique identity. For a management
     node, this is represented by an integer value in the range 1 to 63
     inclusive (previous to MySQL Cluster NDB 6.1.1), or in the range 1
     to 255 inclusive (MySQL Cluster NDB 6.1.1 and later). This ID is
     used by all internal cluster messages for addressing the node, and
     so must be unique for each MySQL Cluster node, regardless of the
     type of node.

     *Note*:

     Data node IDs must be less than 49, regardless of the MySQL
     Cluster version used. If you plan to deploy a large number of data
     nodes, it is a good idea to limit the node IDs for management
     nodes (and API nodes) to values greater than 48.

     `NodeId' is the preferred parameter name to use when identifying
     management nodes beginning with MySQL Cluster NDB 6.2.19, MySQL
     Cluster NDB 6.3.39, MySQL Cluster NDB 7.0.20, and MySQL Cluster
     NDB 7.1.9. Although `Id' continues to be supported for backward
     compatibility, it is now deprecated and generates a warning when
     used.

   * `ExecuteOnComputer'

     This table provides type and value information for the
     ExecuteOnComputer management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   name          [none]        ...           S

     This refers to the `Id' set for one of the computers defined in a
     `[computer]' section of the `config.ini' file.

   * `PortNumber'

     This table provides type and value information for the PortNumber
     management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   unsigned      1186          0 - 64K       N

     This is the port number on which the management server listens for
     configuration requests and management commands.

   * `HostName'

     This table provides type and value information for the HostName
     management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     Specifying this parameter defines the hostname of the computer on
     which the management node is to reside. To specify a hostname
     other than `localhost', either this parameter or
     `ExecuteOnComputer' is required.

   * `LogDestination'

     This table provides type and value information for the
     LogDestination management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   {CONSOLE|SYSLOG|FILE}[see text]    ...           N

     This parameter specifies where to send cluster logging
     information. There are three options in this regard--`CONSOLE',
     `SYSLOG', and `FILE'--with `FILE' being the default:

        * `CONSOLE' outputs the log to `stdout':


               CONSOLE

        * `SYSLOG' sends the log to a `syslog' facility, possible values
          being one of `auth', `authpriv', `cron', `daemon', `ftp',
          `kern', `lpr', `mail', `news', `syslog', `user', `uucp',
          `local0', `local1', `local2', `local3', `local4', `local5',
          `local6', or `local7'.

          *Note*:

          Not every facility is necessarily supported by every
          operating system.


               SYSLOG:facility=syslog

        * `FILE' pipes the cluster log output to a regular file on the
          same machine. The following values can be specified:

             * `filename': The name of the log file.

               Prior to MySQL Cluster NDB 7.0.43 and MySQL Cluster NDB
               7.1.23, the log file's default name, used if `FILE' was
               specified without also setting `filename', was
               `logger.log'. Beginning with MySQL Cluster NDB 7.0.43
               and MySQL Cluster NDB 7.1.23, the default log file name
               used in such cases is `ndb_NODEID_cluster.log'.

             * `maxsize': The maximum size (in bytes) to which the file
               can grow before logging rolls over to a new file. When
               this occurs, the old log file is renamed by appending .N
               to the file name, where N is the next number not yet
               used with this name.

             * `maxfiles': The maximum number of log files.


               FILE:filename=cluster.log,maxsize=1000000,maxfiles=6

          The default value for the `FILE' parameter is
          `FILE:filename=ndb_NODE_ID_cluster.log,maxsize=1000000,maxfiles=6',
          where NODE_ID is the ID of the node.

     It is possible to specify multiple log destinations separated by
     semicolons as shown here:


          CONSOLE;SYSLOG:facility=local0;FILE:filename=/var/log/mgmd

   * `ArbitrationRank'

     This table provides type and value information for the
     ArbitrationRank management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   0-2           1             0 - 2         N

     This parameter is used to define which nodes can act as
     arbitrators. Only management nodes and SQL nodes can be
     arbitrators. `ArbitrationRank' can take one of the following
     values:

        * `0': The node will never be used as an arbitrator.

        * `1': The node has high priority; that is, it will be
          preferred as an arbitrator over low-priority nodes.

        * `2': Indicates a low-priority node which be used as an
          arbitrator only if a node with a higher priority is not
          available for that purpose.

     Normally, the management server should be configured as an
     arbitrator by setting its `ArbitrationRank' to 1 (the default for
     management nodes) and those for all SQL nodes to 0 (the default
     for SQL nodes).

     Beginning with MySQL 5.1.16 and MySQL Cluster NDB 6.1.3, it is
     possible to disable arbitration completely by setting
     `ArbitrationRank' to 0 on all management and SQL nodes. In MySQL
     Cluster NDB 7.0.7 and later releases, you can also control
     arbitration by overriding this parameter; to do this, set the
     `Arbitration' parameter in the `[ndbd default]' section of the
     `config.ini' global configuration file.

   * `ArbitrationDelay'

     This table provides type and value information for the
     ArbitrationDelay management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   milliseconds  0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     An integer value which causes the management server's responses to
     arbitration requests to be delayed by that number of milliseconds.
     By default, this value is 0; it is normally not necessary to
     change it.

   * `DataDir'

     This table provides type and value information for the DataDir
     management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   path          .             ...           N

     This specifies the directory where output files from the
     management server will be placed. These files include cluster log
     files, process output files, and the daemon's process ID (PID)
     file. (For log files, this location can be overridden by setting
     the `FILE' parameter for `LogDestination' as discussed previously
     in this section.)

     The default value for this parameter is the directory in which
     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. is located.

   * `PortNumberStats'

     This table provides type and value information for the
     PortNumberStats management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     MySQL 5.1.0   unsigned      [none]        0 - 64K       N

     This parameter specifies the port number used to obtain
     statistical information from a MySQL Cluster management server. It
     has no default value.

   * `Wan'

     This table provides type and value information for the wan
     management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     NDB 6.1.1     boolean       false         true, false   N

     Use WAN TCP setting as default. Introduced in MySQL Cluster NDB
     6.1.1.

   * `HeartbeatThreadPriority'

     Beginning with MySQL Cluster NDB 6.3.32, MySQL Cluster NDB 7.0.13,
     and MySQL Cluster NDB 7.1.2, it is possible to use this parameter
     to set the scheduling policy and priority of heartbeat threads for
     management and API nodes.

     The syntax for setting this parameter is shown here:


          HeartbeatThreadPriority = POLICY[, PRIORITY]

          POLICY:
            {FIFO | RR}

     When setting this parameter, you must specify a policy. This is
     one of `FIFO' (first in, first out) or `RR' (round robin). The
     policy value is followed optionally by the priority (an integer).

   * `ExtraSendBufferMemory'

     This table provides type and value information for the
     ExtraSendBufferMemory management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     NDB 7.0.39    bytes         0             0 - 32G       N

     This parameter specifies the amount of transporter send buffer
     memory to allocate in addition to any that has been set using
     `TotalSendBufferMemory', `SendBufferMemory', or both.

     This parameter was added in MySQL Cluster NDB 7.0.39 and MySQL
     Cluster NDB 7.1.28. (Bug #14555359)

   * `TotalSendBufferMemory'

     This table provides type and value information for the
     TotalSendBufferMemory management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     NDB 6.4.0     bytes         256K          0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter is available beginning with MySQL Cluster NDB
     6.4.0. It is used to determine the total amount of memory to
     allocate on this node for shared send buffer memory among all
     configured transporters.

     If this parameter is set, its minimum permitted value is 256KB;
     the maxmimum is 4294967039. For more detailed information about
     the behavior and use of `TotalSendBufferMemory' and configuring
     send buffer memory parameters in MySQL Cluster NDB 6.4.0 and
     later, see *Note mysql-cluster-config-send-buffers::.

   * `HeartbeatIntervalMgmdMgmd'

     This table provides type and value information for the
     HeartbeatIntervalMgmdMgmd management node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-mgmd.
     NDB 7.0.40    milliseconds  1500          100 -         N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.29    milliseconds  1500          100 -         N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Specify the interval between heartbeat messages used to determine
     whether another management node is on contact with this one. The
     management node waits after 3 of these intervals to declare the
     connection dead; thus, the default setting of 1500 milliseconds
     causes the management node to wait for approximately 1600 ms
     before timing out.

     This parameter was added in MySQL Cluster NDB 7.0.40 and MySQL
     Cluster NDB 7.1.29. (Bug #16426805)

*Note*:

After making changes in a management node's configuration, it is
necessary to perform a rolling restart of the cluster for the new
configuration to take effect.

To add new management servers to a running MySQL Cluster, it is also
necessary to perform a rolling restart of all cluster nodes after
modifying any existing `config.ini' files. For more information about
issues arising when using multiple management nodes, see *Note
mysql-cluster-limitations-multiple-nodes::.


File: manual.info,  Node: mysql-cluster-ndbd-definition,  Next: mysql-cluster-api-definition,  Prev: mysql-cluster-mgm-definition,  Up: mysql-cluster-config-file

17.3.2.6 Defining MySQL Cluster Data Nodes
..........................................

The `[ndbd]' and `[ndbd default]' sections are used to configure the
behavior of the cluster's data nodes.

`[ndbd]' and `[ndbd default]' are always used as the section names
whether you are using *Note `ndbd': mysql-cluster-programs-ndbd. or (in
MySQL Cluster NDB 6.4.0 and later) *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. binaries for the data node processes.

There are many parameters which control buffer sizes, pool sizes,
timeouts, and so forth. The only mandatory parameters are:

   * Either `ExecuteOnComputer' or `HostName', which must be defined in
     the local `[ndbd]' section.

   * The parameter `NoOfReplicas', which must be defined in the `[ndbd
     default]' section, as it is common to all Cluster data nodes.

*Note*:

It is no longer strictly necessary to set `NoOfReplicas' starting with
MySQL Cluster NDB 6.3.25 and MySQL Cluster NDB 7.0.6, where it acquires
a default value (2). However, it remains good practice to set it
explicitly.

Most data node parameters are set in the `[ndbd default]' section. Only
those parameters explicitly stated as being able to set local values
are permitted to be changed in the `[ndbd]' section. Where present,
`HostName', `NodeId' and `ExecuteOnComputer' _must_ be defined in the
local `[ndbd]' section, and not in any other section of `config.ini'. In
other words, settings for these parameters are specific to one data
node.

For those parameters affecting memory usage or buffer sizes, it is
possible to use `K', `M', or `G' as a suffix to indicate units of 1024,
1024x1024, or 1024x1024x1024. (For example, `100K' means 100 x 1024 =
102400.)  Parameter names and values are currently case-sensitive.

Information about configuration parameters specific to MySQL Cluster
Disk Data tables can be found later in this section (see *Note
mysql-cluster-ndbd-definition-disk-data-parameters::).

Beginning with MySQL Cluster NDB 6.4.0, all of these parameters also
apply to *Note `ndbmtd': mysql-cluster-programs-ndbmtd. (the
multi-threaded version of *Note `ndbd': mysql-cluster-programs-ndbd.).
Two additional data node configuration
parameters--`MaxNoOfExecutionThreads' and `ThreadConfig'--apply to
*Note `ndbmtd': mysql-cluster-programs-ndbmtd. only; these have no
effect when used with *Note `ndbd': mysql-cluster-programs-ndbd. For
more information, see *Note
mysql-cluster-ndbd-definition-ndbmtd-parameters::.  See also *Note
mysql-cluster-programs-ndbmtd::.

Identifying data nodes

The `NodeId' or `Id' value (that is, the data node identifier) can be
allocated on the command line when the node is started or in the
configuration file.

   * `Id'

     This table provides type and value information for the Id data
     node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   unsigned      [none]        1 - 48        IS

     A unique node ID is used as the node's address for all cluster
     internal messages. For data nodes, this is an integer in the range
     1 to 48 inclusive. Each node in the cluster must have a unique
     identifier.

     `NodeId' is the preferred parameter name to use when identifying
     data nodes beginning with MySQL Cluster NDB 6.2.19, MySQL Cluster
     NDB 6.3.39, MySQL Cluster NDB 7.0.20, and MySQL Cluster NDB 7.1.9.
     Although `Id' continues to be supported for backward
     compatibility, it is now deprecated and generates a warning when
     used.

   * `NodeId'

     This table provides type and value information for the NodeId data
     node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   unsigned      [none]        1 - 48        IS

     A unique node ID is used as the node's address for all cluster
     internal messages. For data nodes, this is an integer in the range
     1 to 48 inclusive. Each node in the cluster must have a unique
     identifier.

     `NodeId' is the preferred parameter name to use when identifying
     data nodes beginning with MySQL Cluster NDB 6.2.19, MySQL Cluster
     NDB 6.3.39, MySQL Cluster NDB 7.0.20, and MySQL Cluster NDB 7.1.9.
     Although `Id' continues to be supported for backward
     compatibility, it is now deprecated and generates a warning when
     used.

   * `ExecuteOnComputer'

     This table provides type and value information for the
     ExecuteOnComputer data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   name          [none]        ...           S

     This refers to the `Id' set for one of the computers defined in a
     `[computer]' section.

   * `HostName'

     This table provides type and value information for the HostName
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   name or IP    localhost     ...           N
                   address                                   

     Specifying this parameter defines the hostname of the computer on
     which the data node is to reside. To specify a hostname other than
     `localhost', either this parameter or `ExecuteOnComputer' is
     required.

   * `ServerPort'

     This table provides type and value information for the ServerPort
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   unsigned      [none]        1 - 64K       N

     Each node in the cluster uses a port to connect to other nodes. By
     default, this port is allocated dynamically in such a way as to
     ensure that no two nodes on the same host computer receive the
     same port number, so it should normally not be necessary to
     specify a value for this parameter.

     However, if you need to be able to open specific ports in a
     firewall to permit communication between data nodes and API nodes
     (including SQL nodes), you can set this parameter to the number of
     the desired port in an `[ndbd]' section or (if you need to do this
     for multiple data nodes) the `[ndbd default]' section of the
     `config.ini' file, and then open the port having that number for
     incoming connections from SQL nodes, API nodes, or both.

     *Note*:

     Connections from data nodes to management nodes is done using the
     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. management port
     (the management server's `PortNumber'; see *Note
     mysql-cluster-mgm-definition::) so outgoing connections to that
     port from any data nodes should always be permitted.

   * `TcpBind_INADDR_ANY'

     Setting this parameter to `TRUE' or `1' binds `IP_ADDR_ANY' so
     that connections can be made from anywhere (for autogenerated
     connections). The default is `FALSE' (`0').

     This parameter was added in MySQL Cluster NDB 6.2.0.

   * `NodeGroup'

     This table provides type and value information for the NodeGroup
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.4.0                   [none]        0 - 65536     IS

     This parameter can be used to assign a data node to a specific
     node group. It is read only when the cluster is started for the
     first time, and cannot be used to reassign a data node to a
     different node group online. It is generally not desirable to use
     this parameter in the `[ndbd default]' section of the `config.ini'
     file, and care must be taken not to assign nodes to node groups in
     such a way that an invalid numbers of nodes are assigned to any
     node groups.

     The `NodeGroup' parameter is chiefly intended for use in adding a
     new node group to a running MySQL Cluster without having to
     perform a rolling restart. For this purpose, you should set it to
     65536 (the maximum value). You are not required to set a
     `NodeGroup' value for all cluster data nodes, only for those nodes
     which are to be started and added to the cluster as a new node
     group at a later time. For more information, see *Note
     mysql-cluster-online-add-node-example::.

     This parameter was added in MySQL Cluster NDB 6.4.0.

   * `NoOfReplicas'

     This table provides type and value information for the
     NoOfReplicas data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       [none]        1 - 4         IS
     NDB 6.3.25    integer       2             1 - 4         IS
     NDB 7.0.6     integer       2             1 - 4         IS

     This global parameter can be set only in the `[ndbd default]'
     section, and defines the number of replicas for each table stored
     in the cluster. This parameter also specifies the size of node
     groups. A node group is a set of nodes all storing the same
     information.

     Node groups are formed implicitly. The first node group is formed
     by the set of data nodes with the lowest node IDs, the next node
     group by the set of the next lowest node identities, and so on. By
     way of example, assume that we have 4 data nodes and that
     `NoOfReplicas' is set to 2. The four data nodes have node IDs 2,
     3, 4 and 5. Then the first node group is formed from nodes 2 and
     3, and the second node group by nodes 4 and 5. It is important to
     configure the cluster in such a manner that nodes in the same node
     groups are not placed on the same computer because a single
     hardware failure would cause the entire cluster to fail.

     If no node IDs are provided, the order of the data nodes will be
     the determining factor for the node group. Whether or not explicit
     assignments are made, they can be viewed in the output of the
     management client's `SHOW' command.

     Prior to MySQL Cluster NDB 6.3.25 and MySQL Cluster NDB 7.0.6,
     there was no default value for `NoOfReplicas'; beginning with
     these versions, the default value is 2, which is the recommended
     setting in most common usage scenarios.  (Bug #44746)

     The maximum possible value is 4; _currently, only the values 1 and
     2 are actually supported_.

     *Important*:

     Setting `NoOfReplicas' to 1 means that there is only a single copy
     of all Cluster data; in this case, the loss of a single data node
     causes the cluster to fail because there are no additional copies
     of the data stored by that node.

     The value for this parameter must divide evenly into the number of
     data nodes in the cluster. For example, if there are two data
     nodes, then `NoOfReplicas' must be equal to either 1 or 2, since
     2/3 and 2/4 both yield fractional values; if there are four data
     nodes, then `NoOfReplicas' must be equal to 1, 2, or 4.

   * `DataDir'

     This table provides type and value information for the DataDir
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   path          .             ...           IN

     This parameter specifies the directory where trace files, log
     files, pid files and error logs are placed.

     The default is the data node process working directory.

   * `FileSystemPath'

     This table provides type and value information for the
     FileSystemPath data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   path          DataDir       ...           IN

     This parameter specifies the directory where all files created for
     metadata, REDO logs, UNDO logs (for Disk Data tables), and data
     files are placed. The default is the directory specified by
     `DataDir'.

     *Note*:

     This directory must exist before the *Note `ndbd':
     mysql-cluster-programs-ndbd. process is initiated.

     The recommended directory hierarchy for MySQL Cluster includes
     `/var/lib/mysql-cluster', under which a directory for the node's
     file system is created. The name of this subdirectory contains the
     node ID. For example, if the node ID is 2, this subdirectory is
     named `ndb_2_fs'.

   * `BackupDataDir'

     This table provides type and value information for the
     BackupDataDir data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   path          [see text]    ...           IN

     This parameter specifies the directory in which backups are placed.

     *Important*:

     The string '`/BACKUP'' is always appended to this value. For
     example, if you set the value of `BackupDataDir' to
     `/var/lib/cluster-data', then all backups are stored under
     `/var/lib/cluster-data/BACKUP'. This also means that the
     _effective_ default backup location is the directory named
     `BACKUP' under the location specified by the `FileSystemPath'
     parameter.

*Data Memory, Index Memory, and String Memory*

`DataMemory' and `IndexMemory' are `[ndbd]' parameters specifying the
size of memory segments used to store the actual records and their
indexes. In setting values for these, it is important to understand how
`DataMemory' and `IndexMemory' are used, as they usually need to be
updated to reflect actual usage by the cluster:

   * `DataMemory'

     This table provides type and value information for the DataMemory
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         80M           1M - 1024G    N

     This parameter defines the amount of space (in bytes) available
     for storing database records. The entire amount specified by this
     value is allocated in memory, so it is extremely important that
     the machine has sufficient physical memory to accommodate it.

     The memory allocated by `DataMemory' is used to store both the
     actual records and indexes. There is a 16-byte overhead on each
     record; an additional amount for each record is incurred because
     it is stored in a 32KB page with 128 byte page overhead (see
     below). There is also a small amount wasted per page due to the
     fact that each record is stored in only one page.

     For variable-size table attributes in MySQL 5.1, the data is
     stored on separate data pages, allocated from `DataMemory'.
     Variable-length records use a fixed-size part with an extra
     overhead of 4 bytes to reference the variable-size part. The
     variable-size part has 2 bytes overhead plus 2 bytes per attribute.

     Prior to MySQL Cluster NDB 7.0, the maximum record size was 8052
     bytes; in MySQL Cluster NDB 7.0 and later, it is 14000 bytes.

     The memory space defined by `DataMemory' is also used to store
     ordered indexes, which use about 10 bytes per record. Each table
     row is represented in the ordered index.  A common error among
     users is to assume that all indexes are stored in the memory
     allocated by `IndexMemory', but this is not the case: Only primary
     key and unique hash indexes use this memory; ordered indexes use
     the memory allocated by `DataMemory'. However, creating a primary
     key or unique hash index also creates an ordered index on the same
     keys, unless you specify `USING HASH' in the index creation
     statement. This can be verified by running *Note `ndb_desc -d
     DB_NAME TABLE_NAME': mysql-cluster-programs-ndb-desc. in the
     management client.

     Currently, MySQL Cluster can use a maximum of 512 MB for hash
     indexes per partition, which means in some cases it is possible to
     get `Table is full' errors in MySQL client applications even when
     *Note `ndb_mgm -e "ALL REPORT MEMORYUSAGE"':
     mysql-cluster-programs-ndb-mgm. shows significant free
     `DataMemory'. This can also pose a problem with data node restarts
     on nodes that are heavily loaded with data. You can force *Note
     `NDB': mysql-cluster. to create extra partitions for MySQL Cluster
     tables and thus have more memory available for hash indexes by
     using the `MAX_ROWS' option for *Note `CREATE TABLE':
     create-table. In general, setting `MAX_ROWS' to twice the number
     of rows that you expect to store in the table should be
     sufficient. In MySQL Cluster 7.1.18 and later, you can also use the
     `MinFreePct' configuration parameter to help avoid problems with
     node restarts. (Bug #13436216)

     The memory space allocated by `DataMemory' consists of 32KB pages,
     which are allocated to table fragments. Each table is normally
     partitioned into the same number of fragments as there are data
     nodes in the cluster. Thus, for each node, there are the same
     number of fragments as are set in `NoOfReplicas'.

     In addition, due to the way in which new pages are allocated when
     the capacity of the current page is exhausted, there is an
     additional overhead of approximately 18.75%. When more
     `DataMemory' is required, more than one new page is allocated,
     according to the following formula:


          number of new pages = FLOOR(number of current pages x 0.1875) + 1

     For example, if 15 pages are currently allocated to a given table
     and an insert to this table requires additional storage space, the
     number of new pages allocated to the table is `FLOOR(15 x 0.1875)
     + 1 = FLOOR(2.8125) + 1 = 2 + 1 = 3'. Now 15 + 3 = 18 memory pages
     are allocated to the table. When the last of these 18 pages
     becomes full, `FLOOR(18 x 0.1875) + 1 = FLOOR(3.3750) + 1 = 3 + 1 =
     4' new pages are allocated, so the total number of pages allocated
     to the table is now 22.

     *Note*:

     The `18.75% + 1' overhead is no longer required beginning with
     MySQL Cluster NDB 6.2.3 and MySQL Cluster NDB 6.3.0.

     Once a page has been allocated, it is currently not possible to
     return it to the pool of free pages, except by deleting the table.
     (This also means that `DataMemory' pages, once allocated to a
     given table, cannot be used by other tables.) Performing a node
     recovery also compresses the partition because all records are
     inserted into empty partitions from other live nodes.

     The `DataMemory' memory space also contains UNDO information: For
     each update, a copy of the unaltered record is allocated in the
     `DataMemory'. There is also a reference to each copy in the
     ordered table indexes.  Unique hash indexes are updated only when
     the unique index columns are updated, in which case a new entry in
     the index table is inserted and the old entry is deleted upon
     commit.  For this reason, it is also necessary to allocate enough
     memory to handle the largest transactions performed by
     applications using the cluster. In any case, performing a few
     large transactions holds no advantage over using many smaller
     ones, for the following reasons:

        * Large transactions are not any faster than smaller ones

        * Large transactions increase the number of operations that are
          lost and must be repeated in event of transaction failure

        * Large transactions use more memory

     The default value for `DataMemory' is 80MB; the minimum is 1MB.
     There is no maximum size, but in reality the maximum size has to
     be adapted so that the process does not start swapping when the
     limit is reached. This limit is determined by the amount of
     physical RAM available on the machine and by the amount of memory
     that the operating system may commit to any one process. 32-bit
     operating systems are generally limited to 2-4GB per process;
     64-bit operating systems can use more. For large databases, it may
     be preferable to use a 64-bit operating system for this reason.

   * `IndexMemory'

     This table provides type and value information for the IndexMemory
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         18M           1M - 1T       N

     This parameter controls the amount of storage used for hash
     indexes in MySQL Cluster. Hash indexes are always used for primary
     key indexes, unique indexes, and unique constraints.  When
     defining a primary key or a unique index, two indexes are created,
     one of which is a hash index used for all tuple accesses as well
     as lock handling. This index is also used to enforce unique
     constraints.

     You can estimate the size of a hash index using this formula:


            size  = ( (FRAGMENTS * 32K) + (ROWS * 18) )
                    * REPLICAS

     FRAGMENTS is the number of fragments, REPLICAS is the number of
     replicas (normally 2), and ROWS is the number of rows. If a table
     has one million rows, 8 fragments, and 2 replicas, the expected
     index memory usage is calculated as shown here:


            ((8 * 32K) + (1000000 * 18)) * 2 = ((8 * 32768) + (1000000 * 18)) * 2
            = (262144 + 18000000) * 2
            = 18262144 * 2 = 36524288 bytes = ~35MB

     The default value for `IndexMemory' is 18MB.  The minimum is 1MB.

   * `StringMemory'

     This table provides type and value information for the
     StringMemory data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   % or bytes    0             0 -           S
                                               4294967039    
                                               (0xFFFFFEFF)  
     MySQL 5.1.32  % or bytes    25            0 -           S
                                               4294967039    
                                               (0xFFFFFEFF)  
     MySQL 5.1.6   % or bytes    5             0 -           S
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.1     % or bytes    25            0 -           S
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter determines how much memory is allocated for strings
     such as table names, and is specified in an `[ndbd]' or `[ndbd
     default]' section of the `config.ini' file. A value between `0'
     and `100' inclusive is interpreted as a percent of the maximum
     default value, which is calculated based on a number of factors
     including the number of tables, maximum table name size, maximum
     size of `.FRM' files, `MaxNoOfTriggers', maximum column name size,
     and maximum default column value.

     A value greater than `100' is interpreted as a number of bytes.

     The default value is 25--that is, 25 percent of the default
     maximum. (Previously, prior to MySQL Cluster NDB 6.2.18, MySQL
     Cluster NDB 6.3.24, and MySQL Cluster NDB 7.0.5, the default value
     was 5; prior to MySQL 5.1.6, the default was 0.)

     Under most circumstances, the default value should be sufficient,
     but when you have a great many Cluster tables (1000 or more), it
     is possible to get Error 773 `Out of string memory, please modify
     StringMemory config parameter: Permanent error: Schema error', in
     which case you should increase this value.  `25' (25 percent) is
     not excessive, and should prevent this error from recurring in all
     but the most extreme conditions.

The following example illustrates how memory is used for a table.
Consider this table definition:


     CREATE TABLE example (
       a INT NOT NULL,
       b INT NOT NULL,
       c INT NOT NULL,
       PRIMARY KEY(a),
       UNIQUE(b)
     ) ENGINE=NDBCLUSTER;

For each record, there are 12 bytes of data plus 12 bytes overhead.
Having no nullable columns saves 4 bytes of overhead.  In addition, we
have two ordered indexes on columns `a' and `b' consuming roughly 10
bytes each per record. There is a primary key hash index on the base
table using roughly 29 bytes per record. The unique constraint is
implemented by a separate table with `b' as primary key and `a' as a
column. This other table consumes an additional 29 bytes of index
memory per record in the `example' table as well 8 bytes of record data
plus 12 bytes of overhead.

Thus, for one million records, we need 58MB for index memory to handle
the hash indexes for the primary key and the unique constraint. We also
need 64MB for the records of the base table and the unique index table,
plus the two ordered index tables.

You can see that hash indexes takes up a fair amount of memory space;
however, they provide very fast access to the data in return. They are
also used in MySQL Cluster to handle uniqueness constraints.

Currently, the only partitioning algorithm is hashing and ordered
indexes are local to each node. Thus, ordered indexes cannot be used to
handle uniqueness constraints in the general case.

An important point for both `IndexMemory' and `DataMemory' is that the
total database size is the sum of all data memory and all index memory
for each node group. Each node group is used to store replicated
information, so if there are four nodes with two replicas, there will
be two node groups. Thus, the total data memory available is 2 x
`DataMemory' for each data node.

It is highly recommended that `DataMemory' and `IndexMemory' be set to
the same values for all nodes. Data distribution is even over all nodes
in the cluster, so the maximum amount of space available for any node
can be no greater than that of the smallest node in the cluster.

`DataMemory' and `IndexMemory' can be changed, but decreasing either of
these can be risky; doing so can easily lead to a node or even an
entire MySQL Cluster that is unable to restart due to there being
insufficient memory space. Increasing these values should be
acceptable, but it is recommended that such upgrades are performed in
the same manner as a software upgrade, beginning with an update of the
configuration file, and then restarting the management server followed
by restarting each data node in turn.

Beginning with MySQL Cluster NDB 7.0.29 and MySQL Cluster NDB 7.1.18, a
proportion (5% by default) of data node resources including
`DataMemory' and `IndexMemory' is kept in reserve to insure that the
data node does not exhaust its memory when performing a restart. This
can be adjusted using the `MinFreePct' data node configuration
parameter (default 5) introduced in the same versions of MySQL Cluster.

This table provides type and value information for the MinFreePct data
node configuration parameter

Effective      Type/Units     Default        Range/Values   *Note Restart
Version                                                     Type:
                                                            mysql-cluster-params-ndbd.
NDB 7.0.29     unsigned       5              0 - 100        N
NDB 7.1.18     unsigned       5              0 - 100        N
NDB 7.2.3      unsigned       5              0 - 100        N

Updates do not increase the amount of index memory used. Inserts take
effect immediately; however, rows are not actually deleted until the
transaction is committed.

Transaction parameters

The next few `[ndbd]' parameters that we discuss are important because
they affect the number of parallel transactions and the sizes of
transactions that can be handled by the system.
`MaxNoOfConcurrentTransactions' sets the number of parallel
transactions possible in a node.  `MaxNoOfConcurrentOperations' sets
the number of records that can be in update phase or locked
simultaneously.

Both of these parameters (especially `MaxNoOfConcurrentOperations') are
likely targets for users setting specific values and not using the
default value. The default value is set for systems using small
transactions, to ensure that these do not use excessive memory.

`MaxDMLOperationsPerTransaction', added in MySQL Cluster NDB 7.0.26 and
MySQL Cluster NDB 7.1.15, sets the maximum number of DML operations
that can be performed in a given transaction.

   * `MaxNoOfConcurrentTransactions'

     This table provides type and value information for the
     MaxNoOfConcurrentTransactions data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       4096          32 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Each cluster data node requires a transaction record for each
     active transaction in the cluster. The task of coordinating
     transactions is distributed among all of the data nodes. The total
     number of transaction records in the cluster is the number of
     transactions in any given node times the number of nodes in the
     cluster.

     Transaction records are allocated to individual MySQL servers.
     Each connection to an SQL node requires at least one transaction
     record, plus an additional transaction object per table accessed
     by that connection. This means that a reasonable minimum for this
     parameter is


          MaxNoOfConcurrentTransactions =
              (maximum number of tables accessed in any single transaction + 1)
              * number of cluster SQL nodes

     Suppose that there are 10 SQL nodes using the cluster. A single
     join involving 10 tables requires 11 transaction records; if there
     are 10 such joins in a transaction, then 10 * 11 = 110 transaction
     records are required for this transaction, per SQL node, or 110 *
     10 = 1100 transaction records total. Each data node can be
     expected to handle TotalNoOfConcurrentTransactions / number of
     data nodes. For a MySQL Cluster having 4 data nodes, this would
     mean setting `MaxNoOfConcurrentTransactions' on each data node to
     1100 / 4 = 275. In addition, you should provide for failure
     recovery by ensuring that a single node group can accommodate all
     concurrent transactions; in other words, that each data node's
     MaxNoOfConcurrentTransactions is sufficient to cover a number of
     transaction equal to TotalNoOfConcurrentTransactions / number of
     node groups. If this cluster has a single node group, then
     `MaxNoOfConcurrentTransactions' should be set to 1100 (the same as
     the total number of concurrent transactions for the entire
     cluster).

     In addition, each transaction involves at least one operation; for
     this reason, the value set for `MaxNoOfConcurrentTransactions'
     should always be no more than the value of
     `MaxNoOfConcurrentOperations'.

     This parameter must be set to the same value for all cluster data
     nodes. This is due to the fact that, when a data node fails, the
     oldest surviving node re-creates the transaction state of all
     transactions that were ongoing in the failed node.

     It is possible to change this value using a rolling restart, but
     the amount of traffic on the cluster must be such that no more
     transactions occur than the lower of the old and new levels while
     this is taking place.

     The default value is 4096.

   * `MaxNoOfConcurrentOperations'

     This table provides type and value information for the
     MaxNoOfConcurrentOperations data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       32K           32 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     It is a good idea to adjust the value of this parameter according
     to the size and number of transactions. When performing
     transactions which involve only a few operations and records, the
     default value for this parameter is usually sufficient. Performing
     large transactions involving many records usually requires that
     you increase its value.

     Records are kept for each transaction updating cluster data, both
     in the transaction coordinator and in the nodes where the actual
     updates are performed. These records contain state information
     needed to find UNDO records for rollback, lock queues, and other
     purposes.

     This parameter should be set to the number of records to be
     updated simultaneously in transactions, divided by the number of
     cluster data nodes. For example, in a cluster which has four data
     nodes and which is expected to handle one million concurrent
     updates using transactions, you should set this value to 1000000 /
     4 = 250000. To help provide resiliency against failures, it is
     suggested that you set this parameter to a value that is high
     enough to permit an individual data node to handle the load for its
     node group. In other words, you should set the value equal to
     `total number of concurrent operations / number of node groups'.
     (In the case where there is a single node group, this is the same
     as the total number of concurrent operations for the entire
     cluster.)

     Because each transaction always involves at least one operation,
     the value of `MaxNoOfConcurrentOperations' should always be
     greater than or equal to the value of
     `MaxNoOfConcurrentTransactions'.

     Read queries which set locks also cause operation records to be
     created. Some extra space is allocated within individual nodes to
     accommodate cases where the distribution is not perfect over the
     nodes.

     When queries make use of the unique hash index, there are actually
     two operation records used per record in the transaction. The
     first record represents the read in the index table and the second
     handles the operation on the base table.

     The default value is 32768.

     This parameter actually handles two values that can be configured
     separately. The first of these specifies how many operation
     records are to be placed with the transaction coordinator. The
     second part specifies how many operation records are to be local
     to the database.

     A very large transaction performed on an eight-node cluster
     requires as many operation records in the transaction coordinator
     as there are reads, updates, and deletes involved in the
     transaction. However, the operation records of the are spread over
     all eight nodes. Thus, if it is necessary to configure the system
     for one very large transaction, it is a good idea to configure the
     two parts separately. `MaxNoOfConcurrentOperations' will always be
     used to calculate the number of operation records in the
     transaction coordinator portion of the node.

     It is also important to have an idea of the memory requirements
     for operation records. These consume about 1KB per record.

   * `MaxNoOfLocalOperations'

     This table provides type and value information for the
     MaxNoOfLocalOperations data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       UNDEFINED     32 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     By default, this parameter is calculated as 1.1 x
     `MaxNoOfConcurrentOperations'.  This fits systems with many
     simultaneous transactions, none of them being very large. If there
     is a need to handle one very large transaction at a time and there
     are many nodes, it is a good idea to override the default value by
     explicitly specifying this parameter.

   * `MaxDMLOperationsPerTransaction'

     This table provides type and value information for the
     MaxDMLOperationsPerTransaction data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.26    operations    4294967295    32 -          N
                   (DML)                       4294967295    
     NDB 7.1.15    operations    4294967295    32 -          N
                   (DML)                       4294967295    

     Added in MySQL Cluster NDB 7.0.26 and MySQL Cluster NDB 7.1.15,
     this parameter limits the size of a transaction. The transaction
     is aborted if it requires more than this many DML operations. The
     minimum number of operations per transaction is 32; however, you
     can set `MaxDMLOperationsPerTransaction' to 0 to disable any
     limitation on the number of DML operations per transaction. The
     maximum (and default) is 4294967295.

Transaction temporary storage

The next set of `[ndbd]' parameters is used to determine temporary
storage when executing a statement that is part of a Cluster
transaction. All records are released when the statement is completed
and the cluster is waiting for the commit or rollback.

The default values for these parameters are adequate for most
situations. However, users with a need to support transactions
involving large numbers of rows or operations may need to increase
these values to enable better parallelism in the system, whereas users
whose applications require relatively small transactions can decrease
the values to save memory.

   * `MaxNoOfConcurrentIndexOperations'

     This table provides type and value information for the
     MaxNoOfConcurrentIndexOperations data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       8K            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     For queries using a unique hash index, another temporary set of
     operation records is used during a query's execution phase. This
     parameter sets the size of that pool of records.  Thus, this
     record is allocated only while executing a part of a query. As
     soon as this part has been executed, the record is released. The
     state needed to handle aborts and commits is handled by the normal
     operation records, where the pool size is set by the parameter
     `MaxNoOfConcurrentOperations'.

     The default value of this parameter is 8192. Only in rare cases of
     extremely high parallelism using unique hash indexes should it be
     necessary to increase this value. Using a smaller value is
     possible and can save memory if the DBA is certain that a high
     degree of parallelism is not required for the cluster.

   * `MaxNoOfFiredTriggers'

     This table provides type and value information for the
     MaxNoOfFiredTriggers data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       4000          0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     The default value of `MaxNoOfFiredTriggers' is 4000, which is
     sufficient for most situations. In some cases it can even be
     decreased if the DBA feels certain the need for parallelism in the
     cluster is not high.

     A record is created when an operation is performed that affects a
     unique hash index. Inserting or deleting a record in a table with
     unique hash indexes or updating a column that is part of a unique
     hash index fires an insert or a delete in the index table. The
     resulting record is used to represent this index table operation
     while waiting for the original operation that fired it to
     complete. This operation is short-lived but can still require a
     large number of records in its pool for situations with many
     parallel write operations on a base table containing a set of
     unique hash indexes.

   * `TransactionBufferMemory'

     This table provides type and value information for the
     TransactionBufferMemory data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         1M            1K -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     The memory affected by this parameter is used for tracking
     operations fired when updating index tables and reading unique
     indexes. This memory is used to store the key and column
     information for these operations. It is only very rarely that the
     value for this parameter needs to be altered from the default.

     The default value for `TransactionBufferMemory' is 1MB.

     Normal read and write operations use a similar buffer, whose usage
     is even more short-lived. The compile-time parameter
     `ZATTRBUF_FILESIZE' (found in
     `ndb/src/kernel/blocks/Dbtc/Dbtc.hpp') set to 4000 x 128 bytes
     (500KB). A similar buffer for key information, `ZDATABUF_FILESIZE'
     (also in `Dbtc.hpp') contains 4000 x 16 = 62.5KB of buffer space.
     `Dbtc' is the module that handles transaction coordination.

Scans and buffering

There are additional `[ndbd]' parameters in the `Dblqh' module (in
`ndb/src/kernel/blocks/Dblqh/Dblqh.hpp') that affect reads and updates.
These include `ZATTRINBUF_FILESIZE', set by default to 10000 x 128
bytes (1250KB) and `ZDATABUF_FILE_SIZE', set by default to 10000*16
bytes (roughly 156KB) of buffer space. To date, there have been neither
any reports from users nor any results from our own extensive tests
suggesting that either of these compile-time limits should be increased.

   * `MaxNoOfConcurrentScans'

     This table provides type and value information for the
     MaxNoOfConcurrentScans data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       256           2 - 500       N

     This parameter is used to control the number of parallel scans
     that can be performed in the cluster. Each transaction coordinator
     can handle the number of parallel scans defined for this
     parameter. Each scan query is performed by scanning all partitions
     in parallel. Each partition scan uses a scan record in the node
     where the partition is located, the number of records being the
     value of this parameter times the number of nodes. The cluster
     should be able to sustain `MaxNoOfConcurrentScans' scans
     concurrently from all nodes in the cluster.

     Scans are actually performed in two cases. The first of these
     cases occurs when no hash or ordered indexes exists to handle the
     query, in which case the query is executed by performing a full
     table scan. The second case is encountered when there is no hash
     index to support the query but there is an ordered index. Using
     the ordered index means executing a parallel range scan. The order
     is kept on the local partitions only, so it is necessary to
     perform the index scan on all partitions.

     The default value of `MaxNoOfConcurrentScans' is 256. The maximum
     value is 500.

   * `MaxNoOfLocalScans'

     This table provides type and value information for the
     MaxNoOfLocalScans data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       [see text]    32 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.0     integer       [see text]    32 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Specifies the number of local scan records if many scans are not
     fully parallelized. In MySQL Cluster NDB 7.2.0 and later, when the
     number of local scan records is not provided, it is calculated as
     shown here:


          4 * `MaxNoOfConcurrentScans' * [# data nodes] + 2

     In MySQL Cluster NDB 7.1 and earlier, the default is calculated as
     the product of `MaxNoOfConcurrentScans' and the number of data
     nodes, plus 2. The minimum value is 32.

   * `BatchSizePerLocalScan'

     This table provides type and value information for the
     BatchSizePerLocalScan data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       64            1 - 992       N
     NDB 7.2.1     integer       256           1 - 992       N

     This parameter is used to calculate the number of lock records
     used to handle concurrent scan operations.

     `BatchSizePerLocalScan' has a strong connection to the `BatchSize'
     defined in the SQL nodes.

   * `LongMessageBuffer'

     This table provides type and value information for the
     LongMessageBuffer data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         1M            512K -        N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         4M            512K -        N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.0     bytes         4M            512K -        N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.31    bytes         64M           512K -        N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This is an internal buffer used for passing messages within
     individual nodes and between nodes. In MySQL Cluster NDB 6.4.3 and
     earlier, the default is 1MB; beginning with MySQL Cluster NDB
     7.0.4, this increased to 4MB; the default increased to 64MB in
     MySQL Cluster NDB 7.1.31.

     This parameter seldom needs to be changed from the default.
     However, when replicating a MySQL Cluster using *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. for the data nodes, you may need to
     increase this value to 8MB (or possibly more) to prevent data node
     instability, because *Note `ndbmtd': mysql-cluster-programs-ndbmtd.
     uses much more of this resource than *Note `ndbd':
     mysql-cluster-programs-ndbd.  does. Beginning with MySQL Cluster
     NDB 7.0.13 and MySQL Cluster NDB 7.1.2, this should no longer be
     necessary when using *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. with MySQL Cluster Replication (Bug
     #46914).

   * `MaxParallelScansPerFragment'

     This table provides type and value information for the
     MaxParallelScansPerFragment data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.23    bytes         32            1 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.12    bytes         32            1 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.0     bytes         256           1 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Beginning with MySQL Cluster NDB 7.0.23 and MySQL Cluster NDB
     7.1.12, it is possible to configure the maximum number of parallel
     scans (`TUP' scans and `TUX' scans) allowed before they begin
     queuing for serial handling. (Previously, the maximum number of
     parallel scans per fragment was fixed at 32.) You can increase
     this to take advantage of any unused CPU when performing large
     number of scans in parallel and improve their performance.

     Beginning with MySQL Cluster NDB 7.2.0, the default value for this
     parameter is increased from 32 to 256.

*Memory Allocation*

`MaxAllocate'

This table provides type and value information for the MaxAllocate data
node configuration parameter

Effective      Type/Units     Default        Range/Values   *Note Restart
Version                                                     Type:
                                                            mysql-cluster-params-ndbd.
NDB 6.1.19     unsigned       32M            1M - 1G        N
NDB 6.2.3      unsigned       32M            1M - 1G        N
MySQL 5.1.20   unsigned       32M            1M - 1G        N

This is the maximum size of the memory unit to use when allocating
memory for tables. In cases where *Note `NDB': mysql-cluster. gives
`Out of memory' errors, but it is evident by examining the cluster logs
or the output of `DUMP 1000' (see `DUMP 1000'
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-dump-command-1000.html))
that all available memory has not yet been used, you can increase the
value of this parameter (or `MaxNoOfTables', or both) to cause *Note
`NDB': mysql-cluster. to make sufficient memory available.

This parameter was introduced in MySQL 5.1.20, MySQL Cluster NDB 6.1.12
and MySQL Cluster NDB 6.2.3.

*Hash Map Size*

`DefaultHashMapSize'

This table provides type and value information for the
DefaultHashMapSize data node configuration parameter

Effective      Type/Units     Default        Range/Values   *Note Restart
Version                                                     Type:
                                                            mysql-cluster-params-ndbd.
NDB 7.0.38     LDM threads    240            0 - 3840       N
NDB 7.1.27     LDM threads    240            0 - 3840       N

Beginning with MySQL Cluster NDB 7.0.38 and MySQL Cluster NDB 7.1.26,
the size of the table hash maps used by *Note `NDB': mysql-cluster. is
configurable using this parameter; previously this value was hard-coded.
`DefaultHashMapSize' can take any of three possible values (0, 240,
3840). These values and their effects are described in the following
table:

DefaultHashMapSize parameter values and their effects

Value          Description / Effect
`0'            Use the lowest value set, if any, for this parameter
               among all data nodes and API nodes in the cluster; if it
               is not set on any data or API node, use the default value.
`240'          Original hash map size used by default in all MySQL
               Cluster NDB 7.1 and MySQL Cluster NDB 7.0 (and earlier)
               releases; effectively the only value prior to versions
               7.0.38 and 7.1.26 (when this parameter was introduced).
`3840'         Larger hash map size available beginning with MySQL
               Cluster NDB 7.0.38 and MySQL Cluster NDB 7.1.26

The primary intended use for this parameter is to facilitate upgrades
and esecially downgrades between MySQL Cluster NDB 7.1 and later MySQL
Cluster versions in which the larger hash map size (3840) is the
default; by setting this parameter to 240 prior to performing an
upgrade, you can cause the cluster to continue using the smaller size
for table hash maps, in which case the tables remain compatible with
earlier versions.  `DefaultHashMapSize' can be set for individual data
nodes, API nodes, or both, but setting it once only, in the `[ndbd
default]' section of the `config.ini' file, is the recommended
practice. You can also set this parameter to 0, in which case the
default value is used.

After increasing this parameter, to have existing tables to take
advantage of the new size, you can run *Note `ALTER TABLE ...
REORGANIZE PARTITION': alter-table-partition-operations. on them, after
which they can use the larger hash map size. This is in addition to
performing a rolling restart, which makes the larger hash maps
available to new tables, but does not enable existing tables to use
them.

Decreasing this parameter online after any tables have been created or
modified with `DefaultHashMapSize' equal to 3840 is not currently
supported.

Logging and checkpointing

The following `[ndbd]' parameters control log and checkpoint behavior.

   * `NoOfFragmentLogFiles'

     This table provides type and value information for the
     NoOfFragmentLogFiles data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       8             3 -           IN
                                               4294967039    
                                               (0xFFFFFEFF)  
     MySQL 5.1.0   integer       16            3 -           IN
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets the number of REDO log files for the node, and
     thus the amount of space allocated to REDO logging. Because the
     REDO log files are organized in a ring, it is extremely important
     that the first and last log files in the set (sometimes referred
     to as the `head' and `tail' log files, respectively) do not meet.
     When these approach one another too closely, the node begins
     aborting all transactions encompassing updates due to a lack of
     room for new log records.

     A `REDO' log record is not removed until the required number of
     local checkpoints has been completed since that log record was
     inserted (prior to MySQL Cluster NDB 6.3.8, this was 3 local
     checkpoints; in later versions of MySQL Cluster, only 2 local
     checkpoints are necessary).  Checkpointing frequency is determined
     by its own set of configuration parameters discussed elsewhere in
     this chapter.

     How these parameters interact and proposals for how to configure
     them are discussed in *Note mysql-cluster-config-lcp-params::.

     The default parameter value is 16, which by default means 16 sets
     of 4 16MB files for a total of 1024MB. Beginning with MySQL
     Cluster NDB 6.1.1, the size of the individual log files is
     configurable using the `FragmentLogFileSize' parameter. In
     scenarios requiring a great many updates, the value for
     `NoOfFragmentLogFiles' may need to be set as high as 300 or even
     higher to provide sufficient space for REDO logs.

     If the checkpointing is slow and there are so many writes to the
     database that the log files are full and the log tail cannot be
     cut without jeopardizing recovery, all updating transactions are
     aborted with internal error code 410 (`Out of log file space
     temporarily'). This condition prevails until a checkpoint has
     completed and the log tail can be moved forward.

     *Important*:

     This parameter cannot be changed `on the fly'; you must restart
     the node using `--initial'. If you wish to change this value for
     all data nodes in a running cluster, you can do so using a rolling
     node restart (using `--initial' when starting each data node).

   * `FragmentLogFileSize'

     This table provides type and value information for the
     FragmentLogFileSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.1.11    bytes         16M           4M - 1G       IN

     Setting this parameter enables you to control directly the size of
     redo log files. This can be useful in situations when MySQL
     Cluster is operating under a high load and it is unable to close
     fragment log files quickly enough before attempting to open new
     ones (only 2 fragment log files can be open at one time);
     increasing the size of the fragment log files gives the cluster
     more time before having to open each new fragment log file. The
     default value for this parameter is 16M.  `FragmentLogFileSize'
     was added in MySQL Cluster NDB 6.1.11.

     For more information about fragment log files, see the description
     for `NoOfFragmentLogFiles'.

   * `InitFragmentLogFiles'

     This table provides type and value information for the
     InitFragmentLogFiles data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.19    [see values]  SPARSE        SPARSE, FULL  IN

     By default, fragment log files are created sparsely when
     performing an initial start of a data node--that is, depending on
     the operating system and file system in use, not all bytes are
     necessarily written to disk. Beginning with MySQL Cluster NDB
     6.3.19, it is possible to override this behavior and force all
     bytes to be written regardless of the platform and file system
     type being used by mean of this parameter.

     `InitFragmentLogFiles' takes one of two values:

        * `SPARSE'. Fragment log files are created sparsely. This is
          the default value.

        * `FULL'. Force all bytes of the fragment log file to be
          written to disk.

     Depending on your operating system and file system, setting
     `InitFragmentLogFiles=FULL' may help eliminate I/O errors on
     writes to the REDO log.

   * `MaxNoOfOpenFiles'

     This table provides type and value information for the
     MaxNoOfOpenFiles data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       40            20 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     MySQL 5.1.16  unsigned      0             20 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets a ceiling on how many internal threads to
     allocate for open files. _Any situation requiring a change in this
     parameter should be reported as a bug_.

     The default value is 0. (Prior to MySQL 5.1.16, the default was
     40.) However, the minimum value to which this parameter can be set
     is 20.

   * `InitialNoOfOpenFiles'

     This table provides type and value information for the
     InitialNoOfOpenFiles data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.9   files         27            20 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets the initial number of internal threads to
     allocate for open files.

     The default value is 27.

   * `MaxNoOfSavedMessages'

     This table provides type and value information for the
     MaxNoOfSavedMessages data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       25            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets the maximum number of trace files that are
     kept before overwriting old ones. Trace files are generated when,
     for whatever reason, the node crashes.

     The default is 25 trace files.

   * `MaxLCPStartDelay'

     This table provides type and value information for the
     MaxLCPStartDelay data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.23    seconds       0             0 - 600       N
     NDB 6.4.3     seconds       0             0 - 600       N

     In parallel data node recovery (supported in MySQL Cluster NDB
     6.3.8 and later), only table data is actually copied and
     synchronized in parallel; synchronization of metadata such as
     dictionary and checkpoint information is done in a serial fashion.
     In addition, recovery of dictionary and checkpoint information
     cannot be executed in parallel with performing of local
     checkpoints. This means that, when starting or restarting many
     data nodes concurrently, data nodes may be forced to wait while a
     local checkpoint is performed, which can result in longer node
     recovery times.

     Beginning with MySQL Cluster NDB 6.3.23 and MySQL Cluster NDB
     6.4.3, it is possible to force a delay in the local checkpoint to
     permit more (and possibly all) data nodes to complete metadata
     synchronization; once each data node's metadata synchronization is
     complete, all of the data nodes can recover table data in
     parallel, even while the local checkpoint is being executed.

     To force such a delay, you can set `MaxLCPStartDelay', which
     determines the number of seconds the cluster can wait to begin a
     local checkpoint while data nodes continue to synchronize
     metadata. This parameter should be set in the `[ndbd default]'
     section of the `config.ini' file, so that it is the same for all
     data nodes. The maximum value is 600; the default is 0.

   * `LcpScanProgressTimeout'

     This table provides type and value information for the
     LcpScanProgressTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.40    second        60            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.29    second        60            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     A local checkpoint fragment scan watchdog checks periodically for
     no progress in each fragment scan performed as part of a local
     checkpoint, and shuts down the node if there is no progress after
     a given amount of time has elapsed. Prior to MySQL Cluster NDB
     7.0.39 and MySQL Cluster NDB 7.1.29, this interval is always 60
     seconds (Bug #16630410). In MySQL Cluster NDB 7.0.39, MySQL
     Cluster NDB 7.1.29, and later this interval can be set using the
     `LcpScanProgressTimeout' data node configuration parameter, which
     sets the maximum time for which the local checkpoint can be
     stalled before the LCP fragment scan watchdog shuts down the node.

     The default value is 60 seconds (providing compatibility with
     previous releases). Setting this parameter to 0 disables the LCP
     fragment scan watchdog altogether.

Metadata objects

The next set of `[ndbd]' parameters defines pool sizes for metadata
objects, used to define the maximum number of attributes, tables,
indexes, and trigger objects used by indexes, events, and replication
between clusters.  Note that these act merely as `suggestions' to the
cluster, and any that are not specified revert to the default values
shown.

   * `MaxNoOfAttributes'

     This table provides type and value information for the
     MaxNoOfAttributes data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       1000          32 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets a suggested maximum number of attributes that
     can be defined in the cluster; like `MaxNoOfTables', it is not
     intended to function as a hard upper limit.

     Prior to MySQL Cluster NDB 6.3.45, MySQL Cluster NDB 7.0.26, and
     MySQL Cluster NDB 7.1.15, this parameter was sometimes treated as
     a hard limit for certain operations. This caused problems with
     MySQL Cluster Replication, when it was possible to create more
     tables than could be replicated, and sometimes led to confusion
     when it was possible (or not possible, depending on the
     circumstances) to create more than `MaxNoOfAttributes' attributes.
     (Bug #61684)

     The default value is 1000, with the minimum possible value being
     32. The maximum is 4294967039. Each attribute consumes around 200
     bytes of storage per node due to the fact that all metadata is
     fully replicated on the servers.

     When setting `MaxNoOfAttributes', it is important to prepare in
     advance for any *Note `ALTER TABLE': alter-table. statements that
     you might want to perform in the future. This is due to the fact,
     during the execution of *Note `ALTER TABLE': alter-table. on a
     Cluster table, 3 times the number of attributes as in the original
     table are used, and a good practice is to permit double this
     amount. For example, if the MySQL Cluster table having the
     greatest number of attributes (GREATEST_NUMBER_OF_ATTRIBUTES) has
     100 attributes, a good starting point for the value of
     `MaxNoOfAttributes' would be `6 * GREATEST_NUMBER_OF_ATTRIBUTES =
     600'.

     You should also estimate the average number of attributes per
     table and multiply this by `MaxNoOfTables'. If this value is
     larger than the value obtained in the previous paragraph, you
     should use the larger value instead.

     Assuming that you can create all desired tables without any
     problems, you should also verify that this number is sufficient by
     trying an actual *Note `ALTER TABLE': alter-table. after
     configuring the parameter. If this is not successful, increase
     `MaxNoOfAttributes' by another multiple of `MaxNoOfTables' and
     test it again.

   * `MaxNoOfTables'

     This table provides type and value information for the
     MaxNoOfTables data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       128           8 - 20320     N

     A table object is allocated for each table and for each unique
     hash index in the cluster. This parameter sets a suggested maximum
     number of table objects for the cluster as a whole; like
     `MaxNoOfAttributes', it is not intended to function as a hard
     upper limit.

     Prior to MySQL Cluster NDB 6.3.45, MySQL Cluster NDB 7.0.26, and
     MySQL Cluster NDB 7.1.15, this parameter was sometimes treated as
     a hard limit for certain operations. This caused problems with
     MySQL Cluster Replication, when it was possible to create more
     tables than could be replicated, and sometimes led to confusion
     when it was possible (or not possible, depending on the
     circumstances) to create more than `MaxNoOfTables' tables.

     For each attribute that has a *Note `BLOB': blob. data type an
     extra table is used to store most of the *Note `BLOB': blob. data.
     These tables also must be taken into account when defining the
     total number of tables.

     The default value of this parameter is 128. The minimum is 8 and
     the maximum is 20320. Each table object consumes approximately
     20KB per node.

     *Note*:

     The sum of `MaxNoOfTables', `MaxNoOfOrderedIndexes', and
     `MaxNoOfUniqueHashIndexes' must not exceed `2^32 - 2' (4294967294).

   * `MaxNoOfOrderedIndexes'

     This table provides type and value information for the
     MaxNoOfOrderedIndexes data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       128           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     For each ordered index in the cluster, an object is allocated
     describing what is being indexed and its storage segments. By
     default, each index so defined also defines an ordered index. Each
     unique index and primary key has both an ordered index and a hash
     index.  `MaxNoOfOrderedIndexes' sets the total number of ordered
     indexes that can be in use in the system at any one time.

     The default value of this parameter is 128. Each index object
     consumes approximately 10KB of data per node.

     *Note*:

     The sum of `MaxNoOfTables', `MaxNoOfOrderedIndexes', and
     `MaxNoOfUniqueHashIndexes' must not exceed `2^32 - 2' (4294967294).

   * `MaxNoOfUniqueHashIndexes'

     This table provides type and value information for the
     MaxNoOfUniqueHashIndexes data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       64            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     For each unique index that is not a primary key, a special table
     is allocated that maps the unique key to the primary key of the
     indexed table. By default, an ordered index is also defined for
     each unique index. To prevent this, you must specify the `USING
     HASH' option when defining the unique index.

     The default value is 64. Each index consumes approximately 15KB
     per node.

     *Note*:

     The sum of `MaxNoOfTables', `MaxNoOfOrderedIndexes', and
     `MaxNoOfUniqueHashIndexes' must not exceed `2^32 - 2' (4294967294).

   * `MaxNoOfTriggers'

     This table provides type and value information for the
     MaxNoOfTriggers data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       768           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Internal update, insert, and delete triggers are allocated for
     each unique hash index. (This means that three triggers are
     created for each unique hash index.) However, an _ordered_ index
     requires only a single trigger object. Backups also use three
     trigger objects for each normal table in the cluster.

     Replication between clusters also makes use of internal triggers.

     This parameter sets the maximum number of trigger objects in the
     cluster.

     The default value is 768.

   * `MaxNoOfIndexes'

     This parameter is deprecated. You should use
     `MaxNoOfOrderedIndexes' and `MaxNoOfUniqueHashIndexes' instead.

     This parameter is used only by unique hash indexes. There needs to
     be one record in this pool for each unique hash index defined in
     the cluster.

     The default value of this parameter is 128.

   * `MaxNoOfSubscriptions'

     This table provides type and value information for the
     MaxNoOfSubscriptions data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.2.10    unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.3.7     unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Each *Note `NDB': mysql-cluster. table in a MySQL Cluster requires
     a subscription in the NDB kernel. For some NDB API applications,
     it may be necessary or desirable to change this parameter, which
     became available in MySQL Cluster NDB 6.2.10 and MySQL Cluster NDB
     6.3.7. However, for normal usage with MySQL servers acting as SQL
     nodes, there is not any need to do so.

     The default value for `MaxNoOfSubscriptions' is 0, which is
     treated as equal to `MaxNoOfTables'. Each subscription consumes
     108 bytes.

   * `MaxNoOfSubscribers'

     This table provides type and value information for the
     MaxNoOfSubscribers data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.2.10    unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.3.7     unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter, added in MySQL Cluster NDB 6.2.10 and MySQL
     Cluster NDB 6.3.7, is of interest only when using MySQL Cluster
     Replication. The default value is 0, which is treated as `2 *
     MaxNoOfTables'; that is, there is one subscription per *Note
     `NDB': mysql-cluster. table for each of two MySQL servers (one
     acting as the replication master and the other as the slave). Each
     subscriber uses 16 bytes of memory.

     When using circular replication, multi-master replication, and
     other replication setups involving more than 2 MySQL servers, you
     should increase this parameter to the number of *Note `mysqld':
     mysqld. processes included in replication (this is often, but not
     always, the same as the number of clusters). For example, if you
     have a circular replication setup using three MySQL Clusters, with
     one *Note `mysqld': mysqld. attached to each cluster, and each of
     these *Note `mysqld': mysqld. processes acts as a master and as a
     slave, you should set `MaxNoOfSubscribers' equal to `3 *
     MaxNoOfTables'.

     For more information, see *Note mysql-cluster-replication::.

   * `MaxNoOfConcurrentSubOperations'

     This table provides type and value information for the
     MaxNoOfConcurrentSubOperations data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.2.10    unsigned      256           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.3.7     unsigned      256           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets a ceiling on the number of operations that can
     be performed by all API nodes in the cluster at one time. The
     default value (256) is sufficient for normal operations, and might
     need to be adjusted only in scenarios where there are a great many
     API nodes each performing a high volume of operations concurrently.

     This parameter was added in MySQL Cluster NDB 6.2.10 and MySQL
     Cluster NDB 6.3.7.

Boolean parameters

The behavior of data nodes is also affected by a set of `[ndbd]'
parameters taking on boolean values.  These parameters can each be
specified as `TRUE' by setting them equal to `1' or `Y', and as `FALSE'
by setting them equal to `0' or `N'.

   * `LateAlloc'

     This table provides type and value information for the LateAlloc
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.4.0     numeric       1             0 - 1         N

     Allocate memory for this data node after a connection to the
     management server has been established. Enabled by default.

     Added in MySQL Cluster NDB 6.4.0.

   * `LockPagesInMainMemory'

     This table provides type and value information for the
     LockPagesInMainMemory data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   numeric       0             0 - 2         N
     MySQL 5.1.0   true|false    0             0 - 1         N
                   (1|0)                                     
     MySQL 5.1.15  numeric       0             0 - 2         N

     For a number of operating systems, including Solaris and Linux, it
     is possible to lock a process into memory and so avoid any
     swapping to disk. This can be used to help guarantee the cluster's
     real-time characteristics.

     Beginning with MySQL 5.1.15 and MySQL Cluster NDB 6.1.1, this
     parameter takes one of the integer values `0', `1', or `2', which
     act as follows:

        * `0': Disables locking. This is the default value.

        * `1': Performs the lock after allocating memory for the
          process.

        * `2': Performs the lock before memory for the process is
          allocated.

     Previously, this parameter was a Boolean.  `0' or `false' was the
     default setting, and disabled locking. `1' or `true' enabled
     locking of the process after its memory was allocated.

     *Important*:

     Beginning with MySQL 5.1.15 and MySQL Cluster NDB 6.1.1, it is no
     longer possible to use `true' or `false' for the value of this
     parameter; when upgrading from a previous version, you must change
     the value to `0', `1', or `2'.

     Prior to MySQL Cluster NDB 6.3.31 and MySQL Cluster NDB 7.0.11,
     setting this parameter did not cause the stated memory to be
     allocated when the node was started, but rather only when the
     memory was used by the data node process for other reasons. (Bug
     #37430)

     *Note*:

     If the operating system is not configured to permit unprivileged
     users to lock pages, then the data node process making use of this
     parameter may have to be run as system root.
     (`LockPagesInMainMemory' uses the `mlockall' function. From Linux
     kernel 2.6.9, unprivileged users can lock memory as limited by
     `max locked memory'. For more information, see `ulimit -l' and
     `http://linux.die.net/man/2/mlock').

     *Important*:

     Beginning with `glibc' 2.10, `glibc' uses per-thread arenas to
     reduce lock contention on a shared pool, which consumes real
     memory. In general, a data node process does not need per-thread
     arenas, since it does not perform any memory allocation after
     startup. (This difference in allocators does not appear to affect
     performance significantly.)

     The `glibc' behavior is intended to be configurable via the
     `MALLOC_ARENA_MAX' environment variable, but a bug in this
     mechanism prior to `glibc' 2.16 meant that this variable could not
     be set to less than 8, so that the wasted memory could not be
     reclaimed. (Bug #15907219; see also
     `http://sourceware.org/bugzilla/show_bug.cgi?id=13137' for more
     information concerning this issue.)

     One possible workaround for this problem is to use the
     `LD_PRELOAD' environment variable to preload a `jemalloc' memory
     allocation library to take the place of that supplied with `glibc'.

   * `StopOnError'

     This table provides type and value information for the StopOnError
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   boolean       1             0, 1          N

     This parameter specifies whether a data node process should exit
     or perform an automatic restart when an error condition is
     encountered.

     This parameter's default value is `1'; this means that, by
     default, an error causes the data node process to halt.

   * `CrashOnCorruptedTuple'

     This table provides type and value information for the
     CrashOnCorruptedTuple data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.28,   boolean       false         true, false   S
     5.1.56-ndb-7.1.17                                          
     NDB 7.2.1     boolean       true          true, false   S

     This parameter was introduced in MySQL Cluster NDB 7.0.28 and
     MySQL Cluster NDB 7.1.17. When enabled, it forces a data node to
     shut down whenever it encounters a corrupted tuple.  By default,
     it is disabled.

   * `Diskless'

     This table provides type and value information for the Diskless
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   true|false    false         true, false   IS
                   (1|0)                                     

     It is possible to specify MySQL Cluster tables as _diskless_,
     meaning that tables are not checkpointed to disk and that no
     logging occurs. Such tables exist only in main memory. A
     consequence of using diskless tables is that neither the tables
     nor the records in those tables survive a crash. However, when
     operating in diskless mode, it is possible to run *Note `ndbd':
     mysql-cluster-programs-ndbd. on a diskless computer.

     *Important*:

     This feature causes the _entire_ cluster to operate in diskless
     mode.

     When this feature is enabled, Cluster online backup is disabled.
     In addition, a partial start of the cluster is not possible.

     `Diskless' is disabled by default.

   * `ODirect'

     This table provides type and value information for the ODirect
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.1.11    boolean       false         true, false   N
     NDB 6.2.3     boolean       false         true, false   N
     NDB 6.3.0     boolean       false         true, false   N

     Enabling this parameter causes *Note `NDB': mysql-cluster. to
     attempt using `O_DIRECT' writes for LCP, backups, and redo logs,
     often lowering `kswapd' and CPU usage. When using MySQL Cluster on
     Linux, enable `ODirect' if you are using a 2.6 or later kernel.

     This parameter was added in MySQL 5.1.20, MySQL Cluster NDB
     6.1.11, MySQL Cluster NDB 6.2.3, and MySQL Cluster NDB 6.3.0.

     `ODirect' is disabled by default.

   * `RestartOnErrorInsert'

     This table provides type and value information for the
     RestartOnErrorInsert data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   error code    2             0 - 4         N

     This feature is accessible only when building the debug version
     where it is possible to insert errors in the execution of
     individual blocks of code as part of testing.

     This feature is disabled by default.

   * `CompressedBackup'

     This table provides type and value information for the
     CompressedBackup data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.7     boolean       false         true, false   N

     Setting this parameter to `1' causes backup files to be
     compressed. The compression used is equivalent to `gzip --fast',
     and can save 50% or more of the space required on the data node to
     store uncompressed backup files. Compressed backups can be enabled
     for individual data nodes, or for all data nodes (by setting this
     parameter in the `[ndbd default]' section of the `config.ini'
     file).

     *Important*:

     You cannot restore a compressed backup to a cluster running a
     MySQL version that does not support this feature.

     The default value is `0' (disabled).

     This parameter was introduced in MySQL Cluster NDB 6.3.7.

   * `CompressedLCP'

     This table provides type and value information for the
     CompressedLCP data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.7     boolean       false         true, false   N

     Setting this parameter to `1' causes local checkpoint files to be
     compressed. The compression used is equivalent to `gzip --fast',
     and can save 50% or more of the space required on the data node to
     store uncompressed checkpoint files. Compressed LCPs can be
     enabled for individual data nodes, or for all data nodes (by
     setting this parameter in the `[ndbd default]' section of the
     `config.ini' file).

     *Important*:

     You cannot restore a compressed local checkpoint to a cluster
     running a MySQL version that does not support this feature.

     The default value is `0' (disabled).

     This parameter was introduced in MySQL Cluster NDB 6.3.7.

*Controlling Timeouts, Intervals, and Disk Paging*

There are a number of `[ndbd]' parameters specifying timeouts and
intervals between various actions in Cluster data nodes. Most of the
timeout values are specified in milliseconds. Any exceptions to this
are mentioned where applicable.

   * `TimeBetweenWatchDogCheck'

     This table provides type and value information for the
     TimeBetweenWatchDogCheck data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  6000          70 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     To prevent the main thread from getting stuck in an endless loop
     at some point, a `watchdog' thread checks the main thread. This
     parameter specifies the number of milliseconds between checks. If
     the process remains in the same state after three checks, the
     watchdog thread terminates it.

     This parameter can easily be changed for purposes of
     experimentation or to adapt to local conditions. It can be
     specified on a per-node basis although there seems to be little
     reason for doing so.

     The default timeout is 6000 milliseconds (6 seconds).

   * `TimeBetweenWatchDogCheckInitial'

     This table provides type and value information for the
     TimeBetweenWatchDogCheckInitial data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.20  milliseconds  6000          70 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This is similar to the `TimeBetweenWatchDogCheck' parameter,
     except that `TimeBetweenWatchDogCheckInitial' controls the amount
     of time that passes between execution checks inside a database
     node in the early start phases during which memory is allocated.

     The default timeout is 6000 milliseconds (6 seconds).

     This parameter was added in MySQL 5.1.20.

   * `StartPartialTimeout'

     This table provides type and value information for the
     StartPartialTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  30000         0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter specifies how long the Cluster waits for all data
     nodes to come up before the cluster initialization routine is
     invoked. This timeout is used to avoid a partial Cluster startup
     whenever possible.

     This parameter is overridden when performing an initial start or
     initial restart of the cluster.

     The default value is 30000 milliseconds (30 seconds). 0 disables
     the timeout, in which case the cluster may start only if all nodes
     are available.

   * `StartPartitionedTimeout'

     This table provides type and value information for the
     StartPartitionedTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  60000         0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     If the cluster is ready to start after waiting for
     `StartPartialTimeout' milliseconds but is still possibly in a
     partitioned state, the cluster waits until this timeout has also
     passed. If `StartPartitionedTimeout' is set to 0, the cluster
     waits indefinitely.

     This parameter is overridden when performing an initial start or
     initial restart of the cluster.

     The default timeout is 60000 milliseconds (60 seconds).

   * `StartFailureTimeout'

     This table provides type and value information for the
     StartFailureTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     If a data node has not completed its startup sequence within the
     time specified by this parameter, the node startup fails. Setting
     this parameter to 0 (the default value) means that no data node
     timeout is applied.

     For nonzero values, this parameter is measured in milliseconds.
     For data nodes containing extremely large amounts of data, this
     parameter should be increased. For example, in the case of a data
     node containing several gigabytes of data, a period as long as
     10-15 minutes (that is, 600000 to 1000000 milliseconds) might be
     required to perform a node restart.

   * `StartNoNodeGroupTimeout'

     This table provides type and value information for the
     StartNoNodeGroupTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.24    milliseconds  15000         0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When a data node is configured with `Nodegroup = 65536', is
     regarded as not being assigned to any node group. When that is
     done, the cluster waits `StartNoNodegroupTimeout' milliseconds,
     then treats such nodes as though they had been added to the list
     passed to the `--nowait-nodes' option, and starts. The default
     value is `15000' (that is, the management server waits 15
     seconds). Setting this parameter equal to `0' means that the
     cluster waits indefinitely.

     `StartNoNodegroupTimeout' must be the same for all data nodes in
     the cluster; for this reason, you should always set it in the
     `[ndbd default]' section of the `config.ini' file, rather than for
     individual data nodes.

     This parameter was added in MySQL Cluster NDB 7.0.24 and MySQL
     Cluster NDB 7.1.13. See *Note mysql-cluster-online-add-node::, for
     more information.

   * `HeartbeatIntervalDbDb'

     This table provides type and value information for the
     HeartbeatIntervalDbDb data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  1500          10 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.0     milliseconds  5000          10 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     One of the primary methods of discovering failed nodes is by the
     use of heartbeats. This parameter states how often heartbeat
     signals are sent and how often to expect to receive them. After
     missing three heartbeat intervals in a row, the node is declared
     dead. Thus, the maximum time for discovering a failure through the
     heartbeat mechanism is four times the heartbeat interval.

     In MySQL Cluster NDB 7.2.0 and later, the default heartbeat
     interval is 5000 milliseconds (5 seconds). Previously, the default
     was 1500 milliseconds (1.5 seconds). This parameter must not be
     changed drastically and should not vary widely between nodes. If
     one node uses 5000 milliseconds and the node watching it uses 1000
     milliseconds, obviously the node will be declared dead very
     quickly. This parameter can be changed during an online software
     upgrade, but only in small increments.

     See also *Note mysql-cluster-network-latency-issues::.

   * `HeartbeatIntervalDbApi'

     This table provides type and value information for the
     HeartbeatIntervalDbApi data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  1500          100 -         N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Each data node sends heartbeat signals to each MySQL server (SQL
     node) to ensure that it remains in contact. If a MySQL server
     fails to send a heartbeat in time it is declared `dead,' in which
     case all ongoing transactions are completed and all resources
     released. The SQL node cannot reconnect until all activities
     initiated by the previous MySQL instance have been completed. The
     three-heartbeat criteria for this determination are the same as
     described for `HeartbeatIntervalDbDb'.

     The default interval is 1500 milliseconds (1.5 seconds).  This
     interval can vary between individual data nodes because each data
     node watches the MySQL servers connected to it, independently of
     all other data nodes.

     For more information, see *Note
     mysql-cluster-network-latency-issues::.

   * `HeartbeatOrder'

     This table provides type and value information for the
     HeartbeatOrder data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.35    numeric       0             0 - 65535     S
     NDB 7.0.16    numeric       0             0 - 65535     S
     NDB 7.1.5     numeric       0             0 - 65535     S

     Data nodes send heartbeats to one another in a circular fashion
     whereby each data node monitors the previous one. If a heartbeat
     is not detected by a given data node, this node declares the
     previous data node in the circle `dead' (that is, no longer
     accessible by the cluster). The determination that a data node is
     dead is done globally; in other words; once a data node is
     declared dead, it is regarded as such by all nodes in the cluster.

     It is possible for heartbeats between data nodes residing on
     different hosts to be too slow compared to heartbeats between
     other pairs of nodes (for example, due to a very low heartbeat
     interval or temporary connection problem), such that a data node
     is declared dead, even though the node can still function as part
     of the cluster.

     In this type of situation, it may be that the order in which
     heartbeats are transmitted between data nodes makes a difference
     as to whether or not a particular data node is declared dead. If
     this declaration occurs unnecessarily, this can in turn lead to
     the unnecessary loss of a node group and as thus to a failure of
     the cluster.

     Consider a setup where there are 4 data nodes A, B, C, and D
     running on 2 host computers `host1' and `host2', and that these
     data nodes make up 2 node groups, as shown in the following table:

     This table helps illustrate a setup in which there are four data
     nodes A, B, C, and D running on two host computers, `host1' and
     `host2', with each data node belonging to one of two node groups.

     Node Group             Nodes Running on       Nodes Running on
                            `host1'                `host2'
     _Node Group 0_:        Node A                 Node B
     _Node Group 1_:        Node C                 Node D

     Suppose the heartbeats are transmitted in the order A->B->C->D->A.
     In this case, the loss of the heartbeat between the hosts causes
     node B to declare node A dead and node C to declare node B dead.
     This results in loss of Node Group 0, and so the cluster fails. On
     the other hand, if the order of transmission is A->B->D->C->A (and
     all other conditions remain as previously stated), the loss of the
     heartbeat causes nodes A and D to be declared dead; in this case,
     each node group has one surviving node, and the cluster survives.

     Priot to MySQL Cluster NDB 6.3.35, MySQL Cluster NDB 7.0.16, and
     MySQL Cluster NDB 7.1.5, the order of heartbeat transmission
     between data nodes was always automatically determined by `NDB'.
     However, beginning with these versions, the `HeartbeatOrder'
     configuration parameter makes the order of heartbeat transmission
     user-configurable.

     The default value for `HeartbeatOrder' is zero; allowing the
     default value to be used on all data nodes causes the order of
     heartbeat transmission to be determined by `NDB'. If this
     parameter is used, it must be set to a nonzero value (maximum
     65535) for every data node in the cluster, and this value must be
     unique for each data node; this causes the heartbeat transmission
     to proceed from data node to data node in the order of their
     `HeartbeatOrder' values from lowest to highest (and then directly
     from the data node having the highest `HeartbeatOrder' to the data
     node having the lowest value, to complete the circle). The values
     need not be consecutive; for example, to force the heartbeat
     transmission order A->B->D->C->A in the scenario outlined
     previously, you could set the `HeartbeatOrder' values as shown
     here:

     This table lists each node and the heartbeat order value to
     illustrate the previously described scenario in which
     `HeartbeatOrder' values are set to force a heartbeat transition
     order of A->B->D->C->A.

     Node                               `HeartbeatOrder'
     A                                  10
     B                                  20
     C                                  30
     D                                  25

     To use this parameter to change the heartbeat transmission order
     in a running MySQL Cluster, you must first set `HeartbeatOrder' for
     each data node in the cluster in the global configuration
     (`config.ini') file (or files). To cause the change to take
     effect, you must perform either of the following:

        * A complete shutdown and restart of the entire cluster.

        * 2 rolling restarts of the cluster in succession.  _All nodes
          must be restarted in the same order in both rolling restarts_.

     You can use `DUMP 908' to observe the effect of this parameter in
     the data node logs.

   * `ConnectCheckIntervalDelay'

     This table provides type and value information for the
     ConnectCheckIntervalDelay data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.1.13    string        1500          0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.1     string        0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Enables connection checking between data nodes. A data node that
     fails to respond within an interval of `ConnectCheckIntervalDelay'
     seconds is considered suspect, and is considered dead after two
     such intervals.

   * `TimeBetweenLocalCheckpoints'

     This table provides type and value information for the
     TimeBetweenLocalCheckpoints data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   number of     20            0 - 31        N
                   4-byte                                    
                   words, as a                               
                   base-2                                    
                   logarithm                                 

     This parameter is an exception in that it does not specify a time
     to wait before starting a new local checkpoint; rather, it is used
     to ensure that local checkpoints are not performed in a cluster
     where relatively few updates are taking place. In most clusters
     with high update rates, it is likely that a new local checkpoint
     is started immediately after the previous one has been completed.

     The size of all write operations executed since the start of the
     previous local checkpoints is added. This parameter is also
     exceptional in that it is specified as the base-2 logarithm of the
     number of 4-byte words, so that the default value 20 means 4MB (4 x
     2^20) of write operations, 21 would mean 8MB, and so on up to a
     maximum value of 31, which equates to 8GB of write operations.

     All the write operations in the cluster are added together.
     Setting `TimeBetweenLocalCheckpoints' to 6 or less means that
     local checkpoints will be executed continuously without pause,
     independent of the cluster's workload.

   * `TimeBetweenGlobalCheckpoints'

     This table provides type and value information for the
     TimeBetweenGlobalCheckpoints data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  2000          10 - 32000    N
     NDB 6.2.0     milliseconds  2000          20 - 32000    N

     When a transaction is committed, it is committed in main memory in
     all nodes on which the data is mirrored. However, transaction log
     records are not flushed to disk as part of the commit. The
     reasoning behind this behavior is that having the transaction
     safely committed on at least two autonomous host machines should
     meet reasonable standards for durability.

     It is also important to ensure that even the worst of cases--a
     complete crash of the cluster--is handled properly. To guarantee
     that this happens, all transactions taking place within a given
     interval are put into a global checkpoint, which can be thought of
     as a set of committed transactions that has been flushed to disk.
     In other words, as part of the commit process, a transaction is
     placed in a global checkpoint group. Later, this group's log
     records are flushed to disk, and then the entire group of
     transactions is safely committed to disk on all computers in the
     cluster.

     This parameter defines the interval between global checkpoints.
     The default is 2000 milliseconds.

   * `TimeBetweenEpochs'

     This table provides type and value information for the
     TimeBetweenEpochs data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.2.5     milliseconds  100           0 - 32000     N

     This parameter defines the interval between synchronization epochs
     for MySQL Cluster Replication. The default value is 100
     milliseconds.

     `TimeBetweenEpochs' is part of the implementation of `micro-GCPs',
     which can be used to improve the performance of MySQL Cluster
     Replication. This parameter was introduced in MySQL Cluster NDB
     6.2.5 and MySQL Cluster NDB 6.3.2.

   * `TimeBetweenEpochsTimeout'

     This table provides type and value information for the
     TimeBetweenEpochsTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.22  milliseconds  4000          0 - 32000     N
     MySQL 5.1.51  milliseconds  0             0 - 256000    N

     This parameter defines a timeout for synchronization epochs for
     MySQL Cluster Replication. If a node fails to participate in a
     global checkpoint within the time determined by this parameter,
     the node is shut down. In MySQL Cluster NDB 7.2.0 and later, the
     default value is 0; in other words, the timeout is disabled. This
     represents a change from previous versions of MySQL Cluster, in
     which the default value was 4000 milliseconds (4 seconds).

     `TimeBetweenEpochsTimeout' is part of the implementation of
     `micro-GCPs', which can be used to improve the performance of MySQL
     Cluster Replication. This parameter was introduced in MySQL
     Cluster NDB 6.2.7 and MySQL Cluster NDB 6.3.4.

     The following changes regarding this parameter were made in MySQL
     Cluster NDB 7.0.21 and MySQL Cluster NDB 7.1.10:

        * The maximum possible value for this parameter was increased
          from 32000 milliseconds to 256000 milliseconds.

        * Setting this parameter to zero now has the effect of
          disabling GCP stops caused by save timeouts, commit timeouts,
          or both.

        * The current value of this parameter and a warning are now
          written to the cluster log whenever a GCP save takes longer
          than 1 minute or a GCP save takes longer than 10 seconds.

   * `MaxBufferedEpochs'

     This table provides type and value information for the
     MaxBufferedEpochs data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.2.14    epochs        100           0 - 100000    N

     The number of unprocessed epochs by which a subscribing node can
     lag behind. Exceeding this number causes a lagging subscriber to
     be disconnected.

     The default value of 100 is sufficient for most normal operations.
     If a subscribing node does lag enough to cause disconnections, it
     is usually due to network or scheduling issues with regard to
     processes or threads. (In rare circumstances, the problem may be
     due to a bug in the *Note `NDB': mysql-cluster. client.) It may be
     desirable to set the value lower than the default when epochs are
     longer.

     Disconnection prevents client issues from affecting the data node
     service, running out of memory to buffer data, and eventually
     shutting down. Instead, only the client is affected as a result of
     the disconnect (by, for example gap events in the binary log),
     forcing the client to reconnect or restart the process.

   * `MaxBufferedEpochBytes'

     This table provides type and value information for the
     MaxBufferedEpochBytes data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.52    bytes         26214400      26214400      N
                                               (0x01900000)  
                                               - 4294967039  
                                               (0xFFFFFEFF)  
     NDB 7.0.38    bytes         26214400      26214400      N
                                               (0x01900000)  
                                               - 4294967039  
                                               (0xFFFFFEFF)  
     NDB 7.1.27    bytes         26214400      26214400      N
                                               (0x01900000)  
                                               - 4294967039  
                                               (0xFFFFFEFF)  

     The total number of bytes allocated for buffering epochs by this
     node.

     This parameter was introduced in MySQL Cluster NDB 6.3.52, MySQL
     Cluster NDB 7.0.38, and MySQL Cluster NDB 7.1.27. (Bug #16203623)

   * `TimeBetweenInactiveTransactionAbortCheck'

     This table provides type and value information for the
     TimeBetweenInactiveTransactionAbortCheck data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  1000          1000 -        N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Timeout handling is performed by checking a timer on each
     transaction once for every interval specified by this parameter.
     Thus, if this parameter is set to 1000 milliseconds, every
     transaction will be checked for timing out once per second.

     The default value is 1000 milliseconds (1 second).

   * `TransactionInactiveTimeout'

     This table provides type and value information for the
     TransactionInactiveTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  [see text]    0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter states the maximum time that is permitted to lapse
     between operations in the same transaction before the transaction
     is aborted.

     The default for this parameter is `4G' (also the maximum). For a
     real-time database that needs to ensure that no transaction keeps
     locks for too long, this parameter should be set to a relatively
     small value. The unit is milliseconds.

   * `TransactionDeadlockDetectionTimeout'

     This table provides type and value information for the
     TransactionDeadlockDetectionTimeout data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  1200          50 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When a node executes a query involving a transaction, the node
     waits for the other nodes in the cluster to respond before
     continuing. A failure to respond can occur for any of the
     following reasons:

        * The node is `dead'

        * The operation has entered a lock queue

        * The node requested to perform the action could be heavily
          overloaded.

     This timeout parameter states how long the transaction coordinator
     waits for query execution by another node before aborting the
     transaction, and is important for both node failure handling and
     deadlock detection. In MySQL 5.1.10 and earlier versions, setting
     it too high could cause undesirable behavior in situations
     involving deadlocks and node failure. Beginning with MySQL 5.1.11,
     active transactions occurring during node failures are actively
     aborted by the MySQL Cluster Transaction Coordinator, and so high
     settings are no longer an issue with this parameter.

     The default timeout value is 1200 milliseconds (1.2 seconds).

     Prior to MySQL Cluster NDB versions 6.2.18, 6.3.24, and 7.0.5, the
     effective minimum for this parameter was 100 milliseconds. (Bug
     #44099) Beginning with these versions, the actual minimum is 50
     milliseconds.

   * `DiskSyncSize'

     This table provides type and value information for the
     DiskSyncSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.12  bytes         4M            32K -         N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This is the maximum number of bytes to store before flushing data
     to a local checkpoint file. This is done to prevent write
     buffering, which can impede performance significantly.  This
     parameter is _not_ intended to take the place of
     `TimeBetweenLocalCheckpoints'.

     *Note*:

     When `ODirect' is enabled, it is not necessary to set
     `DiskSyncSize'; in fact, in such cases its value is simply ignored.

     The default value is 4M (4 megabytes).

     This parameter was added in MySQL 5.1.12.

   * `DiskCheckpointSpeed'

     This table provides type and value information for the
     DiskCheckpointSpeed data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.12  bytes         10M           1M -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     The amount of data,in bytes per second, that is sent to disk
     during a local checkpoint. This allocation is shared by DML
     operations and backups (but not backup logging), which means that
     backups started during times of intensive DML may be impaired by
     flooding of the redo log buffer and may fail altogether if the
     contention is sufficiently severe.

     The default value is 10M (10 megabytes per second).

     This parameter was added in MySQL 5.1.12.

   * `DiskCheckpointSpeedInRestart'

     This table provides type and value information for the
     DiskCheckpointSpeedInRestart data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         100M          1M -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     The amount of data,in bytes per second, that is sent to disk
     during a local checkpoint as part of a restart operation.

     The default value is 100M (100 megabytes per second).

     This parameter was added in MySQL 5.1.12.

   * `NoOfDiskPagesToDiskAfterRestartTUP'

     This table provides type and value information for the
     NoOfDiskPagesToDiskAfterRestartTUP data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   8K pages/100  40            1 -           N
                   milliseconds                4294967039    
                                               (0xFFFFFEFF)  

     When executing a local checkpoint, the algorithm flushes all data
     pages to disk. Merely doing so as quickly as possible without any
     moderation is likely to impose excessive loads on processors,
     networks, and disks. To control the write speed, this parameter
     specifies how many pages per 100 milliseconds are to be written.
     In this context, a `page' is defined as 8KB. This parameter is
     specified in units of 80KB per second, so setting
     `NoOfDiskPagesToDiskAfterRestartTUP' to a value of `20' entails
     writing 1.6MB in data pages to disk each second during a local
     checkpoint.  This value includes the writing of UNDO log records
     for data pages. That is, this parameter handles the limitation of
     writes from data memory. (See the entry for `IndexMemory' for
     information about index pages.)

     In short, this parameter specifies how quickly to execute local
     checkpoints. It operates in conjunction with
     `NoOfFragmentLogFiles', `DataMemory', and `IndexMemory'.

     For more information about the interaction between these
     parameters and possible strategies for choosing appropriate values
     for them, see *Note mysql-cluster-config-lcp-params::.

     The default value is 40 (3.2MB of data pages per second).

     *Note*:

     This parameter is deprecated as of MySQL 5.1.6. For MySQL 5.1.12
     and later versions, use `DiskCheckpointSpeed' and `DiskSyncSize'
     instead.

   * `NoOfDiskPagesToDiskAfterRestartACC'

     This table provides type and value information for the
     NoOfDiskPagesToDiskAfterRestartACC data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   8K pages/100  20            1 -           N
                   milliseconds                4294967039    
                                               (0xFFFFFEFF)  

     This parameter uses the same units as
     `NoOfDiskPagesToDiskAfterRestartTUP' and acts in a similar
     fashion, but limits the speed of writing index pages from index
     memory.

     The default value of this parameter is 20 (1.6MB of index memory
     pages per second).

     *Note*:

     This parameter is deprecated as of MySQL 5.1.6. For MySQL 5.1.12
     and later versions, use `DiskCheckpointSpeed' and `DiskSyncSize'.

   * `NoOfDiskPagesToDiskDuringRestartTUP' (DEPRECATED)

     This table provides type and value information for the
     NoOfDiskPagesToDiskDuringRestartTUP data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   8K pages/100  40            1 -           N
                   milliseconds                4294967039    
                                               (0xFFFFFEFF)  

     This parameter is used in a fashion similar to
     `NoOfDiskPagesToDiskAfterRestartTUP' and
     `NoOfDiskPagesToDiskAfterRestartACC', only it does so with regard
     to local checkpoints executed in the node when a node is
     restarting. A local checkpoint is always performed as part of all
     node restarts. During a node restart it is possible to write to
     disk at a higher speed than at other times, because fewer
     activities are being performed in the node.

     This parameter covers pages written from data memory.

     The default value is 40 (3.2MB per second).

     *Note*:

     This parameter is deprecated as of MySQL 5.1.6. For MySQL 5.1.12
     and later versions, use `DiskCheckpointSpeedInRestart' and
     `DiskSyncSize'.

   * `NoOfDiskPagesToDiskDuringRestartACC' (DEPRECATED)

     This table provides type and value information for the
     NoOfDiskPagesToDiskDuringRestartACC data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   8K pages/100  20            1 -           N
                   milliseconds                4294967039    
                                               (0xFFFFFEFF)  

     Controls the number of index memory pages that can be written to
     disk during the local checkpoint phase of a node restart.

     As with `NoOfDiskPagesToDiskAfterRestartTUP' and
     `NoOfDiskPagesToDiskAfterRestartACC', values for this parameter
     are expressed in terms of 8KB pages written per 100 milliseconds
     (80KB/second).

     The default value is 20 (1.6MB per second).

     *Note*:

     This parameter is deprecated as of MySQL 5.1.6. For MySQL 5.1.12
     and later versions, use `DiskCheckpointSpeedInRestart' and
     `DiskSyncSize'.

   * `ArbitrationTimeout'

     This table provides type and value information for the
     ArbitrationTimeout data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   milliseconds  3000          10 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.0     milliseconds  7500          10 -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter specifies how long data nodes wait for a response
     from the arbitrator to an arbitration message. If this is
     exceeded, the network is assumed to have split.

     In MySQL Cluster NDB 7.2.0 and later, the default value is 7500
     milliseconds (7.5 seconds). Previously, this was 3000 milliseconds
     (3 seconds).

   * `Arbitration'

     This table provides type and value information for the Arbitration
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.7     enumeration   Default       Default,      N
                                               Disabled,     
                                               WaitExternal  

     The `Arbitration' parameter, added in MySQL Cluster NDB 7.0.7,
     enables a choice of arbitration schemes, corresponding to one of 3
     possible values for this parameter:

        * Default

          This enables arbitration to proceed normally, as determined
          by the `ArbitrationRank' settings for the management and API
          nodes. This is the default value.

        * Disabled

          Previously, it was possible to disable arbitration only by
          setting `ArbitrationRank' to 0 on all management and API
          nodes. Now, you can now use `Arbitration = Disabled' in the
          `[ndbd default]' section of the `config.ini' file to
          accomplish this task. In this case, any `ArbitrationRank'
          settings are ignored.

        * WaitExternal

          The `Arbitration' parameter also makes it possible to
          configure arbitration in such a way that the cluster waits
          until after the time determined by `ArbitrationTimeout' has
          passed for an external cluster manager application to perform
          arbitration instead of handling arbitration internally. This
          can be done by setting `Arbitration = WaitExternal' in the
          `[ndbd default]' section of the `config.ini' file. For best
          results with the `WaitExternal' setting, it is recommended
          that `ArbitrationTimeout' be 2 times as long as the interval
          required by the external cluster manager to perform
          arbitration.

     *Important*:

     This parameter should be used only in the `[ndbd default]' section
     of the cluster configuration file. The behavior of the cluster is
     unspecified when `Arbitration' is set to different values for
     individual data nodes.

Buffering and logging

Several `[ndbd]' configuration parameters enable the advanced user to
have more control over the resources used by node processes and to
adjust various buffer sizes at need.

These buffers are used as front ends to the file system when writing
log records to disk. If the node is running in diskless mode, these
parameters can be set to their minimum values without penalty due to
the fact that disk writes are `faked' by the *Note `NDB': mysql-cluster.
storage engine's file system abstraction layer.

   * `UndoIndexBuffer'

     This table provides type and value information for the
     UndoIndexBuffer data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   unsigned      2M            1M -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     The UNDO index buffer, whose size is set by this parameter, is
     used during local checkpoints. The *Note `NDB': mysql-cluster.
     storage engine uses a recovery scheme based on checkpoint
     consistency in conjunction with an operational REDO log. To
     produce a consistent checkpoint without blocking the entire system
     for writes, UNDO logging is done while performing the local
     checkpoint. UNDO logging is activated on a single table fragment
     at a time. This optimization is possible because tables are stored
     entirely in main memory.

     The UNDO index buffer is used for the updates on the primary key
     hash index. Inserts and deletes rearrange the hash index; the NDB
     storage engine writes UNDO log records that map all physical
     changes to an index page so that they can be undone at system
     restart. It also logs all active insert operations for each
     fragment at the start of a local checkpoint.

     Reads and updates set lock bits and update a header in the hash
     index entry. These changes are handled by the page-writing
     algorithm to ensure that these operations need no UNDO logging.

     This buffer is 2MB by default. The minimum value is 1MB, which is
     sufficient for most applications. For applications doing extremely
     large or numerous inserts and deletes together with large
     transactions and large primary keys, it may be necessary to
     increase the size of this buffer. If this buffer is too small, the
     NDB storage engine issues internal error code 677 (`Index UNDO
     buffers overloaded').

     *Important*:

     It is not safe to decrease the value of this parameter during a
     rolling restart.

   * `UndoDataBuffer'

     This table provides type and value information for the
     UndoDataBuffer data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   unsigned      16M           1M -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets the size of the UNDO data buffer, which
     performs a function similar to that of the UNDO index buffer,
     except the UNDO data buffer is used with regard to data memory
     rather than index memory. This buffer is used during the local
     checkpoint phase of a fragment for inserts, deletes, and updates.

     Because UNDO log entries tend to grow larger as more operations
     are logged, this buffer is also larger than its index memory
     counterpart, with a default value of 16MB.

     This amount of memory may be unnecessarily large for some
     applications. In such cases, it is possible to decrease this size
     to a minimum of 1MB.

     It is rarely necessary to increase the size of this buffer.  If
     there is such a need, it is a good idea to check whether the disks
     can actually handle the load caused by database update activity. A
     lack of sufficient disk space cannot be overcome by increasing the
     size of this buffer.

     If this buffer is too small and gets congested, the NDB storage
     engine issues internal error code 891 (`Data UNDO buffers
     overloaded').

     *Important*:

     It is not safe to decrease the value of this parameter during a
     rolling restart.

   * `RedoBuffer'

     This table provides type and value information for the RedoBuffer
     data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         8M            1M -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         32M           1M -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     All update activities also need to be logged. The REDO log makes
     it possible to replay these updates whenever the system is
     restarted. The NDB recovery algorithm uses a `fuzzy' checkpoint of
     the data together with the UNDO log, and then applies the REDO log
     to play back all changes up to the restoration point.

     `RedoBuffer' sets the size of the buffer in which the REDO log is
     written. In MySQL Cluster NDB 6.4.3 and earlier, the default value
     is 8MB; beginning with MySQL Cluster NDB 7.0.4, the default is
     32MB. The minimum value is 1MB.

     If this buffer is too small, the *Note `NDB': mysql-cluster.
     storage engine issues error code 1221 (`REDO log buffers
     overloaded'). For this reason, you should exercise care if you
     attempt to decrease the value of `RedoBuffer' as part of an online
     change in the cluster's configuration.

     *Note `ndbmtd': mysql-cluster-programs-ndbmtd. allocates a
     separate buffer for each LDM thread (see `ThreadConfig'). For
     example, with 4 LDM threads, an *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd.  data node actually has 4 buffers
     and allocates `RedoBuffer' bytes to each one, for a total of `4 *
     RedoBuffer' bytes.

   * `EventLogBufferSize'

     This table provides type and value information for the
     EventLogBufferSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.4     bytes         8192          0 - 64K       S

     Controls the size of the circular buffer used for NDB log events
     within data nodes.

     Added in MySQL Cluster NDB 7.0.4.

Controlling log messages

In managing the cluster, it is very important to be able to control the
number of log messages sent for various event types to `stdout'. For
each event category, there are 16 possible event levels (numbered 0
through 15).  Setting event reporting for a given event category to
level 15 means all event reports in that category are sent to `stdout';
setting it to 0 means that there will be no event reports made in that
category.

By default, only the startup message is sent to `stdout', with the
remaining event reporting level defaults being set to 0. The reason for
this is that these messages are also sent to the management server's
cluster log.

An analogous set of levels can be set for the management client to
determine which event levels to record in the cluster log.

   * `LogLevelStartup'

     This table provides type and value information for the
     LogLevelStartup data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       1             0 - 15        N

     The reporting level for events generated during startup of the
     process.

     The default level is 1.

   * `LogLevelShutdown'

     This table provides type and value information for the
     LogLevelShutdown data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       0             0 - 15        N

     The reporting level for events generated as part of graceful
     shutdown of a node.

     The default level is 0.

   * `LogLevelStatistic'

     This table provides type and value information for the
     LogLevelStatistic data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       0             0 - 15        N

     The reporting level for statistical events such as number of
     primary key reads, number of updates, number of inserts,
     information relating to buffer usage, and so on.

     The default level is 0.

   * `LogLevelCheckpoint'

     This table provides type and value information for the
     LogLevelCheckpoint data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   log level     0             0 - 15        N

     The reporting level for events generated by local and global
     checkpoints.

     The default level is 0.

   * `LogLevelNodeRestart'

     This table provides type and value information for the
     LogLevelNodeRestart data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       0             0 - 15        N

     The reporting level for events generated during node restart.

     The default level is 0.

   * `LogLevelConnection'

     This table provides type and value information for the
     LogLevelConnection data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       0             0 - 15        N

     The reporting level for events generated by connections between
     cluster nodes.

     The default level is 0.

   * `LogLevelError'

     This table provides type and value information for the
     LogLevelError data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       0             0 - 15        N

     The reporting level for events generated by errors and warnings by
     the cluster as a whole. These errors do not cause any node failure
     but are still considered worth reporting.

     The default level is 0.

   * `LogLevelCongestion'

     This table provides type and value information for the
     LogLevelCongestion data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   levelr        0             0 - 15        N

     The reporting level for events generated by congestion.  These
     errors do not cause node failure but are still considered worth
     reporting.

     The default level is 0.

   * `LogLevelInfo'

     This table provides type and value information for the
     LogLevelInfo data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   integer       0             0 - 15        N

     The reporting level for events generated for information about the
     general state of the cluster.

     The default level is 0.

   * `MemReportFrequency'

     This table provides type and value information for the
     MemReportFrequency data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.1.0     unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     MySQL 5.1.16  unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter controls how often data node memory usage reports
     are recorded in the cluster log; it is an integer value
     representing the number of seconds between reports.

     Each data node's data memory and index memory usage is logged as
     both a percentage and a number of 32 KB pages of the `DataMemory'
     and `IndexMemory', respectively, set in the `config.ini' file. For
     example, if `DataMemory' is equal to 100 MB, and a given data node
     is using 50 MB for data memory storage, the corresponding line in
     the cluster log might look like this:


          2006-12-24 01:18:16 [MgmSrvr] INFO -- Node 2: Data usage is 50%(1280 32K pages of total 2560)

     `MemReportFrequency' is not a required parameter. If used, it can
     be set for all cluster data nodes in the `[ndbd default]' section
     of `config.ini', and can also be set or overridden for individual
     data nodes in the corresponding `[ndbd]' sections of the
     configuration file. The minimum value--which is also the default
     value--is 0, in which case memory reports are logged only when
     memory usage reaches certain percentages (80%, 90%, and 100%), as
     mentioned in the discussion of statistics events in *Note
     mysql-cluster-log-events::.

     This parameter was added in MySQL Cluster 5.1.16 and MySQL Cluster
     NDB 6.1.0.

   * `StartupStatusReportFrequency'

     This table provides type and value information for the
     StartupStatusReportFrequency data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.4.0     seconds       0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When a data node is started with the `--initial', it initializes
     the redo log file during Start Phase 4 (see *Note
     mysql-cluster-start-phases::). When very large values are set for
     `NoOfFragmentLogFiles', `FragmentLogFileSize', or both, this
     initialization can take a long time. Previous to MySQL Cluster NDB
     6.4.0, only the beginning and end of the redo log file
     initialization process were logged.  Beginning with this version,
     it is possible to force reports on the progress of this process to
     be logged periodically, by means of the
     `StartupStatusReportFrequency' configuration parameter. In this
     case, progress is reported in the cluster log, in terms of both
     the number of files and the amount of space that have been
     initialized, as shown here:


          2009-06-20 16:39:23 [MgmSrvr] INFO -- Node 1: Local redo log file initialization status:
          #Total files: 80, Completed: 60
          #Total MBytes: 20480, Completed: 15557
          2009-06-20 16:39:23 [MgmSrvr] INFO -- Node 2: Local redo log file initialization status:
          #Total files: 80, Completed: 60
          #Total MBytes: 20480, Completed: 15570

     These reports are logged each `StartupStatusReportFrequency'
     seconds during Start Phase 4. If `StartupStatusReportFrequency' is
     0 (the default), then reports are written to the cluster log only
     when at the beginning and at the completion of the redo log file
     initialization process.

Debugging Parameters

Beginning with MySQL Cluster NDB 6.3.36, MySQL Cluster NDB 7.0.17, and
MySQL Cluster NDB 7.1.6, it is possible to cause logging of traces for
events generated by creating and dropping tables using `DictTrace'. This
parameter is useful only in debugging NDB kernel code.  `DictTrace'
takes an integer value; currently, 0 (default - no logging) and 1
(logging enabled) are the only supported values.

Backup parameters

The `[ndbd]' parameters discussed in this section define memory buffers
set aside for execution of online backups.

   * `BackupDataBufferSize'

     This table provides type and value information for the
     BackupDataBufferSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         2M            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.3.23    bytes         16M           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         16M           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     In creating a backup, there are two buffers used for sending data
     to the disk. The backup data buffer is used to fill in data
     recorded by scanning a node's tables. Once this buffer has been
     filled to the level specified as `BackupWriteSize', the pages are
     sent to disk. While flushing data to disk, the backup process can
     continue filling this buffer until it runs out of space. When this
     happens, the backup process pauses the scan and waits until some
     disk writes have completed freeing up memory so that scanning may
     continue.

     In MySQL Cluster NDB 6.4.3 and earlier, the default value is 2MB;
     in MySQL Cluster NDB 7.0.4 and later, it is 16MB.

   * `BackupLogBufferSize'

     This table provides type and value information for the
     BackupLogBufferSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         2M            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.3.23    bytes         16M           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         16M           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     The backup log buffer fulfills a role similar to that played by
     the backup data buffer, except that it is used for generating a
     log of all table writes made during execution of the backup. The
     same principles apply for writing these pages as with the backup
     data buffer, except that when there is no more space in the backup
     log buffer, the backup fails.  For that reason, the size of the
     backup log buffer must be large enough to handle the load caused
     by write activities while the backup is being made. See *Note
     mysql-cluster-backup-configuration::.

     The default value for this parameter should be sufficient for most
     applications. In fact, it is more likely for a backup failure to
     be caused by insufficient disk write speed than it is for the
     backup log buffer to become full. If the disk subsystem is not
     configured for the write load caused by applications, the cluster
     is unlikely to be able to perform the desired operations.

     It is preferable to configure cluster nodes in such a manner that
     the processor becomes the bottleneck rather than the disks or the
     network connections.

     In MySQL Cluster NDB 6.4.3 and earlier, the default value is 2MB;
     in MySQL Cluster NDB 7.0.4 and later, it is 16MB.

   * `BackupMemory'

     This table provides type and value information for the
     BackupMemory data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         4M            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         32M           0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter is simply the sum of `BackupDataBufferSize' and
     `BackupLogBufferSize'.

     In MySQL Cluster NDB 7.0.4 and later, the default value is 16MB +
     16MB = 32MB. (Previously, it was 2MB + 2MB = 4MB.)

     *Important*:

     If `BackupDataBufferSize' and `BackupLogBufferSize' taken together
     exceed the default value for `BackupMemory', then this parameter
     must be set explicitly in the `config.ini' file to their sum.

   * `BackupReportFrequency'

     This table provides type and value information for the
     BackupReportFrequency data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.2.3     seconds       0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter controls how often backup status reports are issued
     in the management client during a backup, as well as how often
     such reports are written to the cluster log (provided cluster
     event logging is configured to permit it--see *Note
     mysql-cluster-logging-and-checkpointing::).
     `BackupReportFrequency' represents the time in seconds between
     backup status reports.

     The default value is 0.

     This parameter was added in MySQL Cluster NDB 6.2.3.

   * `BackupWriteSize'

     This table provides type and value information for the
     BackupWriteSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         32K           2K -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         256K          2K -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter specifies the default size of messages written to
     disk by the backup log and backup data buffers.

     In MySQL Cluster 6.4.3 and earlier, the default value for this
     parameter was 32KB; beginning with MySQL Cluster NDB 7.0.4, it is
     256KB.

   * `BackupMaxWriteSize'

     This table provides type and value information for the
     BackupMaxWriteSize data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.0   bytes         256K          2K -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     MySQL 5.1.32  bytes         1M            2K -          N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.2.1     bytes         1M            2K -          N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter specifies the maximum size of messages written to
     disk by the backup log and backup data buffers.

     In MySQL Cluster 6.4.3 and earlier, the default value for this
     parameter was 256KB; beginning with MySQL Cluster NDB 7.0.4, it is
     1MB.

*Important*:

When specifying these parameters, the following relationships must hold
true. Otherwise, the data node will be unable to start.

   * `BackupDataBufferSize >= BackupWriteSize + 188KB'

   * `BackupLogBufferSize >= BackupWriteSize + 16KB'

   * `BackupMaxWriteSize >= BackupWriteSize'

*MySQL Cluster Realtime Performance Parameters*

The `[ndbd]' parameters discussed in this section are used in
scheduling and locking of threads to specific CPUs on multiprocessor
data node hosts. They were introduced in MySQL Cluster NDB 6.3.4.

*Note*:

To make use of these parameters, the data node process must be run as
system root.

   * `LockExecuteThreadToCPU'

     This table provides type and value information for the
     LockExecuteThreadToCPU data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.4     CPU ID        64K           0 - 64K       N

     Previous to MySQL Cluster NDB 7.0

     This parameter specifies the ID of the CPU assigned to handle the
     *Note `NDBCLUSTER': mysql-cluster.  execution thread. The value of
     this parameter is an integer in the range 0 to 65535 (inclusive).
     The default is 65535.

     MySQL Cluster NDB 7.0 and later (beginning with MySQL Cluster NDB
     6.4.0)

     When used with *Note `ndbd': mysql-cluster-programs-ndbd, this
     parameter (now a string) specifies the ID of the CPU assigned to
     handle the *Note `NDBCLUSTER': mysql-cluster.  execution thread.

     When used with *Note `ndbmtd': mysql-cluster-programs-ndbmtd, the
     value of this parameter is a comma-separated list of CPU IDs
     assigned to handle execution threads. Each CPU ID in the list
     should be an integer in the range 0 to 65535 (inclusive). The
     number of IDs specified should match the number of execution
     threads determined by `MaxNoOfExecutionThreads'.  However, there
     is no guarantee that threads are assigned to CPUs in any given
     order when using this parameter; beginning with in MySQL Cluster
     NDB 7.0.31 and MySQL Cluster NDB 7.1.20, you can obtain more
     finely-grained control of this type using `ThreadConfig'.

     `LockExecuteThreadToCPU' has no default value.

     Prior to MySQL Cluster NDB 7.0.18 and MySQL Cluster NDB 7.1.7, the
     effective maximum value recognized by this parameter as a valid
     CPU ID was 255; using a greater value caused thread locking to be
     disabled. (Bug #56185)

   * `LockMaintThreadsToCPU'

     This table provides type and value information for the
     LockMaintThreadsToCPU data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.4     CPU ID        64K           0 - 64K       N
     NDB 6.4.0     CPU ID        [none]        0 - 64K       N

     This parameter specifies the ID of the CPU assigned to handle
     *Note `NDBCLUSTER': mysql-cluster. maintenance threads.

     The value of this parameter is an integer in the range 0 to 65535
     (inclusive). This parameter was added in MySQL Cluster NDB 6.3.4.
     Prior to MySQL Cluster NDB 6.4.0, the default is 65535; in MySQL
     Cluster NDB 7.0 and later MySQL Cluster release series, there is
     no default value.

   * `RealtimeScheduler'

     This table provides type and value information for the
     RealtimeScheduler data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.4     boolean       false         true, false   N

     Setting this parameter to 1 enables real-time scheduling of data
     node threads.

     Prior to MySQL Cluster NDB 7.0.40 and MySQL Cluster NDB 7.1.29,
     this parameter did not work correctly with data nodes running
     *Note `ndbmtd': mysql-cluster-programs-ndbmtd. (Bug #16961971)

     The default is 0 (scheduling disabled).

   * `SchedulerExecutionTimer'

     This table provides type and value information for the
     SchedulerExecutionTimer data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.4     µsec         50            0 - 11000     N

     This parameter specifies the time in microseconds for threads to
     be executed in the scheduler before being sent.  Setting it to 0
     minimizes the response time; to achieve higher throughput, you can
     increase the value at the expense of longer response times.

     The default is 50 μsec, which our testing shows to increase
     throughput slightly in high-load cases without materially delaying
     requests.

     This parameter was added in MySQL Cluster NDB 6.3.4.

   * `SchedulerSpinTimer'

     This table provides type and value information for the
     SchedulerSpinTimer data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.4     µsec         0             0 - 500       N

     This parameter specifies the time in microseconds for threads to
     be executed in the scheduler before sleeping.

     The default value is 0.

   * `BuildIndexThreads'

     This table provides type and value information for the
     BuildIndexThreads data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.30    numeric       0             0 - 128       S
     NDB 7.0.11    numeric       0             0 - 128       S

     This parameter determines the number of threads to create when
     rebuilding ordered indexes during a system or node start, as well
     as when running *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore.  `--rebuild-indexes'. It is
     supported only when there is more than one fragment for the table
     per data node (for example, when the `MAX_ROWS' option has been
     used with *Note `CREATE TABLE': create-table.).

     Setting this parameter to 0 (the default) disables multi-threaded
     building of ordered indexes.

     This parameter was added in MySQL Cluster NDB 6.3.30 and MySQL
     Cluster NDB 7.0.11. Prior to MySQL Cluster NDB 7.0.16 and MySQL
     Cluster NDB 7.1.5, it was supported only when using *Note `ndbd':
     mysql-cluster-programs-ndbd.; in these and later MySQL Cluster
     releases, `BuildIndexThreads' is also supported for data nodes
     running *Note `ndbmtd': mysql-cluster-programs-ndbmtd. (see Bug
     #54521).

     You can enable multi-threaded builds during data node initial
     restarts by setting the `TwoPassInitialNodeRestartCopy' data node
     configuration parameter to `TRUE'.

   * `TwoPassInitialNodeRestartCopy'

     This table provides type and value information for the
     TwoPassInitialNodeRestartCopy data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.1.11    boolean       false         true, false   N

     In MySQL Cluster NDB 7.1.11 and later, multi-threaded building of
     ordered indexes can be enabled for initial restarts of data nodes
     by setting this configuration parameter to `TRUE', which enables
     two-pass copying of data during initial node restarts.

     You must also set `BuildIndexThreads' to a nonzero value.

   * `Numa'

     This table provides type and value information for the Numa data
     node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.0.20    boolean       1             ...           N
     NDB 7.1.9     boolean       1             ...           N

     *Note `NDB': mysql-cluster. is extremely sensitive to Non-Uniform
     Memory Access settings and multi-CPU systems due to timeouts that
     it can cause. Due to this fact, and because most MySQL Cluster
     users do not employ `numactl', support for NUMA is ignored by
     default by *Note `ndbd': mysql-cluster-programs-ndbd. when running
     on a Linux system. If your Linux system provides NUMA support and
     you wish for data node memory to be subject to NUMA control, you
     can set this parameter equal to 0.

     The `Numa' configuration parameter is supported only on Linux
     systems where `libnuma.so' is installed.

Multi-Threading Configuration Parameters (ndbmtd)

*Note `ndbmtd': mysql-cluster-programs-ndbmtd. runs by default as a
single-threaded process and must be configured to use multiple threads,
using either of two methods, both of which require setting
configuration parameters in the `config.ini' file. The first method is
simply to set an appropriate value for the `MaxNoOfExecutionThreads'
configuration parameter. In MySQL Cluster NDB 7.1.17 and later, a
second method is also supported, whereby it is possible to set up more
complex rules for *Note `ndbmtd': mysql-cluster-programs-ndbmtd.
multi-threading using `ThreadConfig'. The next few paragraphs provide
information about these parameters and their use with multi-threaded
data nodes.

   * `MaxNoOfExecutionThreads'

     This table provides type and value information for the
     MaxNoOfExecutionThreads multi-threaded data node configuration
     parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.4.0     integer       [none]        2 - 8         N
     NDB 7.0.4     integer       2             2 - 8         N

     This parameter controls the number of execution threads used by
     *Note `ndbmtd': mysql-cluster-programs-ndbmtd, up to a maximum of
     8 threads, 4 of which can be LDM (LQH) threads. Although this
     parameter is set in the `[ndbd]' or `[ndbd default]' sections of
     the `config.ini' file, it is exclusive to *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. and does not apply to *Note `ndbd':
     mysql-cluster-programs-ndbd.

     Setting `MaxNoOfExecutionThreads' sets the number of threads by
     type as determined in the following table:

     This table shows `MaxNoOfExecutionThreads' values and the
     corresponding number of threads by thread type (LQH, TC, Send,
     Receive).

     `MaxNoOfExecutionThreads' Value     LDM      TC       Send     Receive
                                         Threads  Threads  Threads  Threads
     0 .. 3                              1        1        0        1
     4 .. 6                              2        1        0        1
     7 .. 8                              4        1        0        1

     There is always one SUMA (replication) thread.

     The thread types are described later in this section (see
     `ThreadConfig').

     Setting this parameter outside the permitted range of values
     causes the management server to abort on startup with the error
     `Error line NUMBER: Illegal value VALUE for parameter
     MaxNoOfExecutionThreads'.

     For `MaxNoOfExecutionThreads', a value of 0 or 1 is rounded up
     internally by *Note `NDB': mysql-cluster. to 2, so that 2 is
     considered this parameter's default and minimum value.

     `MaxNoOfExecutionThreads' is generally intended to be set equal to
     the number of CPU threads available, and to allocate a number of
     threads of each type suitable to typical workloads. It does not
     assign particular threads to specified CPUs. For cases where it is
     desirable to vary from the settings provided, or to bind threads to
     CPUs, you should use `ThreadConfig' instead, which allows you to
     allocate each thread directly to a desired type, CPU, or both.

     The multi-threaded data node process always spawns at least 4
     threads, listed here:

        * 1 local query handler (LDM) thread

        * 1 transaction coordinator (TC) thread

        * 1 receive thread

        * 1 subscription manager (SUMA or replication) thread

     In MySQL Cluster NDB 7.1 and earlier, it is not possible to cause
     *Note `ndbmtd': mysql-cluster-programs-ndbmtd. to use more than 1
     TC thread. (This is possible in MySQL Cluster NDB 7.2.)

   * `ThreadConfig'

     This table provides type and value information for the
     ThreadConfig multi-threaded data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.1.17    string        "             ...           N
     NDB 7.2.3     string        "             ...           N

     This parameter is used with *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. to assign threads of different
     types to different CPUs. Its value is a string whose format has
     the following syntax:


          ThreadConfig := ENTRY[,ENTRY[,...]]

          ENTRY := TYPE={PARAM[,PARAM[,...]]}

          TYPE := ldm | main | recv | rep | io

          PARAM := count=NUMBER | cpubind=CPU_LIST

     The curly braces (`{'...`}') surrounding the list of parameters is
     required, even if there is only one parameter in the list.

     A PARAM (parameter) specifies the number of threads of the given
     type (`count'), the CPUs to which the threads of the given type
     are to be bound (`cpubind'), or both.

     The TYPE attribute represents an NDB thread type. The thread types
     supported in MySQL Cluster NDB 7.1 and the range of permitted
     `count' values for each are provided in the following list:

        * `ldm': Local query handler (`DBLQH' kernel block) that handles
          data. The more LDM threads that are used, the more highly
          partitioned the data becomes. Each LDM thread maintains its
          own sets of data and index partitions, as well as its own
          redo log. In MySQL Cluster NDB 7.1, the maximum is 4 such
          threads.

          Range: 1 - 4.

        * `tc': Transaction coordinator thread (`DBTC' kernel block)
          containing the state of an ongoing transaction. In MySQL
          Cluster NDB 7.1, there can be only 1 TC thread. (In MySQL
          Cluster NDB 7.2, this number is configurable.)

          Range: 1 only.

        * `main': Data dictionary and transaction coordinator (`DBDIH'
          and `DBTC' kernel blocks), providing schema management. This
          is always handled by a single dedicated thread.

          Range: 1 only.

        * `recv': Receive thread (`CMVMI' kernel block). Each receive
          thread handles one or more sockets for communicating with
          other nodes in a MySQL Cluster, with one socket per node.
          Previously, this was limited to a single thread, but MySQL
          Cluster 7.2 implements multiple receive threads (up to 8).

          Range: 1 only.

        * `rep': Replication thread (`SUMA' kernel block). Asynchronous
          replication operations are always handled by a
          single.dedicated thread.

          Range: 1 only.

        * `io': File system and other miscellaneous operations. These
          are not demanding tasks, and are always handled as a group by
          a single, dedicated I/O thread.

          Range: 1 only.

Simple examples:


     # Example 1.

     ThreadConfig=ldm={count=2,cpubind=1,2},main={cpubind=12},rep={cpubind=11}

     # Example 2.

     Threadconfig=main={cpubind=0},ldm={count=4,cpubind=1,2,5,6},io={cpubind=3}

It is usually desirable when configuring thread usage for a data node
host to reserve one or more CPUs for operating system and other tasks.
Thus, for a host machine with 8 CPUs, you might want to use 8 CPU
threads bound to 7 CPUs (leaving one for operating system and other
functions), with 4 LDM threads, 1 TC thread, 1 receive thread, and 1
thread each for schema management, asynchronous replication, and I/O
operations. (This is almost the same distribution of threads used when
`MaxNoOfExecutionThreads' is set equal to 8.) The following
`ThreadConfig' setting performs these assignments, additionally binding
all of these threads to specific CPUs:


     ThreadConfig=ldm{count=4,cpubind=1,2,3,4},main={cpubind=5}, \
     io={cpubind=5},rep={cpubind=6},tc{cpubind=7},recv={cpubind=8}

It should be possible in most cases to bind the main (schema
management) thread and the I/O thread to the same CPU, as we have done
in the example just shown.

In order to take advantage of the enhanced stability that the use of
`ThreadConfig' offers, it is necessary to insure that CPUs are
isolated, and that they not subject to interrupts, or to being
scheduled for other tasks by the operating system. On many Linux
systems, you can do this by setting `IRQBALANCE_BANNED_CPUS' in
`/etc/sysconfig/irqbalance' to `0xFFFFF0', and by using the `isolcpus'
boot option in `grub.conf'. For specific information, see your
operating system or platform documentation.

In MySQL Cluster NDB 7.1 and earlier, it is not possible to cause *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. to use more than 1 TC thread;
this capability is introduced in MySQL Cluster NDB 7.2.

Disk Data Configuration Parameters

Configuration parameters affecting Disk Data behavior include the
following:

   * `DiskPageBufferMemory'

     This table provides type and value information for the
     DiskPageBufferMemory data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     MySQL 5.1.6   bytes         64M           4M - 1T       N

     This determines the amount of space used for caching pages on
     disk, and is set in the `[ndbd]' or `[ndbd default]' section of the
     `config.ini' file. It is measured in bytes. Each page takes up 32
     KB. This means that Cluster Disk Data storage always uses N * 32
     KB memory where N is some nonnegative integer.

     The default value for this parameter is `64M' (2000 pages of 32 KB
     each).

     This parameter was added in MySQL 5.1.6.

     Beginning with MySQL Cluster NDB 7.1.9, you can query the *Note
     `ndbinfo.diskpagebuffer': mysql-cluster-ndbinfo-diskpagebuffer.
     table to help determine whether the value for this parameter
     should be increased to minimize unnecessary disk seeks. See *Note
     mysql-cluster-ndbinfo-diskpagebuffer::, for more information.

   * `SharedGlobalMemory'

     This table provides type and value information for the
     SharedGlobalMemory data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.2.0     bytes         128M          0 - 64T       N
     MySQL 5.1.6   bytes         20M           0 - 64T       N

     This parameter determines the amount of memory that is used for
     log buffers, disk operations (such as page requests and wait
     queues), and metadata for tablespaces, log file groups, `UNDO'
     files, and data files. The shared global memory pool also provides
     memory used for satisfying the memory requirements of the
     `INITIAL_SIZE' and `UNDO_BUFFER_SIZE' options used with *Note
     `CREATE LOGFILE GROUP': create-logfile-group. and *Note `ALTER
     LOGFILE GROUP': alter-logfile-group.  statements, including any
     default value implied for these options by the setting of the
     `InitialLogFileGroup' data node configuration parameter.
     `SharedGlobalMemory' can be set in the `[ndbd]' or `[ndbd
     default]' section of the `config.ini' configuration file, and is
     measured in bytes.

     As of MySQL Cluster NDB 7.2.0, the default value is `128M'.
     (Previously, this was `20M'.)

     This parameter was added in MySQL 5.1.6.

   * `DiskIOThreadPool'

     This table provides type and value information for the
     DiskIOThreadPool data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.4.3     threads       8             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.7     threads       2             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.0     threads       2             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter determines the number of unbound threads used for
     Disk Data file access. Before `DiskIOThreadPool' was introduced,
     exactly one thread was spawned for each Disk Data file, which
     could lead to performance issues, particularly when using very
     large data files. With `DiskIOThreadPool', you can--for
     example--access a single large data file using several threads
     working in parallel.

     This parameter applies to Disk Data I/O threads only.

     The optimum value for this parameter depends on your hardware and
     configuration, and includes these factors:

        * Physical distribution of Disk Data files

          You can obtain better performance by placing data files, undo
          log files, and the data node file system on separate physical
          disks. If you do this with some or all of these sets of
          files, then you can set `DiskIOThreadPool' higher to enable
          separate threads to handle the files on each disk.

        * Disk performance and types

          The number of threads that can be accommodated for Disk Data
          file handling is also dependent on the speed and throughput
          of the disks. Faster disks and higher throughput allow for
          more disk I/O threads. Our test results indicate that
          solid-state disk drives can handle many more disk I/O threads
          than conventional disks, and thus higher values for
          `DiskIOThreadPool'.

     This parameter was added in MySQL Cluster NDB 6.4.0.  Previous to
     MySQL Cluster NDB 6.4.3, it was named `IOThreadPool'. Previous to
     MySQL Cluster NDB 7.0.7, the default value was 8. Beginning with
     MySQL Cluster NDB 7.0.7 and MySQL Cluster NDB 7.1.0, the default
     is 2.

   * Disk Data file system parameters

     The parameters in the following list were added in MySQL Cluster
     NDB 6.2.17, 6.3.22, and 6.4.3 to make it possible to place MySQL
     Cluster Disk Data files in specific directories without the need
     for using symbolic links.

        * `FileSystemPathDD'

          This table provides type and value information for the
          FileSystemPathDD data node configuration parameter

          Effective    Type/Units   Default      Range/Values *Note
          Version                                             Restart
                                                              Type:
                                                              mysql-cluster-params-ndbd.
          NDB 6.3.22   filename     [see text]   ...          IN
          NDB 6.2.17   filename     [see text]   ...          IN
          NDB 6.4.3    filename     [see text]   ...          IN

          If this parameter is specified, then MySQL Cluster Disk Data
          data files and undo log files are placed in the indicated
          directory. This can be overridden for data files, undo log
          files, or both, by specifying values for
          `FileSystemPathDataFiles', `FileSystemPathUndoFiles', or
          both, as explained for these parameters. It can also be
          overridden for data files by specifying a path in the `ADD
          DATAFILE' clause of a *Note `CREATE TABLESPACE':
          create-tablespace. or *Note `ALTER TABLESPACE':
          alter-tablespace.  statement, and for undo log files by
          specifying a path in the `ADD UNDOFILE' clause of a *Note
          `CREATE LOGFILE GROUP': create-logfile-group. or *Note `ALTER
          LOGFILE GROUP': alter-logfile-group.  statement. If
          `FileSystemPathDD' is not specified, then `FileSystemPath' is
          used.

          If a `FileSystemPathDD' directory is specified for a given
          data node (including the case where the parameter is
          specified in the `[ndbd default]' section of the `config.ini'
          file), then starting that data node with `--initial' causes
          all files in the directory to be deleted.

        * `FileSystemPathDataFiles'

          This table provides type and value information for the
          FileSystemPathDataFiles data node configuration parameter

          Effective    Type/Units   Default      Range/Values *Note
          Version                                             Restart
                                                              Type:
                                                              mysql-cluster-params-ndbd.
          NDB 6.3.22   filename     [see text]   ...          IN
          NDB 6.2.17   filename     [see text]   ...          IN
          NDB 6.4.3    filename     [see text]   ...          IN

          If this parameter is specified, then MySQL Cluster Disk Data
          data files are placed in the indicated directory.  This
          overrides any value set for `FileSystemPathDD'.  This
          parameter can be overridden for a given data file by
          specifying a path in the `ADD DATAFILE' clause of a *Note
          `CREATE TABLESPACE': create-tablespace. or *Note `ALTER
          TABLESPACE': alter-tablespace.  statement used to create that
          data file. If `FileSystemPathDataFiles' is not specified, then
          `FileSystemPathDD' is used (or `FileSystemPath', if
          `FileSystemPathDD' has also not been set).

          If a `FileSystemPathDataFiles' directory is specified for a
          given data node (including the case where the parameter is
          specified in the `[ndbd default]' section of the `config.ini'
          file), then starting that data node with `--initial' causes
          all files in the directory to be deleted.

        * `FileSystemPathUndoFiles'

          This table provides type and value information for the
          FileSystemPathUndoFiles data node configuration parameter

          Effective    Type/Units   Default      Range/Values *Note
          Version                                             Restart
                                                              Type:
                                                              mysql-cluster-params-ndbd.
          NDB 6.3.22   filename     [see text]   ...          IN
          NDB 6.2.17   filename     [see text]   ...          IN
          NDB 6.4.3    filename     [see text]   ...          IN

          If this parameter is specified, then MySQL Cluster Disk Data
          undo log files are placed in the indicated directory. This
          overrides any value set for `FileSystemPathDD'.  This
          parameter can be overridden for a given data file by
          specifying a path in the `ADD UNDO' clause of a *Note `CREATE
          LOGFILE GROUP': create-logfile-group. or *Note `CREATE
          LOGFILE GROUP': create-logfile-group. statement used to
          create that data file.  If `FileSystemPathUndoFiles' is not
          specified, then `FileSystemPathDD' is used (or
          `FileSystemPath', if `FileSystemPathDD' has also not been
          set).

          If a `FileSystemPathUndoFiles' directory is specified for a
          given data node (including the case where the parameter is
          specified in the `[ndbd default]' section of the `config.ini'
          file), then starting that data node with `--initial' causes
          all files in the directory to be deleted.

     For more information, see *Note mysql-cluster-disk-data-objects::.

   * Disk Data object creation parameters

     The next two parameters enable you--when starting the cluster for
     the first time--to cause a Disk Data log file group, tablespace,
     or both, to be created without the use of SQL statements.

        * `InitialLogFileGroup'

          This table provides type and value information for the
          InitialLogFileGroup data node configuration parameter

          Effective    Type/Units   Default      Range/Values *Note
          Version                                             Restart
                                                              Type:
                                                              mysql-cluster-params-ndbd.
          NDB 6.3.22   string       [see text]   ...          S
          NDB 6.2.17   string       [see text]   ...          S
          NDB 6.4.3    string       [see text]   ...          S

          This parameter can be used to specify a log file group that
          is created when performing an initial start of the cluster.
          `InitialLogFileGroup' is specified as shown here:


               InitialLogFileGroup = [name=NAME;] [undo_buffer_size=SIZE;] FILE-SPECIFICATION-LIST

               FILE-SPECIFICATION-LIST:
                   FILE-SPECIFICATION[; FILE-SPECIFICATION[; ...]]

               FILE-SPECIFICATION:
                   FILENAME:SIZE

          The `name' of the log file group is optional and defaults to
          `DEFAULT-LG'.  The `undo_buffer_size' is also optional; if
          omitted, it defaults to `64M'. Each FILE-SPECIFICATION
          corresponds to an undo log file, and at least one must be
          specified in the FILE-SPECIFICATION-LIST. Undo log files are
          placed according to any values that have been set for
          `FileSystemPath', `FileSystemPathDD', and
          `FileSystemPathUndoFiles', just as if they had been created
          as the result of a *Note `CREATE LOGFILE GROUP':
          create-logfile-group. or *Note `ALTER LOGFILE GROUP':
          alter-logfile-group.  statement.

          Consider the following:


               InitialLogFileGroup = name=LG1; undo_buffer_size=128M; undo1.log:250M; undo2.log:150M

          This is equivalent to the following SQL statements:


               CREATE LOGFILE GROUP LG1
                   ADD UNDOFILE 'undo1.log'
                   INITIAL_SIZE 250M
                   UNDO_BUFFER_SIZE 128M
                   ENGINE NDBCLUSTER;

               ALTER LOGFILE GROUP LG1
                   ADD UNDOFILE 'undo2.log'
                   INITIAL_SIZE 150M
                   ENGINE NDBCLUSTER;

          This logfile group is created when the data nodes are started
          with `--initial'.

          Resources for the initial log file group are taken from the
          global memory pool whose size is determined by the value of
          the `SharedGlobalMemory' data node configuration parameter;
          if this parameter is set too low and the values set in
          `InitialLogFileGroup' for the logfile group's initial size or
          undo buffer size are too high, the cluster may fail to create
          the default log file group when starting, or fail to start
          altogether.

          This parameter, if used, should always be set in the `[ndbd
          default]' section of the `config.ini' file. The behavior of a
          MySQL Cluster when different values are set on different data
          nodes is not defined.

        * `InitialTablespace'

          This table provides type and value information for the
          InitialTablespace data node configuration parameter

          Effective    Type/Units   Default      Range/Values *Note
          Version                                             Restart
                                                              Type:
                                                              mysql-cluster-params-ndbd.
          NDB 6.3.22   string       [see text]   ...          S
          NDB 6.2.17   string       [see text]   ...          S
          NDB 6.4.3    string       [see text]   ...          S

          This parameter can be used to specify a MySQL Cluster Disk
          Data tablespace that is created when performing an initial
          start of the cluster.  `InitialTablespace' is specified as
          shown here:


               InitialTablespace = [name=NAME;] [extent_size=SIZE;] FILE-SPECIFICATION-LIST

          The `name' of the tablespace is optional and defaults to
          `DEFAULT-TS'.  The `extent_size' is also optional; it
          defaults to `1M'. The FILE-SPECIFICATION-LIST uses the same
          syntax as shown with the `InitialLogfileGroup' parameter, the
          only difference being that each FILE-SPECIFICATION used with
          `InitialTablespace' corresponds to a data file. At least one
          must be specified in the FILE-SPECIFICATION-LIST. Data files
          are placed according to any values that have been set for
          `FileSystemPath', `FileSystemPathDD', and
          `FileSystemPathDataFiles', just as if they had been created
          as the result of a *Note `CREATE TABLESPACE':
          create-tablespace. or *Note `ALTER TABLESPACE':
          alter-tablespace.  statement.

          For example, consider the following line specifying
          `InitialTablespace' in the `[ndbd default]' section of the
          `config.ini' file (as with `InitialLogfileGroup', this
          parameter should always be set in the `[ndbd default]'
          section, as the behavior of a MySQL Cluster when different
          values are set on different data nodes is not defined):


               InitialTablespace = name=TS1; extent_size=8M; data1.dat:2G; data2.dat:4G

          This is equivalent to the following SQL statements:


               CREATE TABLESPACE TS1
                   ADD DATAFILE 'data1.dat'
                   EXTENT_SIZE 8M
                   INITIAL_SIZE 2G
                   ENGINE NDBCLUSTER;

               ALTER TABLESPACE TS1
                   ADD DATAFILE 'data2.dat'
                   INITIAL_SIZE 4G
                   ENGINE NDBCLUSTER;

          This tablespace is created when the data nodes are started
          with `--initial', and can be used whenever creating MySQL
          Cluster Disk Data tables thereafter.

Disk Data and GCP Stop errors

Errors encountered when using Disk Data tables such as `Node NODEID
killed this node because GCP stop was detected' (error 2303) are often
referred to as `GCP stop errors'. Such errors occur when the redo log
is not flushed to disk quickly enough; this is usually due to slow
disks and insufficient disk throughput.

You can help prevent these errors from occurring by using faster disks,
and by placing Disk Data files on a separate disk from the data node
file system. Reducing the value of `TimeBetweenGlobalCheckpoints' tends
to decrease the amount of data to be written for each global
checkpoint, and so may provide some protection against redo log buffer
overflows when trying to write a global checkpoint; however, reducing
this value also permits less time in which to write the GCP, so this
must be done with caution.

In addition, adjusting the cluster configuration as discussed here can
also help:

   * MySQL Cluster NDB 6.2 and 6.3

     When working with large amounts of data on disk under high load,
     the default value for `DiskPageBufferMemory' may not be large
     enough. In such cases, you should increase its value to include
     most of the memory available to the data nodes after accounting
     for index memory, data memory, internal buffers, and memory needed
     by the data node host operating system.

     You can use this formula as a guide:


          DiskPageBufferMemory
            = 0.8
              x (
                  [total memory]
                    - ([operating system memory] + [buffer memory] + DataMemory + IndexMemory)
                )

     Once you have established that sufficient memory is reserved for
     `DataMemory', `IndexMemory', NDB internal buffers, and operating
     system overhead, it is possible (and sometimes desirable) to
     allocate more than the above amount of the remainder to
     `DiskPageBufferMemory'.

   * MySQL Cluster NDB 7.X

     In addition to the considerations given for `DiskPageBufferMemory'
     as explained previously, it is also very important that the
     `DiskIOThreadPool' configuration parameter be set correctly; having
     `DiskIOThreadPool' set too high is very likely to cause GCP stop
     errors (Bug #37227).

GCP stops can be caused by save or commit timeouts; the
`TimeBetweenEpochsTimeout' data node configuration parameter determines
the timeout for commits. However, beginning with MySQL Cluster NDB
7.0.21 and MySQL Cluster NDB 7.1.10, it is possible to disable both
types of timeouts by setting this parameter to 0.

Parameters for configuring send buffer memory allocation (MySQL Cluster
NDB 7.0 and later)

Beginning with MySQL Cluster NDB 6.4.0, send buffer memory is allocated
dynamically from a memory pool shared between all transporters, which
means that the size of the send buffer can be adjusted as necessary.
(Previously, the NDB kernel used a fixed-size send buffer for every
node in the cluster, which was allocated when the node started and
could not be changed while the node was running.) The following data
node configuration parameters were added in MySQL Cluster NDB 6.4.0 to
permit the setting of limits on this memory allocation; this change is
reflected by the addition of the configuration parameters
`TotalSendBufferMemory' and `OverLoadLimit', as well as a change in how
the existing `SendBufferMemory' configuration parameter is used. For
more information, see *Note mysql-cluster-config-send-buffers::.

   * `ExtraSendBufferMemory'

     This parameter specifies the amount of transporter send buffer
     memory to allocate in addition to any set using
     `TotalSendBufferMemory', `SendBufferMemory', or both.

     This parameter was added in MySQL Cluster NDB 7.0.31 and MySQL
     Cluster NDB 7.1.20. (Bug #13633845, Bug #11760629, Bug #53053)

   * `TotalSendBufferMemory'

     This parameter is available beginning with MySQL Cluster NDB
     6.4.0. It is used to determine the total amount of memory to
     allocate on this node for shared send buffer memory among all
     configured transporters.

     Prior to MySQL Cluster NDB 7.0.31 and MySQL Cluster NDB 7.1.20,
     this parameter did not work correctly with *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. (Bug #13633845)

     If this parameter is set, its minimum permitted value is 256KB;
     the maxmimum is 4294967039.

   * `ReservedSendBufferMemory'

     This parameter is present in *Note `NDBCLUSTER': mysql-cluster.
     source code beginning with MySQL Cluster NDB 6.4.0. However, it is
     not currently enabled.

     As of MySQL Cluster NDB 7.0.31 and MySQL Cluster NDB 7.1.20, this
     parameter is deprecated, and is subject to removal in a future
     release of MySQL Cluster (Bug #11760629, Bug #53053).

For more detailed information about the behavior and use of
`TotalSendBufferMemory'

and about configuring send buffer memory parameters in MySQL Cluster
NDB 6.4.0 and later, see *Note mysql-cluster-config-send-buffers::.

*Note*:

Previous to MySQL Cluster NDB 7.0, to add new data nodes to a MySQL
Cluster, it was necessary to shut down the cluster completely, update
the `config.ini' file, and then restart the cluster (that is, you had
to perform a system restart). All data node processes had to be started
with the `--initial' option.

Beginning with MySQL Cluster NDB 7.0, it is possible to add new data
node groups to a running cluster online. See *Note
mysql-cluster-online-add-node::, for more information.

Redo log over-commit handling

Beginning with MySQL Cluster NDB 7.1.10, it is possible to control the
data node's handling of operations when too much time is taken flushing
redo logs to disk. This occurs when a given redo log flush takes longer
than `RedoOverCommitLimit' seconds, more than `RedoOverCommitCounter'
times, causing any pending transactions to be aborted. When this
happens, the API node that sent the transaction can handle the
operations that should have been committed either by queuing the
operations and re-trying them, or by aborting them, as determined by
`DefaultOperationRedoProblemAction'.  The data node configuration
parameters for setting the timeout and number of times it may be
exceeded before the API node takes this action are described in the
following list:

   * `RedoOverCommitCounter'

     This table provides type and value information for the
     RedoOverCommitCounter data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.1.10    numeric       3             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When `RedoOverCommitLimit' is exceeded when trying to write a
     given redo log to disk this many times or more, any transactions
     that were not committed as a result are aborted, and an API node
     where any of these transactions originated handles the operations
     making up those transactions according to its value for
     `DefaultOperationRedoProblemAction' (by either queuing the
     operations to be re-tried, or aborting them).

     `RedoOverCommitCounter' defaults to 3. Set it to 0 to disable the
     limit. This parameter was added in MySQL Cluster NDB 7.1.10.

   * `RedoOverCommitLimit'

     This table provides type and value information for the
     RedoOverCommitLimit data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 7.1.10    seconds       20            0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter sets an upper limit in seconds for trying to write
     a given redo log to disk before timing out. The number of times
     the data node tries to flush this redo log, but takes longer than
     `RedoOverCommitLimit', is kept and compared with
     `RedoOverCommitCounter', and when flushing takes too long more
     times than the value of that parameter, any transactions that were
     not committed as a result of the flush timeout are aborted. When
     this occurs, the API node where any of these transactions
     originated handles the operations making up those transactions
     according to its `DefaultOperationRedoProblemAction' setting (it
     either queues the operations to be re-tried, or aborts them).

     By default, `RedoOverCommitLimit' is 20 seconds. Set to 0 to
     disable checking for redo log flush timeouts. This parameter was
     added in MySQL Cluster NDB 7.1.10.

Controlling restart attempts

Beginning in MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.37, MySQL
Cluster NDB 7.0.18, and MySQL Cluster NDB 7.1.7, it is possible to
exercise more finely-grained control over restart attempts by data
nodes when they fail to start using two data node configuration
parameters added in these releases.  `MaxStartFailRetries' limits the
total number of retries made before giving up on starting the data node;
`StartFailRetryDelay' sets the number of seconds between retry
attempts, as described in the following list:

   * `StartFailRetryDelay'

     This table provides type and value information for the
     StartFailRetryDelay data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.37    unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.18    unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.7     unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.2.19    unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Beginning in MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.37,
     MySQL Cluster NDB 7.0.18, and MySQL Cluster NDB 7.1.7, it is
     possible to set the number of seconds between restart attempts by
     the data node in the event on failure on startup. The default is 0
     (no delay).

     *Note*:

     This parameter is ignored unless `StopOnError' is equal to 0.

   * `MaxStartFailRetries'

     This table provides type and value information for the
     MaxStartFailRetries data node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-ndbd.
     NDB 6.3.37    unsigned      3             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.18    unsigned      3             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.1.7     unsigned      3             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 6.2.19    unsigned      3             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Beginning in MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.37,
     MySQL Cluster NDB 7.0.18, and MySQL Cluster NDB 7.1.7, it is
     possible to limit the number restart attempts made by the data
     node in the event that it fails on startup.  The default is 3
     attempts.

     *Note*:

     This parameter is ignored unless `StopOnError' is equal to 0.


File: manual.info,  Node: mysql-cluster-api-definition,  Next: mysql-cluster-tcp-definition,  Prev: mysql-cluster-ndbd-definition,  Up: mysql-cluster-config-file

17.3.2.7 Defining SQL and Other API Nodes in a MySQL Cluster
............................................................

The `[mysqld]' and `[api]' sections in the `config.ini' file define the
behavior of the MySQL servers (SQL nodes) and other applications (API
nodes) used to access cluster data. None of the parameters shown is
required. If no computer or host name is provided, any host can use
this SQL or API node.

Generally speaking, a `[mysqld]' section is used to indicate a MySQL
server providing an SQL interface to the cluster, and an `[api]'
section is used for applications other than *Note `mysqld': mysqld.
processes accessing cluster data, but the two designations are actually
synonymous; you can, for instance, list parameters for a MySQL server
acting as an SQL node in an `[api]' section.

*Note*:

For a discussion of MySQL server options for MySQL Cluster, see *Note
mysql-cluster-program-options-mysqld::; for information about MySQL
server system variables relating to MySQL Cluster, see *Note
mysql-cluster-system-variables::.

   * `Id'

     This table provides type and value information for the Id API node
     configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   unsigned      [none]        1 - 63        IS
     NDB 6.1.1     unsigned      [none]        1 - 255       IS

     The `Id' is an integer value used to identify the node in all
     cluster internal messages. Prior to MySQL Cluster NDB 6.1.1, the
     permitted range of values for this parameter was 1 to 63
     inclusive. Beginning with MySQL Cluster NDB 6.1.1, the permitted
     range is 1 to 255 inclusive. This value must be unique for each
     node in the cluster, regardless of the type of node.

     *Note*:

     Data node IDs must be less than 49, regardless of the MySQL
     Cluster version used. If you plan to deploy a large number of data
     nodes, it is a good idea to limit the node IDs for API nodes (and
     management nodes) to values greater than 48.

     `NodeId' is the preferred parameter name to use when identifying
     management nodes beginning with MySQL Cluster NDB 6.2.19, MySQL
     Cluster NDB 6.3.39, MySQL Cluster NDB 7.0.20, and MySQL Cluster NDB
     7.1.9. Although `Id' continues to be supported for backward
     compatibility, it is now deprecated and generates a warning when
     used.

   * `ConnectionMap'

     This table provides type and value information for the
     ConnectionMap API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 6.1.0     string        [none]        ...           N

     Specifies which data nodes to connect. Introduced in MySQL Cluster
     NDB 6.1.0.

   * `NodeId'

     This table provides type and value information for the NodeId API
     node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   unsigned      [none]        1 - 63        IS
     NDB 6.1.1     unsigned      [none]        1 - 255       IS

     The `NodeId' is an integer value used to identify the node in all
     cluster internal messages. Prior to MySQL Cluster NDB 6.1.1, the
     permitted range of values for this parameter was 1 to 63
     inclusive. Beginning with MySQL Cluster NDB 6.1.1, the permitted
     range is 1 to 255 inclusive. This value must be unique for each
     node in the cluster, regardless of the type of node.

     *Note*:

     Data node IDs must be less than 49, regardless of the MySQL
     Cluster version used. If you plan to deploy a large number of data
     nodes, it is a good idea to limit the node IDs for API nodes (and
     management nodes) to values greater than 48.

     `NodeId' is the preferred parameter name to use when identifying
     management nodes beginning with MySQL Cluster NDB 6.2.19, MySQL
     Cluster NDB 6.3.39, MySQL Cluster NDB 7.0.20, and MySQL Cluster NDB
     7.1.9. Although `Id' continues to be supported for backward
     compatibility, it is now deprecated and generates a warning when
     used.

   * `ExecuteOnComputer'

     This table provides type and value information for the
     ExecuteOnComputer API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   name          [none]        ...           S

     This refers to the `Id' set for one of the computers (hosts)
     defined in a `[computer]' section of the configuration file.

   * `HostName'

     This table provides type and value information for the HostName
     API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     Specifying this parameter defines the hostname of the computer on
     which the SQL node (API node) is to reside. To specify a hostname,
     either this parameter or `ExecuteOnComputer' is required.

     If no `HostName' or `ExecuteOnComputer' is specified in a given
     `[mysql]' or `[api]' section of the `config.ini' file, then an SQL
     or API node may connect using the corresponding `slot' from any
     host which can establish a network connection to the management
     server host machine.  _This differs from the default behavior for
     data nodes, where `localhost' is assumed for `HostName' unless
     otherwise specified_.

   * `ArbitrationRank'

     This table provides type and value information for the
     ArbitrationRank API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   0-2           0             0 - 2         N

     This parameter defines which nodes can act as arbitrators.  Both
     management nodes and SQL nodes can be arbitrators. A value of 0
     means that the given node is never used as an arbitrator, a value
     of 1 gives the node high priority as an arbitrator, and a value of
     2 gives it low priority. A normal configuration uses the
     management server as arbitrator, setting its `ArbitrationRank' to
     1 (the default for management nodes) and those for all SQL nodes to
     0 (the default for SQL nodes).

     Beginning with MySQL 5.1.16 and MySQL Cluster NDB 6.1.3, it is
     possible to disable arbitration completely by setting
     `ArbitrationRank' to 0 on all management and SQL nodes. In MySQL
     Cluster NDB 7.0.7 and later releases, you can also control
     arbitration by overriding this parameter; to do this, set the
     `Arbitration' parameter in the `[ndbd default]' section of the
     `config.ini' global configuration file.

   * `ArbitrationDelay'

     This table provides type and value information for the
     ArbitrationDelay API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   milliseconds  0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Setting this parameter to any other value than 0 (the default)
     means that responses by the arbitrator to arbitration requests
     will be delayed by the stated number of milliseconds. It is
     usually not necessary to change this value.

   * `BatchByteSize'

     This table provides type and value information for the
     BatchByteSize API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   bytes         32K           1024 - 1M     N
     NDB 7.2.1     bytes         16K           1024 - 1M     N

     For queries that are translated into full table scans or range
     scans on indexes, it is important for best performance to fetch
     records in properly sized batches. It is possible to set the
     proper size both in terms of number of records (`BatchSize') and in
     terms of bytes (`BatchByteSize'). The actual batch size is limited
     by both parameters.

     The speed at which queries are performed can vary by more than 40%
     depending upon how this parameter is set.

     This parameter is measured in bytes. The default value is 32K.

   * `BatchSize'

     This table provides type and value information for the BatchSize
     API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   records       64            1 - 992       N
     NDB 7.2.1     records       256           1 - 992       N

     This parameter is measured in number of records and is by default
     set to 64. The maximum size is 992.

   * `ExtraSendBufferMemory'

     This table provides type and value information for the
     ExtraSendBufferMemory API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 7.0.39    bytes         0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter specifies the amount of transporter send buffer
     memory to allocate in addition to any that has been set using
     `TotalSendBufferMemory', `SendBufferMemory', or both.

     This parameter was added in MySQL Cluster NDB 7.0.39 and MySQL
     Cluster NDB 7.1.28. (Bug #14555359)

   * `HeartbeatThreadPriority'

     Beginning with MySQL Cluster NDB 6.3.32, MySQL Cluster NDB 7.0.13,
     and MySQL Cluster NDB 7.1.2, it is possible to use this parameter
     to set the scheduling policy and priority of heartbeat threads for
     management and API nodes.

     The syntax for setting this parameter is shown here:


          HeartbeatThreadPriority = POLICY[, PRIORITY]

          POLICY:
            {FIFO | RR}

     When setting this parameter, you must specify a policy. This is
     one of `FIFO' (first in, first in) or `RR' (round robin). This
     followed optionally by the priority (an integer).

   * `MaxScanBatchSize'

     This table provides type and value information for the
     MaxScanBatchSize API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     MySQL 5.1.0   bytes         256K          32K - 16M     N

     The batch size is the size of each batch sent from each data node.
     Most scans are performed in parallel to protect the MySQL Server
     from receiving too much data from many nodes in parallel; this
     parameter sets a limit to the total batch size over all nodes.

     The default value of this parameter is set to 256KB. Its maximum
     size is 16MB.

   * `TotalSendBufferMemory'

     This table provides type and value information for the
     TotalSendBufferMemory API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 6.4.0     bytes         256K          0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This parameter is available beginning with MySQL Cluster NDB
     6.4.0. It is used to determine the total amount of memory to
     allocate on this node for shared send buffer memory among all
     configured transporters.

     If this parameter is set, its minimum permitted value is 256KB;
     the maxmimum is 4294967039. For more detailed information about
     the behavior and use of `TotalSendBufferMemory' and configuring
     send buffer memory parameters in MySQL Cluster NDB 6.4.0 and
     later, see *Note mysql-cluster-config-send-buffers::.

   * `AutoReconnect'

     This table provides type and value information for the
     AutoReconnect API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 6.3.26    boolean       false         true, false   N
     NDB 7.0.7     boolean       false         true, false   N

     This parameter is available beginning with MySQL Cluster NDB
     6.3.26 and MySQL Cluster NDB 7.0.7. By default, its value is
     `false', which forces disconnected API nodes (including MySQL
     Servers acting as SQL nodes) the use a new connection to the
     cluster rather than attempting to re-use an existing one, which
     can cause problems when using dynamically-allocated node IDs. (Bug
     #45921)

     *Note*:

     This parameter can be overridden using the NDB API. For more
     information, see `Ndb_cluster_connection::set_auto_reconnect()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection-methods.html#ndb-ndb-cluster-connection-set-auto-reconnect),
     and `Ndb_cluster_connection::get_auto_reconnect()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection-methods.html#ndb-ndb-cluster-connection-get-auto-reconnect).

   * `DefaultOperationRedoProblemAction'

     This table provides type and value information for the
     DefaultOperationRedoProblemAction API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 7.1.10    enumeration   ABORT         ABORT, QUEUE  S
     NDB 7.2.1     enumeration   ABORT         ABORT, QUEUE  S

     This parameter was introduced in MySQL Cluster NDB 7.1.10 (along
     with `RedoOverCommitLimit' and `RedoOverCommitCounter') for
     controlling the data node's handling of operations when too much
     time is taken flushing redo logs to disk. This occurs when a given
     redo log flush takes longer than `RedoOverCommitLimit' seconds,
     more than `RedoOverCommitCounter' times, causing any pending
     transactions to be aborted.

     When this happens, the node can respond in either of two ways,
     according to the value of `DefaultOperationRedoProblemAction',
     listed here:

        * `ABORT': Any pending operations from aborted transactions are
          also aborted.

        * `QUEUE': Pending operations from transactions that were
          aborted are queued up to be re-tried.

     Prior to MySQL Cluster NDB 7.1.26, setting this parameter did not
     have any effect. (Bug #15855588)

   * `DefaultHashMapSize'

     This table provides type and value information for the
     DefaultHashMapSize API node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 7.0.38    LDM threads   240           0 - 3840      N
     NDB 7.1.27    LDM threads   240           0 - 3840      N

     Beginning with MySQL Cluster NDB 7.0.38 and MySQL Cluster NDB
     7.1.26, the size of the table hash maps used by *Note `NDB':
     mysql-cluster. is configurable using this parameter; previously
     this value was hard-coded.  `DefaultHashMapSize' can take any of
     three possible values (0, 240, 3840). These values and their
     effects are described in the following table.

     DefaultHashMapSize parameter values and their effects

     Value         Description / Effect
     `0'           Use the lowest value set, if any, for this parameter
                   among all data nodes and API nodes in the cluster; if
                   it is not set on any data or API node, use the
                   default value.
     `240'         Original hash map size used by default in all MySQL
                   Cluster NDB 7.1 and MySQL Cluster NDB 7.0 (and
                   earlier) releases; effectively the only value prior
                   to versions 7.0.38 and 7.1.26 (when this parameter
                   was introduced).
     `3840'        Larger hash map size available beginning with MySQL
                   Cluster NDB 7.0.38 and MySQL Cluster NDB 7.1.26

     The primary intended use for this parameter is to facilitate
     upgrades and especially downgrades between MySQL Cluster NDB 7.1
     and later MySQL Cluster versions in which the larger hash map size
     (3840) is the default; by setting this parameter to 240 prior to
     performing an upgrade, you can cause the cluster to continue using
     the smaller size for table hash maps, in which case the tables
     remain compatible with earlier versions. `DefaultHashMapSize' can
     be set for individual data nodes, API nodes, or both, but setting
     it once only, in the `[ndbd default]' section of the `config.ini'
     file, is the recommended practice. You can also set this parameter
     to 0, in which case the default value is used.

     After increasing this parameter, to have existing tables to take
     advantage of the new size, you can run *Note `ALTER TABLE ...
     REORGANIZE PARTITION': alter-table-partition-operations. on them,
     after which they can use the larger hash map size. This is in
     addition to performing a rolling restart, which makes the larger
     hash maps available to new tables, but does not enable existing
     tables to use them.

     Decreasing this parameter online after any tables have been
     created or modified with `DefaultHashMapSize' equal to 3840 is not
     currently supported.

   * `Wan'

     This table provides type and value information for the wan API
     node configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-api.
     NDB 6.1.1     boolean       false         true, false   N

     Use WAN TCP setting as default. Introduced in MySQL Cluster NDB
     6.1.1.

You can obtain some information from a MySQL server running as a
Cluster SQL node using *Note `SHOW STATUS': show-status. in the `mysql'
client, as shown here:


     mysql> SHOW STATUS LIKE 'ndb%';
     +-----------------------------+---------------+
     | Variable_name               | Value         |
     +-----------------------------+---------------+
     | Ndb_cluster_node_id         | 5             |
     | Ndb_config_from_host        | 192.168.0.112 |
     | Ndb_config_from_port        | 1186          |
     | Ndb_number_of_storage_nodes | 4             |
     +-----------------------------+---------------+
     4 rows in set (0.02 sec)

For information about these Cluster system status variables, see *Note
server-status-variables::.

*Note*:

To add new SQL or API nodes to the configuration of a running MySQL
Cluster, it is necessary to perform a rolling restart of all cluster
nodes after adding new `[mysqld]' or `[api]' sections to the
`config.ini' file (or files, if you are using more than one management
server). This must be done before the new SQL or API nodes can connect
to the cluster.

It is _not_ necessary to perform any restart of the cluster if new SQL
or API nodes can employ previously unused API slots in the cluster
configuration to connect to the cluster.


File: manual.info,  Node: mysql-cluster-tcp-definition,  Next: mysql-cluster-tcp-definition-direct,  Prev: mysql-cluster-api-definition,  Up: mysql-cluster-config-file

17.3.2.8 MySQL Cluster TCP/IP Connections
.........................................

TCP/IP is the default transport mechanism for all connections between
nodes in a MySQL Cluster. Normally it is not necessary to define TCP/IP
connections; MySQL Cluster automatically sets up such connections for
all data nodes, management nodes, and SQL or API nodes.

*Note*:

For an exception to this rule, see *Note
mysql-cluster-tcp-definition-direct::.

To override the default connection parameters, it is necessary to
define a connection using one or more `[tcp]' sections in the
`config.ini' file. Each `[tcp]' section explicitly defines a TCP/IP
connection between two MySQL Cluster nodes, and must contain at a
minimum the parameters `NodeId1' and `NodeId2', as well as any
connection parameters to override.

It is also possible to change the default values for these parameters
by setting them in the `[tcp default]' section.

*Important*:

Any `[tcp]' sections in the `config.ini' file should be listed _last_,
following all other sections in the file. However, this is not required
for a `[tcp default]' section. This requirement is a known issue with
the way in which the `config.ini' file is read by the MySQL Cluster
management server.

Connection parameters which can be set in `[tcp]' and `[tcp default]'
sections of the `config.ini' file are listed here:

   * `NodeId1'

     This table provides type and value information for the NodeId1 TCP
     configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   numeric       [none]        ...           N

     `NodeId2'

     This table provides type and value information for the NodeId2 TCP
     configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   numeric       [none]        ...           N

     To identify a connection between two nodes it is necessary to
     provide their node IDs in the `[tcp]' section of the configuration
     file. These are the same unique `NodeId' (or `Id') values for each
     of these nodes as described in *Note
     mysql-cluster-api-definition::.

   * `HostName1'

     This table provides type and value information for the HostName1
     TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     `HostName2'

     This table provides type and value information for the HostName1
     TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     The `HostName1' and `HostName2' parameters can be used to specify
     specific network interfaces to be used for a given TCP connection
     between two nodes. The values used for these parameters can be
     hostnames or IP addresses.

   * `OverloadLimit'

     This table provides type and value information for the
     OverloadLimit TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     NDB 6.4.0     bytes         0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Beginning in MySQL Cluster NDB 6.4.0, this parameter can be used
     to determine the amount of unsent data that must be present in the
     send buffer before the connection is considered overloaded. See
     *Note mysql-cluster-config-send-buffers::, for more information.

     Prior to MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16,
     the effective value of this parameter was limited by the size of
     `SendBufferMemory'; beginning with these releases, the actual
     value for `OverloadLimit' (up to the stated maximum of 4G) is used
     instead.

   * `SendBufferMemory'

     This table provides type and value information for the
     SendBufferMemory TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      256K          64K -         N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     unsigned      2M            256K -        N
                                               4294967039    
                                               (0xFFFFFEFF)  

     TCP transporters use a buffer to store all messages before
     performing the send call to the operating system. When this buffer
     reaches 64KB its contents are sent; these are also sent when a
     round of messages have been executed. To handle temporary overload
     situations it is also possible to define a bigger send buffer.

     Prior to MySQL Cluster NDB 7.0, this parameter determines a fixed
     amount of memory allocated at startup for each configured TCP
     connection. Beginning with MySQL Cluster NDB 6.4.0, if this
     parameter is set explicitly, then the memory is not dedicated to
     each transporter; instead, the value used denotes the hard limit
     for how much memory (out of the total available memory--that is,
     `TotalSendBufferMemory') that may be used by a single transporter.
     For more information about configuring dynamic transporter send
     buffer memory allocation in MySQL Cluster NDB 7.0 and later, see
     *Note mysql-cluster-config-send-buffers::.

     In MySQL Cluster NDB 6.4.3 and earlier, the default size of the
     send buffer was 256 KB; in MySQL Cluster NDB 7.0.4 and later, it
     is 2MB, which is the size recommended in most situations. The
     minimum size is 64 KB; the theoretical maximum is 4 GB.

   * `SendSignalId'

     This table provides type and value information for the
     SendSignalId TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   boolean       [see text]    true, false   N

     To be able to retrace a distributed message datagram, it is
     necessary to identify each message. When this parameter is set to
     `Y', message IDs are transported over the network. This feature is
     disabled by default in production builds, and enabled in `-debug'
     builds.

   * `Checksum'

     This table provides type and value information for the Checksum
     TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   boolean       false         true, false   N

     This parameter is a boolean parameter (enabled by setting it to
     `Y' or `1', disabled by setting it to `N' or `0').  It is disabled
     by default. When it is enabled, checksums for all messages are
     calculated before they placed in the send buffer. This feature
     ensures that messages are not corrupted while waiting in the send
     buffer, or by the transport mechanism.

   * `PortNumber' (_OBSOLETE_)

     This formerly specified the port number to be used for listening
     for connections from other nodes. This parameter should no longer
     be used; use the `ServerPort' data node configuration parameter
     for this purpose instead.

   * `ReceiveBufferMemory'

     This table provides type and value information for the
     ReceiveBufferMemory TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   bytes         64K           16K -         N
                                               4294967039    
                                               (0xFFFFFEFF)  
     NDB 7.0.4     bytes         2M            16K -         N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Specifies the size of the buffer used when receiving data from the
     TCP/IP socket.

     In MySQL Cluster NDB 6.4.3 and earlier, the default value of this
     parameter was 64 KB; beginning with MySQL Cluster NDB 7.0.4, 2MB
     is the default. The minimum possible value is 16KB; the
     theoretical maximum is 4GB.

   * `TCP_RCV_BUF_SIZE'

     This table provides type and value information for the
     TCP_RCV_BUF_SIZE TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     NDB 6.1.1     unsigned      70080         1 - 2G        N

     Determines the size of the receive buffer set during TCP
     transporter initialization. The default is recommended for most
     common usage cases.

     `TCP_RCV_BUF_SIZE' was added in MySQL Cluster NDB 6.1.1.

   * `TCP_SND_BUF_SIZE'

     This table provides type and value information for the
     TCP_SND_BUF_SIZE TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     NDB 6.1.1     unsigned      71540         1 - 2G        N

     Determines the size of the send buffer set during TCP transporter
     initialization. The default is recommended for most common usage
     cases.

     `TCP_SND_BUF_SIZE' was added in MySQL Cluster NDB 6.1.1.

   * `TCP_MAXSEG_SIZE'

     This table provides type and value information for the
     TCP_MAXSEG_SIZE TCP configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     NDB 6.1.1     unsigned      0             0 - 2G        N

     Determines the size of the memory set during TCP transporter
     initialization. The default is recommended for most common usage
     cases.

     `TCP_MAXSEG_SIZE' was added in MySQL Cluster NDB 6.1.1.

   * `TcpBind_INADDR_ANY'

     Setting this parameter to `TRUE' or `1' binds `IP_ADDR_ANY' so
     that connections can be made from anywhere (for autogenerated
     connections). The default is `FALSE' (`0').

     This parameter was added in MySQL Cluster NDB 6.2.0.


File: manual.info,  Node: mysql-cluster-tcp-definition-direct,  Next: mysql-cluster-shm-definition,  Prev: mysql-cluster-tcp-definition,  Up: mysql-cluster-config-file

17.3.2.9 MySQL Cluster TCP/IP Connections Using Direct Connections
..................................................................

Setting up a cluster using direct connections between data nodes
requires specifying explicitly the crossover IP addresses of the data
nodes so connected in the `[tcp]' section of the cluster `config.ini'
file.

In the following example, we envision a cluster with at least four
hosts, one each for a management server, an SQL node, and two data
nodes. The cluster as a whole resides on the `172.23.72.*' subnet of a
LAN. In addition to the usual network connections, the two data nodes
are connected directly using a standard crossover cable, and
communicate with one another directly using IP addresses in the
`1.1.0.*' address range as shown:


     # Management Server
     [ndb_mgmd]
     Id=1
     HostName=172.23.72.20

     # SQL Node
     [mysqld]
     Id=2
     HostName=172.23.72.21

     # Data Nodes
     [ndbd]
     Id=3
     HostName=172.23.72.22

     [ndbd]
     Id=4
     HostName=172.23.72.23

     # TCP/IP Connections
     [tcp]
     NodeId1=3
     NodeId2=4
     HostName1=1.1.0.1
     HostName2=1.1.0.2

The `HostName1' and `HostName2' parameters are used only when
specifying direct connections.

The use of direct TCP connections between data nodes can improve the
cluster's overall efficiency by enabling the data nodes to bypass an
Ethernet device such as a switch, hub, or router, thus cutting down on
the cluster's latency. It is important to note that to take the best
advantage of direct connections in this fashion with more than two data
nodes, you must have a direct connection between each data node and
every other data node in the same node group.


File: manual.info,  Node: mysql-cluster-shm-definition,  Next: mysql-cluster-sci-definition,  Prev: mysql-cluster-tcp-definition-direct,  Up: mysql-cluster-config-file

17.3.2.10 MySQL Cluster Shared-Memory Connections
.................................................

MySQL Cluster attempts to use the shared memory transporter and
configure it automatically where possible.  `[shm]' sections in the
`config.ini' file explicitly define shared-memory connections between
nodes in the cluster. When explicitly defining shared memory as the
connection method, it is necessary to define at least `NodeId1',
`NodeId2', and `ShmKey'. All other parameters have default values that
should work well in most cases.

*Important*:

_SHM functionality is considered experimental only_. It is not
officially supported in any current MySQL Cluster release, and testing
results indicate that SHM performance is not appreciably greater than
when using TCP/IP for the transporter.

For these reasons, you must determine for yourself or by using our free
resources (forums, mailing lists) whether SHM can be made to work
correctly in your specific case.

   * `NodeId1'

     This table provides type and value information for the NodeId1
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   numeric       [none]        ...           N

     `NodeId2'

     This table provides type and value information for the NodeId2
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   numeric       [none]        ...           N

     To identify a connection between two nodes it is necessary to
     provide node identifiers for each of them, as `NodeId1' and
     `NodeId2'.

   * `HostName1'

     This table provides type and value information for the HostName1
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     `HostName2'

     This table provides type and value information for the HostName1
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     The `HostName1' and `HostName2' parameters can be used to specify
     specific network interfaces to be used for a given SHM connection
     between two nodes. The values used for these parameters can be
     hostnames or IP addresses.

   * `OverloadLimit'

     This table provides type and value information for the
     OverloadLimit shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     NDB 6.4.0     bytes         0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Beginning in MySQL Cluster NDB 6.4.0, this parameter can be used
     to determine the amount of unsent data that must be present in the
     send buffer before the connection is considered overloaded. See
     *Note mysql-cluster-config-send-buffers::, for more information.

     Prior to MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16,
     the effective value of this parameter was limited by the size of
     `SendBufferMemory'; beginning with these releases, the actual
     value for `OverloadLimit' (up to the stated maximum) is used
     instead.

   * `ShmKey'

     This table provides type and value information for the ShmKey
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      [none]        0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When setting up shared memory segments, a node ID, expressed as an
     integer, is used to identify uniquely the shared memory segment to
     use for the communication. There is no default value.

   * `ShmSize'

     This table provides type and value information for the ShmSize
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   bytes         1M            64K -         N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Each SHM connection has a shared memory segment where messages
     between nodes are placed by the sender and read by the reader. The
     size of this segment is defined by `ShmSize'. The default value is
     1MB.

   * `SendSignalId'

     This table provides type and value information for the
     SendSignalId shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   boolean       false         true, false   N

     To retrace the path of a distributed message, it is necessary to
     provide each message with a unique identifier.  Setting this
     parameter to `Y' causes these message IDs to be transported over
     the network as well. This feature is disabled by default in
     production builds, and enabled in `-debug' builds.

   * `Checksum'

     This table provides type and value information for the Checksum
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   boolean       true          true, false   N

     This parameter is a boolean (`Y'/`N') parameter which is disabled
     by default. When it is enabled, checksums for all messages are
     calculated before being placed in the send buffer.

     This feature prevents messages from being corrupted while waiting
     in the send buffer. It also serves as a check against data being
     corrupted during transport.

   * `SigNum'

     This table provides type and value information for the Signum
     shared memory configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      [none]        0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When using the shared memory transporter, a process sends an
     operating system signal to the other process when there is new
     data available in the shared memory. Should that signal conflict
     with an existing signal, this parameter can be used to change it.
     This is a possibility when using SHM due to the fact that
     different operating systems use different signal numbers.

     The default value of `SigNum' is 0; therefore, it must be set to
     avoid errors in the cluster log when using the shared memory
     transporter. Typically, this parameter is set to 10 in the `[shm
     default]' section of the `config.ini' file.


File: manual.info,  Node: mysql-cluster-sci-definition,  Next: mysql-cluster-config-lcp-params,  Prev: mysql-cluster-shm-definition,  Up: mysql-cluster-config-file

17.3.2.11 SCI Transport Connections in MySQL Cluster
....................................................

`[sci]' sections in the `config.ini' file explicitly define SCI
(Scalable Coherent Interface) connections between cluster nodes.  Using
SCI transporters in MySQL Cluster is supported only when the MySQL
binaries are built using `--with-ndb-sci=/YOUR/PATH/TO/SCI'.  The PATH
should point to a directory that contains at a minimum `lib' and
`include' directories containing SISCI libraries and header files. (See
*Note mysql-cluster-interconnects:: for more information about SCI.)

In addition, SCI requires specialized hardware.

It is strongly recommended to use SCI Transporters only for
communication between *Note `ndbd': mysql-cluster-programs-ndbd.
processes. Note also that using SCI Transporters means that the *Note
`ndbd': mysql-cluster-programs-ndbd. processes never sleep. For this
reason, SCI Transporters should be used only on machines having at least
two CPUs dedicated for use by *Note `ndbd':
mysql-cluster-programs-ndbd. processes.  There should be at least one
CPU per *Note `ndbd': mysql-cluster-programs-ndbd.  process, with at
least one CPU left in reserve to handle operating system activities.

   * `NodeId1'

     This table provides type and value information for the NodeId1 SCI
     configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   numeric       [none]        ...           N

     `NodeId2'

     This table provides type and value information for the NodeId2 SCI
     configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   numeric       [none]        ...           N

     To identify a connection between two nodes it is necessary to
     provide node identifiers for each of them, as `NodeId1' and
     `NodeId2'.

   * `Host1SciId0'

     This table provides type and value information for the Host1SciId0
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      [none]        0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This identifies the SCI node ID on the first Cluster node
     (identified by `NodeId1').

   * `Host1SciId1'

     This table provides type and value information for the Host1SciId1
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     It is possible to set up SCI Transporters for failover between two
     SCI cards which then should use separate networks between the
     nodes. This identifies the node ID and the second SCI card to be
     used on the first node.

   * `Host2SciId0'

     This table provides type and value information for the Host2SciId0
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      [none]        0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     This identifies the SCI node ID on the second Cluster node
     (identified by `NodeId2').

   * `Host2SciId1'

     This table provides type and value information for the Host2SciId1
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When using two SCI cards to provide failover, this parameter
     identifies the second SCI card to be used on the second node.

   * `HostName1'

     This table provides type and value information for the HostName1
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     `HostName2'

     This table provides type and value information for the HostName1
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   name or IP    [none]        ...           N
                   address                                   

     The `HostName1' and `HostName2' parameters can be used to specify
     specific network interfaces to be used for a given SCI connection
     between two nodes. The values used for these parameters can be
     hostnames or IP addresses.

   * `SharedBufferSize'

     This table provides type and value information for the
     SharedBufferSize SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      10M           64K -         N
                                               4294967039    
                                               (0xFFFFFEFF)  

     Each SCI transporter has a shared memory segment used for
     communication between the two nodes. Setting the size of this
     segment to the default value of 1MB should be sufficient for most
     applications. Using a smaller value can lead to problems when
     performing many parallel inserts; if the shared buffer is too
     small, this can also result in a crash of the *Note `ndbd':
     mysql-cluster-programs-ndbd. process.

   * `SendLimit'

     This table provides type and value information for the SendLimit
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   unsigned      8K            128 - 32K     N

     A small buffer in front of the SCI media stores messages before
     transmitting them over the SCI network. By default, this is set to
     8KB. Our benchmarks show that performance is best at 64KB but 16KB
     reaches within a few percent of this, and there was little if any
     advantage to increasing it beyond 8KB.

   * `SendSignalId'

     This table provides type and value information for the
     SendSignalId SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   boolean       true          true, false   N

     To trace a distributed message it is necessary to identify each
     message uniquely. When this parameter is set to `Y', message IDs
     are transported over the network. This feature is disabled by
     default in production builds, and enabled in `-debug' builds.

   * `Checksum'

     This table provides type and value information for the Checksum
     SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     MySQL 5.1.0   boolean       false         true, false   N

     This parameter is a boolean value, and is disabled by default.
     When `Checksum' is enabled, checksums are calculated for all
     messages before they are placed in the send buffer. This feature
     prevents messages from being corrupted while waiting in the send
     buffer. It also serves as a check against data being corrupted
     during transport.

   * `OverloadLimit'

     This table provides type and value information for the
     OverloadLimit SCI configuration parameter

     Effective     Type/Units    Default       Range/Values  *Note
     Version                                                 Restart
                                                             Type:
                                                             mysql-cluster-params-other.
     NDB 6.4.0     bytes         0             0 -           N
                                               4294967039    
                                               (0xFFFFFEFF)  

     When more than this many unsent bytes are in the send buffer, the
     connection is considered overloaded. See *Note
     mysql-cluster-config-send-buffers::, for more information.


File: manual.info,  Node: mysql-cluster-config-lcp-params,  Next: mysql-cluster-config-send-buffers,  Prev: mysql-cluster-sci-definition,  Up: mysql-cluster-config-file

17.3.2.12 Configuring MySQL Cluster Parameters for Local Checkpoints
....................................................................

The parameters discussed in Logging and Checkpointing and in Data
Memory, Index Memory, and String Memory that are used to configure
local checkpoints for a MySQL Cluster do not exist in isolation, but
rather are very much interdepedent on each other.  In this section, we
illustrate how these parameters--including `DataMemory', `IndexMemory',
`NoOfDiskPagesToDiskAfterRestartTUP',
`NoOfDiskPagesToDiskAfterRestartACC', and `NoOfFragmentLogFiles'--relate
to one another in a working Cluster.

*Important*:

The parameters `NoOfDiskPagesToDiskAfterRestartTUP' and
`NoOfDiskPagesToDiskAfterRestartACC' were deprecated in MySQL 5.1.6.
From MySQL 5.1.6 through 5.1.11, disk writes during LCPs took place at
the maximum speed possible. Beginning with MySQL 5.1.12, the speed and
throughput for LCPs are controlled using the parameters `DiskSyncSize',
`DiskCheckpointSpeed', and `DiskCheckpointSpeedInRestart'.  See *Note
mysql-cluster-ndbd-definition::.

In this example, we assume that our application performs the following
numbers of types of operations per hour:

   * 50000 selects

   * 15000 inserts

   * 15000 updates

   * 15000 deletes

We also make the following assumptions about the data used in the
application:

   * We are working with a single table having 40 columns.

   * Each column can hold up to 32 bytes of data.

   * A typical *Note `UPDATE': update. run by the application affects
     the values of 5 columns.

   * No `NULL' values are inserted by the application.

A good starting point is to determine the amount of time that should
elapse between local checkpoints (LCPs). It is worth noting that, in
the event of a system restart, it takes 40-60 percent of this interval
to execute the REDO log--for example, if the time between LCPs is 5
minutes (300 seconds), then it should take 2 to 3 minutes (120 to 180
seconds) for the REDO log to be read.

The maximum amount of data per node can be assumed to be the size of
the `DataMemory' parameter. In this example, we assume that this is 2
GB. The `NoOfDiskPagesToDiskAfterRestartTUP' parameter represents the
amount of data to be checkpointed per unit time--however, this
parameter is actually expressed as the number of 8K memory pages to be
checkpointed per 100 milliseconds. 2 GB per 300 seconds is
approximately 6.8 MB per second, or 700 KB per 100 milliseconds, which
works out to roughly 85 pages per 100 milliseconds.

Similarly, we can calculate `NoOfDiskPagesToDiskAfterRestartACC' in
terms of the time for local checkpoints and the amount of memory
required for indexes--that is, the `IndexMemory'. Assuming that we
permit 512 MB for indexes, this works out to approximately 20 8-KB
pages per 100 milliseconds for this parameter.

Next, we need to determine the number of REDO log files required--that
is, fragment log files--the corresponding parameter being
`NoOfFragmentLogFiles'. We need to make sure that there are sufficient
REDO log files for keeping records for at least 3 local checkpoints (in
MySQL Cluster NDB 6.3.8 and later, we need only allow for 2 local
checkpoints). In a production setting, there are always
uncertainties--for instance, we cannot be sure that disks always
operate at top speed or with maximum throughput. For this reason, it is
best to err on the side of caution, so we double our requirement and
calculate a number of fragment log files which should be enough to keep
records covering 6 local checkpoints (in MySQL Cluster NDB 6.3.8 and
later, a number of fragment log files accommodating 4 local checkpoints
should be sufficient).

It is also important to remember that the disk also handles writes to
the REDO log, so if you find that the amount of data being written to
disk as determined by the values of `NoOfDiskPagesToDiskAfterRestartACC'
and `NoOfDiskPagesToDiskAfterRestartTUP' is approaching the amount of
disk bandwidth available, you may wish to increase the time between
local checkpoints.

Given 5 minutes (300 seconds) per local checkpoint, this means that we
need to support writing log records at maximum speed for 6 * 300 = 1800
seconds (_MySQL Cluster NDB 6.3.8 and later_: 4 * 300 = 1200 seconds).
The size of a REDO log record is 72 bytes plus 4 bytes per updated
column value plus the maximum size of the updated column, and there is
one REDO log record for each table record updated in a transaction, on
each node where the data reside. Using the numbers of operations set
out previously in this section, we derive the following:

   * 50000 select operations per hour yields 0 log records (and thus 0
     bytes), since *Note `SELECT': select.  statements are not recorded
     in the REDO log.

   * 15000 *Note `DELETE': delete. statements per hour is approximately
     5 delete operations per second. (Since we wish to be conservative
     in our estimate, we round up here and in the following
     calculations.) No columns are updated by deletes, so these
     statements consume only 5 operations * 72 bytes per operation =
     360 bytes per second.

   * 15000 *Note `UPDATE': update. statements per hour is roughly the
     same as 5 updates per second. Each update uses 72 bytes, plus 4
     bytes per column * 5 columns updated, plus 32 bytes per column * 5
     columns--this works out to 72 + 20 + 160 = 252 bytes per
     operation, and multiplying this by 5 operation per second yields
     1260 bytes per second.

   * 15000 *Note `INSERT': insert. statements per hour is equivalent to
     5 insert operations per second. Each insert requires REDO log
     space of 72 bytes, plus 4 bytes per record * 40 columns, plus 32
     bytes per column * 40 columns, which is 72 + 160 + 1280 = 1512
     bytes per operation. This times 5 operations per second yields
     7560 bytes per second.

So the total number of REDO log bytes being written per second is
approximately 0 + 360 + 1260 + 7560 = 9180 bytes. Multiplied by 1800
seconds, this yields 16524000 bytes required for REDO logging, or
approximately 15.75 MB. The unit used for `NoOfFragmentLogFiles'
represents a set of 4 16-MB log files--that is, 64 MB.  Thus, the
minimum value (3) for this parameter is sufficient for the scenario
envisioned in this example, since 3 times 64 = 192 MB, or about 12
times what is required; the default value of 8 (or 512 MB) is more than
ample in this case.


File: manual.info,  Node: mysql-cluster-config-send-buffers,  Prev: mysql-cluster-config-lcp-params,  Up: mysql-cluster-config-file

17.3.2.13 Configuring MySQL Cluster Send Buffer Parameters
..........................................................

Formerly, the NDB kernel used a send buffer whose size was fixed at 2MB
for every node in the cluster, which was allocated when the node
started. Because the size of this buffer could not be changed after the
cluster was started, it was necessary to make it large enough in
advance to accommodate the maximum possible load on any transporter
socket. However, this was an inefficient use of memory, since much of
it often went unused, and could result in large amounts of resources
being wasted when scaling up to many API nodes.

Beginning with MySQL Cluster NDB 7.0, this problem is solved by
employing a unified send buffer whose memory is allocated dynamically
from a pool shared by all transporters. This means that the size of the
send buffer can be adjusted as necessary.  Configuration of the unified
send buffer can accomplished by setting the following parameters:

   * TotalSendBufferMemory

     This parameter can be set for all types of MySQL Cluster
     nodes--that is, it can be set in the `[ndbd]', `[mgm]', and
     `[api]' (or `[mysql]') sections of the `config.ini' file. It
     represents the total amount of memory (in bytes) to be allocated
     by each node for which it is set for use among all configured
     transporters. If set, its minimum is 256KB; the maximum is
     4294967039.

     To be backward-compatible with existing configurations, this
     parameter takes as its default value the sum of the maximum send
     buffer sizes of all configured transporters, plus an additional
     32KB (one page) per transporter. The maximum depends on the type
     of transporter, as shown in the following table:

     This table lists transporter types and the maximum send buffer
     size (bytes).

     Transporter          Maximum Send Buffer Size (bytes)
     TCP                  `SendBufferMemory' (default = 2M)
     SCI                  `SendLimit' (default = 8K) plus 16K
     SHM                  20K

     This enables existing configurations to function in close to the
     same way as they did with MySQL Cluster NDB 6.3 and earlier, with
     the same amount of memory and send buffer space available to each
     transporter. However, memory that is unused by one transporter is
     not available to other transporters.

   * OverloadLimit

     This parameter is used in the `config.ini' file `[tcp]' section,
     and denotes the amount of unsent data (in bytes) that must be
     present in the send buffer before the connection is considered
     overloaded.  When such an overload condition occurs, transactions
     that affect the overloaded connection fail with NDB API Error 1218
     (`Send Buffers overloaded in NDB kernel') until the overload
     status passes. The default value is 0, in which case the effective
     overload limit is calculated as `SendBufferMemory * 0.8' for a
     given connection. The maximum value for this parameter is 4G.

   * SendBufferMemory

     In MySQL Cluster NDB 6.3 and earlier, this TCP configuration
     parameter represented the amount of memory allocated at startup
     for each configured TCP connection.  Beginning with MySQL Cluster
     NDB 7.0, this value denotes a hard limit for the amount of memory
     that may be used by a single transporter out of the entire pool
     specified by `TotalSendBufferMemory'.  However, the sum of
     `SendBufferMemory' for all configured transporters may be greater
     than the `TotalSendBufferMemory' that is set for a given node.
     This is a way to save memory when many nodes are in use, as long
     as the maximum amount of memory is never required by all
     transporters at the same time.


File: manual.info,  Node: mysql-cluster-params-overview,  Next: mysql-cluster-options-variables,  Prev: mysql-cluster-config-file,  Up: mysql-cluster-configuration

17.3.3 Overview of MySQL Cluster Configuration Parameters
---------------------------------------------------------

* Menu:

* mysql-cluster-params-ndbd::    MySQL Cluster Data Node Configuration Parameters
* mysql-cluster-params-mgmd::    MySQL Cluster Management Node Configuration Parameters
* mysql-cluster-params-api::     MySQL Cluster SQL Node and API Node Configuration Parameters
* mysql-cluster-params-other::   Other MySQL Cluster Configuration Parameters

The next four sections provide summary tables of MySQL Cluster
configuration parameters used in the `config.ini' file to govern the
cluster's functioning. Each table lists the parameters for one of the
Cluster node process types (*Note `ndbd': mysql-cluster-programs-ndbd,
*Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd, and *Note `mysqld':
mysqld.), and includes the parameter's type as well as its default,
minimum, and maximum values as applicable.

These tables also indicate what type of restart is required (node
restart or system restart)--and whether the restart must be done with
`--initial'--to change the value of a given configuration parameter.

When performing a node restart or an initial node restart, all of the
cluster's data nodes must be restarted in turn (also referred to as a
_rolling restart_). It is possible to update cluster configuration
parameters marked as `node' online--that is, without shutting down the
cluster--in this fashion. An initial node restart requires restarting
each *Note `ndbd': mysql-cluster-programs-ndbd. process with the
`--initial' option.

A system restart requires a complete shutdown and restart of the entire
cluster. An initial system restart requires taking a backup of the
cluster, wiping the cluster file system after shutdown, and then
restoring from the backup following the restart.

In any cluster restart, all of the cluster's management servers must be
restarted for them to read the updated configuration parameter values.

*Important*:

Values for numeric cluster parameters can generally be increased
without any problems, although it is advisable to do so progressively,
making such adjustments in relatively small increments. Many of these
can be increased online, using a rolling restart.

However, decreasing the values of such parameters--whether this is done
using a node restart, node initial restart, or even a complete system
restart of the cluster--is not to be undertaken lightly; it is
recommended that you do so only after careful planning and testing.
This is especially true with regard to those parameters that relate to
memory usage and disk space, such as `MaxNoOfTables',
`MaxNoOfOrderedIndexes', and `MaxNoOfUniqueHashIndexes'.  In addition,
it is the generally the case that configuration parameters relating to
memory and disk usage can be raised using a simple node restart, but
they require an initial node restart to be lowered.

Because some of these parameters can be used for configuring more than
one type of cluster node, they may appear in more than one of the
tables.

*Note*:

`4294967039' often appears as a maximum value in these tables. This
value is defined in the *Note `NDBCLUSTER': mysql-cluster. sources as
`MAX_INT_RNIL' and is equal to `0xFFFFFEFF', or `2^32 - 2^8 - 1'.


File: manual.info,  Node: mysql-cluster-params-ndbd,  Next: mysql-cluster-params-mgmd,  Prev: mysql-cluster-params-overview,  Up: mysql-cluster-params-overview

17.3.3.1 MySQL Cluster Data Node Configuration Parameters
.........................................................

The summary table in this section provides information about parameters
used in the `[ndbd]' or `[ndbd default]' sections of a `config.ini'
file for configuring MySQL Cluster data nodes. For detailed
descriptions and other additional information about each of these
parameters, see *Note mysql-cluster-ndbd-definition::.

Beginning with MySQL Cluster NDB 6.4.0, these parameters also apply to
*Note `ndbmtd': mysql-cluster-programs-ndbmtd, which is a multi-threaded
version of *Note `ndbd': mysql-cluster-programs-ndbd. For more
information, see *Note mysql-cluster-programs-ndbmtd::.

Restart types

Changes in MySQL Cluster configuration parameters do not take effect
until the cluster is restarted. The type of restart required to change
a given parameter is indicated in the summary table as follows:

   * `N'--Node restart: The parameter can be updated using a rolling
     restart (see *Note mysql-cluster-rolling-restart::).

   * `S'--System restart: The cluster must be shut down completely,
     then restarted, to effect a change in this parameter.

   * `I'--Initial restart: Data nodes must be restarted using the
     `--initial' option.

For more information about restart types, see *Note
mysql-cluster-params-overview::.

*Data Node Configuration Parameters*

This table describes MySQL Cluster Data Node configuration parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`Arbitration'                               enumeration  N         NDB 7.0.7
Default                                                            
Default, Disabled, WaitExternal                                    
`ArbitrationTimeout'                        milliseconds N         NDB 7.2.0
7500                                                               
10 / 4294967039 (0xFFFFFEFF)                                       
`BackupDataBufferSize'                      bytes        N         NDB 7.0.4
16M                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`BackupDataDir'                             path         IN        all
                                                                   5.1-based
FileSystemPath                                                     
...                                                                
`BackupLogBufferSize'                       bytes        N         NDB 7.0.4
16M                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`BackupMaxWriteSize'                        bytes        N         5.1.32
1M                                                                 
2K / 4294967039 (0xFFFFFEFF)                                       
`BackupMemory'                              bytes        N         NDB 7.0.4
32M                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`BackupReportFrequency'                     seconds      N         NDB 6.2.3
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`BackupWriteSize'                           bytes        N         NDB 7.0.4
256K                                                               
2K / 4294967039 (0xFFFFFEFF)                                       
`BatchSizePerLocalScan'                     integer      N         NDB 7.2.1
256                                                                
1 / 992                                                            
`BuildIndexThreads'                         numeric      S         NDB
                                                                   7.0.11
0                                                                  
0 / 128                                                            
`CompressedBackup'                          boolean      N         NDB 6.3.7
false                                                              
true, false                                                        
`CompressedLCP'                             boolean      N         NDB 6.3.7
false                                                              
true, false                                                        
`ConnectCheckIntervalDelay'                 string       N         NDB
                                                                   7.1.13
1500                                                               
0 / 4294967039 (0xFFFFFEFF)                                        
`CrashOnCorruptedTuple'                     boolean      S         NDB
                                                                   7.0.28,
                                                                   5.1.56-ndb-7.1.17
false                                                              
true, false                                                        
`DataDir'                                   path         IN        all
                                                                   5.1-based
.                                                                  
...                                                                
`DataMemory'                                bytes        N         all
                                                                   5.1-based
80M                                                                
1M / 1024G                                                         
`DefaultHashMapSize'                        LDM threads  N         NDB
                                                                   7.1.27
240                                                                
0 / 3840                                                           
`DictTrace'                                 bytes        N         5.1.12
undefined                                                          
0 / 100                                                            
`DiskCheckpointSpeed'                       bytes        N         5.1.12
10M                                                                
1M / 4294967039 (0xFFFFFEFF)                                       
`DiskCheckpointSpeedInRestart'              bytes        N         all
                                                                   5.1-based
100M                                                               
1M / 4294967039 (0xFFFFFEFF)                                       
`DiskIOThreadPool'                          threads      N         NDB 7.1.0
2                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`Diskless'                                  true|false   IS        all
                                            (1|0)                  5.1-based
false                                                              
true, false                                                        
`DiskPageBufferMemory'                      bytes        N         5.1.6
64M                                                                
4M / 1T                                                            
`DiskSyncSize'                              bytes        N         5.1.12
4M                                                                 
32K / 4294967039 (0xFFFFFEFF)                                      
`ExecuteOnComputer'                         name         S         all
                                                                   5.1-based
[none]                                                             
...                                                                
`ExtraSendBufferMemory'                     bytes        N         NDB 6.4.0
0                                                                  
0 / 32G                                                            
`FileSystemPath'                            path         IN        all
                                                                   5.1-based
DataDir                                                            
...                                                                
`FileSystemPathDataFiles'                   filename     IN        NDB 6.4.3
[see text]                                                         
...                                                                
`FileSystemPathDD'                          filename     IN        NDB 6.4.3
FileSystemPath                                                     
...                                                                
`FileSystemPathUndoFiles'                   filename     IN        NDB 6.4.3
[see text]                                                         
...                                                                
`FragmentLogFileSize'                       bytes        IN        NDB
                                                                   6.1.11
16M                                                                
4M / 1G                                                            
`HeartbeatIntervalDbApi'                    milliseconds N         all
                                                                   5.1-based
1500                                                               
100 / 4294967039 (0xFFFFFEFF)                                      
`HeartbeatIntervalDbDb'                     milliseconds N         NDB 7.2.0
5000                                                               
10 / 4294967039 (0xFFFFFEFF)                                       
`HeartbeatOrder'                            numeric      S         NDB 7.1.5
0                                                                  
0 / 65535                                                          
`HostName'                                  name or IP   N         all
                                            address                5.1-based
localhost                                                          
...                                                                
`Id'                                        unsigned     IS        all
                                                                   5.1-based
[none]                                                             
1 / 48                                                             
`IndexMemory'                               bytes        N         all
                                                                   5.1-based
18M                                                                
1M / 1T                                                            
`InitFragmentLogFiles'                      [see values] IN        NDB
                                                                   6.3.19
SPARSE                                                             
SPARSE, FULL                                                       
`InitialLogFileGroup'                       string       S         NDB 6.4.3
[see text]                                                         
...                                                                
`InitialNoOfOpenFiles'                      files        N         5.1.9
27                                                                 
20 / 4294967039 (0xFFFFFEFF)                                       
`InitialTablespace'                         string       S         NDB 6.4.3
[see text]                                                         
...                                                                
`IOThreadPool'                              threads      N         NDB 6.4.0
8                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`LateAlloc'                                 numeric      N         NDB 6.4.0
1                                                                  
0 / 1                                                              
`LcpScanProgressTimeout'                    second       N         NDB
                                                                   7.1.29
60                                                                 
0 / 4294967039 (0xFFFFFEFF)                                        
`LockExecuteThreadToCPU'                    CPU ID       N         NDB 6.3.4
64K                                                                
0 / 64K                                                            
`LockMaintThreadsToCPU'                     CPU ID       N         NDB 6.4.0
[none]                                                             
0 / 64K                                                            
`LockPagesInMainMemory'                     numeric      N         5.1.15
0                                                                  
0 / 2                                                              
`LogLevelCheckpoint'                        log level    N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelCongestion'                        levelr       N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelConnection'                        integer      N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelError'                             integer      N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelInfo'                              integer      N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelNodeRestart'                       integer      N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelShutdown'                          integer      N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LogLevelStartup'                           integer      N         all
                                                                   5.1-based
1                                                                  
0 / 15                                                             
`LogLevelStatistic'                         integer      N         all
                                                                   5.1-based
0                                                                  
0 / 15                                                             
`LongMessageBuffer'                         bytes        N         NDB
                                                                   7.1.31
64M                                                                
512K / 4294967039 (0xFFFFFEFF)                                     
`MaxAllocate'                               unsigned     N         5.1.20
32M                                                                
1M / 1G                                                            
`MaxBufferedEpochs'                         epochs       N         NDB
                                                                   6.2.14
100                                                                
0 / 100000                                                         
`MaxBufferedEpochBytes'                     bytes        N         NDB
                                                                   7.1.27
26214400                                                           
26214400 (0x01900000) / 4294967039                                 
(0xFFFFFEFF)                                                       
`MaxDMLOperationsPerTransaction'            operations   N         NDB
                                            (DML)                  7.1.15
4294967295                                                         
32 / 4294967295                                                    
`MaxLCPStartDelay'                          seconds      N         NDB 6.4.3
0                                                                  
0 / 600                                                            
`MaxNoOfAttributes'                         integer      N         all
                                                                   5.1-based
1000                                                               
32 / 4294967039 (0xFFFFFEFF)                                       
`MaxNoOfConcurrentIndexOperations'          integer      N         all
                                                                   5.1-based
8K                                                                 
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfConcurrentOperations'               integer      N         all
                                                                   5.1-based
32K                                                                
32 / 4294967039 (0xFFFFFEFF)                                       
`MaxNoOfConcurrentScans'                    integer      N         all
                                                                   5.1-based
256                                                                
2 / 500                                                            
`MaxNoOfConcurrentSubOperations'            unsigned     N         NDB 6.3.7
256                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfConcurrentTransactions'             integer      N         all
                                                                   5.1-based
4096                                                               
32 / 4294967039 (0xFFFFFEFF)                                       
`MaxNoOfFiredTriggers'                      integer      N         all
                                                                   5.1-based
4000                                                               
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfLocalOperations'                    integer      N         all
                                                                   5.1-based
UNDEFINED                                                          
32 / 4294967039 (0xFFFFFEFF)                                       
`MaxNoOfLocalScans'                         integer      N         NDB 7.2.0
[see text]                                                         
32 / 4294967039 (0xFFFFFEFF)                                       
`MaxNoOfOpenFiles'                          unsigned     N         5.1.16
0                                                                  
20 / 4294967039 (0xFFFFFEFF)                                       
`MaxNoOfOrderedIndexes'                     integer      N         all
                                                                   5.1-based
128                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfSavedMessages'                      integer      N         all
                                                                   5.1-based
25                                                                 
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfSubscribers'                        unsigned     N         NDB 6.3.7
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfSubscriptions'                      unsigned     N         NDB 6.3.7
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfTables'                             integer      N         all
                                                                   5.1-based
128                                                                
8 / 20320                                                          
`MaxNoOfTriggers'                           integer      N         all
                                                                   5.1-based
768                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxNoOfUniqueHashIndexes'                  integer      N         all
                                                                   5.1-based
64                                                                 
0 / 4294967039 (0xFFFFFEFF)                                        
`MaxParallelScansPerFragment'               bytes        N         NDB 7.2.0
256                                                                
1 / 4294967039 (0xFFFFFEFF)                                        
`MaxStartFailRetries'                       unsigned     N         NDB
                                                                   6.2.19
3                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`MemReportFrequency'                        unsigned     N         5.1.16
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`MinFreePct'                                unsigned     N         NDB
                                                                   7.1.18
5                                                                  
0 / 100                                                            
`NodeGroup'                                              IS        NDB 6.4.0
[none]                                                             
0 / 65536                                                          
`NodeId'                                    unsigned     IS        all
                                                                   5.1-based
[none]                                                             
1 / 48                                                             
`NoOfDiskPagesToDiskAfterRestartACC'        8K           N         all
                                            pages/100              5.1-based
                                            milliseconds           
20                                                                 
1 / 4294967039 (0xFFFFFEFF)                                        
`NoOfDiskPagesToDiskAfterRestartTUP'        8K           N         all
                                            pages/100              5.1-based
                                            milliseconds           
40                                                                 
1 / 4294967039 (0xFFFFFEFF)                                        
`NoOfDiskPagesToDiskDuringRestartACC'       8K           N         all
                                            pages/100              5.1-based
                                            milliseconds           
20                                                                 
1 / 4294967039 (0xFFFFFEFF)                                        
`NoOfDiskPagesToDiskDuringRestartTUP'       8K           N         all
                                            pages/100              5.1-based
                                            milliseconds           
40                                                                 
1 / 4294967039 (0xFFFFFEFF)                                        
`NoOfFragmentLogFiles'                      integer      IN        5.1.0
16                                                                 
3 / 4294967039 (0xFFFFFEFF)                                        
`NoOfReplicas'                              integer      IS        NDB 7.0.6
2                                                                  
1 / 4                                                              
`Numa'                                      boolean      N         NDB 7.1.9
1                                                                  
...                                                                
`ODirect'                                   boolean      N         NDB 6.3.0
false                                                              
true, false                                                        
`RealtimeScheduler'                         boolean      N         NDB 6.3.4
false                                                              
true, false                                                        
`RedoBuffer'                                bytes        N         NDB 7.0.4
32M                                                                
1M / 4294967039 (0xFFFFFEFF)                                       
`RedoOverCommitCounter'                     numeric      N         NDB
                                                                   7.1.10
3                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`RedoOverCommitLimit'                       seconds      N         NDB
                                                                   7.1.10
20                                                                 
0 / 4294967039 (0xFFFFFEFF)                                        
`ReservedSendBufferMemory'                  bytes        N         NDB 6.4.0
256K                                                               
0 / 4294967039 (0xFFFFFEFF)                                        
`RestartOnErrorInsert'                      error code   N         all
                                                                   5.1-based
2                                                                  
0 / 4                                                              
`SchedulerExecutionTimer'                   µsec        N         NDB 6.3.4
50                                                                 
0 / 11000                                                          
`SchedulerSpinTimer'                        µsec        N         NDB 6.3.4
0                                                                  
0 / 500                                                            
`ServerPort'                                unsigned     N         all
                                                                   5.1-based
[none]                                                             
1 / 64K                                                            
`SharedGlobalMemory'                        bytes        N         5.1.6
20M                                                                
0 / 64T                                                            
`StartFailRetryDelay'                       unsigned     N         NDB
                                                                   6.2.19
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`StartFailureTimeout'                       milliseconds N         all
                                                                   5.1-based
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`StartNoNodeGroupTimeout'                   milliseconds N         NDB
                                                                   7.0.24
15000                                                              
0 / 4294967039 (0xFFFFFEFF)                                        
`StartPartialTimeout'                       milliseconds N         all
                                                                   5.1-based
30000                                                              
0 / 4294967039 (0xFFFFFEFF)                                        
`StartPartitionedTimeout'                   milliseconds N         all
                                                                   5.1-based
60000                                                              
0 / 4294967039 (0xFFFFFEFF)                                        
`StartupStatusReportFrequency'              seconds      N         NDB 6.4.0
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`StopOnError'                               boolean      N         all
                                                                   5.1-based
1                                                                  
0, 1                                                               
`StringMemory'                              % or bytes   S         5.1.6
5                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`TcpBind_INADDR_ANY'                        boolean      N         NDB 6.2.0
false                                                              
true, false                                                        
`TimeBetweenEpochs'                         milliseconds N         NDB 6.2.5
100                                                                
0 / 32000                                                          
`TimeBetweenEpochsTimeout'                  milliseconds N         5.1.51
0                                                                  
0 / 256000                                                         
`TimeBetweenGlobalCheckpoints'              milliseconds N         NDB 6.2.0
2000                                                               
20 / 32000                                                         
`TimeBetweenInactiveTransactionAbortCheck'  milliseconds N         all
                                                                   5.1-based
1000                                                               
1000 / 4294967039 (0xFFFFFEFF)                                     
`TimeBetweenLocalCheckpoints'               number of    N         all
                                            4-byte                 5.1-based
                                            words, as a            
                                            base-2                 
                                            logarithm              
20                                                                 
0 / 31                                                             
`TimeBetweenWatchDogCheck'                  milliseconds N         all
                                                                   5.1-based
6000                                                               
70 / 4294967039 (0xFFFFFEFF)                                       
`TimeBetweenWatchDogCheckInitial'           milliseconds N         5.1.20
6000                                                               
70 / 4294967039 (0xFFFFFEFF)                                       
`TotalSendBufferMemory'                     bytes        N         NDB 6.4.0
256K                                                               
0 / 4294967039 (0xFFFFFEFF)                                        
`TransactionBufferMemory'                   bytes        N         all
                                                                   5.1-based
1M                                                                 
1K / 4294967039 (0xFFFFFEFF)                                       
`TransactionDeadlockDetectionTimeout'       milliseconds N         all
                                                                   5.1-based
1200                                                               
50 / 4294967039 (0xFFFFFEFF)                                       
`TransactionInactiveTimeout'                milliseconds N         all
                                                                   5.1-based
[see text]                                                         
0 / 4294967039 (0xFFFFFEFF)                                        
`TwoPassInitialNodeRestartCopy'             boolean      N         NDB
                                                                   7.1.11
false                                                              
true, false                                                        
`UndoDataBuffer'                            unsigned     N         all
                                                                   5.1-based
16M                                                                
1M / 4294967039 (0xFFFFFEFF)                                       
`UndoIndexBuffer'                           unsigned     N         all
                                                                   5.1-based
2M                                                                 
1M / 4294967039 (0xFFFFFEFF)                                       

*Multi-Threaded Data Node Configuration Parameters*

This table describes MySQL Cluster Multi-Threaded Data Node
configuration parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`MaxNoOfExecutionThreads'                   integer      N         NDB 7.0.4
2                                                                  
2 / 8                                                              
`ThreadConfig'                              string       N         NDB
                                                                   7.1.17
"                                                                  
...                                                                

*Note*:

Prior to MySQL Cluster NDB 7.0, to add new data nodes to a MySQL
Cluster, it is necessary to shut down the cluster completely, update
the `config.ini' file, and then restart the cluster, starting all data
node processes using the `--initial' option--that is, you must perform
a system restart.

Beginning in MySQL Cluster NDB 7.0, it is possible to add new data node
groups to a running cluster online. For more information, see *Note
mysql-cluster-online-add-node::.


File: manual.info,  Node: mysql-cluster-params-mgmd,  Next: mysql-cluster-params-api,  Prev: mysql-cluster-params-ndbd,  Up: mysql-cluster-params-overview

17.3.3.2 MySQL Cluster Management Node Configuration Parameters
...............................................................

The summary table in this section provides information about parameters
used in the `[ndb_mgmd]' or `[mgm]' sections of a `config.ini' file for
configuring MySQL Cluster management nodes. For detailed descriptions
and other additional information about each of these parameters, see
*Note mysql-cluster-mgm-definition::.

Restart types

Changes in MySQL Cluster configuration parameters do not take effect
until the cluster is restarted. The type of restart required to change
a given parameter is indicated in the summary table as follows:

   * `N'--Node restart: The parameter can be updated using a rolling
     restart (see *Note mysql-cluster-rolling-restart::).

   * `S'--System restart: The cluster must be shut down completely,
     then restarted, to effect a change in this parameter.

   * `I'--Initial restart: Data nodes must be restarted using the
     `--initial' option.

For more information about restart types, see *Note
mysql-cluster-params-overview::.

*Management Node Configuration Parameters*

This table describes MySQL Cluster Management Node configuration
parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`ArbitrationDelay'                          milliseconds N         all
                                                                   5.1-based
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`ArbitrationRank'                           0-2          N         all
                                                                   5.1-based
1                                                                  
0 / 2                                                              
`DataDir'                                   path         N         all
                                                                   5.1-based
.                                                                  
...                                                                
`ExecuteOnComputer'                         name         S         all
                                                                   5.1-based
[none]                                                             
...                                                                
`ExtraSendBufferMemory'                     bytes        N         NDB
                                                                   7.0.39
0                                                                  
0 / 32G                                                            
`HeartbeatIntervalMgmdMgmd'                 milliseconds N         NDB
                                                                   7.1.29
1500                                                               
100 / 4294967039 (0xFFFFFEFF)                                      
`HeartbeatThreadPriority'                   string       S         NDB 7.1.2
[none]                                                             
...                                                                
`HostName'                                  name or IP   N         all
                                            address                5.1-based
[none]                                                             
...                                                                
`Id'                                        unsigned     IS        NDB 6.1.1
[none]                                                             
1 / 255                                                            
`LogDestination'                            {CONSOLE|SYSLOG|FILE}N         all
                                                                   5.1-based
[see text]                                                         
...                                                                
`MaxNoOfSavedEvents'                        unsigned     N         all
                                                                   5.1-based
100                                                                
0 / 4294967039 (0xFFFFFEFF)                                        
`NodeId'                                    unsigned     IS        NDB 6.1.1
[none]                                                             
1 / 255                                                            
`PortNumber'                                unsigned     N         all
                                                                   5.1-based
1186                                                               
0 / 64K                                                            
`PortNumberStats'                           unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 64K                                                            
`TotalSendBufferMemory'                     bytes        N         NDB 6.4.0
256K                                                               
0 / 4294967039 (0xFFFFFEFF)                                        
`wan'                                       boolean      N         NDB 6.1.1
false                                                              
true, false                                                        

*Note*:

After making changes in a management node's configuration, it is
necessary to perform a rolling restart of the cluster for the new
configuration to take effect. See *Note mysql-cluster-mgm-definition::,
for more information.

To add new management servers to a running MySQL Cluster, it is also
necessary perform a rolling restart of all cluster nodes after
modifying any existing `config.ini' files. For more information about
issues arising when using multiple management nodes, see *Note
mysql-cluster-limitations-multiple-nodes::.


File: manual.info,  Node: mysql-cluster-params-api,  Next: mysql-cluster-params-other,  Prev: mysql-cluster-params-mgmd,  Up: mysql-cluster-params-overview

17.3.3.3 MySQL Cluster SQL Node and API Node Configuration Parameters
.....................................................................

The summary table in this section provides information about parameters
used in the `[mysqld]' and `[api]' sections of a `config.ini' file for
configuring MySQL Cluster SQL nodes and API nodes. For detailed
descriptions and other additional information about each of these
parameters, see *Note mysql-cluster-api-definition::.

*Note*:

For a discussion of MySQL server options for MySQL Cluster, see *Note
mysql-cluster-program-options-mysqld::; for information about MySQL
server system variables relating to MySQL Cluster, see *Note
mysql-cluster-system-variables::.

Restart types

Changes in MySQL Cluster configuration parameters do not take effect
until the cluster is restarted. The type of restart required to change
a given parameter is indicated in the summary table as follows:

   * `N'--Node restart: The parameter can be updated using a rolling
     restart (see *Note mysql-cluster-rolling-restart::).

   * `S'--System restart: The cluster must be shut down completely,
     then restarted, to effect a change in this parameter.

   * `I'--Initial restart: Data nodes must be restarted using the
     `--initial' option.

For more information about restart types, see *Note
mysql-cluster-params-overview::.

*SQL Node / API Node Configuration Parameters*

This table describes MySQL Cluster SQL Node / API Node configuration
parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`ArbitrationDelay'                          milliseconds N         all
                                                                   5.1-based
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`ArbitrationRank'                           0-2          N         all
                                                                   5.1-based
0                                                                  
0 / 2                                                              
`AutoReconnect'                             boolean      N         NDB 7.0.7
false                                                              
true, false                                                        
`BatchByteSize'                             bytes        N         NDB 7.2.1
16K                                                                
1024 / 1M                                                          
`BatchSize'                                 records      N         NDB 7.2.1
256                                                                
1 / 992                                                            
`ConnectionMap'                             string       N         NDB 6.1.0
[none]                                                             
...                                                                
`DefaultHashMapSize'                        LDM threads  N         NDB
                                                                   7.1.27
240                                                                
0 / 3840                                                           
`DefaultOperationRedoProblemAction'         enumeration  S         NDB
                                                                   7.1.10
ABORT                                                              
ABORT, QUEUE                                                       
`EventLogBufferSize'                        bytes        S         NDB 7.0.4
8192                                                               
0 / 64K                                                            
`ExecuteOnComputer'                         name         S         all
                                                                   5.1-based
[none]                                                             
...                                                                
`ExtraSendBufferMemory'                     bytes        N         NDB
                                                                   7.0.39
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`HeartbeatThreadPriority'                   string       S         NDB 7.1.2
[none]                                                             
...                                                                
`HostName'                                  name or IP   N         all
                                            address                5.1-based
[none]                                                             
...                                                                
`Id'                                        unsigned     IS        NDB 6.1.1
[none]                                                             
1 / 255                                                            
`MaxScanBatchSize'                          bytes        N         all
                                                                   5.1-based
256K                                                               
32K / 16M                                                          
`NodeId'                                    unsigned     IS        NDB 6.1.1
[none]                                                             
1 / 255                                                            
`TotalSendBufferMemory'                     bytes        N         NDB 6.4.0
256K                                                               
0 / 4294967039 (0xFFFFFEFF)                                        
`wan'                                       boolean      N         NDB 6.1.1
false                                                              
true, false                                                        

*Note*:

To add new SQL or API nodes to the configuration of a running MySQL
Cluster, it is necessary to perform a rolling restart of all cluster
nodes after adding new `[mysqld]' or `[api]' sections to the
`config.ini' file (or files, if you are using more than one management
server). This must be done before the new SQL or API nodes can connect
to the cluster.

It is _not_ necessary to perform any restart of the cluster if new SQL
or API nodes can employ previously unused API slots in the cluster
configuration to connect to the cluster.


File: manual.info,  Node: mysql-cluster-params-other,  Prev: mysql-cluster-params-api,  Up: mysql-cluster-params-overview

17.3.3.4 Other MySQL Cluster Configuration Parameters
.....................................................

The summary tables in this section provide information about parameters
used in the `[computer]', `[tcp]', `[shm]', and `[sci]' sections of a
`config.ini' file for configuring MySQL Cluster management nodes. For
detailed descriptions and other additional information about individual
parameters, see *Note mysql-cluster-tcp-definition::, *Note
mysql-cluster-shm-definition::, or *Note
mysql-cluster-sci-definition::, as appropriate.

Restart types

Changes in MySQL Cluster configuration parameters do not take effect
until the cluster is restarted. The type of restart required to change
a given parameter is indicated in the summary tables as follows:

   * `N'--Node restart: The parameter can be updated using a rolling
     restart (see *Note mysql-cluster-rolling-restart::).

   * `S'--System restart: The cluster must be shut down completely,
     then restarted, to effect a change in this parameter.

   * `I'--Initial restart: Data nodes must be restarted using the
     `--initial' option.

For more information about restart types, see *Note
mysql-cluster-params-overview::.

*Computer Configuration Parameters*

This table describes MySQL Cluster Computer configuration parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`HostName'                                  name or IP   N         all
                                            address                5.1-based
[none]                                                             
...                                                                
`Id'                                        string       IS        all
                                                                   5.1-based
[none]                                                             
...                                                                

*TCP Configuration Parameters*

This table describes MySQL Cluster TCP configuration parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`Checksum'                                  boolean      N         all
                                                                   5.1-based
false                                                              
true, false                                                        
`Group'                                     unsigned     N         all
                                                                   5.1-based
55                                                                 
0 / 200                                                            
`NodeId1'                                   numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`NodeId2'                                   numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`NodeIdServer'                              numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`OverloadLimit'                             bytes        N         NDB 6.4.0
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`PortNumber'                                unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 64K                                                            
`Proxy'                                     string       N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`ReceiveBufferMemory'                       bytes        N         NDB 7.0.4
2M                                                                 
16K / 4294967039 (0xFFFFFEFF)                                      
`SendBufferMemory'                          unsigned     N         NDB 7.0.4
2M                                                                 
256K / 4294967039 (0xFFFFFEFF)                                     
`SendSignalId'                              boolean      N         all
                                                                   5.1-based
[see text]                                                         
true, false                                                        
`TCP_MAXSEG_SIZE'                           unsigned     N         NDB 6.1.1
0                                                                  
0 / 2G                                                             
`TCP_RCV_BUF_SIZE'                          unsigned     N         NDB 6.1.1
70080                                                              
1 / 2G                                                             
`TCP_SND_BUF_SIZE'                          unsigned     N         NDB 6.1.1
71540                                                              
1 / 2G                                                             
`TcpBind_INADDR_ANY'                        boolean      N         NDB 6.2.0
false                                                              
true, false                                                        

*Shared Memory Configuration Parameters*

This table describes MySQL Cluster Shared Memory configuration
parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`Checksum'                                  boolean      N         all
                                                                   5.1-based
true                                                               
true, false                                                        
`Group'                                     unsigned     N         all
                                                                   5.1-based
35                                                                 
0 / 200                                                            
`NodeId1'                                   numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`NodeId2'                                   numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`NodeIdServer'                              numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`OverloadLimit'                             bytes        N         NDB 6.4.0
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`PortNumber'                                unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 64K                                                            
`SendSignalId'                              boolean      N         all
                                                                   5.1-based
false                                                              
true, false                                                        
`ShmKey'                                    unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 4294967039 (0xFFFFFEFF)                                        
`ShmSize'                                   bytes        N         all
                                                                   5.1-based
1M                                                                 
64K / 4294967039 (0xFFFFFEFF)                                      
`Signum'                                    unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 4294967039 (0xFFFFFEFF)                                        

*SCI Configuration Parameters*

This table describes MySQL Cluster SCI configuration parameters

Parameter Name                              Type or      Restart   In
                                            Units        Type      Version
                                                                   ... (and
                                                                   later)
Default Value                                                      
Minimum/Maximum or Permitted Values                                
`Checksum'                                  boolean      N         all
                                                                   5.1-based
false                                                              
true, false                                                        
`Group'                                     unsigned     N         all
                                                                   5.1-based
15                                                                 
0 / 200                                                            
`Host1SciId0'                               unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 4294967039 (0xFFFFFEFF)                                        
`Host1SciId1'                               unsigned     N         all
                                                                   5.1-based
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`Host2SciId0'                               unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 4294967039 (0xFFFFFEFF)                                        
`Host2SciId1'                               unsigned     N         all
                                                                   5.1-based
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`NodeId1'                                   numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`NodeId2'                                   numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`NodeIdServer'                              numeric      N         all
                                                                   5.1-based
[none]                                                             
...                                                                
`OverloadLimit'                             bytes        N         NDB 6.4.0
0                                                                  
0 / 4294967039 (0xFFFFFEFF)                                        
`PortNumber'                                unsigned     N         all
                                                                   5.1-based
[none]                                                             
0 / 64K                                                            
`SendLimit'                                 unsigned     N         all
                                                                   5.1-based
8K                                                                 
128 / 32K                                                          
`SendSignalId'                              boolean      N         all
                                                                   5.1-based
true                                                               
true, false                                                        
`SharedBufferSize'                          unsigned     N         all
                                                                   5.1-based
10M                                                                
64K / 4294967039 (0xFFFFFEFF)                                      


File: manual.info,  Node: mysql-cluster-options-variables,  Next: mysql-cluster-interconnects,  Prev: mysql-cluster-params-overview,  Up: mysql-cluster-configuration

17.3.4 MySQL Server Options and Variables for MySQL Cluster
-----------------------------------------------------------

* Menu:

* mysql-cluster-option-tables::  MySQL Cluster mysqld Option and Variable Reference
* mysql-cluster-program-options-mysqld::  MySQL Server Options for MySQL Cluster
* mysql-cluster-system-variables::  MySQL Cluster System Variables
* mysql-cluster-status-variables::  MySQL Cluster Status Variables

This section provides information about MySQL server options, server
and status variables that are specific to MySQL Cluster.  For general
information on using these, and for other options and variables not
specific to MySQL Cluster, see *Note mysqld-server::.

For MySQL Cluster configuration parameters used in the cluster
configuration file (usually named `config.ini'), see *Note
mysql-cluster-configuration::.


File: manual.info,  Node: mysql-cluster-option-tables,  Next: mysql-cluster-program-options-mysqld,  Prev: mysql-cluster-options-variables,  Up: mysql-cluster-options-variables

17.3.4.1 MySQL Cluster mysqld Option and Variable Reference
...........................................................

The following table provides a list of the command-line options, server
and status variables applicable within `mysqld' when it is running as
an SQL node in a MySQL Cluster. For a table showing _all_ command-line
options, server and status variables available for use with *Note
`mysqld': mysqld, see *Note mysqld-option-tables::.

MySQL Server Options and Variables for MySQL Cluster:  MySQL 5.1, MySQL
Cluster NDB 6.3-7.1

Option or Variable Name

Command Line System Variable Status Variable

Option File Scope Dynamic

Notes

`Handler_discover'

No No Yes

No Both No

DESCRIPTION: Number of times that tables have been discovered

`Ndb_api_wait_exec_complete_count_session'

No No Yes

No Session No

DESCRIPTION: Number of times thread has been blocked while waiting for
execution of an operation to complete in this client session.

`Ndb_api_wait_exec_complete_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of times thread has been blocked while waiting for
execution of an operation to complete by this slave.

`Ndb_api_wait_exec_complete_count'

No No Yes

No Global No

DESCRIPTION: Number of times thread has been blocked while waiting for
execution of an operation to complete by this MySQL Server (SQL node).

`Ndb_api_wait_scan_result_count_session'

No No Yes

No Session No

DESCRIPTION: Number of times thread has been blocked while waiting for
a scan-based signal in this client session.

`Ndb_api_wait_scan_result_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of times thread has been blocked while waiting for
a scan-based signal by this slave.

`Ndb_api_wait_scan_result_count'

No No Yes

No Global No

DESCRIPTION: Number of times thread has been blocked while waiting for
a scan-based signal by this MySQL Server (SQL node).

`Ndb_api_wait_meta_request_count_session'

No No Yes

No Session No

DESCRIPTION: Number of times thread has been blocked waiting for a
metadata-based signal in this client session.

`Ndb_api_wait_meta_request_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of times thread has been blocked waiting for a
metadata-based signal by this slave.

`Ndb_api_wait_meta_request_count'

No No Yes

No Global No

DESCRIPTION: Number of times thread has been blocked waiting for a
metadata-based signal by this MySQL Server (SQL node).

`Ndb_api_wait_nanos_count_session'

No No Yes

No Session No

DESCRIPTION: Total time (in nanoseconds) spent waiting for some type of
signal from the data nodes in this client session.

`Ndb_api_wait_nanos_count_slave'

No No Yes

No Global No

DESCRIPTION: Total time (in nanoseconds) spent waiting for some type of
signal from the data nodes by this slave.

`Ndb_api_wait_nanos_count'

No No Yes

No Global No

DESCRIPTION: Total time (in nanoseconds) spent waiting for some type of
signal from the data nodes by this MySQL Server (SQL node).

`Ndb_api_bytes_sent_count_session'

No No Yes

No Session No

DESCRIPTION: Amount of data (in bytes) sent to the data nodes in this
client session.

`Ndb_api_bytes_sent_count_slave'

No No Yes

No Global No

DESCRIPTION: Amount of data (in bytes) sent to the data nodes by this
slave.

`Ndb_api_bytes_sent_count'

No No Yes

No Global No

DESCRIPTION: Amount of data (in bytes) sent to the data nodes by this
MySQL Server (SQL node).

`Ndb_api_bytes_received_count_session'

No No Yes

No Session No

DESCRIPTION: Amount of data (in bytes) received from the data nodes in
this client session.

`Ndb_api_bytes_received_count_slave'

No No Yes

No Global No

DESCRIPTION: Amount of data (in bytes) received from the data nodes by
this slave.

`Ndb_api_bytes_received_count'

No No Yes

No Global No

DESCRIPTION: Amount of data (in bytes) received from the data nodes by
this MySQL Server (SQL node).

`Ndb_api_trans_start_count_session'

No No Yes

No Session No

DESCRIPTION: Number of transactions started in this client session.

`Ndb_api_trans_start_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of transactions started by this slave.

`Ndb_api_trans_start_count'

No No Yes

No Global No

DESCRIPTION: Number of transactions started by this MySQL Server (SQL
node).

`Ndb_api_trans_commit_count_session'

No No Yes

No Session No

DESCRIPTION: Number of transactions committed in this client session.

`Ndb_api_trans_commit_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of transactions committed by this slave.

`Ndb_api_trans_commit_count'

No No Yes

No Global No

DESCRIPTION: Number of transactions committed by this MySQL Server (SQL
node).

`Ndb_api_trans_abort_count_session'

No No Yes

No Session No

DESCRIPTION: Number of transactions aborted in this client session.

`Ndb_api_trans_abort_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of transactions aborted by this slave.

`Ndb_api_trans_abort_count'

No No Yes

No Global No

DESCRIPTION: Number of transactions aborted by this MySQL Server (SQL
node).

`Ndb_api_trans_close_count_session'

No No Yes

No Session No

DESCRIPTION: Number of transactions aborted (may be greater than the
sum of TransCommitCount and TransAbortCount) in this client session.

`Ndb_api_trans_close_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of transactions aborted (may be greater than the
sum of TransCommitCount and TransAbortCount) by this slave.

`Ndb_api_trans_close_count'

No No Yes

No Global No

DESCRIPTION: Number of transactions aborted (may be greater than the
sum of TransCommitCount and TransAbortCount) by this MySQL Server (SQL
node).

`Ndb_api_pk_op_count_session'

No No Yes

No Session No

DESCRIPTION: Number of operations based on or using primary keys in
this client session.

`Ndb_api_pk_op_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of operations based on or using primary keys by
this slave.

`Ndb_api_pk_op_count'

No No Yes

No Global No

DESCRIPTION: Number of operations based on or using primary keys by
this MySQL Server (SQL node).

`Ndb_api_uk_op_count_session'

No No Yes

No Session No

DESCRIPTION: Number of operations based on or using unique keys in this
client session.

`Ndb_api_uk_op_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of operations based on or using unique keys by this
slave.

`Ndb_api_uk_op_count'

No No Yes

No Global No

DESCRIPTION: Number of operations based on or using unique keys by this
MySQL Server (SQL node).

`Ndb_api_table_scan_count_session'

No No Yes

No Session No

DESCRIPTION: Number of table scans that have been started, including
scans of internal tables, in this client session.

`Ndb_api_table_scan_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of table scans that have been started, including
scans of internal tables, by this slave.

`Ndb_api_table_scan_count'

No No Yes

No Global No

DESCRIPTION: Number of table scans that have been started, including
scans of internal tables, by this MySQL Server (SQL node).

`Ndb_api_range_scan_count_session'

No No Yes

No Session No

DESCRIPTION: Number of range scans that have been started in this
client session.

`Ndb_api_range_scan_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of range scans that have been started by this slave.

`Ndb_api_range_scan_count'

No No Yes

No Global No

DESCRIPTION: Number of range scans that have been started by this MySQL
Server (SQL node).

`Ndb_api_pruned_scan_count_session'

No No Yes

No Session No

DESCRIPTION: Number of scans that have been pruned to a single
partition in this client session.

`Ndb_api_pruned_scan_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of scans that have been pruned to a single
partition by this slave.

`Ndb_api_pruned_scan_count'

No No Yes

No Global No

DESCRIPTION: Number of scans that have been pruned to a single
partition by this MySQL Server (SQL node).

`Ndb_api_scan_batch_count_session'

No No Yes

No Session No

DESCRIPTION: Number of batches of rows received in this client session.

`Ndb_api_scan_batch_count_slave'

No No Yes

No Global No

DESCRIPTION: Number of batches of rows received by this slave.

`Ndb_api_scan_batch_count'

No No Yes

No Global No

DESCRIPTION: Number of batches of rows received by this MySQL Server
(SQL node).

`Ndb_api_read_row_count_session'

No No Yes

No Session No

DESCRIPTION: Total number of rows that have been read in this client
session.

`Ndb_api_read_row_count_slave'

No No Yes

No Global No

DESCRIPTION: Total number of rows that have been read by this slave.

`Ndb_api_read_row_count'

No No Yes

No Global No

DESCRIPTION: Total number of rows that have been read by this MySQL
Server (SQL node).

`Ndb_api_trans_local_read_row_count_session'

No No Yes

No Session No

DESCRIPTION: Total number of rows that have been read in this client
session.

`Ndb_api_trans_local_read_row_count_slave'

No No Yes

No Global No

DESCRIPTION: Total number of rows that have been read by this slave.

`Ndb_api_trans_local_read_row_count'

No No Yes

No Global No

DESCRIPTION: Total number of rows that have been read by this MySQL
Server (SQL node).

`Ndb_api_event_data_count_injector'

No No Yes

No Global No

DESCRIPTION: Number of row change events received by the NDB binlog
injector thread.

`Ndb_api_event_data_count'

No No Yes

No Global No

DESCRIPTION: Number of row change events received by this MySQL Server
(SQL node).

`Ndb_api_event_nondata_count_injector'

No No Yes

No Global No

DESCRIPTION: Number of events received, other than row change events,
by the NDB binlog injector thread.

`Ndb_api_event_nondata_count'

No No Yes

No Global No

DESCRIPTION: Number of events received, other than row change events,
by this MySQL Server (SQL node).

`Ndb_api_event_bytes_count_injector'

No No Yes

No Global No

DESCRIPTION: Number of bytes of events received by the NDB binlog
injector thread.

`Ndb_api_event_bytes_count'

No No Yes

No Global No

DESCRIPTION: Number of bytes of events received by this MySQL Server
(SQL node).

`Ndb_number_of_data_nodes'

No No Yes

No Global No

DESCRIPTION: If the server is part of a MySQL Cluster, the value of
this variable is the number of data nodes in the cluster

`Ndb_conflict_fn_max'

No No Yes

No Global No

DESCRIPTION: If the server is part of a MySQL Cluster involved in
cluster replication, the value of this variable indicates the number of
times that conflict resolution based on "greater timestamp wins" has
been applied

`Ndb_conflict_fn_old'

No No Yes

No Global No

DESCRIPTION: If the server is part of a MySQL Cluster involved in
cluster replication, the value of this variable indicates the number of
times that "same timestamp wins" conflict resolution has been applied

`Ndb_conflict_fn_epoch'

No No Yes

No Global No

DESCRIPTION: Number of rows that have been found in conflict by the
NDB$EPOCH() conflict detection function

`Ndb_conflict_fn_epoch_trans'

No No Yes

No Global No

DESCRIPTION: Number of rows that have been found in conflict by the
NDB$EPOCH_TRANS() conflict detection function

`Ndb_conflict_trans_row_conflict_count'

No No Yes

No Global No

DESCRIPTION: Number of rows found to be in conflict by a transactional
conflict function

`Ndb_conflict_trans_row_reject_count'

No No Yes

No Global No

DESCRIPTION: Total number of rows realigned after being found in
conflict by a transactional conflict function. Includes
Ndb_conflict_trans_row_conflict_count and any rows included in or
dependent on conflicting transactions.

`Ndb_conflict_trans_reject_count'

No No Yes

No Global No

DESCRIPTION: Number of transactions rejected after being found in
conflict by a transactional conflict function.

`Ndb_conflict_trans_detect_iter_count'

No No Yes

No Global No

DESCRIPTION: Number of internal iterations required to commit an epoch
transaction. Should be (slightly) greater than or equal to
Ndb_conflict_trans_conflict_commit_count.

`Ndb_conflict_trans_conflict_commit_count'

No No Yes

No Global No

DESCRIPTION: Number of epoch transactions committed after requiring
transactional conflict handling.

`ndb_optimization_delay'

No Yes No

No Global Yes

DESCRIPTION: Sets the number of milliseconds to wait between processing
sets of rows by OPTIMIZE TABLE on NDB tables.

`ndb_table_temporary'

No Yes No

No Session Yes

DESCRIPTION: NDB tables are not persistent on disk: no schema files are
created and the tables are not logged

`ndb_table_no_logging'

No Yes No

No Session Yes

DESCRIPTION: NDB tables created when this setting is enabled are not
checkpointed to disk (although table schema files are created). The
setting in effect when the table is created with or altered to use
NDBCLUSTER persists for the lifetime of the table.

`ndb_autoincrement_prefetch_sz'

Yes Yes No

Yes Both Yes

DESCRIPTION: NDB auto-increment prefetch size

`ndb-batch-size'

Yes Yes No

Yes Global No

DESCRIPTION: Size (in bytes) to use for NDB transaction batches

`ndb-blob-read-batch-bytes'

Yes Yes No

Yes Both Yes

DESCRIPTION: Specifies size in bytes that large BLOB reads should be
batched into. 0 = no limit.

`ndb-blob-write-batch-bytes'

Yes Yes No

Yes Both Yes

DESCRIPTION: Specifies size in bytes that large BLOB writes should be
batched into. 0 = no limit.

`ndb_cache_check_time'

Yes Yes No

Yes Global Yes

DESCRIPTION: Number of milliseconds between checks of cluster SQL nodes
made by the MySQL query cache

`ndb-cluster-connection-pool'

Yes Yes Yes

Yes Global No

DESCRIPTION: Number of connections to the cluster used by MySQL

`ndb_join_pushdown'

No Yes No

No Both Yes

DESCRIPTION: Enables pushing down of joins to data nodes

`Ndb_execute_count'

No No Yes

No Global No

DESCRIPTION: Provides the number of round trips to the NDB kernel made
by operations

`Ndb_scan_count'

No No Yes

No Global No

DESCRIPTION: The total number of scans executed by NDB since the
cluster was last started

`Ndb_pruned_scan_count'

No No Yes

No Global No

DESCRIPTION: Number of scans executed by NDB since the cluster was last
started where partition pruning could be used

`ndb-connectstring'

Yes No No

Yes

No

DESCRIPTION: Point to the management server that distributes the
cluster configuration

`ndb_extra_logging'

Yes Yes No

Yes Global Yes

DESCRIPTION: Controls logging of MySQL Cluster schema, connection, and
data distribution events in the MySQL error log

`ndb_force_send'

Yes Yes No

Yes Both Yes

DESCRIPTION: Forces sending of buffers to NDB immediately, without
waiting for other threads

`ndb_use_exact_count'

No Yes No

No Both Yes

DESCRIPTION: Use exact row count when planning queries

`ndb-log-apply-status'

Yes Yes No

Yes Global No

DESCRIPTION: Cause a MySQL server acting as a slave to log
mysql.ndb_apply_status updates received from its immediate master in
its own binary log, using its own server ID.  Effective only if the
server is started with the -ndbcluster option.

`ndb_log_apply_status'

Yes Yes No

Yes Global No

DESCRIPTION: Whether or not a MySQL server acting as a slave logs
mysql.ndb_apply_status updates received from its immediate master in
its own binary log, using its own server ID.

`ndb_log_bin'

Yes Yes No

No Both Yes

DESCRIPTION: Write updates to NDB tables in the binary log.  Effective
only if binary logging is enabled with -log-bin.

`ndb_log_binlog_index'

Yes Yes No

No Global Yes

DESCRIPTION: Insert mapping between epochs and binary log positions
into the ndb_binlog_index table. Defaults to ON.  Effective only if
binary logging is enabled on the server.

`ndb-log-orig'

Yes Yes No

Yes Global No

DESCRIPTION: Log originating server id and epoch in
mysql.ndb_binlog_index table.

`ndb_log_orig'

Yes Yes No

Yes Global No

DESCRIPTION: Whether the id and epoch of the originating server are
recorded in the mysql.ndb_binlog_index table. Set using the
-ndb-log-orig option when starting mysqld.

`ndb-log-transaction-id'

Yes Yes No

Yes Global No

DESCRIPTION: Write NDB transaction IDs in the binary log.  Requires
-log-bin-v1-events=OFF.

`ndb_log_transaction_id'

No Yes No

No Global No

DESCRIPTION: Whether NDB transaction IDs are written into the binary
log. (Read-only.)

`ndb_log_updated_only'

Yes Yes No

Yes Global Yes

DESCRIPTION: Log complete rows (ON) or updates only (OFF)

`ndb-log-update-as-write'

Yes Yes No

Yes Global Yes

DESCRIPTION: Toggles logging of updates on the master between updates
(OFF) and writes (ON)

`ndb-log-empty-epochs'

Yes Yes No

Yes Global Yes

DESCRIPTION: When enabled, causes epochs in which there were no changes
to be written to the ndb_apply_status and ndb_binlog_index tables, even
when -log-slave-updates is enabled.

`ndb_log_empty_epochs'

Yes Yes No

Yes Global Yes

DESCRIPTION: When enabled, epochs in which there were no changes are
written to the ndb_apply_status and ndb_binlog_index tables, even when
log_slave_updates is enabled.

`ndb-transid-mysql-connection-map'

Yes No No

No

No

DESCRIPTION: Enable or disable the ndb_transid_mysql_connection_map
plugin; that is, enable or disable the INFORMATION_SCHEMA table having
that name.

`Ndb_pushed_reads'

No No Yes

No Global No

DESCRIPTION: Number of reads executed on the data nodes by pushed-down
joins

`Ndb_pushed_queries_defined'

No No Yes

No Global No

DESCRIPTION: Number of joins that API nodes have attempted to push down
to the data nodes

`Ndb_pushed_queries_dropped'

No No Yes

No Global No

DESCRIPTION: Number of joins that API nodes have tried to push down,
but failed

`Ndb_pushed_queries_executed'

No No Yes

No Global No

DESCRIPTION: Number of joins successfully pushed down and executed on
the data nodes

`ndb-nodeid'

Yes No Yes

Yes Global No

DESCRIPTION: MySQL Cluster node ID for this MySQL server

`ndb-mgmd-host'

Yes No No

Yes

No

DESCRIPTION: Set the host (and port, if desired) for connecting to
management server

`ndb-wait-connected'

Yes Yes No

Yes Global No

DESCRIPTION: Time (in seconds) for the MySQL server to wait for
connection to cluster management and data nodes before accepting MySQL
client connections.

`ndb-wait-setup'

Yes Yes No

Yes Global No

DESCRIPTION: Time (in seconds) for the MySQL server to wait for NDB
engine setup to complete.

`ndbcluster'

Yes No No

Yes

No

DESCRIPTION: Enable NDB Cluster (if this version of MySQL supports it)

Disabled by `--skip-ndbcluster'

`ndbinfo_database'

No Yes No

No Global No

DESCRIPTION: The name used for the NDB information database; read only.

`ndbinfo_max_bytes'

Yes Yes No

No Both Yes

DESCRIPTION: Used for debugging only.

`ndbinfo_max_rows'

Yes Yes No

No Both Yes

DESCRIPTION: Used for debugging only.

`ndbinfo_offline'

No Yes No

No Global Yes

DESCRIPTION: Put the ndbinfo database into offline mode, in which no
rows are returned from tables or views.

`ndbinfo_show_hidden'

Yes Yes No

No Both Yes

DESCRIPTION: Whether to show ndbinfo internal base tables in the mysql
client. The default is OFF.

`ndbinfo_table_prefix'

Yes Yes No

No Both Yes

DESCRIPTION: The prefix to use for naming ndbinfo internal base tables

`ndbinfo_version'

No Yes No

No Global No

DESCRIPTION: The version of the ndbinfo engine; read only.

`server-id-bits'

Yes Yes No

Yes Global No

DESCRIPTION: Sets the number of least significant bits in the server_id
actually used for identifying the server, permitting NDB API
applications to store application data in the most significant bits.
server_id must be less than 2 to the power of this value.

`server_id_bits'

Yes Yes No

Yes Global No

DESCRIPTION: The effective value of server_id if the server was started
with the -server-id-bits option set to a nondefault value.

`slave_allow_batching'

Yes Yes No

Yes Global Yes

DESCRIPTION: Turns update batching on and off for a replication slave

`transaction_allow_batching'

No Yes No

No Session Yes

DESCRIPTION: Allows batching of statements within a transaction.
Disable AUTOCOMMIT to use.

`have_ndbcluster'

No Yes No

No Global No

DESCRIPTION: Whether mysqld supports NDB Cluster tables (set by
-ndbcluster option)

`ndb-deferred-constraints'

Yes Yes No

Yes Both Yes

DESCRIPTION: Specifies that constraint checks on unique indexes (where
these are supported) should be deferred until commit time. Not normally
needed or used; for testing purposes only.

`ndb_deferred_constraints'

Yes Yes No

Yes Both Yes

DESCRIPTION: Specifies that constraint checks should be deferred (where
these are supported). Not normally needed or used; for testing purposes
only.

`ndb-distribution'

Yes Yes No

Yes Global Yes

DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH
or LINHASH, default is KEYHASH)

`ndb_distribution'

Yes Yes No

Yes Global Yes

DESCRIPTION: Default distribution for new tables in NDBCLUSTER (KEYHASH
or LINHASH, default is KEYHASH)

`ndb_eventbuffer_max_alloc'

Yes Yes No

Yes Global Yes

DESCRIPTION: Maximum memory that can be allocated for buffering events
by the NDB API. Defaults to 0 (no limit).

`ndb_index_stat_cache_entries'

Yes No No

Yes

No

DESCRIPTION: Sets the granularity of the statistics by determining the
number of starting and ending keys

`ndb_index_stat_enable'

Yes No No

Yes

No

DESCRIPTION: Use NDB index statistics in query optimization

`ndb_index_stat_option'

Yes No No

Yes

No

DESCRIPTION: Comma-separated list of tunable options for NDB index
statistics; the list should contain no spaces

`ndb_index_stat_update_freq'

Yes No No

Yes

No

DESCRIPTION: How often to query data nodes instead of the statistics
cache

`ndb_optimized_node_selection'

Yes No No

Yes

No

DESCRIPTION: Determines how an SQL node chooses a cluster data node to
use as transaction coordinator

`ndb_report_thresh_binlog_epoch_slip'

Yes No No

Yes

No

DESCRIPTION: This is a threshold on the number of epochs to be behind
before reporting binlog status

`ndb_report_thresh_binlog_mem_usage'

Yes No No

Yes

No

DESCRIPTION: This is a threshold on the percentage of free memory
remaining before reporting binlog status

`ndb_use_transactions'

Yes Yes No

Yes Both Yes

DESCRIPTION: Forces NDB to use a count of records during SELECT
COUNT(*) query planning to speed up this type of query

`ndb_version'

No Yes No

No Global No

DESCRIPTION: Shows build and NDB engine version as an integer.

`ndb_version_string'

No Yes No

No Global No

DESCRIPTION: Shows build information including NDB engine version in
ndb-x.y.z format.

`Ndb_cluster_node_id'

No No Yes

No Both No

DESCRIPTION: If the server is acting as a MySQL Cluster node, then the
value of this variable its node ID in the cluster

`Ndb_config_from_host'

No No Yes

No Both No

DESCRIPTION: The host name or IP address of the Cluster management
server. Formerly Ndb_connected_host

`Ndb_config_from_port'

No No Yes

No Both No

DESCRIPTION: The port for connecting to Cluster management server.
Formerly Ndb_connected_port

`Com_show_ndb_status'

No No Yes

No Both No

DESCRIPTION: Count of SHOW NDB STATUS statements 



File: manual.info,  Node: mysql-cluster-program-options-mysqld,  Next: mysql-cluster-system-variables,  Prev: mysql-cluster-option-tables,  Up: mysql-cluster-options-variables

17.3.4.2 MySQL Server Options for MySQL Cluster
...............................................

This section provides descriptions of *Note `mysqld': mysqld.  server
options relating to MySQL Cluster. For information about *Note
`mysqld': mysqld. options not specific to MySQL Cluster, and for
general information about the use of options with *Note `mysqld':
mysqld, see *Note server-options::.

For information about command-line options used with other MySQL
Cluster processes (*Note `ndbd': mysql-cluster-programs-ndbd, *Note
`ndb_mgmd': mysql-cluster-programs-ndb-mgmd, and *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm.), see *Note
mysql-cluster-program-options-common::. For information about
command-line options used with *Note `NDB': mysql-cluster. utility
programs (such as *Note `ndb_desc': mysql-cluster-programs-ndb-desc,
*Note `ndb_size.pl': mysql-cluster-programs-ndb-size-pl, and *Note
`ndb_show_tables': mysql-cluster-programs-ndb-show-tables.), see *Note
mysql-cluster-programs::.

   * `--ndb-batch-size=#'

     Type and value information for ndb-batch-size

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-batch-size'

     Yes Yes No

     Yes Global No

     MySQL 5.1 numeric 32768 / 0 - 31536000

     DESCRIPTION: Size (in bytes) to use for NDB transaction batches 


     This sets the size in bytes that is used for NDB transaction
     batches.

   * `--ndb-cluster-connection-pool=#'

     Type and value information for ndb-cluster-connection-pool

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-cluster-connection-pool'

     Yes Yes Yes

     Yes Global No

     MySQL 5.1 numeric 1 / 1 - 63

     DESCRIPTION: Number of connections to the cluster used by MySQL 


     By setting this option to a value greater than 1 (the default), a
     *Note `mysqld': mysqld. process can use multiple connections to
     the cluster, effectively mimicking several SQL nodes. Each
     connection requires its own `[api]' or `[mysqld]' section in the
     cluster configuration (`config.ini') file, and counts against the
     maximum number of API connections supported by the cluster.

     Suppose that you have 2 cluster host computers, each running an
     SQL node whose *Note `mysqld': mysqld. process was started with
     `--ndb-cluster-connection-pool=4'; this means that the cluster
     must have 8 API slots available for these connections (instead of
     2). All of these connections are set up when the SQL node connects
     to the cluster, and are allocated to threads in a round-robin
     fashion.

     This option is useful only when running *Note `mysqld': mysqld. on
     host machines having multiple CPUs, multiple cores, or both. For
     best results, the value should be smaller than the total number of
     cores available on the host machine. Setting it to a value greater
     than this is likely to degrade performance severely.

     *Important*:

     Because each SQL node using connection pooling occupies multiple
     API node slots--each slot having its own node ID in the
     cluster--you must _not_ use a node ID as part of the cluster
     connection string when starting any *Note `mysqld': mysqld.
     process that employs connection pooling.

     Setting a node ID in the connection string when using the
     `--ndb-cluster-connection-pool' option causes node ID allocation
     errors when the SQL node attempts to connect to the cluster.

     This option was introduced in MySQL Cluster NDB 6.2.2.  Beginning
     with MySQL Cluster NDB 6.2.16 and MySQL Cluster NDB 6.3.13, the
     value used for this option is available as a system variable (Bug
     #35573).

     Prior to MySQL Cluster NDB 7.0.23 and MySQL Cluster NDB 7.1.12,
     there was also a status variable corresponding to this option;
     however, the status variable was removed as redundant as of these
     versions. (Bug #60119)

   * `--ndb-blob-read-batch-bytes=BYTES'

     Type and value information for ndb-blob-read-batch-bytes

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-blob-read-batch-bytes'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 numeric 65536 / 0 - 4294967295

     DESCRIPTION: Specifies size in bytes that large BLOB reads should
     be batched into. 0 = no limit.  


     This option can be used to set the size (in bytes) for batching of
     *Note `BLOB': blob. data reads in MySQL Cluster applications. When
     this batch size is exceeded by the amount of *Note `BLOB': blob.
     data to be read within the current transaction, any pending *Note
     `BLOB': blob. read operations are immediately executed.

     The maximum value for this option is 4294967295; the default is
     65536. Setting it to 0 has the effect of disabling *Note `BLOB':
     blob. read batching.

     *Note*:

     In NDB API applications, you can control *Note `BLOB': blob. write
     batching with the `setMaxPendingBlobReadBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-setmaxpendingblobreadbytes)
     and `getMaxPendingBlobReadBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-getmaxpendingblobreadbytes)
     methods.

     This option was introduced in MySQL Cluster NDB 7.0.21 and MySQL
     Cluster NDB 7.1.10.

   * `--ndb-blob-write-batch-bytes=BYTES'

     Type and value information for ndb-blob-write-batch-bytes

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-blob-write-batch-bytes'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 numeric 65536 / 0 - 4294967295

     DESCRIPTION: Specifies size in bytes that large BLOB writes should
     be batched into. 0 = no limit.  


     This option can be used to set the size (in bytes) for batching of
     *Note `BLOB': blob. data writes in MySQL Cluster applications.
     When this batch size is exceeded by the amount of *Note `BLOB':
     blob. data to be written within the current transaction, any
     pending *Note `BLOB': blob. write operations are immediately
     executed.

     The maximum value for this option is 4294967295; the default is
     65536. Setting it to 0 has the effect of disabling *Note `BLOB':
     blob. write batching.

     *Note*:

     In NDB API applications, you can control *Note `BLOB': blob. write
     batching with the `setMaxPendingBlobWriteBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-setmaxpendingblobwritebytes)
     and `getMaxPendingBlobWriteBytes()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-getmaxpendingblobwritebytes)
     methods.

     This option was introduced in MySQL Cluster NDB 7.0.21 and MySQL
     Cluster NDB 7.1.10.

   * `--ndb-connectstring=CONNECT_STRING'

     Type and value information for ndb-connectstring

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-connectstring'

     Yes No No

     Yes

     No

     MySQL 5.1 string

     DESCRIPTION: Point to the management server that distributes the
     cluster configuration 


     When using the *Note `NDBCLUSTER': mysql-cluster.  storage engine,
     this option specifies the management server that distributes
     cluster configuration data. See *Note
     mysql-cluster-connection-strings::, for syntax.

   * `--ndb-deferred-constraints=[0|1]'

     Type and value information for ndb-deferred-constraints

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-deferred-constraints'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 integer 0 / 0 - 1

     DESCRIPTION: Specifies that constraint checks on unique indexes
     (where these are supported) should be deferred until commit time.
     Not normally needed or used; for testing purposes only.  


     Controls whether or not constraint checks on unique indexes are
     deferred until commit time, where such checks are supported. `0'
     is the default.

     This option is not normally needed for operation of MySQL Cluster
     or MySQL Cluster Replication, and is intended primarily for use in
     testing.

     This option was added in MySQL Cluster NDB 7.0.28 and MySQL
     Cluster NDB 7.1.14.

   * `--ndb-distribution=[KEYHASH|LINHASH]'

     Type and value information for ndb-distribution

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-distribution'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 enumeration KEYHASH / LINHASH, KEYHASH

     DESCRIPTION: Default distribution for new tables in NDBCLUSTER
     (KEYHASH or LINHASH, default is KEYHASH) 


     Controls the default distribution method for *Note `NDB':
     mysql-cluster. tables. Can be set to either of `KEYHASH' (key
     hashing) or `LINHASH' (linear hashing).  `KEYHASH' is the default.

   * `--ndb-mgmd-host=HOST[:PORT]'

     Type and value information for ndb-mgmd-host

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-mgmd-host'

     Yes No No

     Yes

     No

     MySQL 5.1 string localhost:1186

     DESCRIPTION: Set the host (and port, if desired) for connecting to
     management server 


     Can be used to set the host and port number of a single management
     server for the program to connect to. If the program requires node
     IDs or references to multiple management servers (or both) in its
     connection information, use the `--ndb-connectstring' option
     instead.

   * `--ndbcluster'

     Type and value information for ndbcluster

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbcluster'

     Yes No No

     Yes

     No

     MySQL 5.1 boolean FALSE

     DESCRIPTION: Enable NDB Cluster (if this version of MySQL supports
     it)

     Disabled by `--skip-ndbcluster' 


     The *Note `NDBCLUSTER': mysql-cluster. storage engine is necessary
     for using MySQL Cluster. If a *Note `mysqld': mysqld. binary
     includes support for the *Note `NDBCLUSTER': mysql-cluster.
     storage engine, the engine is disabled by default. Use the
     `--ndbcluster' option to enable it. Use `--skip-ndbcluster' to
     explicitly disable the engine.

   * `--ndb-log-apply-status'

     Type and value information for ndb-log-apply-status

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-log-apply-status'

     Yes Yes No

     Yes Global No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Cause a MySQL server acting as a slave to log
     mysql.ndb_apply_status updates received from its immediate master
     in its own binary log, using its own server ID.  Effective only if
     the server is started with the -ndbcluster option.  


     Causes a slave *Note `mysqld': mysqld. to log any updates received
     from its immediate master to the `mysql.ndb_apply_status' table in
     its own binary log using its own server ID rather than the server
     ID of the master. In a circular or chain replication setting, this
     allows such updates to propagate to the `mysql.ndb_apply_status'
     tables of any MySQL servers configured as slaves of the current
     *Note `mysqld': mysqld.

     In a chain replication setup, using this option allows downstream
     (slave) clusters to be aware of their positions relative to all of
     their upstream contributors (masters).

     In a circular replication setup, this option causes changes to
     `ndb_apply_status' tables to complete the entire circuit,
     eventually propagating back to the originating MySQL Cluster. This
     also allows a cluster acting as a master to see when its changes
     (epochs) have been applied to the other clusters in the circle.

     This option was added in MySQL Cluster NDB 7.0.21 and MySQL
     Cluster NDB 7.1.10. It has no effect unless the MySQL server is
     started with the `--ndbcluster' option.

   * `--ndb-log-orig'

     Type and value information for ndb-log-orig

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-log-orig'

     Yes Yes No

     Yes Global No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Log originating server id and epoch in
     mysql.ndb_binlog_index table.  


     Log the originating server ID and epoch in the `ndb_binlog_index'
     table.

     Note that this makes it possible for a given epoch to have
     multiple rows in `ndb_binlog_index', one for each originating
     epoch.

     For more information, see *Note mysql-cluster-replication-schema::.

   * `--ndb-log-transaction-id'

     Type and value information for ndb-log-transaction-id

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-log-transaction-id'

     Yes Yes No

     Yes Global No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Write NDB transaction IDs in the binary log.
     Requires -log-bin-v1-events=OFF.  


     Causes a slave *Note `mysqld': mysqld. to write the NDB
     transaction ID in each row of the binary log. Such logging
     requires the use of the Version 2 event format for the binary log;
     thus, `--log-bin-use-v1-row-events' must be set to `FALSE' in
     order to use this option.

     This option is available beginning with MySQL Cluster NDB 7.1.16
     (and is not supported in mainline MySQL Server 5.1). It is
     required to enable MySQL Cluster Replication conflict detection
     and resolution using the `NDB$EPOCH_TRANS()' function introduced in
     the same MySQL Cluster release.

     The default value is `FALSE'.

     For more information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `--ndb-nodeid=#'

     Type and value information for ndb-nodeid

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-nodeid'

     Yes No Yes

     Yes Global No

     5.0.45 numeric / 1 - 63

     5.1.5 numeric / 1 - 255

     DESCRIPTION: MySQL Cluster node ID for this MySQL server 


     Set this MySQL server's node ID in a MySQL Cluster.

     Prior to MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB 7.1.4,
     this option can be used _instead_ of specifying the node ID as
     part of the connection string or in the `config.ini' file, or
     permitting the cluster to determine an arbitrary node ID. If you
     use this option, then `--ndb-nodeid' must be specified _before_
     `--ndb-connectstring'. If `--ndb-nodeid' is used _and_ a node ID
     is specified in the connection string, then the MySQL server
     cannot connect to the cluster.

     Beginning with MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB
     7.1.4, the `--ndb-nodeid' option _overrides_ any node ID set with
     `--ndb-connectstring', regardless of the order in which the two
     options are used.

     In addition (regardless of the MySQL Cluster version), if
     `--ndb-nodeid' is used, then either a matching node ID must be
     found in a `[mysqld]' or `[api]' section of `config.ini', or there
     must be an `open' `[mysqld]' or `[api]' section in the file (that
     is, a section without a `NodeId' or `Id' parameter specified).
     This is also true if the node ID is specified as part of the
     connection string.

     Regardless of how the node ID is determined, its is shown as the
     value of the global status variable `Ndb_cluster_node_id' in the
     output of *Note `SHOW STATUS': show-status, and as
     `cluster_node_id' in the `connection' row of the output of *Note
     `SHOW ENGINE NDBCLUSTER STATUS': show-engine.

     For more information about node IDs for MySQL Cluster SQL nodes,
     see *Note mysql-cluster-api-definition::.

   * `--ndb-log-empty-epochs=[0|1]'

     Type and value information for ndb-log-empty-epochs

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-log-empty-epochs'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 boolean OFF

     DESCRIPTION: When enabled, causes epochs in which there were no
     changes to be written to the ndb_apply_status and ndb_binlog_index
     tables, even when -log-slave-updates is enabled.  


     Causes epochs during which there were no changes to be written to
     the `ndb_apply_status' and `ndb_binlog_index' tables, even when
     `--log-slave-updates' is enabled.

     By default this option is disabled. Disabling
     `--ndb-log-empty-epochs' causes epoch transactions with no changes
     not to be written to the binary log, although a row is still
     written even for an empty epoch in `ndb_binlog_index' (Bug #49559,
     Bug #11757505).

     Because `--ndb-log-empty-epochs=1' causes the size of
     `ndb_binlog_index' table to increase independently of the size of
     the binary log, users should be prepared to manage the growth of
     this table, even if they expect the cluster to be idle a large
     part of the time.

     This option was introduced in MySQL Cluster NDB 6.3.21 and MySQL
     Cluster NDB 6.4.1. Prior to MySQL Cluster NDB 6.3.33, MySQL
     Cluster NDB 7.0.14, and MySQL Cluster NDB 7.1.3, setting
     `--ndb-log-empty-epochs=0' also caused no row to be written in
     `ndb_binlog_index' for an empty epoch.

   * `--server-id-bits=#'

     Type and value information for server-id-bits

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `server-id-bits'

     Yes Yes No

     Yes Global No

     MySQL 5.1 numeric 32 / 7 - 32

     DESCRIPTION: Sets the number of least significant bits in the
     server_id actually used for identifying the server, permitting NDB
     API applications to store application data in the most significant
     bits. server_id must be less than 2 to the power of this value.  


     This option indicates the number of least significant bits within
     the 32-bit `server_id' which actually identify the server.
     Indicating that the server is actually identified by fewer than 32
     bits makes it possible for some of the remaining bits to be used
     for other purposes, such as storing user data generated by
     applications using the NDB API's Event API within the `AnyValue'
     of an `OperationOptions' structure (MySQL Cluster uses the
     `AnyValue' to store the server ID).

     When extracting the effective server ID from `server_id' for
     purposes such as detection of replication loops, the server
     ignores the remaining bits. The `--server-id-bits' option is used
     to mask out any irrelevant bits of `server_id' in the IO and SQL
     threads when deciding whether an event should be ignored based on
     the server ID.

     This data can be read from the binary log by *Note `mysqlbinlog':
     mysqlbinlog, provided that it is run with its own
     `--server-id-bits' option set to 32 (the default).

     The value of `server_id' must be less than 2 ^ `server_id_bits';
     otherwise, *Note `mysqld': mysqld. refuses to start.

     This system variable was added in MySQL Cluster NDB 7.0.17 and
     MySQL Cluster NDB 7.1.6; it is supported only in these and later
     releases of MySQL Cluster. It is not supported by the standard
     MySQL Server.

   * `--skip-ndbcluster'

     Type and value information for skip-ndbcluster

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `skip-ndbcluster'

     Yes No No

     Yes

     No

     DESCRIPTION: Disable the NDB Cluster storage engine 


     Disable the *Note `NDBCLUSTER': mysql-cluster. storage engine.
     This is the default for binaries that were built with *Note
     `NDBCLUSTER': mysql-cluster. storage engine support; the server
     allocates memory and other resources for this storage engine only
     if the `--ndbcluster' option is given explicitly. See *Note
     mysql-cluster-quick::, for an example.

   * `ndb-transid-mysql-connection-map=STATE'

     Type and value information for ndb-transid-mysql-connection-map

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-transid-mysql-connection-map'

     Yes No No

     No

     No

     MySQL 5.1 enumeration ON / ON, OFF, FORCE

     DESCRIPTION: Enable or disable the
     ndb_transid_mysql_connection_map plugin; that is, enable or
     disable the INFORMATION_SCHEMA table having that name.  


     Enables or disables the plugin that handles the *Note
     `ndb_transid_mysql_connection_map':
     ndb-transid-mysql-connection-map-table.  table in the
     `INFORMATION_SCHEMA' database.  Takes one of the values `ON',
     `OFF', or `FORCE'.  `ON' (the default) enables the plugin.  `OFF'
     disables the plugin, which makes `ndb_transid_mysql_connection_map'
     inaccessible. `FORCE' keeps the MySQL Server from starting if the
     plugin fails to load and start.

     You can see whether the *Note `ndb_transid_mysql_connection_map':
     ndb-transid-mysql-connection-map-table.  table plugin is running
     by checking the output of *Note `SHOW PLUGINS': show-plugins.

     This option was added in MySQL Cluster NDB 7.1.17.

   * `--ndb-wait-connected=SECONDS'

     Type and value information for ndb-wait-connected

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-wait-connected'

     Yes Yes No

     Yes Global No

     MySQL 5.1 numeric 0 / 0 - 31536000

     5.1.56-ndb-7.1.16, 5.1.56-ndb-7.0.27 numeric 30 / 0 - 31536000

     DESCRIPTION: Time (in seconds) for the MySQL server to wait for
     connection to cluster management and data nodes before accepting
     MySQL client connections.  


     This option sets the period of time that the MySQL server waits
     for connections to MySQL Cluster management and data nodes to be
     established before accepting MySQL client connections. The time is
     specified in seconds.

     Prior to MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16,
     there existed a hard-coded 30-second timeout (which was removed in
     these versions), and the default value for this option was `0'.
     Starting with these releases, the default value is `30', and
     user-supplied values are handled correctly. (Bug #12543299)

   * `--ndb-wait-setup=SECONDS'

     Type and value information for ndb-wait-setup

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb-wait-setup'

     Yes Yes No

     Yes Global No

     MySQL 5.1 numeric 15 / 0 - 31536000

     5.1.56-ndb-7.0.27, 5.1.56-ndb-7.1.16 numeric 30 / 0 - 31536000

     DESCRIPTION: Time (in seconds) for the MySQL server to wait for
     NDB engine setup to complete.  


     This variable shows the period of time that the MySQL server waits
     for the *Note `NDB': mysql-cluster. storage engine to complete
     setup before timing out and treating *Note `NDB': mysql-cluster.
     as unavailable. The time is specified in seconds.

     Prior to MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16,
     the default value for this option was `15'. In these and later
     releases, the default value is `30'. (Bug #12543299)

   * `--ndb_optimization_delay=MILLISECONDS'

     Type and value information for ndb_optimization_delay

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_optimization_delay'

     No Yes No

     No Global Yes

     MySQL 5.1 numeric 10 / 0 - 100000

     DESCRIPTION: Sets the number of milliseconds to wait between
     processing sets of rows by OPTIMIZE TABLE on NDB tables.  


     Set the number of milliseconds to wait between sets of rows by
     *Note `OPTIMIZE TABLE': optimize-table. statements on *Note `NDB':
     mysql-cluster. tables. The default is 10.


File: manual.info,  Node: mysql-cluster-system-variables,  Next: mysql-cluster-status-variables,  Prev: mysql-cluster-program-options-mysqld,  Up: mysql-cluster-options-variables

17.3.4.3 MySQL Cluster System Variables
.......................................

This section provides detailed information about MySQL server system
variables that are specific to MySQL Cluster and the *Note `NDB':
mysql-cluster. storage engine. For system variables not specific to
MySQL Cluster, see *Note server-system-variables::. For general
information on using system variables, see *Note
using-system-variables::.

   * `have_ndbcluster'

     Type and value information for have_ndbcluster

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `have_ndbcluster'

     No Yes No

     No Global No

     MySQL 5.1 boolean

     DESCRIPTION: Whether mysqld supports NDB Cluster tables (set by
     -ndbcluster option) 


     `YES' if *Note `mysqld': mysqld. supports *Note `NDBCLUSTER':
     mysql-cluster. tables.  `DISABLED' if `--skip-ndbcluster' is used.

     This variable is deprecated and is removed in MySQL 5.6. Use *Note
     `SHOW ENGINES': show-engines. instead.

   * `ndb_autoincrement_prefetch_sz'

     Type and value information for ndb_autoincrement_prefetch_sz

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_autoincrement_prefetch_sz'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 numeric 32 / 1 - 256

     5.0.56 numeric 1 / 1 - 256

     5.1.1 numeric 32 / 1 - 256

     5.1.23 numeric 1 / 1 - 256

     5.1.16-ndb-6.2.0 numeric 32 / 1 - 256

     5.1.23-ndb-6.2.10 numeric 1 / 1 - 256

     5.1.19-ndb-6.3.0 numeric 32 / 1 - 256

     5.1.23-ndb-6.3.7 numeric 1 / 1 - 256

     5.1.41-ndb-6.3.31 numeric 1 / 1 - 65536

     5.1.30-ndb-6.4.0 numeric 32 / 1 - 256

     5.1.41-ndb-7.0.11 numeric 1 / 1 - 65536

     DESCRIPTION: NDB auto-increment prefetch size 


     Determines the probability of gaps in an autoincremented column.
     Set it to `1' to minimize this.  Setting it to a high value for
     optimization makes inserts faster, but decreases the likelihood
     that consecutive autoincrement numbers will be used in a batch of
     inserts.  The minimum value is 1. Prior to MySQL 5.1.23, MySQL
     Cluster NDB 6.2.9, and MySQL Cluster NDB 6.3.7, the default value
     was 32; in these and all later versions, the default is 1.  Prior
     to MySQL Cluster NDB 6.3.31 and MySQL Cluster NDB 7.0.11, the
     maximum value was 256; in these and all later versions of MySQL
     Cluster (including all MySQL Cluster NDB 7.1 releases), the
     maximum is 65536 (Bug #50621).

     Beginning with MySQL Cluster NDB 6.2.10, MySQL Cluster NDB 6.3.7,
     and MySQL 5.1.23, this variable affects the number of
     `AUTO_INCREMENT' IDs that are fetched between statements only.
     Within a statement, at least 32 IDs are now obtained at a time.
     Also beginning with these releases, the default value is 1. (Bug
     #31956)

     *Important*:

     This variable does not affect inserts performed using *Note
     `INSERT ... SELECT': insert-select.

   * `ndb_cache_check_time'

     Type and value information for ndb_cache_check_time

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_cache_check_time'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 numeric 0 /  -

     DESCRIPTION: Number of milliseconds between checks of cluster SQL
     nodes made by the MySQL query cache 


     The number of milliseconds that elapse between checks of MySQL
     Cluster SQL nodes by the MySQL query cache. Setting this to 0 (the
     default and minimum value) means that the query cache checks for
     validation on every query.

     The recommended maximum value for this variable is 1000, which
     means that the check is performed once per second. A larger value
     means that the check is performed and possibly invalidated due to
     updates on different SQL nodes less often. It is generally not
     desirable to set this to a value greater than 2000.

   * `ndb_deferred_constraints'

     Type and value information for ndb_deferred_constraints

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_deferred_constraints'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 integer 0 / 0 - 1

     DESCRIPTION: Specifies that constraint checks should be deferred
     (where these are supported). Not normally needed or used; for
     testing purposes only.  


     Controls whether or not constraint checks are deferred, where
     these are supported. `0' is the default.

     This variable was added in MySQL Cluster NDB 7.0.28 and MySQL
     Cluster NDB 7.1.14.

     This variable is not normally needed for operation of MySQL
     Cluster or MySQL Cluster Replication, and is intended primarily
     for use in testing.

   * `ndb_distribution'

     Type and value information for ndb_distribution

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_distribution'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 enumeration KEYHASH / LINHASH, KEYHASH

     DESCRIPTION: Default distribution for new tables in NDBCLUSTER
     (KEYHASH or LINHASH, default is KEYHASH) 


     Controls the default distribution method for *Note `NDB':
     mysql-cluster. tables. Can be set to either of `KEYHASH' (key
     hashing) or `LINHASH' (linear hashing).  `KEYHASH' is the default.

   * `ndb_eventbuffer_max_alloc'

     Type and value information for ndb_eventbuffer_max_alloc

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_eventbuffer_max_alloc'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 numeric 0 / 0 - 4294967295

     DESCRIPTION: Maximum memory that can be allocated for buffering
     events by the NDB API. Defaults to 0 (no limit).  


     Sets the maximum amount memory (in bytes) that can be allocated
     for buffering events by the NDB API. 0 means that no limit is
     imposed, and is the default.

     This variable was added in MySQL Cluster NDB 7.1.29.

   * `ndb_extra_logging'

     Type and value information for ndb_extra_logging

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_extra_logging'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 numeric 0 /  -

     5.1.19-ndb-6.3.0 numeric 1 /  -

     DESCRIPTION: Controls logging of MySQL Cluster schema, connection,
     and data distribution events in the MySQL error log 


     This variable enables recording in the MySQL error log of
     information specific to the *Note `NDB': mysql-cluster.  storage
     engine.

     When this variable is set to 0, the only information specific to
     `NDB' that is written to the MySQL error log relates to
     transaction handling. If it set to a value greater than 0 but less
     than 10, `NDB' table schema and connection events are also logged,
     as well as whether or not conflict resolution is in use, and other
     `NDB' errors and information. If the value is set to 10 or more,
     information about `NDB' internals, such as the progress of data
     distribution among cluster nodes, is also written to the MySQL
     error log.

     This variable was added in MySQL 5.1.6. Prior to MySQL Cluster NDB
     6.3, the default value was 0; in MySQL Cluster NDB 6.3.0 and
     later, the default is 1.

   * `ndb_force_send'

     Type and value information for ndb_force_send

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_force_send'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 boolean TRUE

     DESCRIPTION: Forces sending of buffers to NDB immediately, without
     waiting for other threads 


     Forces sending of buffers to *Note `NDB': mysql-cluster.
     immediately, without waiting for other threads. Defaults to `ON'.

   * `ndb_index_stat_cache_entries'

     Type and value information for ndb_index_stat_cache_entries

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_index_stat_cache_entries'

     Yes No No

     Yes

     No

     MySQL 5.1 numeric 32 / 0 - 4294967295

     DESCRIPTION: Sets the granularity of the statistics by determining
     the number of starting and ending keys 


     Sets the granularity of the statistics by determining the number
     of starting and ending keys to store in the statistics memory
     cache. Zero means no caching takes place; in this case, the data
     nodes are always queried directly.  Default value: `32'.

     *Note*:

     If `ndb_index_stat_enable' is `OFF', then setting this variable has
     no effect.

     This variable is deprecated as of MySQL 5.1.19, and is removed
     from MySQL Cluster NDB 7.1.31 and later.

   * `ndb_index_stat_enable'

     Type and value information for ndb_index_stat_enable

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_index_stat_enable'

     Yes No No

     Yes

     No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Use NDB index statistics in query optimization 


     Use *Note `NDB': mysql-cluster. index statistics in query
     optimization. Defaults to `OFF' prior to MySQL Cluster NDB 7.2;
     `ON' is the default in MySQL Cluster NDB 7.2 and later.

   * `ndb_index_stat_option'

     Type and value information for ndb_index_stat_option

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_index_stat_option'

     Yes No No

     Yes

     No

     MySQL 5.1 string
     loop_enable=1000ms,loop_idle=1000ms,loop_busy=100ms,
     update_batch=1,read_batch=4,idle_batch=32,check_batch=8,
     check_delay=10m,delete_batch=8, clean_delay=1m,error_batch=4,
        error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M,
           cache_lowpct=90,zero_total=0

     5.1.56-ndb-7.1.17 string
     loop_checkon=1000ms,loop_idle=1000ms,loop_busy=100ms,
     update_batch=1,read_batch=4,idle_batch=32,check_batch=32,
     check_delay=1m,delete_batch=8,clean_delay=0,error_batch=4,
     error_delay=1m,evict_batch=8,evict_delay=1m,cache_limit=32M,
      cache_lowpct=90

     DESCRIPTION: Comma-separated list of tunable options for NDB index
     statistics; the list should contain no spaces 


     This variable is used for providing tuning options for NDB index
     statistics generation. The list consist of comma-separated
     name-value pairs of option names and values.  Note that this list
     must not contain any space characters.

     Options not used when setting `ndb_index_stat_option' are not
     changed from their default values. For example, you can set
     `ndb_index_stat_option = 'loop_idle=1000ms,cache_limit=32M''.

     Time values can be optionally suffixed with `s' (seconds) or `ms'
     (milliseconds). Integer values can be suffixed with `K', `M', or
     `G'.

     The names of the options that can be set using this variable are
     shown in the table that follows. The table also provides brief
     descriptions of the options, their default values, and (where
     applicable) their minimum and maximum values.

     `ndb_index_stat_option' options and values

     Name              Description       Default/Units     Minimum/Maximum
     `loop_enable'                       1000 ms           0/4G
     `loop_idle'       Time to sleep     1000 ms           0/4G
                       when idle                           
     `loop_busy'       Time to sleep     100 ms            0/4G
                       when more work                      
                       is waiting                          
     `update_batch'                      1                 0/4G
     `read_batch'                        4                 1/4G
     `idle_batch'                        32                1/4G
     `check_batch'                       8                 1/4G
     `check_delay'     How often to      10 ms             1/4G
                       check for new                       
                       statistics                          
     `delete_batch'                      8                 0/4G
     `clean_delay'                       1 ms              0/4G
     `error_batch'                       4                 1/4G
     `error_delay'                       1 ms              1/4G
     `evict_batch'                       8                 1/4G
     `evict_delay'     Clean LRU cache,  1 ms              0/4G
                       from read time                      
     `cache_limit'     Maximum amount    32 M              0/4G
                       of memory in                        
                       bytes used for                      
                       cached index                        
                       statistics by                       
                       this *Note                          
                       `mysqld':                           
                       mysqld.; clean                      
                       up the cache                        
                       when this is                        
                       exceeded.                           
     `cache_lowpct'                      90                0/100
     `zero_total'      Setting this to   0                 0/1
                       1 causes all                        
                       accumulating                        
                       counters in                         
                       `ndb_index_stat_status'                  
                       to be reset to                      
                       0. Note that the                    
                       option value is                     
                       also reset to 0                     
                       when this is                        
                       done.                               

     `ndb_index_stat_option' was added in MySQL Cluster NDB 7.1.15.

   * `ndb_index_stat_update_freq'

     Type and value information for ndb_index_stat_update_freq

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_index_stat_update_freq'

     Yes No No

     Yes

     No

     MySQL 5.1 numeric 20 / 0 - 4294967295

     DESCRIPTION: How often to query data nodes instead of the
     statistics cache 


     How often to query data nodes instead of the statistics cache. For
     example, a value of `20' (the default) means to direct every 20^th
     query to the data nodes.

     *Note*:

     If `ndb_index_stat_cache_entries' is `0', then setting this
     variable has no effect; in this case, every query is sent directly
     to the data nodes.

     This variable is deprecated as of MySQL 5.1.19, and is removed
     from MySQL Cluster NDB 7.1.31 and later.

   * `ndb_join_pushdown'

     Type and value information for ndb_join_pushdown

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_join_pushdown'

     No Yes No

     No Both Yes

     5.1.51-ndb-7.2.0 boolean TRUE

     DESCRIPTION: Enables pushing down of joins to data nodes 


     Added in MySQL Cluster NDB 7.2.0, this variable controls whether
     joins on *Note `NDB': mysql-cluster. tables are pushed down to the
     NDB kernel (data nodes). Previously, a join was handled using
     multiple accesses of *Note `NDB': mysql-cluster. by the SQL node;
     however, when `ndb_join_pushdown' is enabled, a pushable join is
     sent in its entirety to the data nodes, where it can be
     distributed among the data nodes and executed in parallel on
     multiple copies of the data, with a single, merged result being
     returned to *Note `mysqld': mysqld. This can reduce greatly the
     number of round trips between an SQL node and the data nodes
     required to handle such a join.

     By default, `ndb_join_pushdown' is enabled.

     In order for a join to be pushable, it must meet the following
     conditions:

       1. Only columns can be compared, and all columns to be joined
          must use _exactly_ the same data type.

          This means that expressions such as `t1.a = t2.a + CONSTANT'
          cannot be pushed down, and that (for example) a join on an
          *Note `INT': integer-types. column and a *Note `BIGINT':
          integer-types. column also cannot be pushed down.

       2. Queries referencing *Note `BLOB': blob.  or *Note `TEXT':
          blob. columns are not supported.

       3. Explicit locking is not supported; however, the *Note `NDB':
          mysql-cluster. storage engine's characteristic implicit
          row-based locking is enforced.

          This means that a join using `FOR UPDATE' cannot be pushed
          down.

       4. In order for a join to be pushed down, child tables in the
          join must be accessed using one of the `ref', `eq_ref', or
          `const' access methods, or some combination of these methods.

          Outer joined child tables can only be pushed using `eq_ref'.

          If the root of the pushed join is an `eq_ref' or `const',
          only child tables joined by `eq_ref' can be appended. (A
          table joined by `ref' is likely to become the root of another
          pushed join.)

          If the query optimizer decides on `Using join cache' for a
          candidate child table, that table cannot be pushed as a
          child. However, it may be the root of another set of pushed
          tables.

       5. Joins referencing tables explicitly partitioned by `[LINEAR]
          HASH', `LIST', or `RANGE' currently cannot be pushed down.

     You can see whether a given join can be pushed down by checking it
     with *Note `EXPLAIN': explain.; when the join can be pushed down,
     you can see references to the `pushed join' in the `Extra' column
     of the output, as shown in this example:


          mysql> EXPLAIN
              ->     SELECT e.first_name, e.last_name, t.title, d.dept_name
              ->         FROM employees e
              ->         JOIN dept_emp de ON e.emp_no=de.emp_no
              ->         JOIN departments d ON d.dept_no=de.dept_no
              ->         JOIN titles t ON e.emp_no=t.emp_no\G
          *************************** 1. row ***************************
                     id: 1
            select_type: SIMPLE
                  table: d
                   type: ALL
          possible_keys: PRIMARY
                    key: NULL
                key_len: NULL
                    ref: NULL
                   rows: 9
                  Extra: Parent of 4 pushed join@1
          *************************** 2. row ***************************
                     id: 1
            select_type: SIMPLE
                  table: de
                   type: ref
          possible_keys: PRIMARY,emp_no,dept_no
                    key: dept_no
                key_len: 4
                    ref: employees.d.dept_no
                   rows: 5305
                  Extra: Child of 'd' in pushed join@1
          *************************** 3. row ***************************
                     id: 1
            select_type: SIMPLE
                  table: e
                   type: eq_ref
          possible_keys: PRIMARY
                    key: PRIMARY
                key_len: 4
                    ref: employees.de.emp_no
                   rows: 1
                  Extra: Child of 'de' in pushed join@1
          *************************** 4. row ***************************
                     id: 1
            select_type: SIMPLE
                  table: t
                   type: ref
          possible_keys: PRIMARY,emp_no
                    key: emp_no
                key_len: 4
                    ref: employees.de.emp_no
                   rows: 19
                  Extra: Child of 'e' in pushed join@1
          4 rows in set (0.00 sec)

     *Note*:

     If inner joined child tables are joined by `ref', _and_ the result
     is ordered or grouped by a sorted index, this index cannot provide
     sorted rows, which forces writing to a sorted tempfile.

     Two additional sources of information about pushed join
     performance are available:

       1. The status variables `Ndb_pushed_queries_defined',
          `Ndb_pushed_queries_dropped', `Ndb_pushed_queries_executed',
          and `Ndb_pushed_reads' (all introduced in MySQL Cluster NDB
          7.2.0).

       2. The counters in the *Note `ndbinfo.counters':
          mysql-cluster-ndbinfo-counters. table that belong to the
          `DBSPJ' kernel block. (These counters and the `DBSPJ' block
          were also introduced in MySQL Cluster NDB 7.2.0).  See *Note
          mysql-cluster-ndbinfo-counters::, for information about these
          counters. See also The `DBSPJ' Block
          (http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dbspj.html),
          in the `MySQL Cluster API Developer Guide'.

   * `ndb_log_apply_status'

     Type and value information for ndb_log_apply_status

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_log_apply_status'

     Yes Yes No

     Yes Global No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Whether or not a MySQL server acting as a slave logs
     mysql.ndb_apply_status updates received from its immediate master
     in its own binary log, using its own server ID.  


     A read-only variable which shows whether the server was started
     with the `--ndb-log-apply-status' option.

     This variable was added in MySQL Cluster NDB 7.0.21 and MySQL
     Cluster NDB 7.1.10.

   * `ndb_log_bin'

     Type and value information for ndb_log_bin

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_log_bin'

     Yes Yes No

     No Both Yes

     MySQL 5.1 boolean ON

     DESCRIPTION: Write updates to NDB tables in the binary log.
     Effective only if binary logging is enabled with -log-bin.  


     Causes updates to `NDB' tables to be written to the binary log.
     Setting this variable has no effect if binary logging is not
     already enabled for the server using `log_bin'.  `ndb_log_bin'
     defaults to 1 (ON); normally, there is never any need to change
     this value in a production environment.

     This variable was added in MySQL 5.1.6.

   * `ndb_log_binlog_index'

     Type and value information for ndb_log_binlog_index

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_log_binlog_index'

     Yes Yes No

     No Global Yes

     MySQL 5.1 boolean ON

     DESCRIPTION: Insert mapping between epochs and binary log
     positions into the ndb_binlog_index table. Defaults to ON.
     Effective only if binary logging is enabled on the server.  


     Causes a mapping of epochs to positions in the binary log to be
     inserted into the `ndb_binlog_index' table. Setting this variable
     has no effect if binary logging is not already enabled for the
     server using `log_bin'. (In addition, `ndb_log_bin' must not be
     disabled.) `ndb_log_binlog_index' defaults to `1' (`ON'); normally,
     there is never any need to change this value in a production
     environment.

     This variable was added in MySQL 5.1.6.

   * `ndb_log_orig'

     Type and value information for ndb_log_orig

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_log_orig'

     Yes Yes No

     Yes Global No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Whether the id and epoch of the originating server
     are recorded in the mysql.ndb_binlog_index table. Set using the
     -ndb-log-orig option when starting mysqld.  


     Shows whether the originating server ID and epoch are logged in
     the `ndb_binlog_index' table. Set using the `--ndb-log-orig' server
     option.

     This variable was added in MySQL Cluster NDB 6.3.2.

   * `ndb_optimized_node_selection'

     Type and value information for ndb_optimized_node_selection

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_optimized_node_selection'

     Yes No No

     Yes

     No

     4.1.9 boolean ON

     5.1.22-ndb-6.3.4 numeric 3 / 0 - 3

     DESCRIPTION: Determines how an SQL node chooses a cluster data
     node to use as transaction coordinator 


     Prior to MySQL Cluster NDB 6.3.4

     Causes an SQL node to use the `closest' data node as transaction
     coordinator. Enabled by default. Set to `0' or `OFF' to disable,
     in which case the SQL node uses each data node in the cluster in
     succession. When this option is disabled each SQL thread attempts
     to use a given data node 8 times before proceeding to the next one.

     Beginning with MySQL Cluster NDB 6.3.4

     There are two forms of optimized node selection, described here:

       1. The SQL node uses _promixity_ to determine the transaction
          coordinator; that is, the `closest' data node to the SQL node
          is chosen as the transaction coordinator. For this purpose, a
          data node having a shared memory connection with the SQL node
          is considered to be `closest' to the SQL node; the next
          closest (in order of decreasing proximity) are: TCP
          connection to `localhost'; SCI connection; TCP connection
          from a host other than `localhost'.

       2. The SQL thread uses _distribution awareness_ to select the
          data node. That is, the data node housing the cluster
          partition accessed by the first statement of a given
          transaction is used as the transaction coordinator for the
          entire transaction.  (This is effective only if the first
          statement of the transaction accesses no more than one cluster
          partition.)

     This option takes one of the integer values `0', `1', `2', or `3'.
     `3' is the default. These values affect node selection as follows:

        * `0': Node selection is not optimized.  Each data node is
          employed as the transaction coordinator 8 times before the
          SQL thread proceeds to the next data node. (This is the same
          `round-robin' behavior as caused by setting this option to
          `0' or `OFF' in previous versions of MySQL Cluster.)

        * `1': Proximity to the SQL node is used to determine the
          transaction coordinator. (This is the same behavior as caused
          by setting this option to `1' or `ON' in previous MySQL
          versions.)

        * `2': Distribution awareness is used to select the transaction
          coordinator. However, if the first statement of the
          transaction accesses more than one cluster partition, the SQL
          node reverts to the round-robin behavior seen when this
          option is set to `0'.

        * `3': If distribution awareness can be employed to determine
          the transaction coordinator, then it is used; otherwise
          proximity is used to select the transaction coordinator.
          (This is the default behavior in MySQL Cluster NDB 6.3.4 and
          later.)

     *Important*:

     Beginning with MySQL Cluster NDB 6.3.4, it is no longer possible
     to set `--ndb_optimized_node_selection' to `ON' or `OFF';
     attempting to do so causes *Note `mysqld': mysqld. to abort with
     an error.

   * `ndb_report_thresh_binlog_epoch_slip'

     Type and value information for ndb_report_thresh_binlog_epoch_slip

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_report_thresh_binlog_epoch_slip'

     Yes No No

     Yes

     No

     MySQL 5.1 numeric 3 / 0 - 256

     DESCRIPTION: This is a threshold on the number of epochs to be
     behind before reporting binlog status 


     This is a threshold on the number of epochs to be behind before
     reporting binary log status. For example, a value of `3' (the
     default) means that if the difference between which epoch has been
     received from the storage nodes and which epoch has been applied
     to the binary log is 3 or more, a status message will be sent to
     the cluster log.

   * `ndb_report_thresh_binlog_mem_usage'

     Type and value information for ndb_report_thresh_binlog_mem_usage

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_report_thresh_binlog_mem_usage'

     Yes No No

     Yes

     No

     MySQL 5.1 numeric 10 / 0 - 10

     DESCRIPTION: This is a threshold on the percentage of free memory
     remaining before reporting binlog status 


     This is a threshold on the percentage of free memory remaining
     before reporting binary log status. For example, a value of `10'
     (the default) means that if the amount of available memory for
     receiving binary log data from the data nodes falls below 10%, a
     status message will be sent to the cluster log.

   * `slave_allow_batching'

     Type and value information for slave_allow_batching

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `slave_allow_batching'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 boolean off

     DESCRIPTION: Turns update batching on and off for a replication
     slave 


     Whether or not batched updates are enabled on MySQL Cluster
     replication slaves.

     This variable is available beginning with MySQL Cluster NDB 6.2.3.
     Currently, it is available for *Note `mysqld': mysqld. only as
     supplied with MySQL Cluster or built from the MySQL Cluster
     sources. For more information, see *Note
     mysql-cluster-replication-starting::.

   * `ndb_table_no_logging'

     Type and value information for ndb_table_no_logging

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_table_no_logging'

     No Yes No

     No Session Yes

     MySQL 5.1 boolean FALSE

     DESCRIPTION: NDB tables created when this setting is enabled are
     not checkpointed to disk (although table schema files are
     created). The setting in effect when the table is created with or
     altered to use NDBCLUSTER persists for the lifetime of the table.  


     When this variable is set to `ON' or `1', it causes *Note `NDB':
     mysql-cluster. tables not to be checkpointed to disk. More
     specifically, this setting applies to tables which are created or
     altered using `ENGINE NDB' when `ndb_table_no_logging' is enabled,
     and continues to apply for the lifetime of the table, even if
     `ndb_table_no_logging' is later changed. Suppose that `A', `B',
     `C', and `D' are tables that we create (and perhaps also alter),
     and that we also change the setting for `ndb_table_no_logging' as
     shown here:


          SET @@ndb_table_no_logging = 1;

          CREATE TABLE A ... ENGINE NDB;

          CREATE TABLE B ... ENGINE MYISAM;
          CREATE TABLE C ... ENGINE MYISAM;

          ALTER TABLE B ENGINE NDB;

          SET @@ndb_table_no_logging = 0;

          CREATE TABLE D ... ENGINE NDB;
          ALTER TABLE C ENGINE NDB;

          SET @@ndb_table_no_logging = 1;

     After the previous sequence of events, tables `A' and `B' are not
     checkpointed; `A' was created with `ENGINE NDB' and B was altered
     to use `NDB', both while `ndb_table_no_logging' was enabled.
     However, tables `C' and `D' are logged; `C' was altered to use
     *Note `NDB': mysql-cluster. and `D' was created using `ENGINE
     NDB', both while `ndb_table_no_logging' was disabled. Setting
     `ndb_table_no_logging' back to `1' or `ON' does _not_ cause table
     `C' or `D' to be checkpointed.

     *Note*:

     `ndb_table_no_logging' has no effect on the creation of *Note
     `NDB': mysql-cluster. table schema files; to suppress these, use
     `ndb_table_temporary' instead.

   * `ndb_table_temporary'

     Type and value information for ndb_table_temporary

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_table_temporary'

     No Yes No

     No Session Yes

     MySQL 5.1 boolean FALSE

     DESCRIPTION: NDB tables are not persistent on disk: no schema
     files are created and the tables are not logged 


     When set to `ON' or `1', this variable causes *Note `NDB':
     mysql-cluster. tables not to be written to disk: This means that
     no table schema files are created, and that the tables are not
     logged.

     *Note*:

     Setting this variable currently has no effect in MySQL Cluster NDB
     7.0 and later. This is a known issue; see Bug #34036.

   * `ndb_use_copying_alter_table'

     Type and value information for ndb_use_copying_alter_table

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_use_copying_alter_table'

     No Yes No

     No Both No

     DESCRIPTION: Use copying ALTER TABLE operations in MySQL Cluster 


     Forces *Note `NDB': mysql-cluster. to use copying of tables in the
     event of problems with online *Note `ALTER TABLE': alter-table.
     operations. The default value is `OFF'.

     This variable was added in MySQL 5.1.12.

   * `ndb_version'

     Type and value information for ndb_version

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_version'

     No Yes No

     No Global No

     MySQL 5.1 string

     DESCRIPTION: Shows build and NDB engine version as an integer.  


     `NDB' engine version, as a composite integer.

     This variable was added in MySQL Cluster NDB 7.1.19.

   * `ndb_version_string'

     Type and value information for ndb_version_string

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_version_string'

     No Yes No

     No Global No

     MySQL 5.1 string

     DESCRIPTION: Shows build information including NDB engine version
     in ndb-x.y.z format.  


     `NDB' engine version in `ndb-X.Y.Z' format.

     This variable was added in MySQL Cluster NDB 7.1.19.

   * `ndb_use_exact_count'

     Type and value information for ndb_use_exact_count

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_use_exact_count'

     No Yes No

     No Both Yes

     MySQL 5.1 boolean ON

     5.1.47-ndb-7.1.8 boolean OFF

     DESCRIPTION: Use exact row count when planning queries 


     Forces *Note `NDB': mysql-cluster. to use a count of records
     during `SELECT COUNT(*)' query planning to speed up this type of
     query. Prior to MySQL Cluster NDB 7.1.7, the default value for
     this variable was `ON'. Starting with MySQL Cluster NDB 7.1.8, the
     value of `ndb_use_exact_count' defaults to `OFF', which allows for
     faster queries overall.

   * `ndb_use_transactions'

     Type and value information for ndb_use_transactions

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_use_transactions'

     Yes Yes No

     Yes Both Yes

     MySQL 5.1 boolean ON

     DESCRIPTION: Forces NDB to use a count of records during SELECT
     COUNT(*) query planning to speed up this type of query 


     You can disable *Note `NDB': mysql-cluster. transaction support by
     setting this variable's values to `OFF' (not recommended). The
     default is `ON'.

     *Note*:

     The setting for this variable was not honored in MySQL Cluster NDB
     6.4.3 and MySQL Cluster NDB 7.0.4. (Bug #43236)

   * `transaction_allow_batching'

     Type and value information for transaction_allow_batching

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `transaction_allow_batching'

     No Yes No

     No Session Yes

     MySQL 5.1 boolean FALSE

     DESCRIPTION: Allows batching of statements within a transaction.
     Disable AUTOCOMMIT to use.  


     When set to `1' or `ON', this variable enables batching of
     statements within the same transaction. To use this variable,
     `autocommit' must first be disabled by setting it to `0' or `OFF';
     otherwise, setting `transaction_allow_batching' has no effect.

     It is safe to use this variable with transactions that performs
     writes only, as having it enabled can lead to reads from the
     `before' image. You should ensure that any pending transactions
     are committed (using an explicit *Note `COMMIT': commit. if
     desired) before issuing a *Note `SELECT': select.

     *Important*:

     `transaction_allow_batching' should not be used whenever there is
     the possibility that the effects of a given statement depend on
     the outcome of a previous statement within the same transaction.

     This variable was added in MySQL Cluster NDB 6.3.7, and is
     currently supported in MySQL Cluster only.

The system variables in the following list all relate to the *Note
`ndbinfo': mysql-cluster-ndbinfo. information database.  They were
added in MySQL Cluster NDB 7.1.1.

   * `ndbinfo_database'

     Type and value information for ndbinfo_database

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_database'

     No Yes No

     No Global No

     MySQL 5.1 string ndbinfo

     DESCRIPTION: The name used for the NDB information database; read
     only.  


     Shows the name used for the `NDB' information database; the
     default is `ndbinfo'. This is a read-only variable whose value is
     determined at compile time; you can set it by starting the server
     using `--ndbinfo-database=NAME', which sets the value shown for
     this variable but does not actually change the name used for the
     NDB information database.

   * `ndbinfo_max_bytes'

     Type and value information for ndbinfo_max_bytes

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_max_bytes'

     Yes Yes No

     No Both Yes

     MySQL 5.1 numeric 0 /  -

     DESCRIPTION: Used for debugging only.  


     Used in testing and debugging only.

   * `ndbinfo_max_rows'

     Type and value information for ndbinfo_max_rows

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_max_rows'

     Yes Yes No

     No Both Yes

     MySQL 5.1 numeric 10 /  -

     DESCRIPTION: Used for debugging only.  


     Used in testing and debugging only.

   * `ndbinfo_offline'

     Type and value information for ndbinfo_offline

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_offline'

     No Yes No

     No Global Yes

     MySQL 5.1 boolean OFF

     DESCRIPTION: Put the ndbinfo database into offline mode, in which
     no rows are returned from tables or views.  


     Place the *Note `ndbinfo': mysql-cluster-ndbinfo. database into
     offline mode, in which tables and views can be opened even when
     they do not actually exist, or when they exist but have different
     definitions in *Note `NDB': mysql-cluster. No rows are returned
     from such tables (or views).

   * `ndbinfo_show_hidden'

     Type and value information for ndbinfo_show_hidden

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_show_hidden'

     Yes Yes No

     No Both Yes

     MySQL 5.1 boolean OFF

     DESCRIPTION: Whether to show ndbinfo internal base tables in the
     mysql client. The default is OFF.  


     Whether or not the *Note `ndbinfo': mysql-cluster-ndbinfo.
     database's underlying internal tables are shown in the `mysql'
     client. The default is `OFF'.

   * `ndbinfo_table_prefix'

     Type and value information for ndbinfo_table_prefix

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_table_prefix'

     Yes Yes No

     No Both Yes

     MySQL 5.1 string ndb$

     DESCRIPTION: The prefix to use for naming ndbinfo internal base
     tables 


     The prefix used in naming the ndbinfo database's base tables
     (normally hidden, unless exposed by setting
     `ndbinfo_show_hidden'). This is a read-only variable whose default
     value is ``ndb$''. You can start the server with the
     `--ndbinfo-table-prefix' option, but this merely sets the variable
     and does not change the actual prefix used to name the hidden base
     tables; the prefix itself is determined at compile time.

   * `ndbinfo_version'

     Type and value information for ndbinfo_version

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndbinfo_version'

     No Yes No

     No Global No

     MySQL 5.1 string

     DESCRIPTION: The version of the ndbinfo engine; read only.  


     Shows the version of the *Note `ndbinfo': mysql-cluster-ndbinfo.
     engine in use; read-only.

   * `ndb_log_transaction_id'

     Type and value information for ndb_log_transaction_id

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_log_transaction_id'

     No Yes No

     No Global No

     MySQL 5.1 boolean OFF

     DESCRIPTION: Whether NDB transaction IDs are written into the
     binary log. (Read-only.)  


     This read-only, Boolean system variable shows whether a slave
     *Note `mysqld': mysqld. writes NDB transaction IDs in the binary
     log (required to use `active-active' MySQL Cluster Replication with
     `NDB$EPOCH_TRANS()' conflict detection). To change the setting,
     use the `--ndb-log-transaction-id' option.

     `ndb_log_transaction_id' is available in MySQL Cluster NDB 7.1.16
     and later. It is not supported in mainline MySQL Server 5.1.

     For more information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `ndb_log_empty_epochs'

     Type and value information for ndb_log_empty_epochs

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `ndb_log_empty_epochs'

     Yes Yes No

     Yes Global Yes

     MySQL 5.1 boolean OFF

     DESCRIPTION: When enabled, epochs in which there were no changes
     are written to the ndb_apply_status and ndb_binlog_index tables,
     even when log_slave_updates is enabled.  


     When this variable is set to 0, epoch transactions with no changes
     are not written to the binary log, although a row is still written
     even for an empty epoch in `ndb_binlog_index' (Bug #49559, Bug
     #11757505).

   * `server_id_bits'

     Type and value information for server_id_bits

     Command Line System Variable Status Variable

     Option File Scope Dynamic

     From Version Type Default, Range

     Notes

     `server_id_bits'

     Yes Yes No

     Yes Global No

     MySQL 5.1 numeric 32 / 7 - 32

     DESCRIPTION: The effective value of server_id if the server was
     started with the -server-id-bits option set to a nondefault value.  


     The effective value of `server_id' if the server was started with
     the `--server-id-bits' option set to a nondefault value.

     If the value of `server_id' is greater than or equal to 2 to the
     power of `server_id_bits', *Note `mysqld': mysqld. refuses to
     start.

     This system variable was added in MySQL Cluster NDB 7.0.17 and
     MySQL Cluster NDB 7.1.6; it is supported only in these and later
     releases of MySQL Cluster.  `server_id_bits' is not supported by
     the standard MySQL Server.


File: manual.info,  Node: mysql-cluster-status-variables,  Prev: mysql-cluster-system-variables,  Up: mysql-cluster-options-variables

17.3.4.4 MySQL Cluster Status Variables
.......................................

This section provides detailed information about MySQL server status
variables that relate to MySQL Cluster and the *Note `NDB':
mysql-cluster. storage engine. For status variables not specific to
MySQL Cluster, and for general information on using status variables,
see *Note server-status-variables::.

   * `Handler_discover'

     The MySQL server can ask the *Note `NDBCLUSTER': mysql-cluster.
     storage engine if it knows about a table with a given name. This
     is called discovery.  `Handler_discover' indicates the number of
     times that tables have been discovered using this mechanism.

   * `Ndb_api_wait_exec_complete_count_session'

     The number of times a thread has been blocked in this client
     session while waiting for execution of an operation to complete.
     This includes all `execute()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-execute)
     calls as well as implicit implicit executes for blob and
     auto-increment operations not visible to clients.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_exec_complete_count_slave'

     The number of times a thread has been blocked by this slave while
     waiting for execution of an operation to complete.  This includes
     all `execute()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-execute)
     calls as well as implicit implicit executes for blob and
     auto-increment operations not visible to clients.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_exec_complete_count'

     The number of times a thread has been blocked by this MySQL Server
     (SQL node) while waiting for execution of an operation to
     complete. This includes all `execute()'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-execute)
     calls as well as implicit implicit executes for blob and
     auto-increment operations not visible to clients.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_scan_result_count_session'

     The number of times a thread has been blocked in this client
     session while waiting for a scan-based signal, such as when
     waiting for more results from a scan, or when waiting for a scan
     to close.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_scan_result_count_slave'

     The number of times a thread has been blocked by this slave while
     waiting for a scan-based signal, such as when waiting for more
     results from a scan, or when waiting for a scan to close.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_scan_result_count'

     The number of times a thread has been blocked by this MySQL Server
     (SQL node) while waiting for a scan-based signal, such as when
     waiting for more results from a scan, or when waiting for a scan
     to close.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_meta_request_count_session'

     The number of times a thread has been blocked in this client
     session waiting for a metadata-based signal, such as is expected
     for DDL requests, new epochs, and seizure of transaction records.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_meta_request_count_slave'

     The number of times a thread has been blocked by this slave
     waiting for a metadata-based signal, such as is expected for DDL
     requests, new epochs, and seizure of transaction records.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_meta_request_count'

     The number of times a thread has been blocked by this MySQL Server
     (SQL node) waiting for a metadata-based signal, such as is
     expected for DDL requests, new epochs, and seizure of transaction
     records.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_nanos_count_session'

     Total time (in nanoseconds) spent in this client session waiting
     for any type of signal from the data nodes.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_nanos_count_slave'

     Total time (in nanoseconds) spent by this slave waiting for any
     type of signal from the data nodes.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_wait_nanos_count'

     Total time (in nanoseconds) spent by this MySQL Server (SQL node)
     waiting for any type of signal from the data nodes.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_bytes_sent_count_session'

     Amount of data (in bytes) sent to the data nodes in this client
     session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_bytes_sent_count_slave'

     Amount of data (in bytes) sent to the data nodes by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_bytes_sent_count'

     Amount of data (in bytes) sent to the data nodes by this MySQL
     Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_bytes_received_count_session'

     Amount of data (in bytes) received from the data nodes in this
     client session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_bytes_received_count_slave'

     Amount of data (in bytes) received from the data nodes by this
     slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_bytes_received_count'

     Amount of data (in bytes) received from the data nodes by this
     MySQL Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_start_count_session'

     The number of transactions started in this client session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_start_count_slave'

     The number of transactions started by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_start_count'

     The number of transactions started by this MySQL Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_commit_count_session'

     The number of transactions committed in this client session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_commit_count_slave'

     The number of transactions committed by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_commit_count'

     The number of transactions committed by this MySQL Server (SQL
     node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_abort_count_session'

     The number of transactions aborted in this client session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_abort_count_slave'

     The number of transactions aborted by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_abort_count'

     The number of transactions aborted by this MySQL Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_close_count_session'

     The number of transactions closed in this client session.  This
     value may be greater than the sum of
     `Ndb_api_trans_commit_count_session' and
     `Ndb_api_trans_abort_count_session', since some transactions may
     have been rolled back.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_close_count_slave'

     The number of transactions closed by this slave. This value may be
     greater than the sum of `Ndb_api_trans_commit_count_slave' and
     `Ndb_api_trans_abort_count_slave', since some transactions may
     have been rolled back.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_close_count'

     The number of transactions closed by this MySQL Server (SQL node).
     This value may be greater than the sum of
     `Ndb_api_trans_commit_count' and `Ndb_api_trans_abort_count',
     since some transactions may have been rolled back.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_pk_op_count_session'

     The number of operations in this client session based on or using
     primary keys. This includes operations on blob tables, implicit
     unlock operations, and auto-increment operations, as well as
     user-visible primary key operations.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_pk_op_count_slave'

     The number of operations by this slave based on or using primary
     keys. This includes operations on blob tables, implicit unlock
     operations, and auto-increment operations, as well as user-visible
     primary key operations.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_pk_op_count'

     The number of operations by this MySQL Server (SQL node) based on
     or using primary keys. This includes operations on blob tables,
     implicit unlock operations, and auto-increment operations, as well
     as user-visible primary key operations.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_uk_op_count_session'

     The number of operations in this client session based on or using
     unique keys.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_uk_op_count_slave'

     The number of operations by this slave based on or using unique
     keys.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_uk_op_count'

     The number of operations by this MySQL Server (SQL node) based on
     or using unique keys.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_table_scan_count_session'

     The number of table scans that have been started in this client
     session, including scans of internal tables,.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_table_scan_count_slave'

     The number of table scans that have been started by this slave,
     including scans of internal tables,.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_table_scan_count'

     The number of table scans that have been started by this MySQL
     Server (SQL node), including scans of internal tables,.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_range_scan_count_session'

     The number of range scans that have been started in this client
     session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_range_scan_count_slave'

     The number of range scans that have been started by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_range_scan_count'

     The number of range scans that have been started by this MySQL
     Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_pruned_scan_count_session'

     The number of scans in this client session that have been pruned
     to a single partition.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_pruned_scan_count_slave'

     The number of scans by this slave that have been pruned to a
     single partition.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_pruned_scan_count'

     The number of scans by this MySQL Server (SQL node) that have been
     pruned to a single partition.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_scan_batch_count_session'

     The number of batches of rows received in this client session. 1
     batch is defined as 1 set of scan results from a single fragment.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_scan_batch_count_slave'

     The number of batches of rows received by this slave. 1 batch is
     defined as 1 set of scan results from a single fragment.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_scan_batch_count'

     The number of batches of rows received by this MySQL Server (SQL
     node). 1 batch is defined as 1 set of scan results from a single
     fragment.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_read_row_count_session'

     The total number of rows that have been read in this client
     session. This includes all rows read by any primary key, unique
     key, or scan operation made in this client session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_read_row_count_slave'

     The total number of rows that have been read by this slave.  This
     includes all rows read by any primary key, unique key, or scan
     operation made by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_read_row_count'

     The total number of rows that have been read by this MySQL Server
     (SQL node). This includes all rows read by any primary key, unique
     key, or scan operation made by this MySQL Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_local_read_row_count_session'

     The total number of rows that have been read in this client
     session. This includes all rows read by any primary key, unique
     key, or scan operation made in this client session.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it relates to the current session only, and is not affected by any
     other clients of this *Note `mysqld': mysqld.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_local_read_row_count_slave'

     The total number of rows that have been read by this slave.  This
     includes all rows read by any primary key, unique key, or scan
     operation made by this slave.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope. If this MySQL server does not
     act as a replication slave, or does not use NDB tables, this value
     is always 0.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_trans_local_read_row_count'

     The total number of rows that have been read by this MySQL Server
     (SQL node). This includes all rows read by any primary key, unique
     key, or scan operation made by this MySQL Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_event_data_count_injector'

     The number of row change events received by the NDB binlog
     injector thread.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_event_data_count'

     The number of row change events received by this MySQL Server (SQL
     node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_event_nondata_count_injector'

     The number of events received, other than row change events, by
     the NDB binlog injector thread.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_event_nondata_count'

     The number of events received, other than row change events, by
     this MySQL Server (SQL node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_event_bytes_count_injector'

     The number of bytes of events received by the NDB binlog injector
     thread.

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_api_event_bytes_count'

     The number of bytes of events received by this MySQL Server (SQL
     node).

     Although this variable can be read using either *Note `SHOW GLOBAL
     STATUS': show-status. or *Note `SHOW SESSION STATUS': show-status,
     it is effectively global in scope.

     This variable was added in MySQL Cluster NDB 7.0.22 and MySQL
     Cluster NDB 7.1.11. For more information, see *Note
     mysql-cluster-ndb-api-statistics::.

   * `Ndb_cluster_node_id'

     If the server is acting as a MySQL Cluster node, then the value of
     this variable its node ID in the cluster.

     If the server is not part of a MySQL Cluster, then the value of
     this variable is 0.

   * `Ndb_config_from_host'

     If the server is part of a MySQL Cluster, the value of this
     variable is the host name or IP address of the Cluster management
     server from which it gets its configuration data.

     If the server is not part of a MySQL Cluster, then the value of
     this variable is an empty string.

     Prior to MySQL 5.1.12, this variable was named
     `Ndb_connected_host'.

   * `Ndb_config_from_port'

     If the server is part of a MySQL Cluster, the value of this
     variable is the number of the port through which it is connected
     to the Cluster management server from which it gets its
     configuration data.

     If the server is not part of a MySQL Cluster, then the value of
     this variable is 0.

     Prior to MySQL 5.1.12, this variable was named
     `Ndb_connected_port'.

   * `Ndb_conflict_fn_max'

     Used in MySQL Cluster Replication conflict resolution, this
     variable shows the number of times that a row was not applied on
     the current SQL node due to `greatest timestamp wins' conflict
     resolution since the last time that this *Note `mysqld': mysqld.
     was started.

     This variable was added in MySQL Cluster NDB 6.3.3. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_fn_old'

     Used in MySQL Cluster Replication conflict resolution, this
     variable shows the number of times that a row was not applied as
     the result of `same timestamp wins' conflict resolution on a given
     *Note `mysqld': mysqld.  since the last time it was restarted.

     This variable was added in MySQL Cluster NDB 6.3.4. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_fn_epoch'

     Used in MySQL Cluster Replication conflict resolution, this
     variable shows the number of rows found to be in conflict using
     `NDB$EPOCH()' conflict resolution on a given *Note `mysqld':
     mysqld. since the last time it was restarted.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_fn_epoch_trans'

     Used in MySQL Cluster Replication conflict resolution, this
     variable shows the number of rows found to be in conflict using
     `NDB$EPOCH_TRANS()' conflict resolution on a given *Note `mysqld':
     mysqld. since the last time it was restarted.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_trans_row_conflict_count'

     Used in MySQL Cluster Replication conflict resolution, this status
     variable shows the number of rows found to be directly in-conflict
     by a transactional conflict function on a given *Note `mysqld':
     mysqld. since the last time it was restarted.

     Currently, the only transactional conflict detection function
     supported by MySQL Cluster is NDB$EPOCH_TRANS(), so this status
     variable is effectively the same as `Ndb_conflict_fn_epoch_trans'.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_trans_row_reject_count'

     Used in MySQL Cluster Replication conflict resolution, this status
     variable shows the total number of rows realigned due to being
     determined as conflicting by a transactional conflict detection
     function. This includes not only
     `Ndb_conflict_trans_row_conflict_count', but any rows in or
     dependent on conflicting transactions.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_trans_reject_count'

     Used in MySQL Cluster Replication conflict resolution, this status
     variable shows the number of transactions found to be in conflict
     by a transactional conflict detection function.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_trans_detect_iter_count'

     Used in MySQL Cluster Replication conflict resolution, this shows
     the number of internal iterations required to commit an epoch
     transaction. Should be (slightly) greater than or equal to
     `Ndb_conflict_trans_conflict_commit_count'.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_conflict_trans_conflict_commit_count'

     Used in MySQL Cluster Replication conflict resolution, this shows
     the number of epoch transactions committed after they required
     transactional conflict handling.

     This variable was added in MySQL Cluster NDB 7.1.16. For more
     information, see *Note
     mysql-cluster-replication-conflict-resolution::.

   * `Ndb_execute_count'

     Provides the number of round trips to the *Note `NDB':
     mysql-cluster. kernel made by operations.  Added in MySQL Cluster
     NDB 6.3.6.

   * `Ndb_number_of_data_nodes'

     If the server is part of a MySQL Cluster, the value of this
     variable is the number of data nodes in the cluster.

     If the server is not part of a MySQL Cluster, then the value of
     this variable is 0.

     Prior to MySQL 5.1.12, this variable was named
     `Ndb_number_of_storage_nodes'.

   * `Ndb_pushed_queries_defined'

     The total number of joins pushed down to the NDB kernel for
     distributed handling on the data nodes. Note that joins tested
     using *Note `EXPLAIN': explain. that can be pushed down contribute
     to this number. Added in MySQL Cluster NDB 7.2.0.

   * `Ndb_pushed_queries_dropped'

     The number of joins that were pushed down to the NDB kernel but
     that could not be handled there. Added in MySQL Cluster NDB 7.2.0.

   * `Ndb_pushed_queries_executed'

     The number of joins successfully pushed down to *Note `NDB':
     mysql-cluster. and executed there. Added in MySQL Cluster NDB
     7.2.0.

   * `Ndb_pushed_reads'

     The number of rows returned to *Note `mysqld': mysqld.  from the
     NDB kernel by joins that were pushed down. Note that executing
     *Note `EXPLAIN': explain. on joins that can be pushed down to
     *Note `NDB': mysql-cluster. does not add to this number. Added in
     MySQL Cluster NDB 7.2.0.

   * `Slave_heartbeat_period'

     Shows the replication heartbeat interval (in seconds) on a
     replication slave.

     This variable was added in MySQL Cluster NDB 6.3.4.

   * `Slave_received_heartbeats'

     This counter increments with each replication heartbeat received
     by a replication slave since the last time that the slave was
     restarted or reset, or a *Note `CHANGE MASTER TO':
     change-master-to. statement was issued.

     This variable was added in MySQL Cluster NDB 6.3.4.

   * `Ndb_pruned_scan_count'

     This variable holds a count of the number of scans executed by
     *Note `NDBCLUSTER': mysql-cluster. since the MySQL Cluster was
     last started where *Note `NDBCLUSTER': mysql-cluster. was able to
     use partition pruning.

     Using this variable together with `Ndb_scan_count' can be helpful
     in schema design to maximize the ability of the server to prune
     scans to a single table partition, thereby involving only a single
     data node.

     This variable was added in MySQL Cluster NDB 6.3.25 and MySQL
     Cluster NDB 7.0.5.

   * `Ndb_scan_count'

     This variable holds a count of the total number of scans executed
     by *Note `NDBCLUSTER': mysql-cluster. since the MySQL Cluster was
     last started.

     This variable was added in MySQL Cluster NDB 6.3.25 and MySQL
     Cluster NDB 7.0.5.


File: manual.info,  Node: mysql-cluster-interconnects,  Prev: mysql-cluster-options-variables,  Up: mysql-cluster-configuration

17.3.5 Using High-Speed Interconnects with MySQL Cluster
--------------------------------------------------------

* Menu:

* mysql-cluster-sci-sockets::    Configuring MySQL Cluster to use SCI Sockets
* mysql-cluster-interconnects-performance::  MySQL Cluster Interconnects and Performance

Even before design of *Note `NDBCLUSTER': mysql-cluster.  began in
1996, it was evident that one of the major problems to be encountered
in building parallel databases would be communication between the nodes
in the network. For this reason, *Note `NDBCLUSTER': mysql-cluster. was
designed from the very beginning to permit the use of a number of
different data transport mechanisms. In this Manual, we use the term
_transporter_ for these.

The MySQL Cluster codebase provides for four different transporters:

   * _TCP/IP using 100 Mbps or gigabit Ethernet_, as discussed in *Note
     mysql-cluster-tcp-definition::.

   * _Direct (machine-to-machine) TCP/IP_; although this transporter
     uses the same TCP/IP protocol as mentioned in the previous item,
     it requires setting up the hardware differently and is configured
     differently as well.  For this reason, it is considered a separate
     transport mechanism for MySQL Cluster. See *Note
     mysql-cluster-tcp-definition-direct::, for details.

   * _Shared memory (SHM)_. For more information about SHM, see *Note
     mysql-cluster-shm-definition::.

     *Note*:

     SHM is considered experimental only, and is not officially
     supported.

   * _Scalable Coherent Interface (SCI)_, as described in the next
     section of this chapter, *Note mysql-cluster-sci-definition::.

Most users today employ TCP/IP over Ethernet because it is ubiquitous.
TCP/IP is also by far the best-tested transporter for use with MySQL
Cluster.

We are working to make sure that communication with the *Note `ndbd':
mysql-cluster-programs-ndbd. process is made in `chunks' that are as
large as possible because this benefits all types of data transmission.

For users who desire it, it is also possible to use cluster
interconnects to enhance performance even further. There are two ways
to achieve this: Either a custom transporter can be designed to handle
this case, or you can use socket implementations that bypass the TCP/IP
stack to one extent or another. We have experimented with both of these
techniques using the SCI (Scalable Coherent Interface) technology
developed by Dolphin Interconnect Solutions
(http://www.dolphinics.com/).


File: manual.info,  Node: mysql-cluster-sci-sockets,  Next: mysql-cluster-interconnects-performance,  Prev: mysql-cluster-interconnects,  Up: mysql-cluster-interconnects

17.3.5.1 Configuring MySQL Cluster to use SCI Sockets
.....................................................

It is possible employing Scalable Coherent Interface (SCI) technology
to achieve a significant increase in connection speeds and throughput
between MySQL Cluster data and SQL nodes.  To use SCI, it is necessary
to obtain and install Dolphin SCI network cards and to use the drivers
and other software supplied by Dolphin. You can get information on
obtaining these, from Dolphin Interconnect Solutions
(http://www.dolphinics.com/). SCI SuperSocket or SCI Transporter
support is available for 32-bit and 64-bit Linux, Solaris, Windows, and
other platforms. See the Dolphin documentation referenced later in this
section for more detailed information regarding platforms supported for
SCI.

*Note*:

Prior to MySQL 5.1.20, there were issues with building MySQL Cluster
with SCI support (see Bug #25470), but these have been resolved due to
work contributed by Dolphin. SCI Sockets are now correctly supported
for MySQL Cluster hosts running recent versions of Linux using the
`-max' builds, and versions of MySQL Cluster with SCI Transporter
support can be built using either of `compile-amd64-max-sci' or
`compile-pentium64-max-sci'. Both of these build scripts can be found
in the `BUILD' directory of the MySQL Cluster source trees; it should
not be difficult to adapt them for other platforms. Generally, all that
is necessary is to compile MySQL Cluster with SCI Transporter support
is to configure the MySQL Cluster build using `--with-ndb-sci=/opt/DIS'.

Once you have acquired the required Dolphin hardware and software, you
can obtain detailed information on how to adapt a MySQL Cluster
configured for normal TCP/IP communication to use SCI from the from the
Dolphin SCI online documentation
(http://www.dolphinics.com/support/index_support_sci.html).


File: manual.info,  Node: mysql-cluster-interconnects-performance,  Prev: mysql-cluster-sci-sockets,  Up: mysql-cluster-interconnects

17.3.5.2 MySQL Cluster Interconnects and Performance
....................................................

The *Note `ndbd': mysql-cluster-programs-ndbd. process has a number of
simple constructs which are used to access the data in a MySQL Cluster.
We have created a very simple benchmark to check the performance of
each of these and the effects which various interconnects have on their
performance.

There are four access methods:

   * Primary key access

     This is access of a record through its primary key. In the
     simplest case, only one record is accessed at a time, which means
     that the full cost of setting up a number of TCP/IP messages and a
     number of costs for context switching are borne by this single
     request. In the case where multiple primary key accesses are sent
     in one batch, those accesses share the cost of setting up the
     necessary TCP/IP messages and context switches. If the TCP/IP
     messages are for different destinations, additional TCP/IP
     messages need to be set up.

   * Unique key access

     Unique key accesses are similar to primary key accesses, except
     that a unique key access is executed as a read on an index table
     followed by a primary key access on the table. However, only one
     request is sent from the MySQL Server, and the read of the index
     table is handled by *Note `ndbd': mysql-cluster-programs-ndbd.
     Such requests also benefit from batching.

   * Full table scan

     When no indexes exist for a lookup on a table, a full table scan
     is performed. This is sent as a single request to the *Note
     `ndbd': mysql-cluster-programs-ndbd. process, which then divides
     the table scan into a set of parallel scans on all cluster *Note
     `ndbd': mysql-cluster-programs-ndbd. processes. In future versions
     of MySQL Cluster, an SQL node will be able to filter some of these
     scans.

   * Range scan using ordered index

     When an ordered index is used, it performs a scan in the same
     manner as the full table scan, except that it scans only those
     records which are in the range used by the query transmitted by
     the MySQL server (SQL node). All partitions are scanned in
     parallel when all bound index attributes include all attributes in
     the partitioning key.

With benchmarks developed internally by MySQL for testing simple and
batched primary and unique key accesses, we have found that using SCI
sockets improves performance by approximately 100% over TCP/IP, except
in rare instances when communication performance is not an issue. This
can occur when scan filters make up most of processing time or when
very large batches of primary key accesses are achieved. In that case,
the CPU processing in the *Note `ndbd': mysql-cluster-programs-ndbd.
processes becomes a fairly large part of the overhead.

Using the SCI transporter instead of SCI Sockets is only of interest in
communicating between *Note `ndbd': mysql-cluster-programs-ndbd.
processes. Using the SCI transporter is also only of interest if a CPU
can be dedicated to the *Note `ndbd': mysql-cluster-programs-ndbd.
process because the SCI transporter ensures that this process will never
go to sleep. It is also important to ensure that the *Note `ndbd':
mysql-cluster-programs-ndbd. process priority is set in such a way that
the process does not lose priority due to running for an extended
period of time, as can be done by locking processes to CPUs in Linux
2.6. If such a configuration is possible, the *Note `ndbd':
mysql-cluster-programs-ndbd. process will benefit by 10-70% as compared
with using SCI sockets. (The larger figures will be seen when
performing updates and probably on parallel scan operations as well.)

There are several other optimized socket implementations for computer
clusters, including Myrinet, Gigabit Ethernet, Infiniband and the VIA
interface. However, we have tested MySQL Cluster so far only with SCI
sockets. See *Note mysql-cluster-sci-sockets::, for information on how
to set up SCI sockets using ordinary TCP/IP for MySQL Cluster.


File: manual.info,  Node: mysql-cluster-programs,  Next: mysql-cluster-management,  Prev: mysql-cluster-configuration,  Up: mysql-cluster

17.4 MySQL Cluster Programs
===========================

* Menu:

* mysql-cluster-programs-ndbd::  `ndbd' --- The MySQL Cluster Data Node Daemon
* mysql-cluster-programs-ndbinfo-select-all::  `ndbinfo_select_all' --- Select From ndbinfo Tables
* mysql-cluster-programs-ndbmtd::  `ndbmtd' --- The MySQL Cluster Data Node Daemon (Multi-Threaded)
* mysql-cluster-programs-ndb-mgmd::  `ndb_mgmd' --- The MySQL Cluster Management Server Daemon
* mysql-cluster-programs-ndb-mgm::  `ndb_mgm' --- The MySQL Cluster Management Client
* mysql-cluster-programs-ndb-blob-tool::  `ndb_blob_tool' --- Check and Repair BLOB and TEXT columns of MySQL Cluster Tables
* mysql-cluster-programs-ndb-config::  `ndb_config' --- Extract MySQL Cluster Configuration Information
* mysql-cluster-programs-ndb-cpcd::  `ndb_cpcd' --- Automate Testing for NDB Development
* mysql-cluster-programs-ndb-delete-all::  `ndb_delete_all' --- Delete All Rows from an NDB Table
* mysql-cluster-programs-ndb-desc::  `ndb_desc' --- Describe NDB Tables
* mysql-cluster-programs-ndb-drop-index::  `ndb_drop_index' --- Drop Index from an NDB Table
* mysql-cluster-programs-ndb-drop-table::  `ndb_drop_table' --- Drop an NDB Table
* mysql-cluster-programs-ndb-error-reporter::  `ndb_error_reporter' --- NDB Error-Reporting Utility
* mysql-cluster-programs-ndb-index-stat::  `ndb_index_stat' --- NDB Index Statistics Utility
* mysql-cluster-programs-ndb-print-backup-file::  `ndb_print_backup_file' --- Print NDB Backup File Contents
* mysql-cluster-programs-ndb-print-file::  `ndb_print_file' --- Print NDB Disk Data File Contents
* mysql-cluster-programs-ndb-print-schema-file::  `ndb_print_schema_file' --- Print NDB Schema File Contents
* mysql-cluster-programs-ndb-print-sys-file::  `ndb_print_sys_file' --- Print NDB System File Contents
* mysql-cluster-programs-ndbd-redo-log-reader::  `ndbd_redo_log_reader' --- Check and Print Content of Cluster Redo Log
* mysql-cluster-programs-ndb-restore::  `ndb_restore' --- Restore a MySQL Cluster Backup
* mysql-cluster-programs-ndb-select-all::  `ndb_select_all' --- Print Rows from an NDB Table
* mysql-cluster-programs-ndb-select-count::  `ndb_select_count' --- Print Row Counts for NDB Tables
* mysql-cluster-programs-ndb-show-tables::  `ndb_show_tables' --- Display List of NDB Tables
* mysql-cluster-programs-ndb-size-pl::  `ndb_size.pl' --- NDBCLUSTER Size Requirement Estimator
* mysql-cluster-programs-ndb-waiter::  `ndb_waiter' --- Wait for MySQL Cluster to Reach a Given Status
* mysql-cluster-program-options-common::  Options Common to MySQL Cluster Programs --- Options Common to MySQL Cluster Programs

Using and managing a MySQL Cluster requires several specialized
programs, which we describe in this chapter. We discuss the purposes of
these programs in a MySQL Cluster, how to use the programs, and what
startup options are available for each of them.

These programs include the MySQL Cluster data, management, and SQL node
processes (*Note `ndbd': mysql-cluster-programs-ndbd, *Note `ndbmtd':
mysql-cluster-programs-ndbmtd, *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd, and *Note `mysqld': mysqld.) and the
management client (*Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.).

For information about using *Note `mysqld': mysqld. as a MySQL Cluster
process, see *Note mysql-cluster-mysqld::.

Other *Note `NDB': mysql-cluster. utility, diagnostic, and example
programs are included with the MySQL Cluster distribution.  These
include *Note `ndb_restore': mysql-cluster-programs-ndb-restore, *Note
`ndb_show_tables': mysql-cluster-programs-ndb-show-tables, and *Note
`ndb_config': mysql-cluster-programs-ndb-config. These programs are
also covered in this section.

The final portion of this section contains tables of options that are
common to all the various MySQL Cluster programs.


File: manual.info,  Node: mysql-cluster-programs-ndbd,  Next: mysql-cluster-programs-ndbinfo-select-all,  Prev: mysql-cluster-programs,  Up: mysql-cluster-programs

17.4.1 `ndbd' -- The MySQL Cluster Data Node Daemon
---------------------------------------------------

*Note `ndbd': mysql-cluster-programs-ndbd. is the process that is used
to handle all the data in tables using the NDB Cluster storage engine.
This is the process that empowers a data node to accomplish distributed
transaction handling, node recovery, checkpointing to disk, online
backup, and related tasks.

In a MySQL Cluster, a set of *Note `ndbd': mysql-cluster-programs-ndbd.
processes cooperate in handling data. These processes can execute on the
same computer (host) or on different computers. The correspondences
between data nodes and Cluster hosts is completely configurable.

The following table includes command options specific to the MySQL
Cluster data node program *Note `ndbd': mysql-cluster-programs-ndbd.
Additional descriptions follow the table. For options common to most
MySQL Cluster programs (including *Note `ndbd':
mysql-cluster-programs-ndbd.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndbd program

Format Description Added or Removed

` --initial '

Perform initial start of ndbd, including cleaning the file system.
Consult the documentation before using this option

All MySQL 5.1 based releases

`--nostart',

` -n '

Don't start ndbd immediately; ndbd waits for command to start from
ndb_mgmd

All MySQL 5.1 based releases

`--daemon',

` -d '

Start ndbd as daemon (default); override with -nodaemon

All MySQL 5.1 based releases

` --nodaemon '

Do not start ndbd as daemon; provided for testing purposes

All MySQL 5.1 based releases

` --foreground '

Run ndbd in foreground, provided for debugging purposes (implies
-nodaemon)

All MySQL 5.1 based releases

` --nowait-nodes=list '

Do not wait for these data nodes to start (takes comma-separated list
of node IDs). Also requires -ndb-nodeid to be used.

ADDED: 5.1.9

` --initial-start '

Perform partial initial start (requires -nowait-nodes)

ADDED: 5.1.11

` --bind-address=name '

Local bind address

ADDED: 5.1.12

` --install[=name] '

Used to install the data node process as a Windows service. Does not
apply on non-Windows platforms.

ADDED: NDB 7.0.16, NDB 7.1.5

` --remove[=name] '

Used to remove a data node process that was previously installed as a
Windows service. Does not apply on non-Windows platforms.

ADDED: NDB 7.0.16, NDB 7.1.5

` --connect-retries=# '

Number of times to try contacting the management server; set to -1 to
keep trying indefinitely

ADDED: NDB 7.0.36, NDB 7.1.25

` --connect-delay=# '

Time to wait between attempts to contact a management server, in seconds

ADDED: NDB 7.0.36, NDB 7.1.25 


*Note*:

All of these options also apply to the multi-threaded version of this
program (*Note `ndbmtd': mysql-cluster-programs-ndbmtd, available in
MySQL Cluster NDB 7.0 and later) and you may substitute `*Note
`ndbmtd': mysql-cluster-programs-ndbmtd.' for `*Note `ndbd':
mysql-cluster-programs-ndbd.' wherever the latter occurs in this
section.

   * `--bind-address'

     Options for bind-address

     *Introduced*         5.1.12          
     *Command-Line        `--bind-address=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     Causes *Note `ndbd': mysql-cluster-programs-ndbd. to bind to a
     specific network interface (host name or IP address). This option
     has no default value.

     This option was added in MySQL 5.1.12.

   * `--daemon', `-d'

     Options for daemon

     *Command-Line        `--daemon'        
     Format*                              
                          `-d'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Instructs *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
     `ndbmtd': mysql-cluster-programs-ndbmtd. to execute as a daemon
     process.  This is the default behavior.  `--nodaemon' can be used
     to prevent the process from running as a daemon.

     This option has no effect when running *Note `ndbd':
     mysql-cluster-programs-ndbd. or *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. on Windows platforms.

   * `--nodaemon'

     Options for nodaemon

     *Command-Line        `--nodaemon'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Prevents *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
     `ndbmtd': mysql-cluster-programs-ndbmtd. from executing as a daemon
     process. This option overrides the `--daemon' option. This is
     useful for redirecting output to the screen when debugging the
     binary.

     As of MySQL Cluster NDB 7.0.8, the default behavior for *Note
     `ndbd': mysql-cluster-programs-ndbd. and *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. on Windows is to run in the
     foreground, making this option unnecessary on Windows platforms,
     where it has no effect.  (Bug #45588)

   * `--foreground'

     Options for foreground

     *Command-Line        `--foreground'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Causes *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
     `ndbmtd': mysql-cluster-programs-ndbmtd.  to execute as a
     foreground process, primarily for debugging purposes. This option
     implies the `--nodaemon' option.

     This option has no effect when running *Note `ndbd':
     mysql-cluster-programs-ndbd. or *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. on Windows platforms.

   * `--initial'

     Options for initial

     *Command-Line        `--initial'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Instructs *Note `ndbd': mysql-cluster-programs-ndbd. to perform an
     initial start. An initial start erases any files created for
     recovery purposes by earlier instances of *Note `ndbd':
     mysql-cluster-programs-ndbd. It also re-creates recovery log
     files. Note that on some operating systems this process can take a
     substantial amount of time.

     An `--initial' start is to be used _only_ when starting the *Note
     `ndbd': mysql-cluster-programs-ndbd. process under very special
     circumstances; this is because this option causes all files to be
     removed from the MySQL Cluster file system and all redo log files
     to be re-created. These circumstances are listed here:

        * When performing a software upgrade which has changed the
          contents of any files.

        * When restarting the node with a new version of *Note `ndbd':
          mysql-cluster-programs-ndbd.

        * As a measure of last resort when for some reason the node
          restart or system restart repeatedly fails. In this case, be
          aware that this node can no longer be used to restore data
          due to the destruction of the data files.

     Use of this option prevents the `StartPartialTimeout' and
     `StartPartitionedTimeout' configuration parameters from having any
     effect.

     *Important*:

     This option does _not_ affect either of the following types of
     files:

        * Backup files that have already been created by the affected
          node

        * MySQL Cluster Disk Data files (see *Note
          mysql-cluster-disk-data::).

     This option also has no effect on recovery of data by a data node
     that is just starting (or restarting) from data nodes that are
     already running. This recovery of data occurs automatically, and
     requires no user intervention in a MySQL Cluster that is running
     normally.

     It is permissible to use this option when starting the cluster for
     the very first time (that is, before any data node files have been
     created); however, it is _not_ necessary to do so.

   * `--initial-start'

     Options for initial-start

     *Introduced*         5.1.11          
     *Command-Line        `--initial-start'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     This option is used when performing a partial initial start of the
     cluster. Each node should be started with this option, as well as
     `--nowait-nodes'.

     Suppose that you have a 4-node cluster whose data nodes have the
     IDs 2, 3, 4, and 5, and you wish to perform a partial initial
     start using only nodes 2, 4, and 5--that is, omitting node 3:


          shell> ndbd --ndb-nodeid=2 --nowait-nodes=3 --initial-start
          shell> ndbd --ndb-nodeid=4 --nowait-nodes=3 --initial-start
          shell> ndbd --ndb-nodeid=5 --nowait-nodes=3 --initial-start

     Prior to MySQL 5.1.19, it was not possible to perform DDL
     operations involving Disk Data tables on a partially started
     cluster. (See Bug #24631.)

     When using this option, you must also specify the node ID for the
     data node being started with the `--ndb-nodeid' option.

     This option was added in MySQL 5.1.11.

     *Important*:

     Do not confuse this option with the `--nowait-nodes' option added
     for *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. in MySQL
     Cluster NDB 7.0.10, which can be used to enable a cluster
     configured with multiple management servers to be started without
     all management servers being online.

   * `--nowait-nodes=NODE_ID_1[, NODE_ID_2[, ...]]'

     Options for nowait-nodes

     *Introduced*         5.1.9           
     *Command-Line        `--nowait-nodes=list'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     This option takes a list of data nodes which for which the cluster
     will not wait for before starting.

     This can be used to start the cluster in a partitioned state. For
     example, to start the cluster with only half of the data nodes
     (nodes 2, 3, 4, and 5) running in a 4-node cluster, you can start
     each *Note `ndbd': mysql-cluster-programs-ndbd. process with
     `--nowait-nodes=3,5'. In this case, the cluster starts as soon as
     nodes 2 and 4 connect, and does _not_ wait
     `StartPartitionedTimeout' milliseconds for nodes 3 and 5 to
     connect as it would otherwise.

     If you wanted to start up the same cluster as in the previous
     example without one *Note `ndbd': mysql-cluster-programs-ndbd.
     (say, for example, that the host machine for node 3 has suffered a
     hardware failure) then start nodes 2, 4, and 5 with
     `--nowait-nodes=3'. Then the cluster will start as soon as nodes
     2, 4, and 5 connect and will not wait for node 3 to start.

     This option was added in MySQL 5.1.9.

   * `--nostart', `-n'

     Options for nostart

     *Command-Line        `--nostart'        
     Format*                              
                          `-n'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Instructs *Note `ndbd': mysql-cluster-programs-ndbd. not to start
     automatically. When this option is used, *Note `ndbd':
     mysql-cluster-programs-ndbd. connects to the management server,
     obtains configuration data from it, and initializes communication
     objects. However, it does not actually start the execution engine
     until specifically requested to do so by the management server.
     This can be accomplished by issuing the proper `START' command in
     the management client (see *Note
     mysql-cluster-mgm-client-commands::).

   * `--install[=NAME]'

     Options for install

     *Introduced*         5.1.47-ndb-7.1.5        
     *Command-Line        `--install[=name]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `ndbd'          

     Causes *Note `ndbd': mysql-cluster-programs-ndbd. to be installed
     as a Windows service. Optionally, you can specify a name for the
     service; if not set, the service name defaults to `ndbd'. Although
     it is preferable to specify other *Note `ndbd':
     mysql-cluster-programs-ndbd. program options in a `my.ini' or
     `my.cnf' configuration file, it is possible to use together with
     `--install'. However, in such cases, the `--install' option must
     be specified first, before any other options are given, for the
     Windows service installation to succeed.

     It is generally not advisable to use this option together with the
     `--initial' option, since this causes the data node file system to
     be wiped and rebuilt every time the service is stopped and started.
     Extreme care should also be taken if you intend to use any of the
     other *Note `ndbd': mysql-cluster-programs-ndbd. options that
     affect the starting of data nodes--including `--initial-start',
     `--nostart', and `--nowait-nodes'--together with `--install', and
     you should make absolutely certain you fully understand and allow
     for any possible consequences of doing so.

     The `--install' option has no effect on non-Windows platforms.

     This option became available in MySQL Cluster NDB 7.0.16 and MySQL
     Cluster NDB 7.1.5.

   * `--remove[=NAME]'

     Options for remove

     *Introduced*         5.1.47-ndb-7.1.5        
     *Command-Line        `--remove[=name]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `ndbd'          

     Causes an *Note `ndbd': mysql-cluster-programs-ndbd. process that
     was previously installed as a Windows service to be removed.
     Optionally, you can specify a name for the service to be
     uninstalled; if not set, the service name defaults to `ndbd'.

     The `--remove' option has no effect on non-Windows platforms.

     This option became available in MySQL Cluster NDB 7.0.16 and MySQL
     Cluster NDB 7.1.5.

   * `--connect-retries=#'

     Options for connect-retries

     *Introduced*         5.1.66-ndb-7.1.25        
     *Command-Line        `--connect-retries=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `12'            
     *Min Value*          `-1'            
     *Max Value*          `65535'         

     Determines the number of times that the data node attempts to
     contact a management server when starting. Setting this option to
     -1 causes the data node to keep trying to make contact
     indefinitely. The default is 12 attempts. The time to wait between
     attempts is controlled by the `--connect-delay' option.

     This option was added in MySQL Cluster NDB 7.0.36 and MySQL
     Cluster 7.1.25.

   * `--connect-delay=#'

     Options for connect-delay

     *Introduced*         5.1.66-ndb-7.1.25        
     *Command-Line        `--connect-delay=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `5'             
     *Min Value*          `0'             
     *Max Value*          `3600'          

     Determines the time to wait between attempts to contact a
     management server when starting (the time between attempts is
     controlled by the `--connect-retries' option). The default is 5
     attempts.

     This option was added in MySQL Cluster NDB 7.0.36 and MySQL
     Cluster 7.1.25.

*Note `ndbd': mysql-cluster-programs-ndbd. generates a set of log files
which are placed in the directory specified by `DataDir' in the
`config.ini' configuration file.

These log files are listed below.  NODE_ID is the node's unique
identifier. Note that NODE_ID represents the node's unique identifier.
For example, `ndb_2_error.log' is the error log generated by the data
node whose node ID is `2'.

   * `ndb_NODE_ID_error.log' is a file containing records of all
     crashes which the referenced *Note `ndbd':
     mysql-cluster-programs-ndbd. process has encountered.  Each record
     in this file contains a brief error string and a reference to a
     trace file for this crash. A typical entry in this file might
     appear as shown here:


          Date/Time: Saturday 30 July 2004 - 00:20:01
          Type of error: error
          Message: Internal program error (failed ndbrequire)
          Fault ID: 2341
          Problem data: DbtupFixAlloc.cpp
          Object of reference: DBTUP (Line: 173)
          ProgramName: NDB Kernel
          ProcessID: 14909
          TraceFile: ndb_2_trace.log.2
          ***EOM***

     Listings of possible *Note `ndbd': mysql-cluster-programs-ndbd.
     exit codes and messages generated when a data node process shuts
     down prematurely can be found in `ndbd' Error Messages
     (http://dev.mysql.com/doc/ndbapi/en/ndbd-error-messages.html).

     *Important*:

     _The last entry in the error log file is not necessarily the
     newest one_ (nor is it likely to be). Entries in the error log are
     _not_ listed in chronological order; rather, they correspond to
     the order of the trace files as determined in the
     `ndb_NODE_ID_trace.log.next' file (see below). Error log entries
     are thus overwritten in a cyclical and not sequential fashion.

   * `ndb_NODE_ID_trace.log.TRACE_ID' is a trace file describing
     exactly what happened just before the error occurred. This
     information is useful for analysis by the MySQL Cluster
     development team.

     It is possible to configure the number of these trace files that
     will be created before old files are overwritten.  TRACE_ID is a
     number which is incremented for each successive trace file.

   * `ndb_NODE_ID_trace.log.next' is the file that keeps track of the
     next trace file number to be assigned.

   * `ndb_NODE_ID_out.log' is a file containing any data output by the
     *Note `ndbd': mysql-cluster-programs-ndbd. process. This file is
     created only if *Note `ndbd': mysql-cluster-programs-ndbd. is
     started as a daemon, which is the default behavior.

   * `ndb_NODE_ID.pid' is a file containing the process ID of the *Note
     `ndbd': mysql-cluster-programs-ndbd. process when started as a
     daemon. It also functions as a lock file to avoid the starting of
     nodes with the same identifier.

   * `ndb_NODE_ID_signal.log' is a file used only in debug versions of
     *Note `ndbd': mysql-cluster-programs-ndbd, where it is possible to
     trace all incoming, outgoing, and internal messages with their
     data in the *Note `ndbd': mysql-cluster-programs-ndbd. process.

It is recommended not to use a directory mounted through NFS because in
some environments this can cause problems whereby the lock on the
`.pid' file remains in effect even after the process has terminated.

To start *Note `ndbd': mysql-cluster-programs-ndbd, it may also be
necessary to specify the host name of the management server and the
port on which it is listening. Optionally, one may also specify the node
ID that the process is to use.


     shell> ndbd --connect-string="nodeid=2;host=ndb_mgmd.mysql.com:1186"

See *Note mysql-cluster-connection-strings::, for additional
information about this issue.  *Note mysql-cluster-programs-ndbd::,
describes other options for *Note `ndbd': mysql-cluster-programs-ndbd.

When *Note `ndbd': mysql-cluster-programs-ndbd. starts, it actually
initiates two processes. The first of these is called the `angel
process'; its only job is to discover when the execution process has
been completed, and then to restart the *Note `ndbd':
mysql-cluster-programs-ndbd. process if it is configured to do so.
Thus, if you attempt to kill *Note `ndbd': mysql-cluster-programs-ndbd.
using the Unix *Note `kill': kill. command, it is necessary to kill
both processes, beginning with the angel process. The preferred method
of terminating an *Note `ndbd': mysql-cluster-programs-ndbd. process is
to use the management client and stop the process from there.

The execution process uses one thread for reading, writing, and
scanning data, as well as all other activities. This thread is
implemented asynchronously so that it can easily handle thousands of
concurrent actions. In addition, a watch-dog thread supervises the
execution thread to make sure that it does not hang in an endless loop.
A pool of threads handles file I/O, with each thread able to handle one
open file. Threads can also be used for transporter connections by the
transporters in the *Note `ndbd': mysql-cluster-programs-ndbd. process.
In a multi-processor system performing a large number of operations
(including updates), the *Note `ndbd': mysql-cluster-programs-ndbd.
process can consume up to 2 CPUs if permitted to do so.

For a machine with many CPUs it is possible to use several *Note
`ndbd': mysql-cluster-programs-ndbd. processes which belong to
different node groups; however, such a configuration is still considered
experimental and is not supported for MySQL 5.1 in a production
setting. See *Note mysql-cluster-limitations::.


File: manual.info,  Node: mysql-cluster-programs-ndbinfo-select-all,  Next: mysql-cluster-programs-ndbmtd,  Prev: mysql-cluster-programs-ndbd,  Up: mysql-cluster-programs

17.4.2 `ndbinfo_select_all' -- Select From ndbinfo Tables
---------------------------------------------------------

*Note `ndbinfo_select_all': mysql-cluster-programs-ndbinfo-select-all.
is a client program that selects all rows and columns from one or more
tables in the *Note `ndbinfo': mysql-cluster-ndbinfo. database. It is
included with the MySQL Cluster distribution beginning with MySQL
Cluster NDB 7.1.17.

Not all `ndbinfo' tables can be accessed by this program.
`ndbinfo_select_all' can access the *Note `counters':
mysql-cluster-ndbinfo-counters, *Note `diskpagebuffer':
mysql-cluster-ndbinfo-diskpagebuffer, *Note `logbuffers':
mysql-cluster-ndbinfo-logbuffers, *Note `logspaces':
mysql-cluster-ndbinfo-logspaces, *Note `nodes':
mysql-cluster-ndbinfo-nodes, *Note `resources':
mysql-cluster-ndbinfo-resources, `threadblocks', `threadstat',

and *Note `transporters': mysql-cluster-ndbinfo-transporters. tables.

To select from one or more `ndbinfo' tables using *Note
`ndbinfo_select_all': mysql-cluster-programs-ndbinfo-select-all, it is
necessary to supply the names of the tables when invoking the program as
shown here:


     shell> ndbinfo_select_all TABLE_NAME1  [TABLE_NAME2] [...]

For example:


     shell> ndbinfo_select_all logbuffers logspaces
     == logbuffers ==
     node_id log_type        log_id  log_part        total   used    high
     5       0       0       0       33554432        262144  0
     6       0       0       0       33554432        262144  0
     7       0       0       0       33554432        262144  0
     8       0       0       0       33554432        262144  0
     == logspaces ==
     node_id log_type        log_id  log_part        total   used    high
     5       0       0       0       268435456       0       0
     5       0       0       1       268435456       0       0
     5       0       0       2       268435456       0       0
     5       0       0       3       268435456       0       0
     6       0       0       0       268435456       0       0
     6       0       0       1       268435456       0       0
     6       0       0       2       268435456       0       0
     6       0       0       3       268435456       0       0
     7       0       0       0       268435456       0       0
     7       0       0       1       268435456       0       0
     7       0       0       2       268435456       0       0
     7       0       0       3       268435456       0       0
     8       0       0       0       268435456       0       0
     8       0       0       1       268435456       0       0
     8       0       0       2       268435456       0       0
     8       0       0       3       268435456       0       0
     shell>

The following table includes options that are specific to *Note
`ndbinfo_select_all': mysql-cluster-programs-ndbinfo-select-all.
Additional descriptions follow the table. For options common to most
MySQL Cluster programs (including *Note `ndbinfo_select_all':
mysql-cluster-programs-ndbinfo-select-all.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndbinfo_select_all
program

Format Description Added or Removed

` --delay=# '

Set the delay in seconds between loops. Default is 5.

All MySQL 5.1 based releases

`--loops=#',

` -l '

Set the number of times to perform the select. Default is 1.

All MySQL 5.1 based releases

`--database=db_name',

` -d '

Name of the database where the table located.

All MySQL 5.1 based releases

`--parallelism=#',

` -p '

Set the degree of parallelism.

All MySQL 5.1 based releases 


   * `--delay=`seconds''

     Options for delay

     *Command-Line        `--delay=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `5'             
     *Min Value*          `0'             
     *Max Value*          `MAX_INT'        

     This option sets the number of seconds to wait between executing
     loops. Has no effect if `--loops' is set to 0 or 1.

   * `--loops=`number'', `-l NUMBER'

     Options for loops

     *Command-Line        `--loops=#'        
     Format*                              
                          `-l'            
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `1'             
     *Min Value*          `0'             
     *Max Value*          `MAX_INT'        

     This option sets the number of times to execute the select.  Use
     `--delay' to set the time between loops.


File: manual.info,  Node: mysql-cluster-programs-ndbmtd,  Next: mysql-cluster-programs-ndb-mgmd,  Prev: mysql-cluster-programs-ndbinfo-select-all,  Up: mysql-cluster-programs

17.4.3 `ndbmtd' -- The MySQL Cluster Data Node Daemon (Multi-Threaded)
----------------------------------------------------------------------

*Note `ndbmtd': mysql-cluster-programs-ndbmtd. is a multi-threaded
version of *Note `ndbd': mysql-cluster-programs-ndbd, the process that
is used to handle all the data in tables using the *Note `NDBCLUSTER':
mysql-cluster. storage engine.  *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. is intended for use on host computers
having multiple CPU cores. Except where otherwise noted, *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. functions in the same way as
*Note `ndbd': mysql-cluster-programs-ndbd.; therefore, in this section,
we concentrate on the ways in which *Note `ndbmtd':
mysql-cluster-programs-ndbmtd.  differs from *Note `ndbd':
mysql-cluster-programs-ndbd, and you should consult *Note
mysql-cluster-programs-ndbd::, for additional information about running
MySQL Cluster data nodes that apply to both the single-threaded and
multi-threaded versions of the data node process.

Command-line options and configuration parameters used with *Note
`ndbd': mysql-cluster-programs-ndbd. also apply to *Note `ndbmtd':
mysql-cluster-programs-ndbmtd.  For more information about these
options and parameters, see *Note mysql-cluster-programs-ndbd::, and
*Note mysql-cluster-ndbd-definition::, respectively.

*Note `ndbmtd': mysql-cluster-programs-ndbmtd. is also file
system-compatible with *Note `ndbd': mysql-cluster-programs-ndbd. In
other words, a data node running *Note `ndbd':
mysql-cluster-programs-ndbd. can be stopped, the binary replaced with
*Note `ndbmtd': mysql-cluster-programs-ndbmtd, and then restarted
without any loss of data. (However, when doing this, you must make sure
that `MaxNoOfExecutionThreads' is set to an apppriate value before
restarting the node if you wish for *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. to run in multi-threaded fashion.)
Similarly, an *Note `ndbmtd': mysql-cluster-programs-ndbmtd. binary can
be replaced with *Note `ndbd': mysql-cluster-programs-ndbd. simply by
stopping the node and then starting *Note `ndbd':
mysql-cluster-programs-ndbd. in place of the multi-threaded binary. It
is not necessary when switching between the two to start the data node
binary using `--initial'.

Prior to MySQL Cluster NDB 7.0.6, there were known issues when using
*Note `ndbmtd': mysql-cluster-programs-ndbmtd. with MySQL Cluster Disk
Data tables. If you wish to use multi-threaded data nodes with
disk-based `NDB' tables, you should ensure that you are running MySQL
Cluster NDB 7.0.6 or later (see Bug #41915 and Bug #44915)

Using *Note `ndbmtd': mysql-cluster-programs-ndbmtd. differs from using
*Note `ndbd': mysql-cluster-programs-ndbd. in two key respects:

  1. Because *Note `ndbmtd': mysql-cluster-programs-ndbmtd. runs by
     default in single-threaded mode (that is, it behaves like *Note
     `ndbd': mysql-cluster-programs-ndbd.), you must configure it to use
     multiple threads. This can be done by setting an appropriate value
     in the `config.ini' file for the `MaxNoOfExecutionThreads'
     configuration parameter. For more information about this parameter
     and its use, see *Note
     mysql-cluster-ndbd-definition-ndbmtd-parameters::.

  2. Trace files are generated by critical errors in *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. processes in a somewhat different
     fashion from how these are generated by *Note `ndbd':
     mysql-cluster-programs-ndbd. failures. These differences are
     discussed in more detail in the next few paragraphs.

Like *Note `ndbd': mysql-cluster-programs-ndbd, *Note `ndbmtd':
mysql-cluster-programs-ndbmtd.  generates a set of log files which are
placed in the directory specified by `DataDir' in the `config.ini'
configuration file. Except for trace files, these are generated in the
same way and have the same names as those generated by *Note `ndbd':
mysql-cluster-programs-ndbd.

In the event of a critical error, *Note `ndbmtd':
mysql-cluster-programs-ndbmtd.  generates trace files describing what
happened just prior to the error' occurrence. These files, which can be
found in the data node's `DataDir', are useful for analysis of problems
by the MySQL Cluster Development and Support teams. One trace file is
generated for each *Note `ndbmtd': mysql-cluster-programs-ndbmtd.
thread. The names of these files have the following pattern:


     `ndb_NODE_ID_trace.log.TRACE_ID_tTHREAD_ID',

In this pattern, NODE_ID stands for the data node's unique node ID in
the cluster, TRACE_ID is a trace sequence number, and THREAD_ID is the
thread ID. For example, in the event of the failure of an *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. process running as a MySQL
Cluster data node having the node ID 3 and with
`MaxNoOfExecutionThreads' equal to 4, four trace files are generated in
the data node's data directory. If the is the first time this node has
failed, then these files are named `ndb_3_trace.log.1_t1',
`ndb_3_trace.log.1_t2', `ndb_3_trace.log.1_t3', and
`ndb_3_trace.log.1_t4'. Internally, these trace files follow the same
format as *Note `ndbd': mysql-cluster-programs-ndbd.  trace files.

The *Note `ndbd': mysql-cluster-programs-ndbd. exit codes and messages
that are generated when a data node process shuts down prematurely are
also used by *Note `ndbmtd': mysql-cluster-programs-ndbmtd. See `ndbd'
Error Messages
(http://dev.mysql.com/doc/ndbapi/en/ndbd-error-messages.html), for a
listing of these.

*Note*:

It is possible to use *Note `ndbd': mysql-cluster-programs-ndbd. and
*Note `ndbmtd': mysql-cluster-programs-ndbmtd. concurrently on
different data nodes in the same MySQL Cluster. However, such
configurations have not been tested extensively; thus, we cannot
recommend doing so in a production setting at this time.


File: manual.info,  Node: mysql-cluster-programs-ndb-mgmd,  Next: mysql-cluster-programs-ndb-mgm,  Prev: mysql-cluster-programs-ndbmtd,  Up: mysql-cluster-programs

17.4.4 `ndb_mgmd' -- The MySQL Cluster Management Server Daemon
---------------------------------------------------------------

The management server is the process that reads the cluster
configuration file and distributes this information to all nodes in the
cluster that request it. It also maintains a log of cluster activities.
Management clients can connect to the management server and check the
cluster's status.

The following table includes options that are specific to the MySQL
Cluster management server program *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. Additional descriptions follow the
table. For options common to most MySQL Cluster programs (including
*Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_mgmd program

Format Description Added or Removed

`--config-file=file',

` -f '

Specify the cluster configuration file; in NDB-6.4.0 and later, needs
-reload or -initial to override configuration cache if present

All MySQL 5.1 based releases

`--configdir=directory',

` --config-dir=directory '

Specify the cluster management server's configuration cache directory

ADDED: NDB 6.4.0

` --bind-address=ip_address '

Local bind address

ADDED: NDB 6.2.5, NDB 6.3.2

`--print-full-config',

` -P '

Print full configuration and exit

All MySQL 5.1 based releases

`--daemon',

` -d '

Run ndb_mgmd in daemon mode (default)

All MySQL 5.1 based releases

` --nodaemon '

Do not run ndb_mgmd as a daemon

ADDED: NDB 7.0.8

` --interactive '

Run ndb_mgmd in interactive mode (not officially supported in
production; for testing purposes only)

All MySQL 5.1 based releases

` --log-name=name '

A name to use when writing messages applying to this node in the
cluster log.

ADDED: NDB 7.0.8

` --no-nodeid-checks '

Do not provide any node id checks

All MySQL 5.1 based releases

` --mycnf '

Read cluster configuration data from the my.cnf file

All MySQL 5.1 based releases

` --reload '

Causes the management server to compare the configuration file with its
configuration cache

ADDED: NDB 6.4.0

` --initial '

Causes the management server reload its configuration data from the
configuration file, bypassing the configuration cache

ADDED: NDB 6.4.0

` --nowait-nodes=list '

Do not wait for these management nodes when starting this management
server. Also requires -ndb-nodeid to be used.

ADDED: NDB 7.0.10, NDB 7.1.0

` --config-cache[=TRUE|FALSE] '

Enable the management server configuration cache; TRUE by default.

ADDED: NDB 7.0.15, NDB 7.1.4

` --install[=name] '

Used to install the management server process as a Windows service.
Does not apply on non-Windows platforms.

ADDED: NDB 7.0.16, NDB 7.1.5

` --remove[=name] '

Used to remove a management server process that was previously
installed as a Windows service, optionally specifying the name of the
service to be removed. Does not apply on non-Windows platforms.

ADDED: NDB 7.0.16, NDB 7.1.5 


   * `--bind-address=HOST[:PORT]'

     Options for bind-address

     *Introduced*         5.1.22-ndb-6.3.2        
     *Command-Line        `--bind-address=ip_address'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `[none]'        

     When specified, this option limits management server connections
     by management clients to clients at the specified host name or IP
     address (and possibly port, if this is also specified). In such
     cases, a management client attempting to connect to the management
     server from any other address fails with the error `Unable to
     setup port: HOST:PORT!'

     If the PORT is not specified, the management client attempts to
     use port 1186.

     This option was added in MySQL Cluster NDB 6.2.5 and MySQL Cluster
     NDB 6.3.2.

   * `--no-nodeid-checks'

     Options for no-nodeid-checks

     *Command-Line        `--no-nodeid-checks'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Do not perform any checks of node IDs.

   * `--configdir=PATH'

     Options for configdir

     *Introduced*         5.1.30-ndb-6.4.0        
     *Command-Line        `--configdir=directory'        
     Format*                              
                          `--config-dir=directory'from    
                                  5.1.37-ndb-7.0.8
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `$INSTALLDIR/mysql-cluster'        

     In MySQL Cluster NDB 7.0 and later, specifies the cluster
     management server's configuration cache directory.  Starting with
     MySQL Cluster NDB 7.0.8, `--config-dir' is accepted as an alias for
     this option.

   * `--config-cache'

     Options for config-cache

     *Introduced*         5.1.44-ndb-7.1.4        
     *Command-Line        `--config-cache[=TRUE|FALSE]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     This option, whose default value is `1' (or `TRUE', or `ON'), can
     be used to disable the management server's configuration cache, so
     that it reads its configuration from `config.ini' every time it
     starts (see *Note mysql-cluster-config-file::). You can do this by
     starting the *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.
     process with any one of the following options:

        * `--config-cache=0'

        * `--config-cache=FALSE'

        * `--config-cache=OFF'

        * `--skip-config-cache'

     Using one of the options just listed is effective only if the
     management server has no stored configuration at the time it is
     started. If the management server finds any configuration cache
     files, then the `--config-cache' option or the
     `--skip-config-cache' option is ignored.  Therefore, to disable
     configuration caching, the option should be used the _first_ time
     that the management server is started. Otherwise--that is, if you
     wish to disable configuration caching for a management server that
     has _already_ created a configuration cache--you must stop the
     management server, delete any existing configuration cache files
     manually, then restart the management server with
     `--skip-config-cache' (or with `--config-cache' set equal to 0,
     `OFF', or `FALSE').

     Configuration cache files are normally created in a directory
     named `mysql-cluster' under the installation directory (unless
     this location has been overridden using the `--configdir' option).
     Each time the management server updates its configuration data, it
     writes a new cache file. The files are named sequentially in order
     of creation using the following format:


          ndb_NODE-ID_config.bin.SEQ-NUMBER

     NODE-ID is the management server's node ID; SEQ-NUMBER is a
     sequence number, beginning with 1. For example, if the management
     server's node ID is 5, then the first three configuration cache
     files would, when they are created, be named `ndb_5_config.bin.1',
     `ndb_5_config.bin.2', and `ndb_5_config.bin.3'.

     If your intent is to purge or reload the configuration cache
     without actually disabling caching, you should start *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. with one of the
     options `--reload' or `--initial' instead of `--skip-config-cache'.

     To re-enable the configuration cache, simply restart the
     management server, but without the `--config-cache' or
     `--skip-config-cache' option that was used previously to disable
     the configuration cache.

     This option was added in MySQL Cluster NDB 7.0.15 and MySQL
     Cluster NDB 7.1.4.

     Beginning with MySQL Cluster NDB 7.0.31 and MySQL Cluster NDB
     7.1.20, *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. no
     longer checks for the configuration directory (`--configdir') or
     attempts to create one when `--skip-config-cache' is used. (Bug
     #13428853)

   * `--config-file=FILENAME', `-f FILENAME'

     Options for config-file

     *Command-Line        `--config-file=file'        
     Format*                              
                          `-f'            
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `./config.ini'        
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `[none]'        

     Instructs the management server as to which file it should use for
     its configuration file. By default, the management server looks
     for a file named `config.ini' in the same directory as the *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. executable; otherwise
     the file name and location must be specified explicitly.

     Beginning with MySQL Cluster NDB 6.4.0, this option has no default
     value, and is ignored unless the management server is forced to
     read the configuration file, either because *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. was started with the `--reload' or
     `--initial' option, or because the management server could not
     find any configuration cache. Beginning with MySQL Cluster NDB
     7.0.15 and MySQL Cluster NDB 7.1.4, this option is also read if
     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. was started with
     `--config-cache=OFF'. See *Note mysql-cluster-config-file::, for
     more information.

     Formerly, using this option together with `--initial' caused
     removal of the configuration cache even if the file was not found.
     This issue was resolved in MySQL Cluster NDB 7.0.38 and MySQL
     Cluster NDB 7.1.27. (Bug #1299289)

   * `--mycnf'

     Options for mycnf

     *Command-Line        `--mycnf'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Read configuration data from the `my.cnf' file.

   * `--daemon', `-d'

     Options for daemon

     *Command-Line        `--daemon'        
     Format*                              
                          `-d'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Instructs *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. to
     start as a daemon process. This is the default behavior.

     This option has no effect when running *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. on Windows platforms.

   * `--interactive'

     Options for interactive

     *Command-Line        `--interactive'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Starts *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. in
     interactive mode; that is, an *Note `ndb_mgm':
     mysql-cluster-programs-ndb-mgm. client session is started as soon
     as the management server is running. This option does not start
     any other MySQL Cluster nodes.

   * `--initial'

     Options for initial

     *Introduced*         5.1.30-ndb-6.4.0        
     *Command-Line        `--initial'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Beginning with MySQL Cluster NDB 6.4.0, configuration data is
     cached internally rather than being read from the cluster global
     configuration file each time the management server is started (see
     *Note mysql-cluster-config-file::).  Using this option overrides
     this behavior, by forcing the management server to delete any
     existing cache files, and then to re-read the configuration data
     from the cluster configuration file and to build a new cache.

     This differs in two ways from the `--reload' option. First,
     `--reload' forces the server to check the configuration file
     against the cache and reload its data only if the contents of the
     file are different from the cache. Second, `--reload' does not
     delete any existing cache files.

     If *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. is invoked
     with `--initial' but cannot find a global configuration file, the
     management server cannot start.

     In MySQL Cluster NDB 7.0.8 and later, when starting, the
     management server checks for another management server in the same
     MySQL Cluster and tries to use its configuration data. In other
     words, *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. ignores
     `--initial' unless it is the only management server running. This
     behavior has implications when performing a rolling restart of a
     MySQL Cluster with multiple management nodes. See *Note
     mysql-cluster-rolling-restart::, for more information.

     Formerly, using this option together with the `--config-file'
     option caused removal of the configuration cache even if the file
     was not found. Starting with MySQL Cluster NDB 7.0.38 and MySQL
     Cluster NDB 7.1.27, the cache is cleared in such cases only if the
     configuration file is actually found. (Bug #1299289)

     This option was introduced in MySQL Cluster NDB 6.4.0.

   * `--log-name=NAME'

     Options for log-name

     *Introduced*         5.1.37-ndb-7.0.8        
     *Command-Line        `--log-name=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `MgmtSrvr'        

     Provides a name to be used for this node in the cluster log.

     This option was added in MySQL Cluster NDB 7.0.8.

   * `--nodaemon'

     Options for nodaemon

     *Introduced*         5.1.37-ndb-7.0.8        
     *Command-Line        `--nodaemon'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Instructs *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. not
     to start as a daemon process.

     As of MySQL Cluster NDB 7.0.8, the default behavior for *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. on Windows is to run
     in the foreground, making this option unnecessary on Windows
     platforms. (Bug #45588)

   * `--print-full-config', `-P'

     Options for print-full-config

     *Command-Line        `--print-full-config'        
     Format*                              
                          `-P'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Shows extended information regarding the configuration of the
     cluster. With this option on the command line the *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. process prints
     information about the cluster setup including an extensive list of
     the cluster configuration sections as well as parameters and their
     values. Normally used together with the `--config-file' (`-f')
     option.

   * `--reload'

     Options for reload

     *Introduced*         5.1.30-ndb-6.4.0        
     *Command-Line        `--reload'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Beginning with MySQL Cluster NDB 6.4.0, configuration data is
     stored internally rather than being read from the cluster global
     configuration file each time the management server is started (see
     *Note mysql-cluster-config-file::).  Using this option forces the
     management server to check its internal data store against the
     cluster configuration file and to reload the configuration if it
     finds that the configuration file does not match the cache.
     Existing configuration cache files are preserved, but not used.

     This differs in two ways from the `--initial' option. First,
     `--initial' causes all cache files to be deleted. Second,
     `--initial' forces the management server to re-read the global
     configuration file and construct a new cache.

     If the management server cannot find a global configuration file,
     then the `--reload' option is ignored.

     In MySQL Cluster NDB 7.0.8 and later, when starting, the
     management server checks for another management server in the same
     MySQL Cluster and tries to use its configuration data. In other
     words, *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. ignores
     `--reload' unless it is the only management server running. This
     behavior has implications when performing a rolling restart of a
     MySQL Cluster with multiple management nodes. See *Note
     mysql-cluster-rolling-restart::, for more information.

     This option was introduced in MySQL Cluster NDB 6.4.0.

   * `--nowait-nodes'

     Options for nowait-nodes

     *Introduced*         5.1.39-ndb-7.1.0        
     *Command-Line        `--nowait-nodes=list'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `'              
     *Min Value*          `1'             
     *Max Value*          `255'           

     When starting a MySQL Cluster is configured with two management
     nodes and running MySQL Cluster NDB 7.0 and later, each management
     server normally checks to see whether the other *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. is also operational and whether
     the other management server's configuration is identical to its
     own. However, it is sometimes desirable to start the cluster with
     only one management node (and perhaps to allow the other *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. to be started later).
     This option causes the management node to bypass any checks for
     any other management nodes whose node IDs are passed to this
     option, permitting the cluster to start as though configured to
     use only the management node that was started.

     For purposes of illustration, consider the following portion of a
     `config.ini' file (where we have omitted most of the configuration
     parameters that are not relevant to this example):


          [ndbd]
          NodeId = 1
          HostName = 192.168.0.101

          [ndbd]
          NodeId = 2
          HostName = 192.168.0.102

          [ndbd]
          NodeId = 3
          HostName = 192.168.0.103

          [ndbd]
          NodeId = 4
          HostName = 192.168.0.104

          [ndb_mgmd]
          NodeId = 10
          HostName = 192.168.0.150

          [ndb_mgmd]
          NodeId = 11
          HostName = 192.168.0.151

          [api]
          NodeId = 20
          HostName = 192.168.0.200

          [api]
          NodeId = 21
          HostName = 192.168.0.201

     Assume that you wish to start this cluster using only the
     management server having node ID `10' and running on the host
     having the IP address 192.168.0.150.  (Suppose, for example, that
     the host computer on which you intend to the other management
     server is temporarily unavailable due to a hardware failure, and
     you are waiting for it to be repaired.) To start the cluster in
     this way, use a command line on the machine at 192.168.0.150 to
     enter the following command:


          shell> ndb_mgmd --ndb-nodeid=10 --nowait-nodes=11

     As shown in the preceding example, when using `--nowait-nodes',
     you must also use the `--ndb-nodeid' option to specify the node ID
     of this *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. process.

     You can then start each of the cluster's data nodes in the usual
     way. If you wish to start and use the second management server in
     addition to the first management server at a later time without
     restarting the data nodes, you must start each data node with a
     connection string that references both management servers, like
     this:


          shell> ndbd -c 192.168.0.150,192.168.0.151

     The same is true with regard to the connection string used with
     any *Note `mysqld': mysqld. processes that you wish to start as
     MySQL Cluster SQL nodes connected to this cluster. See *Note
     mysql-cluster-connection-strings::, for more information.

     When used with *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd,
     this option affects the behavior of the management node with
     regard to other management nodes only. Do not confuse it with the
     `--nowait-nodes' option used with *Note `ndbd':
     mysql-cluster-programs-ndbd. (or *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. in MySQL Cluster NDB 7.0 and later)
     to permit a cluster to start with fewer than its full complement
     of data nodes; when used with data nodes, this option affects their
     behavior only with regard to other data nodes.

     Multiple management node IDs may be passed to this option as a
     comma-separated list. Each node ID must be no less than 1 and no
     greater than 255. In practice, it is quite rare to use more than
     two management servers for the same MySQL Cluster (or to have any
     need for doing so); in most cases you need to pass to this option
     only the single node ID for the one management server that you do
     not wish to use when starting the cluster.

     *Note*:

     When you later start the `missing' management server, its
     configuration must match that of the management server that is
     already in use by the cluster.  Otherwise, it fails the
     configuration check performed by the existing management server,
     and does not start.

     This option was introduced in MySQL Cluster NDB 7.0.10 and MySQL
     Cluster NDB 7.1.0.

It is not strictly necessary to specify a connection string when
starting the management server. However, if you are using more than one
management server, a connection string should be provided and each node
in the cluster should specify its node ID explicitly.

See *Note mysql-cluster-connection-strings::, for information about
using connection strings.  *Note mysql-cluster-programs-ndb-mgmd::,
describes other options for *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.

The following files are created or used by *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. in its starting directory, and are
placed in the `DataDir' as specified in the `config.ini' configuration
file. In the list that follows, NODE_ID is the unique node identifier.

   * `config.ini' is the configuration file for the cluster as a whole.
     This file is created by the user and read by the management server.
     *Note mysql-cluster-configuration::, discusses how to set up this
     file.

   * `ndb_NODE_ID_cluster.log' is the cluster events log file. Examples
     of such events include checkpoint startup and completion, node
     startup events, node failures, and levels of memory usage. A
     complete listing of cluster events with descriptions may be found
     in *Note mysql-cluster-management::.

     When the size of the cluster log reaches one million bytes, the
     file is renamed to `ndb_NODE_ID_cluster.log.SEQ_ID', where SEQ_ID
     is the sequence number of the cluster log file. (For example: If
     files with the sequence numbers 1, 2, and 3 already exist, the
     next log file is named using the number `4'.)

   * `ndb_NODE_ID_out.log' is the file used for `stdout' and `stderr'
     when running the management server as a daemon.

   * `ndb_NODE_ID.pid' is the process ID file used when running the
     management server as a daemon.

   * `--install[=NAME]'

     Options for install

     *Introduced*         5.1.47-ndb-7.1.5        
     *Command-Line        `--install[=name]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `ndb_mgmd'        

     Causes *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. to be
     installed as a Windows service. Optionally, you can specify a name
     for the service; if not set, the service name defaults to
     `ndb_mgmd'. Although it is preferable to specify other *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. program options in a
     `my.ini' or `my.cnf' configuration file, it is possible to use
     them together with `--install'. However, in such cases, the
     `--install' option must be specified first, before any other
     options are given, for the Windows service installation to succeed.

     It is generally not advisable to use this option together with the
     `--initial' option, since this causes the configuration cache to
     be wiped and rebuilt every time the service is stopped and
     started. Care should also be taken if you intend to use any other
     *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. options that
     affect the starting of the management server, and you should make
     absolutely certain you fully understand and allow for any possible
     consequences of doing so.

     The `--install' option has no effect on non-Windows platforms.

     This option became available in MySQL Cluster NDB 7.0.16 and MySQL
     Cluster NDB 7.1.5.

   * `--remove[=NAME]'

     Options for remove

     *Introduced*         5.1.47-ndb-7.1.5        
     *Command-Line        `--remove[=name]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `ndb_mgmd'        

     Causes an *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.
     process that was previously installed as a Windows service to be
     removed.  Optionally, you can specify a name for the service to be
     uninstalled; if not set, the service name defaults to `ndb_mgmd'.

     The `--remove' option has no effect on non-Windows platforms.

     This option became available in MySQL Cluster NDB 7.0.16 and MySQL
     Cluster NDB 7.1.5.


File: manual.info,  Node: mysql-cluster-programs-ndb-mgm,  Next: mysql-cluster-programs-ndb-blob-tool,  Prev: mysql-cluster-programs-ndb-mgmd,  Up: mysql-cluster-programs

17.4.5 `ndb_mgm' -- The MySQL Cluster Management Client
-------------------------------------------------------

The *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. management client
process is actually not needed to run the cluster. Its value lies in
providing a set of commands for checking the cluster's status, starting
backups, and performing other administrative functions.  The management
client accesses the management server using a C API. Advanced users can
also employ this API for programming dedicated management processes to
perform tasks similar to those performed by *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm.

To start the management client, it is necessary to supply the host name
and port number of the management server:


     shell> ndb_mgm [HOST_NAME [PORT_NUM]]

For example:


     shell> ndb_mgm ndb_mgmd.mysql.com 1186

The default host name and port number are `localhost' and 1186,
respectively.

The following table includes options that are specific to the MySQL
Cluster management client program *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. Additional descriptions follow the
table. For options common to most MySQL Cluster programs (including
*Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_mgm program

Format Description Added or Removed

`--try-reconnect=#',

` -t '

Specify number of tries for connecting to ndb_mgmd (0 = infinite)

All MySQL 5.1 based releases

`--execute=name',

` -e '

Execute command and exit

All MySQL 5.1 based releases 


   * `--execute=`command'', `-e `command''

     Options for execute

     *Command-Line        `--execute=name'        
     Format*                              
                          `-e'            

     This option can be used to send a command to the MySQL Cluster
     management client from the system shell. For example, either of
     the following is equivalent to executing `SHOW' in the management
     client:


          shell> ndb_mgm -e "SHOW"

          shell> ndb_mgm --execute="SHOW"

     This is analogous to how the `--execute' or `-e' option works with
     the *Note `mysql': mysql. command-line client. See *Note
     command-line-options::.

     *Note*:

     If the management client command to be passed using this option
     contains any space characters, then the command _must_ be enclosed
     in quotation marks.  Either single or double quotation marks may
     be used. If the management client command contains no space
     characters, the quotation marks are optional.

   * `--try-reconnect=NUMBER'

     Options for try-reconnect

     *Command-Line        `--try-reconnect=#'        
     Format*                              
                          `-t'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     If the connection to the management server is broken, the node
     tries to reconnect to it every 5 seconds until it succeeds. By
     using this option, it is possible to limit the number of attempts
     to NUMBER before giving up and reporting an error instead.

Additional information about using *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm.  can be found in *Note
mysql-cluster-mgm-client-commands::.


File: manual.info,  Node: mysql-cluster-programs-ndb-blob-tool,  Next: mysql-cluster-programs-ndb-config,  Prev: mysql-cluster-programs-ndb-mgm,  Up: mysql-cluster-programs

17.4.6 `ndb_blob_tool' -- Check and Repair BLOB and TEXT columns of MySQL Cluster Tables
----------------------------------------------------------------------------------------

This tool, which is available in MySQL Cluster NDB 7.0.4 and later, can
be used to check for and remove orphaned BLOB column parts from *Note
`NDB': mysql-cluster. tables, as well as to generate a file listing any
orphaned parts. It is sometimes useful in diagnosing and repairing
corrupted or damaged `NDB' tables containing *Note `BLOB': blob. or
*Note `TEXT': blob. columns.

The basic syntax for *Note `ndb_blob_tool':
mysql-cluster-programs-ndb-blob-tool. is shown here:


     ndb_blob_tool [OPTIONS] TABLE [COLUMN, ...]

Unless you use the `--help' option, you must specify an action to be
performed by including one or more of the options `--check-orphans',
`--delete-orphans', or `--dump-file'. These options cause *Note
`ndb_blob_tool': mysql-cluster-programs-ndb-blob-tool. to check for
orphaned BLOB parts, remove any orphaned BLOB parts, and generate a dump
file listing orphaned BLOB parts, respectively, and are described in
more detail later in this section.

You must also specify the name of a table when invoking *Note
`ndb_blob_tool': mysql-cluster-programs-ndb-blob-tool. In addition, you
can optionally follow the table name with the (comma-separated) names
of one or more *Note `BLOB': blob. or *Note `TEXT': blob. columns from
that table. If no columns are listed, the tool works on all of the
table's *Note `BLOB': blob. and *Note `TEXT': blob. columns. If you
need to specify a database, use the `--database' (`-d') option.

The `--verbose' option provides additional information in the output
about the tool's progress.

The following table includes options that are specific to *Note
`ndb_blob_tool': mysql-cluster-programs-ndb-blob-tool. Additional
descriptions follow the table. For options common to most MySQL Cluster
programs (including *Note `ndb_blob_tool':
mysql-cluster-programs-ndb-blob-tool.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_blob_tool program

Format Description Added or Removed

` --check-orphans '

Check for orphan blob parts

ADDED: NDB 7.0.4

`--database=db_name',

` -d '

Database to find the table in.

ADDED: NDB 7.0.4

` --delete-orphans '

Delete orphan blob parts

ADDED: NDB 7.0.4

` --dump-file=file '

Write orphan keys to specified file

ADDED: NDB 7.0.4

`--verbose',

` -v '

Verbose output

ADDED: NDB 7.0.4 


   * `--check-orphans'

     Options for check-orphans

     *Introduced*         5.1.32-ndb-7.0.4        
     *Command-Line        `--check-orphans'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Check for orphaned BLOB parts in MySQL Cluster tables.

   * `--database=DB_NAME', `-d'

     Options for database

     *Introduced*         5.1.32-ndb-7.0.4        
     *Command-Line        `--database=db_name'        
     Format*                              
                          `-d'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `[none]'        

     Specify the database to find the table in.

   * `--delete-orphans'

     Options for delete-orphans

     *Introduced*         5.1.32-ndb-7.0.4        
     *Command-Line        `--delete-orphans'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Remove orphaned BLOB parts from MySQL Cluster tables.

   * `--dump-file=FILE'

     Options for dump-file

     *Introduced*         5.1.32-ndb-7.0.4        
     *Command-Line        `--dump-file=file'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `[none]'        

     Writes a list of orphaned BLOB column parts to FILE. The
     information written to the file includes the table key and BLOB
     part number for each orphaned BLOB part.

   * `--verbose'

     Options for verbose

     *Introduced*         5.1.32-ndb-7.0.4        
     *Command-Line        `--verbose'        
     Format*                              
                          `-v'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Provide extra information in the tool's output regarding its
     progress.

*Example*

First we create an `NDB' table in the `test' database, using the *Note
`CREATE TABLE': create-table. statement shown here:


     USE test;

     CREATE TABLE btest (
         c0 BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
         c1 TEXT,
         c2 BLOB
     )   ENGINE=NDB;

Then we insert a few rows into this table, using a series of statements
similar to this one:


     INSERT INTO btest VALUES (NULL, 'x', REPEAT('x', 1000));

When run with `--check-orphans' against this table, *Note
`ndb_blob_tool': mysql-cluster-programs-ndb-blob-tool. generates the
following output:


     shell> ndb_blob_tool --check-orphans --verbose -d test btest
     connected
     processing 2 blobs
     processing blob #0 c1 NDB$BLOB_19_1
     NDB$BLOB_19_1: nextResult: res=1
     total parts: 0
     orphan parts: 0
     processing blob #1 c2 NDB$BLOB_19_2
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=0
     NDB$BLOB_19_2: nextResult: res=1
     total parts: 10
     orphan parts: 0
     disconnected

     NDBT_ProgramExit: 0 - OK

The tool reports that there are no `NDB' BLOB column parts associated
with column `c1', even though `c1' is a *Note `TEXT': blob. column.
This is due to the fact that, in an *Note `NDB': mysql-cluster. table,
only the first 256 bytes of a *Note `BLOB': blob. or *Note `TEXT':
blob. column value are stored inline, and only the excess, if any, is
stored separately; thus, if there are no values using more than 256
bytes in a given column of one of these types, no `BLOB' column parts
are created by `NDB' for this column. See *Note storage-requirements::,
for more information.


File: manual.info,  Node: mysql-cluster-programs-ndb-config,  Next: mysql-cluster-programs-ndb-cpcd,  Prev: mysql-cluster-programs-ndb-blob-tool,  Up: mysql-cluster-programs

17.4.7 `ndb_config' -- Extract MySQL Cluster Configuration Information
----------------------------------------------------------------------

This tool extracts current configuration information for data nodes,
SQL nodes, and API nodes from one of a number of sources: a MySQL
Cluster management node, or its `config.ini' or `my.cnf' file. By
default, the management node is the source for the configuration data;
to override the default, execute ndb_config with the `--config-file' or
`--mycnf' option. Beginning with MySQL Cluster NDB 7.0.27 and MySQL
Cluster NDB 7.1.16, it is also possible to use a data node as the
source by specifying its node ID using `--config_from_node=NODE_ID'.

Beginning with MySQL Cluster NDB 6.3.25 and MySQL Cluster NDB 7.0.6,
*Note `ndb_config': mysql-cluster-programs-ndb-config. can also provide
an offline dump of all configuration parameters which can be used, along
with their default, maximum, and minimum values and other information.
The dump can be produced in either text or XML format; for more
information, see the discussion of the `--configinfo' and `--xml'
options later in this section).

Beginning with MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16,
you can filter the results by section (`DB', `SYSTEM', or
`CONNECTIONS') using one of the options `--nodes', `--system', or
`--connections'.

The following table includes options that are specific to *Note
`ndb_config': mysql-cluster-programs-ndb-config. Additional
descriptions follow the table. For options common to most MySQL Cluster
programs (including *Note `ndb_config':
mysql-cluster-programs-ndb-config.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_config program

Format Description Added or Removed

` --nodes '

Print node information (DB section) only.

All MySQL 5.1 based releases

` --connections '

Print CONNECTIONS section information only. Cannot be used with -nodes
or -system option.

All MySQL 5.1 based releases

`--query=string',

` -q '

One or more query options (attributes)

All MySQL 5.1 based releases

` --host=name '

Specify host

All MySQL 5.1 based releases

` --type=name '

Specify node type

All MySQL 5.1 based releases

`--nodeid',

` --id '

Get configuration of node with this ID

All MySQL 5.1 based releases

`--fields=string',

` -f '

Field separator

All MySQL 5.1 based releases

`--rows=string',

` -r '

Row separator

All MySQL 5.1 based releases

` --config-file=path '

Set the path to config.ini file

All MySQL 5.1 based releases

` --mycnf '

Read configuration data from my.cnf file

All MySQL 5.1 based releases

` -c '

Short form for -ndb-connectstring

ADDED: 5.1.12

` --configinfo '

Dumps information about all NDB configuration parameters in text format
with default, maximum, and minimum values. Use with -xml to obtain XML
output.

ADDED: NDB 6.3.25, NDB 7.0.6

` --configinfo --xml '

Use -xml with -configinfo to obtain a dump of all NDB configuration
parameters in XML format with default, maximum, and minimum values.

ADDED: NDB 6.3.25, NDB 7.0.6

` --system '

Print SYSTEM section information only. Cannot be used with -nodes or
-connections option.

ADDED: NDB 7.0.27, NDB 7.1.16

` --config_from_node=# '

Obtain configuration data from the node having this ID (must be a data
node).

ADDED: NDB 7.0.27, NDB 7.1.16 


   * `--usage', `--help', or `-?'

     Options for help

     *Command-Line        `--help'        
     Format*                              
                          `--usage'        
                          `-?'            

     Causes *Note `ndb_config': mysql-cluster-programs-ndb-config. to
     print a list of available options, and then exit.

   * `--config_from_node=#'

     Options for config_from_node

     *Introduced*         5.1.56-ndb-7.1.16        
     *Command-Line        `--config_from_node=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `none'          
     *Min Value*          `1'             
     *Max Value*          `48'            

     Obtain the cluster's configuration data from the data node that
     has this ID.

     If the node having this ID is not a data node, *Note `ndb_config':
     mysql-cluster-programs-ndb-config. fails with an error. (To obtain
     configuration data from the management node instead, simply omit
     this option.)

     `--config_from_node' was added in MySQL Cluster NDB 7.0.27 and
     MySQL NDB 7.1.16.

   * `--version', `-V'

     Options for version

     *Command-Line        `--version'        
     Format*                              
                          `-V'            

     Causes *Note `ndb_config': mysql-cluster-programs-ndb-config. to
     print a version information string, and then exit.

   * `--ndb-connectstring=CONNECT_STRING'

     Options for ndb-connectstring

     *Command-Line        `--ndb-connectstring=connectstring'        
     Format*                              
                          `--connect-string=connectstring'        
                          `-c'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `localhost:1186'        

     Specifies the connection string to use in connecting to the
     management server. The format for the connection string is the
     same as described in *Note mysql-cluster-connection-strings::, and
     defaults to `localhost:1186'.

     The use of `-c' as a short version for this option is supported
     for *Note `ndb_config': mysql-cluster-programs-ndb-config.
     beginning with MySQL 5.1.12.

   * `--config-file=PATH-TO-FILE'

     Options for config-file

     *Command-Line        `--config-file=path'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `'              

     Gives the path to the management server's configuration file
     (`config.ini'). This may be a relative or absolute path. If the
     management node resides on a different host from the one on which
     *Note `ndb_config': mysql-cluster-programs-ndb-config. is invoked,
     then an absolute path must be used.

   * `--mycnf'

     Options for mycnf

     *Command-Line        `--mycnf'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Read configuration data from the `my.cnf' file.

   * `--query=QUERY-OPTIONS', `-q' QUERY-OPTIONS

     Options for query

     *Command-Line        `--query=string'        
     Format*                              
                          `-q'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     This is a comma-delimited list of _query options_--that is, a list
     of one or more node attributes to be returned. These include `id'
     (node ID), type (node type--that is, `ndbd', `mysqld', or
     `ndb_mgmd'), and any configuration parameters whose values are to
     be obtained.

     For example,

     `--query=id,type,indexmemory,datamemory' returns the node ID, node
     type, `DataMemory', and `IndexMemory' for each node.

     *Note*:

     If a given parameter is not applicable to a certain type of node,
     than an empty string is returned for the corresponding value. See
     the examples later in this section for more information.

   * `--host=HOSTNAME'

     Options for host

     *Command-Line        `--host=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     Specifies the host name of the node for which configuration
     information is to be obtained.

     *Note*:

     While the hostname `localhost' usually resolves to the IP address
     `127.0.0.1', this may not necessarily be true for all operating
     platforms and configurations. This means that it is possible, when
     `localhost' is used in `config.ini', for *Note `ndb_config
     `--host=localhost'': mysql-cluster-programs-ndb-config. to fail if
     *Note `ndb_config': mysql-cluster-programs-ndb-config. is run on a
     different host where `localhost' resolves to a different address
     (for example, on some versions of SUSE Linux, this is
     `127.0.0.2'). In general, for best results, you should use numeric
     IP addresses for all MySQL Cluster configuration values relating
     to hosts, or verify that all MySQL Cluster hosts handle
     `localhost' in the same fashion.

   * `--id=NODE_ID'

     `--nodeid=NODE_ID'

     Options for ndb-nodeid

     *Command-Line        `--ndb-nodeid=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             

     Either of these options can be used to specify the node ID of the
     node for which configuration information is to be obtained.
     `--nodeid' is the preferred form.

   * `--nodes'

     Options for nodes

     *Command-Line        `--nodes'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Tells *Note `ndb_config': mysql-cluster-programs-ndb-config. to
     print information from parameters defined in `DB' sections only.
     Prior to MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16,
     this option had no affect. This option cannot be used together with
     `--connections' or `--system'.

   * `--connections'

     Options for connections

     *Command-Line        `--connections'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Tells *Note `ndb_config': mysql-cluster-programs-ndb-config. to
     print `CONNECTIONS' information only. This option existed prior to
     MySQL Cluster NDB 7.0.27 and MySQL Cluster NDB 7.1.16, but had no
     affect before then. This option cannot be used together with
     `--nodes' or `--system'.

   * `--system'

     Options for system

     *Introduced*         5.1.56-ndb-7.1.16        
     *Command-Line        `--system'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Tells *Note `ndb_config': mysql-cluster-programs-ndb-config. to
     print `SYSTEM' information only.

     This option was introduced in MySQL Cluster NDB 7.0.27 and MySQL
     Cluster NDB 7.1.16. It cannot be used together with the `--nodes'
     or `--system' options.

   * `--type=NODE_TYPE'

     Options for type

     *Command-Line        `--type=name'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `enumeration'        
     *Default*            `[none]'        
     *Valid Values*       `ndbd'          
     `mysqld'                             
     `ndb_mgmd'                           

     Filters results so that only configuration values applying to
     nodes of the specified NODE_TYPE (`ndbd', `mysqld', or `ndb_mgmd')
     are returned.

   * `--fields=DELIMITER', `-f' DELIMITER

     Options for fields

     *Command-Line        `--fields=string'        
     Format*                              
                          `-f'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     Specifies a DELIMITER string used to separate the fields in the
     result. The default is ``,'' (the comma character).

     *Note*:

     If the DELIMITER contains spaces or escapes (such as `\n' for the
     linefeed character), then it must be quoted.

   * `--rows=SEPARATOR', `-r' SEPARATOR

     Options for rows

     *Command-Line        `--rows=string'        
     Format*                              
                          `-r'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     Specifies a SEPARATOR string used to separate the rows in the
     result. The default is a space character.

     *Note*:

     If the SEPARATOR contains spaces or escapes (such as `\n' for the
     linefeed character), then it must be quoted.

   * `--configinfo'

     The `--configinfo' option, added in MySQL Cluster NDB 6.3.25 and
     MySQL Cluster NDB 7.0.6, causes *Note `ndb_config':
     mysql-cluster-programs-ndb-config. to dump a list of each MySQL
     Cluster configuration parameter supported by the MySQL Cluster
     distribution of which *Note `ndb_config':
     mysql-cluster-programs-ndb-config.  is a part, including the
     following information:

        * A brief description of each parameter's purpose, effects, and
          usage

        * The section of the `config.ini' file where the parameter may
          be used

        * The parameter's data type or unit of measurement

        * Where applicable, the parameter's default, minimum, and
          maximum values

        * A brief description of the parameter's purpose, effects, and
          usage

        * MySQL Cluster release version and build information

     By default, this output is in text format. Part of this output is
     shown here:


          shell> ndb_config --configinfo

          ****** SYSTEM ******

          Name (String)
          Name of system (NDB Cluster)
          MANDATORY

          PrimaryMGMNode (Non-negative Integer)
          Node id of Primary ndb_mgmd(MGM) node
          Default: 0 (Min: 0, Max: 4294967039)

          ConfigGenerationNumber (Non-negative Integer)
          Configuration generation number
          Default: 0 (Min: 0, Max: 4294967039)

          ****** DB ******

          MaxNoOfSubscriptions (Non-negative Integer)
          Max no of subscriptions (default 0 == MaxNoOfTables)
          Default: 0 (Min: 0, Max: 4294967039)

          MaxNoOfSubscribers (Non-negative Integer)
          Max no of subscribers (default 0 == 2 * MaxNoOfTables)
          Default: 0 (Min: 0, Max: 4294967039)

          ...

     `--configinfo' `--xml'

     Options for xml

     *Introduced*         5.1.34-ndb-7.0.6        
     *Command-Line        `--configinfo        
     Format*              --xml'          
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `false'         

     You can obtain the output of *Note `ndb_config':
     mysql-cluster-programs-ndb-config.  `--configinfo' as XML by
     adding the `--xml' option (like the `--configinfo' option,
     available beginning with MySQL Cluster NDB 6.3.25 and MySQL
     Cluster NDB 7.0.6).  A portion of the resulting output is shown in
     this example:


          shell> ndb_config --configinfo --xml

          <configvariables protocolversion="1" ndbversionstring="5.1.73-ndb-7.1.34"
                              ndbversion="458758" ndbversionmajor="7" ndbversionminor="0"
                              ndbversionbuild="6">
            <section name="SYSTEM">
              <param name="Name" comment="Name of system (NDB Cluster)" type="string"
                        mandatory="true"/>
              <param name="PrimaryMGMNode" comment="Node id of Primary ndb_mgmd(MGM) node"
                        type="unsigned" default="0" min="0" max="4294967039"/>
              <param name="ConfigGenerationNumber" comment="Configuration generation number"
                        type="unsigned" default="0" min="0" max="4294967039"/>
            </section>
            <section name="NDBD">
              <param name="MaxNoOfSubscriptions"
                        comment="Max no of subscriptions (default 0 == MaxNoOfTables)"
                        type="unsigned" default="0" min="0" max="4294967039"/>
              <param name="MaxNoOfSubscribers"
                        comment="Max no of subscribers (default 0 == 2 * MaxNoOfTables)"
                        type="unsigned" default="0" min="0" max="4294967039"/>

              ...

            </section>

            ...

          </configvariables>

     *Note*:

     Normally, the XML output produced by *Note `ndb_config':
     mysql-cluster-programs-ndb-config.  `--configinfo' `--xml' is
     formatted using one line per element; we have added extra
     whitespace in the previous example, as well as the next one, for
     reasons of legibility. This should not make any difference to
     applications using this output, since most XML processors either
     ignore nonessential whitespace as a matter of course, or can be
     instructed to do so.

     Beginning with MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB
     7.0.10, the XML output also indicates when changing a given
     parameter requires that data nodes be restarted using the
     `--initial' option. This is shown by the presence of an
     `initial="true"' attribute in the corresponding `<param>' element.
     In addition (also beginning with MySQL Cluster NDB 6.3.29 and
     MySQL Cluster NDB 7.0.10), the restart type (`system' or `node') is
     also shown; if a given parameter requires a system restart, this
     is indicated by the presence of a `restart="system"' attribute in
     the corresponding `<param>' element. For example, changing the
     value set for the `Diskless' parameter requires a system initial
     restart, as shown here (with the `restart' and `initial'
     attributes highlighted for visibility):


          <param name="Diskless" comment="Run wo/ disk" type="bool" default="false"
                    _restart="system" initial="true"_/>

     Currently, no `initial' attribute is included in the XML output for
     `<param>' elements corresponding to parameters which do not
     require initial restarts; in other words, `initial="false"' is the
     default, and the value `false' should be assumed if the attribute
     is not present. Similarly, the default restart type is `node'
     (that is, an online or `rolling' restart of the cluster), but the
     `restart' attribute is included only if the restart type is
     `system' (meaning that all cluster nodes must be shut down at the
     same time, then restarted).

     *Important*:

     The `--xml' option can be used only with the `--configinfo'
     option. Using `--xml' without `--configinfo' fails with an error.

     Unlike the options used with this program to obtain current
     configuration data, `--configinfo' and `--xml' use information
     obtained from the MySQL Cluster sources when *Note `ndb_config':
     mysql-cluster-programs-ndb-config. was compiled. For this reason,
     no connection to a running MySQL Cluster or access to a
     `config.ini' or `my.cnf' file is required for these two options.

     Combining other *Note `ndb_config':
     mysql-cluster-programs-ndb-config. options (such as `--query' or
     `--type') with `--configinfo' or `--xml' is not supported.
     Currently, if you attempt to do so, the usual result is that all
     other options besides `--configinfo' or `--xml' are simply
     ignored. _However, this behavior is not guaranteed and is subject
     to change at any time_.  In addition, since *Note `ndb_config':
     mysql-cluster-programs-ndb-config, when used with the
     `--configinfo' option, does not access the MySQL Cluster or read
     any files, trying to specify additional options such as
     `--ndb-connectstring' or `--config-file' with `--configinfo'
     serves no purpose.

*Examples*

  1. To obtain the node ID and type of each node in the cluster:


          shell> ./ndb_config --query=id,type --fields=':' --rows='\n'
          1:ndbd
          2:ndbd
          3:ndbd
          4:ndbd
          5:ndb_mgmd
          6:mysqld
          7:mysqld
          8:mysqld
          9:mysqld

     In this example, we used the `--fields' options to separate the ID
     and type of each node with a colon character (`:'), and the
     `--rows' options to place the values for each node on a new line
     in the output.

  2. To produce a connection string that can be used by data, SQL, and
     API nodes to connect to the management server:


          shell> ./ndb_config --config-file=usr/local/mysql/cluster-data/config.ini \
          --query=hostname,portnumber --fields=: --rows=, --type=ndb_mgmd
          192.168.0.179:1186

  3. This invocation of *Note `ndb_config':
     mysql-cluster-programs-ndb-config. checks only data nodes (using
     the `--type' option), and shows the values for each node's ID and
     host name, as well as the values set for its `DataMemory',
     `IndexMemory', and `DataDir' parameters:


          shell> ./ndb_config --type=ndbd --query=id,host,datamemory,indexmemory,datadir -f ' : ' -r '\n'
          1 : 192.168.0.193 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
          2 : 192.168.0.112 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
          3 : 192.168.0.176 : 83886080 : 18874368 : /usr/local/mysql/cluster-data
          4 : 192.168.0.119 : 83886080 : 18874368 : /usr/local/mysql/cluster-data

     In this example, we used the short options `-f' and `-r' for
     setting the field delimiter and row separator, respectively.

  4. To exclude results from any host except one in particular, use the
     `--host' option:


          shell> ./ndb_config --host=192.168.0.176 -f : -r '\n' -q id,type
          3:ndbd
          5:ndb_mgmd

     In this example, we also used the short form `-q' to determine the
     attributes to be queried.

     Similarly, you can limit results to a node with a specific ID
     using the `--id' or `--nodeid' option.


File: manual.info,  Node: mysql-cluster-programs-ndb-cpcd,  Next: mysql-cluster-programs-ndb-delete-all,  Prev: mysql-cluster-programs-ndb-config,  Up: mysql-cluster-programs

17.4.8 `ndb_cpcd' -- Automate Testing for NDB Development
---------------------------------------------------------

This utility is found in the `libexec' directory. It is part of an
internal automated test framework used in testing and debugging MySQL
Cluster. Because it can control processes on remote systems, it is not
advisable to use *Note `ndb_cpcd': mysql-cluster-programs-ndb-cpcd. in
a production cluster.

The source files for *Note `ndb_cpcd': mysql-cluster-programs-ndb-cpcd.
may be found in the directory `storage/ndb/src/cw/cpcd', in the MySQL
Cluster source tree.

Deprecated feature

As of MySQL Cluster NDB 7.0, this program is deprecated and no longer
actively maintained. It is subject to removal in a future MySQL Cluster
version.


File: manual.info,  Node: mysql-cluster-programs-ndb-delete-all,  Next: mysql-cluster-programs-ndb-desc,  Prev: mysql-cluster-programs-ndb-cpcd,  Up: mysql-cluster-programs

17.4.9 `ndb_delete_all' -- Delete All Rows from an NDB Table
------------------------------------------------------------

*Note `ndb_delete_all': mysql-cluster-programs-ndb-delete-all. deletes
all rows from the given *Note `NDB': mysql-cluster. table. In some
cases, this can be much faster than *Note `DELETE': delete. or even
*Note `TRUNCATE TABLE': truncate-table.

*Usage*


     ndb_delete_all -c CONNECT_STRING TBL_NAME -d DB_NAME

This deletes all rows from the table named TBL_NAME in the database
named DB_NAME. It is exactly equivalent to executing `TRUNCATE
DB_NAME.TBL_NAME' in MySQL.

The following table includes options that are specific to *Note
`ndb_delete_all': mysql-cluster-programs-ndb-delete-all. Additional
descriptions follow the table. For options common to most MySQL Cluster
programs (including *Note `ndb_delete_all':
mysql-cluster-programs-ndb-delete-all.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_delete_all program

Format Description Added or Removed

`--database=dbname',

`-d'

Name of the database in which the table is found

All MySQL 5.1 based releases

`--transactional',

` -t '

Perform the delete in a single transaction (may run out of operations)

All MySQL 5.1 based releases

`--tupscan'

Run tup scan

All MySQL 5.1 based releases

`--diskscan'

Run disk scan

All MySQL 5.1 based releases 


   * `--transactional', `-t'

     Use of this option causes the delete operation to be performed as
     a single transaction.

     *Warning*:

     With very large tables, using this option may cause the number of
     operations available to the cluster to be exceeded.


File: manual.info,  Node: mysql-cluster-programs-ndb-desc,  Next: mysql-cluster-programs-ndb-drop-index,  Prev: mysql-cluster-programs-ndb-delete-all,  Up: mysql-cluster-programs

17.4.10 `ndb_desc' -- Describe NDB Tables
-----------------------------------------

*Note `ndb_desc': mysql-cluster-programs-ndb-desc. provides a detailed
description of one or more *Note `NDB': mysql-cluster. tables.

*Usage*


     ndb_desc -c CONNECT_STRING TBL_NAME -d DB_NAME [-p]

(_MySQL Cluster NDB 7.0.36 and later; MySQL Cluster NDB 7.1.25 and
later:_)


     ndb_desc -c CONNECT_STRING INDEX_NAME -d DB_NAME -t TBL_NAME

*Sample Output*

MySQL table creation and population statements:


     USE test;

     CREATE TABLE fish (
         id INT(11) NOT NULL AUTO_INCREMENT,
         name VARCHAR(20) NOT NULL,
         length_mm INT(11) NOT NULL,
         weight_gm INT(11) NOT NULL,

         PRIMARY KEY pk (id),
         UNIQUE KEY uk (name)
     ) ENGINE=NDB;

     INSERT INTO fish VALUES
         ('','guppy', 35, 2), ('','tuna', 2500, 150000),
         ('','shark', 3000, 110000), ('','manta ray', 1500, 50000),
         ('','grouper', 900, 125000), ('','puffer', 250, 2500);

Output from *Note `ndb_desc': mysql-cluster-programs-ndb-desc.:


     shell> ./ndb_desc -c localhost fish -d test -p
     -- fish --
     Version: 2
     Fragment type: 9
     K Value: 6
     Min load factor: 78
     Max load factor: 80
     Temporary table: no
     Number of attributes: 4
     Number of primary keys: 1
     Length of frm data: 311
     Row Checksum: 1
     Row GCI: 1
     SingleUserMode: 0
     ForceVarPart: 1
     FragmentCount: 2
     TableStatus: Retrieved
     -- Attributes --
     id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
     name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
     length_mm Int NOT NULL AT=FIXED ST=MEMORY
     weight_gm Int NOT NULL AT=FIXED ST=MEMORY

     -- Indexes --
     PRIMARY KEY(id) - UniqueHashIndex
     PRIMARY(id) - OrderedIndex
     uk$unique(name) - UniqueHashIndex
     uk(name) - OrderedIndex

     -- Per partition info --
     Partition  Row count  Commit count  Frag fixed memory ...
     0          2          2             32768             ...
     1          4          4             32768             ...

     ... Frag varsized memory  Extent_space  Free extent_space
     ... 32768                 0             0
     ... 32768                 0             0

     NDBT_ProgramExit: 0 - OK

Information about multiple tables can be obtained in a single
invocation of *Note `ndb_desc': mysql-cluster-programs-ndb-desc. by
using their names, separated by spaces. All of the tables must be in
the same database.

Beginning with MySQL Cluster NDB 7.0.36 and MySQL Cluster NDB 7.1.25,
it is possible to obtain additional information about a specific index
using the `--table' (short form: `-t') option introduced in these
versions and supplying the name of the index as the first argument to
*Note `ndb_desc': mysql-cluster-programs-ndb-desc, as shown here:


     shell> ./ndb_desc uk -d test -t fish
     -- uk --
     Version: 3
     Base table: fish
     Number of attributes: 1
     Logging: 0
     Index type: OrderedIndex
     Index status: Retrieved
     -- Attributes --
     name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
     -- IndexTable 10/uk --
     Version: 3
     Fragment type: FragUndefined
     K Value: 6
     Min load factor: 78
     Max load factor: 80
     Temporary table: yes
     Number of attributes: 2
     Number of primary keys: 1
     Length of frm data: 0
     Row Checksum: 1
     Row GCI: 1
     SingleUserMode: 2
     ForceVarPart: 0
     FragmentCount: 4
     ExtraRowGciBits: 0
     ExtraRowAuthorBits: 0
     TableStatus: Retrieved
     -- Attributes --
     name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
     NDB$TNODE Unsigned [64] PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY
     -- Indexes --
     PRIMARY KEY(NDB$TNODE) - UniqueHashIndex

     NDBT_ProgramExit: 0 - OK

When an index is specified in this way, the `--extra-partition-info' and
`--extra-node-info' options have no effect.

The `Version' column in the output contains the table's schema object
version. For information about interpreting this value, see NDB Schema
Object Versions
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-schema-object-versions.html).

The `Extent_space' and `Free extent_space' columns were added in MySQL
Cluster NDB 6.3.27 and MySQL Cluster NDB 7.0.8. They are applicable
only to `NDB' tables having columns on disk; for tables having only
in-memory columns, these columns always contain the value `0'.

To illustrate their use, we modify the previous example. First, we must
create the necessary Disk Data objects, as shown here:


     CREATE LOGFILE GROUP lg_1
         ADD UNDOFILE 'undo_1.log'
         INITIAL_SIZE 16M
         UNDO_BUFFER_SIZE 2M
         ENGINE NDB;

     ALTER LOGFILE GROUP lg_1
         ADD UNDOFILE 'undo_2.log'
         INITIAL_SIZE 12M
         ENGINE NDB;

     CREATE TABLESPACE ts_1
         ADD DATAFILE 'data_1.dat'
         USE LOGFILE GROUP lg_1
         INITIAL_SIZE 32M
         ENGINE NDB;

     ALTER TABLESPACE ts_1
         ADD DATAFILE 'data_2.dat'
         INITIAL_SIZE 48M
         ENGINE NDB;

(For more information on the statements just shown and the objects
created by them, see *Note mysql-cluster-disk-data-objects::, as well as
*Note create-logfile-group::, and *Note create-tablespace::.)

Now we can create and populate a version of the `fish' table that
stores 2 of its columns on disk (deleting the previous version of the
table first, if it already exists):


     CREATE TABLE fish (
         id INT(11) NOT NULL AUTO_INCREMENT,
         name VARCHAR(20) NOT NULL,
         length_mm INT(11) NOT NULL,
         weight_gm INT(11) NOT NULL,

         PRIMARY KEY pk (id),
         UNIQUE KEY uk (name)
     ) TABLESPACE ts_1 STORAGE DISK
     ENGINE=NDB;

     INSERT INTO fish VALUES
         ('','guppy', 35, 2), ('','tuna', 2500, 150000),
         ('','shark', 3000, 110000), ('','manta ray', 1500, 50000),
         ('','grouper', 900, 125000), ('','puffer', 250, 2500);

When run against this version of the table, *Note `ndb_desc':
mysql-cluster-programs-ndb-desc. displays the following output:


     shell> ./ndb_desc -c localhost fish -d test -p
     -- fish --
     Version: 3
     Fragment type: 9
     K Value: 6
     Min load factor: 78
     Max load factor: 80
     Temporary table: no
     Number of attributes: 4
     Number of primary keys: 1
     Length of frm data: 321
     Row Checksum: 1
     Row GCI: 1
     SingleUserMode: 0
     ForceVarPart: 1
     FragmentCount: 2
     TableStatus: Retrieved
     -- Attributes --
     id Int PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
     name Varchar(20;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
     length_mm Int NOT NULL AT=FIXED ST=DISK
     weight_gm Int NOT NULL AT=FIXED ST=DISK

     -- Indexes --
     PRIMARY KEY(id) - UniqueHashIndex
     PRIMARY(id) - OrderedIndex
     uk$unique(name) - UniqueHashIndex
     uk(name) - OrderedIndex
     -- Per partition info --
     Partition  Row count  Commit count  Frag fixed memory ...
     0          2          2             32768             ...
     1          4          4             32768             ...

     ... Frag varsized memory  Extent_space  Free extent_space
     ... 32768                 0             0
     ... 32768                 0             0

     NDBT_ProgramExit: 0 - OK

This means that 1048576 bytes are allocated from the tablespace for
this table on each partition, of which 1044440 bytes remain free for
additional storage. In other words, 1048576 - 1044440 = 4136 bytes per
partition is currently being used to store the data from this table's
disk-based columns. The number of bytes shown as `Free extent_space' is
available for storing on-disk column data from the `fish' table only;
for this reason, it is not visible when selecting from the *Note
`INFORMATION_SCHEMA.FILES': files-table.  table.

The following table includes options that are specific to *Note
`ndb_desc': mysql-cluster-programs-ndb-desc. Additional descriptions
follow the table. For options common to most MySQL Cluster programs
(including *Note `ndb_desc': mysql-cluster-programs-ndb-desc.), see
*Note mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_desc program

Format Description Added or Removed

`--blob-info',

` -b '

Include partition information for BLOB tables in output. Requires that
the -p option also be used

ADDED: NDB 6.3.32, NDB 7.0.13, NDB 7.1.2

`--database=dbname',

` -d '

Name of database containing table

All MySQL 5.1 based releases

`--extra-node-info',

` -n '

Include partition-to-data-node mappings in output. Requires that the -p
option also be used

ADDED: NDB 6.2.19, NDB 6.3.33, NDB 7.0.14, NDB 7.1.2

`--extra-partition-info',

` -p '

Display information about partitions

All MySQL 5.1 based releases

`--retries=#',

` -r '

Number of times to retry the connection (once per second)

All MySQL 5.1 based releases

`--table=tbl_name',

` -t '

Specify the table in which to find an index. When this option is used,
-p and -n have no effect and are ignored.

ADDED: NDB 7.0.36, NDB 7.1.25

`--unqualified',

` -u '

Use unqualified table names

All MySQL 5.1 based releases 


   * `--blob-info', `-b'

     Include information about subordinate *Note `BLOB': blob. and
     *Note `TEXT': blob. columns.

     Use of this option also requires the use of the
     `--extra-partition-info' (`-p') option.

     This option was added in MySQL Cluster NDB 6.3.32, MySQL Cluster
     NDB 7.0.13, and MySQL Cluster NDB 7.1.2.

   * `--database=DB_NAME', `-d'

     Specify the database in which the table should be found.

   * `--extra-node-info', `-n'

     Include information about the mappings between table partitions
     and the data nodes upon which they reside. This information can be
     useful for verifying distribution awareness mechanisms and
     supporting more efficient application access to the data stored in
     MySQL Cluster.

     Use of this option also requires the use of the
     `--extra-partition-info' (`-p') option.

     This option was added in MySQL Cluster NDB 6.2.19, MySQL Cluster
     NDB 6.3.33, MySQL Cluster NDB 7.0.14, and MySQL Cluster NDB 7.1.2.

   * `--extra-partition-info', `-p'

     Print additional information about the table's partitions.

   * `--retries=#', `-r'

     Try to connect this many times before giving up. One connect
     attempt is made per second.

   * `--table=TBL_NAME', `-t'

     Specify the table in which to look for an index.

     This option was added in MySQL Cluster NDB 7.0.36 and MySQL
     Cluster NDB 7.1.25.

   * `--unqualified', `-u'

     Use unqualified table names.


File: manual.info,  Node: mysql-cluster-programs-ndb-drop-index,  Next: mysql-cluster-programs-ndb-drop-table,  Prev: mysql-cluster-programs-ndb-desc,  Up: mysql-cluster-programs

17.4.11 `ndb_drop_index' -- Drop Index from an NDB Table
--------------------------------------------------------

*Note `ndb_drop_index': mysql-cluster-programs-ndb-drop-index. drops
the specified index from an *Note `NDB': mysql-cluster. table. _It is
recommended that you use this utility only as an example for writing
NDB API applications_--see the Warning later in this section for
details.

*Usage*


     ndb_drop_index -c CONNECT_STRING TABLE_NAME INDEX -d DB_NAME

The statement shown above drops the index named INDEX from the TABLE in
the DATABASE.

The following table includes options that are specific to *Note
`ndb_drop_index': mysql-cluster-programs-ndb-drop-index. Additional
descriptions follow the table. For options common to most MySQL Cluster
programs (including *Note `ndb_drop_index':
mysql-cluster-programs-ndb-drop-index.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_drop_index program

Format Description Added or Removed

`--database=dbname',

`-d'

Name of the database in which the table is found

All MySQL 5.1 based releases 


*Warning*:

_Operations performed on Cluster table indexes using the NDB API are
not visible to MySQL and make the table unusable by a MySQL server_. If
you use this program to drop an index, then try to access the table
from an SQL node, an error results, as shown here:


     shell> ./ndb_drop_index -c localhost dogs ix -d ctest1
     Dropping index dogs/idx...OK

     NDBT_ProgramExit: 0 - OK

     shell> ./mysql -u jon -p ctest1
     Enter password: *******
     Reading table information for completion of table and column names
     You can turn off this feature to get a quicker startup with -A

     Welcome to the MySQL monitor.  Commands end with ; or \g.
     Your MySQL connection id is 7 to server version: 5.1.73-ndb-7.1.34

     Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

     mysql> SHOW TABLES;
     +------------------+
     | Tables_in_ctest1 |
     +------------------+
     | a                |
     | bt1              |
     | bt2              |
     | dogs             |
     | employees        |
     | fish             |
     +------------------+
     6 rows in set (0.00 sec)

     mysql> SELECT * FROM dogs;
     `ERROR 1296 (HY000): Got error 4243 'Index not found' from NDBCLUSTER'

In such a case, your _only_ option for making the table available to
MySQL again is to drop the table and re-create it. You can use either
the SQL statement*Note `DROP TABLE': drop-table. or the *Note
`ndb_drop_table': mysql-cluster-programs-ndb-drop-table. utility (see
*Note mysql-cluster-programs-ndb-drop-table::) to drop the table.


File: manual.info,  Node: mysql-cluster-programs-ndb-drop-table,  Next: mysql-cluster-programs-ndb-error-reporter,  Prev: mysql-cluster-programs-ndb-drop-index,  Up: mysql-cluster-programs

17.4.12 `ndb_drop_table' -- Drop an NDB Table
---------------------------------------------

*Note `ndb_drop_table': mysql-cluster-programs-ndb-drop-table. drops
the specified *Note `NDB': mysql-cluster. table. (If you try to use this
on a table created with a storage engine other than *Note `NDB':
mysql-cluster, the attempt fails with the error `723: No such table
exists'.) This operation is extremely fast; in some cases, it can be an
order of magnitude faster than using a MySQL *Note `DROP TABLE':
drop-table. statement on an *Note `NDB': mysql-cluster.  table.

*Usage*


     ndb_drop_table -c CONNECT_STRING TBL_NAME -d DB_NAME

The following table includes options that are specific to *Note
`ndb_drop_table': mysql-cluster-programs-ndb-drop-table. Additional
descriptions follow the table. For options common to most MySQL Cluster
programs (including *Note `ndb_drop_table':
mysql-cluster-programs-ndb-drop-table.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_drop_table program

Format Description Added or Removed

`--database=dbname',

`-d'

Name of the database in which the table is found

All MySQL 5.1 based releases 



File: manual.info,  Node: mysql-cluster-programs-ndb-error-reporter,  Next: mysql-cluster-programs-ndb-index-stat,  Prev: mysql-cluster-programs-ndb-drop-table,  Up: mysql-cluster-programs

17.4.13 `ndb_error_reporter' -- NDB Error-Reporting Utility
-----------------------------------------------------------

*Note `ndb_error_reporter': mysql-cluster-programs-ndb-error-reporter.
creates an archive from data node and management node log files that
can be used to help diagnose bugs or other problems with a cluster. _It
is highly recommended that you make use of this utility when filing
reports of bugs in MySQL Cluster_.

The following table includes command options specific to the MySQL
Cluster program *Note `ndb_error_reporter':
mysql-cluster-programs-ndb-error-reporter.  Additional descriptions
follow the table. For options common to most MySQL Cluster programs
(including *Note `ndb_error_reporter':
mysql-cluster-programs-ndb-error-reporter.), see *Note
mysql-cluster-program-options-common::.

*Note `ndb_error_reporter': mysql-cluster-programs-ndb-error-reporter.
did not support the `--help' option prior to MySQL Cluster NDB 6.3.52,
MySQL Cluster NDB 7.0.40, and MySQL Cluster NDB 7.1.29 (Bug #11756666,
Bug #48606). The `--connection-timeout' `--dry-scp', and
`--skip-nodegroup' options were also added in these releases (Bug
#16602002).

This table describes command-line options for the ndb_error_reporter
program

Format Description Added or Removed

` --connection-timeout=timeout '

Number of seconds to wait when connecting to nodes before timing out.

ADDED: NDB 6.3.52, NDB 7.0.40, NDB 7.1.29

` --dry-scp '

Disable scp with remote hosts; used only for testing.

ADDED: NDB 6.3.52, NDB 7.0.40, NDB 7.1.29

` --fs '

Include file system data in error report; can use a large amount of
disk space

All MySQL 5.1 based releases

` --skip-nodegroup=nodegroup_id '

Skip all nodes in the node group having this ID.

ADDED: NDB 6.3.52, NDB 7.0.40, NDB 7.1.29 


*Usage*


     ndb_error_reporter PATH/TO/CONFIG-FILE [USERNAME] [OPTIONS]

This utility is intended for use on a management node host, and
requires the path to the management host configuration file (usually
named `config.ini'). Optionally, you can supply the name of a user that
is able to access the cluster's data nodes using SSH, to copy the data
node log files.  *Note `ndb_error_reporter':
mysql-cluster-programs-ndb-error-reporter. then includes all of these
files in archive that is created in the same directory in which it is
run. The archive is named `ndb_error_report_YYYYMMDDHHMMSS.tar.bz2',
where YYYYMMDDHHMMSS is a datetime string.

*Note `ndb_error_reporter': mysql-cluster-programs-ndb-error-reporter.
also accepts the options listed here:

   * `--connection-timeout=TIMEOUT'

     Options for connection-timeout

     *Introduced*         5.1.72-ndb-7.1.29        
     *Command-Line        `--connection-timeout=timeout'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `integer'        
     *Default*            `0'             

     Wait this many seconds when trying to connect to nodes before
     timing out.

   * `--dry-scp'

     Options for dry-scp

     *Introduced*         5.1.72-ndb-7.1.29        
     *Command-Line        `--dry-scp'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Run *Note `ndb_error_reporter':
     mysql-cluster-programs-ndb-error-reporter. without using scp from
     remote hosts. Used for testing only.

   * `--fs'

     Options for fs

     *Command-Line        `--fs'          
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Copy the data node file systems to the management host and include
     them in the archive.

     Because data node file systems can be extremely large, even after
     being compressed, we ask that you please do _not_ send archives
     created using this option to Oracle unless you are specifically
     requested to do so.

   * `--skip-nodegroup=NODEGROUP_ID'

     Options for connection-timeout

     *Introduced*         5.1.72-ndb-7.1.29        
     *Command-Line        `--connection-timeout=timeout'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `integer'        
     *Default*            `0'             

     Skip all nodes belong to the node group having the supplied node
     group ID.


File: manual.info,  Node: mysql-cluster-programs-ndb-index-stat,  Next: mysql-cluster-programs-ndb-print-backup-file,  Prev: mysql-cluster-programs-ndb-error-reporter,  Up: mysql-cluster-programs

17.4.14 `ndb_index_stat' -- NDB Index Statistics Utility
--------------------------------------------------------

*Note `ndb_index_stat': mysql-cluster-programs-ndb-index-stat ...

*Usage*

To obtain basic index statistics about a given *Note `NDB':
mysql-cluster. table, invoke *Note `ndb_index_stat':
mysql-cluster-programs-ndb-index-stat. as shown here, with the name of
the table as the first argument and the name of the database containing
this table specified immediately following it, using the `--database'
(`-d') option:


     ndb_index_stat TABLE -d DATABASE

In this example, we use *Note `ndb_index_stat':
mysql-cluster-programs-ndb-index-stat. to obtain such information about
an `NDB' table named `mytable' in the `test' database:


     shell> ndb_index_stat -d test mytable
     table:City index:PRIMARY fragCount:2
     sampleVersion:3 loadTime:1399585986 sampleCount:1994 keyBytes:7976
     query cache: valid:1 sampleCount:1994 totalBytes:27916
     times in ms: save: 7.133 sort: 1.974 sort per sample: 0.000

     NDBT_ProgramExit: 0 - OK

`sampleVersion' is the version number of the cache from which the
statistics data is taken. Running *Note `ndb_index_stat':
mysql-cluster-programs-ndb-index-stat. with the `--update' option causes
sampleVersion to be incremented.

`loadTime' shows when the cache was last updated. This is expressed as
seconds since the Unix Epoch.

`sampleCount' is the number of index entries found per partition. You
can estimate the total number of entries by multiplying this by the
number of fragments (shown as `fragCount').

sampleCount cab be compared with the cardinality of *Note `SHOW INDEX':
show-index. or *Note `INFORMATION_SCHEMA.STATISTICS': statistics-table,
although the latter two provide a view of the table as a whole, while
*Note `ndb_index_stat': mysql-cluster-programs-ndb-index-stat. provides
a per-fragment average.

`keyBytes' is the number of bytes used by the index. In this example,
the primary key is an integer, which requires four bytes for each
index, so `keyBytes' can be calculated in this case as shown here:


         keyBytes = sampleCount * (4 bytes per index) = 1994 * 4 = 7976

This information can also be obtained using the corresponding column
definitions from *Note `INFORMATION_SCHEMA.COLUMNS': columns-table.
(this requires a MySQL Server and a MySQL client application).

`totalBytes' is the total memory consumed by all indexes on the table,
in bytes.

Timings shown in the preceding examples are specific to each invocation
of *Note `ndb_index_stat': mysql-cluster-programs-ndb-index-stat.

The `--verbose' option provides some additional output, as shown here:


     shell> ndb_index_stat -d test mytable --verbose
     random seed 1337010518
     connected
     loop 1 of 1
     table:mytable index:PRIMARY fragCount:4
     sampleVersion:2 loadTime:1336751773 sampleCount:0 keyBytes:0
     read stats
     query cache created
     query cache: valid:1 sampleCount:0 totalBytes:0
     times in ms: save: 20.766 sort: 0.001
     disconnected

     NDBT_ProgramExit: 0 - OK

     shell>

*Options*

The following table includes options that are specific to the MySQL
Cluster *Note `ndb_index_stat': mysql-cluster-programs-ndb-index-stat.
utility.  Additional descriptions are listed following the table. For
options common to most MySQL Cluster programs (including *Note
`ndb_index_stat': mysql-cluster-programs-ndb-index-stat.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_index_stat program

Format Description Added or Removed

`--database=name',

`-d'

Name of the database containing the table.

All MySQL 5.1 based releases

`--delete'

Delete index statistics for the given table, stopping any auto-update
previously configured.

All MySQL 5.1 based releases

`--update'

Update index statistics for the given table, restarting any auto-update
previously configured.

All MySQL 5.1 based releases

`--dump'

Print the query cache.

All MySQL 5.1 based releases

`--query=#'

Perform a number of random range queries on first key attr (must be int
unsigned).

All MySQL 5.1 based releases

`--sys-drop'

Drop any statistics tables and events in NDB kernel (all statistics are
lost)

All MySQL 5.1 based releases

`--sys-create'

Create all statistics tables and events in NDB kernel, if none of them
already exist

All MySQL 5.1 based releases

`--sys-create-if-not-exist'

Create any statistics tables and events in NDB kernel that do not
already exist.

All MySQL 5.1 based releases

`--sys-create-if-not-valid'

Create any statistics tables or events that do not already exist in the
NDB kernel. after dropping any that are invalid.

All MySQL 5.1 based releases

`--sys-check'

Verify that NDB system index statistics and event tables exist.

All MySQL 5.1 based releases

`--sys-skip-tables'

Do not apply sys-* options to tables.

All MySQL 5.1 based releases

`--sys-skip-events'

Do not apply sys-* options to events.

All MySQL 5.1 based releases

`--verbose',

`-v'

Turn on verbose output

All MySQL 5.1 based releases

`--loops=#'

Set the number of times to perform a given command. Default is 0.

All MySQL 5.1 based releases 


ndb_index_stat statistics options

The following options are used to generate index statistics.  They work
with a given table and database. They cannot be mixed with *Note
ndb-index-stat-options-system::.

   * `--database=NAME', `-d NAME'

     Options for database

     *Command-Line        `--database=name'        
     Format*                              
                          `-d'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `[none]'        
     *Min Value*          `'              
     *Max Value*          `'              

     The name of the database that contains the table being queried.

   * `--delete'

     Options for delete

     *Command-Line        `--delete'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Delete the index statistics for the given table, stopping any
     auto-update that was previously configured.

   * `--update'

     Options for update

     *Command-Line        `--update'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Update the index statistics for the given table, and restart any
     auto-update that previously configured.

   * `--dump'

     Options for dump

     *Command-Line        `--dump'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Dump the contents of the query cache.

   * `--query=#'

     Options for query

     *Command-Line        `--query=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `MAX_INT'        

     Perform random range queries on first key attribute (must be int
     unsigned).

ndb_index_stat system options

The following options are used to generate and update the statistics
tables in the NDB kernel. They cannot be mixed with *Note
ndb-index-stat-options-statistics::.

   * `--sys-drop'

     Options for sys-drop

     *Command-Line        `--sys-drop'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Drop all statistics tables and events in the NDB kernel.  _This
     causes all statistics to be lost_.

   * `--sys-create'

     Options for sys-create

     *Command-Line        `--sys-create'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Create all statistics tables and events in the NDB kernel.  This
     works only if none of them exist previously.

   * `sys-create-if-not-exist'

     Options for sys-create-if-not-exist

     *Command-Line        `--sys-create-if-not-exist'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Create any NDB system statistics tables or events (or both) that
     do not already exist when the program is invoked.

   * `--sys-create-if-not-valid'

     Options for sys-create-if-not-valid

     *Command-Line        `--sys-create-if-not-valid'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Create any NDB system statistics tables or events that do not
     already exist, after dropping any that are invalid.

   * `--sys-check'

     Options for sys-check

     *Command-Line        `--sys-check'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Verify that all required system statistics tables and events exist
     in the NDB kernel.

   * `--sys-skip-tables'

     Options for sys-skip-tables

     *Command-Line        `--sys-skip-tables'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Do not apply any `--sys-*' options to any statistics tables.

   * `--sys-skip-events'

     Options for sys-skip-events

     *Command-Line        `--sys-skip-events'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Do not apply any `--sys-*' options to any events.

   * `--verbose'

     Options for verbose

     *Command-Line        `--verbose'        
     Format*                              
                          `-v'            
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `true'          
     *Min Value*          `'              
     *Max Value*          `'              

     Turn on verbose output.

   * `--loops=#'

     Options for loops

     *Command-Line        `--loops=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             
     *Min Value*          `0'             
     *Max Value*          `MAX_INT'        

     Repeat commands this number of times (for use in testing).


File: manual.info,  Node: mysql-cluster-programs-ndb-print-backup-file,  Next: mysql-cluster-programs-ndb-print-file,  Prev: mysql-cluster-programs-ndb-index-stat,  Up: mysql-cluster-programs

17.4.15 `ndb_print_backup_file' -- Print NDB Backup File Contents
-----------------------------------------------------------------

*Note `ndb_print_backup_file':
mysql-cluster-programs-ndb-print-backup-file. obtains diagnostic
information from a cluster backup file.

*Usage*


     ndb_print_backup_file FILE_NAME

FILE_NAME is the name of a cluster backup file. This can be any of the
files (`.Data', `.ctl', or `.log' file) found in a cluster backup
directory. These files are found in the data node's backup directory
under the subdirectory `BACKUP-#', where # is the sequence number for
the backup. For more information about cluster backup files and their
contents, see *Note mysql-cluster-backup-concepts::.

Like *Note `ndb_print_schema_file':
mysql-cluster-programs-ndb-print-schema-file. and *Note
`ndb_print_sys_file': mysql-cluster-programs-ndb-print-sys-file. (and
unlike most of the other *Note `NDB': mysql-cluster. utilities that are
intended to be run on a management server host or to connect to a
management server) *Note `ndb_print_backup_file':
mysql-cluster-programs-ndb-print-backup-file.  must be run on a cluster
data node, since it accesses the data node file system directly.
Because it does not make use of the management server, this utility can
be used when the management server is not running, and even when the
cluster has been completely shut down.

*Additional Options*

None.


File: manual.info,  Node: mysql-cluster-programs-ndb-print-file,  Next: mysql-cluster-programs-ndb-print-schema-file,  Prev: mysql-cluster-programs-ndb-print-backup-file,  Up: mysql-cluster-programs

17.4.16 `ndb_print_file' -- Print NDB Disk Data File Contents
-------------------------------------------------------------

*Note `ndb_print_file': mysql-cluster-programs-ndb-print-file. obtains
information from a MySQL Cluster Disk Data file.

*Usage*


     ndb_print_file [-v] [-q] FILE_NAME+

FILE_NAME is the name of a MySQL Cluster Disk Data file. Multiple
filenames are accepted, separated by spaces.

Like *Note `ndb_print_schema_file':
mysql-cluster-programs-ndb-print-schema-file. and *Note
`ndb_print_sys_file': mysql-cluster-programs-ndb-print-sys-file. (and
unlike most of the other *Note `NDB': mysql-cluster. utilities that are
intended to be run on a management server host or to connect to a
management server) *Note `ndb_print_file':
mysql-cluster-programs-ndb-print-file. must be run on a MySQL Cluster
data node, since it accesses the data node file system directly.
Because it does not make use of the management server, this utility can
be used when the management server is not running, and even when the
cluster has been completely shut down.

*Additional Options*

*Note `ndb_print_file': mysql-cluster-programs-ndb-print-file. supports
the following options:

   * `-v': Make output verbose.

   * `-q': Suppress output (quiet mode).

   * `--help', `-h', `-?': Suppress output (quiet mode).

     This option did not work correctly prior to MySQL Cluster NDB
     7.1.33. (Bug #17069285)

For more information, see *Note mysql-cluster-disk-data::.


File: manual.info,  Node: mysql-cluster-programs-ndb-print-schema-file,  Next: mysql-cluster-programs-ndb-print-sys-file,  Prev: mysql-cluster-programs-ndb-print-file,  Up: mysql-cluster-programs

17.4.17 `ndb_print_schema_file' -- Print NDB Schema File Contents
-----------------------------------------------------------------

*Note `ndb_print_schema_file':
mysql-cluster-programs-ndb-print-schema-file. obtains diagnostic
information from a cluster schema file.

*Usage*


     ndb_print_schema_file FILE_NAME

FILE_NAME is the name of a cluster schema file. For more information
about cluster schema files, see MySQL Cluster Data Node `FileSystemDir'
Files
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-ndbd-filesystemdir-files.html).

Like *Note `ndb_print_backup_file':
mysql-cluster-programs-ndb-print-backup-file. and *Note
`ndb_print_sys_file': mysql-cluster-programs-ndb-print-sys-file. (and
unlike most of the other *Note `NDB': mysql-cluster. utilities that are
intended to be run on a management server host or to connect to a
management server) `ndb_schema_backup_file' must be run on a cluster
data node, since it accesses the data node file system directly.
Because it does not make use of the management server, this utility can
be used when the management server is not running, and even when the
cluster has been completely shut down.

*Additional Options*

None.


File: manual.info,  Node: mysql-cluster-programs-ndb-print-sys-file,  Next: mysql-cluster-programs-ndbd-redo-log-reader,  Prev: mysql-cluster-programs-ndb-print-schema-file,  Up: mysql-cluster-programs

17.4.18 `ndb_print_sys_file' -- Print NDB System File Contents
--------------------------------------------------------------

*Note `ndb_print_sys_file': mysql-cluster-programs-ndb-print-sys-file.
obtains diagnostic information from a MySQL Cluster system file.

*Usage*


     ndb_print_sys_file FILE_NAME

FILE_NAME is the name of a cluster system file (sysfile). Cluster
system files are located in a data node's data directory (`DataDir');
the path under this directory to system files matches the pattern
`ndb_#_fs/D#/DBDIH/P#.sysfile'.  In each case, the # represents a
number (not necessarily the same number). For more information, see
MySQL Cluster Data Node `FileSystemDir' Files
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-ndbd-filesystemdir-files.html).

Like *Note `ndb_print_backup_file':
mysql-cluster-programs-ndb-print-backup-file. and *Note
`ndb_print_schema_file': mysql-cluster-programs-ndb-print-schema-file.
(and unlike most of the other *Note `NDB': mysql-cluster. utilities
that are intended to be run on a management server host or to connect to
a management server) *Note `ndb_print_backup_file':
mysql-cluster-programs-ndb-print-backup-file.  must be run on a cluster
data node, since it accesses the data node file system directly.
Because it does not make use of the management server, this utility can
be used when the management server is not running, and even when the
cluster has been completely shut down.

*Additional Options*

None.


File: manual.info,  Node: mysql-cluster-programs-ndbd-redo-log-reader,  Next: mysql-cluster-programs-ndb-restore,  Prev: mysql-cluster-programs-ndb-print-sys-file,  Up: mysql-cluster-programs

17.4.19 `ndbd_redo_log_reader' -- Check and Print Content of Cluster Redo Log
-----------------------------------------------------------------------------

Reads a redo log file, checking it for errors, printing its contents in
a human-readable format, or both.  *Note `ndbd_redo_log_reader':
mysql-cluster-programs-ndbd-redo-log-reader. is intended for use
primarily by MySQL Cluster developers and Support personnel in
debugging and diagnosing problems.

This utility was made available as part of default builds beginning
with MySQL Cluster NDB 6.1.3. It remains under development, and its
syntax and behavior are subject to change in future releases. For this
reason, it should be considered experimental at this time.

The C++ source files for *Note `ndbd_redo_log_reader':
mysql-cluster-programs-ndbd-redo-log-reader.  can be found in the
directory `/storage/ndb/src/kernel/blocks/dblqh/redoLogReader'.

The following table includes options that are specific to the MySQL
Cluster program *Note `ndbd_redo_log_reader':
mysql-cluster-programs-ndbd-redo-log-reader.  Additional descriptions
follow the table. For options common to most MySQL Cluster programs
(including *Note `ndbd_redo_log_reader':
mysql-cluster-programs-ndbd-redo-log-reader.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndbd_redo_log_reader
program

Format Description Added or Removed

` -noprint '

Do not print records

All MySQL 5.1 based releases

` -nocheck '

Do not check records for errors

All MySQL 5.1 based releases

` --help '

Print usage information

ADDED: NDB 6.3.53, NDB 7.0.41, NDB 7.1.30 


*Usage*


     ndbd_redo_log_reader FILE_NAME [OPTIONS]

FILE_NAME is the name of a cluster redo log file. redo log files are
located in the numbered directories under the data node's data directory
(`DataDir'); the path under this directory to the redo log files
matches the pattern `ndb_#_fs/D#/LCP/#/T#F#.Data'.  In each case, the #
represents a number (not necessarily the same number). For more
information, see MySQL Cluster Data Node `FileSystemDir' Files
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-ndbd-filesystemdir-files.html).

The name of the file to be read may be followed by one or more of the
options listed here:

   * Options for noprint

     *Command-Line        `-noprint'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     `-noprint': Do not print the contents of the log file.

   * Options for nocheck

     *Command-Line        `-nocheck'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     `-nocheck': Do not check the log file for errors.

   * Options for help

     *Introduced*         5.1.73-ndb-7.1.30        
     *Command-Line        `--help'        
     Format*                              

     `--help': Print usage information.

     Added in MySQL Cluster NDB 6.3.53, MySQL Cluster NDB 7.0.41, and
     MySQL Cluster NDB 7.1.30. (Bug #11749591, Bug #36805)

Like *Note `ndb_print_backup_file':
mysql-cluster-programs-ndb-print-backup-file. and *Note
`ndb_print_schema_file': mysql-cluster-programs-ndb-print-schema-file.
(and unlike most of the *Note `NDB': mysql-cluster. utilities that are
intended to be run on a management server host or to connect to a
management server) *Note `ndbd_redo_log_reader':
mysql-cluster-programs-ndbd-redo-log-reader. must be run on a cluster
data node, since it accesses the data node file system directly.
Because it does not make use of the management server, this utility can
be used when the management server is not running, and even when the
cluster has been completely shut down.


File: manual.info,  Node: mysql-cluster-programs-ndb-restore,  Next: mysql-cluster-programs-ndb-select-all,  Prev: mysql-cluster-programs-ndbd-redo-log-reader,  Up: mysql-cluster-programs

17.4.20 `ndb_restore' -- Restore a MySQL Cluster Backup
-------------------------------------------------------

The cluster restoration program is implemented as a separate
command-line utility *Note `ndb_restore':
mysql-cluster-programs-ndb-restore, which can normally be found in the
MySQL `bin' directory. This program reads the files created as a result
of the backup and inserts the stored information into the database.

*Note `ndb_restore': mysql-cluster-programs-ndb-restore. must be
executed once for each of the backup files that were created by the
`START BACKUP' command used to create the backup (see *Note
mysql-cluster-backup-using-management-client::).  This is equal to the
number of data nodes in the cluster at the time that the backup was
created.

*Note*:

Before using *Note `ndb_restore': mysql-cluster-programs-ndb-restore,
it is recommended that the cluster be running in single user mode,
unless you are restoring multiple data nodes in parallel. See *Note
mysql-cluster-single-user-mode::, for more information.

The following table includes options that are specific to the MySQL
Cluster native backup restoration program *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. Additional descriptions follow the
table. For options common to most MySQL Cluster programs (including
*Note `ndb_restore': mysql-cluster-programs-ndb-restore.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_restore program

Format Description Added or Removed

`--connect',

` -c '

Alias for -connectstring.

All MySQL 5.1 based releases

`--nodeid=#',

` -n '

Back up files from node with this ID

All MySQL 5.1 based releases

`--backupid=#',

` -b '

Restore from the backup with the given ID

All MySQL 5.1 based releases

`--restore_data',

` -r '

Restore table data and logs into NDB Cluster using the NDB API

All MySQL 5.1 based releases

`--restore_meta',

` -m '

Restore metadata to NDB Cluster using the NDB API

All MySQL 5.1 based releases

`--no-upgrade',

` -u '

Do not upgrade array type for varsize attributes which do not already
resize VAR data, and do not change column attributes

ADDED: 5.1.19

`--promote-attributes',

` -A '

Allow attributes to be promoted when restoring data from backup

ADDED: NDB 6.3.8

`--preserve-trailing-spaces',

` -P '

Allow preservation of trailing spaces (including padding) when
promoting fixed-width string types to variable-width types

ADDED: NDB 6.3.8

`--no-restore-disk-objects',

` -d '

Do not restore objects relating to Disk Data

ADDED: 5.1.6

`--restore_epoch',

` -e '

Restore epoch info into the status table. Convenient on a MySQL Cluster
replication slave for starting replication. The row in
mysql.ndb_apply_status with id 0 will be updated/inserted.

All MySQL 5.1 based releases

`--skip-table-check',

` -s '

Skip table structure check during restoring of data

ADDED: 5.1.17

`--parallelism=#',

` -p '

Number of parallel transactions to use while restoring data

All MySQL 5.1 based releases

` --print '

Print metadata, data and log to stdout (equivalent to -print_meta
-print_data -print_log)

All MySQL 5.1 based releases

` --print_meta '

Print metadata to stdout

All MySQL 5.1 based releases

` --print_data '

Print data to stdout

All MySQL 5.1 based releases

` --print_log '

Print to stdout

All MySQL 5.1 based releases

` --backup_path=path '

Path to backup files directory

ADDED: 5.1.17, NDB 6.1.5

`--dont_ignore_systab_0',

` -f '

Do not ignore system table during restore. Experimental only; not for
production use

All MySQL 5.1 based releases

`--ndb-nodegroup-map=map',

` -z '

Nodegroup map for NDBCLUSTER storage engine. Syntax: list of
(source_nodegroup, destination_nodegroup)

All MySQL 5.1 based releases

` --fields-enclosed-by=char '

Fields are enclosed with the indicated character

ADDED: 5.1.18

` --fields-terminated-by=char '

Fields are terminated by the indicated character

ADDED: 5.1.18

` --fields-optionally-enclosed-by '

Fields are optionally enclosed with the indicated character

ADDED: 5.1.18

` --lines-terminated-by=char '

Lines are terminated by the indicated character

ADDED: 5.1.18

` --hex '

Print binary types in hexadecimal format

ADDED: 5.1.18

`--tab=path',

` -T '

Creates a tab-separated .txt file for each table in the given path

ADDED: 5.1.18

` --append '

Append data to a tab-delimited file

ADDED: 5.1.18

` --progress-frequency=# '

Print status of restoration each given number of seconds

All MySQL 5.1 based releases

` --no-binlog '

If a mysqld is connected and using binary logging, do not log the
restored data

ADDED: NDB 6.2.16, NDB 6.3.16

` --verbose=# '

Level of verbosity in output

All MySQL 5.1 based releases

` --include-databases=db-list '

List of one or more databases to restore (excludes those not named)

ADDED: NDB 6.3.22, NDB 6.4.3

` --exclude-databases=db-list '

List of one or more databases to exclude (includes those not named)

ADDED: NDB 6.3.22, NDB 6.4.3

` --include-tables=table-list '

List of one or more tables to restore (excludes those in same database
that are not named); each table reference must include the database name

ADDED: NDB 6.3.22, NDB 6.4.3

` --exclude-tables=table-list '

List of one or more tables to exclude (includes those in the same
database that are not named); each table reference must include the
database name

ADDED: NDB 6.3.22, NDB 6.4.3

` --exclude-missing-columns '

Causes columns from the backup version of a table that are missing from
the version of the table in the database to be ignored.

ADDED: NDB 6.3.26, NDB 7.0.7

` --exclude-missing-tables '

Causes tables from the backup that are missing from the database to be
ignored.

ADDED: NDB 7.1.33

` --disable-indexes '

Causes indexes from a backup to be ignored; may decrease time needed to
restore data.

ADDED: NDB 6.3.31, NDB 7.0.11, NDB 7.1.2

` --rebuild-indexes '

Causes multi-threaded rebuilding of ordered indexes found in the
backup. Number of threads used is determined by setting
BuildIndexThreads parameter.

ADDED: NDB 6.3.31, NDB 7.0.11, NDB 7.1.2

` --skip-broken-objects '

Causes missing blob tables in the backup file to be ignored.

ADDED: NDB 6.3.40, NDB 7.0.21, NDB 7.1.10

` --skip-unknown-objects '

Causes schema objects not recognized by ndb_restore to be ignored when
restoring a backup made from a newer MySQL Cluster version to an older
version.

ADDED: NDB 6.3.34, NDB 7.0.15, NDB 7.1.4

` --rewrite-database=olddb,newdb '

Restores to a database with a different name than the original

ADDED: NDB 6.3.41, NDB 7.0.22, NDB 7.1.11

`--lossy-conversions',

` -L '

Allow lossy conversions of column values (type demotions or changes in
sign) when restoring data from backup

ADDED: NDB 7.1.11

` --restore-privilege-tables '

Restore MySQL privilege tables that were previously moved to NDB.

ADDED: NDB 7.2.0

` --exclude-intermediate-sql-tables[=TRUE|FALSE] '

If TRUE (the default), do not restore any intermediate tables (having
names prefixed with '#sql-') that were left over from copying ALTER
TABLE operations.

ADDED: NDB 7.1.31 


Typical options for this utility are shown here:


     ndb_restore [-c CONNECTION_STRING] -n NODE_ID -b BACKUP_ID \
           [-m] -r --backup_path=/PATH/TO/BACKUP/FILES

Normally, when restoring from a MySQL Cluster backup, *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. requires at a
minimum the `--nodeid' (short form: `-n'), `--backupid' (short form:
`-b'), and `--backup_path' options.

The `-c' option is used to specify a connection string which tells
`ndb_restore' where to locate the cluster management server. (See *Note
mysql-cluster-connection-strings::, for information on connection
strings.) If this option is not used, then *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. attempts to connect to a management
server on `localhost:1186'. This utility acts as a cluster API node,
and so requires a free connection `slot' to connect to the cluster
management server. This means that there must be at least one `[api]'
or `[mysqld]' section that can be used by it in the cluster
`config.ini' file. It is a good idea to keep at least one empty `[api]'
or `[mysqld]' section in `config.ini' that is not being used for a
MySQL server or other application for this reason (see *Note
mysql-cluster-api-definition::).

You can verify that *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. is connected to the cluster by
using the `SHOW' command in the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. management client. You can also
accomplish this from a system shell, as shown here:


     shell> ndb_mgm -e "SHOW"

`-n' is used to specify the node ID of the data node on which the
backups were taken.

The first time you run the *Note `ndb_restore':
mysql-cluster-programs-ndb-restore.  restoration program, you also need
to restore the metadata. In other words, you must re-create the
database tables--this can be done by running it with the
`--restore_meta' (`-m') option.  Restoring the metdata need be done
only on a single data node; this is sufficient to restore it to the
entire cluster. Note that the cluster should have an empty database
when starting to restore a backup. (In other words, you should start
*Note `ndbd': mysql-cluster-programs-ndbd. with `--initial' prior to
performing the restore.)

It is possible to restore data without restoring table metadata.  Prior
to MySQL 5.1.17, *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. did not perform any checks of table
schemas; if a table was altered between the time the backup was taken
and when *Note `ndb_restore': mysql-cluster-programs-ndb-restore. was
run, *Note `ndb_restore': mysql-cluster-programs-ndb-restore. would
still attempt to restore the data to the altered table.

Beginning with MySQL 5.1.17, the default behavior is for *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. to fail with an
error if table data do not match the table schema; this can be
overridden using the `--skip-table-check' or `-s' option. Prior to
MySQL 5.1.21, if this option is used, then *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. attempts to fit data into the
existing table schema, but the result of restoring a backup to a table
schema that does not match the original is unspecified.

Beginning with MySQL Cluster NDB 6.3.35, MySQL Cluster NDB 7.0.16, and
MySQL Cluster NDB 7.1.5, some of the restrictions on mismatches in
column definitions when restoring data using *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. are relaxed; when one of these
types of mismatches is encountered, *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. does not stop with an error as it
did previously, but rather accepts the data and inserts it into the
target table while issuing a warning to the user that this is being
done. This behavior occurs whether or not either of the options
`--skip-table-check' or `--promote-attributes' is in use. These
differences in column definitions are of the following types:

   * Different `COLUMN_FORMAT' settings (`FIXED', `DYNAMIC', `DEFAULT')

   * Different `STORAGE' settings (`MEMORY', `DISK')

   * Different default values

   * Different distribution key settings

Beginning with MySQL Cluster NDB 6.3.8, *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. supports limited _attribute
promotion_ in much the same way that it is supported by MySQL
replication; that is, data backed up from a column of a given type can
generally be restored to a column using a `larger, similar' type. For
example, data from a `CHAR(20)' column can be restored to a column
declared as `VARCHAR(20)', `VARCHAR(30)', or `CHAR(30)'; data from a
*Note `MEDIUMINT': integer-types. column can be restored to a column of
type *Note `INT': integer-types. or *Note `BIGINT': integer-types. See
*Note replication-features-different-data-types::, for a table of type
conversions currently supported by attribute promotion.

Attribute promotion by *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. must be enabled explicitly, as
follows:

  1. Prepare the table to which the backup is to be restored.  *Note
     `ndb_restore': mysql-cluster-programs-ndb-restore. cannot be used
     to re-create the table with a different definition from the
     original; this means that you must either create the table
     manually, or alter the columns which you wish to promote using
     *Note `ALTER TABLE': alter-table. after restoring the table
     metadata but before restoring the data.

  2. Invoke *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
     with the `--promote-attributes' option (short form `-A') when
     restoring the table data. Attribute promotion does not occur if
     this option is not used; instead, the restore operation fails with
     an error.

Prior to MySQL Cluster NDB 7.0.40 and MySQL Cluster NDB 7.1.29,
conversions between character data types and *Note `TEXT': blob. or
*Note `BLOB': blob. were not handled correctly (Bug #17325051).

Prior to MySQL Cluster NDB 7.1.32, demotion of *Note `TEXT': blob. to
*Note `TINYTEXT': blob. was not handled correctly (Bug #18875137).

When converting between character data types and `TEXT' or `BLOB', only
conversions between character types (*Note `CHAR': char. and *Note
`VARCHAR': char.) and binary types (*Note `BINARY': binary-varbinary.
and *Note `VARBINARY': binary-varbinary.) can be performed at the same
time. For example, you cannot promote an *Note `INT': integer-types.
column to *Note `BIGINT': integer-types. while promoting a `VARCHAR'
column to `TEXT' in the same invocation of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore.

Converting between *Note `TEXT': blob. columns using different
character sets is not supported. Beginning with MySQL Cluster NDB
7.1.32, it is expressly disallowed (Bug #18875137).

When performing conversions of character or binary types to `TEXT' or
`BLOB' with *Note `ndb_restore': mysql-cluster-programs-ndb-restore,
you may notice that it creates and uses one or more staging tables named
`TABLE_NAME$STNODE_ID'.  These tables are not needed afterwards, and
are normally deleted by *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. following a successful restoration.

`--lossy-conversions', `-L'

Options for lossy-conversions

*Introduced*           5.1.51-ndb-7.1.11        
*Command-Line Format*  `--lossy-conversions'        
                       `-L'            
                       *Permitted        
                       Values*         
*Type*                 `boolean'        
*Default*              `FALSE'         

This option is intended to complement the `--promote-attributes' option.
Using `--lossy-conversions' allows lossy conversions of column values
(type demotions or changes in sign) when restoring data from backup.
With some exceptions, the rules governing demotion are the same as for
MySQL replication; see *Note
replication-features-different-data-types::, for information about
specific type conversions currently supported by attribute demotion.

*Note `ndb_restore': mysql-cluster-programs-ndb-restore. reports any
truncation of data that it performs during lossy conversions once per
attribute and column.

This option was added in MySQL Cluster NDB 7.1.11.

The `--preserve-trailing-spaces' option is also available beginning
with MySQL Cluster NDB 6.3.8. This option (short form `-R') causes
trailing spaces to be preserved when promoting a fixed-width character
data type to its variable-width equivalent--that is, when promoting a
*Note `CHAR': char. column value to *Note `VARCHAR': char. or a
`BINARY' column value to *Note `VARBINARY': binary-varbinary.
Otherwise, any trailing spaces are dropped from such column values when
they are inserted into the new columns.

*Note*:

Although you can promote *Note `CHAR': char.  columns to *Note
`VARCHAR': char. and `BINARY' columns to *Note `VARBINARY':
binary-varbinary, you cannot promote *Note `VARCHAR': char. columns to
*Note `CHAR': char. or *Note `VARBINARY': binary-varbinary. columns to
`BINARY'.

The `-b' option is used to specify the ID or sequence number of the
backup, and is the same number shown by the management client in the
`Backup BACKUP_ID completed' message displayed upon completion of a
backup. (See *Note mysql-cluster-backup-using-management-client::.)

*Important*:

When restoring cluster backups, you must be sure to restore all data
nodes from backups having the same backup ID. Using files from
different backups will at best result in restoring the cluster to an
inconsistent state, and may fail altogether.

`--restore_epoch' (short form: `-e') adds (or restores) epoch
information to the cluster replication status table. This is useful for
starting replication on a MySQL Cluster replication slave. When this
option is used, the row in the `mysql.ndb_apply_status' having `0' in
the `id' column is updated if it already exists; such a row is inserted
if it does not already exist. (See *Note
mysql-cluster-replication-backups::.)

`--restore_data'

This option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to output *Note `NDB':
mysql-cluster. table data and logs.

`--restore_meta'

This option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to print *Note `NDB':
mysql-cluster. table metadata. Generally, you need only use this option
when restoring the first data node of a cluster; additional data nodes
can obtain the metadata from the first one.

`--restore-privilege-tables'

*Note `ndb_restore': mysql-cluster-programs-ndb-restore. does not by
default restore distributed MySQL privilege tables (MySQL Cluster NDB
7.2.0 and later). This option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to restore the privilege tables.

This works only if the privilege tables were converted to *Note `NDB':
mysql-cluster. before the backup was taken.  For more information, see
*Note mysql-cluster-privilege-distribution::.

`--backup_path'

The path to the backup directory is required; this is supplied to *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. using the
`--backup_path' option, and must include the subdirectory corresponding
to the ID backup of the backup to be restored. For example, if the data
node's `DataDir' is `/var/lib/mysql-cluster', then the backup directory
is `/var/lib/mysql-cluster/BACKUP', and the backup files for the backup
with the ID 3 can be found in `/var/lib/mysql-cluster/BACKUP/BACKUP-3'.
The path may be absolute or relative to the directory in which the
*Note `ndb_restore': mysql-cluster-programs-ndb-restore. executable is
located, and may be optionally prefixed with `backup_path='.

*Note*:

Previous to MySQL 5.1.17 and MySQL Cluster NDB 6.1.5, the path to the
backup directory was specified as shown here, with `backup_path=' being
optional:


     [backup_path=]/PATH/TO/BACKUP/FILES

Beginning with MySQL 5.1.17 and MySQL Cluster NDB 6.1.5, this syntax
changed to `--backup_path=/PATH/TO/BACKUP/FILES', to conform more
closely with options used by other MySQL programs; `--backupid' is
required, and there is no short form for this option.

It is possible to restore a backup to a database with a different
configuration than it was created from. For example, suppose that a
backup with backup ID `12', created in a cluster with two database
nodes having the node IDs `2' and `3', is to be restored to a cluster
with four nodes. Then *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. must be run twice--once for each
database node in the cluster where the backup was taken.  However,
*Note `ndb_restore': mysql-cluster-programs-ndb-restore. cannot always
restore backups made from a cluster running one version of MySQL to a
cluster running a different MySQL version. See *Note
mysql-cluster-upgrade-downgrade::, for more information.

*Important*:

It is not possible to restore a backup made from a newer version of
MySQL Cluster using an older version of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. You can restore a backup made from
a newer version of MySQL to an older cluster, but you must use a copy
of *Note `ndb_restore': mysql-cluster-programs-ndb-restore. from the
newer MySQL Cluster version to do so.

For example, to restore a cluster backup taken from a cluster running
MySQL Cluster NDB 7.1.8 to a cluster running MySQL Cluster NDB 7.0.16,
you must use the *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. that comes with the MySQL Cluster
NDB 7.1.8 distribution.

For more rapid restoration, the data may be restored in parallel,
provided that there is a sufficient number of cluster connections
available. That is, when restoring to multiple nodes in parallel, you
must have an `[api]' or `[mysqld]' section in the cluster `config.ini'
file available for each concurrent *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. process. However, the data files
must always be applied before the logs.

`--no-upgrade'

Formerly, when using *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to restore a backup made from a
MySQL 5.0 cluster to a 5.1 cluster, *Note `VARCHAR': char. columns were
not resized and were recreated using the 5.0 fixed format. Beginning
with MySQL 5.1.19, `ndb_restore' recreates such *Note `VARCHAR': char.
columns using MySQL Cluster 5.1's variable-width format. Also beginning
with MySQL 5.1.19, this behavior can be overridden using the
`--no-upgrade' option (short form: `-u') when running *Note
`ndb_restore': mysql-cluster-programs-ndb-restore.

`--print_data'

The `--print_data' option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to direct its output to `stdout'.

*Note `TEXT': blob. and *Note `BLOB': blob. column values are always
truncated to the first 256 bytes in the output; this cannot currently
be overridden when using `--print_data'.

Beginning with MySQL 5.1.18, several additional options are available
for use with the `--print_data' option in generating data dumps, either
to `stdout', or to a file. These are similar to some of the options
used with *Note `mysqldump': mysqldump, and are shown in the following
list:

   * `--tab', `-T'

     Options for tab

     *Introduced*         5.1.18          
     *Command-Line        `--tab=path'        
     Format*                              
                          `-T'            

     This option causes `--print_data' to create dump files, one per
     table, each named `TBL_NAME.txt'.  It requires as its argument the
     path to the directory where the files should be saved; use `.' for
     the current directory.

   * `--fields-enclosed-by=STRING'

     Options for fields-enclosed-by

     *Introduced*         5.1.18          
     *Command-Line        `--fields-enclosed-by=char'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     Each column values are enclosed by the string passed to this
     option (regardless of data type; see next item).

   * `--fields-optionally-enclosed-by=STRING'

     Options for fields-optionally-enclosed-by

     *Introduced*         5.1.18          
     *Command-Line        `--fields-optionally-enclosed-by'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `'              

     The string passed to this option is used to enclose column values
     containing character data (such as *Note `CHAR': char, *Note
     `VARCHAR': char, *Note `BINARY': binary-varbinary, *Note `TEXT':
     blob, or *Note `ENUM': enum.).

   * `--fields-terminated-by=STRING'

     Options for fields-terminated-by

     *Introduced*         5.1.18          
     *Command-Line        `--fields-terminated-by=char'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `\t             
                          (tab)'          

     The string passed to this option is used to separate column
     values. The default value is a tab character (`\t').

   * `--hex'

     Options for hex

     *Introduced*         5.1.18          
     *Command-Line        `--hex'         
     Format*                              

     If this option is used, all binary values are output in
     hexadecimal format.

   * `--fields-terminated-by=STRING'

     Options for fields-terminated-by

     *Introduced*         5.1.18          
     *Command-Line        `--fields-terminated-by=char'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `\t             
                          (tab)'          

     This option specifies the string used to end each line of output.
     The default is a linefeed character (`\n').

   * `--append'

     Options for append

     *Introduced*         5.1.18          
     *Command-Line        `--append'        
     Format*                              

     When used with the `--tab' and `--print_data' options, this causes
     the data to be appended to any existing files having the same
     names.

*Note*:

If a table has no explicit primary key, then the output generated when
using the `--print_data' option includes the table's hidden primary key.

`--print_meta'

This option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to print all metadata to `stdout'.

`--print_log'

The `--print_log' option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to output its log to `stdout'.

`--print'

Causes *Note `ndb_restore': mysql-cluster-programs-ndb-restore. to
print all data, metadata, and logs to `stdout'. Equivalent to using the
`--print_data', `--print_meta', and `--print_log' options together.

*Note*:

Use of `--print' or any of the `--print_*' options is in effect
performing a dry run. Including one or more of these options causes any
output to be redirected to `stdout'; in such cases, *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. makes no attempt to
restore data or metadata to a MySQL Cluster.

`--dont_ignore_systab_0'

Normally, when restoring table data and metadata, *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. ignores the copy of the *Note
`NDB': mysql-cluster. system table that is present in the backup.
`--dont_ignore_systab_0' causes the system table to be restored. _This
option is intended for experimental and development use only, and is not
recommended in a production environment_.

`--ndb-nodegroup-map', `-z'

This option can be used to restore a backup taken from one node group
to a different node group. Its argument is a list of the form
`SOURCE_NODE_GROUP, TARGET_NODE_GROUP'.

`--no-binlog'

This option prevents any connected SQL nodes from writing data restored
by *Note `ndb_restore': mysql-cluster-programs-ndb-restore. to their
binary logs.  Available beginning with MySQL Cluster NDB 6.2.16 and
MySQL Cluster NDB 6.3.16.

`--no-restore-disk-objects', `-d'

This option stops *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. from restoring any MySQL Cluster
Disk Data objects, such as tablespaces and log file groups; see *Note
mysql-cluster-disk-data::, for more information about these. Added in
MySQL 5.1.6.

`--parallelism=#', `-p'

Determines the maximum number of parallel transactions that *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. tries to use. By
default, this is 128; the minimum is 1, and the maximum is 1024.

`--progress-frequency=N'

Print a status report each N seconds while the backup is in progress. 0
(the default) causes no status reports to be printed. The maximum is
65535.

`--verbose=#'

Sets the level for the verbosity of the output. The minimum is 0; the
maximum is 255. The default value is 1.

Beginning with MySQL 5.1.18, it is possible to restore only selected
databases, or selected tables from a single database, using the syntax
shown here:


     ndb_restore OTHER_OPTIONS DB_NAME,[DB_NAME[,...] | TBL_NAME[,TBL_NAME][,...]]

In other words, you can specify either of the following to be restored:

   * All tables from one or more databases

   * One or more tables from a single database

`--include-databases=DB_NAME[,DB_NAME][,...]'

Options for include-databases

*Introduced*           5.1.32-ndb-6.4.3        
*Command-Line Format*  `--include-databases=db-list'        
                       *Permitted        
                       Values*         
*Type*                 `string'        
*Default*              `'              

`--include-tables=DB_NAME.TBL_NAME[,DB_NAME.TBL_NAME][,...]'

Options for include-tables

*Introduced*           5.1.32-ndb-6.4.3        
*Command-Line Format*  `--include-tables=table-list'        
                       *Permitted        
                       Values*         
*Type*                 `string'        
*Default*              `'              

Beginning with MySQL Cluster NDB 6.3.22 and MySQL Cluster NDB 6.4.3,
you can (and should) use instead the `--include-databases' option or
the `--include-tables' option for restoring only specific databases or
tables, respectively.  `--include-databases' takes a comma-delimited
list of databases to be restored.  `--include-tables' takes a
comma-delimited list of tables (in `DATABASE.TABLE' format) to be
restored.

When `--include-databases' or `--include-tables' is used, only those
databases or tables named by the option are restored; all other
databases and tables are excluded by *Note `ndb_restore':
mysql-cluster-programs-ndb-restore, and are not restored.

The following table shows several invocations of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. using `--include-*' options (other
options possibly required have been omitted for clarity), and the
effects these have on restoring from a MySQL Cluster backup:

This table shows several invocations of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. using `--include-*' options, and
the effects these have on restoring from a MySQL Cluster backup.

Option Used                          Result
`--include-databases=db1'            Only tables in database `db1' are
                                     restored; all tables in all other
                                     databases are ignored
`--include-databases=db1,db2' (or    Only tables in databases `db1' and
`--include-databases=db1'            `db2' are restored; all tables in
`--include-databases=db2')           all other databases are ignored
`--include-tables=db1.t1'            Only table `t1' in database `db1' is
                                     restored; no other tables in `db1'
                                     or in any other database are
                                     restored
`--include-tables=db1.t2,db2.t1' (or Only the table `t2' in database
`--include-tables=db1.t2'            `db1' and the table `t1' in database
`--include-tables=db2.t1')           `db2' are restored; no other tables
                                     in `db1', `db2', or any other
                                     database are restored

Beginning with MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10,
you can use these two options together. For example, the following
causes all tables in databases `db1' and `db2', together with the tables
`t1' and `t2' in database `db3', to be restored (and no other databases
or tables):


     shell> ndb_restore [...] --include-databases=db1,db2 --include-tables=db3.t1,db3.t2

(Again we have omitted other, possibly required, options in the example
just shown.)

*Note*:

Prior to MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10,
multiple `--include-*' options were not handled correctly, and the
result of the options shown in the previous example was that only the
tables `db3.t1' and `db3.t2' were actually restored. (Bug #48907)

`--exclude-databases=DB_NAME[,DB_NAME][,...]'

Options for exclude-databases

*Introduced*           5.1.32-ndb-6.4.3        
*Command-Line Format*  `--exclude-databases=db-list'        
                       *Permitted        
                       Values*         
*Type*                 `string'        
*Default*              `'              

`--exclude-tables=DB_NAME.TBL_NAME[,DB_NAME.TBL_NAME][,...]'

Options for exclude-tables

*Introduced*           5.1.32-ndb-6.4.3        
*Command-Line Format*  `--exclude-tables=table-list'        
                       *Permitted        
                       Values*         
*Type*                 `string'        
*Default*              `'              

Beginning with MySQL Cluster NDB 6.3.22 and MySQL Cluster NDB 6.4.3, it
is possible to prevent one or more databases or tables from being
restored using the *Note `ndb_restore':
mysql-cluster-programs-ndb-restore.  options `--exclude-databases' and
`--exclude-tables'.  `--exclude-databases' takes a comma-delimited list
of one or more databases which should not be restored.
`--exclude-tables' takes a comma-delimited list of one or more tables
(using `DATABASE.TABLE' format) which should not be restored.

When `--exclude-databases' or `--exclude-tables' is used, only those
databases or tables named by the option are excluded; all other
databases and tables are restored by *Note `ndb_restore':
mysql-cluster-programs-ndb-restore.

This table shows several invocations of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. usng `--exclude-*' options (other
options possibly required have been omitted for clarity), and the
effects these options have on restoring from a MySQL Cluster backup:

This table shows several invocations of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. usng `--exclude-*' options, and the
effects these options have on restoring from a MySQL Cluster backup.

Option Used                          Result
`--exclude-databases=db1'            All tables in all databases except
                                     `db1' are restored; no tables in
                                     `db1' are restored
`--exclude-databases=db1,db2' (or    All tables in all databases except
`--exclude-databases=db1'            `db1' and `db2' are restored; no
`--exclude-databases=db2')           tables in `db1' or `db2' are
                                     restored
`--exclude-tables=db1.t1'            All tables except `t1' in database
                                     `db1' are restored; all other
                                     tables in `db1' are restored; all
                                     tables in all other databases are
                                     restored
`--exclude-tables=db1.t2,db2.t1' (or All tables in database `db1' except
`--exclude-tables=db1.t2'            for `t2' and all tables in database
`--exclude-tables=db2.t1)'           `db2' except for table `t1' are
                                     restored; no other tables in `db1'
                                     or `db2' are restored; all tables
                                     in all other databases are restored

Beginning with MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10,
you can use these two options together. For example, the following
causes all tables in all databases _except for_ databases `db1' and
`db2', along with the tables `t1' and `t2' in database `db3', _not_ to
be restored:


     shell> ndb_restore [...] --exclude-databases=db1,db2 --exclude-tables=db3.t1,db3.t2

(Again, we have omitted other possibly necessary options in the
interest of clarity and brevity from the example just shown.)

*Note*:

Prior to MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10,
multiple `--exclude-*' options were not handled correctly, with the
result that the options shown in the previous example caused
ndb_restore to exclude only the tables `db3.t1' and `db3.t2'. (Bug
#48907)

Beginning with MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10,
you can use `--include-*' and `--exclude-*' options together, subject
to the following rules:

   * The actions of all `--include-*' and `--exclude-*' options are
     cumulative.

   * All `--include-*' and `--exclude-*' options are evaluated in the
     order passed to ndb_restore, from right to left.

   * In the event of conflicting options, the first (rightmost) option
     takes precedence. In other words, the first option (going from
     right to left) that matches against a given database or table
     `wins'.

For example, the following set of options causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to restore all tables from database
`db1' except `db1.t1', while restoring no other tables from any other
databases:


     --include-databases=db1 --exclude-tables=db1.t1

However, reversing the order of the options just given simply causes
all tables from database `db1' to be restored (including `db1.t1', but
no tables from any other database), because the `--include-databases'
option, being farthest to the right, is the first match against database
`db1' and thus takes precedence over any other option that matches
`db1' or any tables in `db1':


     --exclude-tables=db1.t1 --include-databases=db1

*Note*:

Prior to MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10, it was
not possible to use `--include-databases' or `--include-tables'
together with `--exclude-databases' or `--exclude-tables', as these
combinations were evaluated inconsistently. (Bug #48907)

`--exclude-missing-columns'

Options for exclude-missing-columns

*Introduced*           5.1.35-ndb-7.0.7        
*Command-Line Format*  `--exclude-missing-columns'        

Beginning with MySQL Cluster NDB 6.3.26 and MySQL Cluster NDB 7.0.7, it
is also possible to restore only selected table columns using the
`--exclude-missing-columns' option. When this option is used, *Note
`ndb_restore': mysql-cluster-programs-ndb-restore.  ignores any columns
missing from tables being restored as compared to the versions of those
tables found in the backup.  This option applies to all tables being
restored. If you wish to apply this option only to selected tables or
databases, you can use it in combination with one or more of the
options described in the previous paragraph to do so, then restore data
to the remaining tables using a complementary set of these options.

`--exclude-missing-tables'

Options for exclude-missing-tables

*Introduced*           5.1.73-ndb-7.1.33        
*Command-Line Format*  `--exclude-missing-tables'        

Beginning with MySQL Cluster NDB 7.1.33, it is also possible to restore
only selected tables columns using this option, which causes *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. to ignore any tables
from the backup that are not found in the target database.

`--disable-indexes'

Options for disable-indexes

*Introduced*           5.1.41-ndb-7.1.2        
*Command-Line Format*  `--disable-indexes'        

Beginning with MySQL Cluster NDB 6.3.31, MySQL Cluster NDB 7.0.11, and
MySQL Cluster NDB 7.1.2, you can use this option with *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. to disable
restoration of indexes during restoration of the data from a native NDB
backup.  Afterwards, you can restore indexes for all tables at once with
multi-threaded building of indexes using `--rebuild-indexes', which
should be faster than rebuilding indexes concurrently for very large
tables.

`--rebuild-indexes'

Options for rebuild-indexes

*Introduced*           5.1.41-ndb-7.1.2        
*Command-Line Format*  `--rebuild-indexes'        

Beginning with MySQL Cluster NDB 6.3.31, MySQL Cluster NDB 7.0.11, and
MySQL Cluster NDB 7.1.2, you can use this option with *Note
`ndb_restore': mysql-cluster-programs-ndb-restore. to cause
multi-threaded rebuilding of the ordered indexes while restoring a
native `NDB' backup. The number of threads used for building ordered
indexes by *Note `ndb_restore': mysql-cluster-programs-ndb-restore. with
this option is controlled by the `BuildIndexThreads' data node
configuration parameter.

It is necessary to use this option only for the first run of *Note
`ndb_restore': mysql-cluster-programs-ndb-restore.; this causes all
ordered indexes to be rebuilt without using `--rebuild-indexes' again
when restoring subsequent nodes. You should use this option prior to
inserting new rows into the database; otherwise, it is possible for a
row to be inserted that later causes a unique constraint violation when
trying to rebuild the indexes.

Rebuilding of unique indexes uses disk write bandwidth for redo logging
and local checkpointing. An insufficient amount of this bandwith can
lead to redo buffer overload or log overload errors. In such cases you
can run *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
`--rebuild-indexes' again; the process resumes at the point where the
error occurred. You can also do this when you have encountered
temporarary errors. You can repeat execution of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore.  `--rebuild-indexes' indefinitely;
you may be able to stop such errors by reducing the value of
`DiskCheckpointSpeed' to provide additional disk bandwidth to redo
logging.

`--skip-broken-objects'

Options for skip-broken-objects

*Introduced*           5.1.51-ndb-7.1.10        
*Command-Line Format*  `--skip-broken-objects'        

This option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to ignore corrupt tables while
reading a native *Note `NDB': mysql-cluster. backup, and to continue
restoring any remaining tables (that are not also corrupted).
Currently, the `--skip-broken-objects' option works only in the case of
missing blob parts tables.

This option was added in MySQL Cluster NDB 6.3.40, MySQL Cluster NDB
7.0.21, and MySQL Cluster NDB 7.1.10.

`--skip-unknown-objects'

Options for skip-unknown-objects

*Introduced*           5.1.44-ndb-7.1.4        
*Command-Line Format*  `--skip-unknown-objects'        

This option causes *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. to ignore any schema objects it
does not recognize while reading a native *Note `NDB': mysql-cluster.
backup. This can be used for restoring a backup made from a cluster
running MySQL Cluster NDB 7.0 to a cluster running MySQL Cluster NDB
6.3.

This option was added in MySQL Cluster NDB 6.3.34, MySQL Cluster NDB
7.0.15, and MySQL Cluster NDB 7.1.4.

`--rewrite-database=OLD_DBNAME,NEW_DBNAME'

Options for rewrite-database

*Introduced*           5.1.51-ndb-7.1.11        
*Command-Line Format*  `--rewrite-database=olddb,newdb'        
                       *Permitted        
                       Values*         
*Type*                 `string'        
*Default*              `none'          

This option makes it possible to restore to a database having a
different name from that used in the backup. For example, if a backup
is made of a database named `products', you can restore the data it
contains to a database named `inventory', use this option as shown here
(omitting any other options that might be required):


     shell> ndb_restore --rewrite-database=product,inventory

The option can be employed multiple times in a single invocation of
*Note `ndb_restore': mysql-cluster-programs-ndb-restore. Thus it is
possible to restore simultaneously from a database named `db1' to a
database named `db2' and from a database named `db3' to one named `db4'
using `--rewrite-database=db1,db2 --rewrite-database=db3,db4'. Other
*Note `ndb_restore': mysql-cluster-programs-ndb-restore. options may be
used between multiple occurrences of `--rewrite-database'.

In the event of conflicts between multiple `--rewrite-database'
options, the last `--rewrite-database' option used, reading from left
to right, is the one that takes effect. For example, if
`--rewrite-database=db1,db2 --rewrite-database=db1,db3' is used, only
`--rewrite-database=db1,db3' is honored, and
`--rewrite-database=db1,db2' is ignored. It is also possible to restore
from multiple databases to a single database, so that
`--rewrite-database=db1,db3 --rewrite-database=db2,db3' restores all
tables and data from databases `db1' and `db2' into database `db3'.

*Important*:

When restoring from multiple backup databases into a single target
database using `--rewrite-database', no check is made for collisions
between table or other object names, and the order in which rows are
restored is not guaranteed. This means that it is possible in such
cases for rows to be overwritten and updates to be lost.

This option was added in MySQL Cluster NDB 6.3.41, MySQL Cluster NDB
7.0.22, and MySQL Cluster NDB 7.1.11.

`--exclude-intermediate-sql-tables[=TRUE|FALSE]'

Options for exclude-intermediate-sql-tables

*Introduced*           5.1.73-ndb-7.1.31        
*Command-Line Format*  `--exclude-intermediate-sql-tables[=TRUE|FALSE]'        
                       *Permitted        
                       Values*         
*Type*                 `boolean'        
*Default*              `TRUE'          

When performing copying *Note `ALTER TABLE': alter-table. operations,
*Note `mysqld': mysqld. creates intermediate tables (whose names are
prefixed with `#sql-'). When `TRUE', the
`--exclude-intermediate-sql-tables' option keeps *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. from restoring such tables that may
have been left over from such operations. This option is `TRUE' by
default.

The `--exclude-intermediate-sql-tables' option was introduced in MySQL
Cluster NDB 7.1.31. (Bug #17882305)

Error reporting

*Note `ndb_restore': mysql-cluster-programs-ndb-restore. reports both
temporary and permanent errors. In the case of temporary errors, it may
able to recover from them. Beginning with MySQL 5.1.12, it reports
`Restore successful, but encountered temporary error, please look at
configuration' in such cases.

*Important*:

After using *Note `ndb_restore': mysql-cluster-programs-ndb-restore. to
initialize a MySQL Cluster for use in circular replication, binary logs
on the SQL node acting as the replication slave are not automatically
created, and you must cause them to be created manually. To cause the
binary logs to be created, issue a *Note `SHOW TABLES': show-tables.
statement on that SQL node before running *Note `START SLAVE':
start-slave. This is a known issue in MySQL Cluster.


File: manual.info,  Node: mysql-cluster-programs-ndb-select-all,  Next: mysql-cluster-programs-ndb-select-count,  Prev: mysql-cluster-programs-ndb-restore,  Up: mysql-cluster-programs

17.4.21 `ndb_select_all' -- Print Rows from an NDB Table
--------------------------------------------------------

*Note `ndb_select_all': mysql-cluster-programs-ndb-select-all. prints
all rows from an *Note `NDB': mysql-cluster. table to `stdout'.

*Usage*


     ndb_select_all -c CONNECT_STRING TBL_NAME -d DB_NAME [> FILE_NAME]

The following table includes options that are specific to the MySQL
Cluster native backup restoration program *Note `ndb_select_all':
mysql-cluster-programs-ndb-select-all. Additional descriptions follow
the table. For options common to most MySQL Cluster programs (including
*Note `ndb_select_all': mysql-cluster-programs-ndb-select-all.), see
*Note mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_select_all program

Format Description Added or Removed

`--database=dbname',

` -d '

Name of the database in which the table is found

All MySQL 5.1 based releases

`--parallelism=#',

` -p '

Degree of parallelism

All MySQL 5.1 based releases

`--lock=#',

` -l '

Lock type

All MySQL 5.1 based releases

`--order=index',

` -o '

Sort resultset according to index whose name is supplied

All MySQL 5.1 based releases

`--descending',

` -z '

Sort resultset in descending order (requires order flag)

All MySQL 5.1 based releases

`--header',

` -h '

Print header (set to 0|FALSE to disable headers in output)

All MySQL 5.1 based releases

`--useHexFormat',

` -x '

Output numbers in hexadecimal format

All MySQL 5.1 based releases

`--delimiter=char',

` -D '

Set a column delimiter

All MySQL 5.1 based releases

` --disk '

Print disk references (useful only for Disk Data tables having
nonindexed columns)

All MySQL 5.1 based releases

` --rowid '

Print rowid

All MySQL 5.1 based releases

` --gci '

Include GCI in output

All MySQL 5.1 based releases

` --gci64 '

Include GCI and row epoch in output

All MySQL 5.1 based releases

`--tup',

` -t '

Scan in tup order

All MySQL 5.1 based releases

` --nodata '

Do not print table column data

All MySQL 5.1 based releases 


   * `--database=DBNAME', `-d' DBNAME

     Name of the database in which the table is found. The default
     value is `TEST_DB'.

   * `parallelism=#', `-p' #

     Specifies the degree of parallelism.

   * `--lock=LOCK_TYPE', `-l LOCK_TYPE'

     Employs a lock when reading the table. Possible values for
     LOCK_TYPE are:

        * `0': Read lock

        * `1': Read lock with hold

        * `2': Exclusive read lock

     There is no default value for this option.

   * `--order=INDEX_NAME', `-o INDEX_NAME'

     Orders the output according to the index named INDEX_NAME. Note
     that this is the name of an index, not of a column, and that the
     index must have been explicitly named when created.

   * `--descending', `-z'

     Sorts the output in descending order. This option can be used only
     in conjunction with the `-o' (`--order') option.

   * `--header=FALSE'

     Excludes column headers from the output.

   * `--useHexFormat' `-x'

     Causes all numeric values to be displayed in hexadecimal format.
     This does not affect the output of numerals contained in strings
     or datetime values.

   * `--delimiter=CHARACTER', `-D CHARACTER'

     Causes the CHARACTER to be used as a column delimiter. Only table
     data columns are separated by this delimiter.

     The default delimiter is the tab character.

   * `--disk'

     Adds a disk reference column to the output. The column is nonempty
     only for Disk Data tables having nonindexed columns.

   * `--rowid'

     Adds a `ROWID' column providing information about the fragments in
     which rows are stored.

   * `--gci'

     Adds a `GCI' column to the output showing the global checkpoint at
     which each row was last updated.  See *Note
     mysql-cluster-overview::, and *Note mysql-cluster-log-events::,
     for more information about checkpoints.

   * `--gci64'

     Adds a `ROW$GCI64' column to the output showing the global
     checkpoint at which each row was last updated, as well as the
     number of the epoch in which this update occurred.

   * `--tupscan', `-t'

     Scan the table in the order of the tuples.

   * `--nodata'

     Causes any table data to be omitted.

*Sample Output*

Output from a MySQL *Note `SELECT': select.  statement:


     mysql> SELECT * FROM ctest1.fish;
     +----+-----------+
     | id | name      |
     +----+-----------+
     |  3 | shark     |
     |  6 | puffer    |
     |  2 | tuna      |
     |  4 | manta ray |
     |  5 | grouper   |
     |  1 | guppy     |
     +----+-----------+
     6 rows in set (0.04 sec)

Output from the equivalent invocation of *Note `ndb_select_all':
mysql-cluster-programs-ndb-select-all.:


     shell> ./ndb_select_all -c localhost fish -d ctest1
     id      name
     3       [shark]
     6       [puffer]
     2       [tuna]
     4       [manta ray]
     5       [grouper]
     1       [guppy]
     6 rows returned

     NDBT_ProgramExit: 0 - OK

Note that all string values are enclosed by square brackets
(``['...`]'') in the output of *Note `ndb_select_all':
mysql-cluster-programs-ndb-select-all. For a further example, consider
the table created and populated as shown here:


     CREATE TABLE dogs (
         id INT(11) NOT NULL AUTO_INCREMENT,
         name VARCHAR(25) NOT NULL,
         breed VARCHAR(50) NOT NULL,
         PRIMARY KEY pk (id),
         KEY ix (name)
     )
     TABLESPACE ts STORAGE DISK
     ENGINE=NDBCLUSTER;

     INSERT INTO dogs VALUES
         ('', 'Lassie', 'collie'),
         ('', 'Scooby-Doo', 'Great Dane'),
         ('', 'Rin-Tin-Tin', 'Alsatian'),
         ('', 'Rosscoe', 'Mutt');

This demonstrates the use of several additional *Note `ndb_select_all':
mysql-cluster-programs-ndb-select-all. options:


     shell> ./ndb_select_all -d ctest1 dogs -o ix -z --gci --disk
     GCI     id name          breed        DISK_REF
     834461  2  [Scooby-Doo]  [Great Dane] [ m_file_no: 0 m_page: 98 m_page_idx: 0 ]
     834878  4  [Rosscoe]     [Mutt]       [ m_file_no: 0 m_page: 98 m_page_idx: 16 ]
     834463  3  [Rin-Tin-Tin] [Alsatian]   [ m_file_no: 0 m_page: 34 m_page_idx: 0 ]
     835657  1  [Lassie]      [Collie]     [ m_file_no: 0 m_page: 66 m_page_idx: 0 ]
     4 rows returned

     NDBT_ProgramExit: 0 - OK

*Note*:

In earlier MySQL Cluster NDB 7.0 and 7.1 releases, *Note
`ndb_select_all': mysql-cluster-programs-ndb-select-all. did not print
any output for `NULL' values as it did in MySQL Cluster NDB 6.3 and
earlier release series. This issue was fixed in MySQL Cluster NDB
7.0.22 and MySQL Cluster NDB 7.1.11. (Bug #60045)


File: manual.info,  Node: mysql-cluster-programs-ndb-select-count,  Next: mysql-cluster-programs-ndb-show-tables,  Prev: mysql-cluster-programs-ndb-select-all,  Up: mysql-cluster-programs

17.4.22 `ndb_select_count' -- Print Row Counts for NDB Tables
-------------------------------------------------------------

*Note `ndb_select_count': mysql-cluster-programs-ndb-select-count.
prints the number of rows in one or more *Note `NDB': mysql-cluster.
tables. With a single table, the result is equivalent to that obtained
by using the MySQL statement `SELECT COUNT(*) FROM TBL_NAME'.

*Usage*


     ndb_select_count [-c CONNECT_STRING] -dDB_NAME TBL_NAME[, TBL_NAME2[, ...]]

The following table includes options that are specific to the MySQL
Cluster native backup restoration program *Note `ndb_select_count':
mysql-cluster-programs-ndb-select-count. Additional descriptions follow
the table. For options common to most MySQL Cluster programs (including
*Note `ndb_select_count': mysql-cluster-programs-ndb-select-count.), see
*Note mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_select_count
program

Format Description Added or Removed

`--database=dbname',

`-d'

Name of the database in which the table is found

All MySQL 5.1 based releases

`--parallelism=#',

`-p'

Degree of parallelism

All MySQL 5.1 based releases

`--lock=#',

`-l'

Lock type

All MySQL 5.1 based releases 


You can obtain row counts from multiple tables in the same database by
listing the table names separated by spaces when invoking this command,
as shown under *Sample Output*.

*Sample Output*


     shell> ./ndb_select_count -c localhost -d ctest1 fish dogs
     6 records in table fish
     4 records in table dogs

     NDBT_ProgramExit: 0 - OK


File: manual.info,  Node: mysql-cluster-programs-ndb-show-tables,  Next: mysql-cluster-programs-ndb-size-pl,  Prev: mysql-cluster-programs-ndb-select-count,  Up: mysql-cluster-programs

17.4.23 `ndb_show_tables' -- Display List of NDB Tables
-------------------------------------------------------

*Note `ndb_show_tables': mysql-cluster-programs-ndb-show-tables.
displays a list of all *Note `NDB': mysql-cluster. database objects in
the cluster. By default, this includes not only both user-created
tables and *Note `NDB': mysql-cluster. system tables, but *Note `NDB':
mysql-cluster.-specific indexes, internal triggers, and MySQL Cluster
Disk Data objects as well.

The following table includes options that are specific to the MySQL
Cluster native backup restoration program *Note `ndb_show_tables':
mysql-cluster-programs-ndb-show-tables. Additional descriptions follow
the table. For options common to most MySQL Cluster programs (including
*Note `ndb_show_tables': mysql-cluster-programs-ndb-show-tables.), see
*Note mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_show_tables
program

Format Description Added or Removed

`--database=string',

` -d '

Specifies the database in which the table is found

All MySQL 5.1 based releases

`--loops=#',

` -l '

Number of times to repeat output

All MySQL 5.1 based releases

`--type=#',

` -t '

Limit output to objects of this type

All MySQL 5.1 based releases

`--unqualified',

` -u '

Do not qualify table names

All MySQL 5.1 based releases

`--parsable',

` -p '

Return output suitable for MySQL LOAD DATA INFILE statement

All MySQL 5.1 based releases

` --show-temp-status '

Show table temporary flag

All MySQL 5.1 based releases 


*Usage*


     ndb_show_tables [-c CONNECT_STRING]

   * `--database', `-d'

     Specifies the name of the database in which the tables are found.

   * `--loops', `-l'

     Specifies the number of times the utility should execute.  This is
     1 when this option is not specified, but if you do use the option,
     you must supply an integer argument for it.

   * `--parsable', `-p'

     Using this option causes the output to be in a format suitable for
     use with *Note `LOAD DATA INFILE': load-data.

   * `--show-temp-status'

     If specified, this causes temporary tables to be displayed.

   * `--type', `-t'

     Can be used to restrict the output to one type of object,
     specified by an integer type code as shown here:

        * `1': System table

        * `2': User-created table

        * `3': Unique hash index

     Any other value causes all *Note `NDB': mysql-cluster.  database
     objects to be listed (the default).

   * `--unqualified', `-u'

     If specified, this causes unqualified object names to be displayed.

*Note*:

Only user-created MySQL Cluster tables may be accessed from MySQL;
system tables such as `SYSTAB_0' are not visible to *Note `mysqld':
mysqld. However, you can examine the contents of system tables using
*Note `NDB': mysql-cluster. API applications such as *Note
`ndb_select_all': mysql-cluster-programs-ndb-select-all. (see *Note
mysql-cluster-programs-ndb-select-all::).


File: manual.info,  Node: mysql-cluster-programs-ndb-size-pl,  Next: mysql-cluster-programs-ndb-waiter,  Prev: mysql-cluster-programs-ndb-show-tables,  Up: mysql-cluster-programs

17.4.24 `ndb_size.pl' -- NDBCLUSTER Size Requirement Estimator
--------------------------------------------------------------

This is a Perl script that can be used to estimate the amount of space
that would be required by a MySQL database if it were converted to use
the *Note `NDBCLUSTER': mysql-cluster.  storage engine. Unlike the
other utilities discussed in this section, it does not require access
to a MySQL Cluster (in fact, there is no reason for it to do so).
However, it does need to access the MySQL server on which the database
to be tested resides.

*Requirements*

   * A running MySQL server. The server instance does not have to
     provide support for MySQL Cluster.

   * A working installation of Perl.

   * The `DBI' module, which can be obtained from CPAN if it is not
     already part of your Perl installation. (Many Linux and other
     operating system distributions provide their own packages for this
     library.)

   * Previous to MySQL 5.1.18, *Note `ndb_size.pl':
     mysql-cluster-programs-ndb-size-pl.  also required the
     `HTML::Template' module and an associated template file
     `share/mysql/ndb_size.tmpl'. Beginning with MySQL 5.1.18,
     `ndb_size.tmpl' is no longer needed (or included).

   * A MySQL user account having the necessary privileges. If you do
     not wish to use an existing account, then creating one using
     `GRANT USAGE ON DB_NAME.*'--where DB_NAME is the name of the
     database to be examined--is sufficient for this purpose.

`ndb_size.pl' can also be found in the MySQL sources in
`storage/ndb/tools'.

The following table includes options that are specific to the MySQL
Cluster program *Note `ndb_size.pl':
mysql-cluster-programs-ndb-size-pl. Additional descriptions follow the
table. For options common to most MySQL Cluster programs (including
*Note `ndb_size.pl': mysql-cluster-programs-ndb-size-pl.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_size.pl program

Format Description Added or Removed

` --database=dbname '

The database or databases to examine; accepts a comma-delimited list;
the default is ALL (use all databases found on the server)

All MySQL 5.1 based releases

` --hostname[:port] '

Specify host and optional port as host[:port]

All MySQL 5.1 based releases

` --socket=file '

Specify a socket to connect to

ADDED: NDB 6.2.5

` --user=string '

Specify a MySQL user name

All MySQL 5.1 based releases

` --password=string '

Specify a MySQL user password

All MySQL 5.1 based releases

` --format=string '

Set output format (text or HTML)

All MySQL 5.1 based releases

` --excludetables=tbl_list '

Skip any tables in a comma-separated list of tables

All MySQL 5.1 based releases

` --excludedbs=db_list '

Skip any databases in a comma-separated list of databases

All MySQL 5.1 based releases

` --savequeries=file '

Saves all queries to the database into the file specified

All MySQL 5.1 based releases

` --loadqueries=file '

Loads all queries from the file specified; does not connect to a
database

All MySQL 5.1 based releases

` --real_table_name=table '

Designates a table to handle unique index size calculations

ADDED: NDB 6.2.5 


*Usage*


     perl ndb_size.pl [--database={DB_NAME|ALL}] [--hostname=HOST[:PORT]] [--socket=SOCKET] \
           [--user=USER] [--password=PASSWORD]  \
           [--help|-h] [--format={html|text}] \
           [--loadqueries=FILE_NAME] [--savequeries=FILE_NAME]

By default, this utility attempts to analyze all databases on the
server. You can specify a single database using the `--database'
option; the default behavior can be made explicit by using `ALL' for
the name of the database. You can also exclude one or more databases by
using the `--excludedbs' option with a comma-separated list of the
names of the databases to be skipped. Similarly, you can cause specific
tables to be skipped by listing their names, separated by commas,
following the optional `--excludetables' option. A host name (and
possibly a port as well) can be specified using `--hostname'; the
default is `localhost'. Beginning with MySQL Cluster NDB 6.3.49, MySQL
Cluster NDB 7.0.32, and MySQL Cluster NDB 7.1.21, you can specify a
port in addition to the host using HOST:PORT format for the value of
`--hostname'. The default port number is 3306. If necessary, you can
also specify a socket; the default is `/var/lib/mysql.sock'.  A MySQL
user name and password can be specified the corresponding options
shown. It also possible to control the format of the output using the
`--format' option; this can take either of the values `html' or `text',
with `text' being the default. An example of the text output is shown
here:


     shell> ndb_size.pl --database=test --socket=/tmp/mysql.sock
     ndb_size.pl report for database: 'test' (1 tables)
     --------------------------------------------------
     Connected to: DBI:mysql:host=localhost;mysql_socket=/tmp/mysql.sock

     Including information for versions: 4.1, 5.0, 5.1

     test.t1
     -------

     DataMemory for Columns (* means varsized DataMemory):
              Column Name            Type  Varsized   Key  4.1  5.0   5.1
          HIDDEN_NDB_PKEY          bigint             PRI    8    8     8
                       c2     varchar(50)         Y         52   52    4*
                       c1         int(11)                    4    4     4
                                                            --   --    --
     Fixed Size Columns DM/Row                              64   64    12
        Varsize Columns DM/Row                               0    0     4

     DataMemory for Indexes:
        Index Name                 Type        4.1        5.0        5.1
           PRIMARY                BTREE         16         16         16
                                                --         --         --
            Total Index DM/Row                  16         16         16

     IndexMemory for Indexes:
                    Index Name        4.1        5.0        5.1
                       PRIMARY         33         16         16
                                       --         --         --
                Indexes IM/Row         33         16         16

     Summary (for THIS table):
                                      4.1        5.0        5.1
         Fixed Overhead DM/Row         12         12         16
                NULL Bytes/Row          4          4          4
                DataMemory/Row         96         96         48
                         (Includes overhead, bitmap and indexes)

       Varsize Overhead DM/Row          0          0          8
        Varsize NULL Bytes/Row          0          0          4
            Avg Varside DM/Row          0          0         16

                      No. Rows          0          0          0

             Rows/32kb DM Page        340        340        680
     Fixedsize DataMemory (KB)          0          0          0

     Rows/32kb Varsize DM Page          0          0       2040
       Varsize DataMemory (KB)          0          0          0

              Rows/8kb IM Page        248        512        512
              IndexMemory (KB)          0          0          0

     Parameter Minimum Requirements
     ------------------------------
     * indicates greater than default

                     Parameter     Default        4.1         5.0         5.1
               DataMemory (KB)       81920          0           0           0
            NoOfOrderedIndexes         128          1           1           1
                    NoOfTables         128          1           1           1
              IndexMemory (KB)       18432          0           0           0
         NoOfUniqueHashIndexes          64          0           0           0
                NoOfAttributes        1000          3           3           3
                  NoOfTriggers         768          5           5           5

For debugging purposes, the Perl arrays containing the queries run by
this script can be read from the file specified using can be saved to a
file using `--savequeries'; a file containing such arrays to be read in
during script execution can be specified using `--loadqueries'. Neither
of these options has a default value.

To produce output in HTML format, use the `--format' option and
redirect the output to a file, as shown here:


     shell> ndb_size.pl --database=test --socket=/tmp/mysql.sock --format=html > ndb_size.html

(Without the redirection, the output is sent to `stdout'.)

The output from this script includes the following information:

   * Minimum values for the `DataMemory', `IndexMemory',
     `MaxNoOfTables', `MaxNoOfAttributes', `MaxNoOfOrderedIndexes',
     `MaxNoOfUniqueHashIndexes', and `MaxNoOfTriggers' configuration
     parameters required to accommodate the tables analyzed.

   * Memory requirements for all of the tables, attributes, ordered
     indexes, and unique hash indexes defined in the database.

   * The `IndexMemory' and `DataMemory' required per table and table
     row.

*Note*:

Prior to MySQL 5.1.23, MySQL Cluster NDB 6.2.5, and MySQL Cluster NDB
6.3.7, `ndb_size.pl' was invoked as shown here:


     perl ndb_size.pl DB_NAME HOSTNAME USERNAME PASSWORD > FILE_NAME.html

For more information about this change, see Bug #28683 and Bug #28253.


File: manual.info,  Node: mysql-cluster-programs-ndb-waiter,  Next: mysql-cluster-program-options-common,  Prev: mysql-cluster-programs-ndb-size-pl,  Up: mysql-cluster-programs

17.4.25 `ndb_waiter' -- Wait for MySQL Cluster to Reach a Given Status
----------------------------------------------------------------------

*Note `ndb_waiter': mysql-cluster-programs-ndb-waiter. repeatedly (each
100 milliseconds) prints out the status of all cluster data nodes until
either the cluster reaches a given status or the `--timeout' limit is
exceeded, then exits. By default, it waits for the cluster to achieve
`STARTED' status, in which all nodes have started and connected to the
cluster. This can be overridden using the `--no-contact' and
`--not-started' options.

The node states reported by this utility are as follows:

   * `NO_CONTACT': The node cannot be contacted.

   * `UNKNOWN': The node can be contacted, but its status is not yet
     known. Usually, this means that the node has received a `START' or
     `RESTART' command from the management server, but has not yet
     acted on it.

   * `NOT_STARTED': The node has stopped, but remains in contact with
     the cluster. This is seen when restarting the node using the
     management client's `RESTART' command.

   * `STARTING': The node's *Note `ndbd': mysql-cluster-programs-ndbd.
     process has started, but the node has not yet joined the cluster.

   * `STARTED': The node is operational, and has joined the cluster.

   * `SHUTTING_DOWN': The node is shutting down.

   * `SINGLE USER MODE': This is shown for all cluster data nodes when
     the cluster is in single user mode.

The following table includes options that are specific to the MySQL
Cluster native backup restoration program *Note `ndb_waiter':
mysql-cluster-programs-ndb-waiter. Additional descriptions follow the
table. For options common to most MySQL Cluster programs (including
*Note `ndb_waiter': mysql-cluster-programs-ndb-waiter.), see *Note
mysql-cluster-program-options-common::.

This table describes command-line options for the ndb_waiter program

Format Description Added or Removed

`--no-contact',

` -n '

Wait for cluster to reach NO CONTACT state

All MySQL 5.1 based releases

` --not-started '

Wait for cluster to reach NOT STARTED state

All MySQL 5.1 based releases

` --single-user '

Wait for cluster to enter single user mode

All MySQL 5.1 based releases

`--timeout=#',

` -t '

Wait this many seconds, then exit whether or not cluster has reached
desired state; default is 2 minutes (120 seconds)

All MySQL 5.1 based releases

` --nowait-nodes=list '

List of nodes not to be waited for.

ADDED: NDB 6.2.1

`--wait-nodes=list',

` -w '

List of nodes to be waited for.

ADDED: NDB 6.3.34, NDB 7.0.15, NDB 7.1.4 


*Usage*


     ndb_waiter [-c CONNECT_STRING]

*Additional Options*

   * `--no-contact', `-n'

     Instead of waiting for the `STARTED' state, *Note `ndb_waiter':
     mysql-cluster-programs-ndb-waiter. continues running until the
     cluster reaches `NO_CONTACT' status before exiting.

   * `--not-started'

     Instead of waiting for the `STARTED' state, *Note `ndb_waiter':
     mysql-cluster-programs-ndb-waiter. continues running until the
     cluster reaches `NOT_STARTED' status before exiting.

   * `--timeout=SECONDS', `-t SECONDS'

     Time to wait. The program exits if the desired state is not
     achieved within this number of seconds. The default is 120 seconds
     (1200 reporting cycles).

   * `--single-user'

     The program waits for the cluster to enter single user mode.

   * `--nowait-nodes=LIST'

     When this option is used, ndb_waiter does not wait for the nodes
     whose IDs are listed. The list is comma-delimited; ranges can be
     indicated by dashes, as shown here:


          shell> ndb_waiter --nowait-nodes=1,3,7-9

     *Important*:

     Do _not_ use this option together with the `--wait-nodes' option.

     This option was added in MySQL Cluster NDB 6.2.1.

   * `--wait-nodes=LIST', `-w LIST'

     When this option is used, *Note `ndb_waiter':
     mysql-cluster-programs-ndb-waiter.  waits only for the nodes whose
     IDs are listed. The list is comma-delimited; ranges can be
     indicated by dashes, as shown here:


          shell> ndb_waiter --wait-nodes=2,4-6,10

     *Important*:

     Do _not_ use this option together with the `--nowait-nodes' option.

     This option was added in MySQL Cluster NDB 6.3.34, 7.0.15, and
     7.1.4.

Sample Output

Shown here is the output from *Note `ndb_waiter':
mysql-cluster-programs-ndb-waiter.  when run against a 4-node cluster
in which two nodes have been shut down and then started again manually.
Duplicate reports (indicated by ``...'') are omitted.


     shell> ./ndb_waiter -c localhost

     Connecting to mgmsrv at (localhost)
     State node 1 STARTED
     State node 2 NO_CONTACT
     State node 3 STARTED
     State node 4 NO_CONTACT
     Waiting for cluster enter state STARTED

     ...

     State node 1 STARTED
     State node 2 UNKNOWN
     State node 3 STARTED
     State node 4 NO_CONTACT
     Waiting for cluster enter state STARTED

     ...

     State node 1 STARTED
     State node 2 STARTING
     State node 3 STARTED
     State node 4 NO_CONTACT
     Waiting for cluster enter state STARTED

     ...

     State node 1 STARTED
     State node 2 STARTING
     State node 3 STARTED
     State node 4 UNKNOWN
     Waiting for cluster enter state STARTED

     ...

     State node 1 STARTED
     State node 2 STARTING
     State node 3 STARTED
     State node 4 STARTING
     Waiting for cluster enter state STARTED

     ...

     State node 1 STARTED
     State node 2 STARTED
     State node 3 STARTED
     State node 4 STARTING
     Waiting for cluster enter state STARTED

     ...

     State node 1 STARTED
     State node 2 STARTED
     State node 3 STARTED
     State node 4 STARTED
     Waiting for cluster enter state STARTED

     NDBT_ProgramExit: 0 - OK

*Note*:

If no connection string is specified, then *Note `ndb_waiter':
mysql-cluster-programs-ndb-waiter. tries to connect to a management on
`localhost', and reports `Connecting to mgmsrv at (null)'.


File: manual.info,  Node: mysql-cluster-program-options-common,  Prev: mysql-cluster-programs-ndb-waiter,  Up: mysql-cluster-programs

17.4.26 Options Common to MySQL Cluster Programs -- Options Common to MySQL Cluster Programs
--------------------------------------------------------------------------------------------

All MySQL Cluster programs accept the options described in this
section, with the following exceptions:

   * *Note `mysqld': mysqld.

   * *Note `ndb_print_backup_file':
     mysql-cluster-programs-ndb-print-backup-file.

   * *Note `ndb_print_schema_file':
     mysql-cluster-programs-ndb-print-schema-file.

   * *Note `ndb_print_sys_file':
     mysql-cluster-programs-ndb-print-sys-file.

Users of earlier MySQL Cluster versions should note that some of these
options have been changed to make them consistent with one another as
well as with *Note `mysqld': mysqld. You can use the `--help' option
with any MySQL Cluster program--with the exception of *Note
`ndb_print_backup_file': mysql-cluster-programs-ndb-print-backup-file,
*Note `ndb_print_schema_file':
mysql-cluster-programs-ndb-print-schema-file, and *Note
`ndb_print_sys_file': mysql-cluster-programs-ndb-print-sys-file.--to
view a list of the options which the program supports.

The options in the following table are common to all MySQL Cluster
executables (except those noted previously in this section).

This table describes command-line options common to all MySQL Cluster
programs

Format Description Added or Removed

`--help',

`--usage',

` -?  '

Display help message and exit

All MySQL 5.1 based releases

`--ndb-connectstring=connectstring',

`--connect-string=connectstring',

` -c '

Set connection string for connecting to ndb_mgmd. Syntax:
[nodeid=<id>;][host=]<hostname>[:<port>].  Overrides entries specified
in NDB_CONNECTSTRING or my.cnf.

All MySQL 5.1 based releases

` --ndb-mgmd-host=host[:port] '

Set the host (and port, if desired) for connecting to management server

All MySQL 5.1 based releases

` --ndb-nodeid=# '

Set node id for this node

All MySQL 5.1 based releases

` --ndb-shm '

Allow for optimization using shared memory connections where available
(was EXPERIMENTAL, later REMOVED)

REMOVED: NDB 7.0.16, NDB 7.1.5

` --ndb-optimized-node-selection '

Select nodes for transactions in a more optimal way

All MySQL 5.1 based releases

` --character-sets-dir=path '

Directory where character sets are installed

All MySQL 5.1 based releases

` --debug=options '

Enable output from debug calls. Can be used only for versions compiled
with debugging enabled

All MySQL 5.1 based releases

` --core-file '

Write core on errors (defaults to TRUE in debug builds)

All MySQL 5.1 based releases

`--version',

` -V '

Output version information and exit

All MySQL 5.1 based releases 


For options specific to individual MySQL Cluster programs, see *Note
mysql-cluster-programs::.

See *Note mysql-cluster-program-options-mysqld::, for *Note `mysqld':
mysqld. options relating to MySQL Cluster.

   * `--help', `--usage', `-?'

     Options for help

     *Command-Line        `--help'        
     Format*                              
                          `--usage'        
                          `-?'            

     Prints a short list with descriptions of the available command
     options.

   * `--character-sets-dir=NAME'

     Options for character-sets-dir

     *Command-Line        `--character-sets-dir=path'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `file           
                          name'           
     *Default*            `'              

     Tells the program where to find character set information.

   * `--ndb-connectstring=CONNECT_STRING',
     `--connect-string=CONNECT_STRING', `-c CONNECT_STRING'

     Options for ndb-connectstring

     *Command-Line        `--ndb-connectstring=connectstring'        
     Format*                              
                          `--connect-string=connectstring'        
                          `-c'            
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `localhost:1186'        

     This option takes a MySQL Cluster connection string that specifies
     the management server for the application to connect to, as shown
     here:


          shell> ndbd --ndb-connectstring="nodeid=2;host=ndb_mgmd.mysql.com:1186"

     For more information, see *Note mysql-cluster-connection-strings::.

   * `--core-file'

     Options for core-file

     *Command-Line        `--core-file'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     Write a core file if the program dies. The name and location of
     the core file are system-dependent. (For MySQL Cluster programs
     nodes running on Linux, the default location is the program's
     working directory--for a data node, this is the node's `DataDir'.)
     For some systems, there may be restrictions or limitations; for
     example, it might be necessary to execute `ulimit -c unlimited'
     before starting the server. Consult your system documentation for
     detailed information.

     If MySQL Cluster was built using the `--debug' option for
     `configure', then `--core-file' is enabled by default. For regular
     builds, `--core-file' is disabled by default.

   * `--debug[=OPTIONS]'

     Options for debug

     *Command-Line        `--debug=options'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `d:t:O,/tmp/ndb_restore.trace'        

     This option can be used only for versions compiled with debugging
     enabled. It is used to enable output from debug calls in the same
     manner as for the *Note `mysqld': mysqld. process.

   * `--ndb-mgmd-host=HOST[:PORT]'

     Options for ndb-mgmd-host

     *Command-Line        `--ndb-mgmd-host=host[:port]'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `string'        
     *Default*            `localhost:1186'        

     Can be used to set the host and port number of a single management
     server for the program to connect to. If the program requires node
     IDs or references to multiple management servers (or both) in its
     connection information, use the `--ndb-connectstring' option
     instead.

   * `--ndb-nodeid=#'

     Options for ndb-nodeid

     *Command-Line        `--ndb-nodeid=#'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `numeric'        
     *Default*            `0'             

     Sets this node's MySQL Cluster node ID. _The range of permitted
     values depends on the node's type (data, management, or API) and
     the MySQL Cluster software version_. See *Note
     mysql-cluster-limitations-limits::, for more information.

   * `--ndb-optimized-node-selection'

     Options for ndb-optimized-node-selection

     *Command-Line        `--ndb-optimized-node-selection'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `TRUE'          

     Optimize selection of nodes for transactions. Enabled by default.

   * `--version', `-V'

     Options for version

     *Command-Line        `--version'        
     Format*                              
                          `-V'            

     Prints the MySQL Cluster version number of the executable.  The
     version number is relevant because not all versions can be used
     together, and the MySQL Cluster startup process verifies that the
     versions of the binaries being used can co-exist in the same
     cluster. This is also important when performing an online
     (rolling) software upgrade or downgrade of MySQL Cluster.

     See *Note mysql-cluster-rolling-restart::), for more information.

   * `--ndb-shm'

     Options for ndb-shm

     *Removed*            5.1.47-ndb-7.1.5        
     *Command-Line        `--ndb-shm'        
     Format*                              
                          *Permitted        
                          Values*         
     *Type*               `boolean'        
     *Default*            `FALSE'         

     In older versions of MySQL Cluster, this experimental option
     allowed the application to use shared memory for optimization when
     available. `--ndb-shm' was removed from all MySQL Cluster programs
     beginning with MySQL Cluster NDB 7.0.16 and MySQL Cluster 7.1.5.


File: manual.info,  Node: mysql-cluster-management,  Next: mysql-cluster-replication,  Prev: mysql-cluster-programs,  Up: mysql-cluster

17.5 Management of MySQL Cluster
================================

* Menu:

* mysql-cluster-start-phases::   Summary of MySQL Cluster Start Phases
* mysql-cluster-mgm-client-commands::  Commands in the MySQL Cluster Management Client
* mysql-cluster-backup::         Online Backup of MySQL Cluster
* mysql-cluster-mysqld::         MySQL Server Usage for MySQL Cluster
* mysql-cluster-rolling-restart::  Performing a Rolling Restart of a MySQL Cluster
* mysql-cluster-event-reports::  Event Reports Generated in MySQL Cluster
* mysql-cluster-logs-ndb-messages::  MySQL Cluster Log Messages
* mysql-cluster-single-user-mode::  MySQL Cluster Single User Mode
* mysql-cluster-sql-statements::  Quick Reference: MySQL Cluster SQL Statements
* mysql-cluster-ndbinfo::        The ndbinfo MySQL Cluster Information Database
* mysql-cluster-security::       MySQL Cluster Security Issues
* mysql-cluster-disk-data::      MySQL Cluster Disk Data Tables
* mysql-cluster-online-add-node::  Adding MySQL Cluster Data Nodes Online
* mysql-cluster-privilege-distribution::  Distributed MySQL Privileges for MySQL Cluster
* mysql-cluster-ndb-api-statistics::  NDB API Statistics Counters and Variables

Managing a MySQL Cluster involves a number of tasks, the first of which
is to configure and start MySQL Cluster. This is covered in *Note
mysql-cluster-configuration::, and *Note mysql-cluster-programs::.

The next few sections cover the management of a running MySQL Cluster.

For information about security issues relating to management and
deployment of a MySQL Cluster, see *Note mysql-cluster-security::.

There are essentially two methods of actively managing a running MySQL
Cluster. The first of these is through the use of commands entered into
the management client whereby cluster status can be checked, log levels
changed, backups started and stopped, and nodes stopped and started.
The second method involves studying the contents of the cluster log
`ndb_NODE_ID_cluster.log'; this is usually found in the management
server's `DataDir' directory, but this location can be overridden using
the `LogDestination' option.  (Recall that NODE_ID represents the
unique identifier of the node whose activity is being logged.) The
cluster log contains event reports generated by *Note `ndbd':
mysql-cluster-programs-ndbd. It is also possible to send cluster log
entries to a Unix system log.

Some aspects of the cluster's operation can be also be monitored from
an SQL node using the *Note `SHOW ENGINE NDB STATUS': show-engine.
statement.

In MySQL Cluster NDB 7.1.1 and later, detailed information about
cluster operations is available in real time through an SQL interface
using the *Note `ndbinfo': mysql-cluster-ndbinfo.  database. For more
information, see *Note mysql-cluster-ndbinfo::.

Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB 7.1.11,
NDB statistics counters provide improved monitoring using the *Note
`mysql': mysql. client. These counters, implemented in the NDB kernel,
relate to operations performed by or affecting `Ndb'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects, such as
starting, closing, and aborting transactions; primary key and unique key
operations; table, range, and pruned scans; blocked threads waiting for
various operations to complete; and data and events sent and received
by MySQL Cluster. The counters are incremented by the NDB kernel
whenever NDB API calls are made or data is sent to or received by the
data nodes.

*Note `mysqld': mysqld. exposes the NDB API statistics counters as
system status variables, which can be identified from the prefix common
to all of their names (`Ndb_api_'). The values of these variables can
be read in the *Note `mysql': mysql. client from the output of a *Note
`SHOW STATUS': show-status. statement, or by querying either the *Note
`SESSION_STATUS': status-table. table or the *Note `GLOBAL_STATUS':
status-table.  table (in the `INFORMATION_SCHEMA' database). By
comparing the values of the status variables before and after the
execution of an SQL statement that acts on *Note `NDB': mysql-cluster.
tables, you can observe the actions taken on the NDB API level that
correspond to this statement, which can be beneficial for monitoring
and performance tuning of MySQL Cluster.

MySQL Enterprise Monitor can also be used to monitor MySQL Servers that
are part of a MySQL Cluster deployment. MySQL Enterprise Monitor 2.3,
added a MySQL Cluster advisor, including a set of graphs providing
information on MySQL Cluster resources, and defining rules for alerts
on key information from data nodes such as `DataMemory' usage. This
information is made available to MySQL Enterprise Monitor 2.3 or later
by any MySQL Server which is connected to the MySQL Cluster, using
*Note `ndbinfo': mysql-cluster-ndbinfo. The advisor could be run
against a single MySQL Server in the Cluster, or against a pair in
order to provide a higher level of availability for the monitoring
service. For more information, see the `MySQL Enterprise Monitor 2.3
Manual' (http://dev.mysql.com/doc/mysql-monitor/2.3/en/index.html).

MySQL Cluster Manager provides an advanced command-line interface that
simplifies many otherwise complex MySQL Cluster management tasks, such
as starting, stopping, or restarting a MySQL Cluster with a large
number of nodes. The MySQL Cluster Manager client also supports
commands for getting and setting the values of most node configuration
parameters as well as *Note `mysqld': mysqld. server options and
variables relating to MySQL Cluster. MySQL Cluster Manager 1.1 provides
support for adding data nodes online. See the `MySQL Cluster Manager
1.1 User Manual'
(http://dev.mysql.com/doc/mysql-cluster-manager/1.1/en/), for more
information.


File: manual.info,  Node: mysql-cluster-start-phases,  Next: mysql-cluster-mgm-client-commands,  Prev: mysql-cluster-management,  Up: mysql-cluster-management

17.5.1 Summary of MySQL Cluster Start Phases
--------------------------------------------

This section provides a simplified outline of the steps involved when
MySQL Cluster data nodes are started. More complete information can be
found in MySQL Cluster Start Phases
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-start-phases.html),
in the ``NDB' Internals Guide'.

These phases are the same as those reported in the output from the
`NODE_ID STATUS' command in the management client (see *Note
mysql-cluster-mgm-client-commands::). In MySQL Cluster NDB 7.1.1 and
later, these start phases are also reported in the `start_phase' column
of the *Note `ndbinfo.nodes': mysql-cluster-ndbinfo-nodes. table.

Start types

There are several different startup types and modes, as shown in the
following list:

   * Initial start

     The cluster starts with a clean file system on all data nodes.
     This occurs either when the cluster started for the very first
     time, or when all data nodes are restarted using the `--initial'
     option.

     *Note*:

     Disk Data files are not removed when restarting a node using
     `--initial'.

   * System restart

     The cluster starts and reads data stored in the data nodes.  This
     occurs when the cluster has been shut down after having been in
     use, when it is desired for the cluster to resume operations from
     the point where it left off.

   * Node restart

     This is the online restart of a cluster node while the cluster
     itself is running.

   * Initial node restart

     This is the same as a node restart, except that the node is
     reinitialized and started with a clean file system.

Setup and initialization (phase -1)

Prior to startup, each data node (*Note `ndbd':
mysql-cluster-programs-ndbd.  process) must be initialized.
Initialization consists of the following steps:

  1. Obtain a node ID

  2. Fetch configuration data

  3. Allocate ports to be used for inter-node communications

  4. Allocate memory according to settings obtained from the
     configuration file

When a data node or SQL node first connects to the management node, it
reserves a cluster node ID. To make sure that no other node allocates
the same node ID, this ID is retained until the node has managed to
connect to the cluster and at least one *Note `ndbd':
mysql-cluster-programs-ndbd. reports that this node is connected. This
retention of the node ID is guarded by the connection between the node
in question and *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.

Normally, in the event of a problem with the node, the node disconnects
from the management server, the socket used for the connection is
closed, and the reserved node ID is freed. However, if a node is
disconnected abruptly--for example, due to a hardware failure in one of
the cluster hosts, or because of network issues--the normal closing of
the socket by the operating system may not take place. In this case,
the node ID continues to be reserved and not released until a TCP
timeout occurs 10 or so minutes later.

To take care of this problem, you can use `PURGE STALE SESSIONS'.
Running this statement forces all reserved node IDs to be checked; any
that are not being used by nodes actually connected to the cluster are
then freed.

Beginning with MySQL 5.1.11, timeout handling of node ID assignments is
implemented. This performs the ID usage checks automatically after
approximately 20 seconds, so that `PURGE STALE SESSIONS' should no
longer be necessary in a normal Cluster start.

After each data node has been initialized, the cluster startup process
can proceed. The stages which the cluster goes through during this
process are listed here:

   * Phase 0

     The `NDBFS' and `NDBCNTR' blocks start (see `NDB' Kernel Blocks
     (http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks.html)).
     Data node file systems are cleared on those data nodes that were
     started with `--initial' option.

   * Phase 1

     In this stage, all remaining *Note `NDB': mysql-cluster. kernel
     blocks are started.  MySQL Cluster connections are set up,
     inter-block communications are established, and heartbeats are
     started.  In the case of a node restart, API node connections are
     also checked.

     *Note*:

     When one or more nodes hang in Phase 1 while the remaining node or
     nodes hang in Phase 2, this often indicates network problems. One
     possible cause of such issues is one or more cluster hosts having
     multiple network interfaces. Another common source of problems
     causing this condition is the blocking of TCP/IP ports needed for
     communications between cluster nodes. In the latter case, this is
     often due to a misconfigured firewall.

   * Phase 2

     The `NDBCNTR' kernel block checks the states of all existing
     nodes. The master node is chosen, and the cluster schema file is
     initialized.

   * Phase 3

     The `DBLQH' and `DBTC' kernel blocks set up communications between
     them. The startup type is determined; if this is a restart, the
     `DBDIH' block obtains permission to perform the restart.

   * Phase 4

     For an initial start or initial node restart, the redo log files
     are created. The number of these files is equal to
     `NoOfFragmentLogFiles'.

     For a system restart:

        * Read schema or schemas.

        * Read data from the local checkpoint.

        * Apply all redo information until the latest restorable global
          checkpoint has been reached.

     For a node restart, find the tail of the redo log.

   * Phase 5

     Most of the database-related portion of a data node start is
     performed during this phase. For an initial start or system
     restart, a local checkpoint is executed, followed by a global
     checkpoint. Periodic checks of memory usage begin during this
     phase, and any required node takeovers are performed.

   * Phase 6

     In this phase, node groups are defined and set up.

   * Phase 7

     The arbitrator node is selected and begins to function. The next
     backup ID is set, as is the backup disk write speed.  Nodes
     reaching this start phase are marked as `Started'. It is now
     possible for API nodes (including SQL nodes) to connect to the
     cluster.

   * Phase 8

     If this is a system restart, all indexes are rebuilt (by `DBDIH').

   * Phase 9

     The node internal startup variables are reset.

   * Phase 100 (OBSOLETE)

     Formerly, it was at this point during a node restart or initial
     node restart that API nodes could connect to the node and begin to
     receive events. Currently, this phase is empty.

   * Phase 101

     At this point in a node restart or initial node restart, event
     delivery is handed over to the node joining the cluster. The
     newly-joined node takes over responsibility for delivering its
     primary data to subscribers. This phase is also referred to as
     _`SUMA' handover phase_.

After this process is completed for an initial start or system restart,
transaction handling is enabled. For a node restart or initial node
restart, completion of the startup process means that the node may now
act as a transaction coordinator.


File: manual.info,  Node: mysql-cluster-mgm-client-commands,  Next: mysql-cluster-backup,  Prev: mysql-cluster-start-phases,  Up: mysql-cluster-management

17.5.2 Commands in the MySQL Cluster Management Client
------------------------------------------------------

In addition to the central configuration file, a cluster may also be
controlled through a command-line interface available through the
management client *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. This
is the primary administrative interface to a running cluster.

Commands for the event logs are given in *Note
mysql-cluster-event-reports::; commands for creating backups and
restoring from them are provided in *Note mysql-cluster-backup::.

Using ndb_mgm with MySQL Cluster Manager

MySQL Cluster Manager handles starting and stopping processes and
tracks their states internally, so it is not necessary to use *Note
`ndb_mgm': mysql-cluster-programs-ndb-mgm. for these tasks for a MySQL
Cluster that is under MySQL Cluster Manager control. it is recommended
_not_ to use the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.
command-line client that comes with the MySQL Cluster distribution to
perform operations that involve starting or stopping nodes. These
include but are not limited to the `START', `STOP', `RESTART', and
`SHUTDOWN' commands. For more information, see MySQL Cluster Manager
Process Commands
(http://dev.mysql.com/doc/mysql-cluster-manager/1.3/en/mcm-process-commands.html).

The management client has the following basic commands. In the listing
that follows, NODE_ID denotes either a database node ID or the keyword
`ALL', which indicates that the command should be applied to all of the
cluster's data nodes.

   * `HELP'

     Displays information on all available commands.

   * `SHOW'

     Displays information on the cluster's status. Possible node status
     values include `UNKNOWN', `NO_CONTACT', `NOT_STARTED', `STARTING',
     `STARTED', `SHUTTING_DOWN', and `RESTARTING'.

     Beginning with MySQL Cluster NDB 6.2.8 and MySQL Cluster NDB
     6.3.6, the output from this command indicates when the cluster is
     in single user mode (status `SINGLE USER MODE').

     Prior to MySQL Cluster NDB 7.0.26 and MySQL Cluster NDB 7.1.5, in
     a cluster having multiple management nodes, this command displayed
     information only for data nodes that were actually connected to
     the current management server; in addition, management servers
     could not find each other until all nodes had been started.
     Beginning with these versions, such issues are fixed (see Bug
     #12352191), and management nodes can be additionally be reported
     with status `RESUME' or `CONNECTED'.

   * `NODE_ID START'

     Brings online the data node identified by NODE_ID (or all data
     nodes).

     `ALL START' works on all data nodes only, and does not affect
     management nodes.

     *Important*:

     To use this command to bring a data node online, the data node
     must have been started using *Note `ndbd `--nostart'':
     mysql-cluster-programs-ndbd. or *Note `ndbd `-n'':
     mysql-cluster-programs-ndbd.

   * `NODE_ID STOP [-a] [-f]'

     Stops the data or management node identified by NODE_ID. Note that
     `ALL STOP' works to stop all data nodes only, and does not affect
     management nodes.

     A node affected by this command disconnects from the cluster, and
     its associated *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd. process terminates.

     The `-a' option causes the node to be stopped immediately, without
     waiting for the completion of any pending transactions.

     Normally, `STOP' fails if the result would cause an incomplete
     cluster. The `-f' option, added in MySQL Cluster NDB 7.0.19 and
     MySQL Cluster NDB 7.1.8, forces the node to shut down without
     checking for this. If this option is used and the result is an
     incomplete cluster, the cluster immediately shuts down.

     *Warning*:

     Use of the `-a' option also disables the safety check otherwise
     performed when `STOP' is invoked to insure that stopping the node
     does not cause an incomplete cluster. In other words, you should
     exercise extreme care when using the `-a' option with the `STOP'
     command, due to the fact that this option makes it possible for
     the cluster to undergo a forced shutdown because it no longer has
     a complete copy of all data stored in *Note `NDB': mysql-cluster.

   * `NODE_ID RESTART [-n] [-i] [-a] [-f]'

     Restarts the data node identified by NODE_ID (or all data nodes).

     Using the `-i' option with `RESTART' causes the data node to
     perform an initial restart; that is, the node's file system is
     deleted and recreated. The effect is the same as that obtained from
     stopping the data node process and then starting it again using
     *Note `ndbd `--initial'': mysql-cluster-programs-ndbd. from the
     system shell. Note that backup files and Disk Data files are not
     removed when this option is used.

     Using the `-n' option causes the data node process to be
     restarted, but the data node is not actually brought online until
     the appropriate `START' command is issued. The effect of this
     option is the same as that obtained from stopping the data node
     and then starting it again using *Note `ndbd `--nostart'':
     mysql-cluster-programs-ndbd. or *Note `ndbd `-n'':
     mysql-cluster-programs-ndbd. from the system shell.

     Using the `-a' causes all current transactions relying on this
     node to be aborted. No GCP check is done when the node rejoins the
     cluster.

     Normally, `RESTART' fails if taking the node offline would result
     in an incomplete cluster. The `-f' option, added in MySQL Cluster
     NDB 7.0.19 and MySQL Cluster NDB 7.1.8, forces the node to restart
     without checking for this. If this option is used and the result
     is an incomplete cluster, the entire cluster is restarted.

   * `NODE_ID STATUS'

     Displays status information for the data node identified by
     NODE_ID (or for all data nodes).

     Beginning with MySQL Cluster NDB 6.2.8 and MySQL Cluster NDB
     6.3.6, the output from this command indicates when the cluster is
     in single user mode.

   * `NODE_ID REPORT REPORT-TYPE'

     Displays a report of type REPORT-TYPE for the data node identified
     by NODE_ID, or for all data nodes using `ALL'.

     Currently, there are two accepted values for REPORT-TYPE:

        * `BackupStatus' provides a status report on a cluster backup
          in progress

        * `MemoryUsage' displays how much data memory and index memory
          is being used by each data node as shown in this example:


               ndb_mgm> ALL REPORT MEMORY

               Node 1: Data usage is 5%(177 32K pages of total 3200)
               Node 1: Index usage is 0%(108 8K pages of total 12832)
               Node 2: Data usage is 5%(177 32K pages of total 3200)
               Node 2: Index usage is 0%(108 8K pages of total 12832)

          In MySQL Cluster NDB 7.1.1 and later, this information is
          also available from the *Note `ndbinfo.memoryusage':
          mysql-cluster-ndbinfo-memoryusage.  table.

     REPORT-TYPE is case-insensitive and `fuzzy'; for `MemoryUsage', you
     can use `MEMORY' (as shown in the prior example), `memory', or
     even simply `MEM' (or `mem'). You can abbreviate `BackupStatus' in
     a similar fashion.

     Prior to MySQL Cluster NDB 7.0.37 and MySQL Cluster NDB 7.1.26,
     `ALL REPORT BackupStatus' did not work correctly with
     multi-threaded data nodes. (Bug #15908907)

     The `REPORT' command was introduced in MySQL Cluster NDB 6.2.3 and
     MySQL Cluster NDB 6.3.0.

   * `ENTER SINGLE USER MODE NODE_ID'

     Enters single user mode, whereby only the MySQL server identified
     by the node ID NODE_ID is permitted to access the database.

     Currently, it is not possible for data nodes to join a MySQL
     Cluster while it is running in single user mode. (Bug #20395)

   * `EXIT SINGLE USER MODE'

     Exits single user mode, enabling all SQL nodes (that is, all
     running *Note `mysqld': mysqld. processes) to access the database.

     *Note*:

     It is possible to use `EXIT SINGLE USER MODE' even when not in
     single user mode, although the command has no effect in this case.

   * `QUIT', `EXIT'

     Terminates the management client.

     This command does not affect any nodes connected to the cluster.

   * `SHUTDOWN'

     Shuts down all cluster data nodes and management nodes. To exit
     the management client after this has been done, use `EXIT' or
     `QUIT'.

     This command does _not_ shut down any SQL nodes or API nodes that
     are connected to the cluster.

   * `CREATE NODEGROUP NODEID[, NODEID, ...]'

     Creates a new MySQL Cluster node group and causes data nodes to
     join it.

     This command is used after adding new data nodes online to a MySQL
     Cluster, and causes them to join a new node group and thus to
     begin participating fully in the cluster. The command takes as its
     sole parameter a comma-separated list of node IDs--these are the
     IDs of the nodes just added and started that are to join the new
     node group. The number of nodes must be the same as the number of
     nodes in each node group that is already part of the cluster (each
     MySQL Cluster node group must have the same number of nodes). In
     other words, if the MySQL Cluster has 2 node groups of 2 data nodes
     each, then the new node group must also have 2 data nodes.

     The node group ID of the new node group created by this command is
     determined automatically, and always the next highest unused node
     group ID in the cluster; it is not possible to set it manually.

     This command was introduced in MySQL Cluster NDB 6.4.0. For more
     information, see *Note mysql-cluster-online-add-node::.

   * `DROP NODEGROUP NODEGROUP_ID'

     Drops the MySQL Cluster node group with the given NODEGROUP_ID.

     This command can be used to drop a node group from a MySQL
     Cluster. `DROP NODEGROUP' takes as its sole argument the node
     group ID of the node group to be dropped.

     `DROP NODEGROUP' acts only to remove the data nodes in the
     effected node group from that node group. It does not stop data
     nodes, assign them to a different node group, or remove them from
     the cluster's configuration. A data node that does not belong to a
     node group is indicated in the output of the management client
     `SHOW' command with `no nodegroup' in place of the node group ID,
     like this (indicated using bold text):


          id=3    @10.100.2.67  (5.1.73-ndb-7.1.34, *no nodegroup*)

     Prior to MySQL Cluster NDB 7.0.4, the `SHOW' output was not
     updated correctly following `DROP NODEGROUP'.  (Bug #43413)

     `DROP NODEGROUP' works only when all data nodes in the node group
     to be dropped are completely empty of any table data and table
     definitions. Since there is currently no way using *Note
     `ndb_mgm': mysql-cluster-programs-ndb-mgm. or the *Note `mysql':
     mysql. client to remove all data from a specific data node or node
     group, this means that the command succeeds only in the two
     following cases:

       1. After issuing `CREATE NODEGROUP' in the *Note `ndb_mgm':
          mysql-cluster-programs-ndb-mgm. client, but before issuing any
          *Note `ALTER ONLINE TABLE ... REORGANIZE PARTITION':
          alter-table. statements in the *Note `mysql': mysql. client.

       2. After dropping all *Note `NDBCLUSTER': mysql-cluster.  tables
          using *Note `DROP TABLE': drop-table.

          *Note `TRUNCATE TABLE': truncate-table. does not work for
          this purpose because this removes only the table data; the
          data nodes continue to store an *Note `NDBCLUSTER':
          mysql-cluster. table's definition until a *Note `DROP TABLE':
          drop-table. statement is issued that causes the table
          metadata to be dropped.

     `DROP NODEGROUP' was introduced in MySQL Cluster NDB 6.4.0. For
     more information, see *Note mysql-cluster-online-add-node::.


File: manual.info,  Node: mysql-cluster-backup,  Next: mysql-cluster-mysqld,  Prev: mysql-cluster-mgm-client-commands,  Up: mysql-cluster-management

17.5.3 Online Backup of MySQL Cluster
-------------------------------------

* Menu:

* mysql-cluster-backup-concepts::  MySQL Cluster Backup Concepts
* mysql-cluster-backup-using-management-client::  Using The MySQL Cluster Management Client to Create a Backup
* mysql-cluster-backup-configuration::  Configuration for MySQL Cluster Backups
* mysql-cluster-backup-troubleshooting::  MySQL Cluster Backup Troubleshooting

The next few sections describe how to prepare for and then to create a
MySQL Cluster backup using the functionality for this purpose found in
the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. management client.
To distinguish this type of backup from a backup made using *Note
`mysqldump': mysqldump, we sometimes refer to it as a `native' MySQL
Cluster backup. (For information about the creation of backups with
*Note `mysqldump': mysqldump, see *Note mysqldump::.) Restoration of
MySQL Cluster backups is done using the *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. utility provided with the MySQL
Cluster distribution; for information about *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. and its use in restoring MySQL
Cluster backups, see *Note mysql-cluster-programs-ndb-restore::.


File: manual.info,  Node: mysql-cluster-backup-concepts,  Next: mysql-cluster-backup-using-management-client,  Prev: mysql-cluster-backup,  Up: mysql-cluster-backup

17.5.3.1 MySQL Cluster Backup Concepts
......................................

A backup is a snapshot of the database at a given time. The backup
consists of three main parts:

   * Metadata

     The names and definitions of all database tables

   * Table records

     The data actually stored in the database tables at the time that
     the backup was made

   * Transaction log

     A sequential record telling how and when data was stored in the
     database

Each of these parts is saved on all nodes participating in the backup.
During backup, each node saves these three parts into three files on
disk:

   * `BACKUP-BACKUP_ID.NODE_ID.ctl'

     A control file containing control information and metadata.  Each
     node saves the same table definitions (for all tables in the
     cluster) to its own version of this file.

   * `BACKUP-BACKUP_ID-0.NODE_ID.data'

     A data file containing the table records, which are saved on a
     per-fragment basis. That is, different nodes save different
     fragments during the backup. The file saved by each node starts
     with a header that states the tables to which the records belong.
     Following the list of records there is a footer containing a
     checksum for all records.

   * `BACKUP-BACKUP_ID.NODE_ID.log'

     A log file containing records of committed transactions.  Only
     transactions on tables stored in the backup are stored in the log.
     Nodes involved in the backup save different records because
     different nodes host different database fragments.

In the listing above, BACKUP_ID stands for the backup identifier and
NODE_ID is the unique identifier for the node creating the file.


File: manual.info,  Node: mysql-cluster-backup-using-management-client,  Next: mysql-cluster-backup-configuration,  Prev: mysql-cluster-backup-concepts,  Up: mysql-cluster-backup

17.5.3.2 Using The MySQL Cluster Management Client to Create a Backup
.....................................................................

Before starting a backup, make sure that the cluster is properly
configured for performing one. (See *Note
mysql-cluster-backup-configuration::.)

The `START BACKUP' command is used to create a backup:


     START BACKUP [BACKUP_ID] [WAIT_OPTION] [SNAPSHOT_OPTION]

     WAIT_OPTION:
     WAIT {STARTED | COMPLETED} | NOWAIT

     SNAPSHOT_OPTION:
     SNAPSHOTSTART | SNAPSHOTEND

Successive backups are automatically identified sequentially, so the
BACKUP_ID, an integer greater than or equal to 1, is optional; if it is
omitted, the next available value is used. If an existing BACKUP_ID
value is used, the backup fails with the error `Backup failed: file
already exists'. If used, the BACKUP_ID must follow `START BACKUP'
immediately, before any other options are used.

Prior to MySQL Cluster NDB 6.2.17, 6.3.23, and 6.4.3, backup IDs
greater than 2147483648 (2^31) were not supported correctly. (Bug
#43042) Beginning with these versions, the maximum possible backup ID
is 4294967296 (2^32).

*Note*:

Prior to MySQL Cluster NDB 7.0.5, when starting a backup using *Note
`ndb_mgm -e "START BACKUP"': mysql-cluster-programs-ndb-mgm, the
BACKUP_ID was required. (Bug #31754)

The WAIT_OPTION can be used to determine when control is returned to
the management client after a `START BACKUP' command is issued, as
shown in the following list:

   * If `NOWAIT' is specified, the management client displays a prompt
     immediately, as seen here:


          ndb_mgm> START BACKUP NOWAIT
          ndb_mgm>

     In this case, the management client can be used even while it
     prints progress information from the backup process.

   * With `WAIT STARTED' the management client waits until the backup
     has started before returning control to the user, as shown here:


          ndb_mgm> START BACKUP WAIT STARTED
          Waiting for started, this may take several minutes
          Node 2: Backup 3 started from node 1
          ndb_mgm>

   * WAIT COMPLETED causes the management client to wait until the
     backup process is complete before returning control to the user.

`WAIT COMPLETED' is the default.

Beginning with MySQL Cluster NDB 6.4.0, a SNAPSHOT_OPTION can be used to
determine whether the backup matches the state of the cluster when
`START BACKUP' was issued, or when it was completed. `SNAPSHOTSTART'
causes the backup to match the state of the cluster when the backup
began; `SNAPSHOTEND' causes the backup to reflect the state of the
cluster when the backup was finished.  `SNAPSHOTEND' is the default,
and matches the behavior found in previous MySQL Cluster releases.

*Note*:

If you use the `SNAPSHOTSTART' option with `START BACKUP', and the
`CompressedBackup' parameter is enabled, only the data and control
files are compressed--the log file is not compressed.

If both a WAIT_OPTION and a SNAPSHOT_OPTION are used, they may be
specified in either order. For example, all of the following commands
are valid, assuming that there is no existing backup having 4 as its ID:


     START BACKUP WAIT STARTED SNAPSHOTSTART
     START BACKUP SNAPSHOTSTART WAIT STARTED
     START BACKUP 4 WAIT COMPLETED SNAPSHOTSTART
     START BACKUP SNAPSHOTEND WAIT COMPLETED
     START BACKUP 4 NOWAIT SNAPSHOTSTART

The procedure for creating a backup consists of the following steps:

  1. Start the management client (*Note `ndb_mgm':
     mysql-cluster-programs-ndb-mgm.), if it not running already.

  2. Execute the START BACKUP command.  This produces several lines of
     output indicating the progress of the backup, as shown here:


          ndb_mgm> START BACKUP
          Waiting for completed, this may take several minutes
          Node 2: Backup 1 started from node 1
          Node 2: Backup 1 started from node 1 completed
           StartGCP: 177 StopGCP: 180
           #Records: 7362 #LogRecords: 0
           Data: 453648 bytes Log: 0 bytes
          ndb_mgm>

  3. When the backup has started the management client displays this
     message:


          Backup BACKUP_ID started from node NODE_ID

     BACKUP_ID is the unique identifier for this particular backup.
     This identifier is saved in the cluster log, if it has not been
     configured otherwise. NODE_ID is the identifier of the management
     server that is coordinating the backup with the data nodes. At
     this point in the backup process the cluster has received and
     processed the backup request. It does not mean that the backup has
     finished. An example of this statement is shown here:


          Node 2: Backup 1 started from node 1

  4. The management client indicates with a message like this one that
     the backup has started:


          Backup BACKUP_ID started from node NODE_ID completed

     As is the case for the notification that the backup has started,
     BACKUP_ID is the unique identifier for this particular backup, and
     NODE_ID is the node ID of the management server that is
     coordinating the backup with the data nodes. This output is
     accompanied by additional information including relevant global
     checkpoints, the number of records backed up, and the size of the
     data, as shown here:


          Node 2: Backup 1 started from node 1 completed
           StartGCP: 177 StopGCP: 180
           #Records: 7362 #LogRecords: 0
           Data: 453648 bytes Log: 0 bytes

It is also possible to perform a backup from the system shell by
invoking *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. with the `-e'
or `--execute' option, as shown in this example:


     shell> ndb_mgm -e "START BACKUP 6 WAIT COMPLETED SNAPSHOTSTART"

When using `START BACKUP' in this way, you must specify the backup ID.

Cluster backups are created by default in the `BACKUP' subdirectory of
the `DataDir' on each data node. This can be overridden for one or more
data nodes individually, or for all cluster data nodes in the
`config.ini' file using the `BackupDataDir' configuration parameter.
The backup files created for a backup with a given BACKUP_ID are stored
in a subdirectory named `BACKUP-BACKUP_ID' in the backup directory.

To abort a backup that is already in progress:

  1. Start the management client.

  2. Execute this command:


          ndb_mgm> ABORT BACKUP BACKUP_ID

     The number BACKUP_ID is the identifier of the backup that was
     included in the response of the management client when the backup
     was started (in the message `Backup BACKUP_ID started from node
     MANAGEMENT_NODE_ID').

  3. The management client will acknowledge the abort request with
     `Abort of backup BACKUP_ID ordered'.

     *Note*:

     At this point, the management client has not yet received a
     response from the cluster data nodes to this request, and the
     backup has not yet actually been aborted.

  4. After the backup has been aborted, the management client will
     report this fact in a manner similar to what is shown here:


          Node 1: Backup 3 started from 5 has been aborted.
            Error: 1321 - Backup aborted by user request: Permanent error: User defined error
          Node 3: Backup 3 started from 5 has been aborted.
            Error: 1323 - 1323: Permanent error: Internal error
          Node 2: Backup 3 started from 5 has been aborted.
            Error: 1323 - 1323: Permanent error: Internal error
          Node 4: Backup 3 started from 5 has been aborted.
            Error: 1323 - 1323: Permanent error: Internal error

     In this example, we have shown sample output for a cluster with 4
     data nodes, where the sequence number of the backup to be aborted
     is `3', and the management node to which the cluster management
     client is connected has the node ID `5'. The first node to complete
     its part in aborting the backup reports that the reason for the
     abort was due to a request by the user. (The remaining nodes
     report that the backup was aborted due to an unspecified internal
     error.)

     *Note*:

     There is no guarantee that the cluster nodes respond to an `ABORT
     BACKUP' command in any particular order.

     The `Backup BACKUP_ID started from node MANAGEMENT_NODE_ID has been
     aborted' messages mean that the backup has been terminated and
     that all files relating to this backup have been removed from the
     cluster file system.

It is also possible to abort a backup in progress from a system shell
using this command:


     shell> ndb_mgm -e "ABORT BACKUP BACKUP_ID"

*Note*:

If there is no backup having the ID BACKUP_ID running when an `ABORT
BACKUP' is issued, the management client makes no response, nor is it
indicated in the cluster log that an invalid abort command was sent.


File: manual.info,  Node: mysql-cluster-backup-configuration,  Next: mysql-cluster-backup-troubleshooting,  Prev: mysql-cluster-backup-using-management-client,  Up: mysql-cluster-backup

17.5.3.3 Configuration for MySQL Cluster Backups
................................................

Five configuration parameters are essential for backup:

   * `BackupDataBufferSize'

     The amount of memory used to buffer data before it is written to
     disk.

   * `BackupLogBufferSize'

     The amount of memory used to buffer log records before these are
     written to disk.

   * `BackupMemory'

     The total memory allocated in a data node for backups. This should
     be the sum of the memory allocated for the backup data buffer and
     the backup log buffer.

   * `BackupWriteSize'

     The default size of blocks written to disk. This applies for both
     the backup data buffer and the backup log buffer.

   * `BackupMaxWriteSize'

     The maximum size of blocks written to disk. This applies for both
     the backup data buffer and the backup log buffer.

More detailed information about these parameters can be found in Backup
Parameters.


File: manual.info,  Node: mysql-cluster-backup-troubleshooting,  Prev: mysql-cluster-backup-configuration,  Up: mysql-cluster-backup

17.5.3.4 MySQL Cluster Backup Troubleshooting
.............................................

If an error code is returned when issuing a backup request, the most
likely cause is insufficient memory or disk space. You should check
that there is enough memory allocated for the backup.

*Important*:

If you have set `BackupDataBufferSize' and `BackupLogBufferSize' and
their sum is greater than 4MB, then you must also set `BackupMemory' as
well.

You should also make sure that there is sufficient space on the hard
drive partition of the backup target.

*Note `NDB': mysql-cluster. does not support repeatable reads, which
can cause problems with the restoration process.  Although the backup
process is `hot', restoring a MySQL Cluster from backup is not a 100%
`hot' process. This is due to the fact that, for the duration of the
restore process, running transactions get nonrepeatable reads from the
restored data. This means that the state of the data is inconsistent
while the restore is in progress.


File: manual.info,  Node: mysql-cluster-mysqld,  Next: mysql-cluster-rolling-restart,  Prev: mysql-cluster-backup,  Up: mysql-cluster-management

17.5.4 MySQL Server Usage for MySQL Cluster
-------------------------------------------

*Note `mysqld': mysqld. is the traditional MySQL server process.  To be
used with MySQL Cluster, *Note `mysqld': mysqld. needs to be built with
support for the *Note `NDBCLUSTER': mysql-cluster. storage engine, as
it is in the precompiled binaries available from
`http://dev.mysql.com/downloads/'. If you build MySQL from source, you
must invoke `configure' with one of the options to enable *Note
`NDBCLUSTER': mysql-cluster.  storage engine support:

   * `--with-plugins=ndbcluster'

   * `--with-plugins=max'

   * `--with-plugins=max-no-innodb'

(`--with-ndbcluster' also works to enable *Note `NDBCLUSTER':
mysql-cluster. support, but is deprecated and so produces a `configure'
warning as of MySQL 5.1.9.)

For information about other MySQL server options and variables relevant
to MySQL Cluster in addition to those discussed in this section, see
*Note mysql-cluster-options-variables::.

If the *Note `mysqld': mysqld. binary has been built with Cluster
support, the *Note `NDBCLUSTER': mysql-cluster.  storage engine is
still disabled by default. You can use either of two possible options
to enable this engine:

   * Use `--ndbcluster' as a startup option on the command line when
     starting *Note `mysqld': mysqld.

   * Insert a line containing `ndbcluster' in the `[mysqld]' section of
     your `my.cnf' file.

An easy way to verify that your server is running with the *Note
`NDBCLUSTER': mysql-cluster. storage engine enabled is to issue the
*Note `SHOW ENGINES': show-engines. statement in the MySQL Monitor
(*Note `mysql': mysql.). You should see the value `YES' as the `Support'
value in the row for *Note `NDBCLUSTER': mysql-cluster. If you see `NO'
in this row or if there is no such row displayed in the output, you are
not running an *Note `NDB': mysql-cluster.-enabled version of MySQL. If
you see `DISABLED' in this row, you need to enable it in either one of
the two ways just described.

To read cluster configuration data, the MySQL server requires at a
minimum three pieces of information:

   * The MySQL server's own cluster node ID

   * The host name or IP address for the management server (MGM node)

   * The number of the TCP/IP port on which it can connect to the
     management server

Node IDs can be allocated dynamically, so it is not strictly necessary
to specify them explicitly.

The *Note `mysqld': mysqld. parameter `ndb-connectstring' is used to
specify the connection string either on the command line when starting
*Note `mysqld': mysqld. or in `my.cnf'. The connection string contains
the host name or IP address where the management server can be found,
as well as the TCP/IP port it uses.

In the following example, `ndb_mgmd.mysql.com' is the host where the
management server resides, and the management server listens for
cluster messages on port 1186:


     shell> mysqld --ndbcluster --ndb-connectstring=ndb_mgmd.mysql.com:1186

See *Note mysql-cluster-connection-strings::, for more information on
connection strings.

Given this information, the MySQL server will be a full participant in
the cluster. (We often refer to a *Note `mysqld': mysqld. process
running in this manner as an SQL node.) It will be fully aware of all
cluster data nodes as well as their status, and will establish
connections to all data nodes. In this case, it is able to use any data
node as a transaction coordinator and to read and update node data.

You can see in the *Note `mysql': mysql. client whether a MySQL server
is connected to the cluster using *Note `SHOW PROCESSLIST':
show-processlist. If the MySQL server is connected to the cluster, and
you have the `PROCESS' privilege, then the first row of the output is
as shown here:


     mysql> SHOW PROCESSLIST \G
     *************************** 1. row ***************************
          Id: 1
        User: system user
        Host:
          db:
     Command: Daemon
        Time: 1
       State: Waiting for event from ndbcluster
        Info: NULL

*Important*:

To participate in a MySQL Cluster, the *Note `mysqld': mysqld.  process
must be started with _both_ the options `--ndbcluster' and
`--ndb-connectstring' (or their equivalents in `my.cnf'). If *Note
`mysqld': mysqld. is started with only the `--ndbcluster' option, or if
it is unable to contact the cluster, it is not possible to work with
*Note `NDB': mysql-cluster. tables, _nor is it possible to create any
new tables regardless of storage engine_. The latter restriction is a
safety measure intended to prevent the creation of tables having the
same names as *Note `NDB': mysql-cluster. tables while the SQL node is
not connected to the cluster. If you wish to create tables using a
different storage engine while the *Note `mysqld': mysqld.  process is
not participating in a MySQL Cluster, you must restart the server
_without_ the `--ndbcluster' option.


File: manual.info,  Node: mysql-cluster-rolling-restart,  Next: mysql-cluster-event-reports,  Prev: mysql-cluster-mysqld,  Up: mysql-cluster-management

17.5.5 Performing a Rolling Restart of a MySQL Cluster
------------------------------------------------------

This section discusses how to perform a _rolling restart_ of a MySQL
Cluster installation, so called because it involves stopping and
starting (or restarting) each node in turn, so that the cluster itself
remains operational. This is often done as part of a _rolling upgrade_
or _rolling downgrade_, where high availability of the cluster is
mandatory and no downtime of the cluster as a whole is permissible.
Where we refer to upgrades, the information provided here also
generally applies to downgrades as well.

There are a number of reasons why a rolling restart might be desirable.
These are described in the next few paragraphs.

Configuration change

To make a change in the cluster's configuration, such as adding an SQL
node to the cluster, or setting a configuration parameter to a new
value.

MySQL Cluster software upgrade or downgrade

To upgrade the cluster to a newer version of the MySQL Cluster software
(or to downgrade it to an older version). This is usually referred to
as a `rolling upgrade' (or `rolling downgrade', when reverting to an
older version of MySQL Cluster).

Change on node host

To make changes in the hardware or operating system on which one or
more MySQL Cluster node processes are running.

System reset (cluster reset)

To reset the cluster because it has reached an undesirable state. In
such cases it is often desirable to reload the data and metadata of one
or more data nodes. This can be done in any of three ways:

   * Start each data node process (*Note `ndbd':
     mysql-cluster-programs-ndbd, or possibly *Note `ndbmtd':
     mysql-cluster-programs-ndbmtd. in MySQL Cluster NDB 7.0 and later)
     with the `--initial' option, which forces the data node to clear
     its file system and to reload all MySQL Cluster data and metadata
     from the other data nodes.

   * Create a backup using the *Note `ndb_mgm':
     mysql-cluster-programs-ndb-mgm. client `BACKUP' command prior to
     performing the restart. Following the upgrade, restore the node or
     nodes using *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore.

     See *Note mysql-cluster-backup::, and *Note
     mysql-cluster-programs-ndb-restore::, for more information.

   * Use *Note `mysqldump': mysqldump. to create a backup prior to the
     upgrade; afterward, restore the dump using *Note `LOAD DATA
     INFILE': load-data.

Resource Recovery

To free memory previously allocated to a table by successive *Note
`INSERT': insert. and *Note `DELETE': delete. operations, for re-use by
other MySQL Cluster tables.

The process for performing a rolling restart may be generalized as
follows:

  1. Stop all cluster management nodes (*Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd.  processes), reconfigure them,
     then restart them.

     (If there are multiple management servers and you are using MySQL
     Cluster NDB 7.0.8 or later, see *Note
     mysql-cluster-rolling-restart-multiple-ndb-mgmd::.)

  2. Stop, reconfigure, then restart each cluster data node (*Note
     `ndbd': mysql-cluster-programs-ndbd. process) in turn.

  3. Stop, reconfigure, then restart each cluster SQL node (*Note
     `mysqld': mysqld. process) in turn.

The specifics for implementing a given rolling upgrade depend upon the
changes being made. A more detailed view of the process is presented
here:

MySQL Cluster Rolling Restarts (By Type)

In the previous diagram, the *Stop* and *Start* steps indicate that the
process must be stopped completely using a shell command (such as *Note
`kill': kill. on most Unix systems) or the management client `STOP'
command, then started again from a system shell by invoking the *Note
`ndbd': mysql-cluster-programs-ndbd. or *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. executable as appropriate. On Windows
(MySQL Cluster NDB 7.1.3 and later), you can also use the system `NET
START' and `NET STOP' commands or the Windows Service Manager to start
and stop nodes which have been installed as Windows services (see *Note
mysql-cluster-install-windows-service::).

*Restart* indicates that the process may be restarted using the *Note
`ndb_mgm': mysql-cluster-programs-ndb-mgm.  management client `RESTART'
command (see *Note mysql-cluster-mgm-client-commands::).

Prior to MySQL Cluster NDB 6.3.29 and MySQL Cluster NDB 7.0.10

When performing an upgrade or downgrade of the cluster software, you
must upgrade or downgrade the management nodes first, then the data
nodes, and finally the SQL nodes. Doing so in any other order may leave
the cluster in an unusable state.

MySQL Cluster NDB 6.3.29 and later; MySQL Cluster NDB 7.0.10 and later

MySQL Cluster supports a more flexible order for upgrading the cluster
nodes. When upgrading a cluster running MySQL Cluster NDB 6.3.29 or
later, or a cluster that is running MySQL Cluster NDB 7.0.10 or later,
you may upgrade API nodes (including SQL nodes) before upgrading the
management nodes, data nodes, or both. In other words, you are
permitted to upgrade the API and SQL nodes in any order. This is
subject to the following provisions:

   * This functionality is intended for use as part of an online
     upgrade only. A mix of node binaries from different MySQL Cluster
     releases is neither intended nor supported for constant, long-term
     use in a production setting.

   * All management nodes must be upgraded before any data nodes are
     upgraded. This remains true regardless of the order in which you
     upgrade the cluster's API and SQL nodes.

   * For MySQL Cluster NDB 6.3, the ability to upgrade API nodes in any
     order relative to upgrading management nodes and data nodes is
     supported only for MySQL Cluster NDB 6.3.29 and later; for MySQL
     Cluster NDB 7.0, it supported only for MySQL Cluster NDB 7.0.10
     and later. This means that, if you are upgrading from a MySQL
     Cluster NDB 6.3 release to a MySQL Cluster NDB 7.0 release, the
     `old' *Note `NDB': mysql-cluster. engine version must be 6.3.29 or
     later, and the `new' *Note `NDB': mysql-cluster. engine version
     must be 7.0.10 or later.

   * When upgrading the cluster from a MySQL Cluster NDB 6.3 release to
     a MySQL Cluster NDB 7.0 release: Once you have started upgrading
     the API nodes, you should not perform DDL operations until all
     management nodes and data nodes have been upgraded. DML operations
     should be unaffected, and can continue while the upgrade is in
     progress.

     However, it is possible to perform DDL from an `old' (NDB 6.3
     version) API node as long as the master data node is also running
     the `old' version of MySQL Cluster. You should keep in mind that a
     data node restart could result in the master node running a `new'
     (NDB 7.0 version) binary while one or more data nodes are still
     using the `old' (NDB 6.3) version; in this situation, no DDL can
     be performed from _any_ API node, because the master data node is
     no longer using an NDB 6.3 binary, but the cluster still contains
     nodes which are not yet using NDB 7.0. For this reason, we
     recommend that you avoid performing DDL at any time while the
     upgrade is in progress.

   * Features specific to the `new' version must not be used until all
     management nodes and data nodes have been upgraded.

     This also applies to any MySQL Server version change that may
     apply, in addition to the NDB engine version change, so do not
     forget to take this into account when planning the upgrade.  (This
     is true for online upgrades of MySQL Cluster in general.)

See also Bug #48528 and Bug #49163.

Rolling restarts with multiple management servers (MySQL Cluster NDB
7.0.8 and later)

A change in MySQL Cluster NDB 7.0.8 in the way in which management
nodes obtain configuration data makes it necessary to alter the
procedure previously outlined, when performing a rolling restart of a
MySQL Cluster with multiple management nodes. (Previously, a management
node checked only its own configuration cache, but in MySQL Cluster NDB
7.0.8 and later, *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.
also checks to see if any other management node is running, and, if so,
tries to use that node's configuration data.) To keep this from
occurring, and to force *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd. to reread its configuration file,
perform the following steps:

  1. Stop all MySQL Cluster *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. processes.

  2. Update all `config.ini' files.

  3. Start a single *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.
     with `--reload', `--initial', or both options as desired.

  4. If you started the first *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. with the `--initial' option, you
     must also start any remaining *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. processes using `--initial'.

     Regardless of any other options used when starting the first *Note
     `ndb_mgmd': mysql-cluster-programs-ndb-mgmd, you should not start
     any remaining *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.
     processes after the first one using `--reload'.

  5. Complete the rolling restarts of the data nodes and API nodes as
     normal.

See also Bug #45495 and Bug #46488.

MySQL Cluster NDB 7.0.24 and later; MySQL Cluster NDB 7.1.13 and later

When performing a rolling restart to update the cluster's
configuration, you can use the `config_generation' column of the *Note
`ndbinfo.nodes': mysql-cluster-ndbinfo-nodes. table to keep track of
which data nodes have been successfully restarted with the new
configuration. See *Note mysql-cluster-ndbinfo-nodes::.


File: manual.info,  Node: mysql-cluster-event-reports,  Next: mysql-cluster-logs-ndb-messages,  Prev: mysql-cluster-rolling-restart,  Up: mysql-cluster-management

17.5.6 Event Reports Generated in MySQL Cluster
-----------------------------------------------

* Menu:

* mysql-cluster-logging-management-commands::  MySQL Cluster Logging Management Commands
* mysql-cluster-log-events::     MySQL Cluster Log Events
* mysql-cluster-log-statistics::  Using CLUSTERLOG STATISTICS in the MySQL Cluster Management Client

In this section, we discuss the types of event logs provided by MySQL
Cluster, and the types of events that are logged.

MySQL Cluster provides two types of event log:

   * The _cluster log_, which includes events generated by all cluster
     nodes. The cluster log is the log recommended for most uses
     because it provides logging information for an entire cluster in a
     single location.

     By default, the cluster log is saved to a file named
     `ndb_NODE_ID_cluster.log', (where NODE_ID is the node ID of the
     management server) in the same directory where the *Note
     `ndb_mgm': mysql-cluster-programs-ndb-mgm. binary resides.

     Cluster logging information can also be sent to `stdout' or a
     `syslog' facility in addition to or instead of being saved to a
     file, as determined by the values set for the `DataDir' and
     `LogDestination' configuration parameters. See *Note
     mysql-cluster-mgm-definition::, for more information about these
     parameters.

   * _Node logs_ are local to each node.

     Output generated by node event logging is written to the file
     `ndb_NODE_ID_out.log' (where NODE_ID is the node's node ID) in the
     node's `DataDir'. Node event logs are generated for both
     management nodes and data nodes.

     Node logs are intended to be used only during application
     development, or for debugging application code.

Both types of event logs can be set to log different subsets of events.

Each reportable event can be distinguished according to three different
criteria:

   * _Category_: This can be any one of the following values: `STARTUP',
     `SHUTDOWN', `STATISTICS', `CHECKPOINT', `NODERESTART',
     `CONNECTION', `ERROR', or `INFO'.

   * _Priority_: This is represented by one of the numbers from 1 to 15
     inclusive, where 1 indicates `most important' and 15 `least
     important.'

   * _Severity Level_: This can be any one of the following values:
     `ALERT', `CRITICAL', `ERROR', `WARNING', `INFO', or `DEBUG'.

Both the cluster log and the node log can be filtered on these
properties.

The format used in the cluster log is as shown here:


     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 1: Data usage is 2%(60 32K pages of total 2560)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 1: Index usage is 1%(24 8K pages of total 2336)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 1: Resource 0 min: 0 max: 639 curr: 0
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 2: Data usage is 2%(76 32K pages of total 2560)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 2: Index usage is 1%(24 8K pages of total 2336)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 2: Resource 0 min: 0 max: 639 curr: 0
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 3: Data usage is 2%(58 32K pages of total 2560)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 3: Index usage is 1%(25 8K pages of total 2336)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 3: Resource 0 min: 0 max: 639 curr: 0
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 4: Data usage is 2%(74 32K pages of total 2560)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 4: Index usage is 1%(25 8K pages of total 2336)
     2007-01-26 19:35:55 [MgmSrvr] INFO     -- Node 4: Resource 0 min: 0 max: 639 curr: 0
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 4: Node 9 Connected
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 1: Node 9 Connected
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 1: Node 9: API 5.1.73-ndb-7.1.34
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 2: Node 9 Connected
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 2: Node 9: API 5.1.73-ndb-7.1.34
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 3: Node 9 Connected
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 3: Node 9: API 5.1.73-ndb-7.1.34
     2007-01-26 19:39:42 [MgmSrvr] INFO     -- Node 4: Node 9: API 5.1.73-ndb-7.1.34
     2007-01-26 19:59:22 [MgmSrvr] ALERT    -- Node 2: Node 7 Disconnected
     2007-01-26 19:59:22 [MgmSrvr] ALERT    -- Node 2: Node 7 Disconnected

Each line in the cluster log contains the following information:

   * A timestamp in `YYYY-MM-DD HH:MM:SS' format.

   * The type of node which is performing the logging. In the cluster
     log, this is always `[MgmSrvr]'.

   * The severity of the event.

   * The ID of the node reporting the event.

   * A description of the event. The most common types of events to
     appear in the log are connections and disconnections between
     different nodes in the cluster, and when checkpoints occur. In
     some cases, the description may contain status information.


File: manual.info,  Node: mysql-cluster-logging-management-commands,  Next: mysql-cluster-log-events,  Prev: mysql-cluster-event-reports,  Up: mysql-cluster-event-reports

17.5.6.1 MySQL Cluster Logging Management Commands
..................................................

*Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. supports a number of
management commands related to the cluster log. In the listing that
follows, NODE_ID denotes either a database node ID or the keyword
`ALL', which indicates that the command should be applied to all of the
cluster's data nodes.

   * `CLUSTERLOG ON'

     Turns the cluster log on.

   * `CLUSTERLOG OFF'

     Turns the cluster log off.

   * `CLUSTERLOG INFO'

     Provides information about cluster log settings.

   * `NODE_ID CLUSTERLOG CATEGORY=THRESHOLD'

     Logs CATEGORY events with priority less than or equal to THRESHOLD
     in the cluster log.

   * `CLUSTERLOG FILTER SEVERITY_LEVEL'

     Toggles cluster logging of events of the specified SEVERITY_LEVEL.

The following table describes the default setting (for all data nodes)
of the cluster log category threshold. If an event has a priority with
a value lower than or equal to the priority threshold, it is reported
in the cluster log.

Note that events are reported per data node, and that the threshold can
be set to different values on different nodes.

This table lists cluster log categories and provides the default
threshold setting (for all data nodes).

Category               Default threshold (All data nodes)
`STARTUP'              *7*
`SHUTDOWN'             *7*
`STATISTICS'           *7*
`CHECKPOINT'           *7*
`NODERESTART'          *7*
`CONNECTION'           *7*
`ERROR'                *15*
`INFO'                 *7*

The `STATISTICS' category can provide a great deal of useful data. See
*Note mysql-cluster-log-statistics::, for more information.

Thresholds are used to filter events within each category. For example,
a `STARTUP' event with a priority of 3 is not logged unless the
threshold for `STARTUP' is set to 3 or higher. Only events with
priority 3 or lower are sent if the threshold is 3.

The following table shows the event severity levels.

*Note*:

These correspond to Unix `syslog' levels, except for `LOG_EMERG' and
`LOG_NOTICE', which are not used or mapped.

This table lists event severity level values along with the event
severity and a description.

Severity       Severity       Description
Level Value                   
*1*            `ALERT'        A condition that should be corrected
                              immediately, such as a corrupted system
                              database
*2*            `CRITICAL'     Critical conditions, such as device errors
                              or insufficient resources
*3*            `ERROR'        Conditions that should be corrected, such
                              as configuration errors
*4*            `WARNING'      Conditions that are not errors, but that
                              might require special handling
*5*            `INFO'         Informational messages
*6*            `DEBUG'        Debugging messages used for *Note
                              `NDBCLUSTER': mysql-cluster.  development

Event severity levels can be turned on or off (using `CLUSTERLOG
FILTER'--see above). If a severity level is turned on, then all events
with a priority less than or equal to the category thresholds are
logged. If the severity level is turned off then no events belonging to
that severity level are logged.

*Important*:

Cluster log levels are set on a per *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd, per subscriber basis. This means that,
in a MySQL Cluster with multiple management servers, using a
`CLUSTERLOG' command in an instance of *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. connected to one management server
affects only logs generated by that management server but not by any of
the others. This also means that, should one of the management servers
be restarted, only logs generated by that management server are
affected by the resetting of log levels caused by the restart.


File: manual.info,  Node: mysql-cluster-log-events,  Next: mysql-cluster-log-statistics,  Prev: mysql-cluster-logging-management-commands,  Up: mysql-cluster-event-reports

17.5.6.2 MySQL Cluster Log Events
.................................

An event report reported in the event logs has the following format:


     DATETIME [STRING] SEVERITY -- MESSAGE

For example:


     09:19:30 2005-07-24 [NDB] INFO -- Node 4 Start phase 4 completed

This section discusses all reportable events, ordered by category and
severity level within each category.

In the event descriptions, GCP and LCP mean `Global Checkpoint' and
`Local Checkpoint', respectively.

*CONNECTION Events*

These events are associated with connections between Cluster nodes.

This table lists events that are associated with connections between
cluster nodes. In order, the table shows the event, priority, severity
level, and provides a description.

Event                     PrioritySeverityDescription
                                  Level   
`Connected'               8       `INFO'  Data nodes connected
`Disconnected'            8       `ALERT' Data nodes disconnected
`CommunicationClosed'     8       `INFO'  SQL node or data node
                                          connection closed
`CommunicationOpened'     8       `INFO'  SQL node or data node
                                          connection open
`ConnectedApiVersion'     8       `INFO'  Connection using API version

*CHECKPOINT Events*

The logging messages shown here are associated with checkpoints.

This table lists events that are associated with checkpoints. In order,
the table shows the event, priority, severity level, and provides a
description.

Event                     PrioritySeverityDescription
                                  Level   
`GlobalCheckpointStarted' 9       `INFO'  Start of GCP: REDO log is
                                          written to disk
`GlobalCheckpointCompleted'10      `INFO'  GCP finished
`LocalCheckpointStarted'  7       `INFO'  Start of LCP: data written to
                                          disk
`LocalCheckpointCompleted'7       `INFO'  LCP completed normally
`LCPStoppedInCalcKeepGci' 0       `ALERT' LCP stopped
`LCPFragmentCompleted'    11      `INFO'  LCP on a fragment has been
                                          completed
`UndoLogBlocked'          7       `INFO'  UNDO logging blocked; buffer
                                          near overflow
`RedoStatus'              7       `INFO'  Redo status

*STARTUP Events*

The following events are generated in response to the startup of a node
or of the cluster and of its success or failure. They also provide
information relating to the progress of the startup process, including
information concerning logging activities.

This table lists events that are generated in response to the startup
of a node or cluster and events that provide information about startup
progress, including information about logging activities. In order, the
table shows the event, priority, severity level, and provides a
description.

Event                     PrioritySeverityDescription
                                  Level   
`NDBStartStarted'         1       `INFO'  Data node start phases
                                          initiated (all nodes starting)
`NDBStartCompleted'       1       `INFO'  Start phases completed, all
                                          data nodes
`STTORRYRecieved'         15      `INFO'  Blocks received after
                                          completion of restart
`StartPhaseCompleted'     4       `INFO'  Data node start phase X
                                          completed
`CM_REGCONF'              3       `INFO'  Node has been successfully
                                          included into the cluster;
                                          shows the node, managing node,
                                          and dynamic ID
`CM_REGREF'               8       `INFO'  Node has been refused for
                                          inclusion in the cluster;
                                          cannot be included in cluster
                                          due to misconfiguration,
                                          inability to establish
                                          communication, or other problem
`FIND_NEIGHBOURS'         8       `INFO'  Shows neighboring data nodes
`NDBStopStarted'          1       `INFO'  Data node shutdown initiated
`NDBStopCompleted'        1       `INFO'  Data node shutdown complete
`NDBStopForced'           1       `ALERT' Forced shutdown of data node
`NDBStopAborted'          1       `INFO'  Unable to shut down data node
                                          normally
`StartREDOLog'            4       `INFO'  New redo log started; GCI keep
                                          X, newest restorable GCI Y
`StartLog'                10      `INFO'  New log started; log part X,
                                          start MB Y, stop MB Z
`UNDORecordsExecuted'     15      `INFO'  Undo records executed
`StartReport'             4       `INFO'  Report started
`LogFileInitStatus'       7       `INFO'  Log file initialization status
`LogFileInitCompStatus'   7       `INFO'  Log file completion status
`StartReadLCP'            10      `INFO'  Start read for local checkpoint
`ReadLCPComplete'         10      `INFO'  Read for local checkpoint
                                          completed
`RunRedo'                 8       `INFO'  Running the redo log
`RebuildIndex'            10      `INFO'  Rebuilding indexes

*NODERESTART Events*

The following events are generated when restarting a node and relate to
the success or failure of the node restart process.

This table lists events that are generated when restarting a node and
that relate to the success or failure of the node restart process. In
order, the table shows the event, priority, severity level, and
provides a description.

Event                     PrioritySeverityDescription
                                  Level   
`NR_CopyDict'             7       `INFO'  Completed copying of dictionary
                                          information
`NR_CopyDistr'            7       `INFO'  Completed copying distribution
                                          information
`NR_CopyFragsStarted'     7       `INFO'  Starting to copy fragments
`NR_CopyFragDone'         10      `INFO'  Completed copying a fragment
`NR_CopyFragsCompleted'   7       `INFO'  Completed copying all fragments
`NodeFailCompleted'       8       `ALERT' Node failure phase completed
`NODE_FAILREP'            8       `ALERT' Reports that a node has failed
`ArbitState'              6       `INFO'  Report whether an arbitrator is
                                          found or not; there are seven
                                          different possible outcomes
                                          when seeking an arbitrator,
                                          listed here:
                                          
                                             * Management server restarts
                                               arbitration thread
                                               [state=X]
                                          
                                             * Prepare arbitrator node X
                                               [ticket=Y]
                                          
                                             * Receive arbitrator node X
                                               [ticket=Y]
                                          
                                             * Started arbitrator node X
                                               [ticket=Y]
                                          
                                             * Lost arbitrator node X -
                                               process failure [state=Y]
                                          
                                             * Lost arbitrator node X -
                                               process exit [state=Y]
                                          
                                             * Lost arbitrator node X
                                               <error msg> [state=Y]
`ArbitResult'             2       `ALERT' Report arbitrator results;
                                          there are eight different
                                          possible results for
                                          arbitration attempts, listed
                                          here:
                                          
                                             * Arbitration check failed:
                                               less than 1/2 nodes left
                                          
                                             * Arbitration check
                                               succeeded: node group
                                               majority
                                          
                                             * Arbitration check failed:
                                               missing node group
                                          
                                             * Network partitioning:
                                               arbitration required
                                          
                                             * Arbitration succeeded:
                                               affirmative response from
                                               node X
                                          
                                             * Arbitration failed:
                                               negative response from node
                                               X
                                          
                                             * Network partitioning: no
                                               arbitrator available
                                          
                                             * Network partitioning: no
                                               arbitrator configured
`GCP_TakeoverStarted'     7       `INFO'  GCP takeover started
`GCP_TakeoverCompleted'   7       `INFO'  GCP takeover complete
`LCP_TakeoverStarted'     7       `INFO'  LCP takeover started
`LCP_TakeoverCompleted'   7       `INFO'  LCP takeover complete (state =
                                          X)
`ConnectCheckStarted'     6       `INFO'  Connection check started
`ConnectCheckCompleted'   6       `INFO'  Connection check completed
`NodeFailRejected'        6       `ALERT' Node failure phase failed

*STATISTICS Events*

The following events are of a statistical nature. They provide
information such as numbers of transactions and other operations,
amount of data sent or received by individual nodes, and memory usage.

This table lists events that are of a statistical nature. In order, the
table shows the event, priority, severity level, and provides a
description.

Event                     PrioritySeverityDescription
                                  Level   
`TransReportCounters'     8       `INFO'  Report transaction statistics,
                                          including numbers of
                                          transactions, commits, reads,
                                          simple reads, writes, concurrent
                                          operations, attribute
                                          information, and aborts
`OperationReportCounters' 8       `INFO'  Number of operations
`TableCreated'            7       `INFO'  Report number of tables created
`JobStatistic'            9       `INFO'  Mean internal job scheduling
                                          statistics
`ThreadConfigLoop'        9       `INFO'  Number of thread configuration
                                          loops
`SendBytesStatistic'      9       `INFO'  Mean number of bytes sent to
                                          node X
`ReceiveBytesStatistic'   9       `INFO'  Mean number of bytes received
                                          from node X
`MemoryUsage'             5       `INFO'  Data and index memory usage
                                          (80%, 90%, and 100%)
`MTSignalStatistics'      9       `INFO'  Multi-threaded signals

*SCHEMA Events*

These events relate to MySQL Cluster schema operations.

This table lists events that relate to MySQL Cluster schema operations.

Event                     PrioritySeverityDescription
`CreateSchemaObject'      8       `INFO'  Schema objected created
`AlterSchemaObject'       8       `INFO'  Schema object updated
`DropSchemaObject'        8       `INFO'  Schema object dropped

*ERROR Events*

These events relate to Cluster errors and warnings. The presence of one
or more of these generally indicates that a major malfunction or
failure has occurred.

This table lists events that relate to cluster errors and warnings. In
order, the table shows the event, priority, severity, and provides a
description.

Event                     PrioritySeverityDescription
`TransporterError'        2       `ERROR' Transporter error
`TransporterWarning'      8       `WARNING'Transporter warning
`MissedHeartbeat'         8       `WARNING'Node X missed heartbeat number Y
`DeadDueToHeartbeat'      8       `ALERT' Node X declared `dead' due to
                                          missed heartbeat
`WarningEvent'            2       `WARNING'General warning event
`SubscriptionStatus'      4       `WARNING'Change in subscription status

*INFO Events*

These events provide general information about the state of the cluster
and activities associated with Cluster maintenance, such as logging and
heartbeat transmission.

This table lists events that provide general information about the
state of the cluster and about activities associated with cluster
maintenance, such as logging and heartbeat transmission. In order, the
table shows the event, priority, severity, and provides a description.

Event                     PrioritySeverityDescription
`SentHeartbeat'           12      `INFO'  Sent heartbeat
`CreateLogBytes'          11      `INFO'  Create log: Log part, log file,
                                          size in MB
`InfoEvent'               2       `INFO'  General informational event
`EventBufferStatus'       7       `INFO'  Event buffer status

*SINGLEUSER Events*

These events are associated with entering and exiting single user mode.

This table lists events relating to single user mode.

Event                     PrioritySeverityDescription
`SingleUser'              7       `INFO'  Entering or exiting single user
                                          mode

*BACKUP Events*

These events provide information about backups being created or
restored.

Event                     PrioritySeverityDescription
`BackupStarted'           7       `INFO'  Backup started
`BackupStatus'            7       `INFO'  Backup status
`BackupCompleted'         7       `INFO'  Backup completed
`BackupFailedToStart'     7       `ALERT' Backup failed to start
`BackupAborted'           7       `ALERT' Backup aborted by user
`RestoreStarted'          7       `INFO'  Started restoring from backup
`RestoreMetaData'         7       `INFO'  Restoring metadata
`RestoreData'             7       `INFO'  Restoring data
`RestoreLog'              7       `INFO'  Restoring log files
`RestoreCompleted'        7       `INFO'  Completed restoring from backup
`SavedEvent'              7       `INFO'  Event saved


File: manual.info,  Node: mysql-cluster-log-statistics,  Prev: mysql-cluster-log-events,  Up: mysql-cluster-event-reports

17.5.6.3 Using CLUSTERLOG STATISTICS in the MySQL Cluster Management Client
...........................................................................

The *Note `NDB': mysql-cluster. management client's `CLUSTERLOG
STATISTICS' command can provide a number of useful statistics in its
output. Counters providing information about the state of the cluster
are updated at 5-second reporting intervals by the transaction
coordinator (TC) and the local query handler (LQH), and written to the
cluster log.

Transaction coordinator statistics

Each transaction has one transaction coordinator, which is chosen by
one of the following methods:

   * In a round-robin fashion

   * By communication proximity

   * (_Beginning with MySQL Cluster NDB 6.3.4_:) By supplying a data
     placement hint when the transaction is started

*Note*:

You can determine which TC selection method is used for transactions
started from a given SQL node using the `ndb_optimized_node_selection'
system variable.

All operations within the same transaction use the same transaction
coordinator, which reports the following statistics:

   * Trans count

     This is the number transactions started in the last interval using
     this TC as the transaction coordinator. Any of these transactions
     may have committed, have been aborted, or remain uncommitted at
     the end of the reporting interval.

     *Note*:

     Transactions do not migrate between TCs.

   * Commit count

     This is the number of transactions using this TC as the
     transaction coordinator that were committed in the last reporting
     interval. Because some transactions committed in this reporting
     interval may have started in a previous reporting interval, it is
     possible for `Commit count' to be greater than `Trans count'.

   * Read count

     This is the number of primary key read operations using this TC as
     the transaction coordinator that were started in the last
     reporting interval, including simple reads.  This count also
     includes reads performed as part of unique index operations. A
     unique index read operation generates 2 primary key read
     operations--1 for the hidden unique index table, and 1 for the
     table on which the read takes place.

   * Simple read count

     This is the number of simple read operations using this TC as the
     transaction coordinator that were started in the last reporting
     interval. This is a subset of `Read count'. Because the value of
     `Simple read count' is incremented at a different point in time
     from `Read count', it can lag behind `Read count' slightly, so it
     is conceivable that `Simple read count' is not equal to `Read
     count' for a given reporting interval, even if all reads made
     during that time were in fact simple reads.

   * Write count

     This is the number of primary key write operations using this TC
     as the transaction coordinator that were started in the last
     reporting interval. This includes all inserts, updates, writes and
     deletes, as well as writes performed as part of unique index
     operations.

     *Note*:

     A unique index update operation can generate multiple PK read and
     write operations on the index table and on the base table.

   * AttrInfoCount

     This is the number of 32-bit data words received in the last
     reporting interval for primary key operations using this TC as the
     transaction coordinator. For reads, this is proportional to the
     number of columns requested. For inserts and updates, this is
     proportional to the number of columns written, and the size of
     their data. For delete operations, this is usually zero.

     Unique index operations generate multiple PK operations and so
     increase this count. However, data words sent to describe the PK
     operation itself, and the key information sent, are _not_ counted
     here. Attribute information sent to describe columns to read for
     scans, or to describe ScanFilters, is also not counted in
     `AttrInfoCount'.

   * Concurrent Operations

     This is the number of primary key or scan operations using this TC
     as the transaction coordinator that were started during the last
     reporting interval but that were not completed. Operations
     increment this counter when they are started and decrement it when
     they are completed; this occurs after the transaction commits.
     Dirty reads and writes--as well as failed operations--decrement
     this counter.

     The maximum value that `Concurrent Operations' can have is the
     maximum number of operations that a TC block can support;
     currently, this is `(2 * MaxNoOfConcurrentOperations) + 16 +
     MaxNoOfConcurrentTransactions'. (For more information about these
     configuration parameters, see the `Transaction Parameters' section
     of *Note mysql-cluster-ndbd-definition::.)

   * Abort count

     This is the number of transactions using this TC as the
     transaction coordinator that were aborted during the last
     reporting interval. Because some transactions that were aborted in
     the last reporting interval may have started in a previous
     reporting interval, `Abort count' can sometimes be greater than
     `Trans count'.

   * Scans

     This is the number of table scans using this TC as the transaction
     coordinator that were started during the last reporting interval.
     This does not include range scans (that is, ordered index scans).

   * Range scans

     This is the number of ordered index scans using this TC as the
     transaction coordinator that were started in the last reporting
     interval.

Local query handler statistics (Operations)

There is 1 cluster event per local query handler block (that is, 1 per
data node process). Operations are recorded in the LQH where the data
they are operating on resides.

*Note*:

A single transaction may operate on data stored in multiple LQH blocks.

The `Operations' statistic provides the number of local operations
performed by this LQH block in the last reporting interval, and
includes all types of read and write operations (insert, update, write,
and delete operations). This also includes operations used to replicate
writes. For example, in a 2-replica cluster, the write to the primary
replica is recorded in the primary LQH, and the write to the backup
will be recorded in the backup LQH. Unique key operations may result in
multiple local operations; however, this does _not_ include local
operations generated as a result of a table scan or ordered index scan,
which are not counted.

Process scheduler statistics

In addition to the statistics reported by the transaction coordinator
and local query handler, each *Note `ndbd':
mysql-cluster-programs-ndbd. process has a scheduler which also
provides useful metrics relating to the performance of a MySQL Cluster.
This scheduler runs in an infinite loop; during each loop the scheduler
performs the following tasks:

  1. Read any incoming messages from sockets into a job buffer.

  2. Check whether there are any timed messages to be executed; if so,
     put these into the job buffer as well.

  3. Execute (in a loop) any messages in the job buffer.

  4. Send any distributed messages that were generated by executing the
     messages in the job buffer.

  5. Wait for any new incoming messages.

Process scheduler statistics include the following:

   * Mean Loop Counter

     This is the number of loops executed in the third step from the
     preceding list. This statistic increases in size as the
     utilization of the TCP/IP buffer improves. You can use this to
     monitor changes in performance as you add new data node processes.

   * Mean send size and Mean receive size

     These statistics enable you to gauge the efficiency of,
     respectively writes and reads between nodes. The values are given
     in bytes. Higher values mean a lower cost per byte sent or
     received; the maximum value is 64K.

To cause all cluster log statistics to be logged, you can use the
following command in the *Note `NDB': mysql-cluster.  management client:


     ndb_mgm> ALL CLUSTERLOG STATISTICS=15

*Note*:

Setting the threshold for `STATISTICS' to 15 causes the cluster log to
become very verbose, and to grow quite rapidly in size, in direct
proportion to the number of cluster nodes and the amount of activity in
the MySQL Cluster.

For more information about MySQL Cluster management client commands
relating to logging and reporting, see *Note
mysql-cluster-logging-management-commands::.


File: manual.info,  Node: mysql-cluster-logs-ndb-messages,  Next: mysql-cluster-single-user-mode,  Prev: mysql-cluster-event-reports,  Up: mysql-cluster-management

17.5.7 MySQL Cluster Log Messages
---------------------------------

* Menu:

* mysql-cluster-logs-cluster-log::  MySQL Cluster: Messages in the Cluster Log
* mysql-cluster-ndb-transporter-errors::  MySQL Cluster: NDB Transporter Errors

This section contains information about the messages written to the
cluster log in response to different cluster log events. It provides
additional, more specific information on *Note `NDB': mysql-cluster.
transporter errors.


File: manual.info,  Node: mysql-cluster-logs-cluster-log,  Next: mysql-cluster-ndb-transporter-errors,  Prev: mysql-cluster-logs-ndb-messages,  Up: mysql-cluster-logs-ndb-messages

17.5.7.1 MySQL Cluster: Messages in the Cluster Log
...................................................

The following table lists the most common *Note `NDB': mysql-cluster.
cluster log messages. For information about the cluster log, log
events, and event types, see *Note mysql-cluster-event-reports::. These
log messages also correspond to log event types in the MGM API; see The
`Ndb_logevent_type' Type
(http://dev.mysql.com/doc/ndbapi/en/mgm-ndb-logevent-type.html), for
related information of interest to Cluster API developers.

This table lists the most common *Note `NDB': mysql-cluster. cluster
log messages. The first column provides the log message and a
description of the log message. The second column lists the
corresponding event name, event type, priority, and severity.

Log Message                                 Event Name
                                            
`Node MGM_NODE_ID: Node DATA_NODE_ID        `Connected'
Connected'                                  
                                            Event Type
Description                                 
                                            `Connection'
The data node having node ID NODE_ID has    
connected to the management server (node    Priority
MGM_NODE_ID).                               
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node MGM_NODE_ID: Node DATA_NODE_ID        `Disconnected'
Disconnected'                               
                                            Event Type
Description                                 
                                            `Connection'
The data node having node ID DATA_NODE_ID   
has disconnected from the management        Priority
server (node MGM_NODE_ID).                  
                                            8
                                            
                                            Severity
                                            
                                            `ALERT'
Log Message                                 Event Name
                                            
`Node DATA_NODE_ID: Communication to Node   `CommunicationClosed'
API_NODE_ID closed'                         
                                            Event Type
Description                                 
                                            `Connection'
The API node or SQL node having node ID     
API_NODE_ID is no longer communicating      Priority
with data node DATA_NODE_ID.                
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node DATA_NODE_ID: Communication to Node   `CommunicationOpened'
API_NODE_ID opened'                         
                                            Event Type
Description                                 
                                            `Connection'
The API node or SQL node having node ID     
API_NODE_ID is now communicating with data  Priority
node DATA_NODE_ID.                          
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node MGM_NODE_ID: Node API_NODE_ID: API    `ConnectedApiVersion'
VERSION'                                    
                                            Event Type
Description                                 
                                            `Connection'
The API node having node ID API_NODE_ID     
has connected to management node            Priority
MGM_NODE_ID using *Note `NDB':              
mysql-cluster. API version VERSION          8
(generally the same as the MySQL version    
number).                                    Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Global checkpoint GCI        `GlobalCheckpointStarted'
started'                                    
                                            Event Type
Description                                 
                                            `Checkpoint'
A global checkpoint with the ID GCI has     
been started; node NODE_ID is the master    Priority
responsible for this global checkpoint.     
                                            9
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Global checkpoint GCI        `GlobalCheckpointCompleted'
completed'                                  
                                            Event Type
Description                                 
                                            `Checkpoint'
The global checkpoint having the ID GCI     
has been completed; node NODE_ID was the    Priority
master responsible for this global          
checkpoint.                                 10
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Local checkpoint LCP         `LocalCheckpointStarted'
started. Keep GCI = CURRENT_GCI oldest      
restorable GCI = OLD_GCI'                   Event Type
                                            
Description                                 `Checkpoint'
                                            
The local checkpoint having sequence ID     Priority
LCP has been started on node NODE_ID. The   
most recent GCI that can be used has the    7
index CURRENT_GCI, and the oldest GCI from  
which the cluster can be restored has the   Severity
index OLD_GCI.                              
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Local checkpoint LCP         `LocalCheckpointCompleted'
completed'                                  
                                            Event Type
Description                                 
                                            `Checkpoint'
The local checkpoint having sequence ID     
LCP on node NODE_ID has been completed.     Priority
                                            
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Local Checkpoint stopped in  `LCPStoppedInCalcKeepGci'
CALCULATED_KEEP_GCI'                        
                                            Event Type
Description                                 
                                            `Checkpoint'
The node was unable to determine the most   
recent usable GCI.                          Priority
                                            
                                            0
                                            
                                            Severity
                                            
                                            `ALERT'
Log Message                                 Event Name
                                            
`Node NODE_ID: Table ID = TABLE_ID,         `LCPFragmentCompleted'
fragment ID = FRAGMENT_ID has completed     
LCP on Node NODE_ID maxGciStarted:          Event Type
STARTED_GCI maxGciCompleted: COMPLETED_GCI' 
                                            `Checkpoint'
Description                                 
                                            Priority
A table fragment has been checkpointed to   
disk on node NODE_ID. The GCI in progress   11
has the index STARTED_GCI, and the most     
recent GCI to have been completed has the   Severity
index COMPLETED_GCI.                        
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: ACC Blocked NUM_1 and TUP    `UndoLogBlocked'
Blocked NUM_2 times last second'            
                                            Event Type
Description                                 
                                            `Checkpoint'
Undo logging is blocked because the log     
buffer is close to overflowing.             Priority
                                            
                                            7
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Start initiated VERSION'     `NDBStartStarted'
                                            
Description                                 Event Type
                                            
Data node NODE_ID, running *Note `NDB':     `StartUp'
mysql-cluster. version VERSION, is          
beginning its startup process.              Priority
                                            
                                            1
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Started VERSION'             `NDBStartCompleted'
                                            
Description                                 Event Type
                                            
Data node NODE_ID, running *Note `NDB':     `StartUp'
mysql-cluster. version VERSION, has started 
successfully.                               Priority
                                            
                                            1
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: STTORRY received after       `STTORRYRecieved'
restart finished'                           
                                            Event Type
Description                                 
                                            `StartUp'
The node has received a signal indicating   
that a cluster restart has completed.       Priority
                                            
                                            15
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Start phase PHASE completed  `StartPhaseCompleted'
(TYPE)'                                     
                                            Event Type
Description                                 
                                            `StartUp'
The node has completed start phase PHASE    
of a TYPE start. For a listing of start     Priority
phases, see *Note                           
mysql-cluster-start-phases::.  (TYPE is     4
one of `initial', `system', `node',         
`initial node', or `<Unknown>'.)            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: CM_REGCONF president =       `CM_REGCONF'
PRESIDENT_ID, own Node = OWN_ID, our        
dynamic id = DYNAMIC_ID'                    Event Type
                                            
Description                                 `StartUp'
                                            
Node PRESIDENT_ID has been selected as      Priority
`president'.  OWN_ID and DYNAMIC_ID should  
always be the same as the ID (NODE_ID) of   3
the reporting node.                         
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: CM_REGREF from Node          `CM_REGREF'
PRESIDENT_ID to our Node NODE_ID. Cause =   
CAUSE'                                      Event Type
                                            
Description                                 `StartUp'
                                            
The reporting node (ID NODE_ID) was unable  Priority
to accept node PRESIDENT_ID as president.   
The CAUSE of the problem is given as one of 8
`Busy', `Election with wait = false', `Not  
president', `Election without selecting new Severity
candidate', or `No such cause'.             
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: We are Node OWN_ID with      `FIND_NEIGHBOURS'
dynamic ID DYNAMIC_ID, our left neighbor    
is Node ID_1, our right is Node ID_2'       Event Type
                                            
Description                                 `StartUp'
                                            
The node has discovered its neighboring     Priority
nodes in the cluster (node ID_1 and node    
ID_2).  NODE_ID, OWN_ID, and DYNAMIC_ID     8
should always be the same; if they are      
not, this indicates a serious               Severity
misconfiguration of the cluster nodes.      
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: TYPE shutdown initiated'     `NDBStopStarted'
                                            
Description                                 Event Type
                                            
The node has received a shutdown signal.    `StartUp'
The TYPE of shutdown is either `Cluster' or 
`Node'.                                     Priority
                                            
                                            1
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Node shutdown completed '[`, `NDBStopCompleted'
ACTION'] [`Initiated by signal SIGNAL.']    
                                            Event Type
Description                                 
                                            `StartUp'
The node has been shut down. This report    
may include an ACTION, which if present is  Priority
one of `restarting', `no start', or         
`initial'. The report may also include a    1
reference to an *Note `NDB':                
mysql-cluster. Protocol SIGNAL; for         Severity
possible signals, refer to Operations and   
Signals                                     `INFO'
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-ndb-protocol-operations-signals.html).
Log Message                                 Event Name
                                            
`Node NODE_ID: Forced node shutdown         `NDBStopForced'
completed '[`, action']`.' [`Occured        
during startphase START_PHASE.'] [`         Event Type
Initiated by SIGNAL.'] [`Caused by error    
ERROR_CODE:                                 `StartUp'
'ERROR_MESSAGE(ERROR_CLASSIFICATION).       
ERROR_STATUS'.' [`(extra info               Priority
EXTRA_CODE)']]                              
                                            1
Description                                 
                                            Severity
The node has been forcibly shut down. The   
ACTION (one of `restarting', `no start',    `ALERT'
or `initial') subsequently being taken, if  
any, is also reported.  If the shutdown     
occurred while the node was starting, the   
report includes the START_PHASE during      
which the node failed. If this was a        
result of a SIGNAL sent to the node, this   
information is also provided (see           
Operations and Signals                      
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-ndb-protocol-operations-signals.html),
for more information). If the error         
causing the failure is known, this is also  
included; for more information about *Note  
`NDB': mysql-cluster.  error messages and   
classifications, see MySQL Cluster API      
Errors                                      
(http://dev.mysql.com/doc/ndbapi/en/ndb-errors.html).
Log Message                                 Event Name
                                            
`Node NODE_ID: Node shutdown aborted'       `NDBStopAborted'
                                            
Description                                 Event Type
                                            
The node shutdown process was aborted by    `StartUp'
the user.                                   
                                            Priority
                                            
                                            1
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: StartLog: [GCI Keep:         `StartREDOLog'
KEEP_POS LastCompleted: LAST_POS            
NewestRestorable: RESTORE_POS]'             Event Type
                                            
Description                                 `StartUp'
                                            
This reports global checkpoints referenced  Priority
during a node start. The redo log prior to  
KEEP_POS is dropped.  LAST_POS is the last  4
global checkpoint in which data node the    
participated; RESTORE_POS is the global     Severity
checkpoint which is actually used to        
restore all data nodes.                     `INFO'
Log Message                                 Event Name
                                            
STARTUP_MESSAGE [_Listed separately; see    `StartReport'
below._]                                    
                                            Event Type
Description                                 
                                            `StartUp'
There are a number of possible startup      
messages that can be logged under           Priority
different circumstances.                    
                                            4
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Node restart completed copy  `NR_CopyDict'
of dictionary information'                  
                                            Event Type
Description                                 
                                            `NodeRestart'
Copying of data dictionary information to   
the restarted node has been completed.      Priority
                                            
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Node restart completed copy  `NR_CopyDistr'
of distribution information'                
                                            Event Type
Description                                 
                                            `NodeRestart'
Copying of data distribution information    
to the restarted node has been completed.   Priority
                                            
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Node restart starting to     `NR_CopyFragsStarted'
copy the fragments to Node NODE_ID'         
                                            Event Type
Description                                 
                                            `NodeRestart'
Copy of fragments to starting data node     
NODE_ID has begun                           Priority
                                            
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Table ID = TABLE_ID,         `NR_CopyFragDone'
fragment ID = FRAGMENT_ID have been copied  
to Node NODE_ID'                            Event Type
                                            
Description                                 `NodeRestart'
                                            
Fragment FRAGMENT_ID from table TABLE_ID    Priority
has been copied to data node NODE_ID        
                                            10
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Node restart completed       `NR_CopyFragsCompleted'
copying the fragments to Node NODE_ID'      
                                            Event Type
Description                                 
                                            `NodeRestart'
Copying of all table fragments to           
restarting data node NODE_ID has been       Priority
completed                                   
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
Any of the following:                       `NodeFailCompleted'
                                            
  1. `Node NODE_ID: Node NODE1_ID completed Event Type
     failure of Node NODE2_ID'              
                                            `NodeRestart'
  2. `All nodes completed failure of Node   
     NODE_ID'                               Priority
                                            
  3. `Node failure of NODE_IDBLOCK          8
     completed'                             
Description                                 Severity
                                            
One of the following (each corresponding    `ALERT'
to the same-numbered message listed above): 
                                            
  1. Data node NODE1_ID has detected the    
     failure of data node NODE2_ID          
                                            
  2. All (remaining) data nodes have        
     detected the failure of data node      
     NODE_ID                                
                                            
  3. The failure of data node NODE_ID has   
     been detected in the BLOCK*Note        
     `NDB': mysql-cluster.  kernel block,   
     where block is 1 of `DBTC', `DBDICT',  
     `DBDIH', or `DBLQH'; for more          
     information, see `NDB' Kernel Blocks   
     (http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks.html)
Log Message                                 Event Name
                                            
`Node MGM_NODE_ID: Node DATA_NODE_ID has    `NODE_FAILREP'
failed.  The Node state at failure was      
STATE_CODE'                                 Event Type
                                            
Description                                 `NodeRestart'
                                            
A data node has failed. Its state at the    Priority
time of failure is described by an          
arbitration state code STATE_CODE: possible 8
state code values can be found in the file  
`include/kernel/signaldata/ArbitSignalData.hpp'.Severity
                                            
                                            `ALERT'
Log Message                                 Event Name
                                            
`President restarts arbitration thread      `ArbitState'
[state=STATE_CODE]' or `Prepare arbitrator  
node NODE_ID [ticket=TICKET_ID]' or         Event Type
`Receive arbitrator node NODE_ID            
[ticket=TICKET_ID]' or `Started arbitrator  `NodeRestart'
node NODE_ID [ticket=TICKET_ID]' or `Lost   
arbitrator node NODE_ID - process failure   Priority
[state=STATE_CODE]' or `Lost arbitrator     
node NODE_ID - process exit                 6
[state=STATE_CODE]' or `Lost arbitrator     
node NODE_ID - ERROR_MESSAGE                Severity
[state=STATE_CODE]'                         
                                            `INFO'
Description                                 
                                            
This is a report on the current state and   
progress of arbitration in the cluster.     
NODE_ID is the node ID of the management    
node or SQL node selected as the            
arbitrator. STATE_CODE is an arbitration    
state code, as found in                     
`include/kernel/signaldata/ArbitSignalData.hpp'.
When an error has occurred, an              
ERROR_MESSAGE, also defined in              
`ArbitSignalData.hpp', is provided.         
TICKET_ID is a unique identifier handed     
out by the arbitrator when it is selected   
to all the nodes that participated in its   
selection; this is used to ensure that      
each node requesting arbitration was one    
of the nodes that took part in the          
selection process.                          
Log Message                                 Event Name
                                            
`Arbitration check lost - less than 1/2     `ArbitResult'
nodes left' or `Arbitration check won -     
all node groups and more than 1/2 nodes     Event Type
left' or `Arbitration check won - node      
group majority' or `Arbitration check lost  `NodeRestart'
- missing node group' or `Network           
partitioning - arbitration required' or     Priority
`Arbitration won - positive reply from node 
NODE_ID' or `Arbitration lost - negative    2
reply from node NODE_ID' or `Network        
partitioning - no arbitrator available' or  Severity
`Network partitioning - no arbitrator       
configured' or `Arbitration failure -       `ALERT'
ERROR_MESSAGE [state=STATE_CODE]'           
                                            
Description                                 
                                            
This message reports on the result of       
arbitration.  In the event of arbitration   
failure, an ERROR_MESSAGE and an            
arbitration STATE_CODE are provided;        
definitions for both of these are found in  
`include/kernel/signaldata/ArbitSignalData.hpp'.
Log Message                                 Event Name
                                            
`Node NODE_ID: GCP Take over started'       `GCP_TakeoverStarted'
                                            
Description                                 Event Type
                                            
This node is attempting to assume           `NodeRestart'
responsibility for the next global          
checkpoint (that is, it is becoming the     Priority
master node)                                
                                            7
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: GCP Take over completed'     `GCP_TakeoverCompleted'
                                            
Description                                 Event Type
                                            
This node has become the master, and has    `NodeRestart'
assumed responsibility for the next global  
checkpoint                                  Priority
                                            
                                            7
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: LCP Take over started'       `LCP_TakeoverStarted'
                                            
Description                                 Event Type
                                            
This node is attempting to assume           `NodeRestart'
responsibility for the next set of local    
checkpoints (that is, it is becoming the    Priority
master node)                                
                                            7
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: LCP Take over completed'     `LCP_TakeoverCompleted'
                                            
Description                                 Event Type
                                            
This node has become the master, and has    `NodeRestart'
assumed responsibility for the next set of  
local checkpoints                           Priority
                                            
                                            7
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Trans. Count =               `TransReportCounters'
TRANSACTIONS, Commit Count = COMMITS, Read  
Count = READS, Simple Read Count =          Event Type
SIMPLE_READS, Write Count = WRITES,         
AttrInfo Count = ATTRINFO_OBJECTS,          `Statistic'
Concurrent Operations =                     
CONCURRENT_OPERATIONS, Abort Count =        Priority
ABORTS, Scans = SCANS, Range scans =        
RANGE_SCANS'                                8
                                            
Description                                 Severity
                                            
This report of transaction activity is      `INFO'
given approximately once every 10 seconds   
Log Message                                 Event Name
                                            
`Node NODE_ID: Operations=OPERATIONS'       `OperationReportCounters'
                                            
Description                                 Event Type
                                            
Number of operations performed by this      `Statistic'
node, provided approximately once every 10  
seconds                                     Priority
                                            
                                            8
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Table with ID = TABLE_ID     `TableCreated'
created'                                    
                                            Event Type
Description                                 
                                            `Statistic'
A table having the table ID shown has been  
created                                     Priority
                                            
                                            7
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Mean loop Counter in doJob   `JobStatistic'
last 8192 times = COUNT'                    
                                            Event Type
Description                                 
                                            `Statistic'
                                            
                                            Priority
                                            
                                            9
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Mean send size to Node = NODE_ID last      `SendBytesStatistic'
4096 sends = BYTES bytes'                   
                                            Event Type
Description                                 
                                            `Statistic'
This node is sending an average of BYTES    
bytes per send to node NODE_ID              Priority
                                            
                                            9
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Mean receive size to Node = NODE_ID last   `ReceiveBytesStatistic'
4096 sends = BYTES bytes'                   
                                            Event Type
Description                                 
                                            `Statistic'
This node is receiving an average of BYTES  
of data each time it receives data from     Priority
node NODE_ID                                
                                            9
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Data usage is                `MemoryUsage'
DATA_MEMORY_PERCENTAGE% (DATA_PAGES_USED    
32K pages of total DATA_PAGES_TOTAL)' /     Event Type
`Node NODE_ID: Index usage is               
INDEX_MEMORY_PERCENTAGE% (INDEX_PAGES_USED  `Statistic'
8K pages of total INDEX_PAGES_TOTAL) '      
                                            Priority
Description                                 
                                            5
This report is generated when a `DUMP       
1000' command is issued in the cluster      Severity
management client; for more information,    
see `DUMP 1000'                             `INFO'
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-dump-command-1000.html),
in MySQL Cluster Internals                  
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals.html)
Log Message                                 Event Name
                                            
`Node NODE1_ID: Transporter to node         `TransporterError'
NODE2_ID reported error ERROR_CODE:         
ERROR_MESSAGE'                              Event Type
                                            
Description                                 `Error'
                                            
A transporter error occurred while          Priority
communicating with node NODE2_ID; for a     
listing of transporter error codes and      2
messages, see `NDB' Transporter Errors      
(http://dev.mysql.com/doc/ndbapi/en/ndb-transporter-errors.html),Severity
in MySQL Cluster Internals                  
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals.html)`ERROR'
Log Message                                 Event Name
                                            
`Node NODE1_ID: Transporter to node         `TransporterWarning'
NODE2_ID reported error ERROR_CODE:         
ERROR_MESSAGE'                              Event Type
                                            
Description                                 `Error'
                                            
A warning of a potential transporter        Priority
problem while communicating with node       
NODE2_ID; for a listing of transporter      8
error codes and messages, see `NDB'         
Transporter Errors                          Severity
(http://dev.mysql.com/doc/ndbapi/en/ndb-transporter-errors.html),
for more information                        `WARNING'
Log Message                                 Event Name
                                            
`Node NODE1_ID: Node NODE2_ID missed        `MissedHeartbeat'
heartbeat HEARTBEAT_ID'                     
                                            Event Type
Description                                 
                                            `Error'
This node missed a heartbeat from node      
NODE2_ID                                    Priority
                                            
                                            8
                                            
                                            Severity
                                            
                                            `WARNING'
Log Message                                 Event Name
                                            
`Node NODE1_ID: Node NODE2_ID declared      `DeadDueToHeartbeat'
dead due to missed heartbeat'               
                                            Event Type
Description                                 
                                            `Error'
This node has missed at least 3 heartbeats  
from node NODE2_ID, and so has declared     Priority
that node `dead'                            
                                            8
                                            
                                            Severity
                                            
                                            `ALERT'
Log Message                                 Event Name
                                            
`Node NODE1_ID: Node Sent Heartbeat to      `SentHeartbeat'
node = NODE2_ID'                            
                                            Event Type
Description                                 
                                            `Info'
This node has sent a heartbeat to node      
NODE2_ID                                    Priority
                                            
                                            12
                                            
                                            Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Event buffer status:         `EventBufferStatus'
used=BYTES_USED (PERCENT_USED%)             
alloc=BYTES_ALLOCATED (PERCENT_AVAILABLE%)  Event Type
max=BYTES_AVAILABLE                         
apply_gci=LATEST_RESTORABLE_GCI             `Info'
latest_gci=LATEST_GCI'                      
                                            Priority
Description                                 
                                            7
This report is seen during heavy event      
buffer usage, for example, when many        Severity
updates are being applied in a relatively   
short period of time; the report shows the  `INFO'
number of bytes and the percentage of event 
buffer memory used, the bytes allocated and 
percentage still available, and the latest  
and latest restorable global checkpoints    
Log Message                                 Event Name
                                            
`Node NODE_ID: Entering single user mode',  `SingleUser'
`Node NODE_ID: Entered single user mode     
Node API_NODE_ID has exclusive access',     Event Type
`Node NODE_ID: Entering single user mode'   
                                            `Info'
Description                                 
                                            Priority
These reports are written to the cluster    
log when entering and exiting single user   7
mode; API_NODE_ID is the node ID of the     
API or SQL having exclusive access to the   Severity
cluster (for more information, see *Note    
mysql-cluster-single-user-mode::); the      `INFO'
message `Unknown single user report         
API_NODE_ID' indicates an error has taken   
place and should never be seen in normal    
operation                                   
Log Message                                 Event Name
                                            
`Node NODE_ID: Backup BACKUP_ID started     `BackupStarted'
from node MGM_NODE_ID'                      
                                            Event Type
Description                                 
                                            `Backup'
A backup has been started using the         
management node having MGM_NODE_ID; this    Priority
message is also displayed in the cluster    
management client when the `START BACKUP'   7
command is issued; for more information,    
see *Note                                   Severity
mysql-cluster-backup-using-management-client::
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Backup BACKUP_ID started     `BackupCompleted'
from node MGM_NODE_ID completed. StartGCP:  
START_GCP StopGCP: STOP_GCP #Records:       Event Type
RECORDS #LogRecords: LOG_RECORDS Data:      
DATA_BYTES bytes Log: LOG_BYTES bytes'      `Backup'
                                            
Description                                 Priority
                                            
The backup having the ID BACKUP_ID has been 7
completed; for more information, see *Note  
mysql-cluster-backup-using-management-client::Severity
                                            
                                            `INFO'
Log Message                                 Event Name
                                            
`Node NODE_ID: Backup request from          `BackupFailedToStart'
MGM_NODE_ID failed to start. Error:         
ERROR_CODE'                                 Event Type
                                            
Description                                 `Backup'
                                            
The backup failed to start; for error       Priority
codes, see MGM`' API Errors                 
(http://dev.mysql.com/doc/ndbapi/en/mgm-errors.html)7
                                            
                                            Severity
                                            
                                            `ALERT'
Log Message                                 Event Name
                                            
`Node NODE_ID: Backup BACKUP_ID started     `BackupAborted'
from MGM_NODE_ID has been aborted. Error:   
ERROR_CODE'                                 Event Type
                                            
Description                                 `Backup'
                                            
The backup was terminated after starting,   Priority
possibly due to user intervention           
                                            7
                                            
                                            Severity
                                            
                                            `ALERT'


File: manual.info,  Node: mysql-cluster-ndb-transporter-errors,  Prev: mysql-cluster-logs-cluster-log,  Up: mysql-cluster-logs-ndb-messages

17.5.7.2 MySQL Cluster: NDB Transporter Errors
..............................................

This section lists error codes, names, and messages that are written to
the cluster log in the event of transporter errors.

This table lists error codes along with error names and error text that
are written to the cluster log in the event of transporter errors.

Error   Error Name                                  Error Text
Code                                                
0x00    TE_NO_ERROR                                 `No error'
0x01    TE_ERROR_CLOSING_SOCKET                     `Error found during
                                                    closing of socket'
0x02    TE_ERROR_IN_SELECT_BEFORE_ACCEPT            `Error found before
                                                    accept. The
                                                    transporter will
                                                    retry'
0x03    TE_INVALID_MESSAGE_LENGTH                   `Error found in
                                                    message (invalid
                                                    message length)'
0x04    TE_INVALID_CHECKSUM                         `Error found in
                                                    message (checksum)'
0x05    TE_COULD_NOT_CREATE_SOCKET                  `Error found while
                                                    creating socket(can't
                                                    create socket)'
0x06    TE_COULD_NOT_BIND_SOCKET                    `Error found while
                                                    binding server socket'
0x07    TE_LISTEN_FAILED                            `Error found while
                                                    listening to server
                                                    socket'
0x08    TE_ACCEPT_RETURN_ERROR                      `Error found during
                                                    accept(accept return
                                                    error)'
0x0b    TE_SHM_DISCONNECT                           `The remote node has
                                                    disconnected'
0x0c    TE_SHM_IPC_STAT                             `Unable to check shm
                                                    segment'
0x0d    TE_SHM_UNABLE_TO_CREATE_SEGMENT             `Unable to create shm
                                                    segment'
0x0e    TE_SHM_UNABLE_TO_ATTACH_SEGMENT             `Unable to attach shm
                                                    segment'
0x0f    TE_SHM_UNABLE_TO_REMOVE_SEGMENT             `Unable to remove shm
                                                    segment'
0x10    TE_TOO_SMALL_SIGID                          `Sig ID too small'
0x11    TE_TOO_LARGE_SIGID                          `Sig ID too large'
0x12    TE_WAIT_STACK_FULL                          `Wait stack was full'
0x13    TE_RECEIVE_BUFFER_FULL                      `Receive buffer was
                                                    full'
0x14    TE_SIGNAL_LOST_SEND_BUFFER_FULL             `Send buffer was
                                                    full,and trying to
                                                    force send fails'
0x15    TE_SIGNAL_LOST                              `Send failed for
                                                    unknown reason(signal
                                                    lost)'
0x16    TE_SEND_BUFFER_FULL                         `The send buffer was
                                                    full, but sleeping
                                                    for a while solved'
0x0017  TE_SCI_LINK_ERROR                           `There is no link
                                                    from this node to the
                                                    switch'
0x18    TE_SCI_UNABLE_TO_START_SEQUENCE             `Could not start a
                                                    sequence, because
                                                    system resources are
                                                    exumed or no sequence
                                                    has been created'
0x19    TE_SCI_UNABLE_TO_REMOVE_SEQUENCE            `Could not remove a
                                                    sequence'
0x1a    TE_SCI_UNABLE_TO_CREATE_SEQUENCE            `Could not create a
                                                    sequence, because
                                                    system resources are
                                                    exempted. Must reboot'
0x1b    TE_SCI_UNRECOVERABLE_DATA_TFX_ERROR         `Tried to send data
                                                    on redundant link but
                                                    failed'
0x1c    TE_SCI_CANNOT_INIT_LOCALSEGMENT             `Cannot initialize
                                                    local segment'
0x1d    TE_SCI_CANNOT_MAP_REMOTESEGMENT             `Cannot map remote
                                                    segment'
0x1e    TE_SCI_UNABLE_TO_UNMAP_SEGMENT              `Cannot free the
                                                    resources used by
                                                    this segment (step 1)'
0x1f    TE_SCI_UNABLE_TO_REMOVE_SEGMENT             `Cannot free the
                                                    resources used by
                                                    this segment (step 2)'
0x20    TE_SCI_UNABLE_TO_DISCONNECT_SEGMENT         `Cannot disconnect
                                                    from a remote segment'
0x21    TE_SHM_IPC_PERMANENT                        `Shm ipc Permanent
                                                    error'
0x22    TE_SCI_UNABLE_TO_CLOSE_CHANNEL              `Unable to close the
                                                    sci channel and the
                                                    resources allocated'


File: manual.info,  Node: mysql-cluster-single-user-mode,  Next: mysql-cluster-sql-statements,  Prev: mysql-cluster-logs-ndb-messages,  Up: mysql-cluster-management

17.5.8 MySQL Cluster Single User Mode
-------------------------------------

_Single user mode_ enables the database administrator to restrict
access to the database system to a single API node, such as a MySQL
server (SQL node) or an instance of *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. When entering single user mode,
connections to all other API nodes are closed gracefully and all
running transactions are aborted. No new transactions are permitted to
start.

Once the cluster has entered single user mode, only the designated API
node is granted access to the database.

You can use the `ALL STATUS' command in the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. client to see when the cluster has
entered single user mode. Beginning with MySQL Cluster NDB 7.1.1, you
can also check the `status' column of the *Note `ndbinfo.nodes':
mysql-cluster-ndbinfo-nodes. table (see *Note
mysql-cluster-ndbinfo-nodes::, for more information).

Example:


     ndb_mgm> ENTER SINGLE USER MODE 5

After this command has executed and the cluster has entered single user
mode, the API node whose node ID is `5' becomes the cluster's only
permitted user.

The node specified in the preceding command must be an API node;
attempting to specify any other type of node will be rejected.

*Note*:

When the preceding command is invoked, all transactions running on the
designated node are aborted, the connection is closed, and the server
must be restarted.

The command `EXIT SINGLE USER MODE' changes the state of the cluster's
data nodes from single user mode to normal mode. API nodes--such as
MySQL Servers--waiting for a connection (that is, waiting for the
cluster to become ready and available), are again permitted to connect.
The API node denoted as the single-user node continues to run (if still
connected) during and after the state change.

Example:


     ndb_mgm> EXIT SINGLE USER MODE

There are two recommended ways to handle a node failure when running in
single user mode:

   * Method 1:

       1. Finish all single user mode transactions

       2. Issue the `EXIT SINGLE USER MODE' command

       3. Restart the cluster's data nodes

   * Method 2:

     Restart database nodes prior to entering single user mode.


File: manual.info,  Node: mysql-cluster-sql-statements,  Next: mysql-cluster-ndbinfo,  Prev: mysql-cluster-single-user-mode,  Up: mysql-cluster-management

17.5.9 Quick Reference: MySQL Cluster SQL Statements
----------------------------------------------------

This section discusses several SQL statements that can prove useful in
managing and monitoring a MySQL server that is connected to a MySQL
Cluster, and in some cases provide information about the cluster itself.

   * *Note `SHOW ENGINE NDB STATUS': show-engine, *Note `SHOW ENGINE
     NDBCLUSTER STATUS': show-engine.

     The output of this statement contains information about the
     server's connection to the cluster, creation and usage of MySQL
     Cluster objects, and binary logging for MySQL Cluster replication.

     See *Note show-engine::, for a usage example and more detailed
     information.

   * *Note `SHOW ENGINES': show-engines.

     This statement can be used to determine whether or not clustering
     support is enabled in the MySQL server, and if so, whether it is
     active.

     See *Note show-engines::, for more detailed information.

     *Note*:

     In MySQL 5.1 and later, this statement does not support a `LIKE'
     clause. However, you can use `LIKE' to filter queries against the
     *Note `INFORMATION_SCHEMA.ENGINES': engines-table.  table, as
     discussed in the next item.

   * `SELECT * FROM INFORMATION_SCHEMA.ENGINES [WHERE ENGINE LIKE
     'NDB%']'

     This is the equivalent of *Note `SHOW ENGINES': show-engines, but
     uses the *Note `ENGINES': engines-table. table of the
     `INFORMATION_SCHEMA' database (available beginning with MySQL
     5.1.5). Unlike the case with the *Note `SHOW ENGINES':
     show-engines. statement, it is possible to filter the results
     using a `LIKE' clause, and to select specific columns to obtain
     information that may be of use in scripts. For example, the
     following query shows whether the server was built with *Note
     `NDB': mysql-cluster. support and, if so, whether it is enabled:


          mysql> SELECT SUPPORT FROM INFORMATION_SCHEMA.ENGINES
              ->   WHERE ENGINE LIKE 'NDB%';
          +---------+
          | support |
          +---------+
          | ENABLED |
          +---------+

     See *Note engines-table::, for more information.

   * `SHOW VARIABLES LIKE 'NDB%''

     This statement provides a list of most server system variables
     relating to the *Note `NDB': mysql-cluster. storage engine, and
     their values, as shown here:


          mysql> SHOW VARIABLES LIKE 'NDB%';
          +-------------------------------------+-------+
          | Variable_name                       | Value |
          +-------------------------------------+-------+
          | ndb_autoincrement_prefetch_sz       | 32    |
          | ndb_cache_check_time                | 0     |
          | ndb_extra_logging                   | 0     |
          | ndb_force_send                      | ON    |
          | ndb_index_stat_cache_entries        | 32    |
          | ndb_index_stat_enable               | OFF   |
          | ndb_index_stat_update_freq          | 20    |
          | ndb_report_thresh_binlog_epoch_slip | 3     |
          | ndb_report_thresh_binlog_mem_usage  | 10    |
          | ndb_use_copying_alter_table         | OFF   |
          | ndb_use_exact_count                 | ON    |
          | ndb_use_transactions                | ON    |
          +-------------------------------------+-------+

     See *Note server-system-variables::, for more information.

   * `SELECT * FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES WHERE
     VARIABLE_NAME LIKE 'NDB%';'

     This statement is the equivalent of the `SHOW' command described
     in the previous item, and provides almost identical output, as
     shown here:


          mysql> SELECT * FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES
              ->   WHERE VARIABLE_NAME LIKE 'NDB%';
          +-------------------------------------+----------------+
          | VARIABLE_NAME                       | VARIABLE_VALUE |
          +-------------------------------------+----------------+
          | NDB_AUTOINCREMENT_PREFETCH_SZ       | 32             |
          | NDB_CACHE_CHECK_TIME                | 0              |
          | NDB_EXTRA_LOGGING                   | 0              |
          | NDB_FORCE_SEND                      | ON             |
          | NDB_INDEX_STAT_CACHE_ENTRIES        | 32             |
          | NDB_INDEX_STAT_ENABLE               | OFF            |
          | NDB_INDEX_STAT_UPDATE_FREQ          | 20             |
          | NDB_REPORT_THRESH_BINLOG_EPOCH_SLIP | 3              |
          | NDB_REPORT_THRESH_BINLOG_MEM_USAGE  | 10             |
          | NDB_USE_COPYING_ALTER_TABLE         | OFF            |
          | NDB_USE_EXACT_COUNT                 | ON             |
          | NDB_USE_TRANSACTIONS                | ON             |
          +-------------------------------------+----------------+

     Unlike the case with the `SHOW' command, it is possible to select
     individual columns. For example:


          mysql> SELECT VARIABLE_VALUE
              ->   FROM INFORMATION_SCHEMA.GLOBAL_VARIABLES
              ->   WHERE VARIABLE_NAME = 'ndb_force_send';
          +----------------+
          | VARIABLE_VALUE |
          +----------------+
          | ON             |
          +----------------+

     See *Note variables-table::, and *Note server-system-variables::,
     for more information.

   * `SHOW STATUS LIKE 'NDB%''

     This statement shows at a glance whether or not the MySQL server
     is acting as a cluster SQL node, and if so, it provides the MySQL
     server's cluster node ID, the host name and port for the cluster
     management server to which it is connected, and the number of data
     nodes in the cluster, as shown here:


          mysql> SHOW STATUS LIKE 'NDB%';
          +--------------------------+---------------+
          | Variable_name            | Value         |
          +--------------------------+---------------+
          | Ndb_cluster_node_id      | 10            |
          | Ndb_config_from_host     | 192.168.0.103 |
          | Ndb_config_from_port     | 1186          |
          | Ndb_number_of_data_nodes | 4             |
          +--------------------------+---------------+

     If the MySQL server was built with clustering support, but it is
     not connected to a cluster, all rows in the output of this
     statement contain a zero or an empty string:


          mysql> SHOW STATUS LIKE 'NDB%';
          +--------------------------+-------+
          | Variable_name            | Value |
          +--------------------------+-------+
          | Ndb_cluster_node_id      | 0     |
          | Ndb_config_from_host     |       |
          | Ndb_config_from_port     | 0     |
          | Ndb_number_of_data_nodes | 0     |
          +--------------------------+-------+

     See also *Note show-status::.

   * `SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS WHERE
     VARIABLE_NAME LIKE 'NDB%';'

     Beginning with MySQL 5.1.12, this statement provides similar
     output to the `SHOW' command discussed in the previous item.
     However, unlike the case with *Note `SHOW STATUS': show-status, it
     is possible using the *Note `SELECT': select. to extract values in
     SQL for use in scripts for monitoring and automation purposes.

     See *Note status-table::, for more information.

Beginning with MySQL Cluster NDB 7.1.1, you can also query the tables
in the *Note `ndbinfo': mysql-cluster-ndbinfo.  information database
for real-time data about many MySQL Cluster operations. See *Note
mysql-cluster-ndbinfo::.


File: manual.info,  Node: mysql-cluster-ndbinfo,  Next: mysql-cluster-security,  Prev: mysql-cluster-sql-statements,  Up: mysql-cluster-management

17.5.10 The ndbinfo MySQL Cluster Information Database
------------------------------------------------------

* Menu:

* mysql-cluster-ndbinfo-arbitrator-validity-detail::  The ndbinfo arbitrator_validity_detail Table
* mysql-cluster-ndbinfo-arbitrator-validity-summary::  The ndbinfo arbitrator_validity_summary Table
* mysql-cluster-ndbinfo-blocks::  The ndbinfo blocks Table
* mysql-cluster-ndbinfo-cluster-operations::  The ndbinfo cluster_operations Table
* mysql-cluster-ndbinfo-cluster-transactions::  The ndbinfo cluster_transactions Table
* mysql-cluster-ndbinfo-config-params::  The ndbinfo config_params Table
* mysql-cluster-ndbinfo-counters::  The ndbinfo counters Table
* mysql-cluster-ndbinfo-diskpagebuffer::  The ndbinfo diskpagebuffer Table
* mysql-cluster-ndbinfo-logbuffers::  The ndbinfo logbuffers Table
* mysql-cluster-ndbinfo-logspaces::  The ndbinfo logspaces Table
* mysql-cluster-ndbinfo-membership::  The ndbinfo membership Table
* mysql-cluster-ndbinfo-memoryusage::  The ndbinfo memoryusage Table
* mysql-cluster-ndbinfo-nodes::  The ndbinfo nodes Table
* mysql-cluster-ndbinfo-pools::  The ndbinfo pools Table
* mysql-cluster-ndbinfo-resources::  The ndbinfo resources Table
* mysql-cluster-ndbinfo-server-operations::  The ndbinfo server_operations Table
* mysql-cluster-ndbinfo-server-transactions::  The ndbinfo server_transactions Table
* mysql-cluster-ndbinfo-threadblocks::  The ndbinfo threadblocks Table
* mysql-cluster-ndbinfo-threadstat::  The ndbinfo threadstat Table
* mysql-cluster-ndbinfo-transporters::  The ndbinfo transporters Table

`ndbinfo' is a database storing containing information specific to
MySQL Cluster, available beginning with MySQL Cluster NDB 7.1.1.

This database contains a number of tables, each providing a different
sort of data about MySQL Cluster node status, resource usage, and
operations. You can find more detailed information about each of these
tables in the next several sections.

`ndbinfo' is included with MySQL Cluster support in the MySQL Server;
no special compilation or configuration steps are required; the tables
are created by the MySQL Server when it connects to the cluster. You
can verify that `ndbinfo' support is active in a given MySQL Server
instance using *Note `SHOW PLUGINS': show-plugins.; if `ndbinfo'
support is enabled, you should see a row containing `ndbinfo' in the
`Name' column and `ACTIVE' in the `Status' column, as shown here
(emphasized text):


     mysql> SHOW PLUGINS;
     +------------+----------+----------------+---------+---------+
     | Name       | Status   | Type           | Library | License |
     +------------+----------+----------------+---------+---------+
     | binlog     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | partition  | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | ARCHIVE    | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | BLACKHOLE  | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | CSV        | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | FEDERATED  | DISABLED | STORAGE ENGINE | NULL    | GPL     |
     | MEMORY     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | InnoDB     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | MyISAM     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | MRG_MYISAM | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | ndbcluster | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     _| ndbinfo    | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |_
     +------------+----------+----------------+---------+---------+
     12 rows in set (0.00 sec)

You can also do this by checking the output of *Note `SHOW ENGINES':
show-engines. for a row that has `ndbinfo' for `Engine' and `YES' for
`Support', as shown here (emphasized text):


     mysql> SHOW ENGINES\G
     *************************** 1. row ***************************
           Engine: ndbcluster
          Support: YES
          Comment: Clustered, fault-tolerant tables
     Transactions: YES
               XA: NO
       Savepoints: NO
     *************************** 2. row ***************************
           Engine: MRG_MYISAM
          Support: YES
          Comment: Collection of identical MyISAM tables
     Transactions: NO
               XA: NO
       Savepoints: NO
     _*************************** 3. row ***************************
           Engine: ndbinfo
          Support: YES
          Comment: MySQL Cluster system information storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO_
     *************************** 4. row ***************************
           Engine: CSV
          Support: YES
          Comment: CSV storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 5. row ***************************
           Engine: MEMORY
          Support: YES
          Comment: Hash based, stored in memory, useful for temporary tables
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 6. row ***************************
           Engine: FEDERATED
          Support: NO
          Comment: Federated MySQL storage engine
     Transactions: NULL
               XA: NULL
       Savepoints: NULL
     *************************** 7. row ***************************
           Engine: ARCHIVE
          Support: YES
          Comment: Archive storage engine
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 8. row ***************************
           Engine: InnoDB
          Support: YES
          Comment: Supports transactions, row-level locking, and foreign keys
     Transactions: YES
               XA: YES
       Savepoints: YES
     *************************** 9. row ***************************
           Engine: MyISAM
          Support: DEFAULT
          Comment: Default engine as of MySQL 3.23 with great performance
     Transactions: NO
               XA: NO
       Savepoints: NO
     *************************** 10. row ***************************
           Engine: BLACKHOLE
          Support: YES
          Comment: /dev/null storage engine (anything you write to it disappears)
     Transactions: NO
               XA: NO
       Savepoints: NO
     10 rows in set (0.00 sec)

If `ndbinfo' support is enabled, then you can access `ndbinfo' using
SQL statements in *Note `mysql': mysql. or another MySQL client. For
example, you can see `ndbinfo' listed in the output of *Note `SHOW
DATABASES': show-databases, as shown here:


     mysql> SHOW DATABASES;
     +--------------------+
     | Database           |
     +--------------------+
     | information_schema |
     | mysql              |
     | ndbinfo            |
     | test               |
     +--------------------+
     4 rows in set (0.00 sec)

If the *Note `mysqld': mysqld. process was not started with the
`--ndbcluster' option, `ndbinfo' is not available and is not displayed
by *Note `SHOW DATABASES': show-databases. If *Note `mysqld': mysqld.
was formerly connected to a MySQL Cluster but the cluster becomes
unavailable (due to events such as cluster shutdown, loss of network
connectivity, and so forth), `ndbinfo' and its tables remain visible,
but an attempt to access any tables (other than `blocks' or
`config_params') fails with `Got error 157 'Connection to NDB failed'
from NDBINFO'.

With the exception of the `blocks' and `config_params' tables, what we
refer to as `ndbinfo' `tables' are actually views generated from
internal *Note `NDB': mysql-cluster.  tables not normally visible to
the MySQL Server.

All `ndbinfo' tables are read-only, and are generated on demand when
queried. Because many of them are generated in parallel by the data
nodes while other are specific to a given SQL node, they are not
guaranteed to provide a consistent snapshot.

In addition, pushing down of joins is not supported on `ndbinfo'
tables; so joining large `ndbinfo' tables can require transfer of a
large amount of data to the requesting API node, even when the query
makes use of a `WHERE' clause.

Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB 7.1.11,
`ndbinfo' tables are not included in the query cache. (Bug #59831)

You can select the `ndbinfo' database with a *Note `USE': use.
statement, and then issue a *Note `SHOW TABLES': show-tables. statement
to obtain a list of tables, just as for any other database, like this:


     mysql> USE ndbinfo;
     Database changed

     mysql> SHOW TABLES;
     +----------------------+
     | Tables_in_ndbinfo    |
     +----------------------+
     | blocks               |
     | cluster_operations   |
     | cluster_transactions |
     | config_params        |
     | counters             |
     | diskpagebuffer       |
     | logbuffers           |
     | logspaces            |
     | memoryusage          |
     | nodes                |
     | resources            |
     | server_operations    |
     | server_transactions  |
     | threadblocks         |
     | threadstat           |
     | transporters         |
     +----------------------+
     16 rows in set (0.04 sec)

The *Note `diskpagebuffer': mysql-cluster-ndbinfo-diskpagebuffer. table
was added in MySQL Cluster NDB 7.1.9.

The *Note `cluster_operations':
mysql-cluster-ndbinfo-cluster-operations, *Note `cluster_transactions':
mysql-cluster-ndbinfo-cluster-transactions, *Note `server_operations':
mysql-cluster-ndbinfo-server-operations, *Note `server_transactions':
mysql-cluster-ndbinfo-server-transactions, *Note `threadblocks':
mysql-cluster-ndbinfo-threadblocks, and *Note `threadstat':
mysql-cluster-ndbinfo-threadstat. tables were added in MySQL Cluster
NDB 7.1.17.

In early versions of MySQL Cluster NDB 7.1, there was an additional
*Note `pools': mysql-cluster-ndbinfo-pools. table in the `ndbinfo'
database; however, this table was removed in MySQL Cluster NDB 7.1.3.

You can execute *Note `SELECT': select. statements against these
tables, just as you would normally expect:


     mysql> SELECT * FROM memoryusage;
     +---------+---------------------+--------+------------+------------+-------------+
     | node_id | memory_type         | used   | used_pages | total      | total_pages |
     +---------+---------------------+--------+------------+------------+-------------+
     |       5 | Data memory         | 753664 |         23 | 1073741824 |       32768 |
     |       5 | Index memory        | 163840 |         20 | 1074003968 |      131104 |
     |       5 | Long message buffer |   2304 |          9 |   67108864 |      262144 |
     |       6 | Data memory         | 753664 |         23 | 1073741824 |       32768 |
     |       6 | Index memory        | 163840 |         20 | 1074003968 |      131104 |
     |       6 | Long message buffer |   2304 |          9 |   67108864 |      262144 |
     +---------+---------------------+--------+------------+------------+-------------+
     6 rows in set (0.02 sec)

More complex queries, such as the two following *Note `SELECT': select.
statements using the *Note `memoryusage':
mysql-cluster-ndbinfo-memoryusage. table, are possible:


     mysql> SELECT SUM(used) as 'Data Memory Used, All Nodes'
          >     FROM memoryusage
          >     WHERE memory_type = 'Data memory';
     +-----------------------------+
     | Data Memory Used, All Nodes |
     +-----------------------------+
     |                        6460 |
     +-----------------------------+
     1 row in set (0.37 sec)

     mysql> SELECT SUM(max) as 'Total IndexMemory Available'
          >     FROM memoryusage
          >     WHERE memory_type = 'Index memory';
     +-----------------------------+
     | Total IndexMemory Available |
     +-----------------------------+
     |                       25664 |
     +-----------------------------+
     1 row in set (0.33 sec)

`ndbinfo' table and column names are case sensitive (as is the name of
the `ndbinfo' database itself). These identifiers are in lowercase.
Trying to use the wrong lettercase results in an error, as shown in this
example:


     mysql> SELECT * FROM nodes;
     +---------+--------+---------+-------------+
     | node_id | uptime | status  | start_phase |
     +---------+--------+---------+-------------+
     |       1 |  13602 | STARTED |           0 |
     |       2 |     16 | STARTED |           0 |
     +---------+--------+---------+-------------+
     2 rows in set (0.04 sec)

     mysql> SELECT * FROM Nodes;
     `ERROR 1146 (42S02): Table 'ndbinfo.Nodes' doesn't exist'

Beginning with MySQL Cluster NDB 7.1.7, *Note `mysqldump': mysqldump.
ignores `ndbinfo' entirely, and excludes it from any output. This is
true even when using the `--databases' or `--all-databases' option.

MySQL Cluster also maintains tables in the `INFORMATION_SCHEMA'
information database, including the *Note `FILES': files-table. table
which contains information about files used for MySQL Cluster Disk Data
storage. For more information, see *Note mysql-cluster-i_s-tables::.


File: manual.info,  Node: mysql-cluster-ndbinfo-arbitrator-validity-detail,  Next: mysql-cluster-ndbinfo-arbitrator-validity-summary,  Prev: mysql-cluster-ndbinfo,  Up: mysql-cluster-ndbinfo

17.5.10.1 The ndbinfo arbitrator_validity_detail Table
......................................................

The `arbitrator_validity_detail' table shows the view that each data
node in the cluster of the arbitrator.  It is a subset of the *Note
`membership': mysql-cluster-ndbinfo-membership. table.

The following table provides information about the columns in the
`arbitrator_validity_detail' table. For each column, the table shows
the name, data type, and a brief description. Additional information
can be found in the notes following the table.

This table describes the columns in the `arbitrator_validity_detail'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            This node's node ID
`arbitrator'           integer            Node ID of arbitrator
`arb_ticket'           string             Internal identifier used to
                                          track arbitration
`arb_connected'        `Yes' or `No'      Whether this node is connected
                                          to the arbitrator
`arb_state'            Enumeration (see   Arbitration state
                       text)              

The node ID is the same as that reported by *Note `ndb_mgm -e "SHOW"':
mysql-cluster-programs-ndb-mgm.

All nodes should show the same `arbitrator' and `arb_ticket' values as
well as the same `arb_state' value. Possible `arb_state' values are
`ARBIT_NULL', `ARBIT_INIT', `ARBIT_FIND', `ARBIT_PREP1', `ARBIT_PREP2',
`ARBIT_START', `ARBIT_RUN', `ARBIT_CHOOSE', `ARBIT_CRASH', and
`UNKNOWN'.

`arb_connected' shows whether the current node is connected to the
`arbitrator'.

Like the *Note `membership': mysql-cluster-ndbinfo-membership. and
*Note `arbitrator_validity_summary':
mysql-cluster-ndbinfo-arbitrator-validity-summary.  tables, this table
was added in MySQL Cluster NDB 7.0.37 and MySQL Cluster NDB 7.1.26.


File: manual.info,  Node: mysql-cluster-ndbinfo-arbitrator-validity-summary,  Next: mysql-cluster-ndbinfo-blocks,  Prev: mysql-cluster-ndbinfo-arbitrator-validity-detail,  Up: mysql-cluster-ndbinfo

17.5.10.2 The ndbinfo arbitrator_validity_summary Table
.......................................................

The `arbitrator_validity_summary' table provides a composite view of
the arbitrator with regard to the cluster's data nodes.

The following table provides information about the columns in the
`arbitrator_validity_summary' table. For each column, the table shows
the name, data type, and a brief description. Additional information
can be found in the notes following the table.

This table describes the columns in the `arbitrator_validity_summary'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`arbitrator'           integer            Node ID of arbitrator
`arb_ticket'           string             Internal identifier used to
                                          track arbitration
`arb_connected'        `Yes' or `No'      Whether this arbitrator is
                                          connected to the cluster
`consensus_count'      integer            Number of data nodes that see
                                          this node as arbitrator

In normal operations, this table should have only 1 row for any
appreciable length of time. If it has more than 1 row for longer than a
few moments, then either not all nodes are connected to the arbitrator,
or all nodes are connected, but do not agree on the same arbitrator.

The `arbitrator' column shows the arbitrator's node ID.

`arb_ticket' is the internal identifier used by this arbitrator.

`arb_connected' shows whether this node is connected to the cluster as
an arbitrator.

Like the *Note `membership': mysql-cluster-ndbinfo-membership. and
*Note `arbitrator_validity_detail':
mysql-cluster-ndbinfo-arbitrator-validity-detail.  tables, this table
was added in MySQL Cluster NDB 7.0.37 and MySQL Cluster NDB 7.1.26.


File: manual.info,  Node: mysql-cluster-ndbinfo-blocks,  Next: mysql-cluster-ndbinfo-cluster-operations,  Prev: mysql-cluster-ndbinfo-arbitrator-validity-summary,  Up: mysql-cluster-ndbinfo

17.5.10.3 The ndbinfo blocks Table
..................................

The `blocks' table is a static table which simply contains the names
and internal IDs of all NDB kernel blocks (see `NDB' Kernel Blocks
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks.html)).
It is for use by the other *Note `ndbinfo': mysql-cluster-ndbinfo.
tables (most of which are actually views) in mapping block numbers to
block names for producing human-readable output.

The following table provides information about the columns in the
`blocks' table. For each column, the table shows the name, data type,
and a brief description. Additional information can be found in the
notes following the table.

This table provides information about the columns in the `blocks'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`block_number'         integer            Block number
`block_name'           string             Block name

To obtain a list of all block names, simply execute `SELECT block_name
FROM ndbinfo.blocks'.  Although this is a static table, its content can
vary between different MySQL Cluster releases.


File: manual.info,  Node: mysql-cluster-ndbinfo-cluster-operations,  Next: mysql-cluster-ndbinfo-cluster-transactions,  Prev: mysql-cluster-ndbinfo-blocks,  Up: mysql-cluster-ndbinfo

17.5.10.4 The ndbinfo cluster_operations Table
..............................................

The `cluster_operations' table provides a per-operation (stateful
primary key op) view of all activity in the MySQL Cluster from the
point of view of the local data management (LQH) blocks (see The
`DBLQH' Block
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dblqh.html)).

The following table provides information about the columns in the
`cluster_operations' table. For each column, the table shows the name,
data type, and a brief description. Additional information can be found
in the notes following the table.

This table provides information about the columns in the
`cluster_operations' table. The table shows the column name, data type,
and provides a brief description.

Column Name            Type               Description
`node_id'              integer            Node ID of reporting LQH block
`block_instance'       integer            LQH block instance
`transid'              integer            Transaction ID
`operation_type'       string             Operation type (see text for
                                          possible values)
`state'                string             Operation state (see text for
                                          possible values)
`tableid'              integer            Table ID
`fragmentid'           integer            Fragment ID
`client_node_id'       integer            Client node ID
`client_block_ref'     integer            Client block reference
`tc_node_id'           integer            Transaction coordinator node ID
`tc_block_no'          integer            Transaction coordinator block
                                          number
`tc_block_instance'    integer            Transaction coordinator block
                                          instance

The transaction ID is a unique 64-bit number which can be obtained
using the NDB API's `getTransactionId()'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-gettransactionid)
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)

The `operation_type' column can take any one of the values `READ',
`READ-SH', `READ-EX', `INSERT', `UPDATE', `DELETE', `WRITE', `UNLOCK',
`REFRESH', `SCAN', `SCAN-SH', `SCAN-EX', or `<unknown>'.

The `state' column can have any one of the values `ABORT_QUEUED',
`ABORT_STOPPED', `COMMITTED', `COMMIT_QUEUED', `COMMIT_STOPPED',
`COPY_CLOSE_STOPPED', `COPY_FIRST_STOPPED', `COPY_STOPPED',
`COPY_TUPKEY', `IDLE', `LOG_ABORT_QUEUED', `LOG_COMMIT_QUEUED',
`LOG_COMMIT_QUEUED_WAIT_SIGNAL', `LOG_COMMIT_WRITTEN',
`LOG_COMMIT_WRITTEN_WAIT_SIGNAL', `LOG_QUEUED', `PREPARED',
`PREPARED_RECEIVED_COMMIT', `SCAN_CHECK_STOPPED', `SCAN_CLOSE_STOPPED',
`SCAN_FIRST_STOPPED', `SCAN_RELEASE_STOPPED', `SCAN_STATE_USED',
`SCAN_STOPPED', `SCAN_TUPKEY', `STOPPED', `TC_NOT_CONNECTED',
`WAIT_ACC', `WAIT_ACC_ABORT', `WAIT_AI_AFTER_ABORT', `WAIT_ATTR',
`WAIT_SCAN_AI', `WAIT_TUP', `WAIT_TUPKEYINFO', `WAIT_TUP_COMMIT', or
`WAIT_TUP_TO_ABORT'. (If the MySQL Server is running with
`ndbinfo_show_hidden' enabled, you can view this list of states by
selecting from the `ndb$dblqh_tcconnect_state' table, which is normally
hidden.)

You can obtain the name of an `NDB' table from its table ID by checking
the output of *Note `ndb_show_tables':
mysql-cluster-programs-ndb-show-tables.

The `fragid' is the same as the partition number seen in the output of
*Note `ndb_desc': mysql-cluster-programs-ndb-desc.
`--extra-partition-info' (short form `-p').

In `client_node_id' and `client_block_ref', `client' refers to a MySQL
Cluster API or SQL node (that is, an NDB API client or a MySQL Server
attached to the cluster).

This table was added in MySQL Cluster NDB 7.1.17.


File: manual.info,  Node: mysql-cluster-ndbinfo-cluster-transactions,  Next: mysql-cluster-ndbinfo-config-params,  Prev: mysql-cluster-ndbinfo-cluster-operations,  Up: mysql-cluster-ndbinfo

17.5.10.5 The ndbinfo cluster_transactions Table
................................................

The `cluster_transactions' table shows information about all ongoing
transactions in a MySQL Cluster.

The following table provides information about the columns in the
`cluster_transactions' table. For each column, the table shows the
name, data type, and a brief description. Additional information can be
found in the notes following the table.

This table provides information about the columns in the
`cluster_transactions' table. The table shows the column name, data
type, and provides a brief description.

Column Name            Type               Description
`node_id'              integer            Node ID of transaction
                                          coordinator
`block_instance'       integer            TC block instance
`transid'              integer            Transaction ID
`state'                string             Operation state (see text for
                                          possible values)
`count_operations'     integer            Number of stateful primary key
                                          operations in transaction
                                          (includes reads with locks, as
                                          well as DML operations)
`outstanding_operations'integer            Operations still being executed
                                          in local data management blocks
`inactive_seconds'     integer            Time spent waiting for API
`client_node_id'       integer            Client node ID
`client_block_ref'     integer            Client block reference

The transaction ID is a unique 64-bit number which can be obtained
using the NDB API's `getTransactionId()'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-gettransactionid)
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)

The `state' column can have any one of the values `CS_ABORTING',
`CS_COMMITTING', `CS_COMMIT_SENT', `CS_COMPLETE_SENT', `CS_COMPLETING',
`CS_CONNECTED', `CS_DISCONNECTED', `CS_FAIL_ABORTED',
`CS_FAIL_ABORTING', `CS_FAIL_COMMITTED', `CS_FAIL_COMMITTING',
`CS_FAIL_COMPLETED', `CS_FAIL_PREPARED', `CS_PREPARE_TO_COMMIT',
`CS_RECEIVING', `CS_REC_COMMITTING', `CS_RESTART',
`CS_SEND_FIRE_TRIG_REQ', `CS_STARTED', `CS_START_COMMITTING',
`CS_START_SCAN', `CS_WAIT_ABORT_CONF', `CS_WAIT_COMMIT_CONF',
`CS_WAIT_COMPLETE_CONF', `CS_WAIT_FIRE_TRIG_REQ'. (If the MySQL Server
is running with `ndbinfo_show_hidden' enabled, you can view this list
of states by selecting from the `ndb$dbtc_apiconnect_state' table,
which is normally hidden.)

In `client_node_id' and `client_block_ref', `client' refers to a MySQL
Cluster API or SQL node (that is, an NDB API client or a MySQL Server
attached to the cluster).

This table was added in MySQL Cluster NDB 7.1.17.


File: manual.info,  Node: mysql-cluster-ndbinfo-config-params,  Next: mysql-cluster-ndbinfo-counters,  Prev: mysql-cluster-ndbinfo-cluster-transactions,  Up: mysql-cluster-ndbinfo

17.5.10.6 The ndbinfo config_params Table
.........................................

The `config_params' table is a static table which provides the names
and internal ID numbers of all MySQL Cluster configuration parameters.

The following table provides information about the columns in the
`config_params' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about the columns in the
`config_params' table. The table shows the column name, data type, and
provides a brief description.

Column Name            Type               Description
`param_number'         integer            The parameter's internal ID
                                          number
`param_name'           string             The name of the parameter

Although this is a static table, its content can vary between MySQL
Cluster installations, since supported parameters can vary due to
differences between software releases, cluster hardware configurations,
and other factors.


File: manual.info,  Node: mysql-cluster-ndbinfo-counters,  Next: mysql-cluster-ndbinfo-diskpagebuffer,  Prev: mysql-cluster-ndbinfo-config-params,  Up: mysql-cluster-ndbinfo

17.5.10.7 The ndbinfo counters Table
....................................

The `counters' table provides running totals of events such as reads
and writes for specific kernel blocks and data nodes. Counts are kept
from the most recent node start or restart; a node start or restart
resets all counters on that node. Not all kernel blocks have all types
of counters.

The following table provides information about the columns in the
`counters' table. For each column, the table shows the name, data type,
and a brief description.  Additional information can be found in the
notes following the table.

This table provides information about the columns in the `counters'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            The data node ID
`block_name'           string             Name of the associated NDB
                                          kernel block (see `NDB' Kernel
                                          Blocks
                                          (http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks.html)).
`block_instance'       integer            Block instance
`counter_id'           integer            The counter's internal ID
                                          number; normally an integer
                                          between 1 and 10, inclusive.
`counter_name'         string             The name of the counter. See
                                          text for names of individual
                                          counters and the NDB kernel
                                          block with which each counter is
                                          associated.
`val'                  integer            The counter's value

Each counter is associated with a particular NDB kernel block.  Prior
to MySQL Cluster NDB 7.2.0, this was limited to either the `DBLQH'
kernel block or the `DBTC' kernel block.

The `OPERATIONS' counter is associated with the `DBLQH' (local query
handler) kernel block (see The `DBLQH' Block
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dblqh.html)).

The `ATTRINFO', `TRANSACTIONS', `COMMITS', `READS', `SIMPLE_READS',
`WRITES', `ABORTS', `TABLE_SCANS', and `RANGE_SCANS' counters are
associated with the DBTC (transaction co-ordinator) kernel block (see
The `DBTC' Block
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dbtc.html)).

MySQL Cluster NDB 7.2.0, as part of its implementation of distributed
pushed-down joins, adds the `LOCAL_TABLE_SCANS_SENT', `READS_RECEIVED',
`PRUNED_RANGE_SCANS_RECEIVED', `RANGE_SCANS_RECEIVED',
`LOCAL_READS_SENT', `CONST_PRUNED_RANGE_SCANS_RECEIVED',
`LOCAL_RANGE_SCANS_SENT', `REMOTE_READS_SENT',
`REMOTE_RANGE_SCANS_SENT', `READS_NOT_FOUND', `SCAN_BATCHES_RETURNED',
`TABLE_SCANS_RECEIVED', and `SCAN_ROWS_RETURNED' counters. These
counters are associated with the `DBSPJ' (select push-down join) kernel
block (see The `DBSPJ' Block
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dbspj.html)).

A number of counters increasing the visibility of transporter overload
and send buffer sizing when troubleshooting such issues were added in
MySQL Cluster NDB 7.0.37 and MySQL Cluster NDB 7.1.26. (Bug #15935206)
For each LQH instance, there is one instance of each counter in the
following list:

   * `LQHKEY_OVERLOAD': Number of primary key requests rejected at the
     LQH block instance due to transporter overload

   * `LQHKEY_OVERLOAD_TC': Count of instances of `LQHKEY_OVERLOAD'
     where the TC node transporter was overloaded

   * `LQHKEY_OVERLOAD_READER': Count of instances of `LQHKEY_OVERLOAD'
     where the API reader (reads only) node was overloaded.

   * `LQHKEY_OVERLOAD_NODE_PEER': Count of instances of
     `LQHKEY_OVERLOAD' where the next backup data node (writes only)
     was overloaded

   * `LQHKEY_OVERLOAD_SUBSCRIBER': Count of instances of
     `LQHKEY_OVERLOAD' where a event subscriber (writes only) was
     overloaded.

   * `LQHSCAN_SLOWDOWNS': Count of instances where a fragment scan
     batch size was reduced due to scanning API transporter overload.


File: manual.info,  Node: mysql-cluster-ndbinfo-diskpagebuffer,  Next: mysql-cluster-ndbinfo-logbuffers,  Prev: mysql-cluster-ndbinfo-counters,  Up: mysql-cluster-ndbinfo

17.5.10.8 The ndbinfo diskpagebuffer Table
..........................................

The `diskpagebuffer' table provides statistics about disk page buffer
usage by MySQL Cluster Disk Data tables.

The following table provides information about the columns in the
`diskpagebuffer' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about the columns in the
`diskpagebuffer' table. The table shows the column names, data type,
and provides a brief description.

Column Name                   Type           Description
`node_id'                     integer        The data node ID
`block_instance'              integer        Block instance
`pages_written'               integer        Number of pages written to
                                             disk.
`pages_written_lcp'           integer        Number of pages written by
                                             local checkpoints.
`pages_read'                  integer        Number of pages read from
                                             disk
`log_waits'                   integer        Number of page writes
                                             waiting for log to be
                                             written to disk
`page_requests_direct_return' integer        Number of requests for pages
                                             that were available in buffer
`page_requests_wait_queue'    integer        Number of requests that had
                                             to wait for pages to become
                                             available in buffer
`page_requests_wait_io'       integer        Number of requests that had
                                             to be read from pages on
                                             disk (pages were unavailable
                                             in buffer)

You can use this table with MySQL Cluster Disk Data tables to determine
whether `DiskPageBufferMemory' is sufficiently large to allow data to
be read from the buffer rather from disk; minimizing disk seeks can
help improve performance of such tables.

You can determine the proportion of reads from `DiskPageBufferMemory' to
the total number of reads using a query such as this one, which obtains
this ratio as a percentage:


     SELECT
       node_id,
       100 * page_requests_direct_return /
         (page_requests_direct_return + page_requests_wait_io)
           AS hit_ratio
     FROM ndbinfo.diskpagebuffer;

The result from this query should be similar to what is shown here,
with one row for each data node in the cluster (in this example, the
cluster has 4 data nodes):


     +---------+-----------+
     | node_id | hit_ratio |
     +---------+-----------+
     |       5 |   97.6744 |
     |       6 |   97.6879 |
     |       7 |   98.1776 |
     |       8 |   98.1343 |
     +---------+-----------+
     4 rows in set (0.00 sec)

`hit_ratio' values approaching 100% indicate that only a very small
number of reads are being made from disk rather than from the buffer,
which means that Disk Data read performance is approaching an optimum
level. If any of these values are less than 95%, this is a strong
indicator that the setting for `DiskPageBufferMemory' needs to be
increased in the `config.ini' file.

*Note*:

A change in `DiskPageBufferMemory' requires a rolling restart of all of
the cluster's data nodes before it takes effect.


File: manual.info,  Node: mysql-cluster-ndbinfo-logbuffers,  Next: mysql-cluster-ndbinfo-logspaces,  Prev: mysql-cluster-ndbinfo-diskpagebuffer,  Up: mysql-cluster-ndbinfo

17.5.10.9 The ndbinfo logbuffers Table
......................................

The `logbuffer' table provides information on MySQL Cluster log buffer
usage.

The following table provides information about the columns in the
`logbuffers' table. For each column, the table shows the name, data
type, and a brief description.

This table provides information about the columns in the `logbuffers'
table. The table shows the column names, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            The ID of this data node.
`log_type'             string             Type of log; one of: `REDO' or
                                          `DD-UNDO'.
`log_id'               integer            The log ID.
`log_part'             integer            The log part number.
`total'                integer            Total space available for this
                                          log.
`used'                 integer            Space used by this log.


File: manual.info,  Node: mysql-cluster-ndbinfo-logspaces,  Next: mysql-cluster-ndbinfo-membership,  Prev: mysql-cluster-ndbinfo-logbuffers,  Up: mysql-cluster-ndbinfo

17.5.10.10 The ndbinfo logspaces Table
......................................

This table provides information about MySQL Cluster log space usage.

The following table provides information about the columns in the
`logspaces' table. For each column, the table shows the name, data
type, and a brief description.

This table provides information about the columns in the `logspaces'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            The ID of this data node.
`log_type'             string             Type of log; one of: `REDO' or
                                          `DD-UNDO'.
`log_id'               integer            The log ID.
`log_part'             integer            The log part number.
`total'                integer            Total space available for this
                                          log.
`used'                 integer            Space used by this log.


File: manual.info,  Node: mysql-cluster-ndbinfo-membership,  Next: mysql-cluster-ndbinfo-memoryusage,  Prev: mysql-cluster-ndbinfo-logspaces,  Up: mysql-cluster-ndbinfo

17.5.10.11 The ndbinfo membership Table
.......................................

The `membership' table describes the view that each data node has of
all the others in the cluster, including node group membership,
president node, arbitrator, arbitrator successor, arbitrator connection
states, and other information.

The following table provides information about the columns in the
`membership' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about the columns in the `membership'
table. The table shows the name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            This node's node ID
`group_id'             integer            Node group to which this node
                                          belongs
`left node'            integer            Node ID of the previous node
`right_node'           integer            Node ID of the next node
`president'            integer            President's node ID
`successor'            integer            Node ID of successor to
                                          president
`succession_order'     integer            Order in which this node
                                          succeeds to presidency
`Conf_HB_order'        integer            -
`arbitrator'           integer            Node ID of arbitrator
`arb_ticket'           string             Internal identifier used to
                                          track arbitration
`arb_state'            Enumeration (see   Arbitration state
                       text)              
`arb_connected'        `Yes' or `No'      Whether this node is connected
                                          to the arbitrator
`connected_rank1_arbs' List of node IDs   Connected arbitrators of rank 1
`connected_rank2_arbs' List of node IDs   Connected arbitrators of rank 1

The node ID and node group ID are the same as reported by *Note
`ndb_mgm -e "SHOW"': mysql-cluster-programs-ndb-mgm.

`left_node' and `right_node' are defined in terms of a model that
connects all data nodes in a circle, in order of their node IDs,
similar to the ordering of the numbers on a clock dial, as shown here:

Arrangement of nodes in a circle

In this example, we have 8 data nodes, numbered 5, 6, 7, 8, 12, 13, 14,
and 15, ordered clockwise in a circle. We determine `left' and `right'
from the interior of the circle. The node to the left of node 5 is node
15, and the node to the right of node 5 is node 6. You can see all these
relationships by running the following query and observing the output:


     mysql> SELECT node_id,left_node,right_node
         -> FROM ndbinfo.membership;
     +---------+-----------+------------+
     | node_id | left_node | right_node |
     +---------+-----------+------------+
     |       5 |        15 |          6 |
     |       6 |         5 |          7 |
     |       7 |         6 |          8 |
     |       8 |         7 |         12 |
     |      12 |         8 |         13 |
     |      13 |        12 |         14 |
     |      14 |        13 |         15 |
     |      15 |        14 |          5 |
     +---------+-----------+------------+
     8 rows in set (0.00 sec)

The designations `left' and `right' are used in the event log in the
same way.

The `president' node is the node viewed by the current node as
responsible for setting an arbitrator (see MySQL Cluster Start Phases
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-start-phases.html)).
If the president fails or becomes disconnected, the current node
expects the node whose ID is shown in the `successor' column to become
the new president. The `succession_order' column shows the place in the
succession queue that the current node views itself as having.

In a normal MySQL Cluster, all data nodes should see the same node as
`president', and the same node (other than the president) as its
`successor'. In addition, the current president should see itself as
`1' in the order of succession, the `successor' node should see itself
as `2', and so on.

All nodes should show the same `arb_ticket' values as well as the same
`arb_state' values.  Possible `arb_state' values are `ARBIT_NULL',
`ARBIT_INIT', `ARBIT_FIND', `ARBIT_PREP1', `ARBIT_PREP2', `ARBIT_START',
`ARBIT_RUN', `ARBIT_CHOOSE', `ARBIT_CRASH', and `UNKNOWN'.

`arb_connected' shows whether this node is connected to the node shown
as this node's `arbitrator'.

The `connected_rank1_arbs' and `connected_rank2_arbs' columns each
display a list of 0 or more arbitrators having an `ArbitrationRank'
equal to 1, or to 2, respectively.

*Note*:

Both management nodes and API nodes are eligible to become arbitrators.

Like the *Note `arbitrator_validity_detail':
mysql-cluster-ndbinfo-arbitrator-validity-detail. and *Note
`arbitrator_validity_summary':
mysql-cluster-ndbinfo-arbitrator-validity-summary.  tables, this table
was added in MySQL Cluster NDB 7.0.37 and MySQL Cluster NDB 7.1.26.


File: manual.info,  Node: mysql-cluster-ndbinfo-memoryusage,  Next: mysql-cluster-ndbinfo-nodes,  Prev: mysql-cluster-ndbinfo-membership,  Up: mysql-cluster-ndbinfo

17.5.10.12 The ndbinfo memoryusage Table
........................................

Querying this table provides information similar to that provided by
the `ALL REPORT MemoryUsage' command in the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. client, or logged by `ALL DUMP 1000'.

The following table provides information about the columns in the
`memoryusage' table in MySQL Cluster NDB 7.1.3 and later. For each
column, the table shows the name, data type, and a brief description.
Additional information can be found in the notes following the table.

This table provides information about the columns in the `memoryusage'
table in MySQL Cluster NDB 7.1.3 and later. The table shows the column
name, data type, and provides a brief description.

Column Name            Type               Description
`node_id'              integer            The node ID of this data node.
`memory_type'          string             One of `Data memory', `Index
                                          memory', or (_MySQL Cluster NDB
                                          7.1.31 and later_) `Long message
                                          buffer'.
`used'                 integer            Number of bytes currently used
                                          for data memory or index memory
                                          by this data node.
`used_pages'           integer            Number of pages currently used
                                          for data memory or index memory
                                          by this data node; see text.
`total'                integer            Total number of bytes of data
                                          memory or index memory
                                          available for this data node;
                                          see text.
`total_pages'          integer            Total number of memory pages
                                          available for data memory or
                                          index memory on this data node;
                                          see text.

The `total' column represents the total amount of memory in bytes
available for the given resource (data memory or index memory) on a
particular data node. This number should be approximately equal to the
setting of the corresponding configuration parameter in the `config.ini'
file.

Suppose that the cluster has 2 data nodes having node IDs `5' and `6',
and the `config.ini' file contains the following:


     [ndbd default]
     DataMemory = 1G
     IndexMemory = 1G

Suppose also that the value of the `LongMessageBuffer' configuration
parameter is allowed to assume its default (64 MB in MySQL Cluster NDB
7.1.31 and later).

The following query shows approximately the same values:


     mysql> SELECT node_id, memory_type, total
          > FROM ndbinfo.memoryusage;
     +---------+---------------------+------------+
     | node_id | memory_type         | total      |
     +---------+---------------------+------------+
     |       5 | Data memory         | 1073741824 |
     |       5 | Index memory        | 1074003968 |
     |       5 | Long message buffer |   67108864 |
     |       6 | Data memory         | 1073741824 |
     |       6 | Index memory        | 1074003968 |
     |       6 | Long message buffer |   67108864 |
     +---------+---------------------+------------+
     6 rows in set (0.00 sec)

In this case, the `total' column values for index memory are slightly
higher than the value set of `IndexMemory' due to internal rounding.

For the `used_pages' and `total_pages' columns, resources are measured
in pages, which are 32K in size for `DataMemory' and 8K for
`IndexMemory'. For long message buffer memory, the page size is 256
bytes.

Long message buffer information can be found in this table beginning
with MySQL Cluster NDB 7.1.31; in earlier versions, only data memory
and index memory were included.

MySQL Cluster NDB 7.1.2 and earlier

The remainder of this section provides information about the
`memoryusage' table as implemented prior to MySQL Cluster NDB 7.1.3.
(If you are using MySQL Cluster NDB 7.1.3 or later, refer to the
beginning of this section.) For each column, the table shown here
provides the name, data type, and a brief description. Additional
information can be found in the notes following the table.

This table provides information about the `memoryusage' table as
implemented prior to MySQL Cluster NDB 7.1.3. The table shows the
column name, data type, and provides a brief description.

Column Name            Type               Description
`node_id'              integer            The node ID of this data node.
`memory_type'          string             One of `Data memory' or `Index
                                          memory'
`used'                 integer            Number of memory pages used;
                                          see text.
`max'                  integer            Total number of memory pages
                                          available; see text.

For the `used' and `max' columns, resources are measured in pages,
which (in MySQL Cluster NDB 7.1.2 and earlier) are 16K in size for
`DataMemory' and 8K for `IndexMemory'. This example shows how to use
this information in obtaining totals for `DataMemory', `IndexMemory',
or both, which you can do by summing across data nodes and table
columns, like this:


     mysql> USE ndbinfo;
     Database changed
     mysql> SET @IPAGE := 8 * 1024;
     Query OK, 0 rows affected (0.03 sec)

     mysql> SET @DPAGE := 2 * @IPAGE;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT
         ->     @DPAGE * SUM(used) as 'Total DataMemory Used',
         ->     @DPAGE * SUM(max) as 'Total DataMemory Available',
         ->     @DPAGE * SUM(used) DIV COUNT(*) as 'Average DataMemory Used Per Node',
         ->     @DPAGE * SUM(max) DIV COUNT(*) as 'Average DataMemory Available Per Node'
         ->         FROM memoryusage WHERE memory_type = 'Data memory'\G
     *************************** 1. row ***************************
                     Total DataMemory Used: 106102784
                Total DataMemory Available: 209977344
          Average DataMemory Used Per Node: 53051392
     Average DataMemory Available Per Node: 104988672
     1 row in set (0.34 sec)

     mysql> SELECT
         ->     @IPAGE * SUM(used) as 'Total IndexMemory Used',
         ->     @IPAGE * SUM(max) as 'Total IndexMemory Available',
         ->     @IPAGE * SUM(used) DIV COUNT(*) as 'Average IndexMemory Used Per Node',
         ->     @IPAGE * SUM(max) DIV COUNT(*) as 'Average IndexMemory Available Per Node'
         ->     FROM memoryusage WHERE memory_type = 'INDEX_MEMORY'\G
     *************************** 1. row ***************************
                     Total IndexMemory Used: 376832
                Total IndexMemory Available: 210239488
          Average IndexMemory Used Per Node: 188416
     Average IndexMemory Available Per Node: 105119744
     1 row in set (0.33 sec)

(We use `DIV' rather than `/' in both queries so that the results in
all of the output columns are integers.)

Prior to MySQL Cluster NDB 7.1.2, the `memory_type' column was named
`DATA_MEMORY'. (Bug #50926)


File: manual.info,  Node: mysql-cluster-ndbinfo-nodes,  Next: mysql-cluster-ndbinfo-pools,  Prev: mysql-cluster-ndbinfo-memoryusage,  Up: mysql-cluster-ndbinfo

17.5.10.13 The ndbinfo nodes Table
..................................

This table contains information on the status of data nodes. For each
data node that is running in the cluster, a corresponding row in this
table provides the node's node ID, status, and uptime. For nodes that
are starting, it also shows the current start phase.

The following table provides information about the columns in the
`nodes' table. For each column, the table shows the name, data type,
and a brief description. Additional information can be found in the
notes following the table.

This table provides information about the columns of the `nodes' table.
The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            The data node's unique node ID
                                          in the cluster.
`uptime'               integer            Time since the node was last
                                          started, in seconds.
`status'               string             Current status of the data
                                          node; see text for possible
                                          values.
`start_phase'          integer            If the data node is starting,
                                          the current start phase.
`config_generation'    integer            The version of the cluster
                                          configuration file in use on
                                          this data node.

The `uptime' column shows the time in seconds that this node has been
running since it was last started or restarted. This is a *Note
`BIGINT': integer-types.  value. This figure includes the time actually
needed to start the node; in other words, this counter starts running
the moment that *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. is first invoked; thus, even
for a node that has not yet finished starting, `uptime' may show a
non-zero value.

The `status' column shows the node's current status. This is one of:
`NOTHING', `CMVMI', `STARTING', `STARTED', `SINGLEUSER', `STOPPING_1',
`STOPPING_2', `STOPPING_3', or `STOPPING_4'.  When the status is
`STARTING', you can see the current start phase in the `start_phase'
column (see later in this section). `SINGLEUSER' is displayed in the
`status' column for all data nodes when the cluster is in single user
mode (see *Note mysql-cluster-single-user-mode::). Seeing one of the
`STOPPING' states does not necessarily mean that the node is shutting
down but can mean rather that it is entering a new state; for example,
if you put the cluster in single user mode, you can sometimes see data
nodes report their state briefly as `STOPPING_2' before the status
changes to `SINGLEUSER'.

The `start_phase' column uses the same range of values as those used in
the output of the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.
client `NODE_ID STATUS' command (see *Note
mysql-cluster-mgm-client-commands::). If the node is not currently
starting, then this column shows `0'. For a listing of MySQL Cluster
start phases with descriptions, see *Note mysql-cluster-start-phases::.

The `config_generation' column was added in MySQL Cluster NDB 7.0.24
and MySQL Cluster NDB 7.1.13. This column shows which version of the
cluster configuration is in effect on each data node. This can be
useful when performing a rolling restart of the cluster in order to
make changes in configuration parameters. For example, from the output
of the following *Note `SELECT': select. statement, you can see that
node 3 is not yet using the latest version of the cluster configuration
(`6') although nodes 1, 2, and 4 are doing so:


     mysql> USE ndbinfo;
     Database changed
     mysql> SELECT * FROM nodes;
     +---------+--------+---------+-------------+-------------------+
     | node_id | uptime | status  | start_phase | config_generation |
     +---------+--------+---------+-------------+-------------------+
     |       1 |  10462 | STARTED |           0 |                 6 |
     |       2 |  10460 | STARTED |           0 |                 6 |
     |       3 |  10457 | STARTED |           0 |                 5 |
     |       4 |  10455 | STARTED |           0 |                 6 |
     +---------+--------+---------+-------------+-------------------+
     2 rows in set (0.04 sec)

Therefore, for the case just shown, you should restart node 3 to
complete the rolling restart of the cluster.

*Note*:

When upgrading to MySQL Cluster NDB 7.0.24 or MySQL Cluster NDB 7.1.13
from a previous version of MySQL Cluster, you should run *Note
`mysql_upgrade': mysql-upgrade. on all MySQL Servers that should
connect to the cluster, in order to enable support for the new
`config_generation' column. Otherwise, when you attempt to access this
table, you get the warning `Table 'ndb$nodes' is defined differently in
NDB, there are more columns available...'

Nodes that are stopped are not accounted for in this table.  Suppose
that you have a MySQL Cluster with 4 data nodes (node IDs 1, 2, 3 and
4), and all nodes are running normally, then this table contains 4
rows, 1 for each data node:


     mysql> USE ndbinfo;
     Database changed
     mysql> SELECT * FROM nodes;
     +---------+--------+---------+-------------+-------------------+
     | node_id | uptime | status  | start_phase | config_generation |
     +---------+--------+---------+-------------+-------------------+
     |       1 |  11776 | STARTED |           0 |                 6 |
     |       2 |  11774 | STARTED |           0 |                 6 |
     |       3 |  11771 | STARTED |           0 |                 6 |
     |       4 |  11769 | STARTED |           0 |                 6 |
     +---------+--------+---------+-------------+-------------------+
     4 rows in set (0.04 sec)

If you shut down one of the nodes, only the nodes that are still
running are represented in the output of this *Note `SELECT': select.
statement, as shown here:


     ndb_mgm> 2 STOP
     Node 2: Node shutdown initiated
     Node 2: Node shutdown completed.
     Node 2 has shutdown.


     mysql> SELECT * FROM nodes;
     +---------+--------+---------+-------------+-------------------+
     | node_id | uptime | status  | start_phase | config_generation |
     +---------+--------+---------+-------------+-------------------+
     |       1 |  11807 | STARTED |           0 |                 6 |
     |       3 |  11802 | STARTED |           0 |                 6 |
     |       4 |  11800 | STARTED |           0 |                 6 |
     +---------+--------+---------+-------------+-------------------+
     3 rows in set (0.02 sec)


File: manual.info,  Node: mysql-cluster-ndbinfo-pools,  Next: mysql-cluster-ndbinfo-resources,  Prev: mysql-cluster-ndbinfo-nodes,  Up: mysql-cluster-ndbinfo

17.5.10.14 The ndbinfo pools Table
..................................

*Important*:

This table was part of the original `ndbinfo' implementation, but was
later removed (in MySQL Cluster NDB 7.1.3). The information in this
section is now obsolete, and subject to removal in a future version of
the documentation.

The `pools' table was originally intended to provide information about
*Note `NDB': mysql-cluster.  memory pool usage, but was later removed.

For each column, this table shows the name, data type, and a brief
description of each `ndbinfo.pools' column (as it appeared prior to
MySQL Cluster NDB 7.1.3).  Additional information can be found in the
notes afterward.

This table provides information about the columns in the
`ndbinfo.pools' table (as it appeared prior to MySQL Cluster NDB
7.1.3). The table shows the column name, data type, and provides a
brief description.

Column Name            Type               Description
`node_id'              integer            The data node's node ID.
`block_name'           string             Name of the NDB kernel block
                                          using this pool.
`block_instance'       integer            Kernel block instance ID.
`pool_name'            string             The name of the pool.
`used'                 integer            Amount of the pool in use.
`total'                integer            Total size of the pool.
`high'                 integer            The maximum used from this pool
                                          (since the node was last
                                          started).
`entry_size'           integer            The size of each object, in
                                          bytes.
`param_name1'          string             Name of a configuration
                                          parameter associated with this
                                          pool (or `NULL'); see text.
`param_name2'          string             Name of a configuration
                                          parameter associated with this
                                          pool (or `NULL'); see text.
`param_name3'          string             Name of a configuration
                                          parameter associated with this
                                          pool (or `NULL'); see text.
`param_name4'          string             Name of a configuration
                                          parameter associated with this
                                          pool (or `NULL'); see text.

The columns `param_name1', `param_name2', `param_name3', and
`param_name4' contain names of configuration parameters that are
associated with a given pool.  If no parameters are associated with the
pool, then all 4 of these columns are `NULL'. For pools that are
associated with configuration parameters, these columns are filled with
non-`NULL' values, but not in any particular order.

You can use a query such as the one shown here to generate a table
showing the associations of pools, NDB kernel blocks, and (where
applicable) configuration parameters:


     SELECT
         DISTINCT(pool_name) as 'Pool',
         block_name as 'Block',
         IF(
             (param_name1 && param_name2 && param_name3 && param_name4) IS NULL,
             '[NONE]',
             REPLACE(
                 TRIM(
                     CONCAT(
                         IFNULL(param_name1, ''),
                         IFNULL(CONCAT(' ', param_name2), ''),
                         IFNULL(CONCAT(' ', param_name3), ''),
                         IFNULL(CONCAT(' ', param_name4), '')
                     )
                 ), ' ', ', '
             )
         ) as 'Parameter(s)'
     FROM pools ORDER BY pool_name;

You may also find the following stored procedure useful. It returns a
list of pools associated with a given configuration parameter, along
with the kernel blocks to which these pools belong. You can see here
the statement used to create this stored procedure along with sample
output for some typical parameters:


     mysql> DELIMITER |
     mysql> CREATE PROCEDURE get_pools (p VARCHAR(50))
         -> BEGIN
         ->     SELECT
         ->         DISTINCT(pool_name) as Pool,
         ->         block_name as Block
         ->     FROM ndbinfo.pools
         ->     WHERE p
         ->           IN (param_name1, param_name2, param_name3, param_name4)
         .>     ORDER BY Pool;
         -> END
         -> |
     Query OK, 0 rows affected (0.02 sec)

     mysql> DELIMITER ;

     mysql> CALL get_pools('MaxNoOfTables');
     +-----------------+------------+
     | pool_name       | block_name |
     +-----------------+------------+
     | Table Record    | DBDICT     |
     | DictObject      | DBDICT     |
     | Index           | DBTC       |
     | Table           | BACKUP     |
     | Trigger         | BACKUP     |
     | Fragment        | BACKUP     |
     | Subscriber      | SUMA       |
     | Table           | SUMA       |
     | Subscription    | SUMA       |
     | Index           | DBTUX      |
     | Descriptor page | DBTUX      |
     +-----------------+------------+
     11 rows in set (0.30 sec)

     Query OK, 0 rows affected (0.30 sec)

     mysql> CALL get_pools('MaxNoOfOrderedIndexes');
     +-----------------+------------+
     | pool_name       | block_name |
     +-----------------+------------+
     | DictObject      | DBDICT     |
     | Index           | DBTC       |
     | Table           | BACKUP     |
     | Trigger         | BACKUP     |
     | Fragment        | BACKUP     |
     | Index           | DBTUX      |
     | Fragment        | DBTUX      |
     | Descriptor page | DBTUX      |
     +-----------------+------------+
     8 rows in set (0.29 sec)


File: manual.info,  Node: mysql-cluster-ndbinfo-resources,  Next: mysql-cluster-ndbinfo-server-operations,  Prev: mysql-cluster-ndbinfo-pools,  Up: mysql-cluster-ndbinfo

17.5.10.15 The ndbinfo resources Table
......................................

This table provides information about data node resource availability
and usage.

These resources are sometimes known as _super-pools_.

The following table provides information about the columns in the
`resources' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about the columns in the `resources'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            The unique node ID of this data
                                          node.
`resource_name'        string             Name of the resource; see text.
`reserved'             integer            The amount reserved for this
                                          resource.
`used'                 integer            The amount actually used by
                                          this resource.
`max'                  integer            The maximum amount of this
                                          resource used, since the node
                                          was last started.

The `resource_name' can be one of `RESERVED', `DISK_OPERATIONS',
`DISK_RECORDS', `DATA_MEMORY', `JOBBUFFER', `FILE_BUFFERS', or
`TRANSPORTER_BUFFERS'.


File: manual.info,  Node: mysql-cluster-ndbinfo-server-operations,  Next: mysql-cluster-ndbinfo-server-transactions,  Prev: mysql-cluster-ndbinfo-resources,  Up: mysql-cluster-ndbinfo

17.5.10.16 The ndbinfo server_operations Table
..............................................

The `server_operations' table contains entries for all ongoing *Note
`NDB': mysql-cluster. operations that the current SQL node (MySQL
Server) is currently involved in. It effectively is a subset of the
*Note `cluster_operations': mysql-cluster-ndbinfo-cluster-operations.
table, in which operations for other SQL and API nodes are not shown.

The following table provides information about the columns in the
`server_operations' table. For each column, the table shows the name,
data type, and a brief description.  Additional information can be
found in the notes following the table.

This table provides information about the columns in the
`server_operations' table. The table shows the column name, data type,
and provides a brief description.

Column Name            Type               Description
`mysql_connection_id'  integer            MySQL Server connection ID
`node_id'              integer            Node ID
`block_instance'       integer            Block instance
`transid'              integer            Transaction ID
`operation_type'       string             Operation type (see text for
                                          possible values)
`state'                string             Operation state (see text for
                                          possible values)
`tableid'              integer            Table ID
`fragmentid'           integer            Fragment ID
`client_node_id'       integer            Client node ID
`client_block_ref'     integer            Client block reference
`tc_node_id'           integer            Transaction coordinator node ID
`tc_block_no'          integer            Transaction coordinator block
                                          number
`tc_block_instance'    integer            Transaction coordinator block
                                          instance

The `mysql_connection_id' is the same as the connection or session ID
shown in the output of *Note `SHOW PROCESSLIST': show-processlist. It
is obtained from the `INFORMATION_SCHEMA' table *Note
`NDB_TRANSID_MYSQL_CONNECTION_MAP':
ndb-transid-mysql-connection-map-table.

The transaction ID is a unique 64-bit number which can be obtained
using the NDB API's `getTransactionId()'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-gettransactionid)
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)

The `operation_type' column can take any one of the values `READ',
`READ-SH', `READ-EX', `INSERT', `UPDATE', `DELETE', `WRITE', `UNLOCK',
`REFRESH', `SCAN', `SCAN-SH', `SCAN-EX', or `<unknown>'.

The `state' column can have any one of the values `ABORT_QUEUED',
`ABORT_STOPPED', `COMMITTED', `COMMIT_QUEUED', `COMMIT_STOPPED',
`COPY_CLOSE_STOPPED', `COPY_FIRST_STOPPED', `COPY_STOPPED',
`COPY_TUPKEY', `IDLE', `LOG_ABORT_QUEUED', `LOG_COMMIT_QUEUED',
`LOG_COMMIT_QUEUED_WAIT_SIGNAL', `LOG_COMMIT_WRITTEN',
`LOG_COMMIT_WRITTEN_WAIT_SIGNAL', `LOG_QUEUED', `PREPARED',
`PREPARED_RECEIVED_COMMIT', `SCAN_CHECK_STOPPED', `SCAN_CLOSE_STOPPED',
`SCAN_FIRST_STOPPED', `SCAN_RELEASE_STOPPED', `SCAN_STATE_USED',
`SCAN_STOPPED', `SCAN_TUPKEY', `STOPPED', `TC_NOT_CONNECTED',
`WAIT_ACC', `WAIT_ACC_ABORT', `WAIT_AI_AFTER_ABORT', `WAIT_ATTR',
`WAIT_SCAN_AI', `WAIT_TUP', `WAIT_TUPKEYINFO', `WAIT_TUP_COMMIT', or
`WAIT_TUP_TO_ABORT'. (If the MySQL Server is running with
`ndbinfo_show_hidden' enabled, you can view this list of states by
selecting from the `ndb$dblqh_tcconnect_state' table, which is normally
hidden.)

You can obtain the name of an `NDB' table from its table ID by checking
the output of *Note `ndb_show_tables':
mysql-cluster-programs-ndb-show-tables.

The `fragid' is the same as the partition number seen in the output of
*Note `ndb_desc': mysql-cluster-programs-ndb-desc.
`--extra-partition-info' (short form `-p').

In `client_node_id' and `client_block_ref', `client' refers to a MySQL
Cluster API or SQL node (that is, an NDB API client or a MySQL Server
attached to the cluster).

This table was added in MySQL Cluster NDB 7.1.17.


File: manual.info,  Node: mysql-cluster-ndbinfo-server-transactions,  Next: mysql-cluster-ndbinfo-threadblocks,  Prev: mysql-cluster-ndbinfo-server-operations,  Up: mysql-cluster-ndbinfo

17.5.10.17 The ndbinfo server_transactions Table
................................................

The `server_transactions' table is subset of the *Note
`cluster_transactions': mysql-cluster-ndbinfo-cluster-transactions.
table, but includes only those transactions in which the current SQL
node (MySQL Server) is a participant, while including the relevant
connection IDs.

The following table provides information about the columns in the
`server_transactions' table. For each column, the table shows the name,
data type, and a brief description. Additional information can be found
in the notes following the table.

This table provides information about columns in the
`server_transactions' table. The table shows the column name, data
type, and provides a brief description.

Column Name            Type               Description
`mysql_connection_id'  integer            MySQL Server connection ID
`node_id'              integer            Transaction coordinator node ID
`block_instance'       integer            Transaction coordinator block
                                          instance
`transid'              integer            Transaction ID
`state'                string             Operation state (see text for
                                          possible values)
`count_operations'     integer            Number of stateful operations
                                          in the transaction
`outstanding_operations'integer            Operations still being executed
                                          by local data management layer
                                          (LQH blocks)
`inactive_seconds'     integer            Time spent waiting for API
`client_node_id'       integer            Client node ID
`client_block_ref'     integer            Client block reference

The `mysql_connection_id' is the same as the connection or session ID
shown in the output of *Note `SHOW PROCESSLIST': show-processlist. It
is obtained from the `INFORMATION_SCHEMA' table *Note
`NDB_TRANSID_MYSQL_CONNECTION_MAP':
ndb-transid-mysql-connection-map-table.

The transaction ID is a unique 64-bit number which can be obtained
using the NDB API's `getTransactionId()'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-gettransactionid)
method. (Currently, the MySQL Server does not expose the NDB API
transaction ID of an ongoing transaction.)

The `state' column can have any one of the values `CS_ABORTING',
`CS_COMMITTING', `CS_COMMIT_SENT', `CS_COMPLETE_SENT', `CS_COMPLETING',
`CS_CONNECTED', `CS_DISCONNECTED', `CS_FAIL_ABORTED',
`CS_FAIL_ABORTING', `CS_FAIL_COMMITTED', `CS_FAIL_COMMITTING',
`CS_FAIL_COMPLETED', `CS_FAIL_PREPARED', `CS_PREPARE_TO_COMMIT',
`CS_RECEIVING', `CS_REC_COMMITTING', `CS_RESTART',
`CS_SEND_FIRE_TRIG_REQ', `CS_STARTED', `CS_START_COMMITTING',
`CS_START_SCAN', `CS_WAIT_ABORT_CONF', `CS_WAIT_COMMIT_CONF',
`CS_WAIT_COMPLETE_CONF', `CS_WAIT_FIRE_TRIG_REQ'. (If the MySQL Server
is running with `ndbinfo_show_hidden' enabled, you can view this list
of states by selecting from the `ndb$dbtc_apiconnect_state' table,
which is normally hidden.)

In `client_node_id' and `client_block_ref', `client' refers to a MySQL
Cluster API or SQL node (that is, an NDB API client or a MySQL Server
attached to the cluster).

This table was added in MySQL Cluster NDB 7.1.17.


File: manual.info,  Node: mysql-cluster-ndbinfo-threadblocks,  Next: mysql-cluster-ndbinfo-threadstat,  Prev: mysql-cluster-ndbinfo-server-transactions,  Up: mysql-cluster-ndbinfo

17.5.10.18 The ndbinfo threadblocks Table
.........................................

The `threadblocks' table associates data nodes, threads, and instances
of `NDB' kernel blocks.

The following table provides information about the columns in the
`threadblocks' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about columns in the `threadblocks'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            Node ID
`thr_no'               integer            Thread ID
`block_name'           string             Block name
`block_instance'       integer            Block instance number

The `block_name' is one of the values found in the `block_name' column
when selecting from the *Note `ndbinfo.blocks':
mysql-cluster-ndbinfo-blocks. table. Although the list of possible
values is static for a given MySQL Cluster release, the list may vary
between releases.

This table was added in MySQL Cluster NDB 7.1.17.


File: manual.info,  Node: mysql-cluster-ndbinfo-threadstat,  Next: mysql-cluster-ndbinfo-transporters,  Prev: mysql-cluster-ndbinfo-threadblocks,  Up: mysql-cluster-ndbinfo

17.5.10.19 The ndbinfo threadstat Table
.......................................

The `threadstat' table provides a rough snapshot of statistics for
threads running in the `NDB' kernel.

The following table provides information about the columns in the
`threadstat' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about the columns in the `threadstat'
table. The table shows the column names, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            Node ID
`thr_no'               integer            Thread ID
`thr_nm'               string             Thread name
`c_loop'               string             Number of loops in main loop
`c_exec'               string             Number of signals executed
`c_wait'               string             Number of times waiting for
                                          additional input
`c_l_sent_prioa'       integer            Number of priority A signals
                                          sent to own node
`c_l_sent_priob'       integer            Number of priority B signals
                                          sent to own node
`c_r_sent_prioa'       integer            Number of priority A signals
                                          sent to remote node
`c_r_sent_priob'       integer            Number of priority B signals
                                          sent to remote node
`os_tid'               integer            OS thread ID
`os_now'               integer            OS time (ms)
`os_ru_utime'          integer            OS user CPU time (µs)
`os_ru_stime'          integer            OS system CPU time (µs)
`os_ru_minflt'         integer            OS page reclaims (soft page
                                          faults)
`os_ru_majflt'         integer            OS page faults (hard page
                                          faults)
`os_ru_nvcsw'          integer            OS voluntary context switches
`os_ru_nivcsw'         integer            OS involuntary context switches

`os_time' uses the system `gettimeofday()' call.

The values of the `os_ru_utime', `os_ru_stime', `os_ru_minflt',
`os_ru_majflt', `os_ru_nvcsw', and `os_ru_nivcsw' columns are obtained
using the system `getrusage()' call, or the equivalent.

Since this table contains counts taken at a given point in time, for
best results it is necessary to query this table periodically and store
the results in an intermediate table or tables. The MySQL Server's
Event Scheduler can be employed to automate such monitoring. For more
information, see *Note events::.

This table was added in MySQL Cluster NDB 7.1.17.


File: manual.info,  Node: mysql-cluster-ndbinfo-transporters,  Prev: mysql-cluster-ndbinfo-threadstat,  Up: mysql-cluster-ndbinfo

17.5.10.20 The ndbinfo transporters Table
.........................................

This table contains information about *Note `NDB': mysql-cluster.
transporters.

The following table provides information about the columns in the
`transporters' table. For each column, the table shows the name, data
type, and a brief description.  Additional information can be found in
the notes following the table.

This table provides information about the columns in the `transporters'
table. The table shows the column name, data type, and provides a brief
description.

Column Name            Type               Description
`node_id'              integer            This data node's unique node ID
                                          in the cluster.
`remote_node_id'       integer            The remote data node's node ID.
`status'               string             Status of the connection.
`remote_address'       string             Name or IP address of the
                                          remote host
`bytes_sent'           integer            Number of bytes sent using this
                                          connection
`bytes_received'                          Number of bytes received using
                                          this connection
`connect_count'                           Number of times connection
                                          established on this transporter
`overloaded'                              1 if this transporter is
                                          currently overloaded, otherwise
                                          0
`overload_count'                          Number of times this
                                          transporter has entered
                                          overload state since connecting
`slowdown'                                1 if this transporter is in
                                          scan slowdown state, otherwise 0
`slowdown_count'                          Number of times this
                                          transporter has entered scan
                                          slowdown state since connecting

For each running data node in the cluster, the `transporters' table
displays a row showing the status of each of that node's connections
with all nodes in the cluster, _including itself_. This information is
shown in the table's _status_ column, which can have any one of the
following values: `CONNECTING', `CONNECTED', `DISCONNECTING', or
`DISCONNECTED'.

Connections to API and management nodes which are configured but not
currently connected to the cluster are shown with status
`DISCONNECTED'. Rows where the `node_id' is that of a data nodes which
is not currently connected are not shown in this table. (This is
similar omission of disconnected nodes in the *Note `ndbinfo.nodes':
mysql-cluster-ndbinfo-nodes. table.

The `remote_address', `bytes_sent', and `bytes_received' columns were
added in MySQL Cluster NDB 7.0.36 and MySQL Cluster NDB 7.1.25. The
`remote_address' is the host name or address for the node whose ID is
shown in the `remote_node_id' column. The `bytes_sent' from this node
and `bytes_received' by this node are the numbers, respectively, of
bytes sent and received by the node using this connection since it was
established; for nodes whose status is `CONNECTING' or `DISCONNECTED',
these columns always display `0'.

The `connect_count', `overloaded', `overload_count' ,`slowdown', and
`slowdown_count' columns were added in MySQL Cluster NDB 7.0.37 and
MySQL Cluster NDB 7.1.26. These counters are reset on connection, and
retain their values after the remote node disconnects. Also beginning
with MySQL Cluster NDB 7.0.37 and MySQL Cluster NDB 7.1.26, the
`bytes_send' and `bytes_received' counters are reset on connection as
well, and so retain their values following disconnection. (Previously,
the values in these columns were reset on disconnection.) (Bug
#15935206)

Assume you have a 5-node cluster consisting of 2 data nodes, 2 SQL
nodes, and 1 management node, as shown in the output of the `SHOW'
command in the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. client:


     ndb_mgm> SHOW
     Connected to Management Server at: localhost:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=1    @10.100.10.1  (5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=2    @10.100.10.2  (5.1.73-ndb-7.1.34, Nodegroup: 0)

     [ndb_mgmd(MGM)] 1 node(s)
     id=10   @10.100.10.10  (5.1.73-ndb-7.1.34)

     [mysqld(API)]   2 node(s)
     id=20   @10.100.10.20  (5.1.73-ndb-7.1.34)
     id=21   @10.100.10.21  (5.1.73-ndb-7.1.34)

There are 10 rows in the `transporters' table--5 for the first data
node, and 5 for the second--assuming that all data nodes are running,
as shown here:


     mysql> SELECT node_id, remote_node_id, status
         ->   FROM ndbinfo.transporters;
     +---------+----------------+---------------+
     | node_id | remote_node_id | status        |
     +---------+----------------+---------------+
     |       1 |              1 | DISCONNECTED  |
     |       1 |              2 | CONNECTED     |
     |       1 |             10 | CONNECTED     |
     |       1 |             20 | CONNECTED     |
     |       1 |             21 | CONNECTED     |
     |       2 |              1 | CONNECTED     |
     |       2 |              2 | DISCONNECTED  |
     |       2 |             10 | CONNECTED     |
     |       2 |             20 | CONNECTED     |
     |       2 |             21 | CONNECTED     |
     +---------+----------------+---------------+
     10 rows in set (0.04 sec)

If you shut down one of the data nodes in this cluster using the
command `2 STOP' in the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. client, then repeat the previous query
(again using the *Note `mysql': mysql. client), this table now shows
only 5 rows--1 row for each connection from the remaining management
node to another node, including both itself and the data node that is
currently offline--and displays `CONNECTING' for the status of each
remaining connection to the data node that is currently offline, as
shown here:


     mysql> SELECT node_id, remote_node_id, status
         ->   FROM ndbinfo.transporters;
     +---------+----------------+---------------+
     | node_id | remote_node_id | status        |
     +---------+----------------+---------------+
     |       1 |              1 | DISCONNECTED  |
     |       1 |              2 | CONNECTING    |
     |       1 |             10 | CONNECTED     |
     |       1 |             20 | CONNECTED     |
     |       1 |             21 | CONNECTED     |
     +---------+----------------+---------------+
     5 rows in set (0.02 sec)


File: manual.info,  Node: mysql-cluster-security,  Next: mysql-cluster-disk-data,  Prev: mysql-cluster-ndbinfo,  Up: mysql-cluster-management

17.5.11 MySQL Cluster Security Issues
-------------------------------------

* Menu:

* mysql-cluster-security-networking-issues::  MySQL Cluster Security and Networking Issues
* mysql-cluster-security-mysql-privileges::  MySQL Cluster and MySQL Privileges
* mysql-cluster-security-mysql-security-procedures::  MySQL Cluster and MySQL Security Procedures

This section discusses security considerations to take into account
when setting up and running MySQL Cluster.

Topics covered in this section include the following:

   * MySQL Cluster and network security issues

   * Configuration issues relating to running MySQL Cluster securely

   * MySQL Cluster and the MySQL privilege system

   * MySQL standard security procedures as applicable to MySQL Cluster


File: manual.info,  Node: mysql-cluster-security-networking-issues,  Next: mysql-cluster-security-mysql-privileges,  Prev: mysql-cluster-security,  Up: mysql-cluster-security

17.5.11.1 MySQL Cluster Security and Networking Issues
......................................................

In this section, we discuss basic network security issues as they
relate to MySQL Cluster. It is extremely important to remember that
MySQL Cluster `out of the box' is not secure; you or your network
administrator must take the proper steps to ensure that your cluster
cannot be compromised over the network.

Cluster communication protocols are inherently insecure, and no
encryption or similar security measures are used in communications
between nodes in the cluster. Because network speed and latency have a
direct impact on the cluster's efficiency, it is also not advisable to
employ SSL or other encryption to network connections between nodes, as
such schemes will effectively slow communications.

It is also true that no authentication is used for controlling API node
access to a MySQL Cluster. As with encryption, the overhead of imposing
authentication requirements would have an adverse impact on Cluster
performance.

In addition, there is no checking of the source IP address for either
of the following when accessing the cluster:

   * SQL or API nodes using `free slots' created by empty `[mysqld]' or
     `[api]' sections in the `config.ini' file

     This means that, if there are any empty `[mysqld]' or `[api]'
     sections in the `config.ini' file, then any API nodes (including
     SQL nodes) that know the management server's host name (or IP
     address) and port can connect to the cluster and access its data
     without restriction. (See *Note
     mysql-cluster-security-mysql-privileges::, for more information
     about this and related issues.)

     *Note*:

     You can exercise some control over SQL and API node access to the
     cluster by specifying a `HostName' parameter for all `[mysqld]' and
     `[api]' sections in the `config.ini' file. However, this also
     means that, should you wish to connect an API node to the cluster
     from a previously unused host, you need to add an `[api]' section
     containing its host name to the `config.ini' file.

     More information is available elsewhere in this chapter about the
     `HostName' parameter. Also see *Note mysql-cluster-quick::, for
     configuration examples using `HostName' with API nodes.

   * Any *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. client

     This means that any cluster management client that is given the
     management server's host name (or IP address) and port (if not the
     standard port) can connect to the cluster and execute any
     management client command. This includes commands such as `ALL
     STOP' and `SHUTDOWN'.

For these reasons, it is necessary to protect the cluster on the
network level. The safest network configuration for Cluster is one
which isolates connections between Cluster nodes from any other network
communications. This can be accomplished by any of the following
methods:

  1. Keeping Cluster nodes on a network that is physically separate
     from any public networks. This option is the most dependable;
     however, it is the most expensive to implement.

     We show an example of a MySQL Cluster setup using such a
     physically segregated network here:

     MySQL Cluster on a private network protected with a hardware
     firewall

     This setup has two networks, one private (solid box) for the
     Cluster management servers and data nodes, and one public (dotted
     box) where the SQL nodes reside. (We show the management and data
     nodes connected using a gigabit switch since this provides the
     best performance.) Both networks are protected from the outside by
     a hardware firewall, sometimes also known as a _network-based
     firewall_.

     This network setup is safest because no packets can reach the
     cluster's management or data nodes from outside the network--and
     none of the cluster's internal communications can reach the
     outside--without going through the SQL nodes, as long as the SQL
     nodes do not permit any packets to be forwarded. This means, of
     course, that all SQL nodes must be secured against hacking
     attempts.

     *Important*:

     With regard to potential security vulnerabilities, an SQL node is
     no different from any other MySQL server. See *Note
     security-against-attack::, for a description of techniques you can
     use to secure MySQL servers.

  2. Using one or more software firewalls (also known as _host-based
     firewalls_) to control which packets pass through to the cluster
     from portions of the network that do not require access to it. In
     this type of setup, a software firewall must be installed on every
     host in the cluster which might otherwise be accessible from
     outside the local network.

     The host-based option is the least expensive to implement, but
     relies purely on software to provide protection and so is the most
     difficult to keep secure.

     This type of network setup for MySQL Cluster is illustrated here:

     MySQL Cluster deployed on a network using software firewalls to
     create public and private zones

     Using this type of network setup means that there are two zones of
     MySQL Cluster hosts. Each cluster host must be able to communicate
     with all of the other machines in the cluster, but only those
     hosting SQL nodes (dotted box) can be permitted to have any
     contact with the outside, while those in the zone containing the
     data nodes and management nodes (solid box) must be isolated from
     any machines that are not part of the cluster. Applications using
     the cluster and user of those applications must _not_ be permitted
     to have direct access to the management and data node hosts.

     To accomplish this, you must set up software firewalls that limit
     the traffic to the type or types shown in the following table,
     according to the type of node that is running on each cluster host
     computer:

     This table lists node types that are accessed in a _host-based
     firewall_ cluster configuration and the traffic to permit for each
     node type.

     Type of Node to   Traffic to Permit
     be Accessed       
     SQL or API node      * It originates from the IP address of a
                            management or data node (using any TCP or UDP
                            port).
                       
                          * It originates from within the network in
                            which the cluster resides and is on the port
                            that your application is using.
     Data node or         * It originates from the IP address of a
     Management node        management or data node (using any TCP or UDP
                            port).
                       
                          * It originates from the IP address of an SQL
                            or API node.
     Any traffic other than that shown in the table for a given node
     type should be denied.

     The specifics of configuring a firewall vary from firewall
     application to firewall application, and are beyond the scope of
     this Manual. `iptables' is a very common and reliable firewall
     application, which is often used with `APF' as a front end to make
     configuration easier. You can (and should) consult the
     documentation for the software firewall that you employ, should
     you choose to implement a MySQL Cluster network setup of this
     type, or of a `mixed' type as discussed under the next item.

  3. It is also possible to employ a combination of the first two
     methods, using both hardware and software to secure the
     cluster--that is, using both network-based and host-based
     firewalls. This is between the first two schemes in terms of both
     security level and cost. This type of network setup keeps the
     cluster behind the hardware firewall, but permits incoming packets
     to travel beyond the router connecting all cluster hosts to reach
     the SQL nodes.

     One possible network deployment of a MySQL Cluster using hardware
     and software firewalls in combination is shown here:

     Network setup for MySQL Cluster using a combination of hardware
     and software firewalls to provide protection

     In this case, you can set the rules in the hardware firewall to
     deny any external traffic except to SQL nodes and API nodes, and
     then permit traffic to them only on the ports required by your
     application.

Whatever network configuration you use, remember that your objective
from the viewpoint of keeping the cluster secure remains the same--to
prevent any unessential traffic from reaching the cluster while
ensuring the most efficient communication between the nodes in the
cluster.

Because MySQL Cluster requires large numbers of ports to be open for
communications between nodes, the recommended option is to use a
segregated network. This represents the simplest way to prevent
unwanted traffic from reaching the cluster.

*Note*:

If you wish to administer a MySQL Cluster remotely (that is, from
outside the local network), the recommended way to do this is to use
`ssh' or another secure login shell to access an SQL node host. From
this host, you can then run the management client to access the
management server safely, from within the Cluster's own local network.

Even though it is possible to do so in theory, it is _not_ recommended
to use *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. to manage a
Cluster directly from outside the local network on which the Cluster is
running.  Since neither authentication nor encryption takes place
between the management client and the management server, this
represents an extremely insecure means of managing the cluster, and is
almost certain to be compromised sooner or later.


File: manual.info,  Node: mysql-cluster-security-mysql-privileges,  Next: mysql-cluster-security-mysql-security-procedures,  Prev: mysql-cluster-security-networking-issues,  Up: mysql-cluster-security

17.5.11.2 MySQL Cluster and MySQL Privileges
............................................

In this section, we discuss how the MySQL privilege system works in
relation to MySQL Cluster and the implications of this for keeping a
MySQL Cluster secure.

Standard MySQL privileges apply to MySQL Cluster tables. This includes
all MySQL privilege types (`SELECT' privilege, `UPDATE' privilege,
`DELETE' privilege, and so on) granted on the database, table, and
column level. As with any other MySQL Server, user and privilege
information is stored in the `mysql' system database. The SQL statements
used to grant and revoke privileges on *Note `NDB': mysql-cluster.
tables, databases containing such tables, and columns within such
tables are identical in all respects with the *Note `GRANT': grant. and
*Note `REVOKE': revoke. statements used in connection with database
objects involving any (other) MySQL storage engine. The same thing is
true with respect to the *Note `CREATE USER': create-user. and *Note
`DROP USER': drop-user. statements.

It is important to keep in mind that, by default, the MySQL grant
tables use the `MyISAM' storage engine.  Because of this, those tables
are not duplicated or shared among MySQL servers acting as SQL nodes in
a MySQL Cluster. By way of example, suppose that two SQL nodes *A* and
*B* are connected to the same MySQL Cluster, which has an *Note `NDB':
mysql-cluster.  table named `mytable' in a database named `mydb', and
that you execute an SQL statement on server *A* that creates a new user
`jon@localhost' and grants this user the `SELECT' privilege on that
table:


     mysql> GRANT SELECT ON mydb.mytable
         ->   TO jon@localhost IDENTIFIED BY 'mypass';

This user is _not_ created on server *B*. For this to take place, the
statement must also be run on server *B*. Similarly, statements run on
server *A* and affecting the privileges of existing users on server *A*
do not affect users on server *B* unless those statements are actually
run on server *B* as well.

In other words, _changes in users and their privileges do not
automatically propagate between SQL nodes by default_. Prior to MySQL
Cluster NDB 7.2, any synchronization of privileges between SQL nodes
must be done either manually or by scripting an application that
periodically synchronizes the privilege tables on all SQL nodes in the
cluster. In MySQL Cluster NDB 7.2 and later, you can enable automatic
distribution of MySQL users and privileges across MySQL Cluster SQL
nodes; see *Note mysql-cluster-privilege-distribution::, for details.

Conversely, because there is no way in MySQL to deny privileges
(privileges can either be revoked or not granted in the first place,
but not denied as such), there is no special protection for *Note
`NDB': mysql-cluster. tables on one SQL node from users that have
privileges on another SQL node. (This is true even if you are not using
the automatic distribution of user privileges available in MySQl
Cluster NDB 7.2 and later.) The most far-reaching example of this is
the MySQL `root' account, which can perform any action on any database
object. In combination with empty `[mysqld]' or `[api]' sections of the
`config.ini' file, this account can be especially dangerous. To
understand why, consider the following scenario:

   * The `config.ini' file contains at least one empty `[mysqld]' or
     `[api]' section. This means that the MySQL Cluster management
     server performs no checking of the host from which a MySQL Server
     (or other API node) accesses the MySQL Cluster.

   * There is no firewall, or the firewall fails to protect against
     access to the MySQL Cluster from hosts external to the network.

   * The host name or IP address of the MySQL Cluster's management
     server is known or can be determined from outside the network.

If these conditions are true, then anyone, anywhere can start a MySQL
Server with `--ndbcluster' `--ndb-connectstring=MANAGEMENT_HOST' and
access this MySQL Cluster. Using the MySQL `root' account, this person
can then perform the following actions:

   * Execute a *Note `SHOW DATABASES': show-databases.  statement to
     obtain a list of all *Note `NDB': mysql-cluster. databases

   * Execute a *Note `SHOW TABLES FROM SOME_DATABASE': show-tables.
     statement to obtain a list of all *Note `NDB': mysql-cluster.
     tables in a given database

   * Run any legal MySQL statements on any of those tables, such as:

        * `SELECT * FROM SOME_TABLE' to read all the data from any table

        * `DELETE FROM SOME_TABLE' to delete all the data from a table

        * `DESCRIBE SOME_TABLE' or `SHOW CREATE TABLE SOME_TABLE' to
          determine the table schema

        * `UPDATE SOME_TABLE SET COLUMN1 = SOME_VALUE' to fill a table
          column with `garbage' data; this could actually cause much
          greater damage than simply deleting all the data

          More insidious variations might include statements like these:


               UPDATE SOME_TABLE SET AN_INT_COLUMN = AN_INT_COLUMN + 1

          or


               UPDATE SOME_TABLE SET A_VARCHAR_COLUMN = REVERSE(A_VARCHAR_COLUMN)

          Such malicious statements are limited only by the imagination
          of the attacker.

     The only tables that would be safe from this sort of mayhem would
     be those tables that were created using storage engines other than
     *Note `NDB': mysql-cluster, and so not visible to a `rogue' SQL
     node.

     *Note*:

     A user who can log in as `root' can also access the
     `INFORMATION_SCHEMA' database and its tables, and so obtain
     information about databases, tables, stored routines, scheduled
     events, and any other database objects for which metadata is
     stored in `INFORMATION_SCHEMA'.

     It is also a very good idea to use different passwords for the
     `root' accounts on different cluster SQL nodes (unless you are
     using distributed privileges as supported in MySQL Cluster NDB 7.2
     and later).

In sum, you cannot have a safe MySQL Cluster if it is directly
accessible from outside your local network.

*Important*:

_Never leave the MySQL root account password empty_. This is just as
true when running MySQL as a MySQL Cluster SQL node as it is when
running it as a standalone (non-Cluster) MySQL Server, and should be
done as part of the MySQL installation process before configuring the
MySQL Server as an SQL node in a MySQL Cluster.

Prior to MySQL Cluster NDB 7.2, you should never convert the system
tables in the `mysql' database to use the *Note `NDB': mysql-cluster.
storage engine. There are a number of reasons why you should not do
this, but the most important reason is this: _Many of the SQL statements
that affect `mysql' tables storing information about user privileges,
stored routines, scheduled events, and other database objects cease to
function if these tables are changed to use any storage engine other
than `MyISAM'_. This is a consequence of various MySQL Server
internals. Beginning with MySQL Cluster NDB 7.2, you can use a stored
procedure provided for this purpose (see *Note
mysql-cluster-privilege-distribution::), but you are strongly advised
not to attempt convert the system tables manually.

Otherwise, if you need to synchronize `mysql' system tables between SQL
nodes, you can use standard MySQL replication to do so, or employ a
script to copy table entries between the MySQL servers.

Summary

The two most important points to remember regarding the MySQL privilege
system with regard to MySQL Cluster are:

  1. Prior to MySQL Cluster NDB 7.2

     Users and privileges established on one SQL node do not
     automatically exist or take effect on other SQL nodes in the
     cluster. Conversely, removing a user or privilege on one SQL node
     in the cluster does not remove the user or privilege from any
     other SQL nodes.

     In MySQL Cluster NDB 7.2 and later

     You can distribute MySQL users and privileges among SQL nodes
     using the SQL script, and the stored procedures it contains, that
     are supplied for this purpose in the MySQL Cluster distribution.

  2. Once a MySQL user is granted privileges on an *Note `NDB':
     mysql-cluster. table from one SQL node in a MySQL Cluster, that
     user can `see' any data in that table regardless of the SQL node
     from which the data originated. (This is true even if you are not
     using the privilege distribution support available in MySQl Cluster
     NDB 7.2 or later.)


File: manual.info,  Node: mysql-cluster-security-mysql-security-procedures,  Prev: mysql-cluster-security-mysql-privileges,  Up: mysql-cluster-security

17.5.11.3 MySQL Cluster and MySQL Security Procedures
.....................................................

In this section, we discuss MySQL standard security procedures as they
apply to running MySQL Cluster.

In general, any standard procedure for running MySQL securely also
applies to running a MySQL Server as part of a MySQL Cluster. First and
foremost, you should always run a MySQL Server as the `mysql' system
user; this is no different from running MySQL in a standard
(non-Cluster) environment. The `mysql' system account should be
uniquely and clearly defined. Fortunately, this is the default behavior
for a new MySQL installation. You can verify that the *Note `mysqld':
mysqld. process is running as the system user `mysql' by using the
system command such as the one shown here:


     shell> ps aux | grep mysql
     root     10467  0.0  0.1   3616  1380 pts/3    S    11:53   0:00 \
       /bin/sh ./mysqld_safe --ndbcluster --ndb-connectstring=localhost:1186
     mysql    10512  0.2  2.5  58528 26636 pts/3    Sl   11:53   0:00 \
       /usr/local/mysql/libexec/mysqld --basedir=/usr/local/mysql \
       --datadir=/usr/local/mysql/var --user=mysql --ndbcluster \
       --ndb-connectstring=localhost:1186 --pid-file=/usr/local/mysql/var/mothra.pid \
       --log-error=/usr/local/mysql/var/mothra.err
     jon      10579  0.0  0.0   2736   688 pts/0    S+   11:54   0:00 grep mysql

If the *Note `mysqld': mysqld. process is running as any other user
than `mysql', you should immediately shut it down and restart it as the
`mysql' user. If this user does not exist on the system, the `mysql'
user account should be created, and this user should be part of the
`mysql' user group; in this case, you should also make sure that the
MySQL data directory on this system (as set using the `--datadir'
option for *Note `mysqld': mysqld.) is owned by the `mysql' user, and
that the SQL node's `my.cnf' file includes `user=mysql' in the
`[mysqld]' section. Alternatively, you can start the MySQL server
process with `--user=mysql' on the command line, but it is preferable
to use the `my.cnf' option, since you might forget to use the
command-line option and so have *Note `mysqld': mysqld. running as
another user unintentionally. The *Note `mysqld_safe': mysqld-safe.
startup script forces MySQL to run as the `mysql' user.

*Important*:

Never run *Note `mysqld': mysqld. as the system root user.  Doing so
means that potentially any file on the system can be read by MySQL, and
thus--should MySQL be compromised--by an attacker.

As mentioned in the previous section (see *Note
mysql-cluster-security-mysql-privileges::), you should always set a
root password for the MySQL Server as soon as you have it running. You
should also delete the anonymous user account that is installed by
default. You can accomplish these tasks using the following statements:


     shell> mysql -u root

     mysql> UPDATE mysql.user
         ->     SET Password=PASSWORD('SECURE_PASSWORD')
         ->     WHERE User='root';

     mysql> DELETE FROM mysql.user
         ->     WHERE User='';

     mysql> FLUSH PRIVILEGES;

Be very careful when executing the *Note `DELETE': delete. statement
not to omit the `WHERE' clause, or you risk deleting _all_ MySQL users.
Be sure to run the *Note `FLUSH PRIVILEGES': flush. statement as soon
as you have modified the `mysql.user' table, so that the changes take
immediate effect. Without *Note `FLUSH PRIVILEGES': flush, the changes
do not take effect until the next time that the server is restarted.

*Note*:

Many of the MySQL Cluster utilities such as *Note `ndb_show_tables':
mysql-cluster-programs-ndb-show-tables, *Note `ndb_desc':
mysql-cluster-programs-ndb-desc, and *Note `ndb_select_all':
mysql-cluster-programs-ndb-select-all. also work without authentication
and can reveal table names, schemas, and data.  By default these are
installed on Unix-style systems with the permissions `wxr-xr-x' (755),
which means they can be executed by any user that can access the
`mysql/bin' directory.

See *Note mysql-cluster-programs::, for more information about these
utilities.


File: manual.info,  Node: mysql-cluster-disk-data,  Next: mysql-cluster-online-add-node,  Prev: mysql-cluster-security,  Up: mysql-cluster-management

17.5.12 MySQL Cluster Disk Data Tables
--------------------------------------

* Menu:

* mysql-cluster-disk-data-objects::  MySQL Cluster Disk Data Objects
* mysql-cluster-disk-data-symlinks::  Using Symbolic Links with Disk Data Objects
* mysql-cluster-disk-data-storage-requirements::  MySQL Cluster Disk Data Storage Requirements

Beginning with MySQL 5.1.6, it is possible to store the nonindexed
columns of *Note `NDB': mysql-cluster. tables on disk, rather than in
RAM as with previous versions of MySQL Cluster.

As part of implementing MySQL Cluster Disk Data work, a number of
improvements were made in MySQL Cluster for the efficient handling of
very large amounts (terabytes) of data during node recovery and
restart. These include a `no-steal' algorithm for synchronizing a
starting node with very large data sets. For more information, see the
paper `Recovery Principles of MySQL Cluster 5.1
(http://www.vldb2005.org/program/paper/wed/p1108-ronstrom.pdf)', by
MySQL Cluster developers Mikael Ronstro"m and Jonas Oreland.

MySQL Cluster Disk Data performance can be influenced by a number of
configuration parameters. For information about these parameters and
their effects, see `MySQL Cluster Disk Data configuration parameters'
and `MySQL Cluster Disk Data storage and `GCP Stop' errors'

The performance of a MySQL Cluster that uses Disk Data storage can also
be greatly improved by separating data node file systems from undo log
files and tablespace data files, which can be done using symbolic
links. For more information, see *Note
mysql-cluster-disk-data-symlinks::.


File: manual.info,  Node: mysql-cluster-disk-data-objects,  Next: mysql-cluster-disk-data-symlinks,  Prev: mysql-cluster-disk-data,  Up: mysql-cluster-disk-data

17.5.12.1 MySQL Cluster Disk Data Objects
.........................................

MySQL Cluster Disk Data storage is implemented using a number of _Disk
Data objects_. These include the following:

   * _Tablespaces_ act as containers for other Disk Data objects.

   * _Undo log files_ undo information required for rolling back
     transactions.

   * One or more undo log files are assigned to a _log file group_,
     which is then assigned to a tablespace.

   * _Data files_ store Disk Data table data. A data file is assigned
     directly to a tablespace.

Undo log files and data files are actual files in the file system of
each data node; by default they are placed in `ndb_NODE_ID_fs' in the
DATADIR specified in the MySQL Cluster `config.ini' file, and where
NODE_ID is the data node's node ID. It is possible to place these
elsewhere by specifying either an absolute or relative path as part of
the filename when creating the undo log or data file. Statements that
create these files are shown later in this section.

MySQL Cluster tablespaces and log file groups are not implemented as
files.

*Important*:

Although not all Disk Data objects are implemented as files, they all
share the same namespace. This means that _each Disk Data object_ must
be uniquely named (and not merely each Disk Data object of a given
type).  For example, you cannot have a tablespace and a log file group
both named `dd1'.

Assuming that you have already set up a MySQL Cluster with all nodes
(including management and SQL nodes) running MySQL 5.1.6 or newer, the
basic steps for creating a Cluster table on disk are as follows:

  1. Create a log file group, and assign one or more undo log files to
     it (an undo log file is also sometimes referred to as an
     _undofile_).

     *Note*:

     In MySQL 5.1 and later, undo log files are necessary only for Disk
     Data tables. They are no longer used for *Note `NDBCLUSTER':
     mysql-cluster. tables that are stored only in memory.

  2. Create a tablespace; assign the log file group, as well as one or
     more data files, to the tablespace.

  3. Create a Disk Data table that uses this tablespace for data
     storage.

Each of these tasks can be accomplished using SQL statements in the
*Note `mysql': mysql. client or other MySQL client application, as
shown in the example that follows.

  1. We create a log file group named `lg_1' using *Note `CREATE
     LOGFILE GROUP': create-logfile-group.  This log file group is to
     be made up of two undo log files, which we name `undo_1.log' and
     `undo_2.log', whose initial sizes are 16 MB and 12 MB,
     respectively. (The default initial size for an undo log file is
     128 MB.) Optionally, you can also specify a size for the log file
     group's undo buffer, or permit it to assume the default value of 8
     MB. In this example, we set the UNDO buffer's size at 2 MB. A log
     file group must be created with an undo log file; so we add
     `undo_1.log' to `lg_1' in this *Note `CREATE LOGFILE GROUP':
     create-logfile-group.  statement:


          CREATE LOGFILE GROUP lg_1
              ADD UNDOFILE 'undo_1.log'
              INITIAL_SIZE 16M
              UNDO_BUFFER_SIZE 2M
              ENGINE NDBCLUSTER;

     To add `undo_2.log' to the log file group, use the following *Note
     `ALTER LOGFILE GROUP': alter-logfile-group. statement:


          ALTER LOGFILE GROUP lg_1
              ADD UNDOFILE 'undo_2.log'
              INITIAL_SIZE 12M
              ENGINE NDBCLUSTER;

     Some items of note:

        * The `.log' file extension used here is not required. We use
          it merely to make the log files easily recognizable.

        * Every *Note `CREATE LOGFILE GROUP': create-logfile-group. and
          *Note `ALTER LOGFILE GROUP': alter-logfile-group. statement
          must include an `ENGINE' clause. In MySQL 5.1 (including
          MySQL Cluster NDB 6.X and 7.X through 7.1), the permitted
          values for this clause are *Note `NDBCLUSTER': mysql-cluster.
          and *Note `NDB': mysql-cluster.

          *Important*:

          In MySQL 5.1.8 and later, there can exist only one log file
          group in the same MySQL Cluster at any given time.

        * When you add an undo log file to a log file group using `ADD
          UNDOFILE 'FILENAME'', a file with the name FILENAME is
          created in the `ndb_NODE_ID_fs' directory within the
          `DataDir' of each data node in the cluster, where NODE_ID is
          the node ID of the data node. Each undo log file is of the
          size specified in the SQL statement. For example, if a MySQL
          Cluster has 4 data nodes, then the *Note `ALTER LOGFILE
          GROUP': alter-logfile-group. statement just shown creates 4
          undo log files, 1 each on in the data directory of each of
          the 4 data nodes; each of these files is named `undo_2.log'
          and each file is 12 MB in size.

        * `UNDO_BUFFER_SIZE' is limited by the amount of system memory
          available.

        * For more information about the *Note `CREATE LOGFILE GROUP':
          create-logfile-group.  statement, see *Note
          create-logfile-group::.  For more information about *Note
          `ALTER LOGFILE GROUP': alter-logfile-group, see *Note
          alter-logfile-group::.

  2. Now we can create a tablespace, which contains files to be used by
     MySQL Cluster Disk Data tables for storing their data. A
     tablespace is also associated with a particular log file group.
     When creating a new tablespace, you must specify the log file
     group which it is to use for undo logging; you must also specify a
     data file. You can add more data files to the tablespace after the
     tablespace is created; it is also possible to drop data files from
     a tablespace (an example of dropping data files is provided later
     in this section).

     Assume that we wish to create a tablespace named `ts_1' which uses
     `lg_1' as its log file group. This tablespace is to contain two
     data files named `data_1.dat' and `data_2.dat', whose initial
     sizes are 32 MB and 48 MB, respectively. (The default value for
     `INITIAL_SIZE' is 128 MB.) We can do this using two SQL
     statements, as shown here:


          CREATE TABLESPACE ts_1
              ADD DATAFILE 'data_1.dat'
              USE LOGFILE GROUP lg_1
              INITIAL_SIZE 32M
              ENGINE NDBCLUSTER;

          ALTER TABLESPACE ts_1
              ADD DATAFILE 'data_2.dat'
              INITIAL_SIZE 48M
              ENGINE NDBCLUSTER;

     The *Note `CREATE TABLESPACE': create-tablespace.  statement
     creates a tablespace `ts_1' with the data file `data_1.dat', and
     associates `ts_1' with log file group `lg_1'. The *Note `ALTER
     TABLESPACE': alter-tablespace. adds the second data file
     (`data_2.dat').

     Some items of note:

        * As is the case with the `.log' file extension used in this
          example for undo log files, there is no special significance
          for the `.dat' file extension; it is used merely for easy
          recognition of data files.

        * When you add a data file to a tablespace using `ADD DATAFILE
          'FILENAME'', a file with the name FILENAME is created in the
          `ndb_NODE_ID_fs' directory within the `DataDir' of each data
          node in the cluster, where NODE_ID is the node ID of the data
          node. Each data file is of the size specified in the SQL
          statement. For example, if a MySQL Cluster has 4 data nodes,
          then the *Note `ALTER TABLESPACE': alter-tablespace.
          statement just shown creates 4 data files, 1 each in the data
          directory of each of the 4 data nodes; each of these files is
          named `data_2.dat' and each file is 48 MB in size.

        * All *Note `CREATE TABLESPACE': create-tablespace. and *Note
          `ALTER TABLESPACE': alter-tablespace.  statements must
          contain an `ENGINE' clause; only tables using the same
          storage engine as the tablespace can be created in the
          tablespace. In MySQL 5.1 (including MySQL Cluster NDB 6.X and
          7.X through 7.1), the only permitted values for this clause
          are *Note `NDBCLUSTER': mysql-cluster. and *Note `NDB':
          mysql-cluster.

        * For more information about the *Note `CREATE TABLESPACE':
          create-tablespace. and *Note `ALTER TABLESPACE':
          alter-tablespace.  statements, see *Note create-tablespace::,
          and *Note alter-tablespace::.

  3. Now it is possible to create a table whose nonindexed columns are
     stored on disk in the tablespace `ts_1':


          CREATE TABLE dt_1 (
              member_id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
              last_name VARCHAR(50) NOT NULL,
              first_name VARCHAR(50) NOT NULL,
              dob DATE NOT NULL,
              joined DATE NOT NULL,
              INDEX(last_name, first_name)
              )
              TABLESPACE ts_1 STORAGE DISK
              ENGINE NDBCLUSTER;

     The `TABLESPACE ... STORAGE DISK' option tells the *Note
     `NDBCLUSTER': mysql-cluster. storage engine to use tablespace
     `ts_1' for disk data storage.

     *Note*:

     Beginning with MySQL Cluster NDB 6.2.5 and MySQL Cluster NDB
     6.3.2, it is also possible to specify whether an individual column
     is stored on disk or in memory by using a `STORAGE' clause as part
     of the column's definition in a *Note `CREATE TABLE':
     create-table. or *Note `ALTER TABLE': alter-table. statement.
     `STORAGE DISK' causes the column to be stored on disk, and
     `STORAGE MEMORY' causes in-memory storage to be used. See *Note
     create-table::, for more information.

     Once table `ts_1' has been created as shown, you can perform *Note
     `INSERT': insert, *Note `SELECT': select, *Note `UPDATE': update,
     and *Note `DELETE': delete. statements on it just as you would
     with any other MySQL table.

     For table `dt_1' as it has been defined here, only the `dob' and
     `joined' columns are stored on disk. This is because there are
     indexes on the `id', `last_name', and `first_name' columns, and so
     data belonging to these columns is stored in RAM. In MySQL 5.1
     (including MySQL Cluster NDB 6.X and 7.X through 7.1), only
     nonindexed columns can be held on disk; indexes and indexed column
     data continue to be stored in memory. This tradeoff between the
     use of indexes and conservation of RAM is something you must keep
     in mind as you design Disk Data tables.

Performance note

The performance of a cluster using Disk Data storage is greatly
improved if Disk Data files are kept on a separate physical disk from
the data node file system. This must be done for each data node in the
cluster to derive any noticeable benefit.

You may use absolute and relative file system paths with `ADD UNDOFILE'
and `ADD DATAFILE'. Relative paths are calculated relative to the data
node's data directory. You may also use symbolic links; see *Note
mysql-cluster-disk-data-symlinks::, for more information and examples.

A log file group, a tablespace, and any Disk Data tables using these
must be created in a particular order. The same is true for dropping
any of these objects:

   * A log file group cannot be dropped as long as any tablespaces are
     using it.

   * A tablespace cannot be dropped as long as it contains any data
     files.

   * You cannot drop any data files from a tablespace as long as there
     remain any tables which are using the tablespace.

   * Beginning with MySQL 5.1.12, it is no longer possible to drop
     files created in association with a different tablespace than the
     one with which the files were created.  (Bug #20053)

For example, to drop all the objects created so far in this section,
you would use the following statements:


     mysql> DROP TABLE dt_1;

     mysql> ALTER TABLESPACE ts_1
         -> DROP DATAFILE 'data_2.dat'
         -> ENGINE NDBCLUSTER;

     mysql> ALTER TABLESPACE ts_1
         -> DROP DATAFILE 'data_1.dat'
         -> ENGINE NDBCLUSTER;

     mysql> DROP TABLESPACE ts_1
         -> ENGINE NDBCLUSTER;

     mysql> DROP LOGFILE GROUP lg_1
         -> ENGINE NDBCLUSTER;

These statements must be performed in the order shown, except that the
two `ALTER TABLESPACE ... DROP DATAFILE' statements may be executed in
either order.

You can obtain information about data files used by Disk Data tables by
querying the *Note `FILES': files-table. table in the
`INFORMATION_SCHEMA' database. An extra ``NULL' row' was added to this
table in MySQL 5.1.14 for providing additional information about undo
log files. For more information and examples of use, see *Note
files-table::.

Beginning with MySQL Cluster NDB 6.3.27 and MySQL Cluster NDB 7.0.8, it
is also possible to view information about allocated and free disk
space for each Disk Data table or table partition using the *Note
`ndb_desc': mysql-cluster-programs-ndb-desc. utility. For more
information, see *Note mysql-cluster-programs-ndb-desc::.


File: manual.info,  Node: mysql-cluster-disk-data-symlinks,  Next: mysql-cluster-disk-data-storage-requirements,  Prev: mysql-cluster-disk-data-objects,  Up: mysql-cluster-disk-data

17.5.12.2 Using Symbolic Links with Disk Data Objects
.....................................................

The performance of a MySQL Cluster that uses Disk Data storage can be
greatly improved by separating data node file systems from undo log
files and tablespace data files and placing these on different disks.
Previous to MySQL Cluster NDB 6.2.17, MySQL Cluster NDB 6.3.22, and
MySQL Cluster NDB 6.4.3, there was no direct support for this in MySQL
Cluster, but it was possible to achieve this separation using symbolic
links as described in this section.

Beginning with MySQL Cluster NDB 6.2.17, MySQL Cluster NDB 6.3.22, and
MySQL Cluster NDB 6.4.3, the data node configuration parameters
`FileSystemPathDD', `FileSystemPathDataFiles', and
`FileSystemPathUndoFiles' make the use of symbolic links for this
purpose unnecessary. For information about these parameters, see *Note
mysql-cluster-ndbd-disk-data-filesystem-parameters::.

Each data node in the cluster creates a file system in the directory
named `ndb_NODE_ID_fs' under the data node's `DataDir' as defined in
the `config.ini' file. In this example, we assume that each data node
host has 3 disks, aliased as `/data0', `/data1', and `/data2', and that
the cluster's `config.ini' includes the following:


     [ndbd default]
     DataDir= /data0

Our objective is to place all Disk Data log files in `/data1', and all
Disk Data data files in `/data2', on each data node host.

*Note*:

In this example, we assume that the cluster's data node hosts are all
using Linux operating systems. For other platforms, you may need to
substitute you operating system's commands for those shown here.

To accomplish this, perform the following steps:

   * Under the data node file system create symbolic links pointing to
     the other drives:


          shell> cd /data0/ndb_2_fs
          shell> ls
          D1  D10  D11  D2  D8  D9  LCP
          shell> ln -s /data0 dnlogs
          shell> ln -s /data1 dndata

     You should now have two symbolic links:


          shell> ls -l --hide=D*
          lrwxrwxrwx 1 user group   30 2007-03-19 13:58 dndata -> /data1
          lrwxrwxrwx 1 user group   30 2007-03-19 13:59 dnlogs -> /data2

     We show this only for the data node with node ID 2; however, you
     must do this for _each_ data node.

   * Now, in the *Note `mysql': mysql. client, create a log file group
     and tablespace using the symbolic links, as shown here:


          mysql> CREATE LOGFILE GROUP lg1
              ->    ADD UNDOFILE 'dnlogs/undo1.log'
              ->    INITIAL_SIZE 150M
              ->    UNDO_BUFFER_SIZE = 1M
              ->    ENGINE=NDBCLUSTER;

          mysql> CREATE TABLESPACE ts1
              ->    ADD DATAFILE 'dndata/data1.log'
              ->    USE LOGFILE GROUP lg1
              ->    INITIAL_SIZE 1G
              ->    ENGINE=NDBCLUSTER;

     Verify that the files were created and placed correctly as shown
     here:


          shell> cd /data1
          shell> ls -l
          total 2099304
          -rw-rw-r--  1 user group 157286400 2007-03-19 14:02 undo1.dat

          shell> cd /data2
          shell> ls -l
          total 2099304
          -rw-rw-r--  1 user group 1073741824 2007-03-19 14:02 data1.dat

   * If you are running multiple data nodes on one host, you must take
     care to avoid having them try to use the same space for Disk Data
     files. You can make this easier by creating a symbolic link in
     each data node file system. Suppose you are using `/data0' for
     both data node file systems, but you wish to have the Disk Data
     files for both nodes on `/data1'. In this case, you can do
     something similar to what is shown here:


          shell> cd /data0
          shell> ln -s /data1/dn2 ndb_2_fs/dd
          shell> ln -s /data1/dn3 ndb_3_fs/dd
          shell> ls -l --hide=D* ndb_2_fs
          lrwxrwxrwx 1 user group   30 2007-03-19 14:22 dd -> /data1/dn2
          shell> ls -l --hide=D* ndb_3_fs
          lrwxrwxrwx 1 user group   30 2007-03-19 14:22 dd -> /data1/dn3

   * Now you can create a logfile group and tablespace using the
     symbolic link, like this:


          mysql> CREATE LOGFILE GROUP lg1
              ->    ADD UNDOFILE 'dd/undo1.log'
              ->    INITIAL_SIZE 150M
              ->    UNDO_BUFFER_SIZE = 1M
              ->    ENGINE=NDBCLUSTER;

          mysql> CREATE TABLESPACE ts1
              ->    ADD DATAFILE 'dd/data1.log'
              ->    USE LOGFILE GROUP lg1
              ->    INITIAL_SIZE 1G
              ->    ENGINE=NDBCLUSTER;

     Verify that the files were created and placed correctly as shown
     here:


          shell> cd /data1
          shell> ls
          dn2        dn3
          shell> ls dn2
          undo1.log        data1.log
          shell> ls dn3
          undo1.log        data1.log


File: manual.info,  Node: mysql-cluster-disk-data-storage-requirements,  Prev: mysql-cluster-disk-data-symlinks,  Up: mysql-cluster-disk-data

17.5.12.3 MySQL Cluster Disk Data Storage Requirements
......................................................

The following items apply to Disk Data storage requirements:

   * Variable-length columns of Disk Data tables take up a fixed amount
     of space. For each row, this is equal to the space required to
     store the largest possible value for that column.

     For general information about calculating these values, see *Note
     storage-requirements::.

     You can obtain an estimate the amount of space available in data
     files and undo log files by querying the *Note
     `INFORMATION_SCHEMA.FILES': files-table. table.  For more
     information and examples, see *Note files-table::.

     *Note*:

     The *Note `OPTIMIZE TABLE': optimize-table.  statement does not
     have any effect on Disk Data tables.

   * In a Disk Data table, the first 256 bytes of a *Note `TEXT': blob.
     or *Note `BLOB': blob. column are stored in memory; only the
     remainder is stored on disk.

   * Each row in a Disk Data table uses 8 bytes in memory to point to
     the data stored on disk. This means that, in some cases,
     converting an in-memory column to the disk-based format can
     actually result in greater memory usage. For example, converting a
     `CHAR(4)' column from memory-based to disk-based format increases
     the amount of `DataMemory' used per row from 4 to 8 bytes.

*Important*:

Starting the cluster with the `--initial' option does _not_ remove Disk
Data files.  You must remove these manually prior to performing an
initial restart of the cluster.

Performance of Disk Data tables can be improved by minimizing the
number of disk seeks by making sure that `DiskPageBufferMemory' is of
sufficient size. You can query the *Note `diskpagebuffer':
mysql-cluster-ndbinfo-diskpagebuffer. table to help determine whether
the value for this parameter needs to be increased.


File: manual.info,  Node: mysql-cluster-online-add-node,  Next: mysql-cluster-privilege-distribution,  Prev: mysql-cluster-disk-data,  Up: mysql-cluster-management

17.5.13 Adding MySQL Cluster Data Nodes Online
----------------------------------------------

* Menu:

* mysql-cluster-online-add-node-remarks::  Adding MySQL Cluster Data Nodes Online: General Issues
* mysql-cluster-online-add-node-basics::  Adding MySQL Cluster Data Nodes Online: Basic procedure
* mysql-cluster-online-add-node-example::  Adding MySQL Cluster Data Nodes Online: Detailed Example

This section describes how to add MySQL Cluster data nodes
`online'--that is, without needing to shut down the cluster completely
and restart it as part of the process. This capability is available in
MySQL Cluster NDB 7.0 (beginning with MySQL Cluster NDB 6.4.0) and
later MySQL Cluster release series.

*Important*:

Currently, you must add new data nodes to a MySQL Cluster as part of a
new node group. In addition, it is not possible to change the number of
replicas (or the number of nodes per node group) online.


File: manual.info,  Node: mysql-cluster-online-add-node-remarks,  Next: mysql-cluster-online-add-node-basics,  Prev: mysql-cluster-online-add-node,  Up: mysql-cluster-online-add-node

17.5.13.1 Adding MySQL Cluster Data Nodes Online: General Issues
................................................................

This section provides general information about the behavior of and
current limitations in adding MySQL Cluster nodes online.

Redistribution of Data

The ability to add new nodes online includes a means to reorganize
*Note `NDBCLUSTER': mysql-cluster. table data and indexes so that they
are distributed across all data nodes, including the new ones, by means
of the *Note `ALTER ONLINE TABLE ... REORGANIZE PARTITION':
alter-table-partition-operations. statement.  Table reorganization of
both in-memory and Disk Data tables is supported. This redistribution
does not currently include unique indexes (only ordered indexes are
redistributed). Prior to MySQL Cluster NDB 7.0.40 and MySQL Cluster NDB
7.1.28, `BLOB' table data is also not redistributed using this method
(Bug #13714148).

The redistribution for *Note `NDBCLUSTER': mysql-cluster.  tables
already existing before the new data nodes were added is not automatic,
but can be accomplished using simple SQL statements in *Note `mysql':
mysql. or another MySQL client application. However, all data and
indexes added to tables created after a new node group has been added
are distributed automatically among all cluster data nodes, including
those added as part of the new node group.

Partial starts

It is possible to add a new node group without all of the new data
nodes being started. It is also possible to add a new node group to a
degraded cluster--that is, a cluster that is only partially started, or
where one or more data nodes are not running. In the latter case, the
cluster must have enough nodes running to be viable before the new node
group can be added.

Effects on ongoing operations

Normal DML operations using MySQL Cluster data are not prevented by the
creation or addition of a new node group, or by table reorganization.
However, it is not possible to perform DDL concurrently with table
reorganization--that is, no other DDL statements can be issued while an
*Note `ALTER TABLE ... REORGANIZE PARTITION': alter-table. statement is
executing. In addition, during the execution of `ALTER TABLE ...
REORGANIZE PARTITION' (or the execution of any other DDL statement), it
is not possible to restart cluster data nodes.

Failure handling

Failures of data nodes during node group creation and table
reorganization are handled as shown in the following table:

This table describes how data node failures during node group creation
and table reorganization are handled. The first column identifies when
the failure occurs (during node group creation or table
reorganization). The second column describes where the failures occur
and is divided into three sub columns (Old data nodes, New data nodes,
and System).

Failure occurs     Failure occurs in:                    
during:                                                  
`Old' data nodes   `New' data nodes   System             
Node group            * If a node        * If a node        * If the
creation                other than         other than         execution of
                        the master         the master         CREATE
                        fails:             fails:             NODEGROUP
                                                              has reached
                        The creation       The creation       the internal
                        of the node        of the node        commit point:
                        group is           group is      
                        always rolled      always rolled      When
                        forward.           forward.           restarted,
                                                              the cluster
                      * If the           * If the             includes the
                        master fails:      master fails:      new node
                                                              group.
                           * If the           * If the        Otherwise it
                             internal           internal      without.
                             commit             commit   
                             point              point       * If the
                             has                has           execution of
                             been               been          CREATE
                             reached:           reached:      NODEGROUP
                                                              has not yet
                             The                The           reached the
                             creation           creation      internal
                             of the             of the        commit point:
                             node               node     
                             group              group         When
                             is                 is            restarted,
                             rolled             rolled        the cluster
                             forward.           forward.      does not
                                                              include the
                           * If the           * If the        new node
                             internal           internal      group.
                             commit             commit   
                             point              point    
                             has not            has not  
                             yet                yet      
                             been               been     
                             reached            reached  
                                                         
                             The                The      
                             creation           creation 
                             of the             of the   
                             node               node     
                             group              group    
                             is                 is       
                             rolled             rolled   
                             back               back     
Table                 * If a node        * If a node        * If the
reorganization          other than         other than         execution of
                        the master         the master         an ALTER
                        fails:             fails:             ONLINE TABLE
                                                              table
                        The table          The table          REORGANIZE
                        reorganization     reorganization     PARTITION
                        is always          is always          statement
                        rolled             rolled             has reached
                        forward.           forward.           the internal
                                                              commit point:
                      * If the           * If the        
                        master fails:      master fails:      When the
                                                              cluster is
                           * If the           * If the        restarted,
                             internal           internal      the data and
                             commit             commit        indexes
                             point              point         belonging to
                             has                has           TABLE are
                             been               been          distributed
                             reached:           reached:      using the
                                                              `new' data
                             The                The           nodes.
                             table              table    
                             reorganization          reorganization   * If the
                             is                 is            execution of
                             rolled             rolled        an ALTER
                             forward.           forward.      ONLINE TABLE
                                                              table
                           * If the           * If the        REORGANIZE
                             internal           internal      PARTITION
                             commit             commit        statement
                             point              point         has not yet
                             has not            has not       reached the
                             yet                yet           internal
                             been               been          commit point:
                             reached            reached  
                                                              When the
                             The                The           cluster is
                             table              table         restarted,
                             reorganization          reorganization     the data and
                             is                 is            indexes
                             rolled             rolled        belonging to
                             back.              back.         TABLE are
                                                              distributed
                                                              using only
                                                              the `old'
                                                              data nodes.
Dropping node groups

The *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. client supports a
`DROP NODEGROUP' command, but it is possible to drop a node group only
when no data nodes in the node group contain any data. Since there is
currently no way to `empty' a specific data node or node group, this
command works only the following two cases:

  1. After issuing `CREATE NODEGROUP' in the *Note `ndb_mgm':
     mysql-cluster-programs-ndb-mgm. client, but before issuing any
     *Note `ALTER ONLINE TABLE ... REORGANIZE PARTITION': alter-table.
     statements in the *Note `mysql': mysql. client.

  2. After dropping all *Note `NDBCLUSTER': mysql-cluster.  tables
     using *Note `DROP TABLE': drop-table.

     *Note `TRUNCATE TABLE': truncate-table. does not work for this
     purpose because the data nodes continue to store the table
     definitions.


File: manual.info,  Node: mysql-cluster-online-add-node-basics,  Next: mysql-cluster-online-add-node-example,  Prev: mysql-cluster-online-add-node-remarks,  Up: mysql-cluster-online-add-node

17.5.13.2 Adding MySQL Cluster Data Nodes Online: Basic procedure
.................................................................

In this section, we list the basic steps required to add new data nodes
to a MySQL Cluster. For a detailed example, see *Note
mysql-cluster-online-add-node-example::.

*Note*:

Beginning with MySQL Cluster NDB 7.0.4, this procedure applies whether
you are using *Note `ndbd': mysql-cluster-programs-ndbd. or *Note
`ndbmtd': mysql-cluster-programs-ndbmtd. binaries for the data node
processes. Previously, this did not work with multi-threaded data
nodes. (Bug #43108)

Assuming that you already have a running MySQL Cluster, adding data
nodes online requires the following steps:

  1. Edit the cluster configuration `config.ini' file, adding new
     `[ndbd]' sections corresponding to the nodes to be added. In the
     case where the cluster uses multiple management servers, these
     changes need to be made to all `config.ini' files used by the
     management servers.

     You must be careful that node IDs for any new data nodes added in
     the `config.ini' file do not overlap node IDs used by existing
     nodes. In the event that you have API nodes using dynamically
     allocated node IDs and these IDs match node IDs that you want to
     use for new data nodes, it is possible to force any such API nodes
     to `migrate', as described later in this procedure.

  2. Perform a rolling restart of all MySQL Cluster management servers.

     *Important*:

     All management servers must be restarted with the `--reload' or
     `--initial' option to force the reading of the new configuration.

  3. Perform a rolling restart of all existing MySQL Cluster data
     nodes. It is not necessary (or usually even desirable) to use
     `--initial' when restarting the existing data nodes.

     If you are using API nodes with dynamically allocated IDs matching
     any node IDs that you wish to assign to new data nodes, you must
     restart all API nodes (including SQL nodes) before restarting any
     of the data nodes processes in this step. This causes any API
     nodes with node IDs that were previously not explicitly assigned
     to relinquish those node IDs and acquire new ones.

  4. Perform a rolling restart of any SQL or API nodes connected to the
     MySQL Cluster.

  5. Start the new data nodes.

     The new data nodes may be started in any order. They can also be
     started concurrently, as long as they are started after the
     rolling restarts of all existing data nodes have been completed,
     and before proceeding to the next step.

  6. Execute one or more `CREATE NODEGROUP' commands in the MySQL
     Cluster management client to create the new node group or node
     groups to which the new data nodes will belong.

  7. Redistribute the cluster's data among all data nodes (including
     the new ones) by issuing an *Note `ALTER ONLINE TABLE ...
     REORGANIZE PARTITION': alter-table. statement in the *Note
     `mysql': mysql. client for each *Note `NDBCLUSTER': mysql-cluster.
     table.

     *Note*:

     This needs to be done only for tables already existing at the time
     the new node group is added. Data in tables created after the new
     node group is added is distributed automatically; however, data
     added to any given table `tbl' that existed before the new nodes
     were added is not distributed using the new nodes until that table
     has been reorganized using *Note `ALTER ONLINE TABLE tbl
     REORGANIZE PARTITION': alter-table.

  8. Reclaim the space freed on the `old' nodes by issuing, for each
     *Note `NDBCLUSTER': mysql-cluster.  table, an *Note `OPTIMIZE
     TABLE': optimize-table.  statement in the *Note `mysql': mysql.
     client.

You can add all the nodes desired, then issue several `CREATE
NODEGROUP' commands in succession to add the new node groups to the
cluster. Prior to MySQL Cluster NDB 7.0.16 and MySQL Cluster NDB 7.1.5,
when adding multiple new node groups to a MySQL Cluster, it was
necessary to add only the nodes to be assigned to a given new node
group, create that node group using `CREATE NODEGROUP', then repeat
this process for each new node group to be added to the cluster.  (Bug
#54497)


File: manual.info,  Node: mysql-cluster-online-add-node-example,  Prev: mysql-cluster-online-add-node-basics,  Up: mysql-cluster-online-add-node

17.5.13.3 Adding MySQL Cluster Data Nodes Online: Detailed Example
..................................................................

In this section we provide a detailed example illustrating how to add
new MySQL Cluster data nodes online, starting with a MySQL Cluster
having 2 data nodes in a single node group and concluding with a
cluster having 4 data nodes in 2 node groups.

Starting configuration

For purposes of illustration, we assume a minimal configuration, and
that the cluster uses a `config.ini' file containing only the following
information:


     [ndbd default]
     DataMemory = 100M
     IndexMemory = 100M
     NoOfReplicas = 2
     DataDir = /usr/local/mysql/var/mysql-cluster

     [ndbd]
     Id = 1
     HostName = 192.168.0.1

     [ndbd]
     Id = 2
     HostName = 192.168.0.2

     [mgm]
     HostName = 192.168.0.10
     Id = 10

     [api]
     Id=20
     HostName = 192.168.0.20

     [api]
     Id=21
     HostName = 192.168.0.21

*Note*:

We have left a gap in the sequence between data node IDs and other
nodes. This make it easier later to assign node IDs that are not
already in use to data nodes which are newly added.

We also assume that you have already started the cluster using the
appropriate command line or `my.cnf' options, and that running `SHOW'
in the management client produces output similar to what is shown here:


     -- NDB Cluster -- Management Client --
     ndb_mgm> SHOW
     Connected to Management Server at: 192.168.0.10:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=1    @192.168.0.1  (5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=2    @192.168.0.2  (5.1.73-ndb-7.1.34, Nodegroup: 0)

     [ndb_mgmd(MGM)] 1 node(s)
     id=10   @192.168.0.10  (5.1.73-ndb-7.1.34)

     [mysqld(API)]   2 node(s)
     id=20   @192.168.0.20  (5.1.73-ndb-7.1.34)
     id=21   @192.168.0.21  (5.1.73-ndb-7.1.34)

Finally, we assume that the cluster contains a single *Note
`NDBCLUSTER': mysql-cluster. table created as shown here:


     USE n;

     CREATE TABLE ips (
         id BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         country_code CHAR(2) NOT NULL,
         type CHAR(4) NOT NULL,
         ip_address varchar(15) NOT NULL,
         addresses BIGINT UNSIGNED DEFAULT NULL,
         date BIGINT UNSIGNED DEFAULT NULL
     )   ENGINE NDBCLUSTER;

The memory usage and related information shown later in this section
was generated after inserting approximately 50000 rows into this table.

*Note*:

In this example, we show the single-threaded *Note `ndbd':
mysql-cluster-programs-ndbd. being used for the data node processes.
However--beginning with MySQL Cluster NDB 7.0.4--you can also apply
this example, if you are using the multi-threaded *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. by substituting *Note `ndbmtd':
mysql-cluster-programs-ndbmtd. for *Note `ndbd':
mysql-cluster-programs-ndbd. wherever it appears in the steps that
follow. (Bug #43108)

Step 1: Update configuration file

Open the cluster global configuration file in a text editor and add
`[ndbd]' sections corresponding to the 2 new data nodes. (We give these
data nodes IDs 3 and 4, and assume that they are to be run on host
machines at addresses 192.168.0.3 and 192.168.0.4, respectively.) After
you have added the new sections, the contents of the `config.ini' file
should look like what is shown here, where the additions to the file
are shown in bold type:


     [ndbd default]
     DataMemory = 100M
     IndexMemory = 100M
     NoOfReplicas = 2
     DataDir = /usr/local/mysql/var/mysql-cluster

     [ndbd]
     Id = 1
     HostName = 192.168.0.1

     [ndbd]
     Id = 2
     HostName = 192.168.0.2

     *[ndbd]
     Id = 3
     HostName = 192.168.0.3

     [ndbd]
     Id = 4
     HostName = 192.168.0.4*

     [mgm]
     HostName = 192.168.0.10
     Id = 10

     [api]
     Id=20
     HostName = 192.168.0.20

     [api]
     Id=21
     HostName = 192.168.0.21

Once you have made the necessary changes, save the file.

Step 2: Restart the management server

Restarting the cluster management server requires that you issue
separate commands to stop the management server and then to start it
again, as follows:

  1. Stop the management server using the management client `STOP'
     command, as shown here:


          ndb_mgm> 10 STOP
          Node 10 has shut down.
          Disconnecting to allow Management Server to shutdown

          shell>

  2. Because shutting down the management server causes the management
     client to terminate, you must start the management server from the
     system shell. For simplicity, we assume that `config.ini' is in
     the same directory as the management server binary, but in
     practice, you must supply the correct path to the configuration
     file.  You must also supply the `--reload' or `--initial' option
     so that the management server reads the new configuration from the
     file rather than its configuration cache. If your shell's current
     directory is also the same as the directory where the management
     server binary is located, then you can invoke the management
     server as shown here:


          shell> ndb_mgmd -f config.ini --reload
          2008-12-08 17:29:23 [MgmSrvr] INFO     -- NDB Cluster Management Server. 5.1.73-ndb-7.1.34
          2008-12-08 17:29:23 [MgmSrvr] INFO     -- Reading cluster configuration from 'config.ini'

If you check the output of `SHOW' in the management client after
restarting the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. process,
you should now see something like this:


     -- NDB Cluster -- Management Client --
     ndb_mgm> SHOW
     Connected to Management Server at: 192.168.0.10:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=1    @192.168.0.1  (5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=2    @192.168.0.2  (5.1.73-ndb-7.1.34, Nodegroup: 0)
     id=3 (not connected, accepting connect from 192.168.0.3)
     id=4 (not connected, accepting connect from 192.168.0.4)

     [ndb_mgmd(MGM)] 1 node(s)
     id=10   @192.168.0.10  (5.1.73-ndb-7.1.34)

     [mysqld(API)]   2 node(s)
     id=20   @192.168.0.20  (5.1.73-ndb-7.1.34)
     id=21   @192.168.0.21  (5.1.73-ndb-7.1.34)

Step 3: Perform a rolling restart of the existing data nodes

This step can be accomplished entirely within the cluster management
client using the `RESTART' command, as shown here:


     ndb_mgm> 1 RESTART
     Node 1: Node shutdown initiated
     Node 1: Node shutdown completed, restarting, no start.
     Node 1 is being restarted

     ndb_mgm> Node 1: Start initiated (version 7.1.34)
     Node 1: Started (version 7.1.34)

     ndb_mgm> 2 RESTART
     Node 2: Node shutdown initiated
     Node 2: Node shutdown completed, restarting, no start.
     Node 2 is being restarted

     ndb_mgm> Node 2: Start initiated (version 7.1.34)

     ndb_mgm> Node 2: Started (version 7.1.34)

*Important*:

After issuing each `X RESTART' command, wait until the management client
reports `Node X: Started (version ...)' _before_ proceeding any further.

Beginning with MySQL Cluster NDB 7.0.24 and MySQL Cluster NDB 7.1.13,
you can verify that all existing data nodes were restarted using the
updated configuration by checking the *Note `ndbinfo.nodes':
mysql-cluster-ndbinfo-nodes. table in the *Note `mysql': mysql. client.

Step 4: Perform a rolling restart of all cluster API nodes

Shut down and restart each MySQL server acting as an SQL node in the
cluster using *Note `mysqladmin shutdown': mysqladmin.  followed by
*Note `mysqld_safe': mysqld-safe. (or another startup script). This
should be similar to what is shown here, where PASSWORD is the MySQL
`root' password for a given MySQL server instance:


     shell> mysqladmin -uroot -pPASSWORD shutdown
     081208 20:19:56 mysqld_safe mysqld from pid file
     /usr/local/mysql/var/tonfisk.pid ended
     shell> mysqld_safe --ndbcluster --ndb-connectstring=192.168.0.10 &
     081208 20:20:06 mysqld_safe Logging to '/usr/local/mysql/var/tonfisk.err'.
     081208 20:20:06 mysqld_safe Starting mysqld daemon with databases
     from /usr/local/mysql/var

Of course, the exact input and output depend on how and where MySQL is
installed on the system, as well as which options you choose to start
it (and whether or not some or all of these options are specified in a
`my.cnf' file).

Step 5: Perform an initial start of the new data nodes

From a system shell on each of the hosts for the new data nodes, start
the data nodes as shown here, using the `--initial' option:


     shell> ndbd -c 192.168.0.10 --initial

*Note*:

Unlike the case with restarting the existing data nodes, you can start
the new data nodes concurrently; you do not need to wait for one to
finish starting before starting the other.

_Wait until both of the new data nodes have started before proceeding
with the next step_. Once the new data nodes have started, you can see
in the output of the management client `SHOW' command that they do not
yet belong to any node group (as indicated with bold type here):


     ndb_mgm> SHOW
     Connected to Management Server at: 192.168.0.10:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=1    @192.168.0.1  (5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=2    @192.168.0.2  (5.1.73-ndb-7.1.34, Nodegroup: 0)
     id=3    @192.168.0.3  (5.1.73-ndb-7.1.34, *no nodegroup*)
     id=4    @192.168.0.4  (5.1.73-ndb-7.1.34, *no nodegroup*)

     [ndb_mgmd(MGM)] 1 node(s)
     id=10   @192.168.0.10  (5.1.73-ndb-7.1.34)

     [mysqld(API)]   2 node(s)
     id=20   @192.168.0.20  (5.1.73-ndb-7.1.34)
     id=21   @192.168.0.21  (5.1.73-ndb-7.1.34)

Step 6: Create a new node group

You can do this by issuing a `CREATE NODEGROUP' command in the cluster
management client.  This command takes as its argument a
comma-separated list of the node IDs of the data nodes to be included
in the new node group, as shown here:


     ndb_mgm> CREATE NODEGROUP 3,4
     Nodegroup 1 created

By issuing `SHOW' again, you can verify that data nodes 3 and 4 have
joined the new node group (again indicated in bold type):


     ndb_mgm> SHOW
     Connected to Management Server at: 192.168.0.10:1186
     Cluster Configuration
     ---------------------
     [ndbd(NDB)]     2 node(s)
     id=1    @192.168.0.1  (5.1.73-ndb-7.1.34, Nodegroup: 0, *)
     id=2    @192.168.0.2  (5.1.73-ndb-7.1.34, Nodegroup: 0)
     id=3    @192.168.0.3  (5.1.73-ndb-7.1.34, *Nodegroup: 1*)
     id=4    @192.168.0.4  (5.1.73-ndb-7.1.34, *Nodegroup: 1*)

     [ndb_mgmd(MGM)] 1 node(s)
     id=10   @192.168.0.10  (5.1.73-ndb-7.1.34)

     [mysqld(API)]   2 node(s)
     id=20   @192.168.0.20  (5.1.73-ndb-7.1.34)
     id=21   @192.168.0.21  (5.1.73-ndb-7.1.34)

Step 7: Redistribute cluster data

When a node group is created, existing data and indexes are not
automatically distributed to the new node group's data nodes, as you
can see by issuing the appropriate `REPORT' command in the management
client:


     ndb_mgm> ALL REPORT MEMORY

     Node 1: Data usage is 5%(177 32K pages of total 3200)
     Node 1: Index usage is 0%(108 8K pages of total 12832)
     Node 2: Data usage is 5%(177 32K pages of total 3200)
     Node 2: Index usage is 0%(108 8K pages of total 12832)
     *Node 3: Data usage is 0%(0 32K pages of total 3200)
     Node 3: Index usage is 0%(0 8K pages of total 12832)
     Node 4: Data usage is 0%(0 32K pages of total 3200)
     Node 4: Index usage is 0%(0 8K pages of total 12832)*

By using *Note `ndb_desc': mysql-cluster-programs-ndb-desc. with the
`-p' option, which causes the output to include partitioning
information, you can see that the table still uses only 2 partitions
(in the `Per partition info' section of the output, shown here in bold
text):


     shell> ndb_desc -c 192.168.0.10 -d n ips -p
     -- ips --
     Version: 1
     Fragment type: 9
     K Value: 6
     Min load factor: 78
     Max load factor: 80
     Temporary table: no
     Number of attributes: 6
     Number of primary keys: 1
     Length of frm data: 340
     Row Checksum: 1
     Row GCI: 1
     SingleUserMode: 0
     ForceVarPart: 1
     FragmentCount: 2
     TableStatus: Retrieved
     -- Attributes --
     id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
     country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
     type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
     ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
     addresses Bigunsigned NULL AT=FIXED ST=MEMORY
     date Bigunsigned NULL AT=FIXED ST=MEMORY

     -- Indexes --
     PRIMARY KEY(id) - UniqueHashIndex
     PRIMARY(id) - OrderedIndex

     *-- Per partition info --
     Partition   Row count   Commit count  Frag fixed memory   Frag varsized memory
     0           26086       26086         1572864             557056
     1           26329       26329         1605632             557056*

     NDBT_ProgramExit: 0 - OK

You can cause the data to be redistributed among all of the data nodes
by performing, for each *Note `NDBCLUSTER': mysql-cluster. table, an
*Note `ALTER ONLINE TABLE ... REORGANIZE PARTITION': alter-table.
statement in the *Note `mysql': mysql. client. After issuing the
statement `ALTER ONLINE TABLE ips REORGANIZE PARTITION', you can see
using *Note `ndb_desc': mysql-cluster-programs-ndb-desc. that the data
for this table is now stored using 4 partitions, as shown here (with
the relevant portions of the output in bold type):


     shell> ndb_desc -c 192.168.0.10 -d n ips -p
     -- ips --
     Version: 16777217
     Fragment type: 9
     K Value: 6
     Min load factor: 78
     Max load factor: 80
     Temporary table: no
     Number of attributes: 6
     Number of primary keys: 1
     Length of frm data: 341
     Row Checksum: 1
     Row GCI: 1
     SingleUserMode: 0
     ForceVarPart: 1
     FragmentCount: 4
     TableStatus: Retrieved
     -- Attributes --
     id Bigint PRIMARY KEY DISTRIBUTION KEY AT=FIXED ST=MEMORY AUTO_INCR
     country_code Char(2;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
     type Char(4;latin1_swedish_ci) NOT NULL AT=FIXED ST=MEMORY
     ip_address Varchar(15;latin1_swedish_ci) NOT NULL AT=SHORT_VAR ST=MEMORY
     addresses Bigunsigned NULL AT=FIXED ST=MEMORY
     date Bigunsigned NULL AT=FIXED ST=MEMORY

     -- Indexes --
     PRIMARY KEY(id) - UniqueHashIndex
     PRIMARY(id) - OrderedIndex

     *-- Per partition info --
     Partition   Row count   Commit count  Frag fixed memory   Frag varsized memory
     0           12981       52296         1572864             557056
     1           13236       52515         1605632             557056
     2           13105       13105         819200              294912
     3           13093       13093         819200              294912*

     NDBT_ProgramExit: 0 - OK

*Note*:

Normally, *Note `ALTER [ONLINE] TABLE TABLE_NAME REORGANIZE PARTITION':
alter-table. is used with a list of partition identifiers and a set of
partition definitions to create a new partitioning scheme for a table
that has already been explicitly partitioned. Its use here to
redistribute data onto a new MySQL Cluster node group is an exception
in this regard; when used in this way, only the name of the table is
used following the `TABLE' keyword, and no other keywords or
identifiers follow `REORGANIZE PARTITION'.

Prior to MySQL Cluster NDB 6.4.3, *Note `ALTER ONLINE TABLE ...
REORGANIZE PARTITION': alter-table. with no `PARTITION_NAMES INTO
(PARTITION_DEFINITIONS)' option did not work correctly with Disk Data
tables or with in-memory *Note `NDBCLUSTER': mysql-cluster. tables
having one or more disk-based columns. (Bug #42549)

For more information, see *Note alter-table::.

In addition, for each table, the *Note `ALTER ONLINE TABLE':
alter-table. statement should be followed by an *Note `OPTIMIZE TABLE':
optimize-table. to reclaim wasted space. You can obtain a list of all
*Note `NDBCLUSTER': mysql-cluster. tables using the following query
against the *Note `INFORMATION_SCHEMA.TABLES': tables-table. table:


     SELECT TABLE_SCHEMA, TABLE_NAME
         FROM INFORMATION_SCHEMA.TABLES
         WHERE ENGINE = 'NDBCLUSTER';

*Note*:

The `INFORMATION_SCHEMA.TABLES.ENGINE' value for a MySQL Cluster table
is always *Note `NDBCLUSTER': mysql-cluster, regardless of whether the
`CREATE TABLE' statement used to create the table (or *Note `ALTER
TABLE': alter-table.  statement used to convert an existing table from
a different storage engine) used *Note `NDB': mysql-cluster. or *Note
`NDBCLUSTER': mysql-cluster. in its `ENGINE' option.

You can see after performing these statements in the output of `ALL
REPORT MEMORY' that the data and indexes are now redistributed between
all cluster data nodes, as shown here:


     ndb_mgm> ALL REPORT MEMORY

     Node 1: Data usage is 5%(176 32K pages of total 3200)
     Node 1: Index usage is 0%(76 8K pages of total 12832)
     Node 2: Data usage is 5%(176 32K pages of total 3200)
     Node 2: Index usage is 0%(76 8K pages of total 12832)
     Node 3: Data usage is 2%(80 32K pages of total 3200)
     Node 3: Index usage is 0%(51 8K pages of total 12832)
     Node 4: Data usage is 2%(80 32K pages of total 3200)
     Node 4: Index usage is 0%(50 8K pages of total 12832)

*Note*:

Since only one DDL operation on *Note `NDBCLUSTER': mysql-cluster.
tables can be executed at a time, you must wait for each *Note `ALTER
ONLINE TABLE ... REORGANIZE PARTITION': alter-table. statement to finish
before issuing the next one.

It is not necessary to issue *Note `ALTER ONLINE TABLE ... REORGANIZE
PARTITION': alter-table. statements for *Note `NDBCLUSTER':
mysql-cluster. tables created _after_ the new data nodes have been
added; data added to such tables is distributed among all data nodes
automatically. However, in *Note `NDBCLUSTER': mysql-cluster. tables
that existed _prior to_ the addition of the new nodes, neither existing
nor new data is distributed using the new nodes until these tables have
been reorganized using *Note `ALTER ONLINE TABLE ... REORGANIZE
PARTITION': alter-table.

Alternative procedure, without rolling restart

It is possible to avoid the need for a rolling restart by configuring
the extra data nodes, but not starting them, when first starting the
cluster. We assume, as before, that you wish to start with two data
nodes--nodes 1 and 2--in one node group and later to expand the cluster
to four data nodes, by adding a second node group consisting of nodes 3
and 4:


     [ndbd default]
     DataMemory = 100M
     IndexMemory = 100M
     NoOfReplicas = 2
     DataDir = /usr/local/mysql/var/mysql-cluster

     [ndbd]
     Id = 1
     HostName = 192.168.0.1

     [ndbd]
     Id = 2
     HostName = 192.168.0.2

     [ndbd]
     Id = 3
     HostName = 192.168.0.3
     Nodegroup = 65536   # MySQL Cluster NDB 7.0.24 and later;
                         # MySQL Cluster NDB 7.1.13 and later

     [ndbd]
     Id = 4
     HostName = 192.168.0.4
     Nodegroup = 65536   # MySQL Cluster NDB 7.0.24 and later;
                         # MySQL Cluster NDB 7.1.13 and later

     [mgm]
     HostName = 192.168.0.10
     Id = 10

     [api]
     Id=20
     HostName = 192.168.0.20

     [api]
     Id=21
     HostName = 192.168.0.21

Prior to MySQL Cluster NDB 7.0.24 and MySQL Cluster NDB 7.1.13, you
must perform the initial start of the cluster using the
`--nowait-nodes' option with *Note `ndbd': mysql-cluster-programs-ndbd.
(or *Note `ndbmtd': mysql-cluster-programs-ndbmtd. in MySQL Cluster NDB
7.0.4 and later) for each of the data nodes that you wish to have
online immediately, so that the cluster does not wait for the remaining
nodes to start:


     shell> ndbd -c 192.168.0.10 --initial --nowait-nodes=3,4

Beginning with MySQL Cluster NDB 7.0.24 and MySQL Cluster NDB 7.1.13,
the data nodes to be brought online at a later time (nodes 3 and 4) can
be configured with `NodeGroup = 65536', in which case it is not
necessary to start the nodes to be started immediately (nodes 1 and 2)
with the `--nowait-nodes' option, so nodes 1 and 2 can each be started
as shown here:


     shell> ndbd -c 192.168.0.10 --initial

The data nodes configured with `NodeGroup = 65536' are treated by the
management server as though you had started nodes 1 and 2 using
`--nowait-nodes=3,4' after waiting for a period of time determined by
the setting for the `StartNoNodeGroupTimeout' data node configuration
parameter (also introduced in MySQL Cluster NDB 7.0.24 and MySQL
Cluster NDB 7.1.13). By default, this is 15 seconds (15000
milliseconds).

*Note*:

`StartNoNodegroupTimeout' must be the same for all data nodes in the
cluster; for this reason, you should always set it in the `[ndbd
default]' section of the `config.ini' file, rather than for individual
data nodes.

When you are ready to add the second node group, you need only perform
the following additional steps:

  1. Start data nodes 3 and 4, invoking the data node process once for
     each new node:


          shell> ndbd -c 192.168.0.10 --initial

  2. Issue the appropriate `CREATE NODEGROUP' command in the management
     client:


          ndb_mgm> CREATE NODEGROUP 3,4

  3. In the *Note `mysql': mysql. client, issue *Note `ALTER ONLINE
     TABLE ... REORGANIZE PARTITION': alter-table. and *Note `OPTIMIZE
     TABLE': optimize-table. statements for each existing *Note
     `NDBCLUSTER': mysql-cluster. table.  (As noted elsewhere in this
     section, existing MySQL Cluster tables cannot use the new nodes
     for data distribution until this has been done.)


File: manual.info,  Node: mysql-cluster-privilege-distribution,  Next: mysql-cluster-ndb-api-statistics,  Prev: mysql-cluster-online-add-node,  Up: mysql-cluster-management

17.5.14 Distributed MySQL Privileges for MySQL Cluster
------------------------------------------------------

MySQL Cluster NDB 7.2 introduces support for distributing MySQL users
and privileges across all SQL nodes in a MySQL Cluster. This support is
not enabled by default; you should follow the procedure outlined in
this section in order to do so.

Normally, each MySQL server's user privilege tables in the `mysql'
database must use the *Note `MyISAM': myisam-storage-engine. storage
engine, which means that a user account and its associated privileges
created on one SQL node are not available on the cluster's other SQL
nodes.  In MySQL Cluster NDB 7.2 and later, an SQL file
`ndb_dist_priv.sql' is provided with the MySQL Cluster distribution.
This file can be found in the `share/mysql' directory in the MySQL
installation directory.

The first step in enabling distributed privileges is to load this
script into a MySQL Server that functions as an SQL node (which we
refer to after this as the _target_ SQL node or MySQL Server). You can
do this by executing the following command from the system shell on the
target SQL node after changing to its MySQL installation directory
(where OPTIONS stands for any additional options needed to connect to
this SQL node):


     shell> mysql OPTIONS -uroot < share/mysql/ndb_dist_priv.sql

Importing `ndb_dist_priv.sql' creates a number of stored routines (six
stored procedures and one stored function) in the `mysql' database on
the target SQL node.  After connecting to the SQL node in the *Note
`mysql': mysql.  client (as the MySQL `root' user), you can verify that
these were created as shown here:


     mysql> SELECT ROUTINE_NAME, ROUTINE_SCHEMA, ROUTINE_TYPE
         ->     FROM INFORMATION_SCHEMA.ROUTINES
         ->     WHERE ROUTINE_NAME LIKE 'mysql_cluster%'
         ->     ORDER BY ROUTINE_TYPE;
     +---------------------------------------------+----------------+--------------+
     | ROUTINE_NAME                                | ROUTINE_SCHEMA | ROUTINE_TYPE |
     +---------------------------------------------+----------------+--------------+
     | mysql_cluster_privileges_are_distributed    | mysql          | FUNCTION     |
     | mysql_cluster_backup_privileges             | mysql          | PROCEDURE    |
     | mysql_cluster_move_grant_tables             | mysql          | PROCEDURE    |
     | mysql_cluster_move_privileges               | mysql          | PROCEDURE    |
     | mysql_cluster_restore_local_privileges      | mysql          | PROCEDURE    |
     | mysql_cluster_restore_privileges            | mysql          | PROCEDURE    |
     | mysql_cluster_restore_privileges_from_local | mysql          | PROCEDURE    |
     +---------------------------------------------+----------------+--------------+

     7 rows in set (0.01 sec)

The stored procedure named `mysql_cluster_move_privileges' creates
backup copies of the existing privilege tables, then converts them to
*Note `NDB': mysql-cluster.

`mysql_cluster_move_privileges' performs the backup and conversion in
two steps. The first step is to call `mysql_cluster_backup_privileges',
which creates two sets of copies in the `mysql' database:

   * A set of local copies that use the *Note `MyISAM':
     myisam-storage-engine. storage engine. Their names are generated
     by adding the suffix `_backup' to the original privilege table
     names.

   * A set of distributed copies that use the *Note `NDBCLUSTER':
     mysql-cluster. storage engine. These tables are named by prefixing
     `ndb_' and appending `_backup' to the names of the original tables.

After the copies are created, `mysql_cluster_move_privileges' invokes
`mysql_cluster_move_grant_tables', which contains the *Note `ALTER
TABLE ... ENGINE = NDB': alter-table. statements that convert the mysql
system tables to *Note `NDB': mysql-cluster.

Normally, you should not invoke either
`mysql_cluster_backup_privileges' or `mysql_cluster_move_grant_tables'
manually; these stored procedures are intended only for use by
`mysql_cluster_move_privileges'.

Although the original privilege tables are backed up automatically, it
is always a good idea to create backups manually of the existing
privilege tables on all affected SQL nodes before proceeding. You can
do this using *Note `mysqldump': mysqldump. in a manner similar to what
is shown here:


     shell> mysqldump OPTIONS -uroot \
         mysql host user db tables_priv columns_priv procs_priv proxies_priv > BACKUP_FILE

To perform the conversion, you must be connected to the target SQL node
using the *Note `mysql': mysql. client (again, as the MySQL `root'
user). Invoke the stored procedure like this:


     mysql> CALL mysql.mysql_cluster_move_privileges();
     Query OK, 0 rows affected (22.32 sec)

Depending on the number of rows in the privilege tables, this procedure
may take some time to execute. If some of the privilege tables are
empty, you may see one or more `No data - zero rows fetched, selected,
or processed' warnings when `mysql_cluster_move_privileges' returns. In
such cases, the warnings may be safely ignored. To verify that the
conversion was successful, you can use the stored function
`mysql_cluster_privileges_are_distributed' as shown here:


     mysql> SELECT CONCAT(
         ->    'Conversion ',
         ->    IF(mysql.mysql_cluster_privileges_are_distributed(), 'succeeded', 'failed'),
         ->    '.')
         ->    AS Result;
     +-----------------------+
     | Result                |
     +-----------------------+
     | Conversion succeeded. |
     +-----------------------+
     1 row in set (0.00 sec)

`mysql_cluster_privileges_are_distributed' checks for the existence of
the distributed privilege tables and returns `1' if all of the
privilege tables are distributed; otherwise, it returns `0'.

You can verify that the backups have been created using a query such as
this one:


     mysql> SELECT TABLE_NAME, ENGINE FROM INFORMATION_SCHEMA.TABLES
         ->     WHERE TABLE_SCHEMA = 'mysql' AND TABLE_NAME LIKE '%backup'
         ->     ORDER BY ENGINE;
     +-------------------------+------------+
     | TABLE_NAME              | ENGINE     |
     +-------------------------+------------+
     | host_backup             | MyISAM     |
     | db_backup               | MyISAM     |
     | columns_priv_backup     | MyISAM     |
     | user_backup             | MyISAM     |
     | tables_priv_backup      | MyISAM     |
     | proxies_priv_backup     | MyISAM     |
     | procs_priv_backup       | MyISAM     |
     | ndb_user_backup         | ndbcluster |
     | ndb_tables_priv_backup  | ndbcluster |
     | ndb_proxies_priv_backup | ndbcluster |
     | ndb_procs_priv_backup   | ndbcluster |
     | ndb_host_backup         | ndbcluster |
     | ndb_db_backup           | ndbcluster |
     | ndb_columns_priv_backup | ndbcluster |
     +-------------------------+------------+
     14 rows in set (0.00 sec)

Once the conversion to distributed privileges has been made, any time a
MySQL user account is created, dropped, or has its privileges updated
on any SQL node, the changes take effect immediately on all other MySQL
servers attached to the cluster.  Once privileges are distributed, any
new MySQL Servers that connect to the cluster automatically participate
in the distribution.

*Note*:

For clients connected to SQL nodes at the time that
`mysql_cluster_move_privileges' is executed, you may need to execute
*Note `FLUSH PRIVILEGES': flush. on those SQL nodes, or to disconnect
and then reconnect the clients, in order for those clients to be able
to see the changes in privileges.

All MySQL user privileges are distributed across all connected MySQL
Servers. This includes any privileges associated with views and stored
routines, even though distribution of views and stored routines
themselves is not currently supported.

In the event that an SQL node becomes disconnected from the cluster
while `mysql_cluster_move_privileges' is running, you must drop its
privilege tables after reconnecting to the cluster, using a statement
such as *Note `DROP TABLE IF EXISTS mysql.user mysql.db
mysql.tables_priv mysql.columns_priv mysql.procs_priv': drop-table.
This causes the SQL node to use the shared privilege tables rather than
its own local versions of them. This is not needed when connecting a
new SQL node to the cluster for the first time.

In the event of an initial restart of the entire cluster (all data
nodes shut down, then started again with `--initial'), the shared
privilege tables are lost. If this happens, you can restore them using
the original target SQL node either from the backups made by
`mysql_cluster_move_privileges' or from a dump file created with *Note
`mysqldump': mysqldump. If you need to use a new MySQL Server to
perform the restoration, you should start it with `--skip-grant-tables'
when connecting to the cluster for the first time; after this, you can
restore the privilege tables locally, then distribute them again using
`mysql_cluster_move_privileges'. After restoring and distributing the
tables, you should restart this MySQL Server without the
`--skip-grant-tables' option.

You can also restore the distributed tables using *Note `ndb_restore':
mysql-cluster-programs-ndb-restore.  `--restore-privilege-tables' from
a backup made using `START BACKUP' in the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. client. (The *Note `MyISAM':
myisam-storage-engine. tables created by
`mysql_cluster_move_privileges' are not backed up by the `START BACKUP'
command.)  *Note `ndb_restore': mysql-cluster-programs-ndb-restore.
does not restore the privilege tables by default; the
`--restore-privilege-tables' option causes it to do so.

You can restore the SQL node's local privileges using either of two
procedures.  `mysql_cluster_restore_privileges' works as follows:

  1. If copies of the `mysql.ndb_*_backup' tables are available,
     attempt to restore the system tables from these.

  2. Otherwise, attempt to restore the system tables from the local
     backups named `*_backup' (without the `ndb_' prefix).

The other procedure, named `mysql_cluster_restore_local_privileges',
restores the system tables from the local backups only, without
checking the `ndb_*' backups.

The system tables re-created by `mysql_cluster_restore_privileges' or
`mysql_cluster_restore_local_privileges' use the MySQL server default
storage engine; they are not shared or distributed in any way, and do
not use MySQL Cluster's *Note `NDB': mysql-cluster. storage engine.

The additional stored procedure
`mysql_cluster_restore_privileges_from_local' is intended for the use of
`mysql_cluster_restore_privileges' and
`mysql_cluster_restore_local_privileges'. It should not be invoked
directly.

*Important*:

Applications that access MySQL Cluster data directly, including NDB API
and ClusterJ applications, are not subject to the MySQL privilege
system. This means that, once you have distributed the grant tables,
they can be freely accessed by such applications, just as they can any
other *Note `NDB': mysql-cluster.  tables. In particular, you should
keep in mind that _NDB API and ClusterJ applications can read and write
user names, host names, password hashes, and any other contents of the
distributed grant tables without any restrictions_.


File: manual.info,  Node: mysql-cluster-ndb-api-statistics,  Prev: mysql-cluster-privilege-distribution,  Up: mysql-cluster-management

17.5.15 NDB API Statistics Counters and Variables
-------------------------------------------------

Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB 7.1.11, a
number of types of statistical counters relating to actions performed
by or affecting `Ndb' (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html)
objects are added. Such actions include starting and closing (or
aborting) transactions; primary key and unique key operations; table,
range, and pruned scans; threads blocked while waiting for the
completion of various operations; and data and events sent and received
by `NDBCLUSTER'. The counters are incremented inside the NDB kernel
whenever NDB API calls are made or data is sent to or received by the
data nodes. *Note `mysqld': mysqld. exposes these counters as system
status variables; their values can be read in the output of *Note `SHOW
STATUS': show-status, or by querying the *Note
`INFORMATION_SCHEMA.SESSION_STATUS': status-table.  or *Note
`INFORMATION_SCHEMA.GLOBAL_STATUS': status-table.  table. By comparing
the values before and after statements operating on *Note `NDB':
mysql-cluster. tables, you can observe the corresponding actions taken
on the API level, and thus the cost of performing the statement.

You can list all of these status variables using the following *Note
`SHOW STATUS': show-status. statement:


     mysql> SHOW STATUS LIKE 'ndb_api%';
     +--------------------------------------------+----------+
     | Variable_name                              | Value    |
     +--------------------------------------------+----------+
     | Ndb_api_wait_exec_complete_count_session   | 0        |
     | Ndb_api_wait_scan_result_count_session     | 0        |
     | Ndb_api_wait_meta_request_count_session    | 0        |
     | Ndb_api_wait_nanos_count_session           | 0        |
     | Ndb_api_bytes_sent_count_session           | 0        |
     | Ndb_api_bytes_received_count_session       | 0        |
     | Ndb_api_trans_start_count_session          | 0        |
     | Ndb_api_trans_commit_count_session         | 0        |
     | Ndb_api_trans_abort_count_session          | 0        |
     | Ndb_api_trans_close_count_session          | 0        |
     | Ndb_api_pk_op_count_session                | 0        |
     | Ndb_api_uk_op_count_session                | 0        |
     | Ndb_api_table_scan_count_session           | 0        |
     | Ndb_api_range_scan_count_session           | 0        |
     | Ndb_api_pruned_scan_count_session          | 0        |
     | Ndb_api_scan_batch_count_session           | 0        |
     | Ndb_api_read_row_count_session             | 0        |
     | Ndb_api_trans_local_read_row_count_session | 0        |
     | Ndb_api_event_data_count_injector          | 0        |
     | Ndb_api_event_nondata_count_injector       | 0        |
     | Ndb_api_event_bytes_count_injector         | 0        |
     | Ndb_api_wait_exec_complete_count_slave     | 0        |
     | Ndb_api_wait_scan_result_count_slave       | 0        |
     | Ndb_api_wait_meta_request_count_slave      | 0        |
     | Ndb_api_wait_nanos_count_slave             | 0        |
     | Ndb_api_bytes_sent_count_slave             | 0        |
     | Ndb_api_bytes_received_count_slave         | 0        |
     | Ndb_api_trans_start_count_slave            | 0        |
     | Ndb_api_trans_commit_count_slave           | 0        |
     | Ndb_api_trans_abort_count_slave            | 0        |
     | Ndb_api_trans_close_count_slave            | 0        |
     | Ndb_api_pk_op_count_slave                  | 0        |
     | Ndb_api_uk_op_count_slave                  | 0        |
     | Ndb_api_table_scan_count_slave             | 0        |
     | Ndb_api_range_scan_count_slave             | 0        |
     | Ndb_api_pruned_scan_count_slave            | 0        |
     | Ndb_api_scan_batch_count_slave             | 0        |
     | Ndb_api_read_row_count_slave               | 0        |
     | Ndb_api_trans_local_read_row_count_slave   | 0        |
     | Ndb_api_wait_exec_complete_count           | 2        |
     | Ndb_api_wait_scan_result_count             | 3        |
     | Ndb_api_wait_meta_request_count            | 27       |
     | Ndb_api_wait_nanos_count                   | 45612023 |
     | Ndb_api_bytes_sent_count                   | 992      |
     | Ndb_api_bytes_received_count               | 9640     |
     | Ndb_api_trans_start_count                  | 2        |
     | Ndb_api_trans_commit_count                 | 1        |
     | Ndb_api_trans_abort_count                  | 0        |
     | Ndb_api_trans_close_count                  | 2        |
     | Ndb_api_pk_op_count                        | 1        |
     | Ndb_api_uk_op_count                        | 0        |
     | Ndb_api_table_scan_count                   | 1        |
     | Ndb_api_range_scan_count                   | 0        |
     | Ndb_api_pruned_scan_count                  | 0        |
     | Ndb_api_scan_batch_count                   | 0        |
     | Ndb_api_read_row_count                     | 1        |
     | Ndb_api_trans_local_read_row_count         | 1        |
     | Ndb_api_event_data_count                   | 0        |
     | Ndb_api_event_nondata_count                | 0        |
     | Ndb_api_event_bytes_count                  | 0        |
     +--------------------------------------------+----------+
     60 rows in set (0.02 sec)

These status variables are also available from the *Note
`SESSION_STATUS': status-table. and *Note `GLOBAL_STATUS': status-table.
tables of the `INFORMATION_SCHEMA' database, as shown here:


     mysql> SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
         ->   WHERE VARIABLE_NAME LIKE 'ndb_api%';
     +--------------------------------------------+----------------+
     | VARIABLE_NAME                              | VARIABLE_VALUE |
     +--------------------------------------------+----------------+
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SESSION   | 2              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT_SESSION     | 0              |
     | NDB_API_WAIT_META_REQUEST_COUNT_SESSION    | 1              |
     | NDB_API_WAIT_NANOS_COUNT_SESSION           | 8144375        |
     | NDB_API_BYTES_SENT_COUNT_SESSION           | 68             |
     | NDB_API_BYTES_RECEIVED_COUNT_SESSION       | 84             |
     | NDB_API_TRANS_START_COUNT_SESSION          | 1              |
     | NDB_API_TRANS_COMMIT_COUNT_SESSION         | 1              |
     | NDB_API_TRANS_ABORT_COUNT_SESSION          | 0              |
     | NDB_API_TRANS_CLOSE_COUNT_SESSION          | 1              |
     | NDB_API_PK_OP_COUNT_SESSION                | 1              |
     | NDB_API_UK_OP_COUNT_SESSION                | 0              |
     | NDB_API_TABLE_SCAN_COUNT_SESSION           | 0              |
     | NDB_API_RANGE_SCAN_COUNT_SESSION           | 0              |
     | NDB_API_PRUNED_SCAN_COUNT_SESSION          | 0              |
     | NDB_API_SCAN_BATCH_COUNT_SESSION           | 0              |
     | NDB_API_READ_ROW_COUNT_SESSION             | 1              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SESSION | 1              |
     | NDB_API_EVENT_DATA_COUNT_INJECTOR          | 0              |
     | NDB_API_EVENT_NONDATA_COUNT_INJECTOR       | 0              |
     | NDB_API_EVENT_BYTES_COUNT_INJECTOR         | 0              |
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SLAVE     | 0              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT_SLAVE       | 0              |
     | NDB_API_WAIT_META_REQUEST_COUNT_SLAVE      | 0              |
     | NDB_API_WAIT_NANOS_COUNT_SLAVE             | 0              |
     | NDB_API_BYTES_SENT_COUNT_SLAVE             | 0              |
     | NDB_API_BYTES_RECEIVED_COUNT_SLAVE         | 0              |
     | NDB_API_TRANS_START_COUNT_SLAVE            | 0              |
     | NDB_API_TRANS_COMMIT_COUNT_SLAVE           | 0              |
     | NDB_API_TRANS_ABORT_COUNT_SLAVE            | 0              |
     | NDB_API_TRANS_CLOSE_COUNT_SLAVE            | 0              |
     | NDB_API_PK_OP_COUNT_SLAVE                  | 0              |
     | NDB_API_UK_OP_COUNT_SLAVE                  | 0              |
     | NDB_API_TABLE_SCAN_COUNT_SLAVE             | 0              |
     | NDB_API_RANGE_SCAN_COUNT_SLAVE             | 0              |
     | NDB_API_PRUNED_SCAN_COUNT_SLAVE            | 0              |
     | NDB_API_SCAN_BATCH_COUNT_SLAVE             | 0              |
     | NDB_API_READ_ROW_COUNT_SLAVE               | 0              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SLAVE   | 0              |
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT           | 4              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT             | 3              |
     | NDB_API_WAIT_META_REQUEST_COUNT            | 28             |
     | NDB_API_WAIT_NANOS_COUNT                   | 53756398       |
     | NDB_API_BYTES_SENT_COUNT                   | 1060           |
     | NDB_API_BYTES_RECEIVED_COUNT               | 9724           |
     | NDB_API_TRANS_START_COUNT                  | 3              |
     | NDB_API_TRANS_COMMIT_COUNT                 | 2              |
     | NDB_API_TRANS_ABORT_COUNT                  | 0              |
     | NDB_API_TRANS_CLOSE_COUNT                  | 3              |
     | NDB_API_PK_OP_COUNT                        | 2              |
     | NDB_API_UK_OP_COUNT                        | 0              |
     | NDB_API_TABLE_SCAN_COUNT                   | 1              |
     | NDB_API_RANGE_SCAN_COUNT                   | 0              |
     | NDB_API_PRUNED_SCAN_COUNT                  | 0              |
     | NDB_API_SCAN_BATCH_COUNT                   | 0              |
     | NDB_API_READ_ROW_COUNT                     | 2              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT         | 2              |
     | NDB_API_EVENT_DATA_COUNT                   | 0              |
     | NDB_API_EVENT_NONDATA_COUNT                | 0              |
     | NDB_API_EVENT_BYTES_COUNT                  | 0              |
     +--------------------------------------------+----------------+
     60 rows in set (0.00 sec)

     mysql> SELECT * FROM INFORMATION_SCHEMA.GLOBAL_STATUS
         ->     WHERE VARIABLE_NAME LIKE 'ndb_api%';
     +--------------------------------------------+----------------+
     | VARIABLE_NAME                              | VARIABLE_VALUE |
     +--------------------------------------------+----------------+
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SESSION   | 2              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT_SESSION     | 0              |
     | NDB_API_WAIT_META_REQUEST_COUNT_SESSION    | 1              |
     | NDB_API_WAIT_NANOS_COUNT_SESSION           | 8144375        |
     | NDB_API_BYTES_SENT_COUNT_SESSION           | 68             |
     | NDB_API_BYTES_RECEIVED_COUNT_SESSION       | 84             |
     | NDB_API_TRANS_START_COUNT_SESSION          | 1              |
     | NDB_API_TRANS_COMMIT_COUNT_SESSION         | 1              |
     | NDB_API_TRANS_ABORT_COUNT_SESSION          | 0              |
     | NDB_API_TRANS_CLOSE_COUNT_SESSION          | 1              |
     | NDB_API_PK_OP_COUNT_SESSION                | 1              |
     | NDB_API_UK_OP_COUNT_SESSION                | 0              |
     | NDB_API_TABLE_SCAN_COUNT_SESSION           | 0              |
     | NDB_API_RANGE_SCAN_COUNT_SESSION           | 0              |
     | NDB_API_PRUNED_SCAN_COUNT_SESSION          | 0              |
     | NDB_API_SCAN_BATCH_COUNT_SESSION           | 0              |
     | NDB_API_READ_ROW_COUNT_SESSION             | 1              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SESSION | 1              |
     | NDB_API_EVENT_DATA_COUNT_INJECTOR          | 0              |
     | NDB_API_EVENT_NONDATA_COUNT_INJECTOR       | 0              |
     | NDB_API_EVENT_BYTES_COUNT_INJECTOR         | 0              |
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT_SLAVE     | 0              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT_SLAVE       | 0              |
     | NDB_API_WAIT_META_REQUEST_COUNT_SLAVE      | 0              |
     | NDB_API_WAIT_NANOS_COUNT_SLAVE             | 0              |
     | NDB_API_BYTES_SENT_COUNT_SLAVE             | 0              |
     | NDB_API_BYTES_RECEIVED_COUNT_SLAVE         | 0              |
     | NDB_API_TRANS_START_COUNT_SLAVE            | 0              |
     | NDB_API_TRANS_COMMIT_COUNT_SLAVE           | 0              |
     | NDB_API_TRANS_ABORT_COUNT_SLAVE            | 0              |
     | NDB_API_TRANS_CLOSE_COUNT_SLAVE            | 0              |
     | NDB_API_PK_OP_COUNT_SLAVE                  | 0              |
     | NDB_API_UK_OP_COUNT_SLAVE                  | 0              |
     | NDB_API_TABLE_SCAN_COUNT_SLAVE             | 0              |
     | NDB_API_RANGE_SCAN_COUNT_SLAVE             | 0              |
     | NDB_API_PRUNED_SCAN_COUNT_SLAVE            | 0              |
     | NDB_API_SCAN_BATCH_COUNT_SLAVE             | 0              |
     | NDB_API_READ_ROW_COUNT_SLAVE               | 0              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT_SLAVE   | 0              |
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT           | 4              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT             | 3              |
     | NDB_API_WAIT_META_REQUEST_COUNT            | 28             |
     | NDB_API_WAIT_NANOS_COUNT                   | 53756398       |
     | NDB_API_BYTES_SENT_COUNT                   | 1060           |
     | NDB_API_BYTES_RECEIVED_COUNT               | 9724           |
     | NDB_API_TRANS_START_COUNT                  | 3              |
     | NDB_API_TRANS_COMMIT_COUNT                 | 2              |
     | NDB_API_TRANS_ABORT_COUNT                  | 0              |
     | NDB_API_TRANS_CLOSE_COUNT                  | 3              |
     | NDB_API_PK_OP_COUNT                        | 2              |
     | NDB_API_UK_OP_COUNT                        | 0              |
     | NDB_API_TABLE_SCAN_COUNT                   | 1              |
     | NDB_API_RANGE_SCAN_COUNT                   | 0              |
     | NDB_API_PRUNED_SCAN_COUNT                  | 0              |
     | NDB_API_SCAN_BATCH_COUNT                   | 0              |
     | NDB_API_READ_ROW_COUNT                     | 2              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT         | 2              |
     | NDB_API_EVENT_DATA_COUNT                   | 0              |
     | NDB_API_EVENT_NONDATA_COUNT                | 0              |
     | NDB_API_EVENT_BYTES_COUNT                  | 0              |
     +--------------------------------------------+----------------+
     60 rows in set (0.00 sec)

Each `Ndb' (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) object has
its own counters. NDB API applications can read the values of the
counters for use in optimization or monitoring. For multi-threaded
clients which use more than one `Ndb'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) object concurrently,
it is also possible to obtain a summed view of counters from all `Ndb'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects belonging to
a given `Ndb_cluster_connection'
(http://dev.mysql.com/doc/ndbapi/en/ndb-ndb-cluster-connection.html).

Four sets of these counters are exposed. One set applies to the current
session only; the other 3 are global. _This is in spite of the fact
that their values can be obtained as either session or global status
variables in the *Note `mysql': mysql.  client_. This means that
specifying the `SESSION' or `GLOBAL' keyword with *Note `SHOW STATUS':
show-status. has no effect on the values reported for NDB API
statistics status variables, and the value for each of these variables
is the same whether the value is obtained from the equivalent column of
the *Note `SESSION_STATUS': status-table. or the *Note `GLOBAL_STATUS':
status-table.  table.

   * _Session counters (session specific)_

     Session counters relate to the `Ndb'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects in use
     by (only) the current session. Use of such objects by other MySQL
     clients does not influence these counts.

     In order to minimize confusion with standard MySQL session
     variables, we refer to the variables that correspond to these NDB
     API session counters as ``_session' variables', with a leading
     underscore.

   * _Slave counters (global)_

     This set of counters relates to the `Ndb'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects used by
     the replication slave SQL thread, if any. If this *Note `mysqld':
     mysqld. does not act as a replication slave, or does not use *Note
     `NDB': mysql-cluster. tables, then all of these counts are 0.

     We refer to the related status variables as ``_slave' variables'
     (with a leading underscore).

   * _Injector counters (global)_

     Injector counters relate to the `Ndb'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) object used to
     listen to cluster events by the binlog injector thread. Even when
     not writing a binary log, *Note `mysqld': mysqld. processes
     attached to a MySQL Cluster continue to listen for some events,
     such as schema changes.

     We refer to the status variables that correspond to NDB API
     injector counters as ``_injector' variables' (with a leading
     underscore).

   * _Server (Global) counters (global)_

     This set of counters relates to all `Ndb'
     (http://dev.mysql.com/doc/ndbapi/en/ndb-ndb.html) objects
     currently used by this *Note `mysqld': mysqld. This includes all
     MySQL client applications, the slave SQL thread (if any), the
     binlog injector, and the *Note `NDB': mysql-cluster. utility
     thread.

     We refer to the status variables that correspond to these counters
     as `global variables' or `*Note `mysqld': mysqld.-level variables'.

You can obtain values for a particular set of variables by additionally
filtering for the substring `session', `slave', or `injector' in the
variable name (along with the common prefix `Ndb_api'). For `_session'
variables, this can be done as shown here:


     mysql> SHOW STATUS LIKE 'ndb_api%session';
     +--------------------------------------------+---------+
     | Variable_name                              | Value   |
     +--------------------------------------------+---------+
     | Ndb_api_wait_exec_complete_count_session   | 2       |
     | Ndb_api_wait_scan_result_count_session     | 0       |
     | Ndb_api_wait_meta_request_count_session    | 1       |
     | Ndb_api_wait_nanos_count_session           | 8144375 |
     | Ndb_api_bytes_sent_count_session           | 68      |
     | Ndb_api_bytes_received_count_session       | 84      |
     | Ndb_api_trans_start_count_session          | 1       |
     | Ndb_api_trans_commit_count_session         | 1       |
     | Ndb_api_trans_abort_count_session          | 0       |
     | Ndb_api_trans_close_count_session          | 1       |
     | Ndb_api_pk_op_count_session                | 1       |
     | Ndb_api_uk_op_count_session                | 0       |
     | Ndb_api_table_scan_count_session           | 0       |
     | Ndb_api_range_scan_count_session           | 0       |
     | Ndb_api_pruned_scan_count_session          | 0       |
     | Ndb_api_scan_batch_count_session           | 0       |
     | Ndb_api_read_row_count_session             | 1       |
     | Ndb_api_trans_local_read_row_count_session | 1       |
     +--------------------------------------------+---------+
     18 rows in set (0.50 sec)

To obtain a listing of the NDB API *Note `mysqld': mysqld.-level status
variables, filter for variable names beginning with `ndb_api' and
ending in `_count', like this:


     mysql> SELECT * FROM INFORMATION_SCHEMA.SESSION_STATUS
         ->     WHERE VARIABLE_NAME LIKE 'ndb_api%count';
     +------------------------------------+----------------+
     | VARIABLE_NAME                      | VARIABLE_VALUE |
     +------------------------------------+----------------+
     | NDB_API_WAIT_EXEC_COMPLETE_COUNT   | 4              |
     | NDB_API_WAIT_SCAN_RESULT_COUNT     | 3              |
     | NDB_API_WAIT_META_REQUEST_COUNT    | 28             |
     | NDB_API_WAIT_NANOS_COUNT           | 53756398       |
     | NDB_API_BYTES_SENT_COUNT           | 1060           |
     | NDB_API_BYTES_RECEIVED_COUNT       | 9724           |
     | NDB_API_TRANS_START_COUNT          | 3              |
     | NDB_API_TRANS_COMMIT_COUNT         | 2              |
     | NDB_API_TRANS_ABORT_COUNT          | 0              |
     | NDB_API_TRANS_CLOSE_COUNT          | 3              |
     | NDB_API_PK_OP_COUNT                | 2              |
     | NDB_API_UK_OP_COUNT                | 0              |
     | NDB_API_TABLE_SCAN_COUNT           | 1              |
     | NDB_API_RANGE_SCAN_COUNT           | 0              |
     | NDB_API_PRUNED_SCAN_COUNT          | 0              |
     | NDB_API_SCAN_BATCH_COUNT           | 0              |
     | NDB_API_READ_ROW_COUNT             | 2              |
     | NDB_API_TRANS_LOCAL_READ_ROW_COUNT | 2              |
     | NDB_API_EVENT_DATA_COUNT           | 0              |
     | NDB_API_EVENT_NONDATA_COUNT        | 0              |
     | NDB_API_EVENT_BYTES_COUNT          | 0              |
     +------------------------------------+----------------+
     21 rows in set (0.09 sec)

Not all counters are reflected in all 4 sets of status variables.  For
the event counters `DataEventsRecvdCount', `NondataEventsRecvdCount',
and `EventBytesRecvdCount', only `_injector' and *Note `mysqld':
mysqld.-level NDB API status variables are available:


     mysql> SHOW STATUS LIKE 'ndb_api%event%';
     +--------------------------------------+-------+
     | Variable_name                        | Value |
     +--------------------------------------+-------+
     | Ndb_api_event_data_count_injector    | 0     |
     | Ndb_api_event_nondata_count_injector | 0     |
     | Ndb_api_event_bytes_count_injector   | 0     |
     | Ndb_api_event_data_count             | 0     |
     | Ndb_api_event_nondata_count          | 0     |
     | Ndb_api_event_bytes_count            | 0     |
     +--------------------------------------+-------+
     6 rows in set (0.00 sec)

`_injector' status variables are not implemented for any other NDB API
counters, as shown here:


     mysql> SHOW STATUS LIKE 'ndb_api%injector%';
     +--------------------------------------+-------+
     | Variable_name                        | Value |
     +--------------------------------------+-------+
     | Ndb_api_event_data_count_injector    | 0     |
     | Ndb_api_event_nondata_count_injector | 0     |
     | Ndb_api_event_bytes_count_injector   | 0     |
     +--------------------------------------+-------+
     3 rows in set (0.00 sec)

The names of the status variables can easily be associated with the
names of the corresponding counters. Each NDB API statistics counter is
listed in the following table with a description as well as the names
of any MySQL server status variables corresponding to this counter.

The first column of this table lists NDB API statistics counter names.
The second column, the rows of which are split into two cells, provides
a description of statistics counter in the first cell, followed by a
list of corresponding MySQL server status variables in the second cell.
Status variables are listed by type in the following order: Session,
Slave, Injector, Server.

Counter Name              Description
Status Variables (by      
statistic type):          
                          
   * Session              
                          
   * Slave                
                          
   * Injector             
                          
   * Server               
`WaitExecCompleteCount'   Number of times thread has been blocked while
                          waiting for execution of an operation to
                          complete. Includes all `execute()'
                          (http://dev.mysql.com/doc/ndbapi/en/ndb-ndbtransaction-methods.html#ndb-ndbtransaction-execute)
                          calls as well as implicit executes for blob
                          operations and auto-increment not visible to
                          clients.
   *                      
     `Ndb_api_wait_exec_complete_count_session'
                          
   *                      
     `Ndb_api_wait_exec_complete_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_wait_exec_complete_count'
`WaitScanResultCount'     Number of times thread has been blocked while
                          waiting for a scan-based signal, such waiting
                          for additional results, or for a scan to close.
   *                      
     `Ndb_api_wait_scan_result_count_session'
                          
   *                      
     `Ndb_api_wait_scan_result_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_wait_scan_result_count'
`WaitMetaRequestCount'    Number of times thread has been blocked
                          waiting for a metadata-based signal; this can
                          occur when waiting for a DDL operation or for
                          an epoch to be started (or ended).
   *                      
     `Ndb_api_wait_meta_request_count_session'
                          
   *                      
     `Ndb_api_wait_meta_request_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_wait_meta_request_count'
`WaitNanosCount'          Total time (in nanoseconds) spent waiting for
                          some type of signal from the data nodes.
   *                      
     `Ndb_api_wait_nanos_count_session'
                          
   *                      
     `Ndb_api_wait_nanos_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_wait_nanos_count'
`BytesSentCount'          Amount of data (in bytes) sent to the data
                          nodes
   *                      
     `Ndb_api_bytes_sent_count_session'
                          
   *                      
     `Ndb_api_bytes_sent_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_bytes_sent_count'
`BytesRecvdCount'         Amount of data (in bytes) received from the
                          data nodes
   *                      
     `Ndb_api_bytes_received_count_session'
                          
   *                      
     `Ndb_api_bytes_received_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_bytes_received_count'
`TransStartCount'         Number of transactions started.
   *                      
     `Ndb_api_trans_start_count_session'
                          
   *                      
     `Ndb_api_trans_start_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_trans_start_count'
`TransCommitCount'        Number of transactions committed.
   *                      
     `Ndb_api_trans_commit_count_session'
                          
   *                      
     `Ndb_api_trans_commit_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_trans_commit_count'
`TransAbortCount'         Number of transactions aborted.
   *                      
     `Ndb_api_trans_abort_count_session'
                          
   *                      
     `Ndb_api_trans_abort_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_trans_abort_count'
`TransCloseCount'         Number of transactions aborted. (This value
                          may be greater than the sum of
                          `TransCommitCount' and `TransAbortCount'.)
   *                      
     `Ndb_api_trans_close_count_session'
                          
   *                      
     `Ndb_api_trans_close_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_trans_close_count'
`PkOpCount'               Number of operations based on or using primary
                          keys. This count includes blob-part table
                          operations, implicit unlocking operations, and
                          auto-increment operations, as well as primary
                          key operations normally visible to MySQL
                          clients.
   *                      
     `Ndb_api_pk_op_count_session'
                          
   *                      
     `Ndb_api_pk_op_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_pk_op_count'
`UkOpCount'               Number of operations based on or using unique
                          keys.
   *                      
     `Ndb_api_uk_op_count_session'
                          
   *                      
     `Ndb_api_uk_op_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_uk_op_count'
`TableScanCount'          Number of table scans that have been started.
                          This includes scans of internal tables.
   *                      
     `Ndb_api_table_scan_count_session'
                          
   *                      
     `Ndb_api_table_scan_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_table_scan_count'
`RangeScanCount'          Number of range scans that have been started.
   *                      
     `Ndb_api_range_scan_count_session'
                          
   *                      
     `Ndb_api_range_scan_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_range_scan_count'
`PrunedScanCount'         Number of scans that have been pruned to a
                          single partition.
   *                      
     `Ndb_api_pruned_scan_count_session'
                          
   *                      
     `Ndb_api_pruned_scan_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_pruned_scan_count'
`ScanBatchCount'          Number of batches of rows received. (A _batch_
                          in this context is a set of scan results from
                          a single fragment.)
   *                      
     `Ndb_api_scan_batch_count_session'
                          
   *                      
     `Ndb_api_scan_batch_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_scan_batch_count'
`ReadRowCount'            Total number of rows that have been read.
                          Includes rows read using primary key, unique
                          key, and scan operations.
   *                      
     `Ndb_api_read_row_count_session'
                          
   *                      
     `Ndb_api_read_row_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_read_row_count'
`TransLocalReadRowCount'  Number of rows read from the data same node on
                          which the transaction was being run.
   *                      
     `Ndb_api_trans_local_read_row_count_session'
                          
   *                      
     `Ndb_api_trans_local_read_row_count_slave'
                          
   * [none]               
                          
   *                      
     `Ndb_api_trans_local_read_row_count'
`DataEventsRecvdCount'    Number of row change events received.
   * [none]               
                          
   * [none]               
                          
   *                      
     `Ndb_api_event_data_count_injector'
                          
   *                      
     `Ndb_api_event_data_count'
`NondataEventsRecvdCount' Number of events received, other than row
                          change events.
   * [none]               
                          
   * [none]               
                          
   *                      
     `Ndb_api_event_nondata_count_injector'
                          
   *                      
     `Ndb_api_event_nondata_count'
`EventBytesRecvdCount'    Number of bytes of events received.
   * [none]               
                          
   * [none]               
                          
   *                      
     `Ndb_api_event_bytes_count_injector'
                          
   *                      
     `Ndb_api_event_bytes_count'
To see all counts of committed transactions--that is, all
`TransCommitCount' counter status variables--you can filter the results
of *Note `SHOW STATUS': show-status. for the substring
`trans_commit_count', like this:


     mysql> SHOW STATUS LIKE '%trans_commit_count%';
     +------------------------------------+-------+
     | Variable_name                      | Value |
     +------------------------------------+-------+
     | Ndb_api_trans_commit_count_session | 1     |
     | Ndb_api_trans_commit_count_slave   | 0     |
     | Ndb_api_trans_commit_count         | 2     |
     +------------------------------------+-------+
     3 rows in set (0.00 sec)

From this you can determine that 1 transaction has been committed in
the current *Note `mysql': mysql. client session, and 2 transactions
have been committed on this *Note `mysqld': mysqld.  since it was last
restarted.

You can see how various NDB API counters are incremented by a given SQL
statement by comparing the values of the corresponding `_session'
status variables immediately before and after performing the statement.
In this example, after getting the initial values from *Note `SHOW
STATUS': show-status, we create in the `test' database an *Note `NDB':
mysql-cluster. table, named `t', that has a single column:


     mysql> SHOW STATUS LIKE 'ndb_api%session%';
     +--------------------------------------------+--------+
     | Variable_name                              | Value  |
     +--------------------------------------------+--------+
     | Ndb_api_wait_exec_complete_count_session   | 2      |
     | Ndb_api_wait_scan_result_count_session     | 0      |
     | Ndb_api_wait_meta_request_count_session    | 3      |
     | Ndb_api_wait_nanos_count_session           | 820705 |
     | Ndb_api_bytes_sent_count_session           | 132    |
     | Ndb_api_bytes_received_count_session       | 372    |
     | Ndb_api_trans_start_count_session          | 1      |
     | Ndb_api_trans_commit_count_session         | 1      |
     | Ndb_api_trans_abort_count_session          | 0      |
     | Ndb_api_trans_close_count_session          | 1      |
     | Ndb_api_pk_op_count_session                | 1      |
     | Ndb_api_uk_op_count_session                | 0      |
     | Ndb_api_table_scan_count_session           | 0      |
     | Ndb_api_range_scan_count_session           | 0      |
     | Ndb_api_pruned_scan_count_session          | 0      |
     | Ndb_api_scan_batch_count_session           | 0      |
     | Ndb_api_read_row_count_session             | 1      |
     | Ndb_api_trans_local_read_row_count_session | 1      |
     +--------------------------------------------+--------+
     18 rows in set (0.00 sec)

     mysql> USE test;
     Database changed
     mysql> CREATE TABLE t (c INT) ENGINE NDBCLUSTER;
     Query OK, 0 rows affected (0.85 sec)

Now you can execute a new *Note `SHOW STATUS': show-status. statement
and observe the changes, as shown here (with the changed rows
highlighted in the output):


     mysql> SHOW STATUS LIKE 'ndb_api%session%';
     +--------------------------------------------+-----------+
     | Variable_name                              | Value     |
     +--------------------------------------------+-----------+_
     | Ndb_api_wait_exec_complete_count_session   | 8         |_
     | Ndb_api_wait_scan_result_count_session     | 0         |
     _| Ndb_api_wait_meta_request_count_session    | 17        |_
     _| Ndb_api_wait_nanos_count_session           | 706871709 |_
     _| Ndb_api_bytes_sent_count_session           | 2376      |_
     _| Ndb_api_bytes_received_count_session       | 3844      |_
     _| Ndb_api_trans_start_count_session          | 4         |_
     _| Ndb_api_trans_commit_count_session         | 4         |_
     | Ndb_api_trans_abort_count_session          | 0         |
     _| Ndb_api_trans_close_count_session          | 4         |_
     _| Ndb_api_pk_op_count_session                | 6         |_
     | Ndb_api_uk_op_count_session                | 0         |
     | Ndb_api_table_scan_count_session           | 0         |
     | Ndb_api_range_scan_count_session           | 0         |
     | Ndb_api_pruned_scan_count_session          | 0         |
     | Ndb_api_scan_batch_count_session           | 0         |
     _| Ndb_api_read_row_count_session             | 2         |_
     | Ndb_api_trans_local_read_row_count_session | 1         |
     +--------------------------------------------+-----------+
     18 rows in set (0.00 sec)

Similarly, you can see the changes in the NDB API statistics counters
caused by inserting a row into `t': Insert the row, then run the same
*Note `SHOW STATUS': show-status. statement used in the previous
example, as shown here:


     mysql> INSERT INTO t VALUES (100);
     Query OK, 1 row affected (0.00 sec)

     mysql> SHOW STATUS LIKE 'ndb_api%session%';
     +--------------------------------------------+-----------+
     | Variable_name                              | Value     |
     +--------------------------------------------+-----------+
     _| Ndb_api_wait_exec_complete_count_session   | 11        |_
     _| Ndb_api_wait_scan_result_count_session     | 6         |_
     _| Ndb_api_wait_meta_request_count_session    | 20        |_
     _| Ndb_api_wait_nanos_count_session           | 707370418 |_
     _| Ndb_api_bytes_sent_count_session           | 2724      |_
     _| Ndb_api_bytes_received_count_session       | 4116      |_
     _| Ndb_api_trans_start_count_session          | 7         |_
     _| Ndb_api_trans_commit_count_session         | 6         |_
     | Ndb_api_trans_abort_count_session          | 0         |
     _| Ndb_api_trans_close_count_session          | 7         |_
     _| Ndb_api_pk_op_count_session                | 8         |_
     | Ndb_api_uk_op_count_session                | 0         |
     _| Ndb_api_table_scan_count_session           | 1         |_
     | Ndb_api_range_scan_count_session           | 0         |
     | Ndb_api_pruned_scan_count_session          | 0         |
     | Ndb_api_scan_batch_count_session           | 0         |
     _| Ndb_api_read_row_count_session             | 3         |_
     _| Ndb_api_trans_local_read_row_count_session | 2         |_
     +--------------------------------------------+-----------+
     18 rows in set (0.00 sec)

We can make a number of observations from these results:

   * Although we created `t' with no explicit primary key, 5 primary
     key operations were performed in doing so (the difference in the
     `before' and `after' values of `Ndb_api_pk_op_count_session', or 6
     minus 1). This reflects the creation of the hidden primary key
     that is a feature of all tables using the *Note `NDB':
     mysql-cluster. storage engine.

   * By comparing successive values for
     `Ndb_api_wait_nanos_count_session', we can see that the NDB API
     operations implementing the *Note `CREATE TABLE': create-table.
     statement waited much longer (706871709 - 820705 = 706051004
     nanoseconds, or approximately 0.7 second) for responses from the
     data nodes than those executed by the *Note `INSERT': insert.
     (707370418 - 706871709 = 498709 ns or roughly .0005 second). The
     execution times reported for these statements in the *Note
     `mysql': mysql.  client correlate roughly with these figures.

     On platforms with without sufficient (nanosecond) time resolution,
     small changes in the value of the `WaitNanosCount' NDB API counter
     due to SQL statements that execute very quickly may not always be
     visible in the values of `Ndb_api_wait_nanos_count_session',
     `Ndb_api_wait_nanos_count_slave', or `Ndb_api_wait_nanos_count'.

   * The *Note `INSERT': insert. statement incremented both the
     `ReadRowCount' and `TransLocalReadRowCount' NDB API statistics
     counters, as reflected by the increased values of
     `Ndb_api_read_row_count_session' and
     `Ndb_api_trans_local_read_row_count_session'.


File: manual.info,  Node: mysql-cluster-replication,  Next: mysql-cluster-news,  Prev: mysql-cluster-management,  Up: mysql-cluster

17.6 MySQL Cluster Replication
==============================

* Menu:

* mysql-cluster-replication-abbreviations::  MySQL Cluster Replication: Abbreviations and Symbols
* mysql-cluster-replication-general::  General Requirements for MySQL Cluster Replication
* mysql-cluster-replication-issues::  Known Issues in MySQL Cluster Replication
* mysql-cluster-replication-schema::  MySQL Cluster Replication Schema and Tables
* mysql-cluster-replication-preparation::  Preparing the MySQL Cluster for Replication
* mysql-cluster-replication-starting::  Starting MySQL Cluster Replication (Single Replication Channel)
* mysql-cluster-replication-two-channels::  Using Two Replication Channels for MySQL Cluster Replication
* mysql-cluster-replication-failover::  Implementing Failover with MySQL Cluster Replication
* mysql-cluster-replication-backups::  MySQL Cluster Backups With MySQL Cluster Replication
* mysql-cluster-replication-multi-master::  MySQL Cluster Replication: Multi-Master and Circular Replication
* mysql-cluster-replication-conflict-resolution::  MySQL Cluster Replication Conflict Resolution

Previous to MySQL 5.1.6, _asynchronous replication_, more usually
referred to simply as `replication', was not available when using MySQL
Cluster. MySQL 5.1.6 introduces master-slave replication of this type
for MySQL Cluster databases. This section explains how to set up and
manage a configuration wherein one group of computers operating as a
MySQL Cluster replicates to a second computer or group of computers. We
assume some familiarity on the part of the reader with standard MySQL
replication as discussed elsewhere in this Manual. (See *Note
replication::).

Normal (non-clustered) replication involves a `master' server and a
`slave' server, the master being the source of the operations and data
to be replicated and the slave being the recipient of these. In MySQL
Cluster, replication is conceptually very similar but can be more
complex in practice, as it may be extended to cover a number of
different configurations including replicating between two complete
clusters. Although a MySQL Cluster itself depends on the *Note `NDB':
mysql-cluster.  storage engine for clustering functionality, it is not
necessary to use *Note `NDB': mysql-cluster. as the storage engine for
the slave's copies of the replicated tables (see *Note
mysql-cluster-replication-ndb-non-ndb::). However, for maximum
availability, it is possible (and preferable) to replicate from one
MySQL Cluster to another, and it is this scenario that we discuss, as
shown in the following figure:

MySQL Cluster-to-Cluster Replication Layout

In this scenario, the replication process is one in which successive
states of a master cluster are logged and saved to a slave cluster.
This process is accomplished by a special thread known as the NDB
binlog injector thread, which runs on each MySQL server and produces a
binary log (`binlog'). This thread ensures that all changes in the
cluster producing the binary log--and not just those changes that are
effected through the MySQL Server--are inserted into the binary log
with the correct serialization order. We refer to the MySQL replication
master and replication slave servers as replication servers or
replication nodes, and the data flow or line of communication between
them as a _replication channel_.

For information about performing point-in-time recovery with MySQL
Cluster and MySQL Cluster Replication, see *Note
mysql-cluster-replication-pitr::.

NDB API _slave status variables

Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB 7.1.11,
NDB API counters provide enhanced monitoring capabilities on MySQL
Cluster replication slaves. These are implelemented as NDB statistics
`_slave' status variables, as seen in the output of *Note `SHOW
STATUS': show-status, or in the results of queries against the *Note
`SESSION_STATUS': status-table. or *Note `GLOBAL_STATUS': status-table.
table in a *Note `mysql': mysql. client session connected to a MySQL
Server that is acting as a slave in MySQL Cluster Replication. By
comparing the values of these status variables before and after the
execution of statements affecting replicated *Note `NDB':
mysql-cluster. tables, you can observe the corresponding actions taken
on the NDB API level by the slave, which can be useful when monitoring
or troubleshooting MySQL Cluster Replication.  *Note
mysql-cluster-ndb-api-statistics::, provides additional information.

Replication from NDB to non-NDB tables

It is possible to replicate *Note `NDB': mysql-cluster.  tables from a
MySQL Cluster acting as the master to tables using other MySQL storage
engines such as *Note `InnoDB': innodb-storage-engine. or *Note
`MyISAM': myisam-storage-engine. on a slave *Note `mysqld': mysqld.
However, because of differences between the version of *Note `mysqld':
mysqld. provided with MySQL Cluster and that included with MySQL Server
5.1, the slave server must also use a *Note `mysqld': mysqld. binary
from the MySQL Cluster distribution. See *Note
mysql-cluster-replication-general::.


File: manual.info,  Node: mysql-cluster-replication-abbreviations,  Next: mysql-cluster-replication-general,  Prev: mysql-cluster-replication,  Up: mysql-cluster-replication

17.6.1 MySQL Cluster Replication: Abbreviations and Symbols
-----------------------------------------------------------

Throughout this section, we use the following abbreviations or symbols
for referring to the master and slave clusters, and to processes and
commands run on the clusters or cluster nodes:

This table lists abbreviations used throughout this section for symbols
referring to master and slave clusters, and to processes and commands
run on the clusters or cluster nodes.

Symbol or          Description (Refers to...)
Abbreviation       
M                  The cluster serving as the (primary) replication
                   master
S                  The cluster acting as the (primary) replication slave
`shellM>'          Shell command to be issued on the master cluster
`mysqlM>'          MySQL client command issued on a single MySQL server
                   running as an SQL node on the master cluster
`mysqlM*>'         MySQL client command to be issued on all SQL nodes
                   participating in the replication master cluster
`shellS>'          Shell command to be issued on the slave cluster
`mysqlS>'          MySQL client command issued on a single MySQL server
                   running as an SQL node on the slave cluster
`mysqlS*>'         MySQL client command to be issued on all SQL nodes
                   participating in the replication slave cluster
C                  Primary replication channel
C'                 Secondary replication channel
M'                 Secondary replication master
S'                 Secondary replication slave


File: manual.info,  Node: mysql-cluster-replication-general,  Next: mysql-cluster-replication-issues,  Prev: mysql-cluster-replication-abbreviations,  Up: mysql-cluster-replication

17.6.2 General Requirements for MySQL Cluster Replication
---------------------------------------------------------

A replication channel requires two MySQL servers acting as replication
servers (one each for the master and slave). For example, this means
that in the case of a replication setup with two replication channels
(to provide an extra channel for redundancy), there will be a total of
four replication nodes, two per cluster.

Replication of a MySQL Cluster as described in this section and those
following is dependent on row-based replication. This means that the
replication master MySQL server must be started with
`--binlog-format=ROW' or `--binlog-format=MIXED', as described in *Note
mysql-cluster-replication-starting::. For general information about
row-based replication, see *Note replication-formats::.

*Important*:

If you attempt to use MySQL Cluster Replication with
`--binlog-format=STATEMENT', replication fails to work properly because
the `ndb_binlog_index' table on the master and the `epoch' column of the
`ndb_apply_status' table on the slave are not updated (see *Note
mysql-cluster-replication-schema::). Instead, only updates on the MySQL
server acting as the replication master propagate to the slave, and no
updates from any other SQL nodes on the master cluster are replicated.

In all MySQL Cluster NDB 6.x and 7.x releases, the default value for
the `--binlog-format' option is `MIXED'.

Each MySQL server used for replication in either cluster must be
uniquely identified among all the MySQL replication servers
participating in either cluster (you cannot have replication servers on
both the master and slave clusters sharing the same ID). This can be
done by starting each SQL node using the `--server-id=ID' option, where
ID is a unique integer. Although it is not strictly necessary, we will
assume for purposes of this discussion that all MySQL Cluster binaries
are of the same release version.

It is generally true in MySQL Replication that both MySQL servers
(*Note `mysqld': mysqld. processes) involved must be compatible with
one another with respect to both the version of the replication
protocol used and the SQL feature sets which they support (see *Note
replication-compatibility::). It is due to such differences between the
binaries in the MySQL Cluster and MySQL Server 5.1 distributions that
MySQL Cluster Replication has the additional requirement that both
*Note `mysqld': mysqld. binaries come from a MySQL Cluster
distribution. The simplest and easiest way to assure that the *Note
`mysqld': mysqld. servers are compatible is to use the same MySQL
Cluster distribution for all master and slave *Note `mysqld': mysqld.
binaries.

We assume that the slave server or cluster is dedicated to replication
of the master, and that no other data is being stored on it.

*Note*:

It is possible to replicate a MySQL Cluster using statement-based
replication. However, in this case, the following restrictions apply:

   * All updates to data rows on the cluster acting as the master must
     be directed to a single MySQL server.

   * It is not possible to replicate a cluster using multiple
     simultaneous MySQL replication processes.

   * Only changes made at the SQL level are replicated.

These are in addition to the other limitations of statement-based
replication as opposed to row-based replication; see *Note
replication-sbr-rbr::, for more specific information concerning the
differences between the two replication formats.


File: manual.info,  Node: mysql-cluster-replication-issues,  Next: mysql-cluster-replication-schema,  Prev: mysql-cluster-replication-general,  Up: mysql-cluster-replication

17.6.3 Known Issues in MySQL Cluster Replication
------------------------------------------------

This section discusses known problems or issues when using replication
with MySQL Cluster in MySQL 5.1 (including MySQL Cluster NDB 6.X and
7.X through 7.1).

Loss of master-slave connection

A loss of connection can occur either between the replication master
SQL node and the replication slave SQL node, or between the replication
master SQL node and the data nodes in the master cluster. In the latter
case, this can occur not only as a result of loss of physical
connection (for example, a broken network cable), but due to the
overflow of data node event buffers; if the SQL node is too slow to
respond, it may be dropped by the cluster (this is controllable to some
degree by adjusting the `MaxBufferedEpochs' and `TimeBetweenEpochs'
configuration parameters). If this occurs, _it is entirely possible for
new data to be inserted into the master cluster without being recorded
in the replication master's binary log_. For this reason, to guarantee
high availability, it is extremely important to maintain a backup
replication channel, to monitor the primary channel, and to fail over
to the secondary replication channel when necessary to keep the slave
cluster synchronized with the master. MySQL Cluster is not designed to
perform such monitoring on its own; for this, an external application
is required.

Prior to MySQL 5.1.18, a MySQL Cluster replication slave *Note
`mysqld': mysqld. had no way of detecting that the connection from the
master had been interrupted. For this reason, it was possible for the
slave to become inconsistent with the master.

Beginning with MySQL 5.1.18, the replication master issues a `gap'
event when connecting or reconnecting to the master cluster. (A gap
event is a type of `incident event,' which indicates an incident that
occurs that affects the contents of the database but that cannot easily
be represented as a set of changes. Examples of incidents are server
crashes, database resynchronization, (some) software updates, and
(some) hardware changes.) When the slave encounters a gap in the
replication log, it stops with an error message. This message is
available in the output of *Note `SHOW SLAVE STATUS':
show-slave-status, and indicates that the SQL thread has stopped due to
an incident registered in the replication stream, and that manual
intervention is required. See *Note
mysql-cluster-replication-failover::, for more information about what
to do in such circumstances.

*Important*:

Because MySQL Cluster is not designed on its own to monitor replication
status or provide failover, if high availability is a requirement for
the slave server or cluster, then you must set up multiple replication
lines, monitor the master *Note `mysqld': mysqld. on the primary
replication line, and be prepared fail over to a secondary line if and
as necessary.  This must be done manually, or possibly by means of a
third-party application. For information about implementing this type
of setup, see *Note mysql-cluster-replication-two-channels::, and *Note
mysql-cluster-replication-failover::.

However, if you are replicating from a standalone MySQL server to a
MySQL Cluster, one channel is usually sufficient.

Multibyte character sets

Previously, there were several known issues with regard to the use of
multibyte characters sets with MySQL Cluster Replication.  These were
resolved in MySQL 5.1.21, MySQL Cluster NDB 6.2.14, and MySQL Cluster
NDB 6.3.11. (See Bug #27404 and Bug #29562.)

Circular replication

Prior to MySQL 5.1.18, circular replication was not supported with
MySQL Cluster replication, due to the fact that all log events created
in a particular MySQL Cluster were wrongly tagged with the server ID of
the MySQL server used as master and not with the server ID of the
originating server.

Beginning with MySQL 5.1.18, this limitation is lifted, as discussed in
the next few paragraphs, in which we consider the example of a
replication setup involving three MySQL Clusters numbered 1, 2, and 3,
in which Cluster 1 acts as the replication master for Cluster 2,
Cluster 2 acts as the master for Cluster 3, and Cluster 3 acts as the
master for Cluster 1. Each cluster has two SQL nodes, with SQL nodes A
and B belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2,
and SQL nodes E and F belonging to Cluster 3.

Circular replication using these clusters is supported as long as the
following conditions are met:

   * The SQL nodes on all masters and slaves are the same

   * All SQL nodes acting as replication masters and slaves are started
     using the `--log-slave-updates' option

This type of circular replication setup is shown in the following
diagram:

MySQL Cluster circular replication scheme in which all master SQL nodes
are also slaves.

In this scenario, SQL node A in Cluster 1 replicates to SQL node C in
Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E
replicates to SQL node A. In other words, the replication line
(indicated by the red arrows in the diagram) directly connects all SQL
nodes used as replication masters and slaves.

It should also be possible to set up circular replication in which not
all master SQL nodes are also slaves, as shown here:

MySQL Cluster circular replication scheme in which all master SQL nodes
are not also necessarily slaves.

In this case, different SQL nodes in each cluster are used as
replication masters and slaves. However, you must _not_ start any of
the SQL nodes using `--log-slave-updates'). This type of circular
replication scheme for MySQL Cluster, in which the line of replication
(again indicated by the red arrows in the diagram) is discontinuous,
should be possible, but it should be noted that it has not yet been
thoroughly tested and must therefore still be considered experimental.

*Note*:

Beginning with MySQL 5.1.24, the *Note `NDB': mysql-cluster. storage
engine uses _idempotent execution mode_, which suppresses duplicate-key
and other errors that otherwise break circular replication of MySQL
Cluster. This is equivalent to setting the global `slave_exec_mode'
system variable to `IDEMPOTENT'.

Idempotent mode is also required for multi-master replication when
using MySQL Cluster (Bug #31609), but it is not necessary to set
`slave_exec_mode' in MySQL Cluster replication since MySQL Cluster does
this automatically, and ignores any attempts to set this variable
explicitly.

MySQL Cluster replication and primary keys

In MySQL 5.1.6, only those *Note `NDB': mysql-cluster.  tables having
explicit primary keys could be replicated. This limitation was lifted
in MySQL 5.1.7. However, in the event of a node failure, errors in
replication of *Note `NDB': mysql-cluster. tables without primary keys
can still occur, due to the possibility of duplicate rows being
inserted in such cases. For this reason, it is highly recommended that
all *Note `NDB': mysql-cluster. tables being replicated have primary
keys.

MySQL Cluster Replication and Unique Keys

Prior to MySQL Cluster NDB 7.0.25 and MySQL Cluster NDB 7.1.14,
operations that updated values of unique key columns of *Note `NDB':
mysql-cluster. tables could result in duplicate-key errors when
replicated. This was due to the ordering of row events in the binary
log according to the partitioning of the base table, which meant that
they could appear in a different order from that in which they were
originally executed. (Bug #11756082)

In MySQL Cluster NDB 7.0.25, MySQL Cluster NDB 7.1.14, and later, this
issue is solved for replication between *Note `NDB': mysql-cluster.
tables by deferring unique key checks until after all table row updates
have been performed.

Deferring constraints in this way is currently supported only by *Note
`NDB': mysql-cluster. Thus, updates of unique keys when replicating
from *Note `NDB': mysql-cluster. to a different storage engine such as
*Note `MyISAM': myisam-storage-engine. or *Note `InnoDB':
innodb-storage-engine. are still not supported.

The problem encountered when replicating without deferred checking of
unique key updates can be illustrated using *Note `NDB': mysql-cluster.
table such as `t', is created and populated on the master (and
replicated to a slave that does not support deferred unique key
updates) as shown here:


     CREATE TABLE t (
         p INT PRIMARY KEY,
         c INT,
         UNIQUE KEY u (c)
     )   ENGINE NDB;

     INSERT INTO t
         VALUES (1,1), (2,2), (3,3), (4,4), (5,5);

The following *Note `UPDATE': update. statement on `t' succeeded on the
master, since the rows affected are processed in the order determined
by the `ORDER BY' option, performed over the entire table:


     UPDATE t SET c = c - 1 ORDER BY p;

However, the same statement failed with a duplicate key error or other
constraint violation on the slave, because the ordering of the row
updates was done for one partition at a time, rather than for the table
as a whole.

*Note*:

In MySQL 5.1.6 and later, every *Note `NDB': mysql-cluster.  table is
implicitly partitioned by key when it is created. This also applies to
all MySQL Cluster NDB 6.x and MySQL Cluster NDB 7.x releases. See *Note
partitioning-key::, for more information.

Restarting with -initial

Restarting the cluster with the `--initial' option causes the sequence
of GCI and epoch numbers to start over from `0'. (This is generally
true of MySQL Cluster and not limited to replication scenarios
involving Cluster.) The MySQL servers involved in replication should in
this case be restarted. After this, you should use the *Note `RESET
MASTER': reset-master. and *Note `RESET SLAVE': reset-slave. statements
to clear the invalid `ndb_binlog_index' and `ndb_apply_status' tables,
respectively.

auto_increment_offset and auto_increment_increment variables

The use of the `auto_increment_offset' and `auto_increment_increment'
server system variables is supported beginning with MySQL 5.1.20.
Previously, these produced unpredictable results when used with *Note
`NDB': mysql-cluster. tables or MySQL Cluster replication.

Replication from NDB to other storage engines

It is possible to replicate an *Note `NDB': mysql-cluster.  table on
the master to a table using a different storage engine on the slave,
taking into account the restrictions listed here:

   * Multi-master and circular replication are not supported (tables on
     both the master and the slave must use the *Note `NDB':
     mysql-cluster. storage engine for this to work).

   * Using a storage engine which does not perform binary logging for
     slave tables requires special handling.

   * Use of a nontransactional storage engine for slave tables also
     requires special handling.

The next few paragraphs provide additional information about each of
the issues just described.

Multiple masters not supported when replicating NDB to other storage
engines

For replication from *Note `NDB': mysql-cluster. to a different storage
engine, the relationship between the two databases must be a simple
master-slave one. This means that circular or master-master replication
is not supported between MySQL Cluster and other storage engines.

In addition, it is not possible to configure more than one replication
channel when replicating between *Note `NDB': mysql-cluster. and a
different storage engine.  (However, a MySQL Cluster database _can_
simultaneously replicate to multiple slave MySQL Cluster databases.) If
the master uses *Note `NDB': mysql-cluster.  tables, it is still
possible to have more than one MySQL Server maintain a binary log of
all changes; however, for the slave to change masters (fail over), the
new master-slave relationship must be explicitly defined on the slave.

Replicating NDB to a slave storage engine that does not perform binary
logging

If you attempt to replicate from a MySQL Cluster to a slave that uses a
storage engine that does not handle its own binary logging, the
replication process aborts with the error `Binary logging not possible
... Statement cannot be written atomically since more than one engine
involved and at least one engine is self-logging' (Error 1595). It is
possible to work around this issue in one of the following ways:

   * Turn off binary logging on the slave

     This can be accomplished by setting `sql_log_bin = 0'.

   * Change the storage engine used for the mysql.ndb_apply_status table

     Causing this table to use an engine that does not handle its own
     binary logging can also eliminate the conflict. This can be done
     by issuing a statement such as *Note `ALTER TABLE
     mysql.ndb_apply_status ENGINE=MyISAM': alter-table. on the slave.
     It is safe to do this when using a non-*Note `NDB': mysql-cluster.
     storage engine on the slave, since you do not then need to worry
     about keeping multiple slave SQL nodes synchronized.

   * Filter out changes to the mysql.ndb_apply_status table on the slave

     This can be done by starting the slave SQL node with
     `--replicate-ignore-table=mysql.ndb_apply_status'.  If you need
     for other tables to be ignored by replication, you might wish to
     use an appropriate `--replicate-wild-ignore-table' option instead.

*Important*:

You should _not_ disable replication or binary logging of
`mysql.ndb_apply_status' or change the storage engine used for this
table when replicating from one MySQL Cluster to another. See *Note
mysql-cluster-replication-issues-filtering::, for details.

Replication from NDB to a nontransactional storage engine

When replicating from *Note `NDB': mysql-cluster. to a nontransactional
storage engine such as *Note `MyISAM': myisam-storage-engine, you may
encounter unnecessary duplicate key errors when replicating *Note
`INSERT ... ON DUPLICATE KEY UPDATE': insert-on-duplicate. statements.
You can suppress these in MySQL Cluster NDB 6.2 and later MySQL Cluster
releases by using `--ndb-log-update-as-write=0', which forces updates
to be logged as writes (rather than as updates).

In addition, when replicating from *Note `NDB': mysql-cluster. to a
storage engine that does not implement transactions, if the slave fails
to apply any row changes from a given transaction, it does not roll
back the rest of the transaction. (This is true when replicating tables
using any transactional storage engine--not only *Note `NDB':
mysql-cluster.--to a nontransactional storage engine.) Because of this,
it cannot be guaranteed that transactional consistency will be
maintained on the slave in such cases.

Replication and binary log filtering rules with replication between
MySQL Clusters

If you are using any of the options `--replicate-do-*',
`--replicate-ignore-*', `--binlog-do-db', or `--binlog-ignore-db' to
filter databases or tables being replicated, care must be taken not to
block replication or binary logging of the `mysql.ndb_apply_status',
which is required for replication between MySQL Clusters to operate
properly. In particular, you must keep in mind the following:

  1. Using `--replicate-do-db=DB_NAME' (and no other `--replicate-do-*'
     or `--replicate-ignore-*' options) means that _only_ tables in
     database DB_NAME are replicated. In this case, you should also use
     `--replicate-do-db=mysql', `--binlog-do-db=mysql', or
     `--replicate-do-table=mysql.ndb_apply_status' to ensure that
     `mysql.ndb_apply_status' is populated on slaves.

     Using `--binlog-do-db=DB_NAME' (and no other `--binlog-do-db'
     options) means that changes _only_ to tables in database DB_NAME
     are written to the binary log. In this case, you should also use
     `--replicate-do-db=mysql', `--binlog-do-db=mysql', or
     `--replicate-do-table=mysql.ndb_apply_status' to ensure that
     `mysql.ndb_apply_status' is populated on slaves.

  2. Using `--replicate-ignore-db=mysql' means that no tables in the
     `mysql' database are replicated. In this case, you should also use
     `--replicate-do-table=mysql.ndb_apply_status' to ensure that
     `mysql.ndb_apply_status' is replicated.

     Using `--binlog-ignore-db=mysql' means that no changes to tables
     in the `mysql' database are written to the binary log. In this
     case, you should also use
     `--replicate-do-table=mysql.ndb_apply_status' to ensure that
     `mysql.ndb_apply_status' is replicated.

You should also remember that each replication rule requires the
following:

  1. Its own `--replicate-do-*' or `--replicate-ignore-*' option, and
     that multiple rules cannot be expressed in a single replication
     filtering option. For information about these rules, see *Note
     replication-options::.

  2. Its own `--binlog-do-db' or `--binlog-ignore-db' option, and that
     multiple rules cannot be expressed in a single binary log
     filtering option. For information about these rules, see *Note
     binary-log::.

If you are replicating a MySQL Cluster to a slave that uses a storage
engine other than *Note `NDB': mysql-cluster, the considerations just
given previously may not apply, as discussed elsewhere in this section.

MySQL Cluster Replication and IPv6

Currently, the NDB API and MGM API do not support IPv6. However,
beginning with MySQL Cluster NDB 6.4.1, MySQL Servers--including those
acting as SQL nodes in a MySQL Cluster--can use IPv6 to contact other
MySQL Servers. This means that you can replicate between MySQL Clusters
using IPv6 to connect the master and slave SQL nodes as shown by the
dotted arrow in the following diagram:

IPv6 Used to Connect Between MySQL Cluster SQL Nodes in Replication

However, all connections originating _within_ the MySQL
Cluster--represented in the preceding diagram by solid arrows--must use
IPv4. In other words, all MySQL Cluster data nodes, management servers,
and management clients must be accessible from one another using IPv4.
In addition, SQL nodes must use IPv4 to communicate with the cluster.

Since there is currently no support in the NDB and MGM APIs for IPv6,
any applications written using these APIs must also make all
connections using IPv4.

Attribute promotion and demotion

Formerly, support in MySQL Cluster for type conversions between columns
of similar but different types on the master and the slave was
extremely limited. However, starting with MySQL Cluster NDB 6.3.33,
7.0.14, and 7.1.3, MySQL Cluster Replication includes support for
attribute promotion and demotion. The implementation of the latter
distinguishes between lossy and non-lossy type conversions, and their
use on the slave can be controlled by setting the
`slave_type_conversions' global server system variable.

For more information about attribute promotion and demotion in MySQL
Cluster, see *Note replication-features-attribute-promotion::.


File: manual.info,  Node: mysql-cluster-replication-schema,  Next: mysql-cluster-replication-preparation,  Prev: mysql-cluster-replication-issues,  Up: mysql-cluster-replication

17.6.4 MySQL Cluster Replication Schema and Tables
--------------------------------------------------

Replication in MySQL Cluster makes use of a number of dedicated tables
in the `mysql' database on each MySQL Server instance acting as an SQL
node in both the cluster being replicated and the replication slave
(whether the slave is a single server or a cluster). These tables are
created during the MySQL installation process by the *Note
`mysql_install_db': mysql-install-db. script, and include a table for
storing the binary log's indexing data. Since the `ndb_binlog_index'
table is local to each MySQL server and does not participate in
clustering, it uses the `MyISAM' storage engine. This means that it must
be created separately on each *Note `mysqld': mysqld.  participating in
the master cluster. (However, the binary log itself contains updates
from all MySQL servers in the cluster to be replicated.) This table is
defined as follows:


     CREATE TABLE `ndb_binlog_index` (
         `Position`  BIGINT(20) UNSIGNED NOT NULL,
         `File`      VARCHAR(255) NOT NULL,
         `epoch`     BIGINT(20) UNSIGNED NOT NULL,
         `inserts`   BIGINT(20) UNSIGNED NOT NULL,
         `updates`   BIGINT(20) UNSIGNED NOT NULL,
         `deletes`   BIGINT(20) UNSIGNED NOT NULL,
         `schemaops` BIGINT(20) UNSIGNED NOT NULL,
         `next_position` bigint(20) unsigned NOT NULL,
         `next_file` varchar(255) NOT NULL,
         PRIMARY KEY (`epoch`)
     ) ENGINE=MYISAM  DEFAULT CHARSET=latin1;

The size of this table is dependent on the number of epochs per binary
log file and the number of binary log files. The number of epochs per
binary log file normally depends on the amount of binary log generated
per epoch and the size of the binary log file, with smaller epochs
resulting in more epochs per file. It should be noted that empty epochs
produce result in inserts to the `ndb_binlog_index' table, even when the
`--ndb-log-empty-epochs' option is `OFF', meaning that the number of
entries per file depends on the length of time that the file is in use;
that is,


     [number of epochs per file] = [time spent per file] / `TimeBetweenEpochs'

A busy MySQL Cluster writes to the binary log regularly and presumably
rotates binary log files more quickly than a quiet one.  This means
that a `quiet' MySQL Cluster with `--ndb-log-empty-epochs=ON' can
actually have a much higher number of `ndb_binlog_index' rows per file
than one with a great deal of activity.

When *Note `mysqld': mysqld. is started with the `--ndb-log-orig'
option, the `orig_server_id' and `orig_epoch' columns store,
respectively, the ID of the server on which the event originated and
the epoch in which the event took place on the originating server,
which is useful in MySQL Cluster replication setups employing multiple
masters. The *Note `SELECT': select. statement used to find the closest
binlog position to the highest applied epoch on the slave in a
multi-master setup (see *Note mysql-cluster-replication-multi-master::)
employs these two columns, which are not indexed. This can lead to
performance issues when trying to fail over, since the query must
perform a table scan, especially when the master has been running with
`--ndb-log-empty-epochs=ON'. You can improve multi-master failover
times by adding an index to these columns, as shown here:


     ALTER TABLE mysql.ndb_binlog_index
         ADD INDEX orig_lookup USING BTREE (orig_server_id, orig_epoch);

Adding this index provides no benefit when replicating from a single
master to a single slave, since the query used to get the binary log
position in such cases makes no use of `orig_server_id' or `orig_epoch'.

The `next_position' and `next_file' columns were added in MySQL Cluster
NDB 7.2.6; see *Note mysql-cluster-replication-failover::, for more
information about using these columns.

*Important*:

Prior to MySQL 5.1.14, the `ndb_binlog_index' table was known as
`binlog_index', and was kept in a separate `cluster' database, which in
MySQL 5.1.7 and earlier was known as the `cluster_replication'
database. Similarly, the `ndb_apply_status' and `ndb_schema' tables
were known as `apply_status' and `schema', and were also found in the
`cluster' (earlier `cluster_replication') database. However, beginning
with MySQL 5.1.14, all MySQL Cluster replication tables reside in the
`mysql' system database.

Information about how this change affects upgrades from MySQL Cluster
5.1.13 and earlier to 5.1.14 and later versions can be found in
`http://dev.mysql.com/doc/relnotes/mysql/5.1/en/news-5-1-14.html'.

Beginning with MySQL Cluster NDB 6.3.2, this table has been changed to
facilitate 3-way replication recovery. Two columns `orig_server_id' and
`orig_epoch' have been added to this table; when *Note `mysqld':
mysqld. is started with the `--ndb-log-orig' option, these columns
store, respectively, the ID of the server on which the event originated
and the epoch in which the event took place on the originating server.
In addition, the table's primary key now includes these two columns.
The modified table definition is shown here:


     CREATE TABLE `ndb_binlog_index` (
         `Position` BIGINT(20) UNSIGNED NOT NULL,
         `File` VARCHAR(255) NOT NULL,
         `epoch` BIGINT(20) UNSIGNED NOT NULL,
         `inserts` INT(10) UNSIGNED NOT NULL,
         `updates` INT(10) UNSIGNED NOT NULL,
         `deletes` INT(10) UNSIGNED NOT NULL,
         `schemaops` INT(10) UNSIGNED NOT NULL,
         `orig_server_id` INT(10) UNSIGNED NOT NULL,
         `orig_epoch` BIGINT(20) UNSIGNED NOT NULL,
         `gci` INT(10) UNSIGNED NOT NULL,
         `next_position` bigint(20) unsigned NOT NULL,
         `next_file` varchar(255) NOT NULL,
         PRIMARY KEY (`epoch`,`orig_server_id`,`orig_epoch`)
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1;

The `gci' column was added in MySQL Cluster NDB 6.2.6 and MySQL Cluster
NDB 6.3.2.

The `next_position' and `next_file' columns were added in MySQL Cluster
NDB 7.0.33 and MySQL Cluster NDB 7.1.22; see *Note
mysql-cluster-replication-failover::, for more information about using
these columns.

The following figure shows the relationship of the MySQL Cluster
replication master server, its binlog injector thread, and the
`mysql.ndb_binlog_index' table.

The replication master cluster, the binlog injector thread, and the
`ndb_binlog_index' table

An additional table, named `ndb_apply_status', is used to keep a record
of the operations that have been replicated from the master to the
slave. Unlike the case with `ndb_binlog_index', the data in this table
is not specific to any one SQL node in the (slave) cluster, and so
`ndb_apply_status' can use the `NDBCLUSTER' storage engine, as shown
here:


     CREATE TABLE `ndb_apply_status` (
         `server_id`   INT(10) UNSIGNED NOT NULL,
         `epoch`       BIGINT(20) UNSIGNED NOT NULL,
         `log_name`    VARCHAR(255) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL,
         `start_pos`   BIGINT(20) UNSIGNED NOT NULL,
         `end_pos`     BIGINT(20) UNSIGNED NOT NULL,
         PRIMARY KEY (`server_id`) USING HASH
     ) ENGINE=NDBCLUSTER   DEFAULT CHARSET=latin1;

The `ndb_apply_status' table is populated only on slaves, which means
that, on the master, this table never contains any rows; thus, there is
no need to allow for `DataMemory' or `IndexMemory' to be allotted to
`ndb_apply_status' there.

Because this table is populated from data originating on the master, it
should be allowed to replicate; any replication filtering or binary log
filtering rules that inadvertently prevent the slave from updating
`ndb_apply_status' or the master from writing into the binary log may
prevent replication between clusters from operating properly. For more
information about potential problems arising from such filtering rules,
see *Note mysql-cluster-replication-issues-filtering::.

The `log_name', `start_pos', and `end_pos' columns were added in MySQL
5.1.18.

*Important*:

If you are using MySQL Cluster replication, see *Note
mysql-cluster-upgrade-downgrade-compatibility-5.1:: before upgrading to
MySQL 5.1.18 or later from an earlier version.

The `ndb_binlog_index' and `ndb_apply_status' tables are created in the
`mysql' database because they should not be explicitly replicated by
the user. User intervention is normally not required to create or
maintain either of these tables, since both `ndb_binlog_index' and the
`ndb_apply_status' are maintained by the *Note `NDB': mysql-cluster.
binary log (binlog) injector thread. This keeps the master *Note
`mysqld': mysqld. process updated to changes performed by the *Note
`NDB': mysql-cluster. storage engine. The *Note `NDB': mysql-cluster.
_binlog injector thread_ receives events directly from the *Note `NDB':
mysql-cluster. storage engine. The *Note `NDB': mysql-cluster. injector
is responsible for capturing all the data events within the cluster,
and ensures that all events which change, insert, or delete data are
recorded in the `ndb_binlog_index' table. The slave I/O thread
transfers the events from the master's binary log to the slave's relay
log.

However, it is advisable to check for the existence and integrity of
these tables as an initial step in preparing a MySQL Cluster for
replication. It is possible to view event data recorded in the binary
log by querying the `mysql.ndb_binlog_index' table directly on the
master. This can be also be accomplished using the *Note `SHOW BINLOG
EVENTS': show-binlog-events. statement on either the replication master
or slave MySQL servers. (See *Note show-binlog-events::.)

You can also obtain useful information from the output of *Note `SHOW
ENGINE NDB STATUS': show-engine.

The `ndb_schema' table is used to track schema changes made to *Note
`NDB': mysql-cluster. tables. It is defined as shown here:


     CREATE TABLE ndb_schema (
         `db` VARBINARY(63) NOT NULL,
         `name` VARBINARY(63) NOT NULL,
         `slock` BINARY(32) NOT NULL,
         `query` BLOB NOT NULL,
         `node_id` INT UNSIGNED NOT NULL,
         `epoch` BIGINT UNSIGNED NOT NULL,
         `id` INT UNSIGNED NOT NULL,
         `version` INT UNSIGNED NOT NULL,
         `type` INT UNSIGNED NOT NULL,
         PRIMARY KEY USING HASH (db,name)
     ) ENGINE=NDB   DEFAULT CHARSET=latin1;

Unlike the two tables previously mentioned in this section, the
`ndb_schema' table is not visible either to MySQL *Note `SHOW': show.
statements, or in any `INFORMATION_SCHEMA' tables; however, it can be
seen in the output of *Note `ndb_show_tables':
mysql-cluster-programs-ndb-show-tables, as shown here:


     shell> ndb_show_tables -t 2
     id    type                 state    logging database     schema   name
     4     UserTable            Online   Yes     mysql        def      ndb_apply_status
     5     UserTable            Online   Yes     ndbworld     def      City
     6     UserTable            Online   Yes     ndbworld     def      Country
     3     UserTable            Online   Yes     mysql        def      NDB$BLOB_2_3
     7     UserTable            Online   Yes     ndbworld     def      CountryLanguage
     _2     UserTable            Online   Yes     mysql        def      ndb_schema_

     NDBT_ProgramExit: 0 - OK

It is also possible to *Note `SELECT': select. from this table in *Note
`mysql': mysql. and other MySQL client applications, as shown here:


     mysql> SELECT * FROM mysql.ndb_schema WHERE name='City' \G
     *************************** 1. row ***************************
          db: ndbworld
        name: City
       slock:
       query: alter table City engine=ndb
     node_id: 4
       epoch: 0
          id: 0
     version: 0
        type: 7
     1 row in set (0.00 sec)

This can sometimes be useful when debugging applications.

*Note*:

When performing schema changes on *Note `NDB': mysql-cluster. tables,
applications should wait until the *Note `ALTER TABLE': alter-table.
statement has returned in the MySQL client connection that issued the
statement before attempting to use the updated definition of the table.

The `ndb_schema' table was added in MySQL 5.1.8.

Beginning with MySQL 5.1.14, if the `ndb_apply_status' table or the
`ndb_schema' table does not exist on the slave, *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. re-creates the missing table or
tables (Bug #14612).

Conflict resolution for MySQL Cluster Replication requires the presence
of an additional `mysql.ndb_replication' table. Currently, this table
must be created manually. For information about how to do this, see
*Note mysql-cluster-replication-conflict-resolution::.


File: manual.info,  Node: mysql-cluster-replication-preparation,  Next: mysql-cluster-replication-starting,  Prev: mysql-cluster-replication-schema,  Up: mysql-cluster-replication

17.6.5 Preparing the MySQL Cluster for Replication
--------------------------------------------------

Preparing the MySQL Cluster for replication consists of the following
steps:

  1. Check all MySQL servers for version compatibility (see *Note
     mysql-cluster-replication-general::).

  2. Create a slave account on the master Cluster with the appropriate
     privileges:


          mysqlM> GRANT REPLICATION SLAVE
               -> ON *.* TO 'SLAVE_USER'@'SLAVE_HOST'
               -> IDENTIFIED BY 'SLAVE_PASSWORD';

     In the previous statement, SLAVE_USER is the slave account user
     name, SLAVE_HOST is the host name or IP address of the replication
     slave, and SLAVE_PASSWORD is the password to assign to this
     account.

     For example, to create a slave user account with the name
     ``myslave',' logging in from the host named ``rep-slave',' and
     using the password ``53cr37',' use the following *Note `GRANT':
     grant.  statement:


          mysqlM> GRANT REPLICATION SLAVE
               -> ON *.* TO 'myslave'@'rep-slave'
               -> IDENTIFIED BY '53cr37';

     For security reasons, it is preferable to use a unique user
     account--not employed for any other purpose--for the replication
     slave account.

  3. Configure the slave to use the master. Using the MySQL Monitor,
     this can be accomplished with the *Note `CHANGE MASTER TO':
     change-master-to. statement:


          mysqlS> CHANGE MASTER TO
               -> MASTER_HOST='MASTER_HOST',
               -> MASTER_PORT=MASTER_PORT,
               -> MASTER_USER='SLAVE_USER',
               -> MASTER_PASSWORD='SLAVE_PASSWORD';

     In the previous statement, MASTER_HOST is the host name or IP
     address of the replication master, MASTER_PORT is the port for the
     slave to use for connecting to the master, SLAVE_USER is the user
     name set up for the slave on the master, and SLAVE_PASSWORD is the
     password set for that user account in the previous step.

     For example, to tell the slave to replicate from the MySQL server
     whose host name is ``rep-master',' using the replication slave
     account created in the previous step, use the following statement:


          mysqlS> CHANGE MASTER TO
               -> MASTER_HOST='rep-master',
               -> MASTER_PORT=3306,
               -> MASTER_USER='myslave',
               -> MASTER_PASSWORD='53cr37';

     For a complete list of options that can be used with this
     statement, see *Note change-master-to::.

     To provide replication backup capability, you also need to add an
     `--ndb-connectstring' option to the slave's `my.cnf' file prior to
     starting the replication process. See *Note
     mysql-cluster-replication-backups::, for details.

     For additional options that can be set in `my.cnf' for replication
     slaves, see *Note replication-options::.

  4. If the master cluster is already in use, you can create a backup
     of the master and load this onto the slave to cut down on the
     amount of time required for the slave to synchronize itself with
     the master. If the slave is also running MySQL Cluster, this can
     be accomplished using the backup and restore procedure described in
     *Note mysql-cluster-replication-backups::.


          ndb-connectstring=MANAGEMENT_HOST[:PORT]

     In the event that you are _not_ using MySQL Cluster on the
     replication slave, you can create a backup with this command on
     the replication master:


          shellM> mysqldump --master-data=1

     Then import the resulting data dump onto the slave by copying the
     dump file over to the slave. After this, you can use the *Note
     `mysql': mysql. client to import the data from the dumpfile into
     the slave database as shown here, where DUMP_FILE is the name of
     the file that was generated using *Note `mysqldump': mysqldump. on
     the master, and DB_NAME is the name of the database to be
     replicated:


          shellS> mysql -u root -p DB_NAME < DUMP_FILE

     For a complete list of options to use with *Note `mysqldump':
     mysqldump, see *Note mysqldump::.

     *Note*:

     If you copy the data to the slave in this fashion, you should make
     sure that the slave is started with the `--skip-slave-start'
     option on the command line, or else include `skip-slave-start' in
     the slave's `my.cnf' file to keep it from trying to connect to the
     master to begin replicating before all the data has been loaded.
     Once the data loading has completed, follow the additional steps
     outlined in the next two sections.

  5. Ensure that each MySQL server acting as a replication master is
     configured with a unique server ID, and with binary logging
     enabled, using the row format. (See *Note replication-formats::.)
     These options can be set either in the master server's `my.cnf'
     file, or on the command line when starting the master *Note
     `mysqld': mysqld. process. See *Note
     mysql-cluster-replication-starting::, for information regarding
     the latter option.


File: manual.info,  Node: mysql-cluster-replication-starting,  Next: mysql-cluster-replication-two-channels,  Prev: mysql-cluster-replication-preparation,  Up: mysql-cluster-replication

17.6.6 Starting MySQL Cluster Replication (Single Replication Channel)
----------------------------------------------------------------------

This section outlines the procedure for starting MySQL Cluster
replication using a single replication channel.

  1. Start the MySQL replication master server by issuing this command:


          shellM> mysqld --ndbcluster --server-id=ID \
                  --log-bin --binlog-format=ROW &

     In the previous statement, ID is this server's unique ID (see
     *Note mysql-cluster-replication-general::). This starts the
     server's *Note `mysqld': mysqld. process with binary logging
     enabled using the proper logging format.

     *Note*:

     You can also start the master with `--binlog-format=MIXED', in
     which case row-based replication is used automatically when
     replicating between clusters. `STATEMENT' based binary logging is
     not supported for MySQL Cluster Replication (see *Note
     mysql-cluster-replication-general::).

  2. Start the MySQL replication slave server as shown here:


          shellS> mysqld --ndbcluster --server-id=ID &

     In the command just shown, ID is the slave server's unique ID. It
     is not necessary to enable logging on the replication slave.

     *Note*:

     You should use the `--skip-slave-start' option with this command
     or else you should include `skip-slave-start' in the slave server's
     `my.cnf' file, unless you want replication to begin immediately.
     With the use of this option, the start of replication is delayed
     until the appropriate *Note `START SLAVE': start-slave.  statement
     has been issued, as explained in Step 4 below.

  3. It is necessary to synchronize the slave server with the master
     server's replication binary log. If binary logging has not
     previously been running on the master, run the following statement
     on the slave:


          mysqlS> CHANGE MASTER TO
               -> MASTER_LOG_FILE='',
               -> MASTER_LOG_POS=4;

     This instructs the slave to begin reading the master's binary log
     from the log's starting point. Otherwise--that is, if you are
     loading data from the master using a backup--see *Note
     mysql-cluster-replication-failover::, for information on how to
     obtain the correct values to use for `MASTER_LOG_FILE' and
     `MASTER_LOG_POS' in such cases.

  4. Finally, you must instruct the slave to begin applying replication
     by issuing this command from the *Note `mysql': mysql. client on
     the replication slave:


          mysqlS> START SLAVE;

     This also initiates the transmission of replication data from the
     master to the slave.

It is also possible to use two replication channels, in a manner
similar to the procedure described in the next section; the differences
between this and using a single replication channel are covered in
*Note mysql-cluster-replication-two-channels::.

Beginning with MySQL Cluster NDB 6.2.3, it is possible to improve
cluster replication performance by enabling _batched updates_. This can
be accomplished by setting the `slave_allow_batching' system variable
on the slave *Note `mysqld': mysqld. processes.  Normally, updates are
applied as soon as they are received.  However, the use of batching
causes updates to be applied in 32 KB batches, which can result in
higher throughput and less CPU usage, particularly where individual
updates are relatively small.

*Note*:

Slave batching works on a per-epoch basis; updates belonging to more
than one transaction can be sent as part of the same batch.

All outstanding updates are applied when the end of an epoch is
reached, even if the updates total less than 32 KB.

Batching can be turned on and off at runtime. To activate it at
runtime, you can use either of these two statements:


     SET GLOBAL slave_allow_batching = 1;
     SET GLOBAL slave_allow_batching = ON;

If a particular batch causes problems (such as a statement whose
effects do not appear to be replicated correctly), slave batching can
be deactivated using either of the following statements:


     SET GLOBAL slave_allow_batching = 0;
     SET GLOBAL slave_allow_batching = OFF;

You can check whether slave batching is currently being used by means
of an appropriate *Note `SHOW VARIABLES': show-variables. statement,
like this one:


     mysql> SHOW VARIABLES LIKE 'slave%';
     +---------------------------+-------+
     | Variable_name             | Value |
     +---------------------------+-------+
     | slave_allow_batching      | ON    |
     | slave_compressed_protocol | OFF   |
     | slave_load_tmpdir         | /tmp  |
     | slave_net_timeout         | 3600  |
     | slave_skip_errors         | OFF   |
     | slave_transaction_retries | 10    |
     +---------------------------+-------+
     6 rows in set (0.00 sec)


File: manual.info,  Node: mysql-cluster-replication-two-channels,  Next: mysql-cluster-replication-failover,  Prev: mysql-cluster-replication-starting,  Up: mysql-cluster-replication

17.6.7 Using Two Replication Channels for MySQL Cluster Replication
-------------------------------------------------------------------

In a more complete example scenario, we envision two replication
channels to provide redundancy and thereby guard against possible
failure of a single replication channel. This requires a total of four
replication servers, two masters for the master cluster and two slave
servers for the slave cluster. For purposes of the discussion that
follows, we assume that unique identifiers are assigned as shown here:

This table lists server IDs (unique identifiers) for the MySQL cluster
replication servers described in the preceding text. The table also
provides a description of each cluster replication server.

Server ID              Description
1                      Master - primary replication channel (_M_)
2                      Master - secondary replication channel (_M'_)
3                      Slave - primary replication channel (_S_)
4                      Slave - secondary replication channel (_S'_)

Setting up replication with two channels is not radically different
from setting up a single replication channel. First, the *Note
`mysqld': mysqld. processes for the primary and secondary replication
masters must be started, followed by those for the primary and
secondary slaves. Then the replication processes may be initiated by
issuing the *Note `START SLAVE': start-slave. statement on each of the
slaves. The commands and the order in which they need to be issued are
shown here:

  1. Start the primary replication master:


          shellM> mysqld --ndbcluster --server-id=1 \
                         --log-bin --binlog-format=ROW &

  2. Start the secondary replication master:


          shellM'> mysqld --ndbcluster --server-id=2 \
                         --log-bin --binlog-format=ROW &

  3. Start the primary replication slave server:


          shellS> mysqld --ndbcluster --server-id=3 \
                         --skip-slave-start &

  4. Start the secondary replication slave:


          shellS'> mysqld --ndbcluster --server-id=4 \
                          --skip-slave-start &

  5. Finally, initiate replication on the primary channel by executing
     the *Note `START SLAVE': start-slave.  statement on the primary
     slave as shown here:


          mysqlS> START SLAVE;

     *Warning*:

     Only the primary channel is to be started at this point. The
     secondary replication channel is to be started only in the event
     that the primary replication channel fails, as described in *Note
     mysql-cluster-replication-failover::.  Running multiple
     replication channels simultaneously can result in unwanted
     duplicate records being created on the replication slaves.

As mentioned previously, it is not necessary to enable binary logging
on replication slaves.


File: manual.info,  Node: mysql-cluster-replication-failover,  Next: mysql-cluster-replication-backups,  Prev: mysql-cluster-replication-two-channels,  Up: mysql-cluster-replication

17.6.8 Implementing Failover with MySQL Cluster Replication
-----------------------------------------------------------

In the event that the primary Cluster replication process fails, it is
possible to switch over to the secondary replication channel. The
following procedure describes the steps required to accomplish this.

  1. Obtain the time of the most recent global checkpoint (GCP).  That
     is, you need to determine the most recent epoch from the
     `ndb_apply_status' table on the slave cluster, which can be found
     using the following query:


          mysqlS'> SELECT @latest:=MAX(epoch)
                ->        FROM mysql.ndb_apply_status;

  2. Using the information obtained from the query shown in Step 1,
     obtain the corresponding records from the `ndb_binlog_index' table
     on the master cluster.

     Prior to MySQL Cluster NDB 7.0.33 and MySQL Cluster 7.1.22, you
     should use the following query to accomplish this task:


          mysqlM'> SELECT
                ->     @file:=SUBSTRING_INDEX(File, '/', -1),
                ->     @pos:=Position
                -> FROM mysql.ndb_binlog_index
                -> WHERE epoch > @latest
                -> ORDER BY epoch ASC LIMIT 1;

     Beginning with MySQL Cluster NDB 7.0.33 and MySQL Cluster NDB
     7.1.22, you can take advantage of the improved binary logging of
     DDL statements implemented in those and later versions by using
     the following query to obtain the needed records from the master's
     `ndb_binlog_index' table:


          mysqlM'> SELECT
                ->     @file:=SUBSTRING_INDEX(next_file, '/', -1),
                ->     @pos:=next_position
                -> FROM mysql.ndb_binlog_index
                -> WHERE epoch = @latest
                -> ORDER BY epoch ASC LIMIT 1;

     In either case, these are the records saved on the master since
     the failure of the primary replication channel. We have employed a
     user variable `@latest' here to represent the value obtained in
     Step 1. Of course, it is not possible for one *Note `mysqld':
     mysqld. instance to access user variables set on another server
     instance directly. These values must be `plugged in' to the second
     query manually or in application code.

     *Important*:

     If (and only if) you use the second of the two queries just shown
     against `ndb_binlog_index' (that is, the query that employs the
     `next_position' and `next_file' columns), you must ensure that the
     slave *Note `mysqld': mysqld. is started with
     `--slave-skip-errors=ddl_exist_errors' before executing *Note
     `START SLAVE': start-slave.  Otherwise, replication may stop with
     duplicate DDL errors.

  3. Now it is possible to synchronize the secondary channel by running
     the following query on the secondary slave server:


          mysqlS'> CHANGE MASTER TO
                ->     MASTER_LOG_FILE='@file',
                ->     MASTER_LOG_POS=@pos;

     Again we have employed user variables (in this case `@file' and
     `@pos') to represent the values obtained in Step 2 and applied in
     Step 3; in practice these values must be inserted manually or using
     application code that can access both of the servers involved.

     *Note*:

     `@file' is a string value such as
     `'/var/log/mysql/replication-master-bin.00001'', and so must be
     quoted when used in SQL or application code.  However, the value
     represented by `@pos' must _not_ be quoted. Although MySQL
     normally attempts to convert strings to numbers, this case is an
     exception.

  4. You can now initiate replication on the secondary channel by
     issuing the appropriate command on the secondary slave *Note
     `mysqld': mysqld.:


          mysqlS'> START SLAVE;

Once the secondary replication channel is active, you can investigate
the failure of the primary and effect repairs. The precise actions
required to do this will depend upon the reasons for which the primary
channel failed.

*Warning*:

The secondary replication channel is to be started only if and when the
primary replication channel has failed. Running multiple replication
channels simultaneously can result in unwanted duplicate records being
created on the replication slaves.

If the failure is limited to a single server, it should (in theory) be
possible to replicate from M to S', or from M' to S; however, this has
not yet been tested.


File: manual.info,  Node: mysql-cluster-replication-backups,  Next: mysql-cluster-replication-multi-master,  Prev: mysql-cluster-replication-failover,  Up: mysql-cluster-replication

17.6.9 MySQL Cluster Backups With MySQL Cluster Replication
-----------------------------------------------------------

* Menu:

* mysql-cluster-replication-auto-sync::  MySQL Cluster Replication: Automating Synchronization of the Replication Slave to the Master Binary Log
* mysql-cluster-replication-pitr::  Point-In-Time Recovery Using MySQL Cluster Replication

This section discusses making backups and restoring from them using
MySQL Cluster replication. We assume that the replication servers have
already been configured as covered previously (see *Note
mysql-cluster-replication-preparation::, and the sections immediately
following). This having been done, the procedure for making a backup
and then restoring from it is as follows:

  1. There are two different methods by which the backup may be started.

        * Method A

          This method requires that the cluster backup process was
          previously enabled on the master server, prior to starting
          the replication process. This can be done by including the
          following line in a `[mysql_cluster]' section in the `my.cnf
          file', where MANAGEMENT_HOST is the IP address or host name
          of the *Note `NDB': mysql-cluster. management server for the
          master cluster, and PORT is the management server's port
          number:


               ndb-connectstring=MANAGEMENT_HOST[:PORT]

          *Note*:

          The port number needs to be specified only if the default
          port (1186) is not being used. See *Note
          mysql-cluster-install-configuration::, for more information
          about ports and port allocation in MySQL Cluster.

          In this case, the backup can be started by executing this
          statement on the replication master:


               shellM> ndb_mgm -e "START BACKUP"

        * Method B

          If the `my.cnf' file does not specify where to find the
          management host, you can start the backup process by passing
          this information to the *Note `NDB': mysql-cluster.
          management client as part of the `START BACKUP' command.
          This can be done as shown here, where MANAGEMENT_HOST and
          PORT are the host name and port number of the management
          server:


               shellM> ndb_mgm MANAGEMENT_HOST:PORT -e "START BACKUP"

          In our scenario as outlined earlier (see *Note
          mysql-cluster-replication-preparation::), this would be
          executed as follows:


               shellM> ndb_mgm rep-master:1186 -e "START BACKUP"

  2. Copy the cluster backup files to the slave that is being brought
     on line. Each system running an *Note `ndbd':
     mysql-cluster-programs-ndbd. process for the master cluster will
     have cluster backup files located on it, and _all_ of these files
     must be copied to the slave to ensure a successful restore. The
     backup files can be copied into any directory on the computer
     where the slave management host resides, so long as the MySQL and
     NDB binaries have read permissions in that directory. In this
     case, we will assume that these files have been copied into the
     directory `/var/BACKUPS/BACKUP-1'.

     It is not necessary that the slave cluster have the same number of
     *Note `ndbd': mysql-cluster-programs-ndbd. processes (data nodes)
     as the master; however, it is highly recommended this number be
     the same. It _is_ necessary that the slave be started with the
     `--skip-slave-start' option, to prevent premature startup of the
     replication process.

  3. Create any databases on the slave cluster that are present on the
     master cluster that are to be replicated to the slave.

     *Important*:

     A *Note `CREATE DATABASE': create-database. (or *Note `CREATE
     SCHEMA': create-database.) statement corresponding to each database
     to be replicated must be executed on each SQL node in the slave
     cluster.

  4. Reset the slave cluster using this statement in the MySQL Monitor:


          mysqlS> RESET SLAVE;

     It is important to make sure that the slave's `ndb_apply_status'
     table does not contain any records prior to running the restore
     process. You can accomplish this by running this SQL statement on
     the slave:


          mysqlS> DELETE FROM mysql.ndb_apply_status;

  5. You can now start the cluster restoration process on the
     replication slave using the *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore.  command for each backup file
     in turn. For the first of these, it is necessary to include the
     `-m' option to restore the cluster metadata:


          shellS> ndb_restore -c SLAVE_HOST:PORT -n NODE-ID \
                  -b BACKUP-ID -m -r DIR

     DIR is the path to the directory where the backup files have been
     placed on the replication slave. For the *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore. commands corresponding to the
     remaining backup files, the `-m' option should _not_ be used.

     For restoring from a master cluster with four data nodes (as shown
     in the figure in *Note mysql-cluster-replication::) where the
     backup files have been copied to the directory
     `/var/BACKUPS/BACKUP-1', the proper sequence of commands to be
     executed on the slave might look like this:


          shellS> ndb_restore -c rep-slave:1186 -n 2 -b 1 -m \
                  -r ./var/BACKUPS/BACKUP-1
          shellS> ndb_restore -c rep-slave:1186 -n 3 -b 1 \
                  -r ./var/BACKUPS/BACKUP-1
          shellS> ndb_restore -c rep-slave:1186 -n 4 -b 1 \
                  -r ./var/BACKUPS/BACKUP-1
          shellS> ndb_restore -c rep-slave:1186 -n 5 -b 1 -e \
                  -r ./var/BACKUPS/BACKUP-1

     *Important*:

     The `-e' (or `--restore_epoch') option in the final invocation of
     *Note `ndb_restore': mysql-cluster-programs-ndb-restore. in this
     example is required in order that the epoch is written to the
     slave `mysql.ndb_apply_status'.  Without this information, the
     slave will not be able to synchronize properly with the master.
     (See *Note mysql-cluster-programs-ndb-restore::.)

  6. Now you need to obtain the most recent epoch from the
     `ndb_apply_status' table on the slave (as discussed in *Note
     mysql-cluster-replication-failover::):


          mysqlS> SELECT @latest:=MAX(epoch)
                  FROM mysql.ndb_apply_status;

  7. Using `@latest' as the epoch value obtained in the previous step,
     you can obtain the correct starting position `@pos' in the correct
     binary log file `@file' from the master's `mysql.ndb_binlog_index'
     table using the query shown here:


          mysqlM> SELECT
               ->     @file:=SUBSTRING_INDEX(File, '/', -1),
               ->     @pos:=Position
               -> FROM mysql.ndb_binlog_index
               -> WHERE epoch > @latest
               -> ORDER BY epoch ASC LIMIT 1;

     In the event that there is currently no replication traffic, you
     can get this information by running *Note `SHOW MASTER STATUS':
     show-master-status. on the master and using the value in the
     `Position' column for the file whose name has the suffix with the
     greatest value for all files shown in the `File' column. However,
     in this case, you must determine this and supply it in the next
     step manually or by parsing the output with a script.

  8. Using the values obtained in the previous step, you can now issue
     the appropriate *Note `CHANGE MASTER TO': change-master-to.
     statement in the slave's *Note `mysql': mysql.  client:


          mysqlS> CHANGE MASTER TO
               ->     MASTER_LOG_FILE='@file',
               ->     MASTER_LOG_POS=@pos;

  9. Now that the slave `knows' from what point in which `binlog' file
     to start reading data from the master, you can cause the slave to
     begin replicating with this standard MySQL statement:


          mysqlS> START SLAVE;

To perform a backup and restore on a second replication channel, it is
necessary only to repeat these steps, substituting the host names and
IDs of the secondary master and slave for those of the primary master
and slave replication servers where appropriate, and running the
preceding statements on them.

For additional information on performing Cluster backups and restoring
Cluster from backups, see *Note mysql-cluster-backup::.


File: manual.info,  Node: mysql-cluster-replication-auto-sync,  Next: mysql-cluster-replication-pitr,  Prev: mysql-cluster-replication-backups,  Up: mysql-cluster-replication-backups

17.6.9.1 MySQL Cluster Replication: Automating Synchronization of the Replication Slave to the Master Binary Log
................................................................................................................

It is possible to automate much of the process described in the
previous section (see *Note mysql-cluster-replication-backups::). The
following Perl script `reset-slave.pl' serves as an example of how you
can do this.


     #!/user/bin/perl -w

     #  file: reset-slave.pl

     #  Copyright (C)2005 MySQL AB

     #  This program is free software; you can redistribute it and/or modify
     #  it under the terms of the GNU General Public License as published by
     #  the Free Software Foundation; either version 2 of the License, or
     #  (at your option) any later version.

     #  This program is distributed in the hope that it will be useful,
     #  but WITHOUT ANY WARRANTY; without even the implied warranty of
     #  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     #  GNU General Public License for more details.

     #  You should have received a copy of the GNU General Public License
     #  along with this program; if not, write to:
     #  Free Software Foundation, Inc.
     #  59 Temple Place, Suite 330
     #  Boston, MA 02111-1307 USA
     #
     #  Version 1.1

     ######################## Includes ###############################

     use DBI;

     ######################## Globals ################################

     my  $m_host='';
     my  $m_port='';
     my  $m_user='';
     my  $m_pass='';
     my  $s_host='';
     my  $s_port='';
     my  $s_user='';
     my  $s_pass='';
     my  $dbhM='';
     my  $dbhS='';

     ####################### Sub Prototypes ##########################

     sub CollectCommandPromptInfo;
     sub ConnectToDatabases;
     sub DisconnectFromDatabases;
     sub GetSlaveEpoch;
     sub GetMasterInfo;
     sub UpdateSlave;

     ######################## Program Main ###########################

     CollectCommandPromptInfo;
     ConnectToDatabases;
     GetSlaveEpoch;
     GetMasterInfo;
     UpdateSlave;
     DisconnectFromDatabases;

     ################## Collect Command Prompt Info ##################

     sub CollectCommandPromptInfo
     {
       ### Check that user has supplied correct number of command line args
       die "Usage:\n
            reset-slave >master MySQL host< >master MySQL port< \n
                        >master user< >master pass< >slave MySQL host< \n
                        >slave MySQL port< >slave user< >slave pass< \n
            All 8 arguments must be passed. Use BLANK for NULL passwords\n"
            unless @ARGV == 8;

       $m_host  =  $ARGV[0];
       $m_port  =  $ARGV[1];
       $m_user  =  $ARGV[2];
       $m_pass  =  $ARGV[3];
       $s_host  =  $ARGV[4];
       $s_port  =  $ARGV[5];
       $s_user  =  $ARGV[6];
       $s_pass  =  $ARGV[7];

       if ($m_pass eq "BLANK") { $m_pass = '';}
       if ($s_pass eq "BLANK") { $s_pass = '';}
     }

     ###############  Make connections to both databases #############

     sub ConnectToDatabases
     {
       ### Connect to both master and slave cluster databases

       ### Connect to master
       $dbhM
         = DBI->connect(
         "dbi:mysql:database=mysql;host=$m_host;port=$m_port",
         "$m_user", "$m_pass")
           or die "Can't connect to Master Cluster MySQL process!
                   Error: $DBI::errstr\n";

       ### Connect to slave
       $dbhS
         = DBI->connect(
               "dbi:mysql:database=mysql;host=$s_host",
               "$s_user", "$s_pass")
         or die "Can't connect to Slave Cluster MySQL process!
                 Error: $DBI::errstr\n";
     }

     ################  Disconnect from both databases ################

     sub DisconnectFromDatabases
     {
       ### Disconnect from master

       $dbhM->disconnect
       or warn " Disconnection failed: $DBI::errstr\n";

       ### Disconnect from slave

       $dbhS->disconnect
       or warn " Disconnection failed: $DBI::errstr\n";
     }

     ######################  Find the last good GCI ##################

     sub GetSlaveEpoch
     {
       $sth = $dbhS->prepare("SELECT MAX(epoch)
                              FROM mysql.ndb_apply_status;")
           or die "Error while preparing to select epoch from slave: ",
                  $dbhS->errstr;

       $sth->execute
           or die "Selecting epoch from slave error: ", $sth->errstr;

       $sth->bind_col (1, \$epoch);
       $sth->fetch;
       print "\tSlave Epoch =  $epoch\n";
       $sth->finish;
     }

     #######  Find the position of the last GCI in the binary log ########

     sub GetMasterInfo
     {
       $sth = $dbhM->prepare("SELECT
                                SUBSTRING_INDEX(File, '/', -1), Position
                              FROM mysql.ndb_binlog_index
                              WHERE epoch > $epoch
                              ORDER BY epoch ASC LIMIT 1;")
           or die "Prepare to select from master error: ", $dbhM->errstr;

       $sth->execute
           or die "Selecting from master error: ", $sth->errstr;

       $sth->bind_col (1, \$binlog);
       $sth->bind_col (2, \$binpos);
       $sth->fetch;
       print "\tMaster binary log =  $binlog\n";
       print "\tMaster binary log position =  $binpos\n";
       $sth->finish;
     }

     ##########  Set the slave to process from that location #########

     sub UpdateSlave
     {
       $sth = $dbhS->prepare("CHANGE MASTER TO
                              MASTER_LOG_FILE='$binlog',
                              MASTER_LOG_POS=$binpos;")
           or die "Prepare to CHANGE MASTER error: ", $dbhS->errstr;

       $sth->execute
            or die "CHANGE MASTER on slave error: ", $sth->errstr;
       $sth->finish;
       print "\tSlave has been updated. You may now start the slave.\n";
     }

     # end reset-slave.pl


File: manual.info,  Node: mysql-cluster-replication-pitr,  Prev: mysql-cluster-replication-auto-sync,  Up: mysql-cluster-replication-backups

17.6.9.2 Point-In-Time Recovery Using MySQL Cluster Replication
...............................................................

_Point-in-time_ recovery--that is, recovery of data changes made since
a given point in time--is performed after restoring a full backup that
returns the server to its state when the backup was made.  Performing
point-in-time recovery of MySQL Cluster tables with MySQL Cluster and
MySQL Cluster Replication can be accomplished using a native *Note
`NDB': mysql-cluster. data backup (taken by issuing `CREATE BACKUP' in
the *Note `ndb_mgm': mysql-cluster-programs-ndb-mgm. client) and
restoring the `ndb_binlog_index' table (from a dump made using *Note
`mysqldump': mysqldump.).

To perform point-in-time recovery of MySQL Cluster, it is necessary to
follow the steps shown here:

  1. Back up all `NDB' databases in the cluster, using the `START
     BACKUP' command in the *Note `ndb_mgm':
     mysql-cluster-programs-ndb-mgm. client (see *Note
     mysql-cluster-backup::).

  2. At some later point, prior to restoring the cluster, make a backup
     of the `mysql.ndb_binlog_index' table. It is probably simplest to
     use *Note `mysqldump': mysqldump. for this task. Also back up the
     binary log files at this time.

     This backup should be updated regularly--perhaps even
     hourly--depending on your needs.

  3. (_Catastrophic failure or error occurs_.)

  4. Locate the last known good backup.

  5. Clear the data node file systems (using *Note `ndbd':
     mysql-cluster-programs-ndbd.  `--initial' or, in MySQL Cluster NDB
     7.0 and later, *Note `ndbmtd': mysql-cluster-programs-ndbmtd.
     `--initial').

     *Note*:

     MySQL Cluster Disk Data tablespace and log files are not removed
     by `--initial'. You must delete these manually.

  6. Use *Note `DROP TABLE': drop-table. or *Note `TRUNCATE TABLE':
     truncate-table. with the `mysql.ndb_binlog_index' table.

  7. Execute *Note `ndb_restore': mysql-cluster-programs-ndb-restore,
     restoring all data.  You must include the `--restore_epoch' option
     when you run *Note `ndb_restore':
     mysql-cluster-programs-ndb-restore, so that the `ndb_apply_status'
     table is populated correctly. (See *Note
     mysql-cluster-programs-ndb-restore::, for more information.)

  8. Restore the `ndb_binlog_index' table from the output of *Note
     `mysqldump': mysqldump. and restore the binary log files from
     backup, if necessary.

  9. Find the epoch applied most recently--that is, the maximum `epoch'
     column value in the `ndb_apply_status' table--as the user variable
     `@LATEST_EPOCH' (emphasized):


          SELECT _@LATEST_EPOCH_:=MAX(epoch)
              FROM mysql.ndb_apply_status;

 10. Find the latest binary log file (`@FIRST_FILE') and position
     (`Position' column value) within this file that correspond to
     `@LATEST_EPOCH' in the `ndb_binlog_index' table:


          SELECT Position, _@FIRST_FILE_:=File
              FROM mysql.ndb_binlog_index
              WHERE epoch > _@LATEST_EPOCH_ ORDER BY epoch ASC LIMIT 1;

 11. Using *Note `mysqlbinlog': mysqlbinlog, replay the binary log
     events from the given file and position up to the point of the
     failure. (See *Note mysqlbinlog::.)

See also *Note point-in-time-recovery::, for more information about the
binary log, replication, and incremental recovery.


File: manual.info,  Node: mysql-cluster-replication-multi-master,  Next: mysql-cluster-replication-conflict-resolution,  Prev: mysql-cluster-replication-backups,  Up: mysql-cluster-replication

17.6.10 MySQL Cluster Replication: Multi-Master and Circular Replication
------------------------------------------------------------------------

Beginning with MySQL 5.1.18, it is possible to use MySQL Cluster in
multi-master replication, including circular replication between a
number of MySQL Clusters.

*Note*:

Prior to MySQL 5.1.18, multi-master replication including circular
replication was not supported with MySQL Cluster replication. This was
because log events created in a particular MySQL Cluster were wrongly
tagged with the server ID of the master rather than the server ID of
the originating server.

Circular replication example

In the next few paragraphs we consider the example of a replication
setup involving three MySQL Clusters numbered 1, 2, and 3, in which
Cluster 1 acts as the replication master for Cluster 2, Cluster 2 acts
as the master for Cluster 3, and Cluster 3 acts as the master for
Cluster 1. Each cluster has two SQL nodes, with SQL nodes A and B
belonging to Cluster 1, SQL nodes C and D belonging to Cluster 2, and
SQL nodes E and F belonging to Cluster 3.

Circular replication using these clusters is supported as long as the
following conditions are met:

   * The SQL nodes on all masters and slaves are the same

   * All SQL nodes acting as replication masters and slaves are started
     using the `--log-slave-updates' option

This type of circular replication setup is shown in the following
diagram:

MySQL Cluster circular replication scheme in which all master SQL nodes
are also slaves.

In this scenario, SQL node A in Cluster 1 replicates to SQL node C in
Cluster 2; SQL node C replicates to SQL node E in Cluster 3; SQL node E
replicates to SQL node A. In other words, the replication line
(indicated by the red arrows in the diagram) directly connects all SQL
nodes used as replication masters and slaves.

It is also possible to set up circular replication in such a way that
not all master SQL nodes are also slaves, as shown here:

MySQL Cluster circular replication scheme in which all master SQL nodes
are not also necessarily slaves.

In this case, different SQL nodes in each cluster are used as
replication masters and slaves. However, you must _not_ start any of
the SQL nodes using `--log-slave-updates'. This type of circular
replication scheme for MySQL Cluster, in which the line of replication
(again indicated by the red arrows in the diagram) is discontinuous,
should be possible, but it should be noted that it has not yet been
thoroughly tested and must therefore still be considered experimental.

Using NDB-native backup and restore to initialize a slave MySQL Cluster

When setting up circular replication, it is possible to initialize the
slave cluster by using the management client `BACKUP' command on one
MySQL Cluster to create a backup and then applying this backup on
another MySQL Cluster using *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. However, this does not
automatically create binary logs on the second MySQL Cluster's SQL node
acting as the replication slave. In order to cause the binary logs to
be created, you must issue a *Note `SHOW TABLES': show-tables.
statement on that SQL node; this should be done prior to running *Note
`START SLAVE': start-slave.

This is a known issue which we intend to address in a future release.

Multi-master failover example

In this section, we discuss failover in a multi-master MySQL Cluster
replication setup with three MySQL Clusters having server IDs 1, 2, and
3. In this scenario, Cluster 1 replicates to Clusters 2 and 3; Cluster
2 also replicates to Cluster 3.  This relationship is shown here:

Multi-master MySQL Cluster replication setup, with three MySQL Clusters

In other words, data replicates from Cluster 1 to Cluster 3 through 2
different routes: directly, and by way of Cluster 2.

Not all MySQL servers taking part in multi-master replication must act
as both master and slave, and a given MySQL Cluster might use different
SQL nodes for different replication channels. Such a case is shown here:

Multi-master MySQL Cluster replication setup, detail with MySQL Servers

MySQL servers acting as replication slaves must be run with the
`--log-slave-updates' option. Which *Note `mysqld': mysqld. processes
require this option is also shown in the preceding diagram.

*Note*:

Using the `--log-slave-updates' option has no effect on servers not
being run as replication slaves.

The need for failover arises when one of the replicating clusters goes
down. In this example, we consider the case where Cluster 1 is lost to
service, and so Cluster 3 loses 2 sources of updates from Cluster 1.
Because replication between MySQL Clusters is asynchronous, there is no
guarantee that Cluster 3's updates originating directly from Cluster 1
are more recent than those received through Cluster 2. You can handle
this by ensuring that Cluster 3 catches up to Cluster 2 with regard to
updates from Cluster 1. In terms of MySQL servers, this means that you
need to replicate any outstanding updates from MySQL server C to server
F.

On server C, perform the following queries:


     mysqlC> SELECT @latest:=MAX(epoch)
          ->     FROM mysql.ndb_apply_status
          ->     WHERE server_id=1;

     mysqlC> SELECT
          ->     @file:=SUBSTRING_INDEX(File, '/', -1),
          ->     @pos:=Position
          ->     FROM mysql.ndb_binlog_index
          ->     WHERE orig_epoch >= @latest
          ->     AND orig_server_id = 1
          ->     ORDER BY epoch ASC LIMIT 1;

*Note*:

You can improve the performance of this query, and thus likely speed up
failover times significantly, by adding the appropriate index to the
`ndb_binlog_index' table. See *Note mysql-cluster-replication-schema::,
for more information.

Copy over the values for @FILE and @POS manually from server C to
server F (or have your application perform the equivalent). Then, on
server F, execute the following *Note `CHANGE MASTER TO':
change-master-to. statement:


     mysqlF> CHANGE MASTER TO
          ->     MASTER_HOST = 'serverC'
          ->     MASTER_LOG_FILE='@file',
          ->     MASTER_LOG_POS=@pos;

Once this has been done, you can issue a *Note `START SLAVE':
start-slave. statement on MySQL server F, and any missing updates
originating from server B will be replicated to server F.

Beginning with MySQL Cluster MySQL Cluster NDB 6.1.29, MySQL Cluster
NDB 6.3.31, MySQL Cluster NDB 7.0.11, and MySQL Cluster NDB 7.1.0, the
*Note `CHANGE MASTER TO': change-master-to.  statement also supports an
`IGNORE_SERVER_IDS' option which takes a comma-separated list of server
IDs and causes events originating from the corresponding servers to be
ignored.  For more information, see *Note change-master-to::, and *Note
show-slave-status::.


File: manual.info,  Node: mysql-cluster-replication-conflict-resolution,  Prev: mysql-cluster-replication-multi-master,  Up: mysql-cluster-replication

17.6.11 MySQL Cluster Replication Conflict Resolution
-----------------------------------------------------

When using a replication setup involving multiple masters (including
circular replication), it is possible that different masters may try to
update the same row on the slave with different data. Conflict
resolution in MySQL Cluster Replication provides a means of resolving
such conflicts by permitting a user-defined resolution column to be
used to determine whether or not an update on a given master should be
applied on the slave.

Some types of conflict resolution supported by MySQL Cluster
(`NDB$OLD()', `NDB$MAX()', `NDB$MAX_DELETE_WIN()') implement this
user-defined column as a `timestamp' column (although its type cannot
be *Note `TIMESTAMP': datetime, as explained later in this section).
These types of conflict resolution are always applied a row-by-row
basis rather than a transactional basis. The epoch-based conflict
resolution functions introduced in MySQL Cluster NDB 7.1.16
(`NDB$EPOCH()' and `NDB$EPOCH_TRANS()') compare the order in which
epochs are replicated (and thus these functions are transactional).
Different methods can be used to compare resolution column values on
the slave when conflicts occur, as explained later in this section; the
method used can be set on a per-table basis.

You should also keep in mind that it is the application's
responsibility to ensure that the resolution column is correctly
populated with relevant values, so that the resolution function can
make the appropriate choice when determining whether to apply an update.

Requirements

Preparations for conflict resolution must be made on both the master
and the slave. These tasks are described in the following list:

   * On the master writing the binary logs, you must determine which
     columns are sent (all columns or only those that have been
     updated). This is done for the MySQL Server as a whole by applying
     the *Note `mysqld': mysqld. startup option `--ndb-log-updated-only'
     (described later in this section) or on a per-table basis by
     entries in the `mysql.ndb_replication' table (see *Note
     mysql-cluster-ndb-replication-table::).

     *Note*:

     If you are replicating tables with very large columns (such as
     *Note `TEXT': blob. or *Note `BLOB': blob. columns),
     `--ndb-log-updated-only' can also be useful for reducing the size
     of the master and slave binary logs and avoiding possible
     replication failures due to exceeding `max_allowed_packet'.

     See *Note replication-features-max-allowed-packet::, for more
     information about this issue.

   * On the slave, you must determine which type of conflict resolution
     to apply (`latest timestamp wins', `same timestamp wins', or
     none). This is done using the `mysql.ndb_replication' system
     table, on a per-table basis (see *Note
     mysql-cluster-ndb-replication-table::).

   * Prior to MySQL Cluster NDB 7.0.31 and MySQL Cluster NDB 7.1.20,
     conflict detection and resolution did not always work properly
     unless set up for *Note `NDB': mysql-cluster.  tables created on
     the same server only (Bug #13578660).

When using the functions `NDB$OLD()', `NDB$MAX()', and
`NDB$MAX_DELETE_WIN()' for timestamp-based conflict resolution, we
often refer to the column used for determining updates as a `timestamp'
column, but the data type of this column is never *Note `TIMESTAMP':
datetime.; rather, its data type should be *Note `INT': integer-types.
(*Note `INTEGER': integer-types.) or *Note `BIGINT': integer-types. The
`timestamp' column should also be `UNSIGNED' and `NOT NULL'.

Master column control

We can see update operations in terms of `before' and `after'
images--that is, the states of the table before and after the update is
applied. Normally, when updating a table with a primary key, the
`before' image is not of great interest; however, when we need to
determine on a per-update basis whether or not to use the updated
values on a replication slave, we need to make sure that both images
are written to the master's binary log. This is done with the
`--ndb-log-update-as-write' option for *Note `mysqld': mysqld, as
described later in this section.

*Important*:

Whether logging of complete rows or of updated columns only is done is
decided when the MySQL server is started, and cannot be changed online;
you must either restart *Note `mysqld': mysqld, or start a new *Note
`mysqld': mysqld. instance with different logging options.

*Logging Full or Partial Rows (-ndb-log-updated-only Option)*

Options for ndb_log_updated_only

*Introduced*           5.1.19-ndb-6.3.0        
*Command-Line Format*  `--ndb-log-updated-only'        
*System Variable Name* `ndb_log_updated_only'        
*Variable Scope*       Global          
*Dynamic Variable*     Yes             
                       *Permitted        
                       Values*         
*Type*                 `boolean'        
*Default*              `ON'            

For purposes of conflict resolution, there are two basic methods of
logging rows, as determined by the setting of the
`--ndb-log-updated-only' option for *Note `mysqld': mysqld.:

   * Log complete rows

   * Log only column data that has been updated--that is, column data
     whose value has been set, regardless of whether or not this value
     was actually changed. This is the default behavior.

It is usually sufficient--and more efficient--to log updated columns
only; however, if you need to log full rows, you can do so by setting
`--ndb-log-updated-only' to `0' or `OFF'.

*-ndb-log-update-as-write Option: Logging Changed Data as Updates*

Options for ndb-log-update-as-write

*Introduced*           5.1.19-ndb-6.3.0,        
                       5.1.22-ndb-6.2.5        
*Command-Line Format*  `--ndb-log-update-as-write'        
*System Variable Name* `ndb_log_update_as_write'        
*Variable Scope*       Global          
*Dynamic Variable*     Yes             
                       *Permitted        
                       Values*         
*Type*                 `boolean'        
*Default*              `ON'            

The setting of the MySQL Server's `--ndb-log-update-as-write' option
determines whether logging is performed with or without the `before'
image. Because conflict resolution is done in the MySQL Server's update
handler, it is necessary to control logging on the master such that
updates are updates and not writes; that is, such that updates are
treated as changes in existing rows rather than the writing of new rows
(even though these replace existing rows). This option is turned on by
default; in other words, updates are treated as writes. (That is,
updates are by default written as `write_row' events in the binary log,
rather than as `update_row' events.) To turn off the option, start the
master *Note `mysqld': mysqld. with `--ndb-log-update-as-write=0' or
`--ndb-log-update-as-write=OFF'.

Conflict resolution control

Conflict resolution is usually enabled on the server where conflicts
can occur. Like logging method selection, it is enabled by entries in
the `mysql.ndb_replication' table.

The ndb_replication system table

To enable conflict resolution, it is necessary to create an
`ndb_replication' table in the `mysql' system database on the master,
the slave, or both, depending on the conflict resolution type and
method to be employed. This table is used to control logging and
conflict resolution functions on a per-table basis, and has one row per
table involved in replication.  `ndb_replication' is created and filled
with control information on the server where the conflict is to be
resolved. In a simple master-slave setup where data can also be changed
locally on the slave this will typically be the slave.  In a more
complex master-master (2-way) replication schema this will usually be
all of the masters involved. Each row in `mysql.ndb_replication'
corresponds to a table being replicated, and specifies how to log and
resolve conflicts (that is, which conflict resolution function, if any,
to use) for that table. The definition of the `mysql.ndb_replication'
table is shown here:


     CREATE TABLE mysql.ndb_replication  (
         db VARBINARY(63),
         table_name VARBINARY(63),
         server_id INT UNSIGNED,
         binlog_type INT UNSIGNED,
         conflict_fn VARBINARY(128),
         PRIMARY KEY USING HASH (db, table_name, server_id)
     )   ENGINE=NDB
     PARTITION BY KEY(db,table_name);

The columns in this table are described in the next few paragraphs.

db

The name of the database containing the table to be replicated.

Beginning with MySQL Cluster NDB 7.0.31 and MySQL Cluster NDB 7.1.20,
you may employ either or both of the wildcards `_' and `%' as part of
the database name. Matching is similar to what is implemented for the
`LIKE' operator.

table_name

The name of the table to be replicated.

Beginning with MySQL Cluster NDB 7.0.31 and MySQL Cluster NDB 7.1.20,
the table name may include either or both of the wildcards `_' and `%'.
Matching is similar to what is implemented for the `LIKE' operator.

server_id

The unique server ID of the MySQL instance (SQL node) where the table
resides.

binlog_type

The type of binary logging to be employed. This is determined as shown
in the following table:

This table lists `binlog_type' values and provides the internal value
and a description for each.

Value   Internal Value                Description
0       `NBT_DEFAULT'                 Use server default
1       `NBT_NO_LOGGING'              Do not log this table in the binary
                                      log
2       `NBT_UPDATED_ONLY'            Only updated attributes are logged
3       `NBT_FULL'                    Log full row, even if not updated
                                      (MySQL server default behavior)
4       `NBT_USE_UPDATE'              (For generating
                                      `NBT_UPDATED_ONLY_USE_UPDATE' and
                                      `NBT_FULL_USE_UPDATE' values
                                      only--not intended for separate use)
5       [_Not used_]                  --
6       `NBT_UPDATED_ONLY_USE_UPDATE' Use updated attributes, even if
        (equal to `NBT_UPDATED_ONLY   values are unchanged
        | NBT_USE_UPDATE')            
7       `NBT_FULL_USE_UPDATE' (equal  Use full row, even if values are
        to `NBT_FULL |                unchanged
        NBT_USE_UPDATE')              

conflict_fn

The conflict resolution function to be applied. This function must be
specified as one of those shown in the following list:

   * *Note mysql-cluster-replication-ndb-old::

   * *Note mysql-cluster-replication-ndb-max::

   * *Note mysql-cluster-replication-ndb-max-delete-win::

   * *Note mysql-cluster-replication-ndb-epoch:: (MySQL Cluster NDB
     7.1.16 and later)

   * *Note mysql-cluster-replication-ndb-epoch-trans:: (MySQL Cluster
     NDB 7.1.16 and later)

   * `NULL'

These functions are described in the next few paragraphs.

NDB$OLD(column_name)

If the value of COLUMN_NAME is the same on both the master and the
slave, then the update is applied; otherwise, the update is not applied
on the slave and an exception is written to the log. This is
illustrated by the following pseudocode:


     if (MASTER_OLD_COLUMN_VALUE == SLAVE_CURRENT_COLUMN_VALUE)
       apply_update();
     else
       log_exception();

This function can be used for `same value wins' conflict resolution.
This type of conflict resolution ensures that updates are not applied
on the slave from the wrong master.

*Important*:

The column value from the master's `before' image is used by this
function.

NDB$MAX(column_name)

If the `timestamp' column value for a given row coming from the master
is higher than that on the slave, it is applied; otherwise it is not
applied on the slave. This is illustrated by the following pseudocode:


     if (MASTER_NEW_COLUMN_VALUE > SLAVE_CURRENT_COLUMN_VALUE)
       apply_update();

This function can be used for `greatest timestamp wins' conflict
resolution. This type of conflict resolution ensures that, in the event
of a conflict, the version of the row that was most recently updated is
the version that persists.

*Important*:

The column value from the master's `after' image is used by this
function.

NDB$MAX_DELETE_WIN(column_name)

This is a variation on `NDB$MAX()'. Due to the fact that no timestamp
is available for a delete operation, a delete using `NDB$MAX()' is in
fact processed as `NDB$OLD'. However, for some use cases, this is not
optimal. For `NDB$MAX_DELETE_WIN()', if the `timestamp' column value
for a given row adding or updating an existing row coming from the
master is higher than that on the slave, it is applied. However, delete
operations are treated as always having the higher value. This is
illustrated in the following pseudocode:


     if ( (MASTER_NEW_COLUMN_VALUE > SLAVE_CURRENT_COLUMN_VALUE)
             ||
           OPERATION.TYPE == "delete")
       apply_update();

This function can be used for `greatest timestamp, delete wins'
conflict resolution. This type of conflict resolution ensures that, in
the event of a conflict, the version of the row that was deleted or
(otherwise) most recently updated is the version that persists.

*Note*:

As with `NDB$MAX()', the column value from the master's `after' image
is the value used by this function.

NDB$EPOCH() and NDB$EPOCH_TRANS()

The `NDB$EPOCH()' function, available beginning with MySQL Cluster NDB
7.1.16, tracks the order in which replicated epochs are applied on a
slave MySQL Cluster relative to changes originating on the slave. This
relative ordering is used to determine whether changes originating on
the slave are concurrent with any changes that originate locally, and
are therefore potentially in conflict.

Most of what follows in the description of `NDB$EPOCH()' also applies to
`NDB$EPOCH_TRANS()'. Any exceptions are noted in the text.

`NDB$EPOCH()' is asymmetric, operating on one MySQL Cluster in a
two-cluster circular replication configuration (sometimes referred to
as `active-active' replication). We refer here to cluster on which it
operates as the primary, and the other as the secondary. The slave on
the primary is responsible for detecting and handling conflicts, while
the slave on the secondary is not involved in any conflict detection or
handling.

When the slave on the primary detects conflicts, it injects events into
its own binary log to compensate for these; this ensures that the
secondary MySQL Cluster eventually realigns itself with the primary and
so keeps the primary and secondary from diverging.  This compensation
and realignment mechanism requires that the primary MySQL Cluster
always wins any conflicts with the secondary--that is, that the
primary's changes are always used rather than those from the secondary
in event of a conflict. This `primary always wins' rule has the
following implications:

   * Operations that change data, once committed on the primary, are
     fully persistent and will not be undone or rolled back by conflict
     detection and resolution.

   * Data read from the primary is fully consistent. Any changes
     committed on the Primary (locally or from the slave) will not be
     reverted later.

   * Operations that change data on the secondary may later be reverted
     if the primary determines that they are in conflict.

   * Individual rows read on the secondary are self-consistent at all
     times, each row always reflecting either a state committed by the
     secondary, or one committed by the primary.

   * Sets of rows read on the secondary may not necessarily be
     consistent at a given single point in time. For
     `NDB$EPOCH_TRANS()', this is a transient state; for `NDB$EPOCH()',
     it can be a persistent state.

   * Assuming a period of sufficient length without any conflicts, all
     data on the secondary MySQL Cluster (eventually) becomes
     consistent with the primary's data.

`NDB$EPOCH()' and `NDB$EPOCH_TRANS()' do not require any user schema
modifications, or application changes to provide conflict detection.
However, careful thought must be given to the schema used, and the
access patterns used, to verify that the complete system behaves within
specified limits.

Each of the `NDB$EPOCH()' and `NDB$EPOCH_TRANS()' functions can take an
optional parameter; this is the number of bits to use to represent the
lower 32 bits of the epoch, and should be set to no less than


     CEIL( LOG2( `TimeBetweenGlobalCheckpoints' / `TimeBetweenEpochs' ), 1)

For the default values of these configuration parameters (2000 and 100
milliseconds, respectively), this gives a value of 5 bits, so the
default value (6) should be sufficient, unless other values are used for
`TimeBetweenGlobalCheckpoints', `TimeBetweenEpochs', or both. A value
that is too small can result in false positives, while one that is too
large could lead to excessive wasted space in the database.

Both `NDB$EPOCH()' and `NDB$EPOCH_TRANS()' insert entries for
conflicting rows into the relevant exceptions tables, provided that
these tables have been defined according to the same exception table
schema rules as described elsewhere in this section (see *Note
mysql-cluster-replication-ndb-old::).  Note that you need to create any
exception table before creating the table with which it is to be used.

As with the other conflict detection functions discussed in this
section, `NDB$EPOCH()' and `NDB$EPOCH_TRANS()' are activated by
including relevant entries in the `mysql.ndb_replication' table (see
*Note mysql-cluster-ndb-replication-table::).  The roles of the primary
and secondary MySQL Clusters in this scenario are fully determined by
`mysql.ndb_replication' table entries.

Because the conflict detection algorithms employed by `NDB$EPOCH()' and
`NDB$EPOCH_TRANS()' are asymmetric, you must use different values for
the primary slave's and secondary slave's `server_id' entries.

Prior to MySQL Cluster NDB 7.1.32, conflict between `DELETE' operations
were handled like those for `UPDATE' operations, and within the same
epoch were considered in conflict. In MySQL Cluster NDB 7.1.32 and
later, a conflict between `DELETE' operations alone is not sufficient
to trigger a conflict using `NDB$EPOCH()' or `NDB$EPOCH_TRANS()', and
the relative placement within epochs does not matter. (Bug "18454499)

NDB$EPOCH() and NDB$EPOCH_TRANS() status variables

MySQL Cluster NDB 7.1.16 introduces several status variables that can
be used to monitor `NDB$EPOCH()' and `NDB$EPOCH_TRANS()' conflict
detection. You can see how many rows have been found in conflict by
`NDB$EPOCH()' since this slave was last restarted from the current
value of the `Ndb_conflict_fn_epoch' system status variable.

`Ndb_conflict_fn_epoch_trans' provides the number of rows that have
been found directly in conflict by `NDB$EPOCH_TRANS()'; the number of
rows actually realigned, including those affected due to their
membership in or dependency on the same transactions as other
conflicting rows, is given by `Ndb_conflict_trans_row_reject_count'.

For more information, see *Note mysql-cluster-status-variables::.

Limitations on NDB$EPOCH()

The following limitations currently apply when using `NDB$EPOCH()' to
perform conflict detection:

   * Conflicts are detected using MySQL Cluster epoch boundaries, with
     granularity proportional to `TimeBetweenEpochs' (default: 100
     milliseconds). The minimum conflict window is the minimum time
     during which concurrent updates to the same data on both clusters
     always report a conflict. This is always a nonzero length of time,
     and is roughly proportional to `2 * (latency + queueing +
     TimeBetweenEpochs)'. This implies that--assuming the default for
     `TimeBetweenEpochs' and ignoring any latency between clusters (as
     well as any queuing delays)--the minimum conflict window size is
     approximately 200 milliseconds. This minimum window should be
     considered when looking at expected application `race' patterns.

   * Additional storage is required for tables using the `NDB$EPOCH()'
     and `NDB$EPOCH_TRANS()' functions; from 1 to 32 bits extra space
     per row is required, depending on the value passed to the function.

   * Conflicts between delete operations may result in divergence
     between the primary and secondary. When a row is deleted on both
     clusters concurrently, the conflict can be detected, but is not
     recorded, since the row is deleted. This means that further
     conflicts during the propagation of any subsequent realignment
     operations will not be detected, which can lead to divergence.

     Deletes should be externally serialized, or routed to one cluster
     only. Alternatively, a separate row should be updated
     transactionally with such deletes and any inserts that follow
     them, so that conflicts can be tracked across row deletes.  This
     may require changes in applications.

   * Only two MySQL Clusters in a circular `active-active'
     configuration are currently supported when using `NDB$EPOCH()' or
     `NDB$EPOCH_TRANS()' for conflict detection.

   * Tables having *Note `BLOB': blob. or *Note `TEXT': blob. columns
     are not currently supported with `NDB$EPOCH()' or
     `NDB$EPOCH_TRANS()'.

NDB$EPOCH_TRANS()

`NDB$EPOCH_TRANS()' extends the `NDB$EPOCH()' function, and, like
`NDB$EPOCH()', is available beginning with MySQL Cluster NDB 7.1.16.
Conflicts are detected and handled in the same way using the `primary
wins all' rule (see *Note mysql-cluster-replication-ndb-epoch::) but
with the extra condition that any other rows updated in the same
transaction in which the conflict occurred are also regarded as being
in conflict. In other words, where `NDB$EPOCH()' realigns individual
conflicting rows on the secondary, `NDB$EPOCH_TRANS()' realigns
conflicting transactions.

In addition, any transactions which are detectably dependent on a
conflicting transaction are also regarded as being in conflict, these
dependencies being determined by the contents of the secondary
cluster's binary log. Since the binary log contains only data
modification operations (inserts, updates, and deletes), only
overlapping data modifications are used to determine dependencies
between transactions.

`NDB$EPOCH_TRANS()' is subject to the same conditions and limitations
as `NDB$EPOCH()', and in addition requires that Version 2 binary log
row events are used (`--log-bin-use-v1-row-events' equal to 0), which
adds a storage overhead of 2 bytes per event in the binary log. In
addition, all transaction IDs must be recorded in the secondary's
binary log (`--ndb-log-transaction-id' option), which adds a further
variable overhead (up to 13 bytes per row).

See *Note mysql-cluster-replication-ndb-epoch::.

NULL

Indicates that conflict resolution is not to be used for the
corresponding table.

Status information

Beginning with MySQL Cluster NDB 6.3.3, a server status variable
`Ndb_conflict_fn_max' provides a count of the number of times that a
row was not applied on the current SQL node due to `greatest timestamp
wins' conflict resolution since the last time that *Note `mysqld':
mysqld. was started.

Beginning with MySQL Cluster NDB 6.3.4, the number of times that a row
was not applied as the result of `same timestamp wins' conflict
resolution on a given *Note `mysqld': mysqld. since the last time it
was restarted is given by the global status variable
`Ndb_conflict_fn_old'. In addition to incrementing
`Ndb_conflict_fn_old', the primary key of the row that was not used is
inserted into an _exceptions table_, as explained later in this section.

Exceptions table

To use the `NDB$OLD()' conflict resolution function, it is also
necessary to create an exceptions table corresponding to each *Note
`NDB': mysql-cluster. table for which this type of conflict resolution
is to be employed. This is also true when using `NDB$EPOCH()' or
`NDB$EPOCH_TRANS()' in MySQL Cluster NDB 7.1.16 and later. The name of
this table is that of the table for which conflict resolution is to be
applied, with the string `$EX' appended. (For example, if the name of
the original table is `mytable', the name of the corresponding
exception table name should be `mytable$EX'.) This table is created as
follows:


     CREATE TABLE ORIGINAL_TABLE$EX  (
         server_id INT UNSIGNED,
         master_server_id INT UNSIGNED,
         master_epoch BIGINT UNSIGNED,
         count INT UNSIGNED,
         ORIGINAL_TABLE_PK_COLUMNS,
         [ADDITIONAL_COLUMNS,]
         PRIMARY KEY(server_id, master_server_id, master_epoch, count)
     ) ENGINE=NDB;

The first four columns are required. Following these columns, the
columns making up the original table's primary key should be copied in
the order in which they are used to define the primary key of the
original table.

*Note*:

The names of the first four columns and the columns matching the
original table's primary key columns are not critical; however, we
suggest for reasons of clarity and consistency, that you use the names
shown here for the `server_id', `master_server_id', `master_epoch', and
`count' columns, and that you use the same names as in the original
table for the columns matching those in the original table's primary
key.

The data types for the columns duplicating the primary key columns of
the original table should be the same as for (or larger than) the
original columns.

Additional columns may optionally be defined following these columns,
but not before any of them; any such extra columns cannot be `NOT
NULL'. The exception table's primary key must be defined as shown. The
exception table must use the *Note `NDB': mysql-cluster. storage
engine. An example that uses `NDB$OLD()' with an exceptions table is
shown later in this section.

*Important*:

The `mysql.ndb_replication' table is read when a data table is set up
for replication, so the row corresponding to a table to be replicated
must be inserted into `mysql.ndb_replication' _before_ the table to be
replicated is created.

Examples

The following examples assume that you have already a working MySQL
Cluster replication setup, as described in *Note
mysql-cluster-replication-preparation::, and *Note
mysql-cluster-replication-starting::.

   * NDB$MAX() example

     Suppose you wish to enable `greatest timestamp wins' conflict
     resolution on table `test.t1', using column `mycol' as the
     `timestamp'.  This can be done using the following steps:

       1. Make sure that you have started the master *Note `mysqld':
          mysqld. with `--ndb-log-update-as-write=OFF'.

       2. On the master, perform this *Note `INSERT': insert. statement:


               INSERT INTO mysql.ndb_replication
                   VALUES ('test', 't1', 0, NULL, 'NDB$MAX(mycol)');

          Inserting a 0 into the `server_id' indicates that all SQL
          nodes accessing this table should use conflict resolution. If
          you want to use conflict resolution on a specific *Note
          `mysqld': mysqld. only, use the actual server ID.

          Inserting `NULL' into the `binlog_type' column has the same
          effect as inserting 0 (`NBT_DEFAULT'); the server default is
          used.

       3. Create the `test.t1' table:


               CREATE TABLE test.t1 (
                   COLUMNS
                   mycol INT UNSIGNED,
                   COLUMNS
               ) ENGINE=NDB;

          Now, when updates are done on this table, conflict resolution
          is applied, and the version of the row having the greatest
          value for `mycol' is written to the slave.

     *Note*:

     Other `binlog_type' options--such as `NBT_UPDATED_ONLY_USE_UPDATE'
     should be used to control logging on the master using the
     `ndb_replication' table rather than by using command-line options.

   * NDB$OLD() example

     Suppose an *Note `NDB': mysql-cluster. table such as the one
     defined here is being replicated, and you wish to enable `same
     timestamp wins' conflict resolution for updates to this table:


          CREATE TABLE test.t2  (
              a INT UNSIGNED NOT NULL,
              b CHAR(25) NOT NULL,
              COLUMNS,
              mycol INT UNSIGNED NOT NULL,
              COLUMNS,
              PRIMARY KEY pk (a, b)
          )   ENGINE=NDB;

     The following steps are required, in the order shown:

       1. First--and _prior_ to creating `test.t2'--you must insert a
          row into the `mysql.ndb_replication' table, as shown here:


               INSERT INTO mysql.ndb_replication
                   VALUES ('test', 't2', 0, NULL, 'NDB$OLD(mycol)');

          Possible values for the `binlog_type' column are shown
          earlier in this section. The value `'NDB$OLD(mycol)'' should
          be inserted into the `conflict_fn' column.

       2. Create an appropriate exceptions table for `test.t2'. The
          table creation statement shown here includes all required
          columns; any additional columns must be declared following
          these columns, and before the definition of the table's
          primary key.


               CREATE TABLE test.t2$EX  (
                   server_id SMALLINT UNSIGNED,
                   master_server_id INT UNSIGNED,
                   master_epoch BIGINT UNSIGNED,
                   count BIGINT UNSIGNED,
                   a INT UNSIGNED NOT NULL,
                   b CHAR(25) NOT NULL,
                   [ADDITIONAL_COLUMNS,]
                   PRIMARY KEY(server_id, master_server_id, master_epoch, count)
               )   ENGINE=NDB;

       3. Create the table `test.t2' as shown previously.

     These steps must be followed for every table for which you wish to
     perform conflict resolution using `NDB$OLD()'. For each such
     table, there must be a corresponding row in
     `mysql.ndb_replication', and there must be an exceptions table in
     the same database as the table being replicated.


File: manual.info,  Node: mysql-cluster-news,  Prev: mysql-cluster-replication,  Up: mysql-cluster

17.7 MySQL Cluster NDB 6.1 - 7.1 Release Notes
==============================================

MySQL Cluster release notes are no longer published in the MySQL
Reference Manual.

Release notes for the changes in each release of MySQL Cluster are
located at MySQL Cluster 7.1 Release Notes
(http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/).


File: manual.info,  Node: partitioning,  Next: stored-programs-views,  Prev: mysql-cluster,  Up: Top

18 Partitioning
***************

* Menu:

* partitioning-overview::        Overview of Partitioning in MySQL
* partitioning-types::           Partitioning Types
* partitioning-management::      Partition Management
* partitioning-pruning::         Partition Pruning
* partitioning-limitations::     Restrictions and Limitations on Partitioning

This chapter discusses MySQL's implementation of _user-defined
partitioning_. You can determine whether your MySQL Server supports
partitioning by means of a *Note `SHOW VARIABLES': show-variables.
statement such as this one:

*Note*:

The `have_partitioning' variable is deprecated, and removed in MySQL
5.6.1.


     mysql> SHOW VARIABLES LIKE '%partition%';

     +-------------------+-------+
     | Variable_name     | Value |
     +-------------------+-------+
     | have_partitioning | YES   |
     +-------------------+-------+
     1 row in set (0.00 sec)

*Note*:

Prior to MySQL 5.1.6, this variable was named `have_partition_engine'.
(Bug #16718)

You can also check the output of the *Note `SHOW PLUGINS':
show-plugins. statement, as shown here:


     mysql> SHOW PLUGINS;
     +------------+----------+----------------+---------+---------+
     | Name       | Status   | Type           | Library | License |
     +------------+----------+----------------+---------+---------+
     | binlog     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     *| partition  | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |*
     | ARCHIVE    | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | BLACKHOLE  | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | CSV        | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | FEDERATED  | DISABLED | STORAGE ENGINE | NULL    | GPL     |
     | MEMORY     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | InnoDB     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | MRG_MYISAM | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | MyISAM     | ACTIVE   | STORAGE ENGINE | NULL    | GPL     |
     | ndbcluster | DISABLED | STORAGE ENGINE | NULL    | GPL     |
     +------------+----------+----------------+---------+---------+
     11 rows in set (0.00 sec)

In MySQL 5.1.5 and later, you can also check the *Note
`INFORMATION_SCHEMA.PLUGINS': plugins-table. table with a query similar
to this one:


     mysql> SELECT
         ->     PLUGIN_NAME as Name,
         ->     PLUGIN_VERSION as Version,
         ->     PLUGIN_STATUS as Status
         -> FROM INFORMATION_SCHEMA.PLUGINS
         -> WHERE PLUGIN_TYPE='STORAGE ENGINE';
     +--------------------+---------+--------+
     | Name               | Version | Status |
     +--------------------+---------+--------+
     | binlog             | 1.0     | ACTIVE |
     | CSV                | 1.0     | ACTIVE |
     | MEMORY             | 1.0     | ACTIVE |
     | MRG_MYISAM         | 1.0     | ACTIVE |
     | MyISAM             | 1.0     | ACTIVE |
     | PERFORMANCE_SCHEMA | 0.1     | ACTIVE |
     | BLACKHOLE          | 1.0     | ACTIVE |
     | ARCHIVE            | 3.0     | ACTIVE |
     | InnoDB             | 5.6     | ACTIVE |
     *| partition          | 1.0     | ACTIVE |*
     +--------------------+---------+--------+
     10 rows in set (0.00 sec)

Whichever of the preceding statements you employ, if you do not see the
`partition' plugin listed with the value `ACTIVE' for the `Status'
column in the output (shown in bold text in each of the examples just
given), then your version of MySQL was not built with partitioning
support.

MySQL 5.1 Community binaries provided by Oracle include partitioning
support. For information about partitioning support offered in
commercial MySQL Server binaries, see `MySQL Enterprise Server 5.1' on
the MySQL Web site at
`http://www.mysql.com/products/enterprise/server.html'.

If you are compiling MySQL 5.1 from source, the build must be
configured using `--with-partition' to enable partitioning. Using
`--with-plugins=max' to configure the build includes this option
automatically. For more information, see *Note source-installation::.

If your MySQL binary is built with partitioning support, nothing
further needs to be done to enable it (for example, no special entries
are required in your `my.cnf' file).

If you want to disable partitioning support, you can start the MySQL
Server with the `--skip-partition' option, in which case the value of
`have_partitioning' is `DISABLED'. When partitioning support is
disabled, you can see any existing partitioned tables and drop them
(although doing this is not advised), but you cannot otherwise
manipulate them or access their data.

See *Note partitioning-overview::, for an introduction to partitioning
and partitioning concepts.

MySQL supports several types of partitioning as well as
subpartitioning; see *Note partitioning-types::, and *Note
partitioning-subpartitions::.

*Note partitioning-management::, covers methods of adding, removing,
and altering partitions in existing partitioned tables.

*Note partitioning-maintenance::, discusses table maintenance commands
for use with partitioned tables.

Beginning with MySQL 5.1.6, the *Note `PARTITIONS': partitions-table.
table in the `INFORMATION_SCHEMA' database provides information about
partitions and partitioned tables. See *Note partitions-table::, for
more information; for some examples of queries against this table, see
*Note partitioning-handling-nulls::.

*Important*:

Partitioned tables created with MySQL versions prior to 5.1.6 cannot be
read by a 5.1.6 or later MySQL Server. In addition, the *Note
`INFORMATION_SCHEMA.TABLES': tables-table. table cannot be used if such
tables are present on a 5.1.6 server.  Beginning with MySQL 5.1.7, a
suitable warning message is generated instead, to alert the user that
incompatible partitioned tables have been found by the server.

If you are using partitioned tables which were created in MySQL 5.1.5
or earlier, be sure to see the Release Notes
(http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) for MySQL 5.1.6 for
more information and suggested workarounds _before_ upgrading to MySQL
5.1.6 or later.

For known issues with partitioning in MySQL 5.1, see *Note
partitioning-limitations::.

You may also find the following resources to be useful when working
with partitioned tables.

Additional Resources

Other sources of information about user-defined partitioning in MySQL
include the following:

   * MySQL Partitioning Forum (http://forums.mysql.com/list.php?106)

     This is the official discussion forum for those interested in or
     experimenting with MySQL Partitioning technology. It features
     announcements and updates from MySQL developers and others. It is
     monitored by members of the Partitioning Development and
     Documentation Teams.

   * Mikael Ronstro"m's Blog (http://mikaelronstrom.blogspot.com/)

     MySQL Partitioning Architect and Lead Developer Mikael Ronstro"m
     frequently posts articles here concerning his work with MySQL
     Partitioning and MySQL Cluster.

   * PlanetMySQL (http://www.planetmysql.org/)

     A MySQL news site featuring MySQL-related blogs, which should be
     of interest to anyone using my MySQL. We encourage you to check
     here for links to blogs kept by those working with MySQL
     Partitioning, or to have your own blog added to those covered.

MySQL 5.1 binaries are available from
`http://dev.mysql.com/downloads/mysql/5.1.html'.  However, for the
latest partitioning bugfixes and feature additions, you can obtain the
source from our Bazaar repository. To enable partitioning, you need to
compile the server using the `--with-partition' option. For more
information about building MySQL, see *Note source-installation::. If
you have problems compiling a partitioning-enabled MySQL 5.1 build,
check the MySQL Partitioning Forum
(http://forums.mysql.com/list.php?106) and ask for assistance there if
you do not find a solution to your problem already posted.


File: manual.info,  Node: partitioning-overview,  Next: partitioning-types,  Prev: partitioning,  Up: partitioning

18.1 Overview of Partitioning in MySQL
======================================

This section provides a conceptual overview of partitioning in MySQL
5.1.

For information on partitioning restrictions and feature limitations,
see *Note partitioning-limitations::.

The SQL standard does not provide much in the way of guidance regarding
the physical aspects of data storage. The SQL language itself is
intended to work independently of any data structures or media
underlying the schemas, tables, rows, or columns with which it works.
Nonetheless, most advanced database management systems have evolved
some means of determining the physical location to be used for storing
specific pieces of data in terms of the file system, hardware or even
both. In MySQL, the `InnoDB' storage engine has long supported the
notion of a tablespace, and the MySQL Server, even prior to the
introduction of partitioning, could be configured to employ different
physical directories for storing different databases (see *Note
symbolic-links::, for an explanation of how this is done).

_Partitioning_ takes this notion a step further, by enabling you to
distribute portions of individual tables across a file system according
to rules which you can set largely as needed. In effect, different
portions of a table are stored as separate tables in different
locations. The user-selected rule by which the division of data is
accomplished is known as a _partitioning function_, which in MySQL can
be the modulus, simple matching against a set of ranges or value lists,
an internal hashing function, or a linear hashing function. The
function is selected according to the partitioning type specified by
the user, and takes as its parameter the value of a user-supplied
expression. This expression can be a column value, a function acting on
one or more column values, or a set of one or more column values,
depending on the type of partitioning that is used.

In the case of `RANGE', `LIST', and [`LINEAR'] `HASH' partitioning, the
value of the partitioning column is passed to the partitioning
function, which returns an integer value representing the number of the
partition in which that particular record should be stored. This
function must be nonconstant and nonrandom. It may not contain any
queries, but may use an SQL expression that is valid in MySQL, as long
as that expression returns either `NULL' or an integer INTVAL such that


     -MAXVALUE <= INTVAL <= MAXVALUE

(`MAXVALUE' is used to represent the least upper bound for the type of
integer in question.  `-MAXVALUE' represents the greatest lower bound.)

For [`LINEAR'] `KEY', the partitioning expression consists of a list of
one or more columns, and the partitioning function is supplied by MySQL.

For more information about permitted partitioning column types and
partitioning functions, see *Note partitioning-types::, as well as
*Note create-table::, which provides partitioning syntax descriptions
and additional examples. For information about restrictions on
partitioning functions, see *Note partitioning-limitations-functions::.

This is known as _horizontal partitioning_--that is, different rows of
a table may be assigned to different physical partitions. MySQL 5.1
does not support _vertical partitioning_, in which different columns of
a table are assigned to different physical partitions. There are not at
this time any plans to introduce vertical partitioning into MySQL 5.1.

For information about determining whether your MySQL Server binary
supports user-defined partitioning, see *Note partitioning::.

For creating partitioned tables, you can use most storage engines that
are supported by your MySQL server; the MySQL partitioning engine runs
in a separate layer and can interact with any of these. In MySQL 5.1,
all partitions of the same partitioned table must use the same storage
engine; for example, you cannot use `MyISAM' for one partition and
`InnoDB' for another. However, there is nothing preventing you from
using different storage engines for different partitioned tables on the
same MySQL server or even in the same database.

MySQL partitioning cannot be used with the `MERGE' or `CSV' storage
engines. Beginning with MySQL 5.1.15, `FEDERATED' tables also cannot be
partitioned (Bug #22451). Prior to MySQL 5.1.6, it was also not
feasible to create a partitioned table using the `BLACKHOLE' storage
engine (Bug #14524). See *Note
partitioning-limitations-storage-engines::.

Partitioning by `KEY' or `LINEAR KEY' is possible with *Note
`NDBCLUSTER': mysql-cluster, but other types of user-defined
partitioning are not supported for tables using this storage engine. In
addition, an *Note `NDBCLUSTER': mysql-cluster. table that employs
user-defined partitioning must have an explicit primary key, and any
columns referenced in the table's partitioning expression must be part
of the primary key. However, if no columns are listed in the `PARTITION
BY KEY' or `PARTITION BY LINEAR KEY' clause of the *Note `CREATE
TABLE': create-table. or *Note `ALTER TABLE':
alter-table-partition-operations. statement used to create or modify a
user-partitioned *Note `NDBCLUSTER': mysql-cluster. table, then the
table is not required to have an explicit primary key.  For more
information, see *Note mysql-cluster-limitations-syntax::.

To employ a particular storage engine for a partitioned table, it is
necessary only to use the `[STORAGE] ENGINE' option just as you would
for a nonpartitioned table. However, you should keep in mind that
`[STORAGE] ENGINE' (and other table options) need to be listed _before_
any partitioning options are used in a *Note `CREATE TABLE':
create-table. statement. This example shows how to create a table that
is partitioned by hash into 6 partitions and which uses the `InnoDB'
storage engine:


     CREATE TABLE ti (id INT, amount DECIMAL(7,2), tr_date DATE)
         ENGINE=INNODB
         PARTITION BY HASH( MONTH(tr_date) )
         PARTITIONS 6;

Each `PARTITION' clause can include a `[STORAGE] ENGINE' option, but in
MySQL 5.1 this has no effect.

*Important*:

Partitioning applies to all data and indexes of a table; you cannot
partition only the data and not the indexes, or vice versa, nor can you
partition only a portion of the table.

Data and indexes for each partition can be assigned to a specific
directory using the `DATA DIRECTORY' and `INDEX DIRECTORY' options for
the `PARTITION' clause of the *Note `CREATE TABLE': create-table.
statement used to create the partitioned table.

Prior to MySQL 5.1.18, these options were permitted even when the
`NO_DIR_IN_CREATE' server SQL mode was in effect (Bug #24633).

The `DATA DIRECTORY' and `INDEX DIRECTORY' options have no effect when
defining partitions for tables using the `InnoDB' storage engine.

`DATA DIRECTORY' and `INDEX DIRECTORY' are not supported for individual
partitions or subpartitions on Windows. Beginning with MySQL 5.1.24,
these options are ignored on Windows, except that a warning is generated
(Bug #30459)-

In addition, `MAX_ROWS' and `MIN_ROWS' can be used to determine the
maximum and minimum numbers of rows, respectively, that can be stored in
each partition. The `MAX_ROWS' option can be useful for causing MySQL
Cluster tables to be created with extra partitions, thus allowing for
greater storage of hash indexes. See the documentation for the
`DataMemory' data node configuration parameter, as well as *Note
mysql-cluster-nodes-groups::, for more information.

Some advantages of partitioning are listed here:

   * Partitioning makes it possible to store more data in one table
     than can be held on a single disk or file system partition.

   * Data that loses its usefulness can often be easily removed from a
     partitioned table by dropping the partition (or partitions)
     containing only that data. Conversely, the process of adding new
     data can in some cases be greatly facilitated by adding one or
     more new partitions for storing specifically that data.

   * Some queries can be greatly optimized in virtue of the fact that
     data satisfying a given `WHERE' clause can be stored only on one
     or more partitions, which automatically excludes any remaining
     partitions from the search. Because partitions can be altered
     after a partitioned table has been created, you can reorganize
     your data to enhance frequent queries that may not have been often
     used when the partitioning scheme was first set up. This ability to
     exclude non-matching partitions (and thus any rows they contain)
     is often referred to as _partition pruning_, and was implemented
     in MySQL 5.1.6. For more information, see *Note
     partitioning-pruning::.

Other benefits usually associated with partitioning include those in
the following list. These features are not currently implemented in
MySQL Partitioning, but are high on our list of priorities.

   * Queries involving aggregate functions such as `SUM()' and
     `COUNT()' can easily be parallelized. A simple example of such a
     query might be `SELECT salesperson_id, COUNT(orders) as order_total
     FROM sales GROUP BY salesperson_id;'. By `parallelized,' we mean
     that the query can be run simultaneously on each partition, and
     the final result obtained merely by summing the results obtained
     for all partitions.

   * Achieving greater query throughput in virtue of spreading data
     seeks over multiple disks.

Be sure to check this section and chapter frequently for updates as
MySQL Partitioning development continues.


File: manual.info,  Node: partitioning-types,  Next: partitioning-management,  Prev: partitioning-overview,  Up: partitioning

18.2 Partitioning Types
=======================

* Menu:

* partitioning-range::           RANGE Partitioning
* partitioning-list::            LIST Partitioning
* partitioning-hash::            HASH Partitioning
* partitioning-key::             KEY Partitioning
* partitioning-subpartitions::   Subpartitioning
* partitioning-handling-nulls::  How MySQL Partitioning Handles NULL

This section discusses the types of partitioning which are available in
MySQL 5.1. These include the types listed here:

   * RANGE partitioning

     This type of partitioning assigns rows to partitions based on
     column values falling within a given range. See *Note
     partitioning-range::.

   * LIST partitioning

     Similar to partitioning by `RANGE', except that the partition is
     selected based on columns matching one of a set of discrete
     values. See *Note partitioning-list::.

   * HASH partitioning

     With this type of partitioning, a partition is selected based on
     the value returned by a user-defined expression that operates on
     column values in rows to be inserted into the table. The function
     may consist of any expression valid in MySQL that yields a
     nonnegative integer value. An extension to this type, `LINEAR
     HASH', is also available. See *Note partitioning-hash::.

   * KEY partitioning

     This type of partitioning is similar to partitioning by `HASH',
     except that only one or more columns to be evaluated are supplied,
     and the MySQL server provides its own hashing function. These
     columns can contain other than integer values, since the hashing
     function supplied by MySQL guarantees an integer result regardless
     of the column data type. An extension to this type, `LINEAR KEY',
     is also available. See *Note partitioning-key::.

A very common use of database partitioning is to segregate data by
date. Some database systems support explicit date partitioning, which
MySQL does not implement in 5.1. However, it is not difficult in MySQL
to create partitioning schemes based on *Note `DATE': datetime, *Note
`TIME': time, or *Note `DATETIME': datetime. columns, or based on
expressions making use of such columns.

When partitioning by `KEY' or `LINEAR KEY', you can use a *Note `DATE':
datetime, *Note `TIME': time, or *Note `DATETIME': datetime. column as
the partitioning column without performing any modification of the
column value.  For example, this table creation statement is perfectly
valid in MySQL:


     CREATE TABLE members (
         firstname VARCHAR(25) NOT NULL,
         lastname VARCHAR(25) NOT NULL,
         username VARCHAR(16) NOT NULL,
         email VARCHAR(35),
         joined DATE NOT NULL
     )
     PARTITION BY KEY(joined)
     PARTITIONS 6;

MySQL's other partitioning types, however, require a partitioning
expression that yields an integer value or `NULL'. If you wish to use
date-based partitioning by `RANGE', `LIST', `HASH', or `LINEAR HASH',
you can simply employ a function that operates on a *Note `DATE':
datetime, *Note `TIME': time, or *Note `DATETIME': datetime. column and
returns such a value, as shown here:


     CREATE TABLE members (
         firstname VARCHAR(25) NOT NULL,
         lastname VARCHAR(25) NOT NULL,
         username VARCHAR(16) NOT NULL,
         email VARCHAR(35),
         joined DATE NOT NULL
     )
     PARTITION BY RANGE( YEAR(joined) ) (
         PARTITION p0 VALUES LESS THAN (1960),
         PARTITION p1 VALUES LESS THAN (1970),
         PARTITION p2 VALUES LESS THAN (1980),
         PARTITION p3 VALUES LESS THAN (1990),
         PARTITION p4 VALUES LESS THAN MAXVALUE
     );

Additional examples of partitioning using dates may be found in the
following sections of this chapter:

   * *Note partitioning-range::

   * *Note partitioning-hash::

   * *Note partitioning-linear-hash::

For more complex examples of date-based partitioning, see the following
sections:

   * *Note partitioning-pruning::

   * *Note partitioning-subpartitions::

MySQL partitioning is optimized for use with the `TO_DAYS()' and
`YEAR()' functions. However, you can use other date and time functions
that return an integer or `NULL', such as `WEEKDAY()', `DAYOFYEAR()', or
`MONTH()'. See *Note date-and-time-functions::, for more information
about such functions.

It is important to remember--regardless of the type of partitioning
that you use--that partitions are always numbered automatically and in
sequence when created, starting with `0'. When a new row is inserted
into a partitioned table, it is these partition numbers that are used in
identifying the correct partition. For example, if your table uses 4
partitions, these partitions are numbered `0', `1', `2', and `3'. For
the `RANGE' and `LIST' partitioning types, it is necessary to ensure
that there is a partition defined for each partition number. For `HASH'
partitioning, the user function employed must return an integer value
greater than `0'. For `KEY' partitioning, this issue is taken care of
automatically by the hashing function which the MySQL server employs
internally.

Names of partitions generally follow the rules governing other MySQL
identifiers, such as those for tables and databases.  However, you
should note that partition names are not case-sensitive. For example,
the following *Note `CREATE TABLE': create-table. statement fails as
shown:


     mysql> CREATE TABLE t2 (val INT)
         -> PARTITION BY LIST(val)(
         ->     PARTITION mypart VALUES IN (1,3,5),
         ->     PARTITION MyPart VALUES IN (2,4,6)
         -> );
     ERROR 1488 (HY000): Duplicate partition name mypart

Failure occurs because MySQL sees no difference between the partition
names `mypart' and `MyPart'.

When you specify the number of partitions for the table, this must be
expressed as a positive, nonzero integer literal with no leading zeros,
and may not be an expression such as `0.8E+01' or `6-2', even if it
evaluates to an integer value. (Beginning with MySQL 5.1.12, decimal
fractions are no longer truncated, but instead are prohibited entirely.)

In the sections that follow, we do not necessarily provide all possible
forms for the syntax that can be used for creating each partition type;
this information may be found in *Note create-table::.


File: manual.info,  Node: partitioning-range,  Next: partitioning-list,  Prev: partitioning-types,  Up: partitioning-types

18.2.1 RANGE Partitioning
-------------------------

A table that is partitioned by range is partitioned in such a way that
each partition contains rows for which the partitioning expression
value lies within a given range. Ranges should be contiguous but not
overlapping, and are defined using the `VALUES LESS THAN' operator. For
the next few examples, suppose that you are creating a table such as the
following to hold personnel records for a chain of 20 video stores,
numbered 1 through 20:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT NOT NULL,
         store_id INT NOT NULL
     );

*Note*:

The `employees' table used here has no primary or unique keys. While
the examples work as shown for purposes of the present discussion, you
should keep in mind that tables are extremely likely in practice to
have primary keys, unique keys, or both, and that allowable choices for
partitioning columns depend on the columns used for these keys, if any
are present. For a discussion of these issues, see *Note
partitioning-limitations-partitioning-keys-unique-keys::.

This table can be partitioned by range in a number of ways, depending
on your needs. One way would be to use the `store_id' column. For
instance, you might decide to partition the table 4 ways by adding a
`PARTITION BY RANGE' clause as shown here:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT NOT NULL,
         store_id INT NOT NULL
     )
     PARTITION BY RANGE (store_id) (
         PARTITION p0 VALUES LESS THAN (6),
         PARTITION p1 VALUES LESS THAN (11),
         PARTITION p2 VALUES LESS THAN (16),
         PARTITION p3 VALUES LESS THAN (21)
     );

In this partitioning scheme, all rows corresponding to employees
working at stores 1 through 5 are stored in partition `p0', to those
employed at stores 6 through 10 are stored in partition `p1', and so
on. Note that each partition is defined in order, from lowest to
highest.  This is a requirement of the `PARTITION BY RANGE' syntax; you
can think of it as being analogous to a series of `if ... elseif ...'
statements in C or Java in this regard.

It is easy to determine that a new row containing the data `(72,
'Michael', 'Widenius', '1998-06-25', NULL, 13)' is inserted into
partition `p2', but what happens when your chain adds a 21^st store?
Under this scheme, there is no rule that covers a row whose `store_id'
is greater than 20, so an error results because the server does not
know where to place it. You can keep this from occurring by using a
`catchall' `VALUES LESS THAN' clause in the *Note `CREATE TABLE':
create-table. statement that provides for all values greater than the
highest value explicitly named:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT NOT NULL,
         store_id INT NOT NULL
     )
     PARTITION BY RANGE (store_id) (
         PARTITION p0 VALUES LESS THAN (6),
         PARTITION p1 VALUES LESS THAN (11),
         PARTITION p2 VALUES LESS THAN (16),
         _PARTITION p3 VALUES LESS THAN MAXVALUE_
     );

*Note*:

Another way to avoid an error when no matching value is found is to use
the `IGNORE' keyword as part of the *Note `INSERT': insert. statement.
For an example, see *Note partitioning-list::. Also see *Note insert::,
for general information about `IGNORE'.

`MAXVALUE' represents an integer value that is always greater than the
largest possible integer value (in mathematical language, it serves as
a _least upper bound_). Now, any rows whose `store_id' column value is
greater than or equal to 16 (the highest value defined) are stored in
partition `p3'. At some point in the future--when the number of stores
has increased to 25, 30, or more--you can use an *Note `ALTER TABLE':
alter-table-partition-operations. statement to add new partitions for
stores 21-25, 26-30, and so on (see *Note partitioning-management::,
for details of how to do this).

In much the same fashion, you could partition the table based on
employee job codes--that is, based on ranges of `job_code' column
values. For example--assuming that two-digit job codes are used for
regular (in-store) workers, three-digit codes are used for office and
support personnel, and four-digit codes are used for management
positions--you could create the partitioned table using the following
statement:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT NOT NULL,
         store_id INT NOT NULL
     )
     PARTITION BY RANGE (job_code) (
         PARTITION p0 VALUES LESS THAN (100),
         PARTITION p1 VALUES LESS THAN (1000),
         PARTITION p2 VALUES LESS THAN (10000)
     );

In this instance, all rows relating to in-store workers would be stored
in partition `p0', those relating to office and support staff in `p1',
and those relating to managers in partition `p2'.

It is also possible to use an expression in `VALUES LESS THAN' clauses.
However, MySQL must be able to evaluate the expression's return value
as part of a `LESS THAN' (`<') comparison.

Rather than splitting up the table data according to store number, you
can use an expression based on one of the two *Note `DATE': datetime.
columns instead. For example, let us suppose that you wish to partition
based on the year that each employee left the company; that is, the
value of `YEAR(separated)'. An example of a *Note `CREATE TABLE':
create-table. statement that implements such a partitioning scheme is
shown here:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT,
         store_id INT
     )
     PARTITION BY RANGE ( YEAR(separated) ) (
         PARTITION p0 VALUES LESS THAN (1991),
         PARTITION p1 VALUES LESS THAN (1996),
         PARTITION p2 VALUES LESS THAN (2001),
         PARTITION p3 VALUES LESS THAN MAXVALUE
     );

In this scheme, for all employees who left before 1991, the rows are
stored in partition `p0'; for those who left in the years 1991 through
1995, in `p1'; for those who left in the years 1996 through 2000, in
`p2'; and for any workers who left after the year 2000, in `p3'.

Beginning with MySQL 5.1.43, it is also possible to partition a table
by `RANGE' based on the value of a *Note `TIMESTAMP': datetime. column,
using the `UNIX_TIMESTAMP()' function, as shown in this example:


     CREATE TABLE quarterly_report_status (
         report_id INT NOT NULL,
         report_status VARCHAR(20) NOT NULL,
         report_updated TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP
     )
     PARTITION BY RANGE ( UNIX_TIMESTAMP(report_updated) ) (
         PARTITION p0 VALUES LESS THAN ( UNIX_TIMESTAMP('2008-01-01 00:00:00') ),
         PARTITION p1 VALUES LESS THAN ( UNIX_TIMESTAMP('2008-04-01 00:00:00') ),
         PARTITION p2 VALUES LESS THAN ( UNIX_TIMESTAMP('2008-07-01 00:00:00') ),
         PARTITION p3 VALUES LESS THAN ( UNIX_TIMESTAMP('2008-10-01 00:00:00') ),
         PARTITION p4 VALUES LESS THAN ( UNIX_TIMESTAMP('2009-01-01 00:00:00') ),
         PARTITION p5 VALUES LESS THAN ( UNIX_TIMESTAMP('2009-04-01 00:00:00') ),
         PARTITION p6 VALUES LESS THAN ( UNIX_TIMESTAMP('2009-07-01 00:00:00') ),
         PARTITION p7 VALUES LESS THAN ( UNIX_TIMESTAMP('2009-10-01 00:00:00') ),
         PARTITION p8 VALUES LESS THAN ( UNIX_TIMESTAMP('2010-01-01 00:00:00') ),
         PARTITION p9 VALUES LESS THAN (MAXVALUE)
     );

Also beginning with MySQL 5.1.43, any other expressions involving *Note
`TIMESTAMP': datetime. values are not permitted. (See Bug #42849.)

*Note*:

It is also possible in MySQL 5.1.43 and later to use
`UNIX_TIMESTAMP(TIMESTAMP_COLUMN)' as a partitioning expression for
tables that are partitioned by `LIST'. However, it is usually not
practical to do so.

Range partitioning is particularly useful when one or more of the
following conditions is true:

   * You want or need to delete `old' data. If you are using the
     partitioning scheme shown immediately above, you can simply use
     `ALTER TABLE employees DROP PARTITION p0;' to delete all rows
     relating to employees who stopped working for the firm prior to
     1991.  (See *Note alter-table::, and *Note
     partitioning-management::, for more information.) For a table with
     a great many rows, this can be much more efficient than running a
     *Note `DELETE': delete. query such as `DELETE FROM employees WHERE
     YEAR(separated) <= 1990;'.

   * You want to use a column containing date or time values, or
     containing values arising from some other series.

   * You frequently run queries that depend directly on the column used
     for partitioning the table. For example, when executing a query
     such as *Note `EXPLAIN PARTITIONS SELECT COUNT(*) FROM employees
     WHERE separated BETWEEN '2000-01-01' AND '2000-12-31' GROUP BY
     store_id;': explain, MySQL can quickly determine that only
     partition `p2' needs to be scanned because the remaining
     partitions cannot contain any records satisfying the `WHERE'
     clause. See *Note partitioning-pruning::, for more information
     about how this is accomplished.


File: manual.info,  Node: partitioning-list,  Next: partitioning-hash,  Prev: partitioning-range,  Up: partitioning-types

18.2.2 LIST Partitioning
------------------------

List partitioning in MySQL is similar to range partitioning in many
ways. As in partitioning by `RANGE', each partition must be explicitly
defined. The chief difference between the two types of partitioning is
that, in list partitioning, each partition is defined and selected
based on the membership of a column value in one of a set of value
lists, rather than in one of a set of contiguous ranges of values. This
is done by using `PARTITION BY LIST(EXPR)' where EXPR is a column value
or an expression based on a column value and returning an integer
value, and then defining each partition by means of a `VALUES IN
(VALUE_LIST)', where VALUE_LIST is a comma-separated list of integers.

*Note*:

In MySQL 5.1, it is possible to match against only a list of integers
(and possibly `NULL'--see *Note partitioning-handling-nulls::) when
partitioning by `LIST'.

Unlike the case with partitions defined by range, list partitions do
not need to be declared in any particular order.  For more detailed
syntactical information, see *Note create-table::.

For the examples that follow, we assume that the basic definition of
the table to be partitioned is provided by the *Note `CREATE TABLE':
create-table. statement shown here:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT,
         store_id INT
     );

(This is the same table used as a basis for the examples in *Note
partitioning-range::.)

Suppose that there are 20 video stores distributed among 4 franchises
as shown in the following table.

This table illustrates an example of 20 video stores distributed among
4 regional franchises, as described in the preceding text.

Region                 Store ID Numbers
North                  3, 5, 6, 9, 17
East                   1, 2, 10, 11, 19, 20
West                   4, 12, 13, 14, 18
Central                7, 8, 15, 16

To partition this table in such a way that rows for stores belonging to
the same region are stored in the same partition, you could use the
*Note `CREATE TABLE': create-table.  statement shown here:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT,
         store_id INT
     )
     PARTITION BY LIST(store_id) (
         PARTITION pNorth VALUES IN (3,5,6,9,17),
         PARTITION pEast VALUES IN (1,2,10,11,19,20),
         PARTITION pWest VALUES IN (4,12,13,14,18),
         PARTITION pCentral VALUES IN (7,8,15,16)
     );

This makes it easy to add or drop employee records relating to specific
regions to or from the table. For instance, suppose that all stores in
the West region are sold to another company.  All rows relating to
employees working at stores in that region can be deleted with an
`ALTER TABLE employees DROP PARTITION pWest' statement, which can be
executed much more efficiently than the equivalent *Note `DELETE':
delete. statement (`DELETE FROM employees WHERE store_id IN
(4,12,13,14,18)').  However, the *Note `ALTER TABLE ... DROP
PARTITION': alter-table. statement also removes the partition itself
from the definition for the table, and you must execute an *Note `ALTER
TABLE ... ADD PARTITION': alter-table. statement to restore the table's
original partitioning scheme. (This problem is resolved in MySQL 5.5,
which adds the *Note `ALTER TABLE ... TRUNCATE PARTITION': alter-table.
statement for removing all rows from a given partition without
affecting the table definition.)

As with `RANGE' partitioning, it is possible to combine `LIST'
partitioning with partitioning by hash or key to produce a composite
partitioning (subpartitioning). See *Note partitioning-subpartitions::.

Unlike the case with `RANGE' partitioning, there is no `catch-all' such
as `MAXVALUE'; all expected values for the partitioning expression
should be covered in `PARTITION ... VALUES IN (...)' clauses. An *Note
`INSERT': insert. statement containing an unmatched partitioning column
value fails with an error, as shown in this example:


     mysql> CREATE TABLE h2 (
         ->   c1 INT,
         ->   c2 INT
         -> )
         -> PARTITION BY LIST(c1) (
         ->   PARTITION p0 VALUES IN (1, 4, 7),
         ->   PARTITION p1 VALUES IN (2, 5, 8)
         -> );
     Query OK, 0 rows affected (0.11 sec)

     mysql> INSERT INTO h2 VALUES (3, 5);
     `ERROR 1525 (HY000): Table has no partition for value 3'

When inserting multiple rows using a single *Note `INSERT': insert.
statement the behavior depends on whether the table uses a
transactional storage engine. For an *Note `InnoDB':
innodb-storage-engine. table, the statement is considered a single
transaction, so the presence of any unmatched values causes the
statement to fail completely, and no rows are inserted. For a table
using a nontransactional storage engine such as *Note `MyISAM':
myisam-storage-engine, any rows coming before the row containing the
unmatched value are inserted, but any coming after it are not.

You can cause this type of error to be ignored by using the `IGNORE'
keyword. If you do so, rows containing unmatched partitioning column
values are not inserted, but any rows with matching values _are_
inserted, and no errors are reported:


     mysql> TRUNCATE h2;
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT * FROM h2;
     Empty set (0.00 sec)

     mysql> INSERT IGNORE INTO h2 VALUES (2, 5), (6, 10), (7, 5), (3, 1), (1, 9);
     Query OK, 3 rows affected (0.00 sec)
     Records: 5  Duplicates: 2  Warnings: 0

     mysql> SELECT * FROM h2;
     +------+------+
     | c1   | c2   |
     +------+------+
     |    7 |    5 |
     |    1 |    9 |
     |    2 |    5 |
     +------+------+
     3 rows in set (0.00 sec)


File: manual.info,  Node: partitioning-hash,  Next: partitioning-key,  Prev: partitioning-list,  Up: partitioning-types

18.2.3 HASH Partitioning
------------------------

* Menu:

* partitioning-linear-hash::     LINEAR HASH Partitioning

Partitioning by `HASH' is used primarily to ensure an even distribution
of data among a predetermined number of partitions. With range or list
partitioning, you must specify explicitly into which partition a given
column value or set of column values is to be stored; with hash
partitioning, MySQL takes care of this for you, and you need only
specify a column value or expression based on a column value to be
hashed and the number of partitions into which the partitioned table is
to be divided.

To partition a table using `HASH' partitioning, it is necessary to
append to the *Note `CREATE TABLE': create-table. statement a
`PARTITION BY HASH (EXPR)' clause, where EXPR is an expression that
returns an integer. This can simply be the name of a column whose type
is one of MySQL's integer types. In addition, you will most likely want
to follow this with a `PARTITIONS NUM' clause, where NUM is a positive
integer representing the number of partitions into which the table is to
be divided.

For example, the following statement creates a table that uses hashing
on the `store_id' column and is divided into 4 partitions:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT,
         store_id INT
     )
     PARTITION BY HASH(store_id)
     PARTITIONS 4;

If you do not include a `PARTITIONS' clause, the number of partitions
defaults to `1'.

Using the `PARTITIONS' keyword without a number following it results in
a syntax error.

You can also use an SQL expression that returns an integer for EXPR.
For instance, you might want to partition based on the year in which an
employee was hired. This can be done as shown here:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT,
         store_id INT
     )
     PARTITION BY HASH( YEAR(hired) )
     PARTITIONS 4;

EXPR must return a nonconstant, nonrandom integer value (in other
words, it should be varying but deterministic), and must not contain
any prohibited constructs as described in *Note
partitioning-limitations::. You should also keep in mind that this
expression is evaluated each time a row is inserted or updated (or
possibly deleted); this means that very complex expressions may give
rise to performance issues, particularly when performing operations
(such as batch inserts) that affect a great many rows at one time.

The most efficient hashing function is one which operates upon a single
table column and whose value increases or decreases consistently with
the column value, as this allows for `pruning' on ranges of partitions.
That is, the more closely that the expression varies with the value of
the column on which it is based, the more efficiently MySQL can use the
expression for hash partitioning.

For example, where `date_col' is a column of type *Note `DATE':
datetime, then the expression `TO_DAYS(date_col)' is said to vary
directly with the value of `date_col', because for every change in the
value of `date_col', the value of the expression changes in a
consistent manner. The variance of the expression `YEAR(date_col)' with
respect to `date_col' is not quite as direct as that of
`TO_DAYS(date_col)', because not every possible change in `date_col'
produces an equivalent change in `YEAR(date_col)'. Even so,
`YEAR(date_col)' is a good candidate for a hashing function, because it
varies directly with a portion of `date_col' and there is no possible
change in `date_col' that produces a disproportionate change in
`YEAR(date_col)'.

By way of contrast, suppose that you have a column named `int_col'
whose type is *Note `INT': integer-types. Now consider the expression
`POW(5-int_col,3) + 6'. This would be a poor choice for a hashing
function because a change in the value of `int_col' is not guaranteed
to produce a proportional change in the value of the expression.
Changing the value of `int_col' by a given amount can produce by widely
different changes in the value of the expression. For example, changing
`int_col' from `5' to `6' produces a change of `-1' in the value of the
expression, but changing the value of `int_col' from `6' to `7'
produces a change of `-7' in the expression value.

In other words, the more closely the graph of the column value versus
the value of the expression follows a straight line as traced by the
equation `y=Cx' where C is some nonzero constant, the better the
expression is suited to hashing. This has to do with the fact that the
more nonlinear an expression is, the more uneven the distribution of
data among the partitions it tends to produce.

In theory, pruning is also possible for expressions involving more than
one column value, but determining which of such expressions are
suitable can be quite difficult and time-consuming. For this reason,
the use of hashing expressions involving multiple columns is not
particularly recommended.

When `PARTITION BY HASH' is used, MySQL determines which partition of
NUM partitions to use based on the modulus of the result of the user
function. In other words, for an expression EXPR, the partition in
which the record is stored is partition number N, where `N = MOD(EXPR,
NUM)'. Suppose that table `t1' is defined as follows, so that it has 4
partitions:


     CREATE TABLE t1 (col1 INT, col2 CHAR(5), col3 DATE)
         PARTITION BY HASH( YEAR(col3) )
         PARTITIONS 4;

If you insert a record into `t1' whose `col3' value is `'2005-09-15'',
then the partition in which it is stored is determined as follows:


     MOD(YEAR('2005-09-01'),4)
     =  MOD(2005,4)
     =  1

MySQL 5.1 also supports a variant of `HASH' partitioning known as
_linear hashing_ which employs a more complex algorithm for determining
the placement of new rows inserted into the partitioned table. See
*Note partitioning-linear-hash::, for a description of this algorithm.

The user function is evaluated each time a record is inserted or
updated. It may also--depending on the circumstances--be evaluated when
records are deleted.

*Note*:

If a table to be partitioned has a `UNIQUE' key, then any columns
supplied as arguments to the `HASH' user function or to the `KEY''s
COLUMN_LIST must be part of that key.


File: manual.info,  Node: partitioning-linear-hash,  Prev: partitioning-hash,  Up: partitioning-hash

18.2.3.1 LINEAR HASH Partitioning
.................................

MySQL also supports linear hashing, which differs from regular hashing
in that linear hashing utilizes a linear powers-of-two algorithm
whereas regular hashing employs the modulus of the hashing function's
value.

Syntactically, the only difference between linear-hash partitioning and
regular hashing is the addition of the `LINEAR' keyword in the
`PARTITION BY' clause, as shown here:


     CREATE TABLE employees (
         id INT NOT NULL,
         fname VARCHAR(30),
         lname VARCHAR(30),
         hired DATE NOT NULL DEFAULT '1970-01-01',
         separated DATE NOT NULL DEFAULT '9999-12-31',
         job_code INT,
         store_id INT
     )
     PARTITION BY LINEAR HASH( YEAR(hired) )
     PARTITIONS 4;

Given an expression EXPR, the partition in which the record is stored
when linear hashing is used is partition number N from among NUM
partitions, where N is derived according to the following algorithm:

  1. Find the next power of 2 greater than NUM. We call this value V;
     it can be calculated as:


          V = POWER(2, CEILING(LOG(2, NUM)))

     (Suppose that NUM is 13. Then `LOG(2,13)' is 3.7004397181411.
     `CEILING(3.7004397181411)' is 4, and V = `POWER(2,4)', which is
     16.)

  2. Set N = F(COLUMN_LIST) & (V - 1).

  3. While N >= NUM:

        * Set V = CEIL(V / 2)

        * Set N = N & (V - 1)

Suppose that the table `t1', using linear hash partitioning and having
6 partitions, is created using this statement:


     CREATE TABLE t1 (col1 INT, col2 CHAR(5), col3 DATE)
         PARTITION BY LINEAR HASH( YEAR(col3) )
         PARTITIONS 6;

Now assume that you want to insert two records into `t1' having the
`col3' column values `'2003-04-14'' and `'1998-10-19''. The partition
number for the first of these is determined as follows:


     V = POWER(2, CEILING( LOG(2,6) )) = 8
     N = YEAR('2003-04-14') & (8 - 1)
        = 2003 & 7
        = 3

     (_3 >= 6 is FALSE: record stored in partition #3_)

The number of the partition where the second record is stored is
calculated as shown here:


     V = 8
     N = YEAR('1998-10-19') & (8-1)
       = 1998 & 7
       = 6

     (_6 >= 6 is TRUE: additional step required_)

     N = 6 & CEILING(8 / 2)
       = 6 & 3
       = 2

     (_2 >= 6 is FALSE: record stored in partition #2_)

The advantage in partitioning by linear hash is that the adding,
dropping, merging, and splitting of partitions is made much faster,
which can be beneficial when dealing with tables containing extremely
large amounts (terabytes) of data. The disadvantage is that data is
less likely to be evenly distributed between partitions as compared
with the distribution obtained using regular hash partitioning.


File: manual.info,  Node: partitioning-key,  Next: partitioning-subpartitions,  Prev: partitioning-hash,  Up: partitioning-types

18.2.4 KEY Partitioning
-----------------------

Partitioning by key is similar to partitioning by hash, except that
where hash partitioning employs a user-defined expression, the hashing
function for key partitioning is supplied by the MySQL server. MySQL
Cluster uses `MD5()' for this purpose; for tables using other storage
engines, the server employs its own internal hashing function which is
based on the same algorithm as `PASSWORD()'.

The syntax rules for `CREATE TABLE ... PARTITION BY KEY' are similar to
those for creating a table that is partitioned by hash. The major
differences are listed here:

   * `KEY' is used rather than `HASH'.

   * `KEY' takes only a list of one or more column names. Beginning
     with MySQL 5.1.5, the column or columns used as the partitioning
     key must comprise part or all of the table's primary key, if the
     table has one.

     Beginning with MySQL 5.1.6, `KEY' takes a list of zero or more
     column names. Where no column name is specified as the
     partitioning key, the table's primary key is used, if there is
     one. For example, the following *Note `CREATE TABLE':
     create-table. statement is valid in MySQL 5.1.6 or later:


          CREATE TABLE k1 (
              id INT NOT NULL PRIMARY KEY,
              name VARCHAR(20)
          )
          PARTITION BY KEY()
          PARTITIONS 2;

     If there is no primary key but there is a unique key, then the
     unique key is used for the partitioning key:


          CREATE TABLE k1 (
              id INT NOT NULL,
              name VARCHAR(20),
              UNIQUE KEY (id)
          )
          PARTITION BY KEY()
          PARTITIONS 2;

     However, if the unique key column were not defined as `NOT NULL',
     then the previous statement would fail.

     In both of these cases, the partitioning key is the `id' column,
     even though it is not shown in the output of *Note `SHOW CREATE
     TABLE': show-create-table. or in the `PARTITION_EXPRESSION' column
     of the *Note `INFORMATION_SCHEMA.PARTITIONS': partitions-table.
     table.

     Unlike the case with other partitioning types, columns used for
     partitioning by `KEY' are not restricted to integer or `NULL'
     values. For example, the following *Note `CREATE TABLE':
     create-table. statement is valid:


          CREATE TABLE tm1 (
              s1 CHAR(32) PRIMARY KEY
          )
          PARTITION BY KEY(s1)
          PARTITIONS 10;

     The preceding statement would _not_ be valid, were a different
     partitioning type to be specified.  (In this case, simply using
     `PARTITION BY KEY()' would also be valid and have the same effect
     as `PARTITION BY KEY(s1)', since `s1' is the table's primary key.)

     For additional information about this issue, see *Note
     partitioning-limitations::.

     *Note*:

     Also beginning with MySQL 5.1.6, tables using the *Note
     `NDBCLUSTER': mysql-cluster. storage engine are implicitly
     partitioned by `KEY', again using the table's primary key as the
     partitioning key. In the event that the MySQL Cluster table has no
     explicit primary key, the `hidden' primary key generated by the
     *Note `NDBCLUSTER': mysql-cluster. storage engine for each MySQL
     Cluster table is used as the partitioning key.

     Beginning with MySQL Cluster NDB 6.2.18, MySQL Cluster NDB 6.3.25,
     and MySQL Cluster NDB 7.0.6, if you define an explicit
     partitioning scheme for an *Note `NDBCLUSTER': mysql-cluster.
     table, the table must have an explicit primary key, and any
     columns used in the partitioning expression must be part of this
     key.  However, if the table uses an `empty' partitioning
     expression--that is, `PARTITION BY KEY()' with no column
     references--then no explicit primary key is required.

     You can observe this partitioning using the *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc. utility (with the `-p' option).

     *Important*:

     For a key-partitioned table using any MySQL storage engine other
     than *Note `NDBCLUSTER': mysql-cluster, you cannot execute an
     `ALTER TABLE DROP PRIMARY KEY', as doing so generates the error
     `ERROR 1466 (HY000): Field in list of fields for partition
     function not found in table'. This is not an issue for MySQL
     Cluster tables which are partitioned by `KEY'; in such cases, the
     table is reorganized using the `hidden' primary key as the table's
     new partitioning key. See *Note mysql-cluster::.

It is also possible to partition a table by linear key. Here is a
simple example:


     CREATE TABLE tk (
         col1 INT NOT NULL,
         col2 CHAR(5),
         col3 DATE
     )
     PARTITION BY LINEAR KEY (col1)
     PARTITIONS 3;

Using `LINEAR' has the same effect on `KEY' partitioning as it does on
`HASH' partitioning, with the partition number being derived using a
powers-of-two algorithm rather than modulo arithmetic. See *Note
partitioning-linear-hash::, for a description of this algorithm and its
implications.


File: manual.info,  Node: partitioning-subpartitions,  Next: partitioning-handling-nulls,  Prev: partitioning-key,  Up: partitioning-types

18.2.5 Subpartitioning
----------------------

Subpartitioning--also known as _composite partitioning_--is the further
division of each partition in a partitioned table. Consider the
following *Note `CREATE TABLE': create-table. statement:


     CREATE TABLE ts (id INT, purchased DATE)
         PARTITION BY RANGE( YEAR(purchased) )
         SUBPARTITION BY HASH( TO_DAYS(purchased) )
         SUBPARTITIONS 2 (
             PARTITION p0 VALUES LESS THAN (1990),
             PARTITION p1 VALUES LESS THAN (2000),
             PARTITION p2 VALUES LESS THAN MAXVALUE
         );

Table `ts' has 3 `RANGE' partitions. Each of these partitions--`p0',
`p1', and `p2'--is further divided into 2 subpartitions. In effect, the
entire table is divided into `3 * 2 = 6' partitions. However, due to the
action of the `PARTITION BY RANGE' clause, the first 2 of these store
only those records with a value less than 1990 in the `purchased'
column.

In MySQL 5.1, it is possible to subpartition tables that are
partitioned by `RANGE' or `LIST'. Subpartitions may use either `HASH'
or `KEY' partitioning.  This is also known as _composite partitioning_.

*Note*:

`SUBPARTITION BY HASH' and `SUBPARTITION BY KEY' generally follow the
same syntax rules as `PARTITION BY HASH' and `PARTITION BY KEY',
respectively. An exception to this is that `SUBPARTITION BY KEY'
(unlike `PARTITION BY KEY') does not currently support a default
column, so the column used for this purpose must be specified, even if
the table has an explicit primary key. This is a known issue which we
are working to address; see *Note
partitioning-limitations-subpartitions::, for more information and an
example.

It is also possible to define subpartitions explicitly using
`SUBPARTITION' clauses to specify options for individual subpartitions.
For example, a more verbose fashion of creating the same table `ts' as
shown in the previous example would be:


     CREATE TABLE ts (id INT, purchased DATE)
         PARTITION BY RANGE( YEAR(purchased) )
         SUBPARTITION BY HASH( TO_DAYS(purchased) ) (
             PARTITION p0 VALUES LESS THAN (1990) (
                 SUBPARTITION s0,
                 SUBPARTITION s1
             ),
             PARTITION p1 VALUES LESS THAN (2000) (
                 SUBPARTITION s2,
                 SUBPARTITION s3
             ),
             PARTITION p2 VALUES LESS THAN MAXVALUE (
                 SUBPARTITION s4,
                 SUBPARTITION s5
             )
         );

Some syntactical items of note are listed here:

   * Each partition must have the same number of subpartitions.

   * If you explicitly define any subpartitions using `SUBPARTITION' on
     any partition of a partitioned table, you must define them all. In
     other words, the following statement will fail:


          CREATE TABLE ts (id INT, purchased DATE)
              PARTITION BY RANGE( YEAR(purchased) )
              SUBPARTITION BY HASH( TO_DAYS(purchased) ) (
                  PARTITION p0 VALUES LESS THAN (1990) (
                      SUBPARTITION s0,
                      SUBPARTITION s1
                  ),
                  PARTITION p1 VALUES LESS THAN (2000),
                  PARTITION p2 VALUES LESS THAN MAXVALUE (
                      SUBPARTITION s2,
                      SUBPARTITION s3
                  )
              );

     This statement would still fail even if it included a
     `SUBPARTITIONS 2' clause.

   * Each `SUBPARTITION' clause must include (at a minimum) a name for
     the subpartition. Otherwise, you may set any desired option for
     the subpartition or allow it to assume its default setting for
     that option.

   * In MySQL 5.1.7 and earlier, names of subpartitions were required
     to be unique within each partition, but did not have to be unique
     within the table as a whole. Beginning with MySQL 5.1.8,
     subpartition names must be unique across the entire table. For
     example, the following *Note `CREATE TABLE': create-table.
     statement is valid in MySQL 5.1.8 and later:


          CREATE TABLE ts (id INT, purchased DATE)
              PARTITION BY RANGE( YEAR(purchased) )
              SUBPARTITION BY HASH( TO_DAYS(purchased) ) (
                  PARTITION p0 VALUES LESS THAN (1990) (
                      SUBPARTITION s0,
                      SUBPARTITION s1
                  ),
                  PARTITION p1 VALUES LESS THAN (2000) (
                      SUBPARTITION s2,
                      SUBPARTITION s3
                  ),
                  PARTITION p2 VALUES LESS THAN MAXVALUE (
                      SUBPARTITION s4,
                      SUBPARTITION s5
                  )
              );

     (The previous statement is also valid for versions of MySQL prior
     to 5.1.8.)

Subpartitions can be used with especially large tables to distribute
data and indexes across many disks. Suppose that you have 6 disks
mounted as `/disk0', `/disk1', `/disk2', and so on. Now consider the
following example:


     CREATE TABLE ts (id INT, purchased DATE)
         PARTITION BY RANGE( YEAR(purchased) )
         SUBPARTITION BY HASH( TO_DAYS(purchased) ) (
             PARTITION p0 VALUES LESS THAN (1990) (
                 SUBPARTITION s0
                     DATA DIRECTORY = '/disk0/data'
                     INDEX DIRECTORY = '/disk0/idx',
                 SUBPARTITION s1
                     DATA DIRECTORY = '/disk1/data'
                     INDEX DIRECTORY = '/disk1/idx'
             ),
             PARTITION p1 VALUES LESS THAN (2000) (
                 SUBPARTITION s2
                     DATA DIRECTORY = '/disk2/data'
                     INDEX DIRECTORY = '/disk2/idx',
                 SUBPARTITION s3
                     DATA DIRECTORY = '/disk3/data'
                     INDEX DIRECTORY = '/disk3/idx'
             ),
             PARTITION p2 VALUES LESS THAN MAXVALUE (
                 SUBPARTITION s4
                     DATA DIRECTORY = '/disk4/data'
                     INDEX DIRECTORY = '/disk4/idx',
                 SUBPARTITION s5
                     DATA DIRECTORY = '/disk5/data'
                     INDEX DIRECTORY = '/disk5/idx'
             )
         );

In this case, a separate disk is used for the data and for the indexes
of each `RANGE'. Many other variations are possible; another example
might be:


     CREATE TABLE ts (id INT, purchased DATE)
         PARTITION BY RANGE(YEAR(purchased))
         SUBPARTITION BY HASH( TO_DAYS(purchased) ) (
             PARTITION p0 VALUES LESS THAN (1990) (
                 SUBPARTITION s0a
                     DATA DIRECTORY = '/disk0'
                     INDEX DIRECTORY = '/disk1',
                 SUBPARTITION s0b
                     DATA DIRECTORY = '/disk2'
                     INDEX DIRECTORY = '/disk3'
             ),
             PARTITION p1 VALUES LESS THAN (2000) (
                 SUBPARTITION s1a
                     DATA DIRECTORY = '/disk4/data'
                     INDEX DIRECTORY = '/disk4/idx',
                 SUBPARTITION s1b
                     DATA DIRECTORY = '/disk5/data'
                     INDEX DIRECTORY = '/disk5/idx'
             ),
             PARTITION p2 VALUES LESS THAN MAXVALUE (
                 SUBPARTITION s2a,
                 SUBPARTITION s2b
             )
         );

Here, the storage is as follows:

   * Rows with `purchased' dates from before 1990 take up a vast amount
     of space, so are split up 4 ways, with a separate disk dedicated
     to the data and to the indexes for each of the two subpartitions
     (`s0a' and `s0b') making up partition `p0'. In other words:

        * The data for subpartition `s0a' is stored on `/disk0'.

        * The indexes for subpartition `s0a' are stored on `/disk1'.

        * The data for subpartition `s0b' is stored on `/disk2'.

        * The indexes for subpartition `s0b' are stored on `/disk3'.

   * Rows containing dates ranging from 1990 to 1999 (partition `p1')
     do not require as much room as those from before 1990. These are
     split between 2 disks (`/disk4' and `/disk5') rather than 4 disks
     as with the legacy records stored in `p0':

        * Data and indexes belonging to `p1''s first subpartition
          (`s1a') are stored on `/disk4'--the data in `/disk4/data',
          and the indexes in `/disk4/idx'.

        * Data and indexes belonging to `p1''s second subpartition
          (`s1b') are stored on `/disk5'--the data in `/disk5/data',
          and the indexes in `/disk5/idx'.

   * Rows reflecting dates from the year 2000 to the present (partition
     `p2') do not take up as much space as required by either of the
     two previous ranges.  Currently, it is sufficient to store all of
     these in the default location.

     In future, when the number of purchases for the decade beginning
     with the year 2000 grows to a point where the default location no
     longer provides sufficient space, the corresponding rows can be
     moved using an `ALTER TABLE ... REORGANIZE PARTITION' statement.
     See *Note partitioning-management::, for an explanation of how
     this can be done.

Beginning with MySQL 5.1.18, the `DATA DIRECTORY' and `INDEX DIRECTORY'
options are not permitted in partition definitions when the
`NO_DIR_IN_CREATE' server SQL mode is in effect. However, this not true
when defining subpartitions; this is a known issue which is fixed in
MySQL 5.5 (Bug #42954).


File: manual.info,  Node: partitioning-handling-nulls,  Prev: partitioning-subpartitions,  Up: partitioning-types

18.2.6 How MySQL Partitioning Handles NULL
------------------------------------------

Partitioning in MySQL does nothing to disallow `NULL' as the value of a
partitioning expression, whether it is a column value or the value of a
user-supplied expression. Even though it is permitted to use `NULL' as
the value of an expression that must otherwise yield an integer, it is
important to keep in mind that `NULL' is not a number. Beginning with
MySQL 5.1.8, the partitioning implementation treats `NULL' as being
less than any non-`NULL' value, just as `ORDER BY' does.

This means that treatment of `NULL' varies between partitioning of
different types, and may produce behavior which you do not expect if
you are not prepared for it.  This being the case, we discuss in this
section how each MySQL partitioning type handles `NULL' values when
determining the partition in which a row should be stored, and provide
examples for each.

Handling of NULL with RANGE partitioning

If you insert a row into a table partitioned by `RANGE' such that the
column value used to determine the partition is `NULL', the row is
inserted into the lowest partition. Consider these two tables in a
database named `p', created as follows:


     mysql> CREATE TABLE t1 (
         ->     c1 INT,
         ->     c2 VARCHAR(20)
         -> )
         -> PARTITION BY RANGE(c1) (
         ->     PARTITION p0 VALUES LESS THAN (0),
         ->     PARTITION p1 VALUES LESS THAN (10),
         ->     PARTITION p2 VALUES LESS THAN MAXVALUE
         -> );
     Query OK, 0 rows affected (0.09 sec)

     mysql> CREATE TABLE t2 (
         ->     c1 INT,
         ->     c2 VARCHAR(20)
         -> )
         -> PARTITION BY RANGE(c1) (
         ->     PARTITION p0 VALUES LESS THAN (-5),
         ->     PARTITION p1 VALUES LESS THAN (0),
         ->     PARTITION p2 VALUES LESS THAN (10),
         ->     PARTITION p3 VALUES LESS THAN MAXVALUE
         -> );
     Query OK, 0 rows affected (0.09 sec)

You can see the partitions created by these two *Note `CREATE TABLE':
create-table. statements using the following query against the *Note
`PARTITIONS': partitions-table. table in the `INFORMATION_SCHEMA'
database:


     mysql> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
          >   FROM INFORMATION_SCHEMA.PARTITIONS
          >   WHERE TABLE_SCHEMA = 'p' AND TABLE_NAME LIKE 't_';
     +------------+----------------+------------+----------------+-------------+
     | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
     +------------+----------------+------------+----------------+-------------+
     | t1         | p0             |          0 |              0 |           0 |
     | t1         | p1             |          0 |              0 |           0 |
     | t1         | p2             |          0 |              0 |           0 |
     | t2         | p0             |          0 |              0 |           0 |
     | t2         | p1             |          0 |              0 |           0 |
     | t2         | p2             |          0 |              0 |           0 |
     | t2         | p3             |          0 |              0 |           0 |
     +------------+----------------+------------+----------------+-------------+
     7 rows in set (0.00 sec)

(For more information about this table, see *Note partitions-table::.)
Now let us populate each of these tables with a single row containing a
`NULL' in the column used as the partitioning key, and verify that the
rows were inserted using a pair of *Note `SELECT': select. statements:


     mysql> INSERT INTO t1 VALUES (NULL, 'mothra');
     Query OK, 1 row affected (0.00 sec)

     mysql> INSERT INTO t2 VALUES (NULL, 'mothra');
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT * FROM t1;
     +------+--------+
     | id   | name   |
     +------+--------+
     | NULL | mothra |
     +------+--------+
     1 row in set (0.00 sec)

     mysql> SELECT * FROM t2;
     +------+--------+
     | id   | name   |
     +------+--------+
     | NULL | mothra |
     +------+--------+
     1 row in set (0.00 sec)

You can see which partitions are used to store the inserted rows by
rerunning the previous query against *Note
`INFORMATION_SCHEMA.PARTITIONS': partitions-table. and inspecting the
output:


     mysql> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
          >   FROM INFORMATION_SCHEMA.PARTITIONS
          >   WHERE TABLE_SCHEMA = 'p' AND TABLE_NAME LIKE 't_';
     +------------+----------------+------------+----------------+-------------+
     | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
     +------------+----------------+------------+----------------+-------------+
     _| t1         | p0             |          1 |             20 |          20 |_
     | t1         | p1             |          0 |              0 |           0 |
     | t1         | p2             |          0 |              0 |           0 |
     _| t2         | p0             |          1 |             20 |          20 |_
     | t2         | p1             |          0 |              0 |           0 |
     | t2         | p2             |          0 |              0 |           0 |
     | t2         | p3             |          0 |              0 |           0 |
     +------------+----------------+------------+----------------+-------------+
     7 rows in set (0.01 sec)

You can also demonstrate that these rows were stored in the lowest
partition of each table by dropping these partitions, and then
re-running the *Note `SELECT': select.  statements:


     mysql> ALTER TABLE t1 DROP PARTITION p0;
     Query OK, 0 rows affected (0.16 sec)

     mysql> ALTER TABLE t2 DROP PARTITION p0;
     Query OK, 0 rows affected (0.16 sec)

     mysql> SELECT * FROM t1;
     Empty set (0.00 sec)

     mysql> SELECT * FROM t2;
     Empty set (0.00 sec)

*Important*:

Prior to MySQL 5.1.8, `RANGE' partitioning treated a partitioning
expression value of `NULL' as 0 with respect to determining placement.
(The only way to circumvent this behavior was to design tables so as
not to permit nulls, usually by declaring columns `NOT NULL'.) If you
have a `RANGE' partitioning scheme that depends on this earlier
behavior, you must re-implement it when upgrading to MySQL 5.1.8 or
later. (Bug #15447)

`NULL' is also treated in this way for partitioning expressions that
use SQL functions. Suppose that we define a table using a *Note `CREATE
TABLE': create-table. statement such as this one:


     CREATE TABLE tndate (
         id INT,
         dt DATE
     )
     PARTITION BY RANGE( YEAR(dt) ) (
         PARTITION p0 VALUES LESS THAN (1990),
         PARTITION p1 VALUES LESS THAN (2000),
         PARTITION p2 VALUES LESS THAN MAXVALUE
     );

As with other MySQL functions, `YEAR(NULL)' returns `NULL'. A row with
a `dt' column value of `NULL' is treated as though the partitioning
expression evaluated to a value less than any other value, and so is
inserted into partition `p0'.

Handling of NULL with LIST partitioning

A table that is partitioned by `LIST' admits `NULL' values if and only
if one of its partitions is defined using that value-list that contains
`NULL'. The converse of this is that a table partitioned by `LIST'
which does not explicitly use `NULL' in a value list rejects rows
resulting in a `NULL' value for the partitioning expression, as shown
in this example:


     mysql> CREATE TABLE ts1 (
         ->     c1 INT,
         ->     c2 VARCHAR(20)
         -> )
         -> PARTITION BY LIST(c1) (
         ->     PARTITION p0 VALUES IN (0, 3, 6),
         ->     PARTITION p1 VALUES IN (1, 4, 7),
         ->     PARTITION p2 VALUES IN (2, 5, 8)
         -> );
     Query OK, 0 rows affected (0.01 sec)

     mysql> INSERT INTO ts1 VALUES (9, 'mothra');
     `ERROR 1504 (HY000): Table has no partition for value 9'

     mysql> INSERT INTO ts1 VALUES (NULL, 'mothra');
     `ERROR 1504 (HY000): Table has no partition for value NULL'

Only rows having a `c1' value between `0' and `8' inclusive can be
inserted into `ts1'. `NULL' falls outside this range, just like the
number `9'. We can create tables `ts2' and `ts3' having value lists
containing `NULL', as shown here:


     mysql> CREATE TABLE ts2 (
         ->     c1 INT,
         ->     c2 VARCHAR(20)
         -> )
         -> PARTITION BY LIST(c1) (
         ->     PARTITION p0 VALUES IN (0, 3, 6),
         ->     PARTITION p1 VALUES IN (1, 4, 7),
         ->     PARTITION p2 VALUES IN (2, 5, 8),
         ->     PARTITION p3 VALUES IN (NULL)
         -> );
     Query OK, 0 rows affected (0.01 sec)

     mysql> CREATE TABLE ts3 (
         ->     c1 INT,
         ->     c2 VARCHAR(20)
         -> )
         -> PARTITION BY LIST(c1) (
         ->     PARTITION p0 VALUES IN (0, 3, 6),
         ->     PARTITION p1 VALUES IN (1, 4, 7, NULL),
         ->     PARTITION p2 VALUES IN (2, 5, 8)
         -> );
     Query OK, 0 rows affected (0.01 sec)

When defining value lists for partitioning, you can (and should) treat
`NULL' just as you would any other value.  For example, both `VALUES IN
(NULL)' and `VALUES IN (1, 4, 7, NULL)' are valid, as are `VALUES IN
(1, NULL, 4, 7)', `VALUES IN (NULL, 1, 4, 7)', and so on. You can
insert a row having `NULL' for column `c1' into each of the tables
`ts2' and `ts3':


     mysql> INSERT INTO ts2 VALUES (NULL, 'mothra');
     Query OK, 1 row affected (0.00 sec)

     mysql> INSERT INTO ts3 VALUES (NULL, 'mothra');
     Query OK, 1 row affected (0.00 sec)

By issuing the appropriate query against *Note
`INFORMATION_SCHEMA.PARTITIONS': partitions-table, you can determine
which partitions were used to store the rows just inserted (we assume,
as in the previous examples, that the partitioned tables were created
in the `p' database):


     mysql> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
          >   FROM INFORMATION_SCHEMA.PARTITIONS
          >   WHERE TABLE_SCHEMA = 'p' AND TABLE_NAME LIKE 'ts_';
     +------------+----------------+------------+----------------+-------------+
     | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
     +------------+----------------+------------+----------------+-------------+
     | ts2        | p0             |          0 |              0 |           0 |
     | ts2        | p1             |          0 |              0 |           0 |
     | ts2        | p2             |          0 |              0 |           0 |
     _| ts2        | p3             |          1 |             20 |          20 |_
     | ts3        | p0             |          0 |              0 |           0 |
     _| ts3        | p1             |          1 |             20 |          20 |_
     | ts3        | p2             |          0 |              0 |           0 |
     +------------+----------------+------------+----------------+-------------+
     7 rows in set (0.01 sec)

As shown earlier in this section, you can also verify which partitions
were used for storing the rows by deleting these partitions and then
performing a *Note `SELECT': select.

Handling of NULL with HASH and KEY partitioning

`NULL' is handled somewhat differently for tables partitioned by `HASH'
or `KEY'. In these cases, any partition expression that yields a `NULL'
value is treated as though its return value were zero. We can verify
this behavior by examining the effects on the file system of creating a
table partitioned by `HASH' and populating it with a record containing
appropriate values.  Suppose that you have a table `th' (also in the
`p' database) created using the following statement:


     mysql> CREATE TABLE th (
         ->     c1 INT,
         ->     c2 VARCHAR(20)
         -> )
         -> PARTITION BY HASH(c1)
         -> PARTITIONS 2;
     Query OK, 0 rows affected (0.00 sec)

The partitions belonging to this table can be viewed using the query
shown here:


     mysql> SELECT TABLE_NAME,PARTITION_NAME,TABLE_ROWS,AVG_ROW_LENGTH,DATA_LENGTH
          >   FROM INFORMATION_SCHEMA.PARTITIONS
          >   WHERE TABLE_SCHEMA = 'p' AND TABLE_NAME ='th';
     +------------+----------------+------------+----------------+-------------+
     | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
     +------------+----------------+------------+----------------+-------------+
     | th         | p0             |          0 |              0 |           0 |
     | th         | p1             |          0 |              0 |           0 |
     +------------+----------------+------------+----------------+-------------+
     2 rows in set (0.00 sec)

Note that `TABLE_ROWS' for each partition is 0.  Now insert two rows
into `th' whose `c1' column values are `NULL' and 0, and verify that
these rows were inserted, as shown here:


     mysql> INSERT INTO th VALUES (NULL, 'mothra'), (0, 'gigan');
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT * FROM th;
     +------+---------+
     | c1   | c2      |
     +------+---------+
     | NULL | mothra  |
     +------+---------+
     |    0 | gigan   |
     +------+---------+
     2 rows in set (0.01 sec)

Recall that for any integer N, the value of `NULL MOD N' is always
`NULL'. For tables that are partitioned by `HASH' or `KEY', this result
is treated for determining the correct partition as `0'. Checking the
*Note `INFORMATION_SCHEMA.PARTITIONS': partitions-table. table once
again, we can see that both rows were inserted into partition `p0':


     mysql> SELECT TABLE_NAME, PARTITION_NAME, TABLE_ROWS, AVG_ROW_LENGTH, DATA_LENGTH
          >   FROM INFORMATION_SCHEMA.PARTITIONS
          >   WHERE TABLE_SCHEMA = 'p' AND TABLE_NAME ='th';
     +------------+----------------+------------+----------------+-------------+
     | TABLE_NAME | PARTITION_NAME | TABLE_ROWS | AVG_ROW_LENGTH | DATA_LENGTH |
     +------------+----------------+------------+----------------+-------------+
     _| th         | p0             |          2 |             20 |          20 |_
     | th         | p1             |          0 |              0 |           0 |
     +------------+----------------+------------+----------------+-------------+
     2 rows in set (0.00 sec)

If you repeat this example using `PARTITION BY KEY' in place of
`PARTITION BY HASH' in the definition of the table, you can verify
easily that `NULL' is also treated like 0 for this type of partitioning.


File: manual.info,  Node: partitioning-management,  Next: partitioning-pruning,  Prev: partitioning-types,  Up: partitioning

18.3 Partition Management
=========================

* Menu:

* partitioning-management-range-list::  Management of RANGE and LIST Partitions
* partitioning-management-hash-key::  Management of HASH and KEY Partitions
* partitioning-maintenance::     Maintenance of Partitions
* partitioning-info::            Obtaining Information About Partitions

MySQL 5.1 provides a number of ways to modify partitioned tables. It is
possible to add, drop, redefine, merge, or split existing partitions.
All of these actions can be carried out using the partitioning
extensions to the *Note `ALTER TABLE':
alter-table-partition-operations. statement *Note alter-table::. There
are also ways to obtain information about partitioned tables and
partitions. We discuss these topics in the sections that follow.

   * For information about partition management in tables partitioned
     by `RANGE' or `LIST', see *Note
     partitioning-management-range-list::.

   * For a discussion of managing `HASH' and `KEY' partitions, see
     *Note partitioning-management-hash-key::.

   * See *Note partitioning-info::, for a discussion of mechanisms
     provided in MySQL 5.1 for obtaining information about partitioned
     tables and partitions.

   * For a discussion of performing maintenance operations on
     partitions, see *Note partitioning-maintenance::.

*Note*:

In MySQL 5.1, all partitions of a partitioned table must have the same
number of subpartitions, and it is not possible to change the
subpartitioning once the table has been created.

The statement *Note `ALTER TABLE ... PARTITION BY ...':
alter-table-partition-operations. is available and is functional
beginning with MySQL 5.1.6; previously in MySQL 5.1, this was accepted
as valid syntax, but the statement did nothing.

To change a table's partitioning scheme, it is necessary only to use the
*Note `ALTER TABLE': alter-table-partition-operations. statement with a
PARTITION_OPTIONS clause. This clause has the same syntax as that as
used with *Note `CREATE TABLE': create-table. for creating a
partitioned table, and always begins with the keywords `PARTITION BY'.
Suppose that you have a table partitioned by range using the following
*Note `CREATE TABLE': create-table. statement:


     CREATE TABLE trb3 (id INT, name VARCHAR(50), purchased DATE)
         PARTITION BY RANGE( YEAR(purchased) ) (
             PARTITION p0 VALUES LESS THAN (1990),
             PARTITION p1 VALUES LESS THAN (1995),
             PARTITION p2 VALUES LESS THAN (2000),
             PARTITION p3 VALUES LESS THAN (2005)
         );

To repartition this table so that it is partitioned by key into two
partitions using the `id' column value as the basis for the key, you
can use this statement:


     ALTER TABLE trb3 PARTITION BY KEY(id) PARTITIONS 2;

This has the same effect on the structure of the table as dropping the
table and re-creating it using `CREATE TABLE trb3 PARTITION BY KEY(id)
PARTITIONS 2;'.

In MySQL 5.1.7 and earlier MySQL 5.1 releases, `ALTER TABLE ... ENGINE
= ...' removed all partitioning from the affected table. Beginning with
MySQL 5.1.8, this statement changes only the storage engine used by the
table, and leaves the table's partitioning scheme intact. As of MySQL
5.1.8, use `ALTER TABLE ... REMOVE PARTITIONING' to remove a table's
partitioning. See *Note alter-table::.

*Important*:

Only a single `PARTITION BY', `ADD PARTITION', `DROP PARTITION',
`REORGANIZE PARTITION', or `COALESCE PARTITION' clause can be used in a
given *Note `ALTER TABLE': alter-table-partition-operations. statement.
If you (for example) wish to drop a partition and reorganize a table's
remaining partitions, you must do so in two separate *Note `ALTER
TABLE': alter-table-partition-operations. statements (one using `DROP
PARTITION' and then a second one using `REORGANIZE PARTITIONS').


File: manual.info,  Node: partitioning-management-range-list,  Next: partitioning-management-hash-key,  Prev: partitioning-management,  Up: partitioning-management

18.3.1 Management of RANGE and LIST Partitions
----------------------------------------------

Range and list partitions are very similar with regard to how the
adding and dropping of partitions are handled. For this reason we
discuss the management of both sorts of partitioning in this section.
For information about working with tables that are partitioned by hash
or key, see *Note partitioning-management-hash-key::. Dropping a
`RANGE' or `LIST' partition is more straightforward than adding one, so
we discuss this first.

Dropping a partition from a table that is partitioned by either `RANGE'
or by `LIST' can be accomplished using the *Note `ALTER TABLE':
alter-table-partition-operations. statement with a `DROP PARTITION'
clause. Here is a very basic example, which supposes that you have
already created a table which is partitioned by range and then
populated with 10 records using the following *Note `CREATE TABLE':
create-table. and *Note `INSERT': insert. statements:


     mysql> CREATE TABLE tr (id INT, name VARCHAR(50), purchased DATE)
         ->     PARTITION BY RANGE( YEAR(purchased) ) (
         ->         PARTITION p0 VALUES LESS THAN (1990),
         ->         PARTITION p1 VALUES LESS THAN (1995),
         ->         PARTITION p2 VALUES LESS THAN (2000),
         ->         PARTITION p3 VALUES LESS THAN (2005)
         ->     );
     Query OK, 0 rows affected (0.01 sec)

     mysql> INSERT INTO tr VALUES
         ->     (1, 'desk organiser', '2003-10-15'),
         ->     (2, 'CD player', '1993-11-05'),
         ->     (3, 'TV set', '1996-03-10'),
         ->     (4, 'bookcase', '1982-01-10'),
         ->     (5, 'exercise bike', '2004-05-09'),
         ->     (6, 'sofa', '1987-06-05'),
         ->     (7, 'popcorn maker', '2001-11-22'),
         ->     (8, 'aquarium', '1992-08-04'),
         ->     (9, 'study desk', '1984-09-16'),
         ->     (10, 'lava lamp', '1998-12-25');
     Query OK, 10 rows affected (0.01 sec)

You can see which items should have been inserted into partition `p2'
as shown here:


     mysql> SELECT * FROM tr
         -> WHERE purchased BETWEEN '1995-01-01' AND '1999-12-31';
     +------+-----------+------------+
     | id   | name      | purchased  |
     +------+-----------+------------+
     |    3 | TV set    | 1996-03-10 |
     |   10 | lava lamp | 1998-12-25 |
     +------+-----------+------------+
     2 rows in set (0.00 sec)

To drop the partition named `p2', execute the following command:


     mysql> ALTER TABLE tr DROP PARTITION p2;
     Query OK, 0 rows affected (0.03 sec)

*Note*:

The *Note `NDBCLUSTER': mysql-cluster. storage engine does not support
`ALTER TABLE ... DROP PARTITION'. It does, however, support the other
partitioning-related extensions to *Note `ALTER TABLE':
alter-table-partition-operations. that are described in this chapter.

It is very important to remember that, _when you drop a partition, you
also delete all the data that was stored in that partition_. You can
see that this is the case by re-running the previous *Note `SELECT':
select.  query:


     mysql> SELECT * FROM tr WHERE purchased
         -> BETWEEN '1995-01-01' AND '1999-12-31';
     Empty set (0.00 sec)

Because of this, the requirement was added in MySQL 5.1.10 that you
have the `DROP' privilege for a table before you can execute `ALTER
TABLE ... DROP PARTITION' on that table.

If you wish to drop all data from all partitions while preserving the
table definition and its partitioning scheme, use the *Note `TRUNCATE
TABLE': truncate-table. statement.  (See *Note truncate-table::.)

If you intend to change the partitioning of a table _without_ losing
data, use `ALTER TABLE ... REORGANIZE PARTITION' instead. See below or
in *Note alter-table::, for information about `REORGANIZE PARTITION'.

If you now execute a *Note `SHOW CREATE TABLE': show-create-table.
statement, you can see how the partitioning makeup of the table has
been changed:


     mysql> SHOW CREATE TABLE tr\G
     *************************** 1. row ***************************
            Table: tr
     Create Table: CREATE TABLE `tr` (
       `id` int(11) default NULL,
       `name` varchar(50) default NULL,
       `purchased` date default NULL
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1
     PARTITION BY RANGE ( YEAR(purchased) ) (
       PARTITION p0 VALUES LESS THAN (1990) ENGINE = MyISAM,
       PARTITION p1 VALUES LESS THAN (1995) ENGINE = MyISAM,
       PARTITION p3 VALUES LESS THAN (2005) ENGINE = MyISAM
     )
     1 row in set (0.01 sec)

When you insert new rows into the changed table with `purchased' column
values between `'1995-01-01'' and `'2004-12-31'' inclusive, those rows
will be stored in partition `p3'. You can verify this as follows:


     mysql> INSERT INTO tr VALUES (11, 'pencil holder', '1995-07-12');
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT * FROM tr WHERE purchased
         -> BETWEEN '1995-01-01' AND '2004-12-31';
     +------+----------------+------------+
     | id   | name           | purchased  |
     +------+----------------+------------+
     |   11 | pencil holder  | 1995-07-12 |
     |    1 | desk organiser | 2003-10-15 |
     |    5 | exercise bike  | 2004-05-09 |
     |    7 | popcorn maker  | 2001-11-22 |
     +------+----------------+------------+
     4 rows in set (0.00 sec)

     mysql> ALTER TABLE tr DROP PARTITION p3;
     Query OK, 0 rows affected (0.03 sec)

     mysql> SELECT * FROM tr WHERE purchased
         -> BETWEEN '1995-01-01' AND '2004-12-31';
     Empty set (0.00 sec)

Note that the number of rows dropped from the table as a result of
`ALTER TABLE ... DROP PARTITION' is not reported by the server as it
would be by the equivalent *Note `DELETE': delete. query.

Dropping `LIST' partitions uses exactly the same `ALTER TABLE ... DROP
PARTITION' syntax as used for dropping `RANGE' partitions. However,
there is one important difference in the effect this has on your use of
the table afterward: You can no longer insert into the table any rows
having any of the values that were included in the value list defining
the deleted partition. (See *Note partitioning-list::, for an example.)

To add a new range or list partition to a previously partitioned table,
use the `ALTER TABLE ... ADD PARTITION' statement. For tables which are
partitioned by `RANGE', this can be used to add a new range to the end
of the list of existing partitions. Suppose that you have a partitioned
table containing membership data for your organization, which is
defined as follows:


     CREATE TABLE members (
         id INT,
         fname VARCHAR(25),
         lname VARCHAR(25),
         dob DATE
     )
     PARTITION BY RANGE( YEAR(dob) ) (
         PARTITION p0 VALUES LESS THAN (1970),
         PARTITION p1 VALUES LESS THAN (1980),
         PARTITION p2 VALUES LESS THAN (1990)
     );

Suppose further that the minimum age for members is 16. As the calendar
approaches the end of 2005, you realize that you will soon be admitting
members who were born in 1990 (and later in years to come). You can
modify the `members' table to accommodate new members born in the years
1990 to 1999 as shown here:


     ALTER TABLE members ADD PARTITION (PARTITION p3 VALUES LESS THAN (2000));

With tables that are partitioned by range, you can use `ADD PARTITION'
to add new partitions to the high end of the partitions list only.
Trying to add a new partition in this manner between or before existing
partitions results in an error as shown here:


     mysql> ALTER TABLE members
          >     ADD PARTITION (
          >     PARTITION n VALUES LESS THAN (1960));
     ERROR 1463 (HY000): VALUES LESS THAN value must be strictly »
        increasing for each partition

You can work around this problem by reorganizing the first partition
into two new ones that split the range between them, like this:


     ALTER TABLE members
         REORGANIZE PARTITION p0 INTO (
             PARTITION n0 VALUES LESS THAN (1960),
             PARTITION n1 VALUES LESS THAN (1970)
     );

Using *Note `SHOW CREATE TABLE': show-create-table. you can see that
the `ALTER TABLE' statement has had the desired effect:


     mysql> SHOW CREATE TABLE members\G
     *************************** 1. row ***************************
            Table: members
     Create Table: CREATE TABLE `members` (
       `id` int(11) DEFAULT NULL,
       `fname` varchar(25) DEFAULT NULL,
       `lname` varchar(25) DEFAULT NULL,
       `dob` date DEFAULT NULL
     ) ENGINE=InnoDB DEFAULT CHARSET=latin1
     /*!50100 PARTITION BY RANGE ( YEAR(dob))
     (PARTITION n0 VALUES LESS THAN (1960) ENGINE = MyISAM,
      PARTITION n1 VALUES LESS THAN (1970) ENGINE = MyISAM,
      PARTITION p1 VALUES LESS THAN (1980) ENGINE = MyISAM,
      PARTITION p2 VALUES LESS THAN (1990) ENGINE = MyISAM,
      PARTITION p3 VALUES LESS THAN (2000) ENGINE = MyISAM) */
     1 row in set (0.00 sec)

See also *Note alter-table-partition-operations::.

You can also use `ALTER TABLE ... ADD PARTITION' to add new partitions
to a table that is partitioned by `LIST'. Suppose a table `tt' is
defined using the following *Note `CREATE TABLE': create-table.
statement:


     CREATE TABLE tt (
         id INT,
         data INT
     )
     PARTITION BY LIST(data) (
         PARTITION p0 VALUES IN (5, 10, 15),
         PARTITION p1 VALUES IN (6, 12, 18)
     );

You can add a new partition in which to store rows having the `data'
column values `7', `14', and `21' as shown:


     ALTER TABLE tt ADD PARTITION (PARTITION p2 VALUES IN (7, 14, 21));

Note that you _cannot_ add a new `LIST' partition encompassing any
values that are already included in the value list of an existing
partition.  If you attempt to do so, an error will result:


     mysql> ALTER TABLE tt ADD PARTITION
          >     (PARTITION np VALUES IN (4, 8, 12));
     ERROR 1465 (HY000): Multiple definition of same constant »
                         in list partitioning

Because any rows with the `data' column value `12' have already been
assigned to partition `p1', you cannot create a new partition on table
`tt' that includes `12' in its value list. To accomplish this, you
could drop `p1', and add `np' and then a new `p1' with a modified
definition. However, as discussed earlier, this would result in the
loss of all data stored in `p1'--and it is often the case that this is
not what you really want to do. Another solution might appear to be to
make a copy of the table with the new partitioning and to copy the data
into it using *Note `CREATE TABLE ... SELECT ...': create-table, then
drop the old table and rename the new one, but this could be very
time-consuming when dealing with a large amounts of data. This also
might not be feasible in situations where high availability is a
requirement.

Beginning with MySQL 5.1.6, you can add multiple partitions in a single
`ALTER TABLE ... ADD PARTITION' statement as shown here:


     CREATE TABLE employees (
       id INT NOT NULL,
       fname VARCHAR(50) NOT NULL,
       lname VARCHAR(50) NOT NULL,
       hired DATE NOT NULL
     )
     PARTITION BY RANGE( YEAR(hired) ) (
       PARTITION p1 VALUES LESS THAN (1991),
       PARTITION p2 VALUES LESS THAN (1996),
       PARTITION p3 VALUES LESS THAN (2001),
       PARTITION p4 VALUES LESS THAN (2005)
     );

     ALTER TABLE employees ADD PARTITION (
         PARTITION p5 VALUES LESS THAN (2010),
         PARTITION p6 VALUES LESS THAN MAXVALUE
     );

Fortunately, MySQL's partitioning implementation provides ways to
redefine partitions without losing data. Let us look first at a couple
of simple examples involving `RANGE' partitioning. Recall the `members'
table which is now defined as shown here:


     mysql> SHOW CREATE TABLE members\G
     *************************** 1. row ***************************
            Table: members
     Create Table: CREATE TABLE `members` (
       `id` int(11) default NULL,
       `fname` varchar(25) default NULL,
       `lname` varchar(25) default NULL,
       `dob` date default NULL
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1
     PARTITION BY RANGE ( YEAR(dob) ) (
       PARTITION p0 VALUES LESS THAN (1970) ENGINE = MyISAM,
       PARTITION p1 VALUES LESS THAN (1980) ENGINE = MyISAM,
       PARTITION p2 VALUES LESS THAN (1990) ENGINE = MyISAM.
       PARTITION p3 VALUES LESS THAN (2000) ENGINE = MyISAM
     )

Suppose that you would like to move all rows representing members born
before 1960 into a separate partition. As we have already seen, this
cannot be done using *Note `ALTER TABLE ... ADD PARTITION':
alter-table-partition-operations. However, you can use another
partition-related extension to *Note `ALTER TABLE':
alter-table-partition-operations. to accomplish this:


     ALTER TABLE members REORGANIZE PARTITION p0 INTO (
         PARTITION s0 VALUES LESS THAN (1960),
         PARTITION s1 VALUES LESS THAN (1970)
     );

In effect, this command splits partition `p0' into two new partitions
`s0' and `s1'. It also moves the data that was stored in `p0' into the
new partitions according to the rules embodied in the two `PARTITION
... VALUES ...' clauses, so that `s0' contains only those records for
which `YEAR(dob)' is less than 1960 and `s1' contains those rows in
which `YEAR(dob)' is greater than or equal to 1960 but less than 1970.

A `REORGANIZE PARTITION' clause may also be used for merging adjacent
partitions. You can return the `members' table to its previous
partitioning as shown here:


     ALTER TABLE members REORGANIZE PARTITION s0,s1 INTO (
         PARTITION p0 VALUES LESS THAN (1970)
     );

No data is lost in splitting or merging partitions using `REORGANIZE
PARTITION'. In executing the above statement, MySQL moves all of the
records that were stored in partitions `s0' and `s1' into partition
`p0'.

The general syntax for `REORGANIZE PARTITION' is shown here:


     ALTER TABLE TBL_NAME
         REORGANIZE PARTITION PARTITION_LIST
         INTO (PARTITION_DEFINITIONS);

Here, TBL_NAME is the name of the partitioned table, and PARTITION_LIST
is a comma-separated list of names of one or more existing partitions
to be changed.  PARTITION_DEFINITIONS is a comma-separated list of new
partition definitions, which follow the same rules as for the
PARTITION_DEFINITIONS list used in *Note `CREATE TABLE': create-table.
(see *Note create-table::). It should be noted that you are not limited
to merging several partitions into one, or to splitting one partition
into many, when using `REORGANIZE PARTITION'. For example, you can
reorganize all four partitions of the `members' table into two, as
follows:


     ALTER TABLE members REORGANIZE PARTITION p0,p1,p2,p3 INTO (
         PARTITION m0 VALUES LESS THAN (1980),
         PARTITION m1 VALUES LESS THAN (2000)
     );

You can also use `REORGANIZE PARTITION' with tables that are
partitioned by `LIST'. Let us return to the problem of adding a new
partition to the list-partitioned `tt' table and failing because the
new partition had a value that was already present in the value-list of
one of the existing partitions. We can handle this by adding a
partition that contains only nonconflicting values, and then
reorganizing the new partition and the existing one so that the value
which was stored in the existing one is now moved to the new one:


     ALTER TABLE tt ADD PARTITION (PARTITION np VALUES IN (4, 8));
     ALTER TABLE tt REORGANIZE PARTITION p1,np INTO (
         PARTITION p1 VALUES IN (6, 18),
         PARTITION np VALUES in (4, 8, 12)
     );

Here are some key points to keep in mind when using `ALTER TABLE ...
REORGANIZE PARTITION' to repartition tables that are partitioned by
`RANGE' or `LIST':

   * The `PARTITION' clauses used to determine the new partitioning
     scheme are subject to the same rules as those used with a *Note
     `CREATE TABLE': create-table. statement.

     Most importantly, you should remember that the new partitioning
     scheme cannot have any overlapping ranges (applies to tables
     partitioned by `RANGE') or sets of values (when reorganizing
     tables partitioned by `LIST').

     *Note*:

     Prior to MySQL 5.1.4, you could not reuse the names of existing
     partitions in the `INTO' clause, even when those partitions were
     being dropped or redefined. See the Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) for MySQL 5.1.4
     for more information.

   * The combination of partitions in the PARTITION_DEFINITIONS list
     should account for the same range or set of values overall as the
     combined partitions named in the PARTITION_LIST.

     For instance, in the `members' table used as an example in this
     section, partitions `p1' and `p2' together cover the years 1980
     through 1999. Therefore, any reorganization of these two
     partitions should cover the same range of years overall.

   * For tables partitioned by `RANGE', you can reorganize only
     adjacent partitions; you cannot skip over range partitions.

     For instance, you could not reorganize the `members' table used as
     an example in this section using a statement beginning with `ALTER
     TABLE members REORGANIZE PARTITION p0,p2 INTO ...' because `p0'
     covers the years prior to 1970 and `p2' the years from 1990
     through 1999 inclusive, and thus the two are not adjacent
     partitions.

   * You cannot use `REORGANIZE PARTITION' to change the table's
     partitioning type; that is, you cannot (for example) change
     `RANGE' partitions to `HASH' partitions or vice versa. You also
     cannot use this command to change the partitioning expression or
     column. To accomplish either of these tasks without dropping and
     re-creating the table, you can use *Note `ALTER TABLE ...
     PARTITION BY ...': alter-table-partition-operations. For example:


          ALTER TABLE members
              PARTITION BY HASH( YEAR(dob) )
              PARTITIONS 8;


File: manual.info,  Node: partitioning-management-hash-key,  Next: partitioning-maintenance,  Prev: partitioning-management-range-list,  Up: partitioning-management

18.3.2 Management of HASH and KEY Partitions
--------------------------------------------

Tables which are partitioned by hash or by key are very similar to one
another with regard to making changes in a partitioning setup, and both
differ in a number of ways from tables which have been partitioned by
range or list. For that reason, this section addresses the modification
of tables partitioned by hash or by key only. For a discussion of
adding and dropping of partitions of tables that are partitioned by
range or list, see *Note partitioning-management-range-list::.

You cannot drop partitions from tables that are partitioned by `HASH'
or `KEY' in the same way that you can from tables that are partitioned
by `RANGE' or `LIST'. However, you can merge `HASH' or `KEY' partitions
using the `ALTER TABLE ... COALESCE PARTITION' statement. Suppose that
you have a table containing data about clients, which is divided into
twelve partitions. The `clients' table is defined as shown here:


     CREATE TABLE clients (
         id INT,
         fname VARCHAR(30),
         lname VARCHAR(30),
         signed DATE
     )
     PARTITION BY HASH( MONTH(signed) )
     PARTITIONS 12;

To reduce the number of partitions from twelve to eight, execute the
following *Note `ALTER TABLE': alter-table-partition-operations.
command:


     mysql> ALTER TABLE clients COALESCE PARTITION 4;
     Query OK, 0 rows affected (0.02 sec)

`COALESCE' works equally well with tables that are partitioned by
`HASH', `KEY', `LINEAR HASH', or `LINEAR KEY'. Here is an example
similar to the previous one, differing only in that the table is
partitioned by `LINEAR KEY':


     mysql> CREATE TABLE clients_lk (
         ->     id INT,
         ->     fname VARCHAR(30),
         ->     lname VARCHAR(30),
         ->     signed DATE
         -> )
         -> PARTITION BY LINEAR KEY(signed)
         -> PARTITIONS 12;
     Query OK, 0 rows affected (0.03 sec)

     mysql> ALTER TABLE clients_lk COALESCE PARTITION 4;
     Query OK, 0 rows affected (0.06 sec)
     Records: 0  Duplicates: 0  Warnings: 0

Note that the number following `COALESCE PARTITION' is the number of
partitions to merge into the remainder--in other words, it is the
number of partitions to remove from the table.

If you attempt to remove more partitions than the table has, the result
is an error like the one shown:


     mysql> ALTER TABLE clients COALESCE PARTITION 18;
     ERROR 1478 (HY000): Cannot remove all partitions, use DROP TABLE instead

To increase the number of partitions for the `clients' table from 12 to
18. use `ALTER TABLE ... ADD PARTITION' as shown here:


     ALTER TABLE clients ADD PARTITION PARTITIONS 6;


File: manual.info,  Node: partitioning-maintenance,  Next: partitioning-info,  Prev: partitioning-management-hash-key,  Up: partitioning-management

18.3.3 Maintenance of Partitions
--------------------------------

A number of table and partition maintenance tasks can be carried out
using SQL statements intended for such purposes on partitioned tables
in MySQL 5.1.

Table maintenance of partitioned tables can be accomplished using the
statements *Note `CHECK TABLE': check-table, *Note `OPTIMIZE TABLE':
optimize-table, *Note `ANALYZE TABLE': analyze-table, and *Note `REPAIR
TABLE': repair-table, which are supported for partitioned tables as of
MySQL 5.1.27.

Also beginning with MySQL 5.1.27, you can use a number of extensions to
*Note `ALTER TABLE': alter-table-partition-operations. for performing
operations of this type on one or more partitions directly, as
described in the following list:

   * Rebuilding partitions

     Rebuilds the partition; this has the same effect as dropping all
     records stored in the partition, then reinserting them. This can
     be useful for purposes of defragmentation.

     Example:


          ALTER TABLE t1 REBUILD PARTITION p0, p1;

   * Optimizing partitions

     If you have deleted a large number of rows from a partition or if
     you have made many changes to a partitioned table with
     variable-length rows (that is, having *Note `VARCHAR': char, *Note
     `BLOB': blob, or *Note `TEXT': blob. columns), you can use *Note
     `ALTER TABLE ... OPTIMIZE PARTITION':
     alter-table-partition-operations. to reclaim any unused space and
     to defragment the partition data file.

     Example:


          ALTER TABLE t1 OPTIMIZE PARTITION p0, p1;

     Using `OPTIMIZE PARTITION' on a given partition is equivalent to
     running `CHECK PARTITION', `ANALYZE PARTITION', and `REPAIR
     PARTITION' on that partition.

     Some MySQL storage engines, including *Note `InnoDB':
     innodb-storage-engine, do not support per-partition optimization;
     in these cases, *Note `ALTER TABLE ... OPTIMIZE PARTITION':
     alter-table-partition-operations. rebuilds the entire table. In
     MySQL 5.1.68 and later, running this statement on such a table
     causes the entire table to rebuilt and analyzed, and an
     appropriate warning to be issued. (Bug #11751825, Bug #42822) Use
     `ALTER TABLE ... REBUILD PARTITION' and `ALTER TABLE ... ANALYZE
     PARTITION' instead, to avoid this issue.

   * Analyzing partitions

     This reads and stores the key distributions for partitions.

     Example:


          ALTER TABLE t1 ANALYZE PARTITION p3;

   * Repairing partitions

     This repairs corrupted partitions.

     Example:


          ALTER TABLE t1 REPAIR PARTITION p0,p1;

   * Checking partitions

     You can check partitions for errors in much the same way that you
     can use *Note `CHECK TABLE': check-table. with nonpartitioned
     tables.

     Example:


          ALTER TABLE trb3 CHECK PARTITION p1;

     This command will tell you if the data or indexes in partition
     `p1' of table `t1' are corrupted. If this is the case, use *Note
     `ALTER TABLE ... REPAIR PARTITION':
     alter-table-partition-operations. to repair the partition.

Each of the statements in the list just shown also supports the keyword
`ALL' in place of the list of partition names. Using `ALL' causes the
statement to act on all partitions in the table.

*Note*:

The statements *Note `ALTER TABLE ... ANALYZE PARTITION':
alter-table-partition-operations, `ALTER TABLE ... CHECK PARTITION',
`ALTER TABLE ...  OPTIMIZE PARTITION', and `ALTER TABLE ...  REPAIR
PARTITION' were originally introduced in MySQL 5.1.5, but did not work
properly and were disabled in MySQL 5.1.24. They were re-introduced in
MySQL 5.1.27. (Bug #20129) The use of these partitioning-specific `ALTER
TABLE' statements with tables which are not partitioned is not
supported; beginning with MySQL 5.1.31, it is expressly not permitted.
(Bug #39434)

*Note `ALTER TABLE ... REBUILD PARTITION':
alter-table-partition-operations. was also introduced in MySQL 5.1.5.

The use of *Note `mysqlcheck': mysqlcheck. and *Note `myisamchk':
myisamchk. is not supported with partitioned tables.

`ANALYZE', `CHECK', `OPTIMIZE', `REBUILD', `REPAIR', and `TRUNCATE'
operations are not supported for subpartitions.


File: manual.info,  Node: partitioning-info,  Prev: partitioning-maintenance,  Up: partitioning-management

18.3.4 Obtaining Information About Partitions
---------------------------------------------

This section discusses obtaining information about existing partitions,
which can be done in a number of ways. Methods of obtaining such
information include the following:

   * Using the *Note `SHOW CREATE TABLE': show-create-table.  statement
     to view the partitioning clauses used in creating a partitioned
     table.

   * Using the *Note `SHOW TABLE STATUS': show-table-status.  statement
     to determine whether a table is partitioned.

   * Querying the *Note `INFORMATION_SCHEMA.PARTITIONS':
     partitions-table.  table.

   * Using the statement *Note `EXPLAIN PARTITIONS SELECT': explain. to
     see which partitions are used by a given *Note `SELECT': select.

As discussed elsewhere in this chapter, *Note `SHOW CREATE TABLE':
show-create-table. includes in its output the `PARTITION BY' clause
used to create a partitioned table. For example:


     mysql> SHOW CREATE TABLE trb3\G
     *************************** 1. row ***************************
            Table: trb3
     Create Table: CREATE TABLE `trb3` (
       `id` int(11) default NULL,
       `name` varchar(50) default NULL,
       `purchased` date default NULL
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1
     PARTITION BY RANGE (YEAR(purchased)) (
       PARTITION p0 VALUES LESS THAN (1990) ENGINE = MyISAM,
       PARTITION p1 VALUES LESS THAN (1995) ENGINE = MyISAM,
       PARTITION p2 VALUES LESS THAN (2000) ENGINE = MyISAM,
       PARTITION p3 VALUES LESS THAN (2005) ENGINE = MyISAM
     )
     1 row in set (0.00 sec)

*Note*:

In early MySQL 5.1 releases, the `PARTITIONS' clause was not shown for
tables partitioned by `HASH' or `KEY'. This issue was fixed in MySQL
5.1.6.

*Note `SHOW TABLE STATUS': show-table-status. works with partitioned
tables. Beginning with MySQL 5.1.9, its output is the same as that for
nonpartitioned tables, except that the `Create_options' column contains
the string `partitioned'. In MySQL 5.1.8 and earlier, the `Engine'
column always contained the value `PARTITION'; beginning with MySQL
5.1.9, this column contains the name of the storage engine used by all
partitions of the table. (See *Note show-table-status::, for more
information about this statement.)

You can also obtain information about partitions from
`INFORMATION_SCHEMA', which contains a *Note `PARTITIONS':
partitions-table. table. See *Note partitions-table::.

Beginning with MySQL 5.1.5, it is possible to determine which
partitions of a partitioned table are involved in a given *Note
`SELECT': select. query using *Note `EXPLAIN PARTITIONS': explain. The
`PARTITIONS' keyword adds a `partitions' column to the output of *Note
`EXPLAIN': explain. listing the partitions from which records would be
matched by the query.

Suppose that you have a table `trb1' created and populated as follows:


     CREATE TABLE trb1 (id INT, name VARCHAR(50), purchased DATE)
         PARTITION BY RANGE(id)
         (
             PARTITION p0 VALUES LESS THAN (3),
             PARTITION p1 VALUES LESS THAN (7),
             PARTITION p2 VALUES LESS THAN (9),
             PARTITION p3 VALUES LESS THAN (11)
         );

     INSERT INTO trb1 VALUES
         (1, 'desk organiser', '2003-10-15'),
         (2, 'CD player', '1993-11-05'),
         (3, 'TV set', '1996-03-10'),
         (4, 'bookcase', '1982-01-10'),
         (5, 'exercise bike', '2004-05-09'),
         (6, 'sofa', '1987-06-05'),
         (7, 'popcorn maker', '2001-11-22'),
         (8, 'aquarium', '1992-08-04'),
         (9, 'study desk', '1984-09-16'),
         (10, 'lava lamp', '1998-12-25');

You can see which partitions are used in a query such as `SELECT * FROM
trb1;', as shown here:


     mysql> EXPLAIN PARTITIONS SELECT * FROM trb1\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: trb1
        partitions: p0,p1,p2,p3
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: 10
             Extra: Using filesort

In this case, all four partitions are searched. However, when a
limiting condition making use of the partitioning key is added to the
query, you can see that only those partitions containing matching
values are scanned, as shown here:


     mysql> EXPLAIN PARTITIONS SELECT * FROM trb1 WHERE id < 5\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: trb1
        partitions: p0,p1
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: 10
             Extra: Using where

*Note `EXPLAIN PARTITIONS': explain. provides information about keys
used and possible keys, just as with the standard *Note `EXPLAIN
SELECT': explain. statement:


     mysql> ALTER TABLE trb1 ADD PRIMARY KEY (id);
     Query OK, 10 rows affected (0.03 sec)
     Records: 10  Duplicates: 0  Warnings: 0

     mysql> EXPLAIN PARTITIONS SELECT * FROM trb1 WHERE id < 5\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: trb1
        partitions: p0,p1
              type: range
     possible_keys: PRIMARY
               key: PRIMARY
           key_len: 4
               ref: NULL
              rows: 7
             Extra: Using where

You should take note of the following restrictions and limitations on
*Note `EXPLAIN PARTITIONS': explain.:

   * You cannot use the `PARTITIONS' and `EXTENDED' keywords together
     in the same *Note `EXPLAIN ... SELECT': explain. statement.
     Attempting to do so produces a syntax error.

   * If *Note `EXPLAIN PARTITIONS': explain. is used to examine a query
     against a nonpartitioned table, no error is produced, but the
     value of the `partitions' column is always `NULL'.

As of MySQL 5.1.28, the `rows' column of *Note `EXPLAIN PARTITIONS':
explain. output always displays the total number of rows in the table.
Previously, this was the number of matching rows (see Bug #35745).

See also *Note explain::.


File: manual.info,  Node: partitioning-pruning,  Next: partitioning-limitations,  Prev: partitioning-management,  Up: partitioning

18.4 Partition Pruning
======================

This section discusses an optimization known as _partition pruning_,
which was implemented for partitioned tables in MySQL 5.1.6. The core
concept behind partition pruning is relatively simple, and can be
described as `Do not scan partitions where there can be no matching
values'. Suppose that you have a partitioned table `t1' defined by this
statement:


     CREATE TABLE t1 (
         fname VARCHAR(50) NOT NULL,
         lname VARCHAR(50) NOT NULL,
         region_code TINYINT UNSIGNED NOT NULL,
         dob DATE NOT NULL
     )
     PARTITION BY RANGE( region_code ) (
         PARTITION p0 VALUES LESS THAN (64),
         PARTITION p1 VALUES LESS THAN (128),
         PARTITION p2 VALUES LESS THAN (192),
         PARTITION p3 VALUES LESS THAN MAXVALUE
     );

Consider the case where you wish to obtain results from a query such as
this one:


     SELECT fname, lname, region_code, dob
         FROM t1
         WHERE region_code > 125 AND region_code < 130;

It is easy to see that none of the rows which ought to be returned will
be in either of the partitions `p0' or `p3'; that is, we need to search
only in partitions `p1' and `p2' to find matching rows. By doing so, it
is possible to expend much less time and effort in finding matching
rows than would be required to scan all partitions in the table. This
`cutting away' of unneeded partitions is known as _pruning_.  When the
optimizer can make use of partition pruning in performing a query,
execution of the query can be an order of magnitude faster than the
same query against a nonpartitioned table containing the same column
definitions and data.

The query optimizer can perform pruning whenever a `WHERE' condition
can be reduced to either one of the following two cases:

   * `PARTITION_COLUMN = CONSTANT'

   * `PARTITION_COLUMN IN (CONSTANT1, CONSTANT2, ..., CONSTANTN)'

In the first case, the optimizer simply evaluates the partitioning
expression for the value given, determines which partition contains
that value, and scans only this partition. In many cases, the equal
sign can be replaced with another arithmetic comparison, including `<',
`>', `<=', `>=', and `<>'. Some queries using `BETWEEN' in the `WHERE'
clause can also take advantage of partition pruning. See the examples
later in this section.

In the second case, the optimizer evaluates the partitioning expression
for each value in the list, creates a list of matching partitions, and
then scans only the partitions in this partition list.

Pruning can also be applied to short ranges, which the optimizer can
convert into equivalent lists of values. For instance, in the previous
example, the `WHERE' clause can be converted to `WHERE region_code IN
(126, 127, 128, 129)'. Then the optimizer can determine that the first
three values in the list are found in partition `p1', the remaining
three values in partition `p2', and that the other partitions contain no
relevant values and so do not need to be searched for matching rows.

This type of optimization can be applied whenever the partitioning
expression consists of an equality or a range which can be reduced to a
set of equalities, or when the partitioning expression represents an
increasing or decreasing relationship. Pruning can also be applied for
tables partitioned on a *Note `DATE': datetime. or *Note `DATETIME':
datetime. column when the partitioning expression uses the `YEAR()' or
`TO_DAYS()' function.

Suppose that table `t2', defined as shown here, is partitioned on a
*Note `DATE': datetime. column:


     CREATE TABLE t2 (
         fname VARCHAR(50) NOT NULL,
         lname VARCHAR(50) NOT NULL,
         region_code TINYINT UNSIGNED NOT NULL,
         dob DATE NOT NULL
     )
     PARTITION BY RANGE( YEAR(dob) ) (
         PARTITION d0 VALUES LESS THAN (1970),
         PARTITION d1 VALUES LESS THAN (1975),
         PARTITION d2 VALUES LESS THAN (1980),
         PARTITION d3 VALUES LESS THAN (1985),
         PARTITION d4 VALUES LESS THAN (1990),
         PARTITION d5 VALUES LESS THAN (2000),
         PARTITION d6 VALUES LESS THAN (2005),
         PARTITION d7 VALUES LESS THAN MAXVALUE
     );

The following queries on `t2' can make of use partition pruning:


     SELECT * FROM t2 WHERE dob = '1982-06-23';

     SELECT * FROM t2 WHERE dob BETWEEN '1991-02-15' AND '1997-04-25';

     SELECT * FROM t2 WHERE dob >= '1984-06-21' AND dob <= '1999-06-21'

In the case of the last query, the optimizer can also act as follows:

  1. _Find the partition containing the low end of the range_.

     `YEAR('1984-06-21')' yields the value `1984', which is found in
     partition `d3'.

  2. _Find the partition containing the high end of the range_.

     `YEAR('1999-06-21')' evaluates to `1999', which is found in
     partition `d5'.

  3. _Scan only these two partitions and any partitions that may lie
     between them_.

     In this case, this means that only partitions `d3', `d4', and `d5'
     are scanned. The remaining partitions may be safely ignored (and
     are ignored).

*Important*:

Invalid `DATE' and `DATETIME' values referenced in the `WHERE' clause
of a query on a partitioned table are treated as `NULL'. This means
that a query such as `SELECT * FROM PARTITIONED_TABLE WHERE DATE_COLUMN
< '2008-12-00'' does not return any values (see Bug #40972).

So far, we have looked only at examples using `RANGE' partitioning, but
pruning can be applied with other partitioning types as well.

Consider a table that is partitioned by `LIST', where the partitioning
expression is increasing or decreasing, such as the table `t3' shown
here. (In this example, we assume for the sake of brevity that the
`region_code' column is limited to values between 1 and 10 inclusive.)


     CREATE TABLE t3 (
         fname VARCHAR(50) NOT NULL,
         lname VARCHAR(50) NOT NULL,
         region_code TINYINT UNSIGNED NOT NULL,
         dob DATE NOT NULL
     )
     PARTITION BY LIST(region_code) (
         PARTITION r0 VALUES IN (1, 3),
         PARTITION r1 VALUES IN (2, 5, 8),
         PARTITION r2 VALUES IN (4, 9),
         PARTITION r3 VALUES IN (6, 7, 10)
     );

For a query such as `SELECT * FROM t3 WHERE region_code BETWEEN 1 AND
3', the optimizer determines in which partitions the values 1, 2, and 3
are found (`r0' and `r1') and skips the remaining ones (`r2' and `r3').

For tables that are partitioned by `HASH' or `KEY', partition pruning
is also possible in cases in which the `WHERE' clause uses a simple `='
relation against a column used in the partitioning expression. Consider
a table created like this:


     CREATE TABLE t4 (
         fname VARCHAR(50) NOT NULL,
         lname VARCHAR(50) NOT NULL,
         region_code TINYINT UNSIGNED NOT NULL,
         dob DATE NOT NULL
     )
     PARTITION BY KEY(region_code)
     PARTITIONS 8;

Any query, such as this one, that compares a column value with a
constant can be pruned:


     SELECT * FROM t4 WHERE region_code = 7;

Pruning can also be employed for short ranges, because the optimizer
can turn such conditions into `IN' relations. For example, using the
same table `t4' as defined previously, queries such as these can be
pruned:


     SELECT * FROM t4 WHERE region_code > 2 AND region_code < 6;

     SELECT * FROM t4 WHERE region_code BETWEEN 3 AND 5;

In both these cases, the `WHERE' clause is transformed by the optimizer
into `WHERE region_code IN (3, 4, 5)'.

*Important*:

This optimization is used only if the range size is smaller than the
number of partitions. Consider this query:


     SELECT * FROM t4 WHERE region_code BETWEEN 4 AND 12;

The range in the `WHERE' clause covers 9 values (4, 5, 6, 7, 8, 9, 10,
11, 12), but `t4' has only 8 partitions. This means that the previous
query cannot be pruned.

Pruning can be used only on integer columns of tables partitioned by
`HASH' or `KEY'. For example, this query on table `t4' cannot use
pruning because `dob' is a *Note `DATE': datetime. column:


     SELECT * FROM t4 WHERE dob >= '2001-04-14' AND dob <= '2005-10-15';

However, if the table stores year values in an *Note `INT':
integer-types. column, then a query having `WHERE year_col >= 2001 AND
year_col <= 2005' can be pruned.

For a table that is partitioned by `KEY', has a composite primary key,
and uses a composite partitioning key, it is possible to perform
pruning for queries meeting the following two criteria:

   * The query must have a `WHERE' clause of the form `pkcol1 = c1 AND
     pkcol2 = c2 AND ...  pkcolN = cN', where `pkcol1' ...  `pkcolN'
     are the partitioning key columns and `c1' ...  `cN' are constant
     values.

   * All columns of the partitioning key must be referenced in the
     `WHERE' clause.

For example, suppose a table named `cities' is created as shown here:


     CREATE TABLE cities (
         id INT NOT NULL AUTO_INCREMENT,
         name CHAR(35) NOT NULL DEFAULT '',
         country_code CHAR(3) NOT NULL DEFAULT '',
         district CHAR(20) NOT NULL DEFAULT '',
         population INT NOT NULL DEFAULT 0,
         PRIMARY KEY (ID, Population)
     )
     PARTITION BY KEY ()
     PARTITIONS 8;

(Note that `PARTITION BY KEY()' is equivalent in this case to
`PARTITION BY KEY(id, population)'.)

Only a query that references both the `id' and `population' columns of
this table can be pruned, as shown here:


     mysql> SELECT * FROM cities WHERE id = 101;
     +-----+------------+--------------+----------+------------+
     | id  | name       | country_code | district | population |
     +-----+------------+--------------+----------+------------+
     | 101 | Godoy Cruz | ARG          | Mendoza  |     206998 |
     +-----+------------+--------------+----------+------------+
     1 row in set (0.00 sec)

     mysql> SELECT * FROM cities WHERE population = 206998;
     +-----+------------+--------------+----------+------------+
     | id  | name       | country_code | district | population |
     +-----+------------+--------------+----------+------------+
     | 101 | Godoy Cruz | ARG          | Mendoza  |     206998 |
     +-----+------------+--------------+----------+------------+
     1 row in set (0.00 sec)

     mysql> EXPLAIN PARTITIONS SELECT * FROM cities WHERE id = 101\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: cities
        partitions: p0,p1,p2,p3,p4,p5,p6,p7
              type: ref
     possible_keys: PRIMARY
               key: PRIMARY
           key_len: 4
               ref: const
              rows: 6
             Extra:
     1 row in set (0.00 sec)

     mysql> EXPLAIN PARTITIONS SELECT * FROM cities WHERE population = 206998\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: cities
        partitions: p0,p1,p2,p3,p4,p5,p6,p7
              type: ALL
     possible_keys: NULL
               key: NULL
           key_len: NULL
               ref: NULL
              rows: 1973
             Extra: Using where
     1 row in set (0.00 sec)

     mysql> EXPLAIN PARTITIONS SELECT * FROM cities WHERE id = 101 AND population = 206998\G
     *************************** 1. row ***************************
                id: 1
       select_type: SIMPLE
             table: cities
        partitions: p2
              type: const
     possible_keys: PRIMARY
               key: PRIMARY
           key_len: 8
               ref: const,const
              rows: 1
             Extra:
     1 row in set (0.00 sec)

This limitation on pruning with composite partitioning keys is removed
in MySQL 5.5.


File: manual.info,  Node: partitioning-limitations,  Prev: partitioning-pruning,  Up: partitioning

18.5 Restrictions and Limitations on Partitioning
=================================================

* Menu:

* partitioning-limitations-partitioning-keys-unique-keys::  Partitioning Keys, Primary Keys, and Unique Keys
* partitioning-limitations-storage-engines::  Partitioning Limitations Relating to Storage Engines
* partitioning-limitations-functions::  Partitioning Limitations Relating to Functions
* partitioning-limitations-locking::  Partitioning and Table-Level Locking

This section discusses current restrictions and limitations on MySQL
partitioning support.

Prohibited constructs

Beginning with MySQL 5.1.12, the following constructs are not permitted
in partitioning expressions:

   * Stored procedures, stored functions, UDFs, or plugins.

   * Declared variables or user variables.

For a list of SQL functions which are permitted in partitioning
expressions, see *Note partitioning-limitations-functions::.

Arithmetic and logical operators

Use of the arithmetic operators `+', `-', and `*' is permitted in
partitioning expressions. However, the result must be an integer value
or `NULL' (except in the case of `[LINEAR] KEY' partitioning, as
discussed elsewhere in this chapter; see *Note partitioning-types::,
for more information).

Beginning with MySQL 5.1.23, the `DIV' operator is also supported, and
the `/' operator is not permitted. (Bug #30188, Bug #33182)

Beginning with MySQL 5.1.12, the bit operators `|', `&', `^', `<<',
`>>', and `~' are not permitted in partitioning expressions.

HANDLER statements

In MySQL 5.1, the *Note `HANDLER': handler. statement is not supported
with partitioned tables.

Server SQL mode

Tables employing user-defined partitioning do not preserve the SQL mode
in effect at the time that they were created. As discussed in *Note
sql-mode::, the results of many MySQL functions and operators may
change according to the server SQL mode. Therefore, a change in the SQL
mode at any time after the creation of partitioned tables may lead to
major changes in the behavior of such tables, and could easily lead to
corruption or loss of data. For these reasons, _it is strongly
recommended that you never change the server SQL mode after creating
partitioned tables_.

Examples

The following examples illustrate some changes in behavior of
partitioned tables due to a change in the server SQL mode:

  1. Error handling

     Suppose that you create a partitioned table whose partitioning
     expression is one such as `COLUMN DIV 0' or `COLUMN MOD 0', as
     shown here:


          mysql> CREATE TABLE tn (c1 INT)
              ->     PARTITION BY LIST(1 DIV c1) (
              ->       PARTITION p0 VALUES IN (NULL),
              ->       PARTITION p1 VALUES IN (1)
              -> );
          Query OK, 0 rows affected (0.05 sec)

     The default behavior for MySQL is to return `NULL' for the result
     of a division by zero, without producing any errors:


          mysql> SELECT @@sql_mode;
          +------------+
          | @@sql_mode |
          +------------+
          |            |
          +------------+
          1 row in set (0.00 sec)

          mysql> INSERT INTO tn VALUES (NULL), (0), (1);
          Query OK, 3 rows affected (0.00 sec)
          Records: 3  Duplicates: 0  Warnings: 0

     However, changing the server SQL mode to treat division by zero as
     an error and to enforce strict error handling causes the same
     *Note `INSERT': insert. statement to fail, as shown here:


          mysql> SET sql_mode='STRICT_ALL_TABLES,ERROR_FOR_DIVISION_BY_ZERO';
          Query OK, 0 rows affected (0.00 sec)

          mysql> INSERT INTO tn VALUES (NULL), (0), (1);
          `ERROR 1365 (22012): Division by 0'

  2. Table accessibility

     Sometimes a change in the server SQL mode can make partitioned
     tables unusable. The following *Note `CREATE TABLE': create-table.
     statement can be executed successfully only if the
     `NO_UNSIGNED_SUBTRACTION' mode is in effect:


          mysql> SELECT @@sql_mode;
          +------------+
          | @@sql_mode |
          +------------+
          |            |
          +------------+
          1 row in set (0.00 sec)

          mysql> CREATE TABLE tu (c1 BIGINT UNSIGNED)
              ->   PARTITION BY RANGE(c1 - 10) (
              ->     PARTITION p0 VALUES LESS THAN (-5),
              ->     PARTITION p1 VALUES LESS THAN (0),
              ->     PARTITION p2 VALUES LESS THAN (5),
              ->     PARTITION p3 VALUES LESS THAN (10),
              ->     PARTITION p4 VALUES LESS THAN (MAXVALUE)
              -> );
          `ERROR 1563 (HY000): Partition constant is out of partition function domain'

          mysql> SET sql_mode='NO_UNSIGNED_SUBTRACTION';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT @@sql_mode;
          +-------------------------+
          | @@sql_mode              |
          +-------------------------+
          | NO_UNSIGNED_SUBTRACTION |
          +-------------------------+
          1 row in set (0.00 sec)

          mysql> CREATE TABLE tu (c1 BIGINT UNSIGNED)
              ->   PARTITION BY RANGE(c1 - 10) (
              ->     PARTITION p0 VALUES LESS THAN (-5),
              ->     PARTITION p1 VALUES LESS THAN (0),
              ->     PARTITION p2 VALUES LESS THAN (5),
              ->     PARTITION p3 VALUES LESS THAN (10),
              ->     PARTITION p4 VALUES LESS THAN (MAXVALUE)
              -> );
          Query OK, 0 rows affected (0.05 sec)

     If you remove the `NO_UNSIGNED_SUBTRACTION' server SQL mode after
     creating `tu', you may no longer be able to access this table:


          mysql> SET sql_mode='';
          Query OK, 0 rows affected (0.00 sec)

          mysql> SELECT * FROM tu;
          `ERROR 1563 (HY000): Partition constant is out of partition function domain'
          mysql> INSERT INTO tu VALUES (20);
          `ERROR 1563 (HY000): Partition constant is out of partition function domain'

Server SQL modes also impact replication of partitioned tables.
Differing SQL modes on master and slave can lead to partitioning
expressions being evaluated differently; this can cause the
distribution of data among partitions to be different in the master's
and slave's copies of a given table, and may even cause inserts into
partitioned tables that succeed on the master to fail on the slave. For
best results, you should always use the same server SQL mode on the
master and on the slave.

Performance considerations

Some affects of partitioning operations on performance are given in the
following list:

   * File system operations

     Partitioning and repartitioning operations (such as *Note `ALTER
     TABLE': alter-table-partition-operations. with `PARTITION BY ...',
     `REORGANIZE PARTITIONS', or `REMOVE PARTITIONING') depend on file
     system operations for their implementation. This means that the
     speed of these operations is affected by such factors as file
     system type and characteristics, disk speed, swap space, file
     handling efficiency of the operating system, and MySQL server
     options and variables that relate to file handling. In particular,
     you should make sure that `large_files_support' is enabled and that
     `open_files_limit' is set properly. For partitioned tables using
     the `MyISAM' storage engine, increasing `myisam_max_sort_file_size'
     may improve performance; partitioning and repartitioning
     operations involving `InnoDB' tables may be made more efficient by
     enabling `innodb_file_per_table'.

     See also *Note partitioning-limitations-max-partitions::.

   * Table locks

     The process executing a partitioning operation on a table takes a
     write lock on the table. Reads from such tables are relatively
     unaffected; pending *Note `INSERT': insert. and *Note `UPDATE':
     update. operations are performed as soon as the partitioning
     operation has completed.

   * Storage engine

     Partitioning operations, queries, and update operations generally
     tend to be faster with `MyISAM' tables than with `InnoDB' or *Note
     `NDB': mysql-cluster. tables.

   * Indexes; partition pruning

     As with nonpartitioned tables, proper use of indexes can speed up
     queries on partitioned tables significantly. In addition,
     designing partitioned tables and queries on these tables to take
     advantage of _partition pruning_ can improve performance
     dramatically.  See *Note partitioning-pruning::, for more
     information.

   * Performance with LOAD DATA

     Prior to MySQL 5.1.23, *Note `LOAD DATA': load-data. performed
     very poorly when importing into partitioned tables. The statement
     now uses buffering to improve performance; however, the buffer
     uses 130 KB memory per partition to achieve this. (Bug #26527)

Maximum number of partitions

The maximum possible number of partitions for a given table (that does
not use the *Note `NDB': mysql-cluster. storage engine) is 1024. This
number includes subpartitions.

The maximum possible number of user-defined partitions for a table
using the *Note `NDBCLUSTER': mysql-cluster. storage engine is
determined according to the version of the MySQL Cluster software being
used, the number of data nodes, and other factors.  See *Note
mysql-cluster-nodes-groups-user-partitioning::, for more information.

If, when creating tables with a large number of partitions (but less
than the maximum), you encounter an error message such as `Got error
... from storage engine: Out of resources when opening file', you may
be able to address the issue by increasing the value of the
`open_files_limit' system variable.  However, this is dependent on the
operating system, and may not be possible or advisable on all
platforms; see *Note not-enough-file-handles::, for more information.
In some cases, using large numbers (hundreds) of partitions may also
not be advisable due to other concerns, so using more partitions does
not automatically lead to better results.

See also *Note partitioning-limitations-file-system-ops::.

Foreign keys not supported for partitioned InnoDB tables

Partitioned tables using the *Note `InnoDB': innodb-storage-engine.
storage engine do not support foreign keys. More specifically, this
means that the following two statements are true:

  1. No definition of an `InnoDB' table employing user-defined
     partitioning may contain foreign key references; no `InnoDB' table
     whose definition contains foreign key references may be
     partitioned.

  2. No `InnoDB' table definition may contain a foreign key reference
     to a user-partitioned table; no `InnoDB' table with user-defined
     partitioning may contain columns referenced by foreign keys.

The scope of the restrictions just listed includes all tables that use
the `InnoDB' storage engine.  *Note `CREATE TABLE':
create-table-foreign-keys. and *Note `ALTER TABLE': alter-table.
statements that would result in tables violating these restrictions are
not allowed.

ALTER TABLE ... ORDER BY

An `ALTER TABLE ... ORDER BY COLUMN' statement run against a
partitioned table causes ordering of rows only within each partition.

Effects on REPLACE statements by modification of primary keys

It can be desirable in some cases (see *Note
partitioning-limitations-partitioning-keys-unique-keys::) to modify a
table's primary key. Be aware that, if your application uses *Note
`REPLACE': replace.  statements and you do this, the results of these
statements can be drastically altered. See *Note replace::, for more
information and an example.

FULLTEXT indexes

Partitioned tables do not support `FULLTEXT' indexes or searches. This
includes partitioned tables employing the *Note `MyISAM':
myisam-storage-engine. storage engine.

Spatial columns

Columns with spatial data types such as `POINT' or `GEOMETRY' cannot be
used in partitioned tables.

Temporary tables

As of MySQL 5.1.8, temporary tables cannot be partitioned. (Bug #17497)

Log tables

Beginning with MySQL 5.1.20, it is no longer possible to partition the
log tables; beginning with that version, an *Note `ALTER TABLE ...
PARTITION BY ...': alter-table-partition-operations. statement on such
a table fails with an error. (Bug #27816)

Data type of partitioning key

A partitioning key must be either an integer column or an expression
that resolves to an integer. The column or expression value may also be
`NULL'. (See *Note partitioning-handling-nulls::.)

The lone exception to this restriction occurs when partitioning by
[`LINEAR'] `KEY', where it is possible to use columns of other types as
partitioning keys, because MySQL's internal key-hashing functions
produce the correct data type from these types. For example, the
following *Note `CREATE TABLE': create-table. statement is valid:


     CREATE TABLE tkc (c1 CHAR)
     PARTITION BY KEY(c1)
     PARTITIONS 4;

This exception does _not_ apply to *Note `BLOB': blob. or *Note `TEXT':
blob. column types.

Subqueries

A partitioning key may not be a subquery, even if that subquery
resolves to an integer value or `NULL'.

Issues with subpartitions

Subpartitions must use `HASH' or `KEY' partitioning. Only `RANGE' and
`LIST' partitions may be subpartitioned; `HASH' and `KEY' partitions
cannot be subpartitioned.

Currently, `SUBPARTITION BY KEY' requires that the subpartitioning
column or columns be specified explicitly, unlike the case with
`PARTITION BY KEY', where it can be omitted (in which case the table's
primary key column is used by default). Consider the table created by
this statement:


     CREATE TABLE ts (
         id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         name VARCHAR(30)
     );

You can create a table having the same columns, partitioned by `KEY',
using a statement such as this one:


     CREATE TABLE ts (
         id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         name VARCHAR(30)
     )
     PARTITION BY KEY()
     PARTITIONS 4;

The previous statement is treated as though it had been written like
this, with the table's primary key column used as the partitioning
column:


     CREATE TABLE ts (
         id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         name VARCHAR(30)
     )
     PARTITION BY KEY(id)
     PARTITIONS 4;

However, the following statement that attempts to create a
subpartitioned table using the default column as the subpartitioning
column fails, and the column must be specified for the statement to
succeed, as shown here:


     mysql> CREATE TABLE ts (
         ->     id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         ->     name VARCHAR(30)
         -> )
         -> PARTITION BY RANGE(id)
         -> SUBPARTITION BY KEY()
         -> SUBPARTITIONS 4
         -> (
         ->     PARTITION p0 VALUES LESS THAN (100),
         ->     PARTITION p1 VALUES LESS THAN (MAXVALUE)
         -> );
     `ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that
     corresponds to your MySQL server version for the right syntax to use near ')'

     mysql> CREATE TABLE ts (
         ->     id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
         ->     name VARCHAR(30)
         -> )
         -> PARTITION BY RANGE(id)
         -> SUBPARTITION BY KEY(id)
         -> SUBPARTITIONS 4
         -> (
         ->     PARTITION p0 VALUES LESS THAN (100),
         ->     PARTITION p1 VALUES LESS THAN (MAXVALUE)
         -> );
     Query OK, 0 rows affected (0.07 sec)

This is a known issue (see Bug #51470).

Query cache not supported

The query cache is not supported for partitioned tables.  Beginning
with MySQL 5.1.63, the query cache is automatically disabled for
queries involving partitioned tables, and cannot be enabled for such
queries. (Bug #53775)

Key cache not supported

Caching is not supported for partitioned tables. The *Note `CACHE
INDEX': cache-index. and *Note `LOAD INDEX INTO CACHE': load-index.
statements, when you attempt to use them on tables having user-defined
partitioning, fail with the errors `The storage engine for the table
doesn't support assign_to_keycache' and `The storage engine for the
table doesn't support preload_keys', respectively. This issue is fixed
in MySQL 5.5.

DELAYED option not supported

Use of *Note `INSERT DELAYED': insert-delayed. to insert rows into a
partitioned table is not supported. Beginning with MySQL 5.1.23,
attempting to do so fails with an error (see Bug #31210).

DATA DIRECTORY and INDEX DIRECTORY options

`DATA DIRECTORY' and `INDEX DIRECTORY' are subject to the following
restrictions when used with partitioned tables:

   * Beginning with MySQL 5.1.23, table-level `DATA DIRECTORY' and
     `INDEX DIRECTORY' options are ignored (see Bug #32091).

   * On Windows, the `DATA DIRECTORY' and `INDEX DIRECTORY' options are
     not supported for individual partitions or subpartitions (Bug
     #30459).

Repairing and rebuilding partitioned tables

The statements *Note `CHECK TABLE': check-table, *Note `OPTIMIZE
TABLE': optimize-table, *Note `ANALYZE TABLE': analyze-table, and *Note
`REPAIR TABLE': repair-table. are supported for partitioned tables
beginning with MySQL 5.1.27. (See Bug #20129.)

In addition, you can use `ALTER TABLE ... REBUILD PARTITION' to rebuild
one or more partitions of a partitioned table; `ALTER TABLE ...
REORGANIZE PARTITION' also causes partitions to be rebuilt. Both of
these statements were added in MySQL 5.1.5. See *Note alter-table::,
for more information about these two statements.

*Note `mysqlcheck': mysqlcheck, *Note `myisamchk': myisamchk, and *Note
`myisampack': myisampack. are not supported with partitioned tables.


File: manual.info,  Node: partitioning-limitations-partitioning-keys-unique-keys,  Next: partitioning-limitations-storage-engines,  Prev: partitioning-limitations,  Up: partitioning-limitations

18.5.1 Partitioning Keys, Primary Keys, and Unique Keys
-------------------------------------------------------

This section discusses the relationship of partitioning keys with
primary keys and unique keys. The rule governing this relationship can
be expressed as follows: All columns used in the partitioning
expression for a partitioned table must be part of every unique key
that the table may have.

In other words, _every unique key on the table must use every column in
the table's partitioning expression_.  (This also includes the table's
primary key, since it is by definition a unique key. This particular
case is discussed later in this section.) For example, each of the
following table creation statements is invalid:


     CREATE TABLE t1 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         UNIQUE KEY (col1, col2)
     )
     PARTITION BY HASH(col3)
     PARTITIONS 4;

     CREATE TABLE t2 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         UNIQUE KEY (col1),
         UNIQUE KEY (col3)
     )
     PARTITION BY HASH(col1 + col3)
     PARTITIONS 4;

In each case, the proposed table would have at least one unique key
that does not include all columns used in the partitioning expression.

Each of the following statements is valid, and represents one way in
which the corresponding invalid table creation statement could be made
to work:


     CREATE TABLE t1 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         UNIQUE KEY (col1, col2, col3)
     )
     PARTITION BY HASH(col3)
     PARTITIONS 4;

     CREATE TABLE t2 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         UNIQUE KEY (col1, col3)
     )
     PARTITION BY HASH(col1 + col3)
     PARTITIONS 4;

This example shows the error produced in such cases:


     mysql> CREATE TABLE t3 (
         ->     col1 INT NOT NULL,
         ->     col2 DATE NOT NULL,
         ->     col3 INT NOT NULL,
         ->     col4 INT NOT NULL,
         ->     UNIQUE KEY (col1, col2),
         ->     UNIQUE KEY (col3)
         -> )
         -> PARTITION BY HASH(col1 + col3)
         -> PARTITIONS 4;
     `ERROR 1491 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function'

The *Note `CREATE TABLE': create-table. statement fails because both
`col1' and `col3' are included in the proposed partitioning key, but
neither of these columns is part of both of unique keys on the table.
This shows one possible fix for the invalid table definition:


     mysql> CREATE TABLE t3 (
         ->     col1 INT NOT NULL,
         ->     col2 DATE NOT NULL,
         ->     col3 INT NOT NULL,
         ->     col4 INT NOT NULL,
         ->     UNIQUE KEY (col1, col2, col3),
         ->     UNIQUE KEY (col3)
         -> )
         -> PARTITION BY HASH(col3)
         -> PARTITIONS 4;
     Query OK, 0 rows affected (0.05 sec)

In this case, the proposed partitioning key `col3' is part of both
unique keys, and the table creation statement succeeds.

The following table cannot be partitioned at all, because there is no
way to include in a partitioning key any columns that belong to both
unique keys:


     CREATE TABLE t4 (
         col1 INT NOT NULL,
         col2 INT NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         UNIQUE KEY (col1, col3),
         UNIQUE KEY (col2, col4)
     );

Since every primary key is by definition a unique key, this restriction
also includes the table's primary key, if it has one. For example, the
next two statements are invalid:


     CREATE TABLE t5 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         PRIMARY KEY(col1, col2)
     )
     PARTITION BY HASH(col3)
     PARTITIONS 4;

     CREATE TABLE t6 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         PRIMARY KEY(col1, col3),
         UNIQUE KEY(col2)
     )
     PARTITION BY HASH( YEAR(col2) )
     PARTITIONS 4;

In both cases, the primary key does not include all columns referenced
in the partitioning expression. However, both of the next two
statements are valid:


     CREATE TABLE t7 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         PRIMARY KEY(col1, col2)
     )
     PARTITION BY HASH(col1 + YEAR(col2))
     PARTITIONS 4;

     CREATE TABLE t8 (
         col1 INT NOT NULL,
         col2 DATE NOT NULL,
         col3 INT NOT NULL,
         col4 INT NOT NULL,
         PRIMARY KEY(col1, col2, col4),
         UNIQUE KEY(col2, col1)
     )
     PARTITION BY HASH(col1 + YEAR(col2))
     PARTITIONS 4;

If a table has no unique keys--this includes having no primary
key--then this restriction does not apply, and you may use any column
or columns in the partitioning expression as long as the column type is
compatible with the partitioning type.

For the same reason, you cannot later add a unique key to a partitioned
table unless the key includes all columns used by the table's
partitioning expression. Consider the partitioned table created as
shown here:


     mysql> CREATE TABLE t_no_pk (c1 INT, c2 INT)
         ->     PARTITION BY RANGE(c1) (
         ->         PARTITION p0 VALUES LESS THAN (10),
         ->         PARTITION p1 VALUES LESS THAN (20),
         ->         PARTITION p2 VALUES LESS THAN (30),
         ->         PARTITION p3 VALUES LESS THAN (40)
         ->     );
     Query OK, 0 rows affected (0.12 sec)

It is possible to add a primary key to `t_no_pk' using either of these
*Note `ALTER TABLE': alter-table-partition-operations. statements:


     #  possible PK
     mysql> ALTER TABLE t_no_pk ADD PRIMARY KEY(c1);
     Query OK, 0 rows affected (0.13 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     # drop this PK
     mysql> ALTER TABLE t_no_pk DROP PRIMARY KEY;
     Query OK, 0 rows affected (0.10 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     #  use another possible PK
     mysql> ALTER TABLE t_no_pk ADD PRIMARY KEY(c1, c2);
     Query OK, 0 rows affected (0.12 sec)
     Records: 0  Duplicates: 0  Warnings: 0

     # drop this PK
     mysql> ALTER TABLE t_no_pk DROP PRIMARY KEY;
     Query OK, 0 rows affected (0.09 sec)
     Records: 0  Duplicates: 0  Warnings: 0

However, the next statement fails, because `c1' is part of the
partitioning key, but is not part of the proposed primary key:


     #  fails with error 1503
     mysql> ALTER TABLE t_no_pk ADD PRIMARY KEY(c2);
     `ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function'

Since `t_no_pk' has only `c1' in its partitioning expression,
attempting to adding a unique key on `c2' alone fails. However, you can
add a unique key that uses both `c1' and `c2'.

These rules also apply to existing nonpartitioned tables that you wish
to partition using *Note `ALTER TABLE ... PARTITION BY':
alter-table-partition-operations. Consider a table `np_pk' created as
shown here:


     mysql> CREATE TABLE np_pk (
         ->     id INT NOT NULL AUTO_INCREMENT,
         ->     name VARCHAR(50),
         ->     added DATE,
         ->     PRIMARY KEY (id)
         -> );
     Query OK, 0 rows affected (0.08 sec)

The following *Note `ALTER TABLE': alter-table-partition-operations.
statement fails with an error, because the `added' column is not part
of any unique key in the table:


     mysql> ALTER TABLE np_pk
         ->     PARTITION BY HASH( TO_DAYS(added) )
         ->     PARTITIONS 4;
     `ERROR 1503 (HY000): A PRIMARY KEY must include all columns in the table's partitioning function'

However, this statement using the `id' column for the partitioning
column is valid, as shown here:


     mysql> ALTER TABLE np_pk
         ->     PARTITION BY HASH(id)
         ->     PARTITIONS 4;
     Query OK, 0 rows affected (0.11 sec)
     Records: 0  Duplicates: 0  Warnings: 0

In the case of `np_pk', the only column that may be used as part of a
partitioning expression is `id'; if you wish to partition this table
using any other column or columns in the partitioning expression, you
must first modify the table, either by adding the desired column or
columns to the primary key, or by dropping the primary key altogether.


File: manual.info,  Node: partitioning-limitations-storage-engines,  Next: partitioning-limitations-functions,  Prev: partitioning-limitations-partitioning-keys-unique-keys,  Up: partitioning-limitations

18.5.2 Partitioning Limitations Relating to Storage Engines
-----------------------------------------------------------

The following limitations apply to the use of storage engines with
user-defined partitioning of tables.

MERGE storage engine

User-defined partitioning and the `MERGE' storage engine are not
compatible. Tables using the `MERGE' storage engine cannot be
partitioned.  Partitioned tables cannot be merged.

FEDERATED storage engine

Partitioning of `FEDERATED' tables is not supported. Beginning with
MySQL 5.1.15, it is not possible to create partitioned `FEDERATED'
tables at all.

CSV storage engine

Partitioned tables using the `CSV' storage engine are not supported.
Starting with MySQL 5.1.12, it is not possible to create partitioned
`CSV' tables at all.

BLACKHOLE storage engine

Prior to MySQL 5.1.6, tables using the `BLACKHOLE' storage engine also
could not be partitioned.

InnoDB storage engine

*Note `InnoDB': innodb-storage-engine. foreign keys and MySQL
partitioning are not compatible. Partitioned `InnoDB' tables cannot
have foreign key references, nor can they have columns referenced by
foreign keys. `InnoDB' tables which have or which are referenced by
foreign keys cannot be partitioned.

In addition, *Note `ALTER TABLE ... OPTIMIZE PARTITION':
alter-table-partition-operations. does not work correctly with
partitioned tables that use the `InnoDB' storage engine. Use `ALTER
TABLE ... REBUILD PARTITION' and `ALTER TABLE ... ANALYZE PARTITION',
instead, for such tables. For more information, see *Note
alter-table-partition-operations::.

NDBCLUSTER storage engine (MySQL Cluster)

Partitioning by `KEY' (including `LINEAR KEY') is the only type of
partitioning supported for the *Note `NDBCLUSTER': mysql-cluster.
storage engine.  Beginning with MySQL 5.1.12, it is not possible to
create a MySQL Cluster table using any partitioning type other than
[`LINEAR'] `KEY', and attempting to do so fails with an error.

In addition, the maximum number of partitions that can be defined for
an *Note `NDBCLUSTER': mysql-cluster. table depends on the number of
data nodes and node groups in the cluster, the version of the MySQL
Cluster software in use, and other factors. See *Note
mysql-cluster-nodes-groups-user-partitioning::, for more information.

Beginning with MySQL Cluster NDB 6.2.18, MySQL Cluster NDB 6.3.25, and
MySQL Cluster NDB 7.0.6, *Note `CREATE TABLE': create-table. and *Note
`ALTER TABLE': alter-table-partition-operations. statements that would
cause a user-partitioned *Note `NDBCLUSTER': mysql-cluster. table not
to meet either or both of the following two requirements are not
permitted, and fail with an error (Bug #40709):

  1. The table must have an explicit primary key.

  2. All columns listed in the table's partitioning expression must be
     part of the primary key.

Exception

If a user-partitioned *Note `NDBCLUSTER': mysql-cluster.  table is
created using an empty column-list (that is, using `PARTITION BY KEY()'
or `PARTITION BY LINEAR KEY()'), then no explicit primary key is
required.

Upgrading partitioned tables

When performing an upgrade, tables which are partitioned by `KEY' and
which use any storage engine other than *Note `NDBCLUSTER':
mysql-cluster. must be dumped and reloaded.

Same storage engine for all partitions

All partitions of a partitioned table must use the same storage engine
and it must be the same storage engine used by the table as a whole. In
addition, if one does not specify an engine on the table level, then
one must do either of the following when creating or altering a
partitioned table:

   * Do _not_ specify any engine for _any_ partition or subpartition

   * Specify the engine for _all_ partitions or subpartitions


File: manual.info,  Node: partitioning-limitations-functions,  Next: partitioning-limitations-locking,  Prev: partitioning-limitations-storage-engines,  Up: partitioning-limitations

18.5.3 Partitioning Limitations Relating to Functions
-----------------------------------------------------

This section discusses limitations in MySQL Partitioning relating
specifically to functions used in partitioning expressions.

Beginning with MySQL 5.1.12, only the MySQL functions allowed in the
following table are allowed in partitioning expressions.

This table lists the functions that are allowed in partitioning
expressions as of MySQL 5.1.12. Functions are presented in a three
column table format and in alphabetical order from left to right.

`ABS()'                  `CEILING()' (see *Note   `DAY()'
                         partitioning-limitations-ceiling-floor::)
`DAYOFMONTH()'           `DAYOFWEEK()'            `DAYOFYEAR()'
`DATEDIFF()'             `EXTRACT()' (see *Note   `FLOOR()' (see *Note
                         partitioning-limitations-extract::)partitioning-limitations-ceiling-floor::)
`HOUR()'                 `MICROSECOND()'          `MINUTE()'
`MOD()'                  `MONTH()'                `QUARTER()'
`SECOND()'               `TIME_TO_SEC()'          `TO_DAYS()'
`UNIX_TIMESTAMP()'       `WEEKDAY()'              `YEAR()'
(permitted in MySQL                               
5.1.43 and later, with                            
*Note `TIMESTAMP':                                
datetime. columns)                                
                         `YEARWEEK()'             

In MySQL 5.1, range optimization can be used only for the `TO_DAYS()'
and `YEAR()' functions. See *Note partitioning-pruning::, for more
information.

CEILING() and FLOOR()

Each of these functions returns an integer only if it is passed an
argument of an exact numeric type, such as one of the *Note `INT':
integer-types. types or *Note `DECIMAL': fixed-point-types. This means,
for example, that the following *Note `CREATE TABLE': create-table.
statement fails with an error, as shown here:


     mysql> CREATE TABLE t (c FLOAT) PARTITION BY LIST( FLOOR(c) )(
         ->     PARTITION p0 VALUES IN (1,3,5),
         ->     PARTITION p1 VALUES IN (2,4,6)
         -> );
     `ERROR 1490 (HY000): The PARTITION function returns the wrong type'

EXTRACT() function with WEEK specifier

The value returned by the `EXTRACT()' function, when used as
`EXTRACT(WEEK FROM COL)', depends on the value of the
`default_week_format' system variable. For this reason, beginning with
MySQL 5.1.55, `EXTRACT()' is no longer permitted as a partitioning
function when it specifies the unit as `WEEK'. (Bug #54483)

See *Note mathematical-functions::, for more information about the
return types of these functions, as well as *Note numeric-types::.


File: manual.info,  Node: partitioning-limitations-locking,  Prev: partitioning-limitations-functions,  Up: partitioning-limitations

18.5.4 Partitioning and Table-Level Locking
-------------------------------------------

For storage engines such as *Note `MyISAM': myisam-storage-engine.
that actually execute table-level locks when executing DML or DDL
statements, such a statement affecting a partitioned table imposes a
lock on the table as a whole; that is, all partitions are locked until
the statement was finished. For example, a *Note `SELECT': select. from
a partitioned `MyISAM' table causes a lock on the entire table.

In practical terms, what this means is that the statements discussed
later in this section tend to execute more slowly as the number of
partitions increases. This limitation is greatly reduced in MySQL 5.6,
with the introduction of _partition lock pruning_ in MySQL 5.6.6.

This is not true for statements effecting partitioned tables using
storage engines such as *Note `InnoDB': innodb-storage-engine, that
employ row-level locking and do not actually perform (or need to
perform) the locks prior to partition pruning.

The next few paragraphs discuss the effects of MySQL statements on
partitioned tables using storage engines that employ table-level locks.

*DML statements*

*Note `SELECT': select. statements lock the entire table. `SELECT'
statements containing unions or joins lock all tables named in the
union or join.

*Note `UPDATE': update. also locks the entire table.

*Note `REPLACE': replace. and *Note `INSERT': insert. (including *Note
`INSERT ... ON DUPLICATE KEY UPDATE': insert-on-duplicate.) lock the
entire table.

*Note `INSERT ... SELECT': insert-select. locks both the source table
and the target table.

*Note*:

*Note `INSERT DELAYED': insert-delayed. is not supported for
partitioned tables.

A *Note `LOAD DATA': load-data.  statement on a partitioned table locks
the entire table.

A trigger on a partitioned table, once activated, locks the entire
table.

*DDL statements*

*Note `CREATE VIEW': create-view. causes a lock on any partitioned
table from which it reads.

*Note `ALTER TABLE': alter-table. locks the affected partitioned table.

*Other statements*

*Note `LOCK TABLES': lock-tables. locks all partitions of a partioned
table.

Evaluating the EXPR in a *Note `CALL stored_procedure(EXPR)': call.
statement locks all partitions of any partitioned table referenced by
EXPR.

*Note `ALTER TABLE': alter-table. also takes a metadata lock on the
table level.


File: manual.info,  Node: stored-programs-views,  Next: information-schema,  Prev: partitioning,  Up: Top

19 Stored Programs and Views
****************************

* Menu:

* stored-programs-defining::     Defining Stored Programs
* stored-routines::              Using Stored Routines (Procedures and Functions)
* triggers::                     Using Triggers
* events::                       Using the Event Scheduler
* views::                        Using Views
* stored-programs-security::     Access Control for Stored Programs and Views
* stored-programs-logging::      Binary Logging of Stored Programs

This chapter discusses stored programs and views, which are database
objects defined in terms of SQL code that is stored on the server for
later execution.

Stored programs include these objects:

   * Stored routines, that is, stored procedures and functions. A
     stored procedure is invoked using the *Note `CALL': call.
     statement. A procedure does not have a return value but can modify
     its parameters for later inspection by the caller. It can also
     generate result sets to be returned to the client program. A
     stored function is used much like a built-in function. you invoke
     it in an expression and it returns a value during expression
     evaluation.

   * Triggers. A trigger is a named database object that is associated
     with a table and that is activated when a particular event occurs
     for the table, such as an insert or update.

   * Events. An event is a task that the server runs according to
     schedule.

Views are stored queries that when referenced produce a result set.  A
view acts as a virtual table.

This chapter describes how to use stored programs and views. The
following sections provide additional information about SQL syntax for
statements related to these objects:

   * For each object type, there are `CREATE', `ALTER', and `DROP'
     statements that control which objects exist and how they are
     defined. See *Note sql-syntax-data-definition::.

   * The *Note `CALL': call. statement is used to invoke stored
     procedures. See *Note call::.

   * Stored program definitions include a body that may use compound
     statements, loops, conditionals, and declared variables. See *Note
     sql-syntax-compound-statements::.


File: manual.info,  Node: stored-programs-defining,  Next: stored-routines,  Prev: stored-programs-views,  Up: stored-programs-views

19.1 Defining Stored Programs
=============================

Each stored program contains a body that consists of an SQL statement.
This statement may be a compound statement made up of several
statements separated by semicolon (`;') characters. For example, the
following stored procedure has a body made up of a *Note `BEGIN ...
END': begin-end. block that contains a *Note `SET': set-statement.
statement and a *Note `REPEAT': repeat. loop that itself contains
another *Note `SET': set-statement.  statement:


     CREATE PROCEDURE dorepeat(p1 INT)
     BEGIN
       SET @x = 0;
       REPEAT SET @x = @x + 1; UNTIL @x > p1 END REPEAT;
     END;

If you use the *Note `mysql': mysql. client program to define a stored
program containing semicolon characters, a problem arises.  By default,
*Note `mysql': mysql. itself recognizes the semicolon as a statement
delimiter, so you must redefine the delimiter temporarily to cause
*Note `mysql': mysql. to pass the entire stored program definition to
the server.

To redefine the *Note `mysql': mysql. delimiter, use the `delimiter'
command. The following example shows how to do this for the
`dorepeat()' procedure just shown. The delimiter is changed to `//' to
enable the entire definition to be passed to the server as a single
statement, and then restored to `;' before invoking the procedure. This
enables the `;' delimiter used in the procedure body to be passed
through to the server rather than being interpreted by *Note `mysql':
mysql.  itself.


     mysql> delimiter //

     mysql> CREATE PROCEDURE dorepeat(p1 INT)
         -> BEGIN
         ->   SET @x = 0;
         ->   REPEAT SET @x = @x + 1; UNTIL @x > p1 END REPEAT;
         -> END
         -> //
     Query OK, 0 rows affected (0.00 sec)

     mysql> delimiter ;

     mysql> CALL dorepeat(1000);
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT @x;
     +------+
     | @x   |
     +------+
     | 1001 |
     +------+
     1 row in set (0.00 sec)

You can redefine the delimiter to a string other than `//', and the
delimiter can consist of a single character or multiple characters. You
should avoid the use of the backslash (``\'') character because that is
the escape character for MySQL.

The following is an example of a function that takes a parameter,
performs an operation using an SQL function, and returns the result. In
this case, it is unnecessary to use `delimiter' because the function
definition contains no internal `;' statement delimiters:


     mysql> CREATE FUNCTION hello (s CHAR(20))
     mysql> RETURNS CHAR(50) DETERMINISTIC
         -> RETURN CONCAT('Hello, ',s,'!');
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT hello('world');
     +----------------+
     | hello('world') |
     +----------------+
     | Hello, world!  |
     +----------------+
     1 row in set (0.00 sec)


File: manual.info,  Node: stored-routines,  Next: triggers,  Prev: stored-programs-defining,  Up: stored-programs-views

19.2 Using Stored Routines (Procedures and Functions)
=====================================================

* Menu:

* stored-routines-syntax::       Stored Routine Syntax
* stored-routines-privileges::   Stored Routines and MySQL Privileges
* stored-routines-metadata::     Stored Routine Metadata
* stored-routines-last-insert-id::  Stored Procedures, Functions, Triggers, and LAST_INSERT_ID()

Stored routines (procedures and functions) are supported in MySQL 5.1.
A stored routine is a set of SQL statements that can be stored in the
server. Once this has been done, clients don't need to keep reissuing
the individual statements but can refer to the stored routine instead.

Stored routines require the `proc' table in the `mysql' database. This
table is created during the MySQL 5.1 installation procedure. If you
are upgrading to MySQL 5.1 from an earlier version, be sure to update
your grant tables to make sure that the `proc' table exists. See *Note
mysql-upgrade::.

Stored routines can be particularly useful in certain situations:

   * When multiple client applications are written in different
     languages or work on different platforms, but need to perform the
     same database operations.

   * When security is paramount. Banks, for example, use stored
     procedures and functions for all common operations. This provides
     a consistent and secure environment, and routines can ensure that
     each operation is properly logged. In such a setup, applications
     and users would have no access to the database tables directly,
     but can only execute specific stored routines.

Stored routines can provide improved performance because less
information needs to be sent between the server and the client. The
tradeoff is that this does increase the load on the database server
because more of the work is done on the server side and less is done on
the client (application) side. Consider this if many client machines
(such as Web servers) are serviced by only one or a few database
servers.

Stored routines also enable you to have libraries of functions in the
database server. This is a feature shared by modern application
languages that enable such design internally (for example, by using
classes). Using these client application language features is
beneficial for the programmer even outside the scope of database use.

MySQL follows the SQL:2003 syntax for stored routines, which is also
used by IBM's DB2. All syntax described here is supported and any
limitations and extensions are documented where appropriate.

*Additional Resources*

   * You may find the Stored Procedures User Forum
     (http://forums.mysql.com/list.php?98) of use when working with
     stored procedures and functions.

   * For answers to some commonly asked questions regarding stored
     routines in MySQL, see *Note faqs-stored-procs::.

   * There are some restrictions on the use of stored routines. See
     *Note stored-program-restrictions::.

   * Binary logging for stored routines takes place as described in
     *Note stored-programs-logging::.


File: manual.info,  Node: stored-routines-syntax,  Next: stored-routines-privileges,  Prev: stored-routines,  Up: stored-routines

19.2.1 Stored Routine Syntax
----------------------------

A stored routine is either a procedure or a function. Stored routines
are created with the *Note `CREATE PROCEDURE': create-procedure. and
*Note `CREATE FUNCTION': create-function. statements (see *Note
create-procedure::). A procedure is invoked using a *Note `CALL': call.
statement (see *Note call::), and can only pass back values using
output variables. A function can be called from inside a statement just
like any other function (that is, by invoking the function's name), and
can return a scalar value. The body of a stored routine can use
compound statements (see *Note sql-syntax-compound-statements::).

Stored routines can be dropped with the *Note `DROP PROCEDURE':
drop-procedure. and *Note `DROP FUNCTION': drop-function. statements
(see *Note drop-procedure::), and altered with the *Note `ALTER
PROCEDURE': alter-procedure. and *Note `ALTER FUNCTION':
alter-function. statements (see *Note alter-procedure::).

A stored procedure or function is associated with a particular
database. This has several implications:

   * When the routine is invoked, an implicit `USE DB_NAME' is
     performed (and undone when the routine terminates).  *Note `USE':
     use. statements within stored routines are not permitted.

   * You can qualify routine names with the database name. This can be
     used to refer to a routine that is not in the current database.
     For example, to invoke a stored procedure `p' or function `f' that
     is associated with the `test' database, you can say `CALL
     test.p()' or `test.f()'.

   * When a database is dropped, all stored routines associated with it
     are dropped as well.

Stored functions cannot be recursive.

Recursion in stored procedures is permitted but disabled by default. To
enable recursion, set the `max_sp_recursion_depth' server system
variable to a value greater than zero. Stored procedure recursion
increases the demand on thread stack space. If you increase the value of
`max_sp_recursion_depth', it may be necessary to increase thread stack
size by increasing the value of `thread_stack' at server startup.  See
*Note server-system-variables::, for more information.

MySQL supports a very useful extension that enables the use of regular
*Note `SELECT': select. statements (that is, without using cursors or
local variables) inside a stored procedure. The result set of such a
query is simply sent directly to the client. Multiple *Note `SELECT':
select.  statements generate multiple result sets, so the client must
use a MySQL client library that supports multiple result sets. This
means the client must use a client library from a version of MySQL at
least as recent as 4.1. The client should also specify the
`CLIENT_MULTI_RESULTS' option when it connects.  For C programs, this
can be done with the *Note `mysql_real_connect()': mysql-real-connect.
C API function. See *Note mysql-real-connect::, and *Note
c-api-multiple-queries::.


File: manual.info,  Node: stored-routines-privileges,  Next: stored-routines-metadata,  Prev: stored-routines-syntax,  Up: stored-routines

19.2.2 Stored Routines and MySQL Privileges
-------------------------------------------

The MySQL grant system takes stored routines into account as follows:

   * The `CREATE ROUTINE' privilege is needed to create stored routines.

   * The `ALTER ROUTINE' privilege is needed to alter or drop stored
     routines. This privilege is granted automatically to the creator
     of a routine if necessary, and dropped from the creator when the
     routine is dropped.

   * The `EXECUTE' privilege is required to execute stored routines.
     However, this privilege is granted automatically to the creator of
     a routine if necessary (and dropped from the creator when the
     routine is dropped). Also, the default `SQL SECURITY'
     characteristic for a routine is `DEFINER', which enables users who
     have access to the database with which the routine is associated
     to execute the routine.

   * If the `automatic_sp_privileges' system variable is 0, the
     `EXECUTE' and `ALTER ROUTINE' privileges are not automatically
     granted to and dropped from the routine creator.

   * The creator of a routine is the account used to execute the
     `CREATE' statement for it. This might not be the same as the
     account named as the `DEFINER' in the routine definition.

The server manipulates the `mysql.proc' table in response to statements
that create, alter, or drop stored routines. It is not supported that
the server will notice manual manipulation of this table.


File: manual.info,  Node: stored-routines-metadata,  Next: stored-routines-last-insert-id,  Prev: stored-routines-privileges,  Up: stored-routines

19.2.3 Stored Routine Metadata
------------------------------

Metadata about stored routines can be obtained as follows:

   * Query the *Note `ROUTINES': routines-table. table of the
     `INFORMATION_SCHEMA' database. See *Note routines-table::.

   * Use the *Note `SHOW CREATE PROCEDURE': show-create-procedure.  and
     *Note `SHOW CREATE FUNCTION': show-create-function.  statements to
     see routine definitions. See *Note show-create-procedure::.

   * Use the *Note `SHOW PROCEDURE STATUS': show-procedure-status.  and
     *Note `SHOW FUNCTION STATUS': show-function-status.  statements to
     see routine characteristics. See *Note show-procedure-status::.

   * `INFORMATION_SCHEMA' does not have a `PARAMETERS' table until
     MySQL 5.5, so applications that need to acquire routine parameter
     information at runtime must use workarounds such as parsing the
     output of `SHOW CREATE' statements or the `param_list' column of
     the `mysql.proc' table.  `param_list' contents can be processed
     from within a stored routine, unlike the output from *Note `SHOW':
     show.


File: manual.info,  Node: stored-routines-last-insert-id,  Prev: stored-routines-metadata,  Up: stored-routines

19.2.4 Stored Procedures, Functions, Triggers, and LAST_INSERT_ID()
-------------------------------------------------------------------

Within the body of a stored routine (procedure or function) or a
trigger, the value of `LAST_INSERT_ID()' changes the same way as for
statements executed outside the body of these kinds of objects (see
*Note information-functions::). The effect of a stored routine or
trigger upon the value of `LAST_INSERT_ID()' that is seen by following
statements depends on the kind of routine:

   * If a stored procedure executes statements that change the value of
     `LAST_INSERT_ID()', the changed value is seen by statements that
     follow the procedure call.

   * For stored functions and triggers that change the value, the value
     is restored when the function or trigger ends, so following
     statements do not see a changed value.


File: manual.info,  Node: triggers,  Next: events,  Prev: stored-routines,  Up: stored-programs-views

19.3 Using Triggers
===================

* Menu:

* trigger-syntax::               Trigger Syntax and Examples
* trigger-metadata::             Trigger Metadata

A trigger is a named database object that is associated with a table,
and that activates when a particular event occurs for the table. Some
uses for triggers are to perform checks of values to be inserted into a
table or to perform calculations on values involved in an update.

A trigger is defined to activate when a statement inserts, updates, or
deletes rows in the associated table. These row operations are trigger
events. For example, rows can be inserted by *Note `INSERT': insert. or
*Note `LOAD DATA': load-data. statements, and an insert trigger
activates for each inserted row. A trigger can be set to activate
either before or after the trigger event. For example, you can have a
trigger activate before each row that is inserted into a table or after
each row that is updated.

*Important*:

MySQL triggers activate only for changes made to tables by SQL
statements. They do not activate for changes in views, nor by changes
to tables made by APIs that do not transmit SQL statements to the MySQL
Server. This means that:

   * Triggers are not activated by changes in `INFORMATION_SCHEMA'
     tables, because these tables are actually views.

   * Triggers are not activated by updates made using the *Note `NDB':
     mysql-cluster. API.

To use triggers if you have upgraded to MySQL 5.1 from an older release
that did not support triggers, you should upgrade your grant tables so
that they contain the trigger-related privileges. See *Note
mysql-upgrade::.

The following sections describe the syntax for creating and dropping
triggers, show some examples of how to use them, and indicate how to
obtain trigger metadata.

*Additional Resources*

   * You may find the Triggers User Forum
     (http://forums.mysql.com/list.php?100) of use when working with
     triggers.

   * For answers to commonly asked questions regarding triggers in
     MySQL, see *Note faqs-triggers::.

   * There are some restrictions on the use of triggers; see *Note
     stored-program-restrictions::.

   * Binary logging for triggers takes place as described in *Note
     stored-programs-logging::.


File: manual.info,  Node: trigger-syntax,  Next: trigger-metadata,  Prev: triggers,  Up: triggers

19.3.1 Trigger Syntax and Examples
----------------------------------

To create a trigger or drop a trigger, use the *Note `CREATE TRIGGER':
create-trigger. or *Note `DROP TRIGGER': drop-trigger. statement,
described in *Note create-trigger::, and *Note drop-trigger::.

Here is a simple example that associates a trigger with a table, to
activate for *Note `INSERT': insert. operations.  The trigger acts as
an accumulator, summing the values inserted into one of the columns of
the table.


     mysql> CREATE TABLE account (acct_num INT, amount DECIMAL(10,2));
     Query OK, 0 rows affected (0.03 sec)

     mysql> CREATE TRIGGER ins_sum BEFORE INSERT ON account
         -> FOR EACH ROW SET @sum = @sum + NEW.amount;
     Query OK, 0 rows affected (0.06 sec)

The *Note `CREATE TRIGGER': create-trigger. statement creates a trigger
named `ins_sum' that is associated with the `account' table. It also
includes clauses that specify the trigger action time, the triggering
event, and what to do when the trigger activates:

   * The keyword `BEFORE' indicates the trigger action time. In this
     case, the trigger activates before each row inserted into the
     table. The other permitted keyword here is `AFTER'.

   * The keyword `INSERT' indicates the trigger event; that is, the
     type of operation that activates the trigger. In the example,
     *Note `INSERT': insert.  operations cause trigger activation. You
     can also create triggers for *Note `DELETE': delete. and *Note
     `UPDATE': update. operations.

   * The statement following `FOR EACH ROW' defines the trigger body;
     that is, the statement to execute each time the trigger activates,
     which occurs once for each row affected by the triggering event.
     In the example, the trigger body is a simple *Note `SET':
     set-statement.  that accumulates into a user variable the values
     inserted into the `amount' column. The statement refers to the
     column as `NEW.amount' which means `the value of the `amount'
     column to be inserted into the new row.'

To use the trigger, set the accumulator variable to zero, execute an
*Note `INSERT': insert. statement, and then see what value the variable
has afterward:


     mysql> SET @sum = 0;
     mysql> INSERT INTO account VALUES(137,14.98),(141,1937.50),(97,-100.00);
     mysql> SELECT @sum AS 'Total amount inserted';
     +-----------------------+
     | Total amount inserted |
     +-----------------------+
     | 1852.48               |
     +-----------------------+

In this case, the value of `@sum' after the *Note `INSERT': insert.
statement has executed is `14.98 + 1937.50 - 100', or `1852.48'.

To destroy the trigger, use a *Note `DROP TRIGGER': drop-trigger.
statement. You must specify the schema name if the trigger is not in
the default schema:


     mysql> DROP TRIGGER test.ins_sum;

If you drop a table, any triggers for the table are also dropped.

Trigger names exist in the schema namespace, meaning that all triggers
must have unique names within a schema. Triggers in different schemas
can have the same name.

In addition to the requirement that trigger names be unique for a
schema, there are other limitations on the types of triggers you can
create. In particular, there cannot be multiple triggers for a given
table that have the same trigger event and action time. For example,
you cannot have two `BEFORE UPDATE' triggers for a table. To work
around this, you can define a trigger that executes multiple statements
by using the *Note `BEGIN ... END': begin-end.  compound statement
construct after `FOR EACH ROW'. (An example appears later in this
section.)

Within the trigger body, the `OLD' and `NEW' keywords enable you to
access columns in the rows affected by a trigger. `OLD' and `NEW' are
MySQL extensions to triggers; they are not case sensitive.

In an `INSERT' trigger, only `NEW.COL_NAME' can be used; there is no
old row. In a `DELETE' trigger, only `OLD.COL_NAME' can be used; there
is no new row. In an `UPDATE' trigger, you can use `OLD.COL_NAME' to
refer to the columns of a row before it is updated and `NEW.COL_NAME' to
refer to the columns of the row after it is updated.

A column named with `OLD' is read only. You can refer to it (if you
have the *Note `SELECT': select.  privilege), but not modify it. You
can refer to a column named with `NEW' if you have the `SELECT'
privilege for it. In a `BEFORE' trigger, you can also change its value
with `SET NEW.COL_NAME = VALUE' if you have the `UPDATE' privilege for
it. This means you can use a trigger to modify the values to be
inserted into a new row or used to update a row. (Such a `SET'
statement has no effect in an `AFTER' trigger because the row change
will have already occurred.)

In a `BEFORE' trigger, the `NEW' value for an `AUTO_INCREMENT' column
is 0, not the sequence number that is generated automatically when the
new row actually is inserted.

By using the *Note `BEGIN ... END': begin-end. construct, you can
define a trigger that executes multiple statements. Within the `BEGIN'
block, you also can use other syntax that is permitted within stored
routines such as conditionals and loops. However, just as for stored
routines, if you use the *Note `mysql': mysql. program to define a
trigger that executes multiple statements, it is necessary to redefine
the *Note `mysql': mysql. statement delimiter so that you can use the
`;' statement delimiter within the trigger definition. The following
example illustrates these points. It defines an `UPDATE' trigger that
checks the new value to be used for updating each row, and modifies the
value to be within the range from 0 to 100.  This must be a `BEFORE'
trigger because the value must be checked before it is used to update
the row:


     mysql> delimiter //
     mysql> CREATE TRIGGER upd_check BEFORE UPDATE ON account
         -> FOR EACH ROW
         -> BEGIN
         ->     IF NEW.amount < 0 THEN
         ->         SET NEW.amount = 0;
         ->     ELSEIF NEW.amount > 100 THEN
         ->         SET NEW.amount = 100;
         ->     END IF;
         -> END;//
     mysql> delimiter ;

It can be easier to define a stored procedure separately and then
invoke it from the trigger using a simple *Note `CALL': call.
statement. This is also advantageous if you want to execute the same
code from within several triggers.

There are limitations on what can appear in statements that a trigger
executes when activated:

   * The trigger cannot use the *Note `CALL': call.  statement to
     invoke stored procedures that return data to the client or that
     use dynamic SQL. (Stored procedures are permitted to return data
     to the trigger through `OUT' or `INOUT' parameters.)

   * The trigger cannot use statements that explicitly or implicitly
     begin or end a transaction, such as *Note `START TRANSACTION':
     commit, *Note `COMMIT': commit, or *Note `ROLLBACK': commit.

See also *Note stored-program-restrictions::.

MySQL handles errors during trigger execution as follows:

   * If a `BEFORE' trigger fails, the operation on the corresponding
     row is not performed.

   * A `BEFORE' trigger is activated by the _attempt_ to insert or
     modify the row, regardless of whether the attempt subsequently
     succeeds.

   * An `AFTER' trigger is executed only if any `BEFORE' triggers and
     the row operation execute successfully.

   * An error during either a `BEFORE' or `AFTER' trigger results in
     failure of the entire statement that caused trigger invocation.

   * For transactional tables, failure of a statement should cause
     rollback of all changes performed by the statement. Failure of a
     trigger causes the statement to fail, so trigger failure also
     causes rollback. For nontransactional tables, such rollback cannot
     be done, so although the statement fails, any changes performed
     prior to the point of the error remain in effect.

In MySQL 5.1, triggers can contain direct references to tables by name,
such as the trigger named `testref' shown in this example:


     CREATE TABLE test1(a1 INT);
     CREATE TABLE test2(a2 INT);
     CREATE TABLE test3(a3 INT NOT NULL AUTO_INCREMENT PRIMARY KEY);
     CREATE TABLE test4(
       a4 INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
       b4 INT DEFAULT 0
     );

     delimiter |

     CREATE TRIGGER testref BEFORE INSERT ON test1
       FOR EACH ROW
       BEGIN
         INSERT INTO test2 SET a2 = NEW.a1;
         DELETE FROM test3 WHERE a3 = NEW.a1;
         UPDATE test4 SET b4 = b4 + 1 WHERE a4 = NEW.a1;
       END;
     |

     delimiter ;

     INSERT INTO test3 (a3) VALUES
       (NULL), (NULL), (NULL), (NULL), (NULL),
       (NULL), (NULL), (NULL), (NULL), (NULL);

     INSERT INTO test4 (a4) VALUES
       (0), (0), (0), (0), (0), (0), (0), (0), (0), (0);

Suppose that you insert the following values into table `test1' as
shown here:


     mysql> INSERT INTO test1 VALUES
         -> (1), (3), (1), (7), (1), (8), (4), (4);
     Query OK, 8 rows affected (0.01 sec)
     Records: 8  Duplicates: 0  Warnings: 0

As a result, the four tables contain the following data:


     mysql> SELECT * FROM test1;
     +------+
     | a1   |
     +------+
     |    1 |
     |    3 |
     |    1 |
     |    7 |
     |    1 |
     |    8 |
     |    4 |
     |    4 |
     +------+
     8 rows in set (0.00 sec)

     mysql> SELECT * FROM test2;
     +------+
     | a2   |
     +------+
     |    1 |
     |    3 |
     |    1 |
     |    7 |
     |    1 |
     |    8 |
     |    4 |
     |    4 |
     +------+
     8 rows in set (0.00 sec)

     mysql> SELECT * FROM test3;
     +----+
     | a3 |
     +----+
     |  2 |
     |  5 |
     |  6 |
     |  9 |
     | 10 |
     +----+
     5 rows in set (0.00 sec)

     mysql> SELECT * FROM test4;
     +----+------+
     | a4 | b4   |
     +----+------+
     |  1 |    3 |
     |  2 |    0 |
     |  3 |    1 |
     |  4 |    2 |
     |  5 |    0 |
     |  6 |    0 |
     |  7 |    1 |
     |  8 |    1 |
     |  9 |    0 |
     | 10 |    0 |
     +----+------+
     10 rows in set (0.00 sec)


File: manual.info,  Node: trigger-metadata,  Prev: trigger-syntax,  Up: triggers

19.3.2 Trigger Metadata
-----------------------

Metadata about triggers can be obtained as follows:

   * Query the *Note `TRIGGERS': triggers-table. table of the
     `INFORMATION_SCHEMA' database. See *Note triggers-table::.

   * Use the *Note `SHOW CREATE TRIGGER': show-create-trigger.
     statement. See *Note show-create-trigger::.

   * Use the *Note `SHOW TRIGGERS': show-triggers.  statement. See
     *Note show-triggers::.


File: manual.info,  Node: events,  Next: views,  Prev: triggers,  Up: stored-programs-views

19.4 Using the Event Scheduler
==============================

* Menu:

* events-overview::              Event Scheduler Overview
* events-configuration::         Event Scheduler Configuration
* events-syntax::                Event Syntax
* events-metadata::              Event Metadata
* events-status-info::           Event Scheduler Status
* events-privileges::            The Event Scheduler and MySQL Privileges

The _MySQL Event Scheduler_ manages the scheduling and execution of
events: Tasks that run according to schedule. Event support was added
in MySQL 5.1.6. The following discussion covers the Event Scheduler and
is divided into the following sections:

   * *Note events-overview::, provides an introduction to and
     conceptual overview of MySQL Events.

   * *Note events-syntax::, discusses the SQL statements for creating,
     altering, and dropping MySQL Events.

   * *Note events-metadata::, shows how to obtain information about
     events and how this information is stored by the MySQL Server.

   * *Note events-privileges::, discusses the privileges required to
     work with events and the ramifications that events have with
     regard to privileges when executing.

Stored routines require the `event' table in the `mysql' database. This
table is created during the MySQL 5.1 installation procedure. If you
are upgrading to MySQL 5.1 from an earlier version, be sure to update
your grant tables to make sure that the `event' table exists. See *Note
mysql-upgrade::.

*Additional Resources*

   * You may find the MySQL Event Scheduler User Forum
     (http://forums.mysql.com/list.php?119) of use when working with
     scheduled events.

   * There are some restrictions on the use of events; see *Note
     stored-program-restrictions::.

   * Binary logging for events takes place as described in *Note
     stored-programs-logging::.


File: manual.info,  Node: events-overview,  Next: events-configuration,  Prev: events,  Up: events

19.4.1 Event Scheduler Overview
-------------------------------

MySQL Events are tasks that run according to a schedule.  Therefore, we
sometimes refer to them as _scheduled_ events. When you create an event,
you are creating a named database object containing one or more SQL
statements to be executed at one or more regular intervals, beginning
and ending at a specific date and time. Conceptually, this is similar
to the idea of the Unix `crontab' (also known as a `cron job') or the
Windows Task Scheduler.

Scheduled tasks of this type are also sometimes known as `temporal
triggers', implying that these are objects that are triggered by the
passage of time. While this is essentially correct, we prefer to use
the term _events_ to avoid confusion with triggers of the type
discussed in *Note triggers::. Events should more specifically not be
confused with `temporary triggers'. Whereas a trigger is a database
object whose statements are executed in response to a specific type of
event that occurs on a given table, a (scheduled) event is an object
whose statements are executed in response to the passage of a specified
time interval.

While there is no provision in the SQL Standard for event scheduling,
there are precedents in other database systems, and you may notice some
similarities between these implementations and that found in the MySQL
Server.

MySQL Events have the following major features and properties:

   * In MySQL 5.1.12 and later, an event is uniquely identified by its
     name and the schema to which it is assigned. (Previously, an event
     was also unique to its definer.)

   * An event performs a specific action according to a schedule.  This
     action consists of an SQL statement, which can be a compound
     statement in a *Note `BEGIN ... END': begin-end. block if desired
     (see *Note sql-syntax-compound-statements::). An event's timing
     can be either _one-time_ or _recurrent_. A one-time event executes
     one time only. A recurrent event repeats its action at a regular
     interval, and the schedule for a recurring event can be assigned a
     specific start day and time, end day and time, both, or neither.
     (By default, a recurring event's schedule begins as soon as it is
     created, and continues indefinitely, until it is disabled or
     dropped.)

     If a repeating event does not terminate within its scheduling
     interval, the result may be multiple instances of the event
     executing simultaneously. If this is undesirable, you should
     institute a mechanism to prevent simultaneous instances. For
     example, you could use the `GET_LOCK()' function, or row or table
     locking.

   * Users can create, modify, and drop scheduled events using SQL
     statements intended for these purposes. Syntactically invalid
     event creation and modification statements fail with an
     appropriate error message. _A user may include statements in an
     event's action which require privileges that the user does not
     actually have_. The event creation or modification statement
     succeeds but the event's action fails. See *Note
     events-privileges:: for details.

   * Many of the properties of an event can be set or modified using
     SQL statements. These properties include the event's name, timing,
     persistence (that is, whether it is preserved following the
     expiration of its schedule), status (enabled or disabled), action
     to be performed, and the schema to which it is assigned. See *Note
     alter-event::.

     The default definer of an event is the user who created the event,
     unless the event has been altered, in which case the definer is
     the user who issued the last *Note `ALTER EVENT': alter-event.
     statement affecting that event. An event can be modified by any
     user having the `EVENT' privilege on the database for which the
     event is defined. (Prior to MySQL 5.1.12, only an event's definer,
     or a user having privileges on the `mysql.event' table, could
     modify a given event.) See *Note events-privileges::.

   * An event's action statement may include most SQL statements
     permitted within stored routines. For restrictions, see *Note
     stored-program-restrictions::.


File: manual.info,  Node: events-configuration,  Next: events-syntax,  Prev: events-overview,  Up: events

19.4.2 Event Scheduler Configuration
------------------------------------

Events are executed by a special _event scheduler thread_; when we
refer to the Event Scheduler, we actually refer to this thread. When
running, the event scheduler thread and its current state can be seen
by users having the `PROCESS' privilege in the output of *Note `SHOW
PROCESSLIST': show-processlist, as shown in the discussion that follows.

The global `event_scheduler' system variable determines whether the
Event Scheduler is enabled and running on the server. Beginning with
MySQL 5.1.12, it has one of these 3 values, which affect event
scheduling as described here:

   * `OFF': The Event Scheduler is stopped. The event scheduler thread
     does not run, is not shown in the output of *Note `SHOW
     PROCESSLIST': show-processlist, and no scheduled events are
     executed. `OFF' is the default value for `event_scheduler'.

     When the Event Scheduler is stopped (`event_scheduler' is `OFF'),
     it can be started by setting the value of `event_scheduler' to
     `ON'. (See next item.)

   * `ON': The Event Scheduler is started; the event scheduler thread
     runs and executes all scheduled events.

     When the Event Scheduler is `ON', the event scheduler thread is
     listed in the output of *Note `SHOW PROCESSLIST':
     show-processlist. as a daemon process, and its state is
     represented as shown here:


          mysql> SHOW PROCESSLIST\G
          *************************** 1. row ***************************
               Id: 1
             User: root
             Host: localhost
               db: NULL
          Command: Query
             Time: 0
            State: NULL
             Info: show processlist
          *************************** 2. row ***************************
               Id: 2
             User: event_scheduler
             Host: localhost
               db: NULL
          Command: Daemon
             Time: 3
            State: Waiting for next activation
             Info: NULL
          2 rows in set (0.00 sec)

     Event scheduling can be stopped by setting the value of
     `event_scheduler' to `OFF'.

   * `DISABLED': This value renders the Event Scheduler nonoperational.
     When the Event Scheduler is `DISABLED', the event scheduler thread
     does not run (and so does not appear in the output of *Note `SHOW
     PROCESSLIST': show-processlist.). In addition, the Event Scheduler
     state cannot be changed at runtime.

If the Event Scheduler status has not been set to `DISABLED',
`event_scheduler' can be toggled between `ON' and `OFF' (using *Note
`SET': set-statement.). It is also possible to use `0' for `OFF', and
`1' for `ON' when setting this variable. Thus, any of the following 4
statements can be used in the *Note `mysql': mysql.  client to turn on
the Event Scheduler:


     SET GLOBAL event_scheduler = ON;
     SET @@global.event_scheduler = ON;
     SET GLOBAL event_scheduler = 1;
     SET @@global.event_scheduler = 1;

Similarly, any of these 4 statements can be used to turn off the Event
Scheduler:


     SET GLOBAL event_scheduler = OFF;
     SET @@global.event_scheduler = OFF;
     SET GLOBAL event_scheduler = 0;
     SET @@global.event_scheduler = 0;

Although `ON' and `OFF' have numeric equivalents, the value displayed
for `event_scheduler' by *Note `SELECT': select. or *Note `SHOW
VARIABLES': show-variables. is always one of `OFF', `ON', or `DISABLED'.
_`DISABLED' has no numeric equivalent_. For this reason, `ON' and `OFF'
are usually preferred over `1' and `0' when setting this variable.

Note that attempting to set `event_scheduler' without specifying it as
a global variable causes an error:


     mysql< SET @@event_scheduler = OFF;
     `ERROR 1229 (HY000): Variable 'event_scheduler' is a GLOBAL
     variable and should be set with SET GLOBAL'

*Important*:

It is possible to set the Event Scheduler to `DISABLED' only at server
startup. If `event_scheduler' is `ON' or `OFF', you cannot set it to
`DISABLED' at runtime. Also, if the Event Scheduler is set to
`DISABLED' at startup, you cannot change the value of `event_scheduler'
at runtime.

To disable the event scheduler, use one of the following two methods:

   * As a command-line option when starting the server:


          --event-scheduler=DISABLED

   * In the server configuration file (`my.cnf', or `my.ini' on Windows
     systems), include the line where it will be read by the server
     (for example, in a `[mysqld]' section):


          event_scheduler=DISABLED

To enable the Event Scheduler, restart the server without the
`--event-scheduler=DISABLED' command-line option, or after removing or
commenting out the line containing `event-scheduler=DISABLED' in the
server configuration file, as appropriate. Alternatively, you can use
`ON' (or `1') or `OFF' (or `0') in place of the `DISABLED' value when
starting the server.

*Note*:

You can issue event-manipulation statements when `event_scheduler' is
set to `DISABLED'. No warnings or errors are generated in such cases
(provided that the statements are themselves valid). However, scheduled
events cannot execute until this variable is set to `ON' (or `1'). Once
this has been done, the event scheduler thread executes all events
whose scheduling conditions are satisfied.

In MySQL 5.1.11, `event_scheduler' behaved as follows: this variable
could take one of the values `0' (or `OFF'), `1' (or `ON'), or `2'.
Setting it to `0' turned event scheduling off, so that the event
scheduler thread did not run; the `event_scheduler' variable could not
be set to this value while the server was running.  Setting it to `1'
so that the event scheduler thread ran and executed scheduled events.
In this state, the event scheduler thread appeared to be sleeping when
viewed with *Note `SHOW PROCESSLIST': show-processlist. When
`event_scheduler' was set to `2' (which was the default value), the
Event Scheduler was considered to be `suspended'; the event scheduler
thread ran and could be seen in the output of *Note `SHOW PROCESSLIST':
show-processlist. (where `Suspended' was displayed in the `State'
column), but did not execute any scheduled events. The value of
`event_scheduler' could be changed only between `1' (or `ON') and `2'
while the server was running. Setting it to `0' (or `OFF') required a
server restart, as did changing its value from `0' (or `OFF') to `1' (or
`ON') or `2'.

Prior to MySQL 5.1.11, `event_scheduler' could take one of only the 2
values `0'|`OFF' or `1'|`ON', and the default value was `0'|`OFF'. It
was also possible to start and stop the event scheduler thread while the
MySQL server was running.

For more information concerning the reasons for these changes in
behavior, see Bug #17619.

Beginning with MySQL 5.1.17, starting the MySQL server with the
`--skip-grant-tables' option causes `event_scheduler' to be set to
`DISABLED', overriding any other value set either on the command line
or in the `my.cnf' or `my.ini' file (Bug #26807).

For SQL statements used to create, alter, and drop events, see *Note
events-syntax::.

MySQL 5.1.6 and later provides an *Note `EVENTS': events-table. table
in the `INFORMATION_SCHEMA' database. This table can be queried to
obtain information about scheduled events which have been defined on
the server. See *Note events-metadata::, and *Note events-table::, for
more information.

For information regarding event scheduling and the MySQL privilege
system, see *Note events-privileges::.


File: manual.info,  Node: events-syntax,  Next: events-metadata,  Prev: events-configuration,  Up: events

19.4.3 Event Syntax
-------------------

MySQL 5.1.6 and later provides several SQL statements for working with
scheduled events:

   * New events are defined using the *Note `CREATE EVENT':
     create-event. statement. See *Note create-event::.

   * The definition of an existing event can be changed by means of the
     *Note `ALTER EVENT': alter-event. statement. See *Note
     alter-event::.

   * When a scheduled event is no longer wanted or needed, it can be
     deleted from the server by its definer using the *Note `DROP
     EVENT': drop-event. statement. See *Note drop-event::. Whether an
     event persists past the end of its schedule also depends on its `ON
     COMPLETION' clause, if it has one. See *Note create-event::.

     An event can be dropped by any user having the `EVENT' privilege
     for the database on which the event is defined. Prior to MySQL
     5.1.12, a user other than the definer required privileges on the
     `mysql.event' table. See *Note events-privileges::.


File: manual.info,  Node: events-metadata,  Next: events-status-info,  Prev: events-syntax,  Up: events

19.4.4 Event Metadata
---------------------

Metadata about events can be obtained as follows:

   * Query the `event' table of the `mysql' database.

   * Query the *Note `EVENTS': events-table. table of the
     `INFORMATION_SCHEMA' database. See *Note events-table::.

   * Use the *Note `SHOW CREATE EVENT': show-create-event.  statement.
     See *Note show-create-event::.

   * Use the *Note `SHOW EVENTS': show-events. statement.  See *Note
     show-events::.

*Event Scheduler Time Representation*

Each session in MySQL has a session time zone (STZ). This is the
session `time_zone' value that is initialized from the server's global
`time_zone' value when the session begins but may be changed during the
session.

The session time zone that is current when a *Note `CREATE EVENT':
create-event. or *Note `ALTER EVENT': alter-event. statement executes is
used to interpret times specified in the event definition. This becomes
the event time zone (ETZ); that is, the time zone that is used for
event scheduling and is in effect within the event as it executes.

For representation of event information in the `mysql.event' table, the
`execute_at', `starts', and `ends' times are converted to UTC and stored
along with the event time zone. This enables event execution to proceed
as defined regardless of any subsequent changes to the server time zone
or daylight saving time effects. The `last_executed' time is also
stored in UTC.

If you select information from `mysql.event', the times just mentioned
are retrieved as UTC values. These times can also be obtained by
selecting from the *Note `INFORMATION_SCHEMA.EVENTS': events-table.
table or from *Note `SHOW EVENTS': show-events, but they are reported
as ETZ values. Other times available from these sources indicate when
an event was created or last altered; these are displayed as STZ
values. The following table summarizes representation of event times.

This table summarizes the representation of event times (as UTC, EZT,
or STZ values) from `mysql.event', *Note `INFORMATION_SCHEMA.EVENTS':
events-table, and *Note `SHOW EVENTS': show-events.

Value              `mysql.event'      *Note              *Note `SHOW
                                      `INFORMATION_SCHEMA.EVENTS':EVENTS':
                                      events-table.      show-events.
Execute at         UTC                ETZ                ETZ
Starts             UTC                ETZ                ETZ
Ends               UTC                ETZ                ETZ
Last executed      UTC                ETZ                n/a
Created            STZ                STZ                n/a
Last altered       STZ                STZ                n/a

The preceding table applies for MySQL 5.1.17 and up. Prior to MySQL
5.1.17, the event time zone is not stored in the `mysql.event' table or
available from *Note `INFORMATION_SCHEMA.EVENTS': events-table. or
*Note `SHOW EVENTS': show-events. Times that are displayed using ETZ
from 5.1.17 and up are displayed in UTC before 5.1.17, as shown in the
following table.

This table summarizes the representation of event times (as UTC, EZT,
or STZ values) from `mysql.event', *Note `INFORMATION_SCHEMA.EVENTS':
events-table, and *Note `SHOW EVENTS': show-events. prior to MySQL
5.1.17.

Value              `mysql.event'      *Note              *Note `SHOW
                                      `INFORMATION_SCHEMA.EVENTS':EVENTS':
                                      events-table.      show-events.
Execute at         UTC                UTC                UTC
Starts             UTC                UTC                UTC
Ends               UTC                UTC                UTC
Last executed      UTC                UTC                n/a
Created            STZ                STZ                n/a
Last altered       STZ                STZ                n/a


File: manual.info,  Node: events-status-info,  Next: events-privileges,  Prev: events-metadata,  Up: events

19.4.5 Event Scheduler Status
-----------------------------

The Event Scheduler writes information about event execution that
terminates with an error or warning to the MySQL Server's error log.
See *Note events-privileges:: for an example.  (Before MySQL 5.1.31,
the Event Scheduler also logged messages when events started execution
and terminated successfully.)

Information about the state of the Event Scheduler for debugging and
troubleshooting purposes can be obtained as follows:

   * In debugging builds of MySQL 5.1.11, you can use the `SHOW
     SCHEDULER STATUS' statement; see *Note show-scheduler-status::.
     This statement was removed in MySQL 5.1.12. We intend to implement
     an SQL statement providing similar functionality in a future MySQL
     release.

   * Beginning with MySQL 5.1.12, event scheduler status information
     can be obtained by running *Note `mysqladmin debug': mysqladmin.
     (see *Note mysqladmin::); after running this command, the server's
     error log contains output relating to the Event Scheduler, similar
     to what is shown here:


          Events status:
          LLA = Last Locked At  LUA = Last Unlocked At
          WOC = Waiting On Condition  DL = Data Locked

          Event scheduler status:
          State      : INITIALIZED
          Thread id  : 0
          LLA        : init_scheduler:313
          LUA        : init_scheduler:318
          WOC        : NO
          Workers    : 0
          Executed   : 0
          Data locked: NO

          Event queue status:
          Element count   : 1
          Data locked     : NO
          Attempting lock : NO
          LLA             : init_queue:148
          LUA             : init_queue:168
          WOC             : NO
          Next activation : 0000-00-00 00:00:00

In statements that occur as part of events executed by the Event
Scheduler, diagnostics messages (not only errors, but also warnings)
are written to the error log, and, on Windows, to the application event
log. For frequently executed events, it is possible for this to result
in many logged messages. For example, for `SELECT ... INTO VAR_LIST'
statements, if the query returns no rows, a warning with error code
1329 occurs (`No data'), and the variable values remain unchanged. If
the query returns multiple rows, error 1172 occurs (`Result consisted
of more than one row'). For either condition, you can avoid having the
warnings be logged by declaring a condition handler; see *Note
declare-handler::. For statements that may retrieve multiple rows,
another strategy is to use `LIMIT 1' to limit the result set to a
single row.


File: manual.info,  Node: events-privileges,  Prev: events-status-info,  Up: events

19.4.6 The Event Scheduler and MySQL Privileges
-----------------------------------------------

To enable or disable the execution of scheduled events, it is necessary
to set the value of the global `event_scheduler' system variable.  This
requires the `SUPER' privilege.

MySQL 5.1.6 introduces a privilege governing the creation,
modification, and deletion of events, the `EVENT' privilege. This
privilege can be bestowed using *Note `GRANT': grant. For example, this
*Note `GRANT': grant. statement confers the `EVENT' privilege for the
schema named `myschema' on the user `jon@ghidora':


     GRANT EVENT ON myschema.* TO jon@ghidora;

(We assume that this user account already exists, and that we wish for
it to remain unchanged otherwise.)

To grant this same user the `EVENT' privilege on all schemas, use the
following statement:


     GRANT EVENT ON *.* TO jon@ghidora;

The `EVENT' privilege has global or schema-level scope. Therefore,
trying to grant it on a single table results in an error as shown:


     mysql> GRANT EVENT ON myschema.mytable TO jon@ghidora;
     `ERROR 1144 (42000): Illegal GRANT/REVOKE command; please
     consult the manual to see which privileges can be used'

It is important to understand that an event is executed with the
privileges of its definer, and that it cannot perform any actions for
which its definer does not have the requisite privileges. For example,
suppose that `jon@ghidora' has the `EVENT' privilege for `myschema'.
Suppose also that this user has the `SELECT' privilege for `myschema',
but no other privileges for this schema. It is possible for
`jon@ghidora' to create a new event such as this one:


     CREATE EVENT e_store_ts
         ON SCHEDULE
           EVERY 10 SECOND
         DO
           INSERT INTO myschema.mytable VALUES (UNIX_TIMESTAMP());

The user waits for a minute or so, and then performs a `SELECT * FROM
mytable;' query, expecting to see several new rows in the table.
Instead, the table is empty. Since the user does not have the `INSERT'
privilege for the table in question, the event has no effect.

If you inspect the MySQL error log (`HOSTNAME.err'), you can see that
the event is executing, but the action it is attempting to perform
fails, as indicated by `RetCode=0':


     060209 22:39:44 [Note]     EVEX EXECUTING event newdb.e [EXPR:10]
     060209 22:39:44 [Note]     EVEX EXECUTED event newdb.e  [EXPR:10]. RetCode=0
     060209 22:39:54 [Note]     EVEX EXECUTING event newdb.e [EXPR:10]
     060209 22:39:54 [Note]     EVEX EXECUTED event newdb.e  [EXPR:10]. RetCode=0
     060209 22:40:04 [Note]     EVEX EXECUTING event newdb.e [EXPR:10]
     060209 22:40:04 [Note]     EVEX EXECUTED event newdb.e  [EXPR:10]. RetCode=0

Since this user very likely does not have access to the error log, it
is possible to verify whether the event's action statement is valid by
executing it directly:


     mysql> INSERT INTO myschema.mytable VALUES (UNIX_TIMESTAMP());
     `ERROR 1142 (42000): INSERT command denied to user
     'jon'@'ghidora' for table 'mytable''

Inspection of the *Note `INFORMATION_SCHEMA.EVENTS': events-table.
table shows that `e_store_ts' exists and is enabled, but its
`LAST_EXECUTED' column is `NULL':


     mysql> SELECT * FROM INFORMATION_SCHEMA.EVENTS
          >     WHERE EVENT_NAME='e_store_ts'
          >     AND EVENT_SCHEMA='myschema'\G
     *************************** 1. row ***************************
        EVENT_CATALOG: NULL
         EVENT_SCHEMA: myschema
           EVENT_NAME: e_store_ts
              DEFINER: jon@ghidora
           EVENT_BODY: SQL
     EVENT_DEFINITION: INSERT INTO myschema.mytable VALUES (UNIX_TIMESTAMP())
           EVENT_TYPE: RECURRING
           EXECUTE_AT: NULL
       INTERVAL_VALUE: 5
       INTERVAL_FIELD: SECOND
             SQL_MODE: NULL
               STARTS: 0000-00-00 00:00:00
                 ENDS: 0000-00-00 00:00:00
               STATUS: ENABLED
        ON_COMPLETION: NOT PRESERVE
              CREATED: 2006-02-09 22:36:06
         LAST_ALTERED: 2006-02-09 22:36:06
        LAST_EXECUTED: NULL
        EVENT_COMMENT:
     1 row in set (0.00 sec)

*Note*:

Prior to MySQL 5.1.12, there was no `EVENT_DEFINITION' column, and
`EVENT_BODY' contained the SQL statement or statements to be executed.
See *Note events-table::, for more information.

To rescind the `EVENT' privilege, use the *Note `REVOKE': revoke.
statement. In this example, the `EVENT' privilege on the schema
`myschema' is removed from the `jon@ghidora' user account:


     REVOKE EVENT ON myschema.* FROM jon@ghidora;

*Important*:

Revoking the `EVENT' privilege from a user does not delete or disable
any events that may have been created by that user.

An event is not migrated or dropped as a result of renaming or dropping
the user who created it.

Suppose that the user `jon@ghidora' has been granted the `EVENT' and
`INSERT' privileges on the `myschema' schema. This user then creates the
following event:


     CREATE EVENT e_insert
         ON SCHEDULE
           EVERY 7 SECOND
         DO
           INSERT INTO myschema.mytable;

After this event has been created, `root' revokes the `EVENT' privilege
for `jon@ghidora'. However, `e_insert' continues to execute, inserting
a new row into `mytable' each seven seconds. The same would be true if
`root' had issued either of these statements:

   * `DROP USER jon@ghidora;'

   * `RENAME USER jon@ghidora TO someotherguy@ghidora;'

You can verify that this is true by examining the `mysql.event' table
(discussed later in this section) or the *Note
`INFORMATION_SCHEMA.EVENTS': events-table. table (see *Note
events-table::) before and after issuing a *Note `DROP USER':
drop-user. or *Note `RENAME USER': rename-user. statement.

Event definitions are stored in the `mysql.event' table, which was
added in MySQL 5.1.6. To drop an event created by another user account,
the MySQL `root' user (or another user with the necessary privileges)
can delete rows from this table. For example, to remove the event
`e_insert' shown previously, `root' can use the following statement:


     DELETE FROM mysql.event
         WHERE db = 'myschema'
           AND definer = 'jon@ghidora'
           AND name = 'e_insert';

It is very important to match the event name, database schema name, and
user account when deleting rows from the `mysql.event' table. This is
because the same user can create different events of the same name in
different schemas.

*Note*:

The namespace for scheduled events changed in MySQL 5.1.12.  Prior to
that MySQL version, different users could create different events
having the same name in the same database; in MySQL 5.1.12 and later,
that is no longer the case. When upgrading to MySQL 5.1.12 or later
from MySQL 5.1.11 or earlier, it is extremely important to make sure
that no events in the same database share the same name, _prior to
performing the upgrade_.

Users' `EVENT' privileges are stored in the `Event_priv' columns of the
`mysql.user' and `mysql.db' tables. In both cases, this column holds
one of the values '`Y'' or '`N''.  '`N'' is the default.
`mysql.user.Event_priv' is set to '`Y'' for a given user only if that
user has the global `EVENT' privilege (that is, if the privilege was
bestowed using `GRANT EVENT ON *.*'). For a schema-level `EVENT'
privilege, *Note `GRANT': grant. creates a row in `mysql.db' and sets
that row's `Db' column to the name of the schema, the `User' column to
the name of the user, and the `Event_priv' column to '`Y''.  There
should never be any need to manipulate these tables directly, since the
*Note `GRANT EVENT': grant. and `REVOKE EVENT' statements perform the
required operations on them.

MySQL 5.1.6 introduces five status variables providing counts of
event-related operations (but _not_ of statements executed by events;
see *Note stored-program-restrictions::). These are:

   * `Com_create_event': The number of *Note `CREATE EVENT':
     create-event. statements executed since the last server restart.

   * `Com_alter_event': The number of *Note `ALTER EVENT': alter-event.
     statements executed since the last server restart.

   * `Com_drop_event': The number of *Note `DROP EVENT': drop-event.
     statements executed since the last server restart.

   * `Com_show_create_event': The number of *Note `SHOW CREATE EVENT':
     show-create-event. statements executed since the last server
     restart.

   * `Com_show_events': The number of *Note `SHOW EVENTS': show-events.
     statements executed since the last server restart.

You can view current values for all of these at one time by running the
statement `SHOW STATUS LIKE '%event%';'.


File: manual.info,  Node: views,  Next: stored-programs-security,  Prev: events,  Up: stored-programs-views

19.5 Using Views
================

* Menu:

* view-syntax::                  View Syntax
* view-algorithms::              View Processing Algorithms
* view-updatability::            Updatable and Insertable Views
* view-metadata::                View Metadata

Views (including updatable views) are available in MySQL Server 5.1.
Views are stored queries that when invoked produce a result set. A view
acts as a virtual table.

To use views if you have upgraded to MySQL 5.1 from an older release
that did not support views, you should upgrade your grant tables so
that they contain the view-related privileges. See *Note
mysql-upgrade::.

The following discussion describes the syntax for creating and dropping
views, and shows some examples of how to use them.

*Additional Resources*

   * You may find the Views User Forum
     (http://forums.mysql.com/list.php?100) of use when working with
     views.

   * For answers to some commonly asked questions regarding views in
     MySQL, see *Note faqs-views::.

   * There are some restrictions on the use of views; see *Note
     view-restrictions::.


File: manual.info,  Node: view-syntax,  Next: view-algorithms,  Prev: views,  Up: views

19.5.1 View Syntax
------------------

The *Note `CREATE VIEW': create-view. statement creates a new view (see
*Note create-view::). To alter the definition of a view or drop a view,
use *Note `ALTER VIEW': alter-view. (see *Note alter-view::), or *Note
`DROP VIEW': drop-view. (see *Note drop-view::).

A view can be created from many kinds of *Note `SELECT': select.
statements. It can refer to base tables or other views. It can use
joins, *Note `UNION': union, and subqueries. The *Note `SELECT':
select. need not even refer to any tables. The following example
defines a view that selects two columns from another table, as well as
an expression calculated from those columns:


     mysql> CREATE TABLE t (qty INT, price INT);
     mysql> INSERT INTO t VALUES(3, 50), (5, 60);
     mysql> CREATE VIEW v AS SELECT qty, price, qty*price AS value FROM t;
     mysql> SELECT * FROM v;
     +------+-------+-------+
     | qty  | price | value |
     +------+-------+-------+
     |    3 |    50 |   150 |
     |    5 |    60 |   300 |
     +------+-------+-------+
     mysql> SELECT * FROM v WHERE qty = 5;
     +------+-------+-------+
     | qty  | price | value |
     +------+-------+-------+
     |    5 |    60 |   300 |
     +------+-------+-------+


File: manual.info,  Node: view-algorithms,  Next: view-updatability,  Prev: view-syntax,  Up: views

19.5.2 View Processing Algorithms
---------------------------------

The optional `ALGORITHM' clause for *Note `CREATE VIEW': create-view. or
*Note `ALTER VIEW': alter-view. is a MySQL extension to standard SQL.
It affects how MySQL processes the view.  `ALGORITHM' takes three
values: `MERGE', `TEMPTABLE', or `UNDEFINED'. The default algorithm is
`UNDEFINED' if no `ALGORITHM' clause is present.

For `MERGE', the text of a statement that refers to the view and the
view definition are merged such that parts of the view definition
replace corresponding parts of the statement.

For `TEMPTABLE', the results from the view are retrieved into a
temporary table, which then is used to execute the statement.

For `UNDEFINED', MySQL chooses which algorithm to use. It prefers
`MERGE' over `TEMPTABLE' if possible, because `MERGE' is usually more
efficient and because a view cannot be updatable if a temporary table
is used.

A reason to choose `TEMPTABLE' explicitly is that locks can be released
on underlying tables after the temporary table has been created and
before it is used to finish processing the statement. This might result
in quicker lock release than the `MERGE' algorithm so that other
clients that use the view are not blocked as long.

A view algorithm can be `UNDEFINED' for three reasons:

   * No `ALGORITHM' clause is present in the *Note `CREATE VIEW':
     create-view. statement.

   * The *Note `CREATE VIEW': create-view. statement has an explicit
     `ALGORITHM = UNDEFINED' clause.

   * `ALGORITHM = MERGE' is specified for a view that can be processed
     only with a temporary table. In this case, MySQL generates a
     warning and sets the algorithm to `UNDEFINED'.

As mentioned earlier, `MERGE' is handled by merging corresponding parts
of a view definition into the statement that refers to the view. The
following examples briefly illustrate how the `MERGE' algorithm works.
The examples assume that there is a view `v_merge' that has this
definition:


     CREATE ALGORITHM = MERGE VIEW v_merge (vc1, vc2) AS
     SELECT c1, c2 FROM t WHERE c3 > 100;

Example 1: Suppose that we issue this statement:


     SELECT * FROM v_merge;

MySQL handles the statement as follows:

   * `v_merge' becomes `t'

   * `*' becomes `vc1, vc2', which corresponds to `c1, c2'

   * The view `WHERE' clause is added

The resulting statement to be executed becomes:


     SELECT c1, c2 FROM t WHERE c3 > 100;

Example 2: Suppose that we issue this statement:


     SELECT * FROM v_merge WHERE vc1 < 100;

This statement is handled similarly to the previous one, except that
`vc1 < 100' becomes `c1 < 100' and the view `WHERE' clause is added to
the statement `WHERE' clause using an `AND' connective (and parentheses
are added to make sure the parts of the clause are executed with
correct precedence). The resulting statement to be executed becomes:


     SELECT c1, c2 FROM t WHERE (c3 > 100) AND (c1 < 100);

Effectively, the statement to be executed has a `WHERE' clause of this
form:


     WHERE (select WHERE) AND (view WHERE)

If the `MERGE' algorithm cannot be used, a temporary table must be used
instead. `MERGE' cannot be used if the view contains any of the
following constructs:

   * Aggregate functions (`SUM()', `MIN()', `MAX()', `COUNT()', and so
     forth)

   * `DISTINCT'

   * `GROUP BY'

   * `HAVING'

   * `LIMIT'

   * *Note `UNION': union. or *Note `UNION ALL': union.

   * Subquery in the select list

   * Refers only to literal values (in this case, there is no
     underlying table)


File: manual.info,  Node: view-updatability,  Next: view-metadata,  Prev: view-algorithms,  Up: views

19.5.3 Updatable and Insertable Views
-------------------------------------

Some views are updatable. That is, you can use them in statements such
as *Note `UPDATE': update, *Note `DELETE': delete, or *Note `INSERT':
insert. to update the contents of the underlying table. For a view to
be updatable, there must be a one-to-one relationship between the rows
in the view and the rows in the underlying table. There are also
certain other constructs that make a view nonupdatable. To be more
specific, a view is not updatable if it contains any of the following:

   * Aggregate functions (`SUM()', `MIN()', `MAX()', `COUNT()', and so
     forth)

   * `DISTINCT'

   * `GROUP BY'

   * `HAVING'

   * *Note `UNION': union. or *Note `UNION ALL': union.

   * Subquery in the select list

   * Certain joins (see additional join discussion later in this
     section)

   * Nonupdatable view in the `FROM' clause

   * A subquery in the `WHERE' clause that refers to a table in the
     `FROM' clause

   * Refers only to literal values (in this case, there is no
     underlying table to update)

   * Uses `ALGORITHM = TEMPTABLE' (use of a temporary table always
     makes a view nonupdatable)

   * Multiple references to any column of a base table.

With respect to insertability (being updatable with *Note `INSERT':
insert. statements), an updatable view is insertable if it also
satisfies these additional requirements for the view columns:

   * There must be no duplicate view column names.

   * The view must contain all columns in the base table that do not
     have a default value.

   * The view columns must be simple column references and not derived
     columns. A derived column is one that is not a simple column
     reference but is derived from an expression. These are examples of
     derived columns:


          3.14159
          col1 + 3
          UPPER(col2)
          col3 / col4
          (SUBQUERY)

A view that has a mix of simple column references and derived columns
is not insertable, but it can be updatable if you update only those
columns that are not derived. Consider this view:


     CREATE VIEW v AS SELECT col1, 1 AS col2 FROM t;

This view is not insertable because `col2' is derived from an
expression. But it is updatable if the update does not try to update
`col2'. This update is permissible:


     UPDATE v SET col1 = 0;

This update is not permissible because it attempts to update a derived
column:


     UPDATE v SET col2 = 0;

It is sometimes possible for a multiple-table view to be updatable,
assuming that it can be processed with the `MERGE' algorithm. For this
to work, the view must use an inner join (not an outer join or a *Note
`UNION': union.). Also, only a single table in the view definition can
be updated, so the `SET' clause must name only columns from one of the
tables in the view. Views that use *Note `UNION ALL': union. are not
permitted even though they might be theoretically updatable, because
the implementation uses temporary tables to process them.

For a multiple-table updatable view, *Note `INSERT': insert. can work
if it inserts into a single table. *Note `DELETE': delete. is not
supported.

*Note `INSERT DELAYED': insert-delayed. is not supported for views.

If a table contains an `AUTO_INCREMENT' column, inserting into an
insertable view on the table that does not include the `AUTO_INCREMENT'
column does not change the value of `LAST_INSERT_ID()', because the side
effects of inserting default values into columns not part of the view
should not be visible.

The `WITH CHECK OPTION' clause can be given for an updatable view to
prevent inserts or updates to rows except those for which the `WHERE'
clause in the SELECT_STATEMENT is true.

In a `WITH CHECK OPTION' clause for an updatable view, the `LOCAL' and
`CASCADED' keywords determine the scope of check testing when the view
is defined in terms of another view. The `LOCAL' keyword restricts the
`CHECK OPTION' only to the view being defined. `CASCADED' causes the
checks for underlying views to be evaluated as well. When neither
keyword is given, the default is `CASCADED'. Consider the definitions
for the following table and set of views:


     mysql> CREATE TABLE t1 (a INT);
     mysql> CREATE VIEW v1 AS SELECT * FROM t1 WHERE a < 2
         -> WITH CHECK OPTION;
     mysql> CREATE VIEW v2 AS SELECT * FROM v1 WHERE a > 0
         -> WITH LOCAL CHECK OPTION;
     mysql> CREATE VIEW v3 AS SELECT * FROM v1 WHERE a > 0
         -> WITH CASCADED CHECK OPTION;

Here the `v2' and `v3' views are defined in terms of another view, `v1'.
`v2' has a `LOCAL' check option, so inserts are tested only against the
`v2' check. `v3' has a `CASCADED' check option, so inserts are tested
not only against its own check, but against those of underlying views.
The following statements illustrate these differences:


     mysql> INSERT INTO v2 VALUES (2);
     Query OK, 1 row affected (0.00 sec)
     mysql> INSERT INTO v3 VALUES (2);
     ERROR 1369 (HY000): CHECK OPTION failed 'test.v3'

MySQL sets a flag, called the view updatability flag, at *Note `CREATE
VIEW': create-view. time. The flag is set to `YES' (true) if *Note
`UPDATE': update. and *Note `DELETE': delete. (and similar operations)
are legal for the view. Otherwise, the flag is set to `NO' (false). The
`IS_UPDATABLE' column in the *Note `INFORMATION_SCHEMA.VIEWS':
views-table. table displays the status of this flag. It means that the
server always knows whether a view is updatable. If the view is not
updatable, statements such *Note `UPDATE': update, *Note `DELETE':
delete, and *Note `INSERT': insert. are illegal and will be rejected.
(Note that even if a view is updatable, it might not be possible to
insert into it, as described elsewhere in this section.)

The updatability of views may be affected by the value of the
`updatable_views_with_limit' system variable. See *Note
server-system-variables::.


File: manual.info,  Node: view-metadata,  Prev: view-updatability,  Up: views

19.5.4 View Metadata
--------------------

Metadata about views can be obtained as follows:

   * Query the *Note `VIEWS': views-table. table of the
     `INFORMATION_SCHEMA' database. See *Note views-table::.

   * Use the *Note `SHOW CREATE VIEW': show-create-view.  statement.
     See *Note show-create-view::.


File: manual.info,  Node: stored-programs-security,  Next: stored-programs-logging,  Prev: views,  Up: stored-programs-views

19.6 Access Control for Stored Programs and Views
=================================================

Stored programs and views are defined prior to use and, when
referenced, execute within a security context that determines their
privileges. These privileges are controlled by their `DEFINER'
attribute, and, if there is one, their `SQL SECURITY' characteristic.

All stored programs (procedures, functions, triggers, and events) and
views can have a `DEFINER' attribute that names a MySQL account. If the
`DEFINER' attribute is omitted from a stored program or view
definition, the default account is the user who creates the object.

In addition, stored routines (procedures and functions) and views can
have a `SQL SECURITY' characteristic with a value of `DEFINER' or
`INVOKER' to specify whether the object executes in definer or invoker
context. If the `SQL SECURITY' characteristic is omitted, the default
is definer context.

Triggers and events have no `SQL SECURITY' characteristic and always
execute in definer context. The server invokes these objects
automatically as necessary, so there is no invoking user.

Definer and invoker security contexts differ as follows:

   * A stored program or view that executes in definer security context
     executes with the privileges of the account named by its `DEFINER'
     attribute. These privileges may be entirely different from those
     of the invoking user. The invoker must have appropriate privileges
     to reference the object (for example, `EXECUTE' to call a stored
     procedure or `SELECT' to select from a view), but when the object
     executes, the invoker's privileges are ignored and only the
     `DEFINER' account privileges matter. If this account has few
     privileges, the object is correspondingly limited in the
     operations it can perform. If the `DEFINER' account is highly
     privileged (such as a `root' account), the object can perform
     powerful operations _no matter who invokes it._

   * A stored routine or view that executes in invoker security context
     can perform only operations for which the invoker has privileges.
     The `DEFINER' attribute can be specified but has no effect for
     objects that execute in invoker context.

Consider the following stored procedure:


     CREATE DEFINER = 'admin'@'localhost' PROCEDURE p1()
     SQL SECURITY DEFINER
     BEGIN
       UPDATE t1 SET counter = counter + 1;
     END;

Any user who has the `EXECUTE' privilege for `p1' can invoke it with a
*Note `CALL': call. statement. However, when `p1' executes, it does so
in `DEFINER' security context and thus executes with the privileges of
`'admin'@'localhost'', the account named in the `DEFINER' attribute.
This account must have the `EXECUTE' privilege for `p1' as well as the
`UPDATE' privilege for the table `t1'. Otherwise, the procedure fails.

Now consider this stored procedure, which is identical to `p1' except
that its `SQL SECURITY' characteristic is `INVOKER':


     CREATE DEFINER = 'admin'@'localhost' PROCEDURE p2()
     SQL SECURITY INVOKER
     BEGIN
       UPDATE t1 SET counter = counter + 1;
     END;

`p2', unlike `p1', executes in `INVOKER' security context. The
`DEFINER' attribute is irrelevant and `p2' executes with the privileges
of the invoking user. `p2' fails if the invoker lacks the `EXECUTE'
privilege for `p2' or the `UPDATE' privilege for the table `t1'.

MySQL uses the following rules to control which accounts a user can
specify in an object `DEFINER' attribute:

   * You can specify a `DEFINER' value other than your own account only
     if you have the `SUPER' privilege.

   * If you do not have the `SUPER' privilege, the only legal user
     value is your own account, either specified literally or by using
     `CURRENT_USER'. You cannot set the definer to some other account.

To minimize the risk potential for stored program and view creation and
use, follow these guidelines:

   * For a stored routine or view, use `SQL SECURITY INVOKER' in the
     object definition when possible so that it can be used only by
     users with permissions appropriate for the operations performed by
     the object.

   * If you create definer-context stored programs or views while using
     an account that has the `SUPER' privilege, specify an explicit
     `DEFINER' attribute that names an account possessing only the
     privileges required for the operations performed by the object.
     Specify a highly privileged `DEFINER' account only when absolutely
     necessary.

   * Administrators can prevent users from specifying highly privileged
     `DEFINER' accounts by not granting them the `SUPER' privilege.

   * Definer-context objects should be written keeping in mind that
     they may be able to access data for which the invoking user has no
     privileges. In some cases, you can prevent reference to these
     objects by not granting unauthorized users particular privileges:

        * A stored procedure or function cannot be referenced by a user
          who does not have the `EXECUTE' privilege for it.

        * A view cannot be referenced by a user who does not have the
          appropriate privilege for it (`SELECT' to select from it,
          `INSERT' to insert into it, and so forth).

     However, no such control exists for triggers because users do not
     reference them directly. A trigger always executes in `DEFINER'
     context and is activated by access to the table with which it is
     associated, even ordinary table accesses by users with no special
     privileges. If the `DEFINER' account is highly privileged, the
     trigger can perform sensitive or dangerous operations. This
     remains true if the `SUPER' and `TRIGGER' privileges needed to
     create the trigger are revoked from the account of the user who
     created it. Administrators should be especially careful about
     granting users that combination of privileges.


File: manual.info,  Node: stored-programs-logging,  Prev: stored-programs-security,  Up: stored-programs-views

19.7 Binary Logging of Stored Programs
======================================

The binary log contains information about SQL statements that modify
database contents. This information is stored in the form of `events'
that describe the modifications. The binary log has two important
purposes:

   * For replication, the binary log is used on master replication
     servers as a record of the statements to be sent to slave servers.
     The master server sends the events contained in its binary log to
     its slaves, which execute those events to make the same data
     changes that were made on the master. See *Note
     replication-implementation::.

   * Certain data recovery operations require use of the binary log.
     After a backup file has been restored, the events in the binary
     log that were recorded after the backup was made are re-executed.
     These events bring databases up to date from the point of the
     backup. See *Note recovery-from-backups::.

However, there are certain binary logging issues that apply with
respect to stored programs (stored procedures and functions, triggers,
and events), if logging occurs at the statement level:

   * In some cases, it is possible that a statement will affect
     different sets of rows on a master and a slave.

   * Replicated statements executed on a slave are processed by the
     slave SQL thread, which has full privileges. It is possible for a
     procedure to follow different execution paths on master and slave
     servers, so a user can write a routine containing a dangerous
     statement that will execute only on the slave where it is
     processed by a thread that has full privileges.

   * If a stored program that modifies data is nondeterministic, it is
     not repeatable. This can result in different data on a master and
     slave, or cause restored data to differ from the original data.

This section describes how MySQL 5.1 handles binary logging for stored
programs. It states the current conditions that the implementation
places on the use of stored programs, and what you can do to avoid
problems. It also provides additional information about the reasons for
these conditions.

In general, the issues described here result when binary logging occurs
at the SQL statement level. If you use row-based binary logging, the
log contains changes made to individual rows as a result of executing
SQL statements. When routines or triggers execute, row changes are
logged, not the statements that make the changes. For stored
procedures, this means that the *Note `CALL': call. statement is not
logged. For stored functions, row changes made within the function are
logged, not the function invocation. For triggers, row changes made by
the trigger are logged. On the slave side, only the row changes are
seen, not the stored program invocation. For general information about
row-based logging, see *Note replication-formats::.

Unless noted otherwise, the remarks here assume that you have enabled
binary logging by starting the server with the `--log-bin' option. (See
*Note binary-log::.) If the binary log is not enabled, replication is
not possible, nor is the binary log available for data recovery.

The current conditions on the use of stored functions in MySQL 5.1 can
be summarized as follows. These conditions do not apply to stored
procedures or Event Scheduler events and they do not apply unless
binary logging is enabled.

   * To create or alter a stored function, you must have the `SUPER'
     privilege, in addition to the `CREATE ROUTINE' or `ALTER ROUTINE'
     privilege that is normally required. (Depending on the `DEFINER'
     value in the function definition, `SUPER' might be required
     regardless of whether binary logging is enabled. See *Note
     create-procedure::.)

   * When you create a stored function, you must declare either that it
     is deterministic or that it does not modify data.  Otherwise, it
     may be unsafe for data recovery or replication.

     By default, for a *Note `CREATE FUNCTION': create-function.
     statement to be accepted, at least one of `DETERMINISTIC', `NO
     SQL', or `READS SQL DATA' must be specified explicitly. Otherwise
     an error occurs:


          ERROR 1418 (HY000): This function has none of DETERMINISTIC, NO SQL,
          or READS SQL DATA in its declaration and binary logging is enabled
          (you *might* want to use the less safe log_bin_trust_function_creators
          variable)

     This function is deterministic (and does not modify data), so it
     is safe:


          CREATE FUNCTION f1(i INT)
          RETURNS INT
          DETERMINISTIC
          READS SQL DATA
          BEGIN
            RETURN i;
          END;

     This function uses `UUID()', which is not deterministic, so the
     function also is not deterministic and is not safe:


          CREATE FUNCTION f2()
          RETURNS CHAR(36) CHARACTER SET utf8
          BEGIN
            RETURN UUID();
          END;

     This function modifies data, so it may not be safe:


          CREATE FUNCTION f3(p_id INT)
          RETURNS INT
          BEGIN
            UPDATE t SET modtime = NOW() WHERE id = p_id;
            RETURN ROW_COUNT();
          END;

     Assessment of the nature of a function is based on the `honesty'
     of the creator: MySQL does not check that a function declared
     `DETERMINISTIC' is free of statements that produce
     nondeterministic results.

   * Although it is possible to create a deterministic stored function
     without specifying `DETERMINISTIC', you cannot as of MySQL 5.1.15
     execute this function using statement-based binary logging. To
     execute such a function, you must use row-based or mixed binary
     logging. Alternatively, if you explicitly specify `DETERMINISTIC'
     in the function definition, you can use any kind of logging,
     including statement-based logging.

   * To relax the preceding conditions on function creation (that you
     must have the `SUPER' privilege and that a function must be
     declared deterministic or to not modify data), set the global
     `log_bin_trust_function_creators' system variable to 1. By
     default, this variable has a value of 0, but you can change it
     like this:


          mysql> SET GLOBAL log_bin_trust_function_creators = 1;

     You can also set this variable by using the
     `--log-bin-trust-function-creators=1' option when starting the
     server.

     If binary logging is not enabled, `log_bin_trust_function_creators'
     does not apply. `SUPER' is not required for function creation
     unless, as described previously, the `DEFINER' value in the
     function definition requires it.

   * For information about built-in functions that may be unsafe for
     replication (and thus cause stored functions that use them to be
     unsafe as well), see *Note replication-features::.

Triggers are similar to stored functions, so the preceding remarks
regarding functions also apply to triggers with the following
exception: *Note `CREATE TRIGGER': create-trigger. does not have an
optional `DETERMINISTIC' characteristic, so triggers are assumed to be
always deterministic. However, this assumption might in some cases be
invalid. For example, the `UUID()' function is nondeterministic (and
does not replicate). You should be careful about using such functions
in triggers.

Triggers can update tables, so error messages similar to those for
stored functions occur with *Note `CREATE TRIGGER': create-trigger. if
you do not have the required privileges. On the slave side, the slave
uses the trigger `DEFINER' attribute to determine which user is
considered to be the creator of the trigger.

The rest of this section provides additional detail about the logging
implementation and its implications. You need not read it unless you
are interested in the background on the rationale for the current
logging-related conditions on stored routine use. This discussion
applies only for statement-based logging, and not for row-based
logging, with the exception of the first item: `CREATE' and `DROP'
statements are logged as statements regardless of the logging mode.

   * The server writes *Note `CREATE EVENT': create-event, *Note
     `CREATE PROCEDURE': create-procedure, *Note `CREATE FUNCTION':
     create-function, *Note `ALTER EVENT': alter-event, *Note `ALTER
     PROCEDURE': alter-procedure, *Note `ALTER FUNCTION':
     alter-function, *Note `DROP EVENT': drop-event, *Note `DROP
     PROCEDURE': drop-procedure, and *Note `DROP FUNCTION':
     drop-function. statements to the binary log.

   * A stored function invocation is logged as a *Note `SELECT':
     select. statement if the function changes data and occurs within a
     statement that would not otherwise be logged. This prevents
     nonreplication of data changes that result from use of stored
     functions in nonlogged statements. For example, *Note `SELECT':
     select.  statements are not written to the binary log, but a *Note
     `SELECT': select. might invoke a stored function that makes
     changes. To handle this, a `SELECT FUNC_NAME()' statement is
     written to the binary log when the given function makes a change.
     Suppose that the following statements are executed on the master:


          CREATE FUNCTION f1(a INT) RETURNS INT
          BEGIN
            IF (a < 3) THEN
              INSERT INTO t2 VALUES (a);
            END IF;
            RETURN 0;
          END;

          CREATE TABLE t1 (a INT);
          INSERT INTO t1 VALUES (1),(2),(3);

          SELECT f1(a) FROM t1;

     When the *Note `SELECT': select. statement executes, the function
     `f1()' is invoked three times. Two of those invocations insert a
     row, and MySQL logs a *Note `SELECT': select. statement for each
     of them. That is, MySQL writes the following statements to the
     binary log:


          SELECT f1(1);
          SELECT f1(2);

     The server also logs a *Note `SELECT': select.  statement for a
     stored function invocation when the function invokes a stored
     procedure that causes an error. In this case, the server writes
     the *Note `SELECT': select.  statement to the log along with the
     expected error code. On the slave, if the same error occurs, that
     is the expected result and replication continues. Otherwise,
     replication stops.

     Note: Before MySQL 5.1.7, you will see these `SELECT FUNC_NAME()'
     statements logged as `DO FUNC_NAME()'. The change to *Note
     `SELECT': select. was made because use of *Note `DO': do. was
     found to yield insufficient control over error code checking.

   * Logging stored function invocations rather than the statements
     executed by a function has a security implication for replication,
     which arises from two factors:

        * It is possible for a function to follow different execution
          paths on master and slave servers.

        * Statements executed on a slave are processed by the slave SQL
          thread which has full privileges.

     The implication is that although a user must have the `CREATE
     ROUTINE' privilege to create a function, the user can write a
     function containing a dangerous statement that will execute only
     on the slave where it is processed by a thread that has full
     privileges. For example, if the master and slave servers have
     server ID values of 1 and 2, respectively, a user on the master
     server could create and invoke an unsafe function `unsafe_func()'
     as follows:


          mysql> delimiter //
          mysql> CREATE FUNCTION unsafe_func () RETURNS INT
              -> BEGIN
              ->   IF @@server_id=2 THEN DANGEROUS_STATEMENT; END IF;
              ->   RETURN 1;
              -> END;
              -> //
          mysql> delimiter ;
          mysql> INSERT INTO t VALUES(unsafe_func());

     The *Note `CREATE FUNCTION': create-function. and *Note `INSERT':
     insert. statements are written to the binary log, so the slave
     will execute them. Because the slave SQL thread has full
     privileges, it will execute the dangerous statement. Thus, the
     function invocation has different effects on the master and slave
     and is not replication-safe.

     To guard against this danger for servers that have binary logging
     enabled, stored function creators must have the `SUPER' privilege,
     in addition to the usual `CREATE ROUTINE' privilege that is
     required. Similarly, to use *Note `ALTER FUNCTION':
     alter-function, you must have the `SUPER' privilege in addition to
     the `ALTER ROUTINE' privilege.  Without the `SUPER' privilege, an
     error will occur:


          ERROR 1419 (HY000): You do not have the SUPER privilege and
          binary logging is enabled (you *might* want to use the less safe
          log_bin_trust_function_creators variable)

     If you do not want to require function creators to have the
     `SUPER' privilege (for example, if all users with the `CREATE
     ROUTINE' privilege on your system are experienced application
     developers), set the global `log_bin_trust_function_creators'
     system variable to 1. You can also set this variable by using the
     `--log-bin-trust-function-creators=1' option when starting the
     server. If binary logging is not enabled,
     `log_bin_trust_function_creators' does not apply. `SUPER' is not
     required for function creation unless, as described previously,
     the `DEFINER' value in the function definition requires it.

   * If a function that performs updates is nondeterministic, it is not
     repeatable. This can have two undesirable effects:

        * It will make a slave different from the master.

        * Restored data will be different from the original data.

     To deal with these problems, MySQL enforces the following
     requirement: On a master server, creation and alteration of a
     function is refused unless you declare the function to be
     deterministic or to not modify data. Two sets of function
     characteristics apply here:

        * The `DETERMINISTIC' and `NOT DETERMINISTIC' characteristics
          indicate whether a function always produces the same result
          for given inputs.  The default is `NOT DETERMINISTIC' if
          neither characteristic is given. To declare that a function
          is deterministic, you must specify `DETERMINISTIC' explicitly.

        * The `CONTAINS SQL', `NO SQL', `READS SQL DATA', and `MODIFIES
          SQL DATA' characteristics provide information about whether
          the function reads or writes data. Either `NO SQL' or `READS
          SQL DATA' indicates that a function does not change data, but
          you must specify one of these explicitly because the default
          is `CONTAINS SQL' if no characteristic is given.

     By default, for a *Note `CREATE FUNCTION': create-function.
     statement to be accepted, at least one of `DETERMINISTIC', `NO
     SQL', or `READS SQL DATA' must be specified explicitly. Otherwise
     an error occurs:


          ERROR 1418 (HY000): This function has none of DETERMINISTIC, NO SQL,
          or READS SQL DATA in its declaration and binary logging is enabled
          (you *might* want to use the less safe log_bin_trust_function_creators
          variable)

     If you set `log_bin_trust_function_creators' to 1, the requirement
     that functions be deterministic or not modify data is dropped.

   * Stored procedure calls are logged at the statement level rather
     than at the *Note `CALL': call. level.  That is, the server does
     not log the *Note `CALL': call. statement, it logs those
     statements within the procedure that actually execute. As a
     result, the same changes that occur on the master will be observed
     on slave servers. This prevents problems that could result from a
     procedure having different execution paths on different machines.

     In general, statements executed within a stored procedure are
     written to the binary log using the same rules that would apply
     were the statements to be executed in standalone fashion. Some
     special care is taken when logging procedure statements because
     statement execution within procedures is not quite the same as in
     nonprocedure context:

        * A statement to be logged might contain references to local
          procedure variables. These variables do not exist outside of
          stored procedure context, so a statement that refers to such
          a variable cannot be logged literally. Instead, each
          reference to a local variable is replaced by this construct
          for logging purposes:


               NAME_CONST(VAR_NAME, VAR_VALUE)

          VAR_NAME is the local variable name, and VAR_VALUE is a
          constant indicating the value that the variable has at the
          time the statement is logged.  `NAME_CONST()' has a value of
          VAR_VALUE, and a `name' of VAR_NAME. Thus, if you invoke this
          function directly, you get a result like this:


               mysql> SELECT NAME_CONST('myname', 14);
               +--------+
               | myname |
               +--------+
               |     14 |
               +--------+

          `NAME_CONST()' enables a logged standalone statement to be
          executed on a slave with the same effect as the original
          statement that was executed on the master within a stored
          procedure.

          The use of `NAME_CONST()' can result in a problem for *Note
          `CREATE TABLE ... SELECT': create-table. statements when the
          source column expressions refer to local variables.
          Converting these references to `NAME_CONST()' expressions can
          result in column names that are different on the master and
          slave servers, or names that are too long to be legal column
          identifiers. A workaround is to supply aliases for columns
          that refer to local variables.  Consider this statement when
          `myvar' has a value of 1:


               CREATE TABLE t1 SELECT myvar;

          That will be rewritten as follows:


               CREATE TABLE t1 SELECT NAME_CONST(myvar, 1);

          To ensure that the master and slave tables have the same
          column names, write the statement like this:


               CREATE TABLE t1 SELECT myvar AS myvar;

          The rewritten statement becomes:


               CREATE TABLE t1 SELECT NAME_CONST(myvar, 1) AS myvar;

        * A statement to be logged might contain references to
          user-defined variables. To handle this, MySQL writes a *Note
          `SET': set-statement.  statement to the binary log to make
          sure that the variable exists on the slave with the same
          value as on the master.  For example, if a statement refers
          to a variable `@my_var', that statement will be preceded in
          the binary log by the following statement, where VALUE is the
          value of `@my_var' on the master:


               SET @my_var = VALUE;

        * Procedure calls can occur within a committed or rolled-back
          transaction. Transactional context is accounted for so that
          the transactional aspects of procedure execution are
          replicated correctly. That is, the server logs those
          statements within the procedure that actually execute and
          modify data, and also logs *Note `BEGIN': commit, *Note
          `COMMIT': commit, and *Note `ROLLBACK': commit.  statements
          as necessary. For example, if a procedure updates only
          transactional tables and is executed within a transaction
          that is rolled back, those updates are not logged. If the
          procedure occurs within a committed transaction, *Note
          `BEGIN': commit.  and *Note `COMMIT': commit. statements are
          logged with the updates. For a procedure that executes within
          a rolled-back transaction, its statements are logged using
          the same rules that would apply if the statements were
          executed in standalone fashion:

             * Updates to transactional tables are not logged.

             * Updates to nontransactional tables are logged because
               rollback does not cancel them.

             * Updates to a mix of transactional and nontransactional
               tables are logged surrounded by *Note `BEGIN': commit.
               and *Note `ROLLBACK': commit.  so that slaves will make
               the same changes and rollbacks as on the master.

   * A stored procedure call is _not_ written to the binary log at the
     statement level if the procedure is invoked from within a stored
     function. In that case, the only thing logged is the statement
     that invokes the function (if it occurs within a statement that is
     logged) or a *Note `DO': do. statement (if it occurs within a
     statement that is not logged). For this reason, care should be
     exercised in the use of stored functions that invoke a procedure,
     even if the procedure is otherwise safe in itself.


File: manual.info,  Node: information-schema,  Next: connectors-apis,  Prev: stored-programs-views,  Up: Top

20 INFORMATION_SCHEMA Tables
****************************

* Menu:

* character-sets-table::         The INFORMATION_SCHEMA CHARACTER_SETS Table
* collations-table::             The INFORMATION_SCHEMA COLLATIONS Table
* collation-character-set-applicability-table::  The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table
* columns-table::                The INFORMATION_SCHEMA COLUMNS Table
* column-privileges-table::      The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table
* engines-table::                The INFORMATION_SCHEMA ENGINES Table
* events-table::                 The INFORMATION_SCHEMA EVENTS Table
* status-table::                 The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables
* variables-table::              The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables
* key-column-usage-table::       The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table
* partitions-table::             The INFORMATION_SCHEMA PARTITIONS Table
* plugins-table::                The INFORMATION_SCHEMA PLUGINS Table
* processlist-table::            The INFORMATION_SCHEMA PROCESSLIST Table
* profiling-table::              The INFORMATION_SCHEMA PROFILING Table
* referential-constraints-table::  The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table
* routines-table::               The INFORMATION_SCHEMA ROUTINES Table
* schemata-table::               The INFORMATION_SCHEMA SCHEMATA Table
* schema-privileges-table::      The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table
* statistics-table::             The INFORMATION_SCHEMA STATISTICS Table
* tables-table::                 The INFORMATION_SCHEMA TABLES Table
* table-constraints-table::      The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table
* table-privileges-table::       The INFORMATION_SCHEMA TABLE_PRIVILEGES Table
* triggers-table::               The INFORMATION_SCHEMA TRIGGERS Table
* user-privileges-table::        The INFORMATION_SCHEMA USER_PRIVILEGES Table
* views-table::                  The INFORMATION_SCHEMA VIEWS Table
* mysql-cluster-i_s-tables::     INFORMATION_SCHEMA Tables for MySQL Cluster
* extended-show::                Extensions to SHOW Statements

`INFORMATION_SCHEMA' provides access to database _metadata_,
information about the MySQL server such as the name of a database or
table, the data type of a column, or access privileges. Other terms
that are sometimes used for this information are _data dictionary_ and
_system catalog_.

*Usage Notes for the INFORMATION_SCHEMA Database*

`INFORMATION_SCHEMA' is a database within each MySQL instance, the
place that stores information about all the other databases that the
MySQL server maintains. The `INFORMATION_SCHEMA' database contains
several read-only tables. They are actually views, not base tables, so
there are no files associated with them, and you cannot set triggers on
them. Also, there is no database directory with that name.

Although you can select `INFORMATION_SCHEMA' as the default database
with a *Note `USE': use.  statement, you can only read the contents of
tables, not perform *Note `INSERT': insert, *Note `UPDATE': update, or
*Note `DELETE': delete. operations on them.

*Example*

Here is an example of a statement that retrieves information from
`INFORMATION_SCHEMA':


     mysql> SELECT table_name, table_type, engine
         -> FROM information_schema.tables
         -> WHERE table_schema = 'db5'
         -> ORDER BY table_name;
     +------------+------------+--------+
     | table_name | table_type | engine |
     +------------+------------+--------+
     | fk         | BASE TABLE | InnoDB |
     | fk2        | BASE TABLE | InnoDB |
     | goto       | BASE TABLE | MyISAM |
     | into       | BASE TABLE | MyISAM |
     | k          | BASE TABLE | MyISAM |
     | kurs       | BASE TABLE | MyISAM |
     | loop       | BASE TABLE | MyISAM |
     | pk         | BASE TABLE | InnoDB |
     | t          | BASE TABLE | MyISAM |
     | t2         | BASE TABLE | MyISAM |
     | t3         | BASE TABLE | MyISAM |
     | t7         | BASE TABLE | MyISAM |
     | tables     | BASE TABLE | MyISAM |
     | v          | VIEW       | NULL   |
     | v2         | VIEW       | NULL   |
     | v3         | VIEW       | NULL   |
     | v56        | VIEW       | NULL   |
     +------------+------------+--------+
     17 rows in set (0.01 sec)

Explanation: The statement requests a list of all the tables in
database `db5', showing just three pieces of information: the name of
the table, its type, and its storage engine.

*Character Set Considerations*

The definition for character columns (for example, `TABLES.TABLE_NAME')
is generally `VARCHAR(N) CHARACTER SET utf8' where N is at least 64.
MySQL uses the default collation for this character set
(`utf8_general_ci') for all searches, sorts, comparisons, and other
string operations on such columns.

Because some MySQL objects are represented as files, searches in
`INFORMATION_SCHEMA' string columns can be affected by file system case
sensitivity. For more information, see *Note
charset-collation-information-schema::.

*INFORMATION_SCHEMA as Alternative to SHOW Statements*

The `SELECT ... FROM INFORMATION_SCHEMA' statement is intended as a
more consistent way to provide access to the information provided by
the various *Note `SHOW': show. statements that MySQL supports (*Note
`SHOW DATABASES': show-databases, *Note `SHOW TABLES': show-tables, and
so forth). Using *Note `SELECT': select. has these advantages, compared
to *Note `SHOW': show.:

   * It conforms to Codd's rules, because all access is done on tables.

   * You can use the familiar syntax of the *Note `SELECT': select.
     statement, and only need to learn some table and column names.

   * The implementor need not worry about adding keywords.

   * You can filter, sort, concatenate, and transform the results from
     `INFORMATION_SCHEMA' queries into whatever format your application
     needs, such as a data structure or a text representation to parse.

   * This technique is more interoperable with other database systems.
     For example, Oracle Database users are familiar with querying
     tables in the Oracle data dictionary.

Because *Note `SHOW': show. is familiar and widely used, the *Note
`SHOW': show. statements remain as an alternative. In fact, along with
the implementation of `INFORMATION_SCHEMA', there are enhancements to
*Note `SHOW': show. as described in *Note extended-show::.

*Privileges*

Each MySQL user has the right to access these tables, but can see only
the rows in the tables that correspond to objects for which the user
has the proper access privileges. In some cases (for example, the
`ROUTINE_DEFINITION' column in the *Note `INFORMATION_SCHEMA.ROUTINES':
routines-table. table), users who have insufficient privileges see
`NULL'.  These restrictions do not apply for *Note `InnoDB':
innodb-storage-engine. tables; you can see them with only the `PROCESS'
privilege.

The same privileges apply to selecting information from
`INFORMATION_SCHEMA' and viewing the same information through *Note
`SHOW': show. statements.  In either case, you must have some privilege
on an object to see information about it.

*Performance Considerations*

`INFORMATION_SCHEMA' queries that search for information from more than
one database might take a long time and impact performance. To check
the efficiency of a query, you can use *Note `EXPLAIN': explain. For
information about using *Note `EXPLAIN': explain. output to tune
`INFORMATION_SCHEMA' queries, see *Note
information-schema-optimization::.

*Standards Considerations*

The implementation for the `INFORMATION_SCHEMA' table structures in
MySQL follows the ANSI/ISO SQL:2003 standard Part 11 `Schemata'. Our
intent is approximate compliance with SQL:2003 core feature F021 `Basic
information schema'.

Users of SQL Server 2000 (which also follows the standard) may notice a
strong similarity. However, MySQL has omitted many columns that are not
relevant for our implementation, and added columns that are
MySQL-specific. One such column is the `ENGINE' column in the *Note
`INFORMATION_SCHEMA.TABLES': tables-table.  table.

To avoid using any name that is reserved in the standard or in DB2, SQL
Server, or Oracle, we changed the names of some columns marked `MySQL
extension'. (For example, we changed `COLLATION' to `TABLE_COLLATION'
in the *Note `TABLES': tables-table. table.) See the list of reserved
words near the end of this article:
`https://web.archive.org/web/20070428032454/http://www.dbazine.com/db2/db2-disarticles/gulutzan5'.

*Conventions in the INFORMATION_SCHEMA Reference Sections*

The following sections describe each of the tables and columns in
`INFORMATION_SCHEMA'. For each column, there are three pieces of
information:

   * ``INFORMATION_SCHEMA' Name' indicates the name for the column in
     the `INFORMATION_SCHEMA' table. This corresponds to the standard
     SQL name unless the `Remarks' field says `MySQL extension.'

   * `*Note `SHOW': show. Name' indicates the equivalent field name in
     the closest *Note `SHOW': show. statement, if there is one.

   * `Remarks' provides additional information where applicable. If
     this field is `NULL', it means that the value of the column is
     always `NULL'.  If this field says `MySQL extension,' the column is
     a MySQL extension to standard SQL.

Many sections indicate what *Note `SHOW': show.  statement is
equivalent to a *Note `SELECT': select.  that retrieves information from
`INFORMATION_SCHEMA'. For *Note `SHOW': show. statements that display
information for the default database if you omit a `FROM DB_NAME'
clause, you can often select information for the default database by
adding an `AND TABLE_SCHEMA = SCHEMA()' condition to the `WHERE' clause
of a query that retrieves information from an `INFORMATION_SCHEMA'
table.

For information about `INFORMATION_SCHEMA' tables specific to the *Note
`NDB': mysql-cluster. storage engine (MySQL Cluster), see *Note
mysql-cluster-i_s-tables::.

For answers to questions that are often asked concerning the
`INFORMATION_SCHEMA' database, see *Note faqs-information-schema::.


File: manual.info,  Node: character-sets-table,  Next: collations-table,  Prev: information-schema,  Up: information-schema

20.1 The INFORMATION_SCHEMA CHARACTER_SETS Table
================================================

The *Note `CHARACTER_SETS': character-sets-table. table provides
information about available character sets.

This table describes the `INFORMATION_SCHEMA' *Note `CHARACTER_SETS':
character-sets-table. table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`CHARACTER_SET_NAME'          `Charset'              
`DEFAULT_COLLATE_NAME'        `Default collation'    
`DESCRIPTION'                 `Description'          MySQL extension
`MAXLEN'                      `Maxlen'               MySQL extension

The following statements are equivalent:


     SELECT * FROM INFORMATION_SCHEMA.CHARACTER_SETS
       [WHERE CHARACTER_SET_NAME LIKE 'WILD']

     SHOW CHARACTER SET
       [LIKE 'WILD']


File: manual.info,  Node: collations-table,  Next: collation-character-set-applicability-table,  Prev: character-sets-table,  Up: information-schema

20.2 The INFORMATION_SCHEMA COLLATIONS Table
============================================

The *Note `COLLATIONS': collations-table. table provides information
about collations for each character set.

This table describes the `INFORMATION_SCHEMA' *Note `COLLATIONS':
collations-table. table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`COLLATION_NAME'              `Collation'            
`CHARACTER_SET_NAME'          `Charset'              MySQL extension
`ID'                          `Id'                   MySQL extension
`IS_DEFAULT'                  `Default'              MySQL extension
`IS_COMPILED'                 `Compiled'             MySQL extension
`SORTLEN'                     `Sortlen'              MySQL extension

   * `COLLATION_NAME' is the collation name.

   * `CHARACTER_SET_NAME' is the name of the character set with which
     the collation is associated.

   * `ID' is the collation ID.

   * `IS_DEFAULT' indicates whether the collation is the default for
     its character set.

   * `IS_COMPILED' indicates whether the character set is compiled into
     the server.

   * `SORTLEN' is related to the amount of memory required to sort
     strings expressed in the character set.

Collation information is also available from the *Note `SHOW
COLLATION': show-collation. statement. The following statements are
equivalent:


     SELECT COLLATION_NAME FROM INFORMATION_SCHEMA.COLLATIONS
       [WHERE COLLATION_NAME LIKE 'WILD']

     SHOW COLLATION
       [LIKE 'WILD']


File: manual.info,  Node: collation-character-set-applicability-table,  Next: columns-table,  Prev: collations-table,  Up: information-schema

20.3 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table
=======================================================================

The *Note `COLLATION_CHARACTER_SET_APPLICABILITY':
collation-character-set-applicability-table.  table indicates what
character set is applicable for what collation. The columns are
equivalent to the first two display fields that we get from *Note `SHOW
COLLATION': show-collation.

This table describes the `INFORMATION_SCHEMA
COLLATION_CHARACTER_SET_APPLICABILITY' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`COLLATION_NAME'              `Collation'            
`CHARACTER_SET_NAME'          `Charset'              


File: manual.info,  Node: columns-table,  Next: column-privileges-table,  Prev: collation-character-set-applicability-table,  Up: information-schema

20.4 The INFORMATION_SCHEMA COLUMNS Table
=========================================

The *Note `COLUMNS': columns-table. table provides information about
columns in tables.

This table describes the `INFORMATION_SCHEMA COLUMNS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`TABLE_CATALOG'                                      `NULL'
`TABLE_SCHEMA'                                       
`TABLE_NAME'                                         
`COLUMN_NAME'                 `Field'                
`ORDINAL_POSITION'                                   see notes
`COLUMN_DEFAULT'              `Default'              
`IS_NULLABLE'                 `Null'                 
`DATA_TYPE'                   `Type'                 
`CHARACTER_MAXIMUM_LENGTH'    `Type'                 
`CHARACTER_OCTET_LENGTH'                             
`NUMERIC_PRECISION'           `Type'                 
`NUMERIC_SCALE'               `Type'                 
`CHARACTER_SET_NAME'                                 
`COLLATION_NAME'              `Collation'            
`COLUMN_TYPE'                 `Type'                 MySQL extension
`COLUMN_KEY'                  `Key'                  MySQL extension
`EXTRA'                       `Extra'                MySQL extension
`PRIVILEGES'                  `Privileges'           MySQL extension
`COLUMN_COMMENT'              `Comment'              MySQL extension

*Notes*:

   * In *Note `SHOW': show, the `Type' display includes values from
     several different *Note `COLUMNS': columns-table. columns.

   * `ORDINAL_POSITION' is necessary because you might want to say
     `ORDER BY ORDINAL_POSITION'. Unlike *Note `SHOW': show, *Note
     `SELECT': select. does not have automatic ordering.

   * `CHARACTER_OCTET_LENGTH' should be the same as
     `CHARACTER_MAXIMUM_LENGTH', except for multibyte character sets.

   * `CHARACTER_SET_NAME' can be derived from `Collation'. For example,
     if you say `SHOW FULL COLUMNS FROM t', and you see in the
     `Collation' column a value of `latin1_swedish_ci', the character
     set is what is before the first underscore: `latin1'.

The following statements are nearly equivalent:


     SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT
       FROM INFORMATION_SCHEMA.COLUMNS
       WHERE table_name = 'TBL_NAME'
       [AND table_schema = 'DB_NAME']
       [AND column_name LIKE 'WILD']

     SHOW COLUMNS
       FROM TBL_NAME
       [FROM DB_NAME]
       [LIKE 'WILD']


File: manual.info,  Node: column-privileges-table,  Next: engines-table,  Prev: columns-table,  Up: information-schema

20.5 The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table
===================================================

The *Note `COLUMN_PRIVILEGES': column-privileges-table. table provides
information about column privileges. This information comes from the
`mysql.columns_priv' grant table.

This table describes the `INFORMATION_SCHEMA COLUMN_PRIVILEGES' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`GRANTEE'                                            `'USER_NAME'@'HOST_NAME''
                                                     value
`TABLE_CATALOG'                                      `NULL'
`TABLE_SCHEMA'                                       
`TABLE_NAME'                                         
`COLUMN_NAME'                                        
`PRIVILEGE_TYPE'                                     
`IS_GRANTABLE'                                       

*Notes*:

   * In the output from *Note `SHOW FULL COLUMNS': show-columns, the
     privileges are all in one field and in lowercase, for example,
     `select,insert,update,references'. In *Note `COLUMN_PRIVILEGES':
     column-privileges-table, there is one privilege per row, in
     uppercase.

   * `PRIVILEGE_TYPE' can contain one (and only one) of these values:
     `SELECT', `INSERT', `UPDATE', `REFERENCES'.

   * If the user has `GRANT OPTION' privilege, `IS_GRANTABLE' should be
     `YES'. Otherwise, `IS_GRANTABLE' should be `NO'. The output does
     not list `GRANT OPTION' as a separate privilege.

The following statements are _not_ equivalent:


     SELECT ... FROM INFORMATION_SCHEMA.COLUMN_PRIVILEGES

     SHOW GRANTS ...


File: manual.info,  Node: engines-table,  Next: events-table,  Prev: column-privileges-table,  Up: information-schema

20.6 The INFORMATION_SCHEMA ENGINES Table
=========================================

The *Note `ENGINES': engines-table. table provides information about
storage engines.

This table describes the `INFORMATION_SCHEMA ENGINES' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`ENGINE'                      `Engine'               MySQL extension
`SUPPORT'                     `Support'              MySQL extension
`COMMENT'                     `Comment'              MySQL extension
`TRANSACTIONS'                `Transactions'         MySQL extension
`XA'                          `XA'                   MySQL extension
`SAVEPOINTS'                  `Savepoints'           MySQL extension

*Notes*:

   * The *Note `ENGINES': engines-table. table is a nonstandard table.
     It was added in MySQL 5.1.5. Its contents correspond to the
     columns of the `SHOW ENGINES' statement. For descriptions of its
     columns, see *Note show-engines::.

See also *Note show-engines::.


File: manual.info,  Node: events-table,  Next: status-table,  Prev: engines-table,  Up: information-schema

20.7 The INFORMATION_SCHEMA EVENTS Table
========================================

The *Note `EVENTS': events-table. table provides information about
scheduled events, which are discussed in *Note events::. The `SHOW
Name' values correspond to column names of the *Note `SHOW EVENTS':
show-events. statement.

This table describes the `INFORMATION_SCHEMA EVENTS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`EVENT_CATALOG'                                      `NULL', MySQL
                                                     extension
`EVENT_SCHEMA'                `Db'                   MySQL extension
`EVENT_NAME'                  `Name'                 MySQL extension
`DEFINER'                     `Definer'              MySQL extension
`TIME_ZONE'                   `Time zone'            MySQL extension
`EVENT_BODY'                                         MySQL extension
`EVENT_DEFINITION'                                   MySQL extension
`EVENT_TYPE'                  `Type'                 MySQL extension
`EXECUTE_AT'                  `Execute at'           MySQL extension
`INTERVAL_VALUE'              `Interval value'       MySQL extension
`INTERVAL_FIELD'              `Interval field'       MySQL extension
`SQL_MODE'                                           MySQL extension
`STARTS'                      `Starts'               MySQL extension
`ENDS'                        `Ends'                 MySQL extension
`STATUS'                      `Status'               MySQL extension
`ON_COMPLETION'                                      MySQL extension
`CREATED'                                            MySQL extension
`LAST_ALTERED'                                       MySQL extension
`LAST_EXECUTED'                                      MySQL extension
`EVENT_COMMENT'                                      MySQL extension
`ORIGINATOR'                  `Originator'           MySQL extension
`CHARACTER_SET_CLIENT'        `character_set_client' MySQL extension
`COLLATION_CONNECTION'        `collation_connection' MySQL extension
`DATABASE_COLLATION'          `Database Collation'   MySQL extension

*Notes*:

   * The *Note `EVENTS': events-table. table is a nonstandard table. It
     was added in MySQL 5.1.6.

   * `EVENT_CATALOG': The value of this column is always `NULL'.

   * `EVENT_SCHEMA': The name of the schema (database) to which this
     event belongs.

   * `EVENT_NAME': The name of the event.

   * `DEFINER': The account of the user who created the event, in
     `'USER_NAME'@'HOST_NAME'' format.

   * `TIME_ZONE': The event time zone, which is the time zone used for
     scheduling the event and that is in effect within the event as it
     executes. The default value is `SYSTEM'.

     This column was added in MySQL 5.1.17. See Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) for MySQL 5.1.17
     for important information if you are using the Event Scheduler and
     are upgrading to MySQL 5.1.17 or later from an earlier version.

   * `EVENT_BODY': The language used for the statements in the event's
     *Note `DO': do.  clause; in MySQL 5.1, this is always `SQL'.

     This column was added in MySQL 5.1.12. It is not to be confused
     with the column of the same name (now named `EVENT_DEFINITION')
     that existed in earlier MySQL versions.

   * `EVENT_DEFINITION': The text of the SQL statement making up the
     event's *Note `DO': do. clause; in other words, the statement
     executed by this event.

     *Note*:

     Prior to MySQL 5.1.12, this column was named `EVENT_BODY'.

   * `EVENT_TYPE': The event repetition type, either `ONE TIME'
     (transient) or `RECURRING' (repeating).

   * `EXECUTE_AT': For a one-time event, this is the *Note `DATETIME':
     datetime. value specified in the `AT' clause of the *Note `CREATE
     EVENT': create-event. statement used to create the event, or of
     the last *Note `ALTER EVENT': alter-event. statement that modified
     the event. The value shown in this column reflects the addition or
     subtraction of any `INTERVAL' value included in the event's `AT'
     clause. For example, if an event is created using `ON SCHEDULE AT
     CURRENT_TIMESTAMP + '1:6' DAY_HOUR', and the event was created at
     2006-02-09 14:05:30, the value shown in this column would be
     `'2006-02-10 20:05:30''.

     If the event's timing is determined by an `EVERY' clause instead
     of an `AT' clause (that is, if the event is recurring), the value
     of this column is `NULL'.

   * `INTERVAL_VALUE': For recurring events, this column contains the
     numeric portion of the event's `EVERY' clause.

     For a one-time event (that is, an event whose timing is determined
     by an `AT' clause), this column is `NULL'.

   * `INTERVAL_FIELD': For recurring events, this column contains the
     units portion of the `EVERY' clause governing the timing of the
     event. Thus, this column contains a value such as '*Note `YEAR':
     year.', '`QUARTER'', '`DAY'', and so on.

     *Note*:

     In early MySQL 5.1 releases, this value was prefixed with
     '`INTERVAL_'', and was displayed as '`INTERVAL_YEAR'',
     '`INTERVAL_QUARTER'', '`INTERVAL_DAY'', and so on.

     For a one-time event (that is, an event whose timing is determined
     by an `AT' clause), this column is `NULL'.

   * `SQL_MODE': The SQL mode in effect when the event was created or
     altered, and under which the event executes. For the permitted
     values, see *Note sql-mode::.

   * `STARTS': For a recurring event whose definition includes a
     `STARTS' clause, this column contains the corresponding *Note
     `DATETIME': datetime. value. As with the `EXECUTE_AT' column, this
     value resolves any expressions used.

     If there is no `STARTS' clause affecting the timing of the event,
     this column is `NULL'.  (Prior to MySQL 5.1.8, it contained
     `0000-00-00 00:00:00' in such cases.)

   * `ENDS': For a recurring event whose definition includes a `ENDS'
     clause, this column contains the corresponding *Note `DATETIME':
     datetime. value. As with the `EXECUTE_AT' column, this value
     resolves any expressions used.

     If there is no `ENDS' clause affecting the timing of the event,
     this column is `NULL'.

   * `STATUS': One of the three values `ENABLED', `DISABLED', or
     `SLAVESIDE_DISABLED'.

     `SLAVESIDE_DISABLED' was added to the list of possible values for
     this column in MySQL 5.1.18. This value indicates that the
     creation of the event occurred on another MySQL server acting as a
     replication master and was replicated to the current MySQL server
     which is acting as a slave, but the event is not presently being
     executed on the slave. See *Note replication-features-invoked::,
     for more information.

   * `ON_COMPLETION': One of the two values `PRESERVE' or `NOT
     PRESERVE'.

   * `CREATED': The date and time when the event was created. This is a
     *Note `TIMESTAMP': datetime. value.

   * `LAST_ALTERED': The date and time when the event was last
     modified. This is a *Note `TIMESTAMP': datetime. value. If the
     event has not been modified since its creation, this column holds
     the same value as the `CREATED' column.

   * `LAST_EXECUTED': The date and time when the event last executed. A
     *Note `DATETIME': datetime.  value. If the event has never
     executed, this column is `NULL'.

     Before MySQL 5.1.23, `LAST_EXECUTED' indicates when event finished
     executing. As of 5.1.23, `LAST_EXECUTED' instead indicates when the
     event started. As a result, the `ENDS' column is never less than
     `LAST_EXECUTED'.

   * `EVENT_COMMENT': The text of a comment, if the event has one. If
     not, the value of this column is an empty string.

   * `ORIGINATOR': The server ID of the MySQL server on which the event
     was created; used in replication.  The default value is 0. This
     column was added in MySQL 5.1.18.

   * `CHARACTER_SET_CLIENT': The session value of the
     `character_set_client' system variable when the event was created.
     This column was added in MySQL 5.1.21.

   * `COLLATION_CONNECTION': The session value of the
     `collation_connection' system variable when the event was created.
     This column was added in MySQL 5.1.21.

   * `DATABASE_COLLATION': The collation of the database with which the
     event is associated. This column was added in MySQL 5.1.21.

*Example*: Suppose that the user `jon@ghidora' creates an event named
`e_daily', and then modifies it a few minutes later using an *Note
`ALTER EVENT': alter-event.  statement, as shown here:


     DELIMITER |

     CREATE EVENT e_daily
         ON SCHEDULE
           EVERY 1 DAY
         COMMENT 'Saves total number of sessions then clears the table each day'
         DO
           BEGIN
             INSERT INTO site_activity.totals (time, total)
               SELECT CURRENT_TIMESTAMP, COUNT(*)
                 FROM site_activity.sessions;
             DELETE FROM site_activity.sessions;
           END |

     DELIMITER ;

     ALTER EVENT e_daily
         ENABLED;

(Note that comments can span multiple lines.)

This user can then run the following *Note `SELECT': select. statement,
and obtain the output shown:


     mysql> SELECT * FROM INFORMATION_SCHEMA.EVENTS
          > WHERE EVENT_NAME = 'e_daily'
          > AND EVENT_SCHEMA = 'myschema'\G
     *************************** 1. row ***************************
            EVENT_CATALOG: NULL
             EVENT_SCHEMA: test
               EVENT_NAME: e_daily
                  DEFINER: me@localhost
                TIME_ZONE: SYSTEM
               EVENT_BODY: SQL
         EVENT_DEFINITION: BEGIN
             INSERT INTO site_activity.totals (time, total)
               SELECT CURRENT_TIMESTAMP, COUNT(*)
                 FROM site_activity.sessions;
             DELETE FROM site_activity.sessions;
           END
               EVENT_TYPE: RECURRING
               EXECUTE_AT: NULL
           INTERVAL_VALUE: 1
           INTERVAL_FIELD: DAY
                 SQL_MODE:
                   STARTS: 2008-09-03 12:13:39
                     ENDS: NULL
                   STATUS: ENABLED
            ON_COMPLETION: NOT PRESERVE
                  CREATED: 2008-09-03 12:13:39
             LAST_ALTERED: 2008-09-03 12:13:39
            LAST_EXECUTED: NULL
            EVENT_COMMENT: Saves total number of sessions then clears the
                           table each day
               ORIGINATOR: 1
     CHARACTER_SET_CLIENT: latin1
     COLLATION_CONNECTION: latin1_swedish_ci
       DATABASE_COLLATION: latin1_swedish_ci

Times in the *Note `EVENTS': events-table. table are displayed using
the event time zone or the current session time zone. Prior to MySQL
5.1.17, some of the times are displayed in UTC rather than the event
time zone. For details, see *Note events-metadata::.

See also *Note show-events::.


File: manual.info,  Node: status-table,  Next: variables-table,  Prev: events-table,  Up: information-schema

20.8 The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables
===================================================================

The *Note `GLOBAL_STATUS': status-table.  and *Note `SESSION_STATUS':
status-table.  tables provide information about server status
variables. Their contents correspond to the information produced by the
*Note `SHOW GLOBAL STATUS': show-status. and *Note `SHOW SESSION
STATUS': show-status. statements (see *Note show-status::).

This table describes the *Note `INFORMATION_SCHEMA GLOBAL_STATUS':
status-table. and *Note `SESSION_STATUS': status-table.  tables.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
VARIABLE_NAME                 Variable_name          
VARIABLE_VALUE                Value                  

*Notes*:

   * The *Note `GLOBAL_STATUS': status-table.  and *Note
     `SESSION_STATUS': status-table.  tables were added in MySQL 5.1.12.

   * The `VARIABLE_VALUE' column for each of these tables is defined as
     `VARCHAR(1024)'.  Previously, this column had the data type
     `DECIMAL(22,7)', but was changed to `VARCHAR(20480)' in 5.1.19 to
     avoid loss of data when working with status variables whose values
     were strings, and shortened to `VARCHAR(1024)' in 5.1.31 to
     improve performance.


File: manual.info,  Node: variables-table,  Next: key-column-usage-table,  Prev: status-table,  Up: information-schema

20.9 The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables
=========================================================================

The *Note `GLOBAL_VARIABLES': variables-table.  and *Note
`SESSION_VARIABLES': variables-table.  tables provide information about
server status variables. Their contents correspond to the information
produced by the *Note `SHOW GLOBAL VARIABLES': show-variables. and
*Note `SHOW SESSION VARIABLES': show-variables. statements (see *Note
show-variables::).

This table describes the *Note `INFORMATION_SCHEMA GLOBAL_VARIABLES':
variables-table. and *Note `SESSION_VARIABLES': variables-table.
tables.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
VARIABLE_NAME                 Variable_name          
VARIABLE_VALUE                Value                  

*Notes*:

   * The *Note `GLOBAL_VARIABLES': variables-table.  and *Note
     `SESSION_VARIABLES': variables-table.  tables were added in MySQL
     5.1.12.

   * The `VARIABLE_VALUE' column for each of these tables is defined as
     `VARCHAR(1024)'.  Previously, this column had the data type *Note
     `LONGTEXT': blob.; this was changed in MySQL 5.1.19 to
     `VARCHAR(20480)' and in 5.1.31 to `VARCHAR(1024)' to make these
     tables consistent with the *Note `GLOBAL_STATUS': status-table.
     and *Note `SESSION_STATUS': status-table.  tables, whose
     definitions were changed in those versions (see *Note
     status-table::).

     For variables with very long values that are not completely
     displayed, use *Note `SELECT': select. as a workaround. For
     example:


          SELECT @@GLOBAL.innodb_data_file_path;


File: manual.info,  Node: key-column-usage-table,  Next: partitions-table,  Prev: variables-table,  Up: information-schema

20.10 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table
===================================================

The *Note `KEY_COLUMN_USAGE': key-column-usage-table. table describes
which key columns have constraints.

This table describes the `INFORMATION_SCHEMA KEY_COLUMN_USAGE' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`CONSTRAINT_CATALOG'                                 `NULL'
`CONSTRAINT_SCHEMA'                                  
`CONSTRAINT_NAME'                                    
`TABLE_CATALOG'                                      
`TABLE_SCHEMA'                                       
`TABLE_NAME'                                         
`COLUMN_NAME'                                        
`ORDINAL_POSITION'                                   
`POSITION_IN_UNIQUE_CONSTRAINT'                       
`REFERENCED_TABLE_SCHEMA'                            
`REFERENCED_TABLE_NAME'                              
`REFERENCED_COLUMN_NAME'                             

*Notes*:

   * If the constraint is a foreign key, then this is the column of the
     foreign key, not the column that the foreign key references.

   * The value of `ORDINAL_POSITION' is the column's position within
     the constraint, not the column's position within the table. Column
     positions are numbered beginning with 1.

   * The value of `POSITION_IN_UNIQUE_CONSTRAINT' is `NULL' for unique
     and primary-key constraints. For foreign-key constraints, it is
     the ordinal position in key of the table that is being referenced.

     Suppose that there are two tables name `t1' and `t3' that have the
     following definitions:


          CREATE TABLE t1
          (
              s1 INT,
              s2 INT,
              s3 INT,
              PRIMARY KEY(s3)
          ) ENGINE=InnoDB;

          CREATE TABLE t3
          (
              s1 INT,
              s2 INT,
              s3 INT,
              KEY(s1),
              CONSTRAINT CO FOREIGN KEY (s2) REFERENCES t1(s3)
          ) ENGINE=InnoDB;

     For those two tables, the *Note `KEY_COLUMN_USAGE':
     key-column-usage-table. table has two rows:

        * One row with `CONSTRAINT_NAME' = `'PRIMARY'', `TABLE_NAME' =
          `'t1'', `COLUMN_NAME' = `'s3'', `ORDINAL_POSITION' = `1',
          `POSITION_IN_UNIQUE_CONSTRAINT' = `NULL'.

        * One row with `CONSTRAINT_NAME' = `'CO'', `TABLE_NAME' =
          `'t3'', `COLUMN_NAME' = `'s2'', `ORDINAL_POSITION' = `1',
          `POSITION_IN_UNIQUE_CONSTRAINT' = `1'.


File: manual.info,  Node: partitions-table,  Next: plugins-table,  Prev: key-column-usage-table,  Up: information-schema

20.11 The INFORMATION_SCHEMA PARTITIONS Table
=============================================

The *Note `PARTITIONS': partitions-table. table provides information
about table partitions. See *Note partitioning::, for more information
about partitioning tables.

This table describes the `INFORMATION_SCHEMA PARTITIONS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`TABLE_CATALOG'                                      MySQL extension
`TABLE_SCHEMA'                                       MySQL extension
`TABLE_NAME'                                         MySQL extension
`PARTITION_NAME'                                     MySQL extension
`SUBPARTITION_NAME'                                  MySQL extension
`PARTITION_ORDINAL_POSITION'                         MySQL extension
`SUBPARTITION_ORDINAL_POSITION'                       MySQL extension
`PARTITION_METHOD'                                   MySQL extension
`SUBPARTITION_METHOD'                                MySQL extension
`PARTITION_EXPRESSION'                               MySQL extension
`SUBPARTITION_EXPRESSION'                            MySQL extension
`PARTITION_DESCRIPTION'                              MySQL extension
`TABLE_ROWS'                                         MySQL extension
`AVG_ROW_LENGTH'                                     MySQL extension
`DATA_LENGTH'                                        MySQL extension
`MAX_DATA_LENGTH'                                    MySQL extension
`INDEX_LENGTH'                                       MySQL extension
`DATA_FREE'                                          MySQL extension
`CREATE_TIME'                                        MySQL extension
`UPDATE_TIME'                                        MySQL extension
`CHECK_TIME'                                         MySQL extension
`CHECKSUM'                                           MySQL extension
`PARTITION_COMMENT'                                  MySQL extension
`NODEGROUP'                                          MySQL extension
`TABLESPACE_NAME'                                    MySQL extension

*Notes*:

   * The *Note `PARTITIONS': partitions-table. table is a nonstandard
     table. It was added in MySQL 5.1.6.

     Each record in this table corresponds to an individual partition
     or subpartition of a partitioned table.

   * `TABLE_CATALOG': This column is always `NULL'.

   * `TABLE_SCHEMA': This column contains the name of the database to
     which the table belongs.

   * `TABLE_NAME': This column contains the name of the table
     containing the partition.

   * `PARTITION_NAME': The name of the partition.

   * `SUBPARTITION_NAME': If the *Note `PARTITIONS': partitions-table.
     table record represents a subpartition, then this column contains
     the name of subpartition; otherwise it is `NULL'.

   * `PARTITION_ORDINAL_POSITION': All partitions are indexed in the
     same order as they are defined, with `1' being the number assigned
     to the first partition. The indexing can change as partitions are
     added, dropped, and reorganized; the number shown is this column
     reflects the current order, taking into account any indexing
     changes.

   * `SUBPARTITION_ORDINAL_POSITION': Subpartitions within a given
     partition are also indexed and reindexed in the same manner as
     partitions are indexed within a table.

   * `PARTITION_METHOD': One of the values `RANGE', `LIST', `HASH',
     `LINEAR HASH', `KEY', or `LINEAR KEY'; that is, one of the
     available partitioning types as discussed in *Note
     partitioning-types::.

   * `SUBPARTITION_METHOD': One of the values `HASH', `LINEAR HASH',
     `KEY', or `LINEAR KEY'; that is, one of the available
     subpartitioning types as discussed in *Note
     partitioning-subpartitions::.

   * `PARTITION_EXPRESSION': This is the expression for the
     partitioning function used in the *Note `CREATE TABLE':
     create-table. or *Note `ALTER TABLE': alter-table. statement that
     created the table's current partitioning scheme.

     For example, consider a partitioned table created in the `test'
     database using this statement:


          CREATE TABLE tp (
              c1 INT,
              c2 INT,
              c3 VARCHAR(25)
          )
          PARTITION BY HASH(c1 + c2)
          PARTITIONS 4;

     The `PARTITION_EXPRESSION' column in a PARTITIONS table record for
     a partition from this table displays `c1 + c2', as shown here:


          mysql> SELECT DISTINCT PARTITION_EXPRESSION
               >     FROM INFORMATION_SCHEMA.PARTITIONS
               >     WHERE TABLE_NAME='tp' AND TABLE_SCHEMA='test';
          +----------------------+
          | PARTITION_EXPRESSION |
          +----------------------+
          | c1 + c2              |
          +----------------------+
          1 row in set (0.09 sec)

   * `SUBPARTITION_EXPRESSION': This works in the same fashion for the
     subpartitioning expression that defines the subpartitioning for a
     table as `PARTITION_EXPRESSION' does for the partitioning
     expression used to define a table's partitioning.

     If the table has no subpartitions, then this column is `NULL'.

   * `PARTITION_DESCRIPTION': This column is used for RANGE and LIST
     partitions. For a `RANGE' partition, it contains the value set in
     the partition's `VALUES LESS THAN' clause, which can be either an
     integer or `MAXVALUE'. For a `LIST' partition, this column
     contains the values defined in the partition's `VALUES IN' clause,
     which is a comma-separated list of integer values.

     For partitions whose `PARTITION_METHOD' is other than `RANGE' or
     `LIST', this column is always `NULL'.

   * `TABLE_ROWS': The number of table rows in the partition.

     For partitioned *Note `InnoDB': innodb-storage-engine. tables, the
     row count given in the `TABLE_ROWS' column is only an estimated
     value used in SQL optimization, and may not always be exact.

     Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
     7.1.11, `TABLE_ROWS' shows correct information for *Note `NDB':
     mysql-cluster. tables.  Previously, for partitions of *Note `NDB':
     mysql-cluster.  tables, the `TABLE_ROWS' column value was always 0.

     For *Note `NDB': mysql-cluster. tables, you can also obtain this
     information using the *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc.  utility.

   * `AVG_ROW_LENGTH': The average length of the rows stored in this
     partition or subpartition, in bytes.

     This is the same as `DATA_LENGTH' divided by `TABLE_ROWS'.

     Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
     7.1.11, `AVG_ROW_LENGTH' includes statistics for partitions of
     *Note `NDB': mysql-cluster. tables, whether the tables use
     implicit or explicit partitioning.  (Previously the value of this
     column was always 0 for partitions of *Note `NDB': mysql-cluster.
     tables.)

     You can also obtain equivalent information using the *Note
     `ndb_desc': mysql-cluster-programs-ndb-desc. utility.

   * `DATA_LENGTH': The total length of all rows stored in this
     partition or subpartition, in bytes--that is, the total number of
     bytes stored in the partition or subpartition.

     Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
     7.1.11, `DATA_LENGTH' shows correct information for in-memory data
     in *Note `NDB': mysql-cluster. tables. Previously, for partitions
     of *Note `NDB': mysql-cluster. tables, the `DATA_LENGTH' column
     value was always 0.

     For *Note `NDB': mysql-cluster. tables, you can also obtain this
     information using the *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc.  utility.

   * `MAX_DATA_LENGTH': The maximum number of bytes that can be stored
     in this partition or subpartition.

     Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
     7.1.11, `MAX_DATA_LENGTH' shows the space allocated for the disk
     part of a MySQL Cluster Disk Data table or fragment. (Previously,
     for partitions of *Note `NDB': mysql-cluster. tables, the
     `MAX_DATA_LENGTH' column value was always `NULL'.)

     For *Note `NDB': mysql-cluster. tables, you can also obtain this
     information using the *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc.  utility.

   * `INDEX_LENGTH': The length of the index file for this partition or
     subpartition, in bytes.

     For partitions of *Note `NDB': mysql-cluster. tables, whether the
     tables use implicit or explicit partitioning, the `INDEX_LENGTH'
     column value is always 0.  However, you can obtain equivalent
     information using the *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc. utility.

   * `DATA_FREE': The number of bytes allocated to the partition or
     subpartition but not used.

     For MySQL Cluster Disk Data tables, beginning with MySQL Cluster
     NDB 7.0.22 and MySQL Cluster NDB 7.1.11, `DATA_FREE' shows the
     space allocated on disk for, but not used by, a Disk Data table or
     fragment on disk.  (Previously, for partitions of *Note `NDB':
     mysql-cluster. tables, the value of this column was always 0.)

     For *Note `NDB': mysql-cluster. tables, you can also obtain this
     information using the *Note `ndb_desc':
     mysql-cluster-programs-ndb-desc.  utility.

   * `CREATE_TIME': The time of the partition's or subpartition's
     creation.

   * `UPDATE_TIME': The time that the partition or subpartition was
     last modified.

   * `CHECK_TIME': The last time that the table to which this partition
     or subpartition belongs was checked.

     *Note*:

     Some storage engines do not update this time; for tables using
     these storage engines, this value is always `NULL'.

   * `CHECKSUM': The checksum value, if any; otherwise, this column is
     `NULL'.

   * `PARTITION_COMMENT': This column contains the text of any comment
     made for the partition.

     In MySQL 5.1, the display width of this column is 80 characters,
     and partition comments which exceed this length are truncated to
     fit. This issue is fixed in MySQL 5.6. (Bug #11748924, Bug #37728)

     The default value for this column is an empty string.

   * `NODEGROUP': This is the nodegroup to which the partition belongs.
     This is relevant only to MySQL Cluster tables; otherwise the value
     of this column is always `0'.

   * `TABLESPACE_NAME': This column contains the name of the tablespace
     to which the partition belongs.  Currently, the value of this
     column is always `DEFAULT'.

   * *Important*:

     If any partitioned tables created in a MySQL version prior to
     MySQL 5.1.6 are present following an upgrade to MySQL 5.1.6 or
     later, it is not possible to *Note `SELECT': select. from, *Note
     `SHOW': show, or *Note `DESCRIBE': describe. the *Note
     `PARTITIONS': partitions-table. table. See the Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/) for MySQL 5.1.6
     _before_ upgrading from MySQL 5.1.5 or earlier to MySQL 5.1.6 or
     later.

   * A nonpartitioned table has one record in *Note
     `INFORMATION_SCHEMA.PARTITIONS': partitions-table.; however, the
     values of the `PARTITION_NAME', `SUBPARTITION_NAME',
     `PARTITION_ORDINAL_POSITION', `SUBPARTITION_ORDINAL_POSITION',
     `PARTITION_METHOD', `SUBPARTITION_METHOD', `PARTITION_EXPRESSION',
     `SUBPARTITION_EXPRESSION', and `PARTITION_DESCRIPTION' columns are
     all `NULL'. (The `PARTITION_COMMENT' column in this case is blank.)

     In MySQL 5.1, there is also only one record in the *Note
     `PARTITIONS': partitions-table. table for a table using the *Note
     `NDBCLUSTER': mysql-cluster. storage engine. The same columns are
     also `NULL' (or empty) as for a nonpartitioned table.


File: manual.info,  Node: plugins-table,  Next: processlist-table,  Prev: partitions-table,  Up: information-schema

20.12 The INFORMATION_SCHEMA PLUGINS Table
==========================================

The *Note `PLUGINS': plugins-table. table provides information about
server plugins.

This table describes the `INFORMATION_SCHEMA PLUGINS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`PLUGIN_NAME'                 `Name'                 MySQL extension
`PLUGIN_VERSION'                                     MySQL extension
`PLUGIN_STATUS'               `Status'               MySQL extension
`PLUGIN_TYPE'                 `Type'                 MySQL extension
`PLUGIN_TYPE_VERSION'                                MySQL extension
`PLUGIN_LIBRARY'              `Library'              MySQL extension
`PLUGIN_LIBRARY_VERSION'                             MySQL extension
`PLUGIN_AUTHOR'                                      MySQL extension
`PLUGIN_DESCRIPTION'                                 MySQL extension
`PLUGIN_LICENSE'                                     MySQL extension

*Notes*:

   * The *Note `PLUGINS': plugins-table. table is a nonstandard table.
     It was added in MySQL 5.1.5.

   * `PLUGIN_NAME' is the name used to refer to the plugin in
     statements such as *Note `INSTALL PLUGIN': install-plugin. and
     *Note `UNINSTALL PLUGIN': uninstall-plugin.

   * `PLUGIN_VERSION' is the version from the plugin's general type
     descriptor.

   * `PLUGIN_STATUS' indicates the plugin status, one of `ACTIVE',
     `INACTIVE', `DISABLED', or `DELETED'.

   * `PLUGIN_TYPE' indicates the type of plugin, such as `STORAGE
     ENGINE' or `INFORMATION_SCHEMA'.

   * `PLUGIN_TYPE_VERSION' is the version from the plugin's
     type-specific descriptor.

   * `PLUGIN_LIBRARY' is the name of the plugin shared object file.
     This is the name used to refer to the plugin file in statements
     such as *Note `INSTALL PLUGIN': install-plugin. and *Note
     `UNINSTALL PLUGIN': uninstall-plugin. This file is located in the
     directory named by the `plugin_dir' system variable. If the
     library name is `NULL', the plugin is compiled in and cannot be
     uninstalled with *Note `UNINSTALL PLUGIN': uninstall-plugin.

   * `PLUGIN_LIBRARY_VERSION' indicates the plugin API interface
     version.

   * `PLUGIN_AUTHOR' names the plugin author.

   * `PLUGIN_DESCRIPTION' provides a short description of the plugin.

   * `PLUGIN_LICENSE' indicates how the plugin is licensed; for
     example, `GPL'. This column was added in MySQL 5.1.12.

For plugins installed with *Note `INSTALL PLUGIN': install-plugin, the
`PLUGIN_NAME' and `PLUGIN_LIBRARY' values are also registered in the
`mysql.plugin' table.

These statements are equivalent:


     SELECT
       PLUGIN_NAME, PLUGIN_STATUS, PLUGIN_TYPE,
       PLUGIN_LIBRARY, PLUGIN_LICENSE
     FROM INFORMATION_SCHEMA.PLUGINS;

     SHOW PLUGINS;

For information about plugin data structures that form the basis of the
information in the *Note `PLUGINS': plugins-table.  table, see *Note
plugin-api::.

Plugin information is also available using the *Note `SHOW PLUGINS':
show-plugins. statement. See *Note show-plugins::.


File: manual.info,  Node: processlist-table,  Next: profiling-table,  Prev: plugins-table,  Up: information-schema

20.13 The INFORMATION_SCHEMA PROCESSLIST Table
==============================================

The *Note `PROCESSLIST': processlist-table. table provides information
about which threads are running.

This table describes the `INFORMATION_SCHEMA PROCESSLIST' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`ID'                          `Id'                   MySQL extension
`USER'                        `User'                 MySQL extension
`HOST'                        `Host'                 MySQL extension
`DB'                          `db'                   MySQL extension
`COMMAND'                     `Command'              MySQL extension
`TIME'                        `Time'                 MySQL extension
`STATE'                       `State'                MySQL extension
`INFO'                        `Info'                 MySQL extension

For an extensive description of the table columns, see *Note
show-processlist::.

*Notes*:

   * The *Note `PROCESSLIST': processlist-table. table is a nonstandard
     table. It was added in MySQL 5.1.7.

   * Like the output from the corresponding *Note `SHOW': show.
     statement, the *Note `PROCESSLIST': processlist-table. table will
     only show information about your own threads, unless you have the
     `PROCESS' privilege, in which case you will see information about
     other threads, too. As an anonymous user, you cannot see any rows
     at all.

   * If an SQL statement refers to *Note
     `INFORMATION_SCHEMA.PROCESSLIST': processlist-table, then MySQL
     will populate the entire table once, when statement execution
     begins, so there is read consistency during the statement. There
     is no read consistency for a multi-statement transaction, though.

The following statements are equivalent:


     SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST

     SHOW FULL PROCESSLIST


File: manual.info,  Node: profiling-table,  Next: referential-constraints-table,  Prev: processlist-table,  Up: information-schema

20.14 The INFORMATION_SCHEMA PROFILING Table
============================================

The *Note `PROFILING': profiling-table. table provides statement
profiling information. Its contents correspond to the information
produced by the *Note `SHOW PROFILES': show-profiles. and *Note `SHOW
PROFILE': show-profile.  statements (see *Note show-profiles::). The
table is empty unless the `profiling' session variable is set to 1.

This table describes the `INFORMATION_SCHEMA PROFILING' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`QUERY_ID'                    `Query_ID'             
`SEQ'                         `'                     
`STATE'                       `Status'               
`DURATION'                    `Duration'             
`CPU_USER'                    `CPU_user'             
`CPU_SYSTEM'                  `CPU_system'           
`CONTEXT_VOLUNTARY'           `Context_voluntary'    
`CONTEXT_INVOLUNTARY'         `Context_involuntary'  
`BLOCK_OPS_IN'                `Block_ops_in'         
`BLOCK_OPS_OUT'               `Block_ops_out'        
`MESSAGES_SENT'               `Messages_sent'        
`MESSAGES_RECEIVED'           `Messages_received'    
`PAGE_FAULTS_MAJOR'           `Page_faults_major'    
`PAGE_FAULTS_MINOR'           `Page_faults_minor'    
`SWAPS'                       `Swaps'                
`SOURCE_FUNCTION'             `Source_function'      
`SOURCE_FILE'                 `Source_file'          
`SOURCE_LINE'                 `Source_line'          

*Notes*:

   * The *Note `PROFILING': profiling-table. table was added in MySQL
     5.1.24 but contains no information unless the *Note `SHOW
     PROFILE': show-profile. feature is enabled. The *Note `SHOW
     PROFILE': show-profile.  feature is not included in binary
     distributions by default until MySQL 5.1.28.

   * `QUERY_ID' is a numeric statement identifier.

   * `SEQ' is a sequence number indicating the display order for rows
     with the same `QUERY_ID' value.

   * `STATE' is the profiling state to which the row measurements apply.

   * `DURATION' indicates how long statement execution remained in the
     given state, in seconds.

   * `CPU_USER' and `CPU_SYSTEM' indicate user and system CPU use, in
     seconds.

   * `CONTEXT_VOLUNTARY' and `CONTEXT_INVOLUNTARY' indicate how many
     voluntary and involuntary context switches occurred.

   * `BLOCK_OPS_IN' and `BLOCK_OPS_OUT' indicate the number of block
     input and output operations.

   * `MESSAGES_SENT' and `MESSAGES_RECEIVED' indicate the number of
     communication messages sent and received.

   * `PAGE_FAULTS_MAJOR' and `PAGE_FAULTS_MINOR' indicate the number of
     major and minor page faults.

   * `SWAPS' indicates how many swaps occurred.

   * `SOURCE_FUNCTION', `SOURCE_FILE', and `SOURCE_LINE' provide
     information indicating where in the source code the profiled state
     executes.


File: manual.info,  Node: referential-constraints-table,  Next: routines-table,  Prev: profiling-table,  Up: information-schema

20.15 The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table
==========================================================

The *Note `REFERENTIAL_CONSTRAINTS': referential-constraints-table.
table provides information about foreign keys.

This table describes the *Note `REFERENTIAL_CONSTRAINTS':
referential-constraints-table.  table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
CONSTRAINT_CATALOG                                   NULL
CONSTRAINT_SCHEMA                                    
CONSTRAINT_NAME                                      
UNIQUE_CONSTRAINT_CATALOG                            NULL
UNIQUE_CONSTRAINT_SCHEMA                             
UNIQUE_CONSTRAINT_NAME                               
MATCH_OPTION                                         
UPDATE_RULE                                          
DELETE_RULE                                          
TABLE_NAME                                           
REFERENCED_TABLE_NAME                                

*Notes*:

   * The *Note `REFERENTIAL_CONSTRAINTS':
     referential-constraints-table. table was added in MySQL 5.1.10. The
     `REFERENCED_TABLE_NAME' column was added in MySQL 5.1.16.

   * `TABLE_NAME' has the same value as `TABLE_NAME' in *Note
     `INFORMATION_SCHEMA.TABLE_CONSTRAINTS': table-constraints-table.

   * `CONSTRAINT_SCHEMA' and `CONSTRAINT_NAME' identify the foreign key.

   * `UNIQUE_CONSTRAINT_SCHEMA', `UNIQUE_CONSTRAINT_NAME', and
     `REFERENCED_TABLE_NAME' identify the referenced key. (Note: Before
     MySQL 5.1.16, `UNIQUE_CONSTRAINT_NAME' incorrectly named the
     referenced table, not the constraint.)

   * The only valid value at this time for `MATCH_OPTION' is `NONE'.

   * The possible values for `UPDATE_RULE' or `DELETE_RULE' are
     `CASCADE', `SET NULL', `SET DEFAULT', `RESTRICT', `NO ACTION'.


File: manual.info,  Node: routines-table,  Next: schemata-table,  Prev: referential-constraints-table,  Up: information-schema

20.16 The INFORMATION_SCHEMA ROUTINES Table
===========================================

The *Note `ROUTINES': routines-table. table provides information about
stored routines (both procedures and functions).  The *Note `ROUTINES':
routines-table. table does not include user-defined functions (UDFs).

The column named ``mysql.proc' name' indicates the `mysql.proc' table
column that corresponds to the *Note `INFORMATION_SCHEMA.ROUTINES':
routines-table. table column, if any.

This table describes the `INFORMATION_SCHEMA ROUTINES' table.

`INFORMATION_SCHEMA' Name     `mysql.proc' Name      Remarks
`SPECIFIC_NAME'               `specific_name'        
`ROUTINE_CATALOG'                                    `NULL'
`ROUTINE_SCHEMA'              `db'                   
`ROUTINE_NAME'                `name'                 
`ROUTINE_TYPE'                `type'                 `{PROCEDURE|FUNCTION}'
`DTD_IDENTIFIER'                                     data type descriptor
`ROUTINE_BODY'                                       `SQL'
`ROUTINE_DEFINITION'          `body or body_utf8'    see Notes
`EXTERNAL_NAME'                                      `NULL'
`EXTERNAL_LANGUAGE'           `language'             `NULL'
`PARAMETER_STYLE'                                    `SQL'
`IS_DETERMINISTIC'            `is_deterministic'     
`SQL_DATA_ACCESS'             `sql_data_access'      
`SQL_PATH'                                           `NULL'
`SECURITY_TYPE'               `security_type'        
`CREATED'                     `created'              
`LAST_ALTERED'                `modified'             
`SQL_MODE'                    `sql_mode'             MySQL extension
`ROUTINE_COMMENT'             `comment'              MySQL extension
`DEFINER'                     `definer'              MySQL extension
`CHARACTER_SET_CLIENT'                               MySQL extension
`COLLATION_CONNECTION'                               MySQL extension
`DATABASE_COLLATION'                                 MySQL extension

*Notes*:

   * MySQL calculates `EXTERNAL_LANGUAGE' thus:

        * If `mysql.proc.language='SQL'', `EXTERNAL_LANGUAGE' is `NULL'

        * Otherwise, `EXTERNAL_LANGUAGE' is what is in
          `mysql.proc.language'. However, we do not have external
          languages yet, so it is always `NULL'.

   * `ROUTINE_DEFINITION' is what is in `mysql.proc.body_utf8' as of
     MySQL 5.1.21, `mysql.proc.body' before 5.1.21.

   * `CREATED': The date and time when the routine was created. This is
     a *Note `TIMESTAMP': datetime. value.

   * `LAST_ALTERED': The date and time when the routine was last
     modified. This is a *Note `TIMESTAMP': datetime. value. If the
     routine has not been modified since its creation, this column holds
     the same value as the `CREATED' column.

   * `SQL_MODE': The SQL mode in effect when the routine was created or
     altered, and under which the routine executes. For the permitted
     values, see *Note sql-mode::.

   * `CHARACTER_SET_CLIENT': The session value of the
     `character_set_client' system variable when the routine was
     created. This column was added in MySQL 5.1.21.

   * `COLLATION_CONNECTION': The session value of the
     `collation_connection' system variable when the routine was
     created. This column was added in MySQL 5.1.21.

   * `DATABASE_COLLATION': The collation of the database with which the
     routine is associated. This column was added in MySQL 5.1.21.


File: manual.info,  Node: schemata-table,  Next: schema-privileges-table,  Prev: routines-table,  Up: information-schema

20.17 The INFORMATION_SCHEMA SCHEMATA Table
===========================================

A schema is a database, so the *Note `SCHEMATA': schemata-table. table
provides information about databases.

This table describes the `INFORMATION_SCHEMA SCHEMATA' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`CATALOG_NAME'                                       `NULL'
`SCHEMA_NAME'                 Database               
`DEFAULT_CHARACTER_SET_NAME'                         
`DEFAULT_COLLATION_NAME'                             
`SQL_PATH'                                           `NULL'

The following statements are equivalent:


     SELECT SCHEMA_NAME AS `Database`
       FROM INFORMATION_SCHEMA.SCHEMATA
       [WHERE SCHEMA_NAME LIKE 'WILD']

     SHOW DATABASES
       [LIKE 'WILD']


File: manual.info,  Node: schema-privileges-table,  Next: statistics-table,  Prev: schemata-table,  Up: information-schema

20.18 The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table
====================================================

The *Note `SCHEMA_PRIVILEGES': schema-privileges-table. table provides
information about schema (database) privileges. This information comes
from the `mysql.db' grant table.

This table describes the `INFORMATION_SCHEMA SCHEMA_PRIVILEGES' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`GRANTEE'                                            `'USER_NAME'@'HOST_NAME''
                                                     value, MySQL extension
`TABLE_CATALOG'                                      `NULL', MySQL
                                                     extension
`TABLE_SCHEMA'                                       MySQL extension
`PRIVILEGE_TYPE'                                     MySQL extension
`IS_GRANTABLE'                                       MySQL extension

*Notes*:

   * This is a nonstandard table. It takes its values from the
     `mysql.db' table.


File: manual.info,  Node: statistics-table,  Next: tables-table,  Prev: schema-privileges-table,  Up: information-schema

20.19 The INFORMATION_SCHEMA STATISTICS Table
=============================================

The *Note `STATISTICS': statistics-table. table provides information
about table indexes.

This table describes the `INFORMATION_SCHEMA STATISTICS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`TABLE_CATALOG'                                      `NULL'
`TABLE_SCHEMA'                                       = Database
`TABLE_NAME'                  `Table'                
`NON_UNIQUE'                  `Non_unique'           
`INDEX_SCHEMA'                                       = Database
`INDEX_NAME'                  `Key_name'             
`SEQ_IN_INDEX'                `Seq_in_index'         
`COLUMN_NAME'                 `Column_name'          
`COLLATION'                   `Collation'            
`CARDINALITY'                 `Cardinality'          
`SUB_PART'                    `Sub_part'             MySQL extension
`PACKED'                      `Packed'               MySQL extension
`NULLABLE'                    `Null'                 MySQL extension
`INDEX_TYPE'                  `Index_type'           MySQL extension
`COMMENT'                     `Comment'              MySQL extension

*Notes*:

   * There is no standard table for indexes. The preceding list is
     similar to what SQL Server 2000 returns for `sp_statistics',
     except that we replaced the name `QUALIFIER' with `CATALOG' and we
     replaced the name `OWNER' with `SCHEMA'.

     Clearly, the preceding table and the output from *Note `SHOW
     INDEX': show-index. are derived from the same parent. So the
     correlation is already close.

The following statements are equivalent:


     SELECT * FROM INFORMATION_SCHEMA.STATISTICS
       WHERE table_name = 'TBL_NAME'
       AND table_schema = 'DB_NAME'

     SHOW INDEX
       FROM TBL_NAME
       FROM DB_NAME


File: manual.info,  Node: tables-table,  Next: table-constraints-table,  Prev: statistics-table,  Up: information-schema

20.20 The INFORMATION_SCHEMA TABLES Table
=========================================

The *Note `TABLES': tables-table. table provides information about
tables in databases.

This table describes the `INFORMATION_SCHEMA TABLES' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`TABLE_CATALOG'                                      `NULL'
`TABLE_SCHEMA'                `Table_'...            
`TABLE_NAME'                  `Table_'...            
`TABLE_TYPE'                                         
`ENGINE'                      `Engine'               MySQL extension
`VERSION'                     `Version'              The version number of
                                                     the table's `.frm'
                                                     file, MySQL extension
`ROW_FORMAT'                  `Row_format'           MySQL extension
`TABLE_ROWS'                  `Rows'                 MySQL extension
`AVG_ROW_LENGTH'              `Avg_row_length'       MySQL extension
`DATA_LENGTH'                 `Data_length'          MySQL extension
`MAX_DATA_LENGTH'             `Max_data_length'      MySQL extension
`INDEX_LENGTH'                `Index_length'         MySQL extension
`DATA_FREE'                   `Data_free'            MySQL extension
`AUTO_INCREMENT'              `Auto_increment'       MySQL extension
`CREATE_TIME'                 `Create_time'          MySQL extension
`UPDATE_TIME'                 `Update_time'          MySQL extension
`CHECK_TIME'                  `Check_time'           MySQL extension
`TABLE_COLLATION'             `Collation'            MySQL extension
`CHECKSUM'                    `Checksum'             MySQL extension
`CREATE_OPTIONS'              `Create_options'       MySQL extension
`TABLE_COMMENT'               `Comment'              MySQL extension

*Notes*:

   * `TABLE_SCHEMA' and `TABLE_NAME' are a single field in a *Note
     `SHOW': show. display, for example `Table_in_db1'.

   * `TABLE_TYPE' should be `BASE TABLE' or `VIEW'. Currently, the
     *Note `TABLES': tables-table. table does not list `TEMPORARY'
     tables.

   * For partitioned tables, beginning with MySQL 5.1.9, the `ENGINE'
     column shows the name of the storage engine used by all
     partitions. (Previously, this column showed `PARTITION' for such
     tables.)

   * The `TABLE_ROWS' column is `NULL' if the table is in the
     `INFORMATION_SCHEMA' database.

     For *Note `InnoDB': innodb-storage-engine. tables, the row count
     is only a rough estimate used in SQL optimization. (This is also
     true if the *Note `InnoDB': innodb-storage-engine. table is
     partitioned.)

   * Prior to MySQL 5.1.12, MySQL Cluster allocated storage for
     variable-width columns in 10-page extents of 32 kilobytes each;
     thus, the `DATA_LENGTH' for such columns was reported in
     increments of 320 KB. Beginning with MySQL 5.1.12, the
     `DATA_LENGTH' column reflects the true amount of storage for
     variable-width columns of *Note `NDB': mysql-cluster. tables. (Bug
     #18413)

     For *Note `NDB': mysql-cluster. tables, `DATA_LENGTH' includes
     data stored in main memory only; the `MAX_DATA_LENGTH' and
     `DATA_FREE' columns apply to Disk Data.

   * Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
     7.1.11, for MySQL Cluster Disk Data tables, `MAX_DATA_LENGTH'
     shows the space allocated for the disk part of a Disk Data table
     or fragment. (In-memory data resource usage is reported by the
     `DATA_LENGTH' column.)

   * Beginning with MySQL 5.1.28, the `DATA_FREE' column shows the free
     space in bytes for `InnoDB' tables.

     Beginning with MySQL Cluster NDB 7.0.22 and MySQL Cluster NDB
     7.1.11, `DATA_FREE' shows the space allocated on disk for, but not
     used by, a Disk Data table or fragment on disk. (In-memory data
     resource usage is reported by the `DATA_LENGTH' column.)

   * We have nothing for the table's default character set.
     `TABLE_COLLATION' is close, because collation names begin with a
     character set name.

   * Beginning with MySQL 5.1.9, the `CREATE_OPTIONS' column shows
     `partitioned' if the table is partitioned.

The following statements are equivalent:


     SELECT table_name FROM INFORMATION_SCHEMA.TABLES
       WHERE table_schema = 'DB_NAME'
       [AND table_name LIKE 'WILD']

     SHOW TABLES
       FROM DB_NAME
       [LIKE 'WILD']


File: manual.info,  Node: table-constraints-table,  Next: table-privileges-table,  Prev: tables-table,  Up: information-schema

20.21 The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table
====================================================

The *Note `TABLE_CONSTRAINTS': table-constraints-table. table describes
which tables have constraints.

This table describes the `INFORMATION_SCHEMA TABLE_CONSTRAINTS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`CONSTRAINT_CATALOG'                                 `NULL'
`CONSTRAINT_SCHEMA'                                  
`CONSTRAINT_NAME'                                    
`TABLE_SCHEMA'                                       
`TABLE_NAME'                                         
`CONSTRAINT_TYPE'                                    

*Notes*:

   * The `CONSTRAINT_TYPE' value can be `UNIQUE', `PRIMARY KEY', or
     `FOREIGN KEY'.

   * The `UNIQUE' and `PRIMARY KEY' information is about the same as
     what you get from the `Key_name' field in the output from *Note
     `SHOW INDEX': show-index. when the `Non_unique' field is `0'.

   * The `CONSTRAINT_TYPE' column can contain one of these values:
     `UNIQUE', `PRIMARY KEY', `FOREIGN KEY', `CHECK'. This is a *Note
     `CHAR': char. (not *Note `ENUM': enum.) column. The `CHECK' value
     is not available until we support `CHECK'.


File: manual.info,  Node: table-privileges-table,  Next: triggers-table,  Prev: table-constraints-table,  Up: information-schema

20.22 The INFORMATION_SCHEMA TABLE_PRIVILEGES Table
===================================================

The *Note `TABLE_PRIVILEGES': table-privileges-table. table provides
information about table privileges. This information comes from the
`mysql.tables_priv' grant table.

This table describes the `INFORMATION_SCHEMA TABLE_PRIVILEGES' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`GRANTEE'                                            `'USER_NAME'@'HOST_NAME''
                                                     value
`TABLE_CATALOG'                                      `NULL'
`TABLE_SCHEMA'                                       
`TABLE_NAME'                                         
`PRIVILEGE_TYPE'                                     
`IS_GRANTABLE'                                       

*Notes*:

   * `PRIVILEGE_TYPE' can contain one (and only one) of these values:
     `SELECT', `INSERT', `UPDATE', `REFERENCES', `ALTER', `INDEX',
     `DROP', `CREATE VIEW'.

The following statements are _not_ equivalent:


     SELECT ... FROM INFORMATION_SCHEMA.TABLE_PRIVILEGES

     SHOW GRANTS ...


File: manual.info,  Node: triggers-table,  Next: user-privileges-table,  Prev: table-privileges-table,  Up: information-schema

20.23 The INFORMATION_SCHEMA TRIGGERS Table
===========================================

The *Note `TRIGGERS': triggers-table. table provides information about
triggers. You must have the `TRIGGER' privilege to access this table
(prior to MySQL 5.1.23, you must have the `SUPER' privilege). You can
see information only for databases and tables for which you have the
`TRIGGER' privilege, or (prior to MySQL 5.1.23) if you have the `SUPER'
privilege).

This table describes the `INFORMATION_SCHEMA TRIGGERS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`TRIGGER_CATALOG'                                    `NULL'
`TRIGGER_SCHEMA'                                     
`TRIGGER_NAME'                `Trigger'              
`EVENT_MANIPULATION'          `Event'                
`EVENT_OBJECT_CATALOG'                               `NULL'
`EVENT_OBJECT_SCHEMA'                                
`EVENT_OBJECT_TABLE'          `Table'                
`ACTION_ORDER'                                       `0'
`ACTION_CONDITION'                                   `NULL'
`ACTION_STATEMENT'            `Statement'            
`ACTION_ORIENTATION'                                 `ROW'
`ACTION_TIMING'               `Timing'               
`ACTION_REFERENCE_OLD_TABLE'                         `NULL'
`ACTION_REFERENCE_NEW_TABLE'                         `NULL'
`ACTION_REFERENCE_OLD_ROW'                           `OLD'
`ACTION_REFERENCE_NEW_ROW'                           `NEW'
`CREATED'                     `Created'              
`SQL_MODE'                    `sql_mode'             MySQL extension
`DEFINER'                     `Definer'              MySQL extension
`CHARACTER_SET_CLIENT'        `character_set_client' MySQL extension
`COLLATION_CONNECTION'        `collation_connection' MySQL extension
`DATABASE_COLLATION'          `Database Collation'   MySQL extension

*Notes*:

   * The names in the `*Note `SHOW': show.  Name' column refer to the
     *Note `SHOW TRIGGERS': show-triggers. statement, not *Note `SHOW
     CREATE TRIGGER': show-create-trigger. See *Note show-triggers::.

   * `TRIGGER_SCHEMA' and `TRIGGER_NAME': The name of the database in
     which the trigger occurs and the trigger name, respectively.

   * `EVENT_MANIPULATION': The trigger event. This is the type of
     operation on the associated table for which the trigger activates.
     The value is `'INSERT'' (a row was inserted), `'DELETE'' (a row was
     deleted), or `'UPDATE'' (a row was modified).

   * `EVENT_OBJECT_SCHEMA' and `EVENT_OBJECT_TABLE': As noted in *Note
     triggers::, every trigger is associated with exactly one table.
     These columns indicate the database in which this table occurs,
     and the table name, respectively.

   * `ACTION_ORDER': The ordinal position of the trigger's action
     within the list of all similar triggers on the same table.
     Currently, this value is always `0', because it is not possible to
     have more than one trigger with the same `EVENT_MANIPULATION' and
     `ACTION_TIMING' on the same table.

   * `ACTION_STATEMENT': The trigger body; that is, the statement
     executed when the trigger activates. This text uses UTF-8 encoding.

   * `ACTION_ORIENTATION': Always contains the value `'ROW''.

   * `ACTION_TIMING': Whether the trigger activates before or after the
     triggering event. The value is `'BEFORE'' or `'AFTER''.

   * `ACTION_REFERENCE_OLD_ROW' and `ACTION_REFERENCE_NEW_ROW': The old
     and new column identifiers, respectively. This means that
     `ACTION_REFERENCE_OLD_ROW' always contains the value `'OLD'' and
     `ACTION_REFERENCE_NEW_ROW' always contains the value `'NEW''.

   * `SQL_MODE': The SQL mode in effect when the trigger was created,
     and under which the trigger executes. For the permitted values,
     see *Note sql-mode::.

   * `DEFINER': The account of the user who created the trigger, in
     `'USER_NAME'@'HOST_NAME'' format. This column was added in MySQL
     5.1.2.

   * `CHARACTER_SET_CLIENT': The session value of the
     `character_set_client' system variable when the trigger was
     created. This column was added in MySQL 5.1.21.

   * `COLLATION_CONNECTION': The session value of the
     `collation_connection' system variable when the trigger was
     created. This column was added in MySQL 5.1.21.

   * `DATABASE_COLLATION': The collation of the database with which the
     trigger is associated. This column was added in MySQL 5.1.21.

   * The following columns currently always contain `NULL':
     `TRIGGER_CATALOG', `EVENT_OBJECT_CATALOG', `ACTION_CONDITION',
     `ACTION_REFERENCE_OLD_TABLE', `ACTION_REFERENCE_NEW_TABLE', and
     `CREATED'.

Example, using the `ins_sum' trigger defined in *Note triggers:::


     mysql> SELECT * FROM INFORMATION_SCHEMA.TRIGGERS
         -> WHERE TRIGGER_SCHEMA='test' AND TRIGGER_NAME='ins_sum'\G
     *************************** 1. row ***************************
                TRIGGER_CATALOG: def
                 TRIGGER_SCHEMA: test
                   TRIGGER_NAME: ins_sum
             EVENT_MANIPULATION: INSERT
           EVENT_OBJECT_CATALOG: def
            EVENT_OBJECT_SCHEMA: test
             EVENT_OBJECT_TABLE: account
                   ACTION_ORDER: 0
               ACTION_CONDITION: NULL
               ACTION_STATEMENT: SET @sum = @sum + NEW.amount
             ACTION_ORIENTATION: ROW
                  ACTION_TIMING: BEFORE
     ACTION_REFERENCE_OLD_TABLE: NULL
     ACTION_REFERENCE_NEW_TABLE: NULL
       ACTION_REFERENCE_OLD_ROW: OLD
       ACTION_REFERENCE_NEW_ROW: NEW
                        CREATED: NULL
                       SQL_MODE:
                        DEFINER: me@localhost
           CHARACTER_SET_CLIENT: utf8
           COLLATION_CONNECTION: utf8_general_ci
             DATABASE_COLLATION: latin1_swedish_ci


File: manual.info,  Node: user-privileges-table,  Next: views-table,  Prev: triggers-table,  Up: information-schema

20.24 The INFORMATION_SCHEMA USER_PRIVILEGES Table
==================================================

The *Note `USER_PRIVILEGES': user-privileges-table. table provides
information about global privileges. This information comes from the
`mysql.user' grant table.

This table describes the `INFORMATION_SCHEMA USER_PRIVILEGES' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`GRANTEE'                                            `'USER_NAME'@'HOST_NAME''
                                                     value, MySQL extension
`TABLE_CATALOG'                                      `NULL', MySQL
                                                     extension
`PRIVILEGE_TYPE'                                     MySQL extension
`IS_GRANTABLE'                                       MySQL extension

*Notes*:

   * This is a nonstandard table. It takes its values from the
     `mysql.user' table.


File: manual.info,  Node: views-table,  Next: mysql-cluster-i_s-tables,  Prev: user-privileges-table,  Up: information-schema

20.25 The INFORMATION_SCHEMA VIEWS Table
========================================

The *Note `VIEWS': views-table. table provides information about views
in databases. You must have the `SHOW VIEW' privilege to access this
table.

This table describes the `INFORMATION_SCHEMA VIEWS' table.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`TABLE_CATALOG'                                      `NULL'
`TABLE_SCHEMA'                                       
`TABLE_NAME'                                         
`VIEW_DEFINITION'                                    
`CHECK_OPTION'                                       
`IS_UPDATABLE'                                       
`DEFINER'                                            
`SECURITY_TYPE'                                      
`CHARACTER_SET_CLIENT'                               MySQL extension
`COLLATION_CONNECTION'                               MySQL extension

*Notes*:

   * The `VIEW_DEFINITION' column has most of what you see in the
     `Create Table' field that *Note `SHOW CREATE VIEW':
     show-create-view. produces. Skip the words before *Note `SELECT':
     select. and skip the words `WITH CHECK OPTION'. Suppose that the
     original statement was:


          CREATE VIEW v AS
            SELECT s2,s1 FROM t
            WHERE s1 > 5
            ORDER BY s1
            WITH CHECK OPTION;

     Then the view definition looks like this:


          SELECT s2,s1 FROM t WHERE s1 > 5 ORDER BY s1

   * The `CHECK_OPTION' column has a value of `NONE', `CASCADE', or
     `LOCAL'.

   * MySQL sets a flag, called the view updatability flag, at *Note
     `CREATE VIEW': create-view. time. The flag is set to `YES' (true)
     if *Note `UPDATE': update. and *Note `DELETE': delete. (and
     similar operations) are legal for the view. Otherwise, the flag is
     set to `NO' (false). The `IS_UPDATABLE' column in the *Note
     `VIEWS': views-table. table displays the status of this flag. It
     means that the server always knows whether a view is updatable. If
     the view is not updatable, statements such *Note `UPDATE': update,
     *Note `DELETE': delete, and *Note `INSERT': insert. are illegal
     and will be rejected. (Note that even if a view is updatable, it
     might not be possible to insert into it; for details, refer to
     *Note create-view::.)

   * `DEFINER': The account of the user who created the view, in
     `'USER_NAME'@'HOST_NAME'' format. `SECURITY_TYPE' has a value of
     `DEFINER' or `INVOKER'.

   * `CHARACTER_SET_CLIENT': The session value of the
     `character_set_client' system variable when the view was created.
     This column was added in MySQL 5.1.21.

   * `COLLATION_CONNECTION': The session value of the
     `collation_connection' system variable when the view was created.
     This column was added in MySQL 5.1.21.

MySQL lets you use different `sql_mode' settings to tell the server the
type of SQL syntax to support. For example, you might use the `ANSI'
SQL mode to ensure MySQL correctly interprets the standard SQL
concatenation operator, the double bar (`||'), in your queries.  If you
then create a view that concatenates items, you might worry that
changing the `sql_mode' setting to a value different from `ANSI' could
cause the view to become invalid. But this is not the case. No matter
how you write out a view definition, MySQL always stores it the same
way, in a canonical form. Here is an example that shows how the server
changes a double bar concatenation operator to a `CONCAT()' function:


     mysql> SET sql_mode = 'ANSI';
     Query OK, 0 rows affected (0.00 sec)

     mysql> CREATE VIEW test.v AS SELECT 'a' || 'b' as col1;
     Query OK, 0 rows affected (0.00 sec)

     mysql> SELECT VIEW_DEFINITION FROM INFORMATION_SCHEMA.VIEWS
         -> WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME = 'v';
     +----------------------------------+
     | VIEW_DEFINITION                  |
     +----------------------------------+
     | select concat('a','b') AS `col1` |
     +----------------------------------+
     1 row in set (0.00 sec)

The advantage of storing a view definition in canonical form is that
changes made later to the value of `sql_mode' will not affect the
results from the view. However an additional consequence is that
comments prior to *Note `SELECT': select. are stripped from the
definition by the server.


File: manual.info,  Node: mysql-cluster-i_s-tables,  Next: extended-show,  Prev: views-table,  Up: information-schema

20.26 INFORMATION_SCHEMA Tables for MySQL Cluster
=================================================

* Menu:

* files-table::                  The INFORMATION_SCHEMA FILES Table
* ndb-transid-mysql-connection-map-table::  The INFORMATION_SCHEMA ndb_transid_mysql_connection_map Table

The following sections provide information about `INFORMATION_SCHEMA'
tables which are specific to MySQL Cluster. The *Note `FILES':
files-table. table was added in MySQL Server 5.1.6 as part of MySQL
Cluster data-on-disk support (it is available in standard MySQL 5.5 but
is not used there). The *Note `ndb_transid_mysql_connection_map':
ndb-transid-mysql-connection-map-table. table was added as part of
additions made to MySQL Cluster's *Note `ndbinfo':
mysql-cluster-ndbinfo. information database in MySQL Cluster NDB
7.1.17; it is implemented as an `INFORMATION_SCHEMA' plugin available
only in MySQL Cluster binaries or source, and does not exist in MySQL
Server 5.1.

Additional statistical and other data about MySQL Cluster transactions,
operations, threads, blocks, and other aspects of performance can be
obtained from the tables in the *Note `ndbinfo': mysql-cluster-ndbinfo.
database. Information about these tables, see *Note
mysql-cluster-ndbinfo::.


File: manual.info,  Node: files-table,  Next: ndb-transid-mysql-connection-map-table,  Prev: mysql-cluster-i_s-tables,  Up: mysql-cluster-i_s-tables

20.26.1 The INFORMATION_SCHEMA FILES Table
------------------------------------------

The *Note `FILES': files-table. table provides information about the
files in which MySQL *Note `NDB': mysql-cluster.  Disk Data tables are
stored.

*Note*:

This table provides information about Disk Data _files_ only; you
cannot use it for determining disk space allocation or availability for
individual `NDB' tables. However, beginning with MySQL Cluster NDB
6.3.27 and MySQL Cluster NDB 7.0.8, it is possible to see how much
space is allocated for each *Note `NDB': mysql-cluster. table having
data stored on disk, as well as how much remains available for storage
of data on disk for that table, using *Note `ndb_desc':
mysql-cluster-programs-ndb-desc. For more information, see *Note
mysql-cluster-programs-ndb-desc::.

This table describes the `INFORMATION_SCHEMA FILES' table. The table
lists `INFORMATION_SCHEMA' names along with the corresponding *Note
`SHOW': show. names (if applicable), and remarks.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`FILE_ID'                                            MySQL extension
`FILE_NAME'                                          MySQL extension
`FILE_TYPE'                                          MySQL extension
`TABLESPACE_NAME'                                    MySQL extension
`TABLE_CATALOG'                                      MySQL extension
`TABLE_SCHEMA'                                       MySQL extension
`TABLE_NAME'                                         MySQL extension
`LOGFILE_GROUP_NAME'                                 MySQL extension
`LOGFILE_GROUP_NUMBER'                               MySQL extension
`ENGINE'                                             MySQL extension
`FULLTEXT_KEYS'                                      MySQL extension
`DELETED_ROWS'                                       MySQL extension
`UPDATE_COUNT'                                       MySQL extension
`FREE_EXTENTS'                                       MySQL extension
`TOTAL_EXTENTS'                                      MySQL extension
`EXTENT_SIZE'                                        MySQL extension
`INITIAL_SIZE'                                       MySQL extension
`MAXIMUM_SIZE'                                       MySQL extension
`AUTOEXTEND_SIZE'                                    MySQL extension
`CREATION_TIME'                                      MySQL extension
`LAST_UPDATE_TIME'                                   MySQL extension
`LAST_ACCESS_TIME'                                   MySQL extension
`RECOVER_TIME'                                       MySQL extension
`TRANSACTION_COUNTER'                                MySQL extension
`VERSION'                                            MySQL extension
`ROW_FORMAT'                                         MySQL extension
`TABLE_ROWS'                                         MySQL extension
`AVG_ROW_LENGTH'                                     MySQL extension
`DATA_LENGTH'                                        MySQL extension
`MAX_DATA_LENGTH'                                    MySQL extension
`INDEX_LENGTH'                                       MySQL extension
`DATA_FREE'                                          MySQL extension
`CREATE_TIME'                                        MySQL extension
`UPDATE_TIME'                                        MySQL extension
`CHECK_TIME'                                         MySQL extension
`CHECKSUM'                                           MySQL extension
`STATUS'                                             MySQL extension
`EXTRA'                                              MySQL extension

*Notes*:

   * `FILE_ID' column values are auto-generated.

   * `FILE_NAME' is the name of an `UNDO' log file created by *Note
     `CREATE LOGFILE GROUP': create-logfile-group. or *Note `ALTER
     LOGFILE GROUP': alter-logfile-group, or of a data file created by
     *Note `CREATE TABLESPACE': create-tablespace. or *Note `ALTER
     TABLESPACE': alter-tablespace.

   * `FILE_TYPE' is one of the values `UNDOFILE' or `DATAFILE'.

     Beginning with MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.32,
     MySQL Cluster NDB 7.0.13, and MySQL Cluster NDB 7.1.2, this column
     can also have the value `TABLESPACE'.

   * `TABLESPACE_NAME' is the name of the tablespace with which the
     file is associated.

   * Currently, the value of the `TABLESPACE_CATALOG' column is always
     `NULL'.

   * `TABLE_NAME' is the name of the Disk Data table with which the
     file is associated, if any.

   * The `LOGFILE_GROUP_NAME' column gives the name of the log file
     group to which the log file or data file belongs.

   * For an `UNDO' log file, the `LOGFILE_GROUP_NUMBER' contains the
     auto-generated ID number of the log file group to which the log
     file belongs.

   * For a MySQL Cluster Disk Data log file or data file, the value of
     the `ENGINE' column is always *Note `NDB': mysql-cluster. or *Note
     `NDBCLUSTER': mysql-cluster.

   * For a MySQL Cluster Disk Data log file or data file, the value of
     the `FULLTEXT_KEYS' column is always empty.

   * The `FREE EXTENTS' column displays the number of extents which
     have not yet been used by the file. The `TOTAL EXTENTS' column
     show the total number of extents allocated to the file.

     The difference between these two columns is the number of extents
     currently in use by the file:


          SELECT TOTAL_EXTENTS - FREE_EXTENTS AS extents_used
              FROM INFORMATION_SCHEMA.FILES
              WHERE FILE_NAME = 'myfile.dat';

     You can approximate the amount of disk space in use by the file by
     multiplying this difference by the value of the `EXTENT_SIZE'
     column, which gives the size of an extent for the file in bytes:


          SELECT (TOTAL_EXTENTS - FREE_EXTENTS) * EXTENT_SIZE AS bytes_used
              FROM INFORMATION_SCHEMA.FILES
              WHERE FILE_NAME = 'myfile.dat';

     Similarly, you can estimate the amount of space that remains
     available in a given file by multiplying `FREE_EXTENTS' by
     `EXTENT_SIZE':


          SELECT FREE_EXTENTS * EXTENT_SIZE AS bytes_free
              FROM INFORMATION_SCHEMA.FILES
              WHERE FILE_NAME = 'myfile.dat';

     *Important*:

     The byte values produced by the preceding queries are
     approximations only, and their precision is inversely proportional
     to the value of `EXTENT_SIZE'.  That is, the larger `EXTENT_SIZE'
     becomes, the less accurate the approximations are.

     It is also important to remember that once an extent is used, it
     cannot be freed again without dropping the data file of which it
     is a part. This means that deletes from a Disk Data table do _not_
     release disk space.

     The extent size can be set in a *Note `CREATE TABLESPACE':
     create-tablespace. statement. See *Note create-tablespace::, for
     more information.

   * The `INITIAL_SIZE' column shows the size in bytes of the file.
     This is the same value that was used in the `INITIAL_SIZE' clause
     of the *Note `CREATE LOGFILE GROUP': create-logfile-group, *Note
     `ALTER LOGFILE GROUP': alter-logfile-group, *Note `CREATE
     TABLESPACE': create-tablespace, or *Note `ALTER TABLESPACE':
     alter-tablespace. statement used to create the file.

     For MySQL Cluster Disk Data files, the value of the `MAXIMUM_SIZE'
     column is always the same as `INITIAL_SIZE', and the
     `AUTOEXTEND_SIZE' column is always empty.

   * The `CREATION_TIME' column shows the date and time when the file
     was created. The `LAST_UPDATE_TIME' column displays the date and
     time when the file was last modified. The `LAST_ACCESSED' column
     provides the date and time when the file was last accessed by the
     server.

     Currently, the values of these columns are as reported by the
     operating system, and are not supplied by the *Note `NDB':
     mysql-cluster. storage engine. Where no value is provided by the
     operating system, these columns display `0000-00-00 00:00:00'.

   * For MySQL Cluster Disk Data files, the value of the `RECOVER_TIME'
     and `TRANSACTION_COUNTER' columns is always `0'.

   * For MySQL Cluster Disk Data files, the following columns are
     always `NULL':

        * `VERSION'

        * `ROW_FORMAT'

        * `TABLE_ROWS'

        * `AVG_ROW_LENGTH'

        * `DATA_LENGTH'

        * `MAX_DATA_LENGTH'

        * `INDEX_LENGTH'

        * `DATA_FREE'

        * `CREATE_TIME'

        * `UPDATE_TIME'

        * `CHECK_TIME'

        * `CHECKSUM'

   * For MySQL Cluster Disk Data files, the value of the `STATUS'
     column is always `NORMAL'.

   * For MySQL Cluster Disk Data files, the `EXTRA' column shows which
     data node the file belongs to, as each data node has its own copy
     of the file.  Suppose that you use this statement on a MySQL
     Cluster with four data nodes:


          CREATE LOGFILE GROUP mygroup
              ADD UNDOFILE 'new_undo.dat'
              INITIAL_SIZE 2G
              ENGINE NDB;

     After running the *Note `CREATE LOGFILE GROUP':
     create-logfile-group. statement successfully, you should see a
     result similar to the one shown here for this query against the
     *Note `FILES': files-table. table:


          mysql> SELECT LOGFILE_GROUP_NAME, FILE_TYPE, EXTRA
              ->     FROM INFORMATION_SCHEMA.FILES
              ->     WHERE FILE_NAME = 'new_undo.dat';
          +--------------------+-------------+----------------+
          | LOGFILE_GROUP_NAME | FILE_TYPE   | EXTRA          |
          +--------------------+-------------+----------------+
          | mygroup            | UNDO FILE   | CLUSTER_NODE=3 |
          | mygroup            | UNDO FILE   | CLUSTER_NODE=4 |
          | mygroup            | UNDO FILE   | CLUSTER_NODE=5 |
          | mygroup            | UNDO FILE   | CLUSTER_NODE=6 |
          +--------------------+-------------+----------------+
          4 rows in set (0.01 sec)

   * The *Note `FILES': files-table. table is a nonstandard table. It
     was added in MySQL 5.1.6.

   * Beginning with MySQL 5.1.14, an additional row is present in the
     *Note `FILES': files-table. table following the creation of a
     logfile group. This row has `NULL' for the value of the
     `FILE_NAME' column. For this row, the value of the `FILE_ID'
     column is always `0', that of the `FILE_TYPE' column is always
     `UNDO FILE', and that of the `STATUS' column is always `NORMAL'.
     Currently, the value of the `ENGINE' column is always *Note
     `NDBCLUSTER': mysql-cluster.

     The `FREE_EXTENTS' column in this row shows the total number of
     free extents available to all undo files belonging to a given log
     file group whose name and number are shown in the
     `LOGFILE_GROUP_NAME' and `LOGFILE_GROUP_NUMBER' columns,
     respectively.

     Suppose there are no existing log file groups on your MySQL
     Cluster, and you create one using the following statement:


          mysql> CREATE LOGFILE GROUP lg1
              ->   ADD UNDOFILE 'undofile.dat'
              ->   INITIAL_SIZE = 16M
              ->   UNDO_BUFFER_SIZE = 1M
              ->   ENGINE = NDB;
          Query OK, 0 rows affected (3.81 sec)

     You can now see this `NULL' row when you query the *Note `FILES':
     files-table. table:


          mysql> SELECT DISTINCT
              ->   FILE_NAME AS File,
              ->   FREE_EXTENTS AS Free,
              ->   TOTAL_EXTENTS AS Total,
              ->   EXTENT_SIZE AS Size,
              ->   INITIAL_SIZE AS Initial
              ->   FROM INFORMATION_SCHEMA.FILES;
          +--------------+---------+---------+------+----------+
          | File         | Free    | Total   | Size | Initial  |
          +--------------+---------+---------+------+----------+
          | undofile.dat |    NULL | 4194304 |    4 | 16777216 |
          | NULL         | 4184068 |    NULL |    4 |     NULL |
          +--------------+---------+---------+------+----------+
          2 rows in set (0.01 sec)

     The total number of free extents available for undo logging is
     always somewhat less than the sum of the `TOTAL_EXTENTS' column
     values for all undo files in the log file group due to overhead
     required for maintaining the undo files. This can be seen by
     adding a second undo file to the log file group, then repeating the
     previous query against the *Note `FILES': files-table.  table:


          mysql> ALTER LOGFILE GROUP lg1
              ->   ADD UNDOFILE 'undofile02.dat'
              ->   INITIAL_SIZE = 4M
              ->   ENGINE = NDB;
          Query OK, 0 rows affected (1.02 sec)

          mysql> SELECT DISTINCT
              ->   FILE_NAME AS File,
              ->   FREE_EXTENTS AS Free,
              ->   TOTAL_EXTENTS AS Total,
              ->   EXTENT_SIZE AS Size,
              ->   INITIAL_SIZE AS Initial
              ->   FROM INFORMATION_SCHEMA.FILES;
          +----------------+---------+---------+------+----------+
          | File           | Free    | Total   | Size | Initial  |
          +----------------+---------+---------+------+----------+
          | undofile.dat   |    NULL | 4194304 |    4 | 16777216 |
          | undofile02.dat |    NULL | 1048576 |    4 |  4194304 |
          | NULL           | 5223944 |    NULL |    4 |     NULL |
          +----------------+---------+---------+------+----------+
          3 rows in set (0.01 sec)

     The amount of free space in bytes which is available for undo
     logging by Disk Data tables using this log file group can be
     approximated by multiplying the number of free extents by the
     initial size:


          mysql> SELECT
              ->   FREE_EXTENTS AS 'Free Extents',
              ->   FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
              ->   FROM INFORMATION_SCHEMA.FILES
              ->   WHERE LOGFILE_GROUP_NAME = 'lg1'
              ->   AND FILE_NAME IS NULL;
          +--------------+------------+
          | Free Extents | Free Bytes |
          +--------------+------------+
          |      5223944 |   20895776 |
          +--------------+------------+
          1 row in set (0.02 sec)

     If you create a MySQL Cluster Disk Data table and then insert some
     rows into it, you can see approximately how much space remains for
     undo logging afterward, for example:


          mysql> CREATE TABLESPACE ts1
              ->   ADD DATAFILE 'data1.dat'
              ->   USE LOGFILE GROUP lg1
              ->   INITIAL_SIZE 512M
              ->   ENGINE = NDB;
          Query OK, 0 rows affected (8.71 sec)

          mysql> CREATE TABLE dd (
              ->   c1 INT NOT NULL PRIMARY KEY,
              ->   c2 INT,
              ->   c3 DATE
              ->   )
              ->   TABLESPACE ts1 STORAGE DISK
              ->   ENGINE = NDB;
          Query OK, 0 rows affected (2.11 sec)

          mysql> INSERT INTO dd VALUES
              ->   (NULL, 1234567890, '2007-02-02'),
              ->   (NULL, 1126789005, '2007-02-03'),
              ->   (NULL, 1357924680, '2007-02-04'),
              ->   (NULL, 1642097531, '2007-02-05');
          Query OK, 4 rows affected (0.01 sec)

          mysql> SELECT
              ->   FREE_EXTENTS AS 'Free Extents',
              ->   FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
              ->   FROM INFORMATION_SCHEMA.FILES
              ->   WHERE LOGFILE_GROUP_NAME = 'lg1'
              ->   AND FILE_NAME IS NULL;
          +--------------+------------+
          | Free Extents | Free Bytes |
          +--------------+------------+
          |      5207565 |   20830260 |
          +--------------+------------+
          1 row in set (0.01 sec)

   * Beginning with MySQL Cluster NDB 6.2.19, MySQL Cluster NDB 6.3.32,
     MySQL Cluster NDB 7.0.13, and MySQL Cluster NDB 7.1.2, an
     additional row is present in the *Note `FILES': files-table. table
     for any tablespace, whether or not any data files are associated
     with the tablespace. This row has `NULL' for the value of the
     `FILE_NAME' column. For this row, the value of the `FILE_ID'
     column is always `0', that of the `FILE_TYPE' column is always
     `TABLESPACE', and that of the `STATUS' column is always `NORMAL'.
     Currently, the value of the `ENGINE' column is always *Note
     `NDBCLUSTER': mysql-cluster.

   * There are no *Note `SHOW': show. statements associated with the
     *Note `FILES': files-table. table.

   * For additional information, and examples of creating and dropping
     MySQL Cluster Disk Data objects, see *Note
     mysql-cluster-disk-data::.


File: manual.info,  Node: ndb-transid-mysql-connection-map-table,  Prev: files-table,  Up: mysql-cluster-i_s-tables

20.26.2 The INFORMATION_SCHEMA ndb_transid_mysql_connection_map Table
---------------------------------------------------------------------

The `ndb_transid_mysql_connection_map' table provides a mapping between
`NDB' transactions, `NDB' transaction coordinators, and MySQL Servers
attached to a MySQL Cluster as API nodes. This information is used when
populating the *Note `server_operations':
mysql-cluster-ndbinfo-server-operations. and *Note
`server_transactions': mysql-cluster-ndbinfo-server-transactions.
tables of the *Note `ndbinfo': mysql-cluster-ndbinfo. MySQL Cluster
information database.

This table describes the `INFORMATION_SCHEMA
ndb_transid_mysql_connection_map' table. The table lists
`INFORMATION_SCHEMA' names along with corresponding *Note `SHOW': show.
names (if applicable), and remarks.

`INFORMATION_SCHEMA' Name     *Note `SHOW': show.    Remarks
                              Name                   
`mysql_connection_id'                                MySQL Server
                                                     connection ID
`node_id'                                            Transaction
                                                     coordinator node ID
`ndb_transid'                                        *Note `NDB':
                                                     mysql-cluster.
                                                     transaction ID

The `mysql_connection_id' is the same as the connection or session ID
shown in the output of *Note `SHOW PROCESSLIST': show-processlist.

There are no `SHOW' statements associated with this table.

This is a nonstandard table, added in MySQL Cluster NDB 7.1.17. It is
implemented as an `INFORMATION_SCHEMA' plugin; you can verify that it
is supported by checking the output of *Note `SHOW PLUGINS':
show-plugins. If `ndb_transid_mysql_connection_map' support is enabled,
the output from this statement includes a plugin having this name, of
type `INFORMATION SCHEMA', and having status `ACTIVE', as shown here
(using emphasized text):


     mysql> SHOW PLUGINS;
     +----------------------------------+--------+--------------------+---------+---------+
     | Name                             | Status | Type               | Library | License |
     +----------------------------------+--------+--------------------+---------+---------+
     | binlog                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | CSV                              | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | MEMORY                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | MRG_MYISAM                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | MyISAM                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | PERFORMANCE_SCHEMA               | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | BLACKHOLE                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | ARCHIVE                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | ndbcluster                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | ndbinfo                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     _| ndb_transid_mysql_connection_map | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |_
     | InnoDB                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     | INNODB_TRX                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | INNODB_LOCKS                     | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | INNODB_LOCK_WAITS                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | INNODB_CMP                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | INNODB_CMP_RESET                 | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | INNODB_CMPMEM                    | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | INNODB_CMPMEM_RESET              | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
     | partition                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
     +----------------------------------+--------+--------------------+---------+---------+

The plugin is enabled by default. You can disable it (or force the
server not to run unless the plugin starts) by starting the server with
the `--ndb-transid-mysql-connection-map' option. If the plugin is
disabled, the status is shown by *Note `SHOW PLUGINS': show-plugins. as
`DISABLED'. The plugin cannot be enabled or disabled at runtime.

Although the names of this table and its columns are displayed using
lowercase, you can use uppercase or lowercase when referring to them in
SQL statements.

For this table to be created, the MySQL Server must be a binary that
wass supplied with the MySQL Cluster distribution, or one that was
built from the MySQL Cluster sources with *Note `NDB': mysql-cluster.
storage engine support enabled.  It is not available in the standard
MySQL 5.1 Server.


File: manual.info,  Node: extended-show,  Prev: mysql-cluster-i_s-tables,  Up: information-schema

20.27 Extensions to SHOW Statements
===================================

Some extensions to *Note `SHOW': show. statements accompany the
implementation of `INFORMATION_SCHEMA':

   * *Note `SHOW': show. can be used to get information about the
     structure of `INFORMATION_SCHEMA' itself.

   * Several *Note `SHOW': show. statements accept a `WHERE' clause
     that provides more flexibility in specifying which rows to display.

`INFORMATION_SCHEMA' is an information database, so its name is
included in the output from *Note `SHOW DATABASES': show-databases.
Similarly, *Note `SHOW TABLES': show-tables. can be used with
`INFORMATION_SCHEMA' to obtain a list of its tables:


     mysql> SHOW TABLES FROM INFORMATION_SCHEMA;
     +---------------------------------------+
     | Tables_in_INFORMATION_SCHEMA          |
     +---------------------------------------+
     | CHARACTER_SETS                        |
     | COLLATIONS                            |
     | COLLATION_CHARACTER_SET_APPLICABILITY |
     | COLUMNS                               |
     | COLUMN_PRIVILEGES                     |
     | ENGINES                               |
     | EVENTS                                |
     | FILES                                 |
     | GLOBAL_STATUS                         |
     | GLOBAL_VARIABLES                      |
     | KEY_COLUMN_USAGE                      |
     | PARTITIONS                            |
     | PLUGINS                               |
     | PROCESSLIST                           |
     | REFERENTIAL_CONSTRAINTS               |
     | ROUTINES                              |
     | SCHEMATA                              |
     | SCHEMA_PRIVILEGES                     |
     | SESSION_STATUS                        |
     | SESSION_VARIABLES                     |
     | STATISTICS                            |
     | TABLES                                |
     | TABLE_CONSTRAINTS                     |
     | TABLE_PRIVILEGES                      |
     | TRIGGERS                              |
     | USER_PRIVILEGES                       |
     | VIEWS                                 |
     +---------------------------------------+
     27 rows in set (0.00 sec)

*Note `SHOW COLUMNS': show-columns. and *Note `DESCRIBE': describe. can
display information about the columns in individual
`INFORMATION_SCHEMA' tables.

*Note `SHOW': show. statements that accept a `LIKE' clause to limit the
rows displayed also permit a `WHERE' clause that specifies more general
conditions that selected rows must satisfy:


     SHOW CHARACTER SET
     SHOW COLLATION
     SHOW COLUMNS
     SHOW DATABASES
     SHOW FUNCTION STATUS
     SHOW INDEX
     SHOW OPEN TABLES
     SHOW PROCEDURE STATUS
     SHOW STATUS
     SHOW TABLE STATUS
     SHOW TABLES
     SHOW TRIGGERS
     SHOW VARIABLES

The `WHERE' clause, if present, is evaluated against the column names
displayed by the *Note `SHOW': show. statement. For example, the *Note
`SHOW CHARACTER SET': show-character-set. statement produces these
output columns:


     mysql> SHOW CHARACTER SET;
     +----------+-----------------------------+---------------------+--------+
     | Charset  | Description                 | Default collation   | Maxlen |
     +----------+-----------------------------+---------------------+--------+
     | big5     | Big5 Traditional Chinese    | big5_chinese_ci     |      2 |
     | dec8     | DEC West European           | dec8_swedish_ci     |      1 |
     | cp850    | DOS West European           | cp850_general_ci    |      1 |
     | hp8      | HP West European            | hp8_english_ci      |      1 |
     | koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |      1 |
     | latin1   | cp1252 West European        | latin1_swedish_ci   |      1 |
     | latin2   | ISO 8859-2 Central European | latin2_general_ci   |      1 |
     ...

To use a `WHERE' clause with *Note `SHOW CHARACTER SET':
show-character-set, you would refer to those column names. As an
example, the following statement displays information about character
sets for which the default collation contains the string `'japanese'':


     mysql> SHOW CHARACTER SET WHERE `Default collation` LIKE '%japanese%';
     +---------+---------------------------+---------------------+--------+
     | Charset | Description               | Default collation   | Maxlen |
     +---------+---------------------------+---------------------+--------+
     | ujis    | EUC-JP Japanese           | ujis_japanese_ci    |      3 |
     | sjis    | Shift-JIS Japanese        | sjis_japanese_ci    |      2 |
     | cp932   | SJIS for Windows Japanese | cp932_japanese_ci   |      2 |
     | eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |      3 |
     +---------+---------------------------+---------------------+--------+

This statement displays the multibyte character sets:


     mysql> SHOW CHARACTER SET WHERE Maxlen > 1;
     +---------+---------------------------+---------------------+--------+
     | Charset | Description               | Default collation   | Maxlen |
     +---------+---------------------------+---------------------+--------+
     | big5    | Big5 Traditional Chinese  | big5_chinese_ci     |      2 |
     | ujis    | EUC-JP Japanese           | ujis_japanese_ci    |      3 |
     | sjis    | Shift-JIS Japanese        | sjis_japanese_ci    |      2 |
     | euckr   | EUC-KR Korean             | euckr_korean_ci     |      2 |
     | gb2312  | GB2312 Simplified Chinese | gb2312_chinese_ci   |      2 |
     | gbk     | GBK Simplified Chinese    | gbk_chinese_ci      |      2 |
     | utf8    | UTF-8 Unicode             | utf8_general_ci     |      3 |
     | ucs2    | UCS-2 Unicode             | ucs2_general_ci     |      2 |
     | cp932   | SJIS for Windows Japanese | cp932_japanese_ci   |      2 |
     | eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |      3 |
     +---------+---------------------------+---------------------+--------+


File: manual.info,  Node: connectors-apis,  Next: extending-mysql,  Prev: information-schema,  Up: Top

21 Connectors and APIs
**********************

* Menu:

* connector-odbc-info::          MySQL Connector/ODBC
* connector-net-info::           MySQL Connector/Net
* connector-j-info::             MySQL Connector/J
* connector-cpp-info::           MySQL Connector/C++
* connector-c-info::             MySQL Connector/C
* connector-python-info::        MySQL Connector/Python
* libmysqld::                    libmysqld, the Embedded MySQL Server Library
* c-api::                        MySQL C API
* apis-php-info::                MySQL PHP API
* apis-perl::                    MySQL Perl API
* apis-python::                  MySQL Python API
* apis-ruby::                    MySQL Ruby APIs
* apis-tcl::                     MySQL Tcl API
* apis-eiffel::                  MySQL Eiffel Wrapper

MySQL Connectors provide connectivity to the MySQL server for client
programs. APIs provide low-level access to the MySQL protocol and MySQL
resources. Both Connectors and the APIs enable you to connect and
execute MySQL statements from another language or environment,
including ODBC, Java (JDBC), Perl, Python, PHP, Ruby, and native C and
embedded MySQL instances.

*Note*:

Connector version numbers do not correlate with MySQL Server version
numbers. See *Note connectors-apis-versions::.

*MySQL Connectors*

Oracle develops a number of connectors:

   * Connector/ODBC
     (http://dev.mysql.com/doc/connector-odbc/en/index.html) provides
     driver support for connecting to MySQL using the Open Database
     Connectivity (ODBC) API. Support is available for ODBC
     connectivity from Windows, Unix, and Mac OS X platforms.

   * Connector/Net
     (http://dev.mysql.com/doc/connector-net/en/index.html) enables
     developers to create .NET applications that connect to MySQL.
     Connector/Net implements a fully functional ADO.NET interface and
     provides support for use with ADO.NET aware tools.  Applications
     that use Connector/Net can be written in any supported .NET
     language.

     The MySQL Visual Studio Plugin
     (http://dev.mysql.com/doc/connector-net/en/connector-net-visual-studio.html)
     works with Connector/Net and Visual Studio 2005. The plugin is a
     MySQL DDEX Provider, which means that you can use the schema and
     data manipulation tools available in Visual Studio to create and
     edit objects within a MySQL database.

   * Connector/J (http://dev.mysql.com/doc/connector-j/en/index.html)
     provides driver support for connecting to MySQL from Java
     applications using the standard Java Database Connectivity (JDBC)
     API.

   * Connector/Python
     (http://dev.mysql.com/doc/connector-python/en/index.html) provides
     driver support for connecting to MySQL from Python applications
     using an API that is compliant with the Python DB API version 2.0
     (http://www.python.org/dev/peps/pep-0249/). No additional Python
     modules or MySQL client libraries are required.

   * Connector/C++
     (http://dev.mysql.com/doc/connector-cpp/en/index.html) enables C++
     applications to connect to MySQL.

   * Connector/C (http://dev.mysql.com/doc/connector-c/en/index.html)
     is a standalone replacement for the MySQL Client Library
     (`libmysqlclient'), to be used for C applications.

*The MySQL C API*

For direct access to using MySQL natively within a C application, there
are two methods:

   * The *Note C API: c-api. provides low-level access to the MySQL
     client/server protocol through the `libmysqlclient' client
     library. This is the primary method used to connect to an instance
     of the MySQL server, and is used both by MySQL command-line
     clients and many of the MySQL Connectors and third-party APIs
     detailed here.

     `libmysqlclient' is included in MySQL distributions and in MySQL
     Connector/C distributions.

   * `libmysqld' is an embedded MySQL server library that enables you
     to embed an instance of the MySQL server into your C applications.

     `libmysqld' is included in MySQL distributions, but not in MySQL
     Connector/C distributions.

See also *Note c-api-implementations::.

To access MySQL from a C application, or to build an interface to MySQL
for a language not supported by the Connectors or APIs in this chapter,
the *Note C API: c-api. is where to start. A number of programmer's
utilities are available to help with the process; see *Note
programs-development::.

*Third-Party MySQL APIs*

The remaining APIs described in this chapter provide an interface to
MySQL from specific application languages. These third-party solutions
are not developed or supported by Oracle. Basic information on their
usage and abilities is provided here for reference purposes only.

All the third-party language APIs are developed using one of two
methods, using `libmysqlclient' or by implementing a _native driver_.
The two solutions offer different benefits:

   * Using _`libmysqlclient'_ offers complete compatibility with MySQL
     because it uses the same libraries as the MySQL client
     applications. However, the feature set is limited to the
     implementation and interfaces exposed through `libmysqlclient' and
     the performance may be lower as data is copied between the native
     language, and the MySQL API components.

   * _Native drivers_ are an implementation of the MySQL network
     protocol entirely within the host language or environment. Native
     drivers are fast, as there is less copying of data between
     components, and they can offer advanced functionality not
     available through the standard MySQL API.  Native drivers are also
     easier for end users to build and deploy because no copy of the
     MySQL client libraries is needed to build the native driver
     components.

*Note connectors-apis-summary:: lists many of the libraries and
interfaces available for MySQL.  *Note connectors-apis-versions:: shows
which MySQL Server versions each connector supports.

*MySQL APIs and Interfaces*

EnvironmentAPI                       Type        Notes
Ada     GNU Ada MySQL Bindings    `libmysqlclient'See MySQL Bindings for GNU
                                              Ada
                                              (http://gnade.sourceforge.net/)
C       C API                     `libmysqlclient'See *Note c-api::.
C       Connector/C               Replacement See MySQL Connector/C
                                  for         Developer Guide
                                  `libmysqlclient'(http://dev.mysql.com/doc/connector-c/en/index.html).
C++     Connector/C++             `libmysqlclient'See MySQL Connector/C++
                                              Developer Guide
                                              (http://dev.mysql.com/doc/connector-cpp/en/index.html).
        MySQL++                   `libmysqlclient'See MySQL++ Web site
                                              (http://tangentsoft.net/mysql++/doc/).
        MySQL wrapped             `libmysqlclient'See MySQL wrapped
                                              (http://www.alhem.net/project/mysql/).
Cocoa   MySQL-Cocoa               `libmysqlclient'Compatible with the
                                              Objective-C Cocoa
                                              environment. See
                                              `http://mysql-cocoa.sourceforge.net/'
D       MySQL for D               `libmysqlclient'See MySQL for D
                                              (http://www.steinmole.de/d/).
Eiffel  Eiffel MySQL              `libmysqlclient'See *Note apis-eiffel::.
Erlang  `erlang-mysql-driver'     `libmysqlclient'See `erlang-mysql-driver'.
                                              (http://code.google.com/p/erlang-mysql-driver/)
Haskell Haskell MySQL Bindings    Native      See Brian O'Sullivan's pure
                                  Driver      Haskell MySQL bindings
                                              (http://www.serpentine.com/blog/software/mysql/).
        `hsql-mysql'              `libmysqlclient'See MySQL driver for Haskell
                                              (http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hsql-mysql-1.7).
Java/JDBCConnector/J               Native      See MySQL Connector/J
                                  Driver      Developer Guide
                                              (http://dev.mysql.com/doc/connector-j/en/index.html).
Kaya    MyDB                      `libmysqlclient'See MyDB
                                              (http://kayalang.org/library/latest/MyDB).
Lua     LuaSQL                    `libmysqlclient'See LuaSQL
                                              (http://www.keplerproject.org/luasql/).
.NET/MonoConnector/Net             Native      See MySQL Connector/Net
                                  Driver      Developer Guide
                                              (http://dev.mysql.com/doc/connector-net/en/index.html).
ObjectiveOBjective Caml MySQL      `libmysqlclient'See MySQL Bindings for
Caml    Bindings                              Objective Caml
                                              (http://raevnos.pennmush.org/code/ocaml-mysql/).
Octave  Database bindings for     `libmysqlclient'See Database bindings for
        GNU Octave                            GNU Octave
                                              (http://octave.sourceforge.net/database/index.html).
ODBC    Connector/ODBC            `libmysqlclient'See MySQL Connector/ODBC
                                              Developer Guide
                                              (http://dev.mysql.com/doc/connector-odbc/en/index.html).
Perl    `DBI'/`DBD::mysql'        `libmysqlclient'See *Note apis-perl::.
        `Net::MySQL'              Native      See `Net::MySQL'
                                  Driver      (http://search.cpan.org/dist/Net-MySQL/MySQL.pm)
                                              at CPAN
PHP     `mysql', `ext/mysql'      `libmysqlclient'See Original MySQL API
        interface (deprecated)                (`Mysql')
                                              (http://dev.mysql.com/doc/apis-php/en/apis-php-mysql.html).
        `mysqli', `ext/mysqli'    `libmysqlclient'See MySQL Improved Extension
        interface                             (`Mysqli')
                                              (http://dev.mysql.com/doc/apis-php/en/apis-php-mysqli.html).
        `PDO_MYSQL'               `libmysqlclient'See MySQL Functions
                                              (PDO_MYSQL) (`MySQL (PDO)')
                                              (http://dev.mysql.com/doc/apis-php/en/apis-php-pdo-mysql.html).
        PDO mysqlnd               Native      
                                  Driver      
Python  Connector/Python          Native      See MySQL Connector/Python
                                  Driver      Developer Guide
                                              (http://dev.mysql.com/doc/connector-python/en/index.html).
        MySQLdb                   `libmysqlclient'See *Note apis-python::.
Ruby    MySQL/Ruby                `libmysqlclient'Uses `libmysqlclient'. See
                                              *Note apis-ruby-mysqlruby::.
        Ruby/MySQL                Native      See *Note
                                  Driver      apis-ruby-rubymysql::.
Scheme  `Myscsh'                  `libmysqlclient'See `Myscsh'
                                              (http://www-pu.informatik.uni-tuebingen.de/users/knauel/myscsh/).
SPL     `sql_mysql'               `libmysqlclient'See `sql_mysql' for SPL
                                              (http://www.clifford.at/spl/spldoc/sql_mysql.html).
Tcl     MySQLtcl                  `libmysqlclient'See *Note apis-tcl::.

*MySQL Connector Versions and MySQL Server Versions*

Connector                            Connector version  MySQL Server
                                                        version
Connector/C                          6.1.0 GA           5.6, 5.5, 5.1,
                                                        5.0, 4.1
Connector/C++                        1.0.5 GA           5.6, 5.5, 5.1
Connector/J                          5.1.8              5.6, 5.5, 5.1,
                                                        5.0, 4.1
Connector/Net                        6.5                5.6, 5.5, 5.1, 5.0
Connector/Net                        6.4                5.6, 5.5, 5.1, 5.0
Connector/Net                        6.3                5.6, 5.5, 5.1, 5.0
Connector/Net                        6.2 (No longer     5.6, 5.5, 5.1, 5.0
                                     supported)         
Connector/Net                        6.1 (No longer     5.6, 5.5, 5.1, 5.0
                                     supported)         
Connector/Net                        6.0 (No longer     5.6, 5.5, 5.1, 5.0
                                     supported)         
Connector/Net                        5.2 (No longer     5.6, 5.5, 5.1, 5.0
                                     supported)         
Connector/Net                        1.0 (No longer     5.0, 4.0
                                     supported)         
Connector/ODBC                       5.1                5.6, 5.5, 5.1,
                                                        5.0, 4.1.1+
Connector/ODBC                       3.51 (Unicode not  5.6, 5.5, 5.1,
                                     supported)         5.0, 4.1


File: manual.info,  Node: connector-odbc-info,  Next: connector-net-info,  Prev: connectors-apis,  Up: connectors-apis

21.1 MySQL Connector/ODBC
=========================

The MySQL Connector/ODBC manual is now published in standalone form,
not as part of the MySQL Reference Manual. For information, see these
documents:

   * Main manual: MySQL Connector/ODBC Developer Guide
     (http://dev.mysql.com/doc/connector-odbc/en/index.html)

   * Release notes: MySQL Connector/ODBC Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-odbc/en/)


File: manual.info,  Node: connector-net-info,  Next: connector-j-info,  Prev: connector-odbc-info,  Up: connectors-apis

21.2 MySQL Connector/Net
========================

The MySQL Connector/Net manual is now published in standalone form, not
as part of the MySQL Reference Manual. For information, see these
documents:

   * Main manual: MySQL Connector/Net Developer Guide
     (http://dev.mysql.com/doc/connector-net/en/index.html)

   * Release notes: MySQL Connector/Net Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-net/en/)


File: manual.info,  Node: connector-j-info,  Next: connector-cpp-info,  Prev: connector-net-info,  Up: connectors-apis

21.3 MySQL Connector/J
======================

The MySQL Connector/J manual is now published in standalone form, not
as part of the MySQL Reference Manual. For information, see these
documents:

   * Main manual: MySQL Connector/J Developer Guide
     (http://dev.mysql.com/doc/connector-j/en/index.html)

   * Release notes: MySQL Connector/J Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-j/en/)


File: manual.info,  Node: connector-cpp-info,  Next: connector-c-info,  Prev: connector-j-info,  Up: connectors-apis

21.4 MySQL Connector/C++
========================

The MySQL Connector/C++ manual is now published in standalone form, not
as part of the MySQL Reference Manual. For information, see these
documents:

   * Main manual: MySQL Connector/C++ Developer Guide
     (http://dev.mysql.com/doc/connector-cpp/en/index.html)

   * Release notes: MySQL Connector/C++ Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-cpp/en/)


File: manual.info,  Node: connector-c-info,  Next: connector-python-info,  Prev: connector-cpp-info,  Up: connectors-apis

21.5 MySQL Connector/C
======================

The MySQL Connector/C manual is now published in standalone form, not
as part of the MySQL Reference Manual. For information, see these
documents:

   * Main manual: MySQL Connector/C Developer Guide
     (http://dev.mysql.com/doc/connector-c/en/index.html)

   * Release notes: MySQL Connector/C Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-c/en/)


File: manual.info,  Node: connector-python-info,  Next: libmysqld,  Prev: connector-c-info,  Up: connectors-apis

21.6 MySQL Connector/Python
===========================

The MySQL Connector/Python manual is now published in standalone form,
not as part of the MySQL Reference Manual. For information, see these
documents:

   * Main manual: MySQL Connector/Python Developer Guide
     (http://dev.mysql.com/doc/connector-python/en/index.html)

   * Release notes: MySQL Connector/Python Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-python/en/)


File: manual.info,  Node: libmysqld,  Next: c-api,  Prev: connector-python-info,  Up: connectors-apis

21.7 libmysqld, the Embedded MySQL Server Library
=================================================

* Menu:

* libmysqld-compiling::          Compiling Programs with libmysqld
* libmysqld-restrictions::       Restrictions When Using the Embedded MySQL Server
* libmysqld-options::            Options with the Embedded Server
* libmysqld-example::            Embedded Server Examples

The embedded MySQL server library makes it possible to run a
full-featured MySQL server inside a client application. The main
benefits are increased speed and more simple management for embedded
applications.

The embedded server library is based on the client/server version of
MySQL, which is written in C/C++. Consequently, the embedded server
also is written in C/C++. There is no embedded server available in
other languages.

The API is identical for the embedded MySQL version and the
client/server version. To change an old threaded application to use the
embedded library, you normally only have to add calls to the following
functions.

*MySQL Embedded Server Library Functions*

This table lists MySQL embedded server library functions and describes
when the functions should be called.

Function               When to Call
*Note                  Call it before any other MySQL function is called,
`mysql_library_init()':preferably early in the `main()' function.
mysql-library-init.    
*Note                  Call it before your program exits.
`mysql_library_end()': 
mysql-library-end.     
*Note                  Call it in each thread you create that accesses
`mysql_thread_init()': MySQL.
mysql-thread-init.     
*Note                  Call it before calling `pthread_exit()'.
`mysql_thread_end()':  
mysql-thread-end.      

Then you must link your code with `libmysqld.a' instead of
`libmysqlclient.a'. To ensure binary compatibility between your
application and the server library, be sure to compile your application
against headers for the same series of MySQL that was used to compile
the server library. For example, if `libmysqld' was compiled against
MySQL 4.1 headers, do not compile your application against MySQL 5.1
headers, or vice versa.

The `mysql_library_XXX()' functions are also included in
`libmysqlclient.a' to enable you to change between the embedded and the
client/server version by just linking your application with the right
library. See *Note mysql-library-init::.

One difference between the embedded server and the standalone server is
that for the embedded server, authentication for connections is
disabled by default. To use authentication for the embedded server,
specify the `--with-embedded-privilege-control' option when you invoke
`configure' to configure your MySQL distribution.


File: manual.info,  Node: libmysqld-compiling,  Next: libmysqld-restrictions,  Prev: libmysqld,  Up: libmysqld

21.7.1 Compiling Programs with libmysqld
----------------------------------------

In precompiled binary MySQL distributions that include `libmysqld', the
embedded server library, MySQL builds the library using the appropriate
vendor compiler if there is one.

To get a `libmysqld' library if you build MySQL from source yourself,
you should configure MySQL with the `--with-embedded-server' option.
See *Note source-configuration-options::.

When you link your program with `libmysqld', you must also include the
system-specific `pthread' libraries and some libraries that the MySQL
server uses. You can get the full list of libraries by executing *Note
`mysql_config --libmysqld-libs': mysql-config.

The correct flags for compiling and linking a threaded program must be
used, even if you do not directly call any thread functions in your
code.

To compile a C program to include the necessary files to embed the
MySQL server library into an executable version of a program, the
compiler will need to know where to find various files and need
instructions on how to compile the program. The following example shows
how a program could be compiled from the command line, assuming that
you are using `gcc', use the GNU C compiler:


     gcc mysql_test.c -o mysql_test -lz \
     `/usr/local/mysql/bin/mysql_config --include --libmysqld-libs`

Immediately following the `gcc' command is the name of the C program
source file. After it, the `-o' option is given to indicate that the
file name that follows is the name that the compiler is to give to the
output file, the compiled program. The next line of code tells the
compiler to obtain the location of the include files and libraries and
other settings for the system on which it is compiled. Because of a
problem with *Note `mysql_config': mysql-config, the option `-lz' (for
compression) is added here. The *Note `mysql_config': mysql-config.
command is contained in backticks, not single quotation marks.

On some non-`gcc' platforms, the embedded library depends on C++
runtime libraries and linking against the embedded library might result
in missing-symbol errors. To solve this, link using a C++ compiler or
explicitly list the required libraries on the link command line.


File: manual.info,  Node: libmysqld-restrictions,  Next: libmysqld-options,  Prev: libmysqld-compiling,  Up: libmysqld

21.7.2 Restrictions When Using the Embedded MySQL Server
--------------------------------------------------------

The embedded server has the following limitations:

   * No user-defined functions (UDFs).

   * No stack trace on core dump.

   * You cannot set this up as a master or a slave (no replication).

   * Very large result sets may be unusable on low memory systems.

   * You cannot connect to an embedded server from an outside process
     with sockets or TCP/IP. However, you can connect to an
     intermediate application, which in turn can connect to an embedded
     server on the behalf of a remote client or outside process.

   * `InnoDB' is not reentrant in the embedded server and cannot be
     used for multiple connections, either successively or
     simultaneously.

   * The Event Scheduler is not available. Because of this, the
     `event_scheduler' system variable is disabled.

Some of these limitations can be changed by editing the `mysql_embed.h'
include file and recompiling MySQL.


File: manual.info,  Node: libmysqld-options,  Next: libmysqld-example,  Prev: libmysqld-restrictions,  Up: libmysqld

21.7.3 Options with the Embedded Server
---------------------------------------

Any options that may be given with the *Note `mysqld': mysqld.  server
daemon, may be used with an embedded server library. Server options may
be given in an array as an argument to the *Note
`mysql_library_init()': mysql-library-init, which initializes the
server. They also may be given in an option file like `my.cnf'. To
specify an option file for a C program, use the `--defaults-file'
option as one of the elements of the second argument of the *Note
`mysql_library_init()': mysql-library-init. function. See *Note
mysql-library-init::, for more information on the *Note
`mysql_library_init()': mysql-library-init. function.

Using option files can make it easier to switch between a client/server
application and one where MySQL is embedded. Put common options under
the `[server]' group. These are read by both MySQL versions.
Client/server-specific options should go under the `[mysqld]' section.
Put options specific to the embedded MySQL server library in the
`[embedded]' section. Options specific to applications go under section
labeled `[ApplicationName_SERVER]'. See *Note option-files::.


File: manual.info,  Node: libmysqld-example,  Prev: libmysqld-options,  Up: libmysqld

21.7.4 Embedded Server Examples
-------------------------------

These two example programs should work without any changes on a Linux
or FreeBSD system. For other operating systems, minor changes are
needed, mostly with file paths. These examples are designed to give
enough details for you to understand the problem, without the clutter
that is a necessary part of a real application. The first example is
very straightforward. The second example is a little more advanced with
some error checking. The first is followed by a command-line entry for
compiling the program. The second is followed by a GNUmake file that
may be used for compiling instead.

*Example 1*

`test1_libmysqld.c'


     #include <stdio.h>
     #include <stdlib.h>
     #include <stdarg.h>
     #include "mysql.h"

     MYSQL *mysql;
     MYSQL_RES *results;
     MYSQL_ROW record;

     static char *server_options[] = \
            { "mysql_test", "--defaults-file=my.cnf", NULL };
     int num_elements = (sizeof(server_options) / sizeof(char *)) - 1;

     static char *server_groups[] = { "libmysqld_server",
                                      "libmysqld_client", NULL };

     int main(void)
     {
        mysql_library_init(num_elements, server_options, server_groups);
        mysql = mysql_init(NULL);
        mysql_options(mysql, MYSQL_READ_DEFAULT_GROUP, "libmysqld_client");
        mysql_options(mysql, MYSQL_OPT_USE_EMBEDDED_CONNECTION, NULL);

        mysql_real_connect(mysql, NULL,NULL,NULL, "database1", 0,NULL,0);

        mysql_query(mysql, "SELECT column1, column2 FROM table1");

        results = mysql_store_result(mysql);

        while((record = mysql_fetch_row(results))) {
           printf("%s - %s \n", record[0], record[1]);
        }

        mysql_free_result(results);
        mysql_close(mysql);
        mysql_library_end();

        return 0;
     }

Here is the command line for compiling the above program:


     gcc test1_libmysqld.c -o test1_libmysqld -lz \
      `/usr/local/mysql/bin/mysql_config --include --libmysqld-libs`

*Example 2*

To try the example, create an `test2_libmysqld' directory at the same
level as the MySQL source directory. Save the `test2_libmysqld.c'
source and the `GNUmakefile' in the directory, and run GNU `make' from
inside the `test2_libmysqld' directory.

`test2_libmysqld.c'


     /*
      * A simple example client, using the embedded MySQL server library
     */

     #include <mysql.h>
     #include <stdarg.h>
     #include <stdio.h>
     #include <stdlib.h>

     MYSQL *db_connect(const char *dbname);
     void db_disconnect(MYSQL *db);
     void db_do_query(MYSQL *db, const char *query);

     const char *server_groups[] = {
       "test2_libmysqld_SERVER", "embedded", "server", NULL
     };

     int
     main(int argc, char **argv)
     {
       MYSQL *one, *two;

       /* mysql_library_init() must be called before any other mysql
        * functions.
        *
        * You can use mysql_library_init(0, NULL, NULL), and it
        * initializes the server using groups = {
        *   "server", "embedded", NULL
        *  }.
        *
        * In your $HOME/.my.cnf file, you probably want to put:

     [test2_libmysqld_SERVER]
     language = /path/to/source/of/mysql/sql/share/english

        * You could, of course, modify argc and argv before passing
        * them to this function.  Or you could create new ones in any
        * way you like.  But all of the arguments in argv (except for
        * argv[0], which is the program name) should be valid options
        * for the MySQL server.
        *
        * If you link this client against the normal mysqlclient
        * library, this function is just a stub that does nothing.
        */
       mysql_library_init(argc, argv, (char **)server_groups);

       one = db_connect("test");
       two = db_connect(NULL);

       db_do_query(one, "SHOW TABLE STATUS");
       db_do_query(two, "SHOW DATABASES");

       mysql_close(two);
       mysql_close(one);

       /* This must be called after all other mysql functions */
       mysql_library_end();

       exit(EXIT_SUCCESS);
     }

     static void
     die(MYSQL *db, char *fmt, ...)
     {
       va_list ap;
       va_start(ap, fmt);
       vfprintf(stderr, fmt, ap);
       va_end(ap);
       (void)putc('\n', stderr);
       if (db)
         db_disconnect(db);
       exit(EXIT_FAILURE);
     }

     MYSQL *
     db_connect(const char *dbname)
     {
       MYSQL *db = mysql_init(NULL);
       if (!db)
         die(db, "mysql_init failed: no memory");
       /*
        * Notice that the client and server use separate group names.
        * This is critical, because the server does not accept the
        * client's options, and vice versa.
        */
       mysql_options(db, MYSQL_READ_DEFAULT_GROUP, "test2_libmysqld_CLIENT");
       if (!mysql_real_connect(db, NULL, NULL, NULL, dbname, 0, NULL, 0))
         die(db, "mysql_real_connect failed: %s", mysql_error(db));

       return db;
     }

     void
     db_disconnect(MYSQL *db)
     {
       mysql_close(db);
     }

     void
     db_do_query(MYSQL *db, const char *query)
     {
       if (mysql_query(db, query) != 0)
         goto err;

       if (mysql_field_count(db) > 0)
       {
         MYSQL_RES   *res;
         MYSQL_ROW    row, end_row;
         int num_fields;

         if (!(res = mysql_store_result(db)))
           goto err;
         num_fields = mysql_num_fields(res);
         while ((row = mysql_fetch_row(res)))
         {
           (void)fputs(">> ", stdout);
           for (end_row = row + num_fields; row < end_row; ++row)
             (void)printf("%s\t", row ? (char*)*row : "NULL");
           (void)fputc('\n', stdout);
         }
         (void)fputc('\n', stdout);
         mysql_free_result(res);
       }
       else
         (void)printf("Affected rows: %lld\n", mysql_affected_rows(db));

       return;

     err:
       die(db, "db_do_query failed: %s [%s]", mysql_error(db), query);
     }

`GNUmakefile'


     # This assumes the MySQL software is installed in /usr/local/mysql
     inc      := /usr/local/mysql/include/mysql
     lib      := /usr/local/mysql/lib

     # If you have not installed the MySQL software yet, try this instead
     #inc      := $(HOME)/mysql-5.1/include
     #lib      := $(HOME)/mysql-5.1/libmysqld

     CC       := gcc
     CPPFLAGS := -I$(inc) -D_THREAD_SAFE -D_REENTRANT
     CFLAGS   := -g -W -Wall
     LDFLAGS  := -static
     # You can change -lmysqld to -lmysqlclient to use the
     # client/server library
     LDLIBS    = -L$(lib) -lmysqld -lz -lm -ldl -lcrypt

     ifneq (,$(shell grep FreeBSD /COPYRIGHT 2>/dev/null))
     # FreeBSD
     LDFLAGS += -pthread
     else
     # Assume Linux
     LDLIBS += -lpthread
     endif

     # This works for simple one-file test programs
     sources := $(wildcard *.c)
     objects := $(patsubst %c,%o,$(sources))
     targets := $(basename $(sources))

     all: $(targets)

     clean:
             rm -f $(targets) $(objects) *.core


File: manual.info,  Node: c-api,  Next: apis-php-info,  Prev: libmysqld,  Up: connectors-apis

21.8 MySQL C API
================

* Menu:

* c-api-implementations::        MySQL C API Implementations
* c-api-multiple-installations::  Simultaneous MySQL Server and MySQL Connector/C Installations
* c-api-example-programs::       Example C API Client Programs
* c-api-building-running-clients::  Building and Running C API Client Programs
* c-api-data-structures::        C API Data Structures
* c-api-function-overview::      C API Function Overview
* c-api-functions::              C API Function Descriptions
* c-api-prepared-statements::    C API Prepared Statements
* c-api-prepared-statement-data-structures::  C API Prepared Statement Data Structures
* c-api-prepared-statement-function-overview::  C API Prepared Statement Function Overview
* c-api-prepared-statement-functions::  C API Prepared Statement Function Descriptions
* c-api-thread-functions::       C API Threaded Function Descriptions
* c-api-embedded-server-functions::  C API Embedded Server Function Descriptions
* c-api-problems::               Common Questions and Problems When Using the C API
* auto-reconnect::               Controlling Automatic Reconnection Behavior
* c-api-multiple-queries::       C API Support for Multiple Statement Execution
* c-api-prepared-statement-problems::  C API Prepared Statement Problems
* c-api-prepared-statement-date-handling::  C API Prepared Statement Handling of Date and Time Values
* c-api-prepared-call-statements::  C API Support for Prepared CALL Statements

The C API provides low-level access to the MySQL client/server protocol
and enables C programs to access database contents. The C API code is
distributed with MySQL and implemented in the `libmysqlclient' library.
See *Note c-api-implementations::.

Most other client APIs use the `libmysqlclient' library to communicate
with the MySQL server. (Exceptions are except Connector/J and
Connector/Net.) This means that, for example, you can take advantage of
many of the same environment variables that are used by other client
programs because they are referenced from the library. For a list of
these variables, see *Note programs-overview::.

For instructions on building client programs using the C API, see *Note
c-api-building-clients::. For programming with threads, see *Note
c-api-threaded-clients::. To create a standalone application which
includes the "server" and "client" in the same program (and does not
communicate with an external MySQL server), see *Note libmysqld::.

*Note*:

If, after an upgrade, you experience problems with compiled client
programs, such as `Commands out of sync' or unexpected core dumps, the
programs were probably compiled using old header or library files. In
this case, check the date of the `mysql.h' file and `libmysqlclient.a'
library used for compilation to verify that they are from the new MySQL
distribution. If not, recompile the programs with the new headers and
libraries.  Recompilation might also be necessary for programs compiled
against the shared client library if the library major version number
has changed (for example, from `libmysqlclient.so.17' to
`libmysqlclient.so.18'). For additional compatibility information, see
*Note c-api-running-clients::.

Clients have a maximum communication buffer size. The size of the
buffer that is allocated initially (16KB) is automatically increased up
to the maximum size (16MB by default). Because buffer sizes are
increased only as demand warrants, simply increasing the maximum limit
does not in itself cause more resources to be used. This size check is
mostly a precaution against erroneous statements and communication
packets.

The communication buffer must be large enough to contain a single SQL
statement (for client-to-server traffic) and one row of returned data
(for server-to-client traffic). Each session's communication buffer is
dynamically enlarged to handle any query or row up to the maximum
limit. For example, if you have *Note `BLOB': blob. values that contain
up to 16MB of data, you must have a communication buffer limit of at
least 16MB (in both server and client). The default maximum built into
the client library is 1GB, but the default maximum in the server is 1MB.
You can increase this by changing the value of the `max_allowed_packet'
parameter at server startup. See *Note server-parameters::.

The MySQL server shrinks each communication buffer to
`net_buffer_length' bytes after each query. For clients, the size of
the buffer associated with a connection is not decreased until the
connection is closed, at which time client memory is reclaimed.


File: manual.info,  Node: c-api-implementations,  Next: c-api-multiple-installations,  Prev: c-api,  Up: c-api

21.8.1 MySQL C API Implementations
----------------------------------

The MySQL C API is a C-based API that client applications written in C
can use to communicate with MySQL Server. Client programs refer to C
API header files at compile time and link to a C API library file at
link time. The library comes in two versions, depending on how the
application is intended to communicate with the server:

   * `libmysqlclient': The client version of the library, used for
     applications that communicate over a network connection as a
     client of a standalone server process.

   * `libmysqld': The embedded server version of the library, used for
     applications intended to include an embedded MySQL server within
     the application itself. The application communicates with its own
     private server instance.

Both libraries have the same interface. In terms of C API calls, an
application communicates with a standalone server the same way it
communicates with an embedded server. A given client can be built to
communicate with a standalone or embedded server, depending on whether
it is linked against `libmysqlclient' or `libmysqld' at build time.

There are two ways to obtain the C API header and library files
required to build C API client programs:

   * Install a MySQL Server distribution. Server distributions include
     both `libmysqlclient' and `libmysqld'.

   * Install a MySQL Connector/C distribution. Connector/C
     distributions include only `libmysqlclient'. They do not include
     `libmysqld'.

For both MySQL Server and MySQL Connector/C, you can install a binary
distribution that contains the C API files pre-built, or you can use a
source distribution and build the C API files yourself.

Normally, you install either a MySQL Server distribution or a MySQL
Connector/C distribution, but not both. For information about issues
involved with simultaneous MySQL Server and MySQL Connector/C
installations, see *Note c-api-multiple-installations::.

The names of the library files to use when linking C API client
applications depend on the library type and platform for which a
distribution is built:

   * On Unix (and Unix-like) sytems, the static library is
     `libmysqlclient.a'. The dynamic library is `libmysqlclient.so' on
     most Unix systems and `libmysqlclient.dylib' on Mac OS X.

     For distributions that include embedded server libraries, the
     corresponding library names begin with `libmysqld' rather than
     `libmysqlclient'.

   * On Windows, the static library is `mysqlclient.lib' and the
     dynamic library is `libmysql.dll'. Windows distributions also
     include `libmysql.lib', a static import library needed for using
     the dynamic library.

     For distributions that include embedded server libraries, the
     corresponding library names are `mysqlserver.lib',
     `libmysqld.dll', and `libmysqld.lib'.

     Windows distributions also include a set of debug libraries.
     These have the same names as the nondebug libraries, but are
     located in the `lib/debug' library. You must use the debug
     libraries when compiling clients built using the debug C runtime.


File: manual.info,  Node: c-api-multiple-installations,  Next: c-api-example-programs,  Prev: c-api-implementations,  Up: c-api

21.8.2 Simultaneous MySQL Server and MySQL Connector/C Installations
--------------------------------------------------------------------

MySQL Server and MySQL Connector/C installation packages both provide
the files needed to build and run MySQL C API client programs. This
section discusses when it is possible to install both products on the
same system. For some packaging formats, this is possible without
conflict. For others, both products cannot be installed at the same
time.

This discussion assumes the use of similar package types for both
products (for example, RPM packages for both products). It does not try
to describe coexistence between packaging types (for example, use of
RPM packages for one product and a `tar' file package for the other).
Nor does it describe coexistence of packages provided by Oracle and
those provided by third-party vendors.

If you install both products, it may be necessary to adjust your
development tools or runtime environment to choose one set of header
files and libraries over the other. See *Note c-api-building-clients::,
and *Note c-api-running-clients::.

`tar' and Zip file packages install under the directory into which you
unpack them. For example, you can unpack MySQL Server and MySQL
Connector/C `tar' packages under `/usr/local' and they will unpack into
distinct directory names without conflict.

Windows MSI installers use their own installation directory, so MySQL
Server and MySQL Connector/C installers do not conflict.

Mac OS X DMG packages install under the same parent directory but in a
different subdirectory, so there is no conflict. For example:


     /usr/local/mysql-5.6.11-osx10.7-x86_64/
     /usr/local/mysql-connector-c-6.1.0-osx10.7-x86/

Solaris PKG packages install under the same parent directory but in a
different subdirectory, so there is no conflict. For example:


     /opt/mysql/mysql
     /opt/mysql/connector-c

The Solaris MySQL Connector/C installer does not create any symlinks
from system directories such as `/usr/bin' or `/usr/lib' into the
installation directory.  That must be done manually if desired after
installation.

For RPM installations, there are several types of RPM packages.  MySQL
Server `shared' and `devel' RPM packages are similar to the
corresponding MySQL Connector/C RPM packages. These RPM package types
cannot coexist because the MySQL Server and MySQL Connector/C RPM
packages use the same installation locations for the client
library-related files.  This means the following conditions hold:

   * If MySQL Server `shared' and `devel' RPM packages are installed,
     they provide the C API headers and libraries, and there is no need
     to install the MySQL Connector/C RPM packages. To install the
     MySQL Connector/C packages anyway, you must first remove the
     corresponding MySQL Server packages.

   * To install MySQL Server RPM packages if you already have MySQL
     Connector/C RPM packages installed, you must first remove the
     MySQL Connector/C RPM packages.

MySQL Server RPM packages other than `shared' and `devel' do not
conflict with MySQL Connector/C packages and can be installed if MySQL
Connector/C is installed. This includes the main server RPM that
includes the *Note `mysqld': mysqld. server itself.


File: manual.info,  Node: c-api-example-programs,  Next: c-api-building-running-clients,  Prev: c-api-multiple-installations,  Up: c-api

21.8.3 Example C API Client Programs
------------------------------------

Many of the clients in MySQL source distributions are written in C,
such as *Note `mysql': mysql, *Note `mysqladmin': mysqladmin, and *Note
`mysqlshow': mysqlshow.  If you are looking for examples that
demonstrate how to use the C API, take a look at these clients: Obtain
a source distribution and look in its `client' directory. See *Note
getting-mysql::.


File: manual.info,  Node: c-api-building-running-clients,  Next: c-api-data-structures,  Prev: c-api-example-programs,  Up: c-api

21.8.4 Building and Running C API Client Programs
-------------------------------------------------

* Menu:

* c-api-building-clients::       Building C API Client Programs
* c-api-threaded-clients::       Writing C API Threaded Client Programs
* c-api-running-clients::        Running C API Client Programs
* c-api-server-client-versions::  C API Server and Client Library Versions

The following sections provide information on building client programs
that use the C API. Topics include compiling and linking clients,
writing threaded clients, and troubleshooting runtime problems.


File: manual.info,  Node: c-api-building-clients,  Next: c-api-threaded-clients,  Prev: c-api-building-running-clients,  Up: c-api-building-running-clients

21.8.4.1 Building C API Client Programs
.......................................

This section provides guidelines for compiling C programs that use the
MySQL C API.

*Compiling MySQL Clients on Unix*

You may need to specify an `-I' option when you compile client programs
that use MySQL header files, so that the compiler can find them. For
example, if the header files are installed in
`/usr/local/mysql/include', use this option in the compile command:


     -I/usr/local/mysql/include

MySQL clients must be linked using the `-lmysqlclient -lz' options in
the link command. You may also need to specify a `-L' option to tell
the linker where to find the library. For example, if the library is
installed in `/usr/local/mysql/lib', use these options in the link
command:


     -L/usr/local/mysql/lib -lmysqlclient -lz

The path names may differ on your system. Adjust the `-I' and `-L'
options as necessary.

To make it simpler to compile MySQL programs on Unix, use the *Note
`mysql_config': mysql-config. script. See *Note mysql-config::.

*Note `mysql_config': mysql-config. displays the options needed for
compiling or linking:


     shell> mysql_config --cflags
     shell> mysql_config --libs

You can run those commands to get the proper options and add them
manually to compilation or link commands. Alternatively, include the
output from *Note `mysql_config': mysql-config. directly within command
lines using backticks:


     shell> gcc -c `mysql_config --cflags` progname.c
     shell> gcc -o progname progname.o `mysql_config --libs`

*Compiling MySQL Clients on Microsoft Windows*

To specify header and library file locations, use the facilities
provided by your development environment.

On Windows, you can link your code with either the dynamic or static C
client library. The static library is named `mysqlclient.lib' and the
dynamic library is named `libmysql.dll'. In addition, the
`libmysql.lib' static import library is needed for using the dynamic
library.

If you link with the static library, failure can occur unless these
conditions are satisfied:

   * The client application must be compiled with the same version of
     Visual Studio used to compile the library.

   * The client application should link the C runtime statically by
     using the `/MT' compiler option.

If the client application is built in debug mode and uses the static
debug C runtime (`/MTd' compiler option), it can link to the
`mysqlclient.lib' static library if that library was built using the
same option.  If the client application uses the dynamic C runtime
(`/MD' option, or `/MDd' option in debug mode), it must be linked to the
`libmysql.dll' dynamic library. It cannot link to the static client
library.

The MSDN page describing the link options can be found here:
`http://msdn.microsoft.com/en-us/library/2kzt1wy3.aspx'

*Troubleshooting Problems Linking to the MySQL Client Library*

Linking with the single-threaded library (`libmysqlclient') may lead to
linker errors related to `pthread' symbols. When using the
single-threaded library, please compile your client with
`MYSQL_CLIENT_NO_THREADS' defined. This can be done on the command line
by using the `-D' option to the compiler, or in your source code before
including the MySQL header files. This define should not be used when
building for use with the thread-safe client library
(`libmysqlclient_r').

If the linker cannot find the MySQL client library, you might get
undefined-reference errors for symbols that start with `mysql_', such
as those shown here:


     /tmp/ccFKsdPa.o: In function `main':
     /tmp/ccFKsdPa.o(.text+0xb): undefined reference to `mysql_init'
     /tmp/ccFKsdPa.o(.text+0x31): undefined reference to `mysql_real_connect'
     /tmp/ccFKsdPa.o(.text+0x69): undefined reference to `mysql_error'
     /tmp/ccFKsdPa.o(.text+0x9a): undefined reference to `mysql_close'

You should be able to solve this problem by adding `-LDIR_PATH
-lmysqlclient' at the end of your link command, where DIR_PATH
represents the path name of the directory where the client library is
located. To determine the correct directory, try this command:


     shell> mysql_config --libs

The output from *Note `mysql_config': mysql-config. might indicate
other libraries that should be specified on the link command as well.
You can include *Note `mysql_config': mysql-config. output directly in
your compile or link command using backticks. For example:


     shell> gcc -o progname progname.o `mysql_config --libs`

If an error occurs at link time that the `floor' symbol is undefined,
link to the math library by adding `-lm' to the end of the compile/link
line.

If you get `undefined reference' errors for the `uncompress' or
`compress' function, add `-lz' to the end of your link command and try
again.

Similarly, if you get undefined-reference errors for other functions
that should exist on your system, such as `connect()', check the manual
page for the function in question to determine which libraries you
should add to the link command.

If you get undefined-reference errors such as the following for
functions that do not exist on your system, it usually means that your
MySQL client library was compiled on a system that is not 100%
compatible with yours:


     mf_format.o(.text+0x201): undefined reference to `__lxstat'

In this case, you should download the latest MySQL or MySQL Connector/C
source distribution and compile the MySQL client library yourself. See
*Note source-installation::, and MySQL Connector/C Developer Guide
(http://dev.mysql.com/doc/connector-c/en/index.html).


File: manual.info,  Node: c-api-threaded-clients,  Next: c-api-running-clients,  Prev: c-api-building-clients,  Up: c-api-building-running-clients

21.8.4.2 Writing C API Threaded Client Programs
...............................................

The client library is almost thread-safe. The biggest problem is that
the subroutines in `net.c' that read from sockets are not
interrupt-safe. This was done with the thought that you might want to
have your own alarm that can break a long read to a server. If you
install interrupt handlers for the `SIGPIPE' interrupt, socket handling
should be thread-safe.

To avoid aborting the program when a connection terminates, MySQL
blocks `SIGPIPE' on the first call to *Note `mysql_library_init()':
mysql-library-init, *Note `mysql_init()': mysql-init, or *Note
`mysql_connect()': mysql-connect. To use your own `SIGPIPE' handler,
first call *Note `mysql_library_init()': mysql-library-init, then
install your handler.

Current binary distributions should have both a normal client library,
`libmysqlclient', and a thread-safe library, `libmysqlclient_r'. For
threaded clients, link against the latter library. If `undefined
symbol' errors occur, in most cases this is because you have not
included the thread libraries on the link/compile command.

The thread-safe client library, `libmysqlclient_r', is thread-safe per
connection. You can let two threads share the same connection with the
following caveats:

   * Multiple threads cannot send a query to the MySQL server at the
     same time on the same connection. In particular, you must ensure
     that between calls to *Note `mysql_query()': mysql-query. and
     *Note `mysql_store_result()': mysql-store-result. in one thread,
     no other thread uses the same connection. You must have a mutex
     lock around your pair of *Note `mysql_query()': mysql-query. and
     *Note `mysql_store_result()': mysql-store-result. calls.  After
     *Note `mysql_store_result()': mysql-store-result.  returns, the
     lock can be released and other threads may query the same
     connection.

     If you use POSIX threads, you can use `pthread_mutex_lock()' and
     `pthread_mutex_unlock()' to establish and release a mutex lock.

   * Many threads can access different result sets that are retrieved
     with *Note `mysql_store_result()': mysql-store-result.

   * To use *Note `mysql_use_result()': mysql-use-result, you must
     ensure that no other thread is using the same connection until the
     result set is closed. However, it really is best for threaded
     clients that share the same connection to use *Note
     `mysql_store_result()': mysql-store-result.

You need to know the following if you have a thread that did not create
the connection to the MySQL database but is calling MySQL functions:

When you call *Note `mysql_init()': mysql-init, MySQL creates a
thread-specific variable for the thread that is used by the debug
library (among other things). If you call a MySQL function before the
thread has called *Note `mysql_init()': mysql-init, the thread does not
have the necessary thread-specific variables in place and you are
likely to end up with a core dump sooner or later. To avoid problems,
you must do the following:

  1. Call *Note `mysql_library_init()': mysql-library-init.  before any
     other MySQL functions. It is not thread-safe, so call it before
     threads are created, or protect the call with a mutex.

  2. Arrange for *Note `mysql_thread_init()': mysql-thread-init. to be
     called early in the thread handler before calling any MySQL
     function. If you call *Note `mysql_init()': mysql-init, it will
     call *Note `mysql_thread_init()': mysql-thread-init. for you.

  3. In the thread, call *Note `mysql_thread_end()': mysql-thread-end.
     before calling `pthread_exit()'. This frees the memory used by
     MySQL thread-specific variables.

The preceding notes regarding *Note `mysql_init()': mysql-init. also
apply to *Note `mysql_connect()': mysql-connect, which calls *Note
`mysql_init()': mysql-init.


File: manual.info,  Node: c-api-running-clients,  Next: c-api-server-client-versions,  Prev: c-api-threaded-clients,  Up: c-api-building-running-clients

21.8.4.3 Running C API Client Programs
......................................

If, after an upgrade, you experience problems with compiled client
programs, such as `Commands out of sync' or unexpected core dumps, the
programs were probably compiled using old header or library files. In
this case, check the date of the `mysql.h' file and `libmysqlclient.a'
library used for compilation to verify that they are from the new MySQL
distribution. If not, recompile the programs with the new headers and
libraries. Recompilation might also be necessary for programs compiled
against the shared client library if the library major version number
has changed (for example, from `libmysqlclient.so.17' to
`libmysqlclient.so.18').

The major client library version determines compatibility. (For
example, for `libmysqlclient.so.18.1.0', the major version is 18.) For
this reason, the libraries shipped with newer versions of MySQL are
drop-in replacements for older versions that have the same major
number. As long as the major library version is the same, you can
upgrade the library and old applications should continue to work with
it.

Undefined-reference errors might occur at runtime when you try to
execute a MySQL program. If these errors specify symbols that start
with `mysql_' or indicate that the `libmysqlclient' library cannot be
found, it means that your system cannot find the shared
`libmysqlclient.so' library. The solution to this problem is to tell
your system to search for shared libraries in the directory where that
library is located. Use whichever of the following methods is
appropriate for your system:

   * Add the path of the directory where `libmysqlclient.so' is located
     to the `LD_LIBRARY_PATH' or `LD_LIBRARY' environment variable.

   * On Mac OS X, add the path of the directory where
     `libmysqlclient.dylib' is located to the `DYLD_LIBRARY_PATH'
     environment variable.

   * Copy the shared-library files (such as `libmysqlclient.so') to
     some directory that is searched by your system, such as `/lib',
     and update the shared library information by executing `ldconfig'.
     Be sure to copy all related files. A shared library might exist
     under several names, using symlinks to provide the alternate names.

Another way to solve this problem is by linking your program statically
with the `-static' option, or by removing the dynamic MySQL libraries
before linking your code.  Before trying the second method, you should
be sure that no other programs are using the dynamic libraries.


File: manual.info,  Node: c-api-server-client-versions,  Prev: c-api-running-clients,  Up: c-api-building-running-clients

21.8.4.4 C API Server and Client Library Versions
.................................................

The string and numeric forms of the MySQL server version are available
at compile time as the values of the `MYSQL_SERVER_VERSION' and
`MYSQL_VERSION_ID' macros, and at runtime as the values of the *Note
`mysql_get_server_info()': mysql-get-server-info. and *Note
`mysql_get_server_version()': mysql-get-server-version.  functions.

The client library version is the MySQL version. For Connector/C, this
is the MySQL version on which the Connector/C distribution is based.
The string and numeric forms of this version are available at compile
time as the values of the `MYSQL_SERVER_VERSION' and `MYSQL_VERSION_ID'
macros, and at runtime as the values of the *Note
`mysql_get_client_info()': mysql-get-client-info. and *Note
`mysql_get_client_version()': mysql-get-client-version.  functions.


File: manual.info,  Node: c-api-data-structures,  Next: c-api-function-overview,  Prev: c-api-building-running-clients,  Up: c-api

21.8.5 C API Data Structures
----------------------------

This section describes C API data structures other than those used for
prepared statements. For information about the latter, see *Note
c-api-prepared-statement-data-structures::.

   * `MYSQL'

     This structure represents a handle to one database connection.  It
     is used for almost all MySQL functions. Do not try to make a copy
     of a `MYSQL' structure. There is no guarantee that such a copy
     will be usable.

   * `MYSQL_RES'

     This structure represents the result of a query that returns rows
     (*Note `SELECT': select, *Note `SHOW': show, *Note `DESCRIBE':
     describe, *Note `EXPLAIN': explain.). The information returned
     from a query is called the _result set_ in the remainder of this
     section.

   * `MYSQL_ROW'

     This is a type-safe representation of one row of data. It is
     currently implemented as an array of counted byte strings.  (You
     cannot treat these as null-terminated strings if field values may
     contain binary data, because such values may contain null bytes
     internally.) Rows are obtained by calling *Note
     `mysql_fetch_row()': mysql-fetch-row.

   * `MYSQL_FIELD'

     This structure contains metadata: information about a field, such
     as the field's name, type, and size. Its members are described in
     more detail later in this section. You may obtain the
     `MYSQL_FIELD' structures for each field by calling *Note
     `mysql_fetch_field()': mysql-fetch-field.  repeatedly. Field
     values are not part of this structure; they are contained in a
     `MYSQL_ROW' structure.

   * `MYSQL_FIELD_OFFSET'

     This is a type-safe representation of an offset into a MySQL field
     list. (Used by *Note `mysql_field_seek()': mysql-field-seek.)
     Offsets are field numbers within a row, beginning at zero.

   * `my_ulonglong'

     The type used for the number of rows and for *Note
     `mysql_affected_rows()': mysql-affected-rows, *Note
     `mysql_num_rows()': mysql-num-rows, and *Note `mysql_insert_id()':
     mysql-insert-id. This type provides a range of `0' to `1.84e19'.

     On some systems, attempting to print a value of type
     `my_ulonglong' does not work. To print such a value, convert it to
     `unsigned long' and use a `%lu' print format. Example:


          printf ("Number of rows: %lu\n",
                  (unsigned long) mysql_num_rows(result));

   * `my_bool'

     A boolean type, for values that are true (nonzero) or false (zero).

The `MYSQL_FIELD' structure contains the members described in the
following list:

   * `char * name'

     The name of the field, as a null-terminated string. If the field
     was given an alias with an `AS' clause, the value of `name' is the
     alias.

   * `char * org_name'

     The name of the field, as a null-terminated string. Aliases are
     ignored. For expressions, the value is an empty string.

   * `char * table'

     The name of the table containing this field, if it is not a
     calculated field. For calculated fields, the `table' value is an
     empty string. If the column is selected from a view, `table' names
     the view. If the table or view was given an alias with an `AS'
     clause, the value of `table' is the alias. For a *Note `UNION':
     union, the value is the empty string.

   * `char * org_table'

     The name of the table, as a null-terminated string. Aliases are
     ignored. If the column is selected from a view, `org_table' names
     the view. For a *Note `UNION': union, the value is the empty
     string.

   * `char * db'

     The name of the database that the field comes from, as a
     null-terminated string. If the field is a calculated field, `db'
     is an empty string. For a *Note `UNION': union, the value is the
     empty string.

   * `char * catalog'

     The catalog name. This value is always `"def"'.

   * `char * def'

     The default value of this field, as a null-terminated string.
     This is set only if you use *Note `mysql_list_fields()':
     mysql-list-fields.

   * `unsigned long length'

     The width of the field. This corresponds to the display length, in
     bytes.

     The server determines the `length' value before it generates the
     result set, so this is the minimum length required for a data type
     capable of holding the largest possible value from the result
     column, without knowing in advance the actual values that will be
     produced by the query for the result set.

   * `unsigned long max_length'

     The maximum width of the field for the result set (the length in
     bytes of the longest field value for the rows actually in the
     result set). If you use *Note `mysql_store_result()':
     mysql-store-result. or *Note `mysql_list_fields()':
     mysql-list-fields, this contains the maximum length for the field.
     If you use *Note `mysql_use_result()': mysql-use-result, the value
     of this variable is zero.

     The value of `max_length' is the length of the string
     representation of the values in the result set. For example, if
     you retrieve a *Note `FLOAT': floating-point-types. column and the
     `widest' value is `-12.345', `max_length' is 7 (the length of
     `'-12.345'').

     If you are using prepared statements, `max_length' is not set by
     default because for the binary protocol the lengths of the values
     depend on the types of the values in the result set. (See *Note
     c-api-prepared-statement-data-structures::.)  If you want the
     `max_length' values anyway, enable the
     `STMT_ATTR_UPDATE_MAX_LENGTH' option with *Note
     `mysql_stmt_attr_set()': mysql-stmt-attr-set. and the lengths will
     be set when you call *Note `mysql_stmt_store_result()':
     mysql-stmt-store-result.  (See *Note mysql-stmt-attr-set::, and
     *Note mysql-stmt-store-result::.)

   * `unsigned int name_length'

     The length of `name'.

   * `unsigned int org_name_length'

     The length of `org_name'.

   * `unsigned int table_length'

     The length of `table'.

   * `unsigned int org_table_length'

     The length of `org_table'.

   * `unsigned int db_length'

     The length of `db'.

   * `unsigned int catalog_length'

     The length of `catalog'.

   * `unsigned int def_length'

     The length of `def'.

   * `unsigned int flags'

     Bit-flags that describe the field. The `flags' value may have zero
     or more of the bits set that are shown in the following table.

     This table lists bit-flag values and provides a description of
     each flag.

     Flag Value                  Flag Description
     `NOT_NULL_FLAG'             Field cannot be `NULL'
     `PRI_KEY_FLAG'              Field is part of a primary key
     `UNIQUE_KEY_FLAG'           Field is part of a unique key
     `MULTIPLE_KEY_FLAG'         Field is part of a nonunique key
     `UNSIGNED_FLAG'             Field has the `UNSIGNED' attribute
     `ZEROFILL_FLAG'             Field has the `ZEROFILL' attribute
     `BINARY_FLAG'               Field has the `BINARY' attribute
     `AUTO_INCREMENT_FLAG'       Field has the `AUTO_INCREMENT' attribute
     `ENUM_FLAG'                 Field is an *Note `ENUM': enum.
     `SET_FLAG'                  Field is a *Note `SET': set.
     `BLOB_FLAG'                 Field is a *Note `BLOB': blob. or *Note
                                 `TEXT': blob. (deprecated)
     `TIMESTAMP_FLAG'            Field is a *Note `TIMESTAMP': datetime.
                                 (deprecated)
     `NUM_FLAG'                  Field is numeric; see additional notes
                                 following table
     `NO_DEFAULT_VALUE_FLAG'     Field has no default value; see
                                 additional notes following table

     Some of these flags indicate data type information and are
     superseded by or used in conjunction with the `MYSQL_TYPE_XXX'
     value in the `field->type' member described later:

        * To check for *Note `BLOB': blob. or *Note `TIMESTAMP':
          datetime. values, check whether `type' is `MYSQL_TYPE_BLOB' or
          `MYSQL_TYPE_TIMESTAMP'. (The `BLOB_FLAG' and `TIMESTAMP_FLAG'
          flags are unneeded.)

        * *Note `ENUM': enum. and *Note `SET': set. values are returned
          as strings. For these, check that the `type' value is
          `MYSQL_TYPE_STRING' and that the `ENUM_FLAG' or `SET_FLAG'
          flag is set in the `flags' value.

     `NUM_FLAG' indicates that a column is numeric. This includes
     columns with a type of `MYSQL_TYPE_DECIMAL', `MYSQL_TYPE_TINY',
     `MYSQL_TYPE_SHORT', `MYSQL_TYPE_LONG', `MYSQL_TYPE_FLOAT',
     `MYSQL_TYPE_DOUBLE', `MYSQL_TYPE_NULL', `MYSQL_TYPE_LONGLONG',
     `MYSQL_TYPE_INT24', and `MYSQL_TYPE_YEAR'.

     `NO_DEFAULT_VALUE_FLAG' indicates that a column has no `DEFAULT'
     clause in its definition. This does not apply to `NULL' columns
     (because such columns have a default of `NULL'), or to
     `AUTO_INCREMENT' columns (which have an implied default value).

     The following example illustrates a typical use of the `flags'
     value:


          if (field->flags & NOT_NULL_FLAG)
              printf("Field cannot be null\n");

     You may use the convenience macros shown in the following table to
     determine the boolean status of the `flags' value.

     This table lists flag status values and provides a description of
     each.

     Flag Status                 Description
     `IS_NOT_NULL(flags)'        True if this field is defined as `NOT
                                 NULL'
     `IS_PRI_KEY(flags)'         True if this field is a primary key
     `IS_BLOB(flags)'            True if this field is a *Note `BLOB':
                                 blob. or *Note `TEXT': blob.
                                 (deprecated; test `field->type' instead)

   * `unsigned int decimals'

     The number of decimals for numeric fields.

   * `unsigned int charsetnr'

     An ID number that indicates the character set/collation pair for
     the field.

     Normally, character values in result sets are converted to the
     character set indicated by the `character_set_results' system
     variable. In this case, `charsetnr' corresponds to the character
     set indicated by that variable.  Character set conversion can be
     suppressed by setting `character_set_results' to `NULL'. In this
     case, `charsetnr' corresponds to the character set of the original
     table column or expression. See also *Note charset-connection::.

     To distinguish between binary and nonbinary data for string data
     types, check whether the `charsetnr' value is 63. If so, the
     character set is `binary', which indicates binary rather than
     nonbinary data. This enables you to distinguish *Note `BINARY':
     binary-varbinary. from *Note `CHAR': char, *Note `VARBINARY':
     binary-varbinary. from *Note `VARCHAR': char, and the *Note
     `BLOB': blob. types from the *Note `TEXT': blob. types.

     `charsetnr' values are the same as those displayed in the `Id'
     column of the *Note `SHOW COLLATION': show-collation. statement or
     the `ID' column of the `INFORMATION_SCHEMA' *Note `COLLATIONS':
     collations-table. table. You can use those information sources to
     see which character set and collation specific `charsetnr' values
     indicate:


          mysql> SHOW COLLATION WHERE Id = 63;
          +-----------+---------+----+---------+----------+---------+
          | Collation | Charset | Id | Default | Compiled | Sortlen |
          +-----------+---------+----+---------+----------+---------+
          | binary    | binary  | 63 | Yes     | Yes      |       1 |
          +-----------+---------+----+---------+----------+---------+

          mysql> SELECT COLLATION_NAME, CHARACTER_SET_NAME
              -> FROM INFORMATION_SCHEMA.COLLATIONS WHERE ID = 33;
          +-----------------+--------------------+
          | COLLATION_NAME  | CHARACTER_SET_NAME |
          +-----------------+--------------------+
          | utf8_general_ci | utf8               |
          +-----------------+--------------------+

   * `enum enum_field_types type'

     The type of the field. The `type' value may be one of the
     `MYSQL_TYPE_' symbols shown in the following table.

     This table lists `MYSQL_TYPE_' values and provides a description
     of each type.

     Type Value              Type Description
     `MYSQL_TYPE_TINY'       *Note `TINYINT': integer-types. field
     `MYSQL_TYPE_SHORT'      *Note `SMALLINT': integer-types. field
     `MYSQL_TYPE_LONG'       *Note `INTEGER': integer-types. field
     `MYSQL_TYPE_INT24'      *Note `MEDIUMINT': integer-types. field
     `MYSQL_TYPE_LONGLONG'   *Note `BIGINT': integer-types. field
     `MYSQL_TYPE_DECIMAL'    *Note `DECIMAL': fixed-point-types. or
                             *Note `NUMERIC': fixed-point-types. field
     `MYSQL_TYPE_NEWDECIMAL' Precision math *Note `DECIMAL':
                             fixed-point-types. or *Note `NUMERIC':
                             fixed-point-types.
     `MYSQL_TYPE_FLOAT'      *Note `FLOAT': floating-point-types. field
     `MYSQL_TYPE_DOUBLE'     *Note `DOUBLE': floating-point-types. or
                             *Note `REAL': floating-point-types. field
     `MYSQL_TYPE_BIT'        *Note `BIT': bit-type. field
     `MYSQL_TYPE_TIMESTAMP'  *Note `TIMESTAMP': datetime. field
     `MYSQL_TYPE_DATE'       *Note `DATE': datetime. field
     `MYSQL_TYPE_TIME'       *Note `TIME': time. field
     `MYSQL_TYPE_DATETIME'   *Note `DATETIME': datetime. field
     `MYSQL_TYPE_YEAR'       *Note `YEAR': year. field
     `MYSQL_TYPE_STRING'     *Note `CHAR': char. or *Note `BINARY':
                             binary-varbinary. field
     `MYSQL_TYPE_VAR_STRING' *Note `VARCHAR': char. or *Note
                             `VARBINARY': binary-varbinary. field
     `MYSQL_TYPE_BLOB'       *Note `BLOB': blob. or *Note `TEXT': blob.
                             field (use `max_length' to determine the
                             maximum length)
     `MYSQL_TYPE_SET'        *Note `SET': set. field
     `MYSQL_TYPE_ENUM'       *Note `ENUM': enum. field
     `MYSQL_TYPE_GEOMETRY'   Spatial field
     `MYSQL_TYPE_NULL'       `NULL'-type field

     You can use the `IS_NUM()' macro to test whether a field has a
     numeric type. Pass the `type' value to `IS_NUM()' and it evaluates
     to TRUE if the field is numeric:


          if (IS_NUM(field->type))
              printf("Field is numeric\n");

     *Note `ENUM': enum. and *Note `SET': set. values are returned as
     strings. For these, check that the `type' value is
     `MYSQL_TYPE_STRING' and that the `ENUM_FLAG' or `SET_FLAG' flag is
     set in the `flags' value.


File: manual.info,  Node: c-api-function-overview,  Next: c-api-functions,  Prev: c-api-data-structures,  Up: c-api

21.8.6 C API Function Overview
------------------------------

The functions available in the C API are summarized here and described
in greater detail in a later section. See *Note c-api-functions::.

*C API Function Names and Descriptions*

Function                Description
*Note `my_init()':      Initialize global variables, and thread handler
my-init.                in thread-safe programs
*Note                   Returns the number of rows
`mysql_affected_rows()':changed/deleted/inserted by the last *Note
mysql-affected-rows.    `UPDATE': update, *Note `DELETE': delete, or
                        *Note `INSERT': insert. query
*Note                   Toggles autocommit mode on/off
`mysql_autocommit()':   
mysql-autocommit.       
*Note                   Changes user and database on an open connection
`mysql_change_user()':  
mysql-change-user.      
*Note                   Return default character set name for current
`mysql_character_set_name()':connection
mysql-character-set-name.
*Note `mysql_close()':  Closes a server connection
mysql-close.            
*Note                   Commits the transaction
`mysql_commit()':       
mysql-commit.           
*Note                   Connects to a MySQL server (this function is
`mysql_connect()':      deprecated; use *Note `mysql_real_connect()':
mysql-connect.          mysql-real-connect.  instead)
*Note                   Creates a database (this function is deprecated;
`mysql_create_db()':    use the SQL statement *Note `CREATE DATABASE':
mysql-create-db.        create-database. instead)
*Note                   Seeks to an arbitrary row number in a query
`mysql_data_seek()':    result set
mysql-data-seek.        
*Note `mysql_debug()':  Does a `DBUG_PUSH' with the given string
mysql-debug.            
*Note                   Drops a database (this function is deprecated;
`mysql_drop_db()':      use the SQL statement *Note `DROP DATABASE':
mysql-drop-db.          drop-database. instead)
*Note                   Makes the server write debug information to the
`mysql_dump_debug_info()':log
mysql-dump-debug-info.  
*Note `mysql_eof()':    Determines whether the last row of a result set
mysql-eof.              has been read (this function is deprecated;
                        *Note `mysql_errno()': mysql-errno. or *Note
                        `mysql_error()': mysql-error. may be used
                        instead)
*Note `mysql_errno()':  Returns the error number for the most recently
mysql-errno.            invoked MySQL function
*Note `mysql_error()':  Returns the error message for the most recently
mysql-error.            invoked MySQL function
*Note                   Escapes special characters in a string for use
`mysql_escape_string()':in an SQL statement
mysql-escape-string.    
*Note                   Returns the type of the next table field
`mysql_fetch_field()':  
mysql-fetch-field.      
*Note                   Returns the type of a table field, given a field
`mysql_fetch_field_direct()':number
mysql-fetch-field-direct.
*Note                   Returns an array of all field structures
`mysql_fetch_fields()': 
mysql-fetch-fields.     
*Note                   Returns the lengths of all columns in the
`mysql_fetch_lengths()':current row
mysql-fetch-lengths.    
*Note                   Fetches the next row from the result set
`mysql_fetch_row()':    
mysql-fetch-row.        
*Note                   Returns the number of result columns for the
`mysql_field_count()':  most recent statement
mysql-field-count.      
*Note                   Puts the column cursor on a specified column
`mysql_field_seek()':   
mysql-field-seek.       
*Note                   Returns the position of the field cursor used
`mysql_field_tell()':   for the last *Note `mysql_fetch_field()':
mysql-field-tell.       mysql-fetch-field.
*Note                   Frees memory used by a result set
`mysql_free_result()':  
mysql-free-result.      
*Note                   Return information about default character set
`mysql_get_character_set_info()':
mysql-get-character-set-info.
*Note                   Returns client version information as a string
`mysql_get_client_info()':
mysql-get-client-info.  
*Note                   Returns client version information as an integer
`mysql_get_client_version()':
mysql-get-client-version.
*Note                   Returns a string describing the connection
`mysql_get_host_info()':
mysql-get-host-info.    
*Note                   Returns the protocol version used by the
`mysql_get_proto_info()':connection
mysql-get-proto-info.   
*Note                   Returns the server version number
`mysql_get_server_info()':
mysql-get-server-info.  
*Note                   Returns version number of server as an integer
`mysql_get_server_version()':
mysql-get-server-version.
*Note                   Return current SSL cipher
`mysql_get_ssl_cipher()':
mysql-get-ssl-cipher.   
*Note                   Encode string in hexadecimal format
`mysql_hex_string()':   
mysql-hex-string.       
*Note `mysql_info()':   Returns information about the most recently
mysql-info.             executed query
*Note `mysql_init()':   Gets or initializes a `MYSQL' structure
mysql-init.             
*Note                   Returns the ID generated for an `AUTO_INCREMENT'
`mysql_insert_id()':    column by the previous query
mysql-insert-id.        
*Note `mysql_kill()':   Kills a given thread
mysql-kill.             
*Note                   Finalize the MySQL C API library
`mysql_library_end()':  
mysql-library-end.      
*Note                   Initialize the MySQL C API library
`mysql_library_init()': 
mysql-library-init.     
*Note                   Returns database names matching a simple regular
`mysql_list_dbs()':     expression
mysql-list-dbs.         
*Note                   Returns field names matching a simple regular
`mysql_list_fields()':  expression
mysql-list-fields.      
*Note                   Returns a list of the current server threads
`mysql_list_processes()':
mysql-list-processes.   
*Note                   Returns table names matching a simple regular
`mysql_list_tables()':  expression
mysql-list-tables.      
*Note                   Checks whether any more results exist
`mysql_more_results()': 
mysql-more-results.     
*Note                   Returns/initiates the next result in
`mysql_next_result()':  multiple-result executions
mysql-next-result.      
*Note                   Returns the number of columns in a result set
`mysql_num_fields()':   
mysql-num-fields.       
*Note                   Returns the number of rows in a result set
`mysql_num_rows()':     
mysql-num-rows.         
*Note                   Sets connect options for *Note
`mysql_options()':      `mysql_real_connect()': mysql-real-connect.
mysql-options.          
*Note `mysql_ping()':   Checks whether the connection to the server is
mysql-ping.             working, reconnecting as necessary
*Note `mysql_query()':  Executes an SQL query specified as a
mysql-query.            null-terminated string
*Note                   Connects to a MySQL server
`mysql_real_connect()': 
mysql-real-connect.     
*Note                   Escapes special characters in a string for use
`mysql_real_escape_string()':in an SQL statement, taking into account the
mysql-real-escape-string.current character set of the connection
*Note                   Executes an SQL query specified as a counted
`mysql_real_query()':   string
mysql-real-query.       
*Note                   Flush or reset tables and caches
`mysql_refresh()':      
mysql-refresh.          
*Note                   Tells the server to reload the grant tables
`mysql_reload()':       
mysql-reload.           
*Note                   Rolls back the transaction
`mysql_rollback()':     
mysql-rollback.         
*Note                   Seeks to a row offset in a result set, using
`mysql_row_seek()':     value returned from *Note `mysql_row_tell()':
mysql-row-seek.         mysql-row-tell.
*Note                   Returns the row cursor position
`mysql_row_tell()':     
mysql-row-tell.         
*Note                   Selects a database
`mysql_select_db()':    
mysql-select-db.        
*Note                   Finalize the MySQL C API library
`mysql_server_end()':   
mysql-server-end.       
*Note                   Initialize the MySQL C API library
`mysql_server_init()':  
mysql-server-init.      
*Note                   Set default character set for current connection
`mysql_set_character_set()':
mysql-set-character-set.
*Note                   Set the *Note `LOAD DATA LOCAL INFILE':
`mysql_set_local_infile_default()':load-data. handler callbacks to their default
mysql-set-local-infile-default.values
*Note                   Install application-specific *Note `LOAD DATA
`mysql_set_local_infile_handler()':LOCAL INFILE': load-data. handler callbacks
mysql-set-local-infile-handler.
*Note                   Sets an option for the connection (like
`mysql_set_server_option()':`multi-statements')
mysql-set-server-option.
*Note                   Returns the SQLSTATE error code for the last
`mysql_sqlstate()':     error
mysql-sqlstate.         
*Note                   Shuts down the database server
`mysql_shutdown()':     
mysql-shutdown.         
*Note                   Prepare to establish SSL connection to server
`mysql_ssl_set()':      
mysql-ssl-set.          
*Note `mysql_stat()':   Returns the server status as a string
mysql-stat.             
*Note                   Retrieves a complete result set to the client
`mysql_store_result()': 
mysql-store-result.     
*Note                   Finalize thread handler
`mysql_thread_end()':   
mysql-thread-end.       
*Note                   Returns the current thread ID
`mysql_thread_id()':    
mysql-thread-id.        
*Note                   Initialize thread handler
`mysql_thread_init()':  
mysql-thread-init.      
*Note                   Returns 1 if the clients are compiled as
`mysql_thread_safe()':  thread-safe
mysql-thread-safe.      
*Note                   Initiates a row-by-row result set retrieval
`mysql_use_result()':   
mysql-use-result.       
*Note                   Returns the warning count for the previous SQL
`mysql_warning_count()':statement
mysql-warning-count.    

Application programs should use this general outline for interacting
with MySQL:

  1. Initialize the MySQL library by calling *Note
     `mysql_library_init()': mysql-library-init. This function exists
     in both the `libmysqlclient' C client library and the `libmysqld'
     embedded server library, so it is used whether you build a regular
     client program by linking with the `-libmysqlclient' flag, or an
     embedded server application by linking with the `-libmysqld' flag.

  2. Initialize a connection handler by calling *Note `mysql_init()':
     mysql-init. and connect to the server by calling *Note
     `mysql_real_connect()': mysql-real-connect.

  3. Issue SQL statements and process their results. (The following
     discussion provides more information about how to do this.)

  4. Close the connection to the MySQL server by calling *Note
     `mysql_close()': mysql-close.

  5. End use of the MySQL library by calling *Note
     `mysql_library_end()': mysql-library-end.

The purpose of calling *Note `mysql_library_init()':
mysql-library-init. and *Note `mysql_library_end()': mysql-library-end.
is to provide proper initialization and finalization of the MySQL
library. For applications that are linked with the client library, they
provide improved memory management. If you do not call *Note
`mysql_library_end()': mysql-library-end, a block of memory remains
allocated. (This does not increase the amount of memory used by the
application, but some memory leak detectors will complain about it.)
For applications that are linked with the embedded server, these calls
start and stop the server.

In a nonmulti-threaded environment, the call to *Note
`mysql_library_init()': mysql-library-init. may be omitted, because
*Note `mysql_init()': mysql-init. will invoke it automatically as
necessary. However, *Note `mysql_library_init()': mysql-library-init.
is not thread-safe in a multi-threaded environment, and thus neither is
*Note `mysql_init()': mysql-init, which calls *Note
`mysql_library_init()': mysql-library-init. You must either call *Note
`mysql_library_init()': mysql-library-init.  prior to spawning any
threads, or else use a mutex to protect the call, whether you invoke
*Note `mysql_library_init()': mysql-library-init. or indirectly through
*Note `mysql_init()': mysql-init. This should be done prior to any
other client library call.

To connect to the server, call *Note `mysql_init()': mysql-init. to
initialize a connection handler, then call *Note
`mysql_real_connect()': mysql-real-connect. with that handler (along
with other information such as the host name, user name, and password).
Upon connection, *Note `mysql_real_connect()': mysql-real-connect. sets
the `reconnect' flag (part of the `MYSQL' structure) to a value of `1'
in versions of the API older than 5.0.3, or `0' in newer versions. A
value of `1' for this flag indicates that if a statement cannot be
performed because of a lost connection, to try reconnecting to the
server before giving up. You can use the `MYSQL_OPT_RECONNECT' option to
*Note `mysql_options()': mysql-options. to control reconnection
behavior. When you are done with the connection, call *Note
`mysql_close()': mysql-close. to terminate it.

While a connection is active, the client may send SQL statements to the
server using *Note `mysql_query()': mysql-query.  or *Note
`mysql_real_query()': mysql-real-query. The difference between the two
is that *Note `mysql_query()': mysql-query. expects the query to be
specified as a null-terminated string whereas *Note
`mysql_real_query()': mysql-real-query. expects a counted string. If
the string contains binary data (which may include null bytes), you
must use *Note `mysql_real_query()': mysql-real-query.

For each non-*Note `SELECT': select. query (for example, *Note
`INSERT': insert, *Note `UPDATE': update, *Note `DELETE': delete.), you
can find out how many rows were changed (affected) by calling *Note
`mysql_affected_rows()': mysql-affected-rows.

For *Note `SELECT': select. queries, you retrieve the selected rows as
a result set. (Note that some statements are *Note `SELECT':
select.-like in that they return rows. These include *Note `SHOW': show,
*Note `DESCRIBE': describe, and *Note `EXPLAIN': explain. Treat these
statements the same way as *Note `SELECT': select. statements.)

There are two ways for a client to process result sets. One way is to
retrieve the entire result set all at once by calling *Note
`mysql_store_result()': mysql-store-result. This function acquires from
the server all the rows returned by the query and stores them in the
client. The second way is for the client to initiate a row-by-row
result set retrieval by calling *Note `mysql_use_result()':
mysql-use-result. This function initializes the retrieval, but does not
actually get any rows from the server.

In both cases, you access rows by calling *Note `mysql_fetch_row()':
mysql-fetch-row. With *Note `mysql_store_result()': mysql-store-result,
*Note `mysql_fetch_row()': mysql-fetch-row. accesses rows that have
previously been fetched from the server. With *Note
`mysql_use_result()': mysql-use-result, *Note `mysql_fetch_row()':
mysql-fetch-row. actually retrieves the row from the server.
Information about the size of the data in each row is available by
calling *Note `mysql_fetch_lengths()': mysql-fetch-lengths.

After you are done with a result set, call *Note `mysql_free_result()':
mysql-free-result. to free the memory used for it.

The two retrieval mechanisms are complementary. Choose the approach
that is most appropriate for each client application. In practice,
clients tend to use *Note `mysql_store_result()': mysql-store-result.
more commonly.

An advantage of *Note `mysql_store_result()': mysql-store-result. is
that because the rows have all been fetched to the client, you not only
can access rows sequentially, you can move back and forth in the result
set using *Note `mysql_data_seek()': mysql-data-seek.  or *Note
`mysql_row_seek()': mysql-row-seek. to change the current row position
within the result set. You can also find out how many rows there are by
calling *Note `mysql_num_rows()': mysql-num-rows. On the other hand,
the memory requirements for *Note `mysql_store_result()':
mysql-store-result. may be very high for large result sets and you are
more likely to encounter out-of-memory conditions.

An advantage of *Note `mysql_use_result()': mysql-use-result.  is that
the client requires less memory for the result set because it maintains
only one row at a time (and because there is less allocation overhead,
*Note `mysql_use_result()': mysql-use-result. can be faster).
Disadvantages are that you must process each row quickly to avoid tying
up the server, you do not have random access to rows within the result
set (you can only access rows sequentially), and the number of rows in
the result set is unknown until you have retrieved them all.
Furthermore, you _must_ retrieve all the rows even if you determine in
mid-retrieval that you've found the information you were looking for.

The API makes it possible for clients to respond appropriately to
statements (retrieving rows only as necessary) without knowing whether
the statement is a *Note `SELECT': select.  You can do this by calling
*Note `mysql_store_result()': mysql-store-result. after each *Note
`mysql_query()': mysql-query. (or *Note `mysql_real_query()':
mysql-real-query.). If the result set call succeeds, the statement was a
*Note `SELECT': select. and you can read the rows.  If the result set
call fails, call *Note `mysql_field_count()': mysql-field-count. to
determine whether a result was actually to be expected. If *Note
`mysql_field_count()': mysql-field-count. returns zero, the statement
returned no data (indicating that it was an *Note `INSERT': insert,
*Note `UPDATE': update, *Note `DELETE': delete, and so forth), and was
not expected to return rows. If *Note `mysql_field_count()':
mysql-field-count. is nonzero, the statement should have returned rows,
but did not. This indicates that the statement was a *Note `SELECT':
select. that failed. See the description for *Note
`mysql_field_count()': mysql-field-count. for an example of how this
can be done.

Both *Note `mysql_store_result()': mysql-store-result. and *Note
`mysql_use_result()': mysql-use-result. enable you to obtain
information about the fields that make up the result set (the number of
fields, their names and types, and so forth). You can access field
information sequentially within the row by calling *Note
`mysql_fetch_field()': mysql-fetch-field.  repeatedly, or by field
number within the row by calling *Note `mysql_fetch_field_direct()':
mysql-fetch-field-direct. The current field cursor position may be
changed by calling *Note `mysql_field_seek()': mysql-field-seek.
Setting the field cursor affects subsequent calls to *Note
`mysql_fetch_field()': mysql-fetch-field. You can also get information
for fields all at once by calling *Note `mysql_fetch_fields()':
mysql-fetch-fields.

For detecting and reporting errors, MySQL provides access to error
information by means of the *Note `mysql_errno()': mysql-errno. and
*Note `mysql_error()': mysql-error. functions. These return the error
code or error message for the most recently invoked function that can
succeed or fail, enabling you to determine when an error occurred and
what it was.


File: manual.info,  Node: c-api-functions,  Next: c-api-prepared-statements,  Prev: c-api-function-overview,  Up: c-api

21.8.7 C API Function Descriptions
----------------------------------

* Menu:

* mysql-affected-rows::          mysql_affected_rows()
* mysql-autocommit::             mysql_autocommit()
* mysql-change-user::            mysql_change_user()
* mysql-character-set-name::     mysql_character_set_name()
* mysql-close::                  mysql_close()
* mysql-commit::                 mysql_commit()
* mysql-connect::                mysql_connect()
* mysql-create-db::              mysql_create_db()
* mysql-data-seek::              mysql_data_seek()
* mysql-debug::                  mysql_debug()
* mysql-drop-db::                mysql_drop_db()
* mysql-dump-debug-info::        mysql_dump_debug_info()
* mysql-eof::                    mysql_eof()
* mysql-errno::                  mysql_errno()
* mysql-error::                  mysql_error()
* mysql-escape-string::          mysql_escape_string()
* mysql-fetch-field::            mysql_fetch_field()
* mysql-fetch-field-direct::     mysql_fetch_field_direct()
* mysql-fetch-fields::           mysql_fetch_fields()
* mysql-fetch-lengths::          mysql_fetch_lengths()
* mysql-fetch-row::              mysql_fetch_row()
* mysql-field-count::            mysql_field_count()
* mysql-field-seek::             mysql_field_seek()
* mysql-field-tell::             mysql_field_tell()
* mysql-free-result::            mysql_free_result()
* mysql-get-character-set-info::  mysql_get_character_set_info()
* mysql-get-client-info::        mysql_get_client_info()
* mysql-get-client-version::     mysql_get_client_version()
* mysql-get-host-info::          mysql_get_host_info()
* mysql-get-proto-info::         mysql_get_proto_info()
* mysql-get-server-info::        mysql_get_server_info()
* mysql-get-server-version::     mysql_get_server_version()
* mysql-get-ssl-cipher::         mysql_get_ssl_cipher()
* mysql-hex-string::             mysql_hex_string()
* mysql-info::                   mysql_info()
* mysql-init::                   mysql_init()
* mysql-insert-id::              mysql_insert_id()
* mysql-kill::                   mysql_kill()
* mysql-library-end::            mysql_library_end()
* mysql-library-init::           mysql_library_init()
* mysql-list-dbs::               mysql_list_dbs()
* mysql-list-fields::            mysql_list_fields()
* mysql-list-processes::         mysql_list_processes()
* mysql-list-tables::            mysql_list_tables()
* mysql-more-results::           mysql_more_results()
* mysql-next-result::            mysql_next_result()
* mysql-num-fields::             mysql_num_fields()
* mysql-num-rows::               mysql_num_rows()
* mysql-options::                mysql_options()
* mysql-ping::                   mysql_ping()
* mysql-query::                  mysql_query()
* mysql-real-connect::           mysql_real_connect()
* mysql-real-escape-string::     mysql_real_escape_string()
* mysql-real-query::             mysql_real_query()
* mysql-refresh::                mysql_refresh()
* mysql-reload::                 mysql_reload()
* mysql-rollback::               mysql_rollback()
* mysql-row-seek::               mysql_row_seek()
* mysql-row-tell::               mysql_row_tell()
* mysql-select-db::              mysql_select_db()
* mysql-set-character-set::      mysql_set_character_set()
* mysql-set-local-infile-default::  mysql_set_local_infile_default()
* mysql-set-local-infile-handler::  mysql_set_local_infile_handler()
* mysql-set-server-option::      mysql_set_server_option()
* mysql-shutdown::               mysql_shutdown()
* mysql-sqlstate::               mysql_sqlstate()
* mysql-ssl-set::                mysql_ssl_set()
* mysql-stat::                   mysql_stat()
* mysql-store-result::           mysql_store_result()
* mysql-thread-id::              mysql_thread_id()
* mysql-use-result::             mysql_use_result()
* mysql-warning-count::          mysql_warning_count()

In the descriptions here, a parameter or return value of `NULL' means
`NULL' in the sense of the C programming language, not a MySQL `NULL'
value.

Functions that return a value generally return a pointer or an integer.
Unless specified otherwise, functions returning a pointer return a
non-`NULL' value to indicate success or a `NULL' value to indicate an
error, and functions returning an integer return zero to indicate
success or nonzero to indicate an error. Note that `nonzero' means just
that. Unless the function description says otherwise, do not test
against a value other than zero:


     if (result)                   /* correct */
         ... error ...

     if (result < 0)               /* incorrect */
         ... error ...

     if (result == -1)             /* incorrect */
         ... error ...

When a function returns an error, the *Errors* subsection of the
function description lists the possible types of errors. You can find
out which of these occurred by calling *Note `mysql_errno()':
mysql-errno. A string representation of the error may be obtained by
calling *Note `mysql_error()': mysql-error.


File: manual.info,  Node: mysql-affected-rows,  Next: mysql-autocommit,  Prev: c-api-functions,  Up: c-api-functions

21.8.7.1 mysql_affected_rows()
..............................

`my_ulonglong mysql_affected_rows(MYSQL *mysql)'

*Description*

*Note `mysql_affected_rows()': mysql-affected-rows. may be called
immediately after executing a statement with *Note `mysql_query()':
mysql-query. or *Note `mysql_real_query()': mysql-real-query. It returns
the number of rows changed, deleted, or inserted by the last statement
if it was an *Note `UPDATE': update, *Note `DELETE': delete, or *Note
`INSERT': insert. For *Note `SELECT': select. statements, *Note
`mysql_affected_rows()': mysql-affected-rows. works like *Note
`mysql_num_rows()': mysql-num-rows.

For *Note `UPDATE': update. statements, the affected-rows value by
default is the number of rows actually changed. If you specify the
`CLIENT_FOUND_ROWS' flag to *Note `mysql_real_connect()':
mysql-real-connect.  when connecting to *Note `mysqld': mysqld, the
affected-rows value is the number of rows `found'; that is, matched by
the `WHERE' clause.

For *Note `REPLACE': replace. statements, the affected-rows value is 2
if the new row replaced an old row, because in this case, one row was
inserted after the duplicate was deleted.

For *Note `INSERT ... ON DUPLICATE KEY UPDATE': insert-on-duplicate.
statements, the affected-rows value is 1 if the row is inserted as a
new row and 2 if an existing row is updated.

Following a *Note `CALL': call. statement for a stored procedure, *Note
`mysql_affected_rows()': mysql-affected-rows. returns the value that it
would return for the last statement executed within the procedure, or
`0' if that statement would return `-1'. Within the procedure, you can
use `ROW_COUNT()' at the SQL level to obtain the affected-rows value
for individual statements.

*Return Values*

An integer greater than zero indicates the number of rows affected or
retrieved. Zero indicates that no records were updated for an *Note
`UPDATE': update. statement, no rows matched the `WHERE' clause in the
query or that no query has yet been executed. -1 indicates that the
query returned an error or that, for a *Note `SELECT': select. query,
*Note `mysql_affected_rows()': mysql-affected-rows. was called prior to
calling *Note `mysql_store_result()': mysql-store-result.

Because *Note `mysql_affected_rows()': mysql-affected-rows.  returns an
unsigned value, you can check for -1 by comparing the return value to
`(my_ulonglong)-1' (or to `(my_ulonglong)~0', which is equivalent).

*Errors*

None.

*Example*


     char *stmt = "UPDATE products SET cost=cost*1.25
                   WHERE group=10";
     mysql_query(&mysql,stmt);
     printf("%ld products updated",
            (long) mysql_affected_rows(&mysql));


File: manual.info,  Node: mysql-autocommit,  Next: mysql-change-user,  Prev: mysql-affected-rows,  Up: c-api-functions

21.8.7.2 mysql_autocommit()
...........................

`my_bool mysql_autocommit(MYSQL *mysql, my_bool mode)'

*Description*

Sets autocommit mode on if `mode' is 1, off if `mode' is 0.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-change-user,  Next: mysql-character-set-name,  Prev: mysql-autocommit,  Up: c-api-functions

21.8.7.3 mysql_change_user()
............................

`my_bool mysql_change_user(MYSQL *mysql, const char *user, const char
*password, const char *db)'

*Description*

Changes the user and causes the database specified by `db' to become
the default (current) database on the connection specified by `mysql'.
In subsequent queries, this database is the default for table
references that include no explicit database specifier.

*Note `mysql_change_user()': mysql-change-user. fails if the connected
user cannot be authenticated or does not have permission to use the
database. In this case, the user and database are not changed.

Pass a `db' parameter of `NULL' if you do not want to have a default
database.

This function resets the session state as if one had done a new connect
and reauthenticated. (See *Note auto-reconnect::.) It always performs a
*Note `ROLLBACK': commit. of any active transactions, closes and drops
all temporary tables, and unlocks all locked tables. Session system
variables are reset to the values of the corresponding global system
variables. Prepared statements are released and *Note `HANDLER':
handler. variables are closed.  Locks acquired with `GET_LOCK()' are
released. These effects occur even if the user did not change.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

The same that you can get from *Note `mysql_real_connect()':
mysql-real-connect, plus:

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

   * `ER_UNKNOWN_COM_ERROR'

     The MySQL server does not implement this command (probably an old
     server).

   * `ER_ACCESS_DENIED_ERROR'

     The user or password was wrong.

   * `ER_BAD_DB_ERROR'

     The database did not exist.

   * `ER_DBACCESS_DENIED_ERROR'

     The user did not have access rights to the database.

   * `ER_WRONG_DB_NAME'

     The database name was too long.

*Example*


     if (mysql_change_user(&mysql, "user", "password", "new_database"))
     {
        fprintf(stderr, "Failed to change user.  Error: %s\n",
                mysql_error(&mysql));
     }


File: manual.info,  Node: mysql-character-set-name,  Next: mysql-close,  Prev: mysql-change-user,  Up: c-api-functions

21.8.7.4 mysql_character_set_name()
...................................

`const char *mysql_character_set_name(MYSQL *mysql)'

*Description*

Returns the default character set name for the current connection.

*Return Values*

The default character set name

*Errors*

None.


File: manual.info,  Node: mysql-close,  Next: mysql-commit,  Prev: mysql-character-set-name,  Up: c-api-functions

21.8.7.5 mysql_close()
......................

`void mysql_close(MYSQL *mysql)'

*Description*

Closes a previously opened connection.  *Note `mysql_close()':
mysql-close. also deallocates the connection handle pointed to by
`mysql' if the handle was allocated automatically by *Note
`mysql_init()': mysql-init. or *Note `mysql_connect()': mysql-connect.

*Return Values*

None.

*Errors*

None.


File: manual.info,  Node: mysql-commit,  Next: mysql-connect,  Prev: mysql-close,  Up: c-api-functions

21.8.7.6 mysql_commit()
.......................

`my_bool mysql_commit(MYSQL *mysql)'

*Description*

Commits the current transaction.

The action of this function is subject to the value of the
`completion_type' system variable. In particular, if the value of
`completion_type' is 2, the server performs a release after terminating
a transaction and closes the client connection. The client program
should call *Note `mysql_close()': mysql-close. to close the connection
from the client side.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-connect,  Next: mysql-create-db,  Prev: mysql-commit,  Up: c-api-functions

21.8.7.7 mysql_connect()
........................

`MYSQL *mysql_connect(MYSQL *mysql, const char *host, const char *user,
const char *passwd)'

*Description*

This function is deprecated. Use *Note `mysql_real_connect()':
mysql-real-connect. instead.

*Note `mysql_connect()': mysql-connect. attempts to establish a
connection to a MySQL database engine running on `host'.  *Note
`mysql_connect()': mysql-connect. must complete successfully before you
can execute any of the other API functions, with the exception of *Note
`mysql_get_client_info()': mysql-get-client-info.

The meanings of the parameters are the same as for the corresponding
parameters for *Note `mysql_real_connect()': mysql-real-connect. with
the difference that the connection parameter may be `NULL'. In this
case, the C API allocates memory for the connection structure
automatically and frees it when you call *Note `mysql_close()':
mysql-close. The disadvantage of this approach is that you cannot
retrieve an error message if the connection fails. (To get error
information from *Note `mysql_errno()': mysql-errno. or *Note
`mysql_error()': mysql-error, you must provide a valid `MYSQL' pointer.)

*Return Values*

Same as for *Note `mysql_real_connect()': mysql-real-connect.

*Errors*

Same as for *Note `mysql_real_connect()': mysql-real-connect.


File: manual.info,  Node: mysql-create-db,  Next: mysql-data-seek,  Prev: mysql-connect,  Up: c-api-functions

21.8.7.8 mysql_create_db()
..........................

`int mysql_create_db(MYSQL *mysql, const char *db)'

*Description*

Creates the database named by the `db' parameter.

This function is deprecated. It is preferable to use *Note
`mysql_query()': mysql-query. to issue an SQL *Note `CREATE DATABASE':
create-database. statement instead.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*


     if(mysql_create_db(&mysql, "my_database"))
     {
        fprintf(stderr, "Failed to create new database.  Error: %s\n",
                mysql_error(&mysql));
     }


File: manual.info,  Node: mysql-data-seek,  Next: mysql-debug,  Prev: mysql-create-db,  Up: c-api-functions

21.8.7.9 mysql_data_seek()
..........................

`void mysql_data_seek(MYSQL_RES *result, my_ulonglong offset)'

*Description*

Seeks to an arbitrary row in a query result set. The `offset' value is
a row number. Specify a value in the range from `0' to *Note
`mysql_num_rows(result)-1': mysql-num-rows.

This function requires that the result set structure contains the
entire result of the query, so *Note `mysql_data_seek()':
mysql-data-seek. may be used only in conjunction with *Note
`mysql_store_result()': mysql-store-result, not with *Note
`mysql_use_result()': mysql-use-result.

*Return Values*

None.

*Errors*

None.


File: manual.info,  Node: mysql-debug,  Next: mysql-drop-db,  Prev: mysql-data-seek,  Up: c-api-functions

21.8.7.10 mysql_debug()
.......................

`void mysql_debug(const char *debug)'

*Description*

Does a `DBUG_PUSH' with the given string.  *Note `mysql_debug()':
mysql-debug. uses the Fred Fish debug library. To use this function,
you must compile the client library to support debugging. See *Note
dbug-package::.

*Return Values*

None.

*Errors*

None.

*Example*

The call shown here causes the client library to generate a trace file
in `/tmp/client.trace' on the client machine:


     mysql_debug("d:t:O,/tmp/client.trace");


File: manual.info,  Node: mysql-drop-db,  Next: mysql-dump-debug-info,  Prev: mysql-debug,  Up: c-api-functions

21.8.7.11 mysql_drop_db()
.........................

`int mysql_drop_db(MYSQL *mysql, const char *db)'

*Description*

Drops the database named by the `db' parameter.

This function is deprecated. It is preferable to use *Note
`mysql_query()': mysql-query. to issue an SQL *Note `DROP DATABASE':
drop-database. statement instead.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*


     if(mysql_drop_db(&mysql, "my_database"))
       fprintf(stderr, "Failed to drop the database: Error: %s\n",
               mysql_error(&mysql));


File: manual.info,  Node: mysql-dump-debug-info,  Next: mysql-eof,  Prev: mysql-drop-db,  Up: c-api-functions

21.8.7.12 mysql_dump_debug_info()
.................................

`int mysql_dump_debug_info(MYSQL *mysql)'

*Description*

Instructs the server to write debugging information to the error log.
The connected user must have the `SUPER' privilege.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-eof,  Next: mysql-errno,  Prev: mysql-dump-debug-info,  Up: c-api-functions

21.8.7.13 mysql_eof()
.....................

`my_bool mysql_eof(MYSQL_RES *result)'

*Description*

This function is deprecated.  *Note `mysql_errno()': mysql-errno. or
*Note `mysql_error()': mysql-error. may be used instead.

*Note `mysql_eof()': mysql-eof. determines whether the last row of a
result set has been read.

If you acquire a result set from a successful call to *Note
`mysql_store_result()': mysql-store-result, the client receives the
entire set in one operation. In this case, a `NULL' return from *Note
`mysql_fetch_row()': mysql-fetch-row. always means the end of the
result set has been reached and it is unnecessary to call *Note
`mysql_eof()': mysql-eof. When used with *Note `mysql_store_result()':
mysql-store-result, *Note `mysql_eof()': mysql-eof. always returns true.

On the other hand, if you use *Note `mysql_use_result()':
mysql-use-result. to initiate a result set retrieval, the rows of the
set are obtained from the server one by one as you call *Note
`mysql_fetch_row()': mysql-fetch-row. repeatedly.  Because an error may
occur on the connection during this process, a `NULL' return value from
*Note `mysql_fetch_row()': mysql-fetch-row. does not necessarily mean
the end of the result set was reached normally.  In this case, you can
use *Note `mysql_eof()': mysql-eof. to determine what happened. *Note
`mysql_eof()': mysql-eof. returns a nonzero value if the end of the
result set was reached and zero if an error occurred.

Historically, *Note `mysql_eof()': mysql-eof.  predates the standard
MySQL error functions *Note `mysql_errno()': mysql-errno. and *Note
`mysql_error()': mysql-error. Because those error functions provide the
same information, their use is preferred over *Note `mysql_eof()':
mysql-eof, which is deprecated. (In fact, they provide more information,
because *Note `mysql_eof()': mysql-eof. returns only a boolean value
whereas the error functions indicate a reason for the error when one
occurs.)

*Return Values*

Zero for success. Nonzero if the end of the result set has been reached.

*Errors*

None.

*Example*

The following example shows how you might use *Note `mysql_eof()':
mysql-eof.:


     mysql_query(&mysql,"SELECT * FROM some_table");
     result = mysql_use_result(&mysql);
     while((row = mysql_fetch_row(result)))
     {
         // do something with data
     }
     if(!mysql_eof(result))  // mysql_fetch_row() failed due to an error
     {
         fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
     }

However, you can achieve the same effect with the standard MySQL error
functions:


     mysql_query(&mysql,"SELECT * FROM some_table");
     result = mysql_use_result(&mysql);
     while((row = mysql_fetch_row(result)))
     {
         // do something with data
     }
     if(mysql_errno(&mysql))  // mysql_fetch_row() failed due to an error
     {
         fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
     }


File: manual.info,  Node: mysql-errno,  Next: mysql-error,  Prev: mysql-eof,  Up: c-api-functions

21.8.7.14 mysql_errno()
.......................

`unsigned int mysql_errno(MYSQL *mysql)'

*Description*

For the connection specified by `mysql', *Note `mysql_errno()':
mysql-errno. returns the error code for the most recently invoked API
function that can succeed or fail. A return value of zero means that no
error occurred.  Client error message numbers are listed in the MySQL
`errmsg.h' header file. Server error message numbers are listed in
`mysqld_error.h'.  Errors also are listed at *Note error-handling::.

Note that some functions like *Note `mysql_fetch_row()':
mysql-fetch-row. do not set *Note `mysql_errno()': mysql-errno. if they
succeed.

A rule of thumb is that all functions that have to ask the server for
information reset *Note `mysql_errno()': mysql-errno. if they succeed.

MySQL-specific error numbers returned by *Note `mysql_errno()':
mysql-errno. differ from SQLSTATE values returned by *Note
`mysql_sqlstate()': mysql-sqlstate. For example, the *Note `mysql':
mysql. client program displays errors using the following format, where
`1146' is the *Note `mysql_errno()': mysql-errno. value and `'42S02''
is the corresponding *Note `mysql_sqlstate()': mysql-sqlstate. value:


     shell> SELECT * FROM no_such_table;
     ERROR 1146 (42S02): Table 'test.no_such_table' doesn't exist

*Return Values*

An error code value for the last `mysql_XXX()' call, if it failed. zero
means no error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-error,  Next: mysql-escape-string,  Prev: mysql-errno,  Up: c-api-functions

21.8.7.15 mysql_error()
.......................

`const char *mysql_error(MYSQL *mysql)'

*Description*

For the connection specified by `mysql', *Note `mysql_error()':
mysql-error. returns a null-terminated string containing the error
message for the most recently invoked API function that failed. If a
function did not fail, the return value of *Note `mysql_error()':
mysql-error. may be the previous error or an empty string to indicate
no error.

A rule of thumb is that all functions that have to ask the server for
information reset *Note `mysql_error()': mysql-error. if they succeed.

For functions that reset *Note `mysql_error()': mysql-error, either of
these two tests can be used to check for an error:


     if(*mysql_error(&mysql))
     {
       // an error occurred
     }

     if(mysql_error(&mysql)[0])
     {
       // an error occurred
     }

The language of the client error messages may be changed by recompiling
the MySQL client library. Currently, you can choose error messages in
several different languages. See *Note error-message-language::.

*Return Values*

A null-terminated character string that describes the error. An empty
string if no error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-escape-string,  Next: mysql-fetch-field,  Prev: mysql-error,  Up: c-api-functions

21.8.7.16 mysql_escape_string()
...............................

Use *Note `mysql_real_escape_string()': mysql-real-escape-string.
instead!

This function is identical to *Note `mysql_real_escape_string()':
mysql-real-escape-string.  except that *Note
`mysql_real_escape_string()': mysql-real-escape-string. takes a
connection handler as its first argument and escapes the string
according to the current character set.  *Note `mysql_escape_string()':
mysql-escape-string. does not take a connection argument and does not
respect the current character set.


File: manual.info,  Node: mysql-fetch-field,  Next: mysql-fetch-field-direct,  Prev: mysql-escape-string,  Up: c-api-functions

21.8.7.17 mysql_fetch_field()
.............................

`MYSQL_FIELD *mysql_fetch_field(MYSQL_RES *result)'

*Description*

Returns the definition of one column of a result set as a `MYSQL_FIELD'
structure. Call this function repeatedly to retrieve information about
all columns in the result set. *Note `mysql_fetch_field()':
mysql-fetch-field.  returns `NULL' when no more fields are left.

*Note `mysql_fetch_field()': mysql-fetch-field. is reset to return
information about the first field each time you execute a new *Note
`SELECT': select. query. The field returned by *Note
`mysql_fetch_field()': mysql-fetch-field.  is also affected by calls to
*Note `mysql_field_seek()': mysql-field-seek.

If you've called *Note `mysql_query()': mysql-query.  to perform a
*Note `SELECT': select. on a table but have not called *Note
`mysql_store_result()': mysql-store-result, MySQL returns the default
blob length (8KB) if you call *Note `mysql_fetch_field()':
mysql-fetch-field. to ask for the length of a *Note `BLOB': blob.
field. (The 8KB size is chosen because MySQL does not know the maximum
length for the *Note `BLOB': blob. This should be made configurable
sometime.) Once you've retrieved the result set, `field->max_length'
contains the length of the largest value for this column in the
specific query.

*Return Values*

The `MYSQL_FIELD' structure for the current column. `NULL' if no
columns are left.

*Errors*

None.

*Example*


     MYSQL_FIELD *field;

     while((field = mysql_fetch_field(result)))
     {
         printf("field name %s\n", field->name);
     }


File: manual.info,  Node: mysql-fetch-field-direct,  Next: mysql-fetch-fields,  Prev: mysql-fetch-field,  Up: c-api-functions

21.8.7.18 mysql_fetch_field_direct()
....................................

`MYSQL_FIELD *mysql_fetch_field_direct(MYSQL_RES *result, unsigned int
fieldnr)'

*Description*

Given a field number `fieldnr' for a column within a result set,
returns that column's field definition as a `MYSQL_FIELD' structure.
Use this function to retrieve the definition for an arbitrary column.
Specify a value for `fieldnr' in the range from 0 to *Note
`mysql_num_fields(result)-1': mysql-num-fields.

*Return Values*

The `MYSQL_FIELD' structure for the specified column.

*Errors*

None.

*Example*


     unsigned int num_fields;
     unsigned int i;
     MYSQL_FIELD *field;

     num_fields = mysql_num_fields(result);
     for(i = 0; i < num_fields; i++)
     {
         field = mysql_fetch_field_direct(result, i);
         printf("Field %u is %s\n", i, field->name);
     }


File: manual.info,  Node: mysql-fetch-fields,  Next: mysql-fetch-lengths,  Prev: mysql-fetch-field-direct,  Up: c-api-functions

21.8.7.19 mysql_fetch_fields()
..............................

`MYSQL_FIELD *mysql_fetch_fields(MYSQL_RES *result)'

*Description*

Returns an array of all `MYSQL_FIELD' structures for a result set. Each
structure provides the field definition for one column of the result
set.

*Return Values*

An array of `MYSQL_FIELD' structures for all columns of a result set.

*Errors*

None.

*Example*


     unsigned int num_fields;
     unsigned int i;
     MYSQL_FIELD *fields;

     num_fields = mysql_num_fields(result);
     fields = mysql_fetch_fields(result);
     for(i = 0; i < num_fields; i++)
     {
        printf("Field %u is %s\n", i, fields[i].name);
     }


File: manual.info,  Node: mysql-fetch-lengths,  Next: mysql-fetch-row,  Prev: mysql-fetch-fields,  Up: c-api-functions

21.8.7.20 mysql_fetch_lengths()
...............................

`unsigned long *mysql_fetch_lengths(MYSQL_RES *result)'

*Description*

Returns the lengths of the columns of the current row within a result
set. If you plan to copy field values, this length information is also
useful for optimization, because you can avoid calling `strlen()'. In
addition, if the result set contains binary data, you *must* use this
function to determine the size of the data, because `strlen()' returns
incorrect results for any field containing null characters.

The length for empty columns and for columns containing `NULL' values
is zero. To see how to distinguish these two cases, see the description
for *Note `mysql_fetch_row()': mysql-fetch-row.

*Return Values*

An array of unsigned long integers representing the size of each column
(not including any terminating null characters).  `NULL' if an error
occurred.

*Errors*

*Note `mysql_fetch_lengths()': mysql-fetch-lengths. is valid only for
the current row of the result set. It returns `NULL' if you call it
before calling *Note `mysql_fetch_row()': mysql-fetch-row. or after
retrieving all rows in the result.

*Example*


     MYSQL_ROW row;
     unsigned long *lengths;
     unsigned int num_fields;
     unsigned int i;

     row = mysql_fetch_row(result);
     if (row)
     {
         num_fields = mysql_num_fields(result);
         lengths = mysql_fetch_lengths(result);
         for(i = 0; i < num_fields; i++)
         {
              printf("Column %u is %lu bytes in length.\n",
                     i, lengths[i]);
         }
     }


File: manual.info,  Node: mysql-fetch-row,  Next: mysql-field-count,  Prev: mysql-fetch-lengths,  Up: c-api-functions

21.8.7.21 mysql_fetch_row()
...........................

`MYSQL_ROW mysql_fetch_row(MYSQL_RES *result)'

*Description*

Retrieves the next row of a result set. When used after *Note
`mysql_store_result()': mysql-store-result, *Note `mysql_fetch_row()':
mysql-fetch-row. returns `NULL' when there are no more rows to retrieve.
When used after *Note `mysql_use_result()': mysql-use-result, *Note
`mysql_fetch_row()': mysql-fetch-row. returns `NULL' when there are no
more rows to retrieve or if an error occurred.

The number of values in the row is given by *Note
`mysql_num_fields(result)': mysql-num-fields. If `row' holds the return
value from a call to *Note `mysql_fetch_row()': mysql-fetch-row,
pointers to the values are accessed as `row[0]' to
`row[mysql_num_fields(result)-1]'.  `NULL' values in the row are
indicated by `NULL' pointers.

The lengths of the field values in the row may be obtained by calling
*Note `mysql_fetch_lengths()': mysql-fetch-lengths.  Empty fields and
fields containing `NULL' both have length 0; you can distinguish these
by checking the pointer for the field value. If the pointer is `NULL',
the field is `NULL'; otherwise, the field is empty.

*Return Values*

A `MYSQL_ROW' structure for the next row.  `NULL' if there are no more
rows to retrieve or if an error occurred.

*Errors*

Note that error is not reset between calls to *Note
`mysql_fetch_row()': mysql-fetch-row.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*


     MYSQL_ROW row;
     unsigned int num_fields;
     unsigned int i;

     num_fields = mysql_num_fields(result);
     while ((row = mysql_fetch_row(result)))
     {
        unsigned long *lengths;
        lengths = mysql_fetch_lengths(result);
        for(i = 0; i < num_fields; i++)
        {
            printf("[%.*s] ", (int) lengths[i],
                   row[i] ? row[i] : "NULL");
        }
        printf("\n");
     }


File: manual.info,  Node: mysql-field-count,  Next: mysql-field-seek,  Prev: mysql-fetch-row,  Up: c-api-functions

21.8.7.22 mysql_field_count()
.............................

`unsigned int mysql_field_count(MYSQL *mysql)'

*Description*

Returns the number of columns for the most recent query on the
connection.

The normal use of this function is when *Note `mysql_store_result()':
mysql-store-result. returned `NULL' (and thus you have no result set
pointer). In this case, you can call *Note `mysql_field_count()':
mysql-field-count. to determine whether *Note `mysql_store_result()':
mysql-store-result.  should have produced a nonempty result. This
enables the client program to take proper action without knowing
whether the query was a *Note `SELECT': select. (or *Note `SELECT':
select.-like) statement. The example shown here illustrates how this
may be done.

See *Note null-mysql-store-result::.

*Return Values*

An unsigned integer representing the number of columns in a result set.

*Errors*

None.

*Example*


     MYSQL_RES *result;
     unsigned int num_fields;
     unsigned int num_rows;

     if (mysql_query(&mysql,query_string))
     {
         // error
     }
     else // query succeeded, process any data returned by it
     {
         result = mysql_store_result(&mysql);
         if (result)  // there are rows
         {
             num_fields = mysql_num_fields(result);
             // retrieve rows, then call mysql_free_result(result)
         }
         else  // mysql_store_result() returned nothing; should it have?
         {
             if(mysql_field_count(&mysql) == 0)
             {
                 // query does not return data
                 // (it was not a SELECT)
                 num_rows = mysql_affected_rows(&mysql);
             }
             else // mysql_store_result() should have returned data
             {
                 fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
             }
         }
     }

An alternative is to replace the *Note `mysql_field_count(&mysql)':
mysql-field-count.  call with *Note `mysql_errno(&mysql)': mysql-errno.
In this case, you are checking directly for an error from *Note
`mysql_store_result()': mysql-store-result. rather than inferring from
the value of *Note `mysql_field_count()': mysql-field-count. whether the
statement was a *Note `SELECT': select.


File: manual.info,  Node: mysql-field-seek,  Next: mysql-field-tell,  Prev: mysql-field-count,  Up: c-api-functions

21.8.7.23 mysql_field_seek()
............................

`MYSQL_FIELD_OFFSET mysql_field_seek(MYSQL_RES *result,
MYSQL_FIELD_OFFSET offset)'

*Description*

Sets the field cursor to the given offset. The next call to *Note
`mysql_fetch_field()': mysql-fetch-field. retrieves the field
definition of the column associated with that offset.

To seek to the beginning of a row, pass an `offset' value of zero.

*Return Values*

The previous value of the field cursor.

*Errors*

None.


File: manual.info,  Node: mysql-field-tell,  Next: mysql-free-result,  Prev: mysql-field-seek,  Up: c-api-functions

21.8.7.24 mysql_field_tell()
............................

`MYSQL_FIELD_OFFSET mysql_field_tell(MYSQL_RES *result)'

*Description*

Returns the position of the field cursor used for the last *Note
`mysql_fetch_field()': mysql-fetch-field. This value can be used as an
argument to *Note `mysql_field_seek()': mysql-field-seek.

*Return Values*

The current offset of the field cursor.

*Errors*

None.


File: manual.info,  Node: mysql-free-result,  Next: mysql-get-character-set-info,  Prev: mysql-field-tell,  Up: c-api-functions

21.8.7.25 mysql_free_result()
.............................

`void mysql_free_result(MYSQL_RES *result)'

*Description*

Frees the memory allocated for a result set by *Note
`mysql_store_result()': mysql-store-result, *Note `mysql_use_result()':
mysql-use-result, *Note `mysql_list_dbs()': mysql-list-dbs, and so
forth.  When you are done with a result set, you must free the memory it
uses by calling *Note `mysql_free_result()': mysql-free-result.

Do not attempt to access a result set after freeing it.

*Return Values*

None.

*Errors*

None.


File: manual.info,  Node: mysql-get-character-set-info,  Next: mysql-get-client-info,  Prev: mysql-free-result,  Up: c-api-functions

21.8.7.26 mysql_get_character_set_info()
........................................

`void mysql_get_character_set_info(MYSQL *mysql, MY_CHARSET_INFO *cs)'

*Description*

This function provides information about the default client character
set. The default character set may be changed with the *Note
`mysql_set_character_set()': mysql-set-character-set.  function.

*Example*

This example shows the fields that are available in the
`MY_CHARSET_INFO' structure:


     if (!mysql_set_character_set(&mysql, "utf8"))
     {
         MY_CHARSET_INFO cs;
         mysql_get_character_set_info(&mysql, &cs);
         printf("character set information:\n");
         printf("character set+collation number: %d\n", cs.number);
         printf("character set name: %s\n", cs.name);
         printf("collation name: %s\n", cs.csname);
         printf("comment: %s\n", cs.comment);
         printf("directory: %s\n", cs.dir);
         printf("multi byte character min. length: %d\n", cs.mbminlen);
         printf("multi byte character max. length: %d\n", cs.mbmaxlen);
     }


File: manual.info,  Node: mysql-get-client-info,  Next: mysql-get-client-version,  Prev: mysql-get-character-set-info,  Up: c-api-functions

21.8.7.27 mysql_get_client_info()
.................................

`const char *mysql_get_client_info(void)'

*Description*

Returns a string that represents the MySQL client library version; for
example, `"5.1.73"'.

The function value is the MySQL version. For Connector/C, this is the
MySQL version on which the Connector/C distribution is based. For more
information, see *Note c-api-server-client-versions::.

*Return Values*

A character string that represents the MySQL client library version.

*Errors*

None.


File: manual.info,  Node: mysql-get-client-version,  Next: mysql-get-host-info,  Prev: mysql-get-client-info,  Up: c-api-functions

21.8.7.28 mysql_get_client_version()
....................................

`unsigned long mysql_get_client_version(void)'

*Description*

Returns an integer that represents the MySQL client library version.
The value has the format `XYYZZ' where `X' is the major version, `YY'
is the release level (or minor version), and `ZZ' is the sub-version
within the release level:


     major_version*10000 + release_level*100 + sub_version

For example, `"5.1.73"' is returned as `50173'.

The function value is the MySQL version. For Connector/C, this is the
MySQL version on which the Connector/C distribution is based. For more
information, see *Note c-api-server-client-versions::.

*Return Values*

An integer that represents the MySQL client library version.

*Errors*

None.


File: manual.info,  Node: mysql-get-host-info,  Next: mysql-get-proto-info,  Prev: mysql-get-client-version,  Up: c-api-functions

21.8.7.29 mysql_get_host_info()
...............................

`const char *mysql_get_host_info(MYSQL *mysql)'

*Description*

Returns a string describing the type of connection in use, including
the server host name.

*Return Values*

A character string representing the server host name and the connection
type.

*Errors*

None.


File: manual.info,  Node: mysql-get-proto-info,  Next: mysql-get-server-info,  Prev: mysql-get-host-info,  Up: c-api-functions

21.8.7.30 mysql_get_proto_info()
................................

`unsigned int mysql_get_proto_info(MYSQL *mysql)'

*Description*

Returns the protocol version used by current connection.

*Return Values*

An unsigned integer representing the protocol version used by the
current connection.

*Errors*

None.


File: manual.info,  Node: mysql-get-server-info,  Next: mysql-get-server-version,  Prev: mysql-get-proto-info,  Up: c-api-functions

21.8.7.31 mysql_get_server_info()
.................................

`const char *mysql_get_server_info(MYSQL *mysql)'

*Description*

Returns a string that represents the MySQL server version; for example,
`"5.1.73"'.

*Return Values*

A character string that represents the MySQL server version.

*Errors*

None.


File: manual.info,  Node: mysql-get-server-version,  Next: mysql-get-ssl-cipher,  Prev: mysql-get-server-info,  Up: c-api-functions

21.8.7.32 mysql_get_server_version()
....................................

`unsigned long mysql_get_server_version(MYSQL *mysql)'

*Description*

Returns an integer that represents the MySQL server version. The value
has the format `XYYZZ' where `X' is the major version, `YY' is the
release level (or minor version), and `ZZ' is the sub-version within
the release level:


     major_version*10000 + release_level*100 + sub_version

For example, `"5.1.73"' is returned as `50173'.

This function is useful in client programs for determining whether some
version-specific server capability exists.

*Return Values*

An integer that represents the MySQL server version.

*Errors*

None.


File: manual.info,  Node: mysql-get-ssl-cipher,  Next: mysql-hex-string,  Prev: mysql-get-server-version,  Up: c-api-functions

21.8.7.33 mysql_get_ssl_cipher()
................................

`const char *mysql_get_ssl_cipher(MYSQL *mysql)'

*Description*

*Note `mysql_get_ssl_cipher()': mysql-get-ssl-cipher. returns the SSL
cipher used for the given connection to the server.  `mysql' is the
connection handler returned from *Note `mysql_init()': mysql-init.

This function was added in MySQL 5.1.11.

*Return Values*

A string naming the SSL cipher used for the connection, or `NULL' if no
cipher is being used.


File: manual.info,  Node: mysql-hex-string,  Next: mysql-info,  Prev: mysql-get-ssl-cipher,  Up: c-api-functions

21.8.7.34 mysql_hex_string()
............................

`unsigned long mysql_hex_string(char *to, const char *from, unsigned
long length)'

*Description*

This function is used to create a legal SQL string that you can use in
an SQL statement. See *Note string-literals::.

The string in `from' is encoded to hexadecimal format, with each
character encoded as two hexadecimal digits.  The result is placed in
`to' and a terminating null byte is appended.

The string pointed to by `from' must be `length' bytes long. You must
allocate the `to' buffer to be at least `length*2+1' bytes long. When
*Note `mysql_hex_string()': mysql-hex-string. returns, the contents of
`to' is a null-terminated string.  The return value is the length of
the encoded string, not including the terminating null character.

The return value can be placed into an SQL statement using either
`0xVALUE' or `X'VALUE'' format.  However, the return value does not
include the `0x' or `X'...''. The caller must supply whichever of those
is desired.

*Example*


     char query[1000],*end;

     end = strmov(query,"INSERT INTO test_table values(");
     end = strmov(end,"0x");
     end += mysql_hex_string(end,"What is this",12);
     end = strmov(end,",0x");
     end += mysql_hex_string(end,"binary data: \0\r\n",16);
     *end++ = ')';

     if (mysql_real_query(&mysql,query,(unsigned int) (end - query)))
     {
        fprintf(stderr, "Failed to insert row, Error: %s\n",
                mysql_error(&mysql));
     }

The `strmov()' function used in the example is included in the
`libmysqlclient' library and works like `strcpy()' but returns a
pointer to the terminating null of the first parameter.

*Return Values*

The length of the value placed into `to', not including the terminating
null character.

*Errors*

None.


File: manual.info,  Node: mysql-info,  Next: mysql-init,  Prev: mysql-hex-string,  Up: c-api-functions

21.8.7.35 mysql_info()
......................

`const char *mysql_info(MYSQL *mysql)'

*Description*

Retrieves a string providing information about the most recently
executed statement, but only for the statements listed here. For other
statements, *Note `mysql_info()': mysql-info.  returns `NULL'. The
format of the string varies depending on the type of statement, as
described here. The numbers are illustrative only; the string contains
values appropriate for the statement.

   * *Note `INSERT INTO ... SELECT ...': insert-select.

     String format: `Records: 100 Duplicates: 0 Warnings: 0'

   * `INSERT INTO ... VALUES (...),(...),(...)...'

     String format: `Records: 3 Duplicates: 0 Warnings: 0'

   * *Note `LOAD DATA INFILE ...': load-data.

     String format: `Records: 1 Deleted: 0 Skipped: 0 Warnings: 0'

   * *Note `ALTER TABLE': alter-table.

     String format: `Records: 3 Duplicates: 0 Warnings: 0'

   * *Note `UPDATE': update.

     String format: `Rows matched: 40 Changed: 40 Warnings: 0'

Note that *Note `mysql_info()': mysql-info. returns a non-`NULL' value
for *Note `INSERT ... VALUES': insert. only for the multiple-row form
of the statement (that is, only if multiple value lists are specified).

*Return Values*

A character string representing additional information about the most
recently executed statement. `NULL' if no information is available for
the statement.

*Errors*

None.


File: manual.info,  Node: mysql-init,  Next: mysql-insert-id,  Prev: mysql-info,  Up: c-api-functions

21.8.7.36 mysql_init()
......................

`MYSQL *mysql_init(MYSQL *mysql)'

*Description*

Allocates or initializes a `MYSQL' object suitable for *Note
`mysql_real_connect()': mysql-real-connect. If `mysql' is a `NULL'
pointer, the function allocates, initializes, and returns a new object.
Otherwise, the object is initialized and the address of the object is
returned. If *Note `mysql_init()': mysql-init. allocates a new object,
it is freed when *Note `mysql_close()': mysql-close. is called to close
the connection.

In a nonmulti-threaded environment, *Note `mysql_init()': mysql-init.
invokes *Note `mysql_library_init()': mysql-library-init.
automatically as necessary. However, *Note `mysql_library_init()':
mysql-library-init. is not thread-safe in a multi-threaded environment,
and thus neither is *Note `mysql_init()': mysql-init. Before calling
*Note `mysql_init()': mysql-init, either call *Note
`mysql_library_init()': mysql-library-init. prior to spawning any
threads, or use a mutex to protect the *Note `mysql_library_init()':
mysql-library-init. call. This should be done prior to any other client
library call.

*Return Values*

An initialized `MYSQL*' handle.  `NULL' if there was insufficient
memory to allocate a new object.

*Errors*

In case of insufficient memory, `NULL' is returned.


File: manual.info,  Node: mysql-insert-id,  Next: mysql-kill,  Prev: mysql-init,  Up: c-api-functions

21.8.7.37 mysql_insert_id()
...........................

`my_ulonglong mysql_insert_id(MYSQL *mysql)'

*Description*

Returns the value generated for an `AUTO_INCREMENT' column by the
previous *Note `INSERT': insert. or *Note `UPDATE': update. statement.
Use this function after you have performed an *Note `INSERT': insert.
statement into a table that contains an `AUTO_INCREMENT' field, or have
used *Note `INSERT': insert. or *Note `UPDATE': update. to set a column
value with `LAST_INSERT_ID(EXPR)'.

The return value of *Note `mysql_insert_id()': mysql-insert-id. is
always zero unless explicitly updated under one of the following
conditions:

   * *Note `INSERT': insert. statements that store a value into an
     `AUTO_INCREMENT' column.  This is true whether the value is
     automatically generated by storing the special values `NULL' or
     `0' into the column, or is an explicit nonspecial value.

   * In the case of a multiple-row *Note `INSERT': insert. statement,
     the return value of *Note `mysql_insert_id()': mysql-insert-id.
     depends on the MySQL server version.

     In MySQL 5.1.12 and later, *Note `mysql_insert_id()':
     mysql-insert-id. returns the first automatically generated
     `AUTO_INCREMENT' value that was successfully inserted. In MySQL
     5.1.11 and earlier, *Note `mysql_insert_id()': mysql-insert-id.
     returns the first automatically generated `AUTO_INCREMENT' value,
     regardless of whether insertion of that value was successful.

     If no rows are successfully inserted, *Note `mysql_insert_id()':
     mysql-insert-id. returns 0.

   * Starting in MySQL 5.1.12, if an *Note `INSERT ... SELECT':
     insert-select. statement is executed, and no automatically
     generated value is successfully inserted, *Note
     `mysql_insert_id()': mysql-insert-id. returns the ID of the last
     inserted row.

   * Starting in MySQL 5.1.12, if an *Note `INSERT ... SELECT':
     insert-select. statement uses `LAST_INSERT_ID(EXPR)', *Note
     `mysql_insert_id()': mysql-insert-id. returns EXPR.

   * *Note `INSERT': insert. statements that generate an
     `AUTO_INCREMENT' value by inserting `LAST_INSERT_ID(EXPR)' into
     any column or by updating any column to `LAST_INSERT_ID(EXPR)'.

   * If the previous statement returned an error, the value of *Note
     `mysql_insert_id()': mysql-insert-id. is undefined.

For 5.1.12 and later, the return value of *Note `mysql_insert_id()':
mysql-insert-id. can be simplified to the following sequence:

  1. If there is an `AUTO_INCREMENT' column, and an automatically
     generated value was successfully inserted, return the first such
     value.

  2. If `LAST_INSERT_ID(EXPR)' occurred in the statement, return EXPR,
     even if there was an `AUTO_INCREMENT' column in the affected table.

  3. The return value varies depending on the statement used.  When
     called after an *Note `INSERT': insert.  statement:

        * If there is an `AUTO_INCREMENT' column in the table, and
          there were some explicit values for this column that were
          successfully inserted into the table, return the last of the
          explicit values.

     When called after an *Note `INSERT ... ON DUPLICATE KEY UPDATE':
     insert-on-duplicate. statement:

        * If there is an `AUTO_INCREMENT' column in the table and there
          were some explicit successfully inserted values or some
          updated values, return the last of the inserted or updated
          values.

*Note `mysql_insert_id()': mysql-insert-id. returns `0' if the previous
statement does not use an `AUTO_INCREMENT' value. If you need to save
the value for later, be sure to call *Note `mysql_insert_id()':
mysql-insert-id. immediately after the statement that generates the
value.

The value of *Note `mysql_insert_id()': mysql-insert-id.  is affected
only by statements issued within the current client connection. It is
not affected by statements issued by other clients.

The `LAST_INSERT_ID()' SQL function returns the value of the first
automatically generated value that was successfully inserted (starting
from 5.1.12) or the first automatically generated value if any rows were
successfully inserted (before 5.1.12).  `LAST_INSERT_ID()' is not reset
between statements because the value of that function is maintained in
the server. Another difference from *Note `mysql_insert_id()':
mysql-insert-id. is that `LAST_INSERT_ID()' is not updated if you set
an `AUTO_INCREMENT' column to a specific nonspecial value. See *Note
information-functions::.

*Note `mysql_insert_id()': mysql-insert-id. returns `0' following a
*Note `CALL': call. statement for a stored procedure that generates an
`AUTO_INCREMENT' value because in this case *Note `mysql_insert_id()':
mysql-insert-id. applies to *Note `CALL': call. and not the statement
within the procedure. Within the procedure, you can use
`LAST_INSERT_ID()' at the SQL level to obtain the `AUTO_INCREMENT'
value.

The reason for the differences between `LAST_INSERT_ID()' and *Note
`mysql_insert_id()': mysql-insert-id. is that `LAST_INSERT_ID()' is
made easy to use in scripts while *Note `mysql_insert_id()':
mysql-insert-id. tries to provide more exact information about what
happens to the `AUTO_INCREMENT' column.

*Return Values*

Described in the preceding discussion.

*Errors*

None.


File: manual.info,  Node: mysql-kill,  Next: mysql-library-end,  Prev: mysql-insert-id,  Up: c-api-functions

21.8.7.38 mysql_kill()
......................

`int mysql_kill(MYSQL *mysql, unsigned long pid)'

*Description*

Asks the server to kill the thread specified by `pid'.

This function is deprecated. It is preferable to use *Note
`mysql_query()': mysql-query. to issue an SQL *Note `KILL': kill.
statement instead.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-library-end,  Next: mysql-library-init,  Prev: mysql-kill,  Up: c-api-functions

21.8.7.39 mysql_library_end()
.............................

`void mysql_library_end(void)'

*Description*

This function finalizes the MySQL library. Call it when you are done
using the library (for example, after disconnecting from the server).
The action taken by the call depends on whether your application is
linked to the MySQL client library or the MySQL embedded server
library. For a client program linked against the `libmysqlclient'
library by using the `-lmysqlclient' flag, *Note `mysql_library_end()':
mysql-library-end. performs some memory management to clean up. For an
embedded server application linked against the `libmysqld' library by
using the `-lmysqld' flag, *Note `mysql_library_end()':
mysql-library-end. shuts down the embedded server and then cleans up.

For usage information, see *Note c-api-function-overview::, and *Note
mysql-library-init::.


File: manual.info,  Node: mysql-library-init,  Next: mysql-list-dbs,  Prev: mysql-library-end,  Up: c-api-functions

21.8.7.40 mysql_library_init()
..............................

`int mysql_library_init(int argc, char **argv, char **groups)'

*Description*

Call this function to initialize the MySQL library before you call any
other MySQL function, whether your application is a regular client
program or uses the embedded server. If the application uses the
embedded server, this call starts the server and initializes any
subsystems (`mysys', `InnoDB', and so forth) that the server uses.

After your application is done using the MySQL library, call *Note
`mysql_library_end()': mysql-library-end. to clean up.  See *Note
mysql-library-end::.

The choice of whether the application operates as a regular client or
uses the embedded server depends on whether you use the
`libmysqlclient' or `libmysqld' library at link time to produce the
final executable. For additional information, see *Note
c-api-function-overview::.

In a nonmulti-threaded environment, the call to *Note
`mysql_library_init()': mysql-library-init. may be omitted, because
*Note `mysql_init()': mysql-init.  will invoke it automatically as
necessary. However, *Note `mysql_library_init()': mysql-library-init.
is not thread-safe in a multi-threaded environment, and thus neither is
*Note `mysql_init()': mysql-init, which calls *Note
`mysql_library_init()': mysql-library-init. You must either call *Note
`mysql_library_init()': mysql-library-init.  prior to spawning any
threads, or else use a mutex to protect the call, whether you invoke
*Note `mysql_library_init()': mysql-library-init. or indirectly through
*Note `mysql_init()': mysql-init.  Do this prior to any other client
library call.

The `argc' and `argv' arguments are analogous to the arguments to
`main()', and enable passing of options to the embedded server. For
convenience, `argc' may be `0' (zero) if there are no command-line
arguments for the server. This is the usual case for applications
intended for use only as regular (nonembedded) clients, and the call
typically is written as *Note `mysql_library_init(0, NULL, NULL)':
mysql-library-init.


     #include <mysql.h>
     #include <stdlib.h>

     int main(void) {
       if (mysql_library_init(0, NULL, NULL)) {
         fprintf(stderr, "could not initialize MySQL library\n");
         exit(1);
       }

       /* Use any MySQL API functions here */

       mysql_library_end();

       return EXIT_SUCCESS;
     }

When arguments are to be passed (`argc' is greater than `0'), the first
element of `argv' is ignored (it typically contains the program name).
*Note `mysql_library_init()': mysql-library-init. makes a copy of the
arguments so it is safe to destroy `argv' or `groups' after the call.

For embedded applications, if you want to connect to an external server
without starting the embedded server, you have to specify a negative
value for `argc'.

The `groups' argument is an array of strings that indicate the groups
in option files from which to read options. See *Note option-files::.
Make the final entry in the array `NULL'. For convenience, if the
`groups' argument itself is `NULL', the `[server]' and `[embedded]'
groups are used by default.


     #include <mysql.h>
     #include <stdlib.h>

     static char *server_args[] = {
       "this_program",       /* this string is not used */
       "--datadir=.",
       "--key_buffer_size=32M"
     };
     static char *server_groups[] = {
       "embedded",
       "server",
       "this_program_SERVER",
       (char *)NULL
     };

     int main(void) {
       if (mysql_library_init(sizeof(server_args) / sizeof(char *),
                             server_args, server_groups)) {
         fprintf(stderr, "could not initialize MySQL library\n");
         exit(1);
       }

       /* Use any MySQL API functions here */

       mysql_library_end();

       return EXIT_SUCCESS;
     }

*Return Values*

Zero for success. Nonzero if an error occurred.


File: manual.info,  Node: mysql-list-dbs,  Next: mysql-list-fields,  Prev: mysql-library-init,  Up: c-api-functions

21.8.7.41 mysql_list_dbs()
..........................

`MYSQL_RES *mysql_list_dbs(MYSQL *mysql, const char *wild)'

*Description*

Returns a result set consisting of database names on the server that
match the simple regular expression specified by the `wild' parameter.
`wild' may contain the wildcard characters ``%'' or ``_'', or may be a
`NULL' pointer to match all databases. Calling *Note
`mysql_list_dbs()': mysql-list-dbs. is similar to executing the query
`SHOW DATABASES [LIKE WILD]'.

You must free the result set with *Note `mysql_free_result()':
mysql-free-result.

*Return Values*

A `MYSQL_RES' result set for success.  `NULL' if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-list-fields,  Next: mysql-list-processes,  Prev: mysql-list-dbs,  Up: c-api-functions

21.8.7.42 mysql_list_fields()
.............................

`MYSQL_RES *mysql_list_fields(MYSQL *mysql, const char *table, const
char *wild)'

*Description*

Returns an empty result set for which the metadata provides information
aobut the columns in the given table that match the simple regular
expression specified by the `wild' parameter. `wild' may contain the
wildcard characters ``%'' or ``_'', or may be a `NULL' pointer to match
all fields. Calling *Note `mysql_list_fields()': mysql-list-fields. is
similar to executing the query `SHOW COLUMNS FROM TBL_NAME [LIKE WILD]'.

It is preferable to use `SHOW COLUMNS FROM TBL_NAME' instead of *Note
`mysql_list_fields()': mysql-list-fields.

You must free the result set with *Note `mysql_free_result()':
mysql-free-result.

*Return Values*

A `MYSQL_RES' result set for success.  `NULL' if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*


     int i;
     MYSQL_RES *tbl_cols = mysql_list_fields(mysql, "mytbl", "f%");

     unsigned int field_cnt = mysql_num_fields(tbl_cols);
     printf("Number of columns: %d\n", field_cnt);

     for (i=0; i < field_cnt; ++i)
     {
       /* col describes i-th column of the table */
       MYSQL_FIELD *col = mysql_fetch_field_direct(tbl_cols, i);
       printf ("Column %d: %s\n", i, col->name);
     }
     mysql_free_result(tbl_cols);


File: manual.info,  Node: mysql-list-processes,  Next: mysql-list-tables,  Prev: mysql-list-fields,  Up: c-api-functions

21.8.7.43 mysql_list_processes()
................................

`MYSQL_RES *mysql_list_processes(MYSQL *mysql)'

*Description*

Returns a result set describing the current server threads. This is the
same kind of information as that reported by *Note `mysqladmin
processlist': mysqladmin. or a *Note `SHOW PROCESSLIST':
show-processlist. query.

You must free the result set with *Note `mysql_free_result()':
mysql-free-result.

*Return Values*

A `MYSQL_RES' result set for success.  `NULL' if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-list-tables,  Next: mysql-more-results,  Prev: mysql-list-processes,  Up: c-api-functions

21.8.7.44 mysql_list_tables()
.............................

`MYSQL_RES *mysql_list_tables(MYSQL *mysql, const char *wild)'

*Description*

Returns a result set consisting of table names in the current database
that match the simple regular expression specified by the `wild'
parameter. `wild' may contain the wildcard characters ``%'' or ``_'',
or may be a `NULL' pointer to match all tables. Calling *Note
`mysql_list_tables()': mysql-list-tables. is similar to executing the
query `SHOW TABLES [LIKE WILD]'.

You must free the result set with *Note `mysql_free_result()':
mysql-free-result.

*Return Values*

A `MYSQL_RES' result set for success.  `NULL' if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-more-results,  Next: mysql-next-result,  Prev: mysql-list-tables,  Up: c-api-functions

21.8.7.45 mysql_more_results()
..............................

`my_bool mysql_more_results(MYSQL *mysql)'

*Description*

This function is used when you execute multiple statements specified as
a single statement string, or when you execute *Note `CALL': call.
statements, which can return multiple result sets.

*Note `mysql_more_results()': mysql-more-results. true if more results
exist from the currently executed statement, in which case the
application must call *Note `mysql_next_result()': mysql-next-result.
to fetch the results.

*Return Values*

`TRUE' (1) if more results exist.  `FALSE' (0) if no more results exist.

In most cases, you can call *Note `mysql_next_result()':
mysql-next-result. instead to test whether more results exist and
initiate retrieval if so.

See *Note c-api-multiple-queries::, and *Note mysql-next-result::.

*Errors*

None.


File: manual.info,  Node: mysql-next-result,  Next: mysql-num-fields,  Prev: mysql-more-results,  Up: c-api-functions

21.8.7.46 mysql_next_result()
.............................

`int mysql_next_result(MYSQL *mysql)'

*Description*

This function is used when you execute multiple statements specified as
a single statement string, or when you use *Note `CALL': call.
statements to execute stored procedures, which can return multiple
result sets.

*Note `mysql_next_result()': mysql-next-result. reads the next
statement result and returns a status to indicate whether more results
exist. If *Note `mysql_next_result()': mysql-next-result. returns an
error, there are no more results.

Before each call to *Note `mysql_next_result()': mysql-next-result, you
must call *Note `mysql_free_result()': mysql-free-result. for the
current statement if it is a statement that returned a result set
(rather than just a result status).

After calling *Note `mysql_next_result()': mysql-next-result. the state
of the connection is as if you had called *Note `mysql_real_query()':
mysql-real-query. or *Note `mysql_query()': mysql-query. for the next
statement. This means that you can call *Note `mysql_store_result()':
mysql-store-result, *Note `mysql_warning_count()': mysql-warning-count,
*Note `mysql_affected_rows()': mysql-affected-rows, and so forth.

If your program uses *Note `CALL': call.  statements to execute stored
procedures, the `CLIENT_MULTI_RESULTS' flag must be enabled.  This is
because each *Note `CALL': call. returns a result to indicate the call
status, in addition to any result sets that might be returned by
statements executed within the procedure. Because *Note `CALL': call.
can return multiple results, process them using a loop that calls *Note
`mysql_next_result()': mysql-next-result. to determine whether there
are more results.

`CLIENT_MULTI_RESULTS' can be enabled when you call *Note
`mysql_real_connect()': mysql-real-connect, either explicitly by
passing the `CLIENT_MULTI_RESULTS' flag itself, or implicitly by
passing `CLIENT_MULTI_STATEMENTS' (which also enables
`CLIENT_MULTI_RESULTS').

It is also possible to test whether there are more results by calling
*Note `mysql_more_results()': mysql-more-results.  However, this
function does not change the connection state, so if it returns true,
you must still call *Note `mysql_next_result()': mysql-next-result. to
advance to the next result.

For an example that shows how to use *Note `mysql_next_result()':
mysql-next-result, see *Note c-api-multiple-queries::.

*Return Values*

This table lists *Note `mysql_next_result()': mysql-next-result. return
values and provides a description of each.

Return Value              Description
0                         Successful and there are more results
-1                        Successful and there are no more results
>0                        An error occurred

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order. For example, if you
     did not call *Note `mysql_use_result()': mysql-use-result. for a
     previous result set.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-num-fields,  Next: mysql-num-rows,  Prev: mysql-next-result,  Up: c-api-functions

21.8.7.47 mysql_num_fields()
............................

`unsigned int mysql_num_fields(MYSQL_RES *result)'

To pass a `MYSQL*' argument instead, use `unsigned int
mysql_field_count(MYSQL *mysql)'.

*Description*

Returns the number of columns in a result set.

Note that you can get the number of columns either from a pointer to a
result set or to a connection handle. You would use the connection
handle if *Note `mysql_store_result()': mysql-store-result. or *Note
`mysql_use_result()': mysql-use-result. returned `NULL' (and thus you
have no result set pointer). In this case, you can call *Note
`mysql_field_count()': mysql-field-count. to determine whether *Note
`mysql_store_result()': mysql-store-result.  should have produced a
nonempty result. This enables the client program to take proper action
without knowing whether the query was a *Note `SELECT': select. (or
*Note `SELECT': select.-like) statement. The example shown here
illustrates how this may be done.

See *Note null-mysql-store-result::.

*Return Values*

An unsigned integer representing the number of columns in a result set.

*Errors*

None.

*Example*


     MYSQL_RES *result;
     unsigned int num_fields;
     unsigned int num_rows;

     if (mysql_query(&mysql,query_string))
     {
         // error
     }
     else // query succeeded, process any data returned by it
     {
         result = mysql_store_result(&mysql);
         if (result)  // there are rows
         {
             num_fields = mysql_num_fields(result);
             // retrieve rows, then call mysql_free_result(result)
         }
         else  // mysql_store_result() returned nothing; should it have?
         {
             if (mysql_errno(&mysql))
             {
                fprintf(stderr, "Error: %s\n", mysql_error(&mysql));
             }
             else if (mysql_field_count(&mysql) == 0)
             {
                 // query does not return data
                 // (it was not a SELECT)
                 num_rows = mysql_affected_rows(&mysql);
             }
         }
     }

An alternative (if you know that your query should have returned a
result set) is to replace the *Note `mysql_errno(&mysql)': mysql-errno.
call with a check whether *Note `mysql_field_count(&mysql)':
mysql-field-count.  returns 0. This happens only if something went
wrong.


File: manual.info,  Node: mysql-num-rows,  Next: mysql-options,  Prev: mysql-num-fields,  Up: c-api-functions

21.8.7.48 mysql_num_rows()
..........................

`my_ulonglong mysql_num_rows(MYSQL_RES *result)'

*Description*

Returns the number of rows in the result set.

The use of *Note `mysql_num_rows()': mysql-num-rows.  depends on
whether you use *Note `mysql_store_result()': mysql-store-result. or
*Note `mysql_use_result()': mysql-use-result. to return the result set.
If you use *Note `mysql_store_result()': mysql-store-result, *Note
`mysql_num_rows()': mysql-num-rows. may be called immediately. If you
use *Note `mysql_use_result()': mysql-use-result, *Note
`mysql_num_rows()': mysql-num-rows. does not return the correct value
until all the rows in the result set have been retrieved.

*Note `mysql_num_rows()': mysql-num-rows. is intended for use with
statements that return a result set, such as *Note `SELECT': select.
For statements such as *Note `INSERT': insert, *Note `UPDATE': update,
or *Note `DELETE': delete, the number of affected rows can be obtained
with *Note `mysql_affected_rows()': mysql-affected-rows.

*Return Values*

The number of rows in the result set.

*Errors*

None.


File: manual.info,  Node: mysql-options,  Next: mysql-ping,  Prev: mysql-num-rows,  Up: c-api-functions

21.8.7.49 mysql_options()
.........................

`int mysql_options(MYSQL *mysql, enum mysql_option option, const void
*arg)'

*Description*

Can be used to set extra connect options and affect behavior for a
connection. This function may be called multiple times to set several
options.

Call *Note `mysql_options()': mysql-options. after *Note
`mysql_init()': mysql-init. and before *Note `mysql_connect()':
mysql-connect. or *Note `mysql_real_connect()': mysql-real-connect.

The `option' argument is the option that you want to set; the `arg'
argument is the value for the option. If the option is an integer,
specify a pointer to the value of the integer as the `arg' argument.

The following list describes the possible options, their effect, and
how `arg' is used for each option. Several of the options apply only
when the application is linked against the `libmysqld' embedded server
library and are unused for applications linked against the
`libmysqlclient' client library. For option descriptions that indicate
`arg' is unused, its value is irrelevant; it is conventional to pass 0.

   * `MYSQL_INIT_COMMAND' (argument type: `char *')

     SQL statement to execute when connecting to the MySQL server.
     Automatically re-executed if reconnection occurs.

   * `MYSQL_OPT_COMPRESS' (argument: not used)

     Use the compressed client/server protocol.

   * `MYSQL_OPT_CONNECT_TIMEOUT' (argument type: `unsigned int *')

     Connect timeout in seconds.

   * `MYSQL_OPT_GUESS_CONNECTION' (argument: not used)

     For an application linked against the `libmysqld' embedded server
     library, this enables the library to guess whether to use the
     embedded server or a remote server. `Guess' means that if the host
     name is set and is not `localhost', it uses a remote server. This
     behavior is the default.  `MYSQL_OPT_USE_EMBEDDED_CONNECTION' and
     `MYSQL_OPT_USE_REMOTE_CONNECTION' can be used to override it. This
     option is ignored for applications linked against the
     `libmysqlclient' client library.

   * `MYSQL_OPT_LOCAL_INFILE' (argument type: optional pointer to
     `unsigned int')

     If no pointer is given or if pointer points to an `unsigned int'
     that has a nonzero value, the `LOAD LOCAL INFILE' statement is
     enabled.

   * `MYSQL_OPT_NAMED_PIPE' (argument: not used)

     Use named pipes to connect to a MySQL server on Windows, if the
     server permits named-pipe connections.

   * `MYSQL_OPT_PROTOCOL' (argument type: `unsigned int *')

     Type of protocol to use. Specify one of the enum values of
     `mysql_protocol_type' defined in `mysql.h'.

   * `MYSQL_OPT_READ_TIMEOUT' (argument type: `unsigned int *')

     The timeout in seconds for each attempt to read from the server.
     There are retries if necessary, so the total effective timeout
     value is three times the option value. You can set the value so
     that a lost connection can be detected earlier than the TCP/IP
     `Close_Wait_Timeout' value of 10 minutes.  Before MySQL 5.1.41,
     this option applies only to TCP/IP connections and, prior to MySQL
     5.1.12, only for Windows.

     Implementation of this timeout uses mechanisms that may not be
     available on all platforms. On such a platform, a client that
     issues a read call might under certain circumstances wait without
     timing out. For example, a client might not time out if the server
     is not responding because it is waiting for a `disk full'
     condition to clear.

   * `MYSQL_OPT_RECONNECT' (argument type: `my_bool *')

     Enable or disable automatic reconnection to the server if the
     connection is found to have been lost. Reconnect is off by
     default; this option provides a way to set reconnection behavior
     explicitly.

     Note: *Note `mysql_real_connect()': mysql-real-connect.
     incorrectly reset the `MYSQL_OPT_RECONNECT' option to its default
     value before MySQL 5.1.6. Therefore, prior to that version, if you
     want reconnect to be enabled for each connection, you must call
     *Note `mysql_options()': mysql-options. with the
     `MYSQL_OPT_RECONNECT' option after each call to *Note
     `mysql_real_connect()': mysql-real-connect. This is not necessary
     as of 5.1.6: Call *Note `mysql_options()': mysql-options. only
     before *Note `mysql_real_connect()': mysql-real-connect. as usual.

   * `MYSQL_OPT_SSL_VERIFY_SERVER_CERT' (argument type: `my_bool *')

     Enable or disable verification of the server's Common Name value
     in its certificate against the host name used when connecting to
     the server. The connection is rejected if there is a mismatch.
     This feature can be used to prevent man-in-the-middle attacks.
     Verification is disabled by default. Added in MySQL 5.1.11.

   * `MYSQL_OPT_USE_EMBEDDED_CONNECTION' (argument: not used)

     For an application linked against the `libmysqld' embedded server
     library, this forces the use of the embedded server for the
     connection.  This option is ignored for applications linked
     against the `libmysqlclient' client library.

   * `MYSQL_OPT_USE_REMOTE_CONNECTION' (argument: not used)

     For an application linked against the `libmysqld' embedded server
     library, this forces the use of a remote server for the
     connection. This option is ignored for applications linked against
     the `libmysqlclient' client library.

   * `MYSQL_OPT_USE_RESULT' (argument: not used)

     This option is unused.

   * `MYSQL_OPT_WRITE_TIMEOUT' (argument type: `unsigned int *')

     The timeout in seconds for each attempt to write to the server.
     There is a retry if necessary, so the total effective timeout
     value is two times the option value.  Before MySQL 5.1.41, this
     option applies only to TCP/IP connections and, prior to MySQL
     5.1.12, only for Windows.

   * `MYSQL_READ_DEFAULT_FILE' (argument type: `char *')

     Read options from the named option file instead of from `my.cnf'.

   * `MYSQL_READ_DEFAULT_GROUP' (argument type: `char *')

     Read options from the named group from `my.cnf' or the file
     specified with `MYSQL_READ_DEFAULT_FILE'.

   * `MYSQL_REPORT_DATA_TRUNCATION' (argument type: `my_bool *')

     Enable or disable reporting of data truncation errors for prepared
     statements using the `error' member of `MYSQL_BIND' structures.
     (Default: enabled.)

   * `MYSQL_SECURE_AUTH' (argument type: `my_bool *')

     Whether to connect to a server that does not support the password
     hashing used in MySQL 4.1.1 and later.

   * `MYSQL_SET_CHARSET_DIR' (argument type: `char *')

     The path name to the directory that contains character set
     definition files.

   * `MYSQL_SET_CHARSET_NAME' (argument type: `char *')

     The name of the character set to use as the default character set.

   * `MYSQL_SET_CLIENT_IP' (argument type: `char *')

     For an application linked against the `libmysqld' embedded server
     library (when `libmysqld' is compiled with authentication
     support), this means that the user is considered to have connected
     from the specified IP address (specified as a string) for
     authentication purposes. This option is ignored for applications
     linked against the `libmysqlclient' client library.

   * `MYSQL_SHARED_MEMORY_BASE_NAME' (argument type: `char *')

     The name of the shared-memory object for communication to the
     server on Windows, if the server supports shared-memory
     connections. Specify the same value as the
     `--shared-memory-base-name' option used for the *Note `mysqld':
     mysqld. server you want to connect to.

The `client' group is always read if you use `MYSQL_READ_DEFAULT_FILE'
or `MYSQL_READ_DEFAULT_GROUP'.

The specified group in the option file may contain the following
options.

This table lists options that may appear in the option file and
provides a description of each option.

Option                    Description
`character-sets-dir=PATH' The directory where character sets are
                          installed.
`compress'                Use the compressed client/server protocol.
`connect-timeout=SECONDS' Connect timeout in seconds. On Linux this
                          timeout is also used for waiting for the first
                          answer from the server.
`database=DB_NAME'        Connect to this database if no database was
                          specified in the connect command.
`debug'                   Debug options.
`default-character-set=CHARSET_NAME'The default character set to use.
`disable-local-infile'    Disable use of *Note `LOAD DATA LOCAL':
                          load-data.
`host=HOST_NAME'          Default host name.
`init-command=STMT'       Statement to execute when connecting to MySQL
                          server. Automatically re-executed if
                          reconnection occurs.
`interactive-timeout=SECONDS'Same as specifying `CLIENT_INTERACTIVE' to
                          *Note `mysql_real_connect()':
                          mysql-real-connect.  See *Note
                          mysql-real-connect::.
`local-infile[={0|1}]'    If no argument or nonzero argument, enable use
                          of *Note `LOAD DATA LOCAL': load-data.;
                          otherwise disable.
`max_allowed_packet=BYTES'Maximum size of packet that client can read
                          from server.
`multi-queries',          Enable multiple result sets from
`multi-results'           multiple-statement executions or stored
                          procedures.
`multi-statements'        Enable the client to send multiple statements
                          in a single string (separated by ``;'').
`password=PASSWORD'       Default password.
`pipe'                    Use named pipes to connect to a MySQL server
                          on Windows.
`port=PORT_NUM'           Default port number.
`protocol={TCP|SOCKET|PIPE|MEMORY}'The protocol to use when connecting to the
                          server.
`return-found-rows'       Tell *Note `mysql_info()': mysql-info. to
                          return found rows instead of updated rows when
                          using *Note `UPDATE': update.
`shared-memory-base-name=NAME'Shared-memory name to use to connect to server.
`socket=PATH'             Default socket file.
`ssl-ca=FILE_NAME'        Certificate Authority file.
`ssl-capath=PATH'         Certificate Authority directory.
`ssl-cert=FILE_NAME'      Certificate file.
`ssl-cipher=CIPHER_LIST'  Permissible SSL ciphers.
`ssl-key=FILE_NAME'       Key file.
`timeout=SECONDS'         Like `connect-timeout'.
`user'                    Default user.

`timeout' has been replaced by `connect-timeout', but `timeout' is
still supported in MySQL 5.1 for backward compatibility.

For more information about option files used by MySQL programs, see
*Note option-files::.

Before MySQL 5.1.18, the `arg' argument was declared as `char *'.

*Return Values*

Zero for success. Nonzero if you specify an unknown option.

*Example*

The following *Note `mysql_options()': mysql-options.  calls request
the use of compression in the client/server protocol, cause options to
be read from the `[odbc]' group of option files, and disable
transaction autocommit mode:


     MYSQL mysql;

     mysql_init(&mysql);
     mysql_options(&mysql,MYSQL_OPT_COMPRESS,0);
     mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"odbc");
     mysql_options(&mysql,MYSQL_INIT_COMMAND,"SET autocommit=0");
     if (!mysql_real_connect(&mysql,"host","user","passwd","database",0,NULL,0))
     {
         fprintf(stderr, "Failed to connect to database: Error: %s\n",
               mysql_error(&mysql));
     }

This code requests that the client use the compressed client/server
protocol and read the additional options from the `odbc' section in the
`my.cnf' file.


File: manual.info,  Node: mysql-ping,  Next: mysql-query,  Prev: mysql-options,  Up: c-api-functions

21.8.7.50 mysql_ping()
......................

`int mysql_ping(MYSQL *mysql)'

*Description*

Checks whether the connection to the server is working. If the
connection has gone down and auto-reconnect is enabled an attempt to
reconnect is made. If the connection is down and auto-reconnect is
disabled, *Note `mysql_ping()': mysql-ping. returns an error.

Auto-reconnect is disabled by default. To enable it, call *Note
`mysql_options()': mysql-options. with the `MYSQL_OPT_RECONNECT'
option. For details, see *Note mysql-options::.

*Note `mysql_ping()': mysql-ping. can be used by clients that remain
idle for a long while, to check whether the server has closed the
connection and reconnect if necessary.

If *Note `mysql_ping()': mysql-ping.) does cause a reconnect, there is
no explicit indication of it. To determine whether a reconnect occurs,
call *Note `mysql_thread_id()': mysql-thread-id. to get the original
connection identifier before calling *Note `mysql_ping()': mysql-ping,
then call *Note `mysql_thread_id()': mysql-thread-id. again to see
whether the identifier has changed.

If reconnect occurs, some characteristics of the connection will have
been reset. For details about these characteristics, see *Note
auto-reconnect::.

*Return Values*

Zero if the connection to the server is active. Nonzero if an error
occurred. A nonzero return does not indicate whether the MySQL server
itself is down; the connection might be broken for other reasons such
as network problems.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-query,  Next: mysql-real-connect,  Prev: mysql-ping,  Up: c-api-functions

21.8.7.51 mysql_query()
.......................

`int mysql_query(MYSQL *mysql, const char *stmt_str)'

*Description*

Executes the SQL statement pointed to by the null-terminated string
`stmt_str'. Normally, the string must consist of a single SQL statement
without a terminating semicolon (``;'') or `\g'. If multiple-statement
execution has been enabled, the string can contain several statements
separated by semicolons. See *Note c-api-multiple-queries::.

*Note `mysql_query()': mysql-query. cannot be used for statements that
contain binary data; you must use *Note `mysql_real_query()':
mysql-real-query. instead.  (Binary data may contain the ``\0''
character, which *Note `mysql_query()': mysql-query. interprets as the
end of the statement string.)

If you want to know whether the statement should return a result set,
you can use *Note `mysql_field_count()': mysql-field-count. to check for
this. See *Note mysql-field-count::.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-real-connect,  Next: mysql-real-escape-string,  Prev: mysql-query,  Up: c-api-functions

21.8.7.52 mysql_real_connect()
..............................

`MYSQL *mysql_real_connect(MYSQL *mysql, const char *host, const char
*user, const char *passwd, const char *db, unsigned int port, const
char *unix_socket, unsigned long client_flag)'

*Description*

*Note `mysql_real_connect()': mysql-real-connect. attempts to establish
a connection to a MySQL database engine running on `host'.  *Note
`mysql_real_connect()': mysql-real-connect. must complete successfully
before you can execute any other API functions that require a valid
`MYSQL' connection handle structure.

The parameters are specified as follows:

   * For the first parameter, specify the address of an existing
     `MYSQL' structure. Before calling *Note `mysql_real_connect()':
     mysql-real-connect, call *Note `mysql_init()': mysql-init. to
     initialize the `MYSQL' structure. You can change a lot of connect
     options with the *Note `mysql_options()': mysql-options. call. See
     *Note mysql-options::.

   * The value of `host' may be either a host name or an IP address. If
     `host' is `NULL' or the string `"localhost"', a connection to the
     local host is assumed. For Windows, the client connects using a
     shared-memory connection, if the server has shared-memory
     connections enabled. Otherwise, TCP/IP is used. For Unix, the
     client connects using a Unix socket file. For local connections,
     you can also influence the type of connection to use with the
     `MYSQL_OPT_PROTOCOL' or `MYSQL_OPT_NAMED_PIPE' options to *Note
     `mysql_options()': mysql-options. The type of connection must be
     supported by the server. For a `host' value of `"."' on Windows,
     the client connects using a named pipe, if the server has
     named-pipe connections enabled. If named-pipe connections are not
     enabled, an error occurs.

   * The `user' parameter contains the user's MySQL login ID. If `user'
     is `NULL' or the empty string `""', the current user is assumed.
     Under Unix, this is the current login name. Under Windows ODBC,
     the current user name must be specified explicitly. See the
     Connector/ODBC section of *Note connectors-apis::.

   * The `passwd' parameter contains the password for `user'. If
     `passwd' is `NULL', only entries in the `user' table for the user
     that have a blank (empty) password field are checked for a match.
     This enables the database administrator to set up the MySQL
     privilege system in such a way that users get different privileges
     depending on whether they have specified a password.

     *Note*:

     Do not attempt to encrypt the password before calling *Note
     `mysql_real_connect()': mysql-real-connect.; password encryption
     is handled automatically by the client API.

   * The `user' and `passwd' parameters use whatever character set has
     been configured for the `MYSQL' object. By default, this is
     `latin1', but can be changed by calling *Note
     `mysql_options(mysql, MYSQL_SET_CHARSET_NAME, "CHARSET_NAME")':
     mysql-options. prior to connecting.

   * `db' is the database name. If `db' is not `NULL', the connection
     sets the default database to this value.

   * If `port' is not 0, the value is used as the port number for the
     TCP/IP connection. Note that the `host' parameter determines the
     type of the connection.

   * If `unix_socket' is not `NULL', the string specifies the socket or
     named pipe to use. Note that the `host' parameter determines the
     type of the connection.

   * The value of `client_flag' is usually 0, but can be set to a
     combination of the following flags to enable certain features.

     This table lists flag names and provides a description of each.

     Flag Name               Flag Description
     `CLIENT_COMPRESS'       Use compression protocol.
     `CLIENT_FOUND_ROWS'     Return the number of found (matched) rows,
                             not the number of changed rows.
     `CLIENT_IGNORE_SIGPIPE' Prevents the client library from installing
                             a `SIGPIPE' signal handler. This can be
                             used to avoid conflicts with a handler that
                             the application has already installed.
     `CLIENT_IGNORE_SPACE'   Permit spaces after function names. Makes
                             all functions names reserved words.
     `CLIENT_INTERACTIVE'    Permit `interactive_timeout' seconds
                             (instead of `wait_timeout' seconds) of
                             inactivity before closing the connection.
                             The client's session `wait_timeout'
                             variable is set to the value of the session
                             `interactive_timeout' variable.
     `CLIENT_LOCAL_FILES'    Enable *Note `LOAD DATA LOCAL': load-data.
                             handling.
     `CLIENT_MULTI_RESULTS'  Tell the server that the client can handle
                             multiple result sets from
                             multiple-statement executions or stored
                             procedures.  This flag is automatically
                             enabled if `CLIENT_MULTI_STATEMENTS' is
                             enabled. See the note following this table
                             for more information about this flag.
     `CLIENT_MULTI_STATEMENTS'Tell the server that the client may send
                             multiple statements in a single string
                             (separated by ``;''). If this flag is not
                             set, multiple-statement execution is
                             disabled. See the note following this table
                             for more information about this flag.
     `CLIENT_NO_SCHEMA'      Do not permit the DB_NAME.TBL_NAME.COL_NAME
                             syntax. This is for ODBC. It causes the
                             parser to generate an error if you use that
                             syntax, which is useful for trapping bugs
                             in some ODBC programs.
     `CLIENT_ODBC'           Unused.
     `CLIENT_SSL'            Use SSL (encrypted protocol). Do not set
                             this option within an application program;
                             it is set internally in the client library.
                             Instead, use *Note `mysql_ssl_set()':
                             mysql-ssl-set.  before calling *Note
                             `mysql_real_connect()': mysql-real-connect.
     `CLIENT_REMEMBER_OPTIONS'Remember options specified by calls to
                             *Note `mysql_options()': mysql-options.
                             Without this option, if *Note
                             `mysql_real_connect()': mysql-real-connect.
                             fails, you must repeat the *Note
                             `mysql_options()': mysql-options.  calls
                             before trying to connect again. With this
                             option, the *Note `mysql_options()':
                             mysql-options.  calls need not be repeated.

If your program uses *Note `CALL': call.  statements to execute stored
procedures, the `CLIENT_MULTI_RESULTS' flag must be enabled.  This is
because each *Note `CALL': call. returns a result to indicate the call
status, in addition to any result sets that might be returned by
statements executed within the procedure. Because *Note `CALL': call.
can return multiple results, process them using a loop that calls *Note
`mysql_next_result()': mysql-next-result. to determine whether there
are more results.

`CLIENT_MULTI_RESULTS' can be enabled when you call *Note
`mysql_real_connect()': mysql-real-connect, either explicitly by
passing the `CLIENT_MULTI_RESULTS' flag itself, or implicitly by
passing `CLIENT_MULTI_STATEMENTS' (which also enables
`CLIENT_MULTI_RESULTS').

If you enable `CLIENT_MULTI_STATEMENTS' or `CLIENT_MULTI_RESULTS', you
should process the result for every call to *Note `mysql_query()':
mysql-query. or *Note `mysql_real_query()': mysql-real-query. by using a
loop that calls *Note `mysql_next_result()': mysql-next-result. to
determine whether there are more results. For an example, see *Note
c-api-multiple-queries::.

For some parameters, it is possible to have the value taken from an
option file rather than from an explicit value in the *Note
`mysql_real_connect()': mysql-real-connect. call. To do this, call
*Note `mysql_options()': mysql-options. with the
`MYSQL_READ_DEFAULT_FILE' or `MYSQL_READ_DEFAULT_GROUP' option before
calling *Note `mysql_real_connect()': mysql-real-connect.  Then, in the
*Note `mysql_real_connect()': mysql-real-connect. call, specify the
`no-value' value for each parameter to be read from an option file:

   * For `host', specify a value of `NULL' or the empty string (`""').

   * For `user', specify a value of `NULL' or the empty string.

   * For `passwd', specify a value of `NULL'. (For the password, a
     value of the empty string in the *Note `mysql_real_connect()':
     mysql-real-connect. call cannot be overridden in an option file,
     because the empty string indicates explicitly that the MySQL
     account must have an empty password.)

   * For `db', specify a value of `NULL' or the empty string.

   * For `port', specify a value of 0.

   * For `unix_socket', specify a value of `NULL'.

If no value is found in an option file for a parameter, its default
value is used as indicated in the descriptions given earlier in this
section.

*Return Values*

A `MYSQL*' connection handle if the connection was successful, `NULL'
if the connection was unsuccessful. For a successful connection, the
return value is the same as the value of the first parameter.

*Errors*

   * `CR_CONN_HOST_ERROR'

     Failed to connect to the MySQL server.

   * `CR_CONNECTION_ERROR'

     Failed to connect to the local MySQL server.

   * `CR_IPSOCK_ERROR'

     Failed to create an IP socket.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SOCKET_CREATE_ERROR'

     Failed to create a Unix socket.

   * `CR_UNKNOWN_HOST'

     Failed to find the IP address for the host name.

   * `CR_VERSION_ERROR'

     A protocol mismatch resulted from attempting to connect to a
     server with a client library that uses a different protocol
     version.

   * `CR_NAMEDPIPEOPEN_ERROR'

     Failed to create a named pipe on Windows.

   * `CR_NAMEDPIPEWAIT_ERROR'

     Failed to wait for a named pipe on Windows.

   * `CR_NAMEDPIPESETSTATE_ERROR'

     Failed to get a pipe handler on Windows.

   * `CR_SERVER_LOST'

     If `connect_timeout' > 0 and it took longer than `connect_timeout'
     seconds to connect to the server or if the server died while
     executing the `init-command'.

*Example*


     MYSQL mysql;

     mysql_init(&mysql);
     mysql_options(&mysql,MYSQL_READ_DEFAULT_GROUP,"your_prog_name");
     if (!mysql_real_connect(&mysql,"host","user","passwd","database",0,NULL,0))
     {
         fprintf(stderr, "Failed to connect to database: Error: %s\n",
               mysql_error(&mysql));
     }

By using *Note `mysql_options()': mysql-options. the MySQL library
reads the `[client]' and `[your_prog_name]' sections in the `my.cnf'
file which ensures that your program works, even if someone has set up
MySQL in some nonstandard way.

Note that upon connection, *Note `mysql_real_connect()':
mysql-real-connect. sets the `reconnect' flag (part of the `MYSQL'
structure) to a value of `1' in versions of the API older than 5.0.3, or
`0' in newer versions. A value of `1' for this flag indicates that if a
statement cannot be performed because of a lost connection, to try
reconnecting to the server before giving up. You can use the
`MYSQL_OPT_RECONNECT' option to *Note `mysql_options()': mysql-options.
to control reconnection behavior.


File: manual.info,  Node: mysql-real-escape-string,  Next: mysql-real-query,  Prev: mysql-real-connect,  Up: c-api-functions

21.8.7.53 mysql_real_escape_string()
....................................

`unsigned long mysql_real_escape_string(MYSQL *mysql, char *to, const
char *from, unsigned long length)'

Note that `mysql' must be a valid, open connection. This is needed
because the escaping depends on the character set in use by the server.

*Description*

This function is used to create a legal SQL string that you can use in
an SQL statement. See *Note string-literals::.

The string in `from' is encoded to an escaped SQL string, taking into
account the current character set of the connection. The result is
placed in `to' and a terminating null byte is appended. Characters
encoded are ``\'', ``''', ``"'', `NUL' (ASCII 0), ``\n'', ``\r'', and
Control+Z. Strictly speaking, MySQL requires only that backslash and
the quote character used to quote the string in the query be escaped.
*Note `mysql_real_escape_string()': mysql-real-escape-string.  quotes
the other characters to make them easier to read in log files. For
comparison, see the quoting rules for literal strings and the `QUOTE()'
SQL function in *Note string-literals::, and *Note string-functions::.

The string pointed to by `from' must be `length' bytes long. You must
allocate the `to' buffer to be at least `length*2+1' bytes long. (In
the worst case, each character may need to be encoded as using two
bytes, and you need room for the terminating null byte.) When *Note
`mysql_real_escape_string()': mysql-real-escape-string.  returns, the
contents of `to' is a null-terminated string. The return value is the
length of the encoded string, not including the terminating null
character.

If you need to change the character set of the connection, use the
*Note `mysql_set_character_set()': mysql-set-character-set.  function
rather than executing a `SET NAMES' (or `SET CHARACTER SET') statement.
*Note `mysql_set_character_set()': mysql-set-character-set. works like
`SET NAMES' but also affects the character set used by *Note
`mysql_real_escape_string()': mysql-real-escape-string, which `SET
NAMES' does not.

*Example*


     char query[1000],*end;

     end = strmov(query,"INSERT INTO test_table values(");
     *end++ = '\'';
     end += mysql_real_escape_string(&mysql, end,"What is this",12);
     *end++ = '\'';
     *end++ = ',';
     *end++ = '\'';
     end += mysql_real_escape_string(&mysql, end,"binary data: \0\r\n",16);
     *end++ = '\'';
     *end++ = ')';

     if (mysql_real_query(&mysql,query,(unsigned int) (end - query)))
     {
        fprintf(stderr, "Failed to insert row, Error: %s\n",
                mysql_error(&mysql));
     }

The `strmov()' function used in the example is included in the
`libmysqlclient' library and works like `strcpy()' but returns a
pointer to the terminating null of the first parameter.

*Return Values*

The length of the value placed into `to', not including the terminating
null character.

*Errors*

None.


File: manual.info,  Node: mysql-real-query,  Next: mysql-refresh,  Prev: mysql-real-escape-string,  Up: c-api-functions

21.8.7.54 mysql_real_query()
............................

`int mysql_real_query(MYSQL *mysql, const char *stmt_str, unsigned long
length)'

*Description*

Executes the SQL statement pointed to by `stmt_str', a string `length'
bytes long. Normally, the string must consist of a single SQL statement
without a terminating semicolon (``;'') or `\g'.  If multiple-statement
execution has been enabled, the string can contain several statements
separated by semicolons. See *Note c-api-multiple-queries::.

*Note `mysql_query()': mysql-query. cannot be used for statements that
contain binary data; you must use *Note `mysql_real_query()':
mysql-real-query. instead.  (Binary data may contain the ``\0''
character, which *Note `mysql_query()': mysql-query. interprets as the
end of the statement string.) In addition, *Note `mysql_real_query()':
mysql-real-query. is faster than *Note `mysql_query()': mysql-query.
because it does not call `strlen()' on the statement string.

If you want to know whether the statement should return a result set,
you can use *Note `mysql_field_count()': mysql-field-count. to check for
this. See *Note mysql-field-count::.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-refresh,  Next: mysql-reload,  Prev: mysql-real-query,  Up: c-api-functions

21.8.7.55 mysql_refresh()
.........................

`int mysql_refresh(MYSQL *mysql, unsigned int options)'

*Description*

This function flushes tables or caches, or resets replication server
information. The connected user must have the `RELOAD' privilege.

The `options' argument is a bit mask composed from any combination of
the following values. Multiple values can be OR'ed together to perform
multiple operations with a single call.

   * `REFRESH_GRANT'

     Refresh the grant tables, like *Note `FLUSH PRIVILEGES': flush.

   * `REFRESH_LOG'

     Flush the logs, like *Note `FLUSH LOGS': flush.

   * `REFRESH_TABLES'

     Flush the table cache, like *Note `FLUSH TABLES': flush.

   * `REFRESH_HOSTS'

     Flush the host cache, like *Note `FLUSH HOSTS': flush.

   * `REFRESH_STATUS'

     Reset status variables, like *Note `FLUSH STATUS': flush.

   * `REFRESH_THREADS'

     Flush the thread cache.

   * `REFRESH_SLAVE'

     On a slave replication server, reset the master server information
     and restart the slave, like *Note `RESET SLAVE': reset-slave.

   * `REFRESH_MASTER'

     On a master replication server, remove the binary log files listed
     in the binary log index and truncate the index file, like *Note
     `RESET MASTER': reset-master.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-reload,  Next: mysql-rollback,  Prev: mysql-refresh,  Up: c-api-functions

21.8.7.56 mysql_reload()
........................

`int mysql_reload(MYSQL *mysql)'

*Description*

Asks the MySQL server to reload the grant tables. The connected user
must have the `RELOAD' privilege.

This function is deprecated. It is preferable to use *Note
`mysql_query()': mysql-query. to issue an SQL *Note `FLUSH PRIVILEGES':
flush. statement instead.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-rollback,  Next: mysql-row-seek,  Prev: mysql-reload,  Up: c-api-functions

21.8.7.57 mysql_rollback()
..........................

`my_bool mysql_rollback(MYSQL *mysql)'

*Description*

Rolls back the current transaction.

The action of this function is subject to the value of the
`completion_type' system variable. In particular, if the value of
`completion_type' is 2, the server performs a release after terminating
a transaction and closes the client connection. The client program
should call *Note `mysql_close()': mysql-close. to close the connection
from the client side.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-row-seek,  Next: mysql-row-tell,  Prev: mysql-rollback,  Up: c-api-functions

21.8.7.58 mysql_row_seek()
..........................

`MYSQL_ROW_OFFSET mysql_row_seek(MYSQL_RES *result, MYSQL_ROW_OFFSET
offset)'

*Description*

Sets the row cursor to an arbitrary row in a query result set.  The
`offset' value is a row offset, typically a value returned from *Note
`mysql_row_tell()': mysql-row-tell. or from *Note `mysql_row_seek()':
mysql-row-seek. This value is not a row number; to seek to a row within
a result set by number, use *Note `mysql_data_seek()': mysql-data-seek.
instead.

This function requires that the result set structure contains the
entire result of the query, so *Note `mysql_row_seek()':
mysql-row-seek. may be used only in conjunction with *Note
`mysql_store_result()': mysql-store-result, not with *Note
`mysql_use_result()': mysql-use-result.

*Return Values*

The previous value of the row cursor. This value may be passed to a
subsequent call to *Note `mysql_row_seek()': mysql-row-seek.

*Errors*

None.


File: manual.info,  Node: mysql-row-tell,  Next: mysql-select-db,  Prev: mysql-row-seek,  Up: c-api-functions

21.8.7.59 mysql_row_tell()
..........................

`MYSQL_ROW_OFFSET mysql_row_tell(MYSQL_RES *result)'

*Description*

Returns the current position of the row cursor for the last *Note
`mysql_fetch_row()': mysql-fetch-row. This value can be used as an
argument to *Note `mysql_row_seek()': mysql-row-seek.

Use *Note `mysql_row_tell()': mysql-row-tell. only after *Note
`mysql_store_result()': mysql-store-result, not after *Note
`mysql_use_result()': mysql-use-result.

*Return Values*

The current offset of the row cursor.

*Errors*

None.


File: manual.info,  Node: mysql-select-db,  Next: mysql-set-character-set,  Prev: mysql-row-tell,  Up: c-api-functions

21.8.7.60 mysql_select_db()
...........................

`int mysql_select_db(MYSQL *mysql, const char *db)'

*Description*

Causes the database specified by `db' to become the default (current)
database on the connection specified by `mysql'. In subsequent queries,
this database is the default for table references that include no
explicit database specifier.

*Note `mysql_select_db()': mysql-select-db. fails unless the connected
user can be authenticated as having permission to use the database.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-set-character-set,  Next: mysql-set-local-infile-default,  Prev: mysql-select-db,  Up: c-api-functions

21.8.7.61 mysql_set_character_set()
...................................

`int mysql_set_character_set(MYSQL *mysql, const char *csname)'

*Description*

This function is used to set the default character set for the current
connection. The string `csname' specifies a valid character set name.
The connection collation becomes the default collation of the character
set. This function works like the `SET NAMES' statement, but also sets
the value of `mysql->charset', and thus affects the character set used
by *Note `mysql_real_escape_string()': mysql-real-escape-string.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Example*


     MYSQL mysql;

     mysql_init(&mysql);
     if (!mysql_real_connect(&mysql,"host","user","passwd","database",0,NULL,0))
     {
         fprintf(stderr, "Failed to connect to database: Error: %s\n",
               mysql_error(&mysql));
     }

     if (!mysql_set_character_set(&mysql, "utf8"))
     {
         printf("New client character set: %s\n",
                mysql_character_set_name(&mysql));
     }


File: manual.info,  Node: mysql-set-local-infile-default,  Next: mysql-set-local-infile-handler,  Prev: mysql-set-character-set,  Up: c-api-functions

21.8.7.62 mysql_set_local_infile_default()
..........................................

`void mysql_set_local_infile_default(MYSQL *mysql);'

*Description*

Sets the `LOAD LOCAL DATA INFILE' handler callback functions to the
defaults used internally by the C client library. The library calls
this function automatically if *Note
`mysql_set_local_infile_handler()': mysql-set-local-infile-handler.
has not been called or does not supply valid functions for each of its
callbacks.

*Return Values*

None.

*Errors*

None.


File: manual.info,  Node: mysql-set-local-infile-handler,  Next: mysql-set-server-option,  Prev: mysql-set-local-infile-default,  Up: c-api-functions

21.8.7.63 mysql_set_local_infile_handler()
..........................................

`void mysql_set_local_infile_handler(MYSQL *mysql, int
(*local_infile_init)(void **, const char *, void *), int
(*local_infile_read)(void *, char *, unsigned int), void
(*local_infile_end)(void *), int (*local_infile_error)(void *, char*,
unsigned int), void *userdata);'

*Description*

This function installs callbacks to be used during the execution of
*Note `LOAD DATA LOCAL INFILE': load-data. statements. It enables
application programs to exert control over local (client-side) data
file reading. The arguments are the connection handler, a set of
pointers to callback functions, and a pointer to a data area that the
callbacks can use to share information.

To use *Note `mysql_set_local_infile_handler()':
mysql-set-local-infile-handler, you must write the following callback
functions:


     int
     local_infile_init(void **ptr, const char *filename, void *userdata);

The initialization function. This is called once to do any setup
necessary, open the data file, allocate data structures, and so forth.
The first `void**' argument is a pointer to a pointer. You can set the
pointer (that is, `*ptr') to a value that will be passed to each of the
other callbacks (as a `void*'). The callbacks can use this pointed-to
value to maintain state information. The `userdata' argument is the
same value that is passed to *Note `mysql_set_local_infile_handler()':
mysql-set-local-infile-handler.

The initialization function should return zero for success, nonzero for
an error.


     int
     local_infile_read(void *ptr, char *buf, unsigned int buf_len);

The data-reading function. This is called repeatedly to read the data
file. `buf' points to the buffer where the read data is stored, and
`buf_len' is the maximum number of bytes that the callback can read and
store in the buffer. (It can read fewer bytes, but should not read
more.)

The return value is the number of bytes read, or zero when no more data
could be read (this indicates EOF). Return a value less than zero if an
error occurs.


     void
     local_infile_end(void *ptr)

The termination function. This is called once after
`local_infile_read()' has returned zero (EOF) or an error. Within this
function, deallocate any memory allocated by `local_infile_init()' and
perform any other cleanup necessary. It is invoked even if the
initialization function returns an error.


     int
     local_infile_error(void *ptr,
                        char *error_msg,
                        unsigned int error_msg_len);

The error-handling function. This is called to get a textual error
message to return to the user in case any of your other functions
returns an error. `error_msg' points to the buffer into which the
message is written, and `error_msg_len' is the length of the buffer.
Write the message as a null-terminated string, at most
`error_msg_len'-1 bytes long.

The return value is the error number.

Typically, the other callbacks store the error message in the data
structure pointed to by `ptr', so that `local_infile_error()' can copy
the message from there into `error_msg'.

After calling *Note `mysql_set_local_infile_handler()':
mysql-set-local-infile-handler.  in your C code and passing pointers to
your callback functions, you can then issue a *Note `LOAD DATA LOCAL
INFILE': load-data. statement (for example, by using *Note
`mysql_query()': mysql-query.). The client library automatically
invokes your callbacks. The file name specified in *Note `LOAD DATA
LOCAL INFILE': load-data. will be passed as the second parameter to the
`local_infile_init()' callback.

*Return Values*

None.

*Errors*

None.


File: manual.info,  Node: mysql-set-server-option,  Next: mysql-shutdown,  Prev: mysql-set-local-infile-handler,  Up: c-api-functions

21.8.7.64 mysql_set_server_option()
...................................

`int mysql_set_server_option(MYSQL *mysql, enum enum_mysql_set_option
option)'

*Description*

Enables or disables an option for the connection.  `option' can have
one of the following values.

This table lists options for *Note `mysql_set_server_option()':
mysql-set-server-option. and provides a description of each option.

Option                               Description
`MYSQL_OPTION_MULTI_STATEMENTS_ON'   Enable multiple-statement support
`MYSQL_OPTION_MULTI_STATEMENTS_OFF'  Disable multiple-statement support

If you enable multiple-statement support, you should retrieve results
from calls to *Note `mysql_query()': mysql-query. or *Note
`mysql_real_query()': mysql-real-query. by using a loop that calls
*Note `mysql_next_result()': mysql-next-result. to determine whether
there are more results. For an example, see *Note
c-api-multiple-queries::.

Enabling multiple-statement support with
`MYSQL_OPTION_MULTI_STATEMENTS_ON' does not have quite the same effect
as enabling it by passing the `CLIENT_MULTI_STATEMENTS' flag to *Note
`mysql_real_connect()': mysql-real-connect.: `CLIENT_MULTI_STATEMENTS'
also enables `CLIENT_MULTI_RESULTS'. If you are using the *Note `CALL':
call. SQL statement in your programs, multiple-result support must be
enabled; this means that `MYSQL_OPTION_MULTI_STATEMENTS_ON' by itself
is insufficient to permit the use of *Note `CALL': call.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `ER_UNKNOWN_COM_ERROR'

     The server did not support *Note `mysql_set_server_option()':
     mysql-set-server-option.  (which is the case that the server is
     older than 4.1.1) or the server did not support the option one
     tried to set.


File: manual.info,  Node: mysql-shutdown,  Next: mysql-sqlstate,  Prev: mysql-set-server-option,  Up: c-api-functions

21.8.7.65 mysql_shutdown()
..........................

`int mysql_shutdown(MYSQL *mysql, enum mysql_enum_shutdown_level
shutdown_level)'

*Description*

Asks the database server to shut down. The connected user must have the
`SHUTDOWN' privilege.  MySQL 5.1 servers support only one type of
shutdown; `shutdown_level' must be equal to `SHUTDOWN_DEFAULT'.
Additional shutdown levels are planned to make it possible to choose
the desired level.  Dynamically linked executables which have been
compiled with older versions of the `libmysqlclient' headers and call
*Note `mysql_shutdown()': mysql-shutdown. need to be used with the old
`libmysqlclient' dynamic library.

The shutdown process is described in *Note server-shutdown::.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-sqlstate,  Next: mysql-ssl-set,  Prev: mysql-shutdown,  Up: c-api-functions

21.8.7.66 mysql_sqlstate()
..........................

`const char *mysql_sqlstate(MYSQL *mysql)'

*Description*

Returns a null-terminated string containing the SQLSTATE error code for
the most recently executed SQL statement. The error code consists of
five characters. `'00000'' means `no error.' The values are specified
by ANSI SQL and ODBC. For a list of possible values, see *Note
error-handling::.

SQLSTATE values returned by *Note `mysql_sqlstate()': mysql-sqlstate.
differ from MySQL-specific error numbers returned by *Note
`mysql_errno()': mysql-errno. For example, the *Note `mysql': mysql.
client program displays errors using the following format, where `1146'
is the *Note `mysql_errno()': mysql-errno. value and `'42S02'' is the
corresponding *Note `mysql_sqlstate()': mysql-sqlstate. value:


     shell> SELECT * FROM no_such_table;
     ERROR 1146 (42S02): Table 'test.no_such_table' doesn't exist

Not all MySQL error numbers are mapped to SQLSTATE error codes.  The
value `'HY000'' (general error) is used for unmapped error numbers.

If you call *Note `mysql_sqlstate()': mysql-sqlstate.  after *Note
`mysql_real_connect()': mysql-real-connect.  fails, *Note
`mysql_sqlstate()': mysql-sqlstate. might not return a useful value.
For example, this happens if a host is blocked by the server and the
connection is closed without any SQLSTATE value being sent to the
client.

*Return Values*

A null-terminated character string containing the SQLSTATE error code.

*See Also*

See *Note mysql-errno::, *Note mysql-error::, and *Note
mysql-stmt-sqlstate::.


File: manual.info,  Node: mysql-ssl-set,  Next: mysql-stat,  Prev: mysql-sqlstate,  Up: c-api-functions

21.8.7.67 mysql_ssl_set()
.........................

`my_bool mysql_ssl_set(MYSQL *mysql, const char *key, const char *cert,
const char *ca, const char *capath, const char *cipher)'

*Description*

*Note `mysql_ssl_set()': mysql-ssl-set. is used for establishing secure
connections using SSL. It must be called before *Note
`mysql_real_connect()': mysql-real-connect.

*Note `mysql_ssl_set()': mysql-ssl-set. does nothing unless SSL support
is enabled in the client library.

`mysql' is the connection handler returned from *Note `mysql_init()':
mysql-init. The other parameters are specified as follows:

   * `key' is the path name to the key file.

   * `cert' is the path name to the certificate file.

   * `ca' is the path name to the certificate authority file.

   * `capath' is the path name to a directory that contains trusted SSL
     CA certificates in PEM format.

   * `cipher' is a list of permissible ciphers to use for SSL
     encryption.

Any unused SSL parameters may be given as `NULL'.

*Return Values*

This function always returns `0'. If SSL setup is incorrect, *Note
`mysql_real_connect()': mysql-real-connect. returns an error when you
attempt to connect.


File: manual.info,  Node: mysql-stat,  Next: mysql-store-result,  Prev: mysql-ssl-set,  Up: c-api-functions

21.8.7.68 mysql_stat()
......................

`const char *mysql_stat(MYSQL *mysql)'

*Description*

Returns a character string containing information similar to that
provided by the *Note `mysqladmin status': mysqladmin.  command. This
includes uptime in seconds and the number of running threads,
questions, reloads, and open tables.

*Return Values*

A character string describing the server status.  `NULL' if an error
occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-store-result,  Next: mysql-thread-id,  Prev: mysql-stat,  Up: c-api-functions

21.8.7.69 mysql_store_result()
..............................

`MYSQL_RES *mysql_store_result(MYSQL *mysql)'

*Description*

After invoking *Note `mysql_query()': mysql-query. or *Note
`mysql_real_query()': mysql-real-query, you must call *Note
`mysql_store_result()': mysql-store-result. or *Note
`mysql_use_result()': mysql-use-result. for every statement that
successfully produces a result set (*Note `SELECT': select, *Note
`SHOW': show, *Note `DESCRIBE': describe, *Note `EXPLAIN': explain,
*Note `CHECK TABLE': check-table, and so forth). You must also call
*Note `mysql_free_result()': mysql-free-result. after you are done with
the result set.

You need not call *Note `mysql_store_result()': mysql-store-result. or
*Note `mysql_use_result()': mysql-use-result. for other statements, but
it does not do any harm or cause any notable performance degradation if
you call *Note `mysql_store_result()': mysql-store-result. in all
cases. You can detect whether the statement has a result set by
checking whether *Note `mysql_store_result()': mysql-store-result.
returns a nonzero value (more about this later).

If you enable multiple-statement support, you should retrieve results
from calls to *Note `mysql_query()': mysql-query. or *Note
`mysql_real_query()': mysql-real-query. by using a loop that calls
*Note `mysql_next_result()': mysql-next-result. to determine whether
there are more results. For an example, see *Note
c-api-multiple-queries::.

If you want to know whether a statement should return a result set, you
can use *Note `mysql_field_count()': mysql-field-count. to check for
this. See *Note mysql-field-count::.

*Note `mysql_store_result()': mysql-store-result. reads the entire
result of a query to the client, allocates a `MYSQL_RES' structure, and
places the result into this structure.

*Note `mysql_store_result()': mysql-store-result. returns a null
pointer if the statement did not return a result set (for example, if
it was an *Note `INSERT': insert.  statement).

*Note `mysql_store_result()': mysql-store-result. also returns a null
pointer if reading of the result set failed. You can check whether an
error occurred by checking whether *Note `mysql_error()': mysql-error.
returns a nonempty string, *Note `mysql_errno()': mysql-errno. returns
nonzero, or *Note `mysql_field_count()': mysql-field-count.  returns
zero.

An empty result set is returned if there are no rows returned.  (An
empty result set differs from a null pointer as a return value.)

After you have called *Note `mysql_store_result()': mysql-store-result.
and gotten back a result that is not a null pointer, you can call *Note
`mysql_num_rows()': mysql-num-rows. to find out how many rows are in
the result set.

You can call *Note `mysql_fetch_row()': mysql-fetch-row.  to fetch rows
from the result set, or *Note `mysql_row_seek()': mysql-row-seek. and
*Note `mysql_row_tell()': mysql-row-tell. to obtain or set the current
row position within the result set.

See *Note null-mysql-store-result::.

*Return Values*

A `MYSQL_RES' result structure with the results. `NULL' (0) if an error
occurred.

*Errors*

*Note `mysql_store_result()': mysql-store-result. resets *Note
`mysql_error()': mysql-error. and *Note `mysql_errno()': mysql-errno.
if it succeeds.

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-thread-id,  Next: mysql-use-result,  Prev: mysql-store-result,  Up: c-api-functions

21.8.7.70 mysql_thread_id()
...........................

`unsigned long mysql_thread_id(MYSQL *mysql)'

*Description*

Returns the thread ID of the current connection. This value can be used
as an argument to *Note `mysql_kill()': mysql-kill. to kill the thread.

If the connection is lost and you reconnect with *Note `mysql_ping()':
mysql-ping, the thread ID changes. This means you should not get the
thread ID and store it for later. You should get it when you need it.

*Note*:

This function does not work correctly if thread IDs become larger than
32 bits, which can occur on some systems. To avoid problems with *Note
`mysql_thread_id()': mysql-thread-id, do not use it. To get the
connection ID, execute a `SELECT CONNECTION_ID()' query and retrieve
the result.

*Return Values*

The thread ID of the current connection.

*Errors*

None.


File: manual.info,  Node: mysql-use-result,  Next: mysql-warning-count,  Prev: mysql-thread-id,  Up: c-api-functions

21.8.7.71 mysql_use_result()
............................

`MYSQL_RES *mysql_use_result(MYSQL *mysql)'

*Description*

After invoking *Note `mysql_query()': mysql-query. or *Note
`mysql_real_query()': mysql-real-query, you must call *Note
`mysql_store_result()': mysql-store-result. or *Note
`mysql_use_result()': mysql-use-result. for every statement that
successfully produces a result set (*Note `SELECT': select, *Note
`SHOW': show, *Note `DESCRIBE': describe, *Note `EXPLAIN': explain,
*Note `CHECK TABLE': check-table, and so forth). You must also call
*Note `mysql_free_result()': mysql-free-result. after you are done with
the result set.

*Note `mysql_use_result()': mysql-use-result. initiates a result set
retrieval but does not actually read the result set into the client like
*Note `mysql_store_result()': mysql-store-result. does.  Instead, each
row must be retrieved individually by making calls to *Note
`mysql_fetch_row()': mysql-fetch-row. This reads the result of a query
directly from the server without storing it in a temporary table or
local buffer, which is somewhat faster and uses much less memory than
*Note `mysql_store_result()': mysql-store-result. The client allocates
memory only for the current row and a communication buffer that may
grow up to `max_allowed_packet' bytes.

On the other hand, you should not use *Note `mysql_use_result()':
mysql-use-result. if you are doing a lot of processing for each row on
the client side, or if the output is sent to a screen on which the user
may type a `^S' (stop scroll). This ties up the server and prevent
other threads from updating any tables from which the data is being
fetched.

When using *Note `mysql_use_result()': mysql-use-result, you must
execute *Note `mysql_fetch_row()': mysql-fetch-row. until a `NULL'
value is returned, otherwise, the unfetched rows are returned as part
of the result set for your next query. The C API gives the error
`Commands out of sync; you can't run this command now' if you forget to
do this!

You may not use *Note `mysql_data_seek()': mysql-data-seek, *Note
`mysql_row_seek()': mysql-row-seek, *Note `mysql_row_tell()':
mysql-row-tell, *Note `mysql_num_rows()': mysql-num-rows, or *Note
`mysql_affected_rows()': mysql-affected-rows. with a result returned
from *Note `mysql_use_result()': mysql-use-result, nor may you issue
other queries until *Note `mysql_use_result()': mysql-use-result. has
finished.  (However, after you have fetched all the rows, *Note
`mysql_num_rows()': mysql-num-rows. accurately returns the number of
rows fetched.)

You must call *Note `mysql_free_result()': mysql-free-result. once you
are done with the result set.

When using the `libmysqld' embedded server, the memory benefits are
essentially lost because memory usage incrementally increases with each
row retrieved until *Note `mysql_free_result()': mysql-free-result. is
called.

*Return Values*

A `MYSQL_RES' result structure.  `NULL' if an error occurred.

*Errors*

*Note `mysql_use_result()': mysql-use-result. resets *Note
`mysql_error()': mysql-error. and *Note `mysql_errno()': mysql-errno.
if it succeeds.

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-warning-count,  Prev: mysql-use-result,  Up: c-api-functions

21.8.7.72 mysql_warning_count()
...............................

`unsigned int mysql_warning_count(MYSQL *mysql)'

*Description*

Returns the number of errors, warnings, and notes generated during
execution of the previous SQL statement.

*Return Values*

The warning count.

*Errors*

None.


File: manual.info,  Node: c-api-prepared-statements,  Next: c-api-prepared-statement-data-structures,  Prev: c-api-functions,  Up: c-api

21.8.8 C API Prepared Statements
--------------------------------

The MySQL client/server protocol provides for the use of prepared
statements. This capability uses the `MYSQL_STMT' statement handler
data structure returned by the *Note `mysql_stmt_init()':
mysql-stmt-init. initialization function. Prepared execution is an
efficient way to execute a statement more than once. The statement is
first parsed to prepare it for execution. Then it is executed one or
more times at a later time, using the statement handle returned by the
initialization function.

Prepared execution is faster than direct execution for statements
executed more than once, primarily because the query is parsed only
once. In the case of direct execution, the query is parsed every time
it is executed. Prepared execution also can provide a reduction of
network traffic because for each execution of the prepared statement,
it is necessary only to send the data for the parameters.

Prepared statements might not provide a performance increase in some
situations. For best results, test your application both with prepared
and nonprepared statements and choose whichever yields best performance.

Another advantage of prepared statements is that it uses a binary
protocol that makes data transfer between client and server more
efficient.

For a list of SQL statements that can be used as prepared statements,
see *Note sql-syntax-prepared-statements::.

As of MySQL 5.1.25, metadata changes to tables or views referred to by
prepared statements are detected and cause automatic repreparation of
the statement when it is next executed. For more information, see *Note
statement-repreparation::.


File: manual.info,  Node: c-api-prepared-statement-data-structures,  Next: c-api-prepared-statement-function-overview,  Prev: c-api-prepared-statements,  Up: c-api

21.8.9 C API Prepared Statement Data Structures
-----------------------------------------------

* Menu:

* c-api-prepared-statement-type-codes::  C API Prepared Statement Type Codes
* c-api-prepared-statement-type-conversions::  C API Prepared Statement Type Conversions

Prepared statements use several data structures:

   * To obtain a statement handle, pass a `MYSQL' connection handler to
     *Note `mysql_stmt_init()': mysql-stmt-init, which returns a
     pointer to a `MYSQL_STMT' data structure. This structure is used
     for further operations with the statement. To specify the
     statement to prepare, pass the `MYSQL_STMT' pointer and the
     statement string to *Note `mysql_stmt_prepare()':
     mysql-stmt-prepare.

   * To provide input parameters for a prepared statement, set up
     `MYSQL_BIND' structures and pass them to *Note
     `mysql_stmt_bind_param()': mysql-stmt-bind-param. To receive
     output column values, set up `MYSQL_BIND' structures and pass them
     to *Note `mysql_stmt_bind_result()': mysql-stmt-bind-result.

   * The `MYSQL_TIME' structure is used to transfer temporal data in
     both directions.

The following discussion describes the prepared statement data types in
detail. For examples that show how to use them, see *Note
mysql-stmt-execute::, and *Note mysql-stmt-fetch::.

   * `MYSQL_STMT'

     This structure is a handle for a prepared statement. A handle is
     created by calling *Note `mysql_stmt_init()': mysql-stmt-init,
     which returns a pointer to a `MYSQL_STMT'. The handle is used for
     all subsequent operations with the statement until you close it
     with *Note `mysql_stmt_close()': mysql-stmt-close, at which point
     the handle becomes invalid.

     The `MYSQL_STMT' structure has no members intended for application
     use. Applications should not try to copy a `MYSQL_STMT' structure.
     There is no guarantee that such a copy will be usable.

     Multiple statement handles can be associated with a single
     connection. The limit on the number of handles depends on the
     available system resources.

   * `MYSQL_BIND'

     This structure is used both for statement input (data values sent
     to the server) and output (result values returned from the server):

        * For input, use `MYSQL_BIND' structures with *Note
          `mysql_stmt_bind_param()': mysql-stmt-bind-param. to bind
          parameter data values to buffers for use by *Note
          `mysql_stmt_execute()': mysql-stmt-execute.

        * For output, use `MYSQL_BIND' structures with *Note
          `mysql_stmt_bind_result()': mysql-stmt-bind-result.  to bind
          buffers to result set columns, for use in fetching rows with
          *Note `mysql_stmt_fetch()': mysql-stmt-fetch.

     To use a `MYSQL_BIND' structure, zero its contents to initialize
     it, then set its members appropriately.  For example, to declare
     and initialize an array of three `MYSQL_BIND' structures, use this
     code:


          MYSQL_BIND bind[3];
          memset(bind, 0, sizeof(bind));

     The `MYSQL_BIND' structure contains the following members for use
     by application programs. For several of the members, the manner of
     use depends on whether the structure is used for input or output.

        * `enum enum_field_types buffer_type'

          The type of the buffer. This member indicates the data type
          of the C language variable bound to a statement parameter or
          result set column. For input, `buffer_type' indicates the
          type of the variable containing the value to be sent to the
          server.  For output, it indicates the type of the variable
          into which a value received from the server should be stored.
          For permissible `buffer_type' values, see *Note
          c-api-prepared-statement-type-codes::.

        * `void *buffer'

          A pointer to the buffer to be used for data transfer. This is
          the address of a C language variable.

          For input, `buffer' is a pointer to the variable in which you
          store the data value for a statement parameter. When you call
          *Note `mysql_stmt_execute()': mysql-stmt-execute, MySQL use
          the value stored in the variable in place of the
          corresponding parameter marker in the statement (specified
          with `?' in the statement string).

          For output, `buffer' is a pointer to the variable in which to
          return a result set column value.  When you call *Note
          `mysql_stmt_fetch()': mysql-stmt-fetch, MySQL stores a column
          value from the current row of the result set in this
          variable. You can access the value when the call returns.

          To minimize the need for MySQL to perform type conversions
          between C language values on the client side and SQL values
          on the server side, use C variables that have types similar
          to those of the corresponding SQL values:

             * For numeric data types, `buffer' should point to a
               variable of the proper numeric C type. For integer
               variables (which can be `char' for single-byte values or
               an integer type for larger values), you should also
               indicate whether the variable has the `unsigned'
               attribute by setting the `is_unsigned' member, described
               later.

             * For character (nonbinary) and binary string data types,
               `buffer' should point to a character buffer.

             * For date and time data types, `buffer' should point to a
               `MYSQL_TIME' structure.

          For guidelines about mapping between C types and SQL types
          and notes about type conversions, see *Note
          c-api-prepared-statement-type-codes::, and *Note
          c-api-prepared-statement-type-conversions::.

        * `unsigned long buffer_length'

          The actual size of `*buffer' in bytes.  This indicates the
          maximum amount of data that can be stored in the buffer. For
          character and binary C data, the `buffer_length' value
          specifies the length of `*buffer' when used with *Note
          `mysql_stmt_bind_param()': mysql-stmt-bind-param. to specify
          input values, or the maximum number of output data bytes that
          can be fetched into the buffer when used with *Note
          `mysql_stmt_bind_result()': mysql-stmt-bind-result.

        * `unsigned long *length'

          A pointer to an `unsigned long' variable that indicates the
          actual number of bytes of data stored in `*buffer'. `length'
          is used for character or binary C data.

          For input parameter data binding, set `*length' to indicate
          the actual length of the parameter value stored in `*buffer'.
          This is used by *Note `mysql_stmt_execute()':
          mysql-stmt-execute.

          For output value binding, MySQL sets `*length' when you call
          *Note `mysql_stmt_fetch()': mysql-stmt-fetch. The *Note
          `mysql_stmt_fetch()': mysql-stmt-fetch. return value
          determines how to interpret the length:

             * If the return value is 0, `*length' indicates the actual
               length of the parameter value.

             * If the return value is `MYSQL_DATA_TRUNCATED', `*length'
               indicates the nontruncated length of the parameter
               value. In this case, the minimum of `*length' and
               `buffer_length' indicates the actual length of the value.

          `length' is ignored for numeric and temporal data types
          because the `buffer_type' value determines the length of the
          data value.

          If you must determine the length of a returned value before
          fetching it, see *Note mysql-stmt-fetch::, for some
          strategies.

        * `my_bool *is_null'

          This member points to a `my_bool' variable that is true if a
          value is `NULL', false if it is not `NULL'. For input, set
          `*is_null' to true to indicate that you are passing a `NULL'
          value as a statement parameter.

          `is_null' is a _pointer_ to a boolean scalar, not a boolean
          scalar, to provide flexibility in how you specify `NULL'
          values:

             * If your data values are always `NULL', use
               `MYSQL_TYPE_NULL' as the `buffer_type' value when you
               bind the column. The other `MYSQL_BIND' members,
               including `is_null', do not matter.

             * If your data values are always `NOT NULL', set `is_null
               = (my_bool*) 0', and set the other members appropriately
               for the variable you are binding.

             * In all other cases, set the other members appropriately
               and set `is_null' to the address of a `my_bool' variable.
               Set that variable's value to true or false appropriately
               between executions to indicate whether the corresponding
               data value is `NULL' or `NOT NULL', respectively.

          For output, when you fetch a row, MySQL sets the value
          pointed to by `is_null' to true or false according to whether
          the result set column value returned from the statement is or
          is not `NULL'.

        * `my_bool is_unsigned'

          This member applies for C variables with data types that can
          be `unsigned' (`char', `short int', `int', `long long int').
          Set `is_unsigned' to true if the variable pointed to by
          `buffer' is `unsigned' and false otherwise. For example, if
          you bind a `signed char' variable to `buffer', specify a type
          code of `MYSQL_TYPE_TINY' and set `is_unsigned' to false. If
          you bind an `unsigned char' instead, the type code is the
          same but `is_unsigned' should be true. (For `char', it is not
          defined whether it is signed or unsigned, so it is best to be
          explicit about signedness by using `signed char' or `unsigned
          char'.)

          `is_unsigned' applies only to the C language variable on the
          client side. It indicates nothing about the signedness of the
          corresponding SQL value on the server side. For example, if
          you use an `int' variable to supply a value for a `BIGINT
          UNSIGNED' column, `is_unsigned' should be false because `int'
          is a signed type. If you use an `unsigned int' variable to
          supply a value for a *Note `BIGINT': integer-types. column,
          `is_unsigned' should be true because `unsigned int' is an
          unsigned type. MySQL performs the proper conversion between
          signed and unsigned values in both directions, although a
          warning occurs if truncation results.

        * `my_bool *error'

          For output, set this member to point to a `my_bool' variable
          to have truncation information for the parameter stored there
          after a row fetching operation. When truncation reporting is
          enabled, *Note `mysql_stmt_fetch()': mysql-stmt-fetch. returns
          `MYSQL_DATA_TRUNCATED' and `*error' is true in the
          `MYSQL_BIND' structures for parameters in which truncation
          occurred. Truncation indicates loss of sign or significant
          digits, or that a string was too long to fit in a column.
          Truncation reporting is enabled by default, but can be
          controlled by calling *Note `mysql_options()': mysql-options.
          with the `MYSQL_REPORT_DATA_TRUNCATION' option.

   * `MYSQL_TIME'

     This structure is used to send and receive *Note `DATE': datetime,
     *Note `TIME': time, *Note `DATETIME': datetime, and *Note
     `TIMESTAMP': datetime. data directly to and from the server. Set
     the `buffer' member to point to a `MYSQL_TIME' structure, and set
     the `buffer_type' member of a `MYSQL_BIND' structure to one of the
     temporal types (`MYSQL_TYPE_TIME', `MYSQL_TYPE_DATE',
     `MYSQL_TYPE_DATETIME', `MYSQL_TYPE_TIMESTAMP').

     The `MYSQL_TIME' structure contains the members listed in the
     following table.

     This table lists members of the `MYSQL_TIME' structure and
     provides a description of each member.

     Member                      Description
     `unsigned int year'         The year
     `unsigned int month'        The month of the year
     `unsigned int day'          The day of the month
     `unsigned int hour'         The hour of the day
     `unsigned int minute'       The minute of the hour
     `unsigned int second'       The second of the minute
     `my_bool neg'               A boolean flag indicating whether the
                                 time is negative
     `unsigned long second_part' The fractional part of the second in
                                 microseconds; currently unused

     Only those parts of a `MYSQL_TIME' structure that apply to a given
     type of temporal value are used. The `year', `month', and `day'
     elements are used for *Note `DATE': datetime, *Note `DATETIME':
     datetime, and *Note `TIMESTAMP': datetime. values. The `hour',
     `minute', and `second' elements are used for *Note `TIME': time,
     *Note `DATETIME': datetime, and *Note `TIMESTAMP': datetime.
     values. See *Note c-api-prepared-statement-date-handling::.


File: manual.info,  Node: c-api-prepared-statement-type-codes,  Next: c-api-prepared-statement-type-conversions,  Prev: c-api-prepared-statement-data-structures,  Up: c-api-prepared-statement-data-structures

21.8.9.1 C API Prepared Statement Type Codes
............................................

The `buffer_type' member of `MYSQL_BIND' structures indicates the data
type of the C language variable bound to a statement parameter or
result set column. For input, `buffer_type' indicates the type of the
variable containing the value to be sent to the server. For output, it
indicates the type of the variable into which a value received from the
server should be stored.

The following table shows the permissible values for the `buffer_type'
member of `MYSQL_BIND' structures for input values sent to the server.
The table shows the C variable types that you can use, the
corresponding type codes, and the SQL data types for which the supplied
value can be used without conversion. Choose the `buffer_type' value
according to the data type of the C language variable that you are
binding. For the integer types, you should also set the `is_unsigned'
member to indicate whether the variable is signed or unsigned.

This table lists C type input variables, corresponding `buffer_type'
values, and the SQL data types for which the supplied value can be used
without conversion.

Input Variable C Type  `buffer_type' Value       SQL Type of Destination
                                                 Value
`signed char'          `MYSQL_TYPE_TINY'         *Note `TINYINT':
                                                 integer-types.
`short int'            `MYSQL_TYPE_SHORT'        *Note `SMALLINT':
                                                 integer-types.
`int'                  `MYSQL_TYPE_LONG'         *Note `INT':
                                                 integer-types.
`long long int'        `MYSQL_TYPE_LONGLONG'     *Note `BIGINT':
                                                 integer-types.
`float'                `MYSQL_TYPE_FLOAT'        *Note `FLOAT':
                                                 floating-point-types.
`double'               `MYSQL_TYPE_DOUBLE'       *Note `DOUBLE':
                                                 floating-point-types.
`MYSQL_TIME'           `MYSQL_TYPE_TIME'         *Note `TIME': time.
`MYSQL_TIME'           `MYSQL_TYPE_DATE'         *Note `DATE': datetime.
`MYSQL_TIME'           `MYSQL_TYPE_DATETIME'     *Note `DATETIME':
                                                 datetime.
`MYSQL_TIME'           `MYSQL_TYPE_TIMESTAMP'    *Note `TIMESTAMP':
                                                 datetime.
`char[]'               `MYSQL_TYPE_STRING'       *Note `TEXT': blob,
                                                 *Note `CHAR': char,
                                                 *Note `VARCHAR': char.
`char[]'               `MYSQL_TYPE_BLOB'         *Note `BLOB': blob,
                                                 *Note `BINARY':
                                                 binary-varbinary, *Note
                                                 `VARBINARY':
                                                 binary-varbinary.
                       `MYSQL_TYPE_NULL'         `NULL'

Use `MYSQL_TYPE_NULL' as indicated in the description for the `is_null'
member in *Note c-api-prepared-statement-data-structures::.

For input string data, use `MYSQL_TYPE_STRING' or `MYSQL_TYPE_BLOB'
depending on whether the value is a character (nonbinary) or binary
string:

   * `MYSQL_TYPE_STRING' indicates character input string data. The
     value is assumed to be in the character set indicated by the
     `character_set_client' system variable. If the server stores the
     value into a column with a different character set, it converts
     the value to that character set.

   * `MYSQL_TYPE_BLOB' indicates binary input string data. The value is
     treated as having the `binary' character set. That is, it is
     treated as a byte string and no conversion occurs.

The following table shows the permissible values for the `buffer_type'
member of `MYSQL_BIND' structures for output values received from the
server. The table shows the SQL types of received values, the
corresponding type codes that such values have in result set metadata,
and the recommended C language data types to bind to the `MYSQL_BIND'
structure to receive the SQL values without conversion. Choose the
`buffer_type' value according to the data type of the C language
variable that you are binding. For the integer types, you should also
set the `is_unsigned' member to indicate whether the variable is signed
or unsigned.

This table shows SQL types of received values, corresponding
`buffer_type' values, and recommended C data type output variables.

SQL Type of Received   `buffer_type' Value       Output Variable C Type
Value                                            
*Note `TINYINT':       `MYSQL_TYPE_TINY'         `signed char'
integer-types.                                   
*Note `SMALLINT':      `MYSQL_TYPE_SHORT'        `short int'
integer-types.                                   
*Note `MEDIUMINT':     `MYSQL_TYPE_INT24'        `int'
integer-types.                                   
*Note `INT':           `MYSQL_TYPE_LONG'         `int'
integer-types.                                   
*Note `BIGINT':        `MYSQL_TYPE_LONGLONG'     `long long int'
integer-types.                                   
*Note `FLOAT':         `MYSQL_TYPE_FLOAT'        `float'
floating-point-types.                            
*Note `DOUBLE':        `MYSQL_TYPE_DOUBLE'       `double'
floating-point-types.                            
*Note `DECIMAL':       `MYSQL_TYPE_NEWDECIMAL'   `char[]'
fixed-point-types.                               
*Note `YEAR': year.    `MYSQL_TYPE_SHORT'        `short int'
*Note `TIME': time.    `MYSQL_TYPE_TIME'         `MYSQL_TIME'
*Note `DATE':          `MYSQL_TYPE_DATE'         `MYSQL_TIME'
datetime.                                        
*Note `DATETIME':      `MYSQL_TYPE_DATETIME'     `MYSQL_TIME'
datetime.                                        
*Note `TIMESTAMP':     `MYSQL_TYPE_TIMESTAMP'    `MYSQL_TIME'
datetime.                                        
*Note `CHAR': char,    `MYSQL_TYPE_STRING'       `char[]'
*Note `BINARY':                                  
binary-varbinary.                                
*Note `VARCHAR': char, `MYSQL_TYPE_VAR_STRING'   `char[]'
*Note `VARBINARY':                               
binary-varbinary.                                
*Note `TINYBLOB':      `MYSQL_TYPE_TINY_BLOB'    `char[]'
blob, *Note                                      
`TINYTEXT': blob.                                
*Note `BLOB': blob,    `MYSQL_TYPE_BLOB'         `char[]'
*Note `TEXT': blob.                              
*Note `MEDIUMBLOB':    `MYSQL_TYPE_MEDIUM_BLOB'  `char[]'
blob, *Note                                      
`MEDIUMTEXT': blob.                              
*Note `LONGBLOB':      `MYSQL_TYPE_LONG_BLOB'    `char[]'
blob, *Note                                      
`LONGTEXT': blob.                                
*Note `BIT': bit-type. `MYSQL_TYPE_BIT'          `char[]'


File: manual.info,  Node: c-api-prepared-statement-type-conversions,  Prev: c-api-prepared-statement-type-codes,  Up: c-api-prepared-statement-data-structures

21.8.9.2 C API Prepared Statement Type Conversions
..................................................

Prepared statements transmit data between the client and server using C
language variables on the client side that correspond to SQL values on
the server side. If there is a mismatch between the C variable type on
the client side and the corresponding SQL value type on the server
side, MySQL performs implicit type conversions in both directions.

MySQL knows the type code for the SQL value on the server side.  The
`buffer_type' value in the `MYSQL_BIND' structure indicates the type
code of the C variable that holds the value on the client side. The two
codes together tell MySQL what conversion must be performed, if any.
Here are some examples:

   * If you use `MYSQL_TYPE_LONG' with an `int' variable to pass an
     integer value to the server that is to be stored into a *Note
     `FLOAT': floating-point-types. column, MySQL converts the value to
     floating-point format before storing it.

   * If you fetch an SQL *Note `MEDIUMINT': integer-types.  column
     value, but specify a `buffer_type' value of `MYSQL_TYPE_LONGLONG'
     and use a C variable of type `long long int' as the destination
     buffer, MySQL converts the *Note `MEDIUMINT': integer-types. value
     (which requires less than 8 bytes) for storage into the `long long
     int' (an 8-byte variable).

   * If you fetch a numeric column with a value of 255 into a `char[4]'
     character array and specify a `buffer_type' value of
     `MYSQL_TYPE_STRING', the resulting value in the array is a 4-byte
     string `'255\0''.

   * MySQL returns *Note `DECIMAL': fixed-point-types. values as the
     string representation of the original server-side value, which is
     why the corresponding C type is `char[]'. For example, `12.345' is
     returned to the client as `'12.345''. If you specify
     `MYSQL_TYPE_NEWDECIMAL' and bind a string buffer to the
     `MYSQL_BIND' structure, *Note `mysql_stmt_fetch()':
     mysql-stmt-fetch. stores the value in the buffer as a string
     without conversion. If instead you specify a numeric variable and
     type code, *Note `mysql_stmt_fetch()': mysql-stmt-fetch. converts
     the string-format *Note `DECIMAL': fixed-point-types.  value to
     numeric form.

   * For the `MYSQL_TYPE_BIT' type code, *Note `BIT': bit-type. values
     are returned into a string buffer, which is why the corresponding
     C type is `char[]'. The value represents a bit string that
     requires interpretation on the client side. To return the value as
     a type that is easier to deal with, you can cause the value to be
     cast to integer using either of the following types of expressions:


          SELECT bit_col + 0 FROM t
          SELECT CAST(bit_col AS UNSIGNED) FROM t

     To retrieve the value, bind an integer variable large enough to
     hold the value and specify the appropriate corresponding integer
     type code.

Before binding variables to the `MYSQL_BIND' structures that are to be
used for fetching column values, you can check the type codes for each
column of the result set. This might be desirable if you want to
determine which variable types would be best to use to avoid type
conversions. To get the type codes, call *Note
`mysql_stmt_result_metadata()': mysql-stmt-result-metadata.  after
executing the prepared statement with *Note `mysql_stmt_execute()':
mysql-stmt-execute. The metadata provides access to the type codes for
the result set as described in *Note mysql-stmt-result-metadata::, and
*Note c-api-data-structures::.

To determine whether output string values in a result set returned from
the server contain binary or nonbinary data, check whether the
`charsetnr' value of the result set metadata is 63 (see *Note
c-api-data-structures::). If so, the character set is `binary', which
indicates binary rather than nonbinary data. This enables you to
distinguish *Note `BINARY': binary-varbinary. from *Note `CHAR': char,
*Note `VARBINARY': binary-varbinary. from *Note `VARCHAR': char, and the
*Note `BLOB': blob. types from the *Note `TEXT': blob. types.

If you cause the `max_length' member of the `MYSQL_FIELD' column
metadata structures to be set (by calling *Note
`mysql_stmt_attr_set()': mysql-stmt-attr-set.), be aware that the
`max_length' values for the result set indicate the lengths of the
longest string representation of the result values, not the lengths of
the binary representation.  That is, `max_length' does not necessarily
correspond to the size of the buffers needed to fetch the values with
the binary protocol used for prepared statements. Choose the size of
the buffers according to the types of the variables into which you
fetch the values. For example, a `TINYINT' column containing the value
-128 might have a `max_length' value of 4. But the binary
representation of any `TINYINT' value requires only 1 byte for storage,
so you can supply a `signed char' variable in which to store the value
and set `is_unsigned' to indicate that values are signed.

As of MySQL 5.1.25, metadata changes to tables or views referred to by
prepared statements are detected and cause automatic repreparation of
the statement when it is next executed. For more information, see *Note
statement-repreparation::.


File: manual.info,  Node: c-api-prepared-statement-function-overview,  Next: c-api-prepared-statement-functions,  Prev: c-api-prepared-statement-data-structures,  Up: c-api

21.8.10 C API Prepared Statement Function Overview
--------------------------------------------------

The functions available for prepared statement processing are
summarized here and described in greater detail in a later section. See
*Note c-api-prepared-statement-functions::.

This table lists functions that are available for C API prepared
statement processing and provides a description of each function.

Function                Description
*Note                   Returns the number of rows changed, deleted, or
`mysql_stmt_affected_rows()':inserted by prepared *Note `UPDATE': update,
mysql-stmt-affected-rows.*Note `DELETE': delete, or *Note `INSERT':
                        insert. statement
*Note                   Gets value of an attribute for a prepared
`mysql_stmt_attr_get()':statement
mysql-stmt-attr-get.    
*Note                   Sets an attribute for a prepared statement
`mysql_stmt_attr_set()':
mysql-stmt-attr-set.    
*Note                   Associates application data buffers with the
`mysql_stmt_bind_param()':parameter markers in a prepared SQL statement
mysql-stmt-bind-param.  
*Note                   Associates application data buffers with columns
`mysql_stmt_bind_result()':in a result set
mysql-stmt-bind-result. 
*Note                   Frees memory used by a prepared statement
`mysql_stmt_close()':   
mysql-stmt-close.       
*Note                   Seeks to an arbitrary row number in a statement
`mysql_stmt_data_seek()':result set
mysql-stmt-data-seek.   
*Note                   Returns the error number for the last statement
`mysql_stmt_errno()':   execution
mysql-stmt-errno.       
*Note                   Returns the error message for the last statement
`mysql_stmt_error()':   execution
mysql-stmt-error.       
*Note                   Executes a prepared statement
`mysql_stmt_execute()': 
mysql-stmt-execute.     
*Note                   Fetches the next row of data from a result set
`mysql_stmt_fetch()':   and returns data for all bound columns
mysql-stmt-fetch.       
*Note                   Fetch data for one column of the current row of
`mysql_stmt_fetch_column()':a result set
mysql-stmt-fetch-column.
*Note                   Returns the number of result columns for the
`mysql_stmt_field_count()':most recent statement
mysql-stmt-field-count. 
*Note                   Free the resources allocated to a statement
`mysql_stmt_free_result()':handle
mysql-stmt-free-result. 
*Note                   Allocates memory for a `MYSQL_STMT' structure and
`mysql_stmt_init()':    initializes it
mysql-stmt-init.        
*Note                   Returns the ID generated for an `AUTO_INCREMENT'
`mysql_stmt_insert_id()':column by a prepared statement
mysql-stmt-insert-id.   
*Note                   Returns the row count from a buffered statement
`mysql_stmt_num_rows()':result set
mysql-stmt-num-rows.    
*Note                   Returns the number of parameters in a prepared
`mysql_stmt_param_count()':statement
mysql-stmt-param-count. 
*Note                   (Return parameter metadata in the form of a
`mysql_stmt_param_metadata()':result set) Currently, this function does nothing
mysql-stmt-param-metadata.
*Note                   Prepares an SQL statement string for execution
`mysql_stmt_prepare()': 
mysql-stmt-prepare.     
*Note                   Resets the statement buffers in the server
`mysql_stmt_reset()':   
mysql-stmt-reset.       
*Note                   Returns prepared statement metadata in the form
`mysql_stmt_result_metadata()':of a result set
mysql-stmt-result-metadata.
*Note                   Seeks to a row offset in a statement result set,
`mysql_stmt_row_seek()':using value returned from *Note
mysql-stmt-row-seek.    `mysql_stmt_row_tell()': mysql-stmt-row-tell.
*Note                   Returns the statement row cursor position
`mysql_stmt_row_tell()':
mysql-stmt-row-tell.    
*Note                   Sends long data in chunks to server
`mysql_stmt_send_long_data()':
mysql-stmt-send-long-data.
*Note                   Returns the SQLSTATE error code for the last
`mysql_stmt_sqlstate()':statement execution
mysql-stmt-sqlstate.    
*Note                   Retrieves a complete result set to the client
`mysql_stmt_store_result()':
mysql-stmt-store-result.

Call *Note `mysql_stmt_init()': mysql-stmt-init. to create a statement
handle, then *Note `mysql_stmt_prepare()': mysql-stmt-prepare. to
prepare the statement string, *Note `mysql_stmt_bind_param()':
mysql-stmt-bind-param. to supply the parameter data, and *Note
`mysql_stmt_execute()': mysql-stmt-execute. to execute the statement.
You can repeat the *Note `mysql_stmt_execute()': mysql-stmt-execute. by
changing parameter values in the respective buffers supplied through
*Note `mysql_stmt_bind_param()': mysql-stmt-bind-param.

You can send text or binary data in chunks to server using *Note
`mysql_stmt_send_long_data()': mysql-stmt-send-long-data. See *Note
mysql-stmt-send-long-data::.

If the statement is a *Note `SELECT': select. or any other statement
that produces a result set, *Note `mysql_stmt_prepare()':
mysql-stmt-prepare. also returns the result set metadata information in
the form of a `MYSQL_RES' result set through *Note
`mysql_stmt_result_metadata()': mysql-stmt-result-metadata.

You can supply the result buffers using *Note
`mysql_stmt_bind_result()': mysql-stmt-bind-result, so that the *Note
`mysql_stmt_fetch()': mysql-stmt-fetch.  automatically returns data to
these buffers. This is row-by-row fetching.

When statement execution has been completed, close the statement handle
using *Note `mysql_stmt_close()': mysql-stmt-close. so that all
resources associated with it can be freed.

If you obtained a *Note `SELECT': select.  statement's result set
metadata by calling *Note `mysql_stmt_result_metadata()':
mysql-stmt-result-metadata, you should also free the metadata using
*Note `mysql_free_result()': mysql-free-result.

*Execution Steps*

To prepare and execute a statement, an application follows these steps:

  1. Create a prepared statement handle with *Note `mysql_stmt_init()':
     mysql-stmt-init. To prepare the statement on the server, call
     *Note `mysql_stmt_prepare()': mysql-stmt-prepare. and pass it a
     string containing the SQL statement.

  2. If the statement will produce a result set, call *Note
     `mysql_stmt_result_metadata()': mysql-stmt-result-metadata.  to
     obtain the result set metadata. This metadata is itself in the
     form of result set, albeit a separate one from the one that
     contains the rows returned by the query. The metadata result set
     indicates how many columns are in the result and contains
     information about each column.

  3. Set the values of any parameters using *Note
     `mysql_stmt_bind_param()': mysql-stmt-bind-param. All parameters
     must be set. Otherwise, statement execution returns an error or
     produces unexpected results.

  4. Call *Note `mysql_stmt_execute()': mysql-stmt-execute. to execute
     the statement.

  5. If the statement produces a result set, bind the data buffers to
     use for retrieving the row values by calling *Note
     `mysql_stmt_bind_result()': mysql-stmt-bind-result.

  6. Fetch the data into the buffers row by row by calling *Note
     `mysql_stmt_fetch()': mysql-stmt-fetch. repeatedly until no more
     rows are found.

  7. Repeat steps 3 through 6 as necessary, by changing the parameter
     values and re-executing the statement.

When *Note `mysql_stmt_prepare()': mysql-stmt-prepare. is called, the
MySQL client/server protocol performs these actions:

   * The server parses the statement and sends the okay status back to
     the client by assigning a statement ID. It also sends total number
     of parameters, a column count, and its metadata if it is a result
     set oriented statement. All syntax and semantics of the statement
     are checked by the server during this call.

   * The client uses this statement ID for the further operations, so
     that the server can identify the statement from among its pool of
     statements.

When *Note `mysql_stmt_execute()': mysql-stmt-execute. is called, the
MySQL client/server protocol performs these actions:

   * The client uses the statement handle and sends the parameter data
     to the server.

   * The server identifies the statement using the ID provided by the
     client, replaces the parameter markers with the newly supplied
     data, and executes the statement. If the statement produces a
     result set, the server sends the data back to the client.
     Otherwise, it sends an okay status and the number of rows changed,
     deleted, or inserted.

When *Note `mysql_stmt_fetch()': mysql-stmt-fetch. is called, the MySQL
client/server protocol performs these actions:

   * The client reads the data from the current row of the result set
     and places it into the application data buffers by doing the
     necessary conversions. If the application buffer type is same as
     that of the field type returned from the server, the conversions
     are straightforward.

If an error occurs, you can get the statement error number, error
message, and SQLSTATE code using *Note `mysql_stmt_errno()':
mysql-stmt-errno, *Note `mysql_stmt_error()': mysql-stmt-error, and
*Note `mysql_stmt_sqlstate()': mysql-stmt-sqlstate, respectively.

*Prepared Statement Logging*

For prepared statements that are executed with the *Note
`mysql_stmt_prepare()': mysql-stmt-prepare. and *Note
`mysql_stmt_execute()': mysql-stmt-execute. C API functions, the server
writes `Prepare' and `Execute' lines to the general query log so that
you can tell when statements are prepared and executed.

Suppose that you prepare and execute a statement as follows:

  1. Call *Note `mysql_stmt_prepare()': mysql-stmt-prepare. to prepare
     the statement string `"SELECT ?"'.

  2. Call *Note `mysql_stmt_bind_param()': mysql-stmt-bind-param.  to
     bind the value `3' to the parameter in the prepared statement.

  3. Call *Note `mysql_stmt_execute()': mysql-stmt-execute. to execute
     the prepared statement.

As a result of the preceding calls, the server writes the following
lines to the general query log:


     Prepare  [1] SELECT ?
     Execute  [1] SELECT 3

Each `Prepare' and `Execute' line in the log is tagged with a `[N]'
statement identifier so that you can keep track of which prepared
statement is being logged. N is a positive integer. If there are
multiple prepared statements active simultaneously for the client, N
may be greater than 1. Each `Execute' lines shows a prepared statement
after substitution of data values for `?' parameters.


File: manual.info,  Node: c-api-prepared-statement-functions,  Next: c-api-thread-functions,  Prev: c-api-prepared-statement-function-overview,  Up: c-api

21.8.11 C API Prepared Statement Function Descriptions
------------------------------------------------------

* Menu:

* mysql-stmt-affected-rows::     mysql_stmt_affected_rows()
* mysql-stmt-attr-get::          mysql_stmt_attr_get()
* mysql-stmt-attr-set::          mysql_stmt_attr_set()
* mysql-stmt-bind-param::        mysql_stmt_bind_param()
* mysql-stmt-bind-result::       mysql_stmt_bind_result()
* mysql-stmt-close::             mysql_stmt_close()
* mysql-stmt-data-seek::         mysql_stmt_data_seek()
* mysql-stmt-errno::             mysql_stmt_errno()
* mysql-stmt-error::             mysql_stmt_error()
* mysql-stmt-execute::           mysql_stmt_execute()
* mysql-stmt-fetch::             mysql_stmt_fetch()
* mysql-stmt-fetch-column::      mysql_stmt_fetch_column()
* mysql-stmt-field-count::       mysql_stmt_field_count()
* mysql-stmt-free-result::       mysql_stmt_free_result()
* mysql-stmt-init::              mysql_stmt_init()
* mysql-stmt-insert-id::         mysql_stmt_insert_id()
* mysql-stmt-num-rows::          mysql_stmt_num_rows()
* mysql-stmt-param-count::       mysql_stmt_param_count()
* mysql-stmt-param-metadata::    mysql_stmt_param_metadata()
* mysql-stmt-prepare::           mysql_stmt_prepare()
* mysql-stmt-reset::             mysql_stmt_reset()
* mysql-stmt-result-metadata::   mysql_stmt_result_metadata()
* mysql-stmt-row-seek::          mysql_stmt_row_seek()
* mysql-stmt-row-tell::          mysql_stmt_row_tell()
* mysql-stmt-send-long-data::    mysql_stmt_send_long_data()
* mysql-stmt-sqlstate::          mysql_stmt_sqlstate()
* mysql-stmt-store-result::      mysql_stmt_store_result()

To prepare and execute queries, use the functions described in detail
in the following sections.

All functions that operate with a `MYSQL_STMT' structure begin with the
prefix `mysql_stmt_'.

To create a `MYSQL_STMT' handle, use the *Note `mysql_stmt_init()':
mysql-stmt-init. function.


File: manual.info,  Node: mysql-stmt-affected-rows,  Next: mysql-stmt-attr-get,  Prev: c-api-prepared-statement-functions,  Up: c-api-prepared-statement-functions

21.8.11.1 mysql_stmt_affected_rows()
....................................

`my_ulonglong mysql_stmt_affected_rows(MYSQL_STMT *stmt)'

*Description*

*Note `mysql_stmt_affected_rows()': mysql-stmt-affected-rows. may be
called immediately after executing a statement with *Note
`mysql_stmt_execute()': mysql-stmt-execute. It is like *Note
`mysql_affected_rows()': mysql-affected-rows. but for prepared
statements. For a description of what the affected-rows value returned
by this function means, See *Note mysql-affected-rows::.

*Errors*

None.

*Example*

See the Example in *Note mysql-stmt-execute::.


File: manual.info,  Node: mysql-stmt-attr-get,  Next: mysql-stmt-attr-set,  Prev: mysql-stmt-affected-rows,  Up: c-api-prepared-statement-functions

21.8.11.2 mysql_stmt_attr_get()
...............................

`my_bool mysql_stmt_attr_get(MYSQL_STMT *stmt, enum enum_stmt_attr_type
option, void *arg)'

*Description*

Can be used to get the current value for a statement attribute.

The `option' argument is the option that you want to get; the `arg'
should point to a variable that should contain the option value. If the
option is an integer, `arg' should point to the value of the integer.

See *Note mysql-stmt-attr-set::, for a list of options and option types.

*Note*:

In MySQL 5.1, *Note `mysql_stmt_attr_get()': mysql-stmt-attr-get.
originally used `unsigned long *', not `my_bool *', for
`STMT_ATTR_UPDATE_MAX_LENGTH'. This was corrected in MySQL 5.1.7.

*Return Values*

Zero for success. Nonzero if `option' is unknown.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-attr-set,  Next: mysql-stmt-bind-param,  Prev: mysql-stmt-attr-get,  Up: c-api-prepared-statement-functions

21.8.11.3 mysql_stmt_attr_set()
...............................

`my_bool mysql_stmt_attr_set(MYSQL_STMT *stmt, enum enum_stmt_attr_type
option, const void *arg)'

*Description*

Can be used to affect behavior for a prepared statement. This function
may be called multiple times to set several options.

The `option' argument is the option that you want to set. The `arg'
argument is the value for the option. `arg' should point to a variable
that is set to the desired attribute value. The variable type is as
indicated in the following table.

The following table shows the possible `option' values.

This table lists *Note `mysql_stmt_attr_set()': mysql-stmt-attr-set.
option values along with the argument type and function of each option.

Option                         Argument Type  Function
`STMT_ATTR_UPDATE_MAX_LENGTH'  `my_bool *'    If set to 1, causes *Note
                                              `mysql_stmt_store_result()':
                                              mysql-stmt-store-result.
                                              to update the metadata
                                              `MYSQL_FIELD->max_length'
                                              value.
`STMT_ATTR_CURSOR_TYPE'        `unsigned      Type of cursor to open for
                               long *'        statement when *Note
                                              `mysql_stmt_execute()':
                                              mysql-stmt-execute. is
                                              invoked. `*arg' can be
                                              `CURSOR_TYPE_NO_CURSOR'
                                              (the default) or
                                              `CURSOR_TYPE_READ_ONLY'.
`STMT_ATTR_PREFETCH_ROWS'      `unsigned      Number of rows to fetch
                               long *'        from server at a time when
                                              using a cursor.  `*arg'
                                              can be in the range from 1
                                              to the maximum value of
                                              `unsigned long'.  The
                                              default is 1.

If you use the `STMT_ATTR_CURSOR_TYPE' option with
`CURSOR_TYPE_READ_ONLY', a cursor is opened for the statement when you
invoke *Note `mysql_stmt_execute()': mysql-stmt-execute. If there is
already an open cursor from a previous *Note `mysql_stmt_execute()':
mysql-stmt-execute. call, it closes the cursor before opening a new one.
*Note `mysql_stmt_reset()': mysql-stmt-reset. also closes any open
cursor before preparing the statement for re-execution.  *Note
`mysql_stmt_free_result()': mysql-stmt-free-result. closes any open
cursor.

If you open a cursor for a prepared statement, *Note
`mysql_stmt_store_result()': mysql-stmt-store-result. is unnecessary,
because that function causes the result set to be buffered on the
client side.

*Return Values*

Zero for success. Nonzero if `option' is unknown.

*Errors*

None.

*Example*

The following example opens a cursor for a prepared statement and sets
the number of rows to fetch at a time to 5:


     MYSQL_STMT *stmt;
     int rc;
     unsigned long type;
     unsigned long prefetch_rows = 5;

     stmt = mysql_stmt_init(mysql);
     type = (unsigned long) CURSOR_TYPE_READ_ONLY;
     rc = mysql_stmt_attr_set(stmt, STMT_ATTR_CURSOR_TYPE, (void*) &type);
     /* ... check return value ... */
     rc = mysql_stmt_attr_set(stmt, STMT_ATTR_PREFETCH_ROWS,
                              (void*) &prefetch_rows);
     /* ... check return value ... */


File: manual.info,  Node: mysql-stmt-bind-param,  Next: mysql-stmt-bind-result,  Prev: mysql-stmt-attr-set,  Up: c-api-prepared-statement-functions

21.8.11.4 mysql_stmt_bind_param()
.................................

`my_bool mysql_stmt_bind_param(MYSQL_STMT *stmt, MYSQL_BIND *bind)'

*Description*

*Note `mysql_stmt_bind_param()': mysql-stmt-bind-param. is used to bind
input data for the parameter markers in the SQL statement that was
passed to *Note `mysql_stmt_prepare()': mysql-stmt-prepare. It uses
`MYSQL_BIND' structures to supply the data.  `bind' is the address of
an array of `MYSQL_BIND' structures. The client library expects the
array to contain one element for each `?' parameter marker that is
present in the query.

Suppose that you prepare the following statement:


     INSERT INTO mytbl VALUES(?,?,?)

When you bind the parameters, the array of `MYSQL_BIND' structures must
contain three elements, and can be declared like this:


     MYSQL_BIND bind[3];

*Note c-api-prepared-statement-data-structures::, describes the members
of each `MYSQL_BIND' element and how they should be set to provide
input values.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_UNSUPPORTED_PARAM_TYPE'

     The conversion is not supported. Possibly the `buffer_type' value
     is invalid or is not one of the supported types.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*

See the Example in *Note mysql-stmt-execute::.


File: manual.info,  Node: mysql-stmt-bind-result,  Next: mysql-stmt-close,  Prev: mysql-stmt-bind-param,  Up: c-api-prepared-statement-functions

21.8.11.5 mysql_stmt_bind_result()
..................................

`my_bool mysql_stmt_bind_result(MYSQL_STMT *stmt, MYSQL_BIND *bind)'

*Description*

*Note `mysql_stmt_bind_result()': mysql-stmt-bind-result. is used to
associate (that is, bind) output columns in the result set to data
buffers and length buffers. When *Note `mysql_stmt_fetch()':
mysql-stmt-fetch. is called to fetch data, the MySQL client/server
protocol places the data for the bound columns into the specified
buffers.

All columns must be bound to buffers prior to calling *Note
`mysql_stmt_fetch()': mysql-stmt-fetch.  `bind' is the address of an
array of `MYSQL_BIND' structures. The client library expects the array
to contain one element for each column of the result set. If you do not
bind columns to `MYSQL_BIND' structures, *Note `mysql_stmt_fetch()':
mysql-stmt-fetch. simply ignores the data fetch. The buffers should be
large enough to hold the data values, because the protocol does not
return data values in chunks.

A column can be bound or rebound at any time, even after a result set
has been partially retrieved. The new binding takes effect the next time
*Note `mysql_stmt_fetch()': mysql-stmt-fetch. is called.  Suppose that
an application binds the columns in a result set and calls *Note
`mysql_stmt_fetch()': mysql-stmt-fetch.  The client/server protocol
returns data in the bound buffers.  Then suppose that the application
binds the columns to a different set of buffers. The protocol places
data into the newly bound buffers when the next call to *Note
`mysql_stmt_fetch()': mysql-stmt-fetch. occurs.

To bind a column, an application calls *Note
`mysql_stmt_bind_result()': mysql-stmt-bind-result. and passes the
type, address, and length of the output buffer into which the value
should be stored.  *Note c-api-prepared-statement-data-structures::,
describes the members of each `MYSQL_BIND' element and how they should
be set to receive output values.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_UNSUPPORTED_PARAM_TYPE'

     The conversion is not supported. Possibly the `buffer_type' value
     is invalid or is not one of the supported types.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*

See the Example in *Note mysql-stmt-fetch::.


File: manual.info,  Node: mysql-stmt-close,  Next: mysql-stmt-data-seek,  Prev: mysql-stmt-bind-result,  Up: c-api-prepared-statement-functions

21.8.11.6 mysql_stmt_close()
............................

`my_bool mysql_stmt_close(MYSQL_STMT *)'

*Description*

Closes the prepared statement.  *Note `mysql_stmt_close()':
mysql-stmt-close. also deallocates the statement handle pointed to by
`stmt'.

If the current statement has pending or unread results, this function
cancels them so that the next query can be executed.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*

See the Example in *Note mysql-stmt-execute::.


File: manual.info,  Node: mysql-stmt-data-seek,  Next: mysql-stmt-errno,  Prev: mysql-stmt-close,  Up: c-api-prepared-statement-functions

21.8.11.7 mysql_stmt_data_seek()
................................

`void mysql_stmt_data_seek(MYSQL_STMT *stmt, my_ulonglong offset)'

*Description*

Seeks to an arbitrary row in a statement result set. The `offset' value
is a row number and should be in the range from `0' to *Note
`mysql_stmt_num_rows(stmt)-1': mysql-stmt-num-rows.

This function requires that the statement result set structure contains
the entire result of the last executed query, so *Note
`mysql_stmt_data_seek()': mysql-stmt-data-seek. may be used only in
conjunction with *Note `mysql_stmt_store_result()':
mysql-stmt-store-result.

*Return Values*

None.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-errno,  Next: mysql-stmt-error,  Prev: mysql-stmt-data-seek,  Up: c-api-prepared-statement-functions

21.8.11.8 mysql_stmt_errno()
............................

`unsigned int mysql_stmt_errno(MYSQL_STMT *stmt)'

*Description*

For the statement specified by `stmt', *Note `mysql_stmt_errno()':
mysql-stmt-errno. returns the error code for the most recently invoked
statement API function that can succeed or fail. A return value of zero
means that no error occurred. Client error message numbers are listed
in the MySQL `errmsg.h' header file. Server error message numbers are
listed in `mysqld_error.h'. Errors also are listed at *Note
error-handling::.

*Return Values*

An error code value. Zero if no error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-error,  Next: mysql-stmt-execute,  Prev: mysql-stmt-errno,  Up: c-api-prepared-statement-functions

21.8.11.9 mysql_stmt_error()
............................

`const char *mysql_stmt_error(MYSQL_STMT *stmt)'

*Description*

For the statement specified by `stmt', *Note `mysql_stmt_error()':
mysql-stmt-error. returns a null-terminated string containing the error
message for the most recently invoked statement API function that can
succeed or fail. An empty string (`""') is returned if no error
occurred. Either of these two tests can be used to check for an error:


     if(*mysql_stmt_errno(stmt))
     {
       // an error occurred
     }

     if (mysql_stmt_error(stmt)[0])
     {
       // an error occurred
     }

The language of the client error messages may be changed by recompiling
the MySQL client library. Currently, you can choose error messages in
several different languages.

*Return Values*

A character string that describes the error. An empty string if no
error occurred.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-execute,  Next: mysql-stmt-fetch,  Prev: mysql-stmt-error,  Up: c-api-prepared-statement-functions

21.8.11.10 mysql_stmt_execute()
...............................

`int mysql_stmt_execute(MYSQL_STMT *stmt)'

*Description*

*Note `mysql_stmt_execute()': mysql-stmt-execute. executes the prepared
query associated with the statement handle. The currently bound
parameter marker values are sent to server during this call, and the
server replaces the markers with this newly supplied data.

Statement processing following *Note `mysql_stmt_execute()':
mysql-stmt-execute. depends on the type of statement:

   * For an *Note `UPDATE': update, *Note `DELETE': delete, or *Note
     `INSERT': insert, the number of changed, deleted, or inserted rows
     can be found by calling *Note `mysql_stmt_affected_rows()':
     mysql-stmt-affected-rows.

   * For a statement such as *Note `SELECT': select. that generates a
     result set, you must call *Note `mysql_stmt_fetch()':
     mysql-stmt-fetch. to fetch the data prior to calling any other
     functions that result in query processing. For more information on
     how to fetch the results, refer to *Note mysql-stmt-fetch::.

     Do not following invocation of *Note `mysql_stmt_execute()':
     mysql-stmt-execute. with a call to *Note `mysql_store_result()':
     mysql-store-result.  or *Note `mysql_use_result()':
     mysql-use-result. Those functions are not intended for processing
     results from prepared statements.

For statements that generate a result set, you can request that *Note
`mysql_stmt_execute()': mysql-stmt-execute. open a cursor for the
statement by calling *Note `mysql_stmt_attr_set()':
mysql-stmt-attr-set. before executing the statement. If you execute a
statement multiple times, *Note `mysql_stmt_execute()':
mysql-stmt-execute.  closes any open cursor before opening a new one.

As of MySQL 5.1.25, metadata changes to tables or views referred to by
prepared statements are detected and cause automatic repreparation of
the statement when it is next executed. For more information, see *Note
statement-repreparation::.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*

The following example demonstrates how to create and populate a table
using *Note `mysql_stmt_init()': mysql-stmt-init, *Note
`mysql_stmt_prepare()': mysql-stmt-prepare, *Note
`mysql_stmt_param_count()': mysql-stmt-param-count, *Note
`mysql_stmt_bind_param()': mysql-stmt-bind-param, *Note
`mysql_stmt_execute()': mysql-stmt-execute, and *Note
`mysql_stmt_affected_rows()': mysql-stmt-affected-rows. The `mysql'
variable is assumed to be a valid connection handle. For an example
that shows how to retrieve data, see *Note mysql-stmt-fetch::.


     #define STRING_SIZE 50

     #define DROP_SAMPLE_TABLE "DROP TABLE IF EXISTS test_table"
     #define CREATE_SAMPLE_TABLE "CREATE TABLE test_table(col1 INT,\
                                                      col2 VARCHAR(40),\
                                                      col3 SMALLINT,\
                                                      col4 TIMESTAMP)"
     #define INSERT_SAMPLE "INSERT INTO \
                            test_table(col1,col2,col3) \
                            VALUES(?,?,?)"

     MYSQL_STMT    *stmt;
     MYSQL_BIND    bind[3];
     my_ulonglong  affected_rows;
     int           param_count;
     short         small_data;
     int           int_data;
     char          str_data[STRING_SIZE];
     unsigned long str_length;
     my_bool       is_null;

     if (mysql_query(mysql, DROP_SAMPLE_TABLE))
     {
       fprintf(stderr, " DROP TABLE failed\n");
       fprintf(stderr, " %s\n", mysql_error(mysql));
       exit(0);
     }

     if (mysql_query(mysql, CREATE_SAMPLE_TABLE))
     {
       fprintf(stderr, " CREATE TABLE failed\n");
       fprintf(stderr, " %s\n", mysql_error(mysql));
       exit(0);
     }

     /* Prepare an INSERT query with 3 parameters */
     /* (the TIMESTAMP column is not named; the server */
     /*  sets it to the current date and time) */
     stmt = mysql_stmt_init(mysql);
     if (!stmt)
     {
       fprintf(stderr, " mysql_stmt_init(), out of memory\n");
       exit(0);
     }
     if (mysql_stmt_prepare(stmt, INSERT_SAMPLE, strlen(INSERT_SAMPLE)))
     {
       fprintf(stderr, " mysql_stmt_prepare(), INSERT failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }
     fprintf(stdout, " prepare, INSERT successful\n");

     /* Get the parameter count from the statement */
     param_count= mysql_stmt_param_count(stmt);
     fprintf(stdout, " total parameters in INSERT: %d\n", param_count);

     if (param_count != 3) /* validate parameter count */
     {
       fprintf(stderr, " invalid parameter count returned by MySQL\n");
       exit(0);
     }

     /* Bind the data for all 3 parameters */

     memset(bind, 0, sizeof(bind));

     /* INTEGER PARAM */
     /* This is a number type, so there is no need
        to specify buffer_length */
     bind[0].buffer_type= MYSQL_TYPE_LONG;
     bind[0].buffer= (char *)&int_data;
     bind[0].is_null= 0;
     bind[0].length= 0;

     /* STRING PARAM */
     bind[1].buffer_type= MYSQL_TYPE_STRING;
     bind[1].buffer= (char *)str_data;
     bind[1].buffer_length= STRING_SIZE;
     bind[1].is_null= 0;
     bind[1].length= &str_length;

     /* SMALLINT PARAM */
     bind[2].buffer_type= MYSQL_TYPE_SHORT;
     bind[2].buffer= (char *)&small_data;
     bind[2].is_null= &is_null;
     bind[2].length= 0;

     /* Bind the buffers */
     if (mysql_stmt_bind_param(stmt, bind))
     {
       fprintf(stderr, " mysql_stmt_bind_param() failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Specify the data values for the first row */
     int_data= 10;             /* integer */
     strncpy(str_data, "MySQL", STRING_SIZE); /* string  */
     str_length= strlen(str_data);

     /* INSERT SMALLINT data as NULL */
     is_null= 1;

     /* Execute the INSERT statement - 1*/
     if (mysql_stmt_execute(stmt))
     {
       fprintf(stderr, " mysql_stmt_execute(), 1 failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Get the number of affected rows */
     affected_rows= mysql_stmt_affected_rows(stmt);
     fprintf(stdout, " total affected rows(insert 1): %lu\n",
                     (unsigned long) affected_rows);

     if (affected_rows != 1) /* validate affected rows */
     {
       fprintf(stderr, " invalid affected rows by MySQL\n");
       exit(0);
     }

     /* Specify data values for second row,
        then re-execute the statement */
     int_data= 1000;
     strncpy(str_data, "
             The most popular Open Source database",
             STRING_SIZE);
     str_length= strlen(str_data);
     small_data= 1000;         /* smallint */
     is_null= 0;               /* reset */

     /* Execute the INSERT statement - 2*/
     if (mysql_stmt_execute(stmt))
     {
       fprintf(stderr, " mysql_stmt_execute, 2 failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Get the total rows affected */
     affected_rows= mysql_stmt_affected_rows(stmt);
     fprintf(stdout, " total affected rows(insert 2): %lu\n",
                     (unsigned long) affected_rows);

     if (affected_rows != 1) /* validate affected rows */
     {
       fprintf(stderr, " invalid affected rows by MySQL\n");
       exit(0);
     }

     /* Close the statement */
     if (mysql_stmt_close(stmt))
     {
       fprintf(stderr, " failed while closing the statement\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

*Note*:

For complete examples on the use of prepared statement functions, refer
to the file `tests/mysql_client_test.c'. This file can be obtained from
a MySQL source distribution or from the Bazaar source repository.


File: manual.info,  Node: mysql-stmt-fetch,  Next: mysql-stmt-fetch-column,  Prev: mysql-stmt-execute,  Up: c-api-prepared-statement-functions

21.8.11.11 mysql_stmt_fetch()
.............................

`int mysql_stmt_fetch(MYSQL_STMT *stmt)'

*Description*

*Note `mysql_stmt_fetch()': mysql-stmt-fetch. returns the next row in
the result set. It can be called only while the result set exists; that
is, after a call to *Note `mysql_stmt_execute()': mysql-stmt-execute.
for a statement such as *Note `SELECT': select. that produces a result
set.

*Note `mysql_stmt_fetch()': mysql-stmt-fetch. returns row data using
the buffers bound by *Note `mysql_stmt_bind_result()':
mysql-stmt-bind-result. It returns the data in those buffers for all
the columns in the current row set and the lengths are returned to the
`length' pointer. All columns must be bound by the application before
it calls *Note `mysql_stmt_fetch()': mysql-stmt-fetch.

By default, result sets are fetched unbuffered a row at a time from the
server. To buffer the entire result set on the client, call *Note
`mysql_stmt_store_result()': mysql-stmt-store-result.  after binding
the data buffers and before calling *Note `mysql_stmt_fetch()':
mysql-stmt-fetch.

If a fetched data value is a `NULL' value, the `*is_null' value of the
corresponding `MYSQL_BIND' structure contains TRUE (1).  Otherwise, the
data and its length are returned in the `*buffer' and `*length'
elements based on the buffer type specified by the application.  Each
numeric and temporal type has a fixed length, as listed in the
following table. The length of the string types depends on the length
of the actual data value, as indicated by `data_length'.

This table lists numeric and temporal MySQL types and provides the
fixed length of each type.

Type                                 Length
`MYSQL_TYPE_TINY'                    1
`MYSQL_TYPE_SHORT'                   2
`MYSQL_TYPE_LONG'                    4
`MYSQL_TYPE_LONGLONG'                8
`MYSQL_TYPE_FLOAT'                   4
`MYSQL_TYPE_DOUBLE'                  8
`MYSQL_TYPE_TIME'                    `sizeof(MYSQL_TIME)'
`MYSQL_TYPE_DATE'                    `sizeof(MYSQL_TIME)'
`MYSQL_TYPE_DATETIME'                `sizeof(MYSQL_TIME)'
`MYSQL_TYPE_STRING'                  `data length'
`MYSQL_TYPE_BLOB'                    `data_length'

In some cases you might want to determine the length of a column value
before fetching it with *Note `mysql_stmt_fetch()': mysql-stmt-fetch.
For example, the value might be a long string or *Note `BLOB': blob.
value for which you want to know how much space must be allocated. To
accomplish this, you can use these strategies:

   * Before invoking *Note `mysql_stmt_fetch()': mysql-stmt-fetch. to
     retrieve individual rows, pass `STMT_ATTR_UPDATE_MAX_LENGTH' to
     *Note `mysql_stmt_attr_set()': mysql-stmt-attr-set, then invoke
     *Note `mysql_stmt_store_result()': mysql-stmt-store-result. to
     buffer the entire result on the client side. Setting the
     `STMT_ATTR_UPDATE_MAX_LENGTH' attribute causes the maximal length
     of column values to be indicated by the `max_length' member of the
     result set metadata returned by *Note
     `mysql_stmt_result_metadata()': mysql-stmt-result-metadata.

   * Invoke *Note `mysql_stmt_fetch()': mysql-stmt-fetch.  with a
     zero-length buffer for the column in question and a pointer in
     which the real length can be stored. Then use the real length with
     *Note `mysql_stmt_fetch_column()': mysql-stmt-fetch-column.


          real_length= 0;

          bind[0].buffer= 0;
          bind[0].buffer_length= 0;
          bind[0].length= &real_length
          mysql_stmt_bind_result(stmt, bind);

          mysql_stmt_fetch(stmt);
          if (real_length > 0)
          {
            data= malloc(real_length);
            bind[0].buffer= data;
            bind[0].buffer_length= real_length;
            mysql_stmt_fetch_column(stmt, bind, 0, 0);
          }

*Return Values*

This table lists return values for *Note `mysql_stmt_fetch()':
mysql-stmt-fetch. and provides a description of each value.

Return Value              Description
0                         Successful, the data has been fetched to
                          application data buffers.
1                         Error occurred. Error code and message can be
                          obtained by calling *Note
                          `mysql_stmt_errno()': mysql-stmt-errno. and
                          *Note `mysql_stmt_error()': mysql-stmt-error.
`MYSQL_NO_DATA'           No more rows/data exists
`MYSQL_DATA_TRUNCATED'    Data truncation occurred

`MYSQL_DATA_TRUNCATED' is returned when truncation reporting is
enabled. To determine which column values were truncated when this
value is returned, check the `error' members of the `MYSQL_BIND'
structures used for fetching values. Truncation reporting is enabled by
default, but can be controlled by calling *Note `mysql_options()':
mysql-options. with the `MYSQL_REPORT_DATA_TRUNCATION' option.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

   * `CR_UNSUPPORTED_PARAM_TYPE'

     The buffer type is `MYSQL_TYPE_DATE', `MYSQL_TYPE_TIME',
     `MYSQL_TYPE_DATETIME', or `MYSQL_TYPE_TIMESTAMP', but the data type
     is not *Note `DATE': datetime, *Note `TIME': time, *Note
     `DATETIME': datetime, or *Note `TIMESTAMP': datetime.

   * All other unsupported conversion errors are returned from *Note
     `mysql_stmt_bind_result()': mysql-stmt-bind-result.

*Example*

The following example demonstrates how to fetch data from a table using
*Note `mysql_stmt_result_metadata()': mysql-stmt-result-metadata, *Note
`mysql_stmt_bind_result()': mysql-stmt-bind-result, and *Note
`mysql_stmt_fetch()': mysql-stmt-fetch. (This example expects to
retrieve the two rows inserted by the example shown in *Note
mysql-stmt-execute::.) The `mysql' variable is assumed to be a valid
connection handle.


     #define STRING_SIZE 50

     #define SELECT_SAMPLE "SELECT col1, col2, col3, col4 \
                            FROM test_table"

     MYSQL_STMT    *stmt;
     MYSQL_BIND    bind[4];
     MYSQL_RES     *prepare_meta_result;
     MYSQL_TIME    ts;
     unsigned long length[4];
     int           param_count, column_count, row_count;
     short         small_data;
     int           int_data;
     char          str_data[STRING_SIZE];
     my_bool       is_null[4];
     my_bool       error[4];

     /* Prepare a SELECT query to fetch data from test_table */
     stmt = mysql_stmt_init(mysql);
     if (!stmt)
     {
       fprintf(stderr, " mysql_stmt_init(), out of memory\n");
       exit(0);
     }
     if (mysql_stmt_prepare(stmt, SELECT_SAMPLE, strlen(SELECT_SAMPLE)))
     {
       fprintf(stderr, " mysql_stmt_prepare(), SELECT failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }
     fprintf(stdout, " prepare, SELECT successful\n");

     /* Get the parameter count from the statement */
     param_count= mysql_stmt_param_count(stmt);
     fprintf(stdout, " total parameters in SELECT: %d\n", param_count);

     if (param_count != 0) /* validate parameter count */
     {
       fprintf(stderr, " invalid parameter count returned by MySQL\n");
       exit(0);
     }

     /* Fetch result set meta information */
     prepare_meta_result = mysql_stmt_result_metadata(stmt);
     if (!prepare_meta_result)
     {
       fprintf(stderr,
              " mysql_stmt_result_metadata(), \
                returned no meta information\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Get total columns in the query */
     column_count= mysql_num_fields(prepare_meta_result);
     fprintf(stdout,
             " total columns in SELECT statement: %d\n",
             column_count);

     if (column_count != 4) /* validate column count */
     {
       fprintf(stderr, " invalid column count returned by MySQL\n");
       exit(0);
     }

     /* Execute the SELECT query */
     if (mysql_stmt_execute(stmt))
     {
       fprintf(stderr, " mysql_stmt_execute(), failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Bind the result buffers for all 4 columns before fetching them */

     memset(bind, 0, sizeof(bind));

     /* INTEGER COLUMN */
     bind[0].buffer_type= MYSQL_TYPE_LONG;
     bind[0].buffer= (char *)&int_data;
     bind[0].is_null= &is_null[0];
     bind[0].length= &length[0];
     bind[0].error= &error[0];

     /* STRING COLUMN */
     bind[1].buffer_type= MYSQL_TYPE_STRING;
     bind[1].buffer= (char *)str_data;
     bind[1].buffer_length= STRING_SIZE;
     bind[1].is_null= &is_null[1];
     bind[1].length= &length[1];
     bind[1].error= &error[1];

     /* SMALLINT COLUMN */
     bind[2].buffer_type= MYSQL_TYPE_SHORT;
     bind[2].buffer= (char *)&small_data;
     bind[2].is_null= &is_null[2];
     bind[2].length= &length[2];
     bind[2].error= &error[2];

     /* TIMESTAMP COLUMN */
     bind[3].buffer_type= MYSQL_TYPE_TIMESTAMP;
     bind[3].buffer= (char *)&ts;
     bind[3].is_null= &is_null[3];
     bind[3].length= &length[3];
     bind[3].error= &error[3];

     /* Bind the result buffers */
     if (mysql_stmt_bind_result(stmt, bind))
     {
       fprintf(stderr, " mysql_stmt_bind_result() failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Now buffer all results to client (optional step) */
     if (mysql_stmt_store_result(stmt))
     {
       fprintf(stderr, " mysql_stmt_store_result() failed\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }

     /* Fetch all rows */
     row_count= 0;
     fprintf(stdout, "Fetching results ...\n");
     while (!mysql_stmt_fetch(stmt))
     {
       row_count++;
       fprintf(stdout, "  row %d\n", row_count);

       /* column 1 */
       fprintf(stdout, "   column1 (integer)  : ");
       if (is_null[0])
         fprintf(stdout, " NULL\n");
       else
         fprintf(stdout, " %d(%ld)\n", int_data, length[0]);

       /* column 2 */
       fprintf(stdout, "   column2 (string)   : ");
       if (is_null[1])
         fprintf(stdout, " NULL\n");
       else
         fprintf(stdout, " %s(%ld)\n", str_data, length[1]);

       /* column 3 */
       fprintf(stdout, "   column3 (smallint) : ");
       if (is_null[2])
         fprintf(stdout, " NULL\n");
       else
         fprintf(stdout, " %d(%ld)\n", small_data, length[2]);

       /* column 4 */
       fprintf(stdout, "   column4 (timestamp): ");
       if (is_null[3])
         fprintf(stdout, " NULL\n");
       else
         fprintf(stdout, " %04d-%02d-%02d %02d:%02d:%02d (%ld)\n",
                          ts.year, ts.month, ts.day,
                          ts.hour, ts.minute, ts.second,
                          length[3]);
       fprintf(stdout, "\n");
     }

     /* Validate rows fetched */
     fprintf(stdout, " total rows fetched: %d\n", row_count);
     if (row_count != 2)
     {
       fprintf(stderr, " MySQL failed to return all rows\n");
       exit(0);
     }

     /* Free the prepared result metadata */
     mysql_free_result(prepare_meta_result);

     /* Close the statement */
     if (mysql_stmt_close(stmt))
     {
       fprintf(stderr, " failed while closing the statement\n");
       fprintf(stderr, " %s\n", mysql_stmt_error(stmt));
       exit(0);
     }


File: manual.info,  Node: mysql-stmt-fetch-column,  Next: mysql-stmt-field-count,  Prev: mysql-stmt-fetch,  Up: c-api-prepared-statement-functions

21.8.11.12 mysql_stmt_fetch_column()
....................................

`int mysql_stmt_fetch_column(MYSQL_STMT *stmt, MYSQL_BIND *bind,
unsigned int column, unsigned long offset)'

*Description*

Fetch one column from the current result set row.  `bind' provides the
buffer where data should be placed. It should be set up the same way as
for *Note `mysql_stmt_bind_result()': mysql-stmt-bind-result.  `column'
indicates which column to fetch. The first column is numbered 0.
`offset' is the offset within the data value at which to begin
retrieving data.  This can be used for fetching the data value in
pieces. The beginning of the value is offset 0.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_INVALID_PARAMETER_NO'

     Invalid column number.

   * `CR_NO_DATA'

     The end of the result set has already been reached.


File: manual.info,  Node: mysql-stmt-field-count,  Next: mysql-stmt-free-result,  Prev: mysql-stmt-fetch-column,  Up: c-api-prepared-statement-functions

21.8.11.13 mysql_stmt_field_count()
...................................

`unsigned int mysql_stmt_field_count(MYSQL_STMT *stmt)'

*Description*

Returns the number of columns for the most recent statement for the
statement handler. This value is zero for statements such as *Note
`INSERT': insert. or *Note `DELETE': delete. that do not produce result
sets.

*Note `mysql_stmt_field_count()': mysql-stmt-field-count. can be called
after you have prepared a statement by invoking *Note
`mysql_stmt_prepare()': mysql-stmt-prepare.

*Return Values*

An unsigned integer representing the number of columns in a result set.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-free-result,  Next: mysql-stmt-init,  Prev: mysql-stmt-field-count,  Up: c-api-prepared-statement-functions

21.8.11.14 mysql_stmt_free_result()
...................................

`my_bool mysql_stmt_free_result(MYSQL_STMT *stmt)'

*Description*

Releases memory associated with the result set produced by execution of
the prepared statement. If there is a cursor open for the statement,
*Note `mysql_stmt_free_result()': mysql-stmt-free-result. closes it.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*


File: manual.info,  Node: mysql-stmt-init,  Next: mysql-stmt-insert-id,  Prev: mysql-stmt-free-result,  Up: c-api-prepared-statement-functions

21.8.11.15 mysql_stmt_init()
............................

`MYSQL_STMT *mysql_stmt_init(MYSQL *mysql)'

*Description*

Create a `MYSQL_STMT' handle. The handle should be freed with *Note
`mysql_stmt_close(MYSQL_STMT *)': mysql-stmt-close.

See also *Note c-api-prepared-statement-data-structures::, for more
information.

*Return Values*

A pointer to a `MYSQL_STMT' structure in case of success. `NULL' if out
of memory.

*Errors*

   * `CR_OUT_OF_MEMORY'

     Out of memory.


File: manual.info,  Node: mysql-stmt-insert-id,  Next: mysql-stmt-num-rows,  Prev: mysql-stmt-init,  Up: c-api-prepared-statement-functions

21.8.11.16 mysql_stmt_insert_id()
.................................

`my_ulonglong mysql_stmt_insert_id(MYSQL_STMT *stmt)'

*Description*

Returns the value generated for an `AUTO_INCREMENT' column by the
prepared *Note `INSERT': insert. or *Note `UPDATE': update. statement.
Use this function after you have executed a prepared *Note `INSERT':
insert. statement on a table which contains an `AUTO_INCREMENT' field.

See *Note mysql-insert-id::, for more information.

*Return Values*

Value for `AUTO_INCREMENT' column which was automatically generated or
explicitly set during execution of prepared statement, or value
generated by `LAST_INSERT_ID(EXPR)' function. Return value is undefined
if statement does not set `AUTO_INCREMENT' value.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-num-rows,  Next: mysql-stmt-param-count,  Prev: mysql-stmt-insert-id,  Up: c-api-prepared-statement-functions

21.8.11.17 mysql_stmt_num_rows()
................................

`my_ulonglong mysql_stmt_num_rows(MYSQL_STMT *stmt)'

*Description*

Returns the number of rows in the result set.

The use of *Note `mysql_stmt_num_rows()': mysql-stmt-num-rows.  depends
on whether you used *Note `mysql_stmt_store_result()':
mysql-stmt-store-result. to buffer the entire result set in the
statement handle. If you use *Note `mysql_stmt_store_result()':
mysql-stmt-store-result, *Note `mysql_stmt_num_rows()':
mysql-stmt-num-rows. may be called immediately. Otherwise, the row
count is unavailable unless you count the rows as you fetch them.

*Note `mysql_stmt_num_rows()': mysql-stmt-num-rows. is intended for use
with statements that return a result set, such as *Note `SELECT':
select. For statements such as *Note `INSERT': insert, *Note `UPDATE':
update, or *Note `DELETE': delete, the number of affected rows can be
obtained with *Note `mysql_stmt_affected_rows()':
mysql-stmt-affected-rows.

*Return Values*

The number of rows in the result set.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-param-count,  Next: mysql-stmt-param-metadata,  Prev: mysql-stmt-num-rows,  Up: c-api-prepared-statement-functions

21.8.11.18 mysql_stmt_param_count()
...................................

`unsigned long mysql_stmt_param_count(MYSQL_STMT *stmt)'

*Description*

Returns the number of parameter markers present in the prepared
statement.

*Return Values*

An unsigned long integer representing the number of parameters in a
statement.

*Errors*

None.

*Example*

See the Example in *Note mysql-stmt-execute::.


File: manual.info,  Node: mysql-stmt-param-metadata,  Next: mysql-stmt-prepare,  Prev: mysql-stmt-param-count,  Up: c-api-prepared-statement-functions

21.8.11.19 mysql_stmt_param_metadata()
......................................

`MYSQL_RES *mysql_stmt_param_metadata(MYSQL_STMT *stmt)'

This function currently does nothing.

*Description*

*Return Values*

*Errors*


File: manual.info,  Node: mysql-stmt-prepare,  Next: mysql-stmt-reset,  Prev: mysql-stmt-param-metadata,  Up: c-api-prepared-statement-functions

21.8.11.20 mysql_stmt_prepare()
...............................

`int mysql_stmt_prepare(MYSQL_STMT *stmt, const char *stmt_str,
unsigned long length)'

*Description*

Given the statement handle returned by *Note `mysql_stmt_init()':
mysql-stmt-init, prepares the SQL statement pointed to by the string
`stmt_str' and returns a status value. The string length should be
given by the `length' argument. The string must consist of a single SQL
statement. You should not add a terminating semicolon (``;'') or `\g'
to the statement.

The application can include one or more parameter markers in the SQL
statement by embedding question mark (`?') characters into the SQL
string at the appropriate positions.

The markers are legal only in certain places in SQL statements.  For
example, they are permitted in the `VALUES()' list of an *Note
`INSERT': insert. statement (to specify column values for a row), or in
a comparison with a column in a `WHERE' clause to specify a comparison
value.  However, they are not permitted for identifiers (such as table
or column names), or to specify both operands of a binary operator such
as the `=' equal sign. The latter restriction is necessary because it
would be impossible to determine the parameter type. In general,
parameters are legal only in Data Manipulation Language (DML)
statements, and not in Data Definition Language (DDL) statements.

The parameter markers must be bound to application variables using
*Note `mysql_stmt_bind_param()': mysql-stmt-bind-param.  before
executing the statement.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

If the prepare operation was unsuccessful (that is, *Note
`mysql_stmt_prepare()': mysql-stmt-prepare. returns nonzero), the error
message can be obtained by calling *Note `mysql_stmt_error()':
mysql-stmt-error.

*Example*

See the Example in *Note mysql-stmt-execute::.


File: manual.info,  Node: mysql-stmt-reset,  Next: mysql-stmt-result-metadata,  Prev: mysql-stmt-prepare,  Up: c-api-prepared-statement-functions

21.8.11.21 mysql_stmt_reset()
.............................

`my_bool mysql_stmt_reset(MYSQL_STMT *stmt)'

*Description*

Resets a prepared statement on client and server to state after
prepare. It resets the statement on the server, data sent using *Note
`mysql_stmt_send_long_data()': mysql-stmt-send-long-data, unbuffered
result sets and current errors. It does not clear bindings or stored
result sets. Stored result sets will be cleared when executing the
prepared statement (or closing it).

To re-prepare the statement with another query, use *Note
`mysql_stmt_prepare()': mysql-stmt-prepare.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.


File: manual.info,  Node: mysql-stmt-result-metadata,  Next: mysql-stmt-row-seek,  Prev: mysql-stmt-reset,  Up: c-api-prepared-statement-functions

21.8.11.22 mysql_stmt_result_metadata()
.......................................

`MYSQL_RES *mysql_stmt_result_metadata(MYSQL_STMT *stmt)'

*Description*

If a statement passed to *Note `mysql_stmt_prepare()':
mysql-stmt-prepare. is one that produces a result set, *Note
`mysql_stmt_result_metadata()': mysql-stmt-result-metadata.  returns
the result set metadata in the form of a pointer to a `MYSQL_RES'
structure that can be used to process the meta information such as
number of fields and individual field information. This result set
pointer can be passed as an argument to any of the field-based API
functions that process result set metadata, such as:

   * *Note `mysql_num_fields()': mysql-num-fields.

   * *Note `mysql_fetch_field()': mysql-fetch-field.

   * *Note `mysql_fetch_field_direct()': mysql-fetch-field-direct.

   * *Note `mysql_fetch_fields()': mysql-fetch-fields.

   * *Note `mysql_field_count()': mysql-field-count.

   * *Note `mysql_field_seek()': mysql-field-seek.

   * *Note `mysql_field_tell()': mysql-field-tell.

   * *Note `mysql_free_result()': mysql-free-result.

The result set structure should be freed when you are done with it,
which you can do by passing it to *Note `mysql_free_result()':
mysql-free-result. This is similar to the way you free a result set
obtained from a call to *Note `mysql_store_result()':
mysql-store-result.

The result set returned by *Note `mysql_stmt_result_metadata()':
mysql-stmt-result-metadata.  contains only metadata. It does not
contain any row results. The rows are obtained by using the statement
handle with *Note `mysql_stmt_fetch()': mysql-stmt-fetch.

*Return Values*

A `MYSQL_RES' result structure.  `NULL' if no meta information exists
for the prepared query.

*Errors*

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*

See the Example in *Note mysql-stmt-fetch::.


File: manual.info,  Node: mysql-stmt-row-seek,  Next: mysql-stmt-row-tell,  Prev: mysql-stmt-result-metadata,  Up: c-api-prepared-statement-functions

21.8.11.23 mysql_stmt_row_seek()
................................

`MYSQL_ROW_OFFSET mysql_stmt_row_seek(MYSQL_STMT *stmt,
MYSQL_ROW_OFFSET offset)'

*Description*

Sets the row cursor to an arbitrary row in a statement result set. The
`offset' value is a row offset that should be a value returned from
*Note `mysql_stmt_row_tell()': mysql-stmt-row-tell. or from *Note
`mysql_stmt_row_seek()': mysql-stmt-row-seek. This value is not a row
number; if you want to seek to a row within a result set by number, use
*Note `mysql_stmt_data_seek()': mysql-stmt-data-seek. instead.

This function requires that the result set structure contains the
entire result of the query, so *Note `mysql_stmt_row_seek()':
mysql-stmt-row-seek. may be used only in conjunction with *Note
`mysql_stmt_store_result()': mysql-stmt-store-result.

*Return Values*

The previous value of the row cursor. This value may be passed to a
subsequent call to *Note `mysql_stmt_row_seek()': mysql-stmt-row-seek.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-row-tell,  Next: mysql-stmt-send-long-data,  Prev: mysql-stmt-row-seek,  Up: c-api-prepared-statement-functions

21.8.11.24 mysql_stmt_row_tell()
................................

`MYSQL_ROW_OFFSET mysql_stmt_row_tell(MYSQL_STMT *stmt)'

*Description*

Returns the current position of the row cursor for the last *Note
`mysql_stmt_fetch()': mysql-stmt-fetch. This value can be used as an
argument to *Note `mysql_stmt_row_seek()': mysql-stmt-row-seek.

You should use *Note `mysql_stmt_row_tell()': mysql-stmt-row-tell. only
after *Note `mysql_stmt_store_result()': mysql-stmt-store-result.

*Return Values*

The current offset of the row cursor.

*Errors*

None.


File: manual.info,  Node: mysql-stmt-send-long-data,  Next: mysql-stmt-sqlstate,  Prev: mysql-stmt-row-tell,  Up: c-api-prepared-statement-functions

21.8.11.25 mysql_stmt_send_long_data()
......................................

`my_bool mysql_stmt_send_long_data(MYSQL_STMT *stmt, unsigned int
parameter_number, const char *data, unsigned long length)'

*Description*

Enables an application to send parameter data to the server in pieces
(or `chunks'). Call this function after *Note
`mysql_stmt_bind_param()': mysql-stmt-bind-param. and before *Note
`mysql_stmt_execute()': mysql-stmt-execute. It can be called multiple
times to send the parts of a character or binary data value for a
column, which must be one of the *Note `TEXT': blob. or *Note `BLOB':
blob. data types.

`parameter_number' indicates which parameter to associate the data
with. Parameters are numbered beginning with 0. `data' is a pointer to
a buffer containing data to be sent, and `length' indicates the number
of bytes in the buffer.

*Note*:

The next *Note `mysql_stmt_execute()': mysql-stmt-execute.  call
ignores the bind buffer for all parameters that have been used with
*Note `mysql_stmt_send_long_data()': mysql-stmt-send-long-data.  since
last *Note `mysql_stmt_execute()': mysql-stmt-execute. or *Note
`mysql_stmt_reset()': mysql-stmt-reset.

If you want to reset/forget the sent data, you can do it with *Note
`mysql_stmt_reset()': mysql-stmt-reset. See *Note mysql-stmt-reset::.

As of MySQL 5.1.57, the `max_long_data_size' system variable controls
the maximum size of parameter values that can be sent with *Note
`mysql_stmt_send_long_data()': mysql-stmt-send-long-data. If this
variable not set at server startup, the default is the value of the
`max_allowed_packet' system variable.  `max_long_data_size' is
deprecated. In MySQL 5.6, it is removed and the maximum parameter size
is controlled by `max_allowed_packet'.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_INVALID_BUFFER_USE'

     The parameter does not have a string or binary type.

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

*Example*

The following example demonstrates how to send the data for a *Note
`TEXT': blob. column in chunks. It inserts the data value `'MySQL - The
most popular Open Source database'' into the `text_column' column. The
`mysql' variable is assumed to be a valid connection handle.


     #define INSERT_QUERY "INSERT INTO \
                           test_long_data(text_column) VALUES(?)"

     MYSQL_BIND bind[1];
     long       length;

     stmt = mysql_stmt_init(mysql);
     if (!stmt)
     {
       fprintf(stderr, " mysql_stmt_init(), out of memory\n");
       exit(0);
     }
     if (mysql_stmt_prepare(stmt, INSERT_QUERY, strlen(INSERT_QUERY)))
     {
       fprintf(stderr, "\n mysql_stmt_prepare(), INSERT failed");
       fprintf(stderr, "\n %s", mysql_stmt_error(stmt));
       exit(0);
     }
      memset(bind, 0, sizeof(bind));
      bind[0].buffer_type= MYSQL_TYPE_STRING;
      bind[0].length= &length;
      bind[0].is_null= 0;

     /* Bind the buffers */
     if (mysql_stmt_bind_param(stmt, bind))
     {
       fprintf(stderr, "\n param bind failed");
       fprintf(stderr, "\n %s", mysql_stmt_error(stmt));
       exit(0);
     }

      /* Supply data in chunks to server */
      if (mysql_stmt_send_long_data(stmt,0,"MySQL",5))
     {
       fprintf(stderr, "\n send_long_data failed");
       fprintf(stderr, "\n %s", mysql_stmt_error(stmt));
       exit(0);
     }

      /* Supply the next piece of data */
      if (mysql_stmt_send_long_data(stmt,0,
                " - The most popular Open Source database",40))
     {
       fprintf(stderr, "\n send_long_data failed");
       fprintf(stderr, "\n %s", mysql_stmt_error(stmt));
       exit(0);
     }

      /* Now, execute the query */
      if (mysql_stmt_execute(stmt))
     {
       fprintf(stderr, "\n mysql_stmt_execute failed");
       fprintf(stderr, "\n %s", mysql_stmt_error(stmt));
       exit(0);
     }


File: manual.info,  Node: mysql-stmt-sqlstate,  Next: mysql-stmt-store-result,  Prev: mysql-stmt-send-long-data,  Up: c-api-prepared-statement-functions

21.8.11.26 mysql_stmt_sqlstate()
................................

`const char *mysql_stmt_sqlstate(MYSQL_STMT *stmt)'

*Description*

For the statement specified by `stmt', *Note `mysql_stmt_sqlstate()':
mysql-stmt-sqlstate. returns a null-terminated string containing the
SQLSTATE error code for the most recently invoked prepared statement
API function that can succeed or fail. The error code consists of five
characters.  `"00000"' means `no error.' The values are specified by
ANSI SQL and ODBC. For a list of possible values, see *Note
error-handling::.

Note that not all MySQL errors are yet mapped to SQLSTATE codes.  The
value `"HY000"' (general error) is used for unmapped errors.

*Return Values*

A null-terminated character string containing the SQLSTATE error code.


File: manual.info,  Node: mysql-stmt-store-result,  Prev: mysql-stmt-sqlstate,  Up: c-api-prepared-statement-functions

21.8.11.27 mysql_stmt_store_result()
....................................

`int mysql_stmt_store_result(MYSQL_STMT *stmt)'

*Description*

Result sets are produced by calling *Note `mysql_stmt_execute()':
mysql-stmt-execute. to executed prepared statements for SQL statements
such as *Note `SELECT': select, *Note `SHOW': show, *Note `DESCRIBE':
describe, and *Note `EXPLAIN': explain. By default, result sets for
successfully executed prepared statements are not buffered on the
client and *Note `mysql_stmt_fetch()': mysql-stmt-fetch. fetches them
one at a time from the server. To cause the complete result set to be
buffered on the client, call *Note `mysql_stmt_store_result()':
mysql-stmt-store-result. after binding data buffers with *Note
`mysql_stmt_bind_result()': mysql-stmt-bind-result. and before calling
*Note `mysql_stmt_fetch()': mysql-stmt-fetch. to fetch rows. (For an
example, see *Note mysql-stmt-fetch::.)

*Note `mysql_stmt_store_result()': mysql-stmt-store-result. is optional
for result set processing, unless you will call *Note
`mysql_stmt_data_seek()': mysql-stmt-data-seek, *Note
`mysql_stmt_row_seek()': mysql-stmt-row-seek, or *Note
`mysql_stmt_row_tell()': mysql-stmt-row-tell. Those functions require a
seekable result set.

It is unnecessary to call *Note `mysql_stmt_store_result()':
mysql-stmt-store-result. after executing an SQL statement that does not
produce a result set, but if you do, it does not harm or cause any
notable performance problem. You can detect whether the statement
produced a result set by checking if *Note
`mysql_stmt_result_metadata()': mysql-stmt-result-metadata.  returns
`NULL'. For more information, refer to *Note
mysql-stmt-result-metadata::.

*Note*:

MySQL does not by default calculate `MYSQL_FIELD->max_length' for all
columns in *Note `mysql_stmt_store_result()': mysql-stmt-store-result.
because calculating this would slow down *Note
`mysql_stmt_store_result()': mysql-stmt-store-result.  considerably and
most applications do not need `max_length'. If you want `max_length' to
be updated, you can call *Note `mysql_stmt_attr_set(MYSQL_STMT,
STMT_ATTR_UPDATE_MAX_LENGTH, &flag)': mysql-stmt-attr-set. to enable
this. See *Note mysql-stmt-attr-set::.

*Return Values*

Zero for success. Nonzero if an error occurred.

*Errors*

   * `CR_COMMANDS_OUT_OF_SYNC'

     Commands were executed in an improper order.

   * `CR_OUT_OF_MEMORY'

     Out of memory.

   * `CR_SERVER_GONE_ERROR'

     The MySQL server has gone away.

   * `CR_SERVER_LOST'

     The connection to the server was lost during the query.

   * `CR_UNKNOWN_ERROR'

     An unknown error occurred.

If the application is linked to the embedded server library, runtime
error messages will indicate the `libmysqld' rather than
`libmysqlclient' library, but the solution to the problem is the same
as just described.


File: manual.info,  Node: c-api-thread-functions,  Next: c-api-embedded-server-functions,  Prev: c-api-prepared-statement-functions,  Up: c-api

21.8.12 C API Threaded Function Descriptions
--------------------------------------------

* Menu:

* my-init::                      my_init()
* mysql-thread-end::             mysql_thread_end()
* mysql-thread-init::            mysql_thread_init()
* mysql-thread-safe::            mysql_thread_safe()

To create a threaded client, use the functions described in the
following sections. See also *Note c-api-threaded-clients::.


File: manual.info,  Node: my-init,  Next: mysql-thread-end,  Prev: c-api-thread-functions,  Up: c-api-thread-functions

21.8.12.1 my_init()
...................

`void my_init(void)'

*Description*

*Note `my_init()': my-init. initializes some global variables that
MySQL needs. If you are using a thread-safe client library, it also
calls *Note `mysql_thread_init()': mysql-thread-init. for this thread.

It is necessary for *Note `my_init()': my-init. to be called early in
the initialization phase of a program's use of the MySQL library.
However, *Note `my_init()': my-init. is automatically called by *Note
`mysql_init()': mysql-init, *Note `mysql_library_init()':
mysql-library-init, *Note `mysql_server_init()': mysql-server-init, and
*Note `mysql_connect()': mysql-connect. If you ensure that your program
invokes one of those functions before any other MySQL calls, there is
no need to invoke *Note `my_init()': my-init. explicitly.

To access the prototype for *Note `my_init()': my-init, your program
should include these header files:


     #include <my_global.h>
     #include <my_sys.h>

*Return Values*

None.


File: manual.info,  Node: mysql-thread-end,  Next: mysql-thread-init,  Prev: my-init,  Up: c-api-thread-functions

21.8.12.2 mysql_thread_end()
............................

`void mysql_thread_end(void)'

*Description*

This function needs to be called before calling `pthread_exit()' to
free memory allocated by *Note `mysql_thread_init()': mysql-thread-init.

*Note `mysql_thread_end()': mysql-thread-end. _is not invoked
automatically by the client library_. It must be called explicitly to
avoid a memory leak.

*Return Values*

None.


File: manual.info,  Node: mysql-thread-init,  Next: mysql-thread-safe,  Prev: mysql-thread-end,  Up: c-api-thread-functions

21.8.12.3 mysql_thread_init()
.............................

`my_bool mysql_thread_init(void)'

*Description*

This function must be called early within each created thread to
initialize thread-specific variables. However, you may not necessarily
need to invoke it explicitly: *Note `mysql_thread_init()':
mysql-thread-init. is automatically called by *Note `my_init()':
my-init, which itself is automatically called by *Note `mysql_init()':
mysql-init, *Note `mysql_library_init()': mysql-library-init, *Note
`mysql_server_init()': mysql-server-init, and *Note `mysql_connect()':
mysql-connect. If you invoke any of those functions, *Note
`mysql_thread_init()': mysql-thread-init. will be called for you.

*Return Values*

Zero for success. Nonzero if an error occurred.


File: manual.info,  Node: mysql-thread-safe,  Prev: mysql-thread-init,  Up: c-api-thread-functions

21.8.12.4 mysql_thread_safe()
.............................

`unsigned int mysql_thread_safe(void)'

*Description*

This function indicates whether the client library is compiled as
thread-safe.

*Return Values*

1 if the client library is thread-safe, 0 otherwise.


File: manual.info,  Node: c-api-embedded-server-functions,  Next: c-api-problems,  Prev: c-api-thread-functions,  Up: c-api

21.8.13 C API Embedded Server Function Descriptions
---------------------------------------------------

* Menu:

* mysql-server-init::            mysql_server_init()
* mysql-server-end::             mysql_server_end()

MySQL applications can be written to use an embedded server. See *Note
libmysqld::. To write such an application, you must link it against the
`libmysqld' library by using the `-lmysqld' flag rather than linking it
against the `libmysqlclient' client library by using the
`-lmysqlclient' flag. However, the calls to initialize and finalize the
library are the same whether you write a client application or one that
uses the embedded server: Call *Note `mysql_library_init()':
mysql-library-init. to initialize the library and *Note
`mysql_library_end()': mysql-library-end. when you are done with it.
See *Note c-api-function-overview::.


File: manual.info,  Node: mysql-server-init,  Next: mysql-server-end,  Prev: c-api-embedded-server-functions,  Up: c-api-embedded-server-functions

21.8.13.1 mysql_server_init()
.............................

`int mysql_server_init(int argc, char **argv, char **groups)'

*Description*

This function initializes the MySQL library, which must be done before
you call any other MySQL function. However, *Note
`mysql_server_init()': mysql-server-init. is deprecated and you should
call *Note `mysql_library_init()': mysql-library-init. instead.  See
*Note mysql-library-init::.

*Return Values*

Zero for success. Nonzero if an error occurred.


File: manual.info,  Node: mysql-server-end,  Prev: mysql-server-init,  Up: c-api-embedded-server-functions

21.8.13.2 mysql_server_end()
............................

`void mysql_server_end(void)'

*Description*

This function finalizes the MySQL library, which should be done when
you are done using the library. However, *Note `mysql_server_end()':
mysql-server-end. is deprecated and *Note `mysql_library_end()':
mysql-library-end. should be used instead. See *Note
mysql-library-end::.

*Return Values*

None.


File: manual.info,  Node: c-api-problems,  Next: auto-reconnect,  Prev: c-api-embedded-server-functions,  Up: c-api

21.8.14 Common Questions and Problems When Using the C API
----------------------------------------------------------

* Menu:

* null-mysql-store-result::      Why mysql_store_result() Sometimes Returns NULL After mysql_query() Returns Success
* query-results::                What Results You Can Get from a Query
* getting-unique-id::            How to Get the Unique ID for the Last Inserted Row


File: manual.info,  Node: null-mysql-store-result,  Next: query-results,  Prev: c-api-problems,  Up: c-api-problems

21.8.14.1 Why mysql_store_result() Sometimes Returns NULL After mysql_query() Returns Success
.............................................................................................

It is possible for *Note `mysql_store_result()': mysql-store-result. to
return `NULL' following a successful call to *Note `mysql_query()':
mysql-query. When this happens, it means one of the following
conditions occurred:

   * There was a `malloc()' failure (for example, if the result set was
     too large).

   * The data could not be read (an error occurred on the connection).

   * The query returned no data (for example, it was an *Note `INSERT':
     insert, *Note `UPDATE': update, or *Note `DELETE': delete.).

You can always check whether the statement should have produced a
nonempty result by calling *Note `mysql_field_count()':
mysql-field-count. If *Note `mysql_field_count()': mysql-field-count.
returns zero, the result is empty and the last query was a statement
that does not return values (for example, an *Note `INSERT': insert. or
a *Note `DELETE': delete.). If *Note `mysql_field_count()':
mysql-field-count. returns a nonzero value, the statement should have
produced a nonempty result. See the description of the *Note
`mysql_field_count()': mysql-field-count. function for an example.

You can test for an error by calling *Note `mysql_error()':
mysql-error. or *Note `mysql_errno()': mysql-errno.


File: manual.info,  Node: query-results,  Next: getting-unique-id,  Prev: null-mysql-store-result,  Up: c-api-problems

21.8.14.2 What Results You Can Get from a Query
...............................................

In addition to the result set returned by a query, you can also get the
following information:

   * *Note `mysql_affected_rows()': mysql-affected-rows.  returns the
     number of rows affected by the last query when doing an *Note
     `INSERT': insert, *Note `UPDATE': update, or *Note `DELETE':
     delete.

     For a fast re-create, use *Note `TRUNCATE TABLE': truncate-table.

   * *Note `mysql_num_rows()': mysql-num-rows. returns the number of
     rows in a result set. With *Note `mysql_store_result()':
     mysql-store-result, *Note `mysql_num_rows()': mysql-num-rows. may
     be called as soon as *Note `mysql_store_result()':
     mysql-store-result.  returns. With *Note `mysql_use_result()':
     mysql-use-result, *Note `mysql_num_rows()': mysql-num-rows. may be
     called only after you have fetched all the rows with *Note
     `mysql_fetch_row()': mysql-fetch-row.

   * *Note `mysql_insert_id()': mysql-insert-id. returns the ID
     generated by the last query that inserted a row into a table with
     an `AUTO_INCREMENT' index. See *Note mysql-insert-id::.

   * Some queries (*Note `LOAD DATA INFILE ...': load-data, *Note
     `INSERT INTO ... SELECT ...': insert-select, *Note `UPDATE':
     update.) return additional information. The result is returned by
     *Note `mysql_info()': mysql-info. See the description for *Note
     `mysql_info()': mysql-info.  for the format of the string that it
     returns.  *Note `mysql_info()': mysql-info. returns a `NULL'
     pointer if there is no additional information.


File: manual.info,  Node: getting-unique-id,  Prev: query-results,  Up: c-api-problems

21.8.14.3 How to Get the Unique ID for the Last Inserted Row
............................................................

If you insert a record into a table that contains an `AUTO_INCREMENT'
column, you can obtain the value stored into that column by calling the
*Note `mysql_insert_id()': mysql-insert-id. function.

You can check from your C applications whether a value was stored in an
`AUTO_INCREMENT' column by executing the following code (which assumes
that you've checked that the statement succeeded). It determines
whether the query was an *Note `INSERT': insert. with an
`AUTO_INCREMENT' index:


     if ((result = mysql_store_result(&mysql)) == 0 &&
         mysql_field_count(&mysql) == 0 &&
         mysql_insert_id(&mysql) != 0)
     {
         used_id = mysql_insert_id(&mysql);
     }

When a new `AUTO_INCREMENT' value has been generated, you can also
obtain it by executing a `SELECT LAST_INSERT_ID()' statement with *Note
`mysql_query()': mysql-query. and retrieving the value from the result
set returned by the statement.

When inserting multiple values, the last automatically incremented
value is returned.

For `LAST_INSERT_ID()', the most recently generated ID is maintained in
the server on a per-connection basis. It is not changed by another
client. It is not even changed if you update another `AUTO_INCREMENT'
column with a nonmagic value (that is, a value that is not `NULL' and
not `0'). Using `LAST_INSERT_ID()' and `AUTO_INCREMENT' columns
simultaneously from multiple clients is perfectly valid. Each client
will receive the last inserted ID for the last statement _that_ client
executed.

If you want to use the ID that was generated for one table and insert
it into a second table, you can use SQL statements like this:


     INSERT INTO foo (auto,text)
         VALUES(NULL,'text');         # generate ID by inserting NULL
     INSERT INTO foo2 (id,text)
         VALUES(LAST_INSERT_ID(),'text');  # use ID in second table

Note that *Note `mysql_insert_id()': mysql-insert-id.  returns the
value stored into an `AUTO_INCREMENT' column, whether that value is
automatically generated by storing `NULL' or `0' or was specified as an
explicit value.  `LAST_INSERT_ID()' returns only automatically
generated `AUTO_INCREMENT' values. If you store an explicit value other
than `NULL' or `0', it does not affect the value returned by
`LAST_INSERT_ID()'.

For more information on obtaining the last ID in an `AUTO_INCREMENT'
column:

   * For information on `LAST_INSERT_ID()', which can be used within an
     SQL statement, see *Note information-functions::.

   * For information on *Note `mysql_insert_id()': mysql-insert-id, the
     function you use from within the C API, see *Note
     mysql-insert-id::.

   * For information on obtaining the auto-incremented value when using
     Connector/J, see Retrieving `AUTO_INCREMENT' Column Values through
     JDBC
     (http://dev.mysql.com/doc/connector-j/en/connector-j-usagenotes-last-insert-id.html).

   * For information on obtaining the auto-incremented value when using
     Connector/ODBC, see Obtaining Auto-Increment Values
     (http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-usagenotes-functionality-last-insert-id.html).


File: manual.info,  Node: auto-reconnect,  Next: c-api-multiple-queries,  Prev: c-api-problems,  Up: c-api

21.8.15 Controlling Automatic Reconnection Behavior
---------------------------------------------------

The MySQL client library can perform an automatic reconnection to the
server if it finds that the connection is down when you attempt to send
a statement to the server to be executed. If auto-reconnect is enabled,
the library tries once to reconnect to the server and send the
statement again.

In MySQL 5.1, auto-reconnect is disabled by default.

If it is important for your application to know that the connection has
been dropped (so that is can exit or take action to adjust for the loss
of state information), be sure that auto-reconnect is disabled. To
ensure this, call *Note `mysql_options()': mysql-options. with the
`MYSQL_OPT_RECONNECT' option:


     my_bool reconnect = 0;
     mysql_options(&mysql, MYSQL_OPT_RECONNECT, &reconnect);

If the connection has gone down, the effect of *Note `mysql_ping()':
mysql-ping. depends on the auto-reconnect state. If auto-reconnect is
enabled, *Note `mysql_ping()': mysql-ping. performs a reconnect.
Otherwise, it returns an error.

Some client programs might provide the capability of controlling
automatic reconnection. For example, *Note `mysql': mysql.  reconnects
by default, but the `--skip-reconnect' option can be used to suppress
this behavior.

If an automatic reconnection does occur (for example, as a result of
calling *Note `mysql_ping()': mysql-ping.), there is no explicit
indication of it. To check for reconnection, call *Note
`mysql_thread_id()': mysql-thread-id. to get the original connection
identifier before calling *Note `mysql_ping()': mysql-ping, then call
*Note `mysql_thread_id()': mysql-thread-id. again to see whether the
identifier changed.

Automatic reconnection can be convenient because you need not implement
your own reconnect code, but if a reconnection does occur, several
aspects of the connection state are reset on the server side and your
application will not be notified.

The connection-related state is affected as follows:

   * Any active transactions are rolled back and autocommit mode is
     reset.

   * All table locks are released.

   * All `TEMPORARY' tables are closed (and dropped).

   * Session system variables are reinitialized to the values of the
     corresponding global system variables, including system variables
     that are set implicitly by statements such as `SET NAMES'.

   * User variable settings are lost.

   * Prepared statements are released.

   * *Note `HANDLER': handler. variables are closed.

   * The value of `LAST_INSERT_ID()' is reset to 0.

   * Locks acquired with `GET_LOCK()' are released.

If the connection drops, it is possible that the session associated
with the connection on the server side will still be running if the
server has not yet detected that the client is no longer connected. In
this case, any locks held by the original connection still belong to
that session, so you may want to kill it by calling *Note
`mysql_kill()': mysql-kill.


File: manual.info,  Node: c-api-multiple-queries,  Next: c-api-prepared-statement-problems,  Prev: auto-reconnect,  Up: c-api

21.8.16 C API Support for Multiple Statement Execution
------------------------------------------------------

By default, *Note `mysql_query()': mysql-query. and *Note
`mysql_real_query()': mysql-real-query. interpret their statement
string argument as a single statement to be executed, and you process
the result according to whether the statement produces a result set (a
set of rows, as for *Note `SELECT': select.) or an affected-rows count
(as for *Note `INSERT': insert, *Note `UPDATE': update, and so forth).

MySQL 5.1 also supports the execution of a string containing multiple
statements separated by semicolon (``;'') characters. This capability
is enabled by special options that are specified either when you
connect to the server with *Note `mysql_real_connect()':
mysql-real-connect. or after connecting by calling` *Note
`mysql_set_server_option()': mysql-set-server-option.

Executing a multiple-statement string can produce multiple result sets
or row-count indicators. Processing these results involves a different
approach than for the single-statement case: After handling the result
from the first statement, it is necessary to check whether more results
exist and process them in turn if so.  To support multiple-result
processing, the C API includes the *Note `mysql_more_results()':
mysql-more-results. and *Note `mysql_next_result()': mysql-next-result.
functions.  These functions are used at the end of a loop that iterates
as long as more results are available. _Failure to process the result
this way may result in a dropped connection to the server._

Multiple-result processing also is required if you execute *Note
`CALL': call. statements for stored procedures. Results from a stored
procedure have these characteristics:

   * Statements within the procedure may produce result sets (for
     example, if it executes *Note `SELECT': select.  statements).
     These result sets are returned in the order that they are produced
     as the procedure executes.

     In general, the caller cannot know how many result sets a
     procedure will return. Procedure execution may depend on loops or
     conditional statements that cause the execution path to differ
     from one call to the next. Therefore, you must be prepared to
     retrieve multiple results.

   * The final result from the procedure is a status result that
     includes no result set. The status indicates whether the procedure
     succeeded or an error occurred.

The multiple statement and result capabilities can be used only with
*Note `mysql_query()': mysql-query. or *Note `mysql_real_query()':
mysql-real-query. They cannot be used with the prepared statement
interface. Prepared statement handles are defined to work only with
strings that contain a single statement. See *Note
c-api-prepared-statements::.

To enable multiple-statement execution and result processing, the
following options may be used:

   * The *Note `mysql_real_connect()': mysql-real-connect.  function
     has a `flags' argument for which two option values are relevant:

        * `CLIENT_MULTI_RESULTS' enables the client program to process
          multiple results. This option _must_ be enabled if you execute
          *Note `CALL': call. statements for stored procedures that
          produce result sets. Otherwise, such procedures result in an
          error `Error 1312 (0A000): PROCEDURE PROC_NAME can't return a
          result set in the given context'.

        * `CLIENT_MULTI_STATEMENTS' enables *Note `mysql_query()':
          mysql-query. and *Note `mysql_real_query()':
          mysql-real-query. to execute statement strings containing
          multiple statements separated by semicolons. This option also
          enables `CLIENT_MULTI_RESULTS' implicitly, so a `flags'
          argument of `CLIENT_MULTI_STATEMENTS' to *Note
          `mysql_real_connect()': mysql-real-connect. is equivalent to
          an argument of `CLIENT_MULTI_STATEMENTS |
          CLIENT_MULTI_RESULTS'. That is, `CLIENT_MULTI_STATEMENTS' is
          sufficient to enable multiple-statement execution and all
          multiple-result processing.

   * After the connection to the server has been established, you can
     use the *Note `mysql_set_server_option()': mysql-set-server-option.
     function to enable or disable multiple-statement execution by
     passing it an argument of `MYSQL_OPTION_MULTI_STATEMENTS_ON' or
     `MYSQL_OPTION_MULTI_STATEMENTS_OFF'. Enabling multiple-statement
     execution with this function also enables processing of `simple'
     results for a multiple-statement string where each statement
     produces a single result, but is _not_ sufficient to permit
     processing of stored procedures that produce result sets.

The following procedure outlines a suggested strategy for handling
multiple statements:

  1. Pass `CLIENT_MULTI_STATEMENTS' to *Note `mysql_real_connect()':
     mysql-real-connect, to fully enable multiple-statement execution
     and multiple-result processing.

  2. After calling *Note `mysql_query()': mysql-query. or *Note
     `mysql_real_query()': mysql-real-query. and verifying that it
     succeeds, enter a loop within which you process statement results.

  3. For each iteration of the loop, handle the current statement
     result, retrieving either a result set or an affected-rows count.
     If an error occurs, exit the loop.

  4. At the end of the loop, call *Note `mysql_next_result()':
     mysql-next-result. to check whether another result exists and
     initiate retrieval for it if so. If no more results are available,
     exit the loop.

One possible implementation of the preceding strategy is shown
following. The final part of the loop can be reduced to a simple test
of whether *Note `mysql_next_result()': mysql-next-result. returns
nonzero. The code as written distinguishes between no more results and
an error, which enables a message to be printed for the latter
occurrence.


     /* connect to server with the CLIENT_MULTI_STATEMENTS option */
     if (mysql_real_connect (mysql, host_name, user_name, password,
         db_name, port_num, socket_name, CLIENT_MULTI_STATEMENTS) == NULL)
     {
       printf("mysql_real_connect() failed\n");
       mysql_close(mysql);
       exit(1);
     }

     /* execute multiple statements */
     status = mysql_query(mysql,
                          "DROP TABLE IF EXISTS test_table;\
                           CREATE TABLE test_table(id INT);\
                           INSERT INTO test_table VALUES(10);\
                           UPDATE test_table SET id=20 WHERE id=10;\
                           SELECT * FROM test_table;\
                           DROP TABLE test_table");
     if (status)
     {
       printf("Could not execute statement(s)");
       mysql_close(mysql);
       exit(0);
     }

     /* process each statement result */
     do {
       /* did current statement return data? */
       result = mysql_store_result(mysql);
       if (result)
       {
         /* yes; process rows and free the result set */
         process_result_set(mysql, result);
         mysql_free_result(result);
       }
       else          /* no result set or error */
       {
         if (mysql_field_count(mysql) == 0)
         {
           printf("%lld rows affected\n",
                 mysql_affected_rows(mysql));
         }
         else  /* some error occurred */
         {
           printf("Could not retrieve result set\n");
           break;
         }
       }
       /* more results? -1 = no, >0 = error, 0 = yes (keep looping) */
       if ((status = mysql_next_result(mysql)) > 0)
         printf("Could not execute statement\n");
     } while (status == 0);

     mysql_close(mysql);


File: manual.info,  Node: c-api-prepared-statement-problems,  Next: c-api-prepared-statement-date-handling,  Prev: c-api-multiple-queries,  Up: c-api

21.8.17 C API Prepared Statement Problems
-----------------------------------------

Here follows a list of the currently known problems with prepared
statements:

   * *Note `TIME': time, *Note `TIMESTAMP': datetime, and *Note
     `DATETIME': datetime. do not support parts of seconds (for
     example, from `DATE_FORMAT()').

   * When converting an integer to string, `ZEROFILL' is honored with
     prepared statements in some cases where the MySQL server does not
     print the leading zeros. (For example, with
     `MIN(NUMBER-WITH-ZEROFILL)').

   * When converting a floating-point number to a string in the client,
     the rightmost digits of the converted value may differ slightly
     from those of the original value.

   * Before MySQL 5.1.17, prepared statements do not use the query
     cache. As of 5.1.17, prepared statements use the query cache under
     the conditions described in *Note query-cache-operation::.

   * Prepared statements do not support multi-statements (that is,
     multiple statements within a single string separated by ``;''
     characters).

   * In MySQL 5.1, prepared *Note `CALL': call. statements cannot invoke
     stored procedures that return result sets because prepared
     statements do not support multiple result sets. Nor can the
     calling application access a stored procedure's `OUT' or `INOUT'
     parameters when the procedure returns. These capabilities are
     supported beginning with MySQL 5.5.


File: manual.info,  Node: c-api-prepared-statement-date-handling,  Next: c-api-prepared-call-statements,  Prev: c-api-prepared-statement-problems,  Up: c-api

21.8.18 C API Prepared Statement Handling of Date and Time Values
-----------------------------------------------------------------

The binary (prepared statement) protocol enables you to send and
receive date and time values (*Note `DATE': datetime, *Note `TIME':
time, *Note `DATETIME': datetime, and *Note `TIMESTAMP': datetime.),
using the `MYSQL_TIME' structure. The members of this structure are
described in *Note c-api-prepared-statement-data-structures::.

To send temporal data values, create a prepared statement using *Note
`mysql_stmt_prepare()': mysql-stmt-prepare. Then, before calling *Note
`mysql_stmt_execute()': mysql-stmt-execute. to execute the statement,
use the following procedure to set up each temporal parameter:

  1. In the `MYSQL_BIND' structure associated with the data value, set
     the `buffer_type' member to the type that indicates what kind of
     temporal value you're sending. For *Note `DATE': datetime, *Note
     `TIME': time, *Note `DATETIME': datetime, or *Note `TIMESTAMP':
     datetime. values, set `buffer_type' to `MYSQL_TYPE_DATE',
     `MYSQL_TYPE_TIME', `MYSQL_TYPE_DATETIME', or
     `MYSQL_TYPE_TIMESTAMP', respectively.

  2. Set the `buffer' member of the `MYSQL_BIND' structure to the
     address of the `MYSQL_TIME' structure in which you pass the
     temporal value.

  3. Fill in the members of the `MYSQL_TIME' structure that are
     appropriate for the type of temporal value to be passed.

Use *Note `mysql_stmt_bind_param()': mysql-stmt-bind-param. to bind the
parameter data to the statement. Then you can call *Note
`mysql_stmt_execute()': mysql-stmt-execute.

To retrieve temporal values, the procedure is similar, except that you
set the `buffer_type' member to the type of value you expect to
receive, and the `buffer' member to the address of a `MYSQL_TIME'
structure into which the returned value should be placed. Use *Note
`mysql_stmt_bind_result()': mysql-stmt-bind-result. to bind the buffers
to the statement after calling *Note `mysql_stmt_execute()':
mysql-stmt-execute. and before fetching the results.

Here is a simple example that inserts *Note `DATE': datetime, *Note
`TIME': time, and *Note `TIMESTAMP': datetime. data. The `mysql'
variable is assumed to be a valid connection handle.


       MYSQL_TIME  ts;
       MYSQL_BIND  bind[3];
       MYSQL_STMT  *stmt;

       strmov(query, "INSERT INTO test_table(date_field, time_field, \
                                    timestamp_field) VALUES(?,?,?");

       stmt = mysql_stmt_init(mysql);
       if (!stmt)
       {
         fprintf(stderr, " mysql_stmt_init(), out of memory\n");
         exit(0);
       }
       if (mysql_stmt_prepare(mysql, query, strlen(query)))
       {
         fprintf(stderr, "\n mysql_stmt_prepare(), INSERT failed");
         fprintf(stderr, "\n %s", mysql_stmt_error(stmt));
         exit(0);
       }

       /* set up input buffers for all 3 parameters */
       bind[0].buffer_type= MYSQL_TYPE_DATE;
       bind[0].buffer= (char *)&ts;
       bind[0].is_null= 0;
       bind[0].length= 0;
       ...
       bind[1]= bind[2]= bind[0];
       ...

       mysql_stmt_bind_param(stmt, bind);

       /* supply the data to be sent in the ts structure */
       ts.year= 2002;
       ts.month= 02;
       ts.day= 03;

       ts.hour= 10;
       ts.minute= 45;
       ts.second= 20;

       mysql_stmt_execute(stmt);
       ..


File: manual.info,  Node: c-api-prepared-call-statements,  Prev: c-api-prepared-statement-date-handling,  Up: c-api

21.8.19 C API Support for Prepared CALL Statements
--------------------------------------------------

In MySQL 5.1, prepared *Note `CALL': call. statements can be used only
for stored procedures that produce at most one result set. Nor can the
calling application use placeholders for `OUT' or `INOUT' parameters.

MySQL 5.5 expands prepared *Note `CALL': call.  statement support for
stored procedures that produce multiple result sets and to provide
placeholder access to `OUT' and `INOUT' parameters.


File: manual.info,  Node: apis-php-info,  Next: apis-perl,  Prev: c-api,  Up: connectors-apis

21.9 MySQL PHP API
==================

The MySQL PHP API manual is now published in standalone form, not as
part of the MySQL Reference Manual. See MySQL and PHP
(http://dev.mysql.com/doc/apis-php/en/index.html).


File: manual.info,  Node: apis-perl,  Next: apis-python,  Prev: apis-php-info,  Up: connectors-apis

21.10 MySQL Perl API
====================

The Perl `DBI' module provides a generic interface for database access.
You can write a DBI script that works with many different database
engines without change. To use DBI with MySQL, install the following:

  1. The `DBI' module.

  2. The `DBD::mysql' module. This is the DataBase Driver (DBD) module
     for Perl.

  3. Optionally, the DBD module for any other type of database server
     you want to access.

Perl DBI is the recommended Perl interface. It replaces an older
interface called `mysqlperl', which should be considered obsolete.

These sections contain information about using Perl with MySQL and
writing MySQL applications in Perl:

   * For installation instructions for Perl DBI support, see *Note
     perl-support::.

   * For an example of reading options from option files, see *Note
     multiple-server-clients::.

   * For secure coding tips, see *Note security-guidelines::.

   * For debugging tips, see *Note using-gdb-on-mysqld::.

   * For some Perl-specific environment variables, see *Note
     environment-variables::.

   * For considerations for running on Mac OS X, see *Note
     macosx-installation-server::.

   * For ways to quote string literals, see *Note string-literals::.

DBI information is available at the command line, online, or in printed
form:

   * Once you have the `DBI' and `DBD::mysql' modules installed, you
     can get information about them at the command line with the
     `perldoc' command:


          shell> perldoc DBI
          shell> perldoc DBI::FAQ
          shell> perldoc DBD::mysql

     You can also use `pod2man', `pod2html', and so on to translate this
     information into other formats.

   * For online information about Perl DBI, visit the DBI Web site,
     `http://dbi.perl.org/'. That site hosts a general DBI mailing
     list. Oracle Corporation hosts a list specifically about
     `DBD::mysql'; see *Note mailing-lists::.

   * For printed information, the official DBI book is `Programming the
     Perl DBI' (Alligator Descartes and Tim Bunce, O'Reilly &
     Associates, 2000).  Information about the book is available at the
     DBI Web site, `http://dbi.perl.org/'.

     For information that focuses specifically on using DBI with MySQL,
     see `MySQL and Perl for the Web' (Paul DuBois, New Riders, 2001).
     This book's Web site is `http://www.kitebird.com/mysql-perl/'.


File: manual.info,  Node: apis-python,  Next: apis-ruby,  Prev: apis-perl,  Up: connectors-apis

21.11 MySQL Python API
======================

`MySQLdb' is a third-party driver that provides MySQL support for
Python, compliant with the Python DB API version 2.0. It can be found at
`http://sourceforge.net/projects/mysql-python/'.

The new MySQL Connector/Python component provides an interface to the
same Python API, and is built into the MySQL Server and supported by
Oracle. See MySQL Connector/Python Developer Guide
(http://dev.mysql.com/doc/connector-python/en/index.html) for details
on the Connector, as well as coding guidelines for Python applications
and sample Python code.


File: manual.info,  Node: apis-ruby,  Next: apis-tcl,  Prev: apis-python,  Up: connectors-apis

21.12 MySQL Ruby APIs
=====================

* Menu:

* apis-ruby-mysqlruby::          The MySQL/Ruby API
* apis-ruby-rubymysql::          The Ruby/MySQL API

Two APIs are available for Ruby programmers developing MySQL
applications:

   * The MySQL/Ruby API is based on the `libmysqlclient' API library.
     For information on installing and using the MySQL/Ruby API, see
     *Note apis-ruby-mysqlruby::.

   * The Ruby/MySQL API is written to use the native MySQL network
     protocol (a native driver). For information on installing and
     using the Ruby/MySQL API, see *Note apis-ruby-rubymysql::.

For background and syntax information about the Ruby language, see Ruby
Programming Language (http://www.ruby-lang.org).


File: manual.info,  Node: apis-ruby-mysqlruby,  Next: apis-ruby-rubymysql,  Prev: apis-ruby,  Up: apis-ruby

21.12.1 The MySQL/Ruby API
--------------------------

The MySQL/Ruby module provides access to MySQL databases using Ruby
through `libmysqlclient'.

For information on installing the module, and the functions exposed, see
MySQL/Ruby (http://tmtm.org/en/mysql/ruby/).


File: manual.info,  Node: apis-ruby-rubymysql,  Prev: apis-ruby-mysqlruby,  Up: apis-ruby

21.12.2 The Ruby/MySQL API
--------------------------

The Ruby/MySQL module provides access to MySQL databases using Ruby
through a native driver interface using the MySQL network protocol.

For information on installing the module, and the functions exposed, see
Ruby/MySQL (http://tmtm.org/en/ruby/mysql/README_en.html).


File: manual.info,  Node: apis-tcl,  Next: apis-eiffel,  Prev: apis-ruby,  Up: connectors-apis

21.13 MySQL Tcl API
===================

`MySQLtcl' is a simple API for accessing a MySQL database server from
the Tcl programming language (http://en.wikipedia.org/wiki/Tcl). It can
be found at `http://www.xdobry.de/mysqltcl/'.


File: manual.info,  Node: apis-eiffel,  Prev: apis-tcl,  Up: connectors-apis

21.14 MySQL Eiffel Wrapper
==========================

Eiffel MySQL is an interface to the MySQL database server using the
Eiffel programming language
(http://en.wikipedia.org/wiki/Eiffel_(programming_language)), written
by Michael Ravits. It can be found at
`http://efsa.sourceforge.net/archive/ravits/mysql.htm'.


File: manual.info,  Node: extending-mysql,  Next: mysql-enterprise,  Prev: connectors-apis,  Up: Top

22 Extending MySQL
******************

* Menu:

* mysql-internals::              MySQL Internals
* plugin-api::                   The MySQL Plugin API
* adding-functions::             Adding New Functions to MySQL
* porting::                      Debugging and Porting MySQL


File: manual.info,  Node: mysql-internals,  Next: plugin-api,  Prev: extending-mysql,  Up: extending-mysql

22.1 MySQL Internals
====================

* Menu:

* mysql-threads::                MySQL Threads
* mysql-test-suite::             The MySQL Test Suite

This chapter describes a lot of things that you need to know when
working on the MySQL code. To track or contribute to MySQL development,
follow the instructions in *Note installing-development-tree::. If you
are interested in MySQL internals, you should also subscribe to our
`internals' mailing list. This list has relatively low traffic. For
details on how to subscribe, please see *Note mailing-lists::. Many
MySQL developers at Oracle Corporation are on the `internals' list and
we help other people who are working on the MySQL code. Feel free to
use this list both to ask questions about the code and to send patches
that you would like to contribute to the MySQL project!


File: manual.info,  Node: mysql-threads,  Next: mysql-test-suite,  Prev: mysql-internals,  Up: mysql-internals

22.1.1 MySQL Threads
--------------------

The MySQL server creates the following threads:

   * Connection manager threads handle client connection requests on
     the network interfaces that the server listens to. On all
     platforms, one manager thread handles TCP/IP connection requests.
     On Unix, this manager thread also handles Unix socket file
     connection requests. On Windows, a manager thread handles
     shared-memory connection requests, and another handles named-pipe
     connection requests. The server does not create threads to handle
     interfaces that it does not listen to. For example, a Windows
     server that does not have support for named-pipe connections
     enabled does not create a thread to handle them.

   * Connection manager threads associate each client connection with a
     thread dedicated to it that handles authentication and request
     processing for that connection. Manager threads create a new
     thread when necessary but try to avoid doing so by consulting the
     thread cache first to see whether it contains a thread that can be
     used for the connection. When a connection ends, its thread is
     returned to the thread cache if the cache is not full.

     For information about tuning the parameters that control thread
     resources, see *Note connection-threads::.

   * On a master replication server, connections from slave servers are
     handled like client connections: There is one thread per connected
     slave.

   * On a slave replication server, an I/O thread is started to connect
     to the master server and read updates from it. An SQL thread is
     started to apply updates read from the master.  These two threads
     run independently and can be started and stopped independently.

   * A signal thread handles all signals. This thread also normally
     handles alarms and calls `process_alarm()' to force timeouts on
     connections that have been idle too long.

   * If `InnoDB' is used, there will be 4 additional threads by
     default. Those are file I/O threads, controlled by the
     `innodb_file_io_threads' parameter. See *Note innodb-parameters::.

   * If *Note `mysqld': mysqld. is compiled with `-DUSE_ALARM_THREAD',
     a dedicated thread that handles alarms is created. This is only
     used on some systems where there are problems with `sigwait()' or
     if you want to use the `thr_alarm()' code in your application
     without a dedicated signal handling thread.

   * If the server is started with the `--flush_time=VAL' option, a
     dedicated thread is created to flush all tables every VAL seconds.

   * Each table for which *Note `INSERT DELAYED': insert-delayed.
     statements are issued gets its own thread.  See *Note
     insert-delayed::.

   * If the event scheduler is active, there is one thread for the
     scheduler, and a thread for each event currently running. See
     *Note events-overview::.

*Note `mysqladmin processlist': mysqladmin. only shows the connection,
*Note `INSERT DELAYED': insert-delayed, replication, and event threads.


File: manual.info,  Node: mysql-test-suite,  Prev: mysql-threads,  Up: mysql-internals

22.1.2 The MySQL Test Suite
---------------------------

The test system that is included in Unix source and binary
distributions makes it possible for users and developers to perform
regression tests on the MySQL code. These tests can be run on Unix.

You can also write your own test cases. For information about the MySQL
Test Framework, including system requirements, see the manual available
at `http://dev.mysql.com/doc/mysqltest/2.0/en/'.

The current set of test cases doesn't test everything in MySQL, but it
should catch most obvious bugs in the SQL processing code, operating
system or library issues, and is quite thorough in testing replication.
Our goal is to have the tests cover 100% of the code. We welcome
contributions to our test suite. You may especially want to contribute
tests that examine the functionality critical to your system because
this ensures that all future MySQL releases work well with your
applications.

The test system consists of a test language interpreter (`mysqltest'),
a Perl script to run all tests (`mysql-test-run.pl'), the actual test
cases written in a special test language, and their expected results.
To run the test suite on your system after a build, type `make test'
from the source root directory, or change location to the `mysql-test'
directory and type `./mysql-test-run.pl'. If you have installed a
binary distribution, change location to the `mysql-test' directory
under the installation root directory (for example,
`/usr/local/mysql/mysql-test'), and run `./mysql-test-run.pl'. All
tests should succeed. If any do not, feel free to try to find out why
and report the problem if it indicates a bug in MySQL. See *Note
bug-reports::.

If one test fails, you should run `mysql-test-run.pl' with the
`--force' option to check whether any other tests fail.

If you have a copy of *Note `mysqld': mysqld. running on the machine
where you want to run the test suite, you do not have to stop it, as
long as it is not using ports `9306' or `9307'. If either of those
ports is taken, you should set the `MTR_BUILD_THREAD' environment
variable to an appropriate value, and the test suite will use a
different set of ports for master, slave, NDB, and Instance Manager).
For example:


     shell> export MTR_BUILD_THREAD=31
     shell> ./mysql-test-run.pl [OPTIONS] [TEST_NAME]

In the `mysql-test' directory, you can run an individual test case with
`./mysql-test-run.pl TEST_NAME'.

If you have a question about the test suite, or have a test case to
contribute, send an email message to the MySQL `internals' mailing
list. See *Note mailing-lists::.


File: manual.info,  Node: plugin-api,  Next: adding-functions,  Prev: mysql-internals,  Up: extending-mysql

22.2 The MySQL Plugin API
=========================

* Menu:

* plugin-api-characteristics::   Plugin API Characteristics
* plugin-api-components::        Plugin API Components
* plugin-types::                 Types of Plugins
* writing-plugins::              Writing Plugins

MySQL 5.1 and up supports a plugin API that enables creation of server
components. Plugins can be loaded at server startup, or loaded and
unloaded at runtime without restarting the server. The API is generic
and does not specify what plugins can do. The components supported by
this interface include, but are not limited to, storage engines,
full-text parser plugins, and server extensions.

For example, full-text parser plugins can be used to replace or augment
the built-in full-text parser. A plugin can parse text into words using
rules that differ from those used by the built-in parser. This can be
useful if you need to parse text with characteristics different from
those expected by the built-in parser.

The plugin interface is more general than the older user-defined
function (UDF) interface.

The plugin interface uses the `plugin' table in the `mysql' database to
record information about plugins that have been installed permanently
with the *Note `INSTALL PLUGIN': install-plugin. statement. This table
is created as part of the MySQL installation process. (If you are
upgrading from a version of MySQL older than 5.1, you should run the
*Note `mysql_upgrade': mysql-upgrade. command to create this table. See
*Note mysql-upgrade::.) Plugins can also be installed for a single
server invocation with the `--plugin-load' option. Plugins installed
this way are not recorded in the `plugin' table. See *Note
server-plugin-loading::.

*Additional Resources*

The book `MySQL 5.1 Plugin Development' by Sergei Golubchik and Andrew
Hutchings provides a wealth of detail about the plugin API. Despite the
fact that the book's title refers to MySQL Server 5.1, most of the
information in it applies to later versions as well.


File: manual.info,  Node: plugin-api-characteristics,  Next: plugin-api-components,  Prev: plugin-api,  Up: plugin-api

22.2.1 Plugin API Characteristics
---------------------------------

The server plugin API has these characteristics:

   * All plugins have several things in common.

     Each plugin has a name that it can be referred to in SQL
     statements, as well as other metadata such as an author and a
     description that provide other information. This information can
     be examined in the *Note `INFORMATION_SCHEMA.PLUGINS':
     plugins-table.  table or using the *Note `SHOW PLUGINS':
     show-plugins. statement.

   * The plugin framework is extendable to accommodate different kinds
     of plugins.

     Although some aspects of the plugin API are common to all types of
     plugins, the API also permits type-specific interface elements so
     that different types of plugins can be created. A plugin with one
     purpose can have an interface most appropriate to its own
     requirements and not the requirements of some other plugin type.

     Interfaces for several types of plugins exist, such as storage
     engines, full-text parser, and `INFORMATION_SCHEMA' tables. Others
     can be added.

   * Plugins can expose information to users.

     A plugin can implement system and status variables that are
     available through the *Note `SHOW VARIABLES': show-variables. and
     *Note `SHOW STATUS': show-status. statements.

   * The plugin API includes versioning information.

     The version information included in the plugin API enables a
     plugin library and each plugin that it contains to be
     self-identifying with respect to the API version that was used to
     build the library. If the API changes over time, the version
     numbers will change, but a server can examine a given plugin
     library's version information to determine whether it supports the
     plugins in the library.

     There are two types of version numbers. The first is the version
     for the general plugin framework itself. Each plugin library
     includes this kind of version number. The second type of version
     applies to individual plugins. Each specific type of plugin has a
     version for its interface, so each plugin in a library has a
     type-specific version number. For example, a library containing a
     full-text parser plugin has a general plugin API version number,
     and the plugin has a version number specific to the full-text
     plugin interface.

   * The plugin API implements security restrictions.

     A plugin library must be installed in a specific dedicated
     directory for which the location is controlled by the server and
     cannot be changed at runtime. Also, the library must contain
     specific symbols that identify it as a plugin library. The server
     will not load something as a plugin if it was not built as a
     plugin.

In some respects, the server plugin API is similar to the older
user-defined function (UDF) API that it supersedes, but the plugin API
has several advantages over the older interface. For example, UDFs had
no versioning information. Also, the newer plugin interface eliminates
the security issues of the older UDF interface. The older interface for
writing nonplugin UDFs permitted libraries to be loaded from any
directory searched by the system's dynamic linker, and the symbols that
identified the UDF library were relatively nonspecific.


File: manual.info,  Node: plugin-api-components,  Next: plugin-types,  Prev: plugin-api-characteristics,  Up: plugin-api

22.2.2 Plugin API Components
----------------------------

The server plugin implementation comprises several components.

SQL statements:

   * *Note `INSTALL PLUGIN': install-plugin. registers a plugin in the
     `mysql.plugin' table and loads the plugin code.

   * *Note `UNINSTALL PLUGIN': uninstall-plugin. unregisters a plugin
     from the `mysql.plugin' table and unloads the plugin code.

   * The `WITH PARSER' clause for full-text index creation associates a
     full-text parser plugin with a given `FULLTEXT' index.

   * *Note `SHOW PLUGINS': show-plugins. displays information about
     server plugins.

Command-line options and system variables:

   * The `--plugin-load' option enables plugins to be loaded at server
     startup time.

   * The `plugin_dir' system variable indicates the location of the
     directory where all plugins must be installed. The value of this
     variable can be specified at server startup with a
     `--plugin_dir=PATH' option. *Note `mysql_config --plugindir':
     mysql-config. displays the default plugin directory path name.

For additional information about plugin loading, see *Note
server-plugin-loading::.

Plugin-related tables:

   * The *Note `INFORMATION_SCHEMA.PLUGINS': plugins-table.  table
     contains plugin information.

   * The `mysql.plugin' table lists each plugin that was installed with
     *Note `INSTALL PLUGIN': install-plugin. and is required for plugin
     use. For new MySQL installations, this table is created during the
     installation process. If you are upgrading from a version of MySQL
     older than 5.1, you should run *Note `mysql_upgrade':
     mysql-upgrade. to update your system tables and create the
     `plugin' table (see *Note mysql-upgrade::).

Source files (the locations indicate where the files are found in MySQL
source distributions):

   * In the `include/mysql' directory, `plugin.h' exposes the public
     plugin API.  This file should be examined by anyone who wants to
     write a plugin library.  `plugin_XXX.h' files provide additional
     information that pertains to specific types of plugins.

   * In the `sql' directory, `sql_plugin.h' and `sql_plugin.cc'
     comprise the internal plugin implementation. These files need not
     be consulted by plugin developers. They may be of interest for
     those who want to know more about how the server handles plugins.


File: manual.info,  Node: plugin-types,  Next: writing-plugins,  Prev: plugin-api-components,  Up: plugin-api

22.2.3 Types of Plugins
-----------------------

* Menu:

* storage-engine-plugins::       Storage Engine Plugins
* full-text-plugins::            Full-Text Parser Plugins
* daemon-plugins::               Daemon Plugins
* information-schema-plugins::   INFORMATION_SCHEMA Plugins

The plugin API enables creation of plugins that implement several
capabilities:

   * Storage engines

   * Full-text parsers

   * Daemons

   * `INFORMATION_SCHEMA' tables

The following sections provide an overview of these plugin types.


File: manual.info,  Node: storage-engine-plugins,  Next: full-text-plugins,  Prev: plugin-types,  Up: plugin-types

22.2.3.1 Storage Engine Plugins
...............................

The pluggable storage engine architecture used by MySQL Server enables
storage engines to be written as plugins and loaded into and unloaded
from a running server. For a description of this architecture, see
*Note pluggable-storage-overview::.

For information on how to use the plugin API to write storage engines,
see MySQL Internals: Writing a Custom Storage Engine
(http://dev.mysql.com/doc/internals/en/custom-engine.html).


File: manual.info,  Node: full-text-plugins,  Next: daemon-plugins,  Prev: storage-engine-plugins,  Up: plugin-types

22.2.3.2 Full-Text Parser Plugins
.................................

MySQL has a built-in parser that it uses by default for full-text
operations (parsing text to be indexed, or parsing a query string to
determine the terms to be used for a search).  For full-text
processing, `parsing' means extracting words from text or a query
string based on rules that define which character sequences make up a
word and where word boundaries lie.

When parsing for indexing purposes, the parser passes each word to the
server, which adds it to a full-text index. When parsing a query
string, the parser passes each word to the server, which accumulates
the words for use in a search.

The parsing properties of the built-in full-text parser are described
in *Note fulltext-search::. These properties include rules for
determining how to extract words from text. The parser is influenced by
certain system variables such as `ft_min_word_len' and
`ft_max_word_len' that cause words shorter or longer to be excluded,
and by the stopword list that identifies common words to be ignored.

The plugin API enables you to provide a full-text parser of your own so
that you have control over the basic duties of a parser. A parser
plugin can operate in either of two roles:

   * The plugin can replace the built-in parser. In this role, the
     plugin reads the input to be parsed, splits it up into words, and
     passes the words to the server (either for indexing or for word
     accumulation).

     One reason to use a parser this way is that you need to use
     different rules from those of the built-in parser for determining
     how to split up input into words. For example, the built-in parser
     considers the text `case-sensitive' to consist of two words `case'
     and `sensitive,' whereas an application might need to treat the
     text as a single word.

   * The plugin can act in conjunction with the built-in parser by
     serving as a front end for it. In this role, the plugin extracts
     text from the input and passes the text to the parser, which
     splits up the text into words using its normal parsing rules. In
     particular, this parsing will be affected by the `ft_XXX' system
     variables and the stopword list.

     One reason to use a parser this way is that you need to index
     content such as PDF documents, XML documents, or `.doc' files. The
     built-in parser is not intended for those types of input but a
     plugin can pull out the text from these input sources and pass it
     to the built-in parser.

It is also possible for a parser plugin to operate in both roles. That
is, it could extract text from nonplaintext input (the front end role),
and also parse the text into words (thus replacing the built-in parser).

A full-text plugin is associated with full-text indexes on a per-index
basis. That is, when you install a parser plugin initially, that does
not cause it to be used for any full-text operations. It simply becomes
available. For example, a full-text parser plugin becomes available to
be named in a `WITH PARSER' clause when creating individual `FULLTEXT'
indexes. To create such an index at table-creation time, do this:


     CREATE TABLE t
     (
       doc CHAR(255),
       FULLTEXT INDEX (doc) WITH PARSER my_parser
     ) ENGINE=MyISAM;

Or you can add the index after the table has been created:


     ALTER TABLE t ADD FULLTEXT INDEX (doc) WITH PARSER my_parser;

The only SQL change for associating the parser with the index is the
`WITH PARSER' clause. Searches are specified as before, with no changes
needed for queries.

When you associate a parser plugin with a `FULLTEXT' index, the plugin
is required for using the index. If the parser plugin is dropped, any
index associated with it becomes unusable. Any attempt to use a table
for which a plugin is not available results in an error, although *Note
`DROP TABLE': drop-table. is still possible.

For more information about full-text plugins, see *Note
writing-full-text-plugins::. MySQL 5.1 only supports full-text plugins
with *Note `MyISAM': myisam-storage-engine.


File: manual.info,  Node: daemon-plugins,  Next: information-schema-plugins,  Prev: full-text-plugins,  Up: plugin-types

22.2.3.3 Daemon Plugins
.......................

A daemon plugin is a simple type of plugin used for code that should be
run by the server but that does not communicate with it. MySQL
distributions include an example daemon plugin that writes periodic
heartbeat messages to a file.

For more information about daemon plugins, see *Note
writing-daemon-plugins::.


File: manual.info,  Node: information-schema-plugins,  Prev: daemon-plugins,  Up: plugin-types

22.2.3.4 INFORMATION_SCHEMA Plugins
...................................

`INFORMATION_SCHEMA' plugins enable the creation of tables containing
server metadata that are exposed to users through the
`INFORMATION_SCHEMA' database. For example, `InnoDB' uses
`INFORMATION_SCHEMA' plugins to provide tables that contain information
about current transactions and locks.

For more information about `INFORMATION_SCHEMA' plugins, see *Note
writing-information-schema-plugins::.


File: manual.info,  Node: writing-plugins,  Prev: plugin-types,  Up: plugin-api

22.2.4 Writing Plugins
----------------------

* Menu:

* writing-plugins-overview::     Overview of Plugin Writing
* plugin-data-structures::       Plugin Data Structures
* compiling-plugin-libraries::   Compiling and Installing Plugin Libraries
* writing-full-text-plugins::    Writing Full-Text Parser Plugins
* writing-daemon-plugins::       Writing Daemon Plugins
* writing-information-schema-plugins::  Writing INFORMATION_SCHEMA Plugins

To create a plugin library, you must provide the required descriptor
information that indicates what plugins the library file contains, and
write the interface functions for each plugin.

Every server plugin must have a general descriptor that provides
information to the plugin API, and a type-specific descriptor that
provides information about the plugin interface for a given type of
plugin. The structure of the general descriptor is the same for all
plugin types. The structure of the type-specific descriptor varies
among plugin types and is determined by the requirements of what the
plugin needs to do. The server plugin interface also enables plugins to
expose status and system variables. These variables become visible
through the *Note `SHOW STATUS': show-status. and *Note `SHOW
VARIABLES': show-variables. statements and the corresponding
`INFORMATION_SCHEMA' tables.

You can write plugins in C or C++ (or another language that can use C
calling conventions). Plugins are loaded and unloaded dynamically, so
your operating system must support dynamic loading and you must have
compiled *Note `mysqld': mysqld.  dynamically (not statically).

A server plugin contains code that becomes part of the running server,
so when you write the plugin, you are bound by any and all constraints
that otherwise apply to writing server code. For example, you may have
problems if you attempt to use functions from the `libstdc++' library.
These constraints may change in future versions of the server, so it is
possible that server upgrades will require revisions to plugins
originally written for older servers. For information about these
constraints, see *Note source-configuration-options::, and *Note
compilation-problems::.


File: manual.info,  Node: writing-plugins-overview,  Next: plugin-data-structures,  Prev: writing-plugins,  Up: writing-plugins

22.2.4.1 Overview of Plugin Writing
...................................

The following procedure provides an overview of the steps needed to
create a plugin library. The next sections provide additional details
on setting plugin data structures and writing specific types of plugins.

  1. In the plugin source file, include the header files that the
     plugin library needs. The `plugin.h' file is required, and the
     library might require other files as well. For example:


          #include <stdlib.h>
          #include <ctype.h>
          #include <mysql/plugin.h>

  2. Set up the descriptor information for the plugin library file.
     This descriptor must contain the general plugin descriptor for
     each server plugin in the file. For more information, see *Note
     server-plugin-descriptors::. In addition, set up the type-specific
     descriptor for each server plugin in the library. Each plugin's
     general descriptor points to its type-specific descriptor.

  3. Write the plugin interface functions for each plugin. Each
     plugin's general plugin descriptor points to the initialization
     and deinitialization functions that the server should invoke when
     it loads and unloads the plugin.  The plugin's type-specific
     description may also point to interface functions.

  4. Set up the status and system variables, if there are any.

  5. Compile the plugin library as a shared library and install it in
     the plugin directory. For more information, see *Note
     compiling-plugin-libraries::.

  6. Register the plugin with the server. For more information, see
     *Note server-plugin-loading::.

  7. Test the plugin to verify that it works properly.


File: manual.info,  Node: plugin-data-structures,  Next: compiling-plugin-libraries,  Prev: writing-plugins-overview,  Up: writing-plugins

22.2.4.2 Plugin Data Structures
...............................

* Menu:

* server-plugin-descriptors::    Library and Plugin Descriptors
* plugin-status-system-variables::  Plugin Status and System Variables

A plugin library file includes descriptor information to indicate what
plugins it contains.

The plugin library must include the following descriptor information:

   * A library descriptor indicates the general server plugin API
     version number used by the library and contains a general plugin
     descriptor for each server plugin in the library. To provide the
     framework for this descriptor, invoke two macros from the
     `plugin.h' header file:


          mysql_declare_plugin(NAME)
           ... ONE OR MORE SERVER PLUGIN DESCRIPTORS HERE ...
          mysql_declare_plugin_end;

     The macros expand to provide a declaration for the API version
     automatically. You must provide the plugin descriptors.

   * Within the library descriptor, each general server plugin is
     described by a `st_mysql_plugin' structure. This plugin descriptor
     structure contains information that is common to every type of
     server plugin: A value that indicates the plugin type; the plugin
     name, author, description, and license type; pointers to the
     initialization and deinitialization functions that the server
     invokes when it loads and unloads the plugin, and pointers to any
     status or system variables the plugin implements.

   * Each general server plugin descriptor within the library
     descriptor also contains a pointer to a type-specific plugin
     descriptor. The structure of the type-specific descriptors varies
     from one plugin type to another because each type of plugin can
     have its own API. A type-specific plugin descriptor contains a
     type-specific API version number and pointers to the functions
     that are needed to implement that plugin type. For example, a
     full-text parser plugin has initialization and deinitialization
     functions, and a main parsing function. The server invokes these
     functions when it uses the plugin to parse text.

The plugin library also contains the interface functions that are
referenced by the general and type-specific descriptors for each plugin
in the library.


File: manual.info,  Node: server-plugin-descriptors,  Next: plugin-status-system-variables,  Prev: plugin-data-structures,  Up: plugin-data-structures

22.2.4.3 Library and Plugin Descriptors
.......................................

Every plugin library must include a library descriptor that contains
the general plugin descriptor for each server plugin in the file. This
section discusses how to write the library and general descriptors for
server plugins.

The library descriptor must define two symbols:

   * `_mysql_plugin_interface_version_' specifies the version number of
     the general plugin framework. This is given by the
     `MYSQL_PLUGIN_INTERFACE_VERSION' symbol, which is defined in the
     `plugin.h' file.

   * `_mysql_plugin_declarations_' defines an array of plugin
     declarations, terminated by a declaration with all members set to
     0. Each declaration is an instance of the `st_mysql_plugin'
     structure (also defined in `plugin.h'). There must be one of these
     for each server plugin in the library.

If the server does not find those two symbols in a library, it does not
accept it as a legal plugin library and rejects it with an error. This
prevents use of a library for plugin purposes unless it was built
specifically as a plugin library.

The conventional way to define the two required symbols is by using the
`mysql_declare_plugin()' and `mysql_declare_plugin_end' macros from the
`plugin.h' file:


     mysql_declare_plugin(NAME)
      ... ONE OR MORE SERVER PLUGIN DESCRIPTORS HERE ...
     mysql_declare_plugin_end;

Each server plugin must have a general descriptor that provides
information to the server plugin API. The general descriptor has the
same structure for all plugin types. The `st_mysql_plugin' structure in
the `plugin.h' file defines this descriptor:


     struct st_mysql_plugin
     {
       int type;             /* the plugin type (a MYSQL_XXX_PLUGIN value)   */
       void *info;           /* pointer to type-specific plugin descriptor   */
       const char *name;     /* plugin name                                  */
       const char *author;   /* plugin author (for I_S.PLUGINS)              */
       const char *descr;    /* general descriptive text (for I_S.PLUGINS)   */
       int license;          /* the plugin license (PLUGIN_LICENSE_XXX)      */
       int (*init)(void *);  /* the function to invoke when plugin is loaded */
       int (*deinit)(void *);/* the function to invoke when plugin is unloaded */
       unsigned int version; /* plugin version (for I_S.PLUGINS)             */
       struct st_mysql_show_var *status_vars;
       struct st_mysql_sys_var **system_vars;
       void * __reserved1;   /* reserved for dependency checking             */
     };

The `st_mysql_plugin' descriptor structure members are used as follows.
`char *' members should be specified as null-terminated strings.

   * `type': The plugin type. This must be one of the plugin-type
     values from `plugin.h':


          /*
            The allowable types of plugins
          */
          #define MYSQL_UDF_PLUGIN             0  /* User-defined function        */
          #define MYSQL_STORAGE_ENGINE_PLUGIN  1  /* Storage Engine               */
          #define MYSQL_FTPARSER_PLUGIN        2  /* Full-text parser plugin      */
          #define MYSQL_DAEMON_PLUGIN          3  /* The daemon/raw plugin type */
          #define MYSQL_INFORMATION_SCHEMA_PLUGIN  4  /* The I_S plugin type */
          ...

     For example, for a full-text parser plugin, the `type' value is
     `MYSQL_FTPARSER_PLUGIN'.

   * `info': A pointer to the type-specific descriptor for the plugin.
     This descriptor's structure depends on the particular type of
     plugin, unlike that of the general plugin descriptor structure. For
     version-control purposes, the first member of the type-specific
     descriptor for every plugin type is expected to be the interface
     version for the type. This enables the server to check the
     type-specific version for every plugin no matter its type.
     Following the version number, the descriptor includes any other
     members needed, such as callback functions and other information
     needed by the server to invoke the plugin properly. Later sections
     on writing particular types of server plugins describe the
     structure of their type-specific descriptors.

   * `name': A string that gives the plugin name. This is the name that
     will be listed in the `mysql.plugin' table and by which you refer
     to the plugin in SQL statements such as *Note `INSTALL PLUGIN':
     install-plugin. and *Note `UNINSTALL PLUGIN': uninstall-plugin, or
     with the `--plugin-load' option.  The name is also visible in the
     *Note `INFORMATION_SCHEMA.PLUGINS': plugins-table.  table or the
     output from *Note `SHOW PLUGINS': show-plugins.

     The plugin name should not begin with the name of any server
     option. If it does, the server will fail to initialize it. For
     example, the server has a `--socket' option, so you should not use
     a plugin name such as `socket', `socket_plugin', and so forth.

   * `author': A string naming the plugin author. This can be whatever
     you like.

   * `desc': A string that provides a general description of the
     plugin. This can be whatever you like.

   * `license': The plugin license type. The value can be one of
     `PLUGIN_LICENSE_PROPRIETARY', `PLUGIN_LICENSE_GPL', or
     `PLUGIN_LICENSE_BSD'.

   * `init': A once-only initialization function, or `NULL' if there is
     no such function. The server executes this function when it loads
     the plugin, which happens for *Note `INSTALL PLUGIN':
     install-plugin. or, for plugins listed in the `mysql.plugin'
     table, at server startup. The function takes one argument that
     points to the internal structure used to identify the plugin. It
     returns zero for success and nonzero for failure.

   * `deinit': A once-only deinitialization function, or `NULL' if
     there is no such function. The server executes this function when
     it unloads the plugin, which happens for *Note `UNINSTALL PLUGIN':
     uninstall-plugin. or, for plugins listed in the `mysql.plugin'
     table, at server shutdown. The function takes one argument that
     points to the internal structure used to identify the plugin It
     returns zero for success and nonzero for failure.

   * `version': The plugin version number.  When the plugin is
     installed, this value can be retrieved from the *Note
     `INFORMATION_SCHEMA.PLUGINS': plugins-table.  table. The value
     includes major and minor numbers. If you write the value as a hex
     constant, the format is `0xMMNN', where MM and `NN' are the major
     and minor numbers, respectively. For example, `0x0302' represents
     version 3.2.

   * `status_vars': A pointer to a structure for status variables
     associated with the plugin, or `NULL' if there are no such
     variables.  When the plugin is installed, these variables are
     displayed in the output of the *Note `SHOW STATUS': show-status.
     statement.

     The `status_vars' member, if not `NULL', points to an array of
     `st_mysql_show_var' structures that describe status variables. See
     *Note plugin-status-system-variables::.

   * `system_vars': A pointer to a structure for system variables
     associated with the plugin, or `NULL' if there are no such
     variables.  These options and system variables can be used to help
     initialize variables within the plugin.

     The `system_vars' member, if not `NULL', points to an array of
     `st_mysql_sys_var' structures that describe system variables. See
     *Note plugin-status-system-variables::.

   * `__reserved1': A placeholder for the future. Currently, it should
     be set to `NULL'.

The server invokes the `init' and `deinit' functions in the general
plugin descriptor only when loading and unloading the plugin. They have
nothing to do with use of the plugin such as happens when an SQL
statement causes the plugin to be invoked.

For example, the descriptor information for a library that contains a
single full-text parser plugin named `simple_parser' looks like this:


     mysql_declare_plugin(ftexample)
     {
       MYSQL_FTPARSER_PLUGIN,      /* type                            */
       &simple_parser_descriptor,  /* descriptor                      */
       "simple_parser",            /* name                            */
       "Oracle Corporation",       /* author                          */
       "Simple Full-Text Parser",  /* description                     */
       PLUGIN_LICENSE_GPL,         /* plugin license                  */
       simple_parser_plugin_init,  /* init function (when loaded)     */
       simple_parser_plugin_deinit,/* deinit function (when unloaded) */
       0x0001,                     /* version                         */
       simple_status,              /* status variables                */
       simple_system_variables,    /* system variables                */
       NULL
     }
     mysql_declare_plugin_end;

For a full-text parser plugin, the type must be
`MYSQL_FTPARSER_PLUGIN'. This is the value that identifies the plugin
as being legal for use in a `WITH PARSER' clause when creating a
`FULLTEXT' index. (No other plugin type is legal for this clause.)

`plugin.h' defines the `mysql_declare_plugin()' and
`mysql_declare_plugin_end' macros like this:


     #ifndef MYSQL_DYNAMIC_PLUGIN
     #define __MYSQL_DECLARE_PLUGIN(NAME, VERSION, PSIZE, DECLS)            \
     int VERSION= MYSQL_PLUGIN_INTERFACE_VERSION;                           \
     int PSIZE= sizeof(struct st_mysql_plugin);                             \
     struct st_mysql_plugin DECLS[]= {
     #else
     #define __MYSQL_DECLARE_PLUGIN(NAME, VERSION, PSIZE, DECLS)            \
     MYSQL_PLUGIN_EXPORT int _mysql_plugin_interface_version_= MYSQL_PLUGIN_INTERFACE_VERSION;         \
     MYSQL_PLUGIN_EXPORT int _mysql_sizeof_struct_st_plugin_= sizeof(struct st_mysql_plugin);          \
     MYSQL_PLUGIN_EXPORT struct st_mysql_plugin _mysql_plugin_declarations_[]= {
     #endif

     #define mysql_declare_plugin(NAME) \
     __MYSQL_DECLARE_PLUGIN(NAME, \
                      builtin_ ## NAME ## _plugin_interface_version, \
                      builtin_ ## NAME ## _sizeof_struct_st_plugin, \
                      builtin_ ## NAME ## _plugin)

     #define mysql_declare_plugin_end ,{0,0,0,0,0,0,0,0,0,0,0,0}}

*Note*:

Those declarations define the `_mysql_plugin_interface_version_' symbol
only if the `MYSQL_DYNAMIC_PLUGIN' symbol is defined. This means that
`-DMYSQL_DYNAMIC_PLUGIN' must be provided as part of the compilation
command to build the plugin as a shared library.

When the macros are used as just shown, they expand to the following
code, which defines both of the required symbols
(`_mysql_plugin_interface_version_' and `_mysql_plugin_declarations_'):


     int _mysql_plugin_interface_version_= MYSQL_PLUGIN_INTERFACE_VERSION;
     int _mysql_sizeof_struct_st_plugin_= sizeof(struct st_mysql_plugin);
     struct st_mysql_plugin _mysql_plugin_declarations_[]= {
     {
       MYSQL_FTPARSER_PLUGIN,      /* type                            */
       &simple_parser_descriptor,  /* descriptor                      */
       "simple_parser",            /* name                            */
       "Oracle Corporation",       /* author                          */
       "Simple Full-Text Parser",  /* description                     */
       PLUGIN_LICENSE_GPL,         /* plugin license                  */
       simple_parser_plugin_init,  /* init function (when loaded)     */
       simple_parser_plugin_deinit,/* deinit function (when unloaded) */
       0x0001,                     /* version                         */
       simple_status,              /* status variables                */
       simple_system_variables,    /* system variables                */
       NULL
     }
       ,{0,0,0,0,0,0,0,0,0,0,0,0}}
     };

The preceding example declares a single plugin in the general
descriptor, but it is possible to declare multiple plugins. List the
declarations one after the other between `mysql_declare_plugin()' and
`mysql_declare_plugin_end', separated by commas.

MySQL server plugins can be written in C or C++ (or another language
that can use C calling conventions). If you write a C++ plugin, one C++
feature that you should not use is nonconstant variables to initialize
global structures.  Members of structures such as the `st_mysql_plugin'
structure should be initialized only with constant variables. The
`simple_parser' descriptor shown earlier is permissible in a C++ plugin
because it satisfies that requirement:


     mysql_declare_plugin(ftexample)
     {
       MYSQL_FTPARSER_PLUGIN,      /* type                            */
       &simple_parser_descriptor,  /* descriptor                      */
       "simple_parser",            /* name                            */
       "Oracle Corporation",       /* author                          */
       "Simple Full-Text Parser",  /* description                     */
       PLUGIN_LICENSE_GPL,         /* plugin license                  */
       simple_parser_plugin_init,  /* init function (when loaded)     */
       simple_parser_plugin_deinit,/* deinit function (when unloaded) */
       0x0001,                     /* version                         */
       simple_status,              /* status variables                */
       simple_system_variables,    /* system variables                */
       NULL
     }
     mysql_declare_plugin_end;

Here is another valid way to write the general descriptor.  It uses
constant variables to indicate the plugin name, author, and description:


     const char *simple_parser_name = "simple_parser";
     const char *simple_parser_author = "Oracle Corporation";
     const char *simple_parser_description = "Simple Full-Text Parser";

     mysql_declare_plugin(ftexample)
     {
       MYSQL_FTPARSER_PLUGIN,      /* type                            */
       &simple_parser_descriptor,  /* descriptor                      */
       simple_parser_name,         /* name                            */
       simple_parser_author,       /* author                          */
       simple_parser_description,  /* description                     */
       PLUGIN_LICENSE_GPL,         /* plugin license                  */
       simple_parser_plugin_init,  /* init function (when loaded)     */
       simple_parser_plugin_deinit,/* deinit function (when unloaded) */
       0x0001,                     /* version                         */
       simple_status,              /* status variables                */
       simple_system_variables,    /* system variables                */
       NULL
     }
     mysql_declare_plugin_end;

However, the following general descriptor is invalid. It uses structure
members to indicate the plugin name, author, and description, but
structures are not considered constant initializers in C++:


     typedef struct
     {
       const char *name;
       const char *author;
       const char *description;
     } plugin_info;

     plugin_info parser_info = {
       "simple_parser",
       "Oracle Corporation",
       "Simple Full-Text Parser"
     };

     mysql_declare_plugin(ftexample)
     {
       MYSQL_FTPARSER_PLUGIN,      /* type                            */
       &simple_parser_descriptor,  /* descriptor                      */
       parser_info.name,           /* name                            */
       parser_info.author,         /* author                          */
       parser_info.description,    /* description                     */
       PLUGIN_LICENSE_GPL,         /* plugin license                  */
       simple_parser_plugin_init,  /* init function (when loaded)     */
       simple_parser_plugin_deinit,/* deinit function (when unloaded) */
       0x0001,                     /* version                         */
       simple_status,              /* status variables                */
       simple_system_variables,    /* system variables                */
       NULL
     }
     mysql_declare_plugin_end;


File: manual.info,  Node: plugin-status-system-variables,  Prev: server-plugin-descriptors,  Up: plugin-data-structures

22.2.4.4 Plugin Status and System Variables
...........................................

The server plugin interface enables plugins to expose status and system
variables using the `status_vars' and `system_vars' members of the
general plugin descriptor.

The `status_vars' member of the general plugin descriptor, if not 0,
points to an array of `st_mysql_show_var' structures, each of which
describes one status variable, followed by a structure with all members
set to 0. The `st_mysql_show_var' structure has this definition:


     struct st_mysql_show_var {
       const char *name;
       char *value;
       enum enum_mysql_show_type type;
     };

When the plugin is installed, the plugin name and the `name' value are
joined with an underscore to form the name displayed by *Note `SHOW
STATUS': show-status.

The following table shows the permissible status variable `type' values
and what the corresponding variable should be.

*Server Plugin Status Variable Types*

Variable Type          Meaning
`SHOW_BOOL'            Pointer to a boolean variable
`SHOW_INT'             Pointer to an integer variable
`SHOW_LONG'            Pointer to a long integer variable
`SHOW_LONGLONG'        Pointer to a longlong integer variable
`SHOW_CHAR'            A string
`SHOW_CHAR_PTR'        Pointer to a string
`SHOW_ARRAY'           Pointer to another `st_mysql_show_var' array
`SHOW_FUNC'            Pointer to a function
`SHOW_DOUBLE'          Pointer to a double

For the `SHOW_FUNC' type, the function is called and fills in its `out'
parameter, which then provides information about the variable to be
displayed. The function has this signature:


     #define SHOW_VAR_FUNC_BUFF_SIZE 1024

     typedef int (*mysql_show_var_func) (void *thd,
                                         struct st_mysql_show_var *out,
                                         char *buf);

The `system_vars' member, if not 0, points to an array of
`st_mysql_sys_var' structures, each of which describes one system
variable (which can also be set from the command-line or configuration
file), followed by a structure with all members set to 0. The
`st_mysql_sys_var' structure is defined as follows:


     struct st_mysql_sys_var {
      int flags;
      const char *name, *comment;
      int (*check)(THD*, struct st_mysql_sys_var *, void*, st_mysql_value*);
      void (*update)(THD*, struct st_mysql_sys_var *, void*, const void*);
     };

Additional fields are append as required depending upon the flags.

For convenience, a number of macros are defined that make creating new
system variables within a plugin much simpler.

Throughout the macros, the following fields are available:

   * `name': An unquoted identifier for the system variable.

   * `varname': The identifier for the static variable. Where not
     available, it is the same as the `name' field.

   * `opt': Additional use flags for the system variable. The following
     table shows the permissible flags.

     *Server Plugin System Variable Flags*

     Flag Value        Description
     `PLUGIN_VAR_READONLY'The system variable is read only
     `PLUGIN_VAR_NOSYSVAR'The system variable is not user visible at runtime
     `PLUGIN_VAR_NOCMDOPT'The system variable is not configurable from the
                       command line
     `PLUGIN_VAR_NOCMDARG'No argument is required at the command line
                       (typically used for boolean variables)
     `PLUGIN_VAR_RQCMDARG'An argument is required at the command line (this
                       is the default)
     `                 An argument is optional at the command line
     PLUGIN_VAR_OPCMDARG'
     `PLUGIN_VAR_MEMALLOC'Used for string variables; indicates that memory
                       is to be allocated for storage of the string

   * `comment': A descriptive comment to be displayed in the server
     help message.  `NULL' if this variable is to be hidden.

   * `check': The check function, `NULL' for default.

   * `update': The update function, `NULL' for default.

   * `default': The variable default value.

   * `minimum': The variable minimum value.

   * `maximum': The variable maximum value.

   * `blocksize': The variable block size.  When the value is set, it
     is rounded to the nearest multiple of `blocksize'.

A system variable may be accessed either by using the static variable
directly or by using the `SYSVAR()'accessor macro. The `SYSVAR()' macro
is provided for completeness. Usually it should be used only when the
code cannot directly access the underlying variable.

For example:


     static int my_foo;
     static MYSQL_SYSVAR_INT(foo_var, my_foo,
                             PLUGIN_VAR_RQCMDARG, "foo comment",
                             NULL, NULL, 0, 0, INT_MAX, 0);
      ...
        SYSVAR(foo_var)= value;
        value= SYSVAR(foo_var);
        my_foo= value;
        value= my_foo;

Session variables may be accessed only through the `THDVAR()' accessor
macro. For example:


     static MYSQL_THDVAR_BOOL(some_flag,
                              PLUGIN_VAR_NOCMDARG, "flag comment",
                              NULL, NULL, FALSE);
      ...
        if (THDVAR(thd, some_flag))
        {
          do_something();
          THDVAR(thd, some_flag)= FALSE;
        }

All global and session system variables must be published to *Note
`mysqld': mysqld. before use. This is done by constructing a
`NULL'-terminated array of the variables and linking to it in the
plugin public interface. For example:


     static struct st_mysql_sys_var *my_plugin_vars[]= {
       MYSQL_SYSVAR(foo_var),
       MYSQL_SYSVAR(some_flag),
       NULL
     };
     mysql_declare_plugin(fooplug)
     {
       MYSQL_..._PLUGIN,
       &plugin_data,
       "fooplug",
       "foo author",
       "This does foo!",
       PLUGIN_LICENSE_GPL,
       foo_init,
       foo_fini,
       0x0001,
       NULL,
       my_plugin_vars,
       NULL
     }
     mysql_declare_plugin_end;

The following convenience macros enable you to declare different types
of system variables:

   * Boolean system variables of type `my_bool', which is a 1-byte
     boolean.  (0 = FALSE, 1 = TRUE)


          MYSQL_THDVAR_BOOL(name, opt, comment, check, update, default)
          MYSQL_SYSVAR_BOOL(name, varname, opt, comment, check, update, default)

   * String system variables of type `char*', which is a pointer to a
     null-terminated string.


          MYSQL_THDVAR_STR(name, opt, comment, check, update, default)
          MYSQL_SYSVAR_STR(name, varname, opt, comment, check, update, default)

   * Integer system variables, of which there are several varieties.

        * An `int' system variable, which is typically a 4-byte signed
          word.


               MYSQL_THDVAR_INT(name, opt, comment, check, update, default, min, max, blk)
               MYSQL_SYSVAR_INT(name, varname, opt, comment, check, update, default,
                              minimum, maximum, blocksize)

        * An `unsigned int' system variable, which is typically a
          4-byte unsigned word.


               MYSQL_THDVAR_UINT(name, opt, comment, check, update, default, min, max, blk)
               MYSQL_SYSVAR_UINT(name, varname, opt, comment, check, update, default,
                               minimum, maximum, blocksize)

        * A `long' system variable, which is typically either a 4- or
          8-byte signed word.


               MYSQL_THDVAR_LONG(name, opt, comment, check, update, default, min, max, blk)
               MYSQL_SYSVAR_LONG(name, varname, opt, comment, check, update, default,
                               minimum, maximum, blocksize)

        * An `unsigned long' system variable, which is typically either
          a 4- or 8-byte unsigned word.


               MYSQL_THDVAR_ULONG(name, opt, comment, check, update, default, min, max, blk)
               MYSQL_SYSVAR_ULONG(name, varname, opt, comment, check, update, default,
                                minimum, maximum, blocksize)

        * A `long long' system variable, which is typically an 8-byte
          signed word.


               MYSQL_THDVAR_LONGLONG(name, opt, comment, check, update,
                                   default, minimum, maximum, blocksize)
               MYSQL_SYSVAR_LONGLONG(name, varname, opt, comment, check, update,
                                   default, minimum, maximum, blocksize)

        * An `unsigned long long' system variable, which is typically
          an 8-byte unsigned word.


               MYSQL_THDVAR_ULONGLONG(name, opt, comment, check, update,
                                    default, minimum, maximum, blocksize)
               MYSQL_SYSVAR_ULONGLONG(name, varname, opt, comment, check, update,
                                    default, minimum, maximum, blocksize)

        * An `unsigned long' system variable, which is typically either
          a 4- or 8-byte unsigned word. The range of possible values is
          an ordinal of the number of elements in the `typelib',
          starting from 0.


               MYSQL_THDVAR_ENUM(name, opt, comment, check, update, default, typelib)
               MYSQL_SYSVAR_ENUM(name, varname, opt, comment, check, update,
                               default, typelib)

        * An `unsigned long long' system variable, which is typically
          an 8-byte unsigned word. Each bit represents an element in the
          `typelib'.


               MYSQL_THDVAR_SET(name, opt, comment, check, update, default, typelib)
               MYSQL_SYSVAR_SET(name, varname, opt, comment, check, update,
                              default, typelib)

Internally, all mutable and plugin system variables are stored in a
`HASH' structure.

Display of the server command-line help text is handled by compiling a
`DYNAMIC_ARRAY' of all variables relevant to command-line options,
sorting them, and then iterating through them to display each option.

When a command-line option has been handled, it is then removed from
the `argv' by the `handle_option()' function (`my_getopt.c'); in
effect, it is consumed.

The server processes command-line options during the plugin
installation process, immediately after the plugin has been
successfully loaded but before the plugin initialization function has
been called

Plugins loaded at runtime do not benefit from any configuration options
and must have usable defaults. Once they are installed, they are loaded
at *Note `mysqld': mysqld. initialization time and configuration
options can be set at the command line or within `my.cnf'.

Plugins should consider the `thd' parameter to be read only.


File: manual.info,  Node: compiling-plugin-libraries,  Next: writing-full-text-plugins,  Prev: plugin-data-structures,  Up: writing-plugins

22.2.4.5 Compiling and Installing Plugin Libraries
..................................................

After your plugin is written, you must compile it and install it. The
procedure for compiling shared objects varies from system to system. If
you build your library using the GNU autotools, `libtool' should be
able to generate the correct compilation commands for your system. If
the library is named `somepluglib', you should end up with a shared
object file that has a name something like `somepluglib.so'. (The file
name might have a different suffix on your system.)

To use the autotools, you'll need to make a few changes to the
configuration files at this point to enable the plugin to be compiled
and installed. Assume that your MySQL distribution is installed at a
base directory of `/usr/local/mysql' and that its header files are
located in the `include' directory under the base directory.

Edit `Makefile.am', which should look something like this:


     #Makefile.am example for a plugin

     pkgplugindir=$(libdir)/mysql/plugin
     INCLUDES= -I$(top_builddir)/include -I$(top_srcdir)/include
     #noinst_LTLIBRARIES= somepluglib.la
     pkgplugin_LTLIBRARIES= somepluglib.la
     somepluglib_la_SOURCES= plugin_example.c
     somepluglib_la_LDFLAGS= -module -rpath $(pkgplugindir)
     somepluglib_la_CFLAGS= -DMYSQL_DYNAMIC_PLUGIN

*Note*:

As mentioned in *Note server-plugin-descriptors::, be sure to specify
`-DMYSQL_DYNAMIC_PLUGIN' as part of the compilation command when you
build the plugin. The `somepluglib_la_CFLAGS' line takes care of this.

Adjust the `INCLUDES' line to specify the path name to the installed
MySQL header files. Edit it to look like this:


     INCLUDES= -I/usr/local/mysql/include

Make sure that the `noinst_LTLIBRARIES' line is commented out or remove
it. Make sure that the `pkglib_LTLIBRARIES' line is not commented out;
it enables the `make install' command.

Set up the files needed for the `configure' command, invoke it, and run
`make':


     shell> autoreconf --force --install --symlink
     shell> ./configure --prefix=/usr/local/mysql
     shell> make

The `--prefix' option to `configure' indicates the MySQL base directory
under which the plugin should be installed. You can see what value to
use for this option with *Note `SHOW VARIABLES': show-variables.:


     mysql> SHOW VARIABLES LIKE 'basedir';
     +---------------+------------------+
     | Variable_name | Value            |
     +---------------+------------------+
     | base          | /usr/local/mysql |
     +---------------+------------------+

The location of the plugin directory where you should install the
library is given by the `plugin_dir' system variable.  For example:


     mysql> SHOW VARIABLES LIKE 'plugin_dir';
     +---------------+-----------------------------------+
     | Variable_name | Value                             |
     +---------------+-----------------------------------+
     | plugin_dir    | /usr/local/mysql/lib/mysql/plugin |
     +---------------+-----------------------------------+

To install the plugin library, use `make':


     shell> make install

Verify that `make install' installed the plugin library in the proper
directory. After installing it, make sure that the library permissions
permit it to be executed by the server.


File: manual.info,  Node: writing-full-text-plugins,  Next: writing-daemon-plugins,  Prev: compiling-plugin-libraries,  Up: writing-plugins

22.2.4.6 Writing Full-Text Parser Plugins
.........................................

MySQL 5.1 only supports full-text parser plugins with *Note `MyISAM':
myisam-storage-engine. For introductory information about full-text
parser plugins, see *Note full-text-plugins::.

A full-text parser server plugin can be used to replace or modify the
built-in full-text parser. This section describes how to write a
full-text parser plugin named `simple_parser'. This plugin performs
parsing based on simpler rules than those used by the MySQL built-in
full-text parser: Words are nonempty runs of whitespace characters.

The instructions use the source code in the `plugin/fulltext' directory
of MySQL source distributions, so change location into that directory.
The following procedure describes how the plugin library is created:

  1. To write a full-text parser plugin, include the following header
     file in the plugin source file. Other MySQL or general header
     files might also be needed, depending on the plugin capabilities
     and requirements.


          #include <mysql/plugin.h>

     `plugin.h' defines the `MYSQL_FTPARSER_PLUGIN' server plugin type
     and the data structures needed to declare the plugin.

  2. Set up the library descriptor for the plugin library file.

     This descriptor contains the general plugin descriptor for the
     server plugin. For a full-text parser plugin, the type must be
     `MYSQL_FTPARSER_PLUGIN'. This is the value that identifies the
     plugin as being legal for use in a `WITH PARSER' clause when
     creating a `FULLTEXT' index. (No other plugin type is legal for
     this clause.)

     For example, the library descriptor for a library that contains a
     single full-text parser plugin named `simple_parser' looks like
     this:


          mysql_declare_plugin(ftexample)
          {
            MYSQL_FTPARSER_PLUGIN,      /* type                            */
            &simple_parser_descriptor,  /* descriptor                      */
            "simple_parser",            /* name                            */
            "Oracle Corporation",       /* author                          */
            "Simple Full-Text Parser",  /* description                     */
            PLUGIN_LICENSE_GPL,         /* plugin license                  */
            simple_parser_plugin_init,  /* init function (when loaded)     */
            simple_parser_plugin_deinit,/* deinit function (when unloaded) */
            0x0001,                     /* version                         */
            simple_status,              /* status variables                */
            simple_system_variables,    /* system variables                */
            NULL
          }
          mysql_declare_plugin_end;

     The `name' member (`simple_parser') indicates the name to use for
     references to the plugin in statements such as *Note `INSTALL
     PLUGIN': install-plugin. or *Note `UNINSTALL PLUGIN':
     uninstall-plugin. This is also the name displayed by *Note `SHOW
     PLUGINS': show-plugins. or *Note `INFORMATION_SCHEMA.PLUGINS':
     plugins-table.

     For more information, see *Note server-plugin-descriptors::.

  3. Set up the type-specific plugin descriptor.

     Each general plugin descriptor in the library descriptor points to
     a type-specific descriptor. For a full-text parser plugin, the
     type-specific descriptor is an instance of the `st_mysql_ftparser'
     structure in the `plugin.h' file:


          struct st_mysql_ftparser
          {
            int interface_version;
            int (*parse)(MYSQL_FTPARSER_PARAM *param);
            int (*init)(MYSQL_FTPARSER_PARAM *param);
            int (*deinit)(MYSQL_FTPARSER_PARAM *param);
          };

     As shown by the structure definition, the descriptor has an
     interface version number and contains pointers to three functions.

     The interface version number is specified using a symbol, which is
     in the form: `MYSQL_XXX_INTERFACE_VERSION'.  For full-text parser
     plugins, the symbol is ``MYSQL_FTPARSER_INTERFACE_VERSION''.  In
     the source code, you will find the actual interface version number
     for the full-text parser plugin defined in
     `include/mysql/plugin.h'.

     The `init' and `deinit' members should point to a function or be
     set to 0 if the function is not needed. The `parse' member must
     point to the function that performs the parsing.

     In the `simple_parser' declaration, that descriptor is indicated by
     `&simple_parser_descriptor'. The descriptor specifies the version
     number for the full-text plugin interface (as given by
     `MYSQL_FTPARSER_INTERFACE_VERSION'), and the plugin's parsing,
     initialization, and deinitialization functions:


          static struct st_mysql_ftparser simple_parser_descriptor=
          {
            MYSQL_FTPARSER_INTERFACE_VERSION, /* interface version      */
            simple_parser_parse,              /* parsing function       */
            simple_parser_init,               /* parser init function   */
            simple_parser_deinit              /* parser deinit function */
          };

     A full-text parser plugin is used in two different contexts,
     indexing and searching. In both contexts, the server calls the
     initialization and deinitialization functions at the beginning and
     end of processing each SQL statement that causes the plugin to be
     invoked. However, during statement processing, the server calls
     the main parsing function in context-specific fashion:

        * For indexing, the server calls the parser for each column
          value to be indexed.

        * For searching, the server calls the parser to parse the
          search string. The parser might also be called for rows
          processed by the statement. In natural language mode, there
          is no need for the server to call the parser. For boolean
          mode phrase searches or natural language searches with query
          expansion, the parser is used to parse column values for
          information that is not in the index. Also, if a boolean mode
          search is done for a column that has no `FULLTEXT' index, the
          built-in parser will be called. (Plugins are associated with
          specific indexes. If there is no index, no plugin is used.)

     The plugin declaration in the general plugin descriptor has `init'
     and `deinit' members that point initialization and deinitialization
     functions, and so does the type-specific plugin descriptor to
     which it points. However, these pairs of functions have different
     purposes and are invoked for different reasons:

        * For the plugin declaration in the general plugin descriptor,
          the initialization and deinitialization functions are invoked
          when the plugin is loaded and unloaded.

        * For the type-specific plugin descriptor, the initialization
          and deinitialization functions are invoked per SQL statement
          for which the plugin is used.

     Each interface function named in the plugin descriptor should
     return zero for success or nonzero for failure, and each of them
     receives an argument that points to a `MYSQL_FTPARSER_PARAM'
     structure containing the parsing context. The structure has this
     definition:


          typedef struct st_mysql_ftparser_param
          {
            int (*mysql_parse)(struct st_mysql_ftparser_param *,
                               char *doc, int doc_len);
            int (*mysql_add_word)(struct st_mysql_ftparser_param *,
                                  char *word, int word_len,
                                  MYSQL_FTPARSER_BOOLEAN_INFO *boolean_info);
            void *ftparser_state;
            void *mysql_ftparam;
            struct charset_info_st *cs;
            char *doc;
            int length;
            int flags;
            enum enum_ftparser_mode mode;
          } MYSQL_FTPARSER_PARAM;

     *Note*:

     The definition shown is current as of MySQL 5.1.12. It is
     incompatible with versions of MySQL 5.1 older than 5.1.12.

     The structure members are used as follows:

        * `mysql_parse': A pointer to a callback function that invokes
          the server's built-in parser. Use this callback when the
          plugin acts as a front end to the built-in parser. That is,
          when the plugin parsing function is called, it should process
          the input to extract the text and pass the text to the
          `mysql_parse' callback.

          The first parameter for this callback function should be the
          `param' value itself:


               param->mysql_parse(param, ...);

          A front end plugin can extract text and pass it all at once
          to the built-in parser, or it can extract and pass text to
          the built-in parser a piece at a time.  However, in this
          case, the built-in parser treats the pieces of text as though
          there are implicit word breaks between them.

        * `mysql_add_word': A pointer to a callback function that adds
          a word to a full-text index or to the list of search terms.
          Use this callback when the parser plugin replaces the built-in
          parser. That is, when the plugin parsing function is called,
          it should parse the input into words and invoke the
          `mysql_add_word' callback for each word.

          The first parameter for this callback function should be the
          `param' value itself:


               param->mysql_add_word(param, ...);

        * `ftparser_state': This is a generic pointer. The plugin can
          set it to point to information to be used internally for its
          own purposes.

        * `mysql_ftparam': This is set by the server. It is passed as
          the first argument to the `mysql_parse' or `mysql_add_word'
          callback.

        * `cs': A pointer to information about the character set of the
          text, or 0 if no information is available.

        * `doc': A pointer to the text to be parsed.

        * `length': The length of the text to be parsed, in bytes.

        * `flags': Parser flags. This is zero if there are no special
          flags. Currently, the only nonzero flag is
          `MYSQL_FTFLAGS_NEED_COPY', which means that
          `mysql_add_word()' must save a copy of the word (that is, it
          cannot use a pointer to the word because the word is in a
          buffer that will be overwritten.) This member was added in
          MySQL 5.1.12.

          This flag might be set or reset by MySQL before calling the
          parser plugin, by the parser plugin itself, or by the
          `mysql_parse()' function.

        * `mode': The parsing mode. This value will be one of the
          following constants:

             * `MYSQL_FTPARSER_SIMPLE_MODE': Parse in fast and simple
               mode, which is used for indexing and for natural
               language queries. The parser should pass to the server
               only those words that should be indexed. If the parser
               uses length limits or a stopword list to determine which
               words to ignore, it should not pass such words to the
               server.

             * `MYSQL_FTPARSER_WITH_STOPWORDS': Parse in stopword mode.
               This is used in boolean searches for phrase matching.
               The parser should pass all words to the server, even
               stopwords or words that are outside any normal length
               limits.

             * `MYSQL_FTPARSER_FULL_BOOLEAN_INFO': Parse in boolean
               mode. This is used for parsing boolean query strings.
               The parser should recognize not only words but also
               boolean-mode operators and pass them to the server as
               tokens using the `mysql_add_word' callback. To tell the
               server what kind of token is being passed, the plugin
               needs to fill in a `MYSQL_FTPARSER_BOOLEAN_INFO'
               structure and pass a pointer to it.

     If the parser is called in boolean mode, the `param->mode' value
     will be `MYSQL_FTPARSER_FULL_BOOLEAN_INFO'. The
     `MYSQL_FTPARSER_BOOLEAN_INFO' structure that the parser uses for
     passing token information to the server looks like this:


          typedef struct st_mysql_ftparser_boolean_info
          {
            enum enum_ft_token_type type;
            int yesno;
            int weight_adjust;
            char wasign;
            char trunc;
            /* These are parser state and must be removed. */
            char prev;
            char *quot;
          } MYSQL_FTPARSER_BOOLEAN_INFO;

     The parser should fill in the structure members as follows:

        * `type': The token type. The following table shows the
          permissible types.

          *Full-Text Parser Token Types*

          Token Value               Meaning
          `FT_TOKEN_EOF'            End of data
          `FT_TOKEN_WORD'           A regular word
          `FT_TOKEN_LEFT_PAREN'     The beginning of a group or
                                    subexpression
          `FT_TOKEN_RIGHT_PAREN'    The end of a group or subexpression
          `FT_TOKEN_STOPWORD'       A stopword

        * `yesno': Whether the word must be present for a match to
          occur. 0 means that the word is optional but increases the
          match relevance if it is present. Values larger than 0 mean
          that the word must be present. Values smaller than 0 mean
          that the word must not be present.

        * `weight_adjust': A weighting factor that determines how much
          a match for the word counts.  It can be used to increase or
          decrease the word's importance in relevance calculations. A
          value of zero indicates no weight adjustment. Values greater
          than or less than zero mean higher or lower weight,
          respectively. The examples at *Note fulltext-boolean::, that
          use the `<' and `>' operators illustrate how weighting works.

        * `wasign': The sign of the weighting factor. A negative value
          acts like the `~' boolean-search operator, which causes the
          word's contribution to the relevance to be negative.

        * `trunc': Whether matching should be done as if the
          boolean-mode `*' truncation operator had been given.

     Plugins should not use the `prev' and `quot' members of the
     `MYSQL_FTPARSER_BOOLEAN_INFO' structure.

     *Note*:

     The boolean operator, `@ distance', is not supported by the
     current plugin parser framework.  For information about boolean
     full-text search operators, see *Note fulltext-boolean::.

  4. Set up the plugin interface functions.

     The general plugin descriptor in the library descriptor names the
     initialization and deinitialization functions that the server
     should invoke when it loads and unloads the plugin. For
     `simple_parser', these functions do nothing but return zero to
     indicate that they succeeded:


          static int simple_parser_plugin_init(void *arg __attribute__((unused)))
          {
            return(0);
          }

          static int simple_parser_plugin_deinit(void *arg __attribute__((unused)))
          {
            return(0);
          }

     Because those functions do not actually do anything, you could
     omit them and specify 0 for each of them in the plugin declaration.

     The type-specific plugin descriptor for `simple_parser' names the
     initialization, deinitialization, and parsing functions that the
     server invokes when the plugin is used. For `simple_parser', the
     initialization and deinitialization functions do nothing:


          static int simple_parser_init(MYSQL_FTPARSER_PARAM *param
                                        __attribute__((unused)))
          {
            return(0);
          }

          static int simple_parser_deinit(MYSQL_FTPARSER_PARAM *param
                                          __attribute__((unused)))
          {
            return(0);
          }

     Here too, because those functions do nothing, you could omit them
     and specify 0 for each of them in the plugin descriptor.

     The main parsing function, `simple_parser_parse()', acts as a
     replacement for the built-in full-text parser, so it needs to
     split text into words and pass each word to the server.  The
     parsing function's first argument is a pointer to a structure that
     contains the parsing context. This structure has a `doc' member
     that points to the text to be parsed, and a `length' member that
     indicates how long the text is. The simple parsing done by the
     plugin considers nonempty runs of whitespace characters to be
     words, so it identifies words like this:


          static int simple_parser_parse(MYSQL_FTPARSER_PARAM *param)
          {
            char *end, *start, *docend= param->doc + param->length;

            for (end= start= param->doc;; end++)
            {
              if (end == docend)
              {
                if (end > start)
                  add_word(param, start, end - start);
                break;
              }
              else if (isspace(*end))
              {
                if (end > start)
                  add_word(param, start, end - start);
                start= end + 1;
              }
            }
            return(0);
          }

     As the parser finds each word, it invokes a function `add_word()'
     to pass the word to the server. `add_word()' is a helper function
     only; it is not part of the plugin interface. The parser passes
     the parsing context pointer to `add_word()', as well as a pointer
     to the word and a length value:


          static void add_word(MYSQL_FTPARSER_PARAM *param, char *word, size_t len)
          {
            MYSQL_FTPARSER_BOOLEAN_INFO bool_info=
              { FT_TOKEN_WORD, 0, 0, 0, 0, ' ', 0 };

            param->mysql_add_word(param, word, len, &bool_info);
          }

     For boolean-mode parsing, `add_word()' fills in the members of the
     `bool_info' structure as described earlier in the discussion of the
     `st_mysql_ftparser_boolean_info' structure.

  5. Set up the status variables. For the `simple_parser' plugin, the
     following status variable array sets up one status variable with a
     value that is static text, and another with a value that is stored
     in a long integer variable:


          long number_of_calls= 0;

          struct st_mysql_show_var simple_status[]=
          {
            {"static", (char *)"just a static text", SHOW_CHAR},
            {"called", (char *)&number_of_calls,     SHOW_LONG},
            {0,0,0}
          };

     When the plugin is installed, the plugin name and the `name' value
     are joined with an underscore to form the name displayed by *Note
     `SHOW STATUS': show-status. For the array just shown, the
     resulting status variable names are `simple_parser_static' and
     `simple_parser_called'. This convention means that you can easily
     display the variables for a plugin using its name:


          mysql> SHOW STATUS LIKE 'simple_parser%';
          +----------------------+--------------------+
          | Variable_name        | Value              |
          +----------------------+--------------------+
          | simple_parser_static | just a static text |
          | simple_parser_called | 0                  |
          +----------------------+--------------------+

  6. To compile and install a plugin library object file, use the
     instructions in *Note compiling-plugin-libraries::. To use the
     library file, it must be installed in the plugin directory (the
     directory named by the `plugin_dir' system variable). For the
     `simple_parser' plugin, it is compiled and installed when you
     build MySQL from source. It is also included in binary
     distributions.  The build process produces a shared object library
     with a name of `mypluglib.so' (the suffix might differ depending
     on your platform).

  7. To use the plugin, register it with the server. For example, to
     register the plugin at runtime, use this statement (changing the
     suffix as necessary):


          mysql> INSTALL PLUGIN simple_parser SONAME 'mypluglib.so';

     For additional information about plugin loading, see *Note
     server-plugin-loading::.

  8. To verify plugin installation, examine the *Note
     `INFORMATION_SCHEMA.PLUGINS': plugins-table.  table or use the
     *Note `SHOW PLUGINS': show-plugins. statement.

  9. Test the plugin to verify that it works properly.

     Create a table that contains a string column and associate the
     parser plugin with a `FULLTEXT' index on the column:


          mysql> CREATE TABLE t (c VARCHAR(255),
              ->   FULLTEXT (c) WITH PARSER simple_parser
              -> ) ENGINE=MyISAM;
          Query OK, 0 rows affected (0.01 sec)

     Insert some text into the table and try some searches.  These
     should verify that the parser plugin treats all nonwhitespace
     characters as word characters:


          mysql> INSERT INTO t VALUES
              ->   ('latin1_general_cs is a case-sensitive collation'),
              ->   ('I\'d like a case of oranges'),
              ->   ('this is sensitive information'),
              ->   ('another row'),
              ->   ('yet another row');
          Query OK, 5 rows affected (0.02 sec)
          Records: 5  Duplicates: 0  Warnings: 0

          mysql> SELECT c FROM t;
          +-------------------------------------------------+
          | c                                               |
          +-------------------------------------------------+
          | latin1_general_cs is a case-sensitive collation |
          | I'd like a case of oranges                      |
          | this is sensitive information                   |
          | another row                                     |
          | yet another row                                 |
          +-------------------------------------------------+
          5 rows in set (0.00 sec)

          mysql> SELECT MATCH(c) AGAINST('case') FROM t;
          +--------------------------+
          | MATCH(c) AGAINST('case') |
          +--------------------------+
          |                        0 |
          |          1.2968142032623 |
          |                        0 |
          |                        0 |
          |                        0 |
          +--------------------------+
          5 rows in set (0.00 sec)

          mysql> SELECT MATCH(c) AGAINST('sensitive') FROM t;
          +-------------------------------+
          | MATCH(c) AGAINST('sensitive') |
          +-------------------------------+
          |                             0 |
          |                             0 |
          |               1.3253291845322 |
          |                             0 |
          |                             0 |
          +-------------------------------+
          5 rows in set (0.01 sec)

          mysql> SELECT MATCH(c) AGAINST('case-sensitive') FROM t;
          +------------------------------------+
          | MATCH(c) AGAINST('case-sensitive') |
          +------------------------------------+
          |                    1.3109166622162 |
          |                                  0 |
          |                                  0 |
          |                                  0 |
          |                                  0 |
          +------------------------------------+
          5 rows in set (0.01 sec)

          mysql> SELECT MATCH(c) AGAINST('I\'d') FROM t;
          +--------------------------+
          | MATCH(c) AGAINST('I\'d') |
          +--------------------------+
          |                        0 |
          |          1.2968142032623 |
          |                        0 |
          |                        0 |
          |                        0 |
          +--------------------------+
          5 rows in set (0.01 sec)

     Note how neither `case' nor `insensitive' match `case-insensitive'
     the way that they would for the built-in parser.


File: manual.info,  Node: writing-daemon-plugins,  Next: writing-information-schema-plugins,  Prev: writing-full-text-plugins,  Up: writing-plugins

22.2.4.7 Writing Daemon Plugins
...............................

A daemon plugin is a simple type of plugin used for code that should be
run by the server but that does not communicate with it. This section
describes how to write a daemon server plugin, using the example plugin
found in the `plugin/daemon_example' directory of MySQL source
distributions. That directory contains the `daemon_example.cc' source
file for a daemon plugin named `daemon_example' that writes a heartbeat
string at regular intervals to a file named `mysql-heartbeat.log' in
the data directory.

To write a daemon plugin, include the following header file in the
plugin source file. Other MySQL or general header files might also be
needed, depending on the plugin capabilities and requirements.


     #include <mysql/plugin.h>

`plugin.h' defines the `MYSQL_DAEMON_PLUGIN' server plugin type and the
data structures needed to declare the plugin.

The `daemon_example.cc' file sets up the library descriptor as follows.
The library descriptor includes a single general server plugin
descriptor.


     mysql_declare_plugin(daemon_example)
     {
       MYSQL_DAEMON_PLUGIN,
       &daemon_example_plugin,
       "daemon_example",
       "Brian Aker",
       "Daemon example, creates a heartbeat beat file in mysql-heartbeat.log",
       PLUGIN_LICENSE_GPL,
       daemon_example_plugin_init, /* Plugin Init */
       daemon_example_plugin_deinit, /* Plugin Deinit */
       0x0100 /* 1.0 */,
       NULL,                       /* status variables                */
       NULL,                       /* system variables                */
       NULL                        /* config options                  */
     }
     mysql_declare_plugin_end;

The `name' member (`daemon_example') indicates the name to use for
references to the plugin in statements such as *Note `INSTALL PLUGIN':
install-plugin. or *Note `UNINSTALL PLUGIN': uninstall-plugin. This is
also the name displayed by *Note `SHOW PLUGINS': show-plugins. or *Note
`INFORMATION_SCHEMA.PLUGINS': plugins-table.

The second member of the plugin descriptor, `daemon_example_plugin',
points to the type-specific daemon plugin descriptor. This structure
consists only of the type-specific API version number:


     struct st_mysql_daemon daemon_example_plugin=
     { MYSQL_DAEMON_INTERFACE_VERSION  };

The type-specific structure has no interface functions. There is no
communication between the server and the plugin, except that the server
calls the initialization and deinitialization functions from the
general plugin descriptor to start and stop the plugin:

   * `daemon_example_plugin_init()' opens the heartbeat file and spawns
     a thread that wakes up periodically and writes the next message to
     the file.

   * `daemon_example_plugin_deinit()' closes the file and performs
     other cleanup.

To compile and install a plugin library object file, use the
instructions in *Note compiling-plugin-libraries::.  To use the library
file, it must be installed in the plugin directory (the directory named
by the `plugin_dir' system variable).  For the `daemon_example' plugin,
it is compiled and installed when you build MySQL from source. It is
also included in binary distributions. The build process produces a
shared object library with a name of `libdaemon_example.so' (the suffix
might differ depending on your platform).

To use the plugin, register it with the server. For example, to
register the plugin at runtime, use this statement (change the suffix
as necessary):


     mysql> INSTALL PLUGIN daemon_example SONAME 'libdaemon_example.so';

For additional information about plugin loading, see *Note
server-plugin-loading::.

To verify plugin installation, examine the *Note
`INFORMATION_SCHEMA.PLUGINS': plugins-table. table or use the *Note
`SHOW PLUGINS': show-plugins.  statement.

While the plugin is loaded, it writes a heartbeat string at regular
intervals to a file named `mysql-heartbeat.log' in the data directory.
This file grows without limit, so after you have satistifed yourself
that the plugin operates correctly, unload it:


     mysql> UNINSTALL PLUGIN daemon_example;


File: manual.info,  Node: writing-information-schema-plugins,  Prev: writing-daemon-plugins,  Up: writing-plugins

22.2.4.8 Writing INFORMATION_SCHEMA Plugins
...........................................

This section describes how to write an `INFORMATION_SCHEMA' table
server plugin. For example code that implements such plugins, see the
`sql/sql_show.cc' file of a MySQL source distribution. You can also
look at the example plugins found in the `InnoDB' source. See the
`handler/i_s.cc' and `handler/ha_innodb.cc' files within the `InnoDB'
source tree (in the `storage/innodb_plugin' directory).

To write an `INFORMATION_SCHEMA' table plugin, include the following
header files in the plugin source file. Other MySQL or general header
files might also be needed, depending on the plugin capabilities and
requirements.


     #include <sql_class.h>
     #include <table.h>

These header files are located in the `sql' directory of MySQL source
distributions. They contain C++ structures, so the source file for an
`INFORMATION_SCHEMA' plugin must be compiled as C++ (not C) code.

The source file for the example plugin developed here is named
`simple_i_s_table.cc'. It creates a simple `INFORMATION_SCHEMA' table
named `SIMPLE_I_S_TABLE' that has two columns named `NAME' and `VALUE'.
The general descriptor for a plugin library that implements the table
looks like this:


     mysql_declare_plugin(simple_i_s_library)
     {
       MYSQL_INFORMATION_SCHEMA_PLUGIN,
       &simple_table_info,                /* type-specific descriptor */
       "SIMPLE_I_S_TABLE",                /* table name */
       "Author Name",                     /* author */
       "Simple INFORMATION_SCHEMA table", /* description */
       PLUGIN_LICENSE_GPL,                /* license type */
       simple_table_init,                 /* init function */
       NULL,
       0x0100,                            /* version = 1.0 */
       NULL,                              /* no status variables */
       NULL,                              /* no system variables */
       NULL                               /* no reserved information */
     }
     mysql_declare_plugin_end;

The `name' member (`SIMPLE_I_S_TABLE') indicates the name to use for
references to the plugin in statements such as *Note `INSTALL PLUGIN':
install-plugin. or *Note `UNINSTALL PLUGIN': uninstall-plugin. This is
also the name displayed by *Note `SHOW PLUGINS': show-plugins. or *Note
`INFORMATION_SCHEMA.PLUGINS': plugins-table.

The `simple_table_info' member of the general descriptor points to the
type-specific descriptor, which consists only of the type-specific API
version number:


     static struct st_mysql_information_schema simple_table_info =
     { MYSQL_INFORMATION_SCHEMA_INTERFACE_VERSION };

The general descriptor points to the initialization and
deinitialization functions:

   * The initialization function provides information about the table
     structure and a function that populates the table.

   * The deinitialization function performs any required cleanup. If no
     cleanup is needed, this descriptor member can be `NULL' (as in the
     example shown).

The initialization function should return 0 for success, 1 if an error
occurs. The function receives a generic pointer, which it should
interpret as a pointer to the table structure:


     static int table_init(void *ptr)
     {
       ST_SCHEMA_TABLE *schema_table= (ST_SCHEMA_TABLE*)ptr;

       schema_table->fields_info= simple_table_fields;
       schema_table->fill_table= simple_fill_table;
       return 0;
     }

The function should set these two members of the table structure:

   * `fields_info': An array of `ST_FIELD_INFO' structures that contain
     information about each column.

   * `fill_table': A function that populates the table.

The array pointed to by `fields_info' should contain one element per
column of the `INFORMATION_SCHEMA' plus a terminating element. The
following `simple_table_fields' array for the example plugin indicates
that `SIMPLE_I_S_TABLE' has two columns.  `NAME' is string-valued with
a length of 10 and `VALUE' is integer-valued with a display width of
20. The last structure marks the end of the array.


     static ST_FIELD_INFO simple_table_fields[]=
     {
       {"NAME", 10, MYSQL_TYPE_STRING, 0, 0 0, 0},
       {"VALUE", 6, MYSQL_TYPE_LONG, 0, MY_I_S_UNSIGNED, 0, 0},
       {0, 0, MYSQL_TYPE_NULL, 0, 0, 0, 0}
     };

For more information about the column information structure, see the
definition of `ST_FIELD_INFO' in the `table.h' header file. The
permissible `MYSQL_TYPE_XXX' type values are those used in the C API;
see *Note c-api-data-structures::.

The `fill_table' member should be set to a function that populates the
table and returns 0 for success, 1 if an error occurs. For the example
plugin, the `simple_fill_table()' function looks like this:


     static int simple_fill_table(THD *thd, TABLE_LIST *tables, COND *cond)
     {
       TABLE *table= tables->table;

       table->field[0]->store("Name 1", 6, system_charset_info);
       table->field[1]->store(1);
       if (schema_table_store_record(thd, table))
         return 1;
       table->field[0]->store("Name 2", 6, system_charset_info);
       table->field[1]->store(2);
       if (schema_table_store_record(thd, table))
         return 1;
       return 0;
     }

For each row of the `INFORMATION_SCHEMA' table, this function
initializes each column, then calls `schema_table_store_record()' to
install the row. The `store()' method arguments depend on the type of
value to be stored. For column 0 (`NAME', a string), `store()' takes a
pointer to a string, its length, and information about the character
set of the string:


     store(const char *to, uint length, CHARSET_INFO *cs);

For column 1 (`VALUE', an integer), `store()' takes the value and a flag
indicating whether it is unsigned:


     store(longlong nr, bool unsigned_value);

For other examples of how to populate `INFORMATION_SCHEMA' tables,
search for instances of `schema_table_store_record()' in `sql_show.cc'.

To compile and install a plugin library object file, see the
instructions in *Note compiling-plugin-libraries::.  To use the library
file, it must be installed in the plugin directory (the directory named
by the `plugin_dir' system variable).

To test the plugin, install it:


     mysql> INSTALL PLUGIN SIMPLE_I_S_TABLE SONAME 'simple_i_s_table.so';

Verify that the table is present:


     mysql> SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
         -> WHERE TABLE_NAME = 'SIMPLE_I_S_TABLE';
     +------------------+
     | TABLE_NAME       |
     +------------------+
     | SIMPLE_I_S_TABLE |
     +------------------+

Try to select from it:


     mysql> SELECT * FROM INFORMATION_SCHEMA.SIMPLE_I_S_TABLE;
     +--------+-------+
     | NAME   | VALUE |
     +--------+-------+
     | Name 1 |     1 |
     | Name 2 |     2 |
     +--------+-------+

Uninstall it:


     mysql> UNINSTALL PLUGIN SIMPLE_I_S_TABLE;


File: manual.info,  Node: adding-functions,  Next: porting,  Prev: plugin-api,  Up: extending-mysql

22.3 Adding New Functions to MySQL
==================================

* Menu:

* udf-features::                 Features of the User-Defined Function Interface
* adding-udf::                   Adding a New User-Defined Function
* adding-native-function::       Adding a New Native Function

There are three ways to add new functions to MySQL:

   * You can add functions through the user-defined function (UDF)
     interface. User-defined functions are compiled as object files and
     then added to and removed from the server dynamically using the
     *Note `CREATE FUNCTION': create-function. and *Note `DROP
     FUNCTION': drop-function. statements. See *Note
     create-function-udf::.

   * You can add functions as native (built-in) MySQL functions.
     Native functions are compiled into the *Note `mysqld': mysqld.
     server and become available on a permanent basis.

   * Another way to add functions is by creating stored functions.
     These are written using SQL statements rather than by compiling
     object code. The syntax for writing stored functions is not
     covered here. See *Note stored-routines::.

Each method of creating compiled functions has advantages and
disadvantages:

   * If you write user-defined functions, you must install object files
     in addition to the server itself. If you compile your function
     into the server, you don't need to do that.

   * Native functions require you to modify a source distribution.
     UDFs do not. You can add UDFs to a binary MySQL distribution.  No
     access to MySQL source is necessary.

   * If you upgrade your MySQL distribution, you can continue to use
     your previously installed UDFs, unless you upgrade to a newer
     version for which the UDF interface changes. For native functions,
     you must repeat your modifications each time you upgrade.

Whichever method you use to add new functions, they can be invoked in
SQL statements just like native functions such as `ABS()' or
`SOUNDEX()'.

See *Note function-resolution::, for the rules describing how the
server interprets references to different kinds of functions.

The following sections describe features of the UDF interface, provide
instructions for writing UDFs, discuss security precautions that MySQL
takes to prevent UDF misuse, and describe how to add native MySQL
functions.

For example source code that illustrates how to write UDFs, take a look
at the `sql/udf_example.c' file that is provided in MySQL source
distributions.


File: manual.info,  Node: udf-features,  Next: adding-udf,  Prev: adding-functions,  Up: adding-functions

22.3.1 Features of the User-Defined Function Interface
------------------------------------------------------

The MySQL interface for user-defined functions provides the following
features and capabilities:

   * Functions can return string, integer, or real values and can
     accept arguments of those same types.

   * You can define simple functions that operate on a single row at a
     time, or aggregate functions that operate on groups of rows.

   * Information is provided to functions that enables them to check
     the number, types, and names of the arguments passed to them.

   * You can tell MySQL to coerce arguments to a given type before
     passing them to a function.

   * You can indicate that a function returns `NULL' or that an error
     occurred.


File: manual.info,  Node: adding-udf,  Next: adding-native-function,  Prev: udf-features,  Up: adding-functions

22.3.2 Adding a New User-Defined Function
-----------------------------------------

* Menu:

* udf-calling::                  UDF Calling Sequences for Simple Functions
* udf-aggr-calling::             UDF Calling Sequences for Aggregate Functions
* udf-arguments::                UDF Argument Processing
* udf-return-values::            UDF Return Values and Error Handling
* udf-compiling::                Compiling and Installing User-Defined Functions
* udf-security::                 User-Defined Function Security Precautions

For the UDF mechanism to work, functions must be written in C or C++
and your operating system must support dynamic loading.  MySQL source
distributions include a file `sql/udf_example.c' that defines five UDF
functions. Consult this file to see how UDF calling conventions work.
The `include/mysql_com.h' header file defines UDF-related symbols and
data structures, although you need not include this header file
directly; it is included by `mysql.h'.

A UDF contains code that becomes part of the running server, so when
you write a UDF, you are bound by any and all constraints that apply to
writing server code. For example, you may have problems if you attempt
to use functions from the `libstdc++' library. These constraints may
change in future versions of the server, so it is possible that server
upgrades will require revisions to UDFs that were originally written
for older servers. For information about these constraints, see *Note
source-configuration-options::, and *Note compilation-problems::.

To be able to use UDFs, you must link *Note `mysqld': mysqld.
dynamically. Don't configure MySQL using
`--with-mysqld-ldflags=-all-static'. If you want to use a UDF that
needs to access symbols from *Note `mysqld': mysqld. (for example, the
`metaphone' function in `sql/udf_example.c' uses
`default_charset_info'), you must link the program with `-rdynamic'
(see `man dlopen'). If you plan to use UDFs, the rule of thumb is to
configure MySQL with `--with-mysqld-ldflags=-rdynamic' unless you have
a very good reason not to.

For each function that you want to use in SQL statements, you should
define corresponding C (or C++) functions. In the following discussion,
the name `xxx' is used for an example function name. To distinguish
between SQL and C/C++ usage, `XXX()' (uppercase) indicates an SQL
function call, and `xxx()' (lowercase) indicates a C/C++ function call.

*Note*:

When using C++ you can encapsulate your C functions within:


     extern "C" { ... }

This ensures that your C++ function names remain readable in the
completed UDF.

The following list describes the C/C++ functions that you write to
implement the interface for a function named `XXX()'. The main function,
`xxx()', is required. In addition, a UDF requires at least one of the
other functions described here, for reasons discussed in *Note
udf-security::.

   * `xxx()'

     The main function. This is where the function result is computed.
     The correspondence between the SQL function data type and the
     return type of your C/C++ function is shown here.

     This table lists SQL function data types and corresponding C/C++
     data types.

     SQL Type          C/C++ Type
     `STRING'          `char *'
     *Note `INTEGER':  `long long'
     integer-types.    
     *Note `REAL':     `double'
     floating-point-types.

     It is also possible to declare a *Note `DECIMAL':
     fixed-point-types. function, but currently the value is returned
     as a string, so you should write the UDF as though it were a
     `STRING' function. `ROW' functions are not implemented.

   * `xxx_init()'

     The initialization function for `xxx()'. If present, it can be
     used for the following purposes:

        * To check the number of arguments to `XXX()'.

        * To verify that the arguments are of a required type or,
          alternatively, to tell MySQL to coerce arguments to the
          required types when the main function is called.

        * To allocate any memory required by the main function.

        * To specify the maximum length of the result.

        * To specify (for *Note `REAL': floating-point-types.
          functions) the maximum number of decimal places in the result.

        * To specify whether the result can be `NULL'.

   * `xxx_deinit()'

     The deinitialization function for `xxx()'.  If present, it should
     deallocate any memory allocated by the initialization function.

When an SQL statement invokes `XXX()', MySQL calls the initialization
function `xxx_init()' to let it perform any required setup, such as
argument checking or memory allocation. If `xxx_init()' returns an
error, MySQL aborts the SQL statement with an error message and does
not call the main or deinitialization functions.  Otherwise, MySQL
calls the main function `xxx()' once for each row. After all rows have
been processed, MySQL calls the deinitialization function
`xxx_deinit()' so that it can perform any required cleanup.

For aggregate functions that work like `SUM()', you must also provide
the following functions:

   * `xxx_clear()'

     Reset the current aggregate value but do not insert the argument
     as the initial aggregate value for a new group.

   * `xxx_add()'

     Add the argument to the current aggregate value.

MySQL handles aggregate UDFs as follows:

  1. Call `xxx_init()' to let the aggregate function allocate any
     memory it needs for storing results.

  2. Sort the table according to the `GROUP BY' expression.

  3. Call `xxx_clear()' for the first row in each new group.

  4. Call `xxx_add()' for each row that belongs in the same group.

  5. Call `xxx()' to get the result for the aggregate when the group
     changes or after the last row has been processed.

  6. Repeat steps 3 to 5 until all rows has been processed

  7. Call `xxx_deinit()' to let the UDF free any memory it has
     allocated.

All functions must be thread-safe. This includes not just the main
function, but the initialization and deinitialization functions as
well, and also the additional functions required by aggregate
functions. A consequence of this requirement is that you are not
permitted to allocate any global or static variables that change! If
you need memory, you should allocate it in `xxx_init()' and free it in
`xxx_deinit()'.


File: manual.info,  Node: udf-calling,  Next: udf-aggr-calling,  Prev: adding-udf,  Up: adding-udf

22.3.2.1 UDF Calling Sequences for Simple Functions
...................................................

This section describes the different functions that you need to define
when you create a simple UDF.  *Note adding-udf::, describes the order
in which MySQL calls these functions.

The main `xxx()' function should be declared as shown in this section.
Note that the return type and parameters differ, depending on whether
you declare the SQL function `XXX()' to return `STRING', *Note
`INTEGER': integer-types, or *Note `REAL': floating-point-types. in the
*Note `CREATE FUNCTION': create-function. statement:

For `STRING' functions:


     char *xxx(UDF_INIT *initid, UDF_ARGS *args,
               char *result, unsigned long *length,
               char *is_null, char *error);

For *Note `INTEGER': integer-types. functions:


     long long xxx(UDF_INIT *initid, UDF_ARGS *args,
                   char *is_null, char *error);

For *Note `REAL': floating-point-types. functions:


     double xxx(UDF_INIT *initid, UDF_ARGS *args,
                   char *is_null, char *error);

*Note `DECIMAL': fixed-point-types. functions return string values and
should be declared the same way as `STRING' functions. `ROW' functions
are not implemented.

The initialization and deinitialization functions are declared like
this:


     my_bool xxx_init(UDF_INIT *initid, UDF_ARGS *args, char *message);

     void xxx_deinit(UDF_INIT *initid);

The `initid' parameter is passed to all three functions. It points to a
`UDF_INIT' structure that is used to communicate information between
functions. The `UDF_INIT' structure members follow. The initialization
function should fill in any members that it wishes to change. (To use
the default for a member, leave it unchanged.)

   * `my_bool maybe_null'

     `xxx_init()' should set `maybe_null' to `1' if `xxx()' can return
     `NULL'. The default value is `1' if any of the arguments are
     declared `maybe_null'.

   * `unsigned int decimals'

     The number of decimal digits to the right of the decimal point.
     The default value is the maximum number of decimal digits in the
     arguments passed to the main function. For example, if the
     function is passed `1.34', `1.345', and `1.3', the default would
     be 3, because `1.345' has 3 decimal digits.

     For arguments that have no fixed number of decimals, the
     `decimals' value is set to 31, which is 1 more than the maximum
     number of decimals permitted for the *Note `DECIMAL':
     fixed-point-types, *Note `FLOAT': floating-point-types, and *Note
     `DOUBLE': floating-point-types. data types.

     A `decimals' value of 31 is used for arguments in cases such as a
     *Note `FLOAT': floating-point-types. or *Note `DOUBLE':
     floating-point-types. column declared without an explicit number
     of decimals (for example, *Note `FLOAT': floating-point-types.
     rather than `FLOAT(10,3)') and for floating-point constants such
     as `1345E-3'. It is also used for string and other nonnumber
     arguments that might be converted within the function to numeric
     form.

     The value to which the `decimals' member is initialized is only a
     default. It can be changed within the function to reflect the
     actual calculation performed.  The default is determined such that
     the largest number of decimals of the arguments is used. If the
     number of decimals is 31 for even one of the arguments, that is the
     value used for `decimals'.

   * `unsigned int max_length'

     The maximum length of the result. The default `max_length' value
     differs depending on the result type of the function. For string
     functions, the default is the length of the longest argument. For
     integer functions, the default is 21 digits. For real functions,
     the default is 13 plus the number of decimal digits indicated by
     `initid->decimals'. (For numeric functions, the length includes
     any sign or decimal point characters.)

     If you want to return a blob value, you can set `max_length' to
     65KB or 16MB. This memory is not allocated, but the value is used
     to decide which data type to use if there is a need to temporarily
     store the data.

   * `char *ptr'

     A pointer that the function can use for its own purposes.  For
     example, functions can use `initid->ptr' to communicate allocated
     memory among themselves. `xxx_init()' should allocate the memory
     and assign it to this pointer:


          initid->ptr = allocated_memory;

     In `xxx()' and `xxx_deinit()', refer to `initid->ptr' to use or
     deallocate the memory.

   * `my_bool const_item'

     `xxx_init()' should set `const_item' to `1' if `xxx()' always
     returns the same value and to `0' otherwise.


File: manual.info,  Node: udf-aggr-calling,  Next: udf-arguments,  Prev: udf-calling,  Up: adding-udf

22.3.2.2 UDF Calling Sequences for Aggregate Functions
......................................................

This section describes the different functions that you need to define
when you create an aggregate UDF.  *Note adding-udf::, describes the
order in which MySQL calls these functions.

   * `xxx_reset()'

     This function is called when MySQL finds the first row in a new
     group. It should reset any internal summary variables and then use
     the given `UDF_ARGS' argument as the first value in your internal
     summary value for the group. Declare `xxx_reset()' as follows:


          void xxx_reset(UDF_INIT *initid, UDF_ARGS *args,
                         char *is_null, char *error);

     `xxx_reset()' is not needed or used in MySQL 5.1, in which the UDF
     interface uses `xxx_clear()' instead. However, you can define both
     `xxx_reset()' and `xxx_clear()' if you want to have your UDF work
     with older versions of the server. (If you do include both
     functions, the `xxx_reset()' function in many cases can be
     implemented internally by calling `xxx_clear()' to reset all
     variables, and then calling `xxx_add()' to add the `UDF_ARGS'
     argument as the first value in the group.)

   * `xxx_clear()'

     This function is called when MySQL needs to reset the summary
     results. It is called at the beginning for each new group but can
     also be called to reset the values for a query where there were no
     matching rows. Declare `xxx_clear()' as follows:


          void xxx_clear(UDF_INIT *initid, char *is_null, char *error);

     `is_null' is set to point to `CHAR(0)' before calling
     `xxx_clear()'.

     If something went wrong, you can store a value in the variable to
     which the `error' argument points. `error' points to a single-byte
     variable, not to a string buffer.

     `xxx_clear()' is required by MySQL 5.1.

   * `xxx_add()'

     This function is called for all rows that belong to the same
     group. You should use it to add the value in the `UDF_ARGS'
     argument to your internal summary variable.


          void xxx_add(UDF_INIT *initid, UDF_ARGS *args,
                       char *is_null, char *error);

The `xxx()' function for an aggregate UDF should be declared the same
way as for a nonaggregate UDF. See *Note udf-calling::.

For an aggregate UDF, MySQL calls the `xxx()' function after all rows
in the group have been processed. You should normally never access its
`UDF_ARGS' argument here but instead return a value based on your
internal summary variables.

Return value handling in `xxx()' should be done the same way as for a
nonaggregate UDF. See *Note udf-return-values::.

The `xxx_reset()' and `xxx_add()' functions handle their `UDF_ARGS'
argument the same way as functions for nonaggregate UDFs. See *Note
udf-arguments::.

The pointer arguments to `is_null' and `error' are the same for all
calls to `xxx_reset()', `xxx_clear()', `xxx_add()' and `xxx()'. You can
use this to remember that you got an error or whether the `xxx()'
function should return `NULL'. You should not store a string into
`*error'!  `error' points to a single-byte variable, not to a string
buffer.

`*is_null' is reset for each group (before calling `xxx_clear()').
`*error' is never reset.

If `*is_null' or `*error' are set when `xxx()' returns, MySQL returns
`NULL' as the result for the group function.


File: manual.info,  Node: udf-arguments,  Next: udf-return-values,  Prev: udf-aggr-calling,  Up: adding-udf

22.3.2.3 UDF Argument Processing
................................

The `args' parameter points to a `UDF_ARGS' structure that has the
members listed here:

   * `unsigned int arg_count'

     The number of arguments. Check this value in the initialization
     function if you require your function to be called with a
     particular number of arguments. For example:


          if (args->arg_count != 2)
          {
              strcpy(message,"XXX() requires two arguments");
              return 1;
          }

     For other `UDF_ARGS' member values that are arrays, array
     references are zero-based. That is, refer to array members using
     index values from 0 to `args->arg_count' - 1.

   * `enum Item_result *arg_type'

     A pointer to an array containing the types for each argument. The
     possible type values are `STRING_RESULT', `INT_RESULT',
     `REAL_RESULT', and `DECIMAL_RESULT'.

     To make sure that arguments are of a given type and return an
     error if they are not, check the `arg_type' array in the
     initialization function. For example:


          if (args->arg_type[0] != STRING_RESULT ||
              args->arg_type[1] != INT_RESULT)
          {
              strcpy(message,"XXX() requires a string and an integer");
              return 1;
          }

     Arguments of type `DECIMAL_RESULT' are passed as strings, so you
     should handle them the same way as `STRING_RESULT' values.

     As an alternative to requiring your function's arguments to be of
     particular types, you can use the initialization function to set
     the `arg_type' elements to the types you want. This causes MySQL
     to coerce arguments to those types for each call to `xxx()'. For
     example, to specify that the first two arguments should be coerced
     to string and integer, respectively, do this in `xxx_init()':


          args->arg_type[0] = STRING_RESULT;
          args->arg_type[1] = INT_RESULT;

     Exact-value decimal arguments such as `1.3' or *Note `DECIMAL':
     fixed-point-types. column values are passed with a type of
     `DECIMAL_RESULT'.  However, the values are passed as strings. If
     you want to receive a number, use the initialization function to
     specify that the argument should be coerced to a `REAL_RESULT'
     value:


          args->arg_type[2] = REAL_RESULT;

   * `char **args'

     `args->args' communicates information to the initialization
     function about the general nature of the arguments passed to your
     function. For a constant argument `i', `args->args[i]' points to
     the argument value. (See later for instructions on how to access
     the value properly.) For a nonconstant argument, `args->args[i]' is
     `0'. A constant argument is an expression that uses only
     constants, such as `3' or `4*7-2' or `SIN(3.14)'. A nonconstant
     argument is an expression that refers to values that may change
     from row to row, such as column names or functions that are called
     with nonconstant arguments.

     For each invocation of the main function, `args->args' contains
     the actual arguments that are passed for the row currently being
     processed.

     If argument `i' represents `NULL', `args->args[i]' is a null
     pointer (0).  If the argument is not `NULL', functions can refer
     to it as follows:

        * An argument of type `STRING_RESULT' is given as a string
          pointer plus a length, to enable handling of binary data or
          data of arbitrary length.  The string contents are available
          as `args->args[i]' and the string length is
          `args->lengths[i]'. Do not assume that the string is
          null-terminated.

        * For an argument of type `INT_RESULT', you must cast
          `args->args[i]' to a `long long' value:


               long long int_val;
               int_val = *((long long*) args->args[i]);

        * For an argument of type `REAL_RESULT', you must cast
          `args->args[i]' to a `double' value:


               double    real_val;
               real_val = *((double*) args->args[i]);

        * For an argument of type `DECIMAL_RESULT', the value is passed
          as a string and should be handled like a `STRING_RESULT'
          value.

        * `ROW_RESULT' arguments are not implemented.

   * `unsigned long *lengths'

     For the initialization function, the `lengths' array indicates the
     maximum string length for each argument. You should not change
     these. For each invocation of the main function, `lengths'
     contains the actual lengths of any string arguments that are
     passed for the row currently being processed. For arguments of
     types `INT_RESULT' or `REAL_RESULT', `lengths' still contains the
     maximum length of the argument (as for the initialization
     function).

   * `char *maybe_null'

     For the initialization function, the `maybe_null' array indicates
     for each argument whether the argument value might be null (0 if
     no, 1 if yes).

   * `char **attributes'

     `args->attributes' communicates information about the names of the
     UDF arguments. For argument `i', the attribute name is available
     as a string in `args->attributes[i]' and the attribute length is
     `args->attribute_lengths[i]'. Do not assume that the string is
     null-terminated.

     By default, the name of a UDF argument is the text of the
     expression used to specify the argument. For UDFs, an argument may
     also have an optional `[AS] ALIAS_NAME' clause, in which case the
     argument name is ALIAS_NAME. The `attributes' value for each
     argument thus depends on whether an alias was given.

     Suppose that a UDF `my_udf()' is invoked as follows:


          SELECT my_udf(expr1, expr2 AS alias1, expr3 alias2);

     In this case, the `attributes' and `attribute_lengths' arrays will
     have these values:


          args->attributes[0] = "expr1"
          args->attribute_lengths[0] = 5

          args->attributes[1] = "alias1"
          args->attribute_lengths[1] = 6

          args->attributes[2] = "alias2"
          args->attribute_lengths[2] = 6

   * `unsigned long *attribute_lengths'

     The `attribute_lengths' array indicates the length of each
     argument name.


File: manual.info,  Node: udf-return-values,  Next: udf-compiling,  Prev: udf-arguments,  Up: adding-udf

22.3.2.4 UDF Return Values and Error Handling
.............................................

The initialization function should return `0' if no error occurred and
`1' otherwise. If an error occurs, `xxx_init()' should store a
null-terminated error message in the `message' parameter. The message
is returned to the client. The message buffer is `MYSQL_ERRMSG_SIZE'
characters long, but you should try to keep the message to less than 80
characters so that it fits the width of a standard terminal screen.

The return value of the main function `xxx()' is the function value,
for `long long' and `double' functions. A string function should return
a pointer to the result and set `*length' to the length (in bytes) of
the return value. For example:


     memcpy(result, "result string", 13);
     *length = 13;

MySQL passes a buffer to the `xxx()' function using the `result'
parameter. This buffer is sufficiently long to hold 255 characters,
which can be multibyte characters. The `xxx()' function can store the
result in this buffer if it fits, in which case the return value should
be a pointer to the buffer. If the function stores the result in a
different buffer, it should return a pointer to that buffer.

If your string function does not use the supplied buffer (for example,
if it needs to return a string longer than 255 characters), you must
allocate the space for your own buffer with `malloc()' in your
`xxx_init()' function or your `xxx()' function and free it in your
`xxx_deinit()' function. You can store the allocated memory in the
`ptr' slot in the `UDF_INIT' structure for reuse by future `xxx()'
calls. See *Note udf-calling::.

To indicate a return value of `NULL' in the main function, set
`*is_null' to `1':


     *is_null = 1;

To indicate an error return in the main function, set `*error' to `1':


     *error = 1;

If `xxx()' sets `*error' to `1' for any row, the function value is
`NULL' for the current row and for any subsequent rows processed by the
statement in which `XXX()' was invoked.  (`xxx()' is not even called
for subsequent rows.)


File: manual.info,  Node: udf-compiling,  Next: udf-security,  Prev: udf-return-values,  Up: adding-udf

22.3.2.5 Compiling and Installing User-Defined Functions
........................................................

Files implementing UDFs must be compiled and installed on the host
where the server runs. This process is described below for the example
UDF file `sql/udf_example.c' that is included in MySQL source
distributions.

If a UDF will be referred to in statements that will be replicated to
slave servers, you must ensure that every slave also has the function
available. Otherwise, replication will fail on the slaves when they
attempt to invoke the function.

The immediately following instructions are for Unix.  Instructions for
Windows are given later in this section.

The `udf_example.c' file contains the following functions:

   * `metaphon()' returns a metaphon string of the string argument.
     This is something like a soundex string, but it is more tuned for
     English.

   * `myfunc_double()' returns the sum of the ASCII values of the
     characters in its arguments, divided by the sum of the length of
     its arguments.

   * `myfunc_int()' returns the sum of the length of its arguments.

   * `sequence([const int])' returns a sequence starting from the given
     number or 1 if no number has been given.

   * `lookup()' returns the IP address for a host name.

   * `reverse_lookup()' returns the host name for an IP address. The
     function may be called either with a single string argument of the
     form `'xxx.xxx.xxx.xxx'' or with four numbers.

   * `avgcost()' returns an average cost. This is an aggregate function.

A dynamically loadable file should be compiled as a sharable object
file, using a command something like this:


     shell> gcc -shared -o udf_example.so udf_example.c

If you are using `gcc' with `configure' and `libtool' (which is how
MySQL is configured), you should be able to create `udf_example.so'
with a simpler command:


     shell> make udf_example.la

After you compile a shared object containing UDFs, you must install it
and tell MySQL about it. Compiling a shared object from `udf_example.c'
using `gcc' directly produces a file named `udf_example.so'. Compiling
the shared object using `make' produces a file named something like
`udf_example.so.0.0.0' in the `.libs' directory (the exact name may
vary from platform to platform). Copy the shared object to the server's
plugin directory and name it `udf_example.so'. This directory is given
by the value of the `plugin_dir' system variable.

*Note*:

This is a change in MySQL 5.1. For earlier versions of MySQL, the
shared object can be located in any directory that is searched by your
system's dynamic linker.

On some systems, the `ldconfig' program that configures the dynamic
linker does not recognize a shared object unless its name begins with
`lib'. In this case you should rename a file such as `udf_example.so' to
`libudf_example.so'.

On Windows, you can compile user-defined functions by using the
following procedure:

  1. Obtain the development source for MySQL 5.1.  See *Note
     getting-mysql::.

  2. Obtain the `CMake' build utility, if necessary, from
     `http://www.cmake.org'.  (Version 2.6 or later is required).

  3. In the source tree, look in the `sql' directory. There are files
     named `udf_example.def' `udf_example.c' there. Copy both files
     from this directory to your working directory.

  4. Create a `CMake' `makefile' (`CMakeLists.txt') with these contents:


          PROJECT(udf_example)

          # Path for MySQL include directory
          INCLUDE_DIRECTORIES("c:/mysql/include")

          ADD_DEFINITIONS("-DHAVE_DLOPEN")
          ADD_LIBRARY(udf_example MODULE udf_example.c udf_example.def)
          TARGET_LINK_LIBRARIES(udf_example wsock32)

  5. Create the VC project and solution files:


          cmake -G "<Generator>"

     Invoking `cmake --help' shows you a list of valid Generators.

  6. Create `udf_example.dll':


          devenv udf_example.sln /build Release

After the shared object file has been installed, notify *Note `mysqld':
mysqld. about the new functions with the following statements. If
object files have a suffix different from `.so' on your system,
substitute the correct suffix throughout (for example, `.dll' on
Windows).


     mysql> CREATE FUNCTION metaphon RETURNS STRING SONAME 'udf_example.so';
     mysql> CREATE FUNCTION myfunc_double RETURNS REAL SONAME 'udf_example.so';
     mysql> CREATE FUNCTION myfunc_int RETURNS INTEGER SONAME 'udf_example.so';
     mysql> CREATE FUNCTION sequence RETURNS INTEGER SONAME 'udf_example.so';
     mysql> CREATE FUNCTION lookup RETURNS STRING SONAME 'udf_example.so';
     mysql> CREATE FUNCTION reverse_lookup
         ->        RETURNS STRING SONAME 'udf_example.so';
     mysql> CREATE AGGREGATE FUNCTION avgcost
         ->        RETURNS REAL SONAME 'udf_example.so';

To delete functions, use *Note `DROP FUNCTION': drop-function.:


     mysql> DROP FUNCTION metaphon;
     mysql> DROP FUNCTION myfunc_double;
     mysql> DROP FUNCTION myfunc_int;
     mysql> DROP FUNCTION sequence;
     mysql> DROP FUNCTION lookup;
     mysql> DROP FUNCTION reverse_lookup;
     mysql> DROP FUNCTION avgcost;

The *Note `CREATE FUNCTION': create-function. and *Note `DROP
FUNCTION': drop-function. statements update the `func' system table in
the `mysql' database. The function's name, type and shared library name
are saved in the table. You must have the `INSERT' or `DELETE'
privilege for the `mysql' database to create or drop functions,
respectively.

You should not use *Note `CREATE FUNCTION': create-function. to add a
function that has previously been created. If you need to reinstall a
function, you should remove it with *Note `DROP FUNCTION':
drop-function.  and then reinstall it with *Note `CREATE FUNCTION':
create-function. You would need to do this, for example, if you
recompile a new version of your function, so that *Note `mysqld':
mysqld. gets the new version. Otherwise, the server continues to use
the old version.

An active function is one that has been loaded with *Note `CREATE
FUNCTION': create-function. and not removed with *Note `DROP FUNCTION':
drop-function. All active functions are reloaded each time the server
starts, unless you start *Note `mysqld': mysqld. with the
`--skip-grant-tables' option. In this case, UDF initialization is
skipped and UDFs are unavailable.


File: manual.info,  Node: udf-security,  Prev: udf-compiling,  Up: adding-udf

22.3.2.6 User-Defined Function Security Precautions
...................................................

MySQL takes several measures to prevent misuse of user-defined
functions.

UDF object files cannot be placed in arbitrary directories.  They must
be located in the server's plugin directory. This directory is given by
the value of the `plugin_dir' system variable.

*Note*:

This is a change in MySQL 5.1. For earlier versions of MySQL, the
shared object can be located in any directory that is searched by your
system's dynamic linker.

To use *Note `CREATE FUNCTION': create-function. or *Note `DROP
FUNCTION': drop-function, you must have the `INSERT' or `DELETE'
privilege, respectively, for the `mysql' database. This is necessary
because those statements add and delete rows from the `mysql.func'
table.

UDFs should have at least one symbol defined in addition to the `xxx'
symbol that corresponds to the main `xxx()' function. These auxiliary
symbols correspond to the `xxx_init()', `xxx_deinit()', `xxx_reset()',
`xxx_clear()', and `xxx_add()' functions.  *Note `mysqld': mysqld. also
supports an `--allow-suspicious-udfs' option that controls whether UDFs
that have only an `xxx' symbol can be loaded. By default, the option is
off, to prevent attempts at loading functions from shared object files
other than those containing legitimate UDFs. If you have older UDFs
that contain only the `xxx' symbol and that cannot be recompiled to
include an auxiliary symbol, it may be necessary to specify the
`--allow-suspicious-udfs' option. Otherwise, you should avoid enabling
this capability.


File: manual.info,  Node: adding-native-function,  Prev: adding-udf,  Up: adding-functions

22.3.3 Adding a New Native Function
-----------------------------------

To add a new native MySQL function, use the procedure described here,
which requires that you use a source distribution. You cannot add
native functions to a binary distribution because it is necessary to
modify MySQL source code and compile MySQL from the modified source. If
you migrate to another version of MySQL (for example, when a new
version is released), you must repeat the procedure with the new
version.

If the new native function will be referred to in statements that will
be replicated to slave servers, you must ensure that every slave server
also has the function available. Otherwise, replication will fail on
the slaves when they attempt to invoke the function.

To add a new native function, follow these steps to modify source files
in the `sql' directory. For MySQL 5.1, the first two steps apply only
as of 5.1.13. For older versions, see the instructions in the
corresponding section of the MySQL 5.0 manual.

  1. Create a subclass for the function in `item_create.cc':

        * If the function takes a fixed number of arguments, create a
          subclass of `Create_func_arg0', `Create_func_arg1',
          `Create_func_arg2', or `Create_func_arg3', respectively,
          depending on whether the function takes zero, one, two, or
          three arguments. For examples, see the `Create_func_uuid',
          `Create_func_abs', `Create_func_pow', and `Create_func_lpad'
          classes.

        * If the function takes a variable number of arguments, create
          a subclass of `Create_native_func'. For an example, see
          `Create_func_concat'.

  2. To provide a name by which the function can be referred to in SQL
     statements, register the name in `item_create.cc' by adding a line
     to this array:


          static Native_func_registry func_array[]

     You can register several names for the same function. For example,
     see the lines for `"LCASE"' and `"LOWER"', which are aliases for
     `Create_func_lcase'.

  3. In `item_func.h', declare a class inheriting from `Item_num_func'
     or `Item_str_func', depending on whether your function returns a
     number or a string.

  4. In `item_func.cc', add one of the following declarations,
     depending on whether you are defining a numeric or string function:


          double   Item_func_newname::val()
          longlong Item_func_newname::val_int()
          String  *Item_func_newname::Str(String *str)

     If you inherit your object from any of the standard items (like
     `Item_num_func'), you probably only have to define one of these
     functions and let the parent object take care of the other
     functions. For example, the `Item_str_func' class defines a
     `val()' function that executes `atof()' on the value returned by
     `::str()'.

  5. If the function is nondeterministic, include the following
     statement in the item constructor to indicate that function
     results should not be cached:


          current_thd->lex->safe_to_cache_query=0;

     A function is nondeterministic if, given fixed values for its
     arguments, it can return different results for different
     invocations.

  6. You should probably also define the following object function:


          void Item_func_newname::fix_length_and_dec()

     This function should at least calculate `max_length' based on the
     given arguments.  `max_length' is the maximum number of characters
     the function may return. This function should also set `maybe_null
     = 0' if the main function can't return a `NULL' value. The
     function can check whether any of the function arguments can
     return `NULL' by checking the arguments' `maybe_null' variable.
     Look at `Item_func_mod::fix_length_and_dec' for a typical example
     of how to do this.

All functions must be thread-safe. In other words, do not use any
global or static variables in the functions without protecting them
with mutexes.

If you want to return `NULL' from `::val()', `::val_int()', or
`::str()', you should set `null_value' to 1 and return 0.

For `::str()' object functions, there are additional considerations to
be aware of:

   * The `String *str' argument provides a string buffer that may be
     used to hold the result. (For more information about the `String'
     type, take a look at the `sql_string.h' file.)

   * The `::str()' function should return the string that holds the
     result, or `(char*) 0' if the result is `NULL'.

   * All current string functions try to avoid allocating any memory
     unless absolutely necessary!


File: manual.info,  Node: porting,  Prev: adding-functions,  Up: extending-mysql

22.4 Debugging and Porting MySQL
================================

* Menu:

* debugging-server::             Debugging a MySQL Server
* debugging-client::             Debugging a MySQL Client
* dbug-package::                 The DBUG Package

This section helps you port MySQL to other operating systems. Do check
the list of currently supported operating systems first. See *Note
general-installation-issues::. If you have created a new port of MySQL,
please let us know so that we can list it here and on our Web site
(http://www.mysql.com/), recommending it to other users.

*Note*:

If you create a new port of MySQL, you are free to copy and distribute
it under the GPL license, but it does not make you a copyright holder
of MySQL.

A working POSIX thread library is needed for the server.

Both the server and the client need a working C++ compiler. We use
`gcc' on many platforms. Other compilers that are known to work are Sun
Studio, HP-UX `aCC', IBM AIX `xlC_r'), Intel `ecc/icc'.  With previous
versions on the respective platforms, we also used Irix `cc' and Compaq
`cxx'.

*Important*:

If you are trying to build MySQL 5.1 with `icc' on the IA64 platform,
and need support for MySQL Cluster, you should first ensure that you
are using `icc' version 9.1.043 or later. (For details, see Bug #21875.)

To compile only the client, use `./configure --without-server'.

If you want or need to change any `Makefile' or the `configure' script,
you also need GNU Automake and Autoconf. See *Note
installing-development-tree::.

All steps needed to remake everything from the most basic files.


     /bin/rm */.deps/*.P
     /bin/rm -f config.cache
     aclocal
     autoheader
     aclocal
     automake
     autoconf
     ./configure --with-debug=full --prefix='your installation directory'

     # The makefiles generated above need GNU make 3.75 or newer.
     # (called gmake below)
     gmake clean all install init-db

If you run into problems with a new port, you may have to do some
debugging of MySQL! See *Note debugging-server::.

*Note*:

Before you start debugging *Note `mysqld': mysqld, first get the test
programs `mysys/thr_alarm' and `mysys/thr_lock' to work. This ensures
that your thread installation has even a remote chance to work!


File: manual.info,  Node: debugging-server,  Next: debugging-client,  Prev: porting,  Up: porting

22.4.1 Debugging a MySQL Server
-------------------------------

* Menu:

* compiling-for-debugging::      Compiling MySQL for Debugging
* making-trace-files::           Creating Trace Files
* making-windows-dumps::         Using pdb to create a Windows crashdump
* using-gdb-on-mysqld::          Debugging mysqld under gdb
* using-stack-trace::            Using a Stack Trace
* using-log-files::              Using Server Logs to Find Causes of Errors in mysqld
* reproducible-test-case::       Making a Test Case If You Experience Table Corruption

If you are using some functionality that is very new in MySQL, you can
try to run *Note `mysqld': mysqld. with the `--skip-new' (which
disables all new, potentially unsafe functionality). See *Note
crashing::.

Binary distributions of MySQL server from Oracle include a specific
debug binary, `mysqld-debug'. This is a build including the debugging
information and is built in the same way as the debug build format
described in *Note compiling-for-debugging::. You should use this build
when debugging the MySQL server.

If *Note `mysqld': mysqld. doesn't want to start, you should verify
that you don't have any `my.cnf' files that interfere with your setup!
You can check your `my.cnf' arguments with *Note `mysqld
--print-defaults': mysqld. and avoid using them by starting with *Note
`mysqld --no-defaults ...': mysqld.

If *Note `mysqld': mysqld. starts to eat up CPU or memory or if it
`hangs,' you can use *Note `mysqladmin processlist status': mysqladmin.
to find out if someone is executing a query that takes a long time. It
may be a good idea to run *Note `mysqladmin -i10 processlist status':
mysqladmin. in some window if you are experiencing performance problems
or problems when new clients can't connect.

The command *Note `mysqladmin debug': mysqladmin. dumps some
information about locks in use, used memory and query usage to the
MySQL log file. This may help solve some problems. This command also
provides some useful information even if you haven't compiled MySQL for
debugging!

If the problem is that some tables are getting slower and slower you
should try to optimize the table with *Note `OPTIMIZE TABLE':
optimize-table. or *Note `myisamchk': myisamchk. See *Note
server-administration::. You should also check the slow queries with
*Note `EXPLAIN': explain.

You should also read the OS-specific section in this manual for
problems that may be unique to your environment. See *Note
general-installation-issues::.


File: manual.info,  Node: compiling-for-debugging,  Next: making-trace-files,  Prev: debugging-server,  Up: debugging-server

22.4.1.1 Compiling MySQL for Debugging
......................................

If you have some very specific problem, you can always try to debug
MySQL. To do this you must configure MySQL with the `--with-debug' or
the `--with-debug=full' option.  You can check whether MySQL was
compiled with debugging by doing: *Note `mysqld --help': mysqld. If the
`--debug' flag is listed with the options then you have debugging
enabled. *Note `mysqladmin ver': mysqladmin. also lists the *Note
`mysqld': mysqld. version as *Note `mysql ... --debug': mysql. in this
case.

If you are using `gcc', the recommended `configure' line is:


     CC=gcc CFLAGS="-O2" CXX=gcc CXXFLAGS="-O2 -felide-constructors \
        -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql \
        --with-debug --with-extra-charsets=complex

This avoids problems with the `libstdc++' library and with C++
exceptions (many compilers have problems with C++ exceptions in
threaded code) and compile a MySQL version with support for all
character sets.

If you suspect a memory overrun error, you can configure MySQL with
`--with-debug=full', which installs a memory allocation (`SAFEMALLOC')
checker. However, running with `SAFEMALLOC' is quite slow, so if you get
performance problems you should start *Note `mysqld': mysqld. with the
`--skip-safemalloc' option. This disables the memory overrun checks for
each call to `malloc()' and `free()'.

If *Note `mysqld': mysqld. stops crashing when you compile it with
`--with-debug', you probably have found a compiler bug or a timing bug
within MySQL. In this case, you can try to add `-g' to the `CFLAGS' and
`CXXFLAGS' variables above and not use `--with-debug'. If *Note
`mysqld': mysqld. dies, you can at least attach to it with `gdb' or use
`gdb' on the core file to find out what happened.

When you configure MySQL for debugging you automatically enable a lot
of extra safety check functions that monitor the health of *Note
`mysqld': mysqld. If they find something `unexpected,' an entry is
written to `stderr', which *Note `mysqld_safe': mysqld-safe. directs to
the error log! This also means that if you are having some unexpected
problems with MySQL and are using a source distribution, the first
thing you should do is to configure MySQL for debugging! (The second
thing is to send mail to a MySQL mailing list and ask for help. See
*Note mailing-lists::. If you believe that you have found a bug, please
use the instructions at *Note bug-reports::.

In the Windows MySQL distribution, `mysqld.exe' is by default compiled
with support for trace files.


File: manual.info,  Node: making-trace-files,  Next: making-windows-dumps,  Prev: compiling-for-debugging,  Up: debugging-server

22.4.1.2 Creating Trace Files
.............................

If the *Note `mysqld': mysqld. server doesn't start or if you can cause
it to crash quickly, you can try to create a trace file to find the
problem.

To do this, you must have a *Note `mysqld': mysqld. that has been
compiled with debugging support. You can check this by executing
`mysqld -V'. If the version number ends with `-debug', it is compiled
with support for trace files. (On Windows, the debugging server is
named *Note `mysqld-debug': mysqld. rather than *Note `mysqld': mysqld.
as of MySQL 4.1.)

Start the *Note `mysqld': mysqld. server with a trace log in
`/tmp/mysqld.trace' on Unix or `\mysqld.trace' on Windows:


     shell> mysqld --debug

On Windows, you should also use the `--standalone' flag to not start
*Note `mysqld': mysqld. as a service. In a console window, use this
command:


     C:\> mysqld-debug --debug --standalone

After this, you can use the `mysql.exe' command-line tool in a second
console window to reproduce the problem. You can stop the *Note
`mysqld': mysqld. server with *Note `mysqladmin shutdown': mysqladmin.

The trace file can become *very large*! To generate a smaller trace
file, you can use debugging options something like this:

*Note `mysqld
--debug=d,info,error,query,general,where:O,/tmp/mysqld.trace': mysqld.

This only prints information with the most interesting tags to the
trace file.

If you make a bug report about this, please only send the lines from
the trace file to the appropriate mailing list where something seems to
go wrong! If you can't locate the wrong place, you can open a bug
report and upload the trace file to the report, so that a MySQL
developer can take a look at it. For instructions, see *Note
bug-reports::.

The trace file is made with the *DBUG* package by Fred Fish.  See *Note
dbug-package::.


File: manual.info,  Node: making-windows-dumps,  Next: using-gdb-on-mysqld,  Prev: making-trace-files,  Up: debugging-server

22.4.1.3 Using pdb to create a Windows crashdump
................................................

Starting with MySQL 5.1.12 the Program Database files (extension `pdb')
are included in the Noinstall distribution of MySQL. These files provide
information for debugging your MySQL installation in the event of a
problem.

The PDB file contains more detailed information about `mysqld' and
other tools that enables more detailed trace and dump files to be
created. You can use these with Dr Watson, `WinDbg' and Visual Studio to
debug *Note `mysqld': mysqld.

For more information on PDB files, see Microsoft Knowledge Base Article
121366 (http://support.microsoft.com/kb/121366/). For more information
on the debugging options available, see Debugging Tools for Windows
(http://www.microsoft.com/whdc/devtools/debugging/default.mspx).

Dr Watson is installed with all Windows distributions, but if you have
installed Windows development tools, Dr Watson may have been replaced
with WinDbg, the debugger included with Visual Studio, or the debugging
tools provided with Borland or Delphi.

To generate a crash file using Dr Watson, follow these steps:

  1. Start Dr Watson by running `drwtsn32.exe' interactively using the
     `-i' option:


          C:\> drwtsn32 -i

  2. Set the `Log File Path' to the directory where you want to store
     trace files.

  3. Make sure `Dump All Thread Contexts' and `Append To Existing Log
     File'.

  4. Uncheck `Dump Symbol Table', `Visual Notification', `Sound
     Notification' and `Create Crash Dump File'.

  5. Set the `Number of Instructions' to a suitable value to capture
     enough calls in the stacktrace.  A value of at 25 should be enough.

Note that the file generated can become very large.


File: manual.info,  Node: using-gdb-on-mysqld,  Next: using-stack-trace,  Prev: making-windows-dumps,  Up: debugging-server

22.4.1.4 Debugging mysqld under gdb
...................................

On most systems you can also start *Note `mysqld': mysqld.  from `gdb'
to get more information if *Note `mysqld': mysqld. crashes.

With some older `gdb' versions on Linux you must use `run --one-thread'
if you want to be able to debug *Note `mysqld': mysqld. threads. In
this case, you can only have one thread active at a time. It is best to
upgrade to `gdb' 5.1 because thread debugging works much better with
this version!

NPTL threads (the new thread library on Linux) may cause problems while
running *Note `mysqld': mysqld. under `gdb'. Some symptoms are:

   * *Note `mysqld': mysqld. hangs during startup (before it writes
     `ready for connections').

   * *Note `mysqld': mysqld. crashes during a `pthread_mutex_lock()' or
     `pthread_mutex_unlock()' call.

In this case, you should set the following environment variable in the
shell before starting `gdb':


     LD_ASSUME_KERNEL=2.4.1
     export LD_ASSUME_KERNEL

When running *Note `mysqld': mysqld. under `gdb', you should disable
the stack trace with `--skip-stack-trace' to be able to catch segfaults
within `gdb'.

In MySQL 4.0.14 and above you should use the `--gdb' option to *Note
`mysqld': mysqld. This installs an interrupt handler for `SIGINT'
(needed to stop *Note `mysqld': mysqld. with `^C' to set breakpoints)
and disable stack tracing and core file handling.

It is very hard to debug MySQL under `gdb' if you do a lot of new
connections the whole time as `gdb' doesn't free the memory for old
threads. You can avoid this problem by starting *Note `mysqld': mysqld.
with `thread_cache_size' set to a value equal to `max_connections' + 1.
In most cases just using `--thread_cache_size=5'' helps a lot!

If you want to get a core dump on Linux if *Note `mysqld': mysqld. dies
with a SIGSEGV signal, you can start *Note `mysqld': mysqld. with the
`--core-file' option. This core file can be used to make a backtrace
that may help you find out why *Note `mysqld': mysqld. died:


     shell> gdb mysqld core
     gdb>   backtrace full
     gdb>   quit

See *Note crashing::.

If you are using `gdb' 4.17.x or above on Linux, you should install a
`.gdb' file, with the following information, in your current directory:


     set print sevenbit off
     handle SIGUSR1 nostop noprint
     handle SIGUSR2 nostop noprint
     handle SIGWAITING nostop noprint
     handle SIGLWP nostop noprint
     handle SIGPIPE nostop
     handle SIGALRM nostop
     handle SIGHUP nostop
     handle SIGTERM nostop noprint

If you have problems debugging threads with `gdb', you should download
gdb 5.x and try this instead. The new `gdb' version has very improved
thread handling!

Here is an example how to debug *Note `mysqld': mysqld.:


     shell> gdb /usr/local/libexec/mysqld
     gdb> run
     ...
     backtrace full # Do this when mysqld crashes

Include the preceding output in a bug report, which you can file using
the instructions in *Note bug-reports::.

If *Note `mysqld': mysqld. hangs, you can try to use some system tools
like `strace' or `/usr/proc/bin/pstack' to examine where *Note
`mysqld': mysqld. has hung.


     strace /tmp/log libexec/mysqld

If you are using the Perl `DBI' interface, you can turn on debugging
information by using the `trace' method or by setting the `DBI_TRACE'
environment variable.


File: manual.info,  Node: using-stack-trace,  Next: using-log-files,  Prev: using-gdb-on-mysqld,  Up: debugging-server

22.4.1.5 Using a Stack Trace
............................

On some operating systems, the error log contains a stack trace if
*Note `mysqld': mysqld. dies unexpectedly. You can use this to find out
where (and maybe why) *Note `mysqld': mysqld. died. See *Note
error-log::. To get a stack trace, you must not compile *Note `mysqld':
mysqld. with the `-fomit-frame-pointer' option to gcc. See *Note
compiling-for-debugging::.

A stack trace in the error log looks something like this:


     mysqld got signal 11;
     Attempting backtrace. You can use the following information
     to find out where mysqld died. If you see no messages after
     this, something went terribly wrong...

     stack_bottom = 0x41fd0110 thread_stack 0x40000
     mysqld(my_print_stacktrace+0x32)[0x9da402]
     mysqld(handle_segfault+0x28a)[0x6648e9]
     /lib/libpthread.so.0[0x7f1a5af000f0]
     /lib/libc.so.6(strcmp+0x2)[0x7f1a5a10f0f2]
     mysqld(_Z21check_change_passwordP3THDPKcS2_Pcj+0x7c)[0x7412cb]
     mysqld(_ZN16set_var_password5checkEP3THD+0xd0)[0x688354]
     mysqld(_Z17sql_set_variablesP3THDP4ListI12set_var_baseE+0x68)[0x688494]
     mysqld(_Z21mysql_execute_commandP3THD+0x41a0)[0x67a170]
     mysqld(_Z11mysql_parseP3THDPKcjPS2_+0x282)[0x67f0ad]
     mysqld(_Z16dispatch_command19enum_server_commandP3THDPcj+0xbb7[0x67fdf8]
     mysqld(_Z10do_commandP3THD+0x24d)[0x6811b6]
     mysqld(handle_one_connection+0x11c)[0x66e05e]

If resolution of function names for the trace fails, the trace contains
less information:


     mysqld got signal 11;
     Attempting backtrace. You can use the following information
     to find out where mysqld died. If you see no messages after
     this, something went terribly wrong...

     stack_bottom = 0x41fd0110 thread_stack 0x40000
     [0x9da402]
     [0x6648e9]
     [0x7f1a5af000f0]
     [0x7f1a5a10f0f2]
     [0x7412cb]
     [0x688354]
     [0x688494]
     [0x67a170]
     [0x67f0ad]
     [0x67fdf8]
     [0x6811b6]
     [0x66e05e]

In the latter case, you can use the *Note `resolve_stack_dump':
resolve-stack-dump. utility to determine where *Note `mysqld': mysqld.
died by using the following procedure:

  1. Copy the numbers from the stack trace to a file, for example
     `mysqld.stack'. The numbers should not include the surrounding
     square brackets:


          0x9da402
          0x6648e9
          0x7f1a5af000f0
          0x7f1a5a10f0f2
          0x7412cb
          0x688354
          0x688494
          0x67a170
          0x67f0ad
          0x67fdf8
          0x6811b6
          0x66e05e

  2. Make a symbol file for the *Note `mysqld': mysqld.  server:


          shell> nm -n libexec/mysqld > /tmp/mysqld.sym

     If *Note `mysqld': mysqld. is not linked statically, use the
     following command instead:


          shell> nm -D -n libexec/mysqld > /tmp/mysqld.sym

     If you want to decode C++ symbols, use the `--demangle', if
     available, to `nm'. If your version of `nm' does not have this
     option, you will need to use the `c++filt' command after the stack
     dump has been produced to demangle the C++ names.

  3. Execute the following command:


          shell> resolve_stack_dump -s /tmp/mysqld.sym -n mysqld.stack

     If you were not able to include demangled C++ names in your symbol
     file, process the *Note `resolve_stack_dump': resolve-stack-dump.
     output using `c++filt':


          shell> resolve_stack_dump -s /tmp/mysqld.sym -n mysqld.stack | c++filt

     This prints out where *Note `mysqld': mysqld. died. If that does
     not help you find out why *Note `mysqld': mysqld. died, you should
     create a bug report and include the output from the preceding
     command with the bug report.

     However, in most cases it does not help us to have just a stack
     trace to find the reason for the problem. To be able to locate the
     bug or provide a workaround, in most cases we need to know the
     statement that killed *Note `mysqld': mysqld. and preferably a
     test case so that we can repeat the problem! See *Note
     bug-reports::.


File: manual.info,  Node: using-log-files,  Next: reproducible-test-case,  Prev: using-stack-trace,  Up: debugging-server

22.4.1.6 Using Server Logs to Find Causes of Errors in mysqld
.............................................................

Note that before starting *Note `mysqld': mysqld. with the general
query log enabled, you should check all your tables with *Note
`myisamchk': myisamchk. See *Note server-administration::.

If *Note `mysqld': mysqld. dies or hangs, you should start *Note
`mysqld': mysqld. with the general query log enabled.  See *Note
query-log::. When *Note `mysqld': mysqld. dies again, you can examine
the end of the log file for the query that killed *Note `mysqld':
mysqld.

If you use the default general query log file, the log is stored in the
database directory as `HOST_NAME.log' In most cases it is the last
query in the log file that killed *Note `mysqld': mysqld, but if
possible you should verify this by restarting *Note `mysqld': mysqld.
and executing the found query from the *Note `mysql': mysql.
command-line tools. If this works, you should also test all complicated
queries that didn't complete.

You can also try the command *Note `EXPLAIN': explain. on all *Note
`SELECT': select. statements that takes a long time to ensure that
*Note `mysqld': mysqld. is using indexes properly. See *Note explain::.

You can find the queries that take a long time to execute by starting
*Note `mysqld': mysqld. with the slow query log enabled. See *Note
slow-query-log::.

If you find the text `mysqld restarted' in the error log file (normally
named `hostname.err') you probably have found a query that causes *Note
`mysqld': mysqld. to fail. If this happens, you should check all your
tables with *Note `myisamchk': myisamchk. (see *Note
server-administration::), and test the queries in the MySQL log files
to see whether one fails. If you find such a query, try first upgrading
to the newest MySQL version.  If this doesn't help and you can't find
anything in the `mysql' mail archive, you should report the bug to a
MySQL mailing list. The mailing lists are described at
`http://lists.mysql.com/', which also has links to online list archives.

If you have started *Note `mysqld': mysqld. with `--myisam-recover',
MySQL automatically checks and tries to repair `MyISAM' tables if they
are marked as 'not closed properly' or 'crashed'. If this happens,
MySQL writes an entry in the `hostname.err' file `'Warning: Checking
table ...'' which is followed by `Warning: Repairing table' if the
table needs to be repaired. If you get a lot of these errors, without
*Note `mysqld': mysqld. having died unexpectedly just before, then
something is wrong and needs to be investigated further. See *Note
server-options::.

It is not a good sign if *Note `mysqld': mysqld. did die unexpectedly,
but in this case, you should not investigate the `Checking table...'
messages, but instead try to find out why *Note `mysqld': mysqld. died.


File: manual.info,  Node: reproducible-test-case,  Prev: using-log-files,  Up: debugging-server

22.4.1.7 Making a Test Case If You Experience Table Corruption
..............................................................

If you get corrupted tables or if *Note `mysqld': mysqld.  always fails
after some update commands, you can test whether this bug is
reproducible by doing the following:

   * Take down the MySQL daemon (with *Note `mysqladmin shutdown':
     mysqladmin.).

   * Make a backup of the tables (to guard against the very unlikely
     case that the repair does something bad).

   * Check all tables with *Note `myisamchk -s database/*.MYI':
     myisamchk. Repair any wrong tables with *Note `myisamchk -r
     database/TABLE.MYI': myisamchk.

   * Make a second backup of the tables.

   * Remove (or move away) any old log files from the MySQL data
     directory if you need more space.

   * Start *Note `mysqld': mysqld. with the binary log enabled. If you
     want to find a query that crashes *Note `mysqld': mysqld, you
     should start the server with both the general query log enabled as
     well. See *Note query-log::, and *Note binary-log::.

   * When you have gotten a crashed table, stop the `mysqld server'.

   * Restore the backup.

   * Restart the *Note `mysqld': mysqld. server *without* the binary log
     enabled.

   * Re-execute the commands with *Note `mysqlbinlog binary-log-file |
     mysql': mysqlbinlog. The binary log is saved in the MySQL database
     directory with the name `hostname-bin.NNNNNN'.

   * If the tables are corrupted again or you can get *Note `mysqld':
     mysqld. to die with the above command, you have found reproducible
     bug that should be easy to fix! FTP the tables and the binary log
     to our bugs database using the instructions given in *Note
     bug-reports::. If you are a support customer, you can use the
     MySQL Customer Support Center `http://www.mysql.com/support/' to
     alert the MySQL team about the problem and have it fixed as soon as
     possible.

You can also use the script *Note `mysql_find_rows': mysql-find-rows.
to just execute some of the update statements if you want to narrow
down the problem.


File: manual.info,  Node: debugging-client,  Next: dbug-package,  Prev: debugging-server,  Up: porting

22.4.2 Debugging a MySQL Client
-------------------------------

To be able to debug a MySQL client with the integrated debug package,
you should configure MySQL with `--with-debug' or `--with-debug=full'.
See *Note source-configuration-options::.

Before running a client, you should set the `MYSQL_DEBUG' environment
variable:


     shell> MYSQL_DEBUG=d:t:O,/tmp/client.trace
     shell> export MYSQL_DEBUG

This causes clients to generate a trace file in `/tmp/client.trace'.

If you have problems with your own client code, you should attempt to
connect to the server and run your query using a client that is known
to work. Do this by running *Note `mysql': mysql. in debugging mode
(assuming that you have compiled MySQL with debugging on):


     shell> mysql --debug=d:t:O,/tmp/client.trace

This provides useful information in case you mail a bug report.  See
*Note bug-reports::.

If your client crashes at some 'legal' looking code, you should check
that your `mysql.h' include file matches your MySQL library file. A
very common mistake is to use an old `mysql.h' file from an old MySQL
installation with new MySQL library.


File: manual.info,  Node: dbug-package,  Prev: debugging-client,  Up: porting

22.4.3 The DBUG Package
-----------------------

The MySQL server and most MySQL clients are compiled with the DBUG
package originally created by Fred Fish. When you have configured MySQL
for debugging, this package makes it possible to get a trace file of
what the program is doing. See *Note making-trace-files::.

This section summarizes the argument values that you can specify in
debug options on the command line for MySQL programs that have been
built with debugging support. For more information about programming
with the DBUG package, see the DBUG manual in the `dbug' directory of
MySQL source distributions. It's best to use a recent distribution to
get the most updated DBUG manual.

The DBUG package can be used by invoking a program with the
`--debug[=DEBUG_OPTIONS]' or `-# [DEBUG_OPTIONS]' option. If you
specify the `--debug' or `-#' option without a DEBUG_OPTIONS value,
most MySQL programs use a default value. The server default is
`d:t:i:o,/tmp/mysqld.trace' on Unix and `d:t:i:O,\mysqld.trace' on
Windows. The effect of this default is:

   * `d': Enable output for all debug macros

   * `t': Trace function calls and exits

   * `i': Add PID to output lines

   * `o,/tmp/mysqld.trace', `O,\mysqld.trace': Set the debug output
     file.

Most client programs use a default DEBUG_OPTIONS value of
`d:t:o,/tmp/PROGRAM_NAME.trace', regardless of platform.

Here are some example debug control strings as they might be specified
on a shell command line:


     --debug=d:t
     --debug=d:f,main,subr1:F:L:t,20
     --debug=d,input,output,files:n
     --debug=d:t:i:O,\\mysqld.trace

For *Note `mysqld': mysqld, it is also possible to change DBUG settings
at runtime by setting the `debug' system variable. This variable has
global and session values:


     mysql> SET GLOBAL debug = 'DEBUG_OPTIONS';
     mysql> SET SESSION debug = 'DEBUG_OPTIONS';

Changes at runtime require the `SUPER' privilege, even for the session
value.

The DEBUG_OPTIONS value is a sequence of colon-separated fields:


     field_1:field_2:...:field_N

Each field within the value consists of a mandatory flag character,
optionally preceded by a `+' or `-' character, and optionally followed
by a comma-delimited list of modifiers:


     [+|-]flag[,modifier,modifier,...,modifier]

The following table describes the permitted flag characters.
Unrecognized flag characters are silently ignored.

*Flag*                                                     *Description*
`d'                                                        Enable output from DBUG_XXX macros for the current state. May be
                                                           followed by a list of keywords, which enables output only for the
                                                           DBUG macros with that keyword. An empty list of keywords enables
                                                           output for all macros.
                                                           
                                                           In MySQL, common debug macro keywords to enable are `enter',
                                                           `exit', `error', `warning', `info', and `loop'.
`D'                                                        Delay after each debugger output line. The argument is the delay,
                                                           in tenths of seconds, subject to machine capabilities. For
                                                           example, `D,20' specifies a delay of two seconds.
`f'                                                        Limit debugging, tracing, and profiling to the list of named
                                                           functions. An empty list enables all functions.  The appropriate
                                                           `d' or `t' flags must still be given; this flag only limits their
                                                           actions if they are enabled.
`F'                                                        Identify the source file name for each line of debug or trace
                                                           output.
`i'                                                        Identify the process with the PID or thread ID for each line of
                                                           debug or trace output.
`L'                                                        Identify the source file line number for each line of debug or
                                                           trace output.
`n'                                                        Print the current function nesting depth for each line of debug
                                                           or trace output.
`N'                                                        Number each line of debug output.
`o'                                                        Redirect the debugger output stream to the specified file. The
                                                           default output is `stderr'.
`O'                                                        Like `o', but the file is really flushed between each write. When
                                                           needed, the file is closed and reopened between each write.
`p'                                                        Limit debugger actions to specified processes. A process must be
                                                           identified with the `DBUG_PROCESS' macro and match one in the
                                                           list for debugger actions to occur.
`P'                                                        Print the current process name for each line of debug or trace
                                                           output.
`r'                                                        When pushing a new state, do not inherit the previous state's
                                                           function nesting level. Useful when the output is to start at the
                                                           left margin.
`S'                                                        Do function `_sanity(_file_,_line_)' at each debugged function
                                                           until `_sanity()' returns something that differs from 0. (Mostly
                                                           used with `safemalloc' to find memory leaks.)
`t'                                                        Enable function call/exit trace lines. May be followed by a list
                                                           (containing only one modifier) giving a numeric maximum trace
                                                           level, beyond which no output occurs for either debugging or
                                                           tracing macros. The default is a compile time option.

The leading `+' or `-' character and trailing list of modifiers are
used for flag characters such as `d' or `f' that can enable a debug
operation for all applicable modifiers or just some of them:

   * With no leading `+' or `-', the flag value is set to exactly the
     modifier list as given.

   * With a leading `+' or `-', the modifiers in the list are added to
     or subtracted from the current modifier list.

The following examples show how this works for the `d' flag. An empty
`d' list enabled output for all debug macros. A nonempty list enables
output only for the macro keywords in the list.

These statements set the `d' value to the modifier list as given:


     mysql> SET debug = 'd';
     mysql> SELECT @@debug;
     +---------+
     | @@debug |
     +---------+
     | d       |
     +---------+
     mysql> SET debug = 'd,error,warning';
     mysql> SELECT @@debug;
     +-----------------+
     | @@debug         |
     +-----------------+
     | d,error,warning |
     +-----------------+

A leading `+' or `-' adds to or subtracts from the current `d' value:


     mysql> SET debug = '+d,loop';
     mysql> SELECT @@debug;
     +----------------------+
     | @@debug              |
     +----------------------+
     | d,error,warning,loop |
     +----------------------+
     mysql> SET debug = '-d,error,loop';
     mysql> SELECT @@debug;
     +-----------+
     | @@debug   |
     +-----------+
     | d,warning |
     +-----------+

Adding to `all macros enabled' results in no change:


     mysql> SET debug = 'd';
     mysql> SELECT @@debug;
     +---------+
     | @@debug |
     +---------+
     | d       |
     +---------+
     mysql> SET debug = '+d,loop';
     mysql> SELECT @@debug;
     +---------+
     | @@debug |
     +---------+
     | d       |
     +---------+

Disabling all enabled macros disables the `d' flag entirely:


     mysql> SET debug = 'd,error,loop';
     mysql> SELECT @@debug;
     +--------------+
     | @@debug      |
     +--------------+
     | d,error,loop |
     +--------------+
     mysql> SET debug = '-d,error,loop';
     mysql> SELECT @@debug;
     +---------+
     | @@debug |
     +---------+
     |         |
     +---------+

*Note*:

The `+' and `-' modifiers are not always handled correctly and can
leave a flag value in an incorrect state. Verify your `debug'-setting
sequence in advance or set it without using `+' or `-'.


File: manual.info,  Node: mysql-enterprise,  Next: workbench,  Prev: extending-mysql,  Up: Top

23 MySQL Enterprise Edition
***************************

* Menu:

* mysql-enterprise-monitor::     MySQL Enterprise Monitor
* mysql-enterprise-backup::      MySQL Enterprise Backup
* mysql-enterprise-security::    MySQL Enterprise Security
* mysql-enterprise-encryption::  MySQL Enterprise Encryption
* mysql-enterprise-audit::       MySQL Enterprise Audit
* mysql-enterprise-thread-pool::  MySQL Enterprise Thread Pool

MySQL Enterprise Edition is a commercial product. Like MySQL Community
Edition, MySQL Enterprise Edition includes MySQL Server, a fully
integrated transaction-safe, ACID-compliant database with full commit,
rollback, crash-recovery, and row-level locking capabilities. In
addition, MySQL Enterprise Edition includes the following components
designed to provide monitoring and online backup, as well as improved
security and scalability:

The following sections briefly discuss each of these components and
indicate where to find more detailed information. To learn more about
commercial products, see http://www.mysql.com/products/.

   * *Note MySQL Enterprise Monitor: mysql-enterprise-monitor.

   * *Note MySQL Enterprise Backup: mysql-enterprise-backup.

   * *Note MySQL Enterprise Security: mysql-enterprise-security.

   * *Note MySQL Enterprise Encryption: mysql-enterprise-encryption.

   * *Note MySQL Enterprise Audit: mysql-enterprise-audit.

   * *Note MySQL Enterprise Thread Pool: mysql-enterprise-thread-pool.


File: manual.info,  Node: mysql-enterprise-monitor,  Next: mysql-enterprise-backup,  Prev: mysql-enterprise,  Up: mysql-enterprise

23.1 MySQL Enterprise Monitor
=============================

MySQL Enterprise Monitor is an enterprise monitoring system for MySQL
that keeps an eye on your MySQL servers, notifies you of potential
issues and problems, and advises you how to fix the issues. MySQL
Enterprise Monitor can monitor all kinds of configurations, from a
single MySQL server that is important to your business, all the way up
to a huge farm of MySQL servers powering a busy web site.

The following discussion briefly summarizes the basic components that
make up the MySQL Enterprise Monitor product. For more information, see
the MySQL Enterprise Monitor manual, available at
`http://dev.mysql.com/doc/mysql-monitor/en/'.

MySQL Enterprise Monitor components can be installed in various
configurations depending on your database and network topology, to give
you the best combination of reliable and responsive monitoring data,
with minimal overhead on the database server machines. A typical MySQL
Enterprise Monitor installation consists of:

   * One or more MySQL servers to monitor. MySQL Enterprise Monitor can
     monitor both Community and Enterprise MySQL server releases.

   * A MySQL Enterprise Monitor Agent for each monitored host.

   * A single MySQL Enterprise Service Manager, which collates
     information from the agents and provides the user interface to the
     collected data.

MySQL Enterprise Monitor is designed to monitor one or more MySQL
servers. The monitoring information is collected by using an agent,
_MySQL Enterprise Monitor Agent_. The agent communicates with the hosts
and MySQL servers that it monitors, collecting variables, status and
health information, and sending this information to the MySQL
Enterprise Service Manager.

The information collected by the agent about each MySQL server and host
you are monitoring is sent to the _MySQL Enterprise Service Manager_.
This server collates all of the information from the agents. As it
collates the information sent by the agents, the MySQL Enterprise
Service Manager continually tests the collected data, comparing the
status of the server to reasonable values. When thresholds are reached,
the server can trigger an event (including an alarm and notification)
to highlight a potential issue, such as low memory, high CPU usage, or
more complex conditions such insufficient buffer sizes and status
information. We call each test, with its associated threshold value, a
_rule_.

These rules, and the alarms and notifications, are each known as a
_MySQL Enterprise Advisors_. Advisors form a critical part of the MySQL
Enterprise Service Manager, as they provide warning information and
troubleshooting advice about potential problems.

The MySQL Enterprise Service Manager includes a web server, and you
interact with it through any web browser. This interface, the MySQL
Enterprise Monitor User Interface, displays all of the information
collected by the agents, and lets you view all of your servers and
their current status as a group or individually. You control and
configure all aspects of the service using the MySQL Enterprise Monitor
User Interface.

The information supplied by the MySQL Enterprise Monitor Agent
processes also includes statistical and query information, which you
can view in the form of graphs. For example, you can view aspects such
as server load, query numbers, or index usage information as a graph
over time. The graph lets you pinpoint problems or potential issues on
your server, and can help diagnose the impact from database or external
problems (such as external system or network failure) by examining the
data from a specific time interval.

The MySQL Enterprise Monitor Agent can also be configured to collect
detailed information about the queries executed on your server,
including the row counts and performance times for executing each
query. You can correlate the detailed query data with the graphical
information to identify which queries were executing when you
experienced a particularly high load, index or other issue. The query
data is supported by a system called Query Analyzer, and the data can
be presented in different ways depending on your needs.


File: manual.info,  Node: mysql-enterprise-backup,  Next: mysql-enterprise-security,  Prev: mysql-enterprise-monitor,  Up: mysql-enterprise

23.2 MySQL Enterprise Backup
============================

MySQL Enterprise Backup performs hot backup operations for MySQL
databases. The product is architected for efficient and reliable
backups of tables created by the InnoDB storage engine. For
completeness, it can also back up tables from MyISAM and other storage
engines.

The following discussion briefly summarizes MySQL Enterprise Backup.
For more information, see the MySQL Enterprise Backup manual, available
at `http://dev.mysql.com/doc/mysql-enterprise-backup/en/'.

Hot backups are performed while the database is running and
applications are reading and writing to it. This type of backup does
not block normal database operations, and it captures even changes that
occur while the backup is happening. For these reasons, hot backups are
desirable when your database `grows up' - when the data is large enough
that the backup takes significant time, and when your data is important
enough to your business that you must capture every last change,
without taking your application, web site, or web service offline.

MySQL Enterprise Backup does a hot backup of all tables that use the
InnoDB storage engine. For tables using MyISAM or other non-InnoDB
storage engines, it does a `warm' backup, where the database continues
to run, but those tables cannot be modified while being backed up. For
efficient backup operations, you can designate InnoDB as the default
storage engine for new tables, or convert existing tables to use the
InnoDB storage engine.


File: manual.info,  Node: mysql-enterprise-security,  Next: mysql-enterprise-encryption,  Prev: mysql-enterprise-backup,  Up: mysql-enterprise

23.3 MySQL Enterprise Security
==============================

MySQL Enterprise Edition provides plugins that implement authentication
using external services:

   * MySQL Enterprise Edition includes an authentication plugin that
     enables MySQL Server to use PAM (Pluggable Authentication Modules)
     to authenticate MySQL users. PAM enables a system to use a
     standard interface to access various kinds of authentication
     methods, such as Unix passwords or an LDAP directory.

   * MySQL Enterprise Edition includes an authentication plugin that
     performs external authentication on Windows, enabling MySQL Server
     to use native Windows services to authenticate client connections.
     Users who have logged in to Windows can connect from MySQL client
     programs to the server based on the information in their
     environment without specifying an additional password.

For more information, see The PAM Authentication Plugin
(http://dev.mysql.com/doc/refman/5.5/en/pam-authentication-plugin.html),
and The Windows Native Authentication Plugin
(http://dev.mysql.com/doc/refman/5.5/en/windows-authentication-plugin.html).

For other related Enterprise security features, see *Note
mysql-enterprise-encryption::.


File: manual.info,  Node: mysql-enterprise-encryption,  Next: mysql-enterprise-audit,  Prev: mysql-enterprise-security,  Up: mysql-enterprise

23.4 MySQL Enterprise Encryption
================================

In MySQL 5.6, MySQL Enterprise Edition includes a set of encryption
functions based on the OpenSSL library that expose OpenSSL capabilities
at the SQL level. These functions enable Enterprise applications to
perform the following operations:

   * Implement added data protection using public-key asymmetric
     cryptography

   * Create public and private keys and digital signatures

   * Perform asymmetric encryption and decryption

   * Use cryptographic hashing for digital signing and data
     verification and validation

For more information, see MySQL Enterprise Encryption Functions
(http://dev.mysql.com/doc/refman/5.6/en/enterprise-encryption.html).


File: manual.info,  Node: mysql-enterprise-audit,  Next: mysql-enterprise-thread-pool,  Prev: mysql-enterprise-encryption,  Up: mysql-enterprise

23.5 MySQL Enterprise Audit
===========================

MySQL Enterprise Edition includes MySQL Enterprise Audit, implemented
using a server plugin. MySQL Enterprise Audit uses the open MySQL Audit
API to enable standard, policy-based monitoring and logging of
connection and query activity executed on specific MySQL servers.
Designed to meet the Oracle audit specification, MySQL Enterprise Audit
provides an out of box, easy to use auditing and compliance solution
for applications that are governed by both internal and external
regulatory guidelines.

When installed, the audit plugin enables MySQL Server to produce a log
file containing an audit record of server activity. The log contents
include when clients connect and disconnect, and what actions they
perform while connected, such as which databases and tables they access.

For more information, see MySQL Enterprise Audit Log Plugin
(http://dev.mysql.com/doc/refman/5.5/en/audit-log-plugin.html).


File: manual.info,  Node: mysql-enterprise-thread-pool,  Prev: mysql-enterprise-audit,  Up: mysql-enterprise

23.6 MySQL Enterprise Thread Pool
=================================

MySQL Enterprise Edition includes the MySQL Thread Pool, implemented
using a server plugin. The default thread-handling model in MySQL
Server executes statements using one thread per client connection. As
more clients connect to the server and execute statements, overall
performance degrades. In MySQL Enterprise Edition, a thread pool plugin
provides an alternative thread-handling model designed to reduce
overhead and improve performance. The plugin implements a thread pool
that increases server performance by efficiently managing statement
execution threads for large numbers of client connections.

For more information, see The Thread Pool Plugin
(http://dev.mysql.com/doc/refman/5.5/en/thread-pool-plugin.html).


File: manual.info,  Node: workbench,  Next: faqs,  Prev: mysql-enterprise,  Up: Top

24 MySQL Workbench
******************

MySQL Workbench provides a graphical tool for working with MySQL Servers
and databases. MySQL Workbench fully supports MySQL Server versions 5.1
and above. It is also compatible with MySQL Server 5.0, but not every
feature of 5.0 may be supported. It does not support MySQL Server
versions 4.x.

The following discussion briefly describes MySQL Workbench capabilities.
For more information, see the MySQL Workbench manual, available at
`http://dev.mysql.com/doc/workbench/en/'.

MySQL Workbench provides five main areas of functionality:

   * *SQL Development*: Enables you to create and manage connections to
     database servers. As well as enabling you to configure connection
     parameters, MySQL Workbench provides the capability to execute SQL
     queries on the database connections using the built-in SQL Editor.
     This functionality replaces that previously provided by the Query
     Browser standalone application.

   * *Data Modeling*: Enables you to create models of your database
     schema graphically, reverse and forward engineer between a schema
     and a live database, and edit all aspects of your database using
     the comprehensive Table Editor. The Table Editor provides
     easy-to-use facilities for editing Tables, Columns, Indexes,
     Triggers, Partitioning, Options, Inserts and Privileges, Routines
     and Views.

   * *Server Administration*: Enables you to create and administer
     server instances.

   * *Data Migration*: Allows you to migrate from Microsoft SQL Server,
     Sybase ASE, SQLite, SQL Anywhere, PostreSQL, and other RDBMS
     tables, objects and data to MySQL. Migration also supports
     migrating from earlier versions of MySQL to the latest releases.

   * *MySQL Enterprise Support*: Support for Enterprise products such
     as MySQL Enterprise Backup and MySQL Audit.

MySQL Workbench is available in two editions, the Community Edition and
the Commercial Edition. The Community Edition is available free of
charge. The Commercial Edition provides additional Enterprise features,
such as database documentation generation, at low cost.


File: manual.info,  Node: faqs,  Next: error-handling,  Prev: workbench,  Up: Top

Appendix A MySQL 5.1 Frequently Asked Questions
***********************************************

* Menu:

* faqs-general::                 MySQL 5.1 FAQ: General
* faqs-storage-engines::         MySQL 5.1 FAQ: Storage Engines
* faqs-sql-modes::               MySQL 5.1 FAQ: Server SQL Mode
* faqs-stored-procs::            MySQL 5.1 FAQ: Stored Procedures and Functions
* faqs-triggers::                MySQL 5.1 FAQ: Triggers
* faqs-views::                   MySQL 5.1 FAQ: Views
* faqs-information-schema::      MySQL 5.1 FAQ: INFORMATION_SCHEMA
* faqs-migration::               MySQL 5.1 FAQ: Migration
* faqs-security::                MySQL 5.1 FAQ: Security
* faqs-mysql-cluster::           MySQL 5.1 FAQ: MySQL Cluster
* faqs-cjk::                     MySQL 5.1 FAQ: MySQL Chinese, Japanese, and Korean Character Sets
* faqs-connectors-apis::         MySQL 5.1 FAQ: Connectors & APIs
* faqs-replication::             MySQL 5.1 FAQ: Replication


File: manual.info,  Node: faqs-general,  Next: faqs-storage-engines,  Prev: faqs,  Up: faqs

A.1 MySQL 5.1 FAQ: General
==========================

*Questions*
   * A.1.1: Which version of MySQL is production-ready (GA)?

   * A.1.2: What is the state of development (non-GA) versions?

   * A.1.3: Can MySQL 5.1 do subqueries?

   * A.1.4: Can MySQL 5.1 perform multiple-table inserts, updates, and
     deletes?

   * A.1.5: Does MySQL 5.1 have a Query Cache? Does it work on Server,
     Instance or Database?

   * A.1.6: Does MySQL 5.1 have Sequences?

   * A.1.7: Does MySQL 5.1 have a `NOW()' function with fractions of
     seconds?

   * A.1.8: Does MySQL 5.1 work with multi-core processors?

   * A.1.9: Why do I see multiple processes for `mysqld'?

   * A.1.10: Have there been there any improvements in error reporting
     when foreign keys fail? Does MySQL now report which column and
     reference failed?

   * A.1.11: Can MySQL 5.1 perform ACID transactions?

*Questions and Answers* *A.1.1: ** Which version of MySQL is
production-ready (GA)?  *

MySQL 5.6, MySQL 5.5, MySQL 5.1, and MySQL 5.0 are supported for
production use.

MySQL 5.6 achieved General Availability (GA) status with MySQL 5.6.10,
which was released for production use on 5 February 2013.

MySQL 5.5 achieved General Availability (GA) status with MySQL 5.5.8,
which was released for production use on 3 December 2010.

MySQL 5.1 achieved General Availability (GA) status with MySQL 5.1.30,
which was released for production use on 14 November 2008.

MySQL 5.0 achieved General Availability (GA) status with MySQL 5.0.15,
which was released for production use on 19 October 2005. Note that
active development for MySQL 5.0 has ended.

*A.1.2: ** What is the state of development (non-GA) versions?  *

MySQL follows a milestone release model that introduces
pre-production-quality features and stabilizes them to release quality
(see `http://dev.mysql.com/doc/mysql-development-cycle/en/index.html').
This process then repeats, so releases cycle between pre-production and
release quality status. Please check the change logs to identify the
status of a given release.

MySQL 5.4 was a development series. Work on this series has ceased.

MySQL 5.7 is being actively developed using the milestone release
methodology described above.

MySQL 6.0 was a development series. Work on this series has ceased.

*A.1.3: ** Can MySQL 5.1 do subqueries?  *

Yes. See *Note subqueries::.

*A.1.4: ** Can MySQL 5.1 perform multiple-table inserts, updates, and
deletes?  *

Yes. For the syntax required to perform multiple-table updates, see
*Note update::; for that required to perform multiple-table deletes,
see *Note delete::.

A multiple-table insert can be accomplished using a trigger whose `FOR
EACH ROW' clause contains multiple *Note `INSERT': insert. statements
within a `BEGIN ... END' block. See *Note triggers::.

*A.1.5: ** Does MySQL 5.1 have a Query Cache? Does it work on Server,
Instance or Database?  *

Yes. The query cache operates on the server level, caching complete
result sets matched with the original query string. If an exactly
identical query is made (which often happens, particularly in web
applications), no parsing or execution is necessary; the result is sent
directly from the cache. Various tuning options are available. See
*Note query-cache::.

*A.1.6: ** Does MySQL 5.1 have Sequences?  *

No. However, MySQL has an `AUTO_INCREMENT' system, which in MySQL 5.1
can also handle inserts in a multi-master replication setup. With the
`auto_increment_increment' and `auto_increment_offset' system
variables, you can set each server to generate auto-increment values
that don't conflict with other servers. The `auto_increment_increment'
value should be greater than the number of servers, and each server
should have a unique offset.

*A.1.7: ** Does MySQL 5.1 have a `NOW()' function with fractions of
seconds?  *

No. This is on the MySQL roadmap as a `rolling feature'. This means
that it is not a flagship feature, but will be implemented, development
time permitting. Specific customer demand may change this scheduling.

However, MySQL does parse time strings with a fractional component. See
*Note time::.

*A.1.8: ** Does MySQL 5.1 work with multi-core processors?  *

Yes. MySQL is fully multi-threaded, and will make use of multiple CPUs,
provided that the operating system supports them.

*A.1.9: ** Why do I see multiple processes for `mysqld'?  *

When using LinuxThreads, you should see a minimum of three *Note
`mysqld': mysqld. processes running. These are in fact threads. There
is one thread for the LinuxThreads manager, one thread to handle
connections, and one thread to handle alarms and signals.

*A.1.10: ** Have there been there any improvements in error reporting
when foreign keys fail? Does MySQL now report which column and
reference failed?  *

The foreign key support in `InnoDB' has seen improvements in each major
version of MySQL. Foreign key support generic to all storage engines is
scheduled for MySQL 6.x; this should resolve any inadequacies in the
current storage engine specific implementation.

*A.1.11: ** Can MySQL 5.1 perform ACID transactions?  *

Yes. All current MySQL versions support transactions. The `InnoDB'
storage engine offers full ACID transactions with row-level locking,
multi-versioning, nonlocking repeatable reads, and all four SQL
standard isolation levels.

The *Note `NDB': mysql-cluster. storage engine supports the `READ
COMMITTED' transaction isolation level only.


File: manual.info,  Node: faqs-storage-engines,  Next: faqs-sql-modes,  Prev: faqs-general,  Up: faqs

A.2 MySQL 5.1 FAQ: Storage Engines
==================================

*Questions*
   * A.2.1: Where can I obtain complete documentation for MySQL storage
     engines and the pluggable storage engine architecture?

   * A.2.2: Are there any new storage engines in MySQL 5.1?

   * A.2.3: Have any storage engines been removed in MySQL 5.1?

   * A.2.4: What are the unique benefits of the `ARCHIVE' storage
     engine?

   * A.2.5: Do the new features in MySQL 5.1 apply to all storage
     engines?

*Questions and Answers* *A.2.1: ** Where can I obtain complete
documentation for MySQL storage engines and the pluggable storage
engine architecture?  *

See *Note storage-engines::. That chapter contains information about
all MySQL storage engines except for the *Note `NDB': mysql-cluster.
storage engine used for MySQL Cluster; *Note `NDB': mysql-cluster. is
covered in *Note mysql-cluster::.

*A.2.2: ** Are there any new storage engines in MySQL 5.1?  *

Yes:

   * The `InnoDB Plugin' is available as an alternative to the built-in
     version of the `InnoDB' storage engine. It includes a number of
     features such as the Barracuda file format, table compression, and
     new configuration options for performance.  As you upgrade to
     MySQL 5.5 and higher, these features become core features of the
     MySQL server, and `InnoDB' becomes the default storage engine for
     new tables.

   * There have been significant improvements in existing storage
     engines, in particular for the *Note `NDB': mysql-cluster. storage
     engine that forms the basis for MySQL Cluster.

   * The *Note `IBMDB2I': se-db2. storage engine is included in the IBM
     i5/OS (TAR packages) and IBM i5/OS (SAVF packages).

*A.2.3: ** Have any storage engines been removed in MySQL 5.1?  *

Yes. MySQL 5.1 no longer supports the `BDB' storage engine. Any existing
`BDB' tables should be converted to another storage engine before
upgrading to MySQL 5.1.

*A.2.4: ** What are the unique benefits of the `ARCHIVE' storage engine?
*

The `ARCHIVE' storage engine is ideally suited for storing large
amounts of data without indexes; it has a very small footprint, and
performs selects using table scans. See *Note archive-storage-engine::,
for details.

*A.2.5: ** Do the new features in MySQL 5.1 apply to all storage
engines?  *

The general new features such as views, stored procedures, triggers,
`INFORMATION_SCHEMA', precision math (*Note `DECIMAL':
fixed-point-types. column type), and the *Note `BIT': bit-type. column
type, apply to all storage engines. There are also additions and
changes for specific storage engines.


File: manual.info,  Node: faqs-sql-modes,  Next: faqs-stored-procs,  Prev: faqs-storage-engines,  Up: faqs

A.3 MySQL 5.1 FAQ: Server SQL Mode
==================================

*Questions*
   * A.3.1: What are server SQL modes?

   * A.3.2: How many server SQL modes are there?

   * A.3.3: How do you determine the server SQL mode?

   * A.3.4: Is the mode dependent on the database or connection?

   * A.3.5: Can the rules for strict mode be extended?

   * A.3.6: Does strict mode impact performance?

   * A.3.7: What is the default server SQL mode when MySQL 5.1 is
     installed?

*Questions and Answers* *A.3.1: ** What are server SQL modes?  *

Server SQL modes define what SQL syntax MySQL should support and what
kind of data validation checks it should perform. This makes it easier
to use MySQL in different environments and to use MySQL together with
other database servers. The MySQL Server apply these modes individually
to different clients. For more information, see *Note sql-mode::.

*A.3.2: ** How many server SQL modes are there?  *

Each mode can be independently switched on and off. See *Note
sql-mode::, for a complete list of available modes.

*A.3.3: ** How do you determine the server SQL mode?  *

You can set the default SQL mode (for *Note `mysqld': mysqld.  startup)
with the `--sql-mode' option. Using the statement *Note `SET
[GLOBAL|SESSION] sql_mode='MODES'': set-statement, you can change the
settings from within a connection, either locally to the connection, or
to take effect globally. You can retrieve the current mode by issuing a
`SELECT @@sql_mode' statement.

*A.3.4: ** Is the mode dependent on the database or connection?  *

A mode is not linked to a particular database. Modes can be set locally
to the session (connection), or globally for the server.  you can
change these settings using *Note `SET [GLOBAL|SESSION]
sql_mode='MODES'': set-statement.

*A.3.5: ** Can the rules for strict mode be extended?  *

When we refer to _strict mode_, we mean a mode where at least one of
the modes `TRADITIONAL', `STRICT_TRANS_TABLES', or `STRICT_ALL_TABLES'
is enabled.  Options can be combined, so you can add restrictions to a
mode.  See *Note sql-mode::, for more information.

*A.3.6: ** Does strict mode impact performance?  *

The intensive validation of input data that some settings requires more
time than if the validation is not done. While the performance impact
is not that great, if you do not require such validation (perhaps your
application already handles all of this), then MySQL gives you the
option of leaving strict mode disabled. However--if you do require
it--strict mode can provide such validation.

*A.3.7: ** What is the default server SQL mode when MySQL 5.1 is
installed?  *

By default, no special modes are enabled. See *Note sql-mode::, for
information about all available modes and MySQL's default behavior.


File: manual.info,  Node: faqs-stored-procs,  Next: faqs-triggers,  Prev: faqs-sql-modes,  Up: faqs

A.4 MySQL 5.1 FAQ: Stored Procedures and Functions
==================================================

*Questions*
   * A.4.1: Does MySQL 5.1 support stored procedures and functions?

   * A.4.2: Where can I find documentation for MySQL stored procedures
     and stored functions?

   * A.4.3: Is there a discussion forum for MySQL stored procedures?

   * A.4.4: Where can I find the ANSI SQL 2003 specification for stored
     procedures?

   * A.4.5: How do you manage stored routines?

   * A.4.6: Is there a way to view all stored procedures and stored
     functions in a given database?

   * A.4.7: Where are stored procedures stored?

   * A.4.8: Is it possible to group stored procedures or stored
     functions into packages?

   * A.4.9: Can a stored procedure call another stored procedure?

   * A.4.10: Can a stored procedure call a trigger?

   * A.4.11: Can a stored procedure access tables?

   * A.4.12: Do stored procedures have a statement for raising
     application errors?

   * A.4.13: Do stored procedures provide exception handling?

   * A.4.14: Can MySQL 5.1 stored routines return result sets?

   * A.4.15: Is `WITH RECOMPILE' supported for stored procedures?

   * A.4.16: Is there a MySQL equivalent to using `mod_plsql' as a
     gateway on Apache to talk directly to a stored procedure in the
     database?

   * A.4.17: Can I pass an array as input to a stored procedure?

   * A.4.18: Can I pass a cursor as an `IN' parameter to a stored
     procedure?

   * A.4.19: Can I return a cursor as an `OUT' parameter from a stored
     procedure?

   * A.4.20: Can I print out a variable's value within a stored routine
     for debugging purposes?

   * A.4.21: Can I commit or roll back transactions inside a stored
     procedure?

   * A.4.22: Do MySQL 5.1 stored procedures and functions work with
     replication?

   * A.4.23: Are stored procedures and functions created on a master
     server replicated to a slave?

   * A.4.24: How are actions that take place inside stored procedures
     and functions replicated?

   * A.4.25: Are there special security requirements for using stored
     procedures and functions together with replication?

   * A.4.26: What limitations exist for replicating stored procedure and
     function actions?

   * A.4.27: Do the preceding limitations affect MySQL's ability to do
     point-in-time recovery?

   * A.4.28: What is being done to correct the aforementioned
     limitations?

*Questions and Answers* *A.4.1: ** Does MySQL 5.1 support stored
procedures and functions?  *

Yes. MySQL 5.1 supports two types of stored routines--stored procedures
and stored functions.

*A.4.2: ** Where can I find documentation for MySQL stored procedures
and stored functions?  *

See *Note stored-routines::.

*A.4.3: ** Is there a discussion forum for MySQL stored procedures?  *

Yes. See http://forums.mysql.com/list.php?98
(http://forums.mysql.com/list.php?98).

*A.4.4: ** Where can I find the ANSI SQL 2003 specification for stored
procedures?  *

Unfortunately, the official specifications are not freely available
(ANSI makes them available for purchase). However, there are
books--such as `SQL-99 Complete, Really' by Peter Gulutzan and Trudy
Pelzer--which give a comprehensive overview of the standard, including
coverage of stored procedures.

*A.4.5: ** How do you manage stored routines?  *

It is always good practice to use a clear naming scheme for your stored
routines. You can manage stored procedures with `CREATE
[FUNCTION|PROCEDURE]', `ALTER [FUNCTION|PROCEDURE]', `DROP
[FUNCTION|PROCEDURE]', and `SHOW CREATE [FUNCTION|PROCEDURE]'. You can
obtain information about existing stored procedures using the *Note
`ROUTINES': routines-table. table in the `INFORMATION_SCHEMA' database
(see *Note routines-table::).

*A.4.6: ** Is there a way to view all stored procedures and stored
functions in a given database?  *

Yes. For a database named DBNAME, use this query on the *Note
`INFORMATION_SCHEMA.ROUTINES': routines-table. table:


     SELECT ROUTINE_TYPE, ROUTINE_NAME
         FROM INFORMATION_SCHEMA.ROUTINES
         WHERE ROUTINE_SCHEMA='DBNAME';

For more information, see *Note routines-table::.

The body of a stored routine can be viewed using *Note `SHOW CREATE
FUNCTION': show-create-function. (for a stored function) or *Note `SHOW
CREATE PROCEDURE': show-create-procedure. (for a stored procedure). See
*Note show-create-procedure::, for more information.

*A.4.7: ** Where are stored procedures stored?  *

In the `proc' table of the `mysql' system database. However, you should
not access the tables in the system database directly. Instead, use
*Note `SHOW CREATE FUNCTION': show-create-function. to obtain
information about stored functions, and *Note `SHOW CREATE PROCEDURE':
show-create-procedure. to obtain information about stored procedures.
See *Note show-create-procedure::, for more information about these
statements.

You can also query the *Note `ROUTINES': routines-table.  table in the
`INFORMATION_SCHEMA' database--see *Note routines-table::, for
information about this table.

*A.4.8: ** Is it possible to group stored procedures or stored functions
into packages?  *

No. This is not supported in MySQL 5.1.

*A.4.9: ** Can a stored procedure call another stored procedure?  *

Yes.

*A.4.10: ** Can a stored procedure call a trigger?  *

A stored procedure can execute an SQL statement, such as an *Note
`UPDATE': update, that causes a trigger to activate.

*A.4.11: ** Can a stored procedure access tables?  *

Yes. A stored procedure can access one or more tables as required.

*A.4.12: ** Do stored procedures have a statement for raising
application errors?  *

Not in MySQL 5.1. The SQL standard `SIGNAL' and `RESIGNAL' statements
are implemented in MySQL 5.5.

*A.4.13: ** Do stored procedures provide exception handling?  *

MySQL implements *Note `HANDLER': handler.  definitions according to
the SQL standard. See *Note declare-handler::, for details.

*A.4.14: ** Can MySQL 5.1 stored routines return result sets?  *

_Stored procedures_ can, but stored functions cannot. If you perform an
ordinary *Note `SELECT': select. inside a stored procedure, the result
set is returned directly to the client. You need to use the MySQL 4.1
(or above) client/server protocol for this to work. This means
that--for instance--in PHP, you need to use the `mysqli' extension
rather than the old `mysql' extension.

*A.4.15: ** Is `WITH RECOMPILE' supported for stored procedures?  *

Not in MySQL 5.1.

*A.4.16: ** Is there a MySQL equivalent to using `mod_plsql' as a
gateway on Apache to talk directly to a stored procedure in the
database?  *

There is no equivalent in MySQL 5.1.

*A.4.17: ** Can I pass an array as input to a stored procedure?  *

Not in MySQL 5.1.

*A.4.18: ** Can I pass a cursor as an `IN' parameter to a stored
procedure?  *

In MySQL 5.1, cursors are available inside stored procedures only.

*A.4.19: ** Can I return a cursor as an `OUT' parameter from a stored
procedure?  *

In MySQL 5.1, cursors are available inside stored procedures only.
However, if you do not open a cursor on a *Note `SELECT': select, the
result will be sent directly to the client. You can also `SELECT INTO'
variables. See *Note select::.

*A.4.20: ** Can I print out a variable's value within a stored routine
for debugging purposes?  *

Yes, you can do this in a _stored procedure_, but not in a stored
function. If you perform an ordinary *Note `SELECT': select. inside a
stored procedure, the result set is returned directly to the client.
You will need to use the MySQL 4.1 (or above) client/server protocol
for this to work. This means that--for instance--in PHP, you need to
use the `mysqli' extension rather than the old `mysql' extension.

*A.4.21: ** Can I commit or roll back transactions inside a stored
procedure?  *

Yes. However, you cannot perform transactional operations within a
stored function.

*A.4.22: ** Do MySQL 5.1 stored procedures and functions work with
replication?  *

Yes, standard actions carried out in stored procedures and functions
are replicated from a master MySQL server to a slave server. There are
a few limitations that are described in detail in *Note
stored-programs-logging::.

*A.4.23: ** Are stored procedures and functions created on a master
server replicated to a slave?  *

Yes, creation of stored procedures and functions carried out through
normal DDL statements on a master server are replicated to a slave, so
the objects will exist on both servers.  `ALTER' and `DROP' statements
for stored procedures and functions are also replicated.

*A.4.24: ** How are actions that take place inside stored procedures and
functions replicated?  *

MySQL records each DML event that occurs in a stored procedure and
replicates those individual actions to a slave server. The actual calls
made to execute stored procedures are not replicated.

Stored functions that change data are logged as function invocations,
not as the DML events that occur inside each function.

*A.4.25: ** Are there special security requirements for using stored
procedures and functions together with replication?  *

Yes. Because a slave server has authority to execute any statement read
from a master's binary log, special security constraints exist for
using stored functions with replication.  If replication or binary
logging in general (for the purpose of point-in-time recovery) is
active, then MySQL DBAs have two security options open to them:

  1. Any user wishing to create stored functions must be granted the
     `SUPER' privilege.

  2. Alternatively, a DBA can set the `log_bin_trust_function_creators'
     system variable to 1, which enables anyone with the standard
     `CREATE ROUTINE' privilege to create stored functions.

*A.4.26: ** What limitations exist for replicating stored procedure and
function actions?  *

Nondeterministic (random) or time-based actions embedded in stored
procedures may not replicate properly. By their very nature, randomly
produced results are not predictable and cannot be exactly reproduced,
and therefore, random actions replicated to a slave will not mirror
those performed on a master. Note that declaring stored functions to be
`DETERMINISTIC' or setting the `log_bin_trust_function_creators' system
variable to 0 will not allow random-valued operations to be invoked.

In addition, time-based actions cannot be reproduced on a slave because
the timing of such actions in a stored procedure is not reproducible
through the binary log used for replication. It records only DML events
and does not factor in timing constraints.

Finally, nontransactional tables for which errors occur during large
DML actions (such as bulk inserts) may experience replication issues in
that a master may be partially updated from DML activity, but no
updates are done to the slave because of the errors that occurred. A
workaround is for a function's DML actions to be carried out with the
`IGNORE' keyword so that updates on the master that cause errors are
ignored and updates that do not cause errors are replicated to the
slave.

*A.4.27: ** Do the preceding limitations affect MySQL's ability to do
point-in-time recovery?  *

The same limitations that affect replication do affect point-in-time
recovery.

*A.4.28: ** What is being done to correct the aforementioned
limitations?  *

As of MySQL 5.1.5, you can choose either statement-based replication or
row-based replication. The original replication implementation is based
on statement-based binary logging.  Row-based binary logging resolves
the limitations mentioned earlier.

Beginning with MySQL 5.1.8, _mixed_ replication is also available (by
starting the server with `--binlog-format=mixed'). This hybrid, `smart'
form of replication `knows' whether statement-level replication can
safely be used, or row-level replication is required.

For additional information, see *Note replication-formats::.


File: manual.info,  Node: faqs-triggers,  Next: faqs-views,  Prev: faqs-stored-procs,  Up: faqs

A.5 MySQL 5.1 FAQ: Triggers
===========================

*Questions*
   * A.5.1: Where can I find the documentation for MySQL 5.1 triggers?

   * A.5.2: Is there a discussion forum for MySQL Triggers?

   * A.5.3: Does MySQL 5.1 have statement-level or row-level triggers?

   * A.5.4: Are there any default triggers?

   * A.5.5: How are triggers managed in MySQL?

   * A.5.6: Is there a way to view all triggers in a given database?

   * A.5.7: Where are triggers stored?

   * A.5.8: Can a trigger call a stored procedure?

   * A.5.9: Can triggers access tables?

   * A.5.10: Can a table have multiple triggers with the same trigger
     event and action time?

   * A.5.11: Can triggers call an external application through a UDF?

   * A.5.12: Is it possible for a trigger to update tables on a remote
     server?

   * A.5.13: Do triggers work with replication?

   * A.5.14: How are actions carried out through triggers on a master
     replicated to a slave?

*Questions and Answers* *A.5.1: ** Where can I find the documentation
for MySQL 5.1 triggers?  *

See *Note triggers::.

*A.5.2: ** Is there a discussion forum for MySQL Triggers?  *

Yes. It is available at `http://forums.mysql.com/list.php?99'.

*A.5.3: ** Does MySQL 5.1 have statement-level or row-level triggers?  *

In MySQL 5.1, all triggers are `FOR EACH ROW'--that is, the trigger is
activated for each row that is inserted, updated, or deleted. MySQL 5.1
does not support triggers using `FOR EACH STATEMENT'.

*A.5.4: ** Are there any default triggers?  *

Not explicitly. MySQL does have specific special behavior for some
*Note `TIMESTAMP': datetime. columns, as well as for columns which are
defined using `AUTO_INCREMENT'.

*A.5.5: ** How are triggers managed in MySQL?  *

In MySQL 5.1, triggers can be created using the *Note `CREATE TRIGGER':
create-trigger. statement, and dropped using *Note `DROP TRIGGER':
drop-trigger. See *Note create-trigger::, and *Note drop-trigger::, for
more about these statements.

Information about triggers can be obtained by querying the *Note
`INFORMATION_SCHEMA.TRIGGERS': triggers-table. table.  See *Note
triggers-table::.

*A.5.6: ** Is there a way to view all triggers in a given database?  *

Yes. You can obtain a listing of all triggers defined on database
`dbname' using a query on the *Note `INFORMATION_SCHEMA.TRIGGERS':
triggers-table. table such as the one shown here:


     SELECT TRIGGER_NAME, EVENT_MANIPULATION, EVENT_OBJECT_TABLE, ACTION_STATEMENT
         FROM INFORMATION_SCHEMA.TRIGGERS
         WHERE TRIGGER_SCHEMA='DBNAME';

For more information about this table, see *Note triggers-table::.

You can also use the *Note `SHOW TRIGGERS': show-triggers. statement,
which is specific to MySQL. See *Note show-triggers::.

*A.5.7: ** Where are triggers stored?  *

Triggers for a table are currently stored in `.TRG' files, with one
such file one per table.

*A.5.8: ** Can a trigger call a stored procedure?  *

Yes.

*A.5.9: ** Can triggers access tables?  *

A trigger can access both old and new data in its own table. A trigger
can also affect other tables, but it is not permitted to modify a table
that is already being used (for reading or writing) by the statement
that invoked the function or trigger.

*A.5.10: ** Can a table have multiple triggers with the same trigger
event and action time?  *

In MySQL 5.1, there cannot be multiple triggers for a given table that
have the same trigger event and action time.  For example, you cannot
have two `BEFORE UPDATE' triggers for a table. This limitation is lifted
in MySQL 5.7.

*A.5.11: ** Can triggers call an external application through a UDF?  *

Yes. For example, a trigger could invoke the `sys_exec()' UDF.

*A.5.12: ** Is it possible for a trigger to update tables on a remote
server?  *

Yes. A table on a remote server could be updated using the `FEDERATED'
storage engine. (See *Note federated-storage-engine::).

*A.5.13: ** Do triggers work with replication?  *

Yes. However, the way in which they work depends whether you are using
MySQL's `classic' statement-based replication available in all versions
of MySQL, or the row-based replication format introduced in MySQL 5.1.

When using statement-based replication, triggers on the slave are
executed by statements that are executed on the master (and replicated
to the slave).

When using row-based replication, triggers are not executed on the
slave due to statements that were run on the master and then replicated
to the slave. Instead, when using row-based replication, the changes
caused by executing the trigger on the master are applied on the slave.

For more information, see *Note replication-features-triggers::.

*A.5.14: ** How are actions carried out through triggers on a master
replicated to a slave?  *

Again, this depends on whether you are using statement-based or
row-based replication.

Statement-based replication

First, the triggers that exist on a master must be re-created on the
slave server. Once this is done, the replication flow works as any
other standard DML statement that participates in replication. For
example, consider a table `EMP' that has an `AFTER' insert trigger,
which exists on a master MySQL server. The same `EMP' table and `AFTER'
insert trigger exist on the slave server as well. The replication flow
would be:

  1. An *Note `INSERT': insert. statement is made to `EMP'.

  2. The `AFTER' trigger on `EMP' activates.

  3. The *Note `INSERT': insert. statement is written to the binary log.

  4. The replication slave picks up the *Note `INSERT': insert.
     statement to `EMP' and executes it.

  5. The `AFTER' trigger on `EMP' that exists on the slave activates.

Row-based replication

When you use row-based replication, the changes caused by executing the
trigger on the master are applied on the slave.  However, the triggers
themselves are not actually executed on the slave under row-based
replication. This is because, if both the master and the slave applied
the changes from the master and--in addition--the trigger causing these
changes were applied on the slave, the changes would in effect be
applied twice on the slave, leading to different data on the master and
the slave.

In most cases, the outcome is the same for both row-based and
statement-based replication. However, if you use different triggers on
the master and slave, you cannot use row-based replication. (This is
because the row-based format replicates the changes made by triggers
executing on the master to the slaves, rather than the statements that
caused the triggers to execute, and the corresponding triggers on the
slave are not executed.) Instead, any statements causing such triggers
to be executed must be replicated using statement-based replication.

For more information, see *Note replication-features-triggers::.


File: manual.info,  Node: faqs-views,  Next: faqs-information-schema,  Prev: faqs-triggers,  Up: faqs

A.6 MySQL 5.1 FAQ: Views
========================

*Questions*
   * A.6.1: Where can I find documentation covering MySQL Views?

   * A.6.2: Is there a discussion forum for MySQL Views?

   * A.6.3: What happens to a view if an underlying table is dropped or
     renamed?

   * A.6.4: Does MySQL 5.1 have table snapshots?

   * A.6.5: Does MySQL 5.1 have materialized views?

   * A.6.6: Can you insert into views that are based on joins?

*Questions and Answers* *A.6.1: ** Where can I find documentation
covering MySQL Views?  *

See *Note views::.

*A.6.2: ** Is there a discussion forum for MySQL Views?  *

Yes. See http://forums.mysql.com/list.php?100
(http://forums.mysql.com/list.php?100)

*A.6.3: ** What happens to a view if an underlying table is dropped or
renamed?  *

After a view has been created, it is possible to drop or alter a table
or view to which the definition refers. To check a view definition for
problems of this kind, use the *Note `CHECK TABLE': check-table.
statement. (See *Note check-table::.)

*A.6.4: ** Does MySQL 5.1 have table snapshots?  *

No.

*A.6.5: ** Does MySQL 5.1 have materialized views?  *

No.

*A.6.6: ** Can you insert into views that are based on joins?  *

It is possible, provided that your *Note `INSERT': insert. statement
has a column list that makes it clear there is only one table involved.

You _cannot_ insert into multiple tables with a single insert on a view.


File: manual.info,  Node: faqs-information-schema,  Next: faqs-migration,  Prev: faqs-views,  Up: faqs

A.7 MySQL 5.1 FAQ: INFORMATION_SCHEMA
=====================================

*Questions*
   * A.7.1: Where can I find documentation for the MySQL
     `INFORMATION_SCHEMA' database?

   * A.7.2: Is there a discussion forum for `INFORMATION_SCHEMA'?

   * A.7.3: Where can I find the ANSI SQL 2003 specification for
     `INFORMATION_SCHEMA'?

   * A.7.4: What is the difference between the Oracle Data Dictionary
     and MySQL's `INFORMATION_SCHEMA'?

   * A.7.5: Can I add to or otherwise modify the tables found in the
     `INFORMATION_SCHEMA' database?

*Questions and Answers* *A.7.1: ** Where can I find documentation for
the MySQL `INFORMATION_SCHEMA' database?  *

See *Note information-schema::

*A.7.2: ** Is there a discussion forum for `INFORMATION_SCHEMA'?  *

See http://forums.mysql.com/list.php?101
(http://forums.mysql.com/list.php?101).

*A.7.3: ** Where can I find the ANSI SQL 2003 specification for
`INFORMATION_SCHEMA'?  *

Unfortunately, the official specifications are not freely available.
(ANSI makes them available for purchase.) However, there are books
available--such as `SQL-99 Complete, Really' by Peter Gulutzan and Trudy
Pelzer--which give a comprehensive overview of the standard, including
`INFORMATION_SCHEMA'.

*A.7.4: ** What is the difference between the Oracle Data Dictionary and
MySQL's `INFORMATION_SCHEMA'?  *

Both Oracle and MySQL provide metadata in tables. However, Oracle and
MySQL use different table names and column names.  MySQL's
implementation is more similar to those found in DB2 and SQL Server,
which also support `INFORMATION_SCHEMA' as defined in the SQL standard.

*A.7.5: ** Can I add to or otherwise modify the tables found in the
`INFORMATION_SCHEMA' database?  *

No. Since applications may rely on a certain standard structure, this
should not be modified. For this reason, _we cannot support bugs or
other issues which result from modifying `INFORMATION_SCHEMA' tables or
data_.


File: manual.info,  Node: faqs-migration,  Next: faqs-security,  Prev: faqs-information-schema,  Up: faqs

A.8 MySQL 5.1 FAQ: Migration
============================

*Questions*
   * A.8.1: Where can I find information on how to migrate from MySQL
     5.0 to MySQL 5.1?

   * A.8.2: How has storage engine (table type) support changed in MySQL
     5.1 from previous versions?

*Questions and Answers* *A.8.1: ** Where can I find information on how
to migrate from MySQL 5.0 to MySQL 5.1?  *

For detailed upgrade information, see *Note upgrading::. Do not skip a
major version when upgrading, but rather complete the process in steps,
upgrading from one major version to the next in each step. This may seem
more complicated, but it will you save time and trouble--if you
encounter problems during the upgrade, their origin will be easier to
identify, either by you or--if you have a MySQL Enterprise
subscription--by MySQL support.

*A.8.2: ** How has storage engine (table type) support changed in MySQL
5.1 from previous versions?  *

Storage engine support has changed as follows:

   * Support for `ISAM' tables was removed in MySQL 5.0 and you should
     now use the `MyISAM' storage engine in place of `ISAM'. To convert
     a table TBLNAME from `ISAM' to `MyISAM', simply issue a statement
     such as this one:

          ALTER TABLE TBLNAME ENGINE=MYISAM;

   * Internal `RAID' for `MyISAM' tables was also removed in MySQL 5.0.
     This was formerly used to allow large tables in file systems that
     did not support file sizes greater than 2GB.  All modern file
     systems allow for larger tables; in addition, there are now other
     solutions such as `MERGE' tables and views.

   * The *Note `VARCHAR': char. column type now retains trailing spaces
     in all storage engines.

   * `MEMORY' tables (formerly known as `HEAP' tables) can also contain
     *Note `VARCHAR': char. columns.


File: manual.info,  Node: faqs-security,  Next: faqs-mysql-cluster,  Prev: faqs-migration,  Up: faqs

A.9 MySQL 5.1 FAQ: Security
===========================

*Questions*
   * A.9.1: Where can I find documentation that addresses security
     issues for MySQL?

   * A.9.2: Does MySQL 5.1 have native support for SSL?

   * A.9.3: Is SSL support be built into MySQL binaries, or must I
     recompile the binary myself to enable it?

   * A.9.4: Does MySQL 5.1 have built-in authentication against LDAP
     directories?

   * A.9.5: Does MySQL 5.1 include support for Roles Based Access
     Control (RBAC)?

*Questions and Answers* *A.9.1: ** Where can I find documentation that
addresses security issues for MySQL?  *

The best place to start is *Note security::.

Other portions of the MySQL Documentation which you may find useful
with regard to specific security concerns include the following:

   * *Note security-guidelines::.

   * *Note security-against-attack::.

   * *Note resetting-permissions::.

   * *Note changing-mysql-user::.

   * *Note udf-security::.

   * *Note security-options::.

   * *Note load-data-local::.

   * *Note postinstallation::.

   * *Note ssl-basics::.

*A.9.2: ** Does MySQL 5.1 have native support for SSL?  *

Most 5.1 binaries have support for SSL connections between the client
and server. See *Note ssl-connections::.

You can also tunnel a connection using SSH, if (for example) the client
application does not support SSL connections. For an example, see *Note
windows-and-ssh::.

*A.9.3: ** Is SSL support be built into MySQL binaries, or must I
recompile the binary myself to enable it?  *

Most 5.1 binaries have SSL enabled for client-server connections that
are secured, authenticated, or both. See *Note ssl-connections::.

*A.9.4: ** Does MySQL 5.1 have built-in authentication against LDAP
directories?  *

Not at this time.

*A.9.5: ** Does MySQL 5.1 include support for Roles Based Access
Control (RBAC)?  *

Not at this time.


File: manual.info,  Node: faqs-mysql-cluster,  Next: faqs-cjk,  Prev: faqs-security,  Up: faqs

A.10 MySQL 5.1 FAQ: MySQL Cluster
=================================

In the following section, we answer questions that are frequently asked
about MySQL Cluster and the *Note `NDBCLUSTER': mysql-cluster. storage
engine.

*Questions*
   * A.10.1: Which versions of the MySQL software support Cluster? Do I
     have to compile from source?

   * A.10.2: What happened to MySQL Cluster NDB 6.4?

   * A.10.3: What do `NDB' and `NDBCLUSTER' mean?

   * A.10.4: What is the difference between using MySQL Cluster versus
     using MySQL Replication?

   * A.10.5: Do I need any special networking to run MySQL Cluster? How
     do computers in a cluster communicate?

   * A.10.6: How many computers do I need to run a MySQL Cluster, and
     why?

   * A.10.7: What do the different computers do in a MySQL Cluster?

   * A.10.8: When I run the `SHOW' command in the MySQL Cluster
     management client, I see a line of output that looks like this:


          id=2    @10.100.10.32  (Version: 5.6.21-ndb-7.3.8 Nodegroup: 0, *)

     What does the `*' mean? How is this node different from the others?

   * A.10.9: With which operating systems can I use MySQL Cluster?

   * A.10.10: What are the hardware requirements for running MySQL
     Cluster?

   * A.10.11: How much RAM do I need to use MySQL Cluster? Is it
     possible to use disk memory at all?

   * A.10.12: What file systems can I use with MySQL Cluster? What about
     network file systems or network shares?

   * A.10.13: Can I run MySQL Cluster nodes inside virtual machines
     (such as those created by VMWare, Parallels, or Xen)?

   * A.10.14: I am trying to populate a MySQL Cluster database. The
     loading process terminates prematurely and I get an error message
     like this one:

     ``ERROR 1114: The table 'my_cluster_table' is full''

     Why is this happening?

   * A.10.15: MySQL Cluster uses TCP/IP. Does this mean that I can run
     it over the Internet, with one or more nodes in remote locations?

   * A.10.16: Do I have to learn a new programming or query language to
     use MySQL Cluster?

   * A.10.17: What programming languages and APIs are supported by MySQL
     Cluster?

   * A.10.18: Does MySQL Cluster include any management tools?

   * A.10.19: How do I find out what an error or warning message means
     when using MySQL Cluster?

   * A.10.20: Is MySQL Cluster transaction-safe? What isolation levels
     are supported?

   * A.10.21: What storage engines are supported by MySQL Cluster?

   * A.10.22: In the event of a catastrophic failure--say, for instance,
     the whole city loses power _and_ my UPS fails--would I lose all my
     data?

   * A.10.23: Is it possible to use `FULLTEXT' indexes with MySQL
     Cluster?

   * A.10.24: Can I run multiple nodes on a single computer?

   * A.10.25: Can I add data nodes to a MySQL Cluster without
     restarting it?

   * A.10.26: Are there any limitations that I should be aware of when
     using MySQL Cluster?

   * A.10.27: Does MySQL Cluster support foreign keys?

   * A.10.28: How do I import an existing MySQL database into a MySQL
     Cluster?

   * A.10.29: How do MySQL Cluster nodes communicate with one another?

   * A.10.30: What is an _arbitrator_?

   * A.10.31: What data types are supported by MySQL Cluster?

   * A.10.32: How do I start and stop MySQL Cluster?

   * A.10.33: What happens to MySQL Cluster data when the MySQL Cluster
     is shut down?

   * A.10.34: Is it a good idea to have more than one management node
     for a MySQL Cluster?

   * A.10.35: Can I mix different kinds of hardware and operating
     systems in one MySQL Cluster?

   * A.10.36: Can I run two data nodes on a single host? Two SQL nodes?

   * A.10.37: Can I use host names with MySQL Cluster?

   * A.10.38: Does MySQL Cluster support IPv6?

   * A.10.39: How do I handle MySQL users in a MySQL Cluster having
     multiple MySQL servers?

   * A.10.40: How do I continue to send queries in the event that one
     of the SQL nodes fails?

   * A.10.41: How do I back up and restore a MySQL Cluster?

   * A.10.42: What is an `angel process'?

*Questions and Answers* *A.10.1: ** Which versions of the MySQL
software support Cluster? Do I have to compile from source?  *

MySQL Cluster is not supported in standard MySQL Server 5.1 releases.
Instead, MySQL Cluster is provided as a separate product. Currently,
the following MySQL Cluster release series are available for production
use:

   * MySQL Cluster NDB 7.1

     This series is a previous General Availability (GA) version of
     MySQL Cluster, still available for production, although we
     recommend that new deployments use MySQL Cluster NDB 7.3. The most
     recent MySQL Cluster NDB 7.1 release can be obtained from
     `http://dev.mysql.com/downloads/cluster/'.

   * MySQL Cluster NDB 7.2

     This series is a General Availability (GA) version of MySQL
     Cluster, still available for production, although we recommend
     that new deployments use the latest MySQL Cluster NDB 7.3 release.
     The most recent MySQL Cluster NDB 7.2 release can be obtained from
     `http://dev.mysql.com/downloads/cluster/'.

   * MySQL Cluster NDB 7.3

     This series is the latest Generally Available (GA) version of
     MySQL Cluster, based on version 7.3 of the *Note `NDB':
     mysql-cluster. storage engine and MySQL Server 5.6. New
     deployments should use the latest release in this series. The most
     recent MySQL Cluster NDB 7.3 release can be obtained from
     `http://dev.mysql.com/downloads/cluster/'.

   * MySQL Cluster NDB 7.4

     This is the current development version of MySQL Cluster, based on
     version 7.4 of the *Note `NDB': mysql-cluster. storage engine and
     MySQL Server 5.6. MySQL Cluster NDB 7.4 is currently available for
     testing and evaluation. The most recent MySQL Cluster NDB 7.4
     release can be obtained from
     `http://dev.mysql.com/downloads/cluster/'.

     For an overview of improvements made in MySQL Cluster NDB 7.4, see
     MySQL Cluster Development in MySQL Cluster NDB 7.4
     (http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-development-5-6-ndb-7-4.html).

You should use MySQL Cluster NDB 7.2 or MySQL Cluster NDB 7.3 for any
new deployments; if you are using an older version of MySQL Cluster,
you should upgrade to one of these soon as possible. For an overview of
improvements made in MySQL Cluster NDB 7.2, see MySQL Cluster
Development in MySQL Cluster NDB 7.2
(http://dev.mysql.com/doc/refman/5.5/en/mysql-cluster-development-5-5-ndb-7-2.html);
for information about improvements made in MySQL Cluster NDB 7.3, see
MySQL Cluster Development in MySQL Cluster NDB 7.3
(http://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-development-5-6-ndb-7-3.html).

You can determine whether your MySQL Server has *Note `NDB':
mysql-cluster. support using one of the statements `SHOW VARIABLES LIKE
'have_%'', *Note `SHOW ENGINES': show-engines, or *Note `SHOW PLUGINS':
show-plugins.

*A.10.2: ** What happened to MySQL Cluster NDB 6.4?  *

Because of the number and impact of new features introduced into MySQL
Cluster following the General Availability of MySQL Cluster NDB 6.3, it
was decided that the following release series represented a `major' new
release series rather than a `minor' one, and should be known as MySQL
Cluster 7.0.

The earliest development versions of MySQL Cluster NDB 7.0 were
originally designated `MySQL Cluster 6.4', and the first four releases
in this series were identified as MySQL Cluster NDB 6.4.0 through NDB
6.4.3. MySQL Cluster NDB 7.0.4 was the fifth MySQL Cluster NDB 7.0
release; it was the successor to MySQL Cluster NDB 6.4.3.

For more information about MySQL Cluster NDB 7.0, see *Note
mysql-cluster-development-5-1-ndb-7-0::, and
`http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/mysql-cluster-news-7-0.html'.

*A.10.3: ** What do `NDB' and `NDBCLUSTER' mean?  *

`NDB' stands for `*N*etwork *D*ata*b*ase'.  *Note `NDB': mysql-cluster.
and *Note `NDBCLUSTER': mysql-cluster. are both names for the storage
engine that enables clustering support in MySQL. While our developers
prefer *Note `NDB': mysql-cluster, either name is correct; both names
appear in our documentation, and either name can be used in the
`ENGINE' option of a *Note `CREATE TABLE': create-table. statement for
creating a MySQL Cluster table.

*A.10.4: ** What is the difference between using MySQL Cluster versus
using MySQL Replication?  *

In traditional MySQL replication, a master MySQL server updates one or
more slaves. Transactions are committed sequentially, and a slow
transaction can cause the slave to lag behind the master.  This means
that if the master fails, it is possible that the slave might not have
recorded the last few transactions. If a transaction-safe engine such as
*Note `InnoDB': innodb-storage-engine. is being used, a transaction
will either be complete on the slave or not applied at all, but
replication does not guarantee that all data on the master and the
slave will be consistent at all times. In MySQL Cluster, all data nodes
are kept in synchrony, and a transaction committed by any one data node
is committed for all data nodes. In the event of a data node failure,
all remaining data nodes remain in a consistent state.

In short, whereas standard MySQL replication is _asynchronous_, MySQL
Cluster is _synchronous_.

Asynchronous replication for MySQL Cluster is available in MySQL 5.1
and later. _MySQL Cluster Replication_ (also sometimes known as
`geo-replication') includes the capability to replicate both between
two MySQL Clusters, and from a MySQL Cluster to a non-Cluster MySQL
server. See *Note mysql-cluster-replication::.

*A.10.5: ** Do I need any special networking to run MySQL Cluster? How
do computers in a cluster communicate?  *

MySQL Cluster is intended to be used in a high-bandwidth environment,
with computers connecting using TCP/IP. Its performance depends
directly upon the connection speed between the cluster's computers. The
minimum connectivity requirements for MySQL Cluster include a typical
100-megabit Ethernet network or the equivalent. We recommend you use
gigabit Ethernet whenever available.

The faster SCI protocol is also supported, but requires special
hardware. See *Note mysql-cluster-interconnects::, for more information
about SCI.

*A.10.6: ** How many computers do I need to run a MySQL Cluster, and
why?  *

A minimum of three computers is required to run a viable cluster.
However, the minimum _recommended_ number of computers in a MySQL
Cluster is four: one each to run the management and SQL nodes, and two
computers to serve as data nodes. The purpose of the two data nodes is
to provide redundancy; the management node must run on a separate
machine to guarantee continued arbitration services in the event that
one of the data nodes fails.

To provide increased throughput and high availability, you should use
multiple SQL nodes (MySQL Servers connected to the cluster). It is also
possible (although not strictly necessary) to run multiple management
servers.

*A.10.7: ** What do the different computers do in a MySQL Cluster?  *

A MySQL Cluster has both a physical and logical organization, with
computers being the physical elements. The logical or functional
elements of a cluster are referred to as _nodes_, and a computer
housing a cluster node is sometimes referred to as a _cluster host_.
There are three types of nodes, each corresponding to a specific role
within the cluster. These are:

   * Management node

     This node provides management services for the cluster as a whole,
     including startup, shutdown, backups, and configuration data for
     the other nodes. The management node server is implemented as the
     application *Note `ndb_mgmd': mysql-cluster-programs-ndb-mgmd.;
     the management client used to control MySQL Cluster is *Note
     `ndb_mgm': mysql-cluster-programs-ndb-mgm. See *Note
     mysql-cluster-programs-ndb-mgmd::, and *Note
     mysql-cluster-programs-ndb-mgm::, for information about these
     programs.

   * Data node

     This type of node stores and replicates data. Data node
     functionality is handled by instances of the *Note `NDB':
     mysql-cluster. data node process *Note `ndbd':
     mysql-cluster-programs-ndbd. For more information, see *Note
     mysql-cluster-programs-ndbd::.

   * SQL node

     This is simply an instance of MySQL Server (*Note `mysqld':
     mysqld.) that is built with support for the *Note `NDBCLUSTER':
     mysql-cluster. storage engine and started with the `--ndb-cluster'
     option to enable the engine and the `--ndb-connectstring' option
     to enable it to connect to a MySQL Cluster management server. For
     more about these options, see *Note
     mysql-cluster-program-options-mysqld::.

     *Note*:

     An _API node_ is any application that makes direct use of Cluster
     data nodes for data storage and retrieval. An SQL node can thus be
     considered a type of API node that uses a MySQL Server to provide
     an SQL interface to the Cluster. You can write such applications
     (that do not depend on a MySQL Server) using the NDB API, which
     supplies a direct, object-oriented transaction and scanning
     interface to MySQL Cluster data; see MySQL Cluster API Overview:
     The NDB API
     (http://dev.mysql.com/doc/ndbapi/en/overview-ndb-api.html), for
     more information.

*A.10.8: ** When I run the `SHOW' command in the MySQL Cluster
management client, I see a line of output that looks like this: *

     id=2    @10.100.10.32  (Version: 5.6.21-ndb-7.3.8 Nodegroup: 0, *)
* What does the `*' mean? How is this node different from the others?  *

The simplest answer is, `It's not something you can control, and it's
nothing that you need to worry about in any case, unless you're a
software engineer writing or analyzing the MySQL Cluster source code'.

If you don't find that answer satisfactory, here's a longer and more
technical version:

A number of mechanisms in MySQL Cluster require distributed
coordination among the data nodes. These distributed algorithms and
protocols include global checkpointing, DDL (schema) changes, and node
restart handling. To make this coordination simpler, the data nodes
`elect' one of their number to act as leader. (This node was once
referred to as a `master', but this terminology was dropped to avoid
confusion with master server in MySQL Replication.) There is no
user-facing mechanism for influencing this selection, which is
completely automatic; the fact that it _is_ automatic is a key part of
MySQL Cluster's internal architecture.

When a node acts as the `leader' for any of these mechanisms, it is
usually the point of coordination for the activity, and the other nodes
act as `followers', carrying out their parts of the activity as
directed by the leader. If the node acting as leader fails, then the
remaining nodes elect a new leader. Tasks in progress that were being
coordinated by the old leader may either fail or be continued by the
new leader, depending on the actual mechanism involved.

It is possible for some of these different mechanisms and protocols to
have different leader nodes, but in general the same leader is chosen
for all of them. The node indicated as the leader in the output of
`SHOW' in the management client is known internally as the `DICT'
manager (see The `DBDICT' Block
(http://dev.mysql.com/doc/ndbapi/en/ndb-internals-kernel-blocks-dbdict.html),
in the `MySQL Cluster API Developer Guide', for more information),
responsible for coordinating DDL and metadata activity.

MySQL Cluster is designed in such a way that the choice of leader has
no discernable effect outside the cluster itself. For example, the
current leader does not have significantly higher CPU or resource usage
than the other data nodes, and failure of the leader should not have a
significantly different impact on the cluster than the failure of any
other data node.

*A.10.9: ** With which operating systems can I use MySQL Cluster?  *

MySQL Cluster is supported on most Unix-like operating systems.
Beginning with MySQL Cluster NDB 7.1.3, MySQL Cluster is also supported
in production on Microsoft Windows operating systems.

For more detailed information concerning the level of support which is
offered for MySQL Cluster on various operating system versions,
operating system distributions, and hardware platforms, please refer to
`http://www.mysql.com/support/supportedplatforms/cluster.html'.

*A.10.10: ** What are the hardware requirements for running MySQL
Cluster?  *

MySQL Cluster should run on any platform for which *Note `NDB':
mysql-cluster.-enabled binaries are available.  For data nodes and API
nodes, faster CPUs and more memory are likely to improve performance,
and 64-bit CPUs are likely to be more effective than 32-bit processors.
There must be sufficient memory on machines used for data nodes to hold
each node's share of the database (see _How much RAM do I Need?_ for
more information). For a computer which is used only for running the
MySQL Cluster management server, the requirements are minimal; a common
desktop PC (or the equivalent) is generally sufficient for this task.
Nodes can communicate through the standard TCP/IP network and hardware.
They can also use the high-speed SCI protocol; however, special
networking hardware and software are required to use SCI (see *Note
mysql-cluster-interconnects::).

*A.10.11: ** How much RAM do I need to use MySQL Cluster? Is it
possible to use disk memory at all?  *

Formerly MySQL Cluster was in-memory only. MySQL 5.1 and later also
provide the ability to store MySQL Cluster on disk. (Note that we have
no plans to backport this capability to previous releases.) See *Note
mysql-cluster-disk-data::, for more information.

For in-memory `NDB' tables, you can use the following formula for
obtaining a rough estimate of how much RAM is needed for each data node
in the cluster:


     (SizeofDatabase x NumberOfReplicas x 1.1 ) / NumberOfDataNodes

To calculate the memory requirements more exactly requires determining,
for each table in the cluster database, the storage space required per
row (see *Note storage-requirements::, for details), and multiplying
this by the number of rows. You must also remember to account for any
column indexes as follows:

   * Each primary key or hash index created for an *Note `NDBCLUSTER':
     mysql-cluster. table requires 21-25 bytes per record. These
     indexes use `IndexMemory'.

   * Each ordered index requires 10 bytes storage per record, using
     `DataMemory'.

   * Creating a primary key or unique index also creates an ordered
     index, unless this index is created with `USING HASH'. In other
     words:

        * A primary key or unique index on a Cluster table normally
          takes up 31 to 35 bytes per record.

        * However, if the primary key or unique index is created with
          `USING HASH', then it requires only 21 to 25 bytes per record.

Note that creating MySQL Cluster tables with `USING HASH' for all
primary keys and unique indexes will generally cause table updates to
run more quickly--in some cases by a much as 20 to 30 percent faster
than updates on tables where `USING HASH' was not used in creating
primary and unique keys. This is due to the fact that less memory is
required (because no ordered indexes are created), and that less CPU
must be utilized (because fewer indexes must be read and possibly
updated). However, it also means that queries that could otherwise use
range scans must be satisfied by other means, which can result in
slower selects.

When calculating Cluster memory requirements, you may find useful the
*Note `ndb_size.pl': mysql-cluster-programs-ndb-size-pl. utility which
is available in recent MySQL 5.1 releases. This Perl script connects to
a current (non-Cluster) MySQL database and creates a report on how much
space that database would require if it used the *Note `NDBCLUSTER':
mysql-cluster. storage engine. For more information, see *Note
mysql-cluster-programs-ndb-size-pl::.

It is especially important to keep in mind that _every MySQL Cluster
table must have a primary key_. The *Note `NDB': mysql-cluster. storage
engine creates a primary key automatically if none is defined; this
primary key is created without `USING HASH'.

You can determine how much memory is being used for storage of MySQL
Cluster data and indexes at any given time using the `REPORT
MEMORYUSAGE' command in the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. client; see *Note
mysql-cluster-mgm-client-commands::, for more information. In addition,
warnings are written to the cluster log when 80% of available
`DataMemory' or `IndexMemory' is in use, and again when usage reaches
85%, 90%, and so on.

*A.10.12: ** What file systems can I use with MySQL Cluster? What about
network file systems or network shares?  *

Generally, any file system that is native to the host operating system
should work well with MySQL Cluster. If you find that a given file
system works particularly well (or not so especially well) with MySQL
Cluster, we invite you to discuss your findings in the MySQL Cluster
Forums (http://forums.mysql.com/list.php?25).

For Windows, we recommend that you use `NTFS' file systems for MySQL
Cluster, just as we do for standard MySQL. We do not test MySQL Cluster
with `FAT' or `VFAT' file systems. Because of this, we do not recommend
their use with MySQL or MySQL Cluster.

MySQL Cluster is implemented as a shared-nothing solution; the idea
behind this is that the failure of a single piece of hardware should
not cause the failure of multiple cluster nodes, or possibly even the
failure of the cluster as a whole. For this reason, the use of network
shares or network file systems is not supported for MySQL Cluster. This
also applies to shared storage devices such as SANs.

*A.10.13: ** Can I run MySQL Cluster nodes inside virtual machines
(such as those created by VMWare, Parallels, or Xen)?  *

This is possible but not recommended for a production environment with
MySQL Cluster versions prior to MySQL Cluster NDB 7.2.

For deployment in virtualized environments, you should use MySQL
Cluster NDB 7.2 or later.

*A.10.14: ** I am trying to populate a MySQL Cluster database. The
loading process terminates prematurely and I get an error message like
this one: ** ``ERROR 1114: The table 'my_cluster_table' is full'' **
Why is this happening?  *

The cause is very likely to be that your setup does not provide
sufficient RAM for all table data and all indexes, _including the
primary key required by the *Note `NDB': mysql-cluster. storage engine
and automatically created in the event that the table definition does
not include the definition of a primary key_.

It is also worth noting that all data nodes should have the same amount
of RAM, since no data node in a cluster can use more memory than the
least amount available to any individual data node. For example, if
there are four computers hosting Cluster data nodes, and three of these
have 3GB of RAM available to store Cluster data while the remaining
data node has only 1GB RAM, then each data node can devote at most 1GB
to MySQL Cluster data and indexes.

In some cases it is possible to get `Table is full' errors in MySQL
client applications even when *Note `ndb_mgm -e "ALL REPORT
MEMORYUSAGE"': mysql-cluster-programs-ndb-mgm. shows significant free
`DataMemory'. You can force *Note `NDB': mysql-cluster. to create extra
partitions for MySQL Cluster tables and thus have more memory available
for hash indexes by using the `MAX_ROWS' option for *Note `CREATE
TABLE': create-table. In general, setting `MAX_ROWS' to twice the
number of rows that you expect to store in the table should be
sufficient.

For similar reasons, you can also sometimes encounter problems with
data node restarts on nodes that are heavily loaded with data. In MySQL
Cluster NDB 7.1 and later, the addition of the `MinFreePct' parameter
helps with this issue by reserving a portion (5% by default) of
`DataMemory' and `IndexMemory' for use in restarts. This reserved
memory is not available for storing *Note `NDB': mysql-cluster. tables
or data.

*A.10.15: ** MySQL Cluster uses TCP/IP. Does this mean that I can run
it over the Internet, with one or more nodes in remote locations?  *

It is _very_ unlikely that a cluster would perform reliably under such
conditions, as MySQL Cluster was designed and implemented with the
assumption that it would be run under conditions guaranteeing dedicated
high-speed connectivity such as that found in a LAN setting using 100
Mbps or gigabit Ethernet--preferably the latter. We neither test nor
warrant its performance using anything slower than this.

Also, it is extremely important to keep in mind that communications
between the nodes in a MySQL Cluster are not secure; they are neither
encrypted nor safeguarded by any other protective mechanism. The most
secure configuration for a cluster is in a private network behind a
firewall, with no direct access to any Cluster data or management nodes
from outside. (For SQL nodes, you should take the same precautions as
you would with any other instance of the MySQL server.) For more
information, see *Note mysql-cluster-security::.

*A.10.16: ** Do I have to learn a new programming or query language to
use MySQL Cluster?  *

_No_. Although some specialized commands are used to manage and
configure the cluster itself, only standard (My)SQL statements are
required for the following operations:

   * Creating, altering, and dropping tables

   * Inserting, updating, and deleting table data

   * Creating, changing, and dropping primary and unique indexes

Some specialized configuration parameters and files are required to set
up a MySQL Cluster--see *Note mysql-cluster-config-file::, for
information about these.

A few simple commands are used in the MySQL Cluster management client
(*Note `ndb_mgm': mysql-cluster-programs-ndb-mgm.) for tasks such as
starting and stopping cluster nodes. See *Note
mysql-cluster-mgm-client-commands::.

*A.10.17: ** What programming languages and APIs are supported by MySQL
Cluster?  *

MySQL Cluster 5.1 and later support the same programming APIs and
languages as the standard MySQL Server, including ODBC, .Net, the MySQL
C API, and numerous drivers for popular scripting languages such as
PHP, Perl, and Python. MySQL Cluster applications written using these
APIs behave similarly to other MySQL applications; they transmit SQL
statements to a MySQL Server (in the case of MySQL Cluster, an SQL
node), and receive responses containing rows of data. For more
information about these APIs, see *Note connectors-apis::.

MySQL Cluster 5.1 and later also support application programming using
the NDB API, which provides a low-level C++ interface to MySQL Cluster
data without needing to go through a MySQL Server. See The NDB API
(http://dev.mysql.com/doc/ndbapi/en/ndbapi.html). In addition, many
*Note `NDBCLUSTER': mysql-cluster.  management functions are exposed by
the C-language MGM API; see The MGM API
(http://dev.mysql.com/doc/ndbapi/en/mgm-api.html), for more information.

MySQL Cluster NDB 7.1 and later also support Java application
programming using ClusterJ, which supports a domain object model of
data using sessions and transactions. See Java and MySQL Cluster
(http://dev.mysql.com/doc/ndbapi/en/mccj-overview-java.html), for more
information.

*A.10.18: ** Does MySQL Cluster include any management tools?  *

MySQL Cluster includes a command line client for performing basic
management functions. See *Note mysql-cluster-programs-ndb-mgm::, and
*Note mysql-cluster-mgm-client-commands::.

MySQL Cluster NDB 7.0 and later is also supported by MySQL Cluster
Manager, a separate product providing an advanced command line interface
that can automate many MySQL Cluster management tasks such as rolling
restarts and configuration changes. For more information about MySQL
Cluster Manager, see MySQL(tm) Cluster Manager 1.3.2 User Manual
(http://dev.mysql.com/doc/mysql-cluster-manager/1.3/en/index.html).

*A.10.19: ** How do I find out what an error or warning message means
when using MySQL Cluster?  *

There are two ways in which this can be done:

   * From within the *Note `mysql': mysql. client, use `SHOW ERRORS' or
     `SHOW WARNINGS' immediately upon being notified of the error or
     warning condition.

   * From a system shell prompt, use *Note `perror --ndb ERROR_CODE':
     perror.

*A.10.20: ** Is MySQL Cluster transaction-safe? What isolation levels
are supported?  *

_Yes_. For tables created with the *Note `NDB': mysql-cluster. storage
engine, transactions are supported. Currently, MySQL Cluster supports
only the `READ COMMITTED' transaction isolation level.

*A.10.21: ** What storage engines are supported by MySQL Cluster?  *

Clustering with MySQL is supported only by the *Note `NDB':
mysql-cluster. storage engine. That is, in order for a table to be
shared between nodes in a MySQL Cluster, the table must be created
using `ENGINE=NDB' (or the equivalent option `ENGINE=NDBCLUSTER').

It is possible to create tables using other storage engines (such as
*Note `InnoDB': innodb-storage-engine. or *Note `MyISAM':
myisam-storage-engine.) on a MySQL server being used with a MySQL
Cluster, but since these tables do not use *Note `NDB': mysql-cluster,
they do not participate in clustering; each such table is strictly
local to the individual MySQL server instance on which it is created.

*A.10.22: ** In the event of a catastrophic failure--say, for instance,
the whole city loses power _and_ my UPS fails--would I lose all my data?
*

All committed transactions are logged. Therefore, although it is
possible that some data could be lost in the event of a catastrophe,
this should be quite limited. Data loss can be further reduced by
minimizing the number of operations per transaction. (It is not a good
idea to perform large numbers of operations per transaction in any
case.)

*A.10.23: ** Is it possible to use `FULLTEXT' indexes with MySQL
Cluster?  *

`FULLTEXT' indexing is currently supported only by the *Note `MyISAM':
myisam-storage-engine. storage engine. See *Note fulltext-search::, for
more information.

*A.10.24: ** Can I run multiple nodes on a single computer?  *

It is possible but not always advisable. One of the chief reasons to
run a cluster is to provide redundancy. To obtain the full benefits of
this redundancy, each node should reside on a separate machine. If you
place multiple nodes on a single machine and that machine fails, you
lose all of those nodes. For this reason, if you do run multiple data
nodes on a single machine, it is _extremely_ important that they be set
up in such a way that the failure of this machine does not cause the
loss of all the data nodes in a given node group.

Given that MySQL Cluster can be run on commodity hardware loaded with a
low-cost (or even no-cost) operating system, the expense of an extra
machine or two is well worth it to safeguard mission-critical data. It
also worth noting that the requirements for a cluster host running a
management node are minimal. This task can be accomplished with a 300
MHz Pentium or equivalent CPU and sufficient RAM for the operating
system, plus a small amount of overhead for the *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.  and *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. processes.

It is acceptable to run multiple cluster data nodes on a single host
that has multiple CPUs, cores, or both. MySQL Cluster NDB 7.0 and later
also provide a multi-threaded version of the data node binary intended
for use on such systems. For more information, see *Note
mysql-cluster-programs-ndbmtd::.

It is also possible in some cases to run data nodes and SQL nodes
concurrently on the same machine; how well such an arrangement performs
is dependent on a number of factors such as number of cores and CPUs as
well as the amount of disk and memory available to the data node and
SQL node processes, and you must take these factors into account when
planning such a configuration.

*A.10.25: ** Can I add data nodes to a MySQL Cluster without restarting
it?  *

In MySQL Cluster NDB 7.0 and later, it is possible to add new data
nodes to a running MySQL Cluster without taking it offline.  For more
information, see *Note mysql-cluster-online-add-node::.

For other types of MySQL Cluster nodes, a rolling restart is all that
is required (see *Note mysql-cluster-rolling-restart::).

(In MySQL Cluster NDB 6.3 and earlier releases, it was not possible to
add new data nodes without shutting down and restarting the MySQL
Cluster.)

*A.10.26: ** Are there any limitations that I should be aware of when
using MySQL Cluster?  *

Limitations on *Note `NDB': mysql-cluster. tables in MySQL NDB 6.3,
MySQL Cluster NDB 7.0, and MySQL Cluster NDB 7.1 include the following:

   * Temporary tables are not supported; a *Note `CREATE TEMPORARY
     TABLE': create-table. statement using `ENGINE=NDB' or
     `ENGINE=NDBCLUSTER' fails with an error.

   * The only types of user-defined partitioning supported for *Note
     `NDBCLUSTER': mysql-cluster. tables are `KEY' and `LINEAR KEY'.
     Trying to create an `NDB' table using any other partitioning type
     fails with an error.

   * `FULLTEXT' indexes are not supported.

   * Index prefixes are not supported. Only complete columns may be
     indexed.

   * Spatial indexes are not supported (although spatial columns can be
     used). See *Note spatial-extensions::.

   * Prior to MySQL Cluster NDB 6.3.19, the *Note `NDBCLUSTER':
     mysql-cluster. storage engine did not support partial transactions
     or partial rollbacks of transactions. Beginning with MySQL Cluster
     NDB 6.3.19, this limitation has been removed, and the behavior of
     *Note `NDBCLUSTER': mysql-cluster. is now in line with that of
     other transactional storage engines (such as *Note `InnoDB':
     innodb-storage-engine.) that can roll back individual statements.

   * Prior to MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB 7.1.4, the
     maximum number of attributes allowed per table was 128; beginning
     with MySQL Cluster NDB 7.0.15 and MySQL Cluster NDB 7.1.4, this
     limit is increased to 512. Attribute names cannot be any longer
     than 31 characters. For each table, the maximum combined length of
     the table and database names is 122 characters.

   * Previous to MySL Cluster NDB 7.0, the maximum size for a table row
     was 8 kilobytes, not counting *Note `BLOB': blob. values. MySQL
     Cluster NDB 7.0 and later support a maximum row length of 14 KB
     (also not including `BLOB' values).

     There is no set limit for the number of rows per `NDB' table.
     Limits on table size depend on a number of factors, in particular
     on the amount of RAM available to each data node.

   * The *Note `NDBCLUSTER': mysql-cluster. engine does not support
     foreign key constraints. As with *Note `MyISAM':
     myisam-storage-engine. tables, if these are specified in a *Note
     `CREATE TABLE': create-table.  or *Note `ALTER TABLE':
     alter-table. statement, they are ignored.

For a complete listing of limitations in MySQL Cluster, see *Note
mysql-cluster-limitations::. See also *Note
mysql-cluster-limitations-resolved::.

*A.10.27: ** Does MySQL Cluster support foreign keys?  *

MySQL Cluster NDB 7.1 and earlier MySQL Cluster releases do not support
foreign key contraints, and ignore foreign keys in *Note `CREATE
TABLE': create-table. statements (similarly to how *Note `MyISAM':
myisam-storage-engine. treats foreign key syntax).

Foreign key support comparable to that found in the *Note `InnoDB':
innodb-storage-engine. storage engine is provided by *Note `NDB':
mysql-cluster. beginning with MySQL Cluster NDB 7.3. Applications
requiring foreign support key should use MySQL Cluster NDB 7.3 or later.

*A.10.28: ** How do I import an existing MySQL database into a MySQL
Cluster?  *

You can import databases into MySQL Cluster much as you would with any
other version of MySQL. Other than the limitations mentioned elsewhere
in this FAQ, the only other special requirement is that any tables to
be included in the cluster must use the *Note `NDB': mysql-cluster.
storage engine.  This means that the tables must be created with
`ENGINE=NDB' or `ENGINE=NDBCLUSTER'.

It is also possible to convert existing tables that use other storage
engines to *Note `NDBCLUSTER': mysql-cluster. using one or more *Note
`ALTER TABLE': alter-table.  statement. However, the definition of the
table must be compatible with the *Note `NDBCLUSTER': mysql-cluster.
storage engine prior to making the conversion. In MySQL 5.1, an
additional workaround is also required; see *Note
mysql-cluster-limitations::, for details.

*A.10.29: ** How do MySQL Cluster nodes communicate with one another?  *

Cluster nodes can communicate through any of three different transport
mechanisms: TCP/IP, SHM (shared memory), and SCI (Scalable Coherent
Interface). Where available, SHM is used by default between nodes
residing on the same cluster host; however, this is considered
experimental. SCI is a high-speed (1 gigabit per second and higher),
high-availability protocol used in building scalable multi-processor
systems; it requires special hardware and drivers. See *Note
mysql-cluster-interconnects::, for more about using SCI as a transport
mechanism for MySQL Cluster.

*A.10.30: ** What is an _arbitrator_?  *

If one or more data nodes in a cluster fail, it is possible that not
all cluster data nodes will be able to `see' one another. In fact, it
is possible that two sets of data nodes might become isolated from one
another in a network partitioning, also known as a `split-brain'
scenario. This type of situation is undesirable because each set of
data nodes tries to behave as though it is the entire cluster. An
arbitrator is required to decide between the competing sets of data
nodes.

When all data nodes in at least one node group are alive, network
partitioning is not an issue, because no single subset of the cluster
can form a functional cluster on its own. The real problem arises when
no single node group has all its nodes alive, in which case network
partitioning (the `split-brain' scenario) becomes possible. Then an
arbitrator is required. All cluster nodes recognize the same node as
the arbitrator, which is normally the management server; however, it is
possible to configure any of the MySQL Servers in the cluster to act as
the arbitrator instead. The arbitrator accepts the first set of cluster
nodes to contact it, and tells the remaining set to shut down.
Arbitrator selection is controlled by the `ArbitrationRank'
configuration parameter for MySQL Server and management server nodes.
In MySQL Cluster NDB 7.0.7 and later, you can also use the
`ArbitrationRank' configuration parameter to control the arbitrator
selection process. For more information about these parameters, see
*Note mysql-cluster-mgm-definition::.

The role of arbitrator does not in and of itself impose any heavy
demands upon the host so designated, and thus the arbitrator host does
not need to be particularly fast or to have extra memory especially for
this purpose.

*A.10.31: ** What data types are supported by MySQL Cluster?  *

MySQL Cluster supports all of the usual MySQL data types, including
those associated with MySQL's spatial extensions; however, the *Note
`NDB': mysql-cluster. storage engine does not support spatial indexes.
(Spatial indexes are supported only by *Note `MyISAM':
myisam-storage-engine.; see *Note spatial-extensions::, for more
information.) In addition, there are some differences with regard to
indexes when used with *Note `NDB': mysql-cluster. tables.

*Note*:

MySQL Cluster Disk Data tables (that is, tables created with
`TABLESPACE ... STORAGE DISK ENGINE=NDB' or `TABLESPACE ... STORAGE DISK
ENGINE=NDBCLUSTER') have only fixed-width rows. This means that (for
example) each Disk Data table record containing a *Note `VARCHAR(255)':
char.  column requires space for 255 characters (as required for the
character set and collation being used for the table), regardless of
the actual number of characters stored therein.

See *Note mysql-cluster-limitations::, for more information about these
issues.

*A.10.32: ** How do I start and stop MySQL Cluster?  *

It is necessary to start each node in the cluster separately, in the
following order:

  1. Start the management node, using the *Note `ndb_mgmd':
     mysql-cluster-programs-ndb-mgmd. command.

     You must include the `-f' or `--config-file' option to tell the
     management node where its configuration file can be found.

  2. Start each data node with the *Note `ndbd':
     mysql-cluster-programs-ndbd.  command.

     Each data node must be started with the `-c' or
     `--ndb-connectstring' option so that the data node knows how to
     connect to the management server.

  3. Start each MySQL Server (SQL node) using your preferred startup
     script, such as *Note `mysqld_safe': mysqld-safe.

     Each MySQL Server must be started with the `--ndbcluster' and
     `--ndb-connectstring' options.  These options cause mysqld to
     enable *Note `NDBCLUSTER': mysql-cluster. storage engine support
     and how to connect to the management server.

Each of these commands must be run from a system shell on the machine
housing the affected node. (You do not have to be physically present at
the machine--a remote login shell can be used for this purpose.) You
can verify that the cluster is running by starting the *Note `NDB':
mysql-cluster.  management client *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm. on the machine housing the management
node and issuing the `SHOW' or `ALL STATUS' command.

To shut down a running cluster, issue the command `SHUTDOWN' in the
management client.  Alternatively, you may enter the following command
in a system shell:


     shell> ndb_mgm -e "SHUTDOWN"

(The quotation marks in this example are optional, since there are no
spaces in the command string following the `-e' option; in addition, the
`SHUTDOWN' command, like other management client commands, is not
case-sensitive.)

Either of these commands causes the *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm, *Note `ndb_mgm':
mysql-cluster-programs-ndb-mgm, and any *Note `ndbd':
mysql-cluster-programs-ndbd.  processes to terminate gracefully. MySQL
servers running as SQL nodes can be stopped using *Note `mysqladmin
shutdown': mysqladmin.

For more information, see *Note mysql-cluster-mgm-client-commands::, and
*Note mysql-cluster-install-shutdown-restart::.

*A.10.33: ** What happens to MySQL Cluster data when the MySQL Cluster
is shut down?  *

The data that was held in memory by the cluster's data nodes is written
to disk, and is reloaded into memory the next time that the cluster is
started.

*A.10.34: ** Is it a good idea to have more than one management node
for a MySQL Cluster?  *

It can be helpful as a fail-safe. Only one management node controls the
cluster at any given time, but it is possible to configure one
management node as primary, and one or more additional management nodes
to take over in the event that the primary management node fails.

See *Note mysql-cluster-config-file::, for information on how to
configure MySQL Cluster management nodes.

*A.10.35: ** Can I mix different kinds of hardware and operating
systems in one MySQL Cluster?  *

Yes, as long as all machines and operating systems have the same
`endianness' (all big-endian or all little-endian).

It is also possible to use software from different MySQL Cluster
releases on different nodes. However, we support this only as part of a
rolling upgrade procedure (see *Note mysql-cluster-rolling-restart::).

*A.10.36: ** Can I run two data nodes on a single host? Two SQL nodes?
*

Yes, it is possible to do this. In the case of multiple data nodes, it
is advisable (but not required) for each node to use a different data
directory. If you want to run multiple SQL nodes on one machine, each
instance of *Note `mysqld': mysqld. must use a different TCP/IP port.
However, in MySQL 5.1, running more than one cluster node of a given
type per machine is generally not encouraged or supported for
production use.

We also advise against running data nodes and SQL nodes together on the
same host, since the *Note `ndbd': mysql-cluster-programs-ndbd. and
*Note `mysqld': mysqld. processes may compete for memory.

*A.10.37: ** Can I use host names with MySQL Cluster?  *

Yes, it is possible to use DNS and DHCP for cluster hosts.  However, if
your application requires `five nines' availability, you should use
fixed (numeric) IP addresses, since making communication between
Cluster hosts dependent on services such as DNS and DHCP introduces
additional potential points of failure.

*A.10.38: ** Does MySQL Cluster support IPv6?  *

MySQL Cluster NDB 7.0 and later support IPv6 for connections between
SQL nodes (MySQL servers). However, connections between all other types
of nodes must use IPv4.

In practical terms, this means that you can use IPv6 for replication
between MySQL Clusters, but connections between nodes in the same MySQL
Cluster must use IPv4. For more information, see *Note
mysql-cluster-replication-issues::.

*A.10.39: ** How do I handle MySQL users in a MySQL Cluster having
multiple MySQL servers?  *

MySQL user accounts and privileges are _not_ automatically propagated
between different MySQL servers accessing the same MySQL Cluster.
Therefore, you must make sure that these are copied between the SQL
nodes yourself. You can do this manually, or automate the task with
scripts.

*Warning*:

Do not attempt to work around this issue by converting the MySQL system
tables to use the *Note `NDBCLUSTER': mysql-cluster. storage engine.
Only the *Note `MyISAM': myisam-storage-engine. storage engine is
supported for these tables.

*A.10.40: ** How do I continue to send queries in the event that one of
the SQL nodes fails?  *

MySQL Cluster does not provide any sort of automatic failover between
SQL nodes. Your application must be prepared to handlethe loss of SQL
nodes and to fail over between them.

*A.10.41: ** How do I back up and restore a MySQL Cluster?  *

You can use the NDB native backup and restore functionality in the
MySQL Cluster management client and the *Note `ndb_restore':
mysql-cluster-programs-ndb-restore. program. See *Note
mysql-cluster-backup::, and *Note mysql-cluster-programs-ndb-restore::.

You can also use the traditional functionality provided for this
purpose in *Note `mysqldump': mysqldump. and the MySQL server.  See
*Note mysqldump::, for more information.

*A.10.42: ** What is an `angel process'?  *

This process monitors and, if necessary, attempts to restart the data
node process. If you check the list of active processes on your system
after starting *Note `ndbd': mysql-cluster-programs-ndbd, you can see
that there are actually 2 processes running by that name, as shown here
(we omit the output from *Note `ndb_mgmd':
mysql-cluster-programs-ndb-mgmd.  and *Note `ndbd':
mysql-cluster-programs-ndbd. for brevity):


     shell> ./ndb_mgmd

     shell> ps aux | grep ndb
     me      23002  0.0  0.0 122948  3104 ?        Ssl  14:14   0:00 ./ndb_mgmd
     me      23025  0.0  0.0   5284   820 pts/2    S+   14:14   0:00 grep ndb

     shell> ./ndbd -c 127.0.0.1 --initial

     shell> ps aux | grep ndb
     me      23002  0.0  0.0 123080  3356 ?        Ssl  14:14   0:00 ./ndb_mgmd
     me      23096  0.0  0.0  35876  2036 ?        Ss   14:14   0:00 ./ndbd -c 127.0.0.1 --initial
     me      23097  1.0  2.4 524116 91096 ?        Sl   14:14   0:00 ./ndbd -c 127.0.0.1 --initial
     me      23168  0.0  0.0   5284   812 pts/2    R+   14:15   0:00 grep ndb

The *Note `ndbd': mysql-cluster-programs-ndbd. process showing 0 memory
and CPU usage is the angel process. It actually does use a very small
amount of each, of course. It simply checks to see if the main *Note
`ndbd': mysql-cluster-programs-ndbd. process (the primary data node
process that actually handles the data) is running. If permitted to do
so (for example, if the `StopOnError' configuration parameter is set to
false--see *Note mysql-cluster-params-ndbd::), the angel process tries
to restart the primary data node process.


File: manual.info,  Node: faqs-cjk,  Next: faqs-connectors-apis,  Prev: faqs-mysql-cluster,  Up: faqs

A.11 MySQL 5.1 FAQ: MySQL Chinese, Japanese, and Korean Character Sets
======================================================================

This set of Frequently Asked Questions derives from the experience of
MySQL's Support and Development groups in handling many inquiries about
CJK (Chinese-Japanese-Korean) issues.

*Questions*
   * A.11.1: What CJK character sets are available in MySQL?

   * A.11.2: I have inserted CJK characters into my table. Why does
     *Note `SELECT': select. display them as `?' characters?

   * A.11.3: What problems should I be aware of when working with the
     Big5 Chinese character set?

   * A.11.4: Why do Japanese character set conversions fail?

   * A.11.5: What should I do if I want to convert SJIS `81CA' to
     `cp932'?

   * A.11.6: How does MySQL represent the Yen (`¥') sign?

   * A.11.7: Does MySQL plan to make a separate character set where
     `5C' is the Yen sign, as at least one other major DBMS does?

   * A.11.8: Of what issues should I be aware when working with Korean
     character sets in MySQL?

   * A.11.9: Why do I get `Incorrect string value' error messages?

   * A.11.10: Why does my GUI front end or browser not display CJK
     characters correctly in my application using Access, PHP, or
     another API?

   * A.11.11: I've upgraded to MySQL 5.1. How can I revert to behavior
     like that in MySQL 4.0 with regard to character sets?

   * A.11.12: Why do some `LIKE' and `FULLTEXT' searches with CJK
     characters fail?

   * A.11.13: How do I know whether character X is available in all
     character sets?

   * A.11.14: Why do CJK strings sort incorrectly in Unicode? (I)

   * A.11.15: Why do CJK strings sort incorrectly in Unicode? (II)

   * A.11.16: Why are my supplementary characters rejected by MySQL?

   * A.11.17: Shouldn't it be `CJKV'?

   * A.11.18: Does MySQL allow CJK characters to be used in database
     and table names?

   * A.11.19: Where can I find translations of the MySQL Manual into
     Chinese, Japanese, and Korean?

   * A.11.20: Where can I get help with CJK and related issues in MySQL?

*Questions and Answers* *A.11.1: ** What CJK character sets are
available in MySQL?  *

The list of CJK character sets may vary depending on your MySQL
version. For example, the `gb18030' character set was not supported
prior to MySQL 5.7.4. However, since the name of the applicable
language appears in the `DESCRIPTION' column for every entry in the
*Note `INFORMATION_SCHEMA.CHARACTER_SETS': character-sets-table.
table, you can obtain a current list of all the non-Unicode CJK
character sets using this query:


     mysql> SELECT CHARACTER_SET_NAME, DESCRIPTION
         -> FROM INFORMATION_SCHEMA.CHARACTER_SETS
         -> WHERE DESCRIPTION LIKE '%Chin%'
         -> OR DESCRIPTION LIKE '%Japanese%'
         -> OR DESCRIPTION LIKE '%Korean%'
         -> ORDER BY CHARACTER_SET_NAME;
     +--------------------+---------------------------------+
     | CHARACTER_SET_NAME | DESCRIPTION                     |
     +--------------------+---------------------------------+
     | big5               | Big5 Traditional Chinese        |
     | cp932              | SJIS for Windows Japanese       |
     | eucjpms            | UJIS for Windows Japanese       |
     | euckr              | EUC-KR Korean                   |
     | gb18030            | China National Standard GB18030 |
     | gb2312             | GB2312 Simplified Chinese       |
     | gbk                | GBK Simplified Chinese          |
     | sjis               | Shift-JIS Japanese              |
     | ujis               | EUC-JP Japanese                 |
     +--------------------+---------------------------------+
     9 rows in set (0.01 sec)

(See *Note character-sets-table::, for more information.)

MySQL supports three variants of the _GB_ (_Guojia Biaozhun_, or
_National Standard_, or _Simplified Chinese_) character sets which are
official in the People's Republic of China: `gb2312', `gbk', and
`gb18030' (added in MySQL 5.7.4).

Sometimes people try to insert `gbk' characters into `gb2312', and it
works most of the time because `gbk' is a superset of `gb2312'--but
eventually they try to insert a rarer Chinese character and it doesn't
work. (See Bug #16072 for an example).

Here, we try to clarify exactly what characters are legitimate in
`gb2312' or `gbk', with reference to the official documents. Please
check these references before reporting `gb2312' or `gbk' bugs.

   * For a complete listing of the `gb2312' characters, ordered
     according to the `gb2312_chinese_ci' collation: gb2312
     (http://www.collation-charts.org/mysql60/by-charset.html#gb2312)

   * MySQL's `gbk' is in reality `Microsoft code page 936'. This
     differs from the official `gbk' for characters `A1A4' (middle dot),
     `A1AA' (em dash), `A6E0-A6F5', and `A8BB-A8C0'.

   * For a listing of `gbk'/Unicode mappings, see
     `http://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WINDOWS/CP936.TXT'.

   * For MySQL's listing of `gbk' characters, see gbk
     (http://www.collation-charts.org/mysql60/by-charset.html#gbk).

*A.11.2: ** I have inserted CJK characters into my table. Why does
*Note `SELECT': select. display them as `?' characters?  *

This problem is usually due to a setting in MySQL that doesn't match
the settings for the application program or the operating system. Here
are some common steps for correcting these types of issues:

   * _Be certain of what MySQL version you are using_.

     Use the statement `SELECT VERSION();' to determine this.

   * _Make sure that the database is actually using the desired
     character set_.

     People often think that the client character set is always the
     same as either the server character set or the character set used
     for display purposes. However, both of these are false
     assumptions. You can make sure by checking the result of `SHOW
     CREATE TABLE TABLENAME' or--better yet--by using this statement:


          SELECT character_set_name, collation_name
              FROM information_schema.columns
              WHERE table_schema = your_database_name
                  AND table_name = your_table_name
                  AND column_name = your_column_name;

   * _Determine the hexadecimal value of the character or characters
     that are not being displayed correctly_.

     You can obtain this information for a column COLUMN_NAME in the
     table TABLE_NAME using the following query:


          SELECT HEX(COLUMN_NAME)
          FROM TABLE_NAME;

     `3F' is the encoding for the `?' character; this means that `?' is
     the character actually stored in the column. This most often
     happens because of a problem converting a particular character
     from your client character set to the target character set.

   * _Make sure that a round trip possible--that is, when you select
     LITERAL (or _INTRODUCER HEXADECIMAL-VALUE), you obtain LITERAL as a
     result_.

     For example, the Japanese Katakana character _Pe_ (`ペ'') exists
     in all CJK character sets, and has the code point value
     (hexadecimal coding) `0x30da'. To test a round trip for this
     character, use this query:


          SELECT 'ペ' AS `ペ`;         /* or SELECT _ucs2 0x30da; */

     If the result is not also `ペ', then the round trip has failed.

     For bug reports regarding such failures, we might ask you to
     follow up with `SELECT HEX('ペ');'. Then we can determine whether
     the client encoding is correct.

   * _Make sure that the problem is not with the browser or other
     application, rather than with MySQL_.

     Use the *Note `mysql': mysql. client program (on Windows: *Note
     `mysql.exe': mysql.) to accomplish this task. If *Note `mysql':
     mysql. displays correctly but your application doesn't, then your
     problem is probably due to system settings.

     To find out what your settings are, use the *Note `SHOW
     VARIABLES': show-variables. statement, whose output should
     resemble what is shown here:


          mysql> SHOW VARIABLES LIKE 'char%';
          +--------------------------+----------------------------------------+
          | Variable_name            | Value                                  |
          +--------------------------+----------------------------------------+
          | character_set_client     | utf8                                   |
          | character_set_connection | utf8                                   |
          | character_set_database   | latin1                                 |
          | character_set_filesystem | binary                                 |
          | character_set_results    | utf8                                   |
          | character_set_server     | latin1                                 |
          | character_set_system     | utf8                                   |
          | character_sets_dir       | /usr/local/mysql/share/mysql/charsets/ |
          +--------------------------+----------------------------------------+
          8 rows in set (0.03 sec)

     These are typical character-set settings for an
     international-oriented client (notice the use of `utf8' Unicode)
     connected to a server in the West (`latin1' is a West Europe
     character set and a default for MySQL).

     Although Unicode (usually the `utf8' variant on Unix, and the
     `ucs2' variant on Windows) is preferable to Latin, it is often not
     what your operating system utilities support best. Many Windows
     users find that a Microsoft character set, such as `cp932' for
     Japanese Windows, is suitable.

     If you cannot control the server settings, and you have no idea
     what your underlying computer is, then try changing to a common
     character set for the country that you're in (`euckr' = Korea;
     `gb18030', `gb2312' or `gbk' = People's Republic of China; `big5'
     = Taiwan; `sjis', `ujis', `cp932', or `eucjpms' = Japan; `ucs2' or
     `utf8' = anywhere). Usually it is necessary to change only the
     client and connection and results settings. There is a simple
     statement which changes all three at once: `SET NAMES'. For
     example:


          SET NAMES 'big5';

     Once the setting is correct, you can make it permanent by editing
     `my.cnf' or `my.ini'. For example you might add lines looking like
     these:


          [mysqld]
          character-set-server=big5
          [client]
          default-character-set=big5

     It is also possible that there are issues with the API
     configuration setting being used in your application; see `Why
     does my GUI front end or browser not display CJK characters
     correctly...?' for more information.

*A.11.3: ** What problems should I be aware of when working with the
Big5 Chinese character set?  *

MySQL supports the Big5 character set which is common in Hong Kong and
Taiwan (Republic of China). MySQL's `big5' is in reality Microsoft code
page 950, which is very similar to the original `big5' character set.
We changed to this

character set starting with MySQL version 4.1.16 / 5.0.16 (as a result
of Bug #12476). For example, the following statements work in current
versions of MySQL, but not in old versions:


     mysql> CREATE TABLE big5 (BIG5 CHAR(1) CHARACTER SET BIG5);
     Query OK, 0 rows affected (0.13 sec)

     mysql> INSERT INTO big5 VALUES (0xf9dc);
     Query OK, 1 row affected (0.00 sec)

     mysql> SELECT * FROM big5;
     +------+
     | big5 |
     +------+
     | 嫺  |
     +------+
     1 row in set (0.02 sec)

A feature request for adding `HKSCS' extensions has been filed. People
who need this extension may find the suggested patch for Bug #13577 to
be of interest.

*A.11.4: ** Why do Japanese character set conversions fail?  *

MySQL supports the `sjis', `ujis', `cp932', and `eucjpms' character
sets, as well as Unicode. A common need is to convert between character
sets. For example, there might be a Unix server (typically with `sjis'
or `ujis') and a Windows client (typically with `cp932').

In the following conversion table, the `ucs2' column represents the
source, and the `sjis', `cp932', `ujis', and `eucjpms' columns
represent the destinations--that is, the last 4 columns provide the
hexadecimal result when we use `CONVERT(ucs2)' or we assign a `ucs2'
column containing the value to an `sjis', `cp932', `ujis', or `eucjpms'
column.

Character Name                ucs2      sjis      cp932     ujis      eucjpms
BROKEN BAR                    00A6      3F        3F        8FA2C3    3F
FULLWIDTH BROKEN BAR          FFE4      3F        FA55      3F        8FA2
YEN SIGN                      00A5      3F        3F        20        3F
FULLWIDTH YEN SIGN            FFE5      818F      818F      A1EF      3F
TILDE                         007E      7E        7E        7E        7E
OVERLINE                      203E      3F        3F        20        3F
HORIZONTAL BAR                2015      815C      815C      A1BD      A1BD
EM DASH                       2014      3F        3F        3F        3F
REVERSE SOLIDUS               005C      815F      5C        5C        5C
FULLWIDTH ""                  FF3C      3F        815F      3F        A1C0
WAVE DASH                     301C      8160      3F        A1C1      3F
FULLWIDTH TILDE               FF5E      3F        8160      3F        A1C1
DOUBLE VERTICAL LINE          2016      8161      3F        A1C2      3F
PARALLEL TO                   2225      3F        8161      3F        A1C2
MINUS SIGN                    2212      817C      3F        A1DD      3F
FULLWIDTH HYPHEN-MINUS        FF0D      3F        817C      3F        A1DD
CENT SIGN                     00A2      8191      3F        A1F1      3F
FULLWIDTH CENT SIGN           FFE0      3F        8191      3F        A1F1
POUND SIGN                    00A3      8192      3F        A1F2      3F
FULLWIDTH POUND SIGN          FFE1      3F        8192      3F        A1F2
NOT SIGN                      00AC      81CA      3F        A2CC      3F
FULLWIDTH NOT SIGN            FFE2      3F        81CA      3F        A2CC

Now consider the following portion of the table.

                                         ucs2        sjis        cp932
NOT SIGN                                 00AC        81CA        3F
FULLWIDTH NOT SIGN                       FFE2        3F          81CA

This means that MySQL converts the `NOT SIGN' (Unicode `U+00AC') to
`sjis' code point `0x81CA' and to `cp932' code point `3F'.  (`3F' is
the question mark (`?')--this is what is always used when the
conversion cannot be performed.

*A.11.5: ** What should I do if I want to convert SJIS `81CA' to
`cp932'?  *

Our answer is: `?'. There are serious complaints about this: many
people would prefer a `loose' conversion, so that `81CA (NOT SIGN)' in
`sjis' becomes `81CA (FULLWIDTH NOT SIGN)' in `cp932'. We are
considering a change to this behavior.

*A.11.6: ** How does MySQL represent the Yen (`¥') sign?  *

A problem arises because some versions of Japanese character sets (both
`sjis' and `euc') treat `5C' as a _reverse solidus_ (`\'--also known as
a backslash), and others treat it as a yen sign (`¥').

MySQL follows only one version of the JIS (Japanese Industrial
Standards) standard description. In MySQL, _`5C' is always the reverse
solidus (`\')_.

*A.11.7: ** Does MySQL plan to make a separate character set where `5C'
is the Yen sign, as at least one other major DBMS does?  *

This is one possible solution to the Yen sign issue; however, this will
not happen in MySQL 5.1 or 6.0.

*A.11.8: ** Of what issues should I be aware when working with Korean
character sets in MySQL?  *

In theory, while there have been several versions of the `euckr'
(_Extended Unix Code Korea_) character set, only one problem has been
noted.

We use the `ASCII' variant of EUC-KR, in which the code point `0x5c' is
REVERSE SOLIDUS, that is `\', instead of the `KS-Roman' variant of
EUC-KR, in which the code point `0x5c' is `WON SIGN'(`₩'). This means
that you cannot convert Unicode `U+20A9' to `euckr':


     mysql> SELECT
         ->     CONVERT('₩' USING euckr) AS euckr,
         ->     HEX(CONVERT('₩' USING euckr)) AS hexeuckr;
     +-------+----------+
     | euckr | hexeuckr |
     +-------+----------+
     | ?     | 3F       |
     +-------+----------+
     1 row in set (0.00 sec)

MySQL's graphic Korean chart is here: euckr
(http://www.collation-charts.org/mysql60/by-charset.html#euckr).

*A.11.9: ** Why do I get `Incorrect string value' error messages?  *

For illustration, we'll create a table with one Unicode (`ucs2') column
and one Chinese (`gb2312') column.


     mysql> CREATE TABLE ch
         -> (ucs2 CHAR(3) CHARACTER SET ucs2,
         -> gb2312 CHAR(3) CHARACTER SET gb2312);
     Query OK, 0 rows affected (0.05 sec)

We'll try to place the rare character `汌' in both columns.


     mysql> INSERT INTO ch VALUES ('A汌B','A汌B');
     Query OK, 1 row affected, 1 warning (0.00 sec)

Ah, there is a warning. Use the following statement to see what it is:


     mysql> SHOW WARNINGS\G
     *************************** 1. row ***************************
       Level: Warning
        Code: 1366
     Message: Incorrect string value: '\xE6\xB1\x8CB' for column 'gb2312' at row 1
     1 row in set (0.00 sec)

So it is a warning about the `gb2312' column only.


     mysql> SELECT ucs2,HEX(ucs2),gb2312,HEX(gb2312) FROM ch;
     +-------+--------------+--------+-------------+
     | ucs2  | HEX(ucs2)    | gb2312 | HEX(gb2312) |
     +-------+--------------+--------+-------------+
     | A汌B | 00416C4C0042 | A?B    | 413F42      |
     +-------+--------------+--------+-------------+
     1 row in set (0.00 sec)

Several things need explanation here:

  1. The fact that it is a `warning' rather than an `error' is
     characteristic of MySQL. We like to try to do what we can, to get
     the best fit, rather than give up.

  2. The `汌' character is not in the `gb2312' character set. We
     described that problem earlier.

  3. If you are using an old version of MySQL, you will probably see a
     different message.

  4. With `sql_mode=TRADITIONAL', there would be an error message,
     rather than a warning.

*A.11.10: ** Why does my GUI front end or browser not display CJK
characters correctly in my application using Access, PHP, or another
API?  *

Obtain a direct connection to the server using the *Note `mysql':
mysql. client (Windows: *Note `mysql.exe': mysql.), and try the same
query there. If *Note `mysql': mysql. responds correctly, then the
trouble may be that your application interface requires initialization.
Use *Note `mysql': mysql. to tell you what character set or sets it
uses with the statement `SHOW VARIABLES LIKE 'char%';'. If you are
using Access, then you are most likely connecting with Connector/ODBC.
In this case, you should check Configuring Connector/ODBC
(http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-configuration.html).
If, for instance, you use `big5', you would enter `SET NAMES 'big5''.
(Note that no `;' is required in this case). If you are using ASP, you
might need to add `SET NAMES' in the code. Here is an example that has
worked in the past:


     <%
     Session.CodePage=0
     Dim strConnection
     Dim Conn
     strConnection="driver={MySQL ODBC 3.51 Driver};server=SERVER;uid=USERNAME;" \
                    & "pwd=PASSWORD;database=DATABASE;stmt=SET NAMES 'big5';"
     Set Conn = Server.CreateObject("ADODB.Connection")
     Conn.Open strConnection
     %>

In much the same way, if you are using any character set other than
`latin1' with Connector/Net, then you must specify the character set in
the connection string. See Connecting to MySQL Using Connector/Net
(http://dev.mysql.com/doc/connector-net/en/connector-net-programming-connecting.html),
for more information.

If you are using PHP, try this:


     <?php
       $link = mysql_connect($host, $usr, $pwd);

       mysql_select_db($db);

       if( mysql_error() ) { print "Database ERROR: " . mysql_error(); }
       mysql_query("SET NAMES 'utf8'", $link);
     ?>

In this case, we used `SET NAMES' to change `character_set_client' and
`character_set_connection' and `character_set_results'.

We encourage the use of the newer `mysqli' extension, rather than
`mysql'. Using `mysqli', the previous example could be rewritten as
shown here:


     <?php
       $link = new mysqli($host, $usr, $pwd, $db);

       if( mysqli_connect_errno() )
       {
         printf("Connect failed: %s\n", mysqli_connect_error());
         exit();
       }

       $link->query("SET NAMES 'utf8'");
     ?>

Another issue often encountered in PHP applications has to do with
assumptions made by the browser. Sometimes adding or changing a
`<meta>' tag suffices to correct the problem: for example, to insure
that the user agent interprets page content as `UTF-8', you should
include `<meta http-equiv="Content-Type" content="text/html;
charset=utf-8">' in the `<head>' of the HTML page.

If you are using Connector/J, see Using Character Sets and Unicode
(http://dev.mysql.com/doc/connector-j/en/connector-j-reference-charsets.html).

*A.11.11: ** I've upgraded to MySQL 5.1. How can I revert to behavior
like that in MySQL 4.0 with regard to character sets?  *

In MySQL Version 4.0, there was a single `global' character set for
both server and client, and the decision as to which character to use
was made by the server administrator.  This changed starting with MySQL
Version 4.1. What happens now is a `handshake', as described in *Note
charset-connection:::

When a client connects, it sends to the server the name of the
character set that it wants to use. The server uses the name to set the
`character_set_client', `character_set_results', and
`character_set_connection' system variables. In effect, the server
performs a `SET NAMES' operation using the character set name.

The effect of this is that you cannot control the client character set
by starting *Note `mysqld': mysqld. with `--character-set-server=utf8'.
However, some of our Asian customers have said that they prefer the
MySQL 4.0 behavior. To make it possible to retain this behavior, we
added a *Note `mysqld': mysqld. switch,
`--character-set-client-handshake', which can be turned off with
`--skip-character-set-client-handshake'.  If you start *Note `mysqld':
mysqld. with `--skip-character-set-client-handshake', then, when a
client connects, it sends to the server the name of the character set
that it wants to use--however, _the server ignores this request from the
client_.

By way of example, suppose that your favorite server character set is
`latin1' (unlikely in a CJK area, but this is the default value).
Suppose further that the client uses `utf8' because this is what the
client's operating system supports. Now, start the server with `latin1'
as its default character set:


     mysqld --character-set-server=latin1

And then start the client with the default character set `utf8':


     mysql --default-character-set=utf8

The current settings can be seen by viewing the output of *Note `SHOW
VARIABLES': show-variables.:


     mysql> SHOW VARIABLES LIKE 'char%';
     +--------------------------+----------------------------------------+
     | Variable_name            | Value                                  |
     +--------------------------+----------------------------------------+
     | character_set_client     | utf8                                   |
     | character_set_connection | utf8                                   |
     | character_set_database   | latin1                                 |
     | character_set_filesystem | binary                                 |
     | character_set_results    | utf8                                   |
     | character_set_server     | latin1                                 |
     | character_set_system     | utf8                                   |
     | character_sets_dir       | /usr/local/mysql/share/mysql/charsets/ |
     +--------------------------+----------------------------------------+
     8 rows in set (0.01 sec)

Now stop the client, and then stop the server using *Note `mysqladmin':
mysqladmin. Then start the server again, but this time tell it to skip
the handshake like so:


     mysqld --character-set-server=utf8 --skip-character-set-client-handshake

Start the client with `utf8' once again as the default character set,
then display the current settings:


     mysql> SHOW VARIABLES LIKE 'char%';
     +--------------------------+----------------------------------------+
     | Variable_name            | Value                                  |
     +--------------------------+----------------------------------------+
     | character_set_client     | latin1                                 |
     | character_set_connection | latin1                                 |
     | character_set_database   | latin1                                 |
     | character_set_filesystem | binary                                 |
     | character_set_results    | latin1                                 |
     | character_set_server     | latin1                                 |
     | character_set_system     | utf8                                   |
     | character_sets_dir       | /usr/local/mysql/share/mysql/charsets/ |
     +--------------------------+----------------------------------------+
     8 rows in set (0.01 sec)

As you can see by comparing the differing results from *Note `SHOW
VARIABLES': show-variables, the server ignores the client's initial
settings if the `--skip-character-set-client-handshake' is used.

*A.11.12: ** Why do some `LIKE' and `FULLTEXT' searches with CJK
characters fail?  *

There is a very simple problem with `LIKE' searches on *Note `BINARY':
binary-varbinary. and *Note `BLOB': blob. columns: we need to know the
end of a character. With multibyte character sets, different characters
might have different octet lengths. For example, in `utf8', `A'
requires one byte but `ペ' requires three bytes, as shown here:


     +-------------------------+---------------------------+
     | OCTET_LENGTH(_utf8 'A') | OCTET_LENGTH(_utf8 'ペ') |
     +-------------------------+---------------------------+
     |                       1 |                         3 |
     +-------------------------+---------------------------+
     1 row in set (0.00 sec)

If we don't know where the first character ends, then we don't know
where the second character begins, in which case even very simple
searches such as `LIKE '_A%'' fail. The solution is to use a regular CJK
character set in the first place, or to convert to a CJK character set
before comparing.

This is one reason why MySQL cannot allow encodings of nonexistent
characters. If it is not strict about rejecting bad input, then it has
no way of knowing where characters end.

For `FULLTEXT' searches, we need to know where words begin and end.
With Western languages, this is rarely a problem because most (if not
all) of these use an easy-to-identify word boundary--the space
character.  However, this is not usually the case with Asian writing. We
could use arbitrary halfway measures, like assuming that all Han
characters represent words, or (for Japanese) depending on changes from
Katakana to Hiragana due to grammatical endings.  However, the only
sure solution requires a comprehensive word list, which means that we
would have to include a dictionary in the server for each Asian
language supported. This is simply not feasible.

*A.11.13: ** How do I know whether character X is available in all
character sets?  *

The majority of simplified Chinese and basic nonhalfwidth Japanese Kana
characters appear in all CJK character sets. This stored procedure
accepts a `UCS-2' Unicode character, converts it to all other character
sets, and displays the results in hexadecimal.


     DELIMITER //

     CREATE PROCEDURE p_convert(ucs2_char CHAR(1) CHARACTER SET ucs2)
     BEGIN

     CREATE TABLE tj
                  (ucs2 CHAR(1) character set ucs2,
                   utf8 CHAR(1) character set utf8,
                   big5 CHAR(1) character set big5,
                   cp932 CHAR(1) character set cp932,
                   eucjpms CHAR(1) character set eucjpms,
                   euckr CHAR(1) character set euckr,
                   gb2312 CHAR(1) character set gb2312,
                   gbk CHAR(1) character set gbk,
                   sjis CHAR(1) character set sjis,
                   ujis CHAR(1) character set ujis);

     INSERT INTO tj (ucs2) VALUES (ucs2_char);

     UPDATE tj SET utf8=ucs2,
                   big5=ucs2,
                   cp932=ucs2,
                   eucjpms=ucs2,
                   euckr=ucs2,
                   gb2312=ucs2,
                   gbk=ucs2,
                   sjis=ucs2,
                   ujis=ucs2;

     /* If there is a conversion problem, UPDATE will produce a warning. */

     SELECT hex(ucs2) AS ucs2,
            hex(utf8) AS utf8,
            hex(big5) AS big5,
            hex(cp932) AS cp932,
            hex(eucjpms) AS eucjpms,
            hex(euckr) AS euckr,
            hex(gb2312) AS gb2312,
            hex(gbk) AS gbk,
            hex(sjis) AS sjis,
            hex(ujis) AS ujis
     FROM tj;

     DROP TABLE tj;

     END//

The input can be any single `ucs2' character, or it can be the code
point value (hexadecimal representation) of that character. For
example, from Unicode's list of `ucs2' encodings and names
(`http://www.unicode.org/Public/UNIDATA/UnicodeData.txt'), we know that
the Katakana character _Pe_ appears in all CJK character sets, and that
its code point value is `0x30da'. If we use this value as the argument
to `p_convert()', the result is as shown here:


     mysql> CALL p_convert(0x30da)//
     +------+--------+------+-------+---------+-------+--------+------+------+------+
     | ucs2 | utf8   | big5 | cp932 | eucjpms | euckr | gb2312 | gbk  | sjis | ujis |
     +------+--------+------+-------+---------+-------+--------+------+------+------+
     | 30DA | E3839A | C772 | 8379  | A5DA    | ABDA  | A5DA   | A5DA | 8379 | A5DA |
     +------+--------+------+-------+---------+-------+--------+------+------+------+
     1 row in set (0.04 sec)

Since none of the column values is `3F'--that is, the question mark
character (`?')--we know that every conversion worked.

*A.11.14: ** Why do CJK strings sort incorrectly in Unicode? (I) *

Sometimes people observe that the result of a `utf8_unicode_ci' or
`ucs2_unicode_ci' search, or of an `ORDER BY' sort is not what they
think a native would expect. Although we never rule out the possibility
that there is a bug, we have found in the past that many people do not
read correctly the standard table of weights for the Unicode Collation
Algorithm. MySQL uses the table found at
`http://www.unicode.org/Public/UCA/4.0.0/allkeys-4.0.0.txt'.  This is
not the first table you will find by navigating from the `unicode.org'
home page, because MySQL uses the older 4.0.0 `allkeys' table, rather
than the more recent 4.1.0 table. (The newer `'520'' collations in
MySQL 5.6 use the 5.2 `allkeys' table.) This is because we are very
wary about changing ordering which affects indexes, lest we bring about
situations such as that reported in Bug #16526, illustrated as follows:


     mysql< CREATE TABLE tj (s1 CHAR(1) CHARACTER SET utf8 COLLATE utf8_unicode_ci);
     Query OK, 0 rows affected (0.05 sec)

     mysql> INSERT INTO tj VALUES ('が'),('か');
     Query OK, 2 rows affected (0.00 sec)
     Records: 2  Duplicates: 0  Warnings: 0

     mysql> SELECT * FROM tj WHERE s1 = 'か';
     +------+
     | s1   |
     +------+
     | が  |
     | か  |
     +------+
     2 rows in set (0.00 sec)

The character in the first result row is not the one that we searched
for. Why did MySQL retrieve it? First we look for the Unicode code
point value, which is possible by reading the hexadecimal number for
the `ucs2' version of the characters:


     mysql> SELECT s1, HEX(CONVERT(s1 USING ucs2)) FROM tj;
     +------+-----------------------------+
     | s1   | HEX(CONVERT(s1 USING ucs2)) |
     +------+-----------------------------+
     | が  | 304C                        |
     | か  | 304B                        |
     +------+-----------------------------+
     2 rows in set (0.03 sec)

Now we search for `304B' and `304C' in the `4.0.0 allkeys' table, and
find these lines:


     304B  ; [.1E57.0020.000E.304B] # HIRAGANA LETTER KA
     304C  ; [.1E57.0020.000E.304B][.0000.0140.0002.3099] # HIRAGANA LETTER GA; QQCM

The official Unicode names (following the `#' mark) tell us the
Japanese syllabary (Hiragana), the informal classification (letter,
digit, or punctuation mark), and the Western identifier (`KA' or `GA',
which happen to be voiced and unvoiced components of the same letter
pair). More importantly, the _primary weight_ (the first hexadecimal
number inside the square brackets) is `1E57' on both lines. For
comparisons in both searching and sorting, MySQL pays attention to the
primary weight only, ignoring all the other numbers. This means that we
are sorting `が' and `か' correctly according to the Unicode
specification. If we wanted to distinguish them, we'd have to use a
non-UCA (Unicode Collation Algorithm) collation (`utf8_bin' or
`utf8_general_ci'), or to compare the `HEX()' values, or use `ORDER BY
CONVERT(s1 USING sjis)'. Being correct `according to Unicode' isn't
enough, of course: the person who submitted the bug was equally
correct. We plan to add another collation for Japanese according to the
JIS X 4061 standard, in which voiced/unvoiced letter pairs like
`KA'/`GA' are distinguishable for ordering purposes.

*A.11.15: ** Why do CJK strings sort incorrectly in Unicode? (II) *

If you are using Unicode (`ucs2' or `utf8'), and you know what the
Unicode sort order is (see *Note faqs-cjk::), but MySQL still seems to
sort your table incorrectly, then you should first verify the table
character set:


     mysql> SHOW CREATE TABLE t\G
     ******************** 1. row ******************
     Table: t
     Create Table: CREATE TABLE `t` (
     `s1` char(1) CHARACTER SET ucs2 DEFAULT NULL
     ) ENGINE=MyISAM DEFAULT CHARSET=latin1
     1 row in set (0.00 sec)

Since the character set appears to be correct, let's see what
information the *Note `INFORMATION_SCHEMA.COLUMNS': columns-table. table
can provide about this column:


     mysql> SELECT COLUMN_NAME, CHARACTER_SET_NAME, COLLATION_NAME
         -> FROM INFORMATION_SCHEMA.COLUMNS
         -> WHERE COLUMN_NAME = 's1'
         -> AND TABLE_NAME = 't';
     +-------------+--------------------+-----------------+
     | COLUMN_NAME | CHARACTER_SET_NAME | COLLATION_NAME  |
     +-------------+--------------------+-----------------+
     | s1          | ucs2               | ucs2_general_ci |
     +-------------+--------------------+-----------------+
     1 row in set (0.01 sec)

(See *Note columns-table::, for more information.)

You can see that the collation is `ucs2_general_ci' instead of
`ucs2_unicode_ci'. The reason why this is so can be found using `SHOW
CHARSET', as shown here:


     mysql> SHOW CHARSET LIKE 'ucs2%';
     +---------+---------------+-------------------+--------+
     | Charset | Description   | Default collation | Maxlen |
     +---------+---------------+-------------------+--------+
     | ucs2    | UCS-2 Unicode | ucs2_general_ci   |      2 |
     +---------+---------------+-------------------+--------+
     1 row in set (0.00 sec)

For `ucs2' and `utf8', the default collation is `general'. To specify a
Unicode collation, use `COLLATE ucs2_unicode_ci'.

*A.11.16: ** Why are my supplementary characters rejected by MySQL?  *

Before MySQL 5.5.3, MySQL does not support supplementary
characters--that is, characters which need more than 3 bytes--for
`UTF-8'. We support only what Unicode calls the _Basic Multilingual
Plane / Plane 0_. Only a few very rare Han characters are
supplementary; support for them is uncommon. This has led to reports
such as that found in Bug #12600, which we rejected as `not a bug'.
With `utf8', we must truncate an input string when we encounter bytes
that we don't understand. Otherwise, we wouldn't know how long the bad
multibyte character is.

One possible workaround is to use `ucs2' instead of `utf8', in which
case the `bad' characters are changed to question marks; however, no
truncation takes place. You can also change the data type to *Note
`BLOB': blob. or *Note `BINARY': binary-varbinary, which perform no
validity checking.

As of MySQL 5.5.3, Unicode support is extended to include supplementary
characters by means of additional Unicode character sets: `utf16',
`utf32', and 4-byte `utf8mb4'.  These character sets support
supplementary Unicode characters outside the Basic Multilingual Plane
(BMP).

*A.11.17: ** Shouldn't it be `CJKV'?  *

No. The term `CJKV' (_Chinese Japanese Korean Vietnamese_) refers to
Vietnamese character sets which contain Han (originally Chinese)
characters. MySQL has no plan to support the old Vietnamese script
using Han characters. MySQL does of course support the modern Vietnamese
script with Western characters.

As of MySQL 5.6, there are Vietnamese collations for Unicode character
sets, as described in *Note charset-unicode-sets::.

*A.11.18: ** Does MySQL allow CJK characters to be used in database and
table names?  *

This issue is fixed in MySQL 5.1, by automatically rewriting the names
of the corresponding directories and files.

For example, if you create a database named `楮' on a server whose
operating system does not support CJK in directory names, MySQL creates
a directory named `@0w@00a5@00ae', which is just a fancy way of
encoding `E6A5AE'--that is, the Unicode hexadecimal representation for
the `楮' character. However, if you run a *Note `SHOW DATABASES':
show-databases. statement, you can see that the database is listed as
`楮'.

*A.11.19: ** Where can I find translations of the MySQL Manual into
Chinese, Japanese, and Korean?  *

A Simplified Chinese version of the Manual, current for MySQL 5.1.12,
can be found at `http://dev.mysql.com/doc/'. The Japanese translation
of the MySQL 4.1 manual can be downloaded from
`http://dev.mysql.com/doc/'.

*A.11.20: ** Where can I get help with CJK and related issues in MySQL?
*

The following resources are available:

   * A listing of MySQL user groups can be found at
     `https://wikis.oracle.com/display/mysql/List+of+MySQL+User+Groups'.

   * View feature requests relating to character set issues at
     `http://tinyurl.com/y6xcuf'.

   * Visit the MySQL Collation Unicode Forum. We are also in the
     process of adding foreign-language forums at
     `http://forums.mysql.com/'.


File: manual.info,  Node: faqs-connectors-apis,  Next: faqs-replication,  Prev: faqs-cjk,  Up: faqs

A.12 MySQL 5.1 FAQ: Connectors & APIs
=====================================

For common questions, issues, and answers relating to the MySQL
Connectors and other APIs, see the following areas of the Manual:

   * *Note c-api-problems::

   * Common Problems with MySQL and PHP
     (http://dev.mysql.com/doc/apis-php/en/apis-php-problems.html)

   * Connector/ODBC Notes and Tips
     (http://dev.mysql.com/doc/connector-odbc/en/connector-odbc-usagenotes.html)

   * Connector/Net Programming
     (http://dev.mysql.com/doc/connector-net/en/connector-net-programming.html)

   * MySQL Connector/J Developer Guide
     (http://dev.mysql.com/doc/connector-j/en/index.html)


File: manual.info,  Node: faqs-replication,  Prev: faqs-connectors-apis,  Up: faqs

A.13 MySQL 5.1 FAQ: Replication
===============================

In the following section, we provide answers to questions that are most
frequently asked about MySQL Replication.

*Questions*
   * A.13.1: Must the slave be connected to the master all the time?

   * A.13.2: Must I enable networking on my master and slave to enable
     replication?

   * A.13.3: How do I know how late a slave is compared to the master?
     In other words, how do I know the date of the last statement
     replicated by the slave?

   * A.13.4: How do I force the master to block updates until the slave
     catches up?

   * A.13.5: What issues should I be aware of when setting up two-way
     replication?

   * A.13.6: How can I use replication to improve performance of my
     system?

   * A.13.7: What should I do to prepare client code in my own
     applications to use performance-enhancing replication?

   * A.13.8: When and how much can MySQL replication improve the
     performance of my system?

   * A.13.9: How can I use replication to provide redundancy or high
     availability?

   * A.13.10: How do I tell whether a master server is using
     statement-based or row-based binary logging format?

   * A.13.11: How do I tell a slave to use row-based replication?

   * A.13.12: How do I prevent *Note `GRANT': grant. and *Note
     `REVOKE': revoke. statements from replicating to slave machines?

   * A.13.13: Does replication work on mixed operating systems (for
     example, the master runs on Linux while slaves run on Mac OS X and
     Windows)?

   * A.13.14: Does replication work on mixed hardware architectures (for
     example, the master runs on a 64-bit machine while slaves run on
     32-bit machines)?

*Questions and Answers* *A.13.1: ** Must the slave be connected to the
master all the time?  *

No, it does not. The slave can go down or stay disconnected for hours
or even days, and then reconnect and catch up on updates.  For example,
you can set up a master/slave relationship over a dial-up link where
the link is up only sporadically and for short periods of time. The
implication of this is that, at any given time, the slave is not
guaranteed to be in synchrony with the master unless you take some
special measures.

To ensure that catchup can occur for a slave that has been
disconnected, you must not remove binary log files from the master that
contain information that has not yet been replicated to the slaves.
Asynchronous replication can work only if the slave is able to continue
reading the binary log from the point where it last read events.

*A.13.2: ** Must I enable networking on my master and slave to enable
replication?  *

Yes, networking must be enabled on the master and slave. If networking
is not enabled, the slave cannot connect to the master and transfer the
binary log. Check that the `skip-networking' option has not been
enabled in the configuration file for either server.

*A.13.3: ** How do I know how late a slave is compared to the master? In
other words, how do I know the date of the last statement replicated by
the slave?  *

Check the `Seconds_Behind_Master' column in the output from *Note `SHOW
SLAVE STATUS': show-slave-status.  See *Note
replication-administration-status::.

When the slave SQL thread executes an event read from the master, it
modifies its own time to the event timestamp. (This is why *Note
`TIMESTAMP': datetime. is well replicated.) In the `Time' column in the
output of *Note `SHOW PROCESSLIST': show-processlist, the number of
seconds displayed for the slave SQL thread is the number of seconds
between the timestamp of the last replicated event and the real time of
the slave machine. You can use this to determine the date of the last
replicated event. Note that if your slave has been disconnected from
the master for one hour, and then reconnects, you may immediately see
large `Time' values such as 3600 for the slave SQL thread in *Note
`SHOW PROCESSLIST': show-processlist. This is because the slave is
executing statements that are one hour old. See *Note
replication-implementation-details::.

*A.13.4: ** How do I force the master to block updates until the slave
catches up?  *

Use the following procedure:

  1. On the master, execute these statements:


          mysql> FLUSH TABLES WITH READ LOCK;
          mysql> SHOW MASTER STATUS;

     Record the replication coordinates (the current binary log file
     name and position) from the output of the *Note `SHOW': show.
     statement.

  2. On the slave, issue the following statement, where the arguments
     to the `MASTER_POS_WAIT()' function are the replication coordinate
     values obtained in the previous step:


          mysql> SELECT MASTER_POS_WAIT('LOG_NAME', LOG_POS);

     The *Note `SELECT': select. statement blocks until the slave
     reaches the specified log file and position.  At that point, the
     slave is in synchrony with the master and the statement returns.

  3. On the master, issue the following statement to enable the master
     to begin processing updates again:


          mysql> UNLOCK TABLES;

*A.13.5: ** What issues should I be aware of when setting up two-way
replication?  *

MySQL replication currently does not support any locking protocol
between master and slave to guarantee the atomicity of a distributed
(cross-server) update. In other words, it is possible for client A to
make an update to co-master 1, and in the meantime, before it
propagates to co-master 2, client B could make an update to co-master 2
that makes the update of client A work differently than it did on
co-master 1. Thus, when the update of client A makes it to co-master 2,
it produces tables that are different from what you have on co-master 1,
even after all the updates from co-master 2 have also propagated. This
means that you should not chain two servers together in a two-way
replication relationship unless you are sure that your updates can
safely happen in any order, or unless you take care of mis-ordered
updates somehow in the client code.

You should also realize that two-way replication actually does not
improve performance very much (if at all) as far as updates are
concerned. Each server must do the same number of updates, just as you
would have a single server do. The only difference is that there is a
little less lock contention because the updates originating on another
server are serialized in one slave thread. Even this benefit might be
offset by network delays.

*A.13.6: ** How can I use replication to improve performance of my
system?  *

Set up one server as the master and direct all writes to it.  Then
configure as many slaves as you have the budget and rackspace for, and
distribute the reads among the master and the slaves. You can also
start the slaves with the `--skip-innodb', `--low-priority-updates', and
`--delay-key-write=ALL' options to get speed improvements on the slave
end. In this case, the slave uses nontransactional `MyISAM' tables
instead of `InnoDB' tables to get more speed by eliminating
transactional overhead.

*A.13.7: ** What should I do to prepare client code in my own
applications to use performance-enhancing replication?  *

See the guide to using replication as a scale-out solution, *Note
replication-solutions-scaleout::.

*A.13.8: ** When and how much can MySQL replication improve the
performance of my system?  *

MySQL replication is most beneficial for a system that processes
frequent reads and infrequent writes. In theory, by using a
single-master/multiple-slave setup, you can scale the system by adding
more slaves until you either run out of network bandwidth, or your
update load grows to the point that the master cannot handle it.

To determine how many slaves you can use before the added benefits
begin to level out, and how much you can improve performance of your
site, you must know your query patterns, and determine empirically by
benchmarking the relationship between the throughput for reads and
writes on a typical master and a typical slave. The example here shows
a rather simplified calculation of what you can get with replication
for a hypothetical system. Let `reads' and `writes' denote the number
of reads and writes per second, respectively.

Let's say that system load consists of 10% writes and 90% reads, and we
have determined by benchmarking that `reads' is 1200 - 2 * `writes'. In
other words, the system can do 1,200 reads per second with no writes,
the average write is twice as slow as the average read, and the
relationship is linear. Suppose that the master and each slave have the
same capacity, and that we have one master and N slaves. Then we have
for each server (master or slave):

`reads' = 1200 - 2 * `writes'

`reads' = 9 * `writes' / (N + 1) (reads are split, but writes
replicated to all slaves)

9 * `writes' / (N + 1) + 2 * `writes' = 1200

`writes' = 1200 / (2 + 9/(N + 1))

The last equation indicates the maximum number of writes for N slaves,
given a maximum possible read rate of 1,200 per second and a ratio of
nine reads per write.

This analysis yields the following conclusions:

   * If N = 0 (which means we have no replication), our system can
     handle about 1200/11 = 109 writes per second.

   * If N = 1, we get up to 184 writes per second.

   * If N = 8, we get up to 400 writes per second.

   * If N = 17, we get up to 480 writes per second.

   * Eventually, as N approaches infinity (and our budget negative
     infinity), we can get very close to 600 writes per second,
     increasing system throughput about 5.5 times. However, with only
     eight servers, we increase it nearly four times.

Note that these computations assume infinite network bandwidth and
neglect several other factors that could be significant on your system.
In many cases, you may not be able to perform a computation similar to
the one just shown that accurately predicts what will happen on your
system if you add N replication slaves. However, answering the
following questions should help you decide whether and by how much
replication will improve the performance of your system:

   * What is the read/write ratio on your system?

   * How much more write load can one server handle if you reduce the
     reads?

   * For how many slaves do you have bandwidth available on your
     network?

*A.13.9: ** How can I use replication to provide redundancy or high
availability?  *

How you implement redundancy is entirely dependent on your application
and circumstances. High-availability solutions (with automatic
failover) require active monitoring and either custom scripts or third
party tools to provide the failover support from the original MySQL
server to the slave.

To handle the process manually, you should be able to switch from a
failed master to a pre-configured slave by altering your application to
talk to the new server or by adjusting the DNS for the MySQL server
from the failed server to the new server.

For more information and some example solutions, see *Note
replication-solutions-switch::.

*A.13.10: ** How do I tell whether a master server is using
statement-based or row-based binary logging format?  *

Check the value of the `binlog_format' system variable:


     mysql> SHOW VARIABLES LIKE 'binlog_format';

The value shown will be one of `STATEMENT', `ROW', or `MIXED'. For
`MIXED' mode, row-based logging is preferred but replication switches
automatically to statement-based logging under certain conditions; for
information about when this may occur, see *Note binary-log-mixed::.

*A.13.11: ** How do I tell a slave to use row-based replication?  *

Slaves automatically know which format to use.

*A.13.12: ** How do I prevent *Note `GRANT': grant. and *Note `REVOKE':
revoke. statements from replicating to slave machines?  *

Start the server with the `--replicate-wild-ignore-table=mysql.%'
option to ignore replication for tables in the `mysql' database.

*A.13.13: ** Does replication work on mixed operating systems (for
example, the master runs on Linux while slaves run on Mac OS X and
Windows)?  *

Yes.

*A.13.14: ** Does replication work on mixed hardware architectures (for
example, the master runs on a 64-bit machine while slaves run on 32-bit
machines)?  *

Yes.


File: manual.info,  Node: error-handling,  Next: news,  Prev: faqs,  Up: Top

Appendix B Errors, Error Codes, and Common Problems
***************************************************

* Menu:

* error-sources::                Sources of Error Information
* error-types::                  Types of Error Values
* error-messages-server::        Server Error Codes and Messages
* error-messages-client::        Client Error Codes and Messages
* problems::                     Problems and Common Errors

This appendix lists common problems and errors that may occur and
potential resolutions, in addition to listing the errors that may
appear when you call MySQL from any host language. The first section
covers problems and resolutions. Detailed information on errors is
provided: One list displays server error messages. Another list
displays client program messages.


File: manual.info,  Node: error-sources,  Next: error-types,  Prev: error-handling,  Up: error-handling

B.1 Sources of Error Information
================================

There are several sources of error information in MySQL:

   * Each SQL statement executed results in an error code, an SQLSTATE
     value, and an error message, as described in *Note error-types::.
     These errors are returned from the server side; see *Note
     error-messages-server::.

   * Errors can occur on the client side, usually involving problems
     communicating with the server; see *Note error-messages-client::.

   * SQL statement warning and error information is available through
     the *Note `SHOW WARNINGS': show-warnings. and *Note `SHOW ERRORS':
     show-errors. statements. The `warning_count' system variable
     indicates the number of errors, warnings, and notes. The
     `error_count' system variable indicates the number of errors. Its
     value excludes warnings and notes.

   * *Note `SHOW SLAVE STATUS': show-slave-status. statement output
     includes information about replication errors occurring on the
     slave side.

   * *Note `SHOW ENGINE INNODB STATUS': show-engine. statement output
     includes information about the most recent foreign key error if a
     *Note `CREATE TABLE': create-table. statement for an *Note
     `InnoDB': innodb-storage-engine. table fails.

   * The *Note `perror': perror. program provides information from the
     command line about error numbers. See *Note perror::.

Descriptions of server and client errors are provided later in this
Appendix. For information about errors related to *Note `InnoDB':
innodb-storage-engine, see *Note innodb-error-handling::.


File: manual.info,  Node: error-types,  Next: error-messages-server,  Prev: error-sources,  Up: error-handling

B.2 Types of Error Values
=========================

When an error occurs in MySQL, the server returns two types of error
values:

   * A MySQL-specific error code. This value is numeric. It is not
     portable to other database systems.

   * An SQLSTATE value. The value is a five-character string (for
     example, `'42S02''). The values are taken from ANSI SQL and ODBC
     and are more standardized.

A message string that provides a textual description of the error is
also available.

When an error occurs, the MySQL error code, SQLSTATE value, and message
string are available using C API functions:

   * MySQL error code: Call *Note `mysql_errno()': mysql-errno.

   * SQLSTATE value: Call *Note `mysql_sqlstate()': mysql-sqlstate.

   * Error message: Call *Note `mysql_error()': mysql-error.

For prepared statements, the corresponding error functions are *Note
`mysql_stmt_errno()': mysql-stmt-errno, *Note `mysql_stmt_sqlstate()':
mysql-stmt-sqlstate, and *Note `mysql_stmt_error()': mysql-stmt-error.
All error functions are described in *Note c-api::.

The number of errors, warnings, and notes for the previous statement
can be obtained by calling *Note `mysql_warning_count()':
mysql-warning-count. See *Note mysql-warning-count::.

The first two characters of an SQLSTATE value indicate the error class:

   * Class = `'00'' indicates success.

   * Class = `'01'' indicates a warning.

   * Class = `'02'' indicates `not found.' This is relevant within the
     context of cursors and is used to control what happens when a
     cursor reaches the end of a data set. This condition also occurs
     for `SELECT ... INTO VAR_LIST' statements that retrieve no rows.

   * Class > `'02'' indicates an exception.


File: manual.info,  Node: error-messages-server,  Next: error-messages-client,  Prev: error-types,  Up: error-handling

B.3 Server Error Codes and Messages
===================================

MySQL programs have access to several types of error information when
the server returns an error. For example, the *Note `mysql': mysql.
client program displays errors using the following format:


     shell> SELECT * FROM no_such_table;
     ERROR 1146 (42S02): Table 'test.no_such_table' doesn't exist

The message displayed contains three types of information:

   * A numeric error code (`1146'). This number is MySQL-specific and
     is not portable to other database systems.

   * A five-character SQLSTATE value (`'42S02'').  The values are taken
     from ANSI SQL and ODBC and are more standardized. Not all MySQL
     error numbers have corresponding SQLSTATE values. In these cases,
     `'HY000'' (general error) is used.

   * A message string that provides a textual description of the error.

For error checking, use error codes, not error messages. Error messages
do not change often, but it is possible. Also if the database
administrator changes the language setting, that affects the language
of error messages.

Error codes are stable across GA releases of a given MySQL series.
Before a series reaches GA status, new codes may still be under
development and subject to change.

Server error information comes from the following source files.  For
details about the way that error information is defined, see the MySQL
Internals Manual (http://dev.mysql.com/doc/internals/en).

   * Error message information is listed in the `share/errmsg.txt' file.
     `%d' and `%s' represent numbers and strings, respectively, that
     are substituted into the Message values when they are displayed.

   * The Error values listed in `share/errmsg.txt' are used to generate
     the definitions in the `include/mysqld_error.h' and
     `include/mysqld_ername.h' MySQL source files.

   * The SQLSTATE values listed in `share/errmsg.txt' are used to
     generate the definitions in the `include/sql_state.h' MySQL source
     file.

Because updates are frequent, it is possible that those files will
contain additional error information not listed here.

   * Error: `1000' SQLSTATE: `HY000' (`ER_HASHCHK')

     Message: hashchk

     Unused.

   * Error: `1001' SQLSTATE: `HY000' (`ER_NISAMCHK')

     Message: isamchk

     Unused.

   * Error: `1002' SQLSTATE: `HY000' (`ER_NO')

     Message: NO

     Used in the construction of other messages.

   * Error: `1003' SQLSTATE: `HY000' (`ER_YES')

     Message: YES

     Used in the construction of other messages.

     Extended *Note `EXPLAIN': explain. format generates Note messages.
     `ER_YES' is used in the `Code' column for these messages in
     subsequent *Note `SHOW WARNINGS': show-warnings. output.

   * Error: `1004' SQLSTATE: `HY000' (`ER_CANT_CREATE_FILE')

     Message: Can't create file '%s' (errno: %d)

     Occurs for failure to copy an `.frm' file to a new location,
     during execution of a `CREATE TABLE DST LIKE SRC' statement when
     the server tries to copy the source table `.frm' file to the
     destination table `.frm' file.

     Possible causes: Permissions problem for source `.frm' file;
     destination `.frm' file already exists but is not writeable.

   * Error: `1005' SQLSTATE: `HY000' (`ER_CANT_CREATE_TABLE')

     Message: Can't create table '%s' (errno: %d)

   * Error: `1006' SQLSTATE: `HY000' (`ER_CANT_CREATE_DB')

     Message: Can't create database '%s' (errno: %d)

   * Error: `1007' SQLSTATE: `HY000' (`ER_DB_CREATE_EXISTS')

     Message: Can't create database '%s'; database exists

     An attempt to create a database failed because the database
     already exists.

     Drop the database first if you really want to replace an existing
     database, or add an `IF NOT EXISTS' clause to the *Note `CREATE
     DATABASE': create-database. statement if to retain an existing
     database without having the statement produce an error.

   * Error: `1008' SQLSTATE: `HY000' (`ER_DB_DROP_EXISTS')

     Message: Can't drop database '%s'; database doesn't exist

   * Error: `1009' SQLSTATE: `HY000' (`ER_DB_DROP_DELETE')

     Message: Error dropping database (can't delete '%s', errno: %d)

   * Error: `1010' SQLSTATE: `HY000' (`ER_DB_DROP_RMDIR')

     Message: Error dropping database (can't rmdir '%s', errno: %d)

   * Error: `1011' SQLSTATE: `HY000' (`ER_CANT_DELETE_FILE')

     Message: Error on delete of '%s' (errno: %d)

   * Error: `1012' SQLSTATE: `HY000' (`ER_CANT_FIND_SYSTEM_REC')

     Message: Can't read record in system table

     Returned by `InnoDB' for attempts to access `InnoDB'
     `INFORMATION_SCHEMA' tables when `InnoDB' is unavailable.

   * Error: `1013' SQLSTATE: `HY000' (`ER_CANT_GET_STAT')

     Message: Can't get status of '%s' (errno: %d)

   * Error: `1014' SQLSTATE: `HY000' (`ER_CANT_GET_WD')

     Message: Can't get working directory (errno: %d)

   * Error: `1015' SQLSTATE: `HY000' (`ER_CANT_LOCK')

     Message: Can't lock file (errno: %d)

   * Error: `1016' SQLSTATE: `HY000' (`ER_CANT_OPEN_FILE')

     Message: Can't open file: '%s' (errno: %d)

   * Error: `1017' SQLSTATE: `HY000' (`ER_FILE_NOT_FOUND')

     Message: Can't find file: '%s' (errno: %d)

   * Error: `1018' SQLSTATE: `HY000' (`ER_CANT_READ_DIR')

     Message: Can't read dir of '%s' (errno: %d)

   * Error: `1019' SQLSTATE: `HY000' (`ER_CANT_SET_WD')

     Message: Can't change dir to '%s' (errno: %d)

   * Error: `1020' SQLSTATE: `HY000' (`ER_CHECKREAD')

     Message: Record has changed since last read in table '%s'

   * Error: `1021' SQLSTATE: `HY000' (`ER_DISK_FULL')

     Message: Disk full (%s); waiting for someone to free some space...

   * Error: `1022' SQLSTATE: `23000' (`ER_DUP_KEY')

     Message: Can't write; duplicate key in table '%s'

   * Error: `1023' SQLSTATE: `HY000' (`ER_ERROR_ON_CLOSE')

     Message: Error on close of '%s' (errno: %d)

   * Error: `1024' SQLSTATE: `HY000' (`ER_ERROR_ON_READ')

     Message: Error reading file '%s' (errno: %d)

   * Error: `1025' SQLSTATE: `HY000' (`ER_ERROR_ON_RENAME')

     Message: Error on rename of '%s' to '%s' (errno: %d)

   * Error: `1026' SQLSTATE: `HY000' (`ER_ERROR_ON_WRITE')

     Message: Error writing file '%s' (errno: %d)

   * Error: `1027' SQLSTATE: `HY000' (`ER_FILE_USED')

     Message: '%s' is locked against change

   * Error: `1028' SQLSTATE: `HY000' (`ER_FILSORT_ABORT')

     Message: Sort aborted

   * Error: `1029' SQLSTATE: `HY000' (`ER_FORM_NOT_FOUND')

     Message: View '%s' doesn't exist for '%s'

   * Error: `1030' SQLSTATE: `HY000' (`ER_GET_ERRNO')

     Message: Got error %d from storage engine

     Check the `%d' value to see what the OS error means. For example,
     28 indicates that you have run out of disk space.

   * Error: `1031' SQLSTATE: `HY000' (`ER_ILLEGAL_HA')

     Message: Table storage engine for '%s' doesn't have this option

   * Error: `1032' SQLSTATE: `HY000' (`ER_KEY_NOT_FOUND')

     Message: Can't find record in '%s'

   * Error: `1033' SQLSTATE: `HY000' (`ER_NOT_FORM_FILE')

     Message: Incorrect information in file: '%s'

   * Error: `1034' SQLSTATE: `HY000' (`ER_NOT_KEYFILE')

     Message: Incorrect key file for table '%s'; try to repair it

   * Error: `1035' SQLSTATE: `HY000' (`ER_OLD_KEYFILE')

     Message: Old key file for table '%s'; repair it!

   * Error: `1036' SQLSTATE: `HY000' (`ER_OPEN_AS_READONLY')

     Message: Table '%s' is read only

   * Error: `1037' SQLSTATE: `HY001' (`ER_OUTOFMEMORY')

     Message: Out of memory; restart server and try again (needed %d
     bytes)

   * Error: `1038' SQLSTATE: `HY001' (`ER_OUT_OF_SORTMEMORY')

     Message: Out of sort memory; increase server sort buffer size

   * Error: `1039' SQLSTATE: `HY000' (`ER_UNEXPECTED_EOF')

     Message: Unexpected EOF found when reading file '%s' (errno: %d)

   * Error: `1040' SQLSTATE: `08004' (`ER_CON_COUNT_ERROR')

     Message: Too many connections

   * Error: `1041' SQLSTATE: `HY000' (`ER_OUT_OF_RESOURCES')

     Message: Out of memory; check if mysqld or some other process uses
     all available memory; if not, you may have to use 'ulimit' to
     allow mysqld to use more memory or you can add more swap space

   * Error: `1042' SQLSTATE: `08S01' (`ER_BAD_HOST_ERROR')

     Message: Can't get hostname for your address

   * Error: `1043' SQLSTATE: `08S01' (`ER_HANDSHAKE_ERROR')

     Message: Bad handshake

   * Error: `1044' SQLSTATE: `42000' (`ER_DBACCESS_DENIED_ERROR')

     Message: Access denied for user '%s'@'%s' to database '%s'

   * Error: `1045' SQLSTATE: `28000' (`ER_ACCESS_DENIED_ERROR')

     Message: Access denied for user '%s'@'%s' (using password: %s)

   * Error: `1046' SQLSTATE: `3D000' (`ER_NO_DB_ERROR')

     Message: No database selected

   * Error: `1047' SQLSTATE: `08S01' (`ER_UNKNOWN_COM_ERROR')

     Message: Unknown command

   * Error: `1048' SQLSTATE: `23000' (`ER_BAD_NULL_ERROR')

     Message: Column '%s' cannot be null

   * Error: `1049' SQLSTATE: `42000' (`ER_BAD_DB_ERROR')

     Message: Unknown database '%s'

   * Error: `1050' SQLSTATE: `42S01' (`ER_TABLE_EXISTS_ERROR')

     Message: Table '%s' already exists

   * Error: `1051' SQLSTATE: `42S02' (`ER_BAD_TABLE_ERROR')

     Message: Unknown table '%s'

   * Error: `1052' SQLSTATE: `23000' (`ER_NON_UNIQ_ERROR')

     Message: Column '%s' in %s is ambiguous


          %s = column name
          %s = location of column (for example, "field list")

     Likely cause: A column appears in a query without appropriate
     qualification, such as in a select list or ON clause.

     Examples:


          mysql> SELECT i FROM t INNER JOIN t AS t2;
          ERROR 1052 (23000): Column 'i' in field list is ambiguous

          mysql> SELECT * FROM t LEFT JOIN t AS t2 ON i = i;
          ERROR 1052 (23000): Column 'i' in on clause is ambiguous

     Resolution:

        * Qualify the column with the appropriate table name:


               mysql> SELECT t2.i FROM t INNER JOIN t AS t2;

        * Modify the query to avoid the need for qualification:


               mysql> SELECT * FROM t LEFT JOIN t AS t2 USING (i);

   * Error: `1053' SQLSTATE: `08S01' (`ER_SERVER_SHUTDOWN')

     Message: Server shutdown in progress

   * Error: `1054' SQLSTATE: `42S22' (`ER_BAD_FIELD_ERROR')

     Message: Unknown column '%s' in '%s'

   * Error: `1055' SQLSTATE: `42000' (`ER_WRONG_FIELD_WITH_GROUP')

     Message: '%s' isn't in GROUP BY

   * Error: `1056' SQLSTATE: `42000' (`ER_WRONG_GROUP_FIELD')

     Message: Can't group on '%s'

   * Error: `1057' SQLSTATE: `42000' (`ER_WRONG_SUM_SELECT')

     Message: Statement has sum functions and columns in same statement

   * Error: `1058' SQLSTATE: `21S01' (`ER_WRONG_VALUE_COUNT')

     Message: Column count doesn't match value count

   * Error: `1059' SQLSTATE: `42000' (`ER_TOO_LONG_IDENT')

     Message: Identifier name '%s' is too long

   * Error: `1060' SQLSTATE: `42S21' (`ER_DUP_FIELDNAME')

     Message: Duplicate column name '%s'

   * Error: `1061' SQLSTATE: `42000' (`ER_DUP_KEYNAME')

     Message: Duplicate key name '%s'

   * Error: `1062' SQLSTATE: `23000' (`ER_DUP_ENTRY')

     Message: Duplicate entry '%s' for key %d

     From 5.1.20: The message returned with this error uses the format
     string for `ER_DUP_ENTRY_WITH_KEY_NAME'.

   * Error: `1063' SQLSTATE: `42000' (`ER_WRONG_FIELD_SPEC')

     Message: Incorrect column specifier for column '%s'

   * Error: `1064' SQLSTATE: `42000' (`ER_PARSE_ERROR')

     Message: %s near '%s' at line %d

   * Error: `1065' SQLSTATE: `42000' (`ER_EMPTY_QUERY')

     Message: Query was empty

   * Error: `1066' SQLSTATE: `42000' (`ER_NONUNIQ_TABLE')

     Message: Not unique table/alias: '%s'

   * Error: `1067' SQLSTATE: `42000' (`ER_INVALID_DEFAULT')

     Message: Invalid default value for '%s'

   * Error: `1068' SQLSTATE: `42000' (`ER_MULTIPLE_PRI_KEY')

     Message: Multiple primary key defined

   * Error: `1069' SQLSTATE: `42000' (`ER_TOO_MANY_KEYS')

     Message: Too many keys specified; max %d keys allowed

   * Error: `1070' SQLSTATE: `42000' (`ER_TOO_MANY_KEY_PARTS')

     Message: Too many key parts specified; max %d parts allowed

   * Error: `1071' SQLSTATE: `42000' (`ER_TOO_LONG_KEY')

     Message: Specified key was too long; max key length is %d bytes

   * Error: `1072' SQLSTATE: `42000' (`ER_KEY_COLUMN_DOES_NOT_EXITS')

     Message: Key column '%s' doesn't exist in table

   * Error: `1073' SQLSTATE: `42000' (`ER_BLOB_USED_AS_KEY')

     Message: BLOB column '%s' can't be used in key specification with
     the used table type

   * Error: `1074' SQLSTATE: `42000' (`ER_TOO_BIG_FIELDLENGTH')

     Message: Column length too big for column '%s' (max = %lu); use
     BLOB or TEXT instead

   * Error: `1075' SQLSTATE: `42000' (`ER_WRONG_AUTO_KEY')

     Message: Incorrect table definition; there can be only one auto
     column and it must be defined as a key

   * Error: `1076' SQLSTATE: `HY000' (`ER_READY')

     Message: %s: ready for connections. Version: '%s' socket: '%s'
     port: %d

   * Error: `1077' SQLSTATE: `HY000' (`ER_NORMAL_SHUTDOWN')

     Message: %s: Normal shutdown

   * Error: `1078' SQLSTATE: `HY000' (`ER_GOT_SIGNAL')

     Message: %s: Got signal %d. Aborting!

   * Error: `1079' SQLSTATE: `HY000' (`ER_SHUTDOWN_COMPLETE')

     Message: %s: Shutdown complete

   * Error: `1080' SQLSTATE: `08S01' (`ER_FORCING_CLOSE')

     Message: %s: Forcing close of thread %ld user: '%s'

   * Error: `1081' SQLSTATE: `08S01' (`ER_IPSOCK_ERROR')

     Message: Can't create IP socket

   * Error: `1082' SQLSTATE: `42S12' (`ER_NO_SUCH_INDEX')

     Message: Table '%s' has no index like the one used in CREATE
     INDEX; recreate the table

   * Error: `1083' SQLSTATE: `42000' (`ER_WRONG_FIELD_TERMINATORS')

     Message: Field separator argument is not what is expected; check
     the manual

   * Error: `1084' SQLSTATE: `42000' (`ER_BLOBS_AND_NO_TERMINATED')

     Message: You can't use fixed rowlength with BLOBs; please use
     'fields terminated by'

   * Error: `1085' SQLSTATE: `HY000' (`ER_TEXTFILE_NOT_READABLE')

     Message: The file '%s' must be in the database directory or be
     readable by all

   * Error: `1086' SQLSTATE: `HY000' (`ER_FILE_EXISTS_ERROR')

     Message: File '%s' already exists

   * Error: `1087' SQLSTATE: `HY000' (`ER_LOAD_INFO')

     Message: Records: %ld Deleted: %ld Skipped: %ld Warnings: %ld

   * Error: `1088' SQLSTATE: `HY000' (`ER_ALTER_INFO')

     Message: Records: %ld Duplicates: %ld

   * Error: `1089' SQLSTATE: `HY000' (`ER_WRONG_SUB_KEY')

     Message: Incorrect prefix key; the used key part isn't a string,
     the used length is longer than the key part, or the storage engine
     doesn't support unique prefix keys

   * Error: `1090' SQLSTATE: `42000' (`ER_CANT_REMOVE_ALL_FIELDS')

     Message: You can't delete all columns with ALTER TABLE; use DROP
     TABLE instead

   * Error: `1091' SQLSTATE: `42000' (`ER_CANT_DROP_FIELD_OR_KEY')

     Message: Can't DROP '%s'; check that column/key exists

   * Error: `1092' SQLSTATE: `HY000' (`ER_INSERT_INFO')

     Message: Records: %ld Duplicates: %ld Warnings: %ld

   * Error: `1093' SQLSTATE: `HY000' (`ER_UPDATE_TABLE_USED')

     Message: You can't specify target table '%s' for update in FROM
     clause

   * Error: `1094' SQLSTATE: `HY000' (`ER_NO_SUCH_THREAD')

     Message: Unknown thread id: %lu

   * Error: `1095' SQLSTATE: `HY000' (`ER_KILL_DENIED_ERROR')

     Message: You are not owner of thread %lu

   * Error: `1096' SQLSTATE: `HY000' (`ER_NO_TABLES_USED')

     Message: No tables used

   * Error: `1097' SQLSTATE: `HY000' (`ER_TOO_BIG_SET')

     Message: Too many strings for column %s and SET

   * Error: `1098' SQLSTATE: `HY000' (`ER_NO_UNIQUE_LOGFILE')

     Message: Can't generate a unique log-filename %s.(1-999)

   * Error: `1099' SQLSTATE: `HY000' (`ER_TABLE_NOT_LOCKED_FOR_WRITE')

     Message: Table '%s' was locked with a READ lock and can't be
     updated

   * Error: `1100' SQLSTATE: `HY000' (`ER_TABLE_NOT_LOCKED')

     Message: Table '%s' was not locked with LOCK TABLES

   * Error: `1101' SQLSTATE: `42000' (`ER_BLOB_CANT_HAVE_DEFAULT')

     Message: BLOB/TEXT column '%s' can't have a default value

   * Error: `1102' SQLSTATE: `42000' (`ER_WRONG_DB_NAME')

     Message: Incorrect database name '%s'

   * Error: `1103' SQLSTATE: `42000' (`ER_WRONG_TABLE_NAME')

     Message: Incorrect table name '%s'

   * Error: `1104' SQLSTATE: `42000' (`ER_TOO_BIG_SELECT')

     Message: The SELECT would examine more than MAX_JOIN_SIZE rows;
     check your WHERE and use SET SQL_BIG_SELECTS=1 or SET
     MAX_JOIN_SIZE=# if the SELECT is okay

   * Error: `1105' SQLSTATE: `HY000' (`ER_UNKNOWN_ERROR')

     Message: Unknown error

   * Error: `1106' SQLSTATE: `42000' (`ER_UNKNOWN_PROCEDURE')

     Message: Unknown procedure '%s'

   * Error: `1107' SQLSTATE: `42000'
     (`ER_WRONG_PARAMCOUNT_TO_PROCEDURE')

     Message: Incorrect parameter count to procedure '%s'

   * Error: `1108' SQLSTATE: `HY000'
     (`ER_WRONG_PARAMETERS_TO_PROCEDURE')

     Message: Incorrect parameters to procedure '%s'

   * Error: `1109' SQLSTATE: `42S02' (`ER_UNKNOWN_TABLE')

     Message: Unknown table '%s' in %s

   * Error: `1110' SQLSTATE: `42000' (`ER_FIELD_SPECIFIED_TWICE')

     Message: Column '%s' specified twice

   * Error: `1111' SQLSTATE: `HY000' (`ER_INVALID_GROUP_FUNC_USE')

     Message: Invalid use of group function

   * Error: `1112' SQLSTATE: `42000' (`ER_UNSUPPORTED_EXTENSION')

     Message: Table '%s' uses an extension that doesn't exist in this
     MySQL version

   * Error: `1113' SQLSTATE: `42000' (`ER_TABLE_MUST_HAVE_COLUMNS')

     Message: A table must have at least 1 column

   * Error: `1114' SQLSTATE: `HY000' (`ER_RECORD_FILE_FULL')

     Message: The table '%s' is full

   * Error: `1115' SQLSTATE: `42000' (`ER_UNKNOWN_CHARACTER_SET')

     Message: Unknown character set: '%s'

   * Error: `1116' SQLSTATE: `HY000' (`ER_TOO_MANY_TABLES')

     Message: Too many tables; MySQL can only use %d tables in a join

   * Error: `1117' SQLSTATE: `HY000' (`ER_TOO_MANY_FIELDS')

     Message: Too many columns

   * Error: `1118' SQLSTATE: `42000' (`ER_TOO_BIG_ROWSIZE')

     Message: Row size too large. The maximum row size for the used
     table type, not counting BLOBs, is %ld. You have to change some
     columns to TEXT or BLOBs

   * Error: `1119' SQLSTATE: `HY000' (`ER_STACK_OVERRUN')

     Message: Thread stack overrun: Used: %ld of a %ld stack. Use
     'mysqld -O thread_stack=#' to specify a bigger stack if needed

   * Error: `1120' SQLSTATE: `42000' (`ER_WRONG_OUTER_JOIN')

     Message: Cross dependency found in OUTER JOIN; examine your ON
     conditions

   * Error: `1121' SQLSTATE: `42000' (`ER_NULL_COLUMN_IN_INDEX')

     Message: Table handler doesn't support NULL in given index. Please
     change column '%s' to be NOT NULL or use another handler

   * Error: `1122' SQLSTATE: `HY000' (`ER_CANT_FIND_UDF')

     Message: Can't load function '%s'

   * Error: `1123' SQLSTATE: `HY000' (`ER_CANT_INITIALIZE_UDF')

     Message: Can't initialize function '%s'; %s

   * Error: `1124' SQLSTATE: `HY000' (`ER_UDF_NO_PATHS')

     Message: No paths allowed for shared library

   * Error: `1125' SQLSTATE: `HY000' (`ER_UDF_EXISTS')

     Message: Function '%s' already exists

   * Error: `1126' SQLSTATE: `HY000' (`ER_CANT_OPEN_LIBRARY')

     Message: Can't open shared library '%s' (errno: %d %s)

   * Error: `1127' SQLSTATE: `HY000' (`ER_CANT_FIND_DL_ENTRY')

     Message: Can't find symbol '%s' in library

   * Error: `1128' SQLSTATE: `HY000' (`ER_FUNCTION_NOT_DEFINED')

     Message: Function '%s' is not defined

   * Error: `1129' SQLSTATE: `HY000' (`ER_HOST_IS_BLOCKED')

     Message: Host '%s' is blocked because of many connection errors;
     unblock with 'mysqladmin flush-hosts'

   * Error: `1130' SQLSTATE: `HY000' (`ER_HOST_NOT_PRIVILEGED')

     Message: Host '%s' is not allowed to connect to this MySQL server

   * Error: `1131' SQLSTATE: `42000' (`ER_PASSWORD_ANONYMOUS_USER')

     Message: You are using MySQL as an anonymous user and anonymous
     users are not allowed to change passwords

   * Error: `1132' SQLSTATE: `42000' (`ER_PASSWORD_NOT_ALLOWED')

     Message: You must have privileges to update tables in the mysql
     database to be able to change passwords for others

   * Error: `1133' SQLSTATE: `42000' (`ER_PASSWORD_NO_MATCH')

     Message: Can't find any matching row in the user table

   * Error: `1134' SQLSTATE: `HY000' (`ER_UPDATE_INFO')

     Message: Rows matched: %ld Changed: %ld Warnings: %ld

   * Error: `1135' SQLSTATE: `HY000' (`ER_CANT_CREATE_THREAD')

     Message: Can't create a new thread (errno %d); if you are not out
     of available memory, you can consult the manual for a possible
     OS-dependent bug

   * Error: `1136' SQLSTATE: `21S01' (`ER_WRONG_VALUE_COUNT_ON_ROW')

     Message: Column count doesn't match value count at row %ld

   * Error: `1137' SQLSTATE: `HY000' (`ER_CANT_REOPEN_TABLE')

     Message: Can't reopen table: '%s'

   * Error: `1138' SQLSTATE: `22004' (`ER_INVALID_USE_OF_NULL')

     Message: Invalid use of NULL value

   * Error: `1139' SQLSTATE: `42000' (`ER_REGEXP_ERROR')

     Message: Got error '%s' from regexp

   * Error: `1140' SQLSTATE: `42000' (`ER_MIX_OF_GROUP_FUNC_AND_FIELDS')

     Message: Mixing of GROUP columns (MIN(),MAX(),COUNT(),...) with no
     GROUP columns is illegal if there is no GROUP BY clause

   * Error: `1141' SQLSTATE: `42000' (`ER_NONEXISTING_GRANT')

     Message: There is no such grant defined for user '%s' on host '%s'

   * Error: `1142' SQLSTATE: `42000' (`ER_TABLEACCESS_DENIED_ERROR')

     Message: %s command denied to user '%s'@'%s' for table '%s'

   * Error: `1143' SQLSTATE: `42000' (`ER_COLUMNACCESS_DENIED_ERROR')

     Message: %s command denied to user '%s'@'%s' for column '%s' in
     table '%s'

   * Error: `1144' SQLSTATE: `42000' (`ER_ILLEGAL_GRANT_FOR_TABLE')

     Message: Illegal GRANT/REVOKE command; please consult the manual
     to see which privileges can be used

   * Error: `1145' SQLSTATE: `42000' (`ER_GRANT_WRONG_HOST_OR_USER')

     Message: The host or user argument to GRANT is too long

   * Error: `1146' SQLSTATE: `42S02' (`ER_NO_SUCH_TABLE')

     Message: Table '%s.%s' doesn't exist

   * Error: `1147' SQLSTATE: `42000' (`ER_NONEXISTING_TABLE_GRANT')

     Message: There is no such grant defined for user '%s' on host '%s'
     on table '%s'

   * Error: `1148' SQLSTATE: `42000' (`ER_NOT_ALLOWED_COMMAND')

     Message: The used command is not allowed with this MySQL version

   * Error: `1149' SQLSTATE: `42000' (`ER_SYNTAX_ERROR')

     Message: You have an error in your SQL syntax; check the manual
     that corresponds to your MySQL server version for the right syntax
     to use

   * Error: `1150' SQLSTATE: `HY000' (`ER_DELAYED_CANT_CHANGE_LOCK')

     Message: Delayed insert thread couldn't get requested lock for
     table %s

   * Error: `1151' SQLSTATE: `HY000' (`ER_TOO_MANY_DELAYED_THREADS')

     Message: Too many delayed threads in use

   * Error: `1152' SQLSTATE: `08S01' (`ER_ABORTING_CONNECTION')

     Message: Aborted connection %ld to db: '%s' user: '%s' (%s)

   * Error: `1153' SQLSTATE: `08S01' (`ER_NET_PACKET_TOO_LARGE')

     Message: Got a packet bigger than 'max_allowed_packet' bytes

   * Error: `1154' SQLSTATE: `08S01' (`ER_NET_READ_ERROR_FROM_PIPE')

     Message: Got a read error from the connection pipe

   * Error: `1155' SQLSTATE: `08S01' (`ER_NET_FCNTL_ERROR')

     Message: Got an error from fcntl()

   * Error: `1156' SQLSTATE: `08S01' (`ER_NET_PACKETS_OUT_OF_ORDER')

     Message: Got packets out of order

   * Error: `1157' SQLSTATE: `08S01' (`ER_NET_UNCOMPRESS_ERROR')

     Message: Couldn't uncompress communication packet

   * Error: `1158' SQLSTATE: `08S01' (`ER_NET_READ_ERROR')

     Message: Got an error reading communication packets

   * Error: `1159' SQLSTATE: `08S01' (`ER_NET_READ_INTERRUPTED')

     Message: Got timeout reading communication packets

   * Error: `1160' SQLSTATE: `08S01' (`ER_NET_ERROR_ON_WRITE')

     Message: Got an error writing communication packets

   * Error: `1161' SQLSTATE: `08S01' (`ER_NET_WRITE_INTERRUPTED')

     Message: Got timeout writing communication packets

   * Error: `1162' SQLSTATE: `42000' (`ER_TOO_LONG_STRING')

     Message: Result string is longer than 'max_allowed_packet' bytes

   * Error: `1163' SQLSTATE: `42000' (`ER_TABLE_CANT_HANDLE_BLOB')

     Message: The used table type doesn't support BLOB/TEXT columns

   * Error: `1164' SQLSTATE: `42000'
     (`ER_TABLE_CANT_HANDLE_AUTO_INCREMENT')

     Message: The used table type doesn't support AUTO_INCREMENT columns

   * Error: `1165' SQLSTATE: `HY000' (`ER_DELAYED_INSERT_TABLE_LOCKED')

     Message: INSERT DELAYED can't be used with table '%s' because it
     is locked with LOCK TABLES

   * Error: `1166' SQLSTATE: `42000' (`ER_WRONG_COLUMN_NAME')

     Message: Incorrect column name '%s'

   * Error: `1167' SQLSTATE: `42000' (`ER_WRONG_KEY_COLUMN')

     Message: The used storage engine can't index column '%s'

   * Error: `1168' SQLSTATE: `HY000' (`ER_WRONG_MRG_TABLE')

     Message: Unable to open underlying table which is differently
     defined or of non-MyISAM type or doesn't exist

   * Error: `1169' SQLSTATE: `23000' (`ER_DUP_UNIQUE')

     Message: Can't write, because of unique constraint, to table '%s'

   * Error: `1170' SQLSTATE: `42000' (`ER_BLOB_KEY_WITHOUT_LENGTH')

     Message: BLOB/TEXT column '%s' used in key specification without a
     key length

   * Error: `1171' SQLSTATE: `42000' (`ER_PRIMARY_CANT_HAVE_NULL')

     Message: All parts of a PRIMARY KEY must be NOT NULL; if you need
     NULL in a key, use UNIQUE instead

   * Error: `1172' SQLSTATE: `42000' (`ER_TOO_MANY_ROWS')

     Message: Result consisted of more than one row

   * Error: `1173' SQLSTATE: `42000' (`ER_REQUIRES_PRIMARY_KEY')

     Message: This table type requires a primary key

   * Error: `1174' SQLSTATE: `HY000' (`ER_NO_RAID_COMPILED')

     Message: This version of MySQL is not compiled with RAID support

   * Error: `1175' SQLSTATE: `HY000'
     (`ER_UPDATE_WITHOUT_KEY_IN_SAFE_MODE')

     Message: You are using safe update mode and you tried to update a
     table without a WHERE that uses a KEY column

   * Error: `1176' SQLSTATE: `42000' (`ER_KEY_DOES_NOT_EXITS')

     Message: Key '%s' doesn't exist in table '%s'

   * Error: `1177' SQLSTATE: `42000' (`ER_CHECK_NO_SUCH_TABLE')

     Message: Can't open table

   * Error: `1178' SQLSTATE: `42000' (`ER_CHECK_NOT_IMPLEMENTED')

     Message: The storage engine for the table doesn't support %s

   * Error: `1179' SQLSTATE: `25000'
     (`ER_CANT_DO_THIS_DURING_AN_TRANSACTION')

     Message: You are not allowed to execute this command in a
     transaction

   * Error: `1180' SQLSTATE: `HY000' (`ER_ERROR_DURING_COMMIT')

     Message: Got error %d during COMMIT

   * Error: `1181' SQLSTATE: `HY000' (`ER_ERROR_DURING_ROLLBACK')

     Message: Got error %d during ROLLBACK

   * Error: `1182' SQLSTATE: `HY000' (`ER_ERROR_DURING_FLUSH_LOGS')

     Message: Got error %d during FLUSH_LOGS

   * Error: `1183' SQLSTATE: `HY000' (`ER_ERROR_DURING_CHECKPOINT')

     Message: Got error %d during CHECKPOINT

   * Error: `1184' SQLSTATE: `08S01' (`ER_NEW_ABORTING_CONNECTION')

     Message: Aborted connection %ld to db: '%s' user: '%s' host: '%s'
     (%s)

   * Error: `1185' SQLSTATE: `HY000' (`ER_DUMP_NOT_IMPLEMENTED')

     Message: The storage engine for the table does not support binary
     table dump

   * Error: `1186' SQLSTATE: `HY000' (`ER_FLUSH_MASTER_BINLOG_CLOSED')

     Message: Binlog closed, cannot RESET MASTER

   * Error: `1187' SQLSTATE: `HY000' (`ER_INDEX_REBUILD')

     Message: Failed rebuilding the index of dumped table '%s'

   * Error: `1188' SQLSTATE: `HY000' (`ER_MASTER')

     Message: Error from master: '%s'

   * Error: `1189' SQLSTATE: `08S01' (`ER_MASTER_NET_READ')

     Message: Net error reading from master

   * Error: `1190' SQLSTATE: `08S01' (`ER_MASTER_NET_WRITE')

     Message: Net error writing to master

   * Error: `1191' SQLSTATE: `HY000' (`ER_FT_MATCHING_KEY_NOT_FOUND')

     Message: Can't find FULLTEXT index matching the column list

   * Error: `1192' SQLSTATE: `HY000' (`ER_LOCK_OR_ACTIVE_TRANSACTION')

     Message: Can't execute the given command because you have active
     locked tables or an active transaction

   * Error: `1193' SQLSTATE: `HY000' (`ER_UNKNOWN_SYSTEM_VARIABLE')

     Message: Unknown system variable '%s'

   * Error: `1194' SQLSTATE: `HY000' (`ER_CRASHED_ON_USAGE')

     Message: Table '%s' is marked as crashed and should be repaired

   * Error: `1195' SQLSTATE: `HY000' (`ER_CRASHED_ON_REPAIR')

     Message: Table '%s' is marked as crashed and last (automatic?)
     repair failed

   * Error: `1196' SQLSTATE: `HY000'
     (`ER_WARNING_NOT_COMPLETE_ROLLBACK')

     Message: Some non-transactional changed tables couldn't be rolled
     back

   * Error: `1197' SQLSTATE: `HY000' (`ER_TRANS_CACHE_FULL')

     Message: Multi-statement transaction required more than
     'max_binlog_cache_size' bytes of storage; increase this mysqld
     variable and try again

   * Error: `1198' SQLSTATE: `HY000' (`ER_SLAVE_MUST_STOP')

     Message: This operation cannot be performed with a running slave;
     run STOP SLAVE first

   * Error: `1199' SQLSTATE: `HY000' (`ER_SLAVE_NOT_RUNNING')

     Message: This operation requires a running slave; configure slave
     and do START SLAVE

   * Error: `1200' SQLSTATE: `HY000' (`ER_BAD_SLAVE')

     Message: The server is not configured as slave; fix in config file
     or with CHANGE MASTER TO

   * Error: `1201' SQLSTATE: `HY000' (`ER_MASTER_INFO')

     Message: Could not initialize master info structure; more error
     messages can be found in the MySQL error log

   * Error: `1202' SQLSTATE: `HY000' (`ER_SLAVE_THREAD')

     Message: Could not create slave thread; check system resources

   * Error: `1203' SQLSTATE: `42000' (`ER_TOO_MANY_USER_CONNECTIONS')

     Message: User %s already has more than 'max_user_connections'
     active connections

   * Error: `1204' SQLSTATE: `HY000' (`ER_SET_CONSTANTS_ONLY')

     Message: You may only use constant expressions with SET

   * Error: `1205' SQLSTATE: `HY000' (`ER_LOCK_WAIT_TIMEOUT')

     Message: Lock wait timeout exceeded; try restarting transaction

   * Error: `1206' SQLSTATE: `HY000' (`ER_LOCK_TABLE_FULL')

     Message: The total number of locks exceeds the lock table size

   * Error: `1207' SQLSTATE: `25000' (`ER_READ_ONLY_TRANSACTION')

     Message: Update locks cannot be acquired during a READ UNCOMMITTED
     transaction

   * Error: `1208' SQLSTATE: `HY000' (`ER_DROP_DB_WITH_READ_LOCK')

     Message: DROP DATABASE not allowed while thread is holding global
     read lock

   * Error: `1209' SQLSTATE: `HY000' (`ER_CREATE_DB_WITH_READ_LOCK')

     Message: CREATE DATABASE not allowed while thread is holding
     global read lock

   * Error: `1210' SQLSTATE: `HY000' (`ER_WRONG_ARGUMENTS')

     Message: Incorrect arguments to %s

   * Error: `1211' SQLSTATE: `42000' (`ER_NO_PERMISSION_TO_CREATE_USER')

     Message: '%s'@'%s' is not allowed to create new users

   * Error: `1212' SQLSTATE: `HY000'
     (`ER_UNION_TABLES_IN_DIFFERENT_DIR')

     Message: Incorrect table definition; all MERGE tables must be in
     the same database

   * Error: `1213' SQLSTATE: `40001' (`ER_LOCK_DEADLOCK')

     Message: Deadlock found when trying to get lock; try restarting
     transaction

   * Error: `1214' SQLSTATE: `HY000' (`ER_TABLE_CANT_HANDLE_FT')

     Message: The used table type doesn't support FULLTEXT indexes

   * Error: `1215' SQLSTATE: `HY000' (`ER_CANNOT_ADD_FOREIGN')

     Message: Cannot add foreign key constraint

   * Error: `1216' SQLSTATE: `23000' (`ER_NO_REFERENCED_ROW')

     Message: Cannot add or update a child row: a foreign key
     constraint fails

   * Error: `1217' SQLSTATE: `23000' (`ER_ROW_IS_REFERENCED')

     Message: Cannot delete or update a parent row: a foreign key
     constraint fails

   * Error: `1218' SQLSTATE: `08S01' (`ER_CONNECT_TO_MASTER')

     Message: Error connecting to master: %s

   * Error: `1219' SQLSTATE: `HY000' (`ER_QUERY_ON_MASTER')

     Message: Error running query on master: %s

   * Error: `1220' SQLSTATE: `HY000' (`ER_ERROR_WHEN_EXECUTING_COMMAND')

     Message: Error when executing command %s: %s

   * Error: `1221' SQLSTATE: `HY000' (`ER_WRONG_USAGE')

     Message: Incorrect usage of %s and %s

   * Error: `1222' SQLSTATE: `21000'
     (`ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT')

     Message: The used SELECT statements have a different number of
     columns

   * Error: `1223' SQLSTATE: `HY000' (`ER_CANT_UPDATE_WITH_READLOCK')

     Message: Can't execute the query because you have a conflicting
     read lock

   * Error: `1224' SQLSTATE: `HY000' (`ER_MIXING_NOT_ALLOWED')

     Message: Mixing of transactional and non-transactional tables is
     disabled

   * Error: `1225' SQLSTATE: `HY000' (`ER_DUP_ARGUMENT')

     Message: Option '%s' used twice in statement

   * Error: `1226' SQLSTATE: `42000' (`ER_USER_LIMIT_REACHED')

     Message: User '%s' has exceeded the '%s' resource (current value:
     %ld)

   * Error: `1227' SQLSTATE: `42000' (`ER_SPECIFIC_ACCESS_DENIED_ERROR')

     Message: Access denied; you need the %s privilege for this
     operation

   * Error: `1228' SQLSTATE: `HY000' (`ER_LOCAL_VARIABLE')

     Message: Variable '%s' is a SESSION variable and can't be used
     with SET GLOBAL

   * Error: `1229' SQLSTATE: `HY000' (`ER_GLOBAL_VARIABLE')

     Message: Variable '%s' is a GLOBAL variable and should be set with
     SET GLOBAL

   * Error: `1230' SQLSTATE: `42000' (`ER_NO_DEFAULT')

     Message: Variable '%s' doesn't have a default value

   * Error: `1231' SQLSTATE: `42000' (`ER_WRONG_VALUE_FOR_VAR')

     Message: Variable '%s' can't be set to the value of '%s'

   * Error: `1232' SQLSTATE: `42000' (`ER_WRONG_TYPE_FOR_VAR')

     Message: Incorrect argument type to variable '%s'

   * Error: `1233' SQLSTATE: `HY000' (`ER_VAR_CANT_BE_READ')

     Message: Variable '%s' can only be set, not read

   * Error: `1234' SQLSTATE: `42000' (`ER_CANT_USE_OPTION_HERE')

     Message: Incorrect usage/placement of '%s'

   * Error: `1235' SQLSTATE: `42000' (`ER_NOT_SUPPORTED_YET')

     Message: This version of MySQL doesn't yet support '%s'

   * Error: `1236' SQLSTATE: `HY000'
     (`ER_MASTER_FATAL_ERROR_READING_BINLOG')

     Message: Got fatal error %d from master when reading data from
     binary log: '%s'

   * Error: `1237' SQLSTATE: `HY000' (`ER_SLAVE_IGNORED_TABLE')

     Message: Slave SQL thread ignored the query because of
     replicate-*-table rules

   * Error: `1238' SQLSTATE: `HY000' (`ER_INCORRECT_GLOBAL_LOCAL_VAR')

     Message: Variable '%s' is a %s variable

   * Error: `1239' SQLSTATE: `42000' (`ER_WRONG_FK_DEF')

     Message: Incorrect foreign key definition for '%s': %s

   * Error: `1240' SQLSTATE: `HY000'
     (`ER_KEY_REF_DO_NOT_MATCH_TABLE_REF')

     Message: Key reference and table reference don't match

   * Error: `1241' SQLSTATE: `21000' (`ER_OPERAND_COLUMNS')

     Message: Operand should contain %d column(s)

   * Error: `1242' SQLSTATE: `21000' (`ER_SUBQUERY_NO_1_ROW')

     Message: Subquery returns more than 1 row

   * Error: `1243' SQLSTATE: `HY000' (`ER_UNKNOWN_STMT_HANDLER')

     Message: Unknown prepared statement handler (%.*s) given to %s

   * Error: `1244' SQLSTATE: `HY000' (`ER_CORRUPT_HELP_DB')

     Message: Help database is corrupt or does not exist

   * Error: `1245' SQLSTATE: `HY000' (`ER_CYCLIC_REFERENCE')

     Message: Cyclic reference on subqueries

   * Error: `1246' SQLSTATE: `HY000' (`ER_AUTO_CONVERT')

     Message: Converting column '%s' from %s to %s

   * Error: `1247' SQLSTATE: `42S22' (`ER_ILLEGAL_REFERENCE')

     Message: Reference '%s' not supported (%s)

   * Error: `1248' SQLSTATE: `42000' (`ER_DERIVED_MUST_HAVE_ALIAS')

     Message: Every derived table must have its own alias

   * Error: `1249' SQLSTATE: `01000' (`ER_SELECT_REDUCED')

     Message: Select %u was reduced during optimization

   * Error: `1250' SQLSTATE: `42000' (`ER_TABLENAME_NOT_ALLOWED_HERE')

     Message: Table '%s' from one of the SELECTs cannot be used in %s

   * Error: `1251' SQLSTATE: `08004' (`ER_NOT_SUPPORTED_AUTH_MODE')

     Message: Client does not support authentication protocol requested
     by server; consider upgrading MySQL client

   * Error: `1252' SQLSTATE: `42000' (`ER_SPATIAL_CANT_HAVE_NULL')

     Message: All parts of a SPATIAL index must be NOT NULL

   * Error: `1253' SQLSTATE: `42000' (`ER_COLLATION_CHARSET_MISMATCH')

     Message: COLLATION '%s' is not valid for CHARACTER SET '%s'

   * Error: `1254' SQLSTATE: `HY000' (`ER_SLAVE_WAS_RUNNING')

     Message: Slave is already running

   * Error: `1255' SQLSTATE: `HY000' (`ER_SLAVE_WAS_NOT_RUNNING')

     Message: Slave already has been stopped

   * Error: `1256' SQLSTATE: `HY000' (`ER_TOO_BIG_FOR_UNCOMPRESS')

     Message: Uncompressed data size too large; the maximum size is %d
     (probably, length of uncompressed data was corrupted)

   * Error: `1257' SQLSTATE: `HY000' (`ER_ZLIB_Z_MEM_ERROR')

     Message: ZLIB: Not enough memory

   * Error: `1258' SQLSTATE: `HY000' (`ER_ZLIB_Z_BUF_ERROR')

     Message: ZLIB: Not enough room in the output buffer (probably,
     length of uncompressed data was corrupted)

   * Error: `1259' SQLSTATE: `HY000' (`ER_ZLIB_Z_DATA_ERROR')

     Message: ZLIB: Input data corrupted

   * Error: `1260' SQLSTATE: `HY000' (`ER_CUT_VALUE_GROUP_CONCAT')

     Message: %d line(s) were cut by GROUP_CONCAT()

   * Error: `1261' SQLSTATE: `01000' (`ER_WARN_TOO_FEW_RECORDS')

     Message: Row %ld doesn't contain data for all columns

   * Error: `1262' SQLSTATE: `01000' (`ER_WARN_TOO_MANY_RECORDS')

     Message: Row %ld was truncated; it contained more data than there
     were input columns

   * Error: `1263' SQLSTATE: `22004' (`ER_WARN_NULL_TO_NOTNULL')

     Message: Column set to default value; NULL supplied to NOT NULL
     column '%s' at row %ld

   * Error: `1264' SQLSTATE: `22003' (`ER_WARN_DATA_OUT_OF_RANGE')

     Message: Out of range value for column '%s' at row %ld

   * Error: `1265' SQLSTATE: `01000' (`WARN_DATA_TRUNCATED')

     Message: Data truncated for column '%s' at row %ld

   * Error: `1266' SQLSTATE: `HY000' (`ER_WARN_USING_OTHER_HANDLER')

     Message: Using storage engine %s for table '%s'

   * Error: `1267' SQLSTATE: `HY000' (`ER_CANT_AGGREGATE_2COLLATIONS')

     Message: Illegal mix of collations (%s,%s) and (%s,%s) for
     operation '%s'

   * Error: `1268' SQLSTATE: `HY000' (`ER_DROP_USER')

     Message: Cannot drop one or more of the requested users

   * Error: `1269' SQLSTATE: `HY000' (`ER_REVOKE_GRANTS')

     Message: Can't revoke all privileges for one or more of the
     requested users

   * Error: `1270' SQLSTATE: `HY000' (`ER_CANT_AGGREGATE_3COLLATIONS')

     Message: Illegal mix of collations (%s,%s), (%s,%s), (%s,%s) for
     operation '%s'

   * Error: `1271' SQLSTATE: `HY000' (`ER_CANT_AGGREGATE_NCOLLATIONS')

     Message: Illegal mix of collations for operation '%s'

   * Error: `1272' SQLSTATE: `HY000' (`ER_VARIABLE_IS_NOT_STRUCT')

     Message: Variable '%s' is not a variable component (can't be used
     as XXXX.variable_name)

   * Error: `1273' SQLSTATE: `HY000' (`ER_UNKNOWN_COLLATION')

     Message: Unknown collation: '%s'

   * Error: `1274' SQLSTATE: `HY000' (`ER_SLAVE_IGNORED_SSL_PARAMS')

     Message: SSL parameters in CHANGE MASTER are ignored because this
     MySQL slave was compiled without SSL support; they can be used
     later if MySQL slave with SSL is started

   * Error: `1275' SQLSTATE: `HY000'
     (`ER_SERVER_IS_IN_SECURE_AUTH_MODE')

     Message: Server is running in -secure-auth mode, but '%s'@'%s' has
     a password in the old format; please change the password to the
     new format

   * Error: `1276' SQLSTATE: `HY000' (`ER_WARN_FIELD_RESOLVED')

     Message: Field or reference '%s%s%s%s%s' of SELECT #%d was
     resolved in SELECT #%d

   * Error: `1277' SQLSTATE: `HY000' (`ER_BAD_SLAVE_UNTIL_COND')

     Message: Incorrect parameter or combination of parameters for
     START SLAVE UNTIL

   * Error: `1278' SQLSTATE: `HY000' (`ER_MISSING_SKIP_SLAVE')

     Message: It is recommended to use -skip-slave-start when doing
     step-by-step replication with START SLAVE UNTIL; otherwise, you
     will get problems if you get an unexpected slave's mysqld restart

   * Error: `1279' SQLSTATE: `HY000' (`ER_UNTIL_COND_IGNORED')

     Message: SQL thread is not to be started so UNTIL options are
     ignored

   * Error: `1280' SQLSTATE: `42000' (`ER_WRONG_NAME_FOR_INDEX')

     Message: Incorrect index name '%s'

   * Error: `1281' SQLSTATE: `42000' (`ER_WRONG_NAME_FOR_CATALOG')

     Message: Incorrect catalog name '%s'

   * Error: `1282' SQLSTATE: `HY000' (`ER_WARN_QC_RESIZE')

     Message: Query cache failed to set size %lu; new query cache size
     is %lu

   * Error: `1283' SQLSTATE: `HY000' (`ER_BAD_FT_COLUMN')

     Message: Column '%s' cannot be part of FULLTEXT index

   * Error: `1284' SQLSTATE: `HY000' (`ER_UNKNOWN_KEY_CACHE')

     Message: Unknown key cache '%s'

   * Error: `1285' SQLSTATE: `HY000' (`ER_WARN_HOSTNAME_WONT_WORK')

     Message: MySQL is started in -skip-name-resolve mode; you must
     restart it without this switch for this grant to work

   * Error: `1286' SQLSTATE: `42000' (`ER_UNKNOWN_STORAGE_ENGINE')

     Message: Unknown table engine '%s'

   * Error: `1287' SQLSTATE: `HY000' (`ER_UNUSED_1')

     Message: '%s' is deprecated; use '%s' instead

     `ER_UNUSED_1' was introduced in 5.1.9, removed after 5.1.19.

   * Error: `1287' SQLSTATE: `HY000' (`ER_WARN_DEPRECATED_SYNTAX')

     Message: '%s' is deprecated and will be removed in a future
     release. Please use %s instead

   * Error: `1288' SQLSTATE: `HY000' (`ER_NON_UPDATABLE_TABLE')

     Message: The target table %s of the %s is not updatable

   * Error: `1289' SQLSTATE: `HY000' (`ER_FEATURE_DISABLED')

     Message: The '%s' feature is disabled; you need MySQL built with
     '%s' to have it working

   * Error: `1290' SQLSTATE: `HY000' (`ER_OPTION_PREVENTS_STATEMENT')

     Message: The MySQL server is running with the %s option so it
     cannot execute this statement

   * Error: `1291' SQLSTATE: `HY000' (`ER_DUPLICATED_VALUE_IN_TYPE')

     Message: Column '%s' has duplicated value '%s' in %s

   * Error: `1292' SQLSTATE: `22007' (`ER_TRUNCATED_WRONG_VALUE')

     Message: Truncated incorrect %s value: '%s'

   * Error: `1293' SQLSTATE: `HY000' (`ER_TOO_MUCH_AUTO_TIMESTAMP_COLS')

     Message: Incorrect table definition; there can be only one
     TIMESTAMP column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE
     clause

   * Error: `1294' SQLSTATE: `HY000' (`ER_INVALID_ON_UPDATE')

     Message: Invalid ON UPDATE clause for '%s' column

   * Error: `1295' SQLSTATE: `HY000' (`ER_UNSUPPORTED_PS')

     Message: This command is not supported in the prepared statement
     protocol yet

   * Error: `1296' SQLSTATE: `HY000' (`ER_GET_ERRMSG')

     Message: Got error %d '%s' from %s

   * Error: `1297' SQLSTATE: `HY000' (`ER_GET_TEMPORARY_ERRMSG')

     Message: Got temporary error %d '%s' from %s

   * Error: `1298' SQLSTATE: `HY000' (`ER_UNKNOWN_TIME_ZONE')

     Message: Unknown or incorrect time zone: '%s'

   * Error: `1299' SQLSTATE: `HY000' (`ER_WARN_INVALID_TIMESTAMP')

     Message: Invalid TIMESTAMP value in column '%s' at row %ld

   * Error: `1300' SQLSTATE: `HY000' (`ER_INVALID_CHARACTER_STRING')

     Message: Invalid %s character string: '%s'

   * Error: `1301' SQLSTATE: `HY000'
     (`ER_WARN_ALLOWED_PACKET_OVERFLOWED')

     Message: Result of %s() was larger than max_allowed_packet (%ld) -
     truncated

   * Error: `1302' SQLSTATE: `HY000' (`ER_CONFLICTING_DECLARATIONS')

     Message: Conflicting declarations: '%s%s' and '%s%s'

   * Error: `1303' SQLSTATE: `2F003' (`ER_SP_NO_RECURSIVE_CREATE')

     Message: Can't create a %s from within another stored routine

   * Error: `1304' SQLSTATE: `42000' (`ER_SP_ALREADY_EXISTS')

     Message: %s %s already exists

   * Error: `1305' SQLSTATE: `42000' (`ER_SP_DOES_NOT_EXIST')

     Message: %s %s does not exist

   * Error: `1306' SQLSTATE: `HY000' (`ER_SP_DROP_FAILED')

     Message: Failed to DROP %s %s

   * Error: `1307' SQLSTATE: `HY000' (`ER_SP_STORE_FAILED')

     Message: Failed to CREATE %s %s

   * Error: `1308' SQLSTATE: `42000' (`ER_SP_LILABEL_MISMATCH')

     Message: %s with no matching label: %s

   * Error: `1309' SQLSTATE: `42000' (`ER_SP_LABEL_REDEFINE')

     Message: Redefining label %s

   * Error: `1310' SQLSTATE: `42000' (`ER_SP_LABEL_MISMATCH')

     Message: End-label %s without match

   * Error: `1311' SQLSTATE: `01000' (`ER_SP_UNINIT_VAR')

     Message: Referring to uninitialized variable %s

   * Error: `1312' SQLSTATE: `0A000' (`ER_SP_BADSELECT')

     Message: PROCEDURE %s can't return a result set in the given
     context

   * Error: `1313' SQLSTATE: `42000' (`ER_SP_BADRETURN')

     Message: RETURN is only allowed in a FUNCTION

   * Error: `1314' SQLSTATE: `0A000' (`ER_SP_BADSTATEMENT')

     Message: %s is not allowed in stored procedures

   * Error: `1315' SQLSTATE: `42000'
     (`ER_UPDATE_LOG_DEPRECATED_IGNORED')

     Message: The update log is deprecated and replaced by the binary
     log; SET SQL_LOG_UPDATE has been ignored. This option will be
     removed in MySQL 5.6.

   * Error: `1316' SQLSTATE: `42000'
     (`ER_UPDATE_LOG_DEPRECATED_TRANSLATED')

     Message: The update log is deprecated and replaced by the binary
     log; SET SQL_LOG_UPDATE has been translated to SET SQL_LOG_BIN.
     This option will be removed in MySQL 5.6.

   * Error: `1317' SQLSTATE: `70100' (`ER_QUERY_INTERRUPTED')

     Message: Query execution was interrupted

   * Error: `1318' SQLSTATE: `42000' (`ER_SP_WRONG_NO_OF_ARGS')

     Message: Incorrect number of arguments for %s %s; expected %u, got
     %u

   * Error: `1319' SQLSTATE: `42000' (`ER_SP_COND_MISMATCH')

     Message: Undefined CONDITION: %s

   * Error: `1320' SQLSTATE: `42000' (`ER_SP_NORETURN')

     Message: No RETURN found in FUNCTION %s

   * Error: `1321' SQLSTATE: `2F005' (`ER_SP_NORETURNEND')

     Message: FUNCTION %s ended without RETURN

   * Error: `1322' SQLSTATE: `42000' (`ER_SP_BAD_CURSOR_QUERY')

     Message: Cursor statement must be a SELECT

   * Error: `1323' SQLSTATE: `42000' (`ER_SP_BAD_CURSOR_SELECT')

     Message: Cursor SELECT must not have INTO

   * Error: `1324' SQLSTATE: `42000' (`ER_SP_CURSOR_MISMATCH')

     Message: Undefined CURSOR: %s

   * Error: `1325' SQLSTATE: `24000' (`ER_SP_CURSOR_ALREADY_OPEN')

     Message: Cursor is already open

   * Error: `1326' SQLSTATE: `24000' (`ER_SP_CURSOR_NOT_OPEN')

     Message: Cursor is not open

   * Error: `1327' SQLSTATE: `42000' (`ER_SP_UNDECLARED_VAR')

     Message: Undeclared variable: %s

   * Error: `1328' SQLSTATE: `HY000' (`ER_SP_WRONG_NO_OF_FETCH_ARGS')

     Message: Incorrect number of FETCH variables

   * Error: `1329' SQLSTATE: `02000' (`ER_SP_FETCH_NO_DATA')

     Message: No data - zero rows fetched, selected, or processed

   * Error: `1330' SQLSTATE: `42000' (`ER_SP_DUP_PARAM')

     Message: Duplicate parameter: %s

   * Error: `1331' SQLSTATE: `42000' (`ER_SP_DUP_VAR')

     Message: Duplicate variable: %s

   * Error: `1332' SQLSTATE: `42000' (`ER_SP_DUP_COND')

     Message: Duplicate condition: %s

   * Error: `1333' SQLSTATE: `42000' (`ER_SP_DUP_CURS')

     Message: Duplicate cursor: %s

   * Error: `1334' SQLSTATE: `HY000' (`ER_SP_CANT_ALTER')

     Message: Failed to ALTER %s %s

   * Error: `1335' SQLSTATE: `0A000' (`ER_SP_SUBSELECT_NYI')

     Message: Subquery value not supported

   * Error: `1336' SQLSTATE: `0A000'
     (`ER_STMT_NOT_ALLOWED_IN_SF_OR_TRG')

     Message: %s is not allowed in stored function or trigger

   * Error: `1337' SQLSTATE: `42000' (`ER_SP_VARCOND_AFTER_CURSHNDLR')

     Message: Variable or condition declaration after cursor or handler
     declaration

   * Error: `1338' SQLSTATE: `42000' (`ER_SP_CURSOR_AFTER_HANDLER')

     Message: Cursor declaration after handler declaration

   * Error: `1339' SQLSTATE: `20000' (`ER_SP_CASE_NOT_FOUND')

     Message: Case not found for CASE statement

   * Error: `1340' SQLSTATE: `HY000' (`ER_FPARSER_TOO_BIG_FILE')

     Message: Configuration file '%s' is too big

   * Error: `1341' SQLSTATE: `HY000' (`ER_FPARSER_BAD_HEADER')

     Message: Malformed file type header in file '%s'

   * Error: `1342' SQLSTATE: `HY000' (`ER_FPARSER_EOF_IN_COMMENT')

     Message: Unexpected end of file while parsing comment '%s'

   * Error: `1343' SQLSTATE: `HY000' (`ER_FPARSER_ERROR_IN_PARAMETER')

     Message: Error while parsing parameter '%s' (line: '%s')

   * Error: `1344' SQLSTATE: `HY000'
     (`ER_FPARSER_EOF_IN_UNKNOWN_PARAMETER')

     Message: Unexpected end of file while skipping unknown parameter
     '%s'

   * Error: `1345' SQLSTATE: `HY000' (`ER_VIEW_NO_EXPLAIN')

     Message: EXPLAIN/SHOW can not be issued; lacking privileges for
     underlying table

   * Error: `1346' SQLSTATE: `HY000' (`ER_FRM_UNKNOWN_TYPE')

     Message: File '%s' has unknown type '%s' in its header

   * Error: `1347' SQLSTATE: `HY000' (`ER_WRONG_OBJECT')

     Message: '%s.%s' is not %s

   * Error: `1348' SQLSTATE: `HY000' (`ER_NONUPDATEABLE_COLUMN')

     Message: Column '%s' is not updatable

   * Error: `1349' SQLSTATE: `HY000' (`ER_VIEW_SELECT_DERIVED')

     Message: View's SELECT contains a subquery in the FROM clause

   * Error: `1350' SQLSTATE: `HY000' (`ER_VIEW_SELECT_CLAUSE')

     Message: View's SELECT contains a '%s' clause

   * Error: `1351' SQLSTATE: `HY000' (`ER_VIEW_SELECT_VARIABLE')

     Message: View's SELECT contains a variable or parameter

   * Error: `1352' SQLSTATE: `HY000' (`ER_VIEW_SELECT_TMPTABLE')

     Message: View's SELECT refers to a temporary table '%s'

   * Error: `1353' SQLSTATE: `HY000' (`ER_VIEW_WRONG_LIST')

     Message: View's SELECT and view's field list have different column
     counts

   * Error: `1354' SQLSTATE: `HY000' (`ER_WARN_VIEW_MERGE')

     Message: View merge algorithm can't be used here for now (assumed
     undefined algorithm)

   * Error: `1355' SQLSTATE: `HY000' (`ER_WARN_VIEW_WITHOUT_KEY')

     Message: View being updated does not have complete key of
     underlying table in it

   * Error: `1356' SQLSTATE: `HY000' (`ER_VIEW_INVALID')

     Message: View '%s.%s' references invalid table(s) or column(s) or
     function(s) or definer/invoker of view lack rights to use them

   * Error: `1357' SQLSTATE: `HY000' (`ER_SP_NO_DROP_SP')

     Message: Can't drop or alter a %s from within another stored
     routine

   * Error: `1358' SQLSTATE: `HY000' (`ER_SP_GOTO_IN_HNDLR')

     Message: GOTO is not allowed in a stored procedure handler

   * Error: `1359' SQLSTATE: `HY000' (`ER_TRG_ALREADY_EXISTS')

     Message: Trigger already exists

   * Error: `1360' SQLSTATE: `HY000' (`ER_TRG_DOES_NOT_EXIST')

     Message: Trigger does not exist

   * Error: `1361' SQLSTATE: `HY000' (`ER_TRG_ON_VIEW_OR_TEMP_TABLE')

     Message: Trigger's '%s' is view or temporary table

   * Error: `1362' SQLSTATE: `HY000' (`ER_TRG_CANT_CHANGE_ROW')

     Message: Updating of %s row is not allowed in %strigger

   * Error: `1363' SQLSTATE: `HY000' (`ER_TRG_NO_SUCH_ROW_IN_TRG')

     Message: There is no %s row in %s trigger

   * Error: `1364' SQLSTATE: `HY000' (`ER_NO_DEFAULT_FOR_FIELD')

     Message: Field '%s' doesn't have a default value

   * Error: `1365' SQLSTATE: `22012' (`ER_DIVISION_BY_ZERO')

     Message: Division by 0

   * Error: `1366' SQLSTATE: `HY000'
     (`ER_TRUNCATED_WRONG_VALUE_FOR_FIELD')

     Message: Incorrect %s value: '%s' for column '%s' at row %ld

   * Error: `1367' SQLSTATE: `22007' (`ER_ILLEGAL_VALUE_FOR_TYPE')

     Message: Illegal %s '%s' value found during parsing

   * Error: `1368' SQLSTATE: `HY000' (`ER_VIEW_NONUPD_CHECK')

     Message: CHECK OPTION on non-updatable view '%s.%s'

   * Error: `1369' SQLSTATE: `HY000' (`ER_VIEW_CHECK_FAILED')

     Message: CHECK OPTION failed '%s.%s'

   * Error: `1370' SQLSTATE: `42000' (`ER_PROCACCESS_DENIED_ERROR')

     Message: %s command denied to user '%s'@'%s' for routine '%s'

   * Error: `1371' SQLSTATE: `HY000' (`ER_RELAY_LOG_FAIL')

     Message: Failed purging old relay logs: %s

   * Error: `1372' SQLSTATE: `HY000' (`ER_PASSWD_LENGTH')

     Message: Password hash should be a %d-digit hexadecimal number

   * Error: `1373' SQLSTATE: `HY000' (`ER_UNKNOWN_TARGET_BINLOG')

     Message: Target log not found in binlog index

   * Error: `1374' SQLSTATE: `HY000' (`ER_IO_ERR_LOG_INDEX_READ')

     Message: I/O error reading log index file

   * Error: `1375' SQLSTATE: `HY000' (`ER_BINLOG_PURGE_PROHIBITED')

     Message: Server configuration does not permit binlog purge

   * Error: `1376' SQLSTATE: `HY000' (`ER_FSEEK_FAIL')

     Message: Failed on fseek()

   * Error: `1377' SQLSTATE: `HY000' (`ER_BINLOG_PURGE_FATAL_ERR')

     Message: Fatal error during log purge

   * Error: `1378' SQLSTATE: `HY000' (`ER_LOG_IN_USE')

     Message: A purgeable log is in use, will not purge

   * Error: `1379' SQLSTATE: `HY000' (`ER_LOG_PURGE_UNKNOWN_ERR')

     Message: Unknown error during log purge

   * Error: `1380' SQLSTATE: `HY000' (`ER_RELAY_LOG_INIT')

     Message: Failed initializing relay log position: %s

   * Error: `1381' SQLSTATE: `HY000' (`ER_NO_BINARY_LOGGING')

     Message: You are not using binary logging

   * Error: `1382' SQLSTATE: `HY000' (`ER_RESERVED_SYNTAX')

     Message: The '%s' syntax is reserved for purposes internal to the
     MySQL server

   * Error: `1383' SQLSTATE: `HY000' (`ER_WSAS_FAILED')

     Message: WSAStartup Failed

   * Error: `1384' SQLSTATE: `HY000' (`ER_DIFF_GROUPS_PROC')

     Message: Can't handle procedures with different groups yet

   * Error: `1385' SQLSTATE: `HY000' (`ER_NO_GROUP_FOR_PROC')

     Message: Select must have a group with this procedure

   * Error: `1386' SQLSTATE: `HY000' (`ER_ORDER_WITH_PROC')

     Message: Can't use ORDER clause with this procedure

   * Error: `1387' SQLSTATE: `HY000' (`ER_LOGGING_PROHIBIT_CHANGING_OF')

     Message: Binary logging and replication forbid changing the global
     server %s

   * Error: `1388' SQLSTATE: `HY000' (`ER_NO_FILE_MAPPING')

     Message: Can't map file: %s, errno: %d

   * Error: `1389' SQLSTATE: `HY000' (`ER_WRONG_MAGIC')

     Message: Wrong magic in %s

   * Error: `1390' SQLSTATE: `HY000' (`ER_PS_MANY_PARAM')

     Message: Prepared statement contains too many placeholders

   * Error: `1391' SQLSTATE: `HY000' (`ER_KEY_PART_0')

     Message: Key part '%s' length cannot be 0

   * Error: `1392' SQLSTATE: `HY000' (`ER_VIEW_CHECKSUM')

     Message: View text checksum failed

   * Error: `1393' SQLSTATE: `HY000' (`ER_VIEW_MULTIUPDATE')

     Message: Can not modify more than one base table through a join
     view '%s.%s'

   * Error: `1394' SQLSTATE: `HY000' (`ER_VIEW_NO_INSERT_FIELD_LIST')

     Message: Can not insert into join view '%s.%s' without fields list

   * Error: `1395' SQLSTATE: `HY000' (`ER_VIEW_DELETE_MERGE_VIEW')

     Message: Can not delete from join view '%s.%s'

   * Error: `1396' SQLSTATE: `HY000' (`ER_CANNOT_USER')

     Message: Operation %s failed for %s

   * Error: `1397' SQLSTATE: `XAE04' (`ER_XAER_NOTA')

     Message: XAER_NOTA: Unknown XID

   * Error: `1398' SQLSTATE: `XAE05' (`ER_XAER_INVAL')

     Message: XAER_INVAL: Invalid arguments (or unsupported command)

   * Error: `1399' SQLSTATE: `XAE07' (`ER_XAER_RMFAIL')

     Message: XAER_RMFAIL: The command cannot be executed when global
     transaction is in the %s state

   * Error: `1400' SQLSTATE: `XAE09' (`ER_XAER_OUTSIDE')

     Message: XAER_OUTSIDE: Some work is done outside global transaction

   * Error: `1401' SQLSTATE: `XAE03' (`ER_XAER_RMERR')

     Message: XAER_RMERR: Fatal error occurred in the transaction
     branch - check your data for consistency

   * Error: `1402' SQLSTATE: `XA100' (`ER_XA_RBROLLBACK')

     Message: XA_RBROLLBACK: Transaction branch was rolled back

   * Error: `1403' SQLSTATE: `42000' (`ER_NONEXISTING_PROC_GRANT')

     Message: There is no such grant defined for user '%s' on host '%s'
     on routine '%s'

   * Error: `1404' SQLSTATE: `HY000' (`ER_PROC_AUTO_GRANT_FAIL')

     Message: Failed to grant EXECUTE and ALTER ROUTINE privileges

   * Error: `1405' SQLSTATE: `HY000' (`ER_PROC_AUTO_REVOKE_FAIL')

     Message: Failed to revoke all privileges to dropped routine

   * Error: `1406' SQLSTATE: `22001' (`ER_DATA_TOO_LONG')

     Message: Data too long for column '%s' at row %ld

   * Error: `1407' SQLSTATE: `42000' (`ER_SP_BAD_SQLSTATE')

     Message: Bad SQLSTATE: '%s'

   * Error: `1408' SQLSTATE: `HY000' (`ER_STARTUP')

     Message: %s: ready for connections. Version: '%s' socket: '%s'
     port: %d %s

   * Error: `1409' SQLSTATE: `HY000'
     (`ER_LOAD_FROM_FIXED_SIZE_ROWS_TO_VAR')

     Message: Can't load value from file with fixed size rows to
     variable

   * Error: `1410' SQLSTATE: `42000' (`ER_CANT_CREATE_USER_WITH_GRANT')

     Message: You are not allowed to create a user with GRANT

   * Error: `1411' SQLSTATE: `HY000' (`ER_WRONG_VALUE_FOR_TYPE')

     Message: Incorrect %s value: '%s' for function %s

   * Error: `1412' SQLSTATE: `HY000' (`ER_TABLE_DEF_CHANGED')

     Message: Table definition has changed, please retry transaction

   * Error: `1413' SQLSTATE: `42000' (`ER_SP_DUP_HANDLER')

     Message: Duplicate handler declared in the same block

   * Error: `1414' SQLSTATE: `42000' (`ER_SP_NOT_VAR_ARG')

     Message: OUT or INOUT argument %d for routine %s is not a variable
     or NEW pseudo-variable in BEFORE trigger

   * Error: `1415' SQLSTATE: `0A000' (`ER_SP_NO_RETSET')

     Message: Not allowed to return a result set from a %s

   * Error: `1416' SQLSTATE: `22003' (`ER_CANT_CREATE_GEOMETRY_OBJECT')

     Message: Cannot get geometry object from data you send to the
     GEOMETRY field

   * Error: `1417' SQLSTATE: `HY000' (`ER_FAILED_ROUTINE_BREAK_BINLOG')

     Message: A routine failed and has neither NO SQL nor READS SQL
     DATA in its declaration and binary logging is enabled; if
     non-transactional tables were updated, the binary log will miss
     their changes

   * Error: `1418' SQLSTATE: `HY000' (`ER_BINLOG_UNSAFE_ROUTINE')

     Message: This function has none of DETERMINISTIC, NO SQL, or READS
     SQL DATA in its declaration and binary logging is enabled (you
     *might* want to use the less safe log_bin_trust_function_creators
     variable)

   * Error: `1419' SQLSTATE: `HY000'
     (`ER_BINLOG_CREATE_ROUTINE_NEED_SUPER')

     Message: You do not have the SUPER privilege and binary logging is
     enabled (you *might* want to use the less safe
     log_bin_trust_function_creators variable)

   * Error: `1420' SQLSTATE: `HY000' (`ER_EXEC_STMT_WITH_OPEN_CURSOR')

     Message: You can't execute a prepared statement which has an open
     cursor associated with it. Reset the statement to re-execute it.

   * Error: `1421' SQLSTATE: `HY000' (`ER_STMT_HAS_NO_OPEN_CURSOR')

     Message: The statement (%lu) has no open cursor.

   * Error: `1422' SQLSTATE: `HY000'
     (`ER_COMMIT_NOT_ALLOWED_IN_SF_OR_TRG')

     Message: Explicit or implicit commit is not allowed in stored
     function or trigger.

   * Error: `1423' SQLSTATE: `HY000' (`ER_NO_DEFAULT_FOR_VIEW_FIELD')

     Message: Field of view '%s.%s' underlying table doesn't have a
     default value

   * Error: `1424' SQLSTATE: `HY000' (`ER_SP_NO_RECURSION')

     Message: Recursive stored functions and triggers are not allowed.

   * Error: `1425' SQLSTATE: `42000' (`ER_TOO_BIG_SCALE')

     Message: Too big scale %d specified for column '%s'. Maximum is
     %lu.

   * Error: `1426' SQLSTATE: `42000' (`ER_TOO_BIG_PRECISION')

     Message: Too big precision %d specified for column '%s'. Maximum
     is %lu.

   * Error: `1427' SQLSTATE: `42000' (`ER_M_BIGGER_THAN_D')

     Message: For float(M,D), double(M,D) or decimal(M,D), M must be >=
     D (column '%s').

   * Error: `1428' SQLSTATE: `HY000' (`ER_WRONG_LOCK_OF_SYSTEM_TABLE')

     Message: You can't combine write-locking of system tables with
     other tables or lock types

   * Error: `1429' SQLSTATE: `HY000'
     (`ER_CONNECT_TO_FOREIGN_DATA_SOURCE')

     Message: Unable to connect to foreign data source: %s

   * Error: `1430' SQLSTATE: `HY000' (`ER_QUERY_ON_FOREIGN_DATA_SOURCE')

     Message: There was a problem processing the query on the foreign
     data source. Data source error: %s

   * Error: `1431' SQLSTATE: `HY000'
     (`ER_FOREIGN_DATA_SOURCE_DOESNT_EXIST')

     Message: The foreign data source you are trying to reference does
     not exist. Data source error: %s

   * Error: `1432' SQLSTATE: `HY000'
     (`ER_FOREIGN_DATA_STRING_INVALID_CANT_CREATE')

     Message: Can't create federated table. The data source connection
     string '%s' is not in the correct format

   * Error: `1433' SQLSTATE: `HY000' (`ER_FOREIGN_DATA_STRING_INVALID')

     Message: The data source connection string '%s' is not in the
     correct format

   * Error: `1434' SQLSTATE: `HY000' (`ER_CANT_CREATE_FEDERATED_TABLE')

     Message: Can't create federated table. Foreign data src error: %s

   * Error: `1435' SQLSTATE: `HY000' (`ER_TRG_IN_WRONG_SCHEMA')

     Message: Trigger in wrong schema

   * Error: `1436' SQLSTATE: `HY000' (`ER_STACK_OVERRUN_NEED_MORE')

     Message: Thread stack overrun: %ld bytes used of a %ld byte stack,
     and %ld bytes needed. Use 'mysqld -O thread_stack=#' to specify a
     bigger stack.

   * Error: `1437' SQLSTATE: `42000' (`ER_TOO_LONG_BODY')

     Message: Routine body for '%s' is too long

   * Error: `1438' SQLSTATE: `HY000'
     (`ER_WARN_CANT_DROP_DEFAULT_KEYCACHE')

     Message: Cannot drop default keycache

   * Error: `1439' SQLSTATE: `42000' (`ER_TOO_BIG_DISPLAYWIDTH')

     Message: Display width out of range for column '%s' (max = %lu)

   * Error: `1440' SQLSTATE: `XAE08' (`ER_XAER_DUPID')

     Message: XAER_DUPID: The XID already exists

   * Error: `1441' SQLSTATE: `22008' (`ER_DATETIME_FUNCTION_OVERFLOW')

     Message: Datetime function: %s field overflow

   * Error: `1442' SQLSTATE: `HY000'
     (`ER_CANT_UPDATE_USED_TABLE_IN_SF_OR_TRG')

     Message: Can't update table '%s' in stored function/trigger
     because it is already used by statement which invoked this stored
     function/trigger.

   * Error: `1443' SQLSTATE: `HY000' (`ER_VIEW_PREVENT_UPDATE')

     Message: The definition of table '%s' prevents operation %s on
     table '%s'.

   * Error: `1444' SQLSTATE: `HY000' (`ER_PS_NO_RECURSION')

     Message: The prepared statement contains a stored routine call
     that refers to that same statement. It's not allowed to execute a
     prepared statement in such a recursive manner

   * Error: `1445' SQLSTATE: `HY000' (`ER_SP_CANT_SET_AUTOCOMMIT')

     Message: Not allowed to set autocommit from a stored function or
     trigger

   * Error: `1446' SQLSTATE: `HY000' (`ER_MALFORMED_DEFINER')

     Message: Definer is not fully qualified

   * Error: `1447' SQLSTATE: `HY000' (`ER_VIEW_FRM_NO_USER')

     Message: View '%s'.'%s' has no definer information (old table
     format). Current user is used as definer. Please recreate the view!

   * Error: `1448' SQLSTATE: `HY000' (`ER_VIEW_OTHER_USER')

     Message: You need the SUPER privilege for creation view with
     '%s'@'%s' definer

   * Error: `1449' SQLSTATE: `HY000' (`ER_NO_SUCH_USER')

     Message: The user specified as a definer ('%s'@'%s') does not exist

   * Error: `1450' SQLSTATE: `HY000' (`ER_FORBID_SCHEMA_CHANGE')

     Message: Changing schema from '%s' to '%s' is not allowed.

   * Error: `1451' SQLSTATE: `23000' (`ER_ROW_IS_REFERENCED_2')

     Message: Cannot delete or update a parent row: a foreign key
     constraint fails (%s)

   * Error: `1452' SQLSTATE: `23000' (`ER_NO_REFERENCED_ROW_2')

     Message: Cannot add or update a child row: a foreign key
     constraint fails (%s)

   * Error: `1453' SQLSTATE: `42000' (`ER_SP_BAD_VAR_SHADOW')

     Message: Variable '%s' must be quoted with `...`, or renamed

   * Error: `1454' SQLSTATE: `HY000' (`ER_TRG_NO_DEFINER')

     Message: No definer attribute for trigger '%s'.'%s'. The trigger
     will be activated under the authorization of the invoker, which
     may have insufficient privileges. Please recreate the trigger.

   * Error: `1455' SQLSTATE: `HY000' (`ER_OLD_FILE_FORMAT')

     Message: '%s' has an old format, you should re-create the '%s'
     object(s)

   * Error: `1456' SQLSTATE: `HY000' (`ER_SP_RECURSION_LIMIT')

     Message: Recursive limit %d (as set by the max_sp_recursion_depth
     variable) was exceeded for routine %s

   * Error: `1457' SQLSTATE: `HY000' (`ER_SP_PROC_TABLE_CORRUPT')

     Message: Failed to load routine %s. The table mysql.proc is
     missing, corrupt, or contains bad data (internal code %d)

     `ER_SP_PROC_TABLE_CORRUPT' was introduced in 5.1.4.

   * Error: `1458' SQLSTATE: `42000' (`ER_SP_WRONG_NAME')

     Message: Incorrect routine name '%s'

     `ER_SP_WRONG_NAME' was introduced in 5.1.7.

   * Error: `1459' SQLSTATE: `HY000' (`ER_TABLE_NEEDS_UPGRADE')

     Message: Table upgrade required. Please do "REPAIR TABLE `%s`" or
     dump/reload to fix it!

     `ER_TABLE_NEEDS_UPGRADE' was introduced in 5.1.7.

   * Error: `1460' SQLSTATE: `42000' (`ER_SP_NO_AGGREGATE')

     Message: AGGREGATE is not supported for stored functions

     `ER_SP_NO_AGGREGATE' was introduced in 5.1.9.

   * Error: `1461' SQLSTATE: `42000'
     (`ER_MAX_PREPARED_STMT_COUNT_REACHED')

     Message: Can't create more than max_prepared_stmt_count statements
     (current value: %lu)

     `ER_MAX_PREPARED_STMT_COUNT_REACHED' was introduced in 5.1.11.

   * Error: `1462' SQLSTATE: `HY000' (`ER_VIEW_RECURSIVE')

     Message: `%s`.`%s` contains view recursion

     `ER_VIEW_RECURSIVE' was introduced in 5.1.11.

   * Error: `1463' SQLSTATE: `42000' (`ER_NON_GROUPING_FIELD_USED')

     Message: non-grouping field '%s' is used in %s clause

     `ER_NON_GROUPING_FIELD_USED' was introduced in 5.1.11.

   * Error: `1464' SQLSTATE: `HY000' (`ER_TABLE_CANT_HANDLE_SPKEYS')

     Message: The used table type doesn't support SPATIAL indexes

     `ER_TABLE_CANT_HANDLE_SPKEYS' was introduced in 5.1.11.

   * Error: `1465' SQLSTATE: `HY000' (`ER_NO_TRIGGERS_ON_SYSTEM_SCHEMA')

     Message: Triggers can not be created on system tables

     `ER_NO_TRIGGERS_ON_SYSTEM_SCHEMA' was introduced in 5.1.12.

   * Error: `1466' SQLSTATE: `HY000' (`ER_REMOVED_SPACES')

     Message: Leading spaces are removed from name '%s'

     `ER_REMOVED_SPACES' was introduced in 5.1.12.

   * Error: `1467' SQLSTATE: `HY000' (`ER_AUTOINC_READ_FAILED')

     Message: Failed to read auto-increment value from storage engine

     `ER_AUTOINC_READ_FAILED' was introduced in 5.1.12.

   * Error: `1468' SQLSTATE: `HY000' (`ER_USERNAME')

     Message: user name

     `ER_USERNAME' was introduced in 5.1.12.

   * Error: `1469' SQLSTATE: `HY000' (`ER_HOSTNAME')

     Message: host name

     `ER_HOSTNAME' was introduced in 5.1.12.

   * Error: `1470' SQLSTATE: `HY000' (`ER_WRONG_STRING_LENGTH')

     Message: String '%s' is too long for %s (should be no longer than
     %d)

     `ER_WRONG_STRING_LENGTH' was introduced in 5.1.12.

   * Error: `1471' SQLSTATE: `HY000' (`ER_NON_INSERTABLE_TABLE')

     Message: The target table %s of the %s is not insertable-into

     `ER_NON_INSERTABLE_TABLE' was introduced in 5.1.12.

   * Error: `1472' SQLSTATE: `HY000' (`ER_ADMIN_WRONG_MRG_TABLE')

     Message: Table '%s' is differently defined or of non-MyISAM type
     or doesn't exist

     `ER_ADMIN_WRONG_MRG_TABLE' was introduced in 5.1.20.

   * Error: `1473' SQLSTATE: `HY000'
     (`ER_TOO_HIGH_LEVEL_OF_NESTING_FOR_SELECT')

     Message: Too high level of nesting for select

     `ER_TOO_HIGH_LEVEL_OF_NESTING_FOR_SELECT' was introduced in 5.1.23.

   * Error: `1474' SQLSTATE: `HY000' (`ER_NAME_BECOMES_EMPTY')

     Message: Name '%s' has become "

     `ER_NAME_BECOMES_EMPTY' was introduced in 5.1.23.

   * Error: `1475' SQLSTATE: `HY000' (`ER_AMBIGUOUS_FIELD_TERM')

     Message: First character of the FIELDS TERMINATED string is
     ambiguous; please use non-optional and non-empty FIELDS ENCLOSED BY

     `ER_AMBIGUOUS_FIELD_TERM' was introduced in 5.1.23.

   * Error: `1476' SQLSTATE: `HY000' (`ER_FOREIGN_SERVER_EXISTS')

     Message: The foreign server, %s, you are trying to create already
     exists.

     `ER_FOREIGN_SERVER_EXISTS' was introduced in 5.1.15.

   * Error: `1477' SQLSTATE: `HY000' (`ER_FOREIGN_SERVER_DOESNT_EXIST')

     Message: The foreign server name you are trying to reference does
     not exist. Data source error: %s

     `ER_FOREIGN_SERVER_DOESNT_EXIST' was introduced in 5.1.15.

   * Error: `1478' SQLSTATE: `HY000' (`ER_ILLEGAL_HA_CREATE_OPTION')

     Message: Table storage engine '%s' does not support the create
     option '%s'

     `ER_ILLEGAL_HA_CREATE_OPTION' was introduced in 5.1.7.

   * Error: `1479' SQLSTATE: `HY000'
     (`ER_PARTITION_REQUIRES_VALUES_ERROR')

     Message: Syntax error: %s PARTITIONING requires definition of
     VALUES %s for each partition

   * Error: `1480' SQLSTATE: `HY000' (`ER_PARTITION_WRONG_VALUES_ERROR')

     Message: Only %s PARTITIONING can use VALUES %s in partition
     definition

   * Error: `1481' SQLSTATE: `HY000' (`ER_CHAR_SET_IN_PART_FIELD_ERROR')

     Message: VARCHAR only allowed if binary collation for partition
     functions

     `ER_CHAR_SET_IN_PART_FIELD_ERROR' was removed after 5.1.5.

   * Error: `1481' SQLSTATE: `HY000' (`ER_PARTITION_MAXVALUE_ERROR')

     Message: MAXVALUE can only be used in last partition definition

   * Error: `1482' SQLSTATE: `HY000' (`ER_PARTITION_SUBPARTITION_ERROR')

     Message: Subpartitions can only be hash partitions and by key

   * Error: `1483' SQLSTATE: `HY000' (`ER_PARTITION_SUBPART_MIX_ERROR')

     Message: Must define subpartitions on all partitions if on one
     partition

     `ER_PARTITION_SUBPART_MIX_ERROR' was introduced in 5.1.9.

   * Error: `1484' SQLSTATE: `HY000'
     (`ER_PARTITION_WRONG_NO_PART_ERROR')

     Message: Wrong number of partitions defined, mismatch with
     previous setting

   * Error: `1485' SQLSTATE: `HY000'
     (`ER_PARTITION_WRONG_NO_SUBPART_ERROR')

     Message: Wrong number of subpartitions defined, mismatch with
     previous setting

   * Error: `1486' SQLSTATE: `HY000'
     (`ER_CONST_EXPR_IN_PARTITION_FUNC_ERROR')

     Message: Constant/Random expression in (sub)partitioning function
     is not allowed

     `ER_CONST_EXPR_IN_PARTITION_FUNC_ERROR' was removed after 5.1.42.

     In 5.1.43: `ER_CONST_EXPR_IN_PARTITION_FUNC_ERROR' was renamed to
     `ER_WRONG_EXPR_IN_PARTITION_FUNC_ERROR'.

   * Error: `1486' SQLSTATE: `HY000'
     (`ER_WRONG_EXPR_IN_PARTITION_FUNC_ERROR')

     Message: Constant, random or timezone-dependent expressions in
     (sub)partitioning function are not allowed

     `ER_WRONG_EXPR_IN_PARTITION_FUNC_ERROR' was introduced in 5.1.43.

     In 5.1.43: `ER_CONST_EXPR_IN_PARTITION_FUNC_ERROR' was renamed to
     `ER_WRONG_EXPR_IN_PARTITION_FUNC_ERROR'.

   * Error: `1487' SQLSTATE: `HY000'
     (`ER_NO_CONST_EXPR_IN_RANGE_OR_LIST_ERROR')

     Message: Expression in RANGE/LIST VALUES must be constant

   * Error: `1488' SQLSTATE: `HY000' (`ER_FIELD_NOT_FOUND_PART_ERROR')

     Message: Field in list of fields for partition function not found
     in table

   * Error: `1489' SQLSTATE: `HY000'
     (`ER_LIST_OF_FIELDS_ONLY_IN_HASH_ERROR')

     Message: List of fields is only allowed in KEY partitions

   * Error: `1490' SQLSTATE: `HY000'
     (`ER_INCONSISTENT_PARTITION_INFO_ERROR')

     Message: The partition info in the frm file is not consistent with
     what can be written into the frm file

   * Error: `1491' SQLSTATE: `HY000'
     (`ER_PARTITION_FUNC_NOT_ALLOWED_ERROR')

     Message: The %s function returns the wrong type

   * Error: `1492' SQLSTATE: `HY000'
     (`ER_PARTITIONS_MUST_BE_DEFINED_ERROR')

     Message: For %s partitions each partition must be defined

   * Error: `1493' SQLSTATE: `HY000' (`ER_RANGE_NOT_INCREASING_ERROR')

     Message: VALUES LESS THAN value must be strictly increasing for
     each partition

   * Error: `1494' SQLSTATE: `HY000'
     (`ER_INCONSISTENT_TYPE_OF_FUNCTIONS_ERROR')

     Message: VALUES value must be of same type as partition function

   * Error: `1495' SQLSTATE: `HY000'
     (`ER_MULTIPLE_DEF_CONST_IN_LIST_PART_ERROR')

     Message: Multiple definition of same constant in list partitioning

   * Error: `1496' SQLSTATE: `HY000' (`ER_DROP_PARTITION_FAILURE')

     Message: Drop partition not supported in this version for this
     handler

     `ER_DROP_PARTITION_FAILURE' was removed after 5.1.5.

   * Error: `1496' SQLSTATE: `HY000' (`ER_PARTITION_ENTRY_ERROR')

     Message: Partitioning can not be used stand-alone in query

   * Error: `1497' SQLSTATE: `HY000'
     (`ER_DROP_PARTITION_WHEN_FK_DEFINED')

     Message: Cannot drop a partition when a foreign key constraint is
     defined on the table

     `ER_DROP_PARTITION_WHEN_FK_DEFINED' was removed after 5.1.5.

   * Error: `1497' SQLSTATE: `HY000' (`ER_MIX_HANDLER_ERROR')

     Message: The mix of handlers in the partitions is not allowed in
     this version of MySQL

   * Error: `1498' SQLSTATE: `HY000' (`ER_PARTITION_NOT_DEFINED_ERROR')

     Message: For the partitioned engine it is necessary to define all
     %s

   * Error: `1499' SQLSTATE: `HY000' (`ER_TOO_MANY_PARTITIONS_ERROR')

     Message: Too many partitions (including subpartitions) were defined

   * Error: `1500' SQLSTATE: `HY000' (`ER_SUBPARTITION_ERROR')

     Message: It is only possible to mix RANGE/LIST partitioning with
     HASH/KEY partitioning for subpartitioning

   * Error: `1501' SQLSTATE: `HY000' (`ER_CANT_CREATE_HANDLER_FILE')

     Message: Failed to create specific handler file

   * Error: `1502' SQLSTATE: `HY000'
     (`ER_BLOB_FIELD_IN_PART_FUNC_ERROR')

     Message: A BLOB field is not allowed in partition function

   * Error: `1503' SQLSTATE: `HY000'
     (`ER_UNIQUE_KEY_NEED_ALL_FIELDS_IN_PF')

     Message: A %s must include all columns in the table's partitioning
     function

   * Error: `1504' SQLSTATE: `HY000' (`ER_NO_PARTS_ERROR')

     Message: Number of %s = 0 is not an allowed value

   * Error: `1505' SQLSTATE: `HY000' (`ER_TABLESPACE_OPTION_ONLY_ONCE')

     Message: It is not allowed to specify %s more than once

     `ER_TABLESPACE_OPTION_ONLY_ONCE' was introduced in 5.1.6, removed
     after 5.1.6.

   * Error: `1505' SQLSTATE: `HY000'
     (`ER_PARTITION_MGMT_ON_NONPARTITIONED')

     Message: Partition management on a not partitioned table is not
     possible

   * Error: `1506' SQLSTATE: `HY000' (`ER_CREATE_TABLESPACE_FAILED')

     Message: Failed to create %s

     `ER_CREATE_TABLESPACE_FAILED' was introduced in 5.1.6, removed
     after 5.1.6.

   * Error: `1506' SQLSTATE: `HY000' (`ER_FOREIGN_KEY_ON_PARTITIONED')

     Message: Foreign key clause is not yet supported in conjunction
     with partitioning

     `ER_FOREIGN_KEY_ON_PARTITIONED' was introduced in 5.1.6.

   * Error: `1507' SQLSTATE: `HY000' (`ER_DROP_TABLESPACE_FAILED')

     Message: Failed to drop %s

     `ER_DROP_TABLESPACE_FAILED' was introduced in 5.1.6, removed after
     5.1.6.

   * Error: `1507' SQLSTATE: `HY000' (`ER_DROP_PARTITION_NON_EXISTENT')

     Message: Error in list of partitions to %s

   * Error: `1508' SQLSTATE: `HY000' (`ER_DROP_LAST_PARTITION')

     Message: Cannot remove all partitions, use DROP TABLE instead

   * Error: `1509' SQLSTATE: `HY000'
     (`ER_COALESCE_ONLY_ON_HASH_PARTITION')

     Message: COALESCE PARTITION can only be used on HASH/KEY partitions

   * Error: `1510' SQLSTATE: `HY000' (`ER_REORG_HASH_ONLY_ON_SAME_NO')

     Message: REORGANIZE PARTITION can only be used to reorganize
     partitions not to change their numbers

     `ER_REORG_HASH_ONLY_ON_SAME_NO' was introduced in 5.1.6.

   * Error: `1511' SQLSTATE: `HY000' (`ER_ALTER_TABLESPACE_FAILED')

     Message: Failed to alter: %s

     `ER_ALTER_TABLESPACE_FAILED' was introduced in 5.1.6, removed
     after 5.1.6.

   * Error: `1511' SQLSTATE: `HY000' (`ER_REORG_NO_PARAM_ERROR')

     Message: REORGANIZE PARTITION without parameters can only be used
     on auto-partitioned tables using HASH PARTITIONs

     `ER_REORG_NO_PARAM_ERROR' was introduced in 5.1.6.

   * Error: `1512' SQLSTATE: `HY000' (`ER_ONLY_ON_RANGE_LIST_PARTITION')

     Message: %s PARTITION can only be used on RANGE/LIST partitions

   * Error: `1513' SQLSTATE: `HY000' (`ER_ADD_PARTITION_SUBPART_ERROR')

     Message: Trying to Add partition(s) with wrong number of
     subpartitions

   * Error: `1514' SQLSTATE: `HY000'
     (`ER_ADD_PARTITION_NO_NEW_PARTITION')

     Message: At least one partition must be added

   * Error: `1515' SQLSTATE: `HY000'
     (`ER_COALESCE_PARTITION_NO_PARTITION')

     Message: At least one partition must be coalesced

   * Error: `1516' SQLSTATE: `HY000' (`ER_REORG_PARTITION_NOT_EXIST')

     Message: More partitions to reorganize than there are partitions

   * Error: `1517' SQLSTATE: `HY000' (`ER_SAME_NAME_PARTITION')

     Message: Duplicate partition name %s

   * Error: `1518' SQLSTATE: `HY000' (`ER_NO_BINLOG_ERROR')

     Message: It is not allowed to shut off binlog on this command

     `ER_NO_BINLOG_ERROR' was introduced in 5.1.6.

   * Error: `1519' SQLSTATE: `HY000' (`ER_CONSECUTIVE_REORG_PARTITIONS')

     Message: When reorganizing a set of partitions they must be in
     consecutive order

   * Error: `1520' SQLSTATE: `HY000' (`ER_REORG_OUTSIDE_RANGE')

     Message: Reorganize of range partitions cannot change total ranges
     except for last partition where it can extend the range

   * Error: `1521' SQLSTATE: `HY000' (`ER_PARTITION_FUNCTION_FAILURE')

     Message: Partition function not supported in this version for this
     handler

     `ER_PARTITION_FUNCTION_FAILURE' was introduced in 5.1.6.

   * Error: `1522' SQLSTATE: `HY000' (`ER_PART_STATE_ERROR')

     Message: Partition state cannot be defined from CREATE/ALTER TABLE

     `ER_PART_STATE_ERROR' was introduced in 5.1.6.

   * Error: `1523' SQLSTATE: `HY000' (`ER_LIMITED_PART_RANGE')

     Message: The %s handler only supports 32 bit integers in VALUES

     `ER_LIMITED_PART_RANGE' was introduced in 5.1.6.

   * Error: `1524' SQLSTATE: `HY000' (`ER_PLUGIN_IS_NOT_LOADED')

     Message: Plugin '%s' is not loaded

   * Error: `1525' SQLSTATE: `HY000' (`ER_EVENT_COL_COUNT_DOESNT_MATCH')

     Message: Column count of %s.%s is wrong. Table probably corrupted

     `ER_EVENT_COL_COUNT_DOESNT_MATCH' was introduced in 5.1.6, removed
     after 5.1.6.

   * Error: `1525' SQLSTATE: `HY000' (`ER_WRONG_VALUE')

     Message: Incorrect %s value: '%s'

     `ER_WRONG_VALUE' was introduced in 5.1.4.

   * Error: `1526' SQLSTATE: `HY000' (`ER_EVENT_CANNOT_LOAD_FROM_TABLE')

     Message: Cannot load from mysql.%s. Table probably corrupted. See
     error log.

     `ER_EVENT_CANNOT_LOAD_FROM_TABLE' was introduced in 5.1.6, removed
     after 5.1.7.

   * Error: `1526' SQLSTATE: `HY000' (`ER_NO_PARTITION_FOR_GIVEN_VALUE')

     Message: Table has no partition for value %s

     `ER_NO_PARTITION_FOR_GIVEN_VALUE' was introduced in 5.1.4.

   * Error: `1527' SQLSTATE: `HY000' (`ER_FILEGROUP_OPTION_ONLY_ONCE')

     Message: It is not allowed to specify %s more than once

     `ER_FILEGROUP_OPTION_ONLY_ONCE' was introduced in 5.1.7.

   * Error: `1528' SQLSTATE: `HY000' (`ER_CREATE_FILEGROUP_FAILED')

     Message: Failed to create %s

     `ER_CREATE_FILEGROUP_FAILED' was introduced in 5.1.7.

   * Error: `1529' SQLSTATE: `HY000' (`ER_DROP_FILEGROUP_FAILED')

     Message: Failed to drop %s

     `ER_DROP_FILEGROUP_FAILED' was introduced in 5.1.7.

   * Error: `1530' SQLSTATE: `HY000' (`ER_TABLESPACE_AUTO_EXTEND_ERROR')

     Message: The handler doesn't support autoextend of tablespaces

     `ER_TABLESPACE_AUTO_EXTEND_ERROR' was introduced in 5.1.6.

   * Error: `1531' SQLSTATE: `HY000' (`ER_WRONG_SIZE_NUMBER')

     Message: A size parameter was incorrectly specified, either number
     or on the form 10M

     `ER_WRONG_SIZE_NUMBER' was introduced in 5.1.6.

   * Error: `1532' SQLSTATE: `HY000' (`ER_SIZE_OVERFLOW_ERROR')

     Message: The size number was correct but we don't allow the digit
     part to be more than 2 billion

     `ER_SIZE_OVERFLOW_ERROR' was introduced in 5.1.6.

   * Error: `1533' SQLSTATE: `HY000' (`ER_ALTER_FILEGROUP_FAILED')

     Message: Failed to alter: %s

     `ER_ALTER_FILEGROUP_FAILED' was introduced in 5.1.7.

   * Error: `1534' SQLSTATE: `HY000' (`ER_BINLOG_ROW_LOGGING_FAILED')

     Message: Writing one row to the row-based binary log failed

     `ER_BINLOG_ROW_LOGGING_FAILED' was introduced in 5.1.5.

   * Error: `1535' SQLSTATE: `HY000' (`ER_BINLOG_ROW_WRONG_TABLE_DEF')

     Message: Table definition on master and slave does not match: %s

     `ER_BINLOG_ROW_WRONG_TABLE_DEF' was introduced in 5.1.5.

   * Error: `1536' SQLSTATE: `HY000' (`ER_BINLOG_ROW_RBR_TO_SBR')

     Message: Slave running with -log-slave-updates must use row-based
     binary logging to be able to replicate row-based binary log events

     `ER_BINLOG_ROW_RBR_TO_SBR' was introduced in 5.1.5.

   * Error: `1537' SQLSTATE: `HY000' (`ER_EVENT_ALREADY_EXISTS')

     Message: Event '%s' already exists

     `ER_EVENT_ALREADY_EXISTS' was introduced in 5.1.6.

   * Error: `1538' SQLSTATE: `HY000' (`ER_EVENT_STORE_FAILED')

     Message: Failed to store event %s. Error code %d from storage
     engine.

     `ER_EVENT_STORE_FAILED' was introduced in 5.1.6.

   * Error: `1539' SQLSTATE: `HY000' (`ER_EVENT_DOES_NOT_EXIST')

     Message: Unknown event '%s'

     `ER_EVENT_DOES_NOT_EXIST' was introduced in 5.1.6.

   * Error: `1540' SQLSTATE: `HY000' (`ER_WARN_DEPRECATED_STATEMENT')

     Message: The '%s' statement is deprecated and will be removed in
     MySQL %s. Please use client programs (e.g. %s) instead.

     `ER_WARN_DEPRECATED_STATEMENT' was introduced in 5.1.7, removed
     after 5.1.7.

   * Error: `1540' SQLSTATE: `HY000' (`ER_EVENT_CANT_ALTER')

     Message: Failed to alter event '%s'

     `ER_EVENT_CANT_ALTER' was introduced in 5.1.6.

   * Error: `1541' SQLSTATE: `HY000' (`ER_WARN_DEPRECATED')

     Message: The syntax '%s' is deprecated and will be removed in
     MySQL %s. Please use %s instead.

     `ER_WARN_DEPRECATED' was introduced in 5.1.9, removed after 5.1.9.

   * Error: `1541' SQLSTATE: `HY000' (`ER_EVENT_DROP_FAILED')

     Message: Failed to drop %s

     `ER_EVENT_DROP_FAILED' was introduced in 5.1.6.

   * Error: `1542' SQLSTATE: `HY000'
     (`ER_EVENT_INTERVAL_NOT_POSITIVE_OR_TOO_BIG')

     Message: INTERVAL is either not positive or too big

     `ER_EVENT_INTERVAL_NOT_POSITIVE_OR_TOO_BIG' was introduced in
     5.1.6.

   * Error: `1543' SQLSTATE: `HY000' (`ER_EVENT_ENDS_BEFORE_STARTS')

     Message: ENDS is either invalid or before STARTS

     `ER_EVENT_ENDS_BEFORE_STARTS' was introduced in 5.1.6.

   * Error: `1544' SQLSTATE: `HY000' (`ER_EVENT_EXEC_TIME_IN_THE_PAST')

     Message: Event execution time is in the past. Event has been
     disabled

     `ER_EVENT_EXEC_TIME_IN_THE_PAST' was introduced in 5.1.6.

   * Error: `1545' SQLSTATE: `HY000' (`ER_EVENT_OPEN_TABLE_FAILED')

     Message: Failed to open mysql.event

     `ER_EVENT_OPEN_TABLE_FAILED' was introduced in 5.1.6.

   * Error: `1546' SQLSTATE: `HY000'
     (`ER_EVENT_NEITHER_M_EXPR_NOR_M_AT')

     Message: No datetime expression provided

     `ER_EVENT_NEITHER_M_EXPR_NOR_M_AT' was introduced in 5.1.6.

   * Error: `1547' SQLSTATE: `HY000'
     (`ER_COL_COUNT_DOESNT_MATCH_CORRUPTED')

     Message: Column count of mysql.%s is wrong. Expected %d, found %d.
     The table is probably corrupted

     `ER_COL_COUNT_DOESNT_MATCH_CORRUPTED' was introduced in 5.1.7.

   * Error: `1548' SQLSTATE: `HY000' (`ER_CANNOT_LOAD_FROM_TABLE')

     Message: Cannot load from mysql.%s. The table is probably corrupted

     `ER_CANNOT_LOAD_FROM_TABLE' was introduced in 5.1.9.

   * Error: `1549' SQLSTATE: `HY000' (`ER_EVENT_CANNOT_DELETE')

     Message: Failed to delete the event from mysql.event

     `ER_EVENT_CANNOT_DELETE' was introduced in 5.1.6.

   * Error: `1550' SQLSTATE: `HY000' (`ER_EVENT_COMPILE_ERROR')

     Message: Error during compilation of event's body

     `ER_EVENT_COMPILE_ERROR' was introduced in 5.1.6.

   * Error: `1551' SQLSTATE: `HY000' (`ER_EVENT_SAME_NAME')

     Message: Same old and new event name

     `ER_EVENT_SAME_NAME' was introduced in 5.1.6.

   * Error: `1552' SQLSTATE: `HY000' (`ER_EVENT_DATA_TOO_LONG')

     Message: Data for column '%s' too long

     `ER_EVENT_DATA_TOO_LONG' was introduced in 5.1.6.

   * Error: `1553' SQLSTATE: `HY000' (`ER_CANT_READ_LOCK_LOG_TABLE')

     Message: You can't use usual read lock with log tables. Try READ
     LOCAL instead

     `ER_CANT_READ_LOCK_LOG_TABLE' was introduced in 5.1.6, removed
     after 5.1.20.

   * Error: `1553' SQLSTATE: `HY000' (`ER_DROP_INDEX_FK')

     Message: Cannot drop index '%s': needed in a foreign key constraint

     `ER_DROP_INDEX_FK' was introduced in 5.1.6.

   * Error: `1554' SQLSTATE: `HY000'
     (`ER_WARN_DEPRECATED_SYNTAX_WITH_VER')

     Message: The syntax '%s' is deprecated and will be removed in
     MySQL %s. Please use %s instead

     `ER_WARN_DEPRECATED_SYNTAX_WITH_VER' was introduced in 5.1.20.

   * Error: `1555' SQLSTATE: `HY000' (`ER_CANT_WRITE_LOCK_LOG_TABLE')

     Message: You can't write-lock a log table. Only read access is
     possible

     `ER_CANT_WRITE_LOCK_LOG_TABLE' was introduced in 5.1.6.

   * Error: `1556' SQLSTATE: `HY000' (`ER_CANT_LOCK_LOG_TABLE')

     Message: You can't use locks with log tables.

     `ER_CANT_LOCK_LOG_TABLE' was introduced in 5.1.21.

   * Error: `1557' SQLSTATE: `23000' (`ER_FOREIGN_DUPLICATE_KEY')

     Message: Upholding foreign key constraints for table '%s', entry
     '%s', key %d would lead to a duplicate entry

     `ER_FOREIGN_DUPLICATE_KEY' was introduced in 5.1.7.

   * Error: `1558' SQLSTATE: `HY000'
     (`ER_COL_COUNT_DOESNT_MATCH_PLEASE_UPDATE')

     Message: Column count of mysql.%s is wrong. Expected %d, found %d.
     Created with MySQL %d, now running %d. Please use mysql_upgrade to
     fix this error.

     `ER_COL_COUNT_DOESNT_MATCH_PLEASE_UPDATE' was introduced in 5.1.7.

   * Error: `1559' SQLSTATE: `HY000'
     (`ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR')

     Message: Cannot switch out of the row-based binary log format when
     the session has open temporary tables

     `ER_TEMP_TABLE_PREVENTS_SWITCH_OUT_OF_RBR' was introduced in 5.1.9.

   * Error: `1560' SQLSTATE: `HY000'
     (`ER_STORED_FUNCTION_PREVENTS_SWITCH_BINLOG_FORMAT')

     Message: Cannot change the binary logging format inside a stored
     function or trigger

     `ER_STORED_FUNCTION_PREVENTS_SWITCH_BINLOG_FORMAT' was introduced
     in 5.1.9.

   * Error: `1561' SQLSTATE: `HY000'
     (`ER_NDB_CANT_SWITCH_BINLOG_FORMAT')

     Message: The NDB cluster engine does not support changing the
     binlog format on the fly yet

     `ER_NDB_CANT_SWITCH_BINLOG_FORMAT' was introduced in 5.1.9.

   * Error: `1562' SQLSTATE: `HY000' (`ER_PARTITION_NO_TEMPORARY')

     Message: Cannot create temporary table with partitions

     `ER_PARTITION_NO_TEMPORARY' was introduced in 5.1.9.

   * Error: `1563' SQLSTATE: `HY000' (`ER_PARTITION_CONST_DOMAIN_ERROR')

     Message: Partition constant is out of partition function domain

     `ER_PARTITION_CONST_DOMAIN_ERROR' was introduced in 5.1.12.

   * Error: `1564' SQLSTATE: `HY000'
     (`ER_PARTITION_FUNCTION_IS_NOT_ALLOWED')

     Message: This partition function is not allowed

     `ER_PARTITION_FUNCTION_IS_NOT_ALLOWED' was introduced in 5.1.12.

   * Error: `1565' SQLSTATE: `HY000' (`ER_DDL_LOG_ERROR')

     Message: Error in DDL log

     `ER_DDL_LOG_ERROR' was introduced in 5.1.11.

   * Error: `1566' SQLSTATE: `HY000' (`ER_NULL_IN_VALUES_LESS_THAN')

     Message: Not allowed to use NULL value in VALUES LESS THAN

     `ER_NULL_IN_VALUES_LESS_THAN' was introduced in 5.1.11.

   * Error: `1567' SQLSTATE: `HY000' (`ER_EVENT_RECURSIVITY_FORBIDDEN')

     Message: Recursivity of EVENT DDL statements is forbidden when
     body is present

     `ER_EVENT_RECURSIVITY_FORBIDDEN' was introduced in 5.1.12, removed
     after 5.1.17.

   * Error: `1567' SQLSTATE: `HY000' (`ER_WRONG_PARTITION_NAME')

     Message: Incorrect partition name

     `ER_WRONG_PARTITION_NAME' was introduced in 5.1.11.

   * Error: `1568' SQLSTATE: `25001' (`ER_CANT_CHANGE_TX_ISOLATION')

     Message: Transaction isolation level can't be changed while a
     transaction is in progress

     `ER_CANT_CHANGE_TX_ISOLATION' was introduced in 5.1.7.

   * Error: `1569' SQLSTATE: `HY000' (`ER_DUP_ENTRY_AUTOINCREMENT_CASE')

     Message: ALTER TABLE causes auto_increment resequencing, resulting
     in duplicate entry '%s' for key '%s'

     `ER_DUP_ENTRY_AUTOINCREMENT_CASE' was introduced in 5.1.12.

   * Error: `1570' SQLSTATE: `HY000' (`ER_EVENT_MODIFY_QUEUE_ERROR')

     Message: Internal scheduler error %d

     `ER_EVENT_MODIFY_QUEUE_ERROR' was introduced in 5.1.11.

   * Error: `1571' SQLSTATE: `HY000' (`ER_EVENT_SET_VAR_ERROR')

     Message: Error during starting/stopping of the scheduler. Error
     code %u

     `ER_EVENT_SET_VAR_ERROR' was introduced in 5.1.11.

   * Error: `1572' SQLSTATE: `HY000' (`ER_PARTITION_MERGE_ERROR')

     Message: Engine cannot be used in partitioned tables

     `ER_PARTITION_MERGE_ERROR' was introduced in 5.1.12.

   * Error: `1573' SQLSTATE: `HY000' (`ER_CANT_ACTIVATE_LOG')

     Message: Cannot activate '%s' log

     `ER_CANT_ACTIVATE_LOG' was introduced in 5.1.12.

   * Error: `1574' SQLSTATE: `HY000' (`ER_RBR_NOT_AVAILABLE')

     Message: The server was not built with row-based replication

     `ER_RBR_NOT_AVAILABLE' was introduced in 5.1.12.

   * Error: `1575' SQLSTATE: `HY000' (`ER_BASE64_DECODE_ERROR')

     Message: Decoding of base64 string failed

     `ER_BASE64_DECODE_ERROR' was introduced in 5.1.12.

   * Error: `1576' SQLSTATE: `HY000' (`ER_EVENT_RECURSION_FORBIDDEN')

     Message: Recursion of EVENT DDL statements is forbidden when body
     is present

     `ER_EVENT_RECURSION_FORBIDDEN' was introduced in 5.1.18.

   * Error: `1577' SQLSTATE: `HY000' (`ER_EVENTS_DB_ERROR')

     Message: Cannot proceed because system tables used by Event
     Scheduler were found damaged at server start

     `ER_EVENTS_DB_ERROR' was introduced in 5.1.12.

   * Error: `1578' SQLSTATE: `HY000' (`ER_ONLY_INTEGERS_ALLOWED')

     Message: Only integers allowed as number here

     `ER_ONLY_INTEGERS_ALLOWED' was introduced in 5.1.12.

   * Error: `1579' SQLSTATE: `HY000' (`ER_UNSUPORTED_LOG_ENGINE')

     Message: This storage engine cannot be used for log tables"

     `ER_UNSUPORTED_LOG_ENGINE' was introduced in 5.1.12.

   * Error: `1580' SQLSTATE: `HY000' (`ER_BAD_LOG_STATEMENT')

     Message: You cannot '%s' a log table if logging is enabled

     `ER_BAD_LOG_STATEMENT' was introduced in 5.1.12.

   * Error: `1581' SQLSTATE: `HY000' (`ER_CANT_RENAME_LOG_TABLE')

     Message: Cannot rename '%s'. When logging enabled, rename to/from
     log table must rename two tables: the log table to an archive
     table and another table back to '%s'

     `ER_CANT_RENAME_LOG_TABLE' was introduced in 5.1.13.

   * Error: `1582' SQLSTATE: `42000'
     (`ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT')

     Message: Incorrect parameter count in the call to native function
     '%s'

     `ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT' was introduced in 5.1.13.

   * Error: `1583' SQLSTATE: `42000'
     (`ER_WRONG_PARAMETERS_TO_NATIVE_FCT')

     Message: Incorrect parameters in the call to native function '%s'

     `ER_WRONG_PARAMETERS_TO_NATIVE_FCT' was introduced in 5.1.13.

   * Error: `1584' SQLSTATE: `42000'
     (`ER_WRONG_PARAMETERS_TO_STORED_FCT')

     Message: Incorrect parameters in the call to stored function '%s'

     `ER_WRONG_PARAMETERS_TO_STORED_FCT' was introduced in 5.1.14.

   * Error: `1585' SQLSTATE: `HY000' (`ER_NATIVE_FCT_NAME_COLLISION')

     Message: This function '%s' has the same name as a native function

     `ER_NATIVE_FCT_NAME_COLLISION' was introduced in 5.1.14.

   * Error: `1586' SQLSTATE: `23000' (`ER_DUP_ENTRY_WITH_KEY_NAME')

     Message: Duplicate entry '%s' for key '%s'

     `ER_DUP_ENTRY_WITH_KEY_NAME' was introduced in 5.1.15.

     From 5.1.20: The format string for this error is also used with
     `ER_DUP_ENTRY'.

   * Error: `1587' SQLSTATE: `HY000' (`ER_BINLOG_PURGE_EMFILE')

     Message: Too many files opened, please execute the command again

     `ER_BINLOG_PURGE_EMFILE' was introduced in 5.1.14.

   * Error: `1588' SQLSTATE: `HY000'
     (`ER_EVENT_CANNOT_CREATE_IN_THE_PAST')

     Message: Event execution time is in the past and ON COMPLETION NOT
     PRESERVE is set. The event was dropped immediately after creation.

     `ER_EVENT_CANNOT_CREATE_IN_THE_PAST' was introduced in 5.1.17.

   * Error: `1589' SQLSTATE: `HY000'
     (`ER_EVENT_CANNOT_ALTER_IN_THE_PAST')

     Message: Event execution time is in the past and ON COMPLETION NOT
     PRESERVE is set. The event was dropped immediately after creation.

     `ER_EVENT_CANNOT_ALTER_IN_THE_PAST' was introduced in 5.1.17.

   * Error: `1590' SQLSTATE: `HY000' (`ER_SLAVE_INCIDENT')

     Message: The incident %s occured on the master. Message: %s

     `ER_SLAVE_INCIDENT' was introduced in 5.1.18.

   * Error: `1591' SQLSTATE: `HY000'
     (`ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENT')

     Message: Table has no partition for some existing values

     `ER_NO_PARTITION_FOR_GIVEN_VALUE_SILENT' was introduced in 5.1.18.

   * Error: `1592' SQLSTATE: `HY000' (`ER_BINLOG_UNSAFE_STATEMENT')

     Message: Statement may not be safe to log in statement format.

     `ER_BINLOG_UNSAFE_STATEMENT' was introduced in 5.1.20.

   * Error: `1593' SQLSTATE: `HY000' (`ER_SLAVE_FATAL_ERROR')

     Message: Fatal error: %s

     `ER_SLAVE_FATAL_ERROR' was introduced in 5.1.20.

   * Error: `1594' SQLSTATE: `HY000' (`ER_SLAVE_RELAY_LOG_READ_FAILURE')

     Message: Relay log read failure: %s

     `ER_SLAVE_RELAY_LOG_READ_FAILURE' was introduced in 5.1.20.

   * Error: `1595' SQLSTATE: `HY000'
     (`ER_SLAVE_RELAY_LOG_WRITE_FAILURE')

     Message: Relay log write failure: %s

     `ER_SLAVE_RELAY_LOG_WRITE_FAILURE' was introduced in 5.1.20.

   * Error: `1596' SQLSTATE: `HY000' (`ER_SLAVE_CREATE_EVENT_FAILURE')

     Message: Failed to create %s

     `ER_SLAVE_CREATE_EVENT_FAILURE' was introduced in 5.1.20.

   * Error: `1597' SQLSTATE: `HY000' (`ER_SLAVE_MASTER_COM_FAILURE')

     Message: Master command %s failed: %s

     `ER_SLAVE_MASTER_COM_FAILURE' was introduced in 5.1.20.

   * Error: `1598' SQLSTATE: `HY000' (`ER_BINLOG_LOGGING_IMPOSSIBLE')

     Message: Binary logging not possible. Message: %s

     `ER_BINLOG_LOGGING_IMPOSSIBLE' was introduced in 5.1.20.

   * Error: `1599' SQLSTATE: `HY000' (`ER_VIEW_NO_CREATION_CTX')

     Message: View `%s`.`%s` has no creation context

     `ER_VIEW_NO_CREATION_CTX' was introduced in 5.1.21.

   * Error: `1600' SQLSTATE: `HY000' (`ER_VIEW_INVALID_CREATION_CTX')

     Message: Creation context of view `%s`.`%s' is invalid

     `ER_VIEW_INVALID_CREATION_CTX' was introduced in 5.1.21.

   * Error: `1601' SQLSTATE: `HY000' (`ER_SR_INVALID_CREATION_CTX')

     Message: Creation context of stored routine `%s`.`%s` is invalid

     `ER_SR_INVALID_CREATION_CTX' was introduced in 5.1.21.

   * Error: `1602' SQLSTATE: `HY000' (`ER_TRG_CORRUPTED_FILE')

     Message: Corrupted TRG file for table `%s`.`%s`

     `ER_TRG_CORRUPTED_FILE' was introduced in 5.1.21.

   * Error: `1603' SQLSTATE: `HY000' (`ER_TRG_NO_CREATION_CTX')

     Message: Triggers for table `%s`.`%s` have no creation context

     `ER_TRG_NO_CREATION_CTX' was introduced in 5.1.21.

   * Error: `1604' SQLSTATE: `HY000' (`ER_TRG_INVALID_CREATION_CTX')

     Message: Trigger creation context of table `%s`.`%s` is invalid

     `ER_TRG_INVALID_CREATION_CTX' was introduced in 5.1.21.

   * Error: `1605' SQLSTATE: `HY000' (`ER_EVENT_INVALID_CREATION_CTX')

     Message: Creation context of event `%s`.`%s` is invalid

     `ER_EVENT_INVALID_CREATION_CTX' was introduced in 5.1.21.

   * Error: `1606' SQLSTATE: `HY000' (`ER_TRG_CANT_OPEN_TABLE')

     Message: Cannot open table for trigger `%s`.`%s`

     `ER_TRG_CANT_OPEN_TABLE' was introduced in 5.1.21.

   * Error: `1607' SQLSTATE: `HY000' (`ER_CANT_CREATE_SROUTINE')

     Message: Cannot create stored routine `%s`. Check warnings

     `ER_CANT_CREATE_SROUTINE' was introduced in 5.1.23.

   * Error: `1608' SQLSTATE: `HY000' (`ER_SLAVE_AMBIGOUS_EXEC_MODE')

     Message: Ambiguous slave modes combination. %s

     `ER_SLAVE_AMBIGOUS_EXEC_MODE' was introduced in 5.1.24.

   * Error: `1609' SQLSTATE: `HY000'
     (`ER_NO_FORMAT_DESCRIPTION_EVENT_BEFORE_BINLOG_STATEMENT')

     Message: The BINLOG statement of type `%s` was not preceded by a
     format description BINLOG statement.

     `ER_NO_FORMAT_DESCRIPTION_EVENT_BEFORE_BINLOG_STATEMENT' was
     introduced in 5.1.24.

   * Error: `1610' SQLSTATE: `HY000' (`ER_SLAVE_CORRUPT_EVENT')

     Message: Corrupted replication event was detected

     `ER_SLAVE_CORRUPT_EVENT' was introduced in 5.1.24.

   * Error: `1611' SQLSTATE: `HY000' (`ER_LOAD_DATA_INVALID_COLUMN')

     Message: Invalid column reference (%s) in LOAD DATA

     `ER_LOAD_DATA_INVALID_COLUMN' was introduced in 5.1.24.

   * Error: `1612' SQLSTATE: `HY000' (`ER_LOG_PURGE_NO_FILE')

     Message: Being purged log %s was not found

     `ER_LOG_PURGE_NO_FILE' was introduced in 5.1.24.

   * Error: `1613' SQLSTATE: `XA106' (`ER_XA_RBTIMEOUT')

     Message: XA_RBTIMEOUT: Transaction branch was rolled back: took
     too long

     `ER_XA_RBTIMEOUT' was introduced in 5.1.30.

   * Error: `1614' SQLSTATE: `XA102' (`ER_XA_RBDEADLOCK')

     Message: XA_RBDEADLOCK: Transaction branch was rolled back:
     deadlock was detected

     `ER_XA_RBDEADLOCK' was introduced in 5.1.30.

   * Error: `1615' SQLSTATE: `HY000' (`ER_NEED_REPREPARE')

     Message: Prepared statement needs to be re-prepared

     `ER_NEED_REPREPARE' was introduced in 5.1.25.

   * Error: `1616' SQLSTATE: `HY000' (`ER_DELAYED_NOT_SUPPORTED')

     Message: DELAYED option not supported for table '%s'

     `ER_DELAYED_NOT_SUPPORTED' was introduced in 5.1.28.

   * Error: `1617' SQLSTATE: `HY000' (`WARN_NO_MASTER_INFO')

     Message: The master info structure does not exist

     `WARN_NO_MASTER_INFO' was introduced in 5.1.31.

   * Error: `1618' SQLSTATE: `HY000' (`WARN_OPTION_IGNORED')

     Message: <%s> option ignored

     `WARN_OPTION_IGNORED' was introduced in 5.1.31.

   * Error: `1619' SQLSTATE: `HY000' (`WARN_PLUGIN_DELETE_BUILTIN')

     Message: Built-in plugins cannot be deleted

     `WARN_PLUGIN_DELETE_BUILTIN' was introduced in 5.1.31.

   * Error: `1620' SQLSTATE: `HY000' (`WARN_PLUGIN_BUSY')

     Message: Plugin is busy and will be uninstalled on shutdown

     `WARN_PLUGIN_BUSY' was introduced in 5.1.31.

   * Error: `1621' SQLSTATE: `HY000' (`ER_VARIABLE_IS_READONLY')

     Message: %s variable '%s' is read-only. Use SET %s to assign the
     value

     `ER_VARIABLE_IS_READONLY' was introduced in 5.1.31.

   * Error: `1622' SQLSTATE: `HY000'
     (`ER_WARN_ENGINE_TRANSACTION_ROLLBACK')

     Message: Storage engine %s does not support rollback for this
     statement. Transaction rolled back and must be restarted

     `ER_WARN_ENGINE_TRANSACTION_ROLLBACK' was introduced in 5.1.33.

   * Error: `1623' SQLSTATE: `HY000' (`ER_SLAVE_HEARTBEAT_FAILURE')

     Message: Unexpected master's heartbeat data: %s

     `ER_SLAVE_HEARTBEAT_FAILURE' was introduced in 5.1.33.

   * Error: `1624' SQLSTATE: `HY000'
     (`ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE')

     Message: The requested value for the heartbeat period %s %s

     `ER_SLAVE_HEARTBEAT_VALUE_OUT_OF_RANGE' was introduced in 5.1.33.

   * Error: `1625' SQLSTATE: `HY000' (`ER_NDB_REPLICATION_SCHEMA_ERROR')

     Message: Bad schema for mysql.ndb_replication table. Message: %s

     `ER_NDB_REPLICATION_SCHEMA_ERROR' was introduced in 5.1.33.

   * Error: `1626' SQLSTATE: `HY000' (`ER_CONFLICT_FN_PARSE_ERROR')

     Message: Error in parsing conflict function. Message: %s

     `ER_CONFLICT_FN_PARSE_ERROR' was introduced in 5.1.33.

   * Error: `1627' SQLSTATE: `HY000' (`ER_EXCEPTIONS_WRITE_ERROR')

     Message: Write to exceptions table failed. Message: %s"

     `ER_EXCEPTIONS_WRITE_ERROR' was introduced in 5.1.33.

   * Error: `1628' SQLSTATE: `HY000' (`ER_TOO_LONG_TABLE_COMMENT')

     Message: Comment for table '%s' is too long (max = %lu)

     `ER_TOO_LONG_TABLE_COMMENT' was introduced in 5.1.33.

   * Error: `1629' SQLSTATE: `HY000' (`ER_TOO_LONG_FIELD_COMMENT')

     Message: Comment for field '%s' is too long (max = %lu)

     `ER_TOO_LONG_FIELD_COMMENT' was introduced in 5.1.33.

   * Error: `1630' SQLSTATE: `42000'
     (`ER_FUNC_INEXISTENT_NAME_COLLISION')

     Message: FUNCTION %s does not exist. Check the 'Function Name
     Parsing and Resolution' section in the Reference Manual

     `ER_FUNC_INEXISTENT_NAME_COLLISION' was introduced in 5.1.36.

   * Error: `1631' SQLSTATE: `HY000' (`ER_DATABASE_NAME')

     Message: Database

     `ER_DATABASE_NAME' was introduced in 5.1.36.

   * Error: `1632' SQLSTATE: `HY000' (`ER_TABLE_NAME')

     Message: Table

     `ER_TABLE_NAME' was introduced in 5.1.36.

   * Error: `1633' SQLSTATE: `HY000' (`ER_PARTITION_NAME')

     Message: Partition

     `ER_PARTITION_NAME' was introduced in 5.1.36.

   * Error: `1634' SQLSTATE: `HY000' (`ER_SUBPARTITION_NAME')

     Message: Subpartition

     `ER_SUBPARTITION_NAME' was introduced in 5.1.36.

   * Error: `1635' SQLSTATE: `HY000' (`ER_TEMPORARY_NAME')

     Message: Temporary

     `ER_TEMPORARY_NAME' was introduced in 5.1.36.

   * Error: `1636' SQLSTATE: `HY000' (`ER_RENAMED_NAME')

     Message: Renamed

     `ER_RENAMED_NAME' was introduced in 5.1.36.

   * Error: `1637' SQLSTATE: `HY000' (`ER_TOO_MANY_CONCURRENT_TRXS')

     Message: Too many active concurrent transactions

     `ER_TOO_MANY_CONCURRENT_TRXS' was introduced in 5.1.38.

   * Error: `1638' SQLSTATE: `HY000'
     (`WARN_NON_ASCII_SEPARATOR_NOT_IMPLEMENTED')

     Message: Non-ASCII separator arguments are not fully supported

     `WARN_NON_ASCII_SEPARATOR_NOT_IMPLEMENTED' was introduced in
     5.1.38.

   * Error: `1639' SQLSTATE: `HY000' (`ER_DEBUG_SYNC_TIMEOUT')

     Message: debug sync point wait timed out

     `ER_DEBUG_SYNC_TIMEOUT' was introduced in 5.1.40.

   * Error: `1640' SQLSTATE: `HY000' (`ER_DEBUG_SYNC_HIT_LIMIT')

     Message: debug sync point hit limit reached

     `ER_DEBUG_SYNC_HIT_LIMIT' was introduced in 5.1.40.


File: manual.info,  Node: error-messages-client,  Next: problems,  Prev: error-messages-server,  Up: error-handling

B.4 Client Error Codes and Messages
===================================

Client error information comes from the following source files:

   * The Error values and the symbols in parentheses correspond to
     definitions in the `include/errmsg.h' MySQL source file.

   * The Message values correspond to the error messages that are
     listed in the `libmysql/errmsg.c' file.  `%d' and `%s' represent
     numbers and strings, respectively, that are substituted into the
     messages when they are displayed.

Because updates are frequent, it is possible that those files will
contain additional error information not listed here.

   * Error: `2000' (`CR_UNKNOWN_ERROR')

     Message: Unknown MySQL error

   * Error: `2001' (`CR_SOCKET_CREATE_ERROR')

     Message: Can't create UNIX socket (%d)

   * Error: `2002' (`CR_CONNECTION_ERROR')

     Message: Can't connect to local MySQL server through socket '%s'
     (%d)

   * Error: `2003' (`CR_CONN_HOST_ERROR')

     Message: Can't connect to MySQL server on '%s' (%d)

   * Error: `2004' (`CR_IPSOCK_ERROR')

     Message: Can't create TCP/IP socket (%d)

   * Error: `2005' (`CR_UNKNOWN_HOST')

     Message: Unknown MySQL server host '%s' (%d)

   * Error: `2006' (`CR_SERVER_GONE_ERROR')

     Message: MySQL server has gone away

   * Error: `2007' (`CR_VERSION_ERROR')

     Message: Protocol mismatch; server version = %d, client version =
     %d

   * Error: `2008' (`CR_OUT_OF_MEMORY')

     Message: MySQL client ran out of memory

   * Error: `2009' (`CR_WRONG_HOST_INFO')

     Message: Wrong host info

   * Error: `2010' (`CR_LOCALHOST_CONNECTION')

     Message: Localhost via UNIX socket

   * Error: `2011' (`CR_TCP_CONNECTION')

     Message: %s via TCP/IP

   * Error: `2012' (`CR_SERVER_HANDSHAKE_ERR')

     Message: Error in server handshake

   * Error: `2013' (`CR_SERVER_LOST')

     Message: Lost connection to MySQL server during query

   * Error: `2014' (`CR_COMMANDS_OUT_OF_SYNC')

     Message: Commands out of sync; you can't run this command now

   * Error: `2015' (`CR_NAMEDPIPE_CONNECTION')

     Message: Named pipe: %s

   * Error: `2016' (`CR_NAMEDPIPEWAIT_ERROR')

     Message: Can't wait for named pipe to host: %s pipe: %s (%lu)

   * Error: `2017' (`CR_NAMEDPIPEOPEN_ERROR')

     Message: Can't open named pipe to host: %s pipe: %s (%lu)

   * Error: `2018' (`CR_NAMEDPIPESETSTATE_ERROR')

     Message: Can't set state of named pipe to host: %s pipe: %s (%lu)

   * Error: `2019' (`CR_CANT_READ_CHARSET')

     Message: Can't initialize character set %s (path: %s)

   * Error: `2020' (`CR_NET_PACKET_TOO_LARGE')

     Message: Got packet bigger than 'max_allowed_packet' bytes

   * Error: `2021' (`CR_EMBEDDED_CONNECTION')

     Message: Embedded server

   * Error: `2022' (`CR_PROBE_SLAVE_STATUS')

     Message: Error on SHOW SLAVE STATUS:

   * Error: `2023' (`CR_PROBE_SLAVE_HOSTS')

     Message: Error on SHOW SLAVE HOSTS:

   * Error: `2024' (`CR_PROBE_SLAVE_CONNECT')

     Message: Error connecting to slave:

   * Error: `2025' (`CR_PROBE_MASTER_CONNECT')

     Message: Error connecting to master:

   * Error: `2026' (`CR_SSL_CONNECTION_ERROR')

     Message: SSL connection error

   * Error: `2027' (`CR_MALFORMED_PACKET')

     Message: Malformed packet

   * Error: `2028' (`CR_WRONG_LICENSE')

     Message: This client library is licensed only for use with MySQL
     servers having '%s' license

   * Error: `2029' (`CR_NULL_POINTER')

     Message: Invalid use of null pointer

   * Error: `2030' (`CR_NO_PREPARE_STMT')

     Message: Statement not prepared

   * Error: `2031' (`CR_PARAMS_NOT_BOUND')

     Message: No data supplied for parameters in prepared statement

   * Error: `2032' (`CR_DATA_TRUNCATED')

     Message: Data truncated

   * Error: `2033' (`CR_NO_PARAMETERS_EXISTS')

     Message: No parameters exist in the statement

   * Error: `2034' (`CR_INVALID_PARAMETER_NO')

     Message: Invalid parameter number

   * Error: `2035' (`CR_INVALID_BUFFER_USE')

     Message: Can't send long data for non-string/non-binary data types
     (parameter: %d)

   * Error: `2036' (`CR_UNSUPPORTED_PARAM_TYPE')

     Message: Using unsupported buffer type: %d (parameter: %d)

   * Error: `2037' (`CR_SHARED_MEMORY_CONNECTION')

     Message: Shared memory: %s

   * Error: `2038' (`CR_SHARED_MEMORY_CONNECT_REQUEST_ERROR')

     Message: Can't open shared memory; client could not create request
     event (%lu)

   * Error: `2039' (`CR_SHARED_MEMORY_CONNECT_ANSWER_ERROR')

     Message: Can't open shared memory; no answer event received from
     server (%lu)

   * Error: `2040' (`CR_SHARED_MEMORY_CONNECT_FILE_MAP_ERROR')

     Message: Can't open shared memory; server could not allocate file
     mapping (%lu)

   * Error: `2041' (`CR_SHARED_MEMORY_CONNECT_MAP_ERROR')

     Message: Can't open shared memory; server could not get pointer to
     file mapping (%lu)

   * Error: `2042' (`CR_SHARED_MEMORY_FILE_MAP_ERROR')

     Message: Can't open shared memory; client could not allocate file
     mapping (%lu)

   * Error: `2043' (`CR_SHARED_MEMORY_MAP_ERROR')

     Message: Can't open shared memory; client could not get pointer to
     file mapping (%lu)

   * Error: `2044' (`CR_SHARED_MEMORY_EVENT_ERROR')

     Message: Can't open shared memory; client could not create %s
     event (%lu)

   * Error: `2045' (`CR_SHARED_MEMORY_CONNECT_ABANDONED_ERROR')

     Message: Can't open shared memory; no answer from server (%lu)

   * Error: `2046' (`CR_SHARED_MEMORY_CONNECT_SET_ERROR')

     Message: Can't open shared memory; cannot send request event to
     server (%lu)

   * Error: `2047' (`CR_CONN_UNKNOW_PROTOCOL')

     Message: Wrong or unknown protocol

   * Error: `2048' (`CR_INVALID_CONN_HANDLE')

     Message: Invalid connection handle

   * Error: `2049' (`CR_SECURE_AUTH')

     Message: Connection using old (pre-4.1.1) authentication protocol
     refused (client option 'secure_auth' enabled)

   * Error: `2050' (`CR_FETCH_CANCELED')

     Message: Row retrieval was canceled by mysql_stmt_close() call

   * Error: `2051' (`CR_NO_DATA')

     Message: Attempt to read column without prior row fetch

   * Error: `2052' (`CR_NO_STMT_METADATA')

     Message: Prepared statement contains no metadata

   * Error: `2053' (`CR_NO_RESULT_SET')

     Message: Attempt to read a row while there is no result set
     associated with the statement

   * Error: `2054' (`CR_NOT_IMPLEMENTED')

     Message: This feature is not implemented yet

   * Error: `2055' (`CR_SERVER_LOST_EXTENDED')

     Message: Lost connection to MySQL server at '%s', system error: %d

     `CR_SERVER_LOST_EXTENDED' was introduced in 5.1.14.

   * Error: `2056' (`CR_STMT_CLOSED')

     Message: Statement closed indirectly because of a preceeding %s()
     call

     `CR_STMT_CLOSED' was introduced in 5.1.18.

   * Error: `2057' (`CR_NEW_STMT_METADATA')

     Message: The number of columns in the result set differs from the
     number of bound buffers. You must reset the statement, rebind the
     result set columns, and execute the statement again

     `CR_NEW_STMT_METADATA' was introduced in 5.1.25.


File: manual.info,  Node: problems,  Prev: error-messages-client,  Up: error-handling

B.5 Problems and Common Errors
==============================

* Menu:

* what-is-crashing::             How to Determine What Is Causing a Problem
* common-errors::                Common Errors When Using MySQL Programs
* installation-issues::          Installation-Related Issues
* administration-issues::        Administration-Related Issues
* query-issues::                 Query-Related Issues
* optimizer-issues::             Optimizer-Related Issues
* table-definition-issues::      Table Definition-Related Issues
* bugs::                         Known Issues in MySQL

This section lists some common problems and error messages that you may
encounter. It describes how to determine the causes of the problems and
what to do to solve them.


File: manual.info,  Node: what-is-crashing,  Next: common-errors,  Prev: problems,  Up: problems

B.5.1 How to Determine What Is Causing a Problem
------------------------------------------------

When you run into a problem, the first thing you should do is to find
out which program or piece of equipment is causing it:

   * If you have one of the following symptoms, then it is probably a
     hardware problems (such as memory, motherboard, CPU, or hard disk)
     or kernel problem:

        * The keyboard does not work. This can normally be checked by
          pressing the Caps Lock key. If the Caps Lock light does not
          change, you have to replace your keyboard.  (Before doing
          this, you should try to restart your computer and check all
          cables to the keyboard.)

        * The mouse pointer does not move.

        * The machine does not answer to a remote machine's pings.

        * Other programs that are not related to MySQL do not behave
          correctly.

        * Your system restarted unexpectedly. (A faulty user-level
          program should never be able to take down your system.)

     In this case, you should start by checking all your cables and run
     some diagnostic tool to check your hardware! You should also check
     whether there are any patches, updates, or service packs for your
     operating system that could likely solve your problem. Check also
     that all your libraries (such as `glibc') are up to date.

     It is always good to use a machine with ECC memory to discover
     memory problems early.

   * If your keyboard is locked up, you may be able to recover by
     logging in to your machine from another machine and executing
     `kbd_mode -a'.

   * Please examine your system log file (`/var/log/messages' or
     similar) for reasons for your problem. If you think the problem is
     in MySQL, you should also examine MySQL's log files. See *Note
     server-logs::.

   * If you do not think you have hardware problems, you should try to
     find out which program is causing problems. Try using `top', `ps',
     Task Manager, or some similar program, to check which program is
     taking all CPU or is locking the machine.

   * Use `top', `df', or a similar program to check whether you are out
     of memory, disk space, file descriptors, or some other critical
     resource.

   * If the problem is some runaway process, you can always try to kill
     it. If it does not want to die, there is probably a bug in the
     operating system.

If after you have examined all other possibilities and you have
concluded that the MySQL server or a MySQL client is causing the
problem, it is time to create a bug report for our mailing list or our
support team. In the bug report, try to give a very detailed
description of how the system is behaving and what you think is
happening. You should also state why you think that MySQL is causing
the problem. Take into consideration all the situations in this
chapter. State any problems exactly how they appear when you examine
your system. Use the `copy and paste' method for any output and error
messages from programs and log files.

Try to describe in detail which program is not working and all symptoms
you see. We have in the past received many bug reports that state only
`the system does not work.' This provides us with no information about
what could be the problem.

If a program fails, it is always useful to know the following
information:

   * Has the program in question made a segmentation fault (did it dump
     core)?

   * Is the program taking up all available CPU time? Check with `top'.
     Let the program run for a while, it may simply be evaluating
     something computationally intensive.

   * If the *Note `mysqld': mysqld. server is causing problems, can you
     get any response from it with *Note `mysqladmin -u root ping':
     mysqladmin. or *Note `mysqladmin -u root processlist': mysqladmin.?

   * What does a client program say when you try to connect to the
     MySQL server? (Try with *Note `mysql': mysql, for example.) Does
     the client jam? Do you get any output from the program?

When sending a bug report, you should follow the outline described in
*Note bug-reports::.


File: manual.info,  Node: common-errors,  Next: installation-issues,  Prev: what-is-crashing,  Up: problems

B.5.2 Common Errors When Using MySQL Programs
---------------------------------------------

* Menu:

* error-access-denied::          Access denied
* can-not-connect-to-server::    Can't connect to [local] MySQL server
* error-lost-connection::        Lost connection to MySQL server
* old-client::                   Client does not support authentication protocol
* password-too-long::            Password Fails When Entered Interactively
* blocked-host::                 Host 'host_name' is blocked
* too-many-connections::         Too many connections
* out-of-memory::                Out of memory
* gone-away::                    MySQL server has gone away
* packet-too-large::             Packet Too Large
* communication-errors::         Communication Errors and Aborted Connections
* full-table::                   The table is full
* cannot-create::                Can't create/write to file
* commands-out-of-sync::         Commands out of sync
* ignoring-user::                Ignoring user
* cannot-find-table::            Table 'tbl_name' doesn't exist
* cannot-initialize-character-set::  Can't initialize character set
* not-enough-file-handles::      'File' Not Found and Similar Errors
* table-corruption::             Table-Corruption Issues

This section lists some errors that users frequently encounter when
running MySQL programs. Although the problems show up when you try to
run client programs, the solutions to many of the problems involves
changing the configuration of the MySQL server.


File: manual.info,  Node: error-access-denied,  Next: can-not-connect-to-server,  Prev: common-errors,  Up: common-errors

B.5.2.1 Access denied
.....................

An `Access denied' error can have many causes. Often the problem is
related to the MySQL accounts that the server permits client programs
to use when connecting. See *Note privilege-system::, and *Note
access-denied::.


File: manual.info,  Node: can-not-connect-to-server,  Next: error-lost-connection,  Prev: error-access-denied,  Up: common-errors

B.5.2.2 Can't connect to [local] MySQL server
.............................................

* Menu:

* can-not-connect-to-server-on-windows::  Connection to MySQL Server Failing on Windows

A MySQL client on Unix can connect to the *Note `mysqld': mysqld.
server in two different ways: By using a Unix socket file to connect
through a file in the file system (default `/tmp/mysql.sock'), or by
using TCP/IP, which connects through a port number. A Unix socket file
connection is faster than TCP/IP, but can be used only when connecting
to a server on the same computer. A Unix socket file is used if you do
not specify a host name or if you specify the special host name
`localhost'.

If the MySQL server is running on Windows, you can connect using
TCP/IP. If the server is started with the `--enable-named-pipe' option,
you can also connect with named pipes if you run the client on the host
where the server is running. The name of the named pipe is `MySQL' by
default. If you do not give a host name when connecting to *Note
`mysqld': mysqld, a MySQL client first tries to connect to the named
pipe. If that does not work, it connects to the TCP/IP port. You can
force the use of named pipes on Windows by using `.' as the host name.

The error (2002) `Can't connect to ...' normally means that there is no
MySQL server running on the system or that you are using an incorrect
Unix socket file name or TCP/IP port number when trying to connect to
the server. You should also check that the TCP/IP port you are using
has not been blocked by a firewall or port blocking service.

The error (2003) `Can't connect to MySQL server on 'SERVER' (10061)'
indicates that the network connection has been refused. You should
check that there is a MySQL server running, that it has network
connections enabled, and that the network port you specified is the one
configured on the server.

Start by checking whether there is a process named *Note `mysqld':
mysqld. running on your server host. (Use `ps xa | grep mysqld' on Unix
or the Task Manager on Windows.) If there is no such process, you should
start the server. See *Note starting-server::.

If a *Note `mysqld': mysqld. process is running, you can check it by
trying the following commands. The port number or Unix socket file name
might be different in your setup.  `host_ip' represents the IP address
of the machine where the server is running.


     shell> mysqladmin version
     shell> mysqladmin variables
     shell> mysqladmin -h `hostname` version variables
     shell> mysqladmin -h `hostname` --port=3306 version
     shell> mysqladmin -h host_ip version
     shell> mysqladmin --protocol=SOCKET --socket=/tmp/mysql.sock version

Note the use of backticks rather than forward quotation marks with the
`hostname' command; these cause the output of `hostname' (that is, the
current host name) to be substituted into the *Note `mysqladmin':
mysqladmin. command. If you have no `hostname' command or are running
on Windows, you can manually type the host name of your machine (without
backticks) following the `-h' option. You can also try `-h 127.0.0.1'
to connect with TCP/IP to the local host.

Make sure that the server has not been configured to ignore network
connections or (if you are attempting to connect remotely) that it has
not been configured to listen only locally on its network interfaces.
If the server was started with `--skip-networking', it will not accept
TCP/IP connections at all. If the server was started with
`--bind-address=127.0.0.1', it will listen for TCP/IP connections only
locally on the loopback interface and will not accept remote
connections.

Check to make sure that there is no firewall blocking access to MySQL.
Your firewall may be configured on the basis of the application being
executed, or the port number used by MySQL for communication (3306 by
default). Under Linux or Unix, check your IP tables (or similar)
configuration to ensure that the port has not been blocked. Under
Windows, applications such as ZoneAlarm or the Windows XP personal
firewall may need to be configured not to block the MySQL port.

Here are some reasons the `Can't connect to local MySQL server' error
might occur:

   * *Note `mysqld': mysqld. is not running on the local host. Check
     your operating system's process list to ensure the *Note `mysqld':
     mysqld. process is present.

   * You're running a MySQL server on Windows with many TCP/IP
     connections to it. If you're experiencing that quite often your
     clients get that error, you can find a workaround here: *Note
     can-not-connect-to-server-on-windows::.

   * Someone has removed the Unix socket file that *Note `mysqld':
     mysqld. uses (`/tmp/mysql.sock' by default). For example, you
     might have a `cron' job that removes old files from the `/tmp'
     directory. You can always run *Note `mysqladmin version':
     mysqladmin. to check whether the Unix socket file that *Note
     `mysqladmin': mysqladmin. is trying to use really exists. The fix
     in this case is to change the `cron' job to not remove
     `mysql.sock' or to place the socket file somewhere else. See *Note
     problems-with-mysql-sock::.

   * You have started the *Note `mysqld': mysqld. server with the
     `--socket=/path/to/socket' option, but forgotten to tell client
     programs the new name of the socket file. If you change the socket
     path name for the server, you must also notify the MySQL clients.
     You can do this by providing the same `--socket' option when you
     run client programs. You also need to ensure that clients have
     permission to access the `mysql.sock' file. To find out where the
     socket file is, you can do:


          shell> netstat -ln | grep mysql

     See *Note problems-with-mysql-sock::.

   * You are using Linux and one server thread has died (dumped core).
     In this case, you must kill the other *Note `mysqld': mysqld.
     threads (for example, with *Note `kill': kill. or with the *Note
     `mysql_zap': mysql-zap. script) before you can restart the MySQL
     server. See *Note crashing::.

   * The server or client program might not have the proper access
     privileges for the directory that holds the Unix socket file or
     the socket file itself. In this case, you must either change the
     access privileges for the directory or socket file so that the
     server and clients can access them, or restart *Note `mysqld':
     mysqld. with a `--socket' option that specifies a socket file name
     in a directory where the server can create it and where client
     programs can access it.

If you get the error message `Can't connect to MySQL server on
some_host', you can try the following things to find out what the
problem is:

   * Check whether the server is running on that host by executing
     `telnet some_host 3306' and pressing the Enter key a couple of
     times. (3306 is the default MySQL port number. Change the value if
     your server is listening to a different port.) If there is a MySQL
     server running and listening to the port, you should get a
     response that includes the server's version number. If you get an
     error such as `telnet: Unable to connect to remote host:
     Connection refused', then there is no server running on the given
     port.

   * If the server is running on the local host, try using *Note
     `mysqladmin -h localhost variables': mysqladmin. to connect using
     the Unix socket file. Verify the TCP/IP port number that the
     server is configured to listen to (it is the value of the `port'
     variable.)

   * If you are running under Linux and Security-Enhanced Linux
     (SELinux) is enabled, make sure you have disabled SELinux
     protection for the `mysqld' process.


File: manual.info,  Node: can-not-connect-to-server-on-windows,  Prev: can-not-connect-to-server,  Up: can-not-connect-to-server

B.5.2.3 Connection to MySQL Server Failing on Windows
.....................................................

When you're running a MySQL server on Windows with many TCP/IP
connections to it, and you're experiencing that quite often your
clients get a `Can't connect to MySQL server' error, the reason might
be that Windows does not allow for enough ephemeral (short-lived) ports
to serve those connections.

The purpose of `TIME_WAIT' is to keep a connection accepting packets
even after the connection has been closed. This is because Internet
routing can cause a packet to take a slow route to its destination and
it may arrive after both sides have agreed to close. If the port is in
use for a new connection, that packet from the old connection could
break the protocol or compromise personal information from the original
connection. The `TIME_WAIT' delay prevents this by ensuring that the
port cannot be reused until after some time has been permitted for
those delayed packets to arrive.

It is safe to reduce `TIME_WAIT' greatly on LAN connections because
there is little chance of packets arriving at very long delays, as they
could through the Internet with its comparatively large distances and
latencies.

Windows permits ephemeral (short-lived) TCP ports to the user. After
any port is closed it will remain in a `TIME_WAIT' status for 120
seconds. The port will not be available again until this time expires.
The default range of port numbers depends on the version of Windows,
with a more limited number of ports in older versions:

   * Windows through Server 2003: Ports in range 1025-5000

   * Windows Vista, Server 2008, and newer: Ports in range 49152-65535

With a small stack of available TCP ports (5000) and a high number of
TCP ports being open and closed over a short period of time along with
the `TIME_WAIT' status you have a good chance for running out of ports.
There are two ways to address this problem:

   * Reduce the number of TCP ports consumed quickly by investigating
     connection pooling or persistent connections where possible

   * Tune some settings in the Windows registry (see below)

* IMPORTANT: The following procedure involves modifying the Windows
registry. Before you modify the registry, make sure to back it up and
make sure that you understand how to restore the registry if a problem
occurs.  For information about how to back up, restore, and edit the
registry, view the following article in the Microsoft Knowledge Base:
`http://support.microsoft.com/kb/256986/EN-US/'.  *

  1. Start Registry Editor (`Regedt32.exe').

  2. Locate the following key in the registry:


          HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

  3. On the `Edit' menu, click `Add Value', and then add the following
     registry value:


          Value Name: MaxUserPort
          Data Type: REG_DWORD
          Value: 65534

     This sets the number of ephemeral ports available to any user. The
     valid range is between 5000 and 65534 (decimal). The default value
     is 0x1388 (5000 decimal).

  4. On the `Edit' menu, click `Add Value', and then add the following
     registry value:


          Value Name: TcpTimedWaitDelay
          Data Type: REG_DWORD
          Value: 30

     This sets the number of seconds to hold a TCP port connection in
     `TIME_WAIT' state before closing. The valid range is between 0
     (zero) and 300 (decimal). The default value is 0x78 (120 decimal).

  5. Quit Registry Editor.

  6. Reboot the machine.

Note: Undoing the above should be as simple as deleting the registry
entries you've created.


File: manual.info,  Node: error-lost-connection,  Next: old-client,  Prev: can-not-connect-to-server,  Up: common-errors

B.5.2.4 Lost connection to MySQL server
.......................................

There are three likely causes for this error message.

Usually it indicates network connectivity trouble and you should check
the condition of your network if this error occurs frequently. If the
error message includes `during query,' this is probably the case you
are experiencing.

Sometimes the `during query' form happens when millions of rows are
being sent as part of one or more queries. If you know that this is
happening, you should try increasing `net_read_timeout' from its
default of 30 seconds to 60 seconds or longer, sufficient for the data
transfer to complete.

More rarely, it can happen when the client is attempting the initial
connection to the server. In this case, if your `connect_timeout' value
is set to only a few seconds, you may be able to resolve the problem by
increasing it to ten seconds, perhaps more if you have a very long
distance or slow connection. You can determine whether you are
experiencing this more uncommon cause by using `SHOW GLOBAL STATUS LIKE
'Aborted_connects''.  It will increase by one for each initial
connection attempt that the server aborts. You may see `reading
authorization packet' as part of the error message; if so, that also
suggests that this is the solution that you need.

If the cause is none of those just described, you may be experiencing a
problem with *Note `BLOB': blob. values that are larger than
`max_allowed_packet', which can cause this error with some clients.
Sometime you may see an `ER_NET_PACKET_TOO_LARGE' error, and that
confirms that you need to increase `max_allowed_packet'.


File: manual.info,  Node: old-client,  Next: password-too-long,  Prev: error-lost-connection,  Up: common-errors

B.5.2.5 Client does not support authentication protocol
.......................................................

The current implementation of the authentication protocol uses a
password hashing algorithm that is incompatible with that used by older
(pre-4.1) clients. Attempts to connect to a 4.1 or newer server with an
older client may fail with the following message:


     shell> mysql
     Client does not support authentication protocol requested
     by server; consider upgrading MySQL client

To deal with this problem, the preferred solution is to upgrade all
client programs to use a 4.1.1 or newer client library. If that is not
possible, use one of the following approaches:

   * To connect to the server with a pre-4.1 client program, use an
     account that still has a pre-4.1-style password.

   * Reset the password to pre-4.1 style for each user that needs to
     use a pre-4.1 client program. This can be done using the *Note
     `SET PASSWORD': set-password.  statement and the `OLD_PASSWORD()'
     function:


          mysql> SET PASSWORD FOR
              -> 'SOME_USER'@'SOME_HOST' = OLD_PASSWORD('NEWPWD');

     Substitute the password you want to use for `NEWPWD' in the
     preceding example. MySQL cannot tell you what the original
     password was, so you'll need to pick a new one.

   * Tell the server to use the older password hashing algorithm by
     default:

       1. Start *Note `mysqld': mysqld. with the `old_passwords' system
          variable set to 1.

       2. Assign an old-format password to each account that has had
          its password updated to the longer 4.1 format. You can
          identify these accounts with the following query:


               mysql> SELECT Host, User, Password FROM mysql.user
                   -> WHERE LENGTH(Password) > 16;

          For each account record displayed by the query, use the
          `Host' and `User' values and assign a password using one of
          the methods described previously.

The `Client does not support authentication protocol' error also can
occur if multiple versions of MySQL are installed but client programs
are dynamically linked and link to an older library. Make sure that
clients use the most recent library version with which they are
compatible. The procedure to do this will depend on your system.

*Note*:

The PHP `mysql' extension does not support the authentication protocol
in MySQL 4.1.1 and higher. This is true regardless of the PHP version
being used. If you wish to use the `mysql' extension with MySQL 4.1 or
newer, you may need to follow one of the options discussed above for
configuring MySQL to work with old clients. The `mysqli' extension
(stands for "MySQL, Improved"; added in PHP 5) is compatible with the
improved password hashing employed in MySQL 4.1 and higher, and no
special configuration of MySQL need be done to use this MySQL client
library. For more information about the `mysqli' extension, see
`http://php.net/mysqli'.

For additional background on password hashing and authentication, see
*Note password-hashing::.


File: manual.info,  Node: password-too-long,  Next: blocked-host,  Prev: old-client,  Up: common-errors

B.5.2.6 Password Fails When Entered Interactively
.................................................

MySQL client programs prompt for a password when invoked with a
`--password' or `-p' option that has no following password value:


     shell> mysql -u USER_NAME -p
     Enter password:

On some systems, you may find that your password works when specified
in an option file or on the command line, but not when you enter it
interactively at the `Enter password:' prompt. This occurs when the
library provided by the system to read passwords limits password values
to a small number of characters (typically eight). That is a problem
with the system library, not with MySQL. To work around it, change your
MySQL password to a value that is eight or fewer characters long, or
put your password in an option file.


File: manual.info,  Node: blocked-host,  Next: too-many-connections,  Prev: password-too-long,  Up: common-errors

B.5.2.7 Host 'host_name' is blocked
...................................

If the following error occurs, it means that *Note `mysqld': mysqld.
has received many connection requests from the given host that were
interrupted in the middle:


     Host 'HOST_NAME' is blocked because of many connection errors.
     Unblock with 'mysqladmin flush-hosts'

The value of the `max_connect_errors' system variable determines how
many successive interrupted connection requests are permitted. (See
*Note server-system-variables::.) After `max_connect_errors' failed
requests without a successful connection, *Note `mysqld': mysqld.
assumes that something is wrong (for example, that someone is trying to
break in), and blocks the host from further connections until you issue
a *Note `FLUSH HOSTS': flush.  statement or execute a *Note `mysqladmin
flush-hosts': mysqladmin. command.

By default, *Note `mysqld': mysqld. blocks a host after 10 connection
errors. You can adjust the value by setting `max_connect_errors' at
server startup:


     shell> mysqld_safe --max_connect_errors=10000 &

The value can also be set at runtime:


     mysql> SET GLOBAL max_connect_errors=10000;

If you get the `Host 'HOST_NAME' is blocked' error message for a given
host, you should first verify that there is nothing wrong with TCP/IP
connections from that host.  If you are having network problems, it
does you no good to increase the value of the `max_connect_errors'
variable.


File: manual.info,  Node: too-many-connections,  Next: out-of-memory,  Prev: blocked-host,  Up: common-errors

B.5.2.8 Too many connections
............................

If you get a `Too many connections' error when you try to connect to
the *Note `mysqld': mysqld.  server, this means that all available
connections are in use by other clients.

The number of connections permitted is controlled by the
`max_connections' system variable. Beginning with MySQL 5.1.15, its
default value is 151 to improve performance when MySQL is used with the
Apache Web server. (Previously, the default was 100.) If you need to
support more connections, you should set a larger value for this
variable.

*Note `mysqld': mysqld. actually permits `max_connections+1' clients to
connect. The extra connection is reserved for use by accounts that have
the `SUPER' privilege. By granting the `SUPER' privilege to
administrators and not to normal users (who should not need it), an
administrator can connect to the server and use *Note `SHOW
PROCESSLIST': show-processlist. to diagnose problems even if the
maximum number of unprivileged clients are connected. See *Note
show-processlist::.

The maximum number of connections MySQL can support depends on the
quality of the thread library on a given platform, the amount of RAM
available, how much RAM is used for each connection, the workload from
each connection, and the desired response time. Linux or Solaris should
be able to support at 500 to 1000 simultaneous connections routinely
and as many as 10,000 connections if you have many gigabytes of RAM
available and the workload from each is low or the response time target
undemanding. Windows is limited to (open tables x 2 + open connections)
< 2048 due to the Posix compatibility layer used on that platform.

Increasing `open-files-limit' may be necessary. Also see *Note
linux-installation::, for how to raise the operating system limit on
how many handles can be used by MySQL.


File: manual.info,  Node: out-of-memory,  Next: gone-away,  Prev: too-many-connections,  Up: common-errors

B.5.2.9 Out of memory
.....................

If you issue a query using the *Note `mysql': mysql. client program and
receive an error like the following one, it means that *Note `mysql':
mysql. does not have enough memory to store the entire query result:


     mysql: Out of memory at line 42, 'malloc.c'
     mysql: needed 8136 byte (8k), memory in use: 12481367 bytes (12189k)
     ERROR 2008: MySQL client ran out of memory

To remedy the problem, first check whether your query is correct. Is it
reasonable that it should return so many rows?  If not, correct the
query and try again. Otherwise, you can invoke *Note `mysql': mysql.
with the `--quick' option. This causes it to use the *Note
`mysql_use_result()': mysql-use-result.  C API function to retrieve the
result set, which places less of a load on the client (but more on the
server).


File: manual.info,  Node: gone-away,  Next: packet-too-large,  Prev: out-of-memory,  Up: common-errors

B.5.2.10 MySQL server has gone away
...................................

This section also covers the related `Lost connection to server during
query' error.

The most common reason for the `MySQL server has gone away' error is
that the server timed out and closed the connection. In this case, you
normally get one of the following error codes (which one you get is
operating system-dependent).

This table lists `MySQL server has gone away' error codes and provides
a description of each.

Error Code                Description
`CR_SERVER_GONE_ERROR'    The client couldn't send a question to the
                          server.
`CR_SERVER_LOST'          The client didn't get an error when writing to
                          the server, but it didn't get a full answer
                          (or any answer) to the question.

By default, the server closes the connection after eight hours if
nothing has happened. You can change the time limit by setting the
`wait_timeout' variable when you start *Note `mysqld': mysqld. See
*Note server-system-variables::.

If you have a script, you just have to issue the query again for the
client to do an automatic reconnection. This assumes that you have
automatic reconnection in the client enabled (which is the default for
the `mysql' command-line client).

Some other common reasons for the `MySQL server has gone away' error
are:

   * You (or the db administrator) has killed the running thread with a
     *Note `KILL': kill.  statement or a *Note `mysqladmin kill':
     mysqladmin. command.

   * You tried to run a query after closing the connection to the
     server. This indicates a logic error in the application that
     should be corrected.

   * A client application running on a different host does not have the
     necessary privileges to connect to the MySQL server from that host.

   * You got a timeout from the TCP/IP connection on the client side.
     This may happen if you have been using the commands: *Note
     `mysql_options(..., MYSQL_OPT_READ_TIMEOUT,...)': mysql-options. or
     *Note `mysql_options(..., MYSQL_OPT_WRITE_TIMEOUT,...)':
     mysql-options. In this case increasing the timeout may help solve
     the problem.

   * You have encountered a timeout on the server side and the
     automatic reconnection in the client is disabled (the `reconnect'
     flag in the `MYSQL' structure is equal to 0).

   * You are using a Windows client and the server had dropped the
     connection (probably because `wait_timeout' expired) before the
     command was issued.

     The problem on Windows is that in some cases MySQL does not get an
     error from the OS when writing to the TCP/IP connection to the
     server, but instead gets the error when trying to read the answer
     from the connection.

     Prior to MySQL 5.1.8, even if the `reconnect' flag in the `MYSQL'
     structure is equal to 1, MySQL does not automatically reconnect
     and re-issue the query as it doesn't know if the server did get
     the original query or not.

     The solution to this is to either do a *Note `mysql_ping()':
     mysql-ping. on the connection if there has been a long time since
     the last query (this is what Connector/ODBC does) or set
     `wait_timeout' on the *Note `mysqld': mysqld. server so high that
     it in practice never times out.

   * You can also get these errors if you send a query to the server
     that is incorrect or too large. If *Note `mysqld': mysqld.
     receives a packet that is too large or out of order, it assumes
     that something has gone wrong with the client and closes the
     connection. If you need big queries (for example, if you are
     working with big *Note `BLOB': blob. columns), you can increase
     the query limit by setting the server's `max_allowed_packet'
     variable, which has a default value of 1MB. You may also need to
     increase the maximum packet size on the client end. More
     information on setting the packet size is given in *Note
     packet-too-large::.

     An *Note `INSERT': insert. or *Note `REPLACE': replace. statement
     that inserts a great many rows can also cause these sorts of
     errors. Either one of these statements sends a single request to
     the server irrespective of the number of rows to be inserted;
     thus, you can often avoid the error by reducing the number of rows
     sent per *Note `INSERT': insert. or *Note `REPLACE': replace.

   * You also get a lost connection if you are sending a packet 16MB or
     larger if your client is older than 4.0.8 and your server is 4.0.8
     and above, or the other way around.

   * It is also possible to see this error if host name lookups fail
     (for example, if the DNS server on which your server or network
     relies goes down). This is because MySQL is dependent on the host
     system for name resolution, but has no way of knowing whether it
     is working--from MySQL's point of view the problem is
     indistinguishable from any other network timeout.

     You may also see the `MySQL server has gone away' error if MySQL
     is started with the `--skip-networking' option.

     Another networking issue that can cause this error occurs if the
     MySQL port (default 3306) is blocked by your firewall, thus
     preventing any connections at all to the MySQL server.

   * You can also encounter this error with applications that fork
     child processes, all of which try to use the same connection to
     the MySQL server. This can be avoided by using a separate
     connection for each child process.

   * You have encountered a bug where the server died while executing
     the query.

You can check whether the MySQL server died and restarted by executing
*Note `mysqladmin version': mysqladmin. and examining the server's
uptime. If the client connection was broken because *Note `mysqld':
mysqld. crashed and restarted, you should concentrate on finding the
reason for the crash. Start by checking whether issuing the query again
kills the server again. See *Note crashing::.

You can get more information about the lost connections by starting
*Note `mysqld': mysqld. with the `--log-warnings=2' option. This logs
some of the disconnected errors in the `hostname.err' file. See *Note
error-log::.

If you want to create a bug report regarding this problem, be sure that
you include the following information:

   * Indicate whether the MySQL server died. You can find information
     about this in the server error log. See *Note crashing::.

   * If a specific query kills *Note `mysqld': mysqld. and the tables
     involved were checked with *Note `CHECK TABLE': check-table.
     before you ran the query, can you provide a reproducible test
     case? See *Note porting::.

   * What is the value of the `wait_timeout' system variable in the
     MySQL server? (*Note `mysqladmin variables': mysqladmin. gives you
     the value of this variable.)

   * Have you tried to run *Note `mysqld': mysqld. with the general
     query log enabled to determine whether the problem query appears
     in the log? (See *Note query-log::.)

See also *Note communication-errors::, and *Note bug-reports::.


File: manual.info,  Node: packet-too-large,  Next: communication-errors,  Prev: gone-away,  Up: common-errors

B.5.2.11 Packet Too Large
.........................

A communication packet is a single SQL statement sent to the MySQL
server, a single row that is sent to the client, or a binary log event
sent from a master replication server to a slave.

The largest possible packet that can be transmitted to or from a MySQL
5.1 server or client is 1GB.

When a MySQL client or the *Note `mysqld': mysqld. server receives a
packet bigger than `max_allowed_packet' bytes, it issues an
`ER_NET_PACKET_TOO_LARGE' error and closes the connection. With some
clients, you may also get a `Lost connection to MySQL server during
query' error if the communication packet is too large.

Both the client and the server have their own `max_allowed_packet'
variable, so if you want to handle big packets, you must increase this
variable both in the client and in the server.

If you are using the *Note `mysql': mysql. client program, its default
`max_allowed_packet' variable is 16MB. To set a larger value, start
*Note `mysql': mysql.  like this:


     shell> mysql --max_allowed_packet=32M

That sets the packet size to 32MB.

The server's default `max_allowed_packet' value is 1MB. You can
increase this if the server needs to handle big queries (for example,
if you are working with big *Note `BLOB': blob. columns). For example,
to set the variable to 16MB, start the server like this:


     shell> mysqld --max_allowed_packet=16M

You can also use an option file to set `max_allowed_packet'. For
example, to set the size for the server to 16MB, add the following
lines in an option file:


     [mysqld]
     max_allowed_packet=16M

It is safe to increase the value of this variable because the extra
memory is allocated only when needed. For example, *Note `mysqld':
mysqld. allocates more memory only when you issue a long query or when
*Note `mysqld': mysqld. must return a large result row. The small
default value of the variable is a precaution to catch incorrect
packets between the client and server and also to ensure that you do
not run out of memory by using large packets accidentally.

You can also get strange problems with large packets if you are using
large *Note `BLOB': blob. values but have not given *Note `mysqld':
mysqld. access to enough memory to handle the query. If you suspect
this is the case, try adding `ulimit -d 256000' to the beginning of the
*Note `mysqld_safe': mysqld-safe. script and restarting *Note `mysqld':
mysqld.


File: manual.info,  Node: communication-errors,  Next: full-table,  Prev: packet-too-large,  Up: common-errors

B.5.2.12 Communication Errors and Aborted Connections
.....................................................

If connection problems occur such as communication errors or aborted
connections, use these sources of information to diagnose problems:

   * The error log. See *Note error-log::.

   * The general query log. See *Note query-log::.

   * The `Aborted_XXX' status variables. See *Note
     server-status-variables::.

If you start the server with the `--log-warnings' option, you might
find messages like this in your error log:


     010301 14:38:23  Aborted connection 854 to db:
     'users' user: 'josh'

If a client successfully connects but later disconnects improperly or
is terminated, the server increments the `Aborted_clients' status
variable, and logs an `Aborted connection' message to the error log.
The cause can be any of the following:

   * The client program did not call *Note `mysql_close()':
     mysql-close. before exiting.

   * The client had been sleeping more than `wait_timeout' or
     `interactive_timeout' seconds without issuing any requests to the
     server. See *Note server-system-variables::.

   * The client program ended abruptly in the middle of a data transfer.

If a client is unable even to connect, the server increments the
`Aborted_connects' status variable. Unsuccessful connection attempts
can occur for the following reasons:

   * A client does not have privileges to connect to a database.

   * A client uses an incorrect password.

   * A connection packet does not contain the right information.

   * It takes more than `connect_timeout' seconds to get a connect
     packet. See *Note server-system-variables::.

If these kinds of things happen, it might indicate that someone is
trying to break into your server! Messages for these types of problems
are logged to the general query log if it is enabled.

Other reasons for problems with aborted clients or aborted connections:

   * The `max_allowed_packet' variable value is too small or queries
     require more memory than you have allocated for *Note `mysqld':
     mysqld. See *Note packet-too-large::.

   * Use of Ethernet protocol with Linux, both half and full duplex.
     Many Linux Ethernet drivers have this bug. You should test for
     this bug by transferring a huge file using FTP between the client
     and server machines. If a transfer goes in burst-pause-burst-pause
     mode, you are experiencing a Linux duplex syndrome. Switch the
     duplex mode for both your network card and hub/switch to either
     full duplex or to half duplex and test the results to determine
     the best setting.

   * A problem with the thread library that causes interrupts on reads.

   * Badly configured TCP/IP.

   * Faulty Ethernets, hubs, switches, cables, and so forth.  This can
     be diagnosed properly only by replacing hardware.

See also *Note gone-away::.


File: manual.info,  Node: full-table,  Next: cannot-create,  Prev: communication-errors,  Up: common-errors

B.5.2.13 The table is full
..........................

If a table-full error occurs, it may be that the disk is full or that
the table has reached its maximum size. The effective maximum table
size for MySQL databases is usually determined by operating system
constraints on file sizes, not by MySQL internal limits. See *Note
table-size-limit::.

This error can occur sometimes for MySQL Cluster tables even when there
appears to be more than sufficient data memory available. See the
documentation for the `DataMemory' MySQL Cluster data node
configuration parameter, as well as *Note mysql-cluster-nodes-groups::,
for more information.


File: manual.info,  Node: cannot-create,  Next: commands-out-of-sync,  Prev: full-table,  Up: common-errors

B.5.2.14 Can't create/write to file
...................................

If you get an error of the following type for some queries, it means
that MySQL cannot create a temporary file for the result set in the
temporary directory:


     Can't create/write to file '\\sqla3fe_0.ism'.

The preceding error is a typical message for Windows; the Unix message
is similar.

One fix is to start *Note `mysqld': mysqld. with the `--tmpdir' option
or to add the option to the `[mysqld]' section of your option file. For
example, to specify a directory of `C:\temp', use these lines:


     [mysqld]
     tmpdir=C:/temp

The `C:\temp' directory must exist and have sufficient space for the
MySQL server to write to. See *Note option-files::.

Another cause of this error can be permissions issues. Make sure that
the MySQL server can write to the `tmpdir' directory.

Check also the error code that you get with *Note `perror': perror. One
reason the server cannot write to a table is that the file system is
full:


     shell> perror 28
     OS error code  28:  No space left on device

If you get an error of the following type during startup, it indicates
that the file system or directory used for storing data files is write
protected. Provided that the write error is to a test file, the error
is not serious and can be safely ignored.

     Can't create test file /usr/local/mysql/data/master.lower-test


File: manual.info,  Node: commands-out-of-sync,  Next: ignoring-user,  Prev: cannot-create,  Up: common-errors

B.5.2.15 Commands out of sync
.............................

If you get `Commands out of sync; you can't run this command now' in
your client code, you are calling client functions in the wrong order.

This can happen, for example, if you are using *Note
`mysql_use_result()': mysql-use-result. and try to execute a new query
before you have called *Note `mysql_free_result()': mysql-free-result.
It can also happen if you try to execute two queries that return data
without calling *Note `mysql_use_result()': mysql-use-result. or *Note
`mysql_store_result()': mysql-store-result. in between.


File: manual.info,  Node: ignoring-user,  Next: cannot-find-table,  Prev: commands-out-of-sync,  Up: common-errors

B.5.2.16 Ignoring user
......................

If you get the following error, it means that when *Note `mysqld':
mysqld. was started or when it reloaded the grant tables, it found an
account in the `user' table that had an invalid password.

`Found wrong password for user 'SOME_USER'@'SOME_HOST'; ignoring user'

As a result, the account is simply ignored by the permission system.

The following list indicates possible causes of and fixes for this
problem:

   * You may be running a new version of *Note `mysqld': mysqld. with
     an old `user' table. You can check this by executing *Note
     `mysqlshow mysql user': mysqlshow. to see whether the `Password'
     column is shorter than 16 characters. If so, you can correct this
     condition by running the `scripts/add_long_password' script.

   * The account has an old password (eight characters long).  Update
     the account in the `user' table to have a new password.

   * You have specified a password in the `user' table without using the
     `PASSWORD()' function. Use *Note `mysql': mysql. to update the
     account in the `user' table with a new password, making sure to
     use the `PASSWORD()' function:


          mysql> UPDATE user SET Password=PASSWORD('NEWPWD')
              -> WHERE User='SOME_USER' AND Host='SOME_HOST';


File: manual.info,  Node: cannot-find-table,  Next: cannot-initialize-character-set,  Prev: ignoring-user,  Up: common-errors

B.5.2.17 Table 'tbl_name' doesn't exist
.......................................

If you get either of the following errors, it usually means that no
table exists in the default database with the given name:


     Table 'TBL_NAME' doesn't exist
     Can't find file: 'TBL_NAME' (errno: 2)

In some cases, it may be that the table does exist but that you are
referring to it incorrectly:

   * Because MySQL uses directories and files to store databases and
     tables, database and table names are case sensitive if they are
     located on a file system that has case-sensitive file names.

   * Even for file systems that are not case sensitive, such as on
     Windows, all references to a given table within a query must use
     the same lettercase.

You can check which tables are in the default database with *Note `SHOW
TABLES': show-tables. See *Note show::.


File: manual.info,  Node: cannot-initialize-character-set,  Next: not-enough-file-handles,  Prev: cannot-find-table,  Up: common-errors

B.5.2.18 Can't initialize character set
.......................................

You might see an error like this if you have character set problems:


     MySQL Connection Failed: Can't initialize character set CHARSET_NAME

This error can have any of the following causes:

   * The character set is a multibyte character set and you have no
     support for the character set in the client. In this case, you
     need to recompile the client by running `configure' with the
     `--with-charset=CHARSET_NAME' or
     `--with-extra-charsets=CHARSET_NAME' option. See *Note
     source-configuration-options::.

     All standard MySQL binaries are compiled with
     `--with-extra-charsets=complex' or (for Windows)
     `--with-extra-charsets=complex', which enables support for all
     multibyte character sets.  See *Note
     source-configuration-options::.

   * The character set is a simple character set that is not compiled
     into *Note `mysqld': mysqld, and the character set definition
     files are not in the place where the client expects to find them.

     In this case, you need to use one of the following methods to
     solve the problem:

        * Recompile the client with support for the character set. See
          *Note source-configuration-options::.

        * Specify to the client the directory where the character set
          definition files are located. For many clients, you can do
          this with the `--character-sets-dir' option.

        * Copy the character definition files to the path where the
          client expects them to be.


File: manual.info,  Node: not-enough-file-handles,  Next: table-corruption,  Prev: cannot-initialize-character-set,  Up: common-errors

B.5.2.19 'File' Not Found and Similar Errors
............................................

If you get `ERROR '...' not found (errno: 23)', `Can't open file: ...
(errno: 24)', or any other error with `errno 23' or `errno 24' from
MySQL, it means that you haven't allocated enough file descriptors for
the MySQL server. You can use the *Note `perror': perror.  utility to
get a description of what the error number means:


     shell> perror 23
     OS error code  23:  File table overflow
     shell> perror 24
     OS error code  24:  Too many open files
     shell> perror 11
     OS error code  11:  Resource temporarily unavailable

The problem here is that *Note `mysqld': mysqld. is trying to keep open
too many files simultaneously. You can either tell *Note `mysqld':
mysqld. not to open so many files at once or increase the number of
file descriptors available to *Note `mysqld': mysqld.

To tell *Note `mysqld': mysqld. to keep open fewer files at a time, you
can make the table cache smaller by reducing the value of the
`table_open_cache' system variable (the default value is 64). This may
not entirely prevent running out of file descriptors because in some
circumstances the server may attempt to extend the cache size
temporarily, as described in *Note table-cache::. Reducing the value of
`max_connections' also reduces the number of open files (the default
value is 100).

To change the number of file descriptors available to *Note `mysqld':
mysqld, you can use the `--open-files-limit' option to *Note
`mysqld_safe': mysqld-safe. or set the `open_files_limit' system
variable. See *Note server-system-variables::. The easiest way to set
these values is to add an option to your option file. See *Note
option-files::. If you have an old version of *Note `mysqld': mysqld.
that does not support setting the open files limit, you can edit the
*Note `mysqld_safe': mysqld-safe. script. There is a commented-out line
`ulimit -n 256' in the script. You can remove the ``#'' character to
uncomment this line, and change the number `256' to set the number of
file descriptors to be made available to *Note `mysqld': mysqld.

`--open-files-limit' and `ulimit' can increase the number of file
descriptors, but only up to the limit imposed by the operating system.
There is also a `hard' limit that can be overridden only if you start
*Note `mysqld_safe': mysqld-safe. or *Note `mysqld': mysqld. as `root'
(just remember that you also need to start the server with the `--user'
option in this case so that it does not continue to run as `root' after
it starts up). If you need to increase the operating system limit on
the number of file descriptors available to each process, consult the
documentation for your system.

*Note*:

If you run the `tcsh' shell, `ulimit' does not work!  `tcsh' also
reports incorrect values when you ask for the current limits. In this
case, you should start *Note `mysqld_safe': mysqld-safe. using `sh'.


File: manual.info,  Node: table-corruption,  Prev: not-enough-file-handles,  Up: common-errors

B.5.2.20 Table-Corruption Issues
................................

If you have started *Note `mysqld': mysqld. with `--myisam-recover',
MySQL automatically checks and tries to repair `MyISAM' tables if they
are marked as 'not closed properly' or 'crashed'. If this happens,
MySQL writes an entry in the `hostname.err' file `'Warning: Checking
table ...'' which is followed by `Warning: Repairing table' if the
table needs to be repaired. If you get a lot of these errors, without
*Note `mysqld': mysqld. having died unexpectedly just before, then
something is wrong and needs to be investigated further.

See also *Note server-options::, and *Note reproducible-test-case::.


File: manual.info,  Node: installation-issues,  Next: administration-issues,  Prev: common-errors,  Up: problems

B.5.3 Installation-Related Issues
---------------------------------

* Menu:

* file-permissions::             Problems with File Permissions


File: manual.info,  Node: file-permissions,  Prev: installation-issues,  Up: installation-issues

B.5.3.1 Problems with File Permissions
......................................

If you have problems with file permissions, the `UMASK' environment
variable might be set incorrectly when *Note `mysqld': mysqld. starts.
For example, MySQL might issue the following error message when you
create a table:


     ERROR: Can't find file: 'path/with/filename.frm' (Errcode: 13)

The default `UMASK' value is `0660'. You can change this behavior by
starting *Note `mysqld_safe': mysqld-safe. as follows:


     shell> UMASK=384  # = 600 in octal
     shell> export UMASK
     shell> mysqld_safe &

By default, MySQL creates database directories with an access
permission value of `0700'. You can modify this behavior by setting the
`UMASK_DIR' variable. If you set its value, new directories are created
with the combined `UMASK' and `UMASK_DIR' values. For example, if you
want to give group access to all new directories, you can do this:


     shell> UMASK_DIR=504  # = 770 in octal
     shell> export UMASK_DIR
     shell> mysqld_safe &

MySQL assumes that the value for `UMASK' or `UMASK_DIR' is in octal if
it starts with a zero.

See *Note environment-variables::.


File: manual.info,  Node: administration-issues,  Next: query-issues,  Prev: installation-issues,  Up: problems

B.5.4 Administration-Related Issues
-----------------------------------

* Menu:

* resetting-permissions::        How to Reset the Root Password
* crashing::                     What to Do If MySQL Keeps Crashing
* full-disk::                    How MySQL Handles a Full Disk
* temporary-files::              Where MySQL Stores Temporary Files
* problems-with-mysql-sock::     How to Protect or Change the MySQL Unix Socket File
* timezone-problems::            Time Zone Problems


File: manual.info,  Node: resetting-permissions,  Next: crashing,  Prev: administration-issues,  Up: administration-issues

B.5.4.1 How to Reset the Root Password
......................................

* Menu:

* resetting-permissions-windows::  Resetting the Root Password: Windows Systems
* resetting-permissions-unix::   Resetting the Root Password: Unix Systems
* resetting-permissions-generic::  Resetting the Root Password: Generic Instructions

If you have never set a `root' password for MySQL, the server does not
require a password at all for connecting as `root'. However, this is
insecure. For instructions on assigning passwords, see *Note
default-privileges::.

If you know the `root' password, but want to change it, see *Note
set-password::.

If you set a `root' password previously, but have forgotten it, you can
set a new password. The following sections provide instructions for
Windows and Unix systems, as well as generic instructions that apply to
any system.


File: manual.info,  Node: resetting-permissions-windows,  Next: resetting-permissions-unix,  Prev: resetting-permissions,  Up: resetting-permissions

B.5.4.2 Resetting the Root Password: Windows Systems
....................................................

On Windows, use the following procedure to reset the password for all
MySQL `root' accounts:

  1. Log on to your system as Administrator.

  2. Stop the MySQL server if it is running. For a server that is
     running as a Windows service, go to the Services manager: From the
     `Start' menu, select `Control Panel', then `Administrative Tools',
     then `Services'. Find the MySQL service in the list and stop it.

     If your server is not running as a service, you may need to use
     the Task Manager to force it to stop.

  3. Create a text file containing the following statements.  Replace
     the password with the password that you want to use.


          UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
          FLUSH PRIVILEGES;

     Write the *Note `UPDATE': update. and *Note `FLUSH': flush.
     statements each on a single line. The *Note `UPDATE': update.
     statement resets the password for all `root' accounts, and the
     *Note `FLUSH': flush. statement tells the server to reload the
     grant tables into memory so that it notices the password change.

  4. Save the file. For this example, the file will be named
     `C:\mysql-init.txt'.

  5. Open a console window to get to the command prompt: From the
     `Start' menu, select `Run', then enter `cmd' as the command to be
     run.

  6. Start the MySQL server with the special `--init-file' option
     (notice that the backslash in the option value is doubled):


          C:\> C:\mysql\bin\mysqld --init-file=C:\\mysql-init.txt

     If you installed MySQL to a location other than `C:\mysql', adjust
     the command accordingly.

     The server executes the contents of the file named by the
     `--init-file' option at startup, changing each `root' account
     password.

     You can also add the `--console' option to the command if you want
     server output to appear in the console window rather than in a log
     file.

     If you installed MySQL using the MySQL Installation Wizard, you
     may need to specify a `--defaults-file' option:


          C:\> "C:\Program Files\MySQL\MySQL Server 5.1\bin\mysqld.exe"
                   --defaults-file="C:\\Program Files\\MySQL\\MySQL Server 5.1\\my.ini"
                   --init-file=C:\\mysql-init.txt

     The appropriate `--defaults-file' setting can be found using the
     Services Manager: From the `Start' menu, select `Control Panel',
     then `Administrative Tools', then `Services'. Find the MySQL
     service in the list, right-click it, and choose the `Properties'
     option. The `Path to executable' field contains the
     `--defaults-file' setting.

  7. After the server has started successfully, delete
     `C:\mysql-init.txt'.

You should now be able to connect to the MySQL server as `root' using
the new password. Stop the MySQL server, then restart it in normal mode
again. If you run the server as a service, start it from the Windows
Services window. If you start the server manually, use whatever command
you normally use.


File: manual.info,  Node: resetting-permissions-unix,  Next: resetting-permissions-generic,  Prev: resetting-permissions-windows,  Up: resetting-permissions

B.5.4.3 Resetting the Root Password: Unix Systems
.................................................

On Unix, use the following procedure to reset the password for all
MySQL `root' accounts. The instructions assume that you will start the
server so that it runs using the Unix login account that you normally
use for running the server. For example, if you run the server using
the `mysql' login account, you should log in as `mysql' before using the
instructions. Alternatively, you can log in as `root', but in this case
you _must_ start *Note `mysqld': mysqld.  with the `--user=mysql'
option.  If you start the server as `root' without using
`--user=mysql', the server may create `root'-owned files in the data
directory, such as log files, and these may cause permission-related
problems for future server startups. If that happens, you will need to
either change the ownership of the files to `mysql' or remove them.

  1. Log on to your system as the Unix user that the *Note `mysqld':
     mysqld. server runs as (for example, `mysql').

  2. Locate the `.pid' file that contains the server's process ID. The
     exact location and name of this file depend on your distribution,
     host name, and configuration. Common locations are
     `/var/lib/mysql/', `/var/run/mysqld/', and
     `/usr/local/mysql/data/'. Generally, the file name has an
     extension of `.pid' and begins with either `mysqld' or your
     system's host name.

     You can stop the MySQL server by sending a normal `kill' (not
     `kill -9') to the *Note `mysqld': mysqld. process, using the path
     name of the `.pid' file in the following command:


          shell> kill `cat /mysql-data-directory/host_name.pid`

     Use backticks (not forward quotation marks) with the `cat'
     command. These cause the output of `cat' to be substituted into the
     `kill' command.

  3. Create a text file containing the following statements.  Replace
     the password with the password that you want to use.


          UPDATE mysql.user SET Password=PASSWORD('MyNewPass') WHERE User='root';
          FLUSH PRIVILEGES;

     Write the *Note `UPDATE': update. and *Note `FLUSH': flush.
     statements each on a single line. The *Note `UPDATE': update.
     statement resets the password for all `root' accounts, and the
     *Note `FLUSH': flush. statement tells the server to reload the
     grant tables into memory so that it notices the password change.

  4. Save the file. For this example, the file will be named
     `/home/me/mysql-init'. The file contains the password, so it
     should not be saved where it can be read by other users. If you
     are not logged in as `mysql' (the user the server runs as), make
     sure that the file has permissions that permit `mysql' to read it.

  5. Start the MySQL server with the special `--init-file' option:


          shell> mysqld_safe --init-file=/home/me/mysql-init &

     The server executes the contents of the file named by the
     `--init-file' option at startup, changing each `root' account
     password.

  6. After the server has started successfully, delete
     `/home/me/mysql-init'.

You should now be able to connect to the MySQL server as `root' using
the new password. Stop the server and restart it normally.


File: manual.info,  Node: resetting-permissions-generic,  Prev: resetting-permissions-unix,  Up: resetting-permissions

B.5.4.4 Resetting the Root Password: Generic Instructions
.........................................................

The preceding sections provide password-resetting instructions for
Windows and Unix systems. Alternatively, on any platform, you can set
the new password using the *Note `mysql': mysql. client (but this
approach is less secure):

  1. Stop *Note `mysqld': mysqld. and restart it with the
     `--skip-grant-tables' option. This enables anyone to connect
     without a password and with all privileges. Because this is
     insecure, you might want to use `--skip-grant-tables' in
     conjunction with `--skip-networking' to prevent remote clients
     from connecting.

  2. Connect to the *Note `mysqld': mysqld. server with this command:


          shell> mysql

  3. Issue the following statements in the *Note `mysql': mysql.
     client. Replace the password with the password that you want to
     use.


          mysql> UPDATE mysql.user SET Password=PASSWORD('MyNewPass')
              ->                   WHERE User='root';
          mysql> FLUSH PRIVILEGES;

     The *Note `FLUSH': flush. statement tells the server to reload the
     grant tables into memory so that it notices the password change.

You should now be able to connect to the MySQL server as `root' using
the new password. Stop the server, then restart it normally (without the
`--skip-grant-tables' and `--skip-networking' options).


File: manual.info,  Node: crashing,  Next: full-disk,  Prev: resetting-permissions,  Up: administration-issues

B.5.4.5 What to Do If MySQL Keeps Crashing
..........................................

Each MySQL version is tested on many platforms before it is released.
This does not mean that there are no bugs in MySQL, but if there are
bugs, they should be very few and can be hard to find. If you have a
problem, it always helps if you try to find out exactly what crashes
your system, because you have a much better chance of getting the
problem fixed quickly.

First, you should try to find out whether the problem is that the *Note
`mysqld': mysqld. server dies or whether your problem has to do with
your client. You can check how long your *Note `mysqld': mysqld. server
has been up by executing *Note `mysqladmin version': mysqladmin. If
*Note `mysqld': mysqld. has died and restarted, you may find the reason
by looking in the server's error log. See *Note error-log::.

On some systems, you can find in the error log a stack trace of where
*Note `mysqld': mysqld. died that you can resolve with the
`resolve_stack_dump' program. See *Note porting::. Note that the
variable values written in the error log may not always be 100% correct.

Many server crashes are caused by corrupted data files or index files.
MySQL updates the files on disk with the `write()' system call after
every SQL statement and before the client is notified about the result.
(This is not true if you are running with `--delay-key-write', in which
case data files are written but not index files.) This means that data
file contents are safe even if *Note `mysqld': mysqld. crashes, because
the operating system ensures that the unflushed data is written to
disk. You can force MySQL to flush everything to disk after every SQL
statement by starting *Note `mysqld': mysqld. with the `--flush' option.

The preceding means that normally you should not get corrupted tables
unless one of the following happens:

   * The MySQL server or the server host was killed in the middle of an
     update.

   * You have found a bug in *Note `mysqld': mysqld. that caused it to
     die in the middle of an update.

   * Some external program is manipulating data files or index files at
     the same time as *Note `mysqld': mysqld.  without locking the
     table properly.

   * You are running many *Note `mysqld': mysqld. servers using the
     same data directory on a system that does not support good file
     system locks (normally handled by the `lockd' lock manager), or
     you are running multiple servers with external locking disabled.

   * You have a crashed data file or index file that contains very
     corrupt data that confused *Note `mysqld': mysqld.

   * You have found a bug in the data storage code. This isn't likely,
     but it is at least possible. In this case, you can try to change
     the storage engine to another engine by using *Note `ALTER TABLE':
     alter-table. on a repaired copy of the table.

Because it is very difficult to know why something is crashing, first
try to check whether things that work for others crash for you. Please
try the following things:

   * Stop the *Note `mysqld': mysqld. server with *Note `mysqladmin
     shutdown': mysqladmin, run *Note `myisamchk --silent --force
     */*.MYI': myisamchk. from the data directory to check all `MyISAM'
     tables, and restart *Note `mysqld': mysqld. This ensures that you
     are running from a clean state. See *Note server-administration::.

   * Start *Note `mysqld': mysqld. with the general query log enabled
     (see *Note query-log::). Then try to determine from the
     information written to the log whether some specific query kills
     the server. About 95% of all bugs are related to a particular
     query. Normally, this is one of the last queries in the log file
     just before the server restarts. See *Note query-log::. If you can
     repeatedly kill MySQL with a specific query, even when you have
     checked all tables just before issuing it, then you have been able
     to locate the bug and should submit a bug report for it. See *Note
     bug-reports::.

   * Try to make a test case that we can use to repeat the problem. See
     *Note porting::.

   * Try running the tests in the `mysql-test' directory and the MySQL
     benchmarks. See *Note mysql-test-suite::. They should test MySQL
     rather well. You can also add code to the benchmarks that
     simulates your application. The benchmarks can be found in the
     `sql-bench' directory in a source distribution or, for a binary
     distribution, in the `sql-bench' directory under your MySQL
     installation directory.

   * Try the `fork_big.pl' script. (It is located in the `tests'
     directory of source distributions.)

   * If you configure MySQL for debugging, it is much easier to gather
     information about possible errors if something goes wrong.
     Configuring MySQL for debugging causes a safe memory allocator to
     be included that can find some errors.  It also provides a lot of
     output about what is happening.  Reconfigure MySQL with the
     `--with-debug' or `--with-debug=full' option to `configure' and
     then recompile. See *Note porting::.

   * Make sure that you have applied the latest patches for your
     operating system.

   * Use the `--skip-external-locking' option to *Note `mysqld':
     mysqld. On some systems, the `lockd' lock manager does not work
     properly; the `--skip-external-locking' option tells *Note
     `mysqld': mysqld. not to use external locking. (This means that
     you cannot run two *Note `mysqld': mysqld. servers on the same data
     directory and that you must be careful if you use *Note
     `myisamchk': myisamchk. Nevertheless, it may be instructive to try
     the option as a test.)

   * Have you tried *Note `mysqladmin -u root processlist': mysqladmin.
     when *Note `mysqld': mysqld.  appears to be running but not
     responding? Sometimes *Note `mysqld': mysqld. is not comatose even
     though you might think so. The problem may be that all connections
     are in use, or there may be some internal lock problem.  *Note
     `mysqladmin -u root processlist': mysqladmin. usually is able to
     make a connection even in these cases, and can provide useful
     information about the current number of connections and their
     status.

   * Run the command *Note `mysqladmin -i 5 status': mysqladmin.  or
     *Note `mysqladmin -i 5 -r status': mysqladmin. in a separate
     window to produce statistics while you run your other queries.

   * Try the following:

       1. Start *Note `mysqld': mysqld. from `gdb' (or another
          debugger). See *Note porting::.

       2. Run your test scripts.

       3. Print the backtrace and the local variables at the three
          lowest levels. In `gdb', you can do this with the following
          commands when *Note `mysqld': mysqld. has crashed inside
          `gdb':


               backtrace
               info local
               up
               info local
               up
               info local

          With `gdb', you can also examine which threads exist with
          `info threads' and switch to a specific thread with `thread
          N', where N is the thread ID.

   * Try to simulate your application with a Perl script to force MySQL
     to crash or misbehave.

   * Send a normal bug report. See *Note bug-reports::. Be even more
     detailed than usual. Because MySQL works for many people, it may
     be that the crash results from something that exists only on your
     computer (for example, an error that is related to your particular
     system libraries).

   * If you have a problem with tables containing dynamic-length rows
     and you are using only *Note `VARCHAR': char. columns (not *Note
     `BLOB': blob. or *Note `TEXT': blob. columns), you can try to
     change all *Note `VARCHAR': char. to *Note `CHAR': char. with
     *Note `ALTER TABLE': alter-table. This forces MySQL to use
     fixed-size rows. Fixed-size rows take a little extra space, but
     are much more tolerant to corruption.

     The current dynamic row code has been in use for several years
     with very few problems, but dynamic-length rows are by nature more
     prone to errors, so it may be a good idea to try this strategy to
     see whether it helps.

   * Do not rule out your server hardware when diagnosing problems.
     Defective hardware can be the cause of data corruption. Particular
     attention should be paid to your memory and disk subsystems when
     troubleshooting hardware.


File: manual.info,  Node: full-disk,  Next: temporary-files,  Prev: crashing,  Up: administration-issues

B.5.4.6 How MySQL Handles a Full Disk
.....................................

This section describes how MySQL responds to disk-full errors (such as
`no space left on device'), and to quota-exceeded errors (such as
`write failed' or `user block limit reached').

This section is relevant for writes to `MyISAM' tables. It also applies
for writes to binary log files and binary log index file, except that
references to `row' and `record' should be understood to mean `event.'

When a disk-full condition occurs, MySQL does the following:

   * It checks once every minute to see whether there is enough space
     to write the current row. If there is enough space, it continues
     as if nothing had happened.

   * Every 10 minutes it writes an entry to the log file, warning about
     the disk-full condition.

To alleviate the problem, you can take the following actions:

   * To continue, you only have to free enough disk space to insert all
     records.

   * To abort the thread, you must use *Note `mysqladmin kill':
     mysqladmin. The thread is aborted the next time it checks the disk
     (in one minute).

   * Other threads might be waiting for the table that caused the
     disk-full condition. If you have several `locked' threads, killing
     the one thread that is waiting on the disk-full condition enables
     the other threads to continue.

Exceptions to the preceding behavior are when you use *Note `REPAIR
TABLE': repair-table. or *Note `OPTIMIZE TABLE': optimize-table. or
when the indexes are created in a batch after *Note `LOAD DATA INFILE':
load-data. or after an *Note `ALTER TABLE': alter-table. statement. All
of these statements may create large temporary files that, if left to
themselves, would cause big problems for the rest of the system. If the
disk becomes full while MySQL is doing any of these operations, it
removes the big temporary files and mark the table as crashed. The
exception is that for *Note `ALTER TABLE': alter-table, the old table
is left unchanged.


File: manual.info,  Node: temporary-files,  Next: problems-with-mysql-sock,  Prev: full-disk,  Up: administration-issues

B.5.4.7 Where MySQL Stores Temporary Files
..........................................

On Unix, MySQL uses the value of the `TMPDIR' environment variable as
the path name of the directory in which to store temporary files. If
`TMPDIR' is not set, MySQL uses the system default, which is usually
`/tmp', `/var/tmp', or `/usr/tmp'.

On Windows, Netware and OS2, MySQL checks in order the values of the
`TMPDIR', `TEMP', and `TMP' environment variables. For the first one
found to be set, MySQL uses it and does not check those remaining. If
none of `TMPDIR', `TEMP', or `TMP' are set, MySQL uses the Windows
system default, which is usually `C:\windows\temp\'.

If the file system containing your temporary file directory is too
small, you can use the `--tmpdir' option to *Note `mysqld': mysqld. to
specify a directory in a file system where you have enough space. On
replication slaves, you can use `--slave-load-tmpdir' to specify a
separate directory for holding temporary files when replicating *Note
`LOAD DATA INFILE': load-data. statements.

The `--tmpdir' option can be set to a list of several paths that are
used in round-robin fashion. Paths should be separated by colon
characters (``:'') on Unix and semicolon characters (``;'') on Windows,
NetWare, and OS/2.

*Note*:

To spread the load effectively, these paths should be located on
different _physical_ disks, not different partitions of the same disk.

If the MySQL server is acting as a replication slave, you should be
sure to set `--slave-load-tmpdir' not to point to a directory that is
on a memory-based file system or to a directory that is cleared when
the server host restarts.  A replication slave needs some of its
temporary files to survive a machine restart so that it can replicate
temporary tables or *Note `LOAD DATA INFILE': load-data. operations. If
files in the slave temporary file directory are lost when the server
restarts, replication fails.

MySQL arranges that temporary files are removed if *Note `mysqld':
mysqld. is terminated. On platforms that support it (such as Unix),
this is done by unlinking the file after opening it. The disadvantage
of this is that the name does not appear in directory listings and you
do not see a big temporary file that fills up the file system in which
the temporary file directory is located. (In such cases, `lsof +L1' may
be helpful in identifying large files associated with *Note `mysqld':
mysqld.)

When sorting (`ORDER BY' or `GROUP BY'), MySQL normally uses one or two
temporary files.  The maximum disk space required is determined by the
following expression:


     (length of what is sorted + sizeof(row pointer))
     * number of matched rows
     * 2

The row pointer size is usually four bytes, but may grow in the future
for really big tables.

For some *Note `SELECT': select. queries, MySQL also creates temporary
SQL tables. These are not hidden and have names of the form `SQL_*'.

*Note `ALTER TABLE': alter-table. creates a temporary copy of the
original table in the same directory as the original table.


File: manual.info,  Node: problems-with-mysql-sock,  Next: timezone-problems,  Prev: temporary-files,  Up: administration-issues

B.5.4.8 How to Protect or Change the MySQL Unix Socket File
...........................................................

The default location for the Unix socket file that the server uses for
communication with local clients is `/tmp/mysql.sock'. (For some
distribution formats, the directory might be different, such as
`/var/lib/mysql' for RPMs.)

On some versions of Unix, anyone can delete files in the `/tmp'
directory or other similar directories used for temporary files. If the
socket file is located in such a directory on your system, this might
cause problems.

On most versions of Unix, you can protect your `/tmp' directory so that
files can be deleted only by their owners or the superuser (`root'). To
do this, set the `sticky' bit on the `/tmp' directory by logging in as
`root' and using the following command:


     shell> chmod +t /tmp

You can check whether the `sticky' bit is set by executing `ls -ld
/tmp'. If the last permission character is `t', the bit is set.

Another approach is to change the place where the server creates the
Unix socket file. If you do this, you should also let client programs
know the new location of the file. You can specify the file location in
several ways:

   * Specify the path in a global or local option file. For example,
     put the following lines in `/etc/my.cnf':


          [mysqld]
          socket=/path/to/socket

          [client]
          socket=/path/to/socket

     See *Note option-files::.

   * Specify a `--socket' option on the command line to *Note
     `mysqld_safe': mysqld-safe. and when you run client programs.

   * Set the `MYSQL_UNIX_PORT' environment variable to the path of the
     Unix socket file.

   * Recompile MySQL from source to use a different default Unix socket
     file location. Define the path to the file with the
     `--with-unix-socket-path' option when you run `configure'. See
     *Note source-configuration-options::.

You can test whether the new socket location works by attempting to
connect to the server with this command:


     shell> mysqladmin --socket=/path/to/socket version


File: manual.info,  Node: timezone-problems,  Prev: problems-with-mysql-sock,  Up: administration-issues

B.5.4.9 Time Zone Problems
..........................

If you have a problem with `SELECT NOW()' returning values in UTC and
not your local time, you have to tell the server your current time
zone. The same applies if `UNIX_TIMESTAMP()' returns the wrong value.
This should be done for the environment in which the server runs; for
example, in *Note `mysqld_safe': mysqld-safe. or *Note `mysql.server':
mysql-server. See *Note environment-variables::.

You can set the time zone for the server with the
`--timezone=TIMEZONE_NAME' option to *Note `mysqld_safe': mysqld-safe.
You can also set it by setting the `TZ' environment variable before you
start *Note `mysqld': mysqld.

The permissible values for `--timezone' or `TZ' are system dependent.
Consult your operating system documentation to see what values are
acceptable.


File: manual.info,  Node: query-issues,  Next: optimizer-issues,  Prev: administration-issues,  Up: problems

B.5.5 Query-Related Issues
--------------------------

* Menu:

* case-sensitivity::             Case Sensitivity in String Searches
* using-date::                   Problems Using DATE Columns
* problems-with-null::           Problems with NULL Values
* problems-with-alias::          Problems with Column Aliases
* nontransactional-tables::      Rollback Failure for Nontransactional Tables
* deleting-from-related-tables::  Deleting Rows from Related Tables
* no-matching-rows::             Solving Problems with No Matching Rows
* problems-with-float::          Problems with Floating-Point Values


File: manual.info,  Node: case-sensitivity,  Next: using-date,  Prev: query-issues,  Up: query-issues

B.5.5.1 Case Sensitivity in String Searches
...........................................

For nonbinary strings (*Note `CHAR': char, *Note `VARCHAR': char, *Note
`TEXT': blob.), string searches use the collation of the comparison
operands. For binary strings (*Note `BINARY': binary-varbinary, *Note
`VARBINARY': binary-varbinary, *Note `BLOB': blob.), comparisons use the
numeric values of the bytes in the operands; this means that for
alphabetic characters, comparisons will be case sensitive.

A comparison between a nonbinary string and binary string is treated as
a comparison of binary strings.

Simple comparison operations (`>=, >, =, <, <=', sorting, and grouping)
are based on each character's `sort value.' Characters with the same
sort value are treated as the same character. For example, if ``e'' and
``e''' have the same sort value in a given collation, they compare as
equal.

The default character set and collation are `latin1' and
`latin1_swedish_ci', so nonbinary string comparisons are case
insensitive by default. This means that if you search with `COL_NAME
LIKE 'a%'', you get all column values that start with `A' or `a'. To
make this search case sensitive, make sure that one of the operands has
a case sensitive or binary collation. For example, if you are comparing
a column and a string that both have the `latin1' character set, you
can use the `COLLATE' operator to cause either operand to have the
`latin1_general_cs' or `latin1_bin' collation:


     COL_NAME COLLATE latin1_general_cs LIKE 'a%'
     COL_NAME LIKE 'a%' COLLATE latin1_general_cs
     COL_NAME COLLATE latin1_bin LIKE 'a%'
     COL_NAME LIKE 'a%' COLLATE latin1_bin

If you want a column always to be treated in case-sensitive fashion,
declare it with a case sensitive or binary collation.  See *Note
create-table::.

To cause a case-sensitive comparison of nonbinary strings to be case
insensitive, use `COLLATE' to name a case-insensitive collation. The
strings in the following example normally are case sensitive, but
`COLLATE' changes the comparison to be case insensitive:


     mysql> SET @s1 = 'MySQL' COLLATE latin1_bin,
         ->     @s2 = 'mysql' COLLATE latin1_bin;
     mysql> SELECT @s1 = @s2;
     +-----------+
     | @s1 = @s2 |
     +-----------+
     |         0 |
     +-----------+
     mysql> SELECT @s1 COLLATE latin1_swedish_ci = @s2;
     +-------------------------------------+
     | @s1 COLLATE latin1_swedish_ci = @s2 |
     +-------------------------------------+
     |                                   1 |
     +-------------------------------------+

A binary string is case sensitive in comparisons. To compare the string
as case insensitive, convert it to a nonbinary string and use `COLLATE'
to name a case-insensitive collation:


     mysql> SET @s = BINARY 'MySQL';
     mysql> SELECT @s = 'mysql';
     +--------------+
     | @s = 'mysql' |
     +--------------+
     |            0 |
     +--------------+
     mysql> SELECT CONVERT(@s USING latin1) COLLATE latin1_swedish_ci = 'mysql';
     +--------------------------------------------------------------+
     | CONVERT(@s USING latin1) COLLATE latin1_swedish_ci = 'mysql' |
     +--------------------------------------------------------------+
     |                                                            1 |
     +--------------------------------------------------------------+

To determine whether a value will compare as a nonbinary or binary
string, use the `COLLATION()' function. This example shows that
`VERSION()' returns a string that has a case-insensitive collation, so
comparisons are case insensitive:


     mysql> SELECT COLLATION(VERSION());
     +----------------------+
     | COLLATION(VERSION()) |
     +----------------------+
     | utf8_general_ci      |
     +----------------------+

For binary strings, the collation value is `binary', so comparisons
will be case sensitive. One context in which you will see `binary' is
for compression and encryption functions, which return binary strings
as a general rule: string:


     mysql> SELECT COLLATION(ENCRYPT('x')), COLLATION(SHA1('x'));
     +-------------------------+----------------------+
     | COLLATION(ENCRYPT('x')) | COLLATION(SHA1('x')) |
     +-------------------------+----------------------+
     | binary                  | binary               |
     +-------------------------+----------------------+


File: manual.info,  Node: using-date,  Next: problems-with-null,  Prev: case-sensitivity,  Up: query-issues

B.5.5.2 Problems Using DATE Columns
...................................

The format of a *Note `DATE': datetime. value is `'YYYY-MM-DD''.
According to standard SQL, no other format is permitted. You should use
this format in *Note `UPDATE': update. expressions and in the `WHERE'
clause of *Note `SELECT': select. statements. For example:


     SELECT * FROM t1 WHERE date >= '2003-05-05';

As a convenience, MySQL automatically converts a date to a number if
the date is used in a numeric context and vice versa. MySQL also
permits a `relaxed' string format when updating and in a `WHERE' clause
that compares a date to a *Note `DATE': datetime, *Note `DATETIME':
datetime, or *Note `TIMESTAMP': datetime. column.  `Relaxed' format
means that any punctuation character may be used as the separator
between parts. For example, `'2004-08-15'' and `'2004#08#15'' are
equivalent. MySQL can also convert a string containing no separators
(such as `'20040815''), provided it makes sense as a date.

When you compare a *Note `DATE': datetime, *Note `TIME': time, *Note
`DATETIME': datetime, or *Note `TIMESTAMP': datetime. to a constant
string with the `<', `<=', `=', `>=', `>', or `BETWEEN' operators,
MySQL normally converts the string to an internal long integer for
faster comparison (and also for a bit more `relaxed' string checking).
However, this conversion is subject to the following exceptions:

   * When you compare two columns

   * When you compare a *Note `DATE': datetime, *Note `TIME': time,
     *Note `DATETIME': datetime, or *Note `TIMESTAMP': datetime. column
     to an expression

   * When you use any comparison method other than those just listed,
     such as `IN' or `STRCMP()'.

For those exceptions, the comparison is done by converting the objects
to strings and performing a string comparison.

To be on the safe side, assume that strings are compared as strings and
use the appropriate string functions if you want to compare a temporal
value to a string.

The special `zero' date `'0000-00-00'' can be stored and retrieved as
`'0000-00-00'.' When a `'0000-00-00'' date is used through
Connector/ODBC, it is automatically converted to `NULL' because ODBC
cannot handle that kind of date.

Because MySQL performs the conversions just described, the following
statements work (assume that `idate' is a *Note `DATE': datetime.
column):


     INSERT INTO t1 (idate) VALUES (19970505);
     INSERT INTO t1 (idate) VALUES ('19970505');
     INSERT INTO t1 (idate) VALUES ('97-05-05');
     INSERT INTO t1 (idate) VALUES ('1997.05.05');
     INSERT INTO t1 (idate) VALUES ('1997 05 05');
     INSERT INTO t1 (idate) VALUES ('0000-00-00');

     SELECT idate FROM t1 WHERE idate >= '1997-05-05';
     SELECT idate FROM t1 WHERE idate >= 19970505;
     SELECT MOD(idate,100) FROM t1 WHERE idate >= 19970505;
     SELECT idate FROM t1 WHERE idate >= '19970505';

However, the following statement does not work:


     SELECT idate FROM t1 WHERE STRCMP(idate,'20030505')=0;

`STRCMP()' is a string function, so it converts `idate' to a string in
`'YYYY-MM-DD'' format and performs a string comparison. It does not
convert `'20030505'' to the date `'2003-05-05'' and perform a date
comparison.

If you enable the `ALLOW_INVALID_DATES' SQL mode, MySQL permits you to
store dates that are given only limited checking: MySQL requires only
that the day is in the range from 1 to 31 and the month is in the range
from 1 to 12.  This makes MySQL very convenient for Web applications
where you obtain year, month, and day in three different fields and you
want to store exactly what the user inserted (without date validation).

MySQL permits you to store dates where the day or month and day are
zero. This is convenient if you want to store a birthdate in a *Note
`DATE': datetime. column and you know only part of the date. To
disallow zero month or day parts in dates, enable the `NO_ZERO_IN_DATE'
SQL mode.

MySQL permits you to store a `zero' value of `'0000-00-00'' as a `dummy
date.' This is in some cases more convenient than using `NULL' values.
If a date to be stored in a *Note `DATE': datetime. column cannot be
converted to any reasonable value, MySQL stores `'0000-00-00''. To
disallow `'0000-00-00'', enable the `NO_ZERO_DATE' SQL mode.

To have MySQL check all dates and accept only legal dates (unless
overridden by `IGNORE'), set the `sql_mode' system variable to
`"NO_ZERO_IN_DATE,NO_ZERO_DATE"'.


File: manual.info,  Node: problems-with-null,  Next: problems-with-alias,  Prev: using-date,  Up: query-issues

B.5.5.3 Problems with NULL Values
.................................

The concept of the `NULL' value is a common source of confusion for
newcomers to SQL, who often think that `NULL' is the same thing as an
empty string `'''. This is not the case. For example, the following
statements are completely different:


     mysql> INSERT INTO my_table (phone) VALUES (NULL);
     mysql> INSERT INTO my_table (phone) VALUES ('');

Both statements insert a value into the `phone' column, but the first
inserts a `NULL' value and the second inserts an empty string. The
meaning of the first can be regarded as `phone number is not known' and
the meaning of the second can be regarded as `the person is known to
have no phone, and thus no phone number.'

To help with `NULL' handling, you can use the `IS NULL' and `IS NOT
NULL' operators and the `IFNULL()' function.

In SQL, the `NULL' value is never true in comparison to any other
value, even `NULL'.  An expression that contains `NULL' always produces
a `NULL' value unless otherwise indicated in the documentation for the
operators and functions involved in the expression. All columns in the
following example return `NULL':


     mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL);

To search for column values that are `NULL', you cannot use an `expr =
NULL' test. The following statement returns no rows, because `expr =
NULL' is never true for any expression:


     mysql> SELECT * FROM my_table WHERE phone = NULL;

To look for `NULL' values, you must use the `IS NULL' test. The
following statements show how to find the `NULL' phone number and the
empty phone number:


     mysql> SELECT * FROM my_table WHERE phone IS NULL;
     mysql> SELECT * FROM my_table WHERE phone = '';

See *Note working-with-null::, for additional information and examples.

You can add an index on a column that can have `NULL' values if you are
using the `MyISAM', `InnoDB', or `MEMORY' storage engine. Otherwise,
you must declare an indexed column `NOT NULL', and you cannot insert
`NULL' into the column.

When reading data with *Note `LOAD DATA INFILE': load-data, empty or
missing columns are updated with `'''. To load a `NULL' value into a
column, use `\N' in the data file. The literal word ``NULL'' may also
be used under some circumstances. See *Note load-data::.

When using `DISTINCT', `GROUP BY', or `ORDER BY', all `NULL' values are
regarded as equal.

When using `ORDER BY', `NULL' values are presented first, or last if
you specify `DESC' to sort in descending order.

Aggregate (summary) functions such as `COUNT()', `MIN()', and `SUM()'
ignore `NULL' values. The exception to this is `COUNT(*)', which counts
rows and not individual column values. For example, the following
statement produces two counts. The first is a count of the number of
rows in the table, and the second is a count of the number of
non-`NULL' values in the `age' column:


     mysql> SELECT COUNT(*), COUNT(age) FROM person;

For some data types, MySQL handles `NULL' values specially. If you
insert `NULL' into a *Note `TIMESTAMP': datetime. column, the current
date and time is inserted. If you insert `NULL' into an integer or
floating-point column that has the `AUTO_INCREMENT' attribute, the next
number in the sequence is inserted.


File: manual.info,  Node: problems-with-alias,  Next: nontransactional-tables,  Prev: problems-with-null,  Up: query-issues

B.5.5.4 Problems with Column Aliases
....................................

An alias can be used in a query select list to give a column a
different name. You can use the alias in `GROUP BY', `ORDER BY', or
`HAVING' clauses to refer to the column:


     SELECT SQRT(a*b) AS root FROM TBL_NAME
       GROUP BY root HAVING root > 0;
     SELECT id, COUNT(*) AS cnt FROM TBL_NAME
       GROUP BY id HAVING cnt > 0;
     SELECT id AS 'Customer identity' FROM TBL_NAME;

Standard SQL disallows references to column aliases in a `WHERE'
clause. This restriction is imposed because when the `WHERE' clause is
evaluated, the column value may not yet have been determined. For
example, the following query is illegal:


     SELECT id, COUNT(*) AS cnt FROM TBL_NAME
       WHERE cnt > 0 GROUP BY id;

The `WHERE' clause determines which rows should be included in the
`GROUP BY' clause, but it refers to the alias of a column value that is
not known until after the rows have been selected, and grouped by the
`GROUP BY'.

In the select list of a query, a quoted column alias can be specified
using identifier or string quoting characters:


     SELECT 1 AS `one`, 2 AS 'two';

Elsewhere in the statement, quoted references to the alias must use
identifier quoting or the reference is treated as a string literal. For
example, this statement groups by the values in column `id', referenced
using the alias ``a`':


     SELECT id AS 'a', COUNT(*) AS cnt FROM TBL_NAME
       GROUP BY `a`;

But this statement groups by the literal string `'a'' and will not work
as expected:


     SELECT id AS 'a', COUNT(*) AS cnt FROM TBL_NAME
       GROUP BY 'a';


File: manual.info,  Node: nontransactional-tables,  Next: deleting-from-related-tables,  Prev: problems-with-alias,  Up: query-issues

B.5.5.5 Rollback Failure for Nontransactional Tables
....................................................

If you receive the following message when trying to perform a *Note
`ROLLBACK': commit, it means that one or more of the tables you used in
the transaction do not support transactions:


     Warning: Some non-transactional changed tables couldn't be rolled back

These nontransactional tables are not affected by the *Note `ROLLBACK':
commit.  statement.

If you were not deliberately mixing transactional and nontransactional
tables within the transaction, the most likely cause for this message
is that a table you thought was transactional actually is not. This can
happen if you try to create a table using a transactional storage
engine that is not supported by your *Note `mysqld': mysqld. server (or
that was disabled with a startup option). If *Note `mysqld': mysqld.
does not support a storage engine, it instead creates the table as a
`MyISAM' table, which is nontransactional.

You can check the storage engine for a table by using either of these
statements:


     SHOW TABLE STATUS LIKE 'TBL_NAME';
     SHOW CREATE TABLE TBL_NAME;

See *Note show-table-status::, and *Note show-create-table::.

You can check which storage engines your *Note `mysqld': mysqld. server
supports by using this statement:


     SHOW ENGINES;

You can also use the following statement, and check the value of the
variable that is associated with the storage engine in which you are
interested:


     SHOW VARIABLES LIKE 'have_%';

For example, to determine whether the `InnoDB' storage engine is
available, check the value of the `have_innodb' variable.

See *Note show-engines::, and *Note show-variables::.


File: manual.info,  Node: deleting-from-related-tables,  Next: no-matching-rows,  Prev: nontransactional-tables,  Up: query-issues

B.5.5.6 Deleting Rows from Related Tables
.........................................

If the total length of the *Note `DELETE': delete. statement for
`related_table' is more than 1MB (the default value of the
`max_allowed_packet' system variable), you should split it into smaller
parts and execute multiple *Note `DELETE': delete. statements. You
probably get the fastest *Note `DELETE': delete.  by specifying only
100 to 1,000 `related_column' values per statement if the
`related_column' is indexed. If the `related_column' isn't indexed, the
speed is independent of the number of arguments in the `IN' clause.


File: manual.info,  Node: no-matching-rows,  Next: problems-with-float,  Prev: deleting-from-related-tables,  Up: query-issues

B.5.5.7 Solving Problems with No Matching Rows
..............................................

If you have a complicated query that uses many tables but that returns
no rows, you should use the following procedure to find out what is
wrong:

  1. Test the query with *Note `EXPLAIN': explain.  to check whether
     you can find something that is obviously wrong. See *Note
     explain::.

  2. Select only those columns that are used in the `WHERE' clause.

  3. Remove one table at a time from the query until it returns some
     rows. If the tables are large, it is a good idea to use `LIMIT 10'
     with the query.

  4. Issue a *Note `SELECT': select. for the column that should have
     matched a row against the table that was last removed from the
     query.

  5. If you are comparing *Note `FLOAT': floating-point-types.  or
     *Note `DOUBLE': floating-point-types. columns with numbers that
     have decimals, you cannot use equality (`=') comparisons. This
     problem is common in most computer languages because not all
     floating-point values can be stored with exact precision. In some
     cases, changing the *Note `FLOAT': floating-point-types. to a
     *Note `DOUBLE': floating-point-types. fixes this. See *Note
     problems-with-float::.

  6. If you still cannot figure out what is wrong, create a minimal
     test that can be run with `mysql test < query.sql' that shows your
     problems. You can create a test file by dumping the tables with
     *Note `mysqldump --quick db_name TBL_NAME_1 ... TBL_NAME_N >
     query.sql': mysqldump. Open the file in an editor, remove some
     insert lines (if there are more than needed to demonstrate the
     problem), and add your *Note `SELECT': select. statement at the end
     of the file.

     Verify that the test file demonstrates the problem by executing
     these commands:


          shell> mysqladmin create test2
          shell> mysql test2 < query.sql

     Attach the test file to a bug report, which you can file using the
     instructions in *Note bug-reports::.


File: manual.info,  Node: problems-with-float,  Prev: no-matching-rows,  Up: query-issues

B.5.5.8 Problems with Floating-Point Values
...........................................

Floating-point numbers sometimes cause confusion because they are
approximate and not stored as exact values. A floating-point value as
written in an SQL statement may not be the same as the value
represented internally. Attempts to treat floating-point values as
exact in comparisons may lead to problems. They are also subject to
platform or implementation dependencies. The *Note `FLOAT':
floating-point-types. and *Note `DOUBLE': floating-point-types. data
types are subject to these issues. For *Note `DECIMAL':
fixed-point-types.  columns, MySQL performs operations with a precision
of 65 decimal digits, which should solve most common inaccuracy
problems.

The following example uses *Note `DOUBLE': floating-point-types. to
demonstrate how calculations that are done using floating-point
operations are subject to floating-point error.


     mysql> CREATE TABLE t1 (i INT, d1 DOUBLE, d2 DOUBLE);
     mysql> INSERT INTO t1 VALUES (1, 101.40, 21.40), (1, -80.00, 0.00),
         -> (2, 0.00, 0.00), (2, -13.20, 0.00), (2, 59.60, 46.40),
         -> (2, 30.40, 30.40), (3, 37.00, 7.40), (3, -29.60, 0.00),
         -> (4, 60.00, 15.40), (4, -10.60, 0.00), (4, -34.00, 0.00),
         -> (5, 33.00, 0.00), (5, -25.80, 0.00), (5, 0.00, 7.20),
         -> (6, 0.00, 0.00), (6, -51.40, 0.00);

     mysql> SELECT i, SUM(d1) AS a, SUM(d2) AS b
         -> FROM t1 GROUP BY i HAVING a <> b;

     +------+-------+------+
     | i    | a     | b    |
     +------+-------+------+
     |    1 |  21.4 | 21.4 |
     |    2 |  76.8 | 76.8 |
     |    3 |   7.4 |  7.4 |
     |    4 |  15.4 | 15.4 |
     |    5 |   7.2 |  7.2 |
     |    6 | -51.4 |    0 |
     +------+-------+------+

The result is correct. Although the first five records look like they
should not satisfy the comparison (the values of `a' and `b' do not
appear to be different), they may do so because the difference between
the numbers shows up around the tenth decimal or so, depending on
factors such as computer architecture or the compiler version or
optimization level. For example, different CPUs may evaluate
floating-point numbers differently.

If columns `d1' and `d2' had been defined as *Note `DECIMAL':
fixed-point-types. rather than *Note `DOUBLE': floating-point-types,
the result of the *Note `SELECT': select. query would have contained
only one row--the last one shown above.

The correct way to do floating-point number comparison is to first
decide on an acceptable tolerance for differences between the numbers
and then do the comparison against the tolerance value. For example, if
we agree that floating-point numbers should be regarded the same if
they are same within a precision of one in ten thousand (0.0001), the
comparison should be written to find differences larger than the
tolerance value:


     mysql> SELECT i, SUM(d1) AS a, SUM(d2) AS b FROM t1
         -> GROUP BY i HAVING ABS(a - b) > 0.0001;
     +------+-------+------+
     | i    | a     | b    |
     +------+-------+------+
     |    6 | -51.4 |    0 |
     +------+-------+------+
     1 row in set (0.00 sec)

Conversely, to get rows where the numbers are the same, the test should
find differences within the tolerance value:


     mysql> SELECT i, SUM(d1) AS a, SUM(d2) AS b FROM t1
         -> GROUP BY i HAVING ABS(a - b) <= 0.0001;
     +------+------+------+
     | i    | a    | b    |
     +------+------+------+
     |    1 | 21.4 | 21.4 |
     |    2 | 76.8 | 76.8 |
     |    3 |  7.4 |  7.4 |
     |    4 | 15.4 | 15.4 |
     |    5 |  7.2 |  7.2 |
     +------+------+------+
     5 rows in set (0.03 sec)

Floating-point values are subject to platform or implementation
dependencies. Suppose that you execute the following statements:


     CREATE TABLE t1(c1 FLOAT(53,0), c2 FLOAT(53,0));
     INSERT INTO t1 VALUES('1e+52','-1e+52');
     SELECT * FROM t1;

On some platforms, the `SELECT' statement returns `inf' and `-inf'. On
others, it returns `0' and `-0'.

An implication of the preceding issues is that if you attempt to create
a replication slave by dumping table contents with *Note `mysqldump':
mysqldump. on the master and reloading the dump file into the slave,
tables containing floating-point columns might differ between the two
hosts.


File: manual.info,  Node: optimizer-issues,  Next: table-definition-issues,  Prev: query-issues,  Up: problems

B.5.6 Optimizer-Related Issues
------------------------------

MySQL uses a cost-based optimizer to determine the best way to resolve
a query. In many cases, MySQL can calculate the best possible query
plan, but sometimes MySQL does not have enough information about the
data at hand and has to make `educated' guesses about the data.

For the cases when MySQL does not do the "right" thing, tools that you
have available to help MySQL are:

   * Use the *Note `EXPLAIN': explain. statement to get information
     about how MySQL processes a query. To use it, just add the keyword
     *Note `EXPLAIN': explain. to the front of your *Note `SELECT':
     select. statement:


          mysql> EXPLAIN SELECT * FROM t1, t2 WHERE t1.i = t2.i;

     *Note `EXPLAIN': explain. is discussed in more detail in *Note
     explain::.

   * Use `ANALYZE TABLE TBL_NAME' to update the key distributions for
     the scanned table. See *Note analyze-table::.

   * Use `FORCE INDEX' for the scanned table to tell MySQL that table
     scans are very expensive compared to using the given index:


          SELECT * FROM t1, t2 FORCE INDEX (index_for_column)
          WHERE t1.col_name=t2.col_name;

     `USE INDEX' and `IGNORE INDEX' may also be useful. See *Note
     index-hints::.

   * Global and table-level `STRAIGHT_JOIN'. See *Note select::.

   * You can tune global or thread-specific system variables. For
     example, start *Note `mysqld': mysqld. with the
     `--max-seeks-for-key=1000' option or use `SET
     max_seeks_for_key=1000' to tell the optimizer to assume that no
     key scan causes more than 1,000 key seeks. See *Note
     server-system-variables::.


File: manual.info,  Node: table-definition-issues,  Next: bugs,  Prev: optimizer-issues,  Up: problems

B.5.7 Table Definition-Related Issues
-------------------------------------

* Menu:

* alter-table-problems::         Problems with ALTER TABLE
* temporary-table-problems::     TEMPORARY Table Problems


File: manual.info,  Node: alter-table-problems,  Next: temporary-table-problems,  Prev: table-definition-issues,  Up: table-definition-issues

B.5.7.1 Problems with ALTER TABLE
.................................

If you get a duplicate-key error when using *Note `ALTER TABLE':
alter-table. to change the character set or collation of a character
column, the cause is either that the new column collation maps two keys
to the same value or that the table is corrupted. In the latter case,
you should run *Note `REPAIR TABLE': repair-table. on the table.

If *Note `ALTER TABLE': alter-table. dies with the following error, the
problem may be that MySQL crashed during an earlier *Note `ALTER
TABLE': alter-table.  operation and there is an old table named `A-XXX'
or `B-XXX' lying around:


     Error on rename of './database/name.frm'
     to './database/B-XXX.frm' (Errcode: 17)

In this case, go to the MySQL data directory and delete all files that
have names starting with `A-' or `B-'. (You may want to move them
elsewhere instead of deleting them.)

*Note `ALTER TABLE': alter-table. works in the following way:

   * Create a new table named `A-XXX' with the requested structural
     changes.

   * Copy all rows from the original table to `A-XXX'.

   * Rename the original table to `B-XXX'.

   * Rename `A-XXX' to your original table name.

   * Delete `B-XXX'.

If something goes wrong with the renaming operation, MySQL tries to
undo the changes. If something goes seriously wrong (although this
shouldn't happen), MySQL may leave the old table as `B-XXX'. A simple
rename of the table files at the system level should get your data back.

If you use *Note `ALTER TABLE': alter-table. on a transactional table
or if you are using Windows or OS/2, *Note `ALTER TABLE': alter-table.
unlocks the table if you had done a *Note `LOCK TABLE': lock-tables. on
it. This is done because `InnoDB' and these operating systems cannot
drop a table that is in use.


File: manual.info,  Node: temporary-table-problems,  Prev: alter-table-problems,  Up: table-definition-issues

B.5.7.2 TEMPORARY Table Problems
................................

The following list indicates limitations on the use of `TEMPORARY'
tables:

   * A `TEMPORARY' table can only be of type `MEMORY', `MyISAM',
     `MERGE', or `InnoDB'.

     Temporary tables are not supported for MySQL Cluster.

   * You cannot refer to a `TEMPORARY' table more than once in the same
     query. For example, the following does not work:


          mysql> SELECT * FROM temp_table, temp_table AS t2;
          ERROR 1137: Can't reopen table: 'temp_table'

     This error also occurs if you refer to a temporary table multiple
     times in a stored function under different aliases, even if the
     references occur in different statements within the function.

   * The *Note `SHOW TABLES': show-tables. statement does not list
     `TEMPORARY' tables.

   * You cannot use `RENAME' to rename a `TEMPORARY' table. However,
     you can use *Note `ALTER TABLE': alter-table. instead:


          mysql> ALTER TABLE orig_name RENAME new_name;

   * There are known issues in using temporary tables with replication.
     See *Note replication-features::, for more information.


File: manual.info,  Node: bugs,  Prev: table-definition-issues,  Up: problems

B.5.8 Known Issues in MySQL
---------------------------

This section lists known issues in recent versions of MySQL.

For information about platform-specific issues, see the installation
and porting instructions in *Note general-installation-issues::, and
*Note porting::.

The following problems are known:

   * Subquery optimization for `IN' is not as effective as for `='.

   * Even if you use `lower_case_table_names=2' (which enables MySQL to
     remember the case used for databases and table names), MySQL does
     not remember the case used for database names for the function
     `DATABASE()' or within the various logs (on case-insensitive
     systems).

   * Dropping a `FOREIGN KEY' constraint does not work in replication
     because the constraint may have another name on the slave.

   * *Note `REPLACE': replace. (and *Note `LOAD DATA': load-data. with
     the *Note `REPLACE': replace. option) does not trigger `ON DELETE
     CASCADE'.

   * `DISTINCT' with `ORDER BY' does not work inside `GROUP_CONCAT()'
     if you do not use all and only those columns that are in the
     `DISTINCT' list.

   * If one user has a long-running transaction and another user drops
     a table that is updated in the transaction, there is small chance
     that the binary log may contain the *Note `DROP TABLE':
     drop-table. statement before the table is used in the transaction
     itself.

   * When inserting a big integer value (between 2^63 and 2^64-1) into
     a decimal or string column, it is inserted as a negative value
     because the number is evaluated in a signed integer context.

   * *Note `FLUSH TABLES WITH READ LOCK': flush. does not block *Note
     `COMMIT': commit. if the server is running without binary logging,
     which may cause a problem (of consistency between tables) when
     doing a full backup.

   * *Note `ANALYZE TABLE': analyze-table, *Note `OPTIMIZE TABLE':
     optimize-table, and *Note `REPAIR TABLE': repair-table. may cause
     problems on tables for which you are using *Note `INSERT DELAYED':
     insert-delayed.

   * Performing `LOCK TABLE ...' and `FLUSH TABLES ...' does not
     guarantee that there isn't a half-finished transaction in progress
     on the table.

   * With statement-based binary logging, the master writes the
     executed queries to the binary log. This is a very fast, compact,
     and efficient logging method that works perfectly in most cases.
     However, it is possible for the data on the master and slave to
     become different if a query is designed in such a way that the
     data modification is nondeterministic (generally not a recommended
     practice, even outside of replication).

     For example:

        * *Note `CREATE TABLE ... SELECT': create-table-select. or
          *Note `INSERT ... SELECT': insert-select. statements that
          insert zero or `NULL' values into an `AUTO_INCREMENT' column.

        * *Note `DELETE': delete. if you are deleting rows from a table
          that has foreign keys with `ON DELETE CASCADE' properties.

        * *Note `REPLACE ... SELECT': replace, `INSERT IGNORE ...
          SELECT' if you have duplicate key values in the inserted data.

     *If and only if the preceding queries have no `ORDER BY' clause
     guaranteeing a deterministic order*.

     For example, for *Note `INSERT ... SELECT': insert-select. with no
     `ORDER BY', the *Note `SELECT': select. may return rows in a
     different order (which results in a row having different ranks,
     hence getting a different number in the `AUTO_INCREMENT' column),
     depending on the choices made by the optimizers on the master and
     slave.

     A query is optimized differently on the master and slave only if:

        * The table is stored using a different storage engine on the
          master than on the slave. (It is possible to use different
          storage engines on the master and slave. For example, you can
          use `InnoDB' on the master, but `MyISAM' on the slave if the
          slave has less available disk space.)

        * MySQL buffer sizes (`key_buffer_size', and so on) are
          different on the master and slave.

        * The master and slave run different MySQL versions, and the
          optimizer code differs between these versions.

     This problem may also affect database restoration using
     `mysqlbinlog|mysql'.

     The easiest way to avoid this problem is to add an `ORDER BY'
     clause to the aforementioned nondeterministic queries to ensure
     that the rows are always stored or modified in the same order.
     Using row-based or mixed logging format also avoids the problem.

   * Log file names are based on the server host name if you do not
     specify a file name with the startup option. To retain the same
     log file names if you change your host name to something else, you
     must explicitly use options such as `--log-bin=OLD_HOST_NAME-bin'.
     See *Note server-options::. Alternatively, rename the old files to
     reflect your host name change. If these are binary logs, you must
     edit the binary log index file and fix the binary log file names
     there as well. (The same is true for the relay logs on a slave
     server.)

   * *Note `mysqlbinlog': mysqlbinlog. does not delete temporary files
     left after a *Note `LOAD DATA INFILE': load-data. statement. See
     *Note mysqlbinlog::.

   * `RENAME' does not work with `TEMPORARY' tables or tables used in a
     `MERGE' table.

   * Due to the way table format (`.frm') files are stored, you cannot
     use character 255 (`CHAR(255)') in table names, column names, or
     enumerations.

   * When using `SET CHARACTER SET', you cannot use translated
     characters in database, table, and column names.

   * You cannot use ``_'' or ``%'' with `ESCAPE' in `LIKE ...  ESCAPE'.

   * Only the first `max_sort_length' bytes are used when comparing
     data values. This means that values cannot reliably be used in
     `GROUP BY', `ORDER BY' or `DISTINCT' if they are not distinct in
     the first `max_sort_length' bytes. To work around this, increase
     the variable value. The default value of `max_sort_length' is 1024
     and can be changed at server startup time or at runtime.

   * Numeric calculations are done with *Note `BIGINT': integer-types.
     or *Note `DOUBLE': floating-point-types. (both are normally 64
     bits long). Which precision you get depends on the function.  The
     general rule is that bit functions are performed with *Note
     `BIGINT': integer-types. precision, `IF()' and `ELT()' with *Note
     `BIGINT': integer-types. or *Note `DOUBLE': floating-point-types.
     precision, and the rest with *Note `DOUBLE': floating-point-types.
     precision.  You should try to avoid using unsigned long long
     values if they resolve to be larger than 63 bits
     (9223372036854775807) for anything other than bit fields.

   * You can have up to 255 *Note `ENUM': enum.  and *Note `SET': set.
     columns in one table.

   * In `MIN()', `MAX()', and other aggregate functions, MySQL
     currently compares *Note `ENUM': enum. and *Note `SET': set.
     columns by their string value rather than by the string's relative
     position in the set.

   * In an *Note `UPDATE': update. statement, columns are updated from
     left to right. If you refer to an updated column, you get the
     updated value instead of the original value. For example, the
     following statement increments `KEY' by `2', *not* `1':


          mysql> UPDATE TBL_NAME SET KEY=KEY+1,KEY=KEY+1;

   * You can refer to multiple temporary tables in the same query, but
     you cannot refer to any given temporary table more than once. For
     example, the following does not work:


          mysql> SELECT * FROM temp_table, temp_table AS t2;
          ERROR 1137: Can't reopen table: 'temp_table'

   * The optimizer may handle `DISTINCT' differently when you are using
     `hidden' columns in a join than when you are not. In a join,
     hidden columns are counted as part of the result (even if they are
     not shown), whereas in normal queries, hidden columns do not
     participate in the `DISTINCT' comparison.

     An example of this is:


          SELECT DISTINCT mp3id FROM band_downloads
                 WHERE userid = 9 ORDER BY id DESC;

     and


          SELECT DISTINCT band_downloads.mp3id
                 FROM band_downloads,band_mp3
                 WHERE band_downloads.userid = 9
                 AND band_mp3.id = band_downloads.mp3id
                 ORDER BY band_downloads.id DESC;

     In the second case, using MySQL Server 3.23.x, you may get two
     identical rows in the result set (because the values in the hidden
     `id' column may differ).

     Note that this happens only for queries that do not have the
     `ORDER BY' columns in the result.

   * If you execute a `PROCEDURE' on a query that returns an empty set,
     in some cases the `PROCEDURE' does not transform the columns.

   * Creation of a table of type `MERGE' does not check whether the
     underlying tables are compatible types.

   * If you use *Note `ALTER TABLE': alter-table. to add a `UNIQUE'
     index to a table used in a `MERGE' table and then add a normal
     index on the `MERGE' table, the key order is different for the
     tables if there was an old, non-`UNIQUE' key in the table. This is
     because *Note `ALTER TABLE': alter-table. puts `UNIQUE' indexes
     before normal indexes to be able to detect duplicate keys as early
     as possible.


File: manual.info,  Node: news,  Next: restrictions,  Prev: error-handling,  Up: Top

Appendix C MySQL Release Notes
******************************

Release notes for MySQL Server and associated products are published in
standalone form, not as part of the MySQL Reference Manual. For release
notes, see these documents:

   * MySQL 5.1 Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql/5.1/en/)

   * MySQL Cluster 7.1 Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql-cluster/7.1/en/)

   * MySQL Connector/ODBC Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-odbc/en/)

   * MySQL Connector/Net Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-net/en/) (includes
     MySQL Visual Studio Plugin release notes)

   * MySQL Connector/J Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-j/en/)

   * MySQL Connector/C++ Release Notes
     (http://dev.mysql.com/doc/relnotes/connector-cpp/en/)

   * MySQL Proxy Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql-proxy/en/)

   * MySQL for Excel Release Notes
     (http://dev.mysql.com/doc/relnotes/mysql-for-excel/en/)


File: manual.info,  Node: restrictions,  Next: licenses-third-party,  Prev: news,  Up: Top

Appendix D Restrictions and Limits
**********************************

* Menu:

* stored-program-restrictions::  Restrictions on Stored Programs
* cursor-restrictions::          Restrictions on Server-Side Cursors
* subquery-restrictions::        Restrictions on Subqueries
* view-restrictions::            Restrictions on Views
* xa-restrictions::              Restrictions on XA Transactions
* charset-restrictions::         Restrictions on Character Sets
* limits::                       Limits in MySQL

The discussion here describes restrictions that apply to the use of
MySQL features such as subqueries or views.


File: manual.info,  Node: stored-program-restrictions,  Next: cursor-restrictions,  Prev: restrictions,  Up: restrictions

D.1 Restrictions on Stored Programs
===================================

These restrictions apply to the features described in *Note
stored-programs-views::.

Some of the restrictions noted here apply to all stored routines; that
is, both to stored procedures and stored functions. There are also some
restrictions specific to stored functions but not to stored procedures.

The restrictions for stored functions also apply to triggers.  There
are also some restrictions specific to triggers.

The restrictions for stored procedures also apply to the *Note `DO':
do. clause of Event Scheduler event definitions. There are also some
restrictions specific to events.

*SQL Statements Not Permitted in Stored Routines*

Stored routines cannot contain arbitrary SQL statements. The following
statements are not permitted:

   * The locking statements *Note `LOCK TABLES': lock-tables. and *Note
     `UNLOCK TABLES': lock-tables.

   * *Note `ALTER VIEW': alter-view. (Before MySQL 5.1.21, this
     restriction is enforced only for stored functions.)

   * *Note `LOAD DATA': load-data. and `LOAD TABLE'.

   * SQL prepared statements (*Note `PREPARE': prepare, *Note
     `EXECUTE': execute, *Note `DEALLOCATE PREPARE':
     deallocate-prepare.) can be used in stored procedures, but not
     stored functions or triggers.  Thus, stored functions and triggers
     cannot use dynamic SQL (where you construct statements as strings
     and then execute them).

   * Generally, statements not permitted in SQL prepared statements are
     also not permitted in stored programs. For a list of statements
     supported as prepared statements, see *Note
     sql-syntax-prepared-statements::.

   * Because local variables are in scope only during stored program
     execution, references to them are not permitted in prepared
     statements created within a stored program. Prepared statement
     scope is the current session, not the stored program, so the
     statement could be executed after the program ends, at which point
     the variables would no longer be in scope. For example, `SELECT
     ... INTO LOCAL_VAR' cannot be used as a prepared statement. This
     restriction also applies to stored procedure and function
     parameters. See *Note prepare::.

   * Inserts cannot be delayed. *Note `INSERT DELAYED': insert-delayed.
     syntax is accepted, but the statement is handled as a normal *Note
     `INSERT': insert.

   * Within all stored programs (stored procedures and functions,
     triggers, and events), the parser treats *Note `BEGIN [WORK]':
     commit.  as the beginning of a *Note `BEGIN ... END': begin-end.
     block. To begin a transaction in this context, use *Note `START
     TRANSACTION': commit. instead.

*Restrictions for Stored Functions*

The following additional statements or operations are not permitted
within stored functions. They are permitted within stored procedures,
except stored procedures that are invoked from within a stored function
or trigger. For example, if you use *Note `FLUSH': flush. in a stored
procedure, that stored procedure cannot be called from a stored
function or trigger.

   * Statements that perform explicit or implicit commit or rollback.
     Support for these statements is not required by the SQL standard,
     which states that each DBMS vendor may decide whether to permit
     them.

   * Statements that return a result set. This includes *Note `SELECT':
     select. statements that do not have an `INTO VAR_LIST' clause and
     other statements such as *Note `SHOW': show, *Note `EXPLAIN':
     explain, and *Note `CHECK TABLE': check-table. A function can
     process a result set either with *Note `SELECT ... INTO VAR_LIST':
     select-into. or by using a cursor and *Note `FETCH': fetch.
     statements.  See *Note select-into::, and *Note cursors::.

   * *Note `FLUSH': flush. statements.

   * Stored functions cannot be used recursively.

   * A stored function or trigger cannot modify a table that is already
     being used (for reading or writing) by the statement that invoked
     the function or trigger.

   * If you refer to a temporary table multiple times in a stored
     function under different aliases, a `Can't reopen table:
     'TBL_NAME`''' error occurs, even if the references occur in
     different statements within the function.

*Restrictions for Triggers*

For triggers, the following additional restrictions apply:

   * Triggers are not activated by foreign key actions.

   * When using row-based replication, triggers on the slave are not
     activated by statements originating on the master. The triggers on
     the slave are activated when using statement-based replication.
     For more information, see *Note replication-features-triggers::.

   * The *Note `RETURN': return. statement is not permitted in
     triggers, which cannot return a value. To exit a trigger
     immediately, use the *Note `LEAVE': leave. statement.

   * Triggers are not permitted on tables in the `mysql' database.

   * The trigger cache does not detect when metadata of the underlying
     objects has changed. If a trigger uses a table and the table has
     changed since the trigger was loaded into the cache, the trigger
     operates using the outdated metadata.

*Restrictions on Calling Stored Procedures*

Before MySQL 5.1.4, *Note `CALL': call. statements cannot be prepared,
meaning that stored procedures cannot be called from dynamic SQL. This
is true both for server-side prepared statements and for SQL prepared
statements.

*Name Conflicts within Stored Routines*

The same identifier might be used for a routine parameter, a local
variable, and a table column. Also, the same local variable name can be
used in nested blocks. For example:


     CREATE PROCEDURE p (i INT)
     BEGIN
       DECLARE i INT DEFAULT 0;
       SELECT i FROM t;
       BEGIN
         DECLARE i INT DEFAULT 1;
         SELECT i FROM t;
       END;
     END;

In such cases, the identifier is ambiguous and the following precedence
rules apply:

   * A local variable takes precedence over a routine parameter or
     table column.

   * A routine parameter takes precedence over a table column.

   * A local variable in an inner block takes precedence over a local
     variable in an outer block.

The behavior that variables take precedence over table columns is
nonstandard.

*Replication Considerations*

Use of stored routines can cause replication problems. This issue is
discussed further in *Note stored-programs-logging::.

The `--replicate-wild-do-table=DB_NAME.TBL_NAME' option applies to
tables, views, and triggers. It does not apply to stored procedures and
functions, or events. To filter statements operating on the latter
objects, use one or more of the `--replicate-*-db' options.

*Introspection Considerations*

`INFORMATION_SCHEMA' does not have a `PARAMETERS' table until MySQL
5.5; this table enables stored routines or client applications to
determine the names, types, and default values of parameters for stored
routines. For releases without this `INFORMATION_SCHEMA.PARAMETERS'
table, to examine these types of metadata, you must use workarounds
such as parsing the output of `SHOW CREATE' statements or the
`param_list' column of the `mysql.proc' table. `param_list' contents
can be processed from within a stored routine, unlike the output from
*Note `SHOW': show.

*Debugging Considerations*

There are no stored routine debugging facilities.

*Unsupported Syntax from the SQL:2003 Standard*

The MySQL stored routine syntax is based on the SQL:2003 standard.  The
following items from that standard are not currently supported:

   * `UNDO' handlers

   * `FOR' loops

*Concurrency Considerations*

To prevent problems of interaction between sessions, when a client
issues a statement, the server uses a snapshot of routines and triggers
available for execution of the statement. That is, the server
calculates a list of procedures, functions, and triggers that may be
used during execution of the statement, loads them, and then proceeds
to execute the statement. While the statement executes, it does not see
changes to routines performed by other sessions.

For maximum concurrency, stored functions should minimize their
side-effects; in particular, updating a table within a stored function
can reduce concurrent operations on that table. A stored function
acquires table locks before executing, to avoid inconsistency in the
binary log due to mismatch of the order in which statements execute and
when they appear in the log. When statement-based binary logging is
used, statements that invoke a function are recorded rather than the
statements executed within the function. Consequently, stored functions
that update the same underlying tables do not execute in parallel. In
contrast, stored procedures do not acquire table-level locks. All
statements executed within stored procedures are written to the binary
log, even for statement-based binary logging. See *Note
stored-programs-logging::.

*Event Scheduler Restrictions*

The following limitations are specific to the Event Scheduler:

   * In MySQL 5.1.6 only, any table referenced in an event's action
     statement must be fully qualified with the name of the schema in
     which it occurs (that is, as `SCHEMA_NAME.TABLE_NAME').

   * Beginning with MySQL 5.1.8, event names are handled in
     case-insensitive fashion. For example, this means that you cannot
     have two events in the same database (and--prior to MySQL
     5.1.12--with the same definer) with the names `anEvent' and
     `AnEvent'.

     *Important*:

     If you have events created in MySQL 5.1.7 or earlier which are
     assigned to the same database and have the same definer, and whose
     names differ only with respect to lettercase, then you must rename
     these events to respect case-sensitive handling before upgrading
     to MySQL 5.1.8 or later.

   * An event may not be created, altered, or dropped by a stored
     routine, trigger, or another event. An event also may not create,
     alter, or drop stored routines or triggers. (Bug #16409, Bug
     #18896)

   * Event timings using the intervals `YEAR', `QUARTER', `MONTH', and
     `YEAR_MONTH' are resolved in months; those using any other
     interval are resolved in seconds. There is no way to cause events
     scheduled to occur at the same second to execute in a given order.
     In addition--due to rounding, the nature of threaded applications,
     and the fact that a nonzero length of time is required to create
     events and to signal their execution--events may be delayed by as
     much as 1 or 2 seconds. However, the time shown in the *Note
     `INFORMATION_SCHEMA.EVENTS': events-table. table's `LAST_EXECUTED'
     column or the `mysql.event' table's `last_executed' column is
     always accurate to within one second of the actual event execution
     time. (See also Bug #16522.)

   * Each execution of the statements contained in the body of an event
     takes place in a new connection; thus, these statements has no
     effect in a given user session on the server's statement counts
     such as `Com_select' and `Com_insert' that are displayed by *Note
     `SHOW STATUS': show-status. However, such counts _are_ updated in
     the global scope.  (Bug #16422)

   * Prior to MySQL 5.1.12, you could not view another user's events in
     the *Note `INFORMATION_SCHEMA.EVENTS': events-table. table.  In
     other words, any query made against this table was treated as
     though it contained the condition `DEFINER = CURRENT_USER()' in
     the `WHERE' clause.

   * Events do not support times later than the end of the Unix Epoch;
     this is approximately the beginning of the year 2038.  Prior to
     MySQL 5.1.8, handling in scheduled events of dates later than this
     was buggy; starting with MySQL 5.1.8, such dates are specifically
     not permitted by the Event Scheduler.  (Bug #16396)

   * In MySQL 5.1.6, *Note `INFORMATION_SCHEMA.EVENTS': events-table.
     shows `NULL' in the `SQL_MODE' column. Beginning with MySQL 5.1.7,
     the `SQL_MODE' displayed is that in effect when the event was
     created.

   * In MySQL 5.1.6, the only way to drop or alter an event created by
     a user who was not the definer of that event was by manipulation
     of the `mysql.event' system table by the MySQL `root' user or by
     another user with privileges on this table. Beginning with MySQL
     5.1.7, *Note `DROP USER': drop-user. drops all events for which
     that user was the definer; also beginning with MySQL 5.1.7 *Note
     `DROP SCHEMA': drop-database. drops all events associated with the
     dropped schema.

   * References to stored functions, user-defined functions, and tables
     in the `ON SCHEDULE' clauses of *Note `CREATE EVENT':
     create-event. and *Note `ALTER EVENT': alter-event. statements are
     not supported. Beginning with MySQL 5.1.13, these sorts of
     references are not permitted. (See Bug #22830 for more
     information.)

   * Generally speaking, statements that are not permitted in stored
     routines or in SQL prepared statements are also not permitted in
     the body of an event. For more information, see *Note
     sql-syntax-prepared-statements::.

   * When upgrading to MySQL 5.1.18 or 5.1.19 from a previous MySQL
     version where scheduled events were in use, the upgrade utilities
     *Note `mysql_upgrade': mysql-upgrade. and *Note
     `mysql_fix_privilege_tables': mysql-fix-privilege-tables. do not
     accommodate changes in system tables relating to the Event
     Scheduler. This issue was fixed in MySQL 5.1.20 (see Bug #28521).

Stored routines and triggers in MySQL Cluster

Stored procedures, stored functions, and triggers are all supported by
tables using the *Note `NDB': mysql-cluster.  storage engine; however,
it is important to keep in mind that they do _not_ propagate
automatically between MySQL Servers acting as Cluster SQL nodes. This
is because of the following:

   * Stored routine definitions are kept in tables in the `mysql'
     system database using the `MyISAM' storage engine, and so do not
     participate in clustering.

   * The `.TRN' and `.TRG' files containing trigger definitions are not
     read by the *Note `NDB': mysql-cluster. storage engine, and are not
     copied between Cluster nodes.

Any stored routine or trigger that interacts with MySQL Cluster tables
must be re-created by running the appropriate *Note `CREATE PROCEDURE':
create-procedure, *Note `CREATE FUNCTION': create-function, or *Note
`CREATE TRIGGER': create-trigger. statements on each MySQL Server that
participates in the cluster where you wish to use the stored routine or
trigger. Similarly, any changes to existing stored routines or triggers
must be carried out explicitly on all Cluster SQL nodes, using the
appropriate `ALTER' or `DROP' statements on each MySQL Server accessing
the cluster.

*Warning*:

Do _not_ attempt to work around the issue described in the first item
mentioned previously by converting any `mysql' database tables to use
the *Note `NDB': mysql-cluster. storage engine.  _Altering the system
tables in the `mysql' database is not supported_ and is very likely to
produce undesirable results.


File: manual.info,  Node: cursor-restrictions,  Next: subquery-restrictions,  Prev: stored-program-restrictions,  Up: restrictions

D.2 Restrictions on Server-Side Cursors
=======================================

Server-side cursors are implemented in the C API using the *Note
`mysql_stmt_attr_set()': mysql-stmt-attr-set. function.  The same
implementation is used for cursors in stored routines. A server-side
cursor enables a result set to be generated on the server side, but not
transferred to the client except for those rows that the client
requests. For example, if a client executes a query but is only
interested in the first row, the remaining rows are not transferred.

In MySQL, a server-side cursor is materialized into an internal
temporary table. Initially, this is a `MEMORY' table, but is converted
to a `MyISAM' table when its size exceeds the minimum value of the
`max_heap_table_size' and `tmp_table_size' system variables.  Note that
the same restrictions apply to internal temporary tables created to
hold the result set for a cursor as for other uses of internal
temporary tables. See *Note internal-temporary-tables::. One limitation
of the implementation is that for a large result set, retrieving its
rows through a cursor might be slow.

Cursors are read only; you cannot use a cursor to update rows.

`UPDATE WHERE CURRENT OF' and `DELETE WHERE CURRENT OF' are not
implemented, because updatable cursors are not supported.

Cursors are nonholdable (not held open after a commit).

Cursors are asensitive.

Cursors are nonscrollable.

Cursors are not named. The statement handler acts as the cursor ID.

You can have open only a single cursor per prepared statement. If you
need several cursors, you must prepare several statements.

You cannot use a cursor for a statement that generates a result set if
the statement is not supported in prepared mode. This includes
statements such as *Note `CHECK TABLE': check-table, `HANDLER READ', and
*Note `SHOW BINLOG EVENTS': show-binlog-events.


File: manual.info,  Node: subquery-restrictions,  Next: view-restrictions,  Prev: cursor-restrictions,  Up: restrictions

D.3 Restrictions on Subqueries
==============================

   * In MySQL 5.1 before 5.1.16, if you compare a `NULL' value to a
     subquery using `ALL', `ANY', or `SOME', and the subquery returns
     an empty result, the comparison might evaluate to the nonstandard
     result of `NULL' rather than to `TRUE' or `FALSE'. As of 5.1.16,
     the comparison evaluates to `TRUE' or `FALSE' except for
     subqueries inside `IS NULL', such as this:


          SELECT ... WHERE NULL IN (SELECT ...) IS NULL

     As of 5.1.32, the `IS NULL' limitation is removed and the
     comparison evaluates to `TRUE' or `FALSE'.

   * Subquery optimization for `IN' is not as effective as for the `='
     operator or for the `IN(VALUE_LIST)' operator.

     A typical case for poor `IN' subquery performance is when the
     subquery returns a small number of rows but the outer query
     returns a large number of rows to be compared to the subquery
     result.

     The problem is that, for a statement that uses an `IN' subquery,
     the optimizer rewrites it as a correlated subquery. Consider the
     following statement that uses an uncorrelated subquery:


          SELECT ... FROM t1 WHERE t1.a IN (SELECT b FROM t2);

     The optimizer rewrites the statement to a correlated subquery:


          SELECT ... FROM t1 WHERE EXISTS (SELECT 1 FROM t2 WHERE t2.b = t1.a);

     If the inner and outer queries return M and N rows, respectively,
     the execution time becomes on the order of O(MxN), rather than
     O(M+N) as it would be for an uncorrelated subquery.

     An implication is that an `IN' subquery can be much slower than a
     query written using an `IN(VALUE_LIST)' operator that lists the
     same values that the subquery would return.

   * In general, you cannot modify a table and select from the same
     table in a subquery. For example, this limitation applies to
     statements of the following forms:


          DELETE FROM t WHERE ... (SELECT ... FROM t ...);
          UPDATE t ... WHERE col = (SELECT ... FROM t ...);
          {INSERT|REPLACE} INTO t (SELECT ... FROM t ...);

     Exception: The preceding prohibition does not apply if you are
     using a subquery for the modified table in the `FROM' clause.
     Example:


          UPDATE t ... WHERE col = (SELECT * FROM (SELECT ... FROM t...) AS _t ...);

     Here the result from the subquery in the `FROM' clause is stored
     as a temporary table, so the relevant rows in `t' have already been
     selected by the time the update to `t' takes place.

   * Row comparison operations are only partially supported:

        * For `EXPR [NOT] IN SUBQUERY', EXPR can be an N-tuple
          (specified using row constructor syntax) and the subquery can
          return rows of N-tuples. The permitted syntax is therefore
          more specifically expressed as `ROW_CONSTRUCTOR [NOT] IN
          TABLE_SUBQUERY'

        * For `EXPR OP {ALL|ANY|SOME} SUBQUERY', EXPR must be a scalar
          value and the subquery must be a column subquery; it cannot
          return multiple-column rows.

     In other words, for a subquery that returns rows of N-tuples, this
     is supported:


          (EXPR_1, ..., EXPR_N) [NOT] IN TABLE_SUBQUERY

     But this is not supported:


          (EXPR_1, ..., EXPR_N) OP {ALL|ANY|SOME} SUBQUERY

     The reason for supporting row comparisons for `IN' but not for the
     others is that `IN' is implemented by rewriting it as a sequence
     of `=' comparisons and `AND' operations.  This approach cannot be
     used for `ALL', `ANY', or `SOME'.

   * Prior to MySQL 5.1.12, row constructors were not well optimized;
     of the following two equivalent expressions, only the second could
     be optimized:


          (col1, col2, ...) = (val1, val2, ...)
          col1 = val1 AND col2 = val2 AND ...

     In MySQL 5.1.12 and later, all row equalities are converted into
     conjunctions of equalities between row elements, and handled by
     the optimizer in the same way. (Bug #16081)

   * Subqueries in the `FROM' clause cannot be correlated subqueries.
     They are materialized in whole (evaluated to produce a result set)
     before evaluating the outer query, so they cannot be evaluated per
     row of the outer query.

   * MySQL does not support `LIMIT' in subqueries for certain subquery
     operators:


          mysql> SELECT * FROM t1
              ->   WHERE s1 IN (SELECT s2 FROM t2 ORDER BY s1 LIMIT 1);
          ERROR 1235 (42000): This version of MySQL doesn't yet support
           'LIMIT & IN/ALL/ANY/SOME subquery'

   * The optimizer is more mature for joins than for subqueries, so in
     many cases a statement that uses a subquery can be executed more
     efficiently if you rewrite it as a join.

     An exception occurs for the case where an `IN' subquery can be
     rewritten as a *Note `SELECT DISTINCT': select. join. Example:


          SELECT col FROM t1 WHERE id_col IN (SELECT id_col2 FROM t2 WHERE CONDITION);

     That statement can be rewritten as follows:


          SELECT DISTINCT col FROM t1, t2 WHERE t1.id_col = t2.id_col AND CONDITION;

     But in this case, the join requires an extra `DISTINCT' operation
     and is not more efficient than the subquery.

   * MySQL permits a subquery to refer to a stored function that has
     data-modifying side effects such as inserting rows into a table.
     For example, if `f()' inserts rows, the following query can modify
     data:


          SELECT ... WHERE x IN (SELECT f() ...);

     This behavior is an extension to the SQL standard. In MySQL, it
     can produce indeterminate results because `f()' might be executed
     a different number of times for different executions of a given
     query depending on how the optimizer chooses to handle it.

     For statement-based or mixed-format replication, one implication
     of this indeterminism is that such a query can produce different
     results on the master and its slaves.


File: manual.info,  Node: view-restrictions,  Next: xa-restrictions,  Prev: subquery-restrictions,  Up: restrictions

D.4 Restrictions on Views
=========================

View processing is not optimized:

   * It is not possible to create an index on a view.

   * Indexes can be used for views processed using the merge algorithm.
     However, a view that is processed with the temptable algorithm is
     unable to take advantage of indexes on its underlying tables
     (although indexes can be used during generation of the temporary
     tables).

Subqueries cannot be used in the `FROM' clause of a view.

There is a general principle that you cannot modify a table and select
from the same table in a subquery. See *Note subquery-restrictions::.

The same principle also applies if you select from a view that selects
from the table, if the view selects from the table in a subquery and
the view is evaluated using the merge algorithm.  Example:


     CREATE VIEW v1 AS
     SELECT * FROM t2 WHERE EXISTS (SELECT 1 FROM t1 WHERE t1.a = t2.a);

     UPDATE t1, v2 SET t1.a = 1 WHERE t1.b = v2.b;

If the view is evaluated using a temporary table, you _can_ select from
the table in the view subquery and still modify that table in the outer
query. In this case the view will be stored in a temporary table and
thus you are not really selecting from the table in a subquery and
modifying it `at the same time.' (This is another reason you might wish
to force MySQL to use the temptable algorithm by specifying `ALGORITHM
= TEMPTABLE' in the view definition.)

You can use *Note `DROP TABLE': drop-table. or *Note `ALTER TABLE':
alter-table. to drop or alter a table that is used in a view
definition. No warning results from the `DROP' or `ALTER' operation,
even though this invalidates the view. Instead, an error occurs later,
when the view is used. *Note `CHECK TABLE': check-table. can be used to
check for views that have been invalidated by `DROP' or `ALTER'
operations.

A view definition is `frozen' by certain statements:

   * If a statement prepared by *Note `PREPARE': prepare. refers to a
     view, the view definition seen each time the statement is executed
     later will be the definition of the view at the time it was
     prepared. This is true even if the view definition is changed
     after the statement is prepared and before it is executed.
     Example:


          CREATE VIEW v AS SELECT RAND();
          PREPARE s FROM 'SELECT * FROM v';
          ALTER VIEW v AS SELECT NOW();
          EXECUTE s;

     The result returned by the *Note `EXECUTE': execute. statement is
     a random number, not the current date and time.

   * If a statement in a stored routine refers to a view, the view
     definition seen by the statement are its definition the first time
     that statement is executed. For example, this means that if the
     statement is executed in a loop, further iterations of the
     statement see the same view definition, even if the definition is
     changed later in the loop. Example:


          CREATE VIEW v AS SELECT 1;
          delimiter //
          CREATE PROCEDURE p ()
          BEGIN
            DECLARE i INT DEFAULT 0;
            WHILE i < 5 DO
              SELECT * FROM v;
              SET i = i + 1;
              ALTER VIEW v AS SELECT 2;
            END WHILE;
          END;
          //
          delimiter ;
          CALL p();

     When the procedure `p()' is called, the *Note `SELECT': select.
     returns 1 each time through the loop, even though the view
     definition is changed within the loop.

     As of MySQL 5.1.21, *Note `ALTER VIEW': alter-view.  is prohibited
     within stored routines, so this restriction does not apply.

With regard to view updatability, the overall goal for views is that if
any view is theoretically updatable, it should be updatable in
practice. This includes views that have *Note `UNION': union. in their
definition.  Currently, not all views that are theoretically updatable
can be updated. The initial view implementation was deliberately written
this way to get usable, updatable views into MySQL as quickly as
possible. Many theoretically updatable views can be updated now, but
limitations still exist:

   * Updatable views with subqueries anywhere other than in the `WHERE'
     clause. Some views that have subqueries in the *Note `SELECT':
     select. list may be updatable.

   * You cannot use *Note `UPDATE': update. to update more than one
     underlying table of a view that is defined as a join.

   * You cannot use *Note `DELETE': delete. to update a view that is
     defined as a join.

There exists a shortcoming with the current implementation of views. If
a user is granted the basic privileges necessary to create a view (the
`CREATE VIEW' and `SELECT' privileges), that user will be unable to
call *Note `SHOW CREATE VIEW': show-create-view.  on that object unless
the user is also granted the `SHOW VIEW' privilege.

That shortcoming can lead to problems backing up a database with *Note
`mysqldump': mysqldump, which may fail due to insufficient privileges.
This problem is described in Bug #22062.

The workaround to the problem is for the administrator to manually
grant the `SHOW VIEW' privilege to users who are granted `CREATE VIEW',
since MySQL doesn't grant it implicitly when views are created.

Views do not have indexes, so index hints do not apply. Use of index
hints when selecting from a view is not permitted.

*Note `SHOW CREATE VIEW': show-create-view. displays view definitions
using an `AS ALIAS_NAME' clause for each column. If a column is created
from an expression, the default alias is the expression text, which can
be quite long. As of MySQL 5.1.23, aliases for column names in *Note
`CREATE VIEW': create-view. statements are checked against the maximum
column length of 64 characters (not the maximum alias length of 256
characters). As a result, views created from the output of *Note `SHOW
CREATE VIEW': show-create-view. fail if any column alias exceeds 64
characters. This can cause problems in the following circumstances for
views with too-long aliases:

   * View definitions fail to replicate to newer slaves that enforce
     the column-length restriction.

   * Dump files created with *Note `mysqldump': mysqldump. cannot be
     loaded into servers that enforce the column-length restriction.

A workaround for either problem is to modify each problematic view
definition to use aliases that provide shorter column names. Then the
view will replicate properly, and can be dumped and reloaded without
causing an error. To modify the definition, drop and create the view
again with *Note `DROP VIEW': drop-view. and *Note `CREATE VIEW':
create-view, or replace the definition with *Note `CREATE OR REPLACE
VIEW': create-view.

For problems that occur when reloading view definitions in dump files,
another workaround is to edit the dump file to modify its *Note `CREATE
VIEW': create-view. statements. However, this does not change the
original view definitions, which may cause problems for subsequent dump
operations.


File: manual.info,  Node: xa-restrictions,  Next: charset-restrictions,  Prev: view-restrictions,  Up: restrictions

D.5 Restrictions on XA Transactions
===================================

XA transaction support is limited to the `InnoDB' storage engine.

For `external XA,' a MySQL server acts as a Resource Manager and client
programs act as Transaction Managers. For `Internal XA', storage
engines within a MySQL server act as RMs, and the server itself acts as
a TM. Internal XA support is limited by the capabilities of individual
storage engines. Internal XA is required for handling XA transactions
that involve more than one storage engine. The implementation of
internal XA requires that a storage engine support two-phase commit at
the table handler level, and currently this is true only for `InnoDB'.

For *Note `XA START': xa-statements, the `JOIN' and `RESUME' clauses
are not supported.

For *Note `XA END': xa-statements, the `SUSPEND [FOR MIGRATE]' clause
is not supported.

The requirement that the BQUAL part of the XID value be different for
each XA transaction within a global transaction is a limitation of the
current MySQL XA implementation. It is not part of the XA specification.

If an XA transaction has reached the `PREPARED' state and the MySQL
server is killed (for example, with *Note `kill -9': kill. on Unix) or
shuts down abnormally, the transaction can be continued after the
server restarts. However, if the client reconnects and commits the
transaction, the transaction will be absent from the binary log even
though it has been committed. This means the data and the binary log
have gone out of synchrony. An implication is that XA cannot be used
safely together with replication.

It is possible that the server will roll back a pending XA transaction,
even one that has reached the `PREPARED' state. This happens if a client
connection terminates and the server continues to run, or if clients
are connected and the server shuts down gracefully. (In the latter
case, the server marks each connection to be terminated, and then rolls
back the `PREPARED' XA transaction associated with it.) It should be
possible to commit or roll back a `PREPARED' XA transaction, but this
cannot be done without changes to the binary logging mechanism.


File: manual.info,  Node: charset-restrictions,  Next: limits,  Prev: xa-restrictions,  Up: restrictions

D.6 Restrictions on Character Sets
==================================

   * Identifiers are stored in `mysql' database tables (`user', `db',
     and so forth) using `utf8', but identifiers can contain only
     characters in the Basic Multilingual Plane (BMP).  Supplementary
     characters are not permitted in identifiers.

   * The `ucs2' character sets has the following restrictions:

        * It cannot be used as a client character set, which means that
          it does not work for `SET NAMES' or `SET CHARACTER SET'. (See
          *Note charset-connection::.)

        * It is currently not possible to use *Note `LOAD DATA INFILE':
          load-data. to load data files that use this character set.

        * `FULLTEXT' indexes cannot be created on a column that this
          character set. However, you can perform `IN BOOLEAN MODE'
          searches on the column without an index.

        * The use of `ENCRYPT()' with this character set is not
          recommended because the underlying system call expects a
          string terminated by a zero byte.

   * The `REGEXP' and `RLIKE' operators work in byte-wise fashion, so
     they are not multibyte safe and may produce unexpected results
     with multibyte character sets. In addition, these operators compare
     characters by their byte values and accented characters may not
     compare as equal even if a given collation treats them as equal.


File: manual.info,  Node: limits,  Prev: charset-restrictions,  Up: restrictions

D.7 Limits in MySQL
===================

* Menu:

* joins-limits::                 Limits of Joins
* database-count-limit::         Limits on Number of Databases and Tables
* table-size-limit::             Limits on Table Size
* column-count-limit::           Limits on Table Column Count and Row Size
* limits-frm-file::              Limits Imposed by .frm File Structure
* limits-windows::               Windows Platform Limitations

This section lists current limits in MySQL 5.1.


File: manual.info,  Node: joins-limits,  Next: database-count-limit,  Prev: limits,  Up: limits

D.7.1 Limits of Joins
---------------------

The maximum number of tables that can be referenced in a single join is
61. This also applies to the number of tables that can be referenced in
the definition of a view.


File: manual.info,  Node: database-count-limit,  Next: table-size-limit,  Prev: joins-limits,  Up: limits

D.7.2 Limits on Number of Databases and Tables
----------------------------------------------

MySQL has no limit on the number of databases. The underlying file
system may have a limit on the number of directories.

MySQL has no limit on the number of tables. The underlying file system
may have a limit on the number of files that represent tables.
Individual storage engines may impose engine-specific constraints.
`InnoDB' permits up to 4 billion tables.


File: manual.info,  Node: table-size-limit,  Next: column-count-limit,  Prev: database-count-limit,  Up: limits

D.7.3 Limits on Table Size
--------------------------

The effective maximum table size for MySQL databases is usually
determined by operating system constraints on file sizes, not by MySQL
internal limits. The following table lists some examples of operating
system file-size limits. This is only a rough guide and is not intended
to be definitive. For the most up-to-date information, be sure to check
the documentation specific to your operating system.

This table lists examples of operating system file-size limits.

Operating System       File-size Limit
Win32 w/ FAT/FAT32     2GB/4GB
Win32 w/ NTFS          2TB (possibly larger)
Linux 2.2-Intel 32-bit 2GB (LFS: 4GB)
Linux 2.4+             (using ext3 file system) 4TB
Solaris 9/10           16TB
Mac OS X w/ HFS+       2TB
NetWare w/NSS file     8TB
system                 

Windows users, please note that FAT and VFAT (FAT32) are _not_
considered suitable for production use with MySQL. Use NTFS instead.

On Linux 2.2, you can get `MyISAM' tables larger than 2GB in size by
using the Large File Support (LFS) patch for the ext2 file system. Most
current Linux distributions are based on kernel 2.4 or higher and
include all the required LFS patches. On Linux 2.4, patches also exist
for ReiserFS to get support for big files (up to 2TB). With JFS and XFS,
petabyte and larger files are possible on Linux.

For a detailed overview about LFS in Linux, have a look at Andreas
Jaeger's `Large File Support in Linux' page at
`http://www.suse.de/~aj/linux_lfs.html'.

If you do encounter a full-table error, there are several reasons why
it might have occurred:

   * The disk might be full.

   * The `InnoDB' storage engine maintains `InnoDB' tables within a
     tablespace that can be created from several files. This enables a
     table to exceed the maximum individual file size. The tablespace
     can include raw disk partitions, which permits extremely large
     tables. The maximum tablespace size is 64TB.

     If you are using `InnoDB' tables and run out of room in the
     `InnoDB' tablespace. In this case, the solution is to extend the
     `InnoDB' tablespace. See *Note innodb-data-log-reconfiguration::.

   * You are using `MyISAM' tables on an operating system that supports
     files only up to 2GB in size and you have hit this limit for the
     data file or index file.

   * You are using a `MyISAM' table and the space required for the
     table exceeds what is permitted by the internal pointer size.
     `MyISAM' permits data and index files to grow up to 256TB by
     default, but this limit can be changed up to the maximum
     permissible size of 65,536TB (256^7 - 1 bytes).

     If you need a `MyISAM' table that is larger than the default limit
     and your operating system supports large files, the *Note `CREATE
     TABLE': create-table.  statement supports `AVG_ROW_LENGTH' and
     `MAX_ROWS' options. See *Note create-table::. The server uses these
     options to determine how large a table to permit.

     If the pointer size is too small for an existing table, you can
     change the options with *Note `ALTER TABLE': alter-table. to
     increase a table's maximum permissible size. See *Note
     alter-table::.


          ALTER TABLE TBL_NAME MAX_ROWS=1000000000 AVG_ROW_LENGTH=NNN;

     You have to specify `AVG_ROW_LENGTH' only for tables with *Note
     `BLOB': blob. or *Note `TEXT': blob. columns; in this case, MySQL
     can't optimize the space required based only on the number of rows.

     To change the default size limit for `MyISAM' tables, set the
     `myisam_data_pointer_size', which sets the number of bytes used
     for internal row pointers. The value is used to set the pointer
     size for new tables if you do not specify the `MAX_ROWS' option.
     The value of `myisam_data_pointer_size' can be from 2 to 7. A
     value of 4 permits tables up to 4GB; a value of 6 permits tables
     up to 256TB.

     You can check the maximum data and index sizes by using this
     statement:


          SHOW TABLE STATUS FROM DB_NAME LIKE 'TBL_NAME';

     You also can use *Note `myisamchk -dv /path/to/table-index-file':
     myisamchk. See *Note show::, or *Note myisamchk::.

     Other ways to work around file-size limits for `MyISAM' tables are
     as follows:

        * If your large table is read only, you can use *Note
          `myisampack': myisampack. to compress it.  *Note
          `myisampack': myisampack. usually compresses a table by at
          least 50%, so you can have, in effect, much bigger tables.
          *Note `myisampack': myisampack. also can merge multiple
          tables into a single table. See *Note myisampack::.

        * MySQL includes a `MERGE' library that enables you to handle a
          collection of `MyISAM' tables that have identical structure
          as a single `MERGE' table.  See *Note merge-storage-engine::.

   * You are using the *Note `NDB': mysql-cluster. storage engine, in
     which case you need to increase the values for the `DataMemory' and
     `IndexMemory' configuration parameters in your `config.ini' file.
     See *Note mysql-cluster-params-ndbd::.

   * You are using the `MEMORY' (`HEAP') storage engine; in this case
     you need to increase the value of the `max_heap_table_size' system
     variable. See *Note server-system-variables::.


File: manual.info,  Node: column-count-limit,  Next: limits-frm-file,  Prev: table-size-limit,  Up: limits

D.7.4 Limits on Table Column Count and Row Size
-----------------------------------------------

There is a hard limit of 4096 columns per table, but the effective
maximum may be less for a given table. The exact limit depends on
several interacting factors.

   * Every table (regardless of storage engine) has a maximum row size
     of 65,535 bytes. Storage engines may place additional constraints
     on this limit, reducing the effective maximum row size.

     The maximum row size constrains the number (and possibly size) of
     columns because the total length of all columns cannot exceed this
     size. For example, `utf8' characters require up to three bytes per
     character, so for a *Note `CHAR(255) CHARACTER SET utf8': char.
     column, the server must allocate 255 x 3 = 765 bytes per value.
     Consequently, a table cannot contain more than 65,535 / 765 = 85
     such columns.

     Storage for variable-length columns includes length bytes, which
     are assessed against the row size. For example, a *Note
     `VARCHAR(255) CHARACTER SET utf8': char. column takes two bytes to
     store the length of the value, so each value can take up to 767
     bytes.

     *Note `BLOB': blob. and *Note `TEXT': blob. columns count from one
     to four plus eight bytes each toward the row-size limit because
     their contents are stored separately from the rest of the row.

     Declaring columns `NULL' can reduce the maximum number of columns
     permitted. For *Note `MyISAM': myisam-storage-engine. tables,
     `NULL' columns require additional space in the row to record
     whether their values are `NULL'. Each `NULL' column takes one bit
     extra, rounded up to the nearest byte. The maximum row length in
     bytes can be calculated as follows:


          row length = 1
                       + (SUM OF COLUMN LENGTHS)
                       + (NUMBER OF NULL COLUMNS + DELETE_FLAG + 7)/8
                       + (NUMBER OF VARIABLE-LENGTH COLUMNS)

     DELETE_FLAG is 1 for tables with static row format. Static tables
     use a bit in the row record for a flag that indicates whether the
     row has been deleted.  DELETE_FLAG is 0 for dynamic tables because
     the flag is stored in the dynamic row header.  For information
     about *Note `MyISAM': myisam-storage-engine.  table formats, see
     *Note myisam-table-formats::.

     For *Note `InnoDB': innodb-storage-engine. tables, storage size is
     the same for `NULL' and `NOT NULL' columns, so the preceding
     calculations do not apply.

     The following statement to create table `t1' succeeds because the
     columns require 32,765 + 2 bytes and 32,766 + 2 bytes, which falls
     within the maximum row size of 65,535 bytes:


          mysql> CREATE TABLE t1
              -> (c1 VARCHAR(32765) NOT NULL, c2 VARCHAR(32766) NOT NULL)
              -> ENGINE = MyISAM CHARACTER SET latin1;
          Query OK, 0 rows affected (0.02 sec)

     The following statement to create table `t2' fails because the
     columns are `NULL' and *Note `MyISAM': myisam-storage-engine.
     requires additional space that causes the row size to exceed
     65,535 bytes:


          mysql> CREATE TABLE t2
              -> (c1 VARCHAR(32765) NULL, c2 VARCHAR(32766) NULL)
              -> ENGINE = MyISAM CHARACTER SET latin1;
          ERROR 1118 (42000): Row size too large. The maximum row size for the
          used table type, not counting BLOBs, is 65535. You have to change some
          columns to TEXT or BLOBs

     The following statement to create table `t3' fails because,
     although the column length is within the maximum length of 65,535
     bytes, two additional bytes are required to record the length,
     which causes the row size to exceed 65,535 bytes:


          mysql> CREATE TABLE t3
              -> (c1 VARCHAR(65535) NOT NULL)
              -> ENGINE = MyISAM CHARACTER SET latin1;
          ERROR 1118 (42000): Row size too large. The maximum row size for the
          used table type, not counting BLOBs, is 65535. You have to change some
          columns to TEXT or BLOBs

     Reducing the column length to 65,533 or less permits the statement
     to succeed.

   * Individual storage engines might impose additional restrictions
     that limit table column count. Examples:

        * *Note `InnoDB': innodb-storage-engine. permits up to 1000
          columns.

        * *Note `InnoDB': innodb-storage-engine. restricts row size to
          something less than half a database page (approximately 8000
          bytes), not including *Note `VARBINARY': binary-varbinary,
          *Note `VARCHAR': char, *Note `BLOB': blob, or *Note `TEXT':
          blob. columns.

        * Different *Note `InnoDB': innodb-storage-engine. storage
          formats (`COMPRESSED', `REDUNDANT') use different amounts of
          page header and trailer data, which affects the amount of
          storage available for rows.

   * Each table has an `.frm' file that contains the table definition.
     The definition affects the content of this file in ways that may
     affect the number of columns permitted in the table. For more
     information, see *Note limits-frm-file::.


File: manual.info,  Node: limits-frm-file,  Next: limits-windows,  Prev: column-count-limit,  Up: limits

D.7.5 Limits Imposed by .frm File Structure
-------------------------------------------

Each table has an `.frm' file that contains the table definition. The
server uses the following expression to check some of the table
information stored in the file against an upper limit of 64KB:


     if (info_length+(ulong) create_fields.elements*FCOMP+288+
         n_length+int_length+com_length > 65535L || int_count > 255)

The portion of the information stored in the `.frm' file that is
checked against the expression cannot grow beyond the 64KB limit, so if
the table definition reaches this size, no more columns can be added.

The relevant factors in the expression are:

   * `info_length' is space needed for `screens.' This is related to
     MySQL's Unireg heritage.

   * `create_fields.elements' is the number of columns.

   * `FCOMP' is 17.

   * `n_length' is the total length of all column names, including one
     byte per name as a separator.

   * `int_length' is related to the list of values for *Note `ENUM':
     enum. and *Note `SET': set. columns. In this context, `int' does
     not mean `integer.' It means `interval,' a term that refers
     collectively to *Note `ENUM': enum. and *Note `SET': set. columns.

   * `int_count' is the number of unique *Note `ENUM': enum. and *Note
     `SET': set. definitions.

   * `com_length' is the total length of column comments.

The expression just described has several implications for permitted
table definitions:

   * Using long column names can reduce the maximum number of columns,
     as can the inclusion of *Note `ENUM': enum. or *Note `SET': set.
     columns, or use of column comments.

   * A table can have no more than 255 unique *Note `ENUM': enum. and
     *Note `SET': set. definitions. Columns with identical element
     lists are considered the same against this limt. For example, if a
     table contains these two columns, they count as one (not two)
     toward this limit because the definitions are identical:


          e1 ENUM('a','b','c')
          e2 ENUM('a','b','c')

   * The sum of the length of element names in the unique *Note `ENUM':
     enum. and *Note `SET': set. definitions counts toward the 64KB
     limit, so although the theoretical limit on number of elements in
     a given *Note `ENUM': enum.  column is 65,535, the practical limit
     is less than 3000.


File: manual.info,  Node: limits-windows,  Prev: limits-frm-file,  Up: limits

D.7.6 Windows Platform Limitations
----------------------------------

The following limitations apply to use of MySQL on the Windows platform:

   * *Number of file descriptors*

     The number of open file descriptors on Windows is limited to a
     maximum of 2048, which may limit the ability to open a large
     number of tables simultaneously. This limit is due not to Windows
     but to C runtime library compatibility functions used to open
     files on Windows that use the POSIX compatibility layer.

     This limitation will also cause problems if you try to set
     `open_files_limit' to a value greater than the 2048 file limit.

   * *Process memory*

     On Windows 32-bit platforms it is not possible by default to use
     more than 2GB of RAM within a single process, including MySQL.
     This is because the physical address limit on Windows 32-bit is
     4GB and the default setting within Windows is to split the virtual
     address space between kernel (2GB) and user/applications (2GB).

     Some versions of Windows have a boot time setting to enable larger
     applications by reducing the kernel application.  Alternatively,
     to use more than 2GB, use a 64-bit version of Windows.

   * *File system aliases*

     When using `MyISAM' tables, you cannot use aliases within Windows
     link to the data files on another volume and then link back to the
     main MySQL `datadir' location.

     This facility is often used to move the data and index files to a
     RAID or other fast solution, while retaining the main `.frm' files
     in the default data directory configured with the `datadir' option.

   * *Limited number of ports*

     Windows systems have about 4,000 ports available for client
     connections, and after a connection on a port closes, it takes two
     to four minutes before the port can be reused. In situations where
     clients connect to and disconnect from the server at a high rate,
     it is possible for all available ports to be used up before closed
     ports become available again. If this happens, the MySQL server
     appears to be unresponsive even though it is running. Note that
     ports may be used by other applications running on the machine as
     well, in which case the number of ports available to MySQL is
     lower.

     For more information about this problem, see
     `http://support.microsoft.com/default.aspx?scid=kb;en-us;196271'.

   * *Concurrent reads*

     MySQL depends on the `pread()' and `pwrite()' system calls to be
     able to mix *Note `INSERT': insert. and *Note `SELECT': select.
     Currently, we use mutexes to emulate `pread()' and `pwrite()'. We
     intend to replace the file level interface with a virtual
     interface in the future so that we can use the
     `readfile()'/`writefile()' interface to get more speed. The
     current implementation limits the number of open files that MySQL
     5.1 can use to 2,048, which means that you cannot run as many
     concurrent threads on Windows as on Unix.

     This problem is fixed in MySQL 5.5.

   * *Blocking read*

     Before MySQL 5.1.41, MySQL uses a blocking read for each
     connection. That has the following implications if named-pipe
     connections are enabled:

        * A connection is not disconnected automatically after eight
          hours, as happens with the Unix version of MySQL.

        * If a connection hangs, it is not possible to break it without
          killing MySQL.

        * *Note `mysqladmin kill': mysqladmin. does not work on a
          sleeping connection.

        * *Note `mysqladmin shutdown': mysqladmin. cannot abort as long
          as there are sleeping connections.

   * **Note `DROP DATABASE': drop-database.*

     You cannot drop a database that is in use by another session.

   * *Case-insensitive names*

     File names are not case sensitive on Windows, so MySQL database
     and table names are also not case sensitive on Windows. The only
     restriction is that database and table names must be specified
     using the same case throughout a given statement. See *Note
     identifier-case-sensitivity::.

   * *Directory and file names*

     On Windows, MySQL Server supports only directory and file names
     that are compatible with the current ANSI code pages.  For
     example, the following Japanese directory name will not work in
     the Western locale (code page 1252):


          datadir="C:/私たちのプロジェクトのデータ"

     The same limitation applies to directory and file names referred
     to in SQL statements, such as the data file path name in *Note
     `LOAD DATA INFILE': load-data.

   * *The ``\'' path name separator character*

     Path name components in Windows are separated by the ``\''
     character, which is also the escape character in MySQL. If you are
     using *Note `LOAD DATA INFILE': load-data. or *Note `SELECT ...
     INTO OUTFILE': select-into, use Unix-style file names with ``/''
     characters:


          mysql> LOAD DATA INFILE 'C:/tmp/skr.txt' INTO TABLE skr;
          mysql> SELECT * INTO OUTFILE 'C:/tmp/skr.txt' FROM skr;

     Alternatively, you must double the ``\'' character:


          mysql> LOAD DATA INFILE 'C:\\tmp\\skr.txt' INTO TABLE skr;
          mysql> SELECT * INTO OUTFILE 'C:\\tmp\\skr.txt' FROM skr;

   * *Problems with pipes*

     Pipes do not work reliably from the Windows command-line prompt.
     If the pipe includes the character `^Z' / `CHAR(24)', Windows
     thinks that it has encountered end-of-file and aborts the program.

     This is mainly a problem when you try to apply a binary log as
     follows:


          C:\> mysqlbinlog BINARY_LOG_FILE | mysql --user=root

     If you have a problem applying the log and suspect that it is
     because of a `^Z' / `CHAR(24)' character, you can use the
     following workaround:


          C:\> mysqlbinlog BINARY_LOG_FILE --result-file=/tmp/bin.sql
          C:\> mysql --user=root --execute "source /tmp/bin.sql"

     The latter command also can be used to reliably read in any SQL
     file that may contain binary data.


File: manual.info,  Node: licenses-third-party,  Prev: restrictions,  Up: Top

Appendix E Licenses for Third-Party Components
**********************************************

* Menu:

* license-antlr-3::              ANTLR 3 License
* license-dtoa::                 dtoa.c License
* license-libedit::              Editline Library (libedit) License
* license-findgtest-cmake::      FindGTest.cmake License
* license-dbug::                 Fred Fish's Dbug Library License
* license-getarg::               getarg License
* license-glib-proxy::           GLib License (for MySQL Proxy)
* license-gnu-gpl-2-0::          GNU General Public License Version 2.0, June 1991
* license-gnu-lgpl-2-1::         GNU Lesser General Public License Version 2.1, February 1999
* license-gnu-libtool::          GNU Libtool License
* license-gnu-readline::         GNU Readline License
* license-google-io-rate-patch::  Google Controlling Master Thread I/O Rate Patch License
* license-google-tcmalloc::      Google Perftools (TCMalloc utility) License
* license-google-smp-patch::     Google SMP Patch License
* license-lib-sql::              lib_sql.cc License
* license-libevent::             libevent License
* license-libiconv-proxy::       Libiconv License
* license-libintl::              libintl License
* license-linux-pam::            Linux-PAM License
* license-lpeg::                 LPeg Library License
* license-lua::                  Lua (liblua) License
* license-luafilesystem::        LuaFileSystem Library License
* license-md5::                  md5 (Message-Digest Algorithm 5) License
* license-memcached::            memcached License
* license-nt-servc::             nt_servc (Windows NT Service class library) License
* license-openpam::              OpenPAM License
* license-paramiko::             Paramiko License
* license-pcre::                 PCRE License
* license-percona-io-threads-patch::  Percona Multiple I/O Threads Patch License
* license-regex::                RegEX-Spencer Library License
* license-us-secure-hash::       RFC 3174 - US Secure Hash Algorithm 1 (SHA1) License
* license-libstring::            Richard A. O'Keefe String Library License
* license-sha1-in-c::            SHA-1 in C License
* license-zlib::                 zlib License

The following is a list of the libraries we have included with the
MySQL Server source and components used to test MySQL. We are thankful
to all individuals that have created these. Some of the components
require that their licensing terms be included in the documentation of
products that include them. Cross references to these licensing terms
are given with the applicable items in the list.

   * Bjorn Benson

     For his safe_malloc (memory checker) package which is used in when
     you build MySQL using one of the `BUILD/compile-*-debug' scripts
     or by manually setting the `-DSAFEMALLOC' flag.

   * GroupLens Research Project

     The MySQL Quality Assurance team would like to acknowledge the use
     of the MovieLens Data Sets (10 million ratings and 100,000 tags
     for 10681 movies by 71567 users) to help test MySQL products and
     to thank the GroupLens Research Project at the University of
     Minnesota for making the data sets available.

*MySQL 5.1*
   * *Note license-dtoa::

   * *Note license-libedit::

   * *Note license-findgtest-cmake::

   * *Note license-dbug::

   * *Note license-getarg::

   * *Note license-gnu-gpl-2-0::

   * *Note license-gnu-libtool::

   * *Note license-gnu-readline::

   * *Note license-google-io-rate-patch::

   * *Note license-google-smp-patch::

   * *Note license-lib-sql::

   * *Note license-md5::

   * *Note license-nt-servc::

   * *Note license-percona-io-threads-patch::

   * *Note license-regex::

   * *Note license-us-secure-hash::

   * *Note license-libstring::

   * *Note license-zlib::

*MySQL Cluster 7.1*
   * *Note license-antlr-3::

   * *Note license-dtoa::

   * *Note license-libedit::

   * *Note license-findgtest-cmake::

   * *Note license-dbug::

   * *Note license-getarg::

   * *Note license-gnu-gpl-2-0::

   * *Note license-gnu-lgpl-2-1::

   * *Note license-gnu-libtool::

   * *Note license-gnu-readline::

   * *Note license-google-io-rate-patch::

   * *Note license-google-tcmalloc::

   * *Note license-google-smp-patch::

   * *Note license-lib-sql::

   * *Note license-libevent::

   * *Note license-linux-pam::

   * *Note license-md5::

   * *Note license-memcached::

   * *Note license-nt-servc::

   * *Note license-openpam::

   * *Note license-paramiko::

   * *Note license-percona-io-threads-patch::

   * *Note license-regex::

   * *Note license-libstring::

   * *Note license-sha1-in-c::

   * *Note license-zlib::

*MySQL Proxy*
   * *Note license-glib-proxy::

   * *Note license-gnu-lgpl-2-1::

   * *Note license-libevent::

   * *Note license-libiconv-proxy::

   * *Note license-libintl::

   * *Note license-lpeg::

   * *Note license-lua::

   * *Note license-luafilesystem::

   * *Note license-pcre::


File: manual.info,  Node: license-antlr-3,  Next: license-dtoa,  Prev: licenses-third-party,  Up: licenses-third-party

E.1 ANTLR 3 License
===================


     The following software may be included in this product:

     ANTLR 3

     ANTLR 3 License
     [The BSD License]
     Copyright (c) 2003-2007, Terence Parr
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:

     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
     * Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in
       the documentation and/or other materials provided with the
       distribution.
     * Neither the name of the author nor the names of its contributors
       may be used to endorse or promote products derived from this
       software without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
     ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-dtoa,  Next: license-libedit,  Prev: license-antlr-3,  Up: licenses-third-party

E.2 dtoa.c License
==================

The following software may be included in this product:

`dtoa.c'


     The author of this software is David M. Gay.

     Copyright (c) 1991, 2000, 2001 by Lucent Technologies.

     Permission to use, copy, modify, and distribute this software for
     any purpose without fee is hereby granted, provided that this entire
     notice is included in all copies of any software which is or includes
     a copy or modification of this software and in all copies of the
     supporting documentation for such software.

     THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
     IMPLIED WARRANTY. IN PARTICULAR, NEITHER THE AUTHOR NOR LUCENT
     MAKES ANY REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
     MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
     PURPOSE.


File: manual.info,  Node: license-libedit,  Next: license-findgtest-cmake,  Prev: license-dtoa,  Up: licenses-third-party

E.3 Editline Library (libedit) License
======================================

The following software may be included in this product:

Editline Library (libedit)

Some files are:


     Copyright (c) 1992, 1993
     The Regents of the University of California. All rights reserved.

     This code is derived from software contributed to
     Berkeley by Christos Zoulas of Cornell University.

     Redistribution and use in source and binary forms,
     with or without modification, are permitted provided
     that the following conditions are met:

     1. Redistributions of source code must retain the
       above copyright notice, this list of conditions
       and the following disclaimer.
     2. Redistributions in binary form must reproduce the
       above copyright notice, this list of conditions and
       the following disclaimer in the documentation and/or
       other materials provided with the distribution.
     3. Neither the name of the University nor the names of
       its contributors may be used to endorse or promote
       products derived from this software without specific
       prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
     BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
     AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
     IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
     OF THE POSSIBILITY OF SUCH DAMAGE.

Some files are:


     Copyright (c) 2001 The NetBSD Foundation, Inc.
     All rights reserved.

     This code is derived from software contributed to The NetBSD Foundation

     by Anthony Mallet.

     Redistribution and use in source and binary forms,
     with or without modification, are permitted provided
     that the following conditions are met:

     1. Redistributions of source code must retain the
        above copyright notice, this list of conditions
        and the following disclaimer.
     2. Redistributions in binary form must reproduce the
         above copyright notice, this list of conditions and the
         following disclaimer in the documentation and/or
         other materials provided with the distribution.

     THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC.
     AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
     WARRANTIES, INCLUDING, BUT NOT LIMITED  TO, THE IMPLIED
     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
     PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
     THE FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY
     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
     USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
     OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
     DAMAGE.

Some files are:


     Copyright (c) 1997 The NetBSD Foundation, Inc.
     All rights reserved.

     This code is derived from software contributed to The NetBSD Foundation

     by Jaromir Dolecek.

     Redistribution and use in source and binary forms,
     with or without modification, are permitted provided
     that the following conditions are met:

     1. Redistributions of source code must retain the
        above copyright notice, this list of conditions
        and the following disclaimer.
     2. Redistributions in binary form must reproduce
         the above copyright notice, this list of conditions
         and the following disclaimer in the documentation
         and/or other materials provided with the distribution.

     THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC.
     AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
     WARRANTIES, INCLUDING, BUT NOT LIMITED  TO, THE IMPLIED
     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
     PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
     THE FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY
     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
     USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
     OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
     DAMAGE.

Some files are:


     Copyright (c) 1998 Todd C. Miller <Todd.Miller@courtesan.com>

     Permission to use, copy, modify, and distribute this
     software for any purpose with or without fee is hereby
     granted, provided that the above copyright notice and
     this permission notice appear in all copies.

     THE SOFTWARE IS PROVIDED "AS IS" AND TODD C. MILLER
     DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
     INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
     AND FITNESS. IN NO EVENT SHALL TODD C. MILLER BE LIABLE
     FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
     DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
     LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
     OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
     ARISING OUT OF OR IN CONNECTION WITH THE USE OR
     PERFORMANCE OF THIS SOFTWARE.


File: manual.info,  Node: license-findgtest-cmake,  Next: license-dbug,  Prev: license-libedit,  Up: licenses-third-party

E.4 FindGTest.cmake License
===========================

The following software may be included in this product:


     FindGTest.cmake helper script (part of CMake)

     Copyright 2009 Kitware, Inc.
     Copyright 2009 Philip Lowman
     Copyright 2009 Daniel Blezek

     Distributed under the OSI-approved BSD License (the "License");
     see accompanying file Copyright.txt for details.

     This software is distributed WITHOUT ANY WARRANTY; without even the
     implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
     See the License for more information.
     ==========================================================================
     (To distributed this file outside of CMake, substitute the full
      License text for the above reference.)

     Thanks to Daniel Blezek  for the GTEST_ADD_TESTS code

     Text of Copyright.txt mentioned above:

     CMake - Cross Platform Makefile Generator
     Copyright 2000-2009 Kitware, Inc., Insight Software Consortium
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:

     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

     * Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.

     * Neither the names of Kitware, Inc., the Insight Software Consortium,
       nor the names of their contributors may be used to endorse or promote
       products derived from this software without specific prior written
       permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-dbug,  Next: license-getarg,  Prev: license-findgtest-cmake,  Up: licenses-third-party

E.5 Fred Fish's Dbug Library License
====================================

The following software may be included in this product:

Fred Fish's Dbug Library


                                     N O T I C E

                        Copyright Abandoned, 1987, Fred Fish

          This previously copyrighted work has been placed into the  public

          domain  by  the  author  and  may be freely used for any purpose,

          private or commercial.

          Because of the number of inquiries I was receiving about the  use

          of this product in commercially developed works I have decided to

          simply make it public domain to further its unrestricted use.   I

          specifically  would  be  most happy to see this material become a

          part of the standard Unix distributions by AT&T and the  Berkeley

          Computer  Science  Research Group, and a standard part of the GNU

          system from the Free Software Foundation.

          I would appreciate it, as a courtesy, if this notice is  left  in

          all copies and derivative works.  Thank you.

          The author makes no warranty of any kind  with  respect  to  this

          product  and  explicitly disclaims any implied warranties of mer-

          chantability or fitness for any particular purpose.

     The dbug_analyze.c file is subject to the following notice:

          Copyright June 1987, Binayak Banerjee
          All rights reserved.

          This program may be freely distributed under the same terms and
          conditions as Fred Fish's Dbug package.


File: manual.info,  Node: license-getarg,  Next: license-glib-proxy,  Prev: license-dbug,  Up: licenses-third-party

E.6 getarg License
==================

The following software may be included in this product:

`getarg' Function (`getarg.h', `getarg.c' files)


     Copyright (c) 1997 - 2000 Kungliga Tekniska Ho"gskolan
     (Royal Institute of Technology, Stockholm, Sweden).
     All rights reserved.

     Redistribution and use in source and binary forms, with
     or without modification, are permitted provided that the
     following conditions are met:

     1. Redistributions of source code must retain the above
        copyright notice, this list of conditions and the
        following disclaimer.
     2. Redistributions in binary form must reproduce the above
        copyright notice, this list of conditions and the following
        disclaimer in the documentation and/or other materials
        provided with the distribution.
     3. Neither the name of the Institute nor the names of its
        contributors may be used to endorse or promote products
        derived from this software without specific prior written
        permission.

     THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
     BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
     AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE FOR ANY
     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
     DAMAGE.


File: manual.info,  Node: license-glib-proxy,  Next: license-gnu-gpl-2-0,  Prev: license-getarg,  Up: licenses-third-party

E.7 GLib License (for MySQL Proxy)
==================================

The following software may be included in this product:


     GLib

     You are receiving a copy of the GLib library in both source
     and object code in the following [proxy install dir]/lib/ and
     [proxy install dir]/licenses/lgpl folders. The terms of the
     Oracle license do NOT apply to the GLib library; it is licensed
     under the following license, separately from the Oracle programs
     you receive. If you do not wish to install this library, you may
     create an "exclude" file and run tar with the X option, as in
     the following example, but the Oracle program might not operate
     properly or at all without the library:
       tar -xvfX <package-tar-file> <exclude-file>
     where the exclude-file contains, e.g.:
       <package-name>/lib/libglib-2.0.so.0.1600.6
       <package-name>/lib/libglib-2.0.so.0
       ...

     Example:
     tar -xvfX mysql-proxy-0.8.1-solaris10-x86-64bit.tar.gz Exclude

     Exclude File:
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libglib-2.0.so
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libglib-2.0.so.0
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libglib-2.0.so.0.1600.6
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libgmodule-2.0.so
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libgmodule-2.0.so.0
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libgmodule-2.0.so.0.1600.6
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libgthread-2.0.so
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libgthread-2.0.so.0
     mysql-proxy-0.8.1-solaris10-x86-64bit/lib/libgthread-2.0.so.0.1600.6
     mysql-proxy-0.8.1-solaris10-x86-64bit/licenses/lgpl/glib-2.16.6.tar.gz

This component is licensed under *Note license-gnu-lgpl-2-1::.


File: manual.info,  Node: license-gnu-gpl-2-0,  Next: license-gnu-lgpl-2-1,  Prev: license-glib-proxy,  Up: licenses-third-party

E.8 GNU General Public License Version 2.0, June 1991
=====================================================


     The following applies to all products licensed under the GNU General
     Public License, Version 2.0: You may not use the identified files
     except in compliance with the GNU General Public License, Version
     2.0 (the "License.") You may obtain a copy of the License at
     http://www.gnu.org/licenses/gpl-2.0.txt. A copy of the license is
     also reproduced below. Unless required by applicable law or agreed
     to in writing, software distributed under the License is distributed
     on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
     either express or implied. See the License for the specific language
     governing permissions and limitations under the License.

     GNU GENERAL PUBLIC LICENSE
     Version 2, June 1991

     Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
     Everyone is permitted to copy and distribute verbatim
     copies of this license document, but changing it is not
     allowed.

                          Preamble

       The licenses for most software are designed to take away your
     freedom to share and change it.  By contrast, the GNU General Public
     License is intended to guarantee your freedom to share and change free
     software--to make sure the software is free for all its users.  This
     General Public License applies to most of the Free Software
     Foundation's software and to any other program whose authors commit to
     using it.  (Some other Free Software Foundation software is covered by
     the GNU Lesser General Public License instead.)  You can apply it to
     your programs, too.

       When we speak of free software, we are referring to freedom, not
     price.  Our General Public Licenses are designed to make sure that you
     have the freedom to distribute copies of free software (and charge for
     this service if you wish), that you receive source code or can get it
     if you want it, that you can change the software or use pieces of it
     in new free programs; and that you know you can do these things.

       To protect your rights, we need to make restrictions that forbid
     anyone to deny you these rights or to ask you to surrender the rights.
     These restrictions translate to certain responsibilities for you if you
     distribute copies of the software, or if you modify it.

       For example, if you distribute copies of such a program, whether
     gratis or for a fee, you must give the recipients all the rights that
     you have.  You must make sure that they, too, receive or can get the
     source code.  And you must show them these terms so they know their
     rights.

       We protect your rights with two steps: (1) copyright the software,
     and (2) offer you this license which gives you legal permission to
     copy, distribute and/or modify the software.

       Also, for each author's protection and ours, we want to make certain
     that everyone understands that there is no warranty for this free
     software.  If the software is modified by someone else and passed on,
     we want its recipients to know that what they have is not the original,
     so that any problems introduced by others will not reflect on the
     original authors' reputations.

       Finally, any free program is threatened constantly by software
     patents.  We wish to avoid the danger that redistributors of a free
     program will individually obtain patent licenses, in effect making the
     program proprietary.  To prevent this, we have made it clear that any
     patent must be licensed for everyone's free use or not licensed at all.

       The precise terms and conditions for copying, distribution and
     modification follow.

                         GNU GENERAL PUBLIC LICENSE
        TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

       0. This License applies to any program or other work which contains
     a notice placed by the copyright holder saying it may be distributed
     under the terms of this General Public License.  The "Program", below,
     refers to any such program or work, and a "work based on the Program"
     means either the Program or any derivative work under copyright law:
     that is to say, a work containing the Program or a portion of it,
     either verbatim or with modifications and/or translated into another
     language.  (Hereinafter, translation is included without limitation in
     the term "modification".)  Each licensee is addressed as "you".

     Activities other than copying, distribution and modification are not
     covered by this License; they are outside its scope.  The act of
     running the Program is not restricted, and the output from the Program
     is covered only if its contents constitute a work based on the
     Program (independent of having been made by running the Program).
     Whether that is true depends on what the Program does.

       1. You may copy and distribute verbatim copies of the Program's
     source code as you receive it, in any medium, provided that you
     conspicuously and appropriately publish on each copy an appropriate
     copyright notice and disclaimer of warranty; keep intact all the
     notices that refer to this License and to the absence of any warranty;
     and give any other recipients of the Program a copy of this License
     along with the Program.

     You may charge a fee for the physical act of transferring a copy, and
     you may at your option offer warranty protection in exchange for a fee.

       2. You may modify your copy or copies of the Program or any portion
     of it, thus forming a work based on the Program, and copy and
     distribute such modifications or work under the terms of Section 1
     above, provided that you also meet all of these conditions:

         a) You must cause the modified files to carry prominent notices
         stating that you changed the files and the date of any change.

         b) You must cause any work that you distribute or publish, that in
         whole or in part contains or is derived from the Program or any
         part thereof, to be licensed as a whole at no charge to all third
         parties under the terms of this License.

         c) If the modified program normally reads commands interactively
         when run, you must cause it, when started running for such
         interactive use in the most ordinary way, to print or display an
         announcement including an appropriate copyright notice and a
         notice that there is no warranty (or else, saying that you provide
         a warranty) and that users may redistribute the program under
         these conditions, and telling the user how to view a copy of this
         License.  (Exception: if the Program itself is interactive but
         does not normally print such an announcement, your work based on
         the Program is not required to print an announcement.)

     These requirements apply to the modified work as a whole.  If
     identifiable sections of that work are not derived from the Program,
     and can be reasonably considered independent and separate works in
     themselves, then this License, and its terms, do not apply to those
     sections when you distribute them as separate works.  But when you
     distribute the same sections as part of a whole which is a work based
     on the Program, the distribution of the whole must be on the terms of
     this License, whose permissions for other licensees extend to the
     entire whole, and thus to each and every part regardless of who wrote it.

     Thus, it is not the intent of this section to claim rights or contest
     your rights to work written entirely by you; rather, the intent is to
     exercise the right to control the distribution of derivative or
     collective works based on the Program.

     In addition, mere aggregation of another work not based on the Program
     with the Program (or with a work based on the Program) on a volume of
     a storage or distribution medium does not bring the other work under
     the scope of this License.

       3. You may copy and distribute the Program (or a work based on it,
     under Section 2) in object code or executable form under the terms of
     Sections 1 and 2 above provided that you also do one of the following:

         a) Accompany it with the complete corresponding machine-readable
         source code, which must be distributed under the terms of Sections
         1 and 2 above on a medium customarily used for software
         interchange; or,

         b) Accompany it with a written offer, valid for at least three
         years, to give any third party, for a charge no more than your
         cost of physically performing source distribution, a complete
         machine-readable copy of the corresponding source code, to be
         distributed under the terms of Sections 1 and 2 above on a medium
         customarily used for software interchange; or,

         c) Accompany it with the information you received as to the offer
         to distribute corresponding source code.  (This alternative is
         allowed only for noncommercial distribution and only if you
         received the program in object code or executable form with such
         an offer, in accord with Subsection b above.)

     The source code for a work means the preferred form of the work for
     making modifications to it.  For an executable work, complete source
     code means all the source code for all modules it contains, plus any
     associated interface definition files, plus the scripts used to
     control compilation and installation of the executable.  However, as
     a special exception, the source code distributed need not include
     anything that is normally distributed (in either source or binary
     form) with the major components (compiler, kernel, and so on) of the
     operating system on which the executable runs, unless that component
     itself accompanies the executable.

     If distribution of executable or object code is made by offering
     access to copy from a designated place, then offering equivalent
     access to copy the source code from the same place counts as
     distribution of the source code, even though third parties are not
     compelled to copy the source along with the object code.

       4. You may not copy, modify, sublicense, or distribute the Program
     except as expressly provided under this License.  Any attempt
     otherwise to copy, modify, sublicense or distribute the Program is
     void, and will automatically terminate your rights under this License.
     However, parties who have received copies, or rights, from you under
     this License will not have their licenses terminated so long as such
     parties remain in full compliance.

       5. You are not required to accept this License, since you have not
     signed it.  However, nothing else grants you permission to modify or
     distribute the Program or its derivative works.  These actions are
     prohibited by law if you do not accept this License.  Therefore, by
     modifying or distributing the Program (or any work based on the
     Program), you indicate your acceptance of this License to do so, and
     all its terms and conditions for copying, distributing or modifying
     the Program or works based on it.

       6. Each time you redistribute the Program (or any work based on the
     Program), the recipient automatically receives a license from the
     original licensor to copy, distribute or modify the Program subject to
     these terms and conditions.  You may not impose any further
     restrictions on the recipients' exercise of the rights granted herein.
     You are not responsible for enforcing compliance by third parties to
     this License.

       7. If, as a consequence of a court judgment or allegation of patent
     infringement or for any other reason (not limited to patent issues),
     conditions are imposed on you (whether by court order, agreement or
     otherwise) that contradict the conditions of this License, they do not
     excuse you from the conditions of this License.  If you cannot
     distribute so as to satisfy simultaneously your obligations under this
     License and any other pertinent obligations, then as a consequence you
     may not distribute the Program at all.  For example, if a patent
     license would not permit royalty-free redistribution of the Program by
     all those who receive copies directly or indirectly through you, then
     the only way you could satisfy both it and this License would be to
     refrain entirely from distribution of the Program.

     If any portion of this section is held invalid or unenforceable under
     any particular circumstance, the balance of the section is intended to
     apply and the section as a whole is intended to apply in other
     circumstances.

     It is not the purpose of this section to induce you to infringe any
     patents or other property right claims or to contest validity of any
     such claims; this section has the sole purpose of protecting the
     integrity of the free software distribution system, which is
     implemented by public license practices.  Many people have made
     generous contributions to the wide range of software distributed
     through that system in reliance on consistent application of that
     system; it is up to the author/donor to decide if he or she is willing
     to distribute software through any other system and a licensee cannot
     impose that choice.

     This section is intended to make thoroughly clear what is believed to
     be a consequence of the rest of this License.

       8. If the distribution and/or use of the Program is restricted in
     certain countries either by patents or by copyrighted interfaces, the
     original copyright holder who places the Program under this License
     may add an explicit geographical distribution limitation excluding
     those countries, so that distribution is permitted only in or among
     countries not thus excluded.  In such case, this License incorporates
     the limitation as if written in the body of this License.

       9. The Free Software Foundation may publish revised and/or new
     versions of the General Public License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.

     Each version is given a distinguishing version number.  If the Program
     specifies a version number of this License which applies to it and
     "any later version", you have the option of following the terms and
     conditions either of that version or of any later version published by
     the Free Software Foundation.  If the Program does not specify a
     version number of this License, you may choose any version ever
     published by the Free Software Foundation.

       10. If you wish to incorporate parts of the Program into other free
     programs whose distribution conditions are different, write to the
     author to ask for permission.  For software which is copyrighted by the
     Free Software Foundation, write to the Free Software Foundation; we
     sometimes make exceptions for this.  Our decision will be guided by the
     two goals of preserving the free status of all derivatives of our free
     software and of promoting the sharing and reuse of software generally.

                                 NO WARRANTY

       11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO
     WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
     EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
     OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND,
     EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
     THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS
     WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
     ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

       12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
     AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU
     FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
     CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
     PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
     RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
     FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF
     SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
     DAMAGES.

                          END OF TERMS AND CONDITIONS

                 How to Apply These Terms to Your New Programs

       If you develop a new program, and you want it to be of the greatest
     possible use to the public, the best way to achieve this is to make it
     free software which everyone can redistribute and change under these terms.

       To do so, attach the following notices to the program.  It is safest
     to attach them to the start of each source file to most effectively
     convey the exclusion of warranty; and each file should have at least
     the "copyright" line and a pointer to where the full notice is found.

         <one line to give the program's name and a brief idea of what it
         does.>
         Copyright (C) <year>  <name of author>

         This program is free software; you can redistribute it and/or
         modify it under the terms of the GNU General Public License as
         published by     the Free Software Foundation; either version
         2 of the License, or (at your option) any later version.

         This program is distributed in the hope that it will be useful,
         but WITHOUT ANY WARRANTY; without even the implied warranty of
         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
         GNU General Public License for more details.

         You should have received a copy of the GNU General Public License
         along with this program; if not, write to the Free Software
         Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
         02110-1301 USA.

     Also add information on how to contact you by electronic and paper mail.

     If the program is interactive, make it output a short notice like this
     when it starts in an interactive mode:

         Gnomovision version 69, Copyright (C) year name of author
         Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
         type 'show w'. This is free software, and you are welcome
         to redistribute it under certain conditions; type 'show c'
         for details.

     The hypothetical commands 'show w' and 'show c' should show the
     appropriate parts of the General Public License.  Of course, the
     commands you use may be called something other than 'show w' and
     'show c'; they could even be mouse-clicks or menu items--whatever
     suits your program.

     You should also get your employer (if you work as a programmer) or your
     school, if any, to sign a "copyright disclaimer" for the program, if
     necessary.  Here is a sample; alter the names:

       Yoyodyne, Inc., hereby disclaims all copyright interest in the
       program 'Gnomovision' (which makes passes at compilers) written
       by James Hacker.

       <signature of Ty Coon>, 1 April 1989
       Ty Coon, President of Vice

     This General Public License does not permit incorporating your program
     into proprietary programs.  If your program is a subroutine library,
     you may consider it more useful to permit linking proprietary
     applications with the library.  If this is what you want to do, use
     the GNU Lesser General Public License instead of this License.


File: manual.info,  Node: license-gnu-lgpl-2-1,  Next: license-gnu-libtool,  Prev: license-gnu-gpl-2-0,  Up: licenses-third-party

E.9 GNU Lesser General Public License Version 2.1, February 1999
================================================================


     The following applies to all products licensed under the
     GNU Lesser General Public License, Version 2.1: You may
     not use the identified files except in compliance with
     the GNU Lesser General Public License, Version 2.1 (the
     "License"). You may obtain a copy of the License at
     http://www.gnu.org/licenses/lgpl-2.1.html. A copy of the
     license is also reproduced below. Unless required by
     applicable law or agreed to in writing, software distributed
     under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
     or implied. See the License for the specific language governing
     permissions and limitations under the License.

                       GNU LESSER GENERAL PUBLIC LICENSE
                            Version 2.1, February 1999

      Copyright (C) 1991, 1999 Free Software Foundation, Inc.
      51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
      Everyone is permitted to copy and distribute verbatim copies
      of this license document, but changing it is not allowed.

     [This is the first released version of the Lesser GPL.  It also counts
      as the successor of the GNU Library Public License, version 2, hence
      the version number 2.1.]

                                 Preamble

       The licenses for most software are designed to take away your
     freedom to share and change it.  By contrast, the GNU General Public
     Licenses are intended to guarantee your freedom to share and change
     free software--to make sure the software is free for all its users.

       This license, the Lesser General Public License, applies to some
     specially designated software packages--typically libraries--of the
     Free Software Foundation and other authors who decide to use it.  You
     can use it too, but we suggest you first think carefully about whether
     this license or the ordinary General Public License is the better
     strategy to use in any particular case, based on the explanations below.

       When we speak of free software, we are referring to freedom of use,
     not price.  Our General Public Licenses are designed to make sure that
     you have the freedom to distribute copies of free software (and charge
     for this service if you wish); that you receive source code or can get
     it if you want it; that you can change the software and use pieces of
     it in new free programs; and that you are informed that you can do
     these things.

       To protect your rights, we need to make restrictions that forbid
     distributors to deny you these rights or to ask you to surrender these
     rights.  These restrictions translate to certain responsibilities for
     you if you distribute copies of the library or if you modify it.

       For example, if you distribute copies of the library, whether gratis
     or for a fee, you must give the recipients all the rights that we gave
     you.  You must make sure that they, too, receive or can get the source
     code.  If you link other code with the library, you must provide
     complete object files to the recipients, so that they can relink them
     with the library after making changes to the library and recompiling
     it.  And you must show them these terms so they know their rights.

       We protect your rights with a two-step method: (1) we copyright the
     library, and (2) we offer you this license, which gives you legal
     permission to copy, distribute and/or modify the library.

       To protect each distributor, we want to make it very clear that
     there is no warranty for the free library.  Also, if the library is
     modified by someone else and passed on, the recipients should know
     that what they have is not the original version, so that the original
     author's reputation will not be affected by problems that might be
     introduced by others.

       Finally, software patents pose a constant threat to the existence of
     any free program.  We wish to make sure that a company cannot
     effectively restrict the users of a free program by obtaining a
     restrictive license from a patent holder.  Therefore, we insist that
     any patent license obtained for a version of the library must be
     consistent with the full freedom of use specified in this license.

       Most GNU software, including some libraries, is covered by the
     ordinary GNU General Public License.  This license, the GNU Lesser
     General Public License, applies to certain designated libraries, and
     is quite different from the ordinary General Public License.  We use
     this license for certain libraries in order to permit linking those
     libraries into non-free programs.

       When a program is linked with a library, whether statically or using
     a shared library, the combination of the two is legally speaking a
     combined work, a derivative of the original library.  The ordinary
     General Public License therefore permits such linking only if the
     entire combination fits its criteria of freedom.  The Lesser General
     Public License permits more lax criteria for linking other code with
     the library.

       We call this license the "Lesser" General Public License because it
     does Less to protect the user's freedom than the ordinary General
     Public License.  It also provides other free software developers Less
     of an advantage over competing non-free programs.  These disadvantages
     are the reason we use the ordinary General Public License for many
     libraries.  However, the Lesser license provides advantages in certain
     special circumstances.

       For example, on rare occasions, there may be a special need to
     encourage the widest possible use of a certain library, so that it
     becomes a de-facto standard.  To achieve this, non-free programs
     must be allowed to use the library.  A more frequent case is that
     a free library does the same job as widely used non-free libraries.
     In this case, there is little to gain by limiting the free library
     to free software only, so we use the Lesser General Public License.

       In other cases, permission to use a particular library in non-free
     programs enables a greater number of people to use a large body of
     free software.  For example, permission to use the GNU C Library in
     non-free programs enables many more people to use the whole GNU
     operating system, as well as its variant, the GNU/Linux operating
     system.

       Although the Lesser General Public License is Less protective of the
     users' freedom, it does ensure that the user of a program that is
     linked with the Library has the freedom and the wherewithal to run
     that program using a modified version of the Library.

       The precise terms and conditions for copying, distribution and
     modification follow.  Pay close attention to the difference between a
     "work based on the library" and a "work that uses the library".  The
     former contains code derived from the library, whereas the latter must
     be combined with the library in order to run.

                       GNU LESSER GENERAL PUBLIC LICENSE
        TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

       0. This License Agreement applies to any software library or other
     program which contains a notice placed by the copyright holder or
     other authorized party saying it may be distributed under the terms of
     this Lesser General Public License (also called "this License").
     Each licensee is addressed as "you".

       A "library" means a collection of software functions and/or data
     prepared so as to be conveniently linked with application programs
     (which use some of those functions and data) to form executables.

       The "Library", below, refers to any such software library or work
     which has been distributed under these terms.  A "work based on the
     Library" means either the Library or any derivative work under
     copyright law: that is to say, a work containing the Library or a
     portion of it, either verbatim or with modifications and/or translated
     straightforwardly into another language.  (Hereinafter, translation is
     included without limitation in the term "modification".)

       "Source code" for a work means the preferred form of the work for
     making modifications to it.  For a library, complete source code means
     all the source code for all modules it contains, plus any associated
     interface definition files, plus the scripts used to control
     compilation and installation of the library.

       Activities other than copying, distribution and modification are not
     covered by this License; they are outside its scope.  The act of
     running a program using the Library is not restricted, and output from
     such a program is covered only if its contents constitute a work based
     on the Library (independent of the use of the Library in a tool for
     writing it).  Whether that is true depends on what the Library does
     and what the program that uses the Library does.

       1. You may copy and distribute verbatim copies of the Library's
     complete source code as you receive it, in any medium, provided that
     you conspicuously and appropriately publish on each copy an
     appropriate copyright notice and disclaimer of warranty; keep intact
     all the notices that refer to this License and to the absence of any
     warranty; and distribute a copy of this License along with the
     Library.

       You may charge a fee for the physical act of transferring a copy,
     and you may at your option offer warranty protection in exchange for a
     fee.

       2. You may modify your copy or copies of the Library or any portion
     of it, thus forming a work based on the Library, and copy and
     distribute such modifications or work under the terms of Section 1
     above, provided that you also meet all of these conditions:

         a) The modified work must itself be a software library.

         b) You must cause the files modified to carry prominent notices
         stating that you changed the files and the date of any change.

         c) You must cause the whole of the work to be licensed at no
         charge to all third parties under the terms of this License.

         d) If a facility in the modified Library refers to a function or a
         table of data to be supplied by an application program that uses
         the facility, other than as an argument passed when the facility
         is invoked, then you must make a good faith effort to ensure that,
         in the event an application does not supply such function or
         table, the facility still operates, and performs whatever part of
         its purpose remains meaningful.

         (For example, a function in a library to compute square roots has
         a purpose that is entirely well-defined independent of the
         application.  Therefore, Subsection 2d requires that any
         application-supplied function or table used by this function must
         be optional: if the application does not supply it, the square
         root function must still compute square roots.)

     These requirements apply to the modified work as a whole.  If
     identifiable sections of that work are not derived from the Library,
     and can be reasonably considered independent and separate works in
     themselves, then this License, and its terms, do not apply to those
     sections when you distribute them as separate works.  But when you
     distribute the same sections as part of a whole which is a work based
     on the Library, the distribution of the whole must be on the terms of
     this License, whose permissions for other licensees extend to the
     entire whole, and thus to each and every part regardless of who wrote
     it.

     Thus, it is not the intent of this section to claim rights or contest
     your rights to work written entirely by you; rather, the intent is to
     exercise the right to control the distribution of derivative or
     collective works based on the Library.

     In addition, mere aggregation of another work not based on the Library
     with the Library (or with a work based on the Library) on a volume of
     a storage or distribution medium does not bring the other work under
     the scope of this License.

       3. You may opt to apply the terms of the ordinary GNU General Public
     License instead of this License to a given copy of the Library.  To do
     this, you must alter all the notices that refer to this License, so
     that they refer to the ordinary GNU General Public License, version 2,
     instead of to this License.  (If a newer version than version 2 of the
     ordinary GNU General Public License has appeared, then you can specify
     that version instead if you wish.)  Do not make any other change in
     these notices.

       Once this change is made in a given copy, it is irreversible for
     that copy, so the ordinary GNU General Public License applies to all
     subsequent copies and derivative works made from that copy.

       This option is useful when you wish to copy part of the code of
     the Library into a program that is not a library.

       4. You may copy and distribute the Library (or a portion or
     derivative of it, under Section 2) in object code or executable form
     under the terms of Sections 1 and 2 above provided that you accompany
     it with the complete corresponding machine-readable source code, which
     must be distributed under the terms of Sections 1 and 2 above on a
     medium customarily used for software interchange.

       If distribution of object code is made by offering access to copy
     from a designated place, then offering equivalent access to copy the
     source code from the same place satisfies the requirement to
     distribute the source code, even though third parties are not
     compelled to copy the source along with the object code.

       5. A program that contains no derivative of any portion of the
     Library, but is designed to work with the Library by being compiled or
     linked with it, is called a "work that uses the Library".  Such a
     work, in isolation, is not a derivative work of the Library, and
     therefore falls outside the scope of this License.

       However, linking a "work that uses the Library" with the Library
     creates an executable that is a derivative of the Library (because it
     contains portions of the Library), rather than a "work that uses the
     library".  The executable is therefore covered by this License.
     Section 6 states terms for distribution of such executables.

       When a "work that uses the Library" uses material from a header file
     that is part of the Library, the object code for the work may be a
     derivative work of the Library even though the source code is not.
     Whether this is true is especially significant if the work can be
     linked without the Library, or if the work is itself a library.  The
     threshold for this to be true is not precisely defined by law.

       If such an object file uses only numerical parameters, data
     structure layouts and accessors, and small macros and small inline
     functions (ten lines or less in length), then the use of the object
     file is unrestricted, regardless of whether it is legally a derivative
     work.  (Executables containing this object code plus portions of the
     Library will still fall under Section 6.)

       Otherwise, if the work is a derivative of the Library, you may
     distribute the object code for the work under the terms of Section 6.
     Any executables containing that work also fall under Section 6,
     whether or not they are linked directly with the Library itself.

       6. As an exception to the Sections above, you may also combine or
     link a "work that uses the Library" with the Library to produce a
     work containing portions of the Library, and distribute that work
     under terms of your choice, provided that the terms permit
     modification of the work for the customer's own use and reverse
     engineering for debugging such modifications.

       You must give prominent notice with each copy of the work that the
     Library is used in it and that the Library and its use are covered by
     this License.  You must supply a copy of this License.  If the work
     during execution displays copyright notices, you must include the
     copyright notice for the Library among them, as well as a reference
     directing the user to the copy of this License.  Also, you must do one
     of these things:

         a) Accompany the work with the complete corresponding
         machine-readable source code for the Library including whatever
         changes were used in the work (which must be distributed under
         Sections 1 and 2 above); and, if the work is an executable linked
         with the Library, with the complete machine-readable "work that
         uses the Library", as object code and/or source code, so that the
         user can modify the Library and then relink to produce a modified
         executable containing the modified Library.  (It is understood
         that the user who changes the contents of definitions files in the
         Library will not necessarily be able to recompile the application
         to use the modified definitions.)

         b) Use a suitable shared library mechanism for linking with the
         Library.  A suitable mechanism is one that (1) uses at run time a
         copy of the library already present on the user's computer system,
         rather than copying library functions into the executable, and (2)
         will operate properly with a modified version of the library, if
         the user installs one, as long as the modified version is
         interface-compatible with the version that the work was made with.

         c) Accompany the work with a written offer, valid for at
         least three years, to give the same user the materials
         specified in Subsection 6a, above, for a charge no more
         than the cost of performing this distribution.

         d) If distribution of the work is made by offering access to copy
         from a designated place, offer equivalent access to copy the above
         specified materials from the same place.

         e) Verify that the user has already received a copy of these
         materials or that you have already sent this user a copy.

       For an executable, the required form of the "work that uses the
     Library" must include any data and utility programs needed for
     reproducing the executable from it.  However, as a special exception,
     the materials to be distributed need not include anything that is
     normally distributed (in either source or binary form) with the major
     components (compiler, kernel, and so on) of the operating system on
     which the executable runs, unless that component itself accompanies
     the executable.

       It may happen that this requirement contradicts the license
     restrictions of other proprietary libraries that do not normally
     accompany the operating system.  Such a contradiction means you cannot
     use both them and the Library together in an executable that you
     distribute.

       7. You may place library facilities that are a work based on the
     Library side-by-side in a single library together with other library
     facilities not covered by this License, and distribute such a combined
     library, provided that the separate distribution of the work based on
     the Library and of the other library facilities is otherwise
     permitted, and provided that you do these two things:

         a) Accompany the combined library with a copy of the same work
         based on the Library, uncombined with any other library
         facilities.  This must be distributed under the terms of the
         Sections above.

         b) Give prominent notice with the combined library of the fact
         that part of it is a work based on the Library, and explaining
         where to find the accompanying uncombined form of the same work.

       8. You may not copy, modify, sublicense, link with, or distribute
     the Library except as expressly provided under this License.  Any
     attempt otherwise to copy, modify, sublicense, link with, or
     distribute the Library is void, and will automatically terminate your
     rights under this License.  However, parties who have received copies,
     or rights, from you under this License will not have their licenses
     terminated so long as such parties remain in full compliance.

       9. You are not required to accept this License, since you have not
     signed it.  However, nothing else grants you permission to modify or
     distribute the Library or its derivative works.  These actions are
     prohibited by law if you do not accept this License.  Therefore, by
     modifying or distributing the Library (or any work based on the
     Library), you indicate your acceptance of this License to do so, and
     all its terms and conditions for copying, distributing or modifying
     the Library or works based on it.

       10. Each time you redistribute the Library (or any work based on the
     Library), the recipient automatically receives a license from the
     original licensor to copy, distribute, link with or modify the Library
     subject to these terms and conditions.  You may not impose any further
     restrictions on the recipients' exercise of the rights granted herein.
     You are not responsible for enforcing compliance by third parties with
     this License.

       11. If, as a consequence of a court judgment or allegation of patent
     infringement or for any other reason (not limited to patent issues),
     conditions are imposed on you (whether by court order, agreement or
     otherwise) that contradict the conditions of this License, they do not
     excuse you from the conditions of this License.  If you cannot
     distribute so as to satisfy simultaneously your obligations under this
     License and any other pertinent obligations, then as a consequence you
     may not distribute the Library at all.  For example, if a patent
     license would not permit royalty-free redistribution of the Library by
     all those who receive copies directly or indirectly through you, then
     the only way you could satisfy both it and this License would be to
     refrain entirely from distribution of the Library.

     If any portion of this section is held invalid or unenforceable under
     any particular circumstance, the balance of the section is intended
     to apply, and the section as a whole is intended to apply in other
     circumstances.

     It is not the purpose of this section to induce you to infringe any
     patents or other property right claims or to contest validity of any
     such claims; this section has the sole purpose of protecting the
     integrity of the free software distribution system which is
     implemented by public license practices.  Many people have made
     generous contributions to the wide range of software distributed
     through that system in reliance on consistent application of that
     system; it is up to the author/donor to decide if he or she is willing
     to distribute software through any other system and a licensee cannot
     impose that choice.

     This section is intended to make thoroughly clear what is believed to
     be a consequence of the rest of this License.

       12. If the distribution and/or use of the Library is restricted in
     certain countries either by patents or by copyrighted interfaces, the
     original copyright holder who places the Library under this License
     may add an explicit geographical distribution limitation excluding
     those countries, so that distribution is permitted only in or among
     countries not thus excluded.  In such case, this License incorporates
     the limitation as if written in the body of this License.

       13. The Free Software Foundation may publish revised and/or new
     versions of the Lesser General Public License from time to time.
     Such new versions will be similar in spirit to the present version,
     but may differ in detail to address new problems or concerns.

     Each version is given a distinguishing version number.  If the Library
     specifies a version number of this License which applies to it and
     "any later version", you have the option of following the terms and
     conditions either of that version or of any later version published by
     the Free Software Foundation.  If the Library does not specify a
     license version number, you may choose any version ever published by
     the Free Software Foundation.

       14. If you wish to incorporate parts of the Library into other free
     programs whose distribution conditions are incompatible with these,
     write to the author to ask for permission.  For software which is
     copyrighted by the Free Software Foundation, write to the Free
     Software Foundation; we sometimes make exceptions for this.  Our
     decision will be guided by the two goals of preserving the free status
     of all derivatives of our free software and of promoting the sharing
     and reuse of software generally.

                                 NO WARRANTY

       15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO
     WARRANTY FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
     EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
     OTHER PARTIES PROVIDE THE LIBRARY "AS IS" WITHOUT WARRANTY OF ANY
     KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE
     IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE
     LIBRARY IS WITH YOU.  SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME
     THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

       16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
     WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
     AND/OR REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU
     FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
     CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
     LIBRARY (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
     RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
     FAILURE OF THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF
     SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
     DAMAGES.

                          END OF TERMS AND CONDITIONS

                How to Apply These Terms to Your New Libraries

       If you develop a new library, and you want it to be of the greatest
     possible use to the public, we recommend making it free software that
     everyone can redistribute and change.  You can do so by permitting
     redistribution under these terms (or, alternatively, under the terms
     of the ordinary General Public License).

       To apply these terms, attach the following notices to the library.
     It is safest to attach them to the start of each source file to most
     effectively convey the exclusion of warranty; and each file should
     have at least the "copyright" line and a pointer to where the full
     notice is found.

         <one line to give the library's name and a brief idea of what it does.>
         Copyright (C) <year>  <name of author>

         This library is free software; you can redistribute it and/or
         modify it under the terms of the GNU Lesser General Public
         License as published by the Free Software Foundation; either
         version 2.1 of the License, or (at your option) any later version.

         This library is distributed in the hope that it will be useful,
         but WITHOUT ANY WARRANTY; without even the implied warranty of
         MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
         Lesser General Public License for more details.

         You should have received a copy of the GNU Lesser General Public
         License along with this library; if not, write to the Free Software
         Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
         02110-1301  USA

     Also add information on how to contact you by electronic and paper mail.

     You should also get your employer (if you work as a programmer) or your
     school, if any, to sign a "copyright disclaimer" for the library, if
     necessary.  Here is a sample; alter the names:

       Yoyodyne, Inc., hereby disclaims all copyright interest in the
       library `Frob' (a library for tweaking knobs) written by James
       Random Hacker.

       <signature of Ty Coon>, 1 April 1990
       Ty Coon, President of Vice

     That's all there is to it!


File: manual.info,  Node: license-gnu-libtool,  Next: license-gnu-readline,  Prev: license-gnu-lgpl-2-1,  Up: licenses-third-party

E.10 GNU Libtool License
========================

The following software may be included in this product:

GNU Libtool (The GNU Portable Library Tool)


     If you are receiving a copy of the Oracle software in
     source code, you are also receiving a copy of two files
     (ltmain.sh and ltdl.h) generated by the GNU Libtool in
     source code. If you received the Oracle software under
     a license other than a commercial (non-GPL) license,
     then the terms of the Oracle license do NOT apply to
     these files from GNU Libtool; they are licensed under
     the following licenses, separately from the Oracle
     programs you receive.

     Oracle elects to use GNU General Public License version
     2 (GPL) for any software where a choice of GPL or GNU
     Lesser/Library General Public License (LGPL) license
     versions are made available with the language indicating
     that GPL/LGPL or any later version may be used, or where
     a choice of which version of the GPL/LGPL is applied is
     unspecified.

     From GNU Libtool:

     ltmain.sh - Provide generalized library-building support
     services.
     NOTE: Changing this file will not affect anything until
     you rerun configure.
     Copyright (C) 1996, 1997, 1998, 1999, 2000, 2001, 2003, 2004,
     2005, 2006, 2007 Free Software Foundation, Inc.
     Originally by Gordon Matzigkeit, 1996

     This program is free software; you can redistribute it
     and/or modify it under the terms of the GNU General
     Public License as published by the Free Software Foundation;
     either version 2 of the License, or (at your option) any
     later version.

     This program is distributed in the hope that it will be
     useful, but WITHOUT ANY WARRANTY; without even the implied
     warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
     PURPOSE. See the GNU General Public License for more
     details. You should have received a copy of the GNU General
     Public License along with this program; if not, write to
     the Free Software Foundation, Inc., 51 Franklin Street,
     Fifth Floor, Boston, MA 02110-1301, USA.

     As a special exception to the GNU General Public License,
     if you distribute this file as part of a program that
     contains a configuration script generated by Autoconf,
     you may include it under the same distribution terms that
     you use for the rest of that program.

This component is licensed under *Note license-gnu-gpl-2-0::


File: manual.info,  Node: license-gnu-readline,  Next: license-google-io-rate-patch,  Prev: license-gnu-libtool,  Up: licenses-third-party

E.11 GNU Readline License
=========================

The following software may be included in this product:

GNU Readline Library


     GNU Readline Library
     With respect to MySQL Server/Cluster software licensed
     under GNU General Public License, you are receiving a
     copy of the GNU Readline Library in source code. The
     terms of any Oracle license that might accompany the
     Oracle programs do NOT apply to the GNU Readline Library;
     it is licensed under the following license, separately
     from the Oracle programs you receive. Oracle elects to
     use GNU General Public License version 2 (GPL) for any
     software where a choice of GPL license versions are
     made available with the language indicating that GPLv2
     or any later version may be used, or where a choice of
     which version of the GPL is applied is unspecified.

This component is licensed under *Note license-gnu-gpl-2-0::


File: manual.info,  Node: license-google-io-rate-patch,  Next: license-google-tcmalloc,  Prev: license-gnu-readline,  Up: licenses-third-party

E.12 Google Controlling Master Thread I/O Rate Patch License
============================================================

The following software may be included in this product:

Google Controlling master thread I/O rate patch


     Copyright (c) 2009, Google Inc.
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:

      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
      * Neither the name of the Google Inc. nor the names of its contributors
        may be used to endorse or promote products derived from this software
        without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
     ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-google-tcmalloc,  Next: license-google-smp-patch,  Prev: license-google-io-rate-patch,  Up: licenses-third-party

E.13 Google Perftools (TCMalloc utility) License
================================================

The following software may be included in this product:


     Google Perftools (TCMalloc utility)

     Copyright (c) 1998-2006, Google Inc.
     All rights reserved.

     Redistribution and use in source and binary forms, with or
     without modification, are permitted provided that the following
     conditions are met:

         * Redistributions of source code must retain the above
           copyright notice, this list of conditions and the following
           disclaimer.
         * Redistributions in binary form must reproduce the above
           copyright notice, this list of conditions and the following
           disclaimer in the documentation and/or other materials provided
           with the distribution.
         * Neither the name of Google Inc. nor the names of its
           contributors may be used to endorse or promote products
           derived from this software without specific prior written
           permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-google-smp-patch,  Next: license-lib-sql,  Prev: license-google-tcmalloc,  Up: licenses-third-party

E.14 Google SMP Patch License
=============================

The following software may be included in this product:

Google SMP Patch


     Google SMP patch

     Copyright (c) 2008, Google Inc.
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:

      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
      * Neither the name of the Google Inc. nor the names of its contributors
        may be used to endorse or promote products derived from this software
        without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
     ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-lib-sql,  Next: license-libevent,  Prev: license-google-smp-patch,  Up: licenses-third-party

E.15 lib_sql.cc License
=======================

The following software may be included in this product:

`lib_sql.cc'


     Copyright (c) 2000
     SWsoft company

     This material is provided "as is", with absolutely no warranty
     expressed or implied. Any use is at your own risk.

     Permission to use or copy this software for any purpose is hereby
     granted without fee, provided the above notices are retained on
     all copies. Permission to modify the code and to distribute modified
     code is granted, provided the above notices are retained, and a
     notice that the code was modified is included with the above copyright
     notice.

     This code was modified by the MySQL team.


File: manual.info,  Node: license-libevent,  Next: license-libiconv-proxy,  Prev: license-lib-sql,  Up: licenses-third-party

E.16 libevent License
=====================

The following software may be included in this product:


     libevent

     Copyright (c) 2000-2007 Niels Provos <provos@citi.umich.edu>
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:
     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
     3. The name of the author may not be used to endorse or promote products
        derived from this software without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE

     ==
     Parts developed by Adam Langley
     ==

     ==
     log.c
     Based on err.c, which was adapted from OpenBSD libc *err*warncode.

     Copyright (c) 2005 Nick Mathewson
     Copyright (c) 2000 Dug Song
     Copyright (c) 1993 The Regents of the University of California.
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:
     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the
        distribution.
     3. Neither the name of the University nor the names of its
        contributors may be used to endorse or promote products derived
        from this software without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS"
     AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
     PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS
     OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
     USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
     IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
     THE POSSIBILITY OF SUCH DAMAGE.
     ==

     ==
     min_heap.h

     Copyright (c) 2006 Maxim Yegorushkin
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:
     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the
        distribution.
     3. The name of the author may not be used to endorse or promote
        products derived from this software without specific prior
        written permission.

     THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS
     OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
     IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
     IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     ==

     ==
     win32.c

     Copyright 2000-2002 Niels Provos
     Copyright 2003 Michael A. Davis
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:
     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the
        distribution.
     3.  The name of the author may not be used to endorse or promote
         products derived from this software without specific prior
         written permission.

     THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS
     OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
     GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
     IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
     IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     ==


File: manual.info,  Node: license-libiconv-proxy,  Next: license-libintl,  Prev: license-libevent,  Up: licenses-third-party

E.17 Libiconv License
=====================

The following software may be included in this product:


     Libiconv

     You may be receiving a copy of the GNU LIBICONV Library with this MySQL
     product. The terms of the Oracle license do NOT apply to the GNU LIBICONV
     Library; it is licensed under the following license, separately from the
     Oracle programs you receive. If you do not wish to install this program,
     you may delete [agent install dir]/lib/libiconv.* and
     [agent install dir]/licenses/lgpl/iconv files.

This component is licensed under *Note license-gnu-lgpl-2-1::.


File: manual.info,  Node: license-libintl,  Next: license-linux-pam,  Prev: license-libiconv-proxy,  Up: licenses-third-party

E.18 libintl License
====================

The following software may be included in this product:

libintl


     Copyright (C) 1994 X Consortium

     Permission is hereby granted, free of charge, to any person obtaining a copy of
     this software and associated documentation files (the "Software"), to deal in
     the Software without restriction, including without limitation the rights to
     use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
     the Software, and to permit persons to whom the Software is furnished to do so,
     subject to the following conditions:

     The above copyright notice and this permission notice shall be included in all
     copies or substantial portions of the Software.

     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
     FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSORTIUM
     BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
     CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
     SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

     Except as contained in this notice, the name of the X Consortium shall not be
     used in advertising or otherwise to promote the sale, use or other dealings in
     this Software without prior written authorization from the X Consortium.

     FSF changes to this file are in the public domain.
      .
     Copyright 1996-2007 Free Software Foundation, Inc. Taken from GNU libtool, 2001

     Originally by Gordon Matzigkeit <gord@gnu.ai.mit.edu>, 1996

     This file is free software; the Free Software Foundation gives unlimited
     permission to copy and/or distribute it, with or without modifications, as long
     as this notice is preserved.
     .
     You are receiving a copy of the libintl library. The terms of the Oracle license
     do NOT apply to the libintl library; it is licensed under the following license,
     separately from the Oracle programs you receive. If you do not wish to install
     this program, you may create an "exclude" file and run tar with the X option.

This component is licensed under *Note license-gnu-lgpl-2-1::.


File: manual.info,  Node: license-linux-pam,  Next: license-lpeg,  Prev: license-libintl,  Up: licenses-third-party

E.19 Linux-PAM License
======================

The following software may be included in this product:


     Linux-PAM (pam-devel, Pluggable authentication modules for Linux)

     Copyright Theodore Ts'o, 1996. All rights reserved.

     (For the avoidance of doubt, Oracle uses and distributes this
     component under the terms below and elects not to do so under
     the GPL even though the GPL is referenced as an option below.)

     Redistribution and use in source and binary forms, with or
     without modification, are permitted provided that the following
     conditions are met:

     1. Redistributions of source code must retain the above copyright
        notice, and the entire permission notice in its entirety,
        including the disclaimer of warranties.
     2. Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in
        the documentation and/or other materials provided with the
        distribution.
     3. The name of the author may not be used to endorse or promote
        products derived from this software without specific prior
        written permission.

     ALTERNATIVELY, this product may be distributed under the terms
     of the GNU Public License, in which case the provisions of the
     GPL are required INSTEAD OF the above restrictions. (This clause
     is necessary due to a potential bad interaction between the GPL
     and the restrictions contained in a BSD-style copyright.)

     THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
     WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
     INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
     OF THE POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-lpeg,  Next: license-lua,  Prev: license-linux-pam,  Up: licenses-third-party

E.20 LPeg Library License
=========================

The following software may be included in this product:


     LPeg

     Use of any of this software is governed by the terms of the license below:

     Copyright (C) 2008 Lua.org, PUC-Rio.

     Permission is hereby granted, free of charge, to any person obtaining a copy of
     this software and associated documentation files (the "Software"), to deal in
     the Software without restriction, including without limitation the rights to
     use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
     the Software, and to permit persons to whom the Software is furnished to do so,
     subject to the following conditions:

     The above copyright notice and this permission notice shall be included in all
     copies or substantial portions of the Software.

     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
     FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
     COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
     IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
     CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


File: manual.info,  Node: license-lua,  Next: license-luafilesystem,  Prev: license-lpeg,  Up: licenses-third-party

E.21 Lua (liblua) License
=========================

The following software may be included in this product:


     Lua (liblua)

     Copyright (C) 1994-2008 Lua.org, PUC-Rio.

     Permission is hereby granted, free of charge, to any person obtaining
     a copy of this software and associated documentation files (the
     "Software"), to deal in the Software without restriction, including
     without limitation the rights to use, copy, modify, merge, publish,
     distribute, sublicense, and/or sell copies of the Software, and to
     permit persons to whom the Software is furnished to do so, subject
     to the following conditions:

     The above copyright notice and this permission notice shall be
     included in all copies or substantial portions of the Software.

     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
     OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
     HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
     WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
     OTHER DEALINGS IN THE SOFTWARE.


File: manual.info,  Node: license-luafilesystem,  Next: license-md5,  Prev: license-lua,  Up: licenses-third-party

E.22 LuaFileSystem Library License
==================================

The following software may be included in this product:


     LuaFileSystem

     Copyright (C) 2003 Kepler Project.

     Permission is hereby granted, free of charge, to any person obtaining
     a copy of this software and associated documentation files (the
     "Software"), to deal in the Software without restriction, including
     without limitation the rights to use, copy, modify, merge, publish,
     distribute, sublicense, and/or sell copies of the Software, and to
     permit persons to whom the Software is furnished to do so, subject
     to the following conditions:

     The above copyright notice and this permission notice shall be
     included in all copies or substantial portions of the Software.

     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
     IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
     ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
     CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
     WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.


File: manual.info,  Node: license-md5,  Next: license-memcached,  Prev: license-luafilesystem,  Up: licenses-third-party

E.23 md5 (Message-Digest Algorithm 5) License
=============================================

The following software may be included in this product:


     md5 (Message-Digest Algorithm 5)

      This code implements the MD5 message-digest algorithm.
      The algorithm is due to Ron Rivest.  This code was
      written by Colin Plumb in 1993, no copyright is claimed.
      This code is in the public domain; do with it what you wish.

      Equivalent code is available from RSA Data Security, Inc.
      This code has been tested against that, and is equivalent,
      except that you don't need to include two pages of legalese
      with every copy.

      The code has been modified by Mikael Ronstroem to handle
      calculating a hash value of a key that is always a multiple
      of 4 bytes long. Word 0 of the calculated 4-word hash value
      is returned as the hash value.


File: manual.info,  Node: license-memcached,  Next: license-nt-servc,  Prev: license-md5,  Up: licenses-third-party

E.24 memcached License
======================

The following software may be included in this product:

memcached


     Copyright (c) 2003, Danga Interactive, Inc.
     All rights reserved.

     Redistribution and use in source and binary forms, with or without
     modification, are permitted provided that the following conditions
     are met:

         * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

         * Redistributions in binary form must reproduce the above
     copyright notice, this list of conditions and the following disclaimer
     in the documentation and/or other materials provided with the
     distribution.

         * Neither the name of the Danga Interactive nor the names of its
     contributors may be used to endorse or promote products derived from
     this software without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-nt-servc,  Next: license-openpam,  Prev: license-memcached,  Up: licenses-third-party

E.25 nt_servc (Windows NT Service class library) License
========================================================

The following software may be included in this product:

nt_servc (Windows NT Service class library)


     Windows NT Service class library
     Copyright Abandoned 1998 Irena Pancirov - Irnet Snc
     This file is public domain and comes with NO WARRANTY of any kind


File: manual.info,  Node: license-openpam,  Next: license-paramiko,  Prev: license-nt-servc,  Up: licenses-third-party

E.26 OpenPAM License
====================

The following software may be included in this product:

OpenPAM


     Copyright (c) 2002-2003 Networks Associates Technology, Inc.
     Copyright (c) 2004-2007 Dag-Erling Sm/orgrav
     All rights reserved.

     This software was developed for the FreeBSD Project by
     ThinkSec AS and Network Associates Laboratories, the
     Security Research Division of Network Associates, Inc.
     under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
     as part of the DARPA CHATS research program.

     Redistribution and use in source and binary forms,
     with or without modification, are permitted provided
     that the following conditions are met:

     1. Redistributions of source code must retain the above
        copyright notice, this list of conditions and the
        following disclaimer.
     2. Redistributions in binary form must reproduce the
        above copyright notice, this list of conditions and
        the following disclaimer in the documentation and/or
        other materials provided with the distribution.
     3. The name of the author may not be used to endorse or
        promote products derived from this software without
        specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
     BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
     AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
     NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
     ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
     IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-paramiko,  Next: license-pcre,  Prev: license-openpam,  Up: licenses-third-party

E.27 Paramiko License
=====================

The following software may be included in this product:


     Paramiko

     You are receiving a copy of Paramiko in both source and object code. The
     terms of the Oracle license do NOT apply to the Paramiko program; it is
     licensed under the following license, separately from the Oracle
     programs you receive. If you do not wish to install this program, you
     may delete the Paramiko folder and all its contents.

This component is licensed under *Note license-gnu-lgpl-2-1::.


File: manual.info,  Node: license-pcre,  Next: license-percona-io-threads-patch,  Prev: license-paramiko,  Up: licenses-third-party

E.28 PCRE License
=================

The following software may be included in this product:

PCRE (Perl Compatible Regular Expressions) Library


     PCRE LICENCE

     PCRE is a library of functions to support regular expressions
     whose syntax and semantics are as close as possible to those
     of the Perl 5 language.

     Release 7 of PCRE is distributed under the terms of the "BSD"
     licence, as specified below. The documentation for PCRE,
     supplied in the "doc" directory, is distributed under the same
     terms as the software itself.

     The basic library functions are written in C and are
     freestanding. Also included in the distribution is a set
     of C++ wrapper functions.

     THE BASIC LIBRARY FUNCTIONS
     ---------------------------
     Written by:       Philip Hazel
     Email local part: ph10
     Email domain:     cam.ac.uk

     University of Cambridge Computing Service,
     Cambridge, England. Phone: +44 1223 334714.

     Copyright (c) 1997-2006 University of Cambridge
     All rights reserved.

     THE C++ WRAPPER FUNCTIONS
     -------------------------
     Contributed by:   Google Inc.

     Copyright (c) 2006, Google Inc.
     All rights reserved.

     THE "BSD" LICENCE
     -----------------

     Redistribution and use in source and binary forms,
     with or without modification, are permitted provided
     that the following conditions are met:

     * Redistributions of source code must retain the above
       copyright notice, this list of conditions and the
       following disclaimer.
     * Redistributions in binary form must reproduce the
       above copyright notice, this list of conditions and
       the following disclaimer in the documentation and/or
       other materials provided with the distribution.
     * Neither the name of the University of Cambridge nor
       the name of Google Inc. nor the names of their contributors
       may be used to endorse or promote products derived from
       this software without specific prior written permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
     CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
     BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
     OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
     OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
     LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
     NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

     End


File: manual.info,  Node: license-percona-io-threads-patch,  Next: license-regex,  Prev: license-pcre,  Up: licenses-third-party

E.29 Percona Multiple I/O Threads Patch License
===============================================

The following software may be included in this product:

Percona Multiple I/O threads patch


     Copyright (c) 2008, 2009 Percona Inc
     All rights reserved.

     Redistribution and use of this software in source and binary forms,
     with or without modification, are permitted provided that the
     following conditions are met:

      * Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.
      * Redistributions in binary form must reproduce the above copyright
        notice, this list of conditions and the following disclaimer in the
        documentation and/or other materials provided with the distribution.
      * Neither the name of Percona Inc. nor the names of its contributors
        may be used to endorse or promote products derived from this software
        without specific prior written permission of Percona Inc.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
     COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
     BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
     ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     POSSIBILITY OF SUCH DAMAGE.


File: manual.info,  Node: license-regex,  Next: license-us-secure-hash,  Prev: license-percona-io-threads-patch,  Up: licenses-third-party

E.30 RegEX-Spencer Library License
==================================

The following software may be included in this product: Henry Spencer's
Regular-Expression Library (RegEX-Spencer)


     Copyright 1992, 1993, 1994 Henry Spencer.  All rights reserved.
     This software is not subject to any license of the American Telephone
     and Telegraph Company or of the Regents of the University of California.

     Permission is granted to anyone to use this software for any purpose on
     any computer system, and to alter it and redistribute it, subject
     to the following restrictions:

     1. The author is not responsible for the consequences of use of this
        software, no matter how awful, even if they arise from flaws in it.

     2. The origin of this software must not be misrepresented, either by
        explicit claim or by omission.  Since few users ever read sources,
        credits must appear in the documentation.

     3. Altered versions must be plainly marked as such, and must not be
        misrepresented as being the original software.  Since few users
        ever read sources, credits must appear in the documentation.

     4. This notice may not be removed or altered.


File: manual.info,  Node: license-us-secure-hash,  Next: license-libstring,  Prev: license-regex,  Up: licenses-third-party

E.31 RFC 3174 - US Secure Hash Algorithm 1 (SHA1) License
=========================================================

The following software may be included in this product:

RFC 3174 - US Secure Hash Algorithm 1 (SHA1)


     RFC 3174 - US Secure Hash Algorithm 1 (SHA1)

     Copyright (C) The Internet Society (2001).  All Rights Reserved.

     This document and translations of it may be copied and furnished to
     others, and derivative works that comment on or otherwise explain it
     or assist in its implementation may be prepared, copied, published
     and distributed, in whole or in part, without restriction of any
     kind, provided that the above copyright notice and this paragraph are
     included on all such copies and derivative works.  However, this
     document itself may not be modified in any way, such as by removing
     the copyright notice or references to the Internet Society or other
     Internet organizations, except as needed for the purpose of
     developing Internet standards in which case the procedures for
     copyrights defined in the Internet Standards process must be
     followed, or as required to translate it into languages other than
     English.

     The limited permissions granted above are perpetual and will not be
     revoked by the Internet Society or its successors or assigns.

     This document and the information contained herein is provided on an
     "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
     TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
     BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
     HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
     MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

     Acknowledgement
     Funding for the RFC Editor function is currently provided by the
     Internet Society.


File: manual.info,  Node: license-libstring,  Next: license-sha1-in-c,  Prev: license-us-secure-hash,  Up: licenses-third-party

E.32 Richard A. O'Keefe String Library License
==============================================

The following software may be included in this product:

Richard A. O'Keefe String Library


     The Richard O'Keefe String Library is subject to the following notice:

     These files are in the public domain.  This includes getopt.c, which
     is the work of Henry Spencer, University of Toronto Zoology, who
     says of it "None of this software is derived from Bell software. I
     had no access to the source for Bell's versions at the time I wrote
     it.  This software is hereby explicitly placed in the public domain.
     It may be used for any purpose on any machine by anyone." I would
     greatly prefer it if *my* material received no military use.

     The t_ctype.h file is subject to the following notice:

     Copyright (C) 1998, 1999 by Pruet Boonma, all rights reserved.
     Copyright (C) 1998 by Theppitak Karoonboonyanan, all rights reserved.

       Permission to use, copy, modify, distribute and sell this software and its
     documentation for any purpose is hereby granted without fee, provided that the above
     copyright notice appear in all copies.

       Smaphan Raruenrom and Pruet Boonma makes no representations about
     the suitability of this software for any purpose. It is provided
     "as is" without express or implied warranty.


File: manual.info,  Node: license-sha1-in-c,  Next: license-zlib,  Prev: license-libstring,  Up: licenses-third-party

E.33 SHA-1 in C License
=======================

The following software may be included in this product:

SHA-1 in C


     SHA-1 in C
     By Steve Reid <steve@edmweb.com>
     100% Public Domain


File: manual.info,  Node: license-zlib,  Prev: license-sha1-in-c,  Up: licenses-third-party

E.34 zlib License
=================

The following software may be included in this product:

zlib

Oracle gratefully acknowledges the contributions of Jean-loup Gailly
and Mark Adler in creating the zlib general purpose compression library
which is used in this product.


     zlib.h -- interface of the 'zlib' general purpose compression library
     Copyright (C) 1995-2004 Jean-loup Gailly and Mark Adler

     zlib.h -- interface of the 'zlib' general purpose compression library
     version 1.2.3, July 18th, 2005
     Copyright (C) 1995-2005 Jean-loup Gailly and Mark Adler

     zlib.h -- interface of the 'zlib' general purpose compression library
     version 1.2.5, April 19th, 2010
     Copyright (C) 1995-2010 Jean-loup Gailly and Mark Adler

     This software is provided 'as-is', without any express or implied warranty.
     In no event will the authors be held liable for any damages arising from the
     use of this software. Permission is granted to anyone to use this software
     for any purpose,including commercial applications, and to alter it and
     redistribute it freely, subject to the following restrictions:

     1. The origin of this software must not be misrepresented; you must not
        claim that you wrote the original software. If you use this software
        in a product, an acknowledgment in the product documentation would
        be appreciated but is not required.
     2. Altered source versions must be plainly marked as such, and must not
        be misrepresented as being the original software.
     3. This notice may not be removed or altered from any source distribution.

     Jean-loup Gailly jloup@gzip.org
     Mark Adler madler@alumni.caltech.edu

[index]
* Menu:

* ! (logical NOT):                       logical-operators.  (line   30)
* != (not equal):                        comparison-operators.
                                                             (line   94)
* ":                                     identifiers.        (line   20)
* #mysql50 identifier prefix <1>:        identifier-mapping. (line   97)
* #mysql50 identifier prefix:            identifiers.        (line  112)
* %:                                     arithmetic-functions.
                                                             (line  125)
* % (modulo):                            mathematical-functions.
                                                             (line  319)
* % (wildcard character):                string-literals.    (line   82)
* & (bitwise AND):                       bit-functions.      (line   30)
* && (logical AND):                      logical-operators.  (line   50)
* () (parentheses):                      operator-precedence.
                                                             (line   49)
* (Control+Z) \Z <1>:                    load-data.          (line  450)
* (Control+Z) \Z:                        string-literals.    (line   80)
* * (multiplication):                    arithmetic-functions.
                                                             (line   86)
* + (addition):                          arithmetic-functions.
                                                             (line   55)
* - (subtraction):                       arithmetic-functions.
                                                             (line   63)
* - (unary minus):                       arithmetic-functions.
                                                             (line   71)
* -? option (MySQL Cluster programs):    mysql-cluster-program-options-common.
                                                             (line  119)
* -c option (MySQL Cluster programs):    mysql-cluster-program-options-common.
                                                             (line  145)
* -c option (ndb_mgmd) (OBSOLETE):       mysql-cluster-programs-ndb-mgmd.
                                                             (line  271)
* -d option (ndb_index_stat):            mysql-cluster-programs-ndb-index-stat.
                                                             (line  202)
* -d option (ndb_mgmd):                  mysql-cluster-programs-ndb-mgmd.
                                                             (line  324)
* -disable option prefix:                option-modifiers.   (line    6)
* -e option (ndb_mgm):                   mysql-cluster-programs-ndb-mgm.
                                                             (line   57)
* -enable option prefix:                 option-modifiers.   (line    6)
* -f option (ndb_mgmd):                  mysql-cluster-programs-ndb-mgmd.
                                                             (line  271)
* -l option (ndbinfo_select_all):        mysql-cluster-programs-ndbinfo-select-all.
                                                             (line  120)
* -loose option prefix:                  option-modifiers.   (line    6)
* -maximum option prefix:                option-modifiers.   (line    6)
* -n option (ndbd):                      mysql-cluster-programs-ndbd.
                                                             (line  338)
* -n option (ndbmtd):                    mysql-cluster-programs-ndbd.
                                                             (line  338)
* -p option:                             password-security-user.
                                                             (line   17)
* -P option (ndb_mgmd):                  mysql-cluster-programs-ndb-mgmd.
                                                             (line  442)
* -password option:                      password-security-user.
                                                             (line   17)
* -skip option prefix:                   option-modifiers.   (line    6)
* -V option (MySQL Cluster programs):    mysql-cluster-program-options-common.
                                                             (line  253)
* .my.cnf file <1>:                      access-denied.      (line  106)
* .my.cnf file <2>:                      password-security-user.
                                                             (line   58)
* .my.cnf file <3>:                      multiple-server-clients.
                                                             (line   34)
* .my.cnf file <4>:                      option-files.       (line    6)
* .my.cnf file:                          connecting.         (line  234)
* .mysql_history file <1>:               password-security-user.
                                                             (line   93)
* .mysql_history file:                   mysql-logging.      (line    6)
* .pid (process ID) file:                myisam-maintenance-schedule.
                                                             (line   17)
* / (division):                          arithmetic-functions.
                                                             (line   96)
* /etc/passwd <1>:                       select-into.        (line   48)
* /etc/passwd:                           security-against-attack.
                                                             (line   86)
* := (assignment operator):              assignment-operators.
                                                             (line   15)
* := (assignment):                       user-variables.     (line    6)
* < (less than):                         comparison-operators.
                                                             (line  114)
* << (left shift) <1>:                   bit-functions.      (line   54)
* << (left shift):                       calculating-days.   (line    6)
* <= (less than or equal):               comparison-operators.
                                                             (line  106)
* <=> (equal to):                        comparison-operators.
                                                             (line   81)
* <> (not equal):                        comparison-operators.
                                                             (line   94)
* = (assignment operator):               assignment-operators.
                                                             (line   72)
* = (assignment):                        user-variables.     (line    6)
* = (equal):                             comparison-operators.
                                                             (line   65)
* > (greater than):                      comparison-operators.
                                                             (line  130)
* >= (greater than or equal):            comparison-operators.
                                                             (line  122)
* >> (right shift):                      bit-functions.      (line   67)
* [api] (MySQL Cluster):                 mysql-cluster-params-api.
                                                             (line    6)
* [computer] (MySQL Cluster):            mysql-cluster-params-other.
                                                             (line    6)
* [mgm] (MySQL Cluster):                 mysql-cluster-params-mgmd.
                                                             (line    6)
* [mysqld] (MySQL Cluster):              mysql-cluster-params-api.
                                                             (line    6)
* [ndb_mgmd] (MySQL Cluster):            mysql-cluster-params-mgmd.
                                                             (line    6)
* [ndbd default] (MySQL Cluster):        mysql-cluster-params-ndbd.
                                                             (line    6)
* [ndbd] (MySQL Cluster):                mysql-cluster-params-ndbd.
                                                             (line    6)
* [sci] (MySQL Cluster):                 mysql-cluster-params-other.
                                                             (line    6)
* [shm] (MySQL Cluster):                 mysql-cluster-params-other.
                                                             (line    6)
* [tcp] (MySQL Cluster):                 mysql-cluster-params-other.
                                                             (line    6)
* \" (double quote):                     string-literals.    (line   75)
* \' (single quote):                     string-literals.    (line   74)
* \. (mysql client command) <1>:         mysql-batch-commands.
                                                             (line    6)
* \. (mysql client command):             batch-mode.         (line   97)
* \0 (ASCII NUL) <1>:                    load-data.          (line  445)
* \0 (ASCII NUL):                        string-literals.    (line   73)
* \\ (escape):                           string-literals.    (line   81)
* \b (backspace) <1>:                    load-data.          (line  446)
* \b (backspace):                        string-literals.    (line   76)
* \n (linefeed) <1>:                     load-data.          (line  447)
* \n (linefeed):                         string-literals.    (line   77)
* \n (newline) <1>:                      load-data.          (line  447)
* \n (newline):                          string-literals.    (line   77)
* \N (NULL):                             load-data.          (line  451)
* \r (carriage return) <1>:              load-data.          (line  448)
* \r (carriage return):                  string-literals.    (line   78)
* \t (tab) <1>:                          load-data.          (line  449)
* \t (tab):                              string-literals.    (line   79)
* \Z (Control+Z) ASCII 26 <1>:           load-data.          (line  450)
* \Z (Control+Z) ASCII 26:               string-literals.    (line   80)
* ^ (bitwise XOR):                       bit-functions.      (line   40)
* _ (wildcard character):                string-literals.    (line   83)
* _rowid:                                create-table.       (line  489)
* `:                                     identifiers.        (line   20)
* abort-slave-event-count option, mysqld: replication-options-slave.
                                                             (line  141)
* aborted clients:                       communication-errors.
                                                             (line    6)
* aborted connection:                    communication-errors.
                                                             (line    6)
* ABS():                                 mathematical-functions.
                                                             (line   52)
* access control:                        connection-access.  (line    6)
* access denied errors:                  error-access-denied.
                                                             (line    6)
* access privileges:                     privilege-system.   (line   16)
* account names:                         account-names.      (line    6)
* accounts, adding privileges:           adding-users.       (line    6)
* accounts, anonymous user:              default-privileges. (line    6)
* accounts, root:                        default-privileges. (line    6)
* ACID <1>:                              innodb-introduction.
                                                             (line    6)
* ACID:                                  ansi-diff-transactions.
                                                             (line    6)
* ACLs:                                  privilege-system.   (line   16)
* ACOS():                                mathematical-functions.
                                                             (line   65)
* activating plugins:                    server-plugin-loading.
                                                             (line    6)
* ActiveState Perl:                      activestate-perl.   (line    6)
* adaptive hash index:                   innodb-adaptive-hash.
                                                             (line    6)
* add-drop-database option, mysqldump:   mysqldump.          (line  340)
* add-drop-table option, mysqldump:      mysqldump.          (line  349)
* add-drop-trigger option, mysqldump:    mysqldump.          (line  354)
* add-locks option, mysqldump:           mysqldump.          (line  366)
* add-user option, mysqlmanager:         instance-manager-command-options.
                                                             (line   27)
* ADDDATE():                             date-and-time-functions.
                                                             (line  149)
* adding, character sets:                adding-character-set.
                                                             (line   12)
* adding, native functions:              adding-native-function.
                                                             (line    6)
* adding, new account privileges:        adding-users.       (line    6)
* adding, new functions:                 adding-functions.   (line   12)
* adding, new user privileges:           adding-users.       (line    6)
* adding, new users:                     unix-postinstallation.
                                                             (line  386)
* adding, user-defined functions:        adding-udf.         (line   15)
* addition (+):                          arithmetic-functions.
                                                             (line   55)
* ADDTIME():                             date-and-time-functions.
                                                             (line  169)
* addtodest option, mysqlhotcopy:        mysqlhotcopy.       (line   90)
* administration of MySQL Cluster:       mysql-cluster-programs-ndb-mgm.
                                                             (line    6)
* administration, server:                mysqladmin.         (line    6)
* administrative programs:               programs-overview.  (line  165)
* AES_DECRYPT():                         encryption-functions.
                                                             (line   93)
* AES_ENCRYPT():                         encryption-functions.
                                                             (line   99)
* After create, thread state:            general-thread-states.
                                                             (line   11)
* age, calculating:                      date-calculations.  (line    6)
* alias names, case sensitivity:         identifier-case-sensitivity.
                                                             (line    6)
* aliases, for expressions:              group-by-extensions.
                                                             (line   87)
* aliases, for tables:                   select.             (line  172)
* aliases, in GROUP BY clauses:          group-by-extensions.
                                                             (line   87)
* aliases, names:                        identifiers.        (line   13)
* aliases, on expressions:               select.             (line  114)
* ALL <1>:                               all-subqueries.     (line    6)
* ALL:                                   select.             (line  374)
* ALL join type, optimizer:              explain-output.     (line  392)
* all-databases option, mysqlcheck:      mysqlcheck.         (line  203)
* all-databases option, mysqldump:       mysqldump.          (line  373)
* all-in-1 option, mysqlcheck:           mysqlcheck.         (line  209)
* all-tablespaces option, mysqldump:     mysqldump.          (line  379)
* allocating local table, thread state:  delayed-insert-thread-states.
                                                             (line   17)
* allow-keywords option, mysqldump:      mysqldump.          (line  389)
* allow-suspicious-udfs option, mysqld:  server-options.     (line   83)
* ALLOW_INVALID_DATES SQL mode:          sql-mode.           (line  124)
* allowold option, mysqlhotcopy:         mysqlhotcopy.       (line   95)
* ALTER COLUMN:                          alter-table.        (line  354)
* ALTER DATABASE:                        alter-database.     (line    6)
* ALTER EVENT:                           alter-event.        (line    6)
* ALTER EVENT, and replication:          replication-features-invoked.
                                                             (line   49)
* ALTER FUNCTION:                        alter-function.     (line    6)
* ALTER LOGFILE GROUP:                   alter-logfile-group.
                                                             (line    6)
* ALTER PROCEDURE:                       alter-procedure.    (line    6)
* ALTER SCHEMA:                          alter-database.     (line    6)
* ALTER SERVER:                          alter-server.       (line    6)
* ALTER TABLE <1>:                       alter-table-problems.
                                                             (line    6)
* ALTER TABLE:                           alter-table.        (line   12)
* ALTER TABLESPACE:                      alter-tablespace.   (line    6)
* ALTER VIEW:                            alter-view.         (line    6)
* altering, database:                    alter-database.     (line    6)
* altering, schema:                      alter-database.     (line    6)
* ANALYSE(), PROCEDURE:                  procedure-analyse.  (line    8)
* analyze option, myisamchk:             myisamchk-other-options.
                                                             (line    9)
* analyze option, mysqlcheck:            mysqlcheck.         (line  215)
* ANALYZE TABLE:                         analyze-table.      (line    6)
* ANALYZE TABLE, and partitioning:       partitioning-maintenance.
                                                             (line    6)
* Analyzing, thread state:               general-thread-states.
                                                             (line   18)
* AND, bitwise:                          bit-functions.      (line   30)
* AND, logical:                          logical-operators.  (line   50)
* angel-pid-file option, mysqlmanager:   instance-manager-command-options.
                                                             (line   32)
* anonymous user <1>:                    request-access.     (line   26)
* anonymous user <2>:                    connection-access.  (line   25)
* anonymous user:                        default-privileges. (line    6)
* ANSI mode, running:                    compatibility.      (line   71)
* ansi option, mysqld:                   server-options.     (line  101)
* ANSI SQL mode:                         sql-mode.           (line   87)
* ANSI_QUOTES SQL mode:                  sql-mode.           (line  142)
* answering questions, etiquette:        mailing-list-use.   (line    6)
* ANY:                                   any-in-some-subqueries.
                                                             (line    6)
* Apache:                                apache.             (line    6)
* API node (MySQL Cluster), defined:     mysql-cluster-basics.
                                                             (line    6)
* API nodes:                             mysql-cluster-mysqld.
                                                             (line    6)
* APIs:                                  connectors-apis.    (line   23)
* APIs, list of:                         packages.           (line    6)
* APIs, Perl:                            apis-perl.          (line    6)
* append option (ndb_restore):           mysql-cluster-programs-ndb-restore.
                                                             (line  757)
* apply_status table (OBSOLETE):         mysql-cluster-replication-schema.
                                                             (line  135)
* approximate-value literals <1>:        precision-math.     (line   14)
* approximate-value literals:            number-literals.    (line    6)
* Arbitration:                           mysql-cluster-ndbd-definition.
                                                             (line 2816)
* ArbitrationDelay <1>:                  mysql-cluster-api-definition.
                                                             (line  172)
* ArbitrationDelay:                      mysql-cluster-mgm-definition.
                                                             (line  237)
* ArbitrationRank <1>:                   mysql-cluster-api-definition.
                                                             (line  144)
* ArbitrationRank:                       mysql-cluster-mgm-definition.
                                                             (line  199)
* ArbitrationTimeout:                    mysql-cluster-ndbd-definition.
                                                             (line 2792)
* arbitrator:                            faqs-mysql-cluster. (line    6)
* arbitrator_validity_detail, ndbinfo table: mysql-cluster-ndbinfo-arbitrator-validity-detail.
                                                             (line    6)
* arbitrator_validity_summary, ndbinfo table: mysql-cluster-ndbinfo-arbitrator-validity-summary.
                                                             (line    6)
* ARCHIVE storage engine <1>:            archive-storage-engine.
                                                             (line    6)
* ARCHIVE storage engine:                storage-engines.    (line   23)
* Area() <1>:                            gis-multipolygon-property-functions.
                                                             (line    8)
* Area():                                gis-polygon-property-functions.
                                                             (line    8)
* argument processing:                   udf-arguments.      (line    6)
* arithmetic expressions:                arithmetic-functions.
                                                             (line   55)
* arithmetic functions:                  bit-functions.      (line    6)
* AS <1>:                                join.               (line    6)
* AS:                                    select.             (line  145)
* AS/400:                                i5os-installation.  (line    6)
* AsBinary():                            gis-format-conversion-functions.
                                                             (line    9)
* ASCII():                               string-functions.   (line  106)
* ASIN():                                mathematical-functions.
                                                             (line   78)
* assignment operator, :=:               assignment-operators.
                                                             (line   15)
* assignment operator, =:                assignment-operators.
                                                             (line   72)
* assignment operators:                  assignment-operators.
                                                             (line    6)
* AsText():                              gis-format-conversion-functions.
                                                             (line   17)
* asynchronous replication:              mysql-cluster-replication.
                                                             (line   20)
* ATAN():                                mathematical-functions.
                                                             (line  102)
* ATAN2():                               mathematical-functions.
                                                             (line  113)
* attackers, security against:           security-against-attack.
                                                             (line    6)
* attribute demotion, replication:       replication-features-different-data-types.
                                                             (line    6)
* attribute promotion, ndb_restore:      mysql-cluster-programs-ndb-restore.
                                                             (line  434)
* attribute promotion, replication:      replication-features-different-data-types.
                                                             (line    6)
* auto-generate-sql option, mysqlslap:   mysqlslap.          (line  209)
* auto-generate-sql-add-autoincrement option, mysqlslap: mysqlslap.
                                                             (line  214)
* auto-generate-sql-execute-number option, mysqlslap: mysqlslap.
                                                             (line  219)
* auto-generate-sql-guid-primary option, mysqlslap: mysqlslap.
                                                             (line  224)
* auto-generate-sql-load-type option, mysqlslap: mysqlslap.  (line  229)
* auto-generate-sql-secondary-indexes option, mysqlslap: mysqlslap.
                                                             (line  237)
* auto-generate-sql-unique-query-number option, mysqlslap: mysqlslap.
                                                             (line  243)
* auto-generate-sql-unique-write-number option, mysqlslap: mysqlslap.
                                                             (line  251)
* auto-generate-sql-write-number option, mysqlslap: mysqlslap.
                                                             (line  257)
* auto-rehash option, mysql:             mysql-command-options.
                                                             (line  152)
* auto-repair option, mysqlcheck:        mysqlcheck.         (line  219)
* AUTO_INCREMENT <1>:                    numeric-types.      (line   15)
* AUTO_INCREMENT:                        example-auto-increment.
                                                             (line    6)
* AUTO_INCREMENT, and NULL values:       problems-with-null. (line   76)
* AUTO_INCREMENT, and replication:       replication-features-auto-increment.
                                                             (line    6)
* auto_increment_increment system variable: replication-options-master.
                                                             (line   26)
* auto_increment_offset system variable: replication-options-master.
                                                             (line  229)
* autoclose option, mysqld_safe:         mysqld-safe.        (line  103)
* autocommit system variable:            server-system-variables.
                                                             (line  599)
* automatic_sp_privileges system variable: server-system-variables.
                                                             (line  639)
* AutoReconnect, API and SQL nodes:      mysql-cluster-api-definition.
                                                             (line  311)
* AVG():                                 group-by-functions. (line   60)
* AVG(DISTINCT):                         group-by-functions. (line   60)
* B-tree indexes:                        innodb-physical-structure.
                                                             (line    6)
* back_log system variable:              server-system-variables.
                                                             (line  667)
* backslash, escape character:           string-literals.    (line    6)
* backspace (\b) <1>:                    load-data.          (line  446)
* backspace (\b):                        string-literals.    (line   76)
* BACKUP Events (MySQL Cluster):         mysql-cluster-log-events.
                                                             (line  297)
* backup identifiers, native backup and restore: mysql-cluster-backup-using-management-client.
                                                             (line  110)
* backup option, myisamchk:              myisamchk-repair-options.
                                                             (line   10)
* backup option, myisampack:             myisampack.         (line   55)
* BACKUP TABLE:                          backup-table.       (line    6)
* backup_path option (ndb_restore):      mysql-cluster-programs-ndb-restore.
                                                             (line  579)
* BackupDataBufferSize <1>:              mysql-cluster-backup-configuration.
                                                             (line    8)
* BackupDataBufferSize:                  mysql-cluster-ndbd-definition.
                                                             (line 3288)
* BackupDataDir:                         mysql-cluster-ndbd-definition.
                                                             (line  312)
* backupid option (ndb_restore):         mysql-cluster-programs-ndb-restore.
                                                             (line  534)
* BackupLogBufferSize <1>:               mysql-cluster-backup-configuration.
                                                             (line   13)
* BackupLogBufferSize:                   mysql-cluster-ndbd-definition.
                                                             (line 3320)
* BackupMaxWriteSize <1>:                mysql-cluster-backup-configuration.
                                                             (line   29)
* BackupMaxWriteSize:                    mysql-cluster-ndbd-definition.
                                                             (line 3439)
* BackupMemory <1>:                      mysql-cluster-backup-configuration.
                                                             (line   18)
* BackupMemory:                          mysql-cluster-ndbd-definition.
                                                             (line 3363)
* BackupReportFrequency:                 mysql-cluster-ndbd-definition.
                                                             (line 3391)
* backups <1>:                           mysql-enterprise-backup.
                                                             (line    6)
* backups:                               backup-and-recovery.
                                                             (line   15)
* backups, database:                     backup-table.       (line    6)
* backups, databases and tables <1>:     mysqlhotcopy.       (line    6)
* backups, databases and tables:         mysqldump.          (line    6)
* backups, in MySQL Cluster <1>:         mysql-cluster-backup-configuration.
                                                             (line    6)
* backups, in MySQL Cluster <2>:         mysql-cluster-backup-using-management-client.
                                                             (line    6)
* backups, in MySQL Cluster <3>:         mysql-cluster-backup-concepts.
                                                             (line    6)
* backups, in MySQL Cluster <4>:         mysql-cluster-backup.
                                                             (line   13)
* backups, in MySQL Cluster:             mysql-cluster-programs-ndb-restore.
                                                             (line    6)
* backups, in MySQL Cluster replication: mysql-cluster-replication-backups.
                                                             (line   11)
* backups, InnoDB:                       innodb-backup.      (line   11)
* backups, troubleshooting, in MySQL Cluster: mysql-cluster-backup-troubleshooting.
                                                             (line    6)
* backups, with mysqldump:               using-mysqldump.    (line   14)
* BackupWriteSize <1>:                   mysql-cluster-backup-configuration.
                                                             (line   24)
* BackupWriteSize:                       mysql-cluster-ndbd-definition.
                                                             (line 3416)
* base64-output option, mysqlbinlog:     mysqlbinlog.        (line  187)
* basedir option, mysql.server:          mysql-server.       (line   36)
* basedir option, mysql_install_db:      mysql-install-db.   (line   63)
* basedir option, mysql_upgrade:         mysql-upgrade.      (line  139)
* basedir option, mysqld:                server-options.     (line  113)
* basedir option, mysqld_safe:           mysqld-safe.        (line  116)
* basedir system variable:               server-system-variables.
                                                             (line  699)
* batch mode:                            batch-mode.         (line    6)
* batch option, mysql:                   mysql-command-options.
                                                             (line  172)
* batch SQL files:                       mysql.              (line   15)
* BatchByteSize:                         mysql-cluster-api-definition.
                                                             (line  190)
* batched updates (MySQL Cluster Replication): mysql-cluster-replication-starting.
                                                             (line   77)
* BatchSize:                             mysql-cluster-api-definition.
                                                             (line  214)
* BatchSizePerLocalScan:                 mysql-cluster-ndbd-definition.
                                                             (line 1003)
* Bazaar tree:                           installing-development-tree.
                                                             (line    6)
* BEGIN <1>:                             begin-end.          (line    6)
* BEGIN:                                 commit.             (line    6)
* BEGIN, labels:                         statement-labels.   (line    6)
* BEGIN, XA transactions:                xa-statements.      (line    6)
* BENCHMARK():                           information-functions.
                                                             (line   33)
* benchmarks <1>:                        custom-benchmarks.  (line    6)
* benchmarks:                            mysql-benchmarks.   (line    6)
* BETWEEN ... AND:                       comparison-operators.
                                                             (line  210)
* big-tables option, mysqld:             server-options.     (line  132)
* big5:                                  faqs-cjk.           (line    6)
* big_tables system variable:            server-system-variables.
                                                             (line  719)
* BIGINT data type:                      numeric-type-overview.
                                                             (line  127)
* BIN():                                 string-functions.   (line  122)
* BINARY:                                cast-functions.     (line   13)
* BINARY data type <1>:                  binary-varbinary.   (line    6)
* BINARY data type:                      string-type-overview.
                                                             (line  154)
* binary distributions, installing:      binary-installation.
                                                             (line    6)
* binary log:                            binary-log.         (line   13)
* binary log, event groups:              set-global-sql-slave-skip-counter.
                                                             (line    6)
* binary logging, and MySQL Cluster:     mysql-cluster-limitations-exclusive-to-cluster.
                                                             (line   22)
* bind-address option (ndb_mgmd):        mysql-cluster-programs-ndb-mgmd.
                                                             (line  137)
* bind-address option, mysql:            mysql-command-options.
                                                             (line  182)
* bind-address option, mysqladmin:       mysqladmin.         (line  304)
* bind-address option, mysqlbinlog:      mysqlbinlog.        (line  235)
* bind-address option, mysqlcheck:       mysqlcheck.         (line  224)
* bind-address option, mysqld:           server-options.     (line  154)
* bind-address option, mysqldump:        mysqldump.          (line  394)
* bind-address option, mysqlimport:      mysqlimport.        (line  131)
* bind-address option, mysqlmanager:     instance-manager-command-options.
                                                             (line   46)
* bind-address option, mysqlshow:        mysqlshow.          (line  116)
* BINLOG:                                binlog.             (line    6)
* Binlog Dump, thread command:           thread-commands.    (line    8)
* BINLOG statement, mysqlbinlog output:  mysqlbinlog-row-events.
                                                             (line    6)
* binlog-do-db option, mysqld:           replication-options-binary-log.
                                                             (line  187)
* binlog-format option, mysqld:          server-options.     (line  198)
* binlog-ignore-db option, mysqld:       replication-options-binary-log.
                                                             (line  315)
* binlog-row-event-max-size option, mysqld: replication-options-binary-log.
                                                             (line   24)
* binlog_cache_size system variable:     replication-options-binary-log.
                                                             (line  430)
* binlog_direct_non_transactional_updates system variable: replication-options-binary-log.
                                                             (line  458)
* binlog_format system variable:         replication-options-binary-log.
                                                             (line  511)
* binlog_format, BLACKHOLE:              replication-features-blackhole.
                                                             (line    6)
* binlog_index table (OBSOLETE):         mysql-cluster-replication-schema.
                                                             (line    6)
* BIT data type:                         numeric-type-overview.
                                                             (line   35)
* bit functions:                         bit-functions.      (line    6)
* bit functions, example:                calculating-days.   (line    6)
* BIT_AND():                             group-by-functions. (line   72)
* BIT_COUNT:                             calculating-days.   (line    6)
* BIT_COUNT():                           bit-functions.      (line   90)
* BIT_LENGTH():                          string-functions.   (line  132)
* BIT_OR:                                calculating-days.   (line    6)
* BIT_OR():                              group-by-functions. (line   81)
* BIT_XOR():                             group-by-functions. (line   88)
* BLACKHOLE storage engine <1>:          blackhole-storage-engine.
                                                             (line    6)
* BLACKHOLE storage engine:              storage-engines.    (line   23)
* BLACKHOLE, binlog_format:              replication-features-blackhole.
                                                             (line    6)
* BLACKHOLE, replication:                replication-features-blackhole.
                                                             (line    6)
* BLOB columns, default values:          blob.               (line   52)
* BLOB columns, indexing <1>:            create-table.       (line  542)
* BLOB columns, indexing:                column-indexes.     (line   15)
* BLOB data type <1>:                    blob.               (line    6)
* BLOB data type:                        string-type-overview.
                                                             (line  183)
* BLOB, inserting binary data:           string-literals.    (line  147)
* BLOB, size:                            storage-requirements.
                                                             (line  199)
* blob-info option, ndb_desc:            mysql-cluster-programs-ndb-desc.
                                                             (line  319)
* Block Nested-Loop join algorithm:      nested-loop-joins.  (line    6)
* block-search option, myisamchk:        myisamchk-other-options.
                                                             (line   18)
* blocks, ndbinfo table:                 mysql-cluster-ndbinfo-blocks.
                                                             (line    6)
* BOOL data type:                        numeric-type-overview.
                                                             (line   45)
* BOOLEAN data type:                     numeric-type-overview.
                                                             (line   45)
* boolean options:                       option-modifiers.   (line    6)
* bootstrap option, mysqld:              server-options.     (line  274)
* Boundary():                            gis-general-property-functions.
                                                             (line   83)
* brackets, square:                      data-types.         (line   41)
* brief option, mysqlaccess:             mysqlaccess.        (line   67)
* buffer pool:                           innodb-buffer-pool. (line    6)
* buffer sizes:                          innodb-buffer-pool. (line    6)
* buffer sizes, client:                  connectors-apis.    (line   23)
* buffer sizes, mysqld server:           server-parameters.  (line    6)
* Buffer():                              spatial-operator-functions.
                                                             (line   11)
* bugs database:                         bug-reports.        (line    6)
* bugs, known:                           bugs.               (line    6)
* bugs, MySQL Cluster, reporting:        mysql-cluster-programs-ndb-error-reporter.
                                                             (line    6)
* bugs, reporting <1>:                   bug-reports.        (line    6)
* bugs, reporting:                       introduction.       (line   78)
* bugs.mysql.com:                        bug-reports.        (line    6)
* builddir option, mysql_install_db:     mysql-install-db.   (line   67)
* BuildIndexThreads:                     mysql-cluster-ndbd-definition.
                                                             (line 3609)
* building, client programs:             c-api-building-clients.
                                                             (line    6)
* bulk_insert_buffer_size system variable: server-system-variables.
                                                             (line  734)
* C API:                                 connectors-apis.    (line   23)
* C API, data types:                     c-api.              (line   28)
* C API, example programs:               c-api-example-programs.
                                                             (line    6)
* C API, functions:                      c-api-function-overview.
                                                             (line    6)
* C API, linking problems:               c-api-building-clients.
                                                             (line   83)
* C prepared statement API, functions <1>: c-api-prepared-statement-function-overview.
                                                             (line    6)
* C prepared statement API, functions:   c-api-prepared-statement-type-conversions.
                                                             (line    6)
* C prepared statement API, type codes:  c-api-prepared-statement-type-codes.
                                                             (line    6)
* C++:                                   connector-cpp-info. (line    6)
* C++ compiler cannot create executables: compilation-problems.
                                                             (line   65)
* C++ compiler, gcc:                     source-configuration-options.
                                                             (line  404)
* C:\my.cnf file:                        multiple-server-clients.
                                                             (line   34)
* CACHE INDEX:                           cache-index.        (line    6)
* CACHE INDEX, and partitioning:         partitioning-limitations.
                                                             (line  419)
* caches, clearing:                      flush.              (line    6)
* calculating, aggregate value for a set of rows: group-by-functions.
                                                             (line    6)
* calculating, cardinality:              show-index.         (line   43)
* calculating, dates:                    date-calculations.  (line    6)
* calendar:                              mysql-calendar.     (line    6)
* CALL:                                  call.               (line    6)
* calling sequences for aggregate functions, UDF: udf-aggr-calling.
                                                             (line    6)
* calling sequences for simple functions, UDF: udf-calling.  (line    6)
* can't create/write to file:            cannot-create.      (line    6)
* cardinality:                           how-to-avoid-table-scan.
                                                             (line    6)
* carriage return (\r) <1>:              load-data.          (line  448)
* carriage return (\r):                  string-literals.    (line   78)
* CASE <1>:                              case.               (line    6)
* CASE:                                  control-flow-functions.
                                                             (line   14)
* case sensitivity, in access checking:  grant-table-structure.
                                                             (line  257)
* case sensitivity, in identifiers:      identifier-case-sensitivity.
                                                             (line    6)
* case sensitivity, in names:            identifier-case-sensitivity.
                                                             (line    6)
* case sensitivity, in searches:         case-sensitivity.   (line    6)
* case sensitivity, in string comparisons: string-comparison-functions.
                                                             (line   17)
* case sensitivity, of database names:   extensions-to-ansi. (line   41)
* case sensitivity, of replication filtering options: replication-rules.
                                                             (line   58)
* case sensitivity, of table names:      extensions-to-ansi. (line   41)
* CAST:                                  cast-functions.     (line   40)
* cast functions:                        cast-functions.     (line    6)
* cast operators:                        cast-functions.     (line    6)
* casts <1>:                             cast-functions.     (line    6)
* casts <2>:                             comparison-operators.
                                                             (line   38)
* casts:                                 type-conversion.    (line    6)
* CC environment variable <1>:           environment-variables.
                                                             (line   18)
* CC environment variable <2>:           compilation-problems.
                                                             (line   93)
* CC environment variable:               source-configuration-options.
                                                             (line  404)
* cc1plus problems:                      compilation-problems.
                                                             (line   38)
* CEIL():                                mathematical-functions.
                                                             (line  126)
* CEILING():                             mathematical-functions.
                                                             (line  130)
* Centroid():                            gis-multipolygon-property-functions.
                                                             (line   13)
* CFLAGS environment variable <1>:       environment-variables.
                                                             (line   18)
* CFLAGS environment variable:           compilation-problems.
                                                             (line   93)
* cflags option, mysql_config:           mysql-config.       (line   13)
* CHANGE MASTER TO:                      change-master-to.   (line    6)
* CHANGE MASTER TO, in MySQL Cluster:    mysql-cluster-replication-preparation.
                                                             (line   39)
* Change user, thread command:           thread-commands.    (line   13)
* ChangeLog:                             news.               (line    6)
* changes to privileges:                 privilege-changes.  (line    6)
* changes, release notes:                news.               (line    6)
* Changing master, thread state:         slave-connection-thread-states.
                                                             (line    9)
* changing socket location:              source-configuration-options.
                                                             (line  382)
* changing, column:                      alter-table.        (line  354)
* changing, field:                       alter-table.        (line  354)
* changing, socket location <1>:         problems-with-mysql-sock.
                                                             (line   27)
* changing, socket location:             automatic-start.    (line  140)
* changing, table <1>:                   alter-table-problems.
                                                             (line    6)
* changing, table:                       alter-table.        (line   12)
* CHAR data type <1>:                    string-types.       (line   14)
* CHAR data type:                        string-type-overview.
                                                             (line   92)
* CHAR VARYING data type:                string-type-overview.
                                                             (line  124)
* CHAR():                                string-functions.   (line  140)
* CHAR_LENGTH():                         string-functions.   (line  185)
* CHARACTER data type:                   string-type-overview.
                                                             (line   92)
* character sets <1>:                    charset.            (line   22)
* character sets:                        source-configuration-options.
                                                             (line  444)
* character sets, adding:                adding-character-set.
                                                             (line   12)
* character sets, and MySQL Cluster (replication): mysql-cluster-replication-issues.
                                                             (line   67)
* character sets, and replication:       replication-features-charset.
                                                             (line    6)
* character sets, repertoire:            charset-repertoire. (line    6)
* character sets, restrictions:          charset-restrictions.
                                                             (line    6)
* CHARACTER VARYING data type:           string-type-overview.
                                                             (line  124)
* character-set-client-handshake option, mysqld: server-options.
                                                             (line  307)
* character-set-filesystem option, mysqld: server-options.   (line  323)
* character-set-server option, mysqld:   server-options.     (line  344)
* character-sets-dir option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  131)
* character-sets-dir option, myisamchk:  myisamchk-repair-options.
                                                             (line   14)
* character-sets-dir option, myisampack: myisampack.         (line   60)
* character-sets-dir option, mysql:      mysql-command-options.
                                                             (line  193)
* character-sets-dir option, mysql_upgrade: mysql-upgrade.   (line  144)
* character-sets-dir option, mysqladmin: mysqladmin.         (line  315)
* character-sets-dir option, mysqlbinlog: mysqlbinlog.       (line  246)
* character-sets-dir option, mysqlcheck: mysqlcheck.         (line  235)
* character-sets-dir option, mysqld:     server-options.     (line  289)
* character-sets-dir option, mysqldump:  mysqldump.          (line  405)
* character-sets-dir option, mysqlimport: mysqlimport.       (line  142)
* character-sets-dir option, mysqlshow:  mysqlshow.          (line  127)
* CHARACTER_LENGTH():                    string-functions.   (line  192)
* character_set_client system variable:  server-system-variables.
                                                             (line  760)
* character_set_connection system variable: server-system-variables.
                                                             (line  799)
* character_set_database system variable: server-system-variables.
                                                             (line  816)
* character_set_filesystem system variable: server-system-variables.
                                                             (line  856)
* character_set_results system variable: server-system-variables.
                                                             (line  886)
* character_set_server system variable:  server-system-variables.
                                                             (line  902)
* character_set_system system variable:  server-system-variables.
                                                             (line  920)
* CHARACTER_SETS, INFORMATION_SCHEMA table: character-sets-table.
                                                             (line    6)
* character_sets_dir system variable:    server-system-variables.
                                                             (line  936)
* characters, multibyte:                 multibyte-characters.
                                                             (line    6)
* charset command, mysql:                mysql-commands.     (line   62)
* charset option, comp_err:              comp-err.           (line   30)
* CHARSET():                             information-functions.
                                                             (line   80)
* check option, myisamchk:               myisamchk-check-options.
                                                             (line    9)
* check option, mysqlcheck:              mysqlcheck.         (line  240)
* check options, myisamchk:              myisamchk-check-options.
                                                             (line    6)
* CHECK TABLE:                           check-table.        (line    6)
* CHECK TABLE, and partitioning:         partitioning-maintenance.
                                                             (line    6)
* check-only-changed option, myisamchk:  myisamchk-check-options.
                                                             (line   14)
* check-only-changed option, mysqlcheck: mysqlcheck.         (line  244)
* check-orphans option, ndb_blob_tool:   mysql-cluster-programs-ndb-blob-tool.
                                                             (line   84)
* check-password-file option, mysqlmanager: instance-manager-command-options.
                                                             (line   50)
* check-upgrade option, mysqlcheck:      mysqlcheck.         (line  249)
* Checking master version, thread state: slave-io-thread-states.
                                                             (line   20)
* checking permissions, thread state:    general-thread-states.
                                                             (line   23)
* checking privileges on cached query, thread state: query-cache-thread-states.
                                                             (line    9)
* checking query cache for query, thread state: query-cache-thread-states.
                                                             (line   14)
* Checking table, thread state:          general-thread-states.
                                                             (line   28)
* checking, tables for errors:           myisam-check.       (line    6)
* CHECKPOINT Events (MySQL Cluster):     mysql-cluster-log-events.
                                                             (line   42)
* checkpoint option, mysqlhotcopy:       mysqlhotcopy.       (line  100)
* Checksum:                              mysql-cluster-tcp-definition.
                                                             (line  173)
* Checksum (MySQL Cluster) <1>:          mysql-cluster-sci-definition.
                                                             (line  201)
* Checksum (MySQL Cluster):              mysql-cluster-shm-definition.
                                                             (line  156)
* checksum errors:                       solaris-installation.
                                                             (line   11)
* CHECKSUM TABLE:                        checksum-table.     (line    6)
* Chinese, Japanese, Korean character sets, frequently asked questions: faqs-cjk.
                                                             (line    6)
* choosing, a MySQL version:             which-version.      (line   18)
* choosing, data types:                  choosing-types.     (line    6)
* chroot option, mysqld:                 server-options.     (line  365)
* chroot option, mysqlhotcopy:           mysqlhotcopy.       (line  105)
* circular replication, in MySQL Cluster <1>: mysql-cluster-replication-conflict-resolution.
                                                             (line    6)
* circular replication, in MySQL Cluster <2>: mysql-cluster-replication-multi-master.
                                                             (line    6)
* circular replication, in MySQL Cluster: mysql-cluster-replication-issues.
                                                             (line   74)
* CJK (Chinese, Japanese, Korean), Access, PHP, etc.: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), availability of specific characters: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), big5: faqs-cjk.           (line    6)
* CJK (Chinese, Japanese, Korean), character sets available: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), characters displayed as question marks: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), CJKV: faqs-cjk.           (line    6)
* CJK (Chinese, Japanese, Korean), collations: faqs-cjk.     (line    6)
* CJK (Chinese, Japanese, Korean), conversion problems with Japanese character sets: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), data truncation: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), Database and table names: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), documentation in Chinese: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), documentation in Japanese: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), documentation in Korean: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), FAQ:  faqs-cjk.           (line    6)
* CJK (Chinese, Japanese, Korean), gb2312, gbk: faqs-cjk.    (line    6)
* CJK (Chinese, Japanese, Korean), Japanese character sets: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), Korean character set: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), LIKE and FULLTEXT: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), MySQL 4.0 behavior: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), ORDER BY treatment: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with Access, PHP, etc.: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with Big5 character sets (Chinese): faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with data truncation: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with euckr character set (Korean): faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with GB character sets (Chinese): faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with LIKE and FULLTEXT: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), problems with Yen sign (Japanese): faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), rejected characters: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), sort order problems: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), sorting problems: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), testing availability of characters: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), Unicode collations: faqs-cjk.
                                                             (line    6)
* CJK (Chinese, Japanese, Korean), Vietnamese: faqs-cjk.     (line    6)
* CJK (Chinese, Japanese, Korean), Yen sign: faqs-cjk.       (line    6)
* clean-password-file option, mysqlmanager: instance-manager-command-options.
                                                             (line   55)
* cleaning up, thread state:             general-thread-states.
                                                             (line   32)
* clear command, mysql:                  mysql-commands.     (line   71)
* clearing, caches:                      flush.              (line    6)
* Clearing, thread state:                event-scheduler-thread-states.
                                                             (line   10)
* client connection threads:             connection-threads. (line    6)
* client programs:                       programs-overview.  (line  124)
* client programs, building:             c-api-building-clients.
                                                             (line    6)
* client tools:                          connectors-apis.    (line   23)
* clients, debugging:                    debugging-client.   (line    6)
* clients, threaded:                     c-api-threaded-clients.
                                                             (line    6)
* CLOSE:                                 close.              (line    6)
* Close stmt, thread command:            thread-commands.    (line   17)
* closing tables, thread state:          general-thread-states.
                                                             (line   37)
* closing, tables:                       table-cache.        (line    6)
* cluster database (OBSOLETE):           mysql-cluster-replication-schema.
                                                             (line    6)
* cluster logs <1>:                      mysql-cluster-logging-management-commands.
                                                             (line    6)
* cluster logs:                          mysql-cluster-event-reports.
                                                             (line   12)
* cluster.binlog_index table (OBSOLETE): mysql-cluster-replication-schema.
                                                             (line    6)
* cluster_operations, ndbinfo table:     mysql-cluster-ndbinfo-cluster-operations.
                                                             (line    6)
* cluster_replication database (OBSOLETE): mysql-cluster-replication-schema.
                                                             (line    6)
* cluster_transactions, ndbinfo table:   mysql-cluster-ndbinfo-cluster-transactions.
                                                             (line    6)
* clustered index, InnoDB:               innodb-index-types. (line    6)
* Clustering:                            mysql-cluster.      (line   16)
* CLUSTERLOG commands (MySQL Cluster):   mysql-cluster-logging-management-commands.
                                                             (line   12)
* CLUSTERLOG STATISTICS command (MySQL Cluster): mysql-cluster-log-statistics.
                                                             (line    6)
* CMake:                                 windows-source-build.
                                                             (line    6)
* COALESCE():                            comparison-operators.
                                                             (line  243)
* COERCIBILITY():                        information-functions.
                                                             (line   92)
* collating, strings:                    string-collating.   (line    6)
* COLLATION():                           information-functions.
                                                             (line  122)
* collation, adding:                     adding-collation.   (line   13)
* collation, INFORMATION_SCHEMA:         charset-collation-information-schema.
                                                             (line    6)
* collation, modifying:                  adding-collation.   (line   59)
* collation, names:                      charset-collation-names.
                                                             (line    6)
* collation-server option, mysqld:       server-options.     (line  384)
* COLLATION_CHARACTER_SET_APPLICABILITY, INFORMATION_SCHEMA table: collation-character-set-applicability-table.
                                                             (line    6)
* collation_connection system variable:  server-system-variables.
                                                             (line  953)
* collation_database system variable:    server-system-variables.
                                                             (line  968)
* collation_server system variable:      server-system-variables.
                                                             (line 1008)
* COLLATIONS, INFORMATION_SCHEMA table:  collations-table.   (line    6)
* column alias, problems:                problems-with-alias.
                                                             (line    6)
* column alias, quoting <1>:             problems-with-alias.
                                                             (line    6)
* column alias, quoting:                 identifiers.        (line   84)
* column comments:                       create-table.       (line  395)
* column format:                         create-table.       (line  400)
* column names, case sensitivity:        identifier-case-sensitivity.
                                                             (line    6)
* column storage:                        create-table.       (line  420)
* column, changing:                      alter-table.        (line  354)
* column, types:                         data-types.         (line   29)
* column-names option, mysql:            mysql-command-options.
                                                             (line  198)
* column-type-info option, mysql:        mysql-command-options.
                                                             (line  202)
* COLUMN_PRIVILEGES, INFORMATION_SCHEMA table: column-privileges-table.
                                                             (line    6)
* columns option, mysqlimport:           mysqlimport.        (line  147)
* columns per table, maximum:            column-count-limit. (line    6)
* columns, displaying:                   mysqlshow.          (line    6)
* columns, indexes:                      column-indexes.     (line    6)
* COLUMNS, INFORMATION_SCHEMA table:     columns-table.      (line    6)
* columns, names:                        identifiers.        (line   13)
* columns, other types:                  other-vendor-data-types.
                                                             (line    6)
* columns, selecting:                    selecting-columns.  (line    6)
* columns, storage requirements:         storage-requirements.
                                                             (line    6)
* comma-separated values data, reading <1>: select-into.     (line  118)
* comma-separated values data, reading:  load-data.          (line  336)
* command options (MySQL Cluster), mysqld: mysql-cluster-program-options-mysqld.
                                                             (line    6)
* command options (MySQL Cluster), ndb_mgm: mysql-cluster-programs-ndb-mgm.
                                                             (line   29)
* command options (MySQL Cluster), ndb_mgmd: mysql-cluster-programs-ndb-mgmd.
                                                             (line   12)
* command options (MySQL Cluster), ndbd: mysql-cluster-programs-ndbd.
                                                             (line   17)
* command options (MySQL Cluster), ndbinfo_select_all: mysql-cluster-programs-ndbinfo-select-all.
                                                             (line   61)
* command options, mysql:                mysql-command-options.
                                                             (line    6)
* command options, mysqladmin:           mysqladmin.         (line  216)
* command options, mysqld:               server-options.     (line    6)
* command syntax:                        manual-conventions. (line  129)
* command-line history, mysql:           mysql-logging.      (line    6)
* command-line options (MySQL Cluster):  mysql-cluster-program-options-common.
                                                             (line    6)
* command-line tool:                     mysql.              (line   15)
* commands out of sync:                  commands-out-of-sync.
                                                             (line    6)
* commands, for binary distribution:     binary-installation.
                                                             (line   78)
* comment syntax:                        comments.           (line    6)
* comments option, mysql:                mysql-command-options.
                                                             (line  208)
* comments option, mysqldump:            mysqldump.          (line  410)
* comments, adding:                      comments.           (line    6)
* comments, starting:                    ansi-diff-comments. (line    6)
* COMMIT <1>:                            commit.             (line    6)
* COMMIT:                                ansi-diff-transactions.
                                                             (line    6)
* commit option, mysqlaccess:            mysqlaccess.        (line   71)
* commit option, mysqlslap:              mysqlslap.          (line  262)
* COMMIT, XA transactions:               xa-statements.      (line    6)
* Committing events to binlog, thread state: mysql-cluster-thread-states.
                                                             (line    6)
* comp_err <1>:                          comp-err.           (line    6)
* comp_err:                              programs-overview.  (line   68)
* comp_err, charset option:              comp-err.           (line   30)
* comp_err, debug option:                comp-err.           (line   35)
* comp_err, debug-info option:           comp-err.           (line   40)
* comp_err, header_file option:          comp-err.           (line   44)
* comp_err, help option:                 comp-err.           (line   26)
* comp_err, in_file option:              comp-err.           (line   48)
* comp_err, name_file option:            comp-err.           (line   53)
* comp_err, out_dir option:              comp-err.           (line   57)
* comp_err, out_file option:             comp-err.           (line   62)
* comp_err, statefile option:            comp-err.           (line   66)
* comp_err, version option:              comp-err.           (line   71)
* compact option, mysqldump:             mysqldump.          (line  417)
* comparison operators:                  comparison-operators.
                                                             (line    6)
* compatibility, between MySQL versions: upgrading-from-previous-series.
                                                             (line    6)
* compatibility, with mSQL:              regexp.             (line   34)
* compatibility, with ODBC <1>:          join.               (line  154)
* compatibility, with ODBC <2>:          create-table.       (line  315)
* compatibility, with ODBC <3>:          comparison-operators.
                                                             (line  164)
* compatibility, with ODBC <4>:          type-conversion.    (line   47)
* compatibility, with ODBC <5>:          numeric-type-overview.
                                                             (line  257)
* compatibility, with ODBC <6>:          identifier-qualifiers.
                                                             (line   48)
* compatibility, with ODBC:              server-system-variables.
                                                             (line 4915)
* compatibility, with Oracle <1>:        explain.            (line   55)
* compatibility, with Oracle <2>:        alter-table.        (line  316)
* compatibility, with Oracle <3>:        group-by-functions. (line  251)
* compatibility, with Oracle:            extensions-to-ansi. (line  102)
* compatibility, with PostgreSQL:        extensions-to-ansi. (line  196)
* compatibility, with standard SQL:      compatibility.      (line   12)
* compatible option, mysqldump:          mysqldump.          (line  432)
* compiler, C++ gcc:                     source-configuration-options.
                                                             (line  404)
* compiling clients, on Unix:            c-api-building-clients.
                                                             (line   11)
* compiling clients, on Windows:         c-api-building-clients.
                                                             (line   52)
* compiling, optimizing:                 system-optimization.
                                                             (line    6)
* compiling, problems:                   compilation-problems.
                                                             (line    6)
* compiling, speed:                      compile-and-link-options.
                                                             (line    6)
* compiling, statically:                 source-configuration-options.
                                                             (line  395)
* compiling, user-defined functions:     udf-compiling.      (line    6)
* complete-insert option, mysqldump:     mysqldump.          (line  451)
* completion_type system variable:       server-system-variables.
                                                             (line 1026)
* composite partitioning:                partitioning-subpartitions.
                                                             (line   27)
* compound statements:                   sql-syntax-compound-statements.
                                                             (line   16)
* compress option, mysql:                mysql-command-options.
                                                             (line  215)
* compress option, mysql_upgrade:        mysql-upgrade.      (line  149)
* compress option, mysqladmin:           mysqladmin.         (line  320)
* compress option, mysqlcheck:           mysqlcheck.         (line  257)
* compress option, mysqldump:            mysqldump.          (line  456)
* compress option, mysqlimport:          mysqlimport.        (line  153)
* compress option, mysqlshow:            mysqlshow.          (line  132)
* compress option, mysqlslap:            mysqlslap.          (line  267)
* COMPRESS():                            encryption-functions.
                                                             (line  149)
* compressed tables <1>:                 compressed-format.  (line    6)
* compressed tables:                     myisampack.         (line    6)
* CompressedBackup:                      mysql-cluster-ndbd-definition.
                                                             (line 1912)
* CompressedLCP:                         mysql-cluster-ndbd-definition.
                                                             (line 1940)
* CONCAT():                              string-functions.   (line  196)
* CONCAT_WS():                           string-functions.   (line  226)
* concatenation, string <1>:             string-functions.   (line  196)
* concatenation, string:                 string-literals.    (line   13)
* concurrency:                           innodb-introduction.
                                                             (line    6)
* concurrency option, mysqlslap:         mysqlslap.          (line  272)
* concurrency, of commits:               innodb-parameters.  (line  529)
* concurrency, of threads:               innodb-parameters.  (line 1988)
* concurrency, tickets:                  innodb-parameters.  (line  554)
* concurrent inserts <1>:                concurrent-inserts. (line    6)
* concurrent inserts:                    internal-locking.   (line   69)
* concurrent_insert system variable:     server-system-variables.
                                                             (line 1074)
* conditions <1>:                        show-warnings.      (line    6)
* conditions:                            show-errors.        (line    6)
* Conditions:                            declare-condition.  (line    6)
* config-cache option (ndb_mgmd):        mysql-cluster-programs-ndb-mgmd.
                                                             (line  195)
* config-file option (ndb_mgmd):         mysql-cluster-programs-ndb-mgmd.
                                                             (line  271)
* config-file option, my_print_defaults: my-print-defaults.  (line   30)
* config-file option, mysqld_multi:      mysqld-multi.       (line  104)
* config-file option, ndb_config:        mysql-cluster-programs-ndb-config.
                                                             (line  214)
* config.cache:                          compilation-problems.
                                                             (line   14)
* config.cache file:                     compilation-problems.
                                                             (line    6)
* config.ini (MySQL Cluster) <1>:        mysql-cluster-programs-ndb-mgmd.
                                                             (line  641)
* config.ini (MySQL Cluster) <2>:        mysql-cluster-config-example.
                                                             (line    6)
* config.ini (MySQL Cluster) <3>:        mysql-cluster-config-file.
                                                             (line   22)
* config.ini (MySQL Cluster):            mysql-cluster-install-configuration.
                                                             (line    6)
* config_from_node option, ndb_config:   mysql-cluster-programs-ndb-config.
                                                             (line  156)
* config_params, ndbinfo table:          mysql-cluster-ndbinfo-config-params.
                                                             (line    6)
* configdir option (ndb_mgmd):           mysql-cluster-programs-ndb-mgmd.
                                                             (line  175)
* configinfo option, ndb_config:         mysql-cluster-programs-ndb-config.
                                                             (line  431)
* configuration files:                   access-denied.      (line  106)
* configuration options:                 source-configuration-options.
                                                             (line    6)
* configuration, MySQL Cluster:          mysql-cluster-params-overview.
                                                             (line   13)
* configure option, -with-low-memory:    compilation-problems.
                                                             (line   38)
* configure script:                      source-configuration-options.
                                                             (line    6)
* configure, disable-grant-options option: source-configuration-options.
                                                             (line  550)
* configure, enable-community-features option: source-configuration-options.
                                                             (line  557)
* configure, enable-debug-sync option:   source-configuration-options.
                                                             (line  505)
* configure, enable-profiling option:    source-configuration-options.
                                                             (line  563)
* configure, enable-thread-safe-client option: source-configuration-options.
                                                             (line  525)
* configure, localstatedir option:       source-configuration-options.
                                                             (line  352)
* configure, prefix option:              source-configuration-options.
                                                             (line  352)
* configure, running after prior invocation: compilation-problems.
                                                             (line   14)
* configure, with-big-tables option:     source-configuration-options.
                                                             (line  540)
* configure, with-charset option:        source-configuration-options.
                                                             (line  444)
* configure, with-client-ldflags option: source-configuration-options.
                                                             (line  395)
* configure, with-collation option:      source-configuration-options.
                                                             (line  444)
* configure, with-debug option:          source-configuration-options.
                                                             (line  488)
* configure, with-embedded-server option: source-configuration-options.
                                                             (line  349)
* configure, with-extra-charsets option: source-configuration-options.
                                                             (line  444)
* configure, with-tcp-port option:       source-configuration-options.
                                                             (line  374)
* configure, with-unix-socket-path option: source-configuration-options.
                                                             (line  382)
* configure, with-zlib-dir option:       source-configuration-options.
                                                             (line  531)
* configure, without-server option:      source-configuration-options.
                                                             (line  334)
* configuring backups, in MySQL Cluster: mysql-cluster-backup-configuration.
                                                             (line    6)
* configuring MySQL Cluster <1>:         mysql-cluster-mysqld.
                                                             (line   49)
* configuring MySQL Cluster <2>:         mysql-cluster-programs-ndb-mgmd.
                                                             (line  641)
* configuring MySQL Cluster <3>:         mysql-cluster-configuration.
                                                             (line   14)
* configuring MySQL Cluster:             mysql-cluster-installation.
                                                             (line   16)
* Configuring MySQL Cluster (concepts):  mysql-cluster-basics.
                                                             (line    6)
* conflict resolution, and ndb_replication system table: mysql-cluster-replication-conflict-resolution.
                                                             (line  158)
* conflict resolution, enabling:         mysql-cluster-replication-conflict-resolution.
                                                             (line  150)
* conflict resolution, in MySQL Cluster Replication: mysql-cluster-replication-conflict-resolution.
                                                             (line    6)
* conflict resolution, mysqld startup options: mysql-cluster-replication-conflict-resolution.
                                                             (line   94)
* connect command, mysql:                mysql-commands.     (line   76)
* Connect Out, thread command:           thread-commands.    (line   25)
* Connect, thread command:               thread-commands.    (line   21)
* connect-delay option (ndbd):           mysql-cluster-programs-ndbd.
                                                             (line  442)
* connect-delay option (ndbmtd):         mysql-cluster-programs-ndbd.
                                                             (line  442)
* connect-retries option (ndbd):         mysql-cluster-programs-ndbd.
                                                             (line  419)
* connect-retries option (ndbmtd):       mysql-cluster-programs-ndbd.
                                                             (line  419)
* connect-string option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  145)
* connect_timeout system variable:       server-system-variables.
                                                             (line 1113)
* connect_timeout variable <1>:          mysqladmin.         (line  489)
* connect_timeout variable:              mysql-command-options.
                                                             (line  658)
* ConnectCheckIntervalDelay:             mysql-cluster-ndbd-definition.
                                                             (line 2296)
* Connecting to master, thread state:    slave-io-thread-states.
                                                             (line   16)
* connecting, remotely with SSH:         windows-and-ssh.    (line    6)
* connecting, to the server <1>:         connecting.         (line    6)
* connecting, to the server:             connecting-disconnecting.
                                                             (line    6)
* connecting, verification:              connection-access.  (line    6)
* CONNECTION Events (MySQL Cluster):     mysql-cluster-log-events.
                                                             (line   22)
* connection string:                     mysql-cluster-connection-strings.
                                                             (line    6)
* connection, aborted:                   communication-errors.
                                                             (line    6)
* connection-timeout option (ndb_error_reporter): mysql-cluster-programs-ndb-error-reporter.
                                                             (line   76)
* CONNECTION_ID():                       information-functions.
                                                             (line  132)
* ConnectionMap:                         mysql-cluster-api-definition.
                                                             (line   59)
* connections option, ndb_config:        mysql-cluster-programs-ndb-config.
                                                             (line  337)
* Connector/C <1>:                       connector-c-info.   (line    6)
* Connector/C:                           connectors-apis.    (line   23)
* Connector/C++ <1>:                     connector-cpp-info. (line    6)
* Connector/C++:                         connectors-apis.    (line   23)
* Connector/J <1>:                       connector-j-info.   (line    6)
* Connector/J:                           connectors-apis.    (line   23)
* Connector/Net <1>:                     connector-net-info. (line    6)
* Connector/Net:                         connectors-apis.    (line   23)
* Connector/ODBC <1>:                    connector-odbc-info.
                                                             (line    6)
* Connector/ODBC:                        connectors-apis.    (line   23)
* Connector/Python <1>:                  connector-python-info.
                                                             (line    6)
* Connector/Python:                      connectors-apis.    (line   23)
* Connectors:                            connectors-apis.    (line   23)
* consistent reads:                      innodb-consistent-read.
                                                             (line    6)
* console option, mysqld:                server-options.     (line  403)
* const table, optimizer <1>:            select.             (line  398)
* const table, optimizer:                explain-output.     (line  240)
* constant table:                        where-optimizations.
                                                             (line   53)
* constraints:                           constraints.        (line   13)
* constraints, foreign keys:             create-table-foreign-keys.
                                                             (line    6)
* CONSTRAINTS, INFORMATION_SCHEMA table: table-constraints-table.
                                                             (line    6)
* Contains():                            spatial-relation-functions-mbr.
                                                             (line   12)
* contributing companies, list of:       supporters.         (line    6)
* contributors, list of:                 contributors.       (line    6)
* control flow functions:                control-flow-functions.
                                                             (line    6)
* CONV():                                mathematical-functions.
                                                             (line  144)
* conventions, syntax:                   manual-conventions. (line    8)
* conventions, typographical:            manual-conventions. (line    8)
* CONVERT:                               cast-functions.     (line   46)
* CONVERT TO:                            alter-table.        (line  527)
* CONVERT_TZ():                          date-and-time-functions.
                                                             (line  180)
* converting HEAP to MyISAM, thread state: general-thread-states.
                                                             (line   44)
* ConvexHull():                          spatial-operator-functions.
                                                             (line   16)
* copy option, mysqlaccess:              mysqlaccess.        (line   78)
* copy to tmp table, thread state:       general-thread-states.
                                                             (line   49)
* copying databases:                     copying-databases.  (line    6)
* copying tables <1>:                    create-table-select.
                                                             (line    6)
* copying tables:                        create-table.       (line 1338)
* Copying to group table, thread state:  general-thread-states.
                                                             (line   55)
* Copying to tmp table on disk, thread state: general-thread-states.
                                                             (line   64)
* Copying to tmp table, thread state:    general-thread-states.
                                                             (line   60)
* core-file option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  168)
* core-file option, mysqld:              server-options.     (line  418)
* core-file-size option, mysqld_safe:    mysqld-safe.        (line  120)
* correct-checksum option, myisamchk:    myisamchk-repair-options.
                                                             (line   19)
* correlated subqueries:                 correlated-subqueries.
                                                             (line    6)
* COS():                                 mathematical-functions.
                                                             (line  165)
* COT():                                 mathematical-functions.
                                                             (line  173)
* count option, myisam_ftdump:           myisam-ftdump.      (line   67)
* count option, mysqladmin:              mysqladmin.         (line  325)
* count option, mysqlshow:               mysqlshow.          (line  137)
* COUNT():                               group-by-functions. (line   95)
* COUNT(DISTINCT):                       group-by-functions. (line  127)
* counters, ndbinfo table:               mysql-cluster-ndbinfo-counters.
                                                             (line    6)
* counting, table rows:                  counting-rows.      (line    6)
* CR_SERVER_GONE_ERROR:                  gone-away.          (line    6)
* CR_SERVER_LOST_ERROR:                  gone-away.          (line    6)
* crash:                                 debugging-server.   (line   16)
* crash, recovery:                       myisam-crash-recovery.
                                                             (line    6)
* crash, repeated:                       crashing.           (line    6)
* crash, replication:                    replication-features-shutdowns.
                                                             (line    6)
* crash-me:                              mysql-benchmarks.   (line   45)
* crash-me program <1>:                  mysql-benchmarks.   (line    6)
* crash-me program:                      portability.        (line    6)
* CrashOnCorruptedTuple:                 mysql-cluster-ndbd-definition.
                                                             (line 1824)
* CRC32():                               mathematical-functions.
                                                             (line  183)
* CREATE ... IF NOT EXISTS, and replication: replication-features-create-if-not-exists.
                                                             (line    6)
* CREATE DATABASE:                       create-database.    (line    6)
* Create DB, thread command:             thread-commands.    (line   29)
* CREATE EVENT:                          create-event.       (line    6)
* CREATE EVENT, and replication:         replication-features-invoked.
                                                             (line   49)
* CREATE FUNCTION <1>:                   create-function-udf.
                                                             (line    6)
* CREATE FUNCTION:                       create-procedure.   (line    6)
* CREATE INDEX:                          create-index.       (line    6)
* CREATE LOGFILE GROUP:                  create-logfile-group.
                                                             (line    6)
* CREATE NODEGROUP command (MySQL Cluster): mysql-cluster-mgm-client-commands.
                                                             (line  210)
* create option, mysqlslap:              mysqlslap.          (line  277)
* CREATE PROCEDURE:                      create-procedure.   (line    6)
* CREATE SCHEMA:                         create-database.    (line    6)
* CREATE SERVER:                         create-server.      (line    6)
* CREATE TABLE:                          create-table.       (line   12)
* CREATE TABLE ... SELECT, and replication: replication-features-create-select.
                                                             (line    6)
* CREATE TABLE, DIRECTORY options, and replication: replication-features-directory.
                                                             (line    6)
* CREATE TABLESPACE:                     create-tablespace.  (line    6)
* CREATE TRIGGER:                        create-trigger.     (line    6)
* CREATE USER:                           create-user.        (line    6)
* CREATE VIEW:                           create-view.        (line    6)
* create-options option, mysqldump:      mysqldump.          (line  461)
* create-schema option, mysqlslap:       mysqlslap.          (line  282)
* Creating delayed handler, thread state: delayed-insert-thread-states.
                                                             (line   22)
* Creating index, thread state:          general-thread-states.
                                                             (line   72)
* Creating sort index, thread state:     general-thread-states.
                                                             (line   77)
* Creating table from master dump, thread state: slave-connection-thread-states.
                                                             (line   14)
* creating table, thread state:          general-thread-states.
                                                             (line   82)
* Creating tmp table, thread state:      general-thread-states.
                                                             (line   87)
* creating user accounts:                create-user.        (line    6)
* creating, bug reports:                 bug-reports.        (line    6)
* creating, database:                    create-database.    (line    6)
* creating, databases:                   database-use.       (line   13)
* creating, default startup options:     option-files.       (line    6)
* creating, function:                    create-function-udf.
                                                             (line    6)
* creating, schema:                      create-database.    (line    6)
* creating, tables:                      creating-tables.    (line    6)
* CROSS JOIN:                            join.               (line    6)
* cross-bootstrap option, mysql_install_db: mysql-install-db.
                                                             (line   72)
* Crosses():                             spatial-relation-functions-mbr.
                                                             (line   17)
* CSV data, reading <1>:                 select-into.        (line  118)
* CSV data, reading:                     load-data.          (line  336)
* csv option, mysqlslap:                 mysqlslap.          (line  293)
* CSV storage engine <1>:                csv-storage-engine. (line   11)
* CSV storage engine:                    storage-engines.    (line   23)
* CURDATE():                             date-and-time-functions.
                                                             (line  210)
* CURRENT_DATE:                          date-and-time-functions.
                                                             (line  222)
* CURRENT_TIME:                          date-and-time-functions.
                                                             (line  226)
* CURRENT_TIMESTAMP:                     date-and-time-functions.
                                                             (line  230)
* CURRENT_USER():                        information-functions.
                                                             (line  142)
* Cursors:                               cursors.            (line   13)
* CURTIME():                             date-and-time-functions.
                                                             (line  235)
* CXX environment variable <1>:          environment-variables.
                                                             (line   18)
* CXX environment variable <2>:          compilation-problems.
                                                             (line   69)
* CXX environment variable:              source-configuration-options.
                                                             (line  404)
* CXXFLAGS environment variable <1>:     environment-variables.
                                                             (line   18)
* CXXFLAGS environment variable:         compilation-problems.
                                                             (line   93)
* daemon option (ndb_mgmd):              mysql-cluster-programs-ndb-mgmd.
                                                             (line  324)
* daemon plugins:                        daemon-plugins.     (line    6)
* Daemon, thread command:                thread-commands.    (line   33)
* DATA DIRECTORY, and replication:       replication-features-directory.
                                                             (line    6)
* data node (MySQL Cluster), defined:    mysql-cluster-basics.
                                                             (line    6)
* data nodes (MySQL Cluster) <1>:        mysql-cluster-programs-ndbmtd.
                                                             (line    6)
* data nodes (MySQL Cluster):            mysql-cluster-programs-ndbd.
                                                             (line    6)
* Data truncation with CJK characters:   faqs-cjk.           (line    6)
* data type, BIGINT:                     numeric-type-overview.
                                                             (line  127)
* data type, BINARY <1>:                 binary-varbinary.   (line    6)
* data type, BINARY:                     string-type-overview.
                                                             (line  154)
* data type, BIT:                        numeric-type-overview.
                                                             (line   35)
* data type, BLOB <1>:                   blob.               (line    6)
* data type, BLOB:                       string-type-overview.
                                                             (line  183)
* data type, BOOL <1>:                   other-vendor-data-types.
                                                             (line    6)
* data type, BOOL:                       numeric-type-overview.
                                                             (line   45)
* data type, BOOLEAN <1>:                other-vendor-data-types.
                                                             (line    6)
* data type, BOOLEAN:                    numeric-type-overview.
                                                             (line   45)
* data type, CHAR <1>:                   string-types.       (line   14)
* data type, CHAR:                       string-type-overview.
                                                             (line   92)
* data type, CHAR VARYING:               string-type-overview.
                                                             (line  124)
* data type, CHARACTER:                  string-type-overview.
                                                             (line   92)
* data type, CHARACTER VARYING:          string-type-overview.
                                                             (line  124)
* data type, DATE <1>:                   datetime.           (line    6)
* data type, DATE:                       date-and-time-type-overview.
                                                             (line   16)
* data type, DATETIME <1>:               datetime.           (line    6)
* data type, DATETIME:                   date-and-time-type-overview.
                                                             (line   23)
* data type, DEC:                        numeric-type-overview.
                                                             (line  188)
* data type, DECIMAL <1>:                precision-math.     (line   14)
* data type, DECIMAL:                    numeric-type-overview.
                                                             (line  172)
* data type, DOUBLE:                     numeric-type-overview.
                                                             (line  216)
* data type, DOUBLE PRECISION:           numeric-type-overview.
                                                             (line  233)
* data type, ENUM <1>:                   enum.               (line    6)
* data type, ENUM:                       string-type-overview.
                                                             (line  245)
* data type, FIXED:                      numeric-type-overview.
                                                             (line  188)
* data type, FLOAT:                      numeric-type-overview.
                                                             (line  196)
* data type, GEOMETRY:                   spatial-datatypes.  (line    6)
* data type, GEOMETRYCOLLECTION:         spatial-datatypes.  (line    6)
* data type, INT:                        numeric-type-overview.
                                                             (line  118)
* data type, INTEGER:                    numeric-type-overview.
                                                             (line  123)
* data type, LINESTRING:                 spatial-datatypes.  (line    6)
* data type, LONG:                       blob.               (line    6)
* data type, LONGBLOB:                   string-type-overview.
                                                             (line  223)
* data type, LONGTEXT:                   string-type-overview.
                                                             (line  233)
* data type, MEDIUMBLOB:                 string-type-overview.
                                                             (line  207)
* data type, MEDIUMINT:                  numeric-type-overview.
                                                             (line  113)
* data type, MEDIUMTEXT:                 string-type-overview.
                                                             (line  214)
* data type, MULTILINESTRING:            spatial-datatypes.  (line    6)
* data type, MULTIPOINT:                 spatial-datatypes.  (line    6)
* data type, MULTIPOLYGON:               spatial-datatypes.  (line    6)
* data type, NATIONAL CHAR:              string-type-overview.
                                                             (line   92)
* data type, NATIONAL VARCHAR:           string-type-overview.
                                                             (line  124)
* data type, NCHAR:                      string-type-overview.
                                                             (line   92)
* data type, NUMERIC:                    numeric-type-overview.
                                                             (line  188)
* data type, NVARCHAR:                   string-type-overview.
                                                             (line  124)
* data type, POINT:                      spatial-datatypes.  (line    6)
* data type, POLYGON:                    spatial-datatypes.  (line    6)
* data type, REAL:                       numeric-type-overview.
                                                             (line  233)
* data type, SET <1>:                    set.                (line    6)
* data type, SET:                        string-type-overview.
                                                             (line  260)
* data type, SMALLINT:                   numeric-type-overview.
                                                             (line  108)
* data type, TEXT <1>:                   blob.               (line    6)
* data type, TEXT:                       string-type-overview.
                                                             (line  194)
* data type, TIME <1>:                   time.               (line    6)
* data type, TIME:                       date-and-time-type-overview.
                                                             (line   62)
* data type, TIMESTAMP <1>:              datetime.           (line    6)
* data type, TIMESTAMP:                  date-and-time-type-overview.
                                                             (line   31)
* data type, TINYBLOB:                   string-type-overview.
                                                             (line  168)
* data type, TINYINT:                    numeric-type-overview.
                                                             (line   40)
* data type, TINYTEXT:                   string-type-overview.
                                                             (line  174)
* data type, VARBINARY <1>:              binary-varbinary.   (line    6)
* data type, VARBINARY:                  string-type-overview.
                                                             (line  161)
* data type, VARCHAR <1>:                string-types.       (line   14)
* data type, VARCHAR:                    string-type-overview.
                                                             (line  124)
* data type, VARCHARACTER:               string-type-overview.
                                                             (line  124)
* data type, YEAR <1>:                   year.               (line    6)
* data type, YEAR:                       date-and-time-type-overview.
                                                             (line   69)
* data types:                            data-types.         (line   29)
* data types, C API:                     c-api.              (line   28)
* data types, overview:                  data-type-overview. (line   12)
* data, importing <1>:                   mysqlimport.        (line    6)
* data, importing:                       mysql-batch-commands.
                                                             (line    6)
* data, loading into tables:             loading-tables.     (line    6)
* data, retrieving:                      retrieving-data.    (line   18)
* data, size:                            data-size.          (line    6)
* data-file-length option, myisamchk:    myisamchk-repair-options.
                                                             (line   23)
* Database information, obtaining:       show.               (line   51)
* database metadata:                     information-schema. (line   36)
* database names, case sensitivity <1>:  identifier-case-sensitivity.
                                                             (line    6)
* database names, case sensitivity:      extensions-to-ansi. (line   41)
* database option (ndb_index_stat):      mysql-cluster-programs-ndb-index-stat.
                                                             (line  202)
* database option, mysql:                mysql-command-options.
                                                             (line  220)
* database option, mysqlbinlog:          mysqlbinlog.        (line  251)
* database option, ndb_blob_tool:        mysql-cluster-programs-ndb-blob-tool.
                                                             (line   98)
* database option, ndb_desc:             mysql-cluster-programs-ndb-desc.
                                                             (line  330)
* database option, ndb_show_tables:      mysql-cluster-programs-ndb-show-tables.
                                                             (line   77)
* DATABASE():                            information-functions.
                                                             (line  212)
* database, altering:                    alter-database.     (line    6)
* database, creating:                    create-database.    (line    6)
* database, deleting:                    drop-database.      (line    6)
* databases option, mysqlcheck:          mysqlcheck.         (line  262)
* databases option, mysqldump:           mysqldump.          (line  466)
* databases, backups:                    backup-and-recovery.
                                                             (line   15)
* databases, copying:                    copying-databases.  (line    6)
* databases, creating:                   database-use.       (line   13)
* databases, defined:                    what-is-mysql.      (line   25)
* databases, displaying:                 mysqlshow.          (line    6)
* databases, dumping <1>:                mysqlhotcopy.       (line    6)
* databases, dumping:                    mysqldump.          (line    6)
* databases, information about:          getting-information.
                                                             (line    6)
* databases, names:                      identifiers.        (line   13)
* databases, replicating:                replication.        (line   13)
* databases, selecting:                  creating-database.  (line    6)
* databases, symbolic links:             symbolic-links-to-databases.
                                                             (line    6)
* databases, using:                      database-use.       (line   13)
* DataDir <1>:                           mysql-cluster-ndbd-definition.
                                                             (line  269)
* DataDir:                               mysql-cluster-mgm-definition.
                                                             (line  255)
* datadir option, mysql.server:          mysql-server.       (line   40)
* datadir option, mysql_install_db:      mysql-install-db.   (line   77)
* datadir option, mysql_upgrade:         mysql-upgrade.      (line  154)
* datadir option, mysqld:                server-options.     (line  446)
* datadir option, mysqld_safe:           mysqld-safe.        (line  125)
* datadir system variable:               server-system-variables.
                                                             (line 1149)
* DataMemory <1>:                        mysql-cluster-config-lcp-params.
                                                             (line    6)
* DataMemory:                            mysql-cluster-ndbd-definition.
                                                             (line  343)
* DATE:                                  using-date.         (line    6)
* date and time functions:               date-and-time-functions.
                                                             (line    6)
* Date and Time types:                   date-and-time-types.
                                                             (line   17)
* date calculations:                     date-calculations.  (line    6)
* DATE columns, problems:                using-date.         (line    6)
* DATE data type <1>:                    datetime.           (line    6)
* DATE data type:                        date-and-time-type-overview.
                                                             (line   16)
* date literals:                         date-and-time-literals.
                                                             (line    6)
* date types:                            storage-requirements.
                                                             (line  137)
* date values, problems:                 datetime.           (line   53)
* DATE():                                date-and-time-functions.
                                                             (line  248)
* DATE_ADD():                            date-and-time-functions.
                                                             (line  269)
* date_format system variable:           server-system-variables.
                                                             (line 1168)
* DATE_FORMAT():                         date-and-time-functions.
                                                             (line  436)
* DATE_SUB():                            date-and-time-functions.
                                                             (line  269)
* DATEDIFF():                            date-and-time-functions.
                                                             (line  256)
* dates, used with partitioning:         partitioning-types. (line   49)
* dates, used with partitioning (examples) <1>: partitioning-pruning.
                                                             (line   73)
* dates, used with partitioning (examples) <2>: partitioning-subpartitions.
                                                             (line   43)
* dates, used with partitioning (examples) <3>: partitioning-hash.
                                                             (line   50)
* dates, used with partitioning (examples): partitioning-range.
                                                             (line  141)
* DATETIME data type <1>:                datetime.           (line    6)
* DATETIME data type:                    date-and-time-type-overview.
                                                             (line   23)
* datetime_format system variable:       server-system-variables.
                                                             (line 1172)
* DAY():                                 date-and-time-functions.
                                                             (line  532)
* DAYNAME():                             date-and-time-functions.
                                                             (line  536)
* DAYOFMONTH():                          date-and-time-functions.
                                                             (line  546)
* DAYOFWEEK():                           date-and-time-functions.
                                                             (line  556)
* DAYOFYEAR():                           date-and-time-functions.
                                                             (line  566)
* db option, mysqlaccess:                mysqlaccess.        (line   82)
* db table, sorting:                     request-access.     (line   51)
* DB2 SQL mode:                          sql-mode.           (line  571)
* DBI interface:                         apis-perl.          (line    6)
* DBI->quote:                            string-literals.    (line  147)
* DBI->trace:                            using-gdb-on-mysqld.
                                                             (line   94)
* DBI/DBD interface:                     apis-perl.          (line    6)
* DBI_TRACE environment variable <1>:    using-gdb-on-mysqld.
                                                             (line   94)
* DBI_TRACE environment variable:        environment-variables.
                                                             (line   18)
* DBI_USER environment variable:         environment-variables.
                                                             (line   18)
* DBUG package:                          dbug-package.       (line    6)
* DCL <1>:                               revoke.             (line    6)
* DCL:                                   grant.              (line    6)
* DDL log:                               ddl-log.            (line    6)
* DEALLOCATE PREPARE <1>:                deallocate-prepare. (line    6)
* DEALLOCATE PREPARE:                    sql-syntax-prepared-statements.
                                                             (line   13)
* debug option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  192)
* debug option, comp_err:                comp-err.           (line   35)
* debug option, make_win_bin_dist:       make-win-bin-dist.  (line   38)
* debug option, my_print_defaults:       my-print-defaults.  (line   36)
* debug option, myisamchk:               myisamchk-general-options.
                                                             (line   21)
* debug option, myisampack:              myisampack.         (line   65)
* debug option, mysql:                   mysql-command-options.
                                                             (line  224)
* debug option, mysql_upgrade:           mysql-upgrade.      (line  159)
* debug option, mysqlaccess:             mysqlaccess.        (line   86)
* debug option, mysqladmin:              mysqladmin.         (line  330)
* debug option, mysqlbinlog:             mysqlbinlog.        (line  342)
* debug option, mysqlcheck:              mysqlcheck.         (line  270)
* debug option, mysqld:                  server-options.     (line  464)
* debug option, mysqldump:               mysqldump.          (line  475)
* debug option, mysqldumpslow:           mysqldumpslow.      (line   53)
* debug option, mysqlhotcopy:            mysqlhotcopy.       (line  111)
* debug option, mysqlimport:             mysqlimport.        (line  158)
* debug option, mysqlmanager:            instance-manager-command-options.
                                                             (line   60)
* debug option, mysqlshow:               mysqlshow.          (line  142)
* debug option, mysqlslap:               mysqlslap.          (line  299)
* debug system variable:                 server-system-variables.
                                                             (line 1176)
* Debug, thread command:                 thread-commands.    (line   38)
* debug-check option, mysql:             mysql-command-options.
                                                             (line  229)
* debug-check option, mysql_upgrade:     mysql-upgrade.      (line  165)
* debug-check option, mysqladmin:        mysqladmin.         (line  335)
* debug-check option, mysqlbinlog:       mysqlbinlog.        (line  347)
* debug-check option, mysqlcheck:        mysqlcheck.         (line  275)
* debug-check option, mysqldump:         mysqldump.          (line  481)
* debug-check option, mysqlimport:       mysqlimport.        (line  163)
* debug-check option, mysqlshow:         mysqlshow.          (line  147)
* debug-check option, mysqlslap:         mysqlslap.          (line  304)
* debug-info option, comp_err:           comp-err.           (line   40)
* debug-info option, mysql:              mysql-command-options.
                                                             (line  234)
* debug-info option, mysql_upgrade:      mysql-upgrade.      (line  170)
* debug-info option, mysqladmin:         mysqladmin.         (line  340)
* debug-info option, mysqlbinlog:        mysqlbinlog.        (line  352)
* debug-info option, mysqlcheck:         mysqlcheck.         (line  280)
* debug-info option, mysqldump:          mysqldump.          (line  486)
* debug-info option, mysqlimport:        mysqlimport.        (line  168)
* debug-info option, mysqlshow:          mysqlshow.          (line  152)
* debug-info option, mysqlslap:          mysqlslap.          (line  309)
* debug-sync-timeout option, mysqld:     server-options.     (line  503)
* debug_sync system variable:            server-system-variables.
                                                             (line 1233)
* debugging support:                     source-configuration-options.
                                                             (line    6)
* debugging, client:                     debugging-client.   (line    6)
* debugging, server:                     debugging-server.   (line   16)
* DEC data type:                         numeric-type-overview.
                                                             (line  188)
* decimal arithmetic:                    precision-math.     (line   14)
* DECIMAL data type <1>:                 precision-math.     (line   14)
* DECIMAL data type:                     numeric-type-overview.
                                                             (line  172)
* decimal point:                         data-types.         (line   37)
* DECLARE:                               declare.            (line    6)
* DECODE():                              encryption-functions.
                                                             (line  183)
* decode_bits myisamchk variable:        myisamchk-general-options.
                                                             (line   84)
* default host name:                     connecting.         (line    6)
* default installation location:         installation-layouts.
                                                             (line    6)
* default options:                       option-files.       (line    6)
* DEFAULT value clause <1>:              create-table.       (line  341)
* DEFAULT value clause:                  data-type-defaults. (line    6)
* default values <1>:                    insert.             (line   73)
* default values <2>:                    create-table.       (line  341)
* default values <3>:                    data-type-defaults. (line    6)
* default values:                        design-limitations. (line   20)
* default values, BLOB and TEXT columns: blob.               (line   52)
* default values, explicit:              data-type-defaults. (line    6)
* default values, implicit:              data-type-defaults. (line    6)
* default values, suppression:           constraint-invalid-data.
                                                             (line    6)
* DEFAULT():                             miscellaneous-functions.
                                                             (line   28)
* DEFAULT, constraint:                   constraint-invalid-data.
                                                             (line    6)
* default, privileges:                   default-privileges. (line    6)
* default-character-set option, mysql:   mysql-command-options.
                                                             (line  242)
* default-character-set option, mysql_upgrade: mysql-upgrade.
                                                             (line  174)
* default-character-set option, mysqladmin: mysqladmin.      (line  345)
* default-character-set option, mysqlcheck: mysqlcheck.      (line  285)
* default-character-set option, mysqld:  server-options.     (line  530)
* default-character-set option, mysqldump: mysqldump.        (line  491)
* default-character-set option, mysqlimport: mysqlimport.    (line  173)
* default-character-set option, mysqlshow: mysqlshow.        (line  157)
* default-collation option, mysqld:      server-options.     (line  548)
* default-mysqld-path option, mysqlmanager: instance-manager-command-options.
                                                             (line   65)
* default-storage-engine option, mysqld: server-options.     (line  564)
* default-table-type option, mysqld:     server-options.     (line  583)
* default-time-zone option, mysqld:      server-options.     (line  599)
* default_week_format system variable:   server-system-variables.
                                                             (line 1272)
* DefaultHashMapSize <1>:                mysql-cluster-api-definition.
                                                             (line  372)
* DefaultHashMapSize:                    mysql-cluster-ndbd-definition.
                                                             (line 1119)
* DefaultOperationRedoProblemAction, API and SQL nodes: mysql-cluster-api-definition.
                                                             (line  339)
* defaults, embedded:                    libmysqld-options.  (line    6)
* defaults-extra-file option <1>:        mysql-install-db.   (line   81)
* defaults-extra-file option:            option-file-options.
                                                             (line   21)
* defaults-extra-file option, my_print_defaults: my-print-defaults.
                                                             (line   42)
* defaults-extra-file option, myisamchk: myisamchk-general-options.
                                                             (line   26)
* defaults-extra-file option, mysql:     mysql-command-options.
                                                             (line  256)
* defaults-extra-file option, mysql_upgrade: mysql-upgrade.  (line  179)
* defaults-extra-file option, mysqladmin: mysqladmin.        (line  350)
* defaults-extra-file option, mysqlbinlog: mysqlbinlog.      (line  357)
* defaults-extra-file option, mysqlcheck: mysqlcheck.        (line  290)
* defaults-extra-file option, mysqld:    server-options.     (line  614)
* defaults-extra-file option, mysqld_multi: mysqld-multi.    (line   72)
* defaults-extra-file option, mysqld_safe: mysqld-safe.      (line  129)
* defaults-extra-file option, mysqldump: mysqldump.          (line  502)
* defaults-extra-file option, mysqlimport: mysqlimport.      (line  182)
* defaults-extra-file option, mysqlshow: mysqlshow.          (line  162)
* defaults-extra-file option, mysqlslap: mysqlslap.          (line  314)
* defaults-file option <1>:              mysql-install-db.   (line   89)
* defaults-file option:                  option-file-options.
                                                             (line   28)
* defaults-file option, my_print_defaults: my-print-defaults.
                                                             (line   32)
* defaults-file option, myisamchk:       myisamchk-general-options.
                                                             (line   33)
* defaults-file option, mysql:           mysql-command-options.
                                                             (line  263)
* defaults-file option, mysql_upgrade:   mysql-upgrade.      (line  186)
* defaults-file option, mysqladmin:      mysqladmin.         (line  357)
* defaults-file option, mysqlbinlog:     mysqlbinlog.        (line  364)
* defaults-file option, mysqlcheck:      mysqlcheck.         (line  297)
* defaults-file option, mysqld:          server-options.     (line  621)
* defaults-file option, mysqld_multi:    mysqld-multi.       (line   70)
* defaults-file option, mysqld_safe:     mysqld-safe.        (line  136)
* defaults-file option, mysqldump:       mysqldump.          (line  509)
* defaults-file option, mysqlimport:     mysqlimport.        (line  189)
* defaults-file option, mysqlmanager:    instance-manager-command-options.
                                                             (line   74)
* defaults-file option, mysqlshow:       mysqlshow.          (line  169)
* defaults-file option, mysqlslap:       mysqlslap.          (line  321)
* defaults-group-suffix option:          option-file-options.
                                                             (line   34)
* defaults-group-suffix option, my_print_defaults: my-print-defaults.
                                                             (line   49)
* defaults-group-suffix option, myisamchk: myisamchk-general-options.
                                                             (line   39)
* defaults-group-suffix option, mysql:   mysql-command-options.
                                                             (line  269)
* defaults-group-suffix option, mysql_upgrade: mysql-upgrade.
                                                             (line  192)
* defaults-group-suffix option, mysqladmin: mysqladmin.      (line  363)
* defaults-group-suffix option, mysqlbinlog: mysqlbinlog.    (line  370)
* defaults-group-suffix option, mysqlcheck: mysqlcheck.      (line  303)
* defaults-group-suffix option, mysqld:  server-options.     (line  627)
* defaults-group-suffix option, mysqldump: mysqldump.        (line  515)
* defaults-group-suffix option, mysqlimport: mysqlimport.    (line  195)
* defaults-group-suffix option, mysqlshow: mysqlshow.        (line  175)
* defaults-group-suffix option, mysqlslap: mysqlslap.        (line  327)
* DEGREES():                             mathematical-functions.
                                                             (line  196)
* delay option (ndbinfo_select_all):     mysql-cluster-programs-ndbinfo-select-all.
                                                             (line  104)
* delay-key-write option, mysqld <1>:    myisam-start.       (line   42)
* delay-key-write option, mysqld:        server-options.     (line  635)
* delay_key_write system variable:       server-system-variables.
                                                             (line 1293)
* DELAYED:                               insert-delayed.     (line    6)
* Delayed insert, thread command:        thread-commands.    (line   42)
* delayed inserts, thread states:        delayed-insert-thread-states.
                                                             (line    6)
* DELAYED, when ignored:                 insert.             (line  235)
* delayed-insert option, mysqldump:      mysqldump.          (line  524)
* delayed_insert_limit:                  insert-delayed.     (line  124)
* delayed_insert_limit system variable:  server-system-variables.
                                                             (line 1341)
* delayed_insert_timeout system variable: server-system-variables.
                                                             (line 1365)
* delayed_queue_size system variable:    server-system-variables.
                                                             (line 1384)
* DELETE:                                delete.             (line    6)
* delete option (ndb_index_stat):        mysql-cluster-programs-ndb-index-stat.
                                                             (line  218)
* delete option, mysqlimport:            mysqlimport.        (line  204)
* DELETE, and MySQL Cluster:             mysql-cluster-limitations-limits.
                                                             (line    9)
* delete-master-logs option, mysqldump:  mysqldump.          (line  529)
* delete-orphans option, ndb_blob_tool:  mysql-cluster-programs-ndb-blob-tool.
                                                             (line  113)
* deleting from main table, thread state: general-thread-states.
                                                             (line   94)
* deleting from reference tables, thread state: general-thread-states.
                                                             (line  100)
* deleting, database:                    drop-database.      (line    6)
* deleting, foreign key <1>:             create-table-foreign-keys.
                                                             (line  214)
* deleting, foreign key:                 alter-table.        (line  487)
* deleting, function:                    drop-function-udf.  (line    6)
* deleting, index <1>:                   drop-index.         (line    6)
* deleting, index:                       alter-table.        (line  361)
* deleting, primary key:                 alter-table.        (line  376)
* deleting, rows:                        deleting-from-related-tables.
                                                             (line    6)
* deleting, schema:                      drop-database.      (line    6)
* deleting, table:                       drop-table.         (line    6)
* deleting, user <1>:                    drop-user.          (line    6)
* deleting, user:                        removing-users.     (line    6)
* deleting, users <1>:                   drop-user.          (line    6)
* deleting, users:                       removing-users.     (line    6)
* deletion, mysql.sock:                  problems-with-mysql-sock.
                                                             (line    6)
* delimiter command, mysql:              mysql-commands.     (line   83)
* delimiter option, mysql:               mysql-command-options.
                                                             (line  277)
* delimiter option, mysqlslap:           mysqlslap.          (line  336)
* delimiter option, ndb_select_all:      mysql-cluster-programs-ndb-select-all.
                                                             (line  172)
* derived tables:                        from-clause-subqueries.
                                                             (line    6)
* des-key-file option, mysqld:           server-options.     (line  667)
* DES_DECRYPT():                         encryption-functions.
                                                             (line  188)
* DES_ENCRYPT():                         encryption-functions.
                                                             (line  209)
* DESC:                                  describe.           (line    6)
* descending option, ndb_select_all:     mysql-cluster-programs-ndb-select-all.
                                                             (line  157)
* DESCRIBE <1>:                          describe.           (line    6)
* DESCRIBE:                              getting-information.
                                                             (line    6)
* description option, myisamchk:         myisamchk-other-options.
                                                             (line   22)
* design, issues:                        bugs.               (line    6)
* design, limitations:                   design-limitations. (line    6)
* detach option, mysqlslap:              mysqlslap.          (line  341)
* development of MySQL Cluster:          mysql-cluster-development.
                                                             (line   16)
* development source tree:               installing-development-tree.
                                                             (line    6)
* Difference():                          spatial-operator-functions.
                                                             (line   21)
* digits:                                data-types.         (line   37)
* Dimension():                           gis-general-property-functions.
                                                             (line    9)
* directory structure, default:          installation-layouts.
                                                             (line    6)
* dirty page:                            innodb-parameters.  (line  261)
* disable named command, mysql:          mysql-command-options.
                                                             (line  282)
* disable-grant-options option, configure: source-configuration-options.
                                                             (line  550)
* disable-indexes option (ndb_restore):  mysql-cluster-programs-ndb-restore.
                                                             (line 1093)
* disable-keys option, mysqldump:        mysqldump.          (line  536)
* disable-log-bin option, mysqlbinlog:   mysqlbinlog.        (line  379)
* DISCARD TABLESPACE <1>:                innodb-multiple-tablespaces.
                                                             (line  170)
* DISCARD TABLESPACE:                    alter-table.        (line  500)
* discard_or_import_tablespace, thread state: general-thread-states.
                                                             (line  105)
* disconnect-slave-event-count option, mysqld: replication-options-slave.
                                                             (line  167)
* disconnecting, from the server:        connecting-disconnecting.
                                                             (line    6)
* Disjoint():                            spatial-relation-functions-mbr.
                                                             (line   35)
* Disk Data tables (MySQL Cluster):      mysql-cluster-disk-data.
                                                             (line   12)
* disk full:                             full-disk.          (line    6)
* disk option, ndb_select_all:           mysql-cluster-programs-ndb-select-all.
                                                             (line  179)
* disk performance:                      disk-issues.        (line    6)
* DiskCheckpointSpeed:                   mysql-cluster-ndbd-definition.
                                                             (line 2614)
* DiskCheckpointSpeedInRestart:          mysql-cluster-ndbd-definition.
                                                             (line 2638)
* DiskIOThreadPool:                      mysql-cluster-ndbd-definition.
                                                             (line 3957)
* Diskless:                              mysql-cluster-ndbd-definition.
                                                             (line 1842)
* diskpagebuffer, ndbinfo table:         mysql-cluster-ndbinfo-diskpagebuffer.
                                                             (line    6)
* DiskPageBufferMemory:                  mysql-cluster-ndbd-definition.
                                                             (line 3898)
* disks, splitting data across:          windows-symbolic-links.
                                                             (line    6)
* DiskSyncSize:                          mysql-cluster-ndbd-definition.
                                                             (line 2586)
* display size:                          data-types.         (line   31)
* display triggers:                      show-triggers.      (line    6)
* display width:                         data-types.         (line   31)
* displaying, database information:      mysqlshow.          (line    6)
* displaying, information, Cardinality:  show-index.         (line   43)
* displaying, information, Collation:    show-index.         (line   38)
* displaying, information, SHOW <1>:     show-tables.        (line    6)
* displaying, information, SHOW <2>:     show-open-tables.   (line    6)
* displaying, information, SHOW <3>:     show-index.         (line    6)
* displaying, information, SHOW <4>:     show-columns.       (line    6)
* displaying, information, SHOW:         show.               (line   51)
* displaying, table status:              show-table-status.  (line    6)
* DISTINCT <1>:                          select.             (line  374)
* DISTINCT <2>:                          distinct-optimization.
                                                             (line    6)
* DISTINCT:                              selecting-columns.  (line   45)
* DISTINCT, AVG():                       group-by-functions. (line   60)
* DISTINCT, COUNT():                     group-by-functions. (line  127)
* DISTINCT, MAX():                       group-by-functions. (line  201)
* DISTINCT, MIN():                       group-by-functions. (line  222)
* DISTINCT, SUM():                       group-by-functions. (line  274)
* DISTINCTROW:                           select.             (line  374)
* distributed privileges (MySQL Cluster): mysql-cluster-privilege-distribution.
                                                             (line    6)
* distributed privileges (MySQL Cluster), and NDB API applications: mysql-cluster-privilege-distribution.
                                                             (line  229)
* DIV:                                   arithmetic-functions.
                                                             (line  114)
* div_precision_increment system variable: server-system-variables.
                                                             (line 1408)
* division (/):                          arithmetic-functions.
                                                             (line   96)
* DNS:                                   host-cache.         (line    6)
* DO:                                    do.                 (line    6)
* DocBook XML, documentation source format: manual-info.     (line   33)
* Documentation, in Chinese:             faqs-cjk.           (line    6)
* Documentation, in Japanese:            faqs-cjk.           (line    6)
* Documentation, in Korean:              faqs-cjk.           (line    6)
* Documenters, list of:                  documenters-translators.
                                                             (line    6)
* dont_ignore_systab_0 option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  798)
* DOUBLE data type:                      numeric-type-overview.
                                                             (line  216)
* DOUBLE PRECISION data type:            numeric-type-overview.
                                                             (line  233)
* double quote (\"):                     string-literals.    (line   75)
* downgrades, MySQL Cluster <1>:         mysql-cluster-rolling-restart.
                                                             (line    6)
* downgrades, MySQL Cluster:             mysql-cluster-upgrade-downgrade.
                                                             (line   12)
* downgrading <1>:                       downgrading.        (line   11)
* downgrading:                           upgrading-downgrading.
                                                             (line   14)
* downloading:                           getting-mysql.      (line    6)
* DROP ... IF EXISTS, and replication:   replication-features-drop-if-exists.
                                                             (line    6)
* DROP DATABASE:                         drop-database.      (line    6)
* Drop DB, thread command:               thread-commands.    (line   46)
* DROP EVENT:                            drop-event.         (line    6)
* DROP FOREIGN KEY <1>:                  create-table-foreign-keys.
                                                             (line  214)
* DROP FOREIGN KEY:                      alter-table.        (line  487)
* DROP FUNCTION <1>:                     drop-function-udf.  (line    6)
* DROP FUNCTION:                         drop-procedure.     (line    6)
* DROP INDEX <1>:                        drop-index.         (line    6)
* DROP INDEX:                            alter-table.        (line  361)
* DROP LOGFILE GROUP:                    drop-logfile-group. (line    6)
* DROP NODEGROUP command (MySQL Cluster): mysql-cluster-mgm-client-commands.
                                                             (line  233)
* DROP PREPARE:                          deallocate-prepare. (line    6)
* DROP PRIMARY KEY:                      alter-table.        (line  376)
* DROP PROCEDURE:                        drop-procedure.     (line    6)
* DROP SCHEMA:                           drop-database.      (line    6)
* DROP SERVER:                           drop-server.        (line    6)
* DROP TABLE:                            drop-table.         (line    6)
* DROP TABLE, and MySQL Cluster:         mysql-cluster-limitations-limits.
                                                             (line    9)
* DROP TABLESPACE:                       drop-tablespace.    (line    6)
* DROP TRIGGER:                          drop-trigger.       (line    6)
* DROP USER:                             drop-user.          (line    6)
* DROP VIEW:                             drop-view.          (line    6)
* drop-user option, mysqlmanager:        instance-manager-command-options.
                                                             (line   86)
* dropping, user <1>:                    drop-user.          (line    6)
* dropping, user:                        removing-users.     (line    6)
* dry-scp option (ndb_error_reporter):   mysql-cluster-programs-ndb-error-reporter.
                                                             (line   91)
* dryrun option, mysqlhotcopy:           mysqlhotcopy.       (line  115)
* DTrace, and memcached:                 ha-memcached-using-dtrace.
                                                             (line    6)
* DUAL:                                  select.             (line   69)
* dump option (ndb_index_stat):          mysql-cluster-programs-ndb-index-stat.
                                                             (line  250)
* dump option, myisam_ftdump:            myisam-ftdump.      (line   71)
* dump-date option, mysqldump:           mysqldump.          (line  546)
* dump-file option, ndb_blob_tool:       mysql-cluster-programs-ndb-blob-tool.
                                                             (line  127)
* DUMPFILE:                              select-into.        (line  127)
* dumping, databases and tables <1>:     mysqlhotcopy.       (line    6)
* dumping, databases and tables:         mysqldump.          (line    6)
* dynamic table characteristics:         dynamic-format.     (line    6)
* edit command, mysql:                   mysql-commands.     (line  118)
* edit-user option, mysqlmanager:        instance-manager-command-options.
                                                             (line   91)
* ego command, mysql:                    mysql-commands.     (line  127)
* Eiffel Wrapper:                        apis-eiffel.        (line    6)
* ELT():                                 string-functions.   (line  244)
* email lists:                           mailing-lists.      (line   10)
* embedded MySQL server library:         libmysqld.          (line   13)
* embedded option, make_win_bin_dist:    make-win-bin-dist.  (line   43)
* embedded option, mysql_config:         mysql-config.       (line   26)
* enable-community-features option, configure: source-configuration-options.
                                                             (line  557)
* enable-debug-sync option, configure:   source-configuration-options.
                                                             (line  505)
* enable-named-pipe option, mysqld:      server-options.     (line  681)
* enable-profiling option, configure:    source-configuration-options.
                                                             (line  563)
* enable-pstack option, mysqld:          server-options.     (line  697)
* enable-thread-safe-client option, configure: source-configuration-options.
                                                             (line  525)
* ENCODE():                              encryption-functions.
                                                             (line  263)
* ENCRYPT():                             encryption-functions.
                                                             (line  279)
* encryption:                            ssl-basics.         (line   18)
* encryption functions:                  encryption-functions.
                                                             (line    6)
* END:                                   begin-end.          (line    6)
* end, thread state:                     general-thread-states.
                                                             (line  110)
* EndPoint():                            gis-linestring-property-functions.
                                                             (line   10)
* engine option, mysqlslap:              mysqlslap.          (line  347)
* engine_condition_pushdown system variable: server-system-variables.
                                                             (line 1449)
* ENGINES, INFORMATION_SCHEMA table:     engines-table.      (line    6)
* ENTER SINGLE USER MODE command (MySQL Cluster): mysql-cluster-mgm-client-commands.
                                                             (line  177)
* entering, queries:                     entering-queries.   (line    6)
* enterprise components, MySQL Enterprise Audit: mysql-enterprise-audit.
                                                             (line    6)
* enterprise components, MySQL Enterprise Backup: mysql-enterprise-backup.
                                                             (line    6)
* enterprise components, MySQL Enterprise Encryption: mysql-enterprise-encryption.
                                                             (line    6)
* enterprise components, MySQL Enterprise Monitor: mysql-enterprise-monitor.
                                                             (line    6)
* enterprise components, MySQL Enterprise Security: mysql-enterprise-security.
                                                             (line    6)
* enterprise components, MySQL Thread Pool: mysql-enterprise-thread-pool.
                                                             (line    6)
* ENUM data type <1>:                    enum.               (line    6)
* ENUM data type:                        string-type-overview.
                                                             (line  245)
* ENUM, size:                            storage-requirements.
                                                             (line  254)
* Envelope():                            gis-general-property-functions.
                                                             (line   23)
* environment variable, CC <1>:          environment-variables.
                                                             (line   18)
* environment variable, CC <2>:          compilation-problems.
                                                             (line   93)
* environment variable, CC:              source-configuration-options.
                                                             (line  404)
* environment variable, CFLAGS <1>:      environment-variables.
                                                             (line   18)
* environment variable, CFLAGS:          compilation-problems.
                                                             (line   93)
* environment variable, CXX <1>:         environment-variables.
                                                             (line   18)
* environment variable, CXX <2>:         compilation-problems.
                                                             (line   69)
* environment variable, CXX:             source-configuration-options.
                                                             (line  404)
* environment variable, CXXFLAGS <1>:    environment-variables.
                                                             (line   18)
* environment variable, CXXFLAGS:        compilation-problems.
                                                             (line   93)
* environment variable, DBI_TRACE <1>:   using-gdb-on-mysqld.
                                                             (line   94)
* environment variable, DBI_TRACE:       environment-variables.
                                                             (line   18)
* environment variable, DBI_USER:        environment-variables.
                                                             (line   18)
* environment variable, HOME <1>:        mysql-logging.      (line    6)
* environment variable, HOME:            environment-variables.
                                                             (line   18)
* environment variable, LD_LIBRARY_PATH: perl-support-problems.
                                                             (line   20)
* environment variable, LD_RUN_PATH <1>: perl-support-problems.
                                                             (line   20)
* environment variable, LD_RUN_PATH <2>: environment-variables.
                                                             (line   18)
* environment variable, LD_RUN_PATH:     solaris-installation-source.
                                                             (line  104)
* environment variable, MYSQL_DEBUG <1>: debugging-client.   (line   10)
* environment variable, MYSQL_DEBUG <2>: programs-overview.  (line  305)
* environment variable, MYSQL_DEBUG:     environment-variables.
                                                             (line   18)
* environment variable, MYSQL_GROUP_SUFFIX: environment-variables.
                                                             (line   18)
* environment variable, MYSQL_HISTFILE <1>: mysql-logging.   (line    6)
* environment variable, MYSQL_HISTFILE:  environment-variables.
                                                             (line   18)
* environment variable, MYSQL_HOME:      environment-variables.
                                                             (line   18)
* environment variable, MYSQL_HOST <1>:  connecting.         (line  246)
* environment variable, MYSQL_HOST:      environment-variables.
                                                             (line   18)
* environment variable, MYSQL_PS1:       environment-variables.
                                                             (line   18)
* environment variable, MYSQL_PWD <1>:   connecting.         (line  246)
* environment variable, MYSQL_PWD <2>:   programs-overview.  (line  305)
* environment variable, MYSQL_PWD:       environment-variables.
                                                             (line   18)
* environment variable, MYSQL_TCP_PORT <1>: multiple-server-clients.
                                                             (line   27)
* environment variable, MYSQL_TCP_PORT <2>: multiple-unix-servers.
                                                             (line   72)
* environment variable, MYSQL_TCP_PORT <3>: programs-overview.
                                                             (line  305)
* environment variable, MYSQL_TCP_PORT:  environment-variables.
                                                             (line   18)
* environment variable, MYSQL_UNIX_PORT <1>: multiple-server-clients.
                                                             (line   27)
* environment variable, MYSQL_UNIX_PORT <2>: multiple-unix-servers.
                                                             (line   72)
* environment variable, MYSQL_UNIX_PORT <3>: programs-overview.
                                                             (line  305)
* environment variable, MYSQL_UNIX_PORT <4>: environment-variables.
                                                             (line   18)
* environment variable, MYSQL_UNIX_PORT: mysql-install-db-problems.
                                                             (line   87)
* environment variable, PATH <1>:        invoking-programs.  (line   49)
* environment variable, PATH <2>:        environment-variables.
                                                             (line   18)
* environment variable, PATH:            unix-postinstallation.
                                                             (line   69)
* environment variable, TMPDIR <1>:      temporary-files.    (line    6)
* environment variable, TMPDIR <2>:      programs-overview.  (line  305)
* environment variable, TMPDIR <3>:      environment-variables.
                                                             (line   18)
* environment variable, TMPDIR:          mysql-install-db-problems.
                                                             (line   87)
* environment variable, TZ <1>:          timezone-problems.  (line    6)
* environment variable, TZ:              environment-variables.
                                                             (line   18)
* environment variable, UMASK <1>:       file-permissions.   (line    6)
* environment variable, UMASK:           environment-variables.
                                                             (line   18)
* environment variable, UMASK_DIR <1>:   file-permissions.   (line   22)
* environment variable, UMASK_DIR:       environment-variables.
                                                             (line   18)
* environment variable, USER <1>:        connecting.         (line  246)
* environment variable, USER:            environment-variables.
                                                             (line   18)
* environment variables <1>:             access-denied.      (line  106)
* environment variables <2>:             setting-environment-variables.
                                                             (line    6)
* environment variables:                 programs-overview.  (line  302)
* environment variables, CXX:            compilation-problems.
                                                             (line   79)
* environment variables, list of:        environment-variables.
                                                             (line    6)
* eq_ref join type, optimizer:           explain-output.     (line  258)
* equal (=):                             comparison-operators.
                                                             (line   65)
* Equals():                              spatial-relation-functions-mbr.
                                                             (line   40)
* Errcode:                               perror.             (line    6)
* errno:                                 perror.             (line    6)
* ERROR Events (MySQL Cluster):          mysql-cluster-log-events.
                                                             (line  250)
* error logs (MySQL Cluster):            mysql-cluster-programs-ndbd.
                                                             (line  473)
* error messages, can't find file:       file-permissions.   (line    6)
* error messages, displaying:            perror.             (line    6)
* error messages, languages:             error-message-language.
                                                             (line    6)
* Error, thread command:                 thread-commands.    (line   50)
* error_count system variable:           server-system-variables.
                                                             (line 1483)
* ERROR_FOR_DIVISION_BY_ZERO SQL mode:   sql-mode.           (line  150)
* errors, access denied:                 error-access-denied.
                                                             (line    6)
* errors, and replication:               replication-features-slaveerrors.
                                                             (line    6)
* errors, checking tables for:           myisam-check.       (line    6)
* errors, common:                        problems.           (line   17)
* errors, directory checksum:            solaris-installation.
                                                             (line   11)
* errors, handling for UDFs:             udf-return-values.  (line    6)
* errors, in subqueries:                 subquery-errors.    (line    6)
* errors, known:                         bugs.               (line    6)
* errors, linking:                       c-api-building-clients.
                                                             (line   83)
* errors, list of:                       common-errors.      (line   28)
* errors, lost connection:               error-lost-connection.
                                                             (line    6)
* errors, reporting:                     bug-reports.        (line    6)
* errors, sources of information:        error-sources.      (line    6)
* escape (\\):                           string-literals.    (line   81)
* escape sequences, option files:        option-files.       (line  173)
* escape sequences, strings:             string-literals.    (line    6)
* estimating, query performance:         estimating-performance.
                                                             (line    6)
* event groups:                          set-global-sql-slave-skip-counter.
                                                             (line    6)
* event log format (MySQL Cluster):      mysql-cluster-log-events.
                                                             (line    6)
* event logs (MySQL Cluster) <1>:        mysql-cluster-logging-management-commands.
                                                             (line    6)
* event logs (MySQL Cluster):            mysql-cluster-event-reports.
                                                             (line   12)
* Event Scheduler:                       events.             (line   15)
* event scheduler:                       stored-programs-views.
                                                             (line   16)
* Event Scheduler, altering events:      alter-event.        (line    6)
* Event Scheduler, and MySQL privileges: events-privileges.  (line    6)
* Event Scheduler, and mysqladmin debug: events-status-info. (line    6)
* Event Scheduler, and replication:      replication-features-invoked.
                                                             (line    6)
* Event Scheduler, and SHOW PROCESSLIST: events-configuration.
                                                             (line   29)
* Event Scheduler, concepts:             events-overview.    (line    6)
* Event Scheduler, creating events:      create-event.       (line    6)
* Event Scheduler, dropping events:      drop-event.         (line    6)
* Event Scheduler, enabling and disabling: events-configuration.
                                                             (line   12)
* Event Scheduler, event metadata:       events-metadata.    (line    6)
* Event Scheduler, obtaining status information <1>: events-status-info.
                                                             (line    6)
* Event Scheduler, obtaining status information: show-scheduler-status.
                                                             (line    6)
* Event Scheduler, SQL statements:       events-syntax.      (line    6)
* Event Scheduler, starting and stopping: events-configuration.
                                                             (line   12)
* event scheduler, thread states:        event-scheduler-thread-states.
                                                             (line    6)
* Event Scheduler, time representation:  events-metadata.    (line   21)
* event severity levels (MySQL Cluster): mysql-cluster-logging-management-commands.
                                                             (line   62)
* event types (MySQL Cluster) <1>:       mysql-cluster-log-events.
                                                             (line   22)
* event types (MySQL Cluster):           mysql-cluster-event-reports.
                                                             (line   49)
* event, restrictions:                   stored-program-restrictions.
                                                             (line    6)
* event-scheduler option, mysqld:        server-options.     (line  731)
* event_scheduler system variable:       server-system-variables.
                                                             (line 1489)
* EventLogBufferSize:                    mysql-cluster-ndbd-definition.
                                                             (line 3010)
* events <1>:                            events.             (line   15)
* events:                                stored-programs-views.
                                                             (line   16)
* events option, mysqldump:              mysqldump.          (line  561)
* events, altering:                      alter-event.        (line    6)
* events, creating:                      create-event.       (line    6)
* events, dropping:                      drop-event.         (line    6)
* EVENTS, INFORMATION_SCHEMA table <1>:  events-table.       (line    6)
* EVENTS, INFORMATION_SCHEMA table:      events-privileges.  (line   77)
* events, metadata:                      events-metadata.    (line    6)
* events, status variables:              events-privileges.  (line  194)
* exact-value literals <1>:              precision-math.     (line   14)
* exact-value literals:                  number-literals.    (line    6)
* example option, mysqld_multi:          mysqld-multi.       (line  118)
* example programs, C API:               c-api-example-programs.
                                                             (line    6)
* EXAMPLE storage engine <1>:            example-storage-engine.
                                                             (line    6)
* EXAMPLE storage engine:                storage-engines.    (line   23)
* examples, compressed tables:           myisampack.         (line  126)
* examples, myisamchk output:            myisamchk-table-info.
                                                             (line    6)
* examples, queries:                     examples.           (line   18)
* exclude-databases option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  938)
* exclude-intermediate-sql-tables option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line 1228)
* exclude-missing-columns option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line 1063)
* exclude-missing-tables option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line 1081)
* exclude-tables option (ndb_restore):   mysql-cluster-programs-ndb-restore.
                                                             (line  949)
* exe-suffix option, make_win_bin_dist:  make-win-bin-dist.  (line   48)
* EXECUTE <1>:                           execute.            (line    6)
* EXECUTE:                               sql-syntax-prepared-statements.
                                                             (line   13)
* execute option (ndb_mgm):              mysql-cluster-programs-ndb-mgm.
                                                             (line   57)
* execute option, mysql:                 mysql-command-options.
                                                             (line  290)
* Execute, thread command:               thread-commands.    (line   52)
* ExecuteOnComputer <1>:                 mysql-cluster-api-definition.
                                                             (line  106)
* ExecuteOnComputer <2>:                 mysql-cluster-ndbd-definition.
                                                             (line  110)
* ExecuteOnComputer:                     mysql-cluster-mgm-definition.
                                                             (line   87)
* executing SQL statements from text files <1>: mysql-batch-commands.
                                                             (line    6)
* executing SQL statements from text files: batch-mode.      (line    6)
* executing, thread state:               general-thread-states.
                                                             (line  117)
* Execution of init_command, thread state: general-thread-states.
                                                             (line  121)
* execution threads (MySQL Cluster):     mysql-cluster-ndbd-definition.
                                                             (line 3700)
* EXISTS, with subqueries:               exists-and-not-exists-subqueries.
                                                             (line    6)
* EXIT command (MySQL Cluster):          mysql-cluster-mgm-client-commands.
                                                             (line  195)
* exit command, mysql:                   mysql-commands.     (line  132)
* EXIT SINGLE USER MODE command (MySQL Cluster): mysql-cluster-mgm-client-commands.
                                                             (line  185)
* exit-info option, mysqld:              server-options.     (line  756)
* EXP():                                 mathematical-functions.
                                                             (line  206)
* expire_logs_days system variable:      server-system-variables.
                                                             (line 1516)
* EXPLAIN <1>:                           explain.            (line    6)
* EXPLAIN:                               using-explain.      (line    6)
* EXPLAIN PARTITIONS:                    partitioning-info.  (line    6)
* EXPLAIN used with partitioned tables:  partitioning-info.  (line    6)
* explicit default values:               data-type-defaults. (line    6)
* EXPORT_SET():                          string-functions.   (line  257)
* expression aliases <1>:                select.             (line  114)
* expression aliases:                    group-by-extensions.
                                                             (line   87)
* expression syntax:                     expressions.        (line    6)
* expressions, extended:                 pattern-matching.   (line    6)
* extend-check option, myisamchk <1>:    myisamchk-repair-options.
                                                             (line   28)
* extend-check option, myisamchk:        myisamchk-check-options.
                                                             (line   18)
* extended option, mysqlcheck:           mysqlcheck.         (line  312)
* extended-insert option, mysqldump:     mysqldump.          (line  566)
* extensions, to standard SQL:           compatibility.      (line   12)
* ExteriorRing():                        gis-polygon-property-functions.
                                                             (line   33)
* external locking <1>:                  general-thread-states.
                                                             (line  316)
* external locking <2>:                  external-locking.   (line    6)
* external locking <3>:                  myisam-crash-recovery.
                                                             (line    6)
* external locking <4>:                  server-system-variables.
                                                             (line 4672)
* external locking:                      server-options.     (line  772)
* external-locking option, mysqld:       server-options.     (line  772)
* extra-file option, my_print_defaults:  my-print-defaults.  (line   44)
* extra-node-info option, ndb_desc:      mysql-cluster-programs-ndb-desc.
                                                             (line  334)
* extra-partition-info option, ndb_desc: mysql-cluster-programs-ndb-desc.
                                                             (line  348)
* EXTRACT():                             date-and-time-functions.
                                                             (line  574)
* extracting, dates:                     date-calculations.  (line    6)
* ExtractValue():                        xml-functions.      (line  152)
* ExtraSendBufferMemory, API nodes:      mysql-cluster-api-definition.
                                                             (line  229)
* ExtraSendBufferMemory, data nodes:     mysql-cluster-ndbd-definition.
                                                             (line 4336)
* ExtraSendBufferMemory, management nodes: mysql-cluster-mgm-definition.
                                                             (line  324)
* failover, in MySQL Cluster replication: mysql-cluster-replication-failover.
                                                             (line    6)
* failover, Java clients:                mysql-cluster-basics.
                                                             (line  116)
* FALSE <1>:                             boolean-literals.   (line    6)
* FALSE:                                 number-literals.    (line    6)
* FALSE, testing for:                    comparison-operators.
                                                             (line  138)
* fast option, myisamchk:                myisamchk-check-options.
                                                             (line   35)
* fast option, mysqlcheck:               mysqlcheck.         (line  321)
* fatal signal 11:                       compilation-problems.
                                                             (line   38)
* features of MySQL:                     features.           (line    6)
* FEDERATED storage engine <1>:          federated-storage-engine.
                                                             (line   13)
* FEDERATED storage engine:              storage-engines.    (line   23)
* FETCH:                                 fetch.              (line    6)
* Fetch, thread command:                 thread-commands.    (line   56)
* Field List, thread command:            thread-commands.    (line   61)
* FIELD():                               string-functions.   (line  276)
* field, changing:                       alter-table.        (line  354)
* fields option, ndb_config:             mysql-cluster-programs-ndb-config.
                                                             (line  391)
* fields-enclosed-by option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  682)
* fields-enclosed-by option, mysqldump <1>: mysqlimport.     (line  210)
* fields-enclosed-by option, mysqldump:  mysqldump.          (line  574)
* fields-escaped-by option, mysqldump <1>: mysqlimport.      (line  214)
* fields-escaped-by option, mysqldump:   mysqldump.          (line  578)
* fields-optionally-enclosed-by option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  697)
* fields-optionally-enclosed-by option, mysqldump <1>: mysqlimport.
                                                             (line  212)
* fields-optionally-enclosed-by option, mysqldump: mysqldump.
                                                             (line  576)
* fields-terminated-by option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  714)
* fields-terminated-by option, mysqldump <1>: mysqlimport.   (line  208)
* fields-terminated-by option, mysqldump: mysqldump.         (line  572)
* FILE:                                  string-functions.   (line  411)
* files, binary log:                     binary-log.         (line   13)
* files, config.cache:                   compilation-problems.
                                                             (line    6)
* files, DDL log:                        ddl-log.            (line    6)
* files, error messages:                 error-message-language.
                                                             (line    6)
* files, general query log:              query-log.          (line    6)
* FILES, INFORMATION_SCHEMA table:       files-table.        (line    6)
* files, log <1>:                        log-file-maintenance.
                                                             (line    6)
* files, log:                            source-configuration-options.
                                                             (line    6)
* files, metadata log:                   ddl-log.            (line    6)
* files, my.cnf:                         replication-features.
                                                             (line   46)
* files, not found message:              file-permissions.   (line    6)
* files, permissions:                    file-permissions.   (line    6)
* files, repairing:                      myisamchk-repair-options.
                                                             (line    6)
* files, script:                         batch-mode.         (line    6)
* files, size limits:                    table-size-limit.   (line    6)
* files, slow query log:                 slow-query-log.     (line    6)
* files, text <1>:                       mysqlimport.        (line    6)
* files, text:                           mysql-batch-commands.
                                                             (line    6)
* files, tmp:                            mysql-install-db-problems.
                                                             (line   73)
* filesort optimization:                 order-by-optimization.
                                                             (line  135)
* FileSystemPath:                        mysql-cluster-ndbd-definition.
                                                             (line  285)
* FileSystemPathDataFiles:               mysql-cluster-ndbd-definition.
                                                             (line 4055)
* FileSystemPathDD:                      mysql-cluster-ndbd-definition.
                                                             (line 4020)
* FileSystemPathUndoFiles:               mysql-cluster-ndbd-definition.
                                                             (line 4085)
* FIND_IN_SET():                         string-functions.   (line  296)
* Finished reading one binlog; switching to next binlog, thread state: master-thread-states.
                                                             (line   17)
* firewalls (software), and MySQL Cluster: mysql-cluster-security-networking-issues.
                                                             (line   98)
* first-slave option, mysqldump:         mysqldump.          (line  584)
* fix-db-names option, mysqlcheck:       mysqlcheck.         (line  325)
* fix-table-names option, mysqlcheck:    mysqlcheck.         (line  331)
* FIXED data type:                       numeric-type-overview.
                                                             (line  188)
* fixed-point arithmetic:                precision-math.     (line   14)
* FLOAT data type:                       numeric-type-overview.
                                                             (line  196)
* floating-point number:                 numeric-type-overview.
                                                             (line  243)
* floating-point values, and replication: replication-features-floatvalues.
                                                             (line    6)
* floats:                                number-literals.    (line    6)
* FLOOR():                               mathematical-functions.
                                                             (line  220)
* FLUSH:                                 flush.              (line    6)
* flush option, mysqld:                  server-options.     (line  796)
* flush system variable:                 server-system-variables.
                                                             (line 1542)
* flush tables:                          mysqladmin.         (line  190)
* FLUSH, and replication:                replication-features-flush.
                                                             (line    6)
* flush-logs option, mysqldump:          mysqldump.          (line  589)
* flush-privileges option, mysqldump:    mysqldump.          (line  601)
* flush_time system variable:            server-system-variables.
                                                             (line 1564)
* Flushing tables, thread state:         general-thread-states.
                                                             (line  132)
* flushlog option, mysqlhotcopy:         mysqlhotcopy.       (line  119)
* FOR UPDATE:                            select.             (line  362)
* FORCE INDEX <1>:                       optimizer-issues.   (line   28)
* FORCE INDEX:                           index-hints.        (line    6)
* FORCE KEY:                             index-hints.        (line    6)
* force option, myisamchk <1>:           myisamchk-repair-options.
                                                             (line   40)
* force option, myisamchk:               myisamchk-check-options.
                                                             (line   39)
* force option, myisampack:              myisampack.         (line   70)
* force option, mysql:                   mysql-command-options.
                                                             (line  297)
* force option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   29)
* force option, mysql_install_db:        mysql-install-db.   (line   96)
* force option, mysql_upgrade:           mysql-upgrade.      (line  201)
* force option, mysqladmin:              mysqladmin.         (line  372)
* force option, mysqlcheck:              mysqlcheck.         (line  337)
* force option, mysqldump:               mysqldump.          (line  609)
* force option, mysqlimport:             mysqlimport.        (line  219)
* force-if-open option, mysqlbinlog:     mysqlbinlog.        (line  393)
* force-read option, mysqlbinlog:        mysqlbinlog.        (line  398)
* foreign key constraints:               create-table-foreign-keys.
                                                             (line    6)
* foreign key constraints, InnoDB:       innodb-foreign-key-constraints.
                                                             (line    6)
* foreign key constraints, restrictions: innodb-foreign-key-constraints.
                                                             (line    6)
* foreign key, constraint <1>:           constraint-foreign-key.
                                                             (line    6)
* foreign key, constraint:               constraint-primary-key.
                                                             (line    6)
* foreign key, deleting <1>:             create-table-foreign-keys.
                                                             (line  214)
* foreign key, deleting:                 alter-table.        (line  487)
* foreign keys <1>:                      alter-table.        (line  456)
* foreign keys <2>:                      example-foreign-keys.
                                                             (line    6)
* foreign keys:                          ansi-diff-foreign-keys.
                                                             (line    6)
* foreign_key_checks system variable:    server-system-variables.
                                                             (line 1585)
* FORMAT():                              string-functions.   (line  312)
* Forums:                                forums.             (line    6)
* FOUND_ROWS():                          information-functions.
                                                             (line  227)
* FragmentLogFileSize:                   mysql-cluster-ndbd-definition.
                                                             (line 1236)
* FreeBSD troubleshooting:               compilation-problems.
                                                             (line  147)
* freeing items, thread state:           general-thread-states.
                                                             (line  126)
* frequently-asked questions about MySQL Cluster: faqs-mysql-cluster.
                                                             (line    6)
* FROM:                                  select.             (line  145)
* FROM_DAYS():                           date-and-time-functions.
                                                             (line  591)
* FROM_UNIXTIME():                       date-and-time-functions.
                                                             (line  603)
* fs option (ndb_error_reporter):        mysql-cluster-programs-ndb-error-reporter.
                                                             (line  107)
* ft_boolean_syntax system variable:     server-system-variables.
                                                             (line 1606)
* ft_max_word_len myisamchk variable:    myisamchk-general-options.
                                                             (line   84)
* ft_max_word_len system variable:       server-system-variables.
                                                             (line 1644)
* ft_min_word_len myisamchk variable:    myisamchk-general-options.
                                                             (line   84)
* ft_min_word_len system variable:       server-system-variables.
                                                             (line 1667)
* ft_query_expansion_limit system variable: server-system-variables.
                                                             (line 1691)
* ft_stopword_file myisamchk variable:   myisamchk-general-options.
                                                             (line   84)
* ft_stopword_file system variable:      server-system-variables.
                                                             (line 1711)
* full disk:                             full-disk.          (line    6)
* full-text parser plugins:              full-text-plugins.  (line    6)
* full-text search:                      fulltext-search.    (line   16)
* FULLTEXT:                              fulltext-search.    (line   16)
* FULLTEXT initialization, thread state: general-thread-states.
                                                             (line  137)
* fulltext join type, optimizer:         explain-output.     (line  303)
* fulltext, stopword list:               fulltext-fine-tuning.
                                                             (line   41)
* function names, parsing:               function-resolution.
                                                             (line    6)
* function names, resolving ambiguity:   function-resolution.
                                                             (line    6)
* function, creating:                    create-function-udf.
                                                             (line    6)
* function, deleting:                    drop-function-udf.  (line    6)
* functions:                             functions.          (line   27)
* functions, and replication:            replication-features-functions.
                                                             (line    6)
* functions, arithmetic:                 bit-functions.      (line    6)
* functions, bit:                        bit-functions.      (line    6)
* functions, C API:                      c-api-function-overview.
                                                             (line    6)
* functions, C prepared statement API <1>: c-api-prepared-statement-function-overview.
                                                             (line    6)
* functions, C prepared statement API:   c-api-prepared-statement-type-conversions.
                                                             (line    6)
* functions, cast:                       cast-functions.     (line    6)
* functions, control flow:               control-flow-functions.
                                                             (line    6)
* functions, date and time:              date-and-time-functions.
                                                             (line    6)
* functions, encryption:                 encryption-functions.
                                                             (line    6)
* functions, for SELECT and WHERE clauses: functions.        (line   27)
* functions, GROUP BY:                   group-by-functions. (line    6)
* functions, grouping:                   operator-precedence.
                                                             (line   49)
* functions, information:                information-functions.
                                                             (line    6)
* functions, mathematical:               mathematical-functions.
                                                             (line   52)
* functions, miscellaneous:              miscellaneous-functions.
                                                             (line    6)
* functions, native, adding:             adding-native-function.
                                                             (line    6)
* functions, new:                        adding-functions.   (line   12)
* functions, stored:                     stored-routines.    (line   13)
* functions, string:                     string-functions.   (line   11)
* functions, string comparison:          string-comparison-functions.
                                                             (line    6)
* functions, user-defined <1>:           adding-functions.   (line   12)
* functions, user-defined <2>:           drop-function-udf.  (line    6)
* functions, user-defined:               create-function-udf.
                                                             (line    6)
* functions, user-defined, adding:       adding-udf.         (line   15)
* gap event:                             mysql-cluster-replication-issues.
                                                             (line   35)
* gap lock, InnoDB <1>:                  innodb-parameters.  (line 1108)
* gap lock, InnoDB <2>:                  innodb-next-key-locking.
                                                             (line    6)
* gap lock, InnoDB <3>:                  innodb-record-level-locks.
                                                             (line    6)
* gap lock, InnoDB:                      innodb-transaction-model.
                                                             (line   62)
* gb2312, gbk:                           faqs-cjk.           (line    6)
* gcc:                                   source-configuration-options.
                                                             (line  404)
* gci option, ndb_select_all:            mysql-cluster-programs-ndb-select-all.
                                                             (line  189)
* gci64 option, ndb_select_all:          mysql-cluster-programs-ndb-select-all.
                                                             (line  196)
* GCP Stop errors (MySQL Cluster):       mysql-cluster-ndbd-definition.
                                                             (line 4263)
* gdb option, mysqld:                    server-options.     (line  816)
* gdb, using:                            using-gdb-on-mysqld.
                                                             (line    6)
* general information:                   introduction.       (line   18)
* General Public License:                what-is-mysql.      (line   54)
* general query log:                     query-log.          (line    6)
* general-log option, mysqld:            server-options.     (line  831)
* general_log system variable:           server-system-variables.
                                                             (line 1741)
* general_log_file system variable:      server-system-variables.
                                                             (line 1765)
* geographic feature:                    spatial-extensions. (line   48)
* GeomCollFromText():                    gis-wkt-functions.  (line   16)
* GeomCollFromWKB():                     gis-wkb-functions.  (line   23)
* geometry:                              spatial-extensions. (line   61)
* GEOMETRY data type:                    spatial-datatypes.  (line    6)
* GEOMETRYCOLLECTION data type:          spatial-datatypes.  (line    6)
* GeometryCollection():                  gis-mysql-specific-functions.
                                                             (line   33)
* GeometryCollectionFromText():          gis-wkt-functions.  (line   16)
* GeometryCollectionFromWKB():           gis-wkb-functions.  (line   23)
* GeometryFromText():                    gis-wkt-functions.  (line   22)
* GeometryFromWKB():                     gis-wkb-functions.  (line   29)
* GeometryN():                           gis-geometrycollection-property-functions.
                                                             (line    8)
* GeometryType():                        gis-general-property-functions.
                                                             (line   40)
* GeomFromText() <1>:                    gis-format-conversion-functions.
                                                             (line   31)
* GeomFromText():                        gis-wkt-functions.  (line   22)
* GeomFromWKB() <1>:                     gis-format-conversion-functions.
                                                             (line   38)
* GeomFromWKB():                         gis-wkb-functions.  (line   29)
* geospatial feature:                    spatial-extensions. (line   58)
* GET_FORMAT():                          date-and-time-functions.
                                                             (line  632)
* GET_LOCK():                            miscellaneous-functions.
                                                             (line   42)
* getting MySQL:                         getting-mysql.      (line    6)
* GIS:                                   spatial-extensions. (line   12)
* GLength() <1>:                         gis-multilinestring-property-functions.
                                                             (line    8)
* GLength():                             gis-linestring-property-functions.
                                                             (line   24)
* global privileges <1>:                 revoke.             (line    6)
* global privileges:                     grant.              (line    6)
* GLOBAL_STATUS, INFORMATION_SCHEMA table: status-table.     (line    6)
* GLOBAL_VARIABLES, INFORMATION_SCHEMA table: variables-table.
                                                             (line    6)
* globalization:                         globalization.      (line   16)
* go command, mysql:                     mysql-commands.     (line  136)
* got handler lock, thread state:        delayed-insert-thread-states.
                                                             (line   26)
* got old table, thread state:           delayed-insert-thread-states.
                                                             (line   32)
* GRANT:                                 grant.              (line    6)
* GRANT statement:                       adding-users.       (line    6)
* grant table distribution (MySQL Cluster): mysql-cluster-privilege-distribution.
                                                             (line    6)
* grant tables, re-creating:             mysql-install-db-problems.
                                                             (line  109)
* grant tables, sorting <1>:             request-access.     (line   51)
* grant tables, sorting:                 connection-access.  (line  130)
* grant tables, structure:               grant-table-structure.
                                                             (line    6)
* grant tables, upgrading:               mysql-fix-privilege-tables.
                                                             (line    6)
* granting, privileges:                  grant.              (line    6)
* GRANTS:                                show-grants.        (line    6)
* greater than (>):                      comparison-operators.
                                                             (line  130)
* greater than or equal (>=):            comparison-operators.
                                                             (line  122)
* greatest timestamp wins (conflict resolution): mysql-cluster-replication-conflict-resolution.
                                                             (line  289)
* greatest timestamp, delete wins (conflict resolution): mysql-cluster-replication-conflict-resolution.
                                                             (line  316)
* GREATEST():                            comparison-operators.
                                                             (line  254)
* GROUP BY:                              group-by-optimization.
                                                             (line   11)
* GROUP BY functions:                    group-by-functions. (line    6)
* GROUP BY, aliases in:                  group-by-extensions.
                                                             (line   87)
* GROUP BY, extensions to standard SQL <1>: select.          (line  220)
* GROUP BY, extensions to standard SQL:  group-by-extensions.
                                                             (line    6)
* GROUP_CONCAT():                        group-by-functions. (line  142)
* group_concat_max_len system variable:  server-system-variables.
                                                             (line 1787)
* grouping, expressions:                 operator-precedence.
                                                             (line   49)
* HANDLER:                               handler.            (line    6)
* Handlers:                              declare-handler.    (line    6)
* handling, errors:                      udf-return-values.  (line    6)
* Has read all relay log; waiting for the slave I/O thread to update it, thread state: slave-sql-thread-states.
                                                             (line   18)
* Has sent all binlog to slave; waiting for binlog to be updated, thread state: master-thread-states.
                                                             (line   22)
* hash partitioning:                     partitioning-hash.  (line   10)
* hash partitions, managing:             partitioning-management-hash-key.
                                                             (line    6)
* hash partitions, splitting and merging: partitioning-management-hash-key.
                                                             (line    6)
* have_archive system variable:          server-system-variables.
                                                             (line 1809)
* have_blackhole_engine system variable: server-system-variables.
                                                             (line 1814)
* have_community_features system variable: server-system-variables.
                                                             (line 1825)
* have_compress system variable:         server-system-variables.
                                                             (line 1819)
* have_crypt system variable:            server-system-variables.
                                                             (line 1834)
* have_csv system variable:              server-system-variables.
                                                             (line 1839)
* have_dynamic_loading system variable:  server-system-variables.
                                                             (line 1847)
* have_example_engine system variable:   server-system-variables.
                                                             (line 1852)
* have_federated_engine system variable: server-system-variables.
                                                             (line 1857)
* have_geometry system variable:         server-system-variables.
                                                             (line 1862)
* have_innodb system variable:           server-system-variables.
                                                             (line 1866)
* have_isam system variable:             server-system-variables.
                                                             (line 1874)
* have_merge_engine system variable:     server-system-variables.
                                                             (line 1880)
* have_openssl system variable:          server-system-variables.
                                                             (line 1886)
* have_partitioning system variable:     server-system-variables.
                                                             (line 1891)
* have_query_cache system variable:      server-system-variables.
                                                             (line 1901)
* have_raid system variable:             server-system-variables.
                                                             (line 1925)
* have_row_based_replication system variable: server-system-variables.
                                                             (line 1906)
* have_rtree_keys system variable:       server-system-variables.
                                                             (line 1931)
* have_ssl system variable:              server-system-variables.
                                                             (line 1936)
* have_symlink system variable:          server-system-variables.
                                                             (line 1946)
* HAVING:                                select.             (line  235)
* header option, ndb_select_all:         mysql-cluster-programs-ndb-select-all.
                                                             (line  162)
* header_file option, comp_err:          comp-err.           (line   44)
* HEAP storage engine <1>:               memory-storage-engine.
                                                             (line    6)
* HEAP storage engine:                   storage-engines.    (line   23)
* HeartbeatIntervalDbApi:                mysql-cluster-ndbd-definition.
                                                             (line 2162)
* HeartbeatIntervalDbDb:                 mysql-cluster-ndbd-definition.
                                                             (line 2128)
* HeartbeatIntervalMgmdMgmd, management nodes: mysql-cluster-mgm-definition.
                                                             (line  366)
* HeartbeatOrder:                        mysql-cluster-ndbd-definition.
                                                             (line 2192)
* HeartbeatThreadPriority <1>:           mysql-cluster-api-definition.
                                                             (line  249)
* HeartbeatThreadPriority:               mysql-cluster-mgm-definition.
                                                             (line  305)
* HELP command (MySQL Cluster):          mysql-cluster-mgm-client-commands.
                                                             (line   34)
* help command, mysql:                   mysql-commands.     (line   52)
* help option (MySQL Cluster programs):  mysql-cluster-program-options-common.
                                                             (line  119)
* help option, comp_err:                 comp-err.           (line   26)
* help option, my_print_defaults:        my-print-defaults.  (line   26)
* help option, myisam_ftdump:            myisam-ftdump.      (line   63)
* HELP option, myisamchk:                myisamchk-general-options.
                                                             (line   16)
* help option, myisamchk:                myisamchk-general-options.
                                                             (line   11)
* help option, myisampack:               myisampack.         (line   51)
* help option, mysql:                    mysql-command-options.
                                                             (line  148)
* help option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   25)
* help option, mysql_find_rows:          mysql-find-rows.    (line   33)
* help option, mysql_install_db:         mysql-install-db.   (line   59)
* help option, mysql_setpermission:      mysql-setpermission.
                                                             (line   30)
* help option, mysql_upgrade:            mysql-upgrade.      (line  135)
* help option, mysql_waitpid:            mysql-waitpid.      (line   28)
* help option, mysqlaccess:              mysqlaccess.        (line   63)
* help option, mysqladmin:               mysqladmin.         (line  300)
* help option, mysqlbinlog:              mysqlbinlog.        (line  183)
* help option, mysqlcheck:               mysqlcheck.         (line  199)
* help option, mysqld:                   server-options.     (line   72)
* help option, mysqld_multi:             mysqld-multi.       (line  100)
* help option, mysqld_safe:              mysqld-safe.        (line   99)
* help option, mysqldump:                mysqldump.          (line  336)
* help option, mysqldumpslow:            mysqldumpslow.      (line   45)
* help option, mysqlhotcopy:             mysqlhotcopy.       (line   86)
* help option, mysqlimport:              mysqlimport.        (line  127)
* help option, mysqlmanager:             instance-manager-command-options.
                                                             (line   23)
* help option, mysqlshow:                mysqlshow.          (line  112)
* help option, mysqlslap:                mysqlslap.          (line  205)
* help option, perror:                   perror.             (line   44)
* help option, resolve_stack_dump:       resolve-stack-dump. (line   22)
* help option, resolveip:                resolveip.          (line   16)
* HELP statement:                        help.               (line    6)
* hex option (ndb_restore):              mysql-cluster-programs-ndb-restore.
                                                             (line  730)
* HEX() <1>:                             mathematical-functions.
                                                             (line  240)
* HEX():                                 string-functions.   (line  326)
* hex-blob option, mysqldump:            mysqldump.          (line  627)
* hexadecimal literals:                  hexadecimal-literals.
                                                             (line    6)
* hexdump option, mysqlbinlog:           mysqlbinlog.        (line  405)
* HIGH_NOT_PRECEDENCE SQL mode:          sql-mode.           (line  172)
* HIGH_PRIORITY:                         select.             (line  381)
* hints:                                 extensions-to-ansi. (line    6)
* hints, index <1>:                      index-hints.        (line    6)
* hints, index:                          select.             (line  154)
* history of MySQL:                      history.            (line    6)
* HOME environment variable <1>:         mysql-logging.      (line    6)
* HOME environment variable:             environment-variables.
                                                             (line   18)
* host name caching:                     host-cache.         (line    6)
* host name resolution:                  host-cache.         (line    6)
* host name, default:                    connecting.         (line    6)
* host option:                           connecting.         (line  137)
* host option, mysql:                    mysql-command-options.
                                                             (line  301)
* host option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   33)
* host option, mysql_setpermission:      mysql-setpermission.
                                                             (line   34)
* host option, mysql_upgrade:            mysql-upgrade.      (line  207)
* host option, mysqlaccess:              mysqlaccess.        (line   90)
* host option, mysqladmin:               mysqladmin.         (line  377)
* host option, mysqlbinlog:              mysqlbinlog.        (line  411)
* host option, mysqlcheck:               mysqlcheck.         (line  341)
* host option, mysqldump:                mysqldump.          (line  622)
* host option, mysqlhotcopy:             mysqlhotcopy.       (line  123)
* host option, mysqlimport:              mysqlimport.        (line  225)
* host option, mysqlshow:                mysqlshow.          (line  184)
* host option, mysqlslap:                mysqlslap.          (line  351)
* host option, ndb_config:               mysql-cluster-programs-ndb-config.
                                                             (line  274)
* host table:                            request-access.     (line  149)
* host table, sorting:                   request-access.     (line   51)
* Host*SciId* parameters:                mysql-cluster-sci-definition.
                                                             (line   52)
* host.frm, problems finding:            unix-postinstallation.
                                                             (line  222)
* HostName <1>:                          mysql-cluster-api-definition.
                                                             (line  120)
* HostName <2>:                          mysql-cluster-ndbd-definition.
                                                             (line  124)
* HostName:                              mysql-cluster-mgm-definition.
                                                             (line  115)
* HostName (MySQL Cluster):              mysql-cluster-security-networking-issues.
                                                             (line   40)
* hostname system variable:              server-system-variables.
                                                             (line 1954)
* HostName1 <1>:                         mysql-cluster-sci-definition.
                                                             (line  118)
* HostName1 <2>:                         mysql-cluster-shm-definition.
                                                             (line   51)
* HostName1:                             mysql-cluster-tcp-definition.
                                                             (line   65)
* HostName2 <1>:                         mysql-cluster-sci-definition.
                                                             (line  130)
* HostName2 <2>:                         mysql-cluster-shm-definition.
                                                             (line   63)
* HostName2:                             mysql-cluster-tcp-definition.
                                                             (line   77)
* HOUR():                                date-and-time-functions.
                                                             (line  673)
* howto option, mysqlaccess:             mysqlaccess.        (line   94)
* html option, mysql:                    mysql-command-options.
                                                             (line  305)
* i-am-a-dummy option, mysql:            mysql-command-options.
                                                             (line  502)
* i5/OS:                                 i5os-installation.  (line    6)
* IBM i5/OS:                             i5os-installation.  (line    6)
* IBMDB2I storage engine:                storage-engines.    (line   23)
* icc, and MySQL Cluster support>:       porting.            (line   32)
* icc, MySQL builds:                     compiler-characteristics.
                                                             (line    6)
* Id <1>:                                mysql-cluster-api-definition.
                                                             (line   26)
* Id <2>:                                mysql-cluster-ndbd-definition.
                                                             (line   64)
* Id:                                    mysql-cluster-mgm-definition.
                                                             (line   20)
* id option, ndb_config:                 mysql-cluster-programs-ndb-config.
                                                             (line  303)
* ID, unique:                            getting-unique-id.  (line    6)
* identifiers:                           identifiers.        (line   13)
* identifiers, case sensitivity:         identifier-case-sensitivity.
                                                             (line    6)
* identifiers, quoting:                  identifiers.        (line   20)
* identity system variable:              server-system-variables.
                                                             (line 1970)
* IF:                                    if.                 (line    6)
* IF():                                  control-flow-functions.
                                                             (line   49)
* IFNULL():                              control-flow-functions.
                                                             (line   88)
* IGNORE INDEX:                          index-hints.        (line    6)
* IGNORE KEY:                            index-hints.        (line    6)
* ignore option, mysqlimport:            mysqlimport.        (line  230)
* IGNORE, with partitioned tables:       insert.             (line  273)
* ignore-builtin-innodb option, mysqld:  innodb-parameters.  (line  147)
* ignore-lines option, mysqlimport:      mysqlimport.        (line  234)
* ignore-spaces option, mysql:           mysql-command-options.
                                                             (line  309)
* ignore-table option, mysqldump:        mysqldump.          (line  634)
* ignore_builtin_innodb system variable: innodb-parameters.  (line  224)
* IGNORE_SPACE SQL mode:                 sql-mode.           (line  188)
* implicit default values:               data-type-defaults. (line    6)
* IMPORT TABLESPACE <1>:                 innodb-multiple-tablespaces.
                                                             (line  170)
* IMPORT TABLESPACE:                     alter-table.        (line  500)
* importing, data <1>:                   mysqlimport.        (line    6)
* importing, data:                       mysql-batch-commands.
                                                             (line    6)
* IN <1>:                                any-in-some-subqueries.
                                                             (line    6)
* IN:                                    comparison-operators.
                                                             (line  270)
* in_file option, comp_err:              comp-err.           (line   48)
* include option, mysql_config:          mysql-config.       (line   22)
* include-databases option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  858)
* include-tables option (ndb_restore):   mysql-cluster-programs-ndb-restore.
                                                             (line  869)
* increasing with replication, speed:    replication.        (line   13)
* incremental recovery:                  point-in-time-recovery.
                                                             (line   11)
* incremental recovery, using MySQL Cluster replication: mysql-cluster-replication-pitr.
                                                             (line    6)
* INDEX DIRECTORY, and replication:      replication-features-directory.
                                                             (line    6)
* index hints <1>:                       index-hints.        (line    6)
* index hints:                           select.             (line  154)
* index join type, optimizer:            explain-output.     (line  373)
* index, deleting <1>:                   drop-index.         (line    6)
* index, deleting:                       alter-table.        (line  361)
* index, rebuilding:                     rebuilding-tables.  (line    6)
* index-record lock, InnoDB <1>:         innodb-parameters.  (line 1108)
* index-record lock, InnoDB <2>:         innodb-next-key-locking.
                                                             (line    6)
* index-record lock, InnoDB <3>:         innodb-record-level-locks.
                                                             (line    6)
* index-record lock, InnoDB:             innodb-transaction-model.
                                                             (line   62)
* index_merge join type, optimizer:      explain-output.     (line  321)
* index_subquery join type, optimizer:   explain-output.     (line  340)
* indexes:                               create-index.       (line    6)
* indexes, and BLOB columns <1>:         create-table.       (line  542)
* indexes, and BLOB columns:             column-indexes.     (line   15)
* indexes, and IS NULL:                  mysql-indexes.      (line  147)
* indexes, and LIKE:                     mysql-indexes.      (line  119)
* indexes, and ndb_restore:              mysql-cluster-programs-ndb-restore.
                                                             (line 1125)
* indexes, and NULL values:              create-table.       (line  521)
* indexes, and TEXT columns <1>:         create-table.       (line  542)
* indexes, and TEXT columns:             column-indexes.     (line   15)
* indexes, assigning to key cache:       cache-index.        (line    6)
* indexes, block size:                   server-system-variables.
                                                             (line 2181)
* indexes, columns:                      column-indexes.     (line    6)
* indexes, leftmost prefix of <1>:       mysql-indexes.      (line   95)
* indexes, leftmost prefix of:           multiple-column-indexes.
                                                             (line   88)
* indexes, multi-column:                 multiple-column-indexes.
                                                             (line    6)
* indexes, multiple-part:                create-index.       (line    6)
* indexes, names:                        identifiers.        (line   13)
* indexes, use of:                       mysql-indexes.      (line    6)
* IndexMemory <1>:                       mysql-cluster-config-lcp-params.
                                                             (line    6)
* IndexMemory:                           mysql-cluster-ndbd-definition.
                                                             (line  469)
* INET_ATON():                           miscellaneous-functions.
                                                             (line  102)
* INET_NTOA():                           miscellaneous-functions.
                                                             (line  129)
* INFO Events (MySQL Cluster):           mysql-cluster-log-events.
                                                             (line  269)
* information functions:                 information-functions.
                                                             (line    6)
* information option, myisamchk:         myisamchk-check-options.
                                                             (line   45)
* INFORMATION_SCHEMA:                    information-schema. (line   36)
* INFORMATION_SCHEMA plugins:            information-schema-plugins.
                                                             (line    6)
* INFORMATION_SCHEMA, and security issues: mysql-cluster-security-mysql-privileges.
                                                             (line  120)
* INFORMATION_SCHEMA, collation and searching: charset-collation-information-schema.
                                                             (line    6)
* INFORMATION_SCHEMA.ENGINES table, and MySQL Cluster: mysql-cluster-sql-statements.
                                                             (line   35)
* INFORMATION_SCHEMA.GLOBAL_STATUS table, and MySQL Cluster: mysql-cluster-sql-statements.
                                                             (line  165)
* INFORMATION_SCHEMA.GLOBAL_VARIABLES table, and MySQL Cluster: mysql-cluster-sql-statements.
                                                             (line   86)
* Init DB, thread command:               thread-commands.    (line   65)
* init, thread state:                    general-thread-states.
                                                             (line  142)
* init-file option, mysqld:              server-options.     (line  852)
* init_connect system variable:          server-system-variables.
                                                             (line 1977)
* init_file system variable:             server-system-variables.
                                                             (line 2018)
* init_slave system variable:            replication-options-slave.
                                                             (line 1345)
* InitFragmentLogFiles:                  mysql-cluster-ndbd-definition.
                                                             (line 1260)
* initial option (ndb_mgmd):             mysql-cluster-programs-ndb-mgmd.
                                                             (line  359)
* initial option (ndbd):                 mysql-cluster-programs-ndbd.
                                                             (line  203)
* initial option (ndbmtd):               mysql-cluster-programs-ndbd.
                                                             (line  203)
* initial-start option (ndbd):           mysql-cluster-programs-ndbd.
                                                             (line  263)
* initial-start option (ndbmtd):         mysql-cluster-programs-ndbd.
                                                             (line  263)
* Initialized, thread state:             event-scheduler-thread-states.
                                                             (line   15)
* InitialLogFileGroup:                   mysql-cluster-ndbd-definition.
                                                             (line 4124)
* InitialNoOfOpenFiles:                  mysql-cluster-ndbd-definition.
                                                             (line 1315)
* InitialTablespace:                     mysql-cluster-ndbd-definition.
                                                             (line 4198)
* INNER JOIN:                            join.               (line    6)
* innochecksum <1>:                      innochecksum.       (line    6)
* innochecksum:                          programs-overview.  (line  165)
* InnoDB:                                innodb-introduction.
                                                             (line    6)
* InnoDB buffer pool:                    innodb-buffer-pool. (line    6)
* innodb option, mysqld:                 innodb-parameters.  (line  183)
* InnoDB storage engine <1>:             innodb-introduction.
                                                             (line    6)
* InnoDB storage engine:                 storage-engines.    (line   23)
* InnoDB tables:                         ansi-diff-transactions.
                                                             (line    6)
* InnoDB, adaptive hash index:           innodb-adaptive-hash.
                                                             (line    6)
* InnoDB, and application feature requirements: mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* InnoDB, applications supported:        mysql-cluster-ndb-innodb-workloads.
                                                             (line    6)
* InnoDB, auto-increment columns:        innodb-auto-increment-handling.
                                                             (line   11)
* InnoDB, autocommit mode <1>:           innodb-transactions-with-different-apis.
                                                             (line    6)
* InnoDB, autocommit mode:               innodb-implicit-commit.
                                                             (line    6)
* InnoDB, availability:                  mysql-cluster-compared.
                                                             (line   36)
* InnoDB, backups:                       innodb-backup.      (line   11)
* InnoDB, clustered index:               innodb-index-types. (line    6)
* InnoDB, compared to MySQL Cluster <1>: mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* InnoDB, compared to MySQL Cluster <2>: mysql-cluster-ndb-innodb-workloads.
                                                             (line    6)
* InnoDB, compared to MySQL Cluster <3>: mysql-cluster-ndb-innodb-engines.
                                                             (line    6)
* InnoDB, compared to MySQL Cluster:     mysql-cluster-compared.
                                                             (line   12)
* InnoDB, configuration parameters:      innodb-parameters.  (line    6)
* InnoDB, configuring data files and memory allocation: innodb-configuration.
                                                             (line   10)
* InnoDB, consistent reads:              innodb-consistent-read.
                                                             (line    6)
* InnoDB, crash recovery:                innodb-recovery.    (line    6)
* InnoDB, data files:                    innodb-data-log-reconfiguration.
                                                             (line    6)
* InnoDB, deadlock detection:            innodb-deadlock-detection.
                                                             (line    6)
* InnoDB, foreign key constraints:       innodb-foreign-key-constraints.
                                                             (line    6)
* InnoDB, gap lock <1>:                  innodb-parameters.  (line 1108)
* InnoDB, gap lock <2>:                  innodb-next-key-locking.
                                                             (line    6)
* InnoDB, gap lock <3>:                  innodb-record-level-locks.
                                                             (line    6)
* InnoDB, gap lock:                      innodb-transaction-model.
                                                             (line   62)
* InnoDB, index-record lock <1>:         innodb-parameters.  (line 1108)
* InnoDB, index-record lock <2>:         innodb-next-key-locking.
                                                             (line    6)
* InnoDB, index-record lock <3>:         innodb-record-level-locks.
                                                             (line    6)
* InnoDB, index-record lock:             innodb-transaction-model.
                                                             (line   62)
* InnoDB, indexes:                       innodb-table-and-index.
                                                             (line   14)
* InnoDB, insert buffering:              innodb-insert-buffering.
                                                             (line    6)
* InnoDB, limits and restrictions:       innodb-restrictions.
                                                             (line    6)
* InnoDB, lock modes:                    innodb-lock-modes.  (line    6)
* InnoDB, locking:                       innodb-transaction-model.
                                                             (line    6)
* InnoDB, locking reads:                 innodb-locking-reads.
                                                             (line    6)
* InnoDB, log files:                     innodb-data-log-reconfiguration.
                                                             (line    6)
* InnoDB, migrating tables:              innodb-migration.   (line    6)
* InnoDB, Monitors <1>:                  innodb-troubleshooting-datadict.
                                                             (line   69)
* InnoDB, Monitors <2>:                  innodb-troubleshooting.
                                                             (line   35)
* InnoDB, Monitors <3>:                  innodb-backup.      (line  120)
* InnoDB, Monitors <4>:                  innodb-monitors.    (line   12)
* InnoDB, Monitors:                      innodb-file-space.  (line   48)
* InnoDB, multi-versioning:              innodb-multi-versioning.
                                                             (line    6)
* InnoDB, next-key lock <1>:             innodb-parameters.  (line 1108)
* InnoDB, next-key lock <2>:             innodb-next-key-locking.
                                                             (line    6)
* InnoDB, next-key lock <3>:             innodb-record-level-locks.
                                                             (line    6)
* InnoDB, next-key lock:                 innodb-transaction-model.
                                                             (line   62)
* InnoDB, NFS <1>:                       innodb-restrictions.
                                                             (line   16)
* InnoDB, NFS:                           innodb-configuration.
                                                             (line   69)
* InnoDB, page size <1>:                 innodb-restrictions.
                                                             (line   83)
* InnoDB, page size:                     innodb-physical-structure.
                                                             (line    6)
* InnoDB, raw partitions:                innodb-raw-devices. (line    6)
* InnoDB, record-level locks <1>:        innodb-parameters.  (line 1108)
* InnoDB, record-level locks <2>:        innodb-next-key-locking.
                                                             (line    6)
* InnoDB, record-level locks <3>:        innodb-record-level-locks.
                                                             (line    6)
* InnoDB, record-level locks:            innodb-transaction-model.
                                                             (line   62)
* InnoDB, replication:                   innodb-and-mysql-replication.
                                                             (line    6)
* InnoDB, row structure:                 innodb-physical-record.
                                                             (line    6)
* InnoDB, secondary index:               innodb-index-types. (line    6)
* InnoDB, semi-consistent read:          innodb-parameters.  (line 1108)
* InnoDB, Solaris 10 x86_64 issues:      solaris-installation.
                                                             (line   11)
* InnoDB, storage requirements:          storage-requirements.
                                                             (line   37)
* InnoDB, system variables:              innodb-parameters.  (line    6)
* InnoDB, tables <1>:                    using-innodb-tables.
                                                             (line    6)
* InnoDB, tables:                        innodb-table-and-index.
                                                             (line   14)
* InnoDB, tables, converting from other storage engines: converting-tables-to-innodb.
                                                             (line    6)
* InnoDB, transaction model:             innodb-transaction-model.
                                                             (line    6)
* InnoDB, troubleshooting:               innodb-troubleshooting.
                                                             (line   15)
* InnoDB, troubleshooting, data dictionary problems: innodb-troubleshooting-datadict.
                                                             (line    6)
* InnoDB, troubleshooting, deadlocks:    innodb-deadlock-detection.
                                                             (line    6)
* InnoDB, troubleshooting, InnoDB error codes: innodb-error-codes.
                                                             (line    6)
* InnoDB, troubleshooting, OS error codes: operating-system-error-codes.
                                                             (line    6)
* InnoDB, troubleshooting, recovery problems: forcing-innodb-recovery.
                                                             (line    6)
* InnoDB, troubleshooting, SQL errors:   innodb-error-handling.
                                                             (line    6)
* innodb-status-file option, mysqld:     innodb-parameters.  (line  197)
* innodb_adaptive_flushing system variable: innodb-parameters.
                                                             (line  245)
* innodb_adaptive_hash_index system variable: innodb-parameters.
                                                             (line  270)
* innodb_additional_mem_pool_size system variable: innodb-parameters.
                                                             (line  295)
* innodb_autoextend_increment system variable: innodb-parameters.
                                                             (line  324)
* innodb_buffer_pool_size system variable: innodb-parameters.
                                                             (line  415)
* innodb_change_buffering system variable: innodb-parameters.
                                                             (line  482)
* innodb_checksums system variable:      innodb-parameters.  (line  507)
* innodb_commit_concurrency system variable: innodb-parameters.
                                                             (line  529)
* innodb_concurrency_tickets system variable: innodb-parameters.
                                                             (line  554)
* innodb_data_file_path system variable: innodb-parameters.  (line  582)
* innodb_data_home_dir system variable:  innodb-parameters.  (line  612)
* innodb_doublewrite system variable:    innodb-parameters.  (line  634)
* innodb_fast_shutdown system variable:  innodb-parameters.  (line  655)
* innodb_file_format system variable:    innodb-parameters.  (line  683)
* innodb_file_format_check system variable: innodb-parameters.
                                                             (line  710)
* innodb_file_per_table system variable: innodb-parameters.  (line  768)
* innodb_flush_log_at_trx_commit system variable: innodb-parameters.
                                                             (line  795)
* innodb_flush_method system variable:   innodb-parameters.  (line  854)
* innodb_force_recovery system variable: innodb-parameters.  (line  935)
* innodb_io_capacity system variable:    innodb-parameters.  (line  964)
* innodb_locks_unsafe_for_binlog system variable: innodb-parameters.
                                                             (line 1093)
* innodb_log_buffer_size system variable: innodb-parameters. (line 1300)
* innodb_log_file_size system variable:  innodb-parameters.  (line 1325)
* innodb_log_files_in_group system variable: innodb-parameters.
                                                             (line 1358)
* innodb_log_group_home_dir system variable: innodb-parameters.
                                                             (line 1379)
* innodb_max_dirty_pages_pct system variable: innodb-parameters.
                                                             (line 1400)
* innodb_max_purge_lag system variable:  innodb-parameters.  (line 1423)
* innodb_mirrored_log_groups system variable: innodb-parameters.
                                                             (line 1472)
* innodb_old_blocks_pct system variable: innodb-parameters.  (line 1476)
* innodb_old_blocks_time system variable: innodb-parameters. (line 1509)
* innodb_open_files system variable:     innodb-parameters.  (line 1550)
* innodb_random_read_ahead system variable: innodb-parameters.
                                                             (line 1577)
* innodb_read_ahead_threshold system variable: innodb-parameters.
                                                             (line 1610)
* innodb_read_io_threads system variable: innodb-parameters. (line 1643)
* innodb_replication_delay system variable: innodb-parameters.
                                                             (line 1675)
* innodb_rollback_on_timeout system variable: innodb-parameters.
                                                             (line 1698)
* innodb_spin_wait_delay system variable: innodb-parameters. (line 1722)
* innodb_stats_method system variable:   innodb-parameters.  (line 1749)
* innodb_stats_on_metadata system variable: innodb-parameters.
                                                             (line 1783)
* innodb_stats_sample_pages system variable: innodb-parameters.
                                                             (line 1815)
* innodb_strict_mode system variable:    innodb-parameters.  (line 1841)
* innodb_support_xa system variable:     innodb-parameters.  (line 1903)
* innodb_sync_spin_loops system variable: innodb-parameters. (line 1943)
* innodb_table_locks system variable:    innodb-parameters.  (line 1965)
* innodb_thread_concurrency system variable: innodb-parameters.
                                                             (line 1988)
* innodb_thread_sleep_delay system variable: innodb-parameters.
                                                             (line 2030)
* innodb_use_sys_malloc system variable: innodb-parameters.  (line 2092)
* innodb_version system variable:        innodb-parameters.  (line 2114)
* innodb_write_io_threads system variable: innodb-parameters.
                                                             (line 2123)
* INSERT <1>:                            insert.             (line   12)
* INSERT:                                insert-speed.       (line    6)
* INSERT ... SELECT:                     insert-select.      (line    6)
* insert buffering:                      innodb-insert-buffering.
                                                             (line    6)
* INSERT DELAYED:                        insert-delayed.     (line    6)
* INSERT statement, grant privileges:    adding-users.       (line  119)
* INSERT():                              string-functions.   (line  346)
* insert, thread state:                  delayed-insert-thread-states.
                                                             (line   72)
* insert-ignore option, mysqldump:       mysqldump.          (line  641)
* insert_id system variable:             server-system-variables.
                                                             (line 2053)
* insertable views, insertable:          view-updatability.  (line    6)
* inserting, speed of:                   insert-speed.       (line    6)
* inserts, concurrent <1>:               concurrent-inserts. (line    6)
* inserts, concurrent:                   internal-locking.   (line   69)
* install option (ndb_mgmd):             mysql-cluster-programs-ndb-mgmd.
                                                             (line  664)
* install option (ndbd):                 mysql-cluster-programs-ndbd.
                                                             (line  360)
* install option (ndbmtd):               mysql-cluster-programs-ndbd.
                                                             (line  360)
* install option, mysqld:                server-options.     (line  879)
* install option, mysqlmanager:          instance-manager-command-options.
                                                             (line   97)
* INSTALL PLUGIN:                        install-plugin.     (line    6)
* install-manual option, mysqld:         server-options.     (line  896)
* installation layouts:                  installation-layouts.
                                                             (line    6)
* installation overview:                 source-installation.
                                                             (line   19)
* installing MySQL Cluster:              mysql-cluster-installation.
                                                             (line   16)
* installing MySQL Cluster, Linux:       mysql-cluster-install-linux.
                                                             (line   12)
* installing MySQL Cluster, Linux binary release: mysql-cluster-install-linux-binary.
                                                             (line    6)
* installing MySQL Cluster, Linux RPM:   mysql-cluster-install-linux-rpm.
                                                             (line    6)
* installing MySQL Cluster, Linux source release: mysql-cluster-install-linux-source.
                                                             (line    6)
* installing MySQL Cluster, Windows:     mysql-cluster-install-windows.
                                                             (line   13)
* installing MySQL Cluster, Windows binary release: mysql-cluster-install-windows-binary.
                                                             (line    6)
* installing MySQL Cluster, Windows source: mysql-cluster-install-windows-source.
                                                             (line    6)
* installing plugins <1>:                install-plugin.     (line    6)
* installing plugins:                    server-plugin-loading.
                                                             (line    6)
* installing, binary distribution:       binary-installation.
                                                             (line    6)
* installing, installing on HP-UX:       hpux-installation.  (line   11)
* installing, installing on IBM-AIX:     aix-installation.   (line   10)
* installing, Linux RPM packages:        linux-installation-rpm.
                                                             (line    6)
* installing, Mac OS X DMG packages:     macosx-installation.
                                                             (line   14)
* installing, overview:                  installing.         (line   24)
* installing, Perl:                      perl-support.       (line   12)
* installing, Perl on Windows:           activestate-perl.   (line    6)
* installing, Solaris PKG packages:      solaris-installation.
                                                             (line   11)
* installing, source distribution:       source-installation.
                                                             (line   19)
* installing, user-defined functions:    udf-compiling.      (line    6)
* INSTR():                               string-functions.   (line  365)
* INT data type:                         numeric-type-overview.
                                                             (line  118)
* integer arithmetic:                    precision-math.     (line   14)
* INTEGER data type:                     numeric-type-overview.
                                                             (line  123)
* integers:                              number-literals.    (line    6)
* interactive option (ndb_mgmd):         mysql-cluster-programs-ndb-mgmd.
                                                             (line  342)
* interactive_timeout system variable:   server-system-variables.
                                                             (line 2059)
* InteriorRingN():                       gis-polygon-property-functions.
                                                             (line   48)
* internal compiler errors:              compilation-problems.
                                                             (line   38)
* internal locking:                      internal-locking.   (line    6)
* internals:                             mysql-internals.    (line   11)
* internationalization:                  globalization.      (line   16)
* Internet Relay Chat:                   irc.                (line    6)
* Intersection():                        spatial-operator-functions.
                                                             (line   26)
* Intersects():                          spatial-relation-functions-mbr.
                                                             (line   44)
* INTERVAL():                            comparison-operators.
                                                             (line  334)
* INTO, SELECT:                          select-into.        (line    6)
* introducer, string literal <1>:        charset-literal.    (line   11)
* introducer, string literal:            string-literals.    (line   35)
* invalid data, constraint:              constraint-invalid-data.
                                                             (line    6)
* invalidating query cache entries, thread state: query-cache-thread-states.
                                                             (line   19)
* IRC:                                   irc.                (line    6)
* IS boolean_value:                      comparison-operators.
                                                             (line  138)
* IS NOT boolean_value:                  comparison-operators.
                                                             (line  147)
* IS NOT NULL:                           comparison-operators.
                                                             (line  202)
* IS NULL <1>:                           comparison-operators.
                                                             (line  156)
* IS NULL:                               is-null-optimization.
                                                             (line    6)
* IS NULL, and indexes:                  mysql-indexes.      (line  147)
* IS_FREE_LOCK():                        miscellaneous-functions.
                                                             (line  140)
* IS_USED_LOCK():                        miscellaneous-functions.
                                                             (line  151)
* IsClosed() <1>:                        gis-multilinestring-property-functions.
                                                             (line   26)
* IsClosed():                            gis-linestring-property-functions.
                                                             (line   42)
* IsEmpty():                             gis-general-property-functions.
                                                             (line   88)
* ISNULL():                              comparison-operators.
                                                             (line  316)
* isolation level:                       innodb-transaction-model.
                                                             (line    6)
* ISOLATION LEVEL:                       set-transaction.    (line    6)
* IsSimple():                            gis-general-property-functions.
                                                             (line   54)
* ITERATE:                               iterate.            (line    6)
* iterations option, mysqlslap:          mysqlslap.          (line  355)
* Japanese character sets, conversion:   faqs-cjk.           (line    6)
* Japanese, Korean, Chinese character sets, frequently asked questions: faqs-cjk.
                                                             (line    6)
* Java:                                  connector-j-info.   (line    6)
* JDBC:                                  connectors-apis.    (line   23)
* jdbc:mysql:loadbalance://:             mysql-cluster-basics.
                                                             (line  116)
* JOIN:                                  join.               (line    6)
* join algorithm, Block Nested-Loop:     nested-loop-joins.  (line    6)
* join algorithm, Nested-Loop:           nested-loop-joins.  (line    6)
* join option, myisampack:               myisampack.         (line   82)
* join type, ALL:                        explain-output.     (line  392)
* join type, const:                      explain-output.     (line  240)
* join type, eq_ref:                     explain-output.     (line  258)
* join type, fulltext:                   explain-output.     (line  303)
* join type, index:                      explain-output.     (line  373)
* join type, index_merge:                explain-output.     (line  321)
* join type, index_subquery:             explain-output.     (line  340)
* join type, range:                      explain-output.     (line  349)
* join type, ref:                        explain-output.     (line  280)
* join type, ref_or_null:                explain-output.     (line  307)
* join type, system:                     explain-output.     (line  235)
* join type, unique_subquery:            explain-output.     (line  329)
* join, nested-loop algorithm:           nested-join-optimization.
                                                             (line  179)
* join_buffer_size system variable:      server-system-variables.
                                                             (line 2082)
* keep_files_on_create system variable:  server-system-variables.
                                                             (line 2148)
* keepold option, mysqlhotcopy:          mysqlhotcopy.       (line  129)
* key cache, assigning indexes to:       cache-index.        (line    6)
* Key cache, MyISAM:                     myisam-key-cache.   (line   15)
* key partitioning:                      partitioning-key.   (line    6)
* key partitions, managing:              partitioning-management-hash-key.
                                                             (line    6)
* key partitions, splitting and merging: partitioning-management-hash-key.
                                                             (line    6)
* key space, MyISAM:                     key-space.          (line    6)
* key_buffer_size myisamchk variable:    myisamchk-general-options.
                                                             (line   84)
* key_buffer_size system variable:       server-system-variables.
                                                             (line 2181)
* key_cache_age_threshold system variable: server-system-variables.
                                                             (line 2283)
* key_cache_block_size system variable:  server-system-variables.
                                                             (line 2306)
* key_cache_division_limit system variable: server-system-variables.
                                                             (line 2326)
* KEY_COLUMN_USAGE, INFORMATION_SCHEMA table: key-column-usage-table.
                                                             (line    6)
* keys:                                  column-indexes.     (line    6)
* keys option, mysqlshow:                mysqlshow.          (line  188)
* keys, foreign <1>:                     example-foreign-keys.
                                                             (line    6)
* keys, foreign:                         ansi-diff-foreign-keys.
                                                             (line    6)
* keys, multi-column:                    multiple-column-indexes.
                                                             (line    6)
* keys, searching on two:                searching-on-two-keys.
                                                             (line    6)
* keys-used option, myisamchk:           myisamchk-repair-options.
                                                             (line   45)
* keywords:                              reserved-words.     (line    6)
* KILL:                                  kill.               (line    6)
* Kill, thread command:                  thread-commands.    (line   69)
* Killed, thread state:                  general-thread-states.
                                                             (line  158)
* Killing slave, thread state:           slave-connection-thread-states.
                                                             (line   21)
* known errors:                          bugs.               (line    6)
* Korean:                                faqs-cjk.           (line    6)
* Korean, Chinese, Japanese character sets, frequently asked questions: faqs-cjk.
                                                             (line    6)
* labels, stored program block:          statement-labels.   (line    6)
* language option, mysqld:               server-options.     (line  914)
* language support, error messages:      error-message-language.
                                                             (line    6)
* language system variable:              server-system-variables.
                                                             (line 2348)
* large page support:                    large-page-support. (line    6)
* large tables, and MySQL Cluster:       create-table.       (line  879)
* large tables, creating in NDB:         create-table.       (line  879)
* large-pages option, mysqld:            server-options.     (line  936)
* large_files_support system variable:   server-system-variables.
                                                             (line 2368)
* large_page_size system variable:       server-system-variables.
                                                             (line 2399)
* large_pages system variable:           server-system-variables.
                                                             (line 2380)
* last row, unique ID:                   getting-unique-id.  (line    6)
* LAST_DAY():                            date-and-time-functions.
                                                             (line  686)
* last_insert_id system variable:        server-system-variables.
                                                             (line 2417)
* LAST_INSERT_ID() <1>:                  insert.             (line  215)
* LAST_INSERT_ID():                      information-functions.
                                                             (line  313)
* LAST_INSERT_ID(), and replication:     replication-features-auto-increment.
                                                             (line    6)
* LAST_INSERT_ID(), and stored routines: stored-routines-last-insert-id.
                                                             (line    6)
* LAST_INSERT_ID(), and triggers:        stored-routines-last-insert-id.
                                                             (line    6)
* LAST_INSERT_ID(), locking considerations: ansi-diff-transactions.
                                                             (line  160)
* LateAlloc:                             mysql-cluster-ndbd-definition.
                                                             (line 1711)
* layout of installation:                installation-layouts.
                                                             (line    6)
* lc_time_names system variable:         server-system-variables.
                                                             (line 2425)
* LCASE():                               string-functions.   (line  380)
* LcpScanProgressTimeout:                mysql-cluster-ndbd-definition.
                                                             (line 1389)
* LD_LIBRARY_PATH environment variable:  perl-support-problems.
                                                             (line   20)
* LD_RUN_PATH environment variable <1>:  perl-support-problems.
                                                             (line   20)
* LD_RUN_PATH environment variable <2>:  environment-variables.
                                                             (line   18)
* LD_RUN_PATH environment variable:      solaris-installation-source.
                                                             (line  104)
* ldata option, mysql_install_db:        mysql-install-db.   (line  102)
* LDML syntax:                           ldml-rules.         (line    6)
* LEAST():                               comparison-operators.
                                                             (line  349)
* LEAVE:                                 leave.              (line    6)
* ledir option, mysqld_safe:             mysqld-safe.        (line  142)
* LEFT JOIN <1>:                         join.               (line    6)
* LEFT JOIN:                             left-join-optimization.
                                                             (line    6)
* LEFT OUTER JOIN:                       join.               (line    6)
* LEFT():                                string-functions.   (line  384)
* leftmost prefix of indexes <1>:        mysql-indexes.      (line   95)
* leftmost prefix of indexes:            multiple-column-indexes.
                                                             (line   88)
* legal names:                           identifiers.        (line   13)
* length option, myisam_ftdump:          myisam-ftdump.      (line   75)
* LENGTH():                              string-functions.   (line  395)
* less than (<):                         comparison-operators.
                                                             (line  114)
* less than or equal (<=):               comparison-operators.
                                                             (line  106)
* libmysqlclient library:                connectors-apis.    (line   23)
* libmysqld:                             libmysqld.          (line   13)
* libmysqld library:                     connectors-apis.    (line   23)
* libmysqld, options:                    libmysqld-options.  (line    6)
* libmysqld-libs option, mysql_config:   mysql-config.       (line   26)
* library, libmysqlclient:               connectors-apis.    (line   23)
* library, libmysqld:                    connectors-apis.    (line   23)
* libs option, mysql_config:             mysql-config.       (line   31)
* libs_r option, mysql_config:           mysql-config.       (line   36)
* license system variable:               server-system-variables.
                                                             (line 2448)
* LIKE:                                  string-comparison-functions.
                                                             (line   20)
* LIKE, and indexes:                     mysql-indexes.      (line  119)
* LIKE, and wildcards:                   mysql-indexes.      (line  119)
* LIMIT <1>:                             select.             (line  297)
* LIMIT <2>:                             information-functions.
                                                             (line  227)
* LIMIT:                                 limit-optimization. (line    6)
* LIMIT, and replication:                replication-features-limit.
                                                             (line    6)
* limitations of MySQL Cluster:          mysql-cluster-limitations.
                                                             (line   20)
* limitations, design:                   design-limitations. (line    6)
* limitations, MySQL Limitations:        limits.             (line   15)
* limitations, replication:              replication-features.
                                                             (line   46)
* limits, file-size:                     table-size-limit.   (line    6)
* limits, InnoDB:                        innodb-restrictions.
                                                             (line    6)
* limits, MySQL Limits, limits in MySQL: limits.             (line   15)
* line-numbers option, mysql:            mysql-command-options.
                                                             (line  315)
* linear hash partitioning:              partitioning-linear-hash.
                                                             (line    6)
* linear key partitioning:               partitioning-key.   (line  112)
* linefeed (\n) <1>:                     load-data.          (line  447)
* linefeed (\n):                         string-literals.    (line   77)
* LineFromText():                        gis-wkt-functions.  (line   27)
* LineFromWKB():                         gis-wkb-functions.  (line   34)
* lines-terminated-by option, mysqldump <1>: mysqlimport.    (line  238)
* lines-terminated-by option, mysqldump: mysqldump.          (line  646)
* LINESTRING data type:                  spatial-datatypes.  (line    6)
* LineString():                          gis-mysql-specific-functions.
                                                             (line   40)
* LineStringFromText():                  gis-wkt-functions.  (line   27)
* LineStringFromWKB():                   gis-wkb-functions.  (line   34)
* linking:                               c-api-building-clients.
                                                             (line    6)
* linking, errors:                       c-api-building-clients.
                                                             (line   83)
* linking, problems:                     c-api-building-clients.
                                                             (line   83)
* linking, speed:                        compile-and-link-options.
                                                             (line    6)
* links, symbolic:                       symbolic-links.     (line   12)
* list partitioning:                     partitioning-list.  (line    6)
* list partitions, adding and dropping:  partitioning-management-range-list.
                                                             (line    6)
* list partitions, managing:             partitioning-management-range-list.
                                                             (line    6)
* list-users option, mysqlmanager:       instance-manager-command-options.
                                                             (line  102)
* literals:                              literals.           (line   16)
* LN():                                  mathematical-functions.
                                                             (line  247)
* LOAD DATA FROM MASTER:                 load-data-from-master.
                                                             (line    6)
* LOAD DATA INFILE <1>:                  problems-with-null. (line   55)
* LOAD DATA INFILE:                      load-data.          (line    6)
* LOAD DATA, and replication:            replication-features-load-data.
                                                             (line    6)
* load emulation:                        mysqlslap.          (line    6)
* LOAD INDEX INTO CACHE, and partitioning: partitioning-limitations.
                                                             (line  419)
* LOAD TABLE FROM MASTER:                load-table-from-master.
                                                             (line    6)
* LOAD_FILE():                           string-functions.   (line  411)
* loading, tables:                       loading-tables.     (line    6)
* local checkpoints (MySQL Cluster):     mysql-cluster-config-lcp-params.
                                                             (line    6)
* local option, mysqlimport:             mysqlimport.        (line  247)
* local-infile option, mysql:            mysql-command-options.
                                                             (line  320)
* local-load option, mysqlbinlog:        mysqlbinlog.        (line  415)
* local-service option, mysqld:          server-options.     (line  965)
* local_infile system variable:          server-system-variables.
                                                             (line 2463)
* localhost, special treatment of:       connecting.         (line   78)
* localization:                          globalization.      (line   16)
* localstatedir option, configure:       source-configuration-options.
                                                             (line  352)
* LOCALTIME:                             date-and-time-functions.
                                                             (line  702)
* LOCALTIMESTAMP:                        date-and-time-functions.
                                                             (line  706)
* LOCATE():                              string-functions.   (line  433)
* LOCK IN SHARE MODE:                    select.             (line  362)
* Lock Monitor, InnoDB:                  innodb-monitors.    (line   12)
* lock option, ndb_select_all:           mysql-cluster-programs-ndb-select-all.
                                                             (line  138)
* LOCK TABLES:                           lock-tables.        (line   12)
* lock-all-tables option, mysqldump:     mysqldump.          (line  652)
* lock-directory option, mysqlslap:      mysqlslap.          (line  359)
* lock-tables option, mysqldump:         mysqldump.          (line  659)
* lock-tables option, mysqlimport:       mysqlimport.        (line  251)
* Locked, thread state:                  general-thread-states.
                                                             (line  167)
* locked_in_memory system variable:      server-system-variables.
                                                             (line 2480)
* LockExecuteThreadToCPU:                mysql-cluster-ndbd-definition.
                                                             (line 3487)
* locking:                               system-optimization.
                                                             (line   15)
* locking methods:                       internal-locking.   (line    6)
* locking, external <1>:                 general-thread-states.
                                                             (line  316)
* locking, external <2>:                 external-locking.   (line    6)
* locking, external <3>:                 myisam-crash-recovery.
                                                             (line    6)
* locking, external <4>:                 server-system-variables.
                                                             (line 4672)
* locking, external:                     server-options.     (line  772)
* locking, internal:                     internal-locking.   (line    6)
* locking, row-level <1>:                internal-locking.   (line    6)
* locking, row-level:                    ansi-diff-transactions.
                                                             (line  167)
* locking, table-level:                  internal-locking.   (line    6)
* LockMaintThreadsToCPU:                 mysql-cluster-ndbd-definition.
                                                             (line 3530)
* LockPagesInMainMemory:                 mysql-cluster-ndbd-definition.
                                                             (line 1727)
* log files:                             source-configuration-options.
                                                             (line    6)
* log files (MySQL Cluster):             mysql-cluster-programs-ndbd.
                                                             (line  464)
* log files (MySQL Cluster), ndbmtd:     mysql-cluster-programs-ndbmtd.
                                                             (line   67)
* log files, maintaining:                log-file-maintenance.
                                                             (line    6)
* log option, mysqld:                    server-options.     (line  979)
* log option, mysqld_multi:              mysqld-multi.       (line  122)
* log option, mysqlmanager:              instance-manager-command-options.
                                                             (line  107)
* log system variable:                   server-system-variables.
                                                             (line 2492)
* LOG():                                 mathematical-functions.
                                                             (line  262)
* log-bin option, mysqld:                replication-options-binary-log.
                                                             (line   45)
* log-bin-index option, mysqld:          replication-options-binary-log.
                                                             (line   74)
* log-bin-trust-function-creators option, mysqld: replication-options-binary-log.
                                                             (line   89)
* log-bin-use-v1-row-events option, mysqld: replication-options-binary-log.
                                                             (line  116)
* log-error option, mysqld:              server-options.     (line 1012)
* log-error option, mysqld_safe:         mysqld-safe.        (line  148)
* log-error option, mysqldump:           mysqldump.          (line  673)
* log-isam option, mysqld:               server-options.     (line 1032)
* log-long-format option, mysqld:        server-options.     (line 1046)
* log-name option (ndb_mgmd):            mysql-cluster-programs-ndb-mgmd.
                                                             (line  406)
* log-output option, mysqld:             server-options.     (line 1064)
* log-queries-not-using-indexes option, mysqld: server-options.
                                                             (line 1106)
* log-short-format option, mysqld <1>:   replication-options-binary-log.
                                                             (line  165)
* log-short-format option, mysqld:       server-options.     (line 1128)
* log-slave-updates option, mysqld:      replication-options-slave.
                                                             (line  181)
* log-slow-admin-statements option, mysqld: server-options.  (line 1142)
* log-slow-queries option, mysqld:       server-options.     (line 1160)
* log-slow-slave-statements option, mysqld: replication-options-slave.
                                                             (line  231)
* log-tc option, mysqld:                 server-options.     (line 1194)
* log-tc-size option, mysqld:            server-options.     (line 1212)
* log-warnings option, mysqld <1>:       replication-options-slave.
                                                             (line  249)
* log-warnings option, mysqld:           server-options.     (line 1228)
* LOG10():                               mathematical-functions.
                                                             (line  305)
* LOG2():                                mathematical-functions.
                                                             (line  291)
* log_bin system variable:               replication-options-binary-log.
                                                             (line  633)
* log_bin_trust_function_creators system variable: server-system-variables.
                                                             (line 2517)
* log_bin_use_v1_row_events system variable: replication-options-binary-log.
                                                             (line  650)
* log_error system variable:             server-system-variables.
                                                             (line 2545)
* log_output system variable:            server-system-variables.
                                                             (line 2563)
* log_queries_not_using_indexes system variable: server-system-variables.
                                                             (line 2593)
* log_slave_updates system variable:     replication-options-binary-log.
                                                             (line  699)
* log_slow_queries system variable:      server-system-variables.
                                                             (line 2612)
* log_warnings system variable:          server-system-variables.
                                                             (line 2636)
* logbuffers, ndbinfo table:             mysql-cluster-ndbinfo-logbuffers.
                                                             (line    6)
* LogDestination:                        mysql-cluster-mgm-definition.
                                                             (line  132)
* logging commands (MySQL Cluster):      mysql-cluster-logging-management-commands.
                                                             (line    6)
* logging slow query, thread state:      general-thread-states.
                                                             (line  171)
* logging, passwords:                    password-logging.   (line    6)
* logical operators:                     logical-operators.  (line    6)
* login, thread state:                   general-thread-states.
                                                             (line  180)
* LogLevelCheckpoint:                    mysql-cluster-ndbd-definition.
                                                             (line 3093)
* LogLevelCongestion:                    mysql-cluster-ndbd-definition.
                                                             (line 3157)
* LogLevelConnection:                    mysql-cluster-ndbd-definition.
                                                             (line 3124)
* LogLevelError:                         mysql-cluster-ndbd-definition.
                                                             (line 3140)
* LogLevelInfo:                          mysql-cluster-ndbd-definition.
                                                             (line 3174)
* LogLevelNodeRestart:                   mysql-cluster-ndbd-definition.
                                                             (line 3109)
* LogLevelShutdown:                      mysql-cluster-ndbd-definition.
                                                             (line 3060)
* LogLevelStartup:                       mysql-cluster-ndbd-definition.
                                                             (line 3044)
* LogLevelStatistic:                     mysql-cluster-ndbd-definition.
                                                             (line 3076)
* logs, and TIMESTAMP:                   upgrading-from-previous-series.
                                                             (line  705)
* logs, flushing:                        server-logs.        (line   40)
* logs, server:                          server-logs.        (line   16)
* logspaces, ndbinfo table:              mysql-cluster-ndbinfo-logspaces.
                                                             (line    6)
* LONG data type:                        blob.               (line    6)
* Long Data, thread command:             thread-commands.    (line   73)
* long_query_time system variable:       server-system-variables.
                                                             (line 2665)
* LONGBLOB data type:                    string-type-overview.
                                                             (line  223)
* LongMessageBuffer:                     mysql-cluster-ndbd-definition.
                                                             (line 1021)
* LONGTEXT data type:                    string-type-overview.
                                                             (line  233)
* LOOP:                                  loop.               (line    6)
* LOOP, labels:                          statement-labels.   (line    6)
* loops option (ndb_index_stat):         mysql-cluster-programs-ndb-index-stat.
                                                             (line  413)
* loops option (ndbinfo_select_all):     mysql-cluster-programs-ndbinfo-select-all.
                                                             (line  120)
* loops option, ndb_show_tables:         mysql-cluster-programs-ndb-show-tables.
                                                             (line   81)
* lossy-conversions option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  491)
* lost connection errors:                error-lost-connection.
                                                             (line    6)
* low-priority option, mysqlimport:      mysqlimport.        (line  256)
* low-priority-updates option, mysqld:   server-options.     (line 1268)
* low_priority_updates system variable:  server-system-variables.
                                                             (line 2698)
* LOWER():                               string-functions.   (line  451)
* lower_case_file_system system variable: server-system-variables.
                                                             (line 2722)
* lower_case_table_names system variable: server-system-variables.
                                                             (line 2740)
* LPAD():                                string-functions.   (line  477)
* LTRIM():                               string-functions.   (line  489)
* Lua:                                   mysql-proxy.        (line   15)
* Mac OS X, installation:                macosx-installation.
                                                             (line   14)
* mailing lists:                         mailing-lists.      (line   10)
* mailing lists, archive location:       mailing-lists.      (line   10)
* mailing lists, guidelines:             mailing-list-use.   (line    6)
* main features of MySQL:                features.           (line    6)
* maintaining, log files:                log-file-maintenance.
                                                             (line    6)
* maintaining, tables:                   myisam-maintenance-schedule.
                                                             (line    6)
* maintenance, tables:                   mysqlcheck.         (line    6)
* make_binary_distribution:              programs-overview.  (line   74)
* MAKE_SET():                            string-functions.   (line  499)
* make_win_bin_dist <1>:                 make-win-bin-dist.  (line    6)
* make_win_bin_dist:                     programs-overview.  (line   80)
* make_win_bin_dist, debug option:       make-win-bin-dist.  (line   38)
* make_win_bin_dist, embedded option:    make-win-bin-dist.  (line   43)
* make_win_bin_dist, exe-suffix option:  make-win-bin-dist.  (line   48)
* make_win_bin_dist, no-debug option:    make-win-bin-dist.  (line   54)
* make_win_bin_dist, no-embedded option: make-win-bin-dist.  (line   58)
* make_win_bin_dist, only-debug option:  make-win-bin-dist.  (line   62)
* MAKEDATE():                            date-and-time-functions.
                                                             (line  710)
* MAKETIME():                            date-and-time-functions.
                                                             (line  723)
* Making temp file, thread state:        slave-sql-thread-states.
                                                             (line   25)
* malicious SQL statements, and MySQL Cluster: mysql-cluster-security-mysql-privileges.
                                                             (line   87)
* manage keys, thread state:             general-thread-states.
                                                             (line  185)
* management client (MySQL Cluster):     mysql-cluster-programs-ndb-mgm.
                                                             (line    6)
* management node (MySQL Cluster), defined: mysql-cluster-basics.
                                                             (line    6)
* management nodes (MySQL Cluster):      mysql-cluster-programs-ndb-mgmd.
                                                             (line    6)
* managing MySQL Cluster:                mysql-cluster-management.
                                                             (line   24)
* managing MySQL Cluster processes:      mysql-cluster-programs.
                                                             (line   35)
* manual, available formats:             manual-info.        (line   33)
* manual, online location:               manual-info.        (line    6)
* manual, syntax conventions:            manual-conventions. (line    8)
* manual, typographical conventions:     manual-conventions. (line    8)
* master-connect-retry option, mysqld:   replication-options-slave.
                                                             (line  282)
* master-data option, mysqldump:         mysqldump.          (line  678)
* master-host option, mysqld:            replication-options-slave.
                                                             (line  338)
* master-info-file option, mysqld:       replication-options-slave.
                                                             (line  356)
* master-password option, mysqld:        replication-options-slave.
                                                             (line  373)
* master-port option, mysqld:            replication-options-slave.
                                                             (line  392)
* master-retry-count option, mysqld:     replication-options-slave.
                                                             (line  411)
* master-ssl option, mysqld:             replication-options-slave.
                                                             (line  441)
* master-ssl-ca option, mysqld:          replication-options-slave.
                                                             (line  441)
* master-ssl-capath option, mysqld:      replication-options-slave.
                                                             (line  441)
* master-ssl-cert option, mysqld:        replication-options-slave.
                                                             (line  441)
* master-ssl-cipher option, mysqld:      replication-options-slave.
                                                             (line  441)
* master-ssl-key option, mysqld:         replication-options-slave.
                                                             (line  441)
* master-user option, mysqld:            replication-options-slave.
                                                             (line  456)
* MASTER_POS_WAIT() <1>:                 master-pos-wait.    (line    6)
* MASTER_POS_WAIT():                     miscellaneous-functions.
                                                             (line  161)
* MATCH ... AGAINST():                   fulltext-search.    (line   16)
* matching, patterns:                    pattern-matching.   (line    6)
* math:                                  precision-math.     (line   14)
* mathematical functions:                mathematical-functions.
                                                             (line   52)
* MAX():                                 group-by-functions. (line  201)
* MAX(DISTINCT):                         group-by-functions. (line  201)
* max-binlog-dump-events option, mysqld: replication-options-binary-log.
                                                             (line  393)
* max-record-length option, myisamchk:   myisamchk-repair-options.
                                                             (line   61)
* max-relay-log-size option, mysqld:     replication-options-slave.
                                                             (line  477)
* max_allowed_packet system variable:    server-system-variables.
                                                             (line 2787)
* max_allowed_packet variable:           mysql-command-options.
                                                             (line  663)
* max_allowed_packet, and replication:   replication-features-max-allowed-packet.
                                                             (line    6)
* max_binlog_cache_size system variable: replication-options-binary-log.
                                                             (line  719)
* max_binlog_size system variable:       replication-options-binary-log.
                                                             (line  769)
* max_connect_errors system variable:    server-system-variables.
                                                             (line 2832)
* max_connections system variable:       server-system-variables.
                                                             (line 2861)
* MAX_CONNECTIONS_PER_HOUR:              user-resources.     (line    6)
* max_delayed_threads system variable:   server-system-variables.
                                                             (line 2903)
* max_error_count system variable:       server-system-variables.
                                                             (line 2932)
* max_heap_table_size system variable:   server-system-variables.
                                                             (line 2954)
* max_insert_delayed_threads system variable: server-system-variables.
                                                             (line 2998)
* max_join_size system variable:         server-system-variables.
                                                             (line 3013)
* max_join_size variable:                mysql-command-options.
                                                             (line  668)
* max_length_for_sort_data system variable: server-system-variables.
                                                             (line 3051)
* max_long_data_size system variable:    server-system-variables.
                                                             (line 3072)
* max_prepared_stmt_count system variable: server-system-variables.
                                                             (line 3098)
* MAX_QUERIES_PER_HOUR:                  user-resources.     (line    6)
* max_relay_log_size system variable:    server-system-variables.
                                                             (line 3129)
* MAX_ROWS, and DataMemory (MySQL Cluster): mysql-cluster-ndbd-definition.
                                                             (line  388)
* MAX_ROWS, and MySQL Cluster <1>:       partitioning-overview.
                                                             (line  141)
* MAX_ROWS, and MySQL Cluster:           create-table.       (line  879)
* MAX_ROWS, and NDB:                     create-table.       (line  879)
* max_seeks_for_key system variable:     server-system-variables.
                                                             (line 3157)
* max_sort_length system variable:       server-system-variables.
                                                             (line 3184)
* max_sp_recursion_depth system variable: server-system-variables.
                                                             (line 3206)
* max_tmp_tables system variable:        server-system-variables.
                                                             (line 3233)
* MAX_UPDATES_PER_HOUR:                  user-resources.     (line    6)
* MAX_USER_CONNECTIONS:                  user-resources.     (line    6)
* max_user_connections system variable:  server-system-variables.
                                                             (line 3237)
* max_write_lock_count system variable:  server-system-variables.
                                                             (line 3275)
* MaxAllocate:                           mysql-cluster-ndbd-definition.
                                                             (line 1093)
* MaxBufferedEpochBytes:                 mysql-cluster-ndbd-definition.
                                                             (line 2472)
* MaxBufferedEpochs:                     mysql-cluster-ndbd-definition.
                                                             (line 2443)
* MAXDB SQL mode:                        sql-mode.           (line  576)
* MaxDMLOperationsPerTransaction:        mysql-cluster-ndbd-definition.
                                                             (line  810)
* maximum memory used:                   mysqladmin.         (line  205)
* maximums, maximum columns per table:   column-count-limit. (line    6)
* maximums, maximum number of databases: database-count-limit.
                                                             (line    6)
* maximums, maximum number of tables:    database-count-limit.
                                                             (line    6)
* maximums, maximum row size:            column-count-limit. (line    6)
* maximums, maximum tables per join:     joins-limits.       (line    6)
* maximums, table size:                  table-size-limit.   (line    6)
* MaxLCPStartDelay:                      mysql-cluster-ndbd-definition.
                                                             (line 1352)
* MaxNoOfAttributes:                     mysql-cluster-ndbd-definition.
                                                             (line 1429)
* MaxNoOfConcurrentIndexOperations:      mysql-cluster-ndbd-definition.
                                                             (line  846)
* MaxNoOfConcurrentOperations:           mysql-cluster-ndbd-definition.
                                                             (line  714)
* MaxNoOfConcurrentScans:                mysql-cluster-ndbd-definition.
                                                             (line  942)
* MaxNoOfConcurrentSubOperations:        mysql-cluster-ndbd-definition.
                                                             (line 1679)
* MaxNoOfConcurrentTransactions:         mysql-cluster-ndbd-definition.
                                                             (line  648)
* MaxNoOfExecutionThreads, ndbmtd:       mysql-cluster-ndbd-definition.
                                                             (line 3700)
* MaxNoOfFiredTriggers:                  mysql-cluster-ndbd-definition.
                                                             (line  874)
* MaxNoOfIndexes:                        mysql-cluster-ndbd-definition.
                                                             (line 1604)
* MaxNoOfLocalOperations:                mysql-cluster-ndbd-definition.
                                                             (line  790)
* MaxNoOfLocalScans:                     mysql-cluster-ndbd-definition.
                                                             (line  975)
* MaxNoOfOpenFiles:                      mysql-cluster-ndbd-definition.
                                                             (line 1291)
* MaxNoOfOrderedIndexes:                 mysql-cluster-ndbd-definition.
                                                             (line 1523)
* MaxNoOfSavedMessages:                  mysql-cluster-ndbd-definition.
                                                             (line 1333)
* MaxNoOfSubscribers:                    mysql-cluster-ndbd-definition.
                                                             (line 1642)
* MaxNoOfSubscriptions:                  mysql-cluster-ndbd-definition.
                                                             (line 1615)
* MaxNoOfTables:                         mysql-cluster-ndbd-definition.
                                                             (line 1484)
* MaxNoOfTriggers:                       mysql-cluster-ndbd-definition.
                                                             (line 1578)
* MaxNoOfUniqueHashIndexes:              mysql-cluster-ndbd-definition.
                                                             (line 1551)
* MaxParallelScansPerFragment:           mysql-cluster-ndbd-definition.
                                                             (line 1061)
* MaxScanBatchSize:                      mysql-cluster-api-definition.
                                                             (line  268)
* MaxStartFailRetries:                   mysql-cluster-ndbd-definition.
                                                             (line 4498)
* MBR <1>:                               spatial-relation-functions-mysql-specific.
                                                             (line    6)
* MBR:                                   spatial-relation-functions-mbr.
                                                             (line    6)
* MBRContains():                         spatial-relation-functions-mysql-specific.
                                                             (line   10)
* MBRDisjoint():                         spatial-relation-functions-mysql-specific.
                                                             (line   26)
* MBREqual():                            spatial-relation-functions-mysql-specific.
                                                             (line   31)
* MBRIntersects():                       spatial-relation-functions-mysql-specific.
                                                             (line   36)
* MBROverlaps():                         spatial-relation-functions-mysql-specific.
                                                             (line   41)
* MBRTouches():                          spatial-relation-functions-mysql-specific.
                                                             (line   49)
* MBRWithin():                           spatial-relation-functions-mysql-specific.
                                                             (line   57)
* MD5():                                 encryption-functions.
                                                             (line  301)
* medium-check option, myisamchk:        myisamchk-check-options.
                                                             (line   49)
* medium-check option, mysqlcheck:       mysqlcheck.         (line  345)
* MEDIUMBLOB data type:                  string-type-overview.
                                                             (line  207)
* MEDIUMINT data type:                   numeric-type-overview.
                                                             (line  113)
* MEDIUMTEXT data type:                  string-type-overview.
                                                             (line  214)
* membership, ndbinfo table:             mysql-cluster-ndbinfo-membership.
                                                             (line    6)
* memlock option, mysqld:                server-options.     (line 1318)
* MEMORY storage engine <1>:             memory-storage-engine.
                                                             (line    6)
* MEMORY storage engine:                 storage-engines.    (line   23)
* MEMORY storage engine, and replication: replication-features-memory.
                                                             (line    6)
* memory usage, myisamchk:               myisamchk-memory.   (line    6)
* memory use <1>:                        memory-use.         (line    6)
* memory use:                            mysqladmin.         (line  199)
* memory use, in MySQL Cluster:          mysql-cluster-limitations-limits.
                                                             (line    9)
* memoryusage, ndbinfo table:            mysql-cluster-ndbinfo-memoryusage.
                                                             (line    6)
* MemReportFrequency:                    mysql-cluster-ndbd-definition.
                                                             (line 3190)
* MERGE storage engine <1>:              merge-storage-engine.
                                                             (line   11)
* MERGE storage engine:                  storage-engines.    (line   23)
* MERGE tables, defined:                 merge-storage-engine.
                                                             (line   11)
* metadata log:                          ddl-log.            (line    6)
* metadata, database:                    information-schema. (line   36)
* metadata, stored routines:             stored-routines-metadata.
                                                             (line    6)
* metadata, triggers:                    trigger-metadata.   (line    6)
* metadata, views:                       view-metadata.      (line    6)
* method option, mysqlhotcopy:           mysqlhotcopy.       (line  133)
* methods, locking:                      internal-locking.   (line    6)
* mgmd (MySQL Cluster), defined:         mysql-cluster-basics.
                                                             (line    6)
* MICROSECOND():                         date-and-time-functions.
                                                             (line  732)
* MID():                                 string-functions.   (line  517)
* MIN():                                 group-by-functions. (line  222)
* MIN(DISTINCT):                         group-by-functions. (line  222)
* min-examined-row-limit option, mysqld: server-options.     (line 1293)
* min_examined_row_limit system variable: server-system-variables.
                                                             (line 3296)
* MinFreePct:                            mysql-cluster-ndbd-definition.
                                                             (line  388)
* minimum bounding rectangle <1>:        spatial-relation-functions-mysql-specific.
                                                             (line    6)
* minimum bounding rectangle:            spatial-relation-functions-mbr.
                                                             (line    6)
* minus, unary (-):                      arithmetic-functions.
                                                             (line   71)
* MINUTE():                              date-and-time-functions.
                                                             (line  743)
* mirror sites:                          getting-mysql.      (line    6)
* miscellaneous functions:               miscellaneous-functions.
                                                             (line    6)
* mixed statements (Replication):        replication-features-transactions.
                                                             (line   38)
* MLineFromText():                       gis-wkt-functions.  (line   32)
* MLineFromWKB():                        gis-wkb-functions.  (line   39)
* MOD (modulo):                          mathematical-functions.
                                                             (line  319)
* MOD():                                 mathematical-functions.
                                                             (line  319)
* modes, batch:                          batch-mode.         (line    6)
* modulo (%):                            mathematical-functions.
                                                             (line  319)
* modulo (MOD):                          mathematical-functions.
                                                             (line  319)
* monitor, terminal:                     tutorial.           (line   16)
* monitoring:                            mysql-enterprise-monitor.
                                                             (line    6)
* monitoring, threads:                   thread-information. (line   19)
* monitoring-interval option, mysqlmanager: instance-manager-command-options.
                                                             (line  126)
* Monitors, InnoDB <1>:                  innodb-troubleshooting-datadict.
                                                             (line   69)
* Monitors, InnoDB <2>:                  innodb-troubleshooting.
                                                             (line   35)
* Monitors, InnoDB <3>:                  innodb-backup.      (line  120)
* Monitors, InnoDB <4>:                  innodb-monitors.    (line   12)
* Monitors, InnoDB:                      innodb-file-space.  (line   48)
* MONTH():                               date-and-time-functions.
                                                             (line  751)
* MONTHNAME():                           date-and-time-functions.
                                                             (line  761)
* MPointFromText():                      gis-wkt-functions.  (line   37)
* MPointFromWKB():                       gis-wkb-functions.  (line   44)
* MPolyFromText():                       gis-wkt-functions.  (line   42)
* MPolyFromWKB():                        gis-wkb-functions.  (line   49)
* mSQL compatibility:                    regexp.             (line   34)
* msql2mysql:                            msql2mysql.         (line    6)
* MSSQL SQL mode:                        sql-mode.           (line  582)
* multi mysqld:                          mysqld-multi.       (line    6)
* multi-column indexes:                  multiple-column-indexes.
                                                             (line    6)
* multi-master replication, in MySQL Cluster <1>: mysql-cluster-replication-conflict-resolution.
                                                             (line    6)
* multi-master replication, in MySQL Cluster: mysql-cluster-replication-multi-master.
                                                             (line    6)
* multibyte character sets:              cannot-initialize-character-set.
                                                             (line    6)
* multibyte character sets, and MySQL Cluster (replication): mysql-cluster-replication-issues.
                                                             (line   67)
* multibyte characters:                  multibyte-characters.
                                                             (line    6)
* MULTILINESTRING data type:             spatial-datatypes.  (line    6)
* MultiLineString():                     gis-mysql-specific-functions.
                                                             (line   46)
* MultiLineStringFromText():             gis-wkt-functions.  (line   32)
* MultiLineStringFromWKB():              gis-wkb-functions.  (line   39)
* multiple servers:                      multiple-servers.   (line   13)
* multiple-part index:                   create-index.       (line    6)
* multiplication (*):                    arithmetic-functions.
                                                             (line   86)
* MULTIPOINT data type:                  spatial-datatypes.  (line    6)
* MultiPoint():                          gis-mysql-specific-functions.
                                                             (line   51)
* MultiPointFromText():                  gis-wkt-functions.  (line   37)
* MultiPointFromWKB():                   gis-wkb-functions.  (line   44)
* MULTIPOLYGON data type:                spatial-datatypes.  (line    6)
* MultiPolygon():                        gis-mysql-specific-functions.
                                                             (line   56)
* MultiPolygonFromText():                gis-wkt-functions.  (line   42)
* MultiPolygonFromWKB():                 gis-wkb-functions.  (line   49)
* MVCC (multi-version concurrency control): innodb-multi-versioning.
                                                             (line    6)
* My, derivation:                        history.            (line    6)
* my.cnf file:                           replication-features.
                                                             (line   46)
* my.cnf, and MySQL Cluster <1>:         mysql-cluster-config-example.
                                                             (line    6)
* my.cnf, and MySQL Cluster <2>:         mysql-cluster-config-file.
                                                             (line   22)
* my.cnf, and MySQL Cluster:             mysql-cluster-install-configuration.
                                                             (line    6)
* my.cnf, in MySQL Cluster:              mysql-cluster-mysqld.
                                                             (line   49)
* my_bool C type:                        c-api-data-structures.
                                                             (line   65)
* my_bool values, printing:              c-api-data-structures.
                                                             (line   65)
* my_init():                             my-init.            (line    6)
* my_print_defaults <1>:                 my-print-defaults.  (line    6)
* my_print_defaults:                     programs-overview.  (line  267)
* my_print_defaults, config-file option: my-print-defaults.  (line   30)
* my_print_defaults, debug option:       my-print-defaults.  (line   36)
* my_print_defaults, defaults-extra-file option: my-print-defaults.
                                                             (line   42)
* my_print_defaults, defaults-file option: my-print-defaults.
                                                             (line   32)
* my_print_defaults, defaults-group-suffix option: my-print-defaults.
                                                             (line   49)
* my_print_defaults, extra-file option:  my-print-defaults.  (line   44)
* my_print_defaults, help option:        my-print-defaults.  (line   26)
* my_print_defaults, no-defaults option: my-print-defaults.  (line   54)
* my_print_defaults, verbose option:     my-print-defaults.  (line   58)
* my_print_defaults, version option:     my-print-defaults.  (line   62)
* my_ulonglong C type:                   c-api-data-structures.
                                                             (line   50)
* my_ulonglong values, printing:         c-api-data-structures.
                                                             (line   50)
* mycnf option, ndb_config:              mysql-cluster-programs-ndb-config.
                                                             (line  232)
* mycnf option, ndb_mgmd:                mysql-cluster-programs-ndb-mgmd.
                                                             (line  311)
* MyISAM key cache:                      myisam-key-cache.   (line   15)
* MyISAM storage engine <1>:             myisam-storage-engine.
                                                             (line   13)
* MyISAM storage engine:                 storage-engines.    (line   23)
* MyISAM, compressed tables <1>:         compressed-format.  (line    6)
* MyISAM, compressed tables:             myisampack.         (line    6)
* MyISAM, converting tables to InnoDB:   converting-tables-to-innodb.
                                                             (line    6)
* myisam-block-size option, mysqld:      server-options.     (line 1368)
* myisam-recover option, mysqld <1>:     myisam-start.       (line   38)
* myisam-recover option, mysqld:         server-options.     (line 1383)
* myisam_block_size myisamchk variable:  myisamchk-general-options.
                                                             (line   84)
* myisam_data_pointer_size system variable: server-system-variables.
                                                             (line 3349)
* myisam_ftdump <1>:                     myisam-ftdump.      (line    6)
* myisam_ftdump:                         programs-overview.  (line  170)
* myisam_ftdump, count option:           myisam-ftdump.      (line   67)
* myisam_ftdump, dump option:            myisam-ftdump.      (line   71)
* myisam_ftdump, help option:            myisam-ftdump.      (line   63)
* myisam_ftdump, length option:          myisam-ftdump.      (line   75)
* myisam_ftdump, stats option:           myisam-ftdump.      (line   79)
* myisam_ftdump, verbose option:         myisam-ftdump.      (line   84)
* myisam_max_sort_file_size system variable: server-system-variables.
                                                             (line 3371)
* myisam_mmap_size system variable:      server-system-variables.
                                                             (line 3404)
* myisam_recover_options system variable: server-system-variables.
                                                             (line 3429)
* myisam_repair_threads system variable: server-system-variables.
                                                             (line 3441)
* myisam_sort_buffer_size myisamchk variable: myisamchk-general-options.
                                                             (line   84)
* myisam_sort_buffer_size system variable: server-system-variables.
                                                             (line 3468)
* myisam_stats_method system variable:   server-system-variables.
                                                             (line 3496)
* myisam_use_mmap system variable:       server-system-variables.
                                                             (line 3532)
* myisamchk <1>:                         myisamchk.          (line   15)
* myisamchk:                             programs-overview.  (line  175)
* myisamchk, analyze option:             myisamchk-other-options.
                                                             (line    9)
* myisamchk, backup option:              myisamchk-repair-options.
                                                             (line   10)
* myisamchk, block-search option:        myisamchk-other-options.
                                                             (line   18)
* myisamchk, character-sets-dir option:  myisamchk-repair-options.
                                                             (line   14)
* myisamchk, check option:               myisamchk-check-options.
                                                             (line    9)
* myisamchk, check-only-changed option:  myisamchk-check-options.
                                                             (line   14)
* myisamchk, correct-checksum option:    myisamchk-repair-options.
                                                             (line   19)
* myisamchk, data-file-length option:    myisamchk-repair-options.
                                                             (line   23)
* myisamchk, debug option:               myisamchk-general-options.
                                                             (line   21)
* myisamchk, defaults-extra-file option: myisamchk-general-options.
                                                             (line   26)
* myisamchk, defaults-file option:       myisamchk-general-options.
                                                             (line   33)
* myisamchk, defaults-group-suffix option: myisamchk-general-options.
                                                             (line   39)
* myisamchk, description option:         myisamchk-other-options.
                                                             (line   22)
* myisamchk, example output:             myisamchk-table-info.
                                                             (line    6)
* myisamchk, extend-check option <1>:    myisamchk-repair-options.
                                                             (line   28)
* myisamchk, extend-check option:        myisamchk-check-options.
                                                             (line   18)
* myisamchk, fast option:                myisamchk-check-options.
                                                             (line   35)
* myisamchk, force option <1>:           myisamchk-repair-options.
                                                             (line   40)
* myisamchk, force option:               myisamchk-check-options.
                                                             (line   39)
* myisamchk, HELP option:                myisamchk-general-options.
                                                             (line   16)
* myisamchk, help option:                myisamchk-general-options.
                                                             (line   11)
* myisamchk, information option:         myisamchk-check-options.
                                                             (line   45)
* myisamchk, keys-used option:           myisamchk-repair-options.
                                                             (line   45)
* myisamchk, max-record-length option:   myisamchk-repair-options.
                                                             (line   61)
* myisamchk, medium-check option:        myisamchk-check-options.
                                                             (line   49)
* myisamchk, no-defaults option:         myisamchk-general-options.
                                                             (line   47)
* myisamchk, no-symlinks option:         myisamchk-repair-options.
                                                             (line   54)
* myisamchk, options:                    myisamchk-general-options.
                                                             (line    6)
* myisamchk, parallel-recover option:    myisamchk-repair-options.
                                                             (line   66)
* myisamchk, print-defaults option:      myisamchk-general-options.
                                                             (line   53)
* myisamchk, quick option:               myisamchk-repair-options.
                                                             (line   72)
* myisamchk, read-only option:           myisamchk-check-options.
                                                             (line   55)
* myisamchk, recover option:             myisamchk-repair-options.
                                                             (line   79)
* myisamchk, safe-recover option:        myisamchk-repair-options.
                                                             (line   92)
* myisamchk, set-auto-increment[ option: myisamchk-other-options.
                                                             (line   28)
* myisamchk, set-character-set option:   myisamchk-repair-options.
                                                             (line  105)
* myisamchk, set-collation option:       myisamchk-repair-options.
                                                             (line  110)
* myisamchk, silent option:              myisamchk-general-options.
                                                             (line   58)
* myisamchk, sort-index option:          myisamchk-other-options.
                                                             (line   36)
* myisamchk, sort-records option:        myisamchk-other-options.
                                                             (line   41)
* myisamchk, sort-recover option:        myisamchk-repair-options.
                                                             (line  116)
* myisamchk, tmpdir option:              myisamchk-repair-options.
                                                             (line  121)
* myisamchk, unpack option:              myisamchk-repair-options.
                                                             (line  131)
* myisamchk, update-state option:        myisamchk-check-options.
                                                             (line   62)
* myisamchk, verbose option:             myisamchk-general-options.
                                                             (line   63)
* myisamchk, version option:             myisamchk-general-options.
                                                             (line   69)
* myisamchk, wait option:                myisamchk-general-options.
                                                             (line   73)
* myisamlog <1>:                         myisamlog.          (line    6)
* myisamlog:                             programs-overview.  (line  180)
* myisampack <1>:                        compressed-format.  (line    6)
* myisampack <2>:                        silent-column-changes.
                                                             (line   72)
* myisampack <3>:                        myisampack.         (line    6)
* myisampack:                            programs-overview.  (line  185)
* myisampack, backup option:             myisampack.         (line   55)
* myisampack, character-sets-dir option: myisampack.         (line   60)
* myisampack, debug option:              myisampack.         (line   65)
* myisampack, force option:              myisampack.         (line   70)
* myisampack, help option:               myisampack.         (line   51)
* myisampack, join option:               myisampack.         (line   82)
* myisampack, silent option:             myisampack.         (line   97)
* myisampack, test option:               myisampack.         (line  101)
* myisampack, tmpdir option:             myisampack.         (line  105)
* myisampack, verbose option:            myisampack.         (line  110)
* myisampack, version option:            myisampack.         (line  115)
* myisampack, wait option:               myisampack.         (line  119)
* mysql <1>:                             mysql.              (line   15)
* mysql:                                 programs-overview.  (line  124)
* mysql \. (command for reading from text files) <1>: mysql-batch-commands.
                                                             (line    6)
* mysql \. (command for reading from text files): batch-mode.
                                                             (line   97)
* MySQL binary distribution:             which-version.      (line   18)
* MYSQL C type:                          c-api-data-structures.
                                                             (line   10)
* MySQL Cluster:                         mysql-cluster.      (line   16)
* MySQL Cluster Disk Data:               mysql-cluster-disk-data.
                                                             (line   12)
* MySQL Cluster Disk Data, creating log file groups: mysql-cluster-disk-data-objects.
                                                             (line   63)
* MySQL Cluster Disk Data, creating tables: mysql-cluster-disk-data-objects.
                                                             (line   43)
* MySQL Cluster Disk Data, creating tablespaces: mysql-cluster-disk-data-objects.
                                                             (line  129)
* MySQL Cluster Disk Data, dropping Disk Data objects: mysql-cluster-disk-data-objects.
                                                             (line  257)
* MySQL Cluster Disk Data, storage requirements: mysql-cluster-disk-data-storage-requirements.
                                                             (line    6)
* MySQL Cluster How-To:                  mysql-cluster-installation.
                                                             (line   16)
* MySQL Cluster in MySQL 5.1:            mysql-cluster-development.
                                                             (line   16)
* MySQL Cluster limitations:             mysql-cluster-limitations.
                                                             (line   20)
* MySQL Cluster limitations, and differences from standard MySQL limits: mysql-cluster-limitations-limits.
                                                             (line    6)
* MySQL Cluster limitations, autodiscovery: mysql-cluster-limitations-resolved.
                                                             (line   53)
* MySQL Cluster limitations, binary logging: mysql-cluster-limitations-exclusive-to-cluster.
                                                             (line   22)
* MySQL Cluster limitations, character sets: mysql-cluster-limitations-resolved.
                                                             (line   84)
* MySQL Cluster limitations, CREATE TABLE statements: mysql-cluster-limitations-resolved.
                                                             (line  133)
* MySQL Cluster limitations, database objects: mysql-cluster-limitations-database-objects.
                                                             (line    6)
* MySQL Cluster limitations, Disk Data storage: mysql-cluster-limitations-disk-data.
                                                             (line    6)
* MySQL Cluster limitations, error handling and reporting: mysql-cluster-limitations-error-handling.
                                                             (line    6)
* MySQL Cluster limitations, geometry data types: mysql-cluster-limitations-syntax.
                                                             (line   86)
* MySQL Cluster limitations, implementation: mysql-cluster-limitations-exclusive-to-cluster.
                                                             (line    6)
* MySQL Cluster limitations, imposed by configuration: mysql-cluster-limitations-limits.
                                                             (line   39)
* MySQL Cluster limitations, INSERT IGNORE, UPDATE IGNORE, and REPLACE statements: mysql-cluster-limitations-resolved.
                                                             (line  139)
* MySQL Cluster limitations, memory usage and transaction handling: mysql-cluster-limitations-transactions.
                                                             (line  112)
* MySQL Cluster limitations, multiple data nodes <1>: mysql-cluster-limitations-resolved.
                                                             (line  108)
* MySQL Cluster limitations, multiple data nodes: mysql-cluster-development-5-1-ndb-6-2.
                                                             (line  140)
* MySQL Cluster limitations, multiple management servers <1>: mysql-cluster-limitations-resolved.
                                                             (line   94)
* MySQL Cluster limitations, multiple management servers: mysql-cluster-limitations-multiple-nodes.
                                                             (line   29)
* MySQL Cluster limitations, multiple MySQL servers: mysql-cluster-limitations-multiple-nodes.
                                                             (line    8)
* MySQL Cluster limitations, partitioning: mysql-cluster-limitations-syntax.
                                                             (line  106)
* MySQL Cluster limitations, performance: mysql-cluster-limitations-performance.
                                                             (line    6)
* MySQL Cluster limitations, replication <1>: mysql-cluster-limitations-resolved.
                                                             (line   35)
* MySQL Cluster limitations, replication: mysql-cluster-limitations-syntax.
                                                             (line  160)
* MySQL Cluster limitations, resolved in current version from previous versions: mysql-cluster-limitations-resolved.
                                                             (line    6)
* MySQL Cluster limitations, syntax:     mysql-cluster-limitations-syntax.
                                                             (line    6)
* MySQL Cluster limitations, transactions: mysql-cluster-limitations-transactions.
                                                             (line    6)
* MySQL Cluster limitations, unsupported features: mysql-cluster-limitations-unsupported.
                                                             (line    6)
* MySQL Cluster Manager, and ndb_mgm:    mysql-cluster-mgm-client-commands.
                                                             (line   17)
* MySQL Cluster NDB 6.x:                 mysql-cluster-development.
                                                             (line   16)
* MySQL Cluster NDB 7.x:                 mysql-cluster-development.
                                                             (line   16)
* MySQL Cluster processes:               mysql-cluster-programs.
                                                             (line   35)
* MySQL Cluster programs:                mysql-cluster-programs.
                                                             (line   35)
* MySQL Cluster replication:             mysql-cluster-replication.
                                                             (line   20)
* MySQL Cluster replication, and -initial option: mysql-cluster-replication-issues.
                                                             (line  206)
* MySQL Cluster replication, and auto_increment* variables: mysql-cluster-replication-issues.
                                                             (line  217)
* MySQL Cluster replication, and circular replication: mysql-cluster-replication-issues.
                                                             (line   74)
* MySQL Cluster replication, and multibyte character sets: mysql-cluster-replication-issues.
                                                             (line   67)
* MySQL Cluster Replication, and NDB API _slave status variables: mysql-cluster-replication.
                                                             (line   63)
* MySQL Cluster replication, and primary key: mysql-cluster-replication-issues.
                                                             (line  139)
* MySQL Cluster replication, and single point of failure: mysql-cluster-replication-two-channels.
                                                             (line    6)
* MySQL Cluster replication, and unique keys: mysql-cluster-replication-issues.
                                                             (line  150)
* MySQL Cluster replication, backups:    mysql-cluster-replication-backups.
                                                             (line   11)
* MySQL Cluster replication, circular replication: mysql-cluster-replication-multi-master.
                                                             (line    6)
* MySQL Cluster replication, concepts <1>: mysql-cluster-replication-general.
                                                             (line    6)
* MySQL Cluster replication, concepts:   mysql-cluster-replication-abbreviations.
                                                             (line    6)
* MySQL Cluster replication, conflict resolution: mysql-cluster-replication-conflict-resolution.
                                                             (line    6)
* MySQL Cluster replication, failover <1>: mysql-cluster-replication-failover.
                                                             (line    6)
* MySQL Cluster replication, failover:   mysql-cluster-replication-two-channels.
                                                             (line    6)
* MySQL Cluster replication, gap event:  mysql-cluster-replication-issues.
                                                             (line   35)
* MySQL Cluster replication, known issues: mysql-cluster-replication-issues.
                                                             (line    6)
* MySQL Cluster replication, loss of connection: mysql-cluster-replication-issues.
                                                             (line   12)
* MySQL Cluster replication, multi-master replication: mysql-cluster-replication-multi-master.
                                                             (line    6)
* MySQL Cluster replication, point-in-time recovery: mysql-cluster-replication-pitr.
                                                             (line    6)
* MySQL Cluster replication, preparing:  mysql-cluster-replication-preparation.
                                                             (line    6)
* MySQL Cluster replication, requirements: mysql-cluster-replication-general.
                                                             (line    6)
* MySQL Cluster replication, reset-slave.pl backup automation script: mysql-cluster-replication-auto-sync.
                                                             (line   11)
* MySQL Cluster replication, restoring from backup: mysql-cluster-replication-backups.
                                                             (line   11)
* MySQL Cluster replication, starting:   mysql-cluster-replication-starting.
                                                             (line    6)
* MySQL Cluster replication, storage engines other than NDB on slave: mysql-cluster-replication-issues.
                                                             (line  261)
* MySQL Cluster replication, synchronization of master and slave: mysql-cluster-replication-auto-sync.
                                                             (line    6)
* MySQL Cluster replication, system tables used: mysql-cluster-replication-schema.
                                                             (line    6)
* MySQL Cluster, "quick" configuration:  mysql-cluster-quick.
                                                             (line    6)
* MySQL Cluster, administration <1>:     mysql-cluster-log-statistics.
                                                             (line    6)
* MySQL Cluster, administration <2>:     mysql-cluster-mgm-client-commands.
                                                             (line    6)
* MySQL Cluster, administration <3>:     mysql-cluster-program-options-common.
                                                             (line    6)
* MySQL Cluster, administration <4>:     mysql-cluster-programs-ndb-mgm.
                                                             (line    6)
* MySQL Cluster, administration <5>:     mysql-cluster-programs-ndb-mgmd.
                                                             (line   12)
* MySQL Cluster, administration <6>:     mysql-cluster-programs-ndbd.
                                                             (line   17)
* MySQL Cluster, administration:         mysql-cluster-program-options-mysqld.
                                                             (line    6)
* MySQL Cluster, and application feature requirements: mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* MySQL Cluster, and character sets:     mysql-cluster-replication-issues.
                                                             (line   67)
* MySQL Cluster, and DNS:                mysql-cluster-installation.
                                                             (line   61)
* MySQL Cluster, and INFORMATION_SCHEMA: mysql-cluster-security-mysql-privileges.
                                                             (line  120)
* MySQL Cluster, and IP addressing:      mysql-cluster-installation.
                                                             (line   61)
* MySQL Cluster, and MySQL privileges:   mysql-cluster-security-mysql-privileges.
                                                             (line    6)
* MySQL Cluster, and MySQL root user <1>: mysql-cluster-security-mysql-security-procedures.
                                                             (line   51)
* MySQL Cluster, and MySQL root user:    mysql-cluster-security-mysql-privileges.
                                                             (line   52)
* MySQL Cluster, and networking:         mysql-cluster-overview-requirements.
                                                             (line    6)
* MySQL Cluster, and transactions <1>:   faqs-mysql-cluster. (line    6)
* MySQL Cluster, and transactions:       mysql-cluster-ndbd-definition.
                                                             (line  440)
* MySQL Cluster, and virtual machines:   faqs-mysql-cluster. (line    6)
* MySQL Cluster, API node <1>:           mysql-cluster-api-definition.
                                                             (line    6)
* MySQL Cluster, API node:               mysql-cluster-basics.
                                                             (line    6)
* MySQL Cluster, applications supported: mysql-cluster-ndb-innodb-workloads.
                                                             (line    6)
* MySQL Cluster, arbitrator:             faqs-mysql-cluster. (line    6)
* MySQL Cluster, availability:           mysql-cluster-compared.
                                                             (line   36)
* MySQL Cluster, available platforms:    mysql-cluster.      (line   72)
* MySQL Cluster, BACKUP Events:          mysql-cluster-log-events.
                                                             (line  297)
* MySQL Cluster, backups <1>:            mysql-cluster-backup-troubleshooting.
                                                             (line    6)
* MySQL Cluster, backups <2>:            mysql-cluster-backup-configuration.
                                                             (line    6)
* MySQL Cluster, backups <3>:            mysql-cluster-backup-using-management-client.
                                                             (line    6)
* MySQL Cluster, backups <4>:            mysql-cluster-backup-concepts.
                                                             (line    6)
* MySQL Cluster, backups <5>:            mysql-cluster-backup.
                                                             (line   13)
* MySQL Cluster, backups:                mysql-cluster-programs-ndb-restore.
                                                             (line    6)
* MySQL Cluster, benchmarks:             mysql-cluster-interconnects-performance.
                                                             (line    6)
* MySQL Cluster, CHECKPOINT Events:      mysql-cluster-log-events.
                                                             (line   42)
* MySQL Cluster, cluster logs <1>:       mysql-cluster-logging-management-commands.
                                                             (line    6)
* MySQL Cluster, cluster logs:           mysql-cluster-event-reports.
                                                             (line   12)
* MySQL Cluster, CLUSTERLOG commands:    mysql-cluster-logging-management-commands.
                                                             (line   12)
* MySQL Cluster, CLUSTERLOG STATISTICS command: mysql-cluster-log-statistics.
                                                             (line    6)
* MySQL Cluster, commands <1>:           mysql-cluster-mgm-client-commands.
                                                             (line    6)
* MySQL Cluster, commands <2>:           mysql-cluster-programs-ndb-mgm.
                                                             (line   29)
* MySQL Cluster, commands <3>:           mysql-cluster-programs-ndb-mgmd.
                                                             (line   12)
* MySQL Cluster, commands <4>:           mysql-cluster-programs-ndbd.
                                                             (line   17)
* MySQL Cluster, commands:               mysql-cluster-program-options-mysqld.
                                                             (line    6)
* MySQL Cluster, compared to InnoDB <1>: mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* MySQL Cluster, compared to InnoDB <2>: mysql-cluster-ndb-innodb-workloads.
                                                             (line    6)
* MySQL Cluster, compared to InnoDB <3>: mysql-cluster-ndb-innodb-engines.
                                                             (line    6)
* MySQL Cluster, compared to InnoDB:     mysql-cluster-compared.
                                                             (line   12)
* MySQL Cluster, compared to standalone MySQL Server <1>: mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* MySQL Cluster, compared to standalone MySQL Server <2>: mysql-cluster-ndb-innodb-workloads.
                                                             (line    6)
* MySQL Cluster, compared to standalone MySQL Server <3>: mysql-cluster-ndb-innodb-engines.
                                                             (line    6)
* MySQL Cluster, compared to standalone MySQL Server: mysql-cluster-compared.
                                                             (line   12)
* MySQL Cluster, compiling with icc:     porting.            (line   32)
* MySQL Cluster, concepts:               mysql-cluster-basics.
                                                             (line    6)
* MySQL Cluster, configuration <1>:      mysql-cluster-mysqld.
                                                             (line   49)
* MySQL Cluster, configuration <2>:      mysql-cluster-programs-ndb-mgmd.
                                                             (line  641)
* MySQL Cluster, configuration <3>:      mysql-cluster-config-lcp-params.
                                                             (line    6)
* MySQL Cluster, configuration <4>:      mysql-cluster-api-definition.
                                                             (line    6)
* MySQL Cluster, configuration <5>:      mysql-cluster-ndbd-definition.
                                                             (line    6)
* MySQL Cluster, configuration <6>:      mysql-cluster-mgm-definition.
                                                             (line    6)
* MySQL Cluster, configuration <7>:      mysql-cluster-computer-definition.
                                                             (line    6)
* MySQL Cluster, configuration <8>:      mysql-cluster-quick.
                                                             (line    6)
* MySQL Cluster, configuration <9>:      mysql-cluster-configuration.
                                                             (line   14)
* MySQL Cluster, configuration:          mysql-cluster-installation.
                                                             (line   16)
* MySQL Cluster, configuration (example): mysql-cluster-config-example.
                                                             (line    6)
* MySQL Cluster, configuration changes:  mysql-cluster-rolling-restart.
                                                             (line   20)
* MySQL Cluster, configuration files <1>: mysql-cluster-config-file.
                                                             (line   22)
* MySQL Cluster, configuration files:    mysql-cluster-install-configuration.
                                                             (line    6)
* MySQL Cluster, configuration parameters <1>: mysql-cluster-params-other.
                                                             (line    6)
* MySQL Cluster, configuration parameters <2>: mysql-cluster-params-api.
                                                             (line    6)
* MySQL Cluster, configuration parameters <3>: mysql-cluster-params-mgmd.
                                                             (line    6)
* MySQL Cluster, configuration parameters <4>: mysql-cluster-params-ndbd.
                                                             (line    6)
* MySQL Cluster, configuration parameters: mysql-cluster-params-overview.
                                                             (line   13)
* MySQL Cluster, configuring:            mysql-cluster-backup-configuration.
                                                             (line    6)
* MySQL Cluster, CONNECTION Events:      mysql-cluster-log-events.
                                                             (line   22)
* MySQL Cluster, connection string:      mysql-cluster-connection-strings.
                                                             (line    6)
* MySQL Cluster, CREATE NODEGROUP command: mysql-cluster-mgm-client-commands.
                                                             (line  210)
* MySQL Cluster, creating large tables:  create-table.       (line  879)
* MySQL Cluster, data node <1>:          mysql-cluster-ndbd-definition.
                                                             (line    6)
* MySQL Cluster, data node:              mysql-cluster-basics.
                                                             (line    6)
* MySQL Cluster, data nodes <1>:         mysql-cluster-programs-ndbmtd.
                                                             (line    6)
* MySQL Cluster, data nodes:             mysql-cluster-programs-ndbd.
                                                             (line    6)
* MySQL Cluster, data types supported:   faqs-mysql-cluster. (line    6)
* MySQL Cluster, defining node hosts:    mysql-cluster-computer-definition.
                                                             (line    6)
* MySQL Cluster, direct connections between nodes: mysql-cluster-tcp-definition-direct.
                                                             (line    6)
* MySQL Cluster, Disk Data tables:       mysql-cluster-disk-data.
                                                             (line   12)
* MySQL Cluster, DROP NODEGROUP command: mysql-cluster-mgm-client-commands.
                                                             (line  233)
* MySQL Cluster, ENTER SINGLE USER MODE command: mysql-cluster-mgm-client-commands.
                                                             (line  177)
* MySQL Cluster, ERROR Events:           mysql-cluster-log-events.
                                                             (line  250)
* MySQL Cluster, error logs:             mysql-cluster-programs-ndbd.
                                                             (line  473)
* MySQL Cluster, error messages:         faqs-mysql-cluster. (line    6)
* MySQL Cluster, event log format:       mysql-cluster-log-events.
                                                             (line    6)
* MySQL Cluster, event logging thresholds: mysql-cluster-logging-management-commands.
                                                             (line   38)
* MySQL Cluster, event logs <1>:         mysql-cluster-logging-management-commands.
                                                             (line    6)
* MySQL Cluster, event logs:             mysql-cluster-event-reports.
                                                             (line   12)
* MySQL Cluster, event severity levels:  mysql-cluster-logging-management-commands.
                                                             (line   62)
* MySQL Cluster, event types <1>:        mysql-cluster-log-events.
                                                             (line   22)
* MySQL Cluster, event types:            mysql-cluster-event-reports.
                                                             (line   49)
* MySQL Cluster, execution threads:      mysql-cluster-ndbd-definition.
                                                             (line 3700)
* MySQL Cluster, EXIT command:           mysql-cluster-mgm-client-commands.
                                                             (line  195)
* MySQL Cluster, EXIT SINGLE USER MODE command: mysql-cluster-mgm-client-commands.
                                                             (line  185)
* MySQL Cluster, FAQ:                    faqs-mysql-cluster. (line    6)
* MySQL Cluster, features added in MySQL 5.1: mysql-cluster-development-5-1.
                                                             (line    6)
* MySQL Cluster, GCP Stop errors:        mysql-cluster-ndbd-definition.
                                                             (line 4263)
* MySQL Cluster, general description:    mysql-cluster-overview.
                                                             (line   15)
* MySQL Cluster, hardware requirements:  faqs-mysql-cluster. (line    6)
* MySQL Cluster, HELP command:           mysql-cluster-mgm-client-commands.
                                                             (line   34)
* MySQL Cluster, HostName parameter, and security: mysql-cluster-security-networking-issues.
                                                             (line   40)
* MySQL Cluster, how to obtain:          faqs-mysql-cluster. (line    6)
* MySQL Cluster, importing existing tables: faqs-mysql-cluster.
                                                             (line    6)
* MySQL Cluster, INFO Events:            mysql-cluster-log-events.
                                                             (line  269)
* MySQL Cluster, information sources:    mysql-cluster.      (line  218)
* MySQL Cluster, insecurity of communication protocols: mysql-cluster-security-networking-issues.
                                                             (line   12)
* MySQL Cluster, installation:           mysql-cluster-installation.
                                                             (line   16)
* MySQL Cluster, installation (Linux):   mysql-cluster-install-linux.
                                                             (line   12)
* MySQL Cluster, installation (Windows): mysql-cluster-install-windows.
                                                             (line   13)
* MySQL Cluster, installing binary (Windows): mysql-cluster-install-windows-binary.
                                                             (line    6)
* MySQL Cluster, installing binary release (Linux): mysql-cluster-install-linux-binary.
                                                             (line    6)
* MySQL Cluster, installing from source (Linux): mysql-cluster-install-linux-source.
                                                             (line    6)
* MySQL Cluster, installing from source (Windows): mysql-cluster-install-windows-source.
                                                             (line    6)
* MySQL Cluster, installing RPM (Linux): mysql-cluster-install-linux-rpm.
                                                             (line    6)
* MySQL Cluster, interconnects:          mysql-cluster-interconnects.
                                                             (line   11)
* MySQL Cluster, Java clients:           mysql-cluster-basics.
                                                             (line  116)
* MySQL Cluster, log files <1>:          mysql-cluster-programs-ndbmtd.
                                                             (line   67)
* MySQL Cluster, log files:              mysql-cluster-programs-ndbd.
                                                             (line  464)
* MySQL Cluster, logging commands:       mysql-cluster-logging-management-commands.
                                                             (line    6)
* MySQL Cluster, management client (ndb_mgm): mysql-cluster-programs-ndb-mgm.
                                                             (line    6)
* MySQL Cluster, management commands:    mysql-cluster-log-statistics.
                                                             (line    6)
* MySQL Cluster, management node <1>:    mysql-cluster-mgm-definition.
                                                             (line    6)
* MySQL Cluster, management node:        mysql-cluster-basics.
                                                             (line    6)
* MySQL Cluster, management nodes:       mysql-cluster-programs-ndb-mgmd.
                                                             (line    6)
* MySQL Cluster, managing:               mysql-cluster-management.
                                                             (line   24)
* MySQL Cluster, master node:            faqs-mysql-cluster. (line    6)
* MySQL Cluster, MAX_ROWS:               create-table.       (line  879)
* MySQL Cluster, memory requirements:    faqs-mysql-cluster. (line    6)
* MySQL Cluster, memory usage and recovery <1>: mysql-cluster-rolling-restart.
                                                             (line   64)
* MySQL Cluster, memory usage and recovery: mysql-cluster-limitations-limits.
                                                             (line    9)
* MySQL Cluster, mgm:                    mysql-cluster-program-options-common.
                                                             (line    6)
* MySQL Cluster, mgm client:             mysql-cluster-mgm-client-commands.
                                                             (line    6)
* MySQL Cluster, mgm management client:  mysql-cluster-log-statistics.
                                                             (line    6)
* MySQL Cluster, mgm process:            mysql-cluster-programs-ndb-mgm.
                                                             (line   29)
* MySQL Cluster, mgmd:                   mysql-cluster-program-options-common.
                                                             (line    6)
* MySQL Cluster, mgmd process:           mysql-cluster-programs-ndb-mgmd.
                                                             (line   12)
* MySQL Cluster, monitoring:             mysql-cluster-ndb-api-statistics.
                                                             (line    6)
* MySQL Cluster, multiple management servers: mysql-cluster-rolling-restart.
                                                             (line  174)
* MySQL Cluster, mysqld options and variables for: mysql-cluster-options-variables.
                                                             (line   13)
* MySQL Cluster, mysqld process <1>:     mysql-cluster-mysqld.
                                                             (line    6)
* MySQL Cluster, mysqld process:         mysql-cluster-program-options-mysqld.
                                                             (line    6)
* MySQL Cluster, ndb_mgm <1>:            mysql-cluster-programs-ndb-mgm.
                                                             (line    6)
* MySQL Cluster, ndb_mgm:                mysql-cluster-install-first-start.
                                                             (line   36)
* MySQL Cluster, ndb_mgmd process:       mysql-cluster-programs-ndb-mgmd.
                                                             (line    6)
* MySQL Cluster, ndb_size.pl (utility):  faqs-mysql-cluster. (line    6)
* MySQL Cluster, ndbd <1>:               mysql-cluster-program-options-common.
                                                             (line    6)
* MySQL Cluster, ndbd:                   mysql-cluster-programs-ndbd.
                                                             (line    6)
* MySQL Cluster, ndbd process <1>:       mysql-cluster-log-statistics.
                                                             (line  164)
* MySQL Cluster, ndbd process:           mysql-cluster-programs-ndbd.
                                                             (line   17)
* MySQL Cluster, ndbinfo_select_all:     mysql-cluster-programs-ndbinfo-select-all.
                                                             (line    6)
* MySQL Cluster, ndbmtd:                 mysql-cluster-programs-ndbmtd.
                                                             (line    6)
* MySQL Cluster, network configuration, and security: mysql-cluster-security-networking-issues.
                                                             (line   59)
* MySQL Cluster, network transporters <1>: mysql-cluster-sci-sockets.
                                                             (line    6)
* MySQL Cluster, network transporters:   mysql-cluster-interconnects.
                                                             (line   11)
* MySQL Cluster, networking <1>:         mysql-cluster-sci-definition.
                                                             (line    6)
* MySQL Cluster, networking <2>:         mysql-cluster-shm-definition.
                                                             (line    6)
* MySQL Cluster, networking:             mysql-cluster-tcp-definition-direct.
                                                             (line    6)
* MySQL Cluster, networking requirements: faqs-mysql-cluster.
                                                             (line    6)
* MySQL Cluster, node failure (single user mode): mysql-cluster-single-user-mode.
                                                             (line   54)
* MySQL Cluster, node identifiers <1>:   mysql-cluster-sci-definition.
                                                             (line   26)
* MySQL Cluster, node identifiers:       mysql-cluster-shm-definition.
                                                             (line   25)
* MySQL Cluster, node logs:              mysql-cluster-event-reports.
                                                             (line   12)
* MySQL Cluster, node types:             faqs-mysql-cluster. (line    6)
* MySQL Cluster, NODERESTART Events:     mysql-cluster-log-events.
                                                             (line  118)
* MySQL Cluster, nodes and node groups:  mysql-cluster-nodes-groups.
                                                             (line    6)
* MySQL Cluster, nodes and types:        mysql-cluster-basics.
                                                             (line    6)
* MySQL Cluster, number of computers required: faqs-mysql-cluster.
                                                             (line    6)
* MySQL Cluster, partitioning support:   mysql-cluster-limitations-syntax.
                                                             (line  106)
* MySQL Cluster, partitions:             mysql-cluster-nodes-groups.
                                                             (line    6)
* MySQL Cluster, performance:            mysql-cluster-interconnects-performance.
                                                             (line    6)
* MySQL Cluster, performing queries:     mysql-cluster-install-example-data.
                                                             (line    6)
* MySQL Cluster, platforms supported:    faqs-mysql-cluster. (line    6)
* MySQL Cluster, preparing for replication: mysql-cluster-replication-preparation.
                                                             (line    6)
* MySQL Cluster, process management:     mysql-cluster-programs.
                                                             (line   35)
* MySQL Cluster, QUIT command:           mysql-cluster-mgm-client-commands.
                                                             (line  195)
* MySQL Cluster, replicas:               mysql-cluster-nodes-groups.
                                                             (line    6)
* MySQL Cluster, replication:            mysql-cluster-replication.
                                                             (line   20)
* MySQL Cluster, REPORT command:         mysql-cluster-mgm-client-commands.
                                                             (line  140)
* MySQL Cluster, requirements:           mysql-cluster-overview-requirements.
                                                             (line    6)
* MySQL Cluster, resetting:              mysql-cluster-rolling-restart.
                                                             (line   38)
* MySQL Cluster, RESTART command:        mysql-cluster-mgm-client-commands.
                                                             (line  101)
* MySQL Cluster, restarting:             mysql-cluster-install-shutdown-restart.
                                                             (line    6)
* MySQL Cluster, restoring backups:      mysql-cluster-programs-ndb-restore.
                                                             (line    6)
* MySQL Cluster, roles of computers:     faqs-mysql-cluster. (line    6)
* MySQL Cluster, rolling restarts (multiple management servers): mysql-cluster-rolling-restart.
                                                             (line  174)
* MySQL Cluster, runtime statistics:     mysql-cluster-log-statistics.
                                                             (line    6)
* MySQL Cluster, SCHEMA Events:          mysql-cluster-log-events.
                                                             (line  239)
* MySQL Cluster, SCI (Scalable Coherent Interface) <1>: mysql-cluster-sci-sockets.
                                                             (line    6)
* MySQL Cluster, SCI (Scalable Coherent Interface): mysql-cluster-sci-definition.
                                                             (line    6)
* MySQL Cluster, security <1>:           faqs-mysql-cluster. (line    6)
* MySQL Cluster, security:               mysql-cluster-security.
                                                             (line   12)
* MySQL Cluster, security procedures:    mysql-cluster-security-mysql-security-procedures.
                                                             (line    6)
* MySQL Cluster, security, and firewalls: mysql-cluster-security-networking-issues.
                                                             (line   98)
* MySQL Cluster, security, and HostName parameter: mysql-cluster-security-networking-issues.
                                                             (line   40)
* MySQL Cluster, security, and network configuration: mysql-cluster-security-networking-issues.
                                                             (line   59)
* MySQL Cluster, security, and network ports: mysql-cluster-security-networking-issues.
                                                             (line  186)
* MySQL Cluster, security, and remote administration: mysql-cluster-security-networking-issues.
                                                             (line  193)
* MySQL Cluster, security, networking:   mysql-cluster-security-networking-issues.
                                                             (line    6)
* MySQL Cluster, shared memory transport: mysql-cluster-shm-definition.
                                                             (line    6)
* MySQL Cluster, SHOW command:           mysql-cluster-mgm-client-commands.
                                                             (line   38)
* MySQL Cluster, SHUTDOWN command:       mysql-cluster-mgm-client-commands.
                                                             (line  201)
* MySQL Cluster, shutting down:          mysql-cluster-install-shutdown-restart.
                                                             (line    6)
* MySQL Cluster, single user mode <1>:   mysql-cluster-single-user-mode.
                                                             (line    6)
* MySQL Cluster, single user mode:       mysql-cluster-mgm-client-commands.
                                                             (line  177)
* MySQL Cluster, SINGLEUSER Events:      mysql-cluster-log-events.
                                                             (line  287)
* MySQL Cluster, SQL node <1>:           mysql-cluster-api-definition.
                                                             (line    6)
* MySQL Cluster, SQL node:               mysql-cluster-basics.
                                                             (line    6)
* MySQL Cluster, SQL nodes:              mysql-cluster-mysqld.
                                                             (line    6)
* MySQL Cluster, SQL statements:         faqs-mysql-cluster. (line    6)
* MySQL Cluster, SQL statements for monitoring: mysql-cluster-sql-statements.
                                                             (line    6)
* MySQL Cluster, START BACKUP command:   mysql-cluster-replication-backups.
                                                             (line   41)
* MySQL Cluster, START command:          mysql-cluster-mgm-client-commands.
                                                             (line   57)
* MySQL Cluster, start phases (summary): mysql-cluster-start-phases.
                                                             (line    6)
* MySQL Cluster, starting:               mysql-cluster-quick.
                                                             (line    6)
* MySQL Cluster, starting and stopping:  faqs-mysql-cluster. (line    6)
* MySQL Cluster, starting nodes <1>:     mysql-cluster-install-first-start.
                                                             (line    6)
* MySQL Cluster, starting nodes:         mysql-cluster-install-windows-initial-start.
                                                             (line    6)
* MySQL Cluster, starting or restarting: mysql-cluster-start-phases.
                                                             (line    6)
* MySQL Cluster, STARTUP Events:         mysql-cluster-log-events.
                                                             (line   65)
* MySQL Cluster, STATISTICS Events:      mysql-cluster-log-events.
                                                             (line  207)
* MySQL Cluster, STATUS command:         mysql-cluster-mgm-client-commands.
                                                             (line  131)
* MySQL Cluster, status variables:       mysql-cluster-status-variables.
                                                             (line    6)
* MySQL Cluster, STOP command:           mysql-cluster-mgm-client-commands.
                                                             (line   72)
* MySQL Cluster, storage requirements:   storage-requirements.
                                                             (line   42)
* MySQL Cluster, Table is full errors:   faqs-mysql-cluster. (line    6)
* MySQL Cluster, thread states:          mysql-cluster-thread-states.
                                                             (line    6)
* MySQL Cluster, trace files:            mysql-cluster-programs-ndbd.
                                                             (line  506)
* MySQL Cluster, transaction handling:   mysql-cluster-limitations-transactions.
                                                             (line  112)
* MySQL Cluster, transporters, Scalable Coherent Interface (SCI): mysql-cluster-sci-definition.
                                                             (line    6)
* MySQL Cluster, transporters, shared memory (SHM): mysql-cluster-shm-definition.
                                                             (line    6)
* MySQL Cluster, transporters, TCP/IP:   mysql-cluster-tcp-definition-direct.
                                                             (line    6)
* MySQL Cluster, troubleshooting backups: mysql-cluster-backup-troubleshooting.
                                                             (line    6)
* MySQL Cluster, upgrades and downgrades <1>: mysql-cluster-rolling-restart.
                                                             (line    6)
* MySQL Cluster, upgrades and downgrades: mysql-cluster-upgrade-downgrade.
                                                             (line   12)
* MySQL Cluster, using tables and data:  mysql-cluster-install-example-data.
                                                             (line    6)
* MySQL Cluster, vs replication:         faqs-mysql-cluster. (line    6)
* mysql command options:                 mysql-command-options.
                                                             (line    6)
* mysql commands, list of:               mysql-commands.     (line   11)
* MySQL Dolphin name:                    history.            (line    6)
* MySQL Enterprise Audit:                mysql-enterprise-audit.
                                                             (line    6)
* MySQL Enterprise Backup:               mysql-enterprise-backup.
                                                             (line    6)
* MySQL Enterprise Encryption:           mysql-enterprise-encryption.
                                                             (line    6)
* MySQL Enterprise Monitor:              mysql-enterprise-monitor.
                                                             (line    6)
* MySQL Enterprise Security:             mysql-enterprise-security.
                                                             (line    6)
* MySQL Enterprise Thread Pool:          mysql-enterprise-thread-pool.
                                                             (line    6)
* MySQL history:                         history.            (line    6)
* mysql history file:                    mysql-logging.      (line    6)
* MySQL Instance Manager:                instance-manager.   (line   16)
* MySQL mailing lists:                   mailing-lists.      (line   10)
* MySQL name:                            history.            (line    6)
* MySQL Notifier:                        windows-notifier.   (line   10)
* MySQL privileges, and MySQL Cluster:   mysql-cluster-security-mysql-privileges.
                                                             (line   10)
* mysql prompt command:                  mysql-commands.     (line  297)
* MySQL server, mysqld <1>:              mysqld-server.      (line   20)
* MySQL server, mysqld:                  mysqld.             (line    6)
* mysql source (command for reading from text files) <1>: mysql-batch-commands.
                                                             (line    6)
* mysql source (command for reading from text files): batch-mode.
                                                             (line   97)
* MySQL source distribution:             which-version.      (line   18)
* MySQL storage engines:                 storage-engines.    (line   23)
* MySQL system tables, and MySQL Cluster: mysql-cluster-security-mysql-privileges.
                                                             (line   23)
* MySQL system tables, and replication:  replication-features-mysqldb.
                                                             (line    6)
* MySQL version:                         getting-mysql.      (line    6)
* mysql, auto-rehash option:             mysql-command-options.
                                                             (line  152)
* mysql, batch option:                   mysql-command-options.
                                                             (line  172)
* mysql, bind-address option:            mysql-command-options.
                                                             (line  182)
* mysql, character-sets-dir option:      mysql-command-options.
                                                             (line  193)
* mysql, charset command:                mysql-commands.     (line   62)
* mysql, clear command:                  mysql-commands.     (line   71)
* mysql, column-names option:            mysql-command-options.
                                                             (line  198)
* mysql, column-type-info option:        mysql-command-options.
                                                             (line  202)
* mysql, comments option:                mysql-command-options.
                                                             (line  208)
* mysql, compress option:                mysql-command-options.
                                                             (line  215)
* mysql, connect command:                mysql-commands.     (line   76)
* mysql, database option:                mysql-command-options.
                                                             (line  220)
* mysql, debug option:                   mysql-command-options.
                                                             (line  224)
* mysql, debug-check option:             mysql-command-options.
                                                             (line  229)
* mysql, debug-info option:              mysql-command-options.
                                                             (line  234)
* mysql, default-character-set option:   mysql-command-options.
                                                             (line  242)
* mysql, defaults-extra-file option:     mysql-command-options.
                                                             (line  256)
* mysql, defaults-file option:           mysql-command-options.
                                                             (line  263)
* mysql, defaults-group-suffix option:   mysql-command-options.
                                                             (line  269)
* MySQL, defined:                        what-is-mysql.      (line    6)
* mysql, delimiter command:              mysql-commands.     (line   83)
* mysql, delimiter option:               mysql-command-options.
                                                             (line  277)
* mysql, disable named commands:         mysql-command-options.
                                                             (line  282)
* mysql, edit command:                   mysql-commands.     (line  118)
* mysql, ego command:                    mysql-commands.     (line  127)
* mysql, execute option:                 mysql-command-options.
                                                             (line  290)
* mysql, exit command:                   mysql-commands.     (line  132)
* mysql, force option:                   mysql-command-options.
                                                             (line  297)
* mysql, go command:                     mysql-commands.     (line  136)
* mysql, help command:                   mysql-commands.     (line   52)
* mysql, help option:                    mysql-command-options.
                                                             (line  148)
* mysql, host option:                    mysql-command-options.
                                                             (line  301)
* mysql, html option:                    mysql-command-options.
                                                             (line  305)
* mysql, i-am-a-dummy option:            mysql-command-options.
                                                             (line  502)
* mysql, ignore-spaces option:           mysql-command-options.
                                                             (line  309)
* MySQL, introduction:                   what-is-mysql.      (line    6)
* mysql, line-numbers option:            mysql-command-options.
                                                             (line  315)
* mysql, local-infile option:            mysql-command-options.
                                                             (line  320)
* mysql, named-commands option:          mysql-command-options.
                                                             (line  328)
* mysql, no-auto-rehash option:          mysql-command-options.
                                                             (line  335)
* mysql, no-beep option:                 mysql-command-options.
                                                             (line  340)
* mysql, no-defaults option:             mysql-command-options.
                                                             (line  344)
* mysql, no-named-commands option:       mysql-command-options.
                                                             (line  350)
* mysql, no-pager option:                mysql-command-options.
                                                             (line  355)
* mysql, no-tee option:                  mysql-command-options.
                                                             (line  360)
* mysql, nopager command:                mysql-commands.     (line  140)
* mysql, notee command:                  mysql-commands.     (line  146)
* mysql, nowarning command:              mysql-commands.     (line  151)
* mysql, one-database option:            mysql-command-options.
                                                             (line  365)
* mysql, pager command:                  mysql-commands.     (line  155)
* mysql, pager option:                   mysql-command-options.
                                                             (line  409)
* mysql, password option:                mysql-command-options.
                                                             (line  418)
* mysql, pipe option:                    mysql-command-options.
                                                             (line  430)
* mysql, port option:                    mysql-command-options.
                                                             (line  435)
* mysql, print command:                  mysql-commands.     (line  177)
* mysql, print-defaults option:          mysql-command-options.
                                                             (line  439)
* mysql, prompt command:                 mysql-commands.     (line  181)
* mysql, prompt option:                  mysql-command-options.
                                                             (line  444)
* MySQL, pronunciation:                  what-is-mysql.      (line  107)
* mysql, protocol option:                mysql-command-options.
                                                             (line  450)
* mysql, quick option:                   mysql-command-options.
                                                             (line  457)
* mysql, quit command:                   mysql-commands.     (line  190)
* mysql, raw option:                     mysql-command-options.
                                                             (line  463)
* mysql, reconnect option:               mysql-command-options.
                                                             (line  495)
* mysql, rehash command:                 mysql-commands.     (line  194)
* mysql, safe-updates option:            mysql-command-options.
                                                             (line  502)
* mysql, secure-auth option:             mysql-command-options.
                                                             (line  510)
* mysql, shared-memory-base-name option: mysql-command-options.
                                                             (line  516)
* mysql, show-warnings option:           mysql-command-options.
                                                             (line  525)
* mysql, sigint-ignore option:           mysql-command-options.
                                                             (line  530)
* mysql, silent option:                  mysql-command-options.
                                                             (line  535)
* mysql, skip-column-names option:       mysql-command-options.
                                                             (line  544)
* mysql, skip-line-numbers option:       mysql-command-options.
                                                             (line  548)
* mysql, socket option:                  mysql-command-options.
                                                             (line  553)
* mysql, source command:                 mysql-commands.     (line  200)
* mysql, SSL options:                    mysql-command-options.
                                                             (line  558)
* mysql, status command:                 mysql-commands.     (line  205)
* mysql, system command:                 mysql-commands.     (line  212)
* mysql, table option:                   mysql-command-options.
                                                             (line  564)
* mysql, tee command:                    mysql-commands.     (line  218)
* mysql, tee option:                     mysql-command-options.
                                                             (line  570)
* mysql, unbuffered option:              mysql-command-options.
                                                             (line  576)
* MySQL, upgrading:                      mysql-upgrade.      (line    6)
* mysql, use command:                    mysql-commands.     (line  232)
* mysql, user option:                    mysql-command-options.
                                                             (line  580)
* mysql, verbose option:                 mysql-command-options.
                                                             (line  584)
* mysql, version option:                 mysql-command-options.
                                                             (line  591)
* mysql, vertical option:                mysql-command-options.
                                                             (line  595)
* mysql, wait option:                    mysql-command-options.
                                                             (line  601)
* mysql, warnings command:               mysql-commands.     (line  236)
* mysql, xml option:                     mysql-command-options.
                                                             (line  606)
* mysql.event table:                     events-privileges.  (line  154)
* mysql.ndb_binlog_index table:          mysql-cluster-replication-schema.
                                                             (line    6)
* mysql.server <1>:                      mysql-server.       (line    6)
* mysql.server:                          programs-overview.  (line   50)
* mysql.server, basedir option:          mysql-server.       (line   36)
* mysql.server, datadir option:          mysql-server.       (line   40)
* mysql.server, pid-file option:         mysql-server.       (line   44)
* mysql.server, service-startup-timeout option: mysql-server.
                                                             (line   49)
* mysql.server, use-manager option:      mysql-server.       (line   63)
* mysql.server, use-mysqld_safe option:  mysql-server.       (line   58)
* mysql.server, user option:             mysql-server.       (line   67)
* mysql.sock, changing location of:      source-configuration-options.
                                                             (line  382)
* mysql.sock, protection:                problems-with-mysql-sock.
                                                             (line    6)
* MYSQL323 SQL mode:                     sql-mode.           (line  587)
* MYSQL40 SQL mode:                      sql-mode.           (line  591)
* mysql_affected_rows():                 mysql-affected-rows.
                                                             (line    6)
* mysql_autocommit():                    mysql-autocommit.   (line    6)
* MYSQL_BIND C type:                     c-api-prepared-statement-data-structures.
                                                             (line   51)
* mysql_change_user():                   mysql-change-user.  (line    6)
* mysql_character_set_name():            mysql-character-set-name.
                                                             (line    6)
* mysql_close():                         mysql-close.        (line    6)
* mysql_cluster_backup_privileges:       mysql-cluster-privilege-distribution.
                                                             (line   60)
* mysql_cluster_move_grant_tables:       mysql-cluster-privilege-distribution.
                                                             (line   73)
* mysql_cluster_move_privileges:         mysql-cluster-privilege-distribution.
                                                             (line   56)
* mysql_cluster_privileges_are_distributed: mysql-cluster-privilege-distribution.
                                                             (line  101)
* mysql_cluster_restore_local_privileges: mysql-cluster-privilege-distribution.
                                                             (line  214)
* mysql_cluster_restore_privileges:      mysql-cluster-privilege-distribution.
                                                             (line  205)
* mysql_cluster_restore_privileges_from_local: mysql-cluster-privilege-distribution.
                                                             (line  223)
* mysql_commit():                        mysql-commit.       (line    6)
* mysql_config:                          mysql-config.       (line    6)
* mysql_config, cflags option:           mysql-config.       (line   13)
* mysql_config, embedded option:         mysql-config.       (line   26)
* mysql_config, include option:          mysql-config.       (line   22)
* mysql_config, libmysqld-libs option:   mysql-config.       (line   26)
* mysql_config, libs option:             mysql-config.       (line   31)
* mysql_config, libs_r option:           mysql-config.       (line   36)
* mysql_config, plugindir option:        mysql-config.       (line   41)
* mysql_config, port option:             mysql-config.       (line   46)
* mysql_config, socket option:           mysql-config.       (line   50)
* mysql_config, version option:          mysql-config.       (line   54)
* mysql_connect():                       mysql-connect.      (line    6)
* mysql_convert_table_format <1>:        mysql-convert-table-format.
                                                             (line    6)
* mysql_convert_table_format:            programs-overview.  (line  221)
* mysql_convert_table_format, force option: mysql-convert-table-format.
                                                             (line   29)
* mysql_convert_table_format, help option: mysql-convert-table-format.
                                                             (line   25)
* mysql_convert_table_format, host option: mysql-convert-table-format.
                                                             (line   33)
* mysql_convert_table_format, password option: mysql-convert-table-format.
                                                             (line   37)
* mysql_convert_table_format, port option: mysql-convert-table-format.
                                                             (line   47)
* mysql_convert_table_format, socket option: mysql-convert-table-format.
                                                             (line   51)
* mysql_convert_table_format, type option: mysql-convert-table-format.
                                                             (line   55)
* mysql_convert_table_format, user option: mysql-convert-table-format.
                                                             (line   60)
* mysql_convert_table_format, verbose option: mysql-convert-table-format.
                                                             (line   64)
* mysql_convert_table_format, version option: mysql-convert-table-format.
                                                             (line   68)
* mysql_create_db():                     mysql-create-db.    (line    6)
* mysql_data_seek():                     mysql-data-seek.    (line    6)
* MYSQL_DEBUG environment variable <1>:  debugging-client.   (line   10)
* MYSQL_DEBUG environment variable <2>:  programs-overview.  (line  305)
* MYSQL_DEBUG environment variable:      environment-variables.
                                                             (line   18)
* mysql_debug():                         mysql-debug.        (line    6)
* mysql_drop_db():                       mysql-drop-db.      (line    6)
* mysql_dump_debug_info():               mysql-dump-debug-info.
                                                             (line    6)
* mysql_eof():                           mysql-eof.          (line    6)
* mysql_errno():                         mysql-errno.        (line    6)
* mysql_error():                         mysql-error.        (line    6)
* mysql_escape_string():                 mysql-escape-string.
                                                             (line    6)
* mysql_fetch_field():                   mysql-fetch-field.  (line    6)
* mysql_fetch_field_direct():            mysql-fetch-field-direct.
                                                             (line    6)
* mysql_fetch_fields():                  mysql-fetch-fields. (line    6)
* mysql_fetch_lengths():                 mysql-fetch-lengths.
                                                             (line    6)
* mysql_fetch_row():                     mysql-fetch-row.    (line    6)
* MYSQL_FIELD C type:                    c-api-data-structures.
                                                             (line   34)
* mysql_field_count() <1>:               mysql-num-fields.   (line    6)
* mysql_field_count():                   mysql-field-count.  (line    6)
* MYSQL_FIELD_OFFSET C type:             c-api-data-structures.
                                                             (line   44)
* mysql_field_seek():                    mysql-field-seek.   (line    6)
* mysql_field_tell():                    mysql-field-tell.   (line    6)
* mysql_find_rows <1>:                   mysql-find-rows.    (line    6)
* mysql_find_rows:                       programs-overview.  (line  226)
* mysql_find_rows, help option:          mysql-find-rows.    (line   33)
* mysql_find_rows, regexp option:        mysql-find-rows.    (line   37)
* mysql_find_rows, rows option:          mysql-find-rows.    (line   41)
* mysql_find_rows, skip-use-db option:   mysql-find-rows.    (line   45)
* mysql_find_rows, start_row option:     mysql-find-rows.    (line   49)
* mysql_fix_extensions <1>:              mysql-fix-extensions.
                                                             (line    6)
* mysql_fix_extensions:                  programs-overview.  (line  232)
* mysql_fix_privilege_tables <1>:        mysql-fix-privilege-tables.
                                                             (line    6)
* mysql_fix_privilege_tables:            programs-overview.  (line   86)
* mysql_free_result():                   mysql-free-result.  (line    6)
* mysql_get_character_set_info():        mysql-get-character-set-info.
                                                             (line    6)
* mysql_get_client_info():               mysql-get-client-info.
                                                             (line    6)
* mysql_get_client_version():            mysql-get-client-version.
                                                             (line    6)
* mysql_get_host_info():                 mysql-get-host-info.
                                                             (line    6)
* mysql_get_proto_info():                mysql-get-proto-info.
                                                             (line    6)
* mysql_get_server_info():               mysql-get-server-info.
                                                             (line    6)
* mysql_get_server_version():            mysql-get-server-version.
                                                             (line    6)
* mysql_get_ssl_cipher():                mysql-get-ssl-cipher.
                                                             (line    6)
* MYSQL_GROUP_SUFFIX environment variable: environment-variables.
                                                             (line   18)
* mysql_hex_string():                    mysql-hex-string.   (line    6)
* MYSQL_HISTFILE environment variable <1>: mysql-logging.    (line    6)
* MYSQL_HISTFILE environment variable:   environment-variables.
                                                             (line   18)
* MYSQL_HOME environment variable:       environment-variables.
                                                             (line   18)
* MYSQL_HOST environment variable <1>:   connecting.         (line  246)
* MYSQL_HOST environment variable:       environment-variables.
                                                             (line   18)
* mysql_info() <1>:                      mysql-info.         (line    6)
* mysql_info() <2>:                      update.             (line   92)
* mysql_info() <3>:                      load-data.          (line  726)
* mysql_info() <4>:                      insert.             (line  211)
* mysql_info():                          alter-table.        (line  603)
* mysql_init():                          mysql-init.         (line    6)
* mysql_insert_id() <1>:                 mysql-insert-id.    (line    6)
* mysql_insert_id() <2>:                 insert.             (line  215)
* mysql_insert_id():                     ansi-diff-transactions.
                                                             (line  160)
* mysql_install_db <1>:                  mysql-install-db.   (line    6)
* mysql_install_db <2>:                  programs-overview.  (line   95)
* mysql_install_db:                      mysql-install-db-problems.
                                                             (line    6)
* mysql_install_db, basedir option:      mysql-install-db.   (line   63)
* mysql_install_db, builddir option:     mysql-install-db.   (line   67)
* mysql_install_db, cross-bootstrap option: mysql-install-db.
                                                             (line   72)
* mysql_install_db, datadir option:      mysql-install-db.   (line   77)
* mysql_install_db, force option:        mysql-install-db.   (line   96)
* mysql_install_db, help option:         mysql-install-db.   (line   59)
* mysql_install_db, ldata option:        mysql-install-db.   (line  102)
* mysql_install_db, rpm option:          mysql-install-db.   (line  112)
* mysql_install_db, skip-name-resolve option: mysql-install-db.
                                                             (line  118)
* mysql_install_db, srcdir option:       mysql-install-db.   (line  123)
* mysql_install_db, user option:         mysql-install-db.   (line  130)
* mysql_install_db, verbose option:      mysql-install-db.   (line  139)
* mysql_install_db, windows option:      mysql-install-db.   (line  143)
* mysql_kill():                          mysql-kill.         (line    6)
* mysql_library_end():                   mysql-library-end.  (line    6)
* mysql_library_init():                  mysql-library-init. (line    6)
* mysql_list_dbs():                      mysql-list-dbs.     (line    6)
* mysql_list_fields():                   mysql-list-fields.  (line    6)
* mysql_list_processes():                mysql-list-processes.
                                                             (line    6)
* mysql_list_tables():                   mysql-list-tables.  (line    6)
* mysql_more_results():                  mysql-more-results. (line    6)
* mysql_next_result():                   mysql-next-result.  (line    6)
* mysql_num_fields():                    mysql-num-fields.   (line    6)
* mysql_num_rows():                      mysql-num-rows.     (line    6)
* mysql_options():                       mysql-options.      (line    6)
* mysql_ping():                          mysql-ping.         (line    6)
* MYSQL_PS1 environment variable:        environment-variables.
                                                             (line   18)
* MYSQL_PWD environment variable <1>:    connecting.         (line  246)
* MYSQL_PWD environment variable <2>:    programs-overview.  (line  305)
* MYSQL_PWD environment variable:        environment-variables.
                                                             (line   18)
* mysql_query() <1>:                     c-api-problems.     (line   12)
* mysql_query():                         mysql-query.        (line    6)
* mysql_real_connect():                  mysql-real-connect. (line    6)
* mysql_real_escape_string() <1>:        mysql-real-escape-string.
                                                             (line    6)
* mysql_real_escape_string() <2>:        string-functions.   (line  573)
* mysql_real_escape_string():            string-literals.    (line  147)
* mysql_real_query():                    mysql-real-query.   (line    6)
* mysql_refresh():                       mysql-refresh.      (line    6)
* mysql_reload():                        mysql-reload.       (line    6)
* MYSQL_RES C type:                      c-api-data-structures.
                                                             (line   17)
* mysql_rollback():                      mysql-rollback.     (line    6)
* MYSQL_ROW C type:                      c-api-data-structures.
                                                             (line   25)
* mysql_row_seek():                      mysql-row-seek.     (line    6)
* mysql_row_tell():                      mysql-row-tell.     (line    6)
* mysql_secure_installation <1>:         mysql-secure-installation.
                                                             (line    6)
* mysql_secure_installation:             programs-overview.  (line  103)
* mysql_select_db():                     mysql-select-db.    (line    6)
* mysql_server_end():                    mysql-server-end.   (line    6)
* mysql_server_init():                   mysql-server-init.  (line    6)
* mysql_set_character_set():             mysql-set-character-set.
                                                             (line    6)
* mysql_set_local_infile_default():      mysql-set-local-infile-default.
                                                             (line    6)
* mysql_set_server_option():             mysql-set-server-option.
                                                             (line    6)
* mysql_setpermission <1>:               mysql-setpermission.
                                                             (line    6)
* mysql_setpermission:                   programs-overview.  (line  239)
* mysql_setpermission, help option:      mysql-setpermission.
                                                             (line   30)
* mysql_setpermission, host option:      mysql-setpermission.
                                                             (line   34)
* mysql_setpermission, password option:  mysql-setpermission.
                                                             (line   38)
* mysql_setpermission, port option:      mysql-setpermission.
                                                             (line   48)
* mysql_setpermission, socket option:    mysql-setpermission.
                                                             (line   52)
* mysql_setpermission, user option:      mysql-setpermission.
                                                             (line   56)
* mysql_shutdown():                      mysql-shutdown.     (line    6)
* mysql_sqlstate():                      mysql-sqlstate.     (line    6)
* mysql_ssl_set():                       mysql-ssl-set.      (line    6)
* mysql_stat():                          mysql-stat.         (line    6)
* MYSQL_STMT C type:                     c-api-prepared-statement-data-structures.
                                                             (line   34)
* mysql_stmt_affected_rows():            mysql-stmt-affected-rows.
                                                             (line    6)
* mysql_stmt_attr_get():                 mysql-stmt-attr-get.
                                                             (line    6)
* mysql_stmt_attr_set():                 mysql-stmt-attr-set.
                                                             (line    6)
* mysql_stmt_bind_param():               mysql-stmt-bind-param.
                                                             (line    6)
* mysql_stmt_bind_result():              mysql-stmt-bind-result.
                                                             (line    6)
* mysql_stmt_close():                    mysql-stmt-close.   (line    6)
* mysql_stmt_data_seek():                mysql-stmt-data-seek.
                                                             (line    6)
* mysql_stmt_errno():                    mysql-stmt-errno.   (line    6)
* mysql_stmt_error():                    mysql-stmt-error.   (line    6)
* mysql_stmt_execute():                  mysql-stmt-execute. (line    6)
* mysql_stmt_fetch():                    mysql-stmt-fetch.   (line    6)
* mysql_stmt_fetch_column():             mysql-stmt-fetch-column.
                                                             (line    6)
* mysql_stmt_field_count():              mysql-stmt-field-count.
                                                             (line    6)
* mysql_stmt_free_result():              mysql-stmt-free-result.
                                                             (line    6)
* mysql_stmt_init():                     mysql-stmt-init.    (line    6)
* mysql_stmt_insert_id():                mysql-stmt-insert-id.
                                                             (line    6)
* mysql_stmt_num_rows():                 mysql-stmt-num-rows.
                                                             (line    6)
* mysql_stmt_param_count():              mysql-stmt-param-count.
                                                             (line    6)
* mysql_stmt_param_metadata():           mysql-stmt-param-metadata.
                                                             (line    6)
* mysql_stmt_prepare():                  mysql-stmt-prepare. (line    6)
* mysql_stmt_reset():                    mysql-stmt-reset.   (line    6)
* mysql_stmt_result_metadata:            mysql-stmt-result-metadata.
                                                             (line    6)
* mysql_stmt_row_seek():                 mysql-stmt-row-seek.
                                                             (line    6)
* mysql_stmt_row_tell():                 mysql-stmt-row-tell.
                                                             (line    6)
* mysql_stmt_send_long_data():           mysql-stmt-send-long-data.
                                                             (line    6)
* mysql_stmt_sqlstate():                 mysql-stmt-sqlstate.
                                                             (line    6)
* mysql_stmt_store_result():             mysql-stmt-store-result.
                                                             (line    6)
* mysql_store_result() <1>:              c-api-problems.     (line   12)
* mysql_store_result():                  mysql-store-result. (line    6)
* MYSQL_TCP_PORT environment variable <1>: multiple-server-clients.
                                                             (line   27)
* MYSQL_TCP_PORT environment variable <2>: multiple-unix-servers.
                                                             (line   72)
* MYSQL_TCP_PORT environment variable <3>: programs-overview.
                                                             (line  305)
* MYSQL_TCP_PORT environment variable:   environment-variables.
                                                             (line   18)
* mysql_thread_end():                    mysql-thread-end.   (line    6)
* mysql_thread_id():                     mysql-thread-id.    (line    6)
* mysql_thread_init():                   mysql-thread-init.  (line    6)
* mysql_thread_safe():                   mysql-thread-safe.  (line    6)
* MYSQL_TIME C type:                     c-api-prepared-statement-data-structures.
                                                             (line  246)
* mysql_tzinfo_to_sql <1>:               mysql-tzinfo-to-sql.
                                                             (line    6)
* mysql_tzinfo_to_sql:                   programs-overview.  (line  108)
* MYSQL_UNIX_PORT environment variable <1>: multiple-server-clients.
                                                             (line   27)
* MYSQL_UNIX_PORT environment variable <2>: multiple-unix-servers.
                                                             (line   72)
* MYSQL_UNIX_PORT environment variable <3>: programs-overview.
                                                             (line  305)
* MYSQL_UNIX_PORT environment variable <4>: environment-variables.
                                                             (line   18)
* MYSQL_UNIX_PORT environment variable:  mysql-install-db-problems.
                                                             (line   87)
* mysql_upgrade <1>:                     access-denied.      (line   87)
* mysql_upgrade <2>:                     mysql-upgrade.      (line    6)
* mysql_upgrade:                         programs-overview.  (line  115)
* mysql_upgrade, basedir option:         mysql-upgrade.      (line  139)
* mysql_upgrade, character-sets-dir option: mysql-upgrade.   (line  144)
* mysql_upgrade, compress option:        mysql-upgrade.      (line  149)
* mysql_upgrade, datadir option:         mysql-upgrade.      (line  154)
* mysql_upgrade, debug option:           mysql-upgrade.      (line  159)
* mysql_upgrade, debug-check option:     mysql-upgrade.      (line  165)
* mysql_upgrade, debug-info option:      mysql-upgrade.      (line  170)
* mysql_upgrade, default-character-set option: mysql-upgrade.
                                                             (line  174)
* mysql_upgrade, defaults-extra-file option: mysql-upgrade.  (line  179)
* mysql_upgrade, defaults-file option:   mysql-upgrade.      (line  186)
* mysql_upgrade, defaults-group-suffix option: mysql-upgrade.
                                                             (line  192)
* mysql_upgrade, force option:           mysql-upgrade.      (line  201)
* mysql_upgrade, help option:            mysql-upgrade.      (line  135)
* mysql_upgrade, host option:            mysql-upgrade.      (line  207)
* mysql_upgrade, mysql_upgrade_info file: mysql-upgrade.     (line  115)
* mysql_upgrade, no-defaults option:     mysql-upgrade.      (line  212)
* mysql_upgrade, password option:        mysql-upgrade.      (line  218)
* mysql_upgrade, pipe option:            mysql-upgrade.      (line  230)
* mysql_upgrade, port option:            mysql-upgrade.      (line  236)
* mysql_upgrade, print-defaults option:  mysql-upgrade.      (line  240)
* mysql_upgrade, protocol option:        mysql-upgrade.      (line  245)
* mysql_upgrade, shared-memory-base-name option: mysql-upgrade.
                                                             (line  252)
* mysql_upgrade, socket option:          mysql-upgrade.      (line  262)
* mysql_upgrade, SSL options:            mysql-upgrade.      (line  267)
* mysql_upgrade, tmpdir option:          mysql-upgrade.      (line  274)
* mysql_upgrade, user option:            mysql-upgrade.      (line  279)
* mysql_upgrade, verbose option:         mysql-upgrade.      (line  284)
* mysql_upgrade, write-binlog option:    mysql-upgrade.      (line  288)
* mysql_upgrade_info file, mysql_upgrade: mysql-upgrade.     (line  115)
* mysql_use_result():                    mysql-use-result.   (line    6)
* mysql_waitpid <1>:                     mysql-waitpid.      (line    6)
* mysql_waitpid:                         programs-overview.  (line  244)
* mysql_waitpid, help option:            mysql-waitpid.      (line   28)
* mysql_waitpid, verbose option:         mysql-waitpid.      (line   32)
* mysql_waitpid, version option:         mysql-waitpid.      (line   37)
* mysql_warning_count():                 mysql-warning-count.
                                                             (line    6)
* mysql_zap <1>:                         mysql-zap.          (line    6)
* mysql_zap:                             programs-overview.  (line  249)
* mysqlaccess <1>:                       mysqlaccess.        (line    6)
* mysqlaccess:                           programs-overview.  (line  190)
* mysqlaccess, brief option:             mysqlaccess.        (line   67)
* mysqlaccess, commit option:            mysqlaccess.        (line   71)
* mysqlaccess, copy option:              mysqlaccess.        (line   78)
* mysqlaccess, db option:                mysqlaccess.        (line   82)
* mysqlaccess, debug option:             mysqlaccess.        (line   86)
* mysqlaccess, help option:              mysqlaccess.        (line   63)
* mysqlaccess, host option:              mysqlaccess.        (line   90)
* mysqlaccess, howto option:             mysqlaccess.        (line   94)
* mysqlaccess, old_server option:        mysqlaccess.        (line   99)
* mysqlaccess, password option:          mysqlaccess.        (line  104)
* mysqlaccess, plan option:              mysqlaccess.        (line  113)
* mysqlaccess, preview option:           mysqlaccess.        (line  117)
* mysqlaccess, relnotes option:          mysqlaccess.        (line  122)
* mysqlaccess, rhost option:             mysqlaccess.        (line  126)
* mysqlaccess, rollback option:          mysqlaccess.        (line  130)
* mysqlaccess, spassword option:         mysqlaccess.        (line  134)
* mysqlaccess, superuser option:         mysqlaccess.        (line  144)
* mysqlaccess, table option:             mysqlaccess.        (line  148)
* mysqlaccess, user option:              mysqlaccess.        (line  152)
* mysqlaccess, version option:           mysqlaccess.        (line  156)
* mysqladmin <1>:                        kill.               (line    6)
* mysqladmin <2>:                        flush.              (line    6)
* mysqladmin <3>:                        show-variables.     (line   10)
* mysqladmin <4>:                        show-status.        (line   10)
* mysqladmin <5>:                        drop-database.      (line   60)
* mysqladmin <6>:                        create-database.    (line   43)
* mysqladmin <7>:                        mysqladmin.         (line    6)
* mysqladmin:                            programs-overview.  (line  129)
* mysqladmin command options:            mysqladmin.         (line  216)
* mysqladmin option, mysqld_multi:       mysqld-multi.       (line  127)
* mysqladmin, bind-address option:       mysqladmin.         (line  304)
* mysqladmin, character-sets-dir option: mysqladmin.         (line  315)
* mysqladmin, compress option:           mysqladmin.         (line  320)
* mysqladmin, count option:              mysqladmin.         (line  325)
* mysqladmin, debug option:              mysqladmin.         (line  330)
* mysqladmin, debug-check option:        mysqladmin.         (line  335)
* mysqladmin, debug-info option:         mysqladmin.         (line  340)
* mysqladmin, default-character-set option: mysqladmin.      (line  345)
* mysqladmin, defaults-extra-file option: mysqladmin.        (line  350)
* mysqladmin, defaults-file option:      mysqladmin.         (line  357)
* mysqladmin, defaults-group-suffix option: mysqladmin.      (line  363)
* mysqladmin, force option:              mysqladmin.         (line  372)
* mysqladmin, help option:               mysqladmin.         (line  300)
* mysqladmin, host option:               mysqladmin.         (line  377)
* mysqladmin, no-beep option:            mysqladmin.         (line  381)
* mysqladmin, no-defaults option:        mysqladmin.         (line  387)
* mysqladmin, password option:           mysqladmin.         (line  393)
* mysqladmin, pipe option:               mysqladmin.         (line  405)
* mysqladmin, port option:               mysqladmin.         (line  410)
* mysqladmin, print-defaults option:     mysqladmin.         (line  414)
* mysqladmin, protocol option:           mysqladmin.         (line  419)
* mysqladmin, relative option:           mysqladmin.         (line  426)
* mysqladmin, shared-memory-base-name option: mysqladmin.    (line  432)
* mysqladmin, silent option:             mysqladmin.         (line  441)
* mysqladmin, sleep option:              mysqladmin.         (line  445)
* mysqladmin, socket option:             mysqladmin.         (line  452)
* mysqladmin, SSL options:               mysqladmin.         (line  457)
* mysqladmin, user option:               mysqladmin.         (line  463)
* mysqladmin, verbose option:            mysqladmin.         (line  467)
* mysqladmin, version option:            mysqladmin.         (line  471)
* mysqladmin, vertical option:           mysqladmin.         (line  475)
* mysqladmin, wait option:               mysqladmin.         (line  480)
* mysqlbinlog <1>:                       mysqlbinlog.        (line   11)
* mysqlbinlog:                           programs-overview.  (line  195)
* mysqlbinlog, base64-output option:     mysqlbinlog.        (line  187)
* mysqlbinlog, bind-address option:      mysqlbinlog.        (line  235)
* mysqlbinlog, character-sets-dir option: mysqlbinlog.       (line  246)
* mysqlbinlog, database option:          mysqlbinlog.        (line  251)
* mysqlbinlog, debug option:             mysqlbinlog.        (line  342)
* mysqlbinlog, debug-check option:       mysqlbinlog.        (line  347)
* mysqlbinlog, debug-info option:        mysqlbinlog.        (line  352)
* mysqlbinlog, defaults-extra-file option: mysqlbinlog.      (line  357)
* mysqlbinlog, defaults-file option:     mysqlbinlog.        (line  364)
* mysqlbinlog, defaults-group-suffix option: mysqlbinlog.    (line  370)
* mysqlbinlog, disable-log-bin option:   mysqlbinlog.        (line  379)
* mysqlbinlog, force-if-open option:     mysqlbinlog.        (line  393)
* mysqlbinlog, force-read option:        mysqlbinlog.        (line  398)
* mysqlbinlog, help option:              mysqlbinlog.        (line  183)
* mysqlbinlog, hexdump option:           mysqlbinlog.        (line  405)
* mysqlbinlog, host option:              mysqlbinlog.        (line  411)
* mysqlbinlog, local-load option:        mysqlbinlog.        (line  415)
* mysqlbinlog, no-defaults option:       mysqlbinlog.        (line  425)
* mysqlbinlog, offset option:            mysqlbinlog.        (line  431)
* mysqlbinlog, password option:          mysqlbinlog.        (line  435)
* mysqlbinlog, port option:              mysqlbinlog.        (line  447)
* mysqlbinlog, position option:          mysqlbinlog.        (line  451)
* mysqlbinlog, print-defaults option:    mysqlbinlog.        (line  456)
* mysqlbinlog, protocol option:          mysqlbinlog.        (line  461)
* mysqlbinlog, read-from-remote-server option: mysqlbinlog.  (line  468)
* mysqlbinlog, result-file option:       mysqlbinlog.        (line  479)
* mysqlbinlog, server-id option:         mysqlbinlog.        (line  483)
* mysqlbinlog, server-id-bits option:    mysqlbinlog.        (line  488)
* mysqlbinlog, set-charset option:       mysqlbinlog.        (line  502)
* mysqlbinlog, shared-memory-base-name option: mysqlbinlog.  (line  508)
* mysqlbinlog, short-form option:        mysqlbinlog.        (line  519)
* mysqlbinlog, socket option:            mysqlbinlog.        (line  525)
* mysqlbinlog, start-datetime option:    mysqlbinlog.        (line  530)
* mysqlbinlog, start-position option:    mysqlbinlog.        (line  545)
* mysqlbinlog, stop-datetime option:     mysqlbinlog.        (line  554)
* mysqlbinlog, stop-position option:     mysqlbinlog.        (line  564)
* mysqlbinlog, to-last-log option:       mysqlbinlog.        (line  573)
* mysqlbinlog, user option:              mysqlbinlog.        (line  581)
* mysqlbinlog, verbose option:           mysqlbinlog.        (line  585)
* mysqlbinlog, version option:           mysqlbinlog.        (line  596)
* mysqlbug:                              mysqlbug.           (line    6)
* mysqlcheck <1>:                        mysqlcheck.         (line    6)
* mysqlcheck:                            programs-overview.  (line  137)
* mysqlcheck, all-databases option:      mysqlcheck.         (line  203)
* mysqlcheck, all-in-1 option:           mysqlcheck.         (line  209)
* mysqlcheck, analyze option:            mysqlcheck.         (line  215)
* mysqlcheck, auto-repair option:        mysqlcheck.         (line  219)
* mysqlcheck, bind-address option:       mysqlcheck.         (line  224)
* mysqlcheck, character-sets-dir option: mysqlcheck.         (line  235)
* mysqlcheck, check option:              mysqlcheck.         (line  240)
* mysqlcheck, check-only-changed option: mysqlcheck.         (line  244)
* mysqlcheck, check-upgrade option:      mysqlcheck.         (line  249)
* mysqlcheck, compress option:           mysqlcheck.         (line  257)
* mysqlcheck, databases option:          mysqlcheck.         (line  262)
* mysqlcheck, debug option:              mysqlcheck.         (line  270)
* mysqlcheck, debug-check option:        mysqlcheck.         (line  275)
* mysqlcheck, debug-info option:         mysqlcheck.         (line  280)
* mysqlcheck, default-character-set option: mysqlcheck.      (line  285)
* mysqlcheck, defaults-extra-file option: mysqlcheck.        (line  290)
* mysqlcheck, defaults-file option:      mysqlcheck.         (line  297)
* mysqlcheck, defaults-group-suffix option: mysqlcheck.      (line  303)
* mysqlcheck, extended option:           mysqlcheck.         (line  312)
* mysqlcheck, fast option:               mysqlcheck.         (line  321)
* mysqlcheck, fix-db-names option:       mysqlcheck.         (line  325)
* mysqlcheck, fix-table-names option:    mysqlcheck.         (line  331)
* mysqlcheck, force option:              mysqlcheck.         (line  337)
* mysqlcheck, help option:               mysqlcheck.         (line  199)
* mysqlcheck, host option:               mysqlcheck.         (line  341)
* mysqlcheck, medium-check option:       mysqlcheck.         (line  345)
* mysqlcheck, no-defaults option:        mysqlcheck.         (line  351)
* mysqlcheck, optimize option:           mysqlcheck.         (line  357)
* mysqlcheck, password option:           mysqlcheck.         (line  361)
* mysqlcheck, pipe option:               mysqlcheck.         (line  373)
* mysqlcheck, port option:               mysqlcheck.         (line  378)
* mysqlcheck, print-defaults option:     mysqlcheck.         (line  382)
* mysqlcheck, protocol option:           mysqlcheck.         (line  387)
* mysqlcheck, quick option:              mysqlcheck.         (line  394)
* mysqlcheck, repair option:             mysqlcheck.         (line  403)
* mysqlcheck, shared-memory-base-name option: mysqlcheck.    (line  408)
* mysqlcheck, silent option:             mysqlcheck.         (line  417)
* mysqlcheck, socket option:             mysqlcheck.         (line  421)
* mysqlcheck, SSL options:               mysqlcheck.         (line  426)
* mysqlcheck, tables option:             mysqlcheck.         (line  432)
* mysqlcheck, use-frm option:            mysqlcheck.         (line  437)
* mysqlcheck, user option:               mysqlcheck.         (line  443)
* mysqlcheck, verbose option:            mysqlcheck.         (line  447)
* mysqlcheck, version option:            mysqlcheck.         (line  452)
* mysqlcheck, write-binlog option:       mysqlcheck.         (line  456)
* mysqld:                                programs-overview.  (line   38)
* mysqld (MySQL Cluster):                mysql-cluster-programs.
                                                             (line   35)
* mysqld option, mysqld_multi:           mysqld-multi.       (line  132)
* mysqld option, mysqld_safe:            mysqld-safe.        (line  152)
* mysqld options:                        server-parameters.  (line   12)
* mysqld options and variables, MySQL Cluster: mysql-cluster-options-variables.
                                                             (line   13)
* mysqld server, buffer sizes:           server-parameters.  (line    6)
* mysqld, abort-slave-event-count option: replication-options-slave.
                                                             (line  141)
* mysqld, allow-suspicious-udfs option:  server-options.     (line   83)
* mysqld, ansi option:                   server-options.     (line  101)
* mysqld, as MySQL Cluster process <1>:  mysql-cluster-mysqld.
                                                             (line    6)
* mysqld, as MySQL Cluster process:      mysql-cluster-program-options-mysqld.
                                                             (line    6)
* mysqld, basedir option:                server-options.     (line  113)
* mysqld, big-tables option:             server-options.     (line  132)
* mysqld, bind-address option:           server-options.     (line  154)
* mysqld, binlog-do-db option:           replication-options-binary-log.
                                                             (line  187)
* mysqld, binlog-format option:          server-options.     (line  198)
* mysqld, binlog-ignore-db option:       replication-options-binary-log.
                                                             (line  315)
* mysqld, binlog-row-event-max-size option: replication-options-binary-log.
                                                             (line   24)
* mysqld, bootstrap option:              server-options.     (line  274)
* mysqld, character-set-client-handshake option: server-options.
                                                             (line  307)
* mysqld, character-set-filesystem option: server-options.   (line  323)
* mysqld, character-set-server option:   server-options.     (line  344)
* mysqld, character-sets-dir option:     server-options.     (line  289)
* mysqld, chroot option:                 server-options.     (line  365)
* mysqld, collation-server option:       server-options.     (line  384)
* mysqld, command options:               server-options.     (line    6)
* mysqld, console option:                server-options.     (line  403)
* mysqld, core-file option:              server-options.     (line  418)
* mysqld, datadir option:                server-options.     (line  446)
* mysqld, debug option:                  server-options.     (line  464)
* mysqld, debug-sync-timeout option:     server-options.     (line  503)
* mysqld, default-character-set option:  server-options.     (line  530)
* mysqld, default-collation option:      server-options.     (line  548)
* mysqld, default-storage-engine option: server-options.     (line  564)
* mysqld, default-table-type option:     server-options.     (line  583)
* mysqld, default-time-zone option:      server-options.     (line  599)
* mysqld, defaults-extra-file option:    server-options.     (line  614)
* mysqld, defaults-file option:          server-options.     (line  621)
* mysqld, defaults-group-suffix option:  server-options.     (line  627)
* mysqld, delay-key-write option <1>:    myisam-start.       (line   42)
* mysqld, delay-key-write option:        server-options.     (line  635)
* mysqld, des-key-file option:           server-options.     (line  667)
* mysqld, disconnect-slave-event-count option: replication-options-slave.
                                                             (line  167)
* mysqld, enable-named-pipe option:      server-options.     (line  681)
* mysqld, enable-pstack option:          server-options.     (line  697)
* mysqld, event-scheduler option:        server-options.     (line  731)
* mysqld, exit-info option:              server-options.     (line  756)
* mysqld, external-locking option:       server-options.     (line  772)
* mysqld, flush option:                  server-options.     (line  796)
* mysqld, gdb option:                    server-options.     (line  816)
* mysqld, general-log option:            server-options.     (line  831)
* mysqld, help option:                   server-options.     (line   72)
* mysqld, ignore-builtin-innodb option:  innodb-parameters.  (line  147)
* mysqld, init-file option:              server-options.     (line  852)
* mysqld, innodb option:                 innodb-parameters.  (line  183)
* mysqld, innodb-status-file option:     innodb-parameters.  (line  197)
* mysqld, install option:                server-options.     (line  879)
* mysqld, install-manual option:         server-options.     (line  896)
* mysqld, language option:               server-options.     (line  914)
* mysqld, large-pages option:            server-options.     (line  936)
* mysqld, local-service option:          server-options.     (line  965)
* mysqld, log option:                    server-options.     (line  979)
* mysqld, log-bin option:                replication-options-binary-log.
                                                             (line   45)
* mysqld, log-bin-index option:          replication-options-binary-log.
                                                             (line   74)
* mysqld, log-bin-trust-function-creators option: replication-options-binary-log.
                                                             (line   89)
* mysqld, log-bin-use-v1-row-events option: replication-options-binary-log.
                                                             (line  116)
* mysqld, log-error option:              server-options.     (line 1012)
* mysqld, log-isam option:               server-options.     (line 1032)
* mysqld, log-long-format option:        server-options.     (line 1046)
* mysqld, log-output option:             server-options.     (line 1064)
* mysqld, log-queries-not-using-indexes option: server-options.
                                                             (line 1106)
* mysqld, log-short-format option <1>:   replication-options-binary-log.
                                                             (line  165)
* mysqld, log-short-format option:       server-options.     (line 1128)
* mysqld, log-slave-updates option:      replication-options-slave.
                                                             (line  181)
* mysqld, log-slow-admin-statements option: server-options.  (line 1142)
* mysqld, log-slow-queries option:       server-options.     (line 1160)
* mysqld, log-slow-slave-statements option: replication-options-slave.
                                                             (line  231)
* mysqld, log-tc option:                 server-options.     (line 1194)
* mysqld, log-tc-size option:            server-options.     (line 1212)
* mysqld, log-warnings option <1>:       replication-options-slave.
                                                             (line  249)
* mysqld, log-warnings option:           server-options.     (line 1228)
* mysqld, low-priority-updates option:   server-options.     (line 1268)
* mysqld, master-connect-retry option:   replication-options-slave.
                                                             (line  282)
* mysqld, master-host option:            replication-options-slave.
                                                             (line  338)
* mysqld, master-info-file option:       replication-options-slave.
                                                             (line  356)
* mysqld, master-password option:        replication-options-slave.
                                                             (line  373)
* mysqld, master-port option:            replication-options-slave.
                                                             (line  392)
* mysqld, master-retry-count option:     replication-options-slave.
                                                             (line  411)
* mysqld, master-ssl option:             replication-options-slave.
                                                             (line  441)
* mysqld, master-ssl-ca option:          replication-options-slave.
                                                             (line  441)
* mysqld, master-ssl-capath option:      replication-options-slave.
                                                             (line  441)
* mysqld, master-ssl-cert option:        replication-options-slave.
                                                             (line  441)
* mysqld, master-ssl-cipher option:      replication-options-slave.
                                                             (line  441)
* mysqld, master-ssl-key option:         replication-options-slave.
                                                             (line  441)
* mysqld, master-user option:            replication-options-slave.
                                                             (line  456)
* mysqld, max-binlog-dump-events option: replication-options-binary-log.
                                                             (line  393)
* mysqld, max-relay-log-size option:     replication-options-slave.
                                                             (line  477)
* mysqld, memlock option:                server-options.     (line 1318)
* mysqld, min-examined-row-limit option: server-options.     (line 1293)
* mysqld, myisam-block-size option:      server-options.     (line 1368)
* mysqld, myisam-recover option <1>:     myisam-start.       (line   38)
* mysqld, myisam-recover option:         server-options.     (line 1383)
* mysqld, MySQL server <1>:              mysqld-server.      (line   20)
* mysqld, MySQL server:                  mysqld.             (line    6)
* mysqld, ndb-batch-size option:         mysql-cluster-program-options-mysqld.
                                                             (line   23)
* mysqld, ndb-blob-read-batch-bytes option: mysql-cluster-program-options-mysqld.
                                                             (line  115)
* mysqld, ndb-blob-write-batch-bytes option: mysql-cluster-program-options-mysqld.
                                                             (line  161)
* mysqld, ndb-cluster-connection-pool option: mysql-cluster-program-options-mysqld.
                                                             (line   49)
* mysqld, ndb-connectstring option:      mysql-cluster-program-options-mysqld.
                                                             (line  208)
* mysqld, ndb-log-apply-status:          mysql-cluster-program-options-mysqld.
                                                             (line  370)
* mysqld, ndb-log-empty-epochs:          mysql-cluster-program-options-mysqld.
                                                             (line  550)
* mysqld, ndb-log-orig:                  mysql-cluster-program-options-mysqld.
                                                             (line  418)
* mysqld, ndb-log-transaction-id:        mysql-cluster-program-options-mysqld.
                                                             (line  451)
* mysqld, ndb-nodeid:                    mysql-cluster-program-options-mysqld.
                                                             (line  492)
* mysqld, ndbcluster option:             mysql-cluster-program-options-mysqld.
                                                             (line  335)
* mysqld, no-defaults option:            server-options.     (line 1436)
* mysqld, old-alter-table option:        server-options.     (line 1442)
* mysqld, old-style-user-limits option:  server-options.     (line 1466)
* mysqld, one-thread option:             server-options.     (line 1482)
* mysqld, open-files-limit option:       server-options.     (line 1496)
* mysqld, partition option:              server-options.     (line 1531)
* mysqld, pid-file option:               server-options.     (line 1546)
* mysqld, plugin option prefix:          server-options.     (line 1567)
* mysqld, plugin-load option:            server-options.     (line 1592)
* mysqld, port option:                   server-options.     (line 1649)
* mysqld, port-open-timeout option:      server-options.     (line 1671)
* mysqld, print-defaults option:         server-options.     (line 1690)
* mysqld, read-only option:              replication-options-slave.
                                                             (line  501)
* mysqld, relay-log option:              replication-options-slave.
                                                             (line  522)
* mysqld, relay-log-index option:        replication-options-slave.
                                                             (line  570)
* mysqld, relay-log-info-file option:    replication-options-slave.
                                                             (line  604)
* mysqld, relay-log-purge option:        replication-options-slave.
                                                             (line  621)
* mysqld, relay-log-space-limit option:  replication-options-slave.
                                                             (line  641)
* mysqld, remove option:                 server-options.     (line 1695)
* mysqld, replicate-do-db option:        replication-options-slave.
                                                             (line  678)
* mysqld, replicate-do-table option:     replication-options-slave.
                                                             (line  868)
* mysqld, replicate-ignore-db option:    replication-options-slave.
                                                             (line  798)
* mysqld, replicate-ignore-table option: replication-options-slave.
                                                             (line  889)
* mysqld, replicate-rewrite-db option:   replication-options-slave.
                                                             (line  911)
* mysqld, replicate-same-server-id option: replication-options-slave.
                                                             (line  960)
* mysqld, replicate-wild-do-table option: replication-options-slave.
                                                             (line  983)
* mysqld, replicate-wild-ignore-table option: replication-options-slave.
                                                             (line 1029)
* mysqld, report-host option:            replication-options-slave.
                                                             (line 1054)
* mysqld, report-password option:        replication-options-slave.
                                                             (line 1078)
* mysqld, report-port option:            replication-options-slave.
                                                             (line 1102)
* mysqld, report-user option:            replication-options-slave.
                                                             (line 1125)
* mysqld, role in MySQL Cluster:         mysql-cluster-basics.
                                                             (line    6)
* mysqld, safe-mode option:              server-options.     (line 1706)
* mysqld, safe-show-database option:     server-options.     (line 1716)
* mysqld, safe-user-create option:       server-options.     (line 1737)
* mysqld, secure-auth option:            server-options.     (line 1762)
* mysqld, secure-file-priv option:       server-options.     (line 1789)
* mysqld, server-id option:              replication-options.
                                                             (line   21)
* mysqld, server-id-bits option:         mysql-cluster-program-options-mysqld.
                                                             (line  597)
* mysqld, shared-memory option:          server-options.     (line 1811)
* mysqld, shared-memory-base-name option: server-options.    (line 1826)
* mysqld, show-slave-auth-info option:   replication-options-slave.
                                                             (line 1149)
* mysqld, skip-concurrent-insert option: server-options.     (line 1840)
* mysqld, skip-event-scheduler option:   server-options.     (line 1846)
* mysqld, skip-grant-tables option:      server-options.     (line 1859)
* mysqld, skip-host-cache option:        server-options.     (line 1883)
* mysqld, skip-innodb option <1>:        innodb-parameters.  (line  217)
* mysqld, skip-innodb option:            server-options.     (line 1889)
* mysqld, skip-merge option:             server-options.     (line 1896)
* mysqld, skip-name-resolve option:      server-options.     (line 1901)
* mysqld, skip-ndbcluster option:        mysql-cluster-program-options-mysqld.
                                                             (line  651)
* mysqld, skip-networking option:        server-options.     (line 1913)
* mysqld, skip-partition option:         server-options.     (line 1921)
* mysqld, skip-safemalloc option:        server-options.     (line 1985)
* mysqld, skip-show-database option:     server-options.     (line 1998)
* mysqld, skip-slave-start option:       replication-options-slave.
                                                             (line 1165)
* mysqld, skip-stack-trace option:       server-options.     (line 2013)
* mysqld, skip-symbolic-links option:    server-options.     (line 1962)
* mysqld, skip-thread-priority option:   server-options.     (line 2025)
* mysqld, slave-load-tmpdir option:      replication-options-slave.
                                                             (line 1199)
* mysqld, slave-max-allowed-packet:      replication-options-slave.
                                                             (line  306)
* mysqld, slave-net-timeout option:      replication-options-slave.
                                                             (line 1235)
* mysqld, slave-skip-errors option:      replication-options-slave.
                                                             (line 1261)
* mysqld, slave_compressed_protocol option: replication-options-slave.
                                                             (line 1180)
* mysqld, slow-query-log option:         server-options.     (line 2045)
* mysqld, socket option:                 server-options.     (line 2066)
* mysqld, sporadic-binlog-dump-fail option: replication-options-binary-log.
                                                             (line  407)
* mysqld, sql-mode option:               server-options.     (line 2091)
* mysqld, SSL options:                   server-options.     (line 1945)
* mysqld, standalone option:             server-options.     (line 1951)
* mysqld, starting:                      changing-mysql-user.
                                                             (line    6)
* mysqld, symbolic-links option:         server-options.     (line 1962)
* mysqld, sysdate-is-now option:         server-options.     (line 2138)
* mysqld, tc-heuristic-recover option:   server-options.     (line 2160)
* mysqld, temp-pool option:              server-options.     (line 2176)
* mysqld, tmpdir option:                 server-options.     (line 2218)
* mysqld, transaction-isolation option:  server-options.     (line 2195)
* mysqld, user option:                   server-options.     (line 2250)
* mysqld, verbose option:                server-options.     (line 2284)
* mysqld, version option:                server-options.     (line 2288)
* mysqld-safe-compatible option, mysqlmanager: instance-manager-command-options.
                                                             (line  155)
* mysqld-version option, mysqld_safe:    mysqld-safe.        (line  161)
* mysqld_multi <1>:                      mysqld-multi.       (line    6)
* mysqld_multi:                          programs-overview.  (line   58)
* mysqld_multi, config-file option:      mysqld-multi.       (line  104)
* mysqld_multi, defaults-extra-file option: mysqld-multi.    (line   72)
* mysqld_multi, defaults-file option:    mysqld-multi.       (line   70)
* mysqld_multi, example option:          mysqld-multi.       (line  118)
* mysqld_multi, help option:             mysqld-multi.       (line  100)
* mysqld_multi, log option:              mysqld-multi.       (line  122)
* mysqld_multi, mysqladmin option:       mysqld-multi.       (line  127)
* mysqld_multi, mysqld option:           mysqld-multi.       (line  132)
* mysqld_multi, no-defaults option:      mysqld-multi.       (line   68)
* mysqld_multi, no-log option:           mysqld-multi.       (line  149)
* mysqld_multi, password option:         mysqld-multi.       (line  154)
* mysqld_multi, silent option:           mysqld-multi.       (line  160)
* mysqld_multi, tcp-ip option:           mysqld-multi.       (line  164)
* mysqld_multi, user option:             mysqld-multi.       (line  172)
* mysqld_multi, verbose option:          mysqld-multi.       (line  177)
* mysqld_multi, version option:          mysqld-multi.       (line  181)
* mysqld_safe <1>:                       mysqld-safe.        (line    6)
* mysqld_safe:                           programs-overview.  (line   45)
* mysqld_safe, autoclose option:         mysqld-safe.        (line  103)
* mysqld_safe, basedir option:           mysqld-safe.        (line  116)
* mysqld_safe, core-file-size option:    mysqld-safe.        (line  120)
* mysqld_safe, datadir option:           mysqld-safe.        (line  125)
* mysqld_safe, defaults-extra-file option: mysqld-safe.      (line  129)
* mysqld_safe, defaults-file option:     mysqld-safe.        (line  136)
* mysqld_safe, help option:              mysqld-safe.        (line   99)
* mysqld_safe, ledir option:             mysqld-safe.        (line  142)
* mysqld_safe, log-error option:         mysqld-safe.        (line  148)
* mysqld_safe, mysqld option:            mysqld-safe.        (line  152)
* mysqld_safe, mysqld-version option:    mysqld-safe.        (line  161)
* mysqld_safe, nice option:              mysqld-safe.        (line  172)
* mysqld_safe, no-defaults option:       mysqld-safe.        (line  177)
* mysqld_safe, open-files-limit option:  mysqld-safe.        (line  182)
* mysqld_safe, pid-file option:          mysqld-safe.        (line  192)
* mysqld_safe, port option:              mysqld-safe.        (line  196)
* mysqld_safe, skip-kill-mysqld option:  mysqld-safe.        (line  202)
* mysqld_safe, skip-syslog option:       mysqld-safe.        (line  212)
* mysqld_safe, socket option:            mysqld-safe.        (line  207)
* mysqld_safe, syslog option:            mysqld-safe.        (line  212)
* mysqld_safe, syslog-tag option:        mysqld-safe.        (line  222)
* mysqld_safe, timezone option:          mysqld-safe.        (line  231)
* mysqld_safe, user option:              mysqld-safe.        (line  237)
* mysqldump <1>:                         mysqldump.          (line    6)
* mysqldump <2>:                         programs-overview.  (line  142)
* mysqldump:                             copying-databases.  (line   49)
* mysqldump, add-drop-database option:   mysqldump.          (line  340)
* mysqldump, add-drop-table option:      mysqldump.          (line  349)
* mysqldump, add-drop-trigger option:    mysqldump.          (line  354)
* mysqldump, add-locks option:           mysqldump.          (line  366)
* mysqldump, all-databases option:       mysqldump.          (line  373)
* mysqldump, all-tablespaces option:     mysqldump.          (line  379)
* mysqldump, allow-keywords option:      mysqldump.          (line  389)
* mysqldump, bind-address option:        mysqldump.          (line  394)
* mysqldump, character-sets-dir option:  mysqldump.          (line  405)
* mysqldump, comments option:            mysqldump.          (line  410)
* mysqldump, compact option:             mysqldump.          (line  417)
* mysqldump, compatible option:          mysqldump.          (line  432)
* mysqldump, complete-insert option:     mysqldump.          (line  451)
* mysqldump, compress option:            mysqldump.          (line  456)
* mysqldump, create-options option:      mysqldump.          (line  461)
* mysqldump, databases option:           mysqldump.          (line  466)
* mysqldump, debug option:               mysqldump.          (line  475)
* mysqldump, debug-check option:         mysqldump.          (line  481)
* mysqldump, debug-info option:          mysqldump.          (line  486)
* mysqldump, default-character-set option: mysqldump.        (line  491)
* mysqldump, defaults-extra-file option: mysqldump.          (line  502)
* mysqldump, defaults-file option:       mysqldump.          (line  509)
* mysqldump, defaults-group-suffix option: mysqldump.        (line  515)
* mysqldump, delayed-insert option:      mysqldump.          (line  524)
* mysqldump, delete-master-logs option:  mysqldump.          (line  529)
* mysqldump, disable-keys option:        mysqldump.          (line  536)
* mysqldump, dump-date option:           mysqldump.          (line  546)
* mysqldump, events option:              mysqldump.          (line  561)
* mysqldump, extended-insert option:     mysqldump.          (line  566)
* mysqldump, fields-enclosed-by option <1>: mysqlimport.     (line  210)
* mysqldump, fields-enclosed-by option:  mysqldump.          (line  574)
* mysqldump, fields-escaped-by option <1>: mysqlimport.      (line  214)
* mysqldump, fields-escaped-by option:   mysqldump.          (line  578)
* mysqldump, fields-optionally-enclosed-by option <1>: mysqlimport.
                                                             (line  212)
* mysqldump, fields-optionally-enclosed-by option: mysqldump.
                                                             (line  576)
* mysqldump, fields-terminated-by option <1>: mysqlimport.   (line  208)
* mysqldump, fields-terminated-by option: mysqldump.         (line  572)
* mysqldump, first-slave option:         mysqldump.          (line  584)
* mysqldump, flush-logs option:          mysqldump.          (line  589)
* mysqldump, flush-privileges option:    mysqldump.          (line  601)
* mysqldump, force option:               mysqldump.          (line  609)
* mysqldump, help option:                mysqldump.          (line  336)
* mysqldump, hex-blob option:            mysqldump.          (line  627)
* mysqldump, host option:                mysqldump.          (line  622)
* mysqldump, ignore-table option:        mysqldump.          (line  634)
* mysqldump, insert-ignore option:       mysqldump.          (line  641)
* mysqldump, lines-terminated-by option <1>: mysqlimport.    (line  238)
* mysqldump, lines-terminated-by option: mysqldump.          (line  646)
* mysqldump, lock-all-tables option:     mysqldump.          (line  652)
* mysqldump, lock-tables option:         mysqldump.          (line  659)
* mysqldump, log-error option:           mysqldump.          (line  673)
* mysqldump, master-data option:         mysqldump.          (line  678)
* mysqldump, no-autocommit option:       mysqldump.          (line  759)
* mysqldump, no-create-db option:        mysqldump.          (line  765)
* mysqldump, no-create-info option:      mysqldump.          (line  771)
* mysqldump, no-data option:             mysqldump.          (line  783)
* mysqldump, no-defaults option:         mysqldump.          (line  791)
* mysqldump, no-set-names option:        mysqldump.          (line  797)
* mysqldump, no-tablespaces option:      mysqldump.          (line  801)
* mysqldump, opt option:                 mysqldump.          (line  810)
* mysqldump, order-by-primary option:    mysqldump.          (line  824)
* mysqldump, password option:            mysqldump.          (line  831)
* mysqldump, pipe option:                mysqldump.          (line  843)
* mysqldump, port option:                mysqldump.          (line  848)
* mysqldump, print-defaults option:      mysqldump.          (line  852)
* mysqldump, problems <1>:               view-restrictions.  (line  114)
* mysqldump, problems:                   mysqldump.          (line 1240)
* mysqldump, protocol option:            mysqldump.          (line  857)
* mysqldump, quick option:               mysqldump.          (line  864)
* mysqldump, quote-names option:         mysqldump.          (line  871)
* mysqldump, replace option:             mysqldump.          (line  880)
* mysqldump, result-file option:         mysqldump.          (line  886)
* mysqldump, routines option:            mysqldump.          (line  894)
* mysqldump, set-charset option:         mysqldump.          (line  924)
* mysqldump, shared-memory-base-name option: mysqldump.      (line  930)
* mysqldump, single-transaction option:  mysqldump.          (line  939)
* mysqldump, skip-comments option:       mysqldump.          (line  978)
* mysqldump, skip-opt option:            mysqldump.          (line  982)
* mysqldump, socket option:              mysqldump.          (line  986)
* mysqldump, SSL options:                mysqldump.          (line  991)
* mysqldump, tab option:                 mysqldump.          (line  997)
* mysqldump, tables option:              mysqldump.          (line 1026)
* mysqldump, triggers option:            mysqldump.          (line 1032)
* mysqldump, tz-utc option:              mysqldump.          (line 1037)
* mysqldump, user option:                mysqldump.          (line 1051)
* mysqldump, using for backups:          using-mysqldump.    (line   14)
* mysqldump, verbose option:             mysqldump.          (line 1055)
* mysqldump, version option:             mysqldump.          (line 1059)
* mysqldump, views <1>:                  view-restrictions.  (line  114)
* mysqldump, views:                      mysqldump.          (line 1240)
* mysqldump, where option:               mysqldump.          (line 1063)
* mysqldump, workarounds <1>:            view-restrictions.  (line  114)
* mysqldump, workarounds:                mysqldump.          (line 1240)
* mysqldump, xml option:                 mysqldump.          (line 1076)
* mysqldumpslow <1>:                     mysqldumpslow.      (line    6)
* mysqldumpslow:                         programs-overview.  (line  201)
* mysqldumpslow, debug option:           mysqldumpslow.      (line   53)
* mysqldumpslow, help option:            mysqldumpslow.      (line   45)
* mysqldumpslow, verbose option:         mysqldumpslow.      (line  103)
* mysqlhotcopy <1>:                      mysqlhotcopy.       (line    6)
* mysqlhotcopy:                          programs-overview.  (line  206)
* mysqlhotcopy, addtodest option:        mysqlhotcopy.       (line   90)
* mysqlhotcopy, allowold option:         mysqlhotcopy.       (line   95)
* mysqlhotcopy, checkpoint option:       mysqlhotcopy.       (line  100)
* mysqlhotcopy, chroot option:           mysqlhotcopy.       (line  105)
* mysqlhotcopy, debug option:            mysqlhotcopy.       (line  111)
* mysqlhotcopy, dryrun option:           mysqlhotcopy.       (line  115)
* mysqlhotcopy, flushlog option:         mysqlhotcopy.       (line  119)
* mysqlhotcopy, help option:             mysqlhotcopy.       (line   86)
* mysqlhotcopy, host option:             mysqlhotcopy.       (line  123)
* mysqlhotcopy, keepold option:          mysqlhotcopy.       (line  129)
* mysqlhotcopy, method option:           mysqlhotcopy.       (line  133)
* mysqlhotcopy, noindices option:        mysqlhotcopy.       (line  137)
* mysqlhotcopy, password option:         mysqlhotcopy.       (line  144)
* mysqlhotcopy, port option:             mysqlhotcopy.       (line  154)
* mysqlhotcopy, quiet option:            mysqlhotcopy.       (line  158)
* mysqlhotcopy, record_log_pos option:   mysqlhotcopy.       (line  162)
* mysqlhotcopy, regexp option:           mysqlhotcopy.       (line  167)
* mysqlhotcopy, resetmaster option:      mysqlhotcopy.       (line  172)
* mysqlhotcopy, resetslave option:       mysqlhotcopy.       (line  176)
* mysqlhotcopy, socket option:           mysqlhotcopy.       (line  180)
* mysqlhotcopy, suffix option:           mysqlhotcopy.       (line  184)
* mysqlhotcopy, tmpdir option:           mysqlhotcopy.       (line  188)
* mysqlhotcopy, user option:             mysqlhotcopy.       (line  192)
* mysqlimport <1>:                       load-data.          (line   34)
* mysqlimport <2>:                       mysqlimport.        (line    6)
* mysqlimport <3>:                       programs-overview.  (line  147)
* mysqlimport:                           copying-databases.  (line   49)
* mysqlimport, bind-address option:      mysqlimport.        (line  131)
* mysqlimport, character-sets-dir option: mysqlimport.       (line  142)
* mysqlimport, columns option:           mysqlimport.        (line  147)
* mysqlimport, compress option:          mysqlimport.        (line  153)
* mysqlimport, debug option:             mysqlimport.        (line  158)
* mysqlimport, debug-check option:       mysqlimport.        (line  163)
* mysqlimport, debug-info option:        mysqlimport.        (line  168)
* mysqlimport, default-character-set option: mysqlimport.    (line  173)
* mysqlimport, defaults-extra-file option: mysqlimport.      (line  182)
* mysqlimport, defaults-file option:     mysqlimport.        (line  189)
* mysqlimport, defaults-group-suffix option: mysqlimport.    (line  195)
* mysqlimport, delete option:            mysqlimport.        (line  204)
* mysqlimport, force option:             mysqlimport.        (line  219)
* mysqlimport, help option:              mysqlimport.        (line  127)
* mysqlimport, host option:              mysqlimport.        (line  225)
* mysqlimport, ignore option:            mysqlimport.        (line  230)
* mysqlimport, ignore-lines option:      mysqlimport.        (line  234)
* mysqlimport, local option:             mysqlimport.        (line  247)
* mysqlimport, lock-tables option:       mysqlimport.        (line  251)
* mysqlimport, low-priority option:      mysqlimport.        (line  256)
* mysqlimport, no-defaults option:       mysqlimport.        (line  262)
* mysqlimport, password option:          mysqlimport.        (line  268)
* mysqlimport, pipe option:              mysqlimport.        (line  280)
* mysqlimport, port option:              mysqlimport.        (line  285)
* mysqlimport, print-defaults option:    mysqlimport.        (line  289)
* mysqlimport, protocol option:          mysqlimport.        (line  294)
* mysqlimport, replace option:           mysqlimport.        (line  301)
* mysqlimport, shared-memory-base-name option: mysqlimport.  (line  311)
* mysqlimport, silent option:            mysqlimport.        (line  320)
* mysqlimport, socket option:            mysqlimport.        (line  324)
* mysqlimport, SSL options:              mysqlimport.        (line  329)
* mysqlimport, use-threads option:       mysqlimport.        (line  339)
* mysqlimport, user option:              mysqlimport.        (line  335)
* mysqlimport, verbose option:           mysqlimport.        (line  344)
* mysqlimport, version option:           mysqlimport.        (line  348)
* mysqlmanager <1>:                      instance-manager.   (line   16)
* mysqlmanager:                          programs-overview.  (line  211)
* mysqlmanager, add-user option:         instance-manager-command-options.
                                                             (line   27)
* mysqlmanager, angel-pid-file option:   instance-manager-command-options.
                                                             (line   32)
* mysqlmanager, bind-address option:     instance-manager-command-options.
                                                             (line   46)
* mysqlmanager, check-password-file option: instance-manager-command-options.
                                                             (line   50)
* mysqlmanager, clean-password-file option: instance-manager-command-options.
                                                             (line   55)
* mysqlmanager, debug option:            instance-manager-command-options.
                                                             (line   60)
* mysqlmanager, default-mysqld-path option: instance-manager-command-options.
                                                             (line   65)
* mysqlmanager, defaults-file option:    instance-manager-command-options.
                                                             (line   74)
* mysqlmanager, drop-user option:        instance-manager-command-options.
                                                             (line   86)
* mysqlmanager, edit-user option:        instance-manager-command-options.
                                                             (line   91)
* mysqlmanager, help option:             instance-manager-command-options.
                                                             (line   23)
* mysqlmanager, install option:          instance-manager-command-options.
                                                             (line   97)
* mysqlmanager, list-users option:       instance-manager-command-options.
                                                             (line  102)
* mysqlmanager, log option:              instance-manager-command-options.
                                                             (line  107)
* mysqlmanager, monitoring-interval option: instance-manager-command-options.
                                                             (line  126)
* mysqlmanager, mysqld-safe-compatible option: instance-manager-command-options.
                                                             (line  155)
* mysqlmanager, password option:         instance-manager-command-options.
                                                             (line  161)
* mysqlmanager, password-file option:    instance-manager-command-options.
                                                             (line  169)
* mysqlmanager, pid-file option:         instance-manager-command-options.
                                                             (line  177)
* mysqlmanager, port option:             instance-manager-command-options.
                                                             (line  184)
* mysqlmanager, print-defaults option:   instance-manager-command-options.
                                                             (line  189)
* mysqlmanager, print-password-line option: instance-manager-command-options.
                                                             (line  194)
* mysqlmanager, remove option:           instance-manager-command-options.
                                                             (line  202)
* mysqlmanager, run-as-service option:   instance-manager-command-options.
                                                             (line  208)
* mysqlmanager, socket option:           instance-manager-command-options.
                                                             (line  214)
* mysqlmanager, standalone option:       instance-manager-command-options.
                                                             (line  220)
* mysqlmanager, user option:             instance-manager-command-options.
                                                             (line  226)
* mysqlmanager, username option:         instance-manager-command-options.
                                                             (line  237)
* mysqlmanager, version option:          instance-manager-command-options.
                                                             (line  242)
* mysqlmanager, wait-timeout option:     instance-manager-command-options.
                                                             (line  246)
* mysqlshow <1>:                         mysqlshow.          (line    6)
* mysqlshow:                             programs-overview.  (line  152)
* mysqlshow, bind-address option:        mysqlshow.          (line  116)
* mysqlshow, character-sets-dir option:  mysqlshow.          (line  127)
* mysqlshow, compress option:            mysqlshow.          (line  132)
* mysqlshow, count option:               mysqlshow.          (line  137)
* mysqlshow, debug option:               mysqlshow.          (line  142)
* mysqlshow, debug-check option:         mysqlshow.          (line  147)
* mysqlshow, debug-info option:          mysqlshow.          (line  152)
* mysqlshow, default-character-set option: mysqlshow.        (line  157)
* mysqlshow, defaults-extra-file option: mysqlshow.          (line  162)
* mysqlshow, defaults-file option:       mysqlshow.          (line  169)
* mysqlshow, defaults-group-suffix option: mysqlshow.        (line  175)
* mysqlshow, help option:                mysqlshow.          (line  112)
* mysqlshow, host option:                mysqlshow.          (line  184)
* mysqlshow, keys option:                mysqlshow.          (line  188)
* mysqlshow, no-defaults option:         mysqlshow.          (line  192)
* mysqlshow, password option:            mysqlshow.          (line  198)
* mysqlshow, pipe option:                mysqlshow.          (line  210)
* mysqlshow, port option:                mysqlshow.          (line  215)
* mysqlshow, print-defaults option:      mysqlshow.          (line  219)
* mysqlshow, protocol option:            mysqlshow.          (line  224)
* mysqlshow, shared-memory-base-name option: mysqlshow.      (line  231)
* mysqlshow, show-table-type option:     mysqlshow.          (line  240)
* mysqlshow, socket option:              mysqlshow.          (line  245)
* mysqlshow, SSL options:                mysqlshow.          (line  250)
* mysqlshow, status option:              mysqlshow.          (line  256)
* mysqlshow, user option:                mysqlshow.          (line  260)
* mysqlshow, verbose option:             mysqlshow.          (line  264)
* mysqlshow, version option:             mysqlshow.          (line  270)
* mysqlslap <1>:                         mysqlslap.          (line    6)
* mysqlslap:                             programs-overview.  (line  157)
* mysqlslap, auto-generate-sql option:   mysqlslap.          (line  209)
* mysqlslap, auto-generate-sql-add-autoincrement option: mysqlslap.
                                                             (line  214)
* mysqlslap, auto-generate-sql-execute-number option: mysqlslap.
                                                             (line  219)
* mysqlslap, auto-generate-sql-guid-primary option: mysqlslap.
                                                             (line  224)
* mysqlslap, auto-generate-sql-load-type option: mysqlslap.  (line  229)
* mysqlslap, auto-generate-sql-secondary-indexes option: mysqlslap.
                                                             (line  237)
* mysqlslap, auto-generate-sql-unique-query-number option: mysqlslap.
                                                             (line  243)
* mysqlslap, auto-generate-sql-unique-write-number option: mysqlslap.
                                                             (line  251)
* mysqlslap, auto-generate-sql-write-number option: mysqlslap.
                                                             (line  257)
* mysqlslap, commit option:              mysqlslap.          (line  262)
* mysqlslap, compress option:            mysqlslap.          (line  267)
* mysqlslap, concurrency option:         mysqlslap.          (line  272)
* mysqlslap, create option:              mysqlslap.          (line  277)
* mysqlslap, create-schema option:       mysqlslap.          (line  282)
* mysqlslap, csv option:                 mysqlslap.          (line  293)
* mysqlslap, debug option:               mysqlslap.          (line  299)
* mysqlslap, debug-check option:         mysqlslap.          (line  304)
* mysqlslap, debug-info option:          mysqlslap.          (line  309)
* mysqlslap, defaults-extra-file option: mysqlslap.          (line  314)
* mysqlslap, defaults-file option:       mysqlslap.          (line  321)
* mysqlslap, defaults-group-suffix option: mysqlslap.        (line  327)
* mysqlslap, delimiter option:           mysqlslap.          (line  336)
* mysqlslap, detach option:              mysqlslap.          (line  341)
* mysqlslap, engine option:              mysqlslap.          (line  347)
* mysqlslap, help option:                mysqlslap.          (line  205)
* mysqlslap, host option:                mysqlslap.          (line  351)
* mysqlslap, iterations option:          mysqlslap.          (line  355)
* mysqlslap, lock-directory option:      mysqlslap.          (line  359)
* mysqlslap, no-defaults option:         mysqlslap.          (line  369)
* mysqlslap, no-drop option:             mysqlslap.          (line  364)
* mysqlslap, number-char-cols option:    mysqlslap.          (line  375)
* mysqlslap, number-int-cols option:     mysqlslap.          (line  380)
* mysqlslap, number-of-queries option:   mysqlslap.          (line  385)
* mysqlslap, only-print option:          mysqlslap.          (line  399)
* mysqlslap, password option:            mysqlslap.          (line  405)
* mysqlslap, pipe option:                mysqlslap.          (line  417)
* mysqlslap, port option:                mysqlslap.          (line  422)
* mysqlslap, post-query option:          mysqlslap.          (line  426)
* mysqlslap, post-system option:         mysqlslap.          (line  432)
* mysqlslap, pre-query option:           mysqlslap.          (line  438)
* mysqlslap, pre-system option:          mysqlslap.          (line  444)
* mysqlslap, preserve-schema option:     mysqlslap.          (line  450)
* mysqlslap, print-defaults option:      mysqlslap.          (line  457)
* mysqlslap, protocol option:            mysqlslap.          (line  462)
* mysqlslap, query option:               mysqlslap.          (line  469)
* mysqlslap, shared-memory-base-name option: mysqlslap.      (line  474)
* mysqlslap, silent option:              mysqlslap.          (line  480)
* mysqlslap, slave option:               mysqlslap.          (line  484)
* mysqlslap, socket option:              mysqlslap.          (line  491)
* mysqlslap, SSL options:                mysqlslap.          (line  496)
* mysqlslap, use-threads option:         mysqlslap.          (line  502)
* mysqlslap, user option:                mysqlslap.          (line  509)
* mysqlslap, verbose option:             mysqlslap.          (line  513)
* mysqlslap, version option:             mysqlslap.          (line  519)
* mysqltest, MySQL Test Suite:           mysql-test-suite.   (line    6)
* NAME_CONST() <1>:                      stored-programs-logging.
                                                             (line  355)
* NAME_CONST():                          miscellaneous-functions.
                                                             (line  183)
* name_file option, comp_err:            comp-err.           (line   53)
* named pipes <1>:                       windows-testing.    (line    6)
* named pipes:                           windows-select-server.
                                                             (line   45)
* named-commands option, mysql:          mysql-command-options.
                                                             (line  328)
* named_pipe system variable:            server-system-variables.
                                                             (line 3551)
* names:                                 identifiers.        (line   13)
* names, case sensitivity:               identifier-case-sensitivity.
                                                             (line    6)
* names, variables:                      user-variables.     (line    6)
* naming, releases of MySQL:             choosing-version.   (line   56)
* NATIONAL CHAR data type:               string-type-overview.
                                                             (line   92)
* NATIONAL VARCHAR data type:            string-type-overview.
                                                             (line  124)
* native backup and restore, backup identifiers: mysql-cluster-backup-using-management-client.
                                                             (line  110)
* native functions, adding:              adding-native-function.
                                                             (line    6)
* native thread support:                 supported-os.       (line    6)
* NATURAL LEFT JOIN:                     join.               (line    6)
* NATURAL LEFT OUTER JOIN:               join.               (line    6)
* NATURAL RIGHT JOIN:                    join.               (line    6)
* NATURAL RIGHT OUTER JOIN:              join.               (line    6)
* NCHAR data type:                       string-type-overview.
                                                             (line   92)
* NDB:                                   faqs-mysql-cluster. (line    6)
* NDB API _slave status variables, and MySQL Cluster Replication: mysql-cluster-replication.
                                                             (line   63)
* NDB API counters (MySQL Cluster):      mysql-cluster-ndb-api-statistics.
                                                             (line    6)
* NDB API counters (MySQL Cluster), scope: mysql-cluster-ndb-api-statistics.
                                                             (line  236)
* NDB API counters (MySQL Cluster), status variables associated with: mysql-cluster-ndb-api-statistics.
                                                             (line  403)
* NDB API counters (MySQL Cluster), types: mysql-cluster-ndb-api-statistics.
                                                             (line  257)
* NDB API, and distributed grant tables: mysql-cluster-privilege-distribution.
                                                             (line  229)
* NDB API, and distributed privileges:   mysql-cluster-privilege-distribution.
                                                             (line  229)
* ndb option, perror:                    perror.             (line   48)
* NDB statistics variables (MySQL Cluster): mysql-cluster-ndb-api-statistics.
                                                             (line    6)
* NDB statistics variables (MySQL Cluster), scope: mysql-cluster-ndb-api-statistics.
                                                             (line  236)
* NDB statistics variables (MySQL Cluster), types: mysql-cluster-ndb-api-statistics.
                                                             (line  257)
* NDB statistics variables, and NDB API counters: mysql-cluster-ndb-api-statistics.
                                                             (line  403)
* NDB storage engine:                    mysql-cluster.      (line   16)
* NDB storage engine, FAQ:               faqs-mysql-cluster. (line    6)
* NDB tables, and MySQL root user:       mysql-cluster-security-mysql-privileges.
                                                             (line   52)
* NDB utilities, security issues:        mysql-cluster-security-mysql-security-procedures.
                                                             (line   78)
* NDB$MAX():                             mysql-cluster-replication-conflict-resolution.
                                                             (line  281)
* NDB$MAX_DELETE_WIN():                  mysql-cluster-replication-conflict-resolution.
                                                             (line  301)
* NDB$OLD:                               mysql-cluster-replication-conflict-resolution.
                                                             (line  259)
* NDB, creating large tables using:      create-table.       (line  879)
* NDB, MAX_ROWS:                         create-table.       (line  879)
* ndb-batch-size option, mysqld:         mysql-cluster-program-options-mysqld.
                                                             (line   23)
* ndb-blob-read-batch-bytes option, mysqld: mysql-cluster-program-options-mysqld.
                                                             (line  115)
* ndb-blob-write-batch-bytes option, mysqld: mysql-cluster-program-options-mysqld.
                                                             (line  161)
* ndb-cluster-connection-pool option, mysqld: mysql-cluster-program-options-mysqld.
                                                             (line   49)
* ndb-connectstring option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  145)
* ndb-connectstring option, mysqld:      mysql-cluster-program-options-mysqld.
                                                             (line  208)
* ndb-connectstring option, ndb_config:  mysql-cluster-programs-ndb-config.
                                                             (line  192)
* ndb-deferred-constraints option (MySQL Cluster): mysql-cluster-program-options-mysqld.
                                                             (line  239)
* ndb-distribution option (MySQL Cluster): mysql-cluster-program-options-mysqld.
                                                             (line  275)
* ndb-log-apply-status option, mysqld:   mysql-cluster-program-options-mysqld.
                                                             (line  370)
* ndb-log-empty-epochs option, mysqld:   mysql-cluster-program-options-mysqld.
                                                             (line  550)
* ndb-log-orig option, mysqld:           mysql-cluster-program-options-mysqld.
                                                             (line  418)
* ndb-log-transaction-id option, mysqld: mysql-cluster-program-options-mysqld.
                                                             (line  451)
* ndb-log-update-as-write (mysqld option): mysql-cluster-replication-conflict-resolution.
                                                             (line   75)
* ndb-mgmd-host option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  207)
* ndb-mgmd-host option (MySQL Cluster):  mysql-cluster-program-options-mysqld.
                                                             (line  303)
* ndb-nodegroup-map option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  807)
* ndb-nodeid option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  224)
* ndb-nodeid option, mysqld:             mysql-cluster-program-options-mysqld.
                                                             (line  492)
* ndb-optimized-node-selection option (MySQL Cluster): mysql-cluster-program-options-common.
                                                             (line  240)
* ndb-shm option (MySQL Cluster programs; OBSOLETE): mysql-cluster-program-options-common.
                                                             (line  270)
* ndb_apply_status table (MySQL Cluster replication) <1>: mysql-cluster-replication-failover.
                                                             (line   10)
* ndb_apply_status table (MySQL Cluster replication): mysql-cluster-replication-schema.
                                                             (line  135)
* ndb_binlog_index table (MySQL Cluster replication) <1>: mysql-cluster-replication-failover.
                                                             (line   19)
* ndb_binlog_index table (MySQL Cluster replication): mysql-cluster-replication-schema.
                                                             (line    6)
* ndb_blob_tool <1>:                     mysql-cluster-programs-ndb-blob-tool.
                                                             (line    6)
* ndb_blob_tool:                         mysql-cluster-programs.
                                                             (line   35)
* ndb_blob_tool, check-orphans option:   mysql-cluster-programs-ndb-blob-tool.
                                                             (line   84)
* ndb_blob_tool, database option:        mysql-cluster-programs-ndb-blob-tool.
                                                             (line   98)
* ndb_blob_tool, delete-orphans option:  mysql-cluster-programs-ndb-blob-tool.
                                                             (line  113)
* ndb_blob_tool, dump-file option:       mysql-cluster-programs-ndb-blob-tool.
                                                             (line  127)
* ndb_blob_tool, verbose option:         mysql-cluster-programs-ndb-blob-tool.
                                                             (line  144)
* ndb_config <1>:                        mysql-cluster-programs-ndb-config.
                                                             (line    6)
* ndb_config:                            mysql-cluster-programs.
                                                             (line   35)
* ndb_config, config-file option:        mysql-cluster-programs-ndb-config.
                                                             (line  214)
* ndb_config, config_from_node option:   mysql-cluster-programs-ndb-config.
                                                             (line  156)
* ndb_config, configinfo option:         mysql-cluster-programs-ndb-config.
                                                             (line  431)
* ndb_config, connections option:        mysql-cluster-programs-ndb-config.
                                                             (line  337)
* ndb_config, fields option:             mysql-cluster-programs-ndb-config.
                                                             (line  391)
* ndb_config, host option:               mysql-cluster-programs-ndb-config.
                                                             (line  274)
* ndb_config, id option:                 mysql-cluster-programs-ndb-config.
                                                             (line  303)
* ndb_config, mycnf option:              mysql-cluster-programs-ndb-config.
                                                             (line  232)
* ndb_config, ndb-connectstring option:  mysql-cluster-programs-ndb-config.
                                                             (line  192)
* ndb_config, nodeid option:             mysql-cluster-programs-ndb-config.
                                                             (line  305)
* ndb_config, nodes option:              mysql-cluster-programs-ndb-config.
                                                             (line  320)
* ndb_config, query option:              mysql-cluster-programs-ndb-config.
                                                             (line  245)
* ndb_config, rows option:               mysql-cluster-programs-ndb-config.
                                                             (line  411)
* ndb_config, system option:             mysql-cluster-programs-ndb-config.
                                                             (line  354)
* ndb_config, type option:               mysql-cluster-programs-ndb-config.
                                                             (line  373)
* ndb_config, usage option:              mysql-cluster-programs-ndb-config.
                                                             (line  144)
* ndb_config, version option:            mysql-cluster-programs-ndb-config.
                                                             (line  181)
* ndb_config, xml option:                mysql-cluster-programs-ndb-config.
                                                             (line  489)
* ndb_cpcd <1>:                          mysql-cluster-programs-ndb-cpcd.
                                                             (line    6)
* ndb_cpcd:                              mysql-cluster-programs.
                                                             (line   35)
* ndb_delete_all <1>:                    mysql-cluster-programs-ndb-delete-all.
                                                             (line    6)
* ndb_delete_all:                        mysql-cluster-programs.
                                                             (line   35)
* ndb_delete_all, transactional option:  mysql-cluster-programs-ndb-delete-all.
                                                             (line   60)
* ndb_desc <1>:                          mysql-cluster-programs-ndb-desc.
                                                             (line    6)
* ndb_desc:                              mysql-cluster-programs.
                                                             (line   35)
* ndb_desc, blob-info option:            mysql-cluster-programs-ndb-desc.
                                                             (line  319)
* ndb_desc, database option:             mysql-cluster-programs-ndb-desc.
                                                             (line  330)
* ndb_desc, extra-node-info option:      mysql-cluster-programs-ndb-desc.
                                                             (line  334)
* ndb_desc, extra-partition-info option: mysql-cluster-programs-ndb-desc.
                                                             (line  348)
* ndb_desc, retries option:              mysql-cluster-programs-ndb-desc.
                                                             (line  352)
* ndb_desc, table option:                mysql-cluster-programs-ndb-desc.
                                                             (line  357)
* ndb_desc, unqualified option:          mysql-cluster-programs-ndb-desc.
                                                             (line  364)
* ndb_dist_priv.sql:                     mysql-cluster-privilege-distribution.
                                                             (line   11)
* ndb_drop_index <1>:                    mysql-cluster-programs-ndb-drop-index.
                                                             (line    6)
* ndb_drop_index:                        mysql-cluster-programs.
                                                             (line   35)
* ndb_drop_table <1>:                    mysql-cluster-programs-ndb-drop-table.
                                                             (line    6)
* ndb_drop_table:                        mysql-cluster-programs.
                                                             (line   35)
* ndb_error_reporter <1>:                mysql-cluster-programs-ndb-error-reporter.
                                                             (line    6)
* ndb_error_reporter:                    mysql-cluster-programs.
                                                             (line   35)
* ndb_error_reporter, options:           mysql-cluster-programs-ndb-error-reporter.
                                                             (line   73)
* ndb_index_stat <1>:                    mysql-cluster-programs-ndb-index-stat.
                                                             (line    6)
* ndb_index_stat:                        mysql-cluster-programs.
                                                             (line   35)
* ndb_index_stat, example:               mysql-cluster-programs-ndb-index-stat.
                                                             (line   24)
* ndb_index_stat, interpreting output:   mysql-cluster-programs-ndb-index-stat.
                                                             (line   24)
* ndb_log_empty_epochs system variable:  mysql-cluster-system-variables.
                                                             (line 1526)
* ndb_log_transaction_id system variable: mysql-cluster-system-variables.
                                                             (line 1490)
* ndb_mgm <1>:                           mysql-cluster-programs-ndb-mgm.
                                                             (line    6)
* ndb_mgm:                               mysql-cluster-programs.
                                                             (line   35)
* ndb_mgm (MySQL Cluster management node client): mysql-cluster-install-first-start.
                                                             (line   36)
* ndb_mgm, using with MySQL Cluster Manager: mysql-cluster-mgm-client-commands.
                                                             (line   17)
* ndb_mgmd <1>:                          mysql-cluster-programs-ndb-mgmd.
                                                             (line    6)
* ndb_mgmd:                              mysql-cluster-programs.
                                                             (line   35)
* ndb_mgmd (MySQL Cluster process):      mysql-cluster-programs-ndb-mgmd.
                                                             (line    6)
* ndb_mgmd (MySQL Cluster), defined:     mysql-cluster-basics.
                                                             (line    6)
* ndb_mgmd, mycnf option:                mysql-cluster-programs-ndb-mgmd.
                                                             (line  311)
* ndb_print_backup_file <1>:             mysql-cluster-programs-ndb-print-backup-file.
                                                             (line    6)
* ndb_print_backup_file:                 mysql-cluster-programs.
                                                             (line   35)
* ndb_print_file <1>:                    mysql-cluster-programs-ndb-print-file.
                                                             (line    6)
* ndb_print_file:                        mysql-cluster-programs.
                                                             (line   35)
* ndb_print_schema_file <1>:             mysql-cluster-programs-ndb-print-schema-file.
                                                             (line    6)
* ndb_print_schema_file:                 mysql-cluster-programs.
                                                             (line   35)
* ndb_print_sys_file <1>:                mysql-cluster-programs-ndb-print-sys-file.
                                                             (line    6)
* ndb_print_sys_file:                    mysql-cluster-programs.
                                                             (line   35)
* ndb_replication system table:          mysql-cluster-replication-conflict-resolution.
                                                             (line  158)
* ndb_restore:                           mysql-cluster-programs-ndb-restore.
                                                             (line    6)
* ndb_restore, and circular replication: mysql-cluster-replication-multi-master.
                                                             (line   64)
* ndb_restore, and distributed privileges: mysql-cluster-privilege-distribution.
                                                             (line  195)
* ndb_restore, append option:            mysql-cluster-programs-ndb-restore.
                                                             (line  757)
* ndb_restore, attribute promotion:      mysql-cluster-programs-ndb-restore.
                                                             (line  434)
* ndb_restore, backup_path option:       mysql-cluster-programs-ndb-restore.
                                                             (line  579)
* ndb_restore, disable-indexes option:   mysql-cluster-programs-ndb-restore.
                                                             (line 1093)
* ndb_restore, dont_ignore_systab_0 option: mysql-cluster-programs-ndb-restore.
                                                             (line  798)
* ndb_restore, errors:                   mysql-cluster-programs-ndb-restore.
                                                             (line 1252)
* ndb_restore, exclude-databases option: mysql-cluster-programs-ndb-restore.
                                                             (line  938)
* ndb_restore, exclude-intermediate-sql-tables option: mysql-cluster-programs-ndb-restore.
                                                             (line 1228)
* ndb_restore, exclude-missing-columns option: mysql-cluster-programs-ndb-restore.
                                                             (line 1063)
* ndb_restore, exclude-missing-tables option: mysql-cluster-programs-ndb-restore.
                                                             (line 1081)
* ndb_restore, exclude-tables option:    mysql-cluster-programs-ndb-restore.
                                                             (line  949)
* ndb_restore, fields-enclosed-by option: mysql-cluster-programs-ndb-restore.
                                                             (line  682)
* ndb_restore, fields-optionally-enclosed-by option: mysql-cluster-programs-ndb-restore.
                                                             (line  697)
* ndb_restore, fields-terminated-by option: mysql-cluster-programs-ndb-restore.
                                                             (line  714)
* ndb_restore, hex option:               mysql-cluster-programs-ndb-restore.
                                                             (line  730)
* ndb_restore, include-databases option: mysql-cluster-programs-ndb-restore.
                                                             (line  858)
* ndb_restore, include-tables option:    mysql-cluster-programs-ndb-restore.
                                                             (line  869)
* ndb_restore, lossy-conversions option: mysql-cluster-programs-ndb-restore.
                                                             (line  491)
* ndb_restore, ndb-nodegroup-map option: mysql-cluster-programs-ndb-restore.
                                                             (line  807)
* ndb_restore, no-binlog option:         mysql-cluster-programs-ndb-restore.
                                                             (line  813)
* ndb_restore, no-restore-disk-objects option: mysql-cluster-programs-ndb-restore.
                                                             (line  820)
* ndb_restore, no-upgrade option:        mysql-cluster-programs-ndb-restore.
                                                             (line  641)
* ndb_restore, parallelism option:       mysql-cluster-programs-ndb-restore.
                                                             (line  828)
* ndb_restore, print option:             mysql-cluster-programs-ndb-restore.
                                                             (line  784)
* ndb_restore, print_data option:        mysql-cluster-programs-ndb-restore.
                                                             (line  653)
* ndb_restore, print_log option:         mysql-cluster-programs-ndb-restore.
                                                             (line  779)
* ndb_restore, print_meta option:        mysql-cluster-programs-ndb-restore.
                                                             (line  774)
* ndb_restore, progress-frequency option: mysql-cluster-programs-ndb-restore.
                                                             (line  834)
* ndb_restore, rebuild-indexes option:   mysql-cluster-programs-ndb-restore.
                                                             (line 1109)
* ndb_restore, restore-privilege-tables option: mysql-cluster-programs-ndb-restore.
                                                             (line  568)
* ndb_restore, rewrite-database option:  mysql-cluster-programs-ndb-restore.
                                                             (line 1179)
* ndb_restore, skip-broken-objects option: mysql-cluster-programs-ndb-restore.
                                                             (line 1145)
* ndb_restore, skip-unknown-objects option: mysql-cluster-programs-ndb-restore.
                                                             (line 1162)
* ndb_restore, tab option:               mysql-cluster-programs-ndb-restore.
                                                             (line  668)
* ndb_restore, typical and required options: mysql-cluster-programs-ndb-restore.
                                                             (line  349)
* ndb_restore, verbose option:           mysql-cluster-programs-ndb-restore.
                                                             (line  840)
* ndb_schema table (MySQL Cluster replication): mysql-cluster-replication-schema.
                                                             (line  201)
* ndb_select_all <1>:                    mysql-cluster-programs-ndb-select-all.
                                                             (line    6)
* ndb_select_all:                        mysql-cluster-programs.
                                                             (line   35)
* ndb_select_all, database option:       mysql-cluster-programs-ndb-select-all.
                                                             (line  129)
* ndb_select_all, delimiter option:      mysql-cluster-programs-ndb-select-all.
                                                             (line  172)
* ndb_select_all, descending option:     mysql-cluster-programs-ndb-select-all.
                                                             (line  157)
* ndb_select_all, disk option:           mysql-cluster-programs-ndb-select-all.
                                                             (line  179)
* ndb_select_all, gci option:            mysql-cluster-programs-ndb-select-all.
                                                             (line  189)
* ndb_select_all, gci64 option:          mysql-cluster-programs-ndb-select-all.
                                                             (line  196)
* ndb_select_all, header option:         mysql-cluster-programs-ndb-select-all.
                                                             (line  162)
* ndb_select_all, lock option:           mysql-cluster-programs-ndb-select-all.
                                                             (line  138)
* ndb_select_all, nodata option:         mysql-cluster-programs-ndb-select-all.
                                                             (line  206)
* ndb_select_all, order option:          mysql-cluster-programs-ndb-select-all.
                                                             (line  151)
* ndb_select_all, parallelism option:    mysql-cluster-programs-ndb-select-all.
                                                             (line  134)
* ndb_select_all, rowid option:          mysql-cluster-programs-ndb-select-all.
                                                             (line  184)
* ndb_select_all, tupscan option:        mysql-cluster-programs-ndb-select-all.
                                                             (line  202)
* ndb_select_all, useHexFormat option:   mysql-cluster-programs-ndb-select-all.
                                                             (line  166)
* ndb_select_count <1>:                  mysql-cluster-programs-ndb-select-count.
                                                             (line    6)
* ndb_select_count:                      mysql-cluster-programs.
                                                             (line   35)
* ndb_show_tables <1>:                   mysql-cluster-programs-ndb-show-tables.
                                                             (line    6)
* ndb_show_tables:                       mysql-cluster-programs.
                                                             (line   35)
* ndb_show_tables, database option:      mysql-cluster-programs-ndb-show-tables.
                                                             (line   77)
* ndb_show_tables, loops option:         mysql-cluster-programs-ndb-show-tables.
                                                             (line   81)
* ndb_show_tables, parsable option:      mysql-cluster-programs-ndb-show-tables.
                                                             (line   87)
* ndb_show_tables, show-temp-status option: mysql-cluster-programs-ndb-show-tables.
                                                             (line   92)
* ndb_show_tables, type option:          mysql-cluster-programs-ndb-show-tables.
                                                             (line   96)
* ndb_show_tables, unqualified option:   mysql-cluster-programs-ndb-show-tables.
                                                             (line  110)
* ndb_size.pl <1>:                       mysql-cluster-programs-ndb-size-pl.
                                                             (line    6)
* ndb_size.pl:                           mysql-cluster-programs.
                                                             (line   35)
* ndb_size.pl (utility):                 faqs-mysql-cluster. (line    6)
* ndb_waiter <1>:                        mysql-cluster-programs-ndb-waiter.
                                                             (line    6)
* ndb_waiter:                            mysql-cluster-programs.
                                                             (line   35)
* ndb_waiter, no-contact option:         mysql-cluster-programs-ndb-waiter.
                                                             (line   99)
* ndb_waiter, not-started option:        mysql-cluster-programs-ndb-waiter.
                                                             (line  105)
* ndb_waiter, nowait-nodes option:       mysql-cluster-programs-ndb-waiter.
                                                             (line  121)
* ndb_waiter, single-user option:        mysql-cluster-programs-ndb-waiter.
                                                             (line  117)
* ndb_waiter, timeout option:            mysql-cluster-programs-ndb-waiter.
                                                             (line  111)
* ndb_waiter, wait-nodes option:         mysql-cluster-programs-ndb-waiter.
                                                             (line  136)
* ndbcluster option, mysqld:             mysql-cluster-program-options-mysqld.
                                                             (line  335)
* NDBCLUSTER storage engine:             mysql-cluster.      (line   16)
* ndbd <1>:                              mysql-cluster-programs-ndbd.
                                                             (line    6)
* ndbd:                                  mysql-cluster-programs.
                                                             (line   35)
* ndbd (MySQL Cluster), defined:         mysql-cluster-basics.
                                                             (line    6)
* ndbd_redo_log_reader:                  mysql-cluster-programs-ndbd-redo-log-reader.
                                                             (line    6)
* ndbinfo database:                      mysql-cluster-ndbinfo.
                                                             (line   29)
* ndbinfo database, and query cache:     mysql-cluster-ndbinfo.
                                                             (line  186)
* ndbinfo database, basic usage:         mysql-cluster-ndbinfo.
                                                             (line  236)
* ndbinfo database, determining support for: mysql-cluster-ndbinfo.
                                                             (line   37)
* ndbinfo_select_all <1>:                mysql-cluster-programs-ndbinfo-select-all.
                                                             (line    6)
* ndbinfo_select_all:                    mysql-cluster-programs.
                                                             (line   35)
* ndbmtd <1>:                            mysql-cluster-programs-ndbmtd.
                                                             (line    6)
* ndbmtd:                                mysql-cluster-programs.
                                                             (line   35)
* ndbmtd, configuration:                 mysql-cluster-ndbd-definition.
                                                             (line 3771)
* ndbmtd, MaxNoOfExecutionThreads:       mysql-cluster-ndbd-definition.
                                                             (line 3700)
* ndbmtd, trace files:                   mysql-cluster-programs-ndbmtd.
                                                             (line   67)
* negative values:                       number-literals.    (line    6)
* nested queries:                        subqueries.         (line   20)
* nested-loop join algorithm:            nested-join-optimization.
                                                             (line  179)
* Nested-Loop join algorithm:            nested-loop-joins.  (line    6)
* net etiquette:                         mailing-list-use.   (line    6)
* net_buffer_length system variable:     server-system-variables.
                                                             (line 3568)
* net_buffer_length variable:            mysql-command-options.
                                                             (line  673)
* net_read_timeout system variable:      server-system-variables.
                                                             (line 3602)
* net_retry_count system variable:       server-system-variables.
                                                             (line 3632)
* net_write_timeout system variable:     server-system-variables.
                                                             (line 3663)
* netmask notation, in account names:    account-names.      (line   89)
* network ports, and MySQL Cluster:      mysql-cluster-security-networking-issues.
                                                             (line  186)
* new features in MySQL 5.1:             mysql-nutshell.     (line    6)
* new features in MySQL Cluster:         mysql-cluster-development.
                                                             (line   16)
* new system variable:                   server-system-variables.
                                                             (line 3690)
* new users, adding:                     unix-postinstallation.
                                                             (line  386)
* newline (\n) <1>:                      load-data.          (line  447)
* newline (\n):                          string-literals.    (line   77)
* next-key lock, InnoDB <1>:             innodb-parameters.  (line 1108)
* next-key lock, InnoDB <2>:             innodb-next-key-locking.
                                                             (line    6)
* next-key lock, InnoDB <3>:             innodb-record-level-locks.
                                                             (line    6)
* next-key lock, InnoDB:                 innodb-transaction-model.
                                                             (line   62)
* NFS, InnoDB <1>:                       innodb-restrictions.
                                                             (line   16)
* NFS, InnoDB:                           innodb-configuration.
                                                             (line   69)
* nice option, mysqld_safe:              mysqld-safe.        (line  172)
* no matching rows:                      no-matching-rows.   (line    6)
* no-auto-rehash option, mysql:          mysql-command-options.
                                                             (line  335)
* no-autocommit option, mysqldump:       mysqldump.          (line  759)
* no-beep option, mysql:                 mysql-command-options.
                                                             (line  340)
* no-beep option, mysqladmin:            mysqladmin.         (line  381)
* no-binlog option (ndb_restore):        mysql-cluster-programs-ndb-restore.
                                                             (line  813)
* no-contact option, ndb_waiter:         mysql-cluster-programs-ndb-waiter.
                                                             (line   99)
* no-create-db option, mysqldump:        mysqldump.          (line  765)
* no-create-info option, mysqldump:      mysqldump.          (line  771)
* no-data option, mysqldump:             mysqldump.          (line  783)
* no-debug option, make_win_bin_dist:    make-win-bin-dist.  (line   54)
* no-defaults option <1>:                mysql-install-db.   (line  106)
* no-defaults option:                    option-file-options.
                                                             (line   43)
* no-defaults option, my_print_defaults: my-print-defaults.  (line   54)
* no-defaults option, myisamchk:         myisamchk-general-options.
                                                             (line   47)
* no-defaults option, mysql:             mysql-command-options.
                                                             (line  344)
* no-defaults option, mysql_upgrade:     mysql-upgrade.      (line  212)
* no-defaults option, mysqladmin:        mysqladmin.         (line  387)
* no-defaults option, mysqlbinlog:       mysqlbinlog.        (line  425)
* no-defaults option, mysqlcheck:        mysqlcheck.         (line  351)
* no-defaults option, mysqld:            server-options.     (line 1436)
* no-defaults option, mysqld_multi:      mysqld-multi.       (line   68)
* no-defaults option, mysqld_safe:       mysqld-safe.        (line  177)
* no-defaults option, mysqldump:         mysqldump.          (line  791)
* no-defaults option, mysqlimport:       mysqlimport.        (line  262)
* no-defaults option, mysqlshow:         mysqlshow.          (line  192)
* no-defaults option, mysqlslap:         mysqlslap.          (line  369)
* no-drop option, mysqlslap:             mysqlslap.          (line  364)
* no-embedded option, make_win_bin_dist: make-win-bin-dist.  (line   58)
* no-log option, mysqld_multi:           mysqld-multi.       (line  149)
* no-named-commands option, mysql:       mysql-command-options.
                                                             (line  350)
* no-nodeid-checks option (ndb_mgmd):    mysql-cluster-programs-ndb-mgmd.
                                                             (line  162)
* no-pager option, mysql:                mysql-command-options.
                                                             (line  355)
* no-restore-disk-objects option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  820)
* no-set-names option, mysqldump:        mysqldump.          (line  797)
* no-symlinks option, myisamchk:         myisamchk-repair-options.
                                                             (line   54)
* no-tablespaces option, mysqldump:      mysqldump.          (line  801)
* no-tee option, mysql:                  mysql-command-options.
                                                             (line  360)
* no-upgrade option (ndb_restore):       mysql-cluster-programs-ndb-restore.
                                                             (line  641)
* NO_AUTO_CREATE_USER SQL mode:          sql-mode.           (line  215)
* NO_AUTO_VALUE_ON_ZERO SQL mode:        sql-mode.           (line  221)
* NO_BACKSLASH_ESCAPES SQL mode:         sql-mode.           (line  240)
* NO_DIR_IN_CREATE SQL mode:             sql-mode.           (line  246)
* NO_ENGINE_SUBSTITUTION SQL mode:       sql-mode.           (line  252)
* NO_FIELD_OPTIONS SQL mode:             sql-mode.           (line  282)
* NO_KEY_OPTIONS SQL mode:               sql-mode.           (line  288)
* NO_TABLE_OPTIONS SQL mode:             sql-mode.           (line  294)
* NO_UNSIGNED_SUBTRACTION SQL mode:      sql-mode.           (line  300)
* NO_ZERO_DATE SQL mode:                 sql-mode.           (line  349)
* NO_ZERO_IN_DATE SQL mode:              sql-mode.           (line  366)
* nodaemon option (ndb_mgmd):            mysql-cluster-programs-ndb-mgmd.
                                                             (line  422)
* nodata option, ndb_select_all:         mysql-cluster-programs-ndb-select-all.
                                                             (line  206)
* node groups (MySQL Cluster):           mysql-cluster-nodes-groups.
                                                             (line    6)
* node logs (MySQL Cluster):             mysql-cluster-event-reports.
                                                             (line   12)
* NodeGroup:                             mysql-cluster-ndbd-definition.
                                                             (line  182)
* NodeId <1>:                            mysql-cluster-api-definition.
                                                             (line   73)
* NodeId <2>:                            mysql-cluster-ndbd-definition.
                                                             (line   87)
* NodeId:                                mysql-cluster-mgm-definition.
                                                             (line   53)
* nodeid option, ndb_config:             mysql-cluster-programs-ndb-config.
                                                             (line  305)
* NodeId1 <1>:                           mysql-cluster-sci-definition.
                                                             (line   26)
* NodeId1 <2>:                           mysql-cluster-shm-definition.
                                                             (line   25)
* NodeId1:                               mysql-cluster-tcp-definition.
                                                             (line   37)
* NodeId2 <1>:                           mysql-cluster-sci-definition.
                                                             (line   37)
* NodeId2 <2>:                           mysql-cluster-shm-definition.
                                                             (line   36)
* NodeId2:                               mysql-cluster-tcp-definition.
                                                             (line   48)
* NODERESTART Events (MySQL Cluster):    mysql-cluster-log-events.
                                                             (line  118)
* nodes option, ndb_config:              mysql-cluster-programs-ndb-config.
                                                             (line  320)
* nodes, ndbinfo table:                  mysql-cluster-ndbinfo-nodes.
                                                             (line    6)
* noindices option, mysqlhotcopy:        mysqlhotcopy.       (line  137)
* nondelimited strings:                  date-and-time-literals.
                                                             (line  122)
* Nontransactional tables:               nontransactional-tables.
                                                             (line    6)
* NoOfDiskPagesToDiskAfterRestartACC (DEPRECATED): mysql-cluster-ndbd-definition.
                                                             (line 2702)
* NoOfDiskPagesToDiskAfterRestartACC, calculating: mysql-cluster-config-lcp-params.
                                                             (line    6)
* NoOfDiskPagesToDiskAfterRestartTUP (DEPRECATED): mysql-cluster-ndbd-definition.
                                                             (line 2658)
* NoOfDiskPagesToDiskAfterRestartTUP, calculating: mysql-cluster-config-lcp-params.
                                                             (line    6)
* NoOfDiskPagesToDiskDuringRestartACC:   mysql-cluster-ndbd-definition.
                                                             (line 2762)
* NoOfDiskPagesToDiskDuringRestartTUP:   mysql-cluster-ndbd-definition.
                                                             (line 2729)
* NoOfFragmentLogFiles:                  mysql-cluster-ndbd-definition.
                                                             (line 1178)
* NoOfFragmentLogFiles, calculating:     mysql-cluster-config-lcp-params.
                                                             (line    6)
* NoOfReplicas:                          mysql-cluster-ndbd-definition.
                                                             (line  213)
* nopager command, mysql:                mysql-commands.     (line  140)
* nostart option (ndbd):                 mysql-cluster-programs-ndbd.
                                                             (line  338)
* nostart option (ndbmtd):               mysql-cluster-programs-ndbd.
                                                             (line  338)
* NOT BETWEEN:                           comparison-operators.
                                                             (line  239)
* not equal (!=):                        comparison-operators.
                                                             (line   94)
* not equal (<>):                        comparison-operators.
                                                             (line   94)
* NOT EXISTS, with subqueries:           exists-and-not-exists-subqueries.
                                                             (line    6)
* NOT IN:                                comparison-operators.
                                                             (line  312)
* NOT LIKE:                              string-comparison-functions.
                                                             (line  173)
* NOT NULL, constraint:                  constraint-invalid-data.
                                                             (line    6)
* NOT REGEXP:                            regexp.             (line   30)
* NOT, logical:                          logical-operators.  (line   30)
* not-started option, ndb_waiter:        mysql-cluster-programs-ndb-waiter.
                                                             (line  105)
* notee command, mysql:                  mysql-commands.     (line  146)
* Notifier:                              windows-notifier.   (line   10)
* NOW():                                 date-and-time-functions.
                                                             (line  771)
* NOWAIT (START BACKUP command):         mysql-cluster-backup-using-management-client.
                                                             (line   43)
* nowait-nodes option (ndb_mgmd):        mysql-cluster-programs-ndb-mgmd.
                                                             (line  502)
* nowait-nodes option (ndbd):            mysql-cluster-programs-ndbd.
                                                             (line  305)
* nowait-nodes option (ndbmtd):          mysql-cluster-programs-ndbd.
                                                             (line  305)
* nowait-nodes option, ndb_waiter:       mysql-cluster-programs-ndb-waiter.
                                                             (line  121)
* nowarning command, mysql:              mysql-commands.     (line  151)
* NUL <1>:                               load-data.          (line  445)
* NUL:                                   string-literals.    (line   73)
* NULL <1>:                              problems-with-null. (line    6)
* NULL:                                  working-with-null.  (line    6)
* NULL value <1>:                        null-values.        (line    6)
* NULL value:                            working-with-null.  (line    6)
* NULL values, and AUTO_INCREMENT columns: problems-with-null.
                                                             (line   76)
* NULL values, and indexes:              create-table.       (line  521)
* NULL values, and TIMESTAMP columns:    problems-with-null. (line   76)
* NULL values, vs. empty values:         problems-with-null. (line    6)
* NULL, ORDER BY <1>:                    select.             (line  212)
* NULL, ORDER BY:                        order-by-optimization.
                                                             (line  115)
* NULL, testing for null <1>:            control-flow-functions.
                                                             (line   88)
* NULL, testing for null:                comparison-operators.
                                                             (line   81)
* NULL, thread state:                    general-thread-states.
                                                             (line  175)
* NULLIF():                              control-flow-functions.
                                                             (line  123)
* Numa:                                  mysql-cluster-ndbd-definition.
                                                             (line 3662)
* number-char-cols option, mysqlslap:    mysqlslap.          (line  375)
* number-int-cols option, mysqlslap:     mysqlslap.          (line  380)
* number-of-queries option, mysqlslap:   mysqlslap.          (line  385)
* numbers:                               number-literals.    (line    6)
* NUMERIC data type:                     numeric-type-overview.
                                                             (line  188)
* numeric precision:                     data-types.         (line   31)
* numeric scale:                         data-types.         (line   37)
* numeric types:                         storage-requirements.
                                                             (line   90)
* numeric-dump-file option, resolve_stack_dump: resolve-stack-dump.
                                                             (line   26)
* NumGeometries():                       gis-geometrycollection-property-functions.
                                                             (line   22)
* NumInteriorRings():                    gis-polygon-property-functions.
                                                             (line   63)
* NumPoints():                           gis-linestring-property-functions.
                                                             (line   72)
* NVARCHAR data type:                    string-type-overview.
                                                             (line  124)
* obtaining information about partitions: partitioning-info. (line    6)
* OCT():                                 string-functions.   (line  521)
* OCTET_LENGTH():                        string-functions.   (line  531)
* ODBC compatibility <1>:                join.               (line  154)
* ODBC compatibility <2>:                create-table.       (line  315)
* ODBC compatibility <3>:                comparison-operators.
                                                             (line  164)
* ODBC compatibility <4>:                type-conversion.    (line   47)
* ODBC compatibility <5>:                numeric-type-overview.
                                                             (line  257)
* ODBC compatibility <6>:                identifier-qualifiers.
                                                             (line   48)
* ODBC compatibility:                    server-system-variables.
                                                             (line 4915)
* ODirect:                               mysql-cluster-ndbd-definition.
                                                             (line 1872)
* offset option, mysqlbinlog:            mysqlbinlog.        (line  431)
* OLAP:                                  group-by-modifiers. (line    6)
* old system variable:                   server-system-variables.
                                                             (line 3712)
* old-alter-table option, mysqld:        server-options.     (line 1442)
* old-style-user-limits option, mysqld:  server-options.     (line 1466)
* old_alter_table system variable:       server-system-variables.
                                                             (line 3740)
* OLD_PASSWORD():                        encryption-functions.
                                                             (line  318)
* old_passwords system variable:         server-system-variables.
                                                             (line 3764)
* old_server option, mysqlaccess:        mysqlaccess.        (line   99)
* ON DUPLICATE KEY UPDATE:               insert.             (line   12)
* one-database option, mysql:            mysql-command-options.
                                                             (line  365)
* one-thread option, mysqld:             server-options.     (line 1482)
* one_shot system variable:              server-system-variables.
                                                             (line 3797)
* online location of manual:             manual-info.        (line    6)
* online upgrades and downgrades (MySQL Cluster): mysql-cluster-rolling-restart.
                                                             (line    6)
* online upgrades and downgrades (MySQL Cluster), order of node updates: mysql-cluster-rolling-restart.
                                                             (line  106)
* only-debug option, make_win_bin_dist:  make-win-bin-dist.  (line   62)
* only-print option, mysqlslap:          mysqlslap.          (line  399)
* ONLY_FULL_GROUP_BY SQL mode:           sql-mode.           (line  388)
* ONLY_FULL_GROUP_BY, SQL mode:          group-by-extensions.
                                                             (line    6)
* OPEN:                                  open.               (line    6)
* Open Source, defined:                  what-is-mysql.      (line   54)
* open tables <1>:                       table-cache.        (line    6)
* open tables:                           mysqladmin.         (line  195)
* open-files-limit option, mysqld:       server-options.     (line 1496)
* open-files-limit option, mysqld_safe:  mysqld-safe.        (line  182)
* open_files_limit system variable:      server-system-variables.
                                                             (line 3802)
* open_files_limit variable:             mysqlbinlog.        (line  606)
* OpenGIS:                               spatial-extensions. (line   12)
* Opening master dump table, thread state: slave-connection-thread-states.
                                                             (line   25)
* Opening mysql.ndb_apply_status, thread state: mysql-cluster-thread-states.
                                                             (line    8)
* Opening table, thread state:           general-thread-states.
                                                             (line  189)
* Opening tables, thread state:          general-thread-states.
                                                             (line  189)
* opening, tables:                       table-cache.        (line    6)
* opens:                                 mysqladmin.         (line  186)
* OpenSSL <1>:                           configuring-for-ssl.
                                                             (line    6)
* OpenSSL:                               ssl-connections.    (line   14)
* operating systems, file-size limits:   table-size-limit.   (line    6)
* operating systems, supported:          supported-os.       (line    6)
* operations, arithmetic:                arithmetic-functions.
                                                             (line   55)
* operators:                             functions.          (line   27)
* operators, assignment <1>:             assignment-operators.
                                                             (line    6)
* operators, assignment:                 user-variables.     (line    6)
* operators, cast <1>:                   cast-functions.     (line    6)
* operators, cast:                       arithmetic-functions.
                                                             (line    6)
* operators, logical:                    logical-operators.  (line    6)
* operators, precedence:                 operator-precedence.
                                                             (line    6)
* opt option, mysqldump:                 mysqldump.          (line  810)
* optimization, subquery:                subquery-optimization-with-exists.
                                                             (line    6)
* optimization, tips:                    miscellaneous-optimization-tips.
                                                             (line    6)
* optimizations <1>:                     index-merge-optimization.
                                                             (line   12)
* optimizations:                         where-optimizations.
                                                             (line    6)
* optimize option, mysqlcheck:           mysqlcheck.         (line  357)
* OPTIMIZE TABLE:                        optimize-table.     (line    6)
* OPTIMIZE TABLE, and partitioning:      partitioning-maintenance.
                                                             (line    6)
* optimizer, and replication:            replication-features-optimizer.
                                                             (line    6)
* optimizer, controlling:                controlling-optimizer.
                                                             (line   11)
* optimizer, query plan evaluation:      controlling-query-plan-evaluation.
                                                             (line    6)
* optimizer, switchable optimizations:   switchable-optimizations.
                                                             (line    6)
* optimizer_prune_level system variable: server-system-variables.
                                                             (line 3827)
* optimizer_search_depth system variable: server-system-variables.
                                                             (line 3849)
* optimizer_switch system variable <1>:  switchable-optimizations.
                                                             (line    6)
* optimizer_switch system variable:      server-system-variables.
                                                             (line 3878)
* optimizing, DISTINCT:                  distinct-optimization.
                                                             (line    6)
* optimizing, filesort:                  order-by-optimization.
                                                             (line  135)
* optimizing, GROUP BY:                  group-by-optimization.
                                                             (line   11)
* optimizing, LEFT JOIN:                 left-join-optimization.
                                                             (line    6)
* optimizing, LIMIT:                     limit-optimization. (line    6)
* optimizing, tables:                    myisam-optimization.
                                                             (line    6)
* optimizing, thread state:              general-thread-states.
                                                             (line  198)
* option files <1>:                      access-denied.      (line  106)
* option files:                          option-files.       (line    6)
* option files, escape sequences:        option-files.       (line  173)
* option prefix, -disable:               option-modifiers.   (line    6)
* option prefix, -enable:                option-modifiers.   (line    6)
* option prefix, -loose:                 option-modifiers.   (line    6)
* option prefix, -maximum:               option-modifiers.   (line    6)
* option prefix, -skip:                  option-modifiers.   (line    6)
* options, boolean:                      option-modifiers.   (line    6)
* options, command-line, mysql:          mysql-command-options.
                                                             (line    6)
* options, command-line, mysqladmin:     mysqladmin.         (line  216)
* options, configure:                    source-configuration-options.
                                                             (line    6)
* options, embedded server:              libmysqld-options.  (line    6)
* options, libmysqld:                    libmysqld-options.  (line    6)
* options, myisamchk:                    myisamchk-general-options.
                                                             (line    6)
* options, provided by MySQL:            tutorial.           (line   16)
* options, replication:                  replication-features.
                                                             (line   46)
* OR <1>:                                index-merge-optimization.
                                                             (line   12)
* OR:                                    searching-on-two-keys.
                                                             (line    6)
* OR Index Merge optimization:           index-merge-optimization.
                                                             (line   12)
* OR, bitwise:                           bit-functions.      (line   20)
* OR, logical:                           logical-operators.  (line   68)
* Oracle compatibility <1>:              explain.            (line   55)
* Oracle compatibility <2>:              alter-table.        (line  316)
* Oracle compatibility <3>:              group-by-functions. (line  251)
* Oracle compatibility:                  extensions-to-ansi. (line  102)
* ORACLE SQL mode:                       sql-mode.           (line  595)
* ORD():                                 string-functions.   (line  535)
* ORDER BY <1>:                          select.             (line  182)
* ORDER BY <2>:                          alter-table.        (line  403)
* ORDER BY:                              sorting-rows.       (line    6)
* ORDER BY, NULL <1>:                    select.             (line  212)
* ORDER BY, NULL:                        order-by-optimization.
                                                             (line  115)
* order option, ndb_select_all:          mysql-cluster-programs-ndb-select-all.
                                                             (line  151)
* order-by-primary option, mysqldump:    mysqldump.          (line  824)
* Out of resources error, and partitioned tables: partitioning-limitations.
                                                             (line  229)
* out-of-range handling:                 out-of-range-and-overflow.
                                                             (line    6)
* out_dir option, comp_err:              comp-err.           (line   57)
* out_file option, comp_err:             comp-err.           (line   62)
* OUTFILE:                               select-into.        (line   48)
* overflow handling:                     out-of-range-and-overflow.
                                                             (line    6)
* Overlaps():                            spatial-relation-functions-mbr.
                                                             (line   48)
* OverloadLimit <1>:                     mysql-cluster-sci-definition.
                                                             (line  219)
* OverloadLimit <2>:                     mysql-cluster-shm-definition.
                                                             (line   80)
* OverloadLimit:                         mysql-cluster-tcp-definition.
                                                             (line   94)
* overview:                              introduction.       (line   18)
* packages, list of:                     packages.           (line    6)
* PAD_CHAR_TO_FULL_LENGTH SQL mode:      sql-mode.           (line  426)
* page size, InnoDB <1>:                 innodb-restrictions.
                                                             (line   83)
* page size, InnoDB:                     innodb-physical-structure.
                                                             (line    6)
* pager command, mysql:                  mysql-commands.     (line  155)
* pager option, mysql:                   mysql-command-options.
                                                             (line  409)
* parallel-recover option, myisamchk:    myisamchk-repair-options.
                                                             (line   66)
* parallelism option (ndb_restore):      mysql-cluster-programs-ndb-restore.
                                                             (line  828)
* parameters, server:                    server-parameters.  (line    6)
* parentheses ( and ):                   operator-precedence.
                                                             (line   49)
* parsable option, ndb_show_tables:      mysql-cluster-programs-ndb-show-tables.
                                                             (line   87)
* partial updates, and replication:      replication-features-slaveerrors.
                                                             (line    6)
* PARTITION:                             partitioning.       (line   14)
* partition management:                  partitioning-management.
                                                             (line   13)
* partition option, mysqld:              server-options.     (line 1531)
* partition pruning:                     partitioning-pruning.
                                                             (line    6)
* partitioning:                          partitioning.       (line   14)
* partitioning information statements:   partitioning-info.  (line    6)
* partitioning keys and primary keys:    partitioning-limitations-partitioning-keys-unique-keys.
                                                             (line    6)
* partitioning keys and unique keys:     partitioning-limitations-partitioning-keys-unique-keys.
                                                             (line    6)
* partitioning, advantages:              partitioning-overview.
                                                             (line  149)
* partitioning, and dates:               partitioning-types. (line   49)
* partitioning, and foreign keys:        partitioning-limitations.
                                                             (line  254)
* partitioning, and FULLTEXT indexes:    partitioning-limitations.
                                                             (line  289)
* partitioning, and key cache:           partitioning-limitations.
                                                             (line  419)
* partitioning, and query cache:         partitioning-limitations.
                                                             (line  412)
* partitioning, and replication:         replication-features-sql-mode.
                                                             (line    6)
* partitioning, and SQL mode <1>:        partitioning-limitations.
                                                             (line   49)
* partitioning, and SQL mode:            replication-features-sql-mode.
                                                             (line    6)
* partitioning, and subqueries:          partitioning-limitations.
                                                             (line  331)
* partitioning, and temporary tables <1>: partitioning-limitations-partitioning-keys-unique-keys.
                                                             (line    6)
* partitioning, and temporary tables:    partitioning-limitations.
                                                             (line  300)
* partitioning, by hash:                 partitioning-hash.  (line   10)
* partitioning, by key:                  partitioning-key.   (line    6)
* partitioning, by linear hash:          partitioning-linear-hash.
                                                             (line    6)
* partitioning, by linear key:           partitioning-key.   (line  112)
* partitioning, by list:                 partitioning-list.  (line    6)
* partitioning, by range:                partitioning-range. (line    6)
* partitioning, concepts:                partitioning-overview.
                                                             (line    6)
* partitioning, data type of partitioning key: partitioning-limitations.
                                                             (line  311)
* partitioning, enabling:                partitioning.       (line   14)
* partitioning, functions allowed in partitioning expressions: partitioning-limitations-functions.
                                                             (line    9)
* partitioning, limitations:             partitioning-limitations.
                                                             (line   13)
* Partitioning, maximum number of partitions: partitioning-limitations.
                                                             (line  229)
* partitioning, operators not permitted in partitioning expressions: partitioning-limitations.
                                                             (line   30)
* partitioning, operators supported in partitioning expressions: partitioning-limitations.
                                                             (line   30)
* partitioning, optimization <1>:        partitioning-pruning.
                                                             (line    6)
* partitioning, optimization:            partitioning-info.  (line   63)
* partitioning, resources:               partitioning.       (line  156)
* partitioning, storage engines (limitations): partitioning-limitations-storage-engines.
                                                             (line    6)
* partitioning, subpartitioning:         partitioning-limitations.
                                                             (line  336)
* partitioning, support:                 partitioning.       (line   14)
* partitioning, support in MySQL Cluster: mysql-cluster-limitations-syntax.
                                                             (line  106)
* partitioning, types:                   partitioning-types. (line   15)
* partitions (MySQL Cluster):            mysql-cluster-nodes-groups.
                                                             (line    6)
* partitions, adding and dropping:       partitioning-management.
                                                             (line   13)
* partitions, analyzing:                 partitioning-maintenance.
                                                             (line    6)
* partitions, checking:                  partitioning-maintenance.
                                                             (line    6)
* PARTITIONS, INFORMATION_SCHEMA table:  partitions-table.   (line    6)
* partitions, managing:                  partitioning-management.
                                                             (line   13)
* partitions, modifying:                 partitioning-management.
                                                             (line   13)
* partitions, optimizing:                partitioning-maintenance.
                                                             (line    6)
* partitions, repairing:                 partitioning-maintenance.
                                                             (line    6)
* partitions, splitting and merging:     partitioning-management.
                                                             (line   13)
* password encryption, reversibility of: encryption-functions.
                                                             (line  369)
* password option:                       connecting.         (line  142)
* password option, mysql:                mysql-command-options.
                                                             (line  418)
* password option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   37)
* password option, mysql_setpermission:  mysql-setpermission.
                                                             (line   38)
* password option, mysql_upgrade:        mysql-upgrade.      (line  218)
* password option, mysqlaccess:          mysqlaccess.        (line  104)
* password option, mysqladmin:           mysqladmin.         (line  393)
* password option, mysqlbinlog:          mysqlbinlog.        (line  435)
* password option, mysqlcheck:           mysqlcheck.         (line  361)
* password option, mysqld_multi:         mysqld-multi.       (line  154)
* password option, mysqldump:            mysqldump.          (line  831)
* password option, mysqlhotcopy:         mysqlhotcopy.       (line  144)
* password option, mysqlimport:          mysqlimport.        (line  268)
* password option, mysqlmanager:         instance-manager-command-options.
                                                             (line  161)
* password option, mysqlshow:            mysqlshow.          (line  198)
* password option, mysqlslap:            mysqlslap.          (line  405)
* PASSWORD() <1>:                        ignoring-user.      (line   26)
* PASSWORD() <2>:                        encryption-functions.
                                                             (line  328)
* PASSWORD() <3>:                        assigning-passwords.
                                                             (line    6)
* PASSWORD():                            connection-access.  (line   38)
* password, root user:                   default-privileges. (line    6)
* password-file option, mysqlmanager:    instance-manager-command-options.
                                                             (line  169)
* passwords, administrator guidelines:   password-security-admin.
                                                             (line    6)
* passwords, for users:                  user-names.         (line    6)
* passwords, forgotten:                  resetting-permissions.
                                                             (line   12)
* passwords, hashing:                    password-hashing.   (line    6)
* passwords, logging:                    password-logging.   (line    6)
* passwords, lost:                       resetting-permissions.
                                                             (line   12)
* passwords, resetting:                  resetting-permissions.
                                                             (line   12)
* passwords, security <1>:               privilege-system.   (line   16)
* passwords, security:                   password-security.  (line   14)
* passwords, setting <1>:                set-password.       (line    6)
* passwords, setting <2>:                grant.              (line  430)
* passwords, setting:                    assigning-passwords.
                                                             (line    6)
* passwords, user guidelines:            password-security-user.
                                                             (line    6)
* PATH environment variable <1>:         invoking-programs.  (line   49)
* PATH environment variable <2>:         environment-variables.
                                                             (line   18)
* PATH environment variable:             unix-postinstallation.
                                                             (line   69)
* path name separators, Windows:         option-files.       (line  195)
* pattern matching <1>:                  regexp.             (line    6)
* pattern matching:                      pattern-matching.   (line    6)
* performance, benchmarks:               custom-benchmarks.  (line    6)
* performance, disk I/O:                 disk-issues.        (line    6)
* performance, estimating:               estimating-performance.
                                                             (line    6)
* performance, improving:                data-size.          (line    6)
* PERIOD_ADD():                          date-and-time-functions.
                                                             (line  817)
* PERIOD_DIFF():                         date-and-time-functions.
                                                             (line  827)
* Perl API:                              apis-perl.          (line    6)
* Perl DBI/DBD, installation problems:   perl-support-problems.
                                                             (line    6)
* Perl, installing:                      perl-support.       (line   12)
* Perl, installing on Windows:           activestate-perl.   (line    6)
* permission checks, effect on speed:    select-optimization.
                                                             (line   25)
* perror <1>:                            perror.             (line    6)
* perror:                                programs-overview.  (line  279)
* perror, -ndb option:                   faqs-mysql-cluster. (line    6)
* perror, help option:                   perror.             (line   44)
* perror, ndb option:                    perror.             (line   48)
* perror, silent option:                 perror.             (line   52)
* perror, verbose option:                perror.             (line   56)
* perror, version option:                perror.             (line   61)
* phantom rows:                          innodb-next-key-locking.
                                                             (line    6)
* PI():                                  mathematical-functions.
                                                             (line  345)
* pid-file option, mysql.server:         mysql-server.       (line   44)
* pid-file option, mysqld:               server-options.     (line 1546)
* pid-file option, mysqld_safe:          mysqld-safe.        (line  192)
* pid-file option, mysqlmanager:         instance-manager-command-options.
                                                             (line  177)
* pid_file system variable:              server-system-variables.
                                                             (line 3918)
* Ping, thread command:                  thread-commands.    (line   78)
* pipe option:                           connecting.         (line  149)
* pipe option, mysql <1>:                mysqlcheck.         (line  373)
* pipe option, mysql:                    mysql-command-options.
                                                             (line  430)
* pipe option, mysql_upgrade:            mysql-upgrade.      (line  230)
* pipe option, mysqladmin:               mysqladmin.         (line  405)
* pipe option, mysqldump:                mysqldump.          (line  843)
* pipe option, mysqlimport:              mysqlimport.        (line  280)
* pipe option, mysqlshow:                mysqlshow.          (line  210)
* pipe option, mysqlslap:                mysqlslap.          (line  417)
* PIPES_AS_CONCAT SQL mode:              sql-mode.           (line  464)
* plan option, mysqlaccess:              mysqlaccess.        (line  113)
* plugin API <1>:                        plugin-api.         (line   13)
* plugin API:                            server-plugins.     (line   11)
* plugin option prefix, mysqld:          server-options.     (line 1567)
* plugin-load option, mysqld:            server-options.     (line 1592)
* plugin_dir system variable:            server-system-variables.
                                                             (line 3936)
* plugindir option, mysql_config:        mysql-config.       (line   41)
* plugins, activating:                   server-plugin-loading.
                                                             (line    6)
* plugins, adding:                       plugin-api.         (line   13)
* plugins, daemon:                       daemon-plugins.     (line    6)
* plugins, full-text parser:             full-text-plugins.  (line    6)
* plugins, INFORMATION_SCHEMA:           information-schema-plugins.
                                                             (line    6)
* PLUGINS, INFORMATION_SCHEMA table:     plugins-table.      (line    6)
* plugins, installing <1>:               install-plugin.     (line    6)
* plugins, installing:                   server-plugin-loading.
                                                             (line    6)
* plugins, server:                       server-plugins.     (line   11)
* plugins, storage engine:               storage-engine-plugins.
                                                             (line    6)
* plugins, uninstalling <1>:             uninstall-plugin.   (line    6)
* plugins, uninstalling:                 server-plugin-loading.
                                                             (line    6)
* POINT data type:                       spatial-datatypes.  (line    6)
* Point():                               gis-mysql-specific-functions.
                                                             (line   61)
* point-in-time recovery:                point-in-time-recovery.
                                                             (line   11)
* point-in-time recovery, using MySQL Cluster replication: mysql-cluster-replication-pitr.
                                                             (line    6)
* PointFromText():                       gis-wkt-functions.  (line   47)
* PointFromWKB():                        gis-wkb-functions.  (line   54)
* PointN():                              gis-linestring-property-functions.
                                                             (line   85)
* PointOnSurface():                      gis-multipolygon-property-functions.
                                                             (line   32)
* PolyFromText():                        gis-wkt-functions.  (line   51)
* PolyFromWKB():                         gis-wkb-functions.  (line   58)
* POLYGON data type:                     spatial-datatypes.  (line    6)
* Polygon():                             gis-mysql-specific-functions.
                                                             (line   65)
* PolygonFromText():                     gis-wkt-functions.  (line   51)
* PolygonFromWKB():                      gis-wkb-functions.  (line   58)
* pools (OBSOLETE), ndbinfo table:       mysql-cluster-ndbinfo-pools.
                                                             (line    6)
* port option:                           connecting.         (line  155)
* port option, mysql:                    mysql-command-options.
                                                             (line  435)
* port option, mysql_config:             mysql-config.       (line   46)
* port option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   47)
* port option, mysql_setpermission:      mysql-setpermission.
                                                             (line   48)
* port option, mysql_upgrade:            mysql-upgrade.      (line  236)
* port option, mysqladmin:               mysqladmin.         (line  410)
* port option, mysqlbinlog:              mysqlbinlog.        (line  447)
* port option, mysqlcheck:               mysqlcheck.         (line  378)
* port option, mysqld:                   server-options.     (line 1649)
* port option, mysqld_safe:              mysqld-safe.        (line  196)
* port option, mysqldump:                mysqldump.          (line  848)
* port option, mysqlhotcopy:             mysqlhotcopy.       (line  154)
* port option, mysqlimport:              mysqlimport.        (line  285)
* port option, mysqlmanager:             instance-manager-command-options.
                                                             (line  184)
* port option, mysqlshow:                mysqlshow.          (line  215)
* port option, mysqlslap:                mysqlslap.          (line  422)
* port system variable:                  server-system-variables.
                                                             (line 3972)
* port-open-timeout option, mysqld:      server-options.     (line 1671)
* portability:                           portability.        (line    6)
* portability, types:                    other-vendor-data-types.
                                                             (line    6)
* porting, to other systems:             porting.            (line   12)
* PortNumber:                            mysql-cluster-mgm-definition.
                                                             (line  101)
* PortNumber (OBSOLETE):                 mysql-cluster-tcp-definition.
                                                             (line  191)
* PortNumberStats:                       mysql-cluster-mgm-definition.
                                                             (line  276)
* ports:                                 security-guidelines.
                                                             (line    6)
* position option, mysqlbinlog:          mysqlbinlog.        (line  451)
* POSITION():                            string-functions.   (line  553)
* post-query option, mysqlslap:          mysqlslap.          (line  426)
* post-system option, mysqlslap:         mysqlslap.          (line  432)
* PostgreSQL compatibility:              extensions-to-ansi. (line  196)
* POSTGRESQL SQL mode:                   sql-mode.           (line  601)
* postinstall, multiple servers:         multiple-servers.   (line   13)
* postinstallation, setup and testing:   postinstallation.   (line   11)
* POW():                                 mathematical-functions.
                                                             (line  357)
* POWER():                               mathematical-functions.
                                                             (line  367)
* pre-query option, mysqlslap:           mysqlslap.          (line  438)
* pre-system option, mysqlslap:          mysqlslap.          (line  444)
* precedence, operator:                  operator-precedence.
                                                             (line    6)
* precision math:                        precision-math.     (line   14)
* precision, arithmetic:                 precision-math.     (line   14)
* precision, numeric:                    data-types.         (line   31)
* prefix option, configure:              source-configuration-options.
                                                             (line  352)
* preload_buffer_size system variable:   server-system-variables.
                                                             (line 3993)
* PREPARE <1>:                           prepare.            (line    6)
* PREPARE:                               sql-syntax-prepared-statements.
                                                             (line   13)
* Prepare, thread command:               thread-commands.    (line   82)
* PREPARE, XA transactions:              xa-statements.      (line    6)
* prepared statements <1>:               c-api-prepared-statements.
                                                             (line    6)
* prepared statements <2>:               deallocate-prepare. (line    6)
* prepared statements <3>:               execute.            (line    6)
* prepared statements <4>:               prepare.            (line    6)
* prepared statements:                   sql-syntax-prepared-statements.
                                                             (line   13)
* prepared statements, repreparation:    statement-repreparation.
                                                             (line    6)
* prepared_stmt_count system variable:   server-system-variables.
                                                             (line 4013)
* preparing, thread state:               general-thread-states.
                                                             (line  202)
* preserve-schema option, mysqlslap:     mysqlslap.          (line  450)
* preserve-trailing-spaces option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  517)
* preview option, mysqlaccess:           mysqlaccess.        (line  117)
* PRIMARY KEY <1>:                       create-table.       (line  462)
* PRIMARY KEY:                           alter-table.        (line  383)
* primary key, constraint:               constraint-primary-key.
                                                             (line    6)
* primary key, deleting:                 alter-table.        (line  376)
* primary keys, and partitioning keys:   partitioning-limitations-partitioning-keys-unique-keys.
                                                             (line    6)
* print command, mysql:                  mysql-commands.     (line  177)
* print option (ndb_restore):            mysql-cluster-programs-ndb-restore.
                                                             (line  784)
* print-defaults option:                 option-file-options.
                                                             (line   49)
* print-defaults option, myisamchk:      myisamchk-general-options.
                                                             (line   53)
* print-defaults option, mysql:          mysql-command-options.
                                                             (line  439)
* print-defaults option, mysql_upgrade:  mysql-upgrade.      (line  240)
* print-defaults option, mysqladmin:     mysqladmin.         (line  414)
* print-defaults option, mysqlbinlog:    mysqlbinlog.        (line  456)
* print-defaults option, mysqlcheck:     mysqlcheck.         (line  382)
* print-defaults option, mysqld:         server-options.     (line 1690)
* print-defaults option, mysqldump:      mysqldump.          (line  852)
* print-defaults option, mysqlimport:    mysqlimport.        (line  289)
* print-defaults option, mysqlmanager:   instance-manager-command-options.
                                                             (line  189)
* print-defaults option, mysqlshow:      mysqlshow.          (line  219)
* print-defaults option, mysqlslap:      mysqlslap.          (line  457)
* print-full-config option (ndb_mgmd):   mysql-cluster-programs-ndb-mgmd.
                                                             (line  442)
* print-password-line option, mysqlmanager: instance-manager-command-options.
                                                             (line  194)
* print_data option (ndb_restore):       mysql-cluster-programs-ndb-restore.
                                                             (line  653)
* print_log option (ndb_restore):        mysql-cluster-programs-ndb-restore.
                                                             (line  779)
* print_meta option (ndb_restore):       mysql-cluster-programs-ndb-restore.
                                                             (line  774)
* privilege information, location:       grant-table-structure.
                                                             (line    6)
* privilege system:                      privilege-system.   (line   16)
* privilege, changes:                    privilege-changes.  (line    6)
* privileges, access:                    privilege-system.   (line   16)
* privileges, adding:                    adding-users.       (line    6)
* privileges, and replication:           replication-features-mysqldb.
                                                             (line    6)
* privileges, default:                   default-privileges. (line    6)
* privileges, deleting <1>:              drop-user.          (line    6)
* privileges, deleting:                  removing-users.     (line    6)
* privileges, display:                   show-grants.        (line    6)
* privileges, dropping <1>:              drop-user.          (line    6)
* privileges, dropping:                  removing-users.     (line    6)
* privileges, granting:                  grant.              (line    6)
* privileges, revoking:                  revoke.             (line    6)
* problems, access denied errors:        error-access-denied.
                                                             (line    6)
* problems, common errors:               problems.           (line   17)
* problems, compiling:                   compilation-problems.
                                                             (line    6)
* problems, DATE columns:                using-date.         (line    6)
* problems, date values:                 datetime.           (line   53)
* problems, installing on IBM-AIX:       aix-installation.   (line   10)
* problems, installing on Solaris:       solaris-installation.
                                                             (line   11)
* problems, installing Perl:             perl-support-problems.
                                                             (line    6)
* problems, linking:                     c-api-building-clients.
                                                             (line   83)
* problems, lost connection errors:      error-lost-connection.
                                                             (line    6)
* problems, reporting <1>:               bug-reports.        (line    6)
* problems, reporting:                   introduction.       (line   78)
* problems, starting the server:         starting-server.    (line    6)
* problems, table locking:               table-locking.      (line    6)
* problems, time zone:                   timezone-problems.  (line    6)
* PROCEDURE:                             select.             (line  352)
* PROCEDURE ANALYSE():                   procedure-analyse.  (line    8)
* procedures, stored:                    stored-routines.    (line   13)
* process management (MySQL Cluster):    mysql-cluster-programs.
                                                             (line   35)
* process support:                       supported-os.       (line    6)
* processes, display:                    show-processlist.   (line    6)
* Processing events from schema table, thread state: mysql-cluster-thread-states.
                                                             (line   14)
* Processing events, thread state:       mysql-cluster-thread-states.
                                                             (line   10)
* processing, arguments:                 udf-arguments.      (line    6)
* PROCESSLIST:                           show-processlist.   (line    6)
* PROCESSLIST, INFORMATION_SCHEMA table: processlist-table.  (line    6)
* Processlist, thread command:           thread-commands.    (line   86)
* profiling system variable:             server-system-variables.
                                                             (line 4033)
* PROFILING, INFORMATION_SCHEMA table:   profiling-table.    (line    6)
* profiling_history_size system variable: server-system-variables.
                                                             (line 4041)
* program options (MySQL Cluster):       mysql-cluster-program-options-common.
                                                             (line    6)
* program variables, setting:            program-variables.  (line    6)
* program-development utilities:         programs-overview.  (line  256)
* programs, administrative:              programs-overview.  (line  165)
* programs, client <1>:                  c-api-building-clients.
                                                             (line    6)
* programs, client:                      programs-overview.  (line  124)
* programs, crash-me:                    portability.        (line    6)
* programs, stored <1>:                  stored-programs-views.
                                                             (line   16)
* programs, stored:                      sql-syntax-compound-statements.
                                                             (line   16)
* programs, utility:                     programs-overview.  (line  165)
* progress-frequency option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  834)
* promote-attributes option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  434)
* prompt command, mysql:                 mysql-commands.     (line  181)
* prompt option, mysql:                  mysql-command-options.
                                                             (line  444)
* prompts, meanings:                     entering-queries.   (line  140)
* pronunciation, MySQL:                  what-is-mysql.      (line  107)
* protocol option:                       connecting.         (line  160)
* protocol option, mysql:                mysql-command-options.
                                                             (line  450)
* protocol option, mysql_upgrade:        mysql-upgrade.      (line  245)
* protocol option, mysqladmin:           mysqladmin.         (line  419)
* protocol option, mysqlbinlog:          mysqlbinlog.        (line  461)
* protocol option, mysqlcheck:           mysqlcheck.         (line  387)
* protocol option, mysqldump:            mysqldump.          (line  857)
* protocol option, mysqlimport:          mysqlimport.        (line  294)
* protocol option, mysqlshow:            mysqlshow.          (line  224)
* protocol option, mysqlslap:            mysqlslap.          (line  462)
* protocol_version system variable:      server-system-variables.
                                                             (line 4049)
* Proxy:                                 mysql-proxy.        (line   15)
* pseudo_thread_id system variable:      server-system-variables.
                                                             (line 4063)
* PURGE BINARY LOGS:                     purge-binary-logs.  (line    6)
* PURGE MASTER LOGS:                     purge-binary-logs.  (line    6)
* PURGE STALE SESSIONS:                  mysql-cluster-start-phases.
                                                             (line   84)
* Purging old relay logs, thread state:  general-thread-states.
                                                             (line  206)
* Python:                                connector-python-info.
                                                             (line    6)
* Python, third-party driver:            apis-python.        (line    6)
* QUARTER():                             date-and-time-functions.
                                                             (line  837)
* queries, entering:                     entering-queries.   (line    6)
* queries, estimating performance:       estimating-performance.
                                                             (line    6)
* queries, examples:                     examples.           (line   18)
* queries, speed of:                     select-optimization.
                                                             (line   25)
* Query Cache:                           query-cache.        (line   13)
* query cache, and ndbinfo database tables: mysql-cluster-ndbinfo.
                                                             (line  186)
* query cache, and partitioned tables:   partitioning-limitations.
                                                             (line  412)
* query cache, thread states:            query-cache-thread-states.
                                                             (line    6)
* query end, thread state:               general-thread-states.
                                                             (line  210)
* query option (ndb_index_stat):         mysql-cluster-programs-ndb-index-stat.
                                                             (line  265)
* query option, mysqlslap:               mysqlslap.          (line  469)
* query option, ndb_config:              mysql-cluster-programs-ndb-config.
                                                             (line  245)
* Query, thread command:                 thread-commands.    (line   90)
* query_alloc_block_size system variable: server-system-variables.
                                                             (line 4077)
* query_cache_limit system variable:     server-system-variables.
                                                             (line 4102)
* query_cache_min_res_unit system variable: server-system-variables.
                                                             (line 4123)
* query_cache_size system variable:      server-system-variables.
                                                             (line 4145)
* query_cache_type system variable:      server-system-variables.
                                                             (line 4175)
* query_cache_wlock_invalidate system variable: server-system-variables.
                                                             (line 4217)
* query_prealloc_size system variable:   server-system-variables.
                                                             (line 4241)
* questions:                             mysqladmin.         (line  176)
* questions, answering:                  mailing-list-use.   (line    6)
* Queueing master event to the relay log, thread state: slave-io-thread-states.
                                                             (line   57)
* quick option, myisamchk:               myisamchk-repair-options.
                                                             (line   72)
* quick option, mysql:                   mysql-command-options.
                                                             (line  457)
* quick option, mysqlcheck:              mysqlcheck.         (line  394)
* quick option, mysqldump:               mysqldump.          (line  864)
* quiet option, mysqlhotcopy:            mysqlhotcopy.       (line  158)
* QUIT command (MySQL Cluster):          mysql-cluster-mgm-client-commands.
                                                             (line  195)
* quit command, mysql:                   mysql-commands.     (line  190)
* Quit, thread command:                  thread-commands.    (line   94)
* quotation marks, in strings:           string-literals.    (line   98)
* QUOTE() <1>:                           mysql-real-escape-string.
                                                             (line   17)
* QUOTE() <2>:                           string-functions.   (line  557)
* QUOTE():                               string-literals.    (line  147)
* quote-names option, mysqldump:         mysqldump.          (line  871)
* quoting:                               string-literals.    (line  147)
* quoting binary data:                   string-literals.    (line  137)
* quoting of identifiers:                identifiers.        (line   20)
* quoting, column alias <1>:             problems-with-alias.
                                                             (line    6)
* quoting, column alias:                 identifiers.        (line   84)
* RADIANS():                             mathematical-functions.
                                                             (line  371)
* RAND():                                mathematical-functions.
                                                             (line  380)
* rand_seed1 system variable:            server-system-variables.
                                                             (line 4268)
* rand_seed2 system variable:            server-system-variables.
                                                             (line 4282)
* range join type, optimizer:            explain-output.     (line  349)
* range partitioning:                    partitioning-range. (line    6)
* range partitions, adding and dropping: partitioning-management-range-list.
                                                             (line    6)
* range partitions, managing:            partitioning-management-range-list.
                                                             (line    6)
* range_alloc_block_size system variable: server-system-variables.
                                                             (line 4286)
* raw option, mysql:                     mysql-command-options.
                                                             (line  463)
* raw partitions:                        innodb-raw-devices. (line    6)
* re-creating, grant tables:             mysql-install-db-problems.
                                                             (line  109)
* READ COMMITTED, transaction isolation level: set-transaction.
                                                             (line  119)
* READ UNCOMMITTED, transaction isolation level: set-transaction.
                                                             (line  145)
* read-from-remote-server option, mysqlbinlog: mysqlbinlog.  (line  468)
* read-only option, myisamchk:           myisamchk-check-options.
                                                             (line   55)
* read-only option, mysqld:              replication-options-slave.
                                                             (line  501)
* read_buffer_size myisamchk variable:   myisamchk-general-options.
                                                             (line   84)
* read_buffer_size system variable:      server-system-variables.
                                                             (line 4317)
* read_only system variable:             server-system-variables.
                                                             (line 4362)
* read_rnd_buffer_size system variable:  server-system-variables.
                                                             (line 4429)
* Reading event from the relay log, thread state: slave-sql-thread-states.
                                                             (line   13)
* Reading from net, thread state:        general-thread-states.
                                                             (line  215)
* Reading master dump table data, thread state: slave-connection-thread-states.
                                                             (line   29)
* REAL data type:                        numeric-type-overview.
                                                             (line  233)
* REAL_AS_FLOAT SQL mode:                sql-mode.           (line  469)
* RealtimeScheduler:                     mysql-cluster-ndbd-definition.
                                                             (line 3551)
* rebuild-indexes option (ndb_restore):  mysql-cluster-programs-ndb-restore.
                                                             (line 1109)
* Rebuilding the index on master dump table, thread state: slave-connection-thread-states.
                                                             (line   33)
* ReceiveBufferMemory:                   mysql-cluster-tcp-definition.
                                                             (line  198)
* reconfiguring:                         compilation-problems.
                                                             (line    6)
* reconnect option, mysql:               mysql-command-options.
                                                             (line  495)
* Reconnecting after a failed binlog dump request, thread state: slave-io-thread-states.
                                                             (line   45)
* Reconnecting after a failed master event read, thread state: slave-io-thread-states.
                                                             (line   70)
* reconnection, automatic:               auto-reconnect.     (line    6)
* record-level locks, InnoDB <1>:        innodb-parameters.  (line 1108)
* record-level locks, InnoDB <2>:        innodb-next-key-locking.
                                                             (line    6)
* record-level locks, InnoDB <3>:        innodb-record-level-locks.
                                                             (line    6)
* record-level locks, InnoDB:            innodb-transaction-model.
                                                             (line   62)
* record_log_pos option, mysqlhotcopy:   mysqlhotcopy.       (line  162)
* recover option, myisamchk:             myisamchk-repair-options.
                                                             (line   79)
* RECOVER, XA transactions:              xa-statements.      (line    6)
* recovery, from crash:                  myisam-crash-recovery.
                                                             (line    6)
* recovery, incremental:                 point-in-time-recovery.
                                                             (line   11)
* recovery, point in time:               point-in-time-recovery.
                                                             (line   11)
* redo log:                              innodb-data-log-reconfiguration.
                                                             (line    6)
* RedoBuffer:                            mysql-cluster-ndbd-definition.
                                                             (line 2970)
* RedoOverCommitCounter, data nodes:     mysql-cluster-ndbd-definition.
                                                             (line 4402)
* RedoOverCommitLimit, data nodes:       mysql-cluster-ndbd-definition.
                                                             (line 4426)
* reducing, data size:                   data-size.          (line    6)
* ref join type, optimizer:              explain-output.     (line  280)
* ref_or_null:                           is-null-optimization.
                                                             (line    6)
* ref_or_null join type, optimizer:      explain-output.     (line  307)
* references:                            alter-table.        (line  456)
* referential integrity:                 innodb-introduction.
                                                             (line    6)
* REFERENTIAL_CONSTRAINTS, INFORMATION_SCHEMA table: referential-constraints-table.
                                                             (line    6)
* Refresh, thread command:               thread-commands.    (line   98)
* REGEXP:                                regexp.             (line   34)
* REGEXP operator:                       regexp.             (line    6)
* regexp option, mysql_find_rows:        mysql-find-rows.    (line   37)
* regexp option, mysqlhotcopy:           mysqlhotcopy.       (line  167)
* Register Slave, thread command:        thread-commands.    (line  103)
* Registering slave on master, thread state: slave-io-thread-states.
                                                             (line   25)
* regular expression syntax:             regexp.             (line    6)
* rehash command, mysql:                 mysql-commands.     (line  194)
* relational databases, defined:         what-is-mysql.      (line   54)
* relative option, mysqladmin:           mysqladmin.         (line  426)
* relay-log option, mysqld:              replication-options-slave.
                                                             (line  522)
* relay-log-index option, mysqld:        replication-options-slave.
                                                             (line  570)
* relay-log-info-file option, mysqld:    replication-options-slave.
                                                             (line  604)
* relay-log-purge option, mysqld:        replication-options-slave.
                                                             (line  621)
* relay-log-space-limit option, mysqld:  replication-options-slave.
                                                             (line  641)
* relay_log system variable:             replication-options-slave.
                                                             (line 1372)
* relay_log_index system variable:       replication-options-slave.
                                                             (line 1389)
* relay_log_info_file system variable:   replication-options-slave.
                                                             (line 1409)
* relay_log_purge system variable:       server-system-variables.
                                                             (line 4461)
* relay_log_space_limit system variable: server-system-variables.
                                                             (line 4479)
* release notes:                         news.               (line    6)
* release numbers:                       which-version.      (line   18)
* RELEASE SAVEPOINT:                     savepoint.          (line    6)
* RELEASE_LOCK():                        miscellaneous-functions.
                                                             (line  217)
* releases, naming scheme:               choosing-version.   (line   56)
* releases, testing:                     choosing-version.   (line  118)
* releases, updating:                    many-versions.      (line    6)
* relnotes option, mysqlaccess:          mysqlaccess.        (line  122)
* reload option (ndb_mgmd):              mysql-cluster-programs-ndb-mgmd.
                                                             (line  462)
* remote administration (MySQL Cluster), and security issues: mysql-cluster-security-networking-issues.
                                                             (line  193)
* remove option (ndb_mgmd):              mysql-cluster-programs-ndb-mgmd.
                                                             (line  700)
* remove option (ndbd):                  mysql-cluster-programs-ndbd.
                                                             (line  397)
* remove option (ndbmtd):                mysql-cluster-programs-ndbd.
                                                             (line  397)
* remove option, mysqld:                 server-options.     (line 1695)
* remove option, mysqlmanager:           instance-manager-command-options.
                                                             (line  202)
* Removing duplicates, thread state:     general-thread-states.
                                                             (line  219)
* removing tmp table, thread state:      general-thread-states.
                                                             (line  226)
* RENAME DATABASE:                       rename-database.    (line    6)
* rename result table, thread state:     general-thread-states.
                                                             (line  236)
* RENAME TABLE:                          rename-table.       (line    6)
* RENAME USER:                           rename-user.        (line    6)
* rename, thread state:                  general-thread-states.
                                                             (line  232)
* renaming user accounts:                rename-user.        (line    6)
* Reopen tables, thread state:           general-thread-states.
                                                             (line  242)
* Repair by sorting, thread state:       general-thread-states.
                                                             (line  248)
* Repair done, thread state:             general-thread-states.
                                                             (line  252)
* repair option, mysqlcheck:             mysqlcheck.         (line  403)
* repair options, myisamchk:             myisamchk-repair-options.
                                                             (line    6)
* REPAIR TABLE:                          repair-table.       (line    6)
* REPAIR TABLE, and partitioning:        partitioning-maintenance.
                                                             (line    6)
* REPAIR TABLE, and replication <1>:     replication-features-repair-table.
                                                             (line    6)
* REPAIR TABLE, and replication:         repair-table.       (line  137)
* Repair with keycache, thread state:    general-thread-states.
                                                             (line  257)
* repair, tables:                        mysqlcheck.         (line    6)
* repairing, tables:                     myisam-repair.      (line    6)
* REPEAT:                                repeat.             (line    6)
* REPEAT():                              string-functions.   (line  577)
* REPEAT, labels:                        statement-labels.   (line    6)
* REPEATABLE READ, transaction isolation level: set-transaction.
                                                             (line   97)
* repertoire, character set:             charset-repertoire. (line    6)
* REPLACE:                               replace.            (line    6)
* replace:                               programs-overview.  (line  284)
* replace option, mysqldump:             mysqldump.          (line  880)
* replace option, mysqlimport:           mysqlimport.        (line  301)
* replace utility:                       replace-utility.    (line    6)
* REPLACE():                             string-functions.   (line  587)
* replicas (MySQL Cluster):              mysql-cluster-nodes-groups.
                                                             (line    6)
* replicate-do-db option, mysqld:        replication-options-slave.
                                                             (line  678)
* replicate-do-table option, mysqld:     replication-options-slave.
                                                             (line  868)
* replicate-ignore-db option, mysqld:    replication-options-slave.
                                                             (line  798)
* replicate-ignore-table option, mysqld: replication-options-slave.
                                                             (line  889)
* replicate-rewrite-db option, mysqld:   replication-options-slave.
                                                             (line  911)
* replicate-same-server-id option, mysqld: replication-options-slave.
                                                             (line  960)
* replicate-wild-do-table option, mysqld: replication-options-slave.
                                                             (line  983)
* replicate-wild-ignore-table option, mysqld: replication-options-slave.
                                                             (line 1029)
* replication:                           replication.        (line   13)
* replication filtering options, and case sensitivity: replication-rules.
                                                             (line   58)
* replication formats, compared:         replication-sbr-rbr.
                                                             (line    6)
* replication implementation:            replication-implementation.
                                                             (line   12)
* replication limitations:               replication-features.
                                                             (line   46)
* replication master, thread states:     master-thread-states.
                                                             (line    6)
* replication masters, statements:       replication-master-sql.
                                                             (line   12)
* replication options:                   replication-features.
                                                             (line   46)
* replication slave, thread states <1>:  slave-connection-thread-states.
                                                             (line    6)
* replication slave, thread states <2>:  slave-sql-thread-states.
                                                             (line    6)
* replication slave, thread states:      slave-io-thread-states.
                                                             (line    6)
* replication slaves, statements:        replication-slave-sql.
                                                             (line   17)
* replication, and AUTO_INCREMENT:       replication-features-auto-increment.
                                                             (line    6)
* replication, and character sets:       replication-features-charset.
                                                             (line    6)
* replication, and CREATE ... IF NOT EXISTS: replication-features-create-if-not-exists.
                                                             (line    6)
* replication, and CREATE TABLE ... SELECT: replication-features-create-select.
                                                             (line    6)
* replication, and DATA DIRECTORY:       replication-features-directory.
                                                             (line    6)
* replication, and DROP ... IF EXISTS:   replication-features-drop-if-exists.
                                                             (line    6)
* replication, and errors on slave:      replication-features-slaveerrors.
                                                             (line    6)
* replication, and floating-point values: replication-features-floatvalues.
                                                             (line    6)
* replication, and FLUSH:                replication-features-flush.
                                                             (line    6)
* replication, and functions:            replication-features-functions.
                                                             (line    6)
* replication, and INDEX DIRECTORY:      replication-features-directory.
                                                             (line    6)
* replication, and invoked features:     replication-features-invoked.
                                                             (line    6)
* replication, and LAST_INSERT_ID():     replication-features-auto-increment.
                                                             (line    6)
* replication, and LIMIT:                replication-features-limit.
                                                             (line    6)
* replication, and LOAD DATA:            replication-features-load-data.
                                                             (line    6)
* replication, and max_allowed_packet:   replication-features-max-allowed-packet.
                                                             (line    6)
* replication, and MEMORY tables:        replication-features-memory.
                                                             (line    6)
* replication, and mysql (system) database: replication-features-mysqldb.
                                                             (line    6)
* replication, and partial updates:      replication-features-slaveerrors.
                                                             (line    6)
* replication, and partitioning:         replication-features-sql-mode.
                                                             (line    6)
* replication, and privileges:           replication-features-mysqldb.
                                                             (line    6)
* replication, and query optimizer:      replication-features-optimizer.
                                                             (line    6)
* replication, and REPAIR TABLE statement <1>: replication-features-repair-table.
                                                             (line    6)
* replication, and REPAIR TABLE statement: repair-table.     (line  137)
* replication, and reserved words:       replication-features-reserved-words.
                                                             (line    6)
* replication, and scheduled events:     replication-features-invoked.
                                                             (line    6)
* replication, and slow query log:       replication-features-logging.
                                                             (line    6)
* replication, and SQL mode:             replication-features-sql-mode.
                                                             (line    6)
* replication, and stored routines:      replication-features-invoked.
                                                             (line    6)
* replication, and temporary tables:     replication-features-temptables.
                                                             (line    6)
* replication, and time zones:           replication-features-timezone.
                                                             (line    6)
* replication, and TIMESTAMP <1>:        replication-features-timestamp.
                                                             (line    6)
* replication, and TIMESTAMP <2>:        replication-features-auto-increment.
                                                             (line    6)
* replication, and TIMESTAMP:            upgrading-from-previous-series.
                                                             (line  705)
* replication, and transactions <1>:     replication-features-transactions.
                                                             (line    6)
* replication, and transactions:         replication-features-timeout.
                                                             (line    6)
* replication, and triggers <1>:         replication-features-triggers.
                                                             (line    6)
* replication, and triggers:             replication-features-invoked.
                                                             (line    6)
* replication, and TRUNCATE TABLE:       replication-features-truncate.
                                                             (line    6)
* replication, and variables:            replication-features-variables.
                                                             (line    6)
* replication, and views:                replication-features-views.
                                                             (line    6)
* replication, asynchronous:             mysql-cluster-replication.
                                                             (line   20)
* replication, attribute demotion:       replication-features-different-data-types.
                                                             (line    6)
* replication, attribute promotion:      replication-features-different-data-types.
                                                             (line    6)
* replication, between MySQL server versions <1>: replication-features-timestamp.
                                                             (line    6)
* replication, between MySQL server versions: upgrading-from-previous-series.
                                                             (line  705)
* replication, BLACKHOLE:                replication-features-blackhole.
                                                             (line    6)
* replication, circular:                 mysql-cluster-replication-issues.
                                                             (line   74)
* replication, crashes:                  replication-features-shutdowns.
                                                             (line    6)
* replication, in MySQL Cluster:         mysql-cluster-replication.
                                                             (line   20)
* replication, row-based vs statement-based: replication-sbr-rbr.
                                                             (line    6)
* replication, safe and unsafe statements: replication-rbr-safe-unsafe.
                                                             (line    6)
* replication, shutdown and restart <1>: replication-features-temptables.
                                                             (line    6)
* replication, shutdown and restart:     replication-features-shutdowns.
                                                             (line    6)
* replication, statements incompatible with STATEMENT format: replication-sbr-rbr.
                                                             (line   38)
* replication, timeouts:                 replication-features-timeout.
                                                             (line    6)
* replication, with differing tables on master and slave: replication-features-differing-tables.
                                                             (line   11)
* replication, with ZFS:                 ha-zfs-replication. (line   12)
* REPORT command (MySQL Cluster):        mysql-cluster-mgm-client-commands.
                                                             (line  140)
* report-host option, mysqld:            replication-options-slave.
                                                             (line 1054)
* report-password option, mysqld:        replication-options-slave.
                                                             (line 1078)
* report-port option, mysqld:            replication-options-slave.
                                                             (line 1102)
* report-user option, mysqld:            replication-options-slave.
                                                             (line 1125)
* report_host system variable:           server-system-variables.
                                                             (line 4499)
* report_password system variable:       server-system-variables.
                                                             (line 4516)
* report_port system variable:           server-system-variables.
                                                             (line 4534)
* report_user system variable:           server-system-variables.
                                                             (line 4554)
* reporting, bugs <1>:                   bug-reports.        (line    6)
* reporting, bugs:                       introduction.       (line   78)
* reporting, errors:                     bug-reports.        (line    6)
* reporting, problems:                   introduction.       (line   78)
* Requesting binlog dump, thread state:  slave-io-thread-states.
                                                             (line   30)
* REQUIRE GRANT option:                  grant.              (line  531)
* reschedule, thread state:              delayed-insert-thread-states.
                                                             (line   76)
* reserved words:                        reserved-words.     (line    6)
* reserved words, and replication:       replication-features-reserved-words.
                                                             (line    6)
* ReservedSendBufferMemory:              mysql-cluster-ndbd-definition.
                                                             (line 4359)
* RESET MASTER:                          reset-master.       (line    6)
* RESET SLAVE:                           reset-slave.        (line    6)
* Reset stmt, thread command:            thread-commands.    (line  107)
* reset-slave.pl:                        mysql-cluster-replication-auto-sync.
                                                             (line   11)
* resetmaster option, mysqlhotcopy:      mysqlhotcopy.       (line  172)
* resetslave option, mysqlhotcopy:       mysqlhotcopy.       (line  176)
* resolve_stack_dump <1>:                resolve-stack-dump. (line    6)
* resolve_stack_dump:                    programs-overview.  (line  272)
* resolve_stack_dump, help option:       resolve-stack-dump. (line   22)
* resolve_stack_dump, numeric-dump-file option: resolve-stack-dump.
                                                             (line   26)
* resolve_stack_dump, symbols-file option: resolve-stack-dump.
                                                             (line   30)
* resolve_stack_dump, version option:    resolve-stack-dump. (line   34)
* resolveip <1>:                         resolveip.          (line    6)
* resolveip:                             programs-overview.  (line  289)
* resolveip, help option:                resolveip.          (line   16)
* resolveip, silent option:              resolveip.          (line   20)
* resolveip, version option:             resolveip.          (line   24)
* resource limits, user accounts <1>:    grant.              (line  498)
* resource limits, user accounts <2>:    user-resources.     (line    6)
* resource limits, user accounts:        server-system-variables.
                                                             (line 3237)
* resources, ndbinfo table:              mysql-cluster-ndbinfo-resources.
                                                             (line    6)
* RESTART command (MySQL Cluster):       mysql-cluster-mgm-client-commands.
                                                             (line  101)
* restarting, the server:                unix-postinstallation.
                                                             (line  273)
* RestartOnErrorInsert:                  mysql-cluster-ndbd-definition.
                                                             (line 1895)
* RESTORE TABLE:                         restore-table.      (line    6)
* restore-privilege-tables option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  568)
* restore_connect option (ndb_restore):  mysql-cluster-programs-ndb-restore.
                                                             (line  360)
* restore_data option (ndb_restore):     mysql-cluster-programs-ndb-restore.
                                                             (line  554)
* restore_epoch option (ndb_restore):    mysql-cluster-programs-ndb-restore.
                                                             (line  546)
* restore_meta option (ndb_restore):     mysql-cluster-programs-ndb-restore.
                                                             (line  560)
* restore_nodeid option (ndb_restore):   mysql-cluster-programs-ndb-restore.
                                                             (line  383)
* restore_skip-table-check option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line  397)
* restoring backups, in MySQL Cluster:   mysql-cluster-programs-ndb-restore.
                                                             (line    6)
* restoring from backup, in MySQL Cluster replication: mysql-cluster-replication-backups.
                                                             (line   11)
* restrictions, character sets:          charset-restrictions.
                                                             (line    6)
* restrictions, events:                  stored-program-restrictions.
                                                             (line    6)
* restrictions, InnoDB:                  innodb-restrictions.
                                                             (line    6)
* restrictions, server-side cursors:     cursor-restrictions.
                                                             (line    6)
* restrictions, stored routines:         stored-program-restrictions.
                                                             (line    6)
* restrictions, subqueries:              subquery-restrictions.
                                                             (line    6)
* restrictions, triggers:                stored-program-restrictions.
                                                             (line    6)
* restrictions, views:                   view-restrictions.  (line    6)
* restrictions, XA transactions:         xa-restrictions.    (line    6)
* result-file option, mysqlbinlog:       mysqlbinlog.        (line  479)
* result-file option, mysqldump:         mysqldump.          (line  886)
* retries option, ndb_desc:              mysql-cluster-programs-ndb-desc.
                                                             (line  352)
* retrieving, data from tables:          retrieving-data.    (line   18)
* RETURN:                                return.             (line    6)
* return (\r) <1>:                       load-data.          (line  448)
* return (\r):                           string-literals.    (line   78)
* return values, UDFs:                   udf-return-values.  (line    6)
* REVERSE():                             string-functions.   (line  599)
* REVOKE:                                revoke.             (line    6)
* revoking, privileges:                  revoke.             (line    6)
* rewrite-database option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line 1179)
* rhost option, mysqlaccess:             mysqlaccess.        (line  126)
* RIGHT JOIN:                            join.               (line    6)
* RIGHT OUTER JOIN:                      join.               (line    6)
* RIGHT():                               string-functions.   (line  609)
* RLIKE:                                 regexp.             (line   34)
* ROLLBACK <1>:                          commit.             (line    6)
* ROLLBACK:                              ansi-diff-transactions.
                                                             (line    6)
* rollback option, mysqlaccess:          mysqlaccess.        (line  130)
* ROLLBACK TO SAVEPOINT:                 savepoint.          (line    6)
* ROLLBACK, XA transactions:             xa-statements.      (line    6)
* Rolling back, thread state:            general-thread-states.
                                                             (line  262)
* rolling restart (MySQL Cluster):       mysql-cluster-rolling-restart.
                                                             (line    6)
* ROLLUP:                                group-by-modifiers. (line    6)
* root password:                         default-privileges. (line    6)
* root user:                             security-guidelines.
                                                             (line    6)
* root user, password resetting:         resetting-permissions.
                                                             (line   12)
* ROUND():                               mathematical-functions.
                                                             (line  481)
* rounding:                              precision-math.     (line   14)
* rounding errors:                       numeric-type-overview.
                                                             (line  139)
* routines option, mysqldump:            mysqldump.          (line  894)
* ROUTINES, INFORMATION_SCHEMA table:    routines-table.     (line    6)
* ROW:                                   row-subqueries.     (line    6)
* row size, maximum:                     column-count-limit. (line    6)
* row subqueries:                        row-subqueries.     (line    6)
* row-based replication, advantages:     replication-sbr-rbr.
                                                             (line  136)
* row-based replication, disadvantages:  replication-sbr-rbr.
                                                             (line  179)
* row-level locking:                     internal-locking.   (line    6)
* ROW_COUNT():                           information-functions.
                                                             (line  602)
* rowid option, ndb_select_all:          mysql-cluster-programs-ndb-select-all.
                                                             (line  184)
* rows option, mysql_find_rows:          mysql-find-rows.    (line   41)
* rows option, ndb_config:               mysql-cluster-programs-ndb-config.
                                                             (line  411)
* rows, counting:                        counting-rows.      (line    6)
* rows, deleting:                        deleting-from-related-tables.
                                                             (line    6)
* rows, locking:                         ansi-diff-transactions.
                                                             (line  167)
* rows, matching problems:               no-matching-rows.   (line    6)
* rows, selecting:                       selecting-rows.     (line    6)
* rows, sorting:                         sorting-rows.       (line    6)
* RPAD():                                string-functions.   (line  620)
* RPM file:                              linux-installation-rpm.
                                                             (line    6)
* rpm option, mysql_install_db:          mysql-install-db.   (line  112)
* RPM Package Manager:                   linux-installation-rpm.
                                                             (line    6)
* RTRIM():                               string-functions.   (line  634)
* Ruby API:                              apis-ruby.          (line   11)
* run-as-service option, mysqlmanager:   instance-manager-command-options.
                                                             (line  208)
* running configure after prior invocation: compilation-problems.
                                                             (line   14)
* running, ANSI mode:                    compatibility.      (line   71)
* running, batch mode:                   batch-mode.         (line    6)
* running, multiple servers:             multiple-servers.   (line   13)
* running, queries:                      entering-queries.   (line    6)
* safe statement (replication), defined: replication-rbr-safe-unsafe.
                                                             (line    6)
* safe-mode option, mysqld:              server-options.     (line 1706)
* safe-recover option, myisamchk:        myisamchk-repair-options.
                                                             (line   92)
* safe-show-database option, mysqld:     server-options.     (line 1716)
* safe-updates option:                   safe-updates.       (line    6)
* safe-updates option, mysql:            mysql-command-options.
                                                             (line  502)
* safe-user-create option, mysqld:       server-options.     (line 1737)
* Sakila:                                history.            (line    6)
* same value wins (conflict resolution): mysql-cluster-replication-conflict-resolution.
                                                             (line  270)
* SAVEPOINT:                             savepoint.          (line    6)
* Saving state, thread state:            general-thread-states.
                                                             (line  266)
* scale, arithmetic:                     precision-math.     (line   14)
* scale, numeric:                        data-types.         (line   37)
* SchedulerExecutionTimer:               mysql-cluster-ndbd-definition.
                                                             (line 3571)
* SchedulerSpinTimer:                    mysql-cluster-ndbd-definition.
                                                             (line 3593)
* SCHEMA Events (MySQL Cluster):         mysql-cluster-log-events.
                                                             (line  239)
* SCHEMA():                              information-functions.
                                                             (line  660)
* schema, altering:                      alter-database.     (line    6)
* schema, creating:                      create-database.    (line    6)
* schema, deleting:                      drop-database.      (line    6)
* SCHEMA_PRIVILEGES, INFORMATION_SCHEMA table: schema-privileges-table.
                                                             (line    6)
* SCHEMATA, INFORMATION_SCHEMA table:    schemata-table.     (line    6)
* SCI (Scalable Coherent Interface) <1>: mysql-cluster-sci-sockets.
                                                             (line    6)
* SCI (Scalable Coherent Interface):     mysql-cluster-sci-definition.
                                                             (line    6)
* script files:                          batch-mode.         (line    6)
* scripts <1>:                           mysqld-multi.       (line    6)
* scripts:                               mysqld-safe.        (line    6)
* scripts, mysql_install_db:             mysql-install-db-problems.
                                                             (line    6)
* scripts, SQL:                          mysql.              (line   15)
* Searching rows for update, thread state: general-thread-states.
                                                             (line  273)
* searching, and case sensitivity:       case-sensitivity.   (line    6)
* searching, full-text:                  fulltext-search.    (line   16)
* searching, MySQL Web pages:            bug-reports.        (line    6)
* searching, two keys:                   searching-on-two-keys.
                                                             (line    6)
* SEC_TO_TIME():                         date-and-time-functions.
                                                             (line  853)
* SECOND():                              date-and-time-functions.
                                                             (line  845)
* secondary index, InnoDB:               innodb-index-types. (line    6)
* secure-auth option, mysql:             mysql-command-options.
                                                             (line  510)
* secure-auth option, mysqld:            server-options.     (line 1762)
* secure-file-priv option, mysqld:       server-options.     (line 1789)
* secure_auth system variable:           server-system-variables.
                                                             (line 4571)
* secure_file_priv system variable:      server-system-variables.
                                                             (line 4596)
* securing a MySQL Cluster:              mysql-cluster-security-mysql-security-procedures.
                                                             (line    6)
* security system:                       privilege-system.   (line   16)
* security, against attackers:           security-against-attack.
                                                             (line    6)
* security, and malicious SQL statements: mysql-cluster-security-mysql-privileges.
                                                             (line   87)
* security, and NDB utilities:           mysql-cluster-security-mysql-security-procedures.
                                                             (line   78)
* SELECT INTO TABLE:                     ansi-diff-select-into-table.
                                                             (line    6)
* SELECT speed:                          select-speed.       (line    6)
* SELECT, INTO:                          select-into.        (line    6)
* SELECT, LIMIT:                         select.             (line   13)
* SELECT, optimizing <1>:                explain.            (line    6)
* SELECT, optimizing:                    using-explain.      (line    6)
* SELECT, Query Cache:                   query-cache.        (line   13)
* select_limit variable:                 mysql-command-options.
                                                             (line  678)
* selecting, databases:                  creating-database.  (line    6)
* semi-consistent read, InnoDB:          innodb-parameters.  (line 1108)
* SendBufferMemory:                      mysql-cluster-tcp-definition.
                                                             (line  118)
* Sending binlog event to slave, thread state: master-thread-states.
                                                             (line   11)
* sending cached result to client, thread state: query-cache-thread-states.
                                                             (line   24)
* SendLimit:                             mysql-cluster-sci-definition.
                                                             (line  170)
* SendSignalId <1>:                      mysql-cluster-sci-definition.
                                                             (line  185)
* SendSignalId <2>:                      mysql-cluster-shm-definition.
                                                             (line  139)
* SendSignalId:                          mysql-cluster-tcp-definition.
                                                             (line  156)
* SEQUENCE:                              example-auto-increment.
                                                             (line    6)
* sequence emulation:                    information-functions.
                                                             (line  562)
* sequences:                             example-auto-increment.
                                                             (line    6)
* SERIAL:                                numeric-type-overview.
                                                             (line    6)
* SERIAL DEFAULT VALUE:                  data-type-defaults. (line   85)
* SERIALIZABLE, transaction isolation level: set-transaction.
                                                             (line  153)
* server administration:                 mysqladmin.         (line    6)
* server plugins:                        server-plugins.     (line   11)
* server variables <1>:                  show-variables.     (line    6)
* server variables:                      server-system-variables.
                                                             (line    6)
* server, connecting <1>:                connecting.         (line    6)
* server, connecting:                    connecting-disconnecting.
                                                             (line    6)
* server, debugging:                     debugging-server.   (line   16)
* server, disconnecting:                 connecting-disconnecting.
                                                             (line    6)
* server, logs:                          server-logs.        (line   16)
* server, restart:                       unix-postinstallation.
                                                             (line  273)
* server, shutdown:                      unix-postinstallation.
                                                             (line  264)
* server, signal handling:               server-signal-response.
                                                             (line    6)
* server, starting:                      unix-postinstallation.
                                                             (line   54)
* server, starting and stopping:         automatic-start.    (line    6)
* server, starting problems:             starting-server.    (line    6)
* server-id option, mysqlbinlog:         mysqlbinlog.        (line  483)
* server-id option, mysqld:              replication-options.
                                                             (line   21)
* server-id-bits option, mysqlbinlog:    mysqlbinlog.        (line  488)
* server-id-bits option, mysqld:         mysql-cluster-program-options-mysqld.
                                                             (line  597)
* server-side cursor, restrictions:      cursor-restrictions.
                                                             (line    6)
* server_id system variable:             server-system-variables.
                                                             (line 4619)
* server_id_bits system variable:        mysql-cluster-system-variables.
                                                             (line 1556)
* server_operations, ndbinfo table:      mysql-cluster-ndbinfo-server-operations.
                                                             (line    6)
* server_transactions, ndbinfo table:    mysql-cluster-ndbinfo-server-transactions.
                                                             (line    6)
* ServerPort:                            mysql-cluster-ndbd-definition.
                                                             (line  141)
* servers, multiple:                     multiple-servers.   (line   13)
* service-startup-timeout option, mysql.server: mysql-server.
                                                             (line   49)
* session variables, and replication:    replication-features-variables.
                                                             (line    6)
* SESSION_STATUS, INFORMATION_SCHEMA table: status-table.    (line    6)
* SESSION_USER():                        information-functions.
                                                             (line  664)
* SESSION_VARIABLES, INFORMATION_SCHEMA table: variables-table.
                                                             (line    6)
* SET:                                   set-statement.      (line    6)
* SET data type <1>:                     set.                (line    6)
* SET data type:                         string-type-overview.
                                                             (line  260)
* SET GLOBAL sql_slave_skip_counter:     set-global-sql-slave-skip-counter.
                                                             (line    6)
* SET OPTION:                            set-statement.      (line    6)
* Set option, thread command:            thread-commands.    (line  111)
* SET PASSWORD:                          set-password.       (line    6)
* SET PASSWORD statement:                assigning-passwords.
                                                             (line    6)
* SET sql_log_bin:                       set-sql-log-bin.    (line    6)
* SET statement, assignment operator:    assignment-operators.
                                                             (line   72)
* SET TRANSACTION:                       set-transaction.    (line    6)
* SET, CHARACTER SET <1>:                set-statement.      (line  180)
* SET, CHARACTER SET:                    charset-connection. (line    6)
* SET, NAMES <1>:                        set-statement.      (line  196)
* SET, NAMES <2>:                        charset-applications.
                                                             (line    6)
* SET, NAMES:                            charset-connection. (line    6)
* SET, ONE_SHOT:                         set-statement.      (line  212)
* SET, size:                             storage-requirements.
                                                             (line  259)
* set-auto-increment[ option, myisamchk: myisamchk-other-options.
                                                             (line   28)
* set-character-set option, myisamchk:   myisamchk-repair-options.
                                                             (line  105)
* set-charset option, mysqlbinlog:       mysqlbinlog.        (line  502)
* set-charset option, mysqldump:         mysqldump.          (line  924)
* set-collation option, myisamchk:       myisamchk-repair-options.
                                                             (line  110)
* setting passwords:                     set-password.       (line    6)
* setting program variables:             program-variables.  (line    6)
* setting, passwords:                    assigning-passwords.
                                                             (line    6)
* setup, postinstallation:               postinstallation.   (line   11)
* setup, thread state:                   general-thread-states.
                                                             (line  287)
* SHA():                                 encryption-functions.
                                                             (line  392)
* SHA1():                                encryption-functions.
                                                             (line  392)
* shared memory transporter:             mysql-cluster-shm-definition.
                                                             (line    6)
* shared-memory option, mysqld:          server-options.     (line 1811)
* shared-memory-base-name option:        connecting.         (line  196)
* shared-memory-base-name option, mysql: mysql-command-options.
                                                             (line  516)
* shared-memory-base-name option, mysql_upgrade: mysql-upgrade.
                                                             (line  252)
* shared-memory-base-name option, mysqladmin: mysqladmin.    (line  432)
* shared-memory-base-name option, mysqlbinlog: mysqlbinlog.  (line  508)
* shared-memory-base-name option, mysqlcheck: mysqlcheck.    (line  408)
* shared-memory-base-name option, mysqld: server-options.    (line 1826)
* shared-memory-base-name option, mysqldump: mysqldump.      (line  930)
* shared-memory-base-name option, mysqlimport: mysqlimport.  (line  311)
* shared-memory-base-name option, mysqlshow: mysqlshow.      (line  231)
* shared-memory-base-name option, mysqlslap: mysqlslap.      (line  474)
* shared_memory system variable:         server-system-variables.
                                                             (line 4642)
* shared_memory_base_name system variable: server-system-variables.
                                                             (line 4657)
* SharedBufferSize:                      mysql-cluster-sci-definition.
                                                             (line  147)
* SharedGlobalMemory:                    mysql-cluster-ndbd-definition.
                                                             (line 3926)
* shell syntax:                          manual-conventions. (line  129)
* ShmKey:                                mysql-cluster-shm-definition.
                                                             (line  104)
* ShmSize:                               mysql-cluster-shm-definition.
                                                             (line  121)
* short-form option, mysqlbinlog:        mysqlbinlog.        (line  519)
* SHOW AUTHORS <1>:                      show-authors.       (line    6)
* SHOW AUTHORS:                          show.               (line   51)
* SHOW BINARY LOGS <1>:                  show-binary-logs.   (line    6)
* SHOW BINARY LOGS:                      show.               (line   51)
* SHOW BINLOG EVENTS <1>:                show-binlog-events. (line    6)
* SHOW BINLOG EVENTS:                    show.               (line   51)
* SHOW CHARACTER SET <1>:                show-character-set. (line    6)
* SHOW CHARACTER SET:                    show.               (line   51)
* SHOW COLLATION <1>:                    show-collation.     (line    6)
* SHOW COLLATION:                        show.               (line   51)
* SHOW COLUMNS <1>:                      show-columns.       (line    6)
* SHOW COLUMNS:                          show.               (line   51)
* SHOW command (MySQL Cluster):          mysql-cluster-mgm-client-commands.
                                                             (line   38)
* SHOW CONTRIBUTORS <1>:                 show-contributors.  (line    6)
* SHOW CONTRIBUTORS:                     show.               (line   51)
* SHOW CREATE DATABASE <1>:              show-create-database.
                                                             (line    6)
* SHOW CREATE DATABASE:                  show.               (line   51)
* SHOW CREATE EVENT:                     show.               (line   51)
* SHOW CREATE FUNCTION <1>:              show-create-function.
                                                             (line    6)
* SHOW CREATE FUNCTION:                  show.               (line   51)
* SHOW CREATE PROCEDURE <1>:             show-create-procedure.
                                                             (line    6)
* SHOW CREATE PROCEDURE:                 show.               (line   51)
* SHOW CREATE SCHEMA <1>:                show-create-database.
                                                             (line    6)
* SHOW CREATE SCHEMA:                    show.               (line   51)
* SHOW CREATE TABLE <1>:                 show-create-table.  (line    6)
* SHOW CREATE TABLE:                     show.               (line   51)
* SHOW CREATE TRIGGER <1>:               show-create-trigger.
                                                             (line    6)
* SHOW CREATE TRIGGER:                   show.               (line   51)
* SHOW CREATE VIEW <1>:                  show-create-view.   (line    6)
* SHOW CREATE VIEW:                      show.               (line   51)
* SHOW DATABASES <1>:                    show-databases.     (line    6)
* SHOW DATABASES:                        show.               (line   51)
* SHOW ENGINE <1>:                       show-engine.        (line    6)
* SHOW ENGINE:                           show.               (line   51)
* SHOW ENGINE INNODB STATUS:             show-engine.        (line    6)
* SHOW ENGINE NDB STATUS <1>:            mysql-cluster-sql-statements.
                                                             (line   10)
* SHOW ENGINE NDB STATUS:                show-engine.        (line    6)
* SHOW ENGINE NDBCLUSTER STATUS <1>:     mysql-cluster-sql-statements.
                                                             (line   10)
* SHOW ENGINE NDBCLUSTER STATUS:         show-engine.        (line    6)
* SHOW ENGINE, and MySQL Cluster:        mysql-cluster-sql-statements.
                                                             (line   10)
* SHOW ENGINES <1>:                      show-engines.       (line    6)
* SHOW ENGINES:                          show.               (line   51)
* SHOW ENGINES, and MySQL Cluster:       mysql-cluster-sql-statements.
                                                             (line   20)
* SHOW ERRORS <1>:                       show-errors.        (line    6)
* SHOW ERRORS:                           show.               (line   51)
* SHOW ERRORS, and MySQL Cluster:        faqs-mysql-cluster. (line    6)
* SHOW EVENTS <1>:                       show-events.        (line    6)
* SHOW EVENTS:                           show.               (line   51)
* SHOW extensions:                       extended-show.      (line    6)
* SHOW FIELDS <1>:                       show-columns.       (line  104)
* SHOW FIELDS:                           show.               (line   51)
* SHOW FUNCTION CODE <1>:                show-function-code. (line    6)
* SHOW FUNCTION CODE:                    show.               (line   51)
* SHOW FUNCTION STATUS <1>:              show-function-status.
                                                             (line    6)
* SHOW FUNCTION STATUS:                  show.               (line   51)
* SHOW GRANTS <1>:                       show-grants.        (line    6)
* SHOW GRANTS:                           show.               (line   51)
* SHOW INDEX <1>:                        show-index.         (line    6)
* SHOW INDEX:                            show.               (line   51)
* SHOW INNODB STATUS:                    show.               (line   51)
* SHOW KEYS <1>:                         show-index.         (line    6)
* SHOW KEYS:                             show.               (line   51)
* SHOW MASTER LOGS <1>:                  show-binary-logs.   (line    6)
* SHOW MASTER LOGS:                      show.               (line   51)
* SHOW MASTER STATUS <1>:                show-master-status. (line    6)
* SHOW MASTER STATUS:                    show.               (line   51)
* SHOW OPEN TABLES <1>:                  show-open-tables.   (line    6)
* SHOW OPEN TABLES:                      show.               (line   51)
* SHOW PLUGINS <1>:                      show-plugins.       (line    6)
* SHOW PLUGINS:                          show.               (line   51)
* SHOW PRIVILEGES <1>:                   show-privileges.    (line    6)
* SHOW PRIVILEGES:                       show.               (line   51)
* SHOW PROCEDURE CODE <1>:               show-procedure-code.
                                                             (line    6)
* SHOW PROCEDURE CODE:                   show.               (line   51)
* SHOW PROCEDURE STATUS <1>:             show-procedure-status.
                                                             (line    6)
* SHOW PROCEDURE STATUS:                 show.               (line   51)
* SHOW PROCESSLIST <1>:                  show-processlist.   (line    6)
* SHOW PROCESSLIST:                      show.               (line   51)
* SHOW PROFILE <1>:                      show-profile.       (line    6)
* SHOW PROFILE:                          show.               (line   51)
* SHOW PROFILES <1>:                     show-profiles.      (line    6)
* SHOW PROFILES <2>:                     show-profile.       (line    6)
* SHOW PROFILES:                         show.               (line   51)
* SHOW SCHEDULER STATUS <1>:             events-status-info. (line    6)
* SHOW SCHEDULER STATUS:                 show.               (line   51)
* SHOW SCHEMAS <1>:                      show-databases.     (line    6)
* SHOW SCHEMAS:                          show.               (line   51)
* SHOW SLAVE HOSTS <1>:                  show-slave-hosts.   (line    6)
* SHOW SLAVE HOSTS:                      show.               (line   51)
* SHOW SLAVE STATUS <1>:                 show-slave-status.  (line    6)
* SHOW SLAVE STATUS:                     show.               (line   51)
* SHOW STATUS:                           show.               (line   51)
* SHOW STATUS, and MySQL Cluster:        mysql-cluster-sql-statements.
                                                             (line  129)
* SHOW STORAGE ENGINES:                  show-engines.       (line    6)
* SHOW TABLE STATUS:                     show.               (line   51)
* SHOW TABLE TYPES:                      show-engines.       (line    6)
* SHOW TABLES <1>:                       show-tables.        (line    6)
* SHOW TABLES:                           show.               (line   51)
* SHOW TRIGGERS <1>:                     show-triggers.      (line    6)
* SHOW TRIGGERS:                         show.               (line   51)
* SHOW VARIABLES:                        show.               (line   51)
* SHOW VARIABLES, and MySQL Cluster:     mysql-cluster-sql-statements.
                                                             (line   59)
* SHOW WARNINGS <1>:                     show-warnings.      (line    6)
* SHOW WARNINGS:                         show.               (line   51)
* SHOW WARNINGS, and MySQL Cluster:      faqs-mysql-cluster. (line    6)
* SHOW with WHERE <1>:                   extended-show.      (line    6)
* SHOW with WHERE:                       information-schema. (line   36)
* SHOW, in MySQL Cluster management client: mysql-cluster-quick.
                                                             (line  154)
* show-slave-auth-info option, mysqld:   replication-options-slave.
                                                             (line 1149)
* show-table-type option, mysqlshow:     mysqlshow.          (line  240)
* show-temp-status option, ndb_show_tables: mysql-cluster-programs-ndb-show-tables.
                                                             (line   92)
* show-warnings option, mysql:           mysql-command-options.
                                                             (line  525)
* showing, database information:         mysqlshow.          (line    6)
* SHUTDOWN command (MySQL Cluster):      mysql-cluster-mgm-client-commands.
                                                             (line  201)
* Shutdown, thread command:              thread-commands.    (line  116)
* shutdown_timeout variable:             mysqladmin.         (line  494)
* shutting down, the server:             unix-postinstallation.
                                                             (line  264)
* Shutting down, thread state:           mysql-cluster-thread-states.
                                                             (line   18)
* sigint-ignore option, mysql:           mysql-command-options.
                                                             (line  530)
* SIGN():                                mathematical-functions.
                                                             (line  548)
* signals, server response:              server-signal-response.
                                                             (line    6)
* SigNum:                                mysql-cluster-shm-definition.
                                                             (line  175)
* silent column changes:                 silent-column-changes.
                                                             (line    6)
* silent option, myisamchk:              myisamchk-general-options.
                                                             (line   58)
* silent option, myisampack:             myisampack.         (line   97)
* silent option, mysql:                  mysql-command-options.
                                                             (line  535)
* silent option, mysqladmin:             mysqladmin.         (line  441)
* silent option, mysqlcheck:             mysqlcheck.         (line  417)
* silent option, mysqld_multi:           mysqld-multi.       (line  160)
* silent option, mysqlimport:            mysqlimport.        (line  320)
* silent option, mysqlslap:              mysqlslap.          (line  480)
* silent option, perror:                 perror.             (line   52)
* silent option, resolveip:              resolveip.          (line   20)
* SIN():                                 mathematical-functions.
                                                             (line  561)
* single quote (\'):                     string-literals.    (line   74)
* single user mode (MySQL Cluster) <1>:  mysql-cluster-single-user-mode.
                                                             (line    6)
* single user mode (MySQL Cluster):      mysql-cluster-mgm-client-commands.
                                                             (line  177)
* single user mode (MySQL Cluster), and ndb_restore: mysql-cluster-programs-ndb-restore.
                                                             (line   19)
* single-transaction option, mysqldump:  mysqldump.          (line  939)
* single-user option, ndb_waiter:        mysql-cluster-programs-ndb-waiter.
                                                             (line  117)
* SINGLEUSER Events (MySQL Cluster):     mysql-cluster-log-events.
                                                             (line  287)
* size of tables:                        table-size-limit.   (line    6)
* sizes, display:                        data-types.         (line   31)
* skip-broken-objects option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line 1145)
* skip-column-names option, mysql:       mysql-command-options.
                                                             (line  544)
* skip-comments option, mysqldump:       mysqldump.          (line  978)
* skip-concurrent-insert option, mysqld: server-options.     (line 1840)
* skip-event-scheduler option, mysqld:   server-options.     (line 1846)
* skip-grant-tables option, mysqld:      server-options.     (line 1859)
* skip-host-cache option, mysqld:        server-options.     (line 1883)
* skip-innodb option, mysqld <1>:        innodb-parameters.  (line  217)
* skip-innodb option, mysqld:            server-options.     (line 1889)
* skip-kill-mysqld option, mysqld_safe:  mysqld-safe.        (line  202)
* skip-line-numbers option, mysql:       mysql-command-options.
                                                             (line  548)
* skip-merge option, mysqld:             server-options.     (line 1896)
* skip-name-resolve option, mysql_install_db: mysql-install-db.
                                                             (line  118)
* skip-name-resolve option, mysqld:      server-options.     (line 1901)
* skip-ndbcluster option, mysqld:        mysql-cluster-program-options-mysqld.
                                                             (line  651)
* skip-networking option, mysqld:        server-options.     (line 1913)
* skip-nodegroup option (ndb_error_reporter): mysql-cluster-programs-ndb-error-reporter.
                                                             (line  126)
* skip-opt option, mysqldump:            mysqldump.          (line  982)
* skip-partition option, mysqld:         server-options.     (line 1921)
* skip-safemalloc option, mysqld:        server-options.     (line 1985)
* skip-show-database option, mysqld:     server-options.     (line 1998)
* skip-slave-start option, mysqld:       replication-options-slave.
                                                             (line 1165)
* skip-ssl option:                       ssl-options.        (line   39)
* skip-stack-trace option, mysqld:       server-options.     (line 2013)
* skip-symbolic-links option, mysqld:    server-options.     (line 1962)
* skip-syslog option, mysqld_safe:       mysqld-safe.        (line  212)
* skip-thread-priority option, mysqld:   server-options.     (line 2025)
* skip-unknown-objects option (ndb_restore): mysql-cluster-programs-ndb-restore.
                                                             (line 1162)
* skip-use-db option, mysql_find_rows:   mysql-find-rows.    (line   45)
* skip_external_locking system variable: server-system-variables.
                                                             (line 4672)
* skip_name_resolve system variable:     server-system-variables.
                                                             (line 4700)
* skip_networking system variable:       server-system-variables.
                                                             (line 4724)
* skip_show_database system variable:    server-system-variables.
                                                             (line 4742)
* slave option, mysqlslap:               mysqlslap.          (line  484)
* slave-load-tmpdir option, mysqld:      replication-options-slave.
                                                             (line 1199)
* slave-max-allowed-packet (mysqld):     replication-options-slave.
                                                             (line  306)
* slave-net-timeout option, mysqld:      replication-options-slave.
                                                             (line 1235)
* slave-skip-errors option, mysqld:      replication-options-slave.
                                                             (line 1261)
* slave_allow_batching:                  mysql-cluster-replication-starting.
                                                             (line   94)
* slave_compressed_protocol option, mysqld: replication-options-slave.
                                                             (line 1180)
* slave_compressed_protocol system variable: replication-options-slave.
                                                             (line 1433)
* slave_exec_mode system variable:       replication-options-slave.
                                                             (line 1451)
* slave_load_tmpdir system variable:     replication-options-slave.
                                                             (line 1523)
* slave_max_allowed_packet system variable: replication-options-slave.
                                                             (line 1491)
* slave_net_timeout system variable:     replication-options-slave.
                                                             (line 1542)
* slave_skip_errors system variable:     replication-options-slave.
                                                             (line 1563)
* slave_transaction_retries system variable: replication-options-slave.
                                                             (line 1591)
* slave_type_conversions system variable: replication-options-slave.
                                                             (line 1619)
* sleep option, mysqladmin:              mysqladmin.         (line  445)
* SLEEP():                               miscellaneous-functions.
                                                             (line  233)
* Sleep, thread command:                 thread-commands.    (line  120)
* slow queries:                          mysqladmin.         (line  181)
* slow query log:                        slow-query-log.     (line    6)
* slow query log, and replication:       replication-features-logging.
                                                             (line    6)
* slow-query-log option, mysqld:         server-options.     (line 2045)
* slow_launch_time system variable:      server-system-variables.
                                                             (line 4767)
* slow_query_log system variable:        server-system-variables.
                                                             (line 4785)
* slow_query_log_file system variable:   server-system-variables.
                                                             (line 4813)
* SMALLINT data type:                    numeric-type-overview.
                                                             (line  108)
* SNAPSHOTEND (START BACKUP command):    mysql-cluster-backup-using-management-client.
                                                             (line   67)
* SNAPSHOTSTART (START BACKUP command):  mysql-cluster-backup-using-management-client.
                                                             (line   67)
* socket location, changing:             source-configuration-options.
                                                             (line  382)
* socket option:                         connecting.         (line  205)
* socket option, mysql:                  mysql-command-options.
                                                             (line  553)
* socket option, mysql_config:           mysql-config.       (line   50)
* socket option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   51)
* socket option, mysql_setpermission:    mysql-setpermission.
                                                             (line   52)
* socket option, mysql_upgrade:          mysql-upgrade.      (line  262)
* socket option, mysqladmin:             mysqladmin.         (line  452)
* socket option, mysqlbinlog:            mysqlbinlog.        (line  525)
* socket option, mysqlcheck:             mysqlcheck.         (line  421)
* socket option, mysqld:                 server-options.     (line 2066)
* socket option, mysqld_safe:            mysqld-safe.        (line  207)
* socket option, mysqldump:              mysqldump.          (line  986)
* socket option, mysqlhotcopy:           mysqlhotcopy.       (line  180)
* socket option, mysqlimport:            mysqlimport.        (line  324)
* socket option, mysqlmanager:           instance-manager-command-options.
                                                             (line  214)
* socket option, mysqlshow:              mysqlshow.          (line  245)
* socket option, mysqlslap:              mysqlslap.          (line  491)
* socket system variable:                server-system-variables.
                                                             (line 4835)
* Solaris installation problems:         solaris-installation.
                                                             (line   11)
* Solaris troubleshooting:               compilation-problems.
                                                             (line  147)
* Solaris x86_64 issues:                 innodb-tuning.      (line    6)
* Solaris, installation:                 solaris-installation.
                                                             (line   11)
* SOME:                                  any-in-some-subqueries.
                                                             (line    6)
* sort-index option, myisamchk:          myisamchk-other-options.
                                                             (line   36)
* sort-records option, myisamchk:        myisamchk-other-options.
                                                             (line   41)
* sort-recover option, myisamchk:        myisamchk-repair-options.
                                                             (line  116)
* sort_buffer_size myisamchk variable:   myisamchk-general-options.
                                                             (line   84)
* sort_buffer_size system variable:      server-system-variables.
                                                             (line 4860)
* sort_key_blocks myisamchk variable:    myisamchk-general-options.
                                                             (line   84)
* Sorting for group, thread state:       general-thread-states.
                                                             (line  292)
* Sorting for order, thread state:       general-thread-states.
                                                             (line  296)
* Sorting index, thread state:           general-thread-states.
                                                             (line  300)
* Sorting result, thread state:          general-thread-states.
                                                             (line  305)
* sorting, data:                         sorting-rows.       (line    6)
* sorting, grant tables <1>:             request-access.     (line   51)
* sorting, grant tables:                 connection-access.  (line  130)
* sorting, table rows:                   sorting-rows.       (line    6)
* SOUNDEX():                             string-functions.   (line  644)
* SOUNDS LIKE:                           string-functions.   (line  684)
* source (mysql client command) <1>:     mysql-batch-commands.
                                                             (line    6)
* source (mysql client command):         batch-mode.         (line   97)
* source command, mysql:                 mysql-commands.     (line  200)
* source distribution, installing:       source-installation.
                                                             (line   19)
* SPACE():                               string-functions.   (line  688)
* spassword option, mysqlaccess:         mysqlaccess.        (line  134)
* Spatial Extensions in MySQL:           spatial-extensions. (line   12)
* spatial functions:                     spatial-function-reference.
                                                             (line    6)
* speed, compiling:                      compile-and-link-options.
                                                             (line    6)
* speed, increasing with replication:    replication.        (line   13)
* speed, inserting:                      insert-speed.       (line    6)
* speed, linking:                        compile-and-link-options.
                                                             (line    6)
* speed, of queries <1>:                 select-speed.       (line    6)
* speed, of queries:                     select-optimization.
                                                             (line   25)
* sporadic-binlog-dump-fail option, mysqld: replication-options-binary-log.
                                                             (line  407)
* SQL mode:                              sql-mode.           (line    6)
* SQL mode, ALLOW_INVALID_DATES:         sql-mode.           (line  124)
* SQL mode, and partitioning <1>:        partitioning-limitations.
                                                             (line   49)
* SQL mode, and partitioning:            replication-features-sql-mode.
                                                             (line    6)
* SQL mode, and replication:             replication-features-sql-mode.
                                                             (line    6)
* SQL mode, ANSI:                        sql-mode.           (line   87)
* SQL mode, ANSI_QUOTES:                 sql-mode.           (line  142)
* SQL mode, DB2:                         sql-mode.           (line  571)
* SQL mode, ERROR_FOR_DIVISION_BY_ZERO:  sql-mode.           (line  150)
* SQL mode, HIGH_NOT_PRECEDENCE:         sql-mode.           (line  172)
* SQL mode, IGNORE_SPACE:                sql-mode.           (line  188)
* SQL mode, MAXDB:                       sql-mode.           (line  576)
* SQL mode, MSSQL:                       sql-mode.           (line  582)
* SQL mode, MYSQL323:                    sql-mode.           (line  587)
* SQL mode, MYSQL40:                     sql-mode.           (line  591)
* SQL mode, NO_AUTO_CREATE_USER:         sql-mode.           (line  215)
* SQL mode, NO_AUTO_VALUE_ON_ZERO:       sql-mode.           (line  221)
* SQL mode, NO_BACKSLASH_ESCAPES:        sql-mode.           (line  240)
* SQL mode, NO_DIR_IN_CREATE:            sql-mode.           (line  246)
* SQL mode, NO_ENGINE_SUBSTITUTION:      sql-mode.           (line  252)
* SQL mode, NO_FIELD_OPTIONS:            sql-mode.           (line  282)
* SQL mode, NO_KEY_OPTIONS:              sql-mode.           (line  288)
* SQL mode, NO_TABLE_OPTIONS:            sql-mode.           (line  294)
* SQL mode, NO_UNSIGNED_SUBTRACTION:     sql-mode.           (line  300)
* SQL mode, NO_ZERO_DATE:                sql-mode.           (line  349)
* SQL mode, NO_ZERO_IN_DATE:             sql-mode.           (line  366)
* SQL mode, ONLY_FULL_GROUP_BY <1>:      group-by-extensions.
                                                             (line    6)
* SQL mode, ONLY_FULL_GROUP_BY:          sql-mode.           (line  388)
* SQL mode, ORACLE:                      sql-mode.           (line  595)
* SQL mode, PAD_CHAR_TO_FULL_LENGTH:     sql-mode.           (line  426)
* SQL mode, PIPES_AS_CONCAT:             sql-mode.           (line  464)
* SQL mode, POSTGRESQL:                  sql-mode.           (line  601)
* SQL mode, REAL_AS_FLOAT:               sql-mode.           (line  469)
* SQL mode, strict:                      sql-mode.           (line  117)
* SQL mode, STRICT_ALL_TABLES:           sql-mode.           (line  476)
* SQL mode, STRICT_TRANS_TABLES:         sql-mode.           (line   93)
* SQL mode, TRADITIONAL:                 sql-mode.           (line  101)
* SQL node (MySQL Cluster), defined:     mysql-cluster-basics.
                                                             (line    6)
* SQL nodes (MySQL Cluster):             mysql-cluster-mysqld.
                                                             (line    6)
* SQL scripts:                           mysql.              (line   15)
* SQL statements relating to MySQL Cluster: mysql-cluster-sql-statements.
                                                             (line    6)
* SQL statements, replication masters:   replication-master-sql.
                                                             (line   12)
* SQL statements, replication slaves:    replication-slave-sql.
                                                             (line   17)
* SQL, defined:                          what-is-mysql.      (line   54)
* SQL-92, extensions to:                 compatibility.      (line   12)
* sql-mode option, mysqld:               server-options.     (line 2091)
* sql_auto_is_null system variable:      server-system-variables.
                                                             (line 4915)
* SQL_BIG_RESULT:                        select.             (line  409)
* sql_big_selects system variable:       server-system-variables.
                                                             (line 4949)
* SQL_BUFFER_RESULT:                     select.             (line  418)
* sql_buffer_result system variable:     server-system-variables.
                                                             (line 4973)
* SQL_CACHE <1>:                         select.             (line  430)
* SQL_CACHE:                             query-cache-in-select.
                                                             (line    9)
* SQL_CALC_FOUND_ROWS:                   select.             (line  425)
* sql_log_bin system variable:           server-system-variables.
                                                             (line 4992)
* sql_log_off system variable:           server-system-variables.
                                                             (line 5008)
* sql_log_update system variable:        server-system-variables.
                                                             (line 5025)
* sql_mode system variable:              server-system-variables.
                                                             (line 5043)
* SQL_NO_CACHE <1>:                      select.             (line  430)
* SQL_NO_CACHE:                          query-cache-in-select.
                                                             (line   14)
* sql_notes system variable:             server-system-variables.
                                                             (line 5091)
* sql_quote_show_create system variable: server-system-variables.
                                                             (line 5101)
* sql_safe_updates system variable:      server-system-variables.
                                                             (line 5110)
* sql_select_limit system variable:      server-system-variables.
                                                             (line 5122)
* sql_slave_skip_counter:                set-global-sql-slave-skip-counter.
                                                             (line    6)
* sql_slave_skip_counter system variable: replication-options-slave.
                                                             (line 1653)
* SQL_SMALL_RESULT:                      select.             (line  409)
* sql_warnings system variable:          server-system-variables.
                                                             (line 5146)
* sql_yacc.cc problems:                  compilation-problems.
                                                             (line   38)
* SQRT():                                mathematical-functions.
                                                             (line  571)
* square brackets:                       data-types.         (line   41)
* srcdir option, mysql_install_db:       mysql-install-db.   (line  123)
* SRID():                                gis-general-property-functions.
                                                             (line   63)
* SSH:                                   windows-and-ssh.    (line    6)
* SSL:                                   ssl-connections.    (line   14)
* ssl option:                            ssl-options.        (line   39)
* SSL options:                           connecting.         (line  218)
* SSL options, mysql:                    mysql-command-options.
                                                             (line  558)
* SSL options, mysql_upgrade:            mysql-upgrade.      (line  267)
* SSL options, mysqladmin:               mysqladmin.         (line  457)
* SSL options, mysqlcheck:               mysqlcheck.         (line  426)
* SSL options, mysqld:                   server-options.     (line 1945)
* SSL options, mysqldump:                mysqldump.          (line  991)
* SSL options, mysqlimport:              mysqlimport.        (line  329)
* SSL options, mysqlshow:                mysqlshow.          (line  250)
* SSL options, mysqlslap:                mysqlslap.          (line  496)
* SSL related options:                   grant.              (line  531)
* SSL, command options:                  ssl-options.        (line    6)
* SSL, configuring:                      configuring-for-ssl.
                                                             (line    6)
* SSL, establishing connections:         using-ssl-connections.
                                                             (line    6)
* SSL, X509 Basics:                      ssl-basics.         (line    6)
* ssl-ca option:                         ssl-options.        (line   81)
* ssl-capath option:                     ssl-options.        (line   94)
* ssl-cert option:                       ssl-options.        (line  118)
* ssl-cipher option:                     ssl-options.        (line  123)
* ssl-key option:                        ssl-options.        (line  220)
* ssl-verify-server-cert option:         ssl-options.        (line  233)
* ssl_ca system variable:                server-system-variables.
                                                             (line 5152)
* ssl_capath system variable:            server-system-variables.
                                                             (line 5171)
* ssl_cert system variable:              server-system-variables.
                                                             (line 5190)
* ssl_cipher system variable:            server-system-variables.
                                                             (line 5209)
* ssl_key system variable:               server-system-variables.
                                                             (line 5227)
* standalone option, mysqld:             server-options.     (line 1951)
* standalone option, mysqlmanager:       instance-manager-command-options.
                                                             (line  220)
* Standard Monitor, InnoDB:              innodb-monitors.    (line   12)
* Standard SQL, differences from <1>:    grant.              (line  656)
* Standard SQL, differences from:        differences-from-ansi.
                                                             (line   14)
* Standard SQL, extensions to <1>:       extensions-to-ansi. (line    6)
* Standard SQL, extensions to:           compatibility.      (line   12)
* standards compatibility:               compatibility.      (line   12)
* START BACKUP, NOWAIT:                  mysql-cluster-backup-using-management-client.
                                                             (line   43)
* START BACKUP, SNAPSHOTEND:             mysql-cluster-backup-using-management-client.
                                                             (line   67)
* START BACKUP, SNAPSHOTSTART:           mysql-cluster-backup-using-management-client.
                                                             (line   67)
* START BACKUP, syntax:                  mysql-cluster-backup-using-management-client.
                                                             (line   10)
* START BACKUP, WAIT COMPLETED:          mysql-cluster-backup-using-management-client.
                                                             (line   62)
* START BACKUP, WAIT STARTED:            mysql-cluster-backup-using-management-client.
                                                             (line   53)
* START command (MySQL Cluster):         mysql-cluster-mgm-client-commands.
                                                             (line   57)
* START SLAVE:                           start-slave.        (line    6)
* START TRANSACTION:                     commit.             (line    6)
* START, XA transactions:                xa-statements.      (line    6)
* start-datetime option, mysqlbinlog:    mysqlbinlog.        (line  530)
* start-position option, mysqlbinlog:    mysqlbinlog.        (line  545)
* start_row option, mysql_find_rows:     mysql-find-rows.    (line   49)
* StartFailRetryDelay:                   mysql-cluster-ndbd-definition.
                                                             (line 4466)
* StartFailureTimeout:                   mysql-cluster-ndbd-definition.
                                                             (line 2072)
* Starting many servers:                 multiple-servers.   (line   13)
* starting slave, thread state:          slave-connection-thread-states.
                                                             (line   37)
* starting, comments:                    ansi-diff-comments. (line    6)
* starting, mysqld:                      changing-mysql-user.
                                                             (line    6)
* starting, the server:                  unix-postinstallation.
                                                             (line   54)
* starting, the server automatically:    automatic-start.    (line    6)
* StartNoNodeGroupTimeout:               mysql-cluster-ndbd-definition.
                                                             (line 2097)
* StartPartialTimeout:                   mysql-cluster-ndbd-definition.
                                                             (line 2023)
* StartPartitionedTimeout:               mysql-cluster-ndbd-definition.
                                                             (line 2048)
* StartPoint():                          gis-linestring-property-functions.
                                                             (line   99)
* STARTUP Events (MySQL Cluster):        mysql-cluster-log-events.
                                                             (line   65)
* startup options, default:              option-files.       (line    6)
* startup parameters:                    server-parameters.  (line    6)
* startup parameters, mysql:             mysql-command-options.
                                                             (line    6)
* startup parameters, mysqladmin:        mysqladmin.         (line  216)
* startup parameters, tuning:            system-optimization.
                                                             (line    6)
* StartupStatusReportFrequency:          mysql-cluster-ndbd-definition.
                                                             (line 3233)
* statefile option, comp_err:            comp-err.           (line   66)
* statement-based replication, advantages: replication-sbr-rbr.
                                                             (line   24)
* statement-based replication, disadvantages: replication-sbr-rbr.
                                                             (line   36)
* statement-based replication, unsafe statements: replication-sbr-rbr.
                                                             (line   38)
* statements, compound:                  sql-syntax-compound-statements.
                                                             (line   16)
* statements, GRANT:                     adding-users.       (line    6)
* statements, INSERT:                    adding-users.       (line  119)
* statements, replication masters:       replication-master-sql.
                                                             (line   12)
* statements, replication slaves:        replication-slave-sql.
                                                             (line   17)
* statically, compiling:                 source-configuration-options.
                                                             (line  395)
* STATISTICS Events (MySQL Cluster):     mysql-cluster-log-events.
                                                             (line  207)
* STATISTICS, INFORMATION_SCHEMA table:  statistics-table.   (line    6)
* Statistics, thread command:            thread-commands.    (line  124)
* statistics, thread state:              general-thread-states.
                                                             (line  310)
* stats option, myisam_ftdump:           myisam-ftdump.      (line   79)
* stats_method myisamchk variable:       myisamchk-general-options.
                                                             (line   84)
* STATUS command (MySQL Cluster):        mysql-cluster-mgm-client-commands.
                                                             (line  131)
* status command, mysql:                 mysql-commands.     (line  205)
* status command, results:               mysqladmin.         (line  165)
* status option, mysqlshow:              mysqlshow.          (line  256)
* status variables <1>:                  show-status.        (line    6)
* status variables:                      server-status-variables.
                                                             (line    6)
* status variables, MySQL Cluster:       mysql-cluster-status-variables.
                                                             (line    6)
* status, tables:                        show-table-status.  (line    6)
* STD():                                 group-by-functions. (line  243)
* STDDEV():                              group-by-functions. (line  251)
* STDDEV_POP():                          group-by-functions. (line  259)
* STDDEV_SAMP():                         group-by-functions. (line  267)
* STOP command (MySQL Cluster):          mysql-cluster-mgm-client-commands.
                                                             (line   72)
* STOP SLAVE:                            stop-slave.         (line    6)
* stop-datetime option, mysqlbinlog:     mysqlbinlog.        (line  554)
* stop-position option, mysqlbinlog:     mysqlbinlog.        (line  564)
* StopOnError:                           mysql-cluster-ndbd-definition.
                                                             (line 1806)
* stopping, the server:                  automatic-start.    (line    6)
* stopword list, user-defined:           fulltext-fine-tuning.
                                                             (line   41)
* storage engine plugins:                storage-engine-plugins.
                                                             (line    6)
* storage engine, ARCHIVE:               archive-storage-engine.
                                                             (line    6)
* storage engine, InnoDB:                innodb-introduction.
                                                             (line    6)
* storage engines, and application feature requirements: mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* storage engines, applications supported: mysql-cluster-ndb-innodb-workloads.
                                                             (line    6)
* storage engines, availability:         mysql-cluster-compared.
                                                             (line   36)
* storage engines, choosing:             storage-engines.    (line   23)
* storage engines, differences between NDB and InnoDB: mysql-cluster-ndb-innodb-engines.
                                                             (line    6)
* storage engines, usage scenarios:      mysql-cluster-ndb-innodb-usage.
                                                             (line    6)
* storage nodes - see data nodes, ndbd:  mysql-cluster-programs-ndbd.
                                                             (line    6)
* storage nodes - see data nodes, ndbd, ndbmtd: mysql-cluster-programs-ndbmtd.
                                                             (line    6)
* storage requirements, data type:       storage-requirements.
                                                             (line    6)
* storage space, minimizing:             data-size.          (line    6)
* storage_engine system variable:        server-system-variables.
                                                             (line 5246)
* stored functions:                      stored-routines.    (line   13)
* stored functions, and INSERT DELAYED:  insert.             (line  239)
* stored procedures:                     stored-routines.    (line   13)
* stored programs <1>:                   stored-programs-views.
                                                             (line   16)
* stored programs:                       sql-syntax-compound-statements.
                                                             (line   16)
* stored routines, and replication:      replication-features-invoked.
                                                             (line    6)
* stored routines, LAST_INSERT_ID():     stored-routines-last-insert-id.
                                                             (line    6)
* stored routines, metadata:             stored-routines-metadata.
                                                             (line    6)
* stored routines, restrictions:         stored-program-restrictions.
                                                             (line    6)
* storing result in query cache, thread state: query-cache-thread-states.
                                                             (line   29)
* storing row into queue, thread state:  delayed-insert-thread-states.
                                                             (line   39)
* STR_TO_DATE():                         date-and-time-functions.
                                                             (line  867)
* STRAIGHT_JOIN <1>:                     explain.            (line   83)
* STRAIGHT_JOIN <2>:                     join.               (line    6)
* STRAIGHT_JOIN <3>:                     select.             (line  392)
* STRAIGHT_JOIN <4>:                     left-join-optimization.
                                                             (line   38)
* STRAIGHT_JOIN <5>:                     explain-output.     (line  777)
* STRAIGHT_JOIN:                         using-explain.      (line   25)
* STRCMP():                              string-comparison-functions.
                                                             (line  201)
* strict SQL mode:                       sql-mode.           (line  117)
* STRICT_ALL_TABLES SQL mode:            sql-mode.           (line  476)
* STRICT_TRANS_TABLES SQL mode:          sql-mode.           (line   93)
* string collating:                      string-collating.   (line    6)
* string comparison functions:           string-comparison-functions.
                                                             (line    6)
* string comparisons, case sensitivity:  string-comparison-functions.
                                                             (line   17)
* string concatenation <1>:              string-functions.   (line  196)
* string concatenation:                  string-literals.    (line   13)
* string functions:                      string-functions.   (line   11)
* string literal introducer <1>:         charset-literal.    (line   11)
* string literal introducer:             string-literals.    (line   35)
* string replacement, replace utility:   replace-utility.    (line    6)
* string types <1>:                      storage-requirements.
                                                             (line  152)
* string types:                          string-types.       (line   14)
* StringMemory:                          mysql-cluster-ndbd-definition.
                                                             (line  506)
* strings, defined:                      string-literals.    (line    6)
* strings, escape sequences:             string-literals.    (line    6)
* strings, nondelimited:                 date-and-time-literals.
                                                             (line  122)
* striping, defined:                     disk-issues.        (line   27)
* SUBDATE():                             date-and-time-functions.
                                                             (line  935)
* SUBPARTITION BY KEY, known issues:     partitioning-limitations.
                                                             (line  340)
* subpartitioning:                       partitioning-subpartitions.
                                                             (line    6)
* subpartitions:                         partitioning-subpartitions.
                                                             (line    6)
* subpartitions, known issues:           partitioning-limitations.
                                                             (line  336)
* subqueries:                            subqueries.         (line   20)
* subqueries, correlated:                correlated-subqueries.
                                                             (line    6)
* subqueries, errors:                    subquery-errors.    (line    6)
* subqueries, optimization:              subquery-optimization-with-exists.
                                                             (line    6)
* subqueries, restrictions:              subquery-restrictions.
                                                             (line    6)
* subqueries, rewriting as joins:        rewriting-subqueries.
                                                             (line    6)
* subqueries, with ALL:                  all-subqueries.     (line    6)
* subqueries, with ANY, IN, SOME:        any-in-some-subqueries.
                                                             (line    6)
* subqueries, with EXISTS:               exists-and-not-exists-subqueries.
                                                             (line    6)
* subqueries, with NOT EXISTS:           exists-and-not-exists-subqueries.
                                                             (line    6)
* subqueries, with ROW:                  row-subqueries.     (line    6)
* subquery:                              subqueries.         (line   20)
* subselects:                            subqueries.         (line   20)
* SUBSTR():                              string-functions.   (line  696)
* SUBSTRING():                           string-functions.   (line  701)
* SUBSTRING_INDEX():                     string-functions.   (line  735)
* SUBTIME():                             date-and-time-functions.
                                                             (line  955)
* subtraction (-):                       arithmetic-functions.
                                                             (line   63)
* suffix option, mysqlhotcopy:           mysqlhotcopy.       (line  184)
* SUM():                                 group-by-functions. (line  274)
* SUM(DISTINCT):                         group-by-functions. (line  274)
* superuser:                             default-privileges. (line    6)
* superuser option, mysqlaccess:         mysqlaccess.        (line  144)
* support, for operating systems:        supported-os.       (line    6)
* suppression, default values:           constraint-invalid-data.
                                                             (line    6)
* symbolic links <1>:                    windows-symbolic-links.
                                                             (line    6)
* symbolic links:                        symbolic-links.     (line   12)
* symbolic-links option, mysqld:         server-options.     (line 1962)
* symbols-file option, resolve_stack_dump: resolve-stack-dump.
                                                             (line   30)
* SymDifference():                       spatial-operator-functions.
                                                             (line   31)
* sync_binlog system variable:           replication-options-binary-log.
                                                             (line  799)
* sync_frm system variable:              server-system-variables.
                                                             (line 5268)
* synchronization of master and slave, in MySQL Cluster Replication: mysql-cluster-replication-auto-sync.
                                                             (line    6)
* Syncing ndb table schema operation and binlog, thread state: mysql-cluster-thread-states.
                                                             (line   20)
* syntax conventions:                    manual-conventions. (line    8)
* syntax, regular expression:            regexp.             (line    6)
* sys-check option (ndb_index_stat):     mysql-cluster-programs-ndb-index-stat.
                                                             (line  351)
* sys-create option (ndb_index_stat):    mysql-cluster-programs-ndb-index-stat.
                                                             (line  303)
* sys-create-if-not-exist option (ndb_index_stat): mysql-cluster-programs-ndb-index-stat.
                                                             (line  319)
* sys-create-if-not-valid option (ndb_index_stat): mysql-cluster-programs-ndb-index-stat.
                                                             (line  335)
* sys-drop option (ndb_index_stat):      mysql-cluster-programs-ndb-index-stat.
                                                             (line  287)
* sys-skip-events option (ndb_index_stat): mysql-cluster-programs-ndb-index-stat.
                                                             (line  382)
* sys-skip-tables option (ndb_index_stat): mysql-cluster-programs-ndb-index-stat.
                                                             (line  367)
* SYSDATE():                             date-and-time-functions.
                                                             (line  967)
* sysdate-is-now option, mysqld:         server-options.     (line 2138)
* syslog option, mysqld_safe:            mysqld-safe.        (line  212)
* syslog-tag option, mysqld_safe:        mysqld-safe.        (line  222)
* system command, mysql:                 mysql-commands.     (line  212)
* System lock, thread state:             general-thread-states.
                                                             (line  316)
* system optimization:                   system-optimization.
                                                             (line    6)
* system option, ndb_config:             mysql-cluster-programs-ndb-config.
                                                             (line  354)
* system table, optimizer <1>:           select.             (line  398)
* system table, optimizer:               explain-output.     (line  235)
* system variable, auto_increment_increment: replication-options-master.
                                                             (line   26)
* system variable, auto_increment_offset: replication-options-master.
                                                             (line  229)
* system variable, autocommit:           server-system-variables.
                                                             (line  599)
* system variable, automatic_sp_privileges: server-system-variables.
                                                             (line  639)
* system variable, back_log:             server-system-variables.
                                                             (line  667)
* system variable, basedir:              server-system-variables.
                                                             (line  699)
* system variable, big_tables:           server-system-variables.
                                                             (line  719)
* system variable, binlog_cache_size:    replication-options-binary-log.
                                                             (line  430)
* system variable, binlog_direct_non_transactional_updates: replication-options-binary-log.
                                                             (line  458)
* system variable, binlog_format:        replication-options-binary-log.
                                                             (line  511)
* system variable, bulk_insert_buffer_size: server-system-variables.
                                                             (line  734)
* system variable, character_set_client: server-system-variables.
                                                             (line  760)
* system variable, character_set_connection: server-system-variables.
                                                             (line  799)
* system variable, character_set_database: server-system-variables.
                                                             (line  816)
* system variable, character_set_filesystem: server-system-variables.
                                                             (line  856)
* system variable, character_set_results: server-system-variables.
                                                             (line  886)
* system variable, character_set_server: server-system-variables.
                                                             (line  902)
* system variable, character_set_system: server-system-variables.
                                                             (line  920)
* system variable, character_sets_dir:   server-system-variables.
                                                             (line  936)
* system variable, collation_connection: server-system-variables.
                                                             (line  953)
* system variable, collation_database:   server-system-variables.
                                                             (line  968)
* system variable, collation_server:     server-system-variables.
                                                             (line 1008)
* system variable, completion_type:      server-system-variables.
                                                             (line 1026)
* system variable, concurrent_insert:    server-system-variables.
                                                             (line 1074)
* system variable, connect_timeout:      server-system-variables.
                                                             (line 1113)
* system variable, datadir:              server-system-variables.
                                                             (line 1149)
* system variable, date_format:          server-system-variables.
                                                             (line 1168)
* system variable, datetime_format:      server-system-variables.
                                                             (line 1172)
* system variable, debug:                server-system-variables.
                                                             (line 1176)
* system variable, debug_sync:           server-system-variables.
                                                             (line 1233)
* system variable, default_week_format:  server-system-variables.
                                                             (line 1272)
* system variable, delay_key_write:      server-system-variables.
                                                             (line 1293)
* system variable, delayed_insert_limit: server-system-variables.
                                                             (line 1341)
* system variable, delayed_insert_timeout: server-system-variables.
                                                             (line 1365)
* system variable, delayed_queue_size:   server-system-variables.
                                                             (line 1384)
* system variable, div_precision_increment: server-system-variables.
                                                             (line 1408)
* system variable, engine_condition_pushdown: server-system-variables.
                                                             (line 1449)
* system variable, error_count:          server-system-variables.
                                                             (line 1483)
* system variable, event_scheduler:      server-system-variables.
                                                             (line 1489)
* system variable, expire_logs_days:     server-system-variables.
                                                             (line 1516)
* system variable, flush:                server-system-variables.
                                                             (line 1542)
* system variable, flush_time:           server-system-variables.
                                                             (line 1564)
* system variable, foreign_key_checks:   server-system-variables.
                                                             (line 1585)
* system variable, ft_boolean_syntax:    server-system-variables.
                                                             (line 1606)
* system variable, ft_max_word_len:      server-system-variables.
                                                             (line 1644)
* system variable, ft_min_word_len:      server-system-variables.
                                                             (line 1667)
* system variable, ft_query_expansion_limit: server-system-variables.
                                                             (line 1691)
* system variable, ft_stopword_file:     server-system-variables.
                                                             (line 1711)
* system variable, general_log:          server-system-variables.
                                                             (line 1741)
* system variable, general_log_file:     server-system-variables.
                                                             (line 1765)
* system variable, group_concat_max_len: server-system-variables.
                                                             (line 1787)
* system variable, have_archive:         server-system-variables.
                                                             (line 1809)
* system variable, have_blackhole_engine: server-system-variables.
                                                             (line 1814)
* system variable, have_community_features: server-system-variables.
                                                             (line 1825)
* system variable, have_compress:        server-system-variables.
                                                             (line 1819)
* system variable, have_crypt:           server-system-variables.
                                                             (line 1834)
* system variable, have_csv:             server-system-variables.
                                                             (line 1839)
* system variable, have_dynamic_loading: server-system-variables.
                                                             (line 1847)
* system variable, have_example_engine:  server-system-variables.
                                                             (line 1852)
* system variable, have_federated_engine: server-system-variables.
                                                             (line 1857)
* system variable, have_geometry:        server-system-variables.
                                                             (line 1862)
* system variable, have_innodb:          server-system-variables.
                                                             (line 1866)
* system variable, have_isam:            server-system-variables.
                                                             (line 1874)
* system variable, have_merge_engine:    server-system-variables.
                                                             (line 1880)
* system variable, have_openssl:         server-system-variables.
                                                             (line 1886)
* system variable, have_partitioning:    server-system-variables.
                                                             (line 1891)
* system variable, have_query_cache:     server-system-variables.
                                                             (line 1901)
* system variable, have_raid:            server-system-variables.
                                                             (line 1925)
* system variable, have_row_based_replication: server-system-variables.
                                                             (line 1906)
* system variable, have_rtree_keys:      server-system-variables.
                                                             (line 1931)
* system variable, have_ssl:             server-system-variables.
                                                             (line 1936)
* system variable, have_symlink:         server-system-variables.
                                                             (line 1946)
* system variable, hostname:             server-system-variables.
                                                             (line 1954)
* system variable, identity:             server-system-variables.
                                                             (line 1970)
* system variable, ignore_builtin_innodb: innodb-parameters. (line  224)
* system variable, init_connect:         server-system-variables.
                                                             (line 1977)
* system variable, init_file:            server-system-variables.
                                                             (line 2018)
* system variable, init_slave:           replication-options-slave.
                                                             (line 1345)
* system variable, innodb_adaptive_flushing: innodb-parameters.
                                                             (line  245)
* system variable, innodb_adaptive_hash_index: innodb-parameters.
                                                             (line  270)
* system variable, innodb_additional_mem_pool_size: innodb-parameters.
                                                             (line  295)
* system variable, innodb_autoextend_increment: innodb-parameters.
                                                             (line  324)
* system variable, innodb_buffer_pool_size: innodb-parameters.
                                                             (line  415)
* system variable, innodb_change_buffering: innodb-parameters.
                                                             (line  482)
* system variable, innodb_checksums:     innodb-parameters.  (line  507)
* system variable, innodb_commit_concurrency: innodb-parameters.
                                                             (line  529)
* system variable, innodb_concurrency_tickets: innodb-parameters.
                                                             (line  554)
* system variable, innodb_data_file_path: innodb-parameters. (line  582)
* system variable, innodb_data_home_dir: innodb-parameters.  (line  612)
* system variable, innodb_doublewrite:   innodb-parameters.  (line  634)
* system variable, innodb_fast_shutdown: innodb-parameters.  (line  655)
* system variable, innodb_file_format:   innodb-parameters.  (line  683)
* system variable, innodb_file_format_check: innodb-parameters.
                                                             (line  710)
* system variable, innodb_file_per_table: innodb-parameters. (line  768)
* system variable, innodb_flush_log_at_trx_commit: innodb-parameters.
                                                             (line  795)
* system variable, innodb_flush_method:  innodb-parameters.  (line  854)
* system variable, innodb_force_recovery: innodb-parameters. (line  935)
* system variable, innodb_io_capacity:   innodb-parameters.  (line  964)
* system variable, innodb_locks_unsafe_for_binlog: innodb-parameters.
                                                             (line 1093)
* system variable, innodb_log_buffer_size: innodb-parameters.
                                                             (line 1300)
* system variable, innodb_log_file_size: innodb-parameters.  (line 1325)
* system variable, innodb_log_files_in_group: innodb-parameters.
                                                             (line 1358)
* system variable, innodb_log_group_home_dir: innodb-parameters.
                                                             (line 1379)
* system variable, innodb_max_dirty_pages_pct: innodb-parameters.
                                                             (line 1400)
* system variable, innodb_max_purge_lag: innodb-parameters.  (line 1423)
* system variable, innodb_mirrored_log_groups: innodb-parameters.
                                                             (line 1472)
* system variable, innodb_old_blocks_pct: innodb-parameters. (line 1476)
* system variable, innodb_old_blocks_time: innodb-parameters.
                                                             (line 1509)
* system variable, innodb_open_files:    innodb-parameters.  (line 1550)
* system variable, innodb_read_ahead_threshold: innodb-parameters.
                                                             (line 1610)
* system variable, innodb_read_io_threads: innodb-parameters.
                                                             (line 1643)
* system variable, innodb_replication_delay: innodb-parameters.
                                                             (line 1675)
* system variable, innodb_rollback_on_timeout: innodb-parameters.
                                                             (line 1698)
* system variable, innodb_spin_wait_delay: innodb-parameters.
                                                             (line 1722)
* system variable, innodb_stats_method:  innodb-parameters.  (line 1749)
* system variable, innodb_stats_on_metadata: innodb-parameters.
                                                             (line 1783)
* system variable, innodb_stats_sample_pages: innodb-parameters.
                                                             (line 1815)
* system variable, innodb_strict_mode:   innodb-parameters.  (line 1841)
* system variable, innodb_support_xa:    innodb-parameters.  (line 1903)
* system variable, innodb_sync_spin_loops: innodb-parameters.
                                                             (line 1943)
* system variable, innodb_table_locks:   innodb-parameters.  (line 1965)
* system variable, innodb_thread_concurrency: innodb-parameters.
                                                             (line 1988)
* system variable, innodb_thread_sleep_delay: innodb-parameters.
                                                             (line 2030)
* system variable, innodb_use_sys_malloc: innodb-parameters. (line 2092)
* system variable, innodb_version:       innodb-parameters.  (line 2114)
* system variable, innodb_write_io_threads: innodb-parameters.
                                                             (line 2123)
* system variable, insert_id:            server-system-variables.
                                                             (line 2053)
* system variable, interactive_timeout:  server-system-variables.
                                                             (line 2059)
* system variable, join_buffer_size:     server-system-variables.
                                                             (line 2082)
* system variable, keep_files_on_create: server-system-variables.
                                                             (line 2148)
* system variable, key_buffer_size:      server-system-variables.
                                                             (line 2181)
* system variable, key_cache_age_threshold: server-system-variables.
                                                             (line 2283)
* system variable, key_cache_block_size: server-system-variables.
                                                             (line 2306)
* system variable, key_cache_division_limit: server-system-variables.
                                                             (line 2326)
* system variable, language:             server-system-variables.
                                                             (line 2348)
* system variable, large_files_support:  server-system-variables.
                                                             (line 2368)
* system variable, large_page_size:      server-system-variables.
                                                             (line 2399)
* system variable, large_pages:          server-system-variables.
                                                             (line 2380)
* system variable, last_insert_id:       server-system-variables.
                                                             (line 2417)
* system variable, lc_time_names:        server-system-variables.
                                                             (line 2425)
* system variable, license:              server-system-variables.
                                                             (line 2448)
* system variable, local_infile:         server-system-variables.
                                                             (line 2463)
* system variable, locked_in_memory:     server-system-variables.
                                                             (line 2480)
* system variable, log:                  server-system-variables.
                                                             (line 2492)
* system variable, log_bin:              replication-options-binary-log.
                                                             (line  633)
* system variable, log_bin_trust_function_creators: server-system-variables.
                                                             (line 2517)
* system variable, log_bin_use_v1_row_events: replication-options-binary-log.
                                                             (line  650)
* system variable, log_error:            server-system-variables.
                                                             (line 2545)
* system variable, log_output:           server-system-variables.
                                                             (line 2563)
* system variable, log_queries_not_using_indexes: server-system-variables.
                                                             (line 2593)
* system variable, log_slave_updates:    replication-options-binary-log.
                                                             (line  699)
* system variable, log_slow_queries:     server-system-variables.
                                                             (line 2612)
* system variable, log_warnings:         server-system-variables.
                                                             (line 2636)
* system variable, long_query_time:      server-system-variables.
                                                             (line 2665)
* system variable, low_priority_updates: server-system-variables.
                                                             (line 2698)
* system variable, lower_case_file_system: server-system-variables.
                                                             (line 2722)
* system variable, lower_case_table_names: server-system-variables.
                                                             (line 2740)
* system variable, max_allowed_packet:   server-system-variables.
                                                             (line 2787)
* system variable, max_binlog_cache_size: replication-options-binary-log.
                                                             (line  719)
* system variable, max_binlog_size:      replication-options-binary-log.
                                                             (line  769)
* system variable, max_connect_errors:   server-system-variables.
                                                             (line 2832)
* system variable, max_connections:      server-system-variables.
                                                             (line 2861)
* system variable, max_delayed_threads:  server-system-variables.
                                                             (line 2903)
* system variable, max_error_count:      server-system-variables.
                                                             (line 2932)
* system variable, max_heap_table_size:  server-system-variables.
                                                             (line 2954)
* system variable, max_insert_delayed_threads: server-system-variables.
                                                             (line 2998)
* system variable, max_join_size:        server-system-variables.
                                                             (line 3013)
* system variable, max_length_for_sort_data: server-system-variables.
                                                             (line 3051)
* system variable, max_long_data_size:   server-system-variables.
                                                             (line 3072)
* system variable, max_prepared_stmt_count: server-system-variables.
                                                             (line 3098)
* system variable, max_relay_log_size:   server-system-variables.
                                                             (line 3129)
* system variable, max_seeks_for_key:    server-system-variables.
                                                             (line 3157)
* system variable, max_sort_length:      server-system-variables.
                                                             (line 3184)
* system variable, max_sp_recursion_depth: server-system-variables.
                                                             (line 3206)
* system variable, max_tmp_tables:       server-system-variables.
                                                             (line 3233)
* system variable, max_user_connections: server-system-variables.
                                                             (line 3237)
* system variable, max_write_lock_count: server-system-variables.
                                                             (line 3275)
* system variable, min_examined_row_limit: server-system-variables.
                                                             (line 3296)
* system variable, myisam_data_pointer_size: server-system-variables.
                                                             (line 3349)
* system variable, myisam_max_sort_file_size: server-system-variables.
                                                             (line 3371)
* system variable, myisam_mmap_size:     server-system-variables.
                                                             (line 3404)
* system variable, myisam_recover_options: server-system-variables.
                                                             (line 3429)
* system variable, myisam_repair_threads: server-system-variables.
                                                             (line 3441)
* system variable, myisam_sort_buffer_size: server-system-variables.
                                                             (line 3468)
* system variable, myisam_stats_method:  server-system-variables.
                                                             (line 3496)
* system variable, myisam_use_mmap:      server-system-variables.
                                                             (line 3532)
* system variable, named_pipe:           server-system-variables.
                                                             (line 3551)
* system variable, ndb_log_empty_epochs: mysql-cluster-system-variables.
                                                             (line 1526)
* system variable, ndb_log_transaction_id: mysql-cluster-system-variables.
                                                             (line 1490)
* system variable, net_buffer_length:    server-system-variables.
                                                             (line 3568)
* system variable, net_read_timeout:     server-system-variables.
                                                             (line 3602)
* system variable, net_retry_count:      server-system-variables.
                                                             (line 3632)
* system variable, net_write_timeout:    server-system-variables.
                                                             (line 3663)
* system variable, new:                  server-system-variables.
                                                             (line 3690)
* system variable, old:                  server-system-variables.
                                                             (line 3712)
* system variable, old_alter_table:      server-system-variables.
                                                             (line 3740)
* system variable, old_passwords:        server-system-variables.
                                                             (line 3764)
* system variable, one_shot:             server-system-variables.
                                                             (line 3797)
* system variable, open_files_limit:     server-system-variables.
                                                             (line 3802)
* system variable, optimizer_prune_level: server-system-variables.
                                                             (line 3827)
* system variable, optimizer_search_depth: server-system-variables.
                                                             (line 3849)
* system variable, optimizer_switch:     server-system-variables.
                                                             (line 3878)
* system variable, pid_file:             server-system-variables.
                                                             (line 3918)
* system variable, plugin_dir:           server-system-variables.
                                                             (line 3936)
* system variable, port:                 server-system-variables.
                                                             (line 3972)
* system variable, preload_buffer_size:  server-system-variables.
                                                             (line 3993)
* system variable, prepared_stmt_count:  server-system-variables.
                                                             (line 4013)
* system variable, profiling:            server-system-variables.
                                                             (line 4033)
* system variable, profiling_history_size: server-system-variables.
                                                             (line 4041)
* system variable, protocol_version:     server-system-variables.
                                                             (line 4049)
* system variable, pseudo_thread_id:     server-system-variables.
                                                             (line 4063)
* system variable, query_alloc_block_size: server-system-variables.
                                                             (line 4077)
* system variable, query_cache_limit:    server-system-variables.
                                                             (line 4102)
* system variable, query_cache_min_res_unit: server-system-variables.
                                                             (line 4123)
* system variable, query_cache_size:     server-system-variables.
                                                             (line 4145)
* system variable, query_cache_type:     server-system-variables.
                                                             (line 4175)
* system variable, query_cache_wlock_invalidate: server-system-variables.
                                                             (line 4217)
* system variable, query_prealloc_size:  server-system-variables.
                                                             (line 4241)
* system variable, rand_seed1:           server-system-variables.
                                                             (line 4268)
* system variable, rand_seed2:           server-system-variables.
                                                             (line 4282)
* system variable, range_alloc_block_size: server-system-variables.
                                                             (line 4286)
* system variable, read_buffer_size:     server-system-variables.
                                                             (line 4317)
* system variable, read_only:            server-system-variables.
                                                             (line 4362)
* system variable, read_rnd_buffer_size: server-system-variables.
                                                             (line 4429)
* system variable, relay_log:            replication-options-slave.
                                                             (line 1372)
* system variable, relay_log_index:      replication-options-slave.
                                                             (line 1389)
* system variable, relay_log_info_file:  replication-options-slave.
                                                             (line 1409)
* system variable, relay_log_purge:      server-system-variables.
                                                             (line 4461)
* system variable, relay_log_space_limit: server-system-variables.
                                                             (line 4479)
* system variable, report_host:          server-system-variables.
                                                             (line 4499)
* system variable, report_password:      server-system-variables.
                                                             (line 4516)
* system variable, report_port:          server-system-variables.
                                                             (line 4534)
* system variable, report_user:          server-system-variables.
                                                             (line 4554)
* system variable, secure_auth:          server-system-variables.
                                                             (line 4571)
* system variable, secure_file_priv:     server-system-variables.
                                                             (line 4596)
* system variable, server_id:            server-system-variables.
                                                             (line 4619)
* system variable, server_id_bits:       mysql-cluster-system-variables.
                                                             (line 1556)
* system variable, shared_memory:        server-system-variables.
                                                             (line 4642)
* system variable, shared_memory_base_name: server-system-variables.
                                                             (line 4657)
* system variable, skip_external_locking: server-system-variables.
                                                             (line 4672)
* system variable, skip_name_resolve:    server-system-variables.
                                                             (line 4700)
* system variable, skip_networking:      server-system-variables.
                                                             (line 4724)
* system variable, skip_show_database:   server-system-variables.
                                                             (line 4742)
* system variable, slave_compressed_protocol: replication-options-slave.
                                                             (line 1433)
* system variable, slave_exec_mode:      replication-options-slave.
                                                             (line 1451)
* system variable, slave_load_tmpdir:    replication-options-slave.
                                                             (line 1523)
* system variable, slave_max_allowed_packet: replication-options-slave.
                                                             (line 1491)
* system variable, slave_net_timeout:    replication-options-slave.
                                                             (line 1542)
* system variable, slave_skip_errors:    replication-options-slave.
                                                             (line 1563)
* system variable, slave_transaction_retries: replication-options-slave.
                                                             (line 1591)
* system variable, slave_type_conversions: replication-options-slave.
                                                             (line 1619)
* system variable, slow_launch_time:     server-system-variables.
                                                             (line 4767)
* system variable, slow_query_log:       server-system-variables.
                                                             (line 4785)
* system variable, slow_query_log_file:  server-system-variables.
                                                             (line 4813)
* system variable, socket:               server-system-variables.
                                                             (line 4835)
* system variable, sort_buffer_size:     server-system-variables.
                                                             (line 4860)
* system variable, sql_auto_is_null:     server-system-variables.
                                                             (line 4915)
* system variable, sql_big_selects:      server-system-variables.
                                                             (line 4949)
* system variable, sql_buffer_result:    server-system-variables.
                                                             (line 4973)
* system variable, sql_log_bin:          server-system-variables.
                                                             (line 4992)
* system variable, sql_log_off:          server-system-variables.
                                                             (line 5008)
* system variable, sql_log_update:       server-system-variables.
                                                             (line 5025)
* system variable, sql_mode:             server-system-variables.
                                                             (line 5043)
* system variable, sql_notes:            server-system-variables.
                                                             (line 5091)
* system variable, sql_quote_show_create: server-system-variables.
                                                             (line 5101)
* system variable, sql_safe_updates:     server-system-variables.
                                                             (line 5110)
* system variable, sql_select_limit:     server-system-variables.
                                                             (line 5122)
* system variable, sql_slave_skip_counter: replication-options-slave.
                                                             (line 1653)
* system variable, sql_warnings:         server-system-variables.
                                                             (line 5146)
* system variable, ssl_ca:               server-system-variables.
                                                             (line 5152)
* system variable, ssl_capath:           server-system-variables.
                                                             (line 5171)
* system variable, ssl_cert:             server-system-variables.
                                                             (line 5190)
* system variable, ssl_cipher:           server-system-variables.
                                                             (line 5209)
* system variable, ssl_key:              server-system-variables.
                                                             (line 5227)
* system variable, storage_engine:       server-system-variables.
                                                             (line 5246)
* system variable, sync_binlog:          replication-options-binary-log.
                                                             (line  799)
* system variable, sync_frm:             server-system-variables.
                                                             (line 5268)
* system variable, system_time_zone:     server-system-variables.
                                                             (line 5288)
* system variable, table_cache:          server-system-variables.
                                                             (line 5314)
* system variable, table_definition_cache: server-system-variables.
                                                             (line 5338)
* system variable, table_lock_wait_timeout: server-system-variables.
                                                             (line 5373)
* system variable, table_open_cache:     server-system-variables.
                                                             (line 5392)
* system variable, table_type:           server-system-variables.
                                                             (line 5419)
* system variable, thread_cache_size:    server-system-variables.
                                                             (line 5436)
* system variable, thread_concurrency:   server-system-variables.
                                                             (line 5468)
* system variable, thread_handling:      server-system-variables.
                                                             (line 5491)
* system variable, thread_stack:         server-system-variables.
                                                             (line 5517)
* system variable, time_format:          server-system-variables.
                                                             (line 5544)
* system variable, time_zone:            server-system-variables.
                                                             (line 5548)
* system variable, timed_mutexes:        server-system-variables.
                                                             (line 5568)
* system variable, timestamp:            server-system-variables.
                                                             (line 5591)
* system variable, tmp_table_size:       server-system-variables.
                                                             (line 5621)
* system variable, tmpdir:               server-system-variables.
                                                             (line 5685)
* system variable, transaction_alloc_block_size: server-system-variables.
                                                             (line 5720)
* system variable, transaction_allow_batching: mysql-cluster-system-variables.
                                                             (line 1245)
* system variable, transaction_prealloc_size: server-system-variables.
                                                             (line 5744)
* system variable, tx_isolation:         server-system-variables.
                                                             (line 5776)
* system variable, unique_checks:        server-system-variables.
                                                             (line 5813)
* system variable, updatable_views_with_limit: server-system-variables.
                                                             (line 5837)
* system variable, version:              server-system-variables.
                                                             (line 5868)
* system variable, version_comment:      server-system-variables.
                                                             (line 5876)
* system variable, version_compile_machine: server-system-variables.
                                                             (line 5892)
* system variable, version_compile_os:   server-system-variables.
                                                             (line 5906)
* system variable, wait_timeout:         server-system-variables.
                                                             (line 5920)
* system variable, warning_count:        server-system-variables.
                                                             (line 5957)
* system variables <1>:                  show-variables.     (line    6)
* system variables <2>:                  using-system-variables.
                                                             (line   11)
* system variables:                      server-system-variables.
                                                             (line    6)
* system variables, and replication:     replication-features-variables.
                                                             (line    6)
* system, privilege:                     privilege-system.   (line   16)
* system, security:                      general-security-issues.
                                                             (line   16)
* system_time_zone system variable:      server-system-variables.
                                                             (line 5288)
* SYSTEM_USER():                         information-functions.
                                                             (line  668)
* tab (\t) <1>:                          load-data.          (line  449)
* tab (\t):                              string-literals.    (line   79)
* tab option (ndb_restore):              mysql-cluster-programs-ndb-restore.
                                                             (line  668)
* tab option, mysqldump:                 mysqldump.          (line  997)
* table aliases:                         select.             (line  172)
* table cache:                           table-cache.        (line    6)
* table description, myisamchk:          myisamchk-table-info.
                                                             (line    6)
* Table Dump, thread command:            thread-commands.    (line  128)
* table is full <1>:                     full-table.         (line    6)
* table is full:                         server-system-variables.
                                                             (line  721)
* Table is full errors (MySQL Cluster):  mysql-cluster-ndbd-definition.
                                                             (line  388)
* Table is full errors, MySQL Cluster:   faqs-mysql-cluster. (line    6)
* Table lock, thread state:              general-thread-states.
                                                             (line  327)
* Table Monitor, InnoDB <1>:             innodb-troubleshooting-datadict.
                                                             (line   69)
* Table Monitor, InnoDB:                 innodb-monitors.    (line   12)
* table names, case sensitivity <1>:     identifier-case-sensitivity.
                                                             (line    6)
* table names, case sensitivity:         extensions-to-ansi. (line   41)
* table option, mysql:                   mysql-command-options.
                                                             (line  564)
* table option, mysqlaccess:             mysqlaccess.        (line  148)
* table option, ndb_desc:                mysql-cluster-programs-ndb-desc.
                                                             (line  357)
* table scans, avoiding:                 how-to-avoid-table-scan.
                                                             (line    6)
* table type, choosing:                  storage-engines.    (line   23)
* table, changing <1>:                   alter-table-problems.
                                                             (line    6)
* table, changing:                       alter-table.        (line   12)
* table, deleting:                       drop-table.         (line    6)
* table, rebuilding:                     rebuilding-tables.  (line    6)
* table, repair:                         rebuilding-tables.  (line    6)
* table, row size:                       storage-requirements.
                                                             (line   24)
* table-level locking:                   internal-locking.   (line    6)
* table_cache system variable:           server-system-variables.
                                                             (line 5314)
* table_definition_cache system variable: server-system-variables.
                                                             (line 5338)
* table_lock_wait_timeout system variable: server-system-variables.
                                                             (line 5373)
* table_open_cache:                      table-cache.        (line    6)
* table_open_cache system variable:      server-system-variables.
                                                             (line 5392)
* TABLE_PRIVILEGES, INFORMATION_SCHEMA table: table-privileges-table.
                                                             (line    6)
* table_type system variable:            server-system-variables.
                                                             (line 5419)
* tables option, mysqlcheck:             mysqlcheck.         (line  432)
* tables option, mysqldump:              mysqldump.          (line 1026)
* tables, BLACKHOLE:                     blackhole-storage-engine.
                                                             (line    6)
* tables, checking:                      myisamchk-check-options.
                                                             (line    6)
* tables, closing:                       table-cache.        (line    6)
* tables, compressed:                    myisampack.         (line    6)
* tables, compressed format:             compressed-format.  (line    6)
* tables, const:                         explain-output.     (line  240)
* tables, constant:                      where-optimizations.
                                                             (line   53)
* tables, copying <1>:                   create-table-select.
                                                             (line    6)
* tables, copying:                       create-table.       (line 1338)
* tables, counting rows:                 counting-rows.      (line    6)
* tables, creating:                      creating-tables.    (line    6)
* tables, CSV:                           csv-storage-engine. (line   11)
* tables, defragment:                    dynamic-format.     (line   16)
* tables, defragmenting <1>:             optimize-table.     (line    6)
* tables, defragmenting:                 myisam-maintenance-schedule.
                                                             (line   39)
* tables, deleting rows:                 deleting-from-related-tables.
                                                             (line    6)
* tables, displaying:                    mysqlshow.          (line    6)
* tables, displaying status:             show-table-status.  (line    6)
* tables, dumping <1>:                   mysqlhotcopy.       (line    6)
* tables, dumping:                       mysqldump.          (line    6)
* tables, dynamic:                       dynamic-format.     (line    6)
* tables, error checking:                myisam-check.       (line    6)
* tables, EXAMPLE:                       example-storage-engine.
                                                             (line    6)
* tables, FEDERATED:                     federated-storage-engine.
                                                             (line   13)
* tables, flush:                         mysqladmin.         (line  190)
* tables, fragmentation:                 optimize-table.     (line    6)
* tables, HEAP:                          memory-storage-engine.
                                                             (line    6)
* tables, host:                          request-access.     (line  149)
* tables, improving performance:         data-size.          (line    6)
* tables, information:                   myisamchk-table-info.
                                                             (line    6)
* tables, information about:             getting-information.
                                                             (line    6)
* TABLES, INFORMATION_SCHEMA table:      tables-table.       (line    6)
* tables, InnoDB:                        innodb-introduction.
                                                             (line    6)
* tables, loading data:                  loading-tables.     (line    6)
* tables, maintenance:                   mysqlcheck.         (line    6)
* tables, maintenance schedule:          myisam-maintenance-schedule.
                                                             (line    6)
* tables, maximum size:                  table-size-limit.   (line    6)
* tables, MEMORY:                        memory-storage-engine.
                                                             (line    6)
* tables, MERGE:                         merge-storage-engine.
                                                             (line   11)
* tables, merging:                       merge-storage-engine.
                                                             (line   11)
* tables, multiple:                      multiple-tables.    (line    6)
* tables, MyISAM:                        myisam-storage-engine.
                                                             (line   13)
* tables, names:                         identifiers.        (line   13)
* tables, open:                          table-cache.        (line    6)
* tables, opening:                       table-cache.        (line    6)
* tables, optimizing:                    myisam-optimization.
                                                             (line    6)
* tables, partitioning:                  merge-storage-engine.
                                                             (line   11)
* tables, repair:                        mysqlcheck.         (line    6)
* tables, repairing:                     myisam-repair.      (line    6)
* tables, retrieving data:               retrieving-data.    (line   18)
* tables, selecting columns:             selecting-columns.  (line    6)
* tables, selecting rows:                selecting-rows.     (line    6)
* tables, sorting rows:                  sorting-rows.       (line    6)
* tables, symbolic links:                symbolic-links-to-tables.
                                                             (line    6)
* tables, system:                        explain-output.     (line  235)
* tables, too many:                      creating-many-tables.
                                                             (line    6)
* tables, unique ID for last row:        getting-unique-id.  (line    6)
* tables, updating:                      ansi-diff-transactions.
                                                             (line    6)
* Tablespace Monitor, InnoDB <1>:        innodb-backup.      (line  120)
* Tablespace Monitor, InnoDB <2>:        innodb-monitors.    (line   12)
* Tablespace Monitor, InnoDB:            innodb-file-space.  (line   48)
* TAN():                                 mathematical-functions.
                                                             (line  583)
* tar, problems on Solaris:              solaris-installation.
                                                             (line   11)
* tc-heuristic-recover option, mysqld:   server-options.     (line 2160)
* Tcl API:                               apis-tcl.           (line    6)
* tcp-ip option, mysqld_multi:           mysqld-multi.       (line  164)
* TCP/IP <1>:                            windows-testing.    (line    6)
* TCP/IP:                                windows-select-server.
                                                             (line   45)
* TCP_MAXSEG_SIZE:                       mysql-cluster-tcp-definition.
                                                             (line  256)
* TCP_RCV_BUF_SIZE:                      mysql-cluster-tcp-definition.
                                                             (line  222)
* TCP_SND_BUF_SIZE:                      mysql-cluster-tcp-definition.
                                                             (line  239)
* tee command, mysql:                    mysql-commands.     (line  218)
* tee option, mysql:                     mysql-command-options.
                                                             (line  570)
* temp-pool option, mysqld:              server-options.     (line 2176)
* temporary file, write access:          mysql-install-db-problems.
                                                             (line   73)
* temporary files:                       temporary-files.    (line    6)
* temporary tables, and replication:     replication-features-temptables.
                                                             (line    6)
* temporary tables, internal:            internal-temporary-tables.
                                                             (line    6)
* temporary tables, problems:            temporary-table-problems.
                                                             (line    6)
* terminal monitor, defined:             tutorial.           (line   16)
* test option, myisampack:               myisampack.         (line  101)
* testing mysqld, mysqltest:             mysql-test-suite.   (line    6)
* testing, connection to the server:     connection-access.  (line    6)
* testing, installation:                 unix-postinstallation.
                                                             (line   54)
* testing, of MySQL releases:            choosing-version.   (line  118)
* testing, postinstallation:             postinstallation.   (line   11)
* TEXT columns, default values:          blob.               (line   52)
* TEXT columns, indexing <1>:            create-table.       (line  542)
* TEXT columns, indexing:                column-indexes.     (line   15)
* TEXT data type <1>:                    blob.               (line    6)
* TEXT data type:                        string-type-overview.
                                                             (line  194)
* text files, importing <1>:             load-data.          (line    6)
* text files, importing <2>:             mysqlimport.        (line    6)
* text files, importing:                 mysql-batch-commands.
                                                             (line    6)
* TEXT, size:                            storage-requirements.
                                                             (line  199)
* thread cache:                          connection-threads. (line    6)
* thread command, Binlog Dump:           thread-commands.    (line    8)
* thread command, Change user:           thread-commands.    (line   13)
* thread command, Close stmt:            thread-commands.    (line   17)
* thread command, Connect:               thread-commands.    (line   21)
* thread command, Connect Out:           thread-commands.    (line   25)
* thread command, Create DB:             thread-commands.    (line   29)
* thread command, Daemon:                thread-commands.    (line   33)
* thread command, Debug:                 thread-commands.    (line   38)
* thread command, Delayed insert:        thread-commands.    (line   42)
* thread command, Drop DB:               thread-commands.    (line   46)
* thread command, Error:                 thread-commands.    (line   50)
* thread command, Execute:               thread-commands.    (line   52)
* thread command, Fetch:                 thread-commands.    (line   56)
* thread command, Field List:            thread-commands.    (line   61)
* thread command, Init DB:               thread-commands.    (line   65)
* thread command, Kill:                  thread-commands.    (line   69)
* thread command, Long Data:             thread-commands.    (line   73)
* thread command, Ping:                  thread-commands.    (line   78)
* thread command, Prepare:               thread-commands.    (line   82)
* thread command, Processlist:           thread-commands.    (line   86)
* thread command, Query:                 thread-commands.    (line   90)
* thread command, Quit:                  thread-commands.    (line   94)
* thread command, Refresh:               thread-commands.    (line   98)
* thread command, Register Slave:        thread-commands.    (line  103)
* thread command, Reset stmt:            thread-commands.    (line  107)
* thread command, Set option:            thread-commands.    (line  111)
* thread command, Shutdown:              thread-commands.    (line  116)
* thread command, Sleep:                 thread-commands.    (line  120)
* thread command, Statistics:            thread-commands.    (line  124)
* thread command, Table Dump:            thread-commands.    (line  128)
* thread command, Time:                  thread-commands.    (line  132)
* thread commands:                       thread-commands.    (line    6)
* thread state, After create:            general-thread-states.
                                                             (line   11)
* thread state, allocating local table:  delayed-insert-thread-states.
                                                             (line   17)
* thread state, Analyzing:               general-thread-states.
                                                             (line   18)
* thread state, Changing master:         slave-connection-thread-states.
                                                             (line    9)
* thread state, Checking master version: slave-io-thread-states.
                                                             (line   20)
* thread state, checking permissions:    general-thread-states.
                                                             (line   23)
* thread state, checking privileges on cached query: query-cache-thread-states.
                                                             (line    9)
* thread state, checking query cache for query: query-cache-thread-states.
                                                             (line   14)
* thread state, Checking table:          general-thread-states.
                                                             (line   28)
* thread state, cleaning up:             general-thread-states.
                                                             (line   32)
* thread state, Clearing:                event-scheduler-thread-states.
                                                             (line   10)
* thread state, closing tables:          general-thread-states.
                                                             (line   37)
* thread state, Committing events to binlog: mysql-cluster-thread-states.
                                                             (line    6)
* thread state, Connecting to master:    slave-io-thread-states.
                                                             (line   16)
* thread state, converting HEAP to MyISAM: general-thread-states.
                                                             (line   44)
* thread state, copy to tmp table:       general-thread-states.
                                                             (line   49)
* thread state, Copying to group table:  general-thread-states.
                                                             (line   55)
* thread state, Copying to tmp table:    general-thread-states.
                                                             (line   60)
* thread state, Copying to tmp table on disk: general-thread-states.
                                                             (line   64)
* thread state, Creating delayed handler: delayed-insert-thread-states.
                                                             (line   22)
* thread state, Creating index:          general-thread-states.
                                                             (line   72)
* thread state, Creating sort index:     general-thread-states.
                                                             (line   77)
* thread state, creating table:          general-thread-states.
                                                             (line   82)
* thread state, Creating table from master dump: slave-connection-thread-states.
                                                             (line   14)
* thread state, Creating tmp table:      general-thread-states.
                                                             (line   87)
* thread state, deleting from main table: general-thread-states.
                                                             (line   94)
* thread state, deleting from reference tables: general-thread-states.
                                                             (line  100)
* thread state, discard_or_import_tablespace: general-thread-states.
                                                             (line  105)
* thread state, end:                     general-thread-states.
                                                             (line  110)
* thread state, executing:               general-thread-states.
                                                             (line  117)
* thread state, Execution of init_command: general-thread-states.
                                                             (line  121)
* thread state, Finished reading one binlog; switching to next binlog: master-thread-states.
                                                             (line   17)
* thread state, Flushing tables:         general-thread-states.
                                                             (line  132)
* thread state, freeing items:           general-thread-states.
                                                             (line  126)
* thread state, FULLTEXT initialization: general-thread-states.
                                                             (line  137)
* thread state, got handler lock:        delayed-insert-thread-states.
                                                             (line   26)
* thread state, got old table:           delayed-insert-thread-states.
                                                             (line   32)
* thread state, Has read all relay log; waiting for the slave I/O thread to update it: slave-sql-thread-states.
                                                             (line   18)
* thread state, Has sent all binlog to slave; waiting for binlog to be updated: master-thread-states.
                                                             (line   22)
* thread state, init:                    general-thread-states.
                                                             (line  142)
* thread state, Initialized:             event-scheduler-thread-states.
                                                             (line   15)
* thread state, insert:                  delayed-insert-thread-states.
                                                             (line   72)
* thread state, invalidating query cache entries: query-cache-thread-states.
                                                             (line   19)
* thread state, Killed:                  general-thread-states.
                                                             (line  158)
* thread state, Killing slave:           slave-connection-thread-states.
                                                             (line   21)
* thread state, Locked:                  general-thread-states.
                                                             (line  167)
* thread state, logging slow query:      general-thread-states.
                                                             (line  171)
* thread state, login:                   general-thread-states.
                                                             (line  180)
* thread state, Making temp file:        slave-sql-thread-states.
                                                             (line   25)
* thread state, manage keys:             general-thread-states.
                                                             (line  185)
* thread state, NULL:                    general-thread-states.
                                                             (line  175)
* thread state, Opening master dump table: slave-connection-thread-states.
                                                             (line   25)
* thread state, Opening mysql.ndb_apply_status: mysql-cluster-thread-states.
                                                             (line    8)
* thread state, Opening table:           general-thread-states.
                                                             (line  189)
* thread state, Opening tables:          general-thread-states.
                                                             (line  189)
* thread state, optimizing:              general-thread-states.
                                                             (line  198)
* thread state, preparing:               general-thread-states.
                                                             (line  202)
* thread state, Processing events:       mysql-cluster-thread-states.
                                                             (line   10)
* thread state, Processing events from schema table: mysql-cluster-thread-states.
                                                             (line   14)
* thread state, Purging old relay logs:  general-thread-states.
                                                             (line  206)
* thread state, query end:               general-thread-states.
                                                             (line  210)
* thread state, Queueing master event to the relay log: slave-io-thread-states.
                                                             (line   57)
* thread state, Reading event from the relay log: slave-sql-thread-states.
                                                             (line   13)
* thread state, Reading from net:        general-thread-states.
                                                             (line  215)
* thread state, Reading master dump table data: slave-connection-thread-states.
                                                             (line   29)
* thread state, Rebuilding the index on master dump table: slave-connection-thread-states.
                                                             (line   33)
* thread state, Reconnecting after a failed binlog dump request: slave-io-thread-states.
                                                             (line   45)
* thread state, Reconnecting after a failed master event read: slave-io-thread-states.
                                                             (line   70)
* thread state, Registering slave on master: slave-io-thread-states.
                                                             (line   25)
* thread state, Removing duplicates:     general-thread-states.
                                                             (line  219)
* thread state, removing tmp table:      general-thread-states.
                                                             (line  226)
* thread state, rename:                  general-thread-states.
                                                             (line  232)
* thread state, rename result table:     general-thread-states.
                                                             (line  236)
* thread state, Reopen tables:           general-thread-states.
                                                             (line  242)
* thread state, Repair by sorting:       general-thread-states.
                                                             (line  248)
* thread state, Repair done:             general-thread-states.
                                                             (line  252)
* thread state, Repair with keycache:    general-thread-states.
                                                             (line  257)
* thread state, Requesting binlog dump:  slave-io-thread-states.
                                                             (line   30)
* thread state, reschedule:              delayed-insert-thread-states.
                                                             (line   76)
* thread state, Rolling back:            general-thread-states.
                                                             (line  262)
* thread state, Saving state:            general-thread-states.
                                                             (line  266)
* thread state, Searching rows for update: general-thread-states.
                                                             (line  273)
* thread state, Sending binlog event to slave: master-thread-states.
                                                             (line   11)
* thread state, sending cached result to client: query-cache-thread-states.
                                                             (line   24)
* thread state, setup:                   general-thread-states.
                                                             (line  287)
* thread state, Shutting down:           mysql-cluster-thread-states.
                                                             (line   18)
* thread state, Sorting for group:       general-thread-states.
                                                             (line  292)
* thread state, Sorting for order:       general-thread-states.
                                                             (line  296)
* thread state, Sorting index:           general-thread-states.
                                                             (line  300)
* thread state, Sorting result:          general-thread-states.
                                                             (line  305)
* thread state, starting slave:          slave-connection-thread-states.
                                                             (line   37)
* thread state, statistics:              general-thread-states.
                                                             (line  310)
* thread state, storing result in query cache: query-cache-thread-states.
                                                             (line   29)
* thread state, storing row into queue:  delayed-insert-thread-states.
                                                             (line   39)
* thread state, Syncing ndb table schema operation and binlog: mysql-cluster-thread-states.
                                                             (line   20)
* thread state, System lock:             general-thread-states.
                                                             (line  316)
* thread state, Table lock:              general-thread-states.
                                                             (line  327)
* thread state, update:                  general-thread-states.
                                                             (line  333)
* thread state, Updating:                general-thread-states.
                                                             (line  337)
* thread state, updating main table:     general-thread-states.
                                                             (line  341)
* thread state, updating reference tables: general-thread-states.
                                                             (line  347)
* thread state, upgrading lock:          delayed-insert-thread-states.
                                                             (line   81)
* thread state, User lock:               general-thread-states.
                                                             (line  352)
* thread state, User sleep:              general-thread-states.
                                                             (line  359)
* thread state, waiting for delay_list:  delayed-insert-thread-states.
                                                             (line   44)
* thread state, Waiting for event from ndbcluster: mysql-cluster-thread-states.
                                                             (line   25)
* thread state, Waiting for first event from ndbcluster: mysql-cluster-thread-states.
                                                             (line   30)
* thread state, waiting for handler insert: delayed-insert-thread-states.
                                                             (line   51)
* thread state, waiting for handler lock: delayed-insert-thread-states.
                                                             (line   56)
* thread state, waiting for handler open: delayed-insert-thread-states.
                                                             (line   62)
* thread state, Waiting for INSERT:      delayed-insert-thread-states.
                                                             (line   86)
* thread state, Waiting for master to send event: slave-io-thread-states.
                                                             (line   49)
* thread state, Waiting for master update: slave-io-thread-states.
                                                             (line   12)
* thread state, Waiting for ndbcluster binlog update to reach current position: mysql-cluster-thread-states.
                                                             (line   32)
* thread state, Waiting for ndbcluster to start: mysql-cluster-thread-states.
                                                             (line   34)
* thread state, Waiting for next activation: event-scheduler-thread-states.
                                                             (line   20)
* thread state, Waiting for release of readlock: general-thread-states.
                                                             (line  363)
* thread state, Waiting for scheduler to stop: event-scheduler-thread-states.
                                                             (line   25)
* thread state, Waiting for schema epoch: mysql-cluster-thread-states.
                                                             (line   36)
* thread state, Waiting for slave mutex on exit <1>: slave-sql-thread-states.
                                                             (line   31)
* thread state, Waiting for slave mutex on exit: slave-io-thread-states.
                                                             (line   84)
* thread state, Waiting for table:       general-thread-states.
                                                             (line  369)
* thread state, Waiting for tables:      general-thread-states.
                                                             (line  369)
* thread state, Waiting for the next event in relay log: slave-sql-thread-states.
                                                             (line    9)
* thread state, Waiting for the slave SQL thread to free enough relay log space: slave-io-thread-states.
                                                             (line   76)
* thread state, Waiting on cond:         general-thread-states.
                                                             (line  383)
* thread state, Waiting on empty queue:  event-scheduler-thread-states.
                                                             (line   30)
* thread state, Waiting to finalize termination: master-thread-states.
                                                             (line   29)
* thread state, Waiting to get readlock: general-thread-states.
                                                             (line  388)
* thread state, Waiting to reconnect after a failed binlog dump request: slave-io-thread-states.
                                                             (line   37)
* thread state, Waiting to reconnect after a failed master event read: slave-io-thread-states.
                                                             (line   62)
* thread state, Writing to net:          general-thread-states.
                                                             (line  394)
* thread states:                         thread-information. (line   19)
* thread states, delayed inserts:        delayed-insert-thread-states.
                                                             (line    6)
* thread states, event scheduler:        event-scheduler-thread-states.
                                                             (line    6)
* thread states, general:                general-thread-states.
                                                             (line    6)
* thread states, MySQL Cluster:          mysql-cluster-thread-states.
                                                             (line    6)
* thread states, query cache:            query-cache-thread-states.
                                                             (line    6)
* thread states, replication master:     master-thread-states.
                                                             (line    6)
* thread states, replication slave <1>:  slave-connection-thread-states.
                                                             (line    6)
* thread states, replication slave <2>:  slave-sql-thread-states.
                                                             (line    6)
* thread states, replication slave:      slave-io-thread-states.
                                                             (line    6)
* thread support:                        supported-os.       (line    6)
* thread_cache_size system variable:     server-system-variables.
                                                             (line 5436)
* thread_concurrency system variable:    server-system-variables.
                                                             (line 5468)
* thread_handling system variable:       server-system-variables.
                                                             (line 5491)
* thread_stack system variable:          server-system-variables.
                                                             (line 5517)
* threadblocks, ndbinfo table:           mysql-cluster-ndbinfo-threadblocks.
                                                             (line    6)
* ThreadConfig:                          mysql-cluster-ndbd-definition.
                                                             (line 3771)
* threaded clients:                      c-api-threaded-clients.
                                                             (line    6)
* ThreadPool:                            mysql-cluster-ndbd-definition.
                                                             (line 3957)
* threads <1>:                           mysql-internals.    (line   11)
* threads <2>:                           show-processlist.   (line    6)
* threads:                               mysqladmin.         (line  172)
* threads, display:                      show-processlist.   (line    6)
* threads, monitoring <1>:               processlist-table.  (line    6)
* threads, monitoring <2>:               show-processlist.   (line    6)
* threads, monitoring:                   thread-information. (line   19)
* threadstat, ndbinfo table:             mysql-cluster-ndbinfo-threadstat.
                                                             (line    6)
* TIME data type <1>:                    time.               (line    6)
* TIME data type:                        date-and-time-type-overview.
                                                             (line   62)
* time literals:                         date-and-time-literals.
                                                             (line    6)
* time representation, Event Scheduler:  events-metadata.    (line   21)
* time types:                            storage-requirements.
                                                             (line  137)
* time zone problems:                    timezone-problems.  (line    6)
* time zone tables:                      mysql-tzinfo-to-sql.
                                                             (line    6)
* time zones, and replication:           replication-features-timezone.
                                                             (line    6)
* time zones, leap seconds:              time-zone-leap-seconds.
                                                             (line    6)
* time zones, support:                   time-zone-support.  (line   11)
* time zones, upgrading:                 time-zone-upgrades. (line    6)
* TIME():                                date-and-time-functions.
                                                             (line 1015)
* Time, thread command:                  thread-commands.    (line  132)
* time_format system variable:           server-system-variables.
                                                             (line 5544)
* TIME_FORMAT():                         date-and-time-functions.
                                                             (line 1108)
* TIME_TO_SEC():                         date-and-time-functions.
                                                             (line 1124)
* time_zone system variable:             server-system-variables.
                                                             (line 5548)
* TimeBetweenEpochs:                     mysql-cluster-ndbd-definition.
                                                             (line 2384)
* TimeBetweenEpochsTimeout:              mysql-cluster-ndbd-definition.
                                                             (line 2404)
* TimeBetweenGlobalCheckpoints:          mysql-cluster-ndbd-definition.
                                                             (line 2351)
* TimeBetweenInactiveTransactionAbortCheck: mysql-cluster-ndbd-definition.
                                                             (line 2500)
* TimeBetweenLocalCheckpoints:           mysql-cluster-ndbd-definition.
                                                             (line 2317)
* TimeBetweenWatchDogCheck:              mysql-cluster-ndbd-definition.
                                                             (line 1975)
* TimeBetweenWatchDogCheckInitial:       mysql-cluster-ndbd-definition.
                                                             (line 2001)
* timed_mutexes system variable:         server-system-variables.
                                                             (line 5568)
* TIMEDIFF():                            date-and-time-functions.
                                                             (line 1030)
* timeout <1>:                           insert-delayed.     (line  129)
* timeout <2>:                           miscellaneous-functions.
                                                             (line   42)
* timeout:                               server-system-variables.
                                                             (line 1113)
* timeout option, ndb_waiter:            mysql-cluster-programs-ndb-waiter.
                                                             (line  111)
* timeout, connect_timeout variable <1>: mysqladmin.         (line  489)
* timeout, connect_timeout variable:     mysql-command-options.
                                                             (line  658)
* timeout, shutdown_timeout variable:    mysqladmin.         (line  494)
* timeouts (replication):                replication-features-timeout.
                                                             (line    6)
* TIMESTAMP data type <1>:               datetime.           (line    6)
* TIMESTAMP data type:                   date-and-time-type-overview.
                                                             (line   31)
* timestamp system variable:             server-system-variables.
                                                             (line 5591)
* TIMESTAMP():                           date-and-time-functions.
                                                             (line 1049)
* TIMESTAMP, and logs:                   upgrading-from-previous-series.
                                                             (line  705)
* TIMESTAMP, and NULL values:            problems-with-null. (line   76)
* TIMESTAMP, and replication <1>:        replication-features-timestamp.
                                                             (line    6)
* TIMESTAMP, and replication <2>:        replication-features-auto-increment.
                                                             (line    6)
* TIMESTAMP, and replication:            upgrading-from-previous-series.
                                                             (line  705)
* TIMESTAMP, initialization and updating: timestamp-initialization.
                                                             (line    6)
* TIMESTAMPADD():                        date-and-time-functions.
                                                             (line 1062)
* TIMESTAMPDIFF():                       date-and-time-functions.
                                                             (line 1084)
* timezone option, mysqld_safe:          mysqld-safe.        (line  231)
* TINYBLOB data type:                    string-type-overview.
                                                             (line  168)
* TINYINT data type:                     numeric-type-overview.
                                                             (line   40)
* TINYTEXT data type:                    string-type-overview.
                                                             (line  174)
* tips, optimization:                    miscellaneous-optimization-tips.
                                                             (line    6)
* tmp_table_size system variable:        server-system-variables.
                                                             (line 5621)
* TMPDIR environment variable <1>:       temporary-files.    (line    6)
* TMPDIR environment variable <2>:       programs-overview.  (line  305)
* TMPDIR environment variable <3>:       environment-variables.
                                                             (line   18)
* TMPDIR environment variable:           mysql-install-db-problems.
                                                             (line   87)
* tmpdir option, myisamchk:              myisamchk-repair-options.
                                                             (line  121)
* tmpdir option, myisampack:             myisampack.         (line  105)
* tmpdir option, mysql_upgrade:          mysql-upgrade.      (line  274)
* tmpdir option, mysqld:                 server-options.     (line 2218)
* tmpdir option, mysqlhotcopy:           mysqlhotcopy.       (line  188)
* tmpdir system variable:                server-system-variables.
                                                             (line 5685)
* to-last-log option, mysqlbinlog:       mysqlbinlog.        (line  573)
* TO_DAYS():                             date-and-time-functions.
                                                             (line 1134)
* tools, command-line:                   mysql.              (line   15)
* tools, list of:                        tools-used-to-create-mysql.
                                                             (line    6)
* tools, mysqld_multi:                   mysqld-multi.       (line    6)
* tools, mysqld_safe:                    mysqld-safe.        (line    6)
* TotalSendBufferMemory, API and SQL nodes: mysql-cluster-api-definition.
                                                             (line  287)
* TotalSendBufferMemory, data nodes:     mysql-cluster-ndbd-definition.
                                                             (line 4345)
* TotalSendBufferMemory, management nodes: mysql-cluster-mgm-definition.
                                                             (line  342)
* Touches():                             spatial-relation-functions-mbr.
                                                             (line   55)
* trace DBI method:                      using-gdb-on-mysqld.
                                                             (line   94)
* trace files (MySQL Cluster):           mysql-cluster-programs-ndbd.
                                                             (line  506)
* trace files, ndbmtd:                   mysql-cluster-programs-ndbmtd.
                                                             (line   67)
* TRADITIONAL SQL mode:                  sql-mode.           (line  101)
* transaction isolation level:           set-transaction.    (line    6)
* transaction isolation level, READ COMMITTED: set-transaction.
                                                             (line  119)
* transaction isolation level, READ UNCOMMITTED: set-transaction.
                                                             (line  145)
* transaction isolation level, REPEATABLE READ: set-transaction.
                                                             (line   97)
* transaction isolation level, SERIALIZABLE: set-transaction.
                                                             (line  153)
* transaction-isolation option, mysqld:  server-options.     (line 2195)
* transaction-safe tables <1>:           innodb-introduction.
                                                             (line    6)
* transaction-safe tables:               ansi-diff-transactions.
                                                             (line    6)
* transaction_alloc_block_size system variable: server-system-variables.
                                                             (line 5720)
* transaction_allow_batching session variable (MySQL Cluster): mysql-cluster-system-variables.
                                                             (line 1245)
* transaction_prealloc_size system variable: server-system-variables.
                                                             (line 5744)
* transactional option, ndb_delete_all:  mysql-cluster-programs-ndb-delete-all.
                                                             (line   60)
* TransactionBufferMemory:               mysql-cluster-ndbd-definition.
                                                             (line  903)
* TransactionDeadlockDetectionTimeout:   mysql-cluster-ndbd-definition.
                                                             (line 2543)
* TransactionInactiveTimeout:            mysql-cluster-ndbd-definition.
                                                             (line 2521)
* transactions:                          innodb-transaction-model.
                                                             (line    6)
* transactions, and replication <1>:     replication-features-transactions.
                                                             (line    6)
* transactions, and replication:         replication-features-timeout.
                                                             (line    6)
* transactions, isolation levels:        innodb-transaction-model.
                                                             (line    6)
* transactions, support <1>:             innodb-introduction.
                                                             (line    6)
* transactions, support:                 ansi-diff-transactions.
                                                             (line    6)
* Translators, list of:                  documenters-translators.
                                                             (line    6)
* transporters, ndbinfo table:           mysql-cluster-ndbinfo-transporters.
                                                             (line    6)
* trigger, restrictions:                 stored-program-restrictions.
                                                             (line    6)
* triggers <1>:                          triggers.           (line   11)
* triggers <2>:                          stored-programs-views.
                                                             (line   16)
* triggers <3>:                          show-triggers.      (line    6)
* triggers <4>:                          drop-trigger.       (line    6)
* triggers:                              create-trigger.     (line    6)
* triggers option, mysqldump:            mysqldump.          (line 1032)
* triggers, and INSERT DELAYED:          insert.             (line  239)
* triggers, and replication <1>:         replication-features-triggers.
                                                             (line    6)
* triggers, and replication:             replication-features-invoked.
                                                             (line    6)
* TRIGGERS, INFORMATION_SCHEMA table:    triggers-table.     (line    6)
* triggers, LAST_INSERT_ID():            stored-routines-last-insert-id.
                                                             (line    6)
* triggers, metadata:                    trigger-metadata.   (line    6)
* TRIM():                                string-functions.   (line  752)
* troubleshooting, FreeBSD:              compilation-problems.
                                                             (line  147)
* troubleshooting, Solaris:              compilation-problems.
                                                             (line  147)
* troubleshooting, with MySQL Enterprise Monitor: mysql-enterprise-monitor.
                                                             (line    6)
* TRUE <1>:                              boolean-literals.   (line    6)
* TRUE:                                  number-literals.    (line    6)
* TRUE, testing for:                     comparison-operators.
                                                             (line  138)
* TRUNCATE TABLE:                        truncate-table.     (line    6)
* TRUNCATE TABLE, and MySQL Cluster:     mysql-cluster-limitations-limits.
                                                             (line    9)
* TRUNCATE TABLE, and replication:       replication-features-truncate.
                                                             (line    6)
* TRUNCATE():                            mathematical-functions.
                                                             (line  593)
* tupscan option, ndb_select_all:        mysql-cluster-programs-ndb-select-all.
                                                             (line  202)
* tutorial:                              tutorial.           (line   16)
* TwoPassInitialNodeRestartCopy:         mysql-cluster-ndbd-definition.
                                                             (line 3644)
* tx_isolation system variable:          server-system-variables.
                                                             (line 5776)
* type codes, C prepared statement API:  c-api-prepared-statement-type-codes.
                                                             (line    6)
* type conversions <1>:                  comparison-operators.
                                                             (line   38)
* type conversions:                      type-conversion.    (line    6)
* type option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   55)
* type option, ndb_config:               mysql-cluster-programs-ndb-config.
                                                             (line  373)
* type option, ndb_show_tables:          mysql-cluster-programs-ndb-show-tables.
                                                             (line   96)
* types, columns <1>:                    choosing-types.     (line    6)
* types, columns:                        data-types.         (line   29)
* types, data:                           data-types.         (line   29)
* types, date:                           storage-requirements.
                                                             (line  137)
* types, Date and Time:                  date-and-time-types.
                                                             (line   17)
* types, numeric:                        storage-requirements.
                                                             (line   90)
* types, of tables:                      storage-engines.    (line   23)
* types, portability:                    other-vendor-data-types.
                                                             (line    6)
* types, string:                         storage-requirements.
                                                             (line  152)
* types, strings:                        string-types.       (line   14)
* types, time:                           storage-requirements.
                                                             (line  137)
* typographical conventions:             manual-conventions. (line    8)
* TZ environment variable <1>:           timezone-problems.  (line    6)
* TZ environment variable:               environment-variables.
                                                             (line   18)
* tz-utc option, mysqldump:              mysqldump.          (line 1037)
* UCASE():                               string-functions.   (line  772)
* UCS-2:                                 charset.            (line   22)
* ucs2 character set:                    charset-unicode-ucs2.
                                                             (line    6)
* UDFs <1>:                              drop-function-udf.  (line    6)
* UDFs:                                  create-function-udf.
                                                             (line    6)
* UDFs, compiling:                       udf-compiling.      (line    6)
* UDFs, defined:                         adding-functions.   (line   12)
* UDFs, return values:                   udf-return-values.  (line    6)
* ulimit:                                not-enough-file-handles.
                                                             (line   34)
* UMASK environment variable <1>:        file-permissions.   (line    6)
* UMASK environment variable:            environment-variables.
                                                             (line   18)
* UMASK_DIR environment variable <1>:    file-permissions.   (line   22)
* UMASK_DIR environment variable:        environment-variables.
                                                             (line   18)
* unary minus (-):                       arithmetic-functions.
                                                             (line   71)
* unbuffered option, mysql:              mysql-command-options.
                                                             (line  576)
* UNCOMPRESS():                          encryption-functions.
                                                             (line  411)
* UNCOMPRESSED_LENGTH():                 encryption-functions.
                                                             (line  425)
* UndoDataBuffer:                        mysql-cluster-ndbd-definition.
                                                             (line 2928)
* UndoIndexBuffer:                       mysql-cluster-ndbd-definition.
                                                             (line 2881)
* UNHEX():                               string-functions.   (line  776)
* Unicode:                               charset.            (line   22)
* Unicode Collation Algorithm:           charset-unicode-sets.
                                                             (line   71)
* UNINSTALL PLUGIN:                      uninstall-plugin.   (line    6)
* uninstalling plugins <1>:              uninstall-plugin.   (line    6)
* uninstalling plugins:                  server-plugin-loading.
                                                             (line    6)
* UNION <1>:                             union.              (line    6)
* UNION:                                 searching-on-two-keys.
                                                             (line    6)
* Union():                               spatial-operator-functions.
                                                             (line   36)
* UNIQUE:                                alter-table.        (line  383)
* unique ID:                             getting-unique-id.  (line    6)
* unique key, constraint:                constraint-primary-key.
                                                             (line    6)
* unique keys, and partitioning keys:    partitioning-limitations-partitioning-keys-unique-keys.
                                                             (line    6)
* unique_checks system variable:         server-system-variables.
                                                             (line 5813)
* unique_subquery join type, optimizer:  explain-output.     (line  329)
* Unix, compiling clients on:            c-api-building-clients.
                                                             (line   11)
* UNIX_TIMESTAMP():                      date-and-time-functions.
                                                             (line 1194)
* UNKNOWN, testing for:                  comparison-operators.
                                                             (line  138)
* unloading, tables:                     retrieving-data.    (line   18)
* UNLOCK TABLES:                         lock-tables.        (line   12)
* unnamed views:                         from-clause-subqueries.
                                                             (line    6)
* unpack option, myisamchk:              myisamchk-repair-options.
                                                             (line  131)
* unqualified option, ndb_desc:          mysql-cluster-programs-ndb-desc.
                                                             (line  364)
* unqualified option, ndb_show_tables:   mysql-cluster-programs-ndb-show-tables.
                                                             (line  110)
* unsafe statement (replication), defined: replication-rbr-safe-unsafe.
                                                             (line    6)
* unsafe statements (replication):       replication-rbr-safe-unsafe.
                                                             (line   40)
* UNSIGNED <1>:                          numeric-types.      (line   15)
* UNSIGNED:                              numeric-type-overview.
                                                             (line    6)
* UNTIL:                                 repeat.             (line    6)
* updatable views:                       view-updatability.  (line    6)
* updatable_views_with_limit system variable: server-system-variables.
                                                             (line 5837)
* UPDATE <1>:                            update.             (line    6)
* UPDATE:                                ansi-diff-update.   (line    6)
* update option (ndb_index_stat):        mysql-cluster-programs-ndb-index-stat.
                                                             (line  234)
* update, thread state:                  general-thread-states.
                                                             (line  333)
* update-state option, myisamchk:        myisamchk-check-options.
                                                             (line   62)
* UpdateXML():                           xml-functions.      (line  284)
* updating main table, thread state:     general-thread-states.
                                                             (line  341)
* updating reference tables, thread state: general-thread-states.
                                                             (line  347)
* updating, releases of MySQL:           many-versions.      (line    6)
* updating, tables:                      ansi-diff-transactions.
                                                             (line    6)
* Updating, thread state:                general-thread-states.
                                                             (line  337)
* upgrades and downgrades (MySQL Cluster), compatibility between versions: mysql-cluster-upgrade-downgrade.
                                                             (line   12)
* upgrades, MySQL Cluster <1>:           mysql-cluster-rolling-restart.
                                                             (line    6)
* upgrades, MySQL Cluster:               mysql-cluster-upgrade-downgrade.
                                                             (line   12)
* upgrading <1>:                         upgrading.          (line   10)
* upgrading:                             upgrading-downgrading.
                                                             (line   14)
* upgrading lock, thread state:          delayed-insert-thread-states.
                                                             (line   81)
* upgrading MySQL:                       mysql-upgrade.      (line    6)
* upgrading, different architecture:     copying-databases.  (line    6)
* upgrading, grant tables:               mysql-fix-privilege-tables.
                                                             (line    6)
* upgrading, to &current-series;:        upgrading-from-previous-series.
                                                             (line    6)
* UPPER():                               string-functions.   (line  820)
* uptime:                                mysqladmin.         (line  168)
* URLs for downloading MySQL:            getting-mysql.      (line    6)
* usage option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  119)
* usage option, ndb_config:              mysql-cluster-programs-ndb-config.
                                                             (line  144)
* USE:                                   use.                (line    6)
* use command, mysql:                    mysql-commands.     (line  232)
* USE INDEX:                             index-hints.        (line    6)
* USE KEY:                               index-hints.        (line    6)
* use-frm option, mysqlcheck:            mysqlcheck.         (line  437)
* use-manager option, mysql.server:      mysql-server.       (line   63)
* use-mysqld_safe option, mysql.server:  mysql-server.       (line   58)
* use-threads option, mysqlimport:       mysqlimport.        (line  339)
* use-threads option, mysqlslap:         mysqlslap.          (line  502)
* useHexFormat option, ndb_select_all:   mysql-cluster-programs-ndb-select-all.
                                                             (line  166)
* user accounts, creating:               create-user.        (line    6)
* user accounts, renaming:               rename-user.        (line    6)
* user accounts, resource limits <1>:    grant.              (line  498)
* user accounts, resource limits <2>:    user-resources.     (line    6)
* user accounts, resource limits:        server-system-variables.
                                                             (line 3237)
* USER environment variable <1>:         connecting.         (line  246)
* USER environment variable:             environment-variables.
                                                             (line   18)
* User lock, thread state:               general-thread-states.
                                                             (line  352)
* user names, and passwords:             user-names.         (line    6)
* user option:                           connecting.         (line  224)
* user option, mysql:                    mysql-command-options.
                                                             (line  580)
* user option, mysql.server:             mysql-server.       (line   67)
* user option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   60)
* user option, mysql_install_db:         mysql-install-db.   (line  130)
* user option, mysql_setpermission:      mysql-setpermission.
                                                             (line   56)
* user option, mysql_upgrade:            mysql-upgrade.      (line  279)
* user option, mysqlaccess:              mysqlaccess.        (line  152)
* user option, mysqladmin:               mysqladmin.         (line  463)
* user option, mysqlbinlog:              mysqlbinlog.        (line  581)
* user option, mysqlcheck:               mysqlcheck.         (line  443)
* user option, mysqld:                   server-options.     (line 2250)
* user option, mysqld_multi:             mysqld-multi.       (line  172)
* user option, mysqld_safe:              mysqld-safe.        (line  237)
* user option, mysqldump:                mysqldump.          (line 1051)
* user option, mysqlhotcopy:             mysqlhotcopy.       (line  192)
* user option, mysqlimport:              mysqlimport.        (line  335)
* user option, mysqlmanager:             instance-manager-command-options.
                                                             (line  226)
* user option, mysqlshow:                mysqlshow.          (line  260)
* user option, mysqlslap:                mysqlslap.          (line  509)
* user privileges, adding:               adding-users.       (line    6)
* user privileges, deleting <1>:         drop-user.          (line    6)
* user privileges, deleting:             removing-users.     (line    6)
* user privileges, dropping <1>:         drop-user.          (line    6)
* user privileges, dropping:             removing-users.     (line    6)
* User sleep, thread state:              general-thread-states.
                                                             (line  359)
* user table, sorting:                   connection-access.  (line  130)
* user variables:                        user-variables.     (line    6)
* user variables, and replication:       replication-features-variables.
                                                             (line    6)
* USER():                                information-functions.
                                                             (line  672)
* User-defined functions <1>:            drop-function-udf.  (line    6)
* User-defined functions:                create-function-udf.
                                                             (line    6)
* user-defined functions, adding <1>:    adding-udf.         (line   15)
* user-defined functions, adding:        adding-functions.   (line   12)
* USER_PRIVILEGES, INFORMATION_SCHEMA table: user-privileges-table.
                                                             (line    6)
* username option, mysqlmanager:         instance-manager-command-options.
                                                             (line  237)
* users, adding:                         unix-postinstallation.
                                                             (line  386)
* users, deleting <1>:                   drop-user.          (line    6)
* users, deleting:                       removing-users.     (line    6)
* users, root:                           default-privileges. (line    6)
* using multiple disks to start data:    windows-symbolic-links.
                                                             (line    6)
* using MySQL Cluster programs:          mysql-cluster-programs.
                                                             (line   35)
* UTC_DATE():                            date-and-time-functions.
                                                             (line 1253)
* UTC_TIME():                            date-and-time-functions.
                                                             (line 1263)
* UTC_TIMESTAMP():                       date-and-time-functions.
                                                             (line 1273)
* UTF-8:                                 charset.            (line   22)
* utf8 character set:                    charset-unicode-utf8.
                                                             (line    6)
* utilities, program-development:        programs-overview.  (line  256)
* utility programs:                      programs-overview.  (line  165)
* UUID():                                miscellaneous-functions.
                                                             (line  243)
* UUID_SHORT():                          miscellaneous-functions.
                                                             (line  293)
* valid numbers, examples:               number-literals.    (line    6)
* VALUES():                              miscellaneous-functions.
                                                             (line  330)
* VAR_POP():                             group-by-functions. (line  282)
* VAR_SAMP():                            group-by-functions. (line  291)
* VARBINARY data type <1>:               binary-varbinary.   (line    6)
* VARBINARY data type:                   string-type-overview.
                                                             (line  161)
* VARCHAR data type <1>:                 string-types.       (line   14)
* VARCHAR data type:                     string-type-overview.
                                                             (line  124)
* VARCHAR, size:                         storage-requirements.
                                                             (line  199)
* VARCHARACTER data type:                string-type-overview.
                                                             (line  124)
* variables, and replication:            replication-features-variables.
                                                             (line    6)
* variables, environment:                programs-overview.  (line  302)
* variables, mysqld:                     server-parameters.  (line   12)
* variables, server:                     show-variables.     (line    6)
* variables, status <1>:                 show-status.        (line    6)
* variables, status:                     server-status-variables.
                                                             (line    6)
* variables, system <1>:                 show-variables.     (line    6)
* variables, system <2>:                 using-system-variables.
                                                             (line   11)
* variables, system:                     server-system-variables.
                                                             (line    6)
* variables, user:                       user-variables.     (line    6)
* VARIANCE():                            group-by-functions. (line  298)
* verbose option (ndb_index_stat):       mysql-cluster-programs-ndb-index-stat.
                                                             (line  397)
* verbose option (ndb_restore):          mysql-cluster-programs-ndb-restore.
                                                             (line  840)
* verbose option, my_print_defaults:     my-print-defaults.  (line   58)
* verbose option, myisam_ftdump:         myisam-ftdump.      (line   84)
* verbose option, myisamchk:             myisamchk-general-options.
                                                             (line   63)
* verbose option, myisampack:            myisampack.         (line  110)
* verbose option, mysql:                 mysql-command-options.
                                                             (line  584)
* verbose option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   64)
* verbose option, mysql_install_db:      mysql-install-db.   (line  139)
* verbose option, mysql_upgrade:         mysql-upgrade.      (line  284)
* verbose option, mysql_waitpid:         mysql-waitpid.      (line   32)
* verbose option, mysqladmin:            mysqladmin.         (line  467)
* verbose option, mysqlbinlog:           mysqlbinlog.        (line  585)
* verbose option, mysqlcheck:            mysqlcheck.         (line  447)
* verbose option, mysqld:                server-options.     (line 2284)
* verbose option, mysqld_multi:          mysqld-multi.       (line  177)
* verbose option, mysqldump:             mysqldump.          (line 1055)
* verbose option, mysqldumpslow:         mysqldumpslow.      (line  103)
* verbose option, mysqlimport:           mysqlimport.        (line  344)
* verbose option, mysqlshow:             mysqlshow.          (line  264)
* verbose option, mysqlslap:             mysqlslap.          (line  513)
* verbose option, ndb_blob_tool:         mysql-cluster-programs-ndb-blob-tool.
                                                             (line  144)
* verbose option, perror:                perror.             (line   56)
* version option (MySQL Cluster programs): mysql-cluster-program-options-common.
                                                             (line  253)
* version option, comp_err:              comp-err.           (line   71)
* version option, my_print_defaults:     my-print-defaults.  (line   62)
* version option, myisamchk:             myisamchk-general-options.
                                                             (line   69)
* version option, myisampack:            myisampack.         (line  115)
* version option, mysql:                 mysql-command-options.
                                                             (line  591)
* version option, mysql_config:          mysql-config.       (line   54)
* version option, mysql_convert_table_format: mysql-convert-table-format.
                                                             (line   68)
* version option, mysql_waitpid:         mysql-waitpid.      (line   37)
* version option, mysqlaccess:           mysqlaccess.        (line  156)
* version option, mysqladmin:            mysqladmin.         (line  471)
* version option, mysqlbinlog:           mysqlbinlog.        (line  596)
* version option, mysqlcheck:            mysqlcheck.         (line  452)
* version option, mysqld:                server-options.     (line 2288)
* version option, mysqld_multi:          mysqld-multi.       (line  181)
* version option, mysqldump:             mysqldump.          (line 1059)
* version option, mysqlimport:           mysqlimport.        (line  348)
* version option, mysqlmanager:          instance-manager-command-options.
                                                             (line  242)
* version option, mysqlshow:             mysqlshow.          (line  270)
* version option, mysqlslap:             mysqlslap.          (line  519)
* version option, ndb_config:            mysql-cluster-programs-ndb-config.
                                                             (line  181)
* version option, perror:                perror.             (line   61)
* version option, resolve_stack_dump:    resolve-stack-dump. (line   34)
* version option, resolveip:             resolveip.          (line   24)
* version system variable:               server-system-variables.
                                                             (line 5868)
* VERSION():                             information-functions.
                                                             (line  691)
* version, choosing:                     which-version.      (line   18)
* version, latest:                       getting-mysql.      (line    6)
* version_comment system variable:       server-system-variables.
                                                             (line 5876)
* version_compile_machine system variable: server-system-variables.
                                                             (line 5892)
* version_compile_os system variable:    server-system-variables.
                                                             (line 5906)
* vertical option, mysql:                mysql-command-options.
                                                             (line  595)
* vertical option, mysqladmin:           mysqladmin.         (line  475)
* Vietnamese:                            faqs-cjk.           (line    6)
* view, restrictions:                    view-restrictions.  (line    6)
* views <1>:                             views.              (line   13)
* views <2>:                             stored-programs-views.
                                                             (line   16)
* views:                                 create-view.        (line    6)
* views, algorithms:                     view-algorithms.    (line    6)
* views, and replication:                replication-features-views.
                                                             (line    6)
* VIEWS, INFORMATION_SCHEMA table:       views-table.        (line    6)
* Views, limitations:                    view-restrictions.  (line  114)
* views, metadata:                       view-metadata.      (line    6)
* Views, privileges:                     view-restrictions.  (line  114)
* Views, problems:                       view-restrictions.  (line  114)
* views, updatable <1>:                  view-updatability.  (line    6)
* views, updatable:                      create-view.        (line    6)
* virtual memory, problems while compiling: compilation-problems.
                                                             (line   38)
* Visual Studio:                         windows-source-build.
                                                             (line    6)
* WAIT COMPLETED (START BACKUP command): mysql-cluster-backup-using-management-client.
                                                             (line   62)
* wait option, myisamchk:                myisamchk-general-options.
                                                             (line   73)
* wait option, myisampack:               myisampack.         (line  119)
* wait option, mysql:                    mysql-command-options.
                                                             (line  601)
* wait option, mysqladmin:               mysqladmin.         (line  480)
* WAIT STARTED (START BACKUP command):   mysql-cluster-backup-using-management-client.
                                                             (line   53)
* wait-nodes option, ndb_waiter:         mysql-cluster-programs-ndb-waiter.
                                                             (line  136)
* wait-timeout option, mysqlmanager:     instance-manager-command-options.
                                                             (line  246)
* wait_timeout system variable:          server-system-variables.
                                                             (line 5920)
* waiting for delay_list, thread state:  delayed-insert-thread-states.
                                                             (line   44)
* Waiting for event from ndbcluster, thread state: mysql-cluster-thread-states.
                                                             (line   25)
* Waiting for first event from ndbcluster, thread state: mysql-cluster-thread-states.
                                                             (line   30)
* waiting for handler insert, thread state: delayed-insert-thread-states.
                                                             (line   51)
* waiting for handler lock, thread state: delayed-insert-thread-states.
                                                             (line   56)
* waiting for handler open, thread state: delayed-insert-thread-states.
                                                             (line   62)
* Waiting for INSERT, thread state:      delayed-insert-thread-states.
                                                             (line   86)
* Waiting for master to send event, thread state: slave-io-thread-states.
                                                             (line   49)
* Waiting for master update, thread state: slave-io-thread-states.
                                                             (line   12)
* Waiting for ndbcluster binlog update to reach current position, thread state: mysql-cluster-thread-states.
                                                             (line   32)
* Waiting for ndbcluster to start, thread state: mysql-cluster-thread-states.
                                                             (line   34)
* Waiting for next activation, thread state: event-scheduler-thread-states.
                                                             (line   20)
* Waiting for release of readlock, thread state: general-thread-states.
                                                             (line  363)
* Waiting for scheduler to stop, thread state: event-scheduler-thread-states.
                                                             (line   25)
* Waiting for schema epoch, thread state: mysql-cluster-thread-states.
                                                             (line   36)
* Waiting for slave mutex on exit, thread state <1>: slave-sql-thread-states.
                                                             (line   31)
* Waiting for slave mutex on exit, thread state: slave-io-thread-states.
                                                             (line   84)
* Waiting for table, thread state:       general-thread-states.
                                                             (line  369)
* Waiting for tables, thread state:      general-thread-states.
                                                             (line  369)
* Waiting for the next event in relay log, thread state: slave-sql-thread-states.
                                                             (line    9)
* Waiting for the slave SQL thread to free enough relay log space, thread state: slave-io-thread-states.
                                                             (line   76)
* Waiting on cond, thread state:         general-thread-states.
                                                             (line  383)
* Waiting on empty queue, thread state:  event-scheduler-thread-states.
                                                             (line   30)
* Waiting to finalize termination, thread state: master-thread-states.
                                                             (line   29)
* Waiting to get readlock, thread state: general-thread-states.
                                                             (line  388)
* Waiting to reconnect after a failed binlog dump request, thread state: slave-io-thread-states.
                                                             (line   37)
* Waiting to reconnect after a failed master event read, thread state: slave-io-thread-states.
                                                             (line   62)
* Wan <1>:                               mysql-cluster-api-definition.
                                                             (line  430)
* Wan:                                   mysql-cluster-mgm-definition.
                                                             (line  291)
* warning_count system variable:         server-system-variables.
                                                             (line 5957)
* warnings command, mysql:               mysql-commands.     (line  236)
* WEEK():                                date-and-time-functions.
                                                             (line 1283)
* WEEKDAY():                             date-and-time-functions.
                                                             (line 1358)
* WEEKOFYEAR():                          date-and-time-functions.
                                                             (line 1369)
* Well-Known Binary format:              gis-wkb-format.     (line    6)
* Well-Known Text format:                gis-wkt-format.     (line    6)
* WHERE:                                 where-optimizations.
                                                             (line    6)
* where option, mysqldump:               mysqldump.          (line 1063)
* WHERE, with SHOW <1>:                  extended-show.      (line    6)
* WHERE, with SHOW:                      information-schema. (line   36)
* WHILE:                                 while.              (line    6)
* WHILE, labels:                         statement-labels.   (line    6)
* widths, display:                       data-types.         (line   31)
* Wildcard character (%):                string-literals.    (line   82)
* Wildcard character (_):                string-literals.    (line   83)
* wildcards, and LIKE:                   mysql-indexes.      (line  119)
* wildcards, in account names:           account-names.      (line   72)
* wildcards, in mysql.columns_priv table: request-access.    (line   59)
* wildcards, in mysql.db table:          request-access.     (line   26)
* wildcards, in mysql.host table:        request-access.     (line   26)
* wildcards, in mysql.procs_priv table:  request-access.     (line   59)
* wildcards, in mysql.tables_priv table: request-access.     (line   59)
* Windows Failover Clustering:           ha-wfc.             (line    6)
* windows option, mysql_install_db:      mysql-install-db.   (line  143)
* Windows Server Failover Clustering:    ha-wfc.             (line    6)
* Windows, compiling clients on:         c-api-building-clients.
                                                             (line   52)
* Windows, MySQL limitations <1>:        limits-windows.     (line    6)
* Windows, MySQL limitations:            limits-frm-file.    (line    6)
* Windows, path name separators:         option-files.       (line  195)
* Windows, upgrading:                    windows-upgrading.  (line    6)
* with-big-tables option:                source-configuration-options.
                                                             (line    6)
* with-big-tables option, configure:     source-configuration-options.
                                                             (line  540)
* with-client-ldflags option, configure: source-configuration-options.
                                                             (line  395)
* with-debug option, configure:          source-configuration-options.
                                                             (line  488)
* with-embedded-server option, configure: source-configuration-options.
                                                             (line  349)
* with-extra-charsets option, configure: source-configuration-options.
                                                             (line  473)
* with-tcp-port option, configure:       source-configuration-options.
                                                             (line  374)
* with-unix-socket-path option, configure: source-configuration-options.
                                                             (line  382)
* with-zlib-dir option, configure:       source-configuration-options.
                                                             (line  531)
* Within():                              spatial-relation-functions-mbr.
                                                             (line   62)
* without-server option:                 source-configuration-options.
                                                             (line    6)
* without-server option, configure:      source-configuration-options.
                                                             (line  334)
* WKB format:                            gis-wkb-format.     (line    6)
* WKT format:                            gis-wkt-format.     (line    6)
* wrappers, Eiffel:                      apis-eiffel.        (line    6)
* write access, tmp:                     mysql-install-db-problems.
                                                             (line   73)
* write-binlog option, mysql_upgrade:    mysql-upgrade.      (line  288)
* write-binlog option, mysqlcheck:       mysqlcheck.         (line  456)
* write_buffer_size myisamchk variable:  myisamchk-general-options.
                                                             (line   84)
* Writing to net, thread state:          general-thread-states.
                                                             (line  394)
* X():                                   gis-point-property-functions.
                                                             (line    9)
* X509/Certificate:                      ssl-basics.         (line   30)
* XA BEGIN:                              xa-statements.      (line    6)
* XA COMMIT:                             xa-statements.      (line    6)
* XA PREPARE:                            xa-statements.      (line    6)
* XA RECOVER:                            xa-statements.      (line    6)
* XA ROLLBACK:                           xa-statements.      (line    6)
* XA START:                              xa-statements.      (line    6)
* XA transactions:                       xa.                 (line   11)
* XA transactions, restrictions:         xa-restrictions.    (line    6)
* XA transactions, transaction identifiers: xa-statements.   (line    6)
* xid, XA transaction identifier:        xa-statements.      (line    6)
* xml option, mysql:                     mysql-command-options.
                                                             (line  606)
* xml option, mysqldump:                 mysqldump.          (line 1076)
* xml option, ndb_config:                mysql-cluster-programs-ndb-config.
                                                             (line  489)
* XOR, bitwise:                          bit-functions.      (line   40)
* XOR, logical:                          logical-operators.  (line   88)
* Y():                                   gis-point-property-functions.
                                                             (line   22)
* yaSSL:                                 configuring-for-ssl.
                                                             (line    6)
* YEAR data type <1>:                    year.               (line    6)
* YEAR data type:                        date-and-time-type-overview.
                                                             (line   69)
* YEAR():                                date-and-time-functions.
                                                             (line 1379)
* YEARWEEK():                            date-and-time-functions.
                                                             (line 1388)
* Yen sign (Japanese):                   faqs-cjk.           (line    6)
* ZEROFILL <1>:                          c-api-prepared-statement-problems.
                                                             (line   13)
* ZEROFILL <2>:                          numeric-types.      (line   15)
* ZEROFILL:                              numeric-type-overview.
                                                             (line    6)
* ZFS:                                   ha-zfs-replication. (line   12)
* | (bitwise OR):                        bit-functions.      (line   20)
* || (logical OR):                       logical-operators.  (line   68)
* ~ (invert bits):                       bit-functions.      (line   80)



Tag Table:
Node: Top167
Node: preface1892
Ref: legalnotice2937
Node: introduction8460
Node: manual-info12084
Node: manual-conventions14446
Node: what-is19586
Node: what-is-mysql19967
Node: features25391
Node: history35375
Node: mysql-nutshell36511
Ref: mysql-nutshell-additions36828
Ref: mysql-nutshell-deprecations44009
Node: development-history45912
Node: information-sources47372
Node: mailing-lists47981
Node: mailing-list-use52972
Node: forums54077
Node: irc54624
Node: mysql-enterprise-information55584
Node: bug-reports56374
Node: compatibility74422
Node: extensions-to-ansi78542
Node: differences-from-ansi88464
Node: ansi-diff-select-into-table89605
Node: ansi-diff-update90508
Node: ansi-diff-transactions91094
Node: ansi-diff-foreign-keys99880
Ref: constraint-foreign-key-deviations102043
Node: ansi-diff-comments104362
Node: constraints107032
Node: constraint-primary-key109040
Node: constraint-foreign-key110401
Node: constraint-invalid-data113257
Node: constraint-enum119143
Node: credits121744
Node: contributors122276
Node: documenters-translators131048
Node: packages133364
Node: tools-used-to-create-mysql134565
Node: supporters135595
Node: installing136533
Node: general-installation-issues142829
Node: supported-os143910
Node: which-version144394
Node: choosing-version145144
Node: choosing-distribution-format151614
Node: many-versions154775
Node: getting-mysql156667
Node: verifying-package-integrity157312
Node: verifying-md5-checksum158463
Node: checking-gpg-signature160625
Node: checking-gpg-signature-windows172219
Ref: gnupg-kleopatra-home172903
Ref: gnupg-kleopatra-find-certificate173149
Ref: gnupg-kleopatra-change-trust173899
Ref: gnupg-kleopatra-decrypt-load174885
Ref: gnupg-kleopatra-decrypt-okay-sig175182
Ref: gnupg-kleopatra-decrypt-invalid-sig175355
Node: checking-rpm-signature175519
Node: installation-layouts177021
Node: compiler-characteristics177903
Node: binary-installation178497
Ref: binary-installation-layout181190
Ref: binary-installation-createsysuser183526
Ref: binary-installation-unpack184425
Ref: binary-installation-postinstall185845
Node: windows-installation186284
Node: windows-installation-layout192438
Node: windows-choosing-package195681
Ref: installer-windows-workflow-msi197929
Ref: installer-windows-workflow-zip198061
Node: windows-using-installer200566
Ref: installer-windows-workflow-installer202066
Node: windows-install-wizard204238
Node: mysql-install-wizard-starting206733
Node: mysql-install-wizard-install-type207489
Node: mysql-install-wizard-custom-install209017
Node: mysql-install-wizard-confirmation-dialog210078
Node: mysql-install-wizard-changes211402
Node: mysql-install-wizard-upgrading215364
Node: windows-installer-msi-quiet217692
Node: windows-installer-uninstalling219853
Node: windows-notifier222041
Ref: windows-notifier-server-instance225524
Ref: windows-notifier-actions226017
Ref: windows-notifier-options227352
Ref: windows-notifier-manage-services227551
Ref: windows-notifier-manage-instances227639
Ref: windows-notifier-add-services228053
Ref: windows-notifier-add-instances228123
Node: windows-notifier-installation228246
Ref: windows-notifier-installation-wmi229620
Ref: windows-notifier-installation-errors239629
Node: mysql-config-wizard240899
Ref: installer-windows-instance-workflow243102
Node: mysql-config-wizard-starting243166
Node: mysql-config-wizard-maintenance246318
Node: mysql-config-wizard-configuration-type247719
Node: mysql-config-wizard-server-type249545
Node: mysql-config-wizard-database-usage251282
Node: mysql-config-wizard-tablespace253537
Node: mysql-config-wizard-connections254701
Node: mysql-config-wizard-networking256217
Node: mysql-config-wizard-character-set257563
Node: mysql-config-wizard-service258835
Node: mysql-config-wizard-security260972
Node: mysql-config-wizard-confirmation263639
Node: mysql-config-wizard-cmdline265450
Node: windows-install-archive272895
Node: windows-extract-archive274244
Node: windows-create-option-file275429
Node: windows-select-server278868
Node: windows-server-first-start281625
Node: windows-start-command-line285285
Node: mysql-installation-windows-path287503
Node: windows-start-service289611
Node: windows-testing296742
Node: windows-troubleshooting298566
Node: windows-upgrading304108
Node: windows-postinstallation307474
Node: macosx-installation312041
Node: macosx-installation-notes314649
Node: macosx-installation-pkg319314
Ref: mysql-installation-layout-macosx320896
Node: macosx-installation-startupitem323879
Node: macosx-installation-prefpane326380
Node: macosx-installation-server329498
Node: linux-installation332021
Node: linux-installation-rpm334081
Ref: mysql-installation-layout-linuxrpm334847
Node: linux-installation-native346861
Node: solaris-installation359204
Node: solaris-installation-pkg362830
Node: solaris-installation-opensolaris365695
Node: aix-installation368823
Node: aix-installation-general369805
Node: hpux-installation370161
Node: hpux-installation-general371515
Node: hpux-installation-depot372556
Node: freebsd-installation374534
Node: i5os-installation376475
Ref: installation-i5os-notes387511
Node: source-installation388260
Node: source-installation-layout392440
Node: installing-source-distribution394233
Node: installing-development-tree400230
Node: source-configuration-options408764
Ref: option_configure_with-collation436001
Ref: option_configure_with-extra-charsets436562
Node: compilation-problems443476
Node: compile-and-link-options451387
Node: windows-source-build453881
Node: solaris-installation-source467463
Node: aix-installation-source472125
Node: hpux-installation-source474754
Node: postinstallation475910
Node: unix-postinstallation477321
Node: mysql-install-db-problems494835
Node: automatic-start501834
Node: starting-server509689
Node: default-privileges517275
Node: upgrading-downgrading528844
Node: upgrading529390
Node: upgrading-from-previous-series536693
Node: downgrading579450
Node: downgrading-to-previous-series583558
Node: downgrading-from-enterprise585881
Node: checking-table-incompatibilities588283
Node: rebuilding-tables594628
Node: copying-databases599952
Node: environment-variables602956
Node: perl-support607620
Node: perl-installation609169
Node: activestate-perl611979
Node: perl-support-problems613149
Node: tutorial615831
Node: connecting-disconnecting617855
Node: entering-queries620599
Node: database-use629483
Node: creating-database632725
Node: creating-tables635148
Node: loading-tables639592
Node: retrieving-data643293
Node: selecting-all644500
Node: selecting-rows646722
Node: selecting-columns650529
Node: sorting-rows652681
Node: date-calculations655582
Node: working-with-null662597
Node: pattern-matching665242
Node: counting-rows672759
Node: multiple-tables677804
Node: getting-information683258
Node: batch-mode686315
Node: examples689544
Node: example-maximum-column691751
Node: example-maximum-row692109
Node: example-maximum-column-group693253
Node: example-maximum-column-group-row693793
Node: example-user-variables695515
Node: example-foreign-keys696609
Node: searching-on-two-keys700870
Node: calculating-days701820
Node: example-auto-increment703000
Node: apache708919
Node: programs709819
Node: programs-overview710908
Node: programs-using722902
Node: invoking-programs723745
Node: connecting727215
Node: program-options737390
Node: command-line-options740082
Node: option-modifiers745455
Node: option-files747513
Node: option-file-options760154
Node: program-variables762273
Node: option-defaults-equals765583
Node: setting-environment-variables772839
Node: programs-server775846
Node: mysqld776486
Node: mysqld-safe777931
Node: mysql-server792800
Node: mysqld-multi795440
Node: programs-installation808776
Node: comp-err809756
Node: make-win-bin-dist811974
Node: mysqlbug814183
Node: mysql-fix-privilege-tables815588
Node: mysql-install-db818544
Node: mysql-secure-installation824087
Node: mysql-tzinfo-to-sql825247
Node: mysql-upgrade827418
Node: programs-client839155
Node: mysql839968
Node: mysql-command-options842184
Node: mysql-commands867954
Node: mysql-logging883136
Node: mysql-server-side-help885549
Node: mysql-batch-commands888469
Node: mysql-tips890295
Node: mysql-input-editing890777
Node: vertical-query-results892694
Node: safe-updates893944
Node: mysql-reconnect895746
Node: mysqladmin897411
Node: mysqlcheck914848
Node: mysqldump933527
Ref: mysqldump-syntax935138
Node: mysqlimport986486
Node: mysqlshow1001247
Node: mysqlslap1011908
Node: programs-admin-utils1033509
Node: innochecksum1035278
Node: myisam-ftdump1037160
Node: myisamchk1040048
Node: myisamchk-general-options1052627
Node: myisamchk-check-options1059920
Node: myisamchk-repair-options1062424
Node: myisamchk-other-options1067346
Node: myisamchk-table-info1069907
Node: myisamchk-memory1084210
Node: myisamlog1087271
Node: myisampack1088879
Node: mysqlaccess1104380
Node: mysqlbinlog1110050
Node: mysqlbinlog-hexdump1139715
Node: mysqlbinlog-row-events1150912
Node: mysqldumpslow1159913
Node: mysqlhotcopy1163470
Node: instance-manager1169912
Node: instance-manager-command-options1172789
Node: instance-manager-configuration-files1182196
Node: instance-manager-startup-process1185751
Node: instance-manager-security-passwords1190694
Node: instance-manager-security-monitoring1197761
Node: instance-manager-security1201519
Node: instance-manager-commands1202448
Node: mysql-convert-table-format1213584
Node: mysql-find-rows1215718
Node: mysql-fix-extensions1217330
Node: mysql-setpermission1218283
Node: mysql-waitpid1220318
Node: mysql-zap1221657
Node: programs-development1223027
Node: msql2mysql1224955
Node: mysql-config1226102
Node: my-print-defaults1229054
Node: resolve-stack-dump1231029
Node: programs-miscellaneous1232241
Node: perror1232639
Node: replace-utility1234297
Node: resolveip1236148
Node: server-administration1236847
Node: mysqld-server1238052
Node: mysqld-option-tables1240058
Node: server-configuration-defaults1325035
Node: server-options1326463
Node: server-system-variables1419020
Node: using-system-variables1673227
Node: structured-system-variables1685541
Node: dynamic-system-variables1690724
Node: server-status-variables1709644
Node: sql-mode1769038
Ref: sql-mode-setting1770050
Ref: sql-mode-important1772023
Ref: sql-mode-full1773398
Ref: sql-mode-strict1788584
Ref: sql-mode-combo1791453
Node: server-plugins1793581
Node: server-plugin-loading1794241
Ref: server-plugin-installing1794798
Ref: server-plugin-activating1798998
Ref: server-plugin-uninstalling1802603
Node: obtaining-plugin-information1803574
Node: server-side-help-support1806302
Node: server-signal-response1808205
Node: server-shutdown1810050
Node: server-logs1814550
Node: log-destinations1817632
Node: error-log1826939
Node: query-log1833768
Node: binary-log1838782
Node: binary-log-formats1853147
Node: binary-log-setting1855529
Node: binary-log-mixed1861115
Node: binary-log-mysql-database1871526
Node: slow-query-log1873274
Node: ddl-log1879262
Node: log-file-maintenance1880660
Node: multiple-servers1885280
Node: multiple-data-directories1890469
Node: multiple-windows-servers1893800
Node: multiple-windows-command-line-servers1894789
Node: multiple-windows-services1897914
Node: multiple-unix-servers1902273
Node: multiple-server-clients1906212
Node: security1908999
Node: general-security-issues1910955
Node: security-guidelines1912036
Node: password-security1917602
Node: password-security-user1918457
Node: password-security-admin1923350
Node: password-logging1924186
Node: password-hashing1925403
Node: application-password-use1943719
Node: security-against-attack1945226
Node: security-options1952493
Node: changing-mysql-user1954946
Node: load-data-local1957308
Node: secure-client-programming1960716
Node: privilege-system1965318
Node: privileges-provided1969909
Node: grant-table-structure1986191
Node: account-names2000388
Node: connection-access2007006
Node: request-access2015592
Node: privilege-changes2024252
Node: access-denied2026565
Node: user-account-management2045049
Node: user-names2046307
Node: adding-users2052386
Node: removing-users2064382
Node: user-resources2064672
Node: assigning-passwords2072273
Node: ssl-connections2076991
Node: ssl-basics2078663
Node: configuring-for-ssl2080917
Node: using-ssl-connections2084309
Node: ssl-options2088686
Node: creating-ssl-certs2099419
Node: windows-and-ssh2113233
Node: account-activity-auditing2114768
Node: backup-and-recovery2119919
Node: backup-types2123069
Node: backup-methods2133094
Node: backup-strategy-example2140303
Node: backup-policy2143804
Node: recovery-from-backups2151329
Node: backup-strategy-summary2153364
Node: using-mysqldump2154410
Node: mysqldump-sql-format2156544
Node: reloading-sql-format-dumps2159604
Node: mysqldump-delimited-text2160917
Node: reloading-delimited-text-dumps2165185
Node: mysqldump-tips2166801
Node: mysqldump-copying-database2167683
Node: mysqldump-copying-to-other-server2168229
Node: mysqldump-stored-programs2169486
Node: mysqldump-definition-data-dumps2170356
Node: mysqldump-upgrade-testing2171378
Node: point-in-time-recovery2172734
Node: point-in-time-recovery-times2177497
Node: point-in-time-recovery-positions2179648
Node: myisam-table-maintenance2182002
Node: myisam-crash-recovery2184674
Node: myisam-check2188307
Node: myisam-repair2190156
Node: myisam-optimization2197853
Node: myisam-maintenance-schedule2199497
Node: optimization2201988
Node: optimize-overview2203133
Node: design-limitations2204938
Node: portability2206686
Node: mysql-benchmarks2210645
Node: custom-benchmarks2213047
Node: execution-plan-information2215185
Node: using-explain2215668
Node: explain-output2217857
Ref: explain-output-columns2219441
Ref: explain-output-column-table2219849
Ref: explain-join-types2227499
Ref: explain-extra-information2233707
Ref: explain-output-interpretation2242989
Node: explain-extended2250033
Node: estimating-performance2254127
Node: statement-optimization2255932
Node: select-optimization2256397
Node: select-speed2259268
Node: where-optimizations2261011
Node: range-optimization2265761
Node: range-access-single-part2266435
Node: range-access-multi-part2270916
Node: index-merge-optimization2276210
Node: index-merge-intersection2279073
Node: index-merge-union2280729
Node: index-merge-sort-union2281786
Node: condition-pushdown-optimization2282549
Node: is-null-optimization2287166
Node: left-join-optimization2289320
Node: nested-loop-joins2292301
Node: nested-join-optimization2296022
Node: outer-join-simplification2309781
Node: order-by-optimization2315564
Node: group-by-optimization2326291
Node: loose-index-scan2327871
Node: tight-index-scan2331588
Node: distinct-optimization2333704
Node: subquery-optimization-with-exists2335243
Node: limit-optimization2347821
Node: how-to-avoid-table-scan2350103
Node: non-select-optimization2352089
Node: insert-speed2352574
Node: update-speed2359304
Node: delete-speed2360199
Node: repair-table-speed2360911
Node: information-schema-optimization2365835
Node: miscellaneous-optimization-tips2381593
Node: controlling-optimizer2392536
Node: controlling-query-plan-evaluation2393041
Node: switchable-optimizations2396094
Node: optimization-indexes2399955
Node: column-indexes2400389
Node: multiple-column-indexes2402510
Node: mysql-indexes2406563
Node: myisam-index-statistics2415515
Node: buffering-caching2421654
Node: myisam-key-cache2422097
Node: shared-key-cache2425975
Node: multiple-key-caches2426802
Node: midpoint-insertion2432307
Node: index-preloading2434854
Node: key-cache-block-size2436664
Node: key-cache-restructuring2437587
Node: innodb-buffer-pool2438967
Node: query-cache2447403
Node: query-cache-operation2451749
Node: query-cache-in-select2458111
Node: query-cache-configuration2459096
Node: query-cache-status-and-maintenance2465608
Node: locking-issues2468455
Node: internal-locking2469444
Node: table-locking2476498
Node: concurrent-inserts2481770
Node: external-locking2484714
Node: optimizing-database-structure2489325
Node: data-size2489894
Node: procedure-analyse2494885
Node: table-cache2496467
Node: creating-many-tables2501960
Node: internal-temporary-tables2502642
Node: optimizing-the-server2506030
Node: system-optimization2506745
Node: server-parameters2508837
Node: connection-threads2525290
Node: memory-use2528552
Node: disk-issues2534399
Node: symbolic-links2538537
Node: symbolic-links-to-databases2539526
Node: symbolic-links-to-tables2540615
Node: windows-symbolic-links2545201
Node: large-page-support2548021
Node: host-cache2552721
Node: thread-information2556566
Node: thread-commands2559646
Node: general-thread-states2562230
Node: delayed-insert-thread-states2574968
Node: query-cache-thread-states2578010
Node: master-thread-states2578974
Node: slave-io-thread-states2580292
Node: slave-sql-thread-states2583597
Node: slave-connection-thread-states2584941
Node: mysql-cluster-thread-states2586318
Node: event-scheduler-thread-states2587400
Node: language-structure2588348
Node: literals2589160
Node: string-literals2589942
Ref: character-escape-sequences2592484
Node: number-literals2596875
Node: date-and-time-literals2598894
Ref: date-and-time-standard-sql-literals2599628
Ref: date-and-time-string-numeric-literals2600160
Node: hexadecimal-literals2606281
Node: boolean-literals2607906
Node: bit-field-literals2608270
Node: null-values2609843
Node: identifiers2610465
Node: identifier-qualifiers2616564
Node: identifier-case-sensitivity2618982
Node: identifier-mapping2626329
Node: function-resolution2633635
Node: reserved-words2644344
Ref: table-reserved-words-5.1.742646621
Ref: table-reserved-words-new-5.12651157
Node: user-variables2651684
Node: expressions2659705
Node: comments2663666
Node: globalization2666527
Node: charset2667617
Node: charset-general2670017
Node: charset-mysql2672708
Node: charset-syntax2678162
Node: charset-server2679862
Node: charset-database2682038
Node: charset-table2684523
Node: charset-column2686185
Node: charset-literal2689538
Node: charset-national2694310
Node: charset-examples2695370
Node: charset-compatibility2697669
Node: charset-connection2698006
Node: charset-applications2705850
Node: charset-errors2711721
Node: charset-collations2713291
Node: charset-collation-names2714122
Node: charset-collate2714611
Node: charset-collate-precedence2715951
Node: charset-collation-charset2716320
Node: charset-collation-expressions2716991
Node: charset-binary-collations2721084
Node: charset-binary-op2726872
Node: charset-collation-effect2729009
Node: charset-collation-information-schema2732299
Node: charset-repertoire2737327
Node: charset-operations2742285
Node: charset-result2742772
Node: charset-convert2745770
Node: charset-show2747253
Node: charset-unicode2752295
Node: charset-unicode-ucs22754609
Node: charset-unicode-utf82755364
Node: charset-metadata2757176
Node: charset-conversion2761353
Node: charset-charsets2765581
Node: charset-unicode-sets2769911
Node: charset-we-sets2775665
Node: charset-ce-sets2779413
Node: charset-se-me-sets2781004
Node: charset-baltic-sets2782606
Node: charset-cyrillic-sets2783432
Node: charset-asian-sets2784681
Node: charset-cp9322787118
Node: error-message-language2793916
Node: adding-character-set2795517
Node: character-arrays2802917
Node: string-collating2806088
Node: multibyte-characters2807131
Node: adding-collation2807999
Node: charset-collation-implementations2811066
Node: adding-collation-choosing-id2815151
Node: adding-collation-simple-8bit2817398
Node: adding-collation-unicode-uca2821214
Node: ldml-collation-example2822709
Node: ldml-rules2828626
Node: charset-configuration2831140
Node: time-zone-support2834440
Node: time-zone-upgrades2842052
Node: time-zone-leap-seconds2847581
Node: locale-support2851171
Node: data-types2858163
Node: data-type-overview2860109
Node: numeric-type-overview2860444
Node: date-and-time-type-overview2871384
Node: string-type-overview2876435
Node: numeric-types2888396
Node: integer-types2890725
Node: fixed-point-types2892122
Node: floating-point-types2894135
Node: bit-type2895901
Node: numeric-type-attributes2896663
Node: out-of-range-and-overflow2899925
Node: date-and-time-types2904343
Node: datetime2909896
Node: time2914778
Node: year2916990
Node: migrating-to-year42919077
Node: timestamp-initialization2924181
Node: fractional-seconds2934315
Node: date-and-time-type-conversion2935181
Node: two-digit-years2938565
Node: string-types2940077
Node: char2940883
Node: binary-varbinary2946937
Node: blob2951002
Node: enum2956540
Ref: enum-using2957580
Ref: enum-indexes2958462
Ref: enum-literals2960212
Ref: enum-nulls2962319
Ref: enum-sorting2963237
Ref: enum-limits2963905
Node: set2965209
Node: spatial-extensions2971317
Node: spatial-datatypes2976238
Node: opengis-geometry-model2977363
Node: gis-geometry-class-hierarchy2978606
Node: gis-class-geometry2981249
Node: gis-class-point2984875
Node: gis-class-curve2985502
Node: gis-class-linestring2986343
Node: gis-class-surface2987024
Node: gis-class-polygon2987741
Node: gis-class-geometrycollection2988961
Node: gis-class-multipoint2989788
Node: gis-class-multicurve2990557
Node: gis-class-multilinestring2991513
Node: gis-class-multisurface2991946
Node: gis-class-multipolygon2992522
Node: using-spatial-data2993991
Node: gis-data-formats2994697
Node: gis-wkt-format2995427
Node: gis-wkb-format2997805
Node: creating-spatial-columns2999553
Node: populating-spatial-columns3000562
Node: fetching-spatial-data3003459
Node: optimizing-spatial-analysis3004390
Node: creating-spatial-indexes3005693
Node: using-spatial-indexes3008184
Node: data-type-defaults3014616
Node: storage-requirements3018335
Ref: data-types-storage-reqs-date-time3024552
Node: choosing-types3031149
Node: other-vendor-data-types3032365
Node: functions3035088
Node: func-op-summary-ref3038444
Node: type-conversion3062395
Node: non-typed-operators3068695
Node: operator-precedence3071472
Node: comparison-operators3073274
Node: logical-operators3086591
Node: assignment-operators3089636
Node: control-flow-functions3093988
Node: string-functions3099106
Node: string-comparison-functions3130205
Node: regexp3139556
Node: numeric-functions3154527
Node: arithmetic-functions3157572
Node: mathematical-functions3161596
Node: date-and-time-functions3181330
Node: mysql-calendar3237721
Node: fulltext-search3239922
Ref: function_match3240558
Node: fulltext-natural-language3244137
Node: fulltext-boolean3255057
Node: fulltext-query-expansion3262182
Node: fulltext-stopwords3265330
Node: fulltext-restrictions3273810
Node: fulltext-fine-tuning3275696
Node: full-text-adding-collation3283447
Node: cast-functions3287815
Node: xml-functions3297360
Node: bit-functions3329800
Node: encryption-functions3332018
Node: information-functions3350310
Node: spatial-analysis-functions3378945
Node: spatial-function-reference3380402
Node: gis-wkt-functions3385421
Node: gis-wkb-functions3387315
Node: gis-mysql-specific-functions3389540
Node: gis-format-conversion-functions3391977
Node: gis-property-functions3393568
Node: gis-general-property-functions3394705
Node: gis-point-property-functions3398345
Node: gis-linestring-property-functions3399359
Node: gis-multilinestring-property-functions3403419
Node: gis-polygon-property-functions3404979
Node: gis-multipolygon-property-functions3407943
Node: gis-geometrycollection-property-functions3409366
Node: spatial-operator-functions3410713
Node: spatial-relation-functions3412249
Node: spatial-relation-functions-mbr3413485
Node: spatial-relation-functions-mysql-specific3415981
Node: miscellaneous-functions3419064
Node: group-by-functions-and-modifiers3433512
Node: group-by-functions3433954
Node: group-by-modifiers3446093
Node: group-by-extensions3455137
Node: precision-math3459294
Node: precision-math-numbers3461784
Node: precision-math-decimal-characteristics3463482
Node: precision-math-expressions3467467
Node: precision-math-rounding3472453
Node: precision-math-examples3474465
Node: sql-syntax3483262
Node: sql-syntax-data-definition3484080
Node: alter-database3486171
Node: alter-event3489681
Node: alter-logfile-group3494624
Node: alter-function3498688
Node: alter-procedure3499841
Node: alter-server3500965
Node: alter-table3501835
Node: alter-table-partition-operations3529752
Node: alter-table-online-operations3543038
Ref: alter-table-online-limitations3548827
Node: alter-table-examples3555155
Node: alter-tablespace3561622
Node: alter-view3565662
Node: create-database3566641
Node: create-event3568603
Node: create-function3584942
Node: create-index3585441
Node: create-logfile-group3596610
Node: create-procedure3602520
Node: create-server3620074
Node: create-table3623054
Ref: create-temporary-table3630126
Node: create-table-select3683429
Node: create-table-foreign-keys3693095
Node: silent-column-changes3708519
Node: create-tablespace3711598
Node: create-trigger3718225
Node: create-view3726047
Node: drop-database3741483
Node: drop-event3743825
Node: drop-function3744642
Node: drop-index3745121
Node: drop-logfile-group3747308
Node: drop-procedure3748327
Node: drop-server3749382
Node: drop-table3750212
Node: drop-tablespace3752125
Node: drop-trigger3753162
Node: drop-view3754376
Node: rename-database3755210
Node: rename-table3756077
Node: truncate-table3758444
Node: sql-syntax-data-manipulation3763680
Node: call3764379
Node: delete3769848
Node: do3781582
Node: handler3782757
Node: insert3787954
Node: insert-select3802704
Node: insert-delayed3806233
Node: insert-on-duplicate3814727
Node: load-data3818203
Node: replace3850123
Node: select3856737
Node: select-into3875717
Node: join3882492
Node: index-hints3903211
Node: union3909706
Node: subqueries3915535
Node: scalar-subqueries3919350
Node: comparisons-using-subqueries3921683
Node: any-in-some-subqueries3923233
Node: all-subqueries3925340
Node: row-subqueries3927045
Node: exists-and-not-exists-subqueries3929590
Node: correlated-subqueries3931664
Node: from-clause-subqueries3933805
Node: subquery-errors3940268
Node: optimizing-subqueries3943072
Node: rewriting-subqueries3947171
Node: update3948799
Node: sql-syntax-transactions3955612
Node: commit3956693
Node: cannot-roll-back3964632
Node: implicit-commit3965360
Node: savepoint3971013
Node: lock-tables3973347
Node: lock-tables-and-transactions3984321
Node: lock-tables-and-triggers3987524
Node: lock-tables-restrictions3989713
Node: set-transaction3993862
Ref: set-transaction-scope3994339
Ref: set-transaction-isolation-level3996410
Node: xa4000938
Node: xa-statements4006677
Node: xa-states4010939
Node: sql-syntax-replication4013919
Node: replication-master-sql4014471
Node: purge-binary-logs4015456
Node: reset-master4018666
Node: set-sql-log-bin4020756
Node: replication-slave-sql4021164
Node: change-master-to4022231
Node: load-data-from-master4034526
Node: load-table-from-master4037803
Node: master-pos-wait4039593
Node: reset-slave4040087
Node: set-global-sql-slave-skip-counter4041930
Node: start-slave4043374
Node: stop-slave4047488
Node: sql-syntax-prepared-statements4049345
Node: prepare4058412
Node: execute4060920
Node: deallocate-prepare4061875
Node: statement-repreparation4062449
Node: sql-syntax-compound-statements4064655
Node: begin-end4065832
Node: statement-labels4067631
Node: declare4069249
Node: stored-program-variables4070033
Node: declare-local-variable4071385
Node: local-variable-scope4072569
Node: flow-control-statements4075267
Node: case4076470
Node: if4078897
Node: iterate4081282
Node: leave4081668
Node: loop4082207
Node: repeat4083326
Node: return4084492
Node: while4085098
Node: cursors4085857
Node: close4087383
Node: declare-cursor4087817
Node: fetch4088923
Node: open4089764
Node: condition-handling4089996
Node: declare-condition4093908
Node: declare-handler4095874
Node: sql-syntax-server-administration4103017
Node: account-management-sql4103609
Node: create-user4104708
Node: drop-user4107548
Node: grant4109062
Ref: grant-privileges4112392
Ref: grant-global-privileges4118771
Ref: grant-database-privileges4119594
Ref: grant-table-privileges4120388
Ref: grant-column-privileges4121076
Ref: grant-routine-privileges4121563
Ref: grant-accounts-passwords4123733
Ref: grant-other-characteristics4128751
Ref: grant-mysql-vs-standard-sql4137327
Node: rename-user4139164
Node: revoke4140541
Node: set-password4142880
Node: table-maintenance-sql4147032
Node: analyze-table4147631
Node: backup-table4149749
Node: check-table4151320
Node: checksum-table4162239
Node: optimize-table4164051
Node: repair-table4170395
Node: restore-table4177580
Node: plugin-sql4179031
Node: create-function-udf4179524
Node: drop-function-udf4182647
Node: install-plugin4183623
Node: uninstall-plugin4188404
Node: set-statement4190170
Node: show4201150
Node: show-authors4206389
Node: show-binary-logs4206780
Node: show-binlog-events4207727
Node: show-character-set4208985
Node: show-collation4210419
Node: show-columns4213260
Node: show-contributors4218140
Node: show-create-database4218621
Node: show-create-event4219858
Node: show-create-function4221998
Node: show-create-procedure4222375
Node: show-create-table4224510
Node: show-create-trigger4225384
Node: show-create-view4227799
Node: show-databases4230531
Node: show-engine4231745
Ref: show-engine-ndb-status4236228
Node: show-engines4243312
Node: show-errors4247852
Node: show-events4249086
Node: show-function-code4254914
Node: show-function-status4255270
Node: show-grants4255667
Node: show-index4257739
Node: show-innodb-status4260098
Node: show-master-status4260497
Node: show-open-tables4261243
Node: show-plugins4262922
Node: show-privileges4265545
Node: show-procedure-code4266995
Node: show-procedure-status4269398
Node: show-processlist4271283
Node: show-profile4276558
Node: show-profiles4283286
Node: show-scheduler-status4283755
Node: show-slave-hosts4285674
Node: show-slave-status4287550
Node: show-status4302901
Node: show-table-status4306086
Node: show-tables4312145
Node: show-triggers4313285
Node: show-variables4316176
Node: show-warnings4321421
Node: other-administrative-sql4327704
Node: binlog4328197
Node: cache-index4328816
Node: flush4331248
Node: kill4339551
Node: load-index4342595
Node: reset4344668
Node: sql-syntax-utility4345687
Node: describe4346050
Node: explain4346442
Node: help4350914
Node: use4357210
Node: storage-engines4358138
Node: storage-engine-compare-transactions4372543
Node: storage-engines-other4374411
Node: storage-engine-setting4375214
Node: pluggable-storage-overview4378076
Node: pluggable-storage4380314
Node: pluggable-storage-common-layer4382098
Node: myisam-storage-engine4385441
Node: myisam-start4395936
Node: key-space4401316
Node: myisam-table-formats4402447
Node: static-format4403617
Node: dynamic-format4406022
Node: compressed-format4409239
Node: myisam-table-problems4411184
Node: corrupted-myisam-tables4411738
Node: myisam-table-close4413807
Node: innodb-storage-engine4416490
Node: innodb-introduction4417420
Node: innodb-configuration4428055
Node: replacing-builtin-innodb4441973
Node: innodb-concepts4447270
Node: innodb-transaction-model4448339
Node: innodb-lock-modes4452097
Node: innodb-consistent-read4458558
Node: innodb-locking-reads4464882
Node: innodb-record-level-locks4469672
Node: innodb-next-key-locking4475227
Node: innodb-locks-set4478527
Node: innodb-implicit-commit4488569
Node: innodb-deadlock-detection4489410
Node: innodb-deadlocks4491353
Node: innodb-multi-versioning4495916
Node: innodb-table-and-index4499544
Node: innodb-index-types4500580
Node: innodb-physical-structure4503081
Node: innodb-insert-buffering4504460
Node: innodb-adaptive-hash4506476
Node: innodb-physical-record4507609
Node: innodb-tablespace4513234
Node: innodb-init4513768
Node: innodb-multiple-tablespaces4517096
Node: innodb-data-log-reconfiguration4526643
Node: innodb-raw-devices4530831
Node: innodb-tables4534298
Node: using-innodb-tables4534988
Node: innodb-transactions-with-different-apis4536691
Node: innodb-migration4538894
Node: converting-tables-to-innodb4540985
Node: innodb-auto-increment-handling4544037
Node: innodb-auto-increment-traditional4545303
Node: innodb-auto-increment-configurable4549364
Node: innodb-foreign-key-constraints4566237
Node: innodb-restrictions4570512
Node: innodb-disk-management4582583
Node: innodb-disk-io4582979
Node: innodb-file-space4584461
Node: innodb-file-defragmenting4588051
Node: innodb-parameters4589740
Node: innodb-tuning4689360
Node: innodb-monitors4698341
Node: innodb-standard-monitor4704331
Node: innodb-tablespace-monitor4718192
Node: innodb-table-monitor4724009
Node: innodb-backup4733387
Node: innodb-recovery4739984
Node: innodb-checkpoints4741366
Node: innodb-and-mysql-replication4743146
Node: innodb-troubleshooting4748446
Node: error-creating-innodb4751014
Node: forcing-innodb-recovery4752592
Node: innodb-troubleshooting-datadict4758187
Node: innodb-error-handling4764023
Node: innodb-error-codes4766981
Node: operating-system-error-codes4770782
Node: se-db24776902
Node: se-db2-installation4778576
Node: se-db2-configuration4779582
Node: se-db2-creating-tables4798615
Node: se-db2-creating-tables-identifiers4799785
Node: se-db2-creating-tables-indexnames4802166
Node: se-db2-data-type-mapping4803387
Node: se-db2-metadata4804007
Node: se-db2-transactions4805631
Node: se-db2-terms4810444
Node: se-db2-notes4812871
Node: se-db2-collations4817567
Node: se-db2-errors4821924
Node: merge-storage-engine4833920
Node: merge-table-advantages4841416
Node: merge-table-problems4845192
Node: memory-storage-engine4854283
Ref: memory-compared-cluster4857014
Node: example-storage-engine4868662
Node: federated-storage-engine4870011
Node: federated-description4871253
Ref: figure-se-federated-structure4872917
Node: federated-create4874191
Node: federated-create-connection4876358
Node: federated-create-server4878960
Node: federated-usagenotes4882416
Node: federated-storage-engine-resources4887987
Node: archive-storage-engine4888403
Node: csv-storage-engine4896223
Node: se-csv-repair4898383
Node: se-csv-limitations4901414
Node: blackhole-storage-engine4902080
Node: ha-overview4908667
Ref: figure_ha-cost-vs-nines4912483
Ref: ha-availability-comparison4912651
Node: ha-ovm-template4916366
Node: ha-drbd4918858
Ref: ha-drbd-overview4920693
Node: ha-wfc4922758
Ref: ha-wfc-overview4923496
Node: ha-vm4925245
Node: ha-vm-aws-setup4928798
Node: ha-vm-aws-instance4932751
Node: ha-vm-aws-deploy4935060
Node: ha-zfs-replication4939236
Node: ha-zfs-config4943980
Node: ha-zfs-mysql4947328
Node: ha-zfs-mysql-recovery4948861
Node: ha-memcached4950667
Ref: ha-memcached-fig-overview4952659
Node: ha-memcached-install4954043
Node: ha-memcached-using4957194
Node: ha-memcached-using-deployment4967441
Node: ha-memcached-using-namespaces4969625
Node: ha-memcached-using-expiry4971059
Node: ha-memcached-using-hashtypes4973312
Ref: ha-memcached-using-hashtypes-fig-selection4975280
Ref: ha-memcached-using-hashtypes-fig-addselect4978464
Node: ha-memcached-using-dtrace4981698
Node: ha-memcached-using-memory4989956
Ref: ha-memcached-fig-slabs4992197
Node: ha-memcached-using-threads4994078
Node: ha-memcached-using-logs4995882
Node: ha-memcached-interfaces5005119
Node: ha-memcached-operations5006891
Node: ha-memcached-mysql-frontend5010198
Ref: ha-memcached-fig-basicflow5012528
Node: ha-memcached-interfaces-libmemcached5013714
Node: ha-memcached-interfaces-libmemcached-base5017773
Node: ha-memcached-interfaces-libmemcached-servers5018946
Node: ha-memcached-interfaces-libmemcached-set5022189
Node: ha-memcached-interfaces-libmemcached-get5027403
Node: ha-memcached-interfaces-libmemcached-behaviors5032026
Node: ha-memcached-interfaces-libmemcached-utilities5036200
Node: ha-memcached-interfaces-perl5038051
Node: ha-memcached-interfaces-python5044875
Node: ha-memcached-interfaces-php5051341
Node: ha-memcached-interfaces-ruby5059620
Node: ha-memcached-interfaces-java5062543
Node: ha-memcached-interfaces-protocol5066654
Ref: ha-memcached-interfaces-protocol-responses5076171
Node: ha-memcached-stats5077673
Node: ha-memcached-stats-general5083524
Node: ha-memcached-stats-slabs5089693
Node: ha-memcached-stats-items5094337
Node: ha-memcached-stats-sizes5096943
Node: ha-memcached-stats-detail5098269
Node: ha-memcached-stats-memcached-tool5100475
Node: ha-memcached-faq5106317
Ref: qandaitem-16-6-5-1-15108171
Ref: qandaitem-16-6-5-1-25108398
Ref: qandaitem-16-6-5-1-35109317
Ref: qandaitem-16-6-5-1-45109587
Ref: qandaitem-16-6-5-1-55110269
Ref: qandaitem-16-6-5-1-65111071
Ref: qandaitem-16-6-5-1-75111575
Ref: qandaitem-16-6-5-1-85112317
Ref: qandaitem-16-6-5-1-95112649
Ref: qandaitem-16-6-5-1-105113216
Ref: qandaitem-16-6-5-1-115113749
Ref: qandaitem-16-6-5-1-125114439
Ref: qandaitem-16-6-5-1-135114668
Ref: qandaitem-16-6-5-1-145114999
Node: mysql-proxy5116552
Node: mysql-proxy-platforms5119379
Node: mysql-proxy-install5120332
Node: mysql-proxy-install-binary5121436
Node: mysql-proxy-install-source5123410
Node: mysql-proxy-install-cvs5124978
Node: mysql-proxy-configuration-windows5126957
Node: mysql-proxy-configuration5129035
Node: mysql-proxy-scripting5151017
Node: mysql-proxy-scripting-injection5156079
Node: mysql-proxy-scripting-structures5158927
Ref: mysql-proxy-scripting-structures-proxy5159669
Ref: mysql-proxy-scripting-structures-connection5160806
Ref: mysql-proxy-scripting-structures-backends5163270
Ref: mysql-proxy-scripting-structures-queries5164671
Ref: mysql-proxy-scripting-structures-response5167371
Ref: mysql-proxy-scripting-structures-resultset5170447
Ref: mysql-proxy-scripting-structures-return-states5172555
Ref: mysql-proxy-scripting-structures-packet-states5173527
Ref: mysql-proxy-scripting-structures-backend-states5173952
Ref: mysql-proxy-scripting-structures-command-constants5174723
Ref: mysql-proxy-scripting-structures-type-constants5176520
Node: mysql-proxy-scripting-connect-server5177949
Node: mysql-proxy-scripting-read-handshake5179452
Node: mysql-proxy-scripting-read-auth5181597
Node: mysql-proxy-scripting-read-auth-result5183041
Node: mysql-proxy-scripting-read-query5184673
Node: mysql-proxy-scripting-read-query-result5188088
Node: mysql-proxy-using5192781
Node: mysql-proxy-using-admin5195244
Node: mysql-proxy-faq5207739
Ref: qandaitem-16-7-6-1-15211763
Ref: qandaitem-16-7-6-1-25212203
Ref: qandaitem-16-7-6-1-35212415
Ref: qandaitem-16-7-6-1-45212602
Ref: qandaitem-16-7-6-1-55212882
Ref: qandaitem-16-7-6-1-65213131
Ref: qandaitem-16-7-6-1-75213371
Ref: qandaitem-16-7-6-1-85213545
Ref: qandaitem-16-7-6-1-95213774
Ref: qandaitem-16-7-6-1-105213890
Ref: qandaitem-16-7-6-1-115214140
Ref: qandaitem-16-7-6-1-125214458
Ref: qandaitem-16-7-6-1-135214733
Ref: qandaitem-16-7-6-1-145214957
Ref: qandaitem-16-7-6-1-155215204
Ref: qandaitem-16-7-6-1-165215424
Ref: qandaitem-16-7-6-1-175215655
Ref: qandaitem-16-7-6-1-185215860
Ref: qandaitem-16-7-6-1-195216037
Ref: qandaitem-16-7-6-1-205216230
Ref: qandaitem-16-7-6-1-215216575
Ref: qandaitem-16-7-6-1-225216942
Ref: qandaitem-16-7-6-1-235217276
Ref: qandaitem-16-7-6-1-245217521
Ref: qandaitem-16-7-6-1-255217826
Ref: qandaitem-16-7-6-1-265218088
Ref: qandaitem-16-7-6-1-275218270
Ref: qandaitem-16-7-6-1-285218553
Ref: qandaitem-16-7-6-1-295218678
Ref: qandaitem-16-7-6-1-305218988
Ref: qandaitem-16-7-6-1-315219213
Node: replication5219504
Node: replication-configuration5223800
Node: replication-howto5227599
Node: replication-howto-masterbaseconfig5231948
Node: replication-howto-slavebaseconfig5233998
Node: replication-howto-repuser5235534
Node: replication-howto-masterstatus5237261
Node: replication-howto-mysqldump5241069
Node: replication-howto-rawdata5242791
Node: replication-howto-newservers5246914
Node: replication-howto-existingdata5248826
Node: replication-howto-additionalslaves5253442
Node: replication-howto-slaveinit5257402
Node: replication-formats5258621
Node: replication-sbr-rbr5262998
Ref: replication-sbr-rbr-sbr-advantages5263974
Ref: replication-sbr-rbr-sbr-disadvantages5264441
Ref: replication-sbr-rbr-rbr-advantages5268268
Ref: replication-sbr-rbr-rbr-disadvantages5270226
Node: replication-rbr-usage5273236
Node: replication-rbr-safe-unsafe5280301
Ref: replication-rbr-safe-unsafe-not5282605
Node: replication-options5285728
Ref: option_mysqld_server-id5286790
Node: replication-options-table5288264
Ref: replication-optvar-summary-table5288698
Ref: binlog-optvar-summary-table5297937
Node: replication-options-master5300600
Ref: replication-sysvars-masters5301590
Node: replication-options-slave5310873
Ref: replication-optvars-slaves5315844
Ref: replication-sysvars-slaves5367506
Node: replication-options-binary-log5380923
Ref: replication-optvars-binlog5381637
Ref: replication-sysvars-binlog5398566
Node: replication-administration5416100
Node: replication-administration-status5416710
Node: replication-administration-pausing5423281
Node: replication-implementation5425375
Node: replication-implementation-details5428032
Node: slave-logs5433701
Node: slave-logs-relaylog5434941
Node: slave-logs-status5438341
Node: replication-rules5444440
Node: replication-rules-db-options5447690
Node: replication-rules-table-options5451387
Node: replication-rules-examples5454907
Node: replication-solutions5458198
Node: replication-solutions-backups5460431
Node: replication-solutions-backups-mysqldump5462463
Node: replication-solutions-backups-rawdata5465166
Node: replication-solutions-backups-read-only5468021
Node: replication-solutions-diffengines5472427
Node: replication-solutions-scaleout5476547
Ref: figure_replication-scaleout5477740
Node: replication-solutions-partitioning5479725
Ref: figure_replication-multi-db5480341
Node: replication-solutions-performance5482570
Ref: figure_replication-performance5483715
Node: replication-solutions-switch5485971
Ref: figure_replication-redundancy-before5487990
Ref: figure_replication-redundancy-after5491081
Node: replication-solutions-ssl5492551
Node: replication-notes5496682
Node: replication-features5497199
Node: replication-features-auto-increment5502150
Node: replication-features-blackhole5506413
Node: replication-features-charset5507499
Node: replication-features-create-if-not-exists5509746
Node: replication-features-create-select5511369
Node: replication-features-current-user5513724
Node: replication-features-create-alter-drop-server5515562
Node: replication-features-drop-if-exists5516201
Node: replication-features-differing-tables5517145
Node: replication-features-more-columns5518232
Node: replication-features-different-data-types5523096
Ref: replication-features-attribute-promotion5530120
Node: replication-features-directory5537377
Node: replication-features-invoked5538361
Node: replication-features-floatvalues5543682
Node: replication-features-flush5544558
Node: replication-features-functions5545996
Node: replication-features-limit5553934
Node: replication-features-load-data5555039
Node: replication-features-logging5556028
Node: replication-features-repair-table5556472
Node: replication-features-shutdowns5557431
Node: replication-features-max-allowed-packet5559918
Node: replication-features-memory5561396
Node: replication-features-temptables5564955
Node: replication-features-mysqldb5567647
Node: replication-features-optimizer5568765
Node: replication-features-reserved-words5569527
Node: replication-features-set-password5571634
Node: replication-features-slaveerrors5572144
Node: replication-features-server-side-help5574499
Node: replication-features-sql-mode5580631
Node: replication-features-timeout5581705
Node: replication-features-timestamp5582580
Node: replication-features-timezone5583504
Node: replication-features-transactions5584547
Node: replication-features-triggers5590472
Node: replication-features-truncate5592332
Node: replication-features-variables5593532
Node: replication-features-views5597777
Node: replication-compatibility5598624
Node: replication-upgrade5602690
Node: replication-problems5606663
Node: replication-bugs5611834
Node: mysql-cluster5614510
Node: mysql-cluster-overview5625097
Node: mysql-cluster-basics5630103
Node: mysql-cluster-nodes-groups5641142
Ref: mysql-cluster-nodes-groups-nodegroup5642395
Ref: mysql-cluster-nodes-groups-partition5643634
Ref: mysql-cluster-nodes-groups-user-partitioning5644021
Ref: mysql-cluster-nodes-groups-replica5645478
Node: mysql-cluster-overview-requirements5648122
Ref: mysql-cluster-network-latency-issues5651243
Node: mysql-cluster-development5654620
Node: mysql-cluster-development-5-1-ndb-7-25659757
Node: mysql-cluster-development-5-1-ndb-7-15664491
Node: mysql-cluster-development-5-1-ndb-7-05690898
Node: mysql-cluster-development-5-1-ndb-6-35722775
Node: mysql-cluster-development-5-1-ndb-6-25745109
Node: mysql-cluster-development-5-1-ndb-6-15754616
Node: mysql-cluster-development-5-15756570
Ref: mysql-cluster-development-5-1-distribution-awareness5760708
Node: mysql-cluster-compared5763117
Node: mysql-cluster-ndb-innodb-engines5766686
Node: mysql-cluster-ndb-innodb-workloads5775042
Node: mysql-cluster-ndb-innodb-usage5777681
Node: mysql-cluster-limitations5779519
Node: mysql-cluster-limitations-syntax5782005
Node: mysql-cluster-limitations-limits5789152
Node: mysql-cluster-limitations-transactions5793591
Node: mysql-cluster-limitations-error-handling5801253
Node: mysql-cluster-limitations-database-objects5802310
Node: mysql-cluster-limitations-unsupported5804085
Node: mysql-cluster-limitations-performance5806256
Node: mysql-cluster-limitations-exclusive-to-cluster5807461
Node: mysql-cluster-limitations-disk-data5809724
Node: mysql-cluster-limitations-multiple-nodes5811380
Node: mysql-cluster-limitations-resolved5814342
Node: mysql-cluster-installation5831359
Node: mysql-cluster-install-linux5838254
Node: mysql-cluster-install-linux-binary5840507
Node: mysql-cluster-install-linux-rpm5848482
Node: mysql-cluster-install-linux-source5855228
Node: mysql-cluster-install-windows5860652
Node: mysql-cluster-install-windows-binary5861975
Node: mysql-cluster-install-windows-source5875429
Node: mysql-cluster-install-windows-initial-start5878322
Node: mysql-cluster-install-windows-service5887252
Node: mysql-cluster-install-configuration5894727
Node: mysql-cluster-install-first-start5900430
Node: mysql-cluster-install-example-data5903358
Node: mysql-cluster-install-shutdown-restart5913084
Node: mysql-cluster-upgrade-downgrade5916057
Node: mysql-cluster-upgrade-downgrade-compatibility-7.x5919123
Node: mysql-cluster-upgrade-downgrade-compatibility-6.x5929124
Ref: mysql-cluster-upgrade-downgrade-compatibility-online-add-drop-column-6-x5931423
Node: mysql-cluster-upgrade-downgrade-compatibility-5.15933866
Ref: mysql-cluster-upgrade-downgrade-compatibility-online-add-drop-column5938429
Node: mysql-cluster-configuration5940506
Node: mysql-cluster-quick5942495
Node: mysql-cluster-config-file5948085
Node: mysql-cluster-config-example5953879
Ref: mysql-cluster-config-ini-sections5960131
Node: mysql-cluster-config-starting5962481
Node: mysql-cluster-connection-strings5976513
Node: mysql-cluster-computer-definition5981564
Ref: id-computer-table5982036
Ref: hostname-computer-table5982882
Node: mysql-cluster-mgm-definition5983461
Ref: id-mgmd-table5984296
Ref: nodeid-mgmd-table5985902
Ref: executeoncomputer-mgmd-table5987539
Ref: portnumber-mgmd-table5988161
Ref: hostname-mgmd-table5988776
Ref: logdestination-mgmd-table5989562
Ref: arbitrationrank-mgmd-table5992197
Ref: arbitrationdelay-mgmd-table5993927
Ref: datadir-mgmd-table5994772
Ref: portnumberstats-mgmd-table5995768
Ref: wan-mgmd-table5996418
Ref: extrasendbuffermemory-mgmd-table5997642
Ref: totalsendbuffermemory-mgmd-table5998460
Ref: heartbeatintervalmgmdmgmd-mgmd-table5999664
Node: mysql-cluster-ndbd-definition6001426
Ref: mysql-cluster-identifying-data-nodes6004135
Ref: id-ndbd-table6004302
Ref: nodeid-ndbd-table6005355
Ref: executeoncomputer-ndbd-table6006423
Ref: hostname-ndbd-table6007012
Ref: serverport-ndbd-table6007782
Ref: nodegroup-ndbd-table6009671
Ref: noofreplicas-ndbd-table6011238
Ref: datadir-ndbd-table6014062
Ref: filesystempath-ndbd-table6014728
Ref: backupdatadir-ndbd-table6015874
Ref: mysql-cluster-data-memory-index-memory-string-memory6016834
Ref: datamemory-ndbd-table6017227
Ref: indexmemory-ndbd-table6023995
Ref: stringmemory-ndbd-table6025576
Ref: ndbparam-ndbd-minfreepct6030708
Ref: minfreepct-ndbd-table6031115
Ref: mysql-cluster-transaction-parameters6031820
Ref: maxnoofconcurrenttransactions-ndbd-table6032703
Ref: maxnoofconcurrentoperations-ndbd-table6036045
Ref: maxnooflocaloperations-ndbd-table6039954
Ref: maxdmloperationspertransaction-ndbd-table6040975
Ref: mysql-cluster-transaction-temporary-storage6042137
Ref: maxnoofconcurrentindexoperations-ndbd-table6042793
Ref: maxnooffiredtriggers-ndbd-table6044290
Ref: transactionbuffermemory-ndbd-table6045797
Ref: mysql-cluster-scans-and-buffering6047259
Ref: maxnoofconcurrentscans-ndbd-table6047778
Ref: maxnooflocalscans-ndbd-table6049496
Ref: batchsizeperlocalscan-ndbd-table6050789
Ref: longmessagebuffer-ndbd-table6051576
Ref: maxparallelscansperfragment-ndbd-table6053750
Ref: mysql-cluster-memory-allocation6055324
Ref: ndbparam-ndbd-maxallocate6055345
Ref: maxallocate-ndbd-table6055360
Ref: mysql-cluster-hash-map-size6056505
Ref: ndbparam-ndbd-defaulthashmapsize6056522
Ref: defaulthashmapsize-ndbd-table6056544
Ref: mysql-cluster-defaulthashmapsize-table6057364
Ref: mysql-cluster-logging-and-checkpointing6059334
Ref: nooffragmentlogfiles-ndbd-table6059462
Ref: fragmentlogfilesize-ndbd-table6062518
Ref: initfragmentlogfiles-ndbd-table6063720
Ref: maxnoofopenfiles-ndbd-table6065082
Ref: initialnoofopenfiles-ndbd-table6066233
Ref: maxnoofsavedmessages-ndbd-table6066991
Ref: maxlcpstartdelay-ndbd-table6067837
Ref: lcpscanprogresstimeout-ndbd-table6069837
Ref: mysql-cluster-metadata-objects6071513
Ref: maxnoofattributes-ndbd-table6071890
Ref: maxnooftables-ndbd-table6074738
Ref: maxnooforderedindexes-ndbd-table6076544
Ref: maxnoofuniquehashindexes-ndbd-table6077858
Ref: maxnooftriggers-ndbd-table6079049
Ref: maxnoofsubscriptions-ndbd-table6080546
Ref: maxnoofsubscribers-ndbd-table6081911
Ref: maxnoofconcurrentsuboperations-ndbd-table6083898
Ref: mysql-cluster-boolean-parameters6085165
Ref: latealloc-ndbd-table6085425
Ref: lockpagesinmainmemory-ndbd-table6086092
Ref: stoponerror-ndbd-table6089638
Ref: crashoncorruptedtuple-ndbd-table6090414
Ref: diskless-ndbd-table6091265
Ref: odirect-ndbd-table6092546
Ref: restartonerrorinsert-ndbd-table6093616
Ref: compressedbackup-ndbd-table6094344
Ref: compressedlcp-ndbd-table6095513
Ref: mysql-cluster-timeouts-intervals-disk-paging6096678
Ref: timebetweenwatchdogcheck-ndbd-table6097000
Ref: timebetweenwatchdogcheckinitial-ndbd-table6098236
Ref: startpartialtimeout-ndbd-table6099259
Ref: startpartitionedtimeout-ndbd-table6100393
Ref: startfailuretimeout-ndbd-table6101480
Ref: startnonodegrouptimeout-ndbd-table6102736
Ref: heartbeatintervaldbdb-ndbd-table6104274
Ref: heartbeatintervaldbapi-ndbd-table6106093
Ref: heartbeatorder-ndbd-table6107564
Ref: connectcheckintervaldelay-ndbd-table6112985
Ref: timebetweenlocalcheckpoints-ndbd-table6114046
Ref: timebetweenglobalcheckpoints-ndbd-table6115900
Ref: timebetweenepochs-ndbd-table6117607
Ref: timebetweenepochstimeout-ndbd-table6118515
Ref: maxbufferedepochs-ndbd-table6120438
Ref: maxbufferedepochbytes-ndbd-table6121881
Ref: timebetweeninactivetransactionabortcheck-ndbd-table6123315
Ref: transactioninactivetimeout-ndbd-table6124295
Ref: transactiondeadlockdetectiontimeout-ndbd-table6125361
Ref: disksyncsize-ndbd-table6127306
Ref: diskcheckpointspeed-ndbd-table6128457
Ref: diskcheckpointspeedinrestart-ndbd-table6129580
Ref: noofdiskpagestodiskafterrestarttup-ndbd-table6130469
Ref: noofdiskpagestodiskafterrestartacc-ndbd-table6132595
Ref: noofdiskpagestodiskduringrestarttup-ndbd-table6133712
Ref: noofdiskpagestodiskduringrestartacc-ndbd-table6135153
Ref: arbitrationtimeout-ndbd-table6136368
Ref: arbitration-ndbd-table6137520
Ref: mysql-cluster-buffering-and-logging6139904
Ref: undoindexbuffer-ndbd-table6140431
Ref: undodatabuffer-ndbd-table6142766
Ref: redobuffer-ndbd-table6144639
Ref: eventlogbuffersize-ndbd-table6146693
Ref: mysql-cluster-controlling-log-messages6147328
Ref: loglevelstartup-ndbd-table6148132
Ref: loglevelshutdown-ndbd-table6148741
Ref: loglevelstatistic-ndbd-table6149361
Ref: loglevelcheckpoint-ndbd-table6150074
Ref: loglevelnoderestart-ndbd-table6150691
Ref: loglevelconnection-ndbd-table6151291
Ref: loglevelerror-ndbd-table6151907
Ref: loglevelcongestion-ndbd-table6152625
Ref: loglevelinfo-ndbd-table6153304
Ref: memreportfrequency-ndbd-table6153937
Ref: startupstatusreportfrequency-ndbd-table6156124
Ref: ndbparam-ndbd-dicttrace6158241
Ref: mysql-cluster-backup-parameters6158662
Ref: backupdatabuffersize-ndbd-table6158826
Ref: backuplogbuffersize-ndbd-table6160531
Ref: backupmemory-ndbd-table6162833
Ref: backupreportfrequency-ndbd-table6164096
Ref: backupwritesize-ndbd-table6165220
Ref: backupmaxwritesize-ndbd-table6166305
Ref: mysql-cluster-realtime-performance-parameters6167851
Ref: lockexecutethreadtocpu-ndbd-table6168222
Ref: lockmaintthreadstocpu-ndbd-table6170274
Ref: realtimescheduler-ndbd-table6171275
Ref: schedulerexecutiontimer-ndbd-table6172121
Ref: schedulerspintimer-ndbd-table6173118
Ref: buildindexthreads-ndbd-table6173770
Ref: twopassinitialnoderestartcopy-ndbd-table6175501
Ref: numa-ndbd-table6176336
Ref: mysql-cluster-ndbd-definition-ndbmtd-parameters6177504
Ref: maxnoofexecutionthreads-ndbmtd-table6178280
Ref: threadconfig-ndbmtd-table6181478
Ref: mysql-cluster-ndbd-definition-disk-data-parameters6186510
Ref: diskpagebuffermemory-ndbd-table6186653
Ref: sharedglobalmemory-ndbd-table6187965
Ref: diskiothreadpool-ndbd-table6189504
Ref: mysql-cluster-ndbd-disk-data-filesystem-parameters6192255
Ref: filesystempathdd-ndbd-table6192561
Ref: filesystempathdatafiles-ndbd-table6194478
Ref: filesystempathundofiles-ndbd-table6196133
Ref: mysql-cluster-ndbd-disk-data-object-creation-parameters6197852
Ref: initiallogfilegroup-ndbd-table6198128
Ref: initialtablespace-ndbd-table6201374
Ref: mysql-cluster-ndbd-definition-gcp-stop-errors6204224
Ref: mysql-cluster-redo-over-commit-handling6209731
Ref: redoovercommitcounter-ndbd-table6210555
Ref: redoovercommitlimit-ndbd-table6211777
Ref: startfailretrydelay-ndbd-table6213877
Ref: maxstartfailretries-ndbd-table6215444
Node: mysql-cluster-api-definition6216973
Ref: id-api-table6218206
Ref: connectionmap-api-table6219778
Ref: nodeid-api-table6220349
Ref: executeoncomputer-api-table6221933
Ref: hostname-api-table6222554
Ref: arbitrationrank-api-table6223755
Ref: arbitrationdelay-api-table6225216
Ref: batchbytesize-api-table6226083
Ref: batchsize-api-table6227194
Ref: extrasendbuffermemory-api-table6227863
Ref: maxscanbatchsize-api-table6229423
Ref: totalsendbuffermemory-api-table6230292
Ref: autoreconnect-api-table6231476
Ref: defaultoperationredoproblemaction-api-table6232932
Ref: defaulthashmapsize-api-table6234432
Ref: wan-api-table6237527
Node: mysql-cluster-tcp-definition6239365
Ref: nodeid1-tcp-table6240913
Ref: ndbparam-tcp-nodeid26241371
Ref: nodeid2-tcp-table6241387
Ref: hostname1-tcp-table6242154
Ref: ndbparam-tcp-hostname26242676
Ref: hostname2-tcp-table6242694
Ref: overloadlimit-tcp-table6243481
Ref: sendbuffermemory-tcp-table6244669
Ref: sendsignalid-tcp-table6246754
Ref: checksum-tcp-table6247527
Ref: receivebuffermemory-tcp-table6248681
Ref: tcp_rcv_buf_size-tcp-table6249816
Ref: tcp_snd_buf_size-tcp-table6250528
Ref: tcp_maxseg_size-tcp-table6251236
Node: mysql-cluster-tcp-definition-direct6252184
Node: mysql-cluster-shm-definition6254076
Ref: nodeid1-shm-table6255233
Ref: ndbparam-shm-nodeid26255701
Ref: nodeid2-shm-table6255717
Ref: hostname1-shm-table6256352
Ref: ndbparam-shm-hostname26256884
Ref: hostname2-shm-table6256902
Ref: overloadlimit-shm-table6257699
Ref: shmkey-shm-table6258881
Ref: shmsize-shm-table6259692
Ref: sendsignalid-shm-table6260528
Ref: checksum-shm-table6261346
Ref: signum-shm-table6262201
Node: mysql-cluster-sci-definition6263450
Ref: nodeid1-sci-table6264860
Ref: ndbparam-sci-nodeid26265318
Ref: nodeid2-sci-table6265334
Ref: host1sciid0-sci-table6265961
Ref: host1sciid1-sci-table6266663
Ref: host2sciid0-sci-table6267508
Ref: host2sciid1-sci-table6268211
Ref: hostname1-sci-table6268949
Ref: ndbparam-sci-hostname26269471
Ref: hostname2-sci-table6269489
Ref: sharedbuffersize-sci-table6270279
Ref: sendlimit-sci-table6271332
Ref: sendsignalid-sci-table6272142
Ref: checksum-sci-table6272896
Ref: overloadlimit-sci-table6273743
Node: mysql-cluster-config-lcp-params6274519
Node: mysql-cluster-config-send-buffers6281143
Node: mysql-cluster-params-overview6285051
Node: mysql-cluster-params-ndbd6288474
Ref: ndbparam-summary-table-ndbd6289994
Ref: ndbparam-summary-table-ndbmtd6323011
Node: mysql-cluster-params-mgmd6324554
Ref: ndbparam-summary-table-mgmd6325817
Node: mysql-cluster-params-api6331106
Ref: ndbparam-summary-table-api6332631
Node: mysql-cluster-params-other6338131
Ref: ndbparam-summary-table-computer6339454
Ref: ndbparam-summary-table-tcp6340561
Ref: ndbparam-summary-table-shm6344853
Ref: ndbparam-summary-table-sci6348455
Node: mysql-cluster-options-variables6352889
Node: mysql-cluster-option-tables6353904
Ref: mysql-cluster-mysqld-optvars-table6354537
Node: mysql-cluster-program-options-mysqld6377065
Ref: ndb-batch-size-detailtable6378275
Ref: ndb-cluster-connection-pool-detailtable6378759
Ref: ndb-blob-read-batch-bytes-detailtable6381359
Ref: ndb-blob-write-batch-bytes-detailtable6382871
Ref: ndb-connectstring-detailtable6384401
Ref: ndb-deferred-constraints-detailtable6385050
Ref: ndb-distribution-detailtable6386009
Ref: ndb-mgmd-host-detailtable6386671
Ref: ndbcluster-detailtable6387366
Ref: ndb-log-apply-status-detailtable6388157
Ref: ndb-log-orig-detailtable6389900
Ref: ndb-log-transaction-id-detailtable6390601
Ref: ndb-nodeid-detailtable6391757
Ref: ndb-log-empty-epochs-detailtable6393830
Ref: server-id-bits-detailtable6395408
Ref: skip-ndbcluster-detailtable6397419
Ref: ndb-transid-mysql-connection-map-detailtable6398155
Ref: ndb-wait-connected-detailtable6399433
Ref: ndb-wait-setup-detailtable6400585
Ref: ndb_optimization_delay-detailtable6401558
Node: mysql-cluster-system-variables6402179
Ref: have_ndbcluster-detailtable6402809
Ref: ndb_autoincrement_prefetch_sz-detailtable6403471
Ref: ndb_cache_check_time-detailtable6405480
Ref: ndb_deferred_constraints-detailtable6406497
Ref: ndb_distribution-detailtable6407357
Ref: ndb_eventbuffer_max_alloc-detailtable6408017
Ref: ndb_extra_logging-detailtable6408712
Ref: ndb_force_send-detailtable6410076
Ref: ndb_index_stat_cache_entries-detailtable6410627
Ref: ndb_index_stat_enable-detailtable6411581
Ref: ndb_index_stat_option-detailtable6412159
Ref: ndb_index_stat_update_freq-detailtable6416908
Ref: ndb_join_pushdown-detailtable6417800
Ref: ndb_log_apply_status-detailtable6424016
Ref: ndb_log_bin-detailtable6424731
Ref: ndb_log_binlog_index-detailtable6425522
Ref: ndb_log_orig-detailtable6426504
Ref: ndb_optimized_node_selection-detailtable6427215
Ref: ndb_report_thresh_binlog_epoch_slip-detailtable6430724
Ref: ndb_report_thresh_binlog_mem_usage-detailtable6431574
Ref: slave_allow_batching-detailtable6432373
Ref: ndb_table_no_logging-detailtable6433158
Ref: ndb_table_temporary-detailtable6435407
Ref: ndb_use_copying_alter_table-detailtable6436214
Ref: ndb_version-detailtable6436809
Ref: ndb_version_string-detailtable6437280
Ref: ndb_use_exact_count-detailtable6437793
Ref: ndb_use_transactions-detailtable6438578
Ref: transaction_allow_batching-detailtable6439332
Ref: ndbinfo_database-detailtable6440872
Ref: ndbinfo_max_bytes-detailtable6441641
Ref: ndbinfo_max_rows-detailtable6442036
Ref: ndbinfo_offline-detailtable6442429
Ref: ndbinfo_show_hidden-detailtable6443168
Ref: ndbinfo_table_prefix-detailtable6443760
Ref: ndbinfo_version-detailtable6444604
Ref: ndb_log_transaction_id-detailtable6445074
Ref: ndb_log_empty_epochs-detailtable6446050
Ref: server_id_bits-detailtable6446779
Node: mysql-cluster-status-variables6447731
Node: mysql-cluster-interconnects6492523
Node: mysql-cluster-sci-sockets6495149
Node: mysql-cluster-interconnects-performance6497192
Node: mysql-cluster-programs6501423
Node: mysql-cluster-programs-ndbd6505381
Ref: mysql-cluster-ndbd-options-table6506576
Node: mysql-cluster-programs-ndbinfo-select-all6527828
Ref: mysql-cluster-ndbinfo_select_all-options-table6531094
Node: mysql-cluster-programs-ndbmtd6532727
Node: mysql-cluster-programs-ndb-mgmd6538727
Ref: mysql-cluster-ndb_mgmd-options-table6539676
Node: mysql-cluster-programs-ndb-mgm6566410
Ref: mysql-cluster-ndb_mgm-options-table6567873
Node: mysql-cluster-programs-ndb-blob-tool6570001
Ref: mysql-cluster-ndb_blob_tool-options-table6572240
Node: mysql-cluster-programs-ndb-config6577097
Ref: mysql-cluster-ndb_config-options-table6578949
Ref: option_ndb_config_nodeid6586444
Ref: option_ndb_config_xml6592528
Node: mysql-cluster-programs-ndb-cpcd6600134
Node: mysql-cluster-programs-ndb-delete-all6601067
Ref: mysql-cluster-ndb_delete_all-options-table6602182
Node: mysql-cluster-programs-ndb-desc6602924
Ref: mysql-cluster-ndb_desc-options-table6611349
Node: mysql-cluster-programs-ndb-drop-index6613848
Ref: mysql-cluster-ndb_drop_index-options-table6614932
Node: mysql-cluster-programs-ndb-drop-table6616727
Ref: mysql-cluster-ndb_drop_table-options-table6617898
Node: mysql-cluster-programs-ndb-error-reporter6618119
Ref: mysql-cluster-ndb_error_reporter-options-table6619479
Node: mysql-cluster-programs-ndb-index-stat6622999
Ref: mysql-cluster-ndb_index_stat-options-table6626679
Ref: ndb-index-stat-options-statistics6628408
Ref: ndb-index-stat-options-system6631073
Node: mysql-cluster-programs-ndb-print-backup-file6635823
Node: mysql-cluster-programs-ndb-print-file6637433
Node: mysql-cluster-programs-ndb-print-schema-file6639112
Node: mysql-cluster-programs-ndb-print-sys-file6640503
Node: mysql-cluster-programs-ndbd-redo-log-reader6642185
Ref: mysql-cluster-ndbd_redo_log_reader-options-table6643682
Ref: option_ndbd_redo_log_reader_noprint6644952
Ref: option_ndbd_redo_log_reader_nocheck6645303
Ref: option_ndbd_redo_log_reader_help6645521
Node: mysql-cluster-programs-ndb-restore6646357
Ref: mysql-cluster-ndb_restore-options-table6647969
Ref: option_ndb_restore_connect6654086
Ref: option_ndb_restore_nodeid6655233
Ref: option_ndb_restore_skip-table-check6655929
Ref: option_ndb_restore_promote-attributes6657819
Ref: option_ndb_restore_lossy-conversions6660851
Ref: option_ndb_restore_preserve-trailing-spaces6661880
Ref: option_ndb_restore_backupid6662680
Ref: option_ndb_restore_restore_epoch6663215
Ref: option_ndb_restore_restore_data6663640
Ref: option_ndb_restore_restore_meta6663794
Ref: option_ndb_restore_restore-privilege-tables6664098
Ref: option_ndb_restore_backup_path6664584
Ref: option_ndb_restore_no-upgrade6667563
Ref: option_ndb_restore_print_data6668146
Ref: option_ndb_restore_print_meta6672270
Ref: option_ndb_restore_print_log6672398
Ref: option_ndb_restore_print6672534
Ref: option_ndb_restore_dont_ignore_systab_06673073
Ref: option_ndb_restore_ndb-nodegroup-map6673489
Ref: option_ndb_restore_no-binlog6673691
Ref: option_ndb_restore_no-restore-disk-objects6673942
Ref: option_ndb_restore_parallelism6674239
Ref: option_ndb_restore_progress-frequency6674464
Ref: option_ndb_restore_verbose6674639
Ref: option_ndb_restore_include-databases6675168
Ref: option_ndb_restore_include-tables6675518
Ref: option_ndb_restore_exclude-databases6678819
Ref: option_ndb_restore_exclude-tables6679169
Ref: option_ndb_restore_exclude-missing-columns6684360
Ref: option_ndb_restore_exclude-missing-tables6685229
Ref: option_ndb_restore_disable-indexes6685672
Ref: option_ndb_restore_rebuild-indexes6686306
Ref: option_ndb_restore_skip-broken-objects6688081
Ref: option_ndb_restore_skip-unknown-objects6688690
Ref: option_ndb_restore_rewrite-database6689283
Ref: option_ndb_restore_exclude-intermediate-sql-tables6691522
Node: mysql-cluster-programs-ndb-select-all6693227
Ref: mysql-cluster-ndb_select_all-options-table6694139
Node: mysql-cluster-programs-ndb-select-count6700083
Ref: mysql-cluster-ndb_select_count-options-table6701161
Node: mysql-cluster-programs-ndb-show-tables6701871
Ref: mysql-cluster-ndb_show_tables-options-table6702939
Node: mysql-cluster-programs-ndb-size-pl6705060
Ref: mysql-cluster-ndb_size_pl-options-table6707181
Ref: option_ndb_size_pl_options6708732
Ref: option_ndb_size_pl_debugging6713229
Ref: option_ndb_size_pl_format6713554
Node: mysql-cluster-programs-ndb-waiter6714631
Ref: mysql-cluster-ndb_waiter-options-table6716664
Ref: mysql-cluster-programs-ndb-waiter-additional-options6717465
Node: mysql-cluster-program-options-common6720830
Ref: mysql-cluster-ndb_common-options-table6722229
Node: mysql-cluster-management6730015
Node: mysql-cluster-start-phases6735901
Node: mysql-cluster-mgm-client-commands6743308
Node: mysql-cluster-backup6755628
Node: mysql-cluster-backup-concepts6757015
Node: mysql-cluster-backup-using-management-client6758866
Node: mysql-cluster-backup-configuration6767876
Node: mysql-cluster-backup-troubleshooting6769036
Node: mysql-cluster-mysqld6770180
Node: mysql-cluster-rolling-restart6775251
Ref: mysql-cluster-rolling-restart-multiple-ndb-mgmd6783130
Node: mysql-cluster-event-reports6785191
Node: mysql-cluster-logging-management-commands6790374
Node: mysql-cluster-log-events6794517
Node: mysql-cluster-log-statistics6810301
Node: mysql-cluster-logs-ndb-messages6819045
Node: mysql-cluster-logs-cluster-log6819677
Node: mysql-cluster-ndb-transporter-errors6866054
Node: mysql-cluster-single-user-mode6872293
Node: mysql-cluster-sql-statements6874704
Node: mysql-cluster-ndbinfo6882465
Node: mysql-cluster-ndbinfo-arbitrator-validity-detail6895679
Node: mysql-cluster-ndbinfo-arbitrator-validity-summary6897847
Node: mysql-cluster-ndbinfo-blocks6899949
Node: mysql-cluster-ndbinfo-cluster-operations6901346
Node: mysql-cluster-ndbinfo-cluster-transactions6905345
Node: mysql-cluster-ndbinfo-config-params6908465
Node: mysql-cluster-ndbinfo-counters6909741
Node: mysql-cluster-ndbinfo-diskpagebuffer6914146
Node: mysql-cluster-ndbinfo-logbuffers6917866
Node: mysql-cluster-ndbinfo-logspaces6919074
Node: mysql-cluster-ndbinfo-membership6920266
Node: mysql-cluster-ndbinfo-memoryusage6925541
Node: mysql-cluster-ndbinfo-nodes6932982
Node: mysql-cluster-ndbinfo-pools6939904
Node: mysql-cluster-ndbinfo-resources6945848
Node: mysql-cluster-ndbinfo-server-operations6947482
Node: mysql-cluster-ndbinfo-server-transactions6951847
Node: mysql-cluster-ndbinfo-threadblocks6955396
Node: mysql-cluster-ndbinfo-threadstat6956753
Node: mysql-cluster-ndbinfo-transporters6959746
Node: mysql-cluster-security6966629
Node: mysql-cluster-security-networking-issues6967538
Node: mysql-cluster-security-mysql-privileges6977625
Node: mysql-cluster-security-mysql-security-procedures6986342
Node: mysql-cluster-disk-data6990622
Node: mysql-cluster-disk-data-objects6992365
Node: mysql-cluster-disk-data-symlinks7005706
Node: mysql-cluster-disk-data-storage-requirements7010741
Node: mysql-cluster-online-add-node7012806
Node: mysql-cluster-online-add-node-remarks7013894
Node: mysql-cluster-online-add-node-basics7024617
Node: mysql-cluster-online-add-node-example7029077
Node: mysql-cluster-privilege-distribution7050904
Node: mysql-cluster-ndb-api-statistics7062420
Node: mysql-cluster-replication7104041
Ref: mysql-cluster-replication-ndb-non-ndb7108645
Node: mysql-cluster-replication-abbreviations7109256
Node: mysql-cluster-replication-general7111027
Node: mysql-cluster-replication-issues7114712
Ref: mysql-cluster-replication-ndb-to-non-ndb7124999
Ref: mysql-cluster-replication-ndb-to-nontransactional7128399
Ref: mysql-cluster-replication-issues-filtering7129446
Node: mysql-cluster-replication-schema7133657
Node: mysql-cluster-replication-preparation7146467
Node: mysql-cluster-replication-starting7151750
Node: mysql-cluster-replication-two-channels7156794
Node: mysql-cluster-replication-failover7159845
Node: mysql-cluster-replication-backups7164479
Node: mysql-cluster-replication-auto-sync7173110
Node: mysql-cluster-replication-pitr7179252
Node: mysql-cluster-replication-multi-master7182779
Node: mysql-cluster-replication-conflict-resolution7189770
Ref: option_mysqld_ndb-log-updated-only7194940
Ref: option_mysqld_ndb-log-update-as-write7196087
Ref: mysql-cluster-ndb-replication-table7197091
Ref: mysql-cluster-replication-ndb-old7200993
Ref: mysql-cluster-replication-ndb-max7201647
Ref: mysql-cluster-replication-ndb-max-delete-win7202296
Ref: mysql-cluster-replication-ndb-epoch7203384
Ref: mysql-cluster-replication-ndb-epoch-statvars7208396
Ref: mysql-cluster-replication-ndb-epoch-limitations7209181
Ref: mysql-cluster-replication-ndb-epoch-trans7211333
Node: mysql-cluster-news7220032
Node: partitioning7220483
Node: partitioning-overview7228550
Node: partitioning-types7238221
Node: partitioning-range7244634
Node: partitioning-list7254693
Node: partitioning-hash7260843
Node: partitioning-linear-hash7267558
Node: partitioning-key7270431
Node: partitioning-subpartitions7275613
Node: partitioning-handling-nulls7285196
Node: partitioning-management7299792
Node: partitioning-management-range-list7303767
Node: partitioning-management-hash-key7321888
Node: partitioning-maintenance7324749
Node: partitioning-info7329110
Node: partitioning-pruning7335474
Node: partitioning-limitations7347288
Ref: partitioning-limitations-file-system-ops7353993
Ref: partitioning-limitations-max-partitions7356239
Ref: partitioning-limitations-subpartitions7360512
Node: partitioning-limitations-partitioning-keys-unique-keys7365026
Node: partitioning-limitations-storage-engines7373739
Node: partitioning-limitations-functions7377692
Ref: partitioning-limitations-ceiling-floor7379451
Ref: partitioning-limitations-extract7380048
Node: partitioning-limitations-locking7380537
Node: stored-programs-views7383072
Node: stored-programs-defining7385393
Node: stored-routines7388388
Node: stored-routines-syntax7391592
Node: stored-routines-privileges7394707
Node: stored-routines-metadata7396340
Node: stored-routines-last-insert-id7397594
Node: triggers7398586
Node: trigger-syntax7400956
Node: trigger-metadata7411165
Node: events7411687
Node: events-overview7413658
Node: events-configuration7418016
Ref: events-event-scheduler-option7418549
Node: events-syntax7425636
Node: events-metadata7426758
Node: events-status-info7430726
Node: events-privileges7433471
Node: views7442212
Node: view-syntax7443429
Node: view-algorithms7444781
Node: view-updatability7448428
Node: view-metadata7454464
Node: stored-programs-security7454861
Node: stored-programs-logging7460941
Node: information-schema7482272
Node: character-sets-table7492532
Node: collations-table7493519
Node: collation-character-set-applicability-table7495250
Node: columns-table7496139
Node: column-privileges-table7498831
Node: engines-table7500635
Node: events-table7501809
Node: status-table7512946
Node: variables-table7514395
Node: key-column-usage-table7516230
Node: partitions-table7518925
Node: plugins-table7530953
Node: processlist-table7534230
Node: profiling-table7536291
Node: referential-constraints-table7539408
Node: routines-table7541435
Node: schemata-table7545044
Node: schema-privileges-table7546031
Node: statistics-table7547217
Node: tables-table7549271
Node: table-constraints-table7553890
Node: table-privileges-table7555311
Node: triggers-table7556625
Node: user-privileges-table7562659
Node: views-table7563752
Node: mysql-cluster-i_s-tables7568326
Node: files-table7569698
Node: ndb-transid-mysql-connection-map-table7586632
Node: extended-show7591825
Node: connectors-apis7597939
Ref: connectors-apis-summary7604009
Ref: connectors-apis-versions7609844
Node: connector-odbc-info7611524
Node: connector-net-info7612083
Node: connector-j-info7612636
Node: connector-cpp-info7613174
Node: connector-c-info7613724
Node: connector-python-info7614265
Node: libmysqld7614832
Ref: refman-apis-libmysqld-mysql-server-library-embeded-functions7615969
Node: libmysqld-compiling7617660
Node: libmysqld-restrictions7620010
Node: libmysqld-options7621155
Node: libmysqld-example7622462
Node: c-api7629583
Node: c-api-implementations7634254
Node: c-api-multiple-installations7637531
Node: c-api-example-programs7640933
Node: c-api-building-running-clients7641507
Node: c-api-building-clients7642227
Node: c-api-threaded-clients7647975
Node: c-api-running-clients7652044
Node: c-api-server-client-versions7654744
Node: c-api-data-structures7655764
Node: c-api-function-overview7670716
Node: c-api-functions7690478
Node: mysql-affected-rows7695612
Node: mysql-autocommit7698416
Node: mysql-change-user7698810
Node: mysql-character-set-name7701256
Node: mysql-close7701654
Node: mysql-commit7702168
Node: mysql-connect7702852
Node: mysql-create-db7704291
Node: mysql-data-seek7705298
Node: mysql-debug7706045
Node: mysql-drop-db7706694
Node: mysql-dump-debug-info7707672
Node: mysql-eof7708404
Node: mysql-errno7711433
Node: mysql-error7712979
Node: mysql-escape-string7714298
Node: mysql-fetch-field7714973
Node: mysql-fetch-field-direct7716688
Node: mysql-fetch-fields7717682
Node: mysql-fetch-lengths7718480
Node: mysql-fetch-row7720198
Node: mysql-field-count7722319
Node: mysql-field-seek7724689
Node: mysql-field-tell7725293
Node: mysql-free-result7725814
Node: mysql-get-character-set-info7726494
Node: mysql-get-client-info7727699
Node: mysql-get-client-version7728363
Node: mysql-get-host-info7729273
Node: mysql-get-proto-info7729740
Node: mysql-get-server-info7730182
Node: mysql-get-server-version7730633
Node: mysql-get-ssl-cipher7731455
Node: mysql-hex-string7732077
Node: mysql-info7734002
Node: mysql-init7735535
Node: mysql-insert-id7736957
Node: mysql-kill7742411
Node: mysql-library-end7743206
Node: mysql-library-init7744199
Node: mysql-list-dbs7748235
Node: mysql-list-fields7749368
Node: mysql-list-processes7751111
Node: mysql-list-tables7752056
Node: mysql-more-results7753165
Node: mysql-next-result7754153
Node: mysql-num-fields7757473
Node: mysql-num-rows7759924
Node: mysql-options7761141
Node: mysql-ping7773137
Node: mysql-query7774953
Node: mysql-real-connect7776373
Node: mysql-real-escape-string7788450
Node: mysql-real-query7791500
Node: mysql-refresh7793146
Node: mysql-reload7794907
Node: mysql-rollback7795747
Node: mysql-row-seek7796446
Node: mysql-row-tell7797515
Node: mysql-select-db7798177
Node: mysql-set-character-set7799171
Node: mysql-set-local-infile-default7800376
Node: mysql-set-local-infile-handler7801050
Node: mysql-set-server-option7804892
Node: mysql-shutdown7807051
Node: mysql-sqlstate7808271
Node: mysql-ssl-set7809959
Node: mysql-stat7811251
Node: mysql-store-result7812100
Node: mysql-thread-id7815821
Node: mysql-use-result7816788
Node: mysql-warning-count7820370
Node: c-api-prepared-statements7820759
Node: c-api-prepared-statement-data-structures7822574
Node: c-api-prepared-statement-type-codes7836176
Node: c-api-prepared-statement-type-conversions7843429
Node: c-api-prepared-statement-function-overview7848896
Node: c-api-prepared-statement-functions7859720
Node: mysql-stmt-affected-rows7861800
Node: mysql-stmt-attr-get7862571
Node: mysql-stmt-attr-set7863528
Node: mysql-stmt-bind-param7867336
Node: mysql-stmt-bind-result7868873
Node: mysql-stmt-close7871376
Node: mysql-stmt-data-seek7872162
Node: mysql-stmt-errno7872953
Node: mysql-stmt-error7873731
Node: mysql-stmt-execute7874785
Node: mysql-stmt-fetch7883117
Node: mysql-stmt-fetch-column7894854
Node: mysql-stmt-field-count7895876
Node: mysql-stmt-free-result7896669
Node: mysql-stmt-init7897244
Node: mysql-stmt-insert-id7897869
Node: mysql-stmt-num-rows7898773
Node: mysql-stmt-param-count7899980
Node: mysql-stmt-param-metadata7900530
Node: mysql-stmt-prepare7900902
Node: mysql-stmt-reset7903279
Node: mysql-stmt-result-metadata7904397
Node: mysql-stmt-row-seek7906466
Node: mysql-stmt-row-tell7907616
Node: mysql-stmt-send-long-data7908320
Node: mysql-stmt-sqlstate7912558
Node: mysql-stmt-store-result7913497
Node: c-api-thread-functions7916475
Node: my-init7917050
Node: mysql-thread-end7918178
Node: mysql-thread-init7918720
Node: mysql-thread-safe7919620
Node: c-api-embedded-server-functions7919989
Node: mysql-server-init7920976
Node: mysql-server-end7921621
Node: c-api-problems7922138
Node: null-mysql-store-result7922658
Node: query-results7924196
Node: getting-unique-id7925965
Node: auto-reconnect7929292
Node: c-api-multiple-queries7932411
Node: c-api-prepared-statement-problems7940297
Node: c-api-prepared-statement-date-handling7941925
Node: c-api-prepared-call-statements7945484
Node: apis-php-info7946109
Node: apis-perl7946420
Node: apis-python7948945
Node: apis-ruby7949636
Node: apis-ruby-mysqlruby7950464
Node: apis-ruby-rubymysql7950844
Node: apis-tcl7951262
Node: apis-eiffel7951590
Node: extending-mysql7951986
Node: mysql-internals7952366
Node: mysql-threads7953311
Node: mysql-test-suite7956521
Node: plugin-api7959217
Node: plugin-api-characteristics7961342
Node: plugin-api-components7964824
Node: plugin-types7967350
Node: storage-engine-plugins7967986
Node: full-text-plugins7968599
Node: daemon-plugins7972825
Node: information-schema-plugins7973312
Node: writing-plugins7973882
Node: writing-plugins-overview7976144
Node: plugin-data-structures7977981
Node: server-plugin-descriptors7980420
Node: plugin-status-system-variables7996709
Node: compiling-plugin-libraries8007445
Node: writing-full-text-plugins8010903
Node: writing-daemon-plugins8035418
Node: writing-information-schema-plugins8039726
Node: adding-functions8046732
Node: udf-features8049340
Node: adding-udf8050230
Node: udf-calling8056684
Node: udf-aggr-calling8061573
Node: udf-arguments8065089
Node: udf-return-values8071477
Node: udf-compiling8073665
Node: udf-security8080148
Node: adding-native-function8081832
Node: porting8086564
Node: debugging-server8088911
Node: compiling-for-debugging8091508
Node: making-trace-files8094227
Node: making-windows-dumps8096207
Node: using-gdb-on-mysqld8098088
Node: using-stack-trace8101586
Node: using-log-files8105773
Node: reproducible-test-case8108746
Node: debugging-client8110970
Node: dbug-package8112214
Node: mysql-enterprise8121737
Node: mysql-enterprise-monitor8123284
Node: mysql-enterprise-backup8127598
Node: mysql-enterprise-security8129262
Node: mysql-enterprise-encryption8130649
Node: mysql-enterprise-audit8131527
Node: mysql-enterprise-thread-pool8132639
Node: workbench8133543
Node: faqs8135782
Node: faqs-general8136818
Ref: qandaitem-A-1-1-18137824
Ref: qandaitem-A-1-1-28138544
Ref: qandaitem-A-1-1-38139213
Ref: qandaitem-A-1-1-48139287
Ref: qandaitem-A-1-1-58139724
Ref: qandaitem-A-1-1-68140181
Ref: qandaitem-A-1-1-78140667
Ref: qandaitem-A-1-1-88141046
Ref: qandaitem-A-1-1-98141232
Ref: qandaitem-A-1-1-108141552
Ref: qandaitem-A-1-1-118141969
Node: faqs-storage-engines8142366
Ref: qandaitem-A-2-1-18142998
Ref: qandaitem-A-2-1-28143371
Ref: qandaitem-A-2-1-38144200
Ref: qandaitem-A-2-1-48144431
Ref: qandaitem-A-2-1-58144726
Node: faqs-sql-modes8145103
Ref: qandaitem-A-3-1-18145720
Ref: qandaitem-A-3-1-28146112
Ref: qandaitem-A-3-1-38146279
Ref: qandaitem-A-3-1-48146715
Ref: qandaitem-A-3-1-58147012
Ref: qandaitem-A-3-1-68147333
Ref: qandaitem-A-3-1-78147778
Node: faqs-stored-procs8147995
Ref: qandaitem-A-4-1-18150594
Ref: qandaitem-A-4-1-28150760
Ref: qandaitem-A-4-1-38150886
Ref: qandaitem-A-4-1-48151043
Ref: qandaitem-A-4-1-58151431
Ref: qandaitem-A-4-1-68151909
Ref: qandaitem-A-4-1-78152568
Ref: qandaitem-A-4-1-88153208
Ref: qandaitem-A-4-1-98153341
Ref: qandaitem-A-4-1-108153416
Ref: qandaitem-A-4-1-118153591
Ref: qandaitem-A-4-1-128153713
Ref: qandaitem-A-4-1-138153900
Ref: qandaitem-A-4-1-148154095
Ref: qandaitem-A-4-1-158154544
Ref: qandaitem-A-4-1-168154632
Ref: qandaitem-A-4-1-178154814
Ref: qandaitem-A-4-1-188154901
Ref: qandaitem-A-4-1-198155049
Ref: qandaitem-A-4-1-208155374
Ref: qandaitem-A-4-1-218155883
Ref: qandaitem-A-4-1-228156050
Ref: qandaitem-A-4-1-238156358
Ref: qandaitem-A-4-1-248156729
Ref: qandaitem-A-4-1-258157148
Ref: qandaitem-A-4-1-268157903
Ref: qandaitem-A-4-1-278159233
Ref: qandaitem-A-4-1-288159411
Node: faqs-triggers8160066
Ref: qandaitem-A-5-1-18161162
Ref: qandaitem-A-5-1-28161259
Ref: qandaitem-A-5-1-38161386
Ref: qandaitem-A-5-1-48161658
Ref: qandaitem-A-5-1-58161876
Ref: qandaitem-A-5-1-68162316
Ref: qandaitem-A-5-1-78162933
Ref: qandaitem-A-5-1-88163069
Ref: qandaitem-A-5-1-98163129
Ref: qandaitem-A-5-1-108163423
Ref: qandaitem-A-5-1-118163748
Ref: qandaitem-A-5-1-128163885
Ref: qandaitem-A-5-1-138164095
Ref: qandaitem-A-5-1-148164861
Node: faqs-views8167001
Ref: qandaitem-A-6-1-18167571
Ref: qandaitem-A-6-1-28167659
Ref: qandaitem-A-6-1-38167805
Ref: qandaitem-A-6-1-48168135
Ref: qandaitem-A-6-1-58168192
Ref: qandaitem-A-6-1-68168252
Node: faqs-information-schema8168534
Ref: qandaitem-A-7-1-18169223
Ref: qandaitem-A-7-1-28169346
Ref: qandaitem-A-7-1-38169497
Ref: qandaitem-A-7-1-48169890
Ref: qandaitem-A-7-1-58170268
Node: faqs-migration8170589
Ref: qandaitem-A-8-1-18170994
Ref: qandaitem-A-8-1-28171527
Node: faqs-security8172506
Ref: qandaitem-A-9-1-18173142
Ref: qandaitem-A-9-1-28173705
Ref: qandaitem-A-9-1-38174040
Ref: qandaitem-A-9-1-48174289
Ref: qandaitem-A-9-1-58174393
Node: faqs-mysql-cluster8174497
Ref: qandaitem-A-10-1-18178748
Ref: qandaitem-A-10-1-28181602
Ref: qandaitem-A-10-1-38182481
Ref: qandaitem-A-10-1-48182984
Ref: qandaitem-A-10-1-58184317
Ref: qandaitem-A-10-1-68184962
Ref: qandaitem-A-10-1-78185702
Ref: qandaitem-A-10-1-88188058
Ref: qandaitem-A-10-1-98190616
Ref: qandaitem-A-10-1-108191149
Ref: qandaitem-A-10-1-118192094
Ref: qandaitem-A-10-1-128195450
Ref: qandaitem-A-10-1-138196547
Ref: qandaitem-A-10-1-148196891
Ref: qandaitem-A-10-1-158198870
Ref: qandaitem-A-10-1-168199950
Ref: qandaitem-A-10-1-178200763
Ref: qandaitem-A-10-1-188202126
Ref: qandaitem-A-10-1-198202785
Ref: qandaitem-A-10-1-208203182
Ref: qandaitem-A-10-1-218203468
Ref: qandaitem-A-10-1-228204202
Ref: qandaitem-A-10-1-238204696
Ref: qandaitem-A-10-1-248204936
Ref: qandaitem-A-10-1-258206809
Ref: qandaitem-A-10-1-268207359
Ref: qandaitem-A-10-1-278210035
Ref: qandaitem-A-10-1-288210623
Ref: qandaitem-A-10-1-298211525
Ref: qandaitem-A-10-1-308212167
Ref: qandaitem-A-10-1-318213973
Ref: qandaitem-A-10-1-328215047
Ref: qandaitem-A-10-1-338217385
Ref: qandaitem-A-10-1-348217627
Ref: qandaitem-A-10-1-358218103
Ref: qandaitem-A-10-1-368218529
Ref: qandaitem-A-10-1-378219231
Ref: qandaitem-A-10-1-388219603
Ref: qandaitem-A-10-1-398220052
Ref: qandaitem-A-10-1-408220677
Ref: qandaitem-A-10-1-418220952
Ref: qandaitem-A-10-1-428221446
Node: faqs-cjk8223093
Ref: qandaitem-A-11-1-18225340
Ref: qandaitem-A-11-1-28228328
Ref: qandaitem-A-11-1-38233955
Ref: qandaitem-A-11-1-48234963
Ref: qandaitem-A-11-1-58237841
Ref: qandaitem-A-11-1-68238158
Ref: qandaitem-A-11-1-78238572
Ref: qandaitem-A-11-1-88238809
Ref: qandaitem-A-11-1-98239720
Ref: qandaitem-A-11-1-108241478
Ref: qandaitem-A-11-1-118244422
Ref: qandaitem-A-11-1-128248907
Ref: qandaitem-A-11-1-138250812
Ref: qandaitem-A-11-1-148253662
Ref: qandaitem-A-11-1-158257009
Ref: qandaitem-A-11-1-168258957
Ref: qandaitem-A-11-1-178260152
Ref: qandaitem-A-11-1-188260624
Ref: qandaitem-A-11-1-198261249
Ref: qandaitem-A-11-1-208261569
Node: faqs-connectors-apis8262057
Node: faqs-replication8262832
Ref: qandaitem-A-13-1-18264676
Ref: qandaitem-A-13-1-28265515
Ref: qandaitem-A-13-1-38265864
Ref: qandaitem-A-13-1-48267029
Ref: qandaitem-A-13-1-58268034
Ref: qandaitem-A-13-1-68269418
Ref: qandaitem-A-13-1-78269998
Ref: qandaitem-A-13-1-88270220
Ref: qandaitem-A-13-1-98273256
Ref: qandaitem-A-13-1-108273980
Ref: qandaitem-A-13-1-118274482
Ref: qandaitem-A-13-1-128274599
Ref: qandaitem-A-13-1-138274862
Ref: qandaitem-A-13-1-148275016
Node: error-handling8275181
Node: error-sources8276050
Node: error-types8277776
Node: error-messages-server8279623
Node: error-messages-client8383343
Node: problems8390624
Node: what-is-crashing8391462
Node: common-errors8395739
Node: error-access-denied8397367
Node: can-not-connect-to-server8397757
Node: can-not-connect-to-server-on-windows8405672
Node: error-lost-connection8409422
Node: old-client8411193
Node: password-too-long8414400
Node: blocked-host8415322
Node: too-many-connections8416900
Node: out-of-memory8418874
Node: gone-away8419835
Node: packet-too-large8427142
Node: communication-errors8429697
Node: full-table8432711
Node: cannot-create8433462
Node: commands-out-of-sync8434977
Node: ignoring-user8435686
Node: cannot-find-table8437112
Node: cannot-initialize-character-set8438111
Node: not-enough-file-handles8439840
Node: table-corruption8442924
Node: installation-issues8443697
Node: file-permissions8443956
Node: administration-issues8445223
Node: resetting-permissions8445821
Node: resetting-permissions-windows8446808
Node: resetting-permissions-unix8450107
Node: resetting-permissions-generic8453544
Node: crashing8455100
Node: full-disk8463782
Node: temporary-files8465906
Node: problems-with-mysql-sock8469085
Node: timezone-problems8471322
Node: query-issues8472257
Node: case-sensitivity8472972
Node: using-date8477474
Node: problems-with-null8482015
Node: problems-with-alias8485399
Node: nontransactional-tables8487170
Node: deleting-from-related-tables8489020
Node: no-matching-rows8489770
Node: problems-with-float8491968
Node: optimizer-issues8496387
Node: table-definition-issues8498174
Node: alter-table-problems8498484
Node: temporary-table-problems8500452
Node: bugs8501729
Node: news8511418
Node: restrictions8512565
Node: stored-program-restrictions8513280
Ref: stored-routine-sql-restrictions8514071
Ref: stored-routines-function-restrictions8516153
Ref: stored-routines-trigger-restrictions8517763
Ref: stored-routine-name-conflicts8518968
Ref: stored-routines-replication-restrictions8519802
Ref: stored-routines-debugging-restrictions8520819
Ref: stored-routines-standard-restrictions8520898
Ref: stored-routines-event-restrictions8522458
Node: cursor-restrictions8528739
Node: subquery-restrictions8530760
Node: view-restrictions8536891
Node: xa-restrictions8544014
Node: charset-restrictions8546295
Node: limits8547837
Node: joins-limits8548406
Node: database-count-limit8548721
Node: table-size-limit8549290
Node: column-count-limit8554771
Node: limits-frm-file8560106
Node: limits-windows8562594
Node: licenses-third-party8568827
Node: license-antlr-38573846
Node: license-dtoa8575745
Node: license-libedit8576714
Node: license-findgtest-cmake8582810
Node: license-dbug8585548
Node: license-getarg8587267
Node: license-glib-proxy8589241
Node: license-gnu-gpl-2-08591146
Node: license-gnu-lgpl-2-18611600
Node: license-gnu-libtool8641234
Node: license-gnu-readline8643851
Node: license-google-io-rate-patch8644927
Node: license-google-tcmalloc8646918
Node: license-google-smp-patch8648935
Node: license-lib-sql8650847
Node: license-libevent8651689
Node: license-libiconv-proxy8658477
Node: license-libintl8659211
Node: license-linux-pam8661636
Node: license-lpeg8664022
Node: license-lua8665477
Node: license-luafilesystem8666883
Node: license-md58668295
Node: license-memcached8669310
Node: license-nt-servc8671174
Node: license-openpam8671682
Node: license-paramiko8673857
Node: license-pcre8674516
Node: license-percona-io-threads-patch8677532
Node: license-regex8679504
Node: license-us-secure-hash8680860
Node: license-libstring8682869
Node: license-sha1-in-c8684382
Node: license-zlib8684701

End Tag Table
